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1.
Xiaohong Gu Tinh Nguyen Mounira Oudina David Martin Bouchra Kidah Joan Jasmin Aziz Rezig Lipiin Sung Eric Byrd Jonathan W. Martin Derek L. Ho Y. C. Jean 《Journal of Coatings Technology and Research》2005,2(7):547-556
Atomic force microscopy (AFM) has been used to study the morphology and microstructure of an amine-cured epoxy before and
after outdoor exposure. Measurements were made from samples prepared in an essentially CO2-free, H2O-free glove box and from samples prepared in ambient conditions. For those prepared in a CO2-free glove box, AFM imaging was conducted on (1) an unexposed air/coating surface, (2) an unexposed coating bulk, (3) an
unexposed coating/substrate interface, and (4) a field exposed air/coating surface. For samples prepared in ambient conditions,
only the unexposed air/coating surface was investigated. The same regions of the exposed samples were scanned periodically
by the AFM to monitor changes in the surface morphology of the coating as UV exposure progressed. Small angle neutron scattering
and Fourier transform infrared spectroscopy (FTIR) studies were performed to verify the microstructure and to follow chemical
changes during outdoor exposure, respectively. The results have shown that amine blushing, which occurs only under ambient
conditions, had a significant effect on the surface morphology and microstructure of the epoxy. The surface morphology of
the samples prepared under CO2-free, dry conditions was generally smooth and homogeneous. However, the interface and the bulk samples clearly revealed a
two-phase structure consisting of bright nodular domains and dark interstitial regions, indicating an inhomogeneous microstructure.
Such heterogeneous structure of the bulk was in good agreement with results obtained by small angle neutron scattering of
unexposed samples and by AFM phase imaging of the degraded sample surface. The relationship between submicrometer physical
changes and molecular chemical degradation is discussed.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago,
IL. 相似文献
2.
Pascale Sabin Bouchra Benjelloun-Mlayah Michel Delmas 《Journal of the American Oil Chemists' Society》1997,74(5):481-489
Two sets of alkyd resins of variable oil lengths with the required properties for offset printing ink formulations, modified
by sunflower and rapeseed oil, were synthetized according to the “monoglyceride” process. The influence of the acyl composition
of the modifying vegetable oil and of the oil content on alkyds’ properties was determined by detailed chemical and rheological
characterization. Molecular structure, size, and molecule size distribution appeared to be linked to these two factors. A
comparative study with two usual linseed oil-modified alkyds led to determination of the more appropriate alkyds for applications
in offset varnishes. 相似文献
3.
Romain Fillières Bouchra Benjelloun-Mlayah Michel Delmas 《Journal of the American Oil Chemists' Society》1995,72(4):427-432
High-performance size-exclusion chromatography (HPSEC) was used to evaluate the influence of different variables affecting
the transesterification of rapeseed oil (RSO) with anhydrous ethanol and sodium ethoxide as catalyst. The effect of temperature,
ethanol/RSO molar ratio, catalyst concentration, and time can be interpreted by observing the variations of the reaction medium
composition. HPSEC has made the quantitation of ethyl esters, mono-, di-, and triglycerides and glycerol possible. The best
results for laboratory-scale reactions were obtained at 80°C with a 6:1 molar ratio of EtOH/RSO and 1% of NaOEt by weight
of RSO. 相似文献
4.
The cell formation is the first step in the design of Cellular Manufacturing systems. It consists of grouping parts with similar processing needs into cells and identifying the set of machines needed to process these parts. The aim is to minimize the material handling costs and maximize the use of the machines. In this paper, the machine reliability and the alternative process routings are taken into account to form the production cells. The presence of these factors in addition to the production volume, operation sequence and production time makes the problem more realistic but also more complex. Most authors solve this kind of problems by mathematical programming approaches that require large amounts of computational efforts. Therefore, a modified version of the Clonal Selection Algorithm is introduced and a local search mechanism is adopted in this paper. The obtained results are compared with those of the Branch and Bound (B&B) method using LINGO software. The comparison reveals the effectiveness and the efficiency of the proposed method in terms of both solution quality and computation time required. 相似文献
5.
Patard Louis; Stoven Veronique; Gharib Bouchra; Bontems Francois; Lallemand Jean-Yves; De Reggi Max 《Protein engineering, design & selection : PEDS》1996,9(11):949-957
Human lithostathine is a 144-residue protein, expressed in variousorgans and pathologies. Several biological functions have beenproposed for this protein. Among others, inhibition of nucleationand growth of CaCO3 crystals in the pancreas and bacterial aggregationhas retained attention, because lithostathine presents highsequence similarities with calcium-dependent (or C-type) lectins.To study its structure-function relationship and compare itwith that of C-type lectins, we have built a model for lithostathine.This model is derived from the only two C-type lectins of knownstructures: rat mannose binding protein and human E-selectin.An original strategy, inspired by that proposed by Havel andSnow, was designed for model building. We have undertaken NMRstudies on the natural protein. Although complete structuredetermination has not yet been achieved, the NMR studies didconfirm the main characteristics of the model. From analysisof the proposed model, we concluded that lithostathine is notexpected to present sugar- or calcium-binding properties. Therefore,the mechanisms of bacterial aggregation and inhibition of CaCO3nucleation and growth have not yet been elucidated. 相似文献
6.
Xiaohong Gu Lipiin Sung Bouchra Kidah Mounira Oudina Cyril Clerici Haiqing Hu Debbie Stanley Walter E. Byrd Jerry Y. C. Jean Tinh Nguyen Jonathan W. Martin 《Journal of Coatings Technology and Research》2009,6(1):67-79
Surface topography and gloss are two related properties affecting the appearance of a polymeric coating system. Upon exposure
to ultraviolet (UV) radiation, the surface topography of a coating becomes more pronounced and, correspondingly, its gloss
generally decreases. However, the surface factors affecting gloss and appearance are difficult to ascertain. In this article,
atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM) measurements have been performed on an amine-cured
epoxy coating system exposed to outdoor environments in Gaithersburg, Maryland. The formation of the protuberances is observed
at the early degradation stages, followed by the appearance of circular pits as exposure continues. At long exposure times,
the circular features enlarge and deepen, resulting in a rough surface topography and crack formation. Fourier Transform Infrared
Spectroscopy (FTIR) study indicates that the oxidation and chain scission reactions are likely the origins of the surface
morphological changes. The relationship between changes in surface roughness and gloss has been analyzed. The root mean square
(RMS) roughness of the coating is related to nanoscale and microscale morphological changes in the surface of the coating
as well as to the gloss retention. A near-linear dependence of RMS roughness with the measurement length scale (L) is found on a double logarithmic scale, i.e., RMS ∼ L
f. The scaling factor, f, decreases with exposure time. The relationship between surface topography, on nano- to microscales,
and the macroscale optical properties such as gloss retention is discussed. Moreover, a recent development in using an angle-resolved
light scattering technique for the measurement of the specular and off-specular reflectance of the UV-exposed specimens is
also demonstrated, and the optical scattering data are compared to the gloss and the roughness results.
相似文献
Xiaohong GuEmail: |
7.
Pascale Sabin Bouchra Benjelloun-Mlayah Michel Delmas 《Journal of the American Oil Chemists' Society》1997,74(10):1227-1233
Two sets of variable oil length, alkyd resins modified by sunflower oil (SOA) and by rapeseed oil (ROA), were evaluated in
offset formulations with mineral oils as diluent. The more suitable alkyds for this kind of application were determined. In
a second experiment, hydrocarbon solvents were substituted by the fatty acid methyl esters derived from rapeseed oil or sunflower
oil to produce ecologically friendly offset printing inks. Finally, the ROA and the SOA were associated with the methyl esters
derived from the same vegetable oil. New properties of the varnishes composed of a vegetable diluent were evaluated. The quickset
formulations with the methyl esters do not need important modifications, as opposed to the heatset formulations. 相似文献
8.
Bouchra Oumokhtar Mohamed Elazhari Mohammed Timinouni Karima Bendahhou Bahia Bennani Mustapha Mahmoud Abelhakim El Ouali Lalami Sanae Berrada Mohammed Arrayhani Tariq Squalli Houssaini 《Hemodialysis international. International Symposium on Home Hemodialysis》2013,17(4):542-547
Staphylococcus aureus, which has its ecological niche in the anterior nares, has been shown to cause a variety of infectious diseases mainly for patients in hemodialysis units. We performed this study to evaluate the prevalence of nasal S. aureus carriage among hemodialysis outpatients, to determine the antimicrobial susceptibility of isolates, to characterize the virulence genes, and to identify associated risk factors. Nares swab specimens were obtained from 70 outpatients on hemodialysis between March and June 2010. Samples were plated immediately onto S. aureus specific media and pattern of antibacterial sensitivity was determined using disk diffusion method. Polymerase chain reaction was used to detect nuc, mecA, and genes encoding staphylococcal toxins. Medical record of patients was explored to determine S.aureus carriage risk factors. Nasal screening identified 42.9% S. aureus carriers with only one (3.3%) methicillin‐resistant S. aureus isolate. Among the methicillin‐susceptible S. aureus isolates, high rate of penicillin resistance (81.8%) has been detected. The identified risk factors were male gender and age ≤ 30 years. Research of virulence factors showed a high genetic diversity among the 30 S. aureus isolates. Twenty‐one (70%) of them had at least one virulence gene, of which 3.3% were Panton‐Valentine leukocidin (lukS/F‐PV) genes. S. aureus carriage must be screened for at regular intervals in hemodialysis patients. Setting up a bacterial surveillance system is one of the strategies to understand the epidemiology of methicillin‐resistant S. aureus, to guide local antibiotic policy and prevent spread of antibiotic‐resistant S. aureus. 相似文献
9.
Bouchra Wahdame Denis Candusso Xavier François Fabien Harel Jean-Marie Kauffmann Gérard Coquery 《International Journal of Hydrogen Energy》2009
Designs of Experiments (DoE) can be of immediate relevance for various research works conducted in the Fuel Cell (FC) area. DoE techniques allow efficient test definitions for rapid conceptions and well-organised characterisations of FC materials and components, individual cells, stacks or even complete generators. In the DoE method, some statistic-based models can be proposed in pre-stages of physical models. The statistical/numerical relations are used to predict the behaviour of the investigated systems as a function of various operating parameters. Some control strategies can also be developed to optimise relevant criteria like FC voltage, fuel consumption, and maximal electrical power or stack lifetime. 相似文献
10.
Soulami Khaoula Belhaj Saidi Mohamed Nabil Honnit Bouchra Anibou Chaimae Tamtaoui Ahmed 《Multimedia Tools and Applications》2019,78(10):12835-12863
Multimedia Tools and Applications - The detection of abnormalities in the breast at an early stage can be so helpful for breast cancer treatment. Currently, mammography is the cheapest and the most... 相似文献