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排序方式: 共有254条查询结果,搜索用时 15 毫秒
21.
Nelso P. Navarro Andrés Mansilla Estela M. Plastino 《Micron (Oxford, England : 1993)》2010,41(7):899-903
Iridaea cordata cultivated in the presence of UVB radiation (UVBR) was studied using transmission electron microscopy. Apical segments were cultivated in 0.97 Wm?2 of UVBR for 40 days, 3 h a day, and compared to a negative control (UVBR absent). UVBR caused modifications, mainly in the cortical cells, including an increased number of cell wall-producing vesicles, in addition to thicker and denser cellular walls, compared to the control. Additionally, cells were observed with an irregular contour and without defined organelles. The increase of cell-wall thickness could be interpreted as an acclimation to UVBR, which could lead to protection from this radiation. 相似文献
22.
Lizarraga L Andrade EM Florit MI Molina FV 《The journal of physical chemistry. B》2005,109(40):18815-18821
The quasi-equilibrium electrochemomechanical behavior of relatively thick polyaniline films in sulfuric acid is investigated through experimental measurements and theoretical modeling. The leucoemeraldine (LE)-emeraldine (EM) conversion, or redox switching, is studied. The dependence of film volume and electrochemical charge is determined as a function of applied potential. It is observed that the film volume follows the charge, showing an expansion during the second half of the LE-EM oxidation. The model postulates the existence of a stable intermediate, protoemeraldine (PE), with a formal potential distribution for the PE-EM reaction. The volume change is modeled statistically considering contributions from mixing, polymer deformation, and electrostatic charge. The model shows very good agreement with the experiments, indicating that, in the conditions studied, the deformation contribution dominates the volume changes as a result of the conformational modifications undergone by the polymer in the PE-EM oxidation. 相似文献
23.
We have studied the ring opening of nonactivated amino aziridines 1 by water under acidic conditions. Depending on the acid used, amino aziridines are cleaved at C-3 or C-2 with high regioselectivity, and total stereoselectivity, affording chiral 2,3-diaminoalkan-1-ols 3 or 1,3-diaminoalkan-2-ols 4 in high yield. 相似文献
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A study of several physicochemical and analytical properties of o,o′-diaminoazobenzene (DAB) is reported and its chemical behaviour discussed from the point of view of Pearson's theory. DAB has been applied to the determination of palladium by means of a new extractocolorimetric method. 相似文献
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Effectiveness of Photodynamic Therapy in Elimination of HPV‐16 and HPV‐18 Associated with CIN I in Mexican Women
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Elizabeth Maldonado Alvarado Martha Olivia Osorio Peralta Alejandra Moreno Vázquez Lydia Alejandra Martínez Guzmán Maria Eugenia Melo Petrone Zulma Iveth Enriquez Mar Dora Estela Jovel Galdamez Bárbara Carrión Solana Guadalupe Balderas Martínez Eduarda Parra Rossana Inés Castellanos Oliveros Rosa Linda Bello Leiva Araceli Espinosa Montesinos Citlalli Barrera Mendoza Selma Eugenia Medina García Eva Ramón Gallegos 《Photochemistry and photobiology》2017,93(5):1269-1275
This study aimed to determine the effectiveness of photodynamic therapy (PDT), using δ‐aminolevulinic acid (5‐ALA), in the elimination of premalignant cervical lesions in Mexican patients with human papillomavirus (HPV) infection and/or cervical intraepithelial neoplasia (CIN). Thirty women diagnosed with CIN I and/or positive for HPV participated in the study. Topical 6% 5‐ALA in gel form was applied to the uterine cervix; after 4 h, the lesion area was irradiated with a light dose of 200 J cm?2 at 635 nm. This procedure was performed three times at 48‐h intervals. Clinical follow‐up was performed at 3, 6, and 12 months after the initial PDT administration, by colposcopy, cervical cytology, histopathological analysis, polymerase chain reaction, and hybrid capture. Of HPV‐infected patients without evidence of CIN I, 80% cleared the infection, while HPV associated with CIN I was eliminated in 83% of patients (P < 0.05). At 12 months, CIN I had regressed in 57% of patients, although this response was not statistically significant. PDT using 6% 5‐ALA is concluded to be effective in eliminating HPV infection associated or not with CIN I. 相似文献
28.
Bartolomei M Carmona-Novillo E Hernández MI Campos-Martínez J Hernández-Lamoneda R 《The Journal of chemical physics》2010,133(12):124311
Completely ab initio global potential energy surfaces (PESs) for the singlet and triplet spin multiplicities of rigid O(2)((3)Σ(g)(-))+O(2)((3)Σ(g)(-)) are reported for the first time. They have been obtained by combining an accurate restricted coupled cluster theory with singles, doubles, and perturbative triple excitations [RCCSD(T)] quintet potential [Bartolomei et al., J. Chem. Phys. 128, 214304 (2008)] with complete active space second order perturbation theory (CASPT2) or, alternatively, multireference configuration interaction (MRCI) calculations of the singlet-quintet and triplet-quintet splittings. Spherical harmonic expansions, containing a large number of terms due to the high anisotropy of the interaction, have been built from the ab initio data. The radial coefficients of these expansions are matched at long range distances with analytical functions based on recent ab initio calculations of the electric properties of the monomers [M. Bartolomei, E. Carmona-Novillo, M. I. Hernández, J. Campos-Martínez, and R. Hernández-Lamoneda, J. Comput. Chem. (2010) (in press)]. The singlet and triplet PESs obtained from either RCCSD(T)-CASPT2 or RCCSD(T)-MRCI calculations are quite similar, although quantitative differences appear in specific terms of the expansion. CASPT2 calculations are the ones giving rise to larger splittings and more attractive interactions, particularly in the region of the absolute minima (in the rectangular D(2h) geometry). The new singlet, triplet, and quintet PESs are tested against second virial coefficient B(T) data and, their spherically averaged components, against integral cross sections measured with rotationally hot effusive beams. Both types of multiconfigurational approaches provide quite similar results, which, in turn, are in good agreement with the measurements. It is found that discrepancies with the experiments could be removed if the PESs were slightly more attractive. In this regard, the most attractive RCCSD(T)-CASPT2 PESs perform slightly better than the RCCSD(T)-MRCI counterpart. 相似文献
29.
The electrochemistry of platinum single crystals is historically reviewed. After a brief revision of historical results dating before the publication of the landmark experiment by J. Clavilier of the flame annealing in 1980, the controversy introduced by this experiment into the surface electrochemistry community is described. Questions about the structure and composition of the platinum surface after the flame annealing and their implications on the characteristic voltammetry of platinum single crystal electrodes were slowly answered in the years that followed the first introduction of this methodology. One of the last questions to be solved was that about the nature of the chemical species responsible for the charge transfer process that leads to the so-called unusual features in the voltammogram. This was solved with the charge displacement experiment. Nowadays, a great deal of knowledge has been gathered about the structure of the interphase between platinum electrodes and electrolytic solutions and also about the electrocatalytic behaviour of platinum surfaces. State-of-the-art information about platinum electrochemistry is provided, with emphasis on results from our group, especially those obtained with a thermodynamic analysis, involving either constant or variable temperatures and with the laser-induced temperature jump method. 相似文献
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