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991.
Water was a suitable medium for Paal–Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented. 相似文献
992.
Esra Bağda Ebru Yabaş Nihat Karakuş 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1813-1820
A cloud point extraction (CPE) procedure was presented for the preconcentration of UO2 2+ ion in different water samples. Tetracycline (TC) is the second most widely used antibiotics in the world and is used as chelating agent. To the best of our knowledge, this is the first work that an antibiotic is used as a chelating agent for CPE of UO2 2+. Besides, the use of TC as complexing agent provides excellent chelating features. TC molecule has large numbers of functional groups (adjacent hydroxyl oxygen atoms and cyclohexanone oxygen atoms, amide groups) which can form stable complex with UO2 2+. After complexation with TC, UO2 2+ ions were quantitatively recovered in Triton X-100 after cooling in the ice bath. 3.0 mL of acetate buffer was added to the surfactant-rich phase prior to its analysis by UV–Vis spectrophotometer. The influence of analytical parameters including pH, buffer volume, TC, Triton X-100 concentrations, bath temperature, incubation time were optimized. The effect of the matrix ions on the recovery of UO2 2+ ions was investigated. The limit of detection was 0.0746 μg mL?1 along with enrichment factor of 14.3 with a R.S.D. of 3.6 %. The proposed procedure was applied to the analysis of various environmental water samples. On the other hand, the electronic distribution of TC molecule is investigated with their frontier molecular orbital density distributions. 相似文献
993.
994.
995.
The hybrid propulsion offers some remarkable advantages like high safety and high specific impulse and thus it is considered a promising technology for the next generation launchers and space systems. The purpose of this work is to validate through numerical simulations a design tool for hybrid rocket motors (HRM). (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
996.
In this paper, the tangential and normal discontinuities at the interface between the scatterer and the matrix are independently modeled, and these relative displacements are directly proportional to the corresponding components of tractions at the interface. The generation of full band-gaps is investigated on the basis of the derived imperfect interface conditions for a sonic plate with an array of acoustic piezoceramic hollow spheres scatterers embedded in an epoxy matrix. The scatterers are made from functionally graded materials with radial polarization. Numerical evaluation has shown that imperfect interface may have a significant effect on the increasing of the length of the full band-gaps. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
997.
Drying of polyacrylamide (PAAm)-κ-carrageenan (κC) composite gels were monitored by using steady-state fluorescence technique.
Disc shaped gels were formed from acrylamide (AAm) and N, N′- methylenebisacrylamide(Bis) with various κ- carrageenan (κC)
contents by free radical crosslinking copolymerization in water. Pyranine (P) was doped as a fluorescence probe, and scattered light, I
sc
, and fluorescence intensities, I, were monitored during drying of these gels. It is observed that fluorescence intensity of pyranine increased as drying time
is increased for all samples. The increase in I was modeled using Stern- Volmer equation and diffusion with moving boundary. It is found that desorption coefficient, D decreased as κC contents were increased. Supporting gravimetrical and volumetric experiments were also carried out during
drying of PAAm- κC composite gels. 相似文献
998.
Resistance towards antibiotics stands out today as a major issue in the clinical act of treatment of bacterial-generated infections.
This process was characterized in proteoliposomes reconstituted from an E.coli strain isolated from invasive infections (blood culture) occurred in patients with a cardio-vascular device admitted for
surgery. Fluorescence spectroscopy and patch-clamp technique have been used. Two types of antibiotics have been targeted:
ceftazidime and ciprofloxacin. Antibiotics addition in proteoliposomes suspension undergoes a quenching in tryptophan residues
from outer membrane porins structure, probably due to the formation of a transient non-fluorescent porin-antibiotic complex.
Patch-clamp recordings revealed strong ion current blockages for both antibiotics, reflecting antibiotic–channel interactions
but with varying strength of interaction. The present study puts forward the mechanism of multidrug-resistance in extended-spectrum
beta-lactamase E.coli strains, as being caused by alterations of the antibiotics transport across the porins of the outer bacterial membrane. 相似文献
999.
Leonard Dăuş 《Applied Categorical Structures》2011,19(6):859-863
We use the concept of a regular object with respect to another object in an arbitrary category, in order to obtain the transfer
of regularity in the sense of Zelmanowitz between the categories R −mod and S −mod, when S is an excellent extension of the ring R. Consequently, if S is an excellent extension of the ring R, then S is von Neumann regular ring if and only if R is also von Neumann regular ring. In the second part, using relative regular modules, we give a new proof of a classical
result: the von Neumann regular property of a ring is Morita invariant. 相似文献
1000.
D. Ieşan 《Nonlinear Analysis: Real World Applications》2011,12(1):513-524
In this paper we present a theory of mixtures of elastic solids with initial stresses and initial heat flux. First, we establish the equations governing the small deformations superposed on nonlinear deformations of mixtures. Then, we derive the basic equations of prestressed mixtures with initial heat flux. The continuous dependence of the solutions upon initial data and body supplies is established. The theory is used to study the deformation of a prestressed spherical shell subjected to constant pressures. 相似文献