Research in cosmic and gamma ray astrophysics

Discussed here is research in cosmic ray and gamma ray astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology. The primary activities discussed involve the development of new instrumentation and techniques for future space flight. In many cases these instrumentation developments were tested in balloon flight instruments designed to conduct new investigations in cosmic ray and gamma ray astrophysics. The results of these investigations are briefly summarized. Specific topics include a quantitative investigation of the solar modulation of cosmic ray protons and helium nuclei, a study of cosmic ray positron and electron spectra in interplanetary and interstellar space, the solar modulation of cosmic rays, an investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances, and a balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon, and nitrogen

Infrared chemical imaging through nondegenerate two-photon absorption in silicon-based cameras

Chemical imaging based on mid-infrared (MIR) spectroscopic contrast is an important technique with a myriad of applications, including biomedical imaging and environmental monitoring. Current MIR cameras, however, lack in performance and are much less affordable compared to mature Si-based devices, which operate in the visible and near-infrared. Here we demonstrate fast MIR chemical imaging through non-degenerate two-photon absorption (NTA) in a standard Si-based charge-coupled device (CCD). We show that wide-field MIR images can be obtained at 100 ms exposure times using picosecond pulse energies of only a few fJ per pixel through NTA directly on the CCD chip. Because this on-chip approach does not rely on phase-matching, it is alignment-free and does not necessitate complex post-processing of the images. We emphasize the utility of this technique through chemically selective MIR imaging of polymers and biological samples, including MIR videos of moving targets, physical processes and live nematodes

Discrete mode laser diodes with ultra narrow linewidth emission <3kHz

Ex-facet, free-running ultra-low linewidth (<3 kHz), single mode laser emission is demonstrated using low cost, regrowth-free ridge waveguide discrete mode Fabry-Perot laser diode chips

Low-level cadmium exposure and cardiovascular outcomes in elderly Australian women: A cohort study

Background Cadmium has been associated with increased risk of cardiovascular disease (CVD) in observational studies, however there has been a limited focus on this relationship in women. Objectives This study investigated the association of urinary cadmium (UCd) concentrations with CVD outcomes and all-cause mortality in elderly Western Australian (WA) women. Methods UCd excretion was measured at baseline in 1359 women, mean age 75.2 ± 2.7 years and 14.5 years of atherosclerotic vascular disease (ASVD) hospitalisations and deaths, including both the principle cause of death and all associated causes of death. Health outcome data were retrieved from the Western Australian Data Linkage System. Cox regression analysis was used to estimate hazard ratios of ASVD and all-cause mortality. UCd was ln-transformed and models were adjusted for demographic and CVD risk factors. Results Median (IQR) concentration of UCd was 0.18 (0.09–0.32) μg/L. In multivariable-adjusted analyses per ln unit (equivalent to ∼2.7 fold) increase in UCd, there was a 36% increase in the risk of death from heart failure and 17% increase in the risk of a heart failure event, respectively (HR = 1.36, 95% CI 1.11–1.67; HR = 1.17, 95% CI 1.01–1.35). When analyses were restricted to never smokers the relationship between UCd and death from heart failure remained (HR 1.29, 95% CI 1.01–1.63). Conclusions This study suggests that even at low levels of exposure cadmium may be associated with heart failure hospitalisations and deaths in older women, however given the dilute nature of these urine samples, the results must be interpreted with caution

The Zwicky Transient Facility: Surveys and Scheduler

We present a novel algorithm for scheduling the observations of time-domain imaging surveys. Our Integer Linear Programming approach optimizes an observing plan for an entire night by assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes. A subsequent optimization step minimizes slew times between each observation. Our optimization metric self-consistently weights contributions from time-varying airmass, seeing, and sky brightness to maximize the transient discovery rate. We describe the implementation of this algorithm on the surveys of the Zwicky Transient Facility and present its on-sky performance.Comment: Published in PASP Focus Issue on the Zwicky Transient Facility (https://dx.doi.org/10.1088/1538-3873/ab0c2a). 13 Pages, 11 Figure

Dietary nitrate intake is associated with muscle function in older women

Background In younger individuals, dietary nitrate supplementation has been shown to improve short‐term vascular and muscle function. The role of higher habitual nitrate intake as part of a typical diet on muscle function in ageing has not been investigated. A cross‐sectional study of relationships between dietary nitrate and measures of muscle function in older community‐dwelling Australian women (n = 1420, ≥70 years) was undertaken. Methods Participants completed a semi‐quantitative food frequency questionnaire assessing dietary intake over the previous year. Total nitrate from vegetables and non‐vegetable sources was calculated from a validated instrument that quantified the nitrate content of food recorded within the food frequency questionnaire. Handgrip strength and timed‐up‐and‐go (TUG) were assessed, representing muscle strength and physical function, respectively. Cut‐points for weak grip strength (kg) and slow TUG (\u3e10.2 s) were selected due to their association with adverse outcomes. Linear and logistic regressions were used to examine the relationship between total nitrate intake and muscle function measures. Results Mean ± standard deviation (SD) total nitrate intake was 79.5 ± 31.2 mg/day, of which 84.5% came from vegetables. Across the unadjusted tertiles of nitrate intake (P= 0.027) and faster TUG (per second, β −0.27, P = 0.001). The proportion of women with weak grip strength (kg) or slow TUG (\u3e10.2 s) was 61.0% and 36.9%, respectively. Each SD higher nitrate intake (31.2 mg/day) was associated with lower odds for weak grip strength (OR 0.84, 95% CI 0.74–0.95, P = 0.005) and slow TUG (OR 0.86, 95% CI 0.76–0.98, P = 0.021). Compared with women in the lowest tertile of nitrate intake, women in the highest nitrate intake tertile had lower odds for weak grip strength (OR 0.65, 95% CI 0.49–0.87, Ptrend=0.004) and slow TUG (OR 0.72, 95% CI 0.53–0.97, Ptrend = 0.044). Conclusions This investigation highlights potential benefits of nitrate‐rich diets on muscle strength and physical function in a large cohort of older women. Considering poor muscle strength and physical function is associated with a range of adverse health outcomes such as falling, fractures, cardiovascular disease, and mortality, increasing dietary nitrate, especially though vegetable consumption may be an effective way to limit age‐related declines in muscle function