A new dynamic module for in-situ nanomechanical testing at high strain rate

In-situ nanomechanical testing is commonly used to probe surface mechanical properties of bulk materials or thin films, like hardness, Young’s modulus, Yield stress…Actually most of the instruments can measure these properties only statically, i.e. a low frequency, leading to property measurement only at low strain rate (usually 10-1s-1 by nanoindentation). This is mainly caused by the low resonance frequency of the system, preventing making tests at higher speed. Performing high dynamic measurements could bring new information on materials properties like deformation mechanism at high strain rate, or high dynamic fatigue properties. A new high dynamic module usable for in-situ mechanical testing has been developed. It is composed of a small piezotube attached directly behind the tip. Because of the small dimensions of the module, his resonance frequency is very high (higher than 50kHz) in comparison to classical nanomechanical testers, permitting to perform and measure precisely the signals at very high frequency. Moreover, it can be used as a sensor and as an actuator, in x, y and z directions which gives to this module a very large range of measurements. Firstly, the characteristics, the performances and the limits of the new high dynamic module will be presented. Secondly some indentations experiments performed at high strain rate on nanocrystalline nickel with the in-situ nanomechanical tester (Alemnis Gmbh) equipped with the high dynamic will be presented and discussed (Fig. 1). Finally, some micropillar compression at high strain rate on the same material will be described and discussed

Sodium thiosulfate, a source of hydrogen sulfide, stimulates endothelial cell proliferation and neovascularization.

Therapies to accelerate vascular repair are currently lacking. Pre-clinical studies suggest that hydrogen sulfide (H <sub>2</sub> S), an endogenous gasotransmitter, promotes angiogenesis. Here, we hypothesized that sodium thiosulfate (STS), a clinically relevant source of H <sub>2</sub> S, would stimulate angiogenesis and vascular repair. STS stimulated neovascularization in WT and LDLR receptor knockout mice following hindlimb ischemia as evidenced by increased leg perfusion assessed by laser Doppler imaging, and capillary density in the gastrocnemius muscle. STS also promoted VEGF-dependent angiogenesis in matrigel plugs in vivo and in the chorioallantoic membrane of chick embryos. In vitro, STS and NaHS stimulated human umbilical vein endothelial cell (HUVEC) migration and proliferation. Seahorse experiments further revealed that STS inhibited mitochondrial respiration and promoted glycolysis in HUVEC. The effect of STS on migration and proliferation was glycolysis-dependent. STS probably acts through metabolic reprogramming of endothelial cells toward a more proliferative glycolytic state. These findings may hold broad clinical implications for patients suffering from vascular occlusive diseases

Preferência alimentar de larvas de Heliconius erato phyllis (lepidoptera : nymphalidae) em relação a duas espécies de passifloraceae

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