bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments on granular rheology: Effects of particle size and fluid viscosity
Authors: Higashi Naoya , Sumita Ikuro
Published: April 2009

We report the results of shear experiments of a thick layer of dry and liquid‐saturated glass beads, a simplified model of fault gouge, in order to clarify and to compare how the particle size and fluid viscosity affect the granular rheology. We sheared sorted glass beads and measured the temporal variation of stress that fluctuates owing to stick‐slip behavior. We found that the stress drop and slip recurrence intervals increase with the particle size because of larger static bulk friction. The forms of stress‐time series data for different particle size are not self‐similar; the form changes toward a sawtooth‐like temporal variation as the particle size increases, which can be characterized using two newly defined dimensionless numbers. In addition, we show that there is a continuous transition from constant slip velocity toward constant stress drop time as the particle size increases. We also determined the shear band width using the time‐lapsed images of the sheared glass beads and found that the number of particles comprising the shear band decreases with the particle size. When the glass beads are saturated with viscous liquid, lubrication causes the rheology to change from frictional to viscous and to increase the slip recurrence interval, and these properties can be used to distinguish from the particle size effects. Under a fixed loading rate, there is a viscosity that minimizes the stress needed for shearing, at which we can separate the frictional and viscous regimes.
Aircraft study of Mountain Chimney Effect of Beijing, China
Authors: Chen Ying , Zhao Chunsheng , Zhang Qiang , Deng Zhaoze , Huang Mengyu , Ma Xincheng
Published: April 2009

In this paper, the three‐dimensional distribution of air pollutants in the Beijing region using aircraft measurements is reported, and Mountain Chimney Effect (MCE) on the distribution of air pollutants in this region is studied. A remarkable two‐pollution‐layer structure was observed by aircraft measurement in Beijing on 18 August 2007. Gaseous and particle pollutants were well mixed with high concentrations in the planetary boundary layer. There was an elevated pollution layer (EPL) at the altitude of 2500–3500 m, and the concentrations of pollutants were high and comparable with that in the planetary boundary layer. Analysis of aircraft measurement indicates that pollutants in the two pollution layers originated from the same source. On the basis of analysis of the Weather Research and Forecasting (WRF)‐TRACER model and wind profile data, the formation of EPL is discussed. The wind flow of Beijing region was dominated by mountain‐valley breeze, which has MCE on the distribution of pollutants in this region. Air pollutants were injected from the planetary boundary layer into the free troposphere due to this effect. These pollutants were subsequently transported back over the city by the elevated northerly wind. Thus the structure of two pollution layers over Beijing is formed. Modeling results show that the persistence of a polluted layer over the boundary layer from the previous day has significant contribution to the surface concentrations of pollutants. When the mixing depth increases, the elevated pollutants are recaptured into planetary boundary layer and mixed downward. The rapid increase of surface concentrations of pollutants may be attributed to the vertical down‐mixing of pollutants.
Characteristics of tropical thin cirrus clouds deduced from joint CloudSat and CALIPSO observations
Authors: Haladay Taryn , Stephens Graeme
Published: April 2009

The joint detection characteristics of both the CloudSat radar and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar are used to study tropical thin cirrus observed between 20°N and 20°S. The thin ice cloud category (TIC‐1) of cirrus consists of those clouds detected by the lidar but not the radar whereas the TIC‐2 cirrus category consists of clouds detected by both sensors. Tropical TIC‐1 cirrus clouds between 20°N and 20°S are high, are optically thin, and have an approximate cloud cover in the defined region of 30%. Almost a third of this occurrence is in the form of single layers of cloudiness without any clouds below. These TIC‐1 clouds also exhibit a marked seasonal variation, especially away from the equator, consistent with the shifts in annual cycle of convection with latitude. Lidar‐based estimates of optical depth, uncorrected for multiple scattering, suggest that the TIC‐1 optical depths range between 0.02 and 0.3. The ice water path of TIC‐1 clouds is also estimated to be between 0.5 and 4 g m−2. The radiative properties of the TIC‐1 clouds are also deduced from CloudSat flux data products at the top, at the bottom, and within the atmosphere. The influence of these clouds on the instantaneous reflected solar fluxes is determined to be less than 2 W m−2. The effects of TIC‐1 clouds on the instantaneous outgoing longwave fluxes are estimated to be ∼20 W m−2, and the impact of these TIC‐1 clouds on the tropics‐wide average of the infrared heating is ∼4 W m−2.
Rapid aerosol particle growth and increase of cloud condensation nucleus activity by secondary aerosol formation and condensation: A case study for regional air pollution in northeastern China
Authors: Wiedensohler A. , Cheng Y. F. , Nowak A. , Wehner B. , Achtert P. , Berghof M. , Birmili W. , Wu Z. J. , Hu M. , Zhu T. , Takegawa N. , Kita K. , Kondo Y. , Lou S. R. , Hofzumahaus A. , Holland F. , Wahner A. , Gunthe S. S. , Rose D. , Su H. , Pöschl U.
Published: April 2009

This study was part of the international field measurement Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing‐2006). We investigated a new particle formation event in a highly polluted air mass at a regional site south of the megacity Beijing and its impact on the abundance and properties of cloud condensation nuclei (CCN). During the 1‐month observation, particle nucleation followed by significant particle growth on a regional scale was observed frequently (∼30%), and we chose 23 August 2006 as a representative case study. Secondary aerosol mass was produced continuously, with sulfate, ammonium, and organics as major components. The aerosol mass growth rate was on average 19 μg m−3 h−1 during the late hours of the day. This growth rate was observed several times during the 1‐month intensive measurements. The nucleation mode grew very quickly into the size range of CCN, and the CCN size distribution was dominated by the growing nucleation mode (up to 80% of the total CCN number concentration) and not as usual by the accumulation mode. At water vapor supersaturations of 0.07–0.86%, the CCN number concentrations reached maximum values of 4000–19,000 cm−3 only 6–14 h after the nucleation event. During particle formation and growth, the effective hygroscopicity parameter κ increased from about 0.1–0.3 to 0.35–0.5 for particles with diameters of 40–90 nm, but it remained nearly constant at ∼0.45 for particles with diameters of ∼190 nm. This result is consistent with aerosol chemical composition data, showing a pronounced increase of sulfate.
Hygroscopic growth of tropospheric particle number size distributions over the North China Plain
Authors: Achtert P. , Birmili W. , Nowak A. , Wehner B. , Wiedensohler A. , Takegawa N. , Kondo Y. , Miyazaki Y. , Hu M. , Zhu T.
Published: April 2009

The hygroscopic growth of atmospheric submicrometer particle size distributions (diameter Dp ranging from 22 to 900 nm) was studied at a rural/suburban site in the North China Plain within the framework of the international Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing‐2006) research project. The goal was to characterize the regional aerosol in the polluted northeastern plain in China. Size descriptive hygroscopic growth factors (DHGFs) were determined as a function of relative humidity (RH) by relating the particle number size distribution at a dry condition (<30%) to those measured at higher RHs (RH = 56, 76, 85, and 91%) for the diameter range from 30 to 300 nm. In the size range of the accumulation mode (Dp > 100 nm), the DHGF are substantially higher than in the Aitken particle mode (Dp < 100 nm) as a result of different chemical composition. The size‐dependent behavior of the DHGF highlights the relevance of particulate sulfate production over the North China Plain, accomplished by secondary formation from the gas phase and, potentially, liquid phase processes in convective clouds. Furthermore, all results concerning the DHGF show a significant dependency on meteorological air masses. The hygroscopic growth of accumulation mode particles correlates significantly with the PM1‐mass fraction of sulfate ions determined by chemical analysis. Finally, this investigation provides a parameterization of the hygroscopic growth of 250‐nm particles, which might be useful when predicting visibility and radiative forcing and performing atmospheric aerosol model validations.
Possible mechanisms of decadal‐scale variation in PO4 concentration in the western North Pacific
Authors: Tadokoro Kazuaki , Ono Tsuneo , Yasuda Iichiro , Osafune Satoshi , Shiomoto Akihiro , Sugisaki Hiroya
Published: April 2009

We suggest possible mechanisms of decadal‐scale variation in PO4 concentration in the Oyashio and Kuroshio‐Oyashio transition waters, western North Pacific. Significant decreasing and increasing trends in PO4 have been observed in the surface and mid‐layers of the ocean in this region, respectively. Synchronous bidecadal‐scale oscillations in PO4 were also found between the two layers. Differences in the relationship of the trends and the oscillation in these layers suggest that they are driven by separate processes. The trend component may be induced by attenuation of water exchange between the two layers. In contrast, the influence of the 18.6‐yr period nodal tidal cycle on the formation rate of intermediate water in the Okhotsk Sea may cause the bidecadal‐scale oscillation. The PO4 concentration showed a significant positive correlation with Neocalanus plumchrus biomass, the dominant mesozooplankton species in the Oyashio and Kuroshio–Oyashio Transition waters. These relationships suggest that the variation in PO4 affected production of N. plumchrus due to changes in primary production.
Rab7: roles in membrane trafficking and disease
Authors: Zhang Ming , Chen Li , Wang Shicong , Wang Tuanlao
Published: April 2009

The endocytosis pathway controls multiple cellular and physiological events. The lysosome is the destination of newly synthesized lysosomal hydrolytic enzymes. Internalized molecules or particles are delivered to the lysosome for degradation through sequential transport along the endocytic pathway. The endocytic pathway is also emerging as a signalling platform, in addition to the well-known role of the plasma membrane for signalling. Rab7 is a late endosome-/lysosome-associated small GTPase, perhaps the only lysosomal Rab protein identified to date. Rab7 plays critical roles in the endocytic processes. Through interaction with its partners (including upstream regulators and downstream effectors), Rab7 participates in multiple regulation mechanisms in endosomal sorting, biogenesis of lysosome [or LRO (lysosome-related organelle)] and phagocytosis. These processes are closely related to substrates degradation, antigen presentation, cell signalling, cell survival and microbial pathogen infection. Consistently, mutations or dysfunctions of Rab7 result in traffic disorders, which cause various diseases, such as neuropathy, cancer and lipid metabolism disease. Rab7 also plays important roles in microbial pathogen infection and survival, as well as in participating in the life cycle of viruses. Here, we give a brief review on the central role of Rab7 in endosomal traffic and summarize the studies focusing on the participation of Rab7 in disease pathogenesis. The underlying mechanism governed by Rab7 and its partners will also be discussed.
Model for the injection of charge through the contacts of organic transistors
Authors: Lara Bullejos P. , Jiménez Tejada J. A. , Rodríguez-Bolívar S. , Deen M. J. , Marinov O.
Published: April 2009

A compact model has been employed in organic thin film transistors (OTFTs) to study the electrical characteristics of the contacts, which are formed between the organic layer and source/drain electrodes of the OTFT. The model shows the importance of interrelating different physical phenomena: charge injection, redox reactions at the interface, and charge drift in the organic semiconductor. The model reproduces and explains several features that have been reported for current-voltage curves, ID-VC, at the contacts of OTFTs. The ID-VC curves are extracted from the experimental output characteristics by two techniques. One technique uses a set of transistors with different channel lengths and a simultaneous extraction of the ID-VC curve and the mobility of carriers in the channel of the transistor. When a set of transistors with different channel lengths is not available, we propose an iterative method for the simultaneous extraction of the ID-VC curve and the mobility by changing the gate bias voltages.
Magnetization reversal in enclosed composite pattern media structure
Authors: Goh Chi-Keong , Yuan Zhi-min , Liu Bo
Published: April 2009

The bit patterned media use one single domain magnetic island to record a bit. It can effectively push the superparamagnetic limit to higher recording densities. In this paper, we present and investigate a composite patterned media structure comprising of soft layer enclosed magnetic islands to significantly improve the writing capability of conventional writer. Systematic micromagnetic simulation studies reveal that the proposed structure has a different domain wall propagation mechanism and has less stringent requirement on the exchange-coupling strength as compared to conventional composite structures.
Comprehensive study of the Raman shifts of strained silicon and germanium
Authors: Peng C.-Y. , Huang C.-F. , Fu Y.-C. , Yang Y.-H. , Lai C.-Y. , Chang S.-T. , Liu C. W.
Published: April 2009

Raman shifts are investigated on silicon and germanium substrates under the uniaxial tensile strain on various substrate orientations. The strain splits the triply degenerate optical (LO, TO) phonons at the zone center (k⃗≈0). The redshifts of Si Raman peaks induced by the tensile strain on all substrate orientations are observed. With the specific polarization of the incident light, however, the unusual blueshifts of Ge Raman peaks induced by the tensile strain are observed on (110) and (111) Ge substrates. By using the suitable phenomenological constants and taking the Raman selection rules into consideration, the experimental results are in reasonable agreement with the lattice dynamical theory.
Exploring the capabilities of quantum optimal dynamic discrimination
Authors: Beltrani Vincent , Ghosh Pritha , Rabitz Herschel
Published: April 2009

Optimal dynamic discrimination (ODD) uses closed-loop learning control techniques to discriminate between similar quantum systems. ODD achieves discrimination by employing a shaped control (laser) pulse to simultaneously exploit the unique quantum dynamics particular to each system, even when they are quite similar. In this work, ODD is viewed in the context of multiobjective optimization, where the competing objectives are the degree of similarity of the quantum systems and the level of controlled discrimination that can be achieved. To facilitate this study, the D-MORPH gradient algorithm is extended to handle multiple quantum systems and multiple objectives. This work explores the trade-off between laser resources (e.g., the length of the pulse, fluence, etc.) and ODD’s ability to discriminate between similar systems. A mechanism analysis is performed to identify the dominant pathways utilized to achieve discrimination between similar systems.
Heterointegrated near-field photodetector for ballistic electron emission luminescence
Authors: Huang Biqin , Appelbaum Ian
Published: April 2009

We use room-temperature ultrahigh-vacuum metal-film wafer bonding to integrate a Si photodetector with a AlGaAs/GaAs-based ballistic electron emission luminescence (BEEL) light emitting device. Our results, using a solid-state tunnel junction to simulate hot-electron injection with a scanning-tunneling probe, show that this design provides a means to achieve successful heterogeneous integration, potentially making BEEL applicable to arbitrary light-emitting semiconductor materials systems.
Metal-insulator transition in ferromagnetic Mn-doped CuO thin films
Authors: Zhang Yaping , Pan Liqing , Gu Yousong , Zhao Fan , Qiu Hongmei , Yin Jinhua , Zhu Hao , Xiao John Q.
Published: April 2009

The ac susceptibility, electrical properties, and magnetotransport properties of the as-prepared MnxCu1−xO thin films (x=7%–29%) were studied in the temperature range of 2–300 K. The susceptibility measurement shows that ferromagnetic transition takes place for the samples with x≥14% below 100 K. The transport properties show the transition from variable-range-hopping to metalliclike behavior at the same transition temperature as the paramagnetism to ferromagnetism transition. The metal-insulator transition is a characteristic feature of magnetic ordering in this material.
Ultrafast photovoltaic effects in miscut Nb-doped SrTiO3 single crystals
Authors: Zhou Na , Zhao Kun , Liu Hao , Lu Zhiqing , Zhao Hui , Tian Lu , Liu Wenwei , Zhao Songqing
Published: April 2009

Picosecond photovoltaic effect in miscut Nb-doped SrTiO3 single crystal has been observed under ultraviolet pulsed laser irradiation at ambient temperature without an applied bias. The 10%–90% rise time and the full width at half maximum are 828 and 670 ps, respectively, which is faster than that of exact cut Nb-doped SrTiO3 single crystal. A model based on terrace structure is put forward to explain the observation.
Mechanical and electronic properties of 5d transition metal diborides MB2 (M=Re, W, Os, Ru)
Authors: Wang Jie , Wang Yun-Jiang
Published: April 2009

First-principles method is used to investigate the structural, mechanical, and electronic properties of 5d transition metal diborides MB2 (M=Re, W, Os, Ru). Our calculations show hexagonal ReB2 and WB2 have much larger elastic moduli and tensile shear strengths than orthorhombic OsB2 and RuB2. The elastic moduli and ideal strength are both calculated to be in a sequence of ReB2>WB2>OsB2>RuB2. Electronic structures show that strong directional covalent B–B and M–B bonds exist in the materials, which is the origin of their high modulus, large strength, and high hardness.
Reducing current loss of laser-driven fast electron beams propagating in solid-density plasmas
Authors: Zhou C. T. , He X. T. , Cao J. M. , Wang X. G. , Wu S. Z.
Published: April 2009

A scheme to reduce the current loss of laser-driven energetic electron beams propagating in solid-density targets is proposed. In the scheme, two intense laser pulses irradiate the solid target consisting of two materials, one enveloping the other. Because of the resistivity and density gradients at the material interface, the first pulse generates tens of megagauss robust interface magnetic fields that can considerably reduce the divergence of the electron beam generated by the second pulse. It is shown that by using a coaxial gold-aluminum target instead of a simple gold target, beam current loss can be lowered by about 30%.
Symmetry and order in systems chemistry
Authors: Wagner Nathaniel , Ashkenasy Gonen
Published: April 2009

Systems chemistry seeks to find fundamental insights into the emergent properties of complex systems and living matter. Thus chemists use a “bottom-up” approach for the design and integration of simple elements as a means of producing self-organized systems that can serve as feasible models. Toward this end, networks of replicating molecules have been produced and their dynamic behavior was analyzed both experimentally and by simulation. In this paper we describe our analysis of the reaction mechanisms which build up these systems. To do so, we revisit models for self-replication and template assisted catalysis and expand them to describe the kinetics of small catalytic networks. From symmetry requirements and reasonable chemical assumptions, it is shown that the construction of increasingly complex networks requires higher order catalysis. Specifically, we explain why low order catalysis, in which a monomeric molecule serves as a template, is incapable of efficiently activating cooperative cross catalytic elements and basic asymmetric sequentially linked units, so that at least second order catalysis, in which dimeric molecules serve as templates, is necessary. These cooperative and asymmetric linked units are required components of more complex molecular networks. We compare our results with other experimental evidence for the centrality of higher order catalysis and discuss the implications of our results on molecular self-organization and other aspects of systems chemistry.
Characterization of fluid-solid phase transition of hard-sphere fluids in cylindrical pore via molecular dynamics simulation
Authors: Huang Huan Cong , Kwak Sang Kyu , Singh Jayant K.
Published: April 2009

Equation of state and structure of hard-sphere fluids confined in a cylindrical hard pore were investigated at the vicinity of fluid-solid transition via molecular dynamics simulation. By constructing artificial closed-packed structures in a cylindrical pore, we explicitly capture the fluid-solid phase transition and coexistence for the pore diameters from 2.17σ to 15σ. There exist some midpore sizes, where the phase coexistence might not exist or not clearly be observable. We found that the axial pressure including coexistence follows oscillatory behavior in different pore sizes; while the pressure tends to decrease toward the bulk value with increasing pore size, the dependence of the varying pressure on the pore size is nonmonotonic due to the substantial change of the alignment of the molecules. The freezing and melting densities corresponding to various pore sizes, which are always found to be lower than those of the bulk system, were accurately obtained with respect to the axial pressure.
Tapping mode microwave impedance microscopy
Authors: Lai K. , Kundhikanjana W. , Peng H. , Cui Y. , Kelly M. A. , Shen Z. X.
Published: April 2009

We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately simulated by the finite-element analysis and the result agrees quantitatively to the experimental data on a series of thin-film dielectric samples. The tapping mode microwave imaging is also superior to the contact mode in that the thermal drift in a long time scale is totally eliminated and an absolute measurement on the dielectric properties is possible. We demonstrated tapping images on working nanodevices, and the data are consistent with the transport results.
Dynamics of a turbulent spin-down flow inside a torus
Authors: Noskov Vitaly , Stepanov Rodion , Denisov Sergey , Frick Peter , Verhille Gautier , Plihon Nicolas , Pinton Jean-François
Published: April 2009

A turbulent screw flow (with Reynolds number exceeding 106) is generated by the sudden stop of a toroidal channel. The working fluid is a gallium alloy and velocity measurements are performed using a dual-axis potential probe. We describe the onset of motion, the development of strongly anisotropic fluctuations, and the final homogenization and decay of turbulence. Our observations are relevant for the relaxation of anisotropic turbulence; they are also in agreement with measurements of magnetohydrodynamic induction processes in this type of flow.
A hydrodynamic switch: Microfluidic separation system for magnetic beads
Authors: Weddemann A. , Wittbracht F. , Auge A. , Hütten A.
Published: April 2009

In this work a device for separating small magnetic particles in continuous flow is introduced, consisting of two microfluidic channels that are connected by a junction channel. Applying two different flow rates, particles can be separated combining hydrodynamic and magnetophoretic effects. The two different flow rates introduce an additional degree of freedom that enables the microfluidic geometry to act as a hydrodynamic switch that can overcome diffusive contributions making the device applicable for particles of the size scale below 100 nm. Theoretical predictions based on finite element methods are compared to experimental observations.
Electrostatically defined few-electron double quantum dot in silicon
Authors: Lim W. H. , Huebl H. , Willems van Beveren L. H. , Rubanov S. , Spizzirri P. G. , Angus S. J. , Clark R. G. , Dzurak A. S.
Published: April 2009

A few-electron double quantum dot was fabricated using metal-oxide-semiconductor-compatible technology and low-temperature transport measurements were performed to study the energy spectrum of the device. The double dot structure is electrically tunable, enabling the interdot coupling to be adjusted over a wide range, as observed in the charge stability diagram. Resonant single-electron tunneling through ground and excited states of the double dot was clearly observed in bias spectroscopy measurements.
Atomic displacement parameters and structural disorder of oxygen ions in the CexZr1−xO2 solid solutions (0.12≤x≤1.0): Possible factors of high catalytic activity of ceria-zirconia catalysts
Authors: Yashima Masatomo , Wakita Takahiro
Published: April 2009

Crystal structures and electron-density distributions of ceria-zirconia CexZr1−xO2 compounds have been studied by the maximum-entropy method (MEM) and MEM-based pattern fitting combined with the Rietveld method using high-angular-resolution synchrotron x-ray powder diffraction data. The isotropic atomic displacement parameter of the oxygen atoms U(O) in Ce0.5Zr0.5O2 has a maximum value in CexZr1−xO2 (0.12≤x≤1.0). Electron-density distribution of Ce0.5Zr0.5O2 shows a large spatial distribution of the oxygen ions. The greater U(O) and large spatial distribution of oxygen ions in Ce0.5Zr0.5O2 are possible factors of its higher catalytic activity.
Surface plasmon-enhanced spontaneous emission rate in an organic light-emitting device structure: Cathode structure for plasmonic application
Authors: Yang Ki Youl , Choi Kyung Cheol , Ahn Chi Won
Published: April 2009

The surface plasmon-enhanced spontaneous emission based on an organic light-emitting device is reported in this paper. For surface plasmon localization, silver nanoparticles were thermally deposited in a high vacuum on cathode that had a 1-nm-thick LiF spacer. Since plasmons provide a strong oscillator decay channel, time-resolved photoluminescence (PL) results displayed a 1.75-fold increased emission rate, and continuous wave PL results showed a twofold enhanced intensity. In addition, LiF film/Ag cluster/LiF film structure resolved the carrier injection problem between the cathode and the organic layer. Thus, the suggested design may follow plasmonic applications for a wider organic optoelectronics.
Predictability of reset switching voltages in unipolar resistance switching
Authors: Lee S. B. , Chae S. C. , Chang S. H. , Noh T. W.
Published: April 2009

In unipolar resistance switching of NiO capacitors, Joule heating in the conducting channels should cause a strong nonlinearity in the low resistance state current-voltage (I-V) curves. Due to the percolating nature of the conducting channels, the reset current IR can be scaled to the nonlinear coefficient Bo of the I-V curves, i.e., IR∝Bo−x. This scaling relationship can be used to predict reset voltages, independent of NiO capacitor size; it can also be applied to TiO2 and FeOy capacitors. Using this relation, we developed an error correction scheme to provide a clear window for separating reset and set voltages in memory operations.
A pentacene-based organic thin film memory transistor
Authors: Mabrook Mohammed F. , Yun Youngjun , Pearson Christopher , Zeze Dagou A. , Petty Michael C.
Published: April 2009

An organic memory device based on a pentacene thin film transistor is demonstrated. Gold nanoparticles have been used as the charge storage elements while a thin film of polymethylmethacrylate formed the gate insulator. The electrical characteristics and the memory behavior of the organic thin film memory transistor (OTFMT) are reported. Under an appropriate gate bias (1 s pulses), the gold nanoparticles are charged and discharged, resulting in significant threshold voltage shifts of the OTFMT. The detailed programing and erasing procedures are reported.
Nanocrystallization mechanism of amorphous Fe78B13Si9
Authors: Sato K. , Murakami H. , Sprengel W. , Schaefer H.-E. , Kobayashi Y.
Published: April 2009

The nanocrystallization mechanism of an amorphous alloy is discussed based on the kinetics of open nanospaces in Fe78B13Si9. There already exists a high concentration of Fe-enriched fluctuated sites with open nanospaces in the amorphous matrix. The structural and compositional fluctuation helps transient short-range Fe diffusion in the metastable amorphous matrix with an increase of temperature, triggering highly concentrated α-Fe nucleation. Along with the growth of α-Fe nucleus, Fe atoms are transferred from the intergranular amorphous phase to Fe-based nanocrystallites. The nanocrystallization of α-Fe is achieved through nucleation by short-range Fe diffusion and its growth by nanovoid-mediated long-range Fe diffusion.
Magnetic tunnel junction sensor with Co/Pt perpendicular anisotropy ferromagnetic layer
Authors: Wei H. X. , Qin Q. H. , Wen Z. C. , Han X. F. , Zhang X.-G.
Published: April 2009

Linear magnetoresistance is an important attribute for magnetic sensor design in space applications, three-dimensional detection of the magnetic field, and high field measurements. Here we demonstrate that a large linear magnetoresistance of up to 22% can be achieved in a magnetic tunnel junction that consists of two ferromagnetic layers, one with out of plane and one with in-plane magnetic anisotropy. The tunneling magnetoresistance with the electrical current perpendicular to the film plane and the magnetic configuration of the device are analyzed.
Development of crystal texture in Nd-lean amorphous Nd9Fe85B6 under hot deformation
Authors: Liu Yanguo , Xu Lei , Wang Qingfeng , Li Wei , Zhang Xiangyi
Published: April 2009

A key challenge in synthesizing anisotropic nanocomposite magnets is to form crystallographic texture for R2Fe14B crystals in R-lean alloys (R=rare earth, R<10 at. %). Here, we demonstrate a (00l) texture development for Nd2Fe14B nanocrystals in a Nd-lean amorphous Nd9Fe85B6 under a hot deformation at a large uniaxial stress of ∼310 MPa. The unusual texture formation is attributed to a preferential nucleation of Nd2Fe14B crystals in amorphous matrix at the large stress. The present study provides an opportunity to yield anisotropic nanocomposite magnets from Nd-lean alloys and thus is of wide interest.
Geometric effects on dislocation nucleation in strained electronics
Authors: Li T. L. , Lee J. H. , Gao Y. F. , Pharr G. M. , Huang M. , Tsui T. Y.
Published: April 2009

Dislocation loops may be nucleated from sharp geometric features in strained micro- and nano-electronic devices. This process is investigated by a dissipative cohesive interface model which treats the dislocation core as a continuous, inhomogeneous lattice slip field. As a representative example, we calculate the critical external stress for dislocation nucleation from the edges/corners of a rectangular stress-free Si3N4 pad on a Si substrate as a function of geometric parameters such as the length-to-height ratio and the three-dimensional shape of the pad. The shapes of the dislocations are also simulated.
Multicolor photodetector based on GaAs quantum rings grown by droplet epitaxy
Authors: Wu Jiang , Li Zhenhua , Shao Dali , Manasreh M. O. , Kunets Vasyl P. , Wang Zhiming M. , Salamo Gregory J. , Weaver B. D.
Published: April 2009

Photoresponse from multicolor photodetector was measured in the spectral range of 0.4–6.0μm as a function of temperature and bias voltage. Devices were fabricated from wafers with an active region of five periods of GaAs quantum rings grown by droplet epitaxy technique on lattice matched Al0.3Ga0.7As barriers. The photoresponse spectra exhibit two broad bands in the visible-near-infrared and midinfrared spectral regions. The visible-near-infrared band, which is due to interband transitions, was observed at temperatures as high as room temperature. On the other hand, the midinfrared band, which is due to intersubband transitions, was observed at temperature lower than 80K.
Sources of antimony in an urban area
Authors: Månsson Nina S. , Hjortenkrans David S. T. , Bergbäck Bo G. , Sörme Louise , Häggerud Agneta V.
Published: April 2009

Environmental context. The global production and use of antimony (Sb) increase together with stocks and emissions, but there are gaps in our knowledge concerning environmental effects. Here, a reconstruction of major Sb flows in an urban area was conducted. The major emission source of Sb identified was wear of brake linings, although other sources may also be of importance, e.g. diffuse emission of flame-retarded goods. Abstract. The present study sets out to analyse the urban metal sources of Sb, by estimating the stock of Sb in use, and to present related flows and emissions in Stockholm, Sweden, in 2005. Antimony was studied with the main methodology of substance flow analysis with existing data, while chemical analysis was used as a complement. No large point sources were found reported to the authorities; hence, the dominating source for Sb is diffuse and originates from goods. The total Sb stock in Stockholm in 2005 was ~430 000 kg (range 110 000–1 700 000 kg) and the total Sb inflow was estimated at 45 000 kg year–1 (range 30 000–67 000 kg). The stock was dominated by flame-retarded goods, cable shielding, glass and accumulators. The Sb emission was estimated at ~720 kg year–1 (range 430–1200 kg year–1). Despite large uncertainties and missing data, the results supported the notion of the importance of brake linings as a source of Sb emissions (710 kg year–1), whereas other goods such as textiles (4.5 kg year–1), tyres (1.4 kg year–1), sinkers, ammunition and polyethylene terephthalate (PET) bottles and packaging were minor sources. However, flame-retarded goods are still poorly quantified and are seen as a potential emission source.
Dynamic DGT speciation analysis and applicability to natural heterogeneous complexes
Authors: Town Raewyn M. , Chakraborty Parthasarathi , van Leeuwen Herman P.
Published: April 2009

Environmental context. The environmental fate and bioavailability of metal ions in natural waters is determined by their thermodynamic stability and kinetic features, both of which are distributed and depend on the metal ion loading of the system. Diffusive gradients in thin film (DGT) is a dynamic technique for metal speciation analysis that measures a certain portion of these complexes as determined by its operational timescale. Reliable interpretation of data furnished by DGT necessitates characterisation of its features for the particular case of heterogeneous complexes.
Abstract. Owing to their inherent heterogeneity, the thermodynamic stability of metal ion complexes with natural ligands is characterised by a distribution, and thus is a function of metal-to-ligand ratio. The kinetic features of such metal complexes are also distributed and can be probed by dynamic speciation techniques. The kinetic regime of the metal complex sample can be manipulated via the metal-to-ligand ratio, and the timescale over which kinetic parameters are actually in effect is defined by the window of the chosen technique. Here we detail the kinetic features of diffusive gradients in thin film (DGT), and show that the range of attainable measurement timescales (τ) is rather limited: variation of the gel layer thickness practically allows only one order of magnitude in τ to be scanned. The more effective use of DGT to probe the distribution of dynamic metal species in heterogeneous systems is via variation of the metal-to-ligand ratio in the sample solution. Compilation of the literature DGT data for natural waters shows that by assuming a Freundlich isotherm relationship, the degree of heterogeneity is reflected in the measured DGT concentration as a function of metal ion loading.
Bioaccumulation of antimony and arsenic in a highly contaminated stream adjacent to the Hillgrove Mine, NSW, Australia
Authors: Telford Kristy , Maher William , Krikowa Frank , Foster Simon , Ellwood Michael J. , Ashley Paul M. , Lockwood Peter V. , Wilson Susan C.
Published: April 2009

Environmental context. Concern over the presence of antimony (Sb) in the environment because of chemical similarities with arsenic (As) has prompted a need to better understand its environmental behaviour and risks. The present study investigates the bioaccumulation and uptake of antimony in a highly contaminated stream near the Hillgrove antimony–gold mine in NSW, Australia, and reports high Sb (and As) concentrations in many components of the ecosystem consisting of three trophic levels, but limited uptake into aboveground parts of riparian vegetation. The data suggest that Sb can transfer into upper trophic levels of a creek ecosystem, but that direct exposure of creek fauna to creek sediment and soil, water and aquatic autotrophs are more important metalloid uptake routes than exposure via riparian vegetation. Abstract. Bioaccumulation and uptake of antimony (Sb) were investigated in a highly contaminated stream, Bakers Creek, running adjacent to mining and processing of Sb–As ores at Hillgrove Mine, NSW, Australia. Comparisons with arsenic (As) were included owing to its co-occurrence at high concentrations. Mean metalloid creek rhizome sediment concentrations were 777 ± 115 μg g–1 Sb and 60 ± 6 μg g–1 As, with water concentrations at 381 ± 23 μg L–1 Sb and 46 ± 2 μg L–1 As. Antimony and As were significantly elevated in aquatic autotrophs (96–212 μg g–1 Sb and 32–245 μg g–1 As) but Sb had a lower uptake efficiency. Both metalloids were elevated in all macroinvertebrates sampled (94–316 μg g–1 Sb and 1.8–62 μg g–1 As) except Sb in gastropods. Metalloids were detected in upper trophic levels although biomagnification was not evident. Metalloid transfer to riparian vegetation leaves from roots and rhizome soil was low but rhizome soil to leaf As concentration ratios were up to 2–3 times greater than Sb concentration ratios. Direct exposure to the rhizosphere sediments and soils, water ingestion and consumption of aquatic autotrophs appear to be the major routes of Sb and As uptake for the fauna of Bakers Creek.
Regulation of the type I protein secretion system by the MisR/MisS two-component system in Neisseria meningitidis
Authors: Sannigrahi Soma , Zhang Xinjian , Tzeng Yih-Ling
Published: April 2009

Neisseria meningitidis, an obligate human pathogen, remains a leading cause of meningitis and fatal sepsis. Meningococci are known to secrete a family of proteins, such as FrpC, with sequence similarity to the repeat-in-toxin (RTX) proteins via the type I secretion system. The meningococcal type I secretion proteins are encoded at two distant genetic loci,NMB1400(hlyB) andNMB1738/1737(hlyD/tolC), and are separated from the RTX toxin-like substrates. We have characterized the promoter elements of bothhlyBandhlyDby primer extension andlacZreporter fusions and revealed the growth phase-dependent upregulation of both genes. In addition, we showed that the MisR/MisS two-component system negatively regulates the expression ofhlyBandhlyD/tolC. Direct binding of MisR tohlyBandhlyDpromoters was demonstrated by electrophoretic mobility shift assay (EMSA), and DNase I protection assays identified MisR binding sites overlapping the promoter elements. Direct repression ofhlyBtranscription by MisR was supported byin vitrotranscription assays. Mutations in the MisR/S system affected, but did not eliminate, the growth phase-dependent upregulation ofhlyB, suggesting additional regulatory mechanisms. Increased secretion of RTX toxin-like proteins was detected in the cell-free media frommisSmutant cultures, indicating that the amounts of extracellular RTX toxin-like proteins are, in part, controlled by the abundance of the type I secretion apparatus. This is, to our knowledge, the first example of a two-component system mediating secretion of cytotoxin family proteins by controlling expression of the type I secretion proteins.
Comparison of virulence factors and expression of specific genes between uropathogenic Escherichia coli and avian pathogenic E. coli in a murine urinary tract infection model and a chicken challenge model
Authors: Zhao Lixiang , Gao Song , Huan Haixia , Xu Xiaojing , Zhu Xiaoping , Yang Weixia , Gao Qingqing , Liu Xiufan
Published: April 2009

Avian pathogenic Escherichia coli (APEC) and uropathogenic E. coli (UPEC) establish infections in extraintestinal habitats of different hosts. As the diversity, epidemiological sources and evolutionary origins of extraintestinal pathogenic E. coli (ExPEC) are so far only partially defined, in the present study,100 APEC isolates and 202 UPEC isolates were compared by their content of virulence genes and phylogenetic groups. The two groups showed substantial overlap in terms of their serogroups, phylogenetic groups and virulence genotypes, including their possession of certain genes associated with large transmissible plasmids of APEC. In a chicken challenge model, both UPEC U17 and APEC E058 had similar LD50, demonstrating that UPEC U17 had the potential to cause significant disease in poultry. To gain further information about the similarities between UPEC and APEC, the in vivo expression of 152 specific genes of UPEC U17 and APEC E058 in both a murine urinary tract infection (UTI) model and a chicken challenge model was compared with that of these strains grown statically to exponential phase in rich medium. It was found that in the same model (murine UTI or chicken challenge), various genes of UPEC U17 and APEC E058 showed a similar tendency of expression. Several iron-related genes were upregulated in the UTI model and/or chicken challenge model, indicating that iron acquisition is important for E. coli to survive in blood or the urinary tract. Based on these results, the potential for APEC to act as human UPEC or as a reservoir of virulence genes for UPEC should be considered. Further, this study compared the transcriptional profile of virulence genes among APEC and UPEC in vivo.
A Francisella novicida pdpA mutant exhibits limited intracellular replication and remains associated with the lysosomal marker LAMP-1
Authors: Schmerk Crystal L. , Duplantis Barry N. , Howard Perry L. , Nano Francis E.
Published: April 2009

Several genes contained in the Francisella pathogenicity island (FPI) encode proteins needed for intracellular growth and virulence of Francisella tularensis. The pdpA gene is the first cistron in the larger of the two operons found in the FPI. In this work we studied the intracellular growth phenotype of a Francisella novicida mutant in the pdpA gene. The ΔpdpA strain was capable of a small amount of intracellular replication but, unlike wild-type F. novicida, remained associated with the lysosomal marker LAMP-1, suggesting that PdpA is necessary for progression from the early phagosome phase of infection. Strains with in cis complementation of the ΔpdpA lesion showed a restoration of intracellular growth to wild-type levels. Infection of macrophages with the ΔpdpA mutant generated a host-cell mRNA profile distinct from that generated by infection with wild-type F. novicida. The transcriptional response of the host macrophage indicates that PdpA functions directly or indirectly to suppress macrophage ability to signal via growth factors, cytokines and adhesion ligands.
Systematic characterization of a novel gal operon in Thermoanaerobacter tengcongensis
Authors: Qian Zhong , Meng Bo , Wang Quanhui , Wang Zhuowei , Zhou Chuanqi , Wang Qian , Tu Shuyang , Lin Liang , Ma Yanhe , Liu Siqi
Published: April 2009

On the basis of theThermoanaerobacter tengcongensisgenome, a novel type ofgaloperon was deduced. The gene expression and biochemical properties of this operon were further characterized. RT-PCR analysis of the intergenic regions suggested that the transcription of thegaloperon was continuous. With gene cloning and enzyme activity assays, TTE1929, TTE1928 and TTE1927 were identified to be GalT, GalK and GalE, respectively. Results elicited from polarimetry assays revealed that TTE1925, a hypothetical protein, was a novel mutarotase, termed MR-Tt. TTE1926 was identified as a regulator that could bind to two operators in the operon promoter. The transcriptional start sites were mapped, and this suggested that there are two promoters in this operon. Expression of thegalgenes was significantly induced by galactose, whereas only MR-Tt expression was detected in glucose-culturedT. tengcongensisat both the mRNA and the protein level. In addition, the abundance ofgalproteins was examined at different temperatures. At temperatures ranging from 60 to 80 °C, the level of MR-Tt protein was relatively stable, but that of the othergalproteins was dramatically decreased. The operator-binding complexes were isolated and identified by electrophoretic mobility shift assay-liquid chromatography (EMSA-LC) MS-MS, which suggested that several regulatory proteins, such as GalR and a sensory histidine kinase, participate in the regulation of thegaloperon.
Strategies for acquiring the phospholipid metabolite inositol in pathogenic bacteria, fungi and protozoa: making it and taking it
Authors: Reynolds Todd B.
Published: April 2009

myo-Inositol (inositol) is an essential nutrient that is used for building phosphatidylinositol and its derivatives in eukaryotes and even in some eubacteria such as the mycobacteria. As a consequence, fungal, protozoan and mycobacterial pathogens must be able to acquire inositol in order to proliferate and cause infection in their hosts. There are two primary mechanisms for acquiring inositol. One is to synthesize inositol from glucose 6-phosphate using two sequentially acting enzymes: inositol-3-phosphate synthase (Ino1p) converts glucose 6-phosphate to inositol 3-phosphate, and then inositol monophosphatase (IMPase) dephosphorylates inositol 3-phosphate to generate inositol. The other mechanism is to import inositol from the environment via inositol transporters. Inositol is readily abundant in the bloodstream of mammalian hosts, providing a source from which many pathogens could potentially import inositol. However, despite this abundance of inositol in the host, some pathogens such as the bacteriumMycobacterium tuberculosisand the protist parasiteTrypanosoma bruceimust be able to make inositolde novoin order to cause disease (M. tuberculosis) or even grow (T. brucei). Other pathogens such as the fungusCandida albicansare equally adept at causing disease by importing inositol or by making itde novo. The role of inositol acquisition in the biology and pathogenesis of the parasiteLeishmaniaand the fungusCryptococcusare being explored as well. The specific strategies used by these pathogens to acquire inositol while in the host are discussed in relation to each pathogen's unique metabolic requirements.