Measurement of the Isolated Nuclear Two-Photon Decay in

The nuclear two-photon or double-gamma (2γ) decay is a second-order electromagnetic process whereby a nucleus in an excited state emits two gamma rays simultaneously. To be able to directly measure the 2γ decay rate in the low-energy regime below the electron-positron pair-creation threshold, we combined the isochronous mode of a storage ring with Schottky resonant cavities. The newly developed technique can be applied to isomers with excitation energies down to ∼100 keV and half-lives as short as ∼10 ms. The half-life for the 2γ decay of the first-excited 0^{+} state in bare ^{72}Ge ions was determined to be 23.9(6) ms, which strongly deviates from expectations.

Isomer depletion as experimental evidence of nuclear excitation by electron capture.

The atomic nucleus and its electrons are often thought of as independent systems that are held together in the atom by their mutual attraction. Their interaction, however, leads to other important effects, such as providing an additional decay mode for excited nuclear states, whereby the nucleus releases energy by ejecting an atomic electron instead of by emitting a γ-ray. This 'internal conversion' has been known for about a hundred years and can be used to study nuclei and their interaction with their electrons. In the inverse process-nuclear excitation by electron capture (NEEC)-a free electron is captured into an atomic vacancy and can excite the nucleus to a higher-energy state, provided that the kinetic energy of the free electron plus the magnitude of its binding energy once captured matches the nuclear energy difference between the two states. NEEC was predicted in 1976 and has not hitherto been observed. Here we report evidence of NEEC in molybdenum-93 and determine the probability and cross-section for the process in a beam-based experimental scenario. Our results provide a standard for the assessment of theoretical models relevant to NEEC, which predict cross-sections that span many orders of magnitude. The greatest practical effect of the NEEC process may be on the survival of nuclei in stellar environments, in which it could excite isomers (that is, long-lived nuclear states) to shorter-lived states. Such excitations may reduce the abundance of the isotope after its production. This is an example of 'isomer depletion', which has been investigated previously through other reactions, but is used here to obtain evidence for NEEC.

Novel Approach to

A novel approach for isomer depletion in ion-atom collisions is proposed and considered theoretically. Analyses are performed for the depletion of the ^{93m}Mo isomer for which an unexpectedly large probability was measured in the beam-based experiment of Chiara et al. [Nature (London) 554, 216 (2018)NATUAS0028-083610.1038/nature25483]. The subsequent attempt at a theoretical description based on state-of-the-art atomic theory did not reproduce the experimental result [Wu et al., Phys. Rev. Lett. 122, 212501 (2019)PRLTAO0031-900710.1103/PhysRevLett.122.212501] and showed a dramatic disagreement with the experiment (by many orders of magnitude). This conflict calls for further research on the nature of isomer depletion mechanisms occurring in atomic processes. Here, we propose to consider the ^{93m}Mo isomer depletion as the nuclear excitation by electron capture in resonant transfer process taking into account the momentum distribution of the target electrons. Although our results only slightly shift the upper theoretical limit for the total ^{93m}Mo isomer depletion probability toward the experimental value, they show the importance of considering the Compton profile in the theoretical description, in particular for the L shell, for which the depletion probability increases by many orders of magnitude.

Direct observation of long-lived isomers in 212Bi.

Long-lived isomers in (212)Bi have been studied following (238)U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of (212)Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.

Discovery of highly excited long-lived isomers in neutron-rich hafnium and tantalum isotopes through direct mass measurements.

A study of cooled ¹97Au projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides ¹8³(,)¹84(,)¹86Hf and ¹86(,)¹87Ta. The results support the prediction of a strongly favored isomer region near neutron number 116.

The use of pronoun anaphora and speaker mood in the interpretation of conversational utterances by right hemisphere brain-damaged patients.

Understanding utterances in conversations requires a listener to weigh the disparate pieces of information present in a discourse. In this study, we examined how right hemisphere brain-damaged (RHD) patients and non-brain-damaged control subjects interpreted responses to questions concerning the location of a person (e.g., "Where's Dad?"). Stimulus vignettes included variation on three factors relevant to discourse comprehension: the mood of a speaker, the plausibility of the answer to a question, and whether the answer contained an anaphoric pronoun linking the response to the preceding question. Relative to the control subjects, the RHD patients made greater than normal use of the presence/absence of an anaphoric pronoun in their utterance interpretations, less than normal use of the speaker's mood, and marginally less than normal use of a response's plausibility. These data show how RHD patients rely on their largely intact linguistic abilities when understanding discourse and how their comprehension goes awry due to their reduced appreciation of other essential aspects of natural communication. The discussion focuses on the variable roles of speaker mood, plausibility, and pronoun anaphora in supporting inferences about a speaker's intended meaning and on the selective nature of RHD patients' impairment in this domain.

Relationships of ozone exposure to pine injury in the Sierra Nevada and San Bernardino Mountains of California, USA.

Hourly ambient ozone exposure data and crown injury measurements were gathered in the Sierra Nevada and San Bernardino Mountains of California to develop relationships between the Ozone Injury Index (OII), the Forest Pest Management Index (FPM), chlorotic mottle, fascicle retention (OII index components) and cumulative ambient ozone indices for Pinus ponderosa Dougl. ex Laws and Pinus jeffreyi Grev. and Balf. Eleven sites located in the mixed conifer forest near ambient ozone monitoring sites were evaluated annually for 4 years. Four other sites in the San Bernardino Mountains were evaluated for 1 year. Analyses showed OII to be functionally equivalent (r2 = 0.96) to the FPM, and to depend only on fascicle retention and chlorotic mottle (R2 = 0.95) of the fourth whorl (or if four whorls are not present at the site, then the last whorl present for the majority of trees). Significant associations were found between OII and 4-year 24-h. summer SUM0, SUM06, W126 and HRS80 ozone indices. Three sites had higher levels of cumulative chlorotic mottle for individual whorls and larger numbers of trees with visible crown injury than other sites with similar cumulative ambient ozone levels. Including an indicator variable to discriminate between these two groups of sites increased R2 and decreased root mean square (RMSE) for all indices, especially SUM0 (R2 = 0.93, RMSE reduced by 46%).

Approximation of nonlinear systems with radial basis function neural networks.

A technique for approximating a continuous function of n variables with a radial basis function (RBF) neural network is presented. The method uses an n-dimensional raised-cosine type of RBF that is smooth, yet has compact support. The RBF network coefficients are low-order polynomial functions of the input. A simple computational procedure is presented which significantly reduces the network training and evaluation time. Storage space is also reduced by allowing for a nonuniform grid of points about which the RBFs are centered. The network output is shown to be continuous and have a continuous first derivative. When the network is used to approximate a nonlinear dynamic system, the resulting system is bounded-input bounded-output stable. For the special case of a linear system, the RBF network representation is exact on the domain over which it is defined, and it is optimal in terms of the number of distinct storage parameters required. Several examples are presented which illustrate the effectiveness of this technique.

Manual ellipsometry made semiautomatic.

A simple, inexpensive mechanical device is described that was designed to provide more effective data acquisition and to fit onto an already existing polarizer wheel drive mechanism of a commercially available, manual ellipsometer. A gas/metal adsorption experiment is used to illustrate typical results. Use procedures are detailed.

On the transport of nematodes by the wind.

The possible effectiveness of atmospheric transport of nematode forms (dry larvae or eggs) as a means for introducing new species to a given environment is examined. Given the measured sedimentation velocities for a range of forms (0.1 >/= Ws >/= 0.6 mps), the necessary conditions on the wind speed required for natural erosion are defined. With these results scenarios for lofting, transport, and diffusion of these forms are examined using relevant gaussian plume models. Results indicate that on rare occasions individuals can be deposited up to 40 km from their original location. Redepositions up to 5 km per erosion event should be fairly common occurances when dry loose soil conditions or dry tillage operations combine with optimal atmospheric conditions and the presence of significant numbers of nematodes at the surface.

Assessing the offspring of workaholic parents: the Children of Workaholics Screening Test.

This study reports initial stages in the development of a self-report instrument that measures offsprings' mental disposition toward their parents' work habits. In an initial sitting, a battery of tests was administered to 207 young adults to assess the reliability and validity of the Children of Workaholics Screening Test. After a 2-wk. interval, the test was administered again. Test-retest reliability, split-half reliability, and concurrent validity are reported. The findings provide strong support for the utility of the Children of Workaholics Screening Test for assessing the offspring of workaholic parents.

Counseling students' attribution of diagnostic credibility to clinical supervisors.

Research on factors influencing diagnostic credibility has not been widespread. In this study, agreement ratings for a clinical diagnosis were compared for two groups of students receiving supervision from differently credentialed hypothetical supervisors. Implications of these findings are discussed relative to preparation practices and improving clinical practice. As 190 students who had completed either less than one-half (n = 112) or more than one-half (n = 78) of their programs in 9 institutions gave mean ratings of about 5 on a 10-point scale, they did not differentially rate diagnostic credibility of the hypothetical supervisors having credentials as psychiatrists, doctorate-holding counselor education faculty, doctorate-holding psychologists, and doctoral students holding master's degrees in counselor education.

Criterion-related validity of the Marital Disaffection Scale as a measure of marital estrangement.

The Marital Disaffection Scale was administered, along with measures of positive feelings towards spouse, problem-drinking behavior of spouse, workaholic behavior of spouse, and marital status, to 323 female members of the American Counseling Association. Scores on the Marital Disaffection Scale showed significant inverse correlations (r = -.94) with positive feelings towards spouse and (rpb = -.63) with marital status. Scores on the Marital Disaffection Scale showed significant positive relationships (r = .36) with spouse's problem drinking behavior and (r = .48) with workaholic behavior of spouse. The results support the use of the Marital Disaffection Scale as a measure of emotional estrangement in marriage.

Spreadsheets simplify sensitivity analysis for capital decisions.

The availability and ease of use of electronic spreadsheets removes the previously cumbersome number crunching burden of sensitivity analysis. In this article, the advantages of sensitivity analysis will be reintroduced and a model will be presented using a pro forma statement for a freestanding magnetic resonance imaging center.

Simulating the loss of PIP: what can hospitals expect?

With the loss of the periodic interim payment (PIP), hospitals will lose the steady flow of income they have become dependent upon. However, with the use of computer simulation, hospital administrators can see how this loss could possibly affect their institutions.

NPV vs. IRR: with capital budgeting, which do you choose?

The standard that defines quality health care rises as new technologies and procedures become available. To the health care financial manager, maintaining quality health care becomes a twofold problem--how to keep up with the latest developments while staying within budget guidelines. Two methods of analyzing capital expenditures are available to the financial manager, IRR and NPV. The latter is the safest and most reliable. NPV takes into account present market conditions and neither penalizes nor overly rewards either the buyer or seller of a particular project. This article is the first of a two-part series on capital budgeting in health care and takes the financial manager beyond the pure arithmetic of NPV and IRR to show the depth and meaning behind the arithmetic.

Inflation, risk, replacement, closure: concerns in capital budgeting.

Four problems can affect the capital budgeting process-inflation, replacement, risk, and closure. Therefore financial managers must consider these problems carefully when making capital budgeting decisions. This article is the second of a two-part series on capital budgeting in health care. It builds on the existing level of knowledge of capital budgeting to give the financial manager confidence in the use of capital budgeting techniques.

≃10 eV ionization shift in Ir Kα2 from a near-coincident Lu K-edge.

Close to an x-ray filter's K-edge the transmission depends strongly on the photon energy. For a few atom pairs, the K-edge of one is only a few tens of eV higher than a K-line energy of another, so that a small change in the line's energy becomes a measurable change in intensity behind such a matching filter. Lutetium's K-edge is ≃27 eV above iridium's Kα(2) line, ≃63.287 keV for cold Ir. A Lu filter reduces this line's intensity by ≃10 % when it is emitted by a plasma, indicating an ionization shift Δε≃10±1 eV.