A large 'Active Magnetic Shield' for a high-precision experiment: nEDM collaboration.

We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about 105 for its inner sensitive volume. The AMS consists of a system of eight complex, feedback-controlled compensation coils constructed on an irregular grid spanned on a volume of less than 1000 m3 around the MSR. The AMS is designed to provide a stable and uniform magnetic-field environment around the MSR, while being reasonably compact. The system can compensate static and variable magnetic fields up to ±50µT (homogeneous components) and ±5µT/m (first-order gradients), suppressing them to a few µT in the sub-Hertz frequency range. The presented design concept and implementation of the AMS fulfills the requirements of the n2EDM experiment and can be useful for other applications, where magnetically silent environments are important and spatial constraints inhibit simpler geometrical solutions.

The design of the n2EDM experiment: nEDM Collaboration.

We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is of the experimental method and setup is given, the sensitivity requirements for the apparatus are derived, and its technical design is described.

Measurement of the Permanent Electric Dipole Moment of the Neutron.

We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating time-reversal invariance. The salient features of this experiment were the use of a ^{199}Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{n}=(0.0±1.1_{stat}±0.2_{sys})×10^{-26} e.cm.

Water-equivalent path length calibration of a prototype proton CT scanner.

PURPOSE: The authors present a calibration method for a prototype proton computed tomography (pCT) scanner. The accuracy of these measurements depends upon careful calibration of the energy detector used to measure the residual energy of the protons that passed through the object. METHODS: A prototype pCT scanner with a cesium iodide (CsI(Tl)) crystal calorimeter was calibrated by measuring the calorimeter response for protons of 200 and 100 MeV initial energies undergoing degradation in polystyrene plates of known thickness and relative stopping power (RSP) with respect to water. Calibration curves for the two proton energies were obtained by fitting a second-degree polynomial to the water-equivalent path length versus calorimeter response data. Using the 100 MeV calibration curve, the RSP values for a variety of tissue-equivalent materials were measured and compared to values obtained from a standard depth-dose range shift measurement using a water-tank. A cylindrical water phantom was scanned with 200 MeV protons and its RSP distribution was reconstructed using the 200 MeV calibration. RESULTS: It is shown that this calibration method produces measured RSP values of various tissue-equivalent materials that agree to within 0.5% of values obtained using an established water-tank method. The mean RSP value of the water phantom reconstruction was found to be 0.995 ± 0.006. CONCLUSIONS: The method presented provides a simple and reliable procedure for calibration of a pCT scanner.

Calibration of a proton beam energy monitor.

Delivery of therapeutic proton beams requires an absolute energy accuracy of +/-0.64 to 0.27 MeV for patch fields and a relative energy accuracy of +/-0.10 to 0.25 MeV for tailoring the depth dose distribution using the energy stacking technique. Achromatic switchyard tunes, which lead to better stability of the beam incident onto the patient, unfortunately limit the ability of switchyard magnet tesla meters to verify the correct beam energy within the tolerances listed above. A new monitor to measure the proton energy before each pulse is transported through the switchyard has been installed into a proton synchrotron. The purpose of this monitor is to correct and/or inhibit beam delivery when the measured beam energy is outside of the tolerances for treatment. The monitor calculates the beam energy using data from two frequency and eight beam position monitors that measure the revolution frequency of the proton bunches and the effective offset of the orbit from the nominal radius of the synchrotron. The new energy monitor has been calibrated by measuring the range of the beam through water and comparing with published range-energy tables for various energies. A relationship between depth dose curves and range-energy tables was first determined using Monte Carlo simulations of particle transport and energy deposition. To reduce the uncertainties associated with typical scanning water phantoms, a new technique was devised in which the beam energy was scanned while fixed thickness water tanks were sandwiched between two fixed parallel plate ionization chambers. Using a multitude of tank sizes, several energies were tested to determine the nominal accelerator orbit radius. After calibration, the energy reported by the control system matched the energy derived by range measurements to better than 0.72 MeV for all nine energies tested between 40 and 255 MeV with an average difference of -0.33 MeV. A study of different combinations of revolution frequency and radial offsets to test the envelope of algorithm accuracy demonstrated a relative accuracy of +/-0.11 MeV for small energy changes between 126 and 250 MeV. These new measurements may serve as a data set for benchmarking range-energy relationships.

Two-dimensional and quasi-three-dimensional dosimetry of hadron and photon beams with the Magic Cube and the Pixel Ionization Chamber.

Two detectors for fast two-dimensional (2D) and quasi-three-dimensional (quasi-3D) verification of the dose delivered by radiotherapy beams have been developed at University and Istituto Nazionale di Fisica Nucleare (INFN) of Torino. The Magic Cube is a stack of strip-segmented ionization chambers interleaved with water-equivalent slabs. The parallel plate ionization chambers have a sensitive area of 24 x 24 cm2, and consist of 0.375 cm wide and 24 cm long strips. There are a total of 64 strips per chamber. The Magic Cube has been tested with the clinical proton beam at Loma Linda University Medical Centre (LLUMC), and was shown to be capable of fast and precise quasi-3D dose verification. The Pixel Ionization Chamber (PXC) is a detector with pixel anode segmentation. It is a 32 x 32 matrix of 1024 cylindrical ionization cells arranged in a square 24 x 24 cm2 area. Each cell has 0.4 cm diameter and 0.55 cm height, at a pitch of 0.75 cm separates the centre of adjacent cells. The sensitive volume of each single ionization cell is 0.07 cm3. The detectors are read out using custom designed front-end microelectronics and a personal computer-based data acquisition system. The PXC has been used to verify dynamic intensity-modulated radiotherapy for head-and-neck and breast cancers.

Microdosimetry spectra of the Loma Linda proton beam and relative biological effectiveness comparisons.

Protons have long been recognized as low LET radiation in radiotherapy. However, a detailed account of LET (linear energy transfer) and RBE (relative biological effectiveness) changes with incident beam energy and depth in tissue is still unresolved. This issue is particularly important for treatment planning, where the physical dose prescription is calculated from a RBE using cobalt as the reference radiation. Any significant RBE changes with energy or depth will be important to incorporate in treatment planning. In this paper we present microdosimetry spectra for the proton beam at various energies and depths and compare the results to cell survival studies performed at Loma Linda. An empirically determined biological weighting function that depends on lineal energy is used to correlate the microdosimetry spectra with cell survival data. We conclude that the variations in measured RBE with beam energy and depth are small until the distal edge of the beam is reached. On the distal edge, protons achieve stopping powers as high as 100 keV/micron, which is reflected in the lineal energy spectra taken there. Lineal energy spectra 5 cm beyond the distal edge of the Bragg peak also show a high LET component but at a dose rate 600 times smaller than observed inside the proton field.

Preservation of salicaceae leaves for phytochemical analyses: Further assessment.

The chemistry of the plant family Salicaceae has been of interest to researchers as diverse as chemical ecologists, chemosystematists, and paper chemists. Continuing the debate on proper methods for preservation of plant material prior to analysis, vacuum-drying was recently advocated, because freeze-drying may cause degradation of phenolic glycosides. This study was conducted to clarify the consequences of freeze-drying for foliar secondary chemicals and to evaluate the consequences of vacuum-drying for primary compounds (protein and carbohydrates). Leaves of quaking aspen (Populus tremuloides) were flash-frozen in liquid nitrogen and freeze-dried or vacuum-dried at room temperature. We then analyzed samples for levels of salicortin and tremulacin (phenolic glycosides), condensed tannins, nitrogen, soluble protein, sugars, and starch. Freeze-drying did not alter the concentrations of phenolic glycosides or tannins, relative to vacuum-drying. Freeze-drying did cause a small and inexplicable decline in nitrogen and soluble protein. Vacuum-drying, however, reduced starch concentrations by 38%. We suggest that the vacuum-drying method be used in studies in which carbohydrates are of no interest. For studies measuring carbohydrates, however, freeze-drying is a better alternative, and should effect no changes in levels of secondary compounds if samples are not allowed to thaw during the drying process.

Deleterious effects of criminal victimization on women's health and medical utilization.

The long-term consequences of criminal victimization on physical health were examined among 390 adult women (74 nonvictims and 316 victims of crime). Data included health status self-ratings and objective service utilization. Findings indicated that severely victimized women, compared with nonvictims, reported more distress and less well-being, made physician visits twice as frequently in the index year, and had outpatient costs that were 2.5 times greater. Criminal victimization severity was the most powerful predictor of physician visits and outpatient costs. Utilization data across 5 years preceding and following crime were obtained from 15 rape victims, 26 physical assault victims, and 27 noncontact crime victims and were compared with five continuous years of utilization among 26 nonvictims. Victims' physician visits increased 15% to 24% during the year of the crime compared with less than 2% change among nonvictims. We conclude that these long-term deleterious effects suggest that criminally victimized women's needs for medical treatment transcend the traditional focus on emergency care and forensic evaluation.

Criminal victimization among primary care medical patients: prevalence, incidence, and physician usage.

The study addressed the extent to which primary care physicians encounter crime victims in their practices. Crime prevalence and incidence rates were calculated from responses to a mailed survey of 2,291 women medical patients (45% response rate). The prevalence of crime victimization was 57%. The 12 month incidence of violent crime was 118 per 1,000 patients. Most notable was the finding that rape incidence was approximately 15 times higher than National Crime Survey estimates for women, even after adjustment for telescoping. Post-crime physician usage was documented by medical chart review. Although few crime victims required hospitalization for injuries, virtually all made out-patient physician visits in each of two post-crime years. The findings suggest that physicians are an important potential source of assistance for traumatized crime victims.

Relation of criminal victimization to health perceptions among women medical patients.

The relation of criminal victimization to health perceptions (self-rated current health) was determined among women health maintenance organization patients. Data were survey responses from 2,291 women (45% response rate), 57% of whom had experienced crime. Reliability was evaluated by assessing 241 respondents both by survey and by interview. Data were analyzed by hierarchical multiple regression, which indicated that criminal victimization was an important predictor of health perceptions even after accounting for the contributions of demographics and other stressful life events with known links to illness. Validity was supported because medical care was actually sought by 92% of crime victims during the 1st year following the crime and by 100% during the 2nd year. Conclusions included the following: (a) Crime victimization history is relevant to health status assessment, and (b) primary care medical populations are an important locus from which crime victims could be identified and their treatment options considered.

Effects of daily activities and social behavior on blood-pressure elevation.

This study examined the effects of daily activities and social behavior on the blood-pressure elevation in 21 normotensives, 20 borderline hypertensives, and 20 sustained essential hypertensives. Blood pressures were recorded over a 24-hr period using an ambulatory monitor while subjects recorded their daily activities and social involvement at each cuff inflation. Results indicated that only a moderate proportion of the blood pressure readings of the two clinical groups exceeded 140/90 mm Hg. Results also suggested that the blood pressures of normotensives were more responsive to changes in physical activity, while the blood pressures of sustained hypertensives were more responsive to social involvement. When group differences emerged on mean blood-pressure elevation, analyses indicated that the two hypertensive groups frequently differed from the normotensive group but rarely from each other. The results suggest that differences in blood-pressure elevation cannot be fully understood without considering behavior and support its continued inclusion in the study of blood pressure.

Behavioral predictors of blood pressure variation in hypertensives and normotensives.

This study examined the relative impact of five behavioral factors--activity, posture, location, social involvement, and tension--on the 24-hr blood pressure (BP) variability of 21 normotensives, 18 borderline hypertensives, and 18 sustained essential hypertensives. Multiple-regression analyses indicated that within each diagnostic group, activity accounted for more variance in BP variability than any other behavioral dimension. For each behavioral dimension examined, the magnitude of the relationship with BP was generally greater for the normotensives than for both hypertensive groups. In contrast, variation due to individuals was a better predictor of BP variability for the two hypertensive groups than for the normotensive group. Number of months hypertensive and use of antihypertensive medication were related to BP variability for the sustained hypertensive group. Findings have implications for the use of ambulatory BP monitors and interpretation of resulting data.