Characterization of a plutonium-beryllium neutron source.

Here we present an investigation of a plutonium-beryllium neutron source available at the Horia Hulubei National Institute of Physics and Nuclear Engineering, Romania, to be used for detector characterization during the implementation of the Extreme Light Infrastructure - Nuclear Physics project. Using several different techniques and instruments, we have measured the isotopic composition for plutonium to be 75% 239Pu and 24% 240Pu, with a minor contribution from other isotopes. Furthermore, we have measured the source activity as of November 20th 2019 to be 2.220(5)×105 neutrons per second with a mean energy of 3.25(17) MeV. We have also measured both the γ-tagged and full neutron energy spectra, and discuss the origin of the observed structure in the neutron energies based on these. All these parameters are of importance both for traceability of nuclear material, radioprotection, and accurate detector characterization.

Electromagnetic character of the competitive γγ/γ-decay from 137mBa.

Second-order processes in physics is a research topic focusing attention from several fields worldwide including, for example, non-linear quantum electrodynamics with high-power lasers, neutrinoless double-ß decay, and stimulated atomic two-photon transitions. For the electromagnetic nuclear interaction, the observation of the competitive double-γ decay from 137mBa has opened up the nuclear structure field for detailed investigation of second-order processes through the manifestation of off-diagonal nuclear polarisability. Here, we confirm this observation with an 8.7σ significance, and an improved value on the double-photon versus single-photon branching ratio as 2.62 × 10-6(30). Our results, however, contradict the conclusions from the original experiment, where the decay was interpreted to be dominated by a quadrupole-quadrupole component. Here, we find a substantial enhancement in the energy distribution consistent with a dominating octupole-dipole character and a rather small quadrupole-quadrupole component in the decay, hindered due to an evolution of the internal nuclear structure. The implied strongly hindered double-photon branching in 137mBa opens up the possibility of the double-photon branching as a feasible tool for nuclear-structure studies on off-diagonal polarisability in nuclei where this hindrance is not present.

Measurement of the first ionization potential of astatine by laser ionization spectroscopy.

The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine.

Ambulatory versus inpatient rotations in teaching third-year students internal medicine.

We studied 63 randomly selected third-year students who split their 10-week medicine clerkship between ambulatory and inpatient components. Compared with their inpatient experience, during the ambulatory rotation, the 63 students felt more like doctors, more responsible for patients, and more able to know and help their patients. Students reported that ambulatory attending staff appeared happier and less stressed, and did not embarrass them as frequently. Compared with their 619 "inpatient" classmates, these 63 "ambulatory" students scored as well on the medicine examination, and were as likely to receive honors (44% vs 41%), and to choose internal medicine residencies (35% vs 34%). In conclusion, students experienced better relationships with their patients and teachers during the ambulatory rotation, which was academically comparable to the inpatient experience.

Ambulatory blood pressure and echocardiographic left ventricular dimensions in elderly hypertensive subjects.

In a consecutive series of 62 hypertensive elderly subjects, the authors studied the relation of blood pressure circadian variations with echocardiographic parameters of left ventricular (LV) hypertrophy. All the subjects were submitted to an ambulatory blood pressure monitoring (ABPM) and to B- and M-mode echocardiography. In the elderly hypertensive group, LV mass index (LVMI) was more strongly related to twenty-four-hour, daytime and nighttime systolic ambulatory blood pressure (r = 0.52, r = 0.37, r = 0.51) than diastolic ambulatory blood pressures were (r = 0.32, r = 0.18, r = 0.33). Casual systolic and diastolic blood pressure (CBP) was found more weakly related to LVMI than ambulatory blood pressures were (r = 0.35, r = 0.26). Elderly hypertensive subjects were divided into two subgroups in relation to the presence (group 1) or absence (group 2) of blood pressure nocturnal decline. No differences were found between these two subgroups in regard to: casual blood pressure values, ambulatory blood pressures in the diurnal period, sex, body surface area, height, weight, and age. LVMIs were computed in all three groups and showed the following results: 89.32 +/- 19.76 in elderly normotensives, 91.21 +/- 31.32 in group 1, and 99.80 +/- 18.21 in group 2. Echocardiographic parameters of LV dimensions and LVMIs were different in group 1 and 2. An inverse correlation, statistically significant, was observed between LVMIs and the nocturnal blood pressure reduction (systolic: r = -0.36, P < 0.05; diastolic: r = -0.29, P < 0.05). These results suggest an association between a smaller LV mass and nocturnal blood pressure decline in elderly hypertensive patients.

[Valley/peak ratio and pressure changes during treatment with fosinopril in hypertensive elderly patients]. / Rapporto valle/picco e variabilità pressoria durante terapia con fosinopril in pazienti anziani ipertesi.

Antihypertensive drug therapy uniformity of efficacy was evaluated in a group of elderly hypertensive subjects with trough-to-peak ratio, after a period of antihypertensive drug therapy with ACE-inhibitor fosinopril. An ambulatory blood pressure monitoring (ABPM) with evaluation of blood pressure variability assessed by standard deviation (S.D.) and coefficient of variation (C.V.) were evaluated in each subjects. Our preliminary data showed that the treatment with fosinopril had satisfactory uniformity of efficacy during all the 24-hour period, with both full dose (20 mg) and reduced dose (10 mg); little influence on blood pressure variability was determined by antihypertensive treatment.

Discrimination of transiently applied mechanical loads: breathing vs. pulling.

Two groups of 24 subjects each attempted to discriminate between large elastic and resistive loads during 50 randomized presentations of each load. Breathers inspired from the loads through a J valve, whereas pullers reciprocally stroked the plunger of a 2-liter syringe connected to the J valve. A range of load durations was obtained in each subject by prematurely unloading approximately one-half of the trials at graded times from their onset. Breathers produced random discrimination scores [50.8 +/- 2.5% (SE) correct] when loaded inspirations were shorter than unloaded inspirations [trials in which both loads induced equal airway pressure (and probably respiratory muscle tension) waveforms] and nonrandom discrimination scores (65.7 +/- 2.8% correct) when loaded inspirations were longer than unloaded inspirations (trials in which both loads induced different waveforms). In contrast, pullers produced nonrandom discrimination scores (62.2 +/- 2.9% correct) when loaded airflow durations were shorter than unloaded inspirations [trials in which both loads induced equal line pressure (and therefore limb muscle tension) waveforms]. Supplemental audio feedback related to instantaneous airflow (an expression of movement) improved load perception in breathers (to 64.2 +/- 3.0% correct; P < 0.01), indicating that airflow feedback introduced load-specific information that was lacking during breathing but redundant during pulling. In support of this hypothesis, airflow feedback by itself enabled a third group of listeners to identify load type with equal accuracy as pullers but with greater accuracy than breathers. These findings suggest that 1) uniformed subjects rely heavily on feedback from airway pressure and/or muscle tension receptors to perceive added loads to breathing and 2) limb mechanoreceptors provide a more sensitive appreciation of movement than do respiratory mechanoreceptors.