100 MHz n.m.r. spectra and conformational analysis of some methyl and trimethyl derivatives of 1-tetralone

The 100 MHz spectra of 2-methyl-, 4-methyl-, 4,5,8-trimethyl- and 4,5,7-trimethyl-1-tetralones have been analysed as 8-spin systems using iterative computation. The monomethyl derivatives exist in inverting half-chair conformations, the 2-methyl group favouring the equatorial site and the 4-methyl group showing equal preference for both axial and equatorial environments. The 5-methyl substituent of the trimethyl derivatives constrains the 4-methyl group to the axial site of rings which adopt non-half-chair conformations. The n.m.r. spectrum of 3-methyl-1-tetralone is also discussed.     

Search for virtual electron capture in the investigation of the internal bremsstrahlung from the decay of 59Ni

The internal bremsstrahlung spectrum from the non-unique second-forbidden pure electron capture decay of ⁵⁹Ni was studied in a limestone low-background chamber using a 20 cm³ Ge(Li) detector, searching for the effects of the virtual electron capture in the spectrum shape of internal bremsstrahlung. Comparing the experimental data with the Cutkosky, Zon-Rapoport and virtual capture theories, the best fit was found for the Zon-Rapoport theory and thus the virtual capture theory is not indispensable to the interpretation of the experiment. Some additional results are also obtained in the present study. Thus, the combination of the nuclear matrix elements λ has been determined, λ = 0.028 ± 0.006, as well as the total disintegration energy $\text{Q(}{}^{59}\text{Ni}\text{-}{}^{59}\text{Co}\text{) = 1075.1 ±1.3}\text{keV}$. The existence of a positive β-branch was proved with an estimated value of 1.05 × 10^?7 for the branching.     

How Ticl3 Catalysts Control the Texture of As-Polymerized Polypropylene

Within a family of catalyst systems wherein TiCl₃ was made by mixing TiCl₄ and aluminum alkyl solutions, the primary particles of TiCl₃ were usually thin, flat polygons with average diameters ranging from 300 to 1000 A. Even in unused catalyst these primary catalyst particles were bound together into large (～30 μ) secondary particles. A small amount of polyolefin which formed from the aluminum alkyl reducing agent aided in cementing the particles. When propylene monomer was introduced to a slurry of secondary catalyst particles in a liquid hydrocarbon, polymer formed at the surfaces of the ultimate solid particles. The resulting polymer flakes, i.e., particles of as-polymerized polypropylene, were several times larger than the secondary catalyst particles from which they grew but they retained the same shape. The primary catalyst particles, not visibly altered by the catalytic reaction which they propagated, were distributed uniformly throughout the flake polymer. Each polymer flake consisted of many thousands of cohering roundish flakelets about a 1/2 μ in diameter. How the flakelets are agglomerated and the extent to which they are coalesced accounts for the flakes' texture. The basic morular structure of the flakes, which was manifested further by their papillary surfaces, was not altered by purification procedures which removed catalyst from the nascent polymer. Although all the flakes had the same basic small-scale structure there were significant coarse textural dissimilarities among them. Some catalysts gave rise to flakes with an open porous texture: other catalysts gave rise to flakes which were dense and compact. In the former, the flakelets were less tightly appressed, and fissures and slits were larger and more numerous than in the latter. The genetic basis for the differences in flake texture resides in the parent catalyst. Secondary catalyst particles whose constituent primary particles are held together in a dense mass produce dense flakes. Conversely, loose aggregates of primary particles produce flakes with loosely aggregated flakelets. Briefly, dissimilarities in catalyst structure carry over to the texture of the flake progeny. Such textural differences contribute importantly to properties of the flake polymer.     

Discovery of Highly Selective Alkyne Semihydrogenation Catalysts Based on First‐Row Transition‐Metallated Porous Organic Polymers

Five different first‐row transition metal precursors (V^III, Cr^III, Mn^II, Co^II, Ni^II) were successfully incorporated into a catechol porous organic polymer (POP) and characterized using ATR‐IR and XAS analysis. The resulting metallated POPs were then evaluated for catalytic alkyne hydrogenation using high‐throughput screening techniques. All POPs were unexpectedly found to be active and selective catalysts for alkyne semihydrogenation. Three of the metallated POPs (V, Cr, Mn) are the first of their kind to be active single‐site hydrogenation catalysts. These results highlight the advantages of using a POP platform to develop new catalysts which are otherwise difficult to achieve through traditional heterogeneous and homogeneous routes.     

干涉条纹图中散斑噪声之滤除

散斑在光学干涉计量中被用作信息载体，但同时它也是严重的噪声。介绍了一种简单有效的滤除散斑噪声的方法，即在加窗富里叶变换域内进行掩模和阈值处理。同富里叶变换和正交小波变换相比，加窗富里叶变换有如下两方面的优点：加窗富里叶基和条纹的高度相似性使得信号与噪声容易分离，而加窗富里叶变换的冗余性则可削弱掩模和阈值处理对信号谱的破坏。此方法的有效性由数值模拟和实验的例子证实。此方法亦可滤除强度型条纹或位相型条纹中其它类型的噪声，如加型噪声。     

Information Theory Applied to Parameter Inference of Pake Doublet Spectra

Magnetic resonance absorption lineshapes can have subtle dependencies on the model parameters that specify the lineshape. To quantify how the model parameters influence the lineshape, it is useful to study simple model systems for which analytical expressions are available. We propose that information theory is a useful tool to quantify how well model parameters may be inferred from a noisy signal. Information theory also allows us to assess the importance of missing parameters from an incomplete model. We do this by monitoring the magnitude of a partition function determined from a suitably defined probability mass function as the model parameters are varied. The optimum parameter set makes the partition function a maximum, which establishes a computable criterion for determining the best model parameter set. Given the availability of a partition function, one may define thermodynamic functions such as the entropy. The optimum parameter set in this interpretation corresponds to the state of maximum entropy. In this work, we observe that at sufficiently low signal to noise ratio, the entropy landscape has no clear maximum, while a related quantity, the Fisher information, always has a clear minimum at the optimum parameter set. The qualitative information we are able to gather from the entropy landscapes is also difficult to assess when the parameters are far from their optimum values, at least for the model system studied here.     

Zur Nachweisung und Bestimmung des Paraffins in Stearinkerzen

Ohne Zusammenfassung     

Boundary Crossing Probabilities for Scan Statistics and Their Applications to Change-Point Detection

This paper gives a brief review of recent developments in change-point detection and in the associated boundary crossing problems. Making use of saddlepoint approximations for Markov random walks, we give further extensions of a basic result on boundary crossing probabilities, leading to detection procedures that are not too de-manding in computational and memory requirements and yet are nearly optimal under several performance criteria.     

An extrapolation method with step size control for nonlinear Volterra integral equations

Summary In [6] it has been shown that the midpoint rule applied to second kind volterra integral equations possesses an asymptotic expansion in even powers of the stepsizeh. In this paper we describe an extrapolation method based on the midpoint rule, together with a mechanism of step size control.