9,178 research outputs found
Effects and importance of penetration and growth of lift on space vehicle response
Wind induced aerodynamic response of Saturn C-5 launch vehicle without fin
Spin and Orbital Splitting in Ferromagnetic Contacted Single Wall Carbon Nanotube Devices
We observed the coulomb blockade phenomena in ferromagnetic contacting single
wall semiconducting carbon nanotube devices. No obvious Coulomb peaks shift was
observed with existing only the Zeeman splitting at 4K. Combining with other
effects, the ferromagnetic leads prevent the orbital spin states splitting with
magnetic field up to 2 Tesla at 4K. With increasing magnetic field further,
both positive or negative coulomb peaks shift slopes are observed associating
with clockwise and anticlockwise orbital state splitting. The strongly
suppressed/enhanced of the conductance has been observed associating with the
magnetic field induced orbital states splitting/converging
Estrogen and progesterone induce persistent increases in p53-dependent apoptosis and suppress mammary tumors in BALB/c-Trp53+/- mice
INTRODUCTION Treatment with estrogen and progesterone (E+P) mimics the protective effect of parity on mammary tumors in rodents and depends upon the activity of p53. The following experiments tested whether exogenous E+P primes p53 to be more responsive to DNA damage and whether these pathways confer resistance to mammary tumors in a mouse model of Li-Fraumeni syndrome. METHODS Mice that differ in p53 status (Trp53+/+, Trp53+/-, Trp53-/-) were treated with E+P for 14 days and then were tested for p53-dependent responses to ionizing radiation. Responses were also examined in parous and age-matched virgins. The effects of hormonal exposures on tumor incidence were examined in BALB/c-Trp53+/- mammary tissues. RESULTS Nuclear accumulation of p53 and apoptotic responses were increased similarly in the mammary epithelium from E+P-treated and parous mice compared with placebo and age-matched virgins. This effect was sustained for at least 7 weeks after E+P treatment and did not depend on the continued presence of ovarian hormones. Hormone stimulation also enhanced apoptotic responses to ionizing radiation in BALB/c-Trp53+/- mice but these responses were intermediate compared with Trp53+/+ and Trp-/- tissues, indicating haploinsufficiency. The appearance of spontaneous mammary tumors was delayed by parity in BALB/c-Trp53+/- mice. The majority of tumors lacked estrogen receptor (ER), but ER+ tumors were observed in both nulliparous and parous mice. However, apoptotic responses to ionizing radiation and tumor incidence did not differ among outgrowths of epithelial transplants from E+P-treated donors and nulliparous donors. CONCLUSION Therefore, E+P and parity confer a sustained increase in p53-mediated apoptosis within the mammary epithelium and suppress mammary tumorigenesis, but this effect was not retained in epithelial outgrowths.This work was supported by grants from the US Army Medical Research and Materiel Command (W81XWH0410385 to KAD and DAMD17-01-1-0315 to ACB) and the National Institutes of Health (RO1-CA095164 to DJJ)
Singlet-Triplet Physics and Shell Filling in Carbon Nanotube Double Quantum Dots
An artifcial two-atomic molecule, also called a double quantum dot (DQD), is
an ideal system for exploring few electron physics. Spin-entanglement between
just two electrons can be explored in such systems where singlet and triplet
states are accessible. These two spin-states can be regarded as the two states
in a quantum two-state system, a so-called singlet-triplet qubit. A very
attractive material for realizing spin based qubits is the carbon nanotube
(CNT), because it is expected to have a very long spin coherence time. Here we
show the existence of a gate-tunable singlet-triplet qubit in a CNT DQD. We
show that the CNT DQD has clear shell structures of both four and eight
electrons, with the singlet-triplet qubit present in the four-electron shells.
We furthermore observe inelastic cotunneling via the singlet and triplet
states, which we use to probe the splitting between singlet and triplet, in
good agreement with theory.Comment: Supplement available at:
http://www.fys.ku.dk/~hij/public/singlet-triple_supp.pd
High magnetic field studies of the Vortex Lattice structure in YBa2Cu3O7
We report on small angle neutron scattering measurements of the vortex
lattice in twin-free YBa2Cu3O7, extending the previously investigated maximum
field of 11~T up to 16.7~T with the field applied parallel to the c axis. This
is the first microscopic study of vortex matter in this region of the
superconducting phase. We find the high field VL displays a rhombic structure,
with a field-dependent coordination that passes through a square configuration,
and which does not lock-in to a field-independent structure. The VL pinning
reduces with increasing temperature, but is seen to affect the VL correlation
length even above the irreversibility temperature of the lattice structure. At
high field and temperature we observe a melting transition, which appears to be
first order, with no detectable signal from a vortex liquid above the
transition
No Evidence for Orbital Loop Currents in Charge Ordered YBaCuO from Polarized Neutron Diffraction
It has been proposed that the pseudogap state of underdoped cuprate
superconductors may be due to a transition to a phase which has circulating
currents within each unit cell. Here, we use polarized neutron diffraction to
search for the corresponding orbital moments in two samples of underdoped
YBaCuO with doping levels and 0.123. In contrast to
some other reports using polarized neutrons, but in agreement with nuclear
magnetic resonance and muon spin rotation measurements, we find no evidence for
the appearance of magnetic order below 300 K. Thus, our experiment suggests
that such order is not an intrinsic property of high-quality cuprate
superconductor single crystals. Our results provide an upper bound for a
possible orbital loop moment which depends on the pattern of currents within
the unit cell. For example, for the CC- pattern proposed by Varma,
we find that the ordered moment per current loop is less than 0.013 for
.Comment: Comments in arXiv:1710.08173v1 fully addresse
Closure statistics in interferometric data
Interferometric visibilities, reflecting the complex correlations between
signals recorded at antennas in an interferometric array, carry information
about the angular structure of a distant source. While unknown antenna gains in
both amplitude and phase can prevent direct interpretation of these
measurements, certain combinations of visibilities called closure phases and
closure amplitudes are independent of antenna gains and provide a convenient
set of robust observables. However, these closure quantities have subtle noise
properties and are generally both linearly and statistically dependent. These
complications have obstructed the proper use of closure quantities in
interferometric analysis, and they have obscured the relationship between
analysis with closure quantities and other analysis techniques such as self
calibration. We review the statistics of closure quantities, noting common
pitfalls that arise when approaching low signal-to-noise due to the nonlinear
propagation of statistical errors. We then develop a strategy for isolating and
fitting to the independent degrees of freedom captured by the closure
quantities through explicit construction of linearly independent sets of
quantities along with their noise covariance in the Gaussian limit, valid for
moderate signal-to-noise, and we demonstrate that model fits have biased
posteriors when this covariance is ignored. Finally, we introduce a unified
procedure for fitting to both closure information and partially calibrated
visibilities, and we demonstrate both analytically and numerically the direct
equivalence of inference based on closure quantities to that based on self
calibration of complex visibilities with unconstrained antenna gains.Comment: 31 pages, 17 figure
A Novel Report of Hatching Plasticity in the Phylum Echinodermata
Hatching plasticity occurs in response to a wide range of stimuli across many animal taxa, including annelids, arthropods, mollusks, and chordates. Despite the prominence of echinoderms in developmental biology and more than 100 years of detailed examination of their development under a variety of conditions, environmentally cued hatching plasticity has never been reported in the phylum Echinodermata. Here we report plasticity in the timing and stage of hatching of embryos of the sand dollar Echinarachnius parma in response to reductions in salinity. Embryos of E. parma increased their time to hatching more than twofold in response to ecologically relevant salinity reductions, while maintaining an otherwise normal developmental schedule. Embryos that experienced the greatest delay in hatching time emerged from the fertilization envelope as fourarm pluteus larvae rather than hatching as blastulae or early gastrulae. Salinity manipulations across multiple male-female pairs indicated high variability in hatching time both within and among clutches, suggesting significant intraspecific variation in developmental responses to salinit
An Analysis of the Menidia Complex in the Mississippi River Valley and in Two Nearby Minor Drainages
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