Study of the reaction238U (α, α′f) atE α=480 MeV

The excitation function of the fission probability P _E E _x) for²³⁸U has been measured in the reaction²³⁸U(α, α′ f) at 480 MeV bombarding energy. The reaction mechanism of this reaction is discussed for excitation energies belowB _nf , the threshold for second chance fission, and aboveB _nf up toE _x =37 MeV. In comparing with results from fission induced by photons and by particle transfer reactions the (α, α′f) reaction gives too low values for the fission probabilityP _f at excitation energies well aboveB _nE . The role of the quasi-elastic knock-out process in this reaction is discussed.     

Novel intramolecular cyclization of N-alkynyl heterocycles containing proximate nucleophiles

Intramolecular cyclization of 2-acyl-1-propargyl-1H-indoles in the presence of ammonia provides an easy entry to pyrazino[1,2-a]indole nucleus.     

Comparison of the major polypeptides of the erythrocyte nuclear envelope

The three most abundant nonhistone polypeptides (molecular weights 75,000, 71,000 and 61,000) of the avian erythrocyte nucleus have previously been isolated in the nuclear envelope fraction. They have been separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis and peptide-mapped after limited enzymatic digestion. Three enzymes -- chymotrypsin, papain and Staphylococcus aureus protease -- were used. Results obtained with each enzyme indicate strong similarities between the three nuclear envelope polypeptides. The amino acid compositions of the two most abundant polypeptides (P75 and P71) have been determined and found to be similar. Further, they readily yield large fragments upon brief alkaline hydrolysis. For both P75, and P71 the degree and the pattern of alkaline fragmentation are almost identical. A 61,000-dalton polypeptide which appears to be P61 is obtained from P75 and P71 by mild acid hydrolysis. These results establish the close chemical similarity of these predominant polypeptides in the erythrocyte nucleus and suggest that they serve related functions.     

A New Entry to Indolo[2,3-a]carbazoles

Abstract: The synthesis of the indolo[2,3-a]carbazole ring is described starting from 3-chloromethylene-1,3-dihydro-indol-2-one 5 and 3-(cyano-ethoxycarbonyl-methyl)-indole-1-carboxylic acid ethyl ester 4.     

σ‐Alkylpalladium Intermediates in Intramolecular Heck Reactions:Isolation and Catalytic Activity

The isolation of σ‐alkylpalladium Heck intermediates, possible when β‐hydride elimination is inhibited, is a rather rare event. Performing intramolecular Heck reactions on N‐allyl‐2‐halobenzylamines in the presence of [Pd(PPh₃)₄], we isolated and characterized a series of stable bridged palladacycles containing an iodine or bromine atom on the palladium atom. Indolyl substrates were also tested for isolation of the corresponding complexes. X‐ray crystallographic analysis of one of the indolyl derivatives revealed the presence of a five‐membered palladacycle with the metal center bearing a PPh₃ ligand and an iodine atom in a cis position with respect to the nitrogen atom. The stability of the σ‐alkylpalladium complexes is probably a consequence of the strong constraint resulting from the bridged junction that hampers the cisoid conformation essential for β‐hydride elimination. Subsequently, the thus obtained bridged five‐membered palladacycles were proven to be effective precatalysts in Heck reactions as well as in cross‐coupling processes such as Suzuki and Stille reactions.     

Palladium-catalyzed C-N bond formation via direct C-H bond functionalization. Recent developments in heterocyclic synthesis

The formation of carbon-nitrogen bonds by reaction between a nitrogen atom and an unactivated carbon-hydrogen bond is a highly atom-economical process that attracted the attention of the chemists in the last two decades. The widely useful amination and hydroamination reactions, which furnish acyclic or cyclic products, give access to various nitrogen-containing basic and fine chemicals. This review highlights recent progress in the development of palladium-catalyzed reactions that occur by direct functionalization of simple carbon-hydrogen bonds to give heterocyclic products. Pd(0)- and Pd(II)-catalyzed reactions are described separately, emphasizing the different behavior of the metal in these two oxidation states.     

Giant resonances in f-p shell nuclei studied by inelastic scattering of 80 MeV 3He ions

Spectra of ⁴⁸Ti, ⁵⁶Fe, ⁵⁹Co and ⁶⁰Ni have been investigated for excitation energies of 10–20 MeV by inelastic scattering of 80 MeV ³He particles. Broad peaks with excitation energies of about $\text{63±1 A}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}\text{MeV}$ and FWHM of 6 MeV have been observed. Much narrower satellite peaks occur at excitation energies about $\text{51±1 A}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}\text{MeV}$. The angular distributions of the sum of these peaks were compared to extended optical model DWBA calculations which confirm the predominant L = 2 character of the GR. A tentative assignment of L = 2 or 4 was made for the 13.5 MeV satellite peak in ⁵⁶Fe. We see no definite evidence for the presence of an L = 1 GR component.     

Phase-shift analysis of spin-correlation coefficients in p-d scattering: A solution to the 2S defect

A phase-shift analysis of combined cross-section and spin-correlation data has been performed for the elastic scattering of protons by deuterons. Reliable doublet phases have been extracted and compared with extensive Faddeev-type calculations using different rank-one separable interactions. The effect of P-wave N-N forces is discussed and intrinsic strengths and range are deduced.     

Pionic excitation of giant resonances in Y

Inelastic scattering of π⁺ and π⁻ exhibits strongly excited giant resonance structures. Besides the giant quadrupole resonance centered around 14 MeV, structures are observed at 16.8 MeV which can be fitted with a mixing of L=0 and L=1, and around 25 MeV (E_x = 110A^−1/3).     

A study of the reaction 2H(π±, p)X

We have studied the excitation function of the reaction ²H(π^±, p)X at a fixed proton angle of 90° for several fixed proton momenta of the detected proton as a function of the incident pion energy. No signal was found for a previous candidate for a dibaryon resonance around a mass of 2.23 GeV. The general trend of the data is reproduced by a multiple scattering theory