bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of the α1L‐adrenoceptor in rat cerebral cortex and possible relationship between α1L‐ and α1A‐adrenoceptors
Authors: Morishima S , Suzuki F , Yoshiki H , Md Anisuzzaman A S , Sathi Z S , Tanaka T , Muramatsu I
Published: January 2008

Background and purpose:

In addition to α1A, α1Band α1D‐adrenoceptors (ARs), putative α1L‐ARs with a low affinity for prazosin have been proposed. The purpose of the present study was to identify the α1A‐AR and clarify its pharmacological profile using a radioligand binding assay.

Experimental approach:

Binding experiments with [3H]‐silodosin and [3H]‐prazosin were performed in intact tissue segments and crude membrane preparations of rat cerebral cortex. Intact tissue binding assays were also conducted in rat tail artery.

Key results:

[3H]‐silodosin at subnanomolar concentrations specifically bound to intact tissue segments and membrane preparations of rat cerebral cortex at the same density (approximately 150 fmol mg−1total tissue protein). The binding sites in intact segments consisted of α1Aand α1L‐ARs that had different affinities for prazosin, while the binding sites in membranes showed an α1A‐AR‐like profile having single high affinity for prazosin. [3H]‐prazosin also bound at subnanomolar concentrations to α1Aand α1B‐ARs but not α1L‐ARs in cerebral cortex; the binding densities being approximately 200 and 290 fmol mg−1protein in the segments and the membranes, respectively. In the segments of tail artery, [3H]‐silodosin only recognized α1A‐ARs, whereas [3H]‐prazosin bound to α1Aand α1B‐ARs.

Conclusions and implications:

The present study clearly reveals the presence of α1L‐ARs as a pharmacologically distinct entity from α1Aand α1B‐ARs in intact tissue segments of rat cerebral cortex but not tail artery. However, the α1L‐ARs disappeared after tissue homogenization, suggesting their decomposition and/or their pharmacological profile changes to that of α1A‐ARs.

British Journal of Pharmacology(2008)153, 1485–1494; doi:10.1038/sj.bjp.0707679; published online 28 January 2008
Development and operation of a Cs-free J-PARC H− ion source
Authors: Oguri H. , Ueno A. , Namekawa Y. , Ohkoshi K. , Kondo Y. , Ikegami K.
Published: January 2008

A cesium-free H− ion source driven with a LaB6 filament was developed for the J-PARC. It was operated for the J-PARC linac beam commissioning, which was started on 20 November 2006. Eight runs of 2 or 3week beam commissioning were done until the end of June 2007. The source was mainly operated with a duty factor of 0.8% (320μs and 25Hz) while providing a 5mA beam typically. Each interval of the runs, precise optimizations, such as the filament position, and so on, are examined. At present, a H− beam with a current of 38mA and a rms normalized emittance of 0.22πmmmrad is extracted with a duty factor of 0.8% (320μs and 25Hz).
Beam extraction from a Hall-type ion accelerator
Authors: Ando Akira , Tashiro Masashi , Hitomi Keiichiro , Hattori Kunihiko , Inutake Masaaki
Published: January 2008

Fundamental characteristics of beam extraction from a Hall-type accelerator working with permanent magnets were investigated. Ions were extracted by an axial electric field Ez in a small annular plasma channel with a radial magnetic field Br. Effects of discharge current and voltage, length of discharge channel, and gas flow rate were examined. It can deliver a large beam current density of more than 100mA∕cm2 with low beam energy of 50eV. By biasing an additional plasma chamber attached at the extraction area, the beam energy was controlled independently of the beam current.
Experimental results of an electron cyclotron resonance oxygen source and a low energy beam transport system for 1MeV integral split ring radio frequency quadruple accelerator upgrade project
Authors: Peng S. X. , Zhang M. , Song Z. Z. , Xu R. , Zhao J. , Yuan Z. X. , Yu J. X. , Chen J. , Guo Z. Y.
Published: January 2008

To meet the requirements of developing separated function radio frequency quadruple (rfq) and upgrading the 1MeV integral split ring rfq accelerator, an electron cyclotron resonance O+ ion source and low energy beam transport (LEBT) system have been developed. Using two Einzel lenses to focus the beam, more than 6mA O+ peak beam current with energy of 22keV can be easily obtained at the end of LEBT when the duty faction is at 1∕6. The normalized root-mean-square emittance of 90% of the beam is about 0.12πmmmrad. By changing the focusing power of lenses, the beam waist can be shifted from 80mm before the beam diaphragm 2to80mm after it. The experimental results will be presented in this article.
Side extraction duoPIGatron-type ion source
Authors: Gushenets V. I. , Oks E. M. , Hershcovitch Ady , Johnson B. M.
Published: January 2008

We have designed and constructed a compact duoPIGatron-type ion source, for possible use in ion implanters, in which ions are extracted from a side aperture in contrast to conventional duoPIGatron sources with axial ion extraction. The size of the side extraction aperture is 1×40mm2. The ion source was developed to study physical and technological aspects relevant to an industrial ion source. The side extraction duoPIGatron has a stable arc, uniformly bright illumination, and dense plasma. The present work describes some operating parameters of the ion source using argon and BF3. Total unanalyzed beam currents were 40mA with Ar at an arc current of 7A and 13mA with BF3 gas at an arc current of 9A.
Modeling of surface-dominated plasmas: From electric thruster to negative ion source
Authors: Taccogna F. , Schneider R. , Longo S. , Capitelli M.
Published: January 2008

This contribution shows two important applications of the particle-in-cell/monte Carlo technique on ion sources: modeling of the Hall thruster SPT-100 for space propulsion and of the rf negative ion source for ITER neutral beam injection. In the first case translational degrees of freedom are involved, while in the second case inner degrees of freedom (vibrational levels) are excited. Computational results show how in both cases, plasma-wall and gas-wall interactions play a dominant role. These are secondary electron emission from the lateral ceramic wall of SPT-100 and electron capture from caesiated surfaces by positive ions and atoms in the rf negative ion source.
Electron cyclotron resonance ion sources with arc-shaped coils
Authors: Suominen P. , Wenander F.
Published: January 2008

The minimum-B magnetic field structure of electron cyclotron resonance ion sources (ECRIS) has conventionally been formed with a combination of solenoids and a hexapole magnet. However, minimum-B structure can also be formed with arc-shaped coils. Recently it was shown that multiply charged heavy-ions can be produced with an ECRIS based on such a structure. In the future, the ARC-ECRIS magnetic field structure can be an interesting option for radioactive ion-beam sources and charge-breeders as well as for high performance ECRIS allowing for 100GHz plasma heating. This paper presents some design aspects of the ARC-ECRIS.
New force replica exchange method and protein folding pathways probed by force-clamp technique
Authors: Kouza Maksim , Hu Chin-Kun , Li Mai Suan
Published: January 2008

We have developed a new extended replica exchange method to study thermodynamics of a system in the presence of external force. Our idea is based on the exchange between different force replicas to accelerate the equilibrium process. This new approach was applied to obtain the force-temperature phase diagram and other thermodynamical quantities of the three-domain ubiquitin. Using the Cα-Go model and the Langevin dynamics, we have shown that the refolding pathways of single ubiquitin depend on which terminus is fixed. If the N end is fixed then the folding pathways are different compared to the case when both termini are free, but fixing the C terminal does not change them. Surprisingly, we have found that the anchoring terminal does not affect the pathways of individual secondary structures of three-domain ubiquitin, indicating the important role of the multidomain construction. Therefore, force-clamp experiments, in which one end of a protein is kept fixed, can probe the refolding pathways of a single free-end ubiquitin if one uses either the polyubiquitin or a single domain with the C terminus anchored. However, it is shown that anchoring one end does not affect refolding pathways of the titin domain I27, and the force-clamp spectroscopy is always capable to predict folding sequencing of this protein. We have obtained the reasonable estimate for unfolding barrier of ubiquitin, using the microscopic theory for the dependence of unfolding time on the external force. The linkage between residue Lys48 and the C terminal of ubiquitin is found to have the dramatic effect on the location of the transition state along the end-to-end distance reaction coordinate, but the multidomain construction leaves the transition state almost unchanged. We have found that the maximum force in the force-extension profile from constant velocity force pulling simulations depends on temperature nonlinearly. However, for some narrow temperature interval this dependence becomes linear, as have been observed in recent experiments.
Ab initio potential energy surface and bound states of the Xe–CO complex
Authors: Wang Zhongquan , Gong Mingyan , Zhang Yu , Feng Eryin , Cui Zhifeng
Published: January 2008

The first two-dimensional potential energy surface for the Xe–CO van der Waals interaction is calculated by the single and double excitation coupled-cluster theory with noniterative treatment of triple excitations. Mixed basis sets, aug-cc-pVQZ for the C and O atoms, and aug-cc-pVQZ-PP for the Xe atom, with an additional (3s3p2d2f1g) set of midbond functions, are used. Our potential energy surface has a single, nearly T-shaped minimum of −131.87cm−1 at Re=7.80a0 and θe=102.5°. Based on the potential, the bound state energies are calculated for seven isotopomers of the Xe–C12O16 complex, seven isotopomers of the Xe–C13O16 complex, and three isotopomers of the Xe–C13O18 complex. Compared with available experimental data, the predicted transition frequencies and spectroscopic constants are in good agreement with the experimental results.
K
selection in one-photon mass-analyzed threshold ionization of CH3I and CD3I to the X̃E3∕22 state cations
Authors: Lee Mina , Bae Yong Jin , Kim Myung Soo
Published: January 2008

One-photon mass-analyzed threshold ionization (MATI) spectra for the X̃E3∕22 states of CH3I+ and CD3I+ were measured using vacuum ultraviolet radiation generated by four-wave mixing in Kr. Spin-orbit density functional theory calculations at the B3LYP/aug-cc-pVTZ level and spin-orbit/Jahn-Teller calculations were made to aid vibrational assignment. Each vibrational band consisted of several peaks due to different ΔK transitions, which could be assigned by using molecular parameters determined in the previous high resolution photodissociation spectroscopic study. Possibility of generating mass-selected, vibronically selected and K-selected ion beam with decent intensity by one-photon MATI was demonstrated. The ionization energies to the X̃E3∕22 states of CH3I+ and CD3I+ corrected for the rotational contribution were 9.5386±0.0006 and 9.5415±0.0006eV, respectively.
Theory of pair connectedness in templated quenched-annealed systems
Authors: Sarkisov Lev
Published: January 2008

Recently, several families of promising porous materials have been proposed where the porous matrix forms in the presence of additional molecules or templates. These materials find applications in separations, sensing, catalysis, and other technologies. For these systems, it is important to understand the connectedness of the matrix species and the porous space. In the first case, this would characterize the integrity of the porous material, whereas the second property is directly related to the accessibility of the interior porous space and thus to the function of the material. Here, we propose an integral equation theory which describes cluster population and percolation phenomena for matrix and template species at the stage of the templated material formation. We also extend this theory to provide structural characterization of the fluid confined in a templated structure. The predictions of the theory are tested for the case of rigid molecular species made of hard sphere interaction sites and compared with computer simulations. We discuss the effect of the system density, species structure, and other parameters on the average cluster size and percolation threshold for the components of the system.
Gyrokinetic theory and simulation of turbulent energy exchange
Authors: Waltz R. E. , Staebler G. M.
Published: January 2008

A previous gyrokinetic theory of turbulent heating [F. L. Hinton and R. E. Waltz, Phys. Plasma 13, 102301 (2006)] is simplified and extended to show that the local radial average of terms in the gyrokinetic turbulent heating (which survive in the drift kinetic limit) are actually closer to a turbulent energy exchange between electrons and ions. The integrated flow for the local exchange is simulated with the GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] delta-f gyrokinetic code and found to be small in a well studied DIII-D [M. A. Mahdavi and J. L. Luxon, “DIII-D Tokamak Special Issue” Fusion Sci. Technol. 48, 2 (2005)] L-mode discharge.
Two simple tests for models of current-induced magnetization switching
Authors: Theodoropoulou N. , Sharma A. , Pratt W. P. , Bass J. , Stiles M. D. , Xiao Jiang
Published: January 2008

We describe two simple tests for models of current-induced magnetization switching due to spin-transfer torque in ferromagnetic/nonmagnetic/ferromagnetic (F/N/F) trilayers. The first involves comparing calculated and measured values of the ratio X=ΔI(Cu)∕ΔI(CuGe), where ΔI=I+−I−, the difference between switching currents for + and − current directions, when only the N-layer is changed from Cu to a dilute CuGe alloy. The Ge in Cu causes a large increase in elastic scattering (large reduction in mean-free path), but only a smaller increase in spin-orbit scattering (leaving the spin-diffusion length still relatively long). The second involves comparing calculated and measured values of the ratios (I+∕I−) for both Cu and CuGe. Unexpectedly, the most sophisticated models generally fit the first ratio least well at both 295 and 4.2K. None of the models agree with the ratio (I+∕I−).
Crystallization of amorphous alloys induced by the radio frequency magnetic field
Authors: Kopcewicz Michael
Published: January 2008

The effect of the rf field induced crystallization of Co-containing amorphous alloys, observed in the rf-Mössbauer study of Fe81−x−yNixCoyZr7B12 alloys, is discussed in detail. This effect was attributed to mechanical deformations originating from magnetostrictive vibrations induced by the rf field (rf-sideband effect). The rf field induced crystallization is particularly large for high magnetostriction Co-containing alloys, and it does not occur in the Co-free alloys with smaller magnetostriction. The magnetostriction origin of the crystallization effect induced by the rf field is supported by the measurements of the magnetostriction constants of the alloys studied.
Ellipsometric in situ measurement of oxidation kinetics and thickness of (C2–C20) alkylsilyl (sub)monolayers
Authors: Prunici Pavel , Hess Peter
Published: January 2008

In situ detection using spectroscopic ellipsometry and Fourier transform infrared (FTIR) spectroscopy was employed to study the oxidation of chemically bonded layers of dimethylsilyl groups, trimethylsilyl groups, and alkylsilyl chains [CH3(CH2)n–Si(CH3)2–] with n=17,11,9,7,3 connected via siloxane bridges to oxide-covered silicon. Vacuum ultraviolet laser-induced oxidation of the organic end groups enhanced the sensitivity and accuracy of the in situ ellipsometric analysis of these ultrathin terminations. In addition, in situ single-reflection FTIR spectroscopy was employed to monitor the C–H stretching frequencies of the methylene and methyl groups. Although the lengths of the attached hydrocarbon chains, using octadecyltrichlorosilane and octadecyldimethylchlorosilane as coupling agents, were similar, the estimated thicknesses of the organic layers were 2.6 and 0.92nm, respectively. For the small dimethylsilyl and trimethylsilyl terminations thicknesses of 0.24 and 0.20nm, respectively, were estimated with a Cauchy dispersion model using n0=1.45 as the refractive index. The observed oxidation kinetics was first order. Different oxidation rate coefficients could be discriminated for alkylsilyl groups with varying chain length.
Effect of Nb on the magnetic properties and microstructure for nanocomposite Nd2Fe14B∕α-Fe alloys by three-dimensional atom probe
Authors: Xu H. , Zhang S. Y. , Tan X. H. , Hou X. L. , Ni J. S. , Yue M.
Published: January 2008

The influence of Nb addition on the magnetic properties and microstructure for nanocomposite Nd9.5Fe79−xCo5NbxB6.5 (x=0,1,2,3) magnets was investigated. The results showed that Nb additon improved the coercivity obviously. An intergranular Nb–Fe–B phase with a chemical composition near the Nb:Fe:B stoichiometry of 1:2:1 between the Nd2Fe14B interface was found for Nd9.5Fe77Co5Nb2B6.5 by a three-dimensional atom probe technique, which provides direct evidence of the improvement of magnetic properties.
Magnetic properties of Sm5(Fe,Co)17 melt-spun ribbons
Authors: Saito Tetsuji
Published: January 2008

An investigation of the synthesis of the Sm5(Fe1−xCox)17 (x=0–0.3) phase and its magnetic properties is presented. The Curie temperature of the amorphous Sm5(Fe,Co)17 melt-spun ribbon phase increases with increasing cobalt content of the Sm5(Fe,Co)17 melt-spun ribbon. Heat treatment of amorphous Sm5(Fe,Co)17 melt-spun ribbons resulted in the formation of the Sm5(Fe,Co)17 and Sm(Fe,Co)3 phases. Annealed Sm5Fe17 melt-spun ribbon exhibited a large coercivity of 36.8kOe with a remanence of 40emu∕g. The remanence of the Sm5Fe17 melt-spun ribbon was increased by the substitution of Co for Fe in the Sm5Fe17 melt-spun ribbon. However, the substitution resulted in a decrease in the coercivity. This was due to the formation of the Sm(Fe,Co)3 phase.
Supercycled homonuclear dipolar decoupling in solid-state NMR: Toward cleaner H1 spectrum and higher spinning rates
Authors: Leskes Michal , Madhu P. K. , Vega Shimon
Published: January 2008

A homonuclear dipolar decoupling scheme based on windowed phase-modulated Lee–Goldburg (wPMLG) pulse sequences that causes a“z-rotation” of the spins for high-resolution proton NMR spectroscopy of solids is described and analyzed. This supercycled scheme suppresses the effect of pulse imperfections on the spectra and significantly relaxes the off-resonance dependence of the line-narrowing efficiency and scale factor. This leads to a broad spectral window that is free of artifacts such as zero lines, image peaks, and localized rotor-radio-frequency resonances. High-resolution H1 spectra and two-dimensional homonuclear H1–H1 correlation spectra of standard amino acids, obtained by a combination of this supercycled scheme with magic angle spinning frequencies up to 25kHz, are demonstrated.
The morphology control of pentacene for write-once-read-many-times memory devices
Authors: Lin Jian , Ma Dongge
Published: January 2008

We realized write-once-read-many-times (WORM) memory devices based on pentacene and demonstrated that the morphology control of the vacuum deposited pentacene thin film is greatly important for achieving the unique nonvolatile memory properties. The resulted memory devices show a high ON/OFF current ratio (104), long retention time (over 12 h), and good storage stability (over 240 h). The reduction of the barrier height caused by a large interface dipole and the damage of the interface dipole under a critical bias voltage have been used to explain the transition processes. The achievement of excellent WORM memory based on pentacene opens up a new application field for organic materials.
Auger recombination in InN thin films
Authors: Jang D.-J. , Lin G.-T. , Hsiao C.-L. , Tu L. W. , Lee M.-E.
Published: January 2008

Auger recombination is studied in InN thin films using an ultrafast time-resolved photoluminescence apparatus. The decay rates are analyzed with nonlinear dependence of the photoluminescence intensity on the carrier concentration. The fitted radiative recombination coefficients at a temperature of 35K are consistent with the theoretical prediction. The Auger rates are small at low carrier concentrations but increase quadratically with the carrier concentration. The Auger activation energies of 4.3 and 9.0meV obtained from the temperature-dependent Auger coefficient indicate that Auger recombination is weakly dependent on temperature and is a phonon-assisted process.
Conversion from transparent antiferromagnet KNiF3 to transparent ferrimagnets
Authors: Manaka H. , Watanabe Y. , Kikunaga K. , Yamamoto T. , Terada N. , Obara K.
Published: January 2008

We succeeded in performing a magnetic conversion from transparent antiferromagnet KNiF3 to transparent ferrimagnets, with a spontaneous ferromagnetic moment by a percolation method. Considering Coulomb repulsion, the origin of the spontaneous ferromagnetic moment is explained by an inhomogeneous antiferromagnetic spin arrangement, even if nonmagnetic ions are dispersed homogenously over KNiF3. The ferromagnetic transition temperature was obtained to be 24–26K. The transmittance at 600–1000nm was excellent. This compound shows an alternative that can be used for an optical isolator that uses commercial semiconductor lasers, and can widely be used in next generation optical information networks.
Effect of donor localization on the magnetic properties of Zn–Co–O system
Authors: Liu Xue-Chao , Shi Er-Wei , Chen Zhi-Zhan , Zhang Tao , Zhang Yong , Chen Bo-Yuan , Huang Wei , Liu Xi , Song Li-Xin , Zhou Ke-Jin , Cui Ming-Qi
Published: January 2008

The effect of donor localization on the magnetic properties of Zn–Co–O system was investigated by resonant inelastic x-ray scattering and first principle calculations. It was found that the ferromagnetic coupling was induced through charge transfer between Co 3d and donor defect. The charge transfer was dependent on the electron localization of donor defect. The electron localization of oxygen vacancy defect was much stronger than that of donor defect formed by the substitution of Al3+ for Zn2+. In order to elucidate the magnetic mechanism, a series of Zn0.95Co0.05O and Zn0.94Co0.05Al0.01O films were prepared under different oxygen partial pressure (PO2). The magnetic properties of Zn0.95Co0.05O films were dependent on PO2, while Zn0.94Co0.05Al0.01O films showed stable ferromagnetism.
Heteroepitaxial growth of ferromagnetic rutile CoxTi1−xO2−δ on GaN (0001)
Authors: Hirose Yasushi , Hitosugi Taro , Kasai Junpei , Furubayashi Yutaka , Nakajima Kiyomi , Chikyow Toyohiro , Konuma Seiji , Shimada Toshihiro , Hasegawa Tetsuya
Published: January 2008

A rutile CoxTi1−xO2−δ (100) film was heteroepitaxially grown on GaN (0001) by pulsed laser deposition. Magneto-optical Kerr effect and cross-sectional transmission electron microscope (TEM) measurements revealed that Co0.03Ti0.97O2−δ films prepared at an oxygen partial pressure of 10−6–10−5Torr with a carrier density ne⩾3×1018cm−3 exhibit room-temperature ferromagnetism without any precipitates or secondary phase. High-resolution TEM observations confirmed that the interface between CoxTi1−xO2−δ and GaN is atomically smooth without intermixing. These results lead us to conclude that CoxTi1−xO2−δ is promising as a spin injector in GaN-based spin-electronic devices.
Toward tunable light propagation and emission in thin nanostructured plasmonic waveguides
Authors: Billaudeau Cyrille , Collin Stéphane , Pardo Fabrice , Bardou Nathalie , Pelouard Jean-Luc
Published: January 2008

High-resolution angle-resolved transmission measurements are carried out through nanostructured plasmonic waveguides made of thin gold films with very narrow slits deposited on GaAs substrates. They reveal transmission intensity modulations along the air/metal surface plasmon band, due to the presence of metal/substrate surface modes. Two propagation regimes have been identified. In this plasmonic waveguide, the radiative emission can be enhanced or inhibited by a slight modification of the refractive index of the substrate (δn∕n≃1%), allowing to control the propagation regime of surface plasmon waves along the air/metal interface.
A generalized heat transfer model for thin film bearings at head-disk interface
Authors: Zhou W. D. , Liu B. , Yu S. K. , Hua W. , Wong C. H.
Published: January 2008

The physics of the heat transfer process from the slider of a hard disk drive to its disk is discussed. A generalized heat transfer model, which incorporates various molecular dynamics models, is proposed to solve the heat transfer problem in thin film bearings at head-disk interface. The proposed model considers the impact of molecular collisions between film molecules and solid surfaces, which plays an important role in the heat transfer of thin film bearings and is expected to improve the accuracy of predicting the thermal protrusion caused by the heating of the slider at the head-disk interface of hard disk drives.
Storage and selective release of optical information based on fractional stimulated Raman adiabatic passage in a solid
Authors: Wang Hai-Hua , Wang Lei , Wei Xiao-Gang , Li Ya-Juan , Du Dun-Mao , Kang Zhi-Hui , Jiang Yun , Gao Jin-Yue
Published: January 2008

We demonstrate storage and selective release of a light pulse in a Pr:YSO crystal, which is based on atomic spin coherence created by fractional stimulated Raman adiabatic passage (STIRAP). The fractional STIRAP gives better storage fidelity compared to STIRAP. Selective release of stored optical information and better storage fidelity have practical applications in information processing and all-optical communication.
High-frequency metallic nanomechanical resonators
Authors: Li T. F. , Pashkin Yu. A. , Astafiev O. , Nakamura Y. , Tsai J. S. , Im H.
Published: January 2008

We developed a technology to fabricate fully metallic doubly clamped beams working as nanomechanical resonators. Measured with a magnetomotive detection scheme, the beams, made of polycrystalline metal films, show as good quality as previously reported ones made of single crystal materials, such as Si, GaAs, AlN, and SiC. Our method is compatible with the conventional fabrication process for nanoscale electronic circuits and thus offers a possibility of easily integrating the beams into superconducting charge and flux qubits and single-electron transistors as well as coupling them to coplanar waveguide resonators.
Variable gearing in pennate muscles
Authors: Azizi Emanuel , Brainerd Elizabeth L. , Roberts Thomas J.
Published: January 2008

Muscle fiber architecture, i.e., the physical arrangement of fibers within a muscle, is an important determinant of a muscle's mechanical function. In pennate muscles, fibers are oriented at an angle to the muscle's line of action and rotate as they shorten, becoming more oblique such that the fraction of force directed along the muscle's line of action decreases throughout a contraction. Fiber rotation decreases a muscle's output force but increases output velocity by allowing the muscle to function at a higher gear ratio (muscle velocity/fiber velocity). The magnitude of fiber rotation, and therefore gear ratio, depends on how the muscle changes shape in the dimensions orthogonal to the muscle's line of action. Here, we show that gear ratio is not fixed for a given muscle but decreases significantly with the force of contraction (
P
< 0.0001). We find that dynamic muscle-shape changes promote fiber rotation at low forces and resist fiber rotation at high forces. As a result, gearing varies automatically with the load, to favor velocity output during low-load contractions and force output for contractions against high loads. Therefore, muscle-shape changes act as an automatic transmission system allowing a pennate muscle to shift from a high gear during rapid contractions to low gear during forceful contractions. These results suggest that variable gearing in pennate muscles provides a mechanism to modulate muscle performance during mechanically diverse functions.
Intrinsically disordered γ-subunit of cGMP phosphodiesterase encodes functionally relevant transient secondary and tertiary structure
Authors: Song Jikui , Guo Lian-Wang , Muradov Hakim , Artemyev Nikolai O. , Ruoho Arnold E. , Markley John L.
Published: January 2008

The retinal phosphodiesterase (PDE6) inhibitory γ-subunit (PDEγ) plays a central role in vertebrate phototransduction through alternate interactions with the catalytic αβ-subunits of PDE6 and the α-subunit of transducin (α
t
). Detailed structural analysis of PDEγ has been hampered by its intrinsic disorder. We present here the NMR solution structure of PDEγ, which reveals a loose fold with transient structural features resembling those seen previously in the x-ray structure of PDEγ
46–87
when bound to α
t
in the transition-state complex. NMR mapping of the interaction between PDEγ
46–87
and the chimeric PDE5/6 catalytic domain confirmed that C-terminal residues 74–87 of PDEγ are involved in the association and demonstrated that its W70 indole group, which is critical for subsequent binding to α
t
, is left free at this stage. These results indicate that the interaction between PDEγ and α
t
during the phototransduction cascade involves the selection of preconfigured transient conformations.
BRCA1 regulates human mammary stem/progenitor cell fate
Authors: Liu Suling , Ginestier Christophe , Charafe-Jauffret Emmanuelle , Foco Hailey , Kleer Celina G. , Merajver Sofia D. , Dontu Gabriela , Wicha Max S.
Published: January 2008

Although it is well established that women with germ-line mutations in the BRCA1 gene have a greatly increased lifetime incidence of breast and ovarian cancer, the molecular mechanisms responsible for this tissue-specific carcinogenesis remain undefined. The majority of these breast cancers are of the basal-like phenotype characterized by lack of expression of ER, PR, and ERBB2. Because this phenotype has been proposed to resemble that of normal breast stem cells, we examined the role of BRCA1 in human mammary stem cell fate. Using both
in vitro
systems and a humanized NOD/SCID mouse model, we demonstrate that BRCA1 expression is required for the differentiation of ER-negative stem/progenitor cells to ER-positive luminal cells. Knockdown of BRCA1 in primary breast epithelial cells leads to an increase in cells displaying the stem/progenitor cell marker ALDH1 and a decrease in cells expressing luminal epithelial markers and estrogen receptor. In breast tissues from women with germ-line BRCA1 mutations, but not normal controls, we detect entire lobules that, although histologically normal, are positive for ALDH1 expression but are negative for the expression of ER. Loss of heterozygosity for BRCA1 was documented in these ALDH1-positive lobules but not in adjacent ALDH1-negative lobules. Taken together, these studies demonstrate that BRCA1 plays a critical role in the differentiation of ER-negative stem/progenitor cells to ER-positive luminal cells. Because BRCA1 also plays a role in DNA repair, our work suggests that loss of BRCA1 may result in the accumulation of genetically unstable breast stem cells, providing prime targets for further carcinogenic events.
Acculturation and adaptation of immigrant adolescents in Greek urban schools
Authors: Motti‐Stefanidi Frosso , Pavlopoulos Vassilis , Obradović Jelena , Masten Ann S.
Published: January 2008

The purpose of this study was to examine the acculturation, psychological well‐being, and school adjustment of Pontian adolescents from the former Soviet Union (FSU‐Pontians), who are immigrants of the diaspora living in Greece, compared with an immigrant group from Albania and native Greek classmates. The sample included 165 FSU‐Pontian immigrants, 272 immigrants from Albania, and their 525 Greek classmates (mean age = 13.7 years). School adjustment data were obtained using multiple methods and informants. Students also reported their subjective well‐being and acculturation via multiple measures. Findings indicated that FSU‐Pontian adolescents, although they are Greek citizens, had a stronger ethnic and a lower host‐national orientation than did Albanian students. Both immigrant groups experienced similar difficulties in school adjustment. Involvement in Greek culture was a salient predictor of school adjustment, while involvement in one's ethnic culture was related to subjective well‐being. Findings suggest that the acculturation expectations of host country members may be related to immigrants' acculturation orientations.
Dimeric heat shock protein 40 binds radial spokes for generating coupled power strokes and recovery strokes of 9 + 2 flagella
Authors: Yang Chun , Owen Heather A. , Yang Pinfen
Published: January 2008

T-shape radial spokes regulate flagellar beating. However, the precise function and molecular mechanism of these spokes remain unclear. Interestingly, Chlamydomonas reinhardtii flagella lacking a dimeric heat shock protein (HSP) 40 at the spokehead–spokestalk juncture appear normal in length and composition but twitch actively while cells jiggle without procession, resembling a central pair (CP) mutant. HSP40− cells begin swimming upon electroporation with recombinant HSP40. Surprisingly, the rescue doesn't require the signature DnaJ domain. Furthermore, the His-Pro-Asp tripeptide that is essential for stimulating HSP70 adenosine triphosphatase diverges in candidate orthologues, including human DnaJB13. Video microscopy reveals hesitance in bend initiation and propagation as well as irregular stalling and stroke switching despite fairly normal waveform. The in vivo evidence suggests that the evolutionarily conserved HSP40 specifically transforms multiple spoke proteins into stable conformation capable of mechanically coupling the CP with dynein motors. This enables 9 + 2 cilia and flagella to bend and switch to generate alternate power strokes and recovery strokes.
Numerical modelling of error field penetration
Authors: Yu Q. , Günter S. , Kikuchi Y. , Finken K.H.
Published: January 2008

Error field (or externally applied helical field) penetration is studied numerically based on the two fluids equations. It is shown that there is a minimum in the required field amplitude when the applied helical field frequency is the same as the mode frequency being determined by both the background equilibrium plasma rotation and the diamagnetic drift. The mode penetration threshold significantly increases as the field frequency deviates from the mode frequency and can become asymmetric on the two sides of the minimum due to parallel heat transport. After mode penetration the nonlinear saturated island width is found to be smaller for a larger electron diamagnetic drift frequency.
Diffusion in a stochastic magnetic field in ASDEX Upgrade
Authors: Dumbrajs O. , Igochine V. , Zohm H.
Published: January 2008

Heat diffusion coefficients in a stochastic magnetic field are determined in the case of frequently interrupted regime of neoclassical tearing modes and of incomplete sawtooth reconnection in the ASDEX Upgrade tokamak. Here the experimentally measured perturbations and profiles are used and the mapping technique is applied. With the derived diffusion coefficients the nonstationary diffusion equation is solved, making it possible to study time evolution of fast MHD phenomena in ASDEX Upgrade. The proposed phenomenological approach relies heavily on experimental information and requires very moderate computing resources.
Pleating coordinates for the Teichmüller space of a punctured torus
Authors: Keen Linda , Series Caroline
Published: January 2008

We construct new coordinates for the Teichmüller space Teich of a punctured torus into

R

×

R

+

{\text {R}} \times {{\text {R}}^ + }

. The coordinates depend on the representation of Teich as a space of marked Kleinian groups

G
μ

{G_\mu }

that depend holomorphically on a parameter

μ
\mu

varying in a simply connected domain in C. They describe the geometry of the hyperbolic manifold

H

3

/

G
μ

{{\text {H}}^3}{\text {/}}{G_\mu }

; they reflect exactly the visual patterns one sees in the limit sets of the groups

G
μ

{G_\mu }

; and they are directly computable from the generators of

G
μ

{G_\mu }

.
One cannot hear the shape of a drum
Authors: Gordon Carolyn , Webb David L. , Wolpert Scott
Published: January 2008

We use an extension of Sunada’s theorem to construct a nonisometric pair of isospectral simply connected domains in the Euclidean plane, thus answering negatively Kac’s question, "can one hear the shape of a drum?" In order to construct simply connected examples, we exploit the observation that an orbifold whose underlying space is a simply connected manifold with boundary need not be simply connected as an orbifold.
The 1-, 2-, and 3-characters determine a group
Authors: Hoehnke H.-J. , Johnson K. W.
Published: January 2008

A set of invariants for a finite group is described. These arise naturally from Frobenius’ early work on the group determinant and provide an answer to a question of Brauer. Whereas it is well known that the ordinary character table of a group does not determine the group uniquely, it is a consequence of the results presented here that a group is determined uniquely by its "3-character" table.
Piercing convex sets
Authors: Alon Noga , Kleitman Daniel J.
Published: January 2008

A family of sets has the

(
p
,
q
)

(p,q)

property if among any p members of the family some q have a nonempty intersection. It is shown that for every

p
≥
q
≥
d
+
1

p \geq q \geq d + 1

there is a

c
=
c
(
p
,
q
,
d
)
>
∞

c = c(p,q,d) > \infty

such that for every family

F

\mathcal {F}

of compact, convex sets in

R
d

{R^d}

that has the (

(
p
,
q
)

(p,q)

) property there is a set of at most c points in

R
d

{R^d}

that intersects each member of

F

\mathcal {F}

. This extends Helly’s Theorem and settles an old problem of Hadwiger and Debrunner.
Keller’s cube-tiling conjecture is false in high dimensions
Authors: Lagarias Jeffrey C. , Shor Peter W.
Published: January 2008

O. H. Keller conjectured in 1930 that in any tiling of

R

n

{\mathbb {R}^n}

by unit n-cubes there exist two of them having a complete facet in common. O. Perron proved this conjecture for

n
≤
6

n \leq 6

. We show that for all

n
≥
10

n \geq 10

there exists a tiling of

R

n

{\mathbb {R}^n}

by unit n-cubes such that no two n-cubes have a complete facet in common.
Is the boundary of a Siegel disk a Jordan curve?
Authors: Rogers James T.
Published: January 2008

Bounded irreducible local Siegel disks include classical Siegel disks of polynomials, bounded irreducible Siegel disks of rational and entire functions, and the examples of Herman and Moeckel. We show that there are only two possibilities for the structure of the boundary of such a disk: either the boundary admits a nice decomposition onto a circle, or it is an indecomposable continuum.
Negatively Ricci curved manifolds
Authors: Lohkamp Joachim
Published: January 2008

In this paper we announce the following result: "Every manifold of dimension

≥

3

\geq \,3

admits a complete negatively Ricci curved metric." Furthermore we describe some sharper results and sketch proofs.
Möbius invariance of knot energy
Authors: Bryson Steve , Freedman Michael H. , He Zheng-Xu , Wang Zhenghan
Published: January 2008

A physically natural potential energy for simple closed curves in

R

3

{\textbf {R}}^{3}

is shown to be invariant under Möbius transformations. This leads to the rapid resolution of several open problems: round circles are precisely the absolute minima for energy; there is a minimum energy threshold below which knotting cannot occur; minimizers within prime knot types exist and are regular. Finally, the number of knot types with energy less than any constant M is estimated.
A counterexample to the rigidity conjecture for rings
Authors: Heitmann Raymond C.
Published: January 2008

An example is constructed of a local ring and a module of finite type and finite projective dimension over that ring such that the module is not rigid. This shows that the rigidity conjecture is false.
Intersecting families of sets and the topology of cones in economics
Authors: Chichilnisky G.
Published: January 2008

Two classical problems in economics, the existence of a market equilibrium and the existence of social choice functions, are formalized here by the properties of a family of cones associated with the economy. It was recently established that a necessary and sufficient condition for solving the former is the nonempty intersection of the family of cones, and one such condition for solving the latter is the acyclicity of the unions of its subfamilies. We show an unexpected but clear connection between the two problems by establishing a duality property of the homology groups of the nerve defined by the family of cones. In particular, we prove that the intersection of the family of cones is nonempty if and only if every subfamily has acyclic unions, thus identifying the two conditions that solve the two economic problems. In addition to their applications to economics, the results are shown to extend significantly several classical theorems, providing unified and simple proofs: Helly’s theorem, Caratheodory’s representation theorem, the Knaster-Kuratowski-Marzukiewicz theorem, Brouwer’s fixed point theorem, and Leray’s theorem on acyclic covers.
Genera of algebraic varieties and counting of lattice points
Authors: Cappell Sylvain E. , Shaneson Julius L.
Published: January 2008

This paper announces results on the behavior of some important algebraic and topological invariants — Euler characteristic, arithmetic genus, and their intersection homology analogues; the signature, etc. — and their associated characteristic classes, under morphisms of projective algebraic varieties. The formulas obtained relate global invariants to singularities of general complex algebraic (or analytic) maps. These results, new even for complex manifolds, are applied to obtain a version of Grothendieck-Riemann-Roch, a calculation of Todd classes of toric varieties, and an explicit formula for the number of integral points in a polytope in Euclidean space with integral vertices.
Closed ideals of the algebra of absolutely convergent Taylor series
Authors: Esterle J. , Strouse E. , Zouakia F.
Published: January 2008

Let

Γ
\Gamma

be the unit circle,

A
(
Γ
)

A(\Gamma )

the Wiener algebra of continuous functions whose series of Fourier coefficients are absolutely convergent, and

A
+

{A^ + }

the subalgebra of

A
(
Γ
)

A(\Gamma )

of functions whose negative coefficients are zero. If I is a closed ideal of

A
+

{A^ + }

, we denote by

S
I

{S_I}

the greatest common divisor of the inner factors of the nonzero elements of I and by

I
A

{I^A}

the closed ideal generated by I in

A
(
Γ
)

A(\Gamma )

. It was conjectured that the equality

I
A

=

S
I

H

∞

∩

I
A

{I^A} = {S_I}{H^{\infty }} \cap {I^A}

holds for every closed ideal I. We exhibit a large class

F

{\mathcal {F}}

of perfect subsets of

Γ
\Gamma

, including the triadic Cantor set, such that the above equality holds whenever

h
(
I
)
∩
Γ
∈

F

h(I) \cap \Gamma \in {\mathcal {F}}

. We also give counterexamples to the conjecture.
Topological entropy of generalized polygon exchanges
Authors: Gutkin Eugene , Haydn Nicolai
Published: January 2008

We obtain geometric upper bounds on the topological entropy of generalized polygon exchange transformations. As an application of our results, we show that billiards in polygons and rational polytops have zero topological entropy.
Secondary invariants and the singularity of the Ruelle zeta-function in the central critical point
Authors: Juhl Andreas
Published: January 2008

The Ruelle zeta-function of the geodesic flow on the sphere bundle

S
(
X
)

S(X)

of an even-dimensional compact locally symmetric space X of rank 1 is a meromorphic function in the complex plane that satisfies a functional equation relating its values in s and -s. The multiplicity of its singularity in the central critical point s = 0 only depends on the hyperbolic structure of the flow and can be calculated by integrating a secondary characteristic class canonically associated to the flow-invariant foliations of

S
(
X
)

S(X)

for which a representing differential form is given.
Mappings with integrable dilatation in higher dimensions
Authors: Manfredi Juan J. , Villamor Enrique
Published: January 2008

Let

F
∈

W

loc

1
,
n

(
Ω
;

R

n

)

{F \in W_{{\text {loc}}}^{1,n}(\Omega ;{\mathbb {R}^n})}

be a mapping with nonnegative Jacobian

J
F

(
x
)
=
det
D
F
(
x
)
≥
0

{{J_F}(x) = \det DF(x) \geq 0}

for a.e. x in a domain

Ω
⊂

R

n

{\Omega \subset {\mathbb {R}^n}}

. The dilatation of F is defined (almost everywhere in

Ω

{\Omega }

) by the formula
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper K left-parenthesis x right-parenthesis equals StartFraction StartAbsoluteValue upper D upper F left-parenthesis x right-parenthesis EndAbsoluteValue Superscript n Baseline Over upper J Subscript upper F Baseline left-parenthesis x right-parenthesis EndFraction period">

K
(
x
)
=

|

D
F
(
x
)

|

n

J
F

(
x
)

.

K(x) = \frac {{|DF(x){|^n}}}{{{J_F}(x)}}.

\]
Iwaniec and Šverák [IS] have conjectured that if

p
≥
n
−
1

{p \geq n - 1}

and

K
∈

L

l
o
c

p

(
Ω
)

{K \in L_{loc}^p(\Omega )}

then F must be continuous, discrete and open. Moreover, they have confirmed this conjecture in the two-dimensional case n = 2. In this article, we verify it in the higher-dimensional case

n
≥
2

{n \geq 2}

whenever

p
>
n
−
1

{p > n - 1}

.
A formula for finding a potential from nodal lines
Authors: McLaughlin Joyce R. , Hald Ole H.
Published: January 2008

In this announcement we consider an eigenvalue problem which arises in the study of rectangular membranes. The mathematical model is an elliptic equation, in potential form, with Dirichlet boundary conditions. We have shown that the potential is uniquely determined, up to an additive constant, by a subset of the nodal lines of the eigenfunctions. A formula is given which, when the additive constant is fixed, yields an approximation to the potential at a dense set of points. An estimate is presented for the error made by the formula.
Bizarre topology is natural in dynamical systems
Authors: Kennedy Judy A. , Yorke James A.
Published: January 2008

We describe an example of a

C

∞

{C^{\infty }}

diffeomorphism on a 7-manifold which has a compact invariant set such that uncountably many of its connected components are pseudocircles. (Any 7-manifold will suffice.) Furthermore, any diffeomorphism which is sufficiently close (in the

C
1

{C^1}

metric) to the constructed map has a similar invariant set, and the dynamics of the map on the invariant set are chaotic.
Realization spaces of 4-polytopes are universal
Authors: Richter-Gebert Jürgen , Ziegler Günter M.
Published: January 2008

Let

P
⊂

R

d

{P \subset \mathbb {R}^{d}}

be a d-dimensional polytope. The realization space of P is the space of all polytopes

P
⊂

R

d

P \subset \mathbb {R}^{d}

that are combinatorially equivalent to P, modulo affine transformations. We report on work by the first author, which shows that realization spaces of 4-dimensional polytopes can be "arbitrarily bad": namely, for every primary semialgebraic set V defined over

Z

{\mathbb {Z}}

, there is a 4-polytope

P
(
V
)

{P(V)}

whose realization space is "stably equivalent" to V. This implies that the realization space of a 4-polytope can have the homotopy type of an arbitrary finite simplicial complex, and that all algebraic numbers are needed to realize all 4-polytopes. The proof is constructive. These results sharply contrast the 3-dimensional case, where realization spaces are contractible and all polytopes are realizable with integral coordinates (Steinitz’s Theorem). No similar universality result was previously known in any fixed dimension.