8,655 research outputs found
Precision Measurement of sin^2 theta_W at a Reactor
This paper presents a strategy for measuring sin^2 theta_W to ~1% at a
reactor-based experiment, using antineutrinos electron elastic scattering. This
error is comparable to the NuTeV, SLAC E158, and APV results on sin^2 theta_W,
but with substantially different contributions to the systematics. An improved
method for identifying antineutrino proton events, which serve both as a
background and as a normalization sample, is described. The measurement can be
performed using the near detector of the presently proposed reactor-based
oscillation experiments. We conclude that an absolute error of delta(sin^2
theta_W)=0.0019 may be achieved.Comment: To be Submitted to Phys. Rev.
Using Reactors to Measure
A next-generation neutrino oscillation experiment using reactor neutrinos
could give important information on the size of mixing angle . The
motivation and goals for a new reactor measurement are discussed in the context
of other measurements using off-axis accelerator neutrino beams. The reactor
measurements give a clean measure of the mixing angle without ambiguities
associated with the size of the other mixing angles, matter effects, and
effects due to CP violation. The key question is whether a next-generation
experiment can reach the needed sensitivity goals to make a measurement for
at the 0.01 level. The limiting factors associated with
a reactor disappearance measurement are described with some ideas of how
sensitivities can be improved. Examples of possible experimental setups are
presented and compared with respect to cost and sensitivity
Effect of oxytocin on free intracellular Ca2+ levels and progesterone release by human granulosa-lutein cells
Oxytocin and its receptor are found in the corpus luteum in a variety of species, including the human. In the present study we used fura-2 microfluorimetry to investigate whether activation of the oxytocin receptor of cultured human granulosa-lutein cells causes intracellular calcium (Ca2+) signals and affects progesterone release. Although after 1 day in culture, cells were not responsive to oxytocin, the number of responsive cells increased steadily during the first 3 days in culture, reaching a maximum on days 4 and 5 (59-66%) and then declined again until day 8. Effective oxytocin concentrations were apparently independent of the culture day, and concentrations as low as 10 nmol/L increased intracellular free Ca2+ levels from 70-140 nmol/L (basal levels) to maximal peak levels of 800 nmol/L. The oxytocin-induced Ca2+ signal was not affected by removal of extracellular Ca2+ with EGTA. Moreover, depletion of intracellular Ca2+ stores by ionomycin treatment rendered the cells unresponsive to oxytocin, pointing also at the intracellular source of the oxytocin-inducible Ca2+ signal. Interestingly, after one single stimulation with oxytocin, cells became refractory to additional stimuli, and only extremely high concentrations of oxytocin induced a second increase in intracellular free Ca2+. To examine the possible effects of oxytocin on progesterone release by cultured cells, we incubated cells on culture day 2 (20% responsive cells in the fura measurements) and culture day 5 (66% responsive cells in the fura measurements) for 24 h with oxytocin (10 nmol/L) and hCG (10,000 IU/L). Although hCG significantly stimulated progesterone release, oxytocin alone was without a stimulatory effect on either day. However, a significant augmentation of the effect of hCG on progesterone release was found in incubations of cells on day 5. Interestingly, the effects of hCG also included stimulation of oxytocin release by cultured granulosa-lutein cells into the culture medium, as determined by RIA. In summary, our data indicate the presence of a functional oxytocin receptor on human granulosa-lutein cells that is linked to Ca2+ as a second messenger released from intracellular Ca2+ stores. The number of oxytocin-responsive cells increases during differentiation in culture. Moreover, oxytocin release induced by hCG and a stimulatory effect of oxytocin on the hCG-induced progesterone production during the period of maximal responsiveness of cultured cells were found. We, therefore, propose that oxytocin may have autocrine and/or paracrine functions in human granulosa-lutein cells, including fine-tuning of progesterone release
The Two-Dimensional Square-Lattice S=1/2 Antiferromagnet Cu(pz)(ClO)
We present an experimental study of the two-dimensional S=1/2 square-lattice
antiferromagnet Cu(pz)(ClO) (pz denotes pyrazine - )
using specific heat measurements, neutron diffraction and cold-neutron
spectroscopy. The magnetic field dependence of the magnetic ordering
temperature was determined from specific heat measurements for fields
perpendicular and parallel to the square-lattice planes, showing identical
field-temperature phase diagrams. This suggest that spin anisotropies in
Cu(pz)(ClO) are small. The ordered antiferromagnetic structure is a
collinear arrangement with the magnetic moments along either the
crystallographic b- or c-axis. The estimated ordered magnetic moment at zero
field is m_0=0.47(5)mu_B and thus much smaller than the available single-ion
magnetic moment. This is evidence for strong quantum fluctuations in the
ordered magnetic phase of Cu(pz)(ClO). Magnetic fields applied
perpendicular to the square-lattice planes lead to an increase of the
antiferromagnetically ordered moment to m_0=0.93(5)mu_B at mu_0H=13.5T -
evidence that magnetic fields quench quantum fluctuations. Neutron spectroscopy
reveals the presence of a gapped spin excitations at the antiferromagnetic zone
center, and it can be explained with a slightly anisotropic nearest neighbor
exchange coupling described by J_1^{xy}=1.563(13)meV and
J_1^z=0.9979(2)J_1^{xy}
Intercalation of graphene on SiC(0001) via ion-implantation
Electronic devices based on graphene technology are catching on rapidly and
the ability to engineer graphene properties at the nanoscale is becoming, more
than ever, indispensable. Here, we present a new procedure of graphene
functionalization on SiC(0001) that paves the way towards the fabrication of
complex graphene electronic chips. The procedure resides on the well-known
ion-implantation technique. The efficiency of the working principle is
demonstrated by the intercalation of the epitaxial graphene layer on SiC(0001)
with Bi atoms, which was not possible following standard procedures. Our
results put forward the ion-beam lithography to nanostructure and functionalize
desired graphene chips
Antiferroquadrupolar Order in the Magnetic Semiconductor TmTe
The physical properties of the antiferroquadrupolar state occurring in TmTe
below TQ=1.8 K have been studied using neutron diffraction in applied magnetic
fields. A field-induced antiferromagnetic component k = (1/2,1/2,1/2) is
observed and, from its magnitude and direction for different orientations of H,
an O(2,2) quadrupole order parameter is inferred. Measurements below TN ~= 0.5
K reveal that the magnetic structure is canted, in agreement with theoretical
predictions for in-plane antiferromagnetism. Complex domain repopulation
effects occur when the field is increased in the ordered phases, with
discontinuities in the superstructure peak intensities above 4 T.Comment: 6 pages, 6 figures, Presented at the International Conference on
Strongly Correlated Electrons with Orbital Degrees of Freedom (ORBITAL 2001),
September 11-14, 2001 (Sendai, JAPAN). To appear in: Journal of the Physical
Society of Japan (2002
Sensitivity of an image plate system in the XUV (60 eV < E < 900 eV)
Phosphor imaging plates (IPs) have been calibrated and proven useful for
quantitative x-ray imaging in the 1 to over 1000 keV energy range. In this
paper we report on calibration measurements made at XUV energies in the 60 to
900 eV energy range using beamline 6.3.2 at the Advanced Light Source at
Lawrence Berkeley National Laboratory. We measured a sensitivity of ~25 plus or
minus 15 counts/pJ over the stated energy range which is compatible with the
sensitivity of Si photodiodes that are used for time-resolved measurements. Our
measurements at 900 eV are consistent with the measurements made by Meadowcroft
et al. at ~1 keV.Comment: 7 pages, 2 figure
Long-Distance Contributions to D^0-D^0bar Mixing Parameters
Long-distance contributions to the - mixing parameters and
are evaluated using latest data on hadronic decays. In particular, we
take on two-body and decays to evaluate the contributions of
two-body intermediate states because they account for of hadronic
decays. Use of the diagrammatic approach has been made to estimate
yet-observed decay modes. We find that is of order a few
and of order from hadronic and modes. These are in good
agreement with the latest direct measurement of - mixing
parameters using the and decays by
BaBar. We estimate the contribution to from the modes using the
factorization model and comment on the single-particle resonance effects and
contributions from other two-body modes involving even-parity states.Comment: 18 pages and 1 figure; footnotes and references added; to appear in
Phys. Rev.
QCD sum rules for the anti-charmed pentaquark
We present a QCD sum rule analysis for the anti-charmed pentaquark state with
and without strangeness. While the sum rules for most of the currents are
either non-convergent or dominated by the continuum, the one for the
non-strange pentaquark current composed of two diquarks and an antiquark, is
convergent and has a structure consistent with a positive parity pentaquark
state after subtracting out the continuum contribution. Arguments are
presented on the similarity between the result of the present analysis and that
based on the constituent quark models, which predict a more stable pentaquark
states when the antiquark is heavy.Comment: 19 pages, 8 figures, REVTex, revised version,new figures added and
references update
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