bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacterial gene abundances as indicators of greenhouse gas emission in soils
Authors: Morales Sergio E , Cosart Theodore , Holben William E
Published: February 2010

Nitrogen fixing and denitrifying bacteria, respectively, control bulk inputs and outputs of nitrogen in soils, thereby mediating nitrogen-based greenhouse gas emissions in an ecosystem. Molecular techniques were used to evaluate the relative abundances of nitrogen fixing, denitrifying and two numerically dominant ribotypes (based on the ⩾97% sequence similarity at the 16S rRNA gene) of bacteria in plots representing 10 agricultural and other land-use practices at the Kellogg biological station long-term ecological research site. Quantification of nitrogen-related functional genes (nitrite reductase, nirS; nitrous oxide reductase, nosZ; and nitrogenase, nifH) as well as two dominant 16S ribotypes (belonging to the phyla Acidobacteria, Thermomicrobia) allowed us to evaluate the hypothesis that microbial community differences are linked to greenhouse gas emissions under different land management practices. Our results suggest that the successional stages of the ecosystem are strongly linked to bacterial functional group abundance, and that the legacy of agricultural practices can be sustained over decades. We also link greenhouse gas emissions with specific compositional responses in the soil bacterial community and assess the use of denitrifying gene abundances as proxies for determining nitrous oxide emissions from soils.
Effects of Metformin and Weight Loss on Serum Alanine Aminotransferase Activity in the Diabetes Prevention Program
Authors: Krakoff Jonathan , Clark Jeanne M. , Crandall Jill P. , Wilson Charlton , Molitch Mark E. , Brancati Frederick L. , Edelstein Sharon L. , Knowler William C. ,   Diabetes Prevention Program Research Group
Published: February 2010

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance, and impaired glucose tolerance. We investigated whether metformin or changes in metabolic measurements (weight, fasting plasma glucose (FPG), or fasting insulin (FI)) improved serum alanine aminotransferase (ALT) activity, as a marker for NAFLD, in the Diabetes Prevention Program (DPP). From 1996 to 1999, 2,153 participants without marked elevations of serum ALT at baseline were randomized (1,081 to placebo, 1,072 to metformin) and treated for an average of 3.2 years. ALT increased during the first 2 years of the study, and was slightly but significantly lower in the participants randomized to metformin. In regression models adjusted for sex, baseline age, FPG, and FI, these differences remained significant, but disappeared after adjustment for weight, FPG, and FI changes at each examination. The 3‐year cumulative incidence for development of abnormal ALT concentrations was not significantly different ((mean ± s.e.) 21.4 ± 1.4% and 24.6 ± 1.4%, P = 0.11) in the metformin vs. placebo groups but was lower in individuals in both groups that lost more weight by the end of year 1 (metformin: 19.4 ± 2.4% vs. 27.5 ± 3.7%, for highest vs. lowest quartile of weight loss; placebo: 18.7 ± 3.4% vs. 28.8 ± 2.6%). Over 3 years of follow‐up in persons at high risk for development of diabetes, serum ALT was consistently lower in those treated with metformin compared with placebo. This effect was mediated by weight loss, indicating that the effects of metformin therapy on ALT is via its effects on weight.
The Human Visceral Fat Depot Has a Unique Inflammatory Profile
Authors: Alvehus Malin , Burén Jonas , Sjöström Michael , Goedecke Julia , Olsson Tommy
Published: February 2010

Obesity can be considered as a low‐grade inflammatory condition, strongly linked to adverse metabolic outcomes. Obesity‐associated adipose tissue inflammation is characterized by infiltration of macrophages and increased cytokine and chemokine production. The distribution of adipose tissue impacts the outcomes of obesity, with the accumulation of fat in visceral adipose tissue (VAT) and deep subcutaneous adipose tissue (SAT), but not superficial SAT, being linked to insulin resistance. We hypothesized that the inflammatory gene expression in deep SAT and VAT is higher than in superficial SAT. A total of 17 apparently healthy women (BMI: 29.3±5.5 kg/m2) were included in the study. Body fat (dual‐energy X‐ray absorptiometry) and distribution (computed tomography) were measured, and insulin sensitivity, blood lipids, and blood pressure were determined. Inflammation‐related differences in gene expression (real‐time PCR) from VAT, superficial and deep SAT biopsies were analyzed using univariate and multivariate data analyses. Using multivariate discrimination analysis, VAT appeared as a distinct depot in adipose tissue inflammation, while the SAT depots had a similar pattern, with respect to gene expression. A significantly elevated (P < 0.01) expression of the CC chemokine receptor 2 (CCR2) and macrophage migration inhibitory factor (MIF) in VAT contributed strongly to the discrimination. In conclusion, the human adipose tissue depots have unique inflammatory patterns, with CCR2 and MIF distinguishing between VAT and the SAT depots.
Interleukin‐6 Receptor Gene Polymorphism Modulates Interleukin‐6 Levels and the Metabolic Syndrome: GBCS‐CVD
Authors: Jiang Chao Qiang , Lam Tai Hing , Liu Bin , Lin Jie Ming , Yue Xiao Jun , Jin Ya Li , Cheung Bernard M.Y. , Thomas G. Neil
Published: February 2010

Interleukin‐6 (IL‐6) is a key pleiotropic cytokine that modulates the inflammatory response. Single‐nucleotide polymorphisms (SNPs) within associated genes may contribute to the metabolic syndrome (MES). We examined the role of the IL‐6 (rs1524107‐C/T) and IL‐6 receptor (IL‐6R, rs8192284‐A/C, Asp358Ala) SNPs in modulating IL‐6 levels and the syndrome. A total of 1,979 older Chinese subjects aged 50–92 years from Guangzhou Biobank Cohort Study (GBCS) were recruited. SNPs were detected using Taqman SNP genotyping kits. IL‐6 was measured using enzyme‐linked immunosorbent assay. The genotype frequencies were 4.9, 33.9, and 61.3% for the IL‐6 CC, CT, and TT, and 12.0, 44.9, and 43.1% for the IL‐6R CC, AC, and AA, respectively. Both SNPs were in Hardy–Weinberg equilibrium. The IL‐6 SNP was not associated with IL‐6 levels or the MES, but was dose‐dependently associated with fibrinogen levels, P = 0.049. IL‐6 levels significantly decreased with increasing proportions of the IL‐6R A‐allele 9.8 ± 4.9, 9.3 ± 4.8, and 8.4 ± 4.3, respectively, P = 0.001. Conversely, the A‐allele was associated with elevated triglyceride, P = 0.009, C‐reactive protein, P = 0.047, and potentially with fasting glucose levels, P = 0.077. There was an increasing prevalence of the MES in those carrying the IL‐6R CC, AC, and AA genotypes at 18.1, 21.5, 25.2%, respectively, P = 0.010. The SNP was a significant independent predictor of the MES after adjusting for general obesity, age, gender and lifestyle, and socioeconomic parameters, P = 0.023. These data, which are in accord with studies from white populations suggest the IL‐6R SNP may play a role in the pathogenesis of the MES possibly through modulating IL‐6 levels.
Estimation of Free‐Living Energy Expenditure Using a Novel Activity Monitor Designed to Minimize Obtrusiveness
Authors: Bonomi Alberto G. , Plasqui Guy , Goris Annelies H.C. , Westerterp Klass R.
Published: February 2010

The aim of this study was to investigate the ability of a novel activity monitor designed to be minimally obtrusive in predicting free‐living energy expenditure. Subjects were 18 men and 12 women (age: 41 ± 11 years, BMI: 24.4 ± 3 kg/m2). The habitual physical activity was monitored for 14 days using a DirectLife triaxial accelerometer for movement registration (TracmorD) (Philips New Wellness Solutions, Lifestyle Incubator, the Netherlands). TracmorD output was expressed as activity counts per day (Cnts/d). Simultaneously, total energy expenditure (TEE) was measured in free living conditions using doubly labeled water (DLW). Activity energy expenditure (AEE) and the physical activity level (PAL) were determined from TEE and sleeping metabolic rate (SMR). A multiple‐linear regression model predicted 76% of the variance in TEE, using as independent variables SMR (partial‐r2 = 0.55, P < 0.001), and Cnts/d (partial r2 = 0.21, P < 0.001). The s.e. of TEE estimates was 0.9 MJ/day or 7.4% of the average TEE. A model based on body mass (partial‐r2 = 0.31, P < 0.001) and Cnts/d (partial‐r2 = 0.23, P < 0.001) predicted 54% of the variance in TEE. Cnts/d were significantly and positively associated with AEE (r = 0.54, P < 0.01), PAL (r = 0.68, P < 0.001), and AEE corrected by body mass (r = 0.71, P < 0.001). This study showed that the TracmorD is a highly accurate instrument for predicting free‐living energy expenditure. The miniaturized design did not harm the ability of the instrument in measuring physical activity and in determining outcome parameters of physical activity such as TEE, AEE, and PAL.
Hydrogen sulfide induces human colon cancer cell proliferation: Role of Akt, ERK and p21
Authors: Cai Wen‐Jie , Wang Ming‐Jie , Ju Li‐Hua , Wang Cheng , Zhu Yi‐Chun
Published: February 2010

H2S (hydrogen sulfide), regarded as the third gaseous transmitter, is implicated in ulcerative colitis and colorectal cancers. The present study investigates the effects of H2S on cell proliferation in human colon cancer HCT 116 cells and SW480 cells. We identified the two key enzymes, CBS and CSE, for H2S synthesis in HCT 116 cells. An exogenously administered H2S donor NaHS induced cell proliferation in a concentration‐dependent manner, with optimal proliferative concentration at 200 μmol/l. NaHS administration increased Akt and ERK phosphorylation. Blockade of Akt and ERK activation attenuated NaHS‐induced cell proliferation. Cell‐cycle analysis showed that NaHS treatment for 6 h decreased the proportion of cells in G0–G1 phase and increased the proportion of cells in S phase. Protein expressions of Cyclin D1 and PCNA (proliferating cell nuclear antigen) were not altered, but the cyclin‐dependent kinase inhibitor p21Waf1/Cip1 was inhibited significantly by NaHS treatment. NaHS significantly reduced NO metabolite levels. In conclusion, NaHS induced human colon cancer cell proliferation. This effect might be mediated by the increase of Akt and ERK phosphorylation and the decrease of p21Waf1/Cip1 expression and NO production. The results suggested a role for H2S in human colonic cancer development.
Mesenchymal stem cell infusion therapy in a carbon tetrachloride‐induced liver fibrosis model affects matrix metalloproteinase expression
Authors: Rabani Vahideh , Shahsavani Mansoureh , Gharavi Marzieh , Piryaei Abbas , Azhdari Zahra , Baharvand Hossein
Published: February 2010

In order to investigate the effects of bone marrow‐derived MSCs (mesenchymal stem cells) in reversing liver fibrosis and to determine their possible mechanism of action, mouse MSCs were infused into the tail vein of a CCl4 injection mouse chronic model. MSCs caused a decrease in liver fibrosis histopathologically, 4 weeks after transplantation. The reduction in liver collagen was confirmed by quantitative analysis. Moreover, lipid peroxidation in the CCl4/MSC group decreased significantly. Quantitative RT (reverse transcription)‐PCR analysis showed administration of MSCs has a significant antifibrotic effect as evidenced by the decrease in expression of liver collagen and increase in MMP13 (matrix metalloproteinase 13) in the CCl4/MSC group when compared with the CCl4 group, 4 weeks after transplantation. The expression of αSMA (smooth muscle actin) and TIMP1 was also down‐regulated in the CCl4/MSC group. Additionally, the expression of MMP9 was significantly up‐regulated in the CCl4‐treated group; however, there was no significant change after MSC injection. Few engrafted cells in the recipient liver and were able to differentiate into albumin‐positive cells. In conclusion, MSCs can enhance recovery of a CCl4‐injured mouse liver through their influence in reducing collagen deposition by possibly affecting expression of MMPs.
Radio frequency-driven proton source with a back-streaming electron dump
Authors: Ji Q. , Sy A. , Kwan J. W.
Published: February 2010

This article describes an rf ion source with a back-streaming electron dump. A quartz tube, brazed to a metal plug at one end, is fused in the center of a flat quartz plate. rf power (at 13.6 MHz) is coupled to generate hydrogen plasma using a planar external antenna bonded to the window. Bonding the water-cooled rf antenna to the quartz window significantly lowers its temperature. The water-cooled metal plug serves as the back-streaming electron dump. At 1800 W, the current density of extracted hydrogen ions reaches approximately 125 mA/cm2.
On nonsingular potentials of Cox–Thompson inversion scheme
Authors: Pálmai Tamás , Apagyi Barnabás
Published: February 2010

We establish a condition for obtaining nonsingular potentials using the Cox–Thompson inverse scattering method with one phase shift. The anomalous singularities of the potentials are avoided by maintaining unique solutions of the underlying Regge–Newton integral equation for the transformation kernel. As a by-product, new inequality sequences of zeros of Bessel functions are discovered.
High-temperature molecular beam epitaxial growth of AlGaN/GaN on GaN templates with reduced interface impurity levels
Authors: Koblmüller G. , Chu R. M. , Raman A. , Mishra U. K. , Speck J. S.
Published: February 2010

We present combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations and low buffer leakage. By exposing the GaN templates to an optimized thermal dissociation step in the plasma-assisted molecular beam epitaxy environment, oxygen, carbon, and, to lesser extent, Si impurities were effectively removed from the regrowth interface under preservation of good interface quality. Residual Si was further compensated by C-doped GaN via CBr4 to yield highly resistive GaN buffer layers. Improved N-rich growth conditions at high growth temperatures were then utilized for subsequent growth of the AlGaN/GaN device structure, yielding smooth surface morphologies and low residual oxygen concentration with large insensitivity to the (Al+Ga)N flux ratio. Room temperature electron mobilities of the two-dimensional electron gas at the AlGaN/GaN interface exceeded >1750 cm2/V s and the dc drain current reached ∼1.1 A/mm at a +1 V bias, demonstrating the effectiveness of the applied methods.
The effect of dust charge fluctuations on lower-hybrid suppression of drift waves in a magnetized plasma cylinder
Authors: Sharma Suresh C. , Gahlot Ajay
Published: February 2010

The nonlinear coupling between drift waves and a lower-hybrid pump wave is studied in a magnetized dusty plasma cylinder. The growth rate and mode frequencies were evaluated based on typical dusty plasma parameters. It is found that the unstable drift mode frequency increases and the growth rate decreases sharply with the relative density of negatively charged dust grains. In addition, the growth rate and unstable mode frequency depend on pump wave amplitudes.
Near infrared quantum cutting in heavy Yb doped Ce0.03Yb3xY(2.97−3x)Al5O12 transparent ceramics for crystalline silicon solar cells
Authors: Lin Hui , Zhou Shengming , Teng Hao , Li Yukun , Li Wenjie , Hou Xiaorui , Jia Tingting
Published: February 2010

Near infrared (NIR) quantum cutting involving the conversion of an absorbed blue photon into two NIR photons emission has been realized in heavy Yb doped Ce0.03Yb3xY(2.97−3x)Al5O12 (x=0.1, 0.25, and 0.5) transparent ceramics. Upon the 467 nm excitation, the energy transfer process was dominated by the cooperative downconversion from the 5d1 state of one Ce3+ ion to the F25/2 state of two Yb3+ ions. The influence of the Ce4+–Yb2+ charge transfer state (CTS) should not contribute much to the energy transfer process for the large energy gap between Ce3+:5d1 and the CTS. The calculated quantum yield of Yb3+ for the x=0.25 sample without concentration quenching was 175.4%.
Pseudobosons, Riesz bases, and coherent states
Authors: Bagarello F.
Published: February 2010

In a recent paper, Trifonov suggested a possible explicit model of a PT-symmetric system based on a modification of the canonical commutation relation. Although being rather intriguing, in his treatment many mathematical aspects of the model have just been neglected, making most of the results of that paper purely formal. For this reason we are reconsidering the same model and we repeat and extend the same construction paying particular attention to all the subtle mathematical points. From our analysis the crucial role of Riesz bases clearly emerges. We also consider coherent states associated with the model.
Dielectric characterization of NixCo1−xFe2O4 nanocrystals thin film over a broad frequency range (1 MHz–3 GHz)
Authors: Bayrakdar Harun , Esmer Kadir
Published: February 2010

We have theoretically and experimentally investigated the dielectric behavior of NixCo1−xFe2O4 nanoparticles (NPs) (where x=0.0, 0.6, and 1.0), which have been synthesized by microwave induced combustion synthesis using urea as fuel. A variation of complex dielectric permittivity at room temperature with frequency in the range 1 MHz–3 GHz has been studied. The permittivity displays atomic polarization and electronic polarization. Particles showed phase purity and crystallinity in powder x-ray diffraction (XRD) analysis. At the same time, NixCo1−xFe2O4 NPs demonstrated a spinel cubic structure from XRD results.
Exciton recombination dynamics in a-plane (Al,Ga)N/GaN quantum wells probed by picosecond photo and cathodoluminescence
Authors: Corfdir P. , Lefebvre P. , Balet L. , Sonderegger S. , Dussaigne A. , Zhu T. , Martin D. , Ganière J.-D. , Grandjean N. , Deveaud-Plédran B.
Published: February 2010

We present a combined low-temperature time-resolved cathodoluminescence and photoluminescence study of exciton recombination mechanisms in a 3.8 nm thick a-plane (Al,Ga)N/GaN quantum well (QW). We observe the luminescence from QW excitons and from excitons localized on basal stacking faults (BSFs) crossing the QW plane, forming quantum wires (QWRs) at the intersection. We show that the dynamics of QW excitons is dominated by their capture on QWRs, with characteristic decay times ranging from 50 to 350 ps, depending on whether the local density of BSFs is large or small. We therefore relate the multiexponential behavior generally observed by time-resolved photoluminescence in non-polar (Al,Ga)/GaN QW to the spatial dependence of QW exciton dynamics on the local BSF density. QWR exciton decay time is independent of the local density in BSFs and its temperature evolution exhibits a zero-dimensional behavior below 60 K. We propose that QWR exciton localization along the wire axis is induced by well-width fluctuation, reproducing in a one-dimensional system the localization processes usually observed in QWs.
Dispersion curves of shear horizontal wave surface velocities in multilayer piezoelectric systems
Authors: Calás H. , Rodriguez-Ramos R. , Otero J. A. , Leija L. , Ramos A. , Monsivais G.
Published: February 2010

A precise knowledge of the frequency responses, velocity dispersion, and distinct vibration modes in multilayer piezoelectric structures would permit the optimization of new designs for electromechanical sensor, actuator, and surface acoustic wave (SAW) filter devices under broad and narrow band conditions. In this paper, the singular-value decomposition technique, combined with the global matrix method and scaling procedure, are applied for studying the solutions of shear stationary waves in symmetric multilayer composite piezoelectric systems. This approach eliminates numerical instabilities sometimes appearing in the analysis of this type of piezoelectric systems, by using a multiple scaling strategy in the global matrix processing. The dispersion curves of the surface velocities, obtained by application of the proposed approach, have shown the presence of clearly separated odd and even bands in such a type of piezoelectric devices, which is explained by considering the eigenstates of the system. Details of this bands pattern are calculated and analyzed.
Damping behavior of bent fiber NSOM probes in water
Authors: Taylor Rod S. , Vobornik Dusan , Lu Zhengfang , Chisholm Roderick A. , Johnston Linda J.
Published: February 2010

The damping behavior of bent fiber near-field scanning optical microscopy (NSOM) probes operating in tapping mode oscillation is investigated in air and water. We show that the significant drop in probe quality factor Q, which occurs at the air-water interface, is due to meniscus damping. As the probe is immersed in water viscous damping adds to the meniscus damping. Damping effects which lead to a progressive drop in the peak tapping mode resonance frequency are accounted for by additional torsional modes of probe vibration. Understanding the damping processes should lead to the design of high sensitivity NSOM probes for scanning soft biological samples under liquid.
Experimental study of a low radio frequency power driven relativistic klystron amplifier
Authors: Li Zheng-Hong
Published: February 2010

Using particle in cell simulation codes, a low radio frequency (rf) power driven relativistic klystron amplifier is designed according to the beam with current of 7.5 kA and voltage of 750 kV with special measures to avoid the mode competition. Simulated power reaches 1.7 GW when the driven rf power is 7.0 kW, the corresponding gain is 53.9 dB. Also the experiment is carried out on a telsa-typed accelerator, whose beam is with current of 8 kA and voltage of 800 kV. The measured rf output power reaches 2.04 GW in the experiment when the input rf power is 62 kW and frequency 2.850 GHz, the corresponding gain is 45.1 dB and efficiency is 32%. The maximum gain reaches 46.7 dB when the input decreases to 39 kW, the corresponding output rf power is 1.84 GW.
Aging-induced two-step ferroelectric-to-paraelectric transition in acceptor-doped ferroelectrics
Authors: Gao Jinghui , Xue Dezhen , Bao Huixin , Zhang Lixue , Zhou Chao , Liu Wenfeng , Chen Wei , Ren Xiaobing
Published: February 2010

It is well known that first-order ferroelectric to paraelectric transition is a one-step transition and it gives rise to one latent heat peak and one permittivity peak during heating. In the present paper, however, we report an unexpected finding; in Mn-doped Ba(Zr0.01Ti0.98Mn0.01)O3−δ the ferroelectric to paraelectric transition proceeds in two steps, after the sample has experienced a prior aging at the differential scanning calorimetry (DSC) peak temperature and followed by cooling down to a fully ferroelectric state. The two-step transition is evidenced by a split DSC peak as well as a split permittivity peak. These abnormal effects can be explained by considering that aging at DSC peak temperature corresponds to aging in a two-phase state (paraelectric+ferroelectric). Such two-phase aging produces two different defect symmetries, which give rise to different stabilities for the same ferroelectric phase and thus results in different reverse transition temperatures.
Nonplanar electrostatic shock waves in dense plasmas
Authors: Masood W. , Rizvi H.
Published: February 2010

Two-dimensional quantum ion acoustic shock waves (QIASWs) are studied in an unmagnetized plasma consisting of electrons and ions. In this regard, a nonplanar quantum Kadomtsev–Petviashvili–Burgers (QKPB) equation is derived using the small amplitude perturbation expansion method. Using the tangent hyperbolic method, an analytical solution of the planar QKPB equation is obtained and subsequently used as the initial profile to numerically solve the nonplanar QKPB equation. It is observed that the increasing number density (and correspondingly the quantum Bohm potential) and kinematic viscosity affect the propagation characteristics of the QIASW. The temporal evolution of the nonplanar QIASW is investigated both in Cartesian and polar planes and the results are discussed from the numerical stand point. The results of the present study may be applicable in the study of propagation of small amplitude localized electrostatic shock structures in dense astrophysical environments.
Coercivity mechanism of nanocomposite Sm-Co/Fe multilayer films
Authors: Zhang Jian , Li Yang-xian , Wang Fang , Shen Bao-gen , Sun Ji-rong
Published: February 2010

The coercivity mechanism of nanocomposite Sm-Co/Fe multilayer films was investigated. It was concluded that the magnetization reversal mechanism of Sm-Co/Fe multilayer films is dominated mainly by domain wall pinning instead of nucleation. The addition of Cu layer between the hard and soft layers causes the change in grain boundary as well as the large variation in anisotropy in the hard layer after annealing, which leads to a strong increase in domain wall pinning, and therefore a significant improvement of the coercivity. This study indicates the potentials of this method to control and improve the magnetic property of nanocomposite multilayer films.
Secondary growth and photoluminescence from erbium implanted silica nanowires
Authors: Shalav A. , Kim T. H. , Elliman R. G.
Published: February 2010

Gold-catalyzed silica nanowires were grown using vapor from the active oxidation of the silicon substrate and then implanted with erbium and annealed. During prolonged annealing at 1100 °C, where the concentration of vapor-phase reactants is sufficient to support nanowire growth, the erbium rich precipitates act as catalysts for the growth of a second generation of nanowires. These secondary nanowires increase in photoluminescence as they grow, suggesting that a fraction of the optically active erbium is incorporated into the growing wire. The resulting luminescent nanostructures have a very large surface-to-volume fraction and are well suited for optical-sensing applications.
Free-electron laser harmonic generation in an electromagnetic-wave wiggler and ion channel guiding
Authors: Mehdian H. , Hasanbeigi A. , Jafari S.
Published: February 2010

A theoretical study of electron trajectories, harmonic generation, and gain in a free-electron laser (FEL) with a linearly polarized electromagnetic-wave wiggler is presented for axial injection of electron beam. The relativistic equation of motion for a single electron has been derived and solved numerically. It is found that the trajectories consist of two regimes. The stability of these regimes has been investigated. The results show that the trajectories are stable except for some parts of the regime one. The effects of interaction on the transverse velocity of the electron are a superposition of two oscillation terms, one at the wiggler frequency and the other at the betatron ion-channel frequency. A detailed analysis of the gain equation in the low-gain-per-pass limit has been employed to investigate FEL operation in higher harmonics generation. The possibility of wave amplification at both wiggler frequency and betatron ion-channel frequency for their odd harmonics has been illustrated.
Ultrasensitive mode-localized mass sensor with electrically tunable parametric sensitivity
Authors: Thiruvenkatanathan P. , Yan J. , Woodhouse J. , Aziz A. , Seshia A. A.
Published: February 2010

We use the phenomena of mode localization and vibration confinement in pairs of weakly coupled, nearly identical microelectromechanical (MEMS) resonators as an ultrasensitive technique of detecting added mass on the resonator. The variations in the eigenstates for induced mass additions are studied and compared with corresponding resonant frequency shifts in pairs of MEMS resonators that are coupled electrostatically. We demonstrate that the relative shifts in the eigenstates can be over three orders of magnitude greater than those in resonant frequency for the same addition of mass. We also investigate the effects of voltage controlled electrical spring tuning on the parametric sensitivity of such sensors and demonstrate sensitivities tunable by over 400%.
Nonexistence of formal first integrals for nonlinear systems under the case of resonance
Authors: Li Wenlei , Xu Zhiguo , Shi Shaoyun
Published: February 2010

In this paper, by using the normal form theory we give some criteria of the nonexistence of formal first integrals for nonlinear systems under resonance. As application, we also give a criterion for nonintegrability of a family of higher order perturbation systems of certain integrable Hamiltonian systems.
Superconducting spintronics: Spin-polarized transport in superconducting junctions with ferromagnetic semiconducting contact
Authors: Tao Y. C. , Hu J. G.
Published: February 2010

Superconducting spintronics is one of the most attractive subjects of spintronics. This article reviews superconducting spintronics based on the superconducting junctions with ferromagnetic semiconducting contact. The authors summarize recent theoretical developments with an emphasis on the interplay between ferromagnetic semiconductor (FS) and superconductor (SC). It is found that the spin-polarized transport in the superconducting junctions exhibits a rich dependence on hole types of FS, mismatches in the effective mass and Fermi velocity of holes between the FS and SC, as well as strengths of potential scattering at the interface. These systems have great intrinsic scientific importance and potential device applications including signal processing and general purpose computing.
Molecular spin valve and spin filter composed of single-molecule magnets
Authors: Zhu L. , Yao K. L. , Liu Z. L.
Published: February 2010

We presented a theoretical study on the spin-polarized transport of one single-molecule magnet. The results show it has spin filter behavior, and can also be used as a molecular spin valve with large abnormal magnetoresistance, which is an excellent candidate for spintronics of molecular devices. It is also found that the steplike features with negative differential resistance in the I-V curve indeed originate from the discreteness and narrow features in the density of states of the molecular levels.
Magnetization enhancement in nanostructured random type MgFe2O4 spinel prepared by soft mechanochemical route
Authors: Antic B. , Jovic N. , Pavlovic M. B. , Kremenovic A. , Manojlović D. , Vucinic-Vasic M. , Nikolić A. S.
Published: February 2010

In this paper we report results of structural, spectroscopic, and magnetic investigations of MgFe2O4 nanoparticles prepared by soft mechanochemical synthesis. MgFe2O4 nanoparticles crystallize in Fd3¯m space group with mixed cation distribution and reduced percentage of Fe3+ at tetrahedral (8a) sites. Discrepancy in the cation distribution compared to that in the bulk Mg–ferrite is one of the highest known. X-ray line broadening analysis reveals crystallite size and strain anisotropy. The saturation magnetization, Msat=62 emu/g measured at 5 K is twice higher than that found in the bulk counterparts. Such high value of Msat is attributed to the low value of cation inversion parameter (δ=0.69), to the core/shell structure of the nanoparticles and to the surface/volume ratio. Mössbauer spectrum collected at room temperature reveals ferrimagnetic ordering between Fe3+ ions in 8a and 16d sites, while zero-field-cooled (ZFC) and field-cooled (FC) M(T) measurements were shown superparamagnetic state above 350 K.
The art of mixing with an admixture of art: Fluids, solids, and visual imagination
Authors: Ottino Julio M.
Published: February 2010

Although creativity is often equated with art, it is just as present in science and technology. The Otto Laporte Lecture provides a forum to cover some of this ground—an opportunity to offer observations about scientific imagination, the role of collaborators and environment, creative processes in general, and even how science evolves. Very little has been written about these topics in the context of fluid dynamics, but I believe that such a viewpoint—understanding why and how scientific discoveries are made—provides significant insights which go far beyond my specific work.
Protein elasticity probed with two synchrotron-based techniques
Authors: Leu Bogdan M. , Alatas Ahmet , Sinn Harald , Alp E. Ercan , Said Ayman H. , Yavaş Hasan , Zhao Jiyong , Sage J. Timothy , Sturhahn Wolfgang
Published: February 2010

Compressibility characterizes three interconnecting properties of a protein: dynamics, structure, and function. The compressibility values for the electron-carrying protein cytochrome c and for other proteins, as well, available in the literature vary considerably. Here, we apply two synchrotron-based techniques––nuclear resonance vibrational spectroscopy and inelastic x-ray scattering––to measure the adiabatic compressibility of this protein. This is the first report of the compressibility of any material measured with this method. Unlike the methods previously used, this novel approach probes the protein globally, at ambient pressure, does not require the separation of protein and solvent contributions to the total compressibility, and uses samples that contain the heme iron, as in the native state. We show, by comparing our results with molecular dynamics predictions, that the compressibility is almost independent of temperature. We discuss potential applications of this method to other materials beyond proteins.
Structured epitaxial graphene growth on SiC by selective graphitization using a patterned AlN cap
Authors: Rubio-Roy Miguel , Zaman Farhana , Hu Yike , Berger Claire , Moseley Michael W. , Meindl James D. , de Heer Walt A.
Published: February 2010

Electronic quality epitaxial graphene has been selectively grown on silicon carbide capped with a patterned aluminum nitride layer, providing a pathway to produce device structures that avoid lithographic patterning of graphene itself. Patterning of the cap exposes SiC where graphene will grow. Capped areas inhibit graphene growth and withstand graphitization temperatures up to 1420°C under 100 Pa of argon pressure. Graphene Hall bars were fabricated and characterized by scanning Raman spectroscopy, ellipsometry, and transport measurements. Hall-mobility is about 600 cm2/V s and can be further enhanced by fine tuning the argon pressure and improving the quality of SiC surface prior to graphitization.
Direct measurement of ferromagnetic ordering in biaxially strained LaCoO3 thin films
Authors: Klie R. F. , Yuan T. , Tanase M. , Yang G. , Ramasse Q.
Published: February 2010

LaCoO 3 undergoes a transition from a nonmagnetic to a paramagnetic semiconductor at 80 K, associated with a spin-state transition of the Co3+ ions. It was proposed that the temperature of the spin-state transition depends strongly on the LaCoO3 lattice parameter, suggesting that strain can stabilize different spin states at different temperatures. By combining atomic-resolution Z-contrast imaging, electron diffraction, and angular-resolved electron energy-loss spectroscopy (EELS) with in situ cooling experiments, we show that epitaxially strained LaCoO3 (001) thin films grown on LaAlO3 (001) do not undergo a low temperature spin-state transition. Our EELS study explores the origins of the ferromagnetic ordering in strained LaCoO3 films.
X-ray absorption and photoemission spectroscopy of zinc protoporphyrin adsorbed on rutile TiO2(110) prepared by in situ electrospray deposition
Authors: Rienzo Anna , Mayor Louise C. , Magnano Graziano , Satterley Christopher J. , Ataman Evren , Schnadt Joachim , Schulte Karina , O’Shea James N.
Published: February 2010

Zinc-protoporphyrin, adsorbed on the rutile TiO2(110) surface, has been studied using photoemission spectroscopy and near-edge absorption fine structure spectroscopy to deduce the nature of the molecule-surface bonding and the chemical environment of the central metal atom. To overcome the difficulties associated with sublimation of the porphyrin molecules, samples were prepared in situ using ultrahigh vacuum electrospray deposition, a technique which facilitates the deposition of nonvolatile and fragile molecules. Monolayers of Zn protoporphyrin are found to bond to the surface via the oxygen atoms of the deprotonated carboxyl groups. The molecules initially lie largely parallel to the surface, reorienting to an upright geometry as the coverage is increased up to a monolayer. For those molecules directly chemisorbed to the surface, the interaction is sufficiently strong to pull the central metal atom out of the molecule.
Cloning and characterisation of ZmZLP1, a gene encoding an endoplasmic reticulum-localised zinc transporter in Zea mays
Authors: Xu Yao-Guang , Wang Bao-Sheng , Yu Jing-Juan , Ao Guang-Ming , Zhao Qian
Published: February 2010

The ZmZLP1 (ZmZIP-like protein) gene was isolated from a cDNA library of Zea mays L. (maize) pollen. Bioinformatics analysis indicated that ZmZLP1 shares many characteristics of the ZIP (ZRT/IRT-like protein) family of metal ion transporters. Under general nutrient conditions, the expression of ZmZLP1 was detected in both mature pollen and, less strongly, in male inflorescences, whereas an induction of the ZmZLP1 transcript was observed in roots after 12 h of zinc deprivation. The visualisation of GFP showed that ZmZLP1 was targeted to the endoplasmic reticulum (ER). To investigate the gene’s functions, we fused ZmZLP1 with the signal peptide of the plasma membrane-localised protein AtIRT1 and transformed this fusion protein into the zinc uptake-deficient yeast (Saccharomyces cerevisiae) strain ZHY3 and the wild-type strain DEY1457. The IRT1-ZmZLP1 transformants grew poorly on zinc-limited medium, and this growth defect was rescued by zinc supplementation, suggesting that ZmZLP1 is responsible for transporting zinc from the ER to the cytoplasm. Further research indicated that ZmZLP1 is involved in the unfolded protein response (UPR) pathway and enhances the heat resistance of yeast cells.
Quantification and modelling of the stomatal, cuticular and crack components of peach fruit surface conductance
Authors: Gibert Caroline , Génard Michel , Vercambre Gilles , Lescourret Françoise
Published: February 2010

This study describes the components of fruit surface conductance. It aims to revise a modelling framework examining water loss across the fruit epidermis in relation to time and fruit growing conditions. For this purpose, cuticular crack surface area, healing artificial wounds in vivo, stomatal number and total fruit surface conductance were quantified during nectarine (Prunus persica L. nucipersica) fruit growth under contrasted irrigation regimes or thinning intensities. The contribution of stomatal component to total conductance decreased very early. A sub-model of the specific cuticular conductance according to fruit age was proposed that accounted for the complex temporal variation of the cuticular component. The occurrence of cracks was modelled by considering the relative expansion rate of the cuticle as a function of fruit fresh mass and relative expansion rate of the fruit. Healing decreased with fruit age. The observed temporal variations of fruit surface conductance and cuticular crack surface area were well simulated by the modified model whatever the fruit growing conditions. Tests on independent data revealed that the model was highly sensitive to parameters related to cuticular crack development and to cuticular properties.
Elevated CO2 atmosphere promotes plant growth and inulin production in the cerrado species Vernonia herbacea
Authors: Oliveira Vanessa F. , Zaidan Lilian B. P. , Braga Márcia R. , Aidar Marcos P. M. , Carvalho Maria Angela M.
Published: February 2010

Carbon allocation in biomass is an important response of plants to the increasing atmospheric [CO2]. The effects of elevated [CO2] are scarcely reported in fructan-accumulating plants and even less in tropical wild species storing this type of carbohydrate. In the present study, the effects of high [CO2] atmosphere was evaluated on growth, biomass allocation and fructan metabolism in Vernonia herbacea (Vell.) Rusby, an Asteraceae from the Brazilian cerrado, which accumulates inulin-type fructans in the underground organs (rhizophores). Plants were cultivated for 120 days in open-top chambers (OTCs) under ambient (~380 μmol mol–1), and elevated (~760 μmol mol–1) [CO2]. Plant growth, photosynthesis, fructan contents, and the activities of fructan metabolising enzymes were analysed in the rhizophores at Time 0 and 15, 30, 60, 90 and 120 days. Plants under elevated [CO2] presented increases in height (40%), photosynthesis (63%) and biomass of aerial (32%) and underground (47%) organs when compared with control plants. Under elevated [CO2] plants also presented higher 1-SST, 1-FFT and invertase activities and lower 1-FEH activity. Although fructan concentration remained unchanged, fructan productivity was higher in plants maintained under elevated [CO2], due to their higher rhizophore biomass. This is the first report on the effects of elevated [CO2] on a plant species bearing underground organs that accumulate fructans. Our results indicate that plants of V. herbacea can benefit from elevated atmospheric [CO2] by increasing growth and carbon allocation for the production of inulin, and may contribute to predict a future scenario for the impact of this atmospheric condition on the herbaceous vegetation of the cerrado.
The contrasting influence of short-term hypoxia on the hydraulic properties of cells and roots of wheat and lupin
Authors: Bramley Helen , Turner Neil C. , Turner David W. , Tyerman Stephen D.
Published: February 2010

Little is known about water flow across intact root cells and roots in response to hypoxia. Responses may be rapid if regulated by aquaporin activity, but only if water crosses membranes. We measured the transport properties of roots and cortical cells of three important crop species in response to hypoxia (0.05 mol O2 m–3): wheat (Triticum aestivum L.), narrow-leafed lupin (Lupinus angustifolius L.) and yellow lupin (Lupinus luteus L.). Hypoxia influenced solute transport within minutes of exposure as indicated by increases in root pressure (Pr) and decreases in turgor pressure (Pc), but these effects were only significant in lupins. Re-aeration returned Pr to original levels in yellow lupin, but in narrow-leafed lupin, Pr declined to zero or lower values without recovery even when re-aerated. Hypoxia inhibited hydraulic conductivity of root cortical cells (Lpc) in all three species, but only inhibited hydraulic conductivity of roots (Lpr) in wheat, indicating different pathways for radial water flow across lupin and wheat roots. The inhibition of Lpr of wheat depended on the length of the root, and inhibition of Lpc in the endodermis could account for the changes in Lpr. During re-aeration, aquaporin activity increased in wheat roots causing an overshoot in Lpr. The results of this study demonstrate that the roots of these species not only vary in hydraulic properties but also vary in their sensitivity to the same external O2 concentration.
Effects of a pharmaceutical mixture at environmentally relevant concentrations on the amphipod Gammarus fossarum
Authors: Dietrich Sabine , Dammel Shana , Ploessl Florian , Bracher Franz , Laforsch Christian
Published: February 2010

The continuous discharge of pharmaceuticals into the environment results in the chronic exposure of aquatic organisms to complex drug mixtures. We examined the influence of a mixture of pharmaceuticals (carbamazepine (CBZ), diclofenac (DIC), metoprolol (MET) and 17α-ethinylestradiol (EE2)) at environmentally relevant (‘env’) and artificially high (‘high’) concentrations on Gammarus fossarum. Different sublethal responses such as moulting, reproduction and the content of the energy-storage component glycogen were analysed. The drug mixture influenced the moulting behaviour of gammarids at both the ‘env’ and ‘high’ concentration levels, leading to a discontinuous increase of body length in successive moults, compared with the constant increase of body length in the control treatment. Moreover, the time between successive moults of animals exposed to the ‘env’ and ‘high’ pharmaceutical concentrations was decreased because of shortened intermoult periods. We observed no significant impact of the pharmaceuticals on reproduction. In addition, the content of glycogen was not significantly affected by the drug mixture. Permanent exposure of G. fossarum to a wider range of pharmaceuticals in natural aquatic systems may influence moulting behaviour and accompanied life-history parameters, followed by severe ecological consequences as gammarids play an important role in many freshwater ecosystems of the northern hemisphere.
Effects of sediment pollution on food webs in a tropical river (Borneo, Indonesia)
Authors: Yule Catherine M. , Boyero Luz , Marchant Richard
Published: February 2010

The impact of pollution on the trophic ecology of the Kelian River (Borneo, Indonesia) was studied by comparing food webs (on the basis of gut analysis and field and laboratory observations) at six sites. The upper sites were in pristine rainforest but the river became increasingly polluted downstream, largely owing to sedimentation from alluvial gold mining activities. Four previous studies all showed a downstream decrease in macroinvertebrates (mean abundance: 272 per 400 cm2 at Site 1 dropped to 2.6 at Site 6; mean number of taxa: 37.6 at Site 1 down to 1.6 at Site 6), and this was highly correlated with suspended solids. Food webs also reflected the effect of pollution. Cleaner sites had more complex food webs, with more elements, links, higher linkage density and higher complexity than did downstream polluted sites, which lacked grazers, shredders and filterers. Several taxa that were grazers at clean sites became collector-gatherers at polluted sites. Despite the enormous impact of pollution, cessation of alluvial mining activities resulted in some recovery. The resilience of the fauna is likely to be enhanced by the tropical conditions with high rainfall, rapid flow rates and high temperatures, coupled with rapid life cycles. Fish distribution and diets did not appear to be affected by pollution.
Residency, space use and movement patterns of juvenile sandbar sharks (Carcharhinus plumbeus) within a Virginia summer nursery area
Authors: Conrath C. L. , Musick J. A.
Published: February 2010

Neonates and juveniles of many large coastal shark species occupy shallow inshore nursery areas during portions of the year. The identification of how these areas are used by large coastal shark populations is an important consideration in conservation and management efforts. An array of passive acoustic receivers was utilised to track the movements of 64 neonate and juvenile sandbar sharks within the Eastern Shore of Virginia summer nursery during the summers of 2003–2005. Residency patterns were variable during each year of the study, with younger sandbar sharks spending more time within the array area than older sharks. The number of detections was positively related to the distance of the receiver inshore from the inlet, indicating that young sandbar sharks preferentially utilise protected, shallow near-shore waters. Neonate and juvenile sandbar sharks tended to be detected more frequently within all areas of the inlet at slack tides, during the night and during early dawn hours. Periodogram analyses indicated that juvenile sharks tend to move in the direction of tidal currents. The present study documents large- and small-scale movement patterns of juvenile sandbar sharks and emphasises the importance of nursery-area habitats for this species.