bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Welded Joints of Automotive Sheets
Authors: Kender Štefan
Published: May 2015

Currently, the laser technology are used a broad-spectrum in combination with modern computer technology, especially in the field of engineering, energetics, electronics, medicine and the military. In engineering laser technologies record in coupling with robotization allowing five dimensional movements the biggest development mainly in the automotive industry. The most commonly are used for the heat processing of materials, cutting and in particular welding. The technology of laser welding is used in various industries. The thermal cycle at laser welding is usually faster than conventional arc technologies that lead to the small widths of welds and heat affected zones. To satisfy of difficult requirements of current time by this technology, it has to constantly develop and progress. Therefore, it is necessary to evaluate the quality of made products and thus to guide the production in direction towards improving their resulting properties. The paper is focused on the evaluation of mechanical properties, metallography and measurement of microhardness of automobile body sheets connected by laser welding.
Analysis of Welds Made by Delta Spot Method
Authors: Viňáš Ján , Kaščák Luboš
Published: May 2015

Resistance spot welding has been widely used in sheet fabrication for several decades. Development of new materials leads to innovation of welding processes. The paper describes the principle of innovative welding method known as Delta Spot and evaluates the properties of Delta Spot joints made by combination of galvanized steel sheets H220PD (a0 = 0.9 mm) and TRIP 40/70+Z100MBO (a0 = 0.77 mm). The quality of welded joints was evaluated by tensile test and metallographic analysis. The influence of the welding parameters on the structure of welded joint was observed too. The properties of Delta Spot joint were compared to the properties of standard resistance spot welds.
Adhesive Bonding Technology at Car - Body Structure – Application of New Coating with Layer Zn/Mg
Authors: Kolnerová Michaela , Sobotka Jiří , Solfronk Pavel , Zuzánek Lukáš
Published: May 2015

The paper deals with the application possibilities of new coatings types on the basis of Zn/Mg and their utilization at car-body production Comparison is done by evaluation bonded joints strength acc. to ISO 11339 for commonly used zinc-coated sheet at production car-body stampings (HDG Z100) with layer of new type on the basis of zinc/magnesium (ZM). Such utilization of new materials also means necessity to carry out test of the individual bonded car-body parts utility properties, mainly at peel loading, in dependence on adhesive type simultaneously with regard to the lubricant which is used in the technological process drawing of stampings and temperature under which is joint loaded. To guarantee required joints quality is one of the crucial criterions for applications new types of coatings in mass production.
Analysis of Thrust Force and Torque in Drilling Process of Particle Board
Authors: Szwajka Krzysztof
Published: May 2015

Particleboard is a wood based composite extensively used in wood working. Drilling is the most commonly used machining process in furniture industries. The surface characteristics and the damage free drilling are significantly influenced by the machining parameters. The thrust force developed during drilling play a major role in gaining the surface quality and minimizing the delamination tendency. In this study trials were made eighteen durability tools for different values of the parameters analyzed cut. Based on the results obtained from the study, the effect of cutting parameters selected signals of axial force and torque cutting. Proposed mathematical models using ANOVA, allowing to estimate the cutting forces.
Wrinkling Prediction and Optimization of Sheet Metal Forming Process by Numerical Simulation
Authors: Slota Ján , Šiser Marek
Published: May 2015

The paper deals with optimization of forming process for AISI 430 stainless steel with nominal thickness 0.4 mm. During forming of sidewall for washing machine drum, some wrinkles remain at the end of forming process in some places. This problem was solved by optimization the geometry of the drawpiece using numerical simulation. During optimization a series of modifications of the part geometry to absolute elimination of wrinkling was performed. On the basis of mechanical tests, the material model was created and imported into the material database of Autoform simulation software.
Ultrasonic Inspection of Thin Duplex Steel Welds by Phased Array
Authors: Hodúlová Erika , Kovaříková Ingrid , Šimeková Beáta , Ulrich Koloman
Published: May 2015

The non-destructive inspection of duplex steels is a big challenge, being composed of ferrite and austenite, have some particularities. When using ultrasound, for instance, its waves propagate well in ferrite, but suffer strong attenuation, scattering and refraction in austenite. The aim of this work is to use the Phased Array ultrasonic inspection method for the thin (4 mm) duplex steel weld joint inspection. The experimental sample was made ​​of duplex steel shaped tube with an outer diameter of 44 mm and a wall thickness of 3.8 mm welded with a laser beam. The experiment was necessary to verify attenuation of duplex steel. On the base material and the weld joint were made the artificial defects, in which the adjusted sensitivity of the ultrasonic device was set.The result of the measuring was the defect echo coming from the weld root layer. The length (about 25 mm) can only be estimated due to the inaccurate constant velocity of probe motion along the surface.
Parameters of Laser Welding and their Influence of Weld Seam
Authors: Balog Peter , Brezinová Janette , Pastorek Peter
Published: May 2015

Lap joints are most used joints in automotive industry. These types of welds are usually created by spot welding, but new technologies who came to automotive industry considerably do weld process faster. Paper deals with laser welding parameters and their influence of weld seams. The parameters of welding are readjusting according to shape of weld, impurities of surface and gap. Steel S500MC with thickness of 1.0 and 2.2 mm was used as the base material. For welding was used fiber laser Ytterbium Laser System YLS with power of 6000 watt from IPG Company. Research was oriented on changing weld parameters and their influence of welds quality. It was found that butt welding joints are sensitive to gap and the gap tolerances which in turn is dependent on material thickness, beam diameter, welding speed and beam quality.
The Analysis of the Shape and Mass of the Frames of Assembly Presses
Authors: Stupavský Michal , Bronček Jozef
Published: May 2015

This article deals with optimization and typing of the frames of the assembly presses which are used for assembly process of rolling bearings. The article describes the solution of technical problem from conception phase of the press frame to the phase of final CAD model design. Final solution contains of proposal for typing of dimensional series with five different sizes for five different press forces. The optimization of the shape and the dimensions, as well as typing, reduces manufacturing cost of the assembly presses. The build dimensions are reduced as well, while required stiffness and strength are preserved.
RP Technology Used for the Production of Metal Parts
Authors: Čapková Veronika , Zetková Ivana
Published: May 2015

Rapid prototyping (RP) is a modern technology which can produce components with very complicated shapes using different materials. This method also allows the production of components with shapes and geometry that would be very difficult to produce using conventional methods such as milling, welding and so on. A 3D printer builds an object from bottom to top, layer by layer. The purpose of this article is to introduce rapid prototyping technology for printing metal products. It focuses on various areas of application, advantages and disadvantages of this manufacturing technology as well as introduction of two methods DMLS (Direct Metal Laser Sintering) and LENS (Laser Engineered Net Shaping).
Analysis of Pearlitic Cold Drawn Steel Wire
Authors: Mihaliková Mária , Lacková Petra , Lišková Anna
Published: May 2015

The effect of microstructure on the mechanical properties of cord steel wires was investigated. Material properties and damage behaviours were identified. Metal cord, for reinforcing articles of an elastomeric material, such as tires, conveyor belts and so on of the single strand type, in particular made up of a plurality of 3, 4 or 6 wires, where in the said wires are twisted together loosely. The metal cord characterized by the fact that the diameter of the individual constituent wires varies between 0.12 and 0.30 mm. Rm tested cord wire was max. 2 946 MPa. Fracture surfaces cords steels were observed.
Analysis of the Reason of Non-Homogeneity of Molded Part from Semi-Crystalline PPS
Authors: Spišák Emil , Duleba Branislav , Gajdoš Ivan
Published: May 2015

This study presents measurement and calculations of crystallization of PPS composite with 40 % of glass fibers on real molded part using differential scanning calorimeter and also FEM simulation of impact of injection mold temperature on the crystallization of same part. Analyzed part had circular shape and samples for testing were taken from 4 different locations marked “3, 6, 9, 12” depending on their position (marked like as at clock face), while location 3 was nearest to the mold intake.
Assessment of the Properties of Paint Films Containing Surface-Treated Silicates
Authors: Nechvílová Kateřina , Kalendová Andrea
Published: May 2015

The objective of this paper is the surface modification of silica pigments layer of polyaniline (PANI), poly (p-phenylendiamine) (PPDA) and chemical layer of zinc ferrite ZnFe2O4. This layer promote adhesively-barrier properties of silica particles without surface-treated. This pigment was specified using physico-chemical parameters (oil absorption, critical pigment volume concentration, density, pH extract and the specific electrical conductivity of pigment extracts). An epoxy ester resin was used as binder for the organic coatings investigated. Organic coatings were prepared in the following volume concentration PVC = 10 %. Organic coatings prepared were subjected to measurement of physical-mechanical properties by the following tests: relative surface hardness, adhesion test, bend test, impact test. Organic coatings were subjected to the following corrosion tests: in an atmosphere of SO2 with water condensation. The results of mechanical and anti-corrosion tests provide evidence that was met premise increase adhesively-barrier properties of newly developed coating films.
Influence of Deformation on the Damage of Zn-Mg Based Protective Coating
Authors: Solfronk Pavel , Sobotka Jiří , Kolnerová Michaela , Zuzánek Lukáš
Published: May 2015

These days are in the automotive industry going to be still more and more used new types of protective coatings on the Zn-Mg basis. The advantage of these coatings is their excellent protection against corrosion of basic material. On the other hand disadvantage is mainly their low formability which takes effect at own stamping process. Such paper deals with the research influence of the deformation on the damage process of this coating. Size of deformation at different stress states was measured with the help of photogrammetry (system ARAMIS). Coating damage process at these stress states was monitored by means of optical and electron microscopy. Results of protective coating Zn-Mg damage process are presented in the form of strain distribution maps and images from optical and electron microscope.
Properties of the Electro-Spark Deposited Coatings - Technology and Applications
Authors: Radek Norbert , Bronček Jozef , Fabian Peter , Pietraszek Jacek , Antoszewski Krzysztof
Published: May 2015

The paper is concerned with the performance properties of electro-spark deposited coatings, which were determined basing on microstructural and roughness analysis and application tests. The studies were conducted using of the tungsten carbide-ceramic electrodes produced by the powder metallurgy hot pressing route. The anti-wear coatings were electro-spark deposited over C45 carbon steel by means of an EIL-8A. These coatings are likely to be applied to increase the abrasive wear resistance of tools and machine parts.
Tribological Properties of Coatings for Sheet Metal Stamping Dies
Authors: Evin Emil , Antoszewski Bogdan , Tomáš Miroslav , Tkáčová Jana , Draganovská Dagmar
Published: May 2015

The conventional and innovative surface technologies are applied to sheet metal stamping dies in order to produce a composite material with properties unattainable in either the base or surface material. To select proper materials for forming dies the systematic evaluation of dies materials, their heat treatment and coatings are required. This paper deals with evaluation of plasma sprayed coatings Cr2O3, Al2O3 and WC12Co by pressure plate-ring test (tester T 05) and deep drawing process. Friction coefficients and seizure of these coatings were studied under dry and wet friction conditions. For different types of die rings (with and without ceramic coatings) the punching forces were measured during deep-drawing process. The results show that the main advantage of application of plasma sprayed coatings on the die contact surfaces under wet friction conditions compare to dies made of the tool steel may be the increase of seizure resistance of stamped part surface. The more significant difference in the friction coefficient values was not observed.
Influence of Pressure in the Nozzle Combustion Chamber on the Porosity and Hardness of WC - Co Coatings Created by HVOF Technology
Authors: Moravec Jaromír , Kaška Václav
Published: May 2015

Thermally sprayed coatings, together with the deposition, belong among the most important technology both in the section of renovation and creation of functional surfaces. With the help of this technology it is possible to considerably improve the working life of the individual functional parts or to improve the range of their service parameters. Thermally sprayed coatings offer great variability both in light of backup materials (steels, non-ferrous metals, plastics), and in light of functional surfaces (metal powders, carbidic mixtures or ceramics). This paper describes individual types of powders with a view to properties and application possibilities of powders on the basis of W carbides with utilization of HVOF technology including a description of such method. Moreover the paper describes destructive and non-destructive tests for thermally created coatings. The experimental part is focused on the influence of pressure in the HVOF nozzle combustion chamber on the porosity and hardness of thermally sprayed coating for W carbide powders with different percentages of Co.
Investigation of Statically Deformed Aluminum Alloy Surface
Authors: Maruschak Pavlo , Konovalenko Igor , Brezinová Janette , Zakiev Islam
Published: May 2015

The peculiarities of the accumulation of structural and mechanical defects on the surface of the D16chT aluminum alloy under significant plastic strains are analyzed. The peculiarities of the surface strain hardening are found, and the geometrical parameters of the relief formations are described. The relationship between multiple cracking and specimen deformation is established. It is proved that the deformation relief parameters can be used to assess damage of the D16chT alloy under static deformation.
Change of Tribological Properties of Zn-Mg Coating in Dependence on Deformation
Authors: Sobotka Jiří , Solfronk Pavel , Kolnerová Michaela , Zuzánek Lukáš
Published: May 2015

Protective coatings on the basis of Zn-Mg are still more a more used in present engineering industry. However their wider using (e.g. in the automotive industry) is still limited by unsufficient and pure knowledge about their behavior in dependence on deformation. Thus this paper is focused on testing tribological properties and their change in dependence on size of deformation. That is why there was used tribological strip drawing test where samples were firstly deformed on different values (15% and 30%). Subsequently were these strips drawn between hardened and non-hardened jaws and there were evaluated different forces necessary to draw a strip and friction coefficient was calculated. Main results (mainly course of friction coefficient on pressure and deformation) were shown as graphs and tables.
Sorption Capable Film Coatings with Variable Conductivity
Authors: Grytsenko Oleksandr , Spišák Emil , Dulebová Ľudmila , Moravskii Volodymyr , Suberlyak Oleg
Published: May 2015

The possibility of formation of coatings based on co-polymers 2-hydroxyethylmethacrylate with polyvinylpirrolidone on different nature surfaces is determined. It is investigated, that adsorption of liquid compositions components to surface-base affects the formation of coating from such compositions. The composite metal-filled coatings are obtained on the basis of synthesized polymers. Such coatings are characterized by variable conductivity dependently on moisture content, pH and low-molecular substances availability.
Days to Return to Participation After a Hamstrings Strain Among American Collegiate Soccer Players
Authors: Cross Kevin M. , Saliba Susan A. , Conaway Mark , Gurka Kelly K. , Hertel Jay
Published: May 2015

Context

Among US collegiate soccer players, the incidence rate and the event characteristics of hamstrings strains differ between sexes, but comparisons in the return-to-participation (RTP) time have not been reported.

Objective

To compare the RTP time between male and female collegiate soccer players and analyze the influence of event characteristics on the RTP time for each sex.

Design

Descriptive epidemiology study.

Setting

Data were collected from collegiate teams that voluntarily participated in the National Collegiate Athletic Association Injury Surveillance System.

Patients or Other Participants

Collegiate soccer athletes who sustained 507 hamstrings strains (306 men, 201 women) during the 2004 through 2009 fall seasons.

Main Outcome Measure(s)

Nonparametric statistics were used to evaluate RTP time differences between sexes and among categories of each event characteristic (ie, time of season, practice or competition, player position). Negative binomial regression was used to model the RTP time for each sex. All analyses were performed separately for first-time and recurrent strains.

Results

We found no differences in the RTP time between sexes for first-time (median: men = 7.0 days, women = 6.0 days; P = .07) or recurrent (median: men = 11 days, women = 5.5 days; P = .06) hamstrings strains. For male players with first-time strains, RTP time was increased when the strain occurred during competition or the in-season/postseason and varied depending on the division of play. Among female players with first-time strains, we found no differences in RTP time within characteristics. For male players with recurrent hamstrings strains, the RTP time was longer when the injury occurred during the in-season/postseason. Among female players with recurrent strains, RTP time was longer for forwards than for midfielders or defenders.

Conclusions

Although we found no differences in the RTP time after hamstrings strains in male and female collegiate soccer players, each sex had unique event characteristics that influenced RTP time.
Real Analysis, Harmonic Analysis and Applications
Authors: Christ Michael , Müller Detlef , Thiele Christoph
Published: May 2015

The workshop has focused on important developments within the last few years in the point of view and methods of real and harmonic Analysis as well as significant concurrent progress in the application of these to various other fields.
Mathematics and Algorithms in Tomography
Authors: Burger Martin , Louis Alfred K. , Quinto Eric Todd
Published: May 2015

This was the ninth Oberwolfach conference on the mathematics of tomography. Modalities represented at the workshop included X-ray tomography, radar, seismic imaging, ultrasound, electron microscopy, impedance imaging, photoacoustic tomography, elastography, emission tomography, X-ray CT, and vector tomography along with a wide range of mathematical analysis.
Low-dimensional Topology and Number Theory
Authors: Gunnells Paul E. , Neumann Walter D. , Sikora Adam S. , Zagier Don B.
Published: May 2015

The workshop brought together topologists and number theorists with the intent of exploring the many tantalizing connections between these areas.
Discrete Geometry
Authors: Bárány Imre , Matoušek Jiří , Rote Günter
Published: May 2015

Several significant new developments have been reported in many branches of discrete geometry at the workshop. The area has strong connections to other fields of mathematics for instance topology, algebraic geometry, combinatorics, and harmonic analysis. Discrete geometry is very active with hundreds of open questions and many solutions. There was a large number of young participants eager to work on these questions, and the future of discrete geometry is very safe.
New Horizons in Statistical Decision Theory
Authors: Gill Richard D. , Guta Madalin , Nussbaum Michael
Published: May 2015

The classical metric theory of statistical models (experiments) has recently been extended towards an asymptotic equivalence paradigm, allowing to classify and relate problems which are essentially infinite dimensional and ill-posed. Modern statistical concepts like these are also being integrated into the emerging field of quantum statistics, which is developing on the background of technological breakthroughs in quantum engineering. The workshop brought together leading experts in these areas, with the goal of establishing a common language, and fostering collaborations between mathematical statisticians, theoretical physicists and experimentalists.
Implementación del sistema ABCD en el CRAI de la Universidad de Cienfuegos
Authors: De la Cruz Medina Ennia , García Valdés Daymé , Chapis Cabrera Elvys
Published: May 2015

Informa diversos aspectos sobre la experiencia de implementación del sistema ABCD en el Centro de Recursos para el Aprendizaje y la Investigación de la Universidad de Cienfuegos.
Nonholonomic Motion Planning Using the Fast Marching Square Method
Authors: Arismendi César , Álvarez David , Garrido Santiago , Moreno Luis
Published: May 2015

This research presents two novel approaches to nonholonomic motion planning. The methodologies presented are based on the standard fast marching square path planning method and its application to car-like robots. Under the first method, the environment is considered as a three-dimensional C-space, with the first two dimensions given by the position of the robot and the third dimension by its orientation. This means that we operate over the configuration space instead of the bi-dimensional environment map. Moreover, the trajectory is computed along the C-space taking into account the dimensions of the vehicle, and thus guaranteeing the absence of collisions. The second method uses the standard fast marching square, and takes advantage of the vector field of the velocities computed during the first step of the method in order to adapt the motion plan to the control inputs that a car-like robot is able to execute. Both methods ensure the smoothness and safety of the calculated paths in addition to providing the control actions to perform the trajectory.
Layer-by-Layer Self-Assembled Graphene Multilayer Films via Covalent Bonds for Supercapacitor Electrodes
Authors: Liu Xianbin , Wen Na , Wang Xiaoli , Zheng Yuying
Published: May 2015

To maximize the utilization of its single-atom thin nature, a facile scheme to fabricate graphene multilayer films via a layer-by-layer self-assembled process was presented. The structure of multilayer films was constructed by covalently bonding graphene oxide (GO) using p-phenylenediamine (PPD) as a covalent cross-linking agent. The assembly process was confirmed to be repeatable and the structure was stable. With the π-π conjugated structure and a large number of spaces in the framework, the graphene multilayer films exhibited excellent electrochemical performance. The uniform ultrathin electrode exhibited a capacitance of 41.71 μF/cm2 at a discharge current of 0.1 μA/cm2, and displayed excellent stability of 88.9 % after 1000 charge-discharge cycles.
The Metropolitan Waterworks Museum: Boston's Story of Water Works Villains, Heroes, and Machinery
Authors: Kempe Marcis
Published: May 2015

The story of Boston Water Works is a tale of water industry heroes who helped build the facilities and establish treatment processes to triumph over the waterborne diseases that plagued the city in the 1800s. Today, the machinery that was used from 1887 to 1974 is housed in the Metropolitan Waterworks Museum, where visitors can view some of the most distinctive and well‐preserved steam pumping engines in the country.
From Student to Professional: A Transition Guided by AWWA
Authors: Cannistraci Daniel J.
Published: May 2015

What does AWWA mean to me? At this time last year, as a master's student fresh off of his first semester of graduate school, I wouldn't have been able to tell you what those initials stood for. One year, two conferences, and a Fresh Ideas Poster Contest later, I can credit AWWA with spearheading my transition from full‐time student to water industry professional.
A Polynomial Delay Algorithm for Generating Connected Induced Subgraphs of a Given Cardinality
Authors: Elbassioni Khaled
Published: May 2015

We give a polynomial delay algorithm, that for any graph G and positive integer k, enumerates all connected induced subgraphs of G of order k. Our algorithm enumerates each subgraph in at most O((kmin{(n−k),k∆})2(∆+logk)) and uses linear space O(n+m), where n and m are respectively the number of vertices and edges of G and ∆ is the maximum degree.
Planar Induced Subgraphs of Sparse Graphs
Authors: Borradaile Glencora , Eppstein David , Zhu Pingan
Published: May 2015

We show that every graph has an induced pseudoforest of at least n−m/4.5 vertices, an induced partial 2-tree of at least n−m/5 vertices, and an induced planar subgraph of at least n−m/5.2174 vertices. These results are constructive, implying linear-time algorithms to find the respective induced subgraphs. We also show that the size of the largest Kh-minor-free graph in a given graph can sometimes be at most n−m/6+o(m).
Catastrophic chromosomal restructuring during genome elimination in plants
Authors: Tan Ek Han , Henry Isabelle M , Ravi Maruthachalam , Bradnam Keith R , Mandakova Terezie , Marimuthu Mohan PA , Korf Ian , Lysak Martin A , Comai Luca , Chan Simon WL
Published: May 2015

Genome instability is associated with mitotic errors and cancer. This phenomenon can lead to deleterious rearrangements, but also genetic novelty, and many questions regarding its genesis, fate and evolutionary role remain unanswered. Here, we describe extreme chromosomal restructuring during genome elimination, a process resulting from hybridization of Arabidopsis plants expressing different centromere histones H3. Shattered chromosomes are formed from the genome of the haploid inducer, consistent with genomic catastrophes affecting a single, laggard chromosome compartmentalized within a micronucleus. Analysis of breakpoint junctions implicates breaks followed by repair through non-homologous end joining (NHEJ) or stalled fork repair. Furthermore, mutation of required NHEJ factor DNA Ligase 4 results in enhanced haploid recovery. Lastly, heritability and stability of a rearranged chromosome suggest a potential for enduring genomic novelty. These findings provide a tractable, natural system towards investigating the causes and mechanisms of complex genomic rearrangements similar to those associated with several human disorders.
A summary of the BARREL campaigns: Technique for studying electron precipitation
Authors: Woodger L. A. , Halford A. J. , Millan R. M. , McCarthy M. P. , Smith D. M. , Bowers G. S. , Sample J. G. , Anderson B. R. , Liang X.
Published: May 2015

The Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) studies the loss of energetic electrons from Earth's radiation belts. BARREL's array of slowly drifting balloon payloads was designed to capitalize on magnetic conjunctions with NASA's Van Allen Probes. Two campaigns were conducted from Antarctica in 2013 and 2014. During the first campaign in January and February of 2013, there were three moderate geomagnetic storms with SYM‐Hmin < −40 nT. Similarly, two minor geomagnetic storms occurred during the second campaign, starting in December of 2013 and continuing on into February of 2014. Throughout the two campaigns, BARREL observed electron precipitation over a wide range of energies and exhibiting temporal structure from hundreds of milliseconds to hours. Relativistic electron precipitation was observed in the dusk to midnight sector, and microburst precipitation was primarily observed near dawn. In this paper we review the two BARREL science campaigns and discuss the data products and analysis techniques as applied to relativistic electron precipitation observed on 19 January 2013.
Pore connectivity, electrical conductivity, and partial water saturation: Network simulations
Authors: Li M. , Tang Y. B. , Bernabé Y. , Zhao J. Z. , Li X. F. , Bai X. Y. , Zhang L. H.
Published: May 2015

The electrical conductivity of brine‐saturated rock is predominantly dependent on the geometry and topology of the pore space. When a resistive second phase (e.g., air in the vadose zone and oil/gas in hydrocarbon reservoirs) displaces the brine, the geometry and topology of the pore space occupied by the electrically conductive phase are changed. We investigated the effect of these changes on the electrical conductivity of rock partially saturated with brine. We simulated drainage and imbibition as invasion and bond percolation processes, respectively, in pipe networks assumed to be perfectly water‐wet. The simulations included the formation of a water film in the pipes invaded by the nonwetting fluid. During simulated drainage/imbibition, we measured the changes in resistivity index as well as a number of relevant microstructural parameters describing the portion of the pore space saturated with water. Except Euler topological number, all quantities considered here showed a significant level of “universality,” i.e., insensitivity to the type of lattice used (simple cubic, body‐centered cubic, or face‐centered cubic). Hence, the coordination number of the pore network appears to be a more effective measure of connectivity than Euler number. In general, the simulated resistivity index did not obey Archie's simple power law. In log‐log scale, the resistivity index curves displayed a substantial downward or upward curvature depending on the presence or absence of a water film. Our network simulations compared relatively well with experimental data sets, which were obtained using experimental conditions and procedures consistent with the simulations. Finally, we verified that the connectivity/heterogeneity model proposed by Bernabé et al. (2011) could be extended to the partial brine saturation case when water films were not present.
A modified Equivalent Source Dipole method to model partially distributed magnetic field measurements, with application to Mercury
Authors: Oliveira J. S. , Langlais B. , Pais M. A. , Amit H.
Published: May 2015

Hermean magnetic field measurements acquired over the northern hemisphere by the MErcury Surface Space ENvironment GEochemistry, and Ranging (MESSENGER) spacecraft provide crucial information on the magnetic field of the planet. We develop a new method, the Time Dependent Equivalent Source Dipole, to model a planetary magnetic field and its secular variation over a limited spatial region. Tests with synthetic data distributed on regular grids as well as at spacecraft positions show that our modeled magnetic field can be upward or downward continued in an altitude range of −300 to 1460 km for regular grids and in a narrower range of 10 to 970 km for spacecraft positions. They also show that the method is not sensitive to a very weak secular variation along MESSENGER orbits. We then model the magnetic field of Mercury during the first four individual sidereal days as measured by MESSENGER using the modified Equivalent Source Dipoles scheme and excluding the secular variation terms. We find a dominantly zonal field with small‐scale nonaxisymmetric features corotating with the Sun in the Mercury Body Fixed system and repeating under similar local time, suggestive of external origin. When modeling the field during one complete solar day, these small‐scale features decrease and the field becomes more axisymmetric. The lack of any coherent nonaxisymmetric feature recovered by our method, which was designed to allow for such small‐scale structures, provides strong evidence for the large‐scale and close‐to‐axisymmetry structure of the internal magnetic field of Mercury.
Isotopic and nutritional evidence for species‐ and site‐specific responses to N deposition and elevated CO2 in temperate forests
Authors: Silva Lucas C. R. , Gómez‐Guerrero Armando , Doane Timothy A. , Horwath William R.
Published: May 2015

In this study we show that the effect of rising atmospheric CO2 levels on forest productivity is influenced by changes in nutrient availability caused by nitrogen (N) deposition. We used a dual‐isotope approach (δ15N and δ13C), combined with dendrochronological and nutritional analyses, to evaluate the response of two dominant tree species in natural forest ecosystems near Mexico City (Pinus hartwegii—pine; Abies religiosa—fir). Our analysis focuses on changes that occurred over the past 50 years at two sites, one under high and one under low N deposition rates. Analyses of carbon isotope composition indicate increasing water‐use efficiency in response to rising CO2 levels for both species and sites but this effect did not lead to improved tree growth. The magnitude and direction of shifts in 13C discrimination indicate a process of acclimation that varied with the rate of N deposition and species traits. Since the 1960s, strong negative responses to N deposition have been observed in fir trees, which showed altered foliar nutrition and growth decline, while the negative impacts of N deposition on pine trees remained undetectable until the 1990s. In recent years, both species have shown significant growth decline under high N deposition despite increasing atmospheric CO2. Multivariate analysis of leaf nutrients indicates that growth decline was prompted by depleted soil macronutrient (P, K, and Ca) and micronutrient (Cu, Fe, Zn, and Mn) availability. At both sites, fir trees were a better indicator of N deposition due to differences in canopy rainfall interception.
Determination of low B/Ca ratios in carbonates using ICP‐QQQ
Authors: Diez Fernández Silvia , Ruiz Encinar Jorge , Sanz‐Medel Alfredo , Isensee Kirsten , Stoll Heather M.
Published: May 2015

The very low B/Ca ratios characteristic of some natural biogenic carbonates, are of interest for research in ocean acidification but represent an analytical challenge. We describe a method using a novel instrument configuration (ICP‐QQQ), for which we are not aware of any previously published geological applications, and for coccoliths, a sample type unique in its low B content and organic phases. Detection limits as low as 0.41 µmol/mol were achieved. Isobaric interferences, out of the reach even for SF‐ICP‐MS, can be solved using this instrument, which permits the safe measurement of the lowest abundance Ca isotope (46Ca). This allows maximizing the B concentration measured (matrix concentration up to 800 ppm Ca) while maintaining both B and Ca signals in counting mode. More significantly for low B samples, the ICP‐QQQ is also able to overcome the interference of the ubiquitous 12C tail on the 11B mass, which otherwise leads to significant overestimates at very low B concentrations. This could be a reason for the significantly lower B/Ca ratios observed for the low B content interlaboratory calibration standards (Carrara and OKA), while matching for the high B content standards was good. Finally, results obtained in the analysis of coccoliths grown in laboratory culture seems to corroborate that SIMS analysis of the samples mounted in Indium leads also to B/Ca overestimates due to porosity effects, as previously observed using LA‐ICP‐MS. This approach also permits the interference‐free measurement of P/Ca and S/Ca ratios, which could be used as indicators of the complete removal of the organic matter from the samples.
Isopycnal mixing by mesoscale eddies significantly impacts oceanic anthropogenic carbon uptake
Authors: Gnanadesikan Anand , Pradal Marie‐Aude , Abernathey Ryan
Published: May 2015

Anthropogenic carbon dioxide uptake varies across Earth System Models for reasons that have remained obscure. When varied within a single model, the lateral eddy mixing coefficient ARedi produces a range of uptake similar to the modeled range. The highest uptake, resulting from a simulation with a constant ARedi of 2400 m2/s, simulates 15% more historical carbon uptake than a model with ARedi = 400 m2/s. A sudden doubling in carbon dioxide produces a 21% range in carbon uptake across the models. Two spatially dependent representations of ARedi produce uptake that lies in the middle of the range of constant values despite predicting very large values in the subtropical gyres. One‐dimensional diffusive models of the type used for integrated assessments can be fit to the simulations, with ARedi accounting for a substantial fraction of the effective vertical diffusion. Such models, however, mask significant regional changes in stratification and biological carbon storage.
Reconsidering emissions of ammonia from chemical fertilizer usage in Midwest USA
Authors: Balasubramanian Srinidhi , Koloutsou‐Vakakis Sotiria , McFarland D. Michael , Rood Mark J.
Published: May 2015

We present alternative methods for estimating spatial surrogates and temporal factors for ammonia (NH3) emissions from chemical fertilizer usage (CFU), in the USA, at spatial and temporal scales used to simulate regional air quality and deposition of reactive nitrogen to ecosystems. The newly developed Improved Spatial Surrogate (ISS) method incorporates year‐specific fertilizer sales data, high resolution and year‐specific crop maps, and local crop nitrogen demands to allocate NH3 emissions at 4 km × 4 km grid cells. Results are compared with the commonly used gridded emission estimates by the Sparse Matrix Operator Kernel Emissions (SMOKE) preprocessor. NH3 emissions over Central Illinois in the USA, estimated at the 4 km × 4 km grid level in SMOKE and ISS methods, exhibit differences between −10% and 120%, with 58% of the grid cells exhibiting more than ±10% difference. Application of the ISS method for a larger domain over the Midwest USA, at 4 km × 4 km, reflected similar differences. We also employed the Denitrification Decomposition (DNDC) model to develop daily temporal factors of NH3 emissions from CFU using multi‐site and multi‐year analyses. Ratio of temporal factors estimated by SMOKE and DNDC methods is 0.54 ± 2.35, with DNDC identifying daily emission peaks 2.5–8 times greater than SMOKE. Identified emission peaks will be useful for future air quality modeling efforts to understand particulate matter episodes, as well as trends in regional particulate matter formation and nitrogen deposition for Midwest USA, using the proposed NH3 emissions inventory.
Smallpox Eradication
Authors: Henderson Donald A
Published: May 2015

In 1967, the World Health Assembly undertook to eradicate smallpox worldwide. Priority was given to this disease, because, throughout history, it had been the most devastating of all human infections. The key elements of program execution included the World Health Organization's (WHO's) success in recruiting the global cooperation of all nations, an especially effective vaccine, a new instrument that facilitated vaccination and a unique strategy for stopping the spread of smallpox infection. The goal of the program was to eliminate smallpox throughout the world in 10 years. It missed the goal by only a few months. Smallpox Eradication was declared by the WHO in 1980 and smallpox vaccination ceased everywhere. The program, its strategies and organisation provided the impetus for a heightened global program of immunisation that includes poliomyelitis, measles, diphtheria, pertussis and tetanus vaccines.

Key Concepts

The eradication of smallpox was far more than a mass vaccination campaign. It was an exceptionally complex effort requiring global participation of countries, practical and applied research, vision and time.

For a global program necessarily involving many different countries, there is need for a primary force to shape strategy, to goad national authorities into action and to redirect the overall program as necessary. WHO is a basic necessity.

A special effort for disease surveillance and epidemic control was a critical basic requirement.

A heat‐stable vaccine meeting international standards was essential.

Different countries and changing circumstances require continuing adaptation.

The strategies and policies developed during the smallpox program proved to be highly relevant to other vaccination programs.
Dulbecco, Renato
Authors: Grignolio Andrea
Published: May 2015

Dulbecco was an Italian‐born American pioneer in molecular virology who showed how tumour viruses can transform normal cells into cancer‐like cells. Dulbecco (1914–2012) invented the plaque assay technique to quantify the number of viral units in a laboratory culture, as well as an enriched synthetic medium suited for rapidly proliferating cell cultures, contributed to the development of polio vaccines in the early 1960s and discovered that the transformation into cancer cell after the infection of certain types of viruses (oncoviruses) was due to the incorporation of virus‐derived genes into the host‐cell genome. For his work, Dulbecco was awarded a shared Nobel Prize in medicine in 1975.
NK
Cell Receptors
Authors: Tian Zhigang , Zhang Cai
Published: May 2015

Natural killer (NK) cell effector functions are regulated by integrated signals across the array of stimulatory and inhibitory receptors engaged upon interaction with target cell surface ligands. A delicate balance between activating and inhibiting receptors determines the outcome of NK cell activation. Moreover, NK cell receptors also instruct or confer the responsiveness of NK cells to activation events at both development and mature stages. In pathological condition, some strategies have been developed to tilt the balance of NK cell receptor signalling, which are involved in the onset and progress of malignant tumour, viral infection and other pertinent diseases. More understanding of the nature of interaction of NK cell receptors and their ligands as well as the regulation mechanisms should facilitate the development of effective therapy.

Key Concepts

The activity of NK cells is regulated by the delicate balance of signals from inhibitory and stimulatory cell surface receptors engaged upon interaction with their ligands.

Inhibitory NK cell receptors for MHC class I molecules not only have a critical role in controlling NK cell responses but also confer the functional competence of NK cells in response to activation signals.

Several models (missing‐self and induced‐self recognition model; licensing, arming, rheostat or cis interaction education model) have been proposed to depict the mechanisms for NK cell recognition and adaption.

Tumour cells and virus have developed various strategies to tilt the balance of NK cell receptor signalling, leading to escape from NK cell‐mediated immunosurveillance.

Therapeutic strategies targeting regulation of NK cell receptor and ligand system have shown great promise for treatment of cancer and viral infectious diseases.
Cell Death during Developmental Processes
Authors: Zakeri Zahra , Loos Ben , Lockshin Richard A
Published: May 2015

Embryonic development and differentiation to adult form depends on orchestration of cell division and death. In embryos, programmed death sculpts form, opens lumens, separates or splits tissue layers, allows tissue layers to fuse and removes vestigial organs. Both the central nervous and immune systems overproduce cells and destroy those that do not form successful synapses or produce unusable antibodies. Cell death is first seen in mammalian embryos when the blastocyst expands, but elsewhere, the first deaths are not seen before the maternal–zygotic transition. Abnormal timing, amount or localisation of cell death leads to abnormalities or death of embryos.

Several signalling pathways trigger cell death. Usually, the signals activate caspases (first discovered in embryonic cell death in nematodes) and lead to apoptosis, although apoptosis is not the only form of cell death. The signalling mechanisms that control cell death in embryos are not well understood, but should be if we hope to understand normal and teratological development.

Key Concepts

Cell death can be seen in both embryonic development and normal growth of adult tissue.

The embryonic cell deaths are highly programmed in that they are predictable in location, time and amount. In the simplest instances, such as in nematodes, control of cell death is under direct control of a small number of genes.

Most but not all of the embryonic deaths are apoptotic.

Embryonic cell to sculpt the embryo and define the boundaries of tissues and organs. In the central nervous system and the immune system, overgrowth (production of excessive cells) and subsequent pruning by cell death generate the high specificity that characterises these systems.

Deregulation of apoptosis can produce many embryonic abnormalities and teratologies and, later in life, produces cancers, autoimmune disease or neurodegenerative disease.

There are many means to study cell death, but only a few are directly applicable to the study of cell death in embryos. Nevertheless, further study is needed to understand the signalling mechanisms that decide the death of cells in specific locations and times.

Autophagy is increasingly recognised as a factor influencing the likelihood of onset of apoptosis and cell death.

New ultra‐resolution fluorescence microscopic techniques, capable of simultaneously analysing energy flux, autophagy and apoptosis, may lead to new insights into these questions.

Learning more about cell death in embryos will help us understand how it is controlled in adults.