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51.
Akari Narayama Sosa Israel González Alejandro Trejo Álvaro Miranda Fernando Salazar Miguel Cruz-Irisson 《Journal of computational chemistry》2020,41(31):2653-2662
Recently, the need of improvement of energy storage has led to the development of Lithium batteries with porous materials as electrodes. Porous Germanium (pGe) has shown promise for the development of new generation Li-ion batteries due to its excellent electronic, and chemical properties, however, the effect of lithium in its properties has not been studied extensively. In this contribution, the effect of surface and interstitial Li on the electronic properties of pGe was studied using a first-principles density functional theory scheme. The porous structures were modeled by removing columns of atoms in the [001] direction and the surface dangling bonds were passivated with H atoms, and then replaced with Li atoms. Also, the effect of a single interstitial Li in the Ge was analyzed. The transition state and the diffusion barrier of the Li in the Ge structure were studied using a quadratic synchronous transit scheme. 相似文献
52.
53.
John C. Baez 《Letters in Mathematical Physics》1994,31(3):213-223
LetP M be a principalG-bundle. We construct well-defined analogs of Lebesgue measure on the spaceA of connections onP and Haar measure on the groupG of gauge transformations. More precisely, we define algebras of cylinder functions on the spacesA,G, andA/G, and define generalized measures on these spaces as continuous linear functionals on the corresponding algebras. Borrowing some ideas from lattice gauge theory, we characterize generalized measures onA,G, andA/G in terms of graphs embedded inM. We use this characterization to construct generalized measures onA andG whenG is compact. The uniform generalized measure onA is invariant under the group of automorphisms ofP. It projects down to the generalized measure onA/G considered by Ashtekar and Lewandowski in the caseG = SU(n). The generalized Haar measure onG is right- and left-invariant as well as Aut(P)-invariant. We show that averaging any generalized measure onA against generalized Haar measure gives aG-invariant generalized measure onA. 相似文献
54.
A new compound was elucidated as 9-acetyl-6-caryophyllen-15-ol. Iridoid glucosides including catalpol, methyl catalpol, 7-deoxy-8-epiloganic
acid, and aucubin, were isolated from leaves of Buddleia parviflora, while the known compounds were identified as dehydrobuddledin A and buddledin C. The structures was elucidated by extensive
1D-2D-NMR spectroscopy.
Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 29–31, January–February, 2008. 相似文献
55.
Daura Vega Moreno Zoraida Sosa Ferrera Jos Juan Santana Rodríguez 《Microchemical Journal》2007,87(2):139-146
Solid-phase microextraction (SPME) and solid-phase extraction (SPE) procedures were coupling with microwave-assisted micellar extraction for organochlorine pesticides residues determination in seaweed samples. They were optimized, compared and discussed.Preliminary experiments were performed in order to study experimental conditions for the extraction of pesticides from spiked seaweed samples with microwave-assisted micellar extraction (MAME) using a non-ionic surfactant (Polyoxyethylene 10 Lauryl Ether). After that, SPME and SPE were used to clean-up and preconcentrate MAME extract prior the analysis by liquid chromatography with photodiode array (PDA) detection.Excellent results were obtained for both procedures. Average pesticide recoveries between 80.5 and 104.3% for MAME-SPME and between 73.9 and 111.5% for MAME-SPE were obtained. Relative standard deviations (RSDs) were lower than 10.3% and 5.3% respectively for all recoveries tested, and LOD between 138–348 ng g− 1 for MAME-SPME and 2–38 ng g− 1 for MAME-SPE were obtained. The method was validated using Soxhlet extraction procedure.Both methods were applied to analyse target organochlorine pesticides in several seaweed samples and results were compared. These results show the great possibilities of combining MAME-SPE-HPLC-UV for the analysis of seaweed samples, improving the selectivity and sensitivity in the determination of organochlorine pesticides analysis for this kind of samples. 相似文献
56.
[structure: see text] A short synthesis of the marine sponge metabolites slagenins A (1), B (2), and C (3) is described. The synthetic route features the preparation of beta-hydroxyimidazolone 4 from ornithine and its subsequent oxidative cyclization to the slagenin core. 相似文献
57.
S. Baez A. P. Balachandran S. Vaidya B. Ydri 《Communications in Mathematical Physics》2000,208(3):787-798
Monopoles and solitons have important topological aspects like quantized fluxes, winding numbers and curved target spaces.
Naive discretizations which substitute a lattice of points for the underlying manifolds are incapable of retaining these features
in a precise way. We study these problems of discrete physics and matrix models and discuss mathematically coherent discretizations
of monopoles and solitons using fuzzy physics and noncommutative geometry. A fuzzy σ-model action for the two-sphere fulfilling
a fuzzy Belavin–Polyakov bound is also put forth.
Received: 13 April 1999 / Accepted: 7 August 1999 相似文献
58.
Gordana Pavlovi Julija Matijevi Sosa 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(9):1117-1119
The title compound, C18H13NO3, exists as a ketoamino tautomer implying a fairly short N—H?O intramolecular hydrogen bond between the 2‐naphthalenone and amino moieties [N?O 2.531 (3) Å] which is enhanced by the π‐electron delocalization effect. The naphthaldimine and 3‐carboxyphenyl fragments are inclined at an angle of 4.41 (7)°, so the molecule is almost planar. The molecules are connected by intermolecular O—H?O hydrogen bonds between the carboxy and keto O atoms, forming infinite chains around the twofold screw axes parallel to b . 相似文献
59.
We analyzed the modifications of the airflow around an NACA 0015 airfoil when the flow was perturbed with electrohydrodynamic
forces. The actuation was produced with a plasma sheet device (PSD) consisting in two bare electrodes flush mounted on the
surface of the wing profile operated to obtain a discharge contouring the body in the inter-electrode space. We analyze the
influence of different parameters of the actuation (frequency, input power, electrodes position) on the aerodynamic performance
of the airfoil, basing our study on measurements of the surface pressure distribution and of the flow fields with particle
image velocimetry technique. The experiments indicated that at moderate Reynolds numbers (150,000 < Re < 333,000) and at high angles of attack, steady or periodic actuations enabled large improvement of the lift and drag/lift
aerodynamic coefficients by reattaching the flow along the extrados. However, to attain the same results steady actuations
required larger power consumption. When exciting the flow with a moderate value of non-dimensional power coefficient (ratio
of electric power flow with the kinetic power flow), a frequency of excitation produced a peak on the coefficients that evaluate
the airfoil performance. This peak in terms of a non-dimensional frequency was close to 0.4 and can be associated to an optimal
frequency of excitation. However, our work indicates that this peak is not constant for all stalled flow conditions and should
be analyzed considering scale factors that take into account the ratio of the length where the forcing acts and the cord length. 相似文献
60.
Dr. Dehui Zhang Igor Macinkovic Dr. Nelmi O. Devarie‐Baez Dr. Jia Pan Dr. Chung‐Min Park Prof. Kate S. Carroll Dr. Milos R. Filipovic Prof. Ming Xian 《Angewandte Chemie (International ed. in English)》2014,53(2):575-581
Protein S‐sulfhydration (forming ‐S‐SH adducts from cysteine residues) is a newly defined oxidative posttranslational modification and plays an important role in H2S‐mediated signaling pathways. In this study we report the first selective, “tag‐switch” method which can directly label protein S‐sulfhydrated residues by forming stable thioether conjugates. Furthermore we demonstrate that H2S alone cannot lead to S‐sulfhydration and that the two possible physiological mechanisms include reaction with protein sulfenic acids (P‐SOH) or the involvement of metal centers which would facilitate the oxidation of H2S to HS.. 相似文献