503 research outputs found
Measurement and modelling of moisture—electrical resistivity relationship of fine-grained unsaturated soils and electrical anisotropy
A methodology for developing resistivity-moisture content relationships of materials associated with a clayey landslide is presented. Key elements of the methodology include sample selection and preparation, laboratory measurement of resistivity with changing moisture content, and the derivation of models describing the relationship between resistivity and moisture content.
Laboratory resistivity measurements show that the techniques utilised (samples and square array) have considerable potential as a means of electropetrophysical calibration of engineering soils and weak rock. Experimental electrical resistivity results show a hierarchy of values dependent on sample lithology, with silty clay exhibiting the lowest resistivities, followed by siltstones and sands, which return the highest resistivities. In addition, finer grained samples show a greater degree of anisotropy between measurement orientations than coarser grained samples.
However, suitability of results in light of issues such as sample cracking and electrical conduction must be identified and accounted for if the results are to be accurately up-scaled to inverted model resistivity results. The existence of directional anisotropy makes model calibration curve selection more difficult due to variability in the range of measured laboratory resistances.
The use of larger measurement array size means that experimental data will be more representative of bulk lithological properties. In addition, use of electrodes with a relatively high surface area (wide diameter) help maintain low contact resistances and repeat measurement error, relative to narrow electrodes.
Variation exists between the fit of experimental data and petrophysical models. Model fit is best for clay-dominated samples but fits less well for sand-dominated samples. Waxman–Smits equation is appropriately applied in this investigation as all samples have considerable clay mineral content, as is shown in non-negligible CEC results. The incorporation of pressure plate suction measurements on samples, allows suction dissipation to be quantified and evaluated alongside moisture content and electrical resistivity
Tensile strength of large-scale incipient rock joints: a laboratory investigation
In this paper, a testing methodology was developed in the laboratory to measure the tensile strength of large-scale incipient rock joints. In the test, an expansive grout was used to develop the tensile force. Each test comprises two phases: Phase i test and Phase ii test. The Phase i test identified sample failure time, while the Phase ii test measured the corresponding tensile force arising from the expansive grout. Ostensibly homogeneous rock samples without incipient joints were firstly tested to establish the methodology. Tensile strength of block samples containing incipient rock joints was then measured using the established testing scheme. The test results have been compared with those obtained from conventional Brazilian and uniaxial tension tests as suggested by ISRM. The proposed approach is capable of giving a measure of tensile strength of large-scale incipient rock joints, although somewhat smaller strength than that from the standard approaches was occasionally measured in the preliminary tests on ostensibly homogeneous samples. Effects of stress concentration, sample scale, loading rate and expansive tensile force on the testing results were discussed. Furthermore, this simple and practical testing scheme is proposed for the measurement of the in situ tensile strength of rock and incipient discontinuities in the field, which if successful will provide a more scientific guidance on the rock mass classification and engineering design
3D ground model development for an active landslide in Lias mudrocks using geophysical, remote sensing and geotechnical methods
A ground model of an active and complex landslide system in instability prone Lias mudrocks of North Yorkshire, UK is developed through an integrated approach, utilising geophysical, geotechnical and remote sensing investigative methods. Surface geomorphology is mapped and interpreted using immersive 3D visualisation software to interpret airborne light detection and ranging data and aerial photographs. Subsurface structure is determined by core logging and 3D electrical resistivity tomography (ERT), which is deployed at two scales of resolution to provide a means of volumetrically characterising the subsurface expression of both site scale (tens of metres) geological structure, and finer (metre to sub-metre) scale earth-flow related structures. Petrophysical analysis of the borehole core samples is used to develop relationships between the electrical and physical formation properties, to aid calibration and interpretation of 3D ERT images. Results of the landslide investigation reveal that an integrated approach centred on volumetric geophysical imaging successfully achieves a detailed understanding of structure and lithology of a complex landslide system, which cannot be achieved through the use of remotely sensed data or discrete intrusive sampling alone
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Chemically enhanced mixed region vapor stripping of TCE-contaminated saturated peat and silty clay soils
The objective of this study was to conduct further testing of MRVS, chemically enhanced with calcium oxide conditioning, on field- contaminated soils collected from beneath the NASA Michoud Rinsewater Impoundment. In this study, residual soil VOC levels as a function of vapor stripping time were measured to quantify VOC removal rates. Physical and chemical soil parameters expected to affect MRVS efficiency were measures. The effects of varying the calcium oxide loadings as well as varying the vapor stripping flow rates on VOC removal were also evaluated. The results of this study will be used to determine whether acceptable removals can be achieved within reasonable treatment times, remediation costs being directly proportional to the latter. The purpose of this report is to document the experimental results of this study, as well as to address issues that were raised after completion of the previous Michoud treatability work
Sugawara-type constraints in hyperbolic coset models
In the conjectured correspondence between supergravity and geodesic models on
infinite-dimensional hyperbolic coset spaces, and E10/K(E10) in particular, the
constraints play a central role. We present a Sugawara-type construction in
terms of the E10 Noether charges that extends these constraints infinitely into
the hyperbolic algebra, in contrast to the truncated expressions obtained in
arXiv:0709.2691 that involved only finitely many generators. Our extended
constraints are associated to an infinite set of roots which are all imaginary,
and in fact fill the closed past light-cone of the Lorentzian root lattice. The
construction makes crucial use of the E10 Weyl group and of the fact that the
E10 model contains both D=11 supergravity and D=10 IIB supergravity. Our
extended constraints appear to unite in a remarkable manner the different
canonical constraints of these two theories. This construction may also shed
new light on the issue of `open constraint algebras' in traditional canonical
approaches to gravity.Comment: 49 page
Patterns of regional lung physiology in cystic fibrosis using ventilation magnetic resonance imaging and multiple-breath washout
Hyperpolarised helium-3 (3He) ventilation magnetic resonance imaging (MRI) and multiple-breath washout (MBW) are sensitive methods for detecting lung disease in cystic fibrosis (CF). We aimed to explore their relationship across a broad range of CF disease severity and patient age, as well as assess the effect of inhaled lung volume on ventilation distribution.32 children and adults with CF underwent MBW and 3He-MRI at a lung volume of end-inspiratory tidal volume (EIVT). In addition, 28 patients performed 3He-MRI at total lung capacity. 3He-MRI scans were quantitatively analysed for ventilation defect percentage (VDP), ventilation heterogeneity index (VHI) and the number and size of individual contiguous ventilation defects. From MBW, the lung clearance index, convection-dependent ventilation heterogeneity (Scond) and convection-diffusion-dependent ventilation heterogeneity (Sacin) were calculated.VDP and VHI at EIVT strongly correlated with lung clearance index (r=0.89 and r=0.88, respectively), Sacin (r=0.84 and r=0.82, respectively) and forced expiratory volume in 1 s (FEV1) (r=-0.79 and r=-0.78, respectively). Two distinct 3He-MRI patterns were highlighted: patients with abnormal FEV1 had significantly (p<0.001) larger, but fewer, contiguous defects than those with normal FEV1, who tended to have numerous small volume defects. These two MRI patterns were delineated by a VDP of ∼10%. At total lung capacity, when compared to EIVT, VDP and VHI reduced in all subjects (p<0.001), demonstrating improved ventilation distribution and regions of volume-reversible and nonreversible ventilation abnormalities
Final state effects on superfluid He in the deep inelastic regime
A study of Final State Effects (FSE) on the dynamic structure function of
superfluid He in the Gersch--Rodriguez formalism is presented. The main
ingredients needed in the calculation are the momentum distribution and the
semidiagonal two--body density matrix. The influence of these ground state
quantities on the FSE is analyzed. A variational form of is used, even
though simpler forms turn out to give accurate results if properly chosen.
Comparison to the experimental response at high momentum transfer is performed.
The predicted response is quite sensitive to slight variations on the value of
the condensate fraction, the best agreement with experiment being obtained with
. Sum rules of the FSE broadening function are also derived and
commented. Finally, it is shown that Gersch--Rodriguez theory produces results
as accurate as those coming from other more recent FSE theories.Comment: 20 pages, RevTex 3.0, 11 figures available upon request, to be appear
in Phys. Rev.
Mirror Symmetry in Physics: The Basics
These notes are aimed at mathematicians working on topics related to mirror
symmetry, but are unfamiliar with the physical origins of this subject. We
explain the physical concepts that enable this surprising duality to exist,
using the torus as an illustrative example. Then, we develop the basic
foundations of conformal field theory so that we can explain how mirror
symmetry was first discovered in that context. Along the way we will uncover a
deep connection between conformal field theories with (2,2) supersymmetry and
Calabi-Yau manifolds. (Based on lectures given during the "Thematic Program on
Calabi-Yau Varieties: Arithmetic, Geometry and Physics" at the Fields Institute
in Toronto, October 10-11, 2013.)Comment: 74 pages, 9 figure
Risk factors associated with Campylobacter jejuni infections in Curacao, Netherlands Antilles
A steady increase in the incidence of Guillain-Barre syndrome (GBS) with a
seasonal preponderance, almost exclusively related to Campylobacter
jejuni, and a rise in the incidence of laboratory-confirmed Campylobacter
enteritis have been reported from Curacao, Netherlands Antilles. We
therefore investigated possible risk factors associated with diarrhea due
to epidemic C. jejuni. Typing by pulsed-field gel electrophoresis
identified four epidemic clones which accounted for almost 60% of the
infections. One hundred six cases were included in a case-control study.
Infections with epidemic clones were more frequently observed in specific
districts in Willemstad, the capital of Curacao. One of these clones
caused infections during the rainy season only and was associated with the
presence of a deep well around the house. Two out of three GBS-related C.
jejuni isolates belonged to an epidemic clone. The observations presented
point toward water as a possible source of Campylobacter infections
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