bluuebunny/crossref_metadata_2025 huggingface dataset:
Phonological awareness and literacy skills in Korean: An examination of the unique role of body-coda units
Authors: KIM YOUNG-SUK
Published: January 2007

This study examines a salient intrasyllabic phonological unit in Korean, the body-coda unit, its role in literacy skills in Korean, and a possible source of the salience of body-coda units in the spoken language. Data were collected from Korean-speaking, monolingual beginning readers (41 kindergarteners, 40 first graders). The results indicate that body-coda boundary (e.g.,ca-t) is more salient than onset–rime boundary (e.g.,c-at) for Korean children and show that children's body-coda awareness is an important predictor of word decoding and spelling in Korean. Furthermore, the analysis of phonological neighbors and frequency of syllable types suggests that a phonotactic feature in Korean, the frequency of consonant–verb syllable type, may be a possible source of the saliency of the body-coda intrasyllabic division for Korean children.
Engineering the Stem Cell Microenvironment
Authors: Metallo Christian M. , Mohr Jeffrey C. , Detzel Christopher J. , de Pablo Juan J. , Van Wie Bernard J. , Palecek Sean P.
Published: January 2007

Multipotent stem cells in the body facilitate tissue regeneration, growth, and wound healing throughout life. The microenvironment in which they reside provides signals that direct these progenitors to proliferate, differentiate, or remain dormant; these factors include soluble molecules, the extracellular matrix, neighboring cells, and physical stimuli. Recent advances in the culture of embryonic stem cells and adult progenitors necessitate an increased understanding of these phenomena. Here, we summarize the interactions between stem cells and their local environment, drawing on in vivo observations and tissue culture studies. In addition, we describe novel methods of characterizing the effects of various environmental factors and review new techniques that enable scientists and engineers to more effectively direct stem cell fate.
Assimilation of seasonal chlorophyll and nutrient data into an adjoint three‐dimensional ocean carbon cycle model: Sensitivity analysis and ecosystem parameter optimization
Authors: Tjiputra Jerry F. , Polzin Dierk , Winguth Arne M. E.
Published: January 2007

An adjoint method is applied to a three‐dimensional global ocean biogeochemical cycle model to optimize the ecosystem parameters on the basis of SeaWiFS surface chlorophyll observation. We showed with identical twin experiments that the model simulated chlorophyll concentration is sensitive to perturbation of phytoplankton and zooplankton exudation, herbivore egestion as fecal pellets, zooplankton grazing, and the assimilation efficiency parameters. The assimilation of SeaWiFS chlorophyll data significantly improved the prediction of chlorophyll concentration, especially in the high‐latitude regions. Experiments that considered regional variations of parameters yielded a high seasonal variance of ecosystem parameters in the high latitudes, but a low variance in the tropical regions. These experiments indicate that the adjoint model is, despite the many uncertainties, generally capable to optimize sensitive parameters and carbon fluxes in the euphotic zone. The best fit regional parameters predict a global net primary production of 36 Pg C yr−1, which lies within the range suggested by Antoine et al. (1996). Additional constraints of nutrient data from the World Ocean Atlas showed further reduction in the model‐data misfit and that assimilation with extensive data sets is necessary.
Quasi‐stationary auroral patches observed at the South Pole Station
Authors: Ebihara Y. , Tanaka Y.‐M. , Takasaki S. , Weatherwax A. T. , Taguchi M.
Published: January 2007

We present quasi‐stationary auroral patches (QSAPs) observed by an all‐sky imager at the South Pole Station (−74.3° CGLAT) on the dayside between ∼0900 and ∼1400 MLT. QSAPs appeared in a closed field line region where I(557.7 nm) ≫ I(630.0 nm) and each patch tends to preserve its form, luminosity, and location for up to several hours. The quasi‐stationary nature of the QSAPs cannot be explained by the traditional role of the corotation electric field because the South Pole is located on the axis of Earth's rotation. The most plausible scenario is that a corotation electric potential, which dominates the convection potential, results in a trapping region of the magnetospheric cold plasmas. On the analogy of the formation of the plasmasphere, the trapping region would capture cold plasmas originated from the ionosphere and result in a locally enhanced plasma density (miniplasmasphere) that may lead to electron scattering through cyclotron wave‐particle interactions. This circumstance may occur when the South Pole is located on a closed field line and the local electric potential is dominated by the corotation potential. QSAPs were also accompanied with periodic fluctuations in the Pc 5 range, which coincide closely with ground magnetic fluctuations. Assuming that the pulsation is associated with field line resonances, we could estimate the equatorial mass density of thermal plasmas, which gradually increased from 0.13 to 0.44 amu cm−3. The increase in the thermal plasma density would support the hypothesis that a miniplasmasphere exists, though further investigation is necessary to confirm it.
Hole mobility enhancement of Si0.2Ge0.8 quantum well channel on Si
Authors: Peng C.-Y. , Yuan F. , Yu C.-Y. , Kuo P.-S. , Lee M. H. , Maikap S. , Hsu C.-H. , Liu C. W.
Published: January 2007

The ultrathin strained Si0.2Ge0.8 quantum well channel (∼5nm) directly grown on Si substrates is demonstrated with low defect density and high hole mobility. The quantum well Si0.2Ge0.8 channel reveals an ∼3.2 times hole current enhancement and an ∼3 times hole mobility enhancement as compared with the bulk Si channel. The output current-voltage characteristics under the external mechanical strain confirm the compressive strain in the channel. The external compressive strain further enhances the hole mobility in a Si0.2Ge0.8 channel.
Intermittency, dissipation, and scaling in two-dimensional magnetohydrodynamic turbulence
Authors: Merrifield J. A. , Chapman S. C. , Dendy R. O.
Published: January 2007

Direct numerical simulations (DNS) provide a means to test phenomenological models for the scaling properties of intermittent MHD turbulence. The well-known model of She and Leveque, when generalized to MHD, is in good agreement with the DNS in three dimensions, however, it does not coincide with DNS in two dimensions (2D). This is resolved here using the results of recent DNS of driven MHD turbulence in 2D which directly determine the scaling of the rate of dissipation. Specifically, a simple modification to generalized refined similarity is proposed that captures the results of the 2D MHD simulations. This leads to a new generalization of She and Leveque in MHD that is coincident with the DNS results in 2D. A key feature of this model is that the most intensely dissipating structures, which are responsible for the intermittency, are thread-like in 2D, independent of whether the underlying phenomenology of the cascade is Kolmogorov or Iroshnikov Kraichnan.
Lock-in amplifier error prediction and correction in frequency sweep measurements
Authors: Sonnaillon Maximiliano Osvaldo , Bonetto Fabian Jose
Published: January 2007

This article proposes an analytical algorithm for predicting errors in lock-in amplifiers (LIAs) working with time-varying reference frequency. Furthermore, a simple method for correcting such errors is presented. The reference frequency can be swept in order to measure the frequency response of a system within a given spectrum. The continuous variation of the reference frequency produces a measurement error that depends on three factors: the sweep speed, the LIA low-pass filters, and the frequency response of the measured system. The proposed error prediction algorithm is based on the final value theorem of the Laplace transform. The correction method uses a double-sweep measurement. A mathematical analysis is presented and validated with computational simulations and experimental measurements.
Polarizability and second hyperpolarizability evaluation of long molecules by the density functional theory with long-range correction
Authors: Sekino Hideo , Maeda Yasuyuki , Kamiya Muneaki , Hirao Kimihiko
Published: January 2007

Polarizabilities and second hyperpolarizabilities of polyacetylene and a hydrogen chain are evaluated by density functional theory (DFT) using a hybrid generalized gradient approximation functional with correct long-range electron-electron interactions. The well known catastrophic overestimate of the hyperpolarizabilities for molecular systems of enhanced length is corrected by the two-electron repulsion operator decomposition technique, integrating the distance-dependent nonlocal exchange effects for long-range interaction, while neither the asymptotically corrected exchange functional for long-range interaction nor ordinary hybrid methods seem to be capable of overcoming the serious drawback of the DFT in polarizability/hyperpolarizability evaluation.
Lattice-mismatch-strain induced inhomogeneities in epitaxial La0.7Ca0.3MnO3 films
Authors: Gao Guanyin , Jin Shaowei , Wu Wenbin
Published: January 2007

Epitaxial La0.7Ca0.3MnO3 (LCMO) films of 15–150nm thick have been grown on SrTiO3(001) [STO(001)] and (LaAlO3)0.3(Sr2AlTaO6)0.7(001) [LSAT(001)] substrates with lattice mismatches of 1.11% and 0.15%, respectively. Asymmetric x-ray reciprocal space mapping was used to determine the strain state evolution in the films. For LCMO/STO(001), as the film thickness increases, at about 30nm a change from fully to partially strained has been induced, and a further annealing at 900°C can fully relax the films. For LCMO/LSAT(001), however, due to the negligible lattice mismatch, even at 15nm the films are almost fully relaxed. Correspondingly, for the fully relaxed LCMO films a paramagnetic to ferromagnetic transition at TC of about 260K was observed, and for those partially relaxed, both the structure and magnetic transition are inhomogeneous, two thickness-dependent TC were detected for each film. The results show strong evidence that the transition temperature is correlated with the strain state in epitaxial LCMO films.
Two-dimensional AlGaInP∕GaInP photonic crystal membrane lasers operating in the visible regime at room temperature
Authors: Chen A. , Chua S. J. , Xing G. C. , Ji W. , Zhang X. H. , Dong J. R. , Jian L. K. , Fitzgerald E. A.
Published: January 2007

The authors report on the fabrication and characterization of visible two-dimensional photonic crystal (PhC) band-edge lasers with AlGaInP∕GaInP multiple-quantum-well active layers. High-quality PhC air-bridge membranes are produced by optimizing the inductively coupled plasma etching process for AlGaInP materials. Room-temperature lasing operation at the wavelengths ranging from 630to690nm is obtained by tuning the PhC lattice parameters. The lasing action originates from high-symmetry band-edge modes, which is verified by three-dimensional finite difference time domain computation.
Electrotunable in-plane one-dimensional photonic structure based on silicon and liquid crystal
Authors: Tolmachev V. A. , Perova T. S. , Grudinkin S. A. , Melnikov V. A. , Astrova E. V. , Zharova Yu. A.
Published: January 2007

The model of the electro-optical effect, due to the reorientation of liquid crystal molecules from a pseudoisotropic to a homeotropic state, in a composite photonic structure with a liquid crystal filler, is elaborated. A composite (110) grooved silicon photonic structure for the middle infrared range was designed and fabricated on a silicon-on-insulator platform. Polarized reflection spectra, demonstrating the electro-optical effect, have been obtained by means of Fourier transform infrared microscopy. The relative shift of the band edge at half intensity in the region of 10μm was found experimentally to be 1.6% compared to 2.2% as predicted by theory.
John Harrison: clockmaker and Copley Medalist. A public memorial at last
Authors: Taylor J.C , Wolfendale A.W
Published: January 2007

The story of John Harrison, the clockmaker who effectively solved the ‘longitude problem’ in the eighteenth century, is a fascinating one. Here was a brilliant inventor who single-handedly took on the might of the astronomical fraternity and turned down Fellowship of the Royal Society, yet accepted its highest accolade—the Copley Medal—and had to enlist the help of King George III in pursuit of the final instalment of the Longitude Prize. This paper deals with the inventiveness of Harrison and the role of the Royal Society in the story and the very recent successful efforts to have his name remembered in perpetuity in Britain by a memorial in Westminster Abbey.
The use of chemical and visual cues in female choice in the butterflyBicyclus anynana
Authors: Costanzo Katie , Monteiro Antónia
Published: January 2007

Investigating the relative importance of multiple cues for mate choice within a species may highlight possible mechanisms that led to the diversification of closely related species in the past. Here, we investigate the importance of close-range pheromones produced by maleBicyclus anynanabutterflies and determine the relative importance of these chemical cues versus visual cues in sexual selection by female choice. We first blocked putative androconial organs on the fore- and hindwings of males, while also manipulating the ability of females to perceive chemical signals via their antenna. We found that male chemical signals were emitted by both fore- and hindwing pairs and that they play an important role in female choice. We subsequently tested the relative importance of these chemical cues versus visual cues, previously identified for this species, and found that they play an equally important role in female choice in our laboratory setting. In addition, females will mate with males with only one signal present and blocking both androconial organs on males seems to interfere with male to male recognition. We discuss the possible functions of these signals and how this bimodal system may be used in intra- and interspecific mate evaluation.
Common carp tissue reactions to surgically implanted radio tags with external antennas
Authors: Bauer C. , Loupal G.
Published: January 2007

Examination of common carp Cyprinus carpio, carrying implanted telemetry transmitters, showed that wound healing was incomplete after 4 months and completed after 1 year. Granulation tissue, which encapsulated the transmitter, adhered to the intestine and liver. The liver was infiltrated by the granulation tissue after 1 year. Epidermal tissue grew down the channel for the antenna, establishing a potential pathway for pathogens. No signs of infections, however, were found.
Water pH and urinary excretion in silver catfish Rhamdia quelen
Authors: Bolner K. C. S. , Baldisserotto B.
Published: January 2007

The effect of acute exposure to different water pH levels on urinary excretion and plasma ion levels in silver catfish Rhamdia quelen was analysed. Fish were exposed to pH 4·0, 5·0, 7·5, 8·0, and 9·0 for 4 days and urine was collected. Other specimens were also exposed to the experimental pH for 24 h and blood was sampled. Urine flow rate, urine and plasma pH showed a significant trend to increase with the increase of water pH. Urinary Na+ excretion rate also increased and ammonia urinary excretion rate decreased with the increase of water pH. There was a significant trend to decrease volume, ammonia, Cl− and Na+ urinary excretion rate with increasing mass in fish exposed to all pH levels studied. Plasma ammonia levels showed a slight decrease in fish exposed to water pH from 4·0 to 8·0, but those exposed to water pH 9·0 presented the highest ammonia levels. Most plasma ions and urinary excretion changes observed in silver catfish exposed to acidic or alkaline water were similar to those already detected in rainbow trout Oncorhynchus mykiss. In addition, the kidney and urinary bladder might participate on acid–base balance in silver catfish, since urine pH changed according to plasma pH.
Pharmacokinetics of etodolac in the horse following oral and intravenous administration
Authors: DAVIS J. L. , PAPICH M. G. , MORTON A. J. , GAYLE J. , BLIKSLAGER A. T. , CAMPBELL N. B.
Published: January 2007

The purpose of this study was to determine the pharmacokinetics of etodolac following oral and intravenous administration to six horses. Additionally,in vitrocyclooxygenase (COX) selectivity assays were performed using equine whole blood. Using a randomized two‐way crossover design, horses were administered etodolac (20 mg/kg) orally or intravenously, with a minimum 3‐week washout period. Plasma samples were collected after administration for analysis using high pressure liquid chromatography with ultraviolet detection. Following intravenous administration, etodolac had a mean plasma half‐life (t1/2) of 2.67 h, volume of distribution (Vd) of 0.29 L/kg and clearance (Cl) of 234.87 mL/h kg. Following oral administration, the average maximum plasma concentration (Cmax) was 32.57 μg/mL with at1/2of 3.02 h. Bioavailability was approximately 77.02%. Results ofin vitroCOX selectivity assays showed that etodolac was only slightly selective for COX‐2 with a COX‐1/COX‐2 selectivity ratio effective concentration (EC)50of 4.32 and for EC80of 4.77. This study showed that etodolac is well absorbed in the horse after oral administration, and may offer a useful alternative for anti‐inflammatory treatment of various conditions in the horse.
Whose turtles are they, anyway?
Authors: MORTIMER JEANNE A. , MEYLAN PETER A. , DONNELLY MARYDELE
Published: January 2007

The hawksbill turtle (Eretmochelys imbricata), listed since 1996 by the IUCN as Critically Endangered and by the Convention on International Trade in Endangered Species (CITES) as an Appendix I species, has been the subject of attention and controversy during the past 10 years due to the efforts of some nations to re‐open banned international trade. The most recent debate has centred on whether it is appropriate for Cuba to harvest hawksbills from shared foraging aggregations within her national waters. In this issue of Molecular Ecology, Bowen et al. have used molecular genetic data to show that such harvests are likely to have deleterious effects on the health of hawksbill populations throughout the Caribbean.
Beyond Negativity: The Effects of Incivility on the Electorate
Authors: Brooks Deborah Jordan , Geer John G.
Published: January 2007

There is much concern among pundits and political observers that incivility undermines our electoral process. Yet we have little evidence that actually documents whether incivility has such pernicious effects. This article seeks to advance our understanding of the influence of incivility on the electorate. We argue that three dimensions are central to understanding both the perceptions and effects of different types of campaign messages: tone (negative versus positive); civility (civil versus uncivil); and focus (issue versus trait‐based message content). Using an experimental manipulation on a large national sample that examines these three dimensions, we find that uncivil attacks in campaigns do not appear to be as worrisome as its detractors fear. While uncivil messages in general—and uncivil trait‐based messages in particular—are usually seen by the public as being less fair, less informative, and less important than both their civil negative and positive counterparts, they are no more likely to lead to detrimental effects among the public. In fact, incivility appears to have some modest positive consequences for the political engagement of the electorate. These findings are important, since attacks and counterattacks will continue to shape the American political landscape.
Gerrymandering Roll Calls in Congress, 1879–2000
Authors: Cox Gary W. , Katz Jonathan N.
Published: January 2007

We argue that the standard toolbox used in electoral studies to assess the bias and responsiveness of electoral systems can also be used to assess the bias and responsiveness of legislative systems. We consider which items in the toolbox are the most appropriate for use in the legislative setting, then apply them to estimate levels of bias in the U.S. House from 1879 to 2000. Our results indicate a systematic bias in favor of the majority party over this period, with the strongest bias arising during the period of “czar rule” (51st–60th Congresses, 1889–1910) and during the post‐packing era (87th–106th Congresses, 1961–2000). This finding is consistent with the majority party possessing a significant advantage, either in “buying” vote options, in setting the agenda, or both.
Political Competition and Policy Adoption: Market Reforms in Latin American Public Utilities
Authors: Murillo Maria Victoria , Martínez‐Gallardo Cecilia
Published: January 2007

This article shows that political competition generates incentives that affect the pace of adoption of market reforms in the context of policy convergence. Previous work shows the effect of financial and technological pressures in promoting policy convergence and the impact of institutional constraints on shaping the pace of policymaking. Controlling for these effects, this article demonstrates the policy effects of political competition and ideological polarization even at a time when ideological policy differences seem to be fading due to policy convergence. This article studies policy adoption using duration analysis for the 18 countries of Latin America during the 1985–2000 period when most of the market reforms in public utilities were adopted.
Alchemy and the Science of Matter
Authors: Smith Pamela
Published: January 2007

Atoms and Alchemy
. Chymistry and the Experimental Origins of the Scientific Revolution.
By William R. Newman
. University of Chicago Press, Chicago, 2006. 272 pp. $75, £47.50. ISBN 9780226576961. Paper, $30, £19. ISBN 9780226576978.

Building on his work on the origins of modern chemistry, Newman argues that the alchemical tradition made a major contribution to the 17th-century reformulation of science that emphasized experiments.
Quarks and the Cosmos
Authors: Turner Michael S.
Published: January 2007

Cosmology is in the midst of a period of revolutionary discovery, propelled by bold ideas from particle physics and by technological advances from gigapixel charge-coupled device cameras to peta-scale computing. The basic features of the universe have now been determined: It is 13.7 billion years old, spatially flat, and expanding at an accelerating rate; it is composed of atoms (4%), exotic dark matter (20%), and dark energy (76%); and there is evidence that galaxies and other structures were seeded by quantum fluctuations. Although we know much about the universe, we understand far less. Poised to dramatically advance our understanding of both the universe and the laws that govern it, cosmology is on the verge of a golden age.
COTILTING CLASSES OF TORSION-FREE MODULES
Authors: ALBRECHT ULRICH , TRLIFAJ JAN
Published: January 2007

A right R-module M is torsion-free (in the sense of Hattori) if [Formula: see text] for all r ∈ R. The class of torsion-free modules is a cotilting class if and only if R is a left p.p.-ring. This paper investigates how the class of torsion-free modules is related to the cotilting classes arising from embeddings of a right (left) non-singular ring R into its maximal right (left) ring of quotients. Several applications are given.
THE STRUCTURE OF A KIND OF SEMIABUNDANT SEMIGROUPS
Authors: ZHANG FENGSHUO , ZHANG RONGHUA
Published: January 2007

In this paper we study semiabundant semigroups whose idempotents form normal subbands. We prove that a semigroup is of this type if and only if it is isomorphic to a quasi-spined product of a left normal band, a right normal band and a semiadequate semigroup.
Inhibition of hypoxia-induced calcium responses in pulmonary arterial smooth muscle by acetazolamide is independent of carbonic anhydrase inhibition
Authors: Shimoda Larissa A. , Luke Trevor , Sylvester J. T. , Shih Hui-Wen , Jain Ahamindra , Swenson Erik R.
Published: January 2007

Hypoxic pulmonary vasoconstriction (HPV) occurs with ascent to high altitude and can contribute to development of high altitude pulmonary edema (HAPE). Vascular smooth muscle contains carbonic anhydrase (CA), and acetazolamide (AZ), a CA inhibitor, blunts HPV and might be useful in the prevention of HAPE. The mechanism by which AZ impairs HPV is uncertain. Originally developed as a diuretic, AZ also has direct effects on systemic vascular smooth muscle, including modulation of pH and membrane potential; however, the effect of AZ on pulmonary arterial smooth muscle cells (PASMCs) is unknown. Since HPV requires Ca2+ influx into PASMCs and can be modulated by pH, we hypothesized that AZ alters hypoxia-induced changes in PASMC intracellular pH (pHi) or Ca2+ concentration ([Ca2+]i). Using fluorescent microscopy, we tested the effect of AZ as well as two other potent CA inhibitors, benzolamide and ethoxzolamide, which exhibit low and high membrane permeability, respectively, on hypoxia-induced responses in PASMCs. Hypoxia caused a significant increase in [Ca2+]i but no change in pHi. All three CA inhibitors slightly decreased basal pHi, but only AZ caused a concentration-dependent decrease in the [Ca2+]i response to hypoxia. AZ had no effect on the KCl-induced increase in [Ca2+]i or membrane potential. N-methyl-AZ, a synthesized compound lacking the unsubstituted sulfonamide group required for CA inhibition, had no effect on pHi but inhibited hypoxia-induced Ca2+ responses. These results suggest that AZ attenuates HPV by selectively inhibiting hypoxia-induced Ca2+ responses via a mechanism independent of CA inhibition, changes in pHi, or membrane potential.
NPY Y1 receptor is involved in ghrelin- and fasting-induced increases in foraging, food hoarding, and food intake
Authors: Keen-Rhinehart Erin , Bartness Timothy J.
Published: January 2007

Fasting triggers a constellation of physiological and behavioral changes, including increases in peripherally produced ghrelin and centrally produced hypothalamic neuropeptide Y (NPY). Refeeding stimulates food intake in most species; however, hamsters primarily increase foraging and food hoarding with smaller increases in food intake. Fasting-induced increases in foraging and food hoarding in Siberian hamsters are mimicked by peripheral ghrelin, central NPY, and NPY Y1 receptor agonist injections. Because fasting stimulates ghrelin and subsequently NPY synthesis/release, it may be that fasting-induced increased hoarding is mediated by NPY Y1 receptor activation. Therefore, we asked: Can an Y1 receptor antagonist block fasting- or ghrelin-induced increases in foraging, food hoarding, and food intake? This was accomplished by injecting the NPY Y1 receptor antagonist 1229U91 intracerebroventricularly in hamsters fasted, fed, or given peripheral ghrelin injections and housed in a running wheel-based food delivery foraging system coupled with simulated-burrow housing. Three foraging conditions were used: 1) no running wheel access, free food, 2) running wheel access, free food, or 3) foraging requirement (10 revolutions/pellet) for food. Fasting was a more potent stimulator of foraging and food hoarding than ghrelin. Concurrent injections of 1229U91 completely blocked fasting- and ghrelin-induced increased foraging and food intake and attenuated, but did not always completely block, fasting- and ghrelin-induced increases in food hoarding. Collectively, these data suggest that the NPY Y1 receptor is important for the effects of ghrelin- and fasting-induced increases in foraging and food intake, but other NPY receptors and/or other neurochemical systems are involved in increases in food hoarding.
Intermittent hypobaric hypoxia exposure does not cause sustained alterations in autonomic control of blood pressure in young athletes
Authors: Fu Qi , Townsend Nathan E. , Shiller S. Michelle , Martini Emily R. , Okazaki Kazunobu , Shibata Shigeki , Truijens Martin J. , Rodríguez Ferran A. , Gore Christopher J. , Stray-Gundersen James , Levine Benjamin D.
Published: January 2007

Intermittent hypoxia (IH), which refers to the discontinuous use of hypoxia to reproduce some key features of altitude acclimatization, is commonly used in athletes to improve their performance. However, variations of IH are also used as a model for sleep apnea, causing sustained sympathoexcitation and hypertension in animals and, thus, raising concerns over the safety of this model. We tested the hypothesis that chronic IH at rest alters autonomic control of arterial pressure in healthy trained individuals. Twenty-two young athletes (11 men and 11 women) were randomly assigned to hypobaric hypoxia (simulated altitude of 4,000–5,500 m) or normoxia (500 m) in a double-blind and placebo-controlled design. Both groups rested in a hypobaric chamber for 3 h/day, 5 days/wk for 4 wk. In the sitting position, resting hemodynamics, including heart rate (HR), blood pressure (BP), cardiac output (Q̇c, C2H2rebreathing), stroke volume (SV = Q̇c/HR), and total peripheral resistance (TPR = mean BP/Q̇c), were measured, dynamic cardiovascular regulation was assessed by spectral and transfer function analysis of cardiovascular variability, and cardiac-vagal baroreflex function was evaluated by a Valsalva maneuver, twice before and 3 days after the last chamber exposure. We found no significant differences in HR, BP, Q̇c, SV, TPR, cardiovascular variability, or cardiac-vagal baroreflex function between the groups at any time. These results suggest that exposure to intermittent hypobaric hypoxia for 4 wk does not cause sustained alterations in autonomic control of BP in young athletes. In contrast to animal studies, we found no secondary evidence for sustained physiologically significant sympathoexcitation in this model.
Age-related changes in multifinger synergies in accurate moment of force production tasks
Authors: Olafsdottir Halla , Zhang Wei , Zatsiorsky Vladimir M. , Latash Mark L.
Published: January 2007

The purpose of this investigation was to document and quantify age-related differences in the coordination of fingers during a task that required production of an accurate time profile of the total moment of force by the four fingers of a hand. We hypothesized that elderly subjects would show a decreased ability to stabilize a time profile of the total moment of force, leading to larger indexes of moment variability compared with young subjects. The subjects followed a trapezoidal template on a computer screen by producing a time profile of the total moment of force while pressing down on force sensors with the four fingers of the right (dominant) hand. To quantify synergies, we used the framework of the uncontrolled manifold hypothesis. The elderly subjects produced larger total force, larger variance of both total force and total moment of force, and larger involvement of fingers that produced moment of force against the required moment direction (antagonist moment). This was particularly prominent during supination efforts. Young subjects showed covariation of commands to fingers across trials that stabilized the moment of total force (moment-stabilizing synergy), while elderly subjects failed to do so. Both subject groups showed similar indexes of covariation of commands to the fingers that stabilized the time profile of the total force. The lack of moment-stabilizing synergies may be causally related to the documented impairment of hand function with age.
Postactivation potentiation in a human muscle: effect on the rate of torque development of tetanic and voluntary isometric contractions
Authors: Baudry Stéphane , Duchateau Jacques
Published: January 2007

Postactivation potentiation (PAP), a mechanism by which the torque of a muscle twitch is increased following a conditioning contraction, is well documented in muscular physiology, but little is known about its effect on the maximal rate of torque development and functional significance during voluntary movements. The objective of this study was to investigate the PAP effect on the rate of isometric torque development of electrically induced and voluntary contractions. To that purpose, the electromechanical responses of the thumb adductor muscles to a single electrical stimulus (twitch), a train of 15 pulses at 250 Hz (HFT250), and during ballistic (i.e., rapid torque development) voluntary contractions at torque levels ranging from 10 to 75% of maximal voluntary contraction (MVC) were recorded before and after a conditioning 6-s MVC. The results showed that the rate of torque development was significantly ( P < 0.001) increased after the conditioning MVC, but the effect was greater for the twitch (∼200%) compared with the HFT250 (∼17%) or ballistic contractions (range: 9–24%). Although twitch potentiation was maximal immediately after the conditioning MVC, maximal potentiation for HFT250 and ballistic contractions was delayed to 1 min after the 6-s MVC. Furthermore, the similar degree of potentiation for the rate of isometric torque development between tetanic and voluntary ballistic contractions indicates that PAP is not related to the modality of muscle activation. These observations suggest that PAP may be considered as a mechanism that can influence our contractions during daily tasks and can be utilized to improve muscle performance in explosive sports.
A New Method to Determine Mean Adult Height from Incomplete Follow-Up Data
Authors: de Ridder Maria A.J. , Stijnen Theo , Hokken-Koelega Anita C.S.
Published: January 2007

Background/Aim: In long-term growth studies with adult height (AH) as outcome, reporting is often required while data are incomplete because some participants have not yet reached AH whereas others might be lost to follow-up. Current practice is to analyze only participants who did reach AH, which can easily give biased results. We introduce a new method into the area of growth research. Methods: We used the data of patients from a registration database and a growth study. The new method uses growth data in time intervals. The percentage of children still growing and the mean growth at each interval are used to determine mean AH. Results: With the new method, estimated mean AHs had smaller bias and standard error than with commonly used methods. The method is not hampered by a correlation between AH and age at reaching AH, unlike methods merely using patients who have reached AH. Conclusion: In contrast to commonly used methods, the new method provides valid results on mean AH when complete actual measurements of AH are not (yet) available, provided that drop-out, if any, is not related to (disappointing) growth. As it also uses observed data of children with incomplete follow-up, the method employs the data more effectively.
Evidence for Decreased Circulating Apelin beyond Heart Involvement in Uremic Cardiomyopathy
Authors: Codognotto Marta , Piccoli Antonio , Zaninotto Martina , Mion Monica , Vertolli Ugo , Tona Francesco , Boffa Giovanni M.
Published: January 2007

Background: Plasma apelin concentration in heart failure has been described in small studies reporting conflicting results. In hemodialysis (HD) patients, apelin decreased more in those with more severe heart involvement. It is unclear if uremia is connected to this reduction irrespective of heart failure. We compared apelin in two cardiomyopathies with different renal function. Methods: Observational study conducted in 30 adult Caucasian outpatients in class I NYHA not affected by diabetes or ischemic heart, 15 with idiopathic dilated cardiomyopathy (DCM) and 15 with uremic dilated cardiomyopathy undergoing HD. Plasma apelin, creatinine, high-sensitivity C-reactive protein, endothelin, NT proB-type natriuretic peptide (NT-proBNP), and Doppler echocardiogram were evaluated. Results: Heart involvement was more severe in the DCM patients (lower ejection fraction, greater diastolic volume index, and worse index of myocardial performance). Median value of apelin in HD patients (19.1 pg/ml) was one third of that in DCM patients (58.2 pg/ml) whereas creatinine, NT-proBNP, and C-reactive protein were 11, 80, and 9 times higher respectively in HD than in DCM patients. Median values of endothelin were comparable in both groups. Apelin was not significantly correlated with any variable. Conclusion: Uremic status was the determinant for decreased plasma apelin in HD patients regardless of the severity of heart involvement.
Efficient Adsorption of Tumor Necrosis Factor with an in vitro Set-Up of the Microspheres-Based Detoxification System
Authors: Weber Viktoria , Hartmann Jens , Linsberger Ingrid , Falkenhagen Dieter
Published: January 2007

Background: The Microsperes-Based Detoxification System (MDS) represents a flexible therapeutic option for various diseases, depending on the specificity of the adsorbents applied. A potential application of the MDS is the supportive therapy of sepsis. Methods: Microadsorbents for tumor necrosis factor (TNF) were prepared by immobilization of anti-TNF antibodies on cellulose (1–10 µm) and applied in an experimental set-up using a pool of human plasma (1 liter) spiked with TNF (800 pg/ml) and its soluble receptors (1,000 pg/ml each). Removal of TNF was compared using a plasma filter and the albumin-permeable filter Albuflow. Results: Addition of 4 (2) g of adsorbent to the filtrate circuit reduced TNF concentrations in the pool by 80% (64%). Removal rates did not differ significantly for the different filters. TNF adsorption was not influenced by the presence of excess TNF receptors. Conclusions: Concentrations of mediators can be efficiently modulated with the MDS using small quantities of specific adsorbents.
Central Command Regulation of Circulatory Function Mediated by Descending Pontine Cholinergic Inputs to Sympathoexcitatory Rostral Ventrolateral Medulla Neurons
Authors: Padley James R. , Kumar Natasha N. , Li Qun , Nguyen Thomas B.V. , Pilowsky Paul M. , Goodchild Ann K.
Published: January 2007

Central command is a feedforward neural mechanism that evokes parallel modifications of motor and cardiovascular function during arousal and exercise. The neural circuitry involved has not been elucidated. We have identified a cholinergic neural circuit that, when activated, mimics effects on tonic and reflex control of circulation similar to those evoked at the onset of and during exercise. Central muscarinic cholinergic receptor (mAChR) activation increased splanchnic sympathetic nerve activity (SNA) as well as the range and gain of the sympathetic baroreflex via activation of mAChR in the rostral ventrolateral medulla (RVLM) in anesthetized artificially ventilated Sprague–Dawley rats. RVLM mAChR activation also attenuated and inhibited the peripheral chemoreflex and somatosympathetic reflex, respectively. Cholinergic terminals made close appositions with a subpopulation of sympathoexcitatory RVLM neurons containing either preproenkephalin mRNA or tyrosine hydroxylase immunoreactivity. M2 and M3 receptor mRNA was present postsynaptically in only non–tyrosine hydroxylase neurons. Cholinergic inputs to the RVLM arise only from the pedunculopontine tegmental nucleus. Chemical activation of this region produced increases in muscle activity, SNA, and blood pressure and enhanced the SNA baroreflex; the latter effect was attenuated by mAChR blockade. These findings indicate a novel role for cholinergic input from the pedunculopontine tegmental nucleus to the RVLM in central cardiovascular command. This pathway is likely to be important during exercise where a centrally evoked facilitation of baroreflex control of the circulation is required to maintain blood flow to active muscle.
Simple Models of Assortment through Environmental Feedback
Authors: Pepper John W.
Published: January 2007

Social evolution depends critically on assortment, or segregation versus even mixing, between cooperators and noncooperators. Altruistic traits, which reduce the absolute fitness of their bearers, cannot evolve without positive assortment (excess segregation). The question of how positive assortment can arise has been controversial, but most evolutionary biologists believe that common descent is the only effective general mechanism. Here I investigate another recently proposed mechanism for generating nonrandom assortment, termed environmental feedback. This requires only that two forms of a trait affect the quality of the local environment differently in such a way that all individuals are more likely to leave low-quality locales. Experiments with simple computational models confirm that environmental feedback generates significant levels of genetic similarity among non-kin within locales. The mechanism is fairly general, and can under some conditions produce levels of genetic similarity comparable to those resulting from close genealogical relationship. Environmental feedback can also generate the negative assortment necessary for the evolution of spiteful traits. Environmental feedback is expected to create positive frequency-dependent selection, which thus favor any social trait that becomes common in the population. Results from this stylized model suggest that environmental feedback could be important in the evolution of both cooperation and spite, within as well as between species.
The Effects of Cultural Learning in Populations of Neural Networks
Authors: Curran Dara , O'Riordan Colm
Published: January 2007

Population learning can be described as the iterative Darwinian process of fitness-based selection and genetic transfer of information leading to populations of higher fitness and is often simulated using genetic algorithms. Cultural learning describes the process of information transfer between individuals in a population through non-genetic means. Cultural learning has been simulated by combining genetic algorithms and neural networks using a teacher-pupil scenario where highly fit individuals are selected as teachers and instruct the next generation. By examining the innate fitness of a population (i.e., the fitness of the population measured before any cultural learning takes place), it is possible to examine the effects of cultural learning on the population's genetic makeup. Our model explores the effect of cultural learning on a population and employs three benchmark sequential decision tasks as the evolutionary task for the population: connect-four, tic-tac-toe, and blackjack. Experiments are conducted with populations employing population learning alone and populations combining population and cultural learning. The article presents results showing the gradual transfer of knowledge from genes to the cultural process, illustrated by the simultaneous decrease in the population's innate fitness and the increase of its acquired fitness measured after learning takes place.
Fast Population Coding
Authors: Huys Quentin J. M. , Zemel Richard S. , Natarajan Rama , Dayan Peter
Published: January 2007

Uncertainty coming from the noise in its neurons and the ill-posed nature of many tasks plagues neural computations. Maybe surprisingly, many studies show that the brain manipulates these forms of uncertainty in a probabilistically consistent and normative manner, and there is now a rich theoretical literature on the capabilities of populations of neurons to implement computations in the face of uncertainty. However, one major facet of uncertainty has received comparatively little attention: time. In a dynamic, rapidly changing world, data are only temporarily relevant. Here, we analyze the computational consequences of encoding stimulus trajectories in populations of neurons. For the most obvious, simple, instantaneous encoder, the correlations induced by natural, smooth stimuli engender a decoder that requires access to information that is nonlocal both in time and across neurons. This formally amounts to a ruinous representation. We show that there is an alternative encoder that is computationally and representationally powerful in which each spike contributes independent information; it is independently decodable, in other words. We suggest this as an appropriate foundation for understanding time-varying population codes. Furthermore, we show how adaptation to temporal stimulus statistics emerges directly from the demands of simple decoding.
Unthinkable Thoughts: Education of Gifted Students
Authors: Gallagher James J.
Published: January 2007

The advent of a new millenium is an appropriate time to consider some “unthinkable thoughts,” those thoughts that make us so uncomfortable that most professionals prefer to ignore them. Yet, if progress is to be made, such challenges to our professional roles must be confronted. Four such ugly questions are considered for gifted education, together with suggested actions to cope with them.

1. Is there really such an entity as a gifted child?

2. Is there such an entity as gifted education?

3. Is there such an entity as special personnel preparation for teachers of gifted students?

4. Is the application of special services for gifted students sufficient in scope and intensity to make a difference in the classroom?

We should recognize that, however we choose to cope with these issues, our status quo, business as usual, is hardly a viable choice for the 21st century.
Economically Disadvantaged Students in a School for the Academically Gifted: A Postpositivist Inquiry into Individual and Family Adjustment
Authors: Borland James H. , Schnur Rachel , Wright Lisa
Published: January 2007

In this paper, we report the results of an inquiry into the effects of the placement of five economical disadvantaged minority students from central Harlem, who were identified in kindergarten as potentially academically gifted through nontraditional means, in a school for gifted students. Achievement and aptitude test data and qualitative data collected during the students' first year at the school support the conclusion that the students were appropriately placed and adjusted well academically socially and emotionally. Follow-up data suggest that the students' academic careers have, in the six years since the original data were collected, for the most part progressed well. We present assertions that begin to explain why these students have succeeded academically despite being at-risk for educational disadvantage. These assertions concern the students themselves, their families, their school, and Project Synergy, through whose activities the students were identified as potentially gifted.
The Research Processes of Gifted Students: A Case Study
Authors: Bishop Kay
Published: January 2007

This case study investigated the research processes and authentic learning experiences of 10 junior high students as they completed independent research projects in a class for gifted students. Students experienced the most difficulty in exploring and forming a focus. Although students used a variety of information resources, they did not access some available information sources and, in some cases, experienced difficulty extracting relevant information. The professional services of public and school librarians were not utilized to assist in the research project. Only 3 of the 10 gifted students demonstrated all of the characteristics of authentic learning in their final products. Suggestions are made on how to alter the process to make independent research projects produce more authentic learning experiences.