8,837 research outputs found
Polar cap observations of thermospheric winds and temperatures at Sondre Stromfjord, Greenland
An agreement of averaged temperatures with mass spectrometer incoherent scatter radar looked reasonable for several nights, but for many nights there are differences: (1) midnight period of cooling, and (2) temperature increases associated with overhead crossings of the auroral belt. The observed rise of the temperature before dawn in conjunction with the high 6300A intensities suggests a connection between the two effects: soft particle precipitation most likely candidate but frictional heating perhaps also a possibility. A comparison with the thermospheric general circulation model calculations also needed. The technique for formulating neutral wind vectors performs well in most cases. The observed patterns show evidence for abatement in the midnight sector in the meridional wind component at the separatix between the two cells with a frequency of the order of 20 to 25%, also observed in radar observations at Sondre Stromfjord. The observed patterns for magnetically quiet conditions show flow characteristic of the auroral belt, westward in evening followed by the midnight surge. The observed patterns for active conditions show dominance either by the evening cell or the morning cell, but most often the former
Effect of lubricant environment on saw damage in silicon wafers
The chemomechanical effect of lubricant environments on the inner diameter (ID) sawing induced surface damage in Si wafers was tested for four different lubricants: water, dielectric oil, and two commercial cutting solutions. The effects of applying different potential on Si crystals during the sawing were also tested. It is indicated that the number and depth of surface damage are sensitive to the chemical nature of the saw lubricant. It is determined that the lubricants that are good catalysts for breaking Si bonds can dampen the out of plane blade vibration more effectively and produce less surface damage. Correlations between the applied potential and the depth of damage in the dielectric oil and one of the commercial cutting solutions and possible mechanisms involved are discussed
Simulation of valveless micropump and mode analysis
In this work, a 3-D simulation is performed to study for the solid-fluid
coupling effect driven by piezoelectric materials and utilizes asymmetric
obstacles to control the flow direction. The result of simulation is also
verified. For a micropump, it is crucial to find the optimal working frequency
which produce maximum net flow rate. The PZT plate vibrates under the first
mode, which is symmetric. Adjusting the working frequency, the maximum flow
rate can be obtained. For the micrpump we studied, the optimal working
frequency is 3.2K Hz. At higher working frequency, say 20K Hz, the fluid-solid
membrane may come out a intermediate mode, which is different from the first
mode and the second mode. It is observed that the center of the mode drifts.
Meanwhile, the result shows that a phase shift lagging when the excitation
force exists in the vibration response. Finally, at even higher working
frequency, say 30K Hz, a second vibration mode is observed.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
The role of initial geometry in experimental models of wound closing
Wound healing assays are commonly used to study how populations of cells,
initialised on a two-dimensional surface, act to close an artificial wound
space. While real wounds have different shapes, standard wound healing assays
often deal with just one simple wound shape, and it is unclear whether varying
the wound shape might impact how we interpret results from these experiments.
In this work, we describe a new kind of wound healing assay, called a sticker
assay, that allows us to examine the role of wound shape in a series of wound
healing assays performed with fibroblast cells. In particular, we show how to
use the sticker assay to examine wound healing with square, circular and
triangular shaped wounds. We take a standard approach and report measurements
of the size of the wound as a function of time. This shows that the rate of
wound closure depends on the initial wound shape. This result is interesting
because the only aspect of the assay that we change is the initial wound shape,
and the reason for the different rate of wound closure is unclear. To provide
more insight into the experimental observations we describe our results
quantitatively by calibrating a mathematical model, describing the relevant
transport phenomena, to match our experimental data. Overall, our results
suggest that the rates of cell motility and cell proliferation from different
initial wound shapes are approximately the same, implying that the differences
we observe in the wound closure rate are consistent with a fairly typical
mathematical model of wound healing. Our results imply that parameter estimates
obtained from an experiment performed with one particular wound shape could be
used to describe an experiment performed with a different shape. This
fundamental result is important because this assumption is often invoked, but
never tested
Batalin-Vilkovisky Integrals in Finite Dimensions
The Batalin-Vilkovisky method (BV) is the most powerful method to analyze
functional integrals with (infinite-dimensional) gauge symmetries presently
known. It has been invented to fix gauges associated with symmetries that do
not close off-shell. Homological Perturbation Theory is introduced and used to
develop the integration theory behind BV and to describe the BV quantization of
a Lagrangian system with symmetries. Localization (illustrated in terms of
Duistermaat-Heckman localization) as well as anomalous symmetries are discussed
in the framework of BV.Comment: 35 page
Time-bin entangled photon holes
The general concept of entangled photon holes is based on a correlated
absence of photon pairs in an otherwise constant optical background. Here we
consider the specialized case when this background is confined to two
well-defined time bins, which allows the formation of time-bin entangled photon
holes. We show that when the typical coherent state background is replaced by a
true single-photon (Fock state) background, the basic time-bin entangled
photon-hole state becomes equivalent to one of the time-bin entangled
photon-pair states. We experimentally demonstrate these ideas using a
parametric down-conversion photon-pair source, linear optics, and
post-selection to violate a Bell inequality with time-bin entangled photon
holes.Comment: 6 pages, 5 figure
New high-efficiency source of photon pairs for engineering quantum entanglement
We have constructed an efficient source of photon pairs using a
waveguide-type nonlinear device and performed a two-photon interference
experiment with an unbalanced Michelson interferometer. Parametric
down-converted photons from the nonlinear device are detected by two detectors
located at the output ports of the interferometer. Because the interferometer
is constructed with two optical paths of different length, photons from the
shorter path arrive at the detector earlier than those from the longer path. We
find that the difference of arrival time and the time window of the coincidence
counter are important parameters which determine the boundary between the
classical and quantum regime. When the time window of the coincidence counter
is smaller than the arrival time difference, fringes of high visibility
(80 10%) were observed. This result is only explained by quantum theory
and is clear evidence for quantum entanglement of the interferometer's optical
paths.Comment: 4 pages, 4 figures, IQEC200
Antiepileptic drugs and suicidality
The risk of suicide in patients with epilepsy is significantly higher than the general population. There are many hypotheses as to the reasons for this, but the potential role of anti-epileptic drugs (AEDs) in increasing suicidality has recently been brought into question. In 2008, the U.S. Food and Drug Administration (FDA) published a warning after a meta-analysis of data from all clinical trials involving AEDs found a suicidality risk of 0.43 per 1000 patients in active drug arms of these clinical trials compared to a rate in the placebo arm of 0.22. While an increased risk for individual AEDs was found in two, the FDA decided to issue a warning for the entire AED class. While this decision and the meta-analysis findings have been considered controversial, and have created concern that this stated risk may dissuade use of AEDs by patients who would benefit from them, it has led to increased awareness of the risk of suicidality and psychiatric co-morbidity in this patient group. In this article, the association of epilepsy and AEDs with psychiatric disease and suicidality are reviewed, perspective as to the significance and limitations of the FDA’s findings are discussed, and some options for suicidality screening and their potential utility in clinical care are evaluated
Kinetic Inductance of Josephson Junction Arrays: Dynamic and Equilibrium Calculations
We show analytically that the inverse kinetic inductance of an
overdamped junction array at low frequencies is proportional to the admittance
of an inhomogeneous equivalent impedance network. The bond in this
equivalent network has an inverse inductance
, where is the Josephson
coupling energy of the bond, is the ground-state phase
of the grain , and is the usual magnetic phase factor. We use this
theorem to calculate for square arrays as large as .
The calculated is in very good agreement with the low-temperature
limit of the helicity modulus calculated by conventional equilibrium
Monte Carlo techniques. However, the finite temperature structure of ,
as a function of magnetic field, is \underline{sharper} than the
zero-temperature , which shows surprisingly weak structure. In
triangular arrays, the equilibrium calculation of yields a series of
peaks at frustrations , where is an integer , consistent with experiment.Comment: 14 pages + 6 postscript figures, 3.0 REVTe
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