1,527 research outputs found

    A Study of the Motion of Air Bubbles Moving Unrestrained in Water

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    This study was designed to improve understanding of the motion of air bubbles in water, in order to make possible more precise mass transfer calculations. An accurate, low cost photographic technique was developed for studying the trajectory of air bubbles rising unrestrained in water. The effect of several variables on velocity and direction of bubble movement was studied. These include: equivalent bubble radius; temperature; contamination; release pressure; vessel size, shape and construction material, and orientation and size of the capillary tube from which the bubbles were released. Air bubble velocities in this work were generally low, as compared to the results of other experiments for air bubbles in distilled or filtered water. For small air bubbles a smooth curve showing increase of velocity with increase in equivalent radius was obtained. When the size of the air bubbles reached the transition region where spherical shape was lost and the path deviated from rectilinearity the velocities increased with bubble radius but considerable scatter was in evidence. It was shown that the amplitude of the bubble oscillation from the rectilinear path increased as the vertical velocity increased. The level of contamination was found to be considerably less than the amount, as stated in the literature, required to cause a reduction in bubble velocity of the magnitude found in this study

    Bose-Einstein condensate coupled to a nanomechanical resonator on an atom chip

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    We theoretically study the coupling of Bose-Einstein condensed atoms to the mechanical oscillations of a nanoscale cantilever with a magnetic tip. This is an experimentally viable hybrid quantum system which allows one to explore the interface of quantum optics and condensed matter physics. We propose an experiment where easily detectable atomic spin-flips are induced by the cantilever motion. This can be used to probe thermal oscillations of the cantilever with the atoms. At low cantilever temperatures, as realized in recent experiments, the backaction of the atoms onto the cantilever is significant and the system represents a mechanical analog of cavity quantum electrodynamics. With high but realistic cantilever quality factors, the strong coupling regime can be reached, either with single atoms or collectively with Bose-Einstein condensates. We discuss an implementation on an atom chip.Comment: published version (5 pages, 3 figures

    The Rigidly Rotating Magnetosphere of Sigma Ori E

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    We attempt to characterize the observed variability of the magnetic helium-strong star sigma Ori E in terms of a recently developed rigidly rotating magnetosphere model. This model predicts the accumulation of circumstellar plasma in two co-rotating clouds, situated in magnetohydrostatic equilibrium at the intersection between magnetic and rotational equators. We find that the model can reproduce well the periodic modulations observed in the star's light curve, H alpha emission-line profile, and longitudinal field strength, confirming that it furnishes an essentially correct, quantitative description of the star's magnetically controlled circumstellar environment.Comment: 4 pages, 3 figures, accepted by Ap

    A Further Note on Federal Causes of Action

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    In the article, I argue that federal causes of action ought to be treated as (1) distinct from substantive rights, (2) synonymous with the availability of a remedy (but not whether a remedy will in fact issue) and (3) distinct from subject matter jurisdiction (unless Congress instructs otherwise). This thesis is built principally on a historical recounting of the cause of action from eighteenth century England to twenty-first century America. In taking an historical approach, I did not mean to argue that federal courts are bound to adhere to centuries-old conceptions of the cause of action. I merely used history to show why the cause of action has taken on various identities and, further, why these identities have changed over time. By closely attending to these changes, we can better determine whether linguistic changes signal substantive changes in doctrine, or are simply loose language

    Timp1 Promotes Cell Survival by Activating the PDK1 Signaling Pathway in Melanoma

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    High TIMP1 expression is associated with poor prognosis in melanoma, where it can bind to CD63 and beta 1 integrin, inducing PI3-kinase pathway and cell survival. Phosphatidylinositol (3,4,5)-trisphosphate (PIP3), generated under phosphatidylinositol-3-kinase (PI3K) activation, enables the recruitment and activation of protein kinase B (PKB/AKT) and phosphoinositide-dependent kinase 1 (PDK1) at the membrane, resulting in the phosphorylation of a host of other proteins. Using a melanoma progression model, we evaluated the impact of Timp1 and AKT silencing, as well as PI3K, PDK1, and protein kinase C (PKC) inhibitors on aggressiveness characteristics. Timp1 downregulation resulted in decreased anoikis resistance, clonogenicity, dacarbazine resistance, and in vivo tumor growth and lung colonization. In metastatic cells, pAKT(Thr308) is highly expressed, contributing to anoikis resistance. We showed that PDK1(Ser241) and PKC beta IISer660 are activated by Timp1 in different stages of melanoma progression, contributing to colony formation and anoikis resistance. Moreover, simultaneous inhibition of Timp1 and AKT in metastatic cells resulted in more effective anoikis inhibition. Our findings demonstrate that Timp1 promotes cell survival with the participation of PDK1 and PKC in melanoma. In addition, Timp1 and AKT act synergistically to confer anoikis resistance in advanced tumor stages. This study brings new insights about the mechanisms by which Timp1 promotes cell survival in melanoma, and points to novel perspectives for therapeutic approaches.Fundacao de Amparo a Pesquisa do Estado de Sao PauloConselho Nacional de Desenvolvimento Cientifico e TecnologicoUniv Fed Sao Paulo, Dept Pharmacol, BR-04039032 Sao Paulo, BrazilUniv Sao Paulo, Sch Med, Canc Inst Sao Paulo, Ctr Translat Invest Oncol LIM 24, BR-01246000 Sao Paulo, BrazilFac Med Santa Casa Sao Paulo, BR-01221020 Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Pharmacol, BR-04039032 Sao Paulo, Brazil|FAPESP: 2010/18715-8FAPESP: 2011/12306-1FAPESP: 2014/13663-0CNPq: 470681/2012-8Web of Scienc

    CuAu-type ordering in epitaxial CuInS<sub>2</sub> films

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    Ordering of Cu and In atoms in near-stoichiometric CuInS2 epitaxial films grown on Si (111) by molecular beam epitaxy was studied by transmission electron microscopy. Nonchalcopyrite ordering of the metal atoms in CuInS2 is observed, which is identified as CuAu-type ordering. Sharp spots in electron diffraction patterns reveal the ordered Cu and In atom planes alternating along the [001] direction over a long range. High-resolution electron microscopy confirms this ordering. The CuAu-ordered structure coexists with the chalcopyrite ordered structure, in agreement with theoretical prediction

    Cavity cooling of a nanomechanical resonator by light scattering

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    We present a novel method for opto-mechanical cooling of sub-wavelength sized nanomechanical resonators. Our scheme uses a high finesse Fabry-Perot cavity of small mode volume, within which the nanoresonator is acting as a position-dependant perturbation by scattering. In return, the back-action induced by the cavity affects the nanoresonator dynamics and can cool its fluctuations. We investigate such cavity cooling by scattering for a nanorod structure and predict that ground-state cooling is within reach.Comment: 4 pages, 3 figure

    First HARPSpol discoveries of magnetic fields in massive stars

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    In the framework of the Magnetism in Massive Stars (MiMeS) project, a HARPSpol Large Program at the 3.6m-ESO telescope has recently started to collect high-resolution spectropolarimetric data of a large number of Southern massive OB stars in the field of the Galaxy and in many young clusters and associations. In this Letter, we report on the first discoveries of magnetic fields in two massive stars with HARPSpol - HD 130807 and HD 122451, and confirm the presence of a magnetic field at the surface of HD 105382 that was previously observed with a low spectral resolution device. The longitudinal magnetic field measurements are strongly varying for HD 130807 from ∼\sim-100 G to ∼\sim700 G. Those of HD 122451 and HD 105382 are less variable with values ranging from ∼\sim-40 to -80 G, and from ∼\sim-300 to -600 G, respectively. The discovery and confirmation of three new magnetic massive stars, including at least two He-weak stars, is an important contribution to one of the MiMeS objectives: the understanding of origin of magnetic fields in massive stars and their impacts on stellar structure and evolution.Comment: 4 pages, 2 figures, accepted for publication in A&A Lette
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