Performance analysis of parallel Schwarz preconditioners in the LES of turbulent channel flows

We present a comparative study of parallel Schwarz preconditioners in the solution of linear systems arising in a Large Eddy Simulation (LES) procedure for turbulent plane channel flows. This procedure applies a time-splitting technique to suitably filtered Navier–Stokes equations, in order to decouple the continuity and momentum equations, and uses a semi-implicit scheme for time integration and finite volumes for space discretisation. This approach requires the solution of four sparse linear systems at each time step, accounting for a large part of the overall simulation; hence the linear system solvers are a crucial component in the whole procedure. Several preconditioners are applied in the simulation of a reference test case for the LES community, using discretisation grids of different sizes, with the aim of analysing the effects of different algorithmic choices defining the preconditioners, and identifying the most effective ones for the selected problem. The preconditioners, coupled with the GMRES method, are run within SParC-LES, a recently developed LES code based on the PSBLAS and MLD2P4 libraries for parallel sparse matrix computations and preconditioning.     

Hybrid MCM-41 grafted by a general microwave-assisted procedure: a characterization study

Hybrid materials obtained through a Microwave-assisted grafting of organic functional groups on mesoporous silica (MCM-41 type) have been characterized by X-ray powder diffraction, TG-DSC, N₂ adsorption, solid state ¹³C- and ²⁹Si-NMR, TEM and SEM. The studied grafting procedure is effective in the preparation of hybrid organosilicas under solvent-free conditions. Microwaves allows an ultra-fast and clean functionalization of the mesoporous materials and the method has been applied to produce a wide series of functional materials. The hybrid materials maintain the original mesoporous structure when the loading of linked organic groups does not exceed 10 %. In this cases, the slight pore volume reduction is linearly correlated to the organic amount in the product. If functional groups able to interact among them through hydrogen bond are used, hybrid materials exhibit high Organic/SiO₂ ratios and low pore volumes due to the formation of a network occluding the pores, where functional groups of free organosilane molecules interacts with the functional groups of molecules linked to the matrix. NMR data confirm that the network is composed by organosilane molecules linked or not to the framework. Acid washing is able to labilize hydrogen bond and open the network. In the case of bulky but chemically inert functionalising agents the network is not produced.     

Critical analysis of the diagnostic value of the flow-volume curve

Changes in the flow-volume curve after administration of a bronchodilator were studied in reversible bronchial obstruction. The concept of isovolume is used in analysis of the curve indices, i.e. it is felt that the index (75, 60, 50, 25% FVC) after administration should be fixed on the curve at the same volume as on the basic curve to enable an indirect account to be taken of changes in flow in function of time, since, if resistance is reduced, the emitted volume varies in the same period even though the conditions promoting the flow are unchanged.     

Bowman-Birk inhibitors in lentil: Heterologous expression,functional characterisation and anti-proliferative properties in human colon cancer cells

A full-length cDNA, encoding a Bowman-Birk protease inhibitor (BBI), was isolated from lentil immature seeds. The deduced amino acid sequence was longer than that of the BBI extracted from lentil seeds and contained two binding sites; the first inhibitory site inhibits trypsin whereas the second one inhibits chymotrypsin. In order to characterize this lentil BBI, a longer (complete) and its C-terminally processed (mature) form were heterologously expressed in the yeast Pichia pastoris. The recombinant BBI proteins proved to be active against trypsin and chymotrypsin, showing K_i values at nanomolar levels. Mass spectrometry analysis revealed that complete BBI was composed of an array of molecular masses, whereas mature BBI showed the presence of a major peak of the expected size. The effects of mature BBI on the growth of human colon adenocarcinoma HT29 and colonic fibroblast CCD-18Co cells were evaluated. Lentil BBI was able to inhibit the growth of such cells at concentrations higher than 19 μM, in a concentration-dependent manner; by contrast, the CCD18-Co cells were unaffected. These data broaden our knowledge of the beneficial biological activities of naturally-occurring BBI proteins and address the need for systematic evaluation of natural variants in order to design novel strategies in preventive medicine.     

Preparation of neutron-activatable holmium nanoparticles for the treatment of ovarian cancer metastases

Nanoparticles containing stable holmium ((165) Ho) are prepared by nanotemplate engineering and subsequently irradiated in a neutron flux to yield (166) Ho, a beta-emitting radiotherapeutic isotope. After intraperitoneal injection to mice bearing SKOV-3 ovarian tumors, significant tumor accumulation of the (166) Ho-nanoparticles is observed by SPECT imaging indicating the potential of these neutron activatable nanoparticles for internal radiation therapy of ovarian cancer metastases.     

Adaptive AMG with coarsening based on compatible weighted matching

We introduce a new composite adaptive Algebraic Multigrid (composite \(\alpha \) AMG) method to solve systems of linear equations without a-priori knowledge or assumption on characteristics of near-null components of the AMG preconditioned problem referred to as algebraic smoothness. Our version of \(\alpha \) AMG is a composite solver built through a bootstrap strategy aimed to obtain a desired convergence rate. The coarsening process employed to build each new solver component relies on a pairwise aggregation scheme based on weighted matching in a graph, successfully exploited for reordering algorithms in sparse direct methods to enhance diagonal dominance, and compatible relaxation. The proposed compatible matching process replaces the commonly used characterization of strength of connection in both the coarse space selection and in the interpolation scheme. The goal is to design a method leading to scalable AMG for a wide class of problems that go beyond the standard elliptic Partial Differential Equations (PDEs). In the present work, we introduce the method and demonstrate its potential when applied to symmetric positive definite linear systems arising from finite element discretization of highly anisotropic elliptic PDEs on structured and unstructured meshes. We also report on some preliminary tests for 2D and 3D elasticity problems as well as on problems from the University of Florida Sparse Matrix Collection.     

Biochemical Traits of Ciauscolo,a Spreadable Typical Italian Dry-Cured Sausage

Abstract: Ciauscolo is a short-ripened fermented sausage manufactured in the Marche region (central Italy) that has recently received a protected geographical indication product classification (PGI). The aim of this study was the exploration of the biochemical traits of this traditional Italian salami, with a special focus on protein and lipid composition. Ciauscolo salami was characterized by pH of 5.1 and 0.91 water activity. A prevalence of lactic acid bacteria in the microbiota was found. The free amino acids and biogenic amines average content was 2657 and 255 mg/kg, respectively. With regards to lipids composition unsaturated fatty acids represented 63% and 72% of total and free fatty acids. Despite these results had wide statistical variability, attributable to differences in the processing parameters and raw matter used, some peculiar traits were found: (1) structural muscular proteins underwent to less proteolysis than sarcoplasmic ones; (2) glycogen phosphorylase, enolase, and aldolase were the most proteolyzed among the sacoplasmic proteins; (3) there was inverse correlation between histamine content and yeasts population, and a direct correlation between the gly-pro content and lactic acid bacteria counts; (4) the content of aspartic acid and methyonine seem to be a possible molecular marker able to distinguish between double and single milling.     

2LEV-D2P4: a package of high-performance preconditioners for scientific and engineering applications

We present a package of parallel preconditioners which implements one-level and two-level Domain Decomposition algorithms on the top of the PSBLAS library for sparse matrix computations. The package, named 2LEV-D2P4 (Two-LEVel Domain Decomposition Parallel Preconditioners Package based on PSBLAS), currently includes various versions of additive Schwarz preconditioners that are combined with a coarse-level correction to obtain two-level preconditioners. A pure algebraic formulation of the preconditioners is considered. 2LEV-D2P4 has been written in Fortran~95, exploiting features such as abstract data type creation, functional overloading and dynamic memory management, while providing a smooth path towards the integration in legacy application codes. The package, used with Krylov solvers implemented in PSBLAS, has been tested on large-scale linear systems arising from model problems and real applications, showing its effectiveness.     

Advanced environments for parallel and distributed applications: a view of current status

In this paper we provide a view of the design and development activity concerning advanced environments for parallel and distributed computing. We start from assessing the main issues driving this research track, in the areas of hardware and software technology and of applications. Then, we identify some key concepts, that can be considered as common guidelines and goals in the development of modern advanced environments, and we come up with a “classification” of these environments into two main classes: programming environments and problems solving environments. Both classes are widely discussed, in light of the key concepts previously outlined, and several examples are provided, in order to give a picture of the current status and trends.