Effect of aspect ratio of vertically aligned copper nanowires in the presence of cellulose nanofibers on the thermal conductivity of epoxy composites

The composites comprising vertically aligned network of copper nanowires (CuNWs) in the presence of cellulose nanofibers were fabricated by using the freeze‐templating method and the effect of aspect ratio (A/R) of CuNWs on the thermal conductivity of epoxy composites was investigated. The thermal conductivity of epoxy composites increased to 0.79 W m^?1 K^?1 at 1.12 vol% of high A/R CuNWs loading, corresponding to the thermal conductivity enhancement of 365% as compared to the pure epoxy. The thermal conductivity of vertically aligned higher A/R CuNWs/epoxy, which is 38.5% and 51.9% higher than those of the lower A/R CuNWs and the randomly aligned CuNWs, respectively. The application of the epoxy composites in heat dissipation was demonstrated by the temperature changes of composites on a hot plate with the increase of heating time. These results indicate that the thermally conductive composites in this study could be applied for thermal dissipating materials in electronic devices.     

An efficient combined DCA and B&;B using DC/SDP relaxation for globally solving binary quadratic programs

This paper addresses a new continuous approach based on the DC (Difference of Convex functions) programming and DC algorithms (DCA) to Binary quadratic programs (BQP) which play a key role in combinatorial optimization. DCA is completely different from other avalaible methods and featured by generating a convergent finite sequence of feasible binary solutions (obtained by solving linear programs with the same constraint set) with decreasing objective values. DCA is quite simple and inexpensive to handle large-scale problems. In particular DCA is explicit, requiring only matrix-vector products for Unconstrained Binary quadratic programs (UBQP), and can then exploit sparsity in the large-scale setting. To check globality of solutions computed by DCA, we introduce its combination with a customized Branch-and-Bound scheme using DC/SDP relaxation. The combined algorithm allows checking globality of solutions computed by DCA and restarting it if necessary and consequently accelerates the B&B approach. Numerical results on several series test problems provided in OR-Library (Beasley in J Global Optim, 8:429–433, 1996), show the robustness and efficiency of our algorithm with respect to standard methods. In particular DCA provides ϵ-optimal solutions in almost all cases after only one restarting and the combined DCA-B&B-SDP always provides (ϵ−)optimal solutions.     

On the generalized Cauchy-Riemann systems

The factorization of the Laplacian by means of first order systems and of second order operators was considered by several authors (see, e.g [2],[3],[4]). In the paper the definition of Cauchy-Riemann system (CR-system) of ordern is given by their symbols. We prove that ifD ⁽ⁿ⁾ is the symbol andD ^{(s, n)} is the sign-matrix of CR-system, then

Dynamics and thermodynamics of the low-temperature strongly interacting Bose gas

We measure the zero-temperature equation of state of a homogeneous Bose gas of (7)Li atoms by analyzing the in situ density distributions of trapped samples. For increasing repulsive interactions our data show a clear departure from mean-field theory and provide a quantitative test of the many-body corrections first predicted in 1957 by Lee, Huang, and Yang [Phys. Rev. 106, 1135 (1957).]. We further probe the dynamic response of the Bose gas to a varying interaction strength and compare it to simple theoretical models. We deduce a lower bound for the value of the universal constant ξ > 0.44(8) that would characterize the universal Bose gas at the unitary limit.     

DC programming techniques for solving a class of nonlinear bilevel programs

We propose a method for finding a global solution of a class of nonlinear bilevel programs, in which the objective function in the first level is a DC function, and the second level consists of finding a Karush-Kuhn-Tucker point of a quadratic programming problem. This method is a combination of the local algorithm DCA in DC programming with a branch and bound scheme well known in discrete and global optimization. Computational results on a class of quadratic bilevel programs are reported.     

Fluorescent biosensor using whole cells in an inorganic translucent matrix

An optical biosensor based on vegetal cells entrapped in an inorganic translucent matrix and fluorescence detection has been developed. The biosensor uses Chlorella vulgaris immobilized in a translucent support produced from sol-gel technology. The translucence of the structure enables the algal active layer to be placed directly in contact with the optical fibers for fluorescence detection. This configuration has many advantages over the use of an opaque support because no space between the optical fibers and the active layer is required to collect fluorescence. This reagentless biosensor allows determination of diuron as an anti-PSII herbicide and its long term activity is assessed.     

A new dissimilarity measure for comparing labeled graphs

We use spectral graph theory to compare graphs that share the same node set, taking into account global graph structures. We propose a general framework using eigendecomposition of graph Laplacians. We show its special cases and propose a new dissimilarity measure that avoid problems of spectral analysis. The new dissimilarity emphasizes the importance of small eigenvalues which are known to carry the main information on graphs. General properties of the dissimilarity are discussed. The dissimilarity provides an efficient and intuitive tool for graph analysis.     

DC programming and DCA for globally solving the value-at-risk

The value-at-risk is an important risk measure that has been used extensively in recent years in portfolio selection and in risk analysis. This problem, with its known bilevel linear program, is reformulated as a polyhedral DC program with the help of exact penalty techniques in DC programming and solved by DCA. To check globality of computed solutions, a global method combining the local algorithm DCA with a well adapted branch-and-bound algorithm is investigated. An illustrative example and numerical simulations are reported, which show the robustness, the globality and the efficiency of DCA.     

DNA analysis of a radiotolerant bacterium Pantoea agglomerans by FT-IR spectroscopy

A radiation tolerance strain, Pantoea agglomerans was isolated from γ-irradiated carrot samples (Daucus carota). D₁₀ determination showed that the radioresistance of this bacterium is five-fold higher than Escherichia coli, both belonging to the family of Enterobacteriaceae. DNA isolated from untreated and irradiated bacterial cells was analyzed by FT-IR spectroscopy to investigate the radiotolerance of this bacterium. At doses <5 kGy, an alteration of the interbase hydrogen networks was observed and characterized mainly by an increase of bands assigned to the carbonyl non-pairing and the free amine groups. Moderate breakage of the DNA backbone and damage of the osidic structure were also observed. Similar spectral profiles were noticed at doses ≥5 kGy, but additional increase of the band intensity of CC and CN suggests damages of nucleobases. High number of asymmetric PO₂⁻ and upper shift of symmetric PO₂⁻ are indicative of DNA strand breaks. Osidic damages were evidenced by decrease of the absorption bands ascribed to deoxyribosyl moieties and by appearance of C–OH band. DNA degradation at high irradiation doses was also noticed by electrophoresis using agarose gel. It appeared that DNA underwent covalent cross-linking, as revealed by agglomeration of DNA in the wells of agarose gel.