950 research outputs found

    Risk programming analysis with imperfect information

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    A Monte Carlo procedure is used to demonstrate the dangers of basing (farm) risk programming on only a few states of nature and to study the impact of applying alternative risk programming methods. Two risk programming formulations are considered, namely mean-variance (E,V) programming and utility efficient (UE) programming. For the particular example of a Norwegian mixed livestock and crop farm, the programming solution is unstable with few states, although the cost of picking a sub-optimal plan declines with increases in number of states. Comparing the E,V results with the UE results shows that there were few discrepancies between the two and the differences which do occur are mainly trivial, thus both methods gave unreliable results in cases with small samples

    Dirty Museum

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    A visual essay consisting of uncaptioned images which recover an item of past auto-ethnographic reflection. The images originate from only one roll of 35 mm B+W film which in 1991 documented the derelict fabric of a pre-restored emotive site in Irish national memory. In Kilmainham Gaol, Dublin the leaders of the Easter 1916 uprising were executed by firing squad. The essay describes author’s failed attempts to engage with the site beyond its solemn facticity

    Influence of a low magnetic field on the thermal diffusivity of Bi-2212

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    The thermal diffusivity of a Bi-2212 polycrystalline sample has been measured under a 1T magnetic field applied perpendicularly to the heat flux. The magnetic contribution to the heat carrier mean free path has been extracted and is found to behave as a simple power law. This behavior can be attributed to a percolation process of electrons in the vortex lattice created by the magnetic field.Comment: 10 pages, 3 figures; to be published in Phys. Rev.

    ADAMTS-4 activity in synovial fluid as a biomarker of inflammation and effusion

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    Objective To evaluate the potential of ADAMTS-4 (aggrecanase -1) activity in synovial fluid (SF) as a biomarker of knee injury and joint disease. Design We have measured ADAMTS-4 activity in the synovial fluid of 170 orthopaedic patients with different degrees of joint pathology, using a commercial ADAMTS-4 fluorescence resonance energy transfer (FRET) substrate assay. Patients were classified at arthroscopy as (i) macroscopically normal, (ii) with an injury of the meniscus, anterior cruciate ligament or chondral/osteochondral defects or (iii) with osteoarthritis, and the influence of independent factors (age, patient group, effusion and synovial inflammation) on ADAMTS-4 activity levels was assessed. Results In most patients (106/170) ADAMTS-4 activity was undetectable; ADAMTS-4 ranged from 0 to 2.8 ng/mL in synovial fluid from patients with an injury, 0–4.1 ng/mL in osteoarthritic patients and 4.0–12.3 ng/mL in patients with large effusions. Four independent variables each significantly influenced ADAMTS-4 activity in synovial fluid (all P < 0.001): age (concordance = 0.69), presence of osteoarthritis (OA) (concordance = 0.66), level of effusion (concordance = 0.78) and inflammation (concordance = 0.68). Not only did effusion influence the amount of ADAMTS-4 activity most strongly, but it also did this in an ordered manner (P < 0.001). Conclusions The main finding of this study is that ADAMTS-4 levels in synovial fluid are most strongly correlated with inflammation and severity of effusion in the knee. Further study is required to determine if it could provide a useful tool to aid clinical diagnoses, indicate treatment, to monitor progression of joint degeneration or OA or alternatively the success of treatment

    Instability of the rhodium magnetic moment as origin of the metamagnetic phase transition in alpha-FeRh

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    Based on ab initio total energy calculations we show that two magnetic states of rhodium atoms together with competing ferromagnetic and antiferromagnetic exchange interactions are responsible for a temperature induced metamagnetic phase transition, which experimentally is observed for stoichiometric alpha-FeRh. A first-principle spin-based model allows to reproduce this first-order metamagnetic transition by means of Monte Carlo simulations. Further inclusion of spacial variation of exchange parameters leads to a realistic description of the experimental magneto-volume effects in alpha-FeRh.Comment: 10 pages, 13 figures, accepted for publication in Phys. Rev.

    The social underpinnings of mental distress in the time of COVID-19 – time for urgent action

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    We argue that predictions of a ‘tsunami’ of mental health problems as a consequence of the pandemic of coronavirus disease 2019 (COVID-19) and the lockdown are overstated; feelings of anxiety and sadness are entirely normal reactions to difficult circumstances, not symptoms of poor mental health. Some people will need specialised mental health support, especially those already leading tough lives; we need immediate reversal of years of underfunding of community mental health services. However, the disproportionate effects of COVID-19 on the most disadvantaged, especially BAME people placed at risk by their social and economic conditions, were entirely predictable. Mental health is best ensured by urgently rebuilding the social and economic supports stripped away over the last decade. Governments must pump funds into local authorities to rebuild community services, peer support, mutual aid and local community and voluntary sector organisations. Health care organisations must tackle racism and discrimination to ensure genuine equal access to universal health care. Government must replace highly conditional benefit systems by something like a universal basic income. All economic and social policies must be subjected to a legally binding mental health audit. This may sound unfeasibly expensive, but the social and economic costs, not to mention the costs in personal and community suffering, though often invisible, are far greater

    Trends in heavy metals, polychlorinated biphenyls and toxicity from sediment cores of the inner River Thames estuary, London, UK

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    River islands (Ait or Eyot) within the inner tidal Thames serve as unique recorders of current and historical estuarine chemical pollution. Sediment cores from Chiswick Ait were assessed for contamination using Microtox® solid phase bioassay, stable isotopes (δ13C, δ15N), heavy metals and polychlorinated biphenyls (PCBs). Microtox® classified these sediments as non-toxic to moderately toxic and bulk isotopes identified a change in organic input. Metals Cu, Zn, Cr, Ni, Cd, Hg and Ag showed parallel rise, peak and fall profiles which when allied to a 207/208Pb and 137Cs based chronology supported major changes in trace metal contributions corresponding to approximate input times of 1940 (rise), 1963 (peak) and 1985 (fall). Metals ranged from Cu 15 to 373 mg kg−1 (mean 141 mg kg−1), Zn 137 to 1331 mg kg−1 (mean 576 mg kg−1), Cr 14–351 mg kg−1 (mean 156 mg kg−1), Pb 10 to 1506 mg kg−1 (mean 402 mg kg−1), As 1 to 107 (mean 38 mg kg−1), Ni 11 to 113 mg kg−1 (mean 63 mg kg−1), Cd 0.2 to 53 mg kg−1 (mean 9 mg kg−1), Hg 1 to 8 mg kg−1 (mean 4.6 mg kg−1) and Ag from 0.7 to 50 mg kg−1 (mean 7.5 mg kg−1). Down core total PCBs ranged from 10.5 to 121 μg kg−1 and mean of 39 μg kg−1. The rise, peak and fall of Cu, Zn, Cr, Ni, Cd and Ag pollution matched local sewage works' treatment discharge records. Whereas the Hg, Pb and As profiles were disconnected, reflecting alternative historic sources and or partitioning behaviour. Comparison to marine sediment quality guidelines indicate that Zn, Pb, Ni, Cd and Hg exceed action level 2, whereas sedimentary Cu, Cr and As concentrations were above action level 1 (no action) but below action level 2 (further investigation required). The river islands of the tidal Thames capture a unique contaminant chemistry record due in part to their location in the tidal frame (salinity minimum) and close proximity to west London

    Observing the First Stars and Black Holes

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    The high sensitivity of JWST will open a new window on the end of the cosmological dark ages. Small stellar clusters, with a stellar mass of several 10^6 M_sun, and low-mass black holes (BHs), with a mass of several 10^5 M_sun should be directly detectable out to redshift z=10, and individual supernovae (SNe) and gamma ray burst (GRB) afterglows are bright enough to be visible beyond this redshift. Dense primordial gas, in the process of collapsing from large scales to form protogalaxies, may also be possible to image through diffuse recombination line emission, possibly even before stars or BHs are formed. In this article, I discuss the key physical processes that are expected to have determined the sizes of the first star-clusters and black holes, and the prospect of studying these objects by direct detections with JWST and with other instruments. The direct light emitted by the very first stellar clusters and intermediate-mass black holes at z>10 will likely fall below JWST's detection threshold. However, JWST could reveal a decline at the faint-end of the high-redshift luminosity function, and thereby shed light on radiative and other feedback effects that operate at these early epochs. JWST will also have the sensitivity to detect individual SNe from beyond z=10. In a dedicated survey lasting for several weeks, thousands of SNe could be detected at z>6, with a redshift distribution extending to the formation of the very first stars at z>15. Using these SNe as tracers may be the only method to map out the earliest stages of the cosmic star-formation history. Finally, we point out that studying the earliest objects at high redshift will also offer a new window on the primordial power spectrum, on 100 times smaller scales than probed by current large-scale structure data.Comment: Invited contribution to "Astrophysics in the Next Decade: JWST and Concurrent Facilities", Astrophysics & Space Science Library, Eds. H. Thronson, A. Tielens, M. Stiavelli, Springer: Dordrecht (2008
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