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151.
152.
153.
Josepha Yohanna de Jesus Eliane Santos de Carvalho Dantas Mairim Russo Serafini Paula dos Passos Menezes Juliana Cordeiro Cardoso Ricardo Luiz Cavalcanti Albuquerque-Jr Jivaldo do Rosário Matos Juliana Ferreira de Oliveira Irwin Rose Alencar de Menezes Francilene Amaral da Silva Adriano Antunes de Souza Araújo 《Journal of Thermal Analysis and Calorimetry》2016,123(3):2003-2012
154.
155.
Luisa C. Melo Murilo S. S. Julião Maria A. L. Milhome Ronaldo F. do Nascimento Djenaine De Souza Pedro de Lima-Neto Adriana N. Correia 《Journal of Analytical Chemistry》2018,73(7):695-704
This work describes the electroanalytical determination of Chlorpyriphos pesticide in natural waters using hanging mercury drop electrode allied to square wave adsorptive cathodic stripping voltammetry. The best responses were obtained in Britton?Robinson buffer solutions at pH 2.0, using a frequency of 100 s–1, a scan increment of 5 mV, a square wave amplitude of 25 mV and an accumulation potential of–0.4 V during 60 s. Therefore, voltammetric responses showed the presence of one well-defined and irreversible reduction peak, at–1.08 V vs. Ag/AgCl/KCl 1.0 M, which involves two electrons in the reduction of carbon?nitrogen bond in the N-heterocyclic system with the participation of protonation equilibrium preceding the electron transfer reaction. Analytical curves were constructed and compared to similar curves performed by gas chromatograph coupled to a selective nitrogen?phosphorus detector, which demonstrates that the proposed methodology is suitable for determining contamination by Chlorpyriphos in complex samples. 相似文献
156.
A numerical treatment for the Dirichlet boundary value problem on regular triangular grids for homogeneous Helmholtz equations is presented, which also applies to the convection-diffusion problems. The main characteristic of the method is that an accuracy estimate is provided in analytical form with a better evaluation than that obtained with the usual finite difference method. Besides, this classical method can be seen as a truncated series approximation to the proposed method. The method is developed from the analytical solutions for the Dirichlet problem on a ball together with an error evaluation of an integral on the corresponding circle, yielding accuracy. Some numerical examples are discussed and the results are compared with other methods, with a consistent advantage to the solution obtained here.
157.
Long holographic lifetimes in bacteriorhodopsin films 总被引:3,自引:0,他引:3
The D85N genetic variant of bacteriorhodopsin (BR) displays a nearly permanent lifetime of the photochromic P(490) state. We present pump-probe measurements that demonstrate this behavior. However, diffraction efficiency measurements made from holograms recorded in a hydrated D85N film show markedly different decay behavior, suggesting that a molecular diffusion process is occurring in the film. Holograms recorded with different grating frequencies display correspondingly different decay times, thus supporting this hypothesis. A thin D85N film was fabricated that was chemically cross linked, resulting in the elimination of diffusion of BR molecules within the polymer matrix. This film exhibits a grating lifetime of the order of weeks or more, thus permitting the long-term holographic storage of information. 相似文献
158.
Vilar MR Botelho do Rego AM Ferraria AM Jugnet Y Noguès C Peled D Naaman R 《The journal of physical chemistry. B》2008,112(23):6957-6964
We present results from high-resolution electron energy loss spectroscopy (HREELS) and XPS studies of self-assembled monolayers of DNA. The monolayers are well-organized and display sharp vibrational peaks in the HREEL spectra. The electrons interact mainly with the backbone of the DNA. The XPS results indicate that, in most of the samples studied, the phosphates on the DNA are not charged. 相似文献
159.
Gaião Eda N dos Santos SR dos Santos VB do Nascimento EC Lima RS de Araújo MC 《Talanta》2008,75(3):792-796
A microcontrolled, portable and inexpensive photometer is proposed. It uses a near infrared light emitting diode (NIR LED) as radiation source, a PbSe photoresistor as infrared detector and a programmable interrupt controller (PIC) microcontroller as control unit. The detector system presents a thermoresistor and a thermoelectric cooling to control the detector temperature and keep the noise at low levels. The microcontroller incorporated total autonomy on the proposed photometer. As its components are inexpensive and of easy acquisition, the proposed NIR LED-photometer is an economical alternative for chemical analyses in small routine, research and/or teaching laboratories. By being portable and microcontrolled, it also allows carrying out field chemical analyses. The instrument was successfully applied on the screening analysis to verify adulteration in gasoline samples. 相似文献
160.
Agricultural residues as sugarcane straw and bagasse are burned in boilers for generation of energy in sugar and alcohol industries.
However, excess of those by-products could be used to obtain products with higher value. Pulping process generates cellulosic
pulps and lignin. The lignin could be oxidized and applied in effluent treatments for heavy metal removal. Oxidized lignin
presents very strong chelating properties. Lignins from sugarcane straw and bagasse were obtained by ethanol–water pulping.
Oxidation of lignins was carried out using acetic acid and Co/Mn/Br catalytical system at 50, 80, and 115 °C for 5 h. Kinetics
of the reaction was accomplished by measuring the UV-visible region. Activation energy was calculated for lignins from sugarcane
straw and bagasse (34.2 and 23.4 kJ mol−1, respectively). The first value indicates higher cross-linked formation. Fourier-transformed infrared spectroscopy data of
samples collected during oxidation are very similar. Principal component analysis applied to spectra shows only slight structure
modifications in lignins after oxidation reaction. 相似文献