link respective routers application host executes read write operations processes directly connected kind data pipe establishment pipe details communication hidden process underlying principles communication implemented lower protocol layers analogy transport layer communication appears host host without knowledge application data structures connecting routers internetworking layer individual network boundaries traversed router prominent component


internet model internet protocol ip ip enables internetworking essence establishes internet two versions internet protocol exist ipv ipv ip addresses dns resolver consults three name servers resolve domain name user visible wwwwikipediaorg determine ipv address locating individual computers network internet provides ip addresses ip addresses used internet infrastructure direct internet packets destinations consist fixed length numbers found within packet ip addresses generally assigned equipment either automatically via dhcp

Formal science
Computer science
Computer communications (networks)
Internet


configured however network also supports addressing systems users generally enter domain names eg enwikipediaorg instead ip addresses easier remember converted domain name system dns ip addresses efficient routing purposes ipv internet protocol version ipv defines ip address bit number ref name rfc ipv initial version used first generation internet still dominant use designed address nbsp billion sup sup hosts however explosive growth internet led


resource managers plan rapid adoption conversion ipv directly interoperable design ipv essence establishes parallel version internet directly accessible ipv software thus translation facilities must exist internetworking nodes must duplicate networking software networks essentially modern computer operating systems support versions internet protocol network infrastructure however lagging development aside complex array physical connections make infrastructure internet facilitated bi multi lateral commercial contracts eg peering agreements


prefix'' ' 'rest field'' ''host identifier'' ' 'rest field'' identifier specific host network interface ''routing prefix'' may expressed classless inter domain routing cidr notation written first address network followed slash character '' '' ending bit length prefix example prefix internet protocol version network starting given address bits allocated network prefix remaining bits reserved host addressing addresses range belong


network ipv address specification large address block sup sup addresses bit routing prefix ipv network may also characterized ' 'subnet mask'' ''netmask'' bitmask applied bitwise operation ip address network yields routing prefix subnet masks also expressed dot decimal notation like address example subnet mask prefix traffic exchanged subnetworks routers routing prefixes source address destination address differ router


serves logical physical boundary subnets benefits subnetting existing network vary deployment scenario address allocation architecture internet using cidr large organizations necessary allocate address space efficiently subnetting may also enhance routing efficiency advantages network management subnetworks administratively controlled different entities larger organization subnets may arranged logically hierarchical architecture partitioning organization 's network address space tree like routing structure routing computers routers use routing tables operating system


direct ip packets reach node different subnetwork routing tables maintained manual configuration automatically routing protocols end nodes typically use default route points toward isp providing transit isp routers use border gateway protocol establish efficient routing across complex connections global internet default gateway node serves forwarding host router networks route specification matches destination ip address packet ietf hardware components internet infrastructure often used


support software systems design standardization process software characterizes internet provides foundation scalability success responsibility architectural design internet software systems assumed internet engineering task force ietf ietf conducts standard setting work groups open individual various aspects internet architecture resulting contributions standards published ''request comments'' rfc documents ietf web site principal methods networking enable internet contained specially designated rfcs


constitute internet standards less rigorous documents simply informative experimental historical document best current practices bcp implementing internet technologies applications services internet carries many applications services prominently world wide web including social media electronic mail mobile applications multiplayer online games internet telephony file sharing streaming media services servers provide services today hosted data centers content often accessed high performance content delivery networks world wide web next computer used tim berners lee cern


became world 's first web server world wide web global collection documents images multimedia applications resources logically interrelated hyperlinks referenced uniform resource identifiers uris provide global system named references uris symbolically identify services web servers databases documents resources provide hypertext transfer protocol http main access protocol world wide web web services also use http communication software systems information transfer sharing exchanging business data logistic one many languages protocols


used communication internet world wide web browser software microsoft 's internet explorer edge mozilla firefox opera apple 's safari google chrome lets users navigate one web page another via hyperlinks embedded documents documents may also contain combination computer data including graphics sounds text video multimedia interactive content runs user interacting page client side software include animations games office applications scientific demonstrations keyword driven internet research using search engines like yahoo bing google users worldwide easy instant access


vast diverse amount online information compared printed media books encyclopedias traditional libraries world wide web enabled decentralization information large scale web enabled individuals organizations publish ideas information potentially large audience online greatly reduced expense time delay publishing web page blog building website involves little initial cost many cost free services available however publishing maintaining large professional web sites attractive diverse date information still difficult expensive proposition many individuals


companies groups use ''web logs'' blogs largely used easily updatable online diaries commercial organizations encourage staff communicate advice areas specialization hope visitors impressed expert knowledge free information attracted corporation result advertising popular web pages lucrative e commerce sale products services directly via web continues grow online advertising form marketing advertising uses internet deliver promotional marketing messages


consumers includes email marketing search engine marketing sem social media marketing many types display advertising including web banner advertising mobile advertising internet advertising revenues united states surpassed cable television nearly exceeded broadcast television ref name iab ref many common online advertising practices controversial increasingly subject regulation web developed typical web page stored completed form web server formatted html complete transmission web browser response request time process creating


serving web pages become dynamic creating flexible design layout content websites often created using content management software initially little content contributors systems may paid staff members organization public fill underlying databases content using editing pages designed purpose casual visitors view read content html form may may editorial approval security systems built process taking newly entered content making available target visitors communication email important


communications service available via internet concept sending electronic text messages parties analogous mailing letters memos predates creation internet pictures documents files sent email attachments email messages cc ed multiple email addresses internet telephony common communications service realized internet name principle internetworking protocol internet protocol lends name voice internet protocol voip idea began early walkie talkie like voice applications personal computers voip systems dominate many markets easy


power failure data transfer file sharing example transferring large amounts data across internet computer file emailed customers colleagues friends attachment uploaded website file transfer protocol ftp server easy download others put shared location onto file server instant use colleagues load bulk downloads many users eased use mirror servers peer peer networks cases access file may


computer file transmission includes manner print publications software products news music film video photography graphics arts turn caused seismic shifts existing industries previously controlled production distribution products streaming media real time delivery digital media immediate consumption enjoyment end users many radio television broadcasters provide internet feeds live audio video productions may also allow time shift viewing listening preview classic clips listen features providers


joined range pure internet broadcasters never air licenses means internet connected device computer something specific used access line media much way previously possible television radio receiver range available types content much wider specialized technical webcasts demand popular multimedia services podcasting variation theme usually audio material downloaded played back computer shifted portable media player listened move


techniques using simple equipment allow anybody little censorship licensing control broadcast audio visual material worldwide digital media streaming increases demand network bandwidth example standard image quality needs mbit link speed sd p hd p quality requires mbit top line hdx quality needs mbit p webcams low cost extension phenomenon webcams give full frame rate video picture either usually small updates slowly internet users watch animals around african waterhole ships panama canal traffic local roundabout


monitor premises live real time video chat rooms video conferencing also popular many uses found personal webcams without two way sound youtube founded february leading website free streaming video two billion users uses html based web player default stream show video files registered users may upload unlimited amount video build personal profile youtube claims users watch hundreds millions upload hundreds thousands videos


daily social impact internet enabled new forms social interaction activities social associations phenomenon given rise scholarly study sociology internet users source data internet users per population members gdp per capita selected countries div style text align center '''internet users per inhabitants''' div small source international telecommunication union small number internet users globally rose nbsp million nbsp billion percent world 's population access computers nbsp billion google searches every day nbsp million internet users reading blogs


nbsp billion videos viewed daily youtube world 's internet users surpassed nbsp billion percent world population two thirds users came richest countries percent europe countries population using internet followed percent americas however asia alone accounted internet users nbsp billion nbsp billion internet users world coming region number china 's internet users surpassed major milestone country 's internet regulatory authority china internet network information centre announced china


nbsp million internet users china world 's leading country terms internet users nbsp million users followed closely india nbsp million users united states distant third nbsp million users however terms penetration china penetration rate compared india 's united states 's estimated nbsp billion people use internet half world 's population prevalent language communication via internet always english may result origin


taken together africa middle east australia oceania ref name inetstats ref internet 's technologies developed enough recent years especially use unicode good facilities available development communication world 's widely used languages however glitches ''mojibake'' incorrect display languages' characters still remain american study percentage men using internet slightly ahead percentage women although difference reversed men logged often spent time online


likely broadband users whereas women tended make use opportunities communicate email men likely use internet pay bills participate auctions recreation downloading music videos men women equally likely use internet shopping banking recent studies indicate women significantly outnumbered men social networking services facebook myspace although ratios varied age addition women watched streaming content whereas men downloaded terms blogs men


actively involved improving online communities internet general surrounding political affairs rights free speech ref name hauben ref internaut refers operators technically highly capable users internet digital citizen refers person using internet order engage society politics government participation gallery mode packed heights px file internetusersbylanguagepiechartsvg div style text align center '''internet users language''' ref name niubl iws ref div file websitesbylanguagepiechartsvg div style text align center '''website content languages''' ref name uofclbwapril ref div gallery usage internet users percentage country 's population''' div source international telecommunication union ref name itu individualsusingtheinternet fixed broadband internet subscriptions br percentage country 's population''' div source


international telecommunication union ref name fixedbroadbanditudynamic http wwwituint itu icteye reporting dynamicreportwizardaspx fixed wired broadband subscriptions per inhabitants dynamic report itu itc eye international telecommunication union retrieved june ref mobile broadband internet subscriptions br percentage country 's population''' div source international telecommunication union ref name moblebroadbanditudynamic http wwwituint itu icteye reporting dynamicreportwizardaspx active mobile broadband subscriptions per inhabitants dynamic report itu itc eye international telecommunication union retrieved june ref internet allows greater flexibility working hours location especially spread unmetered high speed connections internet accessed almost anywhere numerous means including mobile internet devices mobile phones datacards handheld game consoles


homework assignments self guided learning whiling away spare time looking detail interesting fact never easier people access educational information level anywhere internet general world wide web particular important enablers formal informal education internet allows universities particular researchers social behavioral sciences conduct research remotely via virtual laboratories profound changes reach generalizability findings well communication scientists publication results


working computers day messages exchanged even quickly conveniently via email systems may allow files exchanged drawings images shared voice video contact team members content management systems allow collaborating teams work shared sets documents simultaneously without accidentally destroying 's work business project teams share calendars well documents information collaboration occurs wide variety areas including scientific research software development conference planning political activism creative writing social political


collaboration also becoming widespread internet access computer literacy spread internet allows computer users remotely access computers information stores easily access point access may computer security ie authentication encryption technologies depending requirements encouraging new ways working home collaboration information sharing many industries accountant sitting home audit books company based another country server situated third country remotely maintained specialists fourth accounts could


created home working bookkeepers remote locations based information emailed offices world things possible widespread use internet cost private leased lines would made many infeasible practice office worker away desk perhaps side world business trip holiday access emails access data using cloud computing open remote desktop session office pc using secure virtual private network vpn


sports reports plan book vacations pursue personal interests people use chat messaging email make stay touch friends worldwide sometimes way previously pen pals social networking services facebook created new ways socialize interact users sites able add wide variety information pages pursue common interests connect others also possible find existing acquaintances allow communication among existing groups people sites like linkedin foster commercial business connections youtube


flickr specialize users' videos photographs social networking services also widely used businesses organizations promote brands market customers encourage posts go viral black hat social media techniques also employed organizations spam accounts astroturfing risk individuals organizations writing posts especially public posts social networking services especially foolish controversial posts occasionally lead unexpected possibly large scale backlash social media internet users also risk relation


controversial ''offline'' behavior widely made known nature backlash range widely counter arguments public mockery insults hate speech extreme cases rape death threats online disinhibition effect describes tendency many individuals behave stridently offensively online would person significant number feminist women target various forms harassment response posts made social media twitter particular criticised past enough aid victims


online abuse organizations backlash cause overall brand damage especially reported media however always case brand damage eyes people opposing opinion presented organization could sometimes outweighed strengthening brand eyes others furthermore organization individual gives demands others perceive wrong headed provoke counter backlash websites reddit rules forbidding posting personal information individuals also known doxxing due concerns


postings leading mobs large numbers internet users directing harassment specific individuals thereby identified particular reddit rule forbidding posting personal information widely understood imply identifying photos names must censored facebook screenshots posted reddit however interpretation rule relation public twitter posts less clear case like minded people online many ways use direct 's attention public social media posts disagree children also face dangers online


age however policies typically trivial circumvent registering account false birth date significant number children aged join sites anyway social networking services younger children claim provide better levels protection children also exist internet major outlet leisure activity since inception entertaining social experiments muds moos conducted university servers humor related usenet groups receiving much traffic many internet forums sections devoted games funny videos internet pornography


lonely anyone speak thread book claimed internet consolidates aspects human endeavor singular arenas humanity potential members competitors fundamentally negative impacts mental health result successes field activity pervasively visible trumpeted reserved extremely thin sliver world 's exceptional leaving everyone else behind whereas internet expectations success field supported reasonable probabilities achievement village suburb city even state level


expectations internet world virtually certain bring disappointment today always someone else somewhere planet better take one top spot cybersectarianism new organizational form involves highly dispersed small groups practitioners may remain largely anonymous within larger social context operate relative secrecy still linked remotely larger network believers share set practices texts often common devotion particular leader overseas supporters provide funding support domestic practitioners distribute tracts participate


acts resistance share information internal situation outsiders collectively members practitioners sects construct viable virtual communities faith exchanging personal testimonies engaging collective study via email line chat rooms web based message boards particular british government raised concerns prospect young british muslims indoctrinated islamic extremism material internet persuaded join terrorist groups called islamic state potentially committing acts terrorism returning britain fighting syria iraq cyberslacking


add revenue streams using internet build enhance relationships clients partners according international data corporation size worldwide e commerce global business business consumer transactions combined equate nbsp trillion report oxford economics added two together estimate total size digital economy nbsp trillion equivalent roughly global sales much written economic advantages internet enabled commerce also evidence aspects internet maps location aware services may serve reinforce economic inequality


time uber employed full time employees valued nbsp billion valuation avis rent car hertz corporation combined together employed almost people telecommuting telecommuting performance within traditional worker employer relationship facilitated tools groupware virtual private networks conference calling videoconferencing voip work may performed location conveniently worker 's home efficient useful companies allows workers communicate long distances saving significant amounts travel time


cost broadband internet connections become commonplace workers adequate bandwidth home use tools link home corporate intranet internal communication networks collaborative publishing wikis also used academic community sharing dissemination information across institutional international boundaries settings found useful collaboration grant writing strategic planning departmental documentation committee work united states patent trademark office uses wiki allow public collaborate finding prior art relevant examination pending


patent applications queens new york used wiki allow citizens collaborate design planning local park ref name noveck ref english wikipedia largest user base among wikis world wide web ranks top among web sites terms traffic politics political revolutions banner bangkok thai coup d' tat informing thai public 'like' 'share' activities social media could result imprisonment observed june internet achieved new relevance political tool presidential


campaign howard dean united states notable success soliciting donation via internet many political groups use internet achieve new method organizing carrying mission given rise internet activism notably practiced rebels arab spring ref name cascading ref ''the new york times'' suggested social media websites facebook twitter helped people organize political revolutions egypt helping activists organize protests communicate grievances disseminate information many understood internet extension habermasian notion


''public sphere'' observing network communication technologies provide something like global civic forum however incidents politically motivated internet censorship recorded many countries including western democracies philanthropy spread low cost internet access developing countries opened new possibilities peer peer charities allow individuals contribute small amounts charitable projects individuals websites donorschoose globalgiving allow small scale donors direct funds individual projects choice popular twist internet based philanthropy use peer peer lending charitable purposes kiva pioneered


concept offering first web based service publish individual loan profiles funding kiva raises funds local intermediary microfinance organizations post stories updates behalf borrowers lenders contribute little loans choice receive money back borrowers repay kiva falls short pure peer peer charity loans disbursed funded lenders borrowers communicate lenders security internet resources hardware software components target criminal malicious attempts gain


data traffic internet ref name sciam internet ref united states example communications assistance law enforcement act phone calls broadband internet traffic emails web traffic instant messaging etc required available unimpeded real time monitoring federal law enforcement agencies ref name eff calea archive ref ref name eff calea summary ref ref name eff calea faq ref packet capture monitoring data traffic computer network computers communicate internet breaking messages emails images videos web pages files etc small chunks called packets routed network computers reach destination


assembled back complete message packet capture appliance intercepts packets traveling network order examine contents using programs packet capture information ''gathering'' tool ''analysis'' tool gathers messages analyze figure mean programs needed perform traffic analysis sift intercepted data looking important useful information communications assistance law enforcement act us telecommunications providers required install packet sniffing technology allow federal law enforcement


intelligence agencies intercept customers' broadband internet voip traffic large amount data gathered packet capturing requires surveillance software filters reports relevant information use certain words phrases access certain types web sites communicating via email chat certain parties ref name usatoday chatroom ref agencies information awareness office nsa gchq fbi spend billions dollars per year develop purchase implement operate systems interception analysis data ref name zdnet fbi ref similar systems operated iranian secret police


identify suppress dissidents required hardware software allegedly installed german siemens ag finnish nokia censorship internet censorship surveillance country ''' ref name fotn ref ref name oniss nov opennet initiative http opennetnet research data summarized global internet filtering data spreadsheet november http opennetnet research profiles country profiles opennet initiative collaborative partnership citizen lab munk school global affairs university toronto berkman center internet society harvard university secdev group ottawa ref ref name onichildpornlegal due legal concerns opennet initiative check filtering child pornography


classifications focus technical filtering include types censorship ref ref name rwbenemies ref ref name rwbenemies ref div blockquote div style text align center div blockquote governments burma iran north korea mainland china saudi arabia united arab emirates restrict access content internet within territories especially political religious content domain name keyword filters norway denmark finland sweden major internet service providers voluntarily agreed restrict access sites listed authorities list forbidden resources supposed contain known child pornography sites


content list secret ref name register ref many countries including united states enacted laws possession distribution certain material child pornography via internet mandate filter software many free commercially available software programs called content control software available users block offensive websites individual computers networks order limit access children pornographic material depiction violence performance internet heterogeneous network physical characteristics including example data transfer rates connections vary widely


disruption less developed countries vulnerable due small number high capacity links land cables also vulnerable woman digging scrap metal severed connectivity nation armenia internet blackouts affecting almost entire countries achieved governments form internet censorship blockage internet egypt whereby approximately ref name renesys ref networks without access attempt stop mobilization anti government protests energy use estimates internet 's electricity usage subject controversy according


energy used humanity estimate included energy needed build operate periodically replace estimated nbsp million laptops billion smart phones nbsp million servers worldwide well energy routers cell towers optical switches wi fi transmitters cloud storage devices use transmitting internet traffic according non peer reviewed study published shift project french think tank funded corporate sponsors nearly global co sub sub emissions could attributed global data transfer necessary infrastructure study also said online video streaming alone accounted


mike pepper sonet digital november pp nbsp external links http wwwisocorg internet society http wwwlivinginternetcom living internet internet history related information including information many creators internet establishments united states american inventions computer related introductions computer related introductions cultural globalization digital technology mass media technology new media promotion marketing communications public services telegraphy transport systems virtual reality main topic articles


two states factors like currency government policies economy judicial system laws markets influence trade ease justify process trade countries different economic standing modern era international economic organizations formed world trade organization organizations work towards facilitation growth international trade statistical services intergovernmental supranational organizations governmental statistical agencies publish official statistics international trade characteristics global trade product transferred sold party one country party another country

Applied science
Business
International trade


export originating country import country receiving product imports exports accounted country 's current account balance payments trading globally may give consumers countries opportunity exposed new markets products almost every kind product found international market example food clothes spare parts oil jewellery wine stocks currencies water services also traded tourism banking consulting transportation ancient silk road trade routes across eurasia advanced technology including transportation globalization industrialization


outsourcing multinational corporations major impacts international trade system differences domestic trade ports play important role facilitating international trade port new york new jersey grew original harbor convergence hudson river east river upper new york bay international trade principle different domestic trade motivation behavior parties involved trade change fundamentally regardless whether trade across border however practical terms carrying trade


goods services lesser extent trade capital labour factors production trade goods services serve substitute trade factors production instead importing factor production country import goods make intensive use factor production thus embody example import labor intensive goods united states china instead importing chinese labor united states imports goods produced chinese labor one report suggested international


trade increased country hosted network immigrants trade effect weakened immigrants became assimilated new country ref name twsa ref history history international trade chronicles notable events affected trading among various economies theories models several models seek explain factors behind international trade welfare consequences trade pattern trade traded export products center largest countries total international trade volume world merchandise exports following table list largest trading states according


world trade organization class wikitable sortable style text align right bgcolor ececec valign top data sort type number style width rank style width state style width international trade br goods billions usd style width international trade br services billions usd style width total international trade br goods services br billions usd '''''world''''' align left '''''''''' align left '''''' align left '''''' align left '''''' align left ''''''


align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' align left ''''''


align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' align left '''''' top traded commodities value exports class sortable wikitable bgcolor ececec valign top rank commodity value us ' date br information


align center mineral fuels oils distillation products etc align right align center align center electrical electronic equipment align right align center align center machinery nuclear reactors boilers etc align right align center align center vehicles excluding railway align right align center align center plastics articles thereof align right align center align center optical photo technical medical etc apparatus align right align center align center pharmaceutical products align right


align center align center iron steel align right align center align center organic chemicals align right align center align center pearls precious stones metals coins etc align right align center source international trade centre observances united states various us presidents held observances promote big small companies involved export import goods services president george w bush observed world trade week may may may


president barack obama proclaimed may may world trade week may president donald trump proclaimed may may world trade week world trade week third week may every year president declares week world trade week international trade versus local production local food case food production trade offs forms local food distant food production controversial limited studies comparing environmental impact scientists cautioning regionally specific environmental impacts considered effects local food


greenhouse gas emissions may vary per origin target region production study indicated local food crop production alone cannot meet demand food crops current production consumption patterns locations food production ''at time study'' global population km radiuses early ref name phys localfood ref studies found food miles relatively minor factor carbon emissions albeit increased food localization may also enable additional significant environmental benefits recycling energy water nutrients specific foods


regional differences harvest seasons may make environmentally friendly import distant regions local production storage local production greenhouses qualitative differences economic aspects qualitative differences substitutive products different production regions may exist due different legal requirements quality standards different levels controllability local production governance systems may aspects security beyond resource security environmental protection product quality product design health process transforming supply well labor rights may differ well local production reported increase


local employment many cases study claimed international trade increase local employment study found local employment total labor income manufacturing nonmanufacturing negatively affected rising exposure imports local production high income countries rather distant regions may require higher wages workers higher wages incentivize automation could allow automated workers' time reallocated society economic mechanisms converted leisure like time specialization production efficiency regional differences local production may require knowledge transfer technology transfer may able


compete efficiency initially specialized established industries businesses consumer demand without policy measures eco tariffs regional differences may cause specific regions suitable specific production thereby increasing advantages specific trade specific local production forms local products highly localized may able meet efficiency large scale highly consolidated production terms efficiency including environmental impact resource security video explaining findings study water energy land insecurity global supply chains systematic possibly first large scale cross sectoral


analysis water energy land security countries links total sectorial consumption sources showed countries sectors highly exposed exploited insecure degraded resources economic globalization decreased security global supply chains study finds countries exhibit greater exposure resource risks via international trade mainly remote production sources diversifying trading partners unlikely help countries sectors reduce improve resource self sufficiency see also aggressive legalism export control free trade free trade area gravity model


products available statistical collections international trade published statistical services intergovernmental supranational organisations national statistical institutes definitions methodological concepts applied various statistical collections international trade often differ terms definition eg special trade vs general trade coverage reporting thresholds inclusion trade services estimates smuggled goods cross border provision illegal services metadata providing information definitions methods often published along data http comtradeunorg united nations commodity trade database http wwwtrademaporg indexaspx trade map trade statistics international business development http wwwwtoorg english res e statis e statis ehtm wto statistics


portal http wwwoecdorg statsportal en html statistical portal oecd https webarchiveorg web http eppeurostateceuropaeu portal page portal external trade introduction european union international trade goods data http faostatfaoorg site defaultaspx food agricultural trade data fao https wwwseaircoin us import dataaspx usa import data data sources http wwwmacalesteredu research economics page haveman traderesources tradedatahtml resources data trade including gravity model https webarchiveorg web http wwwunescaporg tid aptiad asia pacific trade agreements database aptiad https webarchiveorg web http wwwartnetontradeorg asia pacific research training network trade artnet http witsworldbankorg wits world integrated trade solution wits http wwwmacmaporg market access map online database customs tariffs market requirements https tradedatamonitorcom trade data monitor database monthly import export statistics countries commodities subscription required http wwwexportnationcom reference trade statistics exportnation trade statistics https wwwjimarecom indian export export port product list


external links http atlasmediamitedu en observatory economic complexity https wwwseaircoin global trade dataaspx global trade data mcgill faculty law runs regional trade agreements database contains text almost preferential regional trade agreements world http wwwptasmcgillca ptasmcgillca https fraserstlouisfedorg subject historical documents international trade available fraser official statistics


'''inorganic compounds show rich variety ''' br '''a ''' diborane features unusual bonding br '''b ''' caesium chloride archetypal crystal structure br '''c ''' fp sub sub organometallic complex br '''d ''' silicone 's uses range breast implants silly putty br '''e ''' grubbs' catalyst nobel prize discoverer br '''f ''' zeolites find extensive use molecular sieves br '''g ''' copper ii acetate surprised theoreticians diamagnetism '''inorganic chemistry''' deals synthesis behavior inorganic organometallic compounds field covers chemical compounds carbon based subjects organic chemistry distinction two disciplines far

Natural science
Chemistry
Inorganic chemistry


proportions ions electric charges cancel bulk compound electrically neutral ions described oxidation state ease formation inferred ionization potential cations electron affinity anions parent elements important classes inorganic compounds oxides carbonates sulfates halides many inorganic compounds characterized high melting points inorganic salts typically poor conductors solid state important features include high melting point ease


crystallization salts eg nacl soluble water others eg fes simplest inorganic reaction double displacement mixing two salts ions swapped without change oxidation state redox reactions one reactant ''oxidant'' lowers oxidation state another reactant ' 'reductant'' oxidation state increased net result exchange electrons electron exchange occur indirectly well eg batteries key concept electrochemistry one reactant contains hydrogen atoms reaction take place exchanging protons


acid base chemistry general definition chemical species capable binding electron pairs called lewis acid conversely molecule tends donate electron pair referred lewis base refinement acid base interactions hsab theory takes account polarizability size ions inorganic compounds found nature minerals soil may contain iron sulfide pyrite calcium sulfate gypsum inorganic compounds also found multitasking biomolecules electrolytes sodium chloride energy storage atp construction polyphosphate backbone dna


first important man made inorganic compound ammonium nitrate soil fertilization haber process inorganic compounds synthesized use catalysts vanadium v oxide titanium iii chloride reagents organic chemistry lithium aluminium hydride subdivisions inorganic chemistry organometallic chemistry cluster chemistry bioinorganic chemistry fields active areas research inorganic chemistry aimed toward new catalysts superconductors therapies industrial inorganic chemistry inorganic chemistry highly practical area science traditionally scale nation 's economy could evaluated productivity sulfuric acid


manufacturing fertilizers often begins haber bosch process another practical application industrial inorganic chemistry descriptive inorganic chemistry descriptive inorganic chemistry focuses classification compounds based properties partly classification focuses position periodic table heaviest element element highest atomic weight compound partly grouping compounds structural similarities coordination compounds edta chelates octahedrally coordinated co sup sup ion co edta sup sup classical coordination compounds feature metals bound lone pairs electrons residing main group atoms ligands


group compounds tetrasulfur tetranitride sub sub n sub sub main group compound continues intrigue chemists species feature elements groups ii iii iv vvi vii excluding hydrogen periodic table due often similar reactivity elements group sc la group zn cd hg also generally included lanthanides actinides sometimes included well main group compounds known since beginnings chemistry eg elemental sulfur distillable white phosphorus experiments oxygen sub sub lavoisier priestley


compounds lacking many hydrogen ligands classed inorganic fullerenes buckytubes binary carbon oxides examples tetrasulfur tetranitride sub sub n sub sub diborane b sub sub h sub sub silicones buckminsterfullerene c sub sub transition metal compounds compounds containing metals group considered transition metal compounds compounds metal group sometimes also incorporated group also often classified main group compounds transition metal compounds show rich coordination chemistry varying tetrahedral titanium eg ticl sub sub square planar nickel complexes octahedral coordination complexes cobalt


range transition metals found biologically important compounds iron hemoglobin examples iron pentacarbonyl titanium tetrachloride cisplatin organometallic compounds organolithium reagents often found polymeric form ''n'' butyllithium shown usually organometallic compounds considered contain c h group metal species either main group element transition metal operationally definition organometallic compound relaxed include also highly lipophilic complexes metal carbonyls even metal alkoxides organometallic compounds mainly considered special category


organic ligands often sensitive hydrolysis oxidation necessitating organometallic chemistry employs specialized preparative methods traditional werner type complexes synthetic methodology especially ability manipulate complexes solvents low coordinating power enabled exploration weakly coordinating ligands hydrocarbons h sub sub n sub sub ligands petrochemicals sense area organometallic chemistry greatly benefited relevance industry examples cyclopentadienyliron dicarbonyl dimer c sub sub h sub sub fe co sub sub ch sub sub ferrocene fe c sub sub h sub sub sub sub molybdenum hexacarbonyl mo co sub sub triethylborane et sub sub b tris dibenzylideneacetone dipalladium pd sub sub dba sub sub cluster compounds decaborane powerfully toxic cluster compound boron


ill defined species humic acid water eg coordinated gadolinium complexes employed mri traditionally bioinorganic chemistry focuses electron energy transfer proteins relevant respiration medicinal inorganic chemistry includes study non essential essential elements applications diagnosis therapies examples hemoglobin methylmercury carboxypeptidase solid state compounds yba sub sub cu sub sub sub sub ybco high temperature superconductor able levitate magnet colder critical temperature nbsp k nbsp c important area focuses structure bonding physical properties materials practice solid state


inorganic chemistry uses techniques crystallography gain understanding properties result collective interactions subunits solid included solid state chemistry metals alloys intermetallic derivatives related fields condensed matter physics mineralogy materials science examples silicon chips zeolites yba sub sub cu sub sub sub sub theoretical inorganic chemistry alternative perspective area inorganic chemistry begins bohr model atom using tools models theoretical chemistry computational chemistry expands bonding simple complicated molecules precise quantum


mechanical descriptions multielectron species province inorganic chemistry difficult challenge spawned many semi quantitative semi empirical approaches including molecular orbital theory ligand field theory parallel theoretical descriptions approximate methodologies employed including density functional theory exceptions theories qualitative quantitative extremely important development field example cu sup ii sup sub sub oac sub sub h sub sub sub sub almost diamagnetic room temperature whereas crystal field theory predicts molecule would two unpaired electrons disagreement qualitative theory paramagnetic observation diamagnetic led development models magnetic


coupling exchange interaction improved models led development new magnetic materials new technologies qualitative theories crystal field theory explains fe sup iii sup cn sub sub sup sup one unpaired electron inorganic chemistry greatly benefited qualitative theories theories easier learn require little background quantum theory within main group compounds vsepr theory powerfully predicts least rationalizes structures main group compounds explanation nh sub sub pyramidal whereas clf sub sub shaped transition metals crystal field theory allows one


understand magnetism many simple complexes fe sup iii sup cn sub sub sup sup one unpaired electron whereas fe sup iii sup h sub sub sub sub sup sup five particularly powerful qualitative approach assessing structure reactivity begins classifying molecules according electron counting focusing numbers valence electrons usually central atom molecule molecular symmetry group theory nitrogen dioxide sub sub exhibits ''c sub v sub '' symmetry central construct inorganic chemistry theory molecular symmetry mathematical group theory provides language describe shapes molecules according point group symmetry group theory also enables


factoring simplification theoretical calculations spectroscopic features analyzed described respect symmetry properties ''inter alia'' vibrational electronic states knowledge symmetry properties ground excited states allows one predict numbers intensities absorptions vibrational electronic spectra classic application group theory prediction number c vibrations substituted metal carbonyl complexes common applications symmetry spectroscopy involve vibrational electronic spectra group theory highlights commonalities differences bonding otherwise disparate species


example metal based orbitals transform identically wf sub sub w co sub sub energies populations orbitals differ significantly similar relationship exists co sub sub molecular beryllium difluoride thermodynamics inorganic chemistry alternative quantitative approach inorganic chemistry focuses energies reactions approach highly traditional empirical also useful broad concepts couched thermodynamic terms include redox potential acidity phase changes classic concept inorganic thermodynamics born haber cycle used assessing energies elementary processes electron


affinity cannot observed directly mechanistic inorganic chemistry important aspect inorganic chemistry focuses reaction pathways ie reaction mechanisms main group elements lanthanides mechanisms main group compounds groups usually discussed context organic chemistry organic compounds main group compounds elements heavier c n f often form compounds electrons predicted octet rule explained article hypervalent molecules mechanisms reactions differ organic compounds reason elements lighter


carbon b li well al mg often form electron deficient structures electronically akin carbocations electron deficient species tend react via associative pathways chemistry lanthanides mirrors many aspects chemistry seen aluminium transition metal complexes transition metal main group compounds often react differently important role orbitals bonding strongly influences pathways rates ligand substitution dissociation themes covered articles coordination chemistry ligand associative dissociative pathways observed overarching aspect


mechanistic transition metal chemistry kinetic lability complex illustrated exchange free bound water prototypical complexes h sub sub sub sub sup n sup h sub sub sub sub sup n sup h sub sub h sub sub sub sub sup n sup h sub sub h sub sub denotes isotopically enriched water eg h sub sub sup sup rates water exchange varies orders magnitude across periodic table lanthanide complexes one extreme ir iii species slowest redox reactions redox reactions prevalent transition elements two classes redox reaction considered atom transfer reactions oxidative addition reductive elimination


ligand transfer reactions transmetalation characterization inorganic compounds diverse range elements correspondingly diverse properties resulting derivatives inorganic chemistry closely associated many methods analysis older methods tended examine bulk properties electrical conductivity solutions melting points solubility acidity advent quantum theory corresponding expansion electronic apparatus new tools introduced probe electronic properties inorganic molecules solids often measurements provide insights relevant theoretical models commonly encountered techniques x ray


crystallography technique allows determination molecular structures dual polarisation interferometer technique measures conformation conformational change molecules various forms spectroscopy ultraviolet visible spectroscopy historically important tool since many inorganic compounds strongly colored nmr spectroscopy besides sup sup h sup sup c many nmr active nuclei eg sup sup b sup sup f sup sup p sup sup pt give important information compound properties structure nmr paramagnetic species provide important structural information proton sup sup h nmr also important light hydrogen nucleus easily detected x ray crystallography infrared spectroscopy


mostly absorptions carbonyl ligands electron nuclear double resonance endor spectroscopy ssbauer spectroscopy electron spin resonance esr epr allows measurement environment paramagnetic metal centres electrochemistry cyclic voltammetry related techniques probe redox characteristics compounds synthetic inorganic chemistry although inorganic species obtained pure form nature synthesized chemical plants laboratory inorganic synthetic methods classified roughly according volatility solubility component reactants soluble inorganic compounds prepared using methods organic synthesis metal containing compounds


reactive toward air schlenk line glove box techniques followed volatile compounds gases manipulated vacuum manifolds consisting glass piping interconnected valves entirety evacuated nbsp mm hg less compounds condensed using liquid nitrogen bp nbsp k cryogens solids typically prepared using tube furnaces reactants products sealed containers often made fused silica amorphous sio sub sub sometimes specialized materials welded ta tubes pt boats products reactants transported temperature zones drive reactions


see also important publications inorganic chemistry references


'''information theory''' scientific study quantification storage communication digital information field fundamentally established works harry nyquist ralph hartley claude shannon field intersection probability theory statistics computer science statistical mechanics information engineering electrical engineering key measure information theory entropy entropy quantifies amount uncertainty involved value random variable outcome random process example identifying outcome fair coin flip two equally

Formal science
Computer science
Computer communications (networks)
Information theory


likely outcomes provides less information lower entropy specifying outcome roll die six equally likely outcomes important measures information theory mutual information channel capacity error exponents relative entropy important sub fields information theory include source coding algorithmic complexity theory algorithmic information theory information theoretic security applications fundamental topics information theory include source coding data compression eg zip files channel coding error detection correction eg dsl impact crucial success voyager missions deep space invention compact


disc feasibility mobile phones development internet theory also found applications areas including statistical inference cryptography neurobiology ref name spikes ref perception linguistics evolution function molecular codes bioinformatics thermal physics molecular dynamics quantum computing black holes information retrieval intelligence gathering plagiarism detection pattern recognition anomaly detection even art creation overview information theory studies transmission processing extraction utilization information abstractly information thought resolution uncertainty case communication information noisy channel abstract concept formalized


claude shannon paper entitled ''a mathematical theory communication'' information thought set possible messages goal send messages noisy channel receiver reconstruct message low probability error spite channel noise shannon 's main result noisy channel coding theorem showed limit many channel uses rate information asymptotically achievable equal channel capacity quantity dependent merely statistics channel messages


sent ref name spikes coding theory concerned finding explicit methods called ''codes'' increasing efficiency reducing error rate data communication noisy channels near channel capacity codes roughly subdivided data compression source coding error correction channel coding techniques latter case took many years find methods shannon 's work proved possible third class information theory codes cryptographic algorithms codes ciphers concepts methods results coding theory information theory widely used cryptography cryptanalysis ''see article


ban unit historical application'' historical background landmark event ''establishing'' discipline information theory bringing immediate worldwide attention publication claude e shannon 's classic paper mathematical theory communication ''bell system technical journal'' july october prior paper limited information theoretic ideas developed bell labs implicitly assuming events equal probability harry nyquist 's paper ''certain factors affecting telegraph speed'' contains theoretical section quantifying intelligence line speed transmitted communication system giving


called hartley honor unit scale measure information alan turing used similar ideas part statistical analysis breaking german second world war enigma ciphers much mathematics behind information theory events different probabilities developed field thermodynamics ludwig boltzmann j willard gibbs connections information theoretic entropy thermodynamic entropy including important contributions rolf landauer explored ''entropy thermodynamics information theory'' shannon 's revolutionary groundbreaking paper work


given noisy channel coding theorem practical result shannon hartley law channel capacity gaussian channel well bit new way seeing fundamental unit information quantities information information theory based probability theory statistics information theory often concerns measures information distributions associated random variables important quantities information entropy measure information single random variable mutual information measure information common two random variables former quantity property


probability distribution random variable gives limit rate data generated independent samples given distribution reliably compressed latter property joint distribution two random variables maximum rate reliable communication across noisy channel limit long block lengths channel statistics determined joint distribution choice logarithmic base following formulae determines unit information entropy used common unit information bit based


binary logarithm units include nat based natural logarithm decimal digit based common logarithm follows expression form considered convention equal zero whenever justified math lim p rightarrow p log p math logarithmic base entropy information source based probability mass function source symbol communicated shannon entropy units bits per symbol given math h sum p


log p math probability occurrence th possible value source symbol equation gives entropy units bits per symbol uses logarithm base base measure entropy sometimes called shannon honor entropy also commonly computed using natural logarithm base euler 's number produces measurement entropy nats per symbol sometimes simplifies analysis avoiding need include extra constants formulas bases also possible


less commonly used example logarithm base produce measurement bytes per symbol logarithm base produce measurement decimal digits hartleys per symbol intuitively entropy discrete random variable measure amount ''uncertainty'' associated value distribution known entropy source emits sequence symbols independent identically distributed iid bits per message symbols source data symbols identically


distributed independent entropy message length less entropy bernoulli trial function success probability often called entropy maximized bit per trial two possible outcomes equally probable unbiased coin toss one transmits bits value bits known receiver specific value certainty ahead transmission clear information transmitted however


bit independently equally likely shannons information often called bits transmitted two extremes information quantified follows math mathbb x math set messages could probability math x mathbb x math entropy defined ref name reza ref math h x mathbb e x x sum x mathbb x p x log p x math self information entropy contribution individual message math mathbb e x math expected value


average conditional entropy ref name ash ref math h x mathbb e h x sum p sum x x p x log p x sum xy p xy log p x math entropy conditioned random variable random variable certain value care taken confuse two definitions conditional entropy former common use basic property form conditional entropy math h x h xy h math mutual information transinformation ''mutual information'' measures amount information


obtained one random variable observing another important communication used maximize amount information shared sent received signals mutual information relative given math x mathbb e xy si xy sum xy p xy log frac p xy p x p math ''s''pecific mutual ''i''nformation pointwise mutual information basic property mutual information math x h x h x math knowing ''y'' save average bits encoding ''x'' compared knowing


''y'' mutual information symmetric math x x h x h h xy math mutual information expressed average kullback leibler divergence information gain posterior probability distribution ''x'' given value ''y'' prior distribution ''x'' math x mathbb e p mathrm kl p x p x math words measure much average probability distribution ''x'' change given value ''y'' often recalculated divergence product marginal distributions


actual joint distribution math x mathrm kl p xy p x p math mutual information closely related log likelihood ratio test context contingency tables multinomial distribution pearson 's sup sup test mutual information considered statistic assessing independence pair variables well specified asymptotic distribution kullback leibler divergence information gain ''kullback leibler divergence'' ''information divergence'' ''information gain'' ' 'relative entropy'' way comparing two distributions true probability distribution arbitrary probability distribution compress data manner assumes


distribution underlying data reality correct distribution kullback leibler divergence number average additional bits per datum necessary compression thus defined math mathrm kl p x q x sum x x p x log q x sum x x p x log p x sum x x p x log frac p x q x math although sometimes used 'distance metric' kl divergence true metric since symmetric satisfy triangle inequality making semi quasimetric another interpretation kl divergence unnecessary


surprise introduced prior truth suppose number ''x'' drawn randomly discrete set probability distribution alice knows true distribution bob believes prior distribution bob surprised alice average upon seeing value ''x'' kl divergence objective expected value bob 's subjective surprisal minus alice 's surprisal measured bits ''log'' base way extent bob 's prior wrong


quantified terms unnecessarily surprised expected make quantities important information theoretic quantities include r nyi entropy generalization entropy differential entropy generalization quantities information continuous distributions conditional mutual information coding theory picture showing scratches readable surface cd r music data cds coded using error correcting codes thus still read even minor scratches using error detection correction coding theory one important direct applications information theory


error correcting code adds right kind redundancy ie error correction needed transmit data efficiently faithfully across noisy channel division coding theory compression transmission justified information transmission theorems source channel separation theorems justify use bits universal currency information many contexts however theorems hold situation one transmitting user wishes communicate one receiving user scenarios one transmitter multiple access channel one receiver broadcast channel intermediary helpers


relay channel general networks compression followed transmission may longer optimal network information theory refers multi agent communication models source theory process generates successive messages considered information memoryless source one message independent identically distributed random variable whereas properties ergodicity stationarity impose less restrictive constraints sources stochastic terms well studied right outside information theory rate information ''rate'' average entropy per symbol memoryless sources


merely entropy symbol case stationary stochastic process math r lim n infty h x n x n x n x n ldots math conditional entropy symbol given previous symbols generated general case process necessarily stationary ''average rate'' math r lim n infty frac n h x x dots x n math limit joint entropy per symbol stationary sources two expressions give result information rate defined math r lim n infty frac n x


representing nature ''noise'' channel joint distribution ''x'' ''y'' completely determined channel choice marginal distribution messages choose send channel constraints would like maximize rate information ' 'signal'' communicate channel appropriate measure mutual information maximum mutual information called given math c max f x math capacity following property related communicating


information rate ''r'' ''r'' usually bits per symbol information rate ''r'' ''c'' coding error '' '' large enough ''n'' exists code length ''n'' rate r decoding algorithm maximal probability block error '' '' always possible transmit arbitrarily small block error addition rate ''r'' gt ''c'' impossible transmit arbitrarily small block error ''channel coding'' concerned finding nearly optimal codes used


transmit data noisy channel small coding error rate near channel capacity capacity particular channel models continuous time analog communications channel subject gaussian noise see shannon hartley theorem binary symmetric channel bsc crossover probability ''p'' binary input binary output channel flips input bit probability ''p'' bsc capacity bits per channel use binary entropy function base logarithm file binary symmetric channelsvg binary erasure channel bec erasure probability ''p'' binary input ternary output channel


possible channel outputs third symbol 'e' called erasure erasure represents complete loss information input bit capacity bec bits per channel use file binary erasure channelsvg channels memory directed information practice many channels memory namely time math math channel given conditional probability math p x ix x x math often comfortable use notation math x x ix x x math channel become math p x iy math case capacity given mutual


information rate feedback available directed information rate case either feedback feedback directed informationj equals mutual information applications fields intelligence uses secrecy applications information theoretic concepts apply cryptography cryptanalysis turing 's information unit ban used ultra project breaking german enigma machine code hastening end world war ii europe shannon defined important concept called unicity distance based redundancy plaintext


attempts give minimum amount ciphertext necessary ensure unique decipherability information theory leads us believe much difficult keep secrets might first appear brute force attack break systems based asymmetric key algorithms commonly used methods symmetric key algorithms sometimes called secret key algorithms block ciphers security methods currently comes assumption known attack break practical amount time information theoretic security refers methods one time


pad vulnerable brute force attacks cases positive conditional mutual information plaintext ciphertext conditioned key ensure proper transmission unconditional mutual information plaintext ciphertext remains zero resulting absolutely secure communications words eavesdropper would able improve guess plaintext gaining knowledge ciphertext key however cryptographic system care must used correctly apply even information theoretically secure methods venona project


extractors min entropy value related shannon entropy r nyi entropy r nyi entropy also used evaluating randomness cryptographic systems although related distinctions among measures mean random variable high shannon entropy necessarily satisfactory use extractor cryptography uses seismic exploration one early commercial application information theory field seismic oil exploration work field made possible strip separate unwanted noise desired seismic signal information theory digital signal processing offer


signs exhibit high degree redundancy one message decoded among selection competing ones miscellaneous applications information theory also applications gambling information theory black holes bioinformatics see also algorithmic probability bayesian inference communication theory constructor theory generalization information theory includes quantum information inductive probability info metrics minimum message length minimum description length list important publications philosophy information applications active networking cryptanalysis cryptography cybernetics entropy thermodynamics information theory gambling intelligence information gathering seismic exploration history hartley rvl history information theory shannon ce


timeline information theory yockey hp theory coding theory detection theory estimation theory fisher information information algebra information asymmetry information field theory information geometry information theory measure theory kolmogorov complexity list unsolved problems information theory logic information network coding philosophy information quantum information science source coding concepts ban unit channel capacity communication channel communication source conditional entropy covert channel data compression decoder differential entropy fungible information information fluctuation complexity information entropy joint entropy kullback leibler divergence mutual information pointwise mutual information pmi receiver information theory redundancy r nyi entropy self information unicity distance variety hamming distance references


inference learning algorithms '' cambridge cambridge university press mansuripur ''introduction information theory'' new york prentice hall mceliece r ''the theory information coding'' cambridge pierce jr introduction information theory symbols signals noise dover nd edition reprinted dover reza f ''an introduction information theory'' new york mcgraw hill new york dover stone jv chapter book http jim stonestaffshefacuk bookinfotheory infotheorybookmainhtml information theory tutorial introduction university sheffield england yeung rw '' http iest iecuhkeduhk whyeung book first course information theory '' kluwer academic plenum publishers


yeung rw '' http iest iecuhkeduhk whyeung book information theory network coding '' springer books leon brillouin ''science information theory'' mineola ny dover james gleick ''the information history theory flood'' new york pantheon khinchin ''mathematical foundations information theory'' new york dover h leff f rex editors ''maxwell 's demon entropy information computing'' princeton university press princeton new jersey robert k logan ''what information propagating organization biosphere symbolosphere technosphere econosphere'' toronto demo publishing tom siegfried ''the bit


chemical education'' http wwwitsocorg ieee information theory society https wwwitsocorg resources surveys itsoc monographs surveys reviews computer related introductions computer science cybernetics formal sciences information age claude shannon


antiprotozoals antihelminthics infectious diseases resulted million deaths deaths ref name gdb ref branch medicine focuses infections referred infectious disease types infections caused infectious agents pathogens including bacteria ''mycobacterium tuberculosis'' ''staphylococcus aureus'' ''escherichia coli'' ''clostridium botulinum'' ''salmonella'' spp viruses related agents viroids ''hiv'' ''rhinovirus'' ''lyssaviruses'' ''rabies virus'' ''ebolavirus'' ''severe acute respiratory syndrome coronavirus '' fungi subclassified ascomycota including yeasts ''candida'' common fungal infection filamentous fungi ''aspergillus'' ''pneumocystis'' species dermatophytes

Applied science
Medicine and health
Infectious disease


sometimes termed infestations well sometimes called infections signs symptoms signs symptoms infection depend type disease signs infection affect whole body generally fatigue loss appetite weight loss fevers night sweats chills aches pains others specific individual body parts skin rashes coughing runny nose certain cases infectious diseases may asymptomatic much even course given host latter case disease may defined disease


definition means illness hosts secondarily become ill contact asymptomatic carrier infection synonymous infectious disease infections cause illness host ref name sherris bacterial viral bacterial viral infections cause kinds symptoms difficult distinguish cause specific infection ref name nipa http wwwantibiotics infoorg bact asp bacterial vs viral infections know difference national information program antibiotics ref distinguishing two important since viral infections cannot cured antibiotics whereas bacterial infections


bacterial infection localized redness heat swelling pain one hallmarks bacterial infection local pain pain specific part body example cut occurs infected bacteria pain occurs site infection bacterial throat pain often characterized pain one side throat ear infection likely diagnosed bacterial pain occurs one ear ref name nipa cut produces pus milky colored liquid likely infected cause


pathogenic viruses pathogenic bacteria pathophysiology chain infection chain events lead infection general chain events applies infections sometimes called '''chain infection''' chain events involves several stepswhich include infectious agent reservoir entering susceptible host exit transmission new hosts links must present chronological order infection develop understanding steps helps health care workers target infection prevent occurring first place colonization ingrown toenail pus yellow


resultant inflammation redness swelling around nail infection begins organism successfully enters body grows multiplies referred colonization humans easily infected compromised weakened immune systems increased susceptibility chronic persistent infections individuals suppressed immune system particularly susceptible opportunistic infections entrance host host pathogen interface generally occurs mucosa orifices like oral cavity nose eyes genitalia anus microbe enter open wounds organisms grow


initial site entry many migrate cause systemic infection different organs pathogens grow within host cells intracellular whereas others grow freely bodily fluids wound colonization refers non replicating microorganisms within wound infected wounds replicating organisms exist tissue injured multicellular organisms colonized degree extrinsic organisms vast majority exist either mutualistic commensal relationship host example former anaerobic bacteria species colonizes mammalian colon example latter various


species staphylococcus exist human skin neither colonizations considered infections difference infection colonization often matter circumstance non pathogenic organisms become pathogenic given specific conditions even virulent organism requires certain circumstances cause compromising infection colonizing bacteria ''corynebacteria sp'' ''viridans streptococci'' prevent adhesion colonization pathogenic bacteria thus symbiotic relationship host preventing infection speeding wound healing url status dead ref image depicts steps pathogenic infection variables involved outcome


advanced technologies made apparent humans recent decades microbial colonization common even environments humans think nearly sterile normal bacterial colonization difficult know chronic wounds classified infected much risk progression exists despite huge number wounds seen clinical practice limited quality data evaluated symptoms signs review chronic wounds journal american medical association 's rational clinical examination series quantified importance


increased pain indicator infection review showed useful finding increase level pain likelihood ratio lr range makes infection much likely absence pain negative likelihood ratio range rule infection summary lr disease disease arise host 's protective immune mechanisms compromised organism inflicts damage host microorganisms cause tissue damage releasing variety toxins destructive enzymes example ''clostridium tetani'' releases toxin paralyzes muscles staphylococcus releases toxins


produce shock sepsis infectious agents cause disease hosts example less individuals infected polio develop disease hand infectious agents highly virulent prion causing mad cow disease creutzfeldt jakob disease invariably kills animals people infected persistent infections occur body unable clear organism initial infection persistent infections characterized continual presence infectious organism often latent infection occasional recurrent relapses active infection viruses maintain


persistent infection infecting different cells body viruses acquired never leave body typical example herpes virus tends hide nerves become reactivated specific circumstances arise persistent infections cause millions deaths globally year chronic infections parasites account high morbidity mortality many underdeveloped countries transmission southern house mosquito ''culex quinquefasciatus'' vector transmits pathogens cause west nile fever avian malaria among othersfor infecting organisms survive repeat infection cycle hosts


progeny must leave existing reservoir cause infection elsewhere infection transmission take place via many potential routes '''droplet contact''' also known ' 'respiratory route'' resultant infection termed airborne disease infected person coughs sneezes another person microorganisms suspended warm moist droplets may enter body nose mouth eye surfaces '''fecal oral transmission''' wherein foodstuffs water become contaminated people washing hands preparing food untreated sewage released drinking water supply people eat drink become


infected common fecal oral transmitted pathogens include ''vibrio cholerae'' ''giardia'' species rotaviruses ''entameba histolytica'' ''escherichia coli'' tape worms pathogens cause gastroenteritis '''sexual transmission''' resulting disease called sexually transmitted disease '''oral transmission''' diseases transmitted primarily oral means may caught direct oral contact kissing indirect contact sharing drinking glass cigarette '''transmission direct contact''' diseases transmissible direct contact include athlete 's foot impetigo warts '''vehicle transmission''' transmission inanimate reservoir food water soil '''vertical transmission''' directly


mother embryo fetus baby pregnancy childbirth occur result pre existing infection one acquired pregnancy '''iatrogenic transmission''' due medical procedures injection transplantation infected material '''vector borne transmission''' transmitted vector organism cause disease transmits infection conveying pathogens one host another relationship ''virulence versus transmissibility'' complex disease rapidly fatal host may die microbe passed along another host diagnosis diagnosis


infectious disease sometimes involves identifying infectious agent either directly indirectly practice minor infectious diseases warts cutaneous abscesses respiratory system infections diarrheal diseases diagnosed clinical presentation treated without knowledge specific causative agent conclusions cause disease based upon likelihood patient came contact particular agent presence microbe community epidemiological considerations given sufficient effort known infectious agents specifically identified benefits identification however often greatly outweighed


cost often specific treatment cause obvious outcome infection benign diagnosis infectious disease nearly always initiated medical history physical examination detailed identification techniques involve culture infectious agents isolated patient culture allows identification infectious organisms examining microscopic features detecting presence substances produced pathogens directly identifying organism genotype techniques x rays cat scans pet scans nmr used produce images internal abnormalities resulting


growth infectious agent images useful detection example bone abscess spongiform encephalopathy produced prion symptomatic diagnostics diagnosis aided presenting symptoms individual infectious disease yet usually needs additional diagnostic techniques confirm suspicion signs specifically characteristic indicative disease called pathognomonic signs rare infections symptomatic ref name sternak ref children presence cyanosis rapid breathing poor peripheral perfusion petechial rash increases risk serious infection


change color response certain bacteria others bacteriological plates commonly used clinical identification infectious bacterium microbial culture may also used identification viruses medium case cells grown culture virus infect alter kill case viral identification region dead cells results viral growth called plaque eukaryotic parasites may also grown culture means identifying particular agent absence suitable plate


culture techniques microbes require culture within live animals bacteria ''mycobacterium leprae'' ''treponema pallidum'' grown animals although serological microscopic techniques make use live animals unnecessary viruses also usually identified using alternatives growth culture animals viruses may grown embryonated eggs another useful identification method xenodiagnosis use vector support growth infectious agent chagas disease significant example difficult directly demonstrate presence causative agent ''trypanosoma cruzi'' patient


therefore makes difficult definitively make diagnosis case xenodiagnosis involves use vector chagas agent ''t cruzi'' uninfected triatomine bug takes blood meal person suspected infected bug later inspected growth ''t cruzi'' within gut microscopy another principal tool diagnosis infectious disease microscopy virtually culture techniques discussed rely point microscopic examination definitive identification infectious agent microscopy may carried simple instruments


compound light microscope instruments complex electron microscope samples obtained patients may viewed directly light microscope often rapidly lead identification microscopy often also used conjunction biochemical staining techniques made exquisitely specific used combination antibody based techniques example use antibodies made artificially fluorescent fluorescently labeled antibodies directed bind identify specific antigens present pathogen fluorescence microscope used detect fluorescently labeled antibodies bound internalized antigens within


clinical samples cultured cells technique especially useful diagnosis viral diseases light microscope incapable identifying virus directly microscopic procedures may also aid identifying infectious agents almost cells readily stain number basic dyes due electrostatic attraction negatively charged cellular molecules positive charge dye cell normally transparent microscope using stain increases contrast cell background staining cell dye giemsa stain crystal violet allows


microscopist describe size shape internal external components associations cells response bacteria different staining procedures used taxonomic classification microbes well two methods gram stain acid fast stain standard approaches used classify bacteria diagnosis disease gram stain identifies bacterial groups firmicutes actinobacteria contain many significant human pathogens acid fast staining procedure identifies actinobacterial genera ''mycobacterium'' ''nocardia'' biochemical tests biochemical tests used identification infectious agents include detection


metabolic enzymatic products characteristic particular infectious agent since bacteria ferment carbohydrates patterns characteristic genus species detection fermentation products commonly used bacterial identification acids alcohols gases usually detected tests bacteria grown selective liquid solid media isolation enzymes infected tissue also provide basis biochemical diagnosis infectious disease example humans make neither rna replicases reverse transcriptase presence enzymes characteristic specific types viral infections


visibly obvious various ways dependent upon test example strep throat often diagnosed within minutes based appearance antigens made causative agent ''s pyogenes'' retrieved patient 's throat cotton swab serological tests available usually preferred route identification however tests costly develop reagents used test often require refrigeration serological methods extremely costly although commonly used strep test inexpensive ref name sherris complex serological techniques developed


known immunoassays immunoassays use basic antibody antigen binding basis produce electro magnetic particle radiation signal detected form instrumentation signal unknowns compared standards allowing quantitation target antigen aid diagnosis infectious diseases immunoassays detect measure antigens either infectious agents proteins generated infected organism response foreign agent example immunoassay may detect presence surface protein virus particle immunoassay b


catalog infectious agents grown point virtually significant infectious agents human population identified second infectious agent must grow within human body cause disease essentially must amplify nucleic acids order cause disease amplification nucleic acid infected tissue offers opportunity detect infectious agent using pcr third essential tools directing pcr primers derived genomes infectious agents time genomes known already


thus technological ability detect infectious agent rapidly specifically currently available remaining blockades use pcr standard tool diagnosis cost application neither insurmountable diagnosis diseases benefit development pcr methods clostridial diseases tetanus botulism diseases fundamentally biological poisonings relatively small numbers infectious bacteria produce extremely potent neurotoxins significant proliferation infectious agent occur limits ability pcr


detect presence bacteria metagenomic sequencing given wide range bacterial viral fungal protozoal helminthic pathogens cause debilitating life threatening illnesses ability quickly identify cause infection important yet often challenging example half cases encephalitis severe illness affecting brain remain undiagnosed despite extensive testing using standard care microbiological culture state art clinical laboratory methods metagenomic sequencing based diagnostic tests currently developed clinical use show promise sensitive specific rapid way diagnose infection using single


encompassing test test similar current pcr tests however untargeted whole genome amplification used rather primers specific infectious agent amplification step followed next generation sequencing third generation sequencing alignment comparisons taxonomic classification using large databases thousands pathogen commensal reference genomes simultaneously antimicrobial resistance genes within pathogen plasmid genomes sequenced aligned taxonomically classified pathogen genomes generate antimicrobial resistance profile analogous antibiotic sensitivity testing facilitate antimicrobial stewardship allow optimization treatment using effective drugs


patient 's infection metagenomic sequencing could prove especially useful diagnosis patient immunocompromised ever wider array infectious agents cause serious harm individuals immunosuppression clinical screening must often broader additionally expression symptoms often atypical making clinical diagnosis based presentation difficult thirdly diagnostic methods rely detection antibodies likely fail rapid sensitive specific untargeted test known human pathogens detects presence organism 's dna rather antibodies therefore highly desirable indication tests


usually indication specific identification infectious agent identification aid treatment prevention disease advance knowledge course illness prior development effective therapeutic preventative measures example early prior appearance azt treatment aids course disease closely followed monitoring composition patient blood samples even though outcome would offer patient treatment options part studies appearance


hiv specific communities permitted advancement hypotheses route transmission virus understanding disease transmitted resources could targeted communities greatest risk campaigns aimed reducing number new infections specific serological diagnostic identification later genotypic molecular identification hiv also enabled development hypotheses temporal geographical origins virus well myriad hypothesis ref name sherris development molecular diagnostic tools enabled physicians researchers monitor efficacy


treatment anti retroviral drugs molecular diagnostics commonly used identify hiv healthy people long onset illness used demonstrate existence people genetically resistant hiv infection thus still cure aids great therapeutic predictive benefit identifying virus monitoring virus levels within blood infected individuals patient community large classification subclinical versus clinical latent versus apparent symptomatic infections ''apparent'' ''clinical'' whereas infection active


produce noticeable symptoms may called ''inapparent'' ' 'silent'' ' 'subclinical'' occult infection inactive dormant called ''latent infection'' example latent bacterial infection latent tuberculosis viral infections also latent examples latent viral infections ''herpesviridae'' family word ''infection'' denote presence particular pathogen matter little also often used sense implying ''clinically apparent'' infection words case infectious disease fact occasionally creates ambiguity


prompts usage discussion get around common health professionals speak ''colonization'' rather ''infection'' mean pathogens present clinically apparent infection disease present course infection different terms used describe infections present time ''acute'' infection symptoms develop rapidly course either rapid protracted ''chronic'' infection symptoms usually develop gradually weeks months slow resolve ' 'subacute'' infections symptoms take longer develop acute infections


appearance severity disease resulting pathogen depend upon ability pathogen damage host well ability host resist pathogen however host 's immune system also cause damage host attempt control infection clinicians therefore classify infectious microorganisms microbes according status host defenses either ''primary pathogens'' ''opportunistic pathogens'' ref name pmid ref primary pathogens primary pathogens cause disease result presence activity within normal healthy host intrinsic


secondary infections immunodeficiency injury predisposing factor ref name pmid types infection types infection consist mixed iatrogenic nosocomial community acquired infection mixed infection infection caused two pathogens example appendicitis caused bacteroides fragilis escherichia coli second iatrogenic infection type infection one transmitted health care worker patient nosocomial infection also one occurs health care setting nosocomial infections


acquired hospital stay lastly community acquired infection one infection acquired whole community ref name infectious one manner proving given disease infectious satisfy koch 's postulates first proposed robert koch require first infectious agent identifiable patients disease healthy controls second patients contract infectious agent also develop disease postulates first used discovery mycobacteria species cause tuberculosis ref name pmid ref however koch 's postulates cannot usually


regarded contagious often require medical isolation sometimes loosely called quarantine victims however specialized connotation word contagious contagious disease easy transmissibility always respected popular use infectious diseases commonly transmitted person person direct contact types contact person person droplet spread indirect contact airborne transmission contaminated objects food drinking water animal person contact animal reservoirs insect bites environmental reservoirs another way infectious diseases transmitted anatomic location infections classified anatomic


location organ system infected including urinary tract infection skin infection respiratory tract infection odontogenic infection infection originates within tooth closely surrounding tissues vaginal infections intra amniotic infection addition locations inflammation infection common cause include pneumonia meningitis salpingitis prevention washing one 's hands form hygiene effective way prevent spread infectious disease ref name handhygiene ref techniques like hand washing wearing gowns wearing face masks help prevent infections passed one person another aseptic technique introduced medicine surgery


non living objects antibiotics called prophylactic given prevention rather treatment infection however long term use antibiotics leads resistance bacteria humans become immune antibiotics bacteria thus avoiding using antibiotics longer necessary helps preventing bacteria forming mutations aide antibiotic resistance one ways prevent slow transmission infectious diseases recognize different characteristics various diseases ref name watts ref critical disease characteristics evaluated include virulence distance traveled victims level contagiousness human strains


ebola virus example incapacitate victims extremely quickly kill soon result victims disease opportunity travel far initial infection zone also virus must spread skin lesions permeable membranes eye thus initial stage ebola contagious since victims experience internal hemorrhaging result features spread ebola rapid usually stays within relatively confined geographical area contrast human immunodeficiency virus hiv kills


victims slowly attacking immune system ref name sherris ref result many victims transmit virus individuals even realizing carrying disease also relatively low virulence allows victims travel long distances increasing likelihood epidemic another effective way decrease transmission rate infectious diseases recognize effects small world networks ref name watts epidemics often extensive interactions within hubs groups infected individuals interactions within discrete hubs susceptible individuals despite low interaction discrete hubs


disease jump spread susceptible hub via single interactions infected hub thus infection rates small world networks reduced somewhat interactions individuals within infected hubs eliminated figure however infection rates drastically reduced main focus prevention transmission jumps hubs use needle exchange programs areas high density drug users hiv example successful implementation treatment method another example use ring culling vaccination potentially


susceptible livestock adjacent farms prevent spread foot mouth virus general method prevent transmission vector borne pathogens pest control cases infection merely suspected individuals may quarantined incubation period passed disease manifests person remains healthy groups may undergo quarantine case communities cordon sanitaire may imposed prevent infection spreading beyond community case protective sequestration community public health authorities may implement forms social distancing


school closings control epidemic immunity mary mallon aka typhoid mary asymptomatic carrier typhoid fever course career cook infected people three died infection pathogens result death host offending organism ultimately cleared symptoms disease waned ref name baron process requires immune mechanisms kill inactivate inoculum pathogen specific acquired immunity infectious diseases may mediated antibodies lymphocytes immunity mediated two factors may


little contact agent natural antibodies confer specific protection adults passively transmitted newborns host genetic factors organism target infecting action specific infectious agent called host host harbouring agent mature sexually active stage phase called definitive host intermediate host comes contact larvae stage host anything living attain asexual sexual reproduction clearance pathogens either treatment induced spontaneous


influenced genetic variants carried individual patients instance genotype hepatitis c treated pegylated interferon alpha pegylated interferon alpha b brand names pegasys peg intron combined ribavirin shown genetic polymorphisms near human il b gene encoding interferon lambda associated significant differences treatment induced clearance virus finding originally reported nature showed genotype hepatitis c patients carrying certain genetic variant alleles near il b gene possibly achieve sustained virological response treatment others later report nature demonstrated


genetic variants also associated natural clearance genotype hepatitis c virus treatments infection attacks body ''anti infective'' drugs suppress infection several broad types anti infective drugs exist depending type organism targeted include antibacterial antibiotic including antitubercular antiviral antifungal antiparasitic including antiprotozoal antihelminthic agents depending severity type infection antibiotic may given mouth injection may applied topically severe infections brain usually treated intravenous antibiotics sometimes multiple antibiotics used


case resistance one antibiotic antibiotics work bacteria affect viruses antibiotics work slowing multiplication bacteria killing bacteria common classes antibiotics used medicine include penicillin cephalosporins aminoglycosides macrolides quinolones tetracyclines infections require treatment many self limiting infections treatment may cause side effects benefits antimicrobial stewardship concept healthcare providers treat infection antimicrobial specifically works well target pathogen shortest amount time treat


known highly suspected pathogen respond medication epidemiology disability adjusted life year infectious parasitic diseases per inhabitants million people died infectious diseases world health organization collects information global deaths international classification disease icd code categories following table lists top infectious disease number deaths data included comparison class wikitable sortable '''worldwide mortality due infectious diseases''' rank cause death deaths br millions percentage br


deaths deaths br millions rank style background ffdead n style background ffdead infectious diseases style background ffdead style background ffdead text align center style background ffdead style background ffdead text align center lower respiratory infections style text align center hiv aids style text align center diarrheal diseases style text align center tuberculosis tb style text align center malaria style text align center measles style text align center pertussis style text align center tetanus style text align center


approximately million people died due lower respiratory infections making number leading cause death world historic pandemics great plague marseille killed people city surrounding provinces potential unpredictable explosive impacts infectious diseases major actors human history ref name fauci ref pandemic global epidemic disease affects people extensive geographical area example plague justinian killed europe 's population black death