Resolvability theory for the multiple-access channel

We study the randomness needed for approximating the output distribution of a multiple-access channel, where the original input processes are independent of each other. The approximation is achieved by simulating (possibly alternative) input processes at each of the entries, where the sources of randomness available for the simulators are independent of each other, and the simulators do not cooperate. The resolvability region of a multiple-access channel is defined as the set of all random-bit rate pairs at which accurate output approximation is possible, where the simulation accuracy is measured by the variational distance between finite-dimensional output distributions. Inner and outer bounds on the resolvability region are derived, and close relations between the concepts of resolvability region and capacity region are demonstrated     

Sequential amplitude estimation in multiuser communications

Considers the problem of multiuser amplitude estimation, i.e., the problem of estimating the amplitudes of several digital communications signals superimposed in the same channel. This problem is of importance in communications environments such as spread-spectrum radio networks, in which nonorthogonal multiplexing is used. Multiuser amplitude estimation is a critical prerequisite to the optimum demodulation of such signals using, for example, Verdu's algorithm. In the present paper, a sequential detection-estimation approach is applied to this problem, and several estimation paradigms, including the method of moments and likelihood-based estimators, are considered. The consistency, asymptotic variance, and complexity of these estimators are examined. A new method of constructing a recursive consistent and asymptotically efficient estimation algorithm out of a consistent estimator sequence is also suggested and is applied to the current setup. It is seen that detector-estimators that use these estimators in Verdu's algorithm result, asymptotically, in (known-amplitude) optimum error probabilities with little relative increase in complexity per demodulated bit     

Multifactorial assessment of bulimia nervosa.

Investigated a multifactorial approach to the assessment of bulimia nervosa by means of hierarchical factor analysis. 245 bulimia nervosa patients and 68 patients with either anorexia nervosa or eating disorders not otherwise specified were administered a self-report battery that was organized into 21 dimensions relevant to eating disorder patients. When dimensions from this battery were subjected to hierarchical factor analysis, support for bulimia nervosa as a unique diagnostic category was obtained. However, the emergence of 3 secondary factors and 6 primary factors suggests that bulimia nervosa can also be described more complexly. The emergence of a multifactorial model of bulimia nervosa that incorporates several existing unidimensional models suggests the potential for both divergent and complicated clinical presentation in bulimia nervosa patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiological phosphorylation of protein kinase A at Thr-197 is by a protein kinase A kinase

Phosphorylation of the catalytic subunit of cyclic AMP-dependent protein kinase, or protein kinase A, on Thr-197 is required for optimal enzyme activity, and enzyme isolated from either animal sources or bacterial expression strains is found phosphorylated at this site. Autophosphorylation of Thr-197 occurs in Escherichia coli and in vitro but is an inefficient intermolecular reaction catalyzed primarily by active, previously phosphorylated molecules. In contrast, the Thr-197 phosphorylation of newly synthesized protein kinase A in intact S49 mouse lymphoma cells is both efficient and insensitive to activators or inhibitors of intracellular protein kinase A. Using [35S]methionine-labeled, nonphosphorylated, recombinant catalytic subunit as the substrate in a gel mobility shift assay, we have identified an activity in extracts of protein kinase A-deficient S49 cells that phosphorylates catalytic subunit on Thr-197. The protein kinase A kinase activity partially purified by anion-exchange and hydroxylapatite chromatography is an efficient catalyst of protein kinase A phosphorylation in terms of both a low Km for ATP and a rapid time course. Phosphorylation of wild-type catalytic subunit by the kinase kinase activates the subunit for binding to a pseudosubstrate peptide inhibitor of protein kinase A. By both the gel shift assay and a [gamma-32P]ATP incorporation assay, the enzyme is active on wild-type catalytic subunit and on an inactive mutant with Met substituted for Lys-72 but inactive on a mutant with Ala substituted for Thr-197. Combined with the results from mutant subunits, phosphoamino acid analysis suggests that the enzyme is specific for phosphorylation of Thr-197.     

Latchkey children and susceptibility to peer pressure: An ecological analysis.

Data on adolescents' after-school experiences and their susceptibility to peer pressure were derived from surveys administered to a heterogeneous sample of 865 adolescents in Grades 5–9. Consistent with the findings of previous studies, the results show that Ss who reported home after school were not significantly different from those who were supervised by their parents at home during after-school hours. However, when a 2nd sample of latchkey children (n?=?594) was studied to include greater variation in after-school experiences, Ss who were more removed from adult supervision were found to be more susceptible to peer pressure to engage in antisocial activity. Ss who were home alone were less susceptible to peer pressure than are those who were at a friend's house after school, and those who were at a friend's house, in turn, were less susceptible than were those who describe themselves as "hanging out." Moreover, latchkey Ss whose parents knew their whereabouts and those who had been raised authoritatively were less susceptible to peer influence than were their peers, even if their afternoons were spent in contexts in which adult supervision was lax and susceptibility to peer pressure was generally high. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Function of sulfur dioxide in the kinetic mechanism of oxidation of carbon

Retardation of the gasification reaction of carbon with oxygen by SO₂ was observed. Rates of oxidation were determined by thermal gravimetric analysis (TGA) of a nuclear graphite in the temperature range of 550–700°C, and of a coconut charcoal in the temperature range of 400–505°C. The oxidant gases were dry air containing 0–6% SO₂. Reduction of the rate by SO₂ varied with burn-off. Differential thermal analysis (DTA) was also applied to detect the retardation effect of SO₂. The technique of infrared internal reflection spectroscopy (IRS) was used to examine the surface species of reacted charcoal samples. Absorption bands were assigned to surface carbonyls, lactones, and a chemisorbed SO₂ in the form of sulfate. Chemisorption of SO₂ was attributed to cause the retardation of the oxidation reaction.     

Computing integrals over polynomially defined regions and their boundaries in 2 and 3 dimensions

We use the cylindrical algebraic decomposition algorithms implemented in Mathematica to produce procedures to analytically compute integrals over polynomially defined regions and their boundaries in two and three dimensions. Using these results, we can implement the divergence theorem in three dimensions or the Green's theorems in two dimensions. These theorems are of central importance in the applications of multidimensional integration. They also provide a strong correctness test for the implementation of our results in a computer algebra system. The resulting software can solve many of the two and some of the three dimensional integration problems in vector calculus textbooks. The three dimensional results are being extended. The results in this paper are being included in an automated student assistant for vector calculus.