4,640 research outputs found

    Celiac disease in older persons: A case of seronegative disease

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    A 68-year-old man with a history of smoking (former smoker of 40 cigarettes per day), euthyroid goiter, deep vein thrombosis and depression, came to our attention for weakness, cachexia, abdominal bloating and diarrhea lasting for almost six months. Furthermore, he had lost about 25 kilograms of weight in the last year and was bedridden for three months. Combining the results of serological, histopathological and genetic tests, he was diagnosed with a seronegative celiac disease. Gluten-free diet, combined with nutritional supplements and physical therapy, improved his clinical condition and allowed the recovery of weight and the walking ability. Celiac disease might be suspected in elderly patients with diarrhea, malabsorption, malnutrition and cachexia, but also with other symptoms such as anemia, micronutrients' deiciency, fragility fractures and neurological symptoms

    Laboratory study of spectral induced polarization responses of magnetite - Fe2+ redox reactions in porous media

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    Spectral Induced Polarization (SIP) phase anomalies in field surveys at contaminated sites have previously been shown to correlate with the occurrence of chemically reducing conditions and/or semiconductive minerals, but the reasons for this are not fully understood. We report a systematic laboratory investigation of the role of the semiconductive mineral magnetite and its interaction with redoxactive versus redox-inactive ions in producing such phase anomalies. The SIP responses of quartz sand with 5% magnetite in solutions containing redox-inactive Ca2+, and Ni2+, versus redox-active Fe2+ were measured across the pH ranges corresponding to adsorption of these metals to magnetite. With redox inactive ions Ca2+ and Ni2+, SIP phase response showed no changes across the pH range 4 to10, corresponding to their adsorption, showing ~30 mrad anomalies peaking at ~59 to 74 Hz. These large phase anomalies are probably caused by polarization of the magnetite-solution interfaces. With the redox-active ion Fe2+, frequency of peak phase res onse decreased progressively from ~46 to ~3 Hz as effluent pH increased from 4 to 7, corresponding to progressive adsorption of Fe2+ to the magnetite surface. The latter frequency (3 Hz) corresponds approximately with those of phase anomalies detected in field surveys reported elsewhere. We conclude that pH sensitivity arises from redox reactions between Fe2+ and magnetite surfaces, with transfer of electrical charge through the bulk mineral, as reported in other laboratory investigations. Our results confirm that SIP measurements are sensitive to redox reactions involving charge transfers between adsorbed ions and semiconductive minerals. Phase anomalies seen in field surveys of groundwater contamination and biostimulation may therefore be indicative of iron-reducing conditions, when semiconductive iron minerals such as magnetite are present

    Constraints on convergence: hydrophobic hind legs allow some male pollinator fig wasps early access to submerged females

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    Pollinator fig wasps (Hymenoptera: Agaonidae) display numerous adaptations linked to their obligate association with fig trees (Ficus). Ceratosolen fig wasps pollinate figs that often fill temporarily with liquid, and one clade has males with unusually long hind legs. We investigated their morphology and behaviour. Scanning electron microscopy (SEM) revealed that the cuticle of their hind legs is highly modified and covered with numerous hydrophobic setae and microtrichia that can prevent blockage of the wasps’ large propodeal spiracles by liquids. In deep liquid, the males floated on the surface, but when only a thin layer of liquid was present, the legs allowed males to access females without the risk of drowning. Access to females was facilitated by an air bubble that forms between the hind legs and maintains a column of air between the spiracles and the centre of the figs. Sexual selection should favour males that can gain earlier access to mates, and the modified legs represent an adaptation to achieve this. Convergent adaptations are known in some unrelated non-pollinating fig wasps that develop in similar liquid-filled figs, but these species have enlarged hydrophobic peritremata at the ends of their metasoma to protect the spiracles located there. Unlike non-pollinating fig wasps, pollinator males need to insert their metasoma deep into females’ galls during mating. This difference in mating behaviour has constrained the extent of convergence

    High-Temperature Transport Properties of Yb4−xSmxSb3

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    Polycrystalline L4Sb3 (L = La, Ce, Sm, and Yb) and Yb4−x Sm x Sb3, which crystallizes in the anti-Th3P4 structure type (I-43d no. 220), were synthesized via high-temperature reaction. Structural and chemical characterization were performed by x-ray diffraction and electronic microscopy with energy-dispersive x-ray analysis. Pucks were densified by spark plasma sintering. Transport property measurements showed that these compounds are n-type with low Seebeck coefficients, except for Yb4Sb3, which shows semimetallic behavior with hole conduction above 523 K. By partially substituting Yb by a trivalent rare earth we successfully improved the thermoelectric figure of merit of Yb4Sb3 up to 0.7 at 1273 K

    Electrical conductivity of plasmas of DB white dwarf atmospheres

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    The static electrical conductivity of non-ideal, dense, partially ionized helium plasma was calculated over a wide range of plasma parameters: temperatures 1⋅104Kâ‰ČTâ‰Č1⋅105K1\cdot 10^{4}\textrm{K} \lesssim T \lesssim 1\cdot 10^{5}\textrm{K} and mass density 1×10−6g/cm3â‰Čρâ‰Č2g/cm31 \times 10^{-6} \textrm{g}/\textrm{cm}^{3} \lesssim \rho \lesssim 2 \textrm{g}/\textrm{cm}^{3}. Calculations of electrical conductivity of plasma for the considered range of plasma parameters are of interest for DB white dwarf atmospheres with effective temperatures 1⋅104Kâ‰ČTeffâ‰Č3⋅104K1\cdot 10^{4}\textrm{K} \lesssim T_{eff} \lesssim 3\cdot 10^{4}\textrm{K}. Electrical conductivity of plasma was calculated by using the modified random phase approximation and semiclassical method, adapted for the case of dense, partially ionized plasma. The results were compared with the unique existing experimental data, including the results related to the region of dense plasmas. In spite of low accuracy of the experimental data, the existing agreement with them indicates that results obtained in this paper are correct

    Inter-sectoral and multilevel coordination alone do not reduce deforestation and advance environmental justice:Why bold contestation works when collaboration fails

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    Policy makers, academics, and conservationists often posit that poor coordination between different land use sectors, and between levels of governance, as an underlying challenge for reducing deforestation and forest degradation. This paper analyzes this argument using data from interviews with over 500 respondents from government, nongovernmental organizations, private companies, local and indigenous communities, activists, and individuals involved in 35 diverse land use initiatives in three countries: Peru, Indonesia, and Mexico. We find that while there is strong evidence of widespread coordination failures between sectors and levels, more fundamental political issues preclude effective coordination. We argue that political coalitions act to oppose environmental objectives and to impede their opponents from participating in land use governance. Moreover, we find that where coordination between actors does occur, it does not necessarily produce environmentally sustainable and socially just land use outcomes. Where we do find successful initiatives to reduce deforestation and benefit local people, effective coordination between well-informed actors is often present, but it does not occur spontaneously, and is instead driven by political organizing over time by activists, local people, nongovernmental organizations, and international donors. We suggest that the global environmental community must recognize explicitly these political dimensions of land use governance in order to successfully collaborate with local people to reduce deforestation

    Ferredoxin C2 is required for chlorophyll biosynthesis and accumulation of photosynthetic antennae in Arabidopsis

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    Ferredoxins (Fd) are small iron-sulphur proteins, with sub-types that have evolved for specific redox functions. Ferredoxin C2 (FdC2) proteins are essential Fd homologues conserved in all photosynthetic organisms and a number of different FdC2 functions have been proposed in angiosperms. Here we use RNAi silencing in Arabidopsis thaliana to generate a viable fdC2 mutant line with near-depleted FdC2 protein levels. Mutant leaves have ~50% less chlorophyll a and b, and chloroplasts have poorly developed thylakoid membrane structure. Transcriptomics indicates upregulation of genes involved in stress responses. Although fdC2 antisense plants show increased damage at photosystem II (PSII) when exposed to high light, PSII recovers at the same rate as wild type in the dark. This contradicts literature proposing that FdC2 regulates translation of the D1 subunit of PSII, by binding to psbA transcript. Measurement of chlorophyll biosynthesis intermediates revealed a build-up of Mg-protoporphyrin IX, the substrate of the aerobic cyclase. We localise FdC2 to the inner chloroplast envelope and show that the FdC2 RNAi line has a disproportionately lower protein abundance of antennae proteins, which are nuclear-encoded and must be refolded at the envelope after import
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