bluuebunny/crossref_metadata_2025 huggingface dataset:
Neocortical Dialysate Monoamines of Rats After Acute, Subacute, and Chronic Liver Shunt
Authors: Bergqvist Peter B. F. , Vogels Birgit A. P. M. , Bosman Diederik K. , Maas Martinus A. W. , Hjorth Stephan , Chamuleau Robert A. F. M. , Bengtsson Finn
Published: July 2010

Abstract: Intracerebral microdialysis was applied to monitor the neocortical extracellular levels of the aromatic amino acids phenylalanine, tyrosine, and tryptophan, the neurotransmitters dopamine (DA), noradrenaline (NA), and serotonin (5‐HT), and the metabolites 3,4‐dihydroxyphenylacetic acid (DOPAC) and 5‐hydroxyindole‐3‐acetic acid (5‐HIAA) in rats with various forms of experimental hepatic encephalopathy (HE). The extracellular aromatic amino acid levels were clearly increased in acute, subacute, and chronic HE. No changes compared with controls in the neocortical DA release could be detected in the three experimental HE rat models investigated. The NA release showed a significant increase only in the subacute HE group. These data suggest that HE may not be associated with any major reduction of neocortical DA or NA release as previously suggested. In acute and subacute HE, decreased extracellular DOPAC but elevated 5‐HIAA concentrations were seen. In chronic HE, elevations of both DOPAC and 5‐HIAA were observed. Neocortical 5‐HT release did not change in subacute and chronic HE, whereas it decreased in acute HE compared with control values. Significant increase in extracellular concentrations of 5‐HIAA and of the 5‐HIAA/5‐HT ratio in the present study are in agreement with previously reported increases in 5‐HT turnover in experimental HE. However, a substantially increased 5‐HT turnover in experimental HE does not appear to be related to an increase in neuronal neocortical 5‐HT release.
Enhanced Glial Fibrillary Acidic Protein RNA Response to Fornix Transection in Aged Mice
Authors: Goss James R. , Morgan David G.
Published: July 2010

Abstract: The effects of age on basal and lesion‐induced changes in astrocyte RNA messages reported to respond to neurodegeneration were examined in the mouse brain. The first study found an age‐related increase in glial fibrillary acidic protein RNA throughout the brain. Other astrocyte RNAs remained generally stable with age. We hypothesize this increase is due to astrocytes undergoing a mild reaction to the small amount of synaptic degeneration occurring with usual aging. To test this theory, we used an experimental model of modest synaptic loss in the hippocampus by transecting the fimbria/fornix bundle in mice and examined the same series of messages. In situ hybridization revealed the expected increase in glial fibrillary acidic protein RNA after the lesion; however, we unexpectedly found that aged mice showed a greater magnitude of this response, which appeared to develop more slowly. There was no significant change in the hippocampus for any of the other messages, although responses were observed at the site of transection. This study supports the idea that the age‐related increase in glial fibrillary acidic protein may be secondary to modest synaptic degeneration. We also demonstrated an exaggerated reactive astrocytic response in aged mice, which may be associated with age‐related deficits in reactive synaptogenesis and behavioral recovery in normal aging.
Cloning and Characterization of a Soluble Kynurenine Aminotransferase from Rat Brain: Identity with Kidney Cysteine Conjugate β‐Lyase
Authors: Alberati‐Giani Daniela , Malherbe Pari , Köhler Christer , Lang Gabrielle , Kiefer Vivian , Lahm Hans‐Werner , Cesura Andrea M.
Published: July 2010

Abstract: In this study, we describe the cloning and characterization of a soluble form of kynurenine aminotransferase (KAT, EC 2.6.1.7) present in rat brain. Soluble KAT was purified from rat kidney and the amino acid sequences of four tryptic peptides determined. These peptides were found to belong to the amino acid sequence reported for rat kidney soluble cysteine conjugate β‐lyase, indicating that rat kidney KAT and β‐lyase represent the same molecular entity. Oligonucleotide probes derived from the β‐lyase cDNA were then used as primers for PCR of reverse‐transcribed rat brain poly(A)+ RNA. After subcloning of the resulting PCR fragment and sequencing of the isolated rat brain clone, its oligonucleotide sequence was found to be identical to that reported for the β‐lyase cDNA. Further evidence that the isolated rat brain clone encoded for KAT was obtained by transfecting HEK‐293 cells with a construct containing the coding sequence for the enzyme. The transfected cells exhibited KAT activity and, in the presence of 2 mM pyruvate and 2‐oxoglutarate, the Km values for l‐kynurenine were 1.2 mM and 86.3 µM, respectively. Northern blot analysis of rat kidney, liver, and brain RNA revealed a single species of KAT/β‐lyase mRNA of ∼2.1 kb.
Analysis of the Proenkephalin Second Messenger‐Inducible Enhancer in Rat Striatal Cultures
Authors: Konradi Christine , Cole Rebecca L. , Green Donnella , Senatus Patrick , Leveque Jean‐Christophe , Pollack Alexia E. , Grossbard Sarah J. , Hyman Steven E.
Published: July 2010

Abstract: We have previously shown that in cell extracts from rat striatum, cyclic AMP response element (CRE) binding protein (CREB), rather than AP‐1 proteins, preferentially interacts with the CRE‐2 element of the proenkephalin second messenger‐inducible enhancer, even under conditions in which AP‐1 proteins are highly induced. Here we use primary striatal cultures to permit a more detailed analysis of CRE‐2 function and protein binding in relevant neural cell types. By transfection we find that in primary striatal cultures, as in transformed cell lines, the CRE‐1 and CRE‐2 elements are required for significant induction by cyclic AMP. We report that cyclic AMP induction of the proenkephalin gene in striatal cultures is protein synthesis independent, excluding a role for newly synthesized proteins like c‐Fos. We also show that cyclic AMP induces CREB phosphorylation and that phosphorylated CREB interacts strongly with CRE‐2 and weakly with CRE‐1. The predominant protein bound to CRE‐1 is not CREB, however, and remains to be identified. Despite some prior predictions, we do not find a role for c‐Fos in cyclic AMP regulation of proenkephalin gene expression in neurons.
Epidermal Growth Factor and Basic Fibroblast Growth Factor Protect Dopaminergic Neurons from Glutamate Toxicity in Culture
Authors: Casper Diana , Blum Mariann
Published: July 2010

Abstract: In this report we characterize the toxicity of the excitatory amino acid l‐glutamate with respect to dopaminergic neurons cultured from embryonic rat mesencephalon. We also demonstrate that two growth factors, epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), can protect these neurons from damage. Micromolar concentrations of l‐glutamate, as well as agonists that specifically activate N‐methyl‐d‐aspartate (NMDA) and non‐NMDA receptors, are all toxic to dopamine neurons in a concentration‐dependent manner, as reflected by decreases in high‐affinity dopamine uptake and confirmed by decreases in numbers of tyrosine hydroxylase‐immunoreactive neurons. Although the non‐NMDA receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione could attenuate the effects of quisqualate, treatment with this antagonist could not eliminate the effects of glutamate itself. Similarly, (±)‐2‐amino‐5‐phosphonopentanoic acid was effective against NMDA toxicity but could not protect cells from quisqualate toxicity. Thus, each type of receptor could mediate neurotoxicity independently of the other. The presence of EGF or bFGF in the culture medium conferred a relative resistance of dopaminergic neurons to glutamate and quisqualate neurotoxicity by increased glutamate transport. However, treatment of the cultures with l‐trans‐pyrrolidine‐2,4‐dicarboxylic acid, an inhibitor of glutamate transport, attenuated but did not eliminate the protective effects of both growth factors against glutamate toxicity. When cultures were incubated with conditioned medium from growth factor‐treated cultures, neuroprotection was also achieved. These results suggest that both EGF and bFGF can protect neurons from neurotoxicity in culture by increasing the capacity of the culture for glutamate uptake as well as by the secretion of soluble factors into the medium.
Astroglial Phosphoinositide Hydrolysis During Combined Glucose‐Oxygen Deprivation: Role of the Metabotropic Glutamate Receptor
Authors: Segeleon Joseph E. , Lipscomb Diane C. , Haun Steven E. , Trapp Victoria L. , Horrocks Lloyd A.
Published: July 2010

Abstract: Phosphatidylinositol bisphosphate hydrolysis, leading to the production of myo‐inositol trisphosphate and diacylglycerol, may play a significant role in the pathogenesis of hypoxic‐ischemic brain injury. We used tritiated myo‐inositol phosphate (3H‐IP) accumulation as a means to quantitate phosphoinositide hydrolysis in prelabeled astroglial cultures subjected to combined glucose‐oxygen deprivation. Astroglial cultures exposed to combined glucose‐oxygen deprivation had significantly greater 3H‐IP accumulation compared with cultures exposed to control conditions. To delineate the role of the metabotropic glutamate receptor in astroglial phosphoinositide hydrolysis during combined glucose‐oxygen deprivation, we studied the effects of two metabotropic glutamate receptor antagonists, 2‐amino‐3‐phosphonopropionic acid and (+)‐methyl‐4‐carboxyphenylglycine. 2‐Amino‐3‐phosphonopropionic acid attenuated the accumulation of 3H‐IP during combined glucose‐oxygen deprivation but acted as an agonist under control conditions. (+)‐Methyl‐4‐carboxyphenylglycine had no effect on 3H‐IP accumulation during combined glucose‐oxygen deprivation or under control conditions. These results suggest that activation of astroglial phosphoinositide hydrolysis during combined glucose‐oxygen deprivation may be mediated, at least in part, by the metabotropic glutamate receptor.
Differential Calcitonin Gene‐Related Peptide (CGRP) and Amylin Binding Sites in Nucleus Accumbens and Lung: Potential Models for Studying CGRP/Amylin Receptor Subtypes
Authors: Aiyar Nambi , Baker Elayne , Martin John , Patel Arunbhai , Stadel Jeffrey M. , Willette Robert N. , Barone Frank C.
Published: July 2010

Abstract: Calcitonin gene‐related peptide (CGRP), a 37‐amino‐acid peptide, is a member of a small family of peptides including amylin or islet amyloid polypeptide and salmon calcitonin. These related peptides have been shown to display similar effects on in vitro and in vivo carbohydrate metabolism. The present study was initiated to identify and characterize the binding sites for these peptides in lung and nucleus accumbens membranes prepared from pig and guinea pig. Both tissues in either species displayed high‐affinity (2‐[125I]iodohistidyl10)humanCGRPα ([125I]hCGRPα) binding (IC50 = 0.4–7.7 nM), which was displaced by hCGRP8–37α with equally high affinity (IC50 = 0.4–7.3 nM). High‐affinity binding for [125I]Bolton‐Hunter human amylin ([125I]BH‐h‐amylin) was also observed in these tissues (IC50 = 0.2–6.0 nM). In membranes from the nucleus accumbens of both species, salmon calcitonin competed for amylin binding sites with high affinity (IC50 = 0.1 nM) but was poor in competing for amylin binding in lung membranes. Rat amylin8–37 competed for [125I]hCGRPα binding with higher affinity (IC50 = 5.4 nM) compared with [125I]BH‐h‐amylin binding (IC50 = 200 nM) in porcine nucleus accumbens, whereas in guinea pig nucleus accumbens, the IC50 values for rat amylin8–37 were 117 and 12 nM against [125I]hCGRPα and [125I]BH‐h‐amylin, respectively. Also, functional studies evaluating the activation of adenylate cyclase and generation of cyclic AMP in response to these agonists indicated that hCGRPα (EC50 = 0.3 nM), h‐amylin (EC50 = 150 nM), and salmon calcitonin (EC50 = 1,000 nM) activated adenylate cyclase, resulting in increased cyclic AMP production in porcine lung membranes that was antagonized by hCGRP8–37α. The affinity of hCGRP8–37α was similar for all three peptides. The cyclic AMP responses to amylin and salmon calcitonin were significantly (p < 0.05) lower than that of hCGRPα and not additive, suggesting that they are acting as partial agonists at the same CGRP1‐type receptor in porcine lung membranes. Similar observations were made for guinea pig lung membranes. However, human amylin and salmon calcitonin were weaker than hCGRPα in activating lung adenylate cyclase. None of these peptides activated adenylate cyclase in membranes prepared from the nucleus accumbens of both species. The data from these studies demonstrate both species and tissue differences in the existence of distinct CGRP and amylin binding sites and present a potential opportunity to study further CGRP and amylin receptor subtypes.
The contribution of sidewall light extraction to efficiencies of polygonal light-emitting diodes shaped with laser micromachining
Authors: Wang X. H. , Lai P. T. , Choi H. W.
Published: July 2010

The light extraction efficiencies of InGaN/GaN blue light-emitting diodes (LEDs) of different geometries ranging from a triangle to a decagon have been simulated by ray-tracing. The conventional rectangular LED was found to be the most inefficient among the investigated polygons, and light extraction through the device sidewalls was the key factor. The results were experimentally verified by fabricating LEDs shaped into polygons by nanosecond-pulsed laser micromachining, which proved the simulated results. The mechanism of light extrac-tion in polygonal LEDs is discussed in detail.
Effects of chemical composition and B2 order on phonons in bcc Fe–Co alloys
Authors: Lucas M. S. , Muñoz J. A. , Mauger L. , Li Chen W. , Sheets A. O. , Turgut Z. , Horwath J. , Abernathy D. L. , Stone M. B. , Delaire O. , Xiao Yuming , Fultz B.
Published: July 2010

The phonon density of states (DOS) gives insight into interatomic forces and provides the vibrational entropy, making it a key thermodynamic function for understanding alloy phase transformations. Nuclear resonant inelastic x-ray scattering and inelastic neutron scattering were used to measure the chemical dependence of the DOS of bcc Fe–Co alloys. For the equiatomic alloy, the A2→B2 (chemically disordered→chemically ordered) phase transformation caused measurable changes in the phonon spectrum. The measured change in vibrational entropy upon ordering was −0.02±0.02 kB/atom, suggesting that vibrational entropy results in a reduction in the order–disorder transition temperature by 60±60 K. The Connolly–Williams cluster inversion method was used to obtain interaction DOS (IDOS) curves that show how point and pair variables altered the phonon DOS of disordered bcc Fe–Co alloys. These IDOS curves accurately captured the change in the phonon DOS and vibrational entropy of the B2 ordering transition.
Enhancement of thermoelectric efficiency in a double-quantum-dot molecular junction
Authors: Liu Y. S. , Yang X. F.
Published: July 2010

We propose a high-efficiency molecular junction consisting of a double-coupled-quantum-dot molecule sandwiched between two metallic electrodes. ZT can be enhanced in the Fano-line-shape regime, and it is sensitive to the magnetic flux threading through the double-coupled-quantum-dot molecular junction. This is mainly due to the local density of states in the Fano-line-shape regime may become narrower, and an abrupt changing in the conductance (transmission) spectrum is developed. We find the value of ZT can exceed 1 at room temperature by controlling the chemical potential or magnetic flux. So our results indicate such a molecular junction may be used to the solid-state thermoelectric energy-conversion device at room temperature.
Study of the sticking of a hydrogen atom on a graphite surface using a mixed classical-quantum dynamics method
Authors: Morisset S. , Ferro Y. , Allouche A.
Published: July 2010

The sticking of one hydrogen atom chemisorbed on the (0001) graphite surface is investigated using a mixed classical-quantum method. The phonon modes of the system in the collinear scattering approach are included in the dynamics calculations. The vibrational degrees of freedom of the surface (phonons) are treated classically, while the H-surface motion is treated using a one-dimensional quantum wave packet propagation method. The sticking probabilities are calculated and the individual contributions of the phonon bands to the collision dynamics are analyzed for surface temperatures of 10, 150, and 300 K and hydrogen kinetic energies ranging from 0.13 to 1.08 eV. An analytical form of the sticking probability as a function of the surface temperature is also proposed.
On the effect of hydrodynamic slip on the polarization of a nonconducting spherical particle in an alternating electric field
Authors: Zhao Hui
Published: July 2010

The polarization of a charged, dielectric, spherical particle with a hydrodynamically slipping surface under the influence of a uniform alternating electric field is studied by solving the standard model (the Poisson–Nernst–Planck equations). The dipole moment characterizing the strength of the polarization is computed as a function of the double layer thickness, the electric field frequency, the particle’s surface charge, and the slip length. Our studies reveal that two processes contribute to the dipole moment: ion transport inside the double layer driven by the electric field and the particle’s electrophoretic motion. The hydrodynamic slip will simultaneously impact both processes. In the case of a thick double layer, an approximate analytical expression for the dipole moment of a weakly charged particle with an arbitrary slip length and a small zeta potential ζ [normalized with the thermal voltage (∼25 mV)], accurate within O(ζ2), shows that the polarization is dominated by the particle’s electrophoretic motion and the enhancement of the polarization due to the hydrodynamic slip is primarily attributed to the enhancement of the electrophoretic mobility from the slip. In contrast, for a thin double layer, the dipole moment is governed by ion transport inside the double layer. Asymptotical analytical models conclude that the hydrodynamic slip has more complicated influence on the polarization. At the high-frequency range where the surface conduction is important, the dipole moment is predicted to increase for any zeta potential. On the contrary, at the low-frequency range where the bulk diffusion is significant, the enhancement of the dipole moment due to the slip is lost at large zeta potentials.
Accurate formula for conversion of tunneling current in dynamic atomic force spectroscopy
Authors: Sader John E. , Sugimoto Yoshiaki
Published: July 2010

Recent developments in frequency modulation atomic force microscopy enable simultaneous measurement of frequency shift and time-averaged tunneling current. Determination of the interaction force is facilitated using an analytical formula, valid for arbitrary oscillation amplitudes [Sader and Jarvis, Appl. Phys. Lett. 84, 1801 (2004)]. Here we present the complementary formula for evaluation of the instantaneous tunneling current from the time-averaged tunneling current. This simple and accurate formula is valid for any oscillation amplitude and current law. The resulting theoretical framework allows for simultaneous measurement of the instantaneous tunneling current and interaction force in dynamic atomic force microscopy.
Multiseeded melt growth of bulk Y–Ba–Cu–O using thin film seeds
Authors: Li T. Y. , Wang C. L. , Sun L. J. , Yan S. B. , Cheng L. , Yao X. , Xiong J. , Tao B. W. , Feng J. Q. , Xu X. Y. , Li C. S. , Cardwell D. A.
Published: July 2010

Y–Ba–Cu–O (YBCO) and Sm–Ba–Cu–O thin films have been used for the first time as heterogeneous seeds to multiseed successfully the melt growth of bulk YBCO in a multiseeded melt growth process. The use of thin film seeds, which may be prepared with highly controlled orientation (i.e., with a well-defined a-b plane and precisely known a-direction), is based on their superheating properties and reduces significantly contamination of the bulk sample by the seed material. A variety of grain boundaries were obtained by varying the angle between the seeds. Microstructural studies indicate that the extent of residual melt deposited at the grain boundary decreases with increasing grain boundary contact angle. It is established that the growth front proceeds continuously at the (110)/(110) grain boundary without trapping liquid, which leads to the formation of a clean grain boundary.
Analyses of the ultraviolet spectra of Er3+ in Er2O3 and Er3+ in Y2O3
Authors: Gruber John B. , Burdick Gary W. , Chandra Sreerenjini , Sardar Dhiraj K.
Published: July 2010

The ultraviolet (uv) absorption spectra, representing transitions to all energy levels below 44 500 cm−1 of trivalent erbium (Er3+), have been analyzed for the crystal-field splitting of the multiplet manifolds L2S+1J of Er3+(4f11) in C2 symmetry cation sites in single-crystal cubic Er2O3 and Er3+:Y2O3. A solid solution, without a change in the local symmetry, exists between the two compounds, allowing us to identify the weaker transitions in Er3+:Y2O3 from the stronger transitions observed in the uv spectrum of Er2O3. As a result, we have identified a complete set of energy (Stark) levels for the electronic configuration up to the absorption band-edge of these crystals. A total of 134 Stark levels representing 30 multiplets with energies as high as 44 500 cm−1 have been modeled using a parameterized Hamiltonian defined to operate within the Er3+(4f11) electronic configuration. The crystal-field parameters were determined through use of a Monte Carlo method in which 14 independent crystal-field parameters, Bqk, were given random starting values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviations between 134 calculated-to-experimental Stark levels are 5.55 cm−1 (rms error 4.89 cm−1) and 5.08 cm−1 (rms error 4.47 cm−1) for Er3+ in Er2O3 and for Er3+ in Y2O3, respectively. The excellent and consistent agreement between the experimental and calculated Stark levels in both crystals, together with the predicted sets of wave functions, are important for the ongoing analyses of intensity data and magneto-optical studies on these crystals.
Hole carrier concentration and photoluminescence in magnesium doped InGaN and GaN grown on sapphire and GaN misoriented substrates
Authors: Suski T. , Staszczak G. , Grzanka S. , Czernecki R. , Litwin-Staszewska E. , Piotrzkowski R. , Dmowski L. H. , Khachapuridze A. , Kryśko M. , Perlin P. , Grzegory I.
Published: July 2010

Systematic studies of InxGa1−xN layers (0≤x<0.13) doped with Mg were performed. Samples were grown by metal organic vapor phase epitaxy. Intermediate Mg doping in the range of 2×1019 cm−3 was chosen to achieve a maximum hole carrier concentration, pH (as measured by Hall effect) of 4×1018 cm−3 in samples with high x. We confirmed reports on decreasing resistivity in InxGa1−xN:Mg epitaxial layers observed with increasing x. This finding is very important for applications. In the performed research we attempted to separate contributions to pH increase resulting from increase in In-content and an associated decrease in growth temperature, Tgr (necessary to obtain high x). For this purpose In-content increase was achieved by means of either (i) lowering the growth temperature (from 1020 to 830 °C) or by (ii) varying an intended GaN substrate miscut. We demonstrated that the increase in pH in InxGa1−xN:Mg is caused by higher In concentration while a drop in Tgr plays a secondary role. Studies of photoluminescence in the InGaN:Mg layers exhibit band-to-band radiative recombination which has created much controversy. The most important feature of samples grown at temperatures 860 °C and below, is a green band observed in InGaN:Mg layers (not in GaN:Mg obtained at the same Tgr) dominating the whole spectrum at room temperature. Its maximum shifts from 2.5 to 2.2 eV with increasing x up to 0.13. Presence of this band was previously reported for InGaN:Mg. We present arguments that it originates from deep donor level.
Characteristics of high-k Al2O3 dielectric using ozone-based atomic layer deposition for dual-gated graphene devices
Authors: Lee B. , Mordi G. , Kim M. J. , Chabal Y. J. , Vogel E. M. , Wallace R. M. , Cho K. J. , Colombo L. , Kim J.
Published: July 2010

We present characteristics of dual-gated graphene devices with an Al2O3 gate dielectric formed by an O3-based atomic-layer-deposition process. Raman spectra reveal that a O3 process at 25°C on single-layered graphene introduces the least amount defects, while a substantial number of defects appear at 200 °C. This graphene device with O3-based Al2O3 dielectric demonstrates a heterojunction within the graphene sheet when applying VTG and VBG and possesses good dielectric properties with minimal chemical doping, including a high dielectric constant ∼8, low hysteresis width ∼0.2 V, and low leakage current and a carrier mobility of 5000 cm2/V s 25°C in ambient.
Magnetization dynamics of a CrO2 grain studied by micro-Hall magnetometry
Authors: Das P. , Porrati F. , Wirth S. , Bajpai A. , Huth M. , Ohno Y. , Ohno H. , Müller J.
Published: July 2010

Micro-Hall magnetometry is employed to study the magnetization dynamics of a single, micron-size CrO2 grain. With this technique, we track the motion of a single domain wall, which allows us to probe the distribution of imperfections throughout the material. An external magnetic field along the grain’s easy magnetization direction induces magnetization reversal, giving rise to a series of sharp jumps in magnetization. Supported by micromagnetic simulations, we identify the transition to a state with a single cross-tie domain wall, where pinning/depinning of the wall results in stochastic Barkhausen jumps.
Magnet polepiece design for uniform magnetic force on superparamagnetic beads
Authors: Fallesen Todd , Hill David B. , Steen Matthew , Macosko Jed C. , Bonin Keith , Holzwarth George
Published: July 2010

Here we report construction of a simple electromagnet with novel polepieces which apply a spatially uniform force to superparamagnetic beads in an optical microscope. The wedge-shaped gap was designed to keep ∂Bx/∂y constant and B large enough to saturate the bead. We achieved fields of 300–600 mT and constant gradients of 67 T/m over a sample space of 0.5×4 mm2 in the focal plane of the microscope and 0.05 mm along the microscope optic axis. Within this space the maximum force on a 2.8 μm diameter Dynabead was 12 pN with a spatial variation of approximately 10%. Use of the magnet in a biophysical experiment is illustrated by showing that gliding microtubules propelled by the molecular motor kinesin can be stopped by the force of an attached magnetic bead.
Quartz tube extensometer for observation of Earth tides and local tectonic deformations at the Sopronbánfalva Geodynamic Observatory, Hungary
Authors: Mentes Gy.
Published: July 2010

In May 1990, a quartz tube extensometer was installed in the Sopronbánfalva Geodynamic Observatory of the Geodetic and Geophysical Research Institute (GGRI) of the Hungarian Academy of Sciences for recording Earth tides and recent tectonic movements. The paper describes the construction of the extensometer and a portable calibrator used for the in situ calibration of the instrument. The extensometer is very sensitive. Its scale factor is 2.093±0.032 nm/mV according to the highly precise calibration method developed at the GGRI. Since the stability of extensometers is strongly influenced by the geological structure and properties of the rocks in the vicinity of the recording site, the observatory instrument system was tested by coherence analysis between theoretical (as the input signal) and measured tidal data series (as the output signal). In the semidiurnal tidal frequency band the coherence is better than 0.95, while in the diurnal band it is about 0.8. Probably this is due to the fact that the noise is higher in the diurnal band (0.4–0.5 nstr) than in the semidiurnal band (0.19–0.22 nstr). Coherence analysis between theoretical and measured data corrected for barometric changes yielded a small improvement of coherence in both frequency bands, while using temperature data correction, no observable improvement was obtained. Results of the tidal analysis also show that the observatory instrument system is suitable for recording very small tectonic movements. The 18 years of continuous data series measured by the extensometer prove the high quality of the extensometer. On the basis of investigations, it was pointed out that further efforts should be done to improve the barometric correction method and that correction for ocean load, as well as considering topographic and cavity effects are necessary to increase the accuracy of determining tidal parameters.
Polarization asymmetry and optical modal gain saturation via carrier–photon interaction in ZnO
Authors: Kim Bumjin , Kim Heedae , Park Sungkyun , Kyhm Kwangseuk , Cho Chaeryong
Published: July 2010

The polarization dependence of modal gain was examined in ZnO using a variable stripe length method, where the transverse electric (TE) mode gain was dominant over the transverse magnetic (TM) mode gain due to the polarization asymmetry of the wurtzite structure. Modal gain saturation was also investigated using a modal gain contour map for the wavelength and stripe length. The TE modal gain and degree of polarization increased with increasing stripe length up to a threshold length (∼100 μm). At longer stripe lengths, rapid reduction in the carrier density along the stripe resulted in gain saturation and a spectral redshift.
p-type doping and codoping of ZnO based on nitrogen is ineffective: An ab initio clue
Authors: Cui Ying , Bruneval Fabien
Published: July 2010

Whereas nitrogen is regarded as the best candidate to induce p-type doping in ZnO, the practical results are mainly negative either for monodoping or codoping. We perform first-principles calculations to investigate the p-type nature of boron and nitrogen codoped ZnO. The p-type character can be obtained with the proper BN3 substitutional clusters. We propose a mechanism that explains the difficulties to synthesize p-type ZnO samples: the formation of N2 molecules substituting oxygen, which are donors, energetically prevails over any codoping cluster. This mechanism is very general and explains the experimental instability of N-based doping and codoping versus time and temperature.
Photonic crystal reflectance switching by dye electrophoresis
Authors: Krabbe Joshua D. , Brett Michael J.
Published: July 2010

Reflectivity of a photonic crystal device fabricated by glancing angle deposition may be reversibly altered by infiltration with an absorbing dye solution. An electric field controls the dye ion motion through the photonic crystal. Rapid reflectance changes up to 0.4 in the crystal’s optical band gap are demonstrated. The time evolution of the dye movement process is examined and its operation described. This work may have applications for a passive optical display.
Kyrgyz “revolutions” in 2005 and 2010: comparative analysis of mass mobilization
Authors: Temirkulov Azamat
Published: July 2010

This article compares causes and mechanisms of the mass mobilizations which took place in Kyrgyzstan in 2005 and 2010. The upheavals of 2005, the so called “Tulip Revolution,” led to the ousting of President Akaev who was replaced by Kurmanbek Bakiev. In 2010, Bakiev himself had to flee the country after violent social upheavals. As this analysis shows, the causes for both series of events were similar: neopatrimonial rule and the elite's control of resources together with oppressive tactics stirred up discontent among wide parts of the population and instigated violent protest. The mechanisms of mass mobilization, however, differed considerably. While the revolution of 2005 was carried out as the concerted action of varied political forces and NGOs, which, supported by patronage networks and traditional institutions, offered material and solidary incentives for the crowds, the great mass of people who took part in the 2010 protests were spontaneously mobilized through purposive incentives when news of the killings spread through the media.
Energetic particle driven instability in wall-stabilized high-β plasmas
Authors: Matsunaga G. , Shinohara K. , Aiba N. , Sakamoto Y. , Isayama A. , Asakura N. , Suzuki T. , Takechi M. , Oyama N. , Urano H.
Published: July 2010

We have observed a fishbone-like mode in high-β plasmas above the ideal β limit without a conducting wall. The mode frequency chirps down, and its initial value is close to the precession frequency of trapped fast ions produced by perpendicularly injected neutral beams. This mode can often induce the resistive wall mode (RWM). The mode is observed mainly in the high-βN plasma where an ideal kink-ballooning mode (IKBM) and the RWM are marginally stable. Since this mode and the RWM were simultaneously observed, the mode is attributed to the interaction between the trapped fast ions and a marginally stable IKBM stabilized by a conducting wall. Actually, the MARG2D analysis shows that the IKBM is wall-stabilized and has a real frequency of the same order as the observed mode frequency. From these results, the observed mode was named ‘energetic particle driven wall mode (EWM)’. Moreover, the EWM can change the edge localized mode (ELM) behaviour. For example, it was observed that the ELM was synchronized with the EWM. An energy loss due to the EWM-triggered ELM is smaller, and its frequency becomes higher compared with the usual ELM.
Fast-ion losses induced by ACs and TAEs in the ASDEX Upgrade tokamak
Authors: García-Muñoz M. , Hicks N. , van Voornveld R. , Classen I.G.J. , Bilato R. , Bobkov V. , Brambilla M. , Bruedgam M. , Fahrbach H.-U. , Igochine V. , Jaemsae S. , Maraschek M. , Sassenberg K.
Published: July 2010

The phase-space of convective and diffusive fast-ion losses induced by shear Alfvén eigenmodes has been characterized in the ASDEX Upgrade tokamak. Time-resolved energy and pitch-angle measurements of fast-ion losses correlated in frequency and phase with toroidal Alfvén eigenmodes (TAEs) and Alfvén cascades (ACs) have allowed to identify both loss mechanisms. While single ACs and TAEs eject resonant fast-ions in a convective process, the overlapping of AC and TAE spatial structures leads to a large fast-ion diffusion and loss. The threshold for diffusive fast-ion losses depends on the ion energy (gyroradius). Diffusive fast-ion losses with gyroradius ≈70 mm have been observed with a single TAE for local radial displacements of the magnetic field lines larger than ≈2 mm. Multiple frequency chirping ACs cause an enhancement of the diffusive losses. The ACs and TAEs radial structures have been reconstructed by means of cross-correlation techniques between the fast-ion loss detector and the electron cyclotron emission radiometer.
MeV-range fast ion losses induced by fishbones on JET
Authors: von Thun C. Perez , Perona A. , Johnson T. , Sharapov S.E. , Reich M. , Kiptily V.G. , Cecconello M. , Salmi A. , Goloborod'ko V. Ya , Pinches S.D. , García-Muñoz M. , Darrow D. , Brix M. , Voitsekhovitch I.
Published: July 2010

Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt (MeV) range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The measurements are obtained with a 2D scintillator probe diagnostic installed on JET, which is designed to detect lost ions only above a certain energy threshold (E
min,D ∼ 200 keV). In the case reported here the lost ions are identified as fast protons which had been accelerated to high energies by ICRF minority heating. The energy of the lost protons (∼0.5–4 MeV) is approximately one order of magnitude higher than the energy of the injected beam ions (maximum 130 keV) driving the fishbone. Losses arriving at the probe are enhanced by about a factor 10–20 with respect to MHD-quiescent levels, and are found to increase quadratically with the fishbone amplitude. Using a number of simplifying assumptions, numerical simulations have been performed which combine the HAGIS, MISHKA and SELFO codes (where the distribution function predicted by SELFO has been validated against neutral particle analyser measurements). The losses are found to originate from orbit stochastic diffusion of trapped protons near the plasma boundary or from counter-passing protons deep in the plasma core, which transit under the influence of the fishbone into an unconfined trapped orbit. The simulations show further that the losses are of non-resonant type. The simulated energy and pitch angle distribution of the losses, the temporal behaviour of the losses during a fishbone cycle and the scaling of the losses with the fishbone amplitude are compared with experiment. The simulation results are mostly in broad agreement with experiment, but some of the predictions could not be reconciled with experiment using this model.
Optimization of the active MHD spectroscopy system on JET for the excitation of individual intermediate and high-n Alfvén eigenmodes
Authors: Panis T. , Testa D. , Fasoli A. , Klein A. , Carfantan H. , Blanchard P.
Published: July 2010

The stability of Alfvén eigenmodes (AEs) is studied experimentally in the JET tokamak by observing the plasma response to antenna-driven frequency-sweeping perturbations at the plasma edge. During the 2008/9 experimental campaigns, the complete set of the new antennas was operated and AEs with toroidal mode numbers (n) in the intermediate-n range were excited under various plasma conditions. In this paper, we describe the results of the work achieved on the technical aspects of the diagnostic. The antenna currents have been optimized to improve the antenna–plasma coupling. The mode-tracking system has been upgraded for real-time targeting of modes with specific n. As an example of the optimized performance of the diagnostic, the paper concludes with a report on the damping rates of n = 3–5 toroidal AEs that were measured dynamically while the background plasma parameters were evolving in time.
Neutron emission levels during the ITER zero-activation phase
Authors: Gatu Johnson M. , Hellesen C. , Andersson Sundén E. , Cecconello M. , Conroy S. , Ericsson G. , Gorini G. , Nocente M. , Ronchi E. , Tardocchi M. , Weiszflog M.
Published: July 2010

In recent experiments at JET, a contribution to the neutron emission from reactions between beryllium and 3He, 4He and H has been identified. With the beryllium wall planned for ITER, this raises the question of possible neutron activation during the ITER zero-activation phase. Here, we estimate the neutron emission rates for various heating scenarios foreseen for this ITER phase using Monte Carlo simulations. The emission is seen to be strongly dependent on the scenario chosen and the assumptions involved. We find that fundamental minority heating can contribute on the scale of low temperature deuterium plasmas, depending on minority concentration and ion cyclotron resonance heating (ICRH) power applied. Harmonic ICRH leads to production of tails that can give rise to significant neutron emission rates, while rates from hydrogen beams will be near zero. Better knowledge of the zero-activation phase conditions, and more sophisticated ICRH codes, would be needed to give exact rate predictions. We conclude that rates from the so-called zero-activation plasmas will be significantly lower than expected for the DD or DT phases, but far from zero.
Fast ion redistribution and losses in JET advanced tokamak scenario*
Authors: Nabais F. , Kiptily V.G. , Pinches S.D. , Sharapov S.E.
Published: July 2010

The influence of Alfvén eigenmodes (AEs) (core-localized toroidal Alfvén eigenmode (TAE) and high-m global TAE) on redistribution and loss of fast ions in the advanced tokamak scenario has been investigated in JET dedicated experiments. Temporal evolution of the spatial structure of AEs present in the plasma during q-profile evolution has been calculated with the MISHKA code. On the other hand, fast ion losses with resolution in energy and pitch angle were measured with a scintillator probe, while the internal redistribution of the fast ions was analysed by measuring the temporal evolution of the radial profiles of γ-ray emission coming from the fast ions colliding with the main impurities, Be and C. Correlating the measurements above, it is possible to assess the effect of AEs on redistribution and loss of fast ions. It is found that the TAE localized in the core of the plasma causes a severe redistribution of the fast ions in the plasma centre, leading to a flattening of the vertical profile of γ-ray emission. In addition, the core-localized TAE also causes enhanced fast ion losses. As the core-localized TAE moves radially outwards, a transition to high-m global TAE occurs. In the transformation phase, a coupled mode with components both in the core and in the edge of the plasma exists. The maximum number of losses is normally measured when this coupled mode with a large radial extent is present in the plasma.
A Phosphatidylinositol 3-Kinase/Protein Kinase B-independent Activation of Mammalian Target of Rapamycin Signaling Is Sufficient to Induce Skeletal Muscle Hypertrophy
Authors: Goodman Craig A. , Miu Man Hing , Frey John W. , Mabrey Danielle M. , Lincoln Hannah C. , Ge Yejing , Chen Jie , Hornberger Troy A.
Published: July 2010

It has been widely proposed that signaling by mammalian target of rapamycin (mTOR) is both necessary and sufficient for the induction of skeletal muscle hypertrophy. Evidence for this hypothesis is largely based on studies that used stimuli that activate mTOR via a phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB)-dependent mechanism. However, the stimulation of signaling by PI3K/PKB also can activate several mTOR-independent growth-promoting events; thus, it is not clear whether signaling by mTOR is permissive, or sufficient, for the induction of hypertrophy. Furthermore, the presumed role of mTOR in hypertrophy is derived from studies that used rapamycin to inhibit mTOR; yet, there is very little direct evidence that mTOR is the rapamycin-sensitive element that confers the hypertrophic response. In this study, we determined that, in skeletal muscle, overexpression of Rheb stimulates a PI3K/PKB-independent activation of mTOR signaling, and this is sufficient for the induction of a rapamycin-sensitive hypertrophic response. Transgenic mice with muscle specific expression of various mTOR mutants also were used to demonstrate that mTOR is the rapamycin-sensitive element that conferred the hypertrophic response and that the kinase activity of mTOR is necessary for this event. Combined, these results provide direct genetic evidence that a PI3K/PKB-independent activation of mTOR signaling is sufficient to induce hypertrophy. In summary, overexpression of Rheb activates mTOR signaling via a PI3K/PKB-independent mechanism and is sufficient to induce skeletal muscle hypertrophy. The hypertrophic effects of Rheb are driven through a rapamycin-sensitive (RS) mechanism, mTOR is the RS element that confers the hypertrophy, and the kinase activity of mTOR is necessary for this event.
Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability
Authors: Dijkstra Camelia E. , Larkin Oliver J. , Anthony Paul , Davey Michael R. , Eaves Laurence , Rees Catherine E. D. , Hill Richard J. A.
Published: July 2010

Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to reproduce aspects of weightlessness, on the Earth. We used a superconducting magnet to levitate growing bacterial cultures for up to 18 h, to determine the effect of diamagnetic levitation on all phases of the bacterial growth cycle. We find that diamagnetic levitation increases the rate of population growth in a liquid culture and reduces the sedimentation rate of the cells. Further experiments and microarray gene analysis show that the increase in growth rate is owing to enhanced oxygen availability. We also demonstrate that the magnetic field that levitates the cells also induces convective stirring in the liquid. We present a simple theoretical model, showing how the paramagnetic force on dissolved oxygen can cause convection during the aerobic phases of bacterial growth. We propose that this convection enhances oxygen availability by transporting oxygen around the liquid culture. Since this process results from the strong magnetic field, it is not present in other weightless environments, e.g. in Earth orbit. Hence, these results are of significance and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena.
Detecting phase transitions in supercritical mixtures: an enabling tool for greener chemical reactions
Authors: Ke Jie , Sánchez-Vicente Yolanda , Akien Geoffrey R. , Novitskiy Alexander A. , Comak Gurbuz , Bagratashvili Victor N. , George Michael W. , Poliakoff Martyn
Published: July 2010

Detecting phase transitions in high-pressure CO
2
and supercritical fluids was first attempted in the nineteenth century. By contrast, Green Chemistry, the design and implementation of cleaner methods of manufacturing and processing chemicals, is barely 20 years old. Now, the use of CO
2
as an environmentally more acceptable replacement for traditional solvents for greener chemical reactions is creating the need for new, more rapid methods for elucidating high-pressure phase behaviour. This paper describes the advantages and limitations of a number of approaches, developed in Nottingham, to meet this need, including acoustic measurements, shear-mode quartz sensors, the fibre-optic reflectometer, the use of holey fibres, attenuated total reflectance infrared spectroscopy and pressure drop measurements.
The dynamics of biogeographic ranges in the deep sea
Authors: McClain Craig R. , Hardy Sarah Mincks
Published: July 2010

Anthropogenic disturbances such as fishing, mining, oil drilling, bioprospecting, warming, and acidification in the deep sea are increasing, yet generalities about deep-sea biogeography remain elusive. Owing to the lack of perceived environmental variability and geographical barriers, ranges of deep-sea species were traditionally assumed to be exceedingly large. In contrast, seamount and chemosynthetic habitats with reported high endemicity challenge the broad applicability of a single biogeographic paradigm for the deep sea. New research benefiting from higher resolution sampling, molecular methods and public databases can now more rigorously examine dispersal distances and species ranges on the vast ocean floor. Here, we explore the major outstanding questions in deep-sea biogeography. Based on current evidence, many taxa appear broadly distributed across the deep sea, a pattern replicated in both the abyssal plains and specialized environments such as hydrothermal vents. Cold waters may slow larval metabolism and development augmenting the great intrinsic ability for dispersal among many deep-sea species. Currents, environmental shifts, and topography can prove to be dispersal barriers but are often semipermeable. Evidence of historical events such as points of faunal origin and climatic fluctuations are also evident in contemporary biogeographic ranges. Continued synthetic analysis, database construction, theoretical advancement and field sampling will be required to further refine hypotheses regarding deep-sea biogeography.