bluuebunny/crossref_metadata_2025 huggingface dataset:
Almost perfect sequences applied for ionospheric oblique backscattering detection
Authors: Chen Gang , Zhao Zhengyu , Pu Tianyao , Huang Yujie , Zhu Guoqiang
Published: October 2009

Pseudorandom sequences are often used in radio systems; however, the nonzero out‐of‐phase autocorrelation of many binary sequences induces range sidelobes which significantly reduce the echo signal‐to‐noise ratio (SNR). In this paper, the use of almost perfect sequences, exhibiting zero out‐of‐phase autocorrelation except one value in the middle is examined with reference to common m sequences and perfect sequence. The ambiguity functions demonstrate that it is possible to use the almost perfect sequences for ranging without sidelobes and that their Doppler measurement performance is similar to m sequence of the same length. This is an important result for ionospheric oblique backscattering detection where the echoes are superposed and where range sidelobes can submerge the main lobes of weak signals. The 124‐bit almost perfect sequence and the 127‐bit m sequence are applied to the Wuhan Ionospheric Oblique Backscattering Sounding System for sequence testing. The test results have proven that the almost perfect sequence exhibits a higher echo SNR for the same detection conditions.
A phase field model of unsaturated flow
Authors: Cueto‐Felgueroso L. , Juanes R.
Published: October 2009

We present a phase field model of infiltration that explains the formation of gravity fingers during water infiltration in soil. The model is an extension of the traditional Richards equation, and it introduces a new term, a fourth‐order derivative in space, but not a new parameter. We propose a scaling that links the magnitude of the new term to the relative strength of gravity‐to‐capillary forces already present in Richards' equation. We exploit the thermodynamic framework to design a flow potential that constrains the water saturation to be between 0 and 1, its physically admissible values. The model predicts a saturation overshoot at the wetting front, which is in good agreement with experimental measurements. Two‐dimensional numerical simulations predict gravity fingers with the appearance and characteristics observed in visual laboratory experiments. A linear stability analysis of the model shows that there is a direct relation between saturation overshoot and the strength of the front instability. Therefore our theory supports the conjecture that saturation overshoot, a pileup of water at the wetting front, is a prerequisite for gravity fingering.
Narrowing of T‐cell receptor beta variable repertoire during symptomatic herpesvirus infection in transplant patients
Authors: Wynn Katherine K , Crough Tania , Campbell Scott , McNeil Keith , Galbraith Andrew , Moss Denis J , Silins Sharon L , Bell Scott , Khanna Rajiv
Published: October 2009

Primary infection or recrudescence of latent virus infection in transplant recipients can be manifested either as asymptomatic or symptomatic disease. Here we show that symptomatic human cytomegalovirus (HCMV) or Epstein–Barr virus (EBV) infection or recrudescence following solid organ transplantation (SOT) was coincident with a dramatic skewing of T‐cell receptor beta variable (TRBV) repertoire, with expansions of monoclonal/oligoclonal clonotypes. As the clinical symptoms resolved, the peripheral blood repertoire reverted to a more diverse distribution. In contrast, SOT recipients with asymptomatic or no viral infection or recrudescence showed minimal or no skewing of the T‐cell receptor repertoire to maintain peripheral blood repertoire diversity. More importantly, we show that large monoclonal/oligoclonal repertoire expansions are associated with the loss of HCMV‐specific T‐cell function observed in SOT patients undergoing symptomatic viral infection or recrudescence, whereas SOT recipients who maintain peripheral blood TRBV repertoire diversity and functional antigen‐specific T‐cell responses can resist clinical symptomatic disease in spite of high levels of viral load.
Comparative NMR studies of diffusional water permeability of red blood cells from different species: XVI Dingo (Canis familiaris dingo) and dog (Canis familiaris)
Authors: Benga Gheorghe , Chapman Bogdan E. , Matei Horea , Cox Guy C. , Romeo Tony , Mironescu Eugen , Kuchel Philip W.
Published: October 2009

As part of a programme of comparative measurements of P d (diffusional water permeability) the RBCs (red blood cells) from dingo (Canis familiaris dingo) and greyhound dog (Canis familiaris) were studied. The morphologies of the dingo and greyhound RBCs [examined by light and SEM (scanning electron microscopy)] were found to be very similar, with regard to aspect ratio and size; the mean diameters were estimated to be the same (∼7.2 μm) for both dingo and greyhound RBCs. The water diffusional permeability was monitored by using an Mn2+‐doping 1H NMR technique at 400 MHz. The P d (cm/s) values of dingo and greyhound RBCs were similar: 6.5×10−3 at 25°C, 7.5×10−3 at 30°C, 10×10−3 at 37°C and 11.5×10−3 at 42°C. The inhibitory effect of a mercury‐containing SH (sulfhydryl)‐modifying reagent PCMBS (p‐chloromercuribenzene sulfonate) was investigated. The maximal inhibition of dingo and greyhound RBCs was reached in 15–30 min at 37°C with 2 mmol/l PCMBS. The values of maximal inhibition were in the range 72–74% when measured at 25°C and 30°C, and ∼66% at 37°C. The lowest value of P d (corresponding to the basal permeability to water) was ∼2–3×10−3 cm/s in the temperature range 25–37°C. The E a,d (activation energy of water diffusion) was 25 kJ/mol for dingo RBC and 23 kJ/mol for greyhound RBCs. After incubation with PCMBS, the values of E a,d increased, reaching 46–48 kJ/mol in the condition of maximal inhibition of water exchange. The electrophoretograms of membrane polypeptides of the dingo and greyhound RBCs were compared and seen to be very similar. We postulate that the RBC parameters reported in the present study are characteristic of all canine species and, in particular in the two cases presented here, these parameters have not been changed by the peculiar Australian habitat over the millennia (as in the case of the dingo) or over shorter time periods, decades or centuries (as in the case of the domestic greyhound).
DNA damage and repair in a model of rat vascular injury
Authors: Forte Amalia , Finicelli Mauro , Grossi Mario , Vicchio Mariano , Alessio Nicola , Santé Pasquale , De Feo Marisa , Cotrufo Maurizio , Berrino Liberato , Rossi Francesco , Galderisi Umberto , Cipollaro Marilena
Published: October 2009

Restenosis rates following vascular interventions still limit their long-term success. Oxidative stress plays a relevant role in this pathophysiological phenomenon, but less attention has been devoted to its effects on DNA damage and to the subsequent mechanisms of repair. In the present study, we analysed in a model of arteriotomy-induced stenosis in rat carotid arteries the time-dependent expression of DNA damage markers and of DNA repair genes, together with the assessment of proliferation and apoptosis indexes. The expression of the oxidative DNA damage marker 7,8-dihydro-8-oxo-2′-deoxyguanosine was increased at 3 and 7 days after arteriotomy, with immunostaining distributed in the injured vascular wall and perivascular tissue. Expression of the DNA damage marker phospho-H2A.X was less relevant, but increased from 4 h to 7 days after arteriotomy, with immunostaining prevalently present in the adventitia and, to a lesser extent, in medial smooth muscle cells at the injury site. RT (reverse transcription)–PCR indicated a decrease in eight out of 12 genes involved in the DNA repair machinery we selected from 4 h to 7 days after arteriotomy, with the exception of an increase in the Mutyh and Slk genes (P<0.05). Western blot analysis revealed a decrease in p53 and catalase at 3 days after arteriotomy (P<0.05). A maximal 7% of BrdU-positive cells in the endothelium and media occurred at 7 days after arteriotomy, whereas the apoptotic index peaked at 3 days after injury (P<0.05). In conclusion, our results highlight a persistent DNA damage, presumably related to a temporary decrease in the expression of the DNA repair machinery and of the antioxidant enzyme catalase, playing a role in stenosis progression.
What Are Graduate Students Really Thinking?: A Metacognitive Example
Authors: Madix Christina , Oxley Judith
Published: October 2009

The ability to integrate academic and clinical knowledge to achieve a metacognitive level of performance is paramount to being a strong clinician in the field of speech-language pathology. The support and encouragement provided by supervisors strengthens the students' abilities to develop and integrate their knowledge and strategy use in the clinical setting. This article examines the development of metacognitive thinking skills of two first-year graduate students enrolled in a graduate-level speech-language pathology program during their first semester of clinical practicum. A pilot study utilizing a qualitative approach of semi-structured interviews and video-taped therapy sessions was conducted to illustrate how differently graduate clinicians can mature in their clinical program.
Creating a Philosophy of Supervision Through Personal Narrative
Authors: McCready Vicki , Raleigh Louise
Published: October 2009

A teaching philosophy is described as “a vivid portrait of a person who is intentional about teaching practices and committed to his/her career” (Ohio State University Faculty & TA Development [OSUFTAD], 2005). Being intentional about what one does requires self-reflection, self-analysis, and ultimately self-knowledge. According to Palmer (1998), “We teach who we are… When I do not know myself, I cannot know who my students are,” (p.2). “Good teaching requires self-knowledge; it is a secret hidden in plain sight” (p.3). In this article, readers will be asked to reflect on their own life experiences, values and gifts that have influenced their decision to become clinical supervisors and to incorporate this personal narrative and reflection into the composition of a teaching philosophy, more specifically a philosophy of supervision.
Deinstitutionalization in the Context of Software Exports Policymaking in Costa Rica
Authors: Nicholson Brian , Sahay Sundeep
Published: October 2009

This paper addresses deinstitutionalization from a longitudinal perspective. Drawing on the case of software exports policymaking in Costa Rica, it analyses deinstitutionalization, paying particular attention to formation of dissensus, understood as lack of unanimity on the value of an activity that is sufficient to destabilize institutional norms and activities. The role of cultural and political factors in deinstitutionalization or persistence is considered. Based on the empirical data, a framework for understanding political and cultural dynamics in deinstitutionalization is proposed.
Absorption coefficients of intermediate-band media
Authors: Levy Michael Y. , Honsberg Christiana
Published: October 2009

This paper models the absorption coefficients of an intermediate-band (IB) absorbing medium. Equilibrium absorption coefficients are presented for several IB absorbers, each distinguished by their energy-wavevector dispersion and equilibrium temperature. Nonequilibrium absorption coefficients are also presented for solar cells implemented with IB absorbers. Several simplifying assumptions are made including that the energy-wavevector dispersions are parabolic. The model requires the absolute locations of three quasi-Fermi levels. This is made possible by using two balance equations. One of these, a charge-neutrality condition, necessitates the numerical computation of the carrier statistics in each band of the IB absorber. The use of the incomplete Fermi–Dirac functions makes this possible. The authors conclude that (i) if the concentration of intermediate states is greater than the concentration of carriers in the conduction band and greater than the concentration of carriers in the valence band, then the IB will be partially filled; (ii) an IB absorber may or may not absorb all photons with energies greater than the smallest bandgap in the system; (iii) an IB absorber may permit absorption overlap so that an absorbed photon would likely generate an electron-hole pair across a bandgap other than the largest bandgap less than the energy of the absorbed photon; (iv) as the temperature of the IB absorber approaches absolute zero, the absorption edges resulting from transitions at intermediate levels may blueshift.
Electron induced dissociation of trimethyl (methylcyclopentadienyl) platinum (IV): Total cross section as a function of incident electron energy
Authors: van Dorp W. F. , Wnuk J. D. , Gorham J. M. , Fairbrother D. H. , Madey T. E. , Hagen C. W.
Published: October 2009

The total cross section has been measured for the electron induced dissociation of trimethyl (methylcyclopentadienyl) platinum (IV) [MeCpPt(IV)Me3], a Pt precursor often used in focused electron beam induced processing (FEBIP), for incident electron energies ranging between 3–3 keV. Measurements were performed for the precursor in the adsorbed state under ultrahigh vacuum conditions. The techniques used in this study were temperature programmed desorption, x-ray photoelectron spectroscopy and mass spectrometry. Two surfaces were used in these experiments, amorphous carbon overlayers containing embedded Pt atoms (a:C-Pt), formed by the electron decomposition of the Pt precursor, and atomically clean Au. The results from these three experiments revealed a comparatively low total cross section at 8 eV (4.2±0.3×10−17 cm2 on the a:C-Pt and 1.4±0.1×10−17 cm2 on the Au) that increases with increasing incident electron energy, reaching a maximum at around 150 eV (4.1±0.5×10−16 cm2 on the a:C-Pt and 2.3±0.2×10−16 cm2 on the clean Au), before decreasing at higher incident electron energies, up to 3000 eV. Differences in the measured cross sections between Au and a:C-Pt surfaces demonstrate that the substrate can influence the reaction cross section of adsorbed species. Temperature programmed desorption was also used to measure the adsorption energy of MeCpPt(IV)Me3, which was found to depend on both the substrate and the adsorbate coverage. The work in this paper demonstrates that surface science techniques can be used to quantitatively determine the total cross section of adsorbed FEBIP precursors for electron induced dissociation as a function of incident electron energy. These total cross section values are necessary to obtain quantitatively accurate information from FEBIP models and to compare the reaction efficiencies of different precursors on a quantitative basis.
A note on the definition of deformed exponential and logarithm functions
Authors: Oikonomou Thomas , Bagci G. Baris
Published: October 2009

The recent generalizations of the Boltzmann–Gibbs statistics mathematically rely on the deformed logarithmic and exponential functions defined through some deformation parameters. In the present work, we investigate whether a deformed logarithmic/exponential map is a bijection from R+/R (set of positive real numbers/all real numbers) to R/R+, as their undeformed counterparts. We show that their inverse map exists only in some subsets of the aforementioned (co)domains. Furthermore, we present conditions which a generalized deformed function has to satisfy, so that the most important properties of the ordinary functions are preserved. The fulfillment of these conditions permits us to determine the validity interval of the deformation parameters. We finally apply our analysis to Tsallis q-deformed functions and discuss the interval of concavity of the Rényi entropy.
Advanced techniques for neoclassical tearing mode control in DIII-D
Authors: Volpe F. A. G. , Austin M. E. , La Haye R. J. , Lohr J. , Prater R. , Strait E. J. , Welander A. S.
Published: October 2009

Two techniques were developed at DIII-D [J. L. Luxon, Nucl. Fusion 42, 64 (2002)] to tackle ITER-specific aspects of neoclassical tearing mode (NTM) control, namely, (1) the relatively small size of the rotating islands, smaller than the electron cyclotron current drive (ECCD) deposition region, and (2) the increased tendency of the islands, compared to present devices, to lock to the wall or to the residual error field, in a position not necessarily accessible to ECCD. Modulated ECCD is known to suppress small islands more efficiently, when “broad,” than continuous ECCD. At DIII-D, a NTM of poloidal/toroidal mode numbers m/n=3/2 was completely stabilized by a new technique where oblique electron cyclotron emission acted at the same time as an indicator of good alignment between ECCD and the island, and as a waveform generator, for modulation in synch and in phase with the island O-point. In another experiment, after locking in an unfavorable position, a 2/1 island was steered by externally generated magnetic perturbations, brought in the view of the gyrotrons and partly stabilized by ECCD in the island O-point. Magnetic perturbations were also used to sustain and control the mode rotation, which has the potential for an easier ECCD modulation.
Lithium niobate nanowires synthesis, optical properties, and manipulation
Authors: Grange Rachel , Choi Jae-Woo , Hsieh Chia-Lung , Pu Ye , Magrez Arnaud , Smajda Rita , Forró László , Psaltis Demetri
Published: October 2009

Free-standing lithium niobate nanowires (LiNbO3) are synthesized by the hydrothermal route. The polarization response of the second harmonic generation (SHG) signal is measured in a single nanowire and used to identify the crystal orientation by matching with bulk LiNbO3 nonlinear optical susceptibility. The electrical manipulation of a LiNbO3 nanowire and its monitoring through the SHG signal in a fluidic setup are demonstrated.
Confocal single molecule fluorescence spectroscopy in ultrahigh vacuum
Authors: Blumenfeld Michael L. , Tackett Brandon S. , Schirra Laura K. , Tyler Jason M. , Monti Oliver L. A.
Published: October 2009

We have constructed an ultrahigh vacuum confocal fluorescence microscope with the purpose of performing single molecule spectroscopy under highly defined conditions. The microscope is designed for high stability while affording the capability of sample preparation, sample transfer, and optical detection in ultrahigh vacuum. It achieves near-diffraction-limited performance and allows the observation of single molecule fluorescence dynamics over extended periods of time. The design of the microscope is discussed in detail and the performance is demonstrated with single molecule fluorescence images and trajectories of N,N′-dibutylperylene-3,4,9,10-dicarboxyimide deposited onto several different surfaces. This instrument further enhances the array of available surface science techniques, permitting spectroscopic investigations of molecule-surface interactions at the single molecule level and on insulating surfaces.
Inversion of radial distribution functions to pair forces by solving the Yvon–Born–Green equation iteratively
Authors: Cho Hyung Min , Chu Jhih-Wei
Published: October 2009

We develop a new method to invert the target profiles of radial distribution functions (RDFs) to the pair forces between particles. The target profiles of RDFs can be obtained from all-atom molecular dynamics (MD) simulations or experiments and the inverted pair forces can be used in molecular simulations at a coarse-grained (CG) scale. Our method is based on a variational principle that determines the mean forces between CG sites after integrating out the unwanted degrees of freedom. The solution of this variational principle has been shown to correspond to the Yvon–Born–Green (YBG) equation [Noid et al., J. Phys. Chem. B 111, 4116 (2007)]. To invert RDFs, we solve the YBG equation iteratively by running a CG MD simulation at each step of iteration. A novelty of the iterative-YBG method is that during iteration, CG forces are updated according to the YBG equation without imposing any approximation as is required by other methods. As a result, only three to ten iterations are required to achieve convergence for all cases tested in this work. Furthermore, we show that not only are the target RDFs reproduced by the iterative solution; the profiles of the three-body correlation function in the YBG equation computed from all-atom and CG simulations also have a better agreement. The iterative-YBG method is applied to compute the CG forces of four molecular liquids to illustrate its efficiency and robustness: water, ethane, ethanol, and a water/methanol mixture. Using the resulting CG forces, all of the target RDFs observed in all-atom MD simulations are reproduced. We also show that the iterative-YBG method can be applied with a virial constraint to expand the representability of a CG force field. The iterative-YBG method thus provides a general and robust framework for computing CG forces from RDFs and could be systematically generalized to go beyond pairwise forces and to include higher-body interactions in a CG force field by applying the aforementioned variational principle to derive the corresponding YBG equation for iterative solution.
Quantum mechanical scoring for protein docking
Authors: Cho Art E. , Chung Jae Yoon , Kim Minsup , Park Kichul
Published: October 2009

We develop a docking protocol based on quantum mechanical/molecular mechanical calculations in which quantum mechanical energy is used as scoring. We test the protocol with three groups of examples with various binding site characteristics. The new docking method performs as well as or better than conventional docking methods in all three groups. In particular, for proteins with primarily hydrophobic binding sites, structural motifs with possible π-π interactions are often found and it is shown that these can be better modeled with quantum mechanical scoring docking than force field based methods. It seems that the new method performs in such cases to a great accuracy.
Inverse scattering transform for the Toda hierarchy with steplike finite-gap backgrounds
Authors: Egorova Iryna , Michor Johanna , Teschl Gerald
Published: October 2009

We provide a rigorous treatment of the inverse scattering transform for the entire Toda hierarchy for solutions which are asymptotically close to (in general) different finite-gap solutions as n→±∞.
Molecular simulation of crystal nucleation in n-octane melts
Authors: Yi Peng , Rutledge Gregory C.
Published: October 2009

Homogeneous nucleation of the crystal phase in n-octane melts was studied by molecular simulation with a realistic, united-atom model for n-octane. The structure of the crystal phase and the melting point of n-octane were determined through molecular dynamics simulation and found to agree with experimental results. Molecular dynamics simulations were performed to observe the nucleation events at constant pressure and constant temperature corresponding to about 20% supercooling. Umbrella sampling Monte Carlo simulations were used to calculate the nucleation free energy for three temperatures, ranging from 8% to 20% supercooling, and to reveal details of the critical nucleus for the first time. The cylindrical nucleus model was found to provide a better quantitative description of the critical nucleus than the spherical nucleus model. The interfacial free energies of the cylinder model were calculated from the simulation data. As the temperature increased, the interfacial free energy of the side surface remained relatively unchanged, at 7–8 mJ/m2, whereas the interfacial free energy of the end surface decreased significantly from 5.4 mJ/m2 to about 3 mJ/m2. These results, and the methods employed, provide valuable and quantitative information regarding the rate-limiting step during the solidification of chain molecules, with ramifications for both short alkanes and polymers.
Interactions and microstructures in electric field mediated colloidal assembly
Authors: Juárez Jaime J. , Bevan Michael A.
Published: October 2009

We report video microscopy measurements and computer simulations of quasi-two-dimensional configurations of micron sized colloids in 1 MHz ac electric fields between coplanar thin film electrodes. Interactions of induced dipoles (IDs) with each other and inhomogeneous electric fields (IFs) as a function of concentration and field amplitude produced microstructures including confined hard disk fluids, oriented dipolar chains, and oriented hexagonal close packed crystals. Equilibrium measurements and analyses of single colloids within electric fields were used to directly measure ID-IF interactions in the absence of many body effects. Measurements of concentrated systems were characterized in terms of density profiles across the electrode gap and angular pair distribution functions. In concentrated measurements, an inverse Monte Carlo analysis was used to extract the ID-ID interaction. A single adjustable parameter consistently modified the ID-IF potential and the ID-ID potential to account for weakening of ID as the result of the local particle concentration and configuration.
Reversible resistance switching in La0.225Pr0.4Ca0.375MnO3: The Joule-heat-assisted phase transition
Authors: Yan Z. B. , Wang K. F. , Li S. Z. , Luo S. J. , Liu J.-M.
Published: October 2009

The reversible resistance switching (RS) controlled by current pulse pairs, accompanied with an overshooting relaxation, is observed in bulk La0.225Pr0.4Ca0.375MnO3. We demonstrate that the reversible RS effect is not the result of current-induced intrinsic transition of charge-ordered insulator (COI) into ferromagnetic metal (FMM) phase, but the outcome of Joule-heat-assisted transition between the FMM and COI phases. A local thermal-cycle assisted rearrangement of the FMM phase in the COI matrix is controllable by a current pulse, opening a possibility for multistate memory applications.
Pressure-induced superconductivity in boron-doped Buckypapers
Authors: Nakamura J. , Matsudaira M. , Haruyama J. , Sugiura H. , Tachibana M. , Reppert J. , Rao A. , Nishio T. , Hasegawa Y. , Sano H. , Iye Y.
Published: October 2009

We show creation of paperlike thin film (Buckypaper) consisting of pseudo-two-dimensional network of boron-doped single-walled carbon nanotubes (B-SWNTs) within weakly intertube van der Waals coupling (IVDWC) state. It was formed by sufficiently dissolving as-grown ropes of B-SWNTs and densely assembling them on silicon substrate. We find that superconducting transition temperature (Tc) of 8 K under absent pressure can be induced up to 19 K by applying a small pressure to the film and that a frequency in the radial breathing phonon drastically increases with applying pressure. Discussion about IVDWC and distribution of B-SWNTs diameter imply the strong correlation.
Optimal estimators and asymptotic variances for nonequilibrium path-ensemble averages
Authors: Minh David D. L. , Chodera John D.
Published: October 2009

Existing optimal estimators of nonequilibrium path-ensemble averages are shown to fall within the framework of extended bridge sampling. Using this framework, we derive a general minimal-variance estimator that can combine nonequilibrium trajectory data sampled from multiple path-ensembles to estimate arbitrary functions of nonequilibrium expectations. The framework is also applied to obtain asymptotic variance estimates, which are a useful measure of statistical uncertainty. In particular, we develop asymptotic variance estimates pertaining to Jarzynski’s equality for free energies and the Hummer–Szabo expressions for the potential of mean force, calculated from uni- or bidirectional path samples. These estimators are demonstrated on a model single-molecule pulling experiment. In these simulations, the asymptotic variance expression is found to accurately characterize the confidence intervals around estimators when the bias is small. Hence, the confidence intervals are inaccurately described for unidirectional estimates with large bias, but for this model it largely reflects the true error in a bidirectional estimator derived by Minh and Adib.
Direct imaging of the core-shell effect in positive temperature coefficient of resistance-BaTiO3 ceramics
Authors: Fiorenza Patrick , Lo Nigro Raffaella , Delugas Pietro , Raineri Vito , Mould Andrew G. , Sinclair Derek C.
Published: October 2009

A conductive atomic force microscopy (C-AFM) study on a positive temperature coefficient of resistance (ptcr) BaTiO3 thermistor is reported. The method provides imaging of the dielectric properties with a lateral resolution on the nanometer scale. Measurements were carried out in the temperature range of 25–250 °C to study the conduction mechanisms below and above the ferroelectric-paraelectric transition at ∼130 °C. The effective thickness of the barrier regions associated with the grain-shell and grain boundaries is ∼450–550 nm and is ∼10% of the volume fraction of the grains. The C-AFM results therefore confirm previous impedance spectroscopy studies that show the ptcr-effect to be associated with both the grain boundaries and outer grain-shells of individual grains.
Sharp fall of electrical resistance for a small application of magnetic field on a metastable form of a compound, Tb5Si3, under pressure
Authors: Iyer Kartik K. , Sampathkumaran E. V.
Published: October 2009

We report an unusual sensitivity of electrical resistivity (ρ) to an application of a small magnetic field in an intermetallic compound, Tb5Si3, under pressure. In this compound, there is a magnetic-field-induced first-order magnetic transition at 1.8 K. Under pressure, there is a metastable magnetic phase after reducing the field to zero. This metastable phase is relatively of higher ρ and interestingly a small magnetic field (<2 kOe) in the reverse direction results in a sharp fall of ρ to restore virgin state ρ. The present finding could be relevant in spintronic applications.
Electrical bistabilities and carrier transport mechanisms of write-once-read-many-times memory devices fabricated utilizing ZnO nanoparticles embedded in a polystyrene layer
Authors: Yun Dong Yeol , Kwak Jin Ku , Jung Jae Hun , Kim Tae Whan , Son Dong Ick
Published: October 2009

High-resolution transmission electron microscopy images showed that ZnO nanoparticles were randomly distributed in a polystyrene (PS) layer. Current-voltage (I-V) curves at 300 K for Al/ZnO nanoparticles embedded in PS layer/indium tin oxide devices showed a current bistability with a large ON/OFF ratio of 103 for write-once-read-many-times (WORM) memory devices. The estimated retention time of the ON state for the WORM device was more than 10 years. The carrier transport mechanisms for the WORM memory device are described on the basis of the I-V results.
Bilayer graphene nanoribbon nanoelectromechanical system device: A computational study
Authors: Lam Kai-Tak , Lee Chengkuo , Liang Gengchiau
Published: October 2009

A bilayer graphene nanoribbon nanoelectromechanical device is investigated via first-principle simulations. The output characteristics as a function of interlayer distance are calculated, with the proposed device acting as a displacement and a force sensor. The operating mechanism of a bistable switch based on this device structure is also explored, and in the present floating gate design, a switching gate bias of 5.6 V is required, resulting in an ON-OFF current ratio of 3 orders at a device bias of 20 mV. This minuscule bistable device could potentially be implemented in future semiconductor memory devices and radio frequency communication circuitry.
Toward improved density functionals for the correlation energy
Authors: Thakkar Ajit J. , McCarthy Shane P.
Published: October 2009

Eleven density functionals, including some of the most widely used ones, are tested on their ability to predict nonrelativistic, electron correlation energies for the 17 atoms from He to Ar, the 17 cations from Li+ to K+, and 11 S1 state atoms from Ca to Rn. They all lead to relatively poor predictions for the heavier atoms. Reparametrization of these functionals improves their performance for light atoms but does not alleviate their problems with the heavier, closed-shell atoms. Several novel, few-parameter, density functionals for the correlation energy are developed heuristically. Four new functionals lead to qualitatively improved predictions for the heavier atoms without unreasonably compromising accuracy for the lighter atoms. Further progress would be facilitated by reliable estimates of electron correlation energies for more atoms, particularly heavy ones.
Electrically manipulating the optical sensitivity function in quantum wells for nanoacoustic wave detection
Authors: Wang Pei-Hsun , Wen Yu-Chieh , Guol Shi-Hao , Lai Chih-Ming , Lin Hung-Cheng , Chen Peng-Ren , Shi Jin-Wei , Chyi Jen-Inn , Sun Chi-Kuang
Published: October 2009

We demonstrate electrical control of the optical sensitivity function in multiple quantum wells (MQWs) for nanoacoustic wave detection. This is realized by bias controlling the quantized level and the quasi-Fermi level of carrier-populated InGaN/GaN MQWs. Experimentally, a strongly bias-dependent optical sensitivity was observed when the optical probe transition was near the quasi-Fermi level, which agrees well with the theoretical prediction.
Flow and diffusion of high-stakes test scores
Authors: Marder M. , Bansal D.
Published: October 2009

We apply visualization and modeling methods for convective and diffusive flows to public school mathematics test scores from Texas. We obtain plots that show the most likely future and past scores of students, the effects of random processes such as guessing, and the rate at which students appear in and disappear from schools. We show that student outcomes depend strongly upon economic class, and identify the grade levels where flows of different groups diverge most strongly. Changing the effectiveness of instruction in one grade naturally leads to strongly nonlinear effects on student outcomes in subsequent grades.
Learning sculpts the spontaneous activity of the resting human brain
Authors: Lewis Christopher M. , Baldassarre Antonello , Committeri Giorgia , Romani Gian Luca , Corbetta Maurizio
Published: October 2009

The brain is not a passive sensory-motor analyzer driven by environmental stimuli, but actively maintains ongoing representations that may be involved in the coding of expected sensory stimuli, prospective motor responses, and prior experience. Spontaneous cortical activity has been proposed to play an important part in maintaining these ongoing, internal representations, although its functional role is not well understood. One spontaneous signal being intensely investigated in the human brain is the interregional temporal correlation of the blood-oxygen level-dependent (BOLD) signal recorded at rest by functional MRI (functional connectivity-by-MRI, fcMRI, or BOLD connectivity). This signal is intrinsic and coherent within a number of distributed networks whose topography closely resembles that of functional networks recruited during tasks. While it is apparent that fcMRI networks reflect anatomical connectivity, it is less clear whether they have any dynamic functional importance. Here, we demonstrate that visual perceptual learning, an example of adult neural plasticity, modifies the resting covariance structure of spontaneous activity between networks engaged by the task. Specifically, after intense training on a shape-identification task constrained to one visual quadrant, resting BOLD functional connectivity and directed mutual interaction between trained visual cortex and frontal-parietal areas involved in the control of spatial attention were significantly modified. Critically, these changes correlated with the degree of perceptual learning. We conclude that functional connectivity serves a dynamic role in brain function, supporting the consolidation of previous experience.
Voltage-gated proton channels maintain pH in human neutrophils during phagocytosis
Authors: Morgan Deri , Capasso Melania , Musset Boris , Cherny Vladimir V. , Ríos Eduardo , Dyer Martin J. S. , DeCoursey Thomas E.
Published: October 2009

Phagocytosis of microbial invaders represents a fundamental defense mechanism of the innate immune system. The subsequent killing of microbes is initiated by the respiratory burst, in which nicotinamide adenine dinucleotide phosphate (NADPH) oxidase generates vast amounts of superoxide anion, precursor to bactericidal reactive oxygen species. Cytoplasmic pH regulation is crucial because NADPH oxidase functions optimally at neutral pH, yet produces enormous quantities of protons. We monitored pH
i
in individual human neutrophils during phagocytosis of opsonized zymosan, using confocal imaging of the pH sensing dye SNARF-1, enhanced by shifted excitation and emission ratioing, or SEER. Despite long-standing dogma that Na
+
/H
+
antiport regulates pH during the phagocyte respiratory burst, we show here that voltage-gated proton channels are the first transporter to respond. During the initial phagocytotic event, pH
i
decreased sharply, and recovery required both Na
+
/H
+
antiport and proton current. Inhibiting myeloperoxidase attenuated the acidification, suggesting that diffusion of HOCl into the cytosol comprises a substantial acid load. Inhibiting proton channels with Zn
2+
resulted in profound acidification to levels that inhibit NADPH oxidase. The pH changes accompanying phagocytosis in bone marrow phagocytes from HVCN1-deficient mice mirrored those in control mouse cells treated with Zn
2+
. Both the rate and extent of acidification in HVCN1-deficient cells were twice larger than in control cells. In summary, acid extrusion by proton channels is essential to the production of reactive oxygen species during phagocytosis.
A superior descriptor of random textures and its predictive capacity
Authors: Jiao Y. , Stillinger F. H. , Torquato S.
Published: October 2009

Two-phase random textures abound in a host of contexts, including porous and composite media, ecological structures, biological media, and astrophysical structures. Questions surrounding the spatial structure of such textures continue to pose many theoretical challenges. For example, can two-point correlation functions be identified that can be manageably measured and yet reflect nontrivial higher-order structural information about the textures? We present a solution to this question by probing the information content of the widest class of different types of two-point functions examined to date using inverse “reconstruction” techniques. This enables us to show that a superior descriptor is the two-point cluster function
C
2
(
r
), which is sensitive to topological connectedness information. We demonstrate the utility of
C
2
(
r
) by accurately reconstructing textures drawn from materials science, cosmology, and granular media, among other examples. Our work suggests a theoretical pathway to predict the bulk physical properties of random textures and that also has important ramifications for atomic and molecular systems.
Crystal structure of native RPE65, the retinoid isomerase of the visual cycle
Authors: Kiser Philip D. , Golczak Marcin , Lodowski David T. , Chance Mark R. , Palczewski Krzysztof
Published: October 2009

Vertebrate vision is maintained by the retinoid (visual) cycle, a complex enzymatic pathway that operates in the retina to regenerate the visual chromophore, 11-
cis
-retinal. A key enzyme in this pathway is the microsomal membrane protein RPE65. This enzyme catalyzes the conversion of all-
trans
-retinyl esters to 11-
cis
-retinol in the retinal pigment epithelium (RPE). Mutations in
RPE65
are known to be responsible for a subset of cases of the most common form of childhood blindness, Leber congenital amaurosis (LCA). Although retinoid isomerase activity has been attributed to RPE65, its catalytic mechanism remains a matter of debate. Also, the manner in which RPE65 binds to membranes and extracts retinoid substrates is unclear. To gain insight into these questions, we determined the crystal structure of native bovine RPE65 at 2.14-Å resolution. The structural, biophysical, and biochemical data presented here provide the framework needed for an in-depth understanding of the mechanism of catalytic isomerization and membrane association, in addition to the role mutations that cause LCA have in disrupting protein function.
A long-snouted, multihorned tyrannosaurid from the Late Cretaceous of Mongolia
Authors: Brusatte Stephen L. , Carr Thomas D. , Erickson Gregory M. , Bever Gabe S. , Norell Mark A.
Published: October 2009

Tyrannosaurid theropods are characterized by a generalized body plan, and all well-known taxa possess deep and robust skulls that are optimized for exerting powerful bite forces. The fragmentary Late Cretaceous
Alioramus
appears to deviate from this trend, but its holotype and only known specimen is incomplete and poorly described. A remarkable new tyrannosaurid specimen from the Maastrichtian (Late Cretaceous) of Mongolia, including a nearly complete and well-preserved skull and an extensive postcranium, represents a new species of
Alioramus
,
Alioramus altai
. This specimen conclusively demonstrates that
Alioramus
is a small, gracile, long-snouted carnivore that deviates from other tyrannosaurids in its body plan and presumably its ecological habits. As such, it increases the range of morphological diversity in one of the most familiar extinct clades. Phylogenetic analysis places
Alioramus
deep within the megapredatory Tyrannosauridae, and within the tyrannosaurine subclade that also includes
Tarbosaurus
and
Tyrannosaurus
. Both pneumatization and ornamentation are extreme compared with other tyrannosaurids, and the skull contains eight discrete horns. The new specimen is histologically aged at nine years old but is smaller than other tyrannosaurids of similar age. Despite its divergent cranial form,
Alioramus
is characterized by a similar sequence of ontogenetic changes as the megapredatory
Tyrannosaurus
and
Albertosaurus
, indicating that ontogenetic change is conservative in tyrannosaurids.
Unseen facial and bodily expressions trigger fast emotional reactions
Authors: Tamietto Marco , Castelli Lorys , Vighetti Sergio , Perozzo Paola , Geminiani Giuliano , Weiskrantz Lawrence , de Gelder Beatrice
Published: October 2009

The spontaneous tendency to synchronize our facial expressions with those of others is often termed emotional contagion. It is unclear, however, whether emotional contagion depends on visual awareness of the eliciting stimulus and which processes underlie the unfolding of expressive reactions in the observer. It has been suggested either that emotional contagion is driven by motor imitation (i.e., mimicry), or that it is one observable aspect of the emotional state arising when we see the corresponding emotion in others. Emotional contagion reactions to different classes of consciously seen and “unseen” stimuli were compared by presenting pictures of facial or bodily expressions either to the intact or blind visual field of two patients with unilateral destruction of the visual cortex and ensuing phenomenal blindness. Facial reactions were recorded using electromyography, and arousal responses were measured with pupil dilatation. Passive exposure to unseen expressions evoked faster facial reactions and higher arousal compared with seen stimuli, therefore indicating that emotional contagion occurs also when the triggering stimulus cannot be consciously perceived because of cortical blindness. Furthermore, stimuli that are very different in their visual characteristics, such as facial and bodily gestures, induced highly similar expressive responses. This shows that the patients did not simply imitate the motor pattern observed in the stimuli, but resonated to their affective meaning. Emotional contagion thus represents an instance of truly affective reactions that may be mediated by visual pathways of old evolutionary origin bypassing cortical vision while still providing a cornerstone for emotion communication and affect sharing.
Delay Sensitive, Energy Efficient and Fault Tolerant Distributed Slot Assignment Algorithm for Wireless Sensor Networks under Convergecast Data Traffic
Authors: Bekmezci Ilker , Alagöz Fatih
Published: October 2009

The scarcest resource for most of the wireless sensor networks (WSNs) is energy and the major factor in energy consumption for WSNs is communication. Not only transmission, but also reception is the source of energy consumption. The lore to decrease energy consumption is to turn off the radio circuit when it is not needed. This is why TDMA is advantageous over contention based methods. A time slot assignment algorithm is an essential part of TDMA based systems. Although centralized time slot assignment protocols are preferred in many WSNs, a centralized approach is not scalable. In this article, a new energy efficient, delay sensitive, and fault tolerant distributed time slot assignment algorithm, referred to as ft_DTSM, is proposed for sensor networks under convergecast traffic pattern. ft_DTSM aims at operating with low delay and low energy under faulty nodes assumption. Instead of random access based periods, it assigns slots with the help of tiny request slots. While traditional slot assignment algorithms do not allow assigning the same slot within two hop neighbors, because of the hidden node problem, ft_DTSM can assign, if the assignment is suitable for convergecast traffic. Simulation results have shown that both delay and energy consumption performances of ft_DTSM is superior to existing distributed slot assignment protocols for WSNs. ft_DTSM can also distribute the slots so that the network can continue its operation against a single point of failure. Although ft_DTSM has a somewhat longer execution time, its scalability characteristic may provide application specific time durations.
A Minimalist Path Detection Approach for Wireless Sensor Networks
Authors: Sharifi Mohsen , Aminfar Ali , Abdollahzadeh Elnaz
Published: October 2009

Most object tracking techniques find the exact locations of an object, while many other applications are only interested in the object's path rather than its locations. This provides an opportunity to reduce the existing tracking methods' resource usage by only focusing on the path detection. Taking advantage of this opportunity, this article presents two new minimalist approaches for accurately detecting unknown available passages in a sensor field without requiring the exact locations of the objects. In the first approach, each sensor sends its own location to a base station when it senses an object of interest. The base station uses b-spline curves to build the object's path online. Since each sensor sends its location data just once per new path, the first approach is a minimalist approach. The second approach is offline and uses non-uniform rational b-spline (NURBS) curves. Since NURBS needs weighted locations, each sensor sends its own location in addition to the number of times it has sensed an object based on the object's weight. Using the same simulation models, both approaches greatly reduce power consumption and improve the accuracy of the computed paths. The NURBS approach has proved to be robust on false alarms and improves the accuracy of path detection up to 95 percent, which is very close to detecting the object's actual path.
Passive Sensor Based Multiple Objects Tracking and Association Method in Wireless Sensor Networks
Authors: Cho Shung Han , Lee Jinseok , Hong Sangjin , Cho WeDuke
Published: October 2009

This article presents a method for dynamic data association in wireless sensor networks and addresses the issue of multiple objects tracking. The sensor node used in this article incorporates RFID reader and an acoustic sensor so that two different signals are cooperating for tracking and associating multiple objects. The RFID tag is used for object identification and an acoustic sensor is used for estimating object movements. In the heterogeneous sensor networks, our proposed association method is analyzed with association success, failure, and recovery cases. In addition, 2-dimensional (2D) particle filtering is used for estimating a objects state such as position and velocity. The performance is compared between a single sensor node and multiple sensor nodes in our proposed algorithm. In addition, the association performance with multiple sensor nodes is evaluated as a function of sampling time and object movement behavior. Finally, the effect of the two heterogeneous sensors range difference is analyzed and discussed.