118 research outputs found

    A Central Partition of Molecular Conformational Space.III. Combinatorial Determination of the Volume Spanned by a Molecular System

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    In the first work of this series [physics/0204035] it was shown that the conformational space of a molecule could be described to a fair degree of accuracy by means of a central hyperplane arrangement. The hyperplanes divide the espace into a hierarchical set of cells that can be encoded by the face lattice poset of the arrangement. The model however, lacked explicit rotational symmetry which made impossible to distinguish rotated structures in conformational space. This problem was solved in a second work [physics/0404052] by sorting the elementary 3D components of the molecular system into a set of morphological classes that can be properly oriented in a standard 3D reference frame. This also made possible to find a solution to the problem that is being adressed in the present work: for a molecular system immersed in a heat bath we want to enumerate the subset of cells in conformational space that are visited by the molecule in its thermal wandering. If each visited cell is a vertex on a graph with edges to the adjacent cells, here it is explained how such graph can be built

    Catalytic Asymmetric Synthesis of Bicycloprolines by a 1,3-Dipolar Cycloaddition/Intramolecular Alkylation Strategy

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    This document is the Accepted Manuscript version of a Published Work that appeared in final form inJournal of Organic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.joc.6b01100 to Published Work, see http://pubs.acs.org/page/policy/articlesonrequest/index.htmlThe diastereoselective one-pot synthesis of hexahydrocyclopenta [b] pyrrole derivatives (bicycloprolines) has been achieved by base-mediated reactions of (E)-tert-butyl 6-bromo-2-hexenoate with α-imino esters. The catalytic asymmetric version of this process has been eïŹƒciently achieved using the CuI/(R)-DTBM-Segphos complex as a catalyst following a two-step 1,3-dipolar cycloaddition/intramolecular alkylation sequence.Financial support of this work by the Ministerio de EconomĂ­a y Competitividad and Fondo Europeo de Desarrollo Regional (MINECO CTQ2012-35790 and MINECO/FEDER CTQ2015-66954-P) are gratefully acknowledged. M.G.-E. and A.P.-E. thank the MICINN for predoctoral fellowship

    Development of lens opacities with peculiar characteristics in patients affected by thalassemia major on chelating treatment with deferasirox (ICL670) at the Pediatric Clinic in Monza, Italy.

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    About the 11–14% of patients with thalassemia major (TM) treated with deferasirox (DFO) develops retinopathy and/or lens opacities with an unclear pathogenesis but with a clear age related pattern.[1][1],[2][2] Possible causes can be either iron overload itself or DFO toxicity, with variou

    Prognostic relevance and putative histogenetic role of cytokeratin 7 and MUC5AC expression in Crohn\u2019s disease-associated small bowel carcinoma

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    Most Crohn\u2019s disease-associated small bowel carcinomas (CrD-SBCs) are diagnosed in advanced stage and have poor prognosis. To improve diagnosis and therapy, a better knowledge of tumour precancerous lesions, histotypes and prognostic factors is needed. We investigated histologically and immunohistochemically 52 CrD-SBCs and 51 small bowel carcinomas unrelated to inflammatory disease, together with their tumour-associated mucosa, looking for Crohn-selective changes. Histologic patterns and phenotypic markers potentially predictive of CrD-SBC histogenesis and prognosis were analysed. Cytokeratin 7 or MUC5AC-positive metaplastic changes were found in about half of investigated CrD-SBCs, significantly more frequently than in CrD-unrelated SBCs. They correlated with metaplastic changes of their associated mucosa, while being absent in normal ileal mucosa. Histologic patterns suggestive for progression of some cytokeratin 7 and/or MUC5AC-positive metaplastic lesions into cancer of the same phenotype were also observed. Patient survival analyses showed that tumour cytokeratin 7 or MUC5AC expression and non-cohesive histotype were adverse prognostic factors at univariable analysis, while cytokeratin 7 and non-cohesive histotype were also found to predict worse survival in stage- and age-inclusive multivariable analyses. Besides conventional dysplasia, hyperplasia-like non-conventional lesions were observed in CrD-SBC-associated mucosa, with patterns suggestive for a histogenetic link with adjacent cancer. In conclusion the cytokeratin 7 and/or MUC5AC-positive metaplastic foci and the non-conventional growths may have a role in cancer histogenesis, while tumour cytokeratin 7 and non-cohesive histotype may also predict poor patient survival. Present findings are worth being considered in future prospective histogenetic and clinical studies

    Nature and frequency of respiratory involvement in chronic progressive external ophthalmoplegia

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    Chronic progressive external ophthalmoplegia (CPEO) is a relatively common mitochondrial disorder. Weakness of the extra-ocular, limb girdle and laryngeal muscles are established clinical features. Respiratory muscle involvement however has never been studied systematically, even though respiratory complications are one of the main causes of death. We therefore determined the prevalence and nature of respiratory muscle involvement in 23 patients with genetically confirmed CPEO. The main finding was decreased respiratory muscle strength, both expiratory (76.8% of predicted, p = 0.002) and inspiratory (79.5% of predicted, p = 0.004). Although the inspiratory vital capacity (92.5% of predicted, p = 0.021) and the forced expiratory volume in 1 s (89.3% of predicted, p = 0.002) were below predicted values, both were still within the normal range in the majority of patients. Expiratory weakness was associated with a decreased vital capacity (ρ = 0.502, p = 0.015) and decreased peak expiratory flow (ρ = 0.422, p = 0.045). Moreover, expiratory muscle strength was lower in patients with limb girdle weakness (62.6 ± 26.1% of predicted vs. 98.9 ± 22.5% in patients with normal limb girdle strength, p = 0.003), but was not associated with other clinical features, subjective respiratory complaints, disease severity or disease duration. Since respiratory involvement in CPEO is associated with severe morbidity and mortality, the present data justify periodic assessment of respiratory functions in all CPEO patients

    The acid crater lake of Taal Volcano, Philippines: hydrogeochemical and hydroacoustic data related to the 2010–11 volcanic unrest

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    Studies of the water chemistry of Taal crater lake and echo-sounding surveys have provided new insights into its chemical and physical dynamics. During the volcano-seismic unrest of April 2010–June 2011, the waters of Taal crater lake showed changes in chemical composition and increases in CO2 emissions associated with the seismic unrest. The chemical and isotopic data show that the lake water has contributions from both seawater and meteoric water and receives injections of deep hydrothermal water and gases during periods of intense volcano-seismic unrest. These inflationary periods may lead to faulting of the impermeable cap rock that usually seals the deeper Taal hydrothermal reservoir in response to degassing and convective movements in the underlying Taal magma chamber.Instituto VolcanolĂłgico de Canarias, EspañaEnvironmental Research Division, Instituto TecnolĂłgico y de EnergĂ­as Renovables, EspañaAgencia Insular de EnergĂ­a de Tenerife, EspañaÁrea de GeologĂ­a Marina, Instituto GeolĂłgico y Minero de España, EspañaInstitute of Agriculture and Environment, Massey University, AustraliaPhilippine Institute of Volcanology and Seismology, FilipinasGeochemical Research Center, The University of Tokyo, JapĂłnEarth & Environmental Sciences, Wesleyan University, Estados UnidosPeer reviewe

    Towards sustainable agriculture: fossil-free ammonia

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    Citation: Pfromm, P. H. (2017). Towards sustainable agriculture: Fossil-free ammonia. Journal of Renewable and Sustainable Energy, 9(3), 034702. https://doi.org/10.1063/1.4985090About 40% of our food would not exist without synthetic ammonia (NH3) for fertilization. Yet, NH3 production is energy intensive. About 2% of the world's commercial energy is consumed as fossil fuels for NH3 synthesis based on the century-old Haber-Bosch (H.-B.) process. The state of the art and the opportunities for reducing the fossil energy footprint of industrial H.-B. NH3 synthesis are discussed. It is shown that even a hypothetical utterly revolutionary H.-B. catalyst could not significantly reduce the energy demand of H.-B. NH3 as this is governed by hydrogen production. Renewable energy-enabled, fossil-free NH3 synthesis is then evaluated based on the exceptional and continuing cost decline of renewable electricity. H.-B. syngas (H2, N2) is assumed to be produced by electrolysis and cryogenic air separation, and then supplied to an existing H.-B. synthesis loop. Fossil-free NH3 could be produced for energy costs of about $232 per tonne NH3 without claiming any economic benefits for the avoidance of about 1.5 tonnes of CO2 released per tonne NH3 compared to the most efficient H.-B. implementations. Research into alternatives to the H.-B. process might be best targeted at emerging markets with currently little NH3 synthesis capacity but significant future population growth such as Africa. Reduced capital intensity, good scale-down economics, tolerance for process upsets and contamination, and intermittent operability are some desirable characteristics of NH3 synthesis in less developed markets, and for stranded resources. Processes that are fundamentally different from H.-B. may come to the fore under these specific boundary conditions
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