bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of TAPP1 and TAPP2 adaptor binding to PtdIns(3,4)P2 in regulating insulin sensitivity defined by knock-in analysis
Authors: Wullschleger Stephan , Wasserman David H. , Gray Alex , Sakamoto Kei , Alessi Dario R.
Published: February 2011

Insulin sensitivity is critically dependent on the activity of PI3K (phosphoinositide 3-kinase) and generation of the PtdIns(3,4,5)P3 second messenger. PtdIns(3,4,5)P3 can be broken down to PtdIns(3,4)P2 through the action of the SHIPs (Src-homology-2-domain-containing inositol phosphatases). As PtdIns(3,4)P2 levels peak after those of PtdIns(3,4,5)P3, it has been proposed that PtdIns(3,4)P2 controls a negative-feedback loop that down-regulates the insulin and PI3K network. Previously, we identified two related adaptor proteins termed TAPP [tandem PH (pleckstrin homology)-domain-containing protein] 1 and TAPP2 that specifically bind to PtdIns(3,4)P2 through their C-terminal PH domain. To determine whether TAPP1 and TAPP2 play a role in regulating insulin sensitivity, we generated knock-in mice that express normal endogenous levels of mutant TAPP1 and TAPP2 that are incapable of binding PtdIns(3,4)P2. These homozygous TAPP1R211L/R211LTAPP2R218L/R218L double knock-in mice are viable and exhibit significantly enhanced activation of Akt, a key downstream mediator of insulin signalling. Consistent with increased PI3K and Akt activity, the double knock-in mice display enhanced whole body insulin sensitivity and disposal of glucose uptake into muscle tissues. We also generated wild-type and double TAPP1R211L/R211LTAPP2R218L/R218L knock-in embryonic fibroblasts and found that insulin triggered enhanced production of PtdIns(3,4,5)P3 and Akt activity in the double knock-in fibroblasts. These observations provide the first genetic evidence to support the notion that binding of TAPP1 and TAPP2 adap-tors to PtdIns(3,4)P2 function as negative regulators of the insulin and PI3K signalling pathways.
Finding the process edge: ITIL at Celanese
Authors: Schultze Ulrike
Published: February 2011

Celanese, a global leader in the chemical industry, had spent a number of years implementing a single instance ERP solution and integrating the divisional IT functions into a shared services model. Around 2007, after years of application and IT service growth, many in Celanese IT believed that their internal operations were in desperate need of tighter coordination and process discipline. They looked to Information Technology Infrastructure Library (ITIL) to guide their process integration effort. This case describes the first three years of the IT organization's journey with the ITIL process framework.
Resonancelike dispersion for W-type barium ferrite composites with c-axis anisotropy
Authors: Li Z. W. , Yang Z. H. , Kong L. B.
Published: February 2011

Two types of dispersions, namely, resonancelike and relaxationlike dispersions, and their significantly different high-frequency magnetic properties and attenuation characteristics have been studied for barium ferrite composites BaCoxZn2−xFe16O27 with x=0.5–1.3. The composites with x=0.5, 0.6, and 0.65 have c-axis anisotropy and resonancelike dispersion. For the resonancelike dispersion, a high ratio of μmax″/(μ0′−1) can be achieved and, therefore, even if (μ0′−1) is small, relatively large μmax″ can be still acquired. Due to their high resonance frequency and magnetic loss, the composites can achieve much low reflectivity (RL≤−20 dB) in x to ku bands at small thickness, as compared to composites with c-plane anisotropy. The origin in the two dispersions is attributed to the different types of anisotropy, which lead to much broader resonance-frequency distribution for c-plane anisotropy than for c-axis anisotropy.
Defect induced variation in vibrational and optoelectronic properties of nanocrystalline ZnO powders
Authors: Šćepanović Maja , Grujić-Brojčin Mirjana , Vojisavljević Katarina , Srećković Tatjana
Published: February 2011

Structural disorder of ZnO nanopowders with mean crystallite size down to 15 nm, produced by mechanical activation in high energy mills, has been analyzed by x-ray diffraction and Raman spectroscopy. The influence of such disorder on optical and electronic properties of activated ZnO nanopowders has been investigated using photoluminescence spectroscopy and spectroscopic ellipsometry. A revised interpretation of the resonant enhancement of the first and second order Raman scattering by the E1(LO) phonons in highly disorder ZnO nanopowders has been proposed. Detailed analysis of resonant Raman effects in ZnO powders under sub band gap excitation has given valuable information about defect induced electronic states in the band gap of ZnO. Systematic trend in the electron–phonon coupling strength, with the correlation length which depends on lattice disorder in ZnO, has been also demonstrated.
NATALIE: A 32 detector integrated acquisition system to characterize laser produced energetic particles with nuclear techniques
Authors: Tarisien M. , Plaisir C. , Gobet F. , Hannachi F. , Aléonard M. M. , Rebii A.
Published: February 2011

We present a stand-alone system to characterize the high-energy particles emitted in the interaction of ultrahigh intensity laser pulses with matter. According to the laser and target characteristics, electrons or protons are produced with energies higher than a few mega electron volts. Selected material samples can, therefore, be activated via nuclear reactions. A multidetector, named NATALIE, has been developed to count the β+ activity of these irradiated samples. The coincidence technique used, designed in an integrated system, results in very low background in the data, which is required for low activity measurements. It, therefore, allows a good precision on the nuclear activation yields of the produced radionuclides. The system allows high counting rates and online correction of the dead time. It also provides, online, a quick control of the experiment. Geant4 simulations are used at different steps of the data analysis to deduce, from the measured activities, the energy and angular distributions of the laser-induced particle beams. Two applications are presented to illustrate the characterization of electrons and protons.
On the importance of thermodynamic self-consistency for calculating clusterlike pair correlations in hard-core double Yukawa fluids
Authors: Kim Jung Min , Castañeda-Priego Ramón , Liu Yun , Wagner Norman J.
Published: February 2011

Understanding the mechanisms of clustering in colloids, nanoparticles, and proteins is of significant interest in material science and both chemical and pharmaceutical industries. Recently, using an integral equation theory formalism, Bomont et al. [J. Chem. Phys. 132, 184508 (2010)] studied theoretically the temperature dependence, at a fixed density, of the cluster formation in systems where particles interact with a hard-core double Yukawa potential composed of a short-range attraction and a long-range repulsion. In this paper, we provide evidence that the low-q peak in the static structure factor, frequently associated with the formation of clusters, is a common behavior in systems with competing interactions. In particular, we demonstrate that, based on a thermodynamic self-consistency criterion, accurate structural functions are obtained for different choices of closure relations. Moreover, we explore the dependence of the low-q peak on the particle number density, temperature, and potential parameters. Our findings indicate that enforcing thermodynamic self-consistency is the key factor to calculate both thermodynamic properties and static structure factors, including the low-q behavior, for colloidal dispersions with both attractive and repulsive interactions. Additionally, a simple analysis of the mean number of neighboring particles provides a qualitative description of some of the cluster features.
Lyman-α driven molecule formation on SiO2 surfaces—connection to astrochemistry on dust grains in the interstellar medium
Authors: Rajappan M. , Yuan C. , Yates J. T.
Published: February 2011

As a model for silicate dust grains in the interstellar medium, we have used high area amorphous SiO2 as a surface on which to carry out Lyman-α (10.2 eV) photodecomposition of adsorbed N2O at 71 K and at a coverage of ∼0.3 monolayer. The N2O molecules are adsorbed by hydrogen bonding to surface Si-OH groups. Transmission IR spectroscopy measurements permit the observation of the consumption of adsorbed N2O and the production of various photoproducts. It is observed that in comparison to N2O consumption, the relative rate of formation of the products NO2 and N2O4 made by combination reactions is enhanced significantly on the SiO2 surface. Reactions between photogenerated radicals themselves or between radicals and parent N2O on the SiO2 surface exceed the relative rates observed in the gas phase by factors of up to ∼20. As the complexity of the combination product increases, its relative production rate, compared to the gas phase, increases due to the involvement of multiple surface-combination elementary steps. It is proposed that the enhancement of combination reactions on the SiO2 surface is due to the surface's ability to absorb excess energy evolved during the chemical-bond-forming events on the surface. This principle is probably significant on grain surfaces supporting photochemical processes of astrochemical interest, and indeed is expected. The cross section for adsorbed N2O photodecomposition on the porous SiO2 surface is about 7 × 10−20 cm2 and the quantum yield for the adsorbed molecule decomposition is about 0.006, compared to a quantum yield of 1.46 in the gas phase. This decrease in photon efficiency is attributed to absorption and scattering of Lyman-α radiation by the SiO2 particles.
Electron excitation of the Schumann–Runge continuum, longest band, and second band electronic states in O2
Authors: Suzuki Daisuke , Kato Hidetoshi , Ohkawa Mizuha , Anzai Kazutoshi , Tanaka Hiroshi , Limão-Vieira Paulo , Campbell Laurence , Brunger Michael J.
Published: February 2011

We report measurements of differential and integral cross sections for electron excitation of the Schumann–Runge continuum, longest band, and second band electronic states in molecular oxygen. The energy range of the present study is 15–200 eV, with the angular range of the differential cross section (DCS) measurements from 2 to 130°. A generalized oscillator strength analysis is then employed in order to derive integral cross sections (ICSs) from the corresponding DCSs, and these ICSs are compared with relevant energy and oscillator strength scaled Born cross section (BEf-scaling [Y.-K. Kim, J. Chem. Phys. 126, 064305 (2007)]) results determined as a part of this investigation. Interestingly, while the present Schumann–Runge continuum and second band ICSs were in reasonable agreement with the respective BEf-scaling results, agreement for the longest band was poor below 100 eV with a possible reason for this apparently anomalous behavior being canvassed here. Finally, where possible all present data are compared with the results from earlier measurements and calculations with the level of agreement found being very good in some cases and marginal in others.
Analysis of photonic Doppler velocimetry data based on the continuous wavelet transform
Authors: Liu Shouxian , Wang Detian , Li Tao , Chen Guanghua , Li Zeren , Peng Qixian
Published: February 2011

The short time Fourier transform (STFT) cannot resolve rapid velocity changes in most photonic Doppler velocimetry (PDV) data. A practical analysis method based on the continuous wavelet transform (CWT) was presented to overcome this difficulty. The adaptability of the wavelet family predicates that the continuous wavelet transform uses an adaptive time window to estimate the instantaneous frequency of signals. The local frequencies of signal are accurately determined by finding the ridge in the spectrogram of the CWT and then are converted to target velocity according to the Doppler effects. A performance comparison between the CWT and STFT is demonstrated by a plate-impact experiment data. The results illustrate that the new method is automatic and adequate for analysis of PDV data.
Comment on “A versatile thermoelectric temperature controller with 10 mK reproducibility and 100 mK absolute accuracy” [Rev. Sci. Instrum. 80, 126107 (2009)]
Authors: Sloman Anthony William
Published: February 2011

Libbrecht and Libbrecht recently described a thermoelectric temperature controller for which they claimed an absolute accuracy of 100 mK. They did not specify the heat-dissipation coefficient for their thermistor temperature sensor—which would dissipate more power than is usual in such circuits— nor make any allowance for self-heating in the thermistor. Self-heating can be expected to have introduced more than 100 mK of absolute error in their circuit.
H+ versus D+ transfer from HOD+ to CO2: Bond-selective chemistry and the anomalous effect of bending excitation
Authors: Bell David M. , Boyle Jason M. , Anderson Scott L.
Published: February 2011

Reactions of HOD+ with CO2 have been studied for HOD+ in its ground state, and with one quantum of excitation in each of its vibrational modes: (001)—predominantly OH stretch, 0.396 eV; (010)—bend, 0.153 eV; and (100)—predominantly OD stretch, 0.293 eV. Integral cross sections and product recoil velocities were recorded for collision energies from threshold to 3 eV. The cross sections for both H+ and D+ transfer rise with increasing collision energy from threshold to ∼1 eV, then become weakly dependent of the collision energy. All three vibrational modes enhance the total reactivity, but quite mode specifically. The H+ transfer reaction is enhanced by OH stretch excitation, whereas OD stretch excitation has little effect. Conversely, the D+ transfer reaction is enhanced by OD stretch excitation, while the OH stretch has little effect. Excitation of the bend strongly enhances both channels. The effects of the stretch excitations are consistent with previous studies of neutral HOD mode-selective chemistry, and can be at least qualitatively understood in terms of a late barrier to product formation. The fact that bend excitation produces the largest overall enhancement is surprising, because this is the lowest energy excitation, and is not obviously connected with the reaction coordinates for either H+ or D+ transfer. A rationalization in terms of the effects of water distortion on the potential surface is proposed.
A perturbation analysis of rate theory of self-regulating genes and signaling networks
Authors: Shi Pei-Zhe , Qian Hong
Published: February 2011

A thorough kinetic analysis of the rate theory for stochastic self-regulating gene networks is presented. The chemical master equation kinetic model in terms of a coupled birth–death process is deconstructed into several simpler kinetic modules. We formulate and improve upon the rate theory of self-regulating genes in terms of perturbation theory. We propose a simple five-state scheme as a faithful caricature that elucidates the full kinetics including the “resonance phenomenon” discovered by Walczak et al. [Proc. Natl. Acad. Sci. U.S.A. 102, 18926 (2005)]. The same analysis can be readily applied to other biochemical networks such as phosphorylation signaling with fluctuating kinase activity. Generalization of the present approach can be included in multiple time-scale numerical computations for large biochemical networks.
Atomic force microscope imaging and force measurements at electrified and actively corroding interfaces: Challenges and novel cell design
Authors: Valtiner Markus , Ankah Genesis Ngwa , Bashir Asif , Renner Frank Uwe
Published: February 2011

We report the design of an improved electrochemical cell for atomic force microscope measurements in corrosive electrochemical environments. Our design improvements are guided by experimental requirements for studying corrosive reactions such as selective dissolution, dealloying, pitting corrosion, and/or surface and interface forces at electrified interfaces. Our aim is to examine some of the limitations of typical electrochemical scanning probe microscopy (SPM) experiments and in particular to outline precautions and cell-design elements, which must necessarily be taken into account in order to obtain reliable experimental results. In particular, we discuss electrochemical requirements for typical electrochemical SPM experiments and introduce novel design features to avoid common issues such as crevice formations; we discuss the choice of electrodes and contaminations from ions of reference electrodes. We optimize the cell geometry and introduce standard samples for electrochemical AFM experiments. We have tested the novel design by performing force–distance spectroscopy as a function of the applied electrochemical potential between a bare gold electrode surface and a SAM-coated AFM tip. Topography imaging was tested by studying the well-known dealloying process of a Cu3Au(111) surface up to the critical potential. Our design improvements should be equally applicable to in situ electrochemical scanning tunneling microscope cells.
Realization of optimal bandgaps in solid-solid, solid-air, and hybrid solid-air-solid phononic crystal slabs
Authors: Reinke Charles M. , Su M. F. , Olsson R. H. , El-Kady I.
Published: February 2011

We investigate the optimal conditions for bandgap formation in square-lattice phononic crystal (PnC) slabs composed of a solid matrix with solid or air inclusions. To ensure sufficient impedance mismatch (key for bandgap formation) and fabrication amenability, silicon and silica were chosen as candidate matrix materials with either air or tungsten inclusions. Solid-solid PnCs were found to exhibit larger bandgaps while relaxing the topological constraints as compared to solid-air PnCs for all but the largest filling fractions. We also demonstrate a hybridized lattice incorporating both air and solid inclusions in the matrix that further relaxes the constraints for realizing wide bandgaps.
Transport coefficients for electrons in water vapor: Definition, measurement, and calculation
Authors: Robson R. E. , White R. D. , Ness K. F.
Published: February 2011

Comparison of experimental and theoretical transport data for electron swarms in water vapour over a wide range of fields provides a rigorous test of (e−, H2O) scattering cross sections over a correspondingly broad range of energies. That like should be compared with like is axiomatic, but the definition of transport coefficients at high fields, when non-conservative processes are significant, has long been contentious. This paper revisits and distills the most essential aspects of the definition and calculation of transport coefficients, giving numerical results for the drift velocity and ionisation coefficient of electrons in water vapour. In particular, the relationship between the theoretically calculated bulk drift velocities of [K. F. Ness and R. E. Robson, Phys. Rev. A 38, 1446 (1988)] and the experimental “arrival time spectra” drift velocity data of Hasegawa et al. [J. Phys. D 40(8), 2495 (2007)] is established. This enables the Hasegawa et al. data to be reconciliated with the previous literature, and facilitates selection of the best (e−, H2O) cross section set.
Study of Co/Pd multilayers as a candidate material for next generation magnetic media
Authors: Hu Bing , Amos Nissim , Tian Yuan , Butler John , Litvinov Dmitri , Khizroev Sakhrat
Published: February 2011

We report a combinatorial synthesis study on the magnetic properties of sputter-deposited Co/Pd multilayers with high perpendicular anisotropy and high remnant squareness for magnetic media applications such as magnetic logic systems, bit patterned media, magneto-optical recording, and multilevel three-dimensional (3D) magnetic media. The perpendicular magnetic anisotropy in the multilayers originates from the interfacial anisotropy of the alloylike structure. The deposition conditions and subsequent microstructures of the multilayers are critical factors to determine the magnetic properties of the media. We investigated the dependence of the magnetic properties on the thickness of Co and Pd layers the number of Co/Pd bilayers. For instance, we found that a 0.26-nm-thick layer of Co would produce the highest coercivity value if paired with a 0.55-nm-thick Pd layer. Our results revealed that an Ar+ milling could significantly increase the coercivity of the multilayer media. Further, we discovered that we could control the deposition pressure to achieve either granular or continuous media morphologies corresponding to exchange-coupled or decoupled grains, respectively. Finally, we used the combinatorial synthesis to tailor multilayers’ properties to engineer a eight-level three-layer 3D media.
Effect of surface adsorbed proteins on the photoluminescence of nanodiamond
Authors: Perevedentseva E. , Melnik N. , Tsai C.-Y. , Lin Y.-C. , Kazaryan M. , Cheng C.-L.
Published: February 2011

Nanodiamond has recently attracted great attention for its intrinsic luminescence in the visible range which can be used as a tracking marker in many biological applications. In this work, photoluminescence (PL) of nanodiamonds interacting with biological macromolecules, such as proteins lysozyme and albumin, is studied. Proteins were physically adsorbed on carboxylated nanodiamonds surfaces. The PL spectra of the protein-nanodiamond complex were measured. It is shown that the surface passivation can modify the nanodiamond luminescence properties. Changes in shape and spectral positions of the nanodiamond PL band were observed and found to depend on excitation wavelength. We attribute the effects to the surface energy traps and transfer between protein and surface nanostructures, particular the graphitelike nanoclusters. This study is important for the bio and medical applications of nanodiamonds used as a biocompatible label.
First-principles study of void induced stresses at a diamond (100) grain boundary
Authors: Milas Ivan , Qi Yue , Sheldon Brian W. , Shenoy Vivek B.
Published: February 2011

Density functional theory was used to evaluate the impact of small voids on grain boundary densification in polycrystalline diamond films. The results provide atomic scale insight into tensile stress evolution during polycrystalline film growth, where prior modeling has been largely based on continuum descriptions. Diamond is an ideal material for these studies because the atomic mobility is extremely low and thus a variety of other mechanisms that influence stress evolution can be safely ignored. For the boundary configurations that were investigated, the results indicate that significantly more densification occurs when missing atoms at grain boundaries are clustered together to form nanovoids. Increased densification also occurs with a configuration where missing atoms are in close proximity, but not directly adjacent to each other. Calculations with hydrogen trapped in the nanovoids indicate that repulsive forces can induce compressive stresses instead.
Thermal diffusivity of alkali and silver halide crystals as a function of temperature
Authors: Yu Xueyang , Hofmeister Anne M.
Published: February 2011

The phonon component of thermal diffusivity (D) for ten synthetic single-crystals (LiF, NaCl, NaI, NaI:Tl, KCl, KBr, CsI, CsI:Tl, AgCl, and AgBr) with the B1 and B2 structures was measured from ambient temperature (T) up to ∼1093 K using contact-free, laser-flash analysis, from which effects of ballistic radiative transfer were removed. We investigated optical flats from different manufacturers as well as pellets made from compressed powders of most of the above chemical compositions plus LiI, NaBr, KI, RbCl, RbBr, RbI, CsCl, CsBr, and AgI. Impurities were characterized using various spectroscopic methods. With increasing T,D decreases such that near melting the derivatives ∂D/∂T are low, −0.0006±0.0004 mm2 s−1 K−1. Our results are ∼16% lower than D298 previously obtained with contact methods, which are elevated by ballistic radiative transfer for these infrared (IR) windows, and are well described by either D−1 following a low order polynomial in T, or by D−1∝T+n, where n ranges from 1.0294 to 1.9429. Inverse correlations were found between D298 and both density and thermal expansivity (α). Primitive lattice constant times compressional velocity correlates directly with D but changes much more slowly with temperature. Instead, D(T) is proportional to (TαL)−1 from ∼0 K up to the limit of measurements, in accord with these physical properties being anharmonic. On average, the damped harmonic oscillator–phonon gas model reproduces D298 based on two physical properties: compressional velocity and the damping coefficient (Γ) from analysis of IR reflectivity data. Given large uncertainties in Γ(T), D−1(T) is reproduced for LiF, NaCl, MgO, and the silver halides, for which IR reflectivity data are available. Our correlations show that optical phonons largely govern heat transport of insulators, and permit prediction of D and thus thermal conductivity for simple, diatomic solids.
Micron-scale pattern formation in prestressed polygonal films
Authors: Annabattula R. K. , Onck P. R.
Published: February 2011

In this paper we explore the spontaneous formation of micropatterns in thin prestressed polygonal films using finite element simulations. We study films with different size, thickness, and shape, including square, rectangular, pentagonal, and hexagonal films. Patterns form when the films release the internal eigenstrain by buckling-up, after which the films bond-back to the substrate. After an initial symmetric evolution of the buckling profile, the symmetry of the deflection pattern breaks when the wavelength of wriggles near the film edges decreases. During bond back the deflection morphology converges to a fourfold, fivefold, and sixfold ridging pattern for the square, pentagonal and hexagonal films, respectively, showing a close resemblance with experimental film systems of similar size and shape. Rectangular films of large length to width ratio go through a transition in buckling shapes from the initial Euler mode, through the varicose mode into the antisymmetric telephone-cord mode. For all the film shapes, the ratio of the film height to the effective film width scales with the square root of eigenstrain and is independent of thickness. The bond-back mechanism determines the final wrinkle morphology and is governed by the eigenstrain value at the end of the buckling-up stage and the dimensionless parameter (Γ/EWeq)(Weq/t)3, relating the interface energy to the strain energy in the film.
Ferromagnetic resonance study of Co/Pd/Co/Ni multilayers with perpendicular anisotropy irradiated with helium ions
Authors: Beaujour J.-M. L. , Kent A. D. , Ravelosona D. , Tudosa I. , Fullerton E. E.
Published: February 2011

We present a ferromagnetic resonance (FMR) study of the effect of helium ion irradiation on the magnetic anisotropy, the linewidth and the Gilbert damping of a Co/Ni multilayer coupled to Co/Pd bilayers. The perpendicular magnetic anisotropy decreases linearly with He ion fluence, leading to a transition to in-plane magnetization at a critical fluence of 5×1014 ions/cm2. We find that the damping is nearly independent of fluence but the FMR linewidth at fixed frequency has a maximum near the critical fluence, indicating that the inhomogeneous broadening of the FMR line is a nonmonotonic function of the He ion fluence. Based on an analysis of the angular dependence of the FMR linewidth, the inhomogeneous broadening is associated with spatial variations in the magnitude of the perpendicular magnetic anisotropy. These results demonstrate that ion irradiation may be used to systematically modify the magnetic anisotropy and distribution of magnetic anisotropy parameters of Co/Pd/Co/Ni multilayers for applications and basic physics studies.
The interaction of hyperthermal argon atoms with CO-covered Ru(0001): Scattering and collision-induced desorption
Authors: Ueta Hirokazu , Gleeson Michael A. , Kleyn Aart W.
Published: February 2011

Hyperthermal Ar atoms were scattered under grazing incidence (θi = 60°) from a CO-saturated Ru(0001) surface held at 180 K. Collision-induced desorption involving the ejection of fast CO (∼1 eV) occurs. The angularly resolved in-plane CO desorption distribution has a peak along the surface normal. However, the angular distribution varies with the fractional coverage of the surface. As the total CO coverage decreases, the instantaneous desorption maximum shifts to larger outgoing angles. The results are consistent with a CO desorption process that involves lateral interaction with neighboring molecules. Furthermore, the data indicate that the incident Ar cannot readily penetrate the saturated CO overlayer. Time-of-flight measurements of scattered Ar exhibit two components—fast and slow. The slow component is most evident when scattering from the fully covered surface. The ratio and origin of these components vary with the CO coverage.
Breakup of an electrified viscous thread with charged surfactants
Authors: Conroy D. T. , Matar O. K. , Craster R. V. , Papageorgiou D. T.
Published: February 2011

The dynamics and breakup of electrified viscous jets in the presence of ionic surfactants at the interface are investigated theoretically. Axisymmetric configurations are considered and the jet is surrounded by a concentrically placed cylindrical electrode, which is held at a constant voltage potential. The annular region between the jet and the electrode is taken to be a hydrodynamically passive dielectric medium and an electric field is set up there and drives the flow, along with other physical mechanisms including capillary instability and viscous effects. The jet fluid is taken to be a symmetric electrolyte and proper modeling of the cationic and anionic species is used by considering the Nernst–Planck equations in order to find the volume charge density that influences the electric field in the jet. A positively charged insoluble surfactant is present at the interface, and its evolution, as well as the resulting value of the local surface tension coefficient, is coupled with the voltage potential at the interface. The resulting coupled nonlinear systems are derived and analytical progress is made by carrying out a nonlinear slender jet approximation. The reduced model is described by a number of hydrodynamic, electrical, and electrokinetic parameters, and an extensive computational study is undertaken to elucidate the dynamics along with allied linear properties. It is established that the jet ruptures in finite time provided the outer electrode is sufficiently far away, and numerous examples are given where the dimensionless parameters can be used to control the size of the satellite drops that form beyond the topological transition, as well as the time to break up. It is also shown that pinching solutions follow the self-similar dynamics of clean viscous jets at times close to the breakup time. Finally, a further asymptotic theory is developed for large Debye layers to produce an additional model that incorporates the effects of surface charge diffusion. Numerical solutions establish that the presence of electrostatic and electrokinetic effects increases the sizes of satellites but have a rather weak influence on the time to rupture.
Practical selection of emission lines of He I to determine the photon absorption rate
Authors: Kajita Shin , Ohno Noriyasu
Published: February 2011

A combination of helium line intensities and a collisional radiative model has been used to measure electron density and temperature. However, radiation trapping of resonance lines may disturb the measurements due to disturbances in the population distribution of helium atoms. In this study, we show that the principal contribution of radiation trapping in helium plasma can be evaluated by additionally measuring one or two specific line intensities from the singlet state. The inclusion of the effects of radiation trapping sufficiently compensates for anomalous increases in the electron density and temperature, and consequently yields proper values. An experiment was performed in the divertor simulator NAGDIS-II, and the method's validity was confirmed by comparing the spectroscopically obtained results and the values from the electrostatic probe method.
Diluting the hydrogen bonds in viscous solutions of n-butanol with n-bromobutane: II. A comparison of rotational and translational motions
Authors: Lederle Christina , Hiller Wolf , Gainaru Catalin , Böhmer Roland
Published: February 2011

Mixtures of the monohydroxy alcohol n-butanol with n-bromobutane are investigated via dielectric and nuclear magnetic resonance (NMR) techniques. Static- and pulsed-field gradient proton NMR yielded self-diffusion coefficients as a function of concentration and temperature. To monitor reorientational motions, broadband dielectric and 13C-spin relaxation time measurements were carried out. The latter demonstrate that the structural relaxation stems from the motion of the alkyl chains. By combining data from translational diffusion coefficients with published shear viscosities, hydrodynamic radii were determined that compare favorably with the van der Waals radii of single molecules. The results for the neat alcohol and for the binary mixtures are discussed with respect to a recent transient chain model. The approach of Debye and structural relaxation times at high temperatures, identified as a general feature of monohydroxy alcohols, is also discussed within that framework.
Design and analysis of kinetic energy recovery system for automobiles: Case study for commuters in Edinburgh
Authors: Walsh John , Muneer Tariq , Celik Ali N.
Published: February 2011

Transport and its energetic and environmental impacts affect our daily lives. The transport sector is the backbone of the United Kingdom’s economy with 2.3 million people being employed in this sector. With a high dependency on transport for passengers and freight and with the knowledge that oil reserves are rapidly decreasing a solution has to be identified for conserving fuel. Passenger vehicles account for 61% of the transport fuel consumed in the U.K. and should be seen as a key area to tackle. Despite the introduction and development of electric powered cars, the widespread infrastructure that is required is not in place and has attributed to their slow uptake, as well as the fact that the electric car’s performance is not yet comparable with the conventional internal combustion engine. The benefits of the introduction of kinetic energy recovery systems to be used in conjunction with internal combustion engines and designed such that the system could easily be fitted into future passenger vehicles are examined. In this article, a review of automobile kinetic energy recovery system is presented. It has been argued that the ultracapacitor technology offers a sustainable solution. An optimum design for the urban driving cycle experienced in the city of Edinburgh has been introduced. The potential for fuel savings is also presented.
Condon domain phase diagram for silver
Authors: Kramer R. B. G. , Egorov V. S. , Gasparov V. A. , Jansen A. G. M. , Joss W.
Published: February 2011

We present the Condon domain phase diagram for a silver single crystal measured in magnetic fields up to 28T and temperatures down to 1.3K. A standard ac method with a pickup coil system is used at low frequency for measuring the de Haas-van Alphen effect (dHvA). The transition point from the state of homogeneous magnetization to the inhomogeneous Condon domain state (CDS) is defined as the point where a small irreversibility develops in the dHvA magnetization, as manifested by an extremely nonlinear response in the pickup voltage indicative of a threshold character. The third harmonic content in the ac response is used to determine with high precision the CDS phase boundary. The experimentally determined Condon domain phase diagram is in good agreement with the theoretical prediction calculated by the standard Lifshitz–Kosevich formula.
Upper bounds on Shannon and Rényi entropies for central potentials
Authors: Sánchez-Moreno P. , Zozor S. , Dehesa J. S.
Published: February 2011

The Rényi and Shannon entropies are information-theoretic measures, which have enabled to formulate the position–momentum uncertainty principle in a much more adequate and stringent way than the (variance-based) Heisenberg-like relation. Moreover, they are closely related to various energetic density functionals of quantum systems. Here we derive upper bounds on these quantities in terms of the second-order moment 〈r2〉 for general central potentials. This improves previous results of this type. The proof uses the Rényi maximization procedure with a covariance constraint due to Costa et al. [in Proceedings of the Fourth International Workshop on Energy Minimization Methods in Computer Vision and Pattern Recognition (EMMCVPR), edited by A. Rangarajan, M. A. T. Figueiredo, and J. Zerubia (Springer-Verlag, Lisbon, 2003), [Lect. Notes Comput. Sci. 52, 211 (2003).]] The contributions to these bounds coming from the radial and angular parts of the physical wave functions are taken into account. Finally, the application to the d-dimensional (d ⩾ 3) hydrogenic and oscillator-like systems is provided.
New class of 4-dim Kochen–Specker sets
Authors: Pavičić Mladen , Megill Norman D. , Aravind P. K. , Waegell Mordecai
Published: February 2011

We find a new highly symmetrical and very numerous class (millions of nonisomorphic sets) of 4-dim Kochen–Specker (KS) vector sets. Due to the nature of their geometrical symmetries, they cannot be obtained from previously known ones. We generate the sets from a single set of 60 orthogonal spin vectors and 75 of their tetrads (which we obtained from the 600-cell) by means of our newly developed stripping technique. We also consider critical KS subsets and analyze their geometry. The algorithms and programs for the generation of our KS sets are presented.
Asymptotic expansion for the wave function in a one-dimensional model of inelastic interaction
Authors: Finco Domenico , Teta Alessandro
Published: February 2011

We consider a two-body quantum system in dimension one composed by a test particle interacting with a harmonic oscillator placed at the position a > 0. At time zero the test particle is concentrated around the position R0 with average velocity ±v0 while the oscillator is in its ground state. In a suitable scaling limit, corresponding for the test particle to a semiclassical regime with small energy exchange with the oscillator, we give a complete asymptotic expansion of the wave function of the system in both cases \documentclass[12pt]{minimal}\begin{document}$R_0 <a$\end{document}R0a$\end{document}R0>a.
Dimer pinning and the assignment of semiconductor–adsorbate surface structures
Authors: Smith Phillip V. , Warschkow Oliver , Radny Marian W. , Schofield Steven R. , Belcher Daniel R.
Published: February 2011

It has been observed in scanning tunneling microscopy (STM) that the adsorption of molecules on the (001) surface of a Group IV semiconductor can lead to an asymmetric ordering of the dimers immediately adjacent to the adsorbate. This so-called pinning may occur along the dimer row on only one, or both sides of the adsorbate. Here we present a straightforward methodology for predicting such pinning and illustrate this approach for several different adsorbate structures on the Si(001) surface. This approach extends earlier work by including the effects of coupling across the adsorbate as well as the nearest-neighbor interactions between the chemisorbed dimer and its adjacent dimers. The results are shown to be in excellent agreement with the room temperature experimental STM data. The examples also show how this approach can serve as a powerful tool for discriminating between alternative possible adsorbate structures on a dimerized semiconductor (001) surface, especially in cases of molecular adsorption where the STM measurements provide insufficient details of the underlying atomic structure.
On the structure of the matrix isolated water trimer
Authors: Ceponkus J. , Uvdal P. , Nelander B.
Published: February 2011

Infrared spectra of partially deuterated water trimers have been investigated. It is found that HDO(H2O)2 has a single, bound OD stretching fundamental, (HDO)2H2O two bound OD stretches. (HDO)3 has a single, bound OD stretch and (H2O)3 has a pair of bound OH stretches. Ab initio and density functional theory (DFT) calculations predict that the water trimer has C1 symmetry with six different, isoenergetic minima. These calculations consequently give three numerically different OD stretches for HDO(H2O)2, six for (HDO)2H2O, three for (HDO)3, and three bound OH stretches for (H2O)3. The connection between the observations and the pseudorotation of the trimer is discussed with the help of Wales’ pseudorotation model. It is found that pseudorotation is sufficiently fast to average the effective symmetry of the A3 trimer to C3h and to eliminate the difference between the different ab initio minima for A2B. The only exception is (H2O)3 where the splitting between the different bound OH stretches is largest. Here a doublet is observed due to incomplete averaging. DFT calculations indicate that the D-bonded form of HDO(H2O)2 is between 50 and 60 cm−1 more stable than the H-bonded form. The energy difference is determined by differences in zero point vibration energy of intermolecular librations of the two forms. Attempts to measure the energy difference indicate that the energy difference is larger, of the order of 100 cm−1.
A non-differentiable Noether's theorem
Authors: Cresson Jacky , Greff Isabelle
Published: February 2011

In the framework of the nondifferentiable embedding of Lagrangian systems, defined by Cresson and Greff [non-dierentiable embedding of lagrangian systems and partial dierential equations. Preprint Max-Plank-Institut für Mathematik in den Naturwissenschaften, Leipzig 16, 26 (2010)], we prove a Noether's theorem based on the lifting of one-parameter groups of diffeomorphisms.
Turbulent anomalous transport and anisotropic electron heating in a return current system
Authors: Lee Kuang Wu , Büchner Jörg
Published: February 2011

Anisotropic electron heating due to self-generated electromagnetic turbulences is observed in collisionless return current plasmas. The corresponding energy conversion, electron heating, and associated anomalous momentum transport are investigated by means of a two-dimensional electromagnetic particle-in-cell simulation code. The return current model consists of two counterstreaming electron beams with different temperatures and a stationary ion background. First, a general multifluid dispersion analyzer is presented in a clear matrix form that allows to study electron streaming instabilities. The numerical simulation confirms the predicted electrostatic electron-electron acoustic instability. Generating electromagnetic waves, the system evolves into a nonlinear stage. As a result, the electron drifts are slowed down due to turbulence-induced anomalous momentum exchange. Localized electric and magnetic field fluctuations play major roles in the energy conversion. Perpendicular electron heating follows the growth of magnetic field perturbations and the slowing of the electron drifts. Parallel and perpendicular electron heating occurs at different time scales. It is shown that the longer lasting perpendicular electron heating is caused by preheated parallel electron flows. The deflection of the preheated parallel electron flows in the localized turbulences, which is essentially a two-dimensional effect, leads to perpendicular electron heating even after the saturation of parallel electron heating. We conclude that the self-generated magnetic turbulence dominates the anomalous transport process in the late stage of return current system evolution.
Band structure and accumulation point in the spectrum of quantum collision operator in a one-dimensional molecular chain
Authors: Tay B. A. , Kanki Kazuki , Tanaka Satoshi , Petrosky Tomio
Published: February 2011

We consider the eigenvalue problem of a kinetic collision operator for a quantum Brownian particle interacting with a one-dimensional chain. The quantum nature of the system gives rise to a difference operator. For the one-dimensional case, the momentum space separates into infinite sets of disjoint subspaces dynamically independent of one another. The eigenvalue problem of the collision operator is solved with the continued fraction method. The spectrum is non-negative, possesses an accumulation point, and exhibits a band structure. We also construct the eigenvectors of the collision operator and establish their completeness and orthogonality relations in each momentum subspaces.
An experimental investigation of turbulent thermal convection in water-based alumina nanofluid
Authors: Ni Rui , Zhou Sheng-Qi , Xia Ke-Qing
Published: February 2011

We report heat transfer and flow dynamics measurements of alumina nanofluid in turbulent convective flow. Under the condition of fixed temperature at the top plate and fixed input heat flux at the bottom plate, it has been found that the convective heat transfer coefficient, h, Nusselt number, Nu, and Rayleigh number, Ra, all decrease with the increasing volume fraction ϕ of the nanoparticle. In contrast, the velocity of the convective flow showed no significant change within experimental uncertainty and over the range of nanoparticle concentration of the measurement (from 0% to 1.08%). Under the condition of constant nanoparticle concentration (ϕ=1.08%), a second set of measurements of the heat transport and flow properties have been made over a broad range of Ra (from 2.6×108 to 7.7×109). For heat transport, a transition near Rac≃2.5×109 has been found. For Ra>Rac, the measured Nu of the nanofluid is roughly the same as that of water in terms of both its magnitude and its scaling relation with Ra, which suggests that the nanofluid can be treated as a single phase fluid in this parameter range. For Ra<Rac, Nu becomes smaller than that of the water and the deviation becomes larger with decreasing Ra. In the parameter range of RaRac. This suggests that the significant decrease of the nanofluid Nu comparing to that of water may be caused by the mass diffusion of nanoparticles. Furthermore, measurements of the flow velocity of the bulk nanofluid showed no significant difference from that of water for Ra either above or below Rac. From estimated thermal boundary layer thickness, we found that the deviations of the nanofluid Nu from that of water for Ra<Rac corresponds to the thickening of the thermal boundary layer at both the top and bottom plates. This thickening of the boundary layer at low input heat flux (or low driving strength of the convective flow) cannot be attributed to possible sedimentation of the nanoparticles.