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61.
Martina Mazzoni Lorenzo Franco Alberta Ferrarini Carlo Corvaja Giovanni Zordan Gianfranco Scorrano Michele Maggini 《Liquid crystals》2002,29(2):203-208
A nitroxide [60]fullerene adduct containing a pyrrolidine-1-oxyl group has been synthesized. Its orientational order in the nematic phase of the liquid crystal solvent 4,4'-azoxyanisole (PAA) has been measured from the variation of the EPR spectral parameters on passing from the isotropic to the nematic phase. Highly resolved EPR lines allow for precise evaluation of the shifts of the g , a N and a H values. Since the g and the hyperfine tensors are known, the order matrix could be obtained. This is compared with the one calculated with a theoretical model based on short range solute-solvent interactions, which predicts a considerable degree of orientation of the molecular axes, despite the almost spherical shape of the molecule. The agreement with experimental findings is quite good and it is further improved if a bent structure of the pyrrolidine ring is taken into account. 相似文献
62.
63.
Gianfranco Capriz 《Meccanica》1967,2(4):213-217
Summary To obtain an accurate forecast of the behaviour of a shaft rotating on lubricated bearings under excitation, an adequate model must be introduced to represent the response of the bearings; a linear model of the response is sufficient for many practical purposes, but allowance must be made for the variation of film stiffness, cross-stiffness, etc., with direction. As a consequence the shaft must be assumed to move in an elliptical, rather than circular, whirl. The phenomenon which must be analyzed is thus more complex than that envisaged in König's study, for instance, see Ref. [2]. We show here nevertheless that it is possible to devise an appropriate generalization of the Myklestad-Holzer method, so that the problem can be solved by matrix manipulations.
Sommario Per prevedere con accuratezza l'ampiezza di vibrazione di un asse lievemente sbilanciato che ruoti su supporti lubrificati è necessario rappresentare adeguatamente il comportamento dei supporti stessi.Un modello lineare è sufficiente per molti scopi pratici purchè si tenga conto che la risposta non ha generalmente simmetria assiale. Di conseguenza è necessario poter considerare casi nei quali la traiettoria di ciascun punto dell'asse è ellittica piuttosto che circolare. Perciò si richiede una generalizzazione del metodo di König; generalizzazione che è indicata nel presente lavoro. Il metodo proposto fa però ancora uso di semplici operazioni matriciali.相似文献
64.
Summary We consider continua for which a local configuration exists, whence the instantaneous elastic strain must be measured. Relations involving stress, strain and strain rate are indicated, which are compatible with objectivity and with the Clausius-Duhem inequality. Definitions and a theorem of Coleman and Gurtin regarding continua with internal parameters are adapted to advantage.
Sommario Si studiano continui per i quali esiste una configurazione locale (variabile nel tempo) e a partire dalla quale va misurata istante per istante la deformazione elastica. Si specificano le relazioni permesse dalla disguaglianza di Clausius Duhem e dal principio di obbiettività e si adattano al caso alcune definizioni ed un teorema di Coleman e Gurtin sui continui con parametri interni.相似文献
65.
U. Gianfranco Spizzirri Francesca Iemma Francesco Puoci Feng Xue Wei Gao Giuseppe Cirillo Manuela Curcio Ortensia I. Parisi Nevio Picci 《先进技术聚合物》2011,22(12):1705-1712
Novel stimuli‐responsive hydrophilic microspheres were prepared by free radical polymerization of hydroxyethyl methacrylate (HEMA) and methacrylic acid (MA), as hydrophilic monomers, and N‐isopropylacrylamide (NIPAAm) and N,N′‐ethylenebisacrylamide (EBA), as thermo‐sensitive monomer and crosslinker, respectively. Hydrophilic comonomers were introduced in the macromolecular network to synthesize materials with tunable thermal behavior. In addition, by introducing in the polymerization feed both a hydrophilic and a pH‐sensitive monomer, such as MA, dual stimuli‐responsive (pH and temperature) hydrogels were synthesized. The incorporation of monomers in the network was confirmed by infrared spectroscopy, while the network density and the shape of hydrogels was found to strictly depend on the concentration of monomers in the polymerization feed. Thermal analyses showed negative thermo‐responsive behavior with pronounced water affinity of microspheres at a temperature lower than lower critical solution temperature (LCST). In our experiment, the LCST values of the hydrogels were in the range 34.6–37.5°C, close to the body temperature, and the amount of hydrophilic moieties in the polymeric network allows to collect shrinking/swelling transition temperatures higher than the LCST of NIPAAm homopolymers. In order to test the preformed materials as drug carriers, diclofenac diethylammonium salt (DDA) was chosen and drug entrapment percent was determined. Drug release profiles, in media at different temperature and pH, depend on hydrogels crosslinking degree and drug–bead interactions. By using semi‐empirical equations, the release mechanism was extensively studied and the diffusional contribute was evaluated. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
66.
Amorati R Attanasi OA Favi G Menichetti S Pedulli GF Viglianisi C 《Organic & biomolecular chemistry》2011,9(5):1352-1355
Hydrogenated cardanol and cardols, contained in industrial grade cardanol oil and obtained by distillation of the raw "cashew nut shell liquid" (CNSL), are easily transformed into efficient 4-thiaflavane antioxidants bearing a long alkyl chain on A ring and a catechol group on B ring. 相似文献
67.
Di Michele A Brinchi L Di Profio P Germani R Savelli G Onori G 《Journal of colloid and interface science》2011,358(1):160-166
The critical micelle concentration (cmc) and ionisation degree (α), of micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltripropylammonium bromide (CTPABr) and cetyltripropylammonium chloride (CTPACl) have been measured over a narrow temperature range at 2 degree intervals using electrical conductivity. CTPACl and CTPABr are very soluble in water and were measured in the temperature range 275.15-323.15K. The Krafft temperatures for CTABr and for CTACl are 293.15K and 284.15K, respectively and established a lower temperature limit for our studies on these two surfactants. The cmc vs temperature curves have a smooth minimum near room temperature and α linearly increases with temperature. The changes of cmc and α with temperature are smaller than those associated with the modification of head group size or counterion nature. Using these results, basic thermodynamic quantities associated with the phenomena of micellization have been evaluated. Thermodynamic properties of the surfactant solutions were discussed in terms of temperature dependence of the free energy, enthalpy and entropy of micellization. A close similarity between the effects of change in temperature on protein folding and micellization process appears from the data. 相似文献
68.
Cellulose foams, or sponges, are produced from solutions in ionic liquids by the aqueous acid mediated decomposition of 1-alkyl-3-methylimidazolium-2-carboxylates, where the alkyl group and acid may be selected such that the by-product is the ionic liquid solvent: a by-productless foaming. 相似文献
69.
70.
This communication describes a simple, rapid and cost effective method of embedding a conductive and flexible material within microfluidic devices as a means to realize uniform electric fields within cellular microenvironments. Fluidic channels and electrodes are fabricated by traditional soft-lithography in conjunction with chemical etching of PDMS. Devices can be deformable (thus allowing for a combination of electro-mechanical stimulation), they are made from inexpensive materials and easily assembled by hand; this method is thus accessible to a wide range of laboratories and budgets. 相似文献