bluuebunny/crossref_metadata_2025 huggingface dataset:
Some aspects of a weak WeylHeisenberg algebra deformation
Authors: Boucerredj N , Mebarki N , Benslama A
Published: September 2005

In the weak deformation (WD) approximation of the WeylHeisenberg algebra, the corresponding generalized coherent states and displacement operator are constructed. It is shown that those states, and contrary to the non-deformed Weyl-Heisenberg algebra, are not eigenstates of the annihilation operator. Moreover, and as an alternative to the Chaïchian et al. Q-deformed path integral approach (where Q is the deformation parameter), using the Bargmann Fock representation, we propose in the WD approximation, a general simple formalism. As an application, we calculate the propagator and the wave function of the harmonic oscillator.PACS Nos.: 03.65.Fd, 31.15.Kb
The propagation of powerful femtosecond laser pulses in opticalmedia: physics, applications, and new challenges
Authors: Chin S L , Hosseini S A , Liu W , Luo Q , Théberge F , Aközbek N , Becker A , Kandidov V P , Kosareva O G , Schroeder H
Published: September 2005

When a powerful femtosecond laser pulse propagates in an optical medium, self-focusing occurs. Normally, it is the most powerful part (slice) of the pulse that self-focuses first during its propagation. Self-focusing is balanced by the creation of plasma in the self-focal volume, which defocuses the pulse. This balance leads to a limitation of the peak intensity (intensity clamping). The series of self-foci from different slices of the front part of the pulse give rise to the perception of a so-called filament. The back part of the pulse undergoes self-phase modulation and self-steepening resulting in a strong spectral broadening. The final pulse is a white-light laser pulse (supercontinuum). The physics of such (long distance) filamentation and the self-transformation process are reviewed both in air and in condensed matters. The self-transformation leads to a shorter pulse and is currently being studied for efficient pulse compression to the single and (or) few-cycle level. The efficient generation of a third harmonic in the filament is due to a new phenomenon called self-phase locking. The potential applications in atmospheric sensing and lightning control will be briefly discussed. The capability of melting glass leading to index change will be underlined. The paper will end with an outlook into the future of the field. PACS Nos.: 42.65, 42.65Jx, 42.25, 42.79Qx
Polybrominated diphenyl ethers in an advanced wastewater treatment plant. Part 2: Potential effects on a unique aquatic system
Authors: Rayne Sierra , Ikonomou Michael G
Published: September 2005

Concentrations of the mono- through deca-substituted polybrominated diphenyl ether (PBDE) flame retardants were determined in the aqueous effluent from a tertiary-level wastewater treatment plant (WWTP) that uses post-filtration ultraviolet light disinfection. The WWTP is located in a semi-arid region of British Columbia. Subsequent limnological modeling of receiving waters examined the potential long-term effects of various PBDE-loading scenarios on this unique aquatic system. Over the three decades from 2002 to 2031, total PBDE concentrations in the water column and in suspended and surficial sediments are expected to increase to >120 pg·L–1 and ~1 ng·g–1 wet weight, respectively. Following implementation of a hypothetic halt on PBDE releases into the aquatic system, individual PBDE congener concentrations in the water column and sediments declined by <35% over the ensuing 17-year modeling period after the ban, illustrating the potential long-term problem arising from continued PBDE inputs into aquatic systems worldwide. The results also suggest that PBDEs represent one of the single largest halogenated aromatic loadings to Canadian lakes, rivers, and streams from wastewaters, and their worldwide use continues to increase exponentially. Key words: polybrominated diphenyl ethers (PBDEs), flame retardants, municipal wastewater treatment effluent, contaminant fluxes, limnologic modeling.
Analytical and numerical solutions for a single vertical drain including the effects of vacuum preloading
Authors: Indraratna Buddhima , Rujikiatkamjorn Cholachat , Sathananthan Iyathurai
Published: September 2005

A system of vertical drains combined with vacuum preloading is an effective method to accelerate soil consolidation by promoting radial flow. This study presents the analytical modeling of vertical drains incorporating vacuum preloading in both axisymmetric and plane strain conditions. The effectiveness of the applied vacuum pressure along the drain length is considered. The exact solutions applied on the basis of the unit cell theory are supported by finite element analysis using ABAQUS software. Subsequently, the details of an appropriate matching procedure by transforming permeability and vacuum pressure between axisymmetric and equivalent plane strain conditions are described through analytical and numerical schemes. The effects of the magnitude and distribution of vacuum pressure on soft clay consolidation are examined through average excess pore pressure, consolidation settlement, and time analyses. Lastly, the practical implications of this study are discussed.Key words: consolidation, finite element method, soft clay, vacuum preloading, vertical drains.
Cone tip resistance in sand: modeling, verification, and applications
Authors: Ahmadi M M , Byrne P M , Campanella R G
Published: September 2005

A numerical modeling procedure is presented to evaluate cone tip resistance in sand. The procedure involves a moving boundary simulating cone penetration. The soil is modeled as a MohrCoulomb elasticplastic material with stress-dependent parameters. The procedure is verified by comparing predicted numerical values of cone tip resistance with published experimental measurements from calibration chamber tests. The selected database consists of 59 calibration chamber tests on Ticino sand with different relative densities, overconsolidation ratios, stresses, and boundary conditions. Several applications of the modeling procedure are also presented. The computer program FLAC is used to carry out the analysis.Key words: cone tip resistance, numerical modeling, sand, calibration chamber, Mohr-Coulomb, in situ horizontal stress.
Application of geophysical methods for the investigation of the large gravitational mass movement of Séchilienne, France
Authors: Meric O , Garambois S , Jongmans D , Wathelet M , Chatelain J L , Vengeon J M
Published: September 2005

Several geophysical techniques (electromagnetic profiling, electrical tomography, seismic refraction tomography, and spontaneous potential and seismic noise measurement) were applied in the investigation of the large gravitational mass movement of Séchilienne. France. The aim of this study was to test the ability of these methods to characterize and delineate the rock mass affected by this complex movement in mica schists, whose lateral and vertical limits are still uncertain. A major observation of this study is that all the zones strongly deformed (previously and at present) by the movement are characterized by high electrical resistivity values (>3 kΩ·m), in contrast to the undisturbed mass, which exhibits resistivity values between a few hundred and 1 kΩ·m. As shown by the surface observations and the seismic results, this resistivity increase is due to a high degree of fracturing associated with the creation of air-filled voids inside the mass. Other geophysical techniques were tested along a horizontal transect through the movement, and an outstanding coherency appeared between the geophysical anomalies and the displacement rate curve. These preliminary results illustrate the benefits of combined geophysical techniques for characterizing the rock mass involved in the movement. Results also suggest that monitoring the evolution of the rock mass movement with time-lapse geophysical surveys could be beneficial.Key words: gravitational movement, geophysical methods, Séchilienne.
Risk-based definition of zones for land-use planning in snow avalanche terrain
Authors: McClung D M
Published: September 2005

For avalanche applications, the definition of zones for land-use planning typically involves estimates of both return period and impact pressures as functions of position in the runout zone. Since return period is related to expected avalanche frequency and impact pressure is related to consequences if structures are hit, zone specifications imply a risk-based approach. In this paper, the schemes for definition of zones from three countries (Switzerland, Canada, and Austria) are presented and compared from a mathematical, risk-based framework. The comparison reveals that the Swiss standard is the least conservative and the Austrian standard is the most conservative.Key words: risk, snow avalanches, zoning, return period.
Predicted versus measured soil movements induced by shield tunnelling in the Madrid Metro extension
Authors: Maynar Manuel Melis , Rodriguez Luis Medina
Published: September 2005

A detailed study on the available methods of predicting ground movements due to tunnelling works was carried out during the construction of the Madrid Metro extensions in 19951999 and 19992003. A total of 100 km were built and commissioned during this period. A numerical model was developed to simulate the earth pressure balance (EPB) excavation procedure and to complement some of the deficiencies found in previous analytical or empirical subsidence estimation procedures. Before the beginning of the works, a total of six different methods were used to estimate ground movements generated by the tunnelling works at some monitored sections placed in all five cities linked by the 19992003 extension, and the estimations were published in an earlier paper in this journal. Once all tunnelling works were finished and actual measurements carried out, a number of comparisons between predictions and measurements were made and are included in this paper. Conclusions about the applicability and accuracy of the methods are established with the aim of helping researchers and engineers in their future projects.Key words: ground movements, monitoring, numerical modelling and analysis, settlement, tunnels.
Stand-level response of breeding forest songbirds to multiple levels of partial-cut harvest in four boreal forest types
Authors: Harrison R Bruce , Schmiegelow Fiona K.A , Naidoo Robin
Published: September 2005

We investigated whether impacts on boreal forest songbird communities in northwestern Alberta could be mitigated through a harvesting system that attempts to emulate the local natural disturbance regime. The EMEND (Ecosystem Management by Emulating Natural Disturbance) project is a multidisciplinary experiment to compare clearcuts and partial-retention cuts in four upland cover types with uncut forest and with experimentally burned stands. We studied breeding birds at EMEND between 1998 (pretreatment) and 2000, focusing on their responses to partial harvesting. Partial cuts were generally intermediate (and varied in a linear fashion) between clearcuts and undisturbed forest for community and species measures. Species that declined in abundance in partial cuts were typically dependent on shrubs and trees, whereas species that benefited were typically ground nesters. While partial cutting offered some advantages over clear-cutting in conserving short-term avian diversity, we suggest that low retention levels (i.e., 10%, 20%) cannot be justified from this perspective. The benefits that accrued in these treatments were relatively small, and species that declined or disappeared were typically characteristic of mature forest habitats. Higher retention levels (i.e., 50%, 75%) may conserve some species of concern, but the extent to which these treatments offer productivity advantages over lower residuals requires further study.
Reduction of black spruce seed bank by spruce budworm infestation compromises postfire stand regeneration
Authors: Simard Martin , Payette Serge
Published: September 2005

In the southern boreal forest of eastern Canada, black spruce (Picea mariana (Mill.) BSP) is subjected to both defoliating insect and fire disturbances. As black spruce depends on its aerial seed bank for postfire regeneration, reduction of cone crop during a spruce budworm (Choristoneura fumiferana (Clem.)) outbreak opens a vulnerability window during which stand regeneration could be hindered in the event of a fire. To assess the long-term effect of spruce budworm outbreak on black spruce reproductive potential, cone production and viable seed bank were estimated using cone crop surveys and germination trials in black spruce  lichen woodland stands that sustained different levels of defoliation during the 1980s. Black spruce cone crop was significantly related to the defoliation history of the stands (R2 = 0.89), but not to stand age, basal area, or tree density. Black spruce stands damaged by severe defoliation showed a smaller number of cones, a higher incidence of insect-damaged cones, and a viable seed bank 3 to 17 times smaller than a lightly defoliated stand. The vulnerability window for black spruce regeneration following a spruce budworm outbreak may be as long as 20 years in the study area because black spruce seed bank in heavily defoliated stands has not yet replenished. Our work supports conclusions from stand reconstruction studies that suggest closed-crown sprucemoss stands convert to open lichen woodlands as a result of weak postfire regeneration caused by successive insect and fire disturbances.
Development and testing of models for predicting crown fire rate of spread in conifer forest stands
Authors: Cruz Miguel G , Alexander Martin E , Wakimoto Ronald H
Published: September 2005

The rate of spread of crown fires advancing over level to gently undulating terrain was modeled through nonlinear regression analysis based on an experimental data set pertaining primarily to boreal forest fuel types. The data set covered a significant spectrum of fuel complex and fire behavior characteristics. Crown fire rate of spread was modeled separately for fires spreading in active and passive crown fire regimes. The active crown fire rate of spread model encompassing the effects of 10-m open wind speed, estimated fine fuel moisture content, and canopy bulk density explained 61% of the variability in the data set. Passive crown fire spread was modeled through a correction factor based on a criterion for active crowning related to canopy bulk density. The models were evaluated against independent data sets originating from experimental fires. The active crown fire rate of spread model predicted 42% of the independent experimental crown fire data with an error lower then 25% and a mean absolute percent error of 26%. While the models have some shortcomings and areas in need of improvement, they can be readily utilized in support of fire management decision making and other fire research studies.
The influence of thinning and tree size on the sapwood area / leaf area ratio in coigue
Authors: Gajardo-Caviedes Pablo A , Espinosa Miguel A , González Urcesino del T , Ríos Darcy G
Published: September 2005

The effect of thinning and crown class on the projected leaf area, specific leaf area, and projected leaf area / sapwood area ratio was evaluated in a 48-year-old even-aged stand of coigue (Nothofagus dombeyi (Mirb.) Oerst.). The data were collected through destructive sampling of 27 trees and analyzed with analysis of variance and regression models. The projected leaf area was greater in trees from more intensely thinned stands. The specific leaf area and the projected leaf area / sapwood area ratio did not vary between treatments. The sapwood cross-sectional area at breast height (1.3 m) and at the base of the live crown provided the best fit for the relationship between projected leaf area and sapwood area. The current sapwood area provided the worst fit, suggesting that at an early age, coigue sapwood does not present permeability problems associated with tyloses.
Forest certification costs and global forest product markets and trade: a general equilibrium analysis
Authors: Gan Jianbang
Published: September 2005

The impacts of forest certification costs on the output, price, and trade of forest products were assessed via computable general equilibrium modeling under various scenarios representing tropical, temperate, and global forest certification. Despite causing more severe and extensive impacts, global certification seems more acceptable than regional certification to major timber-producing countries. The regions that would suffer the most from global certification would not be major timber-producing regions, but major net importers of forest products like East Asia. With 5%25% increases in forestry production costs resulting from certification, the world's forestry output would decline by 0.3%5.1%, while the world price would rise by 1.6%34.6%; impacts on global lumber and pulp and paper markets would be much more moderate. In general, forest certification would have larger impacts on trade and price than on output. While causing trade diversion and substitutions between tropical and temperate forest products and affecting regional forest product markets, forest certification would not substantially induce substitutions between wood and nonwood products at the global aggregate level. Because of the possible leakages (deforestation elsewhere) associated with regional certification and the land-use shifts resulting from sectoral production shifts at the regional level, forest certification may not necessarily curb tropical deforestation.
DATA PARALLELISM IN C++ TEMPLATE PROGRAMS: A BARNES-HUT CASE STUDY
Authors: BISCHOF HOLGER , GORLATCH SERGEI , LESHCHINSKIY ROMAN , MÜLLER JENS
Published: September 2005

We describe how C++ programs that use the Standard Template Library (STL) can be systematically parallelized for shared-memory machines. We present our data-parallel template library (DatTeL) and its use in introducing parallelism into sequential STL programs. As a case study, we demonstrate how an STL implementation of the Barnes-Hut algorithm for solving many-body problems can be systematically transformed into a parallel, efficient version using DatTeL. We present experimental results for the multi-threaded version of the resulting parallel program on a SunFire multiprocessor.
QCOLONY: A MULTI-PHEROMONE BEST-FIT QoS ROUTING ALGORITHM AS AN ALTERNATIVE TO SHORTEST-PATH ROUTING ALGORITHMS
Authors: TADRUS SAMIH , BAI LI
Published: September 2005

This paper introduces a new generic routing algorithm called QColony for packet-switched communications networks that support real-time flows. In this context, we introduce both a novel path-selection scheme, namely the best-fit scheme, and a novel routing technique, namely the multi-pheromone technique, inspired by observations of biological ant colonies. Simulation was carried out for our algorithm and two other routing algorithms under various traffic scenarios and different irregular network topologies. Simulation results show that we can achieve good performance for the QColony algorithm. According to our experiments, QColony is able to provide smooth performance for all operating conditions, especially with large networks and under traffic scenarios with failure conditions and improperly functioning nodes. We also demonstrate through simulation that the best-fit scheme is able to deliver higher routing performance than what the shortest-path scheme can achieve.
AN ANT-BASED MULTICASTING PROTOCOL IN MOBILE AD-HOC NETWORK
Authors: ZHANG LIN , SHEN DONGXU , SHAN XIUMING , LI VICTOR O. K.
Published: September 2005

Multicasting protocols deliver data packets from a source node to multiple receivers, and serve a very important function in mobile ad-hoc networks (MANETs). In this paper, a novel receiver-initiated soft-state probabilistic multicasting protocol (RISP) for MANETs is proposed. RISP is inspired by the ant colony's route-seeking mechanism, in which an individual ant chooses the optimal path to its destination through cooperation with others in a totally distributed manner. Imitating the behaviour of ants in nature, RISP introduces probabilistic forwarding and soft-state for making relay decisions that are automatically adaptive to node mobility in MANETs. Compared with other protocols, we show by computer simulations that RISP has lower delivery redundancy, while achieving higher delivery ratio at all mobility scenarios. Furthermore, RISP has lower control overhead.
A GENETIC ALGORITHM FOR THE DESIGN OF MINIMUM-COST TWO-CONNECTED NETWORKS WITH BOUNDED RINGS
Authors: VENTRESCA MARIO , OMBUKI BEATRICE M.
Published: September 2005

This paper presents a genetic algorithm for designing minimum-cost two-connected networks such that the shortest cycle to which each edge belongs to does not exceed a given length. We provide numerical results based on randomly generated graphs found in the literature and compare the solution quality with that of tabu search and branch and bound. The results demonstrate the effectiveness of our algorithm and show promise for tackling ring-based network design problems. This paper is among the first to document the implementation of a genetic algorithm for the design of two-connected networks with the added constraint of bounded rings.
THE EVOLUTION OF HUMAN PHYSICAL ATTRACTIVENESS
Authors: Gangestad Steven W. , Scheyd Glenn J.
Published: September 2005

Everywhere the issue has been examined, people make discriminations about others’ physical attractiveness. Can human standards of physical attractiveness be understood through the lens of evolutionary biology? In the past decade, this question has guided much theoretical and empirical work. In this paper, we (a) outline the basic adaptationist approach that has guided the bulk of this work, (b) describe evolutionary models of signaling that have been applied to understand human physical attractiveness, and (c) discuss and evaluate specific lines of empirical research attempting to address the selective history of human standards of physical attractiveness. We also discuss ways evolutionary scientists have attempted to understand variability in standards of attractiveness across cultures as well as the ways current literature speaks to body modification in modern Western cultures. Though much work has been done, many fundamental questions remain unanswered.
RECENT ETHNOGRAPHIC RESEARCH ON NORTH AMERICAN INDIGENOUS PEOPLES
Authors: Strong Pauline Turner
Published: September 2005

This review article addresses the following question: Given the transformed social, political, and intellectual conditions for ethnographic research among indigenous peoples in North America, what forms has such research come to take at the turn of the twenty-first century? The review considers significant trends and innovations in research sites and topics, research methodologies, theoretical orientations, and forms of representation. It also assesses the distinctive strengths and limitations posed by ethnographic research for scholars engaging with significant dimensions of contemporary indigenous life, including struggles for rights, resources, recognition, and language vitality in both the national and international arenas; the repatriation and sovereignty movements; the development of tribal casinos, tourist complexes, cultural centers, and media outlets; continued social and economic marginalization of many indigenous peoples; and challenges posed by neoliberalism and globalization to tribal governments and economies.
Behavioral Theories and the Neurophysiology of Reward
Authors: Schultz Wolfram
Published: September 2005

The functions of rewards are based primarily on their effects on behavior and are less directly governed by the physics and chemistry of input events as in sensory systems. Therefore, the investigation of neural mechanisms underlying reward functions requires behavioral theories that can conceptualize the different effects of rewards on behavior. The scientific investigation of behavioral processes by animal learning theory and economic utility theory has produced a theoretical framework that can help to elucidate the neural correlates for reward functions in learning, goal-directed approach behavior, and decision making under uncertainty. Individual neurons can be studied in the reward systems of the brain, including dopamine neurons, orbitofrontal cortex, and striatum. The neural activity can be related to basic theoretical terms of reward and uncertainty, such as contiguity, contingency, prediction error, magnitude, probability, expected value, and variance.
Stressful Experience and Learning Across the Lifespan
Authors: Shors Tracey J.
Published: September 2005

It is usually assumed that stressful life events interfere with our ability to acquire new information. However, many studies suggest that stressful experience can enhance processes involved in learning. The types of learning that are enhanced after stressful experiences include classical fear and eyeblink conditioning, as well as processes related to learning about threatening stimuli. Stressful life experiences do seem to interfere with processes involved in memory, often expressed as deficits in the retention or retrieval of information that was acquired prior to and was unrelated to the stressful experience. The trends are limited, as are their implications, because most studies examine adult males, yet the effects of stress on learning processes are influenced by age and sex differences. With respect to mechanisms and anatomical substrates, the effects of stress on learning are usually dependent on the action of stress hormones in combination with neuronal activities within the hippocampus, amygdala, the bed nucleus of the stria terminalis, and the prefrontal cortex.
Trail induces cell migration and invasion in apoptosis-resistant cholangiocarcinoma cells
Authors: Ishimura Norihisa , Isomoto Hajime , Bronk Steven F. , Gores Gregory J.
Published: September 2005

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising agent for cancer therapy; however, many cholangiocarcinoma cells are resistant to TRAIL-mediated apoptosis. Resistance to apoptosis may unmask TRAIL signaling cascades favoring tumor biology. Thus our aim was to examine whether TRAIL is expressed by human cholangiocarcinomas, and if so, to determine whether it promotes a malignant phenotype. To address this objective, TRAIL expression in human liver specimens was evaluated by immunohistochemistry. The effect of TRAIL on tumor cell migration, invasion, and proliferation was examined in three human cholangiocarcinoma cell lines. TRAIL expression was upregulated by cholangiocytes in preneoplastic disease, primary sclerosing cholangitis, and human cholangiocarcinoma specimens. TRAIL promoted tumor cell migration and invasion but did not induce cell proliferation. TRAIL-mediated cell migration and invasion was NF-κB dependent. These data demonstrate that TRAIL promotes cell migration and invasion via a NF-κB-dependent pathway in human cholangiocarcinoma cell lines, an observation that has a potential negative implication for TRAIL in cancer therapy.
Effect of modulation of serotonergic, cholinergic, and nitrergic pathways on murine fundic size and compliance measured by ultrasonomicrometry
Authors: Xue Lin , Locke G. Richard , Camilleri Michael , Schuurkes Jan A. J. , Meulemans Ann , Coulie Bernard J. , Szurszewski Joseph H. , Farrugia Gianrico
Published: September 2005

Reduced fasting or postprandial gastric volumes have been implicated in the pathophysiology of functional dyspepsia. The mechanisms that underlie the control of gastric fundic volume are incompletely understood, partly because of an inability to accurately measure fundic volume in vivo in small animals. Small animals are useful models to evaluate mechanisms, e.g., in knockout animals. The aim of this study was to determine whether an ultrasonometric technique accurately monitors fundic contraction and relaxation in mice in vivo and to determine the effect of modulation of cholinergic, nitrergic, and serotonergic pathways on fundic size and compliance in the intact mouse innervated stomach. Two to four piezoelectric crystals (diameter 1 mm, 24-μm resolution) were glued to the serosal side of fundus and used to measure distance. Validation studies showed excellent correlation between measured changes and actual changes in distances between crystals and excellent reproducibility. The expected responses to pharmacological modulation with bethanechol and nitroglycerin were demonstrated. Atropine increased the distance between the crystals, suggesting a baseline cholinergic regulation of fundic volume. Bethanechol, Nω-nitro-l-arginine, and the 5-HT1B/Dagonist sumatriptan decreased the distance between the crystals, suggesting fundic contraction. Atropine, nitroglycerin, and buspirone caused an increase in intercrystal distance consistent with fundic relaxation. Fundic compliance was investigated by changing intragastric pressure via an implanted catheter. Sumatriptan increased compliance, whereas buspirone increased the distance between crystals but did not change compliance. The data suggest that ultrasonomicrometry is a useful tool that can reproducibly and accurately measure changes in fundic size and the response to pharmacological agents.
Effect of oxygen consumption by measuring method on Po2transients associated with the passage of erythrocytes in capillaries of rat mesentery
Authors: Tsai Amy G. , Cabrales Pedro , Johnson Paul C. , Intaglietta Marcos
Published: September 2005

Golub, Aleksander S., and Roland N. Pittman. Erythrocyte-associated transients in PO2 revealed in capillaries of rat mesentery. Am J Physiol Heart Circ Physiol 288: H2735–H2743 , 2005. Mathematical models have predicted the existence of Po2gradients between erythrocytes in capillaries in the usual case where plasma contributes substantial resistance to oxygen diffusion. According to theoretical predictions, these gradients could be detected as rapid Po2fluctuations (erythrocyte-associated transients, EATs) along the capillary. However, verification of a model and correct choice of its parameters can be made only on the basis of direct experimental measurements. We used phosphorescence quenching microscopy to measure Po2in 52 capillaries of rat mesentery to obtain plasma Po2values 100 times/s at a given point along a capillary. A 532-nm laser generated 10-μs pulses of light, concentrated by a ×100 objective, onto a spot 0.9 μm in diameter. The presence of erythrocytes in the excitation region was detected on the basis of phosphorescence amplitude (PA), proportional to the amount of plasma encountered by the laser beam, and on the basis of the intensity of transmitted laser light (LT), detected by a photodiode placed under the capillary. The data revealed correlated waveforms in PA, LT, and Po2in capillaries. The magnitude of the Po2gradients between erythrocytes and plasma was correlated with average capillary Po2. EATs in Po2were more readily detected in capillaries with relatively low oxygenation. The correlation coefficients between PA and Po2for the half of the capillaries ( n = 26) below the median Po2(mean Po2= 17 mmHg; R = −0.72) was higher than that for the other half (mean Po2= 39 mmHg; R = −0.38). These results support the theoretical predictions of EATs and plasma Po2gradients in capillaries.
Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans
Authors: Romer Lee M. , Haverkamp Hans C. , Lovering Andrew T. , Pegelow David F. , Dempsey Jerome A.
Published: September 2005

The effect of exercise-induced arterial hypoxemia (EIAH) on quadriceps muscle fatigue was assessed in 11 male endurance-trained subjects [peak O2uptake (V̇o2 peak) = 56.4 ± 2.8 ml·kg−1·min−1; mean ± SE]. Subjects exercised on a cycle ergometer at ≥90% V̇o2 peakto exhaustion (13.2 ± 0.8 min), during which time arterial O2saturation (SaO2) fell from 97.7 ± 0.1% at rest to 91.9 ± 0.9% (range 84–94%) at end exercise, primarily because of changes in blood pH (7.183 ± 0.017) and body temperature (38.9 ± 0.2°C). On a separate occasion, subjects repeated the exercise, for the same duration and at the same power output as before, but breathed gas mixtures [inspired O2fraction (FiO2) = 0.25–0.31] that prevented EIAH (SaO2= 97–99%). Quadriceps muscle fatigue was assessed via supramaximal paired magnetic stimuli of the femoral nerve (1–100 Hz). Immediately after exercise at FiO20.21, the mean force response across 1–100 Hz decreased 33 ± 5% compared with only 15 ± 5% when EIAH was prevented ( P < 0.05). In a subgroup of four less fit subjects, who showed minimal EIAH at FiO20.21 (SaO2= 95.3 ± 0.7%), the decrease in evoked force was exacerbated by 35% ( P < 0.05) in response to further desaturation induced via FiO20.17 (SaO2= 87.8 ± 0.5%) for the same duration and intensity of exercise. We conclude that the arterial O2desaturation that occurs in fit subjects during high-intensity exercise in normoxia (−6 ± 1% ΔSaO2from rest) contributes significantly toward quadriceps muscle fatigue via a peripheral mechanism.
Hemoglobin, NO, and 20-HETE interactions in mediating cerebral vasoconstriction following SAH
Authors: Takeuchi Kazuhiko , Miyata Noriyuki , Renic Marija , Harder David R. , Roman Richard J.
Published: September 2005

Recent studies have indicated that 20-hydroxyeicosatetraenoic acid (20-HETE) contributes to the fall in cerebral blood flow (CBF) after subarachnoid hemorrhage (SAH), but the factors that stimulate the production of 20-HETE are unknown. This study examines the role of vasoactive factors released by clotting blood vs. the scavenging of nitric oxide (NO) by hemoglobin (Hb) in the fall in CBF after SAH. Intracisternal (icv) injection of blood produced a greater and more prolonged (120 vs. 30 min) decrease in CBF than that produced by a 4% solution of Hb. Pretreating rats with Nω-nitro-l-arginine methyl ester (l-NAME; 10 mg/kg iv) to block the synthesis of NO had no effect on the fall in CBF produced by an icv injection of blood. l-NAME enhanced rather than attenuated the fall in CBF produced by an icv injection of Hb. Blockade of the synthesis of 20-HETE with TS-011 (0.1 mg/kg iv) prevented the sustained fall in CBF produced by an icv injection of blood and the transient vasoconstrictor response to Hb. Hb (0.1%) reduced the diameter of the basilar artery (BA) of rats in vitro by 10 ± 2%. This response was reversed by TS-011 (100 nM). Pretreatment of vessels with l-NAME (300 μM) reduced the diameter of BA and blocked the subsequent vasoconstrictor response to the addition of Hb to the bath. TS-011 returned the diameter of vessels exposed to l-NAME and Hb to that of control. These results suggest that the fall in CBF after SAH is largely due to the release of vasoactive factors by clotting blood rather than the scavenging of NO by Hb and that 20-HETE contributes the vasoconstrictor response of cerebral vessels to both Hb and blood.
Ionic mechanisms of histamine-induced responses in guinea pig intracardiac neurons
Authors: Hardwick Jean C. , Kotarski Amy F. , Powers Melanie J.
Published: September 2005

Histamine, released from mast cells, can modulate the activity of intrinsic neurons in the guinea pig cardiac plexus. The present study examined the ionic mechanisms underlying the histamine-induced responses in these cells. Histamine evokes a small membrane depolarization and an increase in neuronal excitability. Using intracellular voltage recording from individual intracardiac neurons, we were able to demonstrate that removal of extracellular sodium reduced the membrane depolarization, whereas inhibition of K+ channels by 1 mM Ba2+, 2 mM Cs+, or 5 mM tetraethylammonium had no effect. The depolarization was also not inhibited by either 10 μM Gd3+ or a reduced Cl− solution. The histamine-induced increase in excitability was unaffected by K+ channel inhibitors; however, it was reduced by either blockage of voltage-gated Ca2+ channels with 200 μM Cd2+ or replacement of extracellular Ca2+ with Mg2+. Conversely, alterations in intracellular calcium with thapsigargin or caffeine did not inhibit the histamine-induced effects. However, in cells treated with both thapsigargin and caffeine to deplete internal calcium stores, the histamine-induced increase in excitability was decreased. Treatment with the phospholipase C inhibitor U73122 also prevented both the depolarization and the increase in excitability. From these data, we conclude that histamine, via activation of H1 receptors, activates phospholipase C, which results in 1) the opening of a nonspecific cation channel, such as a transient receptor potential channel 4 or 5; and 2) in combination with either the influx of Ca2+ through voltage-gated channels or the release of internal calcium stores leads to an increase in excitability.
Compensatory kidney growth in estrogen receptor-α null mice
Authors: Sun Jianhong , Langer William J. , Devish Kay , Lane Pascale H.
Published: September 2005

Females are relatively protected in many progressive kidney diseases. Processes of kidney scarring and growth are intricately linked, and female kidneys are smaller than male kidneys. To better understand links between sex, growth, and the kidney, we examined compensatory kidney growth (CKG) after uninephrectomy (Unx) in wild-type and estrogen receptor-α null mice (ERKO). Mice (10 wk old) underwent Unx or sham procedure, with removal of all remaining kidney(s) 48 h later. Studies included kidney weight, renal content of protein, DNA, and insulin-like growth factor-I (IGF-I), serum IGF-I, mean glomerular area, and immunostaining for proliferating cell nuclear antigen (PCNA). Sham Unx produced no differences between left and right kidneys. Unx altered kidney weight, glomerular area, DNA content, IGF-I content, and PCNA regardless of sex or genotype. Females showed greater increases in kidney weight (26 vs. 19%) and glomerular area (73 vs. 51%) than males. Differences in kidney weight were restricted to wild-type females (32% increase); ERKO females showed an increase in kidney weight similar to males (19%). Genotype did not influence glomerular growth in this model. Both male and female mice exhibit hyperplastic growth 48 h after Unx, with more pronounced enlargement in females. Lack of estrogen receptor-α is associated with reduced CKG in females, probably via suppression of proliferation. ERKO mice did not demonstrate any alterations in compensatory glomerular enlargement. Kidney IGF-I content doubled after Unx, regardless of sex or genotype, implicating other mechanisms with regard to these findings.
Nonlinear Modeling of Auditory-Nerve Rate Responses to Wideband Stimuli
Authors: Young Eric D. , Calhoun Barbara M.
Published: September 2005

The spectral selectivity of auditory nerve fibers was characterized by a method based on responses to random-spectrum-shape stimuli. The method models the average discharge rate of fibers for steady stimuli and is based on responses to ≈100 noise-like stimuli with pseudorandom spectral levels in 1/8- or 1/16-octave frequency bins. The model assumes that rate is determined by a linear weighting of the spectrum plus a second-order weighting of all pairs of spectrum values within a certain frequency range of best frequency. The method allows prediction of rate responses to stimuli with arbitrary wideband spectral shapes, thus providing a direct test of the degree of linearity of spectral processing Auditory-nerve fibers are shown to rely mainly on linear weighting of the stimulus spectrum; however, significant second-order terms are present and are important in predicting responses to random-spectrum shape stimuli, although not for predicting responses to noise filtered with cat head-related transfer functions. The second-order terms weight the products of levels at identical frequencies positively and the products of different frequencies negatively. As such, they model both curvature in the rate versus level function and suppressive interactions between different frequency components. The first- and second-order characterizations derived in this method provide a measure of higher-order nonlinearities in neurons, albeit without providing information about temporal characteristics.
A temporal study of gene expression in rat lung following fixed-volume hemorrhage
Authors: Bowman P. D. , Sondeen J. L. , Zhao B. , Coppes V. G. , Nelson J. J. , Dubick M. A. , Vaughan G. M.
Published: September 2005

Previous studies have indicated that hemorrhage may predispose the lung to respiratory distress syndrome. Gene expression profiling with oligonucleotide microarrays was used to evaluate the genetic responses of the lung to hemorrhage. Conscious rats, chronically instrumented with a catheter and telemetry device to record blood pressure, heart rate, and temperature, had 40% of their estimated blood volume removed at a rate of 1 ml/min over 7–10 min. Groups of three or more rats were euthanized at 1, 3, 6, 16, 24, 48, or 72 h following hemorrhage. Two additional groups were unmanipulated controls and instrumented animals with sham hemorrhage. Total RNA was isolated from lung, reverse-transcribed to cDNA, fluorescently labeled, and hybridized to oligonucleotide microarrays probing 5,671 rat genes. After hemorrhage, statistically detectable alteration of expression was seen in ∼0.8% of the genes at some time during the 72-h test period (vs. sham hemorrhage) as determined by false discovery rate statistics in the statistical analysis of microarrays program. A subset was confirmed by RT-PCR analysis. Hemorrhage influenced genes that regulate intracellular signaling and structure, growth factors, and hormonal receptors. There also appeared to be increased expression of genes that may mediate sequestration of neutrophils and mononuclear cells from the circulation. This hemorrhage model, although producing severe hemodynamic alterations, avoided mortality and histological evidence of lung damage, a feature intended to help ensure reliable evaluation of gene expression. These results indicate that gene expression profiling with microarrays provides a new tool for exploring the response of a tissue to systemic blood loss.
The Influence of Dehydroepiandrosterone on Early Pregnancy in Mice
Authors: Sander Valeria , Solano María Emilia , Elia Evelin , Luchetti Carolina Griselda , Di Girolamo Guillermo , Gonzalez Claudio , Motta Alicia B.
Published: September 2005

The aim of the present report was to study the role of high levels of dehydroepiandrosterone (DHEA) on the ovarian function and embryonic resorption during early pregnancy in BALB/c mice. Pregnant animals were injected with DHEA following both the post-implantatory (DHEA-2) and peri-implantatory (DHEA-6) models. Morphological studies of implantation sites showed 40% of embryonic resorption in the DHEA-2 group while 100% of resorption was observed in the DHEA-6 group. Serum samples of both DHEA-2 and DHEA-6 groups showed higher estradiol levels and a lower progesterone concentration than those of control groups. Ovarian prostaglandin E levels after both DHEA-2 and DHEA-6 treatments increased when compared to control groups. The antioxidant metabolite glutathione diminished during both DHEA treatments. In summary, the data presented here suggest that DHEA treatment during early pregnancy modulates the ovarian function and is responsible for embryonic resorption with different degrees depending on when it is administered.
Effects of Injecting Thymulin into the Anterior or Medial Hypothalamus or the Pituitary on Induced Ovulation in Prepubertal Mice
Authors: García Lorena , Hinojosa Lorena , Domínguez Roberto , Chavira Roberto , Rosas Patricia
Published: September 2005

In prepubertal mice, subcutaneous thymulin injection before equine chorionic gonadotrophin (eCG) treatment simulates ovulation; seemingly, the thymulin could be acting at the hypothalamus-pituitary axis level. Objective: This study was designed to analyze the effects of injecting thymulin into the hypothalamus or pituitary on induced ovulation of prepubertal mice. Method: Female mice, 19 days old, were anesthetized with ether and injected with saline solution or thymulin into the anterior or medial hypothalamus or the pituitary and treated with eCG when 20 days old. The ova shed were counted and serum concentrations of 17β-estradiol were measured. In the ovaries, the morphometrical analysis was performed and the atresia evaluated. Results: Ether anesthesia treatment blocked eCG-induced ovulation in almost all animals. Mice anesthetized and treated with eCG and gonadotrophin-releasing hormone (GnRH) or human chorionic gonadotrophin (hCG) ovulated a full quota of ova. Injecting saline solution into the anterior or medial hypothalamus or the pituitary did not reduce the blocking effects of ether anesthesia on induced ovulation, but the incidence of atretic follicles was higher. Injecting thymulin directly into the anterior hypothalamus did not restore ovulation, nor diminish the number of atretic follicles. In contrast, injecting thymulin into the medial hypothalamus restored the ovulation ratio and decreased the percentage of atretic follicles. Similar results were obtained by injecting thymulin into the pituitary, though thymulin treatment in the pituitary resulted in a higher number of ova shed and lower follicular atresia. Conclusion: The present results suggest that thymulin acts at the medial hypothalamus level, facilitating the release of GnRH and at the pituitary level regulating gonadotrophin release.
Current Status of Hepatitis C Virus Infection in Korea
Authors: Jeong Sook-Hyang , Suh Dong Jin
Published: September 2005

Chronic liver disease, including liver cirrhosis and hepatocellular carcinoma (HCC), has been a major cause of mortality in Korea. The prevalence rates of hepatitis C virus (HCV) and hepatitis B virus (HBV) infections in the general population of Korea are approximately 1 and 5%, respectively. The most common genotypes of HCV in Korea are 1b and 2a. The sustained virological response rates after antiviral therapies, including combined interferon-α and ribavirin, have been reported to be 38–59%. The annual incidence of HCC among HCV-related liver cirrhosis has been estimated at 5%, and approximately 12% of HCC is attributable to HCV and 68% to HBV in Korea. The mean age of patients with HCV-related HCC at the time of diagnosis was consistently 10 years older than that of patients with HBV-related HCC. Moreover, HCV-related HCC was accompanied by more advanced liver cirrhosis than HBV-related HCC. Coinfection with HBV seemed to increase the risk of developing HCC in chronic HCV infection. After the successful program of hepatitis B vaccination, HCV infection is now emerging as an important etiology of chronic liver disease in Korea, which warrants more detailed and large-scale studies.
Combined Interferon and Ribavirin Therapy for Chronic Hepatitis C in Taiwan
Authors: Lai Ming-Yang
Published: September 2005

Chronic hepatitis C virus (HCV) infection, including its sequelae, is an important healthcare problem in Taiwan. The seroprevalence of HCV infection in first-time blood donors in Taiwan is 1.2% and an estimated 2–5% in the general population, with a great geographic variation. Genotype 1b is the most prevalent HCV genotype in Taiwan, with a prevalence rate of 50–70%. An increasing incidence of hepatocellular carcinoma (HCC) is mainly attributed to HCV infection, while the declining role of HBV is observed in Taiwan. The seroprevalence of hepatitis B surface antigen among patients with HCC was 90% three decades ago, while recently, chronic HCV infection accounts for more than 30% of HCC patients in the National Taiwan University Hospital. With the advent of a combined conventional interferon (IFN)-α and ribavirin therapy, to which Taiwan has contributed in the early study phase, the sustained virological response rate has been greatly improved compared with IFN monotherapy. The sustained virological response rate in Taiwanese patients treated with the combination therapy for 6 months has reached up to 50–60%, which is higher than that reported in patients from the Western countries receiving a 12-month regimen. It is necessary to searche for the underlying mechanisms for the better treatment outcome with IFN plus ribavirin combination therapy in Taiwanese patients. Whether long-term effects of IFN plus ribavirin therapy can reduce the incidence of HCC needs to be established.