832 research outputs found

    Quantum theory and chemistry: Two propositions

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    Two propositions concerning quantum chemistry are proposed. First, it is proposed that the nonrelativistic Schroedinger equation, where the Hamiltonian operator is associated with an assemblage of nuclei and electrons, can never be arranged to yield specific molecules in the chemists' sense. It is argued that this result is a necessary condition if the Schroedinger has relevancy to chemistry. Second, once a system is in a particular state with regard to interactions among its components (the assemblage of nuclei and electrons), it cannot spontaneously eliminate any of those interactions. This leads to a subtle form of irreversibility

    Modified Iterative Extended Hueckel. 1: Theory

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    Iterative Extended Huekel is modified by inclusion of explicit effective internuclear and electronic interactions. The one electron energies are shown to obey a variational principle because of the form of the effective electronic interactions. The modifications permit mimicking of aspects of valence bond theory with the additional feature that the energies associated with valence bond type structures are explicitly calculated. In turn, a hybrid molecular, orbital valence, bond scheme is introduced which incorporates variant total molecular electronic density distributions similar to the way that Iterative Extended Hueckel incorporates atoms

    Modified Iterative Extended Hueckel. 2: Application to the interaction of Na(+), Na(+)(aq.), Mg(+)-2(aq.) with adenine and thymine

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    Modified Iterative Extended Hueckel, which includes explicit effective internuclear and electronic interactions, is applied to the study of the energetics of Na(+),Mg(+), Na(+) (aqueous), and Mg(+2) (aqueous) ions approaching various possible binding sites on adenine and thymine. Results for the adenine + ion and thymine + ion are in good qualitative agreement with ab initio work on analogous systems. Energy differences between competing sites are in excellent agreement. Hydration appears to be a critical factor in determining favorable binding sites. That the adenine Nl and N3 sites cannot displace a water molecule from the hydrated cation indicates that they are not favorable binding sites in aqueous media. Of those sites investigated, 04 was the most favorable binding site on the thymine for the bare Na(+). However, the 02 site was the most favorable binding site for either hydrated cation

    Organic chemistry on Titan

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    Observations of nonequilibrium phenomena on the Saturn satellite Titan indicate the occurrence of organic chemical evolution. Greenhouse and thermal inversion models of Titan's atmosphere provide environmental constraints within which various pathways for organic chemical synthesis are assessed. Experimental results and theoretical modeling studies suggest that the organic chemistry of the satellite may be dominated by two atmospheric processes: energetic-particle bombardment and photochemistry. Reactions initiated in various levels of the atmosphere by cosmic ray, Saturn wind, and solar wind particle bombardment of a CH4 - N2 atmospheric mixture can account for the C2-hydrocarbons, the UV-visible-absorbing stratospheric haze, and the reddish color of the satellite. Photochemical reactions of CH4 can also account for the presence of C2-hydrocarbons. In the lower Titan atmosphere, photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. Hot H-atom reactions initiated by photo-dissociation of NH3 can couple the chemical reactions of NH3 and CH4 and produce organic matter

    Differentiation of optical isomers through enhanced weak-field interactions

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    The influence of weak field interaction terms due to the cooperative effects which arise from a macroscopic assemblage of interacting sites is studied. Differential adsorption of optical isomers onto an achiral surface is predicted to occur if the surface was continuous and sufficiently large. However, the quantity of discontinuous crystal surfaces did not enhance the percentage of differentiation and thus the procedure of using large quantities of small particles was not a viable technique for obtaining a detectable differentiation of optical isomers on an achiral surface

    Sport and austerity in the UK: an insight into Liverpool 2014

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    The UK’s Comprehensive Spending Review (CSR) in 2010, outlined £81 billion of cuts across government departments by 2014/15. The Conservative-Liberal Democrat reform was premised on the ‘Big Society’ making up for their austere cuts to the state. In this piece, we debate the impact of this on sports development, taking the case study of inner city Liverpool. This example is marked because, on the one hand, it presents cuts to municipal sports facilities which are threatened with closure as a result of shrinking local authority budgets, and on the other this role is partially taken on by an offshoot of Everton Football Club (EFC). The points we debate are: 1) is the change in responsibility from the local authority to a private enterprise, staffed by volunteers, a new turn in sport policy?; and 2) what are the consequences of this on grassroots sport participation

    Investigation of Lunar Surface Chemical Contamination by LEM Descent Engine and Associated Equipment

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    Lunar surface and atmospheric contamination study caused by LEM rocket exhaust and inorganic, organic, and microbiological contaminant

    Principles of Radiation Oncology

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    This chapter in Cancer Concepts: a Guidebook for the Non-Oncologist describes the principles of Radiation Oncology. Radiation Oncology utilizes ionizing radiation to treat cancer (and occasionally a few benign conditions). Radiotherapy or radiation therapy (RT) was initially developed in conjunction with diagnostic radiology, but has evolved into a separate specialty. Currently, more than fifty percent of cancer patients undergo RT at some point during the course of their cancer. Most receive treatment with curative intent (radical therapy); however, patients with incurable disease receive shorter, gentler courses of therapy to relieve cancer-induced symptoms.https://escholarship.umassmed.edu/cancer_concepts/1008/thumbnail.jp

    The poverty of journal publishing

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    The article opens with a critical analysis of the dominant business model of for-profit, academic publishing, arguing that the extraordinarily high profits of the big publishers are dependent upon a double appropriation that exploits both academic labour and universities’ financial resources. Against this model, we outline four possible responses: the further development of open access repositories, a fair trade model of publishing regulation, a renaissance of the university presses, and, finally, a move away from private, for-profit publishing companies toward autonomous journal publishing by editorial boards and academic associations. </jats:p
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