Nonperiodic Optical Flickering In Hz Herculis

NASA NGR 44-012-209NSF GP-25901, GP-41796Astronom

On the Radio Polarization Signature of Efficient and Inefficient Particle Acceleration in Supernova Remnant SN 1006

We present a radio polarization study of SN 1006, based on combined VLA and ATCA observations at 20 cm that resulted in sensitive images with an angular resolution of 10 arcsec. The fractional polarization in the two bright radio and X-ray lobes of the SNR is measured to be 0.17, while in the southeastern sector, where the radio and non-thermal X-ray emission are much weaker, the polarization fraction reaches a value of 0.6 +- 0.2, close to the theoretical limit of 0.7. We interpret this result as evidence of a disordered, turbulent magnetic field in the lobes, where particle acceleration is believed to be efficient, and a highly ordered field in the southeast, where the acceleration efficiency has been shown to be very low. Utilizing the frequency coverage of our observations, an average rotation measure of ~12 rad/m2 is determined from the combined data set, which is then used to obtain the intrinsic direction of the magnetic field vectors. While the orientation of magnetic field vectors across the SNR shell appear radial, a large fraction of the magnetic vectors lie parallel to the Galactic Plane. Along the highly polarized southeastern rim, the field is aligned tangent to the shock, and therefore also nearly parallel to the Galactic Plane. These results strongly suggest that the ambient field surrounding SN 1006 is aligned with this direction (i.e., from northeast to southwest) and that the bright lobes are due to a polar cap geometry. Our study establishes that the most efficient particle acceleration and generation of magnetic turbulence in SN 1006 is attained for shocks in which the magnetic field direction and shock normal are quasi-parallel, while inefficient acceleration and little to no generation of magnetic turbulence obtains for the quasi-perpendicular case.Comment: Accepted for publication in Astronomical Journa

Study of the Juvenile Shrimp Populations of the Galveston Bay System - Study of the Texas Shrimp Populations

Penaeus aztecus, brown shrimp, arrived at the tertiary bays in early April, but grew slowly. In May growth accelerated and emigration from the bay began in June when the shrimp were less than 90 mm long. A second wave of brown shrimp arrived in August. White shrimp, P. setiferus, arrived at the tertiary bays in June. This group of shrimp was followed by two smaller groups in August and October. Brown shrimp were found in Sabine Lake in May. The 1964 white shrimp were found in mid-June. In the fall a second wave of white shrimp was observed. Commercial brown shrimp landings reached a peak in July and August, but fell sharply after September. White shrimp production was high

Study of the Texas Bay Populations of Juvenile Shrimp, Penaeus aztecus, Penaeus setiferus, and Penaeus duorarum

Postlarvae were found entering Aransas Bay in appreciable numbers in the spring of 1963. Late post-larval and early juvenile stages of brown shrimp, Penaeus aztecus, were found in tertiary bays in April. White shrimp, P. setiferus were found in May and June. Brown shrimp grew about 0.8 mm per day, while white shrimp grew about 1.1 mm per day. The first wave appeared to be smaller than latter waves. Small brown shrimp were found moving through the inshore Gulf in large numbers in June and July. White shrimp reached a larger size in the bays in June and July. White shrimp reached a larger size in the bays and supported a large commercial bay fishery. Late fall waves of white shrimp left the bays at a smaller size (probably to escape low water temperatures). Preliminary data indicate the 1963 shrimp landings increased 25% over 1962 landings

Policy Driven Management for Distributed Systems

Separating management policy from the automated managers which interpret the policy facilitates the dynamic change of behavior of a distributed management system. This permits it to adapt to evolutionary changes in the system being managed and to new application requirements. Changing the behavior of automated managers can be achieved by changing the policy without having to reimplement them—this permits the reuse of the managers in different environments. It is also useful to have a clear specification of the policy applying to human managers in an enterprise. This paper describes the work on policy which has come out of two related ESPRIT funded projects, SysMan and IDSM. Two classes of policy are elaborated—authorization policies define what a manager is permitted to do and obligation policies define what a manager must do. Policies are specified as objects which define a relationship between subjects (managers) and targets (managed objects). Domains are used to group the objects to which a policy applies. Policy objects also have attributes specifying the action to be performed and constraints limiting the applicability of the policy. We show how a number of example policies can be modeled using these objects and briefly mention issues relating to policy hierarchy and conflicts between overlapping policies. © 1994, Plenum Publishing Corporation. All rights reserved.Accepted versio

Natural killer cells in the human uterine mucosa

The presence of granulated lymphocytes in the human uterine mucosa, known as decidua during pregnancy, or endometrium otherwise, was first noted in the nineteenth century, but it was not until 1990 that these cells were identified as a type of natural killer (NK) cell. From the outset, uterine NK (uNK) cells were found to be less cytotoxic than their circulating counterparts, peripheral NK (pNK) cells. Recently, unbiased approaches have defined three subpopulations of uNK cells, all of which cluster separately from pNK cells. Here, we review the history of research into uNK cells, including their ability to interact with placental extravillous trophoblast cells and their potential role in regulating placental implantation. We go on to review more recent advances that focus on uNK cell development and heterogeneity and their potential to defend against infection and to mediate memory effects. Finally, we consider how a better understanding of these cells could be leveraged in the future to improve outcomes of pregnancy for mothers and babies

Brightness Distribution in Discrete Radio Sources III. The Structure of the Sources

The visibility functions of 195 radio sources are interpreted in terms of the structure of these sources. Of the 195 sources, 174 are known or presumed to be extragalactic. Seventy-five of these extragalactic sources are resolved with the interferometer spacings used, and complex structure is found in all but 13. In the sources showing complex structure, two similar components with nearly equal intensities are found in 15, 40 show two or more components of unequal intensities, while 7 appear to be a bright core surrounded by a halo. It is suggested that the majority of all extragalactic sources have complex structure. Data are also given on the brightness distributions in the 21 galactic sources observed. In contrast to the extragalactic sources, emission from the galactic sources is typically confined to a single region

Limits on radio emission from pulsar wind nebulae

We report on a sensitive survey for radio pulsar wind nebulae (PWN) towards 27 energetic and/or high velocity pulsars. Observations were carried out at 1.4 GHz using the Very Large Array and the Australia Telescope Compact Array, and utilised pulsar-gating to search for off-pulse emission. These observing parameters resulted in a considerably more sensitive search than previous surveys, and could detect PWN over a much wider range of spatial scales (and hence ambient densities and pulsar velocities). However, no emission clearly corresponding to a PWN was discovered. Based on these non-detections we argue that the young and energetic pulsars in our sample have winds typical of young pulsars, but produce unobservable PWN because they reside in low density (n approx 0.003 cm^-3) regions of the ISM. However, non-detections of PWN around older and less energetic pulsars can only be explained if the radio luminosity of their winds is less than 1e-5 of their spin-down luminosity, implying an efficiency at least an order of magnitude smaller than that seen for young pulsars.Comment: 9 pages, 3 embedded EPS files. Accepted to MNRA

Dimorphism and integration in the pelves of anthropoid primates

The link between obstetric demand (natural selection for birth) and pelvic morphology in anthropoids has remained ambiguous for the past century. Though it is assumed that the dramatic sexual dimorphism seen in modern human pelves is due to obstetric demand, this does not explain why other primates that give birth to relatively small neonates also exhibit pelvic dimorphism. This thesis explores the correlation between obstetric demand and dimorphism and morphological integration in anthropoid pelves. Dimorphism in birth canal and non-obstetric pelvic morphology is present across most primates regardless of obstetric demand, but those primates that give birth to relatively large babies have the most pelvic sexual dimorphism. Sexual dimorphism in sacral breadth is likewise most apparent in species that give birth to large neonates relative to the maternal birth canal. In species that give birth to large neonates, females also have higher magnitudes of integration in birth canal morphology compared to males, but this is not true in species that give birth to small neonates. This study demonstrates a clear link between obstetric demand, pelvic dimorphism, and the magnitudes of pelvic integration in anthropoid primates

When It Isn’t Always Lyme: Expanding the Differential Diagnosis for Acute-Onset Polyarthralgia in the West Virginia Eastern Panhandle

This case presentation discusses a 36 year-old female animal care worker presenting with an acute-onset polyarthropathy during the summer months in a Lyme endemic region. Though she appeared to be a good candidate for the diagnosis of Lyme borreliosis, her screening serology reported negative results and alternative diagnoses were considered. Her subsequent diagnosis with parvovirus B19 acts to remind the general practitioner to have confidence in the accuracy of a negative Lyme screen and, upon negative result, to expand the differential to include less common infections including parvovirus B19. It also highlights the need to remember parvovirus B19 in a similar patient who has the potential to be or to become pregnant during the course of her illness