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排序方式: 共有493条查询结果,搜索用时 234 毫秒
91.
DM Jessen AN Wercholuk B Xiong AL Sargent WE Allen 《The Journal of organic chemistry》2012,77(15):6615-6619
A diarylacetylene fluorophore featuring spatially separated urea and phosphocholine (PC) groups forms a macrocyclic "head-to-tail" dimer stabilized by NH(urea)···OP(PC) hydrogen bonds. At concentrations above ~2 × 10(-5) M in CH(2)Cl(2), the emission intensity of the dimer is quenched by HCO(3)(-) and H(2)PO(4)(-) but not by Cl(-) and NO(3)(-). Under more dilute conditions, all four anions are bound unselectively with association constants on the order of 10(5) M(-1). 相似文献
92.
Andrea Jess Josiah Danielle Twilley Sreejarani Kesavan Pillai Suprakas Sinha Ray Namrita Lall 《Molecules (Basel, Switzerland)》2021,26(7)
Keratinocyte carcinoma (KC) is a form of skin cancer that develops in keratinocytes, which are the predominant cells present in the epidermis layer of the skin. Keratinocyte carcinoma comprises two sub-types, namely basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). This review provides a holistic literature assessment of the origin, diagnosis methods, contributing factors, and current topical treatments of KC. Additionally, it explores the increase in KC cases that occurred globally over the past ten years. One of the principal concepts highlighted in this article is the adverse effects linked to conventional treatment methods of KC and how novel treatment strategies that combine phytochemistry and transdermal drug delivery systems offer an alternative approach for treatment. However, more in vitro and in vivo studies are required to fully assess the efficacy, mechanism of action, and safety profile of these phytochemical based transdermal chemotherapeutics. 相似文献
93.
Danielle L. Gray 《Journal of solid state chemistry》2007,180(5):1527-1532
The interlanthanide compounds Er3SmS6, Er3SmSe6, and Er1.12Sm0.88Se3 have been synthesized from stoichiometric reactions of the elements in a KI salt flux at 1273, 1173, and 1123 K, respectively. Er3SmS6 and Er3SmSe6, which are isostructural and ordered, crystallize in space group P21/m in the ScEr3S6 structure type whereas Er1.12Sm0.88Se3, in which the Er and Sm atoms are disordered, crystallizes in space group Pnma in the U2S3 structure type. Er3SmS6 is a paramagnet with a μeff=11.25(1) μB/mol. From optical measurements a direct band gap of 2.0 eV for light perpendicular to the (100) crystal face of Er3SmSe6 is derived whereas for isostructural Er3SmS6 an optical transition at 2.2-2.4 eV and a broad absorption peak at lower energies are observed. 相似文献
94.
The effect of immobilization in an albumin-glutaraldehyde crosslinked matrix on the structure and activity of a photosystem
I submembrane fraction has been studied. The photosynthetic activity recovered after immobilization was between 35 and 45%
of the oxygen-uptake rates of the native material. Resulting oxygen uptake activities found in immobilized photosystem I preparations
with methylviologen as acceptor were as high as 270 μmol O2 (mg Chl h)-1, An enhancement of photosystem I electron transfer, which is produced by incubation of thylakoid membranes at temperatures
above 30 °C, was detected in native submembrane fractions, but not in the immobilized preparations. It is suggested that the
increased activity at high temperature results from conformational modifications not allowed in the immobilization matrix.
The insensitivity of immobilized photosystem I particles to prolonged storage at 4°C and to strong light exposure, as well
as their high electron-transfer rates, demonstrates that the immobilization procedure used can be successfully applied to
submembrane fractions. 相似文献
95.
Danielle Allard Michel Fontanille Robert E. Prud'Homme 《Journal of polymer science. Part A, Polymer chemistry》1984,22(12):3827-3842
Three series of epoxy/acrylic interpenetrating polymer networks were prepared by the simultaneous polymerization of diglycidyl ether of bisphenol A, crosslinked with an aliphatic diamine, diglycidyl ether of bisphenol A dimethacrylate, bisphenol A dimethacrylate, and diethoxy bisphenol A dimethacrylate. Under the conditions provided it is believed that the two networks form simultaneously but independently. Differential scanning calorimetry and dielectric measurements indicate that these polymer networks are miscible because they exhibit a single, sharp glass transition temperature, the values of which, however, are lower than predicted by the law of mixture. This decrease may be due in part to the dilution of one network by the other and to the resulting breakage of intramolecular interactions. It is also due, in part or in whole, to the presence of solvent and/or monomer impurities that act as plasticizers. 相似文献
96.
Franke D Egger CC Smarsly B Faul CF Tiddy GJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(7):2704-2712
A double-tailed polymerizable (pyrrolylalkyl) ammonium amphiphile has been synthesized, and its interfacial properties and aqueous phase behavior have been studied by polarized optical microscopy and X-ray diffraction. The Krafft temperature is about 27 degrees C, and the critical micelle concentration at 40 degrees C is about 1 mM, as obtained from surface tension measurements, potentiometry, and isothermal titration calorimetry. The lyotropic behavior of the surfactant is found to be of a complex nature. At concentrations higher than the micellar (L1) region, two mesophases have been identified: a second isotropic (L2) phase, which is probably micellar but not fully miscible with water, and a lamellar (L(alpha)) phase, showing interesting alignment properties. Small-angle X-ray scattering analysis of the mesophases has been evaluated in terms of a model of spherical micelles, which describes a mutual arrangement by a structure factor derived from a hard-sphere potential (Percus-Yevick, "PY", approach). Interest in the comprehensive phase behavior of the polymerizable surfactant is based on the desire to integrate the system into a composite material to obtain potentially conducting self-assembled hybrid mesostructures. 相似文献
97.
A new family of potent aminoacid-type organogelators obtained via an easy and unexpensive way is described. We demonstrated that structural variations onto the side chains of the aminoacid derivatives allowed modulations of the gelation properties. The organogelators bearing a benzyl or an isopropyl group (compounds 1e, 2a, and 2c) are able to provide gelation of apolar solvents at very low concentration (0.2 wt %) and to form thermostable gels. 相似文献
98.
Danielle Dowek Galip Tepehan Helmut Madeheim Rainer Hippler 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,22(4):735-740
A polarization study of Lyman-α radiation emitted in collisions of H+, H, He+, and He projectiles with H2 molecules has been performed at projectile energies ranging from 1–25 keV. In H+?H2 and H?H2 collisions, the measured linear polarization is negative at low incident velocities, indicating a preferred alignment of the excited electron charge cloud perpendicular to the incident projectile direction. This is taken as significance for a rotational coupling which in these two collision systems predominantly populates the H(2p ±1) substates. In He+?H2 and He?H2 collisions, the measured linear polarization is about zero and independent of the projectile energy. In these more asymmetric systems,a′?a′ and a′?a″ couplings are now of comparable magnitude. 相似文献
99.
Martine Croisy-Delcey Emile Bisagni Christiane Huel Danielle Zilberfarb Alain Croisy 《Journal of heterocyclic chemistry》1991,28(1):65-71
Using 2-methoxy- and 2,5-dimethoxyacetophenones 8a and 8b as starting materials, 1-chloro-4-methylisoquinoline-5,8-quinone ( 6 ) and its 6-bromo derivative 7 were obtained via multistep sequences. Whereas Diels-Alder condensation of the former compound with homophthalic anhydride ( 22 ) led to a mixture of the two possible isomers: 1-chloro-11-hydroxy-4-methylnaphtho[2,3-g]isoquinoline-5,12-quinone ( 23 ) and 1-chloro-6-hydroxy-4-methylnaphtho[2,3-g]isoquinoline-5,12-quinone ( 24 ), this last tetracyclic chloroquinone was specifically obtained from 6-bromo-1-chloro-4-methylisoquinoline-5,8-quinone ( 7 ) and homophthalic anhydride. The 6,11-dihydroxy derivative was then prepared by ammonium nitrate oxidation or photochemically by cycloaddition of benzocyclobutenedione ( 28 ) and 1-chloro-4-methylisoquinoline-5,8-quinone ( 6 ). Chloro compounds were easily substituted by diamines to provide corresponding 1-amino substituted hydroxy tetracyclic quinones. 相似文献
100.
The synthesis of 3,6-bis(3,4-dimethoxybenzoyl)-1,2,4,5-tetrazine (2) and the scope of its reactivity in inverse electron demand Diels-Alder reactions are disclosed representing the first systematic study of the [4 + 2] cycloaddition reactions of 3,6-diacyl-1,2,4,5-tetrazines. 相似文献