Crystal and Molecular Structure of 3-Methoxy-estra-1,3,5(10)-trien-17β-ol

The crystal structure determination of the title compound was undertaken to determine the conformational flexibility of the steroid skeleton. 3-Methoxy-estra-1,3,5(10)-trien-17β-ol (C₁₉H₂₆O₂) crystallizes in the space group P2₁2₁2₁ with Z = 12, a = 12.589(2), b = 16.274(5), and c = 23.535(6) Å. The structure was solved by direct methods and refined to R = 0.056. Three symmetry independent molecules having different molecular conformations were observed in the crystal. The most flexible region of the molecules is the B ring which adopts following conformations: 7α,8β-half-chair, 8β-sofa, and an intermediate form between half-chair and sofa.     

On the bindings in the crystal phases of Mn

The heterotypism of Mn may be interpreted energetically when a temperature dependent valence electron concentration is supposed which takes on values between 2.2 and 0.6 electrons per atom. The room temperature phase Mn.r (= αMn) belongs to a series of structural types: Cr₃Si, U.h₁ (= βU), Mn.r, which occur in alloy systems such as MoRe_M (M = undetermined mole number) at certain values of the averaged group number (AGN) of the perodic system of chemical elements (rule of Raub). An interpretation of the series by means of the plural-correlations model becomes possible when instead of the (Ekmanian) AGN count another (non-Ekmanian) electron count is used. The phase Mo₃Re (Cr₃Si-type) yields a simple bonding type (binding) which undergoes moderate transformations to form the phases Mo₂Re₃(U.h₁) and MoRe₃(Mn.r) and the binding of MoRe₃ may be taken to be valid also for Mn.r; it corresponds to the valence electron concentration N′^A_b = 2.16. For the high temperature phases Mn.h₁ (= βMn) and Mn.h₂ (= γMn) the values N′^A_b = 1.6 and 1.0 are probable and allow the brass-like structures Mn.h₁ (C20) and Cu(Fl). The binding of Mn.h₂, incidentally, explains the occurrence of the tetragonal metastable phase Mn.m. finally Mn.h₃ (= δMn) crystallizing in the W-type is isodesmic to Fe.h₂ (= δFe), i.e. of the same binding.     

Crystal and molecular structure of 3-methoxy-estra-1,3,5(10)-triene-14β,17β-diol,C19H26O3

The crystal and molecular structure of 3-methoxy-estra-1,3,5(10)-triene-14β,17β-diol has been determined by single crystal X-ray analysis. It crystallizes in the orthorhombic space group P2₁2₁2₁ with cell parameters a = 8.965(2), b = 30.520(7), and c = 6.031(2) A. The structure was solved by the POSIT system and refined by least-squares calculations to the conventional R factor of 0.075. The steroid rings A, B, and C have planar, 7α, 8β-half chair, and chair conformations, respectively. The ring D is intermediate between 13α, 14β-half chair and 13α-envelope. Rings B and C are trans-fused, and rings C and D are cis-fused. There are intra- as well as intermolecular hydrogen bonds between both hydroxyl groups of the steroid molecule.     

Crystal and molecular structure of 3β-hydroxy-5β-estr-8(14)-en-17-one

The title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with 4 formula units C₁₈H₂₆O₂ in the unit cell. The lattice constants are a = 10.356(2) Å, b = 19.743(3) Å, and c = 7.487(1) Å. The structure was solved by direct methods of phases determination and refined by least-squares calculations to the conventional R = 0.054. The configuration and conformation of the molecule were determined and compared with those of Δ-8,14-anhydrodigitoxigenin.     

IR-device Grade (Hg,Cd)Te Crystals Grown by a Modified Bridgman Method

Electrical and photoelectrical properties of IR-devices manufactured on (Hg, Cd)Te-wafers cut from single crystals grown by modified Bridgman method are reported and compared to those of devices made on THM-(Hg, Cd)Te. MIS-structures and photodiodes were used in order to investigate the different materials. The influence of material parameters and device technology respectively is involved in our discussion of device properties. The quality of modified Bridgman-(Hg, Cd)Te was found to be comparable to that of the THM-(Hg, Cd)Te. At T = 80 K and FOV = 60° background limited detectivity of photodiodes with a cut-off wavelength of λ_co = 10.7 μm was achieved.     

Two new marine sediment standard reference materials (SRMs) for the determination of organic contaminants

Two new marine sediment standard reference materials (SRMs), SRM 1941b Organics in Marine Sediment and SRM 1944 New York/New Jersey Waterway Sediment, have been recently issued by the National Institute of Standards and Technology (NIST) for the determination of organic contaminants including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCB) congeners, and chlorinated pesticides. Both sediment SRMs were analyzed using multiple analytical methods including gas chromatography/mass spectrometry (GC/MS) on columns with different selectivity, reversed-phase liquid chromatography with fluorescence detection (for PAHs only), and GC with electron capture detection (for PCBs and pesticides only). SRM 1941b has certified concentrations for 24 PAHs, 29 PCB congeners, and 7 pesticides, and SRM 1944 has certified concentrations for 24 PAHs, 29 PCB congeners, and 4 pesticides. Reference concentrations are also provided for an additional 58 (SRM 1941b) and 39 (SRM 1944) PAHs, PCB congeners, and pesticides. SRM 1944, which was collected from multiple sites within New York/New Jersey coastal waterways, has contaminant concentrations that are generally a factor of 10–20 greater than SRM 1941b, which was collected in the Baltimore (Maryland) harbor. These two SRMs represent the most extensively characterized marine sediment certified reference materials available for the determination of organic contaminants.Electronic Supplementary Material Supplementary material is available in the online version of this article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

Constructing and evaluating alternative frames of discernment

We construct alternative frames of discernment from input belief functions. We assume that the core of each belief function is a subset of a so far unconstructed frame of discernment. The alternative frames are constructed as different cross products of unions of different cores. With the frames constructed the belief functions are combined for each alternative frame. The appropriateness of each frame is evaluated in two ways: (i) we measure the aggregated uncertainty (an entropy measure) of the combined belief functions for that frame to find if the belief functions are interacting in interesting ways, (ii) we measure the conflict in Dempster’s rule when combining the belief functions to make sure they do not exhibit too much internal conflict. A small frame typically yields a small aggregated uncertainty but a large conflict, and vice versa. The most appropriate frame of discernment is that which minimizes a probabilistic sum of the conflict and a normalized aggregated uncertainty of all combined belief functions for that frame of discernment.     

Wafer thickness optimization for silicon solar cells of heterogeneous material quality

In this Letter, we introduce a method of calculating the optimal wafer thickness for silicon solar cells with multicrystalline bulk material. The optimal thickness depends on the relation of bulk recombination to surface recombination and the light trapping. For multicrystalline silicon bulk recombination strongly varies laterally and with injection level, which complicates the calculations. A thickness optimization using the “Efficiency Limiting Bulk Recombination Analysis” (ELBA) takes all these effects correctly into account. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical approaches to time evolution of complex quantum systems

We examine several numerical techniques for the calculation of the dynamics of quantum systems. In particular, we single out an iterative method which is based on expanding the time evolution operator into a finite series of Chebyshev polynomials. The Chebyshev approach benefits from two advantages over the standard time-integration Crank-Nicholson scheme: speedup and efficiency. Potential competitors are semiclassical methods such as the Wigner-Moyal or quantum tomographic approaches. We outline the basic concepts of these techniques and benchmark their performance against the Chebyshev approach by monitoring the time evolution of a Gaussian wave packet in restricted one-dimensional (1D) geometries. Thereby the focus is on tunnelling processes and the motion in anharmonic potentials. Finally we apply the prominent Chebyshev technique to two highly non-trivial problems of current interest: (i) the injection of a particle in a disordered 2D graphene nanoribbon and (ii) the spatiotemporal evolution of polaron states in finite quantum systems. Here, depending on the disorder/electron-phonon coupling strength and the device dimensions, we observe transmission or localisation of the matter wave.