Ergodic properties of computer orbits for simple piecewise monotonic transformations

Using a general model for normalized floating point arithmetic, we study the computer generated orbit of simple piecewise monotonic transformations on [0, 1] of the form τ(x) = kx(mod 1). Conditions under which the computer orbit is eventually exact are established. Moreover it is shown that for sufficiently high precision of computation the computer orbits display the same ergodic properties as the exact orbits of the transformations.     

Clock frequency and latency in synchronous digital systems

The tradeoffs in the design of synchronous digital systems between clock frequency and latency in terms of the circuit characteristics of a pipelined data path are described. A design paradigm relating latency and clock frequency as a function of the level of pipelining is developed for studying the performance of a synchronous system. This perspective permits the development of design equations for constrained and unconstrained design problems which describe these performance parameters in terms of the delays of the logic, interconnect, registers, clock skew, and the number of logic states. These results provide an approach to the design of those synchronous digital systems in which latency and clock frequency are of primary importance. From the behavioral specifications for the proposed system, the designer can use these results to select the best logic architecture and the best available device technology to determine if the performance specifications can be satisfied, and, if so, what design options are available for optimization of other system attributes, such as area     

Sirens, seals, and containers: Reflections on psychotherapy during the 1991 Gulf War.

Presents clinical observations of the impact of the Persian Gulf War on the themes and processes of psychotherapy among a group of Israeli patients. Metaphors of the war period were analyzed in light of contemporary psychoanalytic thinking, with a particular focus on the significance of the sealed room. Issues of the psychotherapeutic technical stance and resistance vs breach in the frame were also addressed, and 2 case vignettes are included. It is concluded that the therapeutic framework is a representational constituent of early experiences pertaining to boundaries, containment, transitionality, and psychic enclosure, and remains sensitive throughout the treatment to vicissitudes of transference or to the reapportionment of psychic space. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

建立基于模型设计文化的最佳策略

本文引入了基于模型设计的概念,突出了其中的一些优点,详细讨论了组织中采用基于模型设计文化的10个最佳策略。这些最佳策略从不同工业领域的公司中收集,包括向基于模型设计的成功或者不成功的过渡。     

Aspects of social and emotional competence in adult attention-deficit/hyperactivity disorder.

Social and emotional competence were evaluated using self-report and behavioral measures in adults with attention-deficit/hyperactivity disorder (ADHD) and controls. Adults with ADHD viewed themselves as less socially competent but more sensitive toward violations of social norms than controls. Films depicting emotional interactions were used to assess linguistic properties of free recall and perceived emotional intensity. Although adults with ADHD used more words to describe the scenes, they used fewer emotion-related words, despite rating the emotions depicted as more intense than did controls. In contrast, no group differences for words depicting social or cognitive processes were observed. Overall, adults with ADHD appear more aware of their problems in social versus emotional skills. Findings may have implications for improving the psychosocial functioning of these adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiplicative Operator Splittings in Nonlinear Diffusion: From Spatial Splitting to Multiple Timesteps

Operator splitting is a powerful concept used in many diversed fields of applied mathematics for the design of effective numerical schemes. Following the success of the additive operator splitting (AOS) in performing an efficient nonlinear diffusion filtering on digital images, we analyze the possibility of using multiplicative operator splittings to process images from different perspectives.We start by examining the potential of using fractional step methods to design a multiplicative operator splitting as an alternative to AOS schemes. By means of a Strang splitting, we attempt to use numerical schemes that are known to be more accurate in linear diffusion processes and apply them on images. Initially we implement the Crank-Nicolson and DuFort-Frankel schemes to diffuse noisy signals in one dimension and devise a simple extrapolation that enables the Crank-Nicolson to be used with high accuracy on these signals. We then combine the Crank-Nicolson in 1D with various multiplicative operator splittings to process images. Based on these ideas we obtain some interesting results. However, from the practical standpoint, due to the computational expenses associated with these schemes and the questionable benefits in applying them to perform nonlinear diffusion filtering when using long timesteps, we conclude that AOS schemes are simple and efficient compared to these alternatives.We then examine the potential utility of using multiple timestep methods combined with AOS schemes, as means to expedite the diffusion process. These methods were developed for molecular dynamics applications and are used efficiently in biomolecular simulations. The idea is to split the forces exerted on atoms into different classes according to their behavior in time, and assign longer timesteps to nonlocal, slowly-varying forces such as the Coulomb and van der Waals interactions, whereas the local forces like bond and angle are treated with smaller timesteps. Multiple timestep integrators can be derived from the Trotter factorization, a decomposition that bears a strong resemblance to a Strang splitting. Both formulations decompose the time propagator into trilateral products to construct multiplicative operator splittings which are second order in time, with the possibility of extending the factorization to higher order expansions. While a Strang splitting is a decomposition across spatial dimensions, where each dimension is subsequently treated with a fractional step, the multiple timestep method is a decomposition across scales. Thus, multiple timestep methods are a realization of the multiplicative operator splitting idea. For certain nonlinear diffusion coefficients with favorable properties, we show that a simple multiple timestep method can improve the diffusion process.     

A novel mutation of presenilin 1 in familial Alzheimer's disease in Israel detected by denaturing gradient gel electrophoresis

Germline mutations in the presenilin 1 (PS1) gene apparently account for the majority of early-onset, familial Alzheimer's disease (AD). Using a mutation-screening strategy (denaturing gradient gel electrophoresis; DGGE), we analyzed a large family with early onset AD and seizures. The patients in this family showed a novel missense mutation in exon 5 of the PS1 gene (A to T change in codon 120, altering glutamine to aspartic acid). This novel mutation is located within the second hydrophilic domain of the molecule, a region not particularly involved in previously described germline mutations, and is of unknown biological significance. These results also demonstrate that DGGE can be used effectively to screen for mutations within this gene.