Geothermal reservoir engineering research

The Stanford University research program on the study of stimulation and reservoir engineering of geothermal resources commenced as an interdisciplinary program in September, 1972. The broad objectives of this program have been: (1) the development of experimental and computational data to evaluate the optimum performance of fracture-stimulated geothermal reservoirs; (2) the development of a geothermal reservoir model to evaluate important thermophysical, hydrodynamic, and chemical parameters based on fluid-energy-volume balances as part of standard reservoir engineering practice; and (3) the construction of a laboratory model of an explosion-produced chimney to obtain experimental data on the processes of in-place boiling, moving flash fronts, and two-phase flow in porous and fractured hydrothermal reservoirs

Child’s play: Exposure to household pesticide use among children in rural, urban and informal areas of South Africa

Background. As part of a larger dermatological investigation undertaken in 1999 - 2001 involving the Department of Dermatology, Groote Schuur Hospital (Cape Town, South Africa) and Nottingham University (UK), household pesticide use was investigated among Xhosa-speaking families living in three areas in South Africa (a rural area, an urban township and an informal settlement).Objectives. The aim was to characterise pesticide use patternsand potential exposures through skin absorption, ingestion and inhalation for this group of South African children.Methods. A standardised questionnaire, which included a section investigating household pesticide use, was administered by four trained fieldworkers to the parents/guardians of the 740 children (25%) aged between 3 and 11 years identified as having atopic dermatitis either by clinical examination or according to the UK criteria (rural N=387,urban N=292, informal N=61).Results. Of the children with atopic dermatitis, 539 (73%) had been exposed to household pesticides. Most childhood exposure (89%) occurred in the informal settlements, followed by 78% in the urban area and 63% in the rural area.Conclusions. This research highlighted considerable home environment pesticide exposure of South African children in lower socio-economic groups in rural, urban and informal areas. As children are particularly vulnerable to the short- and long-term health effects of pesticide exposure, further indepth investigation is needed to ascertain and document the health effects associated with such exposure in the home

A theory of electromagnetic fluctuations for metallic surfaces and van der Waals interactions between metallic bodies

A new general expression is derived for the fluctuating electromagnetic field outside a metal surface, in terms of its surface impedance. It provides a generalization to real metals of Lifshitz theory of molecular interactions between dielectric solids. The theory is used to compute the radiative heat transfer between two parallel metal surfaces at different temperatures. It is shown that a measurement of this quantity may provide an experimental resolution of a long-standing controversy about the effect of thermal corrections on the Casimir force between real metal plates.Comment: 4 pages, 2 figures; typos corrected, minor changes to match the published version in Physical Review Letter

Off-Diagonal Long-Range Order in Bose Liquids: Irrotational Flow and Quantization of Circulation

On the basis of gauge invariance, it is proven in an elementary and straightforward manner, but without invoking any {\it ad hoc} assumption, that the existence of off-diagonal long-range order in one-particle reduced density matrix in Bose liquids implies both the irrotational flow in a simply connected region and the quantization of circulation in a multiply connected region, the two fundamental properties of a Bose superfluid. The origin for both is the phase coherence of condensate wave-functions. Some relevant issues are also addressed.Comment: Revtex, 4 pages, no figure

Superadiabatic transitions in quantum molecular dynamics

We study the dynamics of a molecule’s nuclear wave function near an avoided crossing of two electronic energy levels for one nuclear degree of freedom. We derive the general form of the Schrödinger equation in the nth superadiabatic representation for all n є N. Using these results, we obtain closed formulas for the time development of the component of the wave function in an initially unoccupied energy subspace when a wave packet travels through the transition region. In the optimal superadiabatic representation, which we define, this component builds up monotonically. Finally, we give an explicit formula for the transition wave function away from the avoided crossing, which is in excellent agreement with high-precision numerical calculations

Weak Coupling Phase from Decays of Charged B Mesons to πK\pi K and ππ\pi\pi

The theory of $CP$ violation based on phases in weak couplings in the Cabibbo-Kobayashi-Maskawa (CKM) matrix requires the phase $\gamma \equiv {\rm Arg~} V^*_{ub}$ (in a standard convention) to be nonzero. A measurement of $\gamma$ is proposed based on charged $B$ meson decay rates to $\pi^+ K^0$, $\pi^0 K^+$, $\pi^+ \pi^0$, and the charge-conjugate states. The corresponding branching ratios are expected to be of the order of $10^{-5}$. (submitted to Physical Review Letters)Comment: LaTeX, 8 pages, 2 figures (not included, available upon request), TECHNION-PH-94-7, EFI-94-14, UdeM-LPN-TH-94-19

Dispersive force between dissimilar materials: geometrical effects

We calculate the Casimir force or dispersive van der Waals force between a spherical nanoparticle and a planar substrate, both with arbitrary dielectric properties. We show that the force between a sphere and a plane can be calculated through the interacting surface plasmons of the bodies. Using a Spectral Representation formalism, we show that the force of a sphere made of a material A and a plane made of a material B, differ from the case when the sphere is made of B, and the plane is made of A. We found that the difference depends on the plasma frequency of the materials, the geometry, and the distance of separation between sphere and plane. The differences show the importance of the geometry, and make evident the necessity of realistic descriptions of the sphere-plane system beyond the Derjaguin Approximation or Proximity Theorem Approximation

Hall Coefficient of Equilibrium Supercurrents Flowing inside Superconductors

We study augmented quasiclassical equations of superconductivity with the Lorentz force, which is missing from the standard Ginzburg-Landau and Eilenberger equations. It is shown that the magnetic Lorentz force on equilibrium supercurrents induces finite charge distribution and the resulting electric field to balance the Lorentz force. An analytic expression is obtained for the corresponding Hall coefficient of clean type-II superconductors with simultaneously incorporating the Fermi-surface and gap anisotropies. It has the same sign and magnitude at zero temperature as the normal state for an arbitrary pairing, having no temperature dependence specifically for the s-wave pairing. The gap anisotropy may bring a considerable temperature dependence in the Hall coefficient and can lead to its sign change as a function of temperature, as exemplified for a model d-wave pairing with a two-dimensional Fermi surface. The sign change may be observed in some high-$T_{c}$ superconductors.Comment: 7 pages, 3 figure

Desperately Seeking Non-Standard Phases via Direct CP Violation in b→sg∗b\to sg^\ast Process

Attributing the recent CLEO discovery of $B \to \eta' + X_s$ to originate (primarily) from the fragmentation of an off-shell gluon ($g^*$) via $b \to s + g^*$, $g^* \to g + \eta'$, we emphasize that many such states ($X_g$) should materialize. Indeed the hadronic fragments ($X_g$) of $g^*$ states are closely related to those seen in $\psi \to \gamma (\phi, \omega) + X_g$. A particular final state of considerable interest is $X_g=K^+K^-$. Signals from such states in $B$ decays can be combined to provide a very sensitive search for CP violating phase(s) from non-standard physics. The method should work even if the contribution of these source(s) to the rates is rather small ($\sim10$) to the point that a comparison between theory and experiment may find it extremely difficult to reveal the presence of such a new physics.Comment: 16 pages, 5 figure