Room-Temperature Solid-Matrix Luminescence Spectroscopy of Pyrene and 1-Hydroxypyrene from Optically Clear Sugar Glasses

Room-temperature solid-matrix luminescence was investigated for two model compounds pyrene and 1-hydroxypyrene from optically clear sugar glasses. Several glasses were investigated. Novel glasses were prepared for the first time from binary mixtures of sugars for spectroscopy. Glasses were prepared from glucose/xylose and glucose/maltose. The glucose/maltose gave a superior glass compared to glucose/xylose. The glucose/maltose glass gave the best room temperature phosphorescence (RTP) for pyrene compared to glasses of glucose and maltose without a heavy atom. The RTP was weak for both pyrene and 1-hydroxypyrene without a heavy atom in the glucose glass. The addition of a heavy atom (12% NaI) gave a 44-fold increase in RTP of pyrene and a 10-fold increase in the RTP of 1-hydroxypyrene. Room temperature fluorescence (RTF) of pyrene and 1-hydroxypyrene were easily observed from all the glass systems studied. However, the pyrene RTF intensity varied with the different sugar glass systems studied. Furthermore, a polymer, polyacrylic acid (PAA), was added to the sugar matrix at the level of 1% and 2% to improve the rigidity of the glass matrix. The observed phosphorescence was weak for pyrene at both the 1% and 2% PAA concentrations. A glass prepared with 2% PAA gave the strongest RTP for pyrene. Addition of 12% NaI with 1% polyacrylic acid did improve the RTP of pyrene but it was less than the RTP of pyrene from a glucose glass with 12% NaI by a factor of 2.7. A glucose glass with 12% NaI was the best system for RTP of pyrene.     

Evolutionary events in a mathematical sciences research collaboration network

This study examines long-term trends and shifting behavior in the collaboration network of mathematics literature, using a subset of data from Mathematical Reviews spanning 1985–2009. Rather than modeling the network cumulatively, this study traces the evolution of the “here and now” using fixed-duration sliding windows. The analysis uses a suite of common network diagnostics, including the distributions of degrees, distances, and clustering, to track network structure. Several random models that call these diagnostics as parameters help tease them apart as factors from the values of others. Some behaviors are consistent over the entire interval, but most diagnostics indicate that the network’s structural evolution is dominated by occasional dramatic shifts in otherwise steady trends. These behaviors are not distributed evenly across the network; stark differences in evolution can be observed between two major subnetworks, loosely thought of as “pure” and “applied”, which approximately partition the aggregate. The paper characterizes two major events along the mathematics network trajectory and discusses possible explanatory factors.     

Seeing versus imagining movement in depth.

Six undergraduate students participated in 2 experiments to determine whether the same mechanisms are activated during perception of real vs apparent motion. In Exp 1, Ss judged the quality of rigid motion between pairs of 3-dimensional drawings that differed by a rotation in depth. Rated quality of motion decreased with increasing angular disparity between the figures and with decreasing stimulus duration, regardless of whether the figures were vertical or oblique. In Exp 2, Ss participated in a mental rotation task using the same stimuli and angular disparities. Ss took longer to make decisions about obliquely aligned than vertically aligned stimuli. Results imply that perceived vs imagined movement through the same trajectory involves different processes. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rising verbal intelligence scores: Implications for research and clinical practice.

Evidence suggests that scores on various intelligence tests have been rising at a fast rate. To find out whether performance on the Wechsler Adult Intelligence Scale (WAIS) Vocabulary subtest has also been rising, the authors searched major psychology journals for investigations involving healthy younger and older adult participants and collected the reported WAIS Vocabulary scores. The meta-analysis shows that WAIS Vocabulary scores have been rising at the rate of 0.117/year (corresponding to 1.52 IQ points/decade) for younger adults and 0.367/year (corresponding to 4.79 IQ points/decade) for older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A primal-dual interior point method for optimal power flow dispatching

In this paper, the solution of the optimal power flow dispatching (OPFD) problem by a primal-dual interior point method is considered. Several primal-dual methods for optimal power flow (OPF) have been suggested, all of which are essentially direct extensions of primal-dual methods for linear programming. The aim of the present work is to enhance convergence through two modifications: a filter technique to guide the choice of the step length and an altered search direction in order to avoid convergence to a nonminimizing stationary point. A reduction in computational time is also gained through solving a positive definite matrix for the search direction. Numerical tests on standard IEEE systems and on a realistic network are very encouraging and show that the new algorithm converges where other algorithms fail.     

Preemptive and delay-based mechanisms to provide preference to emergency traffic

Preemptive and delay-based policies are derived here to provide preferential treatment to emergency users as motivated by the need to respond to natural or man-made disasters. These are applied in circuit switched networks or IP-based networks in conjunction with reservation mechanisms at single links or routers where congestion occurs. A unique optimization formulation is provided where policies are constrained by blocking requirements for emergency traffic, then optimized to provide lowest preemption probabilities. An iterative optimization approach is derived for a multi-dimensional Markov chain to provide an approximate solution for a non-linear integer program. Markov state space concerns are mitigated by introducing and analyzing algorithmic simplifications. Polices are found for hard preemption where sessions are interrupted or soft preemption where session quality is reduced. In addition, delay-based approaches are also examined where emergency users are allowed to wait for network resources if they are first blocked. All of the above approaches are compared with each other and with traditional approaches that hold back resources for emergency traffic. The results demonstrate that in general no approach is superior based on network performance characteristics alone. Qualitative factors must also be considered, most notably the nuisance to non-emergency users from preemption.     

Bim: a novel member of the Bcl-2 family that promotes apoptosis

Certain members of the Bcl-2 family inhibit apoptosis while others facilitate this physiological process of cell death. An expression screen for proteins that bind to Bcl-2 yielded a small novel protein, denoted Bim, whose only similarity to any known protein is the short (nine amino acid) BH3 motif shared by most Bcl-2 homologues. Bim provokes apoptosis, and the BH3 region is required for Bcl-2 binding and for most of its cytotoxicity. Like Bcl-2, Bim possesses a hydrophobic C-terminus and localizes to intracytoplasmic membranes. Three Bim isoforms, probably generated by alternative splicing, all induce apoptosis, the shortest being the most potent. Wild-type Bcl-2 associates with Bim in vivo and modulates its death function, whereas Bcl-2 mutants that lack survival function do neither. Significantly, Bcl-xL and Bcl-w, the two closest homologues of Bcl-2, also bind to Bim and inhibit its activity, but more distant viral homologues, adenovirus E1B19K and Epstein-Barr virus BHRF-1, can do neither. Hence, Bim appears to act as a 'death ligand' which can only neutralize certain members of the pro-survival Bcl-2 sub-family.     

Capillary driven flow along interior corners formed by planar walls of varying wettability

Closed-form analytic solutions useful for the design of capillary flows in a variety of containers possessing interior corners were recently collected and reviewed. Low-g drop tower and aircraft experiments performed at NASA to date show excellent agreement between theory and experiment for perfectly wetting fluids. The analytical expressions are general in terms of contact angle, but do not account for variations in contact angle between the various surfaces within the system. Such conditions may be desirable for capillary containment or to compute the behavior of capillary corner flows in containers consisting of different materials with widely varying wetting characteristics. A simple coordinate rotation is employed to recast the governing system of equations for flows in containers with interior corners with differing contact angles on the faces of the corner. The result is that a large number of capillary driven corner flows may be predicted with only slightly modified geometric functions dependent on corner angle and the two (or more) contact angles of the system. A numerical solution is employed to verify the new problem formulation. The benchmarked computations support the use of the existing theoretical approach to geometries with variable wettability. Simple experiments may be performed to confirm the theoretical findings. Favorable agreement between such experiments and the present theory may argue well for the extension of the analytic results to predict fluid performance in future large length scale capillary fluid systems for spacecraft as well as for small scale capillary systems on Earth.     

Rigorous and approximate solutions for the three-conductor lossy transmission lines problem

The coupled first-order linear differential equations governing the voltage and the current on three-conductor lossy (identical) transmission lines are solved by two methods. One method is rigorous, and the other one is approximate and applies in the low- and high-frequency ranges. Although the rigorous solution is a numerical one, the approximate solution consists of explicit expressions that are easy to calculate and give physical insight into the coupling process. Experimental results that are available for two parallel identical lossy wires of finite length situated above a perfectly conducting ground (when only one of the wires is driven by a source) and previously published theoretical results compare satisfactorily with the results obtained by the two methods.<>