946 resultados para Correlated Electrons
Resumo:
Intrinsically disordered proteins (IDPs) are a relatively recently defined class of proteins which, under native conditions, lack a unique tertiary structure whilst maintaining essential biological functions. Functional classification of IDPs have implicated such proteins as being involved in various physiological processes including transcription and translation regulation, signal transduction and protein modification. Actinidia DRM1 (Ade DORMANCY ASSOCIATED GENE 1), represents a robust dormancy marker whose mRNA transcript expression exhibits a strong inverse correlation with the onset of growth following periods of physiological dormancy. Bioinformatic analyses suggest that DRM1 is plant specific and highly conserved at both the nucleotide and protein levels. It is predicted to be an intrinsically disordered protein with two distinct highly conserved domains. Several Actinidia DRM1 homologues, which align into two distinct Actinidia-specific families, Type I and Type II, have been identified. No candidates for the Arabidopsis DRM1-Homologue (AtDRM2) an additional family member, has been identified in Actinidia.
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The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasmaelectrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated.
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Large multisite efforts (e.g., the ENIGMA Consortium), have shown that neuroimaging traits including tract integrity (from DTI fractional anisotropy, FA) and subcortical volumes (from T1-weighted scans) are highly heritable and promising phenotypes for discovering genetic variants associated with brain structure. However, genetic correlations (rg) among measures from these different modalities for mapping the human genome to the brain remain unknown. Discovering these correlations can help map genetic and neuroanatomical pathways implicated in development and inherited risk for disease. We use structural equation models and a twin design to find rg between pairs of phenotypes extracted from DTI and MRI scans. When controlling for intracranial volume, the caudate as well as related measures from the limbic system - hippocampal volume - showed high rg with the cingulum FA. Using an unrelated sample and a Seemingly Unrelated Regression model for bivariate analysis of this connection, we show that a multivariate GWAS approach may be more promising for genetic discovery than a univariate approach applied to each trait separately.
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Approximate calculations are reported on pyrene within the PPP model Hamiltonian using a novel restricted CI scheme which employs both molecular orbital and valence bond techniques. Also reported are detailed full CI results of the PPP model on 2,7-dihydropyrene obtained using the valence bond method. Spectral studies, charge and spin density calculations in ground and excited states, and ring current calculations in the ground state of the molecules are presented. In pyrene, the calculated excitation energies are in good agreement with experiment. The closed structure pi-conjugated molecule pyrene appears to show smaller distortions from the ground state geometry compared with the open structure pi-conjugated molecule 2,7-dihydropyrene. The ground state equilibrium structure of 2,7-dihydropyrene can be viewed as two hexatriene molecules connected by a vinyl crosslink, as is evident from bond order and ring current calculations. This is consistent with the only Kekule resonant structure possible for this molecule.
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Ceramic samples of SrBi2Ta2O9 (SBT) were prepared by the solid state reaction method with a view to study their electrical properties. Reasons as to why SBT shows better fatigue endurance than conventional perovskites like Pb(Zr, Ti)O-3 are looked into. Complex impedance spectroscopy (CIS) was used as a tool to do so. CIS data was acquired over the temperature range from room temperature to 500 degrees C over a wide range of frequencies. Electrical conductivity data indicates that the conductivity in SBT is essentially due to oxygen vacancies and the activation energy for conduction in the high temperature region was found to be 0.95 eV. CIS was used to separate out the bulk and the interfacial contributions to complex impedance.
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With growing population and fast urbanization in Australia, it is a challenging task to maintain our water quality. It is essential to develop an appropriate statistical methodology in analyzing water quality data in order to draw valid conclusions and hence provide useful advices in water management. This paper is to develop robust rank-based procedures for analyzing nonnormally distributed data collected over time at different sites. To take account of temporal correlations of the observations within sites, we consider the optimally combined estimating functions proposed by Wang and Zhu (Biometrika, 93:459-464, 2006) which leads to more efficient parameter estimation. Furthermore, we apply the induced smoothing method to reduce the computational burden. Smoothing leads to easy calculation of the parameter estimates and their variance-covariance matrix. Analysis of water quality data from Total Iron and Total Cyanophytes shows the differences between the traditional generalized linear mixed models and rank regression models. Our analysis also demonstrates the advantages of the rank regression models for analyzing nonnormal data.
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Artifacts in the form of cross peaks have been observed along two- and three-quantum diagonals in single-quantum two-dimensional correlated (COSY) spectra of several peptides and oligonucleotides. These have been identified as due to the presence of a non-equilibrium state of kind I (a state describable by populations which differ from equilibrium) of strongly coupled spins carried over from one experiment to the next in the COSY algorithm.
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Metal Auger intensity ratios of the type Z(CVV)/I(CC'V) and Z(CVV)/Z(CC'C"), where C, C' and C" denote core levels and V stands for a valence level, are shown to increase progressively with the number of valence electrons in the metal in the case of second-row transition metals and their oxides. Metal Auger intensity ratios in chalcogenides of transition metals can be correlated by taking the effective atomic charge on the metal into consideration. The possible use of metal Auger intensity ratios in the study of surface oxidation of second-row transition metals is illustrated in the case of zirconium.
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We have considered a two-band Hubbard model having interlaced Cu-3d(x2−y2) and O-2p(x, y) orbitals representing the CuO2 square planes. Simple CuO2 -cluster calculation suggests that the additional holes created by doping stay mainly on oxygen. Motion of an oxygen hole interlacing with the antiferromagnetically correlated background of copper spins, creates a string of high energy spin configuration of finite length giving mass renormalization. Another hole of opposite spin can now anneal this string tension providing a triangular pairing potential for large pair momentum. The latter implies unusual Bose condensation of the wake-bound compact Bose-like pairs on a non-zero momentum shell. Effect of disorder favouring condensation at the mobility edge is pointed out.
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In this paper we address the problem of transmission of correlated sources over a fading multiple access channel (MAC). We provide sufficient conditions for transmission with given distortions. Next these conditions are specialized to a Gaussian MAC (GMAC). Transmission schemes for discrete and Gaussian sources over a fading GMAC are considered. Various power allocation strategies are also compared.
Resumo:
Iron nanoparticles are embedded in multiwall carbon nanotubes by the chemical vapor deposition, where benzene and ferrocene are taken as precursor materials. Varying quantity of iron particles are embedded in these tubes by taking different amount of ferrocene. These particles exhibit a magnetic moment up to 98 emu/g and an enhanced coercivity in the range of 500-2000 Oe. Negative magnetoresistance similar to 10% is observed in the presence of magnetic field up to 11 T applied at various temperatures in the range of 1.3 K-300 K. It is argued that the enhanced coercivity is due to the shape anisotropy. The negative magnetoresistance is believed to be due to the weak localization and spin dependent scattering of electrons by the ferromagnetic particles. In addition we also observe a dependence of the magnetoresistance on the direction of applied field and this is correlated with the shape anisotropy of the Fe particles.
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The ratio of diffusion coefficient to mobility (D/¿) for electrons has been measured in SF6-air and freon-nitrogen mixtures for various concentrations of SF6 and freon in the mixtures over the range 140¿ E/p¿ 220 V.cm-1 - torr-1. In SF6-air mixtures, the values of D/¿ were always observed to lie intermediate between the values for the pure gases. However, in freon-nitrogen mixtures, with a small concentration (10 percent) of freon in the mixture, the values of D/¿ are found to lie above the boundaries determined by the pure gases. In this mixture, over the lower E/p range (140 to 190) the electrons appear to lose a large fraction of their energy by the excitation of the complex freon molecules, while at higher E/p values (200 to 240), the excitation and consequent deexcitation of nitrogen molecules and its metastables seem to cause an increased rate of ionization of freon molecules.
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Using a perturbation technique, we derive Modified Korteweg—de Vries (MKdV) equations for a mixture of warm-ion fluid (γ i = 3) and hot and non-isothermal electrons (γ e> 1), (i) when deviations from isothermality are finite, and (ii) when deviations from isothermality are small. We obtain stationary solutions for these equations, and compare them with the corresponding solutions for a mixture of warm-ion fluid (γ i = 3) and hot, isothermal electrons (γ i = 1).
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We consider the problem of transmission of correlated discrete alphabet sources over a Gaussian Multiple Access Channel (GMAC). A distributed bit-to-Gaussian mapping is proposed which yields jointly Gaussian codewords. This can guarantee lossless transmission or lossy transmission with given distortions, if possible. The technique can be extended to the system with side information at the encoders and decoder.
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We consider the transmission of correlated Gaussian sources over orthogonal Gaussian channels. It is shown that the Amplify and Forward (AF) scheme which simplifies the design of encoders and the decoder, performs close to the optimal scheme even at high SNR. Also, it outperforms a recently proposed scalar quantizer scheme both in performance and complexity. We also study AF when there is side information at the encoders and decoder.