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991.
An experimental and theoretical study of magnetization curves of Fe/Cr nanometric magnetic films grown with the structure of the quasiperiodic Fibonacci sequence is presented. Fe ferromagnetic films with interfilm exchange coupling provided by intervening Cr non-ferromagnetic layers were grown on MgO (100) by dc magnetron sputtering at 300 °C. The magnetization curves were investigated using the magneto-optical Kerr effect with the external field applied along the easy axis. The theoretical approach for this system is based on a realistic phenomenological model that includes the following contributions to free magnetic energy: Zeeman, cubic magneto-crystalline anisotropy, as well as bilinear and biquadratic exchange energies. Our numerical results are in very good agreement with the experimental data. 相似文献
992.
Garcia CC Angeli JP Freitas FP Gomes OF de Oliveira TF Loureiro AP Di Mascio P Medeiros MH 《Journal of the American Chemical Society》2011,133(24):9140-9143
Acetaldehyde is an environmentally widespread genotoxic aldehyde present in tobacco smoke, vehicle exhaust and several food products. Endogenously, acetaldehyde is produced by the metabolic oxidation of ethanol by hepatic NAD-dependent alcohol dehydrogenase and during threonine catabolism. The formation of DNA adducts has been regarded as a critical factor in the mechanisms of acetaldehyde mutagenicity and carcinogenesis. Acetaldehyde reacts with 2'-deoxyguanosine in DNA to form primarily N(2)-ethylidene-2'-deoxyguanosine. The subsequent reaction of N(2)-ethylidenedGuo with another molecule of acetaldehyde gives rise to 1,N(2)-propano-2'-deoxyguanosine (1,N(2)-propanodGuo), an adduct also found as a product of the crotonaldehyde reaction with dGuo. However, adducts resulting from the reaction of more than one molecule of acetaldehyde in vivo are still controversial. In this study, the unequivocal formation of 1,N(2)-propanodGuo by acetaldehyde was assessed in human cells via treatment with [(13)C(2)]-acetaldehyde. Detection of labeled 1,N(2)-propanodGuo was performed by HPLC/MS/MS. Upon acetaldehyde exposure (703 μM), increased levels of both 1,N(2)-etheno-2'-deoxyguanosine (1,N(2)-εdGuo), which is produced from α,β-unsaturated aldehydes formed during the lipid peroxidation process, and 1,N(2)-propanodGuo were observed. The unequivocal formation of 1,N(2)-propanodGuo in cells exposed to this aldehyde can be used to elucidate the mechanisms associated with acetaldehyde exposure and cancer risk. 相似文献
993.
Diego F.M. Oliveira Jürgen Vollmer Edson D. Leonel 《Physica D: Nonlinear Phenomena》2011,240(4-5):389-396
Some dynamical properties for a Lorentz gas were studied considering both static and time-dependent boundaries. For the static case, it was confirmed that the system has a chaotic component characterized with a positive Lyapunov exponent. For the time-dependent perturbation, the model was described using a four-dimensional nonlinear map. The behaviour of the average velocity is considered in two different situations: (i) non-dissipative and (ii) dissipative dynamics. Our results confirm that unlimited energy growth is observed for the non-dissipative case. However, and totally new for this model, when dissipation via inelastic collisions is introduced, the scenario changes and the unlimited energy growth is suppressed, thus leading to a phase transition from unlimited to limited energy growth. The behaviour of the average velocity is described using scaling arguments. 相似文献
994.
C.M. Chaves A.L. de OliveiraN.A. de Oliveira A. Troper 《Journal of magnetism and magnetic materials》2011,323(6):881-884
Recent experimental results for the magnetic hyperfine field Bhf at the nuclei of s-p impurities such as 119Sn in intermetallic Laves phases RM2 (R=Gd, Tb, Dy, Ho, Er; M=Fe, Co) and 111Cd in R Co2, the impurity occupying a R site indicate that the ratio Bhf/μ3d exhibits different behavior when one goes from RFe2 to RCo2. In this work, we calculate these local moments and the magnetic hyperfine fields. In our model, Bhf has two contributions: one arising from the R ions, and the other arising from magnetic 3d-elements; these separate contributions allow the identification of the origin of different behavior of the ratio mentioned above. For 111Cd in RCo2 we present also the contributions for Bhf in the light rare earth Pr, Nd, Pm, Sm compounds. For the sake of comparison we apply also the model to 111Cd diluted in R Ni2. Our self-consistent magnetic hyperfine field results are in good agreement with those recent experimental data. 相似文献
995.
Louise Oliveira Nascimento Jessica Scremin Gabriel Junquetti Mattos Adriana Gomes Dbora Nobile Clausen Elen Romo Sartori 《Electroanalysis》2020,32(1):191-197
The voltammetric behavior of clopidogrel bisulfate (CLO), an antiplatelet agent, was investigated for the first time in the literature on a cathodically pretreated boron‐doped diamond electrode (CP‐BDDE) using cyclic (CV) and square‐wave voltammetry (SWV). It was observed an anodic peak for CLO, suitable for analytical purposes, at about 1.15 V (vs. Ag/AgCl (3.0 mol L?1 KCl)) by CV in Britton‐Robinson buffer solution (pH 5.0). On the physical‐chemical characterization of the interface phenomena, it was proved that electrode reaction of the analyte was controlled by a diffusion process. At optimized square‐wave parameters (pulse amplitude of 60 mV, frequency of 30 Hz and scan increment of 3 mV), the obtained analytical curve was linear for the CLO concentration range from 0.60 to 60.0 μmol L?1, with a detection limit of 0.60 μmol L?1. The simple, rapid and greener analytical method, based on CP‐BDDE electrochemical sensor, was successfully applied in real samples (pharmaceuticals and urine). 相似文献
996.
Carlos H. S. Mendes Joo G. S. Montenegro Nathalia L. Queiroz Thayane C. S. Moreira Valberes B. Nascimento Severino Carlos B. Oliveira 《Electroanalysis》2020,32(1):19-28
This work presents a study of the electrochemical oxidation of 7‐methylguanine (7‐mGua) in aqueous solution at glassy carbon electrode by cyclic voltammetry, differential pulse voltammetry, square wave voltammetry and electrochemical impedance spectrometry. The anodic behaviour of 7‐mGua was compared with the electro‐oxidation of guanine and 7‐methylguanosine. The results demonstrated that the methyl and ribose groups are not electroactive but strongly influence the oxidation mechanism of these species. The oxidation of 7‐mGua occurred in a single pH‐dependent step, with the withdrawal of two electrons and two protons of C8, to form 8‐oxo‐7‐methylguanine, while the electro‐oxidation of 7‐methylguanosine also occurred in a single pH‐dependent step, however, with the withdrawal of one electron and one proton of C8 to form a hydroxylated product, since its oxidation to 8‐oxo‐7‐methylguanosine is hindered by the presence of the pendant groups. In addition, the oxidation of 7‐mGua was investigated in the presence of DNA and DNA‐bases, leading to the conclusion that the formation of 7‐mGua, from an interaction of DNA with an alkylating agent, would cause an increase on the deoxyguanosine peak current of the DNA‐biosensor, with no interference of any free DNA bases, which demonstrated that DNA‐electrochemical biosensors find application on detecting DNA methylation, opening a new avenue for applications of DNA biosensors. 相似文献
997.
Beninca Cleoci Bisinella Radla Zabian Bassetto Bet Camila Delinski de Oliveira Cristina Soltovski Barboza Raíssa Arantes Colman Tiago André Denck Demiate Ivo Mottin Schnitzler Egon 《Journal of Thermal Analysis and Calorimetry》2020,140(2):743-753
Journal of Thermal Analysis and Calorimetry - The Araucaria angustifolia seed, named pinhão, has a high content of carbohydrates, and it is considered an unconventional starch source. Its... 相似文献
998.
Renata leite Tavares Maria Helena Araújo de Vasconcelos Maria Letícia da Veiga Dutra Aline Barbosa DOliveira Marcos dos Santos Lima Mirian Graciela da Silva Stiebbe Salvadori Ramon de Alencar Pereira Adriano Francisco Alves Yuri Mangueira do Nascimento Josean Fechine Tavares Omar Guzman-Quevedo Jailane de Souza Aquino 《Molecules (Basel, Switzerland)》2020,25(23)
This study evaluated the effect of Mucuna pruriens (MP) administration on neuroinflammation and behavioral and murinometric parameters in obese rats. Proximate composition, oligosaccharide and phenolic compound profile of MP were determined. Wistar adult male rats were randomized into healthy (HG) and obese group (OG). The HG consumed a control chow diet while OG consumed a cafeteria diet for eight weeks. Then, they were subdivided into: Healthy (HG); Healthy with MP administration (HGMP); Obese (OG); Obese with MP administration (OGMP), with the consumption of the respective diets remaining for another eight weeks, in addition to gavage with MP extract to supplemented groups (750 mg/kg weight). MP presented a composition rich in proteins and phenolic compounds, especially catechin, in addition to 1-kestose and levodopa. Supplementation reduced food intake, body weight, and thoracic and abdominal circumferences in obese rats. MP showed anxiolytic and antidepressant effects and reduced morphological damage and expression of interleukin 6 in the hippocampus of obese rats. MP treatment showed satietogenic, slimming, anxiolytic and antidepressant effects, besides to minimizing hippocampal neuroinflammation in obese rats. Our results demonstrated the potential anti-obesity of MP which are probably related to the high content of bioactive compounds present in this plant extract. 相似文献
999.
Bruno Pereira Motta Anderson Kiyoshi Kaga Juliana Oriel Oliveira Maiara Destro Inacio Cledson Ferreira da Silva Paulo Teixeira de Sousa Junior 《Natural product research》2020,34(16):2389-2393
Abstract Long-term hyperglycemia maintenance is responsible for increased protein glycation and formation of advanced glycation end products (AGEs), both are associated with the onset of diabetes mellitus complications. Efforts have been made to discover new agents having antiglycation potential. The aim of this study was to investigate the effects of the hydroethanolic extract and the ethyl acetate and methanolic fractions of Simaba trichilioides roots on the formation of AGEs. In an in vitro model system of protein glycation, incubations with hydroethanolic extract, ethyl acetate or methanolic fractions of S. trichilioides decreased the fluorescent AGEs, and markers of tyrosine and tryptophan oxidation. Protein crosslinking was reduced in the presence of the ethyl acetate fraction of S. trichilioides. Simaba trichilioides roots seem to be a promising source of compounds having ability to prevent glycoxidation changes, with potential applications in complementary therapies for management of diabetic complications. 相似文献
1000.
Naiana G. P. B. Lima Igor P. B. Lima Denise M. C. Barros Thays S. Oliveira Fernanda N. Raffin Túlio F. A. de Lima e Moura Ana C. D. Medeiros Ana P. B. Gomes Cícero F. S. Aragão 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2311-2318
Psoralens are widely used for the treatment of psoriasis. Trioxsalen is a drug prescribed low-dose, belonging to the group of substituted psoralen. The aim of this study was to evaluate the compatibility of trioxsalen with pharmaceutical excipients used in the solid forms by analytical techniques. Binary mixtures between the trioxsalen and pharmaceutical excipients (namely, magnesium stearate, α-lactose, microcrystalline cellulose 102, pregelatinized starch, mannitol, sodium lauryl sulfate, sodium starch glycolate, and croscarmellose sodium) were examined. The trioxsalen–sodium lauryl sulfate mixture displayed some physical interaction based on the DTA and DSC results, but the FTIR study ruled out any chemical change. 相似文献