排序方式: 共有49条查询结果,搜索用时 109 毫秒
21.
Pietrogrande MC Zampolli MG Dondi F Szopa C Sternberg R Buch A Raulin F 《Journal of chromatography. A》2005,1071(1-2):255-261
Gas chromatography-mass spectrometry (GC-MS) will be used in future space exploration missions, in order to seek organic molecules at the surface of Mars, and especially potential chemical indicators of life. Carboxylic acids are among the most expected organic species at the surface of Mars, and they could be numerous in the analysed samples. For this reason, a chemometric method was applied to support the interpretation of chromatograms of carboxylic acid mixtures. The method is based on AutoCovariance Function (ACVF) in order to extract information on the sample--number and chemical structure of the components--and on separation performance. The procedure was applied to standard samples containing targeted compounds which are among the most expected to be present in the Martian soil: n-alkanoic and benzene dicarboxylic acids. ACVF was computed on the obtained chromatograms and plotted versus retention time: peaks of the ACVF plot can be related to specific molecular structures and are diagnostic for chemical identification of compounds. 相似文献
22.
S⦊. Sterliński H. Maleszewska Z. Szopa R. Dybczyński 《Journal of Radioanalytical and Nuclear Chemistry》1980,59(1):141-155
Trace amounts of Ir, Au, Ag, Pt, Zn, Mn, and Cu were determined in high purity palladium by destructive and instrumental neutron
activation analysis (NAA). The latter version of NAA was employed for the determination of Ir, Au and Ag. Special attention
was paid to a new non-destructive method for the determination of silver traces in palladium. The results obtained by both
versions of NAA are critically discussed and compared. 相似文献
23.
Szopa C Sternberg R Coscia D Cottin H Raulin F Goesmann F Rosenbauer H 《Journal of chromatography. A》1999,863(2):157-169
The development of a gas chromatograph for the cometary sampling and composition (COSAC) experiment is described in the context of the preparation for the European Space Agency (ESA) Mission Rosetta for investigation of a cometary nucleus. COSAC is one out of ten experiments on the Rosetta Lander. Its scientific goal is to analyze in situ the chemical composition of the volatile constituents of the nucleus of the target comet P/Wirtanen. Constituted of several (up to eight) capillary wall-coated and porous-layer open tubular columns operating in parallel, the GC system is designed to separate and identify both organic and inorganic compounds which evolve from the comet naturally or are obtained from cometary samples through stepwise heating in a miniaturized pyrolizer. In this first part of our study, dimethylpolysiloxane (DMPS) stationary phases with increasing percentages of diphenyl substituted group (DP) have been investigated. A coupled experimental and theoretical approach has been taken in order to predict chromatographic data. By the use of a four-point experimental calibration (0 to 65% diphenyl group) in conjunction with Pro ezGC modeling software, results in prediction of multicomponent chromatograms with a mean error less than 5% for each compound retention time were obtained, irrespective of the stationary phase's diphenyl content and column physical parameters. The possibility to associate such phases is illustrated by the evolution of coelutions obtained on a non-polar (100% DMPS) and a medium polar (65% DP-DMPS) stationary phase, respectively. This study showed that with a small number of well tuned DP-DMPS columns, the separation and identification of most of the targeted compounds can be achieved with a minimum amount of coelutions and within the experiment requirements. 相似文献
24.
Summary In the framework of the cometary sampling and composition (COSAC) experiment of the European Space Agency (ESA) Rosetta space
mission to a comet, a new generation of porous polymer porous-layer open tubular (PLOT) columns has been investigated with
the aim of separating the light organic compounds targeted by the experiment within the constraints of the operating conditions
used in space. Both styrene-divinylbenzene and ethylene glycol-dimethyl acrylate-divinylbenzene porous polymers can be used
to separate most of the target compounds, but the latter was selected because of its better separating properties. The most
appropriate column characteristics were found to be 10 m length, 0.18 mm internal diameter, and 1–2 μm layer thickness, despite
the low sample-loading capacity of such a column, which impairs its chromatographic performance. The influence of column overloading
on retention properties and efficiency was, therefore, studied. To achieve the separation with optimum sensitivity, and within
the in-situ time allowed for the analysis, it was also demonstrated that the maximum allowed temperature and reduced outlet
pressure are required. Finally, it was shown that in the presence of water, the most abundant volatile compound in comets
the separating properties of the studied columns are conserved. This paper thus demonstrates the suitability of the porous
polymer PLOT column selected for the COSAC experiment and requirements for use in space; it is the first porous polymer PLOT
column to be used in space exploration.
Presented at: 23rd International Symposium on Chromatography, London, UK, October 1–5, 2000 相似文献
25.
Piotr Szopa 《Journal of Mathematical Analysis and Applications》2009,351(1):340-1595
In this paper we consider the solutions of micropolar fluid equations in space dimension two with periodic boundary condition. We show that the strong solutions are analytic in time with values in an appropriate Gevrey class of function, provided that external forces and moments are time-independent and are in a Gevrey class. 相似文献
26.
Global air quality and climate 总被引:1,自引:0,他引:1
AM Fiore V Naik DV Spracklen A Steiner N Unger M Prather D Bergmann PJ Cameron-Smith I Cionni WJ Collins S Dalsøren V Eyring GA Folberth P Ginoux LW Horowitz B Josse JF Lamarque IA Mackenzie T Nagashima FM O'Connor M Righi ST Rumbold DT Shindell RB Skeie K Sudo S Szopa T Takemura G Zeng 《Chemical Society reviews》2012,41(19):6663-6683
Emissions of air pollutants and their precursors determine regional air quality and can alter climate. Climate change can perturb the long-range transport, chemical processing, and local meteorology that influence air pollution. We review the implications of projected changes in methane (CH(4)), ozone precursors (O(3)), and aerosols for climate (expressed in terms of the radiative forcing metric or changes in global surface temperature) and hemispheric-to-continental scale air quality. Reducing the O(3) precursor CH(4) would slow near-term warming by decreasing both CH(4) and tropospheric O(3). Uncertainty remains as to the net climate forcing from anthropogenic nitrogen oxide (NO(x)) emissions, which increase tropospheric O(3) (warming) but also increase aerosols and decrease CH(4) (both cooling). Anthropogenic emissions of carbon monoxide (CO) and non-CH(4) volatile organic compounds (NMVOC) warm by increasing both O(3) and CH(4). Radiative impacts from secondary organic aerosols (SOA) are poorly understood. Black carbon emission controls, by reducing the absorption of sunlight in the atmosphere and on snow and ice, have the potential to slow near-term warming, but uncertainties in coincident emissions of reflective (cooling) aerosols and poorly constrained cloud indirect effects confound robust estimates of net climate impacts. Reducing sulfate and nitrate aerosols would improve air quality and lessen interference with the hydrologic cycle, but lead to warming. A holistic and balanced view is thus needed to assess how air pollution controls influence climate; a first step towards this goal involves estimating net climate impacts from individual emission sectors. Modeling and observational analyses suggest a warming climate degrades air quality (increasing surface O(3) and particulate matter) in many populated regions, including during pollution episodes. Prior Intergovernmental Panel on Climate Change (IPCC) scenarios (SRES) allowed unconstrained growth, whereas the Representative Concentration Pathway (RCP) scenarios assume uniformly an aggressive reduction, of air pollutant emissions. New estimates from the current generation of chemistry-climate models with RCP emissions thus project improved air quality over the next century relative to those using the IPCC SRES scenarios. These two sets of projections likely bracket possible futures. We find that uncertainty in emission-driven changes in air quality is generally greater than uncertainty in climate-driven changes. Confidence in air quality projections is limited by the reliability of anthropogenic emission trajectories and the uncertainties in regional climate responses, feedbacks with the terrestrial biosphere, and oxidation pathways affecting O(3) and SOA. 相似文献
27.
Muszyńska Bożena Maślanka Anna Sułkowska-Ziaja Katarzyna Opoka Włodzimierz Szopa Agnieszka 《平面色谱法杂志一现代薄层色谱法》2014,27(3):210-216
JPC – Journal of Planar Chromatography – Modern TLC - Thin-layer chromatography (TLC) methods coupled with densitometric detection were employed in analyses for the presence of... 相似文献
28.
Ewelina Sobstyl Agnieszka Szopa Micha Dziurka Halina Ekiert Hanna Nikolaichuk Irena Maria Choma 《Molecules (Basel, Switzerland)》2022,27(7)
The effect-directed detection (EDD) of Schisandra rubriflora fruit and leaves extracts was performed to assess their pharmacological properties. The EDD comprised TLC—direct bioautography against Bacillus subtilis, a DPPH assay, as well as α-glucosidase, lipase, tyrosinase, and acetylcholinesterase (AChE) inhibition assays. The leaf extracts showed stronger antioxidant activity than the fruit extract as well as inhibition of tyrosinase and lipase. The fruit extract was found to be extremely active against B. subtilis and to inhibit α-glucosidase and AChE slightly more than the leaf extracts. UHPLC–MS/MS analysis was carried out for the bioactive fractions and pointed to the possible anti-dementia properties of the dibenzocyclooctadiene lignans found in the upper TLC fractions. Gomisin N (518 mg/100 g DW), schisanhenol (454 mg/100 g DW), gomisin G (197 mg/100 g DW), schisandrin A (167 mg/100 g DW), and gomisin O (150 mg/100 g DW) were the quantitatively dominant compounds in the fruit extract. In total, twenty-one lignans were found in the bioactive fractions. 相似文献
29.
Aleksandra Boba Kamil Kostyn Yelyzaveta Kochneva Wioleta Wojtasik Justyna Mierziak Anna Prescha Beata Augustyniak Magdalena Grajzer Jan Szopa Anna Kulma 《Molecules (Basel, Switzerland)》2022,27(9)
Fusarium culmorum is a ubiquitous soil pathogen with a wide host range. In flax (Linum ussitatissimum), it causes foot and root rot and accumulation of mycotoxins in flax products. Fungal infections lead to huge losses in the flax industry. Moreover, due to mycotoxin accumulation, flax products constitute a potential threat to the consumers. We discovered that the defense against this pathogen in flax is based on early oxidative burst among others. In flax plants infected with F. culmorum, the most affected genes are connected with ROS production and processing, callose synthesis and ABA production. We hypothesize that ABA triggers defense mechanism in flax and is a significant player in a successful response to infection. 相似文献
30.
Marta Klimek-Szczykutowicz Micha Dziurka Ivica Blaevi Azra ulovi Magorzata Miazga-Karska Katarzyna Klimek Halina Ekiert Agnieszka Szopa 《Molecules (Basel, Switzerland)》2021,26(15)
The study demonstrated the effects of precursor feeding on the production of glucosinolates (GSLs), flavonoids, polyphenols, saccharides, and photosynthetic pigments in Nasturtium officinale microshoot cultures grown in Plantform bioreactors. It also evaluated the antioxidant and antimicrobial activities of extracts. L-phenylalanine (Phe) and L-tryptophan (Trp) as precursors were tested at 0.05, 0.1, 0.5, 1.0, and 3.0 mM. They were added at the beginning (day 0) or on day 10 of the culture. Microshoots were harvested after 20 days. Microshoots treated with 3.0 mM Phe (day 0) had the highest total GSL content (269.20 mg/100 g DW). The qualitative and quantitative profiles of the GSLs (UHPLC-DAD-MS/MS) were influenced by precursor feeding. Phe at 3.0 mM stimulated the best production of 4-methoxyglucobrassicin (149.99 mg/100 g DW) and gluconasturtiin (36.17 mg/100 g DW). Total flavonoids increased to a maximum of 1364.38 mg/100 g DW with 3.0 mM Phe (day 0), and polyphenols to a maximum of 1062.76 mg/100 g DW with 3.0 mM Trp (day 0). The precursors also increased the amounts of p-coumaric and ferulic acids, and rutoside, and generally increased the production of active photosynthetic pigments. Antioxidant potential increased the most with 0.1 mM Phe (day 0) (CUPRAC, FRAP), and with 0.5 mM Trp (day 10) (DPPH). The extracts of microshoots treated with 3.0 mM Phe (day 0) showed the most promising bacteriostatic activity against microaerobic Gram-positive acne strains (MIC 250–500 µg/mL, 20–21 mm inhibition zones). No extract was cytotoxic to normal human fibroblasts over the tested concentration range (up to 250 μg/mL). 相似文献