bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic field measurements in laser-produced plasmas via proton deflectometry
Authors: Cecchetti C. A. , Borghesi M. , Fuchs J. , Schurtz G. , Kar S. , Macchi A. , Romagnani L. , Wilson P. A. , Antici P. , Jung R. , Osterholtz J. , Pipahl C. A. , Willi O. , Schiavi A. , Notley M. , Neely D.
Published: April 2009

Large magnetic fields generated during laser-matter interaction at irradiances of ∼5×1014 W cm−2 have been measured using a deflectometry technique employing MeV laser-accelerated protons. Azimuthal magnetic fields were identified unambiguously via a characteristic proton deflection pattern and found to have an amplitude of ∼45 T in the outer coronal region. Comparison with magnetohydrodynamic simulations confirms that in this regime the ∇⃗Te×∇⃗ne source is the main field generation mechanism, while additional terms are negligible.
Spectroscopic study of NH-tautomerism in novel cycloketo-tetraphenylporphyrins
Authors: Ermilov Eugeny A. , Büge Bettina , Jasinski Stefan , Jux Norbert , Röder Beate
Published: April 2009

The NH-tautomerism is a fundamental property of all metal-free porphyrins. In the present study it was investigated for three novel nonsymmetrical cycloketo-tetraphenylporphyrins in isotropic solutions. The combination of steady-state absorption and fluorescence techniques with decay-associated fluorescence spectroscopy was demonstrated to be a powerful tool to bring into light the photophysical properties of individual NH-tautomers even at room temperature. For all investigated free-base porphyrins, the equilibrium concentration of one tautomer, named T1, which has a lower frequency of the S0,0→S1,0 transition, was found to be higher than the concentration of the other tautomer, named T2, even at room temperature. Lowering the temperature enriches the population of tautomer T1 and it becomes dominant in absorption and fluorescence. The fluorescence decay time of tautomer T1 was found to be approximately three times shorter compared to that of tautomer T2, whereas both tautomers have similar fluorescence quantum yields. In contrast only one conformation exists for zinc cycloketo-porphyrin, which was used as reference compound.
Compressed ion temperature gradient turbulence in diverted tokamak edge
Authors: Chang C. S. , Ku S. , Diamond P. H. , Lin Z. , Parker S. , Hahm T. S. , Samatova N.
Published: April 2009

It is found from a heat-flux-driven full-f gyrokinetic particle simulation that there is ion temperature gradient (ITG) turbulence across an entire L-mode-like edge density pedestal in a diverted tokamak plasma in which the ion temperature gradient is mild without a pedestal structure, hence the normalized ion temperature gradient parameter ηi=(d log Ti/dr)/(d log n/dr) varies strongly from high (>4 at density pedestal top/shoulder) to low (<2 in the density slope) values. Variation of density and ηi is in the same scale as the turbulence correlation length, compressing the turbulence in the density slope region. The resulting ion thermal flux is on the order of experimentally inferred values. The present study strongly suggests that a localized estimate of the ITG-driven χi will not be valid due to the nonlocal dynamics of the compressed turbulence in an L-mode-type density slope. While the thermal transport and the temperature profile saturate quickly, the E×B rotation shows a longer time damping during the turbulence. In addition, a radially in-out mean potential variation is observed.
Porous plug gas injection systems for studies of hydrocarbon dissociation and transport in the DIII-D tokamak
Authors: McLean A. G. , Davis J. W. , Stangeby P. C. , Brooks N. H. , Ellis R. M. , Haasz A. A. , Rudakov D. L. , West W. P. , Whyte D. G. , Wong C. P. C.
Published: April 2009

A probe has been designed, constructed, and successfully used to inject methane into the DIII-D lower divertor in a manner imitating natural release by chemical erosion. This porous plug injector (PPI) probe consists of a self-contained gas reservoir with an integrated pressure gauge and a 3 cm diameter porous surface through which gas is injected into the lower divertor of the tokamak. The probe is positioned flush with the divertor target surface by means of the divertor materials evaluation system. Two gas delivery systems were developed: in the first, gas flow is regulated by a remotely controlled microvalve and in the second by a fixed micro-orifice flow restrictor. Because of the large area of the porous surface through which gas is admitted, the injected hydrocarbon molecules see a local carbon surface (>90% carbon) similar to that seen by hydrocarbons being emitted by chemical sputtering from surrounding carbon tiles. The distributed gas source also reduces the disturbance to the local plasma while providing sufficient signal for spectroscopic detection. In situ spectroscopic measurements with the PPI in DIII-D allow the direct calibration of response for measured plasma conditions from a known influx of gas.
Thermopower of Co-doped FeSe
Authors: Thomas Evan Lyle , Wong-Ng Winnie , Phelan Daniel , Millican Jasmine N.
Published: April 2009

The effect of cobalt doping on the thermopower of the superconductor FeSe is investigated through electrical and thermal transport measurements. Our results point to the destruction of superconductivity at very low Co concentrations. Thermopower data suggest negative charge carriers along with a large enhancement of the Seebeck coefficient, S, on the order of ≈−80 μV/K near T=100 K.
Ion beam shaping of Au nanoparticles in silica: Particle size and concentration dependence
Authors: Dawi E. A. , Rizza G. , Mink M. P. , Vredenberg A. M. , Habraken F. H. P. M.
Published: April 2009

Irradiation with swift heavy ions of spherical Au nanoparticles confined within a silica matrix shapes them into prolate nanorods and nanowires whose principal axes are aligned along the beam direction. In the present paper, we investigate the role that is played by the initial nanoparticle size and concentration in this so-called ion-shaping mechanism. We have produced silica films wherein Au nanoparticles with average diameters of 15, 30, and 45 nm were embedded within a single plane and have irradiated these films at 300 K at normal incidence with 18, 25, and 54 MeV Ag ions. We demonstrate the existence of both threshold and saturation fluences for the elongation effects mentioned. The values of these critical fluences depend both on the ion energy and the initial nanoparticle size. Moreover, we show that 45 nm Au particles are not deformed when irradiated with 18 MeV Ag ions, such that this value corresponds to an energy threshold for the deformation process. As far as the influence of the nanoparticle concentration on the shaping characteristics is concerned, we have found that above the critical irradiation fluence, the deformation effect becomes very sensitive to the initial concentration of the nanoparticles.
Efficiency of light emission in high aluminum content AlGaN quantum wells
Authors: Shatalov Max , Yang Jinwei , Sun Wenhong , Kennedy Robert , Gaska Remis , Liu Kai , Shur Michael , Tamulaitis Gintautas
Published: April 2009

High quality multiple quantum well Al0.35Ga0.65N active layers with narrow wells designed for ultraviolet (UV) light-emitting diodes using the phonon engineering approach are characterized using quasi-steady-state and time-resolved photoluminescence spectroscopy. The photoluminescence intensity decrease with temperature increasing from 10to300K was very small, and the upper limit of the internal quantum efficiency (IQE) of up to 70% was estimated based on this temperature dependence. Carrier lifetime measurements yielded the lower bound of the IQE to be ∼35% under optical pumping, whereas IQE of ∼25% was estimated from the measured external quantum efficiency and the light extraction efficiency calculated by ray tracing. The observed photoluminescence features and the high IQE are interpreted as a consequence of strong carrier (exciton) localization.
Size effects of the bending stiffness of nanowires
Authors: Li Xian-Fang , Wang Bao-Lin , Lee Kang Yong
Published: April 2009

This paper studies the size effect in the transverse deformation of nanowires or nanoropes subjected to flexural bending. Based on the classic strain-gradient theory, a continuum approach is proposed, in which the strain energy was expressed in terms of the linear strains and strain gradients, and two additional phenomenological internal parameters were introduced. The governing equation for the flexural deformation of the nanowires was derived according to the principle of minimum potential energy. In particular, the deformations of the nanowires under two support conditions were determined explicitly, i.e., a cantilever nanowire and a fixed nanowire. Numerical examples were demonstrated to indicate the dependence of the effective modulus and bending stiffness upon the nanowire diameter and aspect ratio. The predictions given by the present model are consistent very well with the experimental measurements reported in the recent literature. The proposed model can be further used to explain the size effect in other properties of nanowires such as dynamics and thermal properties, among others.
The effect of trap density on the space charge formation in polymeric photorefractive composites
Authors: Oh Jin-Woo , Lee Choongkeun , Kim Nakjoong
Published: April 2009

The effect of trap density on the space charge formation of polymeric photorefractive (PR) composites was studied using the modified Schildkraut differential equation. The densities of electrons, holes, and traps, as well as the rates of generation, recombination, trapping, and detrapping are examined. The steady-state and temporal behaviors of photocurrent and space charge field (Esc) formation dependence on the trap density are also discussed. The charge transport dynamics influenced by the presence of the trap molecules controls the formation of Esc via charge trapping, charge detrapping, and charge recombination. Experimental studies of photocurrent and Esc in poly[methyl-3-(9-carbazolyl) propylsiloxane]-based polymeric PR composites were carried out to demonstrate the applicability of the model.
Structure, dynamics, and rheology of colloid-polymer mixtures: From liquids to gels
Authors: Laurati M. , Petekidis G. , Koumakis N. , Cardinaux F. , Schofield A. B. , Brader J. M. , Fuchs M. , Egelhaaf S. U.
Published: April 2009

We investigate the structural, dynamical, and viscoelastic properties of colloid-polymer mixtures at intermediate colloid volume fraction and varying polymer concentrations, thereby tuning the attractive interactions. Within the examined range of polymer concentrations, the samples varied from fluids to gels. In the liquid phase, an increasing correlation length of the density fluctuations when approaching the gelation boundary was observed by static light scattering and microscopy, indicating clustering and formation of space-spanning networks. Simultaneously, the correlation function determined by dynamic light scattering decays completely, indicating the absence of dynamical arrest. Clustering and formation of transient networks when approaching the gelation boundary is supported by significant changes in the viscoelastic properties of the samples. Upon increasing the polymer concentration beyond the gelation boundary, the rheological properties changed qualitatively again, now they are consistent with the formation of colloidal gels. Our experimental results, namely, the location of the gelation boundary as well as the elastic (storage) and viscous (loss) moduli, are compared to different theoretical models. These include consideration of the escape time as well as predictions for the viscoelastic moduli based on scaling relations and mode coupling theories.
Effect of polymer-filler interaction strengths on the thermodynamic and dynamic properties of polymer nanocomposites
Authors: Goswami Monojoy , Sumpter Bobby G.
Published: April 2009

The structural and dynamical properties of polymer nanocomposites are investigated using stochastic molecular dynamics simulations. For spherical nanoparticles dispersed in a polymer matrix, the results indicate that the polymer-nanoparticle interaction strength and the overall system temperature are primarily responsible for the type of dispersed state (clustering and homogeneous dispersion) achieved. A systematic study probing temperature, polymerization, and polymer-nanoparticle and nanoparticle-nanoparticle interaction strengths has been performed. In this paper, however, we focus the discussion on the results for varying polymer-nanoparticle interaction strengths at different temperatures. By examining the structure and dynamics, we show that there are two kinds of “clustering transitions:” one due to thermodynamic and another due to the dynamical response of the system. From these results, a representative phase diagram is developed that captures the entire simulated space and allows the easy identification of the highly dispersed and the clustered states.
Single-scan measurement of conductance of a quartz crystal microbalance array coupled with resonant markers for biosensing in liquid phase
Authors: Hsiao Hsien-Yi , Chen Richie L. C. , Cheng Tzong-Jih
Published: April 2009

This work presents a method for sensing the viscoelastic property of liquid/solid interface using a quartz crystal microbalance (QCM) array. Each sensor in a QCM array has a unique resonant frequency and can be identified by a single-scan measurement of admittance (or impedance). The resonant frequency encoding at each sensor in an array was realized by connecting a capacitor with a known capacitance, called a resonant marker, to the sensor in series. Changes in the resonant frequency of all sensors in an array can be determined using an impedance analyzer and a program that determines the frequencies at which the conductance is at a local maximum. The sensing method allows every sensor output (resonant frequency) to be obtained without the use of time-consuming multiplexed hardware and software. Adsorptions of biomolecules by multiple sensor are monitored in the liquid phase to demonstrate the feasibility of frequency encoding using resonant markers and the single-scan measurement of conductance of a QCM array.
Behavior of oxygen vacancies in BiFeO3/SrRuO3/SrTiO3(100) and DyScO3(100) heterostructures
Authors: Yuan G. L. , Uedono A.
Published: April 2009

(001)-oriented BiFeO3 and SrRuO3 films were deposited on SrTiO3 and DyScO3 substrates to study oxygen-vacancy density as a function of cooling oxygen pressure. During cooling of as-grown samples at ≤0.01 Torr oxygen pressure, SrRuO3 films decompose, BiFeO3 films can accommodate a significant fraction of oxygen vacancies, SrTiO3 substrates acts as a sink for vacancies, and DyScO3 substrates remaining largely unaffected by oxygen vacancies. These phenomena can be explained according to the electronegativity of the different B-site atoms, because changes in B-site ion valence play a key role in maintaining charge equilibrium during oxygen vacancy production in many ABO3-type oxides.
Determination of the room temperature thermal conductivity of RuO2 by the photothermal deflection technique
Authors: Ferizović Dino , Hussey Lindsay K. , Huang Ying-Sheng , Muñoz Martin
Published: April 2009

A thermal conductivity study of RuO2 single crystals has been carried out via the photothermal deflection technique in transverse configuration at room temperature. The thermal diffusivity and conductivity of RuO2 crystals are determined to be 0.17 cm2 s−1 and 0.50 W cm−1 K−1, respectively. Furthermore, it was found that the thermal conductivity has inversely proportional temperature dependence in the region between 50 and 300 K.
Effectiveness of prescribed fire as a fuel treatment in Californian coniferous forests
Authors: Vaillant Nicole M. , Fites-Kaufman Jo Ann , Stephens Scott L.
Published: April 2009

Effective fire suppression and land use practices over the last century have altered forest structure and increased fuel loads in many forests in the United States, increasing the occurrence of catastrophic wildland fires. The most effective methods to change potential fire behavior are to reduce surface fuels, increase the canopy base height and reduce canopy bulk density. This multi-tiered approach breaks up the continuity of surface, ladder and crown fuels. Effectiveness of fuel treatments is often shown indirectly through fire behavior modeling or directly through monitoring wildland fire effects such as tree mortality. The present study investigates how prescribed fire affected fuel loads, forest structure, potential fire behavior, and modeled tree mortality at 90th and 97.5th percentile fire weather conditions on eight National Forests in California. Prescription burning did not significantly change forest structure at most sites. Total fuel loads (litter, duff, 1, 10, 100, and 1000-h) were reduced by 23 to 78% across the sites. The reduction in fuel loads altered potential fire behavior by reducing fireline intensity and increasing torching index and crowning index at most sites. Predicted tree mortality decreased after treatment as an effect of reduced potential fire behavior and fuel loads. To use limited fuel hazard reduction resources efficiently, more effort could be placed on the evaluation of existing fire hazards because several stands in the present study had little potential for adverse fire effects before prescribed fire was applied.
The influence of leaf water content and isoprenoids on flammability of some Mediterranean woody species
Authors: De Lillis Manuela , Bianco Pietro Massimiliano , Loreto Francesco
Published: April 2009

The impact of water content and isoprenoids on leaf flammability was studied. Field and laboratory experiments were carried out on monoterpene-emitting evergreen broad-leaved species (Quercus ilex, Quercus suber); a needle-leaved species (Pinus halepensis) that emits and stores monoterpenes; an evergreen species (Myrtus communis) that emits isoprene but stores monoterpenes; and a deciduous species (Quercus pubescens) that emits isoprene. Photosynthesis, leaf water content (LWC) and isoprenoid emission were measured. Isoprenoid content was calculated. Temperatures of visible smoke, incandescence and flame appearance were recorded. The LWC significantly correlated with both photosynthesis and isoprenoid emissions. Linear correlation and factorial analysis revealed a positive correlation between temperature of flame appearance and LWC and a negative relationship between temperature of flame appearance and isoprenoid emission. Multiple regression analysis indicated that the temperature of flame appearance was reduced in broadleaved monoterpene-emitting species. In monoterpene emitters, the temperature of flame appearance depended for ~65% on LWC, whereas monoterpene emissions explained ~35% of the dependency. P. halepensis and M. communis, storing high levels of isoprenoids, ignited at high humidity. The results may be explained if isoprenoids indeed facilitate leaf ignition but, being dissolved in water, isoprenoids are also an indicator of a high water content that decreases flammability.
Loss of T-tubules and other changes to surface topography in ventricular myocytes from failing human and rat heart
Authors: Lyon Alexander R. , MacLeod Ken T. , Zhang Yanjun , Garcia Edwin , Kanda Gaelle Kikonda , Lab Max J. , Korchev Yuri E. , Harding Sian E. , Gorelik Julia
Published: April 2009

T-tubular invaginations of the sarcolemma of ventricular cardiomyocytes contain junctional structures functionally coupling L-type calcium channels to the sarcoplasmic reticulum calcium-release channels (the ryanodine receptors), and therefore their configuration controls the gain of calcium-induced calcium release (CICR). Studies primarily in rodent myocardium have shown the importance of T-tubular structures for calcium transient kinetics and have linked T-tubule disruption to delayed CICR. However, there is disagreement as to the nature of T-tubule changes in human heart failure. We studied isolated ventricular myocytes from patients with ischemic heart disease, idiopathic dilated cardiomyopathy, and hypertrophic obstructive cardiomyopathy and determined T-tubule structure with either the fluorescent membrane dye di-8-ANNEPs or the scanning ion conductance microscope (SICM). The SICM uses a scanning pipette to produce a topographic representation of the surface of the live cell by a non-optical method. We have also compared ventricular myocytes from a rat model of chronic heart failure after myocardial infarction. T-tubule loss, shown by both ANNEPs staining and SICM imaging, was pronounced in human myocytes from all etiologies of disease. SICM imaging showed additional changes in surface structure, with flattening and loss of Z-groove definition common to all etiologies. Rat myocytes from the chronic heart failure model also showed both T-tubule and Z-groove loss, as well as increased spark frequency and greater spark amplitude. This study confirms the loss of T-tubules as part of the phenotypic change in the failing human myocyte, but it also shows that this is part of a wider spectrum of alterations in surface morphology.
ChlH, the H subunit of the Mg-chelatase, is an anti-sigma factor for SigE in
Synechocystis
sp. PCC 6803
Authors: Osanai Takashi , Imashimizu Masahiko , Seki Asako , Sato Shusei , Tabata Satoshi , Imamura Sousuke , Asayama Munehiko , Ikeuchi Masahiko , Tanaka Kan
Published: April 2009

Although regulation of sigma factors has been intensively investigated, anti-sigma factors have not been identified in oxygenic photosynthetic organisms. A previous study suggested that the sigma factor, SigE, of the cyanobacterium
Synechocystis
sp. PCC 6803, a positive regulator of sugar catabolism, is posttranslationally activated by light-to-dark transition. In the present study, we found that the H subunit of Mg-chelatase ChlH interacts with sigma factor SigE by yeast two-hybrid screening, and immunoprecipitation analysis revealed that ChlH associates with SigE in a light-dependent manner in vivo. We also found that Mg
2+
promotes the interaction of SigE and ChlH and determines their localization in vitro. In vitro transcription analysis demonstrated that ChlH inhibits the transcription activity of SigE. Based on these results, we propose a model in which ChlH functions as an anti-sigma factor, transducing light signals to SigE in a process mediated by Mg
2+
.
Ecdysone signaling regulates the formation of long-term courtship memory in adult
Drosophila melanogaster
Authors: Ishimoto Hiroshi , Sakai Takaomi , Kitamoto Toshihiro
Published: April 2009

Improved survival is likely linked to the ability to generate stable memories of significant experiences. Considerable evidence in humans and mammalian model animals shows that steroid hormones, which are released in response to emotionally arousing experiences, have an important role in the consolidation of memories of such events. In insects, ecdysone is the major steroid hormone, and it is well characterized with respect to its essential role in coordinating developmental transitions such as larval molting and metamorphosis. However, the functions of ecdysone in adult physiology remain largely elusive. Here, we show that 20-hydroxyecdysone (20E), the active metabolite of ecdysone that is induced by environmental stimuli in adult
Drosophila
, has an important role in the formation of long-term memory (LTM). In male flies, the levels of 20E were found to be significantly increased after courtship conditioning, and exogenous administration of 20E either enhanced or suppressed courtship LTM, depending on the timing of its administration. We also found that mutants in which ecdysone signaling is reduced were defective in LTM, and that an elevation of 20E levels was associated with activation of the cAMP response element binding protein (CREB), an essential regulator of LTM formation. Our results demonstrate that the molting steroid hormone ecdysone in adult
Drosophila
is critical to the evolutionarily conserved strategy that is used for the formation of stable memories. We propose that ecdysone is able to consolidate memories possibly by recapturing molecular and cellular processes that are used for normal neural development.
Nanosculpting reversed wavelength sensitivity into a photoswitchable iGluR
Authors: Numano Rika , Szobota Stephanie , Lau Albert Y. , Gorostiza Pau , Volgraf Matthew , Roux Benoit , Trauner Dirk , Isacoff Ehud Y.
Published: April 2009

Photoswitched tethered ligands (PTLs) can be used to remotely control protein function with light. We have studied the geometric and conformational factors that determine the efficacy of PTL gating in the ionotropic glutamate receptor iGluR6 using a family of photoiosomerizable MAG (maleimide-azobenzene-glutamate) PTLs that covalently attach to the clamshell ligand-binding domain. Experiments and molecular dynamics simulations of the modified proteins show that optical switching depends on 2 factors: (
i
) the relative occupancy of the binding pocket in the 2 photoisomers of MAG and (
ii
) the degree of clamshell closure that is possible given the disposition of the MAG linker. A synthesized short version of MAG turns the channel on in either the
cis
or
trans
state, depending on the point of attachment. This yin/yang optical control makes it possible for 1 wavelength of light to elicit action potentials in one set of neurons, while deexciting a second set of neurons in the same preparation, whereas a second wavelength has the opposite effect. The ability to generate opposite responses with a single PTL and 2 versions of a target channel, which can be expressed in different cell types, paves the way for engineering opponency in neurons that mediate opposing functions.
Extensive remyelination of the CNS leads to functional recovery
Authors: Duncan I. D. , Brower A. , Kondo Y. , Curlee J. F. , Schultz R. D.
Published: April 2009

Remyelination of the CNS in multiple sclerosis is thought to be important to restore conduction and protect axons against degeneration. Yet the role that remyelination plays in clinical recovery of function remains unproven. Here, we show that cats fed an irradiated diet during gestation developed a severe neurologic disease resulting from extensive myelin vacuolation and subsequent demyelination. Despite the severe myelin degeneration, axons remained essentially intact. There was a prompt endogenous response by cells of the oligodendrocyte lineage to the demyelination, with remyelination occurring simultaneously. Cats that were returned to a normal diet recovered slowly so that by 3–4 months they were neurologically normal. Histological examination of the CNS at this point showed extensive remyelination that was especially notable in the optic nerve where almost the entire nerve was remyelinated. Biochemical analysis of the diet and tissues from affected cats showed no dietary deficiencies or toxic accumulations. Thus, although the etiology of this remarkable disease remains unknown, it shows unequivocally that where axons are preserved remyelination is the default pathway in the CNS in nonimmune-mediated demyelinating disease. Most importantly, it confirms the clinical relevance of remyelination and its ability to restore function.
Mice lacking doublecortin and doublecortin-like kinase 2 display altered hippocampal neuronal maturation and spontaneous seizures
Authors: Kerjan Géraldine , Koizumi Hiroyuki , Han Edward B. , Dubé Celine M. , Djakovic Stevan N. , Patrick Gentry N. , Baram Tallie Z. , Heinemann Stephen F. , Gleeson Joseph G.
Published: April 2009

Mutations in doublecortin (
DCX
) are associated with intractable epilepsy in humans, due to a severe disorganization of the neocortex and hippocampus known as classical lissencephaly. However, the basis of the epilepsy in lissencephaly remains unclear. To address potential functional redundancy with murin
Dcx
, we targeted one of the closest homologues, doublecortin-like kinase 2 (
Dclk2
). Here, we report that
Dcx
;
Dclk2
-null mice display frequent spontaneous seizures that originate in the hippocampus, with most animals dying in the first few months of life. Elevated hippocampal expression of c-fos and loss of somatostatin-positive interneurons were identified, both known to correlate with epilepsy.
Dcx
and
Dclk2
are coexpressed in developing hippocampus, and, in their absence, there is dosage-dependent disrupted hippocampal lamination associated with a cell-autonomous simplification of pyramidal dendritic arborizations leading to reduced inhibitory synaptic tone. These data suggest that hippocampal dysmaturation and insufficient receptive field for inhibitory input may underlie the epilepsy in lissencephaly, and suggest potential therapeutic strategies for controlling epilepsy in these patients.
Internalization of eNOS and NO delivery to subcellular targets determine agonist-induced hyperpermeability
Authors: Sánchez Fabiola A. , Rana Roshniben , Kim David D. , Iwahashi Toru , Zheng Ruifang , Lal Brajesh K. , Gordon Donna M. , Meininger Cynthia J. , Durán Walter N.
Published: April 2009

The molecular mechanisms of endothelial nitric oxide synthase (eNOS) regulation of microvascular permeability remain unresolved. Agonist-induced internalization may have a role in this process. We demonstrate here that internalization of eNOS is required to deliver NO to subcellular locations to increase endothelial monolayer permeability to macromolecules. Using dominant-negative mutants of dynamin-2 (dyn2K44A) and caveolin-1 (cav1Y14F), we show that anchoring eNOS-containing caveolae to plasma membrane inhibits hyperpermeability induced by platelet-activating factor (PAF), VEGF in ECV-CD8eNOSGFP (ECV-304 transfected cells) and postcapillary venular endothelial cells (CVEC). We also observed that anchoring caveolar eNOS to the plasma membrane uncouples eNOS phosphorylation at Ser-1177 from NO production. This dissociation occurred in a mutant- and cell-dependent way. PAF induced Ser-1177-eNOS phosphorylation in ECV-CD8eNOSGFP and CVEC transfected with dyn2K44A, but it dephosphorylated eNOS at Ser-1177 in CVEC transfected with cav1Y14F. Interestingly, dyn2K44A eliminated NO production, whereas cav1Y14F caused reduction in NO production in CVEC. NO production by cav1Y14F-transfected CVEC occurred in caveolae bound to the plasma membrane, and was ineffective in causing an increase in permeability. Our study demonstrates that eNOS internalization is required for agonist-induced hyperpermeability, and suggests that a mechanism by which eNOS is activated by phosphorylation at the plasma membrane and its endocytosis is required to deliver NO to subcellular targets to cause hyperpermeability.
Population genomic inference of recombination rates and hotspots
Authors: Wang Ying , Rannala Bruce
Published: April 2009

As more human genomic data become available, fine-scale recombination rate variation can be inferred on a genome-wide scale. Current statistical methods to infer recombination rates that can be applied to moderate, or large, genomic regions are limited to approximated likelihoods. Here, we develop a Bayesian full-likelihood method using Markov Chain Monte Carlo (MCMC) to estimate background recombination rates and hotspots. The probability model is inspired by the observed patterns of recombination at several genomic regions analyzed in sperm-typing studies. Posterior probabilities and Bayes factors of recombination hotspots along chromosomes are inferred. For moderate-size genomic regions (e.g., with <100 SNPs), the full-likelihood method is used. Larger regions are split into subintervals (typically each having between 20 and 50 markers). The likelihood is approximated based on the genealogies for each subinterval. The background recombination rates, hotspots, and parameters are evaluated by using a parallel computing approach and assuming shared parameters across the subintervals. Simulation analyses show that our method can accurately estimate the variation in recombination rates across genomic regions. In particular, clusters of hotspots can be distinguished even though weaker hotspots are present. The method is applied to SNP data from the HLA region, the MS32, and chromosome 19.
State Classification for Humanoid Robots
Authors: Yang Jialun , Gao Feng , Shi Lifeng , Jin Zhenlin
Published: April 2009

In this paper, we decouple the motion‐planning problem of humanoid robots into two sub‐problems, namely topological state planning and detailed motion planning. The state classification plays a key role for the first sub‐problem. We propose several basic states, including lying, sitting, standing and handstanding, abstracted from the daily exercises of human beings. Each basic state is classified further from the topological point of view. Furthermore, generalised function (GF) set theory is applied with the aim of analysing the kinematic characteristics of the end effectors for each state, and meaningful names are assigned for each state. Finally a topological state‐planning example is given to show the effectiveness of this methodology. The results show that the large amounts of states can be described using assigned names, which leads to systematic and universal description of the states for humanoid robots.
Pseudohypha budding patterns of Candida albicans
Authors: Veses Verónica , Gow Neil A.R.
Published: April 2009

Pseudohyphal growth of Candida albicans has been recognized as a morphological growth form that exhibits characteristics that are distinct from those of the budding yeast phase and true hyphal form of this pathogenic fungus. In Saccharomyces cerevisiae, pseudohypha growth involves synchronous unipolar cell divisions that are a modification of the bipolar budding pattern of diploid cells. While pseudohyphae of C. albicans also exhibit unipolar cell divisions, live cell imaging demonstrated departures from the normal unipolar pattern. Buds occasionally followed a bipolar or axial budding event in which buds could be formed from the proximal or distal ends of a parent pseudohypha. This extends the known morphological repertoire of cell division patterns in C. albicans pseudohyphal cells.
Protease-dependent versus -independent cancer cell invasion programs: three-dimensional amoeboid movement revisited
Authors: Sabeh Farideh , Shimizu-Hirota Ryoko , Weiss Stephen J.
Published: April 2009

Tissue invasion during metastasis requires cancer cells to negotiate a stromal environment dominated by cross-linked networks of type I collagen. Although cancer cells are known to use proteinases to sever collagen networks and thus ease their passage through these barriers, migration across extracellular matrices has also been reported to occur by protease-independent mechanisms, whereby cells squeeze through collagen-lined pores by adopting an ameboid phenotype. We investigate these alternate models of motility here and demonstrate that cancer cells have an absolute requirement for the membrane-anchored metalloproteinase MT1-MMP for invasion, and that protease-independent mechanisms of cell migration are only plausible when the collagen network is devoid of the covalent cross-links that characterize normal tissues.
Are There Differences in Hospital Cost Between Patients With Nosocomial Methicillin-ResistantStaphylococcus aureusBloodstream Infection and Those With Methicillin-SusceptibleS. aureusBloodstream Infection?
Authors: Ben-David Debby , Novikov Ilya , Mermel Leonard A.
Published: April 2009

Objective.

To examine the impact of methicillin resistance on in-hospital mortality, length of stay, and hospital cost after the onset of nosocomialStaphylococcus aureusbloodstream infection (BSI).

Design.

A retrospective cohort study.

Setting.

A tertiary care hospital in Rhode Island.

Patients.

A cohort of 182 consecutive patients who developed nosocomial BSI due to methicillin-susceptible and methicillin-resistantS. aureus(MSSA and MRSA, respectively)

Results.

Patients with MRSA BSI had a significantly longer total length of hospital and intensive care unit (ICU) stay before the onset of BSI and a higher average daily cost. Compared with ICU patients with MSSA BSI, those with MRSA BSI had a higher median total hospital cost ($42,137 vs $113,852), higher hospital cost after infection ($17,603 vs $51,492), and greater length of stay after infection (10.5 vs 20.5 days). After multivariable adjustment, ICU patients with MRSA BSI had significantly increased total hospital cost, hospital cost after infection, and length of stay after infection. However, using a propensity score approach, we found that, among ICU patients, the difference in cost after infection and the difference in length of stay after infection for MRSA, compared with MSSA BSI, were not significant. The differences among non-ICU patients who developed MRSA or MSSA BSI were not significant after multivariable adjustment or by propensity score.

Conclusions.

On the basis of propensity score, we found that methicillin resistance did not independently increase hospital cost or length of stay after onset ofS. aureusBSI. We believe that use of a propensity score on a comparable subset of patients may be a better method than multivariable adjustment for assessing the impact of methicillin resistance in cohort studies.
Lens-Like Effect in LiNbO3: Fe Photorefractive Crystal
Authors: Xu Jingjun  , Liu Junmin  , Zhang Guangyin  , Liu Simin
Published: April 2009

The lens-like effects, both photorefractive effect and thermo-optical effect, were studied in the LiNbO3: Fe sheet. The threshold light intensity above which the photorefractive effect was overwhelmed by the thermal effect was determined and the thermo-optical coefficient dn/dTis evaluated by the Z-scanning method. The limiting characteristics of LiNbO3: Fe sheet is examined.
Breakpoint regions and homologous synteny blocks in chromosomes have different evolutionary histories
Authors: Larkin Denis M. , Pape Greg , Donthu Ravikiran , Auvil Loretta , Welge Michael , Lewin Harris A.
Published: April 2009

The persistence of large blocks of homologous synteny and a high frequency of breakpoint reuse are distinctive features of mammalian chromosomes that are not well understood in evolutionary terms. To gain a better understanding of the evolutionary forces that affect genome architecture, synteny relationships among 10 amniotes (human, chimp, macaque, rat, mouse, pig, cattle, dog, opossum, and chicken) were compared at <1 human-Mbp resolution. Homologous synteny blocks (HSBs; N = 2233) and chromosome evolutionary breakpoint regions (EBRs; N = 1064) were identified from pairwise comparisons of all genomes. Analysis of the size distribution of HSBs shared in all 10 species' chromosomes (msHSBs) identified three (>20 Mbp) that are larger than expected by chance. Gene network analysis of msHSBs >3 human-Mbp and EBRs <1 Mbp demonstrated that msHSBs are significantly enriched for genes involved in development of the central nervous and other organ systems, whereas EBRs are enriched for genes associated with adaptive functions. In addition, we found EBRs are significantly enriched for structural variations (segmental duplications, copy number variants, and indels), retrotransposed and zinc finger genes, and single nucleotide polymorphisms. These results demonstrate that chromosome breakage in evolution is nonrandom and that HSBs and EBRs are evolving in distinctly different ways. We suggest that natural selection acts on the genome to maintain combinations of genes and their regulatory elements that are essential to fundamental processes of amniote development and biological organization. Furthermore, EBRs may be used extensively to generate new genetic variation and novel combinations of genes and regulatory elements that contribute to adaptive phenotypes.
The outflow tract of the heart in fishes: anatomy, genes and evolution
Authors: Grimes A. C. , Kirby M. L.
Published: April 2009

A large number of congenital heart defects associated with mortality in humans are those that affect the cardiac outflow tract, and this provides a strong imperative to understand its development during embryogenesis. While there is wide phylogenetic variation in adult vertebrate heart morphology, recent work has demonstrated evolutionary conservation in the early processes of cardiogenesis, including that of the outflow tract. This, along with the utility and high reproductive potential of fish species such asDanio rerio,Oryzias latipesetc., suggests that fishes may provide ideal comparative biological models to facilitate a better understanding of this poorly understood region of the heart. In this review, the authors present the current understanding of both phylogeny and ontogeny of the cardiac outflow tract in fishes and examine how new molecular studies are informing the phylogenetic relationships and evolutionary trajectories that have been proposed. The authors also attempt to address some of the issues of nomenclature that confuse this area of research.
Allergic airway inflammation and susceptibility to pneumococcal pneumonia in a murine model with real-timein vivoevaluation
Authors: Kang C-I , Rouse M S , Patel R , Kita H , Juhn Y J
Published: April 2009

The relationship between allergic airway inflammation and pneumococcal pneumonia is not well understood. We assessed susceptibility to experimental pneumococcal pneumonia in mice with and without allergic airway inflammation. Susceptibility to pneumococcal pneumonia was evaluated by challenging mice with a bioluminescent Streptococcus pneumoniae strain after sensitization with ovalbumin (OVA), with subsequent monitoring of pneumococcal infection using real-time photonic imaging. Of 46 OVA-sensitized mice challenged with pneumococci, 13 (28%) developed imaging findings consistent with pneumococcal pneumonia. In comparison, 28 (57%) of 49 non-sensitized control mice developed pneumococcal pneumonia (P = 0·005). While none of the control group developed meningitis (0%, none of 28), two mice in the OVA-sensitized group developed meningitis (15·4%, two of 13) (P = 0·09). The mean bacterial count in the lung was significantly lower in the OVA-sensitized than the non-sensitized group (8·26 ± 0·69 versus 9·21 ± 0·67 log10 colony-forming units (CFU)/g, P = 0·002). There was a trend towards the mean bacterial count in the spleen being higher in the OVA-sensitized versus the non-sensitized group (8·14 ± 0·89 versus 7·45 ± 1·07 log10 CFU/g, P = 0·071). A high level of interleukin (IL)-4 in lung homogenates was associated with risk of pneumococcal infection independent of sensitization with OVA (odds ratio: 49·7, 95% confidence interval 2·92-846·5, per increment of 1·0 pg/ml). In the murine model studied, acute allergic airway inflammation reduced susceptibility to pneumococcal pneumonia. IL-4 may increase the risk of pneumococcal pneumonia independently of allergic airway inflammation.
Evapotranspiration and water use efficiency in a Chesapeake Bay wetland under carbon dioxide enrichment
Authors: LI JIAHONG , ERICKSON JOHN E. , PERESTA GARY , DRAKE BERT G.
Published: April 2009

Wetlands evapotranspire more water than other ecosystems, including agricultural, forest and grassland ecosystems. However, the effects of elevated atmospheric carbon dioxide (CO2) concentration (Ca) on wetland evapotranspiration (ET) are largely unknown. Here, we present data on 12 years of measurements of ET, net ecosystem CO2 exchange (NEE), and ecosystem water use efficiency (EWUE, i.e. NEE/ET) at 13:00–15:00 hours in July and August for a Scirpus olneyi (C3 sedge) community and a Spartina patens (C4 grass) community exposed to ambient and elevated (ambient+340 μmol mol−1) Ca in a Chesapeake Bay wetland. Although a decrease in stomatal conductance at elevated Ca in the S. olneyi community was counteracted by an increase in leaf area index (LAI) to some extend, ET was still reduced by 19% on average over 12 years. In the S. patens community, LAI was not affected by elevated Ca and the reduction of ET was 34%, larger than in the S. olneyi community. For both communities, the relative reduction in ET by elevated Ca was directly proportional to precipitation due to a larger reduction in stomatal conductance in the control plants as precipitation decreased. NEE was stimulated about 36% at elevated Ca in the S. olneyi community but was not significantly affected by elevated Ca in S. patens community. A negative correlation between salinity and precipitation observed in the field indicated that precipitation affected ET through altered salinity and interacted with growth Ca. This proposed mechanism was supported by a greenhouse study that showed a greater Ca effect on ET in controlled low salinity conditions compared with high salinity. In spite of the differences between the two communities in their responses to elevated Ca, EWUE was increased about 83% by elevated Ca in both the S. olneyi and S. patens communities. These findings suggest that rising Ca could have significant impacts on the hydrologic cycles of coastal wetlands.
Nurse prescriber–patient consultations: a case study in dermatology
Authors: Courtenay Molly , Carey Nicola , Stenner Karen
Published: April 2009

Title.  Nurse prescriber–patient consultations: a case study in dermatology.

Aim.  This paper is a report of a study exploring the content and processes in consultations between nurse prescribers and patients with dermatological conditions.

Background.  Communication skills, consultation time, information and follow‐up are central to the treatment and management of patients with dermatological conditions. The contribution nurses make to the care of these patients has great potential.

Method.  A multiple case study was conducted with 10 practice settings across England in which nurses prescribed medicines for patients with dermatological conditions. Data were collected between June 2006 and September 2007 using semi‐structured interviews (n = 40), patient questionnaires (n = 165/200) and videotaped observations of nurse consultations (n = 40). Data analysis included thematic analysis, descriptive statistics, chi‐square and non‐parametric tests.

Findings.  Nurses believed that their holistic approach to assessment, combined with their prescribing knowledge, improved prescribing decisions. Listening and explanation of treatments were aspects of nurse communication that were rated highly by patients. Listening and dealing sensitively with emotions were also aspects of the videotaped consultations that were rated highly by assessors. Nurses were less consistent in providing information about medicines.

Conclusion.  Triangulated data from this study suggest that nurse prescribing enhances the care of patients with dermatological conditions through improved prescribing decisions. If patients are to be more involved in this decision‐making, nurses must give them more information about their medicines. The benefits of prescribing were most evident in the practices of dermatology specialist nurses. Further evidence is required to identify whether prescribing by specialist nurses offers similar benefits in other therapeutic areas.