Imported measles. A potential control problem

From Dec 23, 1978, through Jan 31, 1979, an outbreak of five laboratory-confirmed cases and four clinical cases of measles occurred in a Vietnamese refugee population living in a single housing complex in Albuquerque, NM. The index cases were in two refugee siblings in whom measles was incubating on arrival in the United States. Despite spread through three subsequent generations of disease transmission within the Vietnamese population, there was no additional spread into the general Albuquerque population. Responsible factors included the age distribution of susceptible persons, the social isolation of the refugee population, and the physical structure of the housing complex. There is a need to identify the problem of imported measles in "ethnic islands" in need of vaccination.     

Formation mechanism of nano-diamond films from energetic species: From experiment to theory

In this paper, a particular class of nano-diamond films deposited by energetic species is described. Deposition is carried out using the direct-current glow-discharge (DC GD) deposition technique from a methane/hydrogen mixture. In this method, film growth occurs from energetic species being accelerated and incorporated into the film surface. The growth of the nano-diamond film occurs on top of a preferentially oriented graphitic precursor with its basal planes perpendicular to the substrate surface. The nano-diamond films consist of an agglomerate of diamond particles with particle sizes in the 3-5 nm range with amorphous grain boundaries. The hydrogen concentration in the graphitic precursor is only a few percent; however, it increases to ∼15-20 at.% in the nano-diamond film.From a microscopic perspective nano-diamond film and growth from energetic species is explained as a sub-surface process in terms of a four-step cyclic process. The DC GD-deposited nano-diamond films were comprehensively explored by a number of complementary techniques. The hydrogen content and its role in nano-diamond film formation were assessed. The experimental methods used in our studies comprise near-edge X-ray adsorption fine structure (NEXAFS) to prove the short-range coordination of the carbon films and indirectly their phase composition. The surface and grain boundary phase composition were investigated by a combination of electron energy loss spectroscopy (EELS) measured as a function of incident electron energy and hydrogen etching experiments. By transmission electron microscopy (TEM), the micro-structural evolution and their visualization were achieved. The density evolution of the films was determined by X-ray reflectivity (XRR). The hydrogen content and its distribution in the films were studied by secondary ion microscopy spectroscopy (SIMS) and elastic recoil detection (ERD). The hydrogen bonding was investigated by high-resolution electron energy loss spectroscopy (HREELS).Most likely, hydrogen is bonded within the amorphous grain boundaries and saturates the nano-diamond particles. The surface of the films is amorphous in nature.     

Multitarget miss distance via optimal assignment

The concept of miss distance-Euclidean, Mahalanobis, etc.-is a fundamental, far-reaching, and taken-for-granted element of the engineering theory and practice of single-target systems. In this paper we introduce a comprehensive L/sub p/-type theory of distance metrics for multitarget (and, more generally, multiobject) systems. We show that this theory extends, and provides a rigorous theoretical basis for, an intuitively appealing optimal-assignment approach proposed by Drummond for evaluating the performance of multitarget tracking algorithms. We describe tractable computational approaches for computing such metrics based on standard optimal assignment or convex optimization techniques. We describe the potentially far-reaching implications of these metrics for applications such as performance evaluation and sensor management. In the former case, we demonstrate the application of multitarget miss-distance metrics as measures of effectiveness (MoEs) for multitarget tracking algorithms.     

Impact of Scaffold Micro and Macro Architecture on Schwann Cell Proliferation under Dynamic Conditions in a Rotating Wall Vessel Bioreactor

Over the last decade tissue engineering has emerged as a powerful alternative to regenerate lost tissues owing to trauma or tumor. Evidence shows that Schwann cell containing scaffolds have improved performance in vivo as compared to scaffolds that depend on cellularization post implantation. However, owing to limited supply of cells from the patients themselves, several approaches have been taken to enhance cell proliferation rates to produce complete and uniform cellularization of scaffolds. The most common approach is the application of a bioreactor to enhance cell proliferation rate and therefore reduce the time needed to obtain sufficiently significant number of glial cells, prior to implantation.In this study, we show the application of a rotating wall bioreactor system for studying Schwann cell proliferation on nanofibrous spiral shaped scaffolds, prepared by solvent casting and salt leaching techniques. The scaffolds were fabricated from polycaprolactone (PCL), which has ideal mechanical properties and upon degradation does not produce acidic byproducts. The spiral scaffolds were coated with aligned or random nanofibers, produced by electrospinning, to provide a substrate that mimics the native extracellular matrix and the essential contact guidance cues.At the 4 day time point, an enhanced rate of cell proliferation was observed on the open structured nanofibrous spiral scaffolds in a rotating wall bioreactor, as compared to static culture conditions. However, the cell proliferation rate on the other contemporary scaffolds architectures such as the tubular and cylindrical scaffolds show reduced cell proliferation in the bioreactor as compared to static conditions, at the same time point. Moreover, the rotating wall bioreactor does not alter the orientation or the phenotype of the Schwann cells on the aligned nanofiber containing scaffolds, wherein, the cells remain aligned along the length of the scaffolds. Therefore, these open structured spiral scaffolds pre-cultured with Schwann cells, in bioreactors could potentially shorten the time needed for grafts for peripheral nerve regeneration.     

Comparison of ultralow-sidelobe-antenna far-field patterns usingthe planar-near-field method and the far-field method

The development of very-low-sidelobe antennas raises the question of whether or not the planar-near-field method can be used to accurately measure these antennas. Previously, scientists at several organizations showed that data taken and processed with the planar-near-field methodology, including probe correction, can be used to accurately measure the sidelobes of very-low-sidelobe antennas. This can be done to levels of -55 dB to -60 dB, relative to the main-beam peak. The present paper highlights these results, including a comparison of the far field, from the planar-near-field method, with the far field, found on a far-field range. The test antenna for the study was a slotted-waveguide array, the low sidelobes for which were known. The near-field measurements were conducted on the NIST planar-near-field facility     

A 90-nm logic technology featuring strained-silicon

A leading-edge 90-nm technology with 1.2-nm physical gate oxide, 45-nm gate length, strained silicon, NiSi, seven layers of Cu interconnects, and low-/spl kappa/ CDO for high-performance dense logic is presented. Strained silicon is used to increase saturated n-type and p-type metal-oxide-semiconductor field-effect transistors (MOSFETs) drive currents by 10% and 25%, respectively. Using selective epitaxial Si/sub 1-x/Ge/sub x/ in the source and drain regions, longitudinal uniaxial compressive stress is introduced into the p-type MOSEFT to increase hole mobility by >50%. A tensile silicon nitride-capping layer is used to introduce tensile strain into the n-type MOSFET and enhance electron mobility by 20%. Unlike all past strained-Si work, the hole mobility enhancement in this paper is present at large vertical electric fields in nanoscale transistors making this strain technique useful for advanced logic technologies. Furthermore, using piezoresistance coefficients it is shown that significantly less strain (/spl sim/5 /spl times/) is needed for a given PMOS mobility enhancement when applied via longitudinal uniaxial compression versus in-plane biaxial tension using the conventional Si/sub 1-x/Ge/sub x/ substrate approach.     

Negative and positive luminescence in midwavelength infrared InAs-GaSb superlattice photodiodes

The quantum efficiency of negative and positive luminescence in binary type-II InAs-GaSb superlattice photodiodes has been investigated in the midinfrared spectral range around the 5-/spl mu/m wavelength. The negative luminescence efficiency is nearly independent on temperature in the entire range from 220 to 325 K. For infrared diodes with a 2-/spl mu/m absorbing layer, processed without anti-reflection coating, a negative luminescence efficiency of 45% is found, indicating very efficient minority carrier extraction. The temperature dependent measurements of the quantum efficiency of the positive luminescence enables for the determination of the capture cross section of the Shockley-Read-Hall centers involved in the competing nonradiative recombination.     

Study of the XeCl laser pumped by a high-intensity electron beam

We present the results of a detailed experimental study of the XeCl laser pumped by a high-intensity electron beam. The laser system was optimized as an oscillator for mixtures of Xe and HCl with Ne, Ar, and Kr diluents. The peak intrinsic efficiency (laser energy out/electron-beam energy deposited) was near 4.5 percent for each of these diluents. Small-signal gain and background absorption were measured as a function of electron-beam deposition rate from 0.4 to 6 MW/ cm³. The ratio of small-signal gain to absorption was found to be constant over this range with a value of ∼5. Measurements of absorption in the presence of a large photon flux indicated that there was no appreciable saturable contribution to the absorption. Measurements of fluorescence from theBandCstates indicate that collisional mixing between these states is very rapid. The formation efficiencies of theBandCstates are estimated to be 0.15 and 0.05, respectively. A vibrational relaxation rate of between 1 and1.5 times 10^{-10}cm³. s^-1was determined. The effect of this finite relaxation rate is to reduce the energy available to the stimulated process by a factor of 0.67-0.75. Estimates of the XeCl* deactivation rates by HCl and electrons were also obtained. A value of1.7 times 10^{-9}cm³. s^-1was obtained for quenching by HCl, and a value ofsim 1 times 10^{-7}cm³. s^-1was estimated for electron deactivation.     

Antenna beamwidth independence of measured rain attenuation on a 28-GHz Earth-space path

Rain attenuation measured at 28 GHz on an earth-space path is independent of antenna beamwidth for beamwidths as small as0.1degand for attenuations up to 30 dB. The measurements imply that angle-of-arrival fluctuations are less than0.02deg.