bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of BMI on Level of Circulating Progenitor Cells
Authors: Bellows Charles F. , Zhang Yan , Simmons Paul J. , Khalsa Amrit S. , Kolonin Mikhail G.
Published: February 2011

Obesity complicates a number of diseases through mechanisms that are poorly defined. Mobilization and recruitment of progenitor cells to pathological sites is an important factor in disease progression. Here, we analyzed the influence of obesity on the systemic circulation of CD34+ cell populations and correlated frequencies of cells displaying previously established cell marker signatures with the BMI. Comparative analysis of peripheral blood mononuclear cells (PBMC) from 12 nonobese (BMI <30 kg/m2) and 14 obese (BMI >30 kg/m2) disease‐free donors by flow cytometry revealed that obesity is associated with a fivefold increased frequency of circulating progenitor cells (CPC), a population consisting of hematopoietic and endothelial precursors. Our data also indicate that obesity is associated with increased frequency of circulating mesenchymal stromal progenitor cells (MSC). In contrast, the frequencies of mature endothelial cells (EC) and CD34‐bright leukocytes are unaffected by obesity. Combined, our results indicate that obesity promotes mobilization of progenitor cells, which may have clinical relevance.
Glycemic Variability in Abdominally Obese Men With Normal Glucose Tolerance as Assessed by Continuous Glucose Monitoring System
Authors: Ma Chun‐Ming , Yin Fu‐Zai , Wang Rui , Qin Chun‐Mei , Liu Bo , Lou Dong‐Hui , Lu Qiang
Published: February 2011

The purpose of this study was to observe both the glycemic variability in abdominally obese men with normal glucose tolerance (NGT) and the relationship between glycemic variability and early atherosclerosis. This case‐control study included 23 abdominally obese men (waist circumference (WC) ≥90 cm) and 23 nonabdominally obese men (WC <90 cm) with NGT who were between 20 and 50 years of age. All subjects were of the Han ethnicity. The cases and controls were age‐matched. A continuous glucose monitoring system (CGMS) was used in this study. With the CGMS, the standard deviation of blood glucose (SDBG) and the mean amplitude of glucose excursion (MAGE) were calculated to estimate glycemic variability. The carotid intima‐media thickness (CIMT) was used as a surrogate marker of early atherosclerosis. Mean blood glucose (MBG) (6.13 ± 0.94 vs. 5.55 ± 0.87 mmol/l), SDBG (0.89 ± 0.34 vs. 0.64 ± 0.24 mmol/l), MAGE (2.05 ± 0.83 vs. 1.57 ± 0.52 mmol/l), and CIMT (0.73 ± 0.12 vs. 0.67 ± 0.05 mm) were significantly higher in the abdominally obese men than in the nonabdominally obese men (P < 0.05). WC positively correlated with MBG (r = 0.302, P = 0.041), SDBG (r = 0.362, P = 0.013), MAGE (r = 0.302, P = 0.041), and CIMT (r = 0.487, P = 0.001). CIMT did not correlate with MBG (r = 0.206, P = 0.169), SDBG (r = 0.114, P = 0.450), and MAGE (r = 0.085, P = 0.574). After multivariate analysis, WC was still significantly associated with MBG (β = 0.025, P = 0.041), SDBG (β = 0.010, P = 0.013), MAGE (β = 0.019, P = 0.042), and CIMT (β = 0.008, P = 0.022). This study demonstrates that glycemic variability is increased in abdominally obese men with NGT. A relationship between glycemic variability and atherosclerosis was not observed in this study and requires further investigation.
Molecular Hydrogen Improves Obesity and Diabetes by Inducing Hepatic FGF21 and Stimulating Energy Metabolism in db/db Mice
Authors: Kamimura Naomi , Nishimaki Kiyomi , Ohsawa Ikuroh , Ohta Shigeo
Published: February 2011

Recent extensive studies have revealed that molecular hydrogen (H2) has great potential for improving oxidative stress‐related diseases by inhaling H2 gas, injecting saline with dissolved H2, or drinking water with dissolved H2 (H2‐water); however, little is known about the dynamic movement of H2 in a body. First, we show that hepatic glycogen accumulates H2 after oral administration of H2‐water, explaining why consumption of even a small amount of H2 over a short span time efficiently improves various disease models. This finding was supported by an in vitro experiment in which glycogen solution maintained H2. Next, we examined the benefit of ad libitum drinking H2‐water to type 2 diabetes using db/db obesity model mice lacking the functional leptin receptor. Drinking H2‐water reduced hepatic oxidative stress, and significantly alleviated fatty liver in db/db mice as well as high fat‐diet‐induced fatty liver in wild‐type mice. Long‐term drinking H2‐water significantly controlled fat and body weights, despite no increase in consumption of diet and water. Moreover, drinking H2‐water decreased levels of plasma glucose, insulin, and triglyceride, the effect of which on hyperglycemia was similar to diet restriction. To examine how drinking H2‐water improves obesity and metabolic parameters at the molecular level, we examined gene‐expression profiles, and found enhanced expression of a hepatic hormone, fibroblast growth factor 21 (FGF21), which functions to enhance fatty acid and glucose expenditure. Indeed, H2 stimulated energy metabolism as measured by oxygen consumption. The present results suggest the potential benefit of H2 in improving obesity, diabetes, and metabolic syndrome.
A water-swap reaction coordinate for the calculation of absolute protein–ligand binding free energies
Authors: Woods Christopher J. , Malaisree Maturos , Hannongbua Supot , Mulholland Adrian J.
Published: February 2011

The accurate prediction of absolute protein–ligand binding free energies is one of the grand challenge problems of computational science. Binding free energy measures the strength of binding between a ligand and a protein, and an algorithm that would allow its accurate prediction would be a powerful tool for rational drug design. Here we present the development of a new method that allows for the absolute binding free energy of a protein–ligand complex to be calculated from first principles, using a single simulation. Our method involves the use of a novel reaction coordinate that swaps a ligand bound to a protein with an equivalent volume of bulk water. This water-swap reaction coordinate is built using an identity constraint, which identifies a cluster of water molecules from bulk water that occupies the same volume as the ligand in the protein active site. A dual topology algorithm is then used to swap the ligand from the active site with the identified water cluster from bulk water. The free energy is then calculated using replica exchange thermodynamic integration. This returns the free energy change of simultaneously transferring the ligand to bulk water, as an equivalent volume of bulk water is transferred back to the protein active site. This, directly, is the absolute binding free energy. It should be noted that while this reaction coordinate models the binding process directly, an accurate force field and sufficient sampling are still required to allow for the binding free energy to be predicted correctly. In this paper we present the details and development of this method, and demonstrate how the potential of mean force along the water-swap coordinate can be improved by calibrating the soft-core Coulomb and Lennard-Jones parameters used for the dual topology calculation. The optimal parameters were applied to calculations of protein–ligand binding free energies of a neuraminidase inhibitor (oseltamivir), with these results compared to experiment. These results demonstrate that the water-swap coordinate provides a viable and potentially powerful new route for the prediction of protein–ligand binding free energies.
Confined thermocapillary motion of a three-dimensional deformable drop
Authors: Brady P. T. , Herrmann M. , Lopez J. M.
Published: February 2011

In this paper, simulations are performed of the thermocapillary motion of three-dimensional and axisymmetric drops in a confined apparatus. The refined level-set grid method is used to track the interface and resolve very small deformations. We compare our results to theoretically predicted thermocapillary migration velocities of drops and to experimentally measured migration velocities in microgravity experiments. The motivation of the present work is to address four important questions surrounding thermocapillary migration. These are as follows. (1) What is the impact of initial conditions on both the initial transient and steady state drop behavior? (2) What is the impact of the domain geometry on drop behavior? (3) Do drops deform for intermediate Marangoni numbers and are those deformations axisymmetric? (4) Can the assumption of constant temperature fluid properties be used when simulating physical experiments? To answer the first question, we explore the parameter space of initial drop temperature distribution and drop holding time. We find that in lower Marangoni number regimes, the drop rapidly settles to a quasisteady state. For larger Marangoni numbers, the initial conditions dominate the drop behavior. To address the second and third questions, we look at the spatial distribution of tangential temperature gradients on the surface of the drop as well as drop deformations and migration velocities. The domain geometry induces nonaxisymmetric deformations and temperature distributions. The results of several axisymmetric runs with realistic physical properties are examined to answer the fourth question. It is found that the variation of material properties influences the drop migration behavior in a nontrivial way.
Study of the structure and dynamics of poly(vinyl pyrrolidone) by molecular dynamics simulations validated by quasielastic neutron scattering and x-ray diffraction experiments
Authors: Busselez Rémi , Arbe Arantxa , Alvarez Fernando , Colmenero Juan , Frick Bernhard
Published: February 2011

Quasielastic neutron scattering, x-ray diffraction measurements, and fully atomistic molecular dynamics simulations have been performed on poly(vinylpyrrolidone) homopolymer above its glass transition temperature. A “prepeak” appears in the x-ray diffraction pattern that shows the typical features of a first amorphous halo. From an effective description of the experimentally accessed incoherent scattering function of hydrogens in terms of a stretched exponential function, we observe enhanced stretching and a momentum-transfer dependence of the characteristic time different from that usually reported for more simple polymers (main-chain polymers or polymers with small side groups). The comparison with both kinds of experimental results has validated the simulations. The analysis of the simulated structure factor points to a nanosegregation of side groups (SG) and main-chains (MC). The detailed insight provided by the simulations on the atomic trajectories reveals a partial and spatially localized decoupling of MC and SG dynamics at length scales between the average SG–SG distance and the characteristic length of the backbone interchain correlations. Anomalous behavior in correlators calculated for the SG subsystem are found, like e.g., logarithmiclike decays of the density–density correlation function. They might be a consequence of the existing large dynamic asymmetry between SG and MC subsystems. Our results suggest that, as the SGs are spatially extended and chemically different from the backbone, they form transient nanosegregated domains. The dynamics of these domains show similar behavior to that found in other systems displaying large dynamic asymmetry.
Channel direction, effective field, and temperature dependencies of hole mobility in (110)-oriented Ge-on-insulator p-channel metal-oxide-semiconductor field-effect transistors fabricated by Ge condensation technique
Authors: Dissanayake Sanjeewa , Zhao Yi , Sugahara S. , Takenaka Mitsuru , Takagi Shinichi
Published: February 2011

This paper experimentally reports the channel direction (θ), effective field (Eeff), and temperature (T) dependencies of hole mobility in (110)-oriented 12-nm-thick accumulation mode Ge-on-insulator (GOI) p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) fabricated by the Ge condensation technique. It is found that, the hole mobility on (110)-oriented GOI surfaces increases with the channel direction tilted from ⟨100⟩ to ⟨110⟩ direction, in contrast to (100)-oriented conventional GOI surfaces. By low temperature measurements, the extracted phonon-limited mobilities (μph) of (110)-oriented GOI surfaces along ⟨110⟩ direction occupy 2.1 and 7.1 of enhancement against (100)-oriented GOI and Si surfaces, respectively, at any T. Through physical insights into the present analyses, μph dependence on T−1.8 suggests the suppression of intervalley phonon scattering at low T as in Si. Also, μph is found to increase with Eeff, which can be regarded as an inherent property of hole mobility on (110)-oriented Ge. By further analyses base on the definition of mobility, the effective mass can be a dominant factor for the mobility anisotropy on (110)-oriented GOI pMOSFETs.
Modeling and simulation of multiple bubble entrainment and interactions with two dimensional vortical flows
Authors: Finn Justin , Shams Ehsan , Apte Sourabh V.
Published: February 2011

Simulations of bubble entrainment and interactions with two dimensional vortical flows are preformed using a discrete element model. In this Eulerian-Lagrangian approach, solution to the carrier phase is obtained using direct numerical simulation whereas motion of subgrid bubbles is modeled using Lagrangian tracking. The volumetric displacement of the fluid by the finite size of the bubbles is modeled along with interphase momentum-exchange for a realistic coupling of the bubbles to the carrier phase. In order to assess the importance of this volumetric coupling effect, even at low overall volume loading, simulations of a small number of microbubbles entrained in a traveling vortex tube are studied in detail. The test case resembles the experiments conducted by Sridhar and Katz [JFM, 1999] on bubble entrainment in vortex rings. It is shown that under some conditions, the entrainment of eight small bubbles, 1100 μm or less in diameter, result in significant levels of vortex distortion when modeled using the volumetric coupling effect. Neglecting these effects, however, does not result in any vortex distortion due to entrained bubbles. The nondimensionalized vortex strength versus bubble settling locations are compared with experimental data to show collapse of the data along the trends observed in experiments only when the volumetric effects are modeled. Qualitative and quantitative assessments of this distortion observed with volumetric coupling are made using three methods; bubble induced vortex asymmetry, relative change in the decay of angular momentum, and relative change in the peak vorticity. It is found that in all cases the volumetric effects result in a relative increase of the vortex decay rate. The concept of a relative reaction force, defined as the ratio of net bubble to fluid reaction to the local driving force of the vortex, is introduced to analyze this effect. It is shown that the global increases in vortex decay rate are directly proportional to the magnitude of this highly local relative reaction force.
Compact microdisk cavity laser with type-II GaSb/GaAs quantum dots
Authors: Hsu K. S. , Chiu T. T. , Lin Wei-Hsun , Chen K. L. , Shih M. H. , Lin Shih-Yen , Chang Yia-Chung
Published: February 2011

Microdisk lasers with active region made of type-II GaSb/GaAs quantum dots on the GaAs substrate have been demonstrated. A microdisk cavity with diameter of 3.9 μm was fabricated from a 225-nm-thick GaAs layer filled with GaSb quantum dots. Lasing at wavelengths near 1000 nm at 150 K was achieved for this microdisk. A high threshold characteristic temperature of 77 K was also observed. It is found that the lasing wavelength matches closely with the first-order whispering-gallery mode of the cavity as obtained from the finite-element method simulation.
Magnetic reversal of cylindrical nickel nanowires with modulated diameters
Authors: Pitzschel Kristina , Bachmann Julien , Martens Stephan , Montero-Moreno Josep M. , Kimling Judith , Meier Guido , Escrig Juan , Nielsch Kornelius , Görlitz Detlef
Published: February 2011

Anodic alumina membranes with modulated pore diameters serve as template for the preparation of magnetic nanowires. Filling the pores with Ni by electrodeposition delivers wires replicating the variation in modulation in pore diameter from 80 to 160 nm. Such structures are of interest for the observation and control of magnetic domain wall motion. Single-object characterization utilizing the magneto-optical Kerr effect magnetometry evidences a strong correlation between geometric parameters and magnetic properties. Ensemble magnetization measurements with a superconducting quantum interference device show the effect of dipolar interactions. Analytical models can reproduce the lowering of coercivity due to the presence of enhanced stray fields within the array. Magnetic force microscopy at individual wires indicates the presence of a strong stray field in the vicinity of the diameter change. The preparation technique demonstrates a mass production method of nano-objects with designed geometric irregularities, which could be used to control the motions of magnetic domain walls.
Spectral identification of diffuse resonances in H2 above the n = 2 dissociation limit
Authors: Ivanov T. I. , de Lange C. A. , Ubachs W.
Published: February 2011

The resonance structure in molecular hydrogen above the n = 2 dissociation limit is experimentally investigated in a 1 XUV + 1 VIS coherent two-step laser excitation process, with subsequent ionization of H(n = 2) products. Diffuse spectral features exhibiting widths of several cm−1 in the excitation range of 118 500–120 500 cm−1 are probed. Information on angular momentum selection rules for parallel and crossed polarizations, combination differences, the para–ortho distinction, extrapolation from rovibrational structure in the bound region below the n = 2 threshold, and mass-selective detection of \documentclass[12pt]{minimal}\begin{document}${\rm H}_2^+$\end{document}H2+ parent and H+ daughter fragments is used as input. This allows for an assignment of the diffuse resonances observed in terms of 1\documentclass[12pt]{minimal}\begin{document}$\Sigma _g^+$\end{document}Σg+, 1Πg, and 1Δg states, specified with vibrational and rotational quantum numbers.
Structural, optical, and electrical properties of Yb-doped ZnO thin films prepared by spray pyrolysis method
Authors: Soumahoro I. , Schmerber G. , Douayar A. , Colis S. , Abd-Lefdil M. , Hassanain N. , Berrada A. , Muller D. , Slaoui A. , Rinnert H. , Dinia A.
Published: February 2011

Yb-doped ZnO thin films were prepared on glass substrates by spray pyrolysis technique in order to investigate the insertion of Yb ions in the ZnO matrix and the related optical properties of the films. The molar ratio of Yb in the spray solution was varied in the range of 0–5 at. %. X-ray diffraction patterns showed that the undoped and Yb-doped ZnO films exhibit the hexagonal wurtzite crystal structure with a preferential orientation along [002] direction. No secondary phase is observed in Yb-doped ZnO films. All films exhibit a transmittance between 75 and 90% in the visible range with a sharp absorption onset about 375 nm corresponding to the fundamental absorption edge at 3.3 eV. The photoluminescence measurements show a clear luminescence band at 980 nm that is characteristic of Yb3+ transition between the electronic levels F25/2 and F27/2. This is an experimental evidence for an efficient energy transfer from ZnO matrix to Yb3+. Hall effect measurements showed low resistivities and high carrier mobilities which makes these films of interest to photovoltaic devices.
Synthesis of single and multi unit-wall MgB2 nanotubes by arc plasma in inert liquid via self-curling mechanism
Authors: Sano Noriaki , Kawanami Osamu , Tamon Hajime
Published: February 2011

Magnesium diboride (MgB2) is known as a promising superconductor due to its high transmission temperature. Similarly to single-wall carbon nanotube, unique characteristics would be seen if a nanotube structure of MgB2 having a unit-wall of Mg and B atomic bilayer is prepared. However, such MgB2 nanotubes have not ever been synthesized. In this article, formation mechanism of unit-wall MgB2 nanotube is elucidated by molecular mechanics calculation. From the viewpoint of energetic stability, the unit-wall will be curled up to form nanotube structure when MgB2 crystal is disassembled to an isolated unit-wall layer. An experiment using arc plasma in inert liquid was utilized to produce unit-wall MgB2 nanotubes. As a result, a single and multiunit-wall MgB2 nanotube was successfully synthesized. In this reaction field, the arc plasma may play a role to produce isolated MgB2 unit-wall fragment, and the cold cathode surface can contribute to preserve MgB2 nanotube structure.
Electron energy loss spectroscopy investigation of Pb and Ti hybridization with O at the PbTiO3/SrTiO3 interface
Authors: Eberg E. , van Helvoort A. T. J. , Takahashi R. , Gass M. , Mendis B. , Bleloch A. , Holmestad R. , Tybell T.
Published: February 2011

Studies of oxide interfaces, and how they affect physical properties, have recently gained large attention. For ferroelectric materials, the evolution of the order parameter close to an interface is important to understand regarding the stability of the ferroelectric phase, and how to optimize devices taking advantage of the polarization at the interface. Here we employ electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy to compare the electronic and structural properties in both bulk and interface regions of epitaxial PbTiO3 thin films grown on SrTiO3 substrates. At the interface, changes in EELS spectra of the Ti-L3,2 and O-K edges, as compared to the bulk of the thin film, reveal a reduction in the hybridization of Ti 3d and Pb 6sp states with O 2p, and thus tetragonal distortion of the TiO6 octahedron. Real-space multiple-scattering calculations of the O-K edge support the experimental results. Moreover, the analysis of the Ti-valence reveals that the change is gradual over ∼2–3 nm. The data implies a decreasing ferroelectric order parameter over ∼2–3 nm close to the PbTiO3/SrTiO3 interface with a nonzero value at the interface with an additional screening of the polarization over ∼1–2 nm into the SrTiO3 substrate from the Ti atoms.
Surface passivation of crystalline silicon by plasma-enhanced chemical vapor deposition double layers of silicon-rich silicon oxynitride and silicon nitride
Authors: Seiffe Johannes , Gautero Luca , Hofmann Marc , Rentsch Jochen , Preu Ralf , Weber Stefan , Eichel Rüdiger A.
Published: February 2011

Excellent surface passivation of crystalline silicon (c-Si) is desired for a number of c-Si based applications ranging from microelectronics to photovoltaics. A plasma-enhanced chemical vapor deposition double layer of amorphous silicon-rich oxynitride and amorphous silicon nitride (SiNx) can provide a nearly perfect passivation after subsequent rapid thermal process (RTP) and light soaking. The resulting effective minority carriers’ lifetime (τeff) is close to the modeled maximum on p-type as well as on n-type c-Si. Restrictions on the RTP of passivated surfaces, typical of other common passivation schemes (e.g., amorphous Si), are relieved by this double layer. Harsher thermal treatments can be adopted while still obtaining salient passivation. Furthermore, characterization of the same, such as, surface photovoltage, capacitance voltage, and electron paramagnetic resonance, enables the reproducibility and the understanding of the passivation scheme under test. It is shown that the strong quality of surface passivation is ensured by a mechanism that emits electrons from shallow donor states in the passivation layer system and therefore creates a positive field effect.
Characterization of AlInN/GaN structures on AlN templates for high-performance ultraviolet photodiodes
Authors: Sakai Yusuke , Khai Pum Chian , Ichikawa Junki , Egawa Takashi , Jimbo Takashi
Published: February 2011

The authors characterize AlInN/GaN structures on AlN templates for high-performance ultraviolet photodiodes. AlInN/GaN structures were grown with various growth parameters by metal organic chemical vapor deposition. In the case of nearly lattice-matched to GaN underlying layers, AlInN/GaN structures are found to have smooth interface. AlInN layers grown at the low pressure are confirmed to have high crystal quality from x-ray diffraction measurements and good surface morphology from atomic force microscope images. The noble AlInN-based photodiodes were fabricated. Their performances show the leakage current of 48 nA at a reverse voltage of 5 V and the cutoff wavelength around 260 nm. A cutoff-wavelength responsivity of 21.84 mA/W is obtained, corresponding to quantum efficiency of 10.6%. It may be possible to realize high-performance ultraviolet photodiodes by further optimizing AlInN/GaN structures.
Stress reduction and performance improvement of phase change memory cell by using Ge2Sb2Te5–TaOx composite films
Authors: Song Sannian , Song Zhitang , Wu Liangcai , Liu Bo , Feng Songlin
Published: February 2011

Ge 2 Sb 2 Te 5 – TaO x  (GST–TaOx) composite films were used as a medium for phase change memory (PCM). As TaOx concentration was increased from 0 to 38.3 mol %, the activation energy for crystallization was increased from 2.01 to 2.40 eV. Compared to GST (6.8%), the GST–TaOx (32.2 mol %) film had a lowered density change during crystallization. Residual stress of the GST–TaOx composite films was reduced by 40%. This improvement was attributed to smaller grain size of the GST–TaOx films, which facilitated the relaxation of the stress via grain boundary diffusion or sliding. Compared to pure GST PCM cell, reset voltage of the GST–TaOx cell was obviously reduced, which was attributed to the reduced thermal conductivity by incorporating TaOx into GST. Meanwhile, PCM cells based on the GST–TaOx composite films possess promising endurance characteristics, implying that they are potential candidates for random access memory.
Fabrication of midinfrared quantum cascade laser via oxygen-enhanced nonselective wet thermal oxidation
Authors: Seibert C. S. , D’Souza M. , Shin J. C. , Mawst L. J. , Botez D. , Hall D. C.
Published: February 2011

A native oxide confined quantum cascade laser operating at λ=5.4 μm was fabricated using oxygen-enhanced nonselective wet thermal oxidation. This process formed an insulating native oxide on the lattice matched In0.53Ga0.47As waveguide core layers and the strain compensated InAlAs/InGaAs active core region after oxidation at 500 °C with 0.7% O2 added relative to the N2 water vapor carrier gas. A device with a threshold current density of Jth=3.2 kA/cm2 was realized.
Hamiltonian walks on the Sierpinski gasket
Authors: Chang Shu-Chiuan , Chen Lung-Chi
Published: February 2011

We derive the exact number of Hamiltonian walks H(n) on the two-dimensional Sierpinski gasket SG(n) at stage n, whose asymptotic behavior is given by $\frac{\sqrt{3}(2\sqrt{3})^{3^{n-1}}}{3} \times (\frac{5^2 \times 7^2 \times 17^2}{2^{12} \times 3^5 \times 13})(16)^n$3(23)3n−13×(52×72×172212×35×13)(16)n. We also obtain the number of Hamiltonian walks with one end at a specific outmost vertex of SG(n), with asymptotic behavior $\frac{\sqrt{3}(2\sqrt{3})^{3^{n-1}}}{3} \times (\frac{7 \times 17}{2^4 \times 3^3})4^n$3(23)3n−13×(7×1724×33)4n. The distribution of Hamiltonian walks on SG(n) with one end at a specific outmost vertex and the other at an arbitrary vertex of SG(n) is investigated. We rigorously prove that the exponent for the mean ℓ displacement between the two end vertices of such Hamiltonian walks on SG(n) is ℓln 2/ln 3 for ℓ > 0.
Dopant homogeneity and transport properties of impurity-doped oxide nanowires
Authors: Klamchuen Annop , Yanagida Takeshi , Kanai Masaki , Nagashima Kazuki , Oka Keisuke , Seki Shu , Suzuki Masaru , Hidaka Yoshiki , Kai Shoichi , Kawai Tomoji
Published: February 2011

Controlling and understanding an impurity doping on semiconductor oxide nanowires grown by the vapor-liquid-solid (VLS) method remains an important challenge. Homogeneous dopant distribution within oxide nanowires has been assumed without the direct evaluations to interpret the transport properties. Here we report the direct measurements of dopant distributions for Ta-doped SnO2 nanowires. We find that differences in dopant incorporations between VLS and vapor-solid growth processes give rise to a heavily doped shell surrounding an underdoped core. Thus, understanding the dopant incorporation pathways is essential to designing and controlling impurity doping on VLS grown oxide nanowires.
Self-established noncollinear oscillation and angular tuning in a quasi-phase-matched mirrorless optical parametric oscillator
Authors: Strömqvist Gustav , Pasiskevicius Valdas , Canalias Carlota
Published: February 2011

We experimentally demonstrate self-established noncollinear interactions in a quasi-phase-matched mirrorless optical parametric oscillator using a periodically-poled KTiOPO4 crystal with submicrometer periodicity. It is shown that the oscillation is established in a very specific geometric configuration where the two possible solutions of the energy and momentum conservation conditions become spatially degenerate and contribute coherently to the gain. In this configuration, the signal and the idler remain mutually counter-propagating. The tuning capabilities of a noncollinear mirrorless optical parametric oscillator are investigated.
Effects of hole doping in electronic states of La1−xSrxMnO3 probed by magnetic Compton scattering
Authors: Mizoroki T. , Itou M. , Taguchi Y. , Iwazumi T. , Sakurai Y.
Published: February 2011

We have carried out magnetic Compton scattering measurements on polycrystalline samples of the perovskite manganites La1−xSrxMnO3 covering the hole-doping range from x=0.1 to x=0.5. Charge and magnetic Compton profiles were measured in order to obtain Compton profiles of spin-wise subbands. By considering the doping-dependency of the subband Compton profiles, we show how the electronic states evolve associated with hole doping. The results indicate that doped holes predominantly enter into the O 2p states in the lightly doped region and the charge transfer occurs from the up-spin Mn 3d to the down-spin Mn 3d states in the heavily doped region.
Detection of immunoglobulins in a laser induced fluorescence system utilizing polydimethysiloxane microchips with advanced surface and optical properties
Authors: Schrott Walter , Nebyla Marek , Přibyl Michal , Šnita Dalimil
Published: February 2011

We developed an automated laser induced fluorescence system utilizing microfluidic chips for detection and quantification of immunoglobulins. Microchips were fabricated from polydimethysiloxane (PDMS) using the so-called “prepolymerization technique.” The microchip structure helped minimize the effects of PDMS autofluorescence and light scattering. Furthermore, a thin and uniform PDMS layer forming the top of the microchip enabled proper focusing and collection of the excitation beam and the emitted fluorescence, respectively. The developed system was tested for the detection of mouse immunoglobulins. The capturing antibodies were immobilized on internal microchannel walls in the form of a polyelectrolyte. We clearly show that this immobilization technique, if correctly realized, gives results with high reproducibility. After sample incubation and washing, secondary antibodies labeled by fluorescein isothiocyanate were introduced into microchannels to build a detectable complex. We show that mouse antibodies can be quantified in a wide concentration range, 0.01–100 μg ml−1. The lower detection limit was below 0.001 μg ml−1 (6.7 pM). The developed laser induced fluorescence (LIF) apparatus is relatively cheap and easy to construct. The total cost of the developed LIF detector is lower than a typical price of plate readers. If compared to classical ELISA (enzyme linked immunosorbent assay) plate systems, the detection of immunoglobulins or other proteins in the developed PDMS microfluidic device brings other important benefits such as reduced time demands (10 min incubation) and low reagent consumption (less than 1 μl). The cost of the developed PDMS chips is comparable with the price of commercial ELISA plates. The main troubleshooting related to the apparatus development is also discussed in order to help potential constructors.
Influence of trimethylaluminum on the growth and properties of HfO2/In0.53Ga0.47As interfaces
Authors: Hwang Yoontae , Engel-Herbert Roman , Stemmer Susanne
Published: February 2011

The growth and the electrical properties of HfO2/In0.53Ga0.47As interfaces are characterized as a function of exposure to trimethylaluminum (TMA) prior to chemical beam deposition of HfO2 from an alkoxide precursor. It is shown that TMA can act as a surfactant for HfO2 growth for (2×4) but not for the group-III-rich (4×2) reconstructed surfaces. The Fermi-level can be unpinned by postdeposition forming gas anneals only for interfaces that were exposed to low doses of TMA at low temperatures. The results are discussed in the context of the interaction between TMA and III-V surfaces.
Runoff, soil loss, and nutrient transport from cropping systems on Red Ferrosols in tropical northern Australia
Authors: Cogle A. L. , Keating M. A. , Langford P. A. , Gunton J. , Webb I. S.
Published: February 2011

Runoff, soil loss, and nutrient loss were assessed on a Red Ferrosol in tropical Australia over 3 years. The experiment was conducted using bounded, 100-m2 field plots cropped to peanuts, maize, or grass. A bare plot, without cover or crop, was also instigated as an extreme treatment. Results showed the importance of cover in reducing runoff, soil loss, and nutrient loss from these soils. Runoff ranged from 13% of incident rainfall for the conventional cultivation to 29% under bare conditions during the highest rainfall year, and was well correlated with event rainfall and rainfall energy. Soil loss ranged from 30 t/ha.year under bare conditions to <6 t/ha.year under cropping. Nutrient losses of 35 kg N and 35 kg P/ha.year under bare conditions and 17 kg N and 11 kg P/ha.year under cropping were measured. Soil carbon analyses showed a relationship with treatment runoff, suggesting that soil properties influenced the rainfall runoff response. The cropping systems model PERFECT was calibrated using runoff, soil loss, and soil water data. Runoff and soil loss showed good agreement with observed data in the calibration, and soil water and yield had reasonable agreement. Long-term runs using historical weather data showed the episodic nature of runoff and soil loss events in this region and emphasise the need to manage land using protective measures such as conservation cropping practices. Farmers involved in related, action-learning activities wished to incorporate conservation cropping findings into their systems but also needed clear production benefits to hasten practice change.
Activity–dormancy transition in the cambial meristem involves stage-specific modulation of auxin response in hybrid aspen
Authors: Baba Kyoko , Karlberg Anna , Schmidt Julien , Schrader Jarmo , Hvidsten Torgeir R. , Bako Laszlo , Bhalerao Rishikesh P.
Published: February 2011

The molecular basis of short-day–induced growth cessation and dormancy in the meristems of perennial plants (e.g., forest trees growing in temperate and high-latitude regions) is poorly understood. Using global transcript profiling, we show distinct stage-specific alterations in auxin responsiveness of the transcriptome in the stem tissues during short-day–induced growth cessation and both the transition to and establishment of dormancy in the cambial meristem of hybrid aspen trees. This stage-specific modulation of auxin signaling appears to be controlled via distinct mechanisms. Whereas the induction of growth cessation in the cambium could involve induction of repressor auxin response factors (ARFs) and down-regulation of activator ARFs, dormancy is associated with perturbation of the activity of the SKP-Cullin-F-box
TIR
(SCF
TIR
) complex, leading to potential stabilization of repressor auxin (AUX)/indole-3-acetic acid (IAA) proteins. Although the role of hormones, such as abscisic acid (ABA) and gibberellic acid (GA), in growth cessation and dormancy is well established, our data now implicate auxin in this process. Importantly, in contrast to most developmental processes in which regulation by auxin involves changes in cellular auxin contents, day-length–regulated induction of cambial growth cessation and dormancy involves changes in auxin responses rather than auxin content.
Inhibition of the interactions between eukaryotic initiation factors 4E and 4G impairs long-term associative memory consolidation but not reconsolidation
Authors: Hoeffer Charles A. , Cowansage Kiriana K. , Arnold Elizabeth C. , Banko Jessica L. , Moerke Nathan J. , Rodriguez Ricard , Schmidt Enrico K. , Klosi Edvin , Chorev Michael , Lloyd Richard E. , Pierre Philippe , Wagner Gerhard , LeDoux Joseph E. , Klann Eric
Published: February 2011

Considerable evidence indicates that the general blockade of protein synthesis prevents both the initial consolidation and the postretrieval reconsolidation of long-term memories. These findings come largely from studies of drugs that block ribosomal function, so as to globally interfere with both cap-dependent and -independent forms of translation. Here we show that intra-amygdala microinfusions of 4EGI-1, a small molecule inhibitor of cap-dependent translation that selectively disrupts the interaction between eukaryotic initiation factors (eIF) 4E and 4G, attenuates fear memory consolidation but not reconsolidation. Using a combination of behavioral and biochemical techniques, we provide both in vitro and in vivo evidence that the eIF4E–eIF4G complex is more stringently required for plasticity induced by initial learning than for that triggered by reactivation of an existing memory.
Ammonia synthons for the multicomponent assembly of complex γ-lactams
Authors: Tan Darlene Q. , Martin Kevin S. , Fettinger James C. , Shaw Jared T.
Published: February 2011

The synthesis of γ-lactams that are unsubstituted at the 1-position (nitrogen) as well as their subsequent
N
-functionalization is reported. A recently discovered four-component reaction (4CR) is employed with either an ammonia precursor or a protected form of ammonia that can be deprotected in a subsequent synthetic step. These methods represent the first multicomponent assembly of complex lactam structures that are unsubstituted at nitrogen. In addition, two methods for the introduction of nitrogen substituents that are not possible through the original 4CR are reported. X-ray crystallographic analysis of representative structures reveals conformational changes in the core structure that will enable future deployment of this chemistry in the design and synthesis of diverse collections of lactams suitable for the discovery of new biological probes.
Profiling the effects of isocitrate dehydrogenase 1 and 2 mutations on the cellular metabolome
Authors: Reitman Zachary J. , Jin Genglin , Karoly Edward D. , Spasojevic Ivan , Yang Jian , Kinzler Kenneth W. , He Yiping , Bigner Darell D. , Vogelstein Bert , Yan Hai
Published: February 2011

Point mutations of the NADP
+
-dependent isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2) occur early in the pathogenesis of gliomas. When mutated, IDH1 and IDH2 gain the ability to produce the metabolite (
R
)-2-hydroxyglutarate (2HG), but the downstream effects of mutant IDH1 and IDH2 proteins or of 2HG on cellular metabolism are unknown. We profiled >200 metabolites in human oligodendroglioma (HOG) cells to determine the effects of expression of IDH1 and IDH2 mutants. Levels of amino acids, glutathione metabolites, choline derivatives, and tricarboxylic acid (TCA) cycle intermediates were altered in mutant IDH1- and IDH2-expressing cells. These changes were similar to those identified after treatment of the cells with 2HG. Remarkably,
N
-acetyl-aspartyl-glutamate (NAAG), a common dipeptide in brain, was 50-fold reduced in cells expressing IDH1 mutants and 8.3-fold reduced in cells expressing IDH2 mutants. NAAG also was significantly lower in human glioma tissues containing IDH mutations than in gliomas without such mutations. These metabolic changes provide clues to the pathogenesis of tumors associated with IDH gene mutations.
Annealing behaviour and crystal structure of RF-sputtered Bi-substituted dysprosium iron-garnet films having excess co-sputtered Bi-oxide content
Authors: Vasiliev M , Nur-E-Alam M , Alameh K , Premchander P , Lee Y T , Kotov V A , Lee Y P
Published: February 2011

We investigate the magneto-optic properties, crystal structure and annealing behaviour of nano-composite media with record-high magneto-optic quality exceeding the levels reported so far in sputtered iron-garnet films. Bi-substituted dysprosium–gallium iron-garnet films having excess bismuth oxide content are deposited using RF co-sputtering, and a range of garnet materials are crystallized using conventional oven-annealing processes. We report, for the first time ever, the results of optimization of thermal processing regimes for various high-performance magneto-optic iron-garnet compositions synthesized and describe the evolution of the optical and magneto-optical properties of garnet-Bi-oxide composite-material films occurring during the annealing processes. The crystallization temperature boundaries of the system (BiDy)3(FeGa)5O12 : Bi2O3 are presented. We also report the results of x-ray diffraction and energy-dispersive x-ray spectroscopy studies of this recently developed class of high-performance magneto-optic composites. Our hypothesis of iron oxides being the cause of excess optical absorption in sputtered Bi-iron-garnet films is confirmed experimentally.
Indirect interband transition in hexagonal GaN
Authors: Lancry O , Farvacque J-L , Pichonat E , Gaquière C
Published: February 2011

In this paper, we report on optical investigations with Raman experiment to underline a new ultraviolet (UV) luminescence band in hexagonal gallium nitride (GaN) at 4.56 eV. GaN is a direct band gap semiconductor, the photoluminescence peak corresponding to the energy gap at 3.43 eV dominates the spectrum. Nevertheless, other electronic interband transitions can appear on the spectrum: the electronic indirect interband transitions. We attribute one of them to the observed new photoluminescence band at 4.56 eV. This interpretation is supported by photoluminescence spectra obtained on three different samples at room temperature and at −50 °C with UV excitation source: mbd-266 nm solid laser (4.66 eV) and by the study of three criteria: the partly opposite parities of initial and final wave function, the implication of acoustic phonons and temperature control.
Longitudinal and transverse discharges with mercury-rare and xenon gases
Authors: Kim Junghyun , Jeong Jongmun , Jin Dongjun , Kim Hyunchul , Han Sangho , Kwon Gichung , Choi Eunha , Cho Guangsup
Published: February 2011

The properties of longitudinal and transverse discharges are investigated with the use of external electrode tubular lamps, with respect to the characteristics of current and voltage, luminance and spectral radiation. With the mercury-rare gases, a high luminance of over 10 000 cd m−2 is readily obtained in the longitudinal discharge with a long positive column where the spectral radiations from Hg are dominant. However, the luminance is extremely low, a few hundred cd m−2, in the transverse discharge with a short gap where all kinds of atom species are ionized and the intensity of the spectral lines from Ne and Ar is rather high. With pure Xe and a mixture of Xe, the transverse discharge is superior to the longitudinal discharge in that the breakdown voltage is low and the luminance for a high pressure above 200 Torr is relatively high.
Nanostructure deposition in the afterglow of a low power barrier discharge
Authors: Sonnenfeld Axel , Papageorgiou Vasileios , Reichen Patrick , Körner Lutz , von Rohr Philipp Rudolf
Published: February 2011

The precipitation of solid-state sphere-like nanostructures from an organosilicon precursor at atmospheric pressure is investigated with the prospect of improving powder flowability by the attachment of nanoscopic spacers to the powder particles' surfaces. Tetramethylsilane (TMS) is admixed to the afterglow of a low power (<0.5 W) barrier discharge (BD). The BD occurs in a single miniature flow channel, where Ar or He enriched with O2 is excited favouring homogeneous gas phase reactions of atomic oxygen and TMS in the afterglow. The chemical and morphological influence of Ar or He on the formation of nanostructures is explored at two positions in the afterglow by Fourier transform infrared spectroscopy and scanning electron microscopy. For the Ar-based BD, larger spherical nanostructures (100–1000 nm) of higher oxide content are obtained, while for He polymeric deposits with characteristic sizes below 100 nm are found. In addition, the processing capability of a BD device, consisting of a set of 64 miniature flow channels, is probed by means of the wettability improvement of polymer powder particles, conveyed through the BD afterglow zone of a multi-channel device. The treatment is shown to decrease the benzyl alcohol contact angle significantly with increasing oxygen feed.
Retarding field energy analyser ion current calibration and transmission
Authors: Denieffe K , Mahony C M O , Maguire P D , Gahan D , Hopkins M B
Published: February 2011

Accurate measurement of ion current density and ion energy distributions (IEDs) is often critical for plasma processes in both industrial and research settings. Retarding field energy analysers (RFEAs) have been used to measure IEDs because they are considered accurate, relatively simple and cost effective. However, their usage for critical measurement of ion current density is less common due to difficulties in estimating the proportion of incident ion current reaching the current collector through the RFEA retarding grids. In this paper an RFEA has been calibrated to measure ion current density from an ion beam at pressures ranging from 0.5 to 50.0 mTorr. A unique method is presented where the currents generated at each of the retarding grids and the RFEA upper face are measured separately, allowing the reduction in ion current to be monitored and accounted for at each stage of ion transit to the collector. From these I–V measurements a physical model is described. Subsequently, a mathematical description is extracted which includes parameters to account for grid transmissions, upper face secondary electron emission and collisionality. Pressure-dependent calibration factors can be calculated from least mean square best fits of the collector current to the model allowing quantitative measurement of ion current density.
Simulation of imaging in tapping-mode atomic-force microscopy: a comparison amongst a variety of approaches
Authors: Pishkenari H N , Mahboobi S H , Meghdari A
Published: February 2011

Models capable of accurate simulation of microcantilever dynamics coupled with complex tip–sample interactions are essential for interpretation and prediction of the imaging results in amplitude modulation or tapping-mode atomic-force microscopy (AM-AFM or TM-AFM). In this paper, four approaches based on combinations of lumped and finite element methods for modelling of cantilever dynamics, and van der Waals and molecular dynamics for modelling of tip–sample interactions, are used to simulate the precise imaging by AM-AFM. Based on the simulated imaging and force determination, the efficiency of different modelling schemes is evaluated. This comparison is performed considering their coincidence with the realistic behaviour of AM-AFM in imaging of nanoscale features. In the conducted simulations, a diamond tip is used to scan a C60 molecule absorbed on a graphite substrate. The effects of amplitude set-point, cantilever stiffness and quality factor on the accuracy of different modelling approaches are studied.