bluuebunny/crossref_metadata_2025 huggingface dataset:
SPECTROSCOPY WITH ELECTRONIC TERAHERTZ TECHNIQUES FOR CHEMICAL AND BIOLOGICAL SENSING
Authors: CHOI MIN K. , TAYLOR KIMBERLY , BETTERMANN ALAN , VAN DER WEIDE DANIEL W.
Published: March 2004

By illuminating the sample with a broadband 10-500 GHz stimulus and coherently detecting the response, we obtain reflection and transmission spectra of common powdered substances, and compare them as a starting point for distinguishing concealed threats in envelopes and on personnel. Because these samples are irregular and their dielectric properties cannot be modulated, the spectral information we obtain is largely qualitative. To show how to gain quantitative information on biological species at micro- and millimeter-wave frequencies, we introduce thermal modulation of a globular protein in solution, and show that changes in microwave reflections coincide with accepted visible absorption spectra, pointing the way toward gaining quantitative chemical and biological spectra from broadband terahertz systems.
Terahertz Applications to Biomolecular Sensing
Authors: Markelz Andrea G. , Whitmire Scott E.
Published: March 2004

THz time domain spectroscopy of biomolecules was performed to determine applicability of the technique for chemical and conformational identification of biomolecules. Measurements were performed on samples of DNA, bovine serum albumin, collagen, hen egg white lysozyme, myoglobin, and bacteriorhodopsin as a function of temperature, hydration and photoexcitation. The results are compared to normal mode calculations. We demonstrate a clear resemblance of the observed broad and near featureless THz absorbance spectrum to the calculated density of normal modes. While the magnitude of the absorbance and the center of the broad response depends on biomolecular species, unique chemical identification would appear challenging. The observed dependence on hydration is in agreement with mass and dielectric loading, and the dependence on temperature is in agreement with decreasing conformational flexibility with reduced temperature. Finally THz absorbance dependence on the biomolecular conformation and mutation is demonstrated for bacteriorhodopsin.
CHARACTERISTICS OF NANO-SCALE COMPOSITES AT THz AND IR SPECTRAL REGIONS
Authors: FEDERICI JOHN F. , GREBEL HAIM
Published: March 2004

Electronic characteristics are difficult to monitor in nanocomposites. Here we describe indirect assessments of these characteristics using THz, Raman and IR spectroscopy. Specifically we seek to gain understanding of the electron mobility in semiconductive and conductive nanostructures for electronic, electrooptic and nonlinear optical purposes.
Continuous-Wave Terahertz Spectroscopy of Plasmas and Biomolecules
Authors: Plusquellic D. F. , Korter T. M. , Fraser G. T. , Lavrich R. J. , Benck E. C. , Bucher C. R. , Walker A. R. Hight , Domenech J. L.
Published: March 2004

Continuous-wave linear-absorption spectroscopy based on THz radiation generated by solid-state photomixers has been applied to the investigation of the dynamics of biomolecules in polyethylene matrices and to line shape studies of HF for diagnostics of semiconductor etching plasmas. The THz spectra of biotin and myoglobin have been obtained using a variable-temperature, cryogenic sampling system. The spectrum of biotin displays a small number of discrete absorptions over the temperature range from 4.2 K to room temperature while the spectrum of myoglobin has no obvious resonance structure at the >10% fractional absorption level. Spectral predictions from the lowest energy ab initio conformations of biotin are in poor agreement with experiment, suggesting the need to include condensed-phase environmental interactions for qualitative predictions of the THz spectrum. Vibrational anharmonicity is used to model the line shapes that result from drastic changes in vibrational sequence level populations of biotin over this temperature range. Anharmonicity factors (χeωe/ωe) at the levels of 0.1% to 0.8% are obtained from non-linear least squares fits of the observed resonances and illustrate their important for refining model predictions. Application of the photomixer system to line shape studies in etching plasmas has been used to study the formation efficiency and translational temperature of HF at 1.2 THz under different operating conditions. These results will aid in understanding the chemistry of industry-standard fluorocarbon and oxygenated fluorocarbon etching plasmas.
HARD NON-VACUUM REGGEON IN THE CKMT MODEL
Authors: ABRAMOVSKY V. A. , DMITRIEV A. V.
Published: March 2004

The CKMT model describing the nucleon structure function F2(x,Q2) in the framework of conventional Regge theory with smooth soft-hard pomeron is modified. Smooth soft-hard non-vacuum reggeon dependence on incoming photon virtuality Q2 is introduced. This dependence has the same functional form as the smooth soft-hard functional Q2 dependence for pomeron in original CKMT model. In region of low W2, better agreement with experimental data is observed.
QUANTUM ENERGY IN A VIBRATING CAVITY
Authors: WȨGRZYN PAWEŁ
Published: March 2004

We discuss the quantized field inside a general one-dimensional cavity system. We recognize the SL (2,R) symmetry being the remainder of the conformal group. The explanation of the lack of the resonance production for the fundamental frequency is given and the asymptotic behavior of the cavity system is properly described.
MULTIVERSE COSMOLOGICAL MODELS
Authors: DAVIES P. C. W.
Published: March 2004

Recent advances in string theory and inflationary cosmology have led to a surge of interest in the possible existence of an ensemble of cosmic regions, or "universes", among the members of which key physical parameters, such as the masses of elementary particles and the coupling constants, might assume different values. The observed values in our cosmic region are then attributed to an observer selection effect (the so-called anthropic principle). The assemblage of universes has been dubbed "the multiverse". In this paper we review the multiverse concept and the criticisms that have been advanced against it on both scientific and philosophical grounds.
DECOMPOSITION OF THE SEMI-SIMPLE GROUP CONNECTION AND COSMIC STRINGS IN THE LORENTZ SPACETIME
Authors: ZHANG PENG-MING , DUAN YI-SHI , REN JI-RONG
Published: March 2004

In a previous paper, we addressed the method of Abelian decomposition to the case of SU (N) Yang–Mills theory. Here, we extend the decomposition method further to the general case. With the Cartan–Weyl basis we decompose semisimple group connection and discuss the SO(3,1) group in particular. In terms of the vierbein projection, we propose two two-forms as the U(1) gauge fields in the SO(3,1) gauge theory and show that these two-forms are just the different cosmic string tensors. Meanwhile, these two-forms indicate that the cosmic strings appear naturally in the Lorentz spacetime, i.e. the torsion in the Riemann–Cartan spacetime is not necessary for the cosmic strings.
SHORT DISTANCE SIGNATURES IN COSMOLOGY: WHY NOT IN BLACK HOLES?
Authors: CASADIO ROBERTO , MERSINI LAURA
Published: March 2004

Current theoretical investigations seem to indicate the possibility of observing signatures of short distance physics in the cosmic microwave background spectrum. We try to gain a deeper understanding on why all information about this regime is lost in the case of black hole radiation but not necessarily so in a cosmological setting by using the moving mirror as a toy model for both backgrounds. The different responses of the Hawking and cosmic microwave background spectra to short distance physics are derived in the appropriate limit when the moving mirror mimics a black hole background or an expanding universe. The different sensitivities to new physics, displayed by both backgrounds, are clarified through an averaging prescription that accounts for the intrinsic uncertainty in their quantum fluctuations. We then proceed to interpret the physical significance of our findings for time-dependent backgrounds in the light of nonlocal string theory.
ON KOOPMAN–VON NEUMANN WAVES II
Authors: GOZZI E. , MAURO D.
Published: March 2004

In this paper, we continue the study started in Ref. 1, of the operatorial formulation of classical mechanics given by Koopman and von Neumann (KvN) in the 1930s. In particular, we show that the introduction of the KvN Hilbert space of complex and square integrable "wave functions" requires an enlargement of the set of the observables of ordinary classical mechanics. The possible role and the meaning of these extra observables is briefly indicated in this work. We also analyze the similarities and differences between non-selective measurements and two-slit experiments in classical and quantum mechanics.
SEARCH FOR DCC IN RELATIVISTIC HEAVY-ION COLLISIONS: POSSIBILITIES AND LIMITATIONS
Authors: MOHANTY B. , NAYAK T. K. , VIYOGI Y. P. , MAHAPATRA D. P.
Published: March 2004

The experimental observation of disoriented chiral condensate is affected due to various physical and detector related effects. We study and quantify the strength of the experimental signal, "neutral pion fraction" within the framework of a simple DCC model, using the analysis methods based on the multi-resolution discrete wavelet technique and by evaluating the signal to background ratio. The scope and limitations of DCC search in heavy-ion collision experiments using various combination of detector systems are investigated.
COLLISIONS BETWEEN ALFVEN WAVE PACKETS IN COSMIC ELECTROMAGNETIC FIELDS
Authors: BERSHADSKII A. , SREENIVASAN K. R.
Published: March 2004

It is shown that collisions between Alfven wave packets and the cascades generated by these collisions in cosmic electromagnetic fields can determine the photon temperature fluctuations for arcminute scales on the last scattering surface.
RELATIVISTIC STAR SOLUTIONS IN HIGHER DIMENSIONS
Authors: PAUL B. C.
Published: March 2004

A class of relativistic solutions of compact star which is in hydrostatic equilibrium is obtained in higher dimensions assuming a spherically symmetric space–time. The space–time geometry is assumed to be a (D-1)-spheroid immersed in a D-dimensional Euclidean space. It is noted that the parameter a which is the measure of spheroidicity of the space–time plays here an important role in determining the equation of state of the matter content in such a star. One obtains a realistic solution when the parameter a picks up values [Formula: see text] for D<9 and [Formula: see text] for space–time dimensions D≥9. It is also observed that the higher dimensional space–time accommodates a more massive compact object for a given size compared to that in the usual four dimensional space–times.
GRAVITOMAGNETIC RESONANCE SHIFT DUE TO A SLOWLY ROTATING COMPACT STAR
Authors: MIRZA BABUR M.
Published: March 2004

The effect of a slowly rotating mass on a forced harmonic oscillator with two degrees of freedom is studied in the weak field approximation. It is found that according to the general theory of relativity there is a shift in the resonant frequency of the oscillator which depends on the density and rotational frequency of the gravitational source. The proposed shift is quite small under normal physical situations however it is estimated that for compact X-ray sources such as white dwarfs, pulsars and neutron stars the shift is quite appreciable.
PROTONEUTRON STAR MODEL WITH NONZERO STRANGENESS CORE
Authors: BEDNAREK ILONA , KȨSKA MARCIN , MAŃKA RYSZARD
Published: March 2004

Protoneutron stars are hot and lepton rich objects formed in type II supernovae. It is natural to regard the evolution of these stars as taking place in several stages. This paper describes results of analysis of protoneutron star evolution for models incorporating an strangeness-rich, neutrino opaque matter equation of state. Of special interest in this paper is the comparison of protoneutron star models for two different phases. One characterized by neutrino trapping and by the value of entropy s=1 and the other, formed when neutrinos leak out of the system, described as a hot deleptonized star. The equation of state adequate for the protoneutron star has been constructed. It has been shown that the maximum stable protoneutron star mass is close to 1.44 M⊙.
DEPENDENCE OF THE X-RAY LUMINOSITY AND PULSAR WIND NEBULA ON DIFFERENT PARAMETERS OF PULSARS AND THE EVOLUTIONARY EFFECTS
Authors: GUSEINOV OKTAY H. , ANKAY AŞKIN , TAGIEVA SEVINÇ O. , TAŞKIN M. ÖZGÜR
Published: March 2004

Dependences of the X-ray luminosity (Lx) of young single pulsars, due to ejection of relativistic particles, on electric field intensity, rate of rotational energy loss (Ė), magnetic field, period, and some other parameters of neutron stars are discussed. Influence of the magnetic field and effects of some other parameters of neutron stars on the Lx-Ė and the Lx-τ (characteristic time) dependences are considered. Evolutionary factors also play an important role in our considerations. Only the pulsars with L2–10 keV>1033erg/s have pulsar wind nebula around them. The pulsars from which γ-ray radiation has been observed have low X-ray luminosity in general.
COVARIANT ANALYSIS OF NEWTONIAN MULTI-FLUID MODELS FOR NEUTRON STARS I: MILNE–CARTAN STRUCTURE AND VARIATIONAL FORMULATION
Authors: CARTER BRANDON , CHAMEL NICOLAS
Published: March 2004

This is the first of a series of articles showing how 4 dimensionally covariant analytical procedures developed in the context of General Relativity can be usefully adapted for application in a purely Newtonian framework where they provide physical insights (e.g. concerning helicity currents) that are not so easy to obtain by the traditional approach based on a 3+1 spacetime decomposition. After an introductory presentation of the relevant Milne spacetime structure and the associated Cartan connection, the essential principles are illustrated by application to the variational formulation of simple barotropic perfect fluid models. This variational treatment is then extended to conservative multiconstituent self-gravitating fluid models of the more general kind that is needed for treating the effects of superfluidity in neutron stars.
PARTICLE PRODUCTION OF COHERENTLY OSCILLATING NONCLASSICAL INFLATON IN FRW UNIVERSE
Authors: VENKATARATNAM K. K. , SURESH P. K.
Published: March 2004

We study particle production of coherently oscillating inflaton in semiclassical theory of gravity by representing inflaton in coherent and squeezed state formalisms. A comparative study of the inflaton in classical gravity with coherent state inflaton in semiclassical gravity is also presented.
SPECIAL RELATIVITY WITH TWO INVARIANT SCALES: MOTIVATION, FERMIONS, BOSONS, LOCALITY, AND CRITIQUE
Authors: AHLUWALIA-KHALILOVA D. V.
Published: March 2004

We present a Master equation for description of fermions and bosons for special relativities with two invariant scales, [Formula: see text], (c and λP). We introduce canonically-conjugate variables (χ0,χ) to (∊,π) of Judes-Visser. Together, they bring in a formal element of linearity and locality in an otherwise non-linear and non-local theory. Special relativities with two invariant scales provide all corrections, say, to the standard model of the high energy physics, in terms of one fundamental constant, λP. It is emphasized that spacetime of special relativities with two invariant scales carries an intrinsic quantum-gravitational character. In an addenda, we also comment on the physical importance of a phase factor that the whole literature on the subject has missed and present a brief critique of [Formula: see text]. In addition, we remark that the most natural and physically viable [Formula: see text] shall require momentum-space and spacetime to be non-commutative with the non-commutativity determined by the spin content and C, P, and T properties of the examined representation space. Therefore, in a physically successful [Formula: see text], the notion of spacetime is expected to be deeply intertwined with specific properties of the test particle.
FULL CAUSAL DISSIPATIVE COSMOLOGIES WITH STIFF MATTER
Authors: MAK M. K. , HARKO T.
Published: March 2004

The general solution of the gravitational field equations for a full causal bulk viscous stiff cosmological fluid, with bulk viscosity coefficient proportional to the energy density to the power 1/4, is obtained in the flat Friedmann–Robertson–Walker geometry. The solution describes a non-inflationary Universe, which starts its evolution from a singular state. The time variation of the scale factor, deceleration parameter, viscous pressure, viscous pressure-thermodynamic pressure ratio, co-moving entropy and Ricci and Kretschmann invariants is considered in detail.
GALACTIC AND ASTROPHYSICAL SIZES FROM SCALAR-TENSOR THEORY OF GRAVITY
Authors: BASINI GIUSEPPE , RICCI MARCO , BONGIORNO FULVIO , CAPOZZIELLO SALVATORE
Published: March 2004

We investigate the weak-field limit of scalar-tensor theory of gravity and show that results are directly depending on the coupling and self-interaction potential of the scalar field. In particular, corrections are derived for the Newtonian potential. We discuss astrophysical applications of the results, in particular the flat rotation curves of spiral galaxies.
THE ACCRETION RATES–LUMINOSITY RELATIONS AND EVOLUTIONARY SEQUENCE OF FSRQs, BL Lac OBJECTS AND RADIO GALAXIES
Authors: XIE G. Z. , ZHOU S. B. , LIU H. T. , CHEN L. E. , MA L.
Published: March 2004

A sample of 39 blazars with well-established rapid variability timescale and bolometric luminosity has been compiled from literature. Based on the assumption that central supermassive black holes (SMBHs) are Kerr black holes, the upper limits of SMBHs were estimated. The masses ranged from 107.2M⊙ to 109.4M⊙, showing a distribution of three subclasses: massive flat spectra radio quasars (FSRQs) and smaller mass BL Lacs, occupy separate regions, while medium mass FSRQ and BL Lac object bridge the gap. In addition, we complied a sample of radio galaxies including 9 sources for which their black holes masses have been derived from the M BH -σ correlation and their optical and infrared data have been well observed. We find that the intrinsic accretion rates are quite different between FSRQs, BL Lacs and the radio galaxies. The diagram of the intrinsic accretion rate–luminosity relations shows that FSRQs occur in the earlier, high luminosity, violent phase of galactic evolution sequence, while BL Lacs occur in the low luminosity, transition phase between quasars and radio galaxies, and the radio galaxies occur in the late stage of the elliptical galaxy evolution sequence. Our theoretical results prove that the evolutionary track of the elliptical galaxy evolutionary sequence is from FSRQs to BL Lacs and then to the radio galaxies. The evolution diagram of blazars derived in this paper seems to be similar to Hertzsprung–Russell diagram of star evolution.
AGRICULTURAL FINANCE REVENUE FUTURES CONTRACT
Authors: GUINVARC'H MARTIAL V. , JANSSEN JACQUES , CORDIER JEAN E.
Published: March 2004

To respond to financial compound risk of farmers, two multiplicative derivative contracts, called respectively revenue futures contract and revenue put option, are proposed. The paper presents the theoretical management strategy of such a contract under the constraint that price and crop yield futures contracts are quoted.

A financial intermediary can thus develop a risk-free management strategy to build a revenue futures contract. This paper opens perspectives on risk management for farmers, on completeness of markets and on new financial intermediation.
DIVIDEND POLICY, TRADING CHARACTERISTICS AND SHARE PRICES: EMPIRICAL EVIDENCE FROM EGYPTIAN FIRMS
Authors: OMRAN MOHAMMED , POINTON JOHN
Published: March 2004

For a sample of 94 firms, using data up to 1999, we find that retentions are more significant than dividends in determining prices of shares that are actively traded on the Egyptian stock market. However, for non-actively traded shares, the accounting book value is the most important determinant. Reductions in dividends are associated with a lack of liquidity and profitability. Dividend increases are linked to higher pre-tax operating profit effects, which outweighed post-tax effects. As to aspects that influence dividend payout ratios of actively traded firms, important factors are gearing and the market to book value, the latter a surrogate for investment opportunities. For non-actively traded firms, a more complex pattern emerges.
CALIBRATION OF MULTIFACTOR MODELS IN ELECTRICITY MARKETS
Authors: BARLOW MARTIN , GUSEV YURI , LAI MANPO
Published: March 2004

Spot prices of electricity and other energy commodities are often modeled by multifactor stochastic processes. This poses a problem of estimating models' parameters based on historical data, i.e. calibrating them to markets. Here we show how a traditional tool of Kalman Filters can be successfuly applied to do this task. We study two mean-reverting log-spot price models and the Pilipovic model using correspondingly Kalman Filter the extended Kalman Filter. The results of applying this method to market data from several power exchanges are discussed.
ANALYTICAL PRICING OF DOUBLE-BARRIER OPTIONS UNDER A DOUBLE-EXPONENTIAL JUMP DIFFUSION PROCESS: APPLICATIONS OF LAPLACE TRANSFORM
Authors: SEPP ARTUR
Published: March 2004

We derive explicit formulas for pricing double (single) barrier and touch options with time-dependent rebates assuming that the asset price follows a double-exponential jump diffusion process. We also consider incorporating time-dependent volatility.

Assuming risk-neutrality, the value of a barrier option satisfies the generalized Black–Scholes equation with the appropriate boundary conditions. We take the Laplace transform of this equation in time and solve it explicitly. Option price and risk parameters are computed via the numerical inversion of the corresponding solution. Numerical examples reveal that the pricing formulas are easy to implement and they result in accurate prices and risk parameters.

Proposed formulas allow fast computing of smile-consistent prices of barrier and touch options.
Role of endothelial nitric oxide synthase in endothelial activation: insights from eNOS knockout endothelial cells
Authors: Kuhlencordt Peter J. , Rosel Eva , Gerszten Robert E. , Morales-Ruiz Manuel , Dombkowski David , Atkinson William J. , Han Fred , Preffer Frederic , Rosenzweig Anthony , Sessa William C. , Gimbrone Michael A. , Ertl Georg , Huang Paul L.
Published: April 2004

The objective of this study was to determine whether absence of endothelial nitric oxide synthase (eNOS) affects the expression of cell surface adhesion molecules in endothelial cells. Murine lung endothelial cells (MLECs) were prepared by immunomagnetic bead selection from wild-type and eNOS knockout mice. Wild-type cells expressed eNOS, but eNOS knockout cells did not. Expression of neuronal NOS and inducible NOS was not detectable in cells of either genotype. Upon stimulation, confluent wild-type MLECs produced significant amounts of NO compared with Nω-monomethyl-l-arginine-treated wild-type cells. eNOS knockout and wild-type cells showed no difference in the expression of E-selectin, P-selectin, intracellular adhesion molecule-1, and vascular cell adhesion molecule-1 as measured by flow cytometry on the surface of platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31)-positive cells. Both eNOS knockout and wild-type cells displayed the characteristics of resting endothelium. Adhesion studies in a parallel plate laminar flow chamber showed no difference in leukocyte-endothelial cell interactions between the two genotypes. Cytokine treatment induced endothelial cell adhesion molecule expression and increased leukocyte-endothelial cell interactions in both genotypes. We conclude that in resting murine endothelial cells, absence of endothelial production of NO by itself does not initiate endothelial cell activation or promote leukocyte-endothelial cell interactions. We propose that eNOS derived NO does not chronically suppress endothelial cell activation in an autocrine fashion but serves to counterbalance signals that mediate activation.
Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans
Authors: Gronfier Claude , Wright Kenneth P. , Kronauer Richard E. , Jewett Megan E. , Czeisler Charles A.
Published: March 2004

It has been shown in animal studies that exposure to brief pulses of bright light can phase shift the circadian pacemaker and that the resetting action of light is most efficient during the first minutes of light exposure. In humans, multiple consecutive days of exposure to brief bright light pulses have been shown to phase shift the circadian pacemaker. The aim of the present study was to determine whether a single sequence of brief bright light pulses administered during the early biological night would phase delay the human circadian pacemaker. Twenty-one healthy young subjects underwent a 6.5-h light exposure session in one of three randomly assigned conditions: 1) continuous bright light of ∼9,500 lux, 2) intermittent bright light (six 15-min bright light pulses of ∼9,500 lux separated by 60 min of very dim light of <1 lux), and 3) continuous very dim light of <1 lux. Twenty subjects were included in the analysis. Core body temperature (CBT) and melatonin were used as phase markers of the circadian pacemaker. Phase delays of CBT and melatonin rhythms in response to intermittent bright light pulses were comparable to those measured after continuous bright light exposure, even though the total exposure to the intermittent bright light represented only 23% of the 6.5-h continuous exposure. These results demonstrate that a single sequence of intermittent bright light pulses can phase delay the human circadian pacemaker and show that intermittent pulses have a greater resetting efficacy on a per minute basis than does continuous exposure.
Metabolic adjustments with the development, treatment, and recurrence of obesity in obesity-prone rats
Authors: MacLean Paul S. , Higgins Janine A. , Johnson Ginger C. , Fleming-Elder Brooke K. , Peters John C. , Hill James O.
Published: March 2004

Obesity is reaching epidemic proportions and predisposes afflicted individuals to several comorbidities. For these individuals, losing weight has proven to be an easier feat than maintaining a reduced weight. In obesity-prone rats, we examined if there is a metabolic propensity to regain weight after a period of significant weight loss. Twenty-four-hour energy expenditure (EE), sleeping metabolic rate (SMR), and nonprotein respiratory quotient (NPRQ) were obtained by indirect calorimetry with urinary nitrogen analysis and normalized to fat mass (FM) and fat-free mass (FFM) acquired by dual-energy X-ray absorptiometry. Obesity-prone rats were examined after free access to a high-fat diet for 16 wk to establish the obese state. They were again examined after 2 wk of calorie restriction, which reduced body weight (14%) and FM (32%). Rats were again examined after a further 8 wk of intake-regulated weight maintenance or ad libitum feeding that led to weight regain. Metabolic data were compared with preobese and age-matched controls. Weight loss suppressed EE and SMR beyond what was expected for the change in metabolic mass. This elevated metabolic efficiency persisted throughout weight maintenance but resolved after 8 wk of regain. Adjusted NPRQ values were elevated in weight-maintained and weight-regaining rats, suggesting a preference for carbohydrate utilization. These data support the concept that weight reduction in obesity is accompanied by metabolic adjustments beyond the drive to consume calories that predispose to weight regain, and some aspects of this adjustment persist with prolonged weight maintenance and during weight regain.
Spinal effects of oxytocin on uterine motility in anesthetized rats
Authors: Benoussaidh Anissa , Maurin Yves , Rampin Olivier
Published: March 2004

The rat uterus receives an innervation from the lumbosacral and thoracolumbar segments of the spinal cord. These segments receive descending oxytocinergic projections from the paraventricular nucleus of the hypothalamus. We tested the hypothesis that oxytocin regulates uterine motility through a spinal site of action. Oxytocin was administered in anesthetized female rats either intrathecally at the lumbosacral or thoracolumbar spinal cord levels or intravenously. Uterine activity was revealed by measuring changes of intrauterine pressure using an indwelling balloon placed in one caudal uterine horn. The uterus displayed a spontaneous activity characterized by intrauterine pressure rises, the frequency, amplitude, and duration of which were dependent on the stage of the estrous cycle. Oxytocin delivered at the lumbosacral level affected the frequency (during proestrus, estrus, and diestrus) and amplitude (during proestrus and estrus) of uterine activity. During estrus, oxytocin delivered at the thoracolumbar level affected the frequency, amplitude, and duration of the intrauterine pressure rises. Intravenous oxytocin not only affected intrauterine pressure rises (namely amplitude during proestrus and estrus and frequency and duration during estrus) but also increased the basal tone during estrus. The effects of lumbosacral oxytocin were partly mimicked by the oxytocin agonist [Thr4,Gly7]-oxytocin blocked by the oxytocin receptor antagonist atosiban and by hexamethonium. Arginine vasopressin delivered at the lumbosacral level had no effect. These results support our hypothesis that oxytocin released by descending paraventriculo-spinal pathways and acting on spinal oxytocin receptors modulates the activity of the uterus. This regulation is cycle dependent.
Evidence that paraventricular nucleus oxytocin neurons link hypothalamic leptin action to caudal brain stem nuclei controlling meal size
Authors: Blevins James E. , Schwartz Michael W. , Baskin Denis G.
Published: March 2004

Hindbrain projections of oxytocin neurons in the parvocellular paraventricular nucleus (pPVN) are hypothesized to transmit leptin signaling from the hypothalamus to the nucleus of the solitary tract (NTS), where satiety signals from the gastrointestinal tract are received. Using immunocytochemistry, we found that an anorectic dose of leptin administered into the third ventricle (3V) increased twofold the number of pPVN oxytocin neurons that expressed Fos. Injections of fluorescent cholera toxin B into the NTS labeled a subset of pPVN oxytocin neurons that expressed Fos in response to 3V leptin. Moreover, 3V administration of an oxytocin receptor antagonist, [d-(CH2)5,Tyr(Me)2,Orn8]-vasotocin (OVT), attenuated the effect of leptin on food intake over a 0.5- to 4-h period ( P < 0.05). Furthermore, to determine whether oxytocin contributes to leptin's potentiation of Fos activation within NTS neurons in response to CCK, we counted the number of Fos-positive neurons in the medial NTS (mNTS) after 3V administration of OVT before 3V leptin and intraperitoneal CCK-8 administration. OVT resulted in a significant 37% decrease ( P < 0.05) in the potentiating effect of leptin on CCK activation of mNTS neuronal Fos expression. Furthermore, 4V OVT stimulated 2-h food intake by 43% ( P < 0.01), whereas 3V OVT at the same dose was ineffective. These findings suggest that release of oxytocin from a descending pPVN-to-NTS pathway contributes to leptin's attenuation of food intake by a mechanism that involves the activation of pPVN oxytocin neurons by leptin, resulting in increased sensitivity of NTS neurons to satiety signals.
Y1- and α1-receptor control of basal hindlimb vascular tone
Authors: Jackson Dwayne N. , Noble Earl G. , Shoemaker J. Kevin
Published: March 2004

The role of endogenous Y1-receptor activation on skeletal muscle vasculature under baseline conditions is currently debated and no in vivo studies have been performed to address this issue. Therefore, this study was designed to address the effect of Y1-receptor and/or α1-adrenoceptor antagonism on basal hindlimb vascular conductance in male Sprague-Dawley rats in vivo. Left hindlimb vascular conductance, carotid artery mean arterial pressure, and heart rate were measured during low volume infusion of N2-(diphenylacetyl)- N-[(4-hydroxyphenyl)methyl]-d-arginine amide (BIBP3226; 100 μg/kg), prazosin (20 μg/kg), and combined blockade to the left hindlimb. Vascular conductance increased 1.5 ± 0.5 μl·min−1·mmHg−1 with BIBP3226 infusion, 1.7 ± 0.5 μl·min−1·mmHg−1 with prazosin infusion, and 4.8 ± 1.0 μl·min−1·mmHg−1 with combined blockade ( P < 0.05). Interestingly, systolic vascular conductance increased in all three conditions, but diastolic vascular conductance only increased in the two conditions where BIBP3226 was present. These data indicate that Y1-receptor activation plays an important role in the regulation of vascular conductance in the resting rat hindlimb. Furthermore, this effect was of the same magnitude as the α1-adrenoceptor contribution. The differential flow profiles following α1 blockade with and without Y1-receptor blockade supports local differences in receptor distribution.
Distributions of lung ventilation and perfusion in prone and supine humans exposed to hypergravity
Authors: Rohdin M. , Petersson J. , Mure M. , Glenny R. W. , Lindahl S. G. E. , Linnarsson D.
Published: March 2004

When normal subjects are exposed to hypergravity [5 times normal gravity (5 G)] there is an impaired arterial oxygenation that is less severe in the prone compared with supine posture. We hypothesized that under these conditions the heterogeneities of ventilation and/or perfusion distributions would be less prominent when subjects were prone compared with supine. Expirograms from a combined rebreathing-single breath washout maneuver (Rohdin M, Sundblad P, and Linnarsson D. J Appl Physiol 96: 1470–1477, 2004) were analyzed for vital capacity (VC), phase III slope, and phase IV amplitude, to analyze heterogeneities in ventilation (Ar) and perfusion [CO2-to-Ar ratio (CO2/Ar)] distribution, respectively. During hypergravity, VC decreased more in the supine than in the prone position (ANOVA, P = 0.02). Phase III slope was more positive for Ar ( P = 0.003) and more negative for CO2/Ar ( P = 0.007) in the supine compared with prone posture at 5 G, in agreement with the notion of a more severe hypergravity-induced ventilation-perfusion mismatch in supine posture. Phase IV amplitude became lower in the supine than in the prone posture for both Ar ( P = 0.02) and CO2/Ar ( P = 0.004) during hypergravity as a result of the more reduced VC in the supine posture. We speculate that results of VC and phase IV amplitude are due to the differences in heart-lung interaction and diaphragm position between postures: a stable position of the heart and diaphragm in prone hypergravity, in contrast to supine in which the weight of the heart and a cephalad shift of the diaphragm compress lung tissue.
Single-Neuron Discharge Properties and Network Activity in Dissociated Cultures of Neocortex
Authors: Giugliano M. , Darbon P. , Arsiero M. , Lüscher H.-R. , Streit J.
Published: March 2004

Cultures of neurons from rat neocortex exhibit spontaneous, temporally patterned, network activity. Such a distributed activity in vitro constitutes a possible framework for combining theoretical and experimental approaches, linking the single-neuron discharge properties to network phenomena. In this work, we addressed the issue of closing the loop, from the identification of the single-cell discharge properties to the prediction of collective network phenomena. Thus, we compared these predictions with the spontaneously emerging network activity in vitro, detected by substrate arrays of microelectrodes. Therefore, we characterized the single-cell discharge properties to Gauss-distributed noisy currents, under pharmacological blockade of the synaptic transmission. Such stochastic currents emulate a realistic input from the network. The mean ( m) and variance ( s2) of the injected current were varied independently, reminiscent of the extended mean-field description of a variety of possible presynaptic network organizations and mean activity levels, and the neuronal response was evaluated in terms of the steady-state mean firing rate ( f). Experimental current-to-spike–rate responses f( m, s2) were similar to those of neurons in brain slices, and could be quantitatively described by leaky integrate-and-fire (IF) point neurons. The identified model parameters were then used in numerical simulations of a network of IF neurons. Such a network reproduced a collective activity, matching the spontaneous irregular population bursting, observed in cultured networks. We finally interpret such a collective activity and its link with model details by the mean-field theory. We conclude that the IF model is an adequate minimal description of synaptic integration and neuronal excitability, when collective network activities are considered in vitro.
Modulation of Coordinated Muscle Activity During Imposed Sinusoidal Hip Movements in Human Spinal Cord Injury
Authors: Steldt Robert E. , Schmit Brian D.
Published: March 2004

Individuals with chronic spinal cord injury (SCI) often demonstrate multijoint reflex activity that is clinically classified as an extensor spasm. These responses are commonly observed in conjunction with an imposed extension movement of the hips, such as movement from a sit to a supine position. Coincidentally, afferent feedback from hip proprioceptors has also been implicated in the control of locomotion in the spinalized cat. Because of this concurrence, we postulated that extensor spasms that are triggered by hip extension might involve activation of organized interneuronal circuits that also have a role in locomotion. If true, imposed oscillations of the hip would be expected to produce activity of the leg musculature in a locomotor pattern. Furthermore, this muscle activity would be entrained to the hip movement. The right hip joints of 10 individuals with chronic SCI, consisting of both complete [American Spinal Injury Association (ASIA) A] and incomplete (ASIA B,C) injuries, were subjected to ramp and hold (10 s) movements at 60°/s and sinusoidal oscillations at 1.2, 1.88, and 2.2 rad/s over ranges from 40 to –15° (±5°) using a custom servomotor system. Surface EMG from seven lower extremity muscles and sagittal-plane joint torques were recorded to characterize the response. Ramp and hold perturbations produced coactivation at the hip, knee, and ankle joints, with a long duration (5–10 s). Sinusoidal perturbations yielded consistent muscle timing patterns that resulted in alternating flexor and extensor joint torques. EMG and joint torques were commonly entrained to the frequency of movement, with rectus femoris, vastus medialis, and soleus activity coinciding with hip extension and medial hamstrings activity occurring during hip flexion. Individual muscle timing patterns were consistent with hip position during normal gait, except for the vastus medialis. These results suggest that reflexes associated with extensor spasms may occur through organized interneuronal pathways, such as spinal centers for locomotion.
Primitive Auditory Stream Segregation: A Neurophysiological Study in the Songbird Forebrain
Authors: Bee Mark A. , Klump Georg M.
Published: March 2004

Auditory stream segregation refers to the perceptual grouping of sounds, to form coherent representations of objects in the acoustic scene, and is a fundamental aspect of hearing and speech perception. The perceptual segregation of simple interleaved tone sequences has been studied in humans and European starlings ( Sturnus vulgaris) using sequences of 2 alternating tones differing in frequency (ABA-ABA-ABA-…). The segregation of A and B tones into separate auditory streams is believed to be promoted by preattentive auditory processes that increase the separation of excitation patterns along a tonotopic gradient. We tested the hypothesis that frequency selectivity and forward masking operate as 2 preattentive processes in sequential stream segregation by recording neural responses in the auditory forebrain of awake starlings to repeated ABA- sequences in which we varied the frequency separation (ΔF) between the A and B tones and the tone repetition time (TRT). The A tones were presented at the neurons' characteristic frequency (CF), and B tones differed from the CF over a one-octave range. Larger ΔF values and shorter TRTs promote the perceptual segregation of alternating tone sequences in humans and also resulted in larger differences in neural responses to alternating CF (A) and non-CF (B) tones. Our results are consistent with the hypothesis that preattentive auditory processes, such as frequency selectivity and forward masking, contribute to the perceptual segregation of sequential acoustic events having different frequencies into separate auditory streams, but also suggest that additional processes may be required to account for all known perceptual effects related to sequential auditory stream segregation.
Asymptotic and numerical solutions for diffusion models for compounded risk reserves with dividend payments
Authors: Shao S. , Chang C. L.
Published: March 2004

We study a family of diffusion models for compounded risk
reserves which account for the investment income earned and for
the inflation experienced on claim amounts. We are interested in
the models in which the dividend payments are paid from the risk
reserves. After defining the process of conditional probability
in finite time, martingale theory turns the nonlinear stochastic
differential equation to a special class of boundary value
problems defined by a parabolic equation with a nonsmooth
coefficient of the convection term. Based on the behavior of the
total income flow, asymptotic and numerical methods are used to
solve the special class of diffusion equations which
govern the conditional ruin probability over finite time.
Worrisome Thoughts About the Diagnosis and Treatment of Patients With Brugada Waves and the Brugada Syndrome
Authors: Ahn Joon , Hurst J. Willis
Published: March 2004

The Brugadas have made a significant contribution to medicine. Their discovery of a new clinical syndrome and ECG abnormalities has created a great deal of interest and has opened Pandora’s box. Here, we discuss some worrisome thoughts about the condition. We stress the need for improved diagnostic criteria and treatment because it is not always possible to perform coronary arteriography, electrophysiological studies, right ventricular myocardial biopsy, and MRI in all patients in whom ST-segment abnormalities are seen in the ECG, especially in patients who are asymptomatic. Accordingly, further research is needed to guide the clinician in the diagnostic and therapeutic problems of patients who have unusual ST segments in leads V
1
and V
3
. We present a patient who illustrates the problem.
Laboratory Markers in the Diagnosis of Venous Thromboembolism
Authors: Caprini Joseph A. , Glase Catherine J. , Anderson Christopher B. , Hathaway Karen
Published: March 2004

Selected blood tests may be useful in the diagnosis of venous thromboembolism (VTE), or in the identification of a congenital or acquired defect associated with the development of VTE. Several studies have shown the D-dimer assay to have a high negative predictive value but poor specificity when used in the detection of VTE. Yet in the emergency room setting, the D-dimer test may be useful if a detailed risk factor analysis for each patient is included in the diagnosis. The presence of such genetic thrombophilia markers as factor V Leiden, prothrombin 20210A mutation, and antiphospholipid antibodies significantly increases a patient’s risk of a thrombotic event. The relative risk of thrombosis in factor V heterozygotes is at least 3 times higher than in the general population, whereas the increased risk of thrombosis in homozygotes is estimated to be 50- to 80-fold greater than those without the defect. Thromboembolic events are reported in approximately one third of antiphospholipid-positive patients. Other markers such as hyperhomocysteinemia and deficiencies of antithrombin, protein C, or protein S, when combined with the previous mutations, significantly increase a patient’s risk of a thrombotic event. We feel that it is important to identify these ultra-high-risk patients to provide adequate counseling about the risk of thrombosis before elective surgical procedures. Often, lifelong anticoagulation may be needed as these patients and family members may need testing before taking birth control pills or hormonal replacement.
Ultrasonography and Diagnosis of Venous Thromboembolism
Authors: Zierler Brenda K.
Published: March 2004

Venous thromboembolism (VTE) consists of two related conditions: pulmonary embolism (PE) and deep vein thrombosis (DVT). Objective testing for VTE is crucial because the clinical diagnosis is nonspecific and insensitive, and the consequences of a missed diagnosis are serious. The purpose of this review is to discuss the utility of venous ultrasonography as the foundation for diagnosis of acute lower extremity DVT. The effectiveness and practicality of venous ultrasonography as a stand-alone examination versus theoretically attractive, but perhaps less practical, combined approaches of ultrasonography with clinical probability assessment and D-dimer testing in the diagnosis of acute DVT is also addressed. Finally, the role of venous ultrasonography in a diagnostic algorithm for suspected PE is discussed.
Contrast Peripheral Phlebography and Pulmonary Angiography for Diagnosis of Thromboembolism
Authors: Andrews R. Torrance
Published: March 2004

At one time, direct intravascular contrast angiography was the standard method for confirmatory diagnosis of venous or pulmonary arterial thromboembolism. Although sensitive and specific, conventional catheter-based contrast imaging is invasive and associated with a risk of phlebitis and thrombosis. These procedures require specialized training and experience in catheter manipulation, as well as specialized vascular imaging equipment. In current practice, less invasive techniques have largely superceded conventional angiography because they can be performed by technologists using widely available, multifunctional apparatus under physician supervision. When results using these newer approaches are inconclusive or impractical, however, catheter-based techniques are still relied on for definitive diagnosis. The purpose of this article is to review the indications, techniques, and interpretations of contrast angiography as applied to venous thromboembolic disease.
À Propos des nouvelles tablettes de Thèbes, I: Les trois divinités ma-ka, o-po-re-i et ko-wa et les trois subordonnées temporelles dans la série Fq
Authors:   Ruijgh
Published: March 2004

Linguistic, philological and historical considerations show that the editors of the new Thebes tablets correctly interpreted ma-ka, o-po-re-i and ko-wa as the dative forms of three theonyms: Mα Γα 'Mother Earth', Oπωρης = oπωρευς 'god of the fruits' (Zeus) and KoρFα (Attic Koρη). The nouns μα 'mother', γα/δα 'earth', να 'little girl' and μνα 'mina' are Pre-Greek loan-words. The following interpretations are proposed for the three temporal clauses in the Fq tablets: Fq 126 o-te tu-wo-te-to oτευoς ετo 'when he (: the priest) had placed the sacrifice (on the altar)'. Fq 130 o-te o-je-ke-te-to oτεoy εκσετo 'when he (: the priest) had exposed the tree-fruits (on the offering table)'. Fq 254 o-te a-pi-e-qe ke-ro- pa-ta oτε αμϕιhεσκwε γερoνταsigmav; παντας 'when he (: the priest) had made all the Elders follow him on both sides', i.e., 'when the priest had led a procession of all the Elders'. The editors correctly interpret de-qo-no (Fq 254) as the dative of δεικwνoς 'person charged with the preparation of sacred meals'.—The appendix contains a discussion of the origin of the passive aorist in-()η-, of oα 'tree-fruits', 'service berries', and of the original connexion between εν-επω 'tell' and επoμαι 'follow'.
Euripides, Hecuba 905-22, Ion 763-803, Bacchae 402-331): text and metre
Authors:   Willink
Published: March 2004

Three passages in the cantica of Euripides are discussed, one from each of the three volumes of the latest Oxford Classical Text. All, in various ways, are of metrical interest, and all contain textual cruces.