Properties of a radiation-induced charge multiplication region in epitaxial silicon diodes

Charge multiplication (CM) in p$^+$n epitaxial silicon pad diodes of 75, 100 and 150 \upmum thickness at high voltages after proton irradiation with 1 MeV neutron equivalent fluences in the order of $10^{16}$ cm$^{-2}$ was studied as an option to overcome the strong trapping of charge carriers in the innermost tracking region of future Super-LHC detectors. Charge collection efficiency (CCE) measurements using the Transient Current Technique (TCT) with radiation of different penetration (670, 830, 1060 nm laser light and $\alpha$-particles with optional absorbers) were used to locate the CM region close to the p$^+$-implantation. The dependence of CM on material, thickness of the epitaxial layer, annealing and temperature was studied. The collected charge in the CM regime was found to be proportional to the deposited charge, uniform over the diode area and stable over a period of several days. Randomly occurring micro discharges at high voltages turned out to be the largest challenge for operation of the diodes in the CM regime. Although at high voltages an increase of the TCT baseline noise was observed, the signal-to-noise ratio was found to improve due to CM for laser light. Possible effects on the charge spectra measured with laser light due to statistical fluctuations in the CM process were not observed. In contrast, the relative width of the spectra increased in the case of $\alpha$-particles, probably due to varying charge deposited in the CM region.Comment: 11 pages, accepted by NIM

FLOTATION KINETICS OF MAGNESIUM HYDROXIDE SEDIMENTED FROM SEA WATER

Synthetic sea water has been taken as a referential sample, in which Mg(OH)2 had been sedimented, in order to reduce biological effects and confirm reproducibility of results of the familiar composition sample. The synthetic sea water was prepared according to the scientifically developed procedure. Flotation experiments were performed in the apparatus for flotation under pressure and recoveries of floated Mg(OH)2 were determined depending on the time of flotation. The results obtained on the referential sample of the synthetic water were also tested on the sample of natural sea water and presented comparatively during work. Flotation kinetics is in most cases described by an equation of the first or second degree. However, it was established that flotation kinetics of Mg(OH)2 as chemical sediment with both types of prepared magnesium hydroxide suspension, sedimented in both the synthetic and natural sea water corresponded to the velocity of reaction n = 1.5 degree, which fully corresponds to Horst Morris’s theoretical postulates in the theory of flotation kinetics

FLOTATION KINETICS OF MAGNESIUM HYDROXIDE SEDIMENTED FROM SEA WATER

Synthetic sea water has been taken as a referential sample, in which Mg(OH)2 had been sedimented, in order to reduce biological effects and confirm reproducibility of results of the familiar composition sample. The synthetic sea water was prepared according to the scientifically developed procedure. Flotation experiments were performed in the apparatus for flotation under pressure and recoveries of floated Mg(OH)2 were determined depending on the time of flotation. The results obtained on the referential sample of the synthetic water were also tested on the sample of natural sea water and presented comparatively during work. Flotation kinetics is in most cases described by an equation of the first or second degree. However, it was established that flotation kinetics of Mg(OH)2 as chemical sediment with both types of prepared magnesium hydroxide suspension, sedimented in both the synthetic and natural sea water corresponded to the velocity of reaction n = 1.5 degree, which fully corresponds to Horst Morris’s theoretical postulates in the theory of flotation kinetics

Application of 4-Chlorobutyryl Group as Amino Protective Group in the Synthesis of 7-(D-2-Amino-2-phenylacetamido)-3-methyl-3-cephem-4-carboxylic Acid (Cephalexin)

4-Chlorobutyryl group was used as amino protective group for n(-)-alpha-phenylglycine (I). N-Hydroxysuccinimide ester III was prepared in high yield but partly racemic. Reaction of III or IV with V afforded epimeric mixtures of N,0-protected cephalexins (VI), which can be separated by crystallisation. The 4-chlorobutyryl group in VII was removed under very mild conditions giving cephalexin (IX) in good yield and purity

Plesni i mikotoksini u uskladištenom kukuruzu

In this study the presence of moulds and mycotoxins in samples of stored maize grains in the period from October 2011 to September 2012 was investigated. Mycological analyses of whole and broken grains showed the presence of species from the genera Alternaria, Aspergillus, Fusarium, Penicillium, Rhizopus and others. Among the Aspergillus and Fusarium genera as potentially toxigenic fungi, Aspergillus flavus was identified with the highest percentage on broken grains (20.38%) whereas F. verticilioides was the predominant species in the whole maize grains (34.04%). In addition, it was obtained that tested samples of stored maize grains were 100% positive with aflatoxin B1 (AFB1), zearalenone (ZON), deoxynivalenol (DON) and fumonisin B1 (FB1) with an average concentration of 1.39 μg kg-1, 71.79 μg kg-1, 128.17 μg kg-1, and 1610.83 μg kg-1, respectively. A significant positive correlation was found between the moisture content and the presence of Fusarium spp. on the broken grains (r = 0.44) and between the moisture content and the concentration of DON (r = 0.61). However, a significant negative correlation was found between moisture content and FB1 (r = -0.34), and between the concentration of ZON and DON mycotoxins (r = -0.58).U radu je ispitivano prisustvo plesni i mikotoksina u uzorcima zrna uskladištenog kukuruza u periodu od oktobra 2011. do septembra 2012. godine. Mikološkim analizama celog i slomljenog zrna kukuruza ustanovljeno je prisustvo vrsta iz rodova Alternaria, Aspergillus, Fusarium, Penicillium, Rhizopus i drugih. Od potencijalno toksigenih vrsta iz rodova Aspergillus i Fusarium, identifikovane su u najvećem procentu A. flavus na slomljenom (20,38%) i F. verticillioides na celom zrnu kukuruza (34,04%). Ispitivani uzorci uskladištenog kukuruza bili su 100% pozitivni sa aflatoksinom B1 (AFB1), zearalenonom (ZON), deoksinivalenolom (DON) i fumonizinom B1 (FB1) sa prosečnim koncentracijama 1,39 μg kg-1, 71,79 μg kg-1, 128,17 μg kg-1 i 1610,83 μg kg-1, respektivno. Statistički značajna pozitivna korelacija ustanovljena je između sadržaja vlage i prisustva Fusarium spp. na slomljenom zrnu kukuruza (r = 0,44), kao i između sadržaja vlage i koncentracije DON (r = 0,61). Statistički značajna negativna korelacija ustanovljena je između sadržaja vlage i FB1 (r = -0,34), kao i između koncentracija ZON i DON mikotoksina (r = -0,58)

Gain and time resolution of 45 μ\mum thin Low Gain Avalanche Detectors before and after irradiation up to a fluence of 101510^{15} neq_{eq}/cm2^2

Low Gain Avalanche Detectors (LGADs) are silicon sensors with a built-in charge multiplication layer providing a gain of typically 10 to 50. Due to the combination of high signal-to-noise ratio and short rise time, thin LGADs provide good time resolutions. LGADs with an active thickness of about 45 $\mu$m were produced at CNM Barcelona. Their gains and time resolutions were studied in beam tests for two different multiplication layer implantation doses, as well as before and after irradiation with neutrons up to $10^{15}$ n$_{eq}$/cm$^2$. The gain showed the expected decrease at a fixed voltage for a lower initial implantation dose, as well as for a higher fluence due to effective acceptor removal in the multiplication layer. Time resolutions below 30 ps were obtained at the highest applied voltages for both implantation doses before irradiation. Also after an intermediate fluence of $3\times10^{14}$ n$_{eq}$/cm$^2$, similar values were measured since a higher applicable reverse bias voltage could recover most of the pre-irradiation gain. At $10^{15}$ n$_{eq}$/cm$^2$, the time resolution at the maximum applicable voltage of 620 V during the beam test was measured to be 57 ps since the voltage stability was not good enough to compensate for the gain layer loss. The time resolutions were found to follow approximately a universal function of gain for all implantation doses and fluences.Comment: 17 page

Supplementary data for the article: Vitorović-Todorović, M. D.; Koukoulitsa, C.; Juranić, I. O.; Mandić, L. M.; Drakulić, B. J. Structural Modifications of 4-Aryl-4-Oxo-2-Aminylbutanamides and Their Acetyl- and Butyrylcholinesterase Inhibitory Activity. Investigation of AChE-Ligand Interactions by Docking Calculations and Molecular Dynamics Simulations. European Journal of Medicinal Chemistry 2014, 81, 158–175. https://doi.org/10.1016/j.ejmech.2014.05.008

Supplementary material for: [https://doi.org/10.1016/j.ejmech.2014.05.008]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1808]Related to accepted version:[http://cherry.chem.bg.ac.rs/handle/123456789/2907

Natural radionuclides in soil profiles surrounding the largest coal-fired power plant in Serbia

This study evaluates the influence of the largest Serbian coal-fired power plant on radionuclide concentrations in soil profiles up to 50 cm in depth. Thirty soil profiles were sampled from the plant surroundings (up to 10 km distance) and analyzed using standard methods for soil physicochemical properties and gamma ray spectrometry for specific activities of natural radionuclides (K-40, Ra-226 and Th-232) Spatial and vertical distribution of radionuclides was determined and analyzed to show the relations between the specific activities in the soil and soil properties and the most influential factors of natural radionuclide variability were identified. The radiological indices for surface soil were calculated and radiological risk assessment was performed. The measured specific activities were similar to values of BACKGROUND: levels for Serbia. The sampling depth did not show any significant influence on specific activities of natural radionuclides. The strongest predictor of specific activities of the investigated radionuclides was soil granulometry. All parameters of radiological risk assessment were below the recommended values and adopted limits. It appears that the coal-fired power plant does not have a significant impact on the spatial and vertical distribution of natural radionuclides in the area of interest, but technologically enhanced natural radioactivity as a consequence of the plant operations was identified within the first 1.5 km from the power plant

Supplementary data for article: Tripkovic, T.; Charvy, C.; Alves, S.; Lolić, A.; Baošić, R.; Nikolić-Mandić, S. D.; Tabet, J. C. Identification of Protein Binders in Artworks by MALDI-TOF/TOF Tandem Mass Spectrometry. Talanta 2013, 113, 49–61. https://doi.org/10.1016/j.talanta.2013.03.071

Supplementary material for: [https://doi.org/10.1016/j.talanta.2013.03.071]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1366