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31.
Feedback phenomenon in laser diodes is applied to low-frequency vibration measurement in the micrometer range on poorly reflecting targets. The laser diode is frequency modulated. Its beam is focused on the vibrating target, and backscattered light is fed back into the laser. The optical laser diode power variation is processed to measure the frequency and amplitude of low-frequency vibrations of amplitude, ~100 nm to 10 mum. Experimental results for sinusoidal and triangular vibrations are compared with theory. 相似文献
32.
Moez Guettari Adel Aschi Riadh Gomati Abdelhafidh Gharbi 《Materials science & engineering. C, Materials for biological applications》2008,28(5-6):811-815
The present work is aimed at studying the thermodynamic behaviour of a polymer in solvents mixture. Dynamic light scattering is used to measure the hydrodynamic radius of polyvinylpyrrolidone (Mw = 360,000 g/mol), in water/methanol solvents mixture, versus the mixed solvents composition at 25 °C. Then, we show that the polymer conformation adopts the Coil–Globule–Coil structure when the methanol molar fraction XA is varied. This transition is attributed to solvent quality change which result from water and methanol complex formation. The polymer contraction rate calculated for each composition takes its maximum value at XA = 0.17. Hildebrand theory assuming the solvents mixture as an equivalent solvent was used to analyze the change in mixed solvents quality. These changes can be attributed to dispersive forces in solvents mixture. 相似文献
33.
Through the variation of their cross sections, the in vivo response of lower back muscles to low loading in an upright seated posture is explored by the Fourier-transform profilometry technique. The maximization of its sensitivity allows us to reach an adequate resolution for the evaluation of low-back displacements. Refinements of the fringe pattern analysis permit the minimization of errors. The experiments show an asymmetric distribution of the displacement during head rotation movements. Significant contribution of the lower back to grasping exertions is also observed. These results are thought to be useful for early defect detection in the lower back. 相似文献
34.
In the present work, we report the effects of C(60)-pretreatments on acute carbon tetrachloride intoxication in rats, a classical model for studying free-radical-mediated liver injury. Our results show that aqueous C(60) suspensions prepared without using any polar organic solvent not only have no acute or subacute toxicity in rodents but they also protect their livers in a dose-dependent manner against free-radical damage. To be sure, according to histopathological examinations and biological tests, pristine C(60) can be considered as a powerful liver-protective agent. 相似文献
35.
Nano-Micro Letters - α-MoO3 ordered nanosheets have been synthesized under hydrothermal conditions using commercial MoO3 and hydroquinone as structuring agent. X-ray diffraction (XRD),... 相似文献
36.
Reversible hydration of amorphous V2O5 has been performed in order to study the effect of water upon the properties of the oxide. A drastic change of the ESR spectrum is observed, which turns from anisotropic to isotropic upon hydration. This has been interpreted in terms of a brownian motion which, by analogy with the V2O5 gels, is supposed to be due to the fibrous texture of the amorphous oxide. 相似文献
37.
38.
L Traissac F Darrouzet F Gharbi PJ Monteyrol D Portmann F Gharbi P Noyon P Vincey 《Canadian Metallurgical Quarterly》1997,118(5):353-358
1. Maintenance of phosphate homeostasis is essential for energy producing and oxygen delivery systems, particularly, when the energy requirements are increased in certain conditions, such as septicaemia. We investigated the phosphaturic response to parathyroid hormone (PTH) in endotoxin (ETx)-treated rats in order to clarify the renal regulation of phosphate excretion during endotoxaemia. 2. Wistar rats that had undergone thyroparathyroidectomy were challenged with either Escherichia coli ETx (n = 8) or saline vehicle (n = 9). Thirty-minute renal clearance tests were done before and after PTH infusion. Rats infused with saline instead of PTH served as time controls for the ETx- (n = 7) and saline-treated (n = 8) rats. 3. In time control rats, ETx administration enhanced phosphate excretion progressively and this was associated with an obvious increase in the level of kidney adenosine 3', 5'-cyclic mono-phosphate (P < 0.005) compared with levels following saline vehicle administration. However, this phosphaturia in late-phase endotoxaemia was not observed in rats infused with PTH; ETx, but not saline vehicle, blunted the PTH-mediated increase in phosphate excretion (P < 0.005). Increased urinary noradrenaline and constant dopamine excretion were observed in endotoxaemic rats. Endotoxin administration produced marked metabolic acidosis and hypocapnia in comparison with the administration of the saline vehicle. 4. To test whether renal tubular sensitivity to parathyroid hormone related-protein (PTHrP) was enhanced during endotoxaemia, phosphaturic response to PTHrP in ETx- (n = 7) and saline-treated rats (n = 7) was examined. Parathyroid hormone related-protein infusion produced phosphaturia in both groups. However, the severity of the phosphaturia after PTHrP infusion was less in ETx-than in saline-treated rats. 5. In summary, although ETx administration causes a progressive increase in phosphate excretion in the absence of PTH, this is overcome by the antiphosphaturic effect of ETx, attenuating PTH-mediated phosphaturia after PTH infusion. 相似文献
39.
F. Gharbi S. Sghaier K. J. Al-Fadhalah T. Benameur 《Journal of Materials Engineering and Performance》2011,20(6):903-910
A newly developed ball burnishing tool was designed and tested for surface finishing of large flat surfaces in a shortest
possible time. Optimization and analysis of the burnishing process were carried on AISI 1010 steel hot-rolled plates using
the Taguchi technique and response surface methodology (RSM) to identify the effect of burnishing parameters (i.e., burnishing
speed, burnishing force, and feed rate) on surface roughness, surface hardness, and microstructure of burnished surfaces.
The optimal burnishing parameters were found after conducting the Taguchi’s L25 matrix experiments and obtaining the response models for the surface roughness and the hardness. It was found that the burnishing
force has the most influential effect on the surface roughness and hardness, followed by the burnishing speed, and least influence
by the feed rate. In addition, microstructural examinations of the burnished surface indicate that burnishing force more than
400 N causes flaking of the burnished surfaces. The optimal burnishing parameters for the steel plates were a combination
of a burnishing speed of 235 rpm, a burnishing force of 400 N, and a feed rate of 0.18 mm/rev. Using these parameters, the
mean surface roughness has been improved from Ra = 2.48 to 1.75 μm, while the hardness increases from 59 to 65.5 HRB. 相似文献
40.
Adel Aschi Abdelhafidh Gharbi Mohamed Daoud Roger Douillard Patrick Calmettes 《Polymer International》2007,56(5):606-612
Structures of β‐casein formed in water with various concentrations of guanidine hydrochloride (GdmCl) were studied by small‐angle neutron scattering (SANS). A transition in structure and properties of the protein seems to occur around a GdmCl concentration of 1.2 mol L?1. The data are interpreted assuming that the protein molecules behave like multi‐block copolymers with alternating hydrophilic and hydrophobic sequences. Below the transition, the protein structure is still native and has a fractal dimension larger than that beyond the transition where the β‐casein has the feature of a three‐dimensional excluded‐volume coil. A possible interpretation of these results is that the presence of salt increases the value of the critical micelle concentration. This allows a comparison of the structure of β‐casein and synthetic macromolecules. We find that, although the protein is short, excluded‐volume interactions between monomers are present, and that the structure of β‐casein is very similar to what was found in dilute solutions of linear polymers in a good solvent. Thus, it is reasonable to assume that above the critical salt concentration, the protein is completely isolated, whereas below, some structure remains present. Copyright © 2006 Society of Chemical Industry 相似文献