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991.
Márcio Yee Adriana M. C. Souza Ticiane S. Valera Nicole R. Demarquette 《Rheologica Acta》2009,48(5):527-541
In this work, the stress relaxation behavior of PMMA/PS blends, with or without random copolymer addition, submitted to step
shear strain experiments in the linear and nonlinear regime was studied. The effect of blend composition (ranging from 10
to 30 wt.% of dispersed phase), viscosity ratio (ranging from 0.1 to 7.5), and random copolymer addition (for concentrations
up to 8 wt.% with respect to the dispersed phase) was evaluated and correlated to the evolution of the morphology of the blends.
All blends presented three relaxation stages: a first fast relaxation which was attributed to the relaxation of the pure phases,
a second one which was characterized by the presence of a plateau, and a third fast one. The relaxation was shown to be faster
for less extended and smaller droplets and to be influenced by coalescence for blends with a dispersed phase concentration
larger than 20 wt.%. The relaxation of the blend was strongly influenced by the matrix viscosity. The addition of random copolymer
resulted in a slower relaxation of the droplets. 相似文献
992.
Adriana Garroni Christopher J. Larsen 《Archive for Rational Mechanics and Analysis》2009,194(2):585-609
We introduce models for static and quasi-static damage in elastic materials, based on a strain threshold, and then investigate
the relationship between these threshold models and the energy-based models introduced in Francfort and Marigo (Eur J Mech
A Solids 12:149–189, 1993) and Francfort and Garroni (Ration Mech Anal 182(1):125–152, 2006). A somewhat surprising result
is that, while classical solutions for the energy models are also threshold solutions, this is shown not to be the case for
nonclassical solutions, that is, solutions with microstructure. A new and arguably more physical definition of solutions with
microstructure for the energy-based model is then given, in which the energy minimality property is satisfied by sequences
of sets that generate the effective elastic tensors, rather than by the tensors themselves. We prove existence for this energy-based
problem, and show that these solutions are also threshold solutions. A by-product of this analysis is that all local minimizers,
in both the classical setting and for the new microstructure definition, are also global minimizers. 相似文献
993.
María Elena Camacho-Moll Adriana Sampayo-Reyes Fabiola Castorena-Torres Gerardo Lozano-Garza Gabriela Alarcn-Galvn Alba Hernndez Ricard Marcos Juan Manuel Alcocer-Gonzlez Reyes Tamez-Guerra Mario Bermúdez de Len 《Molecules (Basel, Switzerland)》2021,26(18)
Arsenic is considered a worldwide pollutant that can be present in drinking water. Arsenic exposure is associated with various diseases, including cancer. Antioxidants as selenite and α-tocopherol-succinate have been shown to modulate arsenic toxic effects. Since changes in STAT3 and PSMD10 gene expression have been associated with carcinogenesis, the aim of this study was to evaluate the effect of arsenic exposure and co-treatments with selenite or α-tocopherol-succinate on the expression of these genes, in the livers of chronically exposed Syrian golden hamsters. Animals were divided into six groups: (i) control, (ii) chronically treated with 100 ppm arsenic, (iii) treated with 6 ppm α-tocopherol-succinate (α-TOS), (iv) treated with 8.5 ppm selenite, (v) treated with arsenic + α-TOS, and (vi) treated with arsenic + selenite. Urine samples and livers were collected after 20 weeks of continuous exposure. The urine samples were analyzed for arsenic species by atomic absorption spectrophotometry, and real-time RT-qPCR analysis was performed for gene expression evaluation. A reduction in STAT3 expression was observed in the selenite-treated group. No differences in PSMD10 expression were found among groups. Histopathological analysis revealed hepatic lymphocytosis in selenite-treated animals. As a conclusion, long-term exposure to arsenic does not significantly alter the expression of STAT3 and PSMD10 oncogenes in the livers of hamsters; however, selenite down-regulates STAT3 expression and provokes lymphocytosis. 相似文献
994.
Gheorghe Ilia Smaranda Iliescu Lavinia Macarie Adriana Popa 《Heteroatom Chemistry》2008,19(4):360-364
The synthesis of tervalent phosphorus esters continues to be a significant area of interest, much of it again directed toward the synthesis of phosphite ligands for metal‐catalyzed reactions. Typically, they were obtained through esterification of the corresponding phosphorus chlorides with the appropriate alcohols in the presence of an amine. In this paper, we present a new method for the synthesis of tervalent phosphorus esters, not yet mentioned in the literature, when potassium phosphate, as a unique base, is used in liquid–solid system. Symmetrical and unsymmetrical phosphites were obtained with good yields (65%–80%) using this method. The compounds were characterized by 31P NMR spectroscopy. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:360–364, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20438 相似文献
995.
Rodrigues MR Lima A Codognoto L Villaverde AB Tavares Pacheco MT Moisés de Oliveira HP 《Journal of fluorescence》2008,18(5):973-977
The microenvironment formed by lauroyl and stearoyl derivatives of chitosan in solution has been studied using two fluorescent
probes, pyrene and nabumetone. Existence or not of microdomains formed by polymolecular associations, the inherent hydrophobicity
of them in aqueous solution, and the influence of degree of substitution (DS) of derivatives were investigated by emission
properties of pyrene and strengthened by the photophysical behavior of nabumetone. Additionally, the ratio between the fluorescence
intensities of first (~372 nm) to the third (~384 nm) bands of the emission spectrum of pyrene was used to determine the critical
aggregation concentration (CAC). In a previous work, it was already reported the characterization of chitosan derivatives
by three spectroscopic techniques (13C-NMR, 1H-NMR and infrared), as well as data on the solubility and swelling-index of them. In addition of that, the new results show
that the investigated lauroyl and stearoyl derivatives of chitosan are expected to be potential models for applications in
the medical field. 相似文献
996.
We have described the stretching and folding of foams in a vertical Hele-Shaw cell containing air and a surfactant solution, from a sequence of upside-down flips. Besides the fractal dimension of the foam, we have observed the logistic growth for the soap film length. The stretching and folding mechanism is present during the foam formation, and this mechanism is observed even after the foam has reached its respective maximum fractal dimension. Observing the motion of bubbles inside the foam, large bubbles present power spectrum associated with random walk motion in both directions, while the small bubbles are scattered like balls in a Galton board. 相似文献
997.
Heloisa R. Cadorim Mauana Schneider Júlia Hinz Fabiana Luvizon Adriana N. Dias 《Analytical letters》2019,52(13):2133-2149
A new procedure for the preconcentration of trace amounts of free Pb and Cd by disposable pipette extraction (DPX) is proposed herein. Recycled cork is used as a biosorbent and the procedure is completely free of organic solvents. The cork was reduced to a powder and characterized by scanning electron microscopy. Several parameters that influence the preconcentration of Pb and Cd with DPX-cork, such as the sample pH, number of extraction cycles, biosorbent mass, and percentage of acid in the desorption step, were studied. The tolerance of DPX-cork with respect to 10 potential interfering ions was also evaluated. Coupled with the high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) technique, the sample preparation method allowed the analytical limits required for quality control (according to the permitted limits established by legislation) to be obtained. The limits of detection for the extraction of a 3.5-mL water sample were 200?ng L?1 for Pb and 100?ng L?1 for Cd. The relative standard deviations were around 7.5% for Pb and 8.0% for Cd. The optimized method was successfully applied to the determination of Cd and Pb in two certified reference materials (water and wastewater) and five water samples (collected from a mangrove, a creek, and the sea). 相似文献
998.
Adriana García Forero Diego Armando Villamizar Mantilla Luis A. Núez Raquel Elvira Ocazionez Elena E. Stashenko Jorge Luis Fuentes 《Photochemistry and photobiology》2019,95(4):1010-1018
This work evaluated the photoprotective and antigenotoxic effects against ultraviolet B (UVB) radiation of flavonoid compounds apigenin, naringenin and pinocembrin. The photoprotective efficacy of these compounds was estimated using in vitro photoprotection indices, and the antigenotoxicity against UVB radiation was evaluated using the SOS chromotest and an enzymatic (proteinase K/T4 endonuclease V enzyme) comet assay in UV‐treated Escherichia coli and human (HEK‐293) cells, respectively. Naringenin and pinocembrin showed maximum UV‐absorption peak in UVC and UVB zones, while apigenin showed UV‐absorption capability from UVC to UVA range. These compounds acted as UV filters reducing UV‐induced genotoxicity, both in bacteria and in human cells. The enzymatic comet assay resulted highly sensitive for detection of UVB‐induced DNA damage in HEK‐293 cells. In this work, the photoprotective potential of these flavonoids was widely discussed. 相似文献
999.
Adriana Araújo de Almeida-Apolonio Fabiana Gomes da Silva Dantas Allan Belarmino Rodrigues Claudia Andréa Lima Cardoso Melyssa Negri Kelly Mari Pires de Oliveira 《Natural product research》2019,33(16):2363-2367
Cryptococcosis is an opportunistic disease with a worldwide distribution. This disease is caused by fungi of the genus Cryptococcus, and its treatment is limited to several antifungals. In this study, the antifungal, cytotoxic and mutagenic properties of ethanol extracts from the bark and leaves of Annona coriacea were evaluated against the standard Cryptococcus species and clinical yeast specimens. Both extracts of A. coriacea showed inhibitory activity of 1.5 mg/mL for all of the yeasts tested. The number of viable cells at the lowest tested concentration was 0.187 mg/mL. The extracts that were tested showed inhibitory activity and reduced the fungal growth of the Cryptococcus gattii species and Cryptococcus neoformans species complexes, suggesting that this plant may be an effective alternative treatment for cryptococcosis. 相似文献
1000.
Isadora Caruso Fontana Oliveira Adriana Dalla Mora Jairo Braga Neto Ákila Lara de Oliveira Carolina Harder Valquíria Miwa Hanai-Yoshida 《Natural product research》2019,33(16):2417-2421
Bothrops jararacussu venom’s (Bj2015) batch was biomonitored quarterly for one year to assess phospholipase A2 (PLA2) activity, immunogenicity, neurotoxicity, and myotoxicity. In silico models were applied to evaluate losses using decay model and recoveries by predictive trend analysis. Mice were immunized with Bj2015. Antibodies were detected by double-immunodiffusion and total protein and albumin were measured. Neuromuscular blockade-induced by 40 μg mL?1 venom solution was carried out using mouse nerve phrenic-diaphragm preparation. Resulting muscles were submitted to light microscopy to evaluate the myotoxicity. PLA2 activity of 0.1 mg mL?1 Bj2015 was measured using 4-nitro-3-(octanoyloxy)benzoic acid as substrate. Over time, greater losses occurred in neurotoxicity than PLA2, but not in myotoxicity and immunogenicity. Concluding, the neurotoxicity decrease can be related to enzymatic losses, including PLA2. Depending on the purpose of use, the collected venom responds on a long time, avoiding unnecessary new collections, improving life quality of animals in captivity and increasing their longevity. 相似文献