Influence of Topology of Highly Porous Methacrylate Polymers on their Mechanical Properties

Porous polymer monoliths are prepared using glycidyl methacrylate and methyl methacrylate as monomers, in both cases crosslinked with ethylene glycol dimethacrylate. Up to 75% porous samples are produced using either emulsion templating or bulk polymerization with porogens. In the case of emulsion templating, a cellular topology with cavities between 3.1 and 5.5 µm is observed for both monomers, while a cauliflower‐like topology is formed in the case of bulk polymerization. The influence of topology features of monoliths on the mechanical properties is studied and for both polymers a dramatic influence, on both compressive moduli and compressive strength, is found. The mechanical parameters, namely elastic modulus and compressive strength are significantly higher for emulsion templated samples.     

Lipidomic Analysis: From Archaea to Mammals

Lipids are among the most important organic compounds found in all living cells, from primitive archaebacteria to flowering plants or mammalian cells. They form part of cell walls and constitute cell storage material. Their biosynthesis and metabolism play key roles in faraway topics such as biofuel production (third‐generation biofuels produced by microorganisms, e.g. algae) and human diseases such as adrenoleukodystrophy, Zellweger syndrome, or Refsum disease. Current lipidomic analysis requires fast and accurate processing of samples and especially their characterization. Because the number of possible lipids and, more specifically, molecular species of lipids is of the order of hundreds to thousands, it is necessary to process huge amounts of data in a short time. There are two basic approaches to lipidomic analysis: shotgun and liquid chromatography–mass spectometry. Both methods have their pros and cons. This review deals with lipidomics not according to the type of ionization or the lipid classes analyzed but according to the types of samples (organisms) under study. Thus, it is divided into lipidomic analysis of archaebacteria, bacteria, yeast, fungi, algae, plants, and animals.     

Application of Second Order TVD and WENO Schemes in Internal Aerodynamics

We deal with the comparison of several finite volume TVD schemes and finite difference ENO schemes and we describe a second order finite volume WENO scheme which was developed for the case of general unstructured meshes. The proposed second order WENO reconstruction is much simpler than the original ENO scheme introduced in [Harten and Chakravarthy 1991]. Moreover, the proposed WENO method is very easily extendible for unstructured meshes in 3D. All above mentioned schemes are applied for the solution of 2D and 3D transonic flows in the turbines and channels and the numerical solution is compared to experimental results or to the results obtained by other authors.     

Iterative weighted finite transductions

We investigate 2-tape weighted finite automata called weighted finite transducers (WFT) and their applications to image processing. We show that probabilistic mutually recursive function systems (PMRFS) can be simulated by iterative weighted fimite transductions. We conjecture that iterative WFT are stronger than PMRFS and give examples of WFT that support this conjecture. We also show that the family of images defined by iterative WFT is closed under continuous invertible WFT relations which include invertible affine transformations as a special case. We give examples of iterative WFT which can compute mathematical functions given by a Taylor series with regular coefficients which cannot be computed by WFA. We discuss the implementation of an efficient image manipulation system which includes the implementation of efficient algorithms for the application of a WFT to an image in either pixel or WFA representation and for composition of WFT. The system also includes the Culik-Kari recursive WFA inference algorithm as a conversion from pixel representation to WFA representation.This work was supported by the National Science Foundation under Grant No. CCR-9202396. The work of the second author was partially supported by Grant of Slovak Academy of Sciences No. 88 and by EC Cooperative Action IC 1000 Algorithms for Future Technologies (Project ALTEC)     

Size-dependent structural and magnetic properties of chemically synthesized Co-Ni-Ga nanoparticles

Phase transitions and magnetic properties of shape-memory materials can be tailored by tuning the size of the constituent materials,such as nanoparticles.However,owing to the lack of suitable synthetic methods for size-controlled Heusler nanoparticles,there is no report on the size dependence of their properties and functionalities.In this contribution,we present the first chemical synthesis of size-selected Co-Ni-Ga Heusler nanoparticles.We also report the structure and magnetic properties of the biphasic Co-Ni-Ga nanoparticles with sizes in the range of 30-84 nm,prepared by a SBA-15 nanoporous silicatemplated approach.The particle sizes could be readily tuned by controlling the loading and concentration of the precursors.The fractions and crystallite sizes of each phase of the Co-Ni-Ga nanoparticles are closely related to their particle size.Enhanced magnetization and decreased coercivity are observed with increasing partide size.The Curie temperature (Tc) of the Co-Ni-Ga nanoparticles also depends on their size.The 84 nm-sized particles exhibit the highest Tc (≈ 1,174 K) among all known Heusler compounds.The very high Curie temperatures of the Co-Ni-Ga nanoparticles render them promising candidates for application in high-temperature shape memory alloy-based devices.     

Kinetics of linoleate oxidation in model systems

Oxidation of methyl linoleate, trilinoleate and linoleic acid has been studied in model systems based on various solid supports. Oxidation was followed by measurement of oxygen absorption, peroxide values and products of oxidation as a function of moisture equilibrium relative humidity. Effects of various metals, histidine and the antioxidants propyl gallate and butylated hydroxytoluene were studied. The results indicate: (a) at 50 C oxidation of protein increases with increasing moisture content and the protein interacts with peroxides changing the overall oxidation rate; (b) increasing moisture content shows the same inhibitory effect on oxidation of trilinoleate as it does on methyl linoleate; (c) the effectiveness of antioxidants is increased with increasing humidity but some chelating agents complexed with metals become catalytic at the higher moisture content; and (d) at moisture contents in the region of capillary condensation, mobility of reactants is enhanced since the rate of oxidation increases significantly. Presented at the AOCS Meeting, New York, October, 1968. Contribution No. 1396, Dept. of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Mass.     

Collisions of electrons with hydrogen atoms I. Package outline and high energy code

Being motivated by the applied researchers’ persisting need for accurate scattering data for the collisions of electrons with hydrogen atoms, we developed a computer package–Hex–that is designed to provide trustworthy results for all basic discrete and continuous processes within non-relativistic framework. The package consists of several computational modules that implement different methods, valid for specific energy regimes. Results of the modules are kept in a common database in the unified form of low-level scattering data (partial-wave T$T$-matrices) and accessed by an interface program which is able to produce various derived quantities like e.g. differential and integral cross sections. This article is the first one of a series of articles that are concerned with the implementation and testing of the modules. Here we give an overview of their structure and present (a) the command-line interface program hex-db that can be also easily compiled into a derived code or used as a backend for a web-page form and (b) simple illustrative module specialized for high energies, hex-dwba, that implements distorted and plane wave Born approximation.     

Diffusion controlled kinetics of crosslinking

Reactions of polymer formation and crosslinking become diffusion controlled when, during the reaction, the increasing glass transition temperature T_g comes close to the reaction temperature, the reaction still goes on below T_g but the reaction rate decreases steeply. A theory is presented relating the apparent rate constant to the difference between the reaction temperature and T_g based on the free volume or the Adam-Gibbs theory of glass transition. The theory is correlated with experiments on curing of diglycidyl ether of bisphenol A with 1,3-propanediamine. The implications for formation of protective films chemically crosslinked are discussed. The presence of a solvent and its evaporation affects the reaction rate through a change in concentrations of reactants as well as in T_g.