1,109 research outputs found
Use of Geophysical Methods in a Geotechnical Investigation
This paper describes a case study in which a geotechnical investigation encountered complex subsurface conditions requiring geophysical methods to supplement test boring data. Electromagnetic (EM) and seismic refraction methods were used to model subsurface conditions at the site of a proposed three-story office building. The three investigative techniques used in this study all revealed bedrock to be at a shallow depth. The test borings provided vertical resolution while the EM and seismic studies yielded lateral resolution. Good correlation was achieved when comparing the results of each method. The EM and seismic methods in conjunction with a test boring program can provide a better understanding of subsurface conditions than can be obtained by any single technique
Strong-field approximation for Coulomb explosion of H_2^+ by short intense laser pulses
We present a simple quantum mechanical model to describe Coulomb explosion of
H by short, intense, infrared laser pulses. The model is based on the
length gauge version of the molecular strong-field approximation and is valid
for pulses shorter than 50 fs where the process of dissociation prior to
ionization is negligible. The results are compared with recent experimental
results for the proton energy spectrum [I. Ben-Itzhak et al., Phys. Rev. Lett.
95, 073002 (2005), B. D. Esry et al., Phys. Rev. Lett. 97, 013003 (2006)]. The
predictions of the model reproduce the profile of the spectrum although the
peak energy is slightly lower than the observations. For comparison, we also
present results obtained by two different tunneling models for this process.Comment: 8 pages, 4 figure
Geophysical studies with laser-beam detectors of gravitational waves
The existing high technology laser-beam detectors of gravitational waves may
find very useful applications in an unexpected area - geophysics. To make
possible the detection of weak gravitational waves in the region of high
frequencies of astrophysical interest, ~ 30 - 10^3 Hz, control systems of laser
interferometers must permanently monitor, record and compensate much larger
external interventions that take place in the region of low frequencies of
geophysical interest, ~ 10^{-5} - 3 X 10^{-3} Hz. Such phenomena as tidal
perturbations of land and gravity, normal mode oscillations of Earth,
oscillations of the inner core of Earth, etc. will inevitably affect the
performance of the interferometers and, therefore, the information about them
will be stored in the data of control systems. We specifically identify the
low-frequency information contained in distances between the interferometer
mirrors (deformation of Earth) and angles between the mirrors' suspensions
(deviations of local gravity vectors and plumb lines). We show that the access
to the angular information may require some modest amendments to the optical
scheme of the interferometers, and we suggest the ways of doing that. The
detailed evaluation of environmental and instrumental noises indicates that
they will not prevent, even if only marginally, the detection of interesting
geophysical phenomena. Gravitational-wave instruments seem to be capable of
reaching, as a by-product of their continuous operation, very ambitious
geophysical goals, such as observation of the Earth's inner core oscillations.Comment: 29 pages including 8 figures, modifications and clarifications in
response to referees' comments, to be published in Class. Quant. Gra
Atmospheric Gravity Perturbations Measured by Ground-Based Interferometer with Suspended Mirrors
A possibility of geophysical measurements using the large scale laser
interferometrical gravitational wave antenna is discussed. An interferometer
with suspended mirrors can be used as a gradiometer measuring variations of an
angle between gravity force vectors acting on the spatially separated
suspensions. We analyze restrictions imposed by the atmospheric noises on
feasibility of such measurements. Two models of the atmosphere are invoked: a
quiet atmosphere with a hydrostatic coupling of pressure and density and a
dynamic model of moving region of the density anomaly (cyclone). Both models
lead to similar conclusions up to numerical factors. Besides the hydrostatic
approximation, we use a model of turbulent atmosphere with the pressure
fluctuation spectrum f^{-7/3} to explore the Newtonian noise in a higher
frequency domain (up to 10 Hz) predicting the gravitational noise background
for modern gravitational wave detectors. Our estimates show that this could
pose a serious problem for realization of such projects. Finally, angular
fluctuations of spatially separated pendula are investigated via computer
simulation for some realistic atmospheric data giving the level estimate
10^{-11} rad/sqrt(Hz) at frequency 10^{-4} Hz. This looks promising for the
possibility of the measurement of weak gravity effects such as Earth inner core
oscillations.Comment: 13 pages, 4 pigures, LaTeX. To be published in Classical and Quantum
Gravit
Analytical modeling for the heat transfer in sheared flows of nanofluids
We developed a model for the enhancement of the heat flux by spherical and
elongated nano- particles in sheared laminar flows of nano-fluids. Besides the
heat flux carried by the nanoparticles the model accounts for the contribution
of their rotation to the heat flux inside and outside the particles. The
rotation of the nanoparticles has a twofold effect, it induces a fluid
advection around the particle and it strongly influences the statistical
distribution of particle orientations. These dynamical effects, which were not
included in existing thermal models, are responsible for changing the thermal
properties of flowing fluids as compared to quiescent fluids. The proposed
model is strongly supported by extensive numerical simulations, demonstrating a
potential increase of the heat flux far beyond the Maxwell-Garnet limit for the
spherical nanoparticles. The road ahead which should lead towards robust
predictive models of heat flux enhancement is discussed.Comment: 14 pages, 10 figures, submitted to PR
Borrelia carolinensis sp. nov., a novel species of the Borrelia burgdorferi sensu lato complex isolated from rodents and a tick from the south-eastern USA
A group of 16 isolates with genotypic characteristics different from those of known species of the Borrelia burgdorferi sensu lato complex were cultured from ear biopsies of the rodents Peromyscus gossypinus and Neotoma floridana trapped at five localities in South Carolina, USA, and from the tick Ixodes minor feeding on N. floridana. Multilocus sequence analysis of members of the novel species, involving the 16S rRNA gene, the 5S–23S (rrf–rrl) intergenic spacer region and the flagellin, ospA and p66 genes, was conducted and published previously and was used to clarify the taxonomic status of the novel group of B. burgdorferi sensu lato isolates. Phylogenetic analysis based on concatenated sequences of the five analysed genomic loci showed that the 16 isolates clustered together but separately from other species in the B. burgdorferi sensu lato complex. The analysed group therefore represents a novel species, formally described here as Borrelia carolinensis sp. nov., with the type strain SCW-22T (=ATCC BAA-1773T =DSM 22119T)
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