Working conditions in South Africa since the end of apartheid a comparison between the agricultural, forestry and mining sectors

International audienc

Electrophoretic behavior of streptavidin complexed to a biotinylated probe : A functional screening assay for biotin-binding proteins

The biotin-binding protein streptavidin exhibits a high stability against thermal denaturation, especially when complexed to biotin. Herein we show that, in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), streptavidin is stabilized at high temperature in the presence of biotinylated fluorescent probes, such as biotin-4-fluorescein, which is incorporated within the binding pocket. In nondenaturing SDS-PAGE, streptavidin is detectable when complexed with biotin-4-fluorescein using a UV-transilluminator. Using biotin-4-fluorescein, the detection limit of streptavidin lies in the same range as with Coomassie blue staining. The functionality of streptavidin mutants can readily be assessed from crude bacterial extracts using biotin-4-fluorescein as a probe in nondenaturing SDS-PAGE

Synesthesia improves sensory memory, when perceptual awareness is high

Empirical evidence suggests that synesthesia is associated with enhanced sensory processing. A separate body of empirical literature suggests that synesthesia is linked to a specific profile of enhanced episodic and working memory performance. However, whether sensory (iconic) memory performance is also affected by synesthesia remains unknown. Therefore, we tested 22 grapheme-color synesthetes and compared their performance in a partial-report paradigm with 22 individually matched non-synesthete controls. Participants were briefly presented with a circular-letter array and required to report the identity of the letter at a probed target location after various delays. Furthermore, they were required to indicate the subjective clarity of the target letter after every trial. The results suggest that sensory memory performance is enhanced in synesthesia, but only when subjective clarity of the target letter is high. Additional exploratory analyses revealed that synesthetic consistency, which is widely used to confirm the genuineness of synesthesia, correlated significantly with performance in the partial report paradigm. We conclude that synesthesia does not generally enhance sensory memory performance, but that synesthetic experiences may enhance sensory memory performance when perceptual awareness of the target is high. Furthermore, the stability of synesthetic associations may be linked to sensory memory performance

Quaternion Singular Value Decomposition based on Bidiagonalization to a Real Matrix using Quaternion Householder Transformations

We present a practical and efficient means to compute the singular value decomposition (svd) of a quaternion matrix A based on bidiagonalization of A to a real bidiagonal matrix B using quaternionic Householder transformations. Computation of the svd of B using an existing subroutine library such as lapack provides the singular values of A. The singular vectors of A are obtained trivially from the product of the Householder transformations and the real singular vectors of B. We show in the paper that left and right quaternionic Householder transformations are different because of the noncommutative multiplication of quaternions and we present formulae for computing the Householder vector and matrix in each case

Caractérisation de nouveaux bitumes-caoutchouc

Les polymères ajoutés au bitume font merveille pour accroître les propriétés bénéfiques de ce dernier. Cependant, les coûts élevés de ces polymères poussent les fabricants à chercher de nouveaux matériaux ayant les mêmes propriétés. Dans cette voie, l'entreprise Bitumar Inc. a fabriqué plusieurs bitumes auxquels du caoutchouc provenant de pneus recyclés a été ajouté. Ce projet de maîtrise visait la caractérisation de ces nouveaux bitumes-caoutchouc. D'abord, des travaux de microscopie ont permis l'obtention d'images de bitume polymère comparables à celles qui se retrouvent dans la documentation scientifique. Ces mêmes travaux de microscopie ont par la suite permis de savoir que les fragments de pneu qui ont été ajoutés au bitume ont été désagrégés jusqu'à l'échelle du micron. Puisque ce projet de recherche visait davantage à connaître l'aspect moléculaire des caoutchoucs au sein du bitume, des analyses en chromatographie liquide à haute performance (HPLC) ont été effectuées."--Résumé abrégé par UMI

Weighted eigenfunction estimates with applications to compressed sensing

Using tools from semiclassical analysis, we give weighted L^\infty estimates for eigenfunctions of strictly convex surfaces of revolution. These estimates give rise to new sampling techniques and provide improved bounds on the number of samples necessary for recovering sparse eigenfunction expansions on surfaces of revolution. On the sphere, our estimates imply that any function having an s-sparse expansion in the first N spherical harmonics can be efficiently recovered from its values at m > s N^(1/6) log^4(N) sampling points.Comment: 25 pages, 5 figure

Electrophysiological correlates and psychoacoustic characteristics of hearing-motion synaesthesia

People with hearing-motion synaesthesia experience sounds from moving or changing (e.g. flickering) visual stimuli. This phenomenon may be one of the most common forms of synaesthesia but it has rarely been studied and there are no studies of its neural basis. We screened for this in a sample of 200+ individuals, and estimated a prevalence of 4.2%. We also document its characteristics: it tends to be induced by physically moving stimuli (more so than static stimuli which imply motion or trigger illusory motion); and the psychoacoustic features are simple (e.g. “whooshing”) with some systematic correspondences to vision (e.g. faster movement is higher pitch). We demonstrate using event-related potentials that it emerges from early perceptual processing of vision. The synaesthetes have a higher amplitude motion-evoked N2 (165-185 msec), with some evidence of group differences as early as 55-75 msec. We discuss similarities between hearing-motion synaesthesia and previous observations that visual motion triggers auditory activity in the congenitally deaf. It is possible that both conditions reflect the maintenance of multisensory pathways found in early development that most people lose but can be retained in certain people in response to sensory deprivation (in the deaf) or, in people with normal hearing, as a result of other differences (e.g. genes predisposing to synaesthesia)

Ambulance Crash Characteristics in the US Defined by the Popular Press: A Retrospective Analysis

Ambulance crashes are a significant risk to prehospital care providers, the patients they are carrying, persons in other vehicles, and pedestrians. No uniform national transportation or medical database captures all ambulance crashes in the United States. A website captures many significant ambulance crashes by collecting reports in the popular media (the website is mentioned in the introduction). This report summaries findings from ambulance crashes for the time period of May 1, 2007 to April 30, 2009. Of the 466 crashes examined, 358 resulted in injuries to prehospital personnel, other vehicle occupants, patients being transported in the ambulance, or pedestrians. A total of 982 persons were injured as a result of ambulance crashes during the time period. Prehospital personnel were the most likely to be injured. Provider safety can and should be improved by ambulance vehicle redesign and the development of improved occupant safety restraints. Seventy-nine (79) crashes resulted in fatalities to some member of the same groups listed above. A total of 99 persons were killed in ambulance crashes during the time period. Persons in other vehicles involved in collisions with ambulances were the most likely to die as a result of crashes. In the urban environment, intersections are a particularly dangerous place for ambulances

The ‘Golden Age’ of synesthesia inquiry in the late Nineteenth Century (1876–1895)

Synesthesia is a rare neurological trait that causes unusual, often cross-sensory, experiences (e.g., seeing colors when listening to music). This article traces the history of synesthesia in the period 1876 to 1895. In this period, there was considerable debate over the nature of synesthesia, its causes, and how it should be named. The issue also attracted the leading thinkers of the time and, within a few years, the number of reported cases of synesthesia jumped from around ten to more than 100. For this reason, this period can be regarded as the “golden age” for synesthesia research in the nineteenth century. In this time, scientists debated whether synesthesia was a form of pathology or an alternative manifestation of intelligence. The differing roles of heredity and environment were contested, and there were several explanations proposed as to its neural basis. These enquiries went to the heart of the debate as to whether synesthetic experiences are special in any way or, instead, a more vivid manifestation of a more general capacity for forming associations