A nonnormal look at polychoric correlations: modeling the change in correlations before and after discretization

Two algorithms for establishing a connection between correlations before and after ordinalization under a wide spectrum of nonnormal underlying bivariate distributions are developed by extending the iteratively found normal-based results via the power polynomials. These algorithms are designed to compute the polychoric correlation when the ordinal correlation is specified, and vice versa, along with the distributional properties of latent, continuous variables that are subsequently ordinalized through thresholds dictated by the marginal proportions. The method has broad applicability in the simulation and random number generation world where modeling the relationships between these correlation types is of interest.     

Nitrosylation of Nitric‐Oxide‐Sensing Regulatory Proteins Containing [4Fe‐4S] Clusters Gives Rise to Multiple Iron–Nitrosyl Complexes

The reaction of protein‐bound iron–sulfur (Fe‐S) clusters with nitric oxide (NO) plays key roles in NO‐mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe‐S clusters has been hampered by a lack of information about the nature of the iron‐nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe‐4S] cluster to sense NO. This work reveals that nitrosylation yields multiple products structurally related to Roussin's Red Ester (RRE, [Fe₂(NO)₄(Cys)₂]) and Roussin's Black Salt (RBS, [Fe₄(NO)₇S₃]. In the latter case, the absence of ³²S/³⁴S shifts in the Fe?S region of the NRVS spectra suggest that a new species, Roussin's Black Ester (RBE), may be formed, in which one or more of the sulfide ligands is replaced by Cys thiolates.     

Stabilized nodal‐based finite element methods for the magnetic induction problem

We consider the time‐dependent magnetic induction model as a step towards the resistive magnetohydrodynamics model in incompressible media. Conforming nodal‐based finite element approximations of the induction model with inf‐sup stable finite elements for the magnetic field and the magnetic pseudo‐pressure are investigated. Based on a residual‐based stabilization technique proposed by Badia and Codina, SIAM J. Numer. Anal. 50 (2012), pp. 398–417, we consider a stabilized nodal‐based finite element method for the numerical solution. Error estimates are given for the semi‐discrete model in space. Finally, we present some examples, for example, for the magnetic flux expulsion problem, Shercliff's test case and singular solutions of the Maxwell problem. Copyright © 2015 John Wiley & Sons, Ltd.     

Cylindrospermopsin determination using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard

Cylindrospermopsin (CYN) was determined by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard. In the selected ion monitoring of LC/ESI-MS, m/z 414 for CYN and 237 for HEPES were monitored using the negative mode; the retention times of CYN and HEPES were 12.41 and 14.21 min, respectively. CYN was determined from peak area ratios of m/z 414/237. By the treatment of an anion exchange cartridge using a buffer at pH 10.5, CYN was isolated and condensed. No interfering peak was observed. Linearity of this method was observed at the range of 0.10-31.12 ng. Total coefficients of variation were 5.1 and 2.9% at 104 and 1038 μg CYN L⁻¹. The quantitative limit at a signal-to-noise (S/N) ratio of 10 was 0.16 ng.CYN concentration in natural waters is low. CYN in waters should be condensed for determination. This method including the treatment for isolation and condensation of CYN is useful for determination of CYN in environmental and/or drinking waters.     

Heavy metal contamination in street dusts of Istanbul (Pendik to Levent) E-5 highway

Street dust composition is an important environmental parameter that should be considered in investigations of environmental pollution originating from traffic. In this study, fifty-six samples of street dusts were collected during the period December 2003-April 2004 from Pendik to Levent on E-5 highway in Istanbul, Turkey. Analyses were determined by graphite furnace atomic absorption spectrometry after digestion using USEPA, 1996 (Method 3050B). The mean concentration levels of Pb, Mn, Zn, Ni, Cd and Cu were found to be 368.3, 747.8, 431.2, 27.1, 0.3 and 191.1 microg/g respectively. Pb, Cu, Zn and Mn mean concentrations in studied areas were higher than levels of these heavy metals according to USEPA (1992) and Republic of Turkey Ministry of Environment and Foresty (2003). Highly significant correlations except for Mn were found between the number of vehicles and heavy metal concentrations.     

Deformation Driven Homogenization of Fracturing Solids

The paper discusses numerical formulations of the homogenization for solids with discrete crack development. We focus on multi–phase microstructures of heterogeneous materials, where fracture occurs in the form of debonding mechanisms as well as matrix cracking. The definition of overall properties critically depends on the developing discontinuities. To this end, we extend continuous formulations [1] to microstructures with discontinuities [2]. The basic underlying structure is a canonical variational formulation in the fully nonlinear range based on incremental energy minimization. We develop algorithms for numerical homogenization of fracturing solids in a deformation–driven context with non–trivial formulations of boundary conditions for (i) linear deformation and (ii) uniform tractions. The overall response of composite materials with fracturing microstructures are investigated. As a key result, we show the significance of the proposed non–trivial formulation of a traction–type boundary condition in the deformation–driven context. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of oxazoline functionalized polypropene using metallocene catalysts

Using two different zirconocene/MAO catalyst systems, propene was copolymerized with the comonomers 2‐(9‐decene‐1‐yl)‐1,3‐oxazoline and 2‐(4‐(10‐undecene‐1‐oxo)phenyl)‐1,3‐oxazoline, respectively. The catalysts used were rac‐Et[Ind]₂ZrCl₂ and rac‐Me₂Si[2‐Me‐4, 5‐BenzInd]₂ZrCl₂. Up to 0.53 mol‐% oxazoline could be incorporated into polypropene. Oxazoline content, molecular weight, degree of isotacticity and melting behavior were dependent on the catalyst system, comonomer structure and comonomer concentration in the feed.     

A fluorescence study on critical exponents during sol-gel phase transition in complex monomeric systems

Methyl methacrylate (MMA), ethyl methacrylate (EMA) and various combinations of MMA with EMA were used during FCC experiments. Pyrene (P_y) was introduced as a fluorescence probe and fluorescence lifetimes from its decay traces were measured during sol-gel phase transitions. The fast transient fluorescence (FTRF) technique was used to study the critical exponents during sol-gel phase transition in free-radical crosslinking copolymerization (FCC). The results were interpreted in the view of percolation theory. The critical exponents of gel fraction, β and weight average degree of polymerization, γ were measured near the point of gel effect and found to be around 0.37 ± 0.015 and 1.69 ± 0.05 in all systems studied respectively.