Techniques for studying gravity waves and turbulence: Horizontal, vertical and temporal resolution needed

One of the most important atmospheric measurements that is needed is a measure of the gravity-wave spectrum. The MST radar has been investigated as means to measure the temporal resolution required to determine gravity-wave oscillations. The required vertical and horizontal resolution is dependent on the particular part of the gravity wave spectrum that is analyzed. Horizontal spacing is also discussed

Interpolation problems in meteor radar analysis, part 7.6A

Meteor echoes come from random points in the observation volume, and are irregularly spaced in time. This precludes the use of fast fourier transformations (FFT) techniques on the raw data to give the spectrum of waves that are present. One way around this obstacle is to restrict our interest to a particular class of waves, and fit a corresponding model to the raw data. It is assumed that there is no horizontal variation across the observation volume for tides, but in the vertical this is certainly not the case. If, in addition, we are interested in other types of waves which may be present and whose periods are unknown, then examining the raw line-of-sight velocities does not tell us how to modify the model, since the line-of-sight direction is not fixed. This is the motivation for interpolation. Interpolation takes a temporal series of line-of-sight velocities, and transforms it to a temporal series of wind velocities for each orthogonal direction. The velocities along a given direction can then be examined readily for any waves in addition to tides

Meteorological and dynamical requirements for MST radar networks: Waves

Studies of wave motions using the MST radar have concentrated on single station time series analyses of gravity waves and tides. Since these radars collect high time resolution data they have the potential to become a significant tool for mesoscale research. In addition, radars are operated almost continuously unattended and, consequently, data sets are available for analyzing longer period wave motions such as tides and planetary scale waves. Although there is much to learn from single station data, the possibilities of new knowledge from a network of radars is exciting. The scales of wave motions in the atmosphere cover a broad range. Consequently the choice of a radar network depends to a large extent on the types of wave motions that are studied. There are many outstanding research problems that would benefit from observations from a MST radar network. In particular, there is a strong need for measurements of gravity wave parameters and equatorial wave motions. Some of the current problems in wave dynamics are discussed

Meteor detection on ST (MST) radars

The ability to detect radar echoes from backscatter due to turbulent irregularities of the radio refractive index in the clear atmosphere has lead to an increasing number of established mesosphere - stratosphere - troposphere (MST or ST) radars. Humidity and temperature variations are responsible for the echo in the troposphere and stratosphere and turbulence acting on electron density gradients provides the echo in the mesosphere. The MST radar and its smaller version, the ST radar, are pulsed Doppler radars operating in the VHF - UHF frequency range. These echoes can be used to determine upper atmosphere winds at little extra cost to the ST radar configuration. In addition, the meteor echoes can supplement mesospheric data from an MST radar. The detection techniques required on the ST radar for delineating meteor echo returns are described

Whose Rights? Why States Should Set the Parameters for Federal Honest Services Mail and Wire Fraud Prosecutions

The citizens and governments of states and localities have a federal statutory right to the honest services of their public officials. The federal statutes that criminalize conduct impinging on this right, however, do not clearly define the parameters of the term honest services, and, as a result, the U.S. Courts of Appeals have differed in their interpretation of what conduct comprises a violation of the statute. The U.S. Courts of Appeals for the Third and Fifth Circuits have held that, in order for there to be a federal crime, the honest services must be owed under state or local law. Meanwhile, the First Circuit has held that such a state or local law violation is not a necessary prerequisite to the federal crime. This Note argues that, due to federalism and the nature of public corruption, the former approach strikes the appropriate balance between state sovereignty and the federal interest in good government

Data base management: MSTRAC (keynote paper), part 8

Technical Aspects of MST radars were discussed. The name of the group is MST Radar Coordination (MSTRAC). The geophysical parameters to be included in the sample data tapes were determined. It was suggested that MSTRAC compile a catalog of existing data at each of the facilities. It is found that: (1) there is a community of interested users for MST data; (2) the initial responses from observatories indicates that interest in MSTRAC is not overwhelming, probably because of time involved; and (3) the program needs reassessment

Quantum Fluctuations and Excitations in Antiferromagnetic Quasicrystals

We study the effects of quantum fluctuations and the excitation spectrum for the antiferromagnetic Heisenberg model on a two-dimensional quasicrystal, by numerically solving linear spin-wave theory on finite approximants of the octagonal tiling. Previous quantum Monte Carlo results for the distribution of local staggered magnetic moments and the static spin structure factor are reproduced well within this approximate scheme. Furthermore, the magnetic excitation spectrum consists of magnon-like low-energy modes, as well as dispersionless high-energy states of multifractal nature. The dynamical spin structure factor, accessible to inelastic neutron scattering, exhibits linear-soft modes at low energies, self-similar structures with bifurcations emerging at intermediate energies, and flat bands in high-energy regions. We find that the distribution of local staggered moments stemming from the inhomogeneity of the quasiperiodic structure leads to a characteristic energy spread in the local dynamical spin susceptibility, implying distinct nuclear magnetic resonance spectra, specific for different local environments.Comment: RevTex, 12 pages with 15 figure

Endovascular Embolization by Transcatheter Delivery of Particles: Past, Present, and Future.

Minimally invasive techniques to occlude flow within blood vessels, initially pioneered in the 1970s with autologous materials and subsequently advanced with increasingly sophisticated engineered biomaterials, are routinely performed for a variety of medical conditions. Contemporary interventional radiologists have at their disposal a wide armamentarium of occlusive agents to treat a range of disease processes through a small incision in the skin. In this review, we provide a historical perspective on endovascular embolization tools, summarize the current state-of-the-art, and highlight burgeoning technologies that promise to advance the field in the near future

Empirical wind model for the middle and lower atmosphere. Part 1: Local time average

The HWM90 thermospheric wind model was revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating zonal and meridional wind profiles representative of the climatological average for various geophysical conditions. Gradient winds from CIRA-86 plus rocket soundings, incoherent scatter radar, MF radar, and meteor radar provide the data base and are supplemented by previous data driven model summaries. Low-order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and longitude (stationary wave 1). The model represents a smoothed compromise between the data sources. Although agreement between various data sources is generally good, some systematic differences are noted, particularly near the mesopause. Root mean square differences between data and model are on the order of 15 m/s in the mesosphere and 10 m/s in the stratosphere for zonal wind, and 10 m/s and 4 m/s, respectively, for meridional wind