888 research outputs found
Incorporation of Traffic Collision Alert System (TCAS) Advisories on Heads-up Displays: Enhanced Pilot Response
This study evaluated the effects that heads-up mounted TCAS displays had on pilot response and workload. Pilot response was evaluated by: (a) response time to a traffic advisory, and (b) number of missed traffic alerts. Workload assessment was accomplished in accordance with NASA\u27s Task Load Index (TLX). Subjects were all licensed pilots with a minimum of a private pilot license and an instrument rating. A total of 32 subjects were randomly assigned to experimental and control groups utilizing HUD-mounted, and conventional, TCAS displays respectively. Performance data was collected during computer-simulated flights, while subjective workload levels were reported at the end. It was found that HUD-mounted TCAS displays yielded better performance results (p=0.05), while resulting in significantly less workload
Feedback control architecture & the bacterial chemotaxis network
Bacteria move towards favourable and away from toxic environments by changing their swimming pattern. This response is regulated by the chemotaxis signalling pathway, which has an important feature: it uses feedback to βresetβ (adapt) the bacterial sensing ability, which allows the bacteria to sense a range of background environmental changes. The role of this feedback has been studied extensively in the simple chemotaxis pathway of Escherichia coli. However it has been recently found that the majority of bacteria have multiple chemotaxis homologues of the E. coli proteins, resulting in more complex pathways. In this paper we investigate the configuration and role of feedback in Rhodobacter sphaeroides, a bacterium containing multiple homologues of the chemotaxis proteins found in E. coli. Multiple proteins could produce different possible feedback configurations, each having different chemotactic performance qualities and levels of robustness to variations and uncertainties in biological parameters and to intracellular noise. We develop four models corresponding to different feedback configurations. Using a series of carefully designed experiments we discriminate between these models and invalidate three of them. When these models are examined in terms of robustness to noise and parametric uncertainties, we find that the non-invalidated model is superior to the others. Moreover, it has a βcascade controlβ feedback architecture which is used extensively in engineering to improve system performance, including robustness. Given that the majority of bacteria are known to have multiple chemotaxis pathways, in this paper we show that some feedback architectures allow them to have better performance than others. In particular, cascade control may be an important feature in achieving robust functionality in more complex signalling pathways and in improving their performance
Full control of the spin-wave damping in a magnetic insulator using spin-orbit torque
Hamadeh, A. et al.Β© 2014 American Physical Society. It is demonstrated that the threshold current for damping compensation can be reached in a 5ββΞΌm diameter YIG(20ββnm)|Pt(7ββnm) disk. The demonstration rests upon the measurement of the ferromagnetic resonance linewidth as a function of Idc using a magnetic resonance force microscope (MRFM). It is shown that the magnetic losses of spin-wave modes existing in the magnetic insulator can be reduced or enhanced by at least a factor of 5 depending on the polarity and intensity of an in-plane dc current Idc flowing through the adjacent normal metal with strong spin-orbit interaction. Complete compensation of the damping of the fundamental mode by spin-orbit torque is reached for a current density of βΌ3Γ1011ββAβ
mβ2, in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime.This research was supported by the French Grants Trinidad (ASTRID 2012 program), by the RTRA Triangle de la Physique grant Spinoscopy, and by the Deutsche Forschungsgemeinschaft. S.βO.βD. and V.βV.βN. acknowledges respectively support from the Russian programs Megagrant No. 2013-220-04-329 and competitive growth of KFU.Peer Reviewe
Quantitative MRFM characterization of the autonomous and forced dynamics in a spin transfer nano-oscillator
Using a magnetic resonance force microscope (MRFM), the power emitted by a
spin transfer nano-oscillator consisting of a normally magnetized PyCuPy
circular nanopillar is measured both in the autonomous and forced regimes. From
the power behavior in the subcritical region of the autonomous dynamics, one
obtains a quantitative measurement of the threshold current and of the noise
level. Their field dependence directly yields both the spin torque efficiency
acting on the thin layer and the nature of the mode which first
auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. From
the MRFM behavior in the forced dynamics, it is then demonstrated that in order
to phase-lock this auto-oscillating mode, the external source must have the
same spatial symmetry as the mode profile, i.e., a uniform microwave field must
be used rather than a microwave current flowing through the nanopillar
One Universal Common Endpoint in Mouse Models of Amyotrophic Lateral Sclerosis
There is no consensus among research laboratories around the world on the criteria that define endpoint in studies involving rodent models of amyotrophic lateral sclerosis (ALS). Data from 4 nutrition intervention studies using 162 G93A mice, a model of ALS, were analyzed to determine if differences exist between the following endpoint criteria: CS 4 (functional paralysis of both hindlimbs), CS 4+ (CS 4 in addition to the earliest age of body weight loss, body condition deterioration or righting reflex), and CS 5 (CS 4 plus righting reflex >20 s). The age (d; mean Β± SD) at which mice reached endpoint was recorded as the unit of measurement. Mice reached CS 4 at 123.9Β±10.3 d, CS 4+ at 126.6Β±9.8 d and CS 5 at 127.6Β±9.8 d, all significantly different from each other (P<0.001). There was a significant positive correlation between CS 4 and CS 5 (rβ=β0.95, P<0.001), CS 4 and CS 4+ (rβ=β0.96, P<0.001), and CS 4+ and CS 5 (rβ=β0.98, P<0.001), with the Bland-Altman plot showing an acceptable bias between all endpoints. Logrank tests showed that mice reached CS 4 24% and 34% faster than CS 4+ (Pβ=β0.046) and CS 5 (Pβ=β0.006), respectively. Adopting CS 4 as endpoint would spare a mouse an average of 4 days (P<0.001) from further neuromuscular disability and poor quality of life compared to CS 5. Alternatively, CS 5 provides information regarding proprioception and severe motor neuron death, both could be important parameters in establishing the efficacy of specific treatments. Converging ethics and discovery, would adopting CS 4 as endpoint compromise the acquisition of insight about the effects of interventions in animal models of ALS
Robust synchronization in networks of cyclic feedback systems
This paper presents a result on the robust synchronization of outputs of statically interconnected non-identical cyclic feedback systems that are used to model, among other processes, gene expression. The result uses incremental versions of the small gain theorem and dissipativity theory to arrive at an upper bound on the norm of the synchronization error between corresponding states, giving a measure of the degree of convergence of the solutions. This error bound is shown to be a function of the difference between the parameters of the interconnected systems, and disappears in the case where the systems are identical, thus retrieving an earlier synchronization result
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The effect of endurance exercise on both skeletal muscle and systemic oxidative stress in previously sedentary obese men
Background: Obesity is associated with low-grade systemic inflammation, in part because of secretion of proinflammatory cytokines, resulting into peripheral insulin resistance (IR). Increased oxidative stress is proposed to link adiposity and chronic inflammation. The effects of endurance exercise in modulating these outcomes in insulin-resistant obese adults remain unclear. We investigated the effect of endurance exercise on markers of oxidative damage (4-hydroxy-2-nonenal (4-HNE), protein carbonyls (PCs)) and antioxidant enzymes (superoxide dismutase (SOD), catalase) in skeletal muscle; urinary markers of oxidative stress (8-hydroxy-2-deoxyguanosine (8-OHdG), 8-isoprostane); and plasma cytokines (C-reactive protein (CRP), interleukin-6 (IL-6), leptin, adiponectin). Methods: Age- and fitness-matched sedentary obese and lean men (n=9 per group) underwent 3 months of moderate-intensity endurance cycling training with a vastus lateralis biopsy, 24-h urine sample and venous blood samples taken before and after the intervention. Results: Obese subjects had increased levels of oxidative damage: 4-HNE (+37% Pβ©½0.03) and PC (+63% Pβ©½0.02); evidence of increased adaptive response to oxidative stress because of elevated levels of copper/zinc SOD (Cu/ZnSOD) protein content (+84% Pβ©½0.01); increased markers of inflammation: CRP (+737% Pβ©½0.0001) and IL-6 (+85% Pβ©½0.03), and these correlated with increased markers of obesity; and increased leptin (+262% Pβ©½0.0001) with lower adiponectin (β27% Pβ©½0.01) levels vs lean controls. Training reduced 4-HNE (β10% Pβ©½0.04), PC (β21% Pβ©½0.05), 8-isoprostane (β26% Pβ©½0.02) and leptin levels (β33% Pβ©½0.01); had a tendency to decrease IL-6 levels (β21% P=0.07) and IR (β17% P=0.10); and increased manganese SOD (MnSOD) levels (+47% Pβ©½0.01). Conclusion: Endurance exercise reduced skeletal muscle-specific and systemic oxidative damage while improving IR and cytokine profile associated with obesity, independent of weight loss. Hence, exercise is a useful therapeutic modality to reduce risk factors associated with the pathogenesis of IR in obesity
Resonant excitation of vortex gyrotropic mode via surface acoustic waves
Finding new energy-efficient methods for exciting magnetization dynamics is
one of the key challenges in magnonics. In this work, we present an approach to
excite the gyrotropic dynamics of magnetic vortices through the phenomenon of
inverse magnetostriction, also known as the Villari effect. We develop an
analytical model based on the Thiele formalism that describes the gyrotropic
motion of the vortex core including the energy contributions due to inverse
magnetostriction. Based on this model, we predict excitations of the vortex
core resonances by surface acoustic waves whose frequency is resonant with the
frequency of the vortex core. We verify the model's prediction using
micromagnetic simulations, and show the dependence of the vortex core's
oscillation radius on the surface acoustic wave amplitude and the static bias
field. Our study contributes to the advancement of energy-efficient magnetic
excitations by relying on voltage-induced driven dynamics, which is an
alternative to conventional current-induced excitations
Evaluation of androgenic activity of allium cepa on spermatogenesis in the rat
Allium cepa (onion) has a beneficial effect on disease treatment worldwide
and has been used since ancient times as a medicinal and food source. Recently
several reports have shown that onion has high antioxidant activity. As antioxidants
have an essential effect on sperm health parameters, we investigated
the effect of the fresh juice of onion bulbs on the spermatogenesis cycle in rats.
Wistar male rats (n = 30) were allocated into 3 groups, control (n = 10) and
two test groups (each of 10). The animals in the test groups were subdivided
into groups of 2 that received fresh onion juice equivalent to 0.5 and 1 g/rat/
/day of fresh onion. The fresh onion juice was administered by gavage for
20 consecutive days. The animals were kept in standard conditions. On the
twentieth day, the testes of rats in all groups were removed and sperm was
collected from the epididymis and was prepared for analysis.
Serum total testosterone significantly increased in all the test groups (p < 0.05),
and levels of LH significantly increased only in the group that received the high
dose of fresh onion juice (p < 0.05), but the level of FSH did not differ between
the experimental and control groups. The percentage of sperm viability and
motility in both test groups significantly increased (p < 0.05), but the sperm
concentration significantly increased only in the group that received the high
dose of freshly extracted onion juice (p < 0.05). It was evident that there was
no difference on sperm morphology and testis weight in test groups compared
to the control group.
In our study, freshly prepared onion juice significantly affected the sperm number,
percentage of viability, and motility; it seems that using 4 g/kg of freshly
prepared onion juice is effective in sperm health parameters
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