Application of DOT-MORSE coupling to the analysis of three-dimensional SNAP shielding problems

The use of discrete ordinates and Monte Carlo techniques to solve radiation transport problems is discussed. A general discussion of two possible coupling schemes is given for the two methods. The calculation of the reactor radiation scattered from a docked service and command module is used as an example of coupling discrete ordinates (DOT) and Monte Carlo (MORSE) calculations

Sustained impact of drought on wet shrublands mediated by soil physical changes

13 páginas.-- 6 figuras.-- 52 referencias.-- The online version of this article (doi:10.1007/s10533-014-0059-y) contains supplementary material, which is available to authorized users.-- Domínguez, María Teresa et al...Projected climate warming may substantially increase carbon emissions from wet organic soils, contributing to a positive feedback between the terrestrial carbon cycle and climate change. Evidence suggests that in these soils the stimulation of soil respiration by warming can be sustained over long periods of time due to the large availability of C substrates. However, the long-term response of wet organic soils to drought remains uncertain. Organo-mineral soils might be particularly vulnerable, because of their limited soil moisture pool to buffer drought events. Using a whole-ecosystem climate-change experiment in North Wales (UK) we show that soil respiration in podzolic (organo-mineral) soils from wet shrublands is more vulnerable to recurrent drought than to warming, and that the drought impact does not attenuate at decadal time scales. Stimulation of soil respiration by drought was linked to major changes in soil structure that led to a 54 % reduction in water holding capacity compared to control. Bryophyte abundance was found to buffer soil moisture losses, moderating soil CO2 efflux under warming. As there was no evidence of change in plant productivity to offset the increased soil C emissions under drought, this response may result in a positive climate feedback. The results indicate the potentially critical role that changes in sub-dominant vegetation and in soil physical properties may have in determining climate change impacts on soil C dynamics.We thank all the CEH staff members who have contributed to the experiment establishment and maintenance over the years, in particular David Williams. This research was funded by the EU projects CLIMOOR, VULCAN and INCREASE FP7-INFRASTRUCTURE-2008-1 (Grant Agreement no. 227628)—the INCREASE project. M.T.D was supported by two postdoctoral fellowships awarded by the Spanish National Science and Technology FoundationPeer reviewe

Why and how to teach the history of economic thought: Economics as historically produced knowledge

This draft chapter for the Elgar International Handbook on Teaching and Learning Economics is intended to give advice to instructors who might be teaching a history of economic thought course to undergraduates for the first time or who have perhaps been teaching for a while but would like to refresh their courses. We sketch the history of courses in the history of economic thought, the expanding scope and research activity in the field, and offer suggestions and resources for a one-semester course. We suggest learning objectives for organizing the course, and discuss supplementary teaching goals (multidisciplinary scholarship and reading/writing instruction) and teaching challenges (time constraints and selection of readings). Our emphasis is on helping students understand economics - past and present - as historically produced knowledge

The Fate of Arginine and Proline Carbon in Squid Tissues

The metabolism of proline and arginine was investigated in kidney, gill, and heart of the pelagic squid, Symplectoteuthis. The rates of CO2 release from 14C-proline exceeded the rates from 14C-arginine. The metabolic rate of arginine and proline was assessed by monitoring the incorporation of arginine-derived carbon into various intermediates. Arginine was metabolized, through ornithine, to proline as well as to glutamate and various subsequent derivatives (alanine, octopine, aspartate, and carboxylic acids). The same components became labeled using 14C-proline as the starting substrate, but only the gill was capable of converting proline to arginine via the urea cycle. In addition, 14C-proline oxidation rates were high enough to exceed those of 14C-glucose in at least three tissues, kidney, heart, and inner mantle muscle

Dysflective cones: Visual function and cone reflectivity in long-term follow-up of acute bilateral foveolitis.

PURPOSE:Confocal adaptive optics scanning laser ophthalmoscope (AOSLO) images provide a sensitive measure of cone structure. However, the relationship between structural findings of diminished cone reflectivity and visual function is unclear. We used fundus-referenced testing to evaluate visual function in regions of apparent cone loss identified using confocal AOSLO images. METHODS:A patient diagnosed with acute bilateral foveolitis had spectral-domain optical coherence tomography (SD-OCT) (Spectralis HRA + OCT system [Heidelberg Engineering, Vista, CA, USA]) images indicating focal loss of the inner segment-outer segment junction band with an intact, but hyper-reflective, external limiting membrane. Five years after symptom onset, visual acuity had improved from 20/80 to 20/25, but the retinal appearance remained unchanged compared to 3 months after symptoms began. We performed structural assessments using SD-OCT, directional OCT (non-standard use of a prototype on loan from Carl Zeiss Meditec) and AOSLO (custom-built system). We also administered fundus-referenced functional tests in the region of apparent cone loss, including analysis of preferred retinal locus (PRL), AOSLO acuity, and microperimetry with tracking SLO (TSLO) (prototype system). To determine AOSLO-corrected visual acuity, the scanning laser was modulated with a tumbling E consistent with 20/30 visual acuity. Visual sensitivity was assessed in and around the lesion using TSLO microperimetry. Complete eye examination, including standard measures of best-corrected visual acuity, visual field tests, color fundus photos, and fundus auto-fluorescence were also performed. RESULTS:Despite a lack of visible cone profiles in the foveal lesion, fundus-referenced vision testing demonstrated visual function within the lesion consistent with cone function. The PRL was within the lesion of apparent cone loss at the fovea. AOSLO visual acuity tests were abnormal, but measurable: for trials in which the stimulus remained completely within the lesion, the subject got 48% correct, compared to 78% correct when the stimulus was outside the lesion. TSLO microperimetry revealed reduced, but detectible, sensitivity thresholds within the lesion. CONCLUSIONS AND IMPORTANCE:Fundus-referenced visual testing proved useful to identify functional cones despite apparent photoreceptor loss identified using AOSLO and SD-OCT. While AOSLO and SD-OCT appear to be sensitive for the detection of abnormal or absent photoreceptors, changes in photoreceptors that are identified with these imaging tools do not correlate completely with visual function in every patient. Fundus-referenced vision testing is a useful tool to indicate the presence of cones that may be amenable to recovery or response to experimental therapies despite not being visible on confocal AOSLO or SD-OCT images

Ariel - Volume 6 Number 3

Editors Mark Dembert J.D. Kanofsky Frank Chervenak John Lammie Curt Cummings Staff Ken Jaffe Bob Sklaroff Halley Faust Jim Burke Nancy Redfern Hans Weltin Photographer Larry Glazerman Overseas Editor Mike Sinason Humorist Jim McCan

Global assessment of nitrogen deposition effects on terrestrial plant diversity : a synthesis

Atmospheric nitrogen (N) deposition is it recognized threat to plant diversity ill temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems. from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now and in the future. This synthesis paper clearly shows that N accumulation is the main driver of changes to species composition across the whole range of different ecosystem types by driving the competitive interactions that lead to composition change and/or making conditions unfavorable for some species. Other effects such its direct toxicity of nitrogen gases and aerosols long-term negative effects of increased ammonium and ammonia availability, soil-mediated effects of acidification, and secondary stress and disturbance are more ecosystem, and site-specific and often play a supporting role. N deposition effects in mediterranean ecosystems have now been identified, leading to a first estimate of an effect threshold. Importantly, ecosystems thought of as not N limited, such as tropical and subtropical systems, may be more vulnerable in the regeneration phase. in situations where heterogeneity in N availability is reduced by atmospheric N deposition, on sandy soils, or in montane areas. Critical loads are effect thresholds for N deposition. and the critical load concept has helped European governments make progress toward reducing N loads on sensitive ecosystems. More needs to be done in Europe and North America. especially for the more sensitive ecosystem types. including several ecosystems of high conservation importance. The results of this assessment Show that the Vulnerable regions outside Europe and North America which have not received enough attention are ecoregions in eastern and Southern Asia (China, India), an important part of the mediterranean ecoregion (California, southern Europe). and in the coming decades several subtropical and tropical parts of Latin America and Africa. Reductions in plant diversity by increased atmospheric N deposition may be more widespread than first thought, and more targeted Studies are required in low background areas, especially in the G200 ecoregions

An application of hybrid life cycle assessment as a decision support framework for green supply chains

In an effort to achieve sustainable operations, green supply chain management has become an important area for firms to concentrate on due to its inherent involvement with all the processes that provide foundations to successful business. Modelling methodologies of product supply chain environmental assessment are usually guided by the principles of life cycle assessment (LCA). However, a review of the extant literature suggests that LCA techniques suffer from a wide range of limitations that prevent a wider application in real-world contexts; hence, they need to be incorporated within decision support frameworks to aid environmental sustainability strategies. Thus, this paper contributes in understanding and overcoming the dichotomy between LCA model development and the emerging practical implementation to inform carbon emissions mitigation strategies within supply chains. Therefore, the paper provides both theoretical insights and a practical application to inform the process of adopting a decision support framework based on a LCA methodology in a real-world scenario. The supply chain of a product from the steel industry is considered to evaluate its environmental impact and carbon ‘hotspots’. The study helps understanding how operational strategies geared towards environmental sustainability can be informed using knowledge and information generated from supply chain environmental assessments, and for highlighting inherent challenges in this process

Experimental evidence for drought induced alternative stable states of soil moisture

Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction