MOND rotation curves for spiral galaxies with Cepheid-based distances

Rotation curves for four spiral galaxies with recently determined Cepheid-based distances are reconsidered in terms of modified Newtonian dynamics (MOND). For two of the objects, NGC 2403 and NGC 7331, the rotation curves predicted by MOND are compatible with the observed curves when these galaxies are taken to be at the Cepheid distance. For NGC 3198, the largest distance for which reasonable agreement is obtained is 10% smaller than the Cepheid-based distance; i.e., MOND clearly prefers a smaller distance. This conclusion is unaltered when new near-infrared photometry of NGC 3198 is taken as the tracer of the stellar mass distribution. For the large Sc spiral, NGC 2841, MOND requires a distance which is at least 20% larger than the Cepheid-based distance. However, the discrepancy of the Tully-Fisher and SNIa distances with the Cepheid determination casts some doubt upon the Cepheid method in this case.Comment: Accepted for publication in astronomy and astrophysics 9 pages, 9 figure

Development of design criteria for an electrochemical water reclamation system

Electrochemical system design to recover water from human urin

Radar measurements of the total cislunar electron content technical report no. 8

Radar measurement of total cislunar electron conten

Parental perception of listening difficulties: an interaction between weaknesses in language processing and ability to sustain attention

(Central) auditory processing disorder ((C)APD) is a controversial diagnostic category which may be an artefact of referral route. Yet referral route must, to some extent, be influenced by a child’s profile of presenting symptoms. This study tested the hypothesis that parental perception of listening difficulty is associated with weaknesses in ability to sustain attention while listening to speech. Forty-four children (24 with listening difficulties) detected targets embedded in a 16-minute story. The targets were either mispronunciations or nonsense words. Sentence context was modulated to separate out effects due to deficits in language processing from effects due to deficits in attention. Children with listening difficulties missed more targets than children with typical listening abilities. Both groups of children were initially sensitive to sentence context, but this declined over time in the children with listening difficulties. A report-based measure of language abilities captured the majority of variance in a measure capturing time-related changes in sensitivity to context. Overall, the findings suggest parents perceive children to have listening, not language difficulties, because weaknesses in language processing only emerge when stressed by the additional demands associated with attending to, and processing, speech over extended periods of time

Human gut Bacteroides capture vitamin B12 via cell surface-exposed lipoproteins.

Human gut Bacteroides use surface-exposed lipoproteins to bind and metabolize complex polysaccharides. Although vitamins and other nutrients are also essential for commensal fitness, much less is known about how commensal bacteria compete with each other or the host for these critical resources. Unlike in Escherichia coli, transport loci for vitamin B12 (cobalamin) and other corrinoids in human gut Bacteroides are replete with conserved genes encoding proteins whose functions are unknown. Here we report that one of these proteins, BtuG, is a surface-exposed lipoprotein that is essential for efficient B12 transport in B. thetaiotaomicron. BtuG binds B12 with femtomolar affinity and can remove B12 from intrinsic factor, a critical B12 transport protein in humans. Our studies suggest that Bacteroides use surface-exposed lipoproteins not only for capturing polysaccharides, but also to acquire key vitamins in the gut

Design and fabrication of highly efficient non-linear optical devices for implementing high-speed optical processing

We present the design and fabrication of micro-cavity semiconductor devices for enhanced Two-Photon-Absorption response, and demonstrate the use of these devices for implementing sensitive autocorrelation measurements on pico-second optical pulses

High-sensitivity two-photon absorption microcavity autocorrelator

A GaAs-AlAs microcavity device has been used as a photodetector in an autocorrelator for measuring the temporal pulsewidth of 1.5-/spl mu/m optical pulses. Enhancement of the two-photon absorption photocurrent due to the microcavity structure results in an autocorrelation (average power times peak power) sensitivity of 9.3/spl times/10/sup -4/ (mW)/sup 2/, which represents two orders of magnitude improvement when compared with conventional autocorrelators

Two-photon absorption in microcavities for optical autocorrelation and sampling

We have designed novel semiconductor microcavity structures for the enhancement of the two-photon absorption (TPA) photocurrent. We report a TPA autocorrelation technique for short optical pulses that uses the microcavity structure instead of a second harmonic generation crystal. Knowledge of these characteristics is important for implementation in applications such as optical switching and sampling in optical time division multiplexed (OTDM) communications systems

A novel approach towards two-photon absorption based detectors

Summary: We have demonstrated that the inherent inefficiency of the TPA process in semiconductors can be overcome by incorporating the semiconductor in a microcavity structure. Proof of concept devices with a 0.27μm Ga0.7Al0.3As active region and two Bragg reflectors with the cavity resonance of 890 nm were fabricated. We measured the TPA photocurrent of these devices and have demonstrated a factor of 12000 enhancement over a nonmicrocavity device at 890 nm. Our active length of 0.27 nm is as efficient as 5.4 mm without a microcavity, overcoming the very long detector lengths limiting the use of TPA in practical autocorrelators, optical switches and sampling devices for real telecommunication systems. The effect of the cavity is to enhance the intra-cavity optical intensity, which leads to an increase in the nonlinear response of the active region. We studied, theoretically and experimentally, the impact of the cavity on the temporal response and the sensitivity of the device, which are critical considerations for commercial applications. This cavity design has a 3 pico-second response time and the autocorrelation trace is comparable with the BBO crystal response for an input 1.6 ps pulse. Devices designed for 1550 nm have also been realised and our measurements indicate these two-photon absorption based detectors are potential candidates for optical autocorrelation of short optical pulses, and for optical switching and sampling in optical time division multiplexed (OTDM) communications systems

Contamination Des Laits Importes Au Mali Par La Melamine

Au Mali l’insuffisance de données scientifiques sur la contamination des aliments en général et du lait en particulier par la Mélamine a motivé la conduite de la présente étude.Dans ce travail, nous avions recherchés la Mélamine dans les laits importés au Mali.Un total de 150 échantillons de laits importés, a été récolté dans le District de Bamako.La détermination de la Mélamine a été effectuée par Immuno-affinité/Méthode ELISA. Les résultats des analyses ont montré que 38 échantillons sur les 150 de laits importés étaient contaminés par la Mélamine. Chez les importateurs, 8 échantillons sur 18 des laits importés étaient contaminés, les taux de contamination variaient de 0,03mg/kg à 0,91 mg/kg. Chez les demi-grossistes 19 échantillons sur 66 des laits importés, étaient contaminés par la Mélamine. Les taux de contamination variaient de 0,01 à 1,14mg/kg. Chez les détaillants, 11 échantillons sur 66 des laits importés étaient contaminés avec des taux de contamination qui variaient de 0,01 à 1,00mg/kg. Les taux moyens de contamination des laits pour les importateurs, les demi-grossistes et les détaillants sont respectivement de (0,20 ; 0,26 ; 0,26) mg/kg. Il est a noté que les taux obtenus sont inférieurs à la norme du Codex Alimentarius qui fixe la limite maximale pour le lait et les aliments contenant le lait à 2,5mg/kg