排序方式: 共有62条查询结果,搜索用时 15 毫秒
21.
The formal solution of a general stargenvalue equation is presented, its properties studied and a geometrical interpretation given in terms of star-hypersurfaces in quantum phase space. Our approach deals with discrete and continuous spectra in a unified fashion and includes a systematic treatment of nondiagonal stargenfunctions. The formalism is used to obtain a complete formal solution of Wigner quantum mechanics in the Heisenberg picture and to write a general formula for the stargenfunctions of Hamiltonians quadratic in the phase space variables in arbitrary dimension. A variety of systems is then used to illustrate the former results. 相似文献
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Rodrigues Denise C. G. A. Suva Silvio S. Prata Arnaldo Marcio R. Felipe Maria das Gracas A. 《Applied biochemistry and biotechnology》1998,(1):869-875
Batch, fed-batch, and semicontinuous fermentation processes were used for the production of xylitol from sugarcane bagasse
hemicellulosic hydrolysate. The best results were achieved by the semicontinuous fermentation process: a xylitol yield of
0.79 g/g with an efficiency of 86% and a volumetric productivity of 0.66 g/L/h. 相似文献
23.
Barthelemy P Prata CA Filocamo SF Immoos CE Maynor BW Hashmi SA Lee SJ Grinstaff MW 《Chemical communications (Cambridge, England)》2005,(10):1261-1263
A neutral uridine-based amphiphile is described which condenses plasmid DNA. AFM studies show that the three distinct structural components of the amphiphile (i.e, nucleobase, alkyl chains, and poly(ethylene glycol)) are required for the formation of DNA-amphiphile supramolecular assemblies on a mica surface. 相似文献
24.
Di Luzio M. Bergamaschi L. Oddone M. Prata M. Salvini A. D’Agostino G. 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(3):723-729
Journal of Radioanalytical and Nuclear Chemistry - The application of the k0-standardization method of neutron activation analysis offers the great advantage to perform multi-elemental analyses... 相似文献
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Characterization of crude oil biomarkers using comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry 下载免费PDF全文
Noroska Gabriela Salazar Mogollón Paloma Santana Prata Jadson Zeni dos Reis Eugênio Vaz dos Santos Neto Fabio Augusto 《Journal of separation science》2016,39(17):3384-3391
Oil samples from Recôncavo basin (NE Brazil), previously analyzed by traditional techniques such as gas chromatography coupled to tandem mass spectrometry, were evaluated using comprehensive two‐dimensional gas chromatography coupled to quadrupole mass spectrometry and comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry along with simplified methods of samples preparation to evaluate the differences and advantages of these analytical techniques to better understand the development of the organic matter in this basin without altering the normal distribution of the compounds in the samples. As a result, the geochemical parameters calculated by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry described better the origin, maturity, and biodegradation of both samples probably by increased selectivity, resolution, and sensitivity inherent of the multidimensional technique. Additionally, the detection of the compounds such as, the C(14α‐) homo‐26‐nor‐17α‐hopane series, diamoretanes, nor‐spergulanes, C19–C26 A‐nor‐steranes and 4α‐methylsteranes resolved and detected by comprehensive two‐dimensional gas chromatography coupled to tandem mass spectrometry were key to classify and differentiate these lacustrine samples according to their maturity and deposition conditions. 相似文献
27.
Prata CA Zhao Y Barthelemy P Li Y Luo D McIntosh TJ Lee SJ Grinstaff MW 《Journal of the American Chemical Society》2004,126(39):12196-12197
Delivering a missing gene or a functional substitute of a defective gene has the potential to revolutionize current medical care. Of the two gene delivery approaches, viral and synthetic vectors, synthetic cationic vectors possess several practical advantages but suffer from poor transfection efficiency. A new approach to gene delivery using charge-reversal amphiphiles is described. This synthetic vector transforms from a cationic to an anionic amphiphile intracellularly. This amphiphile performs two roles: first, it binds and then releases DNA, and second, as an anionic multicharged amphiphile, it destabilizes lipid bilayers. A charge-reversal amphiphile was synthesized and fully characterized, including the supramolecular complex it forms with DNA. Enhanced gene transfection was observed using these vectors compared to current cationic amphiphiles. 相似文献
28.
Patrícia D. Barata Alexandra I. Costa Luís F. V. Ferreira José V. Prata 《Journal of polymer science. Part A, Polymer chemistry》2010,48(22):5040-5052
Novel alternating copolymers comprising bis‐ calix[4]arene‐p‐phenylene ethynylene and m‐phenylene ethynylene units ( CALIX‐m‐PPE ) were synthesized using the Sonogashira‐Hagihara cross‐coupling polymerization. Good isolated yields (60–80%) were achieved for the polymers that show Mn ranging from 1.4 × 104 to 5.1 × 104 gmol?1 (gel permeation chromatography analysis), depending on specific polymerization conditions. The structural analysis of CALIX‐m‐PPE was performed by 1H, 13C, 13C–1H heteronuclear single quantum correlation (HSQC), 13C–1H heteronuclear multiple bond correlation (HMBC), correlation spectroscopy (COSY), and nuclear overhauser effect spectroscopy (NOESY) in addition to Fourier transform‐Infrared spectroscopy and microanalysis allowing its full characterization. Depending on the reaction setup, variable amounts (16–45%) of diyne units were found in polymers although their photophysical properties are essentially the same. It is demonstrated that CALIX‐m‐PPE does not form ground‐ or excited‐state interchain interactions owing to the highly crowded environment of the main‐chain imparted by both calix[4]arene side units which behave as insulators inhibiting main‐chain π–π staking. It was also found that the luminescent properties of CALIX‐m‐PPE are markedly different from those of an all‐p‐linked phenylene ethynylene copolymer ( CALIX‐p‐PPE ) previously reported. The unexpected appearance of a low‐energy emission band at 426 nm, in addition to the locally excited‐state emission (365 nm), together with a quite low fluorescence quantum yield (? = 0.02) and a double‐exponential decay dynamics led to the formulation of an intramolecular exciplex as the new emissive species. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
29.
J.A. Lozano M.P. Kostow E. Brück J.C. de Lima A.T. Prata P.A.P. Wendhausen 《Journal of magnetism and magnetic materials》2008,320(14):e189-e192
The powder metallurgy technique has been exploited as a means to prepare porous magnetocaloric materials. The alloy Mn1.1Fe0.9P0.46As0.54 was previously synthesized by mechanical alloying followed by a solid-state reaction for crystallization and homogenization. Subsequently, the alloy was comminuted and sintered at 1298 K. The obtained sintered product is aimed to be tested in a magnetic regenerator of a prototype machine. 相似文献
30.
We discuss a recent method proposed by Kryukov and Walton to address boundary-value problems in the context of deformation quantization. We compare their method with our own approach and establish a connection between the two formalisms. 相似文献