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Biological fieldwork provision in higher education
Fieldwork is regarded as an important component of many bioscience degree programmes. QAA benchmarks statements refer explicitly to the importance of fieldwork, although give no indication of amounts of field provision expected. Previous research has highlighted the importance of fieldwork to the learning of both subject-specific and transferable skills. However, it is unclear how the amount and type of fieldwork currently offered is being affected by the recent expansion in student numbers and current funding constraints. Here we review contemporary literature and report on the results of a questionnaire completed by bioscience tutors across 33 UK institutions. The results suggest, perhaps contrary to anecdotal evidence, that the amount of fieldwork being undertaken by students is not in decline and that on the whole, programmes contain reasonable amounts of fieldwork. The majority of programmes involved UK-based fieldwork, but a number of programmes also offered ‘exotic’ overseas fieldwork which was considered important in terms of student recruitment as well as exposing students to a diversity of field learning environments. Tutors were very clear about the benefits of fieldwork and the need to be proactive to maintain its provision
On the giant magnon and spike solutions for strings on AdS S
We study solutions for the rotating strings on the sphere with a background
NS-NS field and on the Anti-de-Sitter spacetime. We show the existence of
magnon and single spike solutions on RS in the presence of constant
magnetic field as two limiting cases. We also study the solution for strings on
AdS S with Melvin deformation. The dispersion relations among
various conserved charges are shown to receive finite corrections due to the
deformation parameter. We further study the rotating string on AdS
S geometry with two conserved angular momenta on S and one spin along
the AdS. We show that there exists two kinds of solutions: a circular
string solution and a helical string. We find out the dispersion relation among
various charges and give physical interpretation of these solutions.Comment: 18 pages, 1 figure, typos fixed, minor changes, to appear in JHE
Finite element solution of low bond number sloshing
The dynamics of liquid propellant in a low Bond number environment which are critical to the design of spacecraft systems with respect to orbital propellant transfer and attitude control system were investigated. Digital computer programs were developed for the determination of liquid free surface equilibrium shape, lateral slosh natural vibration mode shapes, and frequencies for a liquid in a container of arbitrary axisymmetric shape with surface tension forces the same order of magnitude as acceleration forces. A finite volume element representation of the liquid was used for the vibration analysis. The liquid free surface equilibrium shapes were computed for several tanks at various contact angles and ullage volumes. A configuration was selected for vibration analysis and lateral slosh mode shapes and natural frequencies were obtained. Results are documented
Effect of wind turbine generator model and siting on wind power changes out of large WECS arrays
Methods of reducing the WECS generation change through selection of the wind turbine model for each site, selection of an appropriate siting configuration, and wind array controls are discussed. An analysis of wind generation change from an echelon and a farm for passage of a thunderstorm is presented. Reduction of the wind generation change over ten minutes is shown to reduce the increase in spinning reserve, unloadable generation and load following requirements on unit commitment when significant WECS generation is present and the farm penetration constraint is satisfied. Controls on the blade pitch angle of all wind turbines in an array or a battery control are shown to reduce both the wind generation change out of an array and the effective farm penetration in anticipation of a storm so that the farm penetration constraint may be satisfied
Enhancing the conductance of a two-electron nanomechanical oscillator
We consider electron transport through a mobile island (i.e., a
nanomechanical oscillator) which can accommodate one or two excess electrons
and show that, in contrast to immobile islands, the Coulomb blockade peaks,
associated with the first and second electrons entering the island, have
different functional dependences on the nano-oscillator parameters when the
island coupling to its leads is asymmetric. In particular, the conductance for
the second electron (i.e., when the island is already charged) is greatly
enhanced in comparison to the conductance of the first electron in the presence
of an external electric field. We also analyze the temperature dependence of
the two conduction peaks and show that these exhibit different functional
behaviors.Comment: 16 pages, 5 figure
Reduction of leukocyte microvascular adherence and preservation of blood-brain barrier function by superoxide-lowering therapies in a piglet model of neonatal asphyxia
Background: Asphyxia is the most common cause of brain damage in newborns. Substantial evidence indicates that leukocyte recruitment in the cerebral vasculature during asphyxia contributes to this damage. We tested the hypothesis that superoxide radical (O2⋅_) promotes an acute post-asphyxial inflammatory response and blood-brain barrier (BBB) breakdown. We investigated the effects of removing O2⋅_ by superoxide dismutase (SOD) or C3, the cell-permeable SOD mimetic, in protecting against asphyxia-related leukocyte recruitment. We also tested the hypothesis that xanthine oxidase activity is one source of this radical.Methods: Anesthetized piglets were tracheostomized, ventilated, and equipped with closed cranial windows for the assessment of post-asphyxial rhodamine 6G-labeled leukocyte-endothelial adherence and microvascular permeability to sodium fluorescein in cortical venules. Asphyxia was induced by discontinuing ventilation. SOD and C3 were administered by cortical superfusion. The xanthine oxidase inhibitor oxypurinol was administered intravenously.Results: Leukocyte-venular adherence significantly increased during the initial 2 h of post-asphyxial reperfusion. BBB permeability was also elevated relative to non-asphyxial controls. Inhibition of O2⋅_ production by oxypurinol, or elimination of O2⋅_ by SOD or C3, significantly reduced rhodamine 6G-labeled leukocyte-endothelial adherence and improved BBB integrity, as measured by sodium fluorescein leak from cerebral microvessels.Conclusion: Using three different strategies to either prevent formation or enhance elimination of O2⋅_ during the post-asphyxial period, we saw both reduced leukocyte adherence and preserved BBB function with treatment. These findings suggest that agents which lower O2⋅_ in brain may be attractive new therapeutic interventions for the protection of the neonatal brain following asphyxia
Reconstructing a pure state of a spin s through three Stern-Gerlach measurements: II
The density matrix of a spin s is fixed uniquely if the probabilities to obtain the value s upon measuring n.S are known for 4s(s+1) appropriately chosen directions n in space. These numbers are just the expectation values of the density operator in coherent spin states, and they can be determined in an experiment carried out with a Stern-Gerlach apparatus. Furthermore, the experimental data can be inverted providing thus a parametrization of the statistical operator by 4s(s+1) positive parameters
New Generation of Massless Dirac Fermions in Graphene under External Periodic Potentials
We show that new massless Dirac fermions are generated when a slowly varying
periodic potential is applied to graphene. These quasiparticles, generated near
the supercell Brillouin zone boundaries with anisotropic group velocity, are
different from the original massless Dirac fermions. The quasiparticle
wavevector (measured from the new Dirac point), the generalized pseudospin
vector, and the group velocity are not collinear. We further show that with an
appropriate periodic potential of triangular symmetry, there exists an energy
window over which the only available states are these quasiparticles, thus,
providing a good system to probe experimentally the new massless Dirac
fermions. The required parameters of external potentials are within the realm
of laboratory conditions.Comment: 4 pages, 4 figure
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