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121.
Laura Marcu Warren S. Grundfest Jean-Michel I. Maarek 《Photochemistry and photobiology》1999,69(6):713-721
To study the photobleaching of the main fluorescent compounds of the arterial wall, we repeatedly measured the time-resolved fluorescence of elastin, collagen and cholesterol during 560 s of excitation with nitrogen laser pulses. Three fluence rate levels were used: 0.72, 7.25 and 21.75 microW/mm2. The irradiation-related changes of the fluorescence intensity and of the time-resolved fluorescence decay constants were characterized for the emission at 390, 430 and 470 nm. The fluorescence intensity at 390 nm decreased by 25-35% when the fluence delivered was 4 mJ/mm2, a common value in fluorescence studies of the arterial wall. Cholesterol fluorescence photobleached the most, and elastin fluorescence photobleached the least. Photobleaching was most intense at 390 nm and least intense at 470 nm such that the emission spectra of the three compounds were markedly distorted by photobleaching. The time-resolved decay constants and the fluorescence lifetime were not altered by irradiation when the fluence was below 4 mJ/mm2. The spectral distortions associated with photobleaching complicate the interpretation of arterial wall fluorescence in terms of tissue content in elastin, collagen and cholesterol. Use of the time-dependent features of the emission that are not altered by photobleaching should increase the accuracy of arterial wall analysis by fluorescence spectroscopy. 相似文献
122.
Gleb S. Pokrovski Jean-Michel Bény Alexandre V. Zotov 《Journal of solution chemistry》1999,28(12):1307-1327
Solubilities of arsenolite (As2O3, cub.) were measured from 22 to 90°C in water–acetone, water–acetic acid, and water—formic acid solutions of compositions ranging from the pure organic compound to pure water. Raman spectra were obtained at ambient temperature on As-containing water–acetic acid and water–acetone solutions. Results show that arsenic solvation by these organic compounds is negligible and hydroxide species dominate As speciation over a wide range of water activity (aH
2
O> 0.01). The solubility data were analyzed using an approach based on stoichiometric hydration reactions. Results show that As2O3 solubility can be described as a function of water activity, independently of the nature of the organic compound, by involving two neutral As hydroxide complexes: As(OH)3 and As(OH)3·4H2O. Stability constants derived for these species indicate that hydration weakens with increasing temperature. Calculations using these constants show that at low temperatures the tetrahydrate As(OH)3·4H2O is dominant in water-rich solutions; by contrast, in high-temperature crustal fluids, As(OH)3 becomes the major As species. The proposed hydration model can be used to analyze solubility of arsenic-bearing minerals and arsenic transport in complex H2O–CO2—electrolyte solutions encountered in natural and industrial environments. 相似文献
123.
Shunichi Fukuzumi Ikuo Nakanishi Jean-Michel Barbe Roger Guilard Eric Van Caemelbecke Ning Guo Karl M. Kadish 《Angewandte Chemie (International ed. in English)》1999,38(7):964-966
Slow electron transfer to manganese(iii) porphyrins results when the macrocycle deviates from planarity. This was demonstrated by measuring the kinetics of homogeneous electron transfer from a series of semiquinone radical anions to synthetic manganese porphyrins (shown schematically; R1=H, Cl, F; R2=H, F). Three of the four porphyrins studied have nonplanar macrocycles. These results could have implications for the role of manganese in biological electron transfer processes. 相似文献
124.
Jean-Michel Adam Lon Ghosez Kendall N. Houk 《Angewandte Chemie (International ed. in English)》1999,38(18):2728-2730
An asymmetric allylmetalation followed by a silicon-stereodirected cycloaddition gives enantiomerically pure bicyclic compounds. The synthesis of enantiopure 1 (see scheme) in a yield of 65–74 %, 93 % ee, and >98 % de provides an illustration of the efficacy of the method. The preferential formation of 1 rather than its diastereoisomer (32:1), during the cycloaddition step, matches the result predicted by RHF and density functional theory studies. 相似文献
125.
Tasuku Onodera Yusuke Morita Michihisa Koyama Nozomu Hatakeyama Hiromitsu Takaba Momoji Kubo Jean-Michel Martin 《Applied Surface Science》2009,256(4):976-979
We investigated the influence of a nanometer scale film structure of a tribofilm generated from zinc dialkyldithiophosphate (ZDDP) anti-wear additive on its mechanical properties using a combined molecular dynamics (MD) and finite element (FE) method. The frictional behavior of an interface between a native iron oxide layer on steel surface and zinc metaphosphate - regarded as a model material of ZDDP tribofilm - was firstly studied using the MD method. The results showed that the iron atoms in the oxide layer diffused into the phosphate layer during the friction process. The zinc atoms in the phosphate layer also diffused into the oxide layer. Significant interdiffusion of iron and zinc atoms was observed with increasing simulation time. Thus, metallic phosphate with a gradient composition of iron and zinc atoms was formed on the phosphate/oxide interface. We then constructed an axisymmetric nanoindentation simulation model from the MD-derived structures at a certain simulation time and carried out a FE calculation. As a result, we found that the rubbed ZDDP tribofilm, including the phosphate with the gradient composition of metallic atoms, showed larger contact stiffness and hardness. The combined MD/FE simulation indicates that the tribofilm becomes stiffer and harder due to the interdiffusion of iron and zinc atoms on the tribofilm/oxide interface. We have found that the gradient composition formation in ZDDP tribofilm during friction process influences on its mechanical properties. 相似文献
126.
Olivier Horner Sophie Neveu Sophie de Montredon Jean-Michel Siaugue Valérie Cabuil 《Journal of nanoparticle research》2009,11(5):1247-1250
Maghemite nanoparticles with sizes in the range 10–110 nm and good monodispersity have been synthesized by co precipitation
at room temperature from Fe2+ and Fe3+ ions by a (N(CH3)4OH) solution, followed by an hydrothermal treatment at 200 °C and an oxidation step with Fe(NO3)3. The influence of the incubation time (at 200 °C) and of the pH of the autoclaved solution on the particles size has been
studied. It was found that the pH value allows to tune the size of the maghemite particles.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
127.
Objective and motivation
Intravascular ultrasound (IVUS) allows in vivo invasive intra-luminal real-time examination of the arterial wall structure. In this study, we aimed to validate for the first time the in vivo IVUS performing as a diagnostic tool by comparison to the well-established histomorphometry approach, in the largely used rat model of carotid angioplasty model that mimics the angioplasty procedure in humans.Methods
Atherosclerotic lesions were allowed to develop during four weeks after balloon catheter inflation of the left carotid artery, whereas the intact right carotid artery was used as control. Four weeks after injury, a Boston Scientific 40 MHz device to perform IVUS exams in vivo on both carotid arteries. Then, both carotid arteries were examined in vitro by histomorphometry and correlation between IVUS and histomorphometric parameters (plaque plus media cross-sectional areas [CSA] and eccentricity index) were researched.Results
After ANOVA analysis, comparative statistical analysis showed significant correlations between IVUS and histomorphometry when examining the intact right carotid artery (r = 0.662 with p < 0.003 for plaque plus media CSA; r = 0.774 with p < 0.002 for eccentricity index), but also when exploring the injured left carotid artery (r = 0.805 with p < 0.0001 for plaque plus media CSA; r = 0.775 with p < 0.002 for eccentricity index).Conclusions and outcome
We report here for the first time the ability of IVUS to study therapeutic vascular effects in vivo in alive rats. This result is of major importance since it will allow this device to be used for restenosis drug testing in rat model of carotid angioplasty. 相似文献128.
A new hybrid organic–inorganic material with the structural formula unit [La(H2O)4(m-PO3C6H4COOH)(m-PO2(OH)C6H4COOH)(m-PO(OH)2C6H4COOH)]2 (or [La(H2O)4C21H18O15P3]2) has been synthesized under hydrothermal condition from La(NO3)3·6H2O and 3-phosphonobenzoic acid (m-PO(OH)2–C6H4–COOH) which is a rigid organic precursor possessing two types of functional groups: phosphonic acid and carboxylic acid. The two units of the produced hybrid are linked together by hydrogen bonds leading to a layered framework composing of by a repetition of inorganic and organic slices. The organic layers consist of dimeric units made of two meta-phosphono-benzoic acid linked together by hydrogen bonds involving their COOH groups. Two kinds of dimeric units are observed: PO3C6H4COOH?HOOCC6H4PO(OH)2, present 2 times in the structure, and PO2(OH)C6H4COOH?HOOCC6H4PO2(OH). The material crystallises in a monoclinic cell (C2/c (15) space group) with the following parameters: a = 42.515(4) Å, b = 7.4378(6) Å, c = 20.307(2) Å, β = 118.031(6)°, V = 5668.2(9) Å3, Z = 4, density = 1.908 g/cm3. 相似文献
129.
Summary: Syndiotactic polystyrene (sPS), an attractive polymer due to its wide range of application, forms polymer-solvent intercalates with a large variety of solvent molecules ranging from liquids to solids. Recently, it has been realized that sPS intercalate prepared from SPS/naphthalene gel is more promising of making mesoporous materials. Here, the composite of sPS/fullerene have been prepared by taking advantage of sublimation of naphthalene. The different techniques as like XRD, SEM, HRTEM, FT-IR, DSC, TGA etc have been employed to characterized sPS/fullerene composite. XRD investigation shows the presence of δ form sPS in the composite. SEM and HRTEM reveal the fibrillar network with fringe like structure in presence of fullerene only and the average diameter of fibril has increased as compared to pure sPS fibrils. The conductivities of these fibrils have been increased with increasing amount of fullerene. 相似文献
130.
Tomohiro Sago Tomokatsu Tokami Hideyuki Itagaki Nobuhide Ishihara Christina Canter Jean-Michel Guenet 《Macromolecular Symposia》2011,303(1):48-55
Summary: Gelation of syndiotactic poly(p-tert-butylstyrene) (sPTBS), a syndiotactic polystyrene (sPS) derivative having a larger side-chain group, was first examined with several solvents. The temperature-concentration phase diagram of sPTBS/trans-decalin gel clearly exhibited that sPTBS formed a polymer-solvent molecular compound with a ratio of 2.7 trans-decalin per one monomer unit. Our polarized fluorescence technique demonstrated that there appeared to exist more spacious free volume among sPTBS chains than sPS in a gel state. A cause determining the morphology of sPTBS with organic solvents was discussed in the present paper. 相似文献