Search results for "hexane"
showing 10 items of 467 documents
Triplet stabilization for enhanced drug photorelease from sunscreen-based photocages
2021
[EN] Recently, sunscreen-based drug photocages have been introduced to provide UV protection to photoactive drugs, thus increasing their photosafety. Here, combined experimental and theoretical studies performed on a photocage based on the commercial UVA filter avobenzone (AB) and on the photosensitizing non-steroidal anti-inflammatory drug ketoprofen (KP) are presented unveiling the photophysical processes responsible for the light-triggered release. Particular attention is paid to solvent stabilization of the drug and UV filter excited states, respectively, which leads to a switching between the triplet excited state energies of the AB and KP units. Most notably, we show that the stabiliz…
Ground and excited state dipole moments of coumarin laser dyes: Investigation by electro-optical absorption and emission methods
1997
Abstract Modified electro-optical absorption and emission methods were used to measure the dipole moments of four efficient coumarin laser dyes (CU1, CU4, CU120, CU334) in the equilibrated ground, excited Franck-Condon and equilibrated excited states. The measurements were performed in cyclohexane (CU1, CU120, CU334) and dioxane (all CUs) at room temperature. Our results show that the charge distribution in CU4 differs substantially from that in the other CUs. The equilibrated ground and excited state dipole moments measured by electro-optical methods are compared with those derived from other measurement techniques and from semiempirical calculations. The possible role of twisted intermole…
Free and bound chlorophenols in kraft pulp bleaching effluents
1992
Abstract Free (F; hexane extractable) and chemically bound (B; alkali extractable) chlorophenols, catechols and guaiacols were measured from effluents of the C and E stages of chlorobleaching of kraft softwood pulp. Ratio B/F was in moste cases nearly one, but for tetrachloroguaiacol B/F was 20 in C and 2.70 in E stage. Organically bound chlorine (OCl) in chlorophenols was less than one percent of the total AOX (Adsorbable Organic Halogen) emitted.
Development and optimization of gas chromatography coupled to high resolution mass spectrometry based method for the sensitive determination of Dechl…
2017
An analytical method has been developed for the trace determination of 10 dechlorane-related compounds (DRCs) in food products by gas chromatography - high resolution mass spectrometry (GC-HRMS). The highest sensitivity of this instrumental analysis method was achieved by selection of the GC column type, optimization of the heated zones within the instrument, and adjusting the electron impact energy. The efficiency of solid phase extraction as clean-up procedure was also optimized. Two different types of cartridges - neutral silica gel and Florisil®, as well as seven organic solvents or their mixtures - n-hexane, cyclohexane, acetone, toluene, n-hexane/ethyl acetate, n-hexane/acetone, and n…
Polychlorinated organic compounds in the Arctic cod liver: trends and profiles
2000
Polychlorinated organic compounds (POCs) have been measured in Arctic cod liver from Vestertana Fjord for a period of 1987-1998. Significant decrease was observed for DDD (p = 0.043), alpha-HCH (p = 0.001), and gamma-HCH (lindane; p = 0.001). Contents of DDE, 2,3,7,8-tetrachlorodibenzofuran, PCBs, chlordanes, chloronaphthalenes, hexachlorobenzene and polychlorodiphenyl ethers had no significant trend. Contents of three hexa- and two heptachlorodibenzofurans and octachlorodibenzofuran increased slightly from 1987 to 1994, but then at very high rate from 1994 to 1998. Trends of HCHs, profiles of PCBs and levels of chlordanes are in accordance with atmospheric long range transport. The hexa-, …
Polychlorinated biphenyls and some pesticides in perch (Perca Fluviatilis) from inland waters of Latvia
1999
Polychlorinated biphenyls (PCBs), DDT - related substances, hexachlorocyclohexane (HCH) isomers and hexachlorobenzene (HCB) were analysed in perch (Perca fluviatilis) from Latvian lakes and rivers. DDE is present in the highest concentrations in all samples; 62–170 ng/g lipid weight in perch from rural areas and 460 ng/g in perch from the Riga area. Individual dominating PCB congeners were in the range 16–45 ng/g and 200–210 ng/g, respectively. The degree of contamination of rural areas in Latvia of these organohalogen substances is in the same range as in background areas in Sweden. Riga, the major urban area in Latvia, is shown to be more polluted with PCBs than other areas in Latvia.
Relationship between the structure of amphiphilic copolymers and their ability to disturb lipid bilayers.
2005
Nonionic amphiphiles and particularly block copolymers of ethylene oxide and propylene oxide (Pluronics) cause pronounced chemosensitization of tumor cells that exhibit multiple resistance to antineoplastic drugs. This effect is due to inhibition of P-glycoprotein (P-gp) responsible for drug efflux. It was suggested that the inhibition of P-gp might be due to changes in its lipid surrounding. Indeed, high dependence of P-gp activity on the membrane microviscosity was demonstrated [Regev et al. (1999) Eur. J. Biochem. 259, 18-24], suggesting that the ability of Pluronics to affect the P-gp activity is mediated by their effect on the membrane structure. We have found recently that adsorption …
Tritylpyridinium tetrakis(pentafluorophenyl)borate as an efficient activator for “constrained-geometry” catalysts in ethylene polymerization
2004
Abstract Ethylene polymerization with linked amido-cyclopentadienyl or “constrained-geometry” titanium catalysts, Ti(η 5 :η 1 -C 5 Me 4 SiMe 2 N t Bu)X 2 (X=Me, Bz, Cl), activated by tritylpyridinium tetrakis(entafluorophenyl)borate, [Ph 3 C(NC 5 H 5 )] [B(C 6 F 5 ) 4 ], and silica-supported tritylpyridinium tetrakis(entafluorophenyl)borate (PySTB) was found to proceed with high activity. 1 H NMR spectra in CD 2 Cl 2 suggest that ([Ti(η 5 :η 1 -C 5 Me 4 ,SiMe 2 N t Bu)Me (NC 5 H 5 )] + is formed as the main cationic species. Using the heterogeneous cocatalyst PySTB in hexane, unexpectedly high ethylene polymerization activity was achieved, giving high molecular weight polyethylenes with exc…
Ethylene and phenylene bridged polysilsesquioxanes functionalized by amine and thiol groups as adsorbents of volatile organic compounds
2007
Abstract Ethylene and phenylene bridged polysilsesquioxane xerogels having amine and thiol groups attached to the surface have been obtained by the sol–gel method from 1,2-bis(triethoxysilyl)ethane or 1,4-bis(triethoxysilyl)benzene and functionalized silanes in the presence of an ammonium fluoride catalyst in an ethanol solution. The synthesized samples have a porous structure (700–850 m2/g) and a high content of functional groups (1.4–1.9 mmol/g). The obtained porous bridged polysilsesquioxanes exhibit a considerable affinity for adsorbing several organic compounds (n-hexane, n-heptane, benzene, cyclohexane, acetonitrile and triethylamine) from the gas phase. The sample with an ethylene br…
A Mutation With Major Effects on Drosophila melanogaster Sex Pheromones
2005
0016-6731 (Print) Comparative Study Journal Article Research Support, Non-U.S. Gov't; Sex pheromones are intraspecific chemical signals that are crucial for mate attraction and discrimination. In Drosophila melanogaster, the predominant hydrocarbons on the cuticle of mature female and male flies are radically different and tend to stimulate or inhibit male courtship, respectively. This sexual difference depends largely upon the number of double bonds (one in males and two in females) added by desaturase enzymes. A mutation was caused by a PGal4 transposon inserted in the desat1 gene that codes for the desaturase crucial for setting these double bonds. Homozygous mutant flies produced 70-90%…