A three dimensional model of the Venusian thermosphere with superrotation

An improved three dimensional spectral model of the thermosphere of Venus is described. The model solves the Navier-Stokes equations and includes nonlinear effects for an arbitrary number of atmospheric species. A two dimensional axisymmetric model of the superrotation of the thermosphere is also presented. This model addresses the Pioneer-Venus mission finding, which suggested the thermospheric rotation rate to be much higher than that of the planet as seen from the asymmetric distribution of hydrogen and helium. Both models include the effects of an anisotropic eddy diffusion that is consistent with atmospheric mixing length theory

A Climatology of Northwest Missouri Snowfall Events: Long Term Trends and Interannual Variability.

The goal of this study was to develop a 50-year statistical climatology of snowfall occurrences using data from a dense network of cooperative station observations covering northwest and central Missouri, and these records were provided by the Missouri Climate Center. This included a study of the long term trends and interannual variability in snowfall occurrence as related to sea surface temperature variations in the Pacific Ocean basin associated with the El Nino and Southern Oscillation (ENSO) and the North Pacific Oscillation (NPO). These trends and variations were then related to four synoptic-scale flow regimes that produce these snowfalls in the Midwest. The results demonstrate that during the snowfall season (Oct - April) the northwest Missouri region can expect about eight snowfall events which produce three or more inches of accumulation. While no significant long-term trend in overall snowfall occurrence was found, a decrease in the number of extreme events (10 or more inches) was noted. Also, fewer snowfall events were found during El Nino years, while more heavy snowfall events occurred during "neutral" years, and these results could be related to synoptic- scale variability. A closer examination of the results demonstrated that El Nino/La Nina related variability in snowfall occurrence was superimposed on longer-term NPO-related variability.This research was supported by the University Corporation for Atmospheric Research (UCAR) Cooperative program for Operational Meteorological Education and Training (COMET) Outreach Programunder award # 98115921

Simulated VLBI Images From Relativistic Hydrodynamic Jet Models

A series of simulated maps showing the appearance in total intensity of flows computed using a recently developed relativistic hydrodynamic code (Duncan \& Hughes 1994: ApJ, 436, L119) are presented. The radiation transfer calculations were performed by assuming the flow is permeated by a magnetic field and fast particle distribution in energy equipartition, with energy density proportional to the hydrodynamic energy density (i.e., pressure). We find that relativistic flows subject to strong perturbations exhibit a density structure consisting of a series of nested bow shocks, and that this structure is evident in the intensity maps for large viewing angles. However, for viewing angles $<30^{\circ}$, differential Doppler boosting leads to a series of axial knots of emission, similar to the pattern exhibited by many VLBI sources. The appearance of VLBI knots is determined primarily by the Doppler boosting of parts of a more extended flow. To study the evolution of a perturbed jet, a time series of maps was produced and an integrated flux light curve created. The light curve shows features characteristic of a radio loud AGN: small amplitude variations and a large outburst. We find that in the absence of perturbations, jets with a modest Lorentz factor ($\sim 5$) exhibit complex intensity maps, while faster jets (Lorentz factor $\sim 10$) are largely featureless. We also study the appearance of kiloparsec jet-counterjet pairs by producing simulated maps at relatively large viewing angles; we conclude that observed hot spot emission is more likely to be associated with the Mach disk than with the outer, bow shock.Comment: 27 pages, uses aasms4.sty; 18 PostScript figures (1.57Mb gziped, 8.67Mb gunziped) available from http://www.astro.lsa.umich.edu/users/hughes/icon_dir/rad.html or by anonymous ftp from ra.astro.lsa.umich.edu in pub/get/hughes. Submitted to Ap.

An analysis of a long-lived MCV observed over the Southern Plains using Potential Vorticity diagnostics.

On the morning of 28 May 1998, a mesoscale convectively-generated vortex (MCV) was observed over the Southern Plains. This MCV was evident in the GOES-8 visual satellite imagery resulting in a spectacular picture. An analysis of this event is offered using many data sources, including products available now via the world-wide-web (WWW), the National Center for Environmental Prediction (NCEP) re-analyses, and Eta model initializations. This MCV developed out of a mesoscale convective system (MCS) that existed during 26 and 27 May over Texas. This MCV was associated with reports of severe weather and heavy precipitation over southern Arkansas. While the MCV is shown to have characteristics similar to other MCV events documented, this event is unique in that it maintained it's character, while propagating further east than other events. A dynamical analysis using potential vorticity diagnostics (PV) shows that the mid-latitude vorticity field strengthened at least partially as a result of diabatic heating. Also, the most severe weather was associated with high values of integrated 500 - 300 hPa PV values over the Southern Plains

Supplement 18, Part 2, Parasite-Subject Catalogue: Parasites: Protozoa

United States Department of Agriculture, Bureau of Animal Industry, National Animal Parasite Laboratory, Veterinary Sciences Research Division, Agricultural Research Servic

Direct ionization and electron capture in M-shell x-ray production by fluorine ions

This article discusses direct ionization and electron capture in M-shell x-ray production by fluorine ions

Hypoglycemia in Type 1 Diabetic Pregnancy: Role of preconception insulin aspart treatment in a randomized study

Objective: A recent randomized trial compared prandial insulin aspart (IAsp) with human insulin in type 1 diabetic pregnancy. The aim of this exploratory analysis was to investigate the incidence of severe hypoglycemia during pregnancy and compare women enrolled preconception with women enrolled during early pregnancy. Research design and methods: IAsp administered immediately before each meal was compared with human insulin administered 30 min before each meal in 99 subjects (44 to IAsp and 55 to human insulin) randomly assigned preconception and in 223 subjects (113 for IAsp and 110 for human insulin) randomly assigned in early pregnancy (<10 weeks). NPH insulin was the basal insulin. Severe hypoglycemia (requiring third-party assistance) was recorded prospectively preconception (where possible), during pregnancy, and postpartum. Relative risk (RR) of severe hypoglycemia was evaluated with a gamma frailty model. Results: Of the patients, 23% experienced severe hypoglycemia during pregnancy with the peak incidence in early pregnancy. In the first half of pregnancy, the RR of severe hypoglycemia in women randomly assigned in early pregnancy/preconception was 1.70 (95% CI 0.91–3.18, P = 0.097); the RR in the second half of pregnancy was 1.35 (0.38–4.77, P = 0.640). In women randomly assigned preconception, severe hypoglycemia rates occurring before and during the first and second halves of pregnancy and postpartum for IAsp versus human insulin were 0.9 versus 2.4, 0.9 versus 2.4, 0.3 versus 1.2, and 0.2 versus 2.2 episodes per patient per year, respectively (NS). Conclusions: These data suggest that initiation of insulin analog treatment preconception rather than during early pregnancy may result in a lower risk of severe hypoglycemia in women with type 1 diabetes

Direct ionization and electron capture in M

This article discusses direct ionization and electron capture in M-shell x-ray production by fluorine ions