Early Signal of Emerging Nuclear Collectivity in Neutron-Rich

Radioactive ^{129}Sb, which can be treated as a proton plus semimagic ^{128}Sn core within the particle-core coupling scheme, was studied by Coulomb excitation. Reduced electric quadrupole transition probabilities, B(E2), for the 2^{+}⊗πg_{7/2} multiplet members and candidate πd_{5/2} state were measured. The results indicate that the total electric quadrupole strength of ^{129}Sb is a factor of 1.39(11) larger than the ^{128}Sn core, which is in stark contrast to the expectations of the empirically successful particle-core coupling scheme. Shell-model calculations performed with two different sets of nucleon-nucleon interactions suggest that this enhanced collectivity is due to constructive quadrupole coherence in the wave functions stemming from the proton-neutron residual interactions, where adding one nucleon to a core near a double-shell closure can have a pronounced effect. The enhanced electric quadrupole strength is an early signal of the emerging nuclear collectivity that becomes dominant away from the shell closure.

Electromagnetic Moments of Radioactive

Radioactive ^{136}Te has two valence protons and two valence neutrons outside of the ^{132}Sn double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon-nucleon interactions. Coulomb excitation of ^{136}Te on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;0_{1}^{+}→2_{1}^{+}), Q(2_{1}^{+}), and g(2_{1}^{+}). The results indicate that the first-excited state, 2_{1}^{+}, composed of the simple 2p⊕2n system, is prolate deformed, and its wave function is dominated by excited valence neutron configurations, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(2_{1}^{+}) to the proton and neutron contributions to the wave function provides unique insight into the nature of emerging collectivity, and g(2_{1}^{+}) was used to differentiate among several state-of-the-art theoretical calculations. Our results are best described by the most recent shell model calculations.

1p3/2 proton-hole state in 132Sn and the shell structure along N = 82.

A low-lying state in 131In82, the one-proton hole nucleus with respect to double magic 132Sn, was observed by its γ decay to the Iπ=1/2- ß-emitting isomer. We identify the new state at an excitation energy of Ex=1353 keV, which was populated both in the ß decay of 131Cd83 and after ß-delayed neutron emission from 132Cd84, as the previously unknown πp3/2 single-hole state with respect to the 132Sn core. Exploiting this crucial new experimental information, shell-model calculations were performed to study the structure of experimentally inaccessible N=82 isotones below 132Sn. The results evidence a surprising absence of proton subshell closures along the chain of N=82 isotones. The consequences of this finding for the evolution of the N=82 shell gap along the r-process path are discussed.

Coulomb excitation of radioactive 132,134,136Te beams and the low B(E2) of 136Te.

The B(E2;0(+)-->2+) values for the first 2+ excited states of neutron-rich 132,134,136Te have been measured using Coulomb excitation of radioactive ion beams. The B(E2) values obtained for 132,134Te are in excellent agreement with expectations based on the systematics of heavy stable Te isotopes, while that for 136Te is unexpectedly small. These results are discussed in terms of proton-neutron configuration mixing and shell-model calculations using realistic effective interactions.

[Congenital visual deficiency: chances and difficulties of management]. / La déficience visuelle congénitale: chances et difficultes d'aménagement.

The traditional theories according to which deprivation of the visual channel is directly responsible for every disturbance observed in children born blind or partially sighted prove to be unsatisfactory; they fail to answer why, given the same visual defect, some children develop in a healthy way while others present a typical picture of infantile psychosis. The authors put forward the following hypotheses: infantile psychosis is always both a sign of and a response to trauma, in the sense developed by Freud in Beyond the Pleasure Principle, which has struck the mother-child dual unit; the high frequency of psychotics among children born blind indicates that blindness is a particularly charged trauma. The traumatic neurosis of the parents and especially of the mother is catastrophic for the child; it is therefore necessary to understand why and how its works, how it can be avoided or dealth with. The authors present a detailed clinical description of the various possible mother-child constellations and regarding unfavourable outcomes, propose preventive measures.

Long duration EEG studies in the case of a psychotic child.

Three biotelemetric examinations and a whole night sleep recording were carried out in an 8-year-old child whose behaviour alternated between excitation and autism with stereotypes. The EEG showed 5 c/sec temporo-parietal sharp wave discharges lasting from 1 sec to 20 min. These discharges were at times unilateral and predominantly right sided, at other times bilateral, without any clinical sign of epilepsy. The chronological distribution of right, left and bilateral discharges during the successive 1 min epochs was computed and related to corresponding 'behavioural states' of the child. The paroxysmal discharges predominated when the child was awake but not involved in any relational activity; during sleep, they mostly appeared during light NREM sleep (stage I) and paradoxical sleep. The significance of these paroxysmal discharges is discussed in relation to stereotyped behaviour, vigilance and early disorganization of biological rhythms.

[Temporal organization of paroxysmal discharges in the child. I. Biotelemetric recordings during wakefulness]. / Organisation temporelle des decharges paroxystiques chez l'enfant. I. enregistrements biotelemetriques de veille.

Based on telemetric recordings performed on 6 children, a study of the time distribution of intra-clinical paroxysmal discharges was carried out. It was tested whether this distribution is stochastic, and if not so, whether is depends upon an internal biological rhythm or upon environmental and behavioural factors. The times of occurrence of paroxysmal discharges, generalized and/or focal or partial, were located by visual inspection, and fed into a computer for statistical evaluation. Discharges and intervals were thus quantified for the overall recording time, for one situation or for groups of situations; the chronological distribution of discharges during successive 300 sec epochs was also computed. In all the cases, the discharge density varied from one moment to the next, but not in random fashion: the hypothesis of an internal modulation of the discharges was verified in some specific cases, more often, the changes in the discharge chronology seemed to be related to modifications of psychophysiological states observed during the successive experimental situations. The factors involved, namely, alertness, specific attention, stress, posture, etc., seemed to play a different role in each case; no simple correlation with the topography of discharges could be established. One explanation does not exclude the other: modulation of the discharges by biological rhythms could at any time be masked by variations due to environmental factors and to the subject's specific reaction to the latter. This type of study presents considerable methodological and interpretative difficulties which tend to emphasize individual differences rather than allowing to draw general laws.

[Paroxysmal discharges in children (author's transl)]. / Les décharges paroxystiques focales, partielles et généralisées chez l'enfant. Etude statistique et chronologique des données obtenues par enregistrements biotélémétriques de veille.

The temporal organisation of infra-clinical paroxysmal discharges was recorded in waking children using biotelemetry. This was studied in terms of two hypotheses: firstly regulation of discharges by an "internal clock" which would explain their periodic modulation; secondly the influence of certain induced or spontaneous psychophysiological situation which could increase or decrease their density. By statistical analysis using semi-automatic programmes, the density of paroxysmal discharges was studied for each experimental situation; the chronological evolution of density was also worked out. These programmes were applied to 6 long biotelemetric recordings. The results obtained show that neither of the hypotheses alone can explain the phenomena observed, and that the paroxysmal discharges probably occur at times determined by a combination of internal factors and multiple situations: modulation linked to more or less stable biological rhythms, and the role of the environment and the subjects' reactions, which intervene to a varying extent to mask natural rhythms.

[Biotelemetric studies in an autistic child (author's transl)]. / Etudes biotéllémétriques répétées chez un enfant psychotique.

Three biotelemetric examinations and a whole night sleep recording were carried out in a 8 year old child whose behavior alternated between exicitation and autism. The E.E.G. showed 5 Hz. temporo-parietal sharp wave discharges lasting from 1 second to 20 minutes. These discharges were at times unilateral and predominantly right sided, at other times being bilateral without clinical signs and unrelated to changes in behavior. The possibility of internal regulation of discharge of discharge production or their dependence on induced situations or psychophysiological states is considered.

[A telemetric study of central rhythms in children]. / Etude telemetrique des rythmes centraux ches l'enfant

Data concerning central (mu) rhythms in children are reported, these rhythms being studied by means of prolonged telemetric recording which makes it possible to study various experimental situations. Several different patterns of mu rhythm were observed in every subject, depending on the experimental situation. The level and the quality of attention on the one hand, immobility on the other, were found to be the two main factors which facilitated the occurrence or the maintenance of mu rhythms. The induction of movement, especially of the hand, was the major cause of blocking pre-existing mu rhythms, but attention alone was also able to provoke the same reaction. These data were compared with those obtained in animals by direct recording from the cortical somaesthetic areas. The respective roles of vigilance, attention and movement are discussed.