Measurement of the total and differential cross sections for the reaction π − p → ηn with the Crystal Ball detector

The first results obtained in 1998 by the Crystal Ball collaboration from a measurement of the total and differential cross sections for the reaction π ^? p → ηn are presented. These new experimental results for the total cross sections are compared with the predictions of the K-matrix model for pion-nucleon scattering. The angular distribution at momenta near the reaction threshold (685 MeV/c) is determined by the S-wave contribution. The P-wave contribution begins to manifest itself from a momentum of 720 MeV/c.     

ESCA-studies on activated silicagel surfaces preconcentrating heavy metal ions

Summary The theoretical ion-exchange capacity of an aminosilylated silicagel surface loaded with dithiocarbamate (DTC) groups was calculated by correlation of the results of a BET measurement, a quantitative determination of the concentration of reactive single hydroxyl groups on the surface, and ESCA intensities. ESCA spectra suggest many functional groups to be thiuram disulfide ones and not DTC ones as believed before. Quantitative ESCA measurements show that aminosilylated silicagel surfaces are only partially transformed to the DTC form. In spite of their chemical instability, the concentration of heavy metal ions (Pb²⁺) in aqueous solution and their ESCA intensities after immobilization on the activated silicagel surface are linearily correlated with each other in the ppm region.Professor Dr. Carl Mahr zum 80. Geburtstag in Dankbarkeit gewidmet.     

Kinetics of the formation of cyclobutane from ethylene

The rate of the thermal reaction of ethylene to form cyclobutane has been measured over the temperature range 723°–786°K and at pressures between 300 and 1300 torr. The equilibrium constant for the system \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$${\rm 2C}_{\rm 2} {\rm H}_{\rm 4}\mathop {\leftrightharpoons}\limits_{kf}^{kr} c - {\rm C}_{\rm 4} {\rm H}_{\rm 8}$$\end{document} was calculated both from the initial rate data and from measurements of the equilibrium concentration of cyclobutane. Agreement with the reported thermodynamic quantities for cyclobutane was satisfactory. The initial rate data gave the following epxression for k_f: while the measurements of the equilibrium concentration of cyclobutane gave the expression for K, .     

Costing,Technological Growth and Generalized Learning Curves

Two analytic innovations are developed for application to aircraft cost estimating. The first incorporates the concept of technological growth explicitly into equations for required manufacturing labour hours. The second generalizes learning curve theory to analytically account for certain asymptotic deficiencies which at present theoretically predict arbitrarily small costs given that production goes on long enough.     

Origin of the Director Tilt in the Lyotropic Smectic C* Analog Phase: Hydration Interactions and Solvent Variations

The origin and long‐range correlation of the director tilt in the recently discovered phase, which is the lyotropic analog of the thermotropic smectic C* (SmC*) liquid crystalline phase, are investigated. Polarized micro‐Raman spectroscopy reveals that the director tilt in the phase originates from a tilting of the aromatic 2‐phenylpyrimidine cores of the surfactant molecules. Optical measurements of the tilt angle show that its magnitude decreases with increasing solvent concentration, suggesting that the long‐range inter‐lamellar correlation of the tilt directions is reduced at increasing thickness of the solvent layers. The phase diagrams with four different solvents (water, formamide, N‐methylformamide, N,N‐dimethylformamide) are investigated, showing that the phase is only formed with those solvents that exhibit a dense network of hydrogen bonds. This observation suggests that these hydrogen bond networks play an essential role in the long‐range correlation of the director tilt between adjacent surfactant layers. To verify this assumption, mixtures with deuterated solvents are investigated, showing that the tilt angle in the phase is indeed reduced by this modification of the solvent′s hydrogen bond network.     

Fat tissue is not a reservoir for radiocesium in wild boars

Meat of wild boars is not only known for high ¹³⁷Cs activity concentrations but also for the remarkable constancy of these levels. Even decades after the Chernobyl accident, the ¹³⁷Cs levels in wild boar meat in Central Europe have not declined but even partly increased. In the present study, we investigated an unusual hypothesis for this very unusual phenomenon: may the boars’ fat tissue act as a reservoir for radiocesium? We investigated fat and muscle tissues of four wild boars in Western Germany and found that the ¹³⁷Cs concentrations in fat were in the range of 10–30% of the respective activities in muscle tissue. Hence, the hypothesis was refuted.

     

Cold neutron energy dependent production of ultracold neutrons in solid deuterium

A measurement of the production of ultracold neutrons from velocity-selected cold neutrons on gaseous and solid deuterium targets is reported. The expected energy dependence for two-particle collisions with well defined neutron and Maxwell-Boltzmann distributed molecular velocities is found for the gas target. The solid target data agree in shape with the phonon density-of-states curve and provide strong evidence for the phonon model including multiphonon excitations.     

Measurement of the Time-Dependent CP Asymmetry in B;{0}-->D_{CP};{(*)}h;{0} Decays

We report a measurement of the time-dependent CP-asymmetry parameters S and C in color-suppressed B{0}-->D{(*)0}h{0} decays, where h{0} is a pi{0}, eta, or omega meson, and the decays to one of the CP eigenstates K+K-, K{S}{0}pi{0}, or K{S}{0}omega. The data sample consists of 383 x 10{6} Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The results are S=-0.56+/-0.23+/-0.05 and C=-0.23+/-0.16+/-0.04, where the first error is statistical and the second is systematic.     

新型N-取代苯基-9-烷基-3-咔唑磺酰脲类化合物的合成及其抗肿瘤活性

以9-烷基咔唑为原料,经磺化、氯化和氨化反应制得9-烷基咔唑-3-磺酰胺(4a和4o);取代苯胺与三光气反应制得取代苯基异氰酸酯(6a~6n,6s,6Ⅳ);4分别与6经缩合反应合成了30个新型的N-取代苯基-9-烷基-3-咔唑磺酰脲类化合物(7a~7Ⅳ),其结构经1H NMR,IR和ESI-MS表征。对7进行了Cdc25B抑制活性筛选。结果表明,在用药浓度为20μg·m L-1时,其中12个化合物对Cdc25B具有良好的抑制活性,抑制率大于90%。