bluuebunny/crossref_metadata_2025 huggingface dataset:
Boundary-Layer Transition Affected by Surface Roughness and Free-Stream Turbulence
Authors: Roberts S. K. , Yaras M. I.
Published: May 2005

This paper presents experimental results documenting the effects of surface roughness and free-stream turbulence on boundary-layer transition. The experiments were conducted on a flat surface, upon which a pressure distribution similar to those prevailing on the suction side of low-pressure turbine blades was imposed. The test matrix consists of five variations in the roughness conditions, at each of three free-stream turbulence intensities (approximately 0.5%, 2.5%, and 4.5%), and two flow Reynolds numbers of 350,000 and 470,000. The ranges of these parameters considered in the study, which are typical of low-pressure turbines, resulted in both attached-flow and separation-bubble transition. The focus of the paper is on separation-bubble transition, but the few attached-flow test cases that occurred under high roughness and free-stream turbulence conditions are also presented for completeness of the test matrix. Based on the experimental results, the effects of surface roughness on the location of transition onset and the rate of transition are quantified, and the sensitivity of these effects to free-stream turbulence is established. The Tollmien–Schlichting instability mechanism is shown to be responsible for transition in each of the test cases presented. The root-mean-square height of the surface roughness elements, their planform size and spacing, and the skewness (bias towards depression or protrusion roughness) of the roughness distribution are shown to be relevant to quantifying the effects of roughness on the transition process.
Unstructured Grid Based Reynolds-Averaged Navier-Stokes Method for Liquid Tank Sloshing
Authors: Rhee Shin Hyung
Published: May 2005

The present study is concerned with liquid tank sloshing at low filling level conditions. The volume of fluid method implemented in a Navier–Stokes computational fluid dynamics code is employed to handle the free-surface flow of liquid sloshing. The geometric reconstruction scheme for the interface representation is employed to ensure sharpness at the free surface. The governing equations are discretized by second order accurate schemes on unstructured grids. Several different computational approaches are verified and numerical uncertainties are assessed. The computational results are validated against existing experimental data, showing good agreement. The capability is demonstrated for a generic membrane-type liquefied natural gas carrier tank with a simplified pump tower inside. The validation results suggest that the present computational approach is both easy to apply and accurate enough for more realistic problems.
Statistical Approach for Estimating Intervals of Certification or Biases of Facilities or Measurement Systems Including Uncertainties
Authors: Stern F. , Olivieri A. , Shao J. , Longo J. , Ratcliffe T.
Published: May 2005

A statistical approach for estimating intervals of certification or biases of facilities or measurement systems including uncertainties is set forth based on M×N-order level testing, which is defined as M repetitions of the same N-order level experiment in M different facilities or in the same facility with M different measurement systems. In the absence of reference values, the mean facility or measurement system is used for assessing intervals of certification or biases. Certification or biases of facilities or measurement systems are defined as processes for assessing probabilistic confidence intervals for facilities or measurement systems for specific tests, data reduction equations, conditions, procedures, and uncertainty analysis. Similarly, subgroup analysis is performed for isolating and assessing levels of differences due to use of different model sizes (scale effects) or measurement systems. An example is provided for towing tank facilities for resistance tests using standard uncertainty analysis procedures based on an international collaboration between three facilities. Although the number of facilities are at a minimum, the results demonstrate the usefulness of an approach and support recommendation of future collaborations between more facilities. Knowledge of intervals of certification or biases is important for design, accrediting facilities or measurement systems, and CFD validation.
NEWTON FLOW AND INTERIOR POINT METHODS IN LINEAR PROGRAMMING
Authors: DEDIEU JEAN-PIERRE , SHUB MIKE
Published: May 2005

We study the geometry of the central paths of linear programming theory. These paths are the solution curves of the Newton vector field of the logarithmic barrier function. This vector field extends to the boundary of the polytope and we study the main properties of this extension: continuity, analyticity, singularities.
STRAIGHTFORWARD COMPUTATION OF SPATIAL EQUILIBRIA OF GEOMETRICALLY EXACT COSSERAT RODS
Authors: HEALEY T. J. , MEHTA P. G.
Published: May 2005

In this paper, we present a well posed "force" based formulation for nonlinearly elastic Cosserat rods with general boundary conditions enabling straightforward, efficient computation of spatial equilibria. We illustrate the ease and utility of our approach in four example problems, each exhibiting large spatial buckling, employing the path-following software AUTO.
EQUATION-FREE, EFFECTIVE COMPUTATION FOR DISCRETE SYSTEMS: A TIME STEPPER BASED APPROACH
Authors: MÖLLER J. , RUNBORG O. , KEVREKIDIS P. G. , LUST K. , KEVREKIDIS I. G.
Published: May 2005

We propose a computer-assisted approach to studying the effective continuum behavior of spatially discrete evolution equations. The advantage of the approach is that the "coarse model" (the continuum, effective equation) need not be explicitly constructed. The method only uses a time-integration code for the discrete problem and judicious choices of initial data and integration times; our bifurcation computations are based on the so-called Recursive Projection Method (RPM) with arc-length continuation [Shroff & Keller, 1993]. The technique is used to monitor features of the genuinely discrete problem such as the pinning of coherent structures and its results are compared to quasi-continuum approaches such as the ones based on Padé approximations.
COMMUTATORS OF SKEW-SYMMETRIC MATRICES
Authors: BLOCH ANTHONY M. , ISERLES ARIEH
Published: May 2005

In this paper we develop a theory for analysing the "radius" of the Lie algebra of a matrix Lie group, which is a measure of the size of its commutators. Complete details are given for the Lie algebra 𝔰𝔬(n) of skew symmetric matrices where we prove [Formula: see text], X, Y ∈ 𝔰𝔬(n), for the Frobenius norm. We indicate how these ideas might be extended to other matrix Lie algebras. We discuss why these ideas are of interest in applications such as geometric integration and optimal control.
MULTIPLE HELICAL PERVERSIONS OF FINITE, INTRISTICALLY CURVED RODS
Authors: DOMOKOS G. , HEALEY T. J.
Published: May 2005

We investigate mechanical spatial equilibria of slender elastic rods with intristic curvature. Our work is, to some extent, motivated by papers [Goriely & Tabor, 1998; Goriely & McMillen 2002]. There such rods of infinite length were recently studied to quantify the behavior of botanical filaments. In particular, an adequate explanation for the existence of helical perversions (the transition between helical segments of opposite handedness) is provided in [Goriely & Tabor, 1998]. However, this theory fails to describe multiple perversions, which can be observed in Nature. In contrast we formulate a two-point boundary-value problem describing rods of finite length with initial curvature and clamped ends. We identify trivial solutions as straight configurations and also k-covered circles, rigorously establish the existence of local bifurcations, and then compute global solutions via the Parallel Hybrid Algorithm [Domokos & Szeberényi, 2004] to find spatially complex equilibria characterized by multiple perversions. Based on computational results and the White–Fuller theorem [White, 1969; Fuller, 1971; Calugareanu, 1961] we describe a heuristic global picture of the bifurcation diagram, which can serve as an explanation for the evolution of physically observable tendril shapes.
AN ALGORITHM FOR FINDING INVARIANT ALGEBRAIC CURVES OF A GIVEN DEGREE FOR POLYNOMIAL PLANAR VECTOR FIELDS
Authors: ŚWIRSZCZ GRZEGORZ
Published: May 2005

Given a system of two autonomous ordinary differential equations whose right-hand sides are polynomials, it is very hard to tell if any nonsingular trajectories of the system are contained in algebraic curves. We present an effective method of deciding whether a given system has an invariant algebraic curve of a given degree. The method also allows the construction of examples of polynomial systems with invariant algebraic curves of a given degree. We present the first known example of a degree 6 algebraic saddle-loop for polynomial system of degree 2, which has been found using the described method. We also present some new examples of invariant algebraic curves of degrees 4 and 5 with an interesting geometry.
BIFURCATIONS AND CONTINUOUS TRANSITIONS OF ATTRACTORS IN AUTONOMOUS AND NONAUTONOMOUS SYSTEMS
Authors: KLOEDEN P. E. , SIEGMUND S.
Published: May 2005

Nonautonomous bifurcation theory studies the change of attractors of nonautonomous systems which are introduced here with the process formalism as well as the skew product formalism.

We present a total stability theorem ensuring the existence of nearby attractors of perturbed systems. They depend continuously on a parameter if and only if the attraction is uniform w.r.t. parameter, i.e. the attractors are equiattracting.

We apply these principles to explicit systems to clarify the meaning of continuous and abrupt transitions of attractors in contrast to bifurcations, i.e. splitting of minimal invariant subsets into others within the attractor. Several examples are treated, including a nonautonomous pitchfork bifurcation.
BIFURCATIONS OF STABLE SETS IN NONINVERTIBLE PLANAR MAPS
Authors: ENGLAND J. P. , KRAUSKOPF B. , OSINGA H. M.
Published: May 2005

Many applications give rise to systems that can be described by maps that do not have a unique inverse. We consider here the case of a planar noninvertible map. Such a map folds the phase plane, so that there are regions with different numbers of preimages. The locus, where the number of preimages changes, is made up of so-called critical curves, that are defined as the images of the locus where the Jacobian is singular. A typical critical curve corresponds to a fold under the map, so that the number of preimages changes by two.

We consider the question of how the stable set of a hyperbolic saddle of a planar noninvertible map changes when a parameter is varied. The stable set is the generalization of the stable manifold for the case of an invertible map. Owing to the changing number of preimages, the stable set of a noninvertible map may consist of finitely or even infinitely many disjoint branches. It is now possible to compute stable sets with the Search Circle algorithm that we developed recently.

We take a bifurcation theory point of view and consider the two basic codimension-one interactions of the stable set with a critical curve, which we call the outer-fold and the inner-fold bifurcations. By taking into account how the stable set is organized globally, these two bifurcations allow one to classify the different possible changes to the structure of a basin of attraction that are reported in the literature. The fundamental difference between the stable set and the unstable manifold is discussed. The results are motivated and illustrated with a single example of a two-parameter family of planar noninvertible maps.
SIMPLE NEURAL NETWORKS THAT OPTIMIZE DECISIONS
Authors: BROWN ERIC , GAO JUAN , HOLMES PHILIP , BOGACZ RAFAL , GILZENRAT MARK , COHEN JONATHAN D.
Published: May 2005

We review simple connectionist and firing rate models for mutually inhibiting pools of neurons that discriminate between pairs of stimuli. Both are two-dimensional nonlinear stochastic ordinary differential equations, and although they differ in how inputs and stimuli enter, we show that they are equivalent under state variable and parameter coordinate changes. A key parameter is gain: the maximum slope of the sigmoidal activation function. We develop piecewise-linear and purely linear models, and one-dimensional reductions to Ornstein–Uhlenbeck processes that can be viewed as linear filters, and show that reaction time and error rate statistics are well approximated by these simpler models. We then pose and solve the optimal gain problem for the Ornstein–Uhlenbeck processes, finding explicit gain schedules that minimize error rates for time-varying stimuli. We relate these to time courses of norepinephrine release in cortical areas, and argue that transient firing rate changes in the brainstem nucleus locus coeruleus may be responsible for approximate gain optimization.
COARSE-GRAINED OBSERVATION OF DISCRETIZED MAPS
Authors: DOMOKOS GÁBOR
Published: May 2005

We investigate why discretized versions fN of one-dimensional ergodic maps f : I → I behave in many ways similarly to their continuous counterparts. We propose to register observations of the N × N discretization fN on a coarse M × M grid, with N = cM, c being an integer. We prove that rounding errors behave like uniformly distributed random variables, and by assuming their independence, the M × M incidence matrix AM associated with the continuous map (indicating which of the M equal subintervals is mapped onto which) can be expected to be identical to the incidence matrix BN,M associated with the aforementioned coarse grid, if [Formula: see text], where deg (f) denotes the degree of f. We show how coarse-grained registration can be used as a "digital" definition of an unstable orbit and how this can be applied in real computations. Combination of these results with ideas from the random map model suggests an intuitive explanation for the statistical similarity between f and fN. Our approach is not a rigorous one, however, we hope that the results will be useful for the computational community and may facilitate a rigourous mathematical description.
NUMERICAL CONTINUATION OF BRANCH POINTS OF EQUILIBRIA AND PERIODIC ORBITS
Authors: DOEDEL E. J. , GOVAERTS W. , KUZNETSOV YU. A. , DHOOGE A.
Published: May 2005

We consider the three-parameter numerical continuation of branch points in dynamical systems, with emphasis on the continuation of branch points of periodic orbits. We consider both, the case of branch points along one-parameter families of limit cycles (typical in systems with symmetry), and the case of branch points along fold-curves of limit cycles (typical in generic systems). We discuss new algorithms based on bordered matrices for both detection and continuation. We apply the techniques to a model of a chemical reactor, a model of an electronic circuit, and a model from celestial mechanics. Our algorithms have been implemented in freely available software.
BIFURCATION TRACKING ALGORITHMS AND SOFTWARE FOR LARGE SCALE APPLICATIONS
Authors: SALINGER A. G. , BURROUGHS E. A. , PAWLOWSKI R. P. , PHIPPS E. T. , ROMERO L. A.
Published: May 2005

We present the set of bifurcation tracking algorithms which have been developed in the LOCA software library to work with large scale application codes that use fully coupled Newton's method with iterative linear solvers. Turning point (fold), pitchfork, and Hopf bifurcation tracking algorithms based on Newton's method have been implemented, with particular attention to the scalability to large problem sizes on parallel computers and to the ease of implementation with new application codes. The ease of implementation is accomplished by using block elimination algorithms to solve the Newton iterations of the augmented bifurcation tracking systems. The applicability of such algorithms for large applications is in doubt since the main computational kernel of these routines is the iterative linear solve of the same matrix that is being driven singular by the algorithm. To test the robustness and scalability of these algorithms, the LOCA library has been interfaced with the MPSalsa massively parallel finite element reacting flows code. A bifurcation analysis of an 1.6 Million unknown model of 3D Rayleigh–Bénard convection in a 5 × 5 × 1 box is successfully undertaken, showing that the algorithms can indeed scale to problems of this size while producing solutions of reasonable accuracy.
A BRIEF SURVEY ON THE NUMERICAL DYNAMICS FOR FUNCTIONAL DIFFERENTIAL EQUATIONS
Authors: GARAY BARNABAS M.
Published: May 2005

This is a survey on discretizing delay equations from a geometric-qualitative view-point. Concepts like compact attractors, hyperbolic periodic orbits, the saddle structure around hyperbolic equilibria, center-unstable manifolds of equilibria, inertial manifolds, structural stability, and Kamke monotonicity are considered. Error estimates for smooth and nonsmooth initial data in various Cj topologies are provided. The emphasis is put on Runge–Kutta methods with natural interpolants. The paper ends with a collection of the related results on retarded functional differential equations with bounded delay.
MULTIPARAMETRIC BIFURCATIONS IN AN ENZYME-CATALYZED REACTION MODEL
Authors: FREIRE E. , PIZARRO L. , RODRÍGUEZ-LUIS A. J. , FERNÁNDEZ-SÁNCHEZ F.
Published: May 2005

An exhaustive analysis of local and global bifurcations in an enzyme-catalyzed reaction model is carried out. The model, given by a planar five-parameter system of autonomous ordinary differential equations, presents a great richness of bifurcations. This enzyme-catalyzed model has been considered previously by several authors, but they only detected a minimal part of the dynamical and bifurcation behavior exhibited by the system.

First, we study local bifurcations of equilibria up to codimension-three (saddle-node, cusps, nondegenerate and degenerate Hopf bifurcations, and nondegenerate and degenerate Bogdanov–Takens bifurcations) by using analytical and numerical techniques. The numerical continuation of curves of global bifurcations allows to improve the results provided by the study of local bifurcations of equilibria and to detect new homoclinic connections of codimension-three. Our analysis shows that such a system exhibits up to sixteen different kinds of homoclinic orbits and thirty different configurations of equilibria and periodic orbits. The coexistence of up to five periodic orbits is also pointed out. Several bifurcation sets are sketched in order to show the dynamical behavior the system exhibits. The different codimension-one and -two bifurcations are organized around five codimension-three degeneracies.
A SURVEY OF METHODS FOR COMPUTING (UN)STABLE MANIFOLDS OF VECTOR FIELDS
Authors: KRAUSKOPF B. , OSINGA H. M. , DOEDEL E. J. , HENDERSON M. E. , GUCKENHEIMER J. , VLADIMIRSKY A. , DELLNITZ M. , JUNGE O.
Published: May 2005

The computation of global invariant manifolds has seen renewed interest in recent years. We survey different approaches for computing a global stable or unstable manifold of a vector field, where we concentrate on the case of a two-dimensional manifold. All methods are illustrated with the same example — the two-dimensional stable manifold of the origin in the Lorenz system.
TRANSPORT IN DYNAMICAL ASTRONOMY AND MULTIBODY PROBLEMS
Authors: DELLNITZ MICHAEL , JUNGE OLIVER , KOON WANG SANG , LEKIEN FRANCOIS , LO MARTIN W. , MARSDEN JERROLD E. , PADBERG KATHRIN , PREIS ROBERT , ROSS SHANE D. , THIERE BIANCA
Published: May 2005

We combine the techniques of almost invariant sets (using tree structured box elimination and graph partitioning algorithms) with invariant manifold and lobe dynamics techniques. The result is a new computational technique for computing key dynamical features, including almost invariant sets, resonance regions as well as transport rates and bottlenecks between regions in dynamical systems. This methodology can be applied to a variety of multibody problems, including those in molecular modeling, chemical reaction rates and dynamical astronomy. In this paper we focus on problems in dynamical astronomy to illustrate the power of the combination of these different numerical tools and their applicability. In particular, we compute transport rates between two resonance regions for the three-body system consisting of the Sun, Jupiter and a third body (such as an asteroid). These resonance regions are appropriate for certain comets and asteroids.
QUANDLES AT FINITE TEMPERATURES III
Authors: BOJARCZUK JOAQUIM , LOPES PEDRO
Published: May 2005

We resume work on telling embeddings of codimension two apart by counting colorings of the corresponding diagrams by given quandles. Previously, we illustrated the efficiency of this approach on classical knots. In the present paper we apply it to knotted surfaces. We recover work of Kamada in telling ribbon knots apart and we distinguish all elements of a class of twist-spun torus knots.
THE BRAID GROUP $B_{n,m}(\mathbb{S}^{2})$ AND A GENERALISATION OF THE FADELL–NEUWIRTH SHORT EXACT SEQUENCE
Authors: GONÇALVES DACIBERG LIMA , GUASCHI JOHN
Published: May 2005

Let m,n ∈ ℕ. We define [Formula: see text] to be the set of (n+m)-braids of the sphere whose associated permutation lies in the subgroup Sn× Smof the symmetric group Sn+mon n+m letters. In a previous paper [13], we showed that if n ≥ 3, then there exists the following generalisation of the Fadell–Neuwirth short exact sequence: [Formula: see text] where [Formula: see text] is the group homomorphism (defined for all n ∈ ℕ) given geometrically by forgetting the last m strings. In this paper we study the splitting of this short exact sequence, as well as the existence of a cross-section for the fibration [Formula: see text] of the quotients of the corresponding configuration spaces.

Our main results are as follows: if n = 1 (respectively, n = 2) then the homomorphism p*and the fibration p admit (respectively, do not admit) a section. If n = 3, then p*and p admit a section if and only if m ≡ 0,2 (mod 3). If n ≥ 4, we show that if p*and p admit a section then m ≡ ε1(n - 1)(n - 2) - ε2n(n - 2) (mod n(n - 1)(n - 2)), where ε1,ε2∈ {0,1}.

Finally, we show that [Formula: see text] is generated by two of its torsion elements.
LOGICS FROM QUANTUM COMPUTATION
Authors: DALLA CHIARA MARIA LUISA , GIUNTINI ROBERTO , LEPORINI ROBERTO
Published: May 2005

The theory of logical gates in quantum computation has suggested new forms of quantum logic, called quantum computational logics. The basic semantic idea is the following: the meaning of a sentence is identified with a quregister (a system of qubits) or, more generally, with a mixture of quregisters (called qumix). In this framework, any sentence α of the language gives rise to a quantum tree: a kind of quantum circuit that transforms the quregister (qumix) associated to the atomic subformulas of α into the quregister (qumix) associated to α. A variant of the quantum computational semantics is represented by the quantum holistic semantics, which permits us to represent entangled meanings. Physical models of quantum computational logics can be built by means of Mach–Zehnder interferometers.
IMPOSSIBILITY OF PERFECT QUANTUM SEALING OF CLASSICAL INFORMATION
Authors: BECHMANN-PASQUINUCCI HELLE , D'ARIANO GIACOMO MAURO , MACCHIAVELLO CHIARA
Published: May 2005

Sealing information means making it publicly available, but with the possibility of knowing if it has been read. Commenting on Ref. 1, we will show that perfect quantum sealing is not possible for perfectly retrievable information, due to the possibility of performing a perfect measurement without disturbance, even on unknown states. The measurement is a collective one, and this makes the protocol of quantum sealing very interesting as the only example of the power of collective measurements in breaking security.
EFFICIENT IMPLEMENTATIONS OF THE QUANTUM FOURIER TRANSFORM: AN EXPERIMENTAL PERSPECTIVE
Authors: DORAI KAVITA , SUTER DIETER
Published: May 2005

The Quantum Fourier transform (QFT) is a key ingredient in most quantum algorithms. We have compared various spin-based quantum computing schemes to implement the QFT from the point of view of their actual time-costs and the accuracy of the implementation. We focus here on an interesting decomposition of the QFT as a product of the non-selective Hadamard transformation followed by multiqubit gates corresponding to square- and higher-roots of controlled-NOT gates. This decomposition requires only O(n) operations and is thus linear in the number of qubits n. The schemes were implemented on a two-qubit NMR quantum information processor and the resultant density matrices reconstructed using standard quantum state tomography techniques. Their experimental fidelities have been measured and compared.
THE DEUTSCH–JOZSA ALGORITHM REVISITED IN THE DOMAIN OF CRYPTOGRAPHICALLY SIGNIFICANT BOOLEAN FUNCTIONS
Authors: MAITRA SUBHAMOY , MUKHOPADHYAY PARTHA
Published: May 2005

Boolean functions are important building blocks in cryptography for their wide application in both stream and block cipher systems. For cryptanalysis of such systems, one tries to find out linear functions that are correlated to the Boolean functions used in the crypto system. Let f be an n-variable Boolean function and its Walsh spectra is denoted by Wf(ω) at the point ω ∈ {0, 1}n. The Boolean function is available in the form of an oracle. We like to find a ω such that Wf(ω) ≠ 0 as this will provide one of the linear functions which are correlated to f. We show that the quantum algorithm proposed by Deutsch and Jozsa7 solves this problem in constant time. However, the best known classical algorithm to solve the problem requires exponential time in n. We also analyze certain classes of cryptographically significant Boolean functions and highlight how the basic Deutsch–Jozsa algorithm performs on them.
CRITERIA OF PARTIAL SEPARABILITY OF MULTIPARTITE QUBIT MIXED STATES
Authors: ZHONG ZAI-ZHE
Published: May 2005

We discuss the partial separability and its criteria problems of multipartite qubit mixed states. First, we strictly define what is the partial separability of a multipartite qubit system. Next, we provide a way of reduction from N-partite qubit density matrixes to bipartite qubit density matrixes, and prove a necessary condition that an N-partite qubit mixed state to be partially separable is its reduction to satisfy the PPT condition.
SUFFICIENT CONDITIONS OF ENTANGLEMENT FOR TRIPARTITE AND HIGHER DIMENSIONAL MULTIPARTITE QUBIT DENSITY MATRIXES
Authors: ZHONG ZAI-ZHE
Published: May 2005

We give the new sufficient conditions of entanglement for multipartite qubit density matrixes. We discuss in detail the case for tripartite qubit density matrixes. As a criterion in concrete applications, its steps are quite simple and easy to operate. Some examples and discussions are given.
ENTANGLEMENT CONCENTRATION AND A QUANTUM REPEATER IN CAVITY QED
Authors: YE LIU , GUO GUANG-CAN
Published: May 2005

A scheme of quantum concentration for unknown atomic entangled states via cavity QED is proposed. During the preparation and the joint measurement of quantum states, the cavity is only virtually excited; thus, the scheme is insensitive to the cavity field states and the cavity decay. In the meanwhile, our setup also provides a demonstration of a quantum repeater in cavity QED in principle.
THE EFFECT OF SPREAD OF THE ATOMIC WAVE FUNCTION ON SOME STATISTICAL PROPERTIES OF THE FIELD
Authors: OSMAN K. I.
Published: May 2005

This paper deals with the system of a two-level atom interacting with a quantized single-mode standing-wave cavity field, which is entangled with the centre-of-mass motion of the atom under the coexistence of the Kerr nonlinearity. We investigate the effect of the spread of the initial atomic wave function on some quantum statistical properties (such as Q distribution function, entropy and phase distribution) with or without the Kerr-like medium. Numerical computations and a discussion of the results are presented.
NOISE INDUCED ENTANGLEMENT
Authors: CHEN J. , YI X. X. , SONG H. S. , ZHOU L.
Published: May 2005

We show that two two-level atoms coupled simultaneously with a third dissipated atom would end up with entangled states. The dissipation of the third atom is supposed to come from its coupling to noises with adjustable intensity. Two kinds of noise, white noise and squeezing white noise, are identified to possess the ability to help preparation of entanglement. We confirm that the entanglement is maximized for intermediate values of the noise intensity with all atoms in the ground state, while it is a monotonic function of the spontaneous rates.
IS THERE A LIQUIDITY CRISIS FOR SMALL, BLACK-OWNED FIRMS?
Authors: COLEMAN SUSAN
Published: May 2005

Loans and trade credit are major sources of short-term debt and liquidity for small firms. This article uses data from the 1998 Survey of Small Business Finances to compare the borrowing experience of small firms owned by black men to those owned by white men. Results reveal that black firm owners were more dependent on loans from non-bank sources than white owners. Black men were significantly more likely to have been turned down for their most recent loan and were more likely to be discouraged from applying for loans. Results also reveal that black men were more likely to be turned down for trade credit. Overall, these findings seem to suggest that firms owned by black men have a more difficult time securing sources of short term debt than those owned by white men.
DOES RURAL LOCATION MATTER? THE SIGNIFICANCE OF A RURAL SETTING FOR SMALL BUSINESSES
Authors: SHIELDS JEFFREY F.
Published: May 2005

Rural settings in the United States have characteristics that present a unique context for small business, often portrayed as adverse. Studies of rural entrepreneurs and small businesses, however, frequently fail to provide data on the rural context and its potential relationship to small business, taking for granted presumed attributes and adverse effects. To develop a better understanding of a rural setting's importance, this research investigated effects of rural geo-demographic and socio-cultural features on 76 small businesses. Results demonstrate that rural geo-demography adversely affects marketability of products and services although there is little adversity for small businesses due to constrained resources (financing, technology, and transportation) or labor issues. Business owners manage their businesses consistent with rural socio-cultural values by relying on strong social ties and word of mouth reputation. However, women-owned businesses experience little adversity due to gender stereotypes. The rural setting considered in the study has varying implications for different types of businesses and for business owners according to how long they have lived in the community. Its effects are neither adverse in all respects nor universal for all small businesses.
TRADITIONAL FARMERS OR MODERN BUSINESSMEN? RELIGIOUS DIFFERENTIATION AND ENTREPRENEURSHIP IN A KLEINE GEMEINDE MENNONITE COMMUNITY IN BELIZE
Authors: ROESSINGH CAREL , SCHOONDERWOERD AMBER
Published: May 2005

This article addresses the religious and entrepreneurial differentiation within Spanish Lookout, a Mennonite community in the Cayo district in Belize, Central America. In spite of the fact that most Mennonites live more or less on the edge of society, they have been able to establish a strong and stable economic position within Belize, although the different communities show a clear variation when it comes to social as well as in economic activities. Since their migration from Mexico to Belize in 1958, the Mennonites of Spanish Lookout, one of the modern communities, have developed a more differentiated economical system with commercial agriculture and agribusiness. The Mennonites maintain a remarkable transnational network, which consists of Mennonite communities and organizations in countries like Canada, the United States of America, and Mexico. These networks introduce innovations on different levels: from modern or better machines, to religious and social changes. The influences from Mennonites outside Belize on the social-economic system of the Spanish Lookout Mennonites, along with the developments within the community, will be the main focus of this article.
SMALL BUSINESS SURVIVAL IN CHINA:GUANXI, LEGITIMACY, AND SOCIAL CAPITAL
Authors: CARLISLE ELLIOT , FLYNN DAVE
Published: May 2005

Previous research suggests that guanxi "costs" are significantly higher for private Chinese enterprises versus all other enterprise types, i.e., state, township and village (TVE), domestic and foreign enterprises. Also, consistent with its cultural context, guanxi is considered to be equally important in business as it is in life for all types of Chinese enterprises. Herein, the discussion is extended to describe the concept of guanxi as a means of garnering social capital in order to maintain legitimacy. Furthermore, some practical means are suggested for entrepreneurs and small business owners to build a necessary foundation for survival.
Activators of AMP-activated protein kinase enhance GLUT4 translocation and its glucose transport activity in 3T3-L1 adipocytes
Authors: Yamaguchi Shinya , Katahira Hiroshi , Ozawa Sachihiko , Nakamichi Yoko , Tanaka Toshiaki , Shimoyama Tatsuhiro , Takahashi Kazuto , Yoshimoto Katsuhiko , Imaizumi Mica Ohara , Nagamatsu Shinya , Ishida Hitoshi
Published: May 2005

To determine whether the increase in glucose uptake following AMP-activated protein kinase (AMPK) activation in adipocytes is mediated by accelerated GLUT4 translocation into plasma membrane, we constructed a chimera between GLUT4 and enhanced green fluorescent protein (GLUT4-eGFP) and transferred its cDNA into the nucleus of 3T3-L1 adipocytes. Then, the dynamics of GLUT4-eGFP translocation were visualized in living cells by means of laser scanning confocal microscopy. It was revealed that the stimulation with 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) and 2,4-dinitrophenol (DNP), known activators of AMPK, promptly accelerates its translocation within 4 min, as was found in the case of insulin stimulation. The insulin-induced GLUT4 translocation was markedly inhibited after addition of wortmannin ( P < 0.01). However, the GLUT4 translocation through AMPK activators AICAR and DNP was not affected by wortmannin. Insulin- and AMPK-activated translocation of GLUT4 was not inhibited by SB-203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK). Glucose uptake was significantly increased after addition of AMPK activators AICAR and DNP ( P < 0.05). AMPK- and insulin-stimulated glucose uptake were similarly suppressed by wortmannin ( P < 0.05–0.01). In addition, SB-203580 also significantly prevented the enhancement of glucose uptake induced by AMPK and insulin ( P < 0.05). These results suggest that AMPK-activated GLUT4 translocation in 3T3-L1 adipocytes is mediated through the insulin-signaling pathway distal to the site of activated phosphatidylinositol 3-kinase or through a signaling system distinct from that activated by insulin. On the other hand, the increase of glucose uptake dependent on AMPK activators AICAR and DNP would be additionally due to enhancement of the intrinsic activity in translocated GLUT4 protein, possibly through a p38 MAPK-dependent mechanism.
Kainate Receptor-Mediated Synaptic Transmission in the Adult Anterior Cingulate Cortex
Authors: Wu Long-Jun , Zhao Ming-Gao , Toyoda Hiroki , Ko Shanelle W. , Zhuo Min
Published: May 2005

Kainate (KA) receptors are expressed widely in the CNS. However, little is known about their functional characterization, molecular identity, and role in synaptic transmission in the forebrain of adult mice. Patch-clamp recordings in genetically modified mice show that postsynaptic KA receptors contribute to fast synaptic transmission in pyramidal neurons in the anterior cingulate cortex (ACC), a forebrain region critical for higher-order cognitive brain functions such as memory and mental disorders. Single-shock stimulation could induce small KA receptor-mediated excitatory postsynaptic currents (KA EPSCs) in the presence of picrotoxin, d-2-amino-5-phosphono-pentanoic acid, and a selective AMPA receptor antagonist, GYKI 53655. KA EPSCs had a significantly slower rise time course and decay time constant compared with AMPA receptor-mediated EPSCs. High-frequency repetitive stimulation significantly facilitated the KA EPSCs. Genetic deletion of the GluR6 or GluR5 subunit significantly reduced, and GluR5 and 6 double knockout completely abolished, KA EPSCs and KA-activated currents in ACC pyramidal neurons. Our results show that KA receptors contribute to synaptic transmission in adult ACC pyramidal neurons and provide a synaptic basis for the physiology and pathology of KA receptors in ACC-related functions.
Physiology of Neuronal Subtypes in the Respiratory–Vocal Integration Nucleus Retroamigualis of the Male Zebra Finch
Authors: Kubke M. F. , Yazaki-Sugiyama Y. , Mooney R. , Wild J. M.
Published: May 2005

Learned vocalizations, such as bird song, require intricate coordination of vocal and respiratory muscles. Although the neural basis for this coordination remains poorly understood, it likely includes direct synaptic interactions between respiratory premotor neurons and vocal motor neurons. In birds, as in mammals, the medullary nucleus retroambigualis (RAm) receives synaptic input from higher level respiratory and vocal control centers and projects to a variety of targets. In birds, these include vocal motor neurons in the tracheosyringeal part of the hypoglossal motor nucleus (XIIts), other respiratory premotor neurons, and expiratory motor neurons in the spinal cord. Although various cell types in RAm are distinct in their anatomical projections, their electrophysiological properties remain unknown. Furthermore, although prior studies have shown that RAm provides both excitatory and inhibitory input onto XIIts motor neurons, the identity of the cells in RAm providing either of these inputs remains to be established. To characterize the different RAm neuron types electrophysiologically, we used intracellular recordings in a zebra finch brain stem slice preparation. Based on numerous differences in intrinsic electrophysiological properties and a principal components analysis, we identified two distinct RAm neuron types (types I and II). Antidromic stimulation methods and intracellular staining revealed that type II neurons, but not type I neurons, provide bilateral synaptic input to XIIts. Paired intracellular recordings in RAm and XIIts further indicated that type II neurons with a hyperpolarization-dependent bursting phenotype are a potential source of inhibitory input to XIIts motor neurons. These results indicate that electrically distinct cell types exist in RAm, affording physiological heterogeneity that may play an important role in respiratory–vocal signaling.
Correlations Between Purkinje Cell Single-Unit Activity and Simultaneously Recorded Field Potentials in the Immediately Underlying Granule Cell Layer
Authors: Lu Huo , Hartmann Mitra J. , Bower James M.
Published: May 2005

Evidence from both anatomical and physiological studies suggests that the ascending segment of the granule cell axon provides a large, driving input to overlying Purkinje cells. In the current experiments, we used dual recording electrodes to simultaneously record spike activity of Purkinje cells and multiunit field potential activity in the directly underlying granule cell layer. These dual recordings were performed both during periods of spontaneous (“background”) firing and also after peripheral tactile stimulation. The results demonstrate that in the large majority of cases, there is a strong positive correlation between spontaneous Purkinje cell simple spikes and spontaneous activity in the immediately underlying granule cell layer. The strength of this correlation was dependent on both the firing rate of the Purkinje cell as well as on the rate of granule cell layer multiunit activity. In addition, for any given pair of recordings, the correlation seen during spontaneous activity accurately predicted the magnitude and time course of responses evoked by peripheral tactile stimulation. These results provide additional evidence that the synapses associated with the ascending segment of the granule cell axon have a substantial influence on Purkinje cell output. This relationship is considered in the context of our ongoing reevaluation of the physiological relationship between cerebellar granule and Purkinje cells.
Gene expression and phenotypic characterization of mouse heart after chronic constant or intermittent hypoxia
Authors: Fan Chenhao , Iacobas Dumitru A. , Zhou Dan , Chen Qiaofang , Lai James K. , Gavrialov Orit , Haddad Gabriel G.
Published: May 2005

Chronic constant hypoxia (CCH), such as in pulmonary diseases or high altitude, and chronic intermittent hypoxia (CIH), such as in sleep apnea, can lead to major changes in the heart. Molecular mechanisms underlying these cardiac alterations are not well understood. We hypothesized that changes in gene expression could help to delineate such mechanisms. The current study used a neonatal mouse model in CCH or CIH combined with cDNA microarrays to determine changes in gene expression in the CCH or CIH mouse heart. Both CCH and CIH induced substantial alterations in gene expression. In addition, a robust right ventricular hypertrophy and cardiac enlargement was found in CCH- but not in CIH-treated mouse heart. On one hand, upregulation in RNA and protein levels of eukaryotic translation initiation factor-2α and -4E (eIF-2α and eIF-4E) was found in CCH, whereas eIF-4E was downregulated in 1- and 2-wk CIH, suggesting that eIF-4E is likely to play an important role in the cardiac hypertrophy observed in CCH-treated mice. On the other hand, the specific downregulation of heart development-related genes (e.g., notch gene homolog-1, MAD homolog-4) and the upregulation of proteolysis genes (e.g., calpain-5) in the CIH heart can explain the lack of hypertrophy in CIH. Interestingly, apoptosis was enhanced in CCH but not CIH, and this was correlated with an upregulation of proapoptotic genes and downregulation of anti-apoptotic genes in CCH. In summary, our results indicate that 1) the pattern of gene response to CCH is different from that of CIH in mouse heart, and 2) the identified expression differences in certain gene groups are helpful in dissecting mechanisms responsible for phenotypes observed.
From Stem Cells to Viable Autologous Semilunar Heart Valve
Authors: Sutherland Fraser W.H. , Perry Tjorvi E. , Yu Ying , Sherwood Megan C. , Rabkin Elena , Masuda Yutaka , Garcia G. Alejandra , McLellan Dawn L. , Engelmayr George C. , Sacks Michael S. , Schoen Frederick J. , Mayer John E.
Published: May 2005

Background—

An estimated 275 000 patients undergo heart valve replacement each year. However, existing solutions for valve replacement are complicated by the morbidity associated with lifelong anticoagulation of mechanical valves and the limited durability of bioprostheses. Recent advances in tissue engineering and our understanding of stem cell biology may provide a lifelong solution to these problems.

Methods and Results—

Mesenchymal stem cells were isolated from ovine bone marrow and characterized by their morphology and antigen expression through immunocytochemistry, flow cytometry, and capacity to differentiate into multiple cell lineages. A biodegradable scaffold was developed and characterized by its tensile strength and stiffness as a function of time in cell-conditioned medium. Autologous semilunar heart valves were then created in vitro using mesenchymal stem cells and the biodegradable scaffold and were implanted into the pulmonary position of sheep on cardiopulmonary bypass. The valves were evaluated by echocardiography at implantation and after 4 months in vivo. Valves were explanted at 4 and 8 months and examined by histology and immunohistochemistry. Valves displayed a maximum instantaneous gradient of 17.2±1.33 mm Hg, a mean gradient of 9.7±1.3 mm Hg, an effective orifice area of 1.35±0.17 cm
2
, and trivial or mild regurgitation at implantation. Gradients changed little over 4 months of follow-up. Histology showed disposition of extracellular matrix and distribution of cell phenotypes in the engineered valves reminiscent of that in native pulmonary valves.

Conclusions—

Stem-cell tissue-engineered heart valves can be created from mesenchymal stem cells in combination with a biodegradable scaffold and function satisfactorily in vivo for periods of >4 months. Furthermore, such valves undergo extensive remodeling in vivo to resemble native heart valves.
Rho-Kinase Inhibitor Improves Increased Vascular Resistance and Impaired Vasodilation of the Forearm in Patients With Heart Failure
Authors: Kishi Takuya , Hirooka Yoshitaka , Masumoto Akihiro , Ito Koji , Kimura Yoshikuni , Inokuchi Kosuke , Tagawa Tatsuya , Shimokawa Hiroaki , Takeshita Akira , Sunagawa Kenji
Published: May 2005

Background—

Rho-kinase is suggested to have an important role in enhanced vasoconstriction in animal models of heart failure (HF). Patients with HF are characterized by increased vasoconstriction and reduced vasodilator responses to reactive hyperemia and exercise. The aim of the present study was to examine whether Rho-kinase is involved in the peripheral circulation abnormalities of HF in humans with the Rho-kinase inhibitor fasudil.

Methods and Results—

Studies were performed in patients with HF (HF group, n=26) and an age-matched control group (n=26). Forearm blood flow was measured with a strain-gauge plethysmograph during intra-arterial infusion of graded doses of fasudil or sodium nitroprusside. Resting forearm vascular resistance (FVR) was significantly higher in the HF group than in the control group. The increase in forearm blood flow evoked by fasudil was significantly greater in the HF group than in the control group. The increased FVR was decreased by fasudil in the HF group toward the level of the control group. By contrast, FVR evoked by sodium nitroprusside was comparable between the 2 groups. Fasudil significantly augmented the impaired ischemic vasodilation during reactive hyperemia after arterial occlusion of the forearm in the HF group but not in the control group. Fasudil did not augment the increased FVR evoked by phenylephrine in the control group significantly.

Conclusions—

These results indicate that Rho-kinase is involved in increased FVR and impaired vasodilation of the forearm in patients with HF.
Twenty-Five–Year Experience With the Björk-Shiley Convexoconcave Heart Valve
Authors: Blot William J. , Ibrahim Michel A. , Ivey Tom D. , Acheson Donald E. , Brookmeyer Ron , Weyman Arthur , Defauw Joseph , Smith J. Kermit , Harrison Donald
Published: May 2005

Background—

The first Björk-Shiley convexoconcave (BSCC) prosthetic heart valves were implanted in 1978. The 25th anniversary provided a stimulus to summarize the research data relevant to BSCC valve fracture, patient management, and current clinical options.

Methods and Results—

Published and unpublished data on the risks of BSCC valve fracture and replacement were compiled, and strategies for identifying candidates for prophylactic valve reoperation were summarized. By December 2003, outlet strut fractures (OSFs), often with fatal outcomes, had been reported in 633 BSCC valves (0.7% of 86 000 valves implanted). Fractures still continue to occur, but average rates of OSFs in 60° valves are now <0.1% per year. OSF risk varies markedly by valve characteristics, especially valve angle and size, with weaker effects associated with other manufacturing variables. OSF risks are mildly lower among women than men but decline sharply with advancing age. The risks of valve replacement typically greatly exceed those of OSF. By comparing individualized estimated risks of OSF versus valve replacement, guidelines have been developed to identify the small percentage of BSCC patients (mostly younger men) who would be expected to have a gain in life expectancy should reoperative surgery be performed.

Conclusions—

Twenty-five years after the initial BSCC valve implants, fractures continue to occur. Continued monitoring of BSCC patients is needed to track and quantify risks and enable periodic updating of guidelines for patients and their physicians.