623 research outputs found
EUV Sunspot Plumes Observed with SOHO
Bright EUV sunspot plumes have been observed in five out of nine sunspot
regions with the Coronal Diagnostic Spectrometer -- CDS on SOHO. In the other
four regions the brightest line emissions may appear inside the sunspot but are
mainly concentrated in small regions outside the sunspot areas. These results
are in contrast to those obtained during the Solar Maximum Mission, but are
compatible with the Skylab mission results. The present observations show that
sunspot plumes are formed in the upper part of the transition region, occur
both in magnetic unipolar-- and bipolar regions, and may extend from the umbra
into the penumbra.Comment: 8 pages, 3 figures, to be published in ApJ Letter
Barnet si stemme ved samlivsbrot. Kva kan barn fortelje om sine opplevingar i samband med foreldra sitt samlivsbrot?
Barn og ungdom kan oppleva at foreldra deira gÄr gjennom eit samlivsbrot, dette pÄverkar dei pÄ mange mÄtar. Fokus i denne undersÞkinga er korleis barn og ungdom kan ha det nÄr foreldra gÄr frÄ kvarandre. Korleis kan det vera Ä leva med foreldra sine under og etter samlivsbrotet? I mastergradsoppgÄva ynskjer eg Ä fÄ fram barna sine stemmer, og om korleis dei opplevde den nye familiesituasjonen. Korleis vart barna ivaretekne av foreldra nÄr dei vaksne var midt oppe i eit samlivsbrot? Klarte dei vaksne, ut frÄ barnet sin stÄstad, Ä vera opptekne av barna sine og sjÄ deira behov i denne perioden? Ein periode som ogsÄ kan vera vanskeleg for dei vaksne.
Tema for mastergradsoppgÄva; Barnet si stemme ved samlivsbrot
Problemstilling;
Kva kan barn fortelje om sine opplevingar i samband med foreldra sitt samlivsbrot?
- Barna sine erfaringar og tankar i ein ny familiesituasjon?
- Kva oppleving hadde barna av Ä bli sett og hÞyrt, og kva kan dei gi av rÄd til vaksne og barn i liknande situasjon
On alternative approaches to Lorentz violation in loop quantum gravity inspired models
Recent claims point out that possible violations of Lorentz symmetry
appearing in some semiclassical models of extended matter dynamics motivated by
loop quantum gravity can be removed by a different choice of canonically
conjugated variables. In this note we show that such alternative is
inconsistent with the choice of variables in the underlying quantum theory
together with the semiclassical approximation, as long as the correspondence
principle is maintained. A consistent choice will violate standard Lorentz
invariance. Thus, to preserve a relativity principle in this framework, the
linear realization of Lorentz symmetry should be extended or superseded.Comment: 4 pages, revtex4, no figures, references adde
Magnetization creep and decay in YBa2Cu3O7âx thin films with artificial nanostructure pinning
Critical current and flux pinning have been studied for YBa_2Cu_3O_7âx thin films with Y_2BaCuO_5 (211) precipitates introduced as layers and as random distributions. The 211 precipitates were introduced during pulsed laser deposition. In the case of the layered sample, the strata were spaced approximately 6.5 nm apart throughout the film thickness. Magnetically determined critical current density (J_c) was then fitted to J_câB^âα above a magnetic field B*, below which a relatively field independent J_c-self-field was observed, consistent with previous results. Values of α were suppressed from the control sample values of α=0.5 to lower values for pinned samples, reaching α=0.2 for the layer pinned 211 sample at low temperatures. M-H was then measured as a function of ramp rate, and U(J) vs J curves were extracted for temperatures from 4.2 to 77 K for pinned and control samples. Direct magnetization decay measurements were made for the 211 layer pinned sample, and good agreement was seen with ramp-rate-derived results. Using U(J)=(U_0âÎŒ)[(J_câJ)^ÎŒâ1]B^âÎœ, values of ÎŒâ
0.6â0.8 were seen for all samples, while Îœâ
0.4 for control samples, 0.1 for layer pinned samples, and 0.2â0.4 for the random pinned samples. The activation energy scale U_0 was 600â700 and 400 K for layer pinned and control samples, respectively, and 400â500 K for the random pinned samples. The values of ÎŒ and Îœ extracted were inconsistent with two dimensional pinning behavior in all cases, even though the layer spacing in the layer pinned sample is smaller than the calculated collective correlation length. While the layer pinned sample is clearly in the collective pinning regime, the artificial defects in the random pinned sample may be in the isolated strong pinning regime
Testing the Equivalence Principle by Lamb shift Energies
The Einstein Equivalence Principle has as one of its implications that the
non-gravitational laws of physics are those of special relativity in any local
freely-falling frame. We consider possible tests of this hypothesis for systems
whose energies are due to radiative corrections, i.e. which arise purely as a
consequence of quantum field theoretic loop effects. Specifically, we evaluate
the Lamb shift transition (as given by the energy splitting between the
and atomic states) within the context of violations of
local position invariance and local Lorentz invariance, as described by the formalism. We compute the associated red shift and time dilation
parameters, and discuss how (high-precision) measurements of these quantities
could provide new information on the validity of the equivalence principle.Comment: 40 pages, latex, epsf, 1 figure, final version which appears in
Physical Review
Maxwell's field coupled nonminimally to quadratic torsion: Induced axion field and birefringence of the vacuum
We consider a possible (parity conserving) interaction between the
electromagnetic field and a torsion field of spacetime. For
generic elementary torsion, gauge invariant coupling terms of lowest order fall
into two classes that are both nonminimal and {\it quadratic} in torsion. These
two classes are displayed explicitly. The first class of the type
yields (undesirable) modifications of the Maxwell equations. The second class
of the type doesn't touch the Maxwell equations but rather
modifies the constitutive tensor of spacetime. Such a modification can be
completely described in the framework of metricfree electrodynamics. We
recognize three physical effects generated by the torsion: (i) An axion field
that induces an {\em optical activity} into spacetime, (ii) a modification of
the light cone structure that yields {\em birefringence} of the vacuum, and
(iii) a torsion dependence of the {\em velocity of light.} We study these
effects in the background of a Friedmann universe with torsion. {\it File
tor17.tex, 02 August 2003}Comment: 6 page
Evaluating Superconducting Ybco Film Properties Using Xray Photoelectron Spectroscopy
Initial results have been recently reported that suggest a potential correlation exists between the full-width-halfmaximum (FWHM) of the Y(3d) peak obtained by x-ray photoelectron spectroscopy (XPS) and the critical current density a YBa2Cu3O7-x film can carry. In particular, the Y(3d5/2) demonstrated a stronger correlation. Transport currents were determined by the 4-point contact method using the 1ÎŒV/cm criterion. An apparent correlation was also suggested between the Y(3d) FWHM and ac loss data points were acquired to further test the usefulness of the correlations. Samples were created by pulsed laser deposition of YBa2Cu3O7-x on LaAlO3 substrates
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