Direct Measurement of Resonances in

We have performed the first direct measurement of two resonances of the ^{7}Be(α,γ)^{11}C reaction with unknown strengths using an intense radioactive ^{7}Be beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of 1.73±0.25(stat)±0.40(syst) eV and 125_{-25}^{+27}(stat)±15(syst) meV, respectively. The present results have reduced the uncertainty in the ^{7}Be(α,γ)^{11}C reaction rate to ∼9.4%-10.7% over T=1.5-3 GK, which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae (νp process). We find no effect of the new, constrained reaction rate on νp-process nucleosynthesis.

Nuclear Force Imprints Revealed on the Elastic Scattering of Protons with

How does nature hold together protons and neutrons to form the wide variety of complex nuclei in the Universe? Describing many-nucleon systems from the fundamental theory of quantum chromodynamics has been the greatest challenge in answering this question. The chiral effective field theory description of the nuclear force now makes this possible but requires certain parameters that are not uniquely determined. Defining the nuclear force needs identification of observables sensitive to the different parametrizations. From a measurement of proton elastic scattering on ^{10}C at TRIUMF and ab initio nuclear reaction calculations, we show that the shape and magnitude of the measured differential cross section is strongly sensitive to the nuclear force prescription.

Measurement of 23Na(α,p)26Mg at Energies Relevant to 26Al Production in Massive Stars.

26Al is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The 23Na(α, p)26Mg reaction has been identified by a sensitivity study as being one of the most important reactions for the production of 26Al in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of 23Na(α, p)26Mg in this sensitivity study. Current experimental data suggest a reaction rate a factor of ∼40 higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range E(c.m.)=1.28-3.15 MeV at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of 26Al, due to this reaction, are determined.

Evidence of soft dipole resonance in

The first conclusive evidence of a dipole resonance in ^{11}Li having isoscalar character observed from inelastic scattering with a novel solid deuteron target is reported. The experiment was performed at the newly commissioned IRIS facility at TRIUMF. The results show a resonance peak at an excitation energy of 1.03±0.03 MeV with a width of 0.51±0.11 MeV (FWHM). The angular distribution is consistent with a dipole excitation in the distorted-wave Born approximation framework. The observed resonance energy together with shell model calculations show the first signature that the monopole tensor interaction is important in ^{11}Li. The first ab initio calculations in the coupled cluster framework are also presented.

11Li Breakup on 208 at energies around the Coulomb barrier.

The inclusive breakup for the (11)Li + (208)Pb reaction at energies around the Coulomb barrier has been measured for the first time. A sizable yield of (9)Li following the (11)Li dissociation has been observed, even at energies well below the Coulomb barrier. Using the first-order semiclassical perturbation theory of Coulomb excitation it is shown that the breakup probability data measured at small angles can be used to extract effective breakup energy as well as the slope of B(E1) distribution close to the threshold. Four-body continuum-discretized coupled-channels calculations, including both nuclear and Coulomb couplings between the target and projectile to all orders, reproduce the measured inclusive breakup cross sections and support the presence of a dipole resonance in the (11)Li continuum at low excitation energy.

Do halo nuclei follow Rutherford elastic scattering at energies below the barrier? The case of 11Li.

The first measurement of the elastic scattering of the halo nucleus 11Li and its core 9Li on 208Pb at energies near the Coulomb barrier is presented. The 11Li+208Pb elastic scattering shows a strong reduction with respect to the Rutherford cross section, even at energies well below the barrier and down to very small scattering angles. This drastic change of the elastic differential cross section observed in 11Li+208Pb is the consequence of the halo structure of 11Li, as it is not observed in the elastic scattering of its core 9Li at the same energies. Four-body continuum-discretized coupled-channels calculations, based on a three-body model of the 11Li projectile, are found to explain the measured angular distributions and confirm that the observed reduction is mainly due to the strong Coulomb coupling to the dipole states in the low-lying continuum of 11Li. These calculations suggest the presence of a low-lying dipole resonance in 11Li close to the breakup threshold.

Measurement of the two-halo neutron transfer reaction (1)H((11)Li, (9)Li)(3)H at 3A MeV.

The p((11)Li, (9)Li)t reaction has been studied for the first time at an incident energy of 3A MeV at the new ISAC-2 facility at TRIUMF. An active target detector MAYA, built at GANIL, was used for the measurement. The differential cross sections have been determined for transitions to the (9)Li ground and first excited states in a wide range of scattering angles. Multistep transfer calculations using different (11)Li model wave functions show that wave functions with strong correlations between the halo neutrons are the most successful in reproducing the observation.

Elastic alpha-12C scattering and the 12C(alpha,gamma)16O E2 S factor.

Angular distributions of 12C(alpha,alpha)12C have been measured for E(alpha) = 2.6-8.2 MeV, at angles from 24 to 166, yielding 12 864 data points. R-matrix analysis of the ratios of elastic scattering yields a reduced width amplitude of gamma12 = 0.47 +/- 0.06 MeV(1/2) for the Ex = 6.917 MeV (2+) state in 16O(a = 5.5 fm). The dependence of the chi2 surface on the interaction radius a has been investigated and a deep minimum is found at a = 5.42(+0.16)(-0.27) fm. Using this value of gamma12, radiative alpha capture and 16N beta-delayed alpha-decay data, the S factor is calculated at E(c.m.) = 300 keV to be S(E2)(300) = 53(+13)(-18) keV b for destructive interference between the subthreshold resonance tail and the ground state E2 direct capture.

[Seasonal changes in cardiovascular indices and monoamine content in the brain of rabbits]. / Sezonnye izmeneniia serdechno-sosudistykh pokazatelei i soderzhaniia monoaminov v mozge krolika.

In our previous studies a rather substantial difference between the initial values of the cerebral blood flow was found. On the other hand the brain monoamine content varies in different months of the year when studied. Comparative analysis of these parameters in rabbit brain was the aim of this paper. The content of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in cortical and subcortical structures and the local cerebral blood flow (ICBF), the systemic arterial pressure (SAP) and pulse rate (PR) were studied. There were found seasonal variations in all parameters. A certain LCBF retardation in subcortical structures and cortex and the weakest effect of the stimulation was observed in May. There was a drop in SAP and some PR increase in the spring (April-May). Brain NA and 5-HT content showed seasonal changes with the lowest values near the winter months and reaching maximum in May as the PR does. Content of DA was low in May. So it seams possible that the ion ICBF in May can be explained by the decrease of brain DA at that time. The ICBF and the reactivity of cerebral microvessels seem to depend on the monoamine content and show seasonal variability.

[An approach to the experimental study of the intracerebral mechanisms regulating the cerebral blood circulation]. / O podkhode k éksperimental'nomu izucheniiu intratserebral'nykh mekhanizmov reguliatsii mozgovogo krovoobrashcheniia.

The principles of planning and conducting experiments in the field of cerebral circulation are discussed. The need in complex methods is emphasized. Own findings (cerebral blood flo EEG, pO2 of the cerebral tissue, systemic blood pressure, breathing, blood gases and pH) are discussed.

[Effect of electric stimulation or lesion of the thalamus on cerebral circulation]. / Vliianie élektrostimuliatsii ili razrusheniia zritel'nogo bugra na mozgovoe krovoobrashchenie.

Local cerebral blood flow (lCBF) in the thalamus and cerebral cortex was determined in 16 alert rabbits after electric stimulation of thalamic nuclei, and in 22 anesthetized dogs after thermocoagulation of posterior part of the thalamus. The cerebrovascular dilatory effect and increase in the lCBF were observed. Rheoelectroencephalographic investigations in 13 patients with parkinsonism subjected to stereotaxic lesion of thalamic ventrolateral nuclei also showed a diffuse reduction of arterial tone and cerebrovascular resistance. The data obtained seem to explain the reactive hyperemia which may develop primarily as a neurogenic reaction and then be maintained by metabolic changes.

[Role of diencephalic structures in the regulation of cerebral blood flow]. / Izuchenie roli diéntsefal'nykh struktur v reguliatsii mozgovogo krovotoka.

The effects of electric stimulation of the thalamus, hypothalamus and septum upon the CBF, pO2 of brain tissue, EEG, general arterial pressure and pneumogram, were studied in 74 rabbits with implanted cerebral electrodes. The stimulation mostly resulted in an increase in local blood flow sometimes accompanied by a decrease in cortical blood flow. Other parameters under study changed infrequently and insignificantly. The regulation of the CBF seems to be maintained by intracerebral mechanisms.

[The role of deep cerebral structures in the regulation of intracerebral microcirculation]. / Izuchenie roli glubinnykh mozgovykh struktur v reguliatsii intracerebral'noi mikrotsirkuliatsii.

Changes of the diameter of microvessels of the rabbit cortex, thalamus, hypothalamus, septum pellucidum, amygdala, hippocampus and globus pallidus were studied during electrical stimulation of these structures. The stimulation of amygdala elicited vasoconstrictive reactions, the stimulation of hypothalamus and septum--vasodilative reactions, the stimulation of thalamus, hippocampus and globus pallidus caused a vasoconstriction in the motor cortex and a vasodilatation in the subcortex. These results suggest participation of the deep brain structures in the regulation of brain microcirculation.

[Correlation between the anticonvulsant and tranquilizing effects of carbamazepine and methindione in experimental temporal epilepsy]. / Sootnoshenie mezhdu protivosudorozhnymi i trankviliziruiushchimi éffektami karbamazepina i metindiona pri éksperimental'noi visochnoi epilepsii

In 16 rabbits with chronic implanted electrodes the authors convened an electrostimulation of the hypocampus, the amygdale body and new cortex which brought to emotional-affective and EEG convulsive reactions. These reactions were inhibited by karbamazepine (150 mg/kg) and methindion (100 and 200 mg/kg) introduced into the gastrum. Karbamazepine possessed most inhibiting effect. The tranquillizing effect of methindion exceedes its anticonvulsive action, due to which it can be used both as an anticonvulsant and tranquilizing preparation. For this reason its combined effect should be most effective in temporal epilepsy.