Point-To-Multipoint Communication Over Broadcast Links

In this paper we study some link control protocols for use in point-to-multipoint communication over broadcast links. We concentrate on automatic repeat request protocols of the go-back-Ntype and define, analyze, and compare three such protocols. A major contribution of this paper is a relatively simple protocol which is easy to implement and performs very well under a wide range of conditions. Our analytical models show that this protocol performs considerably better than the other go-back-Nprotocols, particularly in environments with a large number of receivers.     

Environmental Impact of Two,Adjacent, Hazardous Waste Disposal Sites in the Niagara River Watershed

Sediment core samples were taken from the Niagara River at locations adjacent to the Love Canal and the 102nd Street dumps, two hazardous waste disposal sites in the City of Niagara Falls, New York. The samples were analyzed by capillary gas chromatographic mass spectrometry, and a variety of halogenated organic compounds (including chlorobenzene, -toluene, -naphthalene, -benzyl, and -norbornane derivatives) were identified and quantified. Based on the qualitative and quantitative data obtained, the sources of these pollutants were identified, and the relative migration of chemicals from the two dumps to the Niagara River was established. The impact on the river is localized to the immediate vicinity of the outfall of the sewer draining the Love Canal neighborhood. Remedial action could be as easy as removing 20 truckloads of contaminated sediment from the river.     

Heat of Formation of N-Dimethylaminodiborane

The heat of reaction of N-dimethylaminodiborane with water has been determined according to the reaction: (CH3)2NB2H5(g)+6H2O(liq)=(CH3)2NH(g)+2H3BO3(c)+5H2(g),ΔH(25°C)=−374.99±2.71kj/mole=−89.62±0.65kcal/mole.A combination of this value with the heat of vaporization, and with the heats of formation of boric acid, dimethylamine, and water gives for liquid N-dimethylaminodiborane: ΔHf°(25 °C) = ?36.22 ± 0.75 kcal/mole.     

Evidence that Gq family G proteins do not function in mouse egg activation at fertilization

Embryonic development is initiated after the fertilizing sperm contacts the egg and triggers a process termed "egg activation," resulting in calcium release, cortical granule exocytosis, recruitment of maternal mRNAs, and cell cycle resumption. Heterotrimeric guanine nucleotide-binding proteins (G proteins) may be involved in mouse egg activation since inhibition of G protein beta gamma subunits partially inhibits sperm-induced cell cycle resumption. In addition, specific events of egg activation can be initiated in the absence of sperm by acetylcholine stimulation of mouse eggs overexpressing the human m1 muscarinic receptor, a G protein-coupled receptor. In somatic cell, G proteins in the Gq family couple ligand stimulation of the m1 muscarinic receptor to activation of phospholipase C, resulting in the production of inositol 1,4,5-trisphosphate (IP3) and IP3-mediated release of intracellular calcium. Since IP3-mediated calcium release is involved in egg activation at fertilization, we have examined the role of Gq family G proteins in both sperm-independent (muscarinic receptor-mediated) and sperm-induced egg activation using a function-blocking antibody raised against the common C-terminal region of Gq and G11 proteins. We show that this antibody effectively inhibits Gq family G proteins in mouse eggs by demonstrating that the antibody inhibits egg activation in response to stimulation of the m1 muscarinic receptor. This same antibody, however, does not inhibit sperm-induced egg activation events. These results indicate that although activation of Gq family G proteins can result in egg activation in the mouse, it is unlikely that these proteins are used by the sperm to initiate egg activation at fertilization.     

Three-dimensional ocean chlorophyll distributions from underwater serial-sectioned fluorescence images

An underwater optical serial-sectioning technique is developed to measure in situ three-dimensional distributions of biological particles. The technique involves scanning of a thin plane of laser light through a range of distances parallel to the imaging plane of a digital CCD camera. Images of induced fluorescence in the sequentially illuminated planes are recorded. An inverse method is then used to reconstruct three-dimensional chlorophyll a distributions from the plane images. Computer simulations of the image formation and reconstruction process indicate that the underwater optical serialsectioning technique is practical for in situ determination and analysis of chlorophyll a microstructures for concentrations as low as 0.1 mg of chlorophyll a per cubic meter in 1--m(3) water volumes.     

Monte Carlo modeling of underwater-image formation: validity of the linear and small-angle approximations

A Monte Carlo model has been used to compute a set of point-spread functions (PSF's) and modulation transfer functions (MTF's) that determine underwater-image quality in a range of different environments. The results have been used to analyze the range of application under which a linear-approximation theory holds. Conclusions of the study are that the linear-approximation theory Seems to hold quite well over a broad range of applications. The ramifications of the Wells small-angle-scattering theory that predicts the PSF from a knowledge of the volume-scattering function (VSF) are also considered.

Discrepancies are noted between a predicted and a computationally obtained MTF; these discrepancies increase with range. Therefore, the results of the simulations indicate that the small-angle-scattering theory is more valid at a limited number of attenuation lengths. The results of the simulations indicate that the theory is valid to approximately three attenuation lengths.

     

Lecture to american college of radiology

Image processing applied to medicine is more constrained than in other fields. Lacking means of verification, as is often the case, it is difficult to judge what constitutes a success or how the ideal image should look. Most successful processing efforts to date have been directed at correcting distortions introduced by shortcomings in the imaging equipment itself or methods for filling in missing data sets. Some important headway has been made in processing which is directed at providing a better match to human visual psychophysics particularly in matrix images. The greatest future opportunities appear to lie in image integration of several different imaging modalities of the same body part and utilization of a priori information as a factor in image formation.     

Fermi liquid viscosity in a finite geometry

Forced flow of a Fermi liquid is studied for a cell geometry consisting of two planes with a separation on the order of the mean free path. An approximate transport equation is used to derive an integral equation for the velocity profile, which is solved numerically. Results for the total flux through the cell, which determines the dissipation, are given as a function of the Knudsen number (ratio of cell thickness to mean free path.) Effects of specular reflection at the boundaries are considered. It is found that the dissipation has a minimum at 1/2, and behaves linearly for 3. Implications for present experimentation are discussed.This work was supported in part by the National Aeronautics and Space Administration through grant no. NGR-33-010-188 and the National Science Foundation through grant No. DMR-77-18329.     

Measurement of total acid number (TAN) and TAN boiling point distribution in petroleum products by electrospray ionization mass spectrometry

We report a new method for rapid measurement of total acid number (TAN) and TAN boiling point (BP) distribution for petroleum crude and products. The technology is based on negative ion electrospray ionization mass spectrometry (ESI-MS) for selective ionization of petroleum acid and quantification of acid structures and molecular weight distributions. A chip-based nanoelectrospray system enables microscale (<200 mg) and higher throughput (20 samples/h) measurement. Naphthenic acid structures were assigned based on nominal masses of a set of predefined acid structures. Stearic acid is used as an internal standard to calibrate ESI-MS response factors for quantification purposes. With the use of structure-property correlations, boiling point distributions of TAN values can be calculated from the composition. The rapid measurement of TAN BP distributions by ESI is demonstrated for a series of high-TAN crudes and distillation cuts. TAN values determined by the technique agree well with those by the titration method. The distributed properties compare favorably with those measured by distillation and measurement of TAN of corresponding cuts.