Calculation of partition functions of tetra-atomic molecules

A calculation of partition functions of tetra-atomic molecules performed on the basis of the date obtained by means of the ab initio quantum mechanical method is proposed. The symmetry coordinates are used for partitioning the vibrational secular problem. The results for N₂H₂ and C₂H₂ molecules are presented. The accuracy is found to be comparable with those of results obtained using the experimentally derived structural parameters.     

Metal-catalyzed silacyclopropanation of mono- and disubstituted alkenes

As an alternative to the strongly reducing conditions necessary for the formation of silacyclopropanes, silylene transfer was developed as a mild, functional group tolerant method of silacyclopropanation. Complex silacyclopropanes were formed from functionalized alkenes using cyclohexane di-tert-butyl silacyclopropane, 1, as the source of t-Bu(2)Si. Di-tert-butyl silylene can be generated from 1 through the use of a catalytic amount of a metal salt. At -27 degrees C, silver triflate catalyzes the transfer of t-Bu(2)Si from 1 to mono- and disubstituted alkenes stereospecifically and diastereoselectively. In situ functionalization of silacyclopropanes with catalytic zinc bromide and methyl formate provides for an expedient one-flask synthesis of complex oxasilacyclopentanes from alkenes.     

Energies of electronic states of promoter ions in hydrodesulfurization catalysts

Poly-vinylpyrrolidone-anchored (PVP) supported platinum catalyst (PVP-Pt) and rare earth metals (Sm³⁺, Pr³⁺, Ce³⁺, Nd³⁺and La³⁺) promoted PVP-Pt catalysts were prepared and used in the hydrogenation of o- and m-chloronitrobenzene (CNB) in ethanol at 303 K and atmospheric pressure. It was found that rare earth metals improved the selectivity of chloronitrobenzene to chloroaniline (CAN), while the hydrogenation rate of CNB decreased. In the presence of NaOH, PVP-Pr-Pt and PVP-La-Pt catalysts exhibit the highest selectivity in the hydrogenation of CNB. At the same time different support materials of Pt catalyst (such as polyethylene glycol (PEG), ethyl cellulose (EC)) possessed great influence on catalytic activity and selectivity of p-CAN.This revised version was published online in December 2005 with corrections to the Cover Date.     

Chemical and photochemical synthesis of substituted dihydro-thieno[2',3':4,5]thieno[2,3-c]quinolin-6-ones and tetrahydro-dithieno[2,3-b:2',3'-d]thieno[2'',3''c:2'',3''c']diquinolin-6,14-dione

Some new substituted dihydrothieno[2',3':4,5]thieno[2,3-c]quinolin-6-ones 9- 12 and tetrahydrodithieno[2,3-b: 2',3'-d]thieno[2',3'-c:2',3'-c']diquinolin-6,14-dione (17) were prepared from the corresponding new anilides 5-8 and from the corresponding dianilide 15, respectively, by a multistep combination of chemical and photochemical reactions. All the prepared compounds are of particular interest because they might serve as DNA intercalators in anticancer therapy.     

Total Synthesis of a Natural Cerebroside from Euphorbiaceae

The regioselective total synthesis of the natural cerebroside (2R,15Z)‐N‐{(1S,2S,3R,4R,5Z)‐1‐[(β‐D ‐glucopyranosyloxy)methyl]‐2,3,4‐trihydroxyheptadec‐5‐en‐1‐yl}‐2‐hydroxytetracos‐15‐enamide ( 2 ), originally isolated from Euphorbiaceae, is reported in full detail.     

Development and validation of a sensitive assay for the quantification of imatinib using LC/LC‐MS/MS in human whole blood and cell culture

We developed and validated a semi‐automated LC/LC‐MS/MS assay for the quantification of imatinib in human whole blood and leukemia cells. After protein precipitation, samples were injected into the HPLC system and trapped onto the enrichment column (flow 5 mL/min); extracts were back‐flushed onto the analytical column. Ion transitions [M + H]⁺ of imatinib (m/z = 494.3 → 394.3) and its internal standard trazodone (372.5 → 176.3) were monitored. The range of reliable response was 0.03–75 ng/mL. The inter‐day precisions were: 8.4% (0.03 ng/mL), 7.2% (0.1 ng/mL), 6.5% (1 ng/mL), 8.2% (10 ng/mL) and 4.3% (75 ng/mL) with no interference from ion suppression. Autosampler stability was 24 hs and samples were stable over three freeze–thaw cycles. This semi‐automated method is simple with only one manual step, uses a commercially available internal standard, and has proven to be robust in larger studies. Copyright © 2009 John Wiley & Sons, Ltd.     

Optimization of a flow injection system with amperometric detection for arsenic determination.

A selective and sensitive analytical procedure for rapid arsenic determination by gas-diffusion flow injection analysis with amperometric detection was developed. The method is based on the arsenite reduction by NaBH(4). Derived arsine diffuses through a PTF membrane into the acceptor flow stream and is amperometrically determined on a platinum working electrode. The limit of detection (3 sigma) at room temperature was 5 microg/dm(3) of As(III). The relative standard deviation for a 1 mg/dm(3) As(III) standard was 1.96% for six repetitive injections. Arsenic(V) was determined after its prereduction with potassium iodide. Arsenic determination was not interferred with by 1 mg/dm(3) Sb(III), 5 mg/dm(3) Sn(II), 10 mg/dm(3) Se(IV), 1 mg/dm(3) As(V), 1 mg/dm(3) hydrasine, 1 mg/dm(3) Fe(II) or 0.5 mg/dm(3) Fe(III) solution. The throughput of this method was 60 analyses per hour. This method was successfully applied to arsenic determination in some power plant waste water samples.     

Quantized Frame Expansions with Erasures

Frames have been used to capture significant signal characteristics, provide numerical stability of reconstruction, and enhance resilience to additive noise. This paper places frames in a new setting, where some of the elements are deleted. Since proper subsets of frames are sometimes themselves frames, a quantized frame expansion can be a useful representation even when some transform coefficients are lost in transmission. This yields robustness to losses in packet networks such as the Internet. With a simple model for quantization error, it is shown that a normalized frame minimizes mean-squared error if and only if it is tight. With one coefficient erased, a tight frame is again optimal among normalized frames, both in average and worst-case scenarios. For more erasures, a general analysis indicates some optimal designs. Being left with a tight frame after erasures minimizes distortion, but considering also the transmission rate and possible erasure events complicates optimizations greatly.     

A contribution to the elemental profile of the leaf samples of newly developed Cabernet Franc varieties

The elemental profile of the leaf samples of three Cabernet Franc clone candidates recently developed in Serbia (Nos. 02, 010 and 012) obtained in the last phase of clonal selection was examined within this study by ICP-OES. Optimal content of Al, Fe, Cu and Zn, the metals well known for their links with a number of neurodegenerative disorders including Alzheimer’s disease, has actually highlighted the potential of the leaf sample No. 10 to afford a novel food supplement of natural origin possessing well balanced metal ingredients. Furthermore, lower content of some other elements (Cr, Mn, Ni and Pb) thoroughly supports such a claiming. Finally, the most favourable K/Na ratio observed for the aforementioned sample points out its likely cardioprotectivity. However, two other Cabernet Franc clone candidates might also be recommended for breeding in the same or similar viticultural conditions, since all obtained values were below toxic ones for human consumption.