bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Labeling Parameters on Perfusion-Based fMRI in Nonhuman Primates
Authors: Zappe Anne C , Pfeuffer Josef , Merkle Hellmut , Logothetis Nikos K , Goense Jozien BM
Published: October 2007

The blood oxygenation level-dependent (BOLD) signal is the most commonly used modality of functional magnetic resonance imaging (fMRI) today. Although easy to implement, it is an ambiguous signal since it results from a combination of several hemodynamic factors. Functional cerebral blood flow changes, as measured by using arterial spin labeling (ASL), typically occur in the parenchyma and have been demonstrated to be more closely coupled to neural activation compared with BOLD. However, the intrinsically low signals from ASL techniques have hindered its widespread application to fMRI for basic research and even more so for clinical applications. Here, we report the first implementation of continuous ASL in the anaesthetized macaque at high magnetic field of 7T. The technique was optimized to permit maximum signal-to-noise ratio of functional perfusion-based images at high spatial resolution. The effect of labeling parameters, such as label time and post-label delay ( PLD), on functional cerebral blood flow (fCBF) in the visual cortex was evaluated. Functional cerebral blood flow maps did not change with increasing label time after 2,000 ms, indicating that a label time of 2,000 ms is sufficient for reliable mapping of fCBF. The percent changes obtained using fCBF were better localized to gray matter, than those obtained with BOLD. A short PLD of 200 ms revealed significantly higher fCBF changes at the cortical surface, indicating large-vessel contamination, than a long PLD of 800 ms. However, the effect of the PLD on fCBF was smaller than on baseline CBF. These results are of importance for high-resolution applications, and when accurate quantification is required for studies in monkeys as well as in humans.
Theoretical study of the electronic structure of HXY/XYH radicals (XC,Si;YO,S)
Authors: Pérez-Juste Ignacio , Carballeira Luis
Published: October 2007

The electronic structures of the HXY/XYH compounds (XC,Si;YO,S) on the A′2 electronic ground state were investigated by applying the natural bond orbital (NBO) method to the computed B3LYP∕6-311G** wave functions. Different localized structures are proposed for the HXY and XYH isomers and the central XY unit is described as intermediate between a double and a triple bond in HCO, HCS, HSiO, and HSiS, similar to a double bond in COH, CSH, and SiSH, and clearly a single bond in SiOH. Through the comparison between the NBO results for the diatomic and hydrogenated compounds, the energy preferences on each pair of isomers and the computed geometrical parameters are explained. According to the structures proposed, the HXY compounds are σ radicals with the spin density distributed along the molecular framework, while the XYH compounds are π radicals with most of the unpaired spin located on an almost pure p orbital of the X atom. Finally, the amounts of spin density on natural atomic orbitals provided by the NBO method are used to explain the computed values of the isotropic and anisotropic hyperfine coupling constants.
The amplitude equation for rotating Rayleigh–Bénard convection
Authors: Scheel J. D.
Published: October 2007

The amplitude equation for rotating Rayleigh–Bénard convection is derived from the Boussinesq equations with the Coriolis force included. The vertical boundary conditions are no-slip, and the lateral boundary conditions are either periodic or rigid. In order to keep track of the mean flow, the full system of equations is considered, instead of a potential formulation. A multiple scales perturbation expansion in the control parameter ϵ is performed, and appropriate solvability conditions are imposed. This leads to the usual amplitude equation at order ϵ3∕2, but a new rotation term enters at order ϵ7∕4. This rotation term will cause a change of phase with respect to time, whenever there is a gradient in the amplitude in the direction parallel to the rolls. As a result, rolls terminating perpendicularly to a wall will precess in the direction of rotation. The new rotation term will also cause stationary dislocations to glide perpendicular to the rolls. Amplitude equation results for a specific set of parameters are compared to numerical results from simulations of the full equations. Good agreement for mean flow, wall-induced precession, and dislocation glide is found.
High spontaneous polarization in PbTiO3–BiMeO3 systems with enhanced tetragonality
Authors: Chen Jun , Hu Penghao , Sun Xueyi , Sun Ce , Xing Xianran
Published: October 2007

Pb Ti O 3 – Bi Me O 3 (Me=Fe, Zn1/2Ti1/2, and Zn3/4W1/4) solid solutions exhibit unusually enhanced tetragonality (c/a). Lattice dynamics and structure of PbTiO3–BiMeO3 with enhanced c/a were investigated by Raman scattering technique and x-ray Rietveld method, respectively. The A1(1TO) soft mode, associated with the order parameter spontaneous polarization (PS), abnormally shifts upward, which is different with almost all other PbTiO3-based compounds. It is interesting to find that the A1(1TO) mode increases linearly with the PS displacement. The PS could be basically judged from the variation of A1(1TO) not only with normally reduced c/a but also with unusually enhanced c/a in the PbTiO3-based systems.
Dynamics of conical wire array Z-pinch implosions
Authors: Ampleford D. J. , Lebedev S. V. , Bland S. N. , Bott S. C. , Chittenden J. P. , Jennings C. A. , Kantsyrev V. L. , Safronova A. S. , Ivanov V. V. , Fedin D. A. , Laca P. J. , Yilmaz M. F. , Nalajala V. , Shrestha I. , Williamson K. , Osborne G. , Haboub A. , Ciardi A.
Published: October 2007

A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generators—the MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility’s Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P. Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.
Electron mobility related to scattering caused by the strain variation of AlGaN barrier layer in strained AlGaN∕GaN heterostructures
Authors: Zhao Jianzhi , Lin Zhaojun , Corrigan Timothy D. , Wang Zhen , You Zhidong , Wang Zhanguo
Published: October 2007

Using the measured capacitance-voltage curves of Ni Schottky contacts with different areas on strained AlGaN∕GaN heterostructures and the current-voltage characteristics for the AlGaN∕GaN heterostructure field-effect transistors at low drain-source voltage, we found that the two-dimensional electron gas (2DEG) electron mobility increased as the Ni Schottky contact area increased. When the gate bias increased from negative to positive, the 2DEG electron mobility for the samples increased monotonically except for the sample with the largest Ni Schottky contact area. A new scattering mechanism is proposed, which is based on the polarization Coulomb field scattering related to the strain variation of the AlGaN barrier layer.
Ferromagnetism in GaN induced by Fe ion implantation
Authors: Talut G. , Reuther H. , Zhou Shengqiang , Potzger K. , Eichhorn F. , Stromberg F.
Published: October 2007

We report about magnetic and structural studies on p-type wurtzite GaN implanted with F57e with fluences from 1×1016 cm−2 to 1.6×1017 cm−2 at different temperatures and subsequently subjected to thermal treatment. X-ray diffraction (XRD), transmission electron microscopy (TEM), conversion electron Mössbauer spectroscopy (CEMS), and superconducting quantum interference device magnetometry (SQUID) were used for the crystallographic, electronic, and magnetic characterization of the samples. Room temperature (RT) ferromagnetism was observed in GaN after implantation at 623 K with different fluences and is mainly ascribed to α-Fe precipitations. An additional contribution to the ferromagnetic signal is observed in a Mössbauer spectrum and as a magnetization loop in SQUID in a sample implanted with lowest fluence at 623 K which cannot be related to α-Fe. After implantation at RT with low fluences no ferromagnetism was observed by means of the SQUID. However, in the CEMS a magnetic hyperfine field of 6.8 T was used to fit the experimental spectrum and is discussed in terms of possible origin. Samples implanted at 240 K do not exhibit ferromagnetic properties. Thus, precipitation of α-Fe was successfully reduced by decreasing the implantation temperature. However, this was accompanied by an enhanced crystal damage. Annealing between 973 K and 1123 K resulted in most cases predominantly in the formation of α-Fe clusters. Thermal treatment brought no significant recovery of the crystallinity as was verified by the RBS channeling measurements.
Quasimonoenergetic ion bunches from exploding microstructured targets
Authors: Kovalev V. F. , Bychenkov V. Yu. , Mima K.
Published: October 2007

An analytic model is proposed for generating bunches of light ions up to relativistic energies via Coulomb explosion (CE) of symmetric microstructured targets in plane, cylindrical, and spherical geometries, and the conditions under which CE can exist in a single-flow regime are derived. The time evolution of the mean velocity, density distribution, and energy spectra for accelerated ions is studied, and the CE-driven quasimonoenergetic light ions from bilayered microstructured targets are reported.
Nonplanar oscillatory shear flow: From the continuum to the free-molecular regime
Authors: Emerson David R. , Gu Xiao-Jun , Stefanov Stefan K. , Yuhong Sun , Barber Robert W.
Published: October 2007

The case of oscillatory cylindrical Couette gas flow has been used to investigate the effects of curvature and rarefaction on the dynamic velocity and shear stress profiles. In addition, Stokes’ second problem for a curved surface has been extended to include the effects of slip. It is shown that curvature plays a more important role than slip in determining the penetration depth, but the effects of slip are enhanced if the surface is nonplanar. The current analysis for the oscillatory cylindrical Couette problem presents new analytical solutions in the slip-flow regime and the free-molecular regime. For both cases, direct simulation Monte Carlo data are in good agreement with the analytical solutions. To complete the study throughout the entire Knudsen regime, the direct simulation Monte Carlo method was used to predict the velocity and shear stress in the transition regime. There are marked differences between the solutions obtained for the inner and outer cylinders oscillating, especially at low frequencies. It is shown that if the Knudsen number is large (>1.0), the shear stress tends to the solution for the planar Couette case in the free-molecular regime and is essentially independent of the oscillatory frequency. Moreover, we show that the phenomenon of velocity inversion can occur for oscillatory flow provided the accommodation coefficient of the outer cylinder is small and the frequency is not too high.
Microimprinting and ferroelectric properties of poly(vinylidene fluoride-trifluoroethylene) copolymer films
Authors: Zhang Lei , Ducharme Stephen , Li Jiangyu
Published: October 2007

Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films have been patterned by microimprinting with excellent quality of pattern transferring. Ferroelectricity of the imprinted films has been confirmed by ferroelectric hysteresis and surface potential measurement, and very good correlation is observed between remnant polarization and surface potential of the imprinted films. Imprinted P(VDF-TrFE) films show high remnant polarization and high poling-induced surface potential when the imprinting temperature is around 140°C, suggesting that 140°C is the optimal imprinting temperature for P(VDF-TrFE) films. The patterned ferroelectric P(VDF-TrFE) films can be used for a wide range of applications.
Temperature dependence of polarized electroluminescence from nonpolar m-plane InGaN-based light emitting diodes
Authors: Nakagawa Satoshi , Tsujimura Hiroki , Okamoto Kuniyoshi , Kubota Masashi , Ohta Hiroaki
Published: October 2007

An accurate method of estimating polarized light emission was presented for nonpolar m-plane InGaN-based blue light emitting diodes, where the unpolarized component caused by unintentional light scattering was eliminated as noise. The polarization ratios of electroluminescence (EL) at 300 and 100K were 0.85 and 0.98, respectively. The energy difference between the highest and the second highest valence bands was estimated to be 129meV from the temperature dependence of the spectrally integrated EL intensities under the assumption of Fermi statistics. This value agreed with the one (=118meV) obtained directly from the difference of the EL peak energies between two polarized components, the electric fields perpendicular and parallel to the c axis.
Heat assisted magnetic recording by combined field emission and moderate ionization in air
Authors: Ng K. W. , Leong S. H. , Yuan Z. , Liu B. , Ma Y.
Published: October 2007

The authors report the enhancement of magnetic recording process by the combined field emission and moderate ionization between the write pole and magnetic media in a heat assisted magnetic recording experiment. When appropriate bias voltages are applied across the head-media gap, field emission from the write pole results in a sustainable moderate ionization without catastrophic air breakdown. The elevated media temperature from electron bombardment leads to reduced media coercivity. Our results show a 25% improvement to writing ability on perpendicular magnetic recording media using a modified read/write head. The effect of different combined emission/ionization currents with different read/write linear velocities was also studied.
The Emergent Flux and Effective Temperature of δ Canis Majoris
Authors: Davis J. , Booth A. J. , Ireland M. J. , Jacob A. P. , North J. R. , Owens S. M. , Robertson J. G. , Tango W. J. , Tuthill P. G.
Published: October 2007

New angular diameter determinations for the bright southern F8 supergiant δ CMa enable the bolometric emergent flux and effective temperature of the star to be determined with improved accuracy. The spectral flux distribution and bolometric flux have been determined from published photometry and spectrophotometry and combined with the angular diameter to derive the bolometric emergent flux ℱ = (6.50 ± 0.24) × 107 Wm−2 and the effective temperature Teff = 5818 ± 53 K. The new value for the effective temperature is compared with previous interferometric and infrared flux method determinations. The accuracy of the effective temperature is now limited by the uncertainty in the bolometric flux rather than by the uncertainty in the angular diameter.
Loss of Vac14, a regulator of the signaling lipid phosphatidylinositol 3,5-bisphosphate, results in neurodegeneration in mice
Authors: Zhang Yanling , Zolov Sergey N. , Chow Clement Y. , Slutsky Shalom G. , Richardson Simon C. , Piper Robert C. , Yang Baoli , Nau Johnathan J. , Westrick Randal J. , Morrison Sean J. , Meisler Miriam H. , Weisman Lois S.
Published: October 2007

The signaling lipid, phosphatidylinositol 3,5-bisphosphate (PI(3,5)P
2
), likely functions in multiple signaling pathways. Here, we report the characterization of a mouse mutant lacking Vac14, a regulator of PI(3,5)P
2
synthesis. The mutant mice exhibit massive neurodegeneration, particularly in the midbrain and in peripheral sensory neurons. Cell bodies of affected neurons are vacuolated, and apparently empty spaces are present in areas where neurons should be present. Similar vacuoles are found in cultured neurons and fibroblasts. Selective membrane trafficking pathways, especially endosome-to-TGN retrograde trafficking, are defective. This report, along with a recent report on a mouse with a null mutation in
Fig4
, presents the unexpected finding that the housekeeping lipid, PI(3,5)P
2
, is critical for the survival of neural cells.
An essential role for cortactin in the modulation of the potassium channel Kv1.2
Authors: Williams Michael R. , Markey Jonathan C. , Doczi Megan A. , Morielli Anthony D.
Published: October 2007

Ion channels are key determinants of membrane excitability. The actin cytoskeleton has a central role in morphology, migration, intracellular transport, and signaling. In this article, we show that the actin-binding protein cortactin regulates the potassium channel Kv1.2 and thereby provides a direct link between actin dynamics and membrane excitability. In previous reports, we showed that the tyrosine phosphorylation-mediated suppression of Kv1.2 ionic current occurs by endocytosis of the channel protein. Pull-down assays using recombinant-purified cortactin and Kv1.2 demonstrated that their interaction is direct and reduced by tyrosine phosphorylation of Kv1.2. This finding suggests a link between cortactin and Kv1.2 endocytosis. Here, we confirm that relationship and identify the molecular mechanisms involved. We use FRET to demonstrate that Kv1.2 and cortactin interact
in vivo
. By manipulating the cortactin-binding site within Kv1.2, we confirm that cortactin proximity influences channel function. We used flow cytometry in conjunction with cortactin gene replacement to identify C-terminal tyrosines, the fourth repeat actin-binding domain, and the N-terminal Arp2/3-binding region, as critical to Kv1.2 regulation. Surprisingly, cortactin's dynamin-binding Src homology 3 domain is not required for Kv1.2 endocytosis, despite that process being dynamin-dependent. These findings predict that cortactin-mediated actin remodeling in excitable cells is not only important for cell structure, but may directly impact membrane excitability.
Structural motifs of biomolecules
Authors: Banavar Jayanth R. , Hoang Trinh Xuan , Maddocks John H. , Maritan Amos , Poletto Chiara , Stasiak Andrzej , Trovato Antonio
Published: October 2007

Biomolecular structures are assemblies of emergent anisotropic building modules such as uniaxial helices or biaxial strands. We provide an approach to understanding a marginally compact phase of matter that is occupied by proteins and DNA. This phase, which is in some respects analogous to the liquid crystal phase for chain molecules, stabilizes a range of shapes that can be obtained by sequence-independent interactions occurring intra- and intermolecularly between polymeric molecules. We present a singularity-free self-interaction for a tube in the continuum limit and show that this results in the tube being positioned in the marginally compact phase. Our work provides a unified framework for understanding the building blocks of biomolecules.
Predicting political elections from rapid and unreflective face judgments
Authors: Ballew Charles C. , Todorov Alexander
Published: October 2007

Here we show that rapid judgments of competence based solely on the facial appearance of candidates predicted the outcomes of gubernatorial elections, the most important elections in the United States next to the presidential elections. In all experiments, participants were presented with the faces of the winner and the runner-up and asked to decide who is more competent. To ensure that competence judgments were based solely on facial appearance and not on prior person knowledge, judgments for races in which the participant recognized any of the faces were excluded from all analyses. Predictions were as accurate after a 100-ms exposure to the faces of the winner and the runner-up as exposure after 250 ms and unlimited time exposure (Experiment 1). Asking participants to deliberate and make a good judgment dramatically increased the response times and reduced the predictive accuracy of judgments relative to both judgments made after 250 ms of exposure to the faces and judgments made within a response deadline of 2 s (Experiment 2). Finally, competence judgments collected before the elections in 2006 predicted 68.6% of the gubernatorial races and 72.4% of the Senate races (Experiment 3). These effects were independent of the incumbency status of the candidates. The findings suggest that rapid, unreflective judgments of competence from faces can affect voting decisions.
Loss-of-function mutation in the
prokineticin 2
gene causes Kallmann syndrome and normosmic idiopathic hypogonadotropic hypogonadism
Authors: Pitteloud Nelly , Zhang Chengkang , Pignatelli Duarte , Li Jia-Da , Raivio Taneli , Cole Lindsay W. , Plummer Lacey , Jacobson-Dickman Elka E. , Mellon Pamela L. , Zhou Qun-Yong , Crowley William F.
Published: October 2007

Gonadotropin-releasing hormone (GnRH) deficiency in the human presents either as normosmic idiopathic hypogonadotropic hypogonadism (nIHH) or with anosmia [Kallmann syndrome (KS)]. To date, several loci have been identified to cause these disorders, but only 30% of cases exhibit mutations in known genes. Recently, murine studies have demonstrated a critical role of the prokineticin pathway in olfactory bulb morphogenesis and GnRH secretion. Therefore, we hypothesize that mutations in
prokineticin 2
(
PROK2
) underlie some cases of KS in humans and that animals deficient in
Prok2
would be hypogonadotropic. One hundred IHH probands (50 nIHH and 50 KS) with no known mutations were examined for mutations in the
PROK2
gene. Mutant PROK2s were examined in functional studies, and the reproductive phenotype of the
Prok2
−/−
mice was also investigated. Two brothers with KS and their sister with nIHH harbored a homozygous deletion in the
PROK2
gene (p.[I55fsX1]+[I55fsX1]). Another asymptomatic brother was heterozygous for the deletion, whereas both parents (deceased) had normal reproductive histories. The identified deletion results in a truncated PROK2 protein of 27 amino acids (rather than 81 in its mature form) that lacks bioactivity. In addition,
Prok2
−/−
mice with olfactory bulb defects exhibited disrupted GnRH neuron migration, resulting in a dramatic decrease in GnRH neuron population in the hypothalamus as well as hypogonadotropic hypogonadism. Homozygous loss-of-function
PROK2
mutations cause both KS and nIHH.
Antibodies to CD4-induced sites in HIV gp120 correlate with the control of SHIV challenge in macaques vaccinated with subunit immunogens
Authors: DeVico Anthony , Fouts Timothy , Lewis George K. , Gallo Robert C. , Godfrey Karla , Charurat Manhattan , Harris Ilia , Galmin Lindsey , Pal Ranajit
Published: October 2007

Epitopes located in and around the coreceptor binding site of HIV-1 envelope glycoprotein (gp120) exhibit enhanced exposure after attachment to the CD4 receptor and comprise some of the most conserved and functionally important residues on the viral envelope. Therefore, antibody responses to these epitopes [designated as CD4-induced (CD4i)] should be highly cross-reactive and potentially useful for HIV vaccine development. To address this question, rhesus macaques were vaccinated with subunit immunogens designed to raise humoral responses against CD4i epitopes and challenged rectally with SHIV
162P3
, which encodes a heterologous envelope versus the immunogen. We found that animals vaccinated with a rhesus full-length single-chain (rhFLSC) complex exhibited significantly accelerated clearance of plasma viremia and an absence of long-term tissue viremia compared with unvaccinated control animals. Such control of infection correlated with stronger responses to CD4i epitopes in the rhFLSC-vaccinated animals, compared with macaques immunized with gp120, cross-linked gp120–CD4 complexes, or soluble CD4 alone. These responses were strongly boosted in the rhFLSC-vaccinated animals by SHIV
162P3
infection. The control of infection was not associated with anti-CD4 responses, overall anti-gp120-binding titers, or neutralizing activity measured in conventional assays. Vaccine-naive animals also developed anti-CD4i epitope responses after simian/ human immunodeficiency virus (SHIV) challenge, which appeared later than the overall anti-gp120 responses and in concert with the decline of viremia to a low set point. Collectively, these data suggest that antibodies to CD4i epitopes may play a role in controlling SHIV infection and provide insights for HIV vaccine development.
Picosecond fluctuating protein energy landscape mapped by pressure–temperature molecular dynamics simulation
Authors: Meinhold Lars , Smith Jeremy C. , Kitao Akio , Zewail Ahmed H.
Published: October 2007

Microscopic statistical pressure fluctuations can, in principle, lead to corresponding fluctuations in the shape of a protein energy landscape. To examine this, nanosecond molecular dynamics simulations of lysozyme are performed covering a range of temperatures and pressures. The well known dynamical transition with temperature is found to be pressure-independent, indicating that the effective energy barriers separating conformational substates are not significantly influenced by pressure. In contrast, vibrations within substates stiffen with pressure, due to increased curvature of the local harmonic potential in which the atoms vibrate. The application of pressure is also shown to selectively increase the damping of the anharmonic, low-frequency collective modes in the protein, leaving the more local modes relatively unaffected. The critical damping frequency, i.e., the frequency at which energy is most efficiently dissipated, increases linearly with pressure. The results suggest that an invariant description of protein energy landscapes should be subsumed by a fluctuating picture and that this may have repercussions in, for example, mechanisms of energy dissipation accompanying functional, structural, and chemical relaxation.
Adipogenesis is inhibited by brief, daily exposure to high-frequency, extremely low-magnitude mechanical signals
Authors: Rubin C. T. , Capilla E. , Luu Y. K. , Busa B. , Crawford H. , Nolan D. J. , Mittal V. , Rosen C. J. , Pessin J. E. , Judex S.
Published: October 2007

Obesity, a global pandemic that debilitates millions of people and burdens society with tens of billions of dollars in health care costs, is deterred by exercise. Although it is presumed that the more strenuous a physical challenge the more effective it will be in the suppression of adiposity, here it is shown that 15 weeks of brief, daily exposure to high-frequency mechanical signals, induced at a magnitude well below that which would arise during walking, inhibited adipogenesis by 27% in C57BL/6J mice. The mechanical signal also reduced key risk factors in the onset of type II diabetes, nonesterified free fatty acid and triglyceride content in the liver, by 43% and 39%, respectively. Over 9 weeks, these same signals suppressed fat production by 22% in the C3H.B6–6T congenic mouse strain that exhibits accelerated age-related changes in body composition. In an effort to understand the means by which fat production was inhibited, irradiated mice receiving bone marrow transplants from heterozygous GFP
+
mice revealed that 6 weeks of these low-magnitude mechanical signals reduced the commitment of mesenchymal stem cell differentiation into adipocytes by 19%, indicating that formation of adipose tissue in these models was deterred by a marked reduction in stem cell adipogenesis. Translated to the human, this may represent the basis for the nonpharmacologic prevention of obesity and its sequelae, achieved through developmental, rather than metabolic, pathways.
The role of CD8+CD28−regulatory cells in suppressing myasthenia gravis-associated responses by a dual altered peptide ligand
Authors: Ben-David Hava , Sharabi Amir , Dayan Molly , Sela Michael , Mozes Edna
Published: October 2007

Myasthenia gravis (MG) and experimental autoimmune MG are T cell-dependent antibody-mediated autoimmune diseases. A dual altered peptide ligand (APL), composed of the tandemly arranged two single amino acid analogs of two myasthenogenic peptides, p195-212 and p259-271, down-regulatedin vitroandin vivoMG-associated T cell responses. In the present study, we investigated the role of CD8+CD28−regulatory cells in the mechanism of action of the dual APL. We demonstrated that treatment of mice with the dual APL concomitant with immunization with a myasthenogenic peptide resulted in an increased population of CD8+CD28−cells that express forkhead box P3 (Foxp3). The dual APL inhibited the proliferation of lymph node (LN) cells of the Torpedo acetylcholine receptor-immunized WT C57BL/6 mice, whereas the inhibition was abrogated in CD8−/−knockout mice. Moreover, the dual APL did not inhibit the secretion of IFN-γ by LN cells from CD8−/−mice immunized with Torpedo acetylcholine receptor. However, the mRNA expression of IL-10 and TGF-β by LN cells from CD8−/−mice was up-regulated similarly to that of the WT mice. Furthermore, the dual APL elevated the proapoptotic markers caspases 3 and caspase 8, whereas it down-regulated the antiapoptotic marker Bcl-xL in both CD8−/−and WT mice. Finally, the dual APL-induced CD4+CD25+Foxp3+cells were up-regulated in CD8−/−mice to a similar extent to that observed in the WT mice. Thus, we suggest that CD8+CD28−regulatory cells play a partial role in the mechanism of action by which the dual APL suppresses experimental autoimmune MG-associated T cell responses.
Property of Kelley for the Cartesian products and hyperspaces
Authors: Charatonik Janusz , Charatonik Wlodzimierz
Published: October 2007

A continuum

X
X

having the property of Kelley is constructed such that neither

X
×
[
0
,
1
]

X \times [0,1]

, nor the hyperspace

C
(
X
)

C(X)

, nor small Whitney levels in

C
(
X
)

C(X)

have the property of Kelley. This answers several questions asked in the literature.
A Calabi-Yau threefold with Brauer group (ℤ/8ℤ)²
Authors: Gross Mark , Pavanelli Simone
Published: October 2007

We compute the Brauer group of a Calabi-Yau threefold discovered by the first author and Sorin Popescu, and find it is

(

Z

/

8

Z

)
2

(\mathbb {Z}/8 \mathbb {Z})^2

, the largest known Brauer group of a non-singular Calabi-Yau threefold.
Mod 4 Galois representations and elliptic curves
Authors: Holden Christopher
Published: October 2007

Galois representations

ρ
¯

:

G

Q

→
G

L

2

(

Z

/

n
)

\bar {\rho }: G_{\mathbb Q} \rightarrow GL_{2}(\mathbb Z/n)

with cyclotomic determinant all arise from the

n
n

-torsion of elliptic curves for

n
=
2
,
3
,
5

n=2,3,5

. For

n
=
4

n=4

, we show the existence of more than a million such representations which are surjective and do not arise from any elliptic curve.
A lower bound for the equilateral number of normed spaces
Authors: Swanepoel Konrad , Villa Rafael
Published: October 2007

We show that if the Banach-Mazur distance between an

n
n

-dimensional normed space

X
X

and

ℓ
∞
n

\ell _\infty ^n

is at most

3

/

2

3/2

, then there exist

n
+
1

n+1

equidistant points in

X
X

. By a well-known result of Alon and Milman, this implies that an arbitrary

n
n

-dimensional normed space admits at least

e

c

log
⁡
n

e^{c\sqrt {\log n}}

equidistant points, where

c
>
0

c>0

is an absolute constant. We also show that there exist

n
n

equidistant points in spaces sufficiently close to

ℓ
p
n

\ell _p^n

,

1
>
p
>
∞

1>p>\infty

.
The 𝑟-stability of hypersurfaces with zero Gauss-Kronecker curvature
Authors: Cavalcante Marcos
Published: October 2007

In this paper we give sufficient conditions for a bounded domain in an

r
r

-minimal hypersurface of the Euclidean space to be

r
r

-stable. The Gauss-Kronecker curvature of this hypersurface may be zero on a set of capacity zero.
Submanifolds of real algebraic varieties
Authors: Kucharz W.
Published: October 2007

By the Nash-Tognoli theorem, each compact smooth manifold

M
M

is diffeomorphic to a nonsingular real algebraic set, called an algebraic model of

M
M

. We construct algebraic models

X
X

of

M
M

with controlled behavior of the group of cohomology classes represented by algebraic subsets of

X
X

.
Approximate antilinear eigenvalue problems and related inequalities
Authors: Garcia Stephan
Published: October 2007

If

T
T

is a complex symmetric operator on a separable complex Hilbert space

H

\mathcal H

, then the spectrum

σ
(

|

T

|

)

\sigma (|T|)

of

T
∗

T

\sqrt {T^*T}

can be characterized in terms of a certain approximate antilinear eigenvalue problem. This approach leads to a general inequality (applicable to any bounded operator

T
:

H

→

H

T:\mathcal H\rightarrow \mathcal H

), in terms of the spectra of the selfadjoint operators

Re
⁡
T

\operatorname {Re} T

and

Im
⁡
T

\operatorname {Im} T

, restricting the possible location of elements of

σ
(

|

T

|

)

\sigma (|T|)

. A sharp inequality for the operator norm is produced, and the extremal operators are shown to be complex symmetric.
Local interpolation in Hilbert spaces of Dirichlet series
Authors: Olsen Jan-Fredrik , Seip Kristian
Published: October 2007

We denote by

H

\mathscr {H}

the Hilbert space of ordinary Dirichlet series with square-summable coefficients. The main result is that a bounded sequence of points in the half-plane

σ
>
1

/

2

\sigma >1/2

is an interpolating sequence for

H

\mathscr {H}

if and only if it is an interpolating sequence for the Hardy space

H
2

H^2

of the same half-plane. Similar local results are obtained for Hilbert spaces of ordinary Dirichlet series that relate to Bergman and Dirichlet spaces of the half-plane

σ
>
1

/

2

\sigma >1/2

.
Pencils and infinite dihedral covers of ℙ²
Authors: Bartolo Enrique , Cogolludo José , Tokunaga Hiro-o
Published: October 2007

In this work we study the connection between the existence of finite dihedral covers of the projective plane ramified along an algebraic curve

C
C

, infinite dihedral covers, and pencils of curves containing

C
C

.
Nonnegatively curved vector bundles with large normal holonomy groups
Authors: Tapp Kristopher
Published: October 2007

When

B
B

is a biquotient, we show that there exist vector bundles over

B
B

with metrics of nonnegative curvature whose normal holonomy groups have arbitrarily large dimension.
Characteristic cycles of standard sheaves associated with open orbits
Authors: Božičević Mladen
Published: October 2007

Let

G

R

G_\mathbb R

be a real form of a complex, semisimple Lie group

G
G

. We compute the characteristic cycle of a standard sheaf associated with an open

G

R

G_\mathbb R

-orbit on the partial flag variety of

G
G

. We apply the result to obtain a Rossmann-type integral formula for elliptic coadjoint orbits. These results were previously obtained by the author under the assumption that the rank of

G

R

G_\mathbb R

is equal to the rank of a maximal compact subgroup.
Pseudodifferential operators with C*-algebra-valued symbols: Abstract characterizations
Authors: Melo Severino , Merklen Marcela
Published: October 2007

Given a separable unital C

∗

^*

-algebra

C
C

with norm

|

|

⋅

|

|

||\cdot ||

, let

E
n

E_n

denote the Banach-space completion of the

C
C

-valued Schwartz space on

R

n

\mathbb {R}^{n}

with norm
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue EndAbsoluteValue f StartAbsoluteValue EndAbsoluteValue Subscript 2 Baseline equals StartAbsoluteValue EndAbsoluteValue mathematical left-angle f comma f mathematical right-angle StartAbsoluteValue EndAbsoluteValue Superscript 1 slash 2">

|

|

f

|

|

2

=

|

|

⟨
f
,
f
⟩

|

|

1

/

2

||f||_2=||\langle f,f\rangle ||^{1/2}

,

⟨
f
,
g
⟩
=
∫
f
(
x

)
∗

g
(
x
)
d
x

\langle f,g\rangle =\int f(x)^*g(x)dx

. The assignment of the pseudodifferential operator

A
=
a
(
x
,
D
)

A=a(x,D)

with

C
C

-valued symbol

a
(
x
,
ξ
)

a(x,\xi )

to each smooth function with bounded derivatives

a
∈

B

C

(

R

2
n

)

a\in \mathcal {B}^C (\mathbb {R}^{2n})

defines an injective mapping

O
O

, from

B

C

(

R

2
n

)

\mathcal {B}^C(\mathbb {R}^{2n})

to the set

H

\mathcal {H}

of all operators with smooth orbit under the canonical action of the Heisenberg group on the algebra of all adjointable operators on the Hilbert module

E
n

E_n

. In this paper, we construct a left-inverse

S
S

for

O
O

and prove that

S
S

is injective if

C
C

is commutative. This generalizes Cordes’ description of

H

\mathcal {H}

in the scalar case. Combined with previous results of the second author, our main theorem implies that, given a skew-symmetric

n
×
n

n\times n

matrix

J
J

and if

C
C

is commutative, then any

A
∈

H

A\in \mathcal {H}

which commutes with every pseudodifferential operator with symbol

F
(
x
+
J
ξ
)

F(x+J\xi )

,

F
∈

B

C

(

R

2
n

)

F\in \mathcal {B}^C(\mathbb {R}^{2n})

, is a pseudodifferential operator with symbol

G
(
x
−
J
ξ
)

G(x-J\xi )

, for some

G
∈

B

C

(

R

2
n

)

G\in \mathcal {B}^C(\mathbb {R}^{2n})

. That was conjectured by Rieffel.
Uniform periodic point growth in entropy rank one
Authors: Miles Richard , Ward Thomas
Published: October 2007

We show that algebraic dynamical systems with entropy rank one have uniformly exponentially many periodic points in all directions.
An elementary proof of the triangle inequality for the Wasserstein metric
Authors: Clement Philippe , Desch Wolfgang
Published: October 2007

We give an elementary proof for the triangle inequality of the

p
p

-Wasserstein metric for probability measures on separable metric spaces. Unlike known approaches, our proof does not rely on the disintegration theorem in its full generality; therefore the additional assumption that the underlying space is Radon can be omitted. We also supply a proof, not depending on disintegration, that the Wasserstein metric is complete on Polish spaces.
Positive curvature and eigenfunctions of the Laplacian
Authors: Donnelly Harold
Published: October 2007

Examples are given of noncompact Riemannian manifolds having nonnegative Ricci cuvature and infinitely many square integrable eigenfunctions for the Laplace operator.
On some random thin sets of integers
Authors: Li Daniel , Queffélec Hervé , Rodríguez-Piazza Luis
Published: October 2007

We show how different random thin sets of integers may have different behaviour. First, using a recent deviation inequality of Boucheron, Lugosi and Massart, we give a simpler proof of one of our results in Some new thin sets of integers in harmonic analysis, Journal d’Analyse Mathématique 86 (2002), 105–138, namely that there exist

4
3

\frac {4}{3}

-Rider sets which are sets of uniform convergence and

Λ
(
q
)

\Lambda (q)

-sets for all

q
>
∞

q > \infty

but which are not Rosenthal sets. In a second part, we show, using an older result of Kashin and Tzafriri, that, for

p
>

4
3

p > \frac {4}{3}

, the

p
p

-Rider sets which we had constructed in that paper are almost surely not of uniform convergence.
Global well-posedness of dissipative quasi-geostrophic equations in critical spaces
Authors: Bae Hantaek
Published: October 2007

We prove global well-posedness for the dissipative quasi-geostrophic equation with initial data in critical Besov spaces

B

p
,
q

1
+

2
p

−
2
α

B^{1+ {2 \over p}-2\alpha }_{p,q}

,

0
>
α
≤
1

0> \alpha \leq 1

, provided that the

B

p
,
q

1
+

2
p

−
2
α

B^{1+ {2 \over p}-2\alpha }_{p,q}

norm of the initial data is sufficiently small compared with the dissipative coefficient

κ
\kappa

.
An elementary and constructive solution to Hilbert’s 17th Problem for matrices
Authors: Hillar Christopher , Nie Jiawang
Published: October 2007

We give a short and elementary proof of a theorem of Procesi, Schacher and (independently) Gondard, Ribenboim that generalizes a famous result of Artin. Let

A
A

be an

n
×
n

n \times n

symmetric matrix with entries in the polynomial ring

R

[

x
1

,
…
,

x
m

]

\mathbb R[x_1,\ldots ,x_m]

. The result is that if

A
A

is positive semidefinite for all substitutions

(

x
1

,
…
,

x
m

)
∈

R

m

(x_1,\ldots ,x_m) \in \mathbb R^m

, then

A
A

can be expressed as a sum of squares of symmetric matrices with entries in

R

(

x
1

,
…
,

x
m

)

\mathbb R(x_1,\ldots ,x_m)

. Moreover, our proof is constructive and gives explicit representations modulo the scalar case.
Partial fraction decompositions and trigonometric sum identities
Authors: Chu Wenchang
Published: October 2007

The partial fraction decomposition method is explored to establish several interesting trigonometric function identities, which may have applications to the evaluation of classical multiple hypergeometric series, trigonometric approximation and interpolation.
A Müntz space having no complement in 𝐿₁
Authors: Alam Ihab
Published: October 2007

in

C
(
[
0
,
1
]
)

C([0,1])

. In the present paper, we prove that there is a Müntz space not complemented in

L

1

(
[
0
,
1
]
)

L_{1}([0,1])

.
Exponential Gelfond–Khovanskii formula in dimension one
Authors: Soprunova Evgenia
Published: October 2007

Gelfond and Khovanskii found a formula for the sum of the values of a Laurent polynomial over the zeros of a system of

n
n

Laurent polynomials in

(

C

∖
0

)
n

(\mathbb C\setminus 0)^n

. We expect that a similar formula holds in the case of exponential sums with real frequencies. Here we prove such a formula in dimension one.
Atomic characterization of the Hardy space 𝐻¹_{𝐿}(ℝ) of one-dimensional Schrödinger operators with nonnegative potentials
Authors: Czaja Wojciech , Zienkiewicz Jacek
Published: October 2007

Given a Schrödinger operator

L
=

d
2

d

x
2

−
V
(
x
)

L=\frac {d^2}{dx^2}-V(x)

on

R

\mathbb R

with nonnegative potential

V
V

, we present an atomic characterization of the associated Hardy space

H
L
1

(

R

)

H_L^1 (\mathbb R)

.
Positive solutions in the sense of distributions of singular boundary value problems
Authors: Agarwal Ravi , Perera Kanishka , O’Regan Donal
Published: October 2007

We obtain positive solutions in the sense of distributions of singular boundary value problems using perturbation and variational methods.
Universality of Rank 6 Plücker relations and Grassmann cone preserving maps
Authors: Kasman Alex , Pedings Kathryn , Reiszl Amy , Shiota Takahiro
Published: October 2007

The Plücker relations define a projective embedding of the Grassmann varietyGr(p,n)Gr(p,n). We give another finite set of quadratic equations which defines the same embedding, and whose elements all have rank 6. This is achieved by constructing a certain finite set of linear maps⋀pkn→⋀2k4\bigwedge ^pk^n\to \bigwedge ^2k^4, and pulling back the unique Plücker relation on⋀2k4\bigwedge ^2k^4. We also give a quadratic equation depending on(p+2)(p+2)parameters having the same properties.
Note on a remarkable superposition for a nonlinear equation
Authors: Lindqvist Peter , Manfredi Juan
Published: October 2007

We give a simple proof of—and extend—a superposition principle for the equation

div

(

|

∇
u

|

p
−
2

∇
u
)
≤
0

\mbox {div}(|\nabla u|^{p-2}\nabla u)\leq 0

, discovered by Crandall and Zhang. An integral representation comes as a byproduct. It follows that a class of Riesz potentials is

p
p

-superharmonic.
Using Bcr-Abl to Examine Mechanisms by Which Abl Kinase Regulates Morphogenesis inDrosophila
Authors: Stevens Traci L. , Rogers Edward M. , Koontz Laura M. , Fox Donald T. , Homem Catarina C.F. , Nowotarski Stephanie H. , Artabazon Nicholas B. , Peifer Mark
Published: October 2007

Signaling by the nonreceptor tyrosine kinase Abelson (Abl) plays key roles in normal development, whereas its inappropriate activation helps trigger the development of several forms of leukemia. Abl is best known for its roles in axon guidance, but Abl and its relatives also help regulate embryonic morphogenesis in epithelial tissues. Here, we explore the role of regulation of Abl kinase activity during development. We first compare the subcellular localization of Abl protein and of active Abl, by using a phosphospecific antibody, providing a catalog of places where Abl is activated. Next, we explore the consequences for morphogenesis of overexpressing wild-type Abl or expressing the activated form found in leukemia, Bcr-Abl. We find dose-dependent effects of elevating Abl activity on morphogenetic movements such as head involution and dorsal closure, on cell shape changes, on cell protrusive behavior, and on the organization of the actin cytoskeleton. Most of the effects of Abl activation parallel those caused by reduction in function of its target Enabled. Abl activation leads to changes in Enabled phosphorylation and localization, suggesting a mechanism of action. These data provide new insight into how regulated Abl activity helps direct normal development and into possible biological functions of Bcr-Abl.
CDK5RAP2 Is a Pericentriolar Protein That Functions in Centrosomal Attachment of the γ-Tubulin Ring Complex
Authors: Fong Ka-Wing , Choi Yuk-Kwan , Rattner Jerome B. , Qi Robert Z.
Published: October 2007

Microtubule nucleation and organization by the centrosome require γ-tubulin, a protein that exists in a macromolecular complex called the γ-tubulin ring complex (γTuRC). We report characterization of CDK5RAP2, a novel centrosomal protein whose mutations have been linked to autosomal recessive primary microcephaly. In somatic cells, CDK5RAP2 localizes throughout the pericentriolar material in all stages of the cell cycle. When overexpressed, CDK5RAP2 assembled a subset of centrosomal proteins including γ-tubulin onto the centrosomes or under the microtubule-disrupting conditions into microtubule-nucleating clusters in the cytoplasm. CDK5RAP2 associates with the γTuRC via a short conserved sequence present in several related proteins found in a range of organisms from fungi to mammals. The binding of CDK5RAP2 is required for γTuRC attachment to the centrosome but not for γTuRC assembly. Perturbing CDK5RAP2 function delocalized γ-tubulin from the centrosomes and inhibited centrosomal microtubule nucleation, thus leading to disorganization of interphase microtubule arrays and formation of anastral mitotic spindles. Together, CDK5RAP2 is a pericentriolar structural component that functions in γTuRC attachment and therefore in the microtubule organizing function of the centrosome. Our findings suggest that centrosome malfunction due to the CDK5RAP2 mutations may underlie autosomal recessive primary microcephaly.
Protein Kinase Cδ and Calmodulin Regulate Epidermal Growth Factor Receptor Recycling from Early Endosomes through Arp2/3 Complex and Cortactin
Authors: Lladó Anna , Timpson Paul , Vilà de Muga Sandra , Moretó Jemina , Pol Albert , Grewal Thomas , Daly Roger J. , Enrich Carlos , Tebar Francesc
Published: October 2007

The intracellular trafficking of the epidermal growth factor receptor (EGFR) is regulated by a cross-talk between calmodulin (CaM) and protein kinase Cδ (PKCδ). On inhibition of CaM, PKCδ promotes the formation of enlarged early endosomes and blocks EGFR recycling and degradation. Here, we show that PKCδ impairs EGFR trafficking due to the formation of an F-actin coat surrounding early endosomes. The PKCδ-induced polymerization of actin is orchestrated by the Arp2/3 complex and requires the interaction of cortactin with PKCδ. Accordingly, inhibition of actin polymerization by using cytochalasin D or by overexpression of active cofilin, restored the normal morphology of the organelle and the recycling of EGFR. Similar results were obtained after down-regulation of cortactin and the sequestration of the Arp2/3 complex. Furthermore we demonstrate an interaction of cortactin with CaM and PKCδ, the latter being dependent on CaM inhibition. In summary, this study provides the first evidence that CaM and PKCδ organize actin dynamics in the early endosomal compartment, thereby regulating the intracellular trafficking of EGFR.