11,950 research outputs found
On the arithmetic of Krull monoids with infinite cyclic class group
Let be a Krull monoid with infinite cyclic class group and let denote the set of classes containing prime divisors. We study under
which conditions on some of the main finiteness properties of
factorization theory--such as local tameness, the finiteness and rationality of
the elasticity, the structure theorem for sets of lengths, the finiteness of
the catenary degree, and the existence of monotone and of near monotone chains
of factorizations--hold in . In many cases, we derive explicit
characterizations
The Highly Oscillatory Behavior of Automorphic Distributions for SL(2)
Automorphic distributions for SL(2) arise as boundary values of modular forms
and, in a more subtle manner, from Maass forms. In the case of modular forms of
weight one or of Maass forms, the automorphic distributions have continuous
first antiderivatives. We recall earlier results of one of us on the Holder
continuity of these continuous functions and relate them to results of other
authors; this involves a generalization of classical theorems on Fourier series
by S. Bernstein and Hardy-Littlewood. We then show that the antiderivatives are
non-differentiable at all irrational points, as well as all, or in certain
cases, some rational points. We include graphs of several of these functions,
which clearly display a high degree of oscillation. Our investigations are
motivated in part by properties of "Riemann's nondifferentiable function", also
known as "Weierstrass' function".Comment: 27 pages, 6 Figures; version 2 corrects misprints and updates
reference
Gravity anomaly detection: Apollo/Soyuz
The Goddard Apollo-Soyuz Geodynamics Experiment is described. It was performed to demonstrate the feasibility of tracking and recovering high frequency components of the earth's gravity field by utilizing a synchronous orbiting tracking station such as ATS-6. Gravity anomalies of 5 MGLS or larger having wavelengths of 300 to 1000 kilometers on the earth's surface are important for geologic studies of the upper layers of the earth's crust. Short wavelength Earth's gravity anomalies were detected from space. Two prime areas of data collection were selected for the experiment: (1) the center of the African continent and (2) the Indian Ocean Depression centered at 5% north latitude and 75% east longitude. Preliminary results show that the detectability objective of the experiment was met in both areas as well as at several additional anomalous areas around the globe. Gravity anomalies of the Karakoram and Himalayan mountain ranges, ocean trenches, as well as the Diamantina Depth, can be seen. Maps outlining the anomalies discovered are shown
Hybrid quantum repeater based on dispersive CQED interactions between matter qubits and bright coherent light
We describe a system for long-distance distribution of quantum entanglement,
in which coherent light with large average photon number interacts dispersively
with single, far-detuned atoms or semiconductor impurities in optical cavities.
Entanglement is heralded by homodyne detection using a second bright light
pulse for phase reference. The use of bright pulses leads to a high success
probability for the generation of entanglement, at the cost of a lower initial
fidelity. This fidelity may be boosted by entanglement purification techniques,
implemented with the same physical resources. The need for more purification
steps is well compensated for by the increased probability of success when
compared to heralded entanglement schemes using single photons or weak coherent
pulses with realistic detectors. The principle cause of the lower initial
fidelity is fiber loss; however, spontaneous decay and cavity losses during the
dispersive atom/cavity interactions can also impair performance. We show that
these effects may be minimized for emitter-cavity systems in the weak-coupling
regime as long as the resonant Purcell factor is larger than one, the cavity is
over-coupled, and the optical pulses are sufficiently long. We support this
claim with numerical, semiclassical calculations using parameters for three
realistic systems: optically bright donor-bound impurities such as 19-F:ZnSe
with a moderate-Q microcavity, the optically dim 31-P:Si system with a high-Q
microcavity, and trapped ions in large but very high-Q cavities.Comment: Please consult the published version, where assorted typos are
corrected. It is freely available at http://stacks.iop.org/1367-2630/8/18
Singlet-triplet transition in a single-electron transistor at zero magnetic field
We report sharp peaks in the differential conductance of a single-electron
transistor (SET) at low temperature, for gate voltages at which charge
fluctuations are suppressed. For odd numbers of electrons we observe the
expected Kondo peak at zero bias. For even numbers of electrons we generally
observe Kondo-like features corresponding to excited states. For the latter,
the excitation energy often decreases with gate voltage until a new zero-bias
Kondo peak results. We ascribe this behavior to a singlet-triplet transition in
zero magnetic field driven by the change of shape of the potential that
confines the electrons in the SET.Comment: 4 p., 4 fig., 5 new ref. Rewrote 1st paragr. on p. 4. Revised author
list. More detailed fit results on page 3. A plotting error in the horizontal
axis of Fig. 1b and 3 was corrected, and so were the numbers in the text read
from those fig. Fig. 4 was modified with a better temperature calibration
(changes are a few percent). The inset of this fig. was removed as it is
unnecessary here. Added remarks in the conclusion. Typos are correcte
Spectral longwave emission in the tropics - FTIR measurement at the sea-surface and comparison with fast radiation codes
Longwave emission by the tropical western Pacific atmosphere has been measured at the ocean surface by a Fourier Transform Infrared (FTIR) spectroradiometer deployed aboard the research vessel John Vickers as part of the Central Equatorial Pacific Experiment. The instrument operated throughout a Pacific Ocean crossing, beginning on 7 March 1993 in Honiara, Solomon Islands, and ending on 29 March 1993 in Los Angeles, and recorded longwave emission spectra under atmospheres associated with sea surface temperatures ranging from 291.0 to 302.8 K. Precipitable water vapor abundances ranged from 1.9 to 5.5 column centimeters. Measured emission spectra (downwelling zenith radiance) covered the middle infrared (5-20 mu m) with one inverse centimeter spectral resolution. FTIR measurements made under an entirely clear field of view are compared with spectra generated by LOWTRAN 7 and MODTRAN 2, as well as downwelling flux calculated by the NCAR Community Climate Model (CCM-2) radiation code, using radiosonde profiles as input data for these calculations. In the spectral interval 800-1000 cm(-1), these comparisons show a discrepancy between FTIR data and MODTRAN 2 having an overall variability of 6-7 mW m(-2) sr(-1) cm and a concave shape that may be related to the representation of water vapor continuum emission in MODTRAN 2. Another discrepancy appears in the spectral interval 1200-1300 cm(-1), where MODTRAN 2 appears to overestimate zenith radiance by 5 mW m(-2) sr(-1) cm. These discrepancies appear consistently; however, they become only slightly larger at the highest water vapor abundances. Because these radiance discrepancies correspond to broadband (500-2000 cm(-1)) flux uncertainties of around 3 W m(-2), there appear to be no serious inadequacies with the performance of MODTRAN 2 or LOWTRAN 7 at high atmospheric temperatures and water vapor abundances. On average, CCM-2 flux calculations agree to within 1 W m(-2) with downwelling flux estimates from the FTIR data over all sea surface temperatures, although this result has a scatter of +/-12 W m(-2) at high sea surface temperatures
Striped Magnetic Ground State of the Kagome Lattice in Fe4Si2Sn7O16
We have experimentally identified a new magnetic ground state for the kagome
lattice, in the perfectly hexagonal Fe2+ (3d6, S = 2) compound Fe4Si2Sn7O16.
Representational symmetry analysis of neutron diffraction data shows that below
T_N = 3.5 K, the spins on 2/3 of the magnetic ions order into canted
antiferromagnetic chains, separated by the remaining 1/3 which are
geometrically frustrated and show no long-range order down to at least T = 0.1
K. Moessbauer spectroscopy confirms that there is no static order on the latter
1/3 of the magnetic ions - i.e., they are in a liquid-like rather than a frozen
state - down to at least 1.65 K. A heavily Mn-doped sample
Fe1.45Mn2.55Si2Sn7O16 has the same magnetic structure. Although the propagation
vector q = (0, 1/2 , 1/2 ) breaks hexagonal symmetry, we see no evidence for
magnetostriction in the form of a lattice distortion within the resolution of
our data. We discuss the relationship to partially frustrated magnetic order on
the pyrochlore lattice of Gd2Ti2O7, and to theoretical models that predict
symmetry breaking ground states for perfect kagome lattices.Comment: 5 pages, 5 figure
Removal of luminal content protects the small intestine during hemorrhagic shock but is not sufficient to prevent lung injury.
The small intestine plays a key role in the pathogenesis of multiple organ failure following circulatory shock. Current results show that reduced perfusion of the small intestine compromises the mucosal epithelial barrier, and the intestinal contents (including pancreatic digestive enzymes and partially digested food) can enter the intestinal wall and transport through the circulation or mesenteric lymph to other organs such as the lung. The extent to which the luminal contents of the small intestine mediate tissue damage in the intestine and lung is poorly understood in shock. Therefore, rats were assigned to three groups: No-hemorrhagic shock (HS) control and HS with or without a flushed intestine. HS was induced by reducing the mean arterial pressure (30 mmHg; 90 min) followed by return of shed blood and observation (3 h). The small intestine and lung were analyzed for hemorrhage, neutrophil accumulation, and cellular membrane protein degradation. After HS, animals with luminal contents had increased neutrophil accumulation, bleeding, and destruction of E-cadherin in the intestine. Serine protease activity was elevated in mesenteric lymph fluid collected from a separate group of animals subjected to intestinal ischemia/reperfusion. Serine protease activity was elevated in the plasma after HS but was detected in lungs only in animals with nonflushed lumens. Despite removal of the luminal contents, lung injury occurred in both groups as determined by elevated neutrophil accumulation, permeability, and lung protein destruction. In conclusion, luminal contents significantly increase intestinal damage during experimental HS, suggesting transport of luminal contents across the intestinal wall should be minimized
A tail-like assembly at the portal vertex in intact herpes simplex type-1 virions
Herpes viruses are prevalent and well characterized human pathogens. Despite extensive study, much remains to be learned about the structure of the genome packaging and release machinery in the capsids of these large and complex double-stranded DNA viruses. However, such machinery is well characterized in tailed bacteriophage, which share a common evolutionary origin with herpesvirus. In tailed bacteriophage, the genome exits from the virus particle through a portal and is transferred into the host cell by a complex apparatus (i.e. the tail) located at the portal vertex. Here we use electron cryo-tomography of human herpes simplex type-1 (HSV-1) virions to reveal a previously unsuspected feature at the portal vertex, which extends across the HSV-1 tegument layer to form a connection between the capsid and the viral membrane. The location of this assembly suggests that it plays a role in genome release into the nucleus and is also important for virion architecture
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