12,039 research outputs found
Performance of a steel spar wind turbine blade on the Mod-0 100 kW experimental wind turbine
The performance and loading of a large wind rotor, 38.4 m in diameter and composed of two low-cost steel spar blades were examined. Two blades were fabricated at Lewis Research Center and successfully operated on the Mod-0 wind turbine at Plum Brook. The blades were operated on a tower on which the natural bending frequency were altered by placing the tower on a leaf-spring apparatus. It was found that neither blade performance nor loading were affected significantly by this tower softening technique. Rotor performance exceeded prediction while blade loads were found to be in reasonable agreement with those predicted. Seventy-five hours of operation over a five month period resulted in no deterioration in the blade
Evolutionary Divergence in Developmental Strategies and Neuromodulatory Control Systems of Two Amphibian Locomotor Networks
Attempts to understand the neural mechanisms which produce behaviour must consider both prevailing sensory cues and the central cellular and synaptic changes they direct. At each level, neuromodulation can additionally shape the final output. We have investigated neuromodulation in the developing spinal motor networks in hatchling tadpoles of two closely related amphibians, Xenopus laevis and Rana temporaria to examine the subtle differences in their behaviours that could be attributed to their evolutionary divergence.
At the point of hatching, both species can swim in response to a mechanosensory stimulus, however Rana embryos often display a more forceful, non-locomotory coiling behaviour. Whilst the synaptic drive that underlies these behaviours appears similar, subtle inter-specific differences in neuronal properties shape motor outputs in different ways. For example, Rana neurons express N-methyl-D-aspartate (NMDA)/serotonin (5-HT)-dependent oscillations, not present in hatchling Xenopus and many also exhibit a prominent slow spike after-hyperpolarisation. Such properties may endow the spinal circuitry of Rana with the ability to produce a more flexible range of outputs.
Finally, we compare the roles of the neuromodulators 5-HT, noradrenaline (NA) and nitric oxide (NO) in shaping motor outputs. 5-HT increases burst durations during swimming in both Xenopus and Rana, but 5-HT dramatically slows the cycle period in Rana with little effect in Xenopus. Three distinct, but presumably homologous NO-containing brainstem clusters of neurons have been described, yet the effects of NO differ between species. In Xenopus, NO slows and shortens swimming in a manner similar to NA, yet in Rana NO and NA elicit the non-rhythmic coiling pattern
Innovative Hybridisation of Genetic Algorithms and Neural Networks in Detecting Marker Genes for Leukaemia Cancer
Methods for extracting marker genes that trigger the growth
of cancerous cells from a high level of complexity microarrays are of much interest from the computing community. Through the identified genes, the pathology of cancerous cells can be revealed and early precaution
can be taken to prevent further proliferation of cancerous cells. In this paper, we propose an innovative hybridised gene identification framework based on genetic algorithms and neural networks to identify marker genes for leukaemia disease. Our approach confirms that high classification
accuracy does not ensure the optimal set of genes have been identified and our model delivers a more promising set of genes even with a lower classification accurac
One-Loop Anomaly Mediated Scalar Masses and (g-2)_mu in Pure Gravity Mediation
We consider the effects of non-universalities among sfermion generations in
models of Pure Gravity Mediation (PGM). In PGM models and in many models with
strongly stabilized moduli, the gravitino mass may be O(100) TeV, whereas
gaugino masses, generated through anomalies at 1-loop, remain relatively light
O(1) TeV. In models with scalar mass universality, input scalar masses are
generally very heavy (m_0 \simeq m_{3/2}) resulting in a mass spectrum
resembling that in split supersymmetry. However, if one adopts a no-scale or
partial no-scale structure for the K\"ahler manifold, sfermion masses may
vanish at the tree level. It is usually assumed that the leading order anomaly
mediated contribution to scalar masses appears at 2-loops. However, there are
at least two possible sources for 1-loop scalar masses. These may arise if
Pauli-Villars fields are introduced as messengers of supersymmetry breaking. We
consider the consequences of a spectrum in which the scalar masses associated
with the third generation are heavy (order m_{3/2}) with 1-loop scalar masses
for the first two generations. A similar spectrum is expected to arise in GUT
models based on E_7/SO(10) where the first two generations of scalars act as
pseudo-Nambu-Goldstone bosons. Explicit breaking of this symmetry by the gauge
couplings then generates one-loop masses for the first two generations. In
particular, we show that it may be possible to reconcile the g_mu - 2
discrepancy with potentially observable scalars and gauginos at the LHC.Comment: 30 pages, 30 figure
Dynamical excitations in the collision of 2D Bose-Einstein condensates
We carry out simulations of the collision of two components of an
adiabatically divided, quasi-2D BEC. We identify under, over and critically
damped regimes in the dipole oscillations of the components according to the
balance of internal and centre-of-mass (c.m.) energies of the components and
investigate the creation of internal excitations. We distinguish the behaviour
of this system from previous studies of quasi-1D BEC's. In particular we note
that the nature of the internal excitations is only essentially sensitive to an
initial phase difference between the components in the overdamped regime.Comment: 17 pages, 9 figure
Prospects for Detecting Supersymmetric Dark Matter at Post-LEP Benchmark Points
A new set of supersymmetric benchmark scenarios has recently been proposed in
the context of the constrained MSSM (CMSSM) with universal soft
supersymmetry-breaking masses, taking into account the constraints from LEP, and . These points have previously been used to
discuss the physics reaches of different accelerators. In this paper, we
discuss the prospects for discovering supersymmetric dark matter in these
scenarios. We consider direct detection through spin-independent and
spin-dependent nuclear scattering, as well as indirect detection through relic
annihilations to neutrinos, photons, and positrons. We find that several of the
benchmark scenarios offer good prospects for direct detection via
spin-independent nuclear scattering and indirect detection via muons produced
by neutrinos from relic annihilations inside the Sun, and some models offer
good prospects for detecting photons from relic annihilations in the galactic
centre.Comment: 24 pages, 14 figure
Supersymmetric Dark Matter Detection at Post-LEP Benchmark Points
We review the prospects for discovering supersymmetric dark matter in a
recently proposed set of post-LEP supersymmetric benchmark scenarios. We
consider direct detection through spin-independent nuclear scattering, as well
as indirect detection through relic annihilations to neutrinos, photons, and
positrons. We find that several of the benchmark scenarios offer good prospects
for direct detection through spin-independent nuclear scattering, as well as
indirect detection through muons produced by neutrinos from relic annihilations
in the Sun, and photons from annihilations in the galactic center.Comment: 4 pages, 3 figures, uses RevTeX4, contribution to Snowmass 200
Production of 21 Ne in depth-profiled olivine from a 54 Ma basalt sequence, Eastern Highlands (37° S), Australia
In this study we investigate the cosmogenic neon component in olivine samples from a vertical profile in order to quantify muogenic 21Ne production in this mineral. Samples were collected from an 11 m thick Eocene basalt profile in the Eastern Highlands of southeastern Australia. An eruption age of 54.15 ± 0.36 Ma (2σ) was determined from 40Ar/39Ar step-heating experiments (n = 6) on three whole-rock samples. A 36Cl profile on the section indicated an apparent steady state erosion rate of 4.7 ± 0.5 m Ma−1. The eruption age was used to calculate in situ produced radiogenic 4He and nucleogenic 3He and 21Ne concentrations in olivine. Olivine mineral separates (n = 4), extracted from the upper two metres of the studied profile, reveal cosmogenic 21Ne concentrations that attenuate exponentially with depth. However, olivine (Fo68) extracted from below 2 m does not contain discernible 21Ne aside from magmatic and nucleogenic components, with the exception of one sample that apparently contained equal proportions of nucleogenic and muogenic neon. Modelling results suggest a muogenic neon sea-level high-latitude production rate of 0.02 ± 0.04 to 0.9 ± 1.3 atoms g−1 a−1 (1σ), or <2.5% of spallogenic cosmogenic 21Ne production at Earth’s surface. These data support a key implicit assumption in the literature that accumulation of muogenic 21Ne in olivine in surface samples is likely to be negligible/minimal compared to spallogenic 21Ne
Oxidative Stress Response to Short Duration Bout of Submaximal Aerobic Exercise in Healthy Young Adults
The purpose of this study was to investigate the oxidative stress response to a short duration bout of submaximal exercise in a cohort of healthy young adults. 15 apparently healthy college age males and females completed a modified Bruce-protocol treadmill test to 75–80% of their heart rate reserve. Blood samples collected immediately before (pre-exercise), immediately after, 30, 60 and 120 minutes post-exercise were assayed for total antioxidant capacity (TAC), superoxide disumutase (SOD), thiobarbituric acid-reactive substances (TBARS), and protein carbonyls (PC). SOD activity was significantly increased from pre-exercise levels at 30 minutes (77%), 60 minutes (33%), and 120 minutes (37%) post-exercise. TAC levels were also significantly increased from pre-exercise levels at 60 minutes (30%) and 120 minutes (33%) post-exercise. There were no significant changes in biomarkers for reactive oxygen/nitrogen species (RONS) mediated damage (TBARS and PC) across all post-exercise time points. In a cohort of healthy young adults, a short duration bout of submaximal aerobic exercise elicited increases in antioxidant activity/concentration, but did not evoke changes in oxidative stress-induced damage. These results may suggest that: (1) short duration bouts of submaximal aerobic exercise are sufficient to induce RONS generation; and (2) the antioxidant defense system is capable of protecting against enhanced RONS production induced by a short duration, submaximal exercise bout in healthy young adults
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