902 research outputs found
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The Kinetics of Quartz Dissolution and Precipitation
Silica precipitation in geothermal power plants and in reservoir formations is considered to be a potential problem area in the successful development of geothermal power from liquid dominated resources. In order to gain insight into the significance of this problem and to estimate the rates of precipitation of silica under varying conditions, a literature review and evaluation was made. Data on the kinetics of quartz dissolution and precipitation in water was fitted to an expression derived from absolute rate theory, assuming that the mechanism could be represented by the equation: SiO{sub 2} + 2H{sub 2}O = Si(OH){sub 4}
The C_2 heat-kernel coefficient in the presence of boundary discontinuities
We consider the heat-kernel on a manifold whose boundary is piecewise smooth.
The set of independent geometrical quantities required to construct an
expression for the contribution of the boundary discontinuities to the C_{2}
heat-kernel coefficient is derived in the case of a scalar field with Dirichlet
and Robin boundary conditions. The coefficient is then determined using
conformal symmetry and evaluation on some specific manifolds. For the Robin
case a perturbation technique is also developed and employed. The contributions
to the smeared heat-kernel coefficient and cocycle function are calculated.
Some incomplete results for spinor fields with mixed conditions are also
presented.Comment: 25 pages, LaTe
Plasticity in Unimodal and Multimodal Brain Areas Reflects Multisensory Changes in Self-Face Identification
Nothing provides as strong a sense of self as seeing one's face. Nevertheless, it remains unknown how the brain processes the sense of self during the multisensory experience of looking at one's face in a mirror. Synchronized visuo-tactile stimulation on one's own and another's face, an experience that is akin to looking in the mirror but seeing another's face, causes the illusory experience of ownership over the other person's face and changes in self-recognition. Here, we investigate the neural correlates of this enfacement illusion using fMRI. We examine activity in the human brain as participants experience tactile stimulation delivered to their face, while observing either temporally synchronous or asynchronous tactile stimulation delivered to another's face on either a specularly congruent or incongruent location. Activity in the multisensory right temporo-parietal junction, intraparietal sulcus, and the unimodal inferior occipital gyrus showed an interaction between the synchronicity and the congruency of the stimulation and varied with the self-reported strength of the illusory experience, which was recorded after each stimulation block. Our results highlight the important interplay between unimodal and multimodal information processing for self-face recognition, and elucidate the neurobiological basis for the plasticity required for identifying with our continuously changing visual appearanc
M2K: I. A Jovian mass planet around the M3V star HIP79431
Doppler observations from Keck Observatory reveal the presence of a planet
with Msini of 2.1 Mjup orbiting the M3V star HIP79431. This is the sixth giant
planet to be detected in Doppler surveys of M dwarfs and it is one of the most
massive planets discovered around an M dwarf star. The planet has an orbital
period of 111.7 days and an orbital eccentricity of 0.29. The host star is
metal rich, with an estimated [Fe/H] = +0.4. This is the first planet to emerge
from our new survey of 1600 M-to-K dwarf stars.Comment: 5 figure
Hyperspherical entanglement entropy
The coefficient of the log term in the entanglement entropy associated with
hyperspherical surfaces in flat space-time is shown to equal the conformal
anomaly by conformally transforming Euclideanised space--time to a sphere and
using already existing formulae for the relevant heat--kernel coefficients
after cyclic factoring. The analytical reason for the result is that the
conformal anomaly on the lune has an extremum at the ordinary sphere limit. A
proof is given. Agreement with a recent evaluation of the coefficient is found.Comment: 7 pages. Final revision. Historical comments amended. Minor remarks
adde
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Effect of Dilution and Contaminants on Strength and Hydraulic Conductivity of Sand Grouted With Colloidal Silica Gel
Colloidal silica (CS) is a low-viscosity liquid that can be made to gel by addition of brine. This property allows it to be injected into, or mixed with, soil, so that after gelling the colloidal silica blocks the pore space in the soil and forms a barrier to the flow of contaminated groundwater or non-aqueous liquids (NAPLs). Gelled-in-place CS was first studied for the petroleum industry and later for protecting groundwater quality. Noll investigated the use of colloidal silica diluted so that its solids content was reduced from 30% (a typical nominal value for material as delivered) to values as low as 5%. The more dilute colloids could still be made to gel, although more slowly, and the resulting gel was weaker. Because the proposed application of colloidal silica grout involves emplacing it in the subsurface by permeation, jet grouting, or soil mixing where its role as a barrier will be to resist flow of contaminants, the effects of these contaminants on the properties of the grouted soil is also of interest. This work comprised four tasks. In Task 1, samples of grouted sand were prepared with a range of CS dilutions, for measurement of hydraulic conductivity and unconfined-compressive strength. In Task 2, these properties were measured on samples of grouted sand that incorporated 5% volumetric saturation of NAPLs. In Task 3, samples, prepared without any contaminants, were immersed in contaminant liquids and tested after 30 and 90 days. Task 4 was added because NAPL contamination in the samples of Tasks 2 and 3 impelled modifications in the test methods, and comparison of the results of Task 2 and Task 1 suggested that these modifications had introduced errors. In Task 4, samples were tested both ways, to confirm that in Tasks 2 and 3 strength was underestimated and hydraulic conductivity was overestimated. Despite the existence of these known systematic errors, the inclusion of control samples in Tasks 2 and 3 permits conclusions to be drawn from these data
Whightman function and scalar Casimir densities for a wedge with a cylindrical boundary
Whightman function, vacuum expectation values of the field square, and the
energy-momentum tensor are investigated for a scalar field inside a wedge with
and without a coaxial cylindrical boundary. Dirichlet boundary conditions are
assumed on the bounding surfaces. The vacuum energy-momentum tensor is
evaluated in the general case of the curvature coupling parameter. Making use
of a variant of the generalized Abel-Plana formula, expectation values are
presented as the sum of two terms. The first one corresponds to the geometry
without a cylindrical boundary and the second one is induced by the presence of
this boundary. The asymptotic behaviour of the field square, vacuum energy
density and stresses near the boundaries are investigated. The additional
vacuum forces acting on the wedge sides due the presence of the cylindrical
boundary are evaluated and it is shown that these forces are attractive. As a
limiting case, the geometry of two parallel plates perpendicularly intersected
by a third one is analyzed.Comment: 19 pages, 6 figures, new section is added on the VEVs for the region
outside the cylidrical shell, discussion and references added, accepted for
publication in J. Phys.
Development of a training program to support health care professionals to deliver the SPACE for COPD self-management program
Open access journalBackground: With the growing burden of COPD and associated morbidity and mortality, a need for self-management has been identified. The Self-management Programme of Activity, Coping and Education for Chronic Obstructive Pulmonary Disease (SPACE for COPD) manual was developed to support self-management in COPD patients. Currently, there is no literature available regarding health care professionals’ training needs when supporting patients with COPD on self-management.
Aim: This study sought to identify these needs to inform, design and develop a training program for health care professionals being trained to deliver a self-management program in COPD.
Methods: Fourteen health care professionals from both primary and secondary care COPD services participated in face-to-face semistructured interviews. Thematic analysis was used to produce a framework and identify training needs and views on delivery of the SPACE for COPD self-management program. Components of training were web-based knowledge training, with pre- and posttraining knowledge questionnaires, and a 1-day program to introduce the self-management manual. Feedback was given after training to guide the development of the training program.
Results: Health care professionals were able to identify areas where they required increased knowledge to support patients. This was overwhelming in aspects of COPD seen to be outside of their current clinical role. Skills in goal setting and behavioral change were not elicited as a training need, suggesting a lack of understanding of components of supporting self-management. An increase in knowledge of COPD was demonstrated following the training program.
Conclusion: Both knowledge and skill gaps existed in those who would deliver self-management. Analysis of this has enabled a training program to be designed to address these gaps and enable health care professionals to support patients in self-management.
Keywords: self-management, COPD, health care professionals, trainin
Heat Kernel Expansion for Semitransparent Boundaries
We study the heat kernel for an operator of Laplace type with a
-function potential concentrated on a closed surface. We derive the
general form of the small asymptotics and calculate explicitly several
first heat kernel coefficients.Comment: 16 page
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