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121.
We study a quantum-mechanical system of three particles in a one-dimensional box with two-particle harmonic interactions. The symmetry of the system is described by the point group D3d. Group theory greatly facilitates the application of perturbation theory and the Rayleigh–Ritz variational method. A great advantage is that every irreducible representation can be treated separately. Group theory enables us to predict the connection between the states for the small box length and large box length regimes of the system. We discuss the crossings and avoided crossings of the energy levels as well as other interesting features of the spectrum of the system. 相似文献
122.
Maria A. S. Rios Francisco F. P. Santos Francisco J. N. Maia Selma E. Mazzetto 《Journal of Thermal Analysis and Calorimetry》2013,112(2):921-927
This work shows the evaluation of three antioxidants (2,6-di-t-butyl-4-methylphenol (BHT)—synthetic antioxidant, hydrogenated cardanol (HC), and alkyl hydrogenated cardanol (AHC)—both derived from cashew nut shell liquid) on the thermo-oxidative stability of the soybean biodiesel. The antioxidants were added at concentrations of 200, 300, and 400 ppm, and the oxidative stability of the biofuel with and without antioxidants were investigated by thermogravimetric analysis (TG-DTG and IPDT) and Metrohm 743 Rancimat per the EN 14112 method. The results showed that all antioxidants contributed for the thermo-oxidative stability of the soybean biodiesel as follows: soybean biodiesel < soybean biodiesel + BHT < soybean biodiesel + HC < soybean biodiesel + AHC. In the Rancimat method, the results showed that the antioxidants influenced the biodiesel stability with an increase of at least 71 %. 相似文献
123.
Antonio Doménech‐Carbó María Teresa Doménech‐Carbó Francisco López‐López Francisco Manuel Valle‐Algarra Laura Osete‐Cortina Estrella Arcos‐Von Haartman 《Electroanalysis》2013,25(12):2621-2630
The solid state voltammetric response of Egypt blue, Han blue and ploss blue pigments upon attachment to graphite electrodes in contact with aqueous phosphate buffer at pH 7.0 is studied by voltammetry of microparticles and scanning electrochemical microscopy. Such voltammetric responses, combined with those for synthetic specimens consisting of binary mixtures of the pigment and SiO2 or CaCO3 as well as ternary ones of CaCO3 and SiO2 mixtures allow for the identification of the pigment and the support in samples from wall paintings using different electrochemical parameters, in particular upon performing the Tafel and modified Tafel analysis of voltammetric peaks. Identification of Egypt blue in microsamples of murals from a Roman archaeological site in Castulo (Jaén, Spain) is discussed. 相似文献
124.
Francisco Ardini Francesco Soggia Maria Luisa Abelmoschi Emanuele Magi Marco Grotti 《Analytical and bioanalytical chemistry》2013,405(2-3):665-677
To provide a new insight into the response of plants to abiotic stresses, the ionomic profiles of Nicotiana langsdorffii specimens have been determined before and after exposure to toxic metals (chromium) or drought conditions. The plants were genetically transformed with the rat glucocorticoid receptor (GR) or the gene for Agrobacterium rhizogenes rolC, because these modifications are known to produce an imbalance in phytohormone equilibria and a significant change in the defence response of the plant. Elemental profiles were obtained by developing and applying analytical procedures based on inductively coupled plasma atomic emission and mass spectrometry (ICP–AES/MS). In particular, the removal of isobaric interferences affecting the determination of Cr and V by ICP–MS was accomplished by use of a dynamic reaction cell, after optimization of the relevant conditions. The combined use of ICP atomic emission and mass spectrometry enabled the determination of 29 major and trace elements (Ba, Bi, Ca, Cd, Co, Cr, Cu, Eu, Fe, Ga, K, Li, Mg, Mn, Mo, Na, P, Pb, Pt, Rb, S, Sb, Sn, Sr, Te, V, W, Y, and Zn) in different parts of the plants (roots, stems, and leaves), with high accuracy and precision. Multivariate data processing and study of element distribution patterns provided new information about the ionomic response of the target organism to chemical treatment or water stress. Genetic modification mainly affected the distribution of Bi, Cr, Mo, Na, and S, indicating that these elements were involved in biochemical processes controlled by the GR or rolC genes. Chemical stress strongly affected accumulation of several elements (Ba, Ca, Fe, Ga, K, Li, Mn, Mo, Na, P, Pb, Rb, S, Sn, Te, V, and Zn) in different ways; for Ca, Fe, K, Mn, Na, and P the effect was quite similar to that observed in other studies after treatment with other transition elements, for example Cu and Cd. The effect of water deficit was less evident, mainly consisting in a decrease of Ba, Cr, Na, and Sr in roots. Figure
Roots, stems and leaves of different Nicotiana langsdorffii genotypes exposed to abiotic stresses were analysed by ICP-AES and ICP-MS, obtaining information on the distribution of 29 major and trace elements in the samples 相似文献
125.
Juan Saulo Gonzlez‐Gonzlez Itzia I. Padilla‐Martínez Efrn V. García‐Bez Olivia Franco‐Hernndez Francisco J. Martínez‐Martínez 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(1):66-69
In the title compound, C24H36N6O6·C2H6OS, the carbonyl groups are in an antiperiplanar conformation, with O=C—C=O torsion angles of 178.59 (15) and −172.08 (16)°. An intramolecular hydrogen‐bonding pattern is depicted by four N—H...O interactions, which form two adjacent S(5)S(5) motifs, and an N—H...N interaction, which forms an S(6) ring motif. Intermolecular N—H...O hydrogen bonding and C—H...O soft interactions allow the formation of a meso‐helix. The title compound is the first example of a helical 1,2‐phenylenedioxalamide. The oxalamide traps one molecule of dimethyl sulfoxide through N—H...O hydrogen bonding. C—H...O soft interactions give rise to the two‐dimensional structure. 相似文献
126.
Yulin Ren Francisco Jiménez Ricardo García Milciades Mejía Heebyung Chai Norman R. Farnsworth Djaja D. Soejarto A. Douglas Kinghorn 《Tetrahedron letters》2013
A new sesquiterpene lactone, rufescenolide C (1), the first furanoheliangolide dimer, was isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. Its structure was determined by interpretation of its spectroscopic data, with the absolute configuration being established by analysis of the CD spectrum. A plausible biogenesis of this dimer is proposed. This compound showed potent cytotoxicity with an IC50 value of 150 nM, when tested against HT-29 human colon cancer cells. 相似文献
127.
Elisabeth Siebert Marius Horch Yvonne Rippers Johannes Fritsch Stefan Frielingsdorf Oliver Lenz Francisco VelazquezEscobar Friedrich Siebert Lars Paasche Uwe Kuhlmann Friedhelm Lendzian Maria‐Andrea Mroginski Ingo Zebger Peter Hildebrandt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(19):5267-5270
128.
Ingrid Hauser Ana B. Colaço Julie A. Skjæran Aslak Einbu Kjetill Østgaard Hallvard F. Svendsen Francisco J. Cervantes 《Applied biochemistry and biotechnology》2013,169(4):1449-1458
Large-scale amine-based CO2 capture will generate waste containing large amounts of ammonia, in addition to contaminants such as the actual amine as well as degradation products thereof. Monoethanolamine (MEA) has been a dominant amine applied so far in this context. This study reveals how biological N removal can be achieved even in systems heavily contaminated by MEA in post- as well as pre-denitrification treatment systems, elucidating the rate-limiting factors of nitrification as well as aerobic and denitrifying biodegradation of MEA. The hydrolysis of MEA to ammonia readily occurred both in post- and pre-denitrification treatment systems with a hydraulic retention time of 7 h. MEA removal was ≥99?±?1 % and total nitrogen removal 77?±?10 % in both treatment systems. This study clearly demonstrates the advantage of pre-denitrification over post-denitrification for achieving biological nitrogen removal from MEA-contaminated effluents. Besides the removal of MEA, the removal efficiency of total nitrogen as well as organic matter was high without additional carbon source supplied. 相似文献
129.
David Zanuy Francisco J. Sayago Guillem Revilla-López Gema Ballano Lilach Agemy Venkata Ramana Kotamraju Ana I. Jiménez Carlos Cativiela Ruth Nussinov April M. Sawvel Galen Stucky Erkki Ruoslahti Carlos Alemán 《Journal of computer-aided molecular design》2013,27(1):31-43
We present a chemical strategy to engineer analogs of the tumor-homing peptide CREKA (Cys-Arg-Glu-Lys-Ala), which binds to fibrin and fibrin-associated clotted plasma proteins in tumor vessels (Simberg et al. in Proc Natl Acad Sci USA 104:932–936, 2007) with improved ability to inhibit tumor growth. Computer modeling using a combination of simulated annealing and molecular dynamics were carried out to design targeted replacements aimed at enhancing the stability of the bioactive conformation of CREKA. Because this conformation presents a pocket-like shape with the charged groups of Arg, Glu and Lys pointing outward, non-proteinogenic amino acids α-methyl and N-methyl derivatives of Arg, Glu and Lys were selected, rationally designed and incorporated into CREKA analogs. The stabilization of the bioactive conformation predicted by the modeling for the different CREKA analogs matched the tumor fluorescence results, with tumor accumulation increasing with stabilization. Here we report the modeling, synthetic procedures, and new biological assays used to test the efficacy and utility of the analogs. Combined, our results show how studies based on multi-disciplinary collaboration can converge and lead to useful biomedical advances. 相似文献
130.