bluuebunny/crossref_metadata_2025 huggingface dataset:
What is the Best Training for Vascular access Surgery?
Authors: Lazarides Miltos K. , Georgiadis George S. , Georgakarakos Efstratios I.
Published: February 2015

Questions have been raised whether there is a lack of appropriate training in access creation and maintenance, and if training juniors in arteriovenous (AV) fistulas may affect the outcome. A survey was undertaken to study “experts” opinion in access training using a closed questionnaire. The majority of “experts” consented that there is a lack of appropriate training in access creation and maintenance in a great extent, although they located the main deficit regarding access training in the pre-operative planning and decision making.

Regarding the second question, a literature search revealed only four studies, comparing the outcomes of AV fistulas created either by consultant surgeons or trainees. A meta-analysis performed revealed that 1-year patency rate was not statistically significant different among access procedures created either by consultants or trainees. Access surgery shares the same basic principles with vascular surgery and provides a valuable workload for the trainees and is a necessity to become a building component in all “core” vascular curricula; the required skills can be acquired with the trainees operating independently simple cases, as the latter is not leading to suboptimal outcomes.
Fibrin Sheath Formation and Intimal Thickening after Catheter Placement in Dog Model: Role of Hemodynamic Wall Shear Stress
Authors: Wang Li Hua , Wei Fang , Jia Lan , Lu Zhi , Wang Bo , Dong Hong Ye , Yu Hai Bo , Sun Gui Jiang , Yang Jie , Li Bo , Meng Jia , Zhang Rui Ning , Bi Xue Qing , Chen Hai Yan , Jiang Ai li
Published: February 2015

Purpose

To investigate the role of wall shear stress in aspects of the formation of fibrin sheath and intimal thickening in a dog model.

Methods

Tunneled silicone 14.5-F catheters were inserted into the left internal jugular vein in eight dogs. The dogs were separated into two groups according to catheter indwelling time of 14 and 28 days. All dogs underwent extracorporeal circulation three times a week. Multidetector computed tomography venography (MDCTV) examination was used to examine the catheter tip thrombus. After the animals were sacrificed, histological and immunohistochemistry evaluations were performed to confirm specific cell populations. We used computer modeling to generate wall shear stress profiles for the blood flow through the catheter.

Results

Catheter-related sheaths were identified in all catheter specimens, but there was no fibrin sheath around the catheter tip. There were also differences in wall shear stress between the different venous wall sites. Differences in vein wall thickening at different sites have been found at both 14 days (intima to media (I/M) ratio S1 vs S2: p = 0.01, S3 vs S4: p<0.01) and 28 days (I/M ratio S1 vs S2: p<0.01, S3 vs S4: p<0.05).

Conclusions

After catheter placement, fibrin sheath formation partially covered the catheter. Meanwhile, focal areas of intimal thickening were also seen in the venous wall adjacent to the sites of high wall shear stress. These findings indicate an important role of wall shear stress profiles in fibrin sheath formation and intimal thickening.
Reflections on the “Commemoration of Conflict”
Authors: Van Bavel Marjolein
Published: February 2015

‘The Commemoration of Conflict’, Postgraduate Conference, UCL Department of History, London, UK, May 27, 20142014 marked the 100th anniversary of the beginning of the First World War, an event commemorated in ceremonies and events around the world. This comes as no surprise, considering the central place that both World Wars occupy in our collective memory. But conflict commemoration is not just a modern-day phenomenon, nor have all aspects of war been remembered in the same way. From Simonides’ commemorative epigrams after the Persian Wars and the foundation of Battle Abbey following William the Conqueror’s victory, to the establishment of Decoration Day in memory of American Civil War casualties, communities have memorialized the impact of war in a variety of ways. On the 27th of May, research students in the UCL Department of History organised a Postgraduate Conference titled “The Commemoration of Conflict” that considered how various conflicts from the ancient world to the present were remembered and commemorated.
Selling Online by European Enterprises — Multivariate Analysis Approach
Authors: Žmuk Berislav
Published: February 2015

This paper aims to describe and analyse possible impacts on selling online by enterprises as the main variable under consideration in the study, in selected European countries using five selected independent variables that represent the information and communication technology (ICT) and the economic development level. Data for 31 European countries were analysed. The paper presents recent trends in European enterprises in using online selling as one of many Internet services. Three groups of countries according to the share of enterprises selling online were recognized. The complete picture about the achieved economic and ICT development level in the countries was obtained by conducted clustering where all six variables were included in the analysis. The main research hypothesis was that economic and ICT developments have a significant impact on the share of enterprises that sell online. The conducted factor analysis sorted five observed independent variables into two groups. The multiple linear regression analysis based on the factors showed that both groups have a statistically significant impact on the share of enterprises that sell online. This means that these two factors together have a crucial role in determining the ICT development level in European enterprises.
Development and Evaluation of Controlled Release Bilayer Tablets of Hydrochlorothiazide and Losartan Potassium
Authors: Manoj Kumar Mishra  , Dubey Deepti  , Upamanyu Neeraj
Published: February 2015

The aim of the present research work was to develop bilayer tablet dosage form containing combination of immediate and sustained matrix prepared from Hydrochlorothiazide (HTZ) and Losartan Potassium (LP) respectively for the treatment of hypertension and its associated complications. Immediate release HTZ was prepared using different superdisintegrants. LP sustained layer was prepared by compression technique. Both pre-compression and post-compression parameters were analyzed for all the tablets. In vitro release studies were carried out as per USP in pH (1.2) and phosphate buffer pH (6.8) using USP-XXI type II. Bilayer tablet (F6) formulated using higher concentration of HPMC K 15 exhibiting higher LP release rate (83.553± 0.22) for the period of 12 h. The In vitrorelease profile of drug from sustained matrix could be best expressed by First order as the plot showed highest linearity (R2 = 0.990) and diffusion was the dominating mechanism of drug release. The stability and FTIR studies are also indicating the absence of strong interaction between drug and polymer and compatibility among them.
Uni-directional ciliary membrane protein trafficking by a cytoplasmic retrograde IFT motor and ciliary ectosome shedding
Authors: Cao Muqing , Ning Jue , Hernandez-Lara Carmen I , Belzile Olivier , Wang Qian , Dutcher Susan K , Liu Yanjie , Snell William J
Published: February 2015

The role of the primary cilium in key signaling pathways depends on dynamic regulation of ciliary membrane protein composition, yet we know little about the motors or membrane events that regulate ciliary membrane protein trafficking in existing organelles. Recently, we showed that cilium-generated signaling in Chlamydomonas induced rapid, anterograde IFT-independent, cytoplasmic microtubule-dependent redistribution of the membrane polypeptide, SAG1-C65, from the plasma membrane to the periciliary region and the ciliary membrane. Here, we report that the retrograde IFT motor, cytoplasmic dynein 1b, is required in the cytoplasm for this rapid redistribution. Furthermore, signaling-induced trafficking of SAG1-C65 into cilia is unidirectional and the entire complement of cellular SAG1-C65 is shed during signaling and can be recovered in the form of ciliary ectosomes that retain signal-inducing activity. Thus, during signaling, cells regulate ciliary membrane protein composition through cytoplasmic action of the retrograde IFT motor and shedding of ciliary ectosomes.
Viral-inducible Argonaute18 confers broad-spectrum virus resistance in rice by sequestering a host microRNA
Authors: Wu Jianguo , Yang Zhirui , Wang Yu , Zheng Lijia , Ye Ruiqiang , Ji Yinghua , Zhao Shanshan , Ji Shaoyi , Liu Ruofei , Xu Le , Zheng Hong , Zhou Yijun , Zhang Xin , Cao Xiaofeng , Xie Lianhui , Wu Zujian , Qi Yijun , Li Yi
Published: February 2015

Viral pathogens are a major threat to rice production worldwide. Although RNA interference (RNAi) is known to mediate antiviral immunity in plant and animal models, the mechanism of antiviral RNAi in rice and other economically important crops is poorly understood. Here, we report that rice resistance to evolutionarily diverse viruses requires Argonaute18 (AGO18). Genetic studies reveal that the antiviral function of AGO18 depends on its activity to sequester microRNA168 (miR168) to alleviate repression of rice AGO1 essential for antiviral RNAi. Expression of miR168-resistant AGO1a in ago18 background rescues or increases rice antiviral activity. Notably, stable transgenic expression of AGO18 confers broad-spectrum virus resistance in rice. Our findings uncover a novel cooperative antiviral activity of two distinct AGO proteins and suggest a new strategy for the control of viral diseases in rice.
Interannual variability in the Yucatan Channel flow
Authors: Athié Gabriela , Sheinbaum Julio , Leben Robert , Ochoa José , Shannon Michael R. , Candela Julio
Published: February 2015

Mooring measurements in the Yucatan Channel, from May 2010 to May 2011 and from July 2012 to June 2013 yield a mean transport of 27 and 25 Sv, respectively, with a subinertial standard deviation of 3.5 Sv. These mean transport values are higher than the 23 Sv reported from 21 months of similar measurements (1999–2001). Analysis of low‐frequency variations of a transport proxy based on 20 years of altimetry data indicates that during 1999–2001, the flow through Yucatan Channel was anomalously low. This suggests that a sizable compensation through other channels off the Gulf of Mexico is required to match the transport cable measurements of the Florida Current at 27°N.
Rapid slip‐deficit rates at the eastern margin of the Tibetan Plateau prior to the 2008 Mw 7.9 Wenchuan earthquake
Authors: Thompson T. Ben , Plesch Andreas , Shaw John H. , Meade Brendan J.
Published: February 2015

The Longmen Shan is the steepest topographic front at the India‐Asia collision zone and the site of the Mw 7.9 Wenchuan earthquake. Here to explain the interseismic GPS velocities across the greater Longmen Shan region, we develop a boundary element model including earthquake cycle effects, topography, the westward dipping Beichuan Fault and a ∼20 km deep, shallowly dipping, detachment, inferred from observed afterslip and from structural considerations. Previous analyses which neglected the detachment and earthquake cycle effects have found shortening rates near zero. In contrast, we find that interseismic GPS data are consistent with a shortening rate of 5.7±1.5mm/yr and maximum surface slip‐deficit rate of 9.5±2.5mm/yr. This model unifies the interpretation of geodetic deformation throughout the earthquake cycle and suggests that the Longmen Shan is an active fold‐and‐thrust belt with of Wenchuan‐like recurrence intervals as short as 600 years.
Compounding effects of warm sea surface temperature and reduced sea ice on the extreme circulation over the extratropical North Pacific and North America during the 2013–2014 boreal winter
Authors: Lee Ming‐Ying , Hong Chi‐Cherng , Hsu Huang‐Hsiung
Published: February 2015

Unprecedented atmospheric circulations with extreme weather were observed in the extratropical Northern Hemisphere during the winter of 2013–2014. The anomalous circulations were the manifestation of the Pacific pattern or the North Pacific Oscillation/Western Pacific pattern but with extremely large amplitude. Simulation results suggest that the anomalous atmospheric circulations were constructively induced by anomalous sea surface temperature in the tropical Pacific and extratropical North Pacific, as well as the low sea ice concentration in the Arctic. Natural variability played a major role in inducing the anomaly pattern, whereas the anomalously warm sea surface temperature and low Arctic sea ice concentration in the Bering Sea contributed to the intensity. If the anthropogenic warming has a significant impact on causing the synchronization of the aforementioned anomalies in sea surface temperature and sea ice concentration and this trend continues, severe winters similar to that in 2013–2014 may occur more frequently in the future.
Electron acceleration in the dipolarization front driven by magnetic reconnection
Authors: Huang Can , Wu Mingyu , Lu Quanming , Wang Rongsheng , Wang Shui
Published: February 2015

A large‐scale two‐dimensional (2‐D) particle‐in‐cell simulation is performed in this paper to investigate electron acceleration in the dipolarization front (DF) region during magnetic reconnection. It is found that the DF is mainly driven by an ion outflow which also generates a positive potential region behind the DF. The DF propagates with an almost constant speed and gets growing, while the electrons in the DF region can be highly energized in the perpendicular direction due to betatron acceleration. For the first time, we reveal that there exists a velocity threshold; only the electrons below the threshold can be trapped by the parallel electric potential in the DF region and then energized by betatron acceleration.
Eddy‐driven sediment transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?
Authors: Weijer Wilbert , Maltrud Mathew E. , Homoky William B. , Polzin Kurt L. , Maas Leo R. M.
Published: February 2015

In this study, we address the question whether eddy‐driven transports in the Argentine Basin can be held responsible for enhanced sediment accumulation over the Zapiola Rise, hence accounting for the existence and growth of this sediment drift. To address this question, we perform a 6 year simulation with a strongly eddying ocean model. We release two passive tracers, with settling velocities that are consistent with silt and clay size particles. Our experiments show contrasting behavior between the silt fraction and the lighter clay. Due to its larger settling velocity, the silt fraction reaches a quasisteady state within a few years, with abyssal sedimentation rates that match net input. In contrast, clay settles only slowly, and its distribution is heavily stratified, being transported mainly along isopycnals. Yet, both size classes display a significant and persistent concentration minimum over the Zapiola Rise. We show that the Zapiola Anticyclone, a strong eddy‐driven vortex that circulates around the Zapiola Rise, is a barrier to sediment transport, and hence prevents significant accumulation of sediments on the Rise. We conclude that sediment transport by the turbulent circulation in the Argentine Basin alone cannot account for the preferred sediment accumulation over the Rise. We speculate that resuspension is a critical process in the formation and maintenance of the Zapiola Rise.
Tropical sea surface temperatures for the past four centuries reconstructed from coral archives
Authors: Tierney Jessica E. , Abram Nerilie J. , Anchukaitis Kevin J. , Evans Michael N. , Giry Cyril , Kilbourne K. Halimeda , Saenger Casey P. , Wu Henry C. , Zinke Jens
Published: February 2015

Most annually resolved climate reconstructions of the Common Era are based on terrestrial data, making it a challenge to independently assess how recent climate changes have affected the oceans. Here as part of the Past Global Changes Ocean2K project, we present four regionally calibrated and validated reconstructions of sea surface temperatures in the tropics, based on 57 published and publicly archived marine paleoclimate data sets derived exclusively from tropical coral archives. Validation exercises suggest that our reconstructions are interpretable for much of the past 400 years, depending on the availability of paleoclimate data within, and the reconstruction validation statistics for, each target region. Analysis of the trends in the data suggests that the Indian, western Pacific, and western Atlantic Ocean regions were cooling until modern warming began around the 1830s. The early 1800s were an exceptionally cool period in the Indo‐Pacific region, likely due to multiple large tropical volcanic eruptions occurring in the early nineteenth century. Decadal‐scale variability is a quasi‐persistent feature of all basins. Twentieth century warming associated with greenhouse gas emissions is apparent in the Indian, West Pacific, and western Atlantic Oceans, but we find no evidence that either natural or anthropogenic forcings have altered El Niño–Southern Oscillation‐related variance in tropical sea surface temperatures. Our marine‐based regional paleoclimate reconstructions serve as benchmarks against which terrestrial reconstructions as well as climate model simulations can be compared and as a basis for studying the processes by which the tropical oceans mediate climate variability and change.
First artificial periodic inhomogeneity experiments at HAARP
Authors: Hysell D. L. , McCarrick M. J. , Fallen C. T. , Vierinen J.
Published: February 2015

Experiments involving the generation and detection of artificial periodic inhomogeneities have been performed at the High Frequency Active Auroral Research Program (HAARP) facility. Irregularities were created using powerful X‐mode HF emissions and then probed using short (10 μs) X‐ and O‐mode pulses. Reception was performed using a portable software‐defined receiver together with the crossed rhombic antenna from the local ionosonde. Echoes were observed reliably between about 85 and 140 km altitude with signal‐to‐noise ratios as high as about 30 dB. The Doppler shift of the echoes can be associated with the vertical neutral wind in this altitude range. Small but persistent Doppler shifts were observed. The decay time constant of the echoes is meanwhile indicative of the ambipolar diffusion coefficient which depends on the plasma temperature, composition, and neutral gas density. The measured time constants appear to be consistent with theoretical expectations and imply a methodology for measuring neutral density profiles. The significance of thermospheric vertical neutral wind and density measurements which are difficult to obtain using ground‐based instruments by other means is discussed.
Grain size effects on energy delivery to the streambed and links to bedrock erosion
Authors: Turowski Jens M. , Wyss Carlos R. , Beer Alexander R.
Published: February 2015

Fluvial bedrock erosion rates are thought to be proportional to the energy delivered to the channel bed by impacting bed load particles. Combining methods for field measurements of impact energy and for automatic sensing of grain size distributions in the instrumented channel of the Erlenbach, we show that the larger a bed load grain is, the more efficient it is in transferring energy to the streambed. On average, the largest grain size class contributes only 9% to the total bed load mass but is responsible for more than 40% of the energy delivery. This effect may help to explain the predominance of extreme floods, when large grains are mobile, in driving long‐term erosion. While the mechanistic saltation‐abrasion model accounts for hydraulic forcing of energy delivery, the observed grain size effect is not captured. We suggest that the discrepancy arises from differing transport modes (rolling, sliding, and saltation) not currently captured in modeling.
The probability distribution of intense daily precipitation
Authors: Cavanaugh Nicholas R. , Gershunov Alexander , Panorska Anna K. , Kozubowski Tomasz J.
Published: February 2015

The probability tail structure of over 22,000 weather stations globally is examined in order to identify the physically and mathematically consistent distribution type for modeling the probability of intense daily precipitation and extremes. Results indicate that when aggregating data annually, most locations are to be considered heavy tailed with statistical significance. When aggregating data by season, it becomes evident that the thickness of the probability tail is related to the variability in precipitation causing events and thus that the fundamental cause of precipitation volatility is weather diversity. These results have both theoretical and practical implications for the modeling of high‐frequency climate variability worldwide.
Birnaviruses
Authors: Delmas Bernard
Published: February 2015

Birnaviruses are bisegmented double‐stranded
RNA
viruses infecting animals belonging to different vertebrate and invertebrate phyla. Most of the research efforts on birnaviruses have focused on infectious bursal disease virus (
IBDV
), which is responsible for important losses in the poultry industry. Another economically important birnavirus is infectious pancreatic necrosis virus (
IPNV
) of salmonids. Other birnaviruses (<10) have been isolated from diseased animals, established cell lines or identified by deep sequencing. The reverse genetic systems that have been engineered for
IBDV
and
IPNV
at the end of the 1990s have been powerful tools to dissect the molecular biology of these viruses. During these past 10 years, resolution of the
3D
‐structures of several birnavirus proteins (including their unique replicase/transcriptase, their protease, their capsid protein and ultimately their complete capsid) by X‐ray radiocrystallography,
NMR
and cryo‐electron microscopy shed light on important properties and characteristics of these viruses.

Key Concepts

Birnaviruses are nonenveloped double‐stranded RNA viruses with representatives able to infect animals of invertebrate and vertebrate phyla, but not yet found infecting mammals.

The birnavirus capsid possess a T = 13
laevo
icosahedral symmetry.

Entry of birnavirus into a cell is mediated by a capsid‐associated peptide that deforms and perforates membranes.

The birnavirus virus protein 4 (VP4) protease possess a serine‐lysine catalytic dyad and is homologous to the protease domain of bacterial and organelle ATP‐dependent Lon proteases.

The birnavirus capsid protein VP2 is structurally homologous to the capsid protein of positive‐strand viruses, just like the T = 3 nodaviruses and T = 4 tetraviruses.

The palm subdomain‐based active site of the birnavirus RNA‐dependent RNA‐polymerases is internally permuted to the unique C‐A‐B motif arrangement, a feature shared with permutotetraviruses, a group of positive‐strand RNA viruses.

The capsid proteins of birnaviruses display a high structural polymorphism of their assemblies.
Hepatitis Delta Virus
Authors: Taylor John Marston
Published: February 2015

Several viruses are important causes of acute and chronic infections of the human liver.
Hepatitis delta virus
(
HDV
) is a most unusual agent that is found only in association with

Hepatitis B virus (
HBV
)

.
HDV
can make
HBV
infections more damaging to the liver.
HDV
needs the envelope proteins of
HBV
to achieve virus assembly and infection of new susceptible cells. Thus,
HDV
infections can be prevented with the vaccine against
HBV
envelope proteins.
HDV
has an
RNA
genome that is unique in that it is very small (around 1700 nucleotides) and has a circular conformation. This genome is replicated via redirection of host
RNA
polymerase activity to act on
RNA
templates. This replication is fundamentally different from that of
HBV
, which involves reverse transcription.

Key Concepts

HDV is unlike any other animal virus.

HDV has similarities and yet distinct differences from viroids, agents that infect plants.

HDV only encodes one protein and yet by RNA editing creates an essential second protein.

HDV replicates by redirecting host RNA polymerase activity.

HDV can make HBV infections more pathogenic.
Cellular Thermodynamics: The Molecular and Macroscopic Views
Authors: Wolfe Joe
Published: February 2015

On the macroscopic scale, biology obeys thermodynamics, and this article introduces the laws of thermodynamics and its macroscopic variables, including entropy. The molecular description is often more directly useful to biologists. So this article explains Boltzmann's distribution, which describes how the proportion of molecules having a particular energy depends on energy and temperature, and quantifies the compromise between minimising energy and maximising entropy. This simple law is then used to explain and quantify several aspects of the function and structure of cells. These include Årrhenius' law for reaction rates, the Nernst equation for electrochemical equilibria, and hydraulic and osmotic equilibria between solutions with different compositions. It also explains the equilibrium between different phases (solid, liquid and vapour), the aggregations of molecules in self‐assembly, aspects of the stability and mechanical homeostasis of membranes and entropic forces in biomolecules.

Key Concepts

Cells and components that are physically close together are often approximately in thermal and chemical equilibrium, which allows some powerful observations about their properties.

Cells and tissues sometimes approximate steady state: they input and output energy and matter at approximately equal rates and vary little over time.

Entropy measures the ‘uselessness’ of energy: the biosphere survives by converting energy with low entropy (light from the sun) into energy with high entropy (waste heat lost to the atmosphere and to space).

Entropy also quantifies disorder – but only at a molecular level.

The Boltzmann energy distribution leads directly to a number of important laws and effects relevant to cell biology:

Årrhenius' law of reaction rates,

ion equilibria,

osmotic pressure,

phase equilibria, and

molecular oligamerisation and aggregation.
Iron Deficiency
Authors: Bridges Kenneth R
Published: February 2015

Iron deficiency is a leading cause of anaemia, affecting more than half a billion people worldwide. Depletion of iron stores precedes impaired production of iron‐containing proteins, most importantly haemoglobin. The two important stages of iron deficiency are (1) depletion of iron stores without anaemia and (2) depletion of iron stores with anaemia. The gastrointestinal tract mediates iron uptake into the body but is also the major source of iron loss and iron deficiency. Although anaemia is the most commonly recognised consequence of iron deficiency, injury to other organs has serious consequences that include fatigue, weakness and developmental delay in infants. Maternal iron deficiency during pregnancy can result in poor neonatal low iron stores and heightened risk of neurocognitive impairment. Oral iron supplements are the most convenient form of replacement but attention should be directed to the preparation as tolerance varies greatly depending on the specific iron salt.

Key Concepts

Iron is the second most common metal in the surface of the earth, but absorption is a challenge due to the low solubility of iron salts.

Gastric acidity and weak iron chelators, such as ascorbic acid, greatly facilitate iron absorption that occurs primarily in the duodenum and upper jejunum.

Gastrointestinal blood loss is the most common cause of iron deficiency.

Females of reproductive age suffer a high rate of iron deficiency due to menstrual blood loss.

Iron deficiency often produces anaemia in which extremely low haemoglobin levels are tolerated because of the slow rate of fall from the normal range.

Growth and developmental delay are particularly serious consequences of iron deficiency during infancy, often occurring in the wake of substantial maternal iron deficiency during gestation.

Oral iron is the most convenient form of replacement but often is poorly tolerated when sulphate is the anion in the salt.

A dramatic decline has occurred in serious complications of intravenous iron replacement, including anaphylaxis, with the advent of newer formulations.
Chromatographic Techniques
Authors: Lewis Alastair C
Published: February 2015

Chromatography achieves the physical separation of chemical components in a mixture for either analytical or preparative purposes, based on the unique degree of interaction between each component and the separating medium. Chromatography can be used to isolate a wide range of different chemicals, from permanent gases to macromolecules, metals, ions and organic and inorganic compounds. Chromatography uses gases, liquids or supercritical fluids as the mobile phase to carry analytes through the separating medium, commonly referred to as the column. In the case of liquid chromatography, the column is often a packed tube, and in gas chromatography a wall‐coated capillary. Chromatography is used in many different application areas and is one of the most commonly used laboratory techniques. Chromatography is often coupled with mass spectrometry as a detector.

Key Concepts

Materials found in nature and from man's activities are often highly complex mixtures of different chemicals; isolating and quantifying individual components in such mixtures is a very common measurement requirement.

Chromatography is an analytical method in which a physical separation of individual components in a mixture is achieved.

A sample mixture is solvated in a fluid, which is used to carry it through a separating medium often referred to as a column. The solvating fluid is referred to as the mobile phase and the separating medium as the stationary phase.

Each analyte may interact (e.g. by adsorption) to a unique degree with the stationary phase, resulting in the physical separation of the mixture into its component parts.

The separating medium is often found in the form of a packed column of stationary‐phase material, open tubular column with a wall coating or as a planar coated plate.

Chromatographic methods are very commonly coupled with detectors such as mass spectrometry, which allows for the quantification and identification of analytes as they elute from the column.
Müller,J F T(Fritz)
Authors: West David A
Published: February 2015

Fritz Müller (1822–1897), German naturalist, was one of the great Darwinians of the nineteenth century. Educated in math and science in what was then part of Prussia, he emigrated to Brazil in 1852; in the forests and ocean of the province of Santa Catarina, he found a rich diversity of organisms for study, especially marine and freshwater Crustacea, insects and flowering plants. From original observations of morphology, development, physiology and behaviour, he documented the power of natural selection in the evolution of adaptations. He encountered Darwin'sOrigin of Speciesin its German translation in 1861, tested its salient points in the Crustacea and endorsed them. Although he and Darwin were half a world apart, they recognised many common interests through correspondence and publications, and Müller became Darwin's closest intellectual kin.
N
atta,
G
iulio
Authors: Pasquon Italo
Published: February 2015

Italian polymer chemist (1903–1979) who developed the theory and technology of stereospecific polymerisation. Stereospecific polymerisation has been a revolution in the field of macromolecular chemistry. Besides the discoverer, Natta was its undisputed ruler. With his brilliant insights and tireless work, he was able to guide and coordinate the interdisciplinary work of his collaborators to the discovery and the study of more than a hundred new polymers, over a period of 15 years. The synthesis of isotactic polypropylene was the last great discovery – in terms of economic importance – still possible in the traditional field of industrial chemistry. For several years, the most significant results obtained in the field of stereospecific polymerisation continued to come from Natta's laboratories. Since then, the stereospecific polymerisation continues even nowadays to be the subject of study.
History of Classical Genetics
Authors: Harman Oren , Lamm Ehud
Published: February 2015

Classical genetics has its origin in the 1850s and 1860s, when the Moravian monk Gregor Mendel attempted to formalise the rules of inheritance governing plant hybridisation. In 1909, the Danish biologist Wilhelm Johannsen proposed that there are two sources of variation: one arising from the action of the environment and the other due to variations in Mendel's hereditary factors – entities Johannsen called ‘genes’. When Mendel's laws were rediscovered in 1900, breeding experiments were wedded to cytological observation of chromosomes in the nucleus of organisms – most notably in the fruit fly – and classical genetics was born. The chromosome theory of inheritance that was formulated as a result of this work stated that genes are located linearly on chromosomes and that chromosomal dynamics underlie the patterns of Mendelian inheritance. Towards mid‐century, this work culminated in models of what genes do, and what they are made of.

Key Concepts

Classical genetics refers to the study of the laws of hereditary transmission in living organisms.

Classical genetics has its origin in Gregor Mendel's papers on inheritance in peas, published in 1866.

The chromosome theory of inheritance states that genes are located on chromosomes and that chromosomal dynamics underlie the patterns of Mendelian inheritance.

The ‘genotype’ is the totality of all the organism's genes, whereas the ‘phenotype’ are the characters displayed, which are products of both the underlying genes and the actions of the environment.

A fundamental observation in classical genetics was the ‘one gene, one enzyme’ relationship. It is now known that the relationship between genes and proteins is much more complex.
Splicing of Pre‐m
RNA
Authors: Tu Chi‐Chiang , Tarn Woan‐Yuh
Published: February 2015

The majority of eukaryotic messenger
RNAs
(m
RNAs
) are initially transcribed as intron‐containing precursor m
RNAs
(pre‐m
RNAs
). Removal of introns from each pre‐m
RNA
by splicing is necessary to generate a mature m
RNA
. Pre‐m
RNA
splicing is catalysed by the spliceosome, a large ribonucleoprotein complex that contains five small nuclear
RNAs
and numerous protein factors and forms anew on each intron of nascent transcripts. In higher eukaryotes, alternative splicing of pre‐m
RNA
generates multiple m
RNA
isoforms from a single gene and is regulated by cellular
RNA
‐binding proteins. Alternative splicing not only increases proteome diversity but also has the potential to regulate gene expression levels post‐transcriptionally. Thus, alterative splicing may have a great impact on a wide range of physiological and developmental processes. Defects in pre‐m
RNA
splicing underlie a considerable number of genetic diseases and cancers and may fine‐tune disease severity.

Key Concepts

In most eukaryotic pre‐mRNAs, the coding sequences (exons) are interrupted by stretches of non‐coding sequences (introns).

The spliceosome uses a two‐step transesterification reaction to remove introns and join exons of pre‐mRNAs.

The snRNAs and several conserved spliceosomal protein factors are implicated in the key catalytic steps of splicing.

Alternative splicing extends proteome diversity and regulates gene expression levels.

Alternative splicing is determined by interplay between
trans
‐acting regulatory factors and
cis
‐elements of pre‐mRNAs.

Alteration of
cis
‐elements and aberrant control of
trans
‐acting factors can lead to diseases.
Medical Genetics in Britain: Laying the Foundation (1940s–1960s)
Authors: Zallen Doris T
Published: February 2015

Medical genetics refers to the use of genetic information in the health care setting. This includes research efforts to understand the genetic basis of human illness. It also includes clinical services that use genetic knowledge to provide an assessment of risk for the occurrence of gene‐based disorders, determine an individual's actual genetic status, select treatments and put forth strategies for disease prevention. In Britain, medical genetics as an area of specialty arose out of the activities begun in three separate settings during the period from mid‐1940s through the 1960s: the Clinical Genetics Research Unit at the Institute of Child Health in London, the Paediatric Research Unit at Guy's Hospital in London and the Nuffield Unit of Medical Genetics at the University of Liverpool Medical School. The research programmes and clinical commitments of these separate units, along with the strong links connecting them, provided the foundation on which present‐day medical genetics is built and paved the way for the introduction of “genomic medicine” into twenty‐first century health care.

Key Concepts

Medical genetics, as an area of speciality, emerged late in the twentieth century in Britain largely through the efforts of physicians who, for the most part, had no formal training in genetics but who recognised its importance.

Activities undertaken at three separate medical units, each emphasising different aspects of genetics (pedigree analysis, cytogenetics and genetic variation associated with common disorders), formed the foundation on which medical genetics, as an entity, developed.

Medical genetics was able to grow and establish itself more widely because of the many different types of close interactions among the members of the three founding groups and the support received from existing medical institutions.
Nucleolus: Structure and Function
Authors: Olson Mark OJ , Dundr Miroslav
Published: February 2015

The nucleolus is the nuclear subdomain that assembles ribosomal subunits in eukaryotic cells. The nucleolar organiser regions of chromosomes, which contain the genes for pre‐ribosomal ribonucleic acid (
rRNA
), serve as the foundation for nucleolar structure. The nucleolus disassembles at the beginning of mitosis, its components disperse in various parts of the cell and reassembly occurs during telophase and early
G1
phase. Ribosome assembly begins with transcription of pre‐
rRNA
. During transcription, ribosomal and non‐ribosomal proteins attach to the
rRNA
. Subsequently, there is modification and cleavage of pre‐
rRNA
and incorporation of more ribosomal proteins and
5S rRNA
into maturing pre‐ribosomal complexes. The nucleolus also contains proteins and
RNAs
that are not related to ribosome assembly and a number of new functions for the nucleolus have been identified. These include assembly of signal recognition particles, sensing cellular stress and transport of human immunodeficiency virus 1 (
HIV
‐1) messenger
RNA
.

Key Concepts

The nucleolus, whose primary function is to assemble ribosomes, is the largest structure in the cell nucleus.

The nucleolus organiser regions of chromosomes, which harbour the genes for pre‐rRNA, are the foundation for the nucleolus.

All active nucleoli contain at least two ultrastructural components, the nucleolar dense fibrillar component representing early pre‐ribosomal complexes and the granular component containing more mature pre‐ribosomal particles.

Most nucleoli in higher eukaryotes also contain fibrillar centres, which are the interphase equivalents of the nucleolus organiser regions.

The nucleolus disassembles at the beginning of mitosis and begins to reassemble in telophase.

Ribosome assembly begins with the transcription of pre‐rRNA by RNA polymerase I.

Ribosomal and non‐ribosomal proteins and 5S RNA associate with the pre‐rRNA during and after transcription.

The pre‐rRNA is modified and processed into rRNA with the aid of non‐ribosomal proteins and small nucleolar RNAs.

The nucleolus has numerous other functions including assembly of signal recognition particles, modification of transfer RNAs and sensing cellular stress.
Microtubule Organisation inDictyostelium
Authors: Gräf Ralph
Published: February 2015

Dictyostelium amoebae contain a radial array of microtubules emanating from a single microtubule‐organising centre called centrosome that is bound to the cytosolic face of the nucleus. Their centrosome contains no centrioles but consists of a layered core surrounded by a corona harbouring microtubule nucleation centres. It duplicates in prophase of a closed mitosis and organises a central spindle that drives centrosome separation and chromosome segregation. Dictyostelium microtubules exhibit a differential dynamic behaviour during interphase. Growth and shrinkage is observed only in the periphery but not in the pericentrosomal region. During mitosis, when centrosomes possess no corona, microtubules behave quite dynamically in formation of a central spindle and astral microtubules. Microtubules are associated with a couple of conserved proteins (MAPs), which are involved in centrosome biogenesis and the cross talk of microtubule tips with the actin cell cortex. The latter becomes evident in cytokinesis, when centrosomes with their attached microtubules participate in the positioning of cleavage furrows.

Key Concepts

Dictyostelium amoebae contain a nucleus‐associated centrosome that serves as the only microtubule‐organising centre.

The Dictyostelium centrosome contains no centrioles, but consists of a three‐layered core structure surrounded by a microtubule‐nucleating corona.

If compared to the three major plaques of the yeast spindle pole body, the entire core structure of the Dictyostelium centrosome appears equivalent to the central plaque, while the corona plays a similar role as the inner and outer plaques.

Dictyostelium centrosomes duplicate at the onset of mitosis.

Dictyostelium amoebae show a closed type of mitosis with a persisting nuclear envelope.

Dictyostelium microtubules are quite dynamic during mitosis but show growth and shrinkage only in the periphery during interphase.

Microtubule plus ends regulate actin dynamics at the cell cortex.

Dictyostelium amoebae are a useful model to study the role of the centrosome and microtubules in cell dynamics and disease.
Cerebral Palsy: Treatments and Therapeutics
Authors: Feather‐Schussler Danielle N , Ferguson Tanya S
Published: February 2015

Cerebral palsy (CP) is a non‐progressive motor disorder affecting approximately 3 out of every 1000 infants in the United States. Although it is classified as a motor disorder, the deficits are caused by pre‐ or neonatal brain injury. Unfortunately, there is no cure forCPand currently, symptom management is the only treatment option available. As research begins to unravel the underlying causes and cellular changes leading toCP, potential treatments and therapeutics can be investigated to prevent brain damage following insults. Today, only two therapies are approved for use in the hospital setting: hypothermia and magnesium sulphate. Both of these therapies attempt to lessen the brain damage by slowing processes of inflammation and cell death. Other potential therapies are in clinical trials to test safety and efficacy for use in humans. Some drugs have shown promise in animal models; however, they have not yet been tested in humans. Researchers are searching for a cure.

Key Concepts

There is no cure for cerebral palsy and currently approved treatments target the symptoms of cerebral palsy, not the underlying causes.

Hypothermia and magnesium sulphate are the only two therapeutics used in the hospital setting to slow or lessen brain damage following labour and delivery complications.

Therapeutics targeting the excitatory amino acid neurotransmitter glutamate, along with glutamate receptor and transporter expression and function, appear to be promising.

Drug treatments targeting growth factors and endogenous proteins may be beneficial to reduce cell death leading to cerebral palsy.

Because inflammation plays a role in cerebral palsy, drug treatment that reduces the inflammatory response may also reduce brain damage following insults.
Giant Phononic Anisotropy and Unusual Anharmonicity of Phosphorene: Interlayer Coupling and Strain Engineering
Authors: Cai Yongqing , Ke Qingqing , Zhang Gang , Feng Yuan Ping , Shenoy Vivek B. , Zhang Yong‐Wei
Published: February 2015

Phosphorene, an emerging elemental 2D direct band gap semiconductor with fascinating structural and electronic properties distinctively different from other 2D materials such as graphene and MoS2, is promising for novel nanoelectronic and optoelectronic applications. Phonons, as one of the most important collective excitations, are at the heart of the device performance, as their interactions with electrons and photons govern the carrier mobility and light‐emitting efficiency of the material. Here, through a detailed first‐principles study, it is demonstrated that monolayer phosphorene exhibits a giant phononic anisotropy, and remarkably, this anisotropy is squarely opposite to its electronic counterpart and can be tuned effectively by strain engineering. By sampling the whole Brillouin zone for the monolayer phosphorene, several “hidden” directions are found, along which small‐momentum phonons are “frozen” with strain and possess the smallest degree of anharmonicity. Unexpectedly, these “hidden” directions are intrinsically different from the usually‐studied armchair and zigzag directions. Light is also shed on the anisotropy of interlayer coupling of few‐layer phosphorene by examining the rigid‐layer vibrations. These highly anisotropic and strain‐tunable characteristics of phosphorene offer new possibilities for its applications in thermal management, thermoelectronics, nanoelectronics, and phononics.
Printing Patterned Fine 3D Structures by Manipulating the Three Phase Contact Line
Authors: Wu Lei , Dong Zhichao , Kuang Minxuan , Li Yanan , Li Fengyu , Jiang Lei , Song Yanlin
Published: February 2015

The preparation of fine 3D microstructures is an attractive issue; however, it is limited at large‐area fabrication process and fineness morphology manipulation. Here, we propose a strategy to fabricate controllable 3D structures and morphologies from one single droplet via ink‐jet printing. Based on the surface energy difference between the hydrophilic patterns and hydrophobic surface, the three phase contact line of a droplet contained nanoparticles is forced to pin on the patterned hydrophilic points and asymmetrically dewets on the hydrophobic surface, which leads to various morphologies. Through the regulation of pinning patterns and solution properties, the 3D morphology can be well manipulated. This strategy to control the 3D morphology of nanoparticle assembly based on hydrophilic patterns would be of great importance for fabricating controllable 3D structures.
Hole‐Trapping Effect of the Aliphatic‐Amine Based Electron Injection Materials in the Operation of OLEDs to Facilitate the Electron Injection
Authors: Zhong Zhiming , Hu Zhanhao , Jiang Zhixiong , Wang Jianbin , Chen Yawen , Song Chen , Han Shaohu , Huang Fei , Peng Junbiao , Wang Jian , Cao Yong
Published: February 2015

The organic materials containing aliphatic amine groups (AAGs) are widely used as the electron injection layer (EIL) in the application of organic light‐emitting diodes (OLED) to significantly improve the device performance. The electron injection mechanism is commonly explained by the interface dipole model, which suggests that the dipole layer induced by the electron injection layer at the organic/metal interface elevates the vacuum level on the metal side, thereby reducing the electron injection barrier. The experiments supporting the interface dipole model are generally carried out under the nonoperating condition of the OLEDs in which few holes are present. Our experiments on the OLED devices with neutralized AAG‐EIL dipole reveal that the interface dipole model cannot fully explain the AAG‐EIL's electron injection ability. During the operation of the OLEDs, the aliphatic amine function groups of the AAG‐EIL trap a huge amount of holes, bending the energy level and decreasing the electron tunneling distance. As a result, the reduced electron tunneling distance facilitates the electron injection.