Development of a sodium-pump/neo-lasant photopumped soft X-raylaser

An intense source of sodium pump-line radiation has been created and used to photopump a neon plasma for application to a pulsed-power driven sodium/neo X-ray laser. Properties of the sodium-pump plasma and the neon-lasant plasma required to optimize fluorescence and lasing are determined. The implosion of a sodium-bearing plasma with a megampere pulsed-power driver (Gamble II) is used to produce a linear Z-pinch with up to 25 GW of sodium-pump-line radiation. A separate neon plasma, driven by part of the return current from the imploding sodium plasma, is created parallel to the sodium line source at a distance of 5 cm. Evidence for population inversion is indicated by fluorescence enhancement of the 11-Å resonance line from the n =4 level of neon when pumped by sodium     

The reaction of lead tetraacetate with hydrocarbons

The free radical reaction of lead tetraacetate with hydrocarbons has been investigated. The products of these reactions are the acetate esters. The hydrogen abstracting species from lead tetraacetate is found to have a primary to secondary to tertiary selectivity of 1:27:123 based upon relative reactivities.     

N,N'-bis(substituted phenyl)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimides

The preparation of N,N'-bis(substituted phenyl)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-di-imides by the reaction of 1,2,4,5-benzenetetracarboxylic-1,2:4,5-dianhydride ( 1 ) with aryl-amines and with aryl isocyanates is described. Correlations are made between the properties of these diimides and the nature and position of the substituents in the phenyl ring. The condensation of dianhydride 1 with diisocyanates yields polymers varying from soft elastomers to tough films, depending upon the amount of imide structure in the polymer chain.     

Distribution of a major surface-associated glycoprotein, fibronectin, in cultures of adherent cells

Fibronectin was present in media and cell layers of cultures of adherent cells from human skin, kidney, lung, chest wall, liver, and heart. Cell-surface fibronectin, visualized by immunofluorescence, was in dense fibrillar (cultures from lung), discrete fibrillar (e.g., cultures from skin), or punctate (some cultures from kidney) structures. The subunit sizes of cell-surface fibronectin and fibronectin soluble in medium appeared identical in sodium dodecyl sulfate-polyacrylamide gels. To explain the polymorphism of cell-surface fibronectin, there must be chemical differences among the fibronectins synthesized by different cell strains or factors in the cell layer which influence fibronectin binding and aggregation.     

Functional end-group polymers derived from free-radical chain transfer. I. Kinetic prediction of functionality

The kinetic scheme describing chain transfer in free-radical polymerizations, the Mayo equation, has been rearranged to yield the probability of generating a functional end group by chain transfer (e.g., to a disulfide). The prediction is that a mixture of functional and nonfunctional ends occurs. Examination of literature data shows a number of systems produce more functionality than predicted. Hence, the challenge to devise a new kinetic scheme to account for the increased functionality is made (e.g., by selective reaction of initiator with chain-transfer agent).     

Low energy,variable angle electron-impact excitation of 1,3,5-hexatriene

A mixture of cis and trans 1,3,5-hexatriene has been studied by electron impact at incident electron energies of 20 eV, 40 eV, 50 eV, and 70 eV, at scattering angles from 0° to 80°, and with effective energy resolutions in the range from 0.05 eV to 0.15 eV. Singlet → triplet transitions with maximum intensities at 2.61 eV and 4.11 eV are observed. The lowest energy spin-allowed excitation which can be detected is the electric dipole-allowed $\text{X}$¹ A_g → 1 ¹B_u transition (in the notation appropriate for the trans isomer). No evidence has been found for a spin-allowed but symmetry-forbidden $\text{X}$¹ A_g → 2 ¹A_g excitation in the vicinity of 4.4 eV transition energy. Many other spin-allowed excitations are observed in the 6–11 eV energy-loss region, and the correlation between these features and those observed in high resolution ultraviolet absorption spectra and other electron-impact spectra is discussed.     

An axial periodic fibrillar arrangement of antigenic determinants for fibronectin and procollagen on ascorbate treated human fibroblasts

Fibronectin and collagens are major constituents of the cell matrix of fibroblasts. Fibronectin is a 220,000 dalton glycoprotein that mediates a variety of adhesive functions of cells examined in vitro. Fibronectin is secreted in a soluble form and interacts with collagen to form extracellular filaments. Fibronectin and procollagen type I were localized using the peroxidase anti-peroxidase method. Under standard culture conditions, fibronectin and procollagen were localized to non-periodic 10 nm extracellular fibrils, the cell membrane and plasma membrane vesicles. Ascorbate treatment of cells leads to a new larger fibril with a diameter of approximately 40 nm. Antibodies to fibronectin and procollagen I react to these native collagen fibrils with an axial periodicity of approximately 70 nm. Fibronectin is clearly associated with native collagen fibrils produced by ascorbate treated cells and there is an asymetric distribution or segregation of fibronectin on these collagen fibrils with a 70 nm axial repeat.     

测定手性有机酸对映体纯度的新试剂

用NMR技术测定微量手性化合物的对映体纯度,已有多种方法。其中,加手性镧化物位移试剂法适用面最广,但对有机酸,结果常不理想。另一种使用较广的方法是加手性试剂,将样品中两对映体转变成非对映异构体,然后比较非对映基因NMR信号的强度,确定原样品中对映体的组成比例。国外已出售的手性试