Miller–Urey Spark-Discharge Experiments in the Deuterium World

We designed and conducted a series of primordial-soup Miller-Urey style experiments with deuterated gases and reagents to compare the spark-discharge products of a “deuterated world” with the standard reaction in the “hydrogenated world”. While the deuteration of the system has little effect on the distribution of amino acid products, significant differences are seen in other regions of the product-space. Not only do we observe about 120 new species, we also see significant differences in their distribution if the two hydrogen isotope worlds are compared. Several isotopologue matches can be identified in both, but a large proportion of products have no equivalent in the corresponding isotope world with ca. 43 new species in the D world and ca. 39 new species in the H world. This shows that isotopic exchange (the addition of only one neutron) may lead to significant additional complexity in chemical space under otherwise identical reaction conditions.     

Sensitivity of Pareto Solutions in Multiobjective Optimization

The paper presents a sensitivity analysis of Pareto solutions on the basis of the Karush-Kuhn-Tucker (KKT) necessary conditions applied to nonlinear multiobjective programs (MOP) continuously depending on a parameter. Since the KKT conditions are of the first order, the sensitivity properties are considered in the first approximation. An analogue of the shadow prices, well known for scalar linear programs, is obtained for nonlinear MOPs. Two types of sensitivity are investigated: sensitivity in the state space (on the Pareto set) and sensitivity in the cost function space (on the balance set) for a vector cost function. The results obtained can be used in applications for sensitivity computation under small variations of parameters. Illustrative examples are presented.Research of this author was partially supported by Grant BEC2003-09067-C04-03.Research of this author was partially supported by NSERC Grant RGPIN-3492-00.Research of this author was partially supported by Grant BEC2003-09067-C04-02.     

Sound field reconstruction using acousto-optic tomography

When sound propagates through a medium, it results in pressure fluctuations that change the instantaneous density of the medium. Under such circumstances, the refractive index that characterizes the propagation of light is not constant, but influenced by the acoustic field. This kind of interaction is known as the acousto-optic effect. The formulation of this physical phenomenon into a mathematical problem can be described in terms of the Radon transform, which makes it possible to reconstruct an arbitrary sound field using tomography. The present work derives the fundamental equations governing the acousto-optic effect in air, and demonstrates that it can be measured with a laser Doppler vibrometer in the audible frequency range. The tomographic reconstruction is tested by means of computer simulations and measurements. The main features observed in the simulations are also recognized in the experimental results. The effectiveness of the tomographic reconstruction is further confirmed with representations of the very same sound field measured with a traditional microphone array.     

Preservers of eigenvalue inclusion sets

For a square matrix A, let S(A) be an eigenvalue inclusion set such as the Gershgorin region, the Brauer region in terms of Cassini ovals, and the Ostrowski region. Characterization is obtained for maps Φ on n×n matrices satisfying S(Φ(A)-Φ(B))=S(A-B) for all matrices A and B. From these results, one can deduce the structure of additive or (real) linear maps satisfying S(A)=S(Φ(A)) for every matrix A.     

Voltammetric determination of chlorothalonil and its respective reduction mechanism studied by density functional theory

Journal of Solid State Electrochemistry - A simple, fast, and direct electroanalytical method has been developed for the pesticide chlorothalonil determination using a boron-doped diamond electrode...     

σ-Silane Platinum(II) Complexes as Intermediates in C−Si Bond-Coupling Processes

Platinum complexes [Pt(NHC′)(NHC)][BAr^F] (in which NHC′ denotes a cyclometalated N-heterocyclic carbene ligand, NHC) react with primary silanes RSiH₃ to afford the cyclometalated platinum(II) silyl complexes [Pt(NHC-SiHR′)(NHC)][BAr^F] through a process that involves the formation of C−Si and Pt−Si bonds with concomitant extrusion of H₂. Low-temperature NMR studies indicate that the process proceeds through initial formation of the σ-SiH complexes [Pt(NHC′)(NHC)(HSiH₂R)][BAr^F], which are stable at temperatures below −10 °C. At higher temperatures, activation of one Si−H bond followed by a C−Si coupling reaction generates an agostic SiH platinum hydride derivative [Pt(H)(NHC′-SiH₂R)(NHC)][BAr^F], which undergoes a second Si−H bond activation to afford the final products. Computational modeling of the reaction mechanism indicates that the stereochemistry of the silyl/hydride ligands after the first Si−H bond cleavage dictates the nature of the products, favoring the formation of a C−Si bond over a C−H bond, in contrast to previous results obtained for tertiary silanes. Furthermore, the process involves a trans-to-cis isomerization of the NHC ligand before the second Si−H bond cleavage.     

Aromatization-driven Grob-fragmentation approach toward polyazaacenes. Synthesis and amination of multi-functionalized diazapentacenes

A general approach toward the synthesis of multi-functionalized diazapentacene derivatives 1, using 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene (TDCp, 2), a substituted benzene-1,2-diamine (ADA, 6), and a naphthalene-1,4-dione (BQ, 3) as the building units, is described. The synthesis basically entails three operations: (i) oxidation of the dichloroetheno-bridge in the Diels-Alder cycloadduct 4 of TDCp and 3, (ii) condensation of the 1,2-diketone 5 thus generated with an ADA to give quinoxaline-fused polycyclic compounds 7, followed by (iii) an one-pot, three-reaction process keyed upon the base- or acid-catalyzed aromatization-driven Grob-type fragmentation to produce quinoxaline ring-embedded diazapentaceneesters 1. The diazapentacene derivative 1a underwent the nucleophilic aromatic ipso-amination with primary and secondary amines to afford the amino-substituted derivatives 12, which tend to self-assemble in solid state driven by the cofacial π-stacking interactions, demonstrated by the crystal packing structures of 12a and 12f.     

A fitness for purpose approach to validation and verification of analytical measurements

Accreditation and Quality Assurance - Validation (and in some extension verification) are concepts often applied to analytical procedures (or methods). The new edition of ISO/IEC 17025 clearly...