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51.
Synthesis, characterization and properties of novel thermally stable poly(urethane-oxazolidone) elastomers 总被引:2,自引:0,他引:2
Oxazolidone-incorporated polyurethane elastomers based on hydroxyl terminated polycaprolactone, were synthesized and characterized. Reaction of epoxy-terminated polyurethane with isocyanate librated from a blocked polyisocyanate was the strategy followed. The reaction condition was optimized through preparation of model oxazolidones. Epoxy-terminated polyurethanes were prepared from reaction of glycidol with NCO-terminated polyurethane prepolymers and curing agent was synthesized from the reaction of trimethylol propane, toluene diisocyanate and N-methyl-aniline. Incorporation of heterocyclic oxazolidone groups into the polyurethane backbone caused improvements in thermal and mechanical properties. Investigation of structure-property relationship for prepared elastomers showed that the main determining factors for observed properties were crosslink density, crystallinity and content of oxazolidone rings. 相似文献
52.
Previous hotel performance studies neglected the role of information entropy in feedback processes between input and output management. This paper focuses on this gap by exploring the relationship between hotel performance at the industry level and the capability of learning by doing and adopting best practices using a sample of 153 UK hotels over a 10-year period between 2008–2017. Besides, this research also fills a literature gap by addressing the issues of measuring hotel performance in light of negative outputs. In order to achieve this, we apply a novel Modified slack-based model for the efficiency analysis and Least Absolute Shrinkage and Selection Operator to examine the influence of entropy related variable on efficiency score. The Results indicate that less can be learnt from inputs than from outputs to improve efficiency levels and resource allocation is more balanced than cash flow and liquidity. The findings suggest that market dynamics explains the cash flow generation potential and liquidity. We find that market conditions are increasingly offering the opportunities for learning and improving hotel efficiency. The results report that the distinctive characteristic of superior performance in hotel operations is the capability to match the cash flow generation potential with market opportunities. 相似文献
53.
Yasaman-Sadat?Borghei Morteza?HosseiniEmail author Mohammad?Reza?Ganjali 《Mikrochimica acta》2017,184(8):2671-2677
The authors report on a new approach for the determination of the breast cancer biomarker microRNA-155 (miRNA-155). It is based on the measurement of the fluorescence shift of oligonucleotide-templated copper nanoclusters (DNA-CuNC). A probe DNA was designed that acts as a template for the preparation of CuNC which, under 400 nm excitation, exhibit strong fluorescence enhancement at 490 nm and a 90 nm Stokes shift after binding to target miRNA-155 and formation of a DNA-RNA heteroduplex. Under the optimal conditions, the fluorescence of the DNA-CuNC increases with increasing concentration of miRNA-155 in the range from 50 pM to 10 nM, with a 11 pM detection limit. The assay has excellent selectivity over noncomplementary RNA. The method was applied to the determination of miRNA-155 in the presence of human plasma and saliva. 相似文献
54.
Yasaman-Sadat?Borghei Morteza?HosseiniEmail author Mohammad?Reza?Ganjali 《Mikrochimica acta》2017,184(12):4713-4721
This paper describes a CdTe quantum dot-based fluorescence resonance energy transfer (FRET) based assay for the detection of the breast cancer biomarker microRNA. The method relies on energy transfer between DNA-templated silver nanoclusters (AgNCs) and CdTe QDs. Interaction between double strand oligonucleotide and QDs can be detected qualitatively through gel analysis and quantitatively by the signal amplification from AgNCs to QDs via FRET, best measured at an excitation wavelength of 350 nm and at emission wavelengths of 550 and 590 nm. Three microRNAs (microRNA-21, microRNA-155 and Let-7a) were quantified to verify the feasibility of the method, and a high sensitivity for microRNAs was achieved. Fluorescence intensity increases linearly with the log of the concentration of microRNA 155 in the 5.0 pM to 50 nM range, with a 1.2 pM detection limit. 相似文献
55.
Theoretical investigation of the weak interactions of rare gas atoms with silver clusters by resonance Raman spectroscopy modeling 下载免费PDF全文
The interactions of rare gas atoms (Rg = Ar, Kr, and Xe) with small neutral and cationic silver clusters have been investigated by density functional methods and the effect of these weak interactions on the resonance Raman spectra of the complexes has been evaluated. The resonance Raman technique that depends on the properties of ground and excited state, seems deeply sensitive to the weak rare gas–metal cluster interactions, and the use of inert gases has been proven to be an excellent approach to recognize the ability of this technique to detect extremely weak interactions. In this work, for , and complexes the IR, normal and resonance Raman spectra have been calculated and the effect of rare gas–cluster stretching vibration ( ) on the pattern and the relative intensities of different spectra have been investigated. The resonance Raman spectra for the weakly interacted complexes (with the interaction energies less than ?2.0 kcal/mol) exhibit the vibration with the detectable intensity that its intensity increases by going from Ag6–Ar to Ag6–Xe complex. Moreover, the resonance Raman spectra (based on the excited state gradient approximation) for high intensity nearly degenerate excited states, proved the effect of accumulation of the excited state charge density on the relative intensity of vibration. 相似文献
56.
Morteza Bararjanian Saeed Balalaie Frank Rominger Sanaz Barouti 《Helvetica chimica acta》2010,93(4):777-784
A three‐component reaction of benzaldehyde derivatives, methyl cyanoacetate, and guanidinium carbonate affords 2‐amino‐4‐aryl‐1,6‐dihydro‐6‐oxopyrimidine‐5‐carbonitriles and the four‐component reaction of benzaldehyde derivatives, methyl cyanoacetate, and guanidinium hydrochloride in the presence of piperidine leads to piperidinium salts of pyrimidinones. X‐ray crystallography data confirm self‐assembly and H‐bonding in these compounds. 相似文献
57.
Hosseini M Ganjali MR Tavakoli M Norouzi P Faridbod F Goldooz H Badiei A 《Journal of fluorescence》2011,21(4):1509-1513
A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal
complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)2Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10−7 to 1.0 × 10−5 mol/L of PPi and the detection limit of 2.3 × 10−8 mol/L. The association constant of L-PPi complex was calculated 2.6 × 105 L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I3-, NO3-, CN−, CO32−, Br−, Cl−, F−, H2PO4− and SO42−, which was attributed to higher stability of inorganic complex between pyrophosphate and L. 相似文献
58.
The combination of the Biginelli reaction with click chemistry has been used for the one-pot synthesis of 1,2,3-triazole linked
dihydropyrimidinones from azides, aromatic aldehydes containing a propargyl ether group, urea, and 1,3-dicarbonyl compounds
using Cu(OAc)2/sodium ascorbate as catalyst in acetic acid under mild reaction conditions. 相似文献
59.
Mehdi Kalhor Akbar Mobinikhaledi Javad Jamshidi 《Research on Chemical Intermediates》2013,39(7):3127-3133
A simple and practical procedure for synthesis of 2-arylbenzimidazoles by a one-pot condensation of o-phenylenediamine with aromatic aldehydes in the presence of a catalytic amount of M(NO3)2·6H2O (M = Mn, Fe, Co, Ni, Cu) in ethanol at room temperature is described. Major advantages of this practical procedure are use of a readily available catalyst, high yields, short reaction times, and simplicity of the reaction and workup. 相似文献
60.
A classical system for the preparation of carbonyl compounds from alkenes relies upon ozonolysis of the double bond, followed by reductive cleavage of the ozonide so formed. Among the reagents of choice for such a reduction, triphenylphosphine certainly has enjoyed a widespread use.1 However, in spite of the simplicity of the method, often one can face problems in the purification of the carbonyl compound from unreacted triphenylphosphine, especially if the polarities of both products are very similar. We have encountered such a problem during the preparation of the (20 S)-6β -ethoxy-3 α, 5-cyclo-5α -pregnane-20-carbaldehyde 4 from the suitably protected stigmasterol32. In this case, when triphenylphosphine was used for reduction of ozonide we never could isolate the aldehyde 2 uncontaninated by tripherylphosphine. 相似文献