Progress in Simulations with Twisted Mass Fermions at the Physical Point

In this contribution, results from Nf = 2 lattice QCD simulations at one lattice spacing using twisted mass fermions with a clover term at the physical pion mass are presented. The mass splitting between charged and neutral pions (including the disconnected contribution) is shown to be around 20(20) MeV. Further, a first measurement using the clover twisted mass action of the average momentum fraction of the pion is given. Finally, an analysis of pseudoscalar meson masses and decay constants is presented involving linear interpolations in strange and charm quark masses. Matching to meson mass ratios allows the calculation of quark mass ratios: ms=ml = 27:63(13), mc=ml = 339:6(2:2) and mc=ms = 12:29(10). From this mass matching the quantities fK = 153:9(7:5) MeV, fD = 219(11) MeV, fDs = 255(12) MeV and MDs = 1894(93) MeV are determined without the application of finite volume or discretization artefact corrections and with errors dominated by a preliminary estimate of the lattice spacing.

(Table 2) Planktonic to benthic foraminifera ratios at DSDP Site 63-468

In recent years there has been considerable discussion concerning the biostratigraphic correlations between planktonic zonations and the classical Neogene California benthic foraminiferal stages. One of the primary objectives of IPOD Leg 63 was to investigate these correlations and to determine the possibility of temporal variation of the benthic stages between California land sections and the outer Continental Borderland. In addition, it was anticipated that analyses of the benthic foraminiferal faunas at Site 468 would provide critical information on the paleoenvironmental history of the outer borderland. The provincial benthic Neogene foraminiferal stages were established by Kleinpell (1938) for the Miocene and Natland (1952) for the Pliocene-Pleistocene; both are well-documented in designated type sections. These stages have been used for interbasinal correlations, although time-transgressive problems have been suggested by several authors (Bandy, 1971; Ingle, 1967, 1973; Crouch and Bukry, 1979). An important biostratigraphic sequence occurs at Site 468, significant because of its relatively shallow depth of approximately 1700 meters. The samples yield well-preserved benthic foraminiferal faunas throughout most of the Neogene sequence and are accompanied by abundant well-preserved calcareous and siliceous planktonic assemblages. It is this co-occurrence of both planktonic and benthic faunas that enables the correlation of outer continental margin sediments with those of the classical land-based sections of southern California.

Multi-fluid Eulerian model of an electrospray in a host gas.

An Eulerian multifluid model is used to describe the evolution of an electrospray plume and the flow induced in the surrounding gas by the drag of the electrically charged spray droplets in the space between an injection electrode containing the electrospray source and a collector electrode. The spray is driven by the voltage applied between the two electrodes. Numerical computations and order-of-magnitude estimates for a quiescent gas show that the droplets begin to fly back toward the injection electrode at a certain critical value of the flux of droplets in the spray, which depends very much on the electrical conditions at the injection electrode. As the flux is increased toward its critical value, the electric field induced by the charge of the droplets partially balances the field due to the applied voltage in the vicinity of the injection electrode, leading to a spray that rapidly broadens at a distance from its origin of the order of the stopping distance at which the droplets lose their initial momentum and the effect of their inertia becomes negligible. The axial component of the electric field first changes sign in this region, causing the fly back. The flow induced in the gas significantly changes this picture in the conditions of typical experiments. A gas plume is induced by the drag of the droplets whose entrainment makes the radius of the spray away from the injection electrode smaller than in a quiescent gas, and convects the droplets across the region of negative axial electric field that appears around the origin of the spray when the flux of droplets is increased. This suppresses fly back and allows much higher fluxes to be reached than are possible in a quiescent gas. The limit of large droplet-to-gas mass ratio is discussed. Migration of satellite droplets to the shroud of the spray is reproduced by the Eulerian model, but this process is also affected by the motion of the gas. The gas flow preferentially pushes satellite droplets from the shroud to the core of the spray when the effect of the inertia of the droplets becomes negligible, and thus opposes the well-established electrostatic/inertial mechanism of segregation and may end up concentrating satellite droplets in an intermediate radial region of the spray.

Urokinase Receptor and Fibronectin Regulate the ERKMAPK to p38MAPK Activity Ratios That Determine Carcinoma Cell Proliferation or Dormancy In Vivo

We discovered that a shift between the state of tumorigenicity and dormancy in human carcinoma (HEp3) is attained through regulation of the balance between two classical mitogen-activated protein kinase (MAPK)-signaling pathways, the mitogenic extracellular regulated kinase (ERK) and the apoptotic/growth suppressive stress-activated protein kinase 2 (p38MAPK), and that urokinase plasminogen activator receptor (uPAR) is an important regulator of these events. This is a novel function for uPAR whereby, when expressed at high level, it enters into frequent, activating interactions with the α5β1-integrin, which facilitates the formation of insoluble fibronectin (FN) fibrils. Activation of α5β1-integrin by uPAR generates persistently high level of active ERK necessary for tumor growth in vivo. Our results show that ERK activation is generated through a convergence of two pathways: a positive signal through uPAR-activated α5β1, which activates ERK, and a signal generated by the presence of FN fibrils that suppresses p38 activity. When fibrils are removed or their assembly is blocked, p38 activity increases. Low uPAR derivatives of HEp3 cells, which are growth arrested (dormant) in vivo, have a high p38/ERK activity ratio, but in spite of a similar level of α5β1-integrin, they do not assemble FN fibrils. However, when p38 activity is inhibited by pharmacological (SB203580) or genetic (dominant negative-p38) approaches, their ERK becomes activated, uPAR is overexpressed, α5β1-integrins are activated, and dormancy is interrupted. Restoration of these properties in dormant cells can be mimicked by a direct re-expression of uPAR through transfection with a uPAR-coding plasmid. We conclude that overexpression of uPAR and its interaction with the integrin are responsible for generating two feedback loops; one increases the ERK activity that feeds back by increasing the expression of uPAR. The second loop, through the presence of FN fibrils, suppresses p38 activity, further increasing ERK activity. Together these results indicate that uPAR and its interaction with the integrin should be considered important targets for induction of tumor dormancy.

Michael & Will on the law relating to gas and water.

Mode of access: Internet.

Electronic structure methods applied to gas-carbon reactions

A review is given on the fundamental studies of gas-carbon reactions using electronic structure methods in the last several decades. The three types of electronic structure methods including semi-empirical, ab initio and density functional theory, methods are briefly introduced first, followed by the studies on carbon reactions with hydrogen and oxygen-containing gases (non-catalysed and catalysed). The problems yet to solve and possible promising directions are discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.

Global Results for Solution to the Mass-Critical Schrödinger Equation with Convolution Nonlinearity in R^n

Георги Венков, Христо Генев - Разглеждаме един клас от L^2 - критични нелинейни уравнения на Шрьодингер в R^(1+n) с конволюционна нелинейност от тип Хартри. Целта ни е да установим локалното и глобално съществуване на решенията, както и коректност на задачата на Коши в достатъчно малка околност на нулата в пространството L^2 (R^n). Като естествено следствие на глобалните резултати ние доказваме съществуване на оператор на разсейване за малки начални условия.