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451.
Andrej Osterc 《International journal of environmental analytical chemistry》2013,93(5):553-564
129I is important as an environmental tracer of the biogeochemical cycling of iodine and of the dissemination of nuclear pollution, because anthropogenic 129I has been released from only few point sources and with its short mixing time its distribution therefore reveals the movement of 129I in the environment. A radiochemical neutron activation analysis method was developed to measure the concentration of 129I in soil samples. A procedure to pre-concentrate iodine from up to 150?g of soil was developed and validated using IAEA standard reference material IAEA-375 (Chernobyl soil). The method was applied to determine 129I/127I isotopic ratios as well as 129I and 127I concentrations in soils from several locations in Ukraine collected in 2006, 1996, 1993 and 1989, and from Slovenia, collected at various places in 2009 and 2006. The 127I concentrations in surface soils from Ukraine were in the range 2.3–23.1?µg?g?1 and for 129I (11.1–245.7)?·?10?8?µg?g?1 dry matter with the highest value of 1.47?·?10?3?µg?g?1 found in a soil sample collected in Yaniv, Ukraine in July 1993. In soil samples from Slovenia 127I concentrations ranged 0.73–130?µg?g?1 and 129I (8.0–245.7)?·?10?8?µg?g?1. The 129I/127I isotopic ratios of surface soils from Ukraine were in the range of the order of 10?9–10?5 and of 10?10–10?8 for soils from Slovenia. The highest isotopic ratio 13.6?·?10?5 was found in a soil sample collected in Yaniv, Ukraine in July 1993. 相似文献
452.
Polonca Trebše Boris Recelj Tanja Lukanc Simona Golič Grdadolnik Andrej Petrič Bojan Verček 《合成通讯》2013,43(15):2637-2644
6, 7-Dihydrocyclopenta[b]pyran-2, 5-dione 1 was converted with hydrazines to fused pyridine-2(1H)-ones of type a. In contrast, 2H-1-benzopyran-2, 5-diones 2–4 gave under the same reaction conditions 5-hydrazonobenzopyrans of type b. Calculated heats of formation matched experimental findings. 相似文献
453.
In situ photoexcitation of silver-doped titania nanopowders for activity against bacteria and yeasts
Kowal K Wysocka-Król K Kopaczyńska M Dworniczek E Franiczek R Wawrzyńska M Vargová M Zahoran M Rakovský E Kuš P Plesch G Plecenik A Laffir F Tofail SA Podbielska H 《Journal of colloid and interface science》2011,362(1):50-57
Photocatalytic and in situ microbial activity of the amorphous and annealed states of Ag-doped and un-doped titania were examined. Studies on their structure, morphology, composition, and the photo-absorption characteristics of these materials were performed. These results were correlated with the photocatalytic and microbial activity against methicillin resistant Staphylococcus aureus K324 (MRSA), methicillin susceptible S. aureus ATCC 25923 (MSSA), Escherichia coli PA 170, and yeasts Candida albicans ATCC 90028. The annealed powders containing anatase form of titania exhibited relatively higher photocatalytic activity,corresponding to activity against MRSA,when exposed to UV-A radiation. In comparison, amorphous powders exhibited low photoactivity and showed poor antibacterial performance against MRSA under UV-A exposure. Doping of amorphous titania with Ag resulted in an anti-MRSA effect without exposure to UV radiation. In the Ag-doped crystalline anatase samples, the size of Ag primary nanocrystallites increased, which led to the decrease in the surface concentration of Ag and detriment anti-MRSA activity. 相似文献
454.
Edelson-Averbukh M Shevchenko A Pipkorn R Lehmann WD 《Journal of the American Society for Mass Spectrometry》2011,22(12):2256-2268
Unambiguous differentiation between isobaric sulfated and phosphorylated tyrosine residues (sTyr and pTyr) of proteins by mass spectrometry is challenging, even using high resolution mass spectrometers. Here we show that upon negative ion mode collision-induced dissociation (CID), pTyr- and sTyr-containing peptides exhibit entirely different modification-specific fragmentation patterns leading to a rapid discrimination between the isobaric covalent modifications using the tandem mass spectral data. This study reveals that the ratio between the relative abundances of [M-H-80](-) and [M-H-98](-) fragment ions in ion-trap CID and higher energy collision dissociation (HCD) spectra of singly deprotonated +80 Da Tyr-peptides can be used as a reliable indication of the Tyr modification group nature. For multiply deprotonated +80 Da Tyr-peptides, CID spectra of sTyr- and pTyr-containing sequences can be readily distinguished based on the presence/absence of the [M-nH-79]((n-1)-) and [M-nH-79-NL]((n-1)-) (n=2, 3) fragment ions (NL=neutral loss). 相似文献
455.
Measurement of the appearance of an object consists of a group of measurements to characterize the color and surface finish
of the object. This group of measurements involves the spectral energy distribution of propagated light measured in terms
of reflectance and transmittance, and the spatial energy distribution of that light measured in terms of the bidirectional
reflectance distribution function (BRDF). In this article we present the virtual gonio-spectrophotometer, a device that measures
flux (power) as a function of illumination and observation. Virtual gonio-spectrophotometer measurements allow the determination
of the scattering profile of specimens that can be used to verify the physical characteristics of the computer model used
to simulate the scattering profile. Among the characteristics that we verify is the energy conservation of the computer model.
A virtual gonio-spectrophotometer is utilized to find the correspondence between industrial measurements obtained from gloss
meters and the parameters of a computer reflectance model. 相似文献
456.
Structural properties of effective potential model by liquid state theories 总被引:1,自引:0,他引:1 下载免费PDF全文
This paper investigates the structural properties of a model fluid dictated by an effective inter-particle oscillatory potential by grand canonical ensemble Monte Carlo (GCEMC) simulation and classical liquid state theories.The chosen oscillatory potential incorporates basic interaction terms used in modeling of various complex fluids which is composed of mesoscopic particles dispersed in a solvent bath,the studied structural properties include radial distribution function in bulk and inhomogeneous density distribution profile due to influence of several external fields.The GCEMC results are employed to test the validity of two recently proposed theoretical approaches in the field of atomic fluids.One is an Ornstein-Zernike integral equation theory approach;the other is a third order + second order perturbation density functional theory.Satisfactory agreement between the GCEMC simulation and the pure theories fully indicates the ready adaptability of the atomic fluid theories to effective model potentials in complex fluids,and classifies the proposed theoretical approaches as convenient tools for the investigation of complex fluids under the single component macro-fluid approximation. 相似文献
457.
Jaroslav Galba Juraj Pieanský Andrej Kov
Dominika Oleov Ondrej Cehlr Martin Kertys Petr Kozlík Petra Chaov Barbora Tir
ov Kristin Slí Peter Miku 《Molecules (Basel, Switzerland)》2021,26(2)
Oxandrolone, a synthetic testosterone analog, is used for the treatment of several diseases associated with weight loss. Unfortunately, oxandrolone is abused by many athletes and bodybuilders due to its strong anabolic effect. We have developed and validated a highly sensitive and rapid on-line SPE-UHPLC-MS/MS method for the determination of oxandrolone and simultaneous identification of its major metabolite 17-epi-oxandrolone in urine matrices. Enrichment of the analytes via an integrated solid-phase extraction was achieved using an Acquity UPLC BEH C18 Column. Subsequently, the chromatographic separation of the on-line preconcentrated sample fraction was achieved using an Acquity HSS T3 C18 Column. For the structural identification of these analytes, a high-resolution mass spectrometer Synapt-G2Si coupled to the Acquity M-class nano-LC system with ionKey source was used. A highly sensitive determination of oxandrolone was achieved using a tandem quadrupole mass spectrometer XEVO TQD. The method was successfully validated in the linear range of oxandrolone from 81.63 pg·mL−1 (limit of quantification, LOQ) to 5000 pg·mL−1 in the human urine matrix. It was applied to the analysis of real urine samples obtained from a healthy volunteer after the oral administration of one dose (10 mg) of oxandrolone. Concentration vs. time dependence was tested in the time interval of 4 h–12 days (after oral administration) to demonstrate the ability of the method to detect the renal elimination of oxandrolone from the human body. Favorable performance parameters along with successful application indicate the usefulness of the proposed method for its routine use in antidoping control labs. 相似文献
458.
Dr. Kristína Plevová Dr. Péter Kisszékelyi Dr. Denisa Vargová Samuel Andrejčák Viktor Tóth Lukáš Fertáľ Dr. Erik Rakovský Dr. Juraj Filo Prof. Dr. Radovan Šebesta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(62):15501-15507
Diastereoselective double C−H heteroarylation of chiral ferrocenes provides valuable compounds with multiple functionalities using mild reaction conditions and simple reagents. Pd-Complexes with chiral mono-protected amino acids afforded corresponding heteroarylated ferrocenyl amines in good yields and high diastereomeric purities. In this way, a variety of indole, thiophene, pyrrole, or furan substituents were introduced to the ferrocene moiety. Furthermore, a range of relevant functional groups, for example ketone, ester, chloro, nitro, or silyl, are tolerated by this method. An alternative combination of amino acid and ferrocenyl amine configurations was leveraged to provide the complementary diastereomeric products. The products of C−H heteroarylation can be transformed into corresponding phosphines. Absolute configurations of CH-activation products were confirmed by the combination of X-ray crystallographic analysis and CD spectroscopy. 19F NMR kinetic study and DFT calculations provided insights into the reaction mechanism and reasons governing stereoinduction. 相似文献
459.
Dominika Valachová Michaela Marčeková Dr. Oľga Caletková Dr. Andrej Kolarovič Dr. Pavol Jakubec 《European journal of organic chemistry》2023,26(13):e202201341
Protodenitration, a direct reduction of nitroalkanes to corresponding alkanes, already spans two centuries and is enabled by various reagents. This mini-review provides a historical development of the fundamental transformation and highlights the governing position of the Ono-Tanner reaction employing tributyltin hydride. Due to the unchallenged dominance of the toxic tributyltin hydride and environmentally unpopular solvents sharply contrasting with modern ecological trends, the current situation was dubbed “the last fortress of tin's tyranny.” 相似文献
460.
Čegovnik Tomaž Dobrovoljc Andrej Povh Janez Rogar Matic Tomšič Pavel 《Central European Journal of Operations Research》2023,31(3):833-851
Central European Journal of Operations Research - The measurement of electricity consumption at 15-minute granularity, including for households, is increasingly mandated in the EU and this also... 相似文献