RX J2115-5840: confirmation of a new near-synchronous polar

Schwope et al (1997) suggested that the newly discovered Polar RX J2115-5840 is a near-synchronous system. We have obtained circular polarisation observations of RX J2115-5840 which show that the spin and orbital periods differ by 1.2%. We find the first direct evidence of `pole-switching' in a near-synchronous Polar. Further our data requires that the accretion flow must be directed onto the same magnetic field line at all spin-orbit beat phases implying that at some phases the flow must follow a path around the white dwarf before accreting.Comment: To be published in Proc Annapolis workshop on magnetic CVs, held in July 199

Kinetic Resolution in Asymmetric Epoxidation using Iminium Salt Catalysis

The first reported examples of kinetic resolution in epoxidation reactions using iminium salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes

Investigation of the hydrodynamic properties of a new MRI-resistant programmable hydrocephalus shunt.

BACKGROUND: The Polaris valve is a newly released hydrocephalus shunt that is designed to drain cerebrospinal fluid (CSF) from the brain ventricles or lumbar CSF space. The aim of this study was to bench test the properties of the Polaris shunt, independently of the manufacturer. METHODS: The Polaris Valve is a ball-on-spring valve, which can be adjusted magnetically in vivo. A special mechanism is incorporated to prevent accidental re-adjustment by an external magnetic field. The performance and hydrodynamic properties of the valve were evaluated in the UK Shunt Evaluation Laboratory, Cambridge, UK. RESULTS: The three shunts tested showed good mechanical durability over the 3-month period of testing, and a stable hydrodynamic performance over 45 days. The pressure-flow performance curves, operating, opening and closing pressures were stable. The drainage rate of the shunt increased when a negative outlet pressure (siphoning) was applied. The hydrodynamic parameters fell within the limits specified by the manufacturer and changed according to the five programmed performance levels. Hydrodynamic resistance was dependant on operating pressure, changing from low values of 1.6 mmHg/ml/min at the lowest level to 11.2 mmHg/ml/min at the highest performance level. External programming proved to be easy and reliable. Even very strong magnetic fields (3 Tesla) were not able to change the programming of the valve. However, distortion of magnetic resonance images was present. CONCLUSION: The Polaris Valve is a reliable, adjustable valve. Unlike other adjustable valves (except the Miethke ProGAV valve), the Polaris cannot be accidentally re-adjusted by an external magnetic field.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Simultaneous optical polarimetry and X-ray data of the near synchronous polar RX J2115-5840

We present simultaneous optical polarimetry and X-ray data of the near synchronous polar RX J2115-5840. We model the polarisation data using the Stokes imaging technique of Potter et al. We find that the data are best modelled using a relatively high binary inclination and a small angle between the magnetic and spin axes. We find that for all spin-orbit beat phases, a significant proportion of the accretion flow is directed onto the lower hemisphere of the white dwarf, producing negative circular polarisation. Only for a small fraction of the beat cycle is a proportion of the flow directed onto the upper hemisphere. However, the accretion flow never occurs near the upper magnetic pole, whatever the orientation of the magnetic poles. This indicates the presence of a non-dipole field with the field strength at the upper pole significantly higher. We find that the brightest parts of the hard X-ray emitting region and the cyclotron region are closely coincident.Comment: 9 pages, accepted for publication in MNRAS 2 March 200

Probabilities of Large Earthquakes in the San Francisco Bay Region, California

In 1987 a Working Group on California Earthquake Probabilities was organized by the U.S. Geological Survey at the recommendation of the National Earthquake Prediction Evaluation Council (NEPEC). The membership included representatives from private industry, academia, and the U.S. Geological Survey. The Working Group computed long-term probabilities of earthquakes along the major faults of the San Andreas fault system on the basis of consensus interpretations of information then available. Faults considered by the Working Group included the San Andreas fault proper, the San Jacinto and Imperial-faults of southern California, and the Hayward fault of northern California. The Working Group issued a final report of its findings in 1988 (Working Group, 1988) that was reviewed and endorsed by NEPEC. As a consequence of the magnitude 7.1 Loma Prieta, California, earthquake of October 17, 1989, a second Working Group on California Earthquake Probabilities was organized under the auspices of NEPEC. Its charge was to review and, as necessary, revise the findings of the 1988 report on the probability of large earthquakes in the San Francisco Bay region. In particular, the Working Group was requested to examine the probabilities of large earthquakes in the context of new interpretations or physical changes resulting from the Loma Prieta earthquake. In addition, it was to consider new information pertaining to the San Andreas and other faults in the region obtained subsequent to the release of the 1988 report. Insofar as modified techniques and improved data have been used in this study, the same approach might also, of course, modify the probabilities for southern California. This reevaluation has, however, been specifically limited to the San Francisco Bay region. This report is intended to summarize the collective knowledge and judgments of a diverse group of earthquake scientists to assist in formulation of rational earthquake policies. A considerable body of information about active faults in the San Francisco Bay region leads to the conclusion that major earthquakes are likely within the next tens of years. Several techniques can be used to compute probabilities of future earthquakes, although there are uncertainties about the validity of specific assumptions or models that must be made when applying these techniques. The body of this report describes the data and detailed assumptions that lead to specific probabilities for different fault segments. Additional data and future advances in our understanding of earthquake physics may alter the way that these probabilities are estimated. Even though this uncertainty must be acknowledged, we emphasize that the findings of this report are supported by other lines of argument and are consistent with our best understanding of the likelihood for the occurrence of earthquakes in the San Francisco Bay region

Future Seismic Hazards in Southern California - Phase I: Implications of the 1992 Landers Earthquake Sequence

Southern California and its seismologists received a wake-up call on June 28, 1992. The largest earthquake to strike southern California in 40 years occurred near the town of Landers, located 30 km north of the San Andreas fault. It had a magnitude of 7.5 (M7.5). Three and one-half hours later, a M6.5 aftershock struck the Big Bear area 40 km (kilometers) to the west of Landers. An ad hoc working group was rapidly convened in July, 1992, to evaluate how the Landers-Big Bear earthquake sequence might affect future large earthquakes along major faults in southern California. In particular, what are the chances of large earthquakes in the next few years and how do they compare to previous estimates (such as those of the Working Group on California Earthquake Probabilities -- WGCEP, 1988)? Such an evaluation was made for central California after the Lorna Prieta earthquake of 1989 (WGCEP, 1990). The charge to the Landers ad hoc working group included analyzing the seismicity for the last several years in southern California and the new paleoseismic, geologic, and geodetic data recently available for southern California. To inform the public about the potential hazard of plausible earthquakes, the working group was also asked to map the predicted severity of ground shaking for such earthquakes compared to that from the Landers earthquake

Effect of having private health insurance on the use of health care services: the case of Spain

Background: Several stakeholders have undertaken initiatives to propose solutions towards a more sustainable health system and Spain, as an example of a European country affected by austerity measures, is looking for ways to cut healthcare budgets. Methods: The aim of this paper is to study the effect of private health insurance on health care utilization using the latest micro-data from the European Community Household Panel (ECHP), the Spanish National Health Survey (SNHS) and the European Union Statistics on Income and Living Conditions (EU-SILC). We use matching techniques based on propensity score methods: single match, four matches, bias-adjustment and allowing for heteroskedasticity. Results: The results demonstrate that people with a private health insurance, use the public health system less than individuals without double health insurance coverage. Conclusions: Our conclusions are useful when policy makers design public-private partnership policie