185 research outputs found
A product of the environment: environmental constraint, candidate behavior and the speed of democracy
Elections are the engine that drives democracy. The central question of this
dissertation relates to the speed of that engine: How long does it take for elections to
reflect changing preferences in the electorate? The findings presented in this dissertation
suggest that electoral change is the result of a gradual process of natural selection in
which the political environment, rather than district service activity, is the key variable.
Comparing elections data across different types of district environment, I find evidence
that the environment affects levels of competition and electoral outcomes. Utilizing an
event history statistical model to examine various risk factors for electoral defeat, I find
that the political environment of the district is the most important factor influencing the
risk of defeat even when controlling for district service behaviors. Over time, the district
environment operates as a self-correcting mechanism, purging political misfits and
replacing them with representatives who better reflect the ideology of the district.
Electoral change typically results more from evolution than revolution it may not occur
quickly, and it may not occur in every district, but it does occur when and where it is
needed
Developmental dynamics of cone photoreceptors in the eel
Background: Many fish alter their expressed visual pigments during development. The number of retinal opsins expressed and their type is normally related to the environment in which they live. Eels are known to change the expression of their rod opsins as they mature, but might they also change the expression of their cone opsins?Results: The Rh2 and Sws2 opsin sequences from the European Eel were isolated, sequenced and expressed in vitro for an accurate measurement of their lambda(max) values. In situ hybridisation revealed that glass eels express only rh2 opsin in their cone photoreceptors, while larger yellow eels continue to express rh2 opsin in the majority of their cones, but also have <5% of cones which express sws2 opsin. Silver eels showed the same expression pattern as the larger yellow eels. This observation was confirmed by qPCR (quantitative polymerase chain reaction).Conclusions: Larger yellow and silver European eels express two different cone opsins, rh2 and sws2. This work demonstrates that only the Rh2 cone opsin is present in younger fish (smaller yellow and glass), the sws2 opsin being expressed additionally only by older fish and only in <5% of cone cells
Minimally manipulative method for the expansion of human bone marrow mesenchymal stem cells to treat osseous defects
Copyright © 2019 Hamerly, Tweedell, Hritzo, Nyasembe, Tekwani, Nanayakkara, Walker and Dinglasan. Malaria is a major global health threat, with nearly half the world\u27s population at risk of infection. Given the recently described delayed clearance of parasites by artemisinincombined therapies, new antimalarials are needed to facilitate the global effort toward elimination and eradication. NPC1161 is an 8-aminoquinoline that is derived from primaquine with an improved therapeutic profile compared to the parent compound. The (R)-(-) enantiomer (NPC1161B) has a lower effective dose that results in decreased toxic side effects such as hemolysis compared to the (S)-(+)-enantiomer, making it a promising compound for consideration for clinical development. We explored the effect of NPC1161B on Plasmodium falciparum oocyst and sporozoite development to evaluate its potential transmission-blocking activity viz. its ability to cure mosquitoes of an ongoing infection. When mosquitoes were fed NPC1161B 4 days after P. falciparum infection, we observed that total oocyst numbers were not affected by NPC1161B treatment. However, the sporozoite production capacity of the oocysts was impaired, and salivary gland sporozoite infections were completely blocked, rendering the mosquitoes non-infectious. Importantly, NPC1161B did not require prior liver metabolism for its efficacy as is required in mammalian systems, suggesting that an alternative metabolite is produced in the mosquito that is active against the parasite. We performed liquid chromatography-mass spectrometry (LC-MS)/MS analysis of methanol extracts from the midguts of mosquitoes fed on an NPC1161B (434.15 m/z)-treated blood meal and identified a compound with a mass of 520.2 m/z, likely a conjugate of NPC1161B or an oxidized metabolite. These findings establish NPC1161B, and potentially its metabolites, as transmission-blocking candidates for the treatment of P. falciparum
Fractional Generalization of Gradient Systems
We consider a fractional generalization of gradient systems. We use
differential forms and exterior derivatives of fractional orders. Examples of
fractional gradient systems are considered. We describe the stationary states
of these systems.Comment: 11 pages, LaTe
Animal dietary exposure : overview of current approaches used at EFSA
At EFSA, animal dietary exposure estimates are undertaken by several Panels/Units to assess the risk of feed contaminants, pesticide residues, genetically modified feed and feed additives. Guidance documents describing methodologies for animal dietary exposure assessment are available both at EFSA and international levels. Although appropriate within pertinent regulatory frameworks, the methodologies used to assess animal dietary exposure vary across risk assessment areas. There are different approaches ranging from quick worst-case estimations to more refined methods assessing actual exposure, resulting from the use of a heterogeneous selection of animal populations and default values to estimate feed intake. Furthermore, current feed classification systems in place at international and national levels contain a large and heterogeneous number of feed materials, which may benefit from further harmonisation efforts. This technical report presents an overview of the current approaches in place at EFSA to assess the exposure to chemicals in feed. The possibility for a greater harmonisation of feed classification and terminology is also addressed by comparing the structure of the EU catalogue of feed materials and the Harmonised OECD tables of feedstuffs derived from field crops with the EFSA FoodEx2 system
Fractional Variations for Dynamical Systems: Hamilton and Lagrange Approaches
Fractional generalization of an exterior derivative for calculus of
variations is defined. The Hamilton and Lagrange approaches are considered.
Fractional Hamilton and Euler-Lagrange equations are derived. Fractional
equations of motion are obtained by fractional variation of Lagrangian and
Hamiltonian that have only integer derivatives.Comment: 21 pages, LaTe
Wave Energy
Part of the immense solar energy input to the earth is converted by natural processes into energy associated with ocean waves. The geographical location of the United Kingdom renders it one of the world ' s most favoured countries with respect to the potential availability of wave energy. In principle. the waves reaching our coastal waters from the North Atlantic might satisfy a considerable fraction of our electricity demand provided that reasonably high overall conversion efficiencies can be achieved . Inventors have recognised the power of the sea for many decades. and there has been no lack of ideas on how it might be tapped . But none of the ideas was developed on a substantial scale. since ample and relatively cheap supplies of other resources were always available . In recent years. however. there has been a growing recognition that--on a world scale-the presently used forms of energy may become too expensive,. too scarce or otherwise unavailable to meet our energy needs by themselves . The Government's responsibility is to ensure that as wide a range as possible of energy supply options are available when they may be needed . Research and development can provide the necessary technical and econom i c data on which the ultimate choices can be made . Within this context. the Government announced in 197 6 the start of an R and D programme on wave energy for which the first phase was to be a feasibility study lasting for two years. The funding level has been increased twice since that time to maintain the momentum of the programme in the light of technical progress . The programme has had three main components: -exploratory deve lopment of several different engineering concepts of wave energy converter; -supporting research in relevant engineering and scientific areas : • the collection and analysis of wave data. • analysis of the structural response to wave-induced motions. • mooring. • energy conversion and transm issi on. • environmental aspects ; -working up preliminary reference designs of full scale stations for tech nical and economic appraisal. The purpose of this paper is to review the present state of knowledge of wave energy in the light of the achievements of the first two-year phase of the programme . Development of the converters Four potential designs of converter were adopted for initial study. since the sparse data available were insufficient to enable a single concept to be chosen with confidence. Proposals for alternative concepts are received on a continuing basis and are assessed against a number of criteria: two of them have so far been added to the programme in order to explore new principles Apart from the basic technical differences the six designs differ from each other in their degree of complexity and their state of development. as described in Chapter 3 . Work on two of the designs has been advanced from laboratory wave tanks to the testing of 1 / 1 0th scale models in natural open water at Loch Ness and in the Solent. For all the designs . a combination of theoretical studies. laboratory work and engineering appraisal has clarified the factors which will prove to be the most crucial in determining which of them could be chosen for more extensive development. The programme has progressed from establishing the scientific feasibility of wave energy converters to confirming the engineering feasibility of designing and building some of the designs . In very broad terms: -the early part of the programme placed considerable emphasis on optimising the efficiency of extraction of the wave energy and proving the scientific feasibility ; -the present stage is concerned with the technical viability and is identifying the main cost centres in the designs . which can then be tackled by further R and D; -the immediate future must also place emphasis not only on the problems of construction . operation and maintenance. and on ways in which unit costs may be reduced . but also on the ability to survive in the most severe wave conditions . Whilst the technical feasibility of some types of converter has been established, we are far from the stage of recommending that a full scale generating station should be built . Of the four original concepts. no single design has yet emerged which is outstandingly better than the other designs when all factors are taken into account . The designs have changed considerably in the course of the feasibility study. and a continuing process of evol ution can be expected as in the early stages of any technical development programme. The optimum design may emerge from further changes in one of the original concepts. from a synthesis of ideas or from an alternative concept . The wave energy is distributed over a wide frequency and energy bandwidth and no des ign has yet been optimised to operate at or near peak efficiency over the whole spectrum. However, one of the new concepts introduced into the programme recently may offer significant advantages in this respect. Supporting research The extent of the available data on waves in the sea areas of primary interest is inadequate as yet for the full assessment of the resource . A start has been made in collecting and analysing new data. which will take several years to reach a satisfactory level. The results so far confirm the general point that the locations around the United Kingdom with the most abundant wave energy lie to the west of the Outer Hebrides, where several hundred km of searoom are available with average annual power levels in the range 35-60 kW / m of wavefront. The majority of the designs un der consideration are free-floating and the converters would operate on or near the water surface-- one of the most hostile environments for engineering structures . The ult imate feasibility. technical and economic . of all designs of floating converter will depend upon extensive further work on mooring and anchoring . Whilst over-designed mooring systems based on present knowledge have allowed the open water trials to proceed with the objective of gaining experience . the existing knowledge is not adequate to design cost-effective mooring systems which will ensure survival at full scale under storm conditions . Considerable progress has been made in assessing and under3tanding suitable energy conversion and transmission systems for the various designs of converter , but much more remains to be done to arrive at the most cost-effective solutions . The general engineering difficulties are quite basic and are related to the properties of the natural wave spectrum : -the conversion system must be able to handle large short-term variations in the instantaneous power level ; -the peak power level in the sea (of the order of 10,OOO kW /m) can be many times greater than the average power level (a few tens of kW / m) ; -the primary output is not in a form which can be handled conventionally (it is . of course . variable with time in a complex way). Moreover. apart from the randomness. other general problems arise from the low energy density of the input and the relatively low speeds and frequency of movement induced by the waves . Engineering devices to transmit large amounts of energy under such conditions must themselves be large. heavy and expensive . The efficient generation of electricity requires machinery operating at relatively high and preferably constant speed . The transition from the one regime to the other appears to be more straightforward for systems involving air turbines than for those which do not: some designs of converter may prove to be intractable in this respect. Many possible forms of energy transmission to the mainland have been reviewed . as summarised in Chapter 6 . Whilst it has been recommended that several options should be kept open in the continuing studies it is likely that most attention will be given to electricity. The overall flow of energy from the waves to a final user connected to the electricity grid involves many separate steps . each of which can involve loss of some of the energy . This can have a considerable influence on the system economics and further work in this area will need to concentrate on both reducing the number of steps and increasing the efficiency (including the directional efficiency of t he converters themselves ) of those which must remain . Unless this can be achieved the usable resource will be only a small proportion of our needs : some pointers to substantial improvements are beginning to emerge. Environmental studies have not revealed any major detrimental effects of the converters provided they are well offshore. More information is needed on the behaviour of salmon and herring off the Outer Hebrides to confirm that the fisheries would not be affected significantly by the widespread installation of converters. Concluding remarks: The costing studies of the reference designs which have been evolved so far indicate that wave-produced electricity is likely to be expensive compared with either nuclear or fossil fuels unless some major breakthrough in the engineering can be achieved . However . this does not imply that the possibility of wave energy should be abandoned at this stage . It must be emphasised that the subject is still at a very ear ly state of development and many unknown factors remain to be resolved . Under these circumstances, wave energy is best regarded at present as a possible insurance technology- the consequences of failure of one of our existing major energy supplies are so severe that it is worth paying an insurance premium to explore fully the alternatives . Nevertheless. the evidence from the feasibility study so far does not allow a recommendation for a full-scale development programme to be made at this time . Much more can be achieved to explore and then to narrow the design choices by continuing work at about the 1 / 1 0th scale coupled with . on the one hand . limited trials of some critical components at larger scale and . on the other hand . f urther creative engineering on the drawing board and laboratory work in a new generation of wave tanks (of which the forerunner has been successfully commissioned at Edinburgh University). The programme has generated a broad basis of knowledge of all aspects of wave energy which did not exist before. so that we can now identify clearly the critical problems to be tackled by further work
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Exploring the Fast Ignition Approach to Fusion Energy
Probably the most famous equation in physics is Einstein's E=mc{sup 2}, which was contained within his fifth and final paper that was published in 1905. It is this relationship between energy ( E) and mass ( m) that the fusion process exploits to generate energy. When two isotopes of hydrogen (normally Deuterium and Tritium (DT)) fuse they form helium and a neutron. In this process some of the mass of the hydrogen is converted into energy. In the fast ignition approach to fusion a large driver (such as the NIF laser) is used to compress the DT fuel to extremely high densities and then is ''sparked'' by a high intensity, short-pulse laser. The short-pulse laser energy is converted to an electron beam, which then deposits its energy in the DT fuel. The energy of the electrons in this beam is so large that the electron's mass is increased according to Einstein theory of relativity. Understanding the transport of this relativistic electron beam is critical to the success of fast ignition and is the subject of this poster
Predictability and prediction skill of the boreal summer intraseasonal oscillation in the Intraseasonal Variability Hindcast Experiment
Acute health risks related to the presence of cyanogenic glycosides in raw apricot kernels and products derived from raw apricot kernels
Amygdalin is the major cyanogenic glycoside present in apricot kernels and is degraded to cyanide by chewing or grinding. Cyanide is of high acute toxicity in humans. The lethal dose is reported to be 0.5\u20133.5 mg/kg body weight (bw). An acute reference dose (ARfD) of 20 lg/kg bw was derived from an exposure of 0.105 mg/kg bw associated with a non-toxic blood cyanide level of 20 micro mol (lM), and applying an uncertainty factor of 1.5 to account for toxicokinetic and of 3.16 to account for toxicodynamic inter-individual differences. In the absence of consumption data and thus using highest intakes of kernels promoted (10 and 60 kernels/day for the general population and cancer patients, respectively), exposures exceeded the ARfD 17\u2013413 and 3\u201371 times in toddlers and adults, respectively. The estimated maximum quantity of apricot kernels (or raw apricot material) that can be consumed without exceeding the ARfD is 0.06 and 0.37 g in toddlers and adults, respectively. Thus the ARfD would be exceeded already by consumption of one small kernel in toddlers, while adults could consume three small kernels. However, consumption of less than half of a large kernel could already exceed the ARfD in adults
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