3,183 research outputs found

    Unintended Detrimental Effects of Environmental Policy: The Green Paradox and Beyond

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    Well-intended policies aimed at reducing greenhouse gas emissions may have unintended undesirable consequences. Recently, a large literature has emerged showing under what conditions this so-called 'Green Paradox' may occur. We review this literature and identify the key mechanisms behind these paradoxical policy outcomes and highlight avenues for future research

    Ecological agriculture in South-India : an agro-economic comparison and study of transition

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    This report describes two research programmes carried out on ecological agriculture in South-India. Experiences of twelve farmers in transition towards ecological agriculture are described and analysed. The comparative performance of seven farmer pairs, consisting of one ecological and one conventional reference farm, is analysed in relation to agronomic and economic performanc

    Spatial and temporal patterns of carabid activity-density in cereals do not explain levels of predation on weed seeds

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    Seed predation is an important component of seed mortality of weeds in agro-ecosystems, but the agronomic use and management of this natural weed suppression is hampered by a lack of insight in the underlying ecological processes. In this paper, we investigate whether and how spatial and temporal variation in activity-density of granivorous ground beetles (Coleoptera: Carabidae) results in a corresponding pattern of seed predation. Activity-density of carabids was measured by using pitfall traps in two organic winter wheat fields from March to July 2004. Predation of seeds (Capsella bursa-pastoris, Lamium amplexicaule, Poa annua and Stellaria media) was assessed using seed cards at the same sites and times. As measured by pitfall traps, carabids were the dominant group of insects that had access to the seed cards. In the field, predation of the four different species of seed was in the order: C. bursa-pastoris>P. annua>S. media>L. amplexicaule; and this order of preference was confirmed in the laboratory using the dominant species of carabid. On average, seed predation was higher in the field interior compared to the edge, whereas catches of carabids were highest near the edge. Weeks with elevated seed predation did not concur with high activity-density of carabids. Thus, patterns of spatial and temporal variation in seed predation were not matched by similar patterns in the abundance of granivorous carabid beetles. The lack of correspondence is ascribed to effects of confounding factors, such as weather, the background density of seeds, the composition of the carabid community, and the phenology and physiological state of the beetles. Our results show that differences in seed loss among weed species may be predicted from laboratory trials on preference. However, predator activity-density, as measured in pitfall traps, is an insufficient predictor of seed predation over time and space within a fiel

    Magnetic fields at the periphery of UCHII regions from carbon recombination line observations

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    Several indirect evidences indicate a magnetic origin for the non-thermal width of spectral lines observed toward molecular clouds. In this letter, I suggest that the origin of the non-thermal width of carbon recombination lines (CRLs) observed from photo-dissociation regions (PDRs) near ultra-compact \HII\ regions is magnetic and that the magnitude of the line width is an estimate of the \alfven speed. The magnetic field strengths estimated based on this suggestion compare well with those measured toward molecular clouds with densities similar to PDR densities. I conclude that multi-frequency CRL observations have the potential to form a new tool to determine the field strength near star forming regions.Comment: To appear in ApJ Letter

    Development and first results of a dedicated chronic total occlusion programme

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    Objective To describe the development and first results of a dedicated chronic total occlusion (CTO) programme in a tertiary medical centre. Background Because of the complexity and the increased risk of complications during percutaneous coronary intervention (PCI) for CTO, it is essential that less experienced and evolving CTO centres perform regular quality analyses. Methods We therefore performed analyses to describe the results during the first 3 years of a dedicated CTO programme at a high-volume PCI centre. In addition, we discuss the strategies employed to develop such a programme. Results A total of 179 consecutive patients undergoing 187 CTO procedures were included in the study. The complexity of the CTO lesions increased from a mean J-CTO (Japanese Multicentre CTO Registry) score of 1.3 in 2015 to 2.1 in 2017. In the majority of cases, the antegrade wire escalation technique was performed. Final technical success rate was 78.5% in 175 patients with a single CTO and 80.2% of all 187 CTO procedures. No peri-procedural or in-hospital deaths occurred. One peri-procedural myocardial infarction occurred. Cardiac tamponade occurred in 2 cases, both managed by pericardiocentesis. No urgent cardiac surgery was necessary. Survival and revascularisation rates at 30 days and 1 year were excellent. Conclusion Following initiation of a dedicated CTO programme, using up-to-date techniques and strategies, procedural and clinical outcome were comparable with current standards in established centres

    Prevalence of inappropriate tuberculosis treatment regimens: a systematic review

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    A potential threat to the success of new tuberculosis (TB) drugs is the development of resistance. Using drugs in appropriate regimens, such as those recommended in the World Health Organization (WHO) treatment guidelines, prevents the development of resistance. We performed a systematic review to assess the prevalence of inappropriate prescription of TB drugs for the treatment of TB

    The Elusive Active Nucleus of NGC 4945

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    We present new HST NICMOS observations of NGC 4945, a starburst galaxy hosting a highly obscured active nucleus that is one of the brightest extragalactic sources at 100 keV. The HST data are complemented with ground based [FeII] line and mid--IR observations. A 100pc-scale starburst ring is detected in Pa alpha, while H_2 traces the walls of a super bubble opened by supernova-driven winds. The conically shaped cavity is particularly prominent in Pa alpha equivalent width and in the Pa alpha/H_2 ratio. Continuum images are heavily affected by dust extinction and the nucleus of the galaxy is located in a highly reddened region with an elongated, disk-like morphology. No manifestation of the active nucleus is found, neither a strong point source nor dilution in CO stellar features, which are expected tracers of AGN activity. Even if no AGN traces are detected in the near-IR, with the currently available data it is still not possible to establish whether the bolometric luminosity of the object is powered by the AGN or by the starburst: we demonstrate that the two scenarios constitute equally viable alternatives. However, the absence of any signature other than in the hard X-rays implies that, in both scenarios, the AGN is non-standard: if it dominates, it must be obscured in all directions, conversely, if the starburst dominates, the AGN must lack UV photons with respect to X-rays. An important conclusion is that powerful AGNs can be hidden even at mid-infrared wavelengths and, therefore, the nature of luminous dusty galaxies cannot be always characterized by long-wavelength data alone but must be complemented with sensitive hard X-ray observations.Comment: Accepted for publication in A&A, high quality color pictures available at http://www.arcetri.astro.it/~marconi/colpic.htm

    Molecular gas heating in Arp 299

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    Understanding the heating and cooling mechanisms in nearby (Ultra) luminous infrared galaxies can give us insight into the driving mechanisms in their more distant counterparts. Molecular emission lines play a crucial role in cooling excited gas, and recently, with Herschel Space Observatory we have been able to observe the rich molecular spectrum. CO is the most abundant and one of the brightest molecules in the Herschel wavelength range. CO transitions are observed with Herschel, and together, these lines trace the excitation of CO. We study Arp 299, a colliding galaxy group, with one component harboring an AGN and two more undergoing intense star formation. For Arp 299 A, we present PACS spectrometer observations of high-J CO lines up to J=20-19 and JCMT observations of 13^{13}CO and HCN to discern between UV heating and alternative heating mechanisms. There is an immediately noticeable difference in the spectra of Arp 299 A and Arp 299 B+C, with source A having brighter high-J CO transitions. This is reflected in their respective spectral energy line distributions. We find that photon-dominated regions (PDRs) are unlikely to heat all the gas since a very extreme PDR is necessary to fit the high-J CO lines. In addition, this extreme PDR does not fit the HCN observations, and the dust spectral energy distribution shows that there is not enough hot dust to match the amount expected from such an extreme PDR. Therefore, we determine that the high-J CO and HCN transitions are heated by an additional mechanism, namely cosmic ray heating, mechanical heating, or X-ray heating. We find that mechanical heating, in combination with UV heating, is the only mechanism that fits all molecular transitions. We also constrain the molecular gas mass of Arp 299 A to 3e9 Msun and find that we need 4% of the total heating to be mechanical heating, with the rest UV heating

    Space allowance of young goats during transportation to slaughter = Beladingsdichtheid tijdens het wegtransport van jonge geiten

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    Research was performed during long distance road transportations of young goats (6-8 weeks). Effects of three space allowances on physiological responses (blood parameters, heart rate and body temperature) were measured

    An SMT-based discovery algorithm for C-nets

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    Recently, Causal nets have been proposed as a suitable model for process discovery, due to their declarative semantics and the great expressiveness they possess. In this paper we propose an algorithm to discover a causal net from a set of traces. It is based on encoding the problem as a Satisfiability Modulo Theories (SMT) formula, and uses a binary search strategy to optimize the derived model. The method has been implemented in a prototype tool that interacts with an SMT solver. The experimental results obtained witness the capability of the approach to discover complex behavior in limited time.Postprint (published version
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