bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiyear measurements of the oceanic and atmospheric boundary layers at the Brazil‐Malvinas confluence region
Authors: Pezzi Luciano Ponzi , de Souza Ronald Buss , Acevedo Otávio , Wainer Ilana , Mata Mauricio M. , Garcia Carlos A. E. , de Camargo Ricardo
Published: September 2009

This study analyzes and discusses data taken from oceanic and atmospheric measurements performed simultaneously at the Brazil‐Malvinas Confluence (BMC) region in the southwestern Atlantic Ocean. This area is one of the most dynamical frontal regions of the world ocean. Data were collected during four research cruises in the region once a year in consecutive years between 2004 and 2007. Very few studies have addressed the importance of studying the air‐sea coupling at the BMC region. Lateral temperature gradients at the study region were as high as 0.3°C km−1 at the surface and subsurface. In the oceanic boundary layer, the vertical temperature gradient reached 0.08°C m−1 at 500 m depth. Our results show that the marine atmospheric boundary layer (MABL) at the BMC region is modulated by the strong sea surface temperature (SST) gradients present at the sea surface. The mean MABL structure is thicker over the warmside of the BMC where Brazil Current (BC) waters predominate. The opposite occurs over the coldside of the confluence where waters from the Malvinas (Falkland) Current (MC) are found. The warmside of the confluence presented systematically higher MABL top height compared to the coldside. This type of modulation at the synoptic scale is consistent to what happens in other frontal regions of the world ocean, where the MABL adjusts itself to modifications along the SST gradients. Over warm waters at the BMC region, the MABL static instability and turbulence were increased while winds at the lower portion of the MABL were strong. Over the coldside of the BC/MC front an opposite behavior is found: the MABL is thinner and more stable. Our results suggest that the sea‐level pressure (SLP) was also modulated locally, together with static stability vertical mixing mechanism, by the surface condition during all cruises. SST gradients at the BMC region modulate the synoptic atmospheric pressure gradient. Postfrontal and prefrontal conditions produce opposite thermal advections in the MABL that lead to different pressure intensification patterns across the confluence.
Three‐dimensional modeling of the radiation belts using the Versatile Electron Radiation Belt (VERB) code
Authors: Subbotin D. A. , Shprits Y. Y.
Published: September 2009

Relativistic electrons are hazardous for satellites and humans in space. In this study, we present a detailed description of the Versatile Electron Radiation Belt (VERB) code. The computationally efficient methods described in this report make the VERB code a useful tool for space weather forecasting and nowcasting of the relativistic electron environment. The computational efficiency of the code makes it also appropriate for future use with data assimilation tools to specify the state of the radiation environment and correct imperfect models. We also present several skill scores which can be used to quantify the state of the relativistic electron environment. Our numerical approach is based on the use of two grids: one for radial diffusion and the other for energy and pitch angle diffusion. In this paper, we describe the initial and boundary conditions, the grids and time step used for our simulations, and the tests we conduct to verify the validity of our numerical approaches. Specifically, we perform simulations with time steps ranging from 0.01 to 4 h and number of grid points ranging from 7 to 76 for each of the variables. We compare the results obtained using various spatial resolutions and time steps, giving the relative solution errors for each of the performed simulations on the basis of the developed set of skill scores. The choice of a 0.1 h time step with a grid resolution of 19 × 19 × 19 points was found to be optimal. We compare the block and split methods, showing that the split method is much faster than the block method and sufficiently accurate for time steps of half an hour or less. Additionally, we present an approximate method that simplifies simulation by using only one grid and compare it to the more accurate two‐grid method.
Approximation of internodal conductivities in numerical simulation of one‐dimensional infiltration, drainage, and capillary rise in unsaturated soils
Authors: Szymkiewicz Adam
Published: September 2009

When the unsaturated flow equation is solved with the finite difference method, the water flux between two adjacent nodes of the grid is approximated with a discrete form of Darcy's law. It requires the average value of the hydraulic conductivity in the considered grid block. Since the hydraulic conductivity in unsaturated soil is a highly nonlinear function of the water potential, the nodal conductivities can vary by multiple orders of magnitude, which makes the choice of the appropriate averaging procedure a nontrivial task. In this paper we present a new method to calculate the internodal conductivity for an arbitrary type of the conductivity function and arbitrary large grid size. It is based on the analysis of approximate profiles of the water potential head for steady flow between nodes. Numerical experiments show that the method is reasonably accurate for a wide range of soil types, for both steady and unsteady flow simulations.
Rapid carbon accretion and organic matter pool stabilization in riverine floodplain soils
Authors: Zehetner Franz , Lair Georg J. , Gerzabek Martin H.
Published: September 2009

The importance of wetlands in the global C budget has been recognized in recent years, and the high biomass productivity of riverine floodplains is widely acknowledged. However, soil C dynamics in these ecosystems are still poorly understood and rarely quantified. In this study, we quantify organic C accretion and examine changes of organic matter pools across an age gradient of riverine floodplain soils under different land uses in a warm temperate climate. We find rapid C accumulation during the initial 100 years of soil formation, with rates exceeding 100 g m−2 a−1. We show that floodplain land use strongly affects soil C sequestration and organic matter pool allocation and find that the distribution of different soil organic matter pools reaches a steady state within a few decades of soil development. Our results demonstrate that continually rejuvenated soils on riverine floodplains are strong C sinks but also show that intensive cultivation severely compromises their high C sequestration potential.
Effects of anthropogenic land cover change on the carbon cycle of the last millennium
Authors: Pongratz J. , Reick C. H. , Raddatz T. , Claussen M.
Published: September 2009

Transient simulations are performed over the entire last millennium with a general circulation model that couples the atmosphere, ocean, and the land surface with a closed carbon cycle. This setup applies a high‐detail reconstruction of anthropogenic land cover change (ALCC) as the only forcing to the climate system with two goals: (1) to isolate the effects of ALCC on the carbon cycle and the climate independently of any other natural and anthropogenic disturbance and (2) to assess the importance of preindustrial human activities. With ALCC as only forcing, the terrestrial biosphere experiences a net loss of 96 Gt C over the last millennium, leading to an increase of atmospheric CO2 by 20 ppm. The biosphere‐atmosphere coupling thereby leads to a restoration of 37% and 48% of the primary emissions over the industrial (A.D. 1850–2000) and the preindustrial period (A.D. 800–1850), respectively. Because of the stronger coupling flux over the preindustrial period, only 21% of the 53 Gt C preindustrial emissions remain airborne. Despite the low airborne fraction, atmospheric CO2 rises above natural variability by late medieval times. This suggests that human influence on CO2 began prior to industrialization. Global mean temperatures, however, are not significantly altered until the strong population growth in the industrial period. Furthermore, we investigate the effects of historic events such as epidemics and warfare on the carbon budget. We find that only long‐lasting events such as the Mongol invasion lead to carbon sequestration. The reason for this limited carbon sequestration is indirect emissions from past ALCC that compensate carbon uptake in regrowing vegetation for several decades. Drops in ice core CO2 are thus unlikely to be attributable to human action. Our results indicate that climate‐carbon cycle studies for present and future centuries, which usually start from an equilibrium state around 1850, start from a significantly disturbed state of the carbon cycle.
Precipitation over South America during the Last Glacial Maximum: An analysis of the “amount effect” with a water isotope‐enabled general circulation model
Authors: Lee Jung‐Eun , Johnson Kathleen , Fung Inez
Published: September 2009

Low latitude paleoclimate records from speleothem δ18O measurements are often considered to reflect variations in precipitation amounts. Here we test this interpretation with a water isotope enabled atmospheric general circulation model, comparing modern and Last Glacial Maximum (LGM) controls on the δ18Op in Brazil. We argue that the δ18Op is determined by the contributions from local evaporation (high δ18O) versus water vapor convergence to the region (low δ18O). Our analysis indicates that the amount effect, commonly used to infer precipitation amount from δ18Op in low latitude regions, works only where the isotopic composition of incoming vapor stays relatively constant such as in coastal regions of the subtropics. If the isotopic composition of incoming vapor has changed as a result of the variations in the upstream rainout, δ18Op cannot be used to estimate local precipitation. Our analysis supports the increase of precipitation over northeastern Brazil region during the LGM.
Seepage from a special class of a curved channel with drainage layer at shallow depth
Authors: Chahar Bhagu R.
Published: September 2009

In the present study an inverse method has been used to obtain an exact solution for seepage from a curved channel passing through a homogeneous isotropic porous medium underlain by a drainage layer at shallow depth whose boundary maps along a circle onto the hodograph plane. The solution involves inverse hodograph and Schwarz‐Christoffel transformation. The solution also includes a set of parametric equations for the shape of the channel contour and loci of phreatic line. Variation in the seepage velocity along the channel contour is presented as well. All these expressions involve improper integrals along with accessory parameters. A particular solution corresponding to the water table below the top of the drainage layer has also been deduced from the general solution.
Permanent or Transient Chronic Ischemic Stroke in the Non-Human Primate: Behavioral, Neuroimaging, Histological, and Immunohistochemical Investigations
Authors: Bihel Ebeline , Pro-Sistiaga Palma , Letourneur Annelise , Toutain Jerome , Saulnier Romaric , Insausti Ricardo , Bernaudin Myriam , Roussel Simon , Touzani Omar
Published: September 2009

Using multimodal magnetic resonance imaging (MRI), behavioral, and immunohistochemical analyses, we examined pathological changes at the acute, sub-acute, and chronic stages, induced by permanent or temporary ischemia in the common marmoset. Animals underwent either permanent (pMCAO) or 3-h transient (tMCAO) occlusion of the middle cerebral artery (MCAO) by the intraluminal thread approach. MRI scans were performed at 1 h, 8, and 45 days after MCAO. Sensorimotor deficits were assessed weekly up to 45 days after MCAO. Immunohistological studies were performed to examine neuronal loss, astrogliosis, and neurogenesis. Remote lesions were analyzed using retrograde neuronal tracers. At day 8 (D8), the lesion defined on diffusion tensor imaging (DTI)–MRI and T2-MRI was significantly larger in pMCAO as compared with that in the tMCAO group. At D45, the former still displayed abnormal signals in T2-MRI. Post-mortem analyses revealed widespread neuronal loss and associated astrogliosis to a greater extent in the pMCAO group. Neurogenesis was increased in both groups in the vicinity of the lesion. Disconnections between the caudate and the temporal cortex, and between the parietal cortex and the thalamus, were observed. Sensorimotor impairments were more severe and long-lasting in pMCAO relative to tMCAO. The profile of brain damage and functional deficits seen in the marmoset suggests that this model could be suitable to test therapies against stroke.
Pharmacological Uncoupling of Activation Induced Increases in CBF and CMRO2
Authors: Leithner Christoph , Royl Georg , Offenhauser Nikolas , Füchtemeier Martina , Kohl-Bareis Matthias , Villringer Arno , Dirnagl Ulrich , Lindauer Ute
Published: September 2009

Neurovascular coupling provides the basis for many functional neuroimaging techniques. Nitric oxide (NO), adenosine, cyclooxygenase, CYP450 epoxygenase, and potassium are involved in dilating arterioles during neuronal activation. We combined inhibition of NO synthase, cyclooxygenase, adenosine receptors, CYP450 epoxygenase, and inward rectifier potassium (Kir) channels to test whether these pathways could explain the blood flow response to neuronal activation. Cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) of the somatosensory cortex were measured during forepaw stimulation in 24 rats using a laser Doppler/spectroscopy probe through a cranial window. Combined inhibition reduced CBF responses by two-thirds, somatosensory evoked potentials and activation-induced CMRO2increases remained unchanged, and deoxy-hemoglobin (deoxy-Hb) response was abrogated. This shows that in the rat somatosensory cortex, one-third of the physiological blood flow increase is sufficient to prevent microcirculatory increase of deoxy-Hb concentration during neuronal activity. The large physiological CBF response is not necessary to support small changes in CMRO2. We speculate that the CBF response safeguards substrate delivery during functional activation with a considerable ‘safety factor’. Reduction of the CBF response in pathological states may abolish the BOLD–fMRI signal, without affecting underlying neuronal activity.
Prosody in Parkinson's Disease
Authors: Jones Harrison N.
Published: September 2009

Purpose: Prosodic abnormalities are commonly recognized to be present in the speech of individuals with Parkinson's disease (PD) and hypokinetic dysarthria. Emerging evidence also suggests that deficits in the receptive processing of prosody are present in individuals with PD. This paper reviews aspects of prosody in PD, including the perceptual and acoustic features and their effect on communication; receptive deficits in prosodic processing; and the effects of medical, surgical, and behavioral treatments on prosody.

Methods: Published reports on the above listed aspects of prosody in PD are reviewed and reported.

Results and Conclusions: The perceptual and acoustic characteristics of prosodic impairments in PD are well defined. Perceptually, the principal prosodic features include monopitch, reduced stress, monoloudness, and rate abnormalities. The most common acoustic findings are decreased variability of fundamental frequency (F0) and intensity. A growing literature also suggests that the basal ganglia are critical in receptively processing prosodic information, which is impaired in PD. The role of medical and surgical treatment of PD on speech prosody remains unclear but, overall, appears limited. Behavioral treatments for prosodic disturbance appear promising, though further study is required.
Synthesis and optical properties of infrared-emitting YF3:Nd nanoparticles
Authors: Tan Mei Chee , Kumar G. A. , Riman Richard E. , Brik M. G. , Brown E. , Hommerich U.
Published: September 2009

Nd 3 + -doped YF3 (YF3:Nd) nanoparticles with a size of ∼20 nm were synthesized by solvothermal decomposition of yttrium and neodymium trifluoroacetate precursors in oleylamine. Using the 4f-energy matrix diagonalization procedure various interaction parameters: Slater–Condon (F2, F4, and F6), spin-orbit (ξ), two body interaction (α, β, and γ), Judd parameters (T2, T3, T4, T6, T7, and T8), spin-other-orbit parameters (M0, M2, and M4) and electrostatically correlated spin-orbit interaction parameters (P2, P4, and P6), and the crystal-field parameters (Bqk) were evaluated. The potential of YF3:Nd as a laser host for 1052 nm emission was evaluated by quantitative analysis of the absorption, emission spectra, and fluorescence decay characteristics. Judd–Ofelt parametrization was employed to compute the radiative spectral parameters such as radiative transition probabilities, fluorescence branching ratios, stimulated emission cross sections, and quantum efficiencies of the observed bands in the fluorescence spectrum. Using the measured radiative properties, 75% quantum efficiency was obtained for the principal emission band at 1052 nm when the Nd dopant concentration was 0.25 mol %, with an emission cross section of 0.74×10−20 cm2. Analysis of the energy transfer kinetics showed that at low dopant concentrations of 0.25 mol % dipole-dipole interactions were dominant, whereas energy migration was the leading process at higher dopant concentrations. Quenching by OH impurities was found to be within the limit of optimum amplifier performance where multiphonon relaxation losses were negligible. Preliminary optical characterization showed that these nanocrystalline materials can be potentially used as optical amplifiers and in applications like infrared imaging, security and authentication.
Carbon nanotube pillar arrays for achieving high emission current densities
Authors: Silan Jeremy L. , Niemann Darrell L. , Ribaya Bryan P. , Rahman Mahmud , Meyyappan M. , Nguyen Cattien V.
Published: September 2009

We introduce an innovative geometry carbon nanotube (CNT) field emitter array capable of achieving stable and high current densities. Arrays of toroid CNT pillars were grown directly on bulk metal alloy substrates and on patterned metal catalyst on silicon substrates. Compared to a solid CNT pillar array (CPA), this toroid CPA (tCPA) provides a larger edge area for achieving a higher stable current density of 50 mA/cm2 at an applied dc field of less than 8 V/μm. Electrostatic simulation data confirming the field enhancement at the inner and outer edges of the tCPA are also presented.
Influence of surface chemistry on photoluminescence from deuterium-passivated silicon nanocrystals
Authors: Salivati Navneethakrishnan , Shuall Nimrod , Baskin Emanuel , Garber Valery , McCrate Joseph M. , Ekerdt John G.
Published: September 2009

Although silicon (Si) nanostructures exhibit size dependent light emission, which can be attributed to quantum confinement, the role of surface passivation is not fully understood. Si nanocrystals less than 6 nm in diameter are grown on SiO2 surfaces in an ultrahigh vacuum chamber using hot wire chemical vapor deposition. The surface chemistry of deuterium-passivated Si nanocrystals is studied using temperature programed desorption to follow the formation of surface deuterides and amorphization of Si nanocrystals. The influence of the surface deuteride species and amorphization on the photoluminescence (PL) emitted from Si nanocrystals is reported for an excitation wavelength of 405 nm. No PL is observed from the as-grown unpassivated nanocrystals. The as-grown surfaces are exposed to atomic deuterium at 375 K and PL is measured at 310–315 K. As the deuterium dose is increased, the PL intensity also begins to increase. This can be associated with increasing amounts of mono-, di-, and trideuteride species on the nanocrystal surface, which results in better passivation of the dangling bonds. At high deuterium doses, the surface structure breaks down and amorphization of the top layer of the nanocrystal takes place. Amorphization reduces the PL intensity. Finally, as the nanocrystal size is varied, the PL peak shifts, which is characteristic of quantum confinement.
Surface plasmon resonance and super-resolution imaging by anisotropic superlens
Authors: Wang Changtao , Du Chunlei , Luo Xiangang
Published: September 2009

Surface plasmon resonance with large transversal wave vector occurs at the interface of effective anisotropic metallic media comprising layered metallodielectric films, provided that appropriate permittivity and geometrical parameters are selected. This results in, as demonstrated with analytical investigation and numerical simulation, evanescent waves amplification and super-resolution imaging with extra working distance as a generalization of the superlens [J. B. Pendry, Phys. Rev. Lett. 85, 3966 (2000)].
Numerical simulation of reciprocating turbulent flow in a plane channel
Authors: Di Liberto Massimiliano , Ciofalo Michele
Published: September 2009

Computational results were obtained for oscillatory flow with zero time mean (reciprocating flow) in a plane channel using a finite-volume method. A forcing term that varied cosinusoidally in time was imposed, and its frequency and amplitude were made to vary so as to span a range of regimes from purely laminar to fully turbulent. The results were validated against analytical solutions and literature data. In turbulent flow, although the computational grid did not fully resolve all the turbulence scales, the results were judged to be sufficiently accurate to capture all the essential features of the problem. The present computational results confirmed the existence of four main flow regimes (laminar, disturbed laminar, intermittently turbulent, and fully turbulent), already identified in the previous literature. One of the most interesting results was that the relation between the amplitudes of the forcing term and of the flow rate was found to be approximately linear both in the laminar and in the turbulent regimes; the reasons for this peculiar behavior were investigated and discussed. The influence of oscillation frequency and forcing term amplitude on transition to turbulence was also studied; results were compared with transition criteria proposed in literature, and a flow regime chart was proposed. Finally, the effect of unsteadiness on heat transfer was investigated by imposing different temperatures at the opposite walls of the channel and computing mean and fluctuating temperature distributions and heat transfer rates. The Nusselt number was found to increase significantly even in the disturbed laminar regime and to vary as Re0.8 (as in steady turbulent flow) in the turbulent regime.
Enhanced yield strength of materials: The thinness effect
Authors: Jennett N. M. , Ghisleni R. , Michler J.
Published: September 2009

We show that yield strength is determined by “thinness” i.e., by the smallest dimension of a structure. Compressing wall-like structures of different length to width ratio, using a NanoindenterXP, has allowed us to distinguish between proposed plasticity size effect theories by determining the dimensional dependence of uniaxial plastic deformation of small pillars. We show that yield stress is determined by wall width; the length of the wall making little or no difference. Thus thin structures exhibit the same enhanced yield strength regardless of total size (volume) or surface to volume ratio; nanolayers are as strong as nanoparticles.
Maximum locality in occupied and virtual orbital spaces using a least-change strategy
Authors: Ziółkowski Marcin , Jansík Branislav , Jørgensen Poul , Olsen Jeppe
Published: September 2009

A new strategy is introduced for obtaining localized orthonormal Hartree–Fock (HF) orbitals where the underlying principle is to minimize the size of the transformation matrix from the atomic orbital basis to the HF optimized orbital basis. The new strategy gives both localized occupied and localized virtual orbital spaces. The locality of the occupied orbital space is similar to one obtained using standard localization schemes. For the virtual space, standard localization schemes fail to give local orbitals while the new strategy gives a virtual space which has a locality similar to the one of a Löwdin orthonormalization of the atomic orbital basis. Since Löwdin orthonormalization gives the most local orthonormal basis functions in the sense that they have the largest similarity with the local atomic basis functions, the new strategy thus allows the orthonormal basis to become optimized without introducing significant delocalization.
Lightweight sodium alanate thin films grown by reactive sputtering
Authors: Filippi M. , Rector J. H. , Gremaud R. , van Setten M. J. , Dam B.
Published: September 2009

We report the preparation of sodium alanate, a promising hydrogen storage material, in a thin film form using cosputtering in a reactive atmosphere of atomic hydrogen. We study the phase formation and distribution, and the hydrogen desorption, with a combination of optical and infrared transmission spectroscopy. We show that the hydrogen desorption, the phase segregation, and the role of the dopants in these complex metal hydrides can be monitored with optical measurements. This result shows that a thin film approach can be used for a model study of technologically relevant lightweight metal hydrides.
Enhanced light extraction in nitride light-emitting diodes by epitaxially grown photonic-crystal nanopyramid arrays
Authors: Shields P. A. , Liu C. , Nasir M. , Allsopp D. W. E. , Wang W. N.
Published: September 2009

A photonic crystal has been created on the p-layer of an InGaN light-emitting diode wafer by selective area growth, thus avoiding the etch processes that are detrimental to the active region. Nanopyramid arrays with either hexagonal or Archimedian lattices were grown in apertures defined by nanoimprint lithography. Electroluminescence measurements show that the pyramids improve the on-axis light output by up to 1.9–2.0 times. This technique could be extended to higher aspect ratio nanostructures that will have stronger coupling between the guided modes and the photonic crystal.
Strong correlations via constrained-pairing mean-field theory
Authors: Tsuchimochi Takashi , Scuseria Gustavo E.
Published: September 2009

We present a mean-field approach for accurately describing strong correlations via electron number fluctuations and pairings constrained to an active space. Electron number conservation is broken and correct only on average, but both spin and spatial symmetries are preserved. Optimized natural orbitals and occupations are determined by diagonalization of a mean-field Hamiltonian. This constrained-pairing mean-field theory (CPMFT) yields a two-particle density matrix ansatz that exclusively describes strong correlations. We demonstrate CPMFT accuracy with applications to the metal-insulator transition of large hydrogen clusters and molecular dissociation curves.
Timing jitter of cascade switch superconducting nanowire single photon detectors
Authors: Ejrnaes M. , Casaburi A. , Cristiano R. , Quaranta O. , Marchetti S. , Martucciello N. , Pagano S. , Gaggero A. , Mattioli F. , Leoni R. , Cavalier P. , Villégier J. -C.
Published: September 2009

We investigate the timing jitter in parallel superconducting NbN-nanowire single photon detectors based on a cascade switch mechanism. The measured timing jitter is asymmetric and has an oscillatory dependence on bias current. At the highest bias current the full width at half maximum was 1.5 times larger than an on-chip reference meander NbN nanowire. A physical model of the dynamics occurring during cascade switch is developed, that quantitatively accounts for our observations as a consequence of different nanowire critical currents within the detector.
Specific surface effect on transport properties of NiO/MgO heterostructured nanowires
Authors: Oka Keisuke , Yanagida Takeshi , Nagashima Kazuki , Tanaka Hidekazu , Seki Shu , Honsho Yoshihito , Ishimaru Manabu , Hirata Akihiko , Kawai Tomoji
Published: September 2009

NiO heterostructured nanowires are promising building blocks due to the nonvolatile resistive switching in nanoscale. Here, we report on the noncontact transport measurements of single crystalline NiO/MgO heterostructured nanowires by utilizing a microwave conductivity method. We found the substantial discrepancy up to four orders of magnitude between the heterostructured nanowires and heterothin films on the resistivity when the bulk resistivity increased, whereas the reasonable agreement was found for relatively conductive range. The origin of such huge discrepancy was interpreted in terms of both the large specific surface area of nanowires and the surface transport events of insulative NiO.
Homogeneous linewidth of the P31 bound exciton transition in silicon
Authors: Yang A. , Steger M. , Sekiguchi T. , Thewalt M. L. W. , Ager J. W. , Haller E. E.
Published: September 2009

The optical transitions of the shallow donor bound exciton associated with phosphorus in silicon are a subject of renewed interest due to the recent discovery that these transitions can be used to both read out and initialize the donor electron and nuclear spin in highly enriched S28i. The ultimate limit of these processes will be determined by the natural or homogeneous linewidth which we determine here using spectral hole burning. The observed 10 neV linewidth is only four times the limit set by the bound exciton lifetime.
Suppression of nonradiative processes in long-lived polar GaN/AlN quantum dots
Authors: Renard J. , Kandaswamy P. K. , Monroy E. , Gayral B.
Published: September 2009

We present a temperature-dependent time-resolved photoluminescence study of the nonradiative processes in polar GaN/AlN quantum dots and quantum wells. The photoluminescence decay times of quantum wells drop above 50 K due to the presence of nonradiative recombination centers. In contrast, the three-dimensional carrier confinement in quantum dots efficiently suppresses nonradiative processes up to room temperature, even for radiative decay times reaching the microsecond range.
Melting slope of MgO from molecular dynamics and density functional theory
Authors: Tangney Paul , Scandolo Sandro
Published: September 2009

We combine density functional theory (DFT) with molecular dynamics simulations based on an accurate atomistic force field to calculate the pressure derivative of the melting temperature of magnesium oxide at ambient pressure—a quantity for which a serious disagreement between theory and experiment has existed for almost 15 years. We find reasonable agreement with previous DFT results and with a very recent experimental determination of the slope. We pay particular attention to areas of possible weakness in theoretical calculations and conclude that the long-standing discrepancy with experiment could only be explained by a dramatic failure of existing density functionals or by flaws in the original experiment.
Magnetically controllable nanofluid with tunable thermal conductivity and viscosity
Authors: Shima P. D. , Philip John , Raj Baldev
Published: September 2009

We report the viscosity (η) and thermal conductivity (k) enhancement in a stable magnetic nanofluid containing particles size <10 nm as a function of volume fraction (vol %), shear rate, magnetic field, and time. Without field, the η enhancement of nanoparticle is much larger than that of k. In a nanofluid with 0.078 vol %, the k/η ratio is tunable from 0.725 to 2.35 by controlling the applied field. Our results show that magnetic nanofluids with tunable k/η ratio can be used as multifunctional “smart materials” for miniature cooling cum damping applications.
Badiou's Topology of Action as an Ethical Epistemology of the Event
Authors: Constantinou Marios
Published: September 2009

The aim of this inquiry is to retrieve and rethink in terms of social theory the submerged and equivocal spatialities operant in Badiou's work. I foreground its topological dimension by examining the implications of two critical commentaries on Badiou's work by Juliet Flower MacCannell and Norman Madarasz. I suggest some new directions for theoretical research in the social sciences from a critically appropriated space-syntax perspective which discloses elective affinities between Badiou and Durkheim.
Nutrient losses under simulated rainfall from pasture plots in the Great Lakes District, New South Wales
Authors: Jones Michael G. , Vervoort R. Willem , Cattle Julie
Published: September 2009

Understanding the process by which nutrients and solids enter waterways from pastures in the Great Lakes district, New South Wales, Australia, may assist in maintaining water quality to ensure ongoing environmental and economic sustainability of the region. Rainfall simulations, using a 100-year return storm event, were conducted to determine nutrient and suspended solid concentrations in the runoff of 8 pasture sites in 3 of the catchments in the district. On 5 of the 8 sites, considerable concentrations of N or P were mobilised during the simulated rainfall event, but average nutrient concentrations and total loads across all sites were relatively low and similar to other studies of nutrient runoff from pastures. In addition, low runoff coefficients indicated that runoff is probably not the major pathway for nutrient losses from pasture in this area. Overall, rainfall runoff responses at the sites were similar in the 3 catchments. In contrast, the results suggest that, despite generating more runoff, the sites in the Wang Wauk catchment generated less nutrients in runoff than the sites in the Wallamba and Myall catchments. There was no difference in total suspended solids loads for the sites analysed by catchment. Relationships between soil physical and chemical characteristics and total nutrients loads or cumulative runoff were not strong.
Sequential indicator simulation and indicator kriging estimation of 3-dimensional soil textures
Authors: He Y. , Chen D. , Li B. G. , Huang Y. F. , Hu K. L. , Li Y. , Willett I. R.
Published: September 2009

The complex distribution characteristics of soil textures at a large or regional scale are difficult to understand with the current state of knowledge and limited soil profile data. In this study, an indicator variogram was used to describe the spatial structural characteristics of soil textures of 139 soil profiles. The profiles were 2 m deep with sampling intervals of 0.05 m, from an area of 15 km2 in the North China Plain. The ratios of nugget-to-sill values (SH) of experimental variograms of the soil profiles in the vertical direction were equal to 0, showing strong spatial auto-correlation. In contrast, SH ratios of 0.48–0.81 in the horizontal direction, with sampling distances of ~300 m, showed weaker spatial auto-correlation. Sequential indicator simulation (SIS) and indicator kriging (IK) methods were then used to simulate and estimate the 3D spatial distribution of soil textures. The outcomes of the 2 methods were evaluated by the reproduction of the histogram and variogram, and by mean absolute error of predictions. Simulated results conducted on dense and sparse datasets showed that when denser sample data are used, complex patterns of soil textures can be captured and simulated realisations can reproduce variograms with reasonable fluctuations. When data are sparse, a general pattern of major soil textures still can be captured, with minor textures being poorly simulated or estimated. The results also showed that when data are sufficient, the reproduction of the histogram and variogram by SIS was significantly better than by the IK method for the predominant texture (clay). However, when data are sparse, there is little difference between the 2 methods.
Effect of fertilisation on carbon sequestration in soybean - wheat rotation under two contrasting soils and management practices in the Indian Himalayas
Authors: Bhattacharyya Ranjan , Prakash Ved , Kundu S. , Pandey S. C. , Srivastva A. K. , Gupta H. S.
Published: September 2009

We analysed results of a long-term experiments, initiated in 1973 on a sandy loam soil under rainfed condition and in 1995–96 on a silty clay loam soil under irrigated condition, to determine the influence of using different combinations of mineral fertiliser (NPK) and fertiliser + farmyard manure (FYM) at 10 Mg/ha on soil organic carbon (SOC) content and its changes in the 0–0.45 m soil depth. Fertilisation always caused a net gain in SOC stock. Such gain was positively proportional to the amount of C incorporated into the soils. Concentration of SOC in the 0–0.45 m depth increased by 44% in NPK + FYM treated plots compared with NPK (44.4 Mg C/ha) after 32 years under rainfed condition and by 14% in the NPK + FYM treated plots compared with NPK (41.76 Mg C/ha) after 9 years under irrigation. Mean (across treatments) total C added under the rainfed and irrigated systems was 2.67 and 3.03 Mg/ha.year, respectively. It was estimated that ~20 and 25% of the gross C input contributed towards the increase in SOC content under the rainfed and irrigated systems, respectively. Carbon loss from native soil organic matter (SOM) averaged ~61 and 261 kg C/ha.year under the rainfed and irrigated systems, respectively. Furthermore, mean stabilisation of added C in the plots under the rainfed condition (~16%) was higher than that (~13%) observed under the irrigated condition. Conversion of total added C to SOC was similar in the NPK and NPK + FYM treated plots under both growing conditions. In the NPK + FYM plots, ~38 and 29% of the C added through FYM was accounted for in the form of total SOC under the rainfed and irrigated conditions, respectively. The estimated quantity of biomass C required to maintain equilibrium SOM content under the rainfed and irrigated systems was 0.29 and 1.08 Mg/ha.year. The total annual C input by the soybean–wheat rotation in the unfertilised control plots under rainfed condition was 0.87 Mg/ha.year and with N fertiliser only under the irrigated condition was 1.75 Mg/ha.year. Thus, SOC augmentation under long-term soybean–wheat cropping was due to higher annual C input than the required amount to maintain equilibrium SOM content. Although FYM addition along with NPK improved total SOC stock and carbon sequestration potential, it did not encourage the stabilisation rate of added C. Hence, C stabilisation that takes into account the total C added in the system is a better indicator of assessing SOC sequestration. In summary, mineral fertilisation improved C sequestration capacity of soybean–wheat system in the Indian Himalayas and manure addition along with mineral fertilisers further improved it.
A procedure for mapping the depth to the texture contrast horizon of duplex soils in south-western Australia using ground penetrating radar, GPS and kriging
Authors: Simeoni M. A. , Galloway P. D. , O'Neil A. J. , Gilkes R. J.
Published: September 2009

A procedure for the rapid and accurate mapping of the depth to the texture contrast horizon of duplex soils was trialled. Data were collected using ground-penetrating radar with a 250 MHz antenna at 4 sites in the Esperance region of Western Australia. The contrast at the B horizon was identified using a ‘picking’ process similar to seismic surveys. The GPS data were integrated and depth to B horizon maps produced by kriging. The results were related to core data taken for sites and showed that GPR can provide accurate and detailed subsurface maps with ±0.1 m accuracy for B horizon depth. The influence of B horizon material composition on GPR response was also investigated using amplitude mapping. The spacing between GPR transects can affect map quality, particularly if the lateral variation in the B horizon depth is not adequately sampled by the line spacing selected. With further integration of the data collection and post-processing procedures, this would prove to be a useful tool for farmers and natural resource managers.
Soil organic carbon and physical quality as influenced by long-term application of residue and mineral fertiliser in the North China Plain
Authors: Du Zhangliu , Liu Shufu , Li Kejiang , Ren Tusheng
Published: September 2009

The influences of long-term residue and fertiliser management on soil organic carbon (SOC) and related physical properties were investigated in a wheat (Triticum aestivum L.)–corn (Zea mays L.) double-cropping system in the North China Plain. The experiment was initiated in 1981, including 4 treatments: control (no fertiliser); mineral N and P fertilisers; low residue rate plus N and P fertilisers; and high residue rate plus N and P fertilisers. In June 2006, soil samples were taken from the 0–0.05, 0.05–0.10, and 0.10–0.20 m layers to determinate bulk density (ρb), water-stable aggregates, bulk SOC, and aggregate-associated C concentrations. Soil water retention curves and saturated hydraulic conductivity (Ks) were measured using samples collected from the 0–0.05 and 0.05–0.10 m layers. The results indicated that residue incorporation significantly increased (i.e. improved) bulk SOC and aggregate-associated C concentration, aggregation, Ks, soil matrix and structural porosities, and water retention capacity. The improvements in soil physical properties by mineral N and P fertilisers alone were limited.
Residue input significantly (P < 0.05) increased the value of S, an index of soil physical quality. A high correlation existed between S and SOC concentration, and the key soil physical parameters, suggesting that S was an effective parameter for evaluation of soil physical quality. Our study concluded that a combination of residue with mineral N and P fertilisers improved SOC concentration, and consequent soil physical quality under the wheat–corn double cropping system.
CIB1 functions as a Ca
2+
-sensitive modulator of stress-induced signaling by targeting ASK1
Authors: Yoon Kyoung Wan , Cho Jun-Ho , Lee Jae Keun , Kang Young-Hee , Chae Ji Soo , Kim Young Mok , Kim Jeehyun , Kim Eun Kyung , Kim Sung Eun , Baik Ja-Hyun , Naik Ulhas P. , Cho Ssang-Goo , Choi Eui-Ju
Published: September 2009

Calcium and integrin binding protein 1 (CIB1) is a Ca
2+
-binding protein of 22 kDa that was initially identified as a protein that interacts with integrin α
IIb
. Although it interacts with various proteins and has been implicated in diverse cellular functions, the molecular mechanism by which CIB1 regulates intracellular signaling networks has remained unclear. We now show that, by targeting apoptosis signal-regulating kinase 1 (ASK1), CIB1 negatively regulates stress-activated MAPK signaling pathways. CIB1 was thus shown to bind to ASK1, to interfere with the recruitment of TRAF2 to ASK1, and to inhibit the autophosphorylation of ASK1 on threonine-838, thereby blocking ASK1 activation. Furthermore, CIB1 mitigated apoptotic cell death initiated either by TNF-α in breast cancer MCF7 cells or by 6-hydroxydopamine (6-OHDA) in dopaminergic cells. Ca
2+
influx induced by membrane depolarization reversed the inhibitory effect of CIB1 on 6-OHDA-induced ASK1 activation and cell death in dopaminergic neurons. These observations thus suggest that CIB1 functions as a Ca
2+
-sensitive negative regulator of ASK1-mediated signaling events.
Toll-like receptor 2 dependent immunogenicity of glycoconjugate vaccines containing chemically derived zwitterionic polysaccharides
Authors: Gallorini Simona , Berti Francesco , Mancuso Giuseppe , Cozzi Roberta , Tortoli Marco , Volpini Gianfranco , Telford John L. , Beninati Concetta , Maione Domenico , Wack Andreas
Published: September 2009

Group BStreptococcus(GBS) causes serious infection in neonates and is an important target of vaccine development. Zwitterionic polysaccharides (ZPS), obtained through chemical introduction of positive charges into anionic polysaccharides (PS) from GBS, have the ability to activate human and mouse antigen presenting cells (APCs) through toll-like receptor 2 (TLR2). To generate a polysaccharide vaccine with antigen (Ag) and adjuvant properties in one molecule, we have conjugated ZPS with a carrier protein. ZPS-glycoconjugates induce higher T-cell and Ab responses to carrier and PS, respectively, compared to control PS-glycoconjugates made with the native polysaccharide form. The increased immunogenicity of ZPS-conjugates correlates with their ability to activate dendritic cells (DCs). Moreover, protection of mothers or neonate offspring from lethal GBS challenge is better when mothers are immunized with ZPS-conjugates compared to immunization with PS-conjugates. In TLR2 knockout mice, ZPS-conjugates lose both their increased immunogenicity and protective effect after vaccination. When ZPS are coadministered as adjuvants with unconjugated tetanus toxoid (TT), they have the ability to increase the TT-specific antibody titer. In conclusion, glycoconjugates containing ZPS are potent vaccines. They target Ag to TLR2-expressing APCs and activate these APCs, leading to better T-cell priming and ultimately to higher protective Ab titers. Thus, rational chemical design can generate potent PS-adjuvants with wide application, including glycoconjugates and coadministration with unrelated protein Ags.
Evidence for a ferryl intermediate in a heme-based dioxygenase
Authors: Lewis-Ballester Ariel , Batabyal Dipanwita , Egawa Tsuyoshi , Lu Changyuan , Lin Yu , Marti Marcelo A. , Capece Luciana , Estrin Dario A. , Yeh Syun-Ru
Published: September 2009

In contrast to the wide spectrum of cytochrome P450 monooxygenases, there are only 2 heme-based dioxygenases in humans: tryptophan dioxygenase (hTDO) and indoleamine 2,3-dioxygenase (hIDO). hTDO and hIDO catalyze the same oxidative ring cleavage reaction of L-tryptophan to N-formyl kynurenine, the initial and rate-limiting step of the kynurenine pathway. Despite immense interest, the mechanism by which the 2 enzymes execute the dioxygenase reaction remains elusive. Here, we report experimental evidence for a key ferryl intermediate of hIDO that supports a mechanism in which the 2 atoms of dioxygen are inserted into the substrate via a consecutive 2-step reaction. This finding introduces a paradigm shift in our understanding of the heme-based dioxygenase chemistry, which was previously believed to proceed via simultaneous incorporation of both atoms of dioxygen into the substrate. The ferryl intermediate is not observable during the hTDO reaction, highlighting the structural differences between the 2 dioxygenases, as well as the importance of stereoelectronic factors in modulating the reactions.
Type 2C protein phosphatases directly regulate abscisic acid-activated protein kinases in Arabidopsis
Authors: Umezawa Taishi , Sugiyama Naoyuki , Mizoguchi Masahide , Hayashi Shimpei , Myouga Fumiyoshi , Yamaguchi-Shinozaki Kazuko , Ishihama Yasushi , Hirayama Takashi , Shinozaki Kazuo
Published: September 2009

Abscisic acid (ABA) signaling is important for stress responses and developmental processes in plants. A subgroup of protein phosphatase 2C (group A PP2C) or SNF1-related protein kinase 2 (subclass III SnRK2) have been known as major negative or positive regulators of ABA signaling, respectively. Here, we demonstrate the physical and functional linkage between these two major signaling factors. Group A PP2Cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via dephosphorylation of multiple Ser/Thr residues in the activation loop. This step was suppressed by the RCAR/PYR ABA receptors in response to ABA. However the abi1–1 mutated PP2C did not respond to the receptors and constitutively inactivated SnRK2. Our results demonstrate that group A PP2Cs act as ‘gatekeepers’ of subclass III SnRK2s, unraveling an important regulatory mechanism of ABA signaling.