bluuebunny/crossref_metadata_2025 huggingface dataset:
Remote reference magnetotelluric impedance estimation of wideband data using hybrid algorithm
Authors: Shalivahan  , Sinharay Rajib K. , Bhattacharya Bimalendu B.
Published: November 2006

Precise and accurate determination of the magnetotelluric (MT) impedance is fundamental to valid interpretation. This paper deals with the results of hybrid processing schemes in conjunction with the remote reference (RR), for a typical site out of several sites collected over the wide band data (∼103 to 10−3 Hz). The standard practice of MT impedance estimation is the use of robust processing in conjunction with the remote referencing. The estimation by robust technique helps in reducing the effect of outliers in the electric field but is often not sensitive to the exceptional predictor (magnetic field) data, which are called leverage points. The data processed with robust M estimation (RME) exacerbated the bias problem in the dead band. The application of hybrid (coherence weighted estimation (CWE) + RME, rho‐variance weighting + RME) and extra hybrid (CWE + rho variance + RME) approach helps in reducing the influence of both the outliers in the electric field and the leverage points. These two approaches perform considerably better than either data weighting scheme by itself.
How accurate is “paleomagnetic dating”? New evidence from historical lavas from Mount Etna
Authors: Speranza Fabio , Branca Stefano , Coltelli Mauro , D'Ajello Caracciolo Francesca , Vigliotti Luigi
Published: November 2006

In the last years, paleomagnetism has been increasingly used to provide emplacement ages of loosely dated volcanics. Dating is achieved by comparison of paleomagnetic directions with a given reference curve of the paleosecular variation (PSV) of the geomagnetic field. Recently, a debate has developed on the achievable precision (the α95 value) of the paleomagnetic directions and hence on the accuracy that “paleomagnetic dating” can yield. At 39 different sites from Etna we paleomagnetically investigated 13 flows (four “test flows” with known age, and nine loosely dated flows), emplaced between 122 B.C. and 1865 A.D. We systematically drilled 12 cores per flow spaced in three (far from each other) sites and demagnetized one specimen per core by alternating field cleaning. Results from the four test flows yield age windows effectively encompassing the respective true flow ages, when dating based on Bayesian statistics at a 95% confidence level is adopted. We find α95 values for the flow mean directions ranging between 3.3° and 5.7° (4.5° on average), which translate into accuracies of age determinations of 136–661 years (307 years on average). Such dating uncertainty is likely underestimated, as we disregarded several kinds of errors that might affect both the fidelity of paleomagnetic recording and the PSV reference curve. The strong magnetization of both the underlying terrain and the cooling flow itself and mineral magnetic variations across the flows are the most likely sources for the scatter characterizing the recording process of the magnetic field in volcanic rocks.
Day plots of mixtures of superparamagnetic, single‐domain, pseudosingle‐domain, and multidomain magnetites
Authors: Dunlop David J. , Carter‐Stiglitz Brian
Published: November 2006

We test how well a few hysteresis parameters (saturation remanence Mrs, coercive force Hc and remanent coercivity Hcr) serve to determine the proportions of end‐members in binary mixtures. Our end‐members are six magnetites whose grain sizes are within the superparamagnetic (SP), stable single‐domain (SD, three samples), pseudo‐SD (PSD), and multidomain (MD) ranges (Carter‐Stiglitz et al., 2001). The three SD magnetites have contrasting origins and properties: (1) bacterial magnetite crystals of a single size and coercivity, arranged in chains; (2) natural volcanic magnetites with a narrow distribution of coercivities; and (3) synthetic magnetites precipitated in glass, with a broader coercivity distribution. Our parameter mixing theory assumes linear magnetization curves of the end‐members between zero field and the largest coercive force Hc (that of the SD phase, if present). Similarly remanent hysteresis curves should be linear up to the maximum remanent coercive force Hcr. Three of our mixtures (SP plus bacterial SD, PSD plus bacterial SD, MD plus volcanic SD) had acceptable agreement between predicted and measured dependences of Hc, Hcr and the curve of Mrs/Ms versus. Hcr/Hc (Day plot) on end‐member concentrations. A nonlinear approximation to remanent hysteresis curves gave a reasonable fit to MD plus glass SD results. In this case, Hcr/Hc for the most MD‐rich mixture is larger than Hcr/Hc of either end‐member. Such behavior is characteristic of bimodal mixtures in which Hcr is largely determined by the hard (SD) phase and Hc by the soft (MD) phase. The only mixture that could not be modeled by linear or nonlinear parameter theory was MD plus bacterial SD. The bacterial SD hysteresis loop descends almost vertically at −Hc because of the extremely narrow range of particle sizes and coercivities. In general, linear and nonlinear parameter mixing models are adequate if only an approximate fit to real data is needed. An inversion method using complete magnetization curves as end‐member basis functions is preferable as an unmixing technique. However, comparison of measured data to type curves, for example, on a Day plot, gives a quick indication of what end‐member phases might be involved in the mix and provides additional insight before beginning an inversion.
Toward a new generation of satellite surface products?
Authors: Aires F. , Prigent C.
Published: November 2006

Despite the abundance and variety of remote sensing measurements, land surface characterization from satellite observations is still very challenging. The links between the three sources of surface information, namely the satellite observations, the in situ measurements, and the land surface model outputs, are complex. Innovative techniques have to be developed to merge these information sources and optimize the use of satellite measurements for better surface products and more predictability. Concepts such as multi‐instrument/multiparameter retrieval algorithms are discussed, as well as the synergetic use of satellite observations, model outputs, and in situ data. The need for careful satellite calibration is stressed, and the scaling problem is emphasized. Recent results are reviewed to indicate what the land surface remote sensing problems are and how they might be attacked. Two concrete applications are presented: an “all weather” retrieval of surface skin temperature from combined microwave and infrared observations and a soil moisture analysis from the merging of multisatellite observations and land surface model outputs. This paper is intended to stimulate debates and collaborations between the land surface modelers and the satellite remote sensing community for the design of the next generation of land surface products.
Is solar variability reflected in the Nile River?
Authors: Ruzmaikin Alexander , Feynman Joan , Yung Yuk L.
Published: November 2006

We investigate the possibility that solar variability influences North African climate by using annual records of the water level of the Nile collected in 622–1470 A.D. The time series of these records are nonstationary, in that the amplitudes and frequencies of the quasi‐periodic variations are time‐dependent. We apply the Empirical Mode Decomposition technique especially designed to deal with such time series. We identify two characteristic timescales in the records that may be linked to solar variability: a period of about 88 years and one exceeding 200 years. We show that these timescales are present in the number of auroras reported per decade in the Northern Hemisphere at the same time. The 11‐year cycle is seen in the Nile's high‐water level variations, but it is damped in the low‐water anomalies. We suggest a possible physical link between solar variability and the low‐frequency variations of the Nile water level. This link involves the influence of solar variability on the atmospheric Northern Annual Mode and on its North Atlantic Ocean and Indian Ocean patterns that affect the rainfall over the sources of the Nile in eastern equatorial Africa.
INCF -- new capability for global coordination in neuroinformatics
Authors: Bjaalie Jan
Published: November 2006

The Global Science Forum (GSF) of the OECD has initiated a new international organization, INCF, to further the development of Neuroinformatics as a global effort with the support of all ministers of research within OECD. This presentation explains the background for the establishment of the INCF, outlines some of the goals, and defines the operations of the INCF Secretariat in relation the INCF National nodes and the general neuroscience community.
Pressor responses to ephedrine are not impaired in dopamine β‐hydroxylase knockout mice
Authors: Liles J T , Baber S R , Deng W , Porter J R , Corll C , Murthy S N , Thomas S A , Kadowitz P J
Published: November 2006

Background and Purpose:

Ephedrine and amphetamine can cause substantial increases in systemic arterial pressure. However, the role of endogenous noradrenaline release in mediating the pressor response to ephedrine is controversial. Studies using pharmacologic agents to decrease the synthesis, storage, and release of catecholamines have supported both a direct and an indirect mechanism of action for ephedrine. The purpose of the present study was to determine if endogenous noradrenaline release is required for cardiovascular responses to ephedrine and amphetamine using a genetic mouse model.

Experimental Approach:

Increases in systemic arterial pressure and heart rate in response to ephedrine and amphetamine were investigated and compared in dopamine β‐hydroxylase knockout (Dbh ‐/‐) mice that cannot synthesize noradrenaline. Dbh +/‐ littermates have normal noradrenaline and adrenaline tissue levels, and served as controls in all experiments.

Key Results:

In Dbh ‐/‐ mice the increases in systemic arterial pressure and heart rate in response to i.v. injections of ephedrine were not impaired whereas responses to amphetamine were markedly reduced, when compared with responses in Dbh +/‐ mice. The pressor response to tyramine was abolished whereas pressor responses to noradrenaline, phenylephrine, dopamine, and angiotensin II were similar in Dbh ‐/‐ and Dbh +/‐ mice.

Conclusions and Implications:

The present results in Dbh ‐/‐ mice provide support for the hypothesis that pressor responses to ephedrine are directly mediated whereas responses to amphetamine are dependent on the release of noradrenaline and suggest that Dbh +/‐ and Dbh ‐/‐ mice are useful for the study of direct and indirect mechanisms.

British Journal of Pharmacology (2007) 150, 29–36. doi:10.1038/sj.bjp.0706942
Roles of M2and M3muscarinic receptors in cholinergic nerve‐induced contractions in mouse ileum studied with receptor knockout mice
Authors: Unno T , Matsuyama H , Izumi Y , Yamada M , Wess J , Komori S
Published: November 2006

Background and purpose:

The functional roles of M2and M3muscarinic receptors in neurogenic cholinergic contractions in gastrointestinal tracts remain to be elucidated. To address this issue, we studied cholinergic nerve‐induced contractions in the ileum using mutant mice lacking M2or M3receptor subtypes.

Experimental approach:

Contractile responses to transmural electrical (TE) stimulation were isometrically recorded in ileal segments from M2‐knockout (KO), M3‐KO, M2/M3‐double KO, and wild‐type mice.

Key results:

TE stimulation at 2‐50 Hz frequency‐dependently evoked a fast, brief contraction followed by a slower, longer one in wild‐type, M2‐KO or M3‐KO mouse preparations. Tetrodotoxin blocked both the initial and later contractions, while atropine only inhibited the initial contractions. The initial cholinergic contractions were significantly greater in wild‐type than M2‐KO or M3‐KO mice; the respective mean amplitudes at 50 Hz were 91, 74 and 68 % of 70mM K+‐induced contraction. Pretreatment with pertussis toxin blocked the cholinergic contractions in M3‐KO but not in M2‐KO mice. Cholinergic contractions also remained in wild‐type preparations, but their sizes were reduced by 20‐30 % at 10‐50 Hz. In M2/M3‐double KO mice, TE stimulation evoked only slow, noncholinergic contractions, which were significantly greater in sizes than in any of the other three mouse strains.

Conclusion and Implications:

These results demonstrate that M2and M3receptors participate in mediating cholinergic contractions in mouse ileum with the latter receptors assuming a greater role. Our data also suggest that the lack of both M2and M3receptors causes upregulation of noncholinergic excitatory innervation of the gut smooth muscle.

British Journal of Pharmacology(2006)149, 1022–1030. doi:10.1038/sj.bjp.0706955
Local structure of relaxor Pb(In0.5Nb0.5)O3 ferroelectrics
Authors: Yoneda Y. , Suzuya K. , Mizuki J. , Kohara S.
Published: November 2006

Pb ( In 0.5 Nb 0.5 ) O 3 (PIN) crystals show different ferroelectric features depending on the thermal treatments applied. Different treatments result in an ordered PIN exhibiting an antiferroelectricity, or a disordered PIN exhibiting relaxor behavior. These crystals were examined using synchrotron x-ray diffraction. In addition to the conventional crystallographic refinement, the atomic pair distribution function (PDF) analysis was used. Crystallographic analysis suggests that the average structure of the ordered PIN is different from that of the disordered PIN. However, the PDF analysis, which is more accurate in describing the local structure, shows that the local environments of the ordered and the disordered PIN crystals are quite similar. The difference between the disordered PIN and the ordered PIN is that the atomic displacement is either correlated or not.
Determination of spatial charge separation of diffusing electrons by transient photovoltage measurements
Authors: Mora-Seró Iván , Dittrich Thomas , Garcia-Belmonte Germà , Bisquert Juan
Published: November 2006

It is shown that the surface photovoltage produced by the photoinjected carriers in a layer can be split up into two contributions: total amount of charge, and distance between the centers of charge of the positive and negative carriers. This fact allows us to extract information directly about spatial charge separation of photoinduced charge and its time evolution from surface photovoltage transients. Two cases of particular experimental relevance are analyzed in detail to show the generality of the method: Diffusion photovoltage and tunneling recombination in layers with thickness less than the screening length, and in layers thicker than the screening length, considering also the limit case of diffusion in a semi-infinite space.
A model for the temperature dependence of photoluminescence from self-assembled quantum dots
Authors: Bansal Bhavtosh
Published: November 2006

Photoexcited carriers, distributed among the localized states of self-assembled quantum dots, often show very anomalous temperature dependent photoluminescence characteristics. The temperature dependence of the peak emission energy may be nonmonotonic and the emission linewidth can get narrower with increasing temperature. This paper describes a quasithermodynamic model that naturally explains these observations. Specifically, we introduce a temperature dependent function to parametrize the degree of thermalization of carriers. This function allows us to continuously interpolate between the well-defined low and high temperature limits of the carrier distribution function and to describe the observed anomalies in the photoluminescence spectra with just two fitting parameters. We show that the description is equivalent to assuming that the partially thermalized carriers continue to be described by equilibrium statistics, but with a higher effective temperature. Our treatment of the problem is computationally simpler than the usually employed rate equation based analyses [e.g., S. Sanguinetti et al., Phys. Rev. B 60, 8276 (1999)], which typically also have many more underdetermined fitting parameters. The model is extended to quantum dots with a bimodal size distribution.
Transient capacitance study of switching in the nematic Freedericksz geometry
Authors: Hind J. M. , Smith A. A. T. , Brown C. V.
Published: November 2006

The transient capacitance has been measured for two commercial nematic liquid crystal materials, E7 and MDA01-2012, subjected to an amplitude modulated ac voltage wave form in the planar Freedericksz geometry. The wave form amplitude is modulated in a stepwise fashion between a value above the Freedericksz transition voltage VC [V. Freedericksz and V. Zolina, Trans. Faraday Soc. 29, 919 (1933)], causing switching, and a value below the threshold, where relaxation of the switched profile occurs. For both materials the time evolution of the dielectric permittivity during the switching and relaxation periods is accurately described by nematic continuum theory with a single viscosity provided that the switching voltage is a small multiple of VC.
Relation between the magnetic properties and the crystal and electronic structures of manganese spinels LiNi0.5Mn1.5O4 and LiCu0.5Mn1.5O4−δ (<δ<0.125)
Authors: Biškup N. , Martínez J. L. , Arroyo y de Dompablo M. E. , Díaz-Carrasco P. , Morales J.
Published: November 2006

The magnetic properties of LiM0.5Mn1.5O4 (M=Ni and Cu) spinels, materials of interest as electrodes for Li-ion batteries, have been studied and interpreted with the help of the first-principles calculation method. The magnetic susceptibility of the Ni compound, that behaves virtually as stoichiometric normal spinel, is consistent with the well-established magnetic model of the spinel structure that leads to ferrimagnetism. However, the Cu spinel was oxygen deficient and showed significant divergences from this model. The ferromagnetic component of this spinel was dependent on the calcining temperature and was smaller to that predicted by the magnetic model. The special crystal structure of the spinel, namely, oxygen deficiency and increased occupancy of the tetrahedral sites by Cu ions, satisfactorily explains the more complex magnetic behavior observed, further supported by the results of the first-principles electronic structure computations.
Band gap bowing and electron localization of GaxIn1−xN
Authors: Lee Byounghak , Wang Lin Wang
Published: November 2006

The band gap bowing and the electron localization of GaxIn1−xN are calculated using both the local density approximation (LDA) and screened-exchange local density functional (sX-LDA) methods. The calculated sX-LDA band gaps are in good agreement with the experimentally observed values, with errors of −0.26 and 0.09eV for bulk GaN and InN, respectively. The LDA band gap errors are 1.33 and 0.81eV for GaN and InN, in order. In contrast to the gap itself, the band gap bowing parameter is found to be very similar in sX-LDA and LDA. We identify the localization of hole states in GaxIn1−xN alloys along In–N–In chains. The predicted localization is stronger in sX-LDA.
Simultaneous measurements of photoemission and morphology of various Al alloys during mechanical deformation
Authors: Cai M. , Li W. , Dickinson J. T.
Published: November 2006

We report simultaneous measurements of strain and photoelectron emission from high purity Al (1350), Al–Mg (5052), Al–Mn (3003), Al–Cu (2024), and Al–Mg–Si (6061) alloys under uniaxial tension due to pulsed excimer laser radiation (248nm). The emission of low-energy photoelectrons is sensitive to deformation-induced changes in surface morphology, including the formation of slip lines and slip bands. Alloy composition and surface treatment significantly influence the photoemission during deformation. Surface oxide enhances the signal-to-noise level during photoemission measurement. In the early stage of deformation (strain ⩽0.04), photoemission intensity increases gradually in a nonlinear fashion. While subsequent photoemission increases almost linearly with strain until failure in samples with thin oxide layer (∼31Å), there are two linear segments of photoemission for the samples with oxide of 45Å. The onset of strain localization corresponds to the intersection point of two linear segments, usually at a strain of 0.08–0.20. A constitutive model incorporating microstructure evolution and work hardening during tensile deformation is proposed to qualitatively interpret the growth of the photoemission as a function of strain. Photoemissions from various alloys are interpreted in the light of surface treatment, work function, composition, and microstructural development during deformation.
Single quintuple bond [PhCrCrPh] molecule as a possible molecular switch
Authors: Huang Jiang , Li Qunxing , Ren Hao , Su Haibin , Yang Jinlong
Published: November 2006

The electronic transport properties of a single quintuple bond [PhCrCrPh] molecule sandwiched between two Au(111) surfaces with the trans-bent and linear configurations are studied by a fully self-consistent nonequilibrium Green’s function method combined with density functional theory. The calculated transmission spectra of two chemical isomers are remarkablty distinctive. Theoretical results suggest that the current through the trans-bent configuration is significantly larger than the corresponding linear one. The predicted on-off ratio of currents ranging from around 50 to 200 in the applied bias window [−1.5V, 1.5V] suggests that multiple bond compounds have attractive potential in molecular switch technology.
Microlens array fabrication by laser interference lithography for super-resolution surface nanopatterning
Authors: Lim C. S. , Hong M. H. , Lin Y. , Xie Q. , Luk’yanchuk B. S. , Senthil Kumar A. , Rahman M.
Published: November 2006

A technique for large area and fast speed surface nanopatterning of photopolymer surface with laser irradiation through microlens array (MLA) was demonstrated. The laser beam was split into many focused tiny light spots by a 1μm diameter MLA fabricated by laser interference lithography followed by reflow and reactive ion etching. The fabricated MLA exhibits excellent uniformity and surface quality. Up to 6 250 000 nanopatterns can be fabricated over an area of 5×5mm2 under KrF excimer laser single pulse exposure. A spot size down to 78nm was obtained corresponding to super-resolution of λ∕3, λ is the incident laser wavelength.
Unpinning of the Fermi level at (111)A clean surfaces of epitaxially grown n-type In0.53Ga0.47As
Authors: Perraud Simon , Kanisawa Kiyoshi , Wang Zhao-Zhong , Hirayama Yoshiro
Published: November 2006

Low-temperature scanning tunneling spectroscopy under ultrahigh vacuum was employed to investigate the (111)A clean surface of n-type In0.53Ga0.47As, grown by molecular beam epitaxy on lattice-matched InP substrates. It was found that the surface Fermi level is located in the conduction band, close to the bulk Fermi level, and can be controlled by varying the dopant concentration in the bulk. This observation was confirmed by determining the dispersion relation of electron standing waves resulting from scattering interferences. Such an unpinning of the surface Fermi level strongly contrasts with the pinning phenomenon observed at the (001) clean surface.
Theory of frequency modulated thermal wave imaging for nondestructive subsurface defect detection
Authors: Mulaveesala Ravibabu , Tuli Suneet
Published: November 2006

This letter provides the theory and mathematical analysis in support of a recently proposed frequency modulated thermal wave imaging for nondestructive subsurface defect detection in solids. The authors illustrate how the technique simultaneously combines the advantages of both conventional pulse based thermography as well as modulated lock-in thermography. A specimen is heated for launching thermal waves into the sample, not at a single frequency (lock-in) or at all frequencies (pulse), but in a desired range of frequencies. While peak power requirement is reduced, phase images obtained retain known advantages. Experimental results from a carbon fiber reinforced plastic sample are presented in support.
Piezoelectric composite based on the enhanced flexoelectric effects
Authors: Zhu Wenyi , Fu John Y. , Li Nan , Cross L.
Published: November 2006

In this study, a piezoelectric composite is fabricated from a Ba0.67Sr0.33TiO3 (BST) composition and air, and measured at room temperature (24°C) where the BST is in its paraelectric centric phase. The charge separation mechanism is flexoelectricity, driven by the strain gradient introduced by the pyramidal boundary shapes of each BST building unit of the composite. In spite of the macro (millimeter) dimensions of the building units that inhibit a steep strain gradient, the composite is sufficiently active to be measured by using a conventional Berlincourt d33 meter. The measured values are in good agreement with expectation from the earlier measured flexoelectric coefficient μ11 of the BST and the finite element simulation results of the strain gradient in the pyramid BST units.
Wall behavior of nanodomains as a function of their initial state
Authors: Odagawa Nozomi , Cho Yasuo
Published: November 2006

A method for visualizing ferroelectric domain walls based on higher order nonlinear dielectric detection is proposed. This technique enables the authors to obtain information to visualize the domain wall clearly. Using this method, nanodomain variations with high temperature treatments are observed. The results indicate that the manner of domain variation depends on the state of the domain walls at the time of writing. This result can be explained from the point of view of wall energy transition.
Negative differential resistance from a van Hove singularity in tunnel diodes
Authors: Moffatt Paul , Kim Eugene H.
Published: November 2006

Tunnel diodes with electrodes having a van Hove singularity in their density of states are considered. Results for the I-V characteristics of these devices are presented and analyzed. In particular, it is shown that robust negative differential resistance arises due to the van Hove singularity.
Enhancement of dielectric constant in HfO2 thin films by the addition of Al2O3
Authors: Park Pan Kwi , Kang Sang-Won
Published: November 2006

Hf O 2 films with an enhanced dielectric constant, prepared through phase transition engineering by the addition of Al2O3, were deposited by plasma-enhanced atomic layer deposition adopting a supercycle concept. After an annealing step at 700°C, the tetragonal phase, which is a high-temperature phase of HfO2, was stabilized completely at room temperature and the crystallographic direction was changed to the preferred (002) orientation. As a result, Hf aluminate film with a (002)-oriented tetragonal phase had a dielectric constant of 47, approximately twice as large as the reported value of HfO2 film with a monoclinic phase.
Low-temperature formation (<500°C) of poly-Ge thin-film transistor with NiGe Schottky source/drain
Authors: Sadoh T. , Kamizuru H. , Kenjo A. , Miyao M.
Published: November 2006

Poly-Ge thin-film transistors (TFTs) with Schottky source/drain (S/D) contacts were fabricated on glass by low-temperature (<500°C) processing. First, the annealing characteristics of Ni/crystal-Ge stacked structures were examined. The results indicated that NiGe∕n-Ge Schottky contacts (ϕBn=0.51eV, n=1) with flat interfaces and low reverse leakage current [(2–5)×10−2A∕cm2] could be obtained by choosing an appropriate annealing temperature (200–300°C). Based on this result, p-channel TFTs were fabricated with poly-Ge formed on glass by solid-phase crystallization at 500°C. TFTs showed relatively high hole mobility (about 140cm2∕Vs) with very low S/D parasitic resistance and no kink effect. The potential capability of the proposed devices for high-performance TFTs was demonstrated.
Enhanced flux pinning of air-processed GdBa2Cu3O7−δ superconductors with addition of ZrO2 nanoparticles
Authors: Hu Anming , Xu Caixuan , Izumi Mitsuru , Hirabayashi Izumi , Ichihara Masaki
Published: November 2006

The authors investigate the influence of ZrO2 nanoparticles on microstructure and superconducting properties of GdBa2Cu3O7−δ (Gd123) single domain superconductors grown in air. Experiments show that before Gd123 crystallization ZrO2 nanoparticles react with Gd123 and yield BaZrO3. Transmission electron microscopy evidences that BaZrO3 disperses in Gd123 crystals with a size less than 50nm. A high Jc value of 100000A∕cm2 has been achieved in Gd123 with 0.4M% ZrO2 at 77K and self-field. Compared to the flux pinning effect of submicrometer Gd2BaCuO5 particles, BaZrO3 nanoparticles embedded in Gd123 significantly enhance critical current densities in a wide magnetic field range.
Growth and photoluminescence studies of Zn-doped AlN epilayers
Authors: Nepal N. , Nakarmi M. L. , Jang H. U. , Lin J. Y. , Jiang H. X.
Published: November 2006

Deep ultraviolet time-resolved photoluminescence (PL) spectroscopy has been employed to study Zn-doped AlN epilayers grown by metal-organic chemical vapor deposition. The PL spectra of Zn-doped AlN epilayer exhibited two impurity emission lines at 5.40 and 4.50eV, which were absent in undoped epilayers and assigned to the transitions of free electrons and electrons bound to nitrogen vacancies with three positive charges (0.90eV deep) to the Zn0 acceptors. By comparing PL spectra of Zn- and Mg-doped AlN epilayers with undoped epilayers, it was deduced that Zn energy level is about 0.74eV, which is about 0.23eV deeper than the Mg energy level (0.51eV) in AlN. It is thus concluded that contrary to theoretical prediction, Zn would not be a better candidate than Mg as an acceptor dopant in AlN.
Electrical transport properties of individual disordered multiwalled carbon nanotubes
Authors: Tsai Meng-Yen , Yu Chung-Yi , Yang Chien-Hsin , Tai Nyan-Hwa , Perng Tsong-Pyng , Tu Chien-Ming , Khan Zishan Husain , Liao Yang-Chung , Chi Cheng Chung
Published: November 2006

The electrical transport properties of individual disordered multiwalled carbon nanotubes (MWCNTs), synthesized with the floating catalyst method, have been investigated. The resistivity of such disordered MWCNTs shows T1∕2 dependence over a temperature range of 4.2–263K. The experimental finding can be interpreted in terms of Al’tshuler-Aronov model [Solid State Commun. 30, 115 (1979); Sov. Phys. JETP 50, 968 (1979); Pis’ma. Zh. Eksp. Teor. Fiz. 27, 700 (1978)], in which strong electron-electron interaction leads to a Coulomb gap in the density of electronic states at the Fermi level. Such a wide fitting range of temperature for T1∕2 dependence has never been reported for other materials, implying an extremely short carrier scattering time of the order of femtoseconds.
Local current-voltage characteristics of rough TiO2 layers on TiSi2
Authors: Ilango S. , Raghavan G. , Kamruddin M. , Tyagi A. K.
Published: November 2006

The nature of charge transport across rough, insulating layers of TiO2 on TiSi2 is investigated using conducting atomic force microscopy. The conducting tip, the insulating layer, and the metallic TiSi2 layer constitute a metal-insulator-metal system. This system exhibits a strong correlation between the topographic image and the current image. Based on this observation, the dependence of current-voltage characteristics on the local thickness of the TiO2 layer is examined and analyzed on the basis of the Fowler-Nordheim tunneling mechanism. This analysis indicates that both field emission and trap assisted tunneling contribute to the conduction mechanism. Evidence of switching due to detrapping of charges is also seen in the I-V characteristics, confirming the role of trap states.
Improved quasi-solid dye-sensitized solar cells by composite ionic liquid electrolyte including layered α-zirconium phosphate
Authors: Wang Ning , Lin Hong , Li Jianbao , Li Xin
Published: November 2006

The authors reported a composite quasi-solid electrolyte by adding layered α-zirconium phosphate (α-ZrP) to the iodide/tri-iodide ionic liquid, 1-methyl-3-propylimidazolium dihydrophosphate, electrolyte including 4-tert-butylpyridine, which markedly improved photovoltaic properties of quasisolid dye-sensitized solar cells (DSSCs). When adding 6wt% α-ZrP, photoenergy conversion efficiency of the DSSC increases by a factor of more than 2 to 2.61%, compared to a DSSC without α-ZrP. This enhancement is primarily explained by studying dark reaction, diffusion coefficient of tri-iodide ions, exchange current density in the interface of electrolyte/Pt counterelectrode, and lifetime of electrons in mesoscopic TiO2 film.
Enhanced photoemission from nanostructured surface topologies
Authors: Teki Ranganath , Koratkar Nikhil , Karabacak Tansel , Lu Toh-Ming
Published: November 2006

The authors characterized the photoemission behavior of nanostructured surfaces (specifically Ru and Pt nanorod arrays) and observed an ∼15-fold enhancement in photocurrent for a slanted Ru nanorod array (nanorods tilted at ∼40° to the substrate normal) compared to a planar Ru film. The authors show that the improved performance originates from two basic reasons: (1) increased surface area of the nanorods which enhances the photon-collection probability and (2) single crystal nature of the nanorods which increases electron escape probability due to the absence of grain boundaries. Such nanostructured surfaces show promise in a variety of device applications such as photodetectors, photon counters, and photomultiplier tubes.
Room temperature electron spin relaxation in GaInNAs multiple quantum wells at 1.3μm
Authors: Reith C. , White S. J. , Mazilu M. , Miller A. , Konttinen J. , Guina M. , Pessa M.
Published: November 2006

The authors report a direct measurement of electron spin relaxation in GaInNAs semiconductor multiple quantum wells at room temperature. Multiple quantum wells of widths 5.8, 7, and 8nm exhibiting excitonic absorption around 1.3μm have been studied. Spin relaxation times were found to increase with well width in the range of 77–133ps. The spin relaxation time dependence on first electron confinement energy suggests the Elliot-Yafet mechanism [A. Tackeuchi et al., Physica B 272, 318 (1999)] as the dominant relaxation process.
Theory of three-dimensional subdiffraction imaging
Authors: Marques Ricardo , Freire Manuel J. , Baena Juan D.
Published: November 2006

Subdiffraction image formation and measurement are analyzed. It is shown that subdiffraction imaging devices cannot produce focusing of energy into three-dimensional spots of subdiffraction size. However, three-dimensional subdiffraction imaging is possible as a consequence of a matching/tunneling process.
Phase contrast imaging using photothermally induced phase transitions in liquid crystals
Authors: Yelleswarapu Chandra S. , Kothapalli Sri-Rajasekhar , Aranda Francisco J. , Rao D. V. G. L. N. , Vaillancourt Yvonne R. , Kimball Brian R.
Published: November 2006

Phase contrast imaging is performed for live biological species using photothermal induced birefringence in dye doped liquid crystals. Using typical 4-f configuration, when liquid crystal cell is at back focal plane of Fourier lens, low spatial frequencies at center of Fourier spectrum are intense enough to induce local liquid crystal molecules into isotropic phase, whereas high spatial frequencies on the edges are not intense enough and remain in anisotropic phase. This results in π∕2 phase difference between high and low spatial frequencies. This simple, inexpensive, all-optical, user-friendly, self-adaptive phase contrast imaging technique using low-power laser offers several distinct advantages.
Microwave thin-film transistors using Si nanomembranes on flexible polymer substrate
Authors: Yuan Hao-Chih , Ma Zhenqiang
Published: November 2006

Large-feature-size single-crystal Si thin-film transistors (TFTs) with fT of 1.9GHz and fmax of 3.1GHz were demonstrated on flexible polymer substrate. In this letter, the authors detail the fabrication process that enables TFTs, made on low-temperature flexible substrates, to operate at microwave frequencies under low bias voltages. The outstanding electrical performance results measured from these devices, such as high electron mobility, high current drive capability, and high frequency response characteristics, and the simple process procedures for producing these devices on flexible substrate make flexible electronics highly promising for power-efficient large-area radio-frequency and microwave applications.
An Episode in the ‘Amili Migration to Safavid Iran: Husayn b. ‘Abd al-Samad al-‘Amili's Travel Account
Authors: Stewart Devin J.
Published: November 2006

After emigrating from Ottoman territory to Safavid Iran in the mid-sixteenth century, the Shiite scholar Husayn b. ‘Abd al-Samad al-‘Amili wrote an eloquent letter-cum-travel account describing his experiences to his teacher Zayn al-Din al-‘Amili who had remained in Jabal ‘Amil. A manuscript of this fascinating document has now come to light and been edited twice, in 2001 and 2003. An analysis of the undated letter shows that it was written in 961/1554 and describes a journey that occurred earlier that same year. Husayn's statements do not spell out the exact cause of his flight from Ottoman territory but suggest that he was wary of being denounced to the authorities and felt that his academic career was severely limited there. He evidently supported Safavid legitimacy wholeheartedly, though he harbored misgivings about the moral environment in Iran and had sharp criticisms for Persian religious officials.
The Development of Social Insurance in Iran: Technical-Financial Conditions and Political Rationales, 1941–1960
Authors: Schayegh Cyrus
Published: November 2006

This text brings the case of Iranian social insurance (SI) to bear on the processes shaping Iranian politics from 1941 to 1960. It holds that the political needs of upper class rule (1941–51) and of the early autocratic regime (1953–1960) helped to shape SI's nature, extent, and limits. A key objective was to propagandistically use a minimal version of SI to try undermining communist and workers' trade unionist agitation. Iranian SI had two rationales. Although a few workers demanded SI measures during the Constitutional Revolution, the first SI program (1922, 1931, 1933) covered government employees, i.e. was a function of state-building. This paper focuses on a second program, targeting non-government workers. Starting in 1936 (1943, 1949), it was meant to tackle the social and political challenges posed by a nascent industrial working class. However, throughout the 1940s, workers' SI laws remained a dead letter, and the first integrated SI bureaucracy (1953), although ensuring 180,000 people, was in reality quite inefficient.
A Separate Moldovan Language? The Sociolinguistics of Moldova'sLimba de Stat
Authors: Ciscel Matthew H.
Published: November 2006

The politics of language identity have figured heavily in the history of the people of the Republic of Moldova. Indeed the region's status as a province of Russia, Romania, and then the Soviet Union over the past 200 years has consistently been justified and, at least partially, manipulated on the basis of language issues. At the center of these struggles over language and power has been the linguistic and cultural identity of the region's autochthonous ethnicity and current demographic majority, the Moldovans. In dispute is the degree to which these Moldovans are culturally, historically, and linguistically related to the other Moldovans and Romanians across the Prut River in Romania. Under imperial Russia from 1812 to 1918 and Soviet Russia from 1944 to 1991, a proto-Moldovan identity that eschewed connections to Romania and emphasized contact with Slavic peoples was promoted in the region. Meanwhile, experts from Romania and the West have regularly argued that the eastern Moldovans are indistinguishable, historically, culturally, and linguistically, from their Romanian cousins.
From ‘consulting pupils’ to ‘pupils as researchers’: a situated case narrative
Authors: Thomson Pat , Gunter Helen
Published: November 2006

Schools in England are now being encouraged to ‘personalise’ the curriculum and to consult students about teaching and learning. This article reports on an evaluation of one high school which is working hard to increase student subject choice, introduce integrated curriculum in the middle years and to improve teaching and learning while maintaining a commitment to inclusive and equitable comprehensive education. The authors worked with a small group of students as consultants to develop a ‘student's‐eye’ set of evaluative categories in a school‐wide student survey. They also conducted teacher, student and governor interviews, lesson and meeting observations, and student ‘mind‐mapping’ exercises. In this article, in the light of the findings, the authors discuss the processes they used to work jointly with the student research team, and how they moved from pupils‐as‐consultants to pupils‐as‐researchers, a potentially more transformative/disruptive practice. They query the notion of ‘authentic student voice’ and show it as discursive and heterogeneous: they thus suggest that both a standards and a rights framings of student voice must be regarded critically.
Work environment predictors of beginning teacher burnout
Authors: Goddard Richard , O'Brien Patrick , Goddard Marion
Published: November 2006

This study investigated elements of school environments that explain variance in burnout scores in a sample of university graduates from Brisbane, Australia, two years after they commenced work as teachers. Using a longitudinal survey methodology, 79 beginning teachers completed the Maslach Burnout Inventory (MBI) on four occasions over a two‐year period, first, six weeks after they commenced work as teachers and finally, in the concluding term of their second year of teaching. Beginning teachers also completed the Work Environment Scale each time they were surveyed. The revised Eysenck Personality Questionnaire was administered when the graduands were first surveyed. In a series of hierarchical regression analyses, reports of how innovative the work environment was perceived to be added significantly to the explanation of variance in all three MBI subscales after first controlling for initial levels of burnout and the personality trait Neuroticism.
Qualitative aspects in dual-phase-lag heat conduction
Authors: Quintanilla Ramón , Racke Reinhard
Published: November 2006

We investigate the equation of the dual-phase-lag heat conduction proposed by Tzou. To describe this equation, we use the phase lag of the heat flux and the phase lag of the gradient of the temperature. We analyse the basic properties of the solutions of this problem. First, we prove that when both parameters are positive, the problem is well posed and the spatial decay of solutions is controlled by an exponential of the distance. When the phase lag of the gradient of the temperature is bigger than the phase lag of the heat flux, the problem is exponentially stable (which is a natural property to expect for a heat equation) and the spatial behaviour is controlled by an exponential of the square of the distance. Also, a uniqueness result for unbounded solutions is proved in this case.
The age and evolution of sociality in
Stegodyphus
spiders: a molecular phylogenetic perspective
Authors: Johannesen Jes , Lubin Yael , Smith Deborah R , Bilde Trine , Schneider Jutta M
Published: November 2006

Social, cooperative breeding behaviour is rare in spiders and generally characterized by inbreeding, skewed sex ratios and high rates of colony turnover, processes that when combined may reduce genetic variation and lower individual fitness quickly. On these grounds, social spider species have been suggested to be unstable in evolutionary time, and hence sociality a rare phenomenon in spiders. Based on a partial molecular phylogeny of the genus
Stegodyphus
, we address the hypothesis that social spiders in this genus are evolutionary transient. We estimate the age of the three social species, test whether they represent an ancestral or derived state and assess diversification relative to subsocial congeners. Intraspecific sequence divergence was high in all of the social species, lending no support for the idea that they are young, transient species. The age of the social lineages, constant lineage branching and the likelihood that social species are independently derived suggest that either the social species are ‘caught in sociality’ or they have evolved into cryptic species.
Basal metabolic rate of birds is associated with habitat temperature and precipitation, not primary productivity
Authors: White Craig R , Blackburn Tim M , Martin Graham R , Butler Patrick J
Published: November 2006

A classic example of ecophysiological adaptation is the observation that animals from hot arid environments have lower basal metabolic rates (BMRs, ml O2 min−1) than those from non-arid (luxuriant) ones. However, the term ‘arid’ conceals within it a multitude of characteristics including extreme ambient temperatures (Ta, °C) and low annual net primary productivities (NPPs, g C m−2), both of which have been shown to correlate with BMR. To assess the relationship between environmental characteristics and metabolic rate in birds, we collated BMR measurements for 92 populations representing 90 wild-caught species and examined the relationships between BMR and NPP,Ta, annual temperature range (Tr), precipitation and intra-annual coefficient of variation of precipitation (PCV). Using conventional non-phylogenetic and phylogenetic generalized least-squares approaches, we found no support for a relationship between BMR and NPP, despite including species captured throughout the world in environments spanning a 35-fold range in NPP. Instead, BMR was negatively associated withTaandTr, and positively associated withPCV.
Results of a whole‐genome quantitative trait locus scan for growth, carcass composition and meat quality in a porcine four‐way cross
Authors: Harmegnies N. , Davin F. , De Smet S. , Buys N. , Georges M. , Coppieters W.
Published: November 2006

A whole‐genome quantitative trait locus (QTL) scan for 31 phenotypes related to growth, carcass composition and meat quality was conducted using 1187 progeny of a commercial four‐way cross. Animals were genotyped for 198 microsatellite markers that spanned the entire porcine genome. QTL analysis was conducted to extract information from paternal and maternal meioses separately using a rank‐based nonparametric approach for half‐sib designs. Nine QTL exceeded genome‐wide significance: one QTL affecting growth (average daily gain on SSC1), two QTL influencing carcass composition (fatness on SSC3 and muscle mass on SSC15) and six QTL influencing meat quality (tenderness on SSC4 and SSC14; colour on SSC5, SSC6 and SSCX; and conductivity on SSC16). All but one of these coincided with previously reported QTL. In addition, we present evidence for 78 suggestive QTL with a combined false discovery rate of 40%.