Cross section for inelastic neutron scattering from 193Ir at 6 MeV.

Two samples, one of natural iridium and the other of enriched 193Ir, were irradiated with a monoenergetic neutron beam of energy 6.0 MeV at the Triangle Universities Nuclear Laboratory. The product of the 193Ir [Formula: see text] Ir reaction was determined by means of measuring X-rays following electron conversion of the isomeric state at 80.2 keV in 193Ir. The cross section for inelastic neutron scattering is reported disagreeing with the literature data.

Nuclear deformation and neutron excess as competing effects for dipole strength in the pygmy region.

The electromagnetic dipole strength below the neutron-separation energy has been studied for the xenon isotopes with mass numbers A=124, 128, 132, and 134 in nuclear resonance fluorescence experiments using the γELBE bremsstrahlung facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIγS facility at Triangle Universities Nuclear Laboratory Durham. The systematic study gained new information about the influence of the neutron excess as well as of nuclear deformation on the strength in the region of the pygmy dipole resonance. The results are compared with those obtained for the chain of molybdenum isotopes and with predictions of a random-phase approximation in a deformed basis. It turned out that the effect of nuclear deformation plays a minor role compared with the one caused by neutron excess. A global parametrization of the strength in terms of neutron and proton numbers allowed us to derive a formula capable of predicting the summed E1 strengths in the pygmy region for a wide mass range of nuclides.

Cross-section measurements of the 86Kr(γ,n) reaction to probe the s-process branching at 85Kr.

We have carried out photodisintegration cross-section measurements on 86Kr using monoenergetic photon beams ranging from the neutron separation energy, S(n) = 9.86 MeV, to 13 MeV. We combine our experimental 86Kr(γ,n)85Kr cross section with results from our recent 86Kr(γ,γ') measurement below the neutron separation energy to obtain the complete nuclear dipole response of 86Kr. The new experimental information is used to predict the neutron capture cross section of 85Kr, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise 85Kr(n,γ)86Kr cross section allows us to produce more precise predictions of the 86Kr abundance from s-process models. In particular, we find that the models of the s process in asymptotic giant branch stars of mass <1.5M⊙, where the 13C neutron source burns convectively rather than radiatively, represent a possible solution for the highest 86Kr:82Kr ratios observed in meteoritic stardust SiC grains.

Fine structure of the giant M1 resonance in 90Zr.

The M1 excitations in the nuclide 90Zr have been studied in a photon-scattering experiment with monoenergetic and linearly polarized beams from 7 to 11 MeV. More than 40 J(π)=1+ states have been identified from observed ground-state transitions, revealing the fine structure of the giant M1 resonance with a centroid energy of 9 MeV and a sum strength of 4.17(56) µ(N)(2). The result for the total M1 strength and its fragmentation are discussed in the framework of the three-phonon quasiparticle-phonon model.

Photodisintegration cross section of the reaction (4)He(γ,p)(3)H between 22 and 30 MeV.

The two-body photodisintegration cross section of (4)He into a proton and triton was measured with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. High-pressure (4)He-Xe gas scintillators of various (4)He/Xe ratios served as targets and detectors. Pure Xe gas scintillators were used for background studies. A NaI detector together with a plastic scintillator paddle was employed for determining the incident photon flux. Our comprehensive data set follows the trend of the theoretical calculations of the Trento group very well, although our data are consistently lower in magnitude by about 5%. However, they differ significantly from the majority of the previous data, especially from the recent data of Shima et al. The latter data had put into question the validity of theoretical approaches used to calculate core-collapse supernova explosions and big-bang nucleosynthesis abundances of certain light nuclei.

Spectral structure of the pygmy dipole resonance.

High-sensitivity studies of E1 and M1 transitions observed in the reaction 138Ba(gamma,gamma{'}) at energies below the one-neutron separation energy have been performed using the nearly monoenergetic and 100% linearly polarized photon beams of the HIgammaS facility. The electric dipole character of the so-called "pygmy" dipole resonance was experimentally verified for excitations from 4.0 to 8.6 MeV. The fine structure of the M1 "spin-flip" mode was observed for the first time in N=82 nuclei.

Decay of 1+ states as a new probe of the structure of 0+ shape isomers.

The nuclides 98Mo and 100Mo have been studied in photon-scattering experiments by using bremsstrahlung produced from electron beams with kinetic energies from 3.2 to 3.8 MeV. Six electromagnetic dipole transitions in 98Mo and 19 in 100Mo were observed for the first time in the energy range from 2 to 4 MeV. A specific feature in the two nuclides is the de-excitation of one state with spin J = 1 to the 0+ ground state as well as to the first excited 0+ state, which cannot be explained in standard models. We present a model that allows us to deduce the mixing coefficients for the two 0+ shape-isomeric states from the experimental ratio of the transition strengths from the J = 1 state to the 0+ ground state and to the 0+ excited state.

[Changes in the transverse striated musculature during treatment with the pesticide, Neguvon, and TMB-4 reactivator]. / Promeni v naprechnonabrazdenata muskulatura pri tretirane s pestitsida neguvon i reaktivatora TMB-4.

The authors found that the contractile activity of isolated myofibers as-well as superprecipitation of myosin B were reduced after intoxication of white rats with 1/2 of dose of LD50 of neguvon. The reaktivator of cholinesterase TMB-4 (20 mg/kg) recovered the contractile capability of myofibres even on the third day after treatment, but superprecipitation of myosin B-after the twentieth day.

[Antibiotic action on the embryonic development of the fetuses of amphibians]. / Izsledvane vuzdeistvieto na antibiotitsite vurkhu embrionalnoto razvitie na zarodishi ot zemnovodni.

The effect on the embrionic development of Tr. cristatus of 16 antibiotics (keflin, penicillin, benzazillin, ampicillin, nystatin, kanamycin, streptomycin, novobiocin, brunomycin, erythran, oleandomycin, tetracyclin, chlornytromycin, gentamycin, rimactan, and capreomycin) administered in 3 concentrations was studied. It was established that except kanamycin, keflin and rimactan all the rest damage the embryonic development showing certain phase specifity. Gastrulation turned to be the most sensitive embryonic period.

[Synthesis of multiple forms of brain cholinesterases]. / Sintez mnozhestvennykh form kholinésterazy mozga.

Highly purified multiple forms of brain cholinesterase were isolated by a new method. Eight forms were identified as acetyl cholinesterases, seven forms--as butyryl cholinesterases, four forms--as mixed acetyl- and butyryl cholinesterases and four forms--as aliesterases. Biosynthesis of multiple forms of brain cholinesterase was monitored by following incorporation of 14C-glycine into the purified fractions. Cats were killed at different periods (3 hrs, 3,6 and 9 days) after intoxication with isopropyl hydroxymethyl fluorophosphate. The restoration of the enzymatic activity after the inhibition did not correspond to the incorporation of the labelled amino acid into the enzyme protein. There was a transcient increase in the incorporation of the label after an increase in acetylcholine concentration.

[Multiple forms of brain cholinesterase in phylogenesis and ontogenesis of vertebrates]. / Issledovanie mnozhestvennykh form kholinesterazy mozga v filogeneze i ontogeneze pozvonochnykh

Multiple forms of the brain cholinesterase have been investigated by means of the original technique based on the extraction, ammonium sulphate salting out and gel filtration on Sephadex G-200. It was shown that the number of multiple forms increases in phylogenesis (8 in triton, 13 in rat, 18 in cat, 16 in dog and 23 in man), although their relative enzymic activity decreases. Isolated multiple forms with high molecular weight enzymatically are classified as acetylcholinesterases. In higher brain structures, multiple forms are more numerous. Butyrylcholinesterases and aliesterases are more abundant in lower brain structures. In the neural plate of the developing triton, it is possible to detect the forms with high specific activity, which exceeds that in adult animals.