36,007 research outputs found
Nonlinear Properties of the Semiregular Variable Stars
We demonstrate how, with a purely empirical analysis of the irregular
lightcurve data, one can extract a great deal of information about the stellar
pulsation mechanism. An application to R Sct thus shows that the irregular
lightcurve is the result of the nonlinear interaction of two highly
nonadiabatic pulsation modes, namely a linearly unstable, low frequency mode,
and the second mode that, although linearly stable, gets entrained through a
2:1 resonance. In the parlance of nonlinear dynamics the pulsation is the
result of a 4 dimensional chaotic dynamics.Comment: 8 pages to appear in "Mass-Losing Pulsating Stars and Their
Circumstellar Matter", Eds. Y. Nakada & M.Honma, ASSL Ser. (in press). a
version with better quality figures is available from
http://www.phys.ufl.edu/~buchler
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Interleukin 2 activation of natural killer cells rapidly induces the expression and phosphorylation of the Leu-23 activation antigen.
IL-2 potentiates both growth and cytotoxic function of T lymphocytes and NK cells. Resting peripheral blood NK cells can respond directly to rIL-2, without requirement for accessory cells or cofactors, and enhanced cytotoxicity can be measured within a few hours after exposure to this lymphokine. In this study, we describe an activation antigen, Leu-23, that is rapidly induced and phosphorylated after IL-2 stimulation of NK cells and a subset of low buoyant density T lymphocytes. Previously, it has been uncertain whether all NK cells or only a subset are responsive to IL-2. Since within 18 h after exposure to IL-2, essentially all NK cells express Leu-23, these findings indicate that all peripheral blood NK cells are responsive to stimulation by IL-2. The Leu-23 antigen is a disulfide-bonded homodimer, composed of 24-kD protein subunits with two N-linked oligosaccharides. Appearance of this glycoprotein on NK cells is IL-2 dependent and closely parallels IL-2-induced cytotoxicity against NK-resistant solid tumor cell targets
A case study of argumentation at undergraduate level in history
This article examines two essays by undergraduate students in the first year of study in History at a university in the UK. It also draws on documentary evidence from the department in question and interviews with the students themselves to paint a picture of the way argumentation operates at this level. While no firm conclusions can be drawn, the evidence suggests a department with a high degree of awareness of the importance of argument and argumentation in studying History; and students who are aware and articulate about the problem facing them in constructing essays in the discipline. Suggestions are made about induction into the epistemological and argumentative demands of undergraduate study
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Discourses of marriage in same-sex marriage debates in the UK press 2011–2014
This paper interrogates media representations of same-sex marriage debates in the UK using a combination of corpus linguistics tools and close reading, and drawing on Queer Linguistics. Following related work by Baker (2004), Love and Baker (2015), and Bachmann (2011), we analyse a 1.3 million-word corpus of UK national newspaper texts compiled for the Discourses of Marriage Research Group. Our corpus stretches from September 2011 and the announcement of a government consultation on same-sex marriage, to April 2014 when the first same-sex marriages took place. Using a top-down approach we investigate the discourses drawn upon in same-sex marriage debates (as indexed by keywords and key semantic fields) and uncover the binary social categories used to normalise social structures and hold the same-sex marriage debate in place. We also consider which social actors are (not) given a voice and/or agency and discuss how (same-sex) marriage is constituted
Rotating Hele-Shaw cells with ferrofluids
We investigate the flow of two immiscible, viscous fluids in a rotating
Hele-Shaw cell, when one of the fluids is a ferrofluid and an external magnetic
field is applied. The interplay between centrifugal and magnetic forces in
determining the instability of the fluid-fluid interface is analyzed. The
linear stability analysis of the problem shows that a non-uniform, azimuthal
magnetic field, applied tangential to the cell, tends to stabilize the
interface. We verify that maximum growth rate selection of initial patterns is
influenced by the applied field, which tends to decrease the number of
interface ripples. We contrast these results with the situation in which a
uniform magnetic field is applied normally to the plane defined by the rotating
Hele-Shaw cell.Comment: 12 pages, 3 ps figures, RevTe
Detection of Massive Forming Galaxies at Redshifts Greater than One
The complex problem of when and how galaxies formed has not until recently
been susceptible of direct attack. It has been known for some time that the
excessive number of blue galaxies counted at faint magnitudes implies that a
considerable fraction of the massive star formation in the universe occurred at
z < 3, but, surprisingly, spectroscopic studies of galaxies down to a B
magnitude of 24 found little sign of the expected high-z progenitors of current
massive galaxies, but rather, in large part, small blue galaxies at modest
redshifts z \sim 0.3. This unexpected population has diverted attention from
the possibility that early massive star-forming galaxies might also be found in
the faint blue excess. From KECK spectroscopic observations deep enough to
encompass a large population of z > 1 field galaxies, we can now show directly
that in fact these forming galaxies are present in substantial numbers at B
\sim 24, and that the era from redshifts 1 to 2 was clearly a major period of
galaxy formation. These z > 1 galaxies have very unusual morphologies as seen
in deep HST WFPC2 images.Comment: 10 pages LaTeX + 5 PostScript figures in uuencoded gzipped tar file;
aasms4.sty, flushrt.sty, overcite.sty (the two aastex4.0 and overcite.sty
macros are available from xxx.lanl.gov) Also available (along with style
files) via anonymous ftp to ftp://hubble.ifa.hawaii.edu/pub/preprints .
E-print version of paper adds citation cross-references to other archived
e-prints, where available. To appear in Nature October 19, 199
Brueckner-Hartree-Fock study of circular quantum dots
We calculate ground state energies in the Brueckner-Hartree-Fock theory for
electrons (with ) confined to a circular quantum dot and in
presence of a static magnetic field. Comparison with the predictions of
Hartree-Fock, local-spin-density and exact configuration-interaction theories
is made. We find that the correlations taken into account in
Brueckner-Hartree-Fock calculations give an important contribution to the
ground state energies, specially in strongly confined dots. In this
high-density range, corresponding in practice to self-assembled quantum dots,
the results of Brueckner-Hartree-Fock calculations are close to the exact
values and better than those obtained in the local-spin-density approximation.Comment: Regular articl
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