434 research outputs found
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High pulse rate interferometry using a ruby laser and a cordin model 360 camera
This system was originally developed in support of a dynamic diffraction moire effort, but has obvious applications to other types of imaging, interferometry, and high speed optical measurement techniques. The system includes a holographic grade Apollo ruby laser and a Cordin model 330A high speed film camera. The laser has been modified to generate a train of 1 to 100 or more pulses having individual pulse energies of about 40 mJ and a pulse width under 50 ns. The separation between pulses is currently 8 {mu}s, but is expected to soon be reduced to about 1 {mu}s. The laser pulses are synchronized with the framing sync signals from the Cordin camera, so that an individual interferogram is recorded on each of the available frames (a maximum record length of 80 frames is possible). The system is currently configured as a diffraction moire interferometer that illuminates a specimen diffraction grating with a pair of laser beams. The resulting interferograms are recorded using the Cordin camera. The system and the experimental synchronization method are described and some representative experimental data are presented. 1 ref., 5 figs
Novel evolutionary dynamics of small populations in breast cancer adjuvant and neoadjuvant therapy
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Frictional sliding in layered rock: laboratory-scale experiments
The work is part of the rock mechanics effort for the Yucca Mountain Site Characterization Program. The laboratory-scale experiments are intended to provide high quality data on the mechanical behavior of jointed structures that can be used to validate complex numerical models for rock-mass behavior. Frictional sliding between simulated rock joints was studied using phase shifting moire interferometry. A model, constructed from stacks of machined and sandblasted granite plates, contained a central hole bore normal to the place so that frictional slip would be induced between the plates near the hole under compressive loading. Results show a clear evolution of slip with increasing load. Since the rock was not cycled through loading- unloading, the quantitative differences between the three data sets are probably due to a ``wearing-in`` effect. The highly variable spatial frequency of the data is probably due to the large grain size of the granite and the stochastic frictional processes. An unusual feature of the evolution of slip with increasing load is that as the load gets larger, some plates seem to return to a null position. Figs, 6 refs
Causal construction of the massless vertex diagram
The massless one-loop vertex diagram is constructed by exploiting the causal
structure of the diagram in configuration space, which can be translated
directly into dispersive relations in momentum space.Comment: 14 pages, LATEX with style file, corresponds to published versio
Spectral analysis and zeta determinant on the deformed spheres
We consider a class of singular Riemannian manifolds, the deformed spheres
, defined as the classical spheres with a one parameter family of
singular Riemannian structures, that reduces for to the classical metric.
After giving explicit formulas for the eigenvalues and eigenfunctions of the
metric Laplacian , we study the associated zeta functions
. We introduce a general method to deal with some
classes of simple and double abstract zeta functions, generalizing the ones
appearing in . An application of this method allows to
obtain the main zeta invariants for these zeta functions in all dimensions, and
in particular and . We give
explicit formulas for the zeta regularized determinant in the low dimensional
cases, , thus generalizing a result of Dowker \cite{Dow1}, and we
compute the first coefficients in the expansion of these determinants in powers
of the deformation parameter .Comment: 1 figur
A Systematic Extended Iterative Solution for QCD
An outline is given of an extended perturbative solution of Euclidean QCD
which systematically accounts for a class of nonperturbative effects, while
allowing renormalization by the perturbative counterterms. Proper vertices
Gamma are approximated by a double sequence Gamma[r,p], with r the degree of
rational approximation w.r.t. the QCD mass scale Lambda, nonanalytic in the
coupling g, and p the order of perturbative corrections in g-squared,
calculated from Gamma[r,0] - rather than from the perturbative Feynman rules
Gamma(0)(pert) - as a starting point. The mechanism allowing the
nonperturbative terms to reproduce themselves in the Dyson-Schwinger equations
preserves perturbative renormalizability and is tied to the divergence
structure of the theory. As a result, it restricts the self-consistency problem
for the Gamma[r,0] rigorously - i.e. without decoupling approximations - to the
superficially divergent vertices. An interesting aspect of the scheme is that
rational-function sequences for the propagators allow subsequences describing
short-lived excitations. The method is calculational, in that it allows known
techniques of loop computation to be used while dealing with integrands of
truly nonperturbative content.Comment: 48 pages (figures included). Scope of replacement: correction of a
technical defect; no changes in conten
Surface Instability of Icicles
Quantitatively-unexplained stationary waves or ridges often encircle icicles.
Such waves form when roughly 0.1 mm-thick layers of water flow down the icicle.
These waves typically have a wavelength of 1cm approximately independent of
external temperature, icicle thickness, and the volumetric rate of water flow.
In this paper we show that these waves can not be obtained by naive
Mullins-Sekerka instability, but are caused by a quite new surface instability
related to the thermal diffusion and hydrodynamic effect of thin water flow.Comment: 11 pages, 5 figures, Late
A bacterial-based algorithm to simulate complex adaptive systems
Following a bacterial-based modeling approach, we want to model and analyze the impact of both decentralization and heterogeneity on group behavior and collective learning. Inspired by bacterial conjugation, we have defined an artificial society in which agents' strategies adapt to changes in resources location, allowing migration and survival in a dynamic sugarscape-like scenario. To study the impact of these variables we have simulated a scenario in which resources are limited and localized. We also have defined three constraints in genetic information processing (inhibition of plasmid conjugation, inhibition of plasmid reproduction and inhibition of plasmid mutation). Our results affirmed the hypothesis that efficiency of group adaptation to dynamic environments is better when societies are varied and distributed than when they are homogeneous and centralized
Zeta function method and repulsive Casimir forces for an unusual pair of plates at finite temperature
We apply the generalized zeta function method to compute the Casimir energy
and pressure between an unusual pair of parallel plates at finite temperature,
namely: a perfectly conducting plate and an infinitely permeable one. The high
and low temperature limits of these quantities are discussed; relationships
between high and low temperature limits are estabkished by means of a modified
version of the temperature inversion symmetry.Comment: latex file 9 pages, 3 figure
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