Dual Hard/Soft Gold Catalysis: Intermolecular Friedel–Crafts‐Type α‐Amidoalkylation/Alkyne Hydroarylation Sequences by N‐Acyliminium Ion Chemistry

Gold catalysts have been applied in cascade‐type reactions for the synthesis of different nitrogen‐based compounds. The reactions likely proceed by a new gold‐catalyzed cascade intermolecular α‐amidoalkylation/intramolecular carbocyclization cascade process by unifying both the σ‐ and π‐Lewis acid properties of the gold salts. In the first part of this report we show that the σ‐Lewis acidity of gold(I) and gold(III) could be exploited to efficiently catalyze the nucleophilic substitution of various alkoxy‐ and acetoxylactams. The reaction was found to be applicable to a wide range of cyclic N‐acyliminium ion precursors and various nucleophiles, including allyltrimethylsilane, silyl enol ethers, arenes, and active methylene derivatives. As a logical progression of this study, a combined hard/soft binary catalytic gold system was then used to implement an unprecedented tandem intermolecular Friedel–Crafts amidoalkylation/intramolecular hydroarylation sequence allowing an expedient access to new, complex, fused polyheterocyclic structures from trivial materials.     

Recent trends in ultra‐fast HPLC: New generation superficially porous silica columns

New generation columns, i.e. packed with superficially porous silica particles are available as trade names with following manufacturers: Halo, Ascentis Express, Proshell 120, Kinetex, Accucore, Sunshell, and Nucleoshell. These provide ultra‐fast HPLC separations for a variety of compounds with moderate sample loading capacity and low back pressure. Chemistries of these columns are C₈, C₁₈, RP‐Amide, hydrophilic interaction liquid chromatography, penta fluorophenyl (PFP), F5, and RP‐aqua. Normally, the silica gel particles are of 2.7 and 1.7 μm as total and inner solid core diameters, respectively, with 0.5‐μm‐thick of outer porous layer having 90 Å pore sizes and 150 m²/g surface area. This article describes these new generation columns with special emphasis on their textures and chemistries, separations, optimization, and comparison (inter and intra stationary phases). Besides, future perspectives have also been discussed.     

ARMA model order and parameter estimation using genetic algorithms

A new method for simultaneously determining the order and the parameters of autoregressive moving average (ARMA) models is presented in this article. Given an ARMA (p, q) model in the absence of any information for the order, the correct order of the model (p, q) as well as the correct parameters will be simultaneously determined using genetic algorithms (GAs). These algorithms simply search the order and the parameter spaces to detect their correct values using the GA operators. The proposed method works on the principle of maximizing the GA fitness value relying on the deviation between the actual plant output, with or without an additive noise, and the estimated plant output. Simulation results show in detail the efficiency of the proposed approach. In addition to that, a practical model identification and parameter estimation is conducted in this article with results obtained as desired. The new method is compared with other well-known methods for ARMA model order and parameter estimation.     

Photoinduced effects on the optical constants of a-Ge–Se–Bi chalcogenide glassy thin films

In addition to the conversion from p-type to n-type conductivity that occurs in Ge–Se–Bi thin films when Bi is incorporated in a certain concentration. We found that, when these films were illuminated to UV light, after being annealed at glass transition temperature T _g, the photobleaching is dominant for Ge₂₀Se_80?x Bi _x (x=0, 2.5, and 5 at.%), while for Ge₂₀Se_72.5Bi_7.5 photodarkening is dominant. The photoinduced changes in the optical constants were studied. The refractive index (n) has been analysed according to the Wwmple–DiDominico single oscillator model and the values of E _o and E _d for exposed and unexposed films were determined, respectively. The photostructural effects were discussed in the light of single–double well model proposed by Tanaka and chemical bond approach.     

Invasive weed optimization for model order reduction of linear MIMO systems

In this work, a model order reduction (MOR) technique for a linear multivariable system is proposed using invasive weed optimization (IWO). This technique is applied with the combined advantages of retaining the dominant poles and the error minimization. The state space matrices of the reduced order system are chosen such that the dominant eigenvalues of the full order system are unchanged. The other system parameters are chosen using the invasive weed optimization with objective function to minimize the mean squared errors between the outputs of the full order system and the outputs of the reduced order model when the inputs are unit step. The proposed algorithm has been applied successfully, a 10th order Multiple-Input–Multiple-Output (MIMO) linear model for a practical power system was reduced to a 3rd order and compared with recently published work.     

Exact asymptotic behavior near the boundary to the solution for singular nonlinear Dirichlet problems

We take up the existence and the exact asymptotic behavior near the boundary ∂Ω of the unique classical solution to a singular Dirichlet problem

     

Determination of lead and cadmium in biological samples by potentiometric stripping analysis

Summary The determination of lead and cadmium in biological materials was carried out by potentiometric stripping analysis. Supporting electrolyte was a mixture of NaCl and HCl. In the presence of 4% lumatom in methanol, oxidation potentials of –0.46 V for Pb and –0.68 V for Cd were found (vs. SCE). The method was applied to different standard reference materials (leaves, needles, hair) and was also compared with the differential pulse anodic stripping technique. The latter presented considerable difficulties, in particular by the interference of oxygen.

---

Bestimmung von Blei und Cadmium in biologischem Material durch potentiometrische Stripping-Analyse

Zusammenfassung Als Trägerelektrolyt diente bei diesem Verfahren ein Gemisch von NaCl und HCl. In Gegenwart von 4% Lumatom in Methanol wurden Oxidationspotentiale von –0,46 V für Pb und –0,68 V für Cd (gegen SKE) erhalten. Die Methode wurde auf verschiedene Referenzmaterialien (Laub, Nadeln, Haar) angewendet und auch mit der Differentialpuls-Anodic Stripping-Analyse verglichen. Bei der letzteren ergaben sich größere Schwierigkeiten, hauptsächlich durch störenden Sauerstoff.

     

Models of the axiomatic theory associated with the lattice of subspaces of a finite-dimensional Hilbert space

It is shown that we can associate with the latticeL of subspaces of a separable Hilbert space an axiomatic theory in sentential logic that reflects some of the basic properties of the simplest types of experimental reports in quantum mechanics. It is also shown that every collection of mutually nonorthogonal elements ofL determines a model of the axioms and that, if the Hilbert space is finite dimensional, every model is determined this way.     

N-trialkylsilyl bistrifluoromethanesulfonimides (R3SiNTf2) are powerful catalysts for the highly efficient alpha-amido alkylation reactions of silicon-based nucleophiles

[reaction: see text] In situ formed N-trialkylsilyl bistrifluoromethanesulfonimides (R3SiNTf2) species have been shown to efficiently catalyze the nucleophilic substitution reactions of chiral 5-oxypyrrolidin-2-ones by silicon-based nucleophiles. The reaction rates were significantly accelerated in comparison to the cases where the usual triflate catalysts are used. Adducts were obtained in high yields and usual stereoselectivities within short reaction times, and the process was compatible with a semipreparative scale.     

Composition and electric field effects on the transport properties of Bi doped chalcogenide glasses thin films

The temperature dependence of the DC electrical conductivity σ_DC was measured in the temperature range from 300–500 K. It was found that there are double activation energies, E_σ, for Ge₂₀Se_80−xBi_x (x=0, 2.5 and 5 at%) films, while there is single activation energy for Ge₂₀Se_72.5Bi_7.5. when incorporation of Bi=7.5 at%, the pre-exponential value σ₀ decreases by about six order of magnitude, the activation energy in the extended states E_σ decreases from 0.96 to 0.09 eV. Also the effect of applied electric field was studied and observed that, activation energy in high temperature region increases with increasing electric field; this behavior can be understood assuming that the contribution to the conductivity activation process is due to conduction in the extended states and also due to hopping in the localized states. With the increasing electric field, as former process, which is having high activation energy, becomes more predominant due to the dumping of the carriers in the extended states, the effective activation energy of the system increases, in spite of the fact that the activation energy of the extended states conduction may remain constant. Finally, the electrical data suggests that the addition of bismuth produces localized states near the conduction band edge so that the electrical transport is due to hopping of electrons after being excited into localized states at the conduction band edge.