465 research outputs found

    Societal implications of nanoscience and nanotechnology in developing countries

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    The historically unprecedented developments of nanoscience and nanotechnology, in view of their phenomenal expansion and growth, in conjunction with their convergence with information science and molecular biology, confront our society and natural environment with new challenges. Technological revolutions have shown that discoveries at the frontiers of science have the potential to pave the way for radically innovative and integrated approaches, providing new solutions for some of the most pressing problems. In order to enable decision-makers to respond to what is best for people at large, the societal implications of the newly emerging fields need to be known and understood. Nanotechnology, unlike any other technology, can find applications in virtually all areas of human life. In spite of being an infant at its evolution, some of the known issues related to nanotechnology suggest a wide spectrum of potential societal impacts. The current public nano-discourse provides sociology with a unique opportunity to switch from a merely passive, observational role to an active participating one, especially where the key players involved meet to find joint and concerted solutions for development

    K0 form factor at order p^6 of chiral perturbation theory

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    This paper describes the calculation of the electromagnetic form factor of the K0 meson at order p^6 of chiral perturbation theory which is the next-to-leading order correction to the well-known p^4 result achieved by Gasser and Leutwyler. On the one hand, at order p^6 the chiral expansion contains 1- and 2-loop diagrams which are discussed in detail. Especially, a numerical procedure for calculating the irreducible 2-loop graphs of the sunset topology is presented. On the other hand, the chiral Lagrangian L^6 produces a direct coupling of the K0 current with the electromagnetic field tensor. Due to this coupling one of the unknown parameters of L^6 occurs in the contribution to the K0 charge radius.Comment: 22 pages Latex with 8 figures, Typos corrected, one reference adde

    Dynamic origin of chirality transfer between chiral surface and achiral ligand in Au38 clusters

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    The transfer of chirality between nanomolecules is at the core of several applications in chiral technology such as sensing and catalysis. However, the origin of this phenomenon and how exactly nanoscale objects transfer chirality to molecules in their vicinity remain largely obscure. Here, we show that the transfer of chirality for the intrinsically chiral gold cluster Au38(SR)24 is site dependent; that is, it differs depending on the ligand-binding sites. This is closely related to the dynamic nature of the ligands on the cluster surface. Using a combination of NMR techniques and molecular dynamics simulations, we could assign the four symmetry- unique ligands on the cluster. The study reveals largely different conformational dynamics of the bound ligands, explaining the diverse diastereotopicities observed for the CH2 protons of the ligands. Although chirality is a structural property, our study reveals the importance of dynamics for the transfer of chirality

    Discriminability of tryptophan containing dipeptides using quantum control

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    We show that the coherent manipulation of molecular wavepackets in the excited states of trp-containing dipeptides allows efficient discrimination among them. Optimal dynamic discrimination fails, however, for some dipeptide couples. When considering the limited spectral resources at play (3nm bandwidth at 266nm), we discuss the concept of discriminability, which appears uncorrelated to both static spectra and relaxation lifetime

    Chiral Perturbation Theory Beyond One Loop

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    The existing Chiral Perturbation Theory (ChPT) calculations at order p6p^6 are reviewed. The principles of ChPT and how they are used are introduced. The main part is a review of the two- and three-flavour full two-loop calculations and their comparison with experiment. We restrict the discussion to the mesonic purely strong and semileptonic sector. The review concludes by mentioning the existing results in finite volume, finite temperature and partially quenched ChPT.Comment: 66 pages, review article, some references added plus a few discussions extende

    Modelling and simulating change in reforesting mountain landscapes using a social-ecological framework

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    Natural reforestation of European mountain landscapes raises major environmental and societal issues. With local stakeholders in the Pyrenees National Park area (France), we studied agricultural landscape colonisation by ash (Fraxinus excelsior) to enlighten its impacts on biodiversity and other landscape functions of importance for the valley socio-economics. The study comprised an integrated assessment of land-use and land-cover change (LUCC) since the 1950s, and a scenario analysis of alternative future policy. We combined knowledge and methods from landscape ecology, land change and agricultural sciences, and a set of coordinated field studies to capture interactions and feedback in the local landscape/land-use system. Our results elicited the hierarchically-nested relationships between social and ecological processes. Agricultural change played a preeminent role in the spatial and temporal patterns of LUCC. Landscape colonisation by ash at the parcel level of organisation was merely controlled by grassland management, and in fact depended on the farmer's land management at the whole-farm level. LUCC patterns at the landscape level depended to a great extent on interactions between farm household behaviours and the spatial arrangement of landholdings within the landscape mosaic. Our results stressed the need to represent the local SES function at a fine scale to adequately capture scenarios of change in landscape functions. These findings orientated our modelling choices in the building an agent-based model for LUCC simulation (SMASH - Spatialized Multi-Agent System of landscape colonization by ASH). We discuss our method and results with reference to topical issues in interdisciplinary research into the sustainability of multifunctional landscapes

    One-Dimensional Energy Dispersion of Single-Walled Carbon Nanotubes by Resonant Electron Scattering

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    We characterized the energy band dispersion near the Fermi level in single-walled carbon nanotubes using low-temperature scanning tunneling microscopy. Analysis of energy dependent standing wave oscillations, which result from quantum interference of electrons resonantly scattered by defects, yield a linear energy dispersion near EF, and indicate the importance of parity in scattering for armchair single-walled carbon nanotubes. Additionally, these data provide values of the tight-binding overlap integral and Fermi wavevector in good agreement with previous work, but indicate that the electron coherence length is substantially shortened.Comment: 5 pages, 3 figure

    Randomised controlled trial to evaluate the effect of foot trimming before and after first calving on subsequent lameness episodes and productivity in dairy heifers

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    The objective of this study was to assess both independent and combined effects of routine foot trimming of heifers at 3 weeks pre-calving and 100 days post calving on the first lactation lameness and lactation productivity. A total of 419 pre-calving dairy heifers were recruited from one heifer rearing operation over a 10-month period. Heifers were randomly allocated into one of four foot trimming regimens; pre-calving foot trim and post-calving lameness score (Group TL), pre-calving lameness score and post-calving foot trim (Group LT), pre-calving foot trim and post-calving foot trim (Group TT), and pre-calving lameness score and post-calving lameness score (Group LL, control group). All heifers were scored for lameness at 24 biweekly time points for 1 year following calving, and first lactation milk production data were collected. Following calving, 172/419 (41.1%) of heifers became lame during the study (period prevalence), with lameness prevalence at each time-point following calving ranging from 48/392 (12.2%) at 29–42 days post-calving to 4/379 (1.1%) between 295 and 383 days after calving. The effects of the four treatment groups were not significantly different from each other for overall lameness period prevalence, biweekly lameness point prevalence, time to first lameness event, type of foot lesion identified at dry off claw trimming, or the 4% fat corrected 305-day milk yield. However, increased odds lameness was significantly associated with a pre-calving trim alone (P = 0.044) compared to the reference group LL. The odds of heifer lameness were highest between 0 and 6 weeks post-partum, and heifer farm destination was significantly associated with lameness (OR 2.24), suggesting that even at high standard facilities, environment and management systems have more effect on heifer foot health than trimming

    Consensus guideline for the diagnosis and treatment of tetrahydrobiopterin (BH4) deficiencies

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    Background: Tetrahydrobiopterin (BH4) deficiencies comprise a group of six rare neurometabolic disorders characterized by insufficient synthesis of the monoamine neurotransmitters dopamine and serotonin due to a disturbance of BH4 biosynthesis or recycling. Hyperphenylalaninemia (HPA) is the first diagnostic hallmark for most BH4 deficiencies, apart from autosomal dominant guanosine triphosphate cyclohydrolase I deficiency and sepiapterin reductase deficiency. Early supplementation of neurotransmitter precursors and where appropriate, treatment of HPA results in significant improvement of motor and cognitive function. Management approaches differ across the world and therefore these guidelines have been developed aiming to harmonize and optimize patient care. Representatives of the International Working Group on Neurotransmitter related Disorders (iNTD) developed the guidelines according to the SIGN (Scottish Intercollegiate Guidelines Network) methodology by evaluating all available evidence for the diagnosis and treatment of BH4 deficiencies. Conclusion: Although the total body of evidence in the literature was mainly rated as low or very low, these consensus guidelines will help to harmonize clinical practice and to standardize and improve care for BH4 deficient patients
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