Demonstration of event position reconstruction based on diffusion in the NEXT-white detector

Noble element time projection chambers are a leading technology for rare event detection in physics, such as for dark matter and neutrinoless double beta decay searches. Time projection chambers typically assign event position in the drift direction using the relative timing of prompt scintillation and delayed charge collection signals, allowing for reconstruction of an absolute position in the drift direction. In this paper, alternate methods for assigning event drift distance via quantification of electron diffusion in a pure high pressure xenon gas time projection chamber are explored. Data from the NEXT-White detector demonstrate the ability to achieve good position assignment accuracy for both high- and low-energy events. Using point-like energy deposits from 83mKr calibration electron captures (E ∼ 45  keV), the position of origin of low-energy events is determined to 2 cm precision with bias < 1 mm. A convolutional neural network approach is then used to quantify diffusion for longer tracks (E ≥ 1.5  MeV), from radiogenic electrons, yielding a precision of 3 cm on the event barycenter. The precision achieved with these methods indicates the feasibility energy calibrations of better than 1% FWHM at Qββ in pure xenon, as well as the potential for event fiducialization in large future detectors using an alternate method that does not rely on primary scintillation.

Barium Chemosensors with Dry-Phase Fluorescence for Neutrinoless Double Beta Decay

The nature of the neutrino is one of the major open questions in experimental nuclear and particle physics. The most sensitive known method to establish the Majorana nature of the neutrino is detection of the ultra-rare process of neutrinoless double beta decay. However, identification of one or a handful of decay events within a large mass of candidate isotope, without obfuscation by backgrounds is a formidable experimental challenge. One hypothetical method for achieving ultra- low-background neutrinoless double beta decay sensitivity is the detection of single 136Ba ions produced in the decay of 136Xe ("barium tagging"). To implement such a method, a single-ion-sensitive barium detector must be developed and demonstrated in bulk liquid or dry gaseous xenon. This paper reports on the development of two families of dry-phase barium chemosensor molecules for use in high pressure xenon gas detectors, synthesized specifically for this purpose. One particularly promising candidate, an anthracene substituted aza-18-crown-6 ether, is shown to respond in the dry phase with almost no intrinsic background from the unchelated state, and to be amenable to barium sensing through fluorescence microscopy. This interdisciplinary advance, paired with earlier work demonstrating sensitivity to single barium ions in solution, opens a new path toward single ion detection in high pressure xenon gas.

Restrictive left ventricular filling patterns in very old patients with congestive heart failure: clinical correlates and prognostic significance

OBJECTIVES

In certain younger patients with congestive heart failure (CHF), Doppler/echocardiography has identified a "restrictive" pattern of early diastolic ventricular filling characterized by very rapid early filling and a steep deceleration slope. We asked whether a similar restrictive pattern can be identified in very old patients with CHF, and if so, what are its clinical correlates and prognostic implications.

DESIGN

Retrospective cohort with prospective follow-up.

SETTING

Academic long-term care facility.

PARTICIPANTS

Thirty-nine residents with clinical CHF (age 89 +/- 5 (SD) years)

MEASUREMENTS

Transmitral Doppler flow, clinical characteristics, recurrent CHF episodes, hospitalizations, and mortality were measured.

RESULTS

Fifteen (38%) of the subjects had restrictive filling patterns, characterized by a ratio of early to late flow (E/A) > 1.00 and 24 (62%) had nonrestrictive patterns. The restrictive pattern was associated with a longer duration of CHF, more angina, and higher rate of symptomatic recurrences of CHF.

CONCLUSION

A restrictive diastolic filling pattern may represent a late stage in the evolution of congestive heart failure when left ventricular filling pressure is markedly increased. The treatment of CHF in older patients may need to account for different patterns of diastolic filling.

Getting care to nursing-home patients: a problem and a proposal

Data abstracted from transportation company records showed that nursing home patients made an average of 3.6 trips per year for care out of the nursing home. The bulk of this care (55 per cent) was provided at University Hospital with over a quarter provided at private physicians' offices and community health centers. On the basis of chart abstracts over half the patients had been seen within the previous month, but the quality of that visit was open to question. A means of providing cost-effective primary medical care in the nursing homes using a team of nurse practitioner and social worker is proposed.

The use of utilization review records as a source of data on nursing home care

Data form the Utah nursing home Utilization Review Program, 1970-73, provide a description of the population of nursing home patients in Utah and changes over time in patient medication and measures of activity. These data are analyzed according to type of care in home: personal, intermediate, or comprehensive. The collection of data in utilization review programs can help to evaluate the quality of care as well as appropriateness of placement, provided the information collected is designed with these ends in mind.