7,325 research outputs found
A Review of Existing Organisational Forms of Smallholder Farmers’ Associations and their Contractual Relationships with other Market Participants in the East and Southern African ACP Region
Finding extraterrestrial life using ground-based high-resolution spectroscopy
Exoplanet observations promise one day to unveil the presence of
extraterrestrial life. Atmospheric compounds in strong chemical disequilibrium
would point to large-scale biological activity just as oxygen and methane do in
the Earth's atmosphere. The cancellation of both the Terrestrial Planet Finder
and Darwin missions means that it is unlikely that a dedicated space telescope
to search for biomarker gases in exoplanet atmospheres will be launched within
the next 25 years. Here we show that ground-based telescopes provide a strong
alternative for finding biomarkers in exoplanet atmospheres through transit
observations. Recent results on hot Jupiters show the enormous potential of
high-dispersion spectroscopy to separate the extraterrestrial and telluric
signals making use of the Doppler shift of the planet. The transmission signal
of oxygen from an Earth-twin orbiting a small red dwarf star is only a factor 3
smaller than that of carbon monoxide recently detected in the hot Jupiter tau
Bootis b, albeit such a star will be orders of magnitude fainter. We show that
if Earth-like planets are common, the planned extremely large telescopes can
detect oxygen within a few dozen transits. Ultimately, large arrays of
dedicated flux collector telescopes equipped with high-dispersion spectrographs
can provide the large collecting area needed to perform a statistical study of
life-bearing planets in the solar neighborhood.Comment: 22 pages, 3 figures; published in Ap
Lactate-proton co-transport and its contribution to interstitial acidification during hypoxia in isolated rat spinal roots
Exposure of nervous tissue to hypoxia results in interstitial acidification. There is evidence for concomitant decrease in extracellular pH to the increase in tissue lactate. In the present study, we used double-barrelled pH-sensitive microelectrodes to investigate the link between lactate transport and acid-base homeostasis in isolated rat spinal roots. Addition of different organic anions to the bathing solution at constant bath pH caused transient alkaline shifts in extracellular pH; withdrawal of these compounds resulted in transient acid shifts in extracellular pH. With high anion concentrations (30 mM), the largest changes in extracellular pH were observed with propionate >l-lactate ≈ pyruvate >62; 2-hydroxy-2-methylpropionate. Changes in extracellular pH induced by 10 mMl- andd-lactate were of similar size. Lactate transport inhibitors α-cyano-4-hydroxycinnamic acid and 4,4′-dibenzamidostilbene-2,2′-disulphonic acid significantly reducedl-lactate-induced extracellular pH shifts without affecting propionate-induced changes in extracellular pH. Hypoxia produced an extracellular acidification that was strongly reduced in the presence of α-cyano-4-hydroxycinnamic acid and 4,4′-dibenzamidostilbene-2,2′-disulphonic acid. In contrast, amiloride and 4,4′-di-isothiocyanostilbene-2,2′-disulphonate were without effect on hypoxia-induced acid shifts.
The results indicate the presence of a lactate-proton co-transporter in rat peripheral nerves. This transport system and not Na+/H+ or C1−/HCO−3 exchange seems to be the dominant mechanism responsible for interstitial acidification during nerve hypoxia
Evidence-based urology in practice : heterogeneity in a systematic review meta-analysis
The definitive version is available at www3.interscience.wiley.com.Peer reviewedPreprin
Benchmarking International Food Safety Performance in the Fresh Produce Sector
The objective of this paper is to assess food systems performance in Mediterranean countries to deliver safe food (fresh produce), and to demonstrate the capacity to the satisfaction of private customers and public regulators. To that end, an international benchmarking exercise was developed to assess the quality performance gap in food standards across countries and food systems. The study was carried out in three Mediterranean countries: Spain, Morocco and Turkey and involved an audit of the citrus and tomatoes supply chains, and a comparison with existing "best practice" in infrastructure and management practices at both firm and industry level. The aim was to identify the gaps between fresh produce exporters and a best practice company. To that end, the Spanish fresh produce supply chain was used as the benchmark since in many areas it is more advanced than elsewhere.benchmarking, performance, quality and safety, fresh produce, Mediterranean countries, Food Consumption/Nutrition/Food Safety,
Redundancy in Logic III: Non-Mononotonic Reasoning
Results about the redundancy of circumscriptive and default theories are
presented. In particular, the complexity of establishing whether a given theory
is redundant is establihsed.Comment: minor correction
M<sub>6</sub>L<sub>12</sub>Nanospheres with Multiple C<sub>70</sub>Binding Sites for <sup>1</sup>O<sub>2</sub>Formation in Organic and Aqueous Media
[Image: see text] Singlet oxygen is a potent oxidant with major applications in organic synthesis and medicinal treatment. An efficient way to produce singlet oxygen is the photochemical generation by fullerenes which exhibit ideal thermal and photochemical stability. In this contribution we describe readily accessible M(6)L(12) nanospheres with unique binding sites for fullerenes located at the windows of the nanospheres. Up to four C(70) can be associated with a single nanosphere, presenting an efficient method for fullerene extraction and application. Depending on the functionality located on the outside of the sphere, they act as vehicles for (1)O(2) generation in organic or in aqueous media using white LED light. Excellent productivity in (1)O(2) generation and consecutive oxidation of (1)O(2) acceptors using C(70)⊂[Pd(6)L(12)], C(60)⊂[Pd(6)L(12)] or fullerene soot extract was observed. The methodological design principles allow preparation and application of highly effective multifullerene binding spheres
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