Selenoketene substitution structure

Microwave studies (26.5–40 GHz) of further isotopic species of selenoketene formed by pyrolysis of 1,2,3-selenodiazole (¹²CH₂¹²C^76,77,82Se, ¹²CH₂¹³C⁸⁰Se and ¹³CH₂¹²C⁸⁰Se) and by pyrolysis of 5-deuterio-1,2,3-selenodiazole (¹²CHD¹²C^78,80Se) are reported. In conjunction with earlier results for ¹²CH¹²C^78,80Se an r_s structure has been derived with distances SeC (1.706 Å), CC (1.303 Å), CH (1.0908 A) and a HCH bond angle of 119.7°. The geometry of the CH₂C moiety of selenoketene is closer to allene, CH₂CCH₂, than to ketene, CH₂CO.     

A suggested revised conformation of methylthionitrite as seen by its spectra and preliminary ab initio calculations

A proof has recently been given that gaseous methylthionitrite, CH₃SNO, occurs exclusively (or mainly) in its anti conformation [1]. The present paper claims that existing spectral evidence and ab initio calculations now performed suggest that gaseous methylthionitrite is mainly the syn conformer, the extra stability being of the order 1–2 kcal mol^?1. Methyl group rotation in the syn conformer is hindered by a three-fold barrier of height 689 cm^?1 while the methyl group rotation in the anti conformer is hardly hindered. The syn/anti energy difference and the barriers hindering methyl group rotation closely parallel the corresponding measured quantities in methylnitrite, CH₃ONO.     

Nonabelian K-theory: The nilpotent class of K1 and general stability

A functorial filtration GL _n =S^–1L _n S⁰L _n S ⁱ L _n E _n of the general linear group GL _{n, n} 3, is defined and it is shown for any algebra A, which is a direct limit of module finite algebras, that S^–1 L _n (A)/S⁰L _n (A) is abelian, that S⁰L _n (A) S¹L _n (A) is a descending central series, and that S ⁱ L _n (A) = E _n(A) whenever i the Bass-Serre dimension of A. In particular, the K-functors k ₁ S ⁱ L _n =S ⁱ L _n /E _n are nilpotent for all i 0 over algebras of finite Bass-Serre dimension. Furthermore, without dimension assumptions, the canonical homomorphism S ⁱ L _n (A)/S ⁱ⁺¹ L _n (A)S ⁱ L _{n+ 1}(A)/S ⁱ⁺¹ L _{n + 1} (A) is injective whenever n i + 3, so that one has stability results without stability conditions, and if A is commutative then S⁰L _n (A) agrees with the special linear group SL _n (A), so that the functor S⁰L _n generalizes the functor SL _n to noncommutative rings. Applying the above to subgroups H of GL _n (A), which are normalized by E _n(A), one obtains that each is contained in a sandwich GL _n (A, ) H E _n(A, ) for a unique two-sided ideal of A and there is a descending S⁰L _n (A)-central series GL _n (A, ) S⁰L _n (A, ) S¹L _n (A, ) S ⁱ L _n (A, ) E _n(A, ) such that S ⁱ L _n (A, )=E _n(A, ) whenever i Bass-Serre dimension of A.Dedicated to Alexander Grothendieck on his sixtieth birthday     

Ab initio calculation of electronic circular dichroism fortrans-cyclooctene using London atomic orbitals

Summary The second-quantization magnetic dipole operator that arises when London atomic orbitals are used as basis functions is derived. In atomic units, the magnetic dipole operator is defined as the negative of the first derivative of the electronic Hamiltonian containing the interaction with the external magnetic field. It is shown that for finite basis sets, the gauge origin dependence of the resulting magnetic dipole operator is analogous to that of the exact operator, and that the derived operator converges to the exact operator in the limit of a complete basis set. It is also demonstrated that the length expression for the rotatory strength in linear response calculations gives gauge-origin-independent results. Sample calculations ontrans-cyclooctene and its fragments are presented. Compared to conventional orbitals, the basis set convergence of the rotatory strengths calculated in the length form using London atomic orbitals is favourable. The rotatory strength calculated fortrans-cyclooctene agrees nicely with the corresponding experimental circular dichroism spectrum, but the spectra for the fragment molecules show little resemblance with that oftrans-cyclooctene.Dedicated to Prof. Jan Linderberg     

Basic investigations for laser microanalysis: I. Optical emission spectrometry of laser-produced sample plumes

In order to find optimum conditions for laser ablation and atomization for analytical purposes, time resolved emission spectra of Nd:YAG laser-produced plasma plumes propagating into noble gas atmospheres of different pressures were measured with an optical multichannel analyzer. The time evolution of the plasma temperature was determined. Strong temperature changes were observed depending on the matrix composition. The analytical figures of merit of optical emission spectrometry (OES) of laser-produced sample plasmas were determined using, as examples, measurements of two analytes (silicon and chromium) in homogeneous and low-alloyed standard steel samples.     

The rate of approximation by means of polynomials with restricted coefficients

For a sequenceA = {A_k} _k?1 ^∞ of positive constants letP _A = {p(x): p(x) = Σ _k?1 ⁿ a _k x _k ,n = 1,2, …, ¦a _k ≦ A _k ^k }. We consider the rate of approximation by elements ofP _A , of continuous functions in [0, 1] which vanish at x = 0. Also a classP _A is called “efficient” if globally it guarantees the Jackson rate of approximation. Some necessary conditions for efficiency and some sufficient ones are derived.     

On the magnetoelastic effects within the magnetic domain wall

In terms of molecular field theory we investigate the magnetoelastic phenomena in a ferromagnet with first order phase transition. Special attention is paid to the difference of lattice distortion within and outside the magnetic domain wall. We have shown that in some circumstances, near the Curie temperature, both low and high temperature phases can coexist.     

Mean field theory of self-organized critical phenomena

A mean field theory is presented for the recently discovered self-organized critical phenomena. The critical exponents are calculated and found to be the same as the mean field values for percolation. The power spectrum has 1/f behavior with exponentg4=1.     

Development of an analytical method for the determination of valsartan in commercial drug and sewage sludge samples by HPLC and evaluation of its stability under simulated gastric conditions

An analytical method was developed for determination of valsartan in commercial drug and sewage sludge samples by HPLC–UV using a single wavelength (250 nm). The effect of different environmental storage conditions on the stability of valsartan was examined for a period of 85 days, after which no degradation was observed. The post oral administration stability of the valsartan was also investigated by testing valsartan under simulated gastric conditions. Results obtained showed that the structure of valsartan was conserved over 3.5-h period. The calibration plot of the study was linear over a wide concentration range with a correlation coefficient of 0.9999. The limit of detection and limit of quantitation were found to be 0.014 and 0.046 µ g mL^?1, respectively. The percentage recovery of valsartan from sewage sludge was found to be 99.8%.