Irradiation and measurement devices and methods development for LSNAA applications at the TRIGA-ACPR core

A Large Sample Neutron Activation Analysis (LSNAA) facility has been developed at the TRIGA-Annular Core Pulsed Reactor (ACPR) operated by the Institute for Nuclear Research in Pitesti. The central irradiation cavity of ACPR can accommodate a large irradiation device. The ACPR neutron flux characteristics are well known and spectrum adjustment techniques have been successfully applied to enhance the thermal component of the neutron flux in the central irradiation cavity. An analysis methodology was developed by employing the MCNP (a general Monte Carlo N-particle transport code) code in order to estimate counting efficiency and correction factors for the major perturbing phenomena. The paper presents the development of the experimental device, the results of the neutron flux-spectrum characterization, and preliminary steps to validate the analysis methodology.     

Immobilization of biotinylated hGBP1 in a defined orientation on surfaces is crucial for uniform interaction with analyte proteins and catalytic activity

Guanylate binding proteins (GBPs) belong to the dynamin superfamily of large GTP binding proteins. A biochemical feature common to these proteins is guanosine-triphosphate (GTP) binding leading to self-assembly of the proteins, and this in turn results in higher catalytic GTP hydrolysis activity. In the case of human guanylate binding protein 1 (hGBP1) homodimer formation is observed after binding of nonhydrolyzable GTP analogs like GppNHp. hGBP1 is one of seven GBP isoforms identified in human. While cellular studies suggest heterocomplex formation of various isoforms biochemical binding studies in quantitative terms are lacking. In this work we established a method to study hGBP1 interactions by attaching this protein in a defined orientation to a surface allowing for interaction with molecules from the solution. Briefly, specifically biotinylated hGBP1 is attached to a streptavidin layer on a self-assembled monolayer (SAM) surface allowing for characterization of the packing density of the immobilized protein by surface plasmon resonance (SPR) technology and atomic force microscopy (AFM), respectively. In addition, the enzymatic activity of immobilized hGBP1 and the kinetics of interaction with binding partners in solution are quantified. We present a procedure for attaching an enzyme in a defined orientation to a surface which exposes its active end, the GTPase domain to the solution resulting in a homogeneous population of this enzyme in terms of enzymatic activity and of interaction with soluble proteins.     

Mesoporous Silica Sputter‐Coated onto ITO: Electrochemical Processes,Ion Permeability,and Gold Deposition Through NanoPores

“Simple” silica films of 50 nm and 100 nm thickness are sputter‐coated onto ITO substrates and shown to be structured with in‐planed features of ca. 15 nm and pores <5 nm (based on GISAXS). In electrochemical measurements membrane pore effects are observed. The oxidation current for Fe(CN)₆^4? in aqueous KNO₃ strongly depends on the electrolyte concentration. Poly‐cationic poly(diallyl‐dimethylammonium) (PDDA) cannot enter these pores, but is adsorbed onto the outer surface of the silica film. During gold electrodeposition, PDDA causes growth of “discs”. Gold deposits adhere well and a comparison of glucose electrooxidation activity reveals significant improvements.     

Integral models in unramified mixed characteristic (0, 2) of hermitian orthogonal Shimura varieties of PEL type,Part II

We construct relative PEL type embeddings in mixed characteristic (0, 2) between hermitian orthogonal Shimura varieties of PEL type. We use this to prove the existence of integral canonical models in unramified mixed characteristic (0, 2) of hermitian orthogonal Shimura varieties of PEL type.     

Covering Paths for Planar Point Sets

Given n points in the plane, a covering path is a polygonal path that visits all the points. If no three points are collinear, every covering path requires at least n/2 segments, and n?1 straight line segments obviously suffice even if the covering path is required to be noncrossing. We show that every set of n points in the plane admits a (possibly self-crossing) covering path consisting of n/2+O(n/logn) straight line segments. If the path is required to be noncrossing, we prove that (1?ε)n straight line segments suffice for a small constant ε>0, and we exhibit n-element point sets that require at least 5n/9?O(1) segments in every such path. Further, the analogous question for noncrossing covering trees is considered and similar bounds are obtained. Finally, it is shown that computing a noncrossing covering path for n points in the plane requires Ω(nlogn) time in the worst case.     

Novel synthesis of (d,l)-cis-chrysanthemic acid involving α,α′-dibromination of 2,2,5,5-tetramethylcyclohexane-1,3-dione: application to the enantioselective synthesis of (1R)-cis-chrysanthemic acid

cis-Chrysanthemic acid has been prepared in a few steps from dimethyldimedone via dibromination at alpha positions of each carbonyl carbons. The trans-dibromide which is almost exclusively formed has been isomerized to its cis-stereoisomer by highly chemoselective tandem H/K-K/H exchanges involving potassium bases at low temperature (<−40 °C). Carbocyclization of the potassium enolate intermediate takes place at around −30 °C and provide the bicyclo[3.1.0]-hexane skeleton. Lithiated bases behave differently and mainly lead to Br/M rather than to H/M exchange. We have been unsuccessful in using state of the art enantioselective metallation reactions to achieve the enantioselective synthesis of (1R)-cis-chrysanthemic acid using the disclosed strategy. This therefore still remains challenge.     

gem‐Dimethylcyclopropanation of dibenzylideneacetone using triisopropyl sulfoxonium tetrafluoroborate

The reaction between dibenzylideneacetone (dba) and triisopropyl sulfoxonium tetrafluoroborate has been reinvestigated. The stereochemistry of the major diasteromeric bis(gem‐dimethylcyclopropane) adduct has now been assigned as [(1RS,3RS)‐2,2‐dimethyl‐3‐phenylcyclopropyl][(1SR,3SR)‐2,2‐dimethyl‐3‐phenylcyclopropyl]methanone, C₂₃H₂₆O, by X‐ray crystallographic studies on a twinned crystal. The asymmetric unit contains two molecules of the adduct, the conformations of which differ in the orientation of the phenyl ring relative to the adjacent cyclopropanated double bond. The carbonyl groups of each adduct are aligned approximately along the a axis and in opposite directions to each other. The molecules pack to give a sinusoidal pattern along the b axis. This is the first acyclic bis(dimethylcyclopropyl) ketone for which an X‐ray crystal structure determination has been reported, and is also the first bis‐cyclopropanated dba analogue. The knowledge that the major diastereomer has the meso structure (and therefore the confirmation that the minor isomer is the racemate) will prove invaluable in future studies to utilize bis(dimethylcyclopropyl) ketones as reagents, in rearrangement processes, and as potential ligands and ligand precursors in organometallic chemistry.     

Catalysis of hydrosilylation by well-defined rhodium siloxide complexes immobilized on silica

Rhodium surface siloxide complexes were prepared directly by condensation of the molecular precursors ([{Rh(μ-OSiMe₃)(cod)}₂], [{Rh(μ-OSiMe₃)(tfb)}₂], [{Rh(μ-OSiMe₃)(nbd)}₂]) with silanol groups on silica surface (Aerosil 200 and SBA-15) and their structures were characterized by ¹³C and ²⁹Si CP/MAS NMR spectroscopy. Such single-site complexes were tested for their activity in hydrosilylation of carbon–carbon double bonds with triethoxysilane, heptamethyltrisiloxane and poly(hydro,methyl)(dimethyl)siloxane. The best catalyst appeared to be cyclooctadiene ligand-containing rhodium siloxide complex immobilized on Aerosil which was recycled as many as 20 times without loss of activity and selectivity in hydrosilylation of vinylheptamethyltrisiloxane with heptamethyltrisiloxane. On the ground of CP/MAS NMR measurements it was established that the mechanism of hydrosilylation catalyzed by silica-supported rhodium siloxide complexes is different from that for the complexes in the homogeneous system.     

Uniqueness of the Group Measure Space Decomposition for Popa’s {\mathcal{HT}} Factors

We prove that if ${\Gamma\curvearrowright (X, \mu)}$ is a free ergodic rigid (in the sense of Popa in Ann Math 163:809–889, 2006) probability measure preserving action of a group Γ with positive first ${\ell^2}$ -Betti number, then the II₁ factor ${L^{\infty}(X)\rtimes\Gamma}$ has a unique group measure space Cartan subalgebra, up to unitary conjugacy. We deduce that many ${\mathcal{HT}}$ factors, including the II₁ factors associated with the usual actions ${\Gamma\curvearrowright \mathbb{T^2}}$ and ${\Gamma\curvearrowright}$ ${{\rm SL}_2(\mathbb R)/{\rm SL}_2(\mathbb Z)}$ , where Γ is a non-amenable subgroup of ${{\rm SL}_2(\mathbb Z)}$ , have a unique group measure space decomposition.     

Restricted Kalman filter applied to dynamic style analysis of actuarial funds

We use dynamic style analysis to unveil the strategies followed by Brazilian actuarial funds from January 2004 to August 2008 and investigate whether managers’ decisions were compatible with the intention of protecting the investor against the negative effects of inflation. The main goal of this paper is to show that this methodology is suitable for allowing insurance companies to increase their capacity to monitor the behavior of portfolios and to control the amount of risk they assume. The basic steps of the method are to build and/or choose market indexes capable of characterizing the returns of the main securities available and to apply restricted linear state space models estimated with a Kalman filter with exact initialization. The main conclusions of this paper are the following: (1) the use of exact initialization of the Kalman filter promotes numerical stability; (2) there is no need to consider the entire set of market indicators because a subset containing only three indexes spans the relevant space of investment opportunities; and (3) the actuarial funds’ resources were primarily invested in inflation‐indexed bonds, but fund managers also left room to adjust their exposure to other assets not directly related to the objective of providing protection against inflation. Copyright © 2011 John Wiley & Sons, Ltd.