bluuebunny/crossref_metadata_2025 huggingface dataset:
Microglia‐specific expression of microsomal prostaglandin E2 synthase‐1 contributes to lipopolysaccharide‐induced prostaglandin E2 production
Authors: Ikeda‐Matsuo Yuri , Ikegaya Yuji , Matsuki Norio , Uematsu Satoshi , Akira Shizuo , Sasaki Yasuharu
Published: August 2005

Microsomal prostaglandin E2 synthase (mPGES)‐1 is an inducible protein recently shown to be an important enzyme in inflammatory prostaglandin E2 (PGE2) production in some peripheral inflammatory lesions. However, in inflammatory sites in the brain, the induction of mPGES‐1 is poorly understood. In this study, we demonstrated the expression of mPGES‐1 in the brain parenchyma in a lipopolysaccharide (LPS)‐induced inflammation model. A local injection of LPS into the rat substantia nigra led to the induction of mPGES‐1 in activated microglia. In neuron‐glial mixed cultures, mPGES‐1 was co‐induced with cyclooxygenase‐2 (COX‐2) specifically in microglia, but not in astrocytes, oligodendrocytes or neurons. In microglia‐enriched cultures, the induction of mPGES‐1, the activity of PGES and the production of PGE2 were preceded by the induction of mPGES‐1 mRNA and almost completely inhibited by the synthetic glucocorticoid dexamethasone. The induction of mPGES‐1 and production of PGE2 were also either attenuated or absent in microglia treated with mPGES‐1 antisense oligonucleotide or microglia from mPGES‐1 knockout (KO) mice, respectively, suggesting the necessity of mPGES‐1 for microglial PGE2 production. These results suggest that the activation of microglia contributes to PGE2 production through the concerted de novo synthesis of mPGES‐1 and COX‐2 at sites of inflammation of the brain parenchyma.
Expression and function of α2‐adrenoceptors in zebrafish: drug effects, mRNA and receptor distributions
Authors: Ruuskanen Jori O. , Peitsaro Nina , Kaslin Jan V. M. , Panula Pertti , Scheinin Mika
Published: August 2005

The α2‐adrenoceptors are G‐protein‐coupled receptors that mediate many of the physiological effects of norepinephrine and epinephrine. Mammals have three subtypes of α2‐adrenoceptors, α2A, α2B and α2C. Zebrafish, a teleost fish used widely as a model organism, has five distinct α2‐adrenoceptor genes. The zebrafish has emerged as a powerful tool to study development and genetics, with many mutations causing diseases reminiscent of human diseases. Three of the zebrafish adra2 genes code for orthologues of the mammalian α2‐adrenoceptors, while two genes code for α2Da‐ and α2Db‐ adrenoceptors, representing a duplicated, fourth α2‐adrenoceptor subtype. The three different mammalian α2‐adrenoceptor subtypes have distinct expression patterns in different organs and tissues, and mediate different physiological functions. The zebrafish α2‐adrenergic system, with five different α2‐adrenoceptors, appears more complicated. In order to deduce the physiological functions of the zebrafish α2‐adrenoceptors, we localized the expression of the five different α2‐adrenoceptor subtypes using RT–PCR, mRNA in situ hybridization, and receptor autoradiography using the radiolabelled α2‐adrenoceptor antagonist [ethyl‐3H]RS‐79948–197. Localization of the α2A‐, α2B‐ and α2C‐adrenoceptors in zebrafish shows marked conservation when compared with mammals. The zebrafish α2A, α2Da, and α2Db each partially follow the distribution pattern of the mammalian α2A: a possible indication of subfunction partitioning between these subtypes. The α2‐adrenergic system is functional in zebrafish also in vivo, as demonstrated by marked locomotor inhibition, similarly to mammals, and lightening of skin colour induced by the specific α2‐adrenoceptor agonist, dexmedetomidine. Both effects were antagonized by the specific α2‐adrenoceptor antagonist atipamezole.
Impairment of blood–cerebrospinal fluid barrier properties by retrovirus‐activated T lymphocytes: reduction in cerebrospinal fluid‐to‐blood efflux of prostaglandin E2
Authors: Khuth Seng Thuon , Strazielle Nathalie , Giraudon Pascale , Belin Marie‐Françoise , Ghersi‐Egea Jean‐François
Published: August 2005

The choroid plexus epithelium forms the interface between the blood and the CSF. In conjunction with the tight junctions restricting the paracellular pathway, polarized specific transport systems in the choroidal epithelium allow a fine regulation of CSF‐borne biologically active mediators. The highly vascularized stroma delimited by the choroidal epithelium can be a reservoir for retrovirus‐infected or activated immune cells. In this work, new insight in the implication of the blood–CSF barrier in neuroinfectious and inflammatory diseases is provided by using a differentiated cellular model of the choroidal epithelium, exposed to infected T lymphocytes. We demonstrate that T cells activated by a retroviral infection, but not non‐infected cells, reduce the transporter‐mediated CSF‐to‐blood efflux of organic anions, in particular that of the potent pro‐inflammatory prostaglandin PGE2, via the release of soluble factors. A moderate alteration of the paracellular permeability also occurs. We identified the viral protein Tax, oxygenated free radicals, matrix‐metalloproteinases and pro‐inflammatory cytokines as active molecules released during the exposure of the epithelium to infected T cells. Among them, tumour necrosis factor and interleukin 1 are directly involved in the mechanism underlying the decrease in some choroidal organic anion efflux. Given the strong involvement of CSF‐borne PGE2 in sickness behaviour syndrome, these data suggest that the blood–CSF barrier plays an important role in the pathophysiology of neuroinflammation and neuroinfection, via changes in the transport processes controlling the CSF biodisposition of PGE2.
Effect of neurosteroids on the retinal gabaergic system and electroretinographic activity in the golden hamster
Authors: Jaliffa Carolina O. , Howard Sarah , Hoijman Esteban , Salido Ezequiel , Sarmiento María I. Keller , Arias Pablo , Rosenstein Ruth E.
Published: August 2005

It has been established that neurosteroids can either inhibit or enhance GABAA receptor activity. Although GABA is the main inhibitory neurotransmitter in the mammalian retina, the effects of neurosteroids on retinal GABAergic activity have not been investigated. The aim of this work was to study the neurochemical and electroretinographic effects of neurosteroids in the golden hamster. On one hand, pregnenolone sulfate inhibited and allotetrahydrodeoxycorticosterone increased GABA‐induced [36Cl]– uptake in neurosynaptosomes. On the other hand, in whole retinas, pregnenolone sulfate increased, whereas allotetrahydrodeoxycorticosterone decreased high potassium‐induced [3H]GABA release. The effect of both neurosteroids on GABA release was Ca2+‐dependent, as in its absence release was not altered. The intravitreal injection of pregnenolone sulfate or vigabatrin (an irreversible inhibitor of GABA degradation) significantly decreased scotopic b‐wave amplitude, whereas the opposite effect was evident when bicuculline or allotetrahydrodeoxycorticosterone were injected. A protein with a molecular weight close to that of hamster adrenal cytochrome P450 side‐chain cleavage (P450scc) was detected in the hamster retina. P450scc‐like immunoreactivity was localized in the inner nuclear and the ganglion cell layers. These results indicate that neurosteroids significantly modulate retinal GABAergic neurotransmission and electroretinographic activity. In addition, the selective localization of P450scc suggests that neurosteroid biosynthesis might occur only in some layers of the hamster retina.
ERK1/2 is a negative regulator of homeodomain protein Arix/Phox2a
Authors: Hsieh Marlene M. , Lupas George , Rychlik Jennifer , Dziennis Suzan , Habecker Beth A. , Lewis Elaine J.
Published: August 2005

The homeodomain protein Arix/Phox2a plays a role in the development and maintenance of the noradrenergic cell type by regulating the transcription of genes involved in the biosynthesis and metabolism of noradrenaline. Previous work has shown that Arix/Phox2a is a phosphoprotein, and the phosphorylated form of Arix/Phox2a exhibits poorer DNA‐binding activity than does the dephosphorylated form. Here, we demonstrate that Arix/Phox2a is phosphorylated by extracellular signal‐related kinase (ERK)1/2 at two sites within the N‐terminal transactivation domain. The phosphorylation level of Arix in cultured SH‐SY5Y neuroblastoma cells is reduced when cells are treated with the mitogen activated protein kinase kinase 1 (MEK1) inhibitor UO126. Treatment of sympathetic neurons with the MEK1 inhibitor, PD98059, results in an elevation of mRNAs encoding noradrenergic proteins, dopamine ß‐hydroxylase (DBH) and norepinephrine transporter (NET), but not tyrosine hydroyxlase (TH). Treatment of neuroblastoma cultures with PD98059 increases the interaction of Arix with DBH and NET genes, but not the TH gene. Together, these results suggest that phosphorylation of Arix by ERK1/2 inhibits its ability to interact with target genes, and that both specificity of expression and modulation by external stimuli are monitored through the same transcription factor.
Evidence for low GluR2 AMPA receptor subunit expression at synapses in the rat basolateral amygdala
Authors: Gryder Divina S. , Castaneda Dora C. , Rogawski Michael A.
Published: August 2005

Fast excitatory synaptic responses in basolateral amygdala (BLA) neurons are mainly mediated by ionotropic glutamate receptors of the α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) subtype. AMPA receptors containing an edited GluR2 subunit are calcium impermeable, whereas those that lack this subunit are calcium permeable and also inwardly rectifying. Here, we sought to determine the extent to which synapses in the rat BLA have AMPA receptors with GluR2 subunits. We assessed GluR2 protein expression in the BLA by immunocytochemistry with a GluR2 subunit‐specific antiserum at the light and electron microscopic level; for comparison, a parallel examination was carried out in the hippocampus. We also recorded from amygdala brain slices to examine the voltage‐dependent properties of AMPA receptor‐ mediated evoked synaptic currents in BLA principal neurons. At the light microscopic level, GluR2 immunoreactivity was localized to the perikarya and proximal dendrites of BLA neurons; dense labeling was also present over the pyramidal cell layer of hippocampal subfields CA1 and CA3. In electron micrographs from the BLA, most of the synapses were asymmetrical with pronounced postsynaptic densities (PSD). They contained clear, spherical vesicles apposed to the PSD and were predominantly onto spines (86%), indicating that they are mainly with BLA principal neurons. Only 11% of morphological synapses in the BLA were onto postsynaptic elements that showed GluR2 immunoreactivity, in contrast to hippocampal subfields CA1 and CA3 in which 76% and 71% of postsynaptic elements were labeled (p < 0.001). Synaptic staining in the BLA and hippocampus, when it occurred, was exclusively postsynaptic, and particularly heavy over the PSD. In whole‐cell voltage clamp recordings, 72% of BLA principal neurons exhibited AMPA receptor‐mediated synaptic currents evoked by external capsule stimulation that were inwardly rectifying. Although BLA principal neurons express perikaryal and proximal dendritic GluR2 immunoreactivity, few synapses onto these neurons express GluR2, and a preponderance of principal neurons have inwardly rectifying AMPA‐mediated synaptic currents, suggesting that targeting of GluR2 to synapses is restricted. Many BLA synaptic AMPA receptors are likely to be calcium permeable and could play roles in synaptic plasticity, epileptogenesis and excitoxicity.
Ten polymorphic microsatellite markers in the wandering albatross Diomedea exulans
Authors: DUBOIS MARIE‐PIERRE , JARNE PHILIPPE , JOUVENTIN PIERRE
Published: August 2005

We describe 10 new variable dinucleotide microsatellites in the wandering albatross Diomedea exulans, as well as conditions for multiplexing and simultaneous genotyping sets of loci. Their variability was assessed in two and one populations from the Crozet and Kerguelen archipelagos (southern Indian Ocean), respectively. Two to 13 alleles were detected per population, and the mean gene diversity was around 0.4. The low genetic differentiation suggests that these populations constitute a single panmictic unit. Cross‐species amplification provided some variability at three and five loci in two other marine birds (Bulweria bulwerii and Pagodroma nivea), but none in Calonectris diomedea.
Isolation and characterization of 27 polymorphic microsatellite loci for the common snook, Centropomus undecimalis
Authors: SEYOUM SEIFU , TRINGALI MICHAEL D. , SULLIVAN JAMIE G.
Published: August 2005

Here we describe 32 di‐, tri‐ and tetranucleotide microsatellite loci isolated by PIMA, a polymerase chain reaction (PCR)‐based procedure, for the common snook (Centropomus undecimalis). Five loci were monomorphic, and the remaining loci averaged 6.7 alleles per locus in a sample of 45 common snook. For polymorphic loci, expected heterozygosities ranged from 0.02 to 0.91 (mean = 0.538). Significant departures from Hardy–Weinberg equilibrium expectations occurred in two loci. Exact tests for genotype disequilibrium gave evidence for linkage at one pair of loci. Many cross‐species primer assays yielded PCR fragments of the expected size for 11 species of Centropomus and two species of the confamilial genus Lates.
Development and characterization of ten new microsatellite markers in a mangrove tree species Bruguiera gymnorrhiza (L.)
Authors: ISLAM M. S. , LIAN C. L. , KAMEYAMA N. , WU B. , HOGETSU T.
Published: August 2005

Bruguiera gymnorrhiza is an ecologically and somewhat economically important mangrove tree species. We isolated 10 polymorphic microsatellite loci from B. gymnorrhiza using a dual‐suppression polymerase chain reaction (PCR) technique. These loci provided microsatellite markers with polymorphism of two to five alleles per locus within 216 individuals from nine natural populations of B. gymnorrhiza on Iriomote Island, the Sakishima Islands, Japan. The expected and observed heterozygosities ranged from 0.220 to 0.720 and from 0.104 to 0.447, respectively.
Genetic Approaches to the Study of Aging
Authors: Miller Richard A.
Published: August 2005

Can mouse genetics teach us enough about the biology of aging to guide the search for anti‐aging medicines that can delay late‐life illness? Recent progress gives reason for optimism, with new data showing that changes in single genes can extend average and maximal life span by 40%. Mice with these genetic variants remain healthy, active, and cognitively intact at average ages that correspond to 110–120 years of human life span. Multiple lines of evidence now point to a hormone, IGF‐I, as a key influence on life span, with low IGF‐I levels associated with extended longevity in multiple model systems. The goal of this research is not gene therapy—we have no idea of what genes to change, how to change them, or what harm such changes might do—but instead to use insights from the cell biology and endocrinology of genetically long‐lived mice and other species to help develop drugs that manipulate aging and thus postpone the many diseases and disabilities that are typically troublesome in old age. The complete conquest of cancer or heart disease would each lead to an increase of a mere∼3% in mean life span in humans, i.e. about a tenth of what can be accomplished, today, in laboratory animals of delayed aging. In this context the paltry commitment to research in biological gerontology (six cents per $100 of NIH funding, for example) seems worth reconsideration.
Future Longevity—Demographic Concerns and Consequences
Authors: Kinsella Kevin G.
Published: August 2005

One of gerontology's most intense and ongoing debates centers around the future shape of the human survival curve. Is average life expectancy destined to peak between the ages of 85 and 90, as some would argue, or will new ways be found to sustain the dramatic increase in life expectancy that unfolded during the 20th century? This article considers issues inherent in projecting the number of tomorrow's older people, with a focus on the future course of mortality. Although overall mortality declined in most countries during the past century, the decline has been irregular and has reversed in some countries because of unforeseen epidemics, cause‐specific changes, and sociopolitical upheavals. On the positive side, scientists have identified several promising findings; mortality trajectories at very old ages may decline, old‐age mortality can be altered by social interventions, the number of centenarians is exploding, new chemical entities have a demonstrable effect on life expectancy, and there has been a linear increase in worldwide record‐setting life expectancy during the past 160 years. New projections made by the United Nations peer, for the first time, 300 years into the future. These projections foresee a rise of about 25 years in life expectancy at birth in North America over the next 3 centuries, which some experts today believe to be quite conservative. It is important to recognize the inherent uncertainty in life expectancy projections and how assumptions of future mortality change must—from a policy perspective—be considered in conjunction with potential concomitant changes in fertility and migration.
The Compression of Morbidity Hypothesis: A Review of Research and Prospects for the Future
Authors: Mor Vincent
Published: August 2005

Cross‐national evidence for the validity of the compression of morbidity hypothesis originally proposed by Fries is generally accepted. Generational improvements in education and the increased availability of adaptive technologies and even medical treatments that enhance quality of life have facilitated continued independence of older persons in the industrialized world. Whether this trend continues may depend upon the effect of the obesity epidemic on the next generation of older people.
Why Do They Not Comply with the Law? Illegality and Semi-Legality among Rural-Urban Migrant Entrepreneurs in Beijing
Authors: He Xin
Published: August 2005

Based on in-depth interview materials, this article examines why most rural-urban migrant entrepreneurs in Beijing do not fully comply with a discriminatory license requirement, and in particular, why they prefer license-renting from the locals. This article suggests that the law's lack of legitimacy adds weight to instrumental considerations. But more important, this license-renting practice seems to be reinforced and sustained institutionally by local businesses, law enforcement officers, and the local authorities, because their interests are inextricably intertwined with it. The whole situation constitutes a general equilibrium through which various interests are balanced. This case study thus paints a far more complicated picture of the law's impact on people's behavior than usually assumed. Instrumental concerns, or coercive action and sanctions alone, do not adequately explain people's interaction with the law in a “lawless” circumstance; a whole range of instrumental concerns must be considered, and they, together with sanctions, must be understood in the context of a larger institutional environment in which the interactions of various players unfold.
Apoptosis in normal and diseased oral tissues
Authors: Loro LL , Vintermyr OK , Johannessen AC
Published: August 2005

Apoptotic cell death plays an important role in maintenance of the normal physiological state and in the pathogenesis of diseases in the body. Over the last three decades the molecular mechanisms of apoptosis have been unravelled leading to development of novel therapeutic approaches. This paper aims to present current knowledge of the role of apoptosis in normal oral tissues and in the development of oral diseases.
Coexistence of lymphoepithelial and epidermoid cysts on the floor of the mouth: report of a case
Authors: Epivatianos A , Zaraboukas T , Antoniades D
Published: August 2005

Lymphoepithelial and epidermoid cysts in the oral cavity are uncommon. The coexistence of lymphoepithelial and epidermoid cysts in the oral cavity is extremely rare. Only one case of lymphoepithelial cyst associated with two epidermoid cysts on the floor of the mouth has been reported in the literature and the present report describes a second case where a lymphoepithelial cyst coexisted with an epidermoid cyst on the floor of the mouth. It is likely an accidental trauma that was accompanied by inflammation produced the development of implantation‐keratinizing epidermoid and lymphoepithelial cysts.
Effect of Gravity on Liquid Plug Transport Through an Airway Bifurcation Model
Authors: Zheng Y. , Anderson J. C. , Suresh V. , Grotberg J. B.
Published: August 2005

Many medical therapies require liquid plugs to be instilled into and delivered throughout the pulmonary airways. Improving these treatments requires a better understanding of how liquid distributes throughout these airways. In this study, gravitational and surface mechanisms determining the distribution of instilled liquids are examined experimentally using a bench-top model of a symmetrically bifurcating airway. A liquid plug was instilled into the parent tube and driven through the bifurcation by a syringe pump. The effect of gravity was adjusted by changing the roll angle (ϕ) and pitch angle (γ) of the bifurcation (ϕ=γ=0deg was isogravitational). ϕ determines the relative gravitational orientation of the two daughter tubes: when ϕ≠0deg, one daughter tube was lower (gravitationally favored) compared to the other. γ determines the component of gravity acting along the axial direction of the parent tube: when γ≠0deg, a nonzero component of gravity acts along the axial direction of the parent tube. A splitting ratio Rs, is defined as the ratio of the liquid volume in the upper daughter to the lower just after plug splitting. We measured the splitting ratio, Rs, as a function of: the parent-tube capillary number (Cap); the Bond number (Bo); ϕ; γ; and the presence of pre-existing plugs initially blocking either daughter tube. A critical capillary number (Cac) was found to exist below which no liquid entered the upper daughter (Rs=0), and above which Rs increased and leveled off with Cap. Cac increased while Rs decreased with increasing ϕ, γ, and Bo for blocked and unblocked cases at a given Cap>Cac. Compared to the nonblockage cases, Rs decreased (increased) at a given Cap while Cac increased (decreased) with an upper (lower) liquid blockage. More liquid entered the unblocked daughter with a blockage in one daughter tube, and this effect was larger with larger gravity effect. A simple theoretical model that predicts Rs and Cac is in qualitative agreement with the experiments over a wide range of parameters.
Wave Intensity Analysis of Left Ventricular Filling
Authors: Lanoye L. L. , Vierendeels J. A. , Segers P. , Verdonck P. R.
Published: August 2005

Wave intensity analysis (WIA) is a powerful technique to study pressure and flow velocity waves in the time domain in vascular networks. The method is based on the analysis of energy transported by the wave through computation of the wave intensity dI=dPdU, where dP and dU denote pressure and flow velocity changes per time interval, respectively. In this study we propose an analytical modification to the WIA so that it can be used to study waves in conditions of time varying elastic properties, such as the left ventricle (LV) during diastole. The approach is first analytically elaborated for a one-dimensional elastic tube-model of the left ventricle with a time-dependent pressure-area relationship. Data obtained with a validated quasi-three dimensional axisymmetrical model of the left ventricle are employed to demonstrate this new approach. Along the base-apex axis close to the base wave intensity curves are obtained, both using the standard method and the newly proposed modified method. The main difference between the standard and modified wave intensity pattern occurs immediately after the opening of the mitral valve. Where the standard WIA shows a backward expansion wave, the modified analysis shows a forward compression wave. The proposed modification needs to be taken into account when studying left ventricular relaxation, as it affects the wave type.
Design of a Sterile Organ Culture System for the Ex Vivo Study of Aortic Heart Valves
Authors: Warnock James N. , Konduri Suchitra , He Zhaoming , Yoganathan Ajit P.
Published: August 2005

The biological response of valves to mechanical forces is not well understood. The aim of this study was to design a pulsatile system to enable the ex vivo study of aortic valves when subjected to various hemodynamic conditions. A bioreactor was designed to subject porcine aortic valves to physiological and pathophysiological pressure and flow conditions, while maintaining viability and sterility. Pressure and flow rate could be independently controlled to produce clinically relevant mechanical conditions. The oxygen transfer rate was characterized and sterile operation was achieved over 96hours. The oxygenation capabilities ensure sufficient oxygen transport to valves, allowing operation for extended periods.
Thin-Film Coupled Fluid-Solid Analysis of Flow Through the Ahmed™ Glaucoma Drainage Device
Authors: Stay Matthew S. , Pan Tingrui , Brown J. David , Ziaie Babak , Barocas Victor H.
Published: August 2005

The Ahmed™ glaucoma valve (AGV) is a popular glaucoma drainage device, allowing maintenance of normal intraocular pressure in patients with reduced trabecular outflow facility. The uniquely attractive feature of the AGV, in contrast to other available drainage devices, is its variable resistance in response to changes in flow rate. As a result of this variable resistance, the AGV maintains a pressure drop between 7 and 12mmHg for a wide range of aqueous humor flow rates. In this paper, we demonstrate that the nonlinear behavior of the AGV is a direct result of the flexibility of the valve material. Due to the thin geometry of the system, the leaflets of the AGV were modeled using the von Kármán plate theory coupled to a Reynolds lubrication theory model of the aqueous humor flow through the valve. The resulting two-dimensional coupled steady-state partial differential equation system was solved by the finite element method. The Poisson’s ratio of the valve was set to 0.45, and the modulus was regressed to experimental data, giving a best-fit value 4.2MPa. Simulation results compared favorably with previous experimental studies and our own pressure-drop∕flow-rate data. For an in vitro flow of 1.6μL∕min, we calculated a pressure drop of 5.8mmHg and measured a pressure drop of 5.2±0.4mmHg. As flow rate was increased, pressure drop rose in a strongly sublinear fashion, with a flow rate of 20μL∕min giving a predicted pressure drop of only 10.9mmHg and a measured pressure drop of 10.5±1.1mmHg. The AGV model was then applied to simulate in vivo conditions. For an aqueous humor flow rate of 1.5-3.0μL∕min, the calculated pressure drops were 5.3 and 6.3mmHg.
Magnetic Field-Induced Superconductivity in the Ferromagnet URhGe
Authors: Lévy F. , Sheikin I. , Grenier B. , Huxley A. D.
Published: August 2005

In several metals, including URhGe, superconductivity has recently been observed to appear and coexist with ferromagnetism at temperatures well below that at which the ferromagnetic state forms. However, the material characteristics leading to such a state of coexistence have not yet been fully elucidated. We report that in URhGe there is a magnetic transition where the direction of the spin axis changes when a magnetic field of 12 tesla is applied parallel to the crystal
b
axis. We also report that a second pocket of superconductivity occurs at low temperature for a range of fields enveloping this magnetic transition, well above the field of 2 tesla at which superconductivity is first destroyed. Our findings strongly suggest that excitations in which the spins rotate stimulate superconductivity in the neighborhood of a quantum phase transition under high magnetic field.
Too Wed to the Sea
Authors: Smith Jesse
Published: August 2005

The Science of Saving Venice
.
By Caroline Fletcher and Jane da Mosto
. Umberto Allemandi, Turin, Italy, 2004. 92 pp. Paper, $14.50, £7.99. ISBN 88-422-1310-1.

This profusely illustrated book surveys the nature and causes of the threat flooding poses to Venice as well as proposed solutions.
BENCHMARK RESULTS FOR HIGH-SPEED 4-BIT ACCUMULATORS IMPLEMENTED IN INDIUM PHOSPHIDE DHBT TECHNOLOGY
Authors: TURNER STEVEN EUGENE , KOTECKI DAVID E.
Published: August 2005

High-speed accumulators are frequently used as a benchmark of the high-speed performance and ability to yield large scale circuits in InP double hetereojunction bipolar (DHBT) processes. In previous work, we reported test results of an InP DHBT 4-bit accumulator with 624 transistors operating at 41 GHz clock frequency with a power consumption of 4.1W. In this work, we report on modifications that allow the circuit to operate at a lower supply voltage and a corresponding lower power consumption. Simulation results for this modification indicate that a 16% power reduction can be obtained, while maintaining a high-speed operating frequency of 40 GHz.
NATIVE DEFECT COMPENSATION IN III-ANTIMONIDE BULK SUBSTRATES
Authors: PINO ROBINSON , KO YOUNGOK , DUTTA PARTHA S.
Published: August 2005

As-grown, undoped III-antimonide bulk substrates contain high concentration of native defects resulting in high residual carrier density. In this paper, we have demonstrated that native defects can be compensated in bulk substrates of GaSb , InSb , and Ga 1-x In x Sb via impurity doping and low temperature growth from nonstoichiometric melts and solutions. Decrease in residual carrier concentration up to one order of magnitude at 300 K and three orders of magnitude at 77 K have been achieved.
LIFETIME OF NONEQUILIBRIUM CARRIERS IN AlGaN EPILAYERS WITH HIGH Al MOLAR FRACTION
Authors: MICKEVICIUS J. , ALEKSIEJUNAS R. , SHUR M. S. , ZHANG J. P. , FAREED Q. , GASKA R. , TAMULAITIS G.
Published: August 2005

AlGaN epilayers with different aluminum content have been studied by photoluminescence (PL) and light-induced transient grating (LITG) techniques. The epilayers were grown by conventional metal organic chemical vapor deposition (MOCVD) and by migration enhanced MOCVD (MEMOCVDTM). The carrier lifetime and PL intensity in epilayers containing the same amount of aluminum are shown to be inversely proportional to the dislocation density, which was determined using etch pit technique. The carrier diffusion length is shown to be close to the average distance between two first-neighbor dislocations. Enhancement of the lifetime and PL intensity in epilayers grown on sapphire by MEMOCVDTM is demonstrated.
NOISE CHARACTERISTICS OF 340 nm AND 280 nmGaN-BASED LIGHT EMITTING DIODES
Authors: SAWYER SHAYLA , RUMYANTSEV SERGEY L. , PALA NEZIH , SHUR MICHAEL S. , BILENKO YURIY , GASKA REMIS , KOSTERIN PAVEL V. , SALZBERG BRIAN M.
Published: August 2005

Low frequency fluctuations in light intensity of 340 nm and 280 nm GaN -based light emitting diodes (LEDs) are compared with noise properties of other commercially available UV and visible wavelength LEDs and halogen lamps. At low frequencies, LEDs can exhibit lower levels of noise than halogen lamps. An LED noise quality factor β is estimated for the UV LEDs.
JUNCTION-TEMPERATURE MEASUREMENTS IN GaN UV LIGHT-EMITTING DIODES USING THE DIODE FORWARD VOLTAGE
Authors: XI Y. , SCHUBERT E. F.
Published: August 2005

A theoretical model for the dependence of the diode forward voltage (V f ) on junction temperature (T) is developed. A new expression for d V f / d T is derived that takes into account all relevant contributions to the temperature dependence of the forward voltage including the intrinsic carrier concentration, the bandgap energy, and the effective density of states. Experimental results on the junction temperature of GaN UV LEDs are presented. Excellent agreement between the theoretical and experimental temperature coefficient of the forward voltage ( d V f / d T) is found. The experimentally found linear dependence of the junction temperature on forward current is explained by a thermal conduction model. A thermal resistivity of 342.2 K/W is found for the UV LED.
STABLE HIGH POWER GaN-ON-GaN HEMT
Authors: CHU K. K. , CHAO P. C. , WINDYKA J. A.
Published: August 2005

High power AlGaN/GaN HEMTs on free-standing GaN substrates with excellent stability have been demonstrated for the first time. When operated at a drain bias of 50V, devices without a field plate showed a record CW output power density of 10.0W/mm at 10GHz with an associated power-added efficiency of 45%. The efficiency reaches a maximum of 58% with an output power density of 5.5W/mm under a drain bias of 25V at 10GHz. Long-term stability of device RF operation was also examined. Under ambient conditions, devices biased at 25V and driven at 3dB gain compression remained stable at least up to 1,000 hours, degrading only by 0.35dB in output power. Such results clearly demonstrate the feasibility of GaN - on - GaN HEMT as an alternative device technology to the GaN - on - SiC HEMT in supporting reliable, high performance microwave power applications.
PHOTOCAPACITANCE OF GaAs THIN-FILM STRUCTURES FABRICATED ON A SEMI-INSULATING COMPENSATED SUBSTRATE
Authors: GOREV NIKOLAI B. , KODZHESPIROVA INNA F. , PRIVALOV EVGENY N. , KHUCHUA NINA , KHVEDELIDZE LEVAN , SHUR MICHAEL S.
Published: August 2005

The results of analytical and numerical calculations of the low-frequency and the high-frequency barrier capacitance of GaAs epitaxial and ion-implanted structures fabricated on a semi-insulating compensated substrate are presented. The calculations are done for the samples in the dark and under extrinsic illumination. It is shown that the high-frequency photocapacitance of these structures exhibits a narrow peak, and the low-frequency photocapacitance has a positive peak followed by a negative valley. The underlying physical mechanisms are discussed. Methods for predicting the MESFET threshold voltage and extracting the concentration of vacant deep traps in the vicinity of the film–substrate interface and the epitaxial film thickness using capacitance–voltage measurements under extrinsic illumination are proposed.
GaN MOS-HEMT USING ATOMIC LAYER DEPOSITION Al2O3 AS GATE DIELECTRIC AND SURFACE PASSIVATION
Authors: Ye P. D. , Yang B. , Ng K. K. , Bude J. , Wilk G. D. , Halder S. , Hwang J. C. M.
Published: August 2005

We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic layer deposition (ALD) Al 2 O 3 film as a gate dielectric and for surface passivation simultaneously. Compared to the conventional AlGaN/GaN HEMT of the same design, six order of magnitude smaller gate leakage current and tripled drain current at forward gate bias demonstrate the effectiveness of ALD Al 2 O 3 as a gate dielectric. The high transconductance and high effective two-dimensional electron mobility verify the high-quality of Al 2 O 3/ AlGaN interface with low interface trap density. The Al 2 O 3 passivation effect is also studied by sheet resistance measurement and short pulse drain characterization.
TEMPERATURE DEPENDENT I-V CHARACTERISTICS OF AlGaN/GaN HBTS AND GaN BJTS
Authors: XING HUILI G. , MISHRA UMESH K.
Published: August 2005

DC I-V characteristics of AlGaN/GaN heterojunction bipolar transistors (HBTs) and GaN homojunction bipolar transistors (BJTs) are analyzed in the temperature range of 200-450 K. At low current levels, the adverse effects of poor ohmic contacts coupled with paths of high leakage make it difficult to extract intrinsic device operation ["Explanation of anomalous current gain observed in GaN based bipolar transistors", Xing et al. IEEE Elect. Dev. Lett. 24(1) 2003:p.4-6]. At intermediate current levels, owing to enhanced ionization of Mg in the base, the HBTs show an increase in current gain resulting from mitigated current crowding, and the BJTs show a decrease in current gain resulting from reduction of emitter injection coefficient. The offset voltage dependence on temperature is also explained.
ANALYSIS OF HIGH DC CURRENT GAIN STRUCTURES FOR GaN/InGaN/GaN HBTs
Authors: LI JAMES C. , KEOGH DAVID M. , RAYCHAUDHURI SOUROBH , CONWAY ADAM , QIAO DONGJIANG , ASBECK PETER M.
Published: August 2005

AlGaN/GaN HBTs with DC current gains in excess of 10 have been demonstrated; however, Makimoto et al have recently obtained a DC current gain value exceeding 2000 for a GaN/InGaN/GaN triple mesa DHBT.1,2,3 The experimental demonstration of a GaN -based HBT with such extraordinary DC current gain has motivated the search for new device structures conducive to high DC current gain. Simulations in this work indicate that high DC current gain is difficult to achieve with a uniform, defect-free base layer. We also simulate the electrical characteristics of a new class of DHBT where the base layer is non-uniform. By non-uniformly thinning or perforating the base, the majority of the base would remain thick to minimize the negative impact to base resistance. However, small thinned regions achieve extremely high DC current gain, which can be used to significantly increase the overall DC current gain. This device structure could naturally occur when "V" defects form or Indium is non-uniformly distributed during the base layer growth. The sensitivity of DC current gain to the base thickness range, duty cycle, defect geometry, and defect type is also investigated.
LEAKY SURFACE ACOUSTIC WAVES IN SINGLE-CRYSTAL AlN SUBSTRATE
Authors: BU GANG , CIPLYS DAUMANTAS , SHUR MICHAEL S. , SCHOWALTER LEO J. , SCHUJMAN SANDRA B. , GASKA REMIS
Published: August 2005

We report on the velocity V and the electromechanical coupling coefficient K2 of the first and the second leaky surface acoustic waves in various propagation directions in the a-plane AlN single-crystal. For c-propagation direction, the second leaky wave exhibited the velocity of 11016 m/s and K2 of 0.45%. For this direction, the temperature coefficient of frequency was found to be -30 ppm/°C. A near match of the velocities of the plane and leaky waves in the a-plane AlN allowed us to establish analytical relationships between the piezoelectric and elastic constants. A full set of elastic and piezoelectric constants of AlN has been evaluated by fitting the measured and calculated dependencies of velocities and electromechanical coupling coefficients on the propagation direction for both Rayleigh and leaky waves.
HIGH-VOLTAGE DIAMOND SCHOTTKY RECTIFIERS
Authors: HUANG W. , CHOW T. P. , YANG J. , BUTLER J. E.
Published: August 2005

In this paper, we simulate and fabricate diamond schottky rectifiers. The growth rate of pure diamond single crystal epitaxial is from 0.5 up to 100μm/hr with boron doping concentration around 1 × 1014 cm -3 to 1 × 1016 cm -3. A "liftoff" technology is used to provide the wafer. Theoretical calculation indicates that the diamond shottky rectifier has a significant lower voltage drop than SiC schottky rectifier and comparable with SiC PiN diode with the blocking voltage higher than 10 kV. A maximum 50 kHz operating frequency at switching voltage 25 kV is shown based on thermal limit. Vertical structure devices with 70μm epi layer achieve 18 A/cm2 at 250°C at 7 V forward drop as shown with a breakdown voltage of only 600 V. A breakdown voltage of 8 kV at 100μm distance is recorded for lateral structure devices without ohmic contact (back to back Schottky diodes), 12.4 kV at 300μm distance.
2 KV 4H-SiC DMOSFETS FOR LOW LOSS, HIGH FREQUENCY SWITCHING APPLICATIONS
Authors: RYU SEI-HYUNG , KRISHNASWAMI SUMI , DAS MRINAL , RICHMOND JAMES , ANANT AGARWAL ANANT , PALMOUR JOHN , SCOFIELD JAMES
Published: August 2005

Due to the high critical field in 4 H - SiC , the drain charge and switching loss densities in a SiC power device are approximately 10X higher than that of a silicon device. However, for the same voltage and resistance ratings, the device area is much smaller for the 4 H - SiC device. Therefore, the total drain charge and switching losses are much lower for the 4 H - SiC power device. A 2.3 kV, 13.5 mΩ-cm2 4 H - SiC power DMOSFET with a device area of 2.1 mm × 2.1 mm has been demonstrated. The device showed a stable avalanche at a drain bias of 2.3 kV, and an on-current of 5 A with a VGS of 20 V and a VDS of 2.6 V. Approximately an order of magnitude lower parasitic capacitance values, as compared to those of commercially available silicon power MOSFETs, were measured for the 4 H - SiC power DMOSFET. This suggests that the 4 H - SiC DMOSFET can provide an order of magnitude improvement in switching performance in high speed switching applications.
Precision Measurements of the Semileptonic Charm Decays D0 → π-ℓ+ν and D0 → K-ℓ+ν
Authors:   Representing the CLEO Collaboration., Liu F.
Published: August 2005

We investigate the decays D0 → π-ℓ+ν and D0 → K-ℓ+ν, where ℓ is e or μ, using approximately 7 fb-1 of data collected with the CLEO III detector. We find [Formula: see text]. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and R0 gives [Formula: see text].
Analysis of the Cabbibo Suppressed decay D+ → ρ0μ+ν from FOCUS
Authors:   on behalf of the FOCUS Collaboration., Luiggi Eduardo E.
Published: August 2005

Using data collected by FOCUS, we present a preliminary measurement for the vector meson semileptonic branching ratio [Formula: see text]. Using a sample of 397 ± 42 and 11, 811 ± 151 D+ → ρ0μ+ν and [Formula: see text] events, respectively, we find [Formula: see text].
Analysis of the decays D0 → π-μ+ν and D0 → K-μ+ν in FOCUS
Authors:   On behalf of the FOCUS collaboration., AGOSTINO LORENZO
Published: August 2005

We present a new measurement of the branching ratio of the Cabibbo suppressed decay D0 → π-μ+ν relative to the Cabibbo favored decay D0 → K-μ+ν and an improved measurement of the ratio [Formula: see text]. We also report a new measurement of the q2 dependence of the form factors for D0 → π-μ+ν and D0 → K-μ+ν.
Measurements of Absolute Branching Fractions for Exclusive D0 Semileptonic Decays and Determinations of Vcs and Vcd
Authors:   Representing the CLEO Collaboration., Liu F.
Published: August 2005

Based on a data sample of 60 pb-1 collected at the ψ(3770) resonance with the CLEO-c detector at CESR, we present improved measurements of absolute branching fractions for exclusive D0 semileptonic decays into K-e+ν, π-e+ν and K*-e+ν, and the first observation and measurement of D0 → ρ-e+ν. The determinations of the CKM matrix elements Vcs and Vcd are reviewed.
RECENT RESULTS FROM BES II ψ(2S) DATA
Authors:   Representing the BES Collaboration., GUO ZIJIN
Published: August 2005

Recent results on charmonia decays at BES II are reported, including the measurements of ψ(2S) → Vector-Pseudoscalar, ψ(2S) → Vector-Tensor and [Formula: see text] for a test of the pQCD "12% rule" between ψ(2S) and J/ψ decays; the first observations of χc0 → f0(980)f0(980), [Formula: see text]; and a study of the pentaquark state in ψ(2S) and J/ψ decays.
New Results on Double Charmonium Production in e+e- Annihilation at $\sqrt{s} \approx 10.6~{\rm GeV}$ with the Belle Detector
Authors:   for the Belle Collaboration., Ziegler T.
Published: August 2005

Extending a previous analysis1 the double charmonium production [Formula: see text] and [Formula: see text] has been investigated with a data set of 155 fb-1 with the Belle detector. Theoretical predictions for the cross section are one order of magnitude lower than the measured value and this discrepancy is still not understood. In a very recent update with a dataset of 285 fb-1 strong evidence for a new charmonium state at a mass of 3.940 GeV was found.
SEARCH FOR RADIATIVE PENGUIN DECAYS B+ → ρ+γ, B0 → ρ0γ, AND B0 → ωγ
Authors:   on behalf of BABAR Collaboration., TAN PING
Published: August 2005

A search for the decays B → ρ(770)γ and B0 → ω(782)γ is performed on a sample of 211 million [Formula: see text] events collected by the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring. No evidence for the decays is seen. We set the following limits on the individual branching fractions [Formula: see text], [Formula: see text], and [Formula: see text] at the 90% confidence level (C.L.). We use the quark model to limit the combined branching fraction [Formula: see text] and constrain |Vtd|/|Vts|.
Search for rare leptonic B decays at the Tevatron
Authors: Bernhard Ralf
Published: August 2005

Results of a search for the Flavor-Changing Neutral Current decay [Formula: see text] using [Formula: see text] collision data at [Formula: see text] collected at Fermilab Tevatron collider by the CDF and DØ detectors are presented. CDF reports upper limits on [Formula: see text] and [Formula: see text] at the 95% C.L. using 171 pb-1. The DØ Collaboration used 240 pb-1 to set an even more stringent limit on the branching ratio for [Formula: see text] of 5.0 · 10-7 at the 95% C.L.
Time Dependent Angular Analysis of Bs(d)→ J/ψϕ(K*0) and a measurement of $\frac{\Delta\Gamma_s}{\Gamma_s}$
Authors:   For CDF Collaboration., Li Ke
Published: August 2005

We present preliminary measurements from a combined analysis of lifetimes and transversity amplitudes for [Formula: see text] and [Formula: see text] and present the first direct measurement of the width difference in [Formula: see text] system using 260 pb-1CDF Run II data. For [Formula: see text], we obtain [Formula: see text], [Formula: see text], [Formula: see text]. The [Formula: see text] decay amplitudes and lifetime are also measured.
Study of the B → Xcℓν Decays and Determination of |Vcb|
Authors:   representing the BABAR Collaboration., Golubev Vladimir
Published: August 2005

We report studies of semileptonic decays, B → Xcℓν, based on a sample of 88 million [Formula: see text] events recorded with the BABAR detector. We have measured four moments of the electron energy and hadronic mass distributions and determined the inclusive branching fraction, the CKM matrix element |Vcb|, and other heavy quark parameters, using Heavy Quark Expansions in the kinetic mass scheme. In addition, we have studied a large sample of B0 → D*-ℓ+ν decays and extracted the decay form factors and |Vcb|.
PARITY-EVEN AND PARITY-ODD MESONS IN COVARIANT LIGHT-FRONT APPROACH
Authors: Cheng Hai-Yang
Published: August 2005

Decay constants and form factors for parity-even (s-wave) and parity-odd (p-wave) mesons are studied within a covariant light-front approach. The three universal Isgur-Wise functions for heavy-to-heavy meson transitions are obtained.
B meson wave function in kT factorization
Authors: Liao Hui-Shih
Published: August 2005

We construct a valid definition of the kT-dependent B meson wave function, and then calculate next-to-leading-order corrections. We show that the B meson wave function remains normalizable after taking into account renormalization-group evolution effects, contrary to the observation derived from the collinear factorization theorem.
PROPERTIES OF HEAVY MESON STATES: B** and Bc
Authors:   For the DØ Collaboration., CHEU ELLIOTT
Published: August 2005

Using data collected with the DØ detector in Run II of the Tevatron, we study decays of the B** and [Formula: see text] meson. For the first time the separation of the specific excited states B1 and [Formula: see text] has been observed. In addition, we use the Bc candidates to measure the mass and the lifetime of the Bc.
First Observation of the DsJ(2632) Meson
Authors:   for the SELEX Collaboration., Russ James S.
Published: August 2005

The SELEX Collaboration has announced the first observation of a massive, narrow resonance in the charm-strange system. Seen both in D S η and D 0 K + final states, the meson is unusual both in that it is very narrow despite being far above the strong decay threshold and also in that the [Formula: see text]. Production is also unusual, with a large asymmetry favoring [Formula: see text] over [Formula: see text] production from the Σ- beam.
MEASURING $\mathcal{B}(D^+ \to \mu^+ \nu)$ AND THE PSEUDOSCALAR DECAY CONSTANT fD+
Authors:   Representing the CLEO Collaboration., Menaa N.
Published: August 2005

In 60 pb-1 of data taken on the ψ(3770) resonance with the CLEO-c detector, we find 8 D+ → μ+ν- event candidates that are mostly signal, containing only 1 estimated background. Using this statistically compelling sample, we measure the value of [Formula: see text], and determine fD+ = (198 ± 41 ± 17) MeV .