排序方式: 共有45条查询结果,搜索用时 15 毫秒
1.
Murphy JA Commeureuc AG Snaddon TN McGuire TM Khan TA Hisler K Dewis ML Carling R 《Organic letters》2005,7(7):1427-1429
[reaction: see text] N-Methoxy-N-methylamides (Weinreb amides) are converted efficiently into ketones by reaction with alkylidenetriphenylphosphoranes and in situ hydrolysis of the product. 相似文献
2.
Navara Tanweer Fazal-Ur-Rehman Qazi Gotam Das Afreen Bilgrami Sakeenabi Basha Naseer Ahmed Hammam Ahmed Bahammam Sarah Ahmed Bahammam Syed Nahid Basheer Ali A. Assiry Mohmed Isaqali Karobari Abdul Samad Khan Artak Heboyan 《Molecules (Basel, Switzerland)》2022,27(15)
Erosive beverages cause dissolution of natural teeth and intra-oral restorations, resulting in surface characteristic changes, particularly roughness and degradation. The purpose of this study was to evaluate the surface roughness and topography of a dental ceramic following immersion in locally available erosive solutions. A total of 160 disc specimens of a nano-fluorapatite type ceramic (12 mm diameter and 2 mm thickness) were fabricated and equally distributed into two groups (n = 80) and then evenly distributed among the following five testing groups (n = 16): lemon juice, citrate buffer solution, 4% acetic acid, soft cola drink, and distilled water which served as a control. The surface roughness (Ra) and topography were evaluated using a profilometer and scanning electron microscope at baseline, 24 h, 96 h, and 168 h respectively. Data were analyzed using ANOVA and Tukey’s multiple comparisons (p ≤ 0.05). Surface changes were observed upon exposure to all acidic beverages except distilled water. Amongst all immersion media, 4% acetic acid produced the most severe surface roughness across all time periods (i.e., baseline, 24 h, 96 h, and 168 h). A statistically significant difference in the surface roughness values between all immersion media and across all four time intervals was observed. Erosive agents had a negative effect on the surface roughness and topography of the tested ceramic. The surface roughness increased with increased storage time intervals. 相似文献
3.
[reaction: see text] Indolones are prepared in excellent yield at 80 degrees C in water by radical reaction (aryl radical formation, hydrogen atom abstraction, cyclization, and rearomatization) mediated by the reagent diethylphosphine oxide (DEPO). The reaction features V-501 as a water-soluble initiator; no other additives are needed. The process proceeds at a much lower temperature than is required for efficient reaction with toxic tributyltin hydride in benzene and permits significantly higher isolated yields than the corresponding reaction mediated by ethylpiperidine hypophosphite (EPHP). 相似文献
4.
We consider extensions of certain states. The states are defined on the systems of sets that are closed under the formation of the symmetric difference (concrete quantum logics). These systems can be viewed as certain set‐representable quantum logics enriched with the symmetric difference. We first show how the compactness argument allows us to extend states on Boolean algebras over such systems of sets. We then observe that the extensions are sometimes possible even for non‐Boolean situations. On the other hand, a difference‐closed system can be constructed such that even two‐valued states do not allow for extensions. Finally, we consider these questions in a σ‐complete setup and find a large class of such systems with rather interesting state properties. 相似文献
5.
Tanweer Sohail 《Czechoslovak Mathematical Journal》2010,60(2):411-422
In this paper we compute topological invariants for some configuration spaces of complex projective spaces. We shall describe
Sullivan models for these configuration spaces. 相似文献
6.
Wafa Arif Nosheen Fatima Rana Iqra Saleem Tahreem Tanweer Muhammad Jawad Khan Sohad Abdulkaleg Alshareef Huda M. Sheikh Fatima S. Alaryani Manal Othman AL-Kattan Hanan Ali Alatawi Farid Menaa Aroosa Younis Nadeem 《Molecules (Basel, Switzerland)》2022,27(21)
Resin composites have been widely used in dental restoration. However, polymerization shrinkage and resultant bacterial microleakage are major limitations that may lead to secondary caries. To overcome this, a new type of antibacterial resin composite containing ciprofloxacin-loaded silver nanoparticles (CIP-AgNPs) were synthesized. The chemical reduction approach successfully produced CIP-AgNPs, as demonstrated by FTIR, zeta potential, scanning electron microscopy, and ultraviolet-visible (UV-vis) spectroscopy. CIP-AgNPs were added to resin composites and the antibacterial activity of the dental composite discs were realized against Enterococcus faecalis, Streptococcus mutans, and the Saliva microcosm. The biocompatibility of modified resin composites was assessed and mechanical testing of modified dental composites was also performed. The results indicated that the antibacterial activity and compressive strength of resin composites containing CIP-AgNPs were enhanced compared to the control group. They were also biocompatible when compared to resin composites containing AgNPs. In short, these results established strong ground application for CIP-AgNP-modified dental composite resins. 相似文献
7.
L. Han A. Tanweer J. Szaran S. Halas 《Isotopes in environmental and health studies》2013,49(3):177-183
Abstract A modified technique for the conversion of sulphates and sulphides to SO2 with the mixture of V2O5—SiO2 for sulphur isotopic analyses is described. This technique is more suitable for routine analysis of large number of samples. Modification of the reaction vessel and using manifold inlet system allows to analyse up to 24 samples every day. The modified technique assures the complete yield of SO2, consistent oxygen isotope composition of the SO2 gas and reproducibility of δ34S measurements being within 0.10‰. It is observed, however, oxygen in SO2 produced from sulphides differs in δ18O with respect to that produced from sulphates. 相似文献
8.
Shaeel Ahmed Al-Thabaiti Abdullah Yousif Obaid Ziya Ahmad Khan Tanweer Ahmad Arniza Ghazali Kabir-ud-Din 《Colloid Journal》2012,74(1):125-131
The energetics of clouding in anionic surfactant (SDBS) and tetrabutylammonium bromide system in the presence of additives,
such as ureas, amino acids and sugars is reported. The change of standard Gibbs energy of solubilization (ΔG
s
o) for all of the additives was found to be negative. The values of change of standard enthalpy (ΔH
s
o) and that of standard entropy (TΔS
s
o) values were found to depend on the type and chemistry of the additive. The results were explained on the basis including
chemistry of additives, their effect on water structure, and solubilization of additives either in the micellar or in aqueous
phases. 相似文献
9.
We introduce a new construction technique for orthomodular lattices. In contrast to the preceding constructions, it admits
rich spaces of states (= probability measures), i.e., for each pair of incomparable elements a,c there is a state s such that s(a) = 1 > s(c). This allowed a progress in many questions that were open for a long time; among others we prove that there is a continuum
of varieties of orthomodular lattices with rich state spaces and solve a problem formulated by R. Mayet in 1985. As a by-product
of this research, the uniqueness problem for bounded observables (posed by S. Gudder in 1966) has been solved. As a tool,
we introduce also a new construction –identification of atoms in an orthomodular lattice – which may be of separate interest. 相似文献
10.