High thermal conductivity composites consisting of diamond filler with tungsten coating and copper (silver) matrix

Tungsten coatings with thickness of 5–500 nm are applied onto plane-faced synthetic diamonds with particle sizes of about 430 and 180 μm. The composition and structure of the coatings are investigated using scanning electron microscopy, X-ray spectral analysis, X-ray diffraction, and atomic force microscopy. The composition of the coatings varies within the range W–W₂C–WC. The average roughness, R _a, of the coatings’ surfaces (20–100 nm) increases with the weight–average thickness of the coating. Composites with a thermal conductivity (TC) as high as 900 W m⁻¹ K⁻¹ are obtained by spontaneous infiltration, without the aid of pressure, using the coated diamond grains as a filler, and copper or silver as a binder. The optimal coating thickness for producing a composite with maximal TC is 100–250 nm. For this thickness the heat conductance of coatings as a filler/matrix interface is calculated as G = (2–10) × 10⁷ W m⁻² K⁻¹. The effects of coating composition, thickness and roughness, as well as of impurities, on wettability during the metal impregnation process and on the TC of the composites are considered.     

Parameterized complexity of firefighting

The Firefighter problem is to place firefighters on the vertices of a graph to prevent a fire with known starting point from lighting up the entire graph. In each time step, a firefighter may be placed on an unburned vertex, permanently protecting it, and the fire spreads to all neighboring unprotected vertices of burning vertices. The goal is to let as few vertices burn as possible. In this paper, we consider a generalization of this problem, where at each time step b?1$b?1$ firefighters can be deployed. Our results answer several open questions raised by Cai et al. [8]. We show that this problem is W[1]-hard when parameterized by the number of saved vertices, protected vertices, and burned vertices. We also investigate several combined parameterizations for which the problem is fixed-parameter tractable. Some of our algorithms improve on previously known algorithms. We also establish lower bounds to polynomial kernelization.     

Structure‐Based Design of Small‐Molecule Ligands of Phosphofructokinase‐2 Activating or Inhibiting Glycolysis

Glycolysis lies at the basis of metabolism and cell energy supply. The disregulation of glycolysis is involved in such pathological processes as cancer proliferation, neurodegenerative diseases, and amplification of ischemic damage. Phosphofructokinase‐2 (PFK‐2), a bifunctional enzyme and regulator of glycolytic flux, has recently emerged as a promising anticancer target. Herein, the computer‐aided design of a new class of aminofurazan‐triazole regulators of PFK‐2 is described along with the results of their in vitro evaluation. The aminofurazan‐triazoles differ from other recently described inhibitors of PFK‐2 and demonstrate the ability to modulate glycolytic flux in rat muscle lysate, producing a twofold decrease by inhibitors and fourfold increase by activators. The most potent compounds in the series were shown to inhibit the kinase activity of the hypoxia‐inducible form of PFK‐2, PFKFB3, as well as proliferation of HeLa, lung adenocarcinoma, colon adenocarcinoma, and breast cancer cells at concentrations in the low micromolar range.     

Polyethylene–Silica Nanocomposites with the Structure of Semi‐Interpenetrating Networks

Organic–inorganic nanocomposites with the structure of interpenetrating or semi‐interpenetrating networks are considered as advanced materials, since they have improved thermal and mechanical properties. An alternative approach to the preparation of such hybrid systems is proposed. It is based on the synthesis of silica from the precursor of hyperbranched polyethoxysiloxane by the hydrolytic condensation reaction in the volume of pores of a polymer matrix (bulk porosity is 40 vol%) stretched via the environmental crazing mechanism. Polyethylene–silica nanocomposites with the structure of semi‐interpenetrating networks when the content of silica is not less than 20–25 wt% are obtained. These composites can undergo an additional phase separation at a temperature of 160 °C (above the melting point of polyethylene), which is accompanied by an increase in the size of the polymer phase with the formation of macrophases. At the same time, the environment (orthophosphoric acid), in which the composite is heated, fills the pores that have appeared. As a result, the content of the third component with the new functionality increases up to 50 wt%, which allowed us to impart proton‐conducting properties to the composite material and preserve its shape stability.     

On the Minimum Feedback Vertex Set Problem: Exact and Enumeration Algorithms

We present a time algorithm finding a minimum feedback vertex set in an undirected graph on n vertices. We also prove that a graph on n vertices can contain at most 1.8638 ⁿ minimal feedback vertex sets and that there exist graphs having 105 ^n/10≈1.5926 ⁿ minimal feedback vertex sets. Preliminary extended abstracts of this paper appeared in the proceedings of SWAT’06 [29] and IWPEC’06 [18]. Additional support of F.V. Fomin, S. Gaspers and A.V. Pyatkin by the Research Council of Norway. The work of A.V. Pyatkin was partially supported by grants of the Russian Foundation for Basic Research (project code 05-01-00395), INTAS (project code 04–77–7173). I. Razgon is supported by Science Foundation Ireland (Grant Number 05/IN/I886).     

Rapid simultaneous ultrasensitive immunodetection of five bacterial toxins

Rapid ultrasensitive detection of gastrointestinal pathogens presents a great interest for medical diagnostics and epidemiologic services. Though conventional immunochemical and polymerase chain reaction (PCR)-based methods are sensitive enough for many applications, they usually require several hours for assay, whereas as sensitive but more rapid methods are needed in many practical cases. Here, we report a new microarray-based analytical technique for simultaneous detection of five bacterial toxins: the cholera toxin, the E. coli heat-labile toxin, and three S. aureus toxins (the enterotoxins A and B and the toxic shock syndrome toxin). The assay involves three major steps: electrophoretic collection of toxins on an antibody microarray, labeling of captured antigens with secondary biotinylated antibodies, and detection of biotin labels by scanning the microarray surface with streptavidin-coated magnetic beads in a shear-flow. All the stages are performed in a single flow cell allowing application of electric and magnetic fields as well as optical detection of microarray-bound beads. Replacement of diffusion with a forced transport at all the recognition steps allows one to dramatically decrease both the limit of detection (LOD) and the assay time. We demonstrate here that application of this "active" assay technique to the detection of bacterial toxins in water samples from natural sources and in food samples (milk and meat extracts) allowed one to perform the assay in less than 10 min and to decrease the LOD to 0.1-1 pg/mL for water and to 1 pg/mL for food samples.