Dynamic critical behavior of failure and plastic deformation in the random fiber bundle model

The random fiber bundle (RFB) model, with the strength of the fibers distributed uniformly within a finite interval, is studied under the assumption of global load sharing among all unbroken fibers of the bundle. At any fixed value of the applied stress (load per fiber initially present in the bundle), the fraction of fibers that remain unbroken at successive time steps is shown to follow simple recurrence relations. The model is found to have stable fixed point for applied stress in the range 0 and 1; beyond which total failure of the bundle takes place discontinuously. The dynamic critical behavior near this failure point has been studied for this model analysing the recurrence relations. We also investigated the finite size scaling behavior. At the critical point one finds strict power law decay (with time t) of the fraction of unbroken fibers. The avalanche size distribution for this mean-field dynamics of failure has been studied. The elastic response of the RFB model has also been studied analytically for a specific probability distribution of fiber strengths, where the bundle shows plastic behavior before complete failure, following an initial linear response.Comment: 13 pages, 5 figures, extensively revised and accepted for publication in Phys. Rev.

Exploring the Involvement of the Alternative Respiratory Pathway in Pisum sativum L. Seed Germination

Proceeding PaperOrganic agriculture, recognized as a more sustainable agricultural system, strongly de-pends on the use of highly resilient genotypes. Resilient seeds, with increased tolerance to germinate and provide vigorous seedlings under environmental stresses, currently represent one of the most important agronomical traits. Seed germination involves the activation of several metabolic path-ways, including cellular respiration. Alternative oxidase (AOX), a key enzyme in the alternative respiratory pathway, plays a crucial role in regulating cell reprogramming by controlling metabolic transitions related to the cellular redox state and the variable carbon balance. The involvement of the alternative respiratory pathway during germination was explored by analysis of PsAOX gene/protein expression. Seeds of four Pisum sativum L. cultivars (‘Respect-1′, ‘S134′, ‘G78′ and ‘S91′) were imbibed in sterile tap water for 16 h and metabolic parameters measured by calorespirometry (heat and CO2 emission rates) in a Multi-Cell Differential Scanning Calorimeter in isothermal mode at 25 °C. The involvement of PsAOX was evaluated by transcript quantification (PsAOX1, PsAOX2a, and PsAOX2b) through RT-qPCR, and by of analysing the PsAOX expression through Western blot. The results demonstrate that the cv. ‘S91′, characterized by a low germination rate, exhibited the lowest metabolic heat and CO2 emission rate. However, contrary to expectations, PsAOX transcript accumulation and PsAOX protein expression were significantly higher for ‘S91′ than for the other cultivars. These results indicate that higher levels of AOX (transcript and protein) could be linked to lower metabolic rates for embryo growth when seed germination is compromisedinfo:eu-repo/semantics/publishedVersio

Precursors of catastrophe in the BTW, Manna and random fiber bundle models of failure

We have studied precursors of the global failure in some self-organised critical models of sand-pile (in BTW and Manna models) and in the random fiber bundle model (RFB). In both BTW and Manna model, as one adds a small but fixed number of sand grains (heights) to any central site of the stable pile, the local dynamics starts and continues for an average relaxation time (\tau) and an average number of topplings (\Delta) spread over a radial distance (\xi). We find that these quantities all depend on the average height (h_{av}) of the pile and they all diverge as (h_{av}) approaches the critical height (h_{c}) from below: (\Delta) (\sim (h_{c}-h_{av}))(^{-\delta}), (\tau \sim (h_{c}-h_{av})^{-\gamma}) and (\xi) (\sim) ((h_{c}-h_{av})^{-\nu}). Numerically we find (\delta \simeq 2.0), (\gamma \simeq 1.2) and (\nu \simeq 1.0) for both BTW and Manna model in two dimensions. In the strained RFB model we find that the breakdown susceptibility (\chi) (giving the differential increment of the number of broken fibers due to increase in external load) and the relaxation time (\tau), both diverge as the applied load or stress (\sigma) approaches the network failure threshold (\sigma_{c}) from below: (\chi) (\sim) ((\sigma_{c}) (-)(\sigma)^{-1/2}) and (\tau) (\sim) ((\sigma_{c}) (-)(\sigma)^{-1/2}). These self-organised dynamical models of failure therefore show some definite precursors with robust power laws long before the failure point. Such well-characterised precursors should help predicting the global failure point of the systems in advance.Comment: 13 pages, 9 figures (eps

Blast furnace stove control

This paper outlines the process model and model-based control techniques implemented on the hot blast stoves for the No. 7 Blast Furnace at the Inland Steel facility in East Chicago, Indiana. A detailed heat transfer model of the stoves is developed. It is then used as part of a predictive control scheme to determine the minimum amount of fuel necessary to achieve the blast air requirements. The controller also considers maximum and minimum temperature constraints within the stove

Prevalence of Tritrichomonas foetus in beef bulls slaughtered at two abattoirs in northern Australia

Bovine trichomoniasis, caused by the protozoal parasite Tritrichomonas foetus, is a highly contagious venereal disease characterised by early pregnancy loss, abortion and pyometra. Persistently infected bulls and cows are the primary reservoirs of infection in infected herds. This research investigated the prevalence of T. foetus infection in bulls from properties located across northern Australia and New South Wales. Preputial samples were collected from 606 bulls at slaughter and tested for T. foetus using the VetMAX-Gold Trich Detection Kit (Thermo Fisher Scientific). The apparent prevalence of T. foetus infection varied between regions, with northern regions in the Northern Territory, Queensland and Western Australia showing a prevalence of 15.4%, 13.8% and 11.4%, respectively. There was some evidence of an association between infection and postcode (P = 0.06) and increasing bull age (P = 0.054). This study confirms that T. foetus infection is likely to be present in many beef breeding herds and contributing to lower than expected reproductive performance, particularly across northern Australia