Experimental Search for Neutron to Mirror Neutron Oscillations as an Explanation of the Neutron Lifetime Anomaly.

An unexplained >4σ discrepancy persists between "beam" and "bottle" measurements of the neutron lifetime. A new model proposed that conversions of neutrons n into mirror neutrons n^{'}, part of a dark mirror sector, can increase the apparent neutron lifetime by 1% via a small mass splitting Δm between n and n^{'} inside the 4.6 T magnetic field of the National Institute of Standards and Technology Beam Lifetime experiment. A search for neutron conversions in a 6.6 T magnetic field was performed at the Spallation Neutron Source which excludes this explanation for the neutron lifetime discrepancy.

Osteopenia is associated with wasting in pancreatic adenocarcinoma and predicts survival after surgery.

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest of all common malignancies. Treatment is difficult and often complicated by the presence of cachexia. The clinical portrait of cachexia contributes to the poor prognosis experienced by PDAC patients and worsens therapeutic outcomes. We propose that low bone mineral density is a component of cachexia, which we explore herein through a retrospective review of all patients at our facility that underwent surgery for PDAC between 2011 and 2018 and compared to sex-, age- and comorbidity-matched control individuals. Data were abstracted from the medical record and pre-operative computed tomography scans. Muscle mass and quality were measured at the L3 level and bone mineral density was measured as the radiation attenuation of the lumbar vertebral bodies. Patients with PDAC displayed typical signs of cachexia such as weight loss and radiologically appreciable deterioration of skeletal muscle. Critically, PDAC patients had significantly lower bone mineral density than controls, with 61.2% of PDAC patients categorized as osteopenic compared to 36.8% of controls. PDAC patients classified as osteopenic had significantly reduced survival (1.01 years) compared to patients without osteopenia (2.77 years). The presence of osteopenia was the strongest clinical predictor of 1- and 2-year disease-specific mortality, increasing the risk of death by 107% and 80%, respectively. Osteopenia serves as a test of 2-year mortality with sensitivity of 76% and specificity of 58%. These data therefore identify impaired bone mineral density as a key component of cachexia and predictor of postoperative survival in patients with PDAC. The mechanisms that lead to bone wasting in tumor-bearing hosts deserve further study.

The Florida Pancreas Collaborative Next-Generation Biobank: Infrastructure to Reduce Disparities and Improve Survival for a Diverse Cohort of Patients with Pancreatic Cancer.

Background: Well-annotated, high-quality biorepositories provide a valuable platform to support translational research. However, most biorepositories have poor representation of minority groups, limiting the ability to address health disparities. Methods: We describe the establishment of the Florida Pancreas Collaborative (FPC), the first state-wide prospective cohort study and biorepository designed to address the higher burden of pancreatic cancer (PaCa) in African Americans (AA) compared to Non-Hispanic Whites (NHW) and Hispanic/Latinx (H/L). We provide an overview of stakeholders; study eligibility and design; recruitment strategies; standard operating procedures to collect, process, store, and transfer biospecimens, medical images, and data; our cloud-based data management platform; and progress regarding recruitment and biobanking. Results: The FPC consists of multidisciplinary teams from fifteen Florida medical institutions. From March 2019 through August 2020, 350 patients were assessed for eligibility, 323 met inclusion/exclusion criteria, and 305 (94%) enrolled, including 228 NHW, 30 AA, and 47 H/L, with 94%, 100%, and 94% participation rates, respectively. A high percentage of participants have donated blood (87%), pancreatic tumor tissue (41%), computed tomography scans (76%), and questionnaires (62%). Conclusions: This biorepository addresses a critical gap in PaCa research and has potential to advance translational studies intended to minimize disparities and reduce PaCa-related morbidity and mortality.

First Precision Measurement of the Parity Violating Asymmetry in Cold Neutron Capture on

We report the first precision measurement of the parity-violating asymmetry in the direction of proton momentum with respect to the neutron spin, in the reaction ^{3}He(n,p)^{3}H, using the capture of polarized cold neutrons in an unpolarized active ^{3}He target. The asymmetry is a result of the weak interaction between nucleons, which remains one of the least well-understood aspects of electroweak theory. The measurement provides an important benchmark for modern effective field theory and potential model calculations. Measurements like this are necessary to determine the spin-isospin structure of the hadronic weak interaction. Our asymmetry result is A_{PV}=[1.55±0.97(stat)±0.24(sys)]×10^{-8}, which has the smallest uncertainty of any hadronic parity-violating asymmetry measurement so far.

A sample holder for simultaneous Raman and neutron vibrational spectroscopy.

We have built a sample holder (called a center stick or sample stick) for performing simultaneous Raman and neutron vibrational spectroscopy on samples of material at the VISION neutron vibrational spectrometer of the Spallation Neutron Source at Oak Ridge National Laboratory. This equipment holds material samples in the neutron beam within the cryogenic environment of the VISION spectrometer, allowing for samples to be studied at temperatures as low as 5 K. It also provides the capability for gas to be loaded to or evacuated from the sample while it is loaded at VISION. The optical components for directing and filtering light are located within the cryogenic volume, in physical proximity to the sample. We describe the construction of this sample holder and discuss our first measurements of simultaneous Raman and neutron vibrational spectra. The samples that we report on were of 4-nitrophenol at a temperature of 20 K and of cryogenic hydrogen of a number of different orthohydrogen fractions.

First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen.

We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.0±1.4(stat)±0.2(syst)]×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=[2.6±1.2(stat)±0.2(syst)]×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=[-7.4±3.5(stat)±0.5(syst)]×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.

Observation of coherent elastic neutrino-nucleus scattering.

The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7σ confidence level, using a low-background, 14.6-kilogram CsI[Na] scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the standard model for this process, were observed in high signal-to-background conditions. Improved constraints on nonstandard neutrino interactions with quarks are derived from this initial data set.

Immunoglobulin G subclass levels and antibody responses to the 2009 influenza A (H1N1) monovalent vaccine among human immunodeficiency virus (HIV)-infected and HIV-uninfected adults.

Immunoglobulin (Ig)G levels are important for antibody vaccine responses and IgG subclass deficiencies have been associated with severe 2009 influenza A (H1N1) infections. Studies have demonstrated variations in immune responses to the H1N1 vaccine, but the aetiology of this is unknown. We determined the associations between pre-vaccination overall and influenza-specific IgG subclass levels and 2009 H1N1-specific antibody responses post-vaccination (robust versus poor at day 28) stratified by human immunodeficiency virus (HIV) status. Logistic regression models were utilized to evaluate whether pre-vaccination IgG subclass levels were associated with the antibody response generated post-vaccination. We evaluated 48 participants as part of a clinical study who were stratified by robust versus poor post-vaccination immune responses. Participants had a median age of 35 years; 92% were male and 44% were Caucasian. HIV-infected adults had a median CD4 count of 669 cells/mm(3) , and 79% were receiving highly active anti-retroviral therapy. HIV-infected participants were more likely to have IgG2 deficiency (<240 mg/dl) than HIV-uninfected individuals (62% versus 4%, P < 0·001). No association of pre-vaccination IgG subclass levels (total or influenza-specific) and the antibody response generated by HIN1 vaccination in either group was found. In summary, pre-vaccination IgG subclass levels did not correlate with the ability to develop robust antibody responses to the 2009 influenza A (H1N1) monovalent vaccine. IgG2 deficiencies were common among HIV-infected individuals but did not correlate with poor influenza vaccine responses. Further investigations into the aetiology of disparate vaccine responses are needed.

The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance.

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Ethical considerations in the collection of genetic data from critically ill patients: what do published studies reveal about potential directions for empirical ethics research?

Critical illness trials involving genetic data collection are increasingly commonplace and pose challenges not encountered in less acute settings, related in part to the precipitous, severe and incapacitating nature of the diseases involved. We performed a systematic literature review to understand the nature of such studies conducted to date, and to consider, from an ethical perspective, potential barriers to future investigations. We identified 79 trials enrolling 24 499 subjects. Median (interquartile range) number of participants per study was 263 (116.75-430.75). Of these individuals, 16 269 (66.4%) were Caucasian, 1327 (5.4%) were African American, 1707 (7.0%) were Asian Pacific Islanders and 139 (0.6%) were Latino. For 5020 participants (20.5%), ethnicity was not reported. Forty-eight studies (60.8%) recruited subjects from single centers and all studies examined a relatively small number of genetic markers. Technological advances have rendered it feasible to conduct clinical studies using high-density genome-wide scanning. It will be necessary for future critical illness trials using these approaches to be of greater scope and complexity than those so far reported. Empirical research into issues related to greater ethnic inclusivity, accuracy of substituted judgment and specimen stewardship may be essential for enabling the conduct of such trials.

The Spallation Neutron Source (SNS) project: a fertile ground for radiation protection and shielding challenges.

The Spallation Neutron Source facility presently under construction in the USA consists of a front end, a linac, an accumulator ring, a target station and a neutron instrument hall, producing pulsed neutron beams driven by a proton beam of 1 GeV energy and 1.4 MW power with a repetition rate of 60 Hz. The layout of the facility and the radiation protection and shielding concept of the facility is laid out in numerous examples in a walk from the proton beam generation to the neutron utilisation.

Target station shielding issues at the spallation neutron source.

Recent spallation neutron source shielding activities in support of the neutron beam shutters and the hot cell walls are presented. Existing neutron beam shutters can be replaced with concrete at low power or with concrete and steel at approximately 500 kW of beam power. Potential voids in the hot cell walls are analysed to determine the impact on dose rates as a function of void size. A change in the type of shielding work is noted as the project moved from the early design stages as a 'green field' site to the current stage as a construction project nearing completion, where issues to be addressed are approaching retrofit-type analyses.

HIV risk behavior and HIV testing: a comparison of rates and associated factors among homeless and runaway adolescents in two cities.

This study examined differences in self-reported rates and predictors of HIV testing between homeless and runaway youths in San Diego (N = 1,102) and Los Angeles (N = 1,167). Youths aged 13-23 were recruited from agency and street sites using a stratified probability sampling design. Interviewers administered a structured survey instrument lasting 20 minutes, which assessed youths' involvement in HIV risk-related sexual and drug-use behaviors, contact with outreach workers, and other variables. Significantly more Los Angeles youths (78%) reported testing than did San Diego youths (52%; p < .001). Multivariable analyses controlling for risk behaviors, knowing someone with HIV, and contact with outreach workers indicated that the higher rates of these factors in Los Angeles did not account for the difference in testing rates between the cities. Youths in Los Angeles were still 1.85 times as likely to be tested as San Diego youths (p < .001), possibly a result of differing normative behavior and accessibility of testing services.

Heterogeneity of the mechanical properties of demineralized bone.

Knowledge of the mechanical properties of the collagenous component of bone is required for composite modeling of bone tissue and for understanding the age- and disease-related reductions in the ductility and strength of bone. The overall goal of this study was to investigate the heterogeneity of the mechanical properties of demineralized bone which remains unexplained and may be due to differences in the collagen structure or organization or in experimental protocols. Uniaxial tension tests were conducted to measure the elastic and failure properties of demineralized human femoral (n = 10) and tibial (n = 13) and bovine humeral (n = 8) and tibial (n = 8) cortical bone. Elastic modulus differed between groups (p = 0.02), varying from 275 +/- 94 MPa (mean +/- SD) to 450 + 50 MPa. Similarly, ultimate stress varied across groups from 15 + 4.2 to 26 + 4.7 MPa (p = 0.03). No significant differences in strain-to-failure were observed between any groups in this study (pooled mean of 8.4 +/- 1.6%; p = 0.42). However, Bowman et al. (1996) reported an average ultimate strain of 12.3 +/- 0.5% for demineralized bovine humeral bone, nearly 40% higher than our value. Taken together, it follows that all the monotonic mechanical properties of demineralized bone can display substantial heterogeneity. Future studies directed at explaining such differences may therefore provide insight into aging and disease of bone tissue.

Service utilization among homeless and runaway youth in Los Angeles, California: rates and reasons.

PURPOSE: To describe the service utilization patterns of homeless and runaway youth in a "service-rich" area of Los Angeles, California; identify demographic and other correlates of utilization; and contextualize the findings with qualitative data. METHOD: During Phase 1 of this study, survey data were collected from an ethnically diverse sample of 296 youth aged 13-23 years, recruited from both service and natural "hang-out" sites using systematic sampling methods. During Phase 2, qualitative data were collected from 46 youth of varying ethnicities and lengths of time homeless. RESULTS: Drop-in centers and shelters were the most commonly used services (reported by 78% and 40%, respectively). Other services were used less frequently [e.g., medical services (28%), substance abuse treatment (10%) and mental health services (9%)]. Utilization rates differed by ethnicity, length of time in Los Angeles, and city of first homeless episode (Los Angeles versus all others). Shelter use was strongly associated with use of all other services. Despite youths' generally positive reactions to services, barriers were described including rules perceived to be restrictive, and concerns youth had about confidentiality and mandated reporting. Youth suggested improvements including more targeted services, more long-term services, revised age restrictions, and more and/or better job training and transitional services to get them off the streets. CONCLUSIONS: Because shelters and drop-in centers act as gateways to other services and offer intervention potential for these hard-to-reach youth, it is vital that we understand the perceived barriers to service utilization.

Service utilization among homeless and runaway youth in Los Angeles, California: rates and reasons.

PURPOSE: To describe the service utilization patterns of homeless and runaway youth in a "service-rich" area (Los Angeles, California); identify demographic and other correlates of utilization; and contextualize the findings with qualitative data. METHOD: During Phase 1 of this study, survey data were collected from an ethnically diverse sample of 296 youth aged 13-23 years, recruited from both service and natural "hang-out" sites using systematic sampling methods. During Phase 2, qualitative data were collected from 46 youth of varying ethnicities and lengths of time homeless. RESULTS: Drop-in centers and shelters were the most commonly used services (reported by 78% and 40%, respectively). Other services were used less frequently [e.g., medical services (28%) and substance abuse treatment (10%) and mental health services (9%)]. Utilization rates differed by ethnicity, length of time in Los Angeles, and city of first homeless episode (Los Angeles vs. all others). Shelter use was strongly associated with use of all other services. Despite youths' generally positive reactions to services, barriers were described including restrictive rules, confidentiality and reporting problems, and negative interactions with staff members. Youth suggested improvements including more targeted services, more long-term services, revised age restrictions, and more and/or better job training and transitional services to get them off the streets. CONCLUSIONS: Because shelters and drop-in centers act as gateways to other services and offer intervention potential for these hard-to-reach youth, it is vital that barriers to use of these services are eliminated.

"Substance abuse" disorders among runaway and homeless youth.

This study used systematic sampling methods to recruit a sample of 432 homeless youth from both service and natural "hang-out" sampling sites. According to DSM-III criteria, the majority of respondents were classified as having an alcohol and/or illicit "drug abuse" disorder (71%). The results from multivariate logistic regression analyses indicate that cumulative length of time homeless is positively associated with risk for an "abuse" disorder. The implications of these findings and recommendations for service interventions are discussed.

Quantitation and localization of cartilage degeneration following the induction of osteoarthritis in the rabbit knee.

OBJECTIVE: To develop and apply a new video imaging technique to quantify and localize Indian ink staining of cartilage of the rabbit femorotibial joint after the induction of osteoarthritis by unilateral transection of the anterior cruciate ligament (ACLT). METHODS: Nine weeks after surgery, femora and tibiae from 11 ACLT and contralateral control knees were harvested and positioned to obtain calibrated gray-scale images of the ink-painted articular cartilage surfaces that are opposed with the knee in 90 degrees flexion. Images were processed so that areas of normal cartilage gave a relatively high reflectance score, whereas ink-stained fibrillated cartilage and exposed bone gave low scores. RESULTS: Comparison of the medial and lateral femoral condyles and tibial plateaus (MFC, LFC, MTP, LTP) of control and ACLT knees showed that the area of the MTP not covered by the meniscus had a significantly lower reflectance score (P < 0.001) than other areas. ACLT led to an 11% decrease (P < 0.001) in the overall reflectance score. The reflectance score decreased as a traditional morphological grading of degeneration increased. ACLT-induced degeneration had a predilection for the posteromedial aspects of the joint, and to a lesser extent, the anterolateral aspects. In the tibial plateaus, ACLT caused significant degeneration in the covered, but not the uncovered, areas. Image scores of opposing cartilage surfaces (i.e., MFC vs MTP and LFC vs LTP) were significantly (R = 0.56-0.70, P < 0.001) correlated in ACLT and control knees. DISCUSSION: Identification and characterization of cartilage areas prone to degeneration may be particularly useful for further analysis of biochemical and biomechanical mechanisms in osteoarthritis, as well as the efficacy of therapeutic interventions.