Search for Lepton Number and Flavor Violation in K^{+} and π^{0} Decays

Searches for the lepton number violating K^{+}→π^{-}μ^{+}e^{+} decay and the lepton flavor violating K^{+}→π^{+}μ^{-}e^{+} and π^{0}→μ^{-}e^{+} decays are reported using data collected by the NA62 experiment at CERN in 2017-2018. No evidence for these decays is found and upper limits of the branching ratios are obtained at 90% confidence level: B(K^{+}→π^{-}μ^{+}e^{+})<4.2×10^{-11}, B(K^{+}→π^{+}μ^{-}e^{+})<6.6×10^{-11} and B(π^{0}→μ^{-}e^{+})<3.2×10^{-10}. These results improve by 1 order of magnitude over previous results for these decay modes.

Measured removal rates of chrysotile asbestos fibers from air and comparison with theoretical estimates based on gravitational settling and dilution ventilation

CONTEXT

Industrial hygiene assessments often focus on activity-based airborne asbestos concentration measurements, but few empirical data exist regarding the fiber removal rate from air after activities cease.

OBJECTIVE

Grade 7T chrysotile indoor fiber settling (FS) rates were characterized using air sampling (NIOSH Method 7402).

MATERIALS AND METHODS

Six replicate events were conducted in a 58 m(3) study chamber (ventilation 3.5 ACH), in which chrysotile-contaminated work clothing was manipulated for 15 min followed by 30 min of no activity. The fiber concentration decay constant and removal rate were characterized using an exponential decay model based on the measurements.

RESULTS

Breathing zone airborne chrysotile concentrations decreased by 86% within 15-30 min after fiber disturbance, compared to concentrations during active disturbance (p < 0.05). Estimated mean time required for 99% of the phase contrast microscopy-equivalent (PCME) fibers to be removed from air was approximately 30 min (95% CI: 22-57 min). The observed effective FS velocity was 0.0034 m/s. This settling velocity was between 4.5-fold and 180-fold faster than predicted by two different particulate gravitational settling models. Additionally, PCME concentrations decreased approximately 2.5-fold faster than predicted due to air exchange alone (32 versus 79 min to 99% decrease in concentration).

DISCUSSION

Other measurement studies have reported similar airborne fiber removal rates, supporting the finding that factors other than gravitational settling and dilution ventilation contribute measurably to PCM fiber removal from air (e.g. impaction, agglomeration).

CONCLUSION

Overall, the scientific weight of evidence indicates that the time necessary for removal of 99% of fibers greater than 5 μm in length (with aspect ratios greater than 3:1) is approximately 20-80 min.

Evaluation of take-home exposure and risk associated with the handling of clothing contaminated with chrysotile asbestos

The potential for para-occupational (or take-home) exposures from contaminated clothing has been recognized for the past 60 years. To better characterize the take-home asbestos exposure pathway, a study was performed to measure the relationship between airborne chrysotile concentrations in the workplace, the contamination of work clothing, and take-home exposures and risks. The study included air sampling during two activities: (1) contamination of work clothing by airborne chrysotile (i.e., loading the clothing), and (2) handling and shaking out of the clothes. The clothes were contaminated at three different target airborne chrysotile concentrations (0-0.1 fibers per cubic centimeter [f/cc], 1-2 f/cc, and 2-4 f/cc; two events each for 31-43 minutes; six events total). Arithmetic mean concentrations for the three target loading levels were 0.01 f/cc, 1.65 f/cc, and 2.84 f/cc (National Institute of Occupational Health and Safety [NIOSH] 7402). Following the loading events, six matched 30-minute clothes-handling and shake-out events were conducted, each including 15 minutes of active handling (15-minute means; 0.014-0.097 f/cc) and 15 additional minutes of no handling (30-minute means; 0.006-0.063 f/cc). Percentages of personal clothes-handling TWAs relative to clothes-loading TWAs were calculated for event pairs to characterize exposure potential during daily versus weekly clothes-handling activity. Airborne concentrations for the clothes handler were 0.2-1.4% (eight-hour TWA or daily ratio) and 0.03-0.27% (40-hour TWA or weekly ratio) of loading TWAs. Cumulative chrysotile doses for clothes handling at airborne concentrations tested were estimated to be consistent with lifetime cumulative chrysotile doses associated with ambient air exposure (range for take-home or ambient doses: 0.00044-0.105 f/cc year).

Distinguishing objective from subjective assessments of the severity of medication-related safety events among people with Parkinson's disease: a qualitative study

WHAT IS KNOWN AND OBJECTIVE

Safety events indicating medication-related errors in Parkinson's disease (PD) are common but seldom studied, particularly from lay perspectives. Our objective was to study the meaning and significance to people living with PD of their experience of safety events.

METHODS

Twenty qualitative interviews were conducted by telephone with purposively sampled individuals with PD, a proxy, or both, throughout New Zealand. Themes identified from the data included joint assessments of the objective and subjective severity of the individual safety events.

RESULTS AND DISCUSSION

Most of the events indicated minor objective errors, whose severity was sometimes perceived as major, especially in the face of callous communication.

WHAT IS NEW AND CONCLUSION

Variation between objective and subjective assessments of the severity of possible errors indicated by safety events highlight the importance of distinguishing between, and using, both forms of assessment.

Time-dependent chemical compositions of 13N and 15O induced in air by the operation of a high energy electron accelerator

Time-dependent chemical compositions for 13N and 15O induced in the air atmosphere of a high energy electron accelerator room have been studied using a computer simulation method. A radiation chemistry model was developed to describe the chemical reactions of 13N and 15O species with the air molecules and their radiolytic products. By assuming several chemical forms of 13N and 15O generated by the (gamma, n) reaction, the variations of the concentrations of 13N and 15O species were simulated under a radiation field. From the comparison between the simulations and experiment in a 100 MeV electron linear accelerator (linac) facility, the following conclusions were obtained: (1) Just after the (gamma, n) reaction, 25-50% of 13N and 15O are present as atoms (13N, 15O) and/or their ions (13N+, 15O+) and the remainder as nitrogen and oxygen molecules (13NN, 15OO) and/or their ions (13NN+, 15OO+); (2) Neutralization of 13N+ and 15O+ ions into 13N and 15O atoms occurs instantaneously and the same is the case with the neutralization of 13NN+ and 15OO+ ions to 13NN and 15OO molecules; (3) The neutralized 13N and 15O atoms react with the air molecules and the radiolytic products to form nitrogen oxide compounds and ozone, while 13NN and 15OO remain as these molecules. Factors that control the chemical reactions of 13N and 15O are discussed.

ABC of spinal cord injury. Occupational therapy

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The 'induction' dose of thiopentone. A method of study and preliminary illustrative results

Study of the minimal dose requirements for induction of anaesthesia poses great problems which are solved by the use of a standard administration technique and the abolition of the eyelash reflex as an endpoint. This has been used in 2206 consecutive unselected inductions, in which variables considered to be likely to influence the dosage were recorded. Milligram per kilogram is the most acceptable method of expressing the average dosage of thiopentone. Doses follow a right skew distribution. Women required a significantly lower average dose of thiopentone than men, while obese patients required less than others. Moderate or heavy drinking increased the induction dose but the use of tobacco did not have any influence. The most important factors governing dosage are the physical fitness of the patient and the premedication used. Patients in ASA grades 1 and 2 required significantly more thiopentone than those in grades 3 and 4. This effect is as great as that of premedication in which an opiate with a phenothiazine or hyoscine markedly reduced the induction dose. It was more important than the patient's pre-operative condition with respect to sedation or apprehension. Small doses of opiates or benzodiazepines do not have as much effect on dosage.