20, 21-Azirdin-Steroide: Reaktion von Derivaten der Oxime von 5-Pregnen-20-on,9β,10α-5-Pregnen-20-on und 9β,10α-5,7-Pregnadien-20-on mit Lithiumaluminiumhydrid und von 3β-Hydroxy-5-pregnen-20-on-oxim mit Grignard-Verbindungen

20, 21-Aziridine Steroids: Reaction of Derivatives of the Oximes of 5-Pregnen-20-one, 9β, 10α-5-Pregnen-20-one and 9β, 10α-5,7-Pregnadiene-20-one with Lithium Aluminium Hydride, and of 3β-Hydroxy-5-pregnen-20-one Oxime with Grignard Reagents. Reduction of 3β-hydroxy-5-pregnen-20-one oxime ( 2 ) with LiAlH₄ in tetrahydrofuran yielded 20α-amino-5-pregnen-3β-ol ( 1 ), 20β-amino-5-pregnen-3β-ol ( 3 ), 20β, 21-imino-5-pregnen-3β-ol ( 6 ) and 20β, 21-imino-5-pregnen-3β-ol ( 9 ). The aziridines 6 and 9 were separated via the acetyl derivatives 7 and 10 . The reaction of 6 and 9 with CS₂ gave 5-(3β-hydroxy-5-androsten-17β-yl)-thiazolidine-2-thione ( 8 ). Treatment of the 20-oximes 12 and 15 of the corresponding 9β,10α(retro)-pregnane derivatives with LiAlH₄ gave the aziridines 13 and 16 , respectively. Their deamination led to the diene 14 and triene 17 , respectively. Reduction of isobutyl methyl ketone-oxime with LiAlH₄ in tetrahydrofuran yielded 2-amino-4-methyl-pentane ( 19 ) as main product, 1, 2-imino-4-methyl-pentane ( 22 ) as second product and the epimeric 2,3-imino-4-methyl-pentanes 20 and 21 as minor products. – 3β-Hydroxy-5-pregnen-20-one oxime ( 2 ) was transformed by methylmagnesium iodide in toluene to 20α, 21-imino-20-methyl-5-pregnen-3β-ol ( 23 ) and 20β, 21-imino-20-methyl-5-pregnen-3β-ol ( 26 ). Acetylation of these aziridines was accompanied by elimination reactions leading to 3β-acetoxy-20-methylidene-21-N-acetylamino-5-pregnene ( 30 ) and 3β-acetoxy-20-methyl-21-N-acetylamino-5,17-pregnadiene ( 32 ). The reaction of oxime 2 with ethylmagnesium bromide in toluene gave 20α, 21-imino-20-ethyl-5-pregnen-3β-ol ( 24 ) and 20α,21-imino-20-ethyl-5-pregnen-3β-ol ( 27 ). Acetylation of 24 and 27 led to 3β-acetoxy-20-ethylidene-21-N-acetylamino-5-pregnene ( 31 ), 3β-acetoxy-20-ethyl-21-N-acetylamino-5,17-pregnadiene 33 and 3β, 20-diacetoxy-20-ethyl-21-N-acetylamino-5-pregnene ( 37 ). With phenylmagnesium bromide in toluene the oxime 2 was transformed to 20β, 21-imino-20-phenyl-5-pregnen-3β-ol ( 25 ) and 20β,21-imino-20-phenyl-5-pregnen-3β-ol ( 28 ). Acetylation of 25 and 28 yielded 3β-acetoxy-20-phenyl-21-N-acetylamino-5, 17-pregnadiene ( 34 ) and 3β,20-diacetoxy-20-phenyl-21-N-acetylamino-5-pregnene ( 39 ). LiAlH₄-reduction of 39 gave 3β, 20-dihydroxy-20-phenyl-21-N-ethylamino-5-pregnene ( 41 ). – The 20, 21-aziridines are stable to LiAlH₄. Consequently they are no intermediates in the formation of the 20-amino derivatives obtained from the oxime 2 .     

The influence of nanoparticle fillers on the morphology of a spin-cast thin film polymer blend

Polymer/nanoparticle composite films are receiving growing attention thanks to their potential for application in ultra-thin electronic and optical devices. Polymer blend demixing has been shown to be a suitable technique for the structuring of polymer thin films and the patterning of nanoparticles (NP) within them. In this work we show that the morphology of thin polymer films made by spin-casting a polymer blend solution containing NP fillers on a surface depends strongly on the concentration of NP fillers. More specifically, polystyrene/polymethylmethacrylate (PS/PMMA) films formed from a toluene solution, and which demix following a nucleation and growth mechanism, were studied. It was found that both the height and the surface density of PMMA domains increased as the concentration of CoPt:Cu NPs in the film was increased. We find that similar effects are induced in a NP-free PS/PMMA demixed film upon increasing the molecular weight of the PS molecules. This suggests that under certain conditions the NPs and the polymer molecules in the blend do not behave as separate species but form aggregates.     

A short proof of a theorem of Ruelle

Using the existence of conformal measures in the sense ofSullivan [4] andDenker, Urbaski [2] we give a simple proof of Ruelle's Theorem, that the Hausdorff dimension of a hyperbolic Julia set is the solution of the equationP(R,–tlog|R|)=0.     

On the supermodular knapsack problem

In this paper we introduce binary knapsack problems where the objective function is nonlinear, and investigate their Lagrangean and continuous relaxations. Some of our results generalize previously known theorems concerning linear and quadratic knapsack problems. We investigate in particular the case in which the objective function is supermodular. Under this hypothesis, although the problem remains NP-hard, we show that its Lagrangean dual and its continuous relaxation can be solved in polynomial time. We also comment on the complexity of recognizing supermodular functions. The particular case in which the knapsack constraint is of the cardinality type is also addressed and some properties of its optimal value as a function of the right hand side are derived.Work done while the authors were visiting Rutgers University.     

Analysis of orientations of collagen fibers by novel fiber-tracking software.

Recent evidence supports the notion that biological functions of extracellular matrix (ECM) are highly correlated to not only its composition but also its structure. This article integrates confocal microscopy imaging and image-processing techniques to analyze the microstructural properties of ECM. This report describes a two- and three-dimensional fiber middle-line tracing algorithm that may be used to quantify collagen fibril organization. We utilized computer simulation and statistical analysis to validate the developed algorithm. These algorithms were applied to confocal images of collagen gels made with reconstituted bovine collagen type I, to demonstrate the computation of orientations of individual fibers.     

On-line monitoring of opaque liquids by photoacoustic spectroscopy

A new photoacoustic sensor system for on-line monitoring of highly concentrated and optical opaque liquid samples is presented. The dyeing of textiles is performed with highly concentrated dye solutions with concentrations ranging from 50 mg L(-1) up to 40 g L(-1). For process optimization and control of the wastewater, an on-line monitoring of the dye concentration is needed. Optical transmission measurements allow the determination of the dye concentration in a relatively small range. Samples with concentrations in the upper mg L(-1) and g L(-1) range have to be diluted before the measurement due to their optical opacity. Additionally, light-scattering particles have a strong effect on the transmitted light intensity. By photoacoustic spectroscopy, concentrations in condensed matter can be determined over several orders of magnitude. Furthermore, scattering particles do not generate any photoacoustic signal.     

An explicit quantum chemical method for modeling large solvation shells applied to aminocoumarin C151

The absorption spectra of aminocoumarin C151 in water and n-hexane solution are investigated by an explicit quantum chemical solvent model. We improved the efficiency of the frozen-density embedding scheme, as used in a former study on solvatochromism (J. Chem. Phys. 2005, 122, 094115) to describe very large solvent shells. The computer time used in this new implementation scales approximately linearly (with a low prefactor) with the number of solvent molecules. We test the ability of the frozen-density embedding to describe specific solvent effects due to hydrogen bonding for a small example system, as well as the convergence of the excitation energy with the number of solvent molecules considered in the solvation shell. Calculations with up to 500 water molecules (1500 atoms) in the solvent system are carried out. The absorption spectra are studied for C151 in aqueous or n-hexane solution for direct comparison with experimental data. To obtain snapshots of the dye molecule in solution, for which subsequent excitation energies are calculated, we use a classical molecular dynamics (MD) simulation with a force field adapted to first-principles calculations. In the calculation of solvatochromic shifts between solvents of different polarity, the vertical excitation energy obtained at the equilibrium structure of the isolated chromophore is sometimes taken as a guess for the excitation energy in a nonpolar solvent. Our results show that this is, in general, not an appropriate assumption. This is mainly due to the fact that the solute dynamics is neglected. The experimental shift between n-hexane and water as solvents is qualitatively reproduced, even by the simplest embedding approximation, and the results can be improved by a partial polarization of the frozen density. It is shown that the shift is mainly due to the electronic effect of the water molecules, and the structural effects are similar in n-hexane and water. By including water molecules, which might be directly involved in the excitation, in the embedded region, an agreement with experimental values within 0.05 eV is achieved.     

Studies with trialkylsilyltriflates: new syntheses and applications

Syntheses and applications are described for three useful reagents for silylation of unreactive substrates, $\text{tert}$-butyldimethylsilyl, triisopropylsilyl, and octadecyldimethylsilyl triflate.     

Kristallstruktur von Trisilber(I)amidosulfat-3-Ammoniak-2-Wasser,Ag3SO3N · 3NH3 · 2H2O

An X-ray crystal structure analysis of colourless Ag₃SO₃N · 3NH₃ · 2H₂O was carried out at room temperature:M=504.79, orthorhombic, P2₁2₁2₁,a=6.275 (1) Å,b=11.826 (2) Å,c=14.299 (12) Å,V=1061.10 ų,Z=4,d _x=3.160 Mgm^–3,F(000)=940, Mo K, =0.71069 Å (graphite monochromator), =5.60 mm^–1,R=4.71%,R _w=4.96% (982 reflections, 120 parameters). The structure consists of Ag ribbons; each Ag atom is linearly co-ordinated to two N atoms with distances corresponding to covalent Ag-N bonds; no Ag-O coordination is observed; the N atom of the SO₃N group is surrounded by three Ag atoms; compared to amidosulfuric acid, the SO₃N group shows significant deformation.