Measurements of the longitudinal and lateral development of electromagnetic cascades in lead, copper and aluminum at 6 GeV

The longitudinal and radial development of electromagnetic cascades, initiated by 6 GeV electrons, has been measured in lead, copper and aluminum by means of silver-phosphate dosimeter glasses. The measured energy deposition was compared with Monte-Carlo calculations by Völkel, especially at large depths and radii. Excellent agreement was found for the transition curves up to 40 radiation lengths and for the lateral distributions up to 4 Molière units. Between 4 and 12 Molière units the calculations tend to underestimate the energy deposition.     

Facile and purification free synthesis of peptides utilizing ROMPgel- and ROMPsphere-supported coupling reagents

5-Norbornene-2-carboxaldehyde and norbornadiene were respectively converted into norbornene derivatives functionalized with fluoroformamidinium hexafluorophosphate and 2-bromo-N-methylpyridinium tetrafluoroborate residues. Both these norbornene monomers were ring opening metathesis polymerized or graft copolymerized onto polystyrene cores to produce ROMPgel and ROMPsphere peptide-coupling reagents. These were used to prepare hindered amides, dipeptides and tripeptides with minimal purification in parallel arrays.     

Asymmetric synthesis of alpha-branched primary amines on solid support via novel hydrazine resins

[reaction: see text]. Two novel chiral hydrazine resins for asymmetric solid-phase synthesis have been developed. The enantiopure beta-methoxyamino auxiliaries, derived from trans-4-hydroxy-(S)-proline and (R)-leucine, were attached to Merrifield resin and transformed into their corresponding hydrazines. Immobilization of various aldehydes, followed by 1,2-addition of organolithium reagents to the resulting enantiopure hydrazones and reductive cleavage from the solid support, furnished alpha-branched amines, which were isolated as their corresponding amides in good overall yields and enantiomeric excesses of up to 86%.     

Relations between the electroexcitation of nucleon resonances and the deep inelastic continuum for proton and deuteron targets

New data of the electroexcitation cross section on protons and deuterons in the resonance region are compared with the results in the deep inelastic region for four-momentum transfers q² ? 1.5 (GeV/c)². The Bloom-Gilman sum rule is shown to hold for q² ? 1.2 (GeV/c) while the Rittenberg-Rubinstein sum rule is saturated for q² ? 0.4 (GeV/c)². It is shown that the sum rules do not saturate in a local way.     

Quasi-elastic electron scattering (e,e′p) and (e,e′d) from 6Li in a coincidence experiment

Coincidence cross sections for the reactions ⁶Li(e, e′p) and ⁶Li(e, e′d) have been measured in the region of quasi-elastic scattering. Using incident electrons of 2.5 and 2.7 GeV, the four-momentum transfers to the proton were 6.6 fm^?2, 10.0 fm^?2 and 11.6 fm^?2. The proton coincidence data agree with shell-model distributions assuming a Woods-Saxon potential and including short-range nucleon-nucleon correlations. The best fit to the deuteron coincidence data is obtained with a cluster wave function for the p-nucleons and a harmonic oscillator wave function for the s-nucleons taking into account the deuteron yield from the s-shell. The ratio of the deuteron cross section from ⁶Li divided by the elastic e-d scattering cross section depends only slightly on the four-momentum transfer and has a value of ≈ 2.     

Comparison of inelastic electron and positron scattering cross sections on 12C and 27Al

The ratio R = σ⁺/σ^? of the cross sections for inelastic and electron scattering on ¹²C and ²⁷Al has been measured for four momentum transfers 0.08 (GeV/c)² ?q² ?0.45 (GeV/c)² of the virtual photon and invariant masses 0.95 GeV ? W ? 3.3GeV of the hadronic system. The mean value of the ratio is R = (1.005 ± 0.027). No q², respectively, W dependence of the ratio is observed.     

ROMPgel-supported triphenylphosphine with potential application in parallel synthesis

[reaction: see text] ROMPgel-supported triphenylphosphine was synthesized in three steps (67%) from norbornadiene, 4-bromoiodobenzene, and chlorodiphenylphosphine. The supported reagent has a high loading (2.5 mmol/g) and favorable swelling properties in organic solvents. It has been utilized for the conversion of alcohols to halides, the reduction of ozonides, and the isomerization of alpha,beta-acetylenic esters and in the Staudinger reaction. In general, filtration of the resin from the reaction mixtures and evaporation gave the corresponding products in high yield and purity.