On the Correlation of Torque and Luminosity in GX 1+4

Over five years of daily hard X-ray (>20 keV) monitoring of the 2-min accretion-powered pulsar GX 1+4 with the Compton Gamma Ray Observatory/BATSE large-area detectors has found nearly continuous rapid spin-down, interrupted by a bright 200-d spin-up episode. During spin-down, the torque becomes more negative as the luminosity increases (assuming that the 20-60 keV pulsed flux traces bolometric luminosity), the opposite of what is predicted by standard accretion torque theory. No changes in the shape of the 20-100 keV pulsed energy spectrum were detected, so that a very drastic change in the spectrum below 20 keV or the pulsed fraction would be required to make the 20-60 keV pulsed flux a poor luminosity tracer. These are the first observations which flatly contradict standard magnetic disk accretion theory, and they may have important implications for understanding the spin evolution of X-ray binaries, cataclysmic variables, and protostars. We briefly discuss the possibility that GX 1+4 may be accreting from a retrograde disk during spin-down, as previously suggested.Comment: 10 pages including 3 PS figures. To appear in ApJ Letter

Experimental measurements of Space Station antenna patterns at 60 GHz for EM analysis verification

Complex body scattering is a major problem facing the electromagnetic researcher today. Computer codes are one important method for predicting such scattering. With funding from Langley, Ohio State University has developed such a code. A 30:1 scale model of the Space Station was constructed to be used as a scattering target in the verification of this code. The purpose here is to document the methods used to make these measurements and present the results which will be used by others for code verification

Age-Depth Stratigraphy of Pine Island Glacier Inferred from Airborne Radar and Ice-Core Chronology

Understanding the contribution of the West Antarctic Ice Sheet (WAIS) to past and future sea level has been a major scientific priority over the last three decades. In recent years, observed thinning and ice‐flow acceleration of the marine‐based Pine Island Glacier has highlighted that understanding dynamic changes is critical to predicting the long‐term stability of the WAIS. However, relatively little is known about the evolution of the catchment during the Holocene. Internal Reflecting Horizons (IRHs) provide a cumulative record of accumulation, basal melt and ice dynamics that, if dated, can be used to constrain ice‐flow models. Here, we use airborne radars to trace four spatially‐extensive IRHs deposited in the late Quaternary across the Pine Island Glacier catchment. We use the WAIS Divide ice‐core chronology to assign ages to three IRHs: 4.72 ± 0.28, 6.94 ± 0.31, and 16.50 ± 0.79 ka. We use a 1‐D model, constrained by observational and modelled accumulation rates, to produce an independent validation of our ice‐core‐derived ages and provide an age estimate for our shallowest IRH (2.31‐2.92 ka). We find that our upper three IRHs correspond to three large peaks in sulphate concentrations in the WAIS Divide ice‐core record and hypothesise that the origin of these spatially‐extensive IRHs is from past volcanic activity. The clear correspondence between our IRHs and the ones previously identified over the Weddell Sea Sector, altogether representing ∼20% of the WAIS, indicates that a unique set of stratigraphic markers spanning the Holocene exists over a large part of West Antarctica

Rapid Spin-Up Episodes in the Wind-Fed Accreting Pulsar GX 301-2

The accreting pulsar GX 301-2 (P = 680 s) has been observed continuously by the large-area detectors of the Burst and Transient Source Experiment (BATSE) instrument on the Compton Gamma Ray Observatory since 1991 April 5. Orbital parameters determined from these data are consistent with previous measurements, with improved accuracy in the current orbital epoch. The most striking features in the pulsar frequency history are two steady and rapid spin-up episodes, with ν˙~(3-5)×10^(-12) Hz s^(-1), each lasting for about 30 days. They probably represent the formation of transient accretion disks in this wind-fed pulsar. Except for these spin-up episodes, there are virtually no net changes in the neutron star spin frequency on long timescales. We suggest that the long-term spin-up trend observed since 1984 (ν˙~2×10^(-13) Hz s^(-1)) may be due entirely to brief (~20 days) spin-up episodes similar to those we have discovered. We assess different accretion models and their ability to explain the orbital phase dependence of the observed flux. In addition to the previously observed preperiastron peak at orbital phase 0.956 +/- 0.022, we also find a smaller peak close to apastron at orbital phase 0.498 +/- 0.057. We show that if the companion star's effective temperature is less than 22,000 K, then it must have a mass M_c < 70 M_⊙ and a radius R_c < 85 R_⊙ so as not to overfill the tidal lobe at periastron. In order not to overflow the Roche lobe at periastron, the corresponding values are M_c < 55 M_⊙ and R_c < 68 R_⊙. These constraints are nearly at odds with the reclassification by Kaper et al. of the companion as a B1 Ia + hypergiant

Intensive HST, RXTE and ASCA Monitoring of NGC 3516: Evidence Against Thermal Reprocessing

During 1998 April 13-16, NGC 3516 was monitored almost continuously with HST for 10.3 hr in the UV and 2.8 d in the optical, and simultaneous RXTE and ASCA monitoring covered the same period. The X-rays were strongly variable with the soft (0.5-2 keV) showing stronger variations (~65% peak-to-peak) than the hard (2-10 keV; ~50% peak-to-peak). The optical continuum showed much smaller but highly significant variations: a slow ~2.5% rise followed by a faster ~3.5% decline. The short UV observation did not show significant variability. The soft and hard X-ray light curves were strongly correlated with no significant lag. Likewise, the optical continuum bands (3590 and 5510 A) were also strongly correlated with no measurable lag above limits of <0.15 d. However no significant correlation or simple relationship could be found for the optical and X-ray light curves. These results appear difficult to reconcile with previous reports of correlations between X-ray and optical variations and of measurable lags within the optical band for some other Seyfert 1s. These results also present serious problems for "reprocessing" models in which the X-ray source heats a stratified accretion disk which then reemits in the optical/ultraviolet: the synchronous variations within the optical would suggest that the emitting region is <0.3 lt-d across, while the lack of correlation between X-ray and optical variations would indicate, in the context of this model, that any reprocessing region must be >1 lt-d in size. It may be possible to resolve this conflict by invoking anisotropic emission or special geometry, but the most natural explanation appears to be that the bulk of the optical luminosity is generated by some other mechanism than reprocessing.Comment: 23 pages including 6 figures, accepted for publication in Ap

Phenological Parameters Estimation Tool

The Phenological Parameters Estimation Tool (PPET) is a set of algorithms implemented in MATLAB that estimates key vegetative phenological parameters. For a given year, the PPET software package takes in temporally processed vegetation index data (3D spatio-temporal arrays) generated by the time series product tool (TSPT) and outputs spatial grids (2D arrays) of vegetation phenological parameters. As a precursor to PPET, the TSPT uses quality information for each pixel of each date to remove bad or suspect data, and then interpolates and digitally fills data voids in the time series to produce a continuous, smoothed vegetation index product. During processing, the TSPT displays NDVI (Normalized Difference Vegetation Index) time series plots and images from the temporally processed pixels. Both the TSPT and PPET currently use moderate resolution imaging spectroradiometer (MODIS) satellite multispectral data as a default, but each software package is modifiable and could be used with any high-temporal-rate remote sensing data collection system that is capable of producing vegetation indices. Raw MODIS data from the Aqua and Terra satellites is processed using the TSPT to generate a filtered time series data product. The PPET then uses the TSPT output to generate phenological parameters for desired locations. PPET output data tiles are mosaicked into a Conterminous United States (CONUS) data layer using ERDAS IMAGINE, or equivalent software package. Mosaics of the vegetation phenology data products are then reprojected to the desired map projection using ERDAS IMAGIN

1954 Turf Conference

Attendance (I - XV) Grass Leaves at Work - S.N. Postlethwait (5) Seed Supply and Prices - Gager T. Vaughn (8) Hocus-Pocus in Grass Breeding - Glen W. Burton (11) Techniques and Turf Quality - Fred V. Grau Case Histories of Turf Improvement Programs - O.J. Noer (20) Fertilizer Facts and Fancies - A.J. Ohlrogge (38) Crabgrass Control in Turf - Ralph E. Engel (43) Athletic Field Reseeding - Fred V. Grau (44) Vegetative Grass Potential - W.H. Daniel (48) Who Plays Golf Today? - Herb Graffis (50) Poa Annua & Arsenic Toxicity - W.H. Daniel (53) Replanting Golf Greens - (58) Planting Stolons on Large Areas - A. Linkogel (59) Management, Weather & Disease - Ralph Engel (62) Practical Microscopic Disease Observations - Robert Williams (64

A Review of Virtual Reality Based Training Simulators for Orthopaedic Surgery

This review presents current virtual reality based training simulators for hip, knee and other orthopaedic surgery, including elective and trauma surgical procedures. There have not been any reviews focussing on hip and knee orthopaedic simulators. A comparison of existing simulator features is provided to identify what is missing and what is required to improve upon current simulators. In total 11 total hip replacement pre-operative planning tools were analysed, plus 9 hip trauma fracture training simulators. Additionally 9 knee arthroscopy simulators and 8 other orthopaedic simulators were included for comparison. The findings are that for orthopaedic surgery simulators in general, there is increasing use of patient-specific virtual models which reduce the learning curve. Modelling is also being used for patient-specific implant design and manufacture. Simulators are being increasingly validated for assessment as well as training. There are very few training simulators available for hip replacement, yet more advanced virtual reality is being used for other procedures such as hip trauma and drilling. Training simulators for hip replacement and orthopaedic surgery in general lag behind other surgical procedures for which virtual reality has become more common. Further developments are required to bring hip replacement training simulation up to date with other procedures. This suggests there is a gap in the market for a new high fidelity hip replacement and resurfacing training simulator

Pyrosmalite-(Fe), Fe8Si6O15(OH,Cl)10

Pyrosmalite-(Fe), ideally FeII 8Si6O15(OH,Cl)10 [refined composition in this study: Fe8Si6O15(OH0.814Cl0.186)10·0.45H2O, octa­iron(II) hexa­silicate deca­(chloride/hydroxide) 0.45-hydrate], is a phyllosilicate mineral and a member of the pyrosmalite series (Fe,Mn)8Si6O15(OH,Cl)10, which includes pyrosmalite-(Mn), as well as friedelite and mcgillite, two polytypes of pyrosmalite-(Mn). This study presents the first structure determination of pyrosmalite-(Fe) based on single-crystal X-ray diffraction data from a natural sample from Burguillos del Cerro, Badajos, Spain. Pyrosmalite-(Fe) is isotypic with pyrosmalite-(Mn) and its structure is characterized by a stacking of brucite-type layers of FeO6-octa­hedra alternating with sheets of SiO4 tetra­hedra along [001]. These sheets consist of 12-, six- and four-membered rings of tetra­hedra in a 1:2:3 ratio. In contrast to previous studies on pyrosmalite-(Mn), which all assumed that Cl and one of the four OH-groups occupy the same site, our data on pyrosmalite-(Fe) revealed a split-site structure model with Cl and OH occupying distinct sites. Furthermore, our study appears to suggest the presence of disordered structural water in pyrosmalite-(Fe), consistent with infrared spectroscopic data measured from the same sample. Weak hydrogen bonding between the ordered OH-groups that are part of the brucite-type layers and the terminal silicate O atoms is present

A large-scale experiment finds no evidence that a seismic survey impacts a demersal fish fauna

Seismic surveys are used to locate oil and gas reserves below the seabed and can be a major source of noise in marine environments. Their effects on commercial fisheries are a subject of debate, with experimental studies often producing results that are difficult to interpret. We overcame these issues in a large-scale experiment that quantified the impacts of exposure to a commercial seismic source on an assemblage of tropical demersal fishes targeted by commercial fisheries on the North West Shelf of Western Australia. We show that there were no short-term (days) or long-term (months) effects of exposure on the composition, abundance, size structure, behavior, or movement of this fauna. These multiple lines of evidence suggest that seismic surveys have little impact on demersal fishes in this environment