National Repository of Grey Literature 29 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Production and characterization of micro-size pores for ion track etching applications
Cannavó, Antonino ; Havránek, Vladimír ; Lavrentiev, Vasyl ; Torrisi, L. ; Cutroneo, Mariapompea ; Ceccio, Giovanni ; Torrisi, Alfio ; Horák, Pavel ; Vacík, Jiří
For many years the applications of ion track etch materials have increased considerably, like charged particles detection, molecular identification with nanopores, ion track filters, magnetic studies with nanowires and so on. Over the materials generally used as track detector, the Poly-Allyl-Diglycol Carbonate (PADC), offers many advantages, like its nearly 100 % detection efficiency for charged particle, a high resistance to harsh environment, the lowest detection threshold, a high abrasion resistance and a low production costs. All of these properties have made it particularly attractive material, even if due to its brittleness, obtaining a thin film (less than 500 μm) is still a challenge. In this work, PADC foils have been exposed to a-particles emitted by a thin radioactive source of 241Am and to C ions from the Tandetron 4130 MC accelerator. The latent tracks generated in the polymer have been developed using a standard etching procedure in 6.25 NaOH solution. The dependence of the ion tracks' geometry on the ion beam energy and fluence has been evaluated combining the information obtained through a semiautomatic computer script that selects the etched ion tracks according to their diameter and mean grey value and nanometric resolution images by atomic force microscopy.
Stability of the sodium content in selected botanical reference materials
Kameník, Jan ; Kučera, Jan ; Borovička, Jan ; Havránek, Vladimír
Sodium mass fractions in NIST standard reference materials (SRM) SRM 1547 Peach Leaves and SRM 1515 Apple leaves determined by INAA in our laboratory in recent years has been higher than the certified values. Similarly, increased values were published for SRM 1547 by several other laboratories. The increased Na mass fractions was found also for freshly opened SRM 1547 bottle and for material originating from a different lab. Increased Na mass fractions were confirmed by ICP-MS analysis of both materials. Analysis of archived samples revealed that sodium mass fraction in materials stored in polyethylene capsules is in agreement with the certified values. The sodium content in the glass of SRM 1547 bottle was roughly 10 %. Direct measurement of the Na depth profile by micro-PIXE was not indicative whether Na is released, i.g., by a glass corrosion due to residual humidity in the botanical material. However, a model experiment with freshly prepared and pulverized peach leaves demonstrated that such a scenario is possible for leaf-based materials. Although the study was focused on two NIST materials, the process is possible for any material with rather low Na content.
Ion beams provided by small accelerators for material synthesis and characterization
Macková, Anna ; Havránek, Vladimír
The compact, multipurpose electrostatic tandem accelerators are extensively used for production of ion beams with energies in the range from 400 keV to 24 MeV of almost all elements of the periodic system for the trace element analysis by means of nuclear analytical methods. The ion beams produced by small accelerators have a broad application, mainly for material characterization (Rutherford Back-Scattering spectrometry, Particle Induced X ray Emission analysis, Nuclear Reaction Analysis and Ion-Microprobe with 1 um lateral resolution among others) and for high-energy implantation. Material research belongs to traditionally progressive fields of technology. Due to the continuous miniaturization, the underlying structures are far beyond the analytical limits of the most conventional methods. Ion Beam Analysis (IBA) techniques provide this possibility as they use probes of similar or much smaller dimensions (particles, radiation). Ion beams can be used for the synthesis of new progressive functional nanomaterials for optics, electronics and other applications. Ion beams are extensively used in studies of the fundamental energetic ion interaction with matter as well as in the novel nanostructure synthesis using ion beam irradiation in various amorphous and crystalline materials in order to get structures with extraordinary functional properties. IBA methods serve for investigation of materials coming from material research, industry, micro- and nano-technology, electronics, optics and laser technology, chemical, biological and environmental investigation in general. Main research directions in laboratories employing small accelerators are also the preparation and characterization of micro- and nano-structured materials which are of interest for basic and oriented research in material science, and various studies of biological, geological, environmental and cultural heritage artefacts are provided too.
Comparison of PM2.5 Chemical Composition and Sources at a Rural Background Site.
Pokorná, Petra ; Schwarz, Jaroslav ; Krejčí, R. ; Swietlicki, E. ; Havránek, Vladimír ; Ždímal, Vladimír
The objective of this study is to compare the PM2.5 chemical composition and sources at a rural background site in Central Europe between the years 1993/1994/1995 and 2009/2010. Chemical analysis of PM2.5 for 29/26 elements by PIXE and water-soluble inorganic ions by IC (2009/2010) was performed. The Positive Matrix Factorization (PMF) was applied to the chemical composition of PM2.5 to identify its sources. The results of chemical analysis and source apportionment have been compared. The decrease in time of almost all elements concentrations especially the metals regulated by the EU Directive are evident. The median ratios show significant improvement in levels of analysed elements in PM2.5. Slight increase of K levels points to rise in the residential wood combustion. The apportioned sources in the years 1993/94/95 were brown coal combustion, oil combustion, dust – long-range transport, re-suspended dust/soil and black coal combustion. The industrial combustion of brown/black coal and oil of the regional origin dominated. The six factors in the years 2009/2010 were assigned as sulphate, nitrate, residential heating, industry, re-suspended dust, sea salt + dust/soil – LRT. The secondary sulphate from coal combustion and residential biomass burning of the local origin dominated.
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Source apportionment of atmospheric aerosol fraction using by highly time resolved characterisation
Pokorná, Petra ; Hovorka, Jan (advisor) ; Havránek, Vladimír (referee) ; Schwarz, Jaroslav (referee)
The effective air quality management in the heavy polluted areas has to be based on high-quality monitoring with properly designed monitoring network and targeted measurements, which provided information required to source apportionment. The thesis aim was to apportion sources of atmospheric aerosol based on highly time resolved data of mass concentration of size segregated aerosol, its temporal and spatial variability, elemental composition, OC/EC and size distribution of carcinogenic polyaromatic hydrocarbons. Sampling campaigns went during winter and summer in small settlement Březno by Chomutov, residential area Ostrava - Radvanice a Bartovice and Mladá Boleslav in the years 2008 - 2010, 2012, 2013. We determined mass concentrations of PM10, PM1-10, PM1.15-10 and PM0.15-1.5 and their size fraction ratios. Based on the size ratios, the source apportionment of fine fraction (PM0.15-1.15) with focus on PM0.34-1.15 is crucial. We examined seasonal and spatial variability of PM10, PM.2.5, PM1 and PM1-10. Based on the examination, we obtained representative highly-time resolved data with regards to season and sampling locality. We analysed dynamic of size distribution of particle-bond eight carcinogenic polycyclic hydrocarbons. Based on the results the source apportionment of PM0.34-1.15 is crucial....
Využití velikostní distribuce a elementárního složení městského aerosolu pro odhadu hlavních zdrojů/procesů podmikronových Pražských aerosolu pomocí receptorové modelování metody-Bilinear Positive Matrix Factorization
Thimmaiah, Devraj ; Hovorka, Jan (advisor) ; Havránek, Vladimír (referee) ; Brechler, Josef (referee)
Thesis Summary In this study' the sourcesofambient aerosolsin th€ uÍbanatmosphereofPrague, Czech Republic are apportionedusing bilinear Positive Matrix Faďorization (PMF2). Prior to this worl limited use of PMF techniquehas b€ťÍ' ryplied to Prague aerosols while elsewherearoundthe world, it has beenaaively usedby aerosol scientiststo reap thebenefitsince its fint inÚoduction in tbevea 1993. ln the currentstudy,the combinď pctrte nmber size disributions and readily available gaseous concentration .láa $tÍE 'E.d b ryortioning winter sub.micron particle sources in the urbm atmospbc of hgr. Tlle anbient Particle Number Concentations (PNC) wereotxainedsing r Scmng Mobility Particle Sizer (SMPS) in the size rangebetweeÍr14.ó md 73ó.5 m (Btd9od dianaers) along with the ambient gaseous concentrationsof CO, SQ. l,io, ()O * ]\iQL q, CH4, and Non Methane Hydrocarbons(NMHC) at the reccprr sit< e xllqriped rooftop sampling station(at height about 25m above street leall 25E AsL) be|onging to th€ Institute for Environmentalstuďes, Cbates tJnngsal 0aoe.5ď 4, |7.46"N; longifude-l4o25' 14.92 E). It is situared insi& lb. rDncn$! borni:al garden (area 0.035 km2).The receptoÍsite is shie|dedfrom diÍcctsouccs ofpo|hrin and thereaÍeno streetcanyon conditionsthatmigbt affea Úr sr@ry cmúm The meteorological d-Í. coocÍnmg umd...
Calibration and Exact Characterization of Aerosol Deposit colected by SDI Impactor
Havránek, Vladimír
Ion beam analytical methods as PIXE (Particle induced X-ray emission), PIGE (Particle induced gamma-ray emission) and RBS (Rutherford backscattering spectrometry) are frequently used for elemental analysis of different types of atmospheric aerosol samples in a form of aerosol deposits on thin plastic filters or foils (Alfassi and Peisach, 1991, Johansson and Campbell, 1988). An ideal sample for analysis is thin homogeneous aerosol deposit with known deposit area. However in practice such samples are rare. They are often thick (more than limit for thin target approximation i.e. larger then few hundred micrograms per square centimetres), of irregular shape and unknown deposit area. In such conditions all obtained elemental mass results should be corrected for apparent deposit thickness, deposit homogeneity and effective deposit area.
PM2.5 Chemical Composition at the Rural Background Site Košetice.
Schwarz, Jaroslav ; Cusack, Michael ; Karban, Jindřich ; Chalupníčková, E. ; Havránek, Vladimír ; Smolík, Jiří ; Ždímal, Vladimír
Measurements of atmospheric aerosols at rural background areas are important because they are not influenced by the urban emissions, and are therefore better suited to investigate the influence of long-range transport and trends in concentrations of individual pollutants. Summary of the measurements of total concentration and the concentration of PM10 and PM2.5 components was carried out in the works Putaud et al. (2004, 2010). Although the later work included the measurement of more than 60 stations across Europe, the post-communist countries contained data on PM2.5 from only four locations (Prague, Debrecen, Hungary, and two rural locations). Although Košetice place where this study was made, is also discussed there, it was for only PM10 and total carbon (TC). Therefore, the aim of this study is to fill this information gap, and provide additional information regarding the PM2.5 fraction and composition at the Central European background station Košetice.
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On Usage of Size Segregated Particle Number Concentration to Guess The Origin of PM2.5 at the Rural Background Site Košetice.
Schwarz, Jaroslav ; Cusack, Michael ; Karban, Jindřich ; Chalupníčková, E. ; Havránek, Vladimír ; Smolík, Jiří ; Ždímal, Vladimír
Rural background studies serve mainly to assess the long-range transport influence and long-term trends. However, it is difficult to find a place with no influence of local sources. This is also the case of Košetice observatory having three small settlements within two km from the observatory. Therefore we attempted to analyze if the influence of these or other nearby sources can be seen in our data on PM2.5 chemical composition. Besides other possibilities like specific ratios of various gaseous compounds we concentrated on using size resolved number concentration data because of their dynamics that leads in general into particle growth until they reach accumulation mode. Several similar studies (e.g. Cusack et al. 2013) were performed during recent years.
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Chemical Composition of PM2.5 at Rural Backround Site Košetice
Schwarz, Jaroslav ; Havránek, Vladimír
PM2.5 generally represents fine fraction of atmospheric aerosol. Fine particles may remain in the atmosphere for days or even weeks and therefore they may be transported over long distances. Moreover, they may increase the background levels of atmospheric aerosol mass far from their origin. They have important adverse health effects and in the same time, they influence climate due to their direct and indirect effects on Earth radiative balance. To know the origin of PM2.5 aerosol, its chemical composition can serve as the diary of contacts with aerosol sources and transformations. Therefore it is necessary to study PM2.5 chemical composition if the fine aerosol sources should be revealed. A rural background site study can serve as a basis enabling to determine the real influence of larger sources like cities or an industry.
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National Repository of Grey Literature : 29 records found   1 - 10nextend  jump to record:
See also: similar author names
1 Havránek, Vojtěch
2 Havránek, Václav
2 Havránek, Vít
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