Optical encryption with a reference wave in a joint transform correlator architecture

In this work we introduce a digital holographic configuration in a Joint Transform Correlator (JTC) architecture for encryption purposes. Conceptually, it is a Mach-Zender interferometer, with a JTC in one arm and a reference wave in the other. We describe the practical implementation of this architecture, along with experimental results that support the proposal. We analyze the noise influence caused by intensity saturation during image capture, and this information allows us a filtering process to reduce the information to be handled, with a consequent increase in the speed of the total procedure.     

Colloidal dispersions of monodisperse magnetite nanoparticles modified with poly(ethylene glycol)

Monodisperse magnetite nanoparticles modified with poly(ethylene glycol) (PEG) were synthesized using a silane functionalized PEG obtained by reacting 3-aminopropyl triethoxysilane with carboxylic acid-methoxy PEG (mPEG-COOH) using amide reactions. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential measurements show the particles are monodisperse (sigma(gv) approximately 0.2) and stable in water for pH of 3-9 and ionic strengths, up to 0.3 M NaCl. Thermogravimetric analysis coupled with TEM and DLS indicates formation of a dense graft layer on the particle surface. An analysis of the interparticle interaction energy indicates that the particles are stabilized by strong steric repulsions between PEG chains on their surface.     

Measurement of activity coefficients at infinite dilution for acetonitrile,water, limonene,limonene epoxide and their binary pairs

Activity coefficients at infinite dilution were determined for binary pairs of acetonitrile, water, limonene and limonene epoxide at room temperature using the dilutor technique (inert gas stripping) in a home-made dilutor apparatus. The activity coefficients were predicted with the Aspen Plus software using the Dortmund-modified UNIFAC contribution method. Values predicted by software simulations are in good agreement with experimental data. However, experimental activity coefficients at infinite dilution obtained for limonene + acetonitrile, water + limonene and limonene epoxide + water systems are in disagreement with reported values estimated from LLE or solubility data.     

Taming Radical Intermediates for the Construction of Enantioenriched Trifluoromethylated Quaternary Carbon Centers

Demonstrated herein is the construction of trifluoromethylated quaternary carbon centers by an asymmetric radical transformation. Enantioenriched trifluoromethylated oxindoles were accessed using a hypervalent iodine‐based trifluoromethyl transfer reagent in combination with a magnesium Lewis acid catalyst and PyBOX‐type ligands to achieve up to 99 % ee and excellent chemical yields. Mechanistic studies were performed by experimental and computational methods and suggest a single‐electron transfer induced S_N2‐type mechanism. This example is thereby the first report on the construction of enantioenriched trifluoromethylated carbon centers using hypervalent iodine‐based reagents proceeding through such a reaction pathway.     

On near-best discrete quasi-interpolation on a four-directional mesh

Spline quasi-interpolants are practical and effective approximation operators. In this paper, we construct QIs with optimal approximation orders and small infinity norms called near-best discrete quasi-interpolants which are based on Ω-splines, i.e. B-splines with octagonal supports on the uniform four-directional mesh of the plane. These quasi-interpolants are exact on some space of polynomials and they minimize an upper bound of their infinity norms depending on a finite number of free parameters. We show that this problem has always a solution, in general nonunique. Concrete examples of such quasi-interpolants are given in the last section.     

Pappus’ theorem and a construction of complex Kleinian groups with rich dynamics

Pappus’ theorem is used to produce and study discrete subgroups of PSL(3, ?) with very rich dynamics. We get an example of a subgroup of PSL(3, ?) which is not conjugate to any subgroup of PU(2, 1) nor to any subgroup of Aff(?²), its Kulkarni region of discontinuity is non-empty and its complement, the Kulkarni limit set, contains infinitely many complex projective lines in general position. This construction is based on a representation of the group SL(2, ?) in the projective group PSL(3, ?).     

Cocyclic two-circulant core Hadamard matrices

Journal of Algebraic Combinatorics - The two-circulant core (TCC) construction for Hadamard matrices uses two sequences with almost perfect autocorrelation to construct a Hadamard matrix. A...     

Methyl branching in polyethylene from homopolymerization of ethylene with N‐arylcyano‐β‐diketiminate methallyl nickel‐B(C6F5)3

N‐Arylcyano‐β‐diketiminate methallyl nickel complexes activated with B(C₆F₅)₃ were used in the polymerization of ethylene. The microstructure analysis of obtained polyethylene (PE) was done by differential scanning calorimetry and ¹³C nuclear magnetic resonance (NMR). The branched polymer structures produced by these catalysts were attributed to one step isomerization mechanism of the catalyst along the polymer chain. The ortho or para position of the cyano group with co‐ordinated B(C₆F₅)₃ in both methallyl nickel catalysts influenced the polymer molecular weight, branching, and consequently melting and crystallization temperatures. NMR spectroscopic studies showed predominantly the formation of methyl branches in the obtained PE. Catalysts under study gave linear low‐density PEs with good crystallinities at temperatures of reaction between 50 °C and 70 °C at moderate pressures (12.3 atm). A propylene–ethylene copolymer produced by the metallocene catalyst had the same concentration of branches as the PE synthesized from methallyl nickel/B(C₆F₅)₃. Comparing the two polyolefins with the same degree of branching, it was observed that the polymer obtained with the nickel catalyst proved to be twice more crystalline and had greater T_m. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 452–458     

Reaction of carbon disulphide with bis(γ-mercaptopropylamine) nickel(II)

Summary Carbon disulphide reacts with bis(-mercaptopropylamine)nickel(II) by insertion into the Ni-N bond to yield a planar dithiocarbamate complex, in which the Ni-S bond is broken and a sulphydryl group is formed.