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General Properties (general + property)

Distribution by Scientific Domains

Physics and Astronomy	26%
Chemistry	26%
Mathematics and Statistics	17%
Life Sciences	13%

Selected Abstracts

Models of sensor operations for border surveillance,

NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 1 2008
Roberto Szechtman
Abstract This article is motivated by the diverse array of border threats, ranging from terrorists to arms dealers and human traffickers. We consider a moving sensor that patrols a certain section of a border with the objective to detect infiltrators who attempt to penetrate that section. Infiltrators arrive according to a Poisson process along the border with a specified distribution of arrival location, and disappear a random amount of time after their arrival. The measures of effectiveness are the target (infiltrator) detection rate and the time elapsed from target arrival to target detection. We study two types of sensor trajectories that have constant endpoints, are periodic, and maintain constant speed: (1) a sensor that jumps instantaneously from the endpoint back to the starting-point, and (2) a sensor that moves continuously back and forth. The controlled parameters (decision variables) are the starting and end points of the patrolled sector and the velocity of the sensor. General properties of these trajectories are investigated. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2008 [source]

Growth and characterization of La3Ga5.5Ta0.5O14 crystal

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2004
Haikuan Kong
Abstract La3Ga5.5Ta0.5O14 (LGT) crystal was grown by using the Czochralski method. The as-grown crystal is transparent, free from inclusions and with no cracks. Specific heat, thermal expansion, dielectric constants, transmission spectrum and optical damage threshold of LGT have been measured, and the results show general properties of LGT are similar to that of La3Ga5SiO14 (LGS) crystal. The experiment to research the Q-switch properties of LGT has been performed and the results show LGT possesses smaller electrooptic coefficients than that of LGS and may not be an ideal material used as a Q-switch. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

One-particle density matrix functional for correlation in molecular systems

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2003
Mario Piris
Abstract Based on the analysis of the general properties for the one- and two-particle reduced density matrices, a new natural orbital functional is obtained. It is shown that by partitioning the two-particle reduced density matrix in an antisymmeterized product of one-particle reduced density matrices and a correction ,c we can derive a corrected Hartree,Fock theory. The spin structure of the correction term from the improved Bardeen,Cooper,Schrieffer theory is considered to take into account the correlation between pairs of electrons with antiparallel spins. The analysis affords a nonidempotent condition for the one-particle reduced density matrix. Test calculations of the correlation energy and the dipole moment of several molecules in the ground state demonstrate the reliability of the formalism. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 317,323, 2003 [source]

A parameter-reduced volterra model for dynamic RF power amplifier modeling based on orthonormal basis functions

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2007
M. Isaksson
Abstract A nonlinear dynamic behavioral model for radio frequency power amplifiers is presented. It uses orthonormal basis functions, Kautz functions, with complex poles that are different for each nonlinear order. It has the same general properties as Volterra models, but the number of parameters is significantly smaller. Using frequency weighting the out-of-band model error can be reduced. Using experimental data it was found that the optimal poles were the same for different input powers and for the different nonlinear orders. The optimal poles were also the same for direct and inverse models, which could be explained theoretically to be a general property of nonlinear systems with negligible linear memory effects. The model can be used as either a direct or inverse model with the same model error for power amplifiers with negligible linear memory effects. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source]

Structure, function, and regulation of renal organic anion transporters

MEDICINAL RESEARCH REVIEWS, Issue 6 2002
Guofeng You
Abstract Renal elimination of anionic drugs, xenobiotics, and toxins is necessary for the survival of mammalian species. This process is mediated by vectorial transport from blood to urine through the cooperative functions of specific transporters in the basolateral and apical membranes of the proximal tubule epithelium. The first step of this process is the extraction of organic anions from the peritubular blood plasma into proximal tubule cells largely through the organic anion transporter (OAT) pathway. Therefore, the OAT pathway is one of the major sites for body drug clearance/detoxification. As a result, it is also the site for drug,drug interaction and drug-induced nephrotoxicity. To maximize therapeutic efficacy and minimize toxicity, the structure-function relationships of OATs and their regulation must be defined. The recent cloning and identification of OATs have paved the way for such investigations. This review summarizes the available data on the general properties of OATs, focusing in particular on the recent progress made from the author's laboratory as well as from other's, on the molecular characterization of the structure-function relationships of OATs and their regulatory mechanisms. © 2002 Wiley Periodicals, Inc. Med Res Rev, 22, No. 6, 602,616, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10019 [source]

Massive stars exploding in a He-rich circumstellar medium , I. Type Ibn (SN 2006jc-like) events

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
A. Pastorello
ABSTRACT We present new spectroscopic and photometric data of the Type Ibn supernovae 2006jc, 2000er and 2002ao. We discuss the general properties of this recently proposed supernova family, which also includes SN 1999cq. The early-time monitoring of SN 2000er traces the evolution of this class of objects during the first few days after the shock breakout. An overall similarity in the photometric and spectroscopic evolution is found among the members of this group, which would be unexpected if the energy in these core-collapse events was dominated by the interaction between supernova ejecta and circumstellar medium. Type Ibn supernovae appear to be rather normal Type Ib/c supernova explosions which occur within a He-rich circumstellar environment. SNe Ibn are therefore likely produced by the explosion of Wolf,Rayet progenitors still embedded in the He-rich material lost by the star in recent mass-loss episodes, which resemble known luminous blue variable eruptions. The evolved Wolf,Rayet star could either result from the evolution of a very massive star or be the more evolved member of a massive binary system. We also suggest that there are a number of arguments in favour of a Type Ibn classification for the historical SN 1885A (S-Andromedae), previously considered as an anomalous Type Ia event with some resemblance to SN 1991bg. [source]

The X-ray spectra of Compton-thick Seyfert 2 galaxies as seen by BeppoSAX

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2000
G. Matt
Results from BeppoSAX observations of Compton-thick Seyfert 2 galaxies are summarized and reviewed, and their general properties derived and discussed. In five out of the seven observed sources, the nucleus is directly visible at high X-ray energies, where the photons penetrate absorbers with column densities in the range 1.1,4.3×1024 cm,2 (in the other two sources, NGC 1068 and NGC 7674, the nucleus is instead totally obscured at all energies, implying even larger column densities). In most sources there is unambiguous evidence of a reflection component from optically thick, cold matter, while in two (or maybe four) cases there is also evidence of reflection from ionized matter. For the sources with a measured X-ray luminosity, a comparison with the infrared luminosity is made; while in two cases (the Circinus galaxy and NGC 4945) the IR emission appears to be dominated by starburst activity, in the other three sources (NGC 6240, Mrk 3 and TOL 0109-383) it is likely to be dominated by reprocessing of the UV and X-ray photons emitted by an active galactic nucleus. [source]

Dynameomics: Large-scale assessment of native protein flexibility

PROTEIN SCIENCE, Issue 12 2008
Noah C. Benson
Abstract Structure is only the first step in understanding the interactions and functions of proteins. In this paper, we explore the flexibility of proteins across a broad database of over 250 solvated protein molecular dynamics simulations in water for an aggregate simulation time of ,6 ,s. These simulations are from our Dynameomics project, and these proteins represent approximately 75% of all known protein structures. We employ principal component analysis of the atomic coordinates over time to determine the primary axis and magnitude of the flexibility of each atom in a simulation. This technique gives us both a database of flexibility for many protein fold families and a compact visual representation of a particular protein's native-state conformational space, neither of which are available using experimental methods alone. These tools allow us to better understand the nature of protein motion and to describe its relationship to other structural and dynamical characteristics. In addition to reporting general properties of protein flexibility and detailing many dynamic motifs, we characterize the relationship between protein native-state flexibility and early events in thermal unfolding and show that flexibility predicts how a protein will begin to unfold. We provide evidence that fold families have conserved flexibility patterns, and family members who deviate from the conserved patterns have very low sequence identity. Finally, we examine novel aspects of highly inflexible loops that are as important to structural integrity as conventional secondary structure. These loops, which are difficult if not impossible to locate without dynamic data, may constitute new structural motifs. [source]

Protein interaction networks of Saccharomyces cerevisiae, Caenorhabditis elegans and Drosophila melanogaster: Large-scale organization and robustness

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2006
Dong Li
Abstract High-throughput screens have begun to reveal protein interaction networks in several organisms. To understand the general properties of these protein interaction networks, a systematic analysis of topological structure and robustness was performed on the protein interaction networks of Saccharomyces cerevisiae, Caenorhabditis elegans and Drosophila melanogaster. It shows that the three protein interaction networks have a scale-free and high-degree clustering nature as the consequence of their hierarchical organization. It also shows that they have the small-world property with similar diameter at 4,5. Evaluation of the consequences of random removal of both proteins and interactions from the protein interaction networks suggests their high degree of robustness. Simulation of a protein's removal shows that the protein interaction network's error tolerance is accompanied by attack vulnerability. These fundamental analyses of the networks might serve as a starting point for further exploring complex biological networks and the coming research of "systems biology". [source]

Coin flipping from a cosmic source: On error correction of truly random bits

RANDOM STRUCTURES AND ALGORITHMS, Issue 4 2005
Elchanan Mossel
We study a problem related to coin flipping, coding theory, and noise sensitivity. Consider a source of truly random bits x , {0, 1}n, and k parties, who have noisy version of the source bits yi , {0, 1}n, when for all i and j, it holds that P[y = xj] = 1 , ,, independently for all i and j. That is, each party sees each bit correctly with probability 1 , ,, and incorrectly (flipped) with probability ,, independently for all bits and all parties. The parties, who cannot communicate, wish to agree beforehand on balanced functions fi: {0, 1}n , {0, 1} such that P[f1(y1) = , = fk(yk)] is maximized. In other words, each party wants to toss a fair coin so that the probability that all parties have the same coin is maximized. The function fi may be thought of as an error correcting procedure for the source x. When k = 2,3, no error correction is possible, as the optimal protocol is given by fi(yi) = y. On the other hand, for large values of k, better protocols exist. We study general properties of the optimal protocols and the asymptotic behavior of the problem with respect to k, n, and ,. Our analysis uses tools from probability, discrete Fourier analysis, convexity, and discrete symmetrization. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005 [source]

Generalized mixtures in reliability modelling: Applications to the construction of bathtub shaped hazard models and the study of systems

APPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 3 2009
Jorge Navarro
Abstract In this paper, we obtain and discuss some general properties of hazard rate (HR) functions constructed via generalized mixtures of two members. These results are applied to determine the shape of generalized mixtures of an increasing hazard rate (IHR) model and an exponential model. In addition, we note that these kind of generalized mixtures can be used to construct bathtub-shaped HR models. As examples, we study in detail two cases: when the IHR model chosen is a linear HR function and when the IHR model is the extended exponential-geometric distribution. Finally, we apply the results and show the utility of generalized mixtures in determining the shape of the HR function of different systems, such as mixed systems or consecutive k -out-of- n systems. Copyright © 2008 John Wiley & Sons, Ltd. [source]

On the shape of the mean residual lifetime function

APPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 2 2002
M. S. Finkelstein
Abstract Some general properties of the mean residual life (MRL) function are studied. The analysis is based on the shape of the corresponding failure rate. The conditions under which the failure rate and the reciprocal to the MRL function have asymptotically equivalent behaviour as t,, are discussed. The simplest non-monotone shapes of the functions under consideration (bathtub and upside down bathtub) are also considered. The MRL functions for mixtures of distributions are described via the corresponding conditional probability density functions. The direct proportional model of mixing is characterized and some asymptotic results on the shape of the mixture MRL are obtained. Some simple examples are given. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Partial oxidation and oxidative polymerization of metallothionein

ELECTROPHORESIS, Issue 20 2008
Hajo Haase
Abstract One mechanism for regulation of metal binding to metallothionein (MT) involves the non-enzymatic or enzymatic oxidation of its thiols to disulfides. Formation and speciation of oxidized MT have not been investigated in detail despite the biological significance of this redox biochemistry. While metal ion-bound thiols in MT are rather resistant towards oxidation, free thiols are readily oxidized. MT can be partially oxidized to a state in which some of its thiols remain reduced and bound to metal ions. Analysis of the oxidation products with SDS-PAGE and a thiol-specific labeling technique, employing eosin-5-iodoacetamide, demonstrates higher-order aggregates of MT with intermolecular disulfide linkages. The polymerization follows either non-enzymatic or enzymatic oxidation, indicating that it is a general property of oxidized MT. Supramolecular assemblies of MT add new perspectives to the complex redox and metal equilibria of this protein. [source]

A parameter-reduced volterra model for dynamic RF power amplifier modeling based on orthonormal basis functions

Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2007
J. Thomas
ABSTRACT Dynamical models for 17 early-type galaxies in the Coma cluster are presented. The galaxy sample consists of flattened, rotating as well as non-rotating early-types including cD and S0 galaxies with luminosities between MB=,18.79 and ,22.56. Kinematical long-slit observations cover at least the major-axis and minor-axis and extend to 1,4reff. Axisymmetric Schwarzschild models are used to derive stellar mass-to-light ratios and dark halo parameters. In every galaxy, the best fit with dark matter matches the data better than the best fit without. The statistical significance is over 95 per cent for eight galaxies, around 90 per cent for five galaxies and for four galaxies it is not significant. For the highly significant cases, systematic deviations between models without dark matter and the observed kinematics are clearly seen; for the remaining galaxies, differences are more statistical in nature. Best-fitting models contain 10,50 per cent dark matter inside the half-light radius. The central dark matter density is at least one order of magnitude lower than the luminous mass density, independent of the assumed dark matter density profile. The central phase-space density of dark matter is often orders of magnitude lower than that in the luminous component, especially when the halo core radius is large. The orbital system of the stars along the major-axis is slightly dominated by radial motions. Some galaxies show tangential anisotropy along the minor-axis, which is correlated with the minor-axis Gauss,Hermite coefficient H4. Changing the balance between data-fit and regularization constraints does not change the reconstructed mass structure significantly: model anisotropies tend to strengthen if the weight on regularization is reduced, but the general property of a galaxy to be radially or tangentially anisotropic does not change. This paper is aimed to set the basis for a subsequent detailed analysis of luminous and dark matter scaling relations, orbital dynamics and stellar populations. [source]

Structural stability and heat-induced conformational change of two complement inhibitors: C4b-binding protein and factor H

PROTEIN SCIENCE, Issue 5 2004
Lena Kask
C4BP, C4b-binding protein; FH, factor H; CCP, complement control protein; CD, circular dichroism; FTIR, Fourier transform-infrared spectroscopy; PT, prothrombin; VCP, vaccinia virus complement control protein Abstract The complement inhibitors C4b-binding protein (C4BP) and factor H (FH) both consist of complement control protein (CCP) domains. Here we examined the secondary structure of both proteins by circular dichroism and Fourier-transform infrared technique at temperatures ranging from 30°C,90°C. We found that predominantly ,-sheet structure of both proteins was stable up to 70°C, and that a reversible conformational change toward ,-helix was apparent at temperatures ranging from 70°C to 90°C. The ability of both proteins to inhibit complement was not impaired after incubation at 95°C, exposure to extreme pH conditions, and storage at room temperature for several months. Similar remarkable stability was previously observed for vaccinia virus control protein (VCP), which is also composed of CCP domains; it therefore seems to be a general property of CCP-containing proteins. A typical CCP domain has a hydrophobic core, which is wrapped in ,-sheets and stabilized by two disulphide bridges. How the CCP domains tolerate harsh conditions is unclear, but it could be due to a combination of high content of prolines, hydrophobic residues, and the presence of two disulphide bridges within each domain. These findings are of interest because CCP-containing complement inhibitors have been proposed as clinical agents to be used to control unwanted complement activation that contributes to many diseases. [source]

The acid-induced folded state of Sac7d is the native state

PROTEIN SCIENCE, Issue 10 2000
Jennifer L. Bedell
Abstract Sac7d unfolds at low pH in the absence of salt, with the greatest extent of unfolding obtained at pH 2. We have previously shown that the acid unfolded protein is induced to refold by decreasing the pH to 0 or by addition of salt (McCrary BS, Bedell J, Edmondson SP, Shriver JW, 1998, J Mol Biol 276:203,224). Both near-ultraviolet circular dichroism spectra and ANS fluorescence enhancements indicate that the acid- and salt-induced folded states have a native fold and are not molten globular. 1H, 15N heteronuclear single quantum coherence NMR spectra confirm that the native, acid-, and salt-induced folded states are essentially identical. The most significant differences in amide 1H and 15N chemical shifts are attributed to hydrogen bonding to titrating carboxyl side chains and through-bond inductive effects. The 1H NMR chemical shifts of protons affected by ring currents in the hydrophobic core of the acid- and salt-induced folded states are identical to those observed in the native. The radius of gyration of the acid-induced folded state at pH 0 is shown to be identical to that of the native state at pH 7 by small angle X-ray scattering. We conclude that acid-induced collapse of Sac7d does not lead to a molten globule but proceeds directly to the native state. The folding of Sac7d as a function of pH and anion concentration is summarized with a phase diagram that is similar to those observed for other proteins that undergo acid-induced folding except that the A-state is encompassed by the native state. These results demonstrate that formation of a molten globule is not a general property of proteins that are refolded by acid. [source]

Cell Subpopulation-related Volumetric Parameters: a Complementary Tool of the Modified Hypo-osmotic Swelling Test on Model of Boar Spermatozoa

REPRODUCTION IN DOMESTIC ANIMALS, Issue 5 2000
A. Petrounkina
Content It is a general property of the intact animal cell to swell rapidly in response to hypo-osmotic conditions. The modified hypo-osmotic swelling test (HOS-test) is an indicative test to evaluate the integrity of the plasma membrane by means of an electronic cell counter, based on the relative increase of the cell volume in response to hypo-osmotic conditions. In this study the relationships between the osmotically induced changes of the cell volume of boar spermatozoa as determined by cell counter and the integrity of the membrane as determined by propidium iodide staining (PI) were studied. Boar sperm cell volume distributions were measured under iso-osmotic (300 mosmolar) conditions and after a hypo-osmotic stress (150 mosmolar). The relative volume shift of mean and modal volume were calculated as a proportion coefficient of modal and mean values of the cell volume distributions by transition from iso-osmotic to hypo-osmotic conditions. The volumetric parameters related to the different cell subpopulations were derived from the different peaks of cell volume distributions. PI-staining techniques were used for comparison. The values of the volume shift and of derived percentages of the osmotically inactive cells were correlated negatively and positively, respectively (p < 0.05) with the percentage of the PI-stained cells. This correlation indicates that a relationship exists between membrane functions of the different cell compartments (sperm head and tail) due to the circumstance that the increase of the cell volume in the HOS-test is associated with the morphological changes in the tail and the PI-staining is associated with the membrane integrity and permeability of the head region. The advantage of computer-assisted volume measurement is that a large number of cells (5000,50 000 spermatozoa) can be measured and evaluated during one procedure and in a very short time. The relative volume shift is a quantitative continuous parameter characterizing the osmotic reactivity and membrane functional competence of a cell population and of subpopulations within one ejaculate. This parameter could be useful to evaluate membrane functional competence rapidly and sensitively. Inhalt Es ist eine generelle Eigenschaft membranintakter tierischer Zellen, mit einer Volumenzunahme auf eine hypoosmotische Belastung zu reagieren. Der auf der relativen Vergrößierungdes Zellvolumens basierende modifizierte hypoosmotischeSchwelltest ist ein indikativer Test zur Beurteilung der Membranintegrität mittels eines elektronischen Partikelzählers. In dieser Studie wurden die Zusammenhänge zwischen der mittels der Propidiumjodid-Färbung bestimmten Zellmembranintegrität und den osmotisch induzierten Veränderungen des Zellvolumens von Eberspermien untersucht. Volumenverteilungen von Eberspermien wurden unter isoosmotischen (300 mosmolar) und hypoosmotischen (150 mosmolar) Bedingungen gemessen. Die relative Volumenverschiebung der modalen und mittleren Werte der Volumenverteilung wurde als Quotient aus Modalwerten der Zellvolumenverteilungen und des mittleren Zellvolumens beim Übergang von isotonen zu hypotonen Bedingungen berechnet. Die auf verschiedene Subpopulationen bezogenen volumetrischen Parameter werden aus den originalen Volumenverteilungen berechnet. Der Betrag der Zellvolumenzunahme und die aus den Volumenverteilungen bestimmten Anteile an Zellen mit beschädigter Geißielmembran korrelierten signifikant negativ bzw. positiv (p < 0,05) mit dem Anteil an den Zellen mit beschädigter Kopfmembran, der sich aus der Propidiumjodid-Färbung ergab. Es wird geschlossen, daßi im Verhalten zwischen den Membranen der verschiedenen Zellkompartimente (Spermienkopf und-Geißiel) ein Zusammenhang besteht. Die beschriebene Methode ermöglicht die Analyse großier Zellpopulationen (5.000,50.000 Zellen). Die relative Volumenverschiebung stellt einen quantitativen kontinuierlichen Parameter dar, der den Membranzustand der Eberspermien einer Spermatozoenpopulation und Subpopulationen innerhalb eines Ejakulates charakterisiert. Diese Parameter können zur schnellen und sensitiven Beurteilung der Membranzustandes eingesetzt werden. [source]

The folate metabolic enzyme ALDH1L1 is restricted to the midline of the early CNS, suggesting a role in human neural tube defects

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2007
Todd E. Anthony
Abstract Folate supplementation prevents up to 70% of human neural tube defects (NTDs), although the precise cellular and metabolic sites of action remain undefined. One possibility is that folate modulates the function of metabolic enzymes expressed in cellular populations involved in neural tube closure. Here we show that the folate metabolic enzyme ALDH1L1 is cell-specifically expressed in PAX3-negative radial glia at the midline of the neural tube during early murine embryogenesis. Midline restriction is not a general property of this branch of folate metabolism, as MTHFD1 displays broad and apparently ubiquitous expression throughout the neural tube. Consistent with previous work showing antiproliferative effects in vitro, ALDH1L1 upregulation during central nervous system (CNS) development correlates with reduced proliferation and most midline ALDH1L1+ cells are quiescent. These data provide the first evidence for localized differences in folate metabolism within the early neural tube and suggest that folate might modulate proliferation via effects on midline Aldh1l1+ cells. To begin addressing its role in neurulation, we analyzed a microdeletion mouse strain lacking Aldh1l1 and observed neither increased failure of neural tube closure nor detectable proliferation defects. Although these results indicate that loss-of-function Aldh1l1 mutations do not impair these processes in mice, the specific midline expression of ALDH1L1 and its ability to dominantly suppress proliferation in a folate responsive manner may suggest that mutations contributing to disease are gain-of-function, rather than loss-of-function. Moreover, a role for loss-of-function mutations in human NTDs remains possible, as Mthfr null mice do not develop NTDs even though MTHFR mutations increase human NTD risk. J. Comp. Neurol. 500:368,383, 2007. © 2006 Wiley-Liss, Inc. [source]

Sexual dimorphism of vocal control nuclei in budgerigars (Melopsittacus undulatus) revealed with Nissl and NADPH-d staining

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2005
Steven E. Brauth
Abstract Nissl staining and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry were used to explore the existence of sexual dimorphism in vocal control nuclei of adult budgerigars (Melopsittacus undulatus), a parrot species capable of lifelong vocal learning. Behavioral studies indicate that adult males possess larger vocal repertoires than adult females and learn new calls more quickly. The results of the present study show that the volumes of all vocal nuclei, as measured using both Nissl-stained and NADPH-d-stained material, as well as the total numbers of NADPH-d neurons, were 35,110% greater in males. Furthermore, all vocal nuclei exhibit conspicuous NADPH-d staining compared to surrounding fields in both adult males and females. Nevertheless, there were no significant gender differences in either the intensity of neuropil staining or the densities of NADPH-d neurons in vocal nuclei. Moreover NADPH-d neuron somal shapes were similar in males and females. Diameters of NADPH-d neurons in vocal nuclei were 8.5,32% larger in males than in females. Greater size of NADPH-d neuronal somata in males may be a general property of this cell type in budgerigars because a similar gender difference was found in a visual nucleus, the entopallium, which is not directly associated with the vocal control system and does not exhibit sexual dimorphism in total volume or total NADPH-d neuron numbers. Taken together, the results of the present study favor the hypothesis that superior lifelong vocal learning ability in male budgerigars rests largely on larger volumes of vocal control nuclei in males rather than on sexual dimorphism in the internal composition of vocal nuclei. J. Comp. Neurol. 484:15,27, 2005. © 2005 Wiley-Liss, Inc. [source]

Entanglement of spin chains with general boundaries and of dissipative systems

ANNALEN DER PHYSIK, Issue 7-8 2009
T. Stauber
Abstract We analyze the entanglement properties of spins (qubits) close to the boundary of spin chains in the vicinity of a quantum critical point and show that the concurrence at the boundary is significantly different from the one of bulk spins. We also discuss the von Neumann entropy of dissipative environments in the vicinity of a (boundary) critical point, such as two Ising-coupled Kondo-impurities or the dissipative two-level system. Our results indicate that the entanglement (concurrence and/or von Neumann entropy) changes abruptly at the point where coherent quantum oscillations cease to exist. The phase transition modifies significantly less the entanglement if no symmetry breaking field is applied and we argue that this might be a general property of the entanglement of dissipative systems. We finally analyze the entanglement of an harmonic chain between the two ends as function of the system size. [source]

Entanglement of spin chains with general boundaries and of dissipative systems

Developing the Concept of Transparency for Use in Supply Relationships

BRITISH JOURNAL OF MANAGEMENT, Issue 4 2004
Richard Lamming
Management concern surrounding the supply of goods and services from business to business, and the related attempts to understand the phenomena observed therein, appears to rest upon a broad range of incompatible perspectives, from political science (often limited to considerations of power) to the logistical (akin to manipulation of a great, benign but dynamic jigsaw puzzle). It appears that all perspectives abrade against the difficulties of exchanging information, knowledge and innovation within the relationships between buying and selling organizations and the apparent chronic systemic inefficiency that transactions often represent in this context. This article addresses these concerns, exploring the concept of transparency and the developments necessary for it to be useful in exchanging sensitive information and tacit knowledge in supply relationships. Our central concern is how the understanding of transparency and its commercial importance may change when it is expressed as a manageable element of the relationship between two organizations rather than as a general property of a broader system (e.g. a supply network, industrial sub-sector, geographical cluster) and what utility this differentiation might hold for managers. The conclusion to the article, and the implication for managers, is that transparency might indeed be created and usefully managed within supply relationships but that it would differ fundamentally in meaning from previously posited concepts, with the same name, in different contexts. [source]