Search results for "chemistry [Water]"
showing 10 items of 2369 documents
Design, characterization, and first field deployment of a novel aircraft-based aerosol mass spectrometer combining the laser ablation and flash vapor…
2021
In this paper, we present the design, development, and characteristics of the novel aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols; ERC – European Research Council) and selected results from the first airborne field deployment. The instrument combines two well-established methods of real-time in situ measurements of fine particle chemical composition. The first method is the laser desorption and ionization technique, or laser ablation technique, for single-particle mass spectrometry (here with a frequency-quadrupled Nd:YAG laser at λ = 266 nm). The second method is a combination of thermal particle desorption, also called flash vaporization, and electro…
Enhanced sulfur in the upper troposphere and lower stratosphere in spring 2020
2022
Sulfur compounds in the upper troposphere and lower stratosphere (UTLS) impact the atmosphere radiation budget, either directly as particles or indirectly as precursor gas for new particle formation. In situ measurements in the UTLS are rare but are important to better understand the impact of the sulfur budget on climate. The BLUESKY mission in May and June 2020 explored an unprecedented situation. (1) The UTLS experienced extraordinary dry conditions in spring 2020 over Europe, in comparison to previous years, and (2) the first lockdown of the COVID-19 pandemic caused major emission reductions from industry, ground, and airborne transportation. With the two research aircraft HALO and Falc…
Hydrogenolysis of hydroxymatairesinol on Y derived catalysts: a computational study
2010
Hydrogenolysis of 7-hydroxymatairesinol (HMR) to matairesinol (MAT) occurs on palladium supported acidic catalysts. HMR has three stereochemical centres and naturally exists as a mixture of two diastereoisomers, namely RRR-HMR and SRR-HMR. The latter is significantly more reactive than the former, in the reaction above. In order to elucidate the hydrogenolysis mechanism, simple surface events involving HMR derivatives on aluminated faujasite (H-Y) fragments were simulated by quantum chemical calculations. The metallic function of a Pd/H-Y acidic catalyst was also mimicked by a minimal palladium cluster. Stereochemical evidences pointed already out that water β-elimination on the epimeric ce…
Filling the Gap in the Metallacrown Family: The 9‐MC‐3 Chromium Metallacrown
2021
Abstract In this work, we report on a long‐sought missing complex in the metallacrown family. We synthesized and characterized the novel chromium metallacrown (MC) complex {CrIII(μ 2‐piv)3[9‐MCCr(III)N(shi)‐3](morph)3}⋅MeOH (in which shi3−=salicyl hydroxamate, piv=pivalate, and morph=morpholine). The MC with a 9‐MC‐3 cavity of kinetically inert chromium(III) ions was synthesized by a solvothermal reaction. Magnetization measurements reveal a high spin ground state.
Carbon and nitrogen stable isotope ratios of soils and grasses as indicators of soil characteristics and biological taxa
2019
Abstract The use of stable isotope techniques can assist in understanding interactions of plants with various abiotic and biotic processes. In the research, we focused on carbon (C) and nitrogen (N) isotopes because they are the most important resources influencing plant function and the biogeochemical cycles. The 13C/12C and 15N/14N ratios in plants and in soils and the relationships between these ratios and biological and environmental factors of widely distributed native C3 plants (couch grass, plantain and yarrow) collected from two sites in St. Petersburg, Russia were studied. The soil characteristics of the sites were rather different. This had a significant effect on the isotope rati…
Sr-isotope analysis of speleothems by LA-MC-ICP-MS: High temporal resolution and fast data acquisition
2017
Speleothems are well established climate archives. A wide array of geochemical proxies, including stable isotopes and trace elements are present within speleothems to reconstruct past climate variability. However, each proxy is influenced by multiple factors, often hampering robust interpretation. Sr isotope ratios (87Sr/86Sr) can provide useful information about water residence time and water mixing in the host rock, as they are not fractionated during calcite precipitation. Laser ablation multi-collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has rarely been used for determination of Sr isotope signatures in speleothems, as speleothems often do not possess appropriate…
Impact of hydroxy and octyloxy substituents of phenothiazine based dyes on the photovoltaic performance
2013
Two novel organic dyes containing hydroxy and octyloxy substituents onto a phenothiazine skeleton were synthesized and their effects on the photovoltaic performance were studied. Hydroxy acts as an ancillary anchoring unit along with the carboxylic group, while the phenothiazine modified moiety acts as an electron donor. The photophysical and electrochemical studies revealed that maximum absorbance of the dye with the hydroxy group in the solution was blue shifted and its band gap increased, indicating that donor acceptor strength was reduced as compared to the octyloxy substituted dye. Furthermore, electron lifetime of the organic dye with the hydroxy moiety was shorter due to smaller resi…
Synthesis and photovoltaic performance of dihydrodibenzoazepine-based sensitizers with additional lateral anchor
2013
Three novel metal-free organic dyes with dihydro-5H-dibenzo[b,f]azepine as a donor and cyanoacrylic acid as an anchoring unit were designed as an innovative linear skeleton of D-D-pi-A type of organic dyes. The conversion efficiency of the derived dye-sensitized solar cells is moderate. Among them, the dye with a hydroxy group as an additional anchoring moiety exhibited the highest UV-Vis absorption with a maximum molar extinction coefficient of 24,136 M-1 cm(-1) at lambda(max) = 458 nm and the best photovoltaic performance with an overall power conversion efficiency of 4.88%, while the dye with a carboxy group as an additional anchoring moiety exhibited the lowest conversion efficiency (4.…
Geochemical signature of Paleozoic accretionary complexes of the Central Asian Orogenic Belt in South Mongolia: Constraints on arc environments and c…
2006
Abstract We report a reconnaissance geochemical and Nd-isotopic study for 33 metaigneous and metavolcaniclastic rocks from the ca. 470 to 290 Ma old Gurvan Sayhan, Zoolen, Nemegt Uul, Bayanleg-Hatuu, and Tseel mountain ranges in southern Mongolia, in order to infer tectonic environments, test a recently proposed multiple terrane model, and explore the late-stage development of the southern Central Asian Orogenic Belt (CAOB). Samples from the Gurvan Sayhan and the Zoolen ranges have a predominantly intermediate, calc-alkaline composition; they display LREE enrichment, excess abundances of fluid-soluble elements, and low concentrations of high-field strength elements. These data, in combinati…
Determination of free formaldehyde in cosmetics containing formaldehyde-releasing preservatives by reversed-phase dispersive liquid-liquid microextra…
2017
Abstract An analytical method for the determination of traces of formaldehyde in cosmetic products containing formaldehyde-releasing preservatives has been developed. The method is based on reversed-phase dispersive liquid–liquid microextraction (RP-DLLME), that allows the extraction of highly polar compounds, followed by liquid chromatography–ultraviolet/visible (LC–UV/vis) determination with post-column derivatization. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the selected conditions, a mixture of 500 μL of acetonitrile (disperser solvent) and 50 μL of water (extraction solvent) was rapidly injected into 5 mL of toluene sampl…