bluuebunny/crossref_metadata_2025 huggingface dataset:
STRUCTURE OF IONS AND WATER AROUND A POLYELECTROLYTE IN A POLARIZABLE NANOPORE
Authors: GUO LEI , LUIJTEN ERIK
Published: October 2009

We study the distribution of ions and water within a pore in a polarizable membrane, in the presence of a stiff polyelectrolyte threaded through the pore. In this system, which represents a typical situation during the translocation of DNA, the distribution of both the ions and the water molecules is affected by the induced charges on the surface of the polarizable nanopore. Specifically, the concentration of counterions is enhanced near the surface of the pore, due to the attractive interaction with the induced charges. Conversely, the water within the pore is depleted, as a result of the disruption of hydrogen bonds by the induced charges.
NEW TWO-DIMENSIONAL MASSLESS FIELD THEORY FROM BAGGER–LAMBERT–GUSTAVSSON MODEL
Authors: SANTOS M. A. , VANCEA I. V.
Published: October 2009

By compactifying the Bagger–Lambert–Gustavsson model on ℝ1,1×S1, we obtain a new two-dimensional massless field theory with dynamical fields valued in the Lie three-algebra [Formula: see text] coupled with an SO(1, 1) scalar and vector field which are valued in the set [Formula: see text] of the endomorphisms of the Lie three-algebra. In the limit g BLG →∞ the theory reduces to a supersymmetric Lie three-valued generalization of the Green–Schwarz superstring in the light-cone gauge.
SOME ASPECTS OF NEW CDM MODELS AND CDM DETECTION METHODS
Authors: NUSSINOV SHMUEL
Published: October 2009

We briefly review some recent Cold Dark Matter (CDM) models. Our main focus are charge symmetric models of WIMPs which are not the standard SUSY LSP's (Lightest Supersymmetric Partners). We indicate which experiments are most sensitive to certain aspects of the models. In particular, we discuss the manifestations of the new models in neutrino telescopes and other setups. We also discuss some direct detection experiments and comment on measuring the direction of recoil ions — which is correlated with the direction of the incoming WIMP. This could yield daily variations providing along with the annual modulation signatures for CDM.
AN ADIABATIC HOPPING OF dc ELECTRICAL CONDUCTIVITY STUDIES ON NiO SUBSTITUTED LEAD VANADATE GLASSES
Authors: RAMESH K. V. , MANJULA BHARATHI N. , SRINIVASA RAO B. , APPALA NAIDU P.
Published: October 2009

Glasses of the system x ( NiO ) (50 – x) PbO : 50V 2 O 5 were prepared by melt quenching in the range x = 0 mol % to 15 mol%. Measurements are reported for dc electrical conductivity for the above compositions in the temperature range 300 K–500 K. The experimental results are analyzed with reference to various theoretical models proposed for dc electrical conduction in amorphous semiconductors. The analysis shows that at high temperatures the temperature dependence of dc conductivity is consistent with Mott's model of phonon-assisted hopping conduction, variable range hopping mechanism and Schnakenberg's model mechanism. The hopping in this system is adiabatic in nature.
COMBINATORIAL KNOT INVARIANTS THAT DETECT TREFOILS
Authors: DEVIATOV ROSTISLAV
Published: October 2009

We construct a series of combinatorial quandle-like knot invariants. We color regions of a knot diagram rather than lines and assign a weight to each coloring. Sets of these weights are the invariants we construct (colorings and weights depend on several parameters).

Using these invariants, we prove that left and right trefoils are not isotopic using this invariant (in a particular case).
TOROIDAL SURGERIES ON GENUS TWO KNOTS
Authors: LEE SANGYOP
Published: October 2009

We show that if a genus two hyperbolic knot K in S3 has a toroidal slope r, then |r| ≤ 8. This settles a conjecture of Teragaito for a special case.
ON THE sl(2) FOAM COHOMOLOGY COMPUTATIONS
Authors: CAPRAU CARMEN
Published: October 2009

We show how to use Bar-Natan's "divide and conquer" approach to computation to efficiently compute the universal sl(2) dotted foam cohomology groups, even for big knots and links. We also describe a purely topological version of the sl(2) foam theory, in the sense that no dots are needed on foams.
TORSION OF QUASI-ISOMORPHISMS
Authors: CHUNG JAE-WOOK , LIN XIAO-SONG
Published: October 2009

In this paper, we introduce the notion of Reidemeister torsion for quasi-isomorphisms of based chain complexes over a field. We call a chain map a quasi-isomorphism if its induced homomorphism between homology is an isomorphism. Our notion of torsion generalizes the torsion of acyclic based chain complexes, and is a chain homotopy invariant on the collection of all quasi-isomorphisms from a based chain complex to another. It shares nice properties with torsion of acyclic based chain complexes, like multiplicativity and duality. We will further generalize our torsion to quasi-isomorphisms between free chain complexes over a ring under some mild condition. We anticipate that the study of torsion of quasi-isomorphisms will be fruitful in many directions, and in particular, in the study of links in 3-manifolds.
SOME LIMITS OF THE COLORED ALEXANDER INVARIANT OF THE FIGURE-EIGHT KNOT AND THE VOLUME OF HYPERBOLIC ORBIFOLDS
Authors: CHO JINSEOK , MURAKAMI JUN
Published: October 2009

We calculate certain limits of the colored Alexander invariant of the figure-eight knot for some cases and show that this limit is related to the volume of hyperbolic orbifolds whose singular set is the figure-eight knot.
THE CLASSIFICATION OF SPUN TORUS KNOTS
Authors: WINTER BLAKE
Published: October 2009

Satoh has defined a construction to obtain a ribbon torus knot given a welded knot. This construction is known to be surjective. We show that it is not injective. Using the invariant of the peripheral structure, it is possible to provide a restriction on this failure of injectivity. In particular we also provide an algebraic classification of the construction when restricted to classical knots, where it is equivalent to the torus spinning construction.
THE GEOMETRY OF THE DEHN COMPLEX FOR A SPATIAL GRAPH
Authors: GLASSER DAVID , MCDONNELL LORI , PENDERGHEST KEVIN , VACHA MARY , MEIER JOHN
Published: October 2009

It is well-known that the "all right" metric structure on the Dehn complex of a knot is non-positively curved, or CAT(0), if and only if the knot projection is prime and alternating. We extend these ideas to spatial graphs and introduce the idea of ψ-alternating graphs as the appropriate analog of alternating knots.
CONSTRUCTION OF WAVELET PACKETS ON p-ADIC FIELD
Authors: SHAH FIRDOUS AHMAD
Published: October 2009

Wavelet packets are subsets of a multiresolution analysis and retain many of the orthogonality, smoothness and localization properties of their parent wavelets. In this paper, we study the construction of p-wavelet packets associated with multiresolution p-analysis defined by Farkov for L2(ℝ+). The collection of all dilations and translations of the wavelet packets defines the general wavelet packets and is an overcomplete system.
AN EFFICIENT RATE CONTROL ALGORITHM FOR A WAVELET VIDEO CODEC
Authors: TUN M. , LOO K. K. , COSMAS J.
Published: October 2009

Rate control plays an essential role in video coding and transmission to provide the best video quality at the receiver's end given the constraint of certain network conditions. In this paper, a rate control algorithm using the Quality Factor (QF) optimization method is proposed for the wavelet-based video codec and implemented on an open source Dirac video encoder. A mathematical model which we call Rate-QF (R - QF) model is derived to generate the optimum QF for the current coding frame according to the target bitrate. The proposed algorithm is a complete one pass process and does not require complex mathematical calculation. The process of calculating the QF is quite simple and further calculation is not required for each coded frame. The experimental results show that the proposed algorithm can control the bitrate precisely (within 1% of target bitrate in average). Moreover, the variation of bitrate over each Group of Pictures (GOPs) is lower than that of H.264. This is an advantage in preventing the buffer overflow and underflow for real-time multimedia data streaming.
DAUBECHIES COMPLEX WAVELET TRANSFORM BASED MULTILEVEL SHRINKAGE FOR DEBLURRING OF MEDICAL IMAGES IN PRESENCE OF NOISE
Authors: KHARE ASHISH , TIWARY UMA SHANKER , JEON MOONGU
Published: October 2009

Deblurring in the presence of noise is a hard problem, especially in ultrasonic and CT images. In this paper, we propose a new method of image deblurring in presence of noise, using symmetric Daubechies complex wavelet transform. The proposed method is based on shrinkage of multilevel Daubechies complex wavelet coefficients, and is adaptive as it uses shrinkage function based on the variance of wavelet coefficients as well as the mean and the median of absolute wavelet coefficients at a particular level. The results obtained after the application of the proposed method demonstrate an improved performance over other related methods available in literature.
WAVELET-BASED ARTIFICIAL LIGHT RECEPTOR MODEL FOR HUMAN FACE RECOGNITION
Authors: KABEER V. , NARAYANAN N. K.
Published: October 2009

This paper presents a novel biologically-inspired and wavelet-based model for extracting features of faces from face images. The biological knowledge about the distribution of light receptors, cones and rods, over the surface of the retina, and the way they are associated with the nerve ends for pattern vision forms the basis for the design of this model. A combination of classical wavelet decomposition and wavelet packet decomposition is used for simulating the functional model of cones and rods in pattern vision. The paper also describes the experiments performed for face recognition using the features extracted on the AT & T face database (formerly, ORL face database) containing 400 face images of 40 different individuals. In the recognition stage, we used the Artificial Neural Network Classifier. A feature vector of size 40 is formed for face images of each person and recognition accuracy is computed using the ANN classifier. Overall recognition accuracy obtained for the AT & T face database is 95.5%.
EFFICIENT STATISTICAL MODELING OF WAVELET COEFFICIENTS FOR IMAGE DENOISING
Authors: CHEN YING , JI ZHI-CHENG , HUA CHUN-JIAN
Published: October 2009

Statistical modeling of wavelet coefficients is a critical issue in wavelet domain signal processing. By analyzing the defects of other existing methods, and exploiting the local dependency of wavelet coefficients, an efficient statistical model is proposed. Improved variance estimation of the local wavelet coefficients can be obtained using the new model. Then we apply an approximate minimum mean squared error (MMSE) estimation procedure to restore the wavelet image coefficients. The modeling process is computational cost saving, and the denoising experiments show the algorithm outperforms other approaches in peak-signal-to-noise ratio (PSNR).
LIFTING CONSTRUCTION OF SPLINE DYADIC WAVELET FILTERS WITH ANY NUMBER OF VANISHING MOMENTS
Authors: SUN YANKUI
Published: October 2009

The dyadic lifting schemes, which generalize Sweldens lifting schemes, have been applied to design dyadic wavelet with higher number of vanishing moments. But the existing dyadic lifting methods cannot give the free parameters (i.e. lifting factors) explicitly under vanishing moment constraints, and the exact vanishing moments of the lifted wavelet is unknown a priori. This paper provides a solution of these problems for spline dyadic wavelets. It proposes a novel constructive method for lifting constructing spline dyadic wavelets with desirable numbers of vanishing moments. This new lifting construction scheme can be applied to design spline dyadic wavelet filters with any number of vanishing moments starting from one single dyadic wavelet with 1 or 2 vanishing moments. Its computational advantage is that the lifting factor parameters can be chosen and given explicitly under vanishing moment constraints. At the end of this paper, some spline dyadic wavelet filters are designed by using our method.
ANALOG LOGICAL ELEMENTS AND THEIR USE FOR SIGNAL PROCESSING
Authors: SPIRIDONOV VALERY
Published: October 2009

When n coherent pulses us against additive independent noises un are received, n voltages us + un1, …, us + unn can be obtained in the outputs of a delay line. After addition of these voltages in the matched filter, an improvement of the signal-to-noise ratio SNR is obtained due to random character of summation of the noises and in-phase summation of the signal pulses. As a result, the signal power increases faster than the noise power. However, availability of n pointed voltages enables us to use another processing. It is based on a selection of one of these and of their mean voltages in accordance with its characteristic feature. As shown in the paper, the SNR improvement can be achieved if the selection of the maximum and minimum voltages is performed. The maximum SNR value is obtained by the selection of the noises with the minimum instantaneous power. In this case, the SNR improvement exceeds the one obtained by summation. The results are confirmed by modeling.
A NOTE ON ANALYTIC SIGNALS WITH NONLINEAR PHASE
Authors: CHEN SHOUYIN
Published: October 2009

Instantaneous frequency, defined as the derivative of the phase of a complex analytic representation of the signal, is a basic concept and plays an important role in communication and information processing. It is not unusual to expect that the instantaneous frequency of an analytic signal is nonnegative. In this note, we exhibit new families of analytic signals with band-limited amplitudes and positive nonlinear instantaneous frequencies. The structures of analytic signals with band-limited amplitude and rational as well as linear plus periodic instantaneous frequencies have been analyzed.
TWO-STAGE MULTIPLE DESCRIPTION IMAGE CODING USING TCQ
Authors: LIN CHUNYU , ZHAO YAO , ZHU CE
Published: October 2009

In this paper, we incorporate Trellis Coded Quantization (TCQ) into a two-stage multiple description coding structure to obtain granular gain over two-stage multiple description Scalar Quantizer (SQ). Analysis and experiment on Gaussian signal show that the performance of the proposed scheme can achieve larger gain than that of the two-stage SQ scheme because of better performance of TCQ. The proposed scheme for image coding is shown to be more effective than other relevant multiple description image coding schemes in terms of central-side-distortion rate performance.
A WAVELET-BASED PERCEPTUAL IMAGE CODER INCORPORATING A NEW MODEL FOR COMPRESSION OF COLOR IMAGES
Authors: SREELEKHA G. , SATHIDEVI P. S.
Published: October 2009

A wavelet-based perceptual image coder for the compression of color images is proposed here in which the coding structure is coupled with Human Visual System models to produce high quality images. The major contribution is the development of a new model for the compression of the color components based on psychovisual experiments, which quantifies the optimum amount of compression that can be applied to the color components for a given rate. The model is developed for YCbCr color space and the perceptually uniform CIE Lab color space. A complete coding structure for the compression of color images is developed by incorporating the new perceptual model. The performance of the proposed coder is compared with a wavelet-based coder that uses the quantization stage of the JPEG2000 standard. The perceptual quality of the compressed images is tested using the wavelet-based subjective and objective perceptual quality matrices such as Mean Opinion Score, Visual Information Fidelity and Visual Signal to Noise Ratio. Though the model is developed for a perceptually lossless high quality image compression, results obtained reveal that the proposed structure gives very good perceptual quality compared to the existing schemes for lower bit rates. These advantages make the proposed coder a candidate for replacing the encoder stage of the current image compression standards.
ADMISSIBILITY OF SELF-SIMILAR WEAK SOLUTIONS OF SYSTEMS OF CONSERVATION LAWS IN TWO SPACE VARIABLES AND TIME
Authors: SEVER MICHAEL
Published: October 2009

By means of an example, we postulate that the familiar local entropy conditions on discontinuities are far from sufficient to distinguish admissible weak solutions of systems of conservation laws in two space dimensions and time. We consider the familiar problem of the reflection of an incident shock by a wedge for the "nonlinear wave system", finding a plethora of self-similar weak solutions (or possibly approximate weak solutions) satisfying the usual entropy condition for this system. The multiplicity of such solutions arises from unneeded freedom in the algorithm for constructing solutions, and is directly related to a modest reduction in the assumed regularity of the solution in comparison to that assumed in previous work on this problem. We conclude that if the limit of vanishing viscosity indeed exists for such problems, an additional physical principle is needed to characterize admissible weak solutions.
VISCOUS SHOCK PROFILES FOR 2 × 2 SYSTEMS OF HYPERBOLIC CONSERVATION LAWS WITH AN UMBILIC POINT
Authors: ASAKURA FUMIOKI , YAMAZAKI MITSURU
Published: October 2009

This article analyzes the existence of viscous shock profiles joining two states satisfying the Rankine–Hugoniot condition that comes from hyperbolic 2 × 2 systems of conservation laws having quadratic flux functions with an isolated umbilic point: the point where the characteristic speeds coincide and the Jacobian matrix of the flux functions is diagonalizable. The systems studied in this note are particularly in Schaeffer and Shearer's cases I and II which are relevant to the three-phase Buckley–Leverett model for oil reservoir flow. It is shown that any compressive and overcompressive shocks have a viscous shock profile provided that there are no undercompressive shock with viscous profile having the same propagation speed. The idea of the proof is a generalization of the first theorem of Morse to noncompact level sets. It is also shown that there exists a shock satisfying the Liu–Oleĭnik condition but having no viscous shock profile. In this case, there is an undercompressive shock with viscous shock profile.
RELAXATION APPROXIMATION OF THE KERR MODEL FOR THE THREE-DIMENSIONAL INITIAL-BOUNDARY VALUE PROBLEM
Authors: CARBOU GILLES , HANOUZET BERNARD
Published: October 2009

The electromagnetic wave propagation in a nonlinear medium is described by the Kerr model in the case of an instantaneous response of the material, or by the Kerr–Debye model if the material exhibits a finite response time. Both models are quasilinear hyperbolic and are endowed with a dissipative entropy. The initial-boundary value problem with a maximal-dissipative impedance boundary condition is considered here. When the response time is fixed, in both the one-dimensional and two-dimensional transverse electric cases, the global existence of smooth solutions for the Kerr–Debye system is established. When the response time tends to zero, the convergence of the Kerr–Debye model to the Kerr model is established in the general case, i.e. the Kerr model is the zero relaxation limit of the Kerr–Debye model.
SYMMETRIC-HYPERBOLIC EQUATIONS OF MOTION FOR A HYPERELASTIC MATERIAL
Authors: WAGNER DAVID H.
Published: October 2009

We offer an alternate derivation for the symmetric-hyperbolic formulation of the equations of motion for a hyperelastic material with polyconvex stored energy. The derivation makes it clear that the expanded system is equivalent, for weak solutions, to the original system. We consider motions with variable as well as constant temperature. In addition, we present equivalent Eulerian equations of motion, which are also symmetric-hyperbolic.
TURBULENT SHEAR FLOW: A PARADIGMATIC MULTISCALE PHENOMENON
Authors: LESCHZINER M. A. , FISHPOOL G. M. , LARDEAU S.
Published: October 2009

The paper provides a broad discussion of multiscale and structural features of sheared turbulent flows. Basic phenomenological aspects of turbulence are first introduced, largely in descriptive terms with particular emphasis placed on the range of scales encountered in turbulent flows and in the identification of characteristic scale ranges. There follows a discussion of essential aspects of computational modeling and simulation of turbulence. Finally, the results of simulations for two groups of flows are discussed. These combine shear, separation, and periodicity, the last feature provoked by either a natural instability or by unsteady external forcing. The particular choice of examples is intended to illustrate the capabilities of such simulations to resolve the multiscale nature of complex turbulent flows, as well as the challenges encountered.
3D MODELING OF FRACTURE IN CEMENT-BASED MATERIALS
Authors: SCHLANGEN ERIK , QIAN ZHIWEI
Published: October 2009

In this article, a 3D lattice model is presented to simulate fracture in cement-based materials. In the paper, two applications are shown. The first application is modeling heterogeneous materials containing particle embedded in a matrix. A method is shown for coupling 3D information on the material structure obtained with CT-scanning to the material properties in the model. In the second application, fracture in fiber cement-based materials is modeled. Fibers are explicitly implemented as separate elements connected to the cement matrix via special interface elements. With the model, multiple cracking and ductile global behavior are simulated of the composite material. Variables in the model are the fiber dimensions and properties, the fiber volume in the composite, the bond behavior of fibers and matrix, and the cement matrix properties. These properties can be obtained by testing. Some examples of tests are given in the paper. The model can be used as a design tool for creating fiber (cement-based) composites with any desired mechanical behavior.
MESH-FREE MICROMECHANICAL MODEL FOR WOVEN FABRIC COMPOSITE ELASTIC MODULI
Authors: WEN P. H. , ALIABADI M. H.
Published: October 2009

In this paper, a mesh-free micromechanical material model for evaluation of woven fabric composite elastic moduli is developed. A new and realistic material model based on repeated unit approach with smooth fiber modes is presented. The mesh-free formulation is achieved through consideration of variation of potential energy in a similar manner to the finite element method. Radial basis functions are used as the approximation function in the mesh-free method developed. As no formal element mesh is used to model the matrix, fill and wrap in this approach, the simplicity in meshing is particularly notable. The results obtained for elastic moduli of woven fabric composites are shown to be accurate and in agreement to other available solutions.
MULTISCALE PROGRESSIVE FAILURE ANALYSIS OF PLAIN-WOVEN COMPOSITE MATERIALS
Authors: RAIMONDO L. , ALIABADI M. H.
Published: October 2009

The paper presents an overview of multiscale modeling of advanced fibrous composite materials. Following the review, a nonlinear, fully three-dimensional, numerical model is proposed which is suitable for multiscale elastic and progressive failure analysis of plain-woven composite materials. The proposed model is developed for implementation into the Finite Element code ABAQUS/Explicit as a user-defined subroutine for constant stress (one integration point) solid elements.

The multiscale strategy applied in this paper uses a closed-form solution approach for homogenization of the mesoscale properties of a woven composite. A mosaic model of the woven composite's Representative Volume Element (RVE) is used for deriving the micromechanical relations used for homogenization. The composite RVE model used herein is composed of UD interlacing yarns (fill and warp yarns) and matrix-rich regions. For failure and damage analysis, the following features are implemented in this work: material nonlinearity for pure in-plane shear deformation; physically-based failure criteria for matrix failure in the UD yarns; maximum stress failure criteria for failure of fibers in the UD yarns and of the pure matrix in the resin-rich regions and energy-based damage mechanics.

The proposed strategy, which has been implemented and tested for a special case of an in-plane damage, has some evident advantages compared to the other approaches, especially for application to full-scale simulations, i.e., component and structural scales.

A comparison of the proposed model with experimental data shows a good correlation can be achieved.
A CONDITIONAL RESULT ON THE EXCEPTIONAL SET FOR HARDY–LITTLEWOOD NUMBERS IN SHORT INTERVALS
Authors: LANGUASCO ALESSANDRO
Published: October 2009

Assuming the Generalized Riemann Hypothesis holds, we prove some conditional estimates on the exceptional set in short intervals for the Hardy–Littlewood problem.
ON THE MAXIMUM SIZE OF A (k,l)-SUM-FREE SUBSET OF AN ABELIAN GROUP
Authors: BAJNOK BÉLA
Published: October 2009

A subset A of a given finite abelian group G is called (k,l)-sum-free if the sum of k (not necessarily distinct) elements of A does not equal the sum of l (not necessarily distinct) elements of A. We are interested in finding the maximum size λk,l(G) of a (k,l)-sum-free subset in G.

A (2,1)-sum-free set is simply called a sum-free set. The maximum size of a sum-free set in the cyclic group ℤn was found almost 40 years ago by Diamanda and Yap; the general case for arbitrary finite abelian groups was recently settled by Green and Ruzsa. Here we find the value of λ3,1(ℤn). More generally, a recent paper by Hamidoune and Plagne examines (k,l)-sum-free sets in G when k - l and the order of G are relatively prime; we extend their results to see what happens without this assumption.
ITERATED COMPOSITIONS OF LINEAR OPERATIONS ON SETS OF POSITIVE UPPER DENSITY
Authors: HEGYVÁRI NORBERT , HENNECART FRANÇOIS , PLAGNE ALAIN
Published: October 2009

Starting from a result of Stewart, Tijdeman and Ruzsa on iterated difference sequences, we introduce the notion of iterated compositions of linear operations. We prove a general result on the stability of such compositions (with bounded coefficients) on sets of integers having a positive upper density.
POLYNOMIAL VARIATIONS ON A THEME OF SIERPIŃSKI
Authors: JONES LENNY
Published: October 2009

In 1960, Sierpiński proved that there exist infinitely many odd positive integers k such that k · 2n + 1 is composite for all integers n ≥ 0. Variations of this problem, using polynomials with integer coefficients, and considering reducibility over the rationals, have been investigated by several authors. In particular, if S is the set of all positive integers d for which there exists a polynomial f(x) ∈ ℤ[x], with f(1) ≠ -d, such that f(x)xn + d is reducible over the rationals for all integers n ≥ 0, then what are the elements of S? Interest in this problem stems partially from the fact that if S contains an odd integer, then a question of Erdös and Selfridge concerning the existence of an odd covering of the integers would be resolved. Filaseta has shown that S contains all positive integers d ≡ 0 (mod 4), and until now, nothing else was known about the elements of S. In this paper, we show that S contains infinitely many positive integers d ≡ 6 (mod 12). We also consider the corresponding problem over 𝔽p, and in that situation, we show 1 ∈ S for all primes p.
ON PRIMES IN QUADRATIC PROGRESSIONS
Authors: BAIER STEPHAN , ZHAO LIANGYI
Published: October 2009

We verify the Hardy–Littlewood conjecture on primes in quadratic progressions on average. The results in the present paper significantly improve those of a previous paper by the authors [3].
ON THE FRACTIONAL PARTS OF RATIONAL POWERS
Authors: DUBICKAS ARTŪRAS
Published: October 2009

Let ξ be a non-zero real number, and let a = p/q > 1 be a rational number. We denote by U(a,ξ) and L(a,ξ) the largest and the smallest limit points of the sequence of fractional parts {ξ an}, n = 0,1,2,…, respectively. A possible way to prove Mahler's conjecture claiming that Z-numbers do not exist is to show that U(3/2,ξ) > 1/2 for every ξ > 0. We prove that U(3/2,ξ) cannot belong to [0,1/3) ∪ S, where S is an explicit infinite union of intervals in (1/3,1/2). This result is a corollary to a more general result claiming that, for any rational a > 1, U(a,ξ) cannot lie in a certain union of intervals. We also obtain new inequalities for the difference U(a,ξ) - L(a,ξ). Using them we show that some analogues of Z-numbers do not exist.
EICHLER COHOMOLOGY FOR GENERALIZED MODULAR FORMS
Authors: KNOPP MARVIN , LEHNER JOSEPH , RAJI WISSAM
Published: October 2009

By using Stokes's theorem, we prove an Eichler cohomology theorem for generalized modular forms with some restrictions on the relevant multiplier systems.
THE p-TORSION OF CURVES WITH LARGE p-RANK
Authors: PRIES RACHEL
Published: October 2009

Consider the moduli space of smooth curves of genus g and p-rank f defined over an algebraically closed field k of characteristic p. It is an open problem to classify which group schemes occur as the p-torsion of the Jacobians of these curves for f < g - 1. We prove that the generic point of every component of this moduli space has a-number 1 when f = g - 2 and f = g - 3. Likewise, we show that a generic hyperelliptic curve with p-rank g - 2 has a-number 1 when p ≥ 3. We also show that the locus of curves with p-rank g - 2 and a-number 2 is non-empty with codimension 3 in [Formula: see text] when p ≥ 5. We include some other results when f = g - 3. The proofs are by induction on g while fixing g - f. They use computations about certain components of the boundary of [Formula: see text].
ON THE DIOPHANTINE EQUATION x2 + C = 2yn
Authors: ABU MURIEFAH FADWA S. , LUCA FLORIAN , SIKSEK SAMIR , TENGELY SZABOLCS
Published: October 2009

In this paper, we study the Diophantine equation x2 + C = 2yn in positive integers x,y with gcd (x,y) = 1, where n ≥ 3 and C is a positive integer. If C ≡ 1 (mod 4), we give a very sharp bound for prime values of the exponent n; our main tool here is the result on existence of primitive divisors in Lehmer sequences due to Bilu, Hanrot and Voutier. We illustrate our approach by solving completely the equations x2 + 17a1 = 2yn, x2 + 5a113a2 = 2yn and x2 + 3a111a2 = 2yn.
LENGTH SPECTRA OF NATURAL NUMBERS
Authors: PONG WAI YAN
Published: October 2009

A natural number n can generally be written as a sum of m consecutive natural numbers for various values of m ≥ 1. The length spectrum of n is the set of these admissible m. Two numbers are spectral equivalent if they have the same length spectrum. We show how to compute the equivalence classes of this relation. Moreover, we show that these classes can only have either 1,2 or infinitely many elements.
Bone marrow contributes to the population of pancreatic stellate cells in mice
Authors: Watanabe Takashi , Masamune Atsushi , Kikuta Kazuhiro , Hirota Morihisa , Kume Kiyoshi , Satoh Kennichi , Shimosegawa Tooru
Published: October 2009

Activated pancreatic stellate cells (PSCs) play a pivotal role in the development of pancreatic fibrosis. The origin of activated PSCs has been thought to be transformation of quiescent PSCs residing locally in the pancreas. Recent studies have suggested that bone marrow (BM)-derived cells participate in regeneration processes in various organs. This study aimed to clarify the contribution of BM-derived cells to the population of PSCs in mice. We transplanted BM cells from male enhanced green fluorescent protein transgenic mice into female C57BL/6 mice after lethal irradiation. Eight weeks after BM transplantation, chronic pancreatitis was induced by administration of six intra-abdominal injections of cerulein (50 μg/kg body wt) at 1-h intervals, 3 days per week, for the total of 6 wk. BM-derived cells were tracked by green fluorescent protein expression and in situ hybridization for the Y-chromosome. Eight weeks after BM transplantation, BM-derived cells accounted for 8.7% of the desmin (a marker of PSCs)-positive cells in the pancreas. We could isolate BM-derived cells, which contained lipid droplets and expressed desmin. They could be transformed to myofibroblast-like cells by culture in vitro, further supporting that BM contributed to the population of quiescent PSCs. After induction of pancreatic fibrosis, BM-derived cells accounted for 20.2% of α-smooth muscle actin-positive activated PSCs. The contribution of BM-derived cells to pancreatic ductal cells (positive for cytokeratin-19) was rare and less than 1%. In conclusion, our results suggested that BM-derived cells contributed to the population of PSCs in mice.
CFTR knockdown stimulates lipid synthesis and transport in intestinal Caco-2/15 cells
Authors: Mailhot Geneviève , Ravid Zaava , Barchi Soraya , Moreau Alain , Rabasa-Lhoret Rémi , Levy Emile
Published: October 2009

Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel highly expressed in epithelial cells of the gastrointestinal tract. Mutations in the CFTR gene cause cystic fibrosis (CF), a disease characterized by pancreatic insufficiency, fat malabsorption, and steatorrhea. Despite the administration of pancreatic enzymes to normalize malabsorption, CF patients still experienced lipid fecal loss, nutritional deficiencies, and abnormalities in serum lipid profile, suggesting the presence of intrinsic defects in the intestinal handling of nutrients. The objective of the present study was to assess the impact of CFTR gene knockdown on intracellular lipid metabolism of the intestinal Caco-2/15 cell line. Partial CFTR gene inactivation led to cellular lipid accretion of phospholipids, triglycerides, and cholesteryl esters. Likewise, secretion of these lipid fractions was significantly increased following CFTR gene manipulation. As expected from these findings, the output of triglyceride-rich lipoproteins showed the same increasing pattern. Investigation of the mechanisms underlying these changes revealed that CFTR knockdown resulted in raised levels of apolipoproteins in cells and media and microsomal transfer protein activity, two important factors for the efficient assembly and secretion of lipoproteins. Similarly, scrutiny of the enzymatic monoacylglycerol acyltransferase and diacylglycerol acyltransferase, which exhibit dynamic function in triacylglycerol resynthesis and chylomicron formation in enterocytes, revealed a significant augmentation in their activity. Conversely, cholesterol uptake mediated by Niemann-Pick C1 like 1, Scavenger Receptor Class B Type I, and ATP-binding cassette G8 remains unaffected by genetic modification of CFTR. Collectively, these results highlight the role played by CFTR in intestinal handling of lipids and may suggest that factors other than defective CFTR are responsible for the abnormal intracellular events leading to fat malabsorption in CF patients.
Effects of intravenous fructose on gastric emptying and antropyloroduodenal motility in healthy subjects
Authors: Stevens Julie E. , Doran Selena , Russo Antonietta , O'Donovan Deirdre , Feinle-Bisset Christine , Rayner Christopher K. , Horowitz Michael , Jones Karen L.
Published: October 2009

Gastric emptying (GE) of glucose is regulated closely, not only as a result of inhibitory feedback arising from the small intestine, but also because of the resulting hyperglycemia. Fructose is used widely in the diabetic diet and is known to empty from the stomach slightly faster than glucose but substantially slower than water. The aims of this study were to determine whether intravenous (iv) fructose affects GE and antropyloroduodenal motility and how any effects compare to those induced by iv glucose. Six healthy males (age: 26.7 ± 3.8 yr) underwent concurrent measurements of GE of a solid meal (100 g ground beef labeled with 20 MBq99mTc-sulfur colloid) and antropyloroduodenal motility on three separate days in randomized order during iv infusion of either fructose (0.5 g/kg), glucose (0.5 g/kg), or isotonic saline for 20 min. GE (scintigraphy), antropyloroduodenal motility (manometry), and blood glucose (glucometer) were measured for 120 min. There was a rise in blood glucose ( P < 0.001) after iv glucose (peak 16.4 ± 0.6 mmol/l) but not after fructose or saline. Intravenous glucose and fructose both slowed GE substantially ( P < 0.005 for both), without any significant difference between them. Between t = 0 and 30 min, the number of antral pressure waves was less after both glucose and fructose ( P < 0.002 for both) than saline, and there were more isolated pyloric pressure waves during iv glucose ( P = 0.003) compared with fructose and saline ( P = NS for both) infusions. In conclusion, iv fructose slows GE and modulates gastric motility in healthy subjects, and the magnitude of slowing of GE is comparable to that induced by iv glucose.
Carbohydrate maldigestion induces necrotizing enterocolitis in preterm pigs
Authors: Thymann Thomas , Møller Hanne K. , Stoll Barbara , Støy Ann Cathrine F. , Buddington Randal K. , Bering Stine B. , Jensen Bent B. , Olutoye Oluyinka O. , Siggers Richard H. , Mølbak Lars , Sangild Per T. , Burrin Douglas G.
Published: October 2009

Necrotizing enterocolitis (NEC) remains the most severe gastrointestinal disorder in preterm infants. It is associated with the initiation of enteral nutrition and may be related to immature carbohydrate digestive capacity. We tested the hypothesis that a formula containing maltodextrin vs. a formula containing lactose as the principal source of carbohydrate would predispose preterm pigs to a higher NEC incidence. Cesarean-derived preterm pigs were given total parenteral nutrition for 48 h followed by total enteral nutrition with a lactose-based ( n = 11) or maltodextrin-based ( n = 11) formula for 36 h. A higher incidence (91% vs. 27%) and severity (score of 3.3 vs. 1.8) of NEC were observed in the maltodextrin than in the lactose group. This higher incidence of NEC in the maltodextrin group was associated with significantly lower activities of lactase, maltase, and aminopeptidase; reduced villus height; transiently reduced in vivo aldohexose uptake; and reduced ex vivo aldohexose uptake capacity in the middle region of the small intestine. Bacterial diversity was low for both diets, but alterations in bacterial composition and luminal concentrations of short-chain fatty acids were observed in the maltodextrin group. In a second study, we quantified net portal absorption of aldohexoses (glucose and galactose) during acute jejunal infusion of a maltodextrin- or a lactose-based formula ( n = 8) into preterm pigs. We found lower net portal aldohexose absorption (4% vs. 42%) and greater intestinal recovery of undigested carbohydrate (68% vs. 27%) in pigs acutely perfused with the maltodextrin-based formula than those perfused with the lactose-based formula. The higher digestibility of the lactose than the maltodextrin in the formulas can be attributed to a 5- to 20-fold higher hydrolytic activity of tissue-specific lactase than maltases. We conclude that carbohydrate maldigestion is sufficient to increase the incidence and severity of NEC in preterm pigs.
Pdx1inactivation restricted to the intestinal epithelium in mice alters duodenal gene expression in enterocytes and enteroendocrine cells
Authors: Chen Chin , Fang Rixun , Davis Corrine , Maravelias Charalambos , Sibley Eric
Published: October 2009

Null mutant mice lacking the transcription factor pancreatic and duodenal homeobox 1 (Pdx1) are apancreatic and survive only a few days after birth. The role of Pdx1 in regulating intestinal gene expression has therefore yet to be determined in viable mice with normal pancreatic development. We hypothesized that conditional inactivation of Pdx1 restricted to the intestinal epithelium would alter intestinal gene expression and cell differentiation. Pdx1flox/flox; VilCre mice with intestine-specific Pdx1 inactivation were generated by crossing a transgenic mouse strain expressing Cre recombinase, driven by a mouse villin 1 gene promoter fragment, with a mutant mouse strain homozygous for loxP site-flanked Pdx1. Pdx1 protein is undetectable in all epithelial cells in the intestinal epithelium of Pdx1flox/flox; VilCre mice. Goblet cell number and mRNA abundance for mucin 3 and mucin 13 genes in the proximal small intestine are comparable between Pdx1flox/flox; VilCre and control mice. Similarly, Paneth cell number and expression of Paneth cell-related genes Defa1, Defcr-rs1, and Mmp7 in the proximal small intestine remain statistically unchanged by Pdx1 inactivation. Although the number of enteroendocrine cells expressing chromogranin A/B, gastric inhibitory polypeptide (Gip), or somatostatin (Sst) is unaffected in the Pdx1flox/flox; VilCre mice, mRNA abundance for Gip and Sst is significantly reduced in the proximal small intestine. Conditional Pdx1 inactivation attenuates intestinal alkaline phosphatase (IAP) activity in the duodenal epithelium, consistent with an average 91% decrease in expression of the mouse enterocyte IAP gene, alkaline phosphatase 3 (a novel Pdx1 target candidate), in the proximal small intestine following Pdx1 inactivation. We conclude that Pdx1 is necessary for patterning appropriate gene expression in enterocytes and enteroendocrine cells of the proximal small intestine.
Gross ultrastructural changes and necrotic fiber segments in elbow flexor muscles after maximal voluntary eccentric action in humans
Authors: Lauritzen Fredrik , Paulsen Gøran , Raastad Truls , Bergersen Linda Hildegard , Owe Simen Gylterud
Published: October 2009

Eccentric muscle actions are associated with ultrastructural changes. The severity and types of change depend on the nature of the stimulation protocol, and on the method for assessing such changes, and can be regarded as a continuum from mild changes to pathological-like changes. Most studies describing more severe changes have been performed on animals and only a few in humans, some using electrical stimuli. Hence, a debate has emerged on whether voluntary actions are associated with the pathological-like end of the continuum. The aim of this study was to determine whether severe muscle damage, i.e., extensive ultrastructural changes, is confined to animal studies and studies on humans using electrical stimuli. Second, because there is no generally approved method to quantify the degree of muscle damage, we compared two published methods, analyzing the Z disks or sarcomeres, as well as novel analyses of pathological-like changes. A group of untrained subjects performed 70 voluntary maximal eccentric muscle actions using the elbow flexors. On the basis of large reductions in maximal force-generating capacity (on average, −62 ± 3% immediately after exercise, and −35 ± 6% 9 days later), five subjects were selected for further analysis. Biopsies were taken from m. biceps brachii in both the exercised and nonexercised arm. In exercised muscle, more disrupted (13 ± 4 vs. 3 ± 3%) and destroyed (15 ± 6 vs. 0%) Z disks were found compared with nonexercised muscle. A significant proportion of exercised myofibers had focal (85 ± 5 vs. 11 ± 7%), moderate (65 ± 7 vs. 11 ± 6%), and extreme (38 ± 9 vs. 0%) myofibrillar disruptions. Hypercontracted myofibrils, autophagic vacuoles, granular areas, central nuclei, and necrotic fiber segments were found to various degrees. The present study demonstrates that the more severe end of the continuum of ultrastructural changes occurs in humans after voluntary exercise when maximal eccentric muscle actions are involved.
Reduced volume and increased training intensity elevate muscle Na+-K+pump α2-subunit expression as well as short- and long-term work capacity in humans
Authors: Bangsbo Jens , Gunnarsson Thomas P. , Wendell Jesper , Nybo Lars , Thomassen Martin
Published: October 2009

The present study examined muscle adaptations and alterations in work capacity in endurance-trained runners as a result of a reduced amount of training combined with speed endurance training. For a 6- to 9-wk period, 17 runners were assigned to either a speed endurance group with a 25% reduction in the amount of training but including speed endurance training consisting of six to twelve 30-s sprint runs 3–4 times/wk (SET group n = 12) or a control group ( n = 5), which continued the endurance training (∼55 km/wk). For the SET group, the expression of the muscle Na+-K+pump α2-subunit was 68% higher ( P < 0.05) and the plasma K+level was reduced ( P < 0.05) during repeated intense running after 9 wk. Performance in a 30-s sprint test and the first of the supramaximal exhaustive runs was improved ( P < 0.05) by 7% and 36%, respectively, after the speed endurance training period. In the SET group, maximal O2uptake was unaltered, but the 3-km (3,000-m) time was reduced ( P < 0.05) from 10.4 ± 0.1 to 10.1 ± 0.1 min and the 10-km (10,000-m) time was improved from 37.3 ± 0.4 to 36.3 ± 0.4 min (means ± SE). Muscle protein expression and performance remained unaltered in the control group. The present data suggest that both short- and long-term exercise performances can be improved with a reduction in training volume if speed endurance training is performed and that the Na+-K+pump plays a role in the control of K+homeostasis and in the development of fatigue during repeated high-intensity exercise.
Mechanisms of the inspiratory action of the diaphragm during isolated contraction
Authors: De Troyer André , Leduc Dimitri , Cappello Matteo , Mine Benjamin , Gevenois Pierre Alain , Wilson Theodore A.
Published: October 2009

The lung-expanding action of the diaphragm is primarily related to the descent of the dome produced by the shortening of the muscle fibers. However, when the phrenic nerves in dogs are selectively stimulated at functional residual capacity, the muscle insertions into the lower ribs also move caudally. This rib motion should enhance the descent of the dome and increase the fall in pleural pressure (ΔPpl). To quantify the role of this mechanism in determining ΔPpl during isolated diaphragm contraction and to evaluate the volume dependence of this role, radiopaque markers were attached to muscle bundles in the midcostal region of the muscle in six animals, and the three-dimensional location of the markers during relaxation at different lung volumes and during phrenic nerve stimulation at the same lung volumes was measured using computed tomography. From these data, accurate measurements of muscle length, dome displacement, and lower rib displacement were obtained. The values of dome displacement were then corrected for lower rib displacement, and the values of ΔPpl corresponding to the corrected dome displacements were obtained using the measured relationship between ΔPpl and dome displacement. The measurements showed that phrenic stimulation at all lung volumes causes a caudal displacement of the lower ribs and that this displacement, taken alone, contributes ∼25% of the ΔPpl produced by the diaphragm. To the extent that this lower rib displacement is itself caused by ΔPpl, the lung-expanding action of the diaphragm during isolated contraction may therefore be viewed as a self-facilitating phenomenon.