bluuebunny/crossref_metadata_2025 huggingface dataset:
Sea-surface reverberation fluctuations
Authors: McDaniel Suzanne T.
Published: October 2005

A theory to predict the statistics of sea-surface reverberation is developed and applied to compute the coefficient of variation. Backscattering due to surface roughness is assumed Gaussian, and resonant bubbles or bubble plumes are treated as Poisson-distributed scatterers. With the assumption that a breaking wave produces an exponentially decaying layer of near-resonant bubbles or, alternatively, a single-bubble plume whose scattering strength decays exponentially with time, the backscatter statistics may be related to the mean number of wave-breaking events, and are found to differ markedly in the two cases. Measured coefficients of variation for high-frequency reverberation are inverted to estimate the number of wave-breaking events and compared with oceanographic data with the finding that the hypothesis that backscatter at 3 kHz is due to bubble plumes is inconsistent with the oceanographic data.
Strong Bragg scattering of low-frequency sound from a line source in shallow water. I: One uniform surface wave
Authors: Naciri Mamoun , Mei Chiang C.
Published: October 2005

The propagation of plane sound waves, generated from an underwater line source, and strongly scattered by surface waves directly above the source, is examined. The depth of water is shallow enough so that only one guided mode of sound is present. It is shown that, except in the immediate vicinity of the source, outgoing radiated waves are scattered in two directions. If the emitted sound in both directions has finite envelopes then the envelope of either right-going or left-going waves spreads in both directions. The present theory can be easily modified for any number of guided modes, since only one mode will be resonantly scattered.
Acoustic reflection from quasiperiodic sedimentary sequences
Authors: Holland Charles W. , Muncill Greg
Published: October 2005

A useful theoretical measure of acoustic interaction with the seafloor is the plane wave reflection coefficient (R), which is commonly expressed as bottom loss (−20 log ‖R‖). Predictions indicate that when the seafloor is modeled as a refracting layer over a basement half-space, the bottom loss is proportional to frequency. Bottom loss measurements in the 50–1600-Hz band, however, frequently show a loss that is inversely proportional to frequency. For example, roughly one-third of a set of measured bottom loss data in the North Atlantic exhibit this anomalous frequency dependence. It is concluded that the anomalous frequency dependence is due to sedimentary fine-scale layering arising from turbidity currents. The evidence presented consists of (1) a high correlation between the anomalous bottom loss stations and the bounds of the abyssal plains and (2) favorable predictions between a model accounting for the layering and the measured data. The study area was the western North Atlantic including the Sohm, Hatteras, and Nares abyssal plains. A simple, approximate stochastic model of reflection from a quasiperiodic sedimentary sequence was developed that appears to account for the dominant physical mechanisms important in the reflection process in this type of physiographic province.
Adaptive multichannel combining and equalization for underwater acoustic communications
Authors: Stojanovic M. , Catipovic J. , Proakis J. G.
Published: October 2005

A theoretically optimal multichannel receiver for intersymbol interference communication channels is derived, and its suboptimal versions with linear and decision feedback equalizer are presented. A practical receiver based on any of these structures encounters difficulties in the underwater acoustic channels in which the extended time-varying multipath is accompanied by phase instabilities. A receiver that overcomes these problems by jointly performing adaptive mean-squared error diversity combining, multichannel carrier-phase synchronization and decision feedback equalization is proposed. Its performance is demonstrated on the experimental telemetry data from deep and shallow water long-range acoustic channels. Presented results indicate superior quality of coherent PSK and QAM reception obtained through joint equalization of very few channels.
Finite element formulation of acoustic scattering phenomena with absorbing boundary condition in the frequency domain
Authors: Gan H. , Levin P. L. , Ludwig R.
Published: October 2005

This paper discusses a finite element formulation with an absorbing boundary condition to simulate acoustic scattering phenomena in a general situation, that is, including density as well as sound velocity variations of single and multi-scatterers of arbitrary two-dimensional cross sections. In this model, a Galerkin finite element formulation is incorporated with an absorbing boundary operator that explicitly accounts for the open field problem by mapping the Sommerfeld radiation condition from the far field to the near field. By applying the absorbing boundary operator on the artificial boundary of the finite domain, the truncation errors as well as the artificial reflected power is minimized without compromising the sparsity of the finite element matrix. Performance analysis indicates that the absorbing boundary operator increases the accuracy from O(1/r3/2) to O(1/r9/2). The numerical results are compared with analytical solutions of cylindrical scatterers of different sizes and at different frequencies. Also, the flexibility of the model is demonstrated by simulating inhomogeneous scatterers and multi-scattering configurations.
A clarification of nonexistence problems with the superposition method
Authors: Wilton David T. , Mathews Ian C. , Jeans Richard A.
Published: October 2005

The purpose of this paper is to clarify the question of nonexistence of solutions for the superposition method in acoustic radiation and scattering problems. Recently a number of authors have implemented this method and have claimed that nonexistence or nonuniqueness difficulties do not arise. Numerical evidence appears to support this view. However, this paper shows that the superposition method is a discrete approximation to an equation that does suffer from nonexistence of its solution at certain frequencies. Nonexistence of solutions is demonstrated with some numerical examples and an improved method is discussed.
An analytical evaluation of turbulence-induced flexural noise in planar arrays of extended sensors
Authors: Montgomery Robert E. , Dubus Bertrand
Published: October 2005

Large-area, hull-mounted conformal sonar arrays typically employ extended sensors that are configured to detect acoustic signals by means of thickness strains that are induced by the incident pressure field. In most cases, extended sensors also have an appreciable sensitivity to strains in the lateral dimensions. Thus flexure of such a sensor would induce a signal that would not be differentiated from that of a target. Hull-mounted conformal arrays are evolving toward using lightweight, flexible sensors and support structures; therefore, flexure-induced noise is an ever present concern. This paper presents an analytical approach and a general mathematical model for the noise arising from flexure of the array support plate coupled into the array via the lateral sensitivity of the sensor. The excitation that drives the flexure is assumed to be the turbulent boundary layer created by motion of the platform through the external fluid medium. An analytical expression is derived for the equivalent plane-wave spectral density for this noise source. The result is expressed in terms of the frequency response function of the plate, the wave-number-frequency spectral density of the excitation, and the spatial filtering characteristics of the array. An application is discussed to show that predictions can be obtained in closed form.
Acoustic harmonic radiation from fluid-loaded infinite elastic plates using elasticity theory
Authors: Pathak Ardhendu G. , Stepanishen Peter R.
Published: October 2005

The classical integral transform technique is used to develop the exact formal solution to the problem of harmonic two-dimensional radiation from a fluid-loaded infinite elastic plate subjected to arbitrary loading. Since the theory of elasticity is used to model the plate, no restrictive assumptions are made about the frequency–plate thickness product. The general formulation is then used to address the case of acoustic radiation from a line force-driven plate. A simple expression for the far-field pressure is presented using the stationary phase method. Numerical results are then presented for the far-field pressure patterns for a line force-driven plate at low, intermediate, and high frequencies. The highly directive features of the patterns are related to the in-vacuo dispersion curves of the elastic plate. A comparison of pressure patterns obtained from elasticity and Timoshenko–Mindlin plate theory illustrates the limitations of the latter. Finally the relationship between the plate mode spectrum predicted by the theory of elasticity, the spectral input line admittance of the plate, and the far-field directionality pattern is presented.
Active control of coupled wave propagation in fluid-filled elastic cylindrical shells
Authors: Brévart B. J. , Fuller C. R.
Published: October 2005

A control approach to reduce the total power propagating along fluid-filled elastic cylinders is analytically investigated. The motion of the cylinder is described by the Kennard shell equations fully coupled to the interior acoustic field. The vibration disturbance source is a pre-determined free propagating wave of either n=0 or n=1 circumferential order and the control forces considered are appropriate harmonic line forces radially applied to the structure. The radial displacement of the shell wall at discrete locations downstream of control forces is minimized using feedforward quadratic optimal theory. The difference of total power flow through the system before and after control is then used to evaluate the impact of the fluid on the performance of the control approach. For the breathing circumferential mode (n=0), owing to the coupling between the two media, the fluid decreases the control performance when the disturbance is a structural-type incident wave. When the disturbance is a fluid-type incident wave, with a pressure near field concentrated at the shell wall, significant reductions of the transmitted power flow can be achieved. For the beam mode (n=1), even though the control is applied to the structure, the fluid increases the control performances below the first acoustic cut-off frequency and decreases it above this frequency.
Elastic constants of isotropic cylinders using resonant ultrasound
Authors: Heyliger Paul , Jilani Adel , Ledbetter Hassel , Leisure Robert G. , Wang Ching-Ling
Published: October 2005

A method of ultrasonic resonance is used to determine the elastic constants of isotropic cylinders. As applied in this study, this method implies simultaneous application of approximate techniques to solve for the equations of motion of the cylinder and an experimental measurement of the natural frequencies of free vibration. Optimal estimates for the elastic constants are obtained by minimizing the differences between these values. Two separate examples are considered in this study, with promising results.
Transfer matrix of multilayered absorbing and anisotropic media. Measurements and simulations of ultrasonic wave propagation through composite materials
Authors: Hosten Bernard , Castaings Michel
Published: October 2005

This paper presents an adaptation of the well-known Thomson/Haskell method to introduce anisotropic attenuation into the formulation of the transfer matrix. The expression for the transfer matrix of one elementary ply is modified to take into account the heterogeneity of the generated modes at interfaces between absorbing media. This heterogeneity depends on the direction of propagation and on the anisotropic attenuation of the ply. The transfer matrix of the stratified composite is derived classically from the multiplication of the elementary matrices and leads to the transfer function of the plate. The transmission and reflection coefficients of multilayered viscoelastic anisotropic composite materials can be computed, for any direction of propagation and for any stacking sequence, with a program that requires the viscoelastic characteristics of the ply. The method is tested with PEEK matrix/carbon fibers composites. The viscoelastic properties of the ply were previously measured with a unidirectional composite made of the same elementary ply in a frequency domain where bulk heterogeneous modes can be isolated. To extend these properties to a larger domain, the model assumes that the attenuation is proportional to the frequency. Doing so, the transmission of broadband waveforms can be computed. These waveforms are compared to experimental waveforms transmitted by composites with different stacking sequences.
Loudness adaptation at high frequenciesa)
Authors: Miśkiewicz Andrzej , Scharf Bertram , Hellman Rhona , Meiselman Carol
Published: October 2005

Loudness adaptation was measured for pure tones at 4, 12, 14, and 16 kHz. In three experiments, a total of 87 young listeners judged—by the method of successive magnitude estimation—the loudness of the tones over a 6-min exposure period. Thresholds were measured by an adaptive 2IFC procedure. Although earlier measurements had shown that adaptation near threshold increases with frequency, these new data reveal that the increase is especially marked at higher sensation levels. Thus, at 40 dB SL, over a 6-min period loudness declined by 18% at 4 kHz and by 94% at 16 kHz. Moreover, the 4-kHz tone remained audible for all listeners throughout the 6-min exposure period whereas the 16-kHz tone became inaudible for two-thirds of them by the end of the exposure period. Listeners with relatively low thresholds (<50 dB SPL) at 16 kHz showed much less adaptation at 14 kHz than at 16 kHz and much less than listeners with relatively high thresholds (≳50 dB SPL) at 16 kHz; this latter group showed strong adaptation at 14 kHz. The marked loudness adaptation of steady tones at very high frequencies and relatively high sensation levels is associated with a restricted spread of excitation in the auditory system resulting from the steep rise of the threshold curve at the highest audible frequencies.
Auditory nerve fiber representation of cues to voicing in syllable-final stop consonants
Authors: Sinex D. G.
Published: October 2005

Acoustic cues to the identity of consonants such as /d/ and /t/ vary according to contextual factors such as the position of the consonant within a syllable. However, investigations of the neural coding of consonants have almost always used stimuli in which the consonant occurs in the syllable-initial position. The present experiments examined the peripheral neural representation of spectral and temporal cues that can distinguish between stop consonants /d/ and /t/ in syllable-final position. Stimulus sets consisting of the syllables /hid/, /hit/, /hud/, and /hut/ were recorded by three different talkers. During the consonant closure interval, the spectrum of /d/ was characterized by the presence of a low-frequency ‘‘voice bar.’’ The closure interval for the voiceless consonant /t/ was longer and lacked a voice bar. Most neurons’ responses were characterized by discharge rate decreases at the beginning of the closure interval and by rate increases that marked the release of the consonant closure. Exceptions were seen in the responses of neurons with characteristic frequencies (CFs) below approximately 0.7 kHz to syllables ending in /d/. These neurons responded to the voice bar with discharge rates that could approach the rates elicited by the vowel. The latencies of prominent discharge rate changes were measured for all neurons and used to compute the length of the ‘‘encoded closure interval.’’ The encoded interval was clearly longer for syllables ending in /t/ than in /d/. The encoded interval increased with CF for both consonants but more rapidly for /t/. Differences in the encoded closure interval were small for syllables with different vowels or syllables produced by different talkers.
Time-delay estimation for deterministic transients using second- and higher-order correlations
Authors: Pflug Lisa A. , Ioup George E. , Ioup Juliette W. , Field Robert L. , Leclere James H.
Published: October 2005

Cross-correlation, bicorrelation, and tricorrelation time-delay estimation methods both without and with rectification are compared for finite energy signals (transients). Signals with uncorrelated Gaussian noise distortion as well as signals with propagation distortion, e.g., multipath and attenuation effects, are considered. Measures of performance include calculations of the probabilities of correct time-delay estimation and the standard deviations of all the estimates over appropriate signal-to-noise ratio (SNR) domains, and tables of limiting SNR’s corresponding to small mean deviation from the true time delay. For the known source case with noise-only distortion, the cross-correlation method performs best. For the known source case with propagation distortion and the unknown source case both without and with propagation distortion, the higher-order methods or the cross-correlation method with rectification sometimes show better ability to estimate the exact time delay than the ordinary cross correlation. For all cases, the bicorrelation method is very poor for signals with low skewness of ordinate values, but it can be improved significantly by using rectification. Included is a discussion of the problems encountered when using correlations containing correlation bias for time-delay estimation of energy transients embedded in noise, and arguments for defining correlations using wraparound to overcome the bias in the noise correlation and improve time-delay estimation.
Ensemble average requirement for acoustical measurements in noisy environment using the m-sequence correlation technique
Authors: Zuomin Wang , Chu W. T.
Published: October 2005

This paper describes an experiment that provides additional evidence to demonstrate the possibility of making acoustical measurements in noisy environments by using an m-sequence correlation technique. A criterion for choosing the proper number of synchronous averages is established and a demonstration of making noise reduction measurement between two rooms is also given.
Source imaging with minimum mean-squared error
Authors: Stoughton Roland , Strait Stewart
Published: October 2005

Prior knowledge of source size, shape, and radiation process, and of receiver noise correlations are incorporated in a linear minimum mean-squared error (MMSE) imaging estimator. Its resolution operator and expected squared estimation error are derived and are computed for discrete linear source and receive arrays. These calculations give practical insight into the effects of source size, structure, surface-brightness-to-receive-noise ratio, and receiver geometry on imaging performance. Super-resolution behavior occurs as the natural result of MMSE estimation in regimes where the ratio of source-surface-brightness-to-receiver noise level is large. The expected squared estimation error is a useful tool in array design.
Hybrid ray-mode parametrization of acoustic scattering from submerged thin elastic shells with interior loading
Authors: Felsen L. B. , Guo Y. P.
Published: October 2005

A phenomenologically based hybrid ray-mode synthesis strategy is applied here to reconstruct the backscattered field from a submerged thin cylindrical elastic shell with internal structural loadings, which is insonified by a normally incident time-harmonic plane wave. The strategy is based on the Kirchhoff formulation for the acoustic field which expresses the scattered pressure explicitly in terms of the empty-shell Green’s function augmented by on-surface forces and bending moments that account for the internal effects. Earlier studies have shown that the prominent observable features in the scattered far field may be attributed to waves on the shell and resonant modes associated with the internal system. Accordingly, a ray formulation is utilized for the empty-shell Green’s function, while an angular harmonic (resonant mode) solution is used for the coupling forces and bending moments. This hybrid scheme is shown to reconstruct previously derived harmonic series solutions accurately and efficiently in the intermediate and high-frequency domains.
V(z) curves of layered anisotropic materials for the line-focus acoustic microscope
Authors: Lee Yung-Chun , Kim Jin O. , Achenbach Jan D.
Published: October 2005

V(z) curves for a line-focus acoustic microscope have been calculated in terms of the characteristic functions of the acoustic lens and the reflectance function of the fluid-loaded specimen. More accurate expressions for the characteristic functions of the acoustic lens are presented by taking account of attenuation in the coupling fluid, of the angular dependence of transmission by the antireflection coating on the lens surface, and by making a better estimate of the focal length. The reflectance function has been calculated for anisotropic layers deposited on anisotropic substrates. The calculated V(z) curves have been compared with measurements for isotropic and anisotropic materials, and layered anisotropic materials. The surface acoustic wave velocities obtained from the theoretical and the measured V(z) curves have been compared for the full range of directions of wave propagation. The comparisons of V(z) curves and surface acoustic wave velocities show excellent agreement between theoretical and experimental results.
Imaging ocean-basin reverberation via inversion
Authors: Makris Nicholas C.
Published: October 2005

A technique for imaging large areas of the ocean floor by inverting reverberation data is presented. Acoustic returns measured on a horizontally towed line array have right–left ambiguity about the array’s axis and decreasing cross-range resolution for off-broadside beams and more distant scattering sites. By optimal use of data taken with differing array locations and orientations, right–left ambiguity is eliminated and resolution is maximized. This is accomplished via a global inversion using the array’s known resolving properties. The output of the inversion can be optimally resolved reverberation, scattering coefficient, or physical properties of the seafloor, depending upon the formulation. Simulations are presented to show the general superiority of this approach to data averaging.
Vibrational modes and frequency spectra in piezoelectric ceramic rectangular resonators
Authors: Shuyu Lin , Fucheng Zhang
Published: October 2005

An analytical method for the analysis of piezoelectric ceramic rectangular resonators based on the equivalent elastic theory is presented in which the coupling vibrational modes are considered. The resonance frequency equation of rectangular resonators is derived and the natural frequency spectra are calculated. Theoretical analysis shows that the longitudinal vibrational mode of a piezoelectric ceramic slender rod, the planar radial vibrational mode, and the thickness extensional mode of a piezoelectric ceramic thin plate can be obtained from the theory of this paper. Compared with numerical methods, the method presented here is very simple in computing the natural frequencies and analyzing the eigenmodes of piezoelectric ceramic rectangular resonators. The resonance frequencies obtained from the theory of this paper are in good agreement with the measured results.
Calorie Restriction Promotes Mitochondrial Biogenesis by Inducing the Expression of eNOS
Authors: Nisoli Enzo , Tonello Cristina , Cardile Annalisa , Cozzi Valeria , Bracale Renata , Tedesco Laura , Falcone Sestina , Valerio Alessandra , Cantoni Orazio , Clementi Emilio , Moncada Salvador , Carruba Michele O.
Published: October 2005

Calorie restriction extends life span in organisms ranging from yeast to mammals. Here, we report that calorie restriction for either 3 or 12 months induced endothelial nitric oxide synthase (eNOS) expression and 3′,5′-cyclic guanosine monophosphate formation in various tissues of male mice. This was accompanied by mitochondrial biogenesis, with increased oxygen consumption and adenosine triphosphate production, and an enhanced expression of sirtuin 1. These effects were strongly attenuated in eNOS null-mutant mice. Thus, nitric oxide plays a fundamental role in the processes induced by calorie restriction and may be involved in the extension of life span in mammals.
Coincident Scrapie Infection and Nephritis Lead to Urinary Prion Excretion
Authors: Seeger Harald , Heikenwalder Mathias , Zeller Nicolas , Kranich Jan , Schwarz Petra , Gaspert Ariana , Seifert Burkhardt , Miele Gino , Aguzzi Adriano
Published: October 2005

Prion infectivity is typically restricted to the central nervous and lymphatic systems of infected hosts, but chronic inflammation can expand the distribution of prions. We tested whether chronic inflammatory kidney disorders would trigger excretion of prion infectivity into urine. Urinary proteins from scrapie-infected mice with lymphocytic nephritis induced scrapie upon inoculation into noninfected indicator mice. Prionuria was found in presymptomatic scrapie-infected and in sick mice, whereas neither prionuria nor urinary PrP
Sc
was detectable in prion-infected wild-type or PrP
C
-overexpressing mice, or in nephritic mice inoculated with noninfectious brain. Thus, urine may provide a vector for horizontal prion transmission, and inflammation of excretory organs may influence prion spread.
Antimicrobial Stewardship Programs in Health Care Systems
Authors: MacDougall Conan , Polk Ron E.
Published: October 2005

Antimicrobial stewardship programs in hospitals seek to optimize antimicrobial prescribing in order to improve individual patient care as well as reduce hospital costs and slow the spread of antimicrobial resistance. With antimicrobial resistance on the rise worldwide and few new agents in development, antimicrobial stewardship programs are more important than ever in ensuring the continued efficacy of available antimicrobials. The design of antimicrobial management programs should be based on the best current understanding of the relationship between antimicrobial use and resistance. Such programs should be administered by multidisciplinary teams composed of infectious diseases physicians, clinical pharmacists, clinical microbiologists, and infection control practitioners and should be actively supported by hospital administrators. Strategies for changing antimicrobial prescribing behavior include education of prescribers regarding proper antimicrobial usage, creation of an antimicrobial formulary with restricted prescribing of targeted agents, and review of antimicrobial prescribing with feedback to prescribers. Clinical computer systems can aid in the implementation of each of these strategies, especially as expert systems able to provide patient-specific data and suggestions at the point of care. Antibiotic rotation strategies control the prescribing process by scheduled changes of antimicrobial classes used for empirical therapy. When instituting an antimicrobial stewardship program, a hospital should tailor its choice of strategies to its needs and available resources.
Vaccines for Tuberculosis: Novel Concepts and Recent Progress
Authors: Doherty T. Mark , Andersen Peter
Published: October 2005

Three-quarters of a century after the introduction ofMycobacterium bovisBCG, the first tuberculosis vaccine, new vaccines for tuberculosis are finally entering clinical trials. This breakthrough is based not only on advances in proteomics and genomics which have made the construction of new vaccines possible, but also on a greatly expanded knowledge of the immunology of tuberculosis. Here we review our current understanding of howMycobacterium tuberculosissubverts or survives the host's immune response to cause disease and why the current vaccination strategy, which relies on BCG, is only partially successful in countering the pathogen. This provides a background for describing the new generation of vaccines designed to supplement or replace the current vaccine and the different approaches they take to stimulate immunity againstM. tuberculosis.
OPTIMAL RESULTS FOR THE COMPUTATIONAL COMPLETENESS OF GEMMATING (TISSUE) P SYSTEMS
Authors: FREUND RUDOLF , OSWALD MARION , PĂUN ANDREI
Published: October 2005

Gemmating P systems were introduced as a theoretical model based on the biological idea of the gemmation of mobile membranes. In the general model of extended gemmating P systems, strings are modified either by evolution rules in the membranes or while sending them to another membrane. We here consider the restricted variant of extended gemmating P systems with pre-dynamic rules where strings are only modified at the ends while sending them from one membrane to another one. In a series of papers the number of membranes being sufficient for obtaining computational completeness has steadily been decreased. In this paper we now prove the optimal result, i.e., gemmating P systems only using pre-dynamic rules are already computationally complete with three membranes, even in the non-extended case and with the minimal weight of rules possible. Moreover, we also show that for gemmating tissue P systems two cells suffice, and if we allow the environment to be fully involved in the communication of strings, even one cell together with the environment can manage the task to generate any recursively enumerable language.
QUANTUM BROWNIAN MOTIONS AND NAVIER–STOKES WEAKLY TURBULENCE — A PATH INTEGRAL STUDY
Authors: BOTELHO LUIZ C. L.
Published: October 2005

In this paper, we present a new method to solve exactly the Schrödinger Harmonic oscillator wave equation in the presence of time-dependent parameter. We also apply such technique to solve exactly the problem of random frequency averaged quantum propagator of a harmonic oscillator with white-noise statistics frequency. We still apply our technique to solve exactly the Brownian Quantum Oscillator in the presence of an electric field. Finally, we use these quantum mechanic techniques to solve exactly the Statistical-Turbulence of the Navier–Stokes in a region of fluid random stirring weakly (analytical) coupling through time-dependent Euclidean-Quantum oscillators path-integrals.
EFFECT OF Γ-X CROSSOVER ON THE DONOR BINDING ENERGY IN A QUANTUM WELL
Authors: NITHIANANTHI P. , JAYAKUMAR K.
Published: October 2005

The effect of Γ-X crossover due to the external hydrostatic pressure on the ground state donor binding energy as well as for some low lying excited states for a Quantum well has been investigated by considering the non-parabolicity of the conduction band and pressure dependent spatial dielectric screening. It is observed that the effect of Γ-X crossover is predominant for ground state than for low lying excited states.
Rad is temporally regulated within myogenic progenitor cells during skeletal muscle regeneration
Authors: Hawke Thomas J. , Kanatous Shane B. , Martin Cindy M. , Goetsch Sean C. , Garry Daniel J.
Published: October 2005

The successful use of myogenic progenitor cells for therapeutic applications requires an understanding of the intrinsic and extrinsic cues involved in their regulation. Herein we demonstrate the expression pattern and transcriptional regulation of Rad, a prototypical member of a family of novel Ras-related GTPases, during mammalian development and skeletal muscle regeneration. Rad was identified using microarray analysis, which revealed robust upregulation of its expression during skeletal muscle regeneration. Our current findings demonstrate negligible Rad expression with resting adult skeletal muscle; however, after muscle injury, Rad is expressed within the myogenic progenitor cell population. Rad expression is significantly increased and localized to the myogenic progenitor cell population during the early phases of regeneration and within the newly regenerated myofibers during the later phases of regeneration. Immunohistochemical analysis demonstrated that Rad and MyoD are coexpressed within the myogenic progenitor cell population of regenerating skeletal muscle. This expression profile of Rad during skeletal muscle regeneration is consistent with the proposed roles for Rad in the inhibition of L-type Ca2+ channel activity and the inhibition of Rho/RhoA kinase activity. We also have demonstrated that known myogenic transcription factors (MEF2, MyoD, and Myf-5) can increase the transcriptional activity of the Rad promoter and that this ability is significantly enhanced by the presence of the Ca2+-dependent phosphatase calcineurin. Furthermore, this enhanced transcriptional activity appears to be dependent on the presence of a conserved NFAT binding motif within the Rad promoter. Taken together, these data define Rad as a novel factor within the myogenic progenitor cells of skeletal muscle and identify key regulators of its transcriptional activity.
Feeding a corn oil/sucrose-enriched diet enhances steatohepatitis in sedentary rats
Authors: Rivera C. A. , Abrams S. H. , Tcharmtchi M. H. , Allman M. , Ziba T. T. , Finegold M. J. , Smith C. W.
Published: October 2005

The current study investigated the combined effects of feeding a high-fat/high-sucrose (HF/HS) diet to rodents rendered sedentary via hindlimb unloading (HU). For 3 wk before HU, male Wistar rats were fed chow or a diet in which 32% of calories were derived from corn oil fat and 48% of calories from sucrose. Feeding continued during an additional 3-wk period of HU. Subsequently, blood samples were collected for determination of circulating leukocyte counts, insulin levels, and portal vein endotoxin. Inflammation, necrosis, and steatosis were assessed in formalin-fixed liver sections. No biochemical or histological evidence of injury was observed in control rats fed chow or HF/HS. HU increased circulating neutrophils and resulted in hyperinsulinemia. Mild hepatic fat accumulation and minimal focal necroinflammation were observed in this group. Feeding HF/HS during HU exacerbated hyperinsulinemia, hepatic steatosis, Kupffer cell content, and cytokine expression. Significant portal endotoxemia was noted in HU rats but was not influenced by HF/HS diet. On the other hand, feeding HF/HS significantly enhanced lipid peroxidation end products in liver of HU rats by approximately threefold compared with chow-fed rats. In summary, these findings demonstrate that feeding a high-calorie diet potentiates steatosis and injury in sedentary HU rats. Mechanisms underlying enhanced injury most likely involved lipid peroxidation. Importantly, these findings suggest that dietary manipulation combined with physical inactivity can be used to model steatohepatitis.
Rapid Modulation of GABA Concentration in Human Sensorimotor Cortex During Motor Learning
Authors: Floyer-Lea Anna , Wylezinska Marzena , Kincses Tamas , Matthews Paul M.
Published: October 2005

Movement representations within the human primary motor and somatosensory cortices can be altered by motor learning. Decreases in local GABA concentration and its release may facilitate this plasticity. Here we use in vivo magnetic resonance spectroscopy (MRS) to noninvasively measure serial changes in GABA concentration in humans in a brain region including the primary sensorimotor cortex contralateral to the hand used for an isometric motor sequence learning task. Thirty minutes of motor sequence learning reduced the mean GABA concentration within a 2 × 2 × 2-cm3 voxel by almost 20%. This reduction was specific to motor learning: 30 min of similar, movements with an unlearnable, nonrepetitive sequence were not associated with changes in GABA concentration. No significant changes in GABA concentration were found in the primary sensorimotor cortex ipsilateral to the hand used for learning. These changes suggest remarkably rapid, regionally specific short-term presynaptic modulation of GABAergic input that should facilitate motor learning. Although apparently confined to the contralateral hemisphere, the magnitude of changes seen within a large spectroscopic voxel suggests that these changes occur over a wide local neocortical field.
Fusion of Visuo-ocular and Vestibular Signals in Arm Motor Control
Authors: Guillaud Etienne , Gauthier Gabriel , Vercher Jean-Louis , Blouin Jean
Published: October 2005

Keeping the finger pointing at an Earth-fixed object during body displacements can be achieved if compensatory arm movements counteract the effect of the rotation on the hand's position in space. Here we investigated the fusion of signals that originated from systems having different neurophysiological properties (i.e., the visuo-oculomotor and vestibular systems) in the production of such compensatory arm movements. To this end, we analyzed the subjects' performance in three conditions that differed according to the information they provided about relative target-body motion. This information originated either from the vestibular or visuo-oculomotor system, or from a combination of the two. To highlight the integration of visuo-oculomotor and vestibular signals, we compared the arm response to motion frequencies presumed to allow or not to allow optimal vestibular and oculomotor responses. When they could be used in isolation, the ocular signals allowed long-latency but precise kinematics control of the arm movement, whereas vestibular signals allowed accurate motor response early in the rotation but their contribution declined as body rotation developed. Optimal performance was obtained throughout the whole movement and for all rotation frequencies when the visuo-oculomotor and vestibular signals could be used together. This increase in hand-tracking performance could not be explained by a unimodal model or an additive model of vestibular and ocular cues, even when using weighted signals. Rather, the results supported a functional model in which vestibular and visuo-oculomotor signals have different influences on the temporal and spatial aspects of hand movement compensating for body motion.
Interferon-αcon-1 Treatment of Three Patients with Severe Glucocorticoid-Dependent Asthma
Authors: Kroegel Claus , Bergmann Nicole , Foerster Martin , Workalemahu Grefachew , Machnik Andreas , Mock Bettina , Reissig Angelika
Published: October 2005

We report herein the therapeutic effect of interferon (IFN)-αcon in three patients with severe persistent asthma and long-term oral glucocorticoid treatment. IFN-αcon (9 µg) administered subcutaneously thrice a week over a period of more than 24 months led to a substantial clinical improvement with regard to the number of daily asthma attacks, nighttime disturbance, emergency visits and hospitalizations. In addition, lung function and exercise capacity improved. At the same time, treatment with IFN allowed discontinuation of the daily glucocorticoid dose in all patients for the first time in more than 8 years. Our findings suggest that IFN-αcon leads to a significant clinical improvement while at the same time allowing reduction and discontinuation of the glucocorticoid treatment in severe persistent glucocorticoid-dependent asthma.
The Artist as Reader of the Bible. Visual Exegesis and the Adoration of the Magi
Authors: O'Kane Martin
Published: October 2005

The article explores the processes at work in a painting's engagement of its viewer in biblical subject matter. It accentuates the role of the artist as an active reader of the Bible and not merely an illustrator of biblical scenes, the dynamic that occurs in the text-reader process as paradigmatic for the image-viewer relationship and the important role of the developing tradition that felt the need to change or rewrite the biblical story. The processes are explored in terms of hermeneutics and exegesis: hermeneutics defined as 'the interweaving of language and life within the horizon of the text and within the horizons of traditions and the modern reader' (Gadamer) and exegesis as 'the dialectic between textual meaning and the reader's existence' (Berdini). Applied to the visualization of biblical subject matter, the approaches of Gadamer and Berdini illumine the key role given to the viewer in the visual hermeneutical process. The biblical story of the adoration of the Magi (Matt. 2: 1-12), the first public and universal seeing of Christ and one of the most frequently depicted themes in the entire history of biblical art, is used to illustrate their approach. The emphasis in the biblical narrative on revealing the Christ child to the reader parallels a key concept in Gadamer's hermeneutical aesthetics, namely Darstellung, the way in which a painting facilitates its subject matter in coming forth, in becoming an existential event in the life of the viewer.
SPdb – a signal peptide database
Authors: Choo Khar Heng , Tan Tin Wee , Ranganathan Shoba
Published: October 2005

Background

The signal peptide plays an important role in protein targeting and protein translocation in both prokaryotic and eukaryotic cells. This transient, short peptide sequence functions like a postal address on an envelope by targeting proteins for secretion or for transfer to specific organelles for further processing. Understanding how signal peptides function is crucial in predicting where proteins are translocated. To support this understanding, we present SPdb signal peptide database http://proline.bic.nus.edu.sg/spdb, a repository of experimentally determined and computationally predicted signal peptides.

Results

SPdb integrates information from two sources (a) Swiss-Prot protein sequence database which is now part of UniProt and (b) EMBL nucleotide sequence database. The database update is semi-automated with human checking and verification of the data to ensure the correctness of the data stored. The latest release SPdb release 3.2 contains 18,146 entries of which 2,584 entries are experimentally verified signal sequences; the remaining 15,562 entries are either signal sequences that fail to meet our filtering criteria or entries that contain unverified signal sequences.

Conclusion

SPdb is a manually curated database constructed to support the understanding and analysis of signal peptides. SPdb tracks the major updates of the two underlying primary databases thereby ensuring that its information remains up-to-date.
Mammalian BEX, WEX and GASP genes: Coding and non-coding chimaerism sustained by gene conversion events
Authors: Winter Eitan E , Ponting Chris P
Published: October 2005

Background

The identification of sequence innovations in the genomes of mammals facilitates understanding of human gene function, as well as sheds light on the molecular mechanisms which underlie these changes. Although gene duplication plays a major role in genome evolution, studies regarding concerted evolution events among gene family members have been limited in scope and restricted to protein-coding regions, where high sequence similarity is easily detectable.

Results

We describe a mammalian-specific expansion of more than 20 rapidly-evolving genes on human chromosome Xq22.1. Many of these are highly divergent in their protein-coding regions yet contain a conserved sequence motif in their 5' UTRs which appears to have been maintained by multiple events of concerted evolution. These events have led to the generation of chimaeric genes, each with a 5' UTR and a protein-coding region that possess independent evolutionary histories. We suggest that concerted evolution has occurred via gene conversion independently in different mammalian lineages, and these events have resulted in elevated G+C levels in the encompassing genomic regions. These concerted evolution events occurred within and between genes from three separate protein families ('b rain-e xpressed X-linked' [BEX], WWbp5-like X-linked [WEX] and G-protein-coupled receptor-a ssociated s orting p rotein [GASP]), which often are expressed in mammalian brains and associated with receptor mediated signalling and apoptosis.

Conclusion

Despite high protein-coding divergence among mammalian-specific genes, we identified a DNA motif common to these genes' 5' UTR exons. The motif has undergone concerted evolution events independently of its neighbouring protein-coding regions, leading to formation of evolutionary chimaeric genes. These findings have implications for the identification of non protein-coding regulatory elements and their lineage-specific evolution in mammals.
Frequent attenders in general practice: problem solving treatment provided by nurses [ISRCTN51021015]
Authors: Schreuders B , van Oppen P , van Marwijk HWJ , Smit JH , Stalman WAB
Published: October 2005

Background

There is a need for assistance from primary care mental health workers in general practice in the Netherlands. General practitioners (GPs) experience an overload of frequent attenders suffering from psychological problems. Problem Solving Treatment (PST) is a brief psychological treatment tailored for use in a primary care setting. PST is provided by nurses, and earlier research has shown that it is a treatment at least as effective as usual care. However, research outcomes are not totally satisfying. This protocol describes a randomized clinical trial on the effectiveness of PST provided by nurses for patients in general practice. The results of this study, which currently being carried out, will be presented as soon as they are available.

Methods/design

This study protocol describes the design of a randomized controlled trial to investigate the effectiveness and cost-effectiveness of PST and usual care compared to usual care only.

Patients, 18 years and older, who present psychological problems and are frequent attenders in general practice are recruited by the research assistant. The participants receive questionnaires at baseline, after the intervention, and again after 3 months and 9 months. Primary outcome is the reduction of symptoms, and other outcomes measured are improvement in problem solving skills, psychological and physical well being, daily functioning, social support, coping styles, problem evaluation and health care utilization.

Discussion

Our results may either confirm that PST in primary care is an effective way of dealing with emotional disorders and a promising addition to the primary care in the UK and USA, or may question this assumption. This trial will allow an evaluation of the effects of PST in practical circumstances and in a rather heterogeneous group of primary care patients. This study delivers scientific support for this use and therefore indications for optimal treatment and referral.