bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivation of Frank-Ericksen elastic coefficients for polydomain nematics from mean-field molecular theory for anisotropic particles
Authors: Kröger Martin , Ilg Patrick
Published: July 2007

The complete free energy density, including all eight Frank-Ericksen elastic coefficients and all anisotropic Ericksen-Leslie viscosities of nematic and discotic polydomain nematic liquid crystals are derived from the kinetic model of a spatially inhomogeneous system of uniaxial liquid crystal molecules with given shape. The authors take into account the known anisotropy of the translational diffusion tensor and its dependence on shape, rotational diffusion, and a macroscopic flow field for elongated particles (including disks). In this manuscript they release all of the previously made assumptions about closure relationships or the interrelationship between Frank elastic coefficients (such as a simple quadratic closure, or the one-constant approximation) in order to derive results which not only generalize or improve earlier results, but also apply to more general cases, and for arbitrary forms of the mean-field potential in terms of the scalar order parameter (or temperature). The kinetic model is shown to confirm all proposed inequalities between Frank-Ericksen-Leslie coefficients, i.e., satisfies the main result of the macroscopic approaches. They resolve quantitatively the effect of molecular shape, order parameters, and mean-field strength and form of the mean-field potential on all results, compare with experimental findings, theoretical predictions, and discuss some implications for various special cases of the general result derived in this work.
Concentration fluctuations in nonisothermal reaction-diffusion systems
Authors: Ortiz de Zárate José M. , Sengers Jan V. , Bedeaux Dick , Kjelstrup Signe
Published: July 2007

In this paper a simple reaction-diffusion system, namely a binary fluid mixture with an association-dissociation reaction between the two components, is considered. Fluctuations at hydrodynamic spatiotemporal scales when a temperature gradient is present in this chemically reacting system are studied. First, fluctuating hydrodynamics when the system is in global equilibrium (isothermal) is reviewed. Comparing the two cases, an enhancement of the intensity of concentration fluctuations in the presence of a temperature gradient is predicted. The nonequilibrium concentration fluctuations are spatially long ranged, with an intensity depending on the wave number q. The intensity exhibits a crossover from a ∝q−4 to a ∝q−2 behavior depending on whether the corresponding wavelength is smaller or larger than the penetration depth of the reacting mixture. This opens a possibility to distinguish between diffusion- or activation-controlled regimes of the reaction by measuring these fluctuations. In addition, the possible observation of these fluctuations in nonequilibrium molecular dynamics simulations is considered.
Deformed multivariable Fokker-Planck equations
Authors: Ho Choon-Lin , Sasaki Ryu
Published: July 2007

In this paper new multivariable deformed Fokker-Planck (FP) equations are presented. These deformed FP equations are associated with the Ruijsenaars–Schneider–van Diejen (RSvD)-type systems in the same way that the usual one-variable FP equation is associated with the one-particle Schrödinger equation. As the RSvD systems are the “discrete” counterparts of the celebrated exactly solvable many-body Calogero-Sutherland-Moser systems, the deformed FP equations presented here can be considered as discrete deformations of the ordinary multivariable FP equations.
Extensions to the likelihood maximization approach for finding reaction coordinates
Authors: Peters Baron , Beckham Gregg T. , Trout Bernhardt L.
Published: July 2007

This paper extends our previous work on obtaining reaction coordinates from aimless shooting and likelihood maximization. We introduce a simplified version of aimless shooting and a half-trajectory likelihood score based on the committor probability. Additionally, we analyze and compare the absolute log-likelihood score for perfect and approximate reaction coordinates. We also compare the aimless shooting and likelihood maximization approach to the earlier genetic neural network (GNN) approach of Ma and Dinner [J. Phys. Chem. B 109, 6769 (2005)]. For a fixed number of total trajectories in the GNN approach, the accuracy of the transition state ensemble decreases as the number of trajectories per committor probability estimate increases. This quantitatively demonstrates the benefit of individual committor probability realizations over committor probability estimates. Furthermore, when the least squares score of the GNN approach is applied to individual committor probability realizations, the likelihood score still provides a better approximation to the true transition state surface. Finally, the polymorph transition in terephthalic acid demonstrates that the new half-trajectory likelihood scheme estimates the transition state location more accurately than likelihood schemes based on the probability of being on a transition path.
Line-tied kink modes in cylindrical equilibria with magnetic shear
Authors: Delzanno G. L. , Evstatiev E. G. , Finn J. M.
Published: July 2007

The method described by Evstatiev et al. [Phys. Plasmas 13, 072902 (2006)] to study the linear stability of line-tied modes in cylindrical geometry is applied to screw pinch equilibria with magnetic shear. The method is based on an expansion in eigenfunctions which depend on radius, and for ideal magnetohydrodynamics (MHD) the inclusion in the expansion of singular eigenfunctions (originating from a continuum) is necessary. The method is also applied to study scaling laws for large cylinder lengths L. It is found that the width of the internal layer of the radial displacement for the line-tied mode scales asymptotically as L−2, consistent with the so-called two-mode approximation. This result is valid in the context of both ideal and resistive MHD and is obtained both analytically and numerically.
Numerical verification of the generalized Crooks nonequilibrium work theorem for non-Hamiltonian molecular dynamics simulations
Authors: Chelli Riccardo , Marsili Simone , Barducci Alessandro , Procacci Piero
Published: July 2007

The generalized Crooks theorem (GCT) for deterministic non-Hamiltonian molecular dynamics simulations [Phys. Rev. E 75, 050101 (2007)] connects the probabilities of nonequilibrium realizations switching the system between two thermodynamic states, to the partition functions of these states. In comparison to the “classical” Crooks nonequilibrium work theorem [J. Stat. Phys. 90, 1481 (1998)], which deals with realizations involving only mechanical work, the GCT also accounts for additional work resulting from changes of the intensive and extensive thermodynamic variables of the system. In this article we present a numerical verification of the GCT using a Lennard-Jones fluid model where two particles are subject to a time-dependent external potential. Moreover, in order to switch the system between different thermodynamic states, the temperature and the pressure (or volume), which are controlled through the Martyna-Tobias-Klein equations of motion [J. Chem. Phys. 101, 4177 (1994)], are also varied externally. The free energy difference between states characterized by different distances of the target particles is evaluated using both a standard methodology (pair radial distribution functions) and the GCT. In order to exploit the various options provided by the GCT approach, i.e., the possibility of temperature/pressure/volume changes during the realizations, the free energy difference is recovered via arbitrary thermodynamic cycles. In all tests, the GCT is quantitatively verified.
Magnetoresistance in Sr2FeMoO6:x glass composites
Authors: Sui Yu , Zhang Xingquan , Wang Xianjie , Cheng Jinguang , Su Wenhui , Tang Jinke
Published: July 2007

The effects of interfacial states on the temperature dependence of the magnetoresistance (MR) of Sr2FeMoO6-glass composites have been studied. X-ray diffraction analyses show that the glass is most likely located at the grain boundary without causing a change of the crystal structure of Sr2FeMoO6. The variation of the resistance with temperature and magnetic field indicates that the added glass layer has profound influence on the MR properties. At low temperature, the MR in low fields is enhanced notably because the insulating barrier for the intergranular tunneling is improved by adding the glass layer at the grain surface. However, at high temperature, the MR decreases rapidly with the increase of temperature due to, in addition to the enhancement of spin-independent hopping of electrons through the localized states, the fast decay of spin polarization at the surfaces of the grains. This decay is induced by the separation of the ferromagnetic grains with the nonmagnetic glass layer at the grain boundaries.
Charging of fast spinning spheroidal satellites in sunlight
Authors: Tautz Maurice , Lai Shu T.
Published: July 2007

We present models for a fast spinning, dielectric coated, spheroidal (prolate or oblate) spacecraft charging in sunlight. This work is a generalization of previous treatments of sunlight charging of spherical satellites. The main difference is that the spacecraft geometry can be characterized by a shape parameter that sets the aspect ratio of the spheroids. The models are based on an expansion of the Laplacian potentials external to the spacecraft surface in terms of products of standard Legendre polynomials, describing the polar angle dependence, and modified Legendre functions of the second kind, representing the “radial” behavior. The potential distributions are discussed relative to the corresponding monopole-dipole and monopole-quadrupole configurations in spherical geometry. A Taylor expansion is developed for the potentials when the shape parameter is large (the spherical limit) and expressions are also given in the opposite limit, when the shape parameter goes to zero. As in the spherical case, the potentials produce photosheath barriers which act to block escaping photoelectrons and lead to current balance, allowing sunlight charging to high negative levels. The sheath barrier location and height are calculated numerically, for a wide range of shape parameters. Contour plots are given to depict the potential distributions for sunlight charging of prolate and oblate spheroids at a representative aspect ratio.
External quantum efficiency versus charge carriers mobility in polythiophene/methanofullerene based planar photodetectors
Authors: Caironi M. , Agostinelli T. , Natali D. , Sampietro M. , Cugola R. , Catellani M. , Luzzati S.
Published: July 2007

The paper studies the role of electrons and holes mobility in determining the external quantum efficiency (EQE) in photodetectors based on a 1:1 in weight blend of poly(3-hexylthiophene) (P3HT) and C61-butyric acid methyl ester (PCBM). In order to fairly correlate the optoelectronic properties (efficiency and transient photocurrent) measured on photodetectors with the transport properties measured on field effect transistors, the photodetectors and the transistors have been produced with an identical planar geometry, where in both cases the charges flow occurs in the same direction with respect to the substrate. The measurements have been performed on devices based on pristine P3HT, on pristine PCBM, and on P3HT:PCBM 1:1 blend, before and after annealing, and have revealed the importance of a balanced carrier transport, showing that quantum efficiency increases as long as the mobility of electrons, which are the slowest carrier, increases. On the other end, the response time is mainly affected by the extension of the effective area.
A robust polarization-spectral method for determination of twisted liquid crystal layer parameters
Authors: Yakovlev D. A. , Chigrinov V. G.
Published: July 2007

An experimental method for determining the configurational and optical parameters of the liquid crystal (LC) layers with a twisted structure is proposed. This method provides the determination of the twist angle and orientation of LC structures as well as the spectral dependence of the LC layer retardation. These parameters are estimated from the polarized transmission spectra of LC cell, which are measured using the polarizer-sample-analyzer scheme. In contrast to known methods, the proposed method is insensitive to the presence of moderate anisotropic losses in LC cell (usually, the loss anisotropy is a consequence of the multibeam interference in the thin-layer system including the LC layer); furthermore, the proposed method does not use the small birefringence approximation. The accuracy of the method under various experimental conditions is estimated by numerical modeling.
Rubrene polycrystalline transistor channel achieved through in situ vacuum annealing
Authors: Park Se-W. , Jeong S. H. , Choi Jeong-M. , Hwang Jung Min , Kim Jae Hoon , Im Seongil
Published: July 2007

The authors report on the rubrene polycrystalline film growth for its thin film transistor (TFT) applications. Amorphous rubrene thin film was initially obtained on 200-nm-thick SiO2∕Si substrate at 40°C in a vacuum chamber by thermal evaporation but in situ long time postannealing at the elevated temperatures of 60–80°C transformed the amorphous phase into crystalline. Based on an optimum condition to cover the whole channel area with polycrystalline film, the authors have fabricated a rubrene TFT with a relatively high field effect mobility of 0.002cm2∕Vs, an on/off ratio of ∼104, and a low threshold voltage of −9V.
Ferromagnetic resonance saturation and second order Suhl spin wave instability processes in thin Permalloy films
Authors: Olson Heidi M. , Krivosik Pavol , Srinivasan Kumar , Patton Carl E.
Published: July 2007

High power ferromagnetic resonance (FMR) loss versus static field H profiles and the corresponding spin wave instability threshold microwave field amplitude hcrit vs H butterfly curves were measured for in-plane magnetized thin Permalloy films of thicknesses 35, 57, 74, 104, and 123nm at a nominal pumping frequency of 9.11GHz. Cavity loading and calibration issues that proved to be problematic in past attempts to obtain accurate resonance saturation data over the full FMR profile in ferrites and metal films were resolved through a careful decoupling of the pump field and a full cavity response calibration. The FMR profiles show a drop in the loss peak, a shift in the peak to lower field, a broadening, and the development of a foldover-like asymmetry as the power is increased. The butterfly curves show a minimum hcrit at the low power FMR field and a smooth rounded increase on either side, except for a small kink on the low field side associated with the shift and asymmetry development. Apart from the kink, the second order Suhl spin wave instability theory, suitably modified for thin films, provided good fits to the butterfly curve data through the use of a single spin wave linewidth ΔHk value for each data set. The ΔHk values ranged from 16to35Oe, with the implied critical mode in-plane wave vectors always directed parallel to the static field. These spin wave linewidths translate into Gilbert damping parameter αk values in the 0.002–0.005 range, the same order as expected for intrinsic magnon-electron scattering losses in metal ferromagnets. These αk values are about a factor of 2 smaller than those implied by the low power FMR linewidths. The FMR in-plane precession cone angles at threshold were on the order of 3°–6°.
Alkali metals in perylene-3,4,9,10-tetracarboxylicdianhydride thin films
Authors: Wüsten J. , Heimer K. , Lach S. , Ziegler Ch.
Published: July 2007

n -type doping of the molecular organic semiconductor perylene-3,4,9,10-tetracarboxylicdianhydride (PTCDA) by sodium, potassium, and cesium was carried out. The chemical properties of the doping processes were investigated by means of x-ray photoemission and infrared absorption spectroscopy. Simultaneously the evolution of the occupied electronic states around the transport gap was monitored by ultraviolet photoemission spectroscopy. It was found that the doping ratio depends on the ionization energy of the alkali metal, in particular if compared with the highest occupied molecular orbital ionization energy of the formed alkali-PTCDA complex. Additionally, only in the case of cesium doping, an averaged ratio of two alkali metal atoms per PTCDA was found at the surface. In the case of sodium and potassium, averaged surface doping ratios of only 1.3±0.1 alkali metal atoms per PTCDA molecule can be reached. However, in the bulk phase, nearly complete doping can be reached by all three alkali metals.
Development of a high-efficiency high-resolution particle-induced x-ray emission system for chemical state analysis of environmental samples
Authors: Hasegawa J. , Tada T. , Oguri Y. , Hayashi M. , Toriyama T. , Kawabata T. , Masai K.
Published: July 2007

We have developed a high-efficiency high-resolution particle-induced x-ray emission (PIXE) system employing a von Hamos–type crystal spectrometer for a chemical state identification of trace elements in environmental samples. The energy resolution of the system was determined to be about 0.05% through the observation of SiKα1,2 x rays (1.74keV) from elemental silicon. The throughput efficiency of the system was also evaluated quasitheoretically to be 1.6×10−7 counts/incident proton for SiKα1,2 emission. To demonstrate a chemical state analysis using the high-resolution PIXE system, SiKα1,2 and Kβ x-ray spectra for SiC, Si3N4, and SiO2 were measured and compared. The observed chemical shifts of the SiKα1,2 peaks for SiC, Si3N4, and SiO2 relative to elemental silicon were 0.20, 0.40, and 0.55eV, respectively. The tendency of these shifts were well explained by the effective charges of the silicon atoms calculated by a molecular orbital method.
On-board sample cleaver
Authors: Månsson Martin , Claesson Thomas , Karlsson Ulf O. , Tjernberg Oscar , Pailhés Stéphane , Chang Johan , Mesot Joël , Shi Ming , Patthey Luc , Momono Naoki , Oda Migaku , Ido Masayuki
Published: July 2007

An on-board sample cleaver has been developed in order to cleave small and hard-to-cleave samples. To acquire good cleaves from rigid samples the alignment of the cleaving blade with respect to the internal crystallographic planes is crucial. To have the opportunity to mount the sample and align it to the blade ex situ has many advantages. The design presented has allowed us to cleave very tiny and rigid samples, e.g., the high-temperature superconductor La(2−x)SrxCuO4. Further, in this design the sample and the cleaver will have the same temperature, allowing us to cleave and keep the sample at low temperature. This is a big advantage over prior cleaver systems. As a result, better surfaces and alignments can be realized, which considerably simplifies and improves the experiments.
Mesoscopic structures and two-dimensional hole systems in fully field effect controlled heterostructures
Authors: Willett R. L. , Manfra M. J. , Pfeiffer L. N. , West K. W.
Published: July 2007

Two fundamental extensions to the function of previously described fully field effect two-dimensional (2D) electron heterostructures are presented. First, using the same basic heterostructure design of lithographically defined contacts overlain by both an insulating layer and top gate employed for electron systems, appropriate contact material allows a high mobility 2D hole layer to be populated. Second, a simple method for producing mesoscopic structures in these devices is presented, in which small-scale metallic patterns are placed on the heterostructure under the insulating and global gate layers which allows local carrier density tuning via the overlapping gate arrays. Example devices using these generally applicable methods are demonstrated.
Large remanent polarization in ferroelectric BiFeO3–PbTiO3 thin films on Pt∕Si substrates
Authors: Khan Mikael A. , Comyn Tim P. , Bell Andrew J.
Published: July 2007

Bismuth ferrite–lead titanate thin films in the region of the morphotropic phase boundary, with compositions of (1−x)BiFeO3–xPbTiO3 (0.3<x<0.5), were prepared by pulsed laser deposition on Pt∕Si substrates. X-ray diffraction confirmed the formation of pure perovskite phase at a substrate temperature of 565°C under 75mTorr of oxygen. The films exhibit remanent polarizations with 2Pr up to 100μCcm−2 for a field amplitude of 820kVcm−1 and switchable polarization up to 80μCcm−2.
Experimental determination of the effective minority carrier lifetime in the operation of a quantum-well n-p-n heterojunction bipolar light-emitting transistor of varying base quantum-well design and doping
Authors: Then H. W. , Feng M. , Holonyak N. , Wu C. H.
Published: July 2007

The authors show that the electrical characteristics of an n-p-n transistor structure can be used to determine experimentally, under dynamical operating conditions, the effective carrier lifetime of injected minority carriers in the quantum-well (QW) base region of a heterojunction bipolar light-emitting transistor. The carrier lifetime is progressively reduced from 134ps (no base QW) to ∼35ps by inserting single or double QWs of increasing width to enhance the effective capture cross section for injected carriers (electrons), and is further reduced to ∼10ps by increasing the p-type doping from 5×1018to4×1019cm−3.
Quantitative analyses reveal the importance of regulated Hdmx degradation for P53 activation
Authors: Wang Yunyuan V. , Wade Mark , Wong EeTsin , Li Yao-Cheng , Rodewald Luo Wei , Wahl Geoffrey M.
Published: July 2007

P53 regulates numerous downstream targets to induce cell cycle arrest, senescence, apoptosis, and DNA repair in response to diverse stresses. Hdm2 and Hdmx are critical negative regulators of P53 because Hdm2 regulates P53 abundance, and both can antagonize P53 transactivation. Modest changes in Hdm2 or Hdmx abundance affect P53 regulation, yet quantitative information regarding their endogenous intracellular concentrations and subcellular distributions during a stress response are lacking. We analyzed these parameters in normal and cancer cells after DNA damage. Our data show that the nuclear abundance of Hdm2 and Hdmx relative to P53 limits P53 activity in cells growing in culture. Upon DNA damage, P53 nuclear abundance increases, whereas Hdm2 and Hdmx stability decreases, which greatly limits their ability to antagonize P53, regardless of their levels. These data indicate that the damage-activated switch in Hdm2 ubiquitin ligase preference from P53 to itself and Hdmx is central to P53 activation.
Trk-signaling endosomes are generated by Rac-dependent macroendocytosis
Authors: Valdez Gregorio , Philippidou Polyxeni , Rosenbaum Julie , Akmentin Wendy , Shao Yufang , Halegoua Simon
Published: July 2007

Why neurotrophins and their Trk receptors promote neuronal differentiation and survival whereas receptor tyrosine kinases for other growth factors, such as EGF, do not, has been a long-standing question in neurobiology. We provide evidence that one difference lies in the selective ability of Trk to generate long-lived signaling endosomes. We show that Trk endocytosis is distinguished from the classical clathrin-based endocytosis of EGF receptor (EGFR). Although Trk and EGFR each stimulate membrane ruffling, only Trk undergoes both selective and specific macroendocytosis at ruffles, which uniquely requires the Rho-GTPase, Rac, and the trafficking protein, Pincher. This process leads to Trk-signaling endosomes, which are immature multivesicular bodies that retain Rab5. In contrast, EGFR endosomes rapidly exchange Rab5 for Rab7, thereby transiting into late-endosomes/lysosomes for degradation. Sustained endosomal signaling by Trk does not reflect intrinsic differences between Trk and EGFR, because each elicits long-term Erk-kinase activation from the cell surface. Thus, a population of stable Trk endosomes, formed by specialized macroendocytosis in neurons, provides a privileged endosome-based system for propagation of signals to the nucleus.
The new mutation theory of phenotypic evolution
Authors: Nei Masatoshi
Published: July 2007

Recent studies of developmental biology have shown that the genes controlling phenotypic characters expressed in the early stage of development are highly conserved and that recent evolutionary changes have occurred primarily in the characters expressed in later stages of development. Even the genes controlling the latter characters are generally conserved, but there is a large component of neutral or nearly neutral genetic variation within and between closely related species. Phenotypic evolution occurs primarily by mutation of genes that interact with one another in the developmental process. The enormous amount of phenotypic diversity among different phyla or classes of organisms is a product of accumulation of novel mutations and their conservation that have facilitated adaptation to different environments. Novel mutations may be incorporated into the genome by natural selection (elimination of preexisting genotypes) or by random processes such as genetic and genomic drift. However, once the mutations are incorporated into the genome, they may generate developmental constraints that will affect the future direction of phenotypic evolution. It appears that the driving force of phenotypic evolution is mutation, and natural selection is of secondary importance.
A Protein Interaction Map of the Mitotic Spindle
Authors: Wong Jonathan , Nakajima Yuko , Westermann Stefan , Shang Ching , Kang Jung-seog , Goodner Crystal , Houshmand Pantea , Fields Stanley , Chan Clarence S.M. , Drubin David , Barnes Georjana , Hazbun Tony
Published: July 2007

The mitotic spindle consists of a complex network of proteins that segregates chromosomes in eukaryotes. To strengthen our understanding of the molecular composition, organization, and regulation of the mitotic spindle, we performed a system-wide two-hybrid screen on 94 proteins implicated in spindle function in Saccharomyces cerevisiae. We report 604 predominantly novel interactions that were detected in multiple screens, involving 303 distinct prey proteins. We uncovered a pattern of extensive interactions between spindle proteins reflecting the intricate organization of the spindle. Furthermore, we observed novel connections between kinetochore complexes and chromatin-modifying proteins and used phosphorylation site mutants of NDC80/TID3 to gain insights into possible phospho-regulation mechanisms. We also present analyses of She1p, a novel spindle protein that interacts with the Dam1 kinetochore/spindle complex. The wealth of protein interactions presented here highlights the extent to which mitotic spindle protein functions and regulation are integrated with each other and with other cellular activities.
Enhancement of endothelium‐dependent flow‐mediated vasodilation in hyperthyroidism
Authors: Ho Wan‐Jing , Chen Szu‐Tah , Tsay Pei‐Kwei , Wang Chun‐Li , Hsu Tsu‐Shiu , Kuo Chi‐Tai , Chen Wei‐Jan
Published: July 2007

Objective   Vascular responsiveness changes in hyperthyroid patients remains controversial. This study attempts to determine whether the vasomotor activity can be influenced by hyperthyroid conditions, and, if so, whether changes induced by hyperthyroidism may be restored to normal during the euthyroid state after treatment.

Design   A case‐control clinical study.

Patients and measurements   Forty‐five pretreated hyperthyroid patients (mean age 36·62 ± 10·12 years, 36 female) were compared with 45 gender‐ and age‐matched control subjects (mean age 38·98 ± 11·17 years, 40 female). Brachial artery endothelium‐dependent flow‐mediated vasodilation (FMD) and endothelium‐independent nitroglycerin‐mediated vasodilation (NMD) responses were assessed noninvasively by high‐resolution ultrasound imaging. Among the 45 hyperthyroid patients, 27 patients underwent the same procedures prospectively in the post‐treatment euthyroid state.

Results   The FMD values were significantly increased in hyperthyroid patients vs. those of controls (8·94 ± 5·65%vs. 3·77 ± 3·42%, P < 0·001), whereas NMD levels were not significantly different (18·17 ± 7·76%vs. 17·28 ± 6·63%, P = 0·560). Multiple regression analysis revealed that the presence of hyperthyroidism was the only significant factor associated with FMD. In the follow‐up study of 27 hyperthyroid patients, the FMD values were significantly decreased in the post‐treatment euthyroid state compared with those in the pretreated hyperthyroid state (6·40 ± 4·27%vs. 8·83 ± 4·61%, P = 0·021), although these values were still higher than those of controls.

Conclusions   This study demonstrated that endothelium‐dependent FMD was increased in the hyperthyroid patients, and could be partially restored by treatment with antithyroid agents.
Pharmacokinetics and pharmacodynamics of growth hormone in patients on chronic haemodialysis compared with matched healthy subjects: an open, nonrandomized, parallel‐group trial
Authors: Langbakke Irene H. , Nielsen Jakob N. , Skettrup Mia P. , Harper Angela , Klitgaard Thomas , Weil Angelika , Engelhardt Eva , Lange Martin
Published: July 2007

Background  GH may be beneficial in treating patients with end‐stage renal disease (ESRD). However, the efficacy and safety of GH could be compromised by the potential for accumulation in the circulation.

Objective  The objective was to investigate the pharmacokinetics and safety of GH treatment in ESRD patients.

Design  This was an open, nonrandomized, single‐centre parallel‐group study lasting 8–9 days.

Subjects  Eleven adult ESRD patients and 10 matched healthy individuals received recombinant human GH (50 µg/kg/day for 7 days) by subcutaneous injection; there were two dose reductions (25%) from Day 5/7. ESRD patients underwent dialysis four times.

Measurements  Serum concentrations of GH, insulin‐like growth factor‐I (IGF‐I), insulin‐like growth factor binding protein‐I (IGFBP‐I), IGFBP‐III and GHBP were measured. The primary end‐point was GH exposure [area‐under‐the‐curve (AUC) calculated from the 24‐h profile] on Days 7–8.

Results  GH AUC0–24 h was greater for patients (387·91 ± 134·13 µg h/l) than healthy subjects (225·35 ± 59·63 µg h/l) and the 90% confidence interval (CI) for the estimated patient : healthy subject ratio (1·40–2·07) was not within the acceptance interval (0·67–1·50). GH AUC18–24 h for patients and healthy subjects (3·03 ± 2·71 µg h/l and 6·37 ± 4·21 µg h/l) returned approximately to baseline (2·86 ± 3·91 µg h/l and 1·09 ± 1·43 µg h/l); terminal half‐life (t1/2,z) was shorter for patients (2·28 ± 00·43 h vs. 3·23 ± 00·75 h). No major safety issues were identified.

Conclusions  Results demonstrate a difference between patients and healthy subjects regarding GH AUC0–24 h. However, GH concentrations for both groups were comparable to baseline by 20–22 h, thus GH was not retained in the circulation of ESRD patients.
Why are there few algae on snail shells? The effects of grazing, nutrients and shell chemistry on the algae on shells of Helisoma trivolvis
Authors: ABBOTT LINDSEY L. , BERGEY ELIZABETH A.
Published: July 2007

1. Freshwater snails often lack visible growths of algae on their shells. We tested three possible mechanisms that may account for this (grazing, snail‐derived nutrients and chemical defences), using the ramshorn snail Helisoma trivolvis.

2. The experiments were carried out in floating plastic enclosures in a pond and comprised seven treatments. Grazing treatments were: a lone snail (ungrazed, as self‐grazing does not occur), Helisoma with conspecifics, Helisoma with the co‐occurring pond snail Physa sp., empty shells with Helisoma, and ungrazed empty shells. Nutrient effects were possible in all treatments with occupied shells (lone snail; Helisoma with conspecifics, and with Physa) versus absent in other treatments. Testing for chemical defences compared algae on fresh empty shells, weathered shells (outer organic periostracum layer absent) and boiled fresh shells (with denaturization of susceptible proteins).

3. Diatoms dominated algal assemblages on snail shells. Although the upright diatom Gomphonema gracile was abundant on all shells, it was dominant on the shells of snails housed with other snail grazers (either Helisoma or Physa).

4. Only the lone snail (nutrients but no grazing) showed higher algal biomass, so presumably any nutrient effect in the treatments with grazers was masked. Both Helisoma and Physa were observed apparently grazing on Helisoma shells, and consequently algal biomass in multi‐snail treatments was similar to that on empty shells. Scanning electron microscopy revealed that algal density was highest near the aperture of live snails, but not empty shells; this is consistent with a nutrient addition effect. There was no evidence of chemical defences against algal growth.

5. In soft‐bottomed freshwater habitats with abundant snails, shells of living snails provide nutrient‐augmented substrata that may indirectly boost overall snail production.
A novel calcium‐sensitive potassium conductance is coupled to P2X3subunit containing receptors in myenteric neurons of guinea pig ileum
Authors: Ren J. , Galligan J. J.
Published: July 2007

Abstract This study characterized P2X receptors in guinea pig ileum myenteric S neurons (n = 124)in vitrousing electrophysiological methods. ATP orα,β‐methylene ATP (α,β‐mATP), an agonist at P2X1and P2X3subunit containing receptors, depolarized 103 neurons (85%). Pyridoxal‐phosphate‐6‐azophenyl‐2′,4′ disulfonic acid (10 μmol L−1) blocked ATP‐ andα,β‐mATP‐induced depolarizations. ATP‐induced depolarizations and fast excitatory postsynaptic potentials (fEPSPs) were reduced by trinitrophenyl‐ATP (10 μmol L−1), an antagonist that can block P2X3receptors. Ivermectin (10 μmol L−1), a modulator of P2X4and P2X4/6receptors, had no effect onα,β‐mATP‐induced depolarizations. In 58% of neurons, theα,β‐mATP induced‐depolarization was followed by an afterhyperpolarization (AHP) (P2X‐AHP). Under voltage clamp,α,β‐mATP induced an inward current followed by an outward current which reversed polarity at 0 and −80 mV respectively. The P2X‐AHP was reduced in low extracellular Ca2+solutions. Blockers of large, intermediate and small conductance Ca2+‐activated K+channels or voltage‐gated K+channels did not inhibit the P2X‐AHP. Half of the neurons exhibiting the P2X‐AHP contained nitric oxide synthase (NOS)‐immunoreactivity (ir). In summary, NOS‐ir S neurons express P2X3subunit containing P2X receptors. P2X receptors couple to activation of a Ca2+‐activated K+conductance that mediates an AHP. As P2X receptors contribute to fEPSPs, the P2X‐AHP may modulate S neuron excitability during purinergic synaptic transmission.
Role of histaminergic neurons in hypnotic modulation of brain processing of visceral perception
Authors: Watanabe S. , Hattori T. , Kanazawa M. , Kano M. , Fukudo S.
Published: July 2007

Abstract  Modulating visceral sensation of the body is important to the understanding of emotion formation. Molecules that act during hypnosis and modify visceral pain perception are not known. We tested our hypothesis that hypnotic suggestion changes electrophysiological processing of visceroafferent signals in the human brain and that these conditions are in part dependent on histaminergic neurons. Twelve healthy male subjects were studied on two separate days: a day of treatment with histamine H1 receptor antagonist (d‐chlorpheniramine 100 μg kg−1, intravenously) and another day of that with placebo (saline, the same amount) in a randomized order. We recorded cortical evoked potentials to 100 rectal electrical stimuli after neutral, hyperalgesic or analgesic hypnotic suggestions as given to modulate the visceral perception. Analgesic suggestion reduced the amplitude of the deepest positive peak of viscerosensory evoked potential. Administration of histamine H1 antagonist diminished the attenuation of viscerosensory evoked potential by analgesic suggestion. Our results suggest that central pain modulatory system in the brain is activated by hypnotic suggestion and that brain histamine is a mediator in the hypnotic modulation of visceral sensory pathway as well as in the control of consciousness level. These findings lead us to possible new treatment for control of visceral perception.
No difference in symptoms of irritable bowel syndrome between healthy subjects and patients with recurrent depression in remission
Authors: Karling P. , Danielsson Å. , Adolfsson R. , Norrback K.‐f.
Published: July 2007

Abstract  There is bidirectional comorbidity between anxiety/depression and irritable bowel syndrome (IBS). To investigate the prevalence of IBS symptoms, and factors associated with gastrointestinal symptoms in patients with recurrent depressive disorder. Patients (n = 95) with recurrent type of major depression according to DSM‐IV criteria and sex‐ and age‐matched controls (n = 190) were sent questionnaires investigating symptoms of IBS [Gastrointestinal Symptom Rating Scale (GSRS)‐IBS] and symptoms of anxiety and depression [Hospital Anxiety and Depression Scale (HADS)]. Medical records were checked over a 10‐year period for chronic somatic symptoms or diseases. Seventy‐three patients with unipolar disorder (mean age 63.6 years SD 13.8; range 23–86 years) and 156 controls (mean age 59.2 years SD 11.6, range 21–85 years) responded. Patients with recurrent depression had higher GSRS‐IBS scores and showed a strong correlation between symptoms of IBS and anxiety‐depression (rs = 0.54; P < 0.001). IBS symptoms were also associated with multiple pain symptoms, higher health‐seeking behaviour and selective‐serotonin‐reuptake inhibitor intake. However, patients with recurrent depression (n = 46) in remission (HADS‐Depression score <8) did not have more symptoms of IBS than controls (GSRS‐IBS median score 6.0 vs 6.5; P = 0.46). There is a strong association between symptoms of IBS and symptoms of anxiety and depression, whereas depressive patients in remission do not have more IBS symptoms than controls.
Impaired drinking capacity in patients with functional dyspepsia: intragastric distribution and distal stomach volume
Authors: Van Den Elzen B. D. , Bennink R. J. , Holman R. , Tytgat G. N. , Boeckxstaens G. E.
Published: July 2007

Abstract  The water drink test is a good tool to evoke dyspeptic symptoms. To what extent these symptoms are related to altered gastric distribution is not clear. Therefore, we determined gastric volumes after a drink test using SPECT. After a baseline scan 20 healthy volunteers (HV) and 18 patients with functional dyspepsia (FD) underwent a drink test (100 mL min−1) followed by five scans up to 2 h. Dyspeptic symptoms were scored before every scan. A Wilcoxon signed rank test (P < 0.05) and a mixed effects model were used for statistical analyses. Fasting volumes were significantly higher in FD compared to HV for total, proximal and distal stomach (P < 0.001). Functional dyspeptic patients ingested significantly less water (P < 0.001) and had an impaired filling of the distal part of the stomach (P = 0.001) after the drink test. In FD, bloating (prox. 80%, dist. 56%), pain (prox. 87%, dist. 62%) and fullness (prox. 80%, dist. 59%) were determined more by proximal stomach volume rather than distal stomach volume. These data suggest that drinking capacity is mainly determined by antral volume, with a reduced antral filling in FD compared to HV. The persisting symptoms of bloating, pain and fullness in FD are predominantly associated with proximal stomach volume.
Large‐scale identification of microRNAs from a basal eudicot (Eschscholzia californica) and conservation in flowering plants
Authors: Barakat Abdelali , Wall Kerr , Leebens‐Mack Jim , Wang Yunjiao J. , Carlson John E. , DePamphilis Claude W.
Published: July 2007

MicroRNAs (miRNAs) negatively control gene expression by cleaving or inhibiting the translation of mRNA of target genes, and as such, they play an important role in plant development. Of the 79 plant miRNA families discovered to date, most are from the fully sequenced plant genomes of Arabidopsis, Populus and rice. Here, we identified miRNAs from leaves, roots, stems and flowers at different developmental stages of the basal eudicot species Eschscholzia californica (California poppy) using cloning and capillary sequencing, as well as ultrahigh‐throughput pyrosequencing using the recently introduced 454 sequencing method. In total, we identified a minimum of 173 unique miRNA sequences belonging to 28 miRNA families and seven trans‐acting small interfering RNAs (ta‐siRNAs) conserved in eudicot and monocot species. miR529 and miR537, which have not yet been reported in eudicot species, were detected in California poppy; loci encoding these miRNAs were also found in Arabidopsis and Populus. miR535, which occurs in the moss Physcomitrella patens, was also detected in California poppy, but not in other angiosperms. Several potential miRNA targets were found in cDNA sequences of California poppy. Predicted target genes include transcription factors but also genes implicated in various metabolic processes and in stress defense. Comparative analysis of miRNAs from plants of phylogenetically‐critical basal lineages aid the study of the evolutionary gains and losses of miRNAs in plants as well as their conservation, and lead to discoveries about the miRNAs of even well‐studied model organisms.
Effects of variety, cropping year, location and fertilizer application on nutritive value of durum wheat straw
Authors: Tolera A. , Tsegaye B. , Berg T.
Published: July 2007

This study was carried out to assess the effects of variety, year, location and level of fertilizer application on chemical composition and in sacco dry matter (DM) degradability of durum wheat straw as well as to understand the relationship between straw quality and agronomic traits of the crop and to assess the possibilities of selecting wheat varieties that combine high grain yield with desirable straw quality. Two local (Arendeto and Tikur sinde) and two improved (Boohai and Gerardo) varieties of durum wheat (Triticum turgidum Desf.) were used in the experiment. The four varieties were grown at two locations (Akaki and Ejere) in the years 2001/2002 and 2002/2003 in 5 × 5 m plots in three replications. Diammonium phosphate and urea fertilizers were applied at four levels (0/0, 32/23, 41/23 and 64/46 kg/ha of nitrogen/phosphorus). Straw quality was assessed based on chemical composition and in sacco DM degradability. Correlation of straw quality with grain and straw yield and with other agronomic characteristics of the crop was determined. The potential utility index (a measure that integrates grain and digestible straw yield) was used for ranking of the varieties. The local varieties had higher crude protein (CP) and lower neutral detergent fibre contents and higher digestibility than the improved varieties. The cropping year and location had significant effect on CP content and degradability of the straw, which could be due to climatic variation. However, the fertilizer level did not have any significant effect on straw quality except that the CP content of the straw tended to increase with increasing level of fertilizer application. Based on the potential utility index the varieties ranked, in a decreasing order, as Tikur sinde > Arendeto > Gerardo > Boohai and the ranking was consistent across years and locations. Except the CP content, straw quality was not negatively correlated with grain and straw yield. This indicates that there is a possibility of selecting varieties of wheat that combine high grain and straw yield with desirable straw quality.
Effects of ethylenediaminetetraacetic acid on phytate phosphorus utilization and efficiency of microbial phytase in broiler chicks
Authors: Ebrahimnezhad Y. , Shivazad M. , Taherkhani R. , Nazeradl K.
Published: July 2007

Previous studies have suggested that organic acids may improve P utilization in animals. To evaluate the ability of ethylenediaminetetraacetic acid (EDTA) to improve phytate P utilization and the possible synergistic effect between EDTA and microbial phytase (MP) an experiment was conducted using 360 Ross 308 broiler chicks. The experiment was carried out using a completely randomized design with a 3*2 factorial arrangement (0, 0.1 and 0.2% EDTA and 0 and 500 IU MP). Four replicate of 15 chicks per each were fed dietary treatments including (i) P‐deficient basal diet [0.2% available phosphorus (aP)] (NC); (ii) NC + 500 IU MP per kilogram of diet; (iii) NC + 0.1% EDTA per kilogram of diet; (iv) NC + 0.1% EDTA and 500 IU MP per kilogram of diet; (v) NC + 0.2% EDTA per kilogram; and (vi) NC + 0.2% EDTA + 500 IU MP per kilogram of diet. Weight gain (WG), feed efficiency and serum Ca, P and alkaline phosphatase (ALP) were assessed. Addition of 0.2% EDTA to low aP diets resulted in significantly lower feed consumption (FC) and WG, but 0.1% EDTA did not depress WG compared to NC. Phytase supplementation of P‐deficient diets significantly improved WG and feed efficiency, but it had no effect on FC. Microbial phytase supplementation significantly decreased ALP concentration. Results obtained in our study suggest no synergistic effect between phytase and EDTA in broiler chicks.
Multiple Scedosporium apiospermum brain abscesses after near‐drowning successfully treated with surgery and long‐term voriconazole: a case report
Authors: Leechawengwongs M. , Milindankura S. , Liengudom A. , Chanakul K. , Viranuvatti K. , Clongsusuek P.
Published: July 2007

Scedosporium apiospermum is an emerging fungal pathogen, increasingly recognised as a cause of infection not only in immunocompromised, but also in non‐immunodeficient patients. We present the case of an immunocompetent 21‐year‐old Thai man who experienced recurrent ruptured mycotic aneurysms and developed multiple S. apiospermum brain abscesses following aspiration of polluted water. A combination of surgery and voriconazole was effective in this difficult‐to‐treat case. Voriconazole penetrated the central nervous system (CNS) well and had limited toxicity, despite prolonged treatment. Voriconazole appears to be the antifungal agent of choice in the treatment of CNS scedosporiosis caused by S. apiospermum.
S100B LEVELS IN THE CEREBROSPINAL FLUID OF RATS ARE SEX AND ANAESTHETIC DEPENDENT
Authors: Vicente Évelin , Tramontina Francine , Leite Marina C , Nardin Patricia , Silva Mariane , Karkow Ana R , Adolf Rafael , Lucion Aldo B , Netto Carlos A , Gottfried Carmem , Gonçalves Carlos A
Published: July 2007

In the present study, we investigated the effect of anaesthetics (thiopental, ketamine and halothane) on CSF concentrations of S100B, as well as a possible sex dependence, because several studies have suggested astrocytes as putative targets for oestrogen.

S100B is a calcium‐binding protein that acts as a neurotrophic cytokine and is expressed in the central nervous system, predominantly by astrocytes. At nanomolar concentrations, S100B stimulates neurite outgrowth and glial glutamate uptake, as well as protecting neurons against glutamate excitoxicity.

Peripheral S100B concentrations, particularly in the serum and cerebrospinal fluid (CSF), have been used as a parameter of glial activation or death in several physiological and pathological conditions.

Higher levels of CSF S100B were found when rats were anaesthetized with thiopental; these levels, independently of anaesthetic, were sex dependent. Conversely, no effect of anaesthetic or sex was observed on serum concentrations of S100B.

The increase in CSF concentrations of S100B induced by thiopental was confirmed in non‐anaesthetized neonatal rats and cortical astrocyte cultures.

Assuming CSF S100B as a marker of development, glial activation or even brain damage, investigations regarding the sex dependence of its concentration may be useful in gaining an understanding of sex variations in the behaviour and the pathological course of, as well as susceptibility to, many brain disorders. The findings of the present study reinforce the sex effect on synaptic plasticity and suggest a sex dependence of neural communication mediated by extracellular S100B without restricting the influence of astrocytes on the developmental phase.