Stabilities of nanohydrated thymine radical cations: insights from multiphoton ionization experiments and ab initio calculations

Multi-photon ionization experiments have been carried out on thymine-water clusters in the gas phase. Metastable H2O loss from T+(H2O)n was observed at n ≥ 3 only. Ab initio quantum-chemical calculations of a large range of optimized T+(H2O)n conformers have been performed up to n = 4, enabling binding energies of water to be derived. These decrease smoothly with n, consistent with the general trend of increasing metastable H2O loss in the experimental data. The lowest-energy conformers of T+(H2O)3 and T+(H2O)4 feature intermolecular bonding via charge-dipole interactions, in contrast with the purely hydrogen-bonded neutrals. We found no evidence for a closed hydration shell at n = 4, also contrasting with studies of neutral clusters

Beam test results of 3D pixel detectors constructed with poly-crystalline CVD diamond

As a possible candidate for extremely radiation tolerant tracking devices we present a novel detector design - namely 3D detectors - based on poly-crystalline CVD diamond sensors with a pixel readout. The fabrication of recent 3D detectors as well their results in recent beam tests are presented. We measured the hit efficiency and signal response of two 3D diamond detectors with 50 × 50 μm cell sizes using pixel readout chip technologies currently used at CMS and ATLAS. In all runs, both devices attained efficiencies >98 % in a normal incident test beam of minimum ionising particles. The highest efficiency observed during the beam tests was 99.2 %

Antinomias pós-modernas sobre a natureza Postmodern antinomies on nature

Analisa o vínculo intrínseco entre a elaboração moderna de ciência e a noção de natureza a ela subjacente. Discute as características das posições pós-modernas e inventaria as ideias recorrentes de natureza nas diferentes épocas históricas. Problematiza indicadores de incongruências nas imagens pós-modernas da natureza. Por meio da análise e história conceitual, explicita pontos de tensão nas proposições teóricas pós-modernas em relação às diferentes noções de natureza. Sugere que a equivocidade da noção de natureza produz múltiplos paradoxos e antinomias no pensamento contemporâneo, muitos dos quais tiveram emergência no âmbito da própria modernidade e tornaram-se ainda mais explícitos e intensos na conjuntura tecnocientífica do mundo atual.<br>This article analyzes the intrinsic link between the modern view of science and its underlying idea of nature. After discussing the characteristics of the postmodern positions and summarizing the various conceptions of nature prevalent at different times throughout history, we problematize indicators of incongruity in postmodern images of nature. Our objective, through analysis and conceptual history, is to delineate the points of tensions concerning different notions of nature within postmodern theories. We then suggest that the equivocality of the concept of nature produces multiple paradoxes and antinomies in contemporary thought, many of which emerged within the scope of modernity itself, becoming even more explicit and intense in the current technical and scientific climate

Beam test results of 3D pixel detectors constructed with poly-crystalline CVD diamond

ISSN:1824-803