Experimental observation of mode evolution in single-mode taperedoptical fibers

Step-index single-mode optical fibers were tapered and then cleaved by ion beam milling to allow direct examination of the mode evolution in the taper with a microscope objective and CCD camera. Observation of HE_1m modes is reported in tapered fibers cleaved at diameters ranging from 8 to 35 μm. Theoretical scalar mode fields are fit to the experimental data and the mode transitions are explained by considering coupled mode theory     

Intelligence test potential: Analysis of breadth, depth, and differential prediction.

In a study with 40 undergraduates, 2 measures of "breadth" and 3 measures of "depth" were derived, based on special administration and scoring of the WAIS Similarities subscale. Factor analyses performed on the Similarities indices, the Concept Mastery Test, and Guilford's Tin Can item, indicated that breadth and depth can be distinguished statistically, and multiple regression analyses revealed that the derived measures contributed to improved predictive efficiency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of Site Factors for Seismic Bridge Design in New York City Area

Site factors for seismic bridge design in the New York metropolitan area are evaluated. Several profiles from Brooklyn, Queens, and Manhattan, matching soil categories D and E as defined in the recent New York City Department of Transportation and NEHRP provisions, are analyzed using 1D wave-propagation theory. Dynamic soil properties are derived using state-of-practice correlations with standard penetration resistance and compared to available in situ geophysical measurements. Three different rock motions are used, each modified from real records to match 500- and 2,500-year probabilistic spectra for the region. Results are presented in terms of dimensionless ratios of surface and rock response spectra. The effect of impedance contrast between soil and rock on soil amplification is examined. It is shown that, although seismic hazard in the area is moderate, large surface motions can be generated because of strong site amplification effects that exceed those in the western United States. Derived spectra are compared with current design spectra defined in the 1998 New York City Department of Transportation guidelines and the 1995 New York City Seismic Code. Three issues that are not sufficiently addressed in existing codes are discussed: (1) deep sites containing thick layers of high-plasticity clay; (2) shallow sites with thickness <30 m; and (3) amplification of vertical ground motions.     

Measurement of vorticity in the surface layer using an acoustic echo sounder array

The earth's atmospheric surface layer is usually defined as that region of the lower atmosphere (generally below about 10 m above the earth's surface) where surface friction causes vertical fluxes of heat, moisture and momentum to be constant with height. Within the surface layer, either in response to surface friction or to the atmosphere above, horizontal circular eddies often develop. These circular motions may provide the source of rotation for dust devils so often seen on hot and dry days particularly in desert regions. Also, at larger scales ($\text{～ 1 km in diameter}$) regions of warm and therefore buoyant upward moving air, called thermal plumes, may acquire rotation. These plumes may extend from the earth's surface to more than a kilometer in height on a warm afternoon. Fluid dynamicists quantify this horizontal rotation with a parameter known as the vertical component of vorticity. Vorticity is very difficult to measure in the earth's atmosphere at scales of close to a kilometer because the calculation involves wind-speed differences over horizontal distances of about 500 m. The winds must be measured quite accurately because the differences can be quite small and, therefore, the errors in these measurements are often quite large. This work describes a method of measuring vertical vorticity at scales down to 500 m using an array of three acoustic sounders about 2 m above the earth's surface which overcomes some of the accuracy problems mentioned above. We relate these vorticity measurements to other atmospheric parameters and compute temporal spectra of these quantities to help explain the relationship between vorticity, thermal plume activity, and the smaller-scale dust devils.     

CD4-independent, CCR5-dependent infection of brain capillary endothelial cells by a neurovirulent simian immunodeficiency virus strain

Brain capillary endothelial cells (BCECs) are targets of CD4-independent infection by HIV-1 and simian immunodeficiency virus (SIV) strains in vitro and in vivo. Infection of BCECs may provide a portal of entry for the virus into the central nervous system and could disrupt blood-brain barrier function, contributing to the development of AIDS dementia. We found that rhesus macaque BCECs express chemokine receptors involved in HIV and SIV entry including CCR5, CCR3, CXCR4, and STRL33, but not CCR2b, GPR1, or GPR15. Infection of BCECs by the neurovirulent strain SIV/17E-Fr was completely inhibited by aminooxypentane regulation upon activation, normal T cell expression and secretion in the presence or absence of ligands, but not by eotaxin or antibodies to CD4. We found that the envelope (env) proteins from SIV/17E-Fr and several additional SIV strains mediated cell-cell fusion and virus infection with CD4-negative, CCR5-positive cells. In contrast, fusion with cells expressing the coreceptors STRL33, GPR1, and GPR15 was CD4-dependent. These results show that CCR5 can serve as a primary receptor for SIV in BCECs and suggest a possible CD4-independent mechanism for blood-brain barrier disruption and viral entry into the central nervous system.     

Mechanical properties of amorphous and polycrystalline multilayer systems

Amorphous and polycrystalline multilayer structures containing materials with metallic (Cr, Cr₃C₂), ionic (Al₂O₃) and covalent (SiC) bonding have been prepared by magnetron sputtering and ion plating in a dual-source apparatus. Up to 1000 layers have been deposited with a constant total thickness of 2.3 μm.

Below a single-layer thickness of 10–30 nm the mechanical properties stress and hardness show strong variations. On one hand it is possible that below a certain thickness the mechanical properties of a single layer change (A. Pan and J.E. Greene, Thin Solid Films, 78 (1981) 25–34). On the other hand electrical resistance and electron spin density measurements indicate that electronic effects may be involved. An attempt is made to explain the observed correlations by transport mechanisms of the electrons, by saturation of dangling bonds with delocalized electrons and by changes in the electronic band structure.     

Relative efficacy of Wechsler Adult Intelligence Scale short forms with outpatients.

Rescored 115 WAIS protocols of psychological service outpatients for 7 selected subtest and 2 selected items short forms. Results favor the use of J. D. Pauker's (1963) short form, although research has shown a decrease in correspondence between short-form and Full Scale scores when the short forms are administered separately; also, the 27% misclassification rate for females would probably prohibit its use with this group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)