Magnetoresistance in Sn-Doped In2O3Nanowires

In this work, we present transport measurements of individual Sn-doped In2O3nanowires as a function of temperature and magnetic field. The results showed a localized character of the resistivity at low temperatures as evidenced by the presence of a negative temperature coefficient resistance in temperatures lower than 77 K. The weak localization was pointed as the mechanism responsible by the negative temperature coefficient of the resistance at low temperatures

Temperature dependence of electron properties of Sn doped In2O3 nanobelts

This paper reports on the measurements of transport properties of high crystalline quality Sn doped In2O3 nanobelts. The samples presented metallic conduction in a large range of temperatures; however, at low temperatures, the resistivity showed a slight increase and the current-voltage curves showed a tendency to saturate even in the low-voltage range. From these observations, we discuss some arguments on the possibility of low dimensional conducting channels as the main responsible for the conduction at low temperatures. Additionally, we present an alternative technique for production of low resistance ohmic contacts, which can be further used in devices' construction. (C) 2007 Elsevier B.V. All rights reserved

Electrical characterization of SnO2 : Sb ultrathin films obtained by controlled thickness deposition

A representative study is reported on the electrical properties of SnO2: Sb. ultrathin films (thickness of 40-70 nm) produced by a deposition method based on aqueous colloidal suspensions of 3-5 nm crystalline oxides. The results revealed the films' electrical behavior in a range of 10-300 K, showing a strong dependence on dopant incorporation, with minimum resistivity values in 10 mol % of Sb content. All the samples displayed semiconductor behavior, but the transport mechanism showed a strong dependence on thickness, making it difficult to fit it to well-known models. In thicker films, the mechanism proved to be an intermediary system, with thermally activated and hopping features. Electron hopping was estimated in the range of 0.4-1.9 nm, i.e., in the same order as the particle size. (c) 2007 American Institute of Physics

Impacts of future floods and low flows on the economy in the Meuse basin

The present study shows the factors that modulate the photodamage promoted by phenothiazines. Cytochrome c was irradiated with UV light for 120 min, over a pH range from 4.0 to 8.0, in the absence and in the presence of different concentrations of thioridazine (TR) and fluphenazine (FP). In the absence of phenothiazines, the maximal rate of a Soret band blue shift (nm/min) from 409 to 406 nm was obtained at pH 4.0 (0.028 nm/min). The presence of phenothiazines at the concentration range 10-25 μmol/L amplified and accelerated a cytochrome c blue shift (409 to 405 nm, at a rate = 0.041 nm/min). Above 25 μmol/L, crescent concentrations of phenothiazines contributed to cytochrome c protection with (maximal at 2500 μmol/L). Scanning electronic microscopy revealed the formation of nanostructures. The pH also influenced the effect of low phenothiazine concentrations on cytochrome c. Thus, the predominance of phenothiazine-promoted cytochrome c damage or protection depends on a balance of the following factors: the yield of photo-generated drug cation radicals, which is favored by acidic pH; the stability of the cation radicals, which is favored by the drug aggregation; and the cytochrome c structure, modulated by the pH

pH-Dependent Synthesis of Anisotropic Gold Nanostructures by Bioinspired Cysteine-Containing Peptides

In the present study, alkaline peptides AAAXCX (X = lysine or arginine residues) were designed based on the conserved motif of the enzyme thioredoxin and used for the synthesis of gold nanoparticles (GNPs) in the pH range of 2–11. These peptides were compared with free cysteine, the counterpart acidic peptides AAAECE and γ-ECG (glutathione), and the neutral peptide AAAACA. The objective was to investigate the effect of the amino acids neighboring a cysteine residue on the pH-dependent synthesis of gold nanocrystals. Kohn–Sham density functional theory (KS-DFT) calculations indicated an increase in the reducing capacity of AAAKCK favored by the successive deprotonation of their ionizable groups at increasing pH values. Experimentally, it was observed that gold speciation and the peptide structure also have a strong influence on the synthesis and stabilization of GNPs. AAAKCK produced GNPs at room temperature, in the whole investigated pH range. By contrast, alkaline pH was the best condition for the synthesis of GNP assisted by the AAARCR peptide. The acidic peptides produced GNPs only in the presence of polyethylene glycol, and the synthesis using AAAECE and γ-ECG also required heating. The ionization state of AAAKCK had a strong influence on the preferential growth of the GNPs. Therefore, pH had a remarkable effect on the synthesis, kinetics, size, shape, and polydispersity of GNPs produced using AAAKCK. The AAAKCK peptide produced anisotropic decahedral and platelike nanocrystals at acidic pH values and spherical GNPs at alkaline pH values. Both alkaline peptides were also efficient capping agents for GNPs, but they produced a significant difference in the zeta potential, probably because of different orientations on the gold surface

Oxidative modifications induced by a TR cation radical on cytochrome

<p><b>c</b>.A - Spectral changes of cytochrome <i>c</i> before (light gray line) and after 30 (gray line), and 120 (black line) min UV light irradiation at 254 nm, at pH 4.0. <b>B</b> –The same conditions described for A in the presence of 25 µmol/L TR. <b>C</b> - The same conditions described for Ain the presence of 2.5 mmol/L TR. In this panel, the dashed line represents the original spectrum of cytochrome c before the subtraction of the turbidity sample contribution that resulted in the spectrum shown as a black line <b>D</b> – The effect of different TR concentrations on the rate of Soret band blue shift promoted by UV irradiation. In panel D, the number of asterisks indicates the corresponding spectra shown in panel A (*), B (**), and C (***), from which the data were extracted. The inset shows SEM images and the distribution of particle size obtained for the sample in the condition marked with three asterisks. <b>E</b> – The effect of pH on the rate of Soret band blue shift promoted by UV irradiation in the presence of 25 µmol/L TR. Filled black circles represent the results in the absence of TR and opened circles represent the presence of TR. In panel E, the asterisk in one data point indicates that the point was extracted from the corresponding spectrum shown in panel F. <b>F</b> – The same conditions described for B, at pH 8.0.In this panel, the dashed line represents the original spectra of cytochrome c before the subtraction of the turbidity sample contribution that resulted in the spectrum shown as a black line. Samples containing 3 µmol/L cytochrome <i>c</i> and TR, when indicated, were irradiated in a 5 mmol/L phosphate buffer at 25°C in the cuvette with a 4 mW/cm^-2 as function of 254 nm of excitation at a distance of 4 cm from 1cm² of a selected sample area.</p

Oxidative modifications induced by FP cation radicals on cytochrome

<p><b>c</b>.A - Spectral changes of cytochrome <i>c</i> before (light gray line) and after 30 (gray line), and 120 (black line) min UV light irradiation at 254 nm in the presence of 10µmol/LFP, at pH 4.0. <b>B</b> - The same conditions described for A in the presence of 2.5 mmol/LFP. In this panel, the dashed line represents the original spectra of cytochrome <i>c</i> before the subtraction of the turbidity sample contribution that resulted in the spectrum shown as a black line <b>C</b> – The effect of different FP concentrations on the rate of Soret band blue shift promoted by UV light irradiation. In panel C, the number of asterisks indicates the corresponding spectra shown in panel A (*) and B (**), from which the data were extracted. The inset shows SEM images and the distribution of particle size obtained for the sample in the condition marked with two asterisks. <b>D</b> – The effect of pH onthe rate of Soret band blue shift promoted by UV light irradiation promoted by 10 µmol/L FP. Filled black circles represent the results in the absence of FP and opened circles represent the presence of FP.In panel E, the asterisk in one data point indicates that was the point extracted from the spectra shown in panel E. <b>E</b> – The same conditions described for B, at pH 8.0. In this panel, the dashed line represents the original spectra of cytochrome <i>c</i> before subtraction of the turbidity sample contribution that resulted in the spectrum shown as a black line. Samples containing 3 µmol/Lcytochrome <i>c</i> and FP, when indicated, were irradiated in a 5 mmol/Lphosphate buffer at 25°C in the cuvette with a 4 mW/cm^-2of UV light intensity as function of 254 nm of excitation at a distance of 4 cm from 1cm² of selected sample area.</p

EPR and MCD analysis of cytochrome c modified by phenothiazinesA

<p>- EPR spectra of native cytochrome c; <b>B</b> - EPR spectra of cytochrome <i>c</i> 120 min irradiation in the presence of TR⁺. The spectra were obtained in the presence of 100 µmol/L cytochrome <i>c</i> and 200 µmol/L TR⁺ in a 5 mmol/L phosphate buffer, pH 7.4, at 11 Kelvin, 1 mT of field modulation, and 4 mW of microwave power in the X band. <b>C</b> – EPR spectra of TR at room temperature, which were obtained in the same conditions described for panel B. In this panel, the light gray line represents the spectrum obtained in the absence of cytochrome <i>c</i> and the black line the spectrum obtained in the presence of cytochrome <i>c</i>. Samples containing cytochrome <i>c</i> and TR were irradiated during 120 min in a 5 mmol L^-1phosphate buffer, at 35°C in the cuvette with 4 mW/cm^-2 of UV light intensity as function of 254 nm of excitation at a distance of 4 cm from 1cm² of selected sample area. <b>D</b> - MCD spectra of cytochrome <i>c</i> obtained after 120 min of irradiation in the presence of TR (gray line). In this panel, the dashed line represents the spectrum of an identical concentration of cytochrome <i>c</i> (100 µmol/L), completely converted to the ferrous form by β-mercaptoethanol. The samples were irradiated, with 4 mW cm^-2 of UV light intensity as function of 254 nm of excitation at a distance of 4 cm from 1cm² of selected sample area, in 10 mmol/L universal buffer, pH 5.</p