Theoretical Determination of the Boundary of the Geomagnetic Field in a Steady Solar Wind

Theoretical determination of the boundary of the geomagnetic field in a steady solar win

XMM-Newton First Observation in the Pleiades

We present the first results from a 40 ks Guaranteed Time XMM-Newton pointing in the Pleiades. We detect almost all early-mid dM members in the field and several very low mass (VLM) stars - including the brown dwarf (BD) candidate Roque 9 - and investigate the variation of X-ray activity levels, hardness ratios and flare frequency with spectral type down to the BD regime.Comment: 5 pages, 6 figures, to be published in proceedings of `Stellar Coronae in the Chandra and XMM-Newton Era

Science Fiction Double Feature: Trans Liberation on Twin Earth

What is it to be a woman? What is it to be a man? We start by laying out desiderata for an analysis of 'woman' and 'man': descriptively, it should link these gender categories to sex biology without reducing them to sex biology, and politically, it should help us explain and combat traditional sexism while also allowing us to make sense of the activist view that gendering should be consensual. Using a Putnam-style 'Twin Earth' example, we argue that none of the existing analyses in the feminist literature succeeds in meeting all of our desiderata. Finally, we propose a positive account that we believe can satisfy all the desiderata outlined. According to our theory, the genders 'woman' and 'man' are individuated not by their contemporary connections to sex biology, but by their historical continuity with classes that were originally closely connected to sex biology

Paleoseismic and Slip-Rate Observations along the Honey Lake Fault Zone, Northeastern California, USA

The Honey Lake fault is a major strike-slip fault in northeastern California that accommodates northwest-directed right-lateral shear in the northern Walker Lane. We reexamine the fault’s paleoseismic history and slip rate by evaluating a natural stream bank exposure of the fault and offset terrace riser. Structural and stratigraphic relations within the modern stream cut, radiocarbon ages, and a detailed topographic survey of the offset terrace riser are used to estimate a Holocene fault slip rate of 1.7–0.6 mm/yr or more. We also interpret the occurrence of at least four surface-rupturing earthquakes during the last 7025 calendar years before present (B.P.). Three of the surface-rupturing earthquakes occurred prior to 4670 calendar years B.P. and have interevent times that range between 730 and 990 yr. The stratigraphic record is limited after ~4670 calendar years B.P., and records evidence for at least one more subsequent surface-rupturing earthquake

Probabilistic analysis of cost-effectiveness models: choosing between treatment strategies for gastroesophageal reflux disease

When choosing between mutually exclusive treatment options, it is common to construct a cost-effectiveness frontier on the cost-effectiveness plane that represents efficient points from among the treatment choices. Treatment options internal to the frontier are considered inefficient and are excluded either by strict dominance or by appealing to the principle of extended dominance. However, when uncertainty is considered, options excluded under the baseline analysis may form part of the cost-effectiveness frontier. By adopting a Bayesian approach, where distributions for model parameters are specified, uncertainty in the decision concerning which treatment option should be implemented is addressed directly. The approach is illustrated using an example from a recently published cost-effectiveness analysis of different possible treatment strategies for gastroesophageal reflux disease.It is argued that probabilistic analyses should be encouraged because they have potential to quantify the strength of evidence in favor of particular treatment choices

Modified hydraulic braking system limits angular deceleration to safe values

Conventional spring actuated, hydraulically released, fail-safe disk braking system is modified to control the angular deceleration of a massive antenna. The hydraulic system provides an immediate preset pressure to the spring-loaded brake shoes and holds it at this value to decelerate the antenna at the desired rate

Measurements of antenna polar diagrams and efficiencies using a phase-switched interferometer

It is desirable to know antenna polar patterns and efficiencies accurately. In the past, calibration measurements have been made using balloons and aircraft and more recently satellites. These techniques are usually very expensive. It is shown that under certain circumstances it is possible to use a simpler and inexpensive technique by connecting together the antenna under test with another antenna to form a phase switched interferometer as first described by Ryle (1952). The technique does require a suitable radio source which gives measurable powers when using small antennas and since dipoles have broad patterns, radio sources with similar right ascensions but different declinations to the primary source can be a problem. These problems can partly be overcome by filtering the interference pattern

An XMM-Newton observation of the young open cluster NGC 2547: coronal activity at 30 Myr

We report XMM-Newton observations of the young open cluster NGC 2547 which allow us to characterise coronal activity in solar-type stars at an age of 30 Myr. X-ray emission peaks among G-stars at luminosities (0.3-3keV) of Lx~10^{30.5} erg/s and declines to Lx<=10^{29.0} erg/s among M-stars. Coronal spectra show evidence for multi-temperature differential emission measures and low coronal metal abundances (Z~0.3). The G- and K-type stars follow the same relationship between X-ray activity and Rossby number established in older clusters and field stars, although most solar-type stars in NGC 2547 exhibit saturated/super-saturated X-ray activity levels. Median levels of Lx and Lx/Lbol in the solar-type stars of NGC 2547 are similar to T-Tauri stars of the Orion Nebula cluster (ONC), but an order of magnitude higher than in the older Pleiades. The spread in X-ray activity levels among solar-type stars in NGC 2547 is much smaller than in older or younger clusters. Coronal temperatures increase with Lx, Lx/Lbol and surface X-ray flux. Active solar-type stars in NGC 2547 have coronal temperatures between those in the ONC and the most active older ZAMS stars. A flaring rate (for total flare energies [0.3-3keV] >10^{34} erg) of 1 every 350^{+350}_{-120} ks was found for solar-type stars, similar to rates found in the ONC and Pleiades. Comparison with ROSAT HRI data taken 7 years previously reveals that only 10-15 percent of solar-type stars or stars with Lx>3x10^{29} erg/s exhibit X-ray variability by more than a factor of two. The similar levels of X-ray activity and rate of occurrence for large flares in NGC 2547 and the ONC demonstrate that the X-ray radiation environment around young solar-type stars remains relatively constant over their first 30 Myr (abridged).Comment: Accepted for publication in MNRAS. Electronic tables available from the autho