Negative staining can cause clumping of Bordetella pertussis fimbriae

The state of fimbriae type 2 (Fim 2) and fimbriae type 3 (Fim 3) preparations from Bordetella pertussis were examined by negative stain electron microscopy. Uranyl acetate induced clumping of Fim 3 regardless of pH and was unsuitable as a stain for establishing the state of fimbriae. Both ammonium molybdate and sodium phosphotungstate were able to show the differences in Fim 3 stored at pH 7.2 and pH 9.5.     

K conversion coefficients of transitions in87Sr

TheK conversion coefficients of the 388 and 483 keV transitions in⁸⁷Sr populated in the decay of⁸⁷Y have been measured with Ge(Li) and Si(Li) detectors by the NPG method. We find α _K values of 0.162 ± 0.010 and 0.00260 ± 0.00013 for the 388 and 483 keV transitions, respectively.     

On-line nuclear orientation of70As

On-line nuclear orientation was performed on⁷⁰As. Anisotropy data have been obtained at 8.7mK for 29 gamma transitions. Multipole mixing ratios have been extracted for 17 transitions. Our results are in good agreement with existing data for the ten previously measured transitions. Our first time data for the 1496 keV, 2⁺→2⁺ γ-ray suggest the 2536 keV level is a good candidate for a mixed symmetry level.     

A search for nuclear structure effects in Tm169

The study of nuclear structure effects in internal conversion has been extended to the Tm¹⁶⁹ nucleus. Gamma-gamma, electron-gamma and gamma-electron directional correlations of the 177 keV-131 keV and the 198 keV-110 keV cascades have been measured. The following results were obtained:

$$\begin{array}{l} A_2 (177\gamma - 131\gamma ) = + 0 \cdot 275 \pm 0 \cdot 007,A_4 (177\gamma - 131\gamma ) = - 0 \cdot 005 \pm 0 \cdot 016, \\ A_2 (177\gamma - 131\gamma ) = + 0 \cdot 002 \pm 0 \cdot 007, \\ A_2 (177\gamma - 131K) = + 0 \cdot 497 \pm 0 \cdot 010, \\ A_2 (198\gamma - 110\gamma ) = + 0 \cdot 295 \pm 0 \cdot 007,A_4 (198\gamma - 110\gamma ) = - 0 \cdot 013 \pm 0 \cdot 017, \\ A_2 (198K - 110\gamma ) = + 0 \cdot 001 \pm 0 \cdot 008, \\ A_2 (198\gamma - 110K) = - 0 \cdot 005 \pm 0 \cdot 006. \\ \end{array}$$     

The closure of Teichmüller space

This research is supported in part by NSF DMS-8700627.     

The antiarrhythmic and antiinflammatory activity of a series of tricyclic pyrazoles

A series of tricyclic pyrazoles were prepared from intermediates available from steroid total synthesis and tested for antiarrhythmic and antiinflammatory activity.     

丰中子核113Ru集体转动带的识别

通过对重核²⁵²Cf自发裂变产生的瞬发γ谱的测量,对非常丰中子核¹¹³Ru的能级结构进行了研究,建立了较高自旋态的能级纲图,识别了基于中子h_11/2轨道激发产生的集体转动带,最高自旋态达31/2h.还发现了另一个可能基于9/2^－能级的集体转动带,对新建立的¹¹³Ru的集体带的一些重要特性进行了讨论.     

Kinetics and mechanism of the autoxidation of pentaerythrityl tetraheptanoate at 180–220°C

A kinetic and mechanistic study of the autoxidation of liquid pentaerythrityl tetraheptanoate (PETH) at 180–220°C has been carried out utilizing a stirred-flow reactor. The results are consistent with the occurrence of a chain reaction scheme similar to that proposed for n-hexadecane autoxidation, namely, the formation of monohydroperoxides by the intermolecular abstraction reaction (3), the formation of α,γ- and α,δ-dihydroperoxides and α,γ- and α,δ-hydroperoxyketones by intramolecular peroxy radical abstraction reactions (4) and (4*), the bimolecular termination of peroxy radicals, reaction (6), and the rapid conversion of α,γ-hydroperoxyketones to the corresponding cleavage acids and methyl ketones, reaction (7). Comparisons of various rate parameters for the n-hexadecane and PETH systems reveal that the values of k₇ and (k₃/H atom)/(2 k₆)^1/2 are within experimental uncertainties identical for the two systems at 180°C. The proposed reaction scheme includes the concurrent formation of hydroxy radicals and hydroperoxyketone species. The results of kinetic analysis and the experimentally observed isomer distributions of primary and secondary monohydroperoxide products at high and low oxygen pressures suggest that ≈60% of the hydrogen abstractions from PETH at high oxygen pressures occur by hydroxy radicals.