bluuebunny/crossref_metadata_2025 huggingface dataset:
Three‐dimensional volume‐averaged soil moisture transport model with a scalable parameterization of subgrid topographic variability
Authors: Choi Hyun I. , Kumar Praveen , Liang Xin‐Zhong
Published: April 2007

Subgrid variability of subsurface moisture flux transport is strongly influenced by the local variation of topographic attributes, such as elevation, slope, and curvature. A three‐dimensional volume‐averaged soil moisture transport (VAST) model is developed to incorporate these effects using the volume‐averaged Richards equation. The small‐perturbation approach is used to decompose the equation into mean and fluctuation, which are then averaged over the model grid box. This formulation explicitly incorporates the variability of moisture flux due to subgrid variation of topographic attributes. The model is independent of scale, but the parameters need to be estimated at the model scale. It is demonstrated that the flux contribution from the subgrid variability can be comparable to that of mean flux, particularly under drier moisture conditions. This formulation can be substituted for subsurface moisture transport schemes in most existing land surface models.
An attenuated eddy covariance method for latent heat flux measurements
Authors: Dias Nelson L. , Duarte Henrique F. , Maggiotto Selma R. , Grodzki Leocádio
Published: April 2007

An attenuated eddy covariance (AEC) method is proposed, combining the use of a relatively robust three‐dimensional sonic anemometer and a ventilated capacitive hygrometer‐thermometer (CHT). The CHT is able to resolve a large enough frequency region of the water vapor density turbulent fluctuations to allow corrections for its limited time response in the inertial subrange of the vertical velocity‐humidity cospectrum. This approach is often called the “band‐pass covariance method.” In the present work we propose a technique in which the covariance between the vertical velocity and water vapor density fluctuations is calculated directly in the time domain (as in the standard eddy covariance technique) and then corrected for the effects of wind velocity and sensor temperature. This technique has been tested with the capacitive sensor “uncapped” and “capped” and in both cases compares well (RMSE ≤ 23 W m−2) with eddy covariance measurements using fast response hygrometers.
Seismic interferometry using non‐volcanic tremor in Cascadia
Authors: Chaput J. A. , Bostock M. G.
Published: April 2007

Seismic interferometry to date has focussed on surface waves, due to paucity of deep, high‐frequency noise sources. Here, we investigate use of non‐volcanic tremor on the Cascadia subduction zone as a noise source to recover scattered body‐wave contributions to the Green's function. Tremor data for 2004–2005 recorded at Polaris‐BC stations TWKB, MGCB and LZB were filtered and cross‐correlated. TWKB and MGCB correlations generate a highly reproducible arrival at 4.5 s for combinations of vertical with radial or transverse components. TWKB and LZB correlations are less reproducible, but yield a strong arrival at 3.5 s for 2005. Upon consideration of source/receiver geometry, polarity and timing, we interpret these arrivals to represent reflection‐conversions. Arrival times imply that these signals originate at depths between 9 and 12 km, coincident with an interval of strong reflectivity imaged in the 1987 Lithoprobe Southern Cordillera transect.
Scaling relationship between the duration and the amplitude of non‐volcanic deep low‐frequency tremors
Authors: Watanabe Tomoko , Hiramatsu Yoshihiro , Obara Kazushige
Published: April 2007

We investigate a duration‐amplitude relation of non‐volcanic deep low‐frequency (DLF) tremors in the Tokai region, southwest Japan, to constrain the source process of the tremors. We apply two models to the distribution, one is an exponential model as a scale bound distribution and the other a power law model as a scale invariant distribution. The exponential model shows a better fit to the duration‐amplitude distribution of the tremors than a power law model, implying that the DLF tremors are caused by a scale‐bound source process. The source process of the DLF tremors, therefore, differs from those for earthquakes. We suggest that the non‐volcanic DLF tremor is possibly caused by a fixed source dimension with variable excess pressure of fluid or variable stress drop.
Antileukoproteinase protects against hepatic inflammation, but not apoptosis in the response of D‐galactosamine‐sensitized mice to lipopolysaccharide
Authors: Eipel C , Kidess E , Abshagen K , LeMinh K , Menger M D , Burkhardt H , Vollmar B
Published: April 2007

Background and purpose:

There is major evidence for the strong bi‐directional interrelation of parenchymal cell apoptosis and leukocyte accumulation and inflammation in acute liver injury. Therefore, the aim of this in vivo study was to investigate the anti‐apoptotic and anti‐inflammatory potential of antileukoproteinase (ALP) in a murine model of acute liver failure.

Experimental approach:

C57BL/6J mice were given galactosamine (D‐GalN) and E. coli lipopolysaccharide (LPS) followed by administration of saline or ALP. Besides survival rate, hepatic tissue damage and inflammatory response were analyzed by intravital fluorescence microscopy 6 hours after treatment. In addition, immunohistochemical analysis of NFκB‐p65 and hepatocellular apoptosis, plasma levels of AST/ALT, TNF‐α and IL‐10 were determined.

Key results:

Administration of D‐GalN/LPS provoked hepatic damage, including marked leukocyte recruitment and microvascular perfusion failure, as well as hepatocellular apoptosis and enzyme release. NFκB‐p65 became increasingly detectable in hepatocellular nuclei, accompanied by a rise of TNF‐α and IL‐10 plasma levels. ALP markedly reduced intrahepatic leukocyte accumulation, nuclear translocation of NFκB and plasma levels of TNF‐α and IL‐10. Moreover, liver enzyme levels indicated the absence of necrotic parenchymal cell death. In contrast, ALP failed to block both apoptosis and caspase‐3 levels and the mortality rate of ALP‐treated animals was comparable to that of saline‐treated mice.

Conclusions and implications:

ALP could effectively prevent D‐GalN/LPS‐associated intrahepatic inflammatory responses by inhibition of NFκB activity, but not apoptosis‐driven mortality. Thus, a protease‐inactivating approach such as application of ALP seems to be inadequate in damaged liver where apoptosis represents the predominant mode of cell death.

British Journal of Pharmacology (2007) 151, 406–413; doi:10.1038/sj.bjp.0707230
Differential effects of selective oestrogen receptor modulators (SERMs) tamoxifen, ospemifene and raloxifene on human osteoclasts in vitro
Authors: Michael H , Härkönen P L , Kangas L , Väänänen H K , Hentunen T A
Published: April 2007

Background and purpose:

Several selective oestrogen receptor modulators (SERMs) with oestrogen agonist effects in bone cells and without increased risk of breast and endometrial cancer have been developed. Here, we have investigated the effects of different types of SERMs on osteoclast differentiation, bone resorption and apoptosis in vitro.

Experimental approach:

Human peripheral blood‐derived CD14+ monocytes were cultured on bovine bone slices in the presence of RANKL, M‐CSF, TNF‐α and dexamethasone for seven days. Also, CD14+ monocytes were co‐cultured either with human SaOS‐2 or MG‐63 osteosarcoma cells, in the presence of parathyroid hormone. Osteoclast cultures were treated with different SERMs. TRACP+ multinucleated cells and C‐terminal telopeptide of type I collagen were used as markers for osteoclast formation and bone resorption, respectively.

Key Results:

In CD14+ monocyte cultures, tamoxifen directly inhibited human osteoclast formation and bone resorption, while raloxifene and ospemifene had no inhibitory effect. In the co‐cultures either with SaOS‐2 or MG‐63 cells, ospemifene and raloxifene as well as tamoxifen inhibited osteoclast formation in a concentration‐dependent manner. The inhibitory effect was associated with an increased production of osteoprotegerin. The anti‐oestrogen ICI 182 780 completely reversed the effects of these SERMs.

Conclusion and Implications:

Tamoxifen had an oestrogen receptor dependent, direct, inhibitory effect on human osteoclast differentiation and bone resorption, whereas ospemifene and raloxifene required osteoblastic cells to achieve a similar inhibition. The effects of ospemifene and raloxifene were mediated by oestrogen receptors by a mechanism involving paracrine induction of osteoprotegerin in cultures with osteoblast derived osteosarcoma cells.

British Journal of Pharmacology (2007) 151, 384–395; doi:10.1038/sj.bjp.0707232
Monoterpenoid agonists of TRPV3
Authors: Vogt‐Eisele A K , Weber K , Sherkheli M A , Vielhaber G , Panten J , Gisselmann G , Hatt H
Published: April 2007

Background and purpose:

Transient receptor potential (TRP) V3 is a thermosensitive ion channel expressed predominantly in the skin and neural tissues. It is activated by warmth and the monoterpene camphor and has been hypothesized to be involved in skin sensitization. A selection of monoterpenoid compounds was tested for TRPV3 activation to establish a structure‐function relationship. The related channel TRPM8 is activated by cool temperatures and a number of chemicals, among them the monoterpene (‐)‐menthol. The overlap of the receptor pharmacology between the two channels was investigated.

Experimental approach:

Transfected HEK293 cells were superfused with the test substances. Evoked currents were measured in whole cell patch clamp measurements. Dose‐response curves for the most potent agonists were obtained in Xenopus laevis oocytes.

Key results:

Six monoterpenes significantly more potent than camphor were identified: 6‐tert‐butyl‐m‐cresol, carvacrol, dihydrocarveol, thymol, carveol and (+)‐borneol. Their EC50 is up to 16 times lower than that of camphor. All of these compounds carry a ring‐located hydroxyl group and neither activates TRPM8 to a major extent.

Conclusions and implications:

Terpenoids have long been recognized as medically and pharmacologically active compounds, although their molecular targets have only partially been identified. TRPV3 activation may be responsible for several of the described effects of terpenoids. We show here that TRPV3 is activated by a number of monoterpenes and that a secondary hydroxyl‐group is a structural requirement.

British Journal of Pharmacology (2007) 151, 530–540; doi:10.1038/sj.bjp.0707245
Spatial modelling of brief and long interactions between T cells and dendritic cells
Authors: Beltman Joost B , Marée Athanasius F M , de Boer Rob J
Published: April 2007

In the early phases of an immune response, T cells of appropriate antigen specificity become activated by antigen‐presenting cells in secondary lymphoid organs. Two‐photon microscopy imaging experiments have shown that this stimulation occurs in distinct stages during which T cells exhibit different motilities and interactions with dendritic cells (DCs). In this paper, we utilize the Cellular Potts Model, a model formalism that takes cell shapes and cellular interactions explicitly into account, to simulate the dynamics of, and interactions between, T cells and DCs in the lymph node paracortex. Our three‐dimensional simulations suggest that the initial decrease in T‐cell motility after antigen appearance is due to ‘stop signals’ transmitted by activated DCs to T cells. The long‐lived interactions that occur at a later stage can only be explained by the presence of both stop signals and a high adhesion between specific T cells and antigen‐bearing DCs. Furthermore, our results indicate that long‐lasting contacts with T cells are promoted when DCs retract dendrites that detect a specific contact at lower velocities than other dendrites. Finally, by performing long simulations (after prior fitting to short time scale data) we are able to provide an estimate of the average contact duration between T cells and DCs.
Probe diagnostics of argon-oxygen-tetramethyltin capacitively coupled plasmas for the deposition of tin oxide thin films
Authors: Pulpytel J. , Morscheidt W. , Arefi-Khonsari F.
Published: April 2007

Langmuir probe measurements in nondepositing and depositing rf capacitively coupled (CCP) plasmas are briefly reviewed and compared to the results obtained in our rf system used for the deposition of tin oxide (SnO2) thin films from argon-oxygen-tetamethyltin [Sn(CH3)4] plasmas. Typically in our experimental conditions for tin oxide deposition, values of kTeff= 1.2−1.5 eV and ne=3−5×109 cm−3 were measured. These values are consistent with those generally reported in other depositing discharges. The shape of the electron energy probability function (EEPF), obtained from the Druyvesteyn procedure, was discussed too. As a consequence of the two electron heating mechanisms in capacitively coupled discharges, that is, ohmic and stochastic heating, the electrons have a bi-Maxwellian EEPF at low pressure (in the range of 10−100 mTorr). Moreover, a deep “hole” appears in the EEPF at the energy which could correspond to the resonant peak of the vibrational excitation cross section of some molecules which can be present in the discharge, such as N2, CH4, or CO.
Complete thermodynamically consistent kinetic model of particle nucleation and growth: Numerical study of the applicability of the classical theory of homogeneous nucleation
Authors: Chesnokov Evgeni N. , Krasnoperov Lev N.
Published: April 2007

A complete thermodynamically consistent elementary reaction kinetic model of particle nucleation and growth from supersaturated vapor was developed and numerically evaluated to determine the conditions for the steady-state regime. The model treats all processes recognized in the aerosol science (such as nucleation, condensation, evaporation, agglomeration∕coagulation, etc.) as reversible elementary reactions. It includes all possible forward reactions (i.e., of monomers, dimers, trimers, etc.) together with the thermodynamically consistent reverse processes. The model is built based on the Kelvin approximation, and has two dimensionless parameters: S0—the initial supersaturation and Θ—the dimensionless surface tension. The time evolution of the size distribution function was obtained over the ranges of parameters S0 and Θ. At low initial supersaturations, S0, the steady state is established after a delay, and the steady-state distribution function corresponds to the predictions of the classical nucleation theory. At high initial supersaturations, the depletion of monomers due to condensation on large clusters starts before the establishing of the steady state. The steady state is never reached, and the classical nucleation theory is not applicable. The boundary that separates these two regimes in the two dimensionless parameter space, S0 and Θ, was determined. The model was applied to several experiments on water nucleation in an expansion chamber [J. Wolk and R. Strey, J. Phys. Chem. B 105, 11683 (2001)] and in Laval nozzle [Y. J. Kim et al., J. Phys. Chem. A 108, 4365 (2004)]. The conditions of the experiments performed using Laval nozzle (S0=40–120) were found to be close to the boundary of the non-steady-state regime. Additional calculations have shown that in the non-steady-state regime the nucleation rate is sensitive to the rate constants of the initial steps of the nucleation process, such as the monomer-monomer, monomer-dimer, etc., reactions. This conclusion is particularly important for nucleation from supersaturated water vapor, since these processes for water molecules at and below the atmospheric pressure are in the low pressure limit, and the rate constants can be several orders of magnitude lower than the gas kinetic. In addition, the impact of the thermodynamic inconsistency of the previously developed partially reversible kinetic numerical models was assessed. At typical experimental conditions for water nucleation, S0=10 and Θ=10 (T=250K), the error in the particle nucleation rate introduced by the thermodynamic inconsistency exceeds one order of magnitude.
Misorientations in [001] magnetite thin films studied by electron backscatter diffraction and magnetic force microscopy
Authors: Koblischka-Veneva A. , Koblischka M. R. , Wei J. D. , Zhou Y. , Murphy S. , Mücklich F. , Hartmann U. , Shvets I. V.
Published: April 2007

Magnetite thin films grown on [001] oriented MgO substrates are analyzed by means of electron backscatter diffraction (EBSD) analysis and magnetic force microscopy in applied fields. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution up to 20nm on such ceramic samples. A high image quality of the recorded Kikuchi patterns was achieved enabling multiphase scans and high spatial resolution measurements. Upon annealing in air, the magnetic properties of the magnetite thin films were found to change considerably. Using the EBSD analysis, we find that misoriented grains remaining after the annealing step form small islands with a size of about 100nm. The size and distribution of these islands correspond well to the observations of antiferromagnetic pinning centers within the magnetic domain structures carried out by magnetic force microscopy on the same samples.
Proximity effect of superconductivity and magnetism in the Nd0.7Ca0.3MnO3∕YBa2Cu3O7 bilayer
Authors: Lin J. G. , Hsu Daniel , Wu W. F. , Chiang C. H. , Chan W. C.
Published: April 2007

Temperature and current dependent resistivity are investigated in the single YBa2Cu3O7 layer and the YBa2Cu3O7∕Nd0.7Ca0.3MnO3 (YBCO∕NCMO) bilayer with the thickness of each layer being 200nm. Our results show that the onset temperature (Tcon) of the superconducting transition in YBCO layer is linearly suppressed by current with a rate of 0.1K∕mA. However, Tcon of the NCMO∕YBCO bilayer is reduced effectively from 54to30K with increasing the applied current from 1to40mA, which indicates an enhanced effect of pair breaking by the polarized quasiparticles.
Large enhancement of coercivity of magnetic Co∕Pt nanodots with perpendicular anisotropy
Authors: Zhu F. Q. , Shang Z. , Monet D. , Chien C. L.
Published: April 2007

Nanodots consisting of Co∕Pt multilayer have been fabricated using nanosphere lithography and ion beam etching. The nanodots retained the perpendicular anisotropy as that of the continuous films. However, the coercivity of the nanodots was greatly enhanced, more substantially for smaller nanodots. Concurrently, the remnant magnetization was reduced to 50%–80%. Magnetic force microscopy revealed that the domain pattern of nanodots at the remnant state was largely single domain but with nonperpendicular stray fields on the edges, indicating noncollinear alignment of magnetizations in those regions.
Charge states and quantitative infrared spectroscopy of electrically active oxygen centers in gallium arsenide
Authors: Alt H. Ch. , Gomeniuk Y. V. , Kretzer U.
Published: April 2007

Oxygen-doped gallium arsenide crystals have been investigated by Fourier transform infrared spectroscopy. Samples with the Fermi level at about 0.4eV below the conduction band exhibit under thermal equilibrium conditions both stable states of electrically active oxygen Ooc, identified optically by the associated local vibrational modes at 730 and 715cm−1. Based on the analysis of compensating centers in the material and comparative Hall measurements, the charge states +1 and −1, respectively, are assigned to these bands. This result favors the (AsGa)2–OAs (two arsenic antisites and one off-center substitutional oxygen atom) microscopic model for the Ooc defect, presented recently, and is in disagreement with the earlier isolated OAs models. Systematic investigations related to the quantitative optical spectroscopy of this center using optically induced conversion experiments confirm that the absorption strengths of the two bands differ by 15%. A calibration factor of 3.6×1016cm−1 is suggested for the band at 730cm−1, derived indirectly from the variation of the +1 and −1 charge states with the carbon acceptor concentration.
Comment on “Electron acceleration by a chirped Gaussian laser pulse in vacuum” [Phys. Plasmas 13, 123108 (2006)]
Authors: Gupta D. N. , Hur M. S. , Suk H.
Published: April 2007

Sohbatzadeh et al. [Phys. Plasmas 13, 123108 (2006)] have presented a scheme of vacuum electron acceleration by using a chirped Gaussian laser pulse. They assume a linear polarization of the laser pulse in this scheme. We point out that this might be an important assumption in their work and it can seriously influence the electron energy gain during laser acceleration. In this Comment, the circular polarization of a chirped laser pulse is employed and our results show higher electron energy gains.
Optically detected cyclotron resonance studies of InxGa1−xNyAs1−y∕GaAs quantum wells sandwiched between type-II AlAs∕GaAs superlattices
Authors: Dagnelund D. , Vorona I. , Wang X. J. , Buyanova I. A , Chen W. M. , Geelhaar L. , Riechert H.
Published: April 2007

We report on our results from a systematic study of layered structures containing an InGaNAs∕GaAs single quantum well (SQW) enclosed between staggered type II AlAs∕GaAs superlattices (SL), by the photoluminescence (PL) and optically detected cyclotron resonance (ODCR) techniques. Besides the ODCR signal known to originate from electrons in GaAs, the predominant ODCR peak is shown to be related to carriers with a two-dimensional character and a cyclotron resonance effective mass of m*≈(0.51–0.56)m0. The responsible carriers are ascribed to electrons on the ellipsoidal equienergy surface at the AlAs X point of the Brillouin zone within the SL, based on results from angular and spectral dependences of the ODCR signal. No ODCR signal related to the InGaNAs SQW was detected, presumably due to low carrier mobility despite the high optical quality. Multiple absorption of photons with energy below the band gap energy of the SL and the GaAs barriers was observed, which bears implication on the efficiency of light-emitting devices based on these structures.
Time-reversible ab initio molecular dynamics
Authors: Niklasson Anders M. N. , Tymczak C. J. , Challacombe Matt
Published: April 2007

Time-reversible ab initio molecular dynamics based on a lossless multichannel decomposition for the integration of the electronic degrees of freedom [Phys. Rev. Lett. 97, 123001 (2006)] is explored. The authors present a lossless time-reversible density matrix molecular dynamics scheme. This approach often allows for stable Hartree-Fock simulations using only one single self-consistent field cycle per time step. They also present a generalization, introducing an additional “forcing” term, that in a special case includes a hybrid Lagrangian, i.e., Car-Parrinello-type, method, which can systematically be constrained to the Born-Oppenheimer potential energy surface by using an increasing number of self-consistency cycles in the nuclear force calculations. Furthermore, in analog to the reversible and symplectic leapfrog or velocity Verlet schemes, where not only the position but also the velocity is propagated, the authors propose a Verlet-type density velocity formalism for time-reversible Born-Oppenheimer molecular dynamics.
Magnetic and transport properties of Ni81Fe19∕Al2O3 granular multilayers approaching the superparamagnetic limit
Authors: Bručas R. , Hanson M. , Gunnarsson R. , Wahlström E. , van Kampen M. , Hjörvarsson B. , Lidbaum H. , Leifer K.
Published: April 2007

The magnetic and transport properties of Ni81Fe19∕Al2O3 granular multilayer films were studied in relation to their structural properties as the nominal thickness t of the permalloy (Ni81Fe19) layer was varied near the percolation limit: in the range of 8⩽t⩽16Å while keeping the nominal thickness of the Al2O3 layers constant at 16Å. A good structural quality of the multilayers was demonstrated by low angle x-ray reflectivity measurements, and transmission electron microscopy showed the transition from continuous permalloy layers separated by aluminium oxide layers for t=16Å to metal grains dispersed in the insulator at t=8Å. Magnetization measurements showed the gradual transition from ferromagnetic layers to superparamagnetic clusters and grains that successively become blocked as the temperature decreases. A strong correlation between transport and structural properties was observed in the temperature (T) dependence of the electrical resistance measured with the current in the plane in the range of 2⩽T⩽300K: a gradual change of behavior from continuous permalloy layers with conducting interlayer connections for t=16Å to isolated permalloy grains in a dielectric for the film with t=10Å. The percolation occurs between 12 and 10Å, as deduced both from the magnetic and resistive properties. The discontinuous metal films were analyzed within models for thermally assisted tunneling, yielding estimates of the tunneling barrier for intralayer conduction of about 20meV for t=10Å. A significant magnetic field dependence of the resistance increasing with decreasing temperature was observed in all samples.
Effect of curvature and chirality for hydrogen storage in single-walled carbon nanotubes: A Combined ab initio and Monte Carlo investigation
Authors: Mpourmpakis Giannis , Froudakis George E. , Lithoxoos George P. , Samios Jannis
Published: April 2007

Combined ab initio and grand canonical Monte Carlo simulations have been performed to investigate the dependence of hydrogen storage in single-walled carbon nanotubes (SWCNTs) on both tube curvature and chirality. The ab initio calculations at the density functional level of theory can provide useful information about the nature of hydrogen adsorption in SWCNT selected sites and the binding under different curvatures and chiralities of the tube walls. Further to this, the grand canonical Monte Carlo atomistic simulation technique can model large-scale nanotube systems with different curvature and chiralities and reproduce their storage capacity by calculating the weight percentage of the adsorbed material (gravimetric density) under thermodynamic conditions of interest. The author’s results have shown that with both computational techniques, the nanotube’s curvature plays an important role in the storage process while the chirality of the tube plays none.
Thermomigration in flip-chip SnPb solder joints under alternating current stressing
Authors: Hsiao Hsiang-Yao , Chen Chih
Published: April 2007

Thermomigration in flip-chip solder joints is investigated using alternating currents and infrared microscopy to decouple it from electromigration effect. It is found that the thermal gradient in solder bump can be as high as 2143°C∕cm when 9.2×104A∕cm2 was applied at 100°C. Markers fabricated by focus ion beam are employed to measure the thermomigration rate. The thermomigration flux is measured to be 3.3×1013at.∕cm2. With the known thermal gradient, the molar heat of 26.8kJ∕mole has been obtained for the transport of Pb.
All-optical switching of continuous wave, microsecond lasers with a dye-doped nematic liquid crystal
Authors: Khoo I. C. , Park Jae-Hong , Liou Justin
Published: April 2007

The authors present a theoretical analysis and experimental demonstration of optically self-activated polarization switching process in a 90° twist alignment dye-doped nematic liquid crystal. The underlying mechanisms are laser induced dye-assisted director axis reorientation and order parameter modifications. Experimental observations are in good agreement with the theoretical expectations derived from a modified Jones matrix calculation, and demonstrate the feasibility of designing efficient low threshold polarization and fast switching and optical limiting devices for cw and microsecond lasers.
Reduced surface electron accumulation at InN films by ozone induced oxidation
Authors: Cimalla V. , Lebedev V. , Wang Ch. Y. , Ali M. , Ecke G. , Polyakov V. M. , Schwierz F. , Ambacher O. , Lu H. , Schaff W. J.
Published: April 2007

A room temperature ozone induced oxidation of thin InN films is proposed to improve the electric transport properties. The sheet carrier density is reduced upon oxidation by a value which is in the order of the electron concentration of an untreated InN surface. Thus, ozone effectively passivates the surface defect states on InN and might be an effective method to prepare InN films for electronic applications. A model for the improved electron transport properties is proposed taking into account the decreased surface band bending and the decreased influence of surface electrons on the net mobility of InN layers.
Dielectrophoretic force and torque on an ellipsoid in an arbitrary time varying electric field
Authors: Yang C. Y. , Lei U.
Published: April 2007

The dielectrophoretic force and torque on an ellipsoid were derived in an arbitrary time varying electric field using the effective moment method. The result depends on the local instantaneous electric field felt by the particle and the polarization history experienced by the particle. In addition to the crossing trajectory effect for a moving particle in a nonuniform field in literatures, the polarization history effect is also significant for a particle when it rotates at a speed of the same order or greater than the electric frequency. The result may find applications to the ac electrokinetic manipulation of particles.
Strain-mediated electric-field control of resistance in the La0.85Sr0.15MnO3∕0.7Pb(Mg1∕3Nb2∕3)O3–0.3PbTiO3 structure
Authors: Zheng R. K. , Wang Y. , Chan H. L. W. , Choy C. L. , Luo H. S.
Published: April 2007

The authors have deposited thin films of La0.85Sr0.15MnO3 (LSMO) on 0.7Pb(Mg1∕3Nb2∕3)O3–0.3PbTiO3 (PMN-PT) single-crystal substrates and have achieved modulation of the resistance of the LSMO film by applying an electric field across the PMN-PT substrate whether the LSMO film is in the paramagnetic, ferromagnetic, or charge-ordered state. Piezoelectric measurements show that the electric field gives rise to a lattice strain in the PMN-PT substrate via the converse piezoelectric effect, which then induces a lattice strain and hence a resistance change in the LSMO film. Analysis of the data indicates that the electric-field-induced lattice strain effect dominates over the field effect in the LSMO/PMN-PT structure.
Piezoforce microscopy study of lead-free perovskite Na0.5Bi0.5TiO3 thin films
Authors: Rémondière F. , Wu A. , Vilarinho P. M. , Mercurio J. P.
Published: April 2007

As a promising lead-free ferroelectric material, Na0.5Bi0.5TiO3 (NBT) was synthesized as thin films via a classic 2-methoxyethanol sol-gel route and chemical solution deposition method. Perovskite structure with random orientation of crystallites has been obtained on platinized silicon wafer at low temperature (460°C). Piezoelectric activity in such films was detected using electrical analysis. X-ray diffraction and piezoresponse force microscopy (PFM) have been used to analyze NBT thin films with different microstructures and properties dependent on fabrication and annealing processes.
Spatial distribution of interface trap density in strained channel transistors using the spread of the differential capacitance characteristics in scanning capacitance microscopy measurements
Authors: Wong K. M. , Chim W. K. , Ang K. W. , Yeo Y. C.
Published: April 2007

In this letter, the authors obtain, with nanometer spatial resolution, the local spatial distribution of interface trap density (Dit) at the gate oxide-substrate interface across the channel region of a transistor with silicon germanium source/drain (S/D) stressors. The Dit values were extracted using a theoretical model which is based on the correlation of Dit with the change in the full width at half maximum of the scanning capacitance microscopy differential capacitance characteristics. Results show that Dit increases with spatial location, measured from the center of the channel, towards the S/D regions of the strained channel transistor. The large value of Dit near the S/D regions is possibly due to germanium diffusion into the channel region and other resulting structural defects.
Correlation between carrier recombination and p-type doping in P monodoped and In–P codoped ZnO epilayers
Authors: Ye J. D. , Gu S. L. , Li F. , Zhu S. M. , Zhang R. , Shi Y. , Zheng Y. D. , Sun X. W. , Lo G. Q. , Kwong D. L.
Published: April 2007

The carrier recombination processes in p-type ZnO epilayers with P monodoping and In–P codoping have been studied by temperature-dependent photoluminescence spectroscopy. Good correlations were observed between carrier recombination and acceptor and donor energy levels. The exciton transition feature of acceptor-bound excitons (3.350eV), the free electron-acceptor emission (3.315eV), and the donor-acceptor-pair emission (3.246eV) exhibited different carrier recombination associated various defect complexes. The origins of two broad emissions at ∼2.99 and ∼2.89eV were found to be due to different photoelectron radiative transitions associated with deep level acceptors (isolated Zn vacancies). The acceptor-bound energies for P monodoped and In–P codoped epilayers ∼195 and ∼127meV, respectively. The small binding energy is helpful for acceptor ionization at room temperature, resulting in a high hole concentration in the codoped epilayer.
32
TW
atmospheric white-light laser
Authors: Béjot P. , Bonacina L. , Extermann J. , Moret M. , Wolf J. P. , Ackermann R. , Lascoux N. , Salamé R. , Salmon E. , Kasparian J. , Bergé L. , Champeaux S. , Guet C. , Blanchot N. , Bonville O. , Boscheron A. , Canal P. , Castaldi M. , Hartmann O. , Lepage C. , Marmande L. , Mazataud E. , Mennerat G. , Patissou L. , Prevot V. , Raffestin D. , Ribolzi J.
Published: April 2007

Ultrahigh power laser pulses delivered by the Alisé beamline (26J, 32TW pulses) have been sent vertically into the atmosphere. The highly nonlinear propagation of the beam in the air gives rise to more than 400 self-guided filaments. This extremely powerful bundle of laser filaments generates a supercontinuum propagating up to the stratosphere, beyond 20km. This constitutes the highest power “atmospheric white-light laser” to date.
A missense mutation in the 3-ketodihydrosphingosine reductase
FVT1
as candidate causal mutation for bovine spinal muscular atrophy
Authors: Krebs Stefan , Medugorac Ivica , Röther Susanne , Strässer Katja , Förster Martin
Published: April 2007

The bovine form of the autosomal recessive neurodegenerative disease spinal muscular atrophy (SMA) shows striking similarity to the human form of the disease. It has, however, been mapped to a genomic region not harboring the bovine orthologue of the
SMN
gene, mutation of which causes human SMA. After refinement of the mapping results we analyzed positional and functional candidate genes. One of three candidate genes,
FVT1
, encoding 3-ketodihydrosphingosine reductase, which catalyzes a crucial step in the glycosphingolipid metabolism, showed a G-to-A missense mutation that changes Ala-175 to Thr. The identified mutation is limited to SMA-affected animals and carriers and always appears in context of the founder haplotype. The Ala variant found in healthy animals showed the expected 3-ketodihydrosphingosine reductase activity in an
in vitro
enzyme assay. Importantly, the Thr variant found in SMA animals showed no detectable activity. Surprisingly, in an
in vivo
assay the mutated gene complements the growth defect of a homologous yeast knockout strain as well as the healthy variant. This finding explains the viability of affected newborn calves and the later neuron-specific onset of the disease, which might be due to the high sensitivity of these neurons to changes in housekeeping functions. Taken together, the described mutation in
FVT1
is a strong candidate for causality of SMA in cattle. This result provides an animal model for understanding the underlying mechanisms of the development of SMA and will allow efficient selection against the disease in cattle.
Inducible overexpression of wild-type prion protein in the muscles leads to a primary myopathy in transgenic mice
Authors: Huang Shenghai , Liang Jingjing , Zheng Mengjie , Li Xinyi , Wang Meiling , Wang Ping , Vanegas Difernando , Wu Di , Chakraborty Bikram , Hays Arthur P. , Chen Ken , Chen Shu G. , Booth Stephanie , Cohen Mark , Gambetti Pierluigi , Kong Qingzhong
Published: April 2007

The prion protein (PrP) level in muscle has been reported to be elevated in patients with inclusion-body myositis, polymyositis, dermatomyositis, and neurogenic muscle atrophy, but it is not clear whether the elevated PrP accumulation in the muscles is sufficient to cause muscle diseases. We have generated transgenic mice with muscle-specific expression of PrP under extremely tight regulation by doxycycline, and we have demonstrated that doxycycline-induced overexpression of PrP strictly limited to muscles leads to a myopathy characterized by increased variation of myofiber size, centrally located nuclei, and endomysial fibrosis, in the absence of intracytoplasmic inclusions, rimmed vacuoles, or any evidence of a neurogenic disorder. The PrP-induced myopathy correlates with accumulation of an N-terminal truncated PrP fragment in the muscle, and the muscular PrP displayed consistent mild resistance to protease digestion. Our findings indicate that overexpression of wild-type PrP in skeletal muscles is sufficient to cause a primary myopathy with no signs of peripheral neuropathy, possibly due to accumulation of a cytotoxic truncated form of PrP and/or PrP aggregation.
Noisy information processing through transcriptional regulation
Authors: Libby Eric , Perkins Theodore J. , Swain Peter S.
Published: April 2007

Cells must respond to environmental changes to remain viable, yet the information they receive is often noisy. Through a biochemical implementation of Bayes's rule, we show that genetic networks can act as inference modules, inferring from intracellular conditions the likely state of the extracellular environment and regulating gene expression appropriately. By considering a two-state environment, either poor or rich in nutrients, we show that promoter occupancy is proportional to the (posterior) probability of the high nutrient state given current intracellular information. We demonstrate that single-gene networks inferring and responding to a high environmental state infer best when negatively controlled, and those inferring and responding to a low environmental state infer best when positively controlled. Our interpretation is supported by experimental data from the
lac
operon and should provide a basis for both understanding more complex cellular decision-making and designing synthetic inference circuits.
Combined climate and carbon-cycle effects of large-scale deforestation
Authors: Bala G. , Caldeira K. , Wickett M. , Phillips T. J. , Lobell D. B. , Delire C. , Mirin A.
Published: April 2007

The prevention of deforestation and promotion of afforestation have often been cited as strategies to slow global warming. Deforestation releases CO
2
to the atmosphere, which exerts a warming influence on Earth's climate. However, biophysical effects of deforestation, which include changes in land surface albedo, evapotranspiration, and cloud cover also affect climate. Here we present results from several large-scale deforestation experiments performed with a three-dimensional coupled global carbon-cycle and climate model. These simulations were performed by using a fully three-dimensional model representing physical and biogeochemical interactions among land, atmosphere, and ocean. We find that global-scale deforestation has a net cooling influence on Earth's climate, because the warming carbon-cycle effects of deforestation are overwhelmed by the net cooling associated with changes in albedo and evapotranspiration. Latitude-specific deforestation experiments indicate that afforestation projects in the tropics would be clearly beneficial in mitigating global-scale warming, but would be counterproductive if implemented at high latitudes and would offer only marginal benefits in temperate regions. Although these results question the efficacy of mid- and high-latitude afforestation projects for climate mitigation, forests remain environmentally valuable resources for many reasons unrelated to climate.
A cortical potential reflecting cardiac function
Authors: Gray Marcus A. , Taggart Peter , Sutton Peter M. , Groves David , Holdright Diana R. , Bradbury David , Brull David , Critchley Hugo D.
Published: April 2007

Emotional trauma and psychological stress can precipitate cardiac arrhythmia and sudden death through arrhythmogenic effects of efferent sympathetic drive. Patients with preexisting heart disease are particularly at risk. Moreover, generation of proarrhythmic activity patterns within cerebral autonomic centers may be amplified by afferent feedback from a dysfunctional myocardium. An electrocortical potential reflecting afferent cardiac information has been described, reflecting individual differences in interoceptive sensitivity (awareness of one's own heartbeats). To inform our understanding of mechanisms underlying arrhythmogenesis, we extended this approach, identifying electrocortical potentials corresponding to the cortical expression of afferent information about the integrity of myocardial function during stress. We measured changes in cardiac response simultaneously with electroencephalography in patients with established ventricular dysfunction. Experimentally induced mental stress enhanced cardiovascular indices of sympathetic activity (systolic blood pressure, heart rate, ventricular ejection fraction, and skin conductance) across all patients. However, the functional response of the myocardium varied; some patients increased, whereas others decreased, cardiac output during stress. Across patients, heartbeat-evoked potential amplitude at left temporal and lateral frontal electrode locations correlated with stress-induced changes in cardiac output, consistent with an afferent cortical representation of myocardial function during stress. Moreover, the amplitude of the heartbeat-evoked potential in the left temporal region reflected the proarrhythmic status of the heart (inhomogeneity of left ventricular repolarization). These observations delineate a cortical representation of cardiac function predictive of proarrhythmic abnormalities in cardiac repolarization. Our findings highlight the dynamic interaction of heart and brain in stress-induced cardiovascular morbidity.
SLP-76 mediates and maintains activation of the Tec family kinase ITK via the T cell antigen receptor-induced association between SLP-76 and ITK
Authors: Bogin Yaron , Ainey Carmit , Beach Dvora , Yablonski Deborah
Published: April 2007

ITK (IL-2-inducible T cell kinase), a Tec family protein tyrosine kinase (PTK), is one of three PTKs required for T cell antigen receptor (TCR)-induced activation of phospholipase C-γ1 (PLC-γ1). Like Src and Abl family PTKs, ITK adopts an inactive, “closed” conformation, and its conversion to the active conformation is not well understood, nor have its direct substrates been identified. In a side-by-side comparison of ITK and ZAP-70 (ζ chain-associated protein kinase of 70 kDa), ITK efficiently phosphorylated Y783and Y775of PLC-γ1, two phosphorylation sites that are critical for its activation, whereas ZAP-70 did not. SLP-76 (SH2-domain-containing leukocyte protein of 76 kDa), an adaptor required for TCR-induced activation of PLC-γ1, was required for the phosphorylation of both PLC-γ1 sites in intact cells. Furthermore, this event depended on the N-terminal tyrosines of SLP-76. Likewise, SLP-76, particularly its N-terminal tyrosines, was required for TCR-induced tyrosine phosphorylation and activation of ITK but was not required for the phosphorylation or activation of ZAP-70. Both ZAP-70 and ITK phosphorylated SLP-76in vitro; thus, both PTKs are potential regulators of SLP-76, but only ITK is regulated by SLP-76. Upon TCR stimulation, a small fraction of ITK bound to SLP-76. This fraction, however, encompassed most of the catalytically active ITK. Catalytic activity was lost upon mild elution of ITK from the SLP-76-nucleated complex but was restored upon reconstitution of the complex. We propose that SLP-76 is required for ITK activation; furthermore, an ongoing physical interaction between SLP-76 and ITK is required to maintain ITK in an active conformation.
Unrestrained erythroblast development in Nix
−/−
mice reveals a mechanism for apoptotic modulation of erythropoiesis
Authors: Diwan Abhinav , Koesters Andrew G. , Odley Amy M. , Pushkaran Suvarnamala , Baines Christopher P. , Spike Benjamin T. , Daria Diedre , Jegga Anil G. , Geiger Hartmut , Aronow Bruce J. , Molkentin Jeffery D. , Macleod Kay F. , Kalfa Theodosia A. , Dorn Gerald W.
Published: April 2007

Normal production of RBCs requires that the antiapoptotic protein Bcl-xl be induced at end stages of differentiation in response to erythropoietin (Epo) signaling. The critical proapoptotic pathways inhibited by Bcl-xl in erythroblasts are unknown. We used gene targeting in the mouse to evaluate the BH3-only factor Nix, which is transcriptionally up-regulated during Epo-stimulated
in vitro
erythrocyte differentiation.
Nix
null mice are viable and fertile. Peripheral blood counts revealed a profound reticulocytosis and thrombocytosis despite normal serum Epo levels and blood oxygen tension.
Nix
null mice exhibited massive splenomegaly, with splenic and bone marrow erythroblastosis and reduced apoptosis
in vivo
during erythrocyte maturation. Hematopoietic progenitor populations were unaffected. Cultured
Nix
null erythroid cells were hypersensitive to Epo and resistant to apoptosis stimulated by cytokine deprivation and calcium ionophore. Transcriptional profiling of
Nix
null spleens revealed increased expression of cell cycle and erythroid genes, including Bcl-xl, and diminished expression of cell death and B cell-related genes. Thus, cell-autonomous Nix-mediated apoptosis in opposition to the Epo-induced erythroblast survival pathway appears indispensable for regulation of erythrocyte production and maintenance of hematological homeostasis. These results suggest that physiological codependence and coordinated regulation of pro- and antiapoptotic Bcl2 family members may represent a general regulatory paradigm in hematopoiesis.
Linking crenarchaeal and bacterial nitrification to anammox in the Black Sea
Authors: Lam Phyllis , Jensen Marlene M. , Lavik Gaute , McGinnis Daniel F. , Müller Beat , Schubert Carsten J. , Amann Rudolf , Thamdrup Bo , Kuypers Marcel M. M.
Published: April 2007

Active expression of putative ammonia monooxygenase gene subunit A (
amoA
) of marine group I
Crenarchaeota
has been detected in the Black Sea water column. It reached its maximum, as quantified by reverse-transcription quantitative PCR, exactly at the nitrate maximum or the nitrification zone modeled in the lower oxic zone. Crenarchaeal
amoA
expression could explain 74.5% of the nitrite variations in the lower oxic zone. In comparison,
amoA
expression by γ-proteobacterial ammonia-oxidizing bacteria (AOB) showed two distinct maxima, one in the modeled nitrification zone and one in the suboxic zone. Neither the
amoA
expression by crenarchaea nor that by β-proteobacterial AOB was significantly elevated in this latter zone. Nitrification in the suboxic zone, most likely microaerobic in nature, was verified by
15
NO
2
−
and
15
N
15
N production in
15
NH
4
+
incubations with no measurable oxygen. It provided a direct local source of nitrite for anammox in the suboxic zone. Both ammonia-oxidizing crenarchaea and γ-proteobacterial AOB were important nitrifiers in the Black Sea and were likely coupled to anammox in indirect and direct manners respectively. Each process supplied about half of the nitrite required by anammox, based on
15
N-incubation experiments and modeled calculations. Because anammox is a major nitrogen loss in marine suboxic waters, such nitrification–anammox coupling potentially occurring also in oceanic oxygen minimum zones would act as a short circuit connecting regenerated ammonium to direct nitrogen loss, thus reducing the presumed direct contribution from deep-sea nitrate.