Thin film contamination effects on laser-induced damage of fused silica surfaces at 355 nm

Fused silica windows were artificially contaminated to estimate the resistance of target chamber debris shields against laser damage during NIF operation. Uniform contamination thin films (1 to 5 nm thick) were prepared by sputtering various materials (Au, Al, Cu, and B4C). The loss of transmission of the samples was first measured. They were then tested at 355 nm in air with an 8-ns Nd:YAG laser. The damage morphologies were characterized by Nomarski optical microscopy and SEM. Both theory and experiments showed that metal contamination for films as thin as 1 nm leads to a substantial loss of transmission. The laser damage resistance dropped very uniformly across the entire surface (e.g. 6 J/cm2 for 5 nm of Cu). The damage morphology characterization showed that contrary to clean silica, metal coated samples did not produce pits on the surface. B4C coated silica, on the other hand, led to a higher density of such damage pits. A model for light absorption in the thin film was coupled with a simple heat deposition and diffusion model to perform preliminary theoretical estimates of damage thresholds. The estimates of the loss due to light absorption and reflection pointed out significant .differences between metals (e.g. Al and Au). The damage threshold predictions were in qualitative agreement with experimental measurements

Potencial de aquecimento global de sistemas forrageiros.

A pecuária catarinense apresenta produção animal com base em distintos sistemas forrageiros, mas pouco é sabido sobre o potencial de aquecimento global (PAG) desses sistemas. O objetivo do estudo foi avaliar o PAG de quatro sistemas forrageiros: PN- Pastagem Natural; PMPastagem Natural Melhorada; PP- Pastagem Perene; e PA- Pastagem Anual. O estudo foi conduzido durante 5 anos na EPAGRI, Lages, SC, Brasil. O PAG parcial (PAGp) das pastagens foi calculado considerando a emissão anual de óxido nitroso (N2O) e metano (CH4) do solo e a taxa de sequestro de carbono anual relativa (TSR). A intensidade de emissão de gases de efeito estufa (IEGEE) foi calculada considerando o PAGp e a produção de matéria seca (MS) das pastagens. A emissão de N2O variou de 0,08 a 2,96 Mg CO2eq. ha-1 ano-1 para PN e PA, respectivamente. A PP apresentou o menor influxo de CH4 no solo (-0,018 Mg CO2eq. ha-1 ano- 1), diferindo de PM e PN. A TSR foi negativa para PN, PM e PP indicando potencial mitigador em relação a PA. A produção de MS variou de 6,62 a 13,04 Mg ha-1 para PN e PP, respectivamente. Apesar das diferenças na produtividade, a IEGEE não diferiu entre as pastagens. Os sistemas forrageiros não diferiram quanto ao PAGp, independentemente do manejo do solo e do pasto. Sequestro de Carbono, Manejo de Pastagens, Gases do Efeito Estuf

Emisión acumulada de óxido nitroso (N20) en sistemas pastoriles de la Sierra Catarinense - Brasil.

En este trabajo se evaluaron y compararon la emisión de N2O generados por los sistemas pastoriles más empleados en Santa Catarina, Brasil.Suplemento 1. Edição do 43º Congreso Argentino de Producción Animal

Invited review: Large-scale indirect measurements for enteric methane emissions in dairy cattle: A review of proxies and their potential for use in management and breeding decisions

Publication history: Accepted - 7 December 2016; Published online - 1 February 2017.Efforts to reduce the carbon footprint of milk production through selection and management of low-emitting cows require accurate and large-scale measurements of methane (CH4) emissions from individual cows. Several techniques have been developed to measure CH4 in a research setting but most are not suitable for large-scale recording on farm. Several groups have explored proxies (i.e., indicators or indirect traits) for CH4; ideally these should be accurate, inexpensive, and amenable to being recorded individually on a large scale. This review (1) systematically describes the biological basis of current potential CH4 proxies for dairy cattle; (2) assesses the accuracy and predictive power of single proxies and determines the added value of combining proxies; (3) provides a critical evaluation of the relative merit of the main proxies in terms of their simplicity, cost, accuracy, invasiveness, and throughput; and (4) discusses their suitability as selection traits. The proxies range from simple and low-cost measurements such as body weight and high-throughput milk mid-infrared spectroscopy (MIR) to more challenging measures such as rumen morphology, rumen metabolites, or microbiome profiling. Proxies based on rumen samples are generally poor to moderately accurate predictors of CH4, and are costly and difficult to measure routinely onfarm. Proxies related to body weight or milk yield and composition, on the other hand, are relatively simple, inexpensive, and high throughput, and are easier to implement in practice. In particular, milk MIR, along with covariates such as lactation stage, are a promising option for prediction of CH4 emission in dairy cows. No single proxy was found to accurately predict CH4, and combinations of 2 or more proxies are likely to be a better solution. Combining proxies can increase the accuracy of predictions by 15 to 35%, mainly because different proxies describe independent sources of variation in CH4 and one proxy can correct for shortcomings in the other(s). The most important applications of CH4 proxies are in dairy cattle management and breeding for lower environmental impact. When breeding for traits of lower environmental impact, single or multiple proxies can be used as indirect criteria for the breeding objective, but care should be taken to avoid unfavorable correlated responses. Finally, although combinations of proxies appear to provide the most accurate estimates of CH4, the greatest limitation today is the lack of robustness in their general applicability. Future efforts should therefore be directed toward developing combinations of proxies that are robust and applicable across diverse production systems and environments.Technical and financial support from the COST Action FA1302 of the European Union

Résultats de l'expérience à 4 faisceaux en irradiation sphérique à Limeil

Results obtained on the IRIS implosion experiment are presented. They were obtained using our four beam Nd glass laser system C6, with a nanosecond pulse, with a flux lower than 1014 W/cm2. Firstly, the results are given of a systematic study of absorption efficiency as a function of laser beam focusing conditions onto the target. Secondly, a spatio-temporal study of microballoon implosion with a nanosecond pulse at a moderate flux ( < 1013 W/cm2) is presented.Nous rendons compte de résultats obtenus sur l'expérience d'implosion IRIS réalisée à Limeil au moyen des quatre faisceaux émis par le système laser à verre dopé au NdC6 en impulsion nanoseconde et dans une gamme de flux inférieure à 1014 W/cm2. Dans la première partie nous donnerons les résultats d'une étude systématique de l'efficacité d'absorption en fonction des conditions de focalisation des faisceaux laser sur la cible. La seconde partie concernera l'étude spatio-temporelle de l'implosion de microballons en impulsion nanoseconde et à flux laser modérés (< 1013 W/cm2)