bluuebunny/crossref_metadata_2025 huggingface dataset:
Large transport-induced operation limits of tokamak plasmas
Authors: Guzdar P. N. , Kleva R. G. , Kaw P. K. , Singh R. , LaBombard B. , Greenwald M.
Published: February 2007

The two-dimensional phase space of tokamak edge plasmas identified in the numerical simulations by B. Rogers et al. [Phys. Rev. Lett. 81, 4396 (1998)] provides a unique prescription for the various regimes of operation of tokamak plasmas. Recent observations on Alcator C-Mod of these regimes, identified in terms of the above-mentioned phase-space parameters, is found to be in very good agreement with simulation results of Rogers et al. In this phase space, they identified a boundary at high collisionality that defines a region that is operationally inaccessible owing to very large transport in the edge region of the tokamaks. A second boundary at moderate to low collisionality is also indicated and associated with the transition between the low-confinement mode and the high-confinement mode. The high collisionality boundary is of particular interest since it appears to be fundamentally related to the empirical “density limit” that is observed in tokamaks. In this Letter, we provide a theory that determines the conditions necessary for very high transport and hence the origin of the inaccessible “density limit” in the two-dimensional phase space.
Electrical and optical measurements on the first SCUBA-2 prototype 1280pixel submillimeter superconducting bolometer array
Authors: Woodcraft Adam L. , Ade Peter A. R. , Bintley Dan , House Julian S. , Hunt Cynthia L. , Sudiwala Rashmi V. , Doriese William B. , Duncan William D. , Hilton Gene C. , Irwin Kent D. , Reintsema Carl D. , Ullom Joel N. , Audley Michael D. , Ellis Maureen A. , Holland Wayne S. , MacIntosh Mike , Dunare Camelia C. , Parkes William , Walton Anthony J. , Kycia Jan B. , Halpern Mark , Schulte Eric
Published: February 2007

SCUBA-2 is a submillimeter camera being built for the James Clerk Maxwell Telescope in Hawaii. Bringing CCD style imaging to the submillimeter for the first time, with over 10000pixels, it will provide a revolutionary improvement in sensitivity and mapping speed. We present results of the first tests on a prototype 1280pixel SCUBA-2 subarray; the full instrument will be made up of eight such subarrays. The array is made up of transition edge sensor (TES) detectors, with Mo∕Cu bilayers as the sensing element. To keep the number of wires reasonable, a multiplexed readout is used. Unlike previous TES arrays, an in-focal plane multiplexer configuration is used, in which the multiplexing elements are located beneath each pixel. To achieve the required performance, the detectors are operated at a temperature of approximately 120mK. We describe the results of a basic electrical and optical characterization of the array, demonstrating that it is fully operational. Noise measurements were made on several pixels and gave a noise equivalent power below 2.5×10−17WHZ−0.5, within the requirements for SCUBA-2. The construction of the testbed used to carry out these measurements is also described.
Submicron domain inversion in Mg-doped LiNbO3 using backswitched poling with short voltage pulses
Authors: Chen Yunlin , Yan Weiguo , Wang Dongdong , Chen Shaolin , Zhang Guangyin , Zhu Jiangfeng , Wei Zhiyi
Published: February 2007

The authors describe a technique for fabricating submicron domain inversion structures in MgO:LiNbO3. The method is based on controlled backswitched poling with short voltage pulses. Using this method, short periodic structures consisting of submicron domain patterns have been achieved in Z-cut MgLN crystal. The structure is fully compatible with nonlinear optical integrated waveguide applications. High performance of the submicron domain inversion structure is also demonstrated by evaluating its potential as second harmonic generation.
Equipment for hydrogen absorption-desorption cycling characterization of hydride forming materials
Authors: Meyer G. , Arneodo Larochette P. , Baruj A. , Castro F. J. , Lacharmoise P. , Zacur E. , Talagañis B. A.
Published: February 2007

Hydrogen storage materials suffer different degradation processes when they are cycled, forming and decomposing their associated hydride phases. In order to study these processes, we have designed and built an automated apparatus specifically developed for cycling samples of hydride forming materials by changing the external hydrogen pressure. Instead of the standard open configuration involving a high-pressure, high-quality gas bottle and a vacuum pump, the equipment uses another hydride forming material (in our case LaNi5) as a source and sink of hydrogen. The resulting closed-loop configuration eliminates hydrogen waste and ensures that extremely high purity gas is used during the whole experiment, thanks to the purifying properties of the selected hydride as source/sink. Hydrogen pressure is set by changing the source/sink temperature. Cycles can be performed as fast as one cycle every 5min, a period comparable with typical good hydride forming material kinetics. An example of application of the apparatus is given for 1000 absorption/desorption cycles on a Mm0.8Ca0.2Ni5 sample.
Noncontact deep level photo-thermal spectroscopy: Technique and application to semi-insulating GaAs Wafers
Authors: Xia Jun , Mandelis Andreas
Published: February 2007

A purely optical deep level photothermal spectroscopy has been developed for the defect-state characterization of semi-insulating (SI) GaAs wafers. The methodology utilizes near infrared sub-band-gap absorption to monitor the thermal emission of traps after an optical filling pulse, and the data are analyzed in a rate-window manner by a lock-in amplifier. The technique has been applied to a vertical-gradient-freeze grown SI-GaAs wafer, and the very first results are presented.
A laboratory based system for Laue micro x-ray diffraction
Authors: Lynch P. A. , Stevenson A. W. , Liang D. , Parry D. , Wilkins S. , Tamura N.
Published: February 2007

A laboratory diffraction system capable of illuminating individual grains in a polycrystalline matrix is described. Using a microfocus x-ray source equipped with a tungsten anode and prefigured monocapillary optic, a micro-x-ray diffraction system with a 10 μm beam was developed. The beam profile generated by the ellipsoidal capillary was determined using the “knife edge” approach. Measurement of the capillary performance, indicated a beam divergence of 14 mrad and a useable energy bandpass from 5.5 to 19 keV. Utilizing the polychromatic nature of the incident x-ray beam and application of the Laue indexing software package X-Ray Micro-Diffraction Analysis Software, the orientation and deviatoric strain of single grains in a polycrystalline material can be studied. To highlight the system potential the grain orientation and strain distribution of individual grains in a polycrystalline magnesium alloy (Mg 0.2 wt % Nd) was mapped before and after tensile loading. A basal (0002) orientation was identified in the as-rolled annealed alloy; after tensile loading some grains were observed to undergo an orientation change of 30° with respect to (0002). The applied uniaxial load was measured as an increase in the deviatoric tensile strain parallel to the load axis.
Nanocrystalline diamond enhanced thickness shear mode resonator
Authors: Williams Oliver A. , Mortet Vincent , Daenen Michael , Haenen Ken
Published: February 2007

A nanocrystalline diamond coated thickness shear mode resonator has been fabricated as an alternative to the quartz crystal microbalance. Due to the low temperature phase transition of quartz, the piezoelectric material was replaced with langasite, a piezoelectric with no phase transition up to its melting point. The resulting device shows clear resonant behavior and oscillates in both air and in liquid. The diamond coating shows clear faceting by scanning electron microscopy and sp3 bonding by Raman spectroscopy.
Tunable giant Faraday rotation of exciton in semiconductor quantum wells embedded in a microcavity
Authors: Liu Jiang-Tao , Chang Kai
Published: February 2007

The Faraday rotation of an exciton in a GaAs quantum well (QW) embedded in a microcavity is investigated theoretically. The authors find that the Faraday rotation is enhanced remarkably by the microcavity, with a magnitude about two orders of magnitude larger than that of a single QW without microcavity. The Faraday rotation can be tuned by changing the incident angle of the pump and probe lights, or by varying the temperature or an external electric field. With an appropriate detuning between the cavity mode of the pump and probe lights, the Faraday rotation spectrum displays a strongly asymmetric line shape, which can easily be detected experimentally.
Electrical property improvements of high-k gate oxide by in situ nitrogen incorporation during atomic layer deposition
Authors: Maeng W. J. , Lim S. J. , Kwon Soon-Ju , Kim H.
Published: February 2007

Atomic layer deposition (ALD) process for oxynitrides of high-k gate dielectrics employing NH4OH as a single source for reactants, water and NH3, was studied. By this method, nitrogen was incorporated up to 1–3at.% for ALD Al2O3 and Ta2O5 films from metal organic precursors. A comparative study with water based ALD showed that the electrical properties were improved. The leakage current of oxide films from NH4OH based ALD had been reduced and, more importantly, the dielectric strength was found to be enhanced by more than two orders of magnitude from a time dependent dielectric breakdown measurement.
Circular polarization from a nonmagnetic p-i-n resonant tunneling diode
Authors: de Carvalho H. B. , Brasil M. J. S. P. , Galvão Gobato Y. , Marques G. E. , Galeti H. V. A. , Henini M. , Hill G.
Published: February 2007

The authors investigate the circular polarization of the electro- and photoluminescence emissions from the quantum well and contact layers of a nonmagnetic GaAs–AlAs p-i-n resonant tunneling diode under an external magnetic field. The contact emission evidences the formation of a spin polarized two-dimensional electron gas at the n-accumulation layer. The quantum well electroluminescence presents a strong σ− degree of polarization, even for null Zeeman splitting energies, and a slight bias dependence. The observed circular polarization is mainly attributed to the spin polarization of the electrons injected into the quantum well from the two-dimensional electron gas.
Marcasite osmium nitride with high bulk modulus: First-principles calculations
Authors: Wang Yuan Xu , Arai Masao , Sasaki Taizo
Published: February 2007

The authors propose marcasite OsN2 as a structure of the experimentally synthesized orthorhombic OsN2 compound. From the first-principles calculations, they find that the marcasite structure is more stable than the fluorite and pyrite ones and its lattice constants are in good agreement with the experiment. The calculated elastic constants for marcasite OsN2 satisfy the stability condition. The band structure shows that marcasite OsN2 is metallic. There is a pseudogap around the Fermi level of the total density of states of marcasite OsN2, which may contribute to its stability. The appearance of the pseudogap is mainly caused by the anisotropic connectivity of OsN6 octahedra.
Influence of cathode sputter deposition on organic solar cells
Authors: Ahlswede Erik , Hanisch Jonas , Powalla Michael
Published: February 2007

The sputter deposition technique is usually avoided for organic solar cells, despite its technological advantages, because it may potentially damage the organic absorber layer. The consequences of sputtering on device performance-presumably related to changes in the absorber morphology and defect distribution near the interface-are discussed. Despite its negative influence on as-deposited samples, sputtering in combination with thermal annealing can actually be beneficial for pure aluminum contacts, leading to efficiencies even better than those of cells with thermally evaporated cathodes, mainly due to an enhanced open-circuit voltage.
Office Buildings and the Signature Architect: Piano and Foster in Sydney
Authors: McNeill Donald
Published: February 2007

In this paper I examine the growing trend in commercial office development of the use of globally operative ‘signature’ architects, famed design leaders who are sought out and contracted to provide design products in cities far from their head office. The engagement of two leading international design firms—Renzo Piano Building Workshop and Foster and Partners—by Australian developers for new Sydney office towers (Aurora Place and 126 Phillip Street, respectively) is analyzed in detail. I identify three areas where the design of office buildings is seen to make a commercial difference: in lubricating the planning-approval process in sensitive urban contexts; in adding value to the building through reconciling urban context and architectural form with commercial development rationalities; and in selling the interior space of the building to prospective commercial tenants.
Reviewing Geographies of Memory/Forgetting
Authors: Legg Stephen
Published: February 2007

In this paper I seek to review the literature regarding the spaces of memory and forgetting outside the geographical core of the Western discipline. This takes in two bodies of literature. First, works from outside the geographical discipline on memory and forgetting, as conceived at both the individual and the collective scale. Second, I move beyond the scope of ‘developed’ countries to look at works on memory in India, where subaltern, communal, and rural memories have been explored.
Uneven Environmental Management: A Canadian Comparative Political Ecology
Authors: Reed Maureen G
Published: February 2007

Contemporary researchers of environmental management argue for community-based approaches in which local circumstances, skills, and concerns are respected. However, relying on local capacity opens up the possibility of establishing highly uneven management practices. The purpose of this paper is to explore the roots and effects of uneven environmental management. I develop a conceptual framework that identifies key elements of regional environmental-management regimes and then use it to compare experiences in two areas designated as Canadian biosphere reserves in 2000: Clayoquot Sound, BC, and Redberry Lake, SK. Analysis reveals that differences in property instruments and civic sectors affect the institutional capacity of each locality, opening the door for private forms of environmental governance in Redberry Lake. To explain how property instruments and civic actors operate, I illustrate how processes associated with property exchange, reterritorialization, valuation, and planning work together to produce a relatively robust and public regime at Clayoquot Sound and a more private form of stewardship at Redberry Lake. In consequence, uneven environmental-management practices may take root and reinforce social inequalities across the two regions.
Molecular Affects in Human Geographies
Authors: McCormack Derek P
Published: February 2007

In this paper I engage critically with the relation between affect and the molecular—the former touching upon but not limited to questions of mood and emotion, and the latter registering the power of processes including, but not limited to, the neurochemical. The backdrop to this engagement is an emerging diagram of the molecular processes and pathways in which affect is implicated. The emergence of this diagram not only foregrounds the importance of thinking critically about how affect is caught up in a range of techniques and technologies: it also raises the question of how to attend to molecular affects—and their implication in the matter and movement of thinking—without falling back upon a kind of biological or physiological reductionism. I provide a provisional answer to this question. In doing so I draw support from a range of thinkers, including Lucretius, Spinoza, Deleuze, and Guattari, each of whom points to the possibility of cultivating a kind of molecular logic of sense. In moving towards a conclusion, I speculate about how this logic productively complicates the thinking space of human geography.
Escherichia coli
enzyme IIA
Ntr
regulates the K
+
transporter TrkA
Authors: Lee Chang-Ro , Cho Seung-Hyon , Yoon Mi-Jeong , Peterkofsky Alan , Seok Yeong-Jae
Published: February 2007

The maintenance of ionic homeostasis in response to changes in the environment is essential for all living cells. Although there are still many important questions concerning the role of the major monovalent cation K
+
, cytoplasmic K
+
in bacteria is required for diverse processes. Here, we show that enzyme IIA
Ntr
(EIIA
Ntr
) of the nitrogen-metabolic phosphotransferase system interacts with and regulates the
Escherichia coli
K
+
transporter TrkA. Previously we reported that an
E. coli
K-12 mutant in the
ptsN
gene encoding EIIA
Ntr
was extremely sensitive to growth inhibition by leucine or leucine-containing peptides (LCPs). This sensitivity was due to the requirement of the dephosphorylated form of EIIA
Ntr
for the derepression of
ilvBN
expression. Whereas the
ptsN
mutant is extremely sensitive to LCPs, a
ptsN trkA
double mutant is as resistant as WT. Furthermore, the sensitivity of the
ptsN
mutant to LCPs decreases as the K
+
level in culture media is lowered. We demonstrate that dephosphorylated EIIA
Ntr
, but not its phosphorylated form, forms a tight complex with TrkA that inhibits the accumulation of high intracellular concentrations of K
+
. High cellular K
+
levels in a
ptsN
mutant promote the sensitivity of
E. coli
K-12 to leucine or LCPs by inhibiting both the expression of
ilvBN
and the activity of its gene products. Here, we delineate the similarity of regulatory mechanisms for the paralogous carbon and nitrogen phosphotransferase systems. Dephosphorylated EIIA
Glc
regulates a variety of transport systems for carbon sources, whereas dephosphorylated EIIA
Ntr
regulates the transport system for K
+
, which has global effects related to nitrogen metabolism.
Molecular determinants for the interaction between AMPA receptors and the clathrin adaptor complex AP-2
Authors: Kastning Kathrin , Kukhtina Viktoria , Kittler Josef T. , Chen Guojun , Pechstein Arndt , Enders Sven , Lee Sang Hyoung , Sheng Morgan , Yan Zhen , Haucke Volker
Published: February 2007

α-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors undergo constitutive and ligand-induced internalization that requires dynamin and the clathrin adaptor complex AP-2. We report here that an atypical basic motif within the cytoplasmic tails of AMPA-type glutamate receptors directly associates with μ2-adaptin by a mechanism similar to the recognition of the presynaptic vesicle protein synaptotagmin 1 by AP-2. A synaptotagmin 1-derived AP-2 binding peptide competes the interaction of the AMPA receptor subunit GluR2 with AP-2μ and increases the number of surface active glutamate receptors in living neurons. Moreover, fusion of the GluR2-derived tail peptide with a synaptotagmin 1 truncation mutant restores clathrin/AP-2-dependent internalization of the chimeric reporter protein. These data suggest that common mechanisms regulate AP-2-dependent internalization of pre- and postsynaptic membrane proteins.
Universal width distributions in non-Markovian Gaussian processes
Authors: Santachiara Raoul , Rosso Alberto , Krauth Werner
Published: February 2007

We study the influence of boundary conditions on self-affine random functions
u(t)
in the interval , with independent Gaussian Fourier modes
q of
variance ∼1/q
α. We consider the probability distribution of the mean square width of
u(t)
taken over the whole interval or in a window . Its characteristic function can be expressed in terms of the spectrum of an
infinite matrix. This distribution strongly depends on the boundary conditions of
u(t) for
finite δ, but we show that it is universal (independent of boundary conditions) in the
small-window limit (, ). We compute it directly for arbitrary
α>1, using,
for α<3, an asymptotic expansion formula that we derive. For
α>3, the limiting width distribution is independent of
α. It corresponds to an infinite matrix with a single non-zero eigenvalue. We give the
exact expression for the width distribution in this case. Our calculation allows us
to extract the roughness exponent from the width distribution of experimental
data even in cases where the standard extrapolation method cannot be used.
Military-Authoritarianism in South America: Brazil, Chile, Uruguay and Argentina
Authors: Philip George
Published: February 2007

In recent years, a number of South American countries have been subjected to durable military governments. This phenomenon was not at all foreseen twenty years ago. Four different approaches have been adopted to try to explain this resurgence of authoritarian rule. These have related it to economic change, seen it as a reaction against uncontrolled social mobilization, regarded it as a corporatist throwback to earlier Latin American forms of rule, and related it to changes in South American military institutions after the Cuban Revolution. All four hypotheses will be examined and found wanting (although all have partial validity). Linz's more general paradigm of authoritarian rule is then examined, broadly accepted but found to be excessively static. Finally a more complex ‘two track’ hypothesis is put forward relating to the political evolution of military-authoritarian regimes.
Pharmacological dissection of the human gastro‐oesophageal segment into three sphincteric components
Authors: Brasseur James G. , Ulerich Rhys , Dai Qing , Patel Dalipkumar K. , Soliman Ahmed M. S. , Miller Larry S.
Published: February 2007

Quantifications of gastro‐oesophageal anatomy in cadavers have led some to identify the lower oesophageal sphincter (LOS) with the anatomical gastric sling‐clasp fibres at the oesophago‐cardiac junction (OCJ). However, in vivo studies have led others to argue for two overlapping components proximally displaced from the OCJ: an extrinsic crural sphincter of skeletal muscle and an intrinsic physiological sphincter of circular smooth‐muscle fibres within the abdominal oesophagus. Our aims were to separate and quantify in vivo the skeletal and smooth muscle sphincteric components pharmacologically and clarify the description of the LOS. In two protocols an endoluminal ultrasound‐manometry assembly was drawn through the human gastro‐oesophageal segment to correlate sphincteric pressure with the anatomic crus. In protocol I, fifteen normal subjects maintained the costal diaphragm at inferior/superior positions by full inspiration/expiration (FI/FE) during pull‐throughs. These were repeated after administering atropine to suppress the cholinergic smooth‐muscle sphincter. The cholinergic component was reconstructed by subtracting the atropine‐resistant pressures from the full pressures, referenced to the anatomic crus. To evaluate the extent to which the cholinergic contribution approximated the full smooth‐muscle sphincter, in protocol II seven patients undergoing general anaesthesia for non‐oesophageal pathology were administered cisatracurium to paralyse the crus. The smooth‐muscle sphincter pressures were measured after lung inflation to approximate FI. The cholinergic smooth‐muscle pressure profile in protocol I (FI) matched closely the post‐cisatracurium smooth‐muscle pressure profile in protocol II, and the atropine‐resistant pressure profiles correlated spatially with the crural sling during diaphragmatic displacement. Thus, the atropine‐resistant and cholinergic pressure contributions in protocol I approximated the skeletal and smooth muscle sphincteric components. The smooth‐muscle pressures had well‐defined upper and lower peaks. The upper peak overlapped and displaced rigidly with the crural sling, while the distal peak separated from the crus/upper‐peak by 1.1 cm between FI and FE. These results suggest the existence of separate upper and lower intrinsic smooth‐muscle components. The ‘upper LOS’ overlaps and displaces with the crural sling consistent with a physiological LOS. The distal smooth‐muscle pressure peak defines a ‘lower LOS’ that likely reflects the gastric sling/clasp muscle fibres at the OCJ. The distinct physiology of these three components may underlie aspects of normal sphincteric function, and complexity of sphincter dysfunction.
Persistent inward currents in rat ventral horn neurones
Authors: Theiss Renée D. , Kuo Jason J. , Heckman C. J.
Published: February 2007

Throughout the mammalian spinal cord, interneurones have been shown to exhibit distinct firing patterns in response to a step of injected current. In this study of ventral horn interneurones in a thick slice preparation of the lumbar cord of 11–19‐day‐old‐rats, four distinct firing patterns were observed and classified as repetitive‐firing, repetitive/burst, initial‐burst or single‐spiking. The hypothesis that a persistent sodium current was the predominant determinant of cell firing behaviour was investigated. A slow voltage ramp was used to assess persistent inward currents (PICs). Cells with repetitive‐firing patterns had significantly larger PICs than cells displaying repetitive/burst, initial‐burst or single‐spiking patterns. Repetitive‐firing, repetitive/burst and initial‐burst‐firing cells were reduced to a single‐spiking pattern with the application of riluzole, which also markedly reduced the persistent sodium current. Persistent sodium current was found to account for most of the PIC with only a small contribution from L‐type calcium current. These results suggest that the persistent sodium current plays a major role in determining firing patterns in these cells.
Network oscillations and intrinsic spiking rhythmicity do not covary in monkey sensorimotor areas
Authors: Witham Claire L. , Baker Stuart N.
Published: February 2007

We investigated the relationship between local field potential (LFP) oscillations and intrinsic spiking rhythmicity in the sensorimotor system, because intrinsic rhythmicity has the potential to enhance network oscillations. LFPs and 918 single units were recorded from primary motor cortex (M1), primary somatosensory cortex (S1, areas 3a and 2), posterior parietal cortex (area 5) and the deep cerebellar nuclei (DCN). Some cells were antidromically identified as pyramidal tract neurons (PTNs). In each area the power of ∼20 Hz LFP oscillations was assessed during periods of steady holding, when such oscillations have previously been shown to be maximal in M1. Oscillations were strongest in area 5 and weakest in the DCN. Using a previously developed method, the postspike distance‐to‐threshold trajectory was determined from the interspike interval histogram for each cell. Many cells had significant peaks, suggesting an intrinsic tendency towards rhythmic firing. Surprisingly, trajectory peaks were most common for M1 PTNs (115/146 cells) and rarest for area 5 neurons (12/82 cells). The extent of intrinsic spiking rhythmicity is not therefore simply related to the strength of 20 Hz oscillations in the sensorimotor system. These results suggest that intrinsic rhythmicity is not required for the generation and maintenance of oscillatory activity.
Alterations in endothelial control of the pulmonary circulation in exercising swine with secondary pulmonary hypertension after myocardial infarction
Authors: Merkus Daphne , Houweling Birgit , De Beer Vincent J. , Everon Zaida , Duncker Dirk J.
Published: February 2007

Secondary pulmonary hypertension after myocardial infarction (MI) has been associated with endothelial dysfunction and activation of the endothelin (ET) system. Here, we investigated whether an increased ET‐mediated pulmonary vasoconstrictor influence contributes to pulmonary hypertension after MI, and whether this increased ET vasoconstriction is caused by impaired nitric oxide (NO) and prostanoid production. For this purpose, chronically instrumented swine with and without MI ran on a treadmill at 0–4 km h−1. Mixed ETA/ETBreceptor blockade (tezosentan) was performed in the absence and presence of single or combined inhibition of endothelial NO synthase (eNOS, withNω‐nitro‐l‐arginine) and cyclo‐oxygenase (COX, with indometacin). In normal swine, mixed ETA/ETBblockade decreased pulmonary vascular resistance, but only during exercise. In MI swine, an increased ET‐mediated vasoconstrictor influence was observed in the pulmonary circulation both at rest and during exercise. Inhibition of COX resulted in pulmonary vasoconstriction at rest in MI, but not in normal swine; this vasoconstriction in MI swine was normalized by ETA/ETBreceptor blockade. Inhibition of eNOS enhanced the vasodilator response to ETA/ETBblockade, indicating that NO blunts the pulmonary vasoconstrictor influence of ET. However, this vasodilator response was enhanced to a similar degree in MI and normal swine. In summary, swine with a recent MI are characterized by an exaggerated pulmonary vasoconstrictor influence of ET. This increased ET‐mediated pulmonary vasoconstrictor influence is not caused by a loss of NO bioavailability, and is blunted by an increased prostanoid‐mediated vasodilatation. In conclusion, an increased ET‐mediated vasoconstriction, which does not appear to be the result of loss of endothelial vasodilators, contributes to pulmonary hypertension after MI.
Phase-Change Heat Transfer in Microsystems
Authors: Cheng Ping , Wu Hui-Ying , Hong Fang-Jun
Published: February 2007

Recent work on miscroscale phase-change heat transfer, including flow boiling and flow condensation in microchannnels (with applications to microchannel heat sinks and microheat exchangers) as well as bubble growth and collapse on microheaters under pulse heating (with applications to micropumps and thermal inkjet printerheads), is reviewed. It has been found that isolated bubbles, confined elongated bubbles, annular flow, and mist flow can exist in microchannels during flow boiling. Stable and unstable flow boiling modes may occur in microchannels, depending on the heat to mass flux ratio and inlet subcooling of the liquid. Heat transfer and pressure drop data in flow boiling in microchannels are shown to deviate greatly from correlations for flow boiling in macrochannels. For flow condensation in microchannels, mist flow, annular flow, injection flow, plug-slug flow, and bubbly flows can exist in the microchannels, depending on mass flux and quality. Effects of the dimensionless condensation heat flux and the Reynolds number of saturated steam on transition from annular two-phase flow to slug/plug flow during condensation in microchannels are discussed. Heat transfer and pressured drop data in condensation flow in microchannels, at low mass flux are shown to be higher and lower than those predicted by correlations for condensation flow in macrochannels, respectively. Effects of pulse heating width and heater size on microbubble growth and collapse and its nucleation temperature on a microheater under pulse heating are summarized.
Analytical Formulation for the Temperature Profile by Duhamel’s Theorem in Bodies Subjected to an Oscillatory Heat Source
Authors: Wen Jun , Khonsari M. M.
Published: February 2007

An analytical technique is presented for treating heat conduction problems involving a body experiencing oscillating heat flux on its boundary. The boundary heat flux is treated as a combination of many point heat sources, each of which emits heat intermittently based on the motion of the flux. The working function of the intermittent heat source with respect to time is evaluated by using the Fourier series and temperature profile of each point heat source is derived by using the Duhamel’s theorem. Finally, by superposition of the temperature fields over all the point heat sources, the temperature profile due to the original moving heat flux is determined. Prediction results and verification using finite element method are presented for an oscillatory heat flux in a rectangular domain.
Reversal of Neurological Defects in a Mouse Model of Rett Syndrome
Authors: Guy Jacky , Gan Jian , Selfridge Jim , Cobb Stuart , Bird Adrian
Published: February 2007

Rett syndrome is an autism spectrum disorder caused by mosaic expression of mutant copies of the X-linked
MECP2
gene in neurons. However, neurons do not die, which suggests that this is not a neurodegenerative disorder. An important question for future therapeutic approaches to this and related disorders concerns phenotypic reversibility. Can viable but defective neurons be repaired, or is the damage done during development without normal MeCP2 irrevocable? Using a mouse model, we demonstrate robust phenotypic reversal, as activation of MeCP2 expression leads to striking loss of advanced neurological symptoms in both immature and mature adult animals.
Eccentric treatment for patellar tendinopathy: a prospective randomised short-term pilot study of two rehabilitation protocols
Authors: Frohm Anna , Saartok Tönu , Halvorsen Kjartan , Renström Per
Published: February 2007

Objective:To compare the efficacy and safety of two eccentric rehabilitation protocols for patients with symptomatic patellar tendinopathy. A new eccentric overload training device was compared with the present standard eccentric rehabilitation programme on a decline board.

Design:Prospective, randomised clinical trial.

Setting:Sports rehabilitation clinic, university sports laboratory, supplemented with home exercises.

Patients:20 competitive and recreational athletes, all with clinical diagnosis of patellar tendinopathy, verified by MRI or ultrasound imaging.

Interventions:A 12-week rehabilitation period, either with bilateral eccentric overload strength training using the Bromsman device twice a week or with unilateral eccentric body load training using a decline board twice a week, supplemented with daily home exercises.

Outcome measures:The primary outcome was pain and function, assessed by the Swedish Victorian Institute of Sport Assessment for Patella (VISA-P) score. Secondary outcome measures were isokinetic muscle torque, dynamic function and muscle flexibility, as well as pain level estimations using visual analogue scale (VAS). Side effects were registered.

Results:Both treatment groups improved in the short term according to the VISA-P scores during the 12-week rehabilitation period. However, there were no significant differences between the groups in terms of pain and function. After a 3-month rehabilitation period, most patients could be regarded as improved enough to be able to return to training and sports. No serious side effects were detected in either group.

Conclusion:In patients with patellar tendinopathy pain, two-legged eccentric overload training twice per week, using the new device (Bromsman), was as efficient and safe as the present standard daily eccentric one-legged rehabilitation-training regimen using a decline board.
Automated external defibrillators in Washington State high schools
Authors: Rothmier Justin D , Drezner Jonathan A , Harmon Kimberly G
Published: February 2007

Background:The placement of automated external defibrillators (AEDs) in schools and public sporting venues is a growing national trend.

Objective:To determine the prevalence and use of AEDs in Washington State high schools and to examine the existing emergency preparedness for sudden cardiac arrest (SCA).

Design:Cross-sectional survey.

Setting:High schools in Washington State.

Participants:The principal at each high school in the Washington Interscholastic Activities Association (n = 407) was invited to complete a web-based questionnaire using the National Registry for AED Use in Sports (http://www.AEDSPORTS.com).

Main outcome measurements:The primary outcome measures studied included AED prevalence and location, funding for AEDs, AED training of school personnel, coordination of AED placement with local emergency response agencies, and prior AED use.

Results:118 schools completed the survey (29% response rate). 64 (54%) of the schools have at least one AED on school grounds (mean 1.6, range 1–4). The likelihood of AED placement increased with larger school size (p = 0.044). 60% of AEDs were funded by donations, 27% by the school district and 11% by the school or athletic department itself. Coaches (78%) were the most likely to receive AED training, followed by administrators (72%), school nurses (70%) and teachers (48%). Only 25% of schools coordinated the implementation of AEDs with an outside medical agency and only 6% of schools coordinated with the local emergency medical system. One school reported having used an AED previously to treat SCA in a basketball official who survived after a single shock. The estimated probability of AED use to treat SCA was 1 in 154 schools per year.

Conclusions:Over half of Washington State high schools have an AED on school grounds. AED use occurred in <1% of schools annually and was effective in the treatment of SCA. Funding of AED programmes was mostly through private donations, with little coordination with local emergency response teams. Significant improvement is needed in structuring emergency response plans and training targeted rescuers for an SCA in the high-school setting.
Citius and longius (faster and longer) with no α-actinin-3 in skeletal muscles?
Authors: Lucia Alejandro , Oliván Jesús , Gómez-Gallego Félix , Santiago Catalina , Montil Marta , Foster Carl
Published: February 2007

The muscle protein α-actinin-3 (ACTN3) is normally thought to be expressed in type II muscle fibres and to be necessary for high-power, high-velocity muscle contractions, such as those typically seen in speed/power athletes. The authors report the case of a Spanish elite long jumper (two times Olympian, personal best of 8.26 m) whose genotype for theACTN3gene is577XX(ACTN3 deficient). These data suggest that there might be notable exceptions to the concept thatACTN3is the “gene for speed”.
Using nitric oxide to treat tendinopathy
Authors: Murrell George A C
Published: February 2007

Nitric oxide (NO) is a small free radical generated by a family of enzymes, the nitric oxide synthases (NOSs). Following injury to a tendon, NO is induced by all three isoforms of NOS and NOS activity is also upregulated in tendinopathy. In animal models when NOS activity is inhibited by competitive inhibitors of NOS, tendon healing is reduced. When additional NO is added, tendon healing is enhanced. In humans, in three randomised clinical trials, we have shown that NO delivered via a transdermal patch enhances the subjective and objective recovery of patients with tennis elbow, Achilles tendinosis and supraspinatus tendinosis.
HYBRID TWO SCALES MATHEMATICAL TOOLS FOR ACTIVE PARTICLES MODELLING COMPLEX SYSTEMS WITH LEARNING HIDING DYNAMICS
Authors: CATTANI C. , CIANCIO A.
Published: February 2007

This paper deals with the derivation of hybrid mathematical structures to describe the behavior of large systems of active particles by ordinary differential equations with stochastic coefficients whose evolution is modelled by equations of the mathematical kinetic theory. A preliminary analysis shows how the above tools can be used to model complex systems of interest in applied sciences, with special attention to the immune competition.
QUASISTATIC PROBLEMS IN VISCOPLASTICITY THEORY II: MODELS WITH NONLINEAR HARDENING
Authors: ALBER HANS-DIETER , CHEŁMIŃSKI KRZYSZTOF
Published: February 2007

The existence theory to an internal variable model for viscoelastic or viscoplastic solids at small strain is studied. The model consists of an initial–boundary value problem to a system of linear partial differential equations coupled with nonlinear ordinary differential equations. It belongs to the subclass of monotone type models, which typically describe solids with rate dependent behavior exhibiting nonlinear hardening. The monotone type class includes all generalized standard materials. Solutions are found in Lp and [Formula: see text], the proof is based on monotonicity properties.
ON A HIERARCHY OF APPROXIMATE MODELS FOR FLOWS OF INCOMPRESSIBLE FLUIDS THROUGH POROUS SOLIDS
Authors: RAJAGOPAL K. R.
Published: February 2007

The celebrated equations due to Fick and Darcy are approximations that can be obtained systematically on the basis of numerous assumptions within the context of mixture theory; the equations however not having been developed in such a manner by Fick or Darcy. Relaxing the assumptions made in deriving these equations via mixture theory selectively leads to a hierarchy of mathematical models and it can be shown that popular models due to Brinkman, Biot and many others can be obtained via various approximations. It is shown that a variety of other generalizations are possible in addition to those that are currently in favor, and these might be appropriate for describing interesting technological applications.
STEADY-STATE SOLUTIONS AND ASYMPTOTIC LIMITS ON THE MULTI-DIMENSIONAL SEMICONDUCTOR QUANTUM HYDRODYNAMIC MODEL
Authors: LIANG BO , ZHANG KAIJUN
Published: February 2007

In this paper we study the steady-state quantum hydrodynamic model for semiconductors. The existence of solutions on the bipolar QHD model is obtained in the case of sufficiently small relaxation time. Uniqueness results are showed both in the thermal equilibrium states and the scaled Planck constant being large enough. The relaxation time and dispersive limit are performed on the bipolar and unipolar equations, respectively. In a sense, we have made a complete answer to the original unsolved problems of the steady-state QHD model.
COMBINING ADJOINT STABILIZED METHODS FOR THE ADVECTION-DIFFUSION-REACTION PROBLEM
Authors: HAUKE GUILLERMO , SANGALLI GIANCARLO , DOWEIDAR MOHAMED H.
Published: February 2007

Computational methods for the advection-diffusion-reaction transport equation are still a challenge. Although there exist globally stable methods, oscillations around sharp layers such as boundary, inner and outflow layers, are typical in multi-dimensional flows. In this paper a variational formulation that combines two types of stabilization integrals is proposed, namely an adjoint stabilization and a gradient adjoint stabilization. Two free parameters are chosen by imposing one-dimensional superconvergence. Then, when applied to multi-dimensional flows, the method presents better local stability than the present stabilized methods. Furthermore, in the advective-diffusive limit and for piecewise linear functional spaces, the method recovers the classical SUPG method.
Anthrax Toxin: Receptor Binding, Internalization, Pore Formation, and Translocation
Authors: Young John A.T. , Collier R. John
Published: February 2007

Anthrax toxin consists of three nontoxic proteins that self-assemble at the surface of receptor-bearing mammalian cells or in solution, yielding a series of toxic complexes. Two of the proteins, called Lethal Factor (LF) and Edema Factor (EF), are enzymes that act on cytosolic substrates. The third, termed Protective Antigen (PA), is a multifunctional protein that binds to receptors, orchestrates the assembly and internalization of the complexes, and delivers them to the endosome. There, the PA moiety forms a pore in the endosomal membrane and promotes translocation of LF and EF to the cytosol. Recent advances in understanding the entry process include insights into how PA recognizes its two known receptors and its ligands, LF and EF; how the PA:receptor interaction influences the pH-dependence of pore formation; and how the pore functions in promoting translocation of LF and EF across the endosomal membrane.
The Nonsense-Mediated Decay RNA Surveillance Pathway
Authors: Chang Yao-Fu , Imam J. Saadi , Wilkinson Miles F.
Published: February 2007

Nonsense-mediated mRNA decay (NMD) is a quality-control mechanism that selectively degrades mRNAs harboring premature termination (nonsense) codons. If translated, these mRNAs can produce truncated proteins with dominant-negative or deleterious gain-of-function activities. In this review, we describe the molecular mechanism of NMD. We first cover conserved factors known to be involved in NMD in all eukaryotes. We then describe a unique protein complex that is deposited on mammalian mRNAs during splicing, which defines a stop codon as premature. Interaction between this exon-junction complex (EJC) and NMD factors assembled at the upstream stop codon triggers a series of steps that ultimately lead to mRNA decay. We discuss whether these proofreading events preferentially occur during a “pioneer” round of translation in higher and lower eukaryotes, their cellular location, and whether they can use alternative EJC factors or act independent of the EJC.
Mitochondrial-Nuclear Communications
Authors: Ryan Michael T. , Hoogenraad Nicholas J.
Published: February 2007

Mitochondria cannot be made de novo but replicate by a mechanism of recruitment of new proteins, which are added to preexisting subcompartments. Although mitochondria have their own DNA, more than 98% of the total protein complement of the organelle is encoded by the nuclear genome. Mitochondrial biogenesis requires a coordination of expression of two genomes and therefore cross talk between the nucleus and mitochondria. In mammals, regulation of mitochondrial biogenesis and proliferation is influenced by external factors, such as nutrients, hormones, temperature, exercise, hypoxia, and aging. This complexity points to the existence of a coordinated and tightly regulated network connecting different pathways. Communications are also required for eliciting mitochondrial responses to specific stress pathways. This review covers the mechanisms of mitochondrial biogenesis and the way cells respond to external signals to maintain mitochondrial function and cellular homeostasis.
Membrane Protein Structure: Prediction versus Reality
Authors: Elofsson Arne , Heijne Gunnar von
Published: February 2007

Since high-resolution structural data are still scarce, different kinds of theoretical structure prediction algorithms are of major importance in membrane protein biochemistry. But how well do the current prediction methods perform? Which structural features can be predicted and which cannot? And what can we expect in the next few years?
Biochemistry and Physiology of Cyclic Nucleotide Phosphodiesterases: Essential Components in Cyclic Nucleotide Signaling
Authors: Conti Marco , Beavo Joseph
Published: February 2007

Although cyclic nucleotide phosphodiesterases (PDEs) were described soon after the discovery of cAMP, their complexity and functions in signaling is only recently beginning to become fully realized. We now know that at least 100 different PDE proteins degrade cAMP and cGMP in eukaryotes. A complex PDE gene organization and a large number of PDE splicing variants serve to fine-tune cyclic nucleotide signals and contribute to specificity in signaling. Here we review some of the major concepts related to our understanding of PDE function and regulation including: (a) the structure of catalytic and regulatory domains and arrangement in holoenzymes; (b) PDE integration into signaling complexes; (c) the nature and function of negative and positive feedback circuits that have been conserved in PDEs from prokaryotes to human; (d) the emerging association of mutant PDE alleles with inherited diseases; and (e) the role of PDEs in generating subcellular signaling compartments.
DNA Replication and Transcription in Mammalian Mitochondria
Authors: Falkenberg Maria , Larsson Nils-Göran , Gustafsson Claes M.
Published: February 2007

The mitochondrion was originally a free-living prokaryotic organism, which explains the presence of a compact mammalian mitochondrial DNA (mtDNA) in contempory mammalian cells. The genome encodes for key subunits of the electron transport chain and RNA components needed for mitochondrial translation. Nuclear genes encode the enzyme systems responsible for mtDNA replication and transcription. Several of the key components of these systems are related to proteins replicating and transcribing DNA in bacteriophages. This observation has led to the proposition that some genes required for DNA replication and transcription were acquired together from a phage early in the evolution of the eukaryotic cell, already at the time of the mitochondrial endosymbiosis. Recent years have seen a rapid development in our molecular understanding of these machineries, but many aspects still remain unknown.