Switching to Directional Antennas with Constant Increase in Radius and Hop Distance

For any angle α<2π, we show that any connected communication graph that is induced by a set P of n transceivers using omni-directional antennas of radius 1, can be replaced by a strongly connected communication graph, in which each transceiver in P is equipped with a directional antenna of angle α and radius r _dir, for some constant r _dir=r _dir(α). Moreover, the new communication graph is a c-spanner of the original graph, for some constant c=c(α), with respect to number of hops.     

A stochastic controller for a scalar linear system with additive Cauchy noise

A stochastic control scheme is developed for scalar, discrete-time, and linear-dynamic systems driven by Cauchy distributed process and measurement noises. When addressing the optimal control problem for such systems, the standard quadratic cost criteria cannot be used. In this study we introduce a new objective function that is functionally similar to the Cauchy probability density function. The performance index, defined as the expectation of this objective function with respect to the Cauchy densities, exists. The dynamic programming solution to the fixed and finite horizon optimal control problem that uses this performance index appears to be intractable. Therefore, a moving horizon optimal model predictive control problem is implemented, for which the conditional expected value of the objective function and its gradients can be computed in closed   form and without assumptions such as certainty equivalence. Numerical results are shown for this m$m$-step model predictive optimal controller and compared to a similar, Linear-Exponential-Gaussian model predictive controller. An essential difference between the Cauchy and Gaussian controllers when applied to a system with Cauchy noises is that, while the Gaussian controller is linear and reacts strongly to all noise pulses, the Cauchy controller can differentiate between measurement and process noise pulses by ignoring the former while responding to the latter. This property of the Cauchy controller occurs when an impulsive measurement noise is more likely than an impulsive process noise. The Cauchy and Gaussian controllers react similarly when applied to a system with Gaussian noises, demonstrating the robustness of the proposed control scheme.     

Compressive system identification: Sequential methods and entropy bounds

In the first part of this work, a novel Kalman filtering-based method is introduced for estimating the coefficients of sparse, or more broadly, compressible autoregressive models using fewer observations than normally required. By virtue of its (unscented) Kalman filter mechanism, the derived method essentially addresses the main difficulties attributed to the underlying estimation problem. In particular, it facilitates sequential processing of observations and is shown to attain a good recovery performance, particularly under substantial deviations from ideal conditions, those which are assumed to hold true by the theory of compressive sensing. In the remaining part of this paper we derive a few information-theoretic bounds pertaining to the problem at hand. The obtained bounds establish the relation between the complexity of the autoregressive process and the attainable estimation accuracy through the use of a novel measure of complexity. This measure is used in this work as a substitute to the generally incomputable restricted isometric property.     

The impact of print exposure quality and inference construction on syllogistic reasoning.

This study extended the work of S. Siddiqui, R. F. West, and K. E. Stanovich (1998), who studied the link between general print exposure and syllogistic reasoning. It was hypothesized that exposure to certain text structures that contain well-delineated logical forms, such as popularized scientific texts, would be a better predictor of deductive reasoning skill than general print exposure, which is not sensitive to the quality of an individual's reading activity. Furthermore, it was predicted that the ability to generate explanatory bridging inferences while reading would also be predictive of syllogistic reasoning. Undergraduate students (N = 112) were tested for vocabulary, nonverbal cognitive ability, exposure to general print, exposure to popularized scientific literature, and the ability to comprehend texts distinguished by the number of inferences that must be generated to support comprehension. Hierarchical multiple regression analyses showed that a combined measure of exposure to general and scientific literature was a significant predictor of syllogistic reasoning ability. Additionally, the ability to comprehend high-inference-load texts was related to solving syllogisms that were inconsistent with world knowledge, indicating an overlap in deductive reasoning skill and text comprehension processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypocomplementemic autosomal recessive hemolytic uremic syndrome with decreased factor H

We describe the clinical course, complement components, and pathological findings of 10 infants with autosomal recessive hemolytic uremic syndrome (HUS). All patients were members of one extended highly inbred Bedouin kindred. The median age of presentation was 2 weeks (range 1-20 weeks). Eight patients died, 2 patients are alive, on dialysis. Renal biopsies revealed thrombotic microangiopathy with a predominant early arteriolar involvement and subsequent development of ischemic glomerular changes. Immunofluorescence was positive for C3 in glomeruli. All patients had low complement components levels during and between relapses, and in some this was evident soon after birth and prior to the onset of symptoms. This deficiency could not be normalized by repeated plasma transfusions. Biosynthetic labelling of patients' fibroblasts demonstrated normal rates of C3 protein synthesis. Serum factor H levels were greatly decreased or absent in 4 patients tested and moderately decreased in 15 of 23 healthy unaffected siblings and patients. This defect may cause complement activation and consumption, possibly at the endothelial cell level.     

Verbal paired-associates learning in chronic schizophrenics as a function of positive and negative evaluation.

Seventy-two chronic schizophrenics (36 regressed and 36 partially remitted) and 36 normals were given paired associates of 2 levels of association strength and 2 levels of intralist response competition to learn under positive, negative, and nonevaluation conditions. Regressed schizophrenics showed maximum decrement on low-association word pairs following positive evaluation. This was especially true for those Ss with low self-esteem. These findings suggest that heightened arousal resulting from dissonance between a negative self-image and positive evaluation of performance can lead to behavioral decrement in a difficult task requiring novel associations, such decrement being congruent with the Hull-Spence behavior theory and the Yerkes-Dodson hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In silico design of small RNA switches

The discovery of natural RNA sensors that respond to a change in the environment by a conformational switch can be utilized for various biotechnological and nanobiotechnological advances. One class of RNA sensors is the riboswitch: an RNA genetic control element that is capable of sensing small molecules, responding to a deviation in ligand concentration with a structural change. Riboswitches are modularly built from smaller components. Computational methods can potentially be utilized in assembling these building block components and offering improvements in the biochemical design process. We describe a computational procedure to design RNA switches from building blocks with favorable properties. To achieve maximal throughput for genetic control purposes, future designer RNA switches can be assembled based on a computerized preprocessing buildup of the constituent domains, namely the aptamer and the expression platform in the case of a synthetic riboswitch. Conformational switching is enabled by the RNA versatility to possess two highly stable states that are energetically close to each other but topologically distinct, separated by an energy barrier between them. Initially, computer simulations can produce a list of short sequences that switch between two conformers when trigerred by point mutations or temperature. The short sequences should possess an additional desirable property; when these selected small RNA switch segments are attached to various aptamers, the ligand binding mechanism should replace the aforementioned event triggers, which will no longer be effective for crossing the energy barrier. In the assembled RNA sequence, energy minimization folding predictions should then show no difference between the folded structure of the entire sequence relative to the folded structure of each of its constituents. Moreover, energy minimization methods applied on the entire sequence could aid at this preprocessing stage by exhibiting high mutational robustness to capture the stability of the formed hairpin in the expression platform. The above computer-assisted assembly procedure together with application specific considerations may further be tailored for therapeutic gene regulation. Index Terms-Design of RNA switches, energy minimization methods, RNA folding predictions.