Atomic nanolithography patterning of submicron features: writing an organic self-assembled monolayer with cold bright Cs atom beams

Cs atom beams, transversely collimated and cooled, passing through material masks in the form of arrays of reactive-ion-etched hollow Si pyramidal tips and optical masks formed by intense standing light waves, write submicron features on self-assembled monolayers (SAMs). Features with widths as narrow as 43 ± 6 nm and spatial resolution limited only by the grain boundaries of the substrate have been realized in SAMs of alkanethiols. The material masks write two-dimensional arrays of submicron holes; the optical masks result in parallel lines spaced by half the optical wavelength. Both types of feature are written to the substrate by exposure of the masked SAM to the Cs flux and a subsequent wet chemical etch. For the arrays of pyramidal tips, acting as passive shadow masks, the resolution and size of the resultant feature depends on the distance of the mask array from the SAM, an effect caused by the residual divergence of the Cs atom beam. The standing wave optical mask acts as an array of microlenses focusing the atom flux onto the substrate. Atom 'pencils' writing on SAMs have the potential to create arbitrary submicron figures in massively parallel arrays. The smallest features and highest resolutions were realized with SAMs grown on smooth, sputtered gold substrates.

Acumulo e eliminacao de Cs-137 pela alga gracilaria caudata e peixe abudefduf saxatilis .Modelo compartimental

Dissertacao (Mestrado)

3D-grafiikan selaintekniikat, erikoistapauksena karttasovellukset

Harava on karttapohjainen kyselypalvelu, jonka avulla voidaan kerätä tietoa erilaisista kyselykohteista. Harava-kyselypalvelussa kyselyihin voidaan vastata muun muassa tekstikentillä, monivalinnoilla ja merkitsemällä alueita ja pisteitä karttapohjaan. Tutkielman tavoitteena oli löytää Harava-kyselypalvelun 2D-karttojen rinnalle 3D-karttavaihtoehto. Aluksi tutkittiin, mitä eri vaihtoehtoja löytyy 3D-komponenttien esittämiseen selaimessa. Tutkituista vaihtoehdoista parhaimmaksi tähän tarkoitukseen osoittautui WebGL-kirjasto. WebGL-kirjaston käyttö suoraan osoittautui vaikeaksi, joten etsittiin rajapintaa, jonka avulla WebGL-kirjaston käyttö helpottuisi. Käsittelyyn otettiin karttapalveluita sekä 3D-mallien esittämiseen tarkoitettuja JavaScript-kirjastoja, jotka käyttävät WebGL-kirjastoa rajapinnan kautta. Näistä sopivimmaksi osoittautui Cesium. Cesium on JavaScript-kirjasto, jonka avulla voidaan toteuttaa 2D-kartta ja 3D-karttapallo sekä upottaa karttapohjaan 3D-elementtejä.

Resonant five-body recombination in an ultracold gas of bosonic atoms

We combine theory and experiment to investigate five-body recombination in an ultracold gas of atomic cesium at negative scattering length. A refined theoretical model, in combination with extensive laboratory tunability of the interatomic interactions, enables the five-body resonant recombination rate to be calculated and measured. The position of the new observed recombination feature agrees with a recent theoretical prediction and supports the prediction of a family of universal cluster states at negative a that are tied to an Efimov trimer.

Fukushima-derived radionuclides in sediments of the Japanese Pacific Ocean coast and various Japanese water samples (seawater, tap water, and coolant water of Fukushima Daiichi reactor unit 5)

We investigated Ocean sediments and seawater from inside the Fukushima exclusion zone and found radiocesium (134Cs and 137Cs) up to 800 Bq kg-1 as well as 90Sr up to 5.6 Bq kg-1. This is one of the first reports on radiostrontium in sea sediments from the Fukushima exclusion zone. Seawater exhibited contamination levels up to 5.3 Bq kg-1 radiocesium. Tap water from Tokyo from weeks after the accident exhibited detectable but harmless activities of radiocesium (well below the regulatory limit). Analysis of the Unit 5 reactor coolant (finding only 3H and even low 129I) leads to the conclusion that the purification techniques for reactor coolant employed at Fukushima Daiichi are very effective.

Effective and ecological half-lives of 90Sr and 137Cs observed in wheat and rice in Japan

Published pre-Fukushima food monitoring data from 1963 to 1995 were used to study the long-term presence of 137Cs and 90Sr in rice and wheat. Effective half-lives (T eff) were calculated for rice (137Cs: 5.6 years; 90Sr: 6.7 years) and wheat (137Cs: 3.5 years; 90Sr: 6.2 years), respectively. In rice, 137Cs exhibits a longer T eff because putrefaction processes will lead to the formation of NH4 + ions that are efficient ion exchangers for mineral-adsorbed cesium ions, hence making it more readily available to the plant. Knowledge on the long-term behavior of radiocesium and radiostrontium will be important for Japanese food-safety campaigns after the Fukushima nuclear accident.

Desenvolvimento de fontes radioativas seladas imobilizadas em resina epóxi para verificação de detectores utilizados em medicina nuclear

Dissertação (Mestrado em Tecnologia Nuclear)