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41.
Jacob John R. Suriyakala Selvin Thomas Jude Martin Mendez Anitha Pius Sabu Thomas 《Journal of Materials Science》2010,45(11):2892-2901
Morphology, mechanical properties, thermal stability and gas transport behaviour of interpenetrating polymer networks (IPNs)
based on PI/PMMA have been investigated using various techniques. Crosslinking level of both phases and concentration of PMMA
were found to have noticeable effects on the compatibility of immiscible components during IPN formation. Effect of crosslinking
was studied by preparing IPNs with varying amount of crosslinker concentration in each phase. Crosslinking of both phases
facilitated deeper interpenetrations between both networks, and certain degree of compatibility is attained during IPN formation.
Nanometre-sized domains were observed for highly crosslinked IPN. Lower concentration of PMMA was found to favour phase mixing
more effectively than others. DSC curve of 65/35 IPN showed a broad transition arising from the α and β-relaxations of PMMA
due to the higher flexibility attained by mixing with the highly mobile PI chains. The mechanical properties of the IPNs were
correlated to the morphology of the system and 50/50 composition showed maximum mechanical properties among the studied compositions.
Mode of mechanical failure, thermal stability and gas transport behaviour were also analysed. IPNs having nanometre-sized
domains showed least gas permeability among the studied samples. 相似文献
42.
A numerical algorithm is presented for the solution of low Mach number unsteady nonisothermal flows at moderate Reynolds numbers (Re ~ 100) with variable transport properties. The low Mach number limit is approached by using a relaxation method of the pseudo-compressibility type that has proved to be numerically robust and accurate enough to be used in industrial applications. Time integration is explicit and space integration is based on a finite point approach. Solver validation includes a sensitivity analysis and a comparison with previously published results concerning the flow around heated cylinders at different Re and temperature loadings. Then, the solver is applied to calculate the flow of a reacting mixture past a thin catalytic wire, a problem of interest for power MEMS design (micro catalytic reactors), aiming to determine the chemical-to-thermal energy conversion rate at the catalytic wire. 相似文献
43.
Gislaine Cristina Roma Patrícia Rosa De Oliveira Andrea Mendez Araujo Gervásio Henrique Bechara Maria Izabel Camargo Mathias 《Microscopy research and technique》2012,75(12):1732-1736
Pyrethroids such as permethrin are synthetic compounds widely used in the agriculture of many countries to combat plagues and in domestic products, such as acaricides. Not so long ago these chemicals were characterized as non‐toxic for non‐target organisms; however, recent studies have showed that these compounds could present toxic potential for many organisms. In this sense, this study presents genotoxic and mutagenic potential of permethrin administered intraperitoneally in mice under artificial conditions by the use of micronucleus assay in the peripheral blood of these animals. The mice were divided into five groups: group I = negative control (distilled water), group II = positive control (cyclophosphamide), group III = 30% of permethrin LD50 (96 mg/kg), group IV = 50% of permethrin LD50 (160 mg/kg), and group V = 80% of permethrin LD50 (256 mg/kg). The peripheral blood was collected 24, 48, and 72 h after treatment. Results showed that all the tested permethrin dosages presented genotoxic and mutagenic effects 24 h after treatment, which would contradict the classification of this chemical product as moderately toxic, i.e., unable to cause damages to the cell DNA. Microsc. Res. Tech. © 2012 Wiley Periodicals, Inc. 相似文献
44.
Mendez DL Kim D Chruszcz M Stephens GE Minor W Khorasanizadeh S Elgin SC 《Chembiochem : a European journal of chemical biology》2011,12(7):1084-1096
Drosophila melanogaster heterochromatin protein 1a (HP1a) is essential for compacted heterochromatin structure and the associated gene silencing. Its chromo shadow domain (CSD) is well known for binding to peptides that contain a PXVXL motif. Heterochromatin protein 2 (HP2) is a non-histone chromosomal protein that associates with HP1a in the pericentric heterochromatin, telomeres, and the fourth chromosome. Using NMR spectroscopy, fluorescence polarization, and site-directed mutagenesis, we identified an LCVKI motif in HP2 that binds to the HP1a CSD. The binding affinity of the HP2 fragment is approximately two orders of magnitude higher than that of peptides from PIWI (with a PRVKV motif), AF10 (with a PLVVL motif), or CG15356 (with LYPLL and LSIVA motifs). To delineate differential interactions of the HP1a CSD, we characterized its structure, backbone dynamics, and dimerization constant. We found that the dimerization constant is bracketed by the affinities of HP2 and PIWI, which dock to the same HP1a homodimer surface. This suggests that HP2, but not PIWI, interaction can drive the homodimerization of HP1a. Interestingly, the integrity of the disordered C-terminal extension (CTE) of HP1a is essential for discriminatory binding, whereas swapping the PXVXL motifs does not confer specificity. Serine phosphorylation at the peptide binding surface of the CSD is thought to regulate heterochromatin assembly. Glutamic acid substitution at these sites destabilizes HP1a dimers, but improves the interaction with both binding partners. Our studies underscore the importance of CSD dimerization and cooperation with the CTE in forming distinct complexes of HP1a. 相似文献
45.
46.
JP Mendez R Schiavon L Diaz-Cueto AI Ruiz P Canto D S?derlund V Diaz-Sanchez A Ulloa-Aguirre 《Canadian Metallurgical Quarterly》1998,83(10):3523-3526
In true hermaphroditism diverse phenotypes and karyotypes are found; there are no distinctive laboratory features that can distinguish it from other intersex disorders, thus the diagnosis is made by the histological findings. Existence of Leydig cells is demonstrated by testosterone levels above the female range; however, presence of ovarian tissue cannot be ascertained because of the absence of a reliable functional test. Unless appropriate biopsies are performed or the whole gonad is removed, there is a risk of not diagnosing true hermaphroditism. To find a reliable test that can differentiate patients with true hermaphroditism from those with other intersex disorders, we investigated the estradiol (E2) response to human menopausal gonadotropins (hMG) in infants with genital ambiguity. These results were correlated with the histological findings. Eleven infants with genital ambiguity and four with a high scrotal testis were stimulated every 12 h with 2 IU/kg hMG. If E2 rose above 80 pg/mL (cut-off point), the test was discontinued; if after 7 days E2 remained below 80 pg/mL, the hMG dose was doubled and stimulation extended for 7 additional days. In five patients in whom true hermaphroditism was later histologically demonstrated, E2 rose above 80 pg/mL. In two of them, ovarian tissue was removed and hMG stimulation repeated; no response above our cut-off point was observed during the second test. The maximal E2 response to hMG in the remaining 10 individuals was 43 pg/mL; after laparotomy or gonadal biopsies no ovarian tissue was found. The hMG stimulation test can be considered a reliable and safe dynamic procedure for demonstrating the presence or absence of ovarian tissue in infants with genital ambiguity. 相似文献
47.
48.
S C Nova Derivi M H Marques Mendez M C Rezende Rodrígues M Leonor Fernandes 《Archivos latinoamericanos de nutrición》1988,38(4):965-978
The purpose of the present study was to estimate dietary fiber components in raw vegetables and processed by different methods. Samples of 8 raw, 15 boiled, 5 fermented, 5 fried and 2 canned vegetables were analyzed. Results indicated the sample vegetables after being boiled, canned, fermented and fried, presented alterations in the dietary fiber insoluble and soluble components, e.i., by interaction or solubility tending to an increase or decrease of its components. Results obtained in the dietary fiber components of processed vegetables, in the sample analyzed, presented variations among them with the different processing techniques. 相似文献
49.
P Curley M Nestor K Collins I Saporoschetz M Mendez JA Mannick ML Rodrick 《Canadian Metallurgical Quarterly》1996,110(2):583-588
BACKGROUND & AIMS: The role of the cytokine interleukin 2 (IL-2) has long been recognized as central to normal immunologic function and defense against infection after burns and trauma, but little effort has been directed towards its role in acute pancreatitis (AP), which also has a high mortality related to sepsis. This study investigated the potential role of IL-2 in mice with diet-induced AP. METHODS: AP was induced in mice by 10 days of feeding a choline-deficient, ethionine-supplemented diet. T-helper (CD4) cells were estimated, and T-cell mitogen-stimulated splenocyte proliferation and IL-2 production in vitro were measured on days 3, 7, and 10. RESULTS: Significant reduction in IL-2 production was found on day 3 (32%; P < 0.05) and day 10 (48%; P < 0.005). Administration of intraperitoneal lipopolysaccharide on day 10 was associated with reduced IL-2 production (P < 0.025) 4 hours later and 90% mortality in animals with AP. In vivo therapy with recombinant IL-2 improved in vitro IL-2 secretion (P < 0.05) and reduced lipopolysaccharide-induced mortality (P = 0.036). CONCLUSIONS: Murine diet-induced AP is associated with impaired immune function and increased susceptibility to sepsis and may be a valuable tool in the investigation of immunomodulation in AP. 相似文献
50.
K Ogura PI Terasaki C Johnson R Mendez JT Rosenthal R Ettenger DC Martin E Dainko L Cohen T Mackett 《Canadian Metallurgical Quarterly》1993,56(2):294-298
This study was conducted to determine the efficacy of the T cell flow cytometry crossmatch (T-FCXM) test in 841 first cadaver donor transplants. Results showed one-year graft survival rates were 82% for T-FCXM-negative patients, compared with 75% for T-FCXM-positive patients (P = 0.01). Early one-month graft failure was 13 percentage points higher in those with a positive T-FCXM than those with a negative T-FCXM. The positive crossmatch patients also had more frequent immunological failures. A positive T-FCXM was found in 39% of the sensitized patients (PRA > 10%) and 8% of those who had not been sensitized. Patients with a positive T-FCXM in either category had a 74% graft survival rate. Thus, most of the T-FCXM-positive results occurred in patients with complement-fixing antibodies. It is suggested that flow cytometry crossmatching (FCXM) be used prospectively, despite the fact that many patients with a positive crossmatch did have successful transplants (TXs). In the current climate of a cadaver kidney scarcity and large recipient waiting pools, utilization of kidneys for patients with the highest probability of success seems a most prudent policy. 相似文献