bluuebunny/crossref_metadata_2025 huggingface dataset:
The vasoactive peptides urotensin II and urotensin II-related peptide regulate astrocyte activity through common and distinct mechanisms: involvement in cell proliferation
Authors: Jarry Marie , Diallo Mickaël , Lecointre Céline , Desrues Laurence , Tokay Tursonjan , Chatenet David , Leprince Jérôme , Rossi Oriana , Vaudry Hubert , Tonon Marie-Christine , Prézeau Laurent , Castel Hélène , Gandolfo Pierrick
Published: March 2010

UII (urotensin II) and its paralogue URP (UII-related peptide) are two vasoactive neuropeptides whose respective central actions are currently unknown. In the present study, we have compared the mechanism of action of URP and UII on cultured astrocytes. Competition experiments performed with [125I]UII showed the presence of very-high- and high-affinity binding sites for UII, and a single high-affinity site for URP. Both UII and URP provoked a membrane depolarization accompanied by a decrease in input resistance, stimulated the release of endozepines, neuropeptides specifically produced by astroglial cells, and generated an increase in [Ca2+]c (cytosolic Ca2+ concentration). The UII/URP-induced [Ca2+]c elevation was PTX (pertussis toxin)-insensitive, and was blocked by the PLC (phospholipase C) inhibitor U73122 or the InsP3 channel blocker 2-APB (2-aminoethoxydiphenylborane). The addition of the Ca2+ chelator EGTA reduced the peak and abolished the plateau phase, whereas the T-type Ca2+ channel blocker mibefradil totally inhibited the Ca2+ response evoked by both peptides. However, URP and UII induced a mono- and bi-phasic dose-dependent increase in [Ca2+]c and provoked short- and long-lasting Ca2+ mobilization respectively. Similar mono- and bi-phasic dose-dependent increases in [3H]inositol incorporation into polyphosphoinositides in astrocytes was obtained, but the effect of UII was significantly reduced by PTX, although BRET (bioluminescence resonance energy transfer) experiments revealed that both UII and URP recruited Gαo-protein. Finally, UII, but not URP, exerted a dose-dependent mitogenic activity on astrocytes. Therefore we described that URP and UII exert not only similar, but also divergent actions on astrocyte activity, with UII exhibiting a broader range of activities at physiological peptide concentrations.
Analysis of the interactions between the C-terminal cytoplasmic domains of KCNQ1 and KCNE1 channel subunits
Authors: Zheng Renjian , Thompson Keith , Obeng-Gyimah Edmond , Alessi Dana , Chen Jerri , Cheng Huiyong , McDonald Thomas V.
Published: March 2010

Ion channel subunits encoded by KCNQ1 and KCNE1 produce the slowly activating K+ current (IKs) that plays a central role in myocardial repolarization. The KCNQ1 α-subunit and the KCNE1 β-subunit assemble with their membrane-spanning segments interacting, resulting in transformation of channel activation kinetics. We recently reported a functional interaction involving C-terminal portions of the two subunits with ensuing regulation of channel deactivation. In the present study, we provide evidence characterizing a physical interaction between the KCNQ1-CT (KCNE1 C-terminus) and the KCNE1-CT (KCNE1 C-terminus). When expressed in cultured cells, the KCNE1-CT co-localized with KCNQ1, co-immunoprecipitated with KCNQ1 and perturbed deactivation kinetics of the KCNQ1 currents. Purified KCNQ1-CT and KCNE1-CT physically interacted in pull-down experiments, indicating a direct association. Deletion analysis of KCNQ1-CT indicated that the KCNE1-CT binds to a KCNQ1 region just after the last transmembrane segment, but N-terminal to the tetramerization domain. SPR (surface plasmon resonance) corroborated the pull-down results, showing that the most proximal region (KCNQ1 amino acids 349–438) contributed most to the bimolecular interaction with a dissociation constant of ~4 μM. LQT (long QT) mutants of the KCNE1-CT, D76N and W87F, retained binding to the KCNQ1-CT with comparable affinity, indicating that these disease-causing mutations do not alter channel behaviour by disruption of the association. Several LQT mutations involving the KCNQ1-CT, however, showed various effects on KCNQ1/KCNE1 association. Our results indicate that the KCNQ1-CT and the KCNE1-CT comprise an independent interaction domain that may play a role in IKs channel regulation that is potentially affected in some LQTS (LQT syndrome) mutations.
Signal peptide peptidase (SPP) assembles with substrates and misfolded membrane proteins into distinct oligomeric complexes
Authors: Schrul Bianca , Kapp Katja , Sinning Irmgard , Dobberstein Bernhard
Published: March 2010

SPP (signal peptide peptidase) is an aspartyl intramembrane cleaving protease, which processes a subset of signal peptides, and is linked to the quality control of ER (endoplasmic reticulum) membrane proteins. We analysed SPP interactions with signal peptides and other membrane proteins by co-immunoprecipitation assays. We found that SPP interacts specifically and tightly with a large range of newly synthesized membrane proteins, including signal peptides, preproteins and misfolded membrane proteins, but not with all co-expressed type II membrane proteins. Signal peptides are trapped by the catalytically inactive SPP mutant SPPD/A. Preproteins and misfolded membrane proteins interact with both SPP and the SPPD/A mutant, and are not substrates for SPP-mediated intramembrane proteolysis. Proteins interacting with SPP are found in distinct complexes of different sizes. A signal peptide is mainly trapped in a 200 kDa SPP complex, whereas a preprotein is predominantly found in a 600 kDa SPP complex. A misfolded membrane protein is detected in 200, 400 and 600 kDa SPP complexes. We conclude that SPP not only processes signal peptides, but also collects preproteins and misfolded membrane proteins that are destined for disposal.
VDAC1 cysteine residues: topology and function in channel activity and apoptosis
Authors: Aram Lior , Geula Shay , Arbel Nir , Shoshan-Barmatz Varda
Published: March 2010

The VDAC (voltage-dependent anion channel) is proposed to control metabolic cross-talk between mitochondria and the cytosol, as well as apoptotic cell death. It has been suggested that apoptosis is modulated by the oxidation state of VDAC. Since cysteine residues are the major target for oxidation/reduction, we verified whether one or both VDAC1 cysteine residues are involved in VDAC1-mediated transport or apoptosis activities. To assess the function of VDAC1 cysteine residues in channel activity and to probe cysteine topology with respect to facing the pore or the bilayer, we used thiol-modifying agents, namely membrane-permeable NEM (N-ethylmaleimide), bulky charged 5-FM (fluorescein-5-maleimide) and the cross-linking reagent BMOE [bis(maleimido)ethane]. Bilayer-reconstituted VDAC conductance was decreased by 5-FM, but not by NEM, whereas 5-FM had no effect on NEM-labelled VDAC conductance. BMOE caused the formation of dimeric VDAC1, suggesting that one of the two VDAC1 cysteine residues is exposed and available for cross-linking. The results thus suggest that one of the VDAC1 cysteine residues faces the VDAC pore, whereas the second is oriented towards the lipid bilayer. Mutated rat VDAC1 in which the two cysteine residues, Cys127 and Cys232, were replaced by alanine residues showed channel activity like native VDAC1 and, when expressed in cells, was localized to mitochondria. Human VDAC1-shRNA (small hairpin RNA)- or -siRNA (small interfering RNA)-treated cells, expressing low levels of endogenous human VDAC1 together with native or cysteine-less rat VDAC1, undergo apoptosis as induced by overexpression of these VDAC1 or upon treatment with reactive oxygen species-producing agents, H2O2, As2O3 or selenite, suggesting that the two cysteine residues are not required for apoptosis or VDAC1 oligomerization.
Adaptor protein 2 regulates receptor-mediated endocytosis and cyst formation inGiardia lamblia
Authors: Rivero Maria R. , Vranych Cecilia V. , Bisbal Mariano , Maletto Belkys A. , Ropolo Andrea S. , Touz Maria C.
Published: March 2010

The parasite Giardia lamblia possesses PVs (peripheral vacuoles) that function as both endosomes and lysosomes and are implicated in the adaptation, differentiation and survival of the parasite in different environments. The mechanisms by which Giardia traffics essential proteins to these organelles and regulates their secretion have important implications in the control of parasite dissemination. In the present study, we describe the participation of the heterotetrameric clathrin-adaptor protein gAP2 (Giardia adaptor protein 2) complex in lysosomal protein trafficking. A specific monoclonal antibody against the medium subunit (gμ2) of gAP2 showed localization of this complex to the PVs, cytoplasm and plasma membrane in the growing trophozoites. gAP2 also co-localized with clathrin in the PVs, suggesting its involvement in endocytosis. Uptake experiments using standard molecules for the study of endocytosis revealed that gAP2 specifically participated in the endocytosis of LDL (low-density lipoprotein). Targeted down-regulation of the gene encoding gμ2 in growing and encysting trophozoites resulted in a large decrease in the amount of cell growth and cyst wall formation, suggesting a distinct mechanism in which gAP2 is directly involved in both endocytosis and vesicular trafficking.
Surface expression of CXCR4 in unrestricted somatic stem cells and its regulation by growth factors
Authors: Ahmadbeigi Naser , Seyedjafari Ehsan , Gheisari Yousof , Atashi Amir , Omidkhoda Azadeh , Soleimani Masoud
Published: March 2010

Umbilical cord blood‐derived USSCs (unrestricted somatic stem cells) have recently been considered as a potential source for stem cell therapy and transplantation due to their characteristics such as easy accessibility, low immunogenicity, self‐renewing and multilineage differentiation potential. Stem cell homing is a key factor in successful transplantation, which is regulated by CXCR4 in stem cells. In this study, we evaluated the expression of CXCR4 in USSCs different passages. Moreover, the effect of VEGF (vascular endothelial growth factor) and IGF‐1 (insulin‐like growth factor 1) on its expression was assessed. It was shown that the expression of CXCR4 in USSCs decreased with the increase in passage number. It was also revealed that VEGF increased surface expression and mRNA level of CXCR4 in USSCs, while IGF‐1 decreased its expression. When VEGF and IGF‐1 were administered simultaneously, CXCR4 expression was increased, but the expression level was less than VEGF alone. Finally, it was shown that over‐expression of CXCR4 enhanced the migratory capacity of USSCs. The increase of CXCR4 expression, here caused by VEGF in USSCs, can improve the efficacy of stem cell therapy and transplantation after long‐term culture of stem cells before clinical use.
Superhydrophilic TiO2 surface without photocatalytic activation
Authors: Zorba Vassilia , Chen Xiaobo , Mao Samuel S.
Published: March 2010

Since the discovery of extreme surface wetting phenomenon induced by ultraviolet photocatalysis, TiO2 has become the material of choice for environmental friendly applications such as self-cleaning coatings. Nevertheless, it remains a significant challenge to realize surfaces exhibiting persistent superhydrophilicity but without the need of external stimuli. We report a bioinspired TiO2 nanostructure that shows extreme superhydrophilicity without the need of light activation, and with stability against successive wetting-dewetting cycles. This ultimate TiO2 wetting surface exhibits high transmittance from near ultraviolet to the infrared, thus enabling practical antifogging technologies where transparency is critical.
Verification and validation for magnetic fusion
Authors: Greenwald Martin
Published: March 2010

Dramatic progress in the scope and power of plasma simulations over the past decade has extended our understanding of these complex phenomena. However, as codes embody imperfect models for physical reality, a necessary step toward developing a predictive capability is demonstrating agreement, without bias, between simulations and experimental results. While comparisons between computer calculations and experimental data are common, there is a compelling need to make these comparisons more systematic and more quantitative. Tests of models are divided into two phases, usually called verification and validation. Verification is an essentially mathematical demonstration that a chosen physical model, rendered as a set of equations, has been accurately solved by a computer code. Validation is a physical process which attempts to ascertain the extent to which the model used by a code correctly represents reality within some domain of applicability, to some specified level of accuracy. This paper will cover principles and practices for verification and validation including lessons learned from related fields.
Microscopic origin of slow dynamics at the good glass forming composition range in Zr1−xCux metallic liquids
Authors: Hao S. G. , Wang C. Z. , Kramer M. J. , Ho K. M.
Published: March 2010

We have studied the structure and dynamics of a series of Zr1−xCux metallic liquids at temperatures of 1500 and 1300 K. We found that as the Cu composition increases, the Zr–Zr order undergoes considerable transition, which can be attributed to the different size of Zr and Cu atoms. The diffusivities of both Cu and Zr atoms become lower at the composition range corresponding to good glass forming region, i.e., 0.50≤x≤0.70. We found that the lower diffusivities for the intermediate composition range are correlated with the concentration of some specific clusters, including icosahedra, which can be screened out automatically and unbiasedly by using direct atomic dynamics analysis. Our analysis for the dynamic properties of high temperature liquids of ZrCu metallic alloys shows that the icosahedral clusters together with some other pentagon-rich Voronoi clusters are responsible for slowing dynamics. Cluster lifetime analysis indicates that the slow clusters mobility could be originated in their energy.
Experimental approaches to zero-field spin splitting in a gated high-mobility In0.53Ga0.47As/InP quantum well structure: Weak antilocalization and beating pattern
Authors: Zhou Y. M. , Yu G. , Wei L. M. , Gao K. H. , Zhou W. Z. , Lin T. , Shang L. Y. , Guo S. L. , Chu J. H. , Dai N. , Austing D. G.
Published: March 2010

We report on the strong spin-orbit (SO) interaction in a gated high-mobility In0.53Ga0.47As/InP quantum well two-dimensional electron gas. We establish that the SO interaction is dominated by the Rashba mechanism. The Rashba coupling parameters determined from analysis of both weak antilocalization and the beating pattern in the Shubnikov–de Haas oscillations are in reasonable agreement, and the small difference between them was explained by a magnetic-field-dependent effective g factor. The zero-field spin splitting shows nonmonotonic behavior with a maximum as the electron density is varied with the applied gate voltage. This is related to strong Rashba SO coupling in our sample.
Note: Influence of rinsing and drying routines on growth of multilayer thin films using automated deposition system
Authors: Gamboa Daniel , Priolo Morgan A. , Ham Aaron , Grunlan Jaime C.
Published: March 2010

A versatile, high speed robot for layer-by-layer deposition of multifunctional thin films, which integrates concepts from previous dipping systems, has been designed with dramatic improvements in software, positioning, rinsing, drying, and waste removal. This system exploits the electrostatic interaction of oppositely charged species to deposit nanolayers (1–10 nm thick) from water onto the surface of a substrate. Dip times and number of deposited layers are adjustable through a graphical user interface. In between dips the system spray rinses and dries the substrate by positioning it in the two-tiered rinse-dry station. This feature significantly reduces processing time and provides the flexibility to choose from four different procedures for rinsing and drying. Assemblies of natural montmorillonite clay and polyethylenimine are deposited onto 175 μm poly(ethylene terephthalate) film to demonstrate the utility of this automated deposition system. By altering the type of rinse-dry procedure, these clay-based assemblies are shown to exhibit variations in film thickness and oxygen transmission rate. This type of system reproducibly deposits films containing 20 or more layers and may also be useful for other types of coatings that make use of dipping.
Static and dynamic magnetic properties of monodispersed Mn0.5Zn0.5Fe2O4 nanomagnetic particles
Authors: Parekh Kinnari , Upadhyay R. V.
Published: March 2010

Static and dynamic magnetic properties of oleic acid/oleyamine coated Mn–Zn ferrite nanoparticles of diameter 82 Å are reported. The zero-field-cooled peak temperature decreases with increasing magnetic field and obeys the well known de Almeida–Thouless line. The zero-field-cooled magnetization data are simulated by assuming noninteracting magnetic particles with uniaxial anisotropy and lognormal particle size distribution. The relevant parameters give the values of particle diameter (D) 80 Å, standard deviation 0.3 in ln(D), and the anisotropy constant K to be 5.8×105 erg/cm3. The observed higher value of standard deviation is due to the interparticle interaction. The complex magnetic susceptibility was measured as a function of temperature for frequencies ranging from 67 to 1800 Hz. The temperature at which the maximum in the ac-susceptibility curve is observed is well accounted by the Vogel–Fulcher law for both χ′ and χ″. The peak is also observed in a plot of χ″/χ′ versus temperature, which may mean the existence of magnetic aftereffect, and furthermore, it has an Arrhenius as well as Vogel–Fulcher law type dependence. An observed nonthermal activation type relaxation mechanism at 12 K is attributed to possible quantum tunneling effect in Mn–Zn ferrite nanoparticles.
Multiple mode exciton-vibrational coupling in H-aggregates: Synergistic enhancement of the quantum yield
Authors: Spano F. C. , Silvestri Leonardo
Published: March 2010

The impact of exciton-vibrational coupling involving fast and slow vibrational modes on absorption and emission in molecular H-aggregates is investigated using a multimode Holstein Hamiltonian. For H-aggregates composed of rigid molecules the radiative decay rate is rigorously zero due to the asymmetry of the lowest energy exciton. Increasing the Huang–Rhys factors of the coupled modes results in an increase of the radiative efficiency through increased sideband emission. Coupling to a spectrally unresolved slow mode leads to an apparent increase in the 0−0 intensity of the vibronic progression of the fast mode, thereby mimicking a distribution of molecular transition frequencies (diagonal disorder). In the intermediate coupling regime, the radiative efficiency of the aggregate exceeds the sum of the fast-mode-only and slow-mode-only radiative efficiencies. The mechanism underlying the synergistic enhancement of the radiative yield is similar to that which causes spectral splitting in the absorption spectrum of quaterthiophene crystals. [L. Silvestri et al., J. Chem. Phys. 130, 234701 (2009)]. The results here qualitatively account for the robust emission efficiency of hexaphenyl microcrystallites where the slow torsional motion involving the interphenyl dihedral angle in conjunction with the fast ring breathing mode conspire to enhance the quantum yield.
Present status of theoretical modeling the magnetoelectric effect in magnetostrictive-piezoelectric nanostructures. Part I: Low frequency and electromechanical resonance ranges
Authors: Bichurin M. I. , Petrov V. M. , Averkin S. V. , Liverts E.
Published: March 2010

Mechanical deformations of a magnetostrictive-piezoelectric bilayer result in the interaction between the magnetic and electric subsystems. This review reports the models for describing the distinctive features of magnetoelectric (ME) interactions in ferrite-piezoelectric nanostructures at low-frequencies and in electromechanical resonance region. Expressions for ME coefficients are obtained using the solution of elastostatic/elastodynamic and electrostatic and magnetostatic equations. The ME voltage coefficients are estimated from known material parameters. The models take into account the clamping effect of substrate, flexural deformations, and the contribution of lattice mismatch between composite phases and substrate to ME coupling. Lattice mismatch effect has been taken into account by using the classical Landau–Ginsburg–Devonshire phenomenological thermodynamic theory. For a nickel ferrite-lead zirconate titanate nanobilayer on SrTiO3 substrates, the strength of low-frequency ME interactions is shown to be weaker than for thick film bilayers due to the strong clamping effects of the substrate. However, flexural deformations result in the considerably lower rate of change in ME voltage coefficient with substrate thickness compared to the case when neglecting the flexural strains. To avoid the strong clamping effects of the substrate, nanopillars of a magnetostrictive material in a piezoelectric matrix can be used as an alternative. The further methods of increasing the ME coupling in nanostructures are discussed.
Present status of theoretical modeling the magnetoelectric effect in magnetostrictive-piezoelectric nanostructures. Part II: Magnetic and magnetoacoustic resonance ranges
Authors: Bichurin M. I. , Petrov V. M. , Averkin S. V. , Liverts E.
Published: March 2010

We presented here the theoretical analysis of high frequency magnetoelectric (ME) effects for a ferrite-piezoelectric bilayer and a detailed treatment for electric field induced resonance field shift for ferromagnetic resonance (FMR) in layered structures. ME effects in a single-crystal ferrite-piezoelectric bilayer in the magnetoelastic resonance region are considered. The theory predicts a giant ME effect at magnetoacoustic resonance. The enhancement in ME effect predicted by our theory arises from interaction between elastic modes and the uniform precession mode, resulting in magnetoelastic modes. The peak ME voltage coefficient appears at the coincidence of acoustic resonance and FMR frequencies. In our calculations, we suppose that the layer thickness is sufficiently large to neglect the influence of strain relaxation on average stresses in the structures that determine the ME voltage coefficient. The work presented here will certainly be of interest for the design and analysis of electrically controlled high-frequency devices. Microwave devices of magnetic type with electrical control have unique advantages over traditional ferrite and semiconductor analogs.
Atomic force microscopy with a 12-electrode piezoelectric tube scanner
Authors: Yong Yuen K. , Ahmed Bilal , Moheimani S. O. Reza
Published: March 2010

This paper presents a piezoelectric tube scanner with a novel electrode pattern and describes how it may be used for simultaneous sensing and actuation. The electrodes are arranged such that the tube is driven in an antisymmetrical manner, resulting in a collocated system suitable for positive position feedback (PPF). A PPF controller is designed to damp the scanner’s resonance. Piezoelectric strain-induced voltage is used as measurement. The device is then installed into an atomic force microscope to obtain open- and closed-loop images of a grating at 10, 15.6, and 31 Hz scan rates. The closed-loop images are noticeably superior to the open-loop images, illustrating the effectiveness of the proposed scanner when used simultaneously as a sensor and an actuator.
Engineering directed excitonic energy transfer
Authors: Perdomo Alejandro , Vogt Leslie , Najmaie Ali , Aspuru-Guzik Alan
Published: March 2010

We provide an intuitive platform for engineering exciton transfer dynamics. We show that careful consideration of the spectral density, which describes the system-bath interaction, leads to opportunities to engineer exciton transfer. Since excitons in nanostructures are proposed for use in quantum information processing and artificial photosynthetic designs, our approach paves the way for engineering a wide range of desired exciton dynamics. We carefully describe the validity of the model and use experimentally relevant material parameters to show counter-intuitive examples of directed exciton transfer in a linear chain of quantum dots.
Terahertz lasers based on optically pumped multiple graphene structures with slot-line and dielectric waveguides
Authors: Ryzhii V. , Dubinov A. A. , Otsuji T. , Mitin V. , Shur M. S.
Published: March 2010

Terahertz (THz) lasers on optically pumped multiple-graphene-layer (MGL) structures as their active region are proposed and evaluated. The developed device model accounts for the interband and intraband transitions in the degenerate electron-hole plasma generated by optical radiation in the MGL structure and the losses in the slot or dielectric waveguide. The THz laser gain and the conditions of THz lasing are found. It is shown that the lasers under consideration can operate at frequencies ≳1 THz at room temperatures.
The influence of impurities on the performance of the dielectric barrier discharge
Authors: Martens T. , Bogaerts A. , Brok W. J. M. , van Dijk J.
Published: March 2010

In this letter, we investigate the effect of various levels of nitrogen impurity on the electrical performance of an atmospheric pressure dielectric barrier discharge in helium. We illustrate the different current profiles that are obtained, which exhibit one or more discharge pulses per half cycle and evaluate their performance in ionizing the discharge and dissipating the power. It is shown that flat and broad current profiles perform the best in ionizing the discharge and use the least amount of power per generated charged particle.
Nonlinear dynamics of a thin liquid film on an axially oscillating cylindrical surface
Authors: Haimovich Ory , Oron Alexander
Published: March 2010

We have derived a nonlinear evolution equation describing the dynamics of an axisymmetric liquid film on a cylindrical surface subjected to axial harmonic oscillation. We have found that the capillary long-time film rupture typical for the case of a film on a static cylinder can be arrested if the substrate is forced with a sufficiently high amplitude and/or frequency. The threshold for the rupture prevention is determined by the product of the dimensionless amplitude and frequency of forcing, whereas the value of this product is independent of forcing parameters. This threshold delineates the borderline between the ruptured and nonruptured subdomains. A typical pattern in the nonruptured subdomain consists of a single drop within the periodic domain, whereas the number of drops in the ruptured subdomain varies with the forcing amplitude when the rest of parameters remains fixed. The amplitude of film thickness norm in the parameter domain corresponding to nonruptured states of the system was found to increase with the distance from criticality, which is typical for forward bifurcation.
Orientation, distribution, and deposition of elongated, inertial fibers in turbulent channel flow
Authors: Marchioli Cristian , Fantoni Marco , Soldati Alfredo
Published: March 2010

In this paper, the dispersion of rigid, highly elongated fibers in a turbulent channel flow is investigated. Fibers are treated as prolate ellipsoidal particles which move according to their inertia and to hydrodynamic drag and rotate according to hydrodynamic torques. The orientational behavior of fibers is examined together with their preferential distribution, near-wall accumulation, and wall deposition: all these phenomena are interpreted in connection with turbulence dynamics near the wall. In this work a wide range of fiber classes, characterized by different elongation (quantified by the fiber aspect ratio, λ) and different inertia (quantified by a suitably defined fiber response time, τp) is considered. A parametric study in the (λ,τp)-space confirms that, in the vicinity of the wall, fibers tend to align with the mean streamwise flow direction. However, this aligned configuration is unstable, particularly for higher inertia of the fiber, and can be maintained for rather short times before fibers are set into rotation in the vertical plane. A more complex situation is observed in the spanwise and wall-normal flow directions, where fiber inertia and elongation destabilize near-wall alignment in a nontrivial fashion. Fiber orientational behavior and fiber translational behavior are observed to influence the process of fiber accumulation at the wall. Comparing the behavior of fibers with that of spherical particles, it is observed that the aspect ratio has little or no effect on clustering, preferential distribution, and segregation; yet it does affect the wallward drift velocity of the fibers in such a way that longer fibers tend to deposit at higher rates. No preferential orientation and no significant segregation is observed in the channel centerline, confirming that the role of inertia and, in particular, of elongation becomes less important in and beyond the logarithmic layer.
Influence of BaZrO3 dopant concentration on properties of YBa2Cu3O6+x films in magnetic fields up to 30 T
Authors: Huhtinen H. , Irjala M. , Paturi P. , Shakhov M. A. , Laiho R.
Published: March 2010

The effect of BaZrO3 (BZO) dopant concentration on superconducting properties in YBa2Cu3O6+x thin films is investigated in a wide magnetic field range up to 30 T. Based on the magnetization and resistivity measurements, the optimal BZO concentration for flux pinning is found to be 4% up to 20 T and increasing up to around 8% in higher fields. This result is qualitatively explained by a model where more BZO is needed in order to organize optimal columnar defect structure at high fields because the amount of single BZO particles acting as isotropic point pinning centers is increased, especially in high BZO concentrations. This means that for applications of thin film or coated conductor structures carried out at high magnetic fields, even higher dopant concentration than used in a low-field range should be produced in order to attain the optimal flux pinning conditions.
The shear viscosity of rigid water models
Authors: González Miguel Angel , Abascal José L. F.
Published: March 2010

In this work, the shear viscosity at ambient conditions of several water models (SPC/E, TIP4P, TIP5P, and TIP4P/2005) is evaluated using the Green–Kubo formalism. The performance of TIP4P/2005 is excellent, that of SPC/E and TIP5P is more or less acceptable, whereas TIP4P and especially TIP3P give a poor agreement with experiment. Further calculations have been carried out for TIP4P/2005 to provide a wider assessment of its performance. In accordance with experimental data, TIP4P/2005 predicts a minimum in the shear viscosity for the 273 K isotherm, a shift in the minimum toward lower pressures at 298 K, and its disappearance at 373 K.
Heterotwin formation during growth of nanolayered Al-TiN composites
Authors: Bhattacharyya Dhriti , Liu Xiang-Yang , Genc Arda , Fraser Hamish L. , Hoagland Richard G. , Misra Amit
Published: March 2010

High stacking fault energy (SFE) materials such as Al do not form twins easily. Here, the authors report, through high-resolution transmission electron microscopy, that Al layers in an alternating Al/TiN composite grow in a twin relationship to both the TiN and the underlying Al layers. Density functional theory based ab initio modeling reveals that nitrogen termination in the {111} growth plane of the TiN layers greatly favors the growth of twin oriented Al layers on them. This finding provides a definite way of creating a twin-modulated structure in high SFE materials.
A surface locking instability for atomic intercalation into a solid electrode
Authors: Haftbaradaran Hamed , Gao Huajian , Curtin W. A.
Published: March 2010

By introducing a coupling between internal stresses and activation energy for diffusion in the classical theory of diffusion induced stresses, a class of nonconventional solutions has been found for atomic intercalation into a solid electrode, indicative of a surface locking instability once the product between electrode dimension and charging rate exceeds a critical value. This finding may have important implications for the lithium ion battery technology.
Long-range corrected density functional theory study on static second hyperpolarizabilities of singlet diradical systems
Authors: Kishi Ryohei , Bonness Sean , Yoneda Kyohei , Takahashi Hideaki , Nakano Masayoshi , Botek Edith , Champagne Benoît , Kubo Takashi , Kamada Kenji , Ohta Koji , Tsuneda Takao
Published: March 2010

Within the spin-unrestricted density functional theory (DFT) the long-range correction (LC) scheme combined with the Becke–Lee–Yang–Parr exchange-correlation functional, referred to as LC-UBLYP method, has been applied to the calculation of the second hyperpolarizability (γ) of open-shell singlet diradical systems of increasing complexity and has demonstrated good performance: (i) for the simplest H2 dissociation model, the γ values calculated by the LC-UBLYP method significantly overshoot the full configuration interaction result but reproduce qualitatively the evolution of γ as a function of the diradical character, (ii) for small singlet diradical 1,3-dipole systems, the diradical character dependence of γ determined by the UCCSD and UCCSD(T) reference methods is reproduced semiquantitatively by the LC-UBLYP method except in the small diradical character region, where the spin-unrestricted solutions coincide with spin-restricted solutions, (iii) the LC-UBLYP method also closely reproduces the UCCSD(T) results on the diradical character dependence of γ of the p-quinodimethane model system, particularly in the intermediate and large diradical character regions, whereas it shows an abrupt change for a diradical character (y) close to 0.2 originating from the triplet instability, (iv) the reliability of LC-UBLYP to reproduce reference coupled cluster results on open-shell singlet systems with intermediate and large diradical characters has also been substantiated in the case of γ of 1,4-bis-(imidazol-2-ylidene)-cyclohexa-2,5-diene (BI2Y), then (v), for real systems built from a pair of phenalenyl radicals separated by a conjugated linker, the LC-UBLYP results have been found to closely match the UBHandHLYP values—which, for small systems are in good agreement with those obtained using correlated molecular orbital methods—whereas the UB3LYP results can be much different. These results are not only important from the viewpoint of an efficient determination of the nonlinear optical properties of open-shell singlet systems, but also from the viewpoint of defining new challenges for elaborating improved exchange-correlation functionals.
Features of polymer chain dynamics as revealed by intermolecular nuclear magnetic dipole-dipole interaction: Model calculations and field-cycling NMR relaxometry
Authors: Fatkullin N. , Gubaidullin A. , Stapf S.
Published: March 2010

Proton NMR phenomena such as spin-lattice relaxation, free-induction decays, and solid echoes are analyzed with respect to contributions by intermolecular dipole-dipole interactions in polymer melts. The intermolecular dipole-dipole correlation function is calculated by taking into account the correlation hole effect characteristic for polymer melts. It is shown that the ratio between the intra- and intermolecular contributions to NMR measurands depends on the degree of isotropy of chain dynamics anticipated in different models. This, in particular, refers to the tube/reptation model that is intrinsically anisotropic in clear contrast to n-renormalized Rouse models, where no such restriction is implied. Due to anisotropy, the tube/reptation model predicts that the intramolecular contribution to the dipole-dipole correlation function increases with time relative to the intermolecular contribution. Therefore, the intramolecular contribution is expected to dominate NMR measurands by tendency at long times (or low frequencies). On the other hand, the isotropic nature of the n-renormalized Rouse model suggests that the intermolecular contribution tends to prevail on long-time scales (or low frequencies). Actually, theoretical estimations and the analysis of experimental spin-lattice relaxation data indicate that the intermolecular contribution to proton NMR measurands is no longer negligible for times longer than 10−7 s–10−6 s corresponding to frequencies below the megahertz regime. Interpretations not taking this fact into account need to be reconsidered. The systematic investigation of intermolecular interactions in long-time/low frequency proton NMR promises the revelation of the dynamic features of segment displacements relative to each other in polymer melts.
Photoluminescence and positron annihilation studies on Mg-doped nitrogen-polarity semipolar (101¯1¯) GaN heteroepitaxial layers grown by metalorganic vapor phase epitaxy
Authors: Onuma T. , Uedono A. , Asamizu H. , Sato H. , Kaeding J. F. , Iza M. , DenBaars S. P. , Nakamura S. , Chichibu S. F.
Published: March 2010

The influences of enhanced stacking fault (SF) formation, which is peculiar to nitrogen-(N-) polarity growth and lattice-mismatched semipolar heteroepitaxy, on the electrical properties of (101¯1¯) Mg-doped GaN (GaN:Mg) epilayers were investigated. Although the residual donor concentration was higher than (0001) GaN because of N-polar growth, comparatively low Mg doping (3×1019 cm−3) gave a hole concentration approximately 1.5×1018 cm−3, which was an order of magnitude higher than (0001) GaN:Mg. As the acceptor ionization energy estimated from low temperature photoluminescence was quite similar for (101¯1¯) and (0001) GaN:Mg, the high Mg activation seems to result with the aid of high density SFs. Because the Doppler broadening S parameter for the positron annihilation measurement, which reflects the concentration or size of negatively charged cation vacancies, of (101¯1¯) GaN:Mg was smaller than (0001) case, (101¯1¯) orientation is well suited to Mg-doping.
Thermal and flexoelectric effects on nematodynamics in a microvolume cylindrical cavity
Authors: Zakharov A. V. , Vakulenko A. A. , Romano Silvano
Published: March 2010

We have considered a homogeneously aligned liquid crystal (HALC) microvolume, confined between two infinitely long horizontal coaxial cylinders subjected to both a temperature gradient ∇T and radially applied electric field E. We have investigated dynamic field pumping, i.e., studied the interaction between director, velocity, electric fields, as well as, a radially applied temperature gradient, where the inner cylinder is kept at a lower temperature than the outer one. Flexoelectric polarization P has been taken into account as well, and modeled via the classical Meyer treatment. In order to elucidate the role of ∇T, E, and P in producing hydrodynamic flow, we have carried out a numerical study of a system of hydrodynamic equations including director reorientation, fluid flow, and temperature redistribution across the HALC cavity. Calculations show that there exists a range of parameter values (voltage and curvature of the inner cylinder) producing a kinklike orientation process in the system, as well as a nonstandard pumping regime with maximum flow near the hot cylinder.
The proximity of the strain induced effect to improve the electron mobility in a silicon-carbon source-drain structure of n-channel metal-oxide-semiconductor field-effect transistors
Authors: Hsieh E. R. , Chung Steve S.
Published: March 2010

The source/drain in an n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET) with solid phase epitaxial (SPE) implanted Si:C before the spacer formation is proposed. Compared to the conventional nMOSFET with SPE implanted Si:C after the spacer formation, it brings in proximity to the device channel and shows great improvement of electron mobility via the stronger tensile strain effect. Experimental measurements showed that the electron mobility in the proposed process is increased by 105% over that of the control devices. At a gate length of 40 nm, an increase of more than 67% for the drain current, comparing to those of the conventional Si:C source/drain nMOSFET, has been achieved.
Investigating addition effect of hafnium in InZnO thin film transistors using a solution process
Authors: Jeong Woong Hee , Kim Gun Hee , Shin Hyun Soo , Du Ahn Byung , Kim Hyun Jae , Ryu Myung-Kwan , Park Kyung-Bae , Seon Jong-Baek , Lee Sang Yoon
Published: March 2010

The effects of adding Hf into a InZnO (IZO) system, particularly the electrical characteristics of their thin film and thin film transistors (TFTs), were investigated as a function of atomic concentration from 0 to 10 at. % of Hf and Ga/Zn. Because Hf has a high affinity for oxygen in IZO system, the Hf suppresses carrier generation more effectively than does Ga. At 10 at. % of Hf/Zn atomic concentration, the HfInZnO TFTs showed wider on-to-off ratios than those of GaInZnO TFTs due to the low standard-electrode-potential of Hf and sharp subthreshold swings due to low trap density.
Nucleation and growth of nickel nanoclusters on graphene Moiré on Rh(111)
Authors: Sicot M. , Bouvron S. , Zander O. , Rüdiger U. , Dedkov Yu. S. , Fonin M.
Published: March 2010

Regularly sized Ni nanoclusters (NCs) have been grown on a graphene Moiré on Rh(111). Using scanning tunneling microscopy, we determine that initial growth of Ni at 150 K leads to preferential nucleation of monodispersed NCs at specific sites of the Moiré superstructure. However, a defined long-range ordering of NCs with increasing coverage is not observed. Room temperature Ni deposition leads to the formation of flat triangular-shaped islands which are well-matched to the Moiré registry.
Highly polarized Raman scattering anisotropy in single GaN nanowires
Authors: Schäfer-Nolte E. O. , Stoica T. , Gotschke T. , Limbach F. , Sutter E. , Sutter P. , Calarco R.
Published: March 2010

Single GaN nanowires and larger GaN ensembles are investigated by Raman spectroscopy. Spectra of nanowire ensembles prove the high crystal quality and are in agreement with selection rules for the wurtzite structure. Single nanowires are studied with a spatial resolution of the order of 400 nm for different polarization directions of the incident laser beam relative to the nanowire axis. In the single wire spectrum, only the A1(TO) was observed and the Raman intensity was suppressed for perpendicular polarization. These results confirm that Raman scattering in isolated GaN nanowires is governed by size effects.
Electron mobility increase in submicronic transistors integrated on ultrathin silicon membranes subjected to high mechanical stress
Authors: Bercu Bogdan , Montès Laurent , Rochette Florent , Mouis Mireille , Xin Xu , Morfouli Panagiota
Published: March 2010

In this contribution we investigate an original method to apply high values of biaxial stress: The integration of submicronic fully depleted silicon on insulator transistors on ultrathin silicon membranes. The membranes are micromachined in the device substrate, the buried oxide facilitating the control of the membrane thickness below 1 μm. High values of biaxial stress can thus be applied on the transistor channel without the drawbacks of conventional methods. The experimental results obtained using 750 nm thick membranes are presented. The piezoresistive longitudinal coefficient obtained for strained silicon on insulator wafer (240×10−12 Pa−1) is in good agreement with the results obtained by the four-probe bending method.
Influence of the hole blocking layer on blue phosphorescent organic light-emitting devices using 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole as host material
Authors: Seidler Nico , Reineke Sebastian , Walzer Karsten , Lüssem Björn , Tomkeviciene Ausra , Grazulevicius Juozas V. , Leo Karl
Published: March 2010

Organic blue light-emitting devices are essential for the development of future light sources and display technology. Here, we present a highly efficient host-guest system suitable for blue light emission, consisting of the wide gap host material 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole (TCz1) and the phosphorescent blue emitter iridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic). We investigate charge carrier balance as a function of hole blocking layer thickness. For optimized structures, devices with a quantum efficiency as high as 14.3% and a luminous efficacy of 21 lm/W at a luminance of 1000 cd/m2 are realized.
Effects of oxygen incorporation in GeSbTe films on electrical properties and thermal stability
Authors: Jang Moon Hyung , Park Seung Jong , Lim Dong Hyeok , Park Sung Jin , Cho Mann-Ho , Cho Seong Jin , Cho Yoon Ho , Lee Jong-Heun
Published: March 2010

Oxygen incorporated Ge2Sb2Te5 (GST) films were prepared by an ion beam sputtering deposition method. I-V curves of the oxygen incorporated GST active layer showed that the threshold voltage (Vth) varied, depending on the level of incorporated oxygen. In the case of a GST film with an elevated oxygen content of 30.8%, the GST layer melted at 9.02 V due to the instability conferred by the high oxygen content. The formation of Ge-deficient hexagonal phases such as GeSb2Te4 and Sb2Te3 appear to be responsible for the Vth variation. Impedance analyses indicated that the resistance in GST films with oxygen contents of 16.7% and 21.7% had different origins. Thermal desorption spectroscopy data indicate that moisture and hydrocarbons were more readily desorbed at higher oxygen content because the oxygen incorporated GST films are more hydrophilic than undoped GST films.
Race, Affect, and Emotion: Young People, Racism, and Graffiti in the Postcolonial English Suburbs
Authors: Nayak Anoop
Published: March 2010

The majority of studies on young people, race, and racism have focused upon multiethnic inner-city areas. This can have the unintended effect of locating the ‘problem’ of race within the sites where ethnic minorities reside and upon their racially marked bodies. To disrupt this way of looking I attempt to turn the geography of racism ‘inside out’ by recognising the predominantly white English suburbs as a complex site of emotion where racist graffiti, violence, and social deprivation may preside. Here, it is suggested that a ‘global sense of place’ can be evoked through a postcolonial reading of the suburbs and used to unsettle the familiar emotional-laden landscapes of whiteness. Secondly, through ethnography with young people who self-identify as a Skinhead gang, I seek to provide a meaningful geography of racism that engages with emotion, bodily encounters, and events as they become charged with feeling and affect. Thirdly, the ethnography considers the practice of whiteness and white territoriality. In these encounters race and racism are approached as an event or happening that may be given material weight through inscriptions of racist graffiti, emotional sentiments regarding ideas of white suburban belonging, and physical manifestations of popular racism. I conclude that studies of race and racism need to better engage with the visceral way in which affect and emotion seep into the lives of young people and enable the idea of race to pass from immanence to emergence in daily encounters.
Den use by the spotted-tailed quoll Dasyurus maculatus in south-eastern Australia.
Authors: Belcher C. A. , Darrant J. P.
Published: March 2010

Den use was investigated by radio-tracking 28 spotted-tailed quolls (Dasyurus maculatus) at three sites in south-eastern Australia. Dens were recorded in rock crevices, caves and boulder tumbles, hollow logs, tree hollows and windrows and in small wombat (Vombatus ursinus) and rabbit (Oryctolagus cuniculus) burrows. Two D. maculatus were recorded using more than 15 dens during this study. Rock dens appeared to be preferred over hollow log dens. D. maculatus denned alone, except when rearing young and possibly during mating. Females used a number of maternal dens while rearing young, some maternal dens were used in consecutive years.