Abstract Lac is the only known natural resin of animal origin. It is the secretion of a tiny insect known as Kerriar lacca (formally called Laceifer lacca). The lac-forming tiny insect grows on some types of trees, mostly abundant in tropical countries, including India. The secretion of the lac insect hardens in air and forms a covering on the body of the insect. This covering or the nest forms a continuous incrustation on the branches of the host trees. Lac is collected by scraping the incrustation from the branches of the trees. 相似文献
Chiral 3‐methanesulfonyl‐1‐Boc‐pyrrolidine and piperidine were reacted with sodium phenolates, resulting in a mixture of displacement and elimination products. Following carbamate deprotection and pH adjustment, the 3‐pyrroline and tetrahydropyridine by‐products resulting from elimination were easily removed through aqueous partitioning and/or concentration. Although the pyrrolidines were formed with a high degree of optical purity, slight racemization was observed for the piperidine case because elevated temperatures were required to effect displacement. 相似文献
In this paper, analogous to chance constraints, real-life necessity and possibility constraints in the context of a multi-item dynamic production-inventory control system are defined and defuzzified following fuzzy relations. Hence, a realistic multi-item production-inventory model with shortages and fuzzy constraints has been formulated and solved for optimal production with the objective of having minimum cost. Here, the rate of production is assumed to be a function of time and considered as a control variable. Also the present system produces some defective units along with the perfect ones and the rate of produced defective units is constant. Here demand of the good units is time dependent and known and the defective units are of no use. The space required per unit item, available storage space and investment capital are assumed to be imprecise. The space and budget constraints are of necessity and/or possibility types. The model is formulated as an optimal control problem and solved for optimum production function using Pontryagin’s optimal control policy, the Kuhn–Tucker conditions and generalized reduced gradient (GRG) technique. The model is illustrated numerically and values of demand, optimal production function and stock level are presented in both tabular and graphical forms. The sensitivity of the cost functional due to the changes in confidence level of imprecise constraints is also presented. 相似文献
The reaction between 1,3-cyclohexanediones and chalcones (or their vinilogs) in the presence of 2.5 equiv of cerium(IV) ammonium nitrate afforded trans-2-arylcarbonyl-3-aryl (or styryl)-2,3,6,7-tetrahydrobenzofuran-4(5H)-ones in good to excellent yields and in high diastereoselectivities. The method was also extended to the preparation of derivatives of the 5,6-dihydro-2H-cyclopenta[b]furan-4(3H)-one system. The fused 2,3-dihydrofuran derivatives were transformed into 1-alkyl-2-acyl-3-aryl-6,7-dihydroindole-4(5H)-ones by 2,3-dehydrogenation followed by reaction with primary amines. The direct reaction of the tetrahydrobenzofuran-4(5H)-one compounds derived from dimedone with amines gave 1-alkyl-2-alkylimino-3-aryl-6,7-dihydroindole-4(5H)-ones, while starting materials derived from 1,3-cyclohexanedione underwent an unprecedented 2-deacylation reaction and gave 1-alkyl-3-aryl-6,7-dihydroindole-4(5H)-ones. 相似文献
Four new coordination polymers of cadmium(II) with hexamethylenetetramine (htm) have been synthesized and characterized by routine physicochemical techniques as well as by X-ray single crystal structure analysis. They are [CdBr(htm)(SCN)(H2O)2·CH3OH]n (1), [CdI(htm)(SCN)(H2O)2·0.5(CH3OH)]n (2), [Cd2(htm)3(SCN)4(H2O)]n·nH2O (3) and [Cd3Br6(htm)2(H2O)5·(htm)(H2O)6]n (4). Complexes 1, 2 and 3 exhibit 1D polymeric structure and complex 4 shows a 2D undulated layered arrangement, containing Cd6(htm)6 hexagonal units as building block, which extended to a 3D supramolecular architecture through hydrogen bonding. Thorough thermal investigation suggest that as far as the thermal stability of Cd(II)-htm bond is concerned it attains the maximum in complex 1 and minimum in complex 4. In case of complex 3 the thermal study inferred that CdS end product was obtained at ∼730 °C, whereas in case of other complexes the thermally stable end product remained unidentified. Solid state fluorescence study shows that all the complexes are luminescent at room temperature except complex 3. 相似文献
(PPh4)2[MoO(O2)2(SHAH)]·H2O and PPh4[MoO(O2)2(HBA)] (SHAH3 = 2-hydroxybenzohydroxamic acid and HBAH = 2-hydroxybenzoic acid) have been synthesized and characterized by physico-chemical
and spectroscopic methods. In addition, the second complex has been structurally characterized by single-crystal X-ray diffraction
analysis. We have compared the catalytic activities of these two new complexes, together with the previously reported PPh4[MoO(O2)2(BZ)] (BZH = benzoic acid), with respect to the epoxidation of alkenes. The hydroxamate complex is the most efficient catalyst
among the three complexes, showing excellent catalytic activity for the substrates cyclohexene, cyclooctene, cinnamyl alcohol,
pent-4-en-1-ol and hex-1-ene. 相似文献
Molecular diversity : A cerium(IV) ammonium nitrate (CAN) catalyzed, four‐component reaction from very simple acyclic starting materials afforded densely substituted tetrahydropyridines, which were transformed into homoquinolizines by using a γ‐alkylation–ring‐closing metathesis (RCM) sequence (see scheme).
natY foil was irradiated by 20 MeV proton to produce no-carrier-added 88,89Zr. A comparative evaluation on radioanalytical separation methods of 88,89Zr was carried out from irradiated target matrix by both liquid–liquid (LLX) and solid–liquid (SLX) extraction methods using
di-(2-ethylhexyl) phosphoric acid (HDEHP) dissolved in cyclohexane as liquid cation exchanger and Dowex 50W-X8 H+ form (20–50 mesh) as solid cation exchanger. Both the methods offer good separation and high yield of nca 88,89Zr but SLX offers much higher separation factor and better yield. 相似文献
An inventory model for a deteriorating item (seasonal product) with linearly displayed stock dependent demand is developed in imprecise environment (involving both fuzzy and random parameters) under inflation and time value of money. It is assumed that time horizon, i.e., period of business is random and follows exponential distribution with a known mean. The resultant effect of inflation and time value of money is assumed as fuzzy in nature. The particular case, when resultant effect of inflation and time value is crisp in nature, is also analyzed. A genetic algorithm (GA) is developed with roulette wheel selection, arithmetic crossover, random mutation. For crisp inflation effect, the total expected profit for the planning horizon is maximized using the above GA to derive optimal inventory decision. On the other hand when inflationary effect is fuzzy then the above expected profit is fuzzy in nature too. Since optimization of fuzzy objective is not well defined, the optimistic/pessimistic return of the expected profit is obtained using possibility/necessity measure of fuzzy event. Fuzzy simulation process is proposed to determine this optimistic/pessimistic return. Finally a fuzzy simulation based GA is developed and is used to maximize the above optimistic/pessimistic return to get optimal decision. The models are illustrated with some numerical examples and some sensitivity analyses have been presented. 相似文献