12,186 research outputs found
The 2D/3D dynamics of wall-bounded low-Rm magnetohydrodynamic (MHD) turbulence
No full textWith this experimental study, we give evidence that the dynamics of low-Rm MHD turbulence depends on the diffusion length l_z, which corresponds to the distance over which the Lorentz force is able to diffuse momentum before it is balanced by inertia
An overview of the effect of ageing on hand function
No full textEffective hand function involves many complex interrelated processes. Proprioceptive and sensory feedback mechanisms need to be complete, as well as sound hand to eye coordination. Intrinsic and extrinsic hand musculature needs to be well controlled before hand function can truly be smoothly coordinated and effective. In older people, there may be a decrease in hand function without evident trauma or disease. A natural decline in hand function is to be expected in the older population. However, this is not necessarily an irreversible loss – many of the conditions associated with loss of hand function are not a consequence of ageing so much as a consequence of inactivity. This article provides a critical review of the literature on the effect of the ageing process on hand function
Triangular Constellations in Flows
No full textParticles advected on the surface of a fluid can exhibit fractal clustering. The local structure of a fractal set is described by its dimension , which is the exponent of a power-law relating the mass in a ball to its radius : . It is desirable to characterise the {\em shapes} of constellations of points sampling a fractal measure, as well as their masses. The simplest example is the distribution of shapes of triangles formed by triplets of points, which we investigate for fractals generated by chaotic dynamical systems. The most significant parameter describing the triangle shape is the ratio of its area to the radius of gyration squared. We show that the probability density of has a phase transition: is independent of and approximately uniform below a critical flow compressibility , which we estimate. For the distribution appears to be described by two power laws: when , and when
Cooperatives and Contracting in Agriculture: The Case of West Liberty Foods, October 2005
No full textThe West Liberty Foods turkey cooperative was formed in 1996 to purchase the assets
and assume operations of Louis Rich Foods (an investor-owned processing rm), which, at
the time, announced the imminent shutdown of its West Liberty, Iowa, processing facility.
We study the creation and performance of this �new generation� cooperative using eld
interviews with grower members and company management. We describe changes, before
and after the buyout, in the contractual apparatus used for procuring live turkeys, and in
the communication requirements, work expectations, and nancial positions of growers.
During the private ownership period, most of the inputs (except labor and facilities) were
provided by the rm; there was substantial supervision of the growers' actions; growers
faced little price and production risk; and growers' equity was due largely to ownership of land and other farm assets. Our interviews reveal that, after cooperative formation,
growers were exposed to considerable additional risk; monitoring of growers by the rm
was less intensive; grower time and effort commitments to turkey production increased
substantially; and a signicant fraction of rm (cooperative) equity came from growers'
willingness to leverage their farm and personal assets (and hence indirectly their existing relationships with local lenders). We argue that some of these changes are consistent with a nancial contract where asset pledging and its corollary risk generate higher work effort by growers and a reduction in agency rents. These economies likely compensate for an organizational deadweight loss traditionally associated with cooperative governance
THE COMPLEXITY OF COMPUTING THE SIGN OF THE TUTTE POLYNOMIAL
Get PDF(c) 2014 Society for Industrial and Applied Mathematic
Exact two-dimensionalization of low-magnetic-Reynolds-number flows subject to a strong magnetic field
No full textWe investigate the behavior of flows, including turbulent flows, driven by a horizontal body-force and subject to a vertical magnetic field, with the following question in mind: for very strong applied magnetic field, is the flow mostly two-dimensional, with remaining weak three-dimensional fluctuations, or does it become exactly 2D, with no dependence along the vertical? We restrict attention to low-magnetic-Reynolds number (Rm) flow. Because liquid metals have low magnetic Prandtl number, such low- flows can have a kinetic Reynolds number as large as one million and therefore be strongly turbulent. We first focus on the quasi-static approximation, i.e. the asymptotic limit of vanishing magnetic Reynolds number Rm << 1: we prove that the flow becomes exactly 2D asymptotically in time, regardless of the initial condition and provided the interaction parameter N is larger than a threshold value. We call this property absolute two-dimensionalization: the attractor of the system is necessarily a (possibly turbulent) 2D flow. We then consider the full-magnetohydrodynamic equations and we prove that, for low enough Rm and large enough N, the flow becomes exactly two-dimensional in the long-time limit provided the initial vertically-dependent perturbations are infinitesimal. We call this phenomenon linear two-dimensionalization: the (possibly turbulent) 2D flow is an attractor of the dynamics, but it is not necessarily the only attractor of the system. Some 3D attractors may also exist and be attained for strong enough initial 3D perturbations. These results shed some light on the existence of a dissipative anomaly for magnetohydrodynamic flows subject to a strong external magnetic field
The Effect of the Adoption of Environmental Strategies on Green Product Development: A Study of Companies on World Sustainability Indices
No full textTo face the environmental sustainability challenge, a growing number of companies are shifting (or are planning to shift) toward more sustainability-oriented business models, adopting environmental strategies and developing green products. In this paper, we study the influence of the adoption of different environmental strategies on green product development and compare the behaviour of two samples of companies, assumed to have different levels of commitment towards sustainability: 255 companies listed in the Dow Jones Sustainability World Index and 255 in the Dow Jones Titans Indexes. These companies are worldwide located and belong to several industries. Data have been collected through the content analysis of companies' web-sites and documents, by means of specific keywords, and analyzed though regression. Results show that green product development cannot be conceived as a standing alone practice within companies, but it needs to be supported by environmental strategies. In particular, companies more committed to environmental sustainability develop green products through a comprehensive adoption of environmental strategies
The Decay of Wall Bounded MHD Turbulence at Low RM
No full textWe have developed a new spectral method to simulate flows with very fine boundary layers present. We apply it to calculate the evolution of freely decaying MHD turbulence between isolating walls. By comparison them with results obtained in fully periodic domain we quantify the influence of the channel walls on the character of freely decaying MHD turbulence
Superoxide, neuroleptics and ubiquinone and cytochrome b5 reductases in brain and lymphocytes from normals and schizophrenic patients
No full textThe effects of the neuroleptic flupenthixol on the expression of the genes coding for the mitochondrial ubiquinone and cytochrome b5 reductases have been studied because of the importance of these enzymes in energy metabolism, oxidative stress and also because similar but oppositely directed changes have been previously observed in the cerebral cortex from schizophrenics. The neuroleptic flupenthixol reduces the expression in rats of the gene coding for NADH-cytochrome b5 reductase as measured by in situ hybridisation and its enzymic manifestation. Flupenthixol also reduces the enzymic activity of the mitochondrial NADH-ubiquinone reductase, and it has been previously shown that mRNA from the mitochondrially coded parts of the enzyme are reduced by the drug. Both the cis- and therapeutically less active trans-flupenthixol were found to produce these changes in rats. Post-mortem brain tissue from schizophrenics who have received neuroleptic medication have reduced levels of both reductases as measured enzymically, Lymphocyte samples from schizophrenics also have reduced levels of both reductases compared with normals. The superoxide anion O2- is the principle agent of oxidative stress and both the cytochrome b5 and the ubiquinone reductase enzymes were semi-purified from sheep liver and shown to produce appreciable amounts of superoxide. Superoxide production is reduced in brain homogenates from rats treated with flupenthixol. Its production is also reduced in brain tissue and lymphocytes from schizophrenics receiving neuroleptic medication. We conclude that neuroleptic medication reduces the expression of both the ubiquinone and cytochrome b5 reductase and among the effects of this reduction is a decrease in the production of neurotoxic superoxid
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