bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface plasmon enhanced photoconductance of gold nanoparticle arrays with incorporated alkane linkers
Authors: Mangold M. A. , Weiss C. , Calame M. , Holleitner A. W.
Published: April 2009

We report on a photoconductive gain effect in two-dimensional arrays of gold nanoparticles (NPs) in which alkane molecules are inserted. The NP arrays are formed by a self-assembly process from alkanethiol-coated gold NPs, and subsequently they are patterned on a Si/SiO2 chip by a microcontact printing technique. We find that the photoconductance of the arrays is strongly enhanced at the frequency of the surface plasmon of the NPs. We interpret the observation as a bolometric enhancement in the conductance of the NP arrays upon excitation of the surface plasmon resonance.
Quasimonoenergic collimated electrons from the ionization of nitrogen by a chirped intense laser pulse
Authors: Singh Kunwar Pal , Sajal Vivek
Published: April 2009

A scheme is proposed for quasimonoenergic collimated GeV electrons generated during ionization of nitrogen by a chirped intense laser pulse. The electrons accelerated by a laser pulse without a frequency chirp are known for poor-quality beams. If a suitable frequency chirp is introduced, then the energy of the electrons increases significantly. It is shown that quasimonoenergic collimated GeV electrons can be produced using a right choice of laser spot size, frequency chirp, and pulse duration.
Optimal sampling efficiency in Monte Carlo simulation with an approximate potential
Authors: Coe Joshua D. , Sewell Thomas D. , Shaw M. Sam
Published: April 2009

Building on the work of Iftimie et al. [J. Chem. Phys. 113, 4852 (2000)] and Gelb [J. Chem. Phys. 118, 7747 (2003)], Boltzmann sampling of an approximate potential (the “reference” system) is used to build a Markov chain in the isothermal-isobaric ensemble. At the end points of the chain, the energy is evaluated at a more accurate level (the “full” system) and a composite move encompassing all of the intervening steps is accepted on the basis of a modified Metropolis criterion. For reference system chains of sufficient length, consecutive full energies are statistically decorrelated and thus far fewer are required to build ensemble averages with a given variance. Without modifying the original algorithm, however, the maximum reference chain length is too short to decorrelate full configurations without dramatically lowering the acceptance probability of the composite move. This difficulty stems from the fact that the reference and full potentials sample different statistical distributions. By manipulating the thermodynamic variables characterizing the reference system (pressure and temperature, in this case), we maximize the average acceptance probability of composite moves, lengthening significantly the random walk between consecutive full energy evaluations. In this manner, the number of full energy evaluations needed to precisely characterize equilibrium properties is dramatically reduced. The method is applied to a model fluid, but implications for sampling high-dimensional systems with ab initio or density functional theory potentials are discussed.
Net transport due to noise-induced internal reciprocating motion
Authors: Makhnovskii Yurii A. , Rozenbaum Viktor M. , Yang Dah-Yen , Lin Sheng Hsien
Published: April 2009

We consider a system of two coupled Brownian particles fluctuating between two states. The fluctuations are produced by both equilibrium thermal and external nonthermal noise, the transition rates depending on the interparticle distance. An externally induced modulation of the transition rates acts on the internal degree of freedom (the interparticle distance) and generates reciprocating motion along this coordinate. The system moves unidirectionally due to rectification of the internal motion by asymmetric friction fluctuations and thus operates as a dimeric motor that converts input energy into net movement. The properties of the motor are primarily determined by the properties of the reciprocating engine, represented by the interparticle distance dynamics. Two main mechanisms are recognized by which the engine operates: energetic and informational. In the physically important cases where only one of the motion-inducing mechanisms is operative, exact solutions can be found for the model with linearly coupled particles. We focus on the informational mechanism, in which thermal noise is involved as a vital component and the reciprocating velocity exhibits a rich behavior as a function of the model parameters. An efficient rectification method for the reciprocating motion is also discussed.
On higher order corrections to gyrokinetic Vlasov–Poisson equations in the long wavelength limit
Authors: Lee W. W. , Kolesnikov R. A.
Published: April 2009

In this paper, a simple iterative procedure is presented for obtaining the higher order E×B and dE/dt (polarization) drifts associated with the gyrokinetic Vlasov–Poisson equations in the long wavelength limit of k⊥ρi∼o(ϵ) and k⊥L∼o(1), where ρi is the ion gyroradius, L is the scale length of the background inhomogeneity, and ϵ is a smallness parameter. It can be shown that these new higher order k⊥ρi terms, which are also related to the higher order perturbations of the electrostatic potential ϕ, should have negligible effects on turbulent and neoclassical transport in tokamaks regardless of the form of the background distribution and the amplitude of the perturbation. To address further the issue of a non-Maxwellian plasma, higher order finite Larmor radius terms in the gyrokinetic Poisson’s equation have been studied and shown to be unimportant as well. On the other hand, the terms of o(k⊥2ρi2) and k⊥L∼o(1) can, indeed, have an impact on microturbulence, especially in the linear stage, such as those arising from the difference between the guiding center and the gyrocenter densities due to the presence of the background gradients. These results will be compared to a recent study questioning the validity of the commonly used gyrokinetic equations for long time simulations.
Effect of ion temperature on arbitrary amplitude ion acoustic solitary waves in quantum electron-ion plasmas
Authors: Chatterjee Prasanta , Roy Kaushik , Muniandy Sithi V. , Yap S. L. , Wong C. S.
Published: April 2009

Using Sagdeev’s pseudopotential technique, the effect of ion temperature on the arbitrary amplitude ion acoustic solitary waves in quantum electron-ion plasma is studied. In addition, the effect of ion temperature on the region of existence, as well as on the shape of the solitary waves, is also investigated extensively. It is shown that for large amplitude solitary wave, quantum parameter H does not play any role in determining the region of existence and on the amplitude of the solitary waves. However, H has a significant effect on the width of the solitary wave. It is worth noting that our results are in agreement with previous investigations when the effect of ion temperature is neglected.
Polarimetric detection of laser induced ultrashort magnetic pulses in overdense plasma
Authors: Kahaly Subhendu , Mondal S. , Kumar G. Ravindra , Sengupta S. , Das A. , Kaw P. K.
Published: April 2009

The interaction of intense (∼1016 W cm−2), subpicosecond pulses with solid targets can generate highly directional jets of hot electrons. These electrons can propagate in the solid along with the counterpropagating return shielding currents. The spontaneous magnetic field that is generated by these currents, captures in its time evolution, important information about the dynamics of the complex transport processes. By using a two pulse pump-probe polarimetric technique the temporal evolution of multimegagauss magnetic fields is measured for optically polished BK7 glass targets, each coated with a thin layer of either copper or silver. A simple model is then used for explaining the observations and for deducing quantitative information about the transport of hot electrons.
Effect of concentration on the thermodynamics of sodium chloride aqueous solutions in the supercooled regime
Authors: Corradini D. , Gallo P. , Rovere M.
Published: April 2009

Molecular dynamics simulations are performed on two sodium chloride solutions in TIP4P water with concentrations c=1.36 mol/kg and c=2.10 mol/kg upon supercooling. The isotherms and isochores planes are calculated. The temperature of maximum density line and the limit of mechanical stability line are obtained from the analysis of the thermodynamic planes. The comparison of the results shows that for densities well above the limit of mechanical stability, the isotherms and isochores of the sodium chloride aqueous solution shift to lower pressures upon increasing concentration while the limit of mechanical stability is very similar to that of bulk water for both concentrations. We also find that the temperature of maximum density line shifts to lower pressures and temperatures upon increasing concentration. Indications of the presence of a liquid-liquid coexistence are found for both concentrations.
GaN-based light-emitting diode with textured indium tin oxide transparent layer coated with Al2O3 powder
Authors: Kim T. K. , Kim S. H. , Yang S. S. , Son J. K. , Lee K. H. , Hong Y. G. , Shim K. H. , Yang J. W. , Lim K. Y. , Bae S. J. , Yang G. M.
Published: April 2009

Surface-textured InGaN/GaN light-emitting diodes (LEDs) coated with transparent Al2O3 powder were fabricated by natural lithography combined with inductively coupled plasma etching. For surface texturing, 300 nm size Al2O3 powder is used as an etching mask by simply coating the surface using a spin-coating process. Also, the powders are left on the surface after surface texturing to further increase extraction efficiency. At 20 mA, the light output power of the textured indium tin oxide (ITO) InGaN/GaN LEDs coated with the Al2O3 powder is enhanced by ∼112% compared with the conventional nontextured ITO LED. The enhanced light output power is attributed to the improved extraction efficiency resulting from an overall decrease in the total internal reflection due to the textured surface and the Al2O3 powder coating.
High-speed InGaAs/InP-based single-photon detector with high efficiency
Authors: Xu Lilin , Wu E , Gu Xiaorong , Jian Yi , Wu Guang , Zeng Heping
Published: April 2009

An efficient single-photon detector at telecom wavelength of 1.55 μm was realized with an InGaAs/InP avalanche photodiode at −30 °C. By implementing a short gating pulse and optimizing the self-differencing circuit, a detection efficiency of 29.3% was achieved with an error count probability of 6% at the gating frequency of 200 MHz, paving the way for the high-efficiency and low-noise fast detection of the infrared single photons.
Ab initio calculations of elastic properties of Ru1−xNixAl superalloys
Authors: Bleskov I. D. , Smirnova E. A. , Vekilov Yu. Kh. , Korzhavyi P. A. , Johansson B. , Katsnelson M. , Vitos L. , Abrikosov I. A. , Isaev E. I.
Published: April 2009

Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1−xNixAl alloys. We have found that the elastic constants C′ and C11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru–Ni–Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.
Detection of Ga suboxides and their impact on III-V passivation and Fermi-level pinning
Authors: Hinkle C. L. , Milojevic M. , Brennan B. , Sonnet A. M. , Aguirre-Tostado F. S. , Hughes G. J. , Vogel E. M. , Wallace R. M.
Published: April 2009

The passivation of interface states remains an important problem for III-V based semiconductor devices. The role of the most stable bound native oxides GaOx (0.5≤x≤1.5) is of particular interest. Using monochromatic x-ray photoelectron spectroscopy in conjunction with controlled GaAs(100) and InGaAs(100) surfaces, a stable suboxide (Ga2O) bond is detected at the interface but does not appear to be detrimental to device characteristics. In contrast, the removal of the Ga 3+ oxidation state (Ga2O3) is shown to result in the reduction of frequency dispersion in capacitors and greatly improved performance in III-V based devices.
Doping and characterization of boron atoms in nanocrystalline silicon particles
Authors: Sato Keisuke , Fukata Naoki , Hirakuri Kenji
Published: April 2009

Boron (B) doping into nanocrystalline-silicon (nc-Si) particles was achieved by cosputtering of Si chips/B chips/silica disk targets and subsequent annealing at 1100 °C. The average diameter of B-doped particles was less than 4.3 nm, and the content of B was about 14.3 at. %. The observation of EELS spectrum of B-K edge and x-ray photoelectron spectroscopy spectra of B 1s, and that of B local vibrational peaks and the Fano effect by micro-Raman scattering measurements clearly demonstrate that B atoms were doped and electrically activated in the particles, indicating the formation of electrically active p-type nc-Si particles.
Effect of poloidal inhomogeneity in plasma parameters on edge anomalous transport
Authors: Löchel D. , Tokar M. Z. , Hochbruck M. , Reiser D.
Published: April 2009

It is demonstrated that anomalous transport at the plasma edge in tokamaks is essentially affected by poloidal inhomogeneities in the plasma temperature and density arising, e.g., by the formation of multifaceted asymmetric radiation from the edge at the density limit.
Structures and reactions of methanol molecules on cobalt cluster ions studied by infrared photodissociation spectroscopy
Authors: Hirabayashi Shinichi , Okawa Ryuji , Ichihashi Masahiko , Kawazoe Yoshiyuki , Kondow Tamotsu
Published: April 2009

Structures of methanol molecules chemisorbed on cobalt cluster ions, Con+ (n=2–6), were investigated by infrared photodissociation (IR-PD) spectroscopy in the wavenumber range of 3400–4000 cm−1. All the IR-PD spectra measured exhibit an intense peak in the region of the OH stretching vibration. In the IR-PD spectra of Co2+(CH3OH)2,3 and Co3+(CH3OH)3, weak peaks were observed additionally in the vicinity of 3000 cm−1, being assignable to the CH stretching vibration. The comparison of the experimental results with the calculated ones leads us to conclude that (1) molecularly chemisorbed species, Con+(CH3OH)m (m=1–3), and dissociatively chemisorbed species, Con+(CH3OH)m−1(CH3)(OH), are dominant and (2) the methanol dehydrogenation proceeds via an intermediate, Con+(CH3)(OH).
Improved theoretical approximation for the ion drag force in collisionless plasma with strong ion-grain coupling
Authors: Khrapak S. A. , Nosenko V. , Morfill G. E. , Merlino R.
Published: April 2009

We point out a deficiency in our previous analytic calculation of the ion drag force for conditions of the experiment by Nosenko et al. [Phys. Plasmas 14, 103702 (2007)]. An inaccurate approximation is corrected and the ion drag force is recalculated. The improved model yields better overall agreement with the experimental results as compared to the original calculation.
Disinfection of E. coli by nonthermal microplasma electrolysis in normal saline solution
Authors: Sakiyama Yukinori , Tomai Takaaki , Miyano Masaru , Graves David B.
Published: April 2009

We present a unique method to inactivate microorganisms in 0.9% NaCl solution (normal saline solution) by means of microplasmas. The device consists of a thin titanium wire covered by a glass tube for insulation except the tip and a ground electrode. Application of an asymmetric high-frequency, high voltage results in the formation of microbubbles at both electrodes. Repetitive light emission is observed in the vicinity of the powered electrode. We employed E. coli bacteria to investigate the disinfection efficiency of the device. More than 99.5% of E. coli were deactivated in 180 s. The survival curve showed biphasic behavior.
A novel actuation method of transporting droplets by using electrical charging of droplet in a dielectric fluid
Authors: Jung Yong-Mi , Kang In Seok
Published: April 2009

We evaluate the feasibility of manipulating droplets in two dimensions by exploiting Coulombic forces acting on conductive droplets immersed in a dielectric fluid. When a droplet suspended in an immiscible fluid is located near an electrode under a dc voltage, the droplet can be charged by direct contact, by charge transfer along an electrically conducting path, or by both mechanisms. This process is called electrical charging of droplet (ECOD). This charged droplet may then be transported rapidly by exploiting Coulombic forces. We experimentally demonstrate electrical actuation of a charged droplet by applying voltage sequences. A charged droplet is two dimensionally actuated by following the direction of the electrical field signal. The droplet does not contact the surface of the microfluidic chip when it moves. This characteristic is very advantageous because treatments of the substrate surfaces of microfluidic chip become simpler. In order to test the feasibility of using ECOD in a droplet-based microreactor, electrocoalescence of two oppositely charged droplets is also studied. When two droplets approach each other due to Coulombic attraction, a liquid bridge is formed between them. We postulate that if the applied electric field is weaker than a certain critical level, the two droplets coalesce instantaneously when the charges are exchanged and redistributed through this liquid bridge.
Autonomously motile catalytic nanomotors by bubble propulsion
Authors: Gibbs J. G. , Zhao Y.-P.
Published: April 2009

A bubble propulsion model based on catalyzed hydrogen peroxide decomposition and momentum change via O2 bubbles detaching from the catalytic surface is proposed to explain the autonomous motion of catalytic nanomotors. The propelling force closely depends upon the surface tension of the liquid as well as the bulk concentration of hydrogen peroxide, and the model predictions are supported by the experimental data of Pt-coated spherical silica microbead motors.
Pressure-driven transport of particles through a converging-diverging microchannel
Authors: Ai Ye , Joo Sang W. , Jiang Yingtao , Xuan Xiangchun , Qian Shizhi
Published: April 2009

Pressure-driven transport of particles through a symmetric converging-diverging microchannel is studied by solving a coupled nonlinear system, which is composed of the Navier–Stokes and continuity equations using the arbitrary Lagrangian–Eulerian finite-element technique. The predicted particle translation is in good agreement with existing experimental observations. The effects of pressure gradient, particle size, channel geometry, and a particle’s initial location on the particle transport are investigated. The pressure gradient has no effect on the ratio of the translational velocity of particles through a converging-diverging channel to that in the upstream straight channel. Particles are generally accelerated in the converging region and then decelerated in the diverging region, with the maximum translational velocity at the throat. For particles with diameters close to the width of the channel throat, the usual acceleration process is divided into three stages: Acceleration, deceleration, and reacceleration instead of a monotonic acceleration. Moreover, the maximum translational velocity occurs at the end of the first acceleration stage rather than at the throat. Along the centerline of the microchannel, particles do not rotate, and the closer a particle is located near the channel wall, the higher is its rotational velocity. Analysis of the transport of two particles demonstrates the feasibility of using a converging-diverging microchannel for passive (biological and synthetic) particle separation and ordering.
Molecular orientation of CuPc thin films on C60/Ag(111)
Authors: Huang Han , Chen Wei , Chen Shi , Qi Dong Chen , Gao Xing Yu , Wee Andrew Thye Shen
Published: April 2009

The molecular orientation of copper(II) phthalocyanine (CuPc) thin films on monolayer C60 on Ag(111) was studied by in situ near-edge x-ray absorption fine structure measurements and low-temperature scanning tunneling microscopy. It is found that in densely packed thin films, CuPc molecules adopt a standing-up configuration with the molecular π-plane tilting slightly from the surface normal on monolayer C60.
Electrical breakdown and ultrahigh electrical energy density in poly(vinylidene fluoride-hexafluoropropylene) copolymer
Authors: Zhou Xin , Zhao Xuanhe , Suo Zhigang , Zou Chen , Runt James , Liu Sheng , Zhang Shihai , Zhang Q. M.
Published: April 2009

This paper investigates the electrical breakdown of a polar fluoropolymer, poly(vinylidene fluoride-hexafluoropropylene) which exhibits an exceptionally high discharged electrical energy density (>25 J/cm3). It is shown that above room temperature, the breakdown strength decreases with temperature. It is further shown that such a temperature dependence of breakdown strength is consistent with the electromechanical breakdown model by taking into consideration of the plastic deformation of semicrystalline polymers.
Doping modulation in GaN imaged by cross-sectional scanning tunneling microscopy
Authors: Eisele H. , Ivanova L. , Borisova S. , Dähne M. , Winkelnkemper M. , Ebert Ph.
Published: April 2009

We investigated the imaging mechanisms of a Si doping modulation in GaN by cross-sectional scanning tunneling microscopy (STM). The Si doping modulation gives rise to a voltage and tip dependent height modulation of at least 0.4 Å. The origin of the height modulation in constant-current STM images is traced to two mechanisms. A doping-induced modu-lation of the band edge energies yields a voltage dependent electronic contrast and an additional mechanical relaxation of the doping-induced strain at the cleavage surface is respon-sible for a voltage independent modulation of 0.35 Å.
Comment on “Control of magnetic-field effect on electro-luminescence in Alq3-based organic light emitting diodes” [Appl. Phys. Lett. 88, 123501 (2006)]
Authors: Kalinowski J. , Cocchi M. , Di Marco P. , Fattori V.
Published: April 2009

In a recently published paper by [Odaka et al., Appl. Phys. Lett. 88, 123501 (2006)], the authors explain their experimental observations of a weak magnetic field effect on electroluminescence from Alq3-based light emitting diodes by the magnetic field-induced evolution of singlet-to-triplet spin conversion of loosely bound electron-hole pairs, suggesting the originality of their explanation.
Single nanoparticle alignment by atomic force microscopy indentation
Authors: Shin ChaeHo , Jeon InSu , Jeon SeungHee , Khim Zheong G.
Published: April 2009

Unavoidable bulge formation during an indentation process is a serious obstacle to trapping nanoparticles in dent holes or trenches. We found an easy method of removing polymethyl methacrylate (PMMA) bulges formed during atomic force microscopy indentation. The method allowed the creation of dent holes or trenches in PMMA without bulges, which, using capillary interaction, allowed us to place 40-nm-diameter Au particles at precise locations. Furthermore, we could adjust the gap distance (∼10 nm) between the nanoparticle and the bottom electrode. The method will be helpful in characterizing the nanoparticles and molecules and, ultimately, will help in the development of nanoparitcle- or molecule-attached devices.
Organic manuring for soil biological health and productivity of a wheat - soybean cropping system in the Vertisols of central India
Authors: Behera U. K.
Published: April 2009

Soybean (Glycine max (L.) Merr.)–wheat (Triticum aestivum L.) is the dominant cropping system in the Vertisols of central India due to congenial climate, development of agro-industries, and export opportunities. Both are high-value crops, and raising them using organics may further improve produce quality and help in sustaining long-term productivity of the system. Information is lacking on how to sustain the system with the sole use of organics or biofertilisers in Vertisols. A long-term study was made during 1995–2002 at Indore, India, to evaluate the effectiveness of 3 organic manures [farmyard manure (FYM), poultry manure (PM) and vermicompost (VC) at varying rates] and biofertilisers (Azotobacter + phosphate solubilising bacteria) on productivity, grain quality, soil fertility, and profitability of a wheat–soybean cropping system. Grain yield of wheat was significantly increased with PM at 2.5–10 t/ha or FYM at 10–20 t/ha compared with the control. However, the highest productivity was obtained with PM at 10 t/ha, which even performed better than NPK, indicating that NPK fertilisers alone did not provide adequate and balanced nutrition for potential yield of the crop. Quality parameters of durum wheat, viz. protein content, hectolitre weight and sedimentation value, increased, while yellow berry content decreased significantly with PM at 2.5–10.0 t/ha compared with the control. Soybean yields were significantly influenced by the residual effect of organic manuring treatment applied to wheat. The treatment receiving PM at 10 t/ha produced the highest grain yield of wheat. However, this treatment could not produce a similar response in soybean yield due to production of excessive vegetative growth, adversely affecting grain yield. Superiority of PM over FYM, vermicompost and biofertilisers was evident in the overall profitability of the system. Various soil fertility parameters including chemical and biological properties showed conspicuous improvement over the initial status under the FYM and PM treatments. Microbial biomass C and activities of phosphatase and dehydrogenase were increased significantly with applications of manures. Sustainability yield index was maximum under PM at 5–10 t/ha, followed by NPK. Results suggested that application of PM at 5–10 t/ha to wheat was essential for improving productivity, grain quality, profitability, soil health, and sustainability of a wheat–soybean system.
Spatial and seasonal patterns in climate change, temperatures, and precipitation across the United States
Authors: Portmann Robert W. , Solomon Susan , Hegerl Gabriele C.
Published: April 2009

Changes in climate during the 20th century differ from region to region across the United States. We provide strong evidence that spatial variations in US temperature trends are linked to the hydrologic cycle, and we also present unique information on the seasonal and latitudinal structure of the linkage. We show that there is a statistically significant inverse relationship between trends in daily temperature and average daily precipitation across regions. This linkage is most pronounced in the southern United States (30–40°N) during the May-June time period and, to a lesser extent, in the northern United States (40–50°N) during the July-August time period. It is strongest in trends in maximum temperatures (
T
max
) and 90th percentile exceedance trends (90PET), and less pronounced in the
T
max
10PET and the corresponding
T
min
statistics, and it is robust to changes in analysis period. Although previous studies suggest that areas of increased precipitation may have reduced trends in temperature compared with drier regions, a change in sign from positive to negative trends suggests some additional cause. We show that trends in precipitation may account for some, but not likely all, of the cause point to evidence that shows that dynamical patterns (El Niño/Southern Oscillation, North Atlantic Oscillation, etc.) cannot account for the observed effects during May-June. We speculate that changing aerosols, perhaps related to vegetation changes, and increased strength of the aerosol direct and indirect effect may play a role in the observed linkages between these indices of temperature change and the hydrologic cycle.
Feedback inactivation of D-serine synthesis by NMDA receptor-elicited translocation of serine racemase to the membrane
Authors: Balan Livia , Foltyn Veronika N. , Zehl Martin , Dumin Elena , Dikopoltsev Elena , Knoh Diana , Ohno Yusuke , Kihara Akio , Jensen Ole N. , Radzishevsky Inna S. , Wolosker Herman
Published: April 2009

D-serine is a physiological coagonist of N-methyl D-aspartate receptors (NMDARs) that plays a major role in several NMDAR-dependent events. In this study we investigate mechanisms regulating D-serine production by the enzyme serine racemase (SR). We now report that NMDAR activation promotes translocation of SR to the plasma membrane, which dramatically reduces the enzyme activity. Membrane-bound SR isolated from rat brain is not extracted from the membrane by high detergent and salt concentration, indicating a strong association. Colocalization studies indicate that most membrane-bound SR is located at the plasma membrane and dendrites, with much less SR observed in other types of membrane. NMDAR activation promotes translocation of the cytosolic SR to the membrane, resulting in reduced D-serine synthesis, and this effect is averted by blockade of NMDARs. In primary neuronal cultures, SR translocation to the membrane is blocked by a palmitoylation inhibitor, indicating that membrane binding is mediated by fatty acid acylation of SR. In agreement, we found that SR is acylated in transfected neuroblastoma cells using [
3
H]palmitate or [
3
H]octanoic acid as precursors. In contrast to classical
S
-palmitoylation of cysteines, acylation of SR occurs through the formation of an oxyester bond with serine or threonine residues. In addition, we show that phosphorylation of Thr-227 is also required for steady-state binding of SR to the membrane under basal, nonstimulated condition. We propose that the inhibition of D-serine synthesis caused by translocation of SR to the membrane provides a fail-safe mechanism to prevent NMDAR overactivation in vicinal cells or synapses.
Epithelial sodium channel regulated by differential composition of a signaling complex
Authors: Soundararajan Rama , Melters Daniël , Shih I-Chia , Wang Jian , Pearce David
Published: April 2009

Hormonal control of transepithelial sodium (Na
+
) transport utilizes phosphatidylinositide 3′-kinase (PI3K) and Raf–MAPK/ERK kinase (MEK)–ERK-dependent signaling pathways, which impact numerous cell functions. How signals transmitted by these pathways are sorted and appropriately transmitted to alter Na
+
transport without altering other physiologic processes is not well understood. Here, we report the identification of a signaling complex that selectively modulates the cell surface expression of the epithelial sodium channel (ENaC), an ion channel that is essential for fluid and electrolyte balance in mammals. Raf-1 and the ubiquitin ligase, Nedd4-2, are constitutively-expressed inhibitory components of this ENaC regulatory complex, which interact with, and decrease the expression of, cell surface ENaC. The activities of Nedd4-2 and Raf-1 are inhibited cooperatively by the PI3K-dependent kinase serum- and glucocorticoid-induced kinase 1 (SGK1), and the Raf-1-interacting protein glucocorticoid-induced leucine zipper (GILZ1), which are aldosterone-stimulated components of the complex. Together, SGK1 and GILZ1 synergistically stimulate ENaC cell surface expression. Interestingly, GILZ1 and SGK1 do not have synergistic, and in fact have opposite, effects on an unrelated activity, FKHRL1-driven gene transcription. Together, these data suggest that GILZ1 and SGK1 provide a physical and functional link between the PI3K- and Raf-1-dependent signaling modules and represent a unique mechanism for specifically controlling Na
+
transport without inappropriately activating other cell functions.
Neural correlates of admiration and compassion
Authors: Immordino-Yang Mary Helen , McColl Andrea , Damasio Hanna , Damasio Antonio
Published: April 2009

In an fMRI experiment, participants were exposed to narratives based on true stories designed to evoke admiration and compassion in 4 distinct categories: admiration for virtue (AV), admiration for skill (AS), compassion for social/psychological pain (CSP), and compassion for physical pain (CPP). The goal was to test hypotheses about recruitment of homeostatic, somatosensory, and consciousness-related neural systems during the processing of pain-related (compassion) and non-pain-related (admiration) social emotions along 2 dimensions: emotions about other peoples' social/psychological conditions (AV, CSP) and emotions about others' physical conditions (AS, CPP). Consistent with theoretical accounts, the experience of all 4 emotions engaged brain regions involved in interoceptive representation and homeostatic regulation, including anterior insula, anterior cingulate, hypothalamus, and mesencephalon. However, the study also revealed a previously undescribed pattern within the posteromedial cortices (the ensemble of precuneus, posterior cingulate cortex, and retrosplenial region), an intriguing territory currently known for its involvement in the default mode of brain operation and in self-related/consciousness processes: emotions pertaining to social/psychological and physical situations engaged different networks aligned, respectively, with interoceptive and exteroceptive neural systems. Finally, within the anterior insula, activity correlated with AV and CSP peaked later and was more sustained than that associated with CPP. Our findings contribute insights on the functions of the posteromedial cortices and on the recruitment of the anterior insula in social emotions concerned with physical versus psychological pain.
IFN-γ receptor signaling mediates spinal microglia activation driving neuropathic pain
Authors: Tsuda Makoto , Masuda Takahiro , Kitano Junko , Shimoyama Hiroshi , Tozaki-Saitoh Hidetoshi , Inoue Kazuhide
Published: April 2009

Neuropathic pain, a highly debilitating pain condition that commonly occurs after nerve damage, is a reflection of the aberrant excitability of dorsal horn neurons. This pathologically altered neurotransmission requires a communication with spinal microglia activated by nerve injury. However, how normal resting microglia become activated remains unknown. Here we show that in naive animals spinal microglia express a receptor for the cytokine IFN-γ (IFN-γR) in a cell-type-specific manner and that stimulating this receptor converts microglia into activated cells and produces a long-lasting pain hypersensitivity evoked by innocuous stimuli (tactile allodynia, a hallmark symptom of neuropathic pain). Conversely, ablating IFN-γR severely impairs nerve injury-evoked microglia activation and tactile allodynia without affecting microglia in the contralateral dorsal horn or basal pain sensitivity. We also find that IFN-γ-stimulated spinal microglia show up-regulation of Lyn tyrosine kinase and purinergic P2X
4
receptor, crucial events for neuropathic pain, and genetic approaches provide evidence linking these events to IFN-γR-dependent microglial and behavioral alterations. These results suggest that IFN-γR is a key element in the molecular machinery through which resting spinal microglia transform into an activated state that drives neuropathic pain.
Mangroves protected villages and reduced death toll during Indian super cyclone
Authors: Das Saudamini , Vincent Jeffrey R.
Published: April 2009

Protection against coastal disasters has been identified as an important service of mangrove ecosystems. Empirical studies on this service have been criticized, however, for using small samples and inadequately controlling for confounding factors. We used data on several hundred villages to test the impact of mangroves on human deaths during a 1999 super cyclone that struck Orissa, India. We found that villages with wider mangroves between them and the coast experienced significantly fewer deaths than ones with narrower or no mangroves. This finding was robust to the inclusion of a wide range of other variables to our statistical model, including controls for the historical extent of mangroves. Although mangroves evidently saved fewer lives than an early warning issued by the government, the retention of remaining mangroves in Orissa is economically justified even without considering the many benefits they provide to human society besides storm-protection services.
Complexity in bacterial cell–cell communication: Quorum signal integration and subpopulation signaling in the
Bacillus subtilis
phosphorelay
Authors: Bischofs Ilka B. , Hug Joshua A. , Liu Aiwen W. , Wolf Denise M. , Arkin Adam P.
Published: April 2009

A common form of quorum sensing in Gram-positive bacteria is mediated by peptides that act as phosphatase regulators (Phr) of receptor aspartyl phosphatases (Raps). In
Bacillus subtilis
, several Phr signals are integrated in sporulation phosphorelay signal transduction. We theoretically demonstrate that the phosphorelay can act as a computational machine performing a sensitive division operation of kinase-encoded signals by quorum-modulated Rap signals, indicative of cells computing a “food per cell” estimate to decide whether to enter sporulation. We predict expression from the
rapA-phrA
operon to bifurcate as relative environmental signals change in a developing population. We experimentally observe that the
rapA-phrA
operon is heterogeneously induced in sporulating microcolonies. Uninduced cells sporulate rather synchronously early on, whereas the RapA/PhrA subpopulation sporulates less synchronously throughout later stationary phase. Moreover, we show that cells sustain PhrA expression during periods of active growth. Together with the model, these findings suggest that the phosphorelay may normalize environmental signals by the size of the (sub)population actively competing for nutrients (as signaled by PhrA). Generalizing this concept, the various Phrs could facilitate subpopulation communication in dense isogenic communities to control the physiological strategies followed by differentiated subpopulations by interpreting (environmental) signals based on the spatiotemporal community structure.
Antigen-specific Vγ2Vδ2 T effector cells confer homeostatic protection against pneumonic plaque lesions
Authors: Huang Dan , Chen Crystal Y. , Ali Zahida , Shao Lingyun , Shen Ling , Lockman Hank A. , Barnewall Roy E. , Sabourin Carol , Eestep James , Reichenberg Armin , Hintz Martin , Jomaa Hassan , Wang Richard , Chen Zheng W.
Published: April 2009

The possibility that Vγ2Vδ2 T effector cells can confer protection against pulmonary infectious diseases has not been tested. We have recently demonstrated that single-dose (
E
)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) plus IL-2 treatment can induce prolonged accumulation of Vγ2Vδ2 T effector cells in lungs. Here, we show that a delayed HMBPP/IL-2 administration after inhalational
Yersinia pestis
infection induced marked expansion of Vγ2Vδ2 T cells but failed to control extracellular plague bacterial replication/infection. Surprisingly, despite the absence of infection control, expansion of Vγ2Vδ2 T cells after HMBPP/IL-2 treatment led to the attenuation of inhalation plague lesions in lungs. Consistently, HMBPP-activated Vγ2Vδ2 T cells accumulated and localized in pulmonary interstitials surrounding small blood vessels and airway mucosa in the lung tissues with no or mild plague lesions. These infiltrating Vγ2Vδ2 T cells produced FGF-7, a homeostatic mediator against tissue damages. In contrast, control macaques treated with glucose plus IL-2 or glucose alone exhibited severe hemorrhages and necrosis in most lung lobes, with no or very few Vγ2Vδ2 T cells detectable in lung tissues. The findings are consist with the paradigm that circulating Vγ2Vδ2 T cells can traffic to lungs for homeostatic protection against tissue damages in infection.
Phytochromes promote seedling light responses by inhibiting four negatively-acting phytochrome-interacting factors
Authors: Shin Jieun , Kim Keunhwa , Kang Hyojin , Zulfugarov Ismayil S. , Bae Gabyong , Lee Choon-Hwan , Lee Doheon , Choi Giltsu
Published: April 2009

PIF3 is a phytochrome-interacting basic helix–loop–helix transcription factor that negatively regulates light responses, including hypocotyl elongation, cotyledon opening, and hypocotyl negative gravitropism. However, the role of PIF3 in chlorophyll biosynthesis has not been clearly defined. Here, we show that PIF3 also negatively regulates chlorophyll biosynthesis by repressing biosynthetic genes in the dark. Consistent with the gene expression patterns, the etiolated
pif3
mutant accumulated a higher amount of protochlorophyllide and was bleached severely when transferred into light. The photobleaching phenotype of
pif3
could be suppressed by the
gun5
mutation and mimicked by overexpression of
GUN5
. When 4 negative phytochrome-interacting protein genes (
PIF1
,
PIF3
,
PIF4
, and
PIF5
) were mutated, the resulting quadruple mutant seedlings displayed constitutive photomorphogenic phenotypes, including short hypocotyls, open cotyledons, and disrupted hypocotyl gravitropism in the dark. Microarray analysis further confirmed that the dark-grown quadruple mutant has a gene expression pattern similar to that of red light-grown WT. Together, our data indicate that 4 phytochrome-interacting proteins are required for skotomorphogenesis and phytochromes activate photomorphogenesis by inhibiting these factors.
Neandertal birth canal shape and the evolution of human childbirth
Authors: Weaver Timothy D. , Hublin Jean-Jacques
Published: April 2009

Childbirth is complicated in humans relative to other primates. Unlike the situation in great apes, human neonates are about the same size as the birth canal, making passage difficult. The birth mechanism (the series of rotations that the neonate must undergo to successfully negotiate its mother's birth canal) distinguishes humans not only from great apes, but also from lesser apes and monkeys. Tracing the evolution of human childbirth is difficult, because the pelvic skeleton, which forms the margins of the birth canal, tends to survive poorly in the fossil record. Only 3 female individuals preserve fairly complete birth canals, and they all date to earlier phases of human evolution. Here we present a virtual reconstruction of a female Neandertal pelvis from Tabun, Israel. The size of Tabun's reconstructed birth canal indicates that childbirth was about as difficult in Neandertals as in present-day humans, but the canal's shape indicates that Neandertals had a more primitive birth mechanism. A significant shift in childbirth apparently occurred quite late in human evolution, during the last few hundred thousand years. Such a late shift underscores the uniqueness of human childbirth and the divergent evolutionary trajectories of Neandertals and the lineage leading to present-day humans.
PhycomycesMADB interacts with MADA to form the primary photoreceptor complex for fungal phototropism
Authors: Sanz Catalina , Rodríguez-Romero Julio , Idnurm Alexander , Christie John M. , Heitman Joseph , Corrochano Luis M. , Eslava Arturo P.
Published: April 2009

The fungusPhycomyces blakesleeanusreacts to environmental signals, including light, gravity, touch, and the presence of nearby objects, by changing the speed and direction of growth of its fruiting body (sporangiophore). Phototropism, growth toward light, shares many features in fungi and plants but the molecular mechanisms remain to be fully elucidated.Phycomycesmutants with altered phototropism were isolated ≈40 years ago and found to have mutations in themadgenes. All of the responses to light inPhycomycesrequire the products of themadAandmadBgenes. We showed thatmadAencodes a protein similar to theNeurosporablue-light photoreceptor, zinc-finger protein WC-1. We show here thatmadBencodes a protein similar to theNeurosporazinc-finger protein WC-2. MADA and MADB interact to form a complex in yeast 2-hybrid assays and when coexpressed inE. coli, providing evidence that phototropism and other responses to light are mediated by a photoresponsive transcription factor complex. ThePhycomycesgenome contains 3 genes similar towc-1, and 4 genes similar towc-2, many of which are regulated by light in amadAormadBdependent manner. We did not detect any interactions between additional WC proteins in yeast 2-hybrid assays, which suggest that MADA and MADB form the major photoreceptor complex inPhycomyces. However, the presence of multiplewcgenes inPhycomycesmay enable perception across a broad range of light intensities, and may provide specialized photoreceptors for distinct photoresponses.
Mechanism of drug inhibition and drug resistance of influenza A M2 channel
Authors: Pielak Rafal M. , Schnell Jason R. , Chou James J.
Published: April 2009

The influenza A virus M2 proton channel equilibrates pH across the viral membrane during entry and across the trans-Golgi membrane of infected cells during viral maturation. It is an important target of adamantane-family antiviral drugs, but drug resistance has become a critical problem. Two different sites for drug interaction have been proposed. One is a lipid-facing pocket between 2 adjacent transmembrane helices (around Asp-44), at which the drug binds and inhibits proton conductance allosterically. The other is inside the pore (around Ser-31), at which the drug directly blocks proton passage. Here, we describe structural and functional experiments on the mechanism of drug inhibition and resistance. The solution structure of the S31N drug-resistant mutant of M2, a mutant of the highly pathogenic avian influenza subtype H5N1, shows that replacing Ser-31 with Asn has little effect on the structure of the channel pore, but dramatically reduces drug binding to the allosteric site. Mutagenesis and liposomal proton flux assays show that replacing the key residue (Asp-44) in the lipid-facing binding pocket with Ala has a dramatic effect on drug sensitivity, but that the channel remains fully drug sensitive when replacing Ser-31 with Ala. Chemical cross-linking studies indicate an inverse correlation between channel stability and drug resistance. The lipid-facing pocket contains residues from 2 adjacent channel-forming helices. Therefore, it is present only when the helices are tightly packed in the closed conformation. Thus, drug-resistant mutants impair drug binding by destabilizing helix–helix assembly.
On the Emergence of Personal Infinitives in the History of Spanish
Authors: Sitaridou Ioanna
Published: April 2009

The aim of this article is twofold: (a) To evaluate the learned source for the rise of personal infinitives in the history of Spanish, and (b) to address the issue of the origin of personal infinitives from the perspective of language acquisition. It is argued, by means of novel empirical evidence derived from the Corpus del Español, that the Latin Accusativus cum Infinitivo source is responsible for the personal infinitive in complement position in Old Castilian (in line with Pountain 1998). However, this learned source is not the source of the Modern Spanish personal infinitive in adjunct position. For the latter, an acquisitional scenario is put forward whereby changes in the primary linguistic data (cf. Lightfoot 1999) made adjunct personal infinitives possible.