On ergodic stopping and impulsive control problems for nonuniformly ergodic Markov processes

In this paper we study optimal stopping and impulse control with a long-run average cost functional for ergodic Markov processes, which transition semigroupP _t converges uniformly on compact sets to a unique invariant measure, ast. We restrict the class of strategies to so-called stopping rules and obtain continuity of value functions and characterization of optimal rules.     

Molecular dynamics studies of polyurethane nanocomposite hydrogels

Polyurethane PEO-based hydrogels have a broad range of biomedical applicability. They are attractive for drug-controlled delivery systems, surgical implants and wound healing dressings. In this study, a PEO based polyurethane hydrogels containing Cloisite® 30B, an organically modified clay mineral, was synthesized. Structure of nanocomposite hydrogels was determined using XRD technique. Its molecular dynamics was studied by means of NMR spectroscopy, DMA and DSC analysis. The mechanical properties and thermal stability of the systems were improved by incorporation of clay and controlled by varying the clay content in polymeric matrix. Molecular dynamics of polymer chains depends on interaction of Cloisite® 30B nanoparticles with soft segments of polyurethanes. The characteristic nanosize effect is observed.     

Automatic stabilization of relative counting losses in gamma-ray spectrometry of short-lived nuclides

An electronic circuit for the stabilization of the relative counting losses due to dead time and pile-up effects is described. The circuit consists of two independent channel: for stabilization of dead time and pile-up, respectively. The stabilizer (circuit) receives continously information on temporary dead time and pile-up in a spectrometer and owing to feed back the relative counting losses (in peaks) are constant during the measuring time and can be easily calculated. Patent pending.     

The Effect of Chromatographic Conditions on the Separation of Selected Alkaloids on Silica Layers

JPC – Journal of Planar Chromatography – Modern TLC - Alkaloid standards have been chromatographed on silica layers with a variety of aqueous and nonaqueous mobile phases. The effect on...     

Preparation and characterization of rigid polyurethane–polyglycerol nanocomposite foams

This work reports on the preparation of polyurethane–polyisocyanurate (PUR–PIR) foams containing different polyglycerols and layered silicate nanoclays. The rigid polyurethane foams were obtained in a laboratory scale, in a single step method, from a two-component system with a NCO to OH groups ratio equal to two. The reaction mixture consisted of the proper amounts of a commercial oligoetherpolyol, polyglycerol, catalysts, water, nanofiller, and polymeric diphenylmethane diisocyanate. The obtained foams containing 6% of one of three types of montmorillonite (MMT) (Cloisite 30B, Laponite RD, Bentonite) were characterized in terms of their structure, density, brittleness, compressive strength and thermal stability. The nanocomposite foams showed a higher number of cells with a smaller cell size in the presence of MMT, while the foams modified with nanofiller Cloisite 30B presented the best compressive strength and the best fire resistance.     

Application of DIC Technique to Concrete—Study on Objectivity of Measured Surface Displacements

The measurements of the width of a localized zone on the surface of notched concrete beams under quasi-static three-point bending were performed using the 2D Digital Image Correlation technique. Different image length resolutions, image search patches and distances between search patch centres were tested. Attention was paid to the accuracy and objectivity of surface displacements measured. An original method was proposed to determine the width of localized zones above the notch based on experiments.     

Calculations of fracture process zones on meso-scale in notched concrete beams subjected to three-point bending

The paper describes investigations on fracture process zones (FPZ) at meso-scale in notched concrete beams subjected to quasi-static three-point bending. The simulations were carried out with the FEM using isotropic damage constitutive model enhanced by a characteristic length of micro-structure by means of a non-local theory. Concrete was modelled as a random heterogeneous three-phase material. The effect of the beam size, aggregate distribution, aggregate density, aggregate shape, aggregate size and characteristic length on the width and shape of FPZ and load-displacement curve was numerically investigated. The numerical results were compared with own test results using Digital Image Correlation method (Skar?yński et al., 2009a), the tests by Le Bellěgo et al., (2003) and the size effect law by Ba?ant (2004).     

3D-Hit: fast structural comparison of proteins on multicore architectures

3D-Hit is a well established method for rapid detection of structural similarities between proteins, which is widely used in various bioinformatics web servers (MetaServer, GRDB, 3D-Fun, Rosetta, etc.). The algorithm decomposes proteins into set of overlaping segments of 9–13 residues, then tries to match them using root mean square distance metric. The best aligned pairs of segments are selected as seeds for futher analysis. Those initial hits are expanded by iterative process in order to construct the global structural alignment by concatenating pairs of matching segments. The method has the same accuracy as the other state-of-the-art structural comparison algorithms (LGscore2, DALI), yet it provides much faster processing times, and can be used in a high-throughput setup as the structural module of bioinformatics pipelines. The method is optimized in terms of speed and accuracy to work on novel computer architectures, such as PowerXCell8i and Sun Constellation System. Here, we provide the source code of the 3D-Hit program, describe selected architectures on which the software was ported, present programing models, point out significant porting steps and sumarize performance comparisons.     

A Gauss type law for gravity with a cosmological constant

It is shown that Komar's conserved quantities can be generalized to space-times with a cosmological constant in which matter, electric charge, and massless scalar field are sources. In the special case of the Kerr-Newman-de Sitter solution, treated as a solution external to matter sources, these quantities are equal to the global mass and angular momentum of its source. They are determined regardless of any local distribution of the mass and angular momentum of sources in addition to the electric charge given by the classical Gauss' law.     

Synthesis and thermal studies of flexible polyurethane nanocomposite foams obtained using nanoclay modified with flame retardant compound

This work presents thermal studies of nanocomposites based on the flexible polyurethane (PU) matrix and filled using montmorillonite organically modified with organophosphorus flame retardant compound. Flexible PU nanocomposite foams were prepared in the reaction carried out between reactive alcoholic hydroxyl and isocyanate groups with the ratio of NCO to OH groups equal to 1.05. The amount of an organoclay ranging from 3 to 9 vol% was added to the polyol component of the resin before mixing with isocyanate. The apparent density of PU foams was ranging from 0.066 to 0.077 g cm^?1. Thermal properties of the flexible PU nanocomposite foams were investigated by thermogravimetry and dynamical mechanical analysis. Glass transition temperatures (T _g) were defined as maximum peak on tanδ curve. Thermal decomposition was observed at 310–320 °C (calculated from the onset of TG curve). Tensile strength of the PU foams was determined using mechanical test. The microstructure of the nanoparticles and the composites was investigated by X-ray diffraction. Finally, it was confirmed that the thermal and mechanical properties of flexible PU nanocomposite depend on the amount of nanoclay.