Search results for "Clima"
showing 10 items of 6069 documents
Initial approaches in benchmarking and round robin testing for proton exchange membrane water electrolyzers
2019
Abstract As ever-increasing amounts of renewable electricity enter the energy supply mix on a regional, national and international basis, greater emphasis is being placed on energy conversion and storage technologies to deal with the oscillations, excess and lack of electricity. Hydrogen generation via proton exchange membrane water electrolysis (PEMWE) is one technology that offers a pathway to store large amounts of electricity in the form of hydrogen. The challenges to widespread adoption of PEM water electrolyzers lie in their high capital and operating costs which both need to be reduced through R&D. An evaluation of reported PEMWE performance data in the literature reveals that there …
Comparative high-resolution chemostratigraphy of the Bonarelli Level from the reference Bottaccione section (Umbria-Marche Apennines) and from an equ…
2006
The Bonarelli Level (BL) from the upper Cenomanian portion of the reference Bottaccione section (central Italy) is characterized by the presence of black shales containing high TOC concentrations (up to 17%) and amounts of CaCO3 near to zero. In the absence of carbonate and, consequently, of relative carbon- and oxygen-isotopic data, the elemental geochemistry revealed to be a very useful tool to obtain information about the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean during the OAE2. Based on several geochemical proxies (Rb, V, Ni, Cr, Si, Ba), the BL is interpreted as a high-productivity event driven by increasingly warm and humid climatic conditions promoting an a…
Suppression of new particle formation from monoterpene oxidation by NO<sub>x</sub>
2014
Abstract. The impact of nitrogen oxides (NOx = NO + NO2) on new particle formation (NPF) and on photochemical ozone production from real plant volatile organic compound (BVOC) emissions was studied in a laboratory setup. At high NOx conditions ([BVOC] / [NOx] < 7, [NOx] > 23 ppb) new particle formation was suppressed. Instead, photochemical ozone formation was observed resulting in higher hydroxyl radical (OH) and lower nitrogen monoxide (NO) concentrations. When [NO] was reduced back to levels below 1 ppb by OH reactions, NPF was observed. Adding high amounts of NOx caused NPF to be slowed by orders of magnitude compared to analogous experiments at low NOx conditions ([NOx] ~300 ppt)…
In situ submicron organic aerosol characterization at a boreal forest research station during HUMPPA-COPEC 2010 using soft and hard ionization mass s…
2013
The chemical composition of submicron aerosol during the comprehensive field campaign HUMPPA-COPEC 2010 at Hyytiälä, Finland, is presented. The focus lies on online measurements of organic acids, which were achieved by using atmospheric pressure chemical ionization (APCI) ion trap mass spectrometry (IT-MS). These measurements were accompanied by aerosol mass spectrometry (AMS) measurements and Fourier transform infrared spectroscopy (FTIR) of filter samples, all showing a high degree of correlation. The soft ionization mass spectrometer alternated between gas-phase measurements solely and measuring the sum of gas and particle phase. The AMS measurements of C, H and O elemental composition s…
Composition, crystallization conditions and genesis of sulfide-saturated parental melts of olivine-phyric rocks from Kamchatsky Mys (Kamchatka, Russi…
2020
Highlights • Parental melts of sulfide-bearing KM rocks have near primary MORB-like composition. • Crystallization of these S-saturated melts occurred in near-surface conditions. • Extensive fractionation and crustal assimilation are not the causes of S-saturation. • S content in melts can be restored by accounting for daughter sulfide globules. Abstract Sulfide liquids that immiscibly separate from silicate melts in different magmatic processes accumulate chalcophile metals and may represent important sources of the metals in Earth's crust for the formation of ore deposits. Sulfide phases commonly found in some primitive mid-ocean ridge basalts (MORB) may support the occurrence of sulfide …
Soil microbial and microfaunal communities and organic matter quality in reindeer winter and summer ranges in Finnish subarctic mountain birch forests
2008
Abstract Reindeer husbandry has significant influences on the aboveground plant communities and the structure of the mountain birch forests in the Fennoscandian subarctic. We investigated how the reindeer-mediated aboveground changes affect soil microbial and microfaunal communities and enzymatic activities. We hypothesized that in areas with intensive summer browsing by reindeer, the carbon flow to belowground is reduced, but the carbon substances are more readily degradable. This is likely to influence both the abundance and the trophic structure of microbial and microfaunal communities. However, despite large differences in the vegetation, the reindeer ranges did not differ in the amount…
Estimating the contribution of organic acids to northern hemispheric continental organic aerosol
2015
Using chemical ionization mass spectrometry to detect particle-phase acids (acid-CIMS) and aerosol mass spectrometry (AMS) measurements from Colorado, USA, and two studies in Hyytiala, Finland, we quantify the fraction of organic aerosol (OA) mass that is composed of molecules with acid functional groups (facid). Molecules containing one or more carboxylic acid functionality contributed approximately 29% (45-51%) of the OA mass in Colorado (Finland). Organic acid mass concentration correlates well with AMS m/z 44 (primarily CO2+), a commonly used marker for highly oxidized aerosol. Using the average empirical relationship between AMS m/z 44 and organic acids in these three studies, together…
Merging shuttle reactions and paired electrolysis for reversible vicinal dihalogenations
2021
Vicinal dibromides and dichlorides are important commodity chemicals and indispensable synthetic intermediates in modern chemistry that are traditionally synthesized using hazardous elemental chlorine and bromine. Meanwhile, the environmental persistence of halogenated pollutants necessitates improved approaches to accelerate their remediation. Here, we introduce an electrochemically assisted shuttle (e-shuttle) paradigm for the facile and scalable interconversion of alkenes and vicinal dihalides, a class of reactions that can be used both to synthesize useful dihalogenated molecules from simple alkenes and to recycle waste material through retro-dihalogenation. The reaction is demonstrated…
Coupling Adsorption and Biological Technologies for Multicomponent and Fluctuating Volatile Organic Compounds Emissions Abatement: Laboratory-Scale E…
2015
The capacity of activated carbon as a buffer pretreatment combined with biotrickling filtration for volatile organic compound (VOC) removal has been studied. The adsorption capacity of commercial activated carbons for m-xylene, acetone and n-butyl acetate (typical paint solvents) was evaluated, including the response to the interchanging of adsorbed compounds and to mixtures over fluctuating inlet conditions. The adsorption of m-xylene and n-butyl acetate was mainly irreversible and more than three times higher than for acetone. The prior use of activated carbon influenced adsorption and buffer capacities in consecutive adsorption/desorption cycles. The Dubinin–Radushkevich equation was use…
Investigations on the geographical variability of the human transferrins.
1971
On the basis of own and from the widely scattered literature compiled materials the geographical distribution of the transferrin alleles is discussed. They reveal a characteristic distribution pattern, as the slow Tf variants produced by TfD alleles are obviously more frequent in tropical than in non-tropical populations. Considering similar results in cattle and its interpretation by Ashton (1958, 1965), it is hypothesized, that the relatively high TfΓ frequencies in tropical biotops might be a selective adaptation to their special climatic conditions. In this connection an association between slowly moving transferrin proteins in man and tolerance to hotter climates — as could be found in…