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We report on a search for a new, short-range, spin-dependent interaction using a modified version of the experimental apparatus used to measure the permanent neutron electric dipole moment at the Paul Scherrer Institute. This interaction, which could be mediated by axion-like particles, concerned the unpolarized nucleons (protons and neutrons) near the material surfaces of the apparatus and polarized ultracold neutrons stored in vacuum. The dominant systematic uncertainty resulting from magnetic-field gradients was controlled to an unprecedented level of approximately 4 pT cm −1 using an array of optically-pumped cesium vapor magnetometers and magnetic-field maps independently recorded using a dedicated measurement device. No signature of a theoretically predicted new interaction was found, and we set a new limit on the product of the scalar and the pseudoscalar couplings g s g p λ 2 < 8.3 × 10 − 28 m 2 (95% C.L.) in a range of 5  µ m < λ < 25  mm for the monopole–dipole interaction. This new result confirms and improves our previous limit by a factor of 2.7 and provides the current tightest limit obtained with free neutrons.

We report on a search for ultralow-mass axionlike dark matter by analyzing the ratio of the spin-precession frequencies of stored ultracold neutrons and Hg199 atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 10−24≤ma≤10−17eV . Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40.

High-precision searches for an electric dipole moment of the neutron (nEDM) require stable and uniform magnetic field environments. We present the recent achievements of degaussing and equilibrating the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute. We present the final degaussing configuration that will be used for n2EDM after numerous studies. The optimized procedure results in a residual magnetic field that has been reduced by a factor of two. The ultra-low field is achieved with the full magnetic-field-coil system, and a large vacuum vessel installed, both in the MSR. In the inner volume of ∼ 1.4 m 3 , the field is now more uniform and below 300 pT. In addition, the procedure is faster and dissipates less heat into the magnetic environment, which in turn, reduces its thermal relaxation time from 12 h down to 1.5 h .

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 10 5 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 m 3 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 ± 50 μ T (homogeneous components) and ± 5 μ T/m (first-order gradients), suppressing them to a few μ T 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.

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 [Formula omitted] 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 m [Formula omitted] 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 [Formula omitted] (homogeneous components) and [Formula omitted] (first-order gradients), suppressing them to a few [Formula omitted] 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.

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.

OBJECTIVES: Animal inhalation studies and theoretical models suggest that the pattern of formation of benzene metabolites changes as exposure to benzene increases. To determine if this occurs in humans, benzene metabolites in urine samples collected as part of a cross sectional study of occupationally exposed workers in Shanghai, China were measured. METHODS: With organic vapour monitoring badges, 38 subjects were monitored during their full workshift for inhalation exposure to benzene. The benzene urinary metabolites phenol, catechol, hydroquinone, and muconic acid were measured with an isotope dilution gas chromatography mass spectroscopy assay and strongly correlated with concentrations of benzene air. For the subgroup of workers (n = 27) with urinary phenol > 50 ng/g creatinine (above which phenol is considered to be a specific indicator of exposure to benzene), concentrations of each of the four metabolites were calculated as a ratio of the sum of the concentrations of all four metabolites (total metabolites) and were compared in workers exposed to > 25 ppm v < or = 25 ppm. RESULTS: The median, 8 hour time weighted average exposure to benzene was 25 ppm. Relative to the lower exposed workers, the ratio of phenol and catechol to total metabolites increased by 6.0% (p = 0.04) and 22.2% (p = 0.007), respectively, in the more highly exposed workers. By contrast, the ratio of hydroquinone and muconic acid to total metabolites decreased by 18.8% (p = 0.04) and 26.7% (p = 0.006), respectively. Similar patterns were found when metabolite ratios were analysed as a function of internal benzene dose (defined as total urinary benzene metabolites), although catechol showed a more complex, quadratic relation with increasing dose. CONCLUSIONS: These results, which are consistent with previous animal studies, show that the relative production of benzene metabolites is a function of exposure level. If the toxic benzene metabolites are assumed to be derived from hydroquinone, ring opened products, or both, these results suggests that the risk for adverse health outcomes due to exposure to benzene may have a supralinear relation with external dose, and that linear extrapolation of the toxic effects of benzene in highly exposed workers to lower levels of exposure may underestimate risk.

Little is known about pesticide exposure among farmworkers, and even less is known about the exposure associated with performing specific farm tasks. Using a random sample of 213 farmworkers in 24 communities and labor camps in eastern Washington State, we examined the association between occupational task and organophosphate (OP) pesticide residues in dust and OP metabolite concentrations in urine samples of adult farmworkers and their children. The data are from a larger study that sought to test a culturally appropriate intervention to break the take-home pathway of pesticide exposure. Commonly reported farm tasks were harvesting or picking (79.2%), thinning (64.2%), loading plants or produce (42.2%), planting or transplanting (37.6%), and pruning (37.2%). Mixing, loading, or applying pesticide formulations was reported by 20% of our sample. Workers who thinned were more likely than those who did not to have detectable levels of azinphos-methyl in their house dust (92.1% vs. 72.7%; p = 0.001) and vehicle dust (92.6% vs. 76.5%; p = 0.002). Thinning was associated with higher urinary pesticide metabolite concentrations in children (91.9% detectable vs. 81.3%; p = 0.02) but not in adults. Contrary to expectation, workers who reported mixing, loading, or applying pesticide formulations had lower detectable levels of pesticide residues in their house or vehicle dust, compared with those who did not perform these job tasks, though the differences were not significant. Future research should evaluate workplace protective practices of fieldworkers and the adequacy of reentry intervals for pesticides used during thinning.

Congener-specific PCB analysis allows use of toxic equivalency (TEQ) TCDD-based risk assessment approaches when analytical methods are sufficiently sensitive. Many efforts to analyze fish samples for PCB congeners report the majority of samples as non-detects; these data are of little use for human health risk assessment if the limits of analytical detection exceed levels of potential health concern. However, increasing analytical sensitivity is costly and technically difficult. An approach to assess analytical sensitivity needs for risk assessment by defining toxicological endpoints of concern and acceptable risk levels is presented. This framework was applied to assessment of potential PCB TEQ cancer risks to the general United States population and tribal consumers of Columbia River fish, but may be easily adjusted for other situations. A probabilistic model was used to calculate the necessary analytical sensitivity for PCB TEQ cancer risk assessment using the Environmental Protection Agency's new draft cancer risk slope factor for TCDD and fish consumption data. Desired levels of analytical sensitivity were estimated for the congener expected to contribute the most to PCB TEQ, PCB 126, and compared to limits of detection for various analytical methods. The financial and health value of methods with different levels of analytical sensitivity were compared using a value of information approach, which includes analytical cost and cost of potential health outcomes, and a proposed risk assessment utility approach which considers the relative health protectiveness of analytical options non-monetarily. Sensitivity analyses indicate that average consumption rate, cancer risk slope factor choice, and knowledge of existing PCB contamination are important considerations for planning PCB congener analysis.

This study was conducted to determine the biological effects of inhaled ^{238}{\\rm PuO}{}_{2}$ over the life spans of 144 beagle dogs. The dogs inhaled one of two sizes of monodisperse aerosols of ^{238}{\\rm PuO}{}_{2}$ to achieve graded levels of initial lung burden (ILB). The aerosols also contained ^{169}{\\rm Yb}$ to provide a γ-ray-emitting label for the ^{238}{\\rm Pu}$ inhaled by each dog. Excreta were collected periodically over each dog's life span to estimate plutonium excretion; at death, the tissues were analyzed radiochemically for plutonium activity. The tissue content and the amount of plutonium excreted were used to estimate the ILB. These data for each dog were used in a dosimetry model to estimate tissue doses. The lung, skeleton and liver received the highest α-particle doses, ranging from 0.16-68 Gy for the lung, 0.08-8.7 Gy for the skeleton and 0.18-19 Gy for the liver. At death, all dogs were necropsied, and all organs and lesions were sampled and examined by histopathology. Findings of non-neoplastic changes included neutropenia and lymphopenia that developed in a dose-related fashion soon after inhalation exposure. These effects persisted for up to 5 years in some animals, but no other health effects could be related to the blood changes observed. Radiation pneumonitis was observed among the dogs with the highest ILBs. Deaths from radiation pneumonitis occurred from 1.5 to 5.4 years after exposure. Tumors of the lung, skeleton and liver occurred beginning at about 3 years after exposure. Bone tumors found in 93 dogs were the most common cause of death. Lung tumors found in 46 dogs were the second most common cause of death. Liver tumors, which were found in 20 dogs but were the cause of death in only 2 dogs, occurred later than tumors in bone and lung. Tumors in these three organs often occurred in the same animal and were competing causes of death. These findings in dogs suggest that similar dose-related biological effects could be expected in humans accidentally exposed to ^{238}{\\rm PuO}{}_{2}$.