A simplified Time Reversal method used to localize vibrations sources in a complex structure

The main issue while dealing with problems due to structural vibrations is the identification of the sources that create annoyance. One of the experimental processes that permit to tackle this reverse problem uses Time Reversal method to localize the origin of the vibration detected on the surface of a structure.The Time Reversal experiment is based on a principle of time symmetry of waves propagation in a media. Using transceivers located on the structure, one can record its state of vibration. If all the signals recorded by the transceivers are reversed in time and reemitted from the position where they have been recorded, the resulting vibration will converge back to the point where it was originally emitted. In the standard approach, localization is observed both in time and space. We propose here a simplified localization process based on space localization only. We will apply this method on a complex industrial structure, stimulated with bursts. We shall show in the article the influence of certain parameters such as the number of transceivers or the structure complexity. Finally, all the tests presented hereby will allow us showing that the Time Reversal method is a very efficient and very easy to use method.     

New highly sensitive rodent and human tests for soluble amyloid precursor protein alpha quantification: preclinical and clinical applications in Alzheimer’s disease

Background

Exposure to ethanol during early development triggers severe neuronal death by activating multiple stress pathways and causes neurological disorders, such as fetal alcohol effects or fetal alcohol syndrome. This study investigated the effect of ethanol on intracellular events that predispose developing neurons for apoptosis via calcium-mediated signaling. Although the underlying molecular mechanisms of ethanol neurotoxicity are not completely determined, mitochondrial dysfunction, altered calcium homeostasis and apoptosis-related proteins have been implicated in ethanol neurotoxicity. The present study was designed to evaluate the neuroprotective mechanisms of metformin (Met) and thymoquinone (TQ) during ethanol toxicity in rat prenatal cortical neurons at gestational day (GD) 17.5.

Results

We found that Met and TQ, separately and synergistically, increased cell viability after ethanol (100 mM) exposure for 12 hours and attenuated the elevation of cytosolic free calcium [Ca²⁺]_c. Furthermore, Met and TQ maintained normal physiological mitochondrial transmembrane potential (????_M), which is typically lowered by ethanol exposure. Increased cytosolic free [Ca²⁺]_c and lowered mitochondrial transmembrane potential after ethanol exposure significantly decreased the expression of a key anti-apoptotic protein (Bcl-2), increased expression of Bax, and stimulated the release of cytochrome-c from mitochondria. Met and TQ treatment inhibited the apoptotic cascade by increasing Bcl-2 expression. These compounds also repressed the activation of caspase-9 and caspase-3 and reduced the cleavage of PARP-1. Morphological conformation of cell death was assessed by TUNEL, Fluoro-Jade-B, and PI staining. These staining methods demonstrated more cell death after ethanol treatment, while Met, TQ or Met plus TQ prevented ethanol-induced apoptotic cell death.

Conclusion

These findings suggested that Met and TQ are strong protective agents against ethanol-induced neuronal apoptosis in primary rat cortical neurons. The collective data demonstrated that Met and TQ have the potential to ameliorate ethanol neurotoxicity and revealed a possible protective target mechanism for the damaging effects of ethanol during early brain development.     

Etude par resonance magnetique nucleaire de composes organiques contenant des chalcogenes: Partie IV. Le disulfure de diphényle et ses analogues sélénié et telluré

NMR measurements (¹H, ¹³C, ⁷⁷Se) of diphenyl dichalcogenides are reported. They confirm the molecular conformation deduced from other physical experiments. Steric inhibitions are responsible for the conformation in the Te compound, while, in the S and Se compounds, the heteroatom lone pairs interact to some extent with the π systems of the rings.More fundamental discussions of the measured parameters are made, including the somewhat controversial existence of the title compounds in solution.