Existence Of The Magnetorotational Instability

By posing and solving a global axisymmetric eigenvalue problem on an infinite domain with modes vanishing at zero and infinity for a differentially rotating MHD plasma, the conditions for the occurrence of a purely growing low-frequency mode known as the magnetorotational instability (MRI) are mapped. It is shown that the MRI criterion drawn from the "local dispersion relation" is at best inadequate and may even be misleading. The physics of the MRI is rather nuanced. It is dictated by the details of the radial profile of the rotation velocity Omega(r) and not just by the sign and the magnitude of its gradient, Omega'. The salient features of the class of profiles for which the MRI-like eigenmodes may occur are given along with the eigenspectrum. For a variety of other profiles, it is shown that an unstable magnetorotational mode is not a valid eigensolution.Institute for Fusion Studie

Modeling of short scale turbulence in the solar wind

The solar wind serves as a laboratory for investigating magnetohydrodynamic turbulence under conditions irreproducible on the terra firma. Here we show that the frame work of Hall magnetohydrodynamics (HMHD), which can support three quadratic invariants and allows nonlinear states to depart fundamentally from the Alfv&#233;nic, is capable of reproducing in the inertial range the three branches of the observed solar wind magnetic fluctuation spectrum - the Kolmogorov branch <i>f</i>^-5/3 steepening to <i>f</i>^-&alpha;₁ with <!-- MATH $alpha_1{simeq}3{-}4$ --> <IMG WIDTH='61' HEIGHT='29' ALIGN='MIDDLE' BORDER='0' src='http://www.nonlin-processes-geophys.net/12/75/2005/npg-12-75-img3.gif' ALT='$alpha_1{simeq}3{-}4$'> on the high frequency side and flattening to <i>f</i>^-1 on the low frequency side. These fluctuations are found to be associated with the nonlinear Hall-MHD Shear Alfv&#233;n waves. The spectrum of the concomitant whistler type fluctuations is very different from the observed one. Perhaps the relatively stronger damping of the whistler fluctuations may cause their unobservability. The issue of equipartition of energy through the so called Alfv&#233;n ratio acquires a new status through its dependence, now, on the spatial scale

Computer aided FEA simulation of EN45A parabolic leaf spring

This paper describes computer aided finite element analysis of parabolic leaf spring. The present work is an improvement in design of EN45A parabolic leaf spring used by a light commercial automotive vehicle. Development of a leaf spring is a long process which requires lots of test to validate the design and manufacturing variables. A three-layer parabolic leaf spring of EN45A has been taken for this work. The thickness of leaves varies from center to the outer side following a parabolic pattern. These leaf springs are designed to become lighter, but also provide a much improved ride to the vehicle through a reduction on interleaf friction. The CAD modeling of parabolic leaf spring has been done in CATIA V5 and for analysis the model is imported in ANSYS-11 workbench. The finite element analysis (FEA) of the leaf spring has been carried out by initially discretizing the model into finite number of elements and nodes and then applying the necessary boundary conditions. Maximum displacement, directional displacement, equivalent stress and weight of the assembly are the output targets of this analysis for comparison & validation of the work

Evaluation of Power Management Strategy for Renewable Microgrid System

This paper presents the evaluation and control of renewable energy sources based micro-grid system having solar photovoltaic, wind turbine generator, fuel cell and diesel engine generator. A battery storage system has also been installed to provide unintrupted power supply and to store excess power. The proposed micro-grid system is simulated on Matlab/Simulink software and the performance has been analysied with two cases considering different environmental conditions to check the optimal performance of the system. In the first case, the solar photovoltaic, fuel cell, diesel engine generator and battery storage system has been considered and in the second case, the solar photovoltaic source is replaced by the wind turbines. For both the cases, simulation has been done for 300 seconds to findout the optimal fulfilment of the demand. The time domain analysis has been done by varying the solar irradiance and wind speed in respective cases to check the system performance. This work shows the efficient control of various distributed energy resources in the micro-grid system and meeting the load demand efficiently

The Gravity of Entrepreneurs’ Network Ties on the growth of the Business in Sri Lanka

Using the business performances of the firm we investigated how network ties (NT) interfere to obtain business growth in Sri Lankan context. As NT consist of two constructs which are social NT and business NT, this study aims to what extent both constructs engaged to the growth of the business in distinctly. It was mainly hypothesized that entrepreneurs who have high NT could perform more than others who engaged with lack of NT in same context.  Finally results confirmed that NT has a positive impact on business growth. However, results indicated that business NT has significant influence on business growth than social NT. The results of the study have important implications to the existing entrepreneurs, potential entrepreneurs, investors, researchers, consultants and policy makers. Keywords: Network Ties, Social Network Ties, Business Network Ties, Business Performanc

Reversible plasticity in amorphous materials

A fundamental assumption in our understanding of material rheology is that when microscopic deformations are reversible, the material responds elastically to external loads. Plasticity, i.e. dissipative and irreversible macroscopic changes in a material, is assumed to be the consequence of irreversible microscopic events. Here we show direct evidence for reversible plastic events at the microscopic scale in both experiments and simulations of two-dimensional foam. In the simulations, we demonstrate a link between reversible plastic rearrangement events and pathways in the potential energy landscape of the system. These findings represent a fundamental change in our understanding of materials--microscopic reversibility does not necessarily imply elasticity.Comment: Revised pape

Glucose lowering strategies with insulin

open access journalPeople with type 1 diabetes must use insulin and a large fraction of those with type 2 condition also do so. Many therefore struggle with the unpredictable balancing of insulin dose with calorie intake and utility. A healthy pancreas makes meticulous adjustment on a continuous basis that present therapeutic insulin administration cannot match. However, much progress has been made to make it simpler to inject both background and fast-acting boost insulins with a view to better mimicking normal pancreatic output. The present fast insulins are reviewed with accent on the primary amino acid structures of the biosynthetic types that diffuse more quickly than regular insulin that associates in hexamers. This makes boost doses kinetically and clinically more effective, allowing people to inject better estimated boost and corrective doses. Formulation advances are discussed for their present and potential contributions. The newer slow-acting insulins are also described and compared, their advantage also being kinetic with a lower likelihood of inducing overnight hypoglycaemia when used optimally. Finally, the appreciation of the advantages of alternative routes of administration such as oral and peritoneal are included in this review because of the possibility of altering the hepatic to peripheral ratio, the reasons for which are more effective but less obesogenic insulin activity. The logistics of oral insulin are summarised in terms of the risks to the insulin structure, the facilitation of paracellular uptake at the apical surface and the paradoxically advantageous hepatic first pass. Other non-invasive routes are also included in the review

What is the origin of pancreatic adenocarcinoma?

The concept of pancreatic cancer origin is controversial. Acinar, ductal or islet cells have been hypothesized as the cell of origin. The pros and cons of each of these hypotheses are discussed. Based on the world literature and recent observations, pancreatic cells seem to have potential for phenotypical transdifferentiation, i.e ductal-islet, ductal-acinar, acinar-ductal, acinar-islet, islet-acinar and islet-ductal cells. Although the possibility is discussed that cancer may arise from either islet, ductal or acinar cells, the circumstances favoring the islet cells as the tumor cell origin include their greater transdifferentiation potency into both pancreatic and extrapancreatic cells, the presence of a variety of carcinogen-metabolizing enzymes, some of which are present exclusively in islet cells and the growth factor-rich environment of islets