bluuebunny/crossref_metadata_2025 huggingface dataset:
On the horizontal and temporal structure of noctilucent clouds as observed by satellite and lidar at ALOMAR (69N)
Authors: Baumgarten G. , Chandran A. , Fiedler J. , Hoffmann P. , Kaifler N. , Lumpe J. , Merkel A. , Randall C. E. , Rusch D. , Thomas G.
Published: December 2011

Simultaneous and common volume observations of Noctilucent Clouds (NLC) and Polar Mesospheric Clouds (PMC) have been performed above the ALOMAR research station in Northern Norway (69°N, 16°E) from ground and space, respectively. A detailed case study on August 5, 2008 shows that the measured particle sizes and T‐matrix simulations of the optical properties allow to combine the two observation techniques. From the ground, the observations were performed by lidar sounding of the temporal evolution of the cloud at two locations separated by about 40 km, before, during and after the coincidence. From space, the CIPS instrument onboard the AIM satellite observed the horizontal structure of the cloud. Using mesospheric radar wind measurements at ALOMAR the advection of the cloud particles is calculated and the temporal evolution of the cloud as seen from ground is compared with the horizontal structure observed from satellite. This comparison allows estimation of the timescales during which the clouds behave as passive tracers. We find that during this case study cloud structures larger than about 5 km × 5 km and oscillations slower than about one minute behaved like a passive tracer for up to one hour corresponding to horizontal scales of about 300 km. However, if the cloud shows wave structures with brightness modulations of 20% microphysical changes might take place on scales of minutes and kilometers.
ITRF2008 contribution to glacial isostatic adjustment and recent ice melting assessment
Authors: Métivier Laurent , Collilieux Xavier , Altamimi Zuheir
Published: December 2011

We investigate what information station vertical velocities of the ITRF2008 provide on global geodetic parameters and by extension on glacial isostatic adjustment (GIA) and recent ice melting (RIM) processes. We infer degree‐2 spherical harmonic coefficients (SHC) of the Earth figure change and theJ2 gravity rate (J˙2), which we compare with five GIA models. We find J˙2 to be (0.0 ± 2.4) × 10−11 yr−1, which is consistent with recent studies that propose a J˙2 change in the 1990s, due to RIM whose contribution to the J˙2 would be today around (3.5–4.0 ± 2.4) × 10−11 yr−1. Such results favor Peltier (2004) VM2 or Paulson et al. (2007) GIA models. The ITRF2008 SHC that are directly impacted by the GIA rotational feedback, confirm with a good precision recent results from GRACE mission that initiated a debate on GIA rotational feedback and about Peltier GIA model quality. We find a coefficient consistent with Paulson's (and other) model and more than 7 times smaller than coefficients in Peltier's models. Two explanations are possible: (1) if the model of Peltier (2004) VM2 were to be correct, then the strong rotational feedback in the model must be counteracted by a strong rotational feedback in the opposite direction generated by current ice loss, (2) if the model of Paulson et al. (2007) were to be correct, therefore GIA and RIM separately induce negligible rotational feedbacks. Both answers are quite extreme and call for more investigation on GIA modeling and rotational feedback.
Decoupled Holocene variability in surface and thermocline water temperatures of the Indo‐Pacific Warm Pool
Authors: Dang Haowen , Jian Zhimin , Bassinot Franck , Qiao Peijun , Cheng Xinrong
Published: December 2011

The Holocene variability in sea surface and thermocline water temperatures (SST and TWT) in the Indo‐Pacific Warm Pool (IPWP) has been reconstructed by planktonic foraminiferal Mg/Ca from sediments of the western tropical Philippine Sea. Afterward the Younger Dryas interval (YD), SST warmed gradually till ∼10 ka and remained approximately constant afterwards, but TWT rose more rapidly to a peak between ∼12 and ∼10 ka and then declined by ∼1.5°C through the Holocene. The trend of TWT closely followed the boreal summer insolation and could be correlated to tropical climate changes represented by southward movement of the Inter‐tropical Convergence Zone (ITCZ) and related changes in East Asian monsoons.
Observations of radiocarbon in CO2 at seven global sampling sites in the Scripps flask network: Analysis of spatial gradients and seasonal cycles
Authors: Graven Heather D. , Guilderson Thomas P. , Keeling Ralph F.
Published: December 2011

High precision measurements of Δ14C were conducted for monthly samples of CO2from seven global stations over 2‐ to 16‐year periods ending in 2007. Mean Δ14C over 2005–07 in the Northern Hemisphere was 5 ‰ lower than Δ14C in the Southern Hemisphere, similar to recent observations from I. Levin. This is a significant shift from 1988–89 when Δ14C in the Northern Hemisphere was slightly higher than the South. The influence of fossil fuel CO2 emission and transport was simulated for each of the observation sites by the TM3 atmospheric transport model and compared to other models that participated in the Transcom 3 Experiment. The simulated interhemispheric gradient caused by fossil fuel CO2 emissions was nearly the same in both 1988–89 and 2005–07, due to compensating effects from rising emissions and decreasing sensitivity of Δ14C to fossil fuel CO2. The observed 5 ‰ shift must therefore have been caused by non‐fossil influences, most likely due to changes in the air‐sea14C flux in the Southern Ocean. Seasonal cycles with higher Δ14C in summer or fall were evident at most stations, with largest amplitudes observed at Point Barrow (71°N) and La Jolla (32°N). Fossil fuel emissions do not account for the seasonal cycles of Δ14C in either hemisphere, indicating strong contributions from non‐fossil influences, most likely from stratosphere‐troposphere exchange.
Airborne and ground‐based observations of a weekend effect in ozone, precursors, and oxidation products in the California South Coast Air Basin
Authors: Pollack I. B. , Ryerson T. B. , Trainer M. , Parrish D. D. , Andrews A. E. , Atlas E. L. , Blake D. R. , Brown S. S. , Commane R. , Daube B. C. , de Gouw J. A. , Dubé W. P. , Flynn J. , Frost G. J. , Gilman J. B. , Grossberg N. , Holloway J. S. , Kofler J. , Kort E. A. , Kuster W. C. , Lang P. M. , Lefer B. , Lueb R. A. , Neuman J. A. , Nowak J. B. , Novelli P. C. , Peischl J. , Perring A. E. , Roberts J. M. , Santoni G. , Schwarz J. P. , Spackman J. R. , Wagner N. L. , Warneke C. , Washenfelder R. A. , Wofsy S. C. , Xiang B.
Published: December 2011

Airborne and ground‐based measurements during the CalNex (California Research at the Nexus of Air Quality and Climate Change) field study in May/June 2010 show a weekend effect in ozone in the South Coast Air Basin (SoCAB) consistent with previous observations. The well‐known and much‐studied weekend ozone effect has been attributed to weekend reductions in nitrogen oxide (NOx = NO + NO2) emissions, which affect ozone levels via two processes: (1) reduced ozone loss by titration and (2) enhanced photochemical production of ozone due to an increased ratio of non‐methane volatile organic compounds (VOCs) to NOx. In accord with previous assessments, the 2010 airborne and ground‐based data show an average decrease in NOx of 46 ± 11% and 34 ± 4%, respectively, and an average increase in VOC/NOxratio of 48 ± 8% and 43 ± 22%, respectively, on weekends. This work extends current understanding of the weekend ozone effect in the SoCAB by identifying its major causes and quantifying their relative importance from the available CalNex data. Increased weekend production of a VOC‐NOxoxidation product, peroxyacetyl nitrate, compared to a radical termination product, nitric acid, indicates a significant contribution from increased photochemical production on weekends. Weekday‐to‐weekend differences in the products of NOx oxidation show 45 ± 13% and 42 ± 12% more extensive photochemical processing and, when compared with odd oxygen (Ox = O3 + NO2), 51 ± 14% and 22 ± 17% greater ozone production efficiency on weekends in the airborne and ground‐based data, respectively, indicating that both contribute to higher weekend ozone levels in the SoCAB.
Forchheimer flow in gently sloping layers: Application to drainage of porous asphalt
Authors: Eck B. J. , Barrett M. E. , Charbeneau R. J.
Published: December 2011

This paper presents analytical solutions for the problem of steady one‐dimensional Forchheimer flow in an unconfined layer. The study's motivation is the drainage behavior of a highway pavement called permeable friction course. Permeable friction course is a layer of porous asphalt placed on top of impermeable pavement. Porous overlays are growing in popularity because they reduce noise, mitigate the hazards of wet weather driving, and produce cleaner runoff. Several of these benefits occur because water drains within the pavement rather than on the road surface. Drainage from the friction course is essentially that of an unconfined aquifer and has been successfully modeled using Darcy's law and the Dupuit‐Forchheimer assumptions. Under certain cases, drainage may occur outside of the range where Darcy's law applies. The purpose of this paper is to identify cases where the assumption of Darcy flow is violated, develop analytical solutions based on Forchheimer's equation, and compare the solutions with those obtained for the Darcy case. The principle assumptions used in this analysis are that the relationship between hydraulic gradient and specific discharge is quadratic in nature (Forchheimer's equation) and that the Dupuit‐Forchheimer assumptions apply. Comparing the Darcy and Forchheimer solutions leads to a new criterion for assessing the applicability of Darcy's law termed the discharge ratio.
Recovery of Stressed Microorganisms
Authors: Stephens P. J. , Mackey B. M.
Published: December 2011

Microorganisms present in processed food, water or the environment may be injured and hence more exacting in their growth requirements. Such organisms may be difficult to detect because they fail to grow on the selective media normally used in their isolation. However, under suitable conditions, injured cells can repair cellular damage and recover all their normal properties, including virulence. An appreciation of the nature of sublethal injury and its repair is therefore important in detecting and enumerating microbes. Injured cells may show an extended lag phase, restricted temperature range for growth and increased sensitivity to selective agents, salt, acidity and oxidative stress. In some cases it has been possible to identify the site of cellular injury leading to the observed phenotype. For example, damage to the Gram-negative outer membrane causes increased sensitivity to bile salts and some antibiotics, whilst disruption of cytoplasmic membrane function is probably related to increased sensitivity to salt and acid. Oxidative stress may arise from reactive oxygen species generated metabolically or present in trace amounts in recovery media. The reasons underlying some effects, such as a restricted temperature range for growth, are unknown. In order to recover injured cells it is necessary to allow resuscitation to take place on non-selective solid or in liquid media. In addition to improving the sensitivity of detection methods, resuscitation improves consistency and reduces variability between laboratories.

Recent developments in recovering injured cells have focused on defining the time needed for repair of individual cells within a population and in formulating resuscitation media and/or conditions to avoid exposing cells to oxidative stress. The need to monitor the performance (selectivity and productivity) of selective enrichment media as a quality control exercise is well established. It is now apparent that monitoring the performance of non-selective pre-enrichment or recovery media is equally important. This is particularly true when considering the development and application of new end-point detection systems that employ nucleic acid or immunological techniques.
Culture Media for Lactic Acid Bacteria
Authors: Schillinger U. , Holzapfel W. H.
Published: December 2011

This review deals with culture media for the detection, selective isolation and cultivation of different groups of lactic acid bacteria (LAB). Numerous elective and semi-selective media are available and currently used for LAB. Most of them have been developed to isolate certain groups of LAB from a specific habitat, such as meat or dairy products. These media can be rendered more selective by the addition of specific inhibitory agents or by reducing the pH. Members of the genera Lactobacillus, Leuconostoc, Pediococcus and Weissella (so-called LLPW group) share a number of physiological similarities and generally respond in the same way to conditions or compounds inhibitory to non-LAB. Therefore, most culture media developed for the detection of Lactobacillus or Leuconostoc are not completely selective for the respective genus. Carnobacteria can easily be distinguished from the LLPW group by their non-aciduric nature. However, because of physiological similarities to the genus Enterococcus, such as ability to grow at pH values up to 9.5, media developed for the selective isolation of Carnobacterium do not suppress growth of enterococci which often share the same habitat. Several useful selective media are available for beer pediococci, Tetragenococcus and Oenococcus, organisms characterised by specific properties associated with their adaptation to special environments. Because of the growing interest in probiotic strains and the inhabitants of the intestine, many media have been proposed in recent years for selective isolation of particular species or strains from those habitats, typically containing mixed populations of different LAB. Similarily, the increasing attention to safety aspects of LAB used as starter or probiotic cultures has emphasised the need for the development of a suitable medium for testing susceptibility to antibiotics.
Culture Media for the Isolation of Shigella spp.
Authors: Aminul Islam Mohammad
Published: December 2011

Shigella is adapted to humans as the only natural host, although it can infect higher primates. Ingestion of contaminated food or water is the most common route of transmission of Shigella in adults. Shigellosis is mainly a problem in low-income countries in Asia and Africa, where it has been considered endemic. Sporadic cases of Shigella infection have also been reported from moderate- to high-income countries, most of which are associated with travelling to Shigella endemic countries. Over the years, only a few studies have been done on the development and evaluation of culture media for their isolation. Culture media that have been used for isolation of Shigella spp. are not very specific or sensitive and are also used for other Enterobacteriaceae. For food and water samples, enrichment in a non-selective broth followed by plating onto three culture media of varied selectivity can be used for the maximum recovery of Shigella spp. These media, along with some recent developments on culture media for the detection and selective isolation of these bacteria, are the focus of this review.
Culture Media for the Isolation of Diarrhoeagenic Escherichia coli from Foods
Authors: Heuvelink Annet E.
Published: December 2011

The species Escherichia coli contains both diarrhoeagenic and non-diarrhoeagenic strains and it is very important to have methods available which can differentiate between them. Adequate culture methods have been developed for the isolation of verocytotoxin-producing E. coli (VTEC) of serogroup 0 157 from foods. However, at present no single isolation procedure is available for the recovery of all VTEC causing severe human disease. Additionally, there are still no simple sensitive procedures available for the direct cultivation of strains of the other groups of diarrhoeagenic E. coli. The isolation of these organisms will best be accomplished by a combination of culture and molecular biological methods.

In this review, some comparative studies of the media described for VTEC, especially VTEC O157, are noted and the difficulties associated with the isolation and enumeration of these organisms considered. Modified tryptone soya broth supplemented with novobiocin or modified E. coli broth supplemented with novobiocin and incubated at 41–42°C are the most appropriate selective enrichments. Injured VTEC O157 cells require pre-enrichment in a non-selective broth. Methods for the isolation of VTEC O157 should include sorbitol MacConkey agar supplemented with cefixime and potassium tellurite as the most effective isolation medium for typical sorbitol non-fermenting VTEC O157, and a second isolation medium not based on the fermentation of sorbitol but, for instance, on β-D-glucuronidase activity. Where the numbers of background flora are low, washed sheep blood agar supplemented with calcium (“EHEC agar”) may be used.
Culture Media for the Isolation of Aeromonas spp. and Plesiomonas shigelloides
Authors: Perales Ildefonso
Published: December 2011

The genera Aeromonas and Plesiomonas, previously included in the family Vibrionaceae, are now reclassified in the family Aeromonadaceae and Enterobacteriaceae, respectively. They are primarily aquatic inhabitants. Aeromonas taxonomy has changed considerably in recent years and now at least 19 phenospecies have been defined. Although identification to the species level of the most commonly found Aeromonas can be done on the basis of a limited number of biochemical tests, identification of some species is more difficult. Plesiomonas sligelloides is the only species of the genus Plesiomonas.

Culture media components used for Aeromonas and Plesiomonas isolation is reviewed here. This chapter also reports on the media used for the isolation of Aeromonas and Plesiomonas from foods and comparative studies.

In the case of Aeromonas spp., the most promising media are starch ampicillin agar (SAA) and bile salts Irgasan brilliant green (BSIBG) agar as plating media, and alkaline peptone water (APW) or trypticase soy broth ampicillin (TSBA) as enrichment broths. With regard to P. shigelloides, it is more difficult to make recommendations, but enrichment in APW or tetrathionate broth without iodine and plating on inositol brilliant green bile salts agar (IBB) and Plesiomonas agar (PL) can be useful.
Converting Photons to Electron and Proton Shifts from Water for Fuel Production
Authors: Herrero Christian , Costentin Cyrille , Aukauloo Ally
Published: December 2011

The production of fuels using sunlight, water and carbon dioxide is one of the most important challenges facing scientists today. Nature has been performing this reaction for more than 2 billion years using solar energy to remove protons and electrons from water, generate oxygen and store the energy in the chemical bonds of sugars. This process, photosynthesis, is the energy input for life.

Over the last two decades important advances have been made in the field of artificial photosynthesis spanning the fields of light absorption, formation of long-lived charge separated states, water oxidation reactions, and reductive processes aimed at fuel production. Of these, the design of efficient water oxidation catalysts based on earth abundant transition metal seems the most challenging problem. In this chapter, we describe the advances that have been accomplished in each of the steps necessary to achieve a molecular photo-catalyst for the oxidation of water.
Metal Complex of Hydrogenase Active Sites
Authors: Dawson Joe , Ghiotto Fabio , McMaster Jonathan , Schröder Martin
Published: December 2011

This article reviews the synthesis and chemistry of complexes that are of relevance to the structure and catalysis observed at the active sites of [NiFe], [FeFe] and [Fe] hydrogenase enzymes. Both structural and functional modelling of these biosites has been accomplished using ligand design to assemble low molecular weight metal complexes incorporating polythiolate coordination at the metal centre, coupled to appropriate amine, phosphine, cyanide and CO co-ligands. Exchange of ligands and the use of alternative metal centres, particularly Ru and Co, are discussed, and recent developments leading to the incorporation of proton relays and photoactive moieties are highlighted as strategies to generate photocatalysts for hydrogen production and oxidation for use in fuel cells.
Redox Active Protein Maquettes: Multi-functional “Green Enzymes”
Authors: Murray James
Published: December 2011

In the next fifty years humanity faces unprecedented challenges in the development of alternative energy sources to fossil fuels. One possible solution is the harvesting of sunlight to generate fuels, which could be achieved by the use of artificial enzymes. A promising approach to the development of artificial enzymes is the construction of protein ‘maquettes’ – smaller models of larger proteins that can bind functional cofactors. Such maquettes have demonstrated a variety of functions such as electron transfer and reversible oxygen binding. They can be inserted into membranes and linked to create larger systems. Future challenges include the development of hydrogenase and water oxidation activities into maquette-like systems and the coupling of proton and electron transfers.
Light-activated Bioconjugate Complexes
Authors: Hvasanov David , Goldstein Daniel C , Thordarson Pall
Published: December 2011

This Chapter describes the various methods that are available for linking synthetic and biological light-activated or light-harvesting units to electron acceptors. The bioconjugate approaches discussed are divided into classical and non-classical approaches. The classical methods include modification of amine (lysine and α-N-terminus), cysteine, histidine, tyrosine and glutamine residues of the target proteins. Non-classical approaches discussed include recombinant methods for introducing non-natural amino acids, ‘click’ chemistry, carbonyl condensation and Michael addition reactions. Emphasis will be on examples from the literature that describe the bioconjugation of synthetic light-activated chromophores to redox proteins. The Chapter concludes with a few recent examples from the literature on light-activated chromophore-electron acceptor bioconjugates, including cytochrome complexes modified with Ru-organometallic complexes and Photosystem I modified with metallic nanoparticle electron acceptors.
DMXAA (Vadimezan, ASA404) is a multi-kinase inhibitor targeting VEGFR2 in particular
Authors: Buchanan Christina M. , Shih Jen-Hsing , Astin Jonathan W. , Rewcastle Gordon W. , Flanagan Jack U. , Crosier Philip S. , Shepherd Peter R.
Published: December 2011

The flavone acetic acid derivative DMXAA [5,6-dimethylXAA (xanthenone-4-acetic acid), Vadimezan, ASA404] is a drug that displayed vascular-disrupting activity and induced haemorrhagic necrosis and tumour regression in pre-clinical animal models. Both immune-mediated and non-immune-mediated effects contributed to the tumour regression. The vascular disruption was less in human tumours, with immune-mediated effects being less prominent, but nonetheless DMXAA showed promising effects in Phase II clinical trials in non-small-cell lung cancer. However, these effects were not replicated in Phase III clinical trials. It has been difficult to understand the differences between the pre-clinical findings and the later clinical trials as the molecular targets for the agent have never been clearly established. To investigate the mechanism of action, we sought to determine whether DMXAA might target protein kinases. We found that, at concentrations achieved in blood during clinical trials, DMXAA has inhibitory effects against several kinases, with most potent effects being on members of the VEGFR (vascular endothelial growth factor receptor) tyrosine kinase family. Some analogues of DMXAA were even more effective inhibitors of these kinases, in particular 2-MeXAA (2-methylXAA) and 6-MeXAA (6-methylXAA). The inhibitory effects were greatest against VEGFR2 and, consistent with this, we found that DMXAA, 2-MeXAA and 6-MeXAA were able to block angiogenesis in zebrafish embryos and also inhibit VEGFR2 signalling in HUVECs (human umbilical vein endothelial cells). Taken together, these results indicate that at least part of the effects of DMXAA are due to it acting as a multi-kinase inhibitor and that the anti-VEGFR activity in particular may contribute to the non-immune-mediated effects of DMXAA on the vasculature.
One-dimensional phonon effects in direct molecular dynamics method for thermal conductivity determination
Authors: Hu L. , Evans W. J. , Keblinski P.
Published: December 2011

We demonstrate that the use of the direct, heat source/sink method for thermal conductivity determination via molecular dynamics simulation leads to diverging thermal conductivity with increasing simulation cell length when the cross section of the cell is kept constant. A phonon transport theory based analysis shows that this divergence arises due to discrete phonon phase space sampling leading to behavior characteristics of one-dimensional systems, which are known for size divergent thermal conductivity. We also show that the divergence is particularly strong for thermal conductivity along the elastically soft direction in anisotropic crystals.
Note: Temperature derivative of the refractive index of binary mixtures measured by using a new thermodiffusion cell
Authors: Croccolo F. , Plantier F. , Galliero G. , Pijaudier-Cabot G. , Saghir M. Z. , Dubois F. , Van Vaerenbergh S. , Montel F. , Bataller H.
Published: December 2011

A thermodiffusion cell is developed for performing Soret experiments on binary mixtures at high pressure and in the presence of a porous medium. The cell is validated by performing experiments at atmospheric pressure. The experiments are performed by applying different temperature gradients to binary mixtures in order to determine their thermal contrast factor. These measurements provide a first demonstration of the good reproducibility of this kind of measurements upon calibration.
Statics of polymer droplets on deformable surfaces
Authors: Léonforte F. , Müller M.
Published: December 2011

The equilibrium properties of polymer droplets on a soft deformable surface are investigated by molecular dynamics simulations of a bead-spring model. The surface consists of a polymer brush with irreversibly end-tethered linear homopolymer chains onto a flat solid substrate. We tune the softness of the surface by varying the grafting density. Droplets are comprised of bead-spring polymers of various chain lengths. First, both systems, brush and polymer liquid, are studied independently in order to determine their static and dynamic properties. In particular, using a numerical implementation of an AFM experiment, we measure the shear modulus of the brush surface and compare the results to theoretical predictions. Then, we study the wetting behavior of polymer droplets with different surface/drop compatibility and on substrates that differ in softness. Density profiles reveal, under certain conditions, the formation of a wetting ridge beneath the three-phase contact line. Cap-shaped droplets and cylindrical droplets are also compared to estimate the effect of the line tension with respect to the droplet size. Finally, the results of the simulations are compared to a phenomenological free-energy calculation that accounts for the surface tensions and the compliance of the soft substrate. Depending on the surface/drop compatibility, surface softness, and drop size, a transition between two regimes is observed: from one where the drop surface energy balances the adhesion with the surface, which is the classical Young-Dupré wetting regime, to another one where a coupling occurs between adhesion, droplet and surface elastic energies.
Electrical conductivity in Li2O2 and its role in determining capacity limitations in non-aqueous Li-O2 batteries
Authors: Viswanathan V. , Thygesen K. S. , Hummelshøj J. S. , Nørskov J. K. , Girishkumar G. , McCloskey B. D. , Luntz A. C.
Published: December 2011

Non-aqueous Li-air or Li-O2 cells show considerable promise as a very high energy density battery couple. Such cells, however, show sudden death at capacities far below their theoretical capacity and this, among other problems, limits their practicality. In this paper, we show that this sudden death arises from limited charge transport through the growing Li2O2 film to the Li2O2-electrolyte interface, and this limitation defines a critical film thickness, above which it is not possible to support electrochemistry at the Li2O2–electrolyte interface. We report both electrochemical experiments using a reversible internal redox couple and a first principles metal-insulator-metal charge transport model to probe the electrical conductivity through Li2O2 films produced during Li-O2 discharge. Both experiment and theory show a “sudden death” in charge transport when film thickness is ∼5 to 10 nm. The theoretical model shows that this occurs when the tunneling current through the film can no longer support the electrochemical current. Thus, engineering charge transport through Li2O2 is a serious challenge if Li-O2 batteries are ever to reach their potential.
Thermal properties of ionic systems near the liquid-liquid critical point
Authors: Méndez-Castro Pablo , Troncoso Jacobo , Pérez-Sánchez Germán , Peleteiro José , Romaní Luis
Published: December 2011

Isobaric heat capacity per unit volume, Cp, and excess molar enthalpy, hE, were determined in the vicinity of the critical point for a set of binary systems formed by an ionic liquid and a molecular solvent. Moreover, and, since critical composition had to be accurately determined, liquid-liquid equilibrium curves were also obtained using a calorimetric method. The systems were selected with a view on representing, near room temperature, examples from clearly solvophobic to clearly coulombic behavior, which traditionally was related with the electric permittivity of the solvent. The chosen molecular compounds are: ethanol, 1-butanol, 1-hexanol, 1,3-dichloropropane, and diethylcarbonate, whereas ionic liquids are formed by imidazolium-based cations and tetrafluoroborate or bis-(trifluromethylsulfonyl)amide anions. The results reveal that solvophobic critical behavior—systems with molecular solvents of high dielectric permittivity—is very similar to that found for molecular binary systems. However, coulombic systems—those with low permittivity molecular solvents—show strong deviations from the results usually found for these magnitudes near the liquid-liquid phase transition. They present an extremely small critical anomaly in Cp—several orders of magnitude lower than those typically obtained for binary mixtures—and extremely low hE—for one system even negative, fact not observed, up to date, for any liquid-liquid transition in the nearness of an upper critical solution temperature.
Capillary filling with giant liquid/solid slip: Dynamics of water uptake by carbon nanotubes
Authors: Joly Laurent
Published: December 2011

This article discusses the way the standard description of capillary filling dynamics has to be modified to account for liquid/solid slip in nanometric pores. It focuses, in particular, on the case of a large slip length compared to the pore size. It is shown that the liquid viscosity does not play a role, and that the flow is only controlled by the friction coefficient of the liquid at the wall. Moreover, in the Washburn regime, the filling velocity does not depend on the tube radius. Finally, molecular dynamics simulations suggest that this standard description fails to describe the early stage of capillary filling of carbon nanotubes by water, since viscous dissipation at the tube entrance must be taken into account.
Oxygen deficiency and grain boundary-related giant relaxation in Ba(Zr,Ti)O3 ceramics
Authors: Ciomaga Cristina E. , Buscaglia Maria T. , Buscaglia Vincenzo , Mitoseriu Liliana
Published: December 2011

The influence of the oxygen vacancies on the dielectric response of BaZr0.10Ti0.90O3 ceramics prepared by solid-state reaction and sintered at 1400 °C for 2 h was investigated. The as-sintered ceramic exhibits a giant relaxation with a shift of the transition temperature from ∼85 °C to above 170 °C in the frequency ranges of 1 Hz–100 kHz, with high losses above unity and two components in the complex impedance plot. A complex dielectric relaxation response, with at least two thermally activated defect mechanisms with activation energies of ∼0.2 eV below the transition temperature and ∼0.7 eV for higher temperatures in the range of 85 °C–170 °C was determined. The observed giant relaxation is an extrinsic effect related to the oxygen deficiency, inhomogeneous distributed in the ceramic grain and not to the relaxor behavior of this system. After a post-annealing treatment at 1000 °C for 50 h, the dielectric response is completely changed: the permittivity vs. temperature dependences present maxima located at around Tm ≈ 90 °C, with almost no frequency dispersion. The conductivity spectra remained almost unchanged after the annealing, showing that the level of oxygen deficiency in this case is related to dielectric relaxations and not to the ac-conductivity dispersion. Two thermally activated dielectric relaxation processes were still identified, but with activation energies of ∼2.7 eV below the transition temperature and of ∼0.87 eV for higher temperatures in the range of 85 °C–170 °C. The high frequency relaxation process is almost suppressed by the reoxidation and its activation energy increased with more than one order in magnitude. One single component in the complex impedance plot found after reoxidation shows that the annealing allowed the homogenization of the oxygen level within the ceramic grains.
First principles study of adsorption of O2 on Al surface with hybrid functionals
Authors: Liu Heng-Rui , Xiang Hongjun , Gong X. G.
Published: December 2011

Adsorption of O2 molecule on Al surface has been a long standing puzzle for the first principles calculation. We have studied the adsorption of O2 molecule on the Al(111) surface using hybrid functionals. In contrast to the previous local-density approximation/gradient-corrected approximation, the present calculations with hybrid functionals successfully predict that O2 molecule can be absorbed on the Al(111) surface with a barrier around 0.2–0.4 eV, which is in good agreement with experiments. Our calculations predict that the lowest unoccupied molecular orbital of O2 molecule is higher than the Fermi level of the Al(111) surface, which is responsible for the barrier of the O2 adsorption.
Relating hysteresis and electrochemistry in graphene field effect transistors
Authors: Veligura Alina , Zomer Paul J. , Vera-Marun Ivan J. , Józsa Csaba , Gordiichuk Pavlo I. , van Wees Bart J.
Published: December 2011

Hysteresis and commonly observed p-doping of graphene based field effect transistors (FETs) have been discussed in reports over the last few years. However, the interpretation of experimental works differs; and the mechanism behind the appearance of the hysteresis and the role of charge transfer between graphene and its environment is not clarified yet. We analyze the relation between electrochemical and electronic properties of graphene FETs in a moist environment extracted from the standard back gate dependence of the graphene resistance. We argue that graphene based FETs on a regular SiO2 substrate exhibit behavior that corresponds to electrochemically induced hysteresis in ambient conditions, and can be caused by a charge trapping mechanism associated with sensitivity of graphene to the local pH.
Study of slow oxide trap creating random telegraph noise within a gate edge overlap region in inversion mode
Authors: Cho Heung-Jae , Son Younghwan , Jang Seunghyun , Shin Hyungcheol
Published: December 2011

We investigated a slow oxide trap causing a random telegraph noise (RTN) within a gate edge overlap region in an inversion mode at metal/high-k dielectric nMOSFETs. The oxide trap was observed to generate RTN only in gate leakage current (Ig RTN) without in drain current (Id RTN) in the inversion mode. Through the analysis of the RTN dependence on drain, source, and body bias, we found that the oxide trap in the dielectric exists not within the channel area but within the gate edge overlap region, resulting in the absence of Id RTN.
Effect of air breakdown with a focusing lens on ultrashort laser ablation
Authors: Hu Wenqian , Shin Yung C. , King Galen
Published: December 2011

The effect of air breakdown on ultrashort laser ablation is investigated in this letter using an integrated simulation method on atomistic level. The generation of air breakdown with different laser peak power densities in the range from 1013 to 1016 W/cm2 and various focusing conditions is analyzed. Air breakdown is generated directly from laser energy absorption through avalanche ionization at a high power density (over 1014 W/cm2), while at a lower power density, air breakdown is assisted by a metal target near the focal region. The laser energy loss due to air breakdown and its effect on laser ablation are studied.
High-performance nonvolatile write-once-read-many-times memory devices with ZnO nanoparticles embedded in polymethylmethacrylate
Authors: Thanh Dao Toan , Viet Tran Thu , Higashimine Koichi , Okada Hiromasa , Mott Derrick , Maenosono Shinya , Murata Hideyuki
Published: December 2011

A mixture of ZnO nanoparticles and polymethylmethacrylate was used as an active layer in a nonvolatile resistive memory device. Current-voltage characteristics of the device showed nonvolatile write-once-read-many-times memory behavior with a switching time on the order of μs. The device exhibited an on/off ratio of 104, retention time of >105 s, and number of readout of >4 × 104 times under a read voltage of 0.5 V. The emission, cross-sectional high-resolution transmission electron microscopy (TEM), scanning TEM-high angle annular dark field imaging, and energy dispersive x-ray spectroscopy elemental mapping measurements suggest that the electrical switching originates from the formation of conduction paths.
Understand distribution of carbon dioxide to interpret crop growth data: Australian grains free-air carbon dioxide enrichment experiment
Authors: Mollah Mahabubur , Partington Debra , Fitzgerald Genn
Published: December 2011

Carbon dioxide (CO2) is the most important greenhouse gas, predicted to increase globally from currently 386 to 550 μmol mol–1 by 2050 and cause significant stimulation to plant growth. Consequently, in 2007 and 2008, Australian grains free-air carbon dioxide enrichment (AGFACE) facilities were established at Horsham (36°45′07″S lat., 142°06′52″E long., 127 m elevation) and Walpeup (35°07′20″S lat., 142°00′18″E long., 103 m elevation) in Victoria, Australia to investigate the effects of elevated CO2, water supply and nitrogen fertiliser on crop growth. Understanding the distribution patterns of CO2 inside AGFACE rings is crucial for the interpretation of the crop growth data. In the AGFACE system, the engineering performance goal was set as having at least 80% of the ring area with a CO2 concentration [CO2] at or above 90% of the target concentration at the ring-centre for 80% of the time. The [CO2] was highly variable near the ring-edge where CO2 is emitted and declined non-linearly with the distance downwind and wind speeds. Larger rings maintained the target [CO2] of 550 μmol mol–1 at the ring-centres better than the smaller rings. The spatial variation of [CO2] depended on ring size and the gap between fumigation and canopy heights but not on wind speeds. The variations in the inner 80% of the rings were found to be higher in smaller rings, implying that the larger rings had more areas of relatively uniform [CO2] to conduct experiments.
Growth hormone regulation of follicular growth
Authors: Lucy Matthew C.
Published: December 2011

The somatotropic axis – consisting of growth hormone (GH), the insulin-like growth factors 1 and 2 (IGF1 and IGF2), GH binding protein (GHBP), IGF binding proteins (IGFBPs) 1 to 6, and the cell-surface receptors for GH and the IGFs – has major effects on growth, lactation and reproduction. The primary target tissues for GH are involved in growth and metabolism. The functionality of the somatotropic axis depends in part on the expression of liver GH receptor (GHR), which determines the amount of IGF1 released from the liver in response to GH. The IGF1 acts as a pleiotropic growth factor and also serves as the endocrine negative feedback signal controlling pituitary GH secretion. Growth hormone and IGF1 undergo dynamic changes throughout the life cycle, particularly when animals are either growing, early post partum or lactating. Cells within the reproductive tract can respond directly to GH but to a lesser degree than the primary target tissues. The major impact that GH has on reproduction, therefore, may be secondary to its systemic effects on metabolism (including insulin sensitivity) or secondary to the capacity for GH to control IGF1 secretion. Insulin-like growth factor 1 and IGFBP are also synthesised within the ovary and this local synthesis is a component of the collective IGF1 action on the follicle. Future studies of GH should focus on its direct effects on the follicle as well as its indirect effects mediated by shifts in nutrient metabolism, insulin sensitivity, IGF1 and IGFBP.
11 SEASONAL EFFECT ON PREGNANCY RATES AND EARLY EMBRYONIC MORTALITY IN PLURIPAROUS MEDITERRANEAN BUFFALOES (BUBALUS BUBALIS) FOLLOWING ARTIFICIAL INSEMINATION WITH SEXED SEMEN
Authors: Vecchio D. , Neglia G. , Bella A. , Rossi P. , Senatore E. M. , Presicce G. A. , Gasparrini B.
Published: December 2011

Recently, the inclusion of sexed semen technology under field conditions in Mediterranean buffalo heifers has already proved feasible, resulting in pregnancy rates similar to what is ordinarily achieved with conventional nonsexed semen. A seasonal species within the latitudes currently reared in Italy, buffaloes tend to perform better reproductively during the period of the year of decreasing day length. In this study, sexed and nonsexed semen from four bulls has been used in two farms in the south of Italy. Following Ovsynch synchronization, 152 pluriparous buffaloes selected after screening for good general and reproductive health were subjected to AI in two periods of the year: (1) September to October and (2) January to February. Sexed and nonsexed semen was randomly used via AI with a total concentration of 2 × 106 and 20 × 106 spermatozoa per single straw, respectively. Pearson's chi-square test and Fisher's exact test were used for evaluation of data. Neither a bull nor farm effect on pregnancy rates was detected and therefore data for these two variables were pooled. Overall, combining the data from the two periods investigated, the use of sexed semen resulted in pregnancy rates at 28 days following AI similar to the use of nonsexed semen: 50/79; 63.2% vs 44/73; 60.2% (P = 0.70), respectively. Confirmation of pregnancy at 45 days post-AI also resulted in similar rates for both sexed and nonsexed semen: 49.3% vs 45.2% (P = 0.60), respectively. When individually considering each of the two periods investigated, the use of sexed semen in the months of September to October gave pregnancy rates at 28 days post-AI similar to nonsexed semen: 54.5% vs 56% (P = 0.88) and similarly at 45 days post-AI: 45.4% vs 48.7% (P = 0.75). A similar trend was observed in the months of January to February at 28 days post-AI for sexed and nonsexed semen: 74.2% vs 65.6% (P = 0.43) and similarly at 45 days post-AI: 54.2% vs 40.6% (P = 0.26). The use of sexed semen did not influence the pattern of late embryonic mortality (LEM) checked at 45 days post AI, whereas the season was a significant variable affecting LEM. In fact, when combining data for both sexed and nonsexed semen, LEM rate was found to be higher (P = 0.05) during the months of January to February (15/47; 31.9%), with the following individual values for sexed semen 7/26 (26.9%) and nonsexed semen 8/21 (38.1%), when compared with LEM rate during the months of September to October (7/47; 14.8%), with the following individual values for sexed semen 4/24 (16.6%) and nonsexed semen 3/23 (13.0%). In conclusion, although pregnancy rates were reported to be higher in the months of January to February when compared with the months of September to October, the former months seemed to affect more profoundly LEM for both sexed and nonsexed semen.
126 INFLUENCE OF PERIPHERAL PROGESTERONE CONCENTRATION ON MORPHOLOGICAL OOCYTE QUALITY IN REPEATED OVUM PICKUP SESSIONS
Authors: Schlüter N. , Hanstedt A. , Knauer K. , Stinshoff H. , Wrenzycki C.
Published: December 2011

Today, ovum pickup (OPU) followed by in vitro production (IVP) of bovine embryos is an integral part of many breeding programs. The quality of the obtained cumulus–oocyte complexes (COC) limits the success of embryo production. The developmental competence of the COC is dependent on several factors, including the stage of the oestrous cycle, the stage of follicular development and the follicular diameter. The aim of the present study was to determine the influence of circulating progesterone (P4) concentrations during repeated OPU sessions on the morphological quality of bovine COC. Cumulus–oocyte complexes were aspirated twice weekly for 5 to 6 weeks from 12 Holstein Friesian heifers. The first OPU session took place on Day 7 of the oestrous cycle (ovulation = Day 0). During each session, number and diameter of the punctuated follicles and diameter, consistency and cavities in the corpus luteum (CL) were recorded. Follicles were assigned to 3 groups according to their diameter (3 to 5 mm = small follicles; 6 to 8 mm = intermediate follicles; >8 mm = large follicles). Additionally, blood samples were taken at the time of each OPU session and blood P4 concentration was determined using a radioimmunoassay. The COC were categorised as IVP-suitable (round, ≥3 layers of cumulus cells, homo- or heterogeneous ooplasm) or unsuitable according to their morphological quality. All animals showed signs of oestrus accompanied by the presence of large follicles during the course of the OPU sessions. Statistical analysis was performed by an ANOVA followed by a Tukey test. A P-value of <0.05 was considered significant. The mean (±s.e.m.) cycle lengths for all heifers were 23.8 ± 4.6 days. Following the aspiration of a large follicle, a CL-like structure could be detected (referred to as “induced CL”). According to the P4 concentrations, the cycle was divided into 4 phases: natural CL phase (nCL; P4 ≥1 ng mL–1), follicle phase 1 (Fp1; P4 <1 ng mL–1), induced CL phase (iCL; P4 ≥1 ng mL–1), or follicle phase 2 (Fp2; P4 <1 ng mL–1). During the nCL phase, blood P4 concentrations were significantly higher than during the iCL phase (4.9 ± 2.3 ng mL–1, n = 12 vs 3.0 ± 1.6 ng mL–1, n = 10). There were no differences in follicle numbers, the diameter distribution of follicles, recovery rates, or number of retrieved IVP-suitable COC (nCL: 3.1 ± 3.4; Fp1: 3.3 ± 3.7; iCL: 2.7 ± 3.0; Fp2: 3.7 ± 3.7; Table 1). In summary, circulating P4 concentrations had no effect on follicle number, diameter, recovery rate, or IVP suitability of recovered COC.

Table 1.Number of follicles, retrieved oocytes, follicle sizes and recovery rates of the ovum pickup (OPU) sessions