The Application of Ranging Techniques to Navigation and Traffic Control

During the last decade a variety of ground- and airbased radio aids have been implemented in efforts to solve major military problems in navigation and guidance, and command, control and communications. Because of significant advances in space technology and avionics, satellite-based systems to provide position-fixing data by means of ranging and range-differencing techniques, and to provide communications capability, have been shown to be feasible and attractive, and to have unique technical and operational advantages. World-wide coverage, essentially instantaneously availability, and threedimensional position-fixing accuracy of a few tens of feet seem feasible. In the civil area, demand for improved communications over the oceans, and for improved air traffic control over both the U.S. and the oceans, may be met by space-based systems. Indeed, the Office of Telecommunications Policy has recently called for a satellite telecommunications service for over-ocean aeronautical operations. A developing view supports the use of satellite-ranging techniques and satellite communications to provide for certain fundamental air traffic control functions over the U. S. in the period through the 1990s. From a satellite and data processing point of view, it appears feasible to implement in the early 1980s a system which could provide surveillance data to the order of 100 feet in three dimensions; an emergency communications capability corresponding to the operational notion of intermittent positive control; data for accurate autonomous navigation and for terminal approach and blind landing. These capabilities would be available to aircraft to an extent depending on its investment in avionics. To accomplish the implied objectives requires the establishment of organized and systematic R&D programs, including a well conceived evaluation methodology

Interstellar Scattering Towards the Galactic Center as Probed by OH/IR Stars

Angular broadening measurements are reported of 20 OH/IR stars near the galactic center. This class of sources is known to have bright, intrinsically compact (less than or equal to 20 mas) maser components within their circumstellar shells. VLBA antennas and the VLA were used to perform a MKII spectral line VLBI experiment. The rapid drop in correlated flux with increasing baseline, especially for sources closest to the galactic center, is attributed to interstellar scattering. Angular diameters were measured for 13 of our sources. Lower limits were obtained for the remaining seven. With the data, together with additional data taken from the literature, the distribution was determined of interstellar scattering toward the galactic center. A region was found of pronounced scattering nearly centered on SgrA*. Two interpretations are considered for the enhanced scattering. One hypothesis is that the scattering is due to a clump of enhanced turbulence, such as those that lie along lines of sight to other known objects, that has no physical relationship to the galactic center. The other model considers the location of the enhanced scattering to arise in the galactic center itself. The physical implications of the models yield information on the nature of interstellar scattering

Use of cell morphology to evaluate the effect of a peroxidase gene on cell death induction thresholds in tobacco

Tobacco suspension cultures were subjected to a range of heat stresses and used to compare morphological aspects of programmed cell death (PCD) and necrosis. Cells undergoing PCD were found to display characteristic death morphology, caused by cytoplasmic retraction of the protoplast, and to have cleaved DNA. We evaluated if the morphological characteristics of PCD could be used to monitor changes in cell death induction thresholds in transgenic cell cultures with high levels of peroxidase activity. Again, using a heat shock assay, we show that tobacco cell cultures with elevated levels of peroxidase have higher cell death induction threshold levels than wild type tobacco cell cultures. Thus, assessing PCD associated morphological changes can report on the effect of altering peroxidase genes on cell death activation in tobacco. This study demonstrates that PCD morphology could routinely be used to monitor the effects of introduced genes on programmed cell death induction thresholds in plants

VLBI study of water maser emission in the Seyfert 2 galaxy NGC5793. I: Imaging blueshifted emission and the parsec-scale jet

We present the first result of VLBI observations of the blueshifted water maser emission from the type 2 Seyfert galaxy NGC5793, which we combine with new and previous VLBI observations of continuum emission at 1.7, 5.0, 8.4, 15, and 22 GHz. Maser emission was detected earlier in single-dish observations and found to have both red- and blueshifted features relative to the systemic velocity. We could image only the blueshifted emission, which is located 3.6 pc southwest of the 22 GHz continuum peak. The blueshifted emission was found to originate in two clusters that are separated by 0.7 milliarcsecond (0.16 pc). No compact continuum emission was found within 3.6 pc of the maser spot. A compact continuum source showing a marginally inverted spectrum between 1.7 and 5.0 GHz was found 4.2 pc southwest of the maser position. The spectral turnover might be due to synchrotron self-absorption caused by a shock in the jet owing to collision with dense gas, or it might be due to free-free absorption in an ionized screen possibly the inner part of a disk, foreground to the jet. The water maser may be part of a maser disk. If so, it would be rotating in the opposite sense to the highly inclined galactic disk observed in CO emission. We estimate a binding mass within 1 pc of the presumed nucleus to be on the order of 10^7 Msun. Alternatively, the maser emission could result from the amplification of a radio jet by foreground circumnuclear molecular gas. In this case, the high blueshift of the maser emission might mean that the masing region is moving outward away from the molecular gas surrounding an active nucleus.Comment: 20 pages, 6 figures, to appear in ApJ, Oct. 200

The 3-D kinematics of water masers around the semiregular variable RT Virginis

We report observations of water masers around the semiregular variable RT Virginis (RT Vir), which have been made with the Very Long Baseline Array (VLBA) of the National Radio Astronomy Observatory (NRAO) at five epochs, each separated by three weeks of time. We detected about 60 maser features at each epoch. Overall, 61 features, detected at least twice, were tracked by their radial velocities and proper motions. The 3-D maser kinematics exhibited a circumstellar envelope that is expanding roughly spherically with a velocity of about 8 km/s. Asymmetries in both the spatial and velocity distributions of the maser features were found in the envelope, but less significant than that found in other semiregular variables. Systematic radial-velocity drifts of individual maser features were found with amplitudes of <= 2 km/s/yr. For one maser feature, we found a quadratic position shift with time along a straight line on the sky. This apparent motion indicates an acceleration with an amplitude of 33 km/s/yr, implying the passage of a shock wave driven by the stellar pulsation of RT Vir. The acceleration motion is likely seen only on the sky plane because of a large velocity gradient formed in the accelerating maser region. We estimated the distance to RT Vir to be about 220 pc on the basis of both the statistical parallax and model-fitting methods for the maser kinematics.Comment: 18 pages, 8 figures. Accepted to appear in the Astrophysical Journa

A magnetically collimated jet from an evolved star

Planetary nebulae often have asymmetric shapes, which could arise due to collimated jets from evolved stars before evolution to the planetary nebula phase. The source of jet collimation in these stars is unknown. Magnetic fields are thought to collimate outflows that are observed in many other astrophysical sources, such as active galactic nuclei and proto-stars, although hitherto there are no direct observations of both the magnetic field direction and strength in any collimated jet. Theoretical models have shown that magnetic fields could also be the dominant source of collimation of jet in evolved stars. Here we report measurements of the polarization of water vapour masers that trace the precessing jet emanating from the asymptotic giant branch star W43A at 2.6 kpc from the Sun, which is undergoing rapid evolution into a planetary nebula. The masers occur in two clusters at opposing tips of the jets, ~1,000 AU from the star. We find direct evidence that the magnetic field is collimating the jet.Comment: Published in Nature 440 (March 2nd 2006). High-res figures can be found at http://www.jb.man.ac.uk/~wouter/papers/w43a/w43a.htm

Establishing the validity of the Personality Assessment Inventory drug and alcohol scales in a corrections sample

Abstract Although not originally designed for implementation in correctional settings, researchers and clinicians have begun to use the Personality Assessment Inventory (PAI) to assess offenders. A relatively small number of studies have made attempts to validate the alcohol and drug abuse scales of the PAI, and only a very few studies have validated those scales in nonclinical correctional samples. The current study examined evidence of convergent and discriminant validity for the substance abuse scales on the PAI in a large, nonclinical sample of offenders. The net sample for the current study consisted of 1,120 federal inmates. Both the drug abuse and alcohol scales showed good convergent validity through high correlations with relevant proximal and distal indicators of substance use across multiple measures from several data sources. Discriminant validity was established as neither scale showed any &quot;erroneous&quot; correlations after controlling for the other scale. Implications for future research and practice are discussed

Increased frequency of Tim-3 expressing T cells is associated with symptomatic West Nile virus infection

More than a decade after West Nile virus (WNV) entered North America, and despite a significant increase in reported cases during the 2012 and 2013 seasons, no treatment or vaccine for humans is available. Although antiviral T cells contribute to the control of WNV, little is known about their regulation during acute infection. We analyzed the expression of Tim-3 and PD-1, two recently identified T cell negative immune checkpoint receptors, over the course of WNV infection. Symptomatic WNV+ donors exhibited higher frequencies of Tim-3+ cells than asymptomatic subjects within naïve/early differentiated CD28+/-CD57-CD4+ and differentiated CD28-CD57-CD8+ T cells. Our study links Tim-3-expression on T cells during acute WNV infection with the development of symptomatic disease, suggesting Tim-3 and its ligands could be targeted therapeutically to alter anti-WNV immunity and improve disease outcome

A critical narrative analysis of shared decision-making in acute, inpatient mental health care

Shared decision-making (SDM) is a high priority in healthcare policy and is complementary to the recovery philosophy in mental health care. This agenda has been operationalised within the Values-Based Practice (VBP) framework, which offers a theoretical and practical model to promote democratic interprofessional approaches to decision-making. However, these are limited by a lack of recognition of the implications of power implicit within the mental health system. This study considers issues of power within the context of decision-making and examines to what extent decisions about patients? care on acute in-patient wards are perceived to be shared. Focus groups were conducted with 46 mental health professionals, service users, and carers. The data were analysed using the framework of critical narrative analysis (CNA). The findings of the study suggested each group constructed different identity positions, which placed them as inside or outside of the decision-making process. This reflected their view of themselves as best placed to influence a decision on behalf of the service user. In conclusion, the discourse of VBP and SDM needs to take account of how differentials of power and the positioning of speakers affect the context in which decisions take place

Informed, Involved and Influential: The 3 I's model of Shared Decision Making in Mental Health Care

Collaboration between service users and mental health professionals is at the heart of values based practice and shared decision making. However, there has been limited analysis of the implications of these approaches within a healthcare context that involves depriving service users of their freedom. This article proposes a framework that aims to promote shared decision making which acknowledges, all participants must be Informed, Involved and Influential in the decision-making process. However, these are fluid; they refer to a sliding scale of influence that moves between these different positions depending on context, capacity and desire to influence