Brush-like fibers on the human chromosome periphery

A brush-like border apparently composed of fibers protruding from metaphase chromosomes of human lymphocytes was observed for the first time using transmission (TEM) and scanning electron microscopy (SEM). On the basis of size and sensitivity to colcemid, the fibers may be related to microtubules and spindle organization. The brush-like fibers were observed when chemically fixed metaphase chromosome spreads were placed on glass slides and maintained under "wet" conditions (not allowed to air dry after fixation for conventional cytogenetic protocols) until postfixation protocols for TEM and SEM were performed. The purpose of this study was to establish the occurrence of the brush-like fibers and to determine the effects of colcemid on these fibers.     

Autonomous over-the-horizon navigation using LIDAR data

In this paper we present the approach for autonomous planetary exploration developed at the Canadian Space Agency. The goal of this work is to enable autonomous navigation to remote locations, well beyond the sensing horizon of the rover, with minimal interaction with a human operator. We employ LIDAR range sensors due to their accuracy, long range and robustness in the harsh lighting conditions of space. Irregular Triangular Meshes (ITMs) are used for representing the environment, providing an accurate, yet compact, spatial representation. In this paper a novel path-planning technique through the ITM is introduced, which guides the rover through flat terrain and safely away from obstacles. Experiments performed in CSA’s Mars emulation terrain, validating our approach, are also presented.     

Quantifying stochastic error propagation in Bayesian parametric estimates using non-linear parameters of Anopheles gambiae s.l. habitats

Reliable models of the transmission intensity of malaria, based on vector mosquito aquatic habitat larval productivity, are urgently needed, especially in endemic areas of Sub-Saharan Africa (SSA). Such models are fundamental for estimating the scale of the problem, and, hence, the resources needed to combat malaria in urban environments. These models also provide benchmarks for assessing the progress of control and indicate the geographical regions that should be prioritized. In this research, individual urban aquatic habitats of Anopheles gambiae s.l., a major malaria vector in SSA, were examined in terms of their spatial covariations by modelling ecologically sampled predictor variables within a Bayesian framework. Field sampling was conducted in two urban environments in Kenya, from July 2005 to December 2006. QuickBird satellite data, encompassing visible and near-infrared (NIR) bands, were selected to synthesize images of An. gambiae s.l. aquatic habitats. Statistical Analysis Software (SAS) was used to explore univariate statistics, correlations and distributions, and to perform Poisson regression analyses. These preliminary tests showed good type I error control mechanisms and precise parameter estimates. The model coefficients were then used to define expectations for prior distributions in a Markov chain Monte Carlo (MCMC) analysis. By specifying coefficient estimates in a Bayesian framework, depth of habitat was found to be a significant predictor, positively associated with urban An. gambiae s.l. aquatic habitats. There was no significant autocorrelation present in either the residual error or the predictor variable depth of habitat.     

Dynamic portfolio choice: a simulation-and-regression approach

Simulation-and-regression algorithms have become a standard tool for solving dynamic programs in many areas, in particular financial engineering and computational economics. In virtually all cases, the regression is performed on the state variables, for example on current market prices. However, it is possible to regress on decision variables as well, and this opens up new possibilities. We present numerical evidence of the performance of such an algorithm, in the context of dynamic portfolio choices in discrete-time (and thus incomplete) markets. The problem is fundamentally the one considered in some recent papers that also use simulations and/or regressions: discrete time, multi-period reallocation, and maximization of terminal utility. In contrast to that literature, we regress on decision variables and we do not rely on Taylor expansions nor derivatives of the utility function. Only basic tools are used, bundled in a dynamic programming framework: simulations—which can be black-boxed—as a representation of exogenous state variable dynamics; regression surfaces, as non-anticipative representations of expected future utility; and nonlinear or quadratic optimization, to identify the best portfolio choice at each time step. The resulting approach is simple, highly flexible and offers good performance in time and precision.     

Do Images of Biskyrmions Show Type‐II Bubbles?

The intense research effort investigating magnetic skyrmions and their applications for spintronics has yielded reports of more exotic objects including the biskyrmion, which consists of a bound pair of counter‐rotating vortices of magnetization. Biskyrmions have been identified only from transmission electron microscopy images and have not been observed by other techniques, nor seen in simulations carried out under realistic conditions. Here, quantitative Lorentz transmission electron microscopy, X‐ray holography, and micromagnetic simulations are combined to search for biskyrmions in MnNiGa, a material in which they have been reported. Only type‐I and type‐II magnetic bubbles are found and images purported to show biskyrmions can be explained as type‐II bubbles viewed at an angle to their axes. It is not the magnetization but the magnetic flux density resulting from this object that forms the counter‐rotating vortices.     

Visual stimulation facilitates penile responses to vibration in men with and without erectile disorder.

This study compared reflexogenic and psychogenic penile responses in men with and without erectile disorder. It was hypothesized that men with psychogenic erectile dysfunction respond minimally to vibrotactile stimulation. An enhancement of penile responses was expected when vibration was combined with erotic film. Patients were 50 men with psychogenic erectile dysfunction, 45 men with organic erectile dysfunction, and 50 sexually functional men. The combination of film and vibration resulted in stronger penile responses than the stimuli presented separately. Men with psychogenic erectile dysfunction and sexually functional men did not differ in responses to film and film-and-vibration conditions. As predicted, responses of the 2 groups were different in the vibration condition. Interpretations are provided in terms of attention and appraisal. The findings are relevant to the development of psychophysiological diagnostic procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Order statistics and selection methods of evolutionary algorithms

Selection methods are essential components of evolutionary algorithms (EAs). This paper reviews five popular selection methods used in EAs. The algorithms are examined using the cumulants of the fitness distribution of the selected individuals. The cumulants are calculated using order statistics. The method presented here considers finite populations of arbitrary size. The results show important differences among the selection methods considered, even when they are configured to have the same selection intensity.     

Optimum design of a parallel robot using neuro-genetic algorithm

Journal of Mechanical Science and Technology - There are some advantages of parallel robots over serial ones, such as strong structure, big payload ratio with respect to the weight, and good...