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141.
Peptide natural products displaying a wide range of biological activities have become important drug candidates over the years. Microorganisms have been a powerful source of such bioactive peptides, and Streptomyces have yielded many novel natural products thus far. In an effort to uncover such new, meaningful compounds, the metabolome of Streptomyces acidiscabies was analyzed thoroughly. Three new compounds, scabimycins A–C (1–3), were discovered, and their chemical structures were elucidated by NMR spectroscopy. The relative and absolute configurations were determined using ROESY NMR experiments and advanced Marfey’s method. 相似文献
142.
Halyna Lopushanska Andriy Lopushansky 《Mathematical Methods in the Applied Sciences》2019,42(9):3327-3340
We find the conditions for the unique solvability of the inverse problem for a time‐fractional diffusion equation with Schwarz‐type distributions in the right‐hand sides. This problem is to find a generalized solution of the Cauchy problem and an unknown space‐dependent part of an equation's right‐hand side under a time‐integral overdetermination condition. 相似文献
143.
144.
We apply Algorithm Robust to various problems in multiple objective discrete optimization. Algorithm Robust is a general procedure
that is designed to solve bicriteria optimization problems. The algorithm performs a weight space search in which the weights
are utilized in min-max type subproblems. In this paper, we experiment with Algorithm Robust on the bicriteria knapsack problem,
the bicriteria assignment problem, and the bicriteria minimum cost network flow problem. We look at a heuristic variation
that is based on controlling the weight space search and has an indirect control on the sample of efficient solutions generated.
We then study another heuristic variation which generates samples of the efficient set with quality guarantees. We report
results of computational experiments. 相似文献
145.
Lucjan Strekowski J. Christian Mason Hyeran Lee Martial Say Gabor Patonay 《Journal of heterocyclic chemistry》2004,41(2):227-232
Three methods were used to synthesize a series of the title compounds. The ketones absorb in the visible region, and upon protonation (pH<6) they are converted to hydroxy‐substituted heptamethine cyanines that show an intense absorption in the near‐infrared region (>700 nm). The conversion is reversible and depends solely on pH conditions. 相似文献
146.
Yaroshchuk AE Boiko YP Makovetskiy AL 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):7680-7690
We have demonstrated that with a composite nanoporous ceramic membrane in a batch membrane cell it is technically feasible to switch off the trans-membrane hydrostatic pressure difference within tens of milliseconds. That enabled us to resolve practically the whole time evolution of transient filtration potential. Measurements of the latter have been complemented by measurements of steady-state salt rejection by the composite membrane and by measurements of the streaming potential and hydraulic permeability of membrane supports available separately. A theory has been developed in terms of network thermodynamics for the electrical response of a bilayer membrane to a pressure perturbation. In combination with the results of salt rejection measurements, from the time transients of filtration potential we could determine the ion transport numbers within the nanoporous layer. Besides that, from the dependence of steady-state salt rejection on the trans-membrane volume flow, we have determined the diffusion permeability of and the salt reflection coefficient in the nanoporous layer. This has enabled us to estimate the contributions of Donnan and non-Donnan mechanisms to the rejection of ions by the nanoporous membrane used in this study. It has been unexpectedly found that the Donnan exclusion played only a secondary role. Our hypothesis is that the non-Donnan exclusion of ions from the nanopores might be caused by changes in water properties in nanoconfinement. Proceeding from the results of steady-state filtration experiments with the membrane and the support, we also concluded that the nanoporous layer was imperfection-free and had a quite narrow pore size distribution, which made it a suitable object for fundamental studies of ion transfer mechanisms in nanopores. 相似文献
147.
Borodin A Yamazaki M Kishimoto N Ohno K 《The journal of physical chemistry. A》2005,109(21):4721-4727
Penning ionization of formic acid (HCOOH), acetic acid (CH3COOH), and methyl formate (HCOOCH3) upon collision with metastable He*(2(3)S) atoms was studied by collision-energy/electron-energy-resolved two-dimensional Penning ionization electron spectroscopy (2D-PIES). Anisotropy of interaction between the target molecule and He*(2(3)S) was investigated based on the collision energy dependence of partial ionization cross sections (CEDPICS) obtained from 2D-PIES as well as ab initio molecular orbital calculations for the access of a metastable atom to the target molecule. For the interaction potential calculations, a Li atom was used in place of He*(2(3)S) metastable atom because of its well-known similarity in interaction with targets. The results indicate that in the studied collision energy range the attractive potential localizes around the oxygen atoms and that the potential well at the carbonyl oxygen atom is at least twice as much as that at the hydroxyl oxygen. Moreover we can notice that attractive potential is highly anisotropic. Repulsive interactions can be found around carbon atoms and the methyl group. 相似文献
148.
Recently, a new morphology of porous Cu3Sn with lamellar structure is observed. Several possible explanations of the formation are proposed and compared. The most reasonable one seems to be the one based on a theory of flux-driven cellular precipitation in open system. Outflux of Sn from Cu6Sn5 generates simultaneously supersaturation with vacancies and with copper leading to the eutectoid-like transformation β → α + γ (where γ is void). The transformation is complete due to a complete outflux of Sn from the Cu6Sn5 phase. Simple formulae for prediction of the lamellar structure parameters and the propagation velocity are obtained and compared reasonably with experimental data. The suggested model can be interpreted as one more case of the flux-driven phase transformations in open systems. 相似文献
149.
150.