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121.
Maria Raquel Cavalcanti Inácio Maria de Fátima Vitória de Moura Kássio Michell Gomes de Lima 《Vibrational Spectroscopy》2011,57(2):342-345
This paper proposes a methodology for the classification and determination of total protein in milk powder using near infrared reflectance spectrometry (NIRS) and variable selection. Two brands of milk powder were acquired from three Brazilian cities (Natal-RN, Salvador-BA and Rio de Janeiro-RJ). The protein content of 38 samples was determined by the Kjeldahl method and NIRS analysis. Principal component regression (PCR) and partial least squares (PLS) multivariate calibrations were used to predict the total protein. Soft independent modeling of class analogy (SIMCA) was also used for full-spectrum classification, resulting in almost 100% classification accuracy, regardless of the significance level adopted for the F-test. Using this strategy, it was feasible to classify powder milk rapidly and nondestructively without the need for various analytical determinations. Concerning the multivariate calibration models, the results show that PCR, PLS and MLR-SPA models are good for predicting total protein in powder milk; the respective root mean square errors of prediction (RMSEP) were 0.28 (PCR), 0.25 (PLS), 0.11 wt% (MLR-SPA) with an average sample protein content of 8.1 wt%. The results obtained in this investigation suggest that the proposed methodology is a promising alternative for the determination of total protein in milk powder. 相似文献
122.
123.
Positive photoresists are widely used in lithographic process for the fabrication of relief components. When exposed to UV radiation they suffer chemical reactions modifying their chemical and physical properties. Aiming to follow molecular modifications among two different photoresists unexposed and previously exposed to ultraviolet light we have employed spectroscopic techniques coupled with mass spectrometry in the study of the AZ-1518 and AZ-4620 photoresists. The photon stimulated ion desorption (PSID) technique following the S K-edge NEXAFS spectrum was employed at the brazilian synchrotron light source (LNLS), during single-bunch operation and using time-of-flight mass spectrometry (TOF-MS) for ion analysis. NEXAFS and PSID mass spectra on both AZ-1518 and AZ-4620 photoresists (unexposed and exposed) were obtained and relative desorption ion yield curves determined for the main fragments as a function of the photon energy. They present marked different PSID spectra. Fragments related to the photochemical decomposition of the AZ-1518 photoresist could be clearly identified differently from the AZ-4620. Studies on the hardness of both photoresists were performed using O2 plasma reactive ion etching (RIE) technique, analyzed by scanning electron microscopy (SEM) and used to explain different desorption yields in the PSID spectra. These results show that the PSID technique is adequate to investigate structural changes in molecular level in different unexposed and exposed photoresists, which is crucial for improving our knowledge about the breakup process. 相似文献
124.
Let A be a finitely generated abelian group. We describe the automorphism group Aut(A) using the rank of A and its torsion part p-part A
p
.
For a finite abelian p-group A of type (k
1, ..., k
n
), simple necessary and sufficient conditions for an n × n-matrix over integers to be associated with an automorphism of A are presented. Then, the automorphism group Aut(A) for a finite p-group A of type (k
1, k
2) is analyzed.
This work has begin during the visit of the second author to the Faculty of Mathematics and Computer Science, Nicolaus Copernicus
University during the period July 31–August 13, 2005. This visit was supported by the Nicolaus Copernicus University and a
grant from Cnpq. 相似文献
125.
Tércio de Freitas Paulo Solange de Oliveira Pinheiro Maria Aparecida S. Da Silva Luiz Gonzaga de França Lopes Lucidalva S. Pinheiro Gil F. A. Aquino Márcia Laudelina Arruda Temperini Pedro de Lima Neto Izaura Cirino Nogueira Diógenes 《Electroanalysis》2009,21(9):1081-1089
STM and impedance results of the self‐assembled monolayer (SAM) formed with thionicotinamide (TNA) on gold indicate the presence of defects that increase with the immersion time of the electrode in the TNA solution affecting the SAM electroactivity toward the electron transfer reaction of the cytochrome c metalloprotein and [Fe(CN)6]4? and [Ru(NH3)6]3+ complexes. It was observed that this electroactivity was also affected by the pH of the electrolyte solution. SERS and STM data indicate sulfur coordination to the surface with contribution of the NH2 group. From the dependence of the TNA surface coverage on the temperature and concentration in solution, thermodynamic parameters of adsorption were determined. 相似文献
126.
B J Shields J J Lima P F Binkley C V Leier J J MacKichan 《Journal of chromatography. A》1986,378(1):163-171
This paper presents a rapid, simple and economical method for assaying pindolol concentrations in plasma and urine by high-performance liquid chromatography using ultraviolet detection. It is sensitive enough for use in single-dose pharmacokinetic studies and may also be used to determine pindolol concentrations in the plasma from patients taking the drug, provided that the patient is not taking any of the drugs which interfere with the method. Drugs which were found to interfere with the pindolol peak are quinidine, n-acetylprocainamide and lidocaine. Disopyramide, oxprenolol and levobunolol interfered with the internal standard peak. 相似文献
127.
In this article we present the first results obtained for nanostructured γ-Ni20Zn80 alloy prepared by a thermo-mechanical (TM) process developed in our laboratory. The process uses the energy stored in the defect structure, generated via mechanical milling of the nickel, to accelerate the reaction in the solid state, allowing a more rapid alloy formation. The process presents several advantages, when compared with techniques currently used for the production of this class of materials. The X-ray diffraction pattern for the alloy produced by the TM process is compared with that measured for the same alloy, produced by the mechanical alloying technique. The results show that the TM process holds the potential to become a valuable alternative method for the production of nanostructured materials. 相似文献
128.
Isolda C. Mendes Fernanda B. Costa Geraldo M. de Lima José D. Ardisson Isabel Garcia-Santos Alfonso Castiñeiras Heloisa Beraldo 《Polyhedron》2009,28(6):1179-1185
Reaction of tin tetrachloride with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives gave [Sn(2Am4DH)Cl3] (1), [Sn(2Am4Me)Cl3] (2), [Sn(2Am4Et)Cl3] (3) and [Sn(2Am4Ph)Cl3] (4) as products, in which an anionic thiosemicarbazone coordinates to the metal centre along with three chloride ions. The crystal structures of 1 and 2 were determined. The thiosemicarbazones were moderately active against Candida albicans and Pseudomonas aeruginosa. Upon coordination to tin(IV) the antimicrobial activity of the thiosemicarbazones increases. The studied compounds proved to be toxic to Artemia salina, suggesting that they could present cytotoxic activity against solid tumors. 相似文献
129.
A. R. Lopes M. H.F. Bettega M.T. do N. Varella M. A.P. Lima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(3):385-392
We report elastic (rotationally summed) and rotationally resolved
cross-sections for scattering of low-energy electrons by the
C3H4 isomers allene, propyne, and cyclopropene, which belong
to the D2d, C3v, and C2v groups, respectively. We
employed the Schwinger multichannel method with pseudopotentials at
the static-exchange approximation, combined with the
adiabatic-nuclei-rotation (ANR) approximation to calculate the
rotational excitation cross-sections for energies ranging from 5
to 30 eV. Our rotational resolved cross-sections show the isomer effect
more strongly related to scattering potentials of different molecular
geometries and to transition selection rules than to differences in mass
distribution which account for the energy spacing in the rotational
spectra of the molecules. 相似文献
130.
Rayne S. S. Magalhães Karina C. De Lima Diego S. G. de Almeida Joelma F. De Mesquita Elis C. A. Eleutherio 《Applied biochemistry and biotechnology》2017,181(3):914-924
In some pathogens, trehalose biosynthesis is induced in response to stress as a protection mechanism. This pathway is an attractive target for antimicrobials as neither the enzymes, Tps1, and Tps2, nor is trehalose present in humans. Accumulation of T6P in Candida albicans, achieved by deletion of TPS2, resulted in strong reduction of fungal virulence. In this work, the effect of T6P on Tps1 activity was evaluated. Saccharomyces cerevisiae, C. albicans, and Candida tropicalis were used as experimental models. As expected, a heat stress induced both trehalose accumulation and increased Tps1 activity. However, the addition of 125 μM T6P to extracts obtained from stressed cells totally abolished or reduced in 50 and 60 % the induction of Tps1 activity in S. cerevisiae, C. tropicalis, and C. albicans, respectively. According to our results, T6P is an uncompetitive inhibitor of S. cerevisiae Tps1. This kind of inhibitor is able to decrease the rate of reaction to zero at increased concentrations. Based on the similarities found in sequence and function between Tps1 of S. cerevisiae and some pathogens and on the inhibitory effect of T6P on Tps1 activity observed in vitro, novel drugs can be developed for the treatment of infectious diseases caused by organisms whose infectivity and survival on the host depend on trehalose. 相似文献