bluuebunny/crossref_metadata_2025 huggingface dataset:
The recovery of glow-plasma structure in atmospheric radio frequency microplasmas at very small gaps
Authors: Zhang Yuan-Tao , Shang Wan-Li
Published: November 2011

In atmospheric radio frequency discharges at 13.56 MHz, with the electrode gap reduced, the sheath region eventually occupies a main portion of the electrode spacing and the bulk plasma region is significantly compressed. The computational results in this letter based on a one-dimensional fluid model show that by increasing the excitation frequency over 13.56 MHz, the traditional glow-plasma structure could gradually recover even at very small sizes with a well defined quasineutral plasma region, and the electron density is improved but the electric fields in sheath region are reduced. This study indicates that the excitation frequency can be used to modulate the discharge structure and then tailor the plasma-surface interaction in atmospheric microplasmas.
Velocity-controlled guiding of electron in graphene: Analogy of optical waveguides
Authors: Yuan Jian-Hui , Cheng Ze , Zeng Qi-Jun , Zhang Jun-Pei , Zhang Jian-Jun
Published: November 2011

Motivated by the realization of the Dirac point with tunable Fermi velocity in low-dimensional systems, we investigate the guided modes in graphene waveguides corresponding to the electron motion (or the hole motion) in a symmetric velocity barrier. We find that the fundamental mode always exists, but the higher-order mode may disappear. These discrete guided modes imply that there is a lowest cutoff frequency for an incident electron and that the incident electrons with different angles may have different minimum cutoff frequencies. These interesting features will be helpful for the investigation on an electronic fiber.
Evaporation rate of nucleating clusters
Authors: Zapadinsky Evgeni
Published: November 2011

The Becker-Döring kinetic scheme is the most frequently used approach to vapor liquid nucleation. In the present study it has been extended so that master equations for all cluster configurations are included into consideration. In the Becker-Döring kinetic scheme the nucleation rate is calculated through comparison of the balanced steady state and unbalanced steady state solutions of the set of kinetic equations. It is usually assumed that the balanced steady state produces equilibrium cluster distribution, and the evaporation rates are identical in the balanced and unbalanced steady state cases. In the present study we have shown that the evaporation rates are not identical in the equilibrium and unbalanced steady state cases. The evaporation rate depends on the number of clusters at the limit of the cluster definition. We have shown that the ratio of the number of n-clusters at the limit of the cluster definition to the total number of n-clusters is different in equilibrium and unbalanced steady state cases. This causes difference in evaporation rates for these cases and results in a correction factor to the nucleation rate. According to rough estimation it is 10−1 by the order of magnitude and can be lower if carrier gas effectively equilibrates the clusters. The developed approach allows one to refine the correction factor with Monte Carlo and molecular dynamic simulations.
The influence of overconstraint on the spatial distribution of mobility in an amorphous network
Authors: de Souza Vanessa K. , Harrowell Peter
Published: November 2011

It is proposed that the dynamic heterogeneities of an amorphous material are strongly correlated with the spatial distribution of unconstrained degrees of freedom in the associated network of mechanical constraints. This latter distribution is shown to depend sensitively on whether or not overconstraints are permitted in the constraint network. When overconstraints are avoided, relaxation is achieved with few bond rearrangements and the susceptibility χ4 increases monotonically with increasing constraint density, in contrast to the case of a random network. This behaviour is associated with the marginal stability of the isostatic rigid cluster as opposed to the more robust structures generated when redundant bonds are permitted.
“Up” versus “down” alignment and hydration structures of solutes at the air/water interface revealed by heterodyne-detected electronic sum frequency generation with classical molecular dynamics simulation
Authors: Yamaguchi Shoichi , Watanabe Hidekazu , Mondal Sudip Kumar , Kundu Achintya , Tahara Tahei
Published: November 2011

We unambiguously demonstrate the “up” versus “down” alignment of a pair of prototypical solute molecules adsorbed at the air/water interface for the first time using heterodyne-detected electronic sum frequency generation spectroscopy. This molecular alignment is also reproduced by classical molecular dynamics (MD) simulation theoretically. Furthermore, the MD simulation indicates distinctly different interface-specific hydration structures around the two solute molecules, which dictate the molecular alignment at the interface. It is concluded that the hydrophilicity difference between the terminal functional groups of the solute governs the molecular orientation and surrounding hydration structures at the interface.
Electronic structure of Al-doped ZnO transparent conductive thin films studied by x-ray absorption and emission spectroscopies
Authors: Huang W. H. , Sun S. J. , Chiou J. W. , Chou H. , Chan T. S. , Lin H.-J. , Kumar Krishna , Guo J.-H.
Published: November 2011

This study used O K-, Zn L3-, Zn K-, and Al K-edges x-ray absorption near-edge structure (XANES) and O K-edge x-ray emission spectroscopy (XES) measurements to investigate the electronic structure of transparent Al-doped ZnO (AZO) thin film conductors. The samples were prepared on glass substrates at a low temperature near 77 K by using a standard RF sputtering method. High-purity Ne (5N) was used as the sputtering gas. The crystallography of AZO thin films gradually transformed from the ZnO wurtize structure to an amorphous structure during sample deposition, which suggests the suitability to grow on flexible substrates, eliminating the severe degradation due to fragmentation by repeated bending. The O K- and Zn L3-edges XANES spectra of AZO thin films revealed a decrease in the number of both O 2p and Zn 3d unoccupied states when the pressure of Ne was increased from 5 to 100 mTorr. In contrast, Al K-edges XANES spectra showed that the number of unoccupied states of Al 3p increased in conjunction with the pressure of Ne, indicating an electron transfer from Al to O atoms, and suggesting that Al doping increases the negative effective charge of oxygen ions. XES and XANES spectra of O 2p states at the O K-edge also revealed that Al doping not only raised the conduction-band-minimum, but also increased the valence-band-maximum and the band-gap. The results indicate that the reduction in conductivity of AZO thin films is due to the generation of ionic characters, the increase in band-gap, and the decrease in density of unoccupied states of oxygen.
First-principles study of Ge dangling bonds in GeO2 and correlation with electron spin resonance at Ge/GeO2 interfaces
Authors: Houssa M. , Pourtois G. , Afanas’ev V. V. , Stesmans A.
Published: November 2011

The g-tensors of dangling bonds at defective Ge atoms in GeO2 are computed using density functional theory. The isotropic g-values of these defects are found to increase with the number of Ge backbonds. By comparing these calculations with the isotropic g-value of a Ge-related defect at Ge/GeO2 interfaces, recently observed by electron spin resonance (ESR) experiments, we tentatively identify this defect as a Ge2O≡Ge• center, i.e., a dangling bond on a Ge atom backbonded to two Ge atoms and one O atom, likely present near the Ge/GeO2 interface. The interaction of this defect with molecular hydrogen is investigated using first-principles molecular dynamics simulations. Our simulations predict that the Ge dangling bond can be hardly passivated by H2 molecules, in agreement with the electron spin resonance study.
Characterization of luminescent silicon carbide nanocrystals prepared by reactive bonding and subsequent wet chemical etching
Authors: Beke David , Szekrényes Zsolt , Balogh István , Veres Miklós , Fazakas Éva , Varga Lajos K. , Kamarás Katalin , Czigány Zsolt , Gali Adam
Published: November 2011

Fabrication of nanosized silicon carbide crystals is a crucial aspect for many biomedical applications. Here, we report an effective fabrication method of silicon carbide nanocrystals based on the reactive bonding method followed by electroless wet chemical etching. Our samples show strong violet-blue emission in the 410–450 nm region depending on the used solvents. Raman and infrared measurements unraveled the surface bonding structure of the fabricated nanoparticles being different from silicon carbide microcrystals. This might give an opportunity to use standard chemistry methods for biological functionalization of such nanoparticles.
Localized and collective magnetoplasmon excitations in AlGaN/GaN-based grating-gate terahertz modulators
Authors: Nogajewski K. , Łusakowski J. , Knap W. , Popov V. V. , Teppe F. , Rumyantsev S. L. , Shur M. S.
Published: November 2011

Magnetotransport and magnetooptics investigations of plasmon excitations in large-area grating-gate terahertz modulators based on AlGaN/GaN high-electron-mobility transistors with different grating-gate duty cycle are reported. We demonstrate that the effect of the gate potential on the ungated region extends beyond the conventional fringing effect distance, ranging over 250–350 nm instead of expected 26–30 nm. This phenomenon enables excitation of the localized gated magnetoplasmon modes only if the inter-finger spacing in the grating gate exceeds 350 nm. For narrower slits, only the collective gated magnetoplasmon modes extending over the entire period of the structure can be excited.
Efficient channel-plasmon excitation by nano-mirrors
Authors: Radko Ilya P. , Holmgaard Tobias , Han Zhanghua , Pedersen Kjeld , Bozhevolnyi Sergey I.
Published: November 2011

We demonstrate a configuration for efficient channel-plasmon mode excitation using tapered terminations of V-shaped groove waveguides. The plasmon excitation is achieved by directly illuminating tapers of gold V-grooves with a focused laser beam, incident normally onto the sample surface. For near-infrared wavelengths, we find experimentally as well as numerically, by conducting three-dimensional finite-difference time-domain calculations, that the efficiency of channel-plasmon mode excitation exceeds 10% in the optimum configuration, which is the highest experimentally observed efficiency of coupling from free-propagation light into a nanoscale-size waveguide.
Hole-transport limited S-shaped I-V curves in planar heterojunction organic photovoltaic cells
Authors: Zhang Minlu , Wang Hui , Tang C. W.
Published: November 2011

Current-voltage (I-V) characteristics of planar heterojunction organic photovoltaic cells based on N′,N′-Di-[(1-naphthyl)-N′,N′-diphenyl]-1,1′-biphenyl)-4,4′-diamine (NPB) and C60 are investigated. Through variation of the layer thickness and composition, specifically chemical doping NPB with MoOx, we show that the hole-transport limitation in the NPB layer is the determining factor in shaping the I-V characteristics of NPB/C60 cells.
Evaluation of resist sensitivity in extreme ultraviolet/soft x-ray region for next-generation lithography
Authors: Oyama Tomoko Gowa , Oshima Akihiro , Washio Masakazu , Tagawa Seiichi
Published: November 2011

At and below the 11 nm node, shortening the exposure wavelength to >10 nm (extreme ultraviolet (EUV)/soft x-ray region), especially at 6.6-6.8 nm, has been discussed as next-generation EUV lithography. In this study, dose/sensitivities of typical resists were obtained at several wavelengths down to 3.1 nm and were found to depend on the wavelength. However, it was confirmed that the absorbed dose, calculated from the dose/sensitivity and the respective linear absorption coefficient, was almost independent of the wavelength and constant for each resist. Thus, the resist sensitivity for next-generation lithography was predicted at wavelengths <10 nm.
Anomalous antiferromagnetic coupling in Fe/Si/Fe structures with Co “dusting”
Authors: Gareev R. R. , Buchmeier M. , Kiessling M. , Woltersdorf G. , Back C. H.
Published: November 2011

We report on anomalous antiferromagnetic coupling in Fe/Si/Fe epitaxial structures with interfacial cobalt “dusting”. Antiferromagnetic coupling exceeds 75 μJ/m2 for a 2.0 nm-thick Si spacer and is still detectable for a 2.3 nm-thick spacer at room temperature. From room temperature to T**∼150K the magnetization follows Bloch's law and the coupling shows metallic-type behaviour; for lower temperatures the coupling is of insulating type. Below T*∼50K an additional magnetic signal arises and the coupling becomes metallic-type again. We relate the observed features to the formation of inter-diffused magnetic FeCo-silicides with a Curie temperature close to 50 K.
X band bifrequency coaxial relativistic backward wave oscillator
Authors: Wang Dong , Qin Fen , Chen Dai-Bing , Wen Jie , Jin Xiao
Published: November 2011

An idea of azimuthally dividing the slow wave structure (SWS) of a relativistic backward wave oscillator (RBWO) into two parts is introduced to realize a bifrequency oscillation. To enhance the stability of this device, two sectorial waveguides are inserted into the SWS specially. The synchronization condition that is necessary to get a sustainable microwave output is derived. In Particle in cell simulation, bifrequency microwave at frequencies of 9.7 GHz and 9.87 GHz is generated with average power of 0.66 GW, conversion efficiency is 15.8% when beam voltage is 520 kV and current 8 kA.
Material design of ionic liquids to show temperature-sensitive LCST-type phase transition after mixing with water
Authors: Kohno Yuki , Arai Hiroki , Saita Shohei , Ohno Hiroyuki
Published: November 2011

Phosphonium cations bearing different alkyl chains were coupled with several common anions so as to prepare ionic liquids (ILs) with diverse hydrophobicity. A temperature-driven phase behaviour of the mixture of various ILs and water has been examined. A few ILs were found to exhibit temperature-sensitive lower critical solution temperature (LCST)-type phase transition after mixing with water. The phase separation temperature (Tc) of the IL/water mixtures depended strongly on the hydrophobicity of the component ions as well as mixing ratio. The number of water molecules per ion pair in the IL phase (mwater) increased dramatically upon cooling. The temperature dependence of this parameter was found to be useful to predict the possibility of the ILs to show the LCST-type phase behaviour after mixing with water. Since the value of mwater depended on the ion structure, especially on the hydrophobicity, the Tc was accurately set out by suitably mixing two ILs with different hydrophobicity.
Three-Component Mannich-like Reaction of 2-Aminoimidazole
Authors: Shengule Sudhir R. , Karuso Peter
Published: November 2011

A three-component reaction of 2-aminoimidazole with various aldehydes and amines is described that generates 4-substituted 2-aminoimidazoles containing a new chiral centre, a new C–C bond and a new C–N bond. The reactions can be conducted in water and require only sodium carbonate as reagent.
Inorganic arsenic and iron(II) distributions in sediment porewaters investigated by a combined DGT–colourimetric DET technique
Authors: Bennett William W. , Teasdale Peter R. , Welsh David T. , Panther Jared G. , Stewart Ryan R. , Price Helen L. , Jolley Dianne F.
Published: November 2011

Environmental contextContamination of aquatic ecosystems with inorganic arsenic is a concern for both environmental and human health. Sediments are an important sink for dissolved arsenic, but they may also act as a source of arsenic because of human-induced changes in aquatic systems. This paper describes a new approach for investigating the status of inorganic arsenic in sediments, based on recent developments in diffusion-based sediment sampling techniques.
AbstractA new approach for investigating the biogeochemistry of inorganic arsenic and iron(II) in freshwater, estuarine and marine sediments is reported. The recently developed Metsorb diffusive gradients in thin films (DGT) technique for the measurement of total inorganic arsenic and the colourimetric diffusive equilibration in thin films (DET) technique for the measurement of iron(II), were utilised in combination to determine co-located depth profiles of both solutes in sediment porewaters. DGT-measured porewater arsenic concentrations were typically less than 40 nM, whereas iron(II) concentrations reached up to 704 µM. Statistically significant (P < 0.0002) correlations between porewater arsenic and iron(II) profiles were observed (R > 0.92) in mesocosms of each sediment type. This approach to investigating arsenic and iron geochemistry in sediments allows the in-situ determination of arsenic and iron species at exactly the same location in the sediment at 3-mm resolution for arsenic and 1-mm resolution for iron(II). The technique was capable of detecting very low concentrations of arsenic, with a detection limit of 0.27 nM (0.02 µg L–1) for a 48-h deployment time. Porewater iron(II), which is often present over a wide range of concentrations, was detectable up to 2000 µM. This study shows the application of these recently developed DGT and DET techniques for the in-situ investigation of inorganic arsenic and iron biogeochemistry in sediments. This approach has the potential to enable simple, yet highly representative assessment of the biogeochemical status of arsenic and iron in a variety of natural sediments, including groundwater sediments where mobilised arsenic is responsible for significant human health risks.
Declines of freshwater turtles associated with climatic drying in Australia
Authors: Chessman Bruce C.
Published: November 2011

Context While much attention has been paid to the effects of global temperature increases on the geographical ranges and phenologies of plants and animals, less is known about the impacts of climatically driven alteration of water regimes. Aims To assess how three species of freshwater turtle in Australia’s Murray–Darling Basin have responded to long-term decline in river flow and floodplain inundation due to climatic drying and water diversions. Methods Turtle populations were sampled in a section of the Murray River and its floodplain in 1976–82 following a wet period and in 2009–11 at the end of the most severe drought on record. Catch per unit effort, proportional abundance in different habitat types and population structure were assessed in both periods. Key results Catch per unit effort in baited hoop nets declined by 91% for the eastern snake-necked turtle (Chelodina longicollis) and 69% for the Murray turtle (Emydura macquarii), but did not change significantly for the broad-shelled turtle (Chelodina expansa). In addition, total catches from a range of sampling methods revealed a significantly reduced proportion of juvenile C. longicollis and E. macquarii in 2009–11, suggesting a fall in recruitment. Key conclusions The decline of C. longicollis was likely due mainly to drought-induced loss of critical floodplain habitat in the form of temporary water bodies, and that of E. macquarii to combined effects of drought and predation on recruitment. C. expansa seems to have fared better than the other two species because it is less vulnerable to nest predation than E. macquarii and better able than C. longicollis to find adequate nutrition in the permanent waters that remain during extended drought. Implications Declining water availability may be a widespread threat to freshwater turtles given predicted global impacts of climate change and water withdrawals on river flows. Understanding how each species uses particular habitats and how climatic and non-climatic threats interact would facilitate identification of vulnerable populations and planning of conservation actions.
Distribution, abundance and demography of green pythons (Morelia viridis) in Cape York Peninsula, Australia
Authors: Natusch Daniel James Deans , Natusch David Francis Stewart
Published: November 2011

The green python (Morelia viridis) is an iconic snake species highly sought after in the pet trade and is the target of illegal collection. Despite their popularity, some important ecological attributes of green pythons remain unknown, making their effective conservation management difficult. Detection-only surveys were conducted throughout the potential range of the green python in Australia, and intensive mark–recapture surveys were conducted in the areas where there have been previous records. In total, 298 green pythons were located in the Iron, McIlwraith and Kawadji–Ngaachi ranges of Cape York, distributed over an estimated area of 2289 km2, where they frequented rainforest habitats and adjacent vine thickets. They were not found in the Lockerbie Scrub or Jardine River Catchment, despite anecdotal records. Green python density was estimated to be 540 km–2 in the Iron Range and 200 km–2 in the McIlwraith Range, where the percentages of adults captured were 56% and 83%, respectively. The differences between abundance and population demographics in the Iron and McIlwraith ranges may be due to differences in prey abundance and the impacts of collection. The results of this study provide baseline data to conservation managers and policy makers for the future conservation management of this species in Australia.
Mevalonate governs interdependency of ergosterol and siderophore biosyntheses in the fungal pathogen
Aspergillus fumigatus
Authors: Yasmin Sabiha , Alcazar-Fuoli Laura , Gründlinger Mario , Puempel Thomas , Cairns Timothy , Blatzer Michael , Lopez Jordi F. , Grimalt Joan O. , Bignell Elaine , Haas Hubertus
Published: November 2011

Aspergillus fumigatus
is the most common airborne fungal pathogen for humans. In this mold, iron starvation induces production of the siderophore triacetylfusarinine C (TAFC). Here we demonstrate a link between TAFC and ergosterol biosynthetic pathways, which are both critical for virulence and treatment of fungal infections. Consistent with mevalonate being a limiting prerequisite for TAFC biosynthesis, we observed increased expression of 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase (Hmg1) under iron starvation, reduced TAFC biosynthesis following lovastatin-mediated Hmg1 inhibition, and increased TAFC biosynthesis following Hmg1 overexpression. We identified enzymes, the acyl-CoA ligase SidI and the enoyl-CoA hydratase SidH, linking biosynthesis of mevalonate and TAFC, deficiency of which under iron starvation impaired TAFC biosynthesis, growth, oxidative stress resistance, and murine virulence. Moreover, inactivation of these enzymes alleviated TAFC-derived biosynthetic demand for mevalonate, as evidenced by increased resistance to lovastatin. Concordant with bilateral demand for mevalonate, iron starvation decreased the ergosterol content and composition, a phenotype that is mitigated in TAFC-lacking mutants.
Cosmochemical evidence for astrophysical processes during the formation of our solar system
Authors: MacPherson Glenn J. , Boss Alan
Published: November 2011

Through the laboratory study of ancient solar system materials such as meteorites and comet dust, we can recognize evidence for the same star-formation processes in our own solar system as those that we can observe now through telescopes in nearby star-forming regions. High temperature grains formed in the innermost region of the solar system ended up much farther out in the solar system, not only the asteroid belt but even in the comet accretion region, suggesting a huge and efficient process of mass transport. Bi-polar outflows, turbulent diffusion, and marginal gravitational instability are the likely mechanisms for this transport. The presence of short-lived radionuclides in the early solar system, especially
60
Fe,
26
Al, and
41
Ca, requires a nearby supernova shortly before our solar system was formed, suggesting that the Sun was formed in a massive star-forming region similar to Orion or Carina. Solar system formation may have been “triggered” by ionizing radiation originating from massive O and B stars at the center of an expanding HII bubble, one of which may have later provided the supernova source for the short-lived radionuclides. Alternatively, a supernova shock wave may have simultaneously triggered the collapse and injected the short-lived radionuclides. Because the Sun formed in a region where many other stars were forming more or less contemporaneously, the bi-polar outflows from all such stars enriched the local region in interstellar silicate and oxide dust. This may explain several observed anomalies in the meteorite record: a near absence of
detectable
(no extreme isotopic properties) presolar silicate grains and a dichotomy in the isotope record between
26
Al and nucleosynthetic (nonradiogenic) anomalies.
P-glycoprotein regulates blood–testis barrier dynamics via its effects on the occludin/zonula occludens 1 (ZO-1) protein complex mediated by focal adhesion kinase (FAK)
Authors: Su Linlin , Mruk Dolores D. , Lui Wing-Yee , Lee Will M. , Cheng C. Yan
Published: November 2011

The blood–testis barrier (BTB), one of the tightest blood–tissue barriers in the mammalian body, creates an immune-privileged site for postmeiotic spermatid development to avoid the production of antibodies against spermatid-specific antigens, many of which express transiently during spermiogenesis and spermiation. However, the BTB undergoes extensive restructuring at stage VIII of the epithelial cycle to facilitate the transit of preleptotene spermatocytes and to prepare for meiosis. This action thus prompted us to investigate whether this stage can be a physiological window for the delivery of therapeutic and/or contraceptive drugs across the BTB to exert their effects at the immune-privileged site. Herein, we report findings that P-glycoprotein, an ATP-dependent efflux drug transporter and an integrated component of the occludin/zonula occludens 1 (ZO-1) adhesion complex at the BTB, structurally interacted with focal adhesion kinase (FAK), creating the occludin/ZO-1/FAK/P-glycoprotein regulatory complex. Interestingly, a knockdown of P-glycoprotein by RNAi was found to impede Sertoli cell BTB function, making the tight junction (TJ) barrier “leaky.” This effect was mediated by changes in the protein phosphorylation status of occludin via the action of FAK, thereby affecting the endocytic vesicle-mediated protein trafficking events that destabilized the TJ barrier. However, the silencing of P-glycoprotein, although capable of impeding drug transport across the BTB and TJ permeability barrier function, was not able to induce the BTB to be “freely” permeable to adjudin. These findings indicate that P-glycoprotein is involved in BTB restructuring during spermatogenesis but that P-glycoprotein–mediated restructuring does not “open up” the BTB to make it freely permeable to drugs.
Spatially selective colonization of the arthropod intestine through activation of
Vibrio cholerae
biofilm formation
Authors: Purdy Alexandra E. , Watnick Paula I.
Published: November 2011

Vibrio cholerae
is an estuarine bacterium and the human pathogen responsible for the diarrheal disease cholera. In the environment, arthropods are proposed to be carriers and reservoirs of
V. cholerae
. However, the molecular basis of the association between
V. cholerae
and viable arthropods has not been elucidated previously. Here, we show that the
V. cholerae Vibrio
polysaccharide (VPS)-dependent biofilm is highly activated upon entry into the arthropod intestine and is specifically required for colonization of the arthropod rectum. Although the
V. cholerae
VPS-dependent biofilm has been studied in the laboratory for many years, the function of this biofilm in the natural habitats of
V. cholerae
has been elusive. Our results provide evidence that the VPS-dependent biofilm is required for intestinal colonization of an environmental host.
Equitable decision making is associated with neural markers of intrinsic value
Authors: Zaki Jamil , Mitchell Jason P.
Published: November 2011

Standard economic and evolutionary models assume that humans are fundamentally selfish. On this view, any acts of prosociality—such as cooperation, giving, and other forms of altruism—result from covert attempts to avoid social injunctions against selfishness. However, even in the absence of social pressure, individuals routinely forego personal gain to share resources with others. Such anomalous giving cannot be accounted for by standard models of social behavior. Recent observations have suggested that, instead, prosocial behavior may reflect an intrinsic value placed on social ideals such as equity and charity. Here, we show that, consistent with this alternative account, making equitable interpersonal decisions engaged neural structures involved in computing subjective value, even when doing so required foregoing material resources. By contrast, making inequitable decisions produced activity in the anterior insula, a region linked to the experience of subjective disutility. Moreover, inequity-related insula response predicted individuals’ unwillingness to make inequitable choices. Together, these data suggest that prosocial behavior is not simply a response to external pressure, but instead represents an intrinsic, and intrinsically social, class of reward.
Measuring time with different neural chronometers during a synchronization-continuation task
Authors: Merchant Hugo , Zarco Wilbert , Pérez Oswaldo , Prado Luis , Bartolo Ramón
Published: November 2011

Temporal information processing is critical for many complex behaviors including speech and music cognition, yet its neural substrate remains elusive. We examined the neurophysiological properties of medial premotor cortex (MPC) of two Rhesus monkeys during the execution of a synchronization-continuation tapping task that includes the basic sensorimotor components of a variety of rhythmic behaviors. We show that time-keeping in the MPC is governed by separate cell populations. One group encoded the time remaining for an action, showing activity whose duration changed as a function of interval duration, reaching a peak at similar magnitudes and times with respect to the movement. The other cell group showed a response that increased in duration or magnitude as a function of the elapsed time from the last movement. Hence, the sensorimotor loops engaged during the task may depend on the cyclic interplay between different neuronal chronometers that quantify the time passed and the remaining time for an action.
Force-free swimming of a model helical flagellum in viscoelastic fluids
Authors: Liu Bin , Powers Thomas R. , Breuer Kenneth S.
Published: November 2011

We precisely measure the force-free swimming speed of a rotating helix in viscous and viscoelastic fluids. The fluids are highly viscous to replicate the low Reynolds number environment of microorganisms. The helix, a macroscopic scale model for the bacterial flagellar filament, is rigid and rotated at a constant rate while simultaneously translated along its axis. By adjusting the translation speed to make the net hydrodynamic force vanish, we measure the force-free swimming speed as a function of helix rotation rate, helix geometry, and fluid properties. We compare our measurements of the force-free swimming speed of a helix in a high-molecular weight silicone oil with predictions for the swimming speed in a Newtonian fluid, calculated using slender-body theories and a boundary-element method. The excellent agreement between theory and experiment in the Newtonian case verifies the high accuracy of our experiments. For the viscoelastic fluid, we use a polymer solution of polyisobutylene dissolved in polybutene. This solution is a Boger fluid, a viscoselastic fluid with a shear-rate-independent viscosity. The elasticity is dominated by a single relaxation time. When the relaxation time is short compared to the rotation period, the viscoelastic swimming speed is close to the viscous swimming speed. As the relaxation time increases, the viscoelastic swimming speed increases relative to the viscous speed, reaching a peak when the relaxation time is comparable to the rotation period. As the relaxation time is further increased, the viscoelastic swimming speed decreases and eventually falls below the viscous swimming speed.
Nuclear RNAi maintains heritable gene silencing in
Caenorhabditis elegans
Authors: Burton Nick O. , Burkhart Kirk B. , Kennedy Scott
Published: November 2011

RNA interference (RNAi) is heritable in
Caenorhabditis elegans
; the progeny of
C. elegans
exposed to dsRNA inherit the ability to silence genes that were targeted by RNAi in the previous generation. Here we investigate the mechanism of RNAi inheritance in
C. elegans
. We show that exposure of animals to dsRNA results in the heritable expression of siRNAs and the heritable deposition of histone 3 lysine 9 methylation (H3K9me) marks in progeny. siRNAs are detectable before the appearance of H3K9me marks, suggesting that chromatin marks are not directly inherited but, rather, reestablished in inheriting progeny. Interestingly, H3K9me marks appear more prominently in inheriting progeny than in animals directly exposed to dsRNA, suggesting that germ-line transmission of silencing signals may enhance the efficiency of siRNA-directed H3K9me. Finally, we show that the nuclear RNAi (Nrde) pathway maintains heritable RNAi silencing in
C. elegans
. The Argonaute (Ago) NRDE-3 associates with heritable siRNAs and, acting in conjunction with the nuclear RNAi factors NRDE-1, NRDE-2, and NRDE-4, promotes siRNA expression in inheriting progeny. These results demonstrate that siRNA expression is heritable in
C. elegans
and define an RNAi pathway that promotes the maintenance of RNAi silencing and siRNA expression in the progeny of animals exposed to dsRNA.
Mathematical modeling of prostate cancer progression in response to androgen ablation therapy
Authors: Jain Harsh Vardhan , Clinton Steven K. , Bhinder Arvinder , Friedman Avner
Published: November 2011

Prostate cancer progression depends in part on the complex interactions between testosterone, its active metabolite DHT, and androgen receptors. In a metastatic setting, the first line of treatment is the elimination of testosterone. However, such interventions are not curative because cancer cells evolve via multiple mechanisms to a castrate-resistant state, allowing progression to a lethal outcome. It is hypothesized that administration of antiandrogen therapy in an intermittent, as opposed to continuous, manner may bestow improved disease control with fewer treatment-related toxicities. The present study develops a biochemically motivated mathematical model of antiandrogen therapy that can be tested prospectively as a predictive tool. The model includes “personalized” parameters, which address the heterogeneity in the predicted course of the disease under various androgen-deprivation schedules. Model simulations are able to capture a variety of clinically observed outcomes for “average” patient data under different intermittent schedules. The model predicts that in the absence of a competitive advantage of androgen-dependent cancer cells over castration-resistant cancer cells, intermittent scheduling can lead to more rapid treatment failure as compared to continuous treatment. However, increasing a competitive advantage for hormone-sensitive cells swings the balance in favor of intermittent scheduling, delaying the acquisition of genetic or epigenetic alterations empowering androgen resistance. Given the near universal prevalence of antiandrogen treatment failure in the absence of competing mortality, such modeling has the potential of developing into a useful tool for incorporation into clinical research trials and ultimately as a prognostic tool for individual patients.
Antemortem trauma and survival in the late Middle Pleistocene human cranium from Maba, South China
Authors: Wu Xiu-Jie , Schepartz Lynne A. , Liu Wu , Trinkaus Erik
Published: November 2011

Paleopathological assessment of the late Middle Pleistocene archaic human cranium from Maba, South China, has documented a right frontal squamous exocranially concave and ridged lesion with endocranial protrusion. Differential diagnosis indicates that it resulted from localized blunt force trauma, due to an accident or, more probably, interhuman aggression. As such it joins a small sample of pre-last glacial maximum Pleistocene human remains with probable evidence of humanly induced trauma. Its remodeled condition also indicates survival of a serious pathological condition, a circumstance that is increasingly documented for archaic and modern
Homo
through the Pleistocene.
The role of cell type-specific responses in IFN-β therapy of multiple sclerosis
Authors: Zula Joana A. , Green Holly C. , Ransohoff Richard M. , Rudick Richard A. , Stark George R. , van Boxel-Dezaire Anette H. H.
Published: November 2011

The mechanism of IFN-β therapy in relapsing-remitting multiple sclerosis (RRMS) is not well understood, but induction of apoptosis in specific leukocyte subsets is likely to be important. Enhanced expression ofTNFSF10or TNF-related apoptosis-inducing ligand (TRAIL) mRNA in unseparated leukocytes has been put forward as a therapeutic response marker, but it is unclear which leukocyte subsets expressTRAIL. We investigated the basis of TRAIL expression in response to IFN-β by studying activation of STATs 1, 3, and 5, p38 MAPK, and NF-κB in different leukocyte subsets of patients with RRMS. Monocytes, B cells, and T cells showed substantial differences in the activation of p38 and the STATs in response to i.m. injection of IFN-β1a or stimulation in vitro. Induction of cell-surface TRAIL, analyzed in nine leukocyte subsets, was observed only on monocytes and granulocytes and correlated with the activation of p38 and/or NF-κB in these subsets only, in agreement with previous work in fibroblasts showing that the induction of TRAIL in response to IFN-β depends on the activation of p38 and NF-κB as well as STATs 1 and 2. We propose that, in myeloid cells, the differential activation of p38 and NF-κB and induction of TRAIL, which sensitizes cells to apoptosis, can help to explain differences in responsiveness to IFN-β therapy among patients with RRMS and, furthermore, that such differential patterns of activation and expression may also be important in understanding the therapeutic responses to IFN-α/β in hepatitis and cancer.
Role of checkpoint kinase 1 (Chk1) in the mechanisms of resistance to histone deacetylase inhibitors
Authors: Lee Ju-Hee , Choy Megan L. , Ngo Lang , Venta-Perez Gisela , Marks Paul A.
Published: November 2011

Histone deacetylase inhibitors (HDACi) are a new group of anticancer drugs with tumor selective toxicity. Normal cells are relatively resistant to HDACi-induced cell death compared with cancer cells. Previously, we found that vorinostat induces DNA breaks in normal and transformed cells, which normal but not cancer cells can repair. In this study, we found that checkpoint kinase 1 (Chk1), a component of the G2 DNA damage checkpoint, is important in the resistance of normal cells to HDACi in vitro and in vivo. Inhibition of Chk1 activity with Chk1 inhibitor (UCN-01, AZD7762, or CHIR-124) in normal cells increases their sensitivity to HDACi (vorinostat, romidepsin, or entinostat) induced cell death, associated with extensive mitotic disruption. Mitotic abnormalities included loss of sister chromatid cohesion and chromosomal disruption. Inhibition of Chk1 did increase HDACi-induced cell death of transformed cells. Thus, Chk1 is an important factor in the resistance of normal cells, and some transformed cells, to HDACi-induced cell death. Use of Chk1 inhibitors in combination with anticancer agents to treat cancers may be associated with substantial toxicity.
Lethal mitochondrial cardiomyopathy in a hypomorphic
Med30
mouse mutant is ameliorated by ketogenic diet
Authors: Krebs Philippe , Fan Weiwei , Chen Yen-Hui , Tobita Kimimasa , Downes Michael R. , Wood Malcolm R. , Sun Lei , Li Xiaohong , Xia Yu , Ding Ning , Spaeth Jason M. , Moresco Eva Marie Y. , Boyer Thomas G. , Lo Cecilia Wen Ya , Yen Jeffrey , Evans Ronald M. , Beutler Bruce
Published: November 2011

Deficiencies of subunits of the transcriptional regulatory complex Mediator generally result in embryonic lethality, precluding study of its physiological function. Here we describe a missense mutation in
Med30
causing progressive cardiomyopathy in homozygous mice that, although viable during lactation, show precipitous lethality 2–3 wk after weaning. Expression profiling reveals pleiotropic changes in transcription of cardiac genes required for oxidative phosphorylation and mitochondrial integrity. Weaning mice to a ketogenic diet extends viability to 8.5 wk. Thus, we establish a mechanistic connection between Mediator and induction of a metabolic program for oxidative phosphorylation and fatty acid oxidation, in which lethal cardiomyopathy is mitigated by dietary intervention.
VPS35 haploinsufficiency increases Alzheimer’s disease neuropathology
Authors: Wen Lei , Tang Fu-Lei , Hong Yan , Luo Shi-Wen , Wang Chun-Lei , He Wanxia , Shen Chengyong , Jung Ji-Ung , Xiong Fei , Lee Dae-hoon , Zhang Quan-Guang , Brann Darrell , Kim Tae-Wan , Yan Riqiang , Mei Lin , Xiong Wen-Cheng
Published: November 2011

VPS35, a major component of the retromer complex, is important for endosome-to-Golgi retrieval of membrane proteins. Although implicated in Alzheimer’s disease (AD), how VPS35 regulates AD-associated pathology is unknown. In this paper, we show that hemizygous deletion of Vps35 in the Tg2576 mouse model of AD led to earlier-onset AD-like phenotypes, including cognitive memory deficits, defective long-term potentiation, and impaired postsynaptic glutamatergic neurotransmission in young adult age. These deficits correlated well with an increase of β-amyloid peptide (Aβ) level in the mutant hippocampus. We further demonstrate that VPS35 is predominantly expressed in pyramidal neurons of young adult hippocampus and interacts with BACE1, a protease responsible for Aβ production. Loss of VPS35 function in the mouse hippocampus increased BACE1 activity. Suppression of VPS35 expression in culture decreased BACE1 trans-Golgi localization but enriched it in endosomes. These results demonstrate an essential role for VPS35 in suppression of AD neuropathology and in inhibition of BACE1 activation and Aβ production by promoting BACE1 endosome-to-Golgi retrieval.
An appreciation of Ralph Marvin Steinman (1943–2011)
Authors: Moberg Carol L.
Published: November 2011

Ralph Steinman, an editor at the Journal of Experimental Medicine since 1978, shared the 2011 Nobel Prize in Physiology or Medicine for his discovery of dendritic cells (DCs) and their role in immunity. Ralph never knew. He died of pancreatic cancer on September 30, 3 days before the Nobel announcement. Unaware of his death at the time of their announcement, the Nobel Committee made the unprecedented decision that his award would stand. Ralph was the consummate physician-scientist to the end. After his diagnosis, he actively participated in his 4.5 years of treatments, creating experimental therapies using his own DCs in conjunction with the therapies devised by his physicians, all the while traveling, lecturing, and most of all pursuing new investigations in his laboratory. For 38 years—from his discovery of DCs to his Nobel Prize—Ralph pioneered the criteria and methods used to identify, isolate, grow, and study DCs. He and his colleagues demonstrated that DCs are initiators of immunity and regulators of tolerance. In his most recent studies, Ralph was harnessing the specialized features of DCs to design improved vaccines. The following synopsis describes some of his seminal discoveries.
Remembering Ralph Steinman
Authors: Banchereau Jacques , Cohn Fern , Inaba Kayo , Muller Bill , Mellman Ira , Nathan Carl , Nussenzweig Michel , O’Garra Anne , Seder Bob , Schuler Gerold , Sher Alan
Published: November 2011

As detailed in the Appreciation piece written by Carol Moberg, Ralph’s discovery and investigation of DCs constituted an enormous contribution to immunology. However, Ralph’s influence extended far beyond the strictly scientific. Below, some of Ralph’s closest colleagues and friends reflect on the long-lasting effects of his unwavering mentorship, enthusiasm, generosity, and friendship.

Also in this issue is a Perspective, originally commissioned by Ralph and written by Robin Weiss and Peter Vogt. Ralph passed away before he could read this engaging piece, which celebrates the centennial of the publication in the JEM of the Nobel Prize-winning work of Peyton Rous. In addition to their Nobel Prizes, Ralph and Peyton Rous shared the distinctions of being long-time leaders of Rockefeller laboratories and editors of this journal.
Sensitivity and specificity analysis of fringing-field dielectric spectroscopy applied to a multi-layer system modelling the human skin
Authors: Huclova Sonja , Baumann Dirk , Talary Mark S , Fröhlich Jürg
Published: November 2011

The sensitivity and specificity of dielectric spectroscopy for the detection of dielectric changes inside a multi-layered structure is investigated. We focus on providing a base for sensing physiological changes in the human skin, i.e. in the epidermal and dermal layers. The correlation between changes of the human skin's effective permittivity and changes of dielectric parameters and layer thickness of the epidermal and dermal layers is assessed using numerical simulations. Numerical models include fringing-field probes placed directly on a multi-layer model of the skin. The resulting dielectric spectra in the range from 100 kHz up to 100 MHz for different layer parameters and sensor geometries are used for a sensitivity and specificity analysis of this multi-layer system. First, employing a coaxial probe, a sensitivity analysis is performed for specific variations of the parameters of the epidermal and dermal layers. Second, the specificity of this system is analysed based on the roots and corresponding sign changes of the computed dielectric spectra and their first and second derivatives. The transferability of the derived results is shown by a comparison of the dielectric spectra of a coplanar probe and a scaled coaxial probe. Additionally, a comparison of the sensitivity of a coaxial probe and an interdigitated probe as a function of electrode distance is performed. It is found that the sensitivity for detecting changes of dielectric properties in the epidermal and dermal layers strongly depends on frequency. Based on an analysis of the dielectric spectra, changes in the effective dielectric parameters can theoretically be uniquely assigned to specific changes in permittivity and conductivity. However, in practice, measurement uncertainties may degrade the performance of the system.
On the identifiability of binary Segre products
Authors: Bocci Cristiano , Chiantini Luca
Published: November 2011

We prove that a product of

m
>
5

m>5

copies of

P

1

\mathbb {P}^1

, embedded in the projective space

P

r

\mathbb {P}^r

by the standard Segre embedding, is

k
k

-identifiable (i.e. a general point of the secant variety

S
k

(
X
)

S^k(X)

is contained in only one

(
k
+
1
)

(k+1)

-secant

k
k

-space), for all

k
k

such that

k
+
1
≤

2

m
−
1

/

m

k+1\leq 2^{m-1}/m

.
Diabetes in Children
Authors: Saravanan Santhana L. , Mohanty Rabin
Published: November 2011

Aretaeus, a Greek physician and disciple of Hippocrates first coined the term diabetes, which means siphon in Greek. He described the disease as ‘melting down of the flesh and limbs into the urine’. There was no treatment available until insulin was discovered in 1921 by Banting and Best. Diabetes is the second most common chronic disease in childhood after asthma. Around 25% of newly diagnosed children present with diabetic ketoacidosis (DKA). Chronic hyperglycaemia can lead to long-term complications. The role of the GP is to diagnose children early in their presentation to prevent DKA, refer them to the multidisciplinary diabetes team, coordinate care in the community and provide advice regarding management during day-to-day activities.