The conjugate gradient algorithm for solving Hermitian positive definite linear systems is usually combined with preconditioning in order to speed up convergence. In recent years, there has been a revival of polynomial preconditioning, motivated by the attractive features of the method on modern architectures. Standard techniques for choosing the preconditioning polynomial are based only on bou...

Some algorithmic aspects of systems of PDEs based simulations can be better clarified by means of symbolic computation techniques. This is very important since numerical simulations heavily rely on solving systems of PDEs. For the large-scale problems we deal with in today’s standard applications, it is necessary to rely on iterative Krylov methods that are scalable (i.e., weakly dependent on t...

We introduce a class of preconditioners for general sparsematrices based on the Birkhoff–von Neumann decomposition of doubly stochastic matrices. These preconditioners are aimed primarily at solving challenging linear systems with highly unstructured and indefinite coefficient matrices. We present some theoretical results and numerical experiments on linear systems from a variety of applications.

ILU-type preconditioning techniques are widely recognized as being an extremely effective approach to providing efficient solvers[1]. These techniques have been used to increase the performance and reliability of Krylov subspace methods. However, a drawback of these approaches is that it is difficult to choose appropriate values for the preconditioner tuning parameters[2]. Usually, parameter se...

Non-linear optimization problems suffer from local minima. When we use gradient based iterative solvers on these problems, we often find the final solution highly dependent on the initial guess. Here we introduce preconditioning and show how it helps resolve in our current problem—bidirectional deconvolution. The results in three data examples show that preconditioning helps us get a more spiky...

Background: Occupational noise-induced hearing loss (ONIHL) is a hearing disorder that affects workers all over the world. Preconditioning with several mild or less potent stressors will effectively prevent the development of noise-induced hearing loss. This study investigated the possible preventive effects of normobaric hyperoxia preconditioning on preventing the noise-induced hearing impairm...

Abstract Naïve T cells and regulatory cells, when purified, do not proliferate to the common cytokine receptor γ-chain family cytokines interleukin (IL)-2, IL-7 or IL-15, despite their expression of cognate receptors. Cell-to-cell contact with dendritic (DCs) enabled proliferation cell these cytokines, independent antigen recognition stimulation. This effect lasted after separation from DCs, en...

organ damage after reperfusion of previously viable ischemic tissues is defined as ischemia/reperfusion injury. the pathophysiology of ischemia/reperfusion injury involves cellular effect of ischemia, reactive oxygen species and inflammatory cascade. protection against ischemia/reperfusion injury may be achieved by preconditioning or postconditioning. in this review, we discuss basic mechanisms...

objective(s):gentamicin sulphate (gs) nephrotoxicity seems to be related to the generation of reactive oxygen species. there is evidence that oxygen preconditioning increases the activity of antioxidant enzymes. materials and methods: forty eight female rats were divided into 6 groups (n=8) as follows: group 1 was the control, group 2 received daily gs, groups 3,4 and 5 received oxygen 2 hr/day...

conclusions the pattern of pretreatment with o2 could change this potential and highly protective strategy against cp-induced nephropathy to an ineffective or even mildly deteriorating one. therefore, o2 administration before cp injection to patients with cancer, for therapeutic purposes or as a preconditioning approach, should be performed and investigated with caution until exact effects of d...