161,899 research outputs found
Digital numerically controlled oscillator
The frequency and phase of an output signal from an oscillator circuit are controlled with accuracy by a digital input word. Positive and negative alterations in output frequency are both provided for by translating all values of input words so that they are positive. The oscillator reference frequency is corrected only in one direction, by adding phase to the output frequency of the oscillator. The input control word is translated to a single algebraic sign and the digital 1 is added thereto. The translated input control word is then accumulated. A reference clock signal having a frequency at an integer multiple of the desired frequency of the output signal is generated. The accumulated control word is then compared with a threshold level. The output signal is adjusted in a single direction by dividing the frequency of the reference clock signal by a first integer or by an integer different from the first integer
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Effect of cell density on thrombin binding to a specific site on bovine vascular endothelial cells.
We studied thrombin binding to proliferating and confluent endothelial cells derived from bovine vascular endothelium. [125]thrombin was incubated with nonconfluent or confluent endothelial cells and both the total amount bound and the amount linked in a 77,000-dalton thrombin-cell complex were determined. Approximately 230,000 molecules of thrombin bound per cell in nonconfluent cultures compared to 12,800 molecules per cell in confluent cultures. Approximately 67,7000 thrombin molecules were bound in an apparently covalent complex, Mr = 77,000, with each cell in sparse cultures, whereas only 4,600 thrombin molecules per cell were bound in this complex with confluent cultures. Similar studies with [125I]thrombin and endothelial cells derived from bovine cornea revealed no difference either in the total amount of thrombin bound or in the amount bound in the 77,000-dalton complex using sparse or confluent cultures. When confluent vascular endothelial cultures were wounded, additional cellular binding sites for the 77,000-dalton complex with thrombin appeared within 24 h. A 237% increase in the amount of thrombin bound to these sites was induced by a wound which resulted in a 20% decrease in cell number in the monolayer. There was no significant increase in thrombin binding to other cellular sites at 24 h. These experiments provide evidence that the first change in thrombin binding after injury is an increase in the cellular sites involved in the 77,000-dalton complex, and suggest that thrombin binding to endothelial cells may be important in the vascular response to injury
Gauge invariant dressed holon and spinon in doped cuprates
We develop a partial charge-spin separation fermion-spin theory implemented
the gauge invariant dressed holon and spinon. In this novel approach, the
physical electron is decoupled as the gauge invariant dressed holon and spinon,
with the dressed holon behaviors like a spinful fermion, and represents the
charge degree of freedom together with the phase part of the spin degree of
freedom, while the dressed spinon is a hard-core boson, and represents the
amplitude part of the spin degree of freedom, then the electron single
occupancy local constraint is satisfied. Within this approach, the charge
transport and spin response of the underdoped cuprates is studied. It is shown
that the charge transport is mainly governed by the scattering from the dressed
holons due to the dressed spinon fluctuation, while the scattering from the
dressed spinons due to the dressed holon fluctuation dominates the spin
response.Comment: 8 pages, Revtex, three figures are include
Causality in Non-Commutative Quantum Field Theories
We study causality in non-commutative quantum field theory with a space-space
non-commutativity. We employ the S-operator approach of Bogoliubov-Shirkov(BS).
We generalize the BS criterion of causality to the noncommutative theory. The
criterion to test causality leads to a nonzero difference between T*-product
and T-product as a condition of causality violation for a spacelike separation.
We discuss two examples; one in a scalar theory and one in the Yukawa theory.
In particular, in the context of a non-commutative Yukawa theory, with the
interaction Lagrangian , is observed to
be causality violating even in case of space-space noncommutativity for which
\theta^{0i}=0.
\Comment: 18 pages, LaTeX; A few changes in sections 3.2,3.3 and
SU(4) Theory for Spin Systems with Orbital Degeneracy
The isotropic limit of spin systems with orbital degeneracy is shown to have
global SU(4) symmetry. On many 2D lattices, the ground state does not posses
long range order, which may explain the observed spin liquid properties of
. In the SU(4) Neel ordered state, spin-spin correlations can be
antiferromagneitc between two neighboring sites with parallel magnetic moments.Comment: 11 pages, 2 figures. submitted to PR
Neutrino mixing matrix in the 3-3-1 model with heavy leptons and symmetry
We study the lepton sector in the model based on the local gauge group
which do not contain particles with
exotic electric charges. The seesaw mechanism and discrete symmetry are
introduced into the model to understand why neutrinos are especially light and
the observed pattern of neutrino mixing. The model provides a method for
obtaining the tri-bimaximal mixing matrix in the leading order. A non-zero
mixing angle presents in the modified mixing matrix.Comment: 10 page
Medium-induced multi-photon radiation
We study the spectrum of multi-photon radiation off a fast quark in medium in
the BDMPS/ASW approach. We reproduce the medium-induced one-photon radiation
spectrum in dipole approximation, and go on to calculate the two-photon
radiation in the Moli\`{e}re limit. We find that in this limit the LPM effect
holds for medium-induced two-photon ladder emission.Comment: 5 pages, 1 figure. Proceedings of Hot Quarks 2010, La Londe Les
Maures, Franc
Towards Semantic Fast-Forward and Stabilized Egocentric Videos
The emergence of low-cost personal mobiles devices and wearable cameras and
the increasing storage capacity of video-sharing websites have pushed forward a
growing interest towards first-person videos. Since most of the recorded videos
compose long-running streams with unedited content, they are tedious and
unpleasant to watch. The fast-forward state-of-the-art methods are facing
challenges of balancing the smoothness of the video and the emphasis in the
relevant frames given a speed-up rate. In this work, we present a methodology
capable of summarizing and stabilizing egocentric videos by extracting the
semantic information from the frames. This paper also describes a dataset
collection with several semantically labeled videos and introduces a new
smoothness evaluation metric for egocentric videos that is used to test our
method.Comment: Accepted for publication and presented in the First International
Workshop on Egocentric Perception, Interaction and Computing at European
Conference on Computer Vision (EPIC@ECCV) 201
Towards Laser Driven Hadron Cancer Radiotherapy: A Review of Progress
It has been known for about sixty years that proton and heavy ion therapy is
a very powerful radiation procedure for treating tumours. It has an innate
ability to irradiate tumours with greater doses and spatial selectivity
compared with electron and photon therapy and hence is a tissue sparing
procedure. For more than twenty years powerful lasers have generated high
energy beams of protons and heavy ions and hence it has been frequently
speculated that lasers could be used as an alternative to RF accelerators to
produce the particle beams necessary for cancer therapy. The present paper
reviews the progress made towards laser driven hadron cancer therapy and what
has still to be accomplished to realise its inherent enormous potential.Comment: 40 pages, 24 figure
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