bluuebunny/crossref_metadata_2025 huggingface dataset:
Time‐lapse geophysical imaging of soil moisture dynamics in tropical deltaic soils: An aid to interpreting hydrological and geochemical processes
Authors: Robinson D. A. , Lebron I. , Kocar B. , Phan K. , Sampson M. , Crook N. , Fendorf S.
Published: March 2009

A fundamental, and often intriguing question, in hydrology is “where does the water go?” This becomes particularly difficult to observe when water arrives at the ground surface and infiltrates into soils. The development of rapid, campaign‐style imaging methods that do not need to be left in situ are therefore of great interest in tracking subsurface hydrological redistribution. We present a novel geophysical imaging approach identifying spatiotemporal variation consistent with soil water redistribution in a tropical deltaic soil. The intention is to provide additional insight into spatiotemporal soil hydrological/biogeochemical processes. The bulk soil electrical conductivity response (ECa) is primarily controlled by the clay content and type, the ions retained in the soil solution (ECe), and the soil water content (θ). Clay content can be assumed to be temporally static, whereas θ and ECeare temporally dynamic. By imaging over time, we can attempt to tease apart these contributing factors. In nonsaline soils θ is the major contributor to temporal changes in ECa. By exploiting an intensive rainfall event (75 mm), with time series spatial ECameasurements, before and after the event, we were able to identify zones of water depletion and accumulation and to provide an indication of the time required for the soil to return to its prior state. In addition, locations with more clay and salts were identified through response surface‐directed soil sampling. We found important spatiotemporal variation across the level 4 ha field site that from visual inspection appeared uniform.
Genesis of tropical cyclone Nargis revealed by multiple satellite observations
Authors: Kikuchi Kazuyoshi , Wang Bin , Fudeyasu Hironori
Published: March 2009

Tropical cyclone (TC) Nargis recently battered Myanmar on May 2 2008 is one of the most deadly tropical storms in history. Nargis was initiated by an abnormally strong intraseasonal westerly event associated with Madden‐Julian oscillation (MJO) in the eastern Indian Ocean. An incipient cyclonic disturbance emerged as an emanation of Rossby wave‐induced vortex when the intraseasonal convective anomaly reached the Maritime Continent. The northeastward movement of MJO convection facilitated further development of the disturbance. The incipient disturbance became a tropical disturbance (TD) with a central warm‐core structure on April 26. The further development from the TD to TC formation on April 28 is characterized by two distinctive stages: a radial contraction followed by a rapid intensification. The processes responsible for contraction and rapid intensification are discussed by diagnosis of multiple satellite data. This proposed new scenario is instrumental for understanding how a major TC develops in the northern Indian Ocean.
Predators promote defence of rhizosphere bacterial populations by selective feeding on non-toxic cheaters
Authors: Jousset Alexandre , Rochat Laurène , Péchy-Tarr Maria , Keel Christoph , Scheu Stefan , Bonkowski Michael
Published: March 2009

Soil pseudomonads increase their competitiveness by producing toxic secondary metabolites, which inhibit competitors and repel predators. Toxin production is regulated by cell–cell signalling and efficiently protects the bacterial population. However, cell communication is unstable, and natural populations often contain signal blind mutants displaying an altered phenotype defective in exoproduct synthesis. Such mutants are weak competitors, and we hypothesized that their fitness depends on natural communities on the exoproducts of wild-type bacteria, especially defence toxins. We established mixed populations of wild-type and signal blind, non-toxic gacS-deficient mutants of Pseudomonas fluorescens CHA0 in batch and rhizosphere systems. Bacteria were grazed by representatives of the most important bacterial predators in soil, nematodes (Caenorhabditis elegans) and protozoa (Acanthamoeba castellanii). The gacS mutants showed a negative frequency-dependent fitness and could reach up to one-third of the population, suggesting that they rely on the exoproducts of the wild-type bacteria. Both predators preferentially consumed the mutant strain, but populations with a low mutant load were resistant to predation, allowing the mutant to remain competitive at low relative density. The results suggest that signal blind Pseudomonas increase their fitness by exploiting the toxins produced by wild-type bacteria, and that predation promotes the production of bacterial defence compounds by selectively eliminating non-toxic mutants. Therefore, predators not only regulate population dynamics of soil bacteria but also structure the genetic and phenotypic constitution of bacterial communities.
Rapid Reversal of Anticoagulation Reduces Hemorrhage Volume in a Mouse Model of Warfarin-Associated Intracerebral Hemorrhage
Authors: Foerch Christian , Arai Ken , Van Cott Elizabeth Merrill , van Leyen Klaus , Lo Eng H
Published: March 2009

Warfarin-associated intracerebral hemorrhage (W-ICH) is a severe type of stroke. There is no consensus on the optimal treatment for W-ICH. Using a mouse model, we tested whether the rapid reversal of anticoagulation using human prothrombin complex concentrate (PCC) can reduce hemorrhagic blood volume. Male CD-1 mice were treated with warfarin (2 mg/kg over 24 h), resulting in a mean (± s.d.) International Normalized Ratio of 3.5 ± 0.9. First, we showed that an intravenous administration of human PCC rapidly reversed anticoagulation in mice. Second, a stereotactic injection of collagenase was administered to induce hemorrhage in the right striatum. Forty-five minutes later, the animals were randomly treated with PCC (100 U/kg) or saline IV ( n = 12 per group). Twenty-four hours after hemorrhage induction, hemorrhagic blood volume was quantified using a photometric hemoglobin assay. The mean hemorrhagic blood volume was reduced in PCC-treated animals (6.5 ± 3.1 μL) compared with saline controls (15.3 ± 11.2 μL, P = 0.015). In the saline group, 45% of the mice developed large hematomas (i.e., > 15 μL). In contrast, such extensive lesions were never found in the PCC group. We provide experimental data suggesting PCC to be an effective acute treatment for W-ICH in terms of reducing hemorrhagic blood volume. Future studies are needed to assess the therapeutic potential emerging from our finding for human W-ICH.
Imaging capabilities of etched (100) and (210) garnet films
Authors: Tkachuk S. , Bowen D. , Krafft C. , Mayergoyz I. D.
Published: March 2009

Imaging capabilities of etched (100) and (210) oriented garnet films are studied and compared. It is demonstrated that the etching of out-of-plane (100) garnet films may result in drastic reduction in saturation fields. Concurrently, the appreciable increase in contrast and resolution of images produced by the etched films has been observed.
Thermomagnetic properties of single crystal Ni54Fe19Ga27 Heusler alloys
Authors: Basso Vittorio , Balma Davide , Sasso Carlo P. , Küpferling Michaela , Vasiliev Alexander , Chumlyakov Yuri
Published: March 2009

Thermomagnetic properties of off-stoichiometric Ni54Fe19Ga27 Heusler alloys are measured by a laboratory differential scanning calorimeter employing Peltier cells and working under magnetic field. We find that the transition temperature from martensite (M) to austenite (A) is TM→A=5.3 °C and from A to M is TA→M=0.2 °C with a thermal hysteresis of 5.1 °C. The entropy change associated with the first order transformation is 15 J kg−1 K−1. By direct measurement and by Clausius–Clapeyron equation, we find that the effect of the magnetic field is a shift of transition temperatures of 0.2 K T−1.
Cr-doping effect on the orbital fluctuation of heavily doped Nd1−xSrxMnO3 (x≈0.625)
Authors: Tasaki R. , Fukushima S. , Akaki M. , Akahoshi D. , Kuwahara H.
Published: March 2009

We have investigated the Cr-doping effect of Nd0.375Sr0.625MnO3 near the phase boundary between the x2-y2 and 3z2-r2 orbital-ordered states, where a ferromagnetic correlation and concomitant large magnetoresistance are observed owing to orbital fluctuation. Cr-doping steeply suppresses the ferromagnetic correlation and magnetoresistance in Nd0.375Sr0.625Mn1−yCryO3 with 0≤y≤0.05, while they reappear in 0.05<y≤0.10. Such a re-entrant behavior implies that a phase boundary is located at y=0.05, or a phase crossover occurs across y=0.05.
Effects of pinning defects on current-perpendicular-to-plane magnetic recording heads
Authors: Chen Laurence , Liu Feng , Stoev Kroum , Li Shaoping , Ho Michael , Mao Sining
Published: March 2009

Effects of pining defects (PDs) on performance of magnetic recording reader are studied micromagnetically. The pinning defects could be present in antiferromagnet (AFM) and synthetic AFM. Presence of pinning defects results in nonuniform pinned layer rotation at parallel (P) state as well as transfer curve (TC) artifacts at antiparallel (AP) state. The high field property, especially rolling off of TC in AP state, is also associated with different types of pinning defects. Time domain baseline popping noise as a result of PDs has been captured in thermal Landau–Lifshitz–Gilbert simulation, which is caused by switching of local magnetic states as a result of either AP pinning spot or P exchange coupling spots with certain dispersion.
Peculiar features of electron spin resonance spectra in (Ca,Na)-doped lanthanum manganites
Authors: Tovstolytkin A. I. , Pogorily A. M. , Podyalovskii D. I.
Published: March 2009

Analysis of the ESR spectra for powdered samples of (Ca,Na)-doped manganites is performed in the temperature range 220–320K. It is shown that the samples under investigation are characterized by a broadened para-to ferromagnetic transition and complicated spectra within the transitional region. It is concluded that a satisfactory interpretation of the resonance data within the transitional region is possible only if the interference of coexisting phases is taken into account. Under these conditions, the resonance field for the paramagnetic phase is shown to increase with decreasing temperature, while that for the ferromagnetic phase first decreases and then approaches a value characteristic of the uniformly magnetized ferromagnetic sample. It is noted that the results obtained are in compliance with those predicted theoretically for spherical particles containing a mixture of the paramagnetic and ferromagnetic phases.
The effect of n-H2 impurity on the heat capacity of solid Ne
Authors: Bagatskii M. I. , Minchina I. Ya. , Parbuzin V. S.
Published: March 2009

The alloy Ne-5.1% n-H2 is investigated calorimetrically under equilibrium vapor pressure in an interval of 0.9–25K. The magnitude and temperature dependence of the heat capacity Csol(T) of the alloy at T=11–20K are found to be strongly dependent on the conditions of sample preparation. The temperature dependence of Csol(T) for the sample prepared in a calorimeter by direct condensation of a gas mixture at T≈15K exhibits a smeared maximum near the triple-point temperature of hydrogen and a phase transition at T=17.1K. The detected features of Csol(T) indicate that preparation of solid Ne–n-H2 from the gas phase leads to the formation of a long-lived nonequilibrium phase of Ne with high H2 concentrations and a small portion of H2 inclusions with low Ne concentrations. The phase transition is caused by decomposition of this phase. The phase does not recover on cooling of the sample after the phase transition. It is found that the rate of ortho-para conversion of the H2 molecules in the Ne–n-H2 solid solutions is higher than in solid H2.
Theoretical model for the experimental magnetization data from the layered III-VI diluted magnetic semiconductor In1-xMnxSe (x=0.014 & 0.027)
Authors: Meda D. , Blackburn J. H. , Maxwell L. , Garner J. , Pekarek T. M. , Miotkowski I. , Ramdas A. K.
Published: March 2009

The magnetization of In1-xMnxSe is calculated and measured from 140 to 400 K in magnetic fields up to 7 T for two crystals with concentrations x=0.014 and 0.027. The Mn ions enter the InSe bulk crystal substitutionally at the In lattice site and are responsible for the observed magnetization of the sample. A singlet model of isolated Mn ions with a spin-orbit coupling parameter of 38 cm−1 fits the experimental data from two different concentration samples for temperatures ranging from 140 to 400 K in fields up to 7 T. This agreement between the experimental magnetization and the theoretical magnetization for In1-xMnxSe expands our theoretical understanding of the III-VI diluted magnetic semiconductor (DMS) by adding a Se-based system and complements previous agreement reported for only two other III-VI DMS (Ga1-xMnxS and In1-xMnxS).
Internal state populations and velocity distributions of monatomic species ejected after the 1064 nm laser irradiation of barium
Authors: Rossa Maximiliano , Rinaldi Carlos A. , Ferrero Juan C.
Published: March 2009

The plumes accompanying 1064 nm nanosecond pulsed laser ablation of barium in vacuum at three moderate incident laser fluences in the range of 5.3–10.8 J/cm2 have been studied using both wavelength and time resolved optical emission spectroscopy and time-of-flight laser-induced fluorescence. Neutral atoms and both singly and doubly charged monatomic cations in excited states up to near the corresponding ionization limits are identified in the optical emission spectra. The population distributions of low-lying (≤1.41 eV) “dark” states of Ba atoms measured by laser-induced fluorescence revel that the metastable D3J and D12 abundances in the plume are higher than predictions based on assuming a Boltzmann distribution. The D3J and D12 populations are seen, respectively, to decrease slightly and nearly no vary with raising fluence, which contrasts with the increasing trend that is observed in the ground-state Ba(S10) population. At all fluences, the time-of-flight distributions of the whole dark states and of various of the emitting levels are bimodal and well described by Maxwell–Boltzmann and shifted Maxwell–Boltzmann velocity functions, respectively, with different average translational temperatures ⟨T⟩ for each state. The ⟨T⟩ values for the dark states are insensitive to the fluence, while for all emitting species marked variations of ⟨T⟩ with fluence are found. These observations have been rationalized in terms of material ejection from the target being dominated by a phase explosion mechanism, which is the main contributor to the Ba(S10) population. Thermionic emission from the target surface can also release initial densities of free electrons and cations which, at the prevailing irradiances, will arguably interact with the incident laser radiation by inverse bremsstrahlung, leading to further excitation and ionization of the various plume species. Such a heating mechanism ensures that the energy injected to the plume will alter the propagation velocities of the primary inverse bremsstrahlung absorbers, i.e., cations, to a major extent than those of neutral atoms with increasing fluence. Electron-ion recombination occurring early in the plume expansion can lead to the generation of both neutral and ionic species in a manifold of long-lived Rydberg states, from which a radiative cascade will likely ensue. The distinct fluence dependences of the Ba(D3J) and Ba(D12) populations and velocity distributions show up the major complexity that distinguishes their populating mechanisms with respect to the remaining species.
The static-exchange electron-water pseudopotential, in conjunction with a polarizable water model: A new Hamiltonian for hydrated-electron simulations
Authors: Jacobson Leif D. , Williams Christopher F. , Herbert John M.
Published: March 2009

Previously, Turi and Borgis [J. Chem. Phys. 117, 6186 (2002)] parametrized an electron-water interaction potential, intended for use in simulations of hydrated electrons, by considering H2O− in the “static exchange” (essentially, frozen-core Hartree–Fock) approximation, then applying an approximate Phillips–Kleinman procedure to construct a one-electron pseudopotential representing the electron-water interaction. To date, this pseudopotential has been used exclusively in conjunction with a simple point charge water model that is parametrized for bulk water and yields poor results for small, neutral water clusters. Here, we extend upon the work of Turi and Borgis by reparametrizing the electron-water pseudopotential for use with the AMOEBA water model, which performs well for neutral clusters. The result is a one-electron model Hamiltonian for (H2O)n−, in which the one-electron wave function polarizes the water molecules, and vice versa, in a fully self-consistent fashion. The new model is fully variational and analytic energy gradients are available. We have implemented the new model using a modified Davidson algorithm to compute eigenstates, with the unpaired electron represented on a real-space grid. Comparison to ab initio electronic structure calculations for (H2O)n− cluster isomers ranging from n=2 to n=35 reveals that the new model is significantly more accurate than the Turi–Borgis model, for both relative isomer energies and for vertical electron detachment energies. Electron-water polarization interactions are found to be much more significant for cavity states of the unpaired electron than for surface states.
Defect evolution and hydrodynamic effects in lamellar ordering process of two-dimensional quenched block copolymers
Authors: Song Kai-Xu , Sun Zhao-Yan , An Li-Jia
Published: March 2009

The effects of hydrodynamic interactions on the lamellar ordering process for two-dimensional quenched block copolymers in the presence of extended defects and the topological defect evolutions in lamellar ordering process are numerically investigated by means of a model based on lattice Boltzmann method and self-consistent field theory. By observing the evolution of the average size of domains, it is found that the domain growth is faster with stronger hydrodynamic effects. The morphological patterns formed also appear different. To study the defect evolution, a defect density is defined and is used to explore the defect evolutions in lamellar ordering process. Our simulation results show that the hydrodynamics effects can reduce the density of defects. With our model, the relations between the Flory–Huggins interaction parameter χ, the length of the polymer chains N, and the defect evolutions are studied. It is found that χN is an important parameter for defect evolutions. Furthermore, the evolution behavior of the defect densities and the average size of domains are compared and the differences are discussed.
Impact of laser-accelerated micron-size projectile on dense plasma
Authors: Wang J. W. , Yu Wei , Lei A. L. , Yu M. Y. , Cai H. B. , Wang Xin , Chen J. , Wong A. Y.
Published: March 2009

The impact of a laser-accelerated micron-size projectile on a dense plasma target is studied using two-dimensional particle-in-cell simulations. The projectile is first accelerated by an ultraintense laser. It then impinges on the dense plasma target and merges with the latter. Part of the kinetic energy of the laser-accelerated ions in the projectile is deposited in the fused target, and an extremely high concentration of plasma ions with a mean kinetic energy needed for fusion reaction is induced. The interaction is thus useful for laser-driven impact fusion and as a compact neutron source.
Effect of Al-diffusion-induced positive flatband voltage shift on the electrical characteristics of Al-incorporated high-k metal-oxide-semiconductor field-effective transistor
Authors: Wang Wenwu , Akiyama Koji , Mizubayashi Wataru , Nabatame Toshihide , Ota Hiroyuki , Toriumi Akira
Published: March 2009

We systematically studied what effect Al diffusion from high-k dielectrics had on the flatband voltage (Vfb) of Al-incorporated high-k gate stacks. An anomalous positive shift fin Vfb with the decreasing equivalent oxide thickness (EOT) of high-k gate stacks is reported. As the SiO2 interfacial layer is aggressively thinned in Al-incorporated HfxAl1−xOy gate stacks with a metal-gate electrode, the Vfb first lies on the well known linear Vfb-EOT plot and deviates toward the positive-voltage direction (Vfb roll-up), followed by shifting toward negative voltage (Vfb roll-off). We demonstrated that the Vfb roll-up behavior remarkably decreases the threshold voltage (Vth) of p-type metal-oxide-semiconductor field-effect transistors (p-MOSFETs), and does not cause severe degradation in the characteristics of hole mobility. The Vfb roll-up behavior, which is independent of gate materials but strongly dependent on high-k dielectrics, was ascribed to variations in fixed charges near the SiO2/Si interface, which are caused by Al diffusion from HfxAl1−xOy through SiO2 to the SiO2/Si interface. These results indicate that anomalous positive shift in Vfb, i.e., Vfb roll-up, should be taken into consideration in quantitatively adjusting Vfb in thin EOT regions and that it could be used to further tune Vth in p-MOSFETs.
Polarization labeling spectroscopy of highly excited Π1 and Σ1+ states in NaLi
Authors: Bang Nguyen Huy , Grochola A. , Jastrzebski W. , Kowalczyk P.
Published: March 2009

Two previously unknown Π1 states and one Σ1+ state of NaLi are experimentally investigated in the energy region of 34 000–36 000 cm−1 above the bottom of the molecular ground state potential well by using polarization labeling spectroscopy technique. Potential energy curves are deduced for all three states from the observed rovibrational levels. The identity of the observed states is discussed in relation with the recently published theoretical calculations on electronic structure of NaLi by Petsalakis et al. [J. Chem. Phys. 129, 054306 (2008)] and Mabrouk and Berriche [J. Phys. B41, 155101 (2008)].
Clarifications to the limitations of the s-α equilibrium model for gyrokinetic computations of turbulence
Authors: Lapillonne X. , Brunner S. , Dannert T. , Jolliet S. , Marinoni A. , Villard L. , Görler T. , Jenko F. , Merz F.
Published: March 2009

In the context of gyrokinetic flux-tube simulations of microturbulence in magnetized toroidal plasmas, different treatments of the magnetic equilibrium are examined. Considering the Cyclone DIII-D base case parameter set [Dimits et al., Phys. Plasmas 7, 969 (2000)], significant differences in the linear growth rates, the linear and nonlinear critical temperature gradients, and the nonlinear ion heat diffusivities are observed between results obtained using either an s-α or a magnetohydrodynamic (MHD) equilibrium. Similar disagreements have been reported previously [Redd et al., Phys. Plasmas 6, 1162 (1999)]. In this paper it is shown that these differences result primarily from the approximation made in the standard implementation of the s-α model, in which the straight field line angle is identified to the poloidal angle, leading to inconsistencies of order ε (ε=a/R is the inverse aspect ratio, a the minor radius and R the major radius). An equilibrium model with concentric, circular flux surfaces and a correct treatment of the straight field line angle gives results very close to those using a finite ε, low β MHD equilibrium. Such detailed investigation of the equilibrium implementation is of particular interest when comparing flux tube and global codes. It is indeed shown here that previously reported agreements between local and global simulations in fact result from the order ε inconsistencies in the s-α model, coincidentally compensating finite ρ∗ effects in the global calculations, where ρ∗=ρs/a with ρs the ion sound Larmor radius. True convergence between local and global simulations is finally obtained by correct treatment of the geometry in both cases, and considering the appropriate ρ∗→0 limit in the latter case.
Step decoration of chiral metal surfaces
Authors: Han Jeong Woo , Kitchin John R. , Sholl David S.
Published: March 2009

Highly stepped metal surfaces can define intrinsically chiral structures and these chiral surfaces can potentially be used to separate chiral molecules. The decoration of steps on these surfaces with additional metal atoms is one potential avenue for improving the enantiospecificity of these surfaces. For a successful step decoration, the additional metal atoms should ideally remain at the kinked step sites on the surface. We performed density functional theory (DFT) calculations to identify pairs of metal adatoms and metal surfaces where this kind of step decoration could be thermodynamically stable. These calculations have identified multiple stable examples of step decoration. Using our DFT results, we developed a model to predict surface segregation on a wide range of stepped metal surfaces. With this model, we have estimated the stability of step decoration without further DFT calculations for surface segregation for all combinations of the 3d, 4d, and 5d metals.
Temperature-induced tilt transition in the nematic phase of liquid crystal possessing smectic C-nematic phase sequence
Authors: Barbero Giovanni , Komitov Lachezar
Published: March 2009

A temperature-induced transition from homeotropic to tilted alignment in the nematic phase of a liquid crystal with smectic C-nematic phase sequence was observed. The homeotropic alignment of the nematic phase at temperatures near the nematic-isotropic transition was found to undergo a continuous change to tilted one on decreasing the temperature. The appearance of smectic-C-like order at the solid surface on approaching the smectic C-nematic transition is assumed to be the origin of this temperature-induced alignment transition.
Electrical spin injection into Si: A comparison between Fe/Si Schottky and Fe/Al2O3 tunnel contacts
Authors: Kioseoglou G. , Hanbicki A. T. , Goswami R. , van ‘t Erve O. M. J. , Li C. H. , Spanos G. , Thompson P. E. , Jonker B. T.
Published: March 2009

We compare electrical spin injection from Fe into Si n-i-p heterostructures using different tunnel barriers—a reversed biased Fe/Si Schottky contact and a Fe/Al2O3 barrier. The electroluminescence (EL) spectra are dominated by transverse acoustic and optical phonon emission for both types of structures. The circular polarization of the EL tracks the Fe magnetization, confirming that the spin-polarized electrons originate from the Fe in each case. However, the polarization is lower for the Fe/Si contact than for the Fe/Al2O3 contact. Transmission electron microscopy reveals a complex interface and intermixing for Fe/Si that is absent in Fe/Al2O3/Si.
Search for the most stable Ca@C44 isomer: Structural stability and electronic property investigations
Authors: Tang Shu-Wei , Sun Li-Li , Sun Hao , Feng Jing-Dong , Wang Rong-Shun , Chang Ying-Fei , Hao Li-Zhu
Published: March 2009

Stimulated by the mass spectroscopic observation of the metallofullerene Ca@C44, we have performed a systematic investigation to search for the most stable isomer using HF/3-21G∼LanL2DZ, HF/6-31+G(d), B3LYP/6-31+G(d), and MP2/6-31+G(d)//B3LYP/6-31+G(d) methods. The Ca@C44 (D2:53) isomer with eight adjacent pentagons in the fullerene framework is predicted to possess the lowest energy. The thermodynamics stability explorations of Ca@C44 isomers at different temperatures show that Ca@C44 (D2:53) is the most thermodynamically stable in the temperature range of absolute zero to 4000 K. The encapsulation of Ca atom in C44 fullerene is exothermic, and the electronic structure of Ca@C44 (D2:53) can be described formally as Ca2+@C442−. Further analysis on the frontier molecular orbitals and density of states of Ca@C44 (D2:53) suggests that both highest occupied molecular orbital and lowest unoccupied molecular orbital are carbonlike with low Ca character, and the carbon cage possesses high chemical activity. In addition, the vibrational spectrum of Ca@C44 (D2:53) has been simulated and analyzed to gain an insight into the metal-cage vibrations.
Swelling of polymers in porous media
Authors: Sung Bong June , Chang Rakwoo , Yethiraj Arun
Published: March 2009

The swelling of polymers in random matrices is studied using computer simulations and percolation theory. The model system consists of freely jointed hard sphere chains in a matrix of hard spheres fixed in space. The average size of the polymer is a nonmonotonic function of the matrix volume fraction, ϕm. For low values of ϕm the polymer size decreases as ϕm is increased but beyond a certain value of ϕm the polymer size increases as ϕm is increased. The qualitative behavior is similar for three different types of matrices. In order to study the relationship between the polymer swelling and pore percolation, we use the Voronoi tessellation and a percolation theory to map the matrix onto an irregular lattice, with bonds being considered connected if a particle can pass directly between the two vertices they connect. The simulations confirm the scaling relation RG∼(p−pc)δ0Nν, where RG is the radius of gyration, N is the polymer degree of polymerization, p is the number of connected bonds, and pc is the value of p at the percolation threshold, with universal exponents δ0(≈−0.126±0.005) and ν(≈0.6±0.01). The values of the exponents are consistent with predictions of scaling theory.
Reliability analysis of the low resistance state stability of Ge0.3Se0.7 based solid electrolyte nonvolatile memory cells
Authors: Soni R. , Meuffels P. , Kohlstedt H. , Kügeler C. , Waser R.
Published: March 2009

We report on the low resistance state (LRS) stability analysis of Ge0.3Se0.7 based solid electrolyte nonvolatile memory cells under elevated temperature and bias current stress conditions. The activation energy was found to be about 1.02 eV, which is comparable to that of an electromigration-induced failure process. Experimental results also show that there is trade-off between the LRS stability and the thickness of Ge0.3Se0.7 layer.
Metal-oxide-semiconductor capacitors with erbium oxide dielectrics on In0.53Ga0.47As channels
Authors: Hwang Yoontae , Wistey Mark A. , Cagnon Joël , Engel-Herbert Roman , Stemmer Susanne
Published: March 2009

Erbium oxide dielectrics with a thickness of ∼6 nm were fabricated in situ on In0.53Ga0.47As channels. Leakage current and capacitance densities were characterized as a function of applied voltage using metal-oxide-semiconductor capacitors with two different top electrode materials, Pt and Al. Leakage current densities were less than 10−3 A/cm2 at gate voltages up to ±2 V. The capacitance densities were lower with the Al electrode, which was attributed to a low-permittivity aluminum oxide layer at the electrode interface. The capacitors with the Pt electrode showed a pronounced increase in the capacitance in the depletion region at frequencies as high as 1 MHz, which was not observed for the Al electrode. Possible origins of the differences in the capacitance-voltage characteristics with Pt and Al electrodes are discussed.
Effect of Title on Eye-Movement Exploration of Cubist Paintings by Fernand Léger
Authors: Kapoula Zoi , Daunys Gintautas , Herbez Olivier , Yang Qing
Published: March 2009

Franklin et al (1993, Leonardo26 103–108) reported that title information influenced the interpretation of paintings but not the way observers explore and look at the paintings; in their study subjects used a hand pointer to indicate where they looked. We used eye-movement recording and examined the effect of title on eye-movement exploration of nonrealistic cubist paintings giving rise to free interpretation. Three paintings by Fernand Léger were used: The Wedding contained high density of small fragments of real human faces, limbs, or arbitrary fragments mixed with large plane surfaces; The Alarm Clock consisted of arbitrary fragments creating perception of a person; Contrast of Forms contained forms and cylinders. Different groups of naive subjects explored paintings without knowing the title (spontaneous condition), with the instruction to invent a title (active condition), and after announcement of the authentic title (driven condition). Exploration time was unrestricted and eye movements were recorded by Chronos video-oculography.

Fixation duration was found to increase in the driven condition relative to active condition; such increase occurred for all paintings. In contrast, fixation-duration variability remained stable over all title conditions. Saccade amplitude increased in the driven condition for Contrast of Forms. Increase of fixation duration and of saccade size are attributed to additional cognitive analysis, ie search fitting between the title and the painting. When comparing paintings within each title condition, The Wedding produced different results than the other paintings: longer exploration time (in spontaneous condition), higher fixation duration variability (in spontaneous and driven conditions), but smaller saccade sizes (in active and driven conditions). The differences are attributed to visual aspects (high density of small fragments) but also to complex semantic analysis of multiple segments of faces and limbs contained by this painting.

Spatial distribution of fixation time was highly selective, with a preponderance of the central area that was the most fixated for all paintings and all title conditions. In the driven condition, however, loci of most frequent fixations were different than in the other conditions from the first 5 s; particularly for The Alarm Clock the title drove the eyes rapidly on the inconspicuous fragment of the clock. Our findings go against Franklin's conclusions. We conclude that title information influences both physiological parameters of eye movements and the distribution of fixation time over different selected areas of the painting.
Adult-Like Competence in Perceptual Encoding of Facial Configuration by the Right Hemisphere Emerges after 10 Years of Age
Authors: Anes Michael D , Short Lindsey A
Published: March 2009

In the present study, we examined ascription of bizarreness to faces in a ratings task by children aged 8–10 and 11–13 years, and by adults. Configural information was manipulated subtly (a single eye was inverted) or in a more salient manner (eye and mouth were inverted). By utilizing brief presentations we restricted initial processing of the manipulations to one hemisphere. Right-hemispheric sensitivity to the manipulations was seen in higher ratings for (viewer-centered) left-sided manipulations than for right-sided manipulations. The youngest group showed significantly less right-hemisphere sensitivity to the manipulations in upright faces than the adults, but children aged 11–13 years were similar to adults. The three age groups were equivalently able to detect the stronger eye and mouth manipulation. In all, children's performance approached that of adults gradually in this task, which emphasizes immediate perceptual encoding of faces and for which memorial demands are minimal.
Successive radiations, not stasis, in the South American primate fauna
Authors: Hodgson Jason A. , Sterner Kirstin N. , Matthews Luke J. , Burrell Andrew S. , Jani Rachana A. , Raaum Ryan L. , Stewart Caro-Beth , Disotell Todd R.
Published: March 2009

The earliest Neotropical primate fossils complete enough for taxonomic assessment,
Dolichocebus
,
Tremacebus
, and
Chilecebus
, date to approximately 20 Ma. These have been interpreted as either closely related to extant forms or as extinct stem lineages. The former hypothesis of morphological stasis requires most living platyrrhine genera to have diverged before 20 Ma. To test this hypothesis, we collected new complete mitochondrial genomes from
Aotus lemurinus
,
Saimiri sciureus
,
Saguinus oedipus
,
Ateles belzebuth
, and
Callicebus donacophilus.
We combined these with published sequences from
Cebus albifrons
and other primates to infer the mitochondrial phylogeny. We found support for a cebid/atelid clade to the exclusion of the pitheciids. Then, using Bayesian methods and well-supported fossil calibration constraints, we estimated that the platyrrhine most recent common ancestor (MRCA) dates to 19.5 Ma, with all major lineages diverging by 14.3 Ma. Next, we estimated catarrhine divergence dates on the basis of platyrrhine divergence scenarios and found that only a platyrrhine MRCA less than 21 Ma is concordant with the catarrhine fossil record. Finally, we calculated that 33% more change in the rate of evolution is required for platyrrhine divergences consistent with the morphologic stasis hypothesis than for a more recent radiation. We conclude that
Dolichocebus
,
Tremacebus
, and
Chilecebus
are likely too old to be crown platyrrhines, suggesting they were part of an extinct early radiation. We note that the crown platyrrhine radiation was concomitant with the radiation of 2 South American xenarthran lineages and follows a global temperature peak and tectonic activity in the Andes.
Spite and virulence in the bacterium
Pseudomonas aeruginosa
Authors: Inglis R. Fredrik , Gardner Andy , Cornelis Pierre , Buckling Angus
Published: March 2009

Social interactions within populations of pathogenic microbes may play an important role in determining disease virulence. One such ubiquitous interaction is the production of anticompetitor toxins; an example of a spiteful behavior, because it results in direct fitness costs to both the actor and recipient. Following from predictions made by mathematical models, we carried out experiments using the bacterium
Pseudomonas aeruginosa
to test under what social conditions toxin (bacteriocin) production is favored and how this in turn affects virulence in the larvae of the wax moth
Galleria mellonella
. Consistent with theory, we found that the growth of bacteriocin producers relative to sensitive non-producers is maximized when toxin producers are at intermediate frequencies in the population. Furthermore, growth rate and virulence in caterpillars was minimized when bacteriocin producers have the greatest relative growth advantage. These results suggest that spiteful interactions may play an important role in the population dynamics and virulence of natural bacterial infections.
Recruitment of adult-generated neurons into functional hippocampal networks contributes to updating and strengthening of spatial memory
Authors: Trouche Stéphanie , Bontempi Bruno , Roullet Pascal , Rampon Claire
Published: March 2009

The dentate gyrus (DG), a hippocampal subregion, continuously produces new neurons in the adult mammalian brain that become functionally integrated into existing neural circuits. To what extent this form of plasticity contributes to memory functions remains to be elucidated. Using mapping of activity-dependent gene expression, we visualized in mice injected with the birthdating marker 5-bromo-2′-deoxyuridine the recruitment of new neurons in a set of controlled water maze procedures that engage specific spatial memory processes and require hippocampal–cortical networks. Here, we provide new evidence that adult-generated hippocampal neurons make a specific but differential contribution to the processing of remote spatial memories. First, we show that new neurons in the DG are recruited into neuronal networks that support retrieval of remote spatial memory and that their activation is situation-specific. We further reveal that once selected, new hippocampal neurons are durably incorporated into memory circuits, and also that their recruitment into hippocampal networks contributes predominantly to the updating and strengthening of a previously encoded memory. We find that initial spatial training during a critical period, when new neurons are more receptive to surrounding neuronal activity, favors their subsequent recruitment upon remote memory retrieval. We therefore hypothesize that new neurons activated during this critical period become tagged so that once mature, they are preferentially recruited into hippocampal networks underlying remote spatial memory representation when encountering a similar experience.
Nramp1 promotes efficient macrophage recycling of iron following erythrophagocytosis in vivo
Authors: Soe-Lin Shan , Apte Sameer S. , Andriopoulos Billy , Andrews Marc C. , Schranzhofer Matthias , Kahawita Tanya , Garcia-Santos Daniel , Ponka Prem
Published: March 2009

Natural resistance-associated macrophage protein 1 (Nramp1) is a divalent metal transporter expressed exclusively in phagocytic cells. We hypothesized that macrophage Nramp1 may participate in the recycling of iron acquired from phagocytosed senescent erythrocytes. To evaluate the role of Nramp1 in vivo, the iron parameters of WT and KO mice were analyzed after acute and chronic induction of hemolytic anemia. We found that untreated KO mice exhibited greater serum transferrin saturation and splenic iron content with higher duodenal ferroportin (Fpn) and divalent metal transporter 1 (DMT1) expression. Furthermore, hepatocyte iron content and hepcidin mRNA levels were dramatically lower in KO mice, indicating that hepcidin levels can be regulated by low-hepatocyte iron stores despite increased transferrin saturation. After acute treatment with the hemolytic agent phenylhydrazine (Phz), KO mice experienced a significant decrease in transferrin saturation and hematocrit, whereas WT mice were relatively unaffected. After a month-long Phz regimen, KO mice retained markedly increased quantities of iron within the liver and spleen and exhibited more pronounced splenomegaly and reticulocytosis than WT mice. After injection of59Fe-labeled heat-damaged reticulocytes, KO animals accumulated erythrophagocytosed59Fe within their liver and spleen, whereas WT animals efficiently recycled phagocytosed59Fe to the marrow and erythrocytes. These data imply that without Nramp1, iron accumulates within the liver and spleen during erythrophagocytosis and hemolytic anemia, supporting our hypothesis that Nramp1 promotes efficient hemoglobin iron recycling in macrophages. Our observations suggest that mutations inNramp1could result in a novel form of human hereditary iron overload.
Gene deregulation and spatial genome reorganization near breakpoints prior to formation of translocations in anaplastic large cell lymphoma
Authors: Mathas Stephan , Kreher Stephan , Meaburn Karen J. , Jöhrens Korinna , Lamprecht Björn , Assaf Chalid , Sterry Wolfram , Kadin Marshall E. , Daibata Masanori , Joos Stefan , Hummel Michael , Stein Harald , Janz Martin , Anagnostopoulos Ioannis , Schrock Evelin , Misteli Tom , Dörken Bernd
Published: March 2009

Although the identification and characterization of translocations have rapidly increased, little is known about the mechanisms of how translocations occur in vivo. We used anaplastic large cell lymphoma (ALCL) with and without the characteristic t(2;5)(p23;q35) translocation to study the mechanisms of formation of translocations and of ALCL transformation. We report deregulation of several genes located near the ALCL translocation breakpoint, regardless of whether the tumor contains the t(2;5). The affected genes include the oncogenic transcription factor Fra2 (located on 2p23), the HLH protein Id2 (2p25), and the oncogenic tyrosine kinase CSF1-receptor (5q33.1). Their up-regulation promotes cell survival and repression of T cell-specific gene expression programs that are characteristic for ALCL. The deregulated genes are in spatial proximity within the nuclear space of t(2;5)-negative ALCL cells, facilitating their translocation on induction of double-strand breaks. These data suggest that deregulation of breakpoint-proximal genes occurs before the formation of translocations, and that aberrant transcriptional activity of genomic regions is linked to their propensity to undergo chromosomal translocations. Also, our data demonstrate that deregulation of breakpoint-proximal genes has a key role in ALCL.
Populations of auditory cortical neurons can accurately encode acoustic space across stimulus intensity
Authors: Miller Lee M. , Recanzone Gregg H.
Published: March 2009

The auditory cortex is critical for perceiving a sound's location. However, there is no topographic representation of acoustic space, and individual auditory cortical neurons are often broadly tuned to stimulus location. It thus remains unclear how acoustic space is represented in the mammalian cerebral cortex and how it could contribute to sound localization. This report tests whether the firing rates of populations of neurons in different auditory cortical fields in the macaque monkey carry sufficient information to account for horizontal sound localization ability. We applied an optimal neural decoding technique, based on maximum likelihood estimation, to populations of neurons from 6 different cortical fields encompassing core and belt areas. We found that the firing rate of neurons in the caudolateral area contain enough information to account for sound localization ability, but neurons in other tested core and belt cortical areas do not. These results provide a detailed and plausible population model of how acoustic space could be represented in the primate cerebral cortex and support a dual stream processing model of auditory cortical processing.
Characterizing a model human gut microbiota composed of members of its two dominant bacterial phyla
Authors: Mahowald Michael A. , Rey Federico E. , Seedorf Henning , Turnbaugh Peter J. , Fulton Robert S. , Wollam Aye , Shah Neha , Wang Chunyan , Magrini Vincent , Wilson Richard K. , Cantarel Brandi L. , Coutinho Pedro M. , Henrissat Bernard , Crock Lara W. , Russell Alison , Verberkmoes Nathan C. , Hettich Robert L. , Gordon Jeffrey I.
Published: March 2009

The adult human distal gut microbial community is typically dominated by 2 bacterial phyla (divisions), the Firmicutes and the Bacteroidetes. Little is known about the factors that govern the interactions between their members. Here, we examine the niches of representatives of both phyla in vivo. Finished genome sequences were generated fromEubacterium rectaleandE. eligens, which belong to Clostridium Cluster XIVa, one of the most common gut Firmicute clades. Comparison of these and 25 other gut Firmicutes and Bacteroidetes indicated that the Firmicutes possess smaller genomes and a disproportionately smaller number of glycan-degrading enzymes. Germ-free mice were then colonized withE. rectaleand/or a prominent human gut Bacteroidetes,Bacteroides thetaiotaomicron, followed by whole-genome transcriptional profiling, high-resolution proteomic analysis, and biochemical assays of microbial–microbial and microbial–host interactions.B. thetaiotaomicronadapts toE. rectaleby up-regulating expression of a variety of polysaccharide utilization loci encoding numerous glycoside hydrolases, and by signaling the host to produce mucosal glycans that it, but notE. rectale, can access.E. rectaleadapts toB. thetaiotaomicronby decreasing production of its glycan-degrading enzymes, increasing expression of selected amino acid and sugar transporters, and facilitating glycolysis by reducing levels of NADH, in part via generation of butyrate from acetate, which in turn is used by the gut epithelium. This simplified model of the human gut microbiota illustrates niche specialization and functional redundancy within members of its major bacterial phyla, and the importance of host glycans as a nutrient foundation that ensures ecosystem stability.