bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and properties of poly(sodium acrylate‐co‐2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid)/attapulgite as a salt‐resistant superabsorbent composite
Authors: Qi Xiaohua , Liu Mingzhu , Zhang Fen , Chen Zhenbin
Published: November 2008

A novel salt‐resistant superabsorbent composite was prepared by copolymerization of partially neutralized acrylic acid, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid (AMPS) and attapulgite (APT). To enhance the swelling rate (SR) of the copolymer, sodium bicarbonate was used as a foaming agent in the course of copolymerization. Furthermore, for improving the properties of swollen hydrogel, such as strength, resilience and dispersion, the copolymer was surface‐crosslinked with glycerine and sodium silicate, and then the surface‐crosslinked copolymer was blended with aluminum sulfate and sodium carbonate in post treatment process. The influences of some reaction conditions, such as amount of AMPS, APT, and initiator, and neutralization degree of acrylic acid on water absorbency in 0.9 wt% NaCl aqueous solution both under atmospheric pressure (WA) and load (WAP, P ≈ 2 × 103 Pa) were investigated. In addition, the effect of them on SR was also studied. The WA and WAP of the superabsorbent composite prepared under optimal conditions in 0.9 wt% NaCl aqueous solution were 52 g·g−1 and 8 g·g−1, respectively. Besides, the SR was fast, and it could reach 0.393 mL·(g·s)−1. Moreover, the swollen hydrogel possessed excellent salt resistance, hydrogel resilience and dispersion. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
Thermoforming triangular troughs
Authors: Lieg Katie Lynn , Giacomin A. Jeffrey
Published: November 2008

This analysis for thermoforming triangular troughs focuses on the manufacturing process speed and follows the method of Kershner and Giacomin for thermoforming cones. We distinguish between what happens before and after (free versus constrained forming) the melt touches the prismatic mold. Neither free nor constrained forming yields analytical solutions for the required forming time. Our analysis is restricted to the fabrication of triangular troughs from nearly Newtonian melts, the second simplest relevant problem in commercial thermoforming. The simplest relevant problem, thermoforming cones, yielded analytical solutions for the forming time. Whenever we thermoform straight edges into rigid packaging, the problem of a melt stretching into a triangular trough arises. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
Preparation and characterization of pore wall‐functionalized three‐dimensionally ordered macroporous syndiotactic polystyrene
Authors: Zhang Xu , Yan Weidong , Yang Huifang , Liu Binyuan , Liu Pange
Published: November 2008

A versatile method for the modification of three‐dimensionally ordered macroporous (3DOM) highly syndiotactic polystyrene via chloromethylation at the pore walls has been demonstrated. This was followed by reaction with dimethylamine to establish a versatile approach to functionalization of such macroporous polymers. High syndiotacticity of 3DOM sPS is necessary for maintenance of the morphology of the original ordered pore structure after chloromethylation. The relative content of chloromethyl groups was shown to be 1.89 mmol/g3DOM sPS by TG‐titration. The functionalized 3DOM sPS was characterized by SEM, FT‐IR, and DSC to demonstrate that chloromethylation had occurred at the pore walls and that the dimethylamino moiety had replaced the chlorine atom of the chloromethyl group. DSC examination of the modified polymer indicated that the crystallinity of 3DOM sPS is little affected by functionalization. Thus the excellent properties of sPS are retained by the functionalized material. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
TCOs for nip thin film silicon solar cells
Authors: Söderström T. , Haug F.‐J. , Niquille X. , Ballif C.
Published: November 2008

Substrate configuration allows for the deposition of thin film silicon (Si) solar cells on non‐transparent substrates such as plastic sheets or metallic foils. In this work, we develop processes compatible with low Tgplastics. The amorphous Si (a‐Si:H) and microcrystalline Si (µc‐Si:H) films are deposited by plasma enhanced chemical vapour deposition, at very high excitation frequencies (VHF‐PECVD). We investigate the optical behaviour of single and triple junction devices prepared with different back and front contacts. The back contact consists either of a 2D periodic grid with moderate slope, or of low pressure CVD (LP‐CVD) ZnO with random pyramids of various sizes. The front contacts are either a 70 nm thick, nominally flat ITO or a rough 2 µm thick LP‐CVD ZnO. We observe that, for a‐Si:H, the cell performance depends critically on the combination of thin flat or thick rough front TCOs and the back contact. Indeed, for a‐Si:H, a thick LP‐CVD ZnO front contact provides more light trapping on the 2D periodic substrate. Then, we investigate the influence of the thick and thin TCOs in conjunction with thick absorbers (µc‐Si:H). Because of the different nature of the optical systems (thick against thin absorber layer), the antireflection effect of ITO becomes more effective and the structure with the flat TCO provides as much light trapping as the rough LP‐CVD ZnO. Finally, the conformality of the layers is investigated and guidelines are given to understand the effectiveness of the light trapping in devices deposited on periodic gratings. Copyright © 2008 John Wiley & Sons, Ltd.
CordNet: Toward a Distributed Behavior Model for Emergency Response Coordination
Authors: Hossain Liaquat , Kuti Matthew
Published: November 2008

Existing studies of coordination theory in human networks have looked at coordination problems requiring stable working relationships with no environmental uncertainties. With emergency response management demanding distributed coordination in volatile situations, the designs of existing models are useful as a building block, yet flawed for application. We hypothesize that changes to interconnectedness of nodes in the network may have implications on the potential to coordinate. To test our hypotheses, we investigate survey data from state law enforcement, state emergency services, and local law enforcement by performing agency-based (macro) and cross-agency (micro) analysis to identify attributes of each network and coordination.
Optimization of InGaN/(In,Al,Ga)N based near UV‐LEDs by MQW strain balancing with in‐situ wafer bow sensor
Authors: Knauer A. , Kolbe T. , Einfeldt S. , Weyers M. , Kneissl M. , Zettler T.
Published: November 2008

A high resolution curvature sensor was used for in‐situ monitoring of the strain state during the growth of the InGaN multiple‐quantum‐well (MQW) for near UV light emitting diodes (LEDs). The LED heterostructures were grown by metal‐organic vapor phase epitaxy. LEDs containing different Inx Al0.16Ga0.84–x N barrier layers were compared. The results were correlated with the external quantum efficiency (EQE) and the current induced shift of the emission wavelength of the LEDs. It was found that strain‐compensated or slightly compressively strained Inx Al0.16Ga0.84–x N barrier layers in the MQW, for which the net polarization in the InGaN quantum wells is close to zero, result in the highest EQE and in a stable emission wavelength independent of the drive current. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent progress in nonpolar LEDs as polarized light emitters
Authors: Masui Hisashi , Schmidt Mathew , Fellows Natalie , Yamada Hisashi , Iso Kenji , Speck James S. , Nakamura Shuji , DenBaars Steven P.
Published: November 2008

The present article provides an overview of developments in nonpolar‐oriented GaN‐based materials as polarized light emitters over the past 15 years. The strong interest in nonpolar materials emerged around 1996, but nonpolar‐oriented light‐emitting diodes were not demonstrated until 2004. The later technological key achievement was the commercialization of nonpolar‐oriented bulk GaN substrates; it is now feasible to discuss the electronic band structure of such high‐quality nonpolar GaN as well as device applications of polarized light emitters. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison of numerical solutions to the Eady frontogenesis problem
Authors: Cullen M. J. P.
Published: November 2008

The semi‐geostrophic solution to the Eady frontogenesis problem is believed to represent an asymptotic limit of the full Euler equations as the Rossby number tends to zero. This is investigated using numerical solutions. The exercise is non‐trivial because the semi‐geostrophic solution is discontinuous, and so may not be found as the limit of the Eulerian form of the equations. It is shown that solutions of the two‐dimensional compressible Euler equations converge to a singular limit with geostrophic balance in the cross‐front direction. The convergence is at the expected second‐order rate in Rossby number up to the formation of the discontinuity and at a first‐order rate for some time afterwards. Numerical robustness can be assured and the degree of convergence improved if a quasi‐monotone form of interpolation is used in the semi‐Lagrangian advection. Direct integrations of a semi‐geostrophic model using standard numerical methods require significant computational compromises, and give a somewhat smoothed version of this limit. © Crown Copyright 2008. Reproduced with the permission of HMSO. Published by John Wiley & Sons, Ltd.
Transition metal atoms on oxide supports density functional calculations
Authors: Halim W. S. Abdel , Shalabi A. S. , Soliman K. A.
Published: November 2008

The adsorption properties of Cu, Ag, Ni, and Pd atoms on O2−, F, and F+ sites of MgO, CaO, SrO, and BaO (001) surfaces have been studied by means of density functional calculations. The examined clusters were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The adsorption properties have been analyzed with reference to the basicity and energy gap of the oxide support in addition to orbital interactions. While the free Ni d9s1 triplet ground state is preserved on adsorption on the O2− sites of MgO, CaO, and SrO surfaces, it is no longer preserved on the O2− site of BaO. For all adsorbates considered, adsorption is found to be stronger on F+ sites compared with regular O2− sites. While on the O2− site, Pd and Ni form the most stable complexes, on the F site, Pd and Cu form the most stable counterparts. On the F+ site, the single valence electron of Cu and Ag atoms couples with the unpaired electron of the vacancy forming a covalent bond. As a result, the adsorption energies of these atoms on the F+ site are stronger than those on the F and O2− sites. The adsorption properties correlate linearly with the basicity and energy gap of the oxide support in addition to orbital interactions. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Inequivalent electron densities derived from an approximate correlated ground‐state wave function using the Hiller–Sucher–Feinberg identity: Comparisons with quantum Monte Carlo densities for He and Ne atoms
Authors: Amovilli Claudio , March Norman H.
Published: November 2008

The Hiller–Sucher–Feinberg (HSF) identity is combined with the three‐parameter correlated wave function of Chandrasekhar in order to generate an alternative electron density ρ(r) for the He atom. This and the conventional “local” operator form of ρ(r) are then compared with a diffusion quantum Monte Carlo density. An exact limiting relation is also presented, via HSF identity, between the one‐particle density matrix and the pair density in a many‐electron atom, which transcends its Hartree–Fock counterpart and has no N‐representability difficulties. For the Ne atom, the accuracy of the semiempirical correlated electron density recently obtained by Cordero et al. (Phys. Rev. A 2007, 75, 052502) using fine‐tuning of Hartree–Fock theory was assessed by appealing to the ground‐state density from diffusion quantum Monte Carlo. The high accuracy of the Cordero et al. density was thereby confirmed. A HSF calculation on neon, with a correlated many‐body wave function as starting point, is a worthwhile future aim. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Computational study of TNT synthesis in solvated nitration reaction systems
Authors: Liu Min‐Hsien , Cheng Ken‐Fa , Chen Cheng , Hong Yaw‐Sun
Published: November 2008

Mononitrotoluene (MNT) was incorporated into solvated reaction systems and was subjected to subsequent nitration (electrophilic and free radical substitution) to obtain corresponding dinitrotoluene (DNT) and trinitrotoluene (TNT) products. In the electrophilic nitration system, the energy barrier of the reaction to produce o,p‐dinitrotoluene from p‐nitrotoluene was found to decrease from 62.7 to 14.7 kJ/mol to 9.2 kJ/mol in solventless, hydrated, and methanol‐solvated molecular reaction systems, respectively. Further nitration to produce TNT in related solventless and solvated systems also led to a stepwise decreasing trend in the required energy, from 297.6 to 118.6 kJ/mol to 42.8 kJ/mol. Comparative synthesis using ·NO2 as the nitrating reagent to obtain o,p‐DNT or TNT in the hydrated system shows a lower reaction energy barrier than that of the same reaction in the solventless system. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Theoretical studies on structures and electronic spectra of linear carbon chains C2nH+ (n = 1−5)
Authors: Zhang Jinglai , Li Yonghong , Li Junfeng , Chen Xing , Cao Zexing
Published: November 2008

The density functional theory (DFT) and the complete active space self‐consistent‐field (CASSCF) method have been used for full geometry optimization of carbon chains C2nH+ (n = 1–5) in their ground states and selected excited states, respectively. Calculations show that C2nH+ (n = 1–5) have stable linear structures with the ground state of X3Π for C2H+ or X3Σ− for other species. The excited‐state properties of C2nH+ have been investigated by the multiconfigurational second‐order perturbation theory (CASPT2), and predicted vertical excitation energies show good agreement with the available experimental values. On the basis of our calculations, the unsolved observed bands in previous experiments have been interpreted. CASSCF/CASPT2 calculations also have been used to explore the vertical emission energy of selected low‐lying states in C2nH+ (n = 1–5). Present results indicate that the predicted vertical excitation and emission energies of C2nH+ have similar size dependences, and they gradually decrease as the chain size increases. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Structural and optical characterization of thermally evaporated cadmium sulfide thin films
Authors: Derin H. , Kantarlı K.
Published: November 2008

The article reports the structural and optical properties of vacuum‐evaporated cadmium sulfide (CdS) films with different thicknesses at room temperature. The structural investigations performed by means of X‐ray diffraction (XRD) technique have showed that all the films have the zinc‐blende structure, a face‐centered cubic form with lattice constants a = b = c = 5.82 Å and point group F43m. Crystallite sizes calculated from Scherrer relation are in the range of 173–345 Å. So far, because the optical parameters of the metastable cubic CdS have not been so well known, we apply spectroscopic ellipsometry to determine the thickness, optical constants and energy band gap of CdS thin film deposited by thermal evaporation onto opaque gold substrate, a perfect reflectivity and inert metal. As shown the measured spectral behavior of the optical constants and the band gap value of CdS thin film are in agreement with those obtained by the reflectance and transmittance methods. The energy band gap of CdS thin film determined from the spectral behavior of the absorption coefficient is about 2.46 eV. Copyright © 2008 John Wiley & Sons, Ltd.
A passivity‐based control of Euler‐Lagrange systems with a non‐quadratic Lagrangian
Authors: Jungnickel U. , Kielau G. , Maißer P. , Müller A.
Published: November 2008

In this paper, the classical augmented PD control method is extended to a passivity‐based control of Euler‐Lagrange systems with a non‐quadratic Lagrangian. It is assumed that the systems are fully actuated. The problem is treated with two geometrically different approaches. The first approach is dealing with state space control in the configuration space by introducing the kinetic energy via the Legendre transformation of the kinetic co‐energy. The second approach considers the system's dynamics in the event space endowed with a Finsler metric based on the kinetic co‐energy. It is shown that the control laws of both approaches achieve uniformly asymptotically stable trajectory tracking.
On Airy functions and stresses in nonisotropic heterogeneous 2d‐elasticity
Authors: Kulikov A. , Nazarov S.A. , Sweers G.
Published: November 2008

Problems in elasticity are described by relations between the displacement field u, the strain or deformation tensor ε, and the stress tensor σ. In 2D elasticity and if volume forces are absent, one may also consider an elastic potential. We explain these settings for a domain Ω with finitely many holes. On such domains the problem for the displacement and the potential problem are not necessarily equivalent. We will also recall the relation between these quantities. We conclude the paper with the potential setting for some specific problems in semi‐periodic domains with infinite many holes. Also the setting for non‐smooth domains is addressed.
Intakes of total fat, saturated, monounsaturated and polyunsaturated fatty acids in Irish children, teenagers and adults
Authors: Joyce Triona , Wallace Alison J , McCarthy Sinead N , Gibney Michael J
Published: November 2008

Recommendations limiting the intake of total fat, SFA, MUFA and PUFA have been established in several countries with the aim of reducing the risk of chronic diseases such as CVD. Studies have shown that intakes of total fat and SFA are above desired recommended intake levels across a wide range of age and sex groups. In addition, intakes of PUFA and MUFA are often reported to be less than the desired recommended intake levels. The aims of the present paper are to provide the first data on estimates of current intakes and main food sources of SFA, MUFA and PUFA in Irish children (aged 5–12 years), teenagers (aged 13–17 years) and adults (aged 18–64 years) and to analyse compliance with current dietary recommendations. Data for this analysis were based on the North/South Ireland Food Consumption Survey (n1379, 18–64 years), the National Children’s Food Survey (n594, 5–12 years) and the National Teen Food Survey (n441, 13–17 years). Results showed that SFA intakes in Irish children, teenagers and adults are high, with only 6 % of children, 11 % of teenagers and 21 % of adults in compliance with the recommended daily intake. The main food groups that contributed to SFA intakes were whole milk; fresh meat; meat products; biscuits, cakes, buns and pastries; and sugars, confectionery and preserves.
Maternal fish and other seafood intakes during pregnancy and child neurodevelopment at age 4 years
Authors: Mendez Michelle A , Torrent Maties , Julvez Jordi , Ribas-Fitó Nuria , Kogevinas Manolis , Sunyer Jordi
Published: November 2008

Objective

To analyse the relationship between maternal intakes of fish and other seafood during pregnancy and child neurodevelopment at age 4 years. Although pregnant women are advised to limit seafood intakes because of possible neurotoxin contamination, several studies suggest that overall maternal seafood intakes are associated with improved child neurodevelopment, perhaps because of higher DHA intakes.

Design

The study uses data from a prospective birth cohort study. Maternal seafood intakes were assessed using a semi-quantitative FFQ administered shortly after delivery. Multivariate linear regression was used to estimate associations between seafood consumption and scores on the McCarthy Scales of Children’s Abilities (MCSA). Analyses were stratified by breast-feeding duration as breast milk is a source of DHA during the postnatal phase of the brain growth spurt.

Setting

Menorca, Spain, 1997–2001.

Subjects

Full-term children (n392) with data on maternal diet in pregnancy, breast-feeding duration and neurodevelopment at age 4 years.

Results

Among children breast-fed for <6 months, maternal fish intakes of >2–3 times/week were associated with significantly higher scores on several MCSA subscales compared with intakes ≤1 time/week. There was no association among children breast-fed for longer periods. Maternal intakes of other seafood (shellfish/squid) were, however, inversely associated with scores on several subscales, regardless of breast-feeding duration.

Conclusions

The study suggests that moderately high intakes of fish, but not other seafood, during pregnancy may be beneficial for neurodevelopment among children breast-fed for <6 months. Further research in other populations with high seafood intakes and data on additional potential confounders are needed to confirm this finding.
Understanding Policy Diffusion across Feminist Social Movements: The
Case of Gender Mainstreaming in Eastern Germany
Authors: Guenther Katja M.
Published: November 2008

Gender mainstreaming emerged on the European policy scene in the mid-1990s as an
innovative and controversial policy tool for reducing gender inequalities. The
European Union seeks to propagate the practice of gender mainstreaming both
within EU institutions and among member states. Feminist scholars and policy
elites have discussed and debated gender mainstreaming widely but have yet to
consider how local feminist activists, who could play a central role in
diffusing gender mainstreaming, understand, interpret, and respond to this
agenda. This article examines whether and why local feminist movements in two
cities in eastern Germany adopt gender mainstreaming into their advocacy
agendas. Consideration of the characteristics of the contexts in which local
feminist movements are embedded clarifies the conditions under which social
movements rally around new policy paradigms.
Current variability of the Kuroshio near the separation point from the western boundary
Authors: Itoh S. , Sugimoto T.
Published: November 2008

Direct current measurements were conducted from April 2003 to March 2004 to investigate the current variability of the Kuroshio near the separation point from the western boundary. During the study period, the main stream of the Kuroshio flowed northeastward in the upper layer slightly offshore from the array of four mooring systems, while a southwestward current was observed in the intermediate layer on the coastal side of the array. Analyses based on the velocity and temperature measurement of the mooring meter array revealed eddy‐to‐mean kinetic and mean‐to‐eddy potential energy conversion in both the upper and intermediate layers. Downstream‐propagating waves detected as significant extended empirical orthogonal functions (EEOFs) are predominant over velocity fluctuations of periods shorter than 50 days, explaining 67% of the total variance. The five apparent wave groups have periods of 7–18 days, wavelengths of 220–380 km, and phase velocities of 22–30 cm s−1, respectively, similar to the values reported in previous studies of upstream regions. Although the phase velocity at a given wavelength in the Kuroshio is lower than that in the Gulf Stream, the dispersion tendency (i.e., that phase velocity increases with decreasing period and wavelength) is the same for both currents. The relatively low phase velocity of the Kuroshio is considered to reflect its relatively low background velocity. Data regarding growth rate, vertical phase lags, and energetics suggest that kinetic energy in this region is transferred from small to large scales mainly via eddies resulting from baroclinic instability, which is possibly related to synoptic‐scale path variability and the penetration of areas of high kinetic energy into the Kuroshio Extension.
Experimental petrology of the Mars Pathfinder rock composition: Constraints on the interpretation of Martian reflectance spectra
Authors: Singletary S. J. , Grove T. L.
Published: November 2008

Experiments to determine the crystallization sequence of the Mars Pathfinder (MPF) rock composition have been carried out to explore the range of possible mineral assemblages in this SiO2‐rich (57.4 wt %) Martian igneous rock. Recent Mars Global Surveyor thermal emission spectrometer observations have suggested the presence of large volumes of andesitic lava covering the northern hemisphere of Mars, but this interpretation has been called into question. Experimentally produced mineral assemblages can be used to infer spectral characteristics that would exist in andesitic lavas similar in composition to the MPF rock. The inferred spectra could then be used with remotely sensed data to further constrain the identity of surface rock types on Mars. We performed a series of experiments at 0.1 MPa at the quartz‐fayalite‐magnetite and iron‐quartz‐fayalite oxygen buffers and 100 MPa at the Ni‐NiO oxygen buffer using the calculated soil free MPF composition. Potential mineralogies for a lava with the MPF composition would be SiO2 (57 wt %), FeO (18 wt %) rich glass, plagioclase, quartz, augite, and Fe‐Ti oxides. A contoured pyroxene quadrilateral (with band I and II minima) was used to predict pyroxene composition on the basis of reflectance spectra. Using the quadrilateral in reverse, the augite produced in the experimental series should have band I and II minima at 0.97 μm and 2.15 μm, respectively. The absence of the 1‐μm minima in the Imager for Mars Pathfinder (IMP) spectra could be due to masking phases, possibly the Fe‐Ti oxides produced in our experiments at 1000°C.
Observations of the structure and evolution of surface and flight‐level wind asymmetries in Hurricane Rita (2005)
Authors: Rogers Robert , Uhlhorn Eric
Published: November 2008

Knowledge of the magnitude and distribution of surface winds, including the structure of azimuthal asymmetries in the wind field, are important factors for tropical cyclone forecasting. With its ability to remotely measure surface wind speeds, the stepped frequency microwave radiometer (SFMR) has assumed a prominent role for the operational tropical cyclone forecasting community. An example of this instrument's utility is presented here, where concurrent measurements of aircraft flight‐level and SFMR surface winds are used to document the wind field evolution over three days in Hurricane Rita (2005). The amplitude and azimuthal location (phase) of the wavenumber‐1 asymmetry in the storm‐relative winds varied at both levels over time. The peak was found to the right of storm track at both levels on the first day. By the third day, the peak in flight‐level storm‐relative winds remained to the right of storm track, but it shifted to left of storm track at the surface, resulting in a 60‐degree shift between the surface and flight‐level and azimuthal variations in the ratio of surface to flight‐level winds. The asymmetric differences between the surface and flight‐level maximum wind radii also varied, indicating a vortex whose tilt was increasing.
Local rainfall‐SST relationship on subseasonal time scales in satellite observations and CFS
Authors: Wu Renguang , Kirtman Ben P. , Pegion Kathy
Published: November 2008

The present study documents local rainfall‐SST relationship on subseasonal time scales in the tropical Indo‐western Pacific region based on satellite observations and the Climate Forecast System (CFS). It is found that the intensity of subseasonal air‐sea coupling strongly depends on the season with most prominent interaction in the summer hemisphere. The time lag between rainfall and SST displays pronounced spatial variations and asymmetric feature. In observations, the regions of the atmosphere forcing the SST tend to shift to subtropics compared to those of the SST forcing the atmosphere. In the CFS, the regions of the atmosphere forcing the SST tend to be collocated with those of the SST forcing the atmosphere. The CFS captures reasonably well the seasonality in the intensity of air‐sea coupling, but probably with an overestimation of the coupling strength. The SST response to the atmosphere takes longer time in the CFS compared to observations.
Observed relation between evapotranspiration and soil moisture in the North American monsoon region
Authors: Vivoni Enrique R. , Moreno Hernan A. , Mascaro Giuseppe , Rodriguez Julio C. , Watts Christopher J. , Garatuza‐Payan Jaime , Scott Russell L.
Published: November 2008

Soil moisture control on evapotranspiration is poorly understood in ecosystems experiencing seasonal greening. In this study, we utilize a set of multi‐year observations at four eddy covariance sites along a latitudinal gradient in vegetation greening to infer the ET‐θ relation during the North American monsoon. Results reveal significant seasonal, interannual and ecosystem variations in the observed ET‐θ relation directly linked to vegetation greening. In particular, monsoon‐dominated ecosystems adjust their ET‐θ relation, through changes in unstressed ET and plant stress threshold, to cope with differences in water availability. Comparisons of the observed relations to the North American Regional Reanalysis dataset reveal large biases that increase where vegetation greening is more significant. The analysis presented here can be used to guide improvements in land surface model parameterization in water‐limited ecosystems.
DWM07 global empirical model of upper thermospheric storm‐induced disturbance winds
Authors: Emmert J. T. , Drob D. P. , Shepherd G. G. , Hernandez G. , Jarvis M. J. , Meriwether J. W. , Niciejewski R. J. , Sipler D. P. , Tepley C. A.
Published: November 2008

We present a global empirical disturbance wind model (DWM07) that represents average geospace‐storm‐induced perturbations of upper thermospheric (200–600 km altitude) neutral winds. DWM07 depends on the following three parameters: magnetic latitude, magnetic local time, and the 3‐h Kp geomagnetic activity index. The latitude and local time dependences are represented by vector spherical harmonic functions (up to degree 10 in latitude and order 3 in local time), and the Kp dependence is represented by quadratic B‐splines. DWM07 is the storm time thermospheric component of the new Horizontal Wind Model (HWM07), which is described in a companion paper. DWM07 is based on data from the Wind Imaging Interferometer on board the Upper Atmosphere Research Satellite, the Wind and Temperature Spectrometer on board Dynamics Explorer 2, and seven ground‐based Fabry‐Perot interferometers. The perturbation winds derived from the three data sets are in good mutual agreement under most conditions, and the model captures most of the climatological variations evident in the data.
Implications of postseismic gravity change following the great 2004 Sumatra‐Andaman earthquake from the regional harmonic analysis of GRACE intersatellite tracking data
Authors: Han Shin‐Chan , Sauber Jeanne , Luthcke Scott B. , Ji Chen , Pollitz Fred F.
Published: November 2008

We report Gravity Recovery and Climate Experiment (GRACE) satellite observations of coseismic displacements and postseismic transients from the great Sumatra‐Andaman Islands (thrust event; Mw ∼9.2) earthquake in December 2004. Instead of using global spherical harmonic solutions of monthly gravity fields, we estimated the gravity changes directly using intersatellite range‐rate data with regionally concentrated spherical Slepian basis functions every 15‐day interval. We found significant step‐like (coseismic) and exponential‐like (postseismic) behavior in the time series of estimated coefficients (from May 2003 to April 2007) for the spherical Slepian functions. After deriving coseismic slip estimates from seismic and geodetic data that spanned different time intervals, we estimated and evaluated postseismic relaxation mechanisms with alternate asthenosphere viscosity models. The large spatial coverage and uniform accuracy of our GRACE solution enabled us to clearly delineate a postseismic transient signal in the first 2 years of postearthquake GRACE data. Our preferred interpretation of the long‐wavelength components of the postseismic gravity change is biviscous viscoelastic flow. We estimated a transient viscosity of 5 × 1017 Pa s and a steady state viscosity of 5 × 1018–1019 Pa s. Additional years of the GRACE observations should provide improved steady state viscosity estimates. In contrast to our interpretation of coseismic gravity change, the prominent postearthquake positive gravity change around the Nicobar Islands is accounted for by seafloor uplift with less postseismic perturbation in intrinsic density in the region surrounding the earthquake.
Remote sensing data assimilation for a prognostic phenology model
Authors: Stöckli R. , Rutishauser T. , Dragoni D. , O'Keefe J. , Thornton P. E. , Jolly M. , Lu L. , Denning A. S.
Published: November 2008

Predicting the global carbon and water cycle requires a realistic representation of vegetation phenology in climate models. However most prognostic phenology models are not yet suited for global applications, and diagnostic satellite data can be uncertain and lack predictive power. We present a framework for data assimilation of Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR) and Leaf Area Index (LAI) from the MODerate Resolution Imaging Spectroradiometer (MODIS) to constrain empirical temperature, light, moisture and structural vegetation parameters of a prognostic phenology model. We find that data assimilation better constrains structural vegetation parameters than climate control parameters. Improvements are largest for drought‐deciduous ecosystems where correlation of predicted versus satellite‐observed FPAR and LAI increases from negative to 0.7–0.8. Data assimilation effectively overcomes the cloud‐ and aerosol‐related deficiencies of satellite data sets in tropical areas. Validation with a 49‐year‐long phenology data set reveals that the temperature‐driven start of season (SOS) is light limited in warm years. The model has substantial skill (R = 0.73) to reproduce SOS inter‐annual and decadal variability. Predicted SOS shows a higher inter‐annual variability with a negative bias of 5–20 days compared to species‐level SOS. It is however accurate to within 1–2 days compared to SOS derived from net ecosystem exchange (NEE) measurements at a FLUXNET tower. The model only has weak skill to predict end of season (EOS). Use of remote sensing data assimilation for phenology model development is encouraged but validation should be extended with phenology data sets covering mediterranean, tropical and arctic ecosystems.
Inhibition of destructive autoimmune arthritis in FcγRIIa transgenic mice by small chemical entities
Authors: Pietersz Geoffrey A , Mottram Patricia L , van de Velde Nicholas C , Sardjono Caroline Tan , Esparon Sandra , Ramsland Paul A , Moloney Gerard , Baell Jonathan B , McCarthy Tom D , Matthews Barry R , Powell Maree S , Hogarth P Mark
Published: November 2008

The interaction of immune complexes with the human Fc receptor, FcγRIIa, initiates the release of inflammatory mediators and is implicated in the pathogenesis of human autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus, so this FcR is a potential target for therapy. We have used the three‐dimensional structure of an FcγRIIa dimer to design small molecule inhibitors, modeled on a distinct groove and pocket created by receptor dimerization, adjacent to the ligand‐binding sites. These small chemical entities (SCEs) blocked immune complex‐induced platelet activation and aggregation and tumor necrosis factor secretion from macrophages in a human cell line and transgenic mouse macrophages. The SCE appeared specific for FcγRIIa, as they inhibited only immune complex‐induced responses and had no effect on responses to stimuli unrelated to FcR, for example platelet stimulation with arachidonic acid. In vivo testing of the SCE in FcγRIIa transgenic mice showed that they inhibited the development and stopped the progression of collagen‐induced arthritis (CIA). The SCEs were more potent than methotrexate and anti‐CD3 in sustained suppression of CIA. Thus, in vitro and in vivo activity of these SCE FcγRIIa receptor antagonists demonstrated their potential as anti‐inflammatory agents for autoimmune diseases involving immune complexes.
T‐lymphocyte interaction with stromal, bone and hematopoietic cells in the bone marrow
Authors: Di Rosa Francesca
Published: November 2008

Mature T cells in the bone marrow (BM) are in constant exchange with the blood pool. Within the BM, T‐cell recognition of antigen presented by dendritic cell (DC) can occur, nevertheless it is thought that BM T cells mostly receive non‐antigenic signals by either stimulatory, for example, interleukin (IL)‐7, IL‐15, tumor necrosis factor family members, or inhibitory molecules, for example, transforming growth factor‐β. The net balance is in favor of T‐cell proliferation. Indeed, the percentage of proliferating T cells is higher in the BM than in spleen and lymph nodes, both within CD4 and CD8 T cells. High numbers of memory T cells proliferate in the BM, as they preferentially home to the BM and have an increased turnover as compared with naive T cells. I propose here that the BM plays an essential role in maintaining normal peripheral T‐lymphocyte numbers and antigen‐specific memory for both CD4 and CD8 T cells. I also discuss BM T‐cell contribution to the homeostasis of bone metabolism as well as of hematopoiesis. It emerges that BM T cells play unexpected roles in several diseases, for example AIDS and osteoporosis. A better knowledge on BM T cells has implications for currently used clinical interventions, for example, vaccination, BM transplantation, mesenchymal stem cell‐based therapies.
Back to the thymus: peripheral T cells come home
Authors: Hale J Scott , Fink Pamela J
Published: November 2008

The thymus has long been known as the generative organ for the T‐cell arm of the immune system. To perform this role, the thymus was thought to require protection from antigenic and cellular insult from the ‘outside world’, with the notable exception of the continual influx of progenitor cells required to initiate the complicated process of T‐cell differentiation. Overwhelming evidence that mature T cells can recirculate and persist in the thymus has required us to revamp this earlier view of the thymus as detached from outside influence. In this review, we consider the evidence for T‐cell recirculation into the thymus, discuss the likely means and location of mature T‐cell entry, and speculate on the potential consequences of such close apposition between differentiating thymocytes and mature recirculating lymphocytes.
The bone marrow perisinusoidal niche for recirculating B cells and the positive selection of bone marrow‐derived B lymphocytes
Authors: Pillai Shiv , Cariappa Annaiah
Published: November 2008

A unique ‘second’ niche for follicular B cells has been described in the extravascular compartment of the bone marrow surrounding vascular sinusoids. The occupancy of this niche by B cells presumably evolved to facilitate humoral immune responses to blood‐borne pathogens. B cells appear to be sustained in this niche by bone marrow dendritic cells and are lost from this compartment in certain mutant mice. We discuss here what is known regarding the mechanisms of entry and egress of B cells from the perisinusoidal niche and also consider the function of the bone marrow as a secondary lymphoid organ. Although immature B cells can mature into follicular B cells in this niche as well as in the spleen, the lineage commitment event that accompanies positive selection of B cells occurs only in the spleen.
Equivalent magnetic charge in helicoidal magnets
Authors: Muscia Roberto
Published: November 2008

In this paper we show that magnetostatic models of permanent magnets, based on distributions of magnetic charge and shaped by a helicoidal geometry of cylindrical type, have the volume charge density ρM equal to zero. This result is valid when (i) the modulus of the vector physical magnetization density M has a constant value in all the points of the helicoidal magnet and (ii) M has the same direction of an oriented straight line having a constant angle with respect to the normal line of a cylindrical helix. Another case study concerns the permanent magnets with conchospiral geometry and magnetization M. For this kind of magnet we show that, in general, ρM≠0. Furthermore, in relation to the nonobvious result ρM=0 obtained for the cylindrical helicoidal permanent magnets, some geometrical physical considerations are illustrated. With reference to these observations, in order to understand if ρM is equal to zero or not without considering divergence computation, the possibility of defining a criterion based only on the geometry and magnetization of the magnet is discussed. Finally, an application of the results obtained from the previous analysis is shown. After drawing an analytical formulation of the surface charge density σM relative to a cylindrical helicoidal magnet, a complete evaluation of the field distribution around this magnet is performed. The results are presented by using cylindrical polar graphics of the magnetic flux B.
Testing the effect of surface coatings on alkali atom polarization lifetimes
Authors: Seltzer S. J. , Rampulla D. M. , Rivillon-Amy S. , Chabal Y. J. , Bernasek S. L. , Romalis M. V.
Published: November 2008

The evaluation of different surface coatings used in alkali metal atomic magnetometers is necessary for the improvement of sensitivity of these devices. A method to measure the polarization lifetime of alkali atoms in the region between substrates with different coatings was developed to determine the effectiveness of the coating at preserving alkali spin polarization as well as chemical compatibility and high-temperature stability. Multiple coatings can be compared under identical experimental conditions, using an experimental geometry that allows surface characterization before and after evaluation of the polarization lifetime. Multilayered, cross-linked octadecyltrichlorosilane films, alkyltrichlorosilane monolayers, and octadecylphosphonic acid monolayers were evaluated using this approach.
Lower-hybrid drift and Buneman instabilities in current sheets with guide field
Authors: Yoon P. H. , Lui A. T. Y.
Published: November 2008

Lower-hybrid drift and Buneman instabilities operate in current sheets with or without the guide field. The lower-hybrid drift instability is a universal instability in that it operates for all parameters. In contrast, the excitation of Buneman instability requires sufficiently thin current sheet. That is, the relative electron-ion drift speed must exceed the threshold in order for Buneman instability to operate. Traditionally, the two instabilities were treated separately with different mathematical formalisms. In a recent paper, an improved electrostatic dispersion relation was derived that is valid for both unstable modes [P. H. Yoon and A. T. Y. Lui, Phys. Plasmas 15, 072101 (2008)]. However, the actual numerical analysis was restricted to a one-dimensional situation. The present paper generalizes the previous analysis and investigates the two-dimensional nature of both instabilities. It is found that the lower-hybrid drift instability is a flute mode satisfying k⋅B=0 and k⋅∇n=0, where k represents the wave number for the most unstable mode, B stands for the total local magnetic field, and ∇n is the density gradient. This finding is not totally unexpected. However, a somewhat surprising finding is that the Buneman instability is a field-aligned mode characterized by k×B=0 and k⋅∇n=0, rather than being a beam-aligned instability.
Density matrix formulation of the nuclear-electronic orbital approach with explicit electron-proton correlation
Authors: Chakraborty Arindam , Hammes-Schiffer Sharon
Published: November 2008

The density matrix formulation of the nuclear-electronic orbital explicitly correlated Hartree–Fock (NEO-XCHF) approach for including electron-proton correlation in mixed nuclear-electronic wave functions is presented. This approach is based on a general ansatz for the nuclear-electronic wave function that includes explicit dependence on the nuclear-electronic distances with Gaussian-type geminal functions. The NEO-XCHF approach is extended to treat multielectron, multiproton systems and to describe a broader class of systems that require a more general form of the wave function, such as open-shell and multireference wave functions. General expressions are derived for the one-particle and two-particle densities, as well as the total energy. In addition, expressions for the total energy and Fock matrices in an atomic orbital basis are derived for the special case of a closed-shell electronic system. The resulting Hartree–Fock–Roothaan equations can be solved iteratively to self consistency. An advantage of the density matrix representation is that it facilitates the development of approximate NEO-XCHF methods in which specified high-order density terms are neglected to decrease the computational expense. Another advantage of the density matrix representation is that it provides the foundation for the development of electron-proton functionals within the framework of density functional theory, thereby enabling a consistent treatment of both electron-electron and electron-proton correlation in a computationally practical manner.
Compressible proper orthogonal decomposition/Galerkin reduced-order model of self-sustained oscillations in a cavity
Authors: Gloerfelt Xavier
Published: November 2008

The direct computation of the noise has become a powerful tool in aeroacoustics but is still very expensive to study long-time dynamics, to explore a range of parameters, or to apply the control theory. A promising technique to circumvent this difficulty is the use of low-dimensional proper orthogonal decomposition (POD)/Galerkin models as governing equations. Most of the studies have considered the incompressible Navier–Stokes equations. The derivation of a simple Galerkin model is trickier in the compressible regime. Two methods, one based on an isentropic assumption, the other involving the specific volume, are applied to the flow over an open cavity including the radiated noise. The two-dimensional application shows that the dynamical systems converge to an erroneous state after long-time integration. This drift is due to a lack of dissipation attributed to the pressure terms at the outlet, to the differences between the original and projected equations, or to rounding errors. Different stabilization strategies are tested to improve the reliability of the model. A calibration of the coefficients is seen to lead to asymptotically stable models. The extension to a three-dimensional cavity, where two modes coexist, shows the extreme sensitivity of the POD/Galerkin models to small perturbations. A calibrated model is able to reproduce short-time dynamics and the effect of the mean field in triadic nonlinear energy transfer is investigated.