Enhanced sequential carrier capture into individual quantum dots and quantum posts controlled by surface acoustic waves

Individual self-assembled Quantum Dots and Quantum Posts are studied under the influence of a surface acoustic wave. In optical experiments we observe an acoustically induced switching of the occupancy of the nanostructures along with an overall increase of the emission intensity. For Quantum Posts, switching occurs continuously from predominantely charged excitons (dissimilar number of electrons and holes) to neutral excitons (same number of electrons and holes) and is independent on whether the surface acoustic wave amplitude is increased or decreased. For quantum dots, switching is non-monotonic and shows a pronounced hysteresis on the amplitude sweep direction. Moreover, emission of positively charged and neutral excitons is observed at high surface acoustic wave amplitudes. These findings are explained by carrier trapping and localization in the thin and disordered two-dimensional wetting layer on top of which Quantum Dots nucleate. This limitation can be overcome for Quantum Posts where acoustically induced charge transport is highly efficient in a wide lateral Matrix-Quantum Well.Comment: 11 pages, 5 figure

In situ polymerisation of isoeugenol as a green consolidation method for waterlogged archaeological wood

Waterlogged archaeological wood is often in need of consolidation prior to drying to prevent shrinkage and cracking of the object. There is a need for new greener materials (than for example polyethylene glycol) and methods for consolidation to be developed. The use of wood-based components could provide good interaction between the consolidant and the remaining wood structure and would also support a shift away from fossil fuel-based materials to those with more sustainable sources. Based on this, lignin-like structures have been investigated for their ability to consolidate waterlogged archaeological wood. The in situ formation of a lignin-like material has been carried out using isoeugenol polymerised by horse radish peroxidase in aqueous solution. The formation of the oligomeric/polymeric materials within the wood following this reaction has been determined by Attenuated Total Reflectance Fourier Transform Infra Red (ATR-FTIR) spectroscopy. The oligomers remaining in solution have been characterised by ATR-FTIR and nuclear magnetic resonance (NMR) spectroscopy as well as analytical ultracentrifugation, showing that they have a weight average Mw of 0.4–0.9 kDa and a lignin-like structure rich in the β-5′ moiety. Therefore, this approach is proposed as a basis to further develop a green consolidation method for waterlogged archaeological wood

Wpływ warunków beztlenowych na skład mikroorganizmów zasiedlających współczesne drewno na stanowisku archeologicznym w Biskupinie

From 2003 year a research project was initiated in Biskupin with monitoring of physical, chemical and microbiological parameters of deposed archaeological wood in wet peat soil on sp1 and sp4 sites. In this paper colonization by microorganisms of a temporary oak wood (Quercus sp.) and pine wood (Pinus sylvestris L.) deposed during four years in the similar anoxic conditions in flooded sites were observed. The results of the performed investigations showed on an interesting microbial community as colonizators of wood samples, outside and inside them, including a lignocellulotic bacteria and microscopic fungi, responsible for wood decomposition, and pathogenic, toxinogenic microorganisms, eg: Pseudomonas aeruginosa, Aeromonas hydrophila / caviae, Clostridium perfringens bacteria and Aspergillus fumigatus, Penicillium spp., and Candida spp. fungi.Od wielu lat na stanowiskach archeologicznych obronnego osiedla kultury łużyckiej z VIII w. p.n.e. w Biskupinie prowadzone są badania fizykochemiczne, mikrobiologiczne i konserwatorskie zabytkowego drewna archeologicznego. W celu rozpoznania zagrożeń mikrobiologicznych, na jakie wciąż narażone jest to zabytkowe drewno, badania mikrobiologiczne rozszerzono o współczesne drewno dębu (Quercus sp.) i sosny (Pinus sylvestris L.), przechowywane przez 4 lata w warunkach anoksji w glebie torfowej na stanowiskach sp1 i sp4. Stwierdzono różnorodność glebowych względnie i bezwzględnie beztlenowych kolonizatorów, np. celulolitycznych bakterii i grzybów mikroskopowych, zdolnych do rozkładu drewna, a także patogenów, np. Pseudomonas aeruginosa, Aeromonas hydrophila/caviae, Clostridium perfringens oraz grzybów Aspergillus fumigatus, Penicillium spp. i Candida spp

Possibilities of carbon dioxide industrial utilization- research on CO2 application in synthesis gas production

Konieczność obniżania emisji ditlenku węgla z sektora energetycznego - zgodnie z polityką klimatyczną UE - wymagać będzie w najbliższych latach wskazania metod jego utylizacji lub zagospodarowania. O ile metody wydzielania ditlenku węgla wydają się znane i opanowane (wymagają jednak dostosowania skali przerobu takich instalacji), to metody jego dalszego zagospodarowania otwierają ścieżkę poszukiwań dla wielu ośrodków badawczych. W przypadku krajowych uwarunkowań geologicznych i zagospodarowania terenu, składowanie wydzielonego ditlenku węgla może być problematyczne. Wynika stąd potrzeba zaproponowania konkretnych rozwiązań jego przemysłowego zastosowania. W artykule dokonano przeglądu możliwych zastosowań ditlenku węgla (przemysł chemiczny, spożywczy). Dokonano charakterystyki katalizatora zol-żel, stosowanego w badaniach reformingu metanu ditlenkiem węgla. Prezentacja wyników badań suchego reformingu gazu ziemnego ditlenkiem węgla obejmuje wyniki uzyskane dla dwóch katalizatorów niklowych: przemysłowego (INS Puławy - katalizator G-0117-7H) i otrzymanego metodą zol-żel. Określono współczynniki konwersji, uzyskane w procesie suchego reformingu w reaktorze przepływowym dla różnych stosunków substratów na wejściu CO2/CH4. Omówiono podstawowe problemy procesowe, związane z zastosowaniem ditlenku węgla w procesie reformingu metanu - tworzenie depozytów węglowych.The European Union has steadily strengthened and multiplied its actions to achieving maximum CO2 emission reduction from the energy sector. A wide range of separation and capture of CO2 from gas streams technologies currently exist. Carbon capture and storage is one of the potential method of controlling greenhouse gas emissions, but to solve the CO2 emission problem we need to develop new industrial CO2 recycle method. So, this paper focused on possibilities of CO2 industrial utilization. Recently, carbon dioxide reforming of methane becomes more attractive way to utilize carbon dioxide. It has been demonstrated that carbon dioxide reforming of methane produces synthesis gas (H2/CO =1), which is useful for the synthesis of acetic acid, dimethyl ether, hydrocarbons and oxo-alcohols. Carbon deposition over catalysts surface is the main problem for carbon dioxide reforming with methane. Therefore, the better activity and stability of catalysts are necessary to be improved. In this work, the carbon dioxide reforming of methane on commercial (INS Puławy G-0117-7H) and new sol-gel Ni-based catalyst was investigated. The carbon dioxide reforming of methane operated under molar ratio of CH4:CO2 = 1:1; 1:2; 2;1 at two different temperatures, 600 and 700?C. Results of the carbon dioxide reforming of methane showed activity with promising low carbonaceous deposition. The methane conversion increased with temperature growth, the molar ratio of obtained synthesis H2/CO was about 1 for CH4:CO2 = 1:1

Hydrostatic-Pressure Deep Level Transient Spectroscopy Study of the Heteroantisite Antimony Level in GaAs

We present some preliminary results of the first hydrostatic-pressure study of the electronic level related to the Sb-heteroantisite defect in GaAs. We studied two kinds of n-type GaAs samples doped with antimony: bulk samples grown by liquid encapsulated Czochralski method and thin layers grown by metalorganic chemical vapour deposition technique. We found strongly nonlinear pressure dependence of the activation energy of the emission rate for the level. Moreover, the results obtained for the bulk material were fairly different from those obtained for thin metalorganic chemical vapour deposition layers. The possible explanation of this difference is presented