Elliptical flux vortices in YBa2Cu3O7

The most energetically favorable vortex in YBa2Cu3O7 forms perpendicular to an anisotropic plane. This vortex is elliptical in shape and is distinguished by an effective interchange of London penetration depths from one axis of the ellipse to another. By generalizing qualitatively from the isotropic to the anisotropic case, we suggest that the flux flow resistivity for the vortex that forms perpendicular to an anistropic plane should have a preferred direction. Similar reasoning indicates that the Kosterlitz-Thouless transition temperature for a vortex mediated transition should be lower if the vortex is elliptical in shape

The Status of Computer-Related Elective Courses in Public Secondary Schools in Tennessee

The problem was to determine the status of computer-related elective courses in public secondary schools in Tennessee. A descriptive research design was used for this study. A search was made to locate public secondary schools which housed grade twelve and whose curricula were in keeping with State requirements for a diploma. A search of Preliminary Reports was made of identified schools to determine those which offered a computer-related elective course. A questionnaire was sent to teachers of computer-related course electives. The data were examined and presented in narrative form with the use of appropriate tables. The following findings emerged: (1) There were 306 schools in Tennessee in 1979-80 which housed grade twelve and whose curriculum was reflective of State diploma requirements. Twenty-four of these schools (8 percent) offered one or more computer courses. There were twenty-one computer math courses and six computer programming courses. There were thirty-two total class sections of computer-related courses. (2) There were 568 students enrolled in computer-related courses for the first semester of the 1979-80 school year. The average school enrollment was 1254 and the average student-teacher ratio was 1:19.5. The teacher-student ratio in computer-related classes was 1:17.5. (3) There were twenty-seven certified persons teaching computer courses in 1979-80. One held a specialist degree, two held master\u27s plus forty-five hours, fourteen held master\u27s and ten held bachelor\u27s degrees. Twenty-four were endorsed in math, two in science and one in business. Twenty of the twenty-seven held multiple endorsements. (4) The majority of schools awarded both a minimum and a maximum of one-half unit of credit with a range of one-half to two. (5) Computers and terminals were available for student use in computer courses and were primarily housed in the classroom where the course was taught. (6) Software was produced primarily by staff and/or students. (7) No decreases were reported for the 1980-81 offerings of computer-related courses. Increases were reported by less than 25 percent of the respondents in the study. (8) Objectives of computer-related courses were awareness and introductory in nature. Simple programming was included in schools which offered more than one-half Carnegie unit credit as maximum. (9) In comparison with information gained from opinion survey to forty-nine State Departments of Education, Tennessee ranks in the lower 18 percent of states where less than 10 percent of the secondary schools offer one or more computer-related courses

Ultrabroad-bandwidth multifrequency Raman generation

We report on the modeling of transient stimulated rotational Raman scattering in H2 gas. We predict a multifrequency output, spanning a bandwidth greater than the pump frequency, that may be generated without any significant delay with respect to the pump pulses. The roles of dispersion and transiency are quantified

Transverse effects in multifrequency Raman generation

The theory of ultrabroadband multifrequency Raman generation is extended, for the first time, to allow for beam-propagation effects in one and two transverse dimensions. We show that a complex transverse structure develops even when diffraction is neglected. In the general case, we examine how the ultrabroadband multifrequency Raman generation process is affected by the intensity, phase quality, and width of the input beams, and by the length of the Raman medium. The evolution of power spectra, intensity profiles, and global characteristics of the multifrequency beams are investigated and explained. In the two-dimensional transverse case, bandwidths comparable to the optical carrier frequency, spanning the whole visible spectrum and beyond, are still achievable

Caution: examinations in progress - the operation of neighbourhood plan examinations in England

Gavin Parker, Kat Salter and Hannah Hickman look at what experience to date tells us about how the examination stage in the neighbourhood plan production process is being undertaken, and the issues and associated questions emerging from that experience

Extrasolar Asteroid Mining as Forensic Evidence for Extraterrestrial Intelligence

The development of civilisations like ours into spacefaring, multi-planet entities requires significant raw materials to construct vehicles and habitats. Interplanetary debris, including asteroids and comets, may provide such a source of raw materials. In this article we present the hypothesis that extraterrestrial intelligences (ETIs) engaged in asteroid mining may be detectable from Earth. Considering the detected disc of debris around Vega as a template, we explore the observational signatures of targeted asteroid mining (TAM), such as unexplained deficits in chemical species, changes in the size distribution of debris and other thermal signatures which may be detectable in the spectral energy distribution (SED) of a debris disc. We find that individual observational signatures of asteroid mining can be explained by natural phenomena, and as such they cannot provide conclusive detections of ETIs. But, it may be the case that several signatures appearing in the same system will prove harder to model without extraterrestrial involvement. Therefore signatures of TAM are not detections of ETI in their own right, but as part of "piggy-back" studies carried out in tandem with conventional debris disc research, they could provide a means of identifying unusual candidate systems for further study using other SETI techniques.Comment: 15 pages, 2 figures, accepted for publication in the International Journal of Astrobiolog

IN-SITU STRESS AND FRACTURE CHARACTERIZATION FOR PLANNING OF AN EGS STIMULATION IN THE DESERT PEAK GEOTHERMAL FIELD, NEVADA

An integrated study of natural fracture geometry, fluid flow and stress was conducted in Desert Peak well 27-15 in preparation for development of an Enhanced Geothermal System (EGS) through hydraulic stimulation. This stimulation will be carried out at depths of ~3000 to 3500 ft in units comprised of silicified rhyolite tuffs and metamorphosed mudstones at ambient temperatures of ~180 to 195° C. Our previous analyses of borehole image logs from this well showed that the current minimum horizontal principal stress, Shmin, is oriented 114 ± 17º and that numerous fractures in the planned stimulation interval are optimally oriented for normal faulting. As an extension of this earlier work, a hydraulic fracturing stress measurement was conducted at the top of the intended stimulation interval and indicates that the magnitude of Shmin is 1995 ± 60 psi, which is ~0.61 of the calculated vertical (overburden) stress at this depth. This Shmin magnitude is somewhat higher than expected for frictional failure on optimally oriented normal faults under current reservoir pressures given typical laboratory measurements of sliding friction (Byerlee’s Law). However, Coulomb failure calculations using coefficients of friction derived from laboratory tests on representative core samples from a nearby well (Lutz et al., 2010) indicate that shear failure could be induced on well-oriented preexisting fractures in well 27-15 once fluid pressures are increased by several hundred psi above the ambient formation fluid pressure. This geomechanical model will be tested during hydraulic stimulation of well 27-15, which is intended to enhance formation permeability through selfpropping shear failure. If this stimulation is successful, then preferential activation of normal faults should generate a zone of enhanced permeability propagating to the SSW, in the direction of nearby geothermal injection and production wells, and to the NNE, into an unexploited portion of the field

Report on televiewer log and stress measurements in core hole USW G-2, Nevada Test Site, October-November, 1982

Hydraulic fracturing stress measurements and a borehole televiewer log were obtained in hole USW G-2 at Yucca Mountain, Nevada, to depths of 1200 m. Results indicate that at the depths tested, the minimum and maximum horizontal stresses are less than the vertical stress, corresponding to a normal faulting stress regime. Drilling-induced hydrofractures seen in the televiewer log imply a least horizontal principal stress direction of N 60° W to N 65° W. For reasonable values of the coefficient of friction, the magnitude of the least horizontal stress is close to the value at which slip would occur on preexisting faults of optimal orientation (strike N 25° E to N 30° E and dipping 60° to 67°). The prominent drilling-induced fractures seen in the televiewer log are believed to have been caused by excess downhole pressures applied during drilling the hole. Many throughgoing fractures are also seen in the televiewer log; most of these are high angle, stringking N 10° E to N 40° E. These fractures show a general decrease in angle of dip with depth. Stress-induced wellbore breakouts are seen at depths below 1050 m. The average N 60° W azimuth of these breakouts agrees very closely with the N 60° W to N 65° W direction of least horizontal principal stress inferred from the drilling-induced hydrofracs