bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuous measurements of flow rate in a shallow gravel‐bed river by a new acoustic system
Authors: Kawanisi K. , Razaz M. , Ishikawa K. , Yano J. , Soltaniasl M.
Published: April 2012

The continuous measurement of river discharge for long periods of time is crucial in water resource studies. However, the accurate estimation of river discharge is a difficult and labor‐intensive procedure; thus, a robust and efficient method of measurement is required. Continuous measurements of flowrate have been carried out in a wide, shallow gravel bed river (water depth ≈ 0.6 m under low‐flow conditions, width ≈ 115 m) using Fluvial Acoustic Tomography System (FATS) that has 25 kHz broadband transducers with horizontally omnidirectional and vertically hemispherical beam patterns. Reciprocal sound transmissions were performed between the two acoustic stations located diagonally on both sides of the river. The horizontal distance between the transducers was 301.96 m. FATS enabled the measurement of the depth‐ and range‐averaged sound speed and flow velocity along the ray path. In contrast to traditional point/transect measurements of discharge, in a fraction of a second, FATS covers the entire cross section of river in a single measurement. The flow rates measured by FATS were compared to those estimated by moving boat Acoustic Doppler Current Profiler (ADCP) and rating curve (RC) methods. FATS estimates were in good agreement with ADCP estimates over a range of 20 to 65 m3 s−1. The RMS of residual between the two measurements was 2.41 m3 s−1. On the other hand the flowrate by RC method fairly agreed with FATS estimates for greater discharges than around 40 m3 s−1. This inconsistency arises from biased RC estimates in low flows. Thus, the flow rates derived from FATS could be considered reliable.
Neuronal caspase 2 activity and function requires RAIDD, but not PIDD
Authors: Ribe Elena M. , Jean Ying Y. , Goldstein Rebecca L. , Manzl Claudia , Stefanis Leonidas , Villunger Andreas , Troy Carol M.
Published: April 2012

Caspase 2 was initially identified as a neuronally expressed developmentally down-regulated gene (HUGO gene nomenclature CASP2) and has been shown to be required for neuronal death induced by several stimuli, including NGF (nerve growth factor) deprivation and Aβ (β-amyloid). In non-neuronal cells the PIDDosome, composed of caspase 2 and two death adaptor proteins, PIDD (p53-inducible protein with a death domain) and RAIDD {RIP (receptor-interacting protein)-associated ICH-1 [ICE (interleukin-1β-converting enzyme)/CED-3 (cell-death determining 3) homologue 1] protein with a death domain}, has been proposed as the caspase 2 activation complex, although the absolute requirement for the PIDDosome is not clear. To investigate the requirement for the PIDDosome in caspase-2-dependent neuronal death, we have examined the necessity for each component in induction of active caspase 2 and in execution of caspase-2-dependent neuronal death. We find that both NGF deprivation and Aβ treatment of neurons induce active caspase 2 and that induction of this activity depends on expression of RAIDD, but is independent of PIDD expression. We show that treatment of wild-type or PIDD-null neurons with Aβ or NGF deprivation induces formation of a complex of caspase 2 and RAIDD. We also show that caspase-2-dependent execution of neurons requires RAIDD, not PIDD. Caspase 2 activity can be induced in neurons from PIDD-null mice, and NGF deprivation or Aβ use caspase 2 and RAIDD to execute death of these neurons.
Different molecular bases underlie the mitochondrial respiratory activity in the homoeothermic spadices of Symplocarpus renifolius and the transiently thermogenic appendices of Arum maculatum
Authors: Kakizaki Yusuke , Moore Anthony L. , Ito Kikukatsu
Published: April 2012

Symplocarpus renifolius and Arum maculatum are known to produce significant heat during the course of their floral development, but they use different regulatory mechanisms, i.e. homoeothermic compared with transient thermogenesis. To further clarify the molecular basis of species-specific thermogenesis in plants, in the present study we have analysed the native structures and expression patterns of the mitochondrial respiratory components in S. renifolius and A. maculatum. Our comparative analysis using Blue native PAGE combined with nano LC (liquid chromatography)-MS/MS (tandem MS) has revealed that the constituents of the respiratory complexes in both plants were basically similar, but that several mitochondrial components appeared to be differently expressed in their thermogenic organs. Namely, complex II in S. renifolius was detected as a 340 kDa product, suggesting an oligomeric or supramolecular structure in vivo. Moreover, the expression of an external NAD(P)H dehydrogenase was found to be higher in A. maculatum than in S. renifolius, whereas an internal NAD(P)H dehydrogenase was expressed at a similar level in both species. Alternative oxidase was detected as smear-like signals that were elongated on the first dimension with a peak at around 200 kDa in both species. The significance and implication of these data are discussed in terms of thermoregulation in plants.
The crystal structure of human α1-microglobulin reveals a potential haem-binding site
Authors: Meining Winfried , Skerra Arne
Published: April 2012

We describe the 2.3 Å (1 Å=0.1 nm) X-ray structure of α1m (α1-microglobulin), an abundant protein in human blood plasma, which reveals the β-barrel fold typical for lipocalins with a deep pocket lined by four loops at its open rim. Loop #1 harbours the residue Cys34 which is responsible for covalent cross-linking with plasma IgA. A single disulfide bond between Cys72 and Cys169 connects the C-terminal segment to the β-barrel, as in many other lipocalins. The exposed imidazole side chains of His122 and His123 in loop #4 give rise to a double Ni2+-binding site together with a crystallographic neighbour. The closest structural relatives of α1m are the complement protein component C8γ, the L-prostaglandin D synthase and lipocalin 15, three other structurally characterized members of the lipocalin family in humans that have only distant sequence similarity. In contrast with these, α1m is initially expressed as a bifunctional fusion protein with the protease inhibitor bikunin. Neither the electron density nor ESI–MS (electrospray ionization MS) provide evidence for a chromophore bound to the recombinant α1m, also known as ‘yellow/brown lipocalin’. However, the three side chains of Lys92, Lys118 and Lys130 that were reported to be involved in covalent chromophore binding appear to be freely accessible to ligands accommodated in the hydrophobic pocket. A structural feature similar to the well-known Cys–Pro haem-binding motif indicates the presence of a haem-binding site within the loop region of α1m, which explains previous biochemical findings and supports a physiological role in haem scavenging, as well as redox-mediated detoxification.
Mittelfristige Ergebnisse nach Implantation einer Pyrocarbonprothese bei Fingermittelgelenksarthrose
Authors: Heers G. , Telisselis P. , Winkler F. , Grifka J. , Borisch N.
Published: April 2012

Ziel: Evaluation mittelfristiger klinischer und radiologischer Ergebnisse der ungekoppelten Pyrocarbonprothese (Ascension®) in der Behandlung der schmerzhaften idiopathischen Arthrose des Fingermittelgelenks. Methode: In dieser Studie konnten 13 implantierte Prothesen (10 Patienten) nach durchschnittlich 71 Monaten retrospektiv klinisch und radiologisch analysiert werden. Ergebnisse: Das durchschnittliche postoperative Bewegungsausmaß lag bei 52° (± 27° STD). Eine Luxation der Komponenten wurde bislang nicht beobachtet. Auch ein Ausbau einer Prothese war bisher nicht erforderlich. Eine radiologisch signifikante periprothetische Lysezone (≥ 1 mm) wurde bei 7 Prothesen beobachtet. In 3 Fällen kam es dabei zu einer Wanderung der Komponenten und in 1 Fall zu einer Lockerung der Prothese mit Drehung der proximalen Komponente um die Längsachse. Radiologisch unauffällig waren nur 6 Prothesen mit regulärer Stellung der Komponenten. Schlussfolgerung: Nach durchschnittlich 6 Jahren postoperativ besteht eine hohe Komplikationsrate mit einer eingeschränkten Beweglichkeit. Bei anzunehmender fehlender Osteointegration bestehen bei der Hälfte der Patienten radiologische Veränderungen. Das postoperative Bewegungsausmaß zeigt eine hohe Varianz, was bei der Patientenaufklärung berücksichtigt werden muss.
Molecular beam epitaxial growth and characterization of InSb1 − xNx on GaAs for long wavelength infrared applications
Authors: Patra Nimai C. , Bharatan Sudhakar , Li Jia , Tilton Michael , Iyer Shanthi
Published: April 2012

Recent research progress and findings in InSbN have attracted great attention due to its use in long wavelength infrared applications. A large bandgap reduction in InSb resulting from high N incorporation with minimal crystal defects is challenging due to relatively small atomic size of N. Hence optimization of growth conditions plays an important role in the growth of high-quality InSbN epilayers for device purposes. In this paper, we report on the correlation of structural, vibrational, electrical, and optical properties of molecular beam epitaxially grown InSbN epilayers grown on GaAs substrates, as a function of varying growth temperatures. Two dimensional growths of InSb and InSbN were confirmed from dynamic reflection high energy electron diffraction patterns and growth parameters were optimized. High crystalline quality of the epilayers is attested to by a low full width at half maximum of 200 arcsec from high resolution x-ray diffraction (HRXRD) scans and by the high intensity and well-resolved InSb longitudinal optical (LO) and 2nd order InSb LO mode observed from micro-Raman spectroscopy. The N incorporation in these InSbN epilayers is estimated to be 1.4% based on HRXRD simulation. X-ray photoelectron spectroscopy (XPS) studies reveal that most of the N present in the layers are in the form of In-N bonding. Variation of the lattice disorder with growth temperature is correlated with the types of N bonding present, the carrier concentration and mobility, observed in the corresponding XPS spectra and Hall measurements, respectively. XPS analysis, HRXRD scans, and Raman spectral analysis indicate that lower growth temperature favors In-N bonding which dictates N incorporation in the substitutional sites and lattice disorder, whereas, high growth temperature promotes the formation of In-N-Sb bonding. The best room temperature and 77 K electrical transport parameters and maximum redshift in the absorption edge have been achieved in the InSbN epilayer grown in the 290 °C ∼ 330 °C temperature range.
Constructing “non-Kerrness” on compact domains
Authors: Bäckdahl Thomas , Kroon Juan A. Valiente
Published: April 2012

Given a compact domain of a three-dimensional hypersurface on a vacuum spacetime, a scalar (the “non-Kerrness”) is constructed by solving a Dirichlet problem for a second order elliptic system. If such scalar vanishes, and a set of conditions are satisfied at a point, then the domain of dependence of the compact domain is locally isometric to a portion of a member of the Kerr family of solutions to the Einstein field equations. This construction is expected to be of relevance in the analysis of numerical simulations of black hole spacetimes.
Effect of doping on polarization profiles and switching in semiconducting ferroelectric thin films
Authors: Shenoy Vivek B. , Xiao Yu , Bhattacharya Kaushik
Published: April 2012

This paper proposes a theory to describe the polarization and switching behavior of ferroelectrics that are also wide-gap semiconductors. The salient feature of our theory is that it does not make any a priori assumption about either the space charge distribution or the polarization profile. The theory is used to study a metal-ferroelectric-metal capacitor configuration, where the ferroelectric is n-type doped. The main result of our work is a phase diagram as a function of doping level and thickness that shows different phases, namely, films with polarization profiles that resemble that of undoped classical ferroelectrics, paraelectric, and a new head-to-tail domain structure. We have identified a critical doping level, which depends on the energy barrier in the Landau energy and the built-in potential, which is decided by the electronic structures of both the film and the electrodes. When the doping level is below this critical value, the behavior of the films is almost classical. We see a depleted region, which extends through the film when the film thickness is very small, but is confined to two boundary layers near the electrodes for large film thickness. When the doping level is higher than the critical value, the behavior is classical for only very thin films. Thicker films at this doping level are forced into a tail-to-tail configuration with three depletion layers, lose their ferroelectricity, and may thus be described as nonlinear dielectric or paraelectric. For films which are doped below the critical level, we show that the field required for switching starts out at the classical coercive field for very thin films, but gradually decreases.
Spatially modulated photoluminescence properties in dynamically strained GaAs/AlAs quantum wells by surface acoustic wave
Authors: Sogawa Tetsuomi , Sanada Haruki , Gotoh Hideki , Yamaguchi Hiroshi , Santos Paulo V.
Published: April 2012

Spatially resolved photoluminescence (PL) spectra and polarization anisotropy were investigated in GaAs/AlAs dynamic wires, which were formed by applying a surface acoustic wave (SAW) on GaAs/AlAs quantum wells along the [110] or [1-10] direction. A synchronized excitation method clearly demonstrates that the band gap energies are spatially modulated by the travelling-SAW-induced strain. It is found that both the spatial PL modulation and anisotropic polarization properties depend on the SAW direction. The spatial modulation of the polarization anisotropies and their dependence on the strain-induced valence band mixing are also discussed theoretically.
Quantization and fractional quantization of currents in periodically driven stochastic systems. II. Full counting statistics
Authors: Chernyak Vladimir Y. , Klein John R. , Sinitsyn Nikolai A.
Published: April 2012

We study Markovian stochastic motion on a graph with finite number of nodes and adiabatically periodically driven transition rates. We show that, under general conditions, the quantized currents that appear at low temperatures are a manifestation of topological invariants in the counting statistics of currents. This observation provides an approach for classification of topological properties of the counting statistics, as well as for extensions of the phenomenon of the robust quantization of currents at low temperatures to the properties of the counting statistics which persist to finite temperatures.
Chromium-oxide enhancement of photo-oxidation of CdSe/ZnS quantum dot solids
Authors: Sadeghi S. M. , Nejat A. , Weimer J. J. , Alipour G.
Published: April 2012

In this paper, we report the results of depositing CdSe/ZnS quantum dots (QDs) on Cr coated substrates. Compared to such QDs on glass surfaces, the emission peak blueshifts and broadens much more rapidly. The acceleration of the process is presented by showing the relative intensity, position, and full-width as a function of time for various laser intensities, and the effects on photoinduced fluorescence enhancement and photo-oxidiation are discussed. We also consider the thickness of the Cr layer and photo-induced heating, showing this factor should instead lead to a redshift of the peak. Oxidation of colloidal QDs is known to cause blueshifts and broadening of emission peaks (photobleaching). We attribute the faster photobleaching of QDs on Cr films to enhancement in the oxidation of the ZnS shell by catalytic or direct chemical reactions with chromium oxides. As a working hypothesis, this leads to additional paths for breakdown of the otherwise protective nature of the shell.
Ordering of anisotropic polarizable polymer chains on the full many-body level
Authors: Dean David S. , Podgornik Rudolf
Published: April 2012

We study the effect of dielectric anisotropy of polymers on their equilibrium ordering within mean-field theory, but with a formalism that takes into account the full n-body nature of van der Waals (vdW) forces. Dielectric anisotropy within polymers is to be expected as the electronic properties of the polymer will typically be different along the polymer than across its cross section. It is therefore physically intuitive that larger charge fluctuations can be induced along the chain than perpendicular to it. We show that this dielectric anisotropy leads to n-body interactions which can induce an isotropic-nematic transition. The two body and three body components of the full vdW interaction are extracted and it is shown how the two body term behaves like the phenomenological self-aligning-pairwise nematic interaction. At the three body interaction level we see that the nematic phase that is energetically favorable is discotic, however, on the full n-body interaction level we find that the normal axial nematic phase is always the stable ordered phase. The n-body nature of our approach also shows that the key parameter driving the nematic-isotropic transition is the bare persistence length of the polymer chain.
Measurement and control of residual amplitude modulation in optical phase modulation
Authors: Li Liufeng , Liu Fang , Wang Chun , Chen Lisheng
Published: April 2012

Residual amplitude modulation is one of the major sources of instability in ultra-sensitive optical detections based on frequency modulation. Using a MgO·LiNbO3 electro-optic crystal, we systematically measure the temperature and polarization dependence of residual amplitude modulation and our experimental results are in good agreement with a previous theoretical analysis. After optical phase modulation, two independent arms including optical detection and frequency demodulation are employed to closely examine the instability of the residual amplitude modulation. Residual amplitude modulation below 25 ppm is obtained with an active cancellation scheme in which the crystal temperature is varied so as to zero the baseline drifts with different origins. Possible improvements for better suppression and stability are discussed.
Atomic imaging of atomic layer deposition oxide nucleation with trimethylaluminum on As-rich InGaAs(001) 2 × 4 vs Ga/In-rich InGaAs(001) 4 × 2
Authors: Melitz Wilhelm , Kent Tyler , Kummel Andrew C. , Droopad Ravi , Holland Martin , Thayne Iain
Published: April 2012

Formation of a contaminant free, flat, electrically passive interface to a gate oxide such as a-Al2O3 is the critical step in fabricating III-V metal oxide semiconductor field effect transistors; while the bulk oxide is amorphous, the interface may need to be ordered to prevent electrical defect formation. A two temperature in situ cleaning process is shown to produce a clean, flat group III or group V rich InGaAs surface. The dependence of initial surface reconstruction and dosing temperature of the seeding of aluminum with trimethylaluminum dosing is observed to produce an ordered unpinned passivation layer on InGaAs(001)-(4 × 2) surface at sample temperatures below 190 °C. Conversely, the InGaAs(001)-(2 × 4) surface is shown to generate an unpinned passivation layer with a seeding temperature up to 280 °C. For both reconstructions, the chemical drive force is consistent with formation of As-Al-As bonds. The optimal seed layer protects the surface from background contamination.
Experimental confirmation of temperature dependent negative capacitance in ferroelectric field effect transistor
Authors: Salvatore Giovanni A. , Rusu Alexandru , Ionescu Adrian M.
Published: April 2012

In this paper, we report the basic design conditions and the experimental confirmation of a temperature dependent negative capacitance (NC) effect in a ferroelectric field-effect-transistor (Fe-FET). We find that the internal voltage amplification peaks of a metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structure are correlated with the S-shape of the polarization versus electrical field characteristics. The internal voltage amplification is responsible for the subthreshold swing reduction in a Fe-FET; this effect cancels out when the temperature is increased close to the Curie temperature because of the narrowing of the NC region and because of the saturation of the amplification. A counter-clockwise rotation of the P-V loops with an associated increase of the dP/dV slope with the temperature is reported, which corresponds to an increase of the overall ferroelectric capacitance with the temperature. Finally, we theoretically and experimentally demonstrate that an optimum temperature exists at which the amplification gets its maximum.
Analytic model for the efficiency droop in semiconductors with asymmetric carrier-transport properties based on drift-induced reduction of injection efficiency
Authors: Lin Guan-Bo , Meyaard David , Cho Jaehee , Fred Schubert E. , Shim Hyunwook , Sone Cheolsoo
Published: April 2012

An analytic model is developed for the droop in the efficiency-versus-current curve for light-emitting diodes (LEDs) made from semiconductors having strong asymmetry in carrier concentration and mobility. For pn-junction diodes made of such semiconductors, the high-injection condition is generalized to include mobilities. Under high-injection conditions, electron drift in the p-type layer causes a reduction in injection efficiency. The drift-induced leakage term is shown to have a 3rd and 4th power dependence on the carrier concentration in the active region; the values of the 3rd- and 4th-order coefficients are derived. The model is suited to explain experimental efficiency-versus-current curves of LEDs.
An origami tunable metamaterial
Authors: Fuchi Kazuko , Diaz Alejandro R. , Rothwell Edward J. , Ouedraogo Raoul O. , Tang Junyan
Published: April 2012

The transmission characteristics of a folded surface decorated with a periodic arrangement of split-ring resonators is investigated. The folding pattern has one displacement degree of freedom, allowing motion that can be used to adjust the separation between the rings. When the geometry of the folded surface is varied by mechanical means, the change in spacing between the rings causes a shift in resonance frequency, making the surface mechanically tunable.
Metal-insulator transition in doped Ca2RuO4: Potential application in bolometric detection
Authors: Fobes D. , Vehstedt E. , Peng J. , Wang G. C. , Liu T. J. , Mao Z. Q.
Published: April 2012

We report that the first-order metal-insulator (MI) transition in perovskite ruthenate Ca2RuO4 can be tuned to a nearly second order transition with the transition temperature close to room temperature via Sr, Ti, and Fe chemical doping. The resistivity near this transition ranges from 10-2-10-1Ω-cm. The maximum temperature coefficient of resistance TCR(= −(1/R)dR/dT near the transition exceeds 0.4 K−1. This MI transition can also be tuned by a relatively small bias-current. These properties suggest that doped calcium ruthenates can be considered an alternative material for improving upon existing bolometric technologies.
Non-equilibrium Green’s function calculation for GaN-based terahertz-quantum cascade laser structures
Authors: Yasuda H. , Kubis T. , Hosako I. , Hirakawa K.
Published: April 2012

We theoretically investigated GaN-based resonant phonon terahertz-quantum cascade laser (QCL) structures for possible high-temperature operation by using the non-equilibrium Green’s function method. It was found that the GaN-based THz-QCL structures do not necessarily have a gain sufficient for lasing, even though the thermal backfilling and the thermally activated phonon scattering are effectively suppressed. The main reason for this is the broadening of the subband levels caused by a very strong interaction between electrons and longitudinal optical (LO) phonons in GaN.
Non-localized trapping effects in AlGaN/GaN heterojunction field-effect transistors subjected to on-state bias stress
Authors: Hu Cheng-Yu , Hashizume Tamotsu
Published: April 2012

For AlGaN/GaN heterojunction field-effect transistors, on-state-bias-stress (on-stress)-induced trapping effects were observed across the entire drain access region, not only at the gate edge. However, during the application of on-stress, the highest electric field was only localized at the drain side of the gate edge. Using the location of the highest electric field as a reference, the trapping effects at the gate edge and at the more distant access region were referred to as localized and non-localized trapping effect, respectively. Using two-dimensional-electron-gas sensing-bar (2DEG-sensing-bar) and dual-gate structures, the non-localized trapping effects were investigated and the trap density was measured to be ∼1.3 × 1012 cm−2. The effect of passivation was also discussed. It was found that both surface leakage currents and hot electrons are responsible for the non-localized trapping effects with hot electrons having the dominant effect. Since hot electrons are generated from the 2DEG channel, it is highly likely that the involved traps are mainly in the GaN buffer layer. Using monochromatic irradiation (1.24–2.81 eV), the trap levels responsible for the non-localized trapping effects were found to be located at 0.6–1.6 eV from the valence band of GaN. Both trap-assisted impact ionization and direct channel electron injection are proposed as the possible mechanisms of the hot-electron-related non-localized trapping effect. Finally, using the 2DEG-sensing-bar structure, we directly confirmed that blocking gate injected electrons is an important mechanism of Al2O3 passivation.
A high resolution and large solid angle x-ray Raman spectroscopy end-station at the Stanford Synchrotron Radiation Lightsource
Authors: Sokaras D. , Nordlund D. , Weng T.-C. , Mori R. Alonso , Velikov P. , Wenger D. , Garachtchenko A. , George M. , Borzenets V. , Johnson B. , Qian Q. , Rabedeau T. , Bergmann U.
Published: April 2012

We present a new x-ray Raman spectroscopy end-station recently developed, installed, and operated at the Stanford Synchrotron Radiation Lightsource. The end-station is located at wiggler beamline 6-2 equipped with two monochromators-Si(111) and Si(311) as well as collimating and focusing optics. It consists of two multi-crystal Johann type spectrometers arranged on intersecting Rowland circles of 1 m diameter. The first one, positioned at the forward scattering angles (low-q), consists of 40 spherically bent and diced Si(110) crystals with 100 mm diameters providing about 1.9% of 4π sr solid angle of detection. When operated in the (440) order in combination with the Si (311) monochromator, an overall energy resolution of 270 meV is obtained at 6462.20 eV. The second spectrometer, consisting of 14 spherically bent Si(110) crystal analyzers (not diced), is positioned at the backward scattering angles (high-q) enabling the study of non-dipole transitions. The solid angle of this spectrometer is about 0.9% of 4π sr, with a combined energy resolution of 600 meV using the Si (311) monochromator. These features exceed the specifications of currently existing relevant instrumentation, opening new opportunities for the routine application of this photon-in/photon-out hard x-ray technique to emerging research in multidisciplinary scientific fields, such as energy-related sciences, material sciences, physical chemistry, etc.
Coarse-grained modeling of the structural states and transition underlying the powerstroke of dynein motor domain
Authors: Zheng Wenjun
Published: April 2012

This study aims to model a minimal dynein motor domain capable of motor function, which consists of the linker domain, six AAA+ modules (AAA1–AAA6), coiled coil stalk, and C-terminus domain. To this end, we have used the newly solved X-ray structures of dynein motor domain to perform a coarse-grained modeling of dynein's post- and pre-powerstroke conformation and the conformational transition between them. First, we have used normal mode analysis to identify a single normal mode that captures the coupled motions of AAA1–AAA2 closing and linker domain rotation, which enables the ATP-driven recovery stroke of dynein. Second, based on the post-powerstroke conformation solved crystallographically, we have modeled dynein's pre-powerstroke conformation by computationally inducing AAA1–AAA2 closing and sliding of coiled coil stalk, and the resulting model features a linker domain near the pre-powerstroke position and a slightly tilted stalk. Third, we have modeled the conformational transition from pre- to post-powerstroke conformation, which predicts a clear sequence of structural events that couple microtubule binding, powerstroke and product release, and supports a signaling path from stalk to AAA1 via AAA3 and AAA4. Finally, we have found that a closed AAA3–AAA4 interface (compatible with nucleotide binding) is essential to the mechano-chemical coupling in dynein. Our modeling not only offers unprecedented structural insights to the motor function of dynein as described by past single-molecule, fluorescence resonance energy transfer, and electron microscopy studies, but also provides new predictions for future experiments to test.
Self-passivation of transparent single-walled carbon nanotube films on plastic substrates by microwave-induced rapid nanowelding
Authors: Tark Han Joong , Kim Daeho , Suk Kim Jun , Kwon Seol Seung , Yol Jeong Seung , Jin Jeong Hee , Suk Chang Won , Lee Geon-Woong , Jung Sunshin
Published: April 2012

We developed a straightforward method for enhancing the environmental stability of transparent single-walled carbon nanotube (SWCNT) network films on plastic substrates using a rapid microwave heating to produce SWCNT film–substrate nanowelding without any chemicals. The selective heating of SWCNTs induced by microwave irradiation leads to embedding the SWCNTs in the substrate, even within 10 s, without distortion of the substrate. The SWCNTs-embedded surface of the substrate played the role of a self-passivation layer that protected the SWCNTs from water molecules. The sheet resistance values of the nanowelded films had not increased more than 10%.
Snake states and Klein tunneling in a graphene Hall bar with a pn-junction
Authors: Barbier M. , Papp G. , Peeters F. M.
Published: April 2012

The Hall (RH) and bend (RB) resistances of a graphene Hall bar structure containing a pn-junction are calculated when in the ballistic regime. The simulations are done using the billiard model. Introducing a pn-junction—dividing the Hall bar geometry in two regions—leads to two distinct regimes exhibiting very different physics: (1) both regions are of n-type and (2) one region is n-type and the other p-type. In regime (1), a “Hall plateau”—an enhancement of the resistance—appears for RH. On the other hand, in regime (2), we found a negative RH, which approaches zero for large B. The bend resistance is highly asymmetric in regime (2) and the resistance increases with increasing magnetic field B in one direction while it reduces to zero in the other direction.
Conductivity mechanism of nanosized silver layer embedded in indium zinc oxide
Authors: Sun Jian , Lai Weng Soon , Gong Hao
Published: April 2012

Silver (Ag) embedding in indium zinc oxide (IZO) leads to abnormal conductivity behavior for IZO-Ag-IZO (IAI) system. When Ag layer is thinner than a critical Ag thickness, the IAI sample shows semiconductor behavior, and its resistivity is unexpectedly higher than that of IZO but decreases with an increase in Ag thickness. After surpassing the critical thickness, metallic conduction characteristics appear and the resistivity is lower than IZO and decreases with further increasing Ag thickness. A conduction model/formula is proposed, by which experimental data are well fitted. Haacke figure of merit can be 3 times higher than that of IZO.
Photovoltaic infrared detection with p-type graded barrier heterostructures
Authors: Pitigala P. K. D. D. P. , Matsik S. G. , Perera A. G. U. , Khanna S. P. , Li L. H. , Linfield E. H. , Wasilewski Z. R. , Buchanan M. , Liu H. C.
Published: April 2012

Photovoltaic infrared detectors have significant advantages over photoconductive detectors due to zero bias operation, requiring low power and having reduced low frequency noise. They also exhibit no thermally assisted tunneling currents, leading to higher operating temperatures. p-type emitter/graded barrier GaAs/AlxGa1−xAs structures were tested as photovoltaic detectors in the infrared region, operating under uncooled conditions and without an applied bias voltage. A photovoltaic responsivity of 450 mV/W was obtained with a detectivity (D*) of 1.2 × 106 Jones at a peak wavelength 1.8 μm at 300 K. Responsivity and D* increased to ∼1.2 V/W and 2.8 × 106 Jones, respectively, at 280 K. A non-linear improvement in responsivity was observed with increased emitter thickness.
Breakdown voltage reliability improvement in gas-discharge tube surge protectors employing graphite field emitters
Authors: Žumer Marko , Zajec Bojan , Rozman Robert , Nemanič Vincenc
Published: April 2012

Gas-discharge tube (GDT) surge protectors are known for many decades as passive units used in low-voltage telecom networks for protection of electrical components from transient over-voltages (discharging) such as lightning. Unreliability of the mean turn-on DC breakdown voltage and the run-to-run variability has been overcome successfully in the past by adding, for example, a radioactive source inside the tube. Radioisotopes provide a constant low level of free electrons, which trigger the breakdown. In the last decades, any concept using environmentally harmful compounds is not acceptable anymore and new solutions were searched. In our application, a cold field electron emitter source is used as the trigger for the gas discharge but with no activating compound on the two main electrodes. The patent literature describes in details the implementation of the so-called trigger wires (auxiliary electrodes) made of graphite, placed in between the two main electrodes, but no physical explanation has been given yet. We present experimental results, which show that stable cold field electron emission current in the high vacuum range originating from the nano-structured edge of the graphite layer is well correlated to the stable breakdown voltage of the GDT surge protector filled with a mixture of clean gases.
2D particle-in-cell simulations of ion acceleration in laser irradiated submicron clusters including field ionization
Authors: Psikal J. , Klimo O. , Limpouch J.
Published: April 2012

The interaction of femtosecond laser pulses with submicron water clusters is studied here by two-dimensional particle-in-cell simulations. Field ionization is included in our simulations using Ammosov–Delone–Krainov ionization rate. We search for optimum laser and cluster parameters to obtain quasimonoenergetic beam of protons accelerated from the cluster. For the laser amplitude a0≈3 used in recent experiments, the optimum cluster size is about 150 nm for the generation of pronounced peak in proton energy distribution function at maximum energy and the optimum laser pulse duration is about 40–80 fs. Various initial density profiles of cluster plasma, formed due to insufficient laser pulse contrast and prepulses, are involved in this study, including underdense clusters.
Lateral spin transport through bulk silicon
Authors: Li Jing , Appelbaum Ian
Published: April 2012

Using ballistic hot electron techniques, we demonstrate lateral spin transport through a bulk Si wafer. Despite a wide spin transport time distribution caused by transport path variation in the 400 μm-thick Si channel, the absence of a buried interface in close proximity increases the observed spin lifetime to approximately 100 ns at 61 K. The relative insensitivity of this lifetime to temperature variation (and its absolute magnitude) indicates a contribution from an extrinsic depolarization mechanism such as disorder and defects at the exposed air/Si interface in the transport region between injector and detector.
Pattern formation in a reaction-diffusion-advection system with wave instability
Authors: Berenstein Igal
Published: April 2012

In this paper, we show by means of numerical simulations how new patterns can emerge in a system with wave instability when a unidirectional advective flow (plug flow) is added to the system. First, we introduce a three variable model with one activator and two inhibitors with similar kinetics to those of the Oregonator model of the Belousov-Zhabotinsky reaction. For this model, we explore the type of patterns that can be obtained without advection, and then explore the effect of different velocities of the advective flow for different patterns. We observe standing waves, and with flow there is a transition from out of phase oscillations between neighboring units to in-phase oscillations with a doubling in frequency. Also mixed and clustered states are generated at higher velocities of the advective flow. There is also a regime of “waving Turing patterns” (quasi-stationary structures that come close and separate periodically), where low advective flow is able to stabilize the stationary Turing pattern. At higher velocities, superposition and interaction of patterns are observed. For both types of patterns, at high velocities of the advective field, the known flow distributed oscillations are observed.
Lock-in detection for pulsed electrically detected magnetic resonance
Authors: Hoehne Felix , Dreher Lukas , Behrends Jan , Fehr Matthias , Huebl Hans , Lips Klaus , Schnegg Alexander , Suckert Max , Stutzmann Martin , Brandt Martin S.
Published: April 2012

We show that in pulsed electrically detected magnetic resonance (pEDMR) signal modulation in combination with a lock-in detection scheme can reduce the low-frequency noise level by one order of magnitude and in addition removes the microwave-induced non-resonant background. This is exemplarily demonstrated for spin-echo measurements in phosphorus-doped silicon. The modulation of the signal is achieved by cycling the phase of the projection pulse used in pEDMR for the readout of the spin state.
Ferromagnetic nickel silicide nanowires for isolating primary CD4+ T lymphocytes
Authors: Kim Dong-Joo , Seol Jin-Kyeong , Lee Mi-Ri , Hyung Jung-Hwan , Kim Gil-Sung , Ohgai Takeshi , Lee Sang-Kwon
Published: April 2012

Direct CD4+ T lymphocytes were separated from whole mouse splenocytes using 1-dimensional ferromagnetic nickel silicide nanowires (NiSi NWs). NiSi NWs were prepared by silver-assisted wet chemical etching of silicon and subsequent deposition and annealing of Ni. This method exhibits a separation efficiency of ∼93.5%, which is comparable to that of the state-of-the-art superparamagnetic bead-based cell capture (∼96.8%). Furthermore, this research shows potential for separation of other lymphocytes, B, natural killer and natural killer T cells, and even rare tumor cells simply by changing the biotin-conjugated antibodies.
FeNi-based magnetoimpedance multilayers: Tailoring of the softness by magnetic spacers
Authors: Svalov A. V. , Fernandez E. , Garcia-Arribas A. , Alonso J. , Fdez-Gubieda M. L. , Kurlyandskaya G. V.
Published: April 2012

The microstructure and magnetic properties of sputtered permalloy films and FeNi(170 nm)/X/FeNi(170 nm) (X = Co, Fe, Gd, Gd-Co) sandwiches were studied. Laminating of the thick FeNi film with various spacers was done in order to control the magnetic softness of FeNi-based multilayers. In contrast to the Co and Fe spacers, Gd and Gd-Co magnetic spacers improved the softness of the FeNi/X/FeNi sandwiches. The magnetoimpedance responses were measured for [FeNi/Ti(6 nm)]2/FeNi and [FeNi/Gd(2 nm)]2/FeNi multilayers in a frequency range of 1–500 MHz: for all frequencies under consideration the highest magnetoimpedance variation was observed for [FeNi/Gd(2 nm)]2/FeNi multilayers.
Nano-electron beam induced current and hole charge dynamics through uncapped Ge nanocrystals
Authors: Marchand A. , El Hdiy A. , Troyon M. , Amiard G. , Ronda A. , Berbezier I.
Published: April 2012

Dynamics of hole storage in spherical Ge nanocrystals (NCs) formed by a two step dewetting/nucleation process on an oxide layer grown on an n-doped 〈001〉 silicon substrate is studied using a nano-electron beam induced current technique. Carrier generation is produced by an electron beam irradiation. The generated current is collected by an atomic force microscope—tip in contact mode at a fixed position away from the beam spot of about 0.5 µm. This distance represents the effective diffusion length of holes. The time constants of holes charging are determined and the effect of the NC size is underlined.
Flow biosensing and sampling in indirect electrochemical detection
Authors: Lamberti Francesco , Luni Camilla , Zambon Alessandro , Andrea Serra Pier , Giomo Monica , Elvassore Nicola
Published: April 2012

Miniaturization in biological analyses has several advantages, such as sample volume reduction and fast response time. The integration of miniaturized biosensors within lab-on-a-chip setups under flow conditions is highly desirable, not only because it simplifies process handling but also because measurements become more robust and operator-independent. In this work, we study the integration of flow amperometric biosensors within a microfluidic platform when analyte concentration is indirectly measured. As a case study, we used a platinum miniaturized glucose biosensor, where glucose is enzymatically converted to H2O2 that is oxidized at the electrode. The experimental results produced are strongly coupled to a theoretical analysis of fluid dynamic conditions affecting the electrochemical response of the sensor. We verified that the choice of the inlet flow rate is a critical parameter in flow biosensors, because it affects both glucose and H2O2 transport, to and from the electrode. We identify optimal flow rate conditions for accurate sensing at high time resolution. A dimensionless theoretical analysis allows the extension of the results to other sensing systems according to fluid dynamic similarity principles. Furthermore, we developed a microfluidic design that connects a sampling unit to the biosensor, in order to decouple the sampling flow rate from that of the actual measurement.
Thermal performance of a focusing type collector for paraffin wax melting
Authors: Kurchania A. K. , Panwar N. L. , Mishra Dinesh , Salvi B. L.
Published: April 2012

A solar paraboloid concentrator was designed and developed for paraffin wax melting having 1.32 m2 aperture area and 0.25 m focal length. The performance of the system was evaluated in terms of optical efficiency factor (F′no) and overall heat loss factor (F′UL) by sensible water heating and cooling tests, respectively. The values of the optical efficiency factor (F′no) and overall heat loss factor (F′UL) were found to be 0.2125 and 39.46 W/m2 K, respectively.
Thermal performance of a passive test room with a Trombe wall in Tunisia
Authors: Dimassi N. , Dehmani L.
Published: April 2012

A great amount of energy consumption occurs in buildings due to indoor heating, cooling, ventilation, and lighting. Among these, the energy consumed for heating in buildings has the biggest proportion of consumption. So, the use of renewable sources of energy such as solar energy is the ideal solution to reduce the energy bill. In this context, proper structure elements and architecture need to be considered for the utilization of solar energy in passive ways and for decreasing energy losses to a great extent. The Trombe wall is an excellent passive solar system which relies on natural driving forces and on storing energy. This paper reports on an experimental investigation of a test room containing a Trombe wall in Borj Cedria Tunisia and compares the wall performance for different periods of the year (autumn, winter, and spring). In this study, the phenomenon of natural convection has been highlighted with accuracy measurement and the thermal behavior of the wall was also investigated. In consequence of the experimental study, the convective and the conductive flux were quantified and the thermal efficiency of the wall during the studied periods was estimated. From the comparison of results, the best efficiency of the wall equal to 45% was obtained in the winter period. The operating efficiency is also good in autumn period and the wall offers a good potential of heating.
Note: Self Q-switched Nd:YVO4 laser at 914 nm
Authors: Gupta Pradeep K. , Singh Amarjeet , Sharma Sunil K. , Mukhopadhyay Pranab K. , Bindra Kushvinder S. , Oak Shrikant M.
Published: April 2012

By exploiting the saturable nature of re-absorption loss under the quasi-three-level laser transition self Q-switching operation in Nd:YVO4 laser at 914 nm is demonstrated. The stable self-pulsing operation was observed with Nd:YVO4 crystal with doping concentration of 0.3 at.%. At an incident pump power of 30 W around 600 mW of average power was obtained. Individual pulse energy and FWHM pulse duration were experimentally measured to be 10 μJ and 460 ns, respectively. The performance of the laser was analyzed with the help of a rate equation model. The simulation results show good agreement with the experiment.
microRNA-301a regulation of a T-helper 17 immune response controls autoimmune demyelination
Authors: Mycko Marcin P. , Cichalewska Maria , Machlanska Agnieszka , Cwiklinska Hanna , Mariasiewicz Magdalena , Selmaj Krzysztof W.
Published: April 2012

MicroRNAs (miRNAs) are an emerging group of short, noncoding RNAs that play an important role in regulating expression of classical genes. Thus far little is known about their role in autoimmune demyelination. In this study, we analyzed changes in the miRNA profile in CD4
+
T cells that occurred during the recognition of the myelin autoantigen, MOG
35–55
. We found that, both in vivo and in vitro, myelin antigen stimulation resulted in significant up-regulation of miR-301a, miR-21, and miR-155. Furthermore, these three miRNAs were overexpressed in T cells infiltrating the CNS in animals with experimental autoimmune encephalomyelitis. Use of specific miRNA antagonists, antagomirs, revealed that miR-301a contributed to the development of the T-helper type 17 subset via targeting the IL-6/23–STAT3 pathway. This contribution appeared to be mediated by the miR-301a effect on the expression of the PIAS3, a potent inhibitor of the STAT3 pathway. Manipulation of miR-301a levels or PIAS3 expression in myelin-specific CD4
+
T cells led to significant changes in the severity of experimental autoimmune encephalomyelitis. Thus, we have identified a role of miR-301a in regulating the function of myelin-reactive T-helper type 17 cells, supporting a role for miR-301a and PIAS3 as candidates for therapeutic targets for controlling of autoimmune demyelination.
Single amino acid radiocarbon dating of Upper Paleolithic modern humans
Authors: Marom Anat , McCullagh James S. O. , Higham Thomas F. G. , Sinitsyn Andrey A. , Hedges Robert E. M.
Published: April 2012

Archaeological bones are usually dated by radiocarbon measurement of extracted collagen. However, low collagen content, contamination from the burial environment, or museum conservation work, such as addition of glues, preservatives, and fumigants to “protect” archaeological materials, have previously led to inaccurate dates. These inaccuracies in turn frustrate the development of archaeological chronologies and, in the Paleolithic, blur the dating of such key events as the dispersal of anatomically modern humans. Here we describe a method to date hydroxyproline found in collagen (∼10% of collagen carbon) as a bone-specific biomarker that removes impurities, thereby improving dating accuracy and confidence. This method is applied to two important sites in Russia and allows us to report the earliest direct ages for the presence of anatomically modern humans on the Russian Plain. These dates contribute considerably to our understanding of the emergence of the Mid-Upper Paleolithic and the complex suite of burial behaviors that begin to appear during this period.