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21.
Smrati Gupta Dirk Kuckling Katja Kretschmer Veena Choudhary Hans‐Jürgen Adler 《Journal of polymer science. Part A, Polymer chemistry》2007,45(4):669-679
The aim of this work was the development of a versatile route for the preparation of temperature‐ and pH‐responsive hydrogels with small dimensions. The copolymerization of N,N‐dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2′‐azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro‐ and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature‐ and pH‐responsive behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669–679, 2007 相似文献
22.
Summary Iron complexation with 2,3-pyridinediol is used to detect iron specifically in presence of common ions present in the scheme of qualitative analysis. The method finds use in detection of iron in alloys, salts and medicinal preparations.
Zusammenfassung Die Komplexbildung des Eisens mit 2,3-Pyridindiol wurde für den spezifischen Nachweis dieses Elements in Gegenwart üblicher Ionen im Analysengang verwendet. Dieser Nachweis wurde in Legierungen, in Salzen und in pharmazeutischen Präparaten durchgeführt.相似文献
23.
The kinetics of ruthenium(VI) catalyzed oxidation of 2-methoxyethanol by hexacyanoferrate(III) ion in an aqueous alkaline
medium at constant ionic strength shows zero order dependence on hexacyanoferrate(III) and first order dependence on Ru(VI).
Dependence of substrate concentration shows a Michaelis – Menten type behaviour. The rate increases with the decrease in alkali
concentration. A reaction mechanism involves the formation of an intermediate complex between the substrate and ruthenium(VI).
This complex decomposes slowly, producing ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in subsequent steps.
The theoretical rate law obtained is in complete agreement with the experimental observations. 相似文献
24.
Maxia A Frau MA Foddis C Lancioni MC Kasture V Kasture S 《Natural product research》2012,26(5):438-445
In the traditional Sardinian system of medicine, Rubia peregrina L. (Rubiaceae) is reported as an aphrodisiac herb. Since the aphrodisiacs may also have antioxidant and dopaminergic activities, the aim of this study was to study the effect of ethanolic extract of aerial parts of R. peregrina for the scavenging of free DPPH radicals and the inhibition of haloperidol-induced catalepsy in mice and reserpine-induced orofacial dyskinesia in rats. The extract exhibited significant antioxidant activity in a free radical DPPH assay with IC(50)?=?55.6?μg?mL(-1), which was very close to IC(50) of ascorbic acid. The extract of R. peregrina (100 and 200?mg?kg(-1) intraperitoneally, i.p.) significantly inhibited haloperidol (1?mg?kg(-1) i.p.) - induced catalepsy in mice (p?0.01). In rats, the extract (200?mg?kg(-1) i.p.) significantly (p?0.01) inhibited the orofacial dyskinesia induced by intraperitoneal administration of reserpine (1?mg?kg(-1) on days 1, 3 and 5). This study demonstrates that R. peregrina has antioxidant activity and improves the dopaminergic function. Results therefore justify the development of further experiments to investigate the psychopharmacological profile of R. peregrina. 相似文献
25.
Dhayal V Chaudhary A Choudhary BL Nagar M Bohra R Mobin SM Mathur P 《Dalton transactions (Cambridge, England : 2003)》2012,41(31):9439-9450
[Zr(OPr(i))(4)·Pr(i)OH] reacts with [HOSi(O(t)Bu)(3)] in anhydrous benzene in 1:1 and 1:2 molar ratios to afford alkoxy zirconosiloxane precursors of the types [Zr(OPr(i))(3){OSi(O(t)Bu)(3)}] (A) and [Zr(OPr(i))(2){OSi(O(t)Bu)(3)}(2)] (B), respectively. Further reactions of A or B with glycols in 1:1 molar ratio afforded six chemically modified precursors of the types [Zr(OPr(i))(OGO){OSi(O(t)Bu)(3)}] (1A-3A) and [Zr(OGO){OSi(O(t)Bu)(3)}(2)] (1B-3B), respectively [where G = (-CH(2)-)(2) (1A, 1B); (-CH(2)-)(3) (2A, 2B) and (-CH(2)CH(2)CH(CH(3)-)} (3A, 3B)]. The precursors A and B are viscous liquids, which solidify on ageing whereas the other products are all solids, soluble in common organic solvents. These were characterized by elemental analyses, molecular weight measurements, FAB mass, FTIR, (1)H, (13)C and (29)Si-NMR studies. Cryoscopic molecular weight measurements of all the products, as well as the FAB mass studies of 3A and 3B, indicate their monomeric nature. However, FAB mass spectrum of the solidified B suggests that it exists in dimeric form. Single crystal structure analysis of [Zr{OSi(O(t)Bu)(3)}(4)(H(2)O)(2)]·2H(2)O (3b) (R(fac) = 11.9%) as well as that of corresponding better quality crystals of [Ti(O(t)Bu){OSi(O(t)Bu)(3)}(3)] (4) (R(fac) = 5.97%) indicate the presence of a M-O-Si bond. TG analyses of 3A, B, and 3B indicate the formation of zirconia-silica materials of the type ZrO(2)·SiO(2) from 3A and ZrO(2)·2SiO(2) from B or 3B at low decomposition temperatures (≤200 °C). The desired homogenous nano-sized zirconia-silica materials [ZrO(2)·nSiO(2)] have been obtained easily from the precursors A and B as well as from the glycol modified precursors 3A and 3B by hydrolytic sol-gel process in organic media without using any acid or base catalyst, and these were characterized by powder XRD patterns, SEM images, EDX analyses and IR spectroscopy. 相似文献
26.
Pata V Ahmed F Discher DE Dant N 《Langmuir : the ACS journal of surfaces and colloids》2004,20(10):3888-3893
The commonly held model for membrane dissolution by detergents/surfactants requires lipid transport from the inner to the outer bilayer leaflet ('flip-flop'). Although applicable to many systems, it fails in cases where cross-bilayer transport of membrane components is suppressed. In this paper we investigate the mechanism for surfactant-induced solubilization of polymeric bilayers. To that end, we examine the dissolution of a series of increasingly thick, polymer-based vesicles (polymersomes) by a nonionic surfactant, Triton X-100, using dynamic light scattering. We find that increasing the bilayer thickness imparts better resistance to dissolution, so that the concentration required for solubilization, after a fixed amount of time, increases nearly linearly with membrane thickness. Combining our experimental data with a theoretical model, we show that the dominant mechanism for the surfactant-induced dissolution of polymeric vesicles, where polymer flip-flop across the membrane is suppressed, is the surfactant transport through the bilayer. This mechanism is different both qualitatively and quantitatively from the mechanisms by which surfactants dissolve pure lipid vesicles. 相似文献
27.
Carcel CM Laha JK Loewe RS Thamyongkit P Schweikart KH Misra V Bocian DF Lindsey JS 《The Journal of organic chemistry》2004,69(20):6739-6750
A molecular approach to information storage employs redox-active molecules tethered to an electroactive surface. Zinc porphyrins tethered to Au(111) or Si(100) provide a benchmark for studies of information storage. Three sets of porphyrins have been synthesized for studies of the interplay of molecular design and charge-storage properties: (1) A set of porphyrins is described for probing the effect of surface attachment atom on electron-transfer kinetics. Each porphyrin bears a meso-CH2X group for surface attachment where X = OH, SAc, or SeAc. (2) A set of porphyrins is described for studying the effect of surface-charge density in monolayers. Each porphyrin bears a benzyl alcohol for surface attachment and three nonlinking meso substituents of a controlled degree of bulkiness. (3) A set of porphyrins is described that enables investigation of on-chip patterning of the electrolyte. Each porphyrin bears a formyl group distal to the surface attachment group for subsequent derivatization with a molecular entity that comprises the electrolyte. Taken together, this collection of molecules enables a variety of studies to elucidate design issues in molecular-based information storage. 相似文献
28.
One‐pot synthesis of various unsymmetrical 2‐bromo‐5‐pyridylselenium compounds has been carried out under non‐cryogenic conditions by selective single bromine–magnesium exchange of 2,5‐dibromopyridine using isopropylmagnesium chloride. This exchange gives 2‐bromo‐5‐pyridylmagnesium chloride, which upon the insertion of elemental selenium followed by the treatment with alkyl halide gives the title compounds in good yield. This exchange has also been extended towards bromine–magnesium exchange of 2‐bromopyridine for the improved synthesis of 2‐pyridylselenium compounds. The molecular structure of 2‐bromo‐5‐selenopyridyltribromomethane has been examined by single crystal X‐ray diffraction. This compound crystallizes in the monoclinic space group P21/n. From the molecular structure it was found that intermolecular BrBr, NSe and SeBr interactions control its crystal packing. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
29.
A simple, accurate, and sensitive spectrophotometric method for the determination of promethazine hydrochloride (PMH), prochlorperazine
maleate (PCPM), trifluoperazine hydrochloride (TFPH), trimeperazine tartrate (TMT), fluphenazine dihydrochloride (FH), and
trifluopromazine hydrochloride (TPH) is described. The method is based on the oxidation of the studied drugs by a known excess
of chloramine-T in a hydrochloric acid medium and subsequent determination of the unreacted oxidant by interacting it with
iodide in the same acid medium. Liberated iodine subsequently reacts with starch to form a stable starch-iodine complex. The
reacted oxidant corresponds to the drug content. The colored complex exhibits a maximum absorption at 590 nm. The apparent
molar absorptivity and Sandell sensitivity values are in the range 4.07 × 104 − 1.18 × 105 L/mol cm and 45.00−95.00 ng/cm2, respectively. The proposed method has been applied to the assay of phenothiazine drugs in pure and dosage forms. The reliability
of the analysis was established using parallel determination by the reference method.
The text was submitted by the authors in English. 相似文献
30.
P. H. Veena Subhash Abel K. Rajagopal V. K. Pravin 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2006,57(3):447-463
This paper deals with the study of heat transfer characteristics in the laminar boundary layer flow of a visco-elastic fluid
over a linearly stretching continuous surface with variable wall temperature subjected to suction or blowing. The study considers
the effects of frictional heating (viscous dissipation) and internal heat generation or absorption. An analysis has been carried
out for two different cases of heating processes namely: (i) Prescribed surface temperature (PST) and (ii) Prescribed wall
heat flux (PHF) to get the effect of visco-elastic parameter for various situations. Further increase of visco-elastic parameter
is to decrease the skin friction on the sheet. The solutions for the temperature and the heat transfer characteristics are
obtained in terms of Kummers function.
Received: June 16, 2004; revised: February 8, 2005 相似文献