Radiocarbon (14C) is an isotopic tracer used to address a wide range of scientific research questions. However, contamination by elevated levels of 14C is deleterious to natural-level laboratory workspaces and accelerator mass spectrometer facilities designed to precisely measure small amounts of 14C. The risk of contaminating materials and facilities intended for natural-level 14C with elevated-level 14C-labeled materials has dictated near complete separation of research groups practicing profoundly different measurements. Such separation can hinder transdisciplinary research initiatives, especially in remote and isolated field locations where both natural-level and elevated-level radiocarbon applications may be useful. This paper outlines the successful collaboration between researchers making natural-level 14C measurements and researchers using 14C-labeled materials during a subglacial drilling project in West Antarctica (SALSA 2018–2019). Our strict operating protocol allowed us to successfully carry out 14C labeling experiments within close quarters at our remote field camp without contaminating samples of sediment and water intended for natural level 14C measurements. Here we present our collaborative protocol for maintaining natural level 14C cleanliness as a framework for future transdisciplinary radiocarbon collaborations.

The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.

Cats represent a potential source of Coxiella burnetii, the aetiological agent of Q fever in humans. The prevalence and risk factors of C. burnetii infection in farm, pet and feral cats were studied in Quebec, Canada, using a cross-sectional study. Serum samples were tested using a specific enzyme-linked immunosorbent assay (ELISA) for the presence of antibodies against C. burnetii, whereas rectal swabs were assayed using real-time quantitative polymerase chain reaction (qPCR) for the molecular detection of the bacteria. Potential risk factors for farm cats were investigated using clinical examinations, questionnaires and results from a concurrent study on C. burnetii farm status. A total of 184 cats were tested: 59 from ruminant farms, 73 pets and 52 feral cats. Among farm cats, 2/59 (3.4%) were ELISA-positive, 3/59 (5.1%) were ELISA-doubtful and 1/59 (1.7%) was qPCR-positive. All pets and feral cats were negative to C. burnetii ELISA and qPCR. Farm cat positivity was associated with a positive C. burnetii status on the ruminant farm (prevalence ratio = 7.6, P = 0.03). Our results suggest that although pet and feral cats do not seem to pose a great C. burnetii risk to public health, more active care should be taken when in contact with cats from ruminant farms.

Introduction: Suicidal thoughts and self-harm are disproportionately prevalent among older adults but are frequently overlooked by emergency physicians. Objective: This study aims to explore the characteristics of older adults visiting the ED for suicidal thoughts or voluntary intoxications. Methods: All older adults (□ 65 years old) who visited one of the five CHU de Quebec’ EDs in 2016 were eligible. The medical charts of patients who reported suicidal thoughts or intoxication in triage or received a relevant discharge diagnosis were reviewed. Involuntary intoxications were excluded. Descriptive statistics were used to present the results. Results: Results: A total of 478 ED visits were identified, of which 332 ED visits (n= 279 patients) were included. The mean age of the ED cohort was 72.6 (standard deviation 6.8) years old and 41.6% were female. Mood disorders (41.2%) and alcoholism (40.5%) were common. Most included patients had a diagnosis of voluntary intoxication (73.2%), including two suicides (0.6%). Following 109 ED visits (30.0%), patients were referred for a mental health assessment. Half of all ED visits resulted in a discharge by the emergency physician (50.0%), while 27.4% were admitted for in-patient care. In the subsequent year (2017), 38.4% returned to the ED for suicidal ideations or self-harm of which 7.9% attended the ED □ 5 times. Conclusion: ED visits for suicidal thoughts and voluntary intoxication in older adults are more common among men with known mood disorders or alcoholism. Referral for a mental health assessment is inconsistent. ED-initiated interventions designed for this population are needed.

Replicate radiocarbon (14C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0–1.5 and mass range 6 μg–2 mg carbon, are used to determine both the mass and radiocarbon content of the blank carbon introduced during sample processing and measurement in our laboratory. These data are used to model, separately for organic and inorganic samples, the blank contribution and subsequently “blank correct” measured unknowns in the mass range 25–100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented.

This study investigates the interaction of picosecond laser pulses with sapphire and brass in air using scanning electron microscopy. A picosecond laser system operating at a wavelength of 785 nm, pulse width of 110 ps, and variable repetition rate (1–1000 Hz) was used in this study. The pulse width applied in this work was not widely investigated as it lies in the gap between ultrashort (femtosecond) and long (nanosecond) pulse width lasers. Different surface morphologies were identified using secondary electron and backscattered electron imaging of the ablated material. Thermal ablation effects were more dominant in brass than in sapphire. Exfoliation and fractures of sapphire were observed at high laser fluence. Compared with brass, multiple laser pulses were necessary to initiate ablation in sapphire due to its poor absorption to the incident laser wavelength. Ablation rate of sapphire was lower than that of brass due to the dissipation of a portion of the laser energy due to heating and fracturing of the surface.

This paper highlights new research on the biomineralization of otoliths and uses a mineralogical approach to understand mechanisms of crystal growth and metal incorporation into otoliths. Petrographic observations of the nucleation of otolith growth in the core for several fish species reveals that sagittal otoliths appear to nucleate around a few or many nucleation sites (primordia) and that these sites vary in size (ranging in diameter from 1 to 20 μm), depending on the species. Spectroscopic data show a large Mn-enrichment in the primordia within the core but the reasons for this enrichment are still unclear (e.g. organic matter or possibly another material other than CaCO3). This study also provides the first multi trace-element data for endolymph fluid and the growing otolith; we found large enrichments (Ca and Sr) and depletions (Na, K, Zn and Rb) of elements in the otolith relative to the endolymph. The last part of this paper examines the effect of crystal structure on the microchemistry ofotoliths. Our investigation helps understand how the chemical characteristics of the metal ions (i.e. ionic radii) and the crystalline structure interact to cause differential trace-metal uptake between the CaCO3 polymorphs, aragonite and vaterite.

We estimate the blank carbon mass over the course of a typical Ramped PyrOx (RPO) analysis (150–1000°C; 5°C×min–1) to be (3.7±0.6) μg C with an Fm value of 0.555±0.042 and a δ13C value of (–29.0±0.1) ‰ VPDB. Additionally, we provide equations for RPO Fm and δ13C blank corrections, including associated error propagation. By comparing RPO mass-weighted mean and independently measured bulk δ13C values for a compilation of environmental samples and standard reference materials (SRMs), we observe a small yet consistent 13C depletion within the RPO instrument (mean–bulk: μ=–0.8‰; ±1σ=0.9‰; n=66). In contrast, because they are fractionation-corrected by definition, mass-weighted mean Fm values accurately match bulk measurements (mean–bulk: μ=0.005; ±1σ=0.014; n=36). Lastly, we show there exists no significant intra-sample δ13C variability across carbonate SRM peaks, indicating minimal mass-dependent kinetic isotope fractionation during RPO analysis. These data are best explained by a difference in activation energy between 13C- and 12C-containing compounds (13–12∆E) of 0.3–1.8 J×mol–1, indicating that blank and mass-balance corrected RPO δ13C values accurately retain carbon source isotope signals to within 1–2‰.

Triaxial experiments, at confining pressures in the range 0–13.79 MPa, have been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 × 10−5 to 5 × 10−5s−1 and at four temperatures in the range of −1° to −16°C. Depending on test conditions, the ice failed by one of four possible modes ductile deformation, due to extensive non-interacting microcracks; fracture along a shear plane followed by continuous or stick-slip sliding; large-scale brittle fracture; and combined ductile and shear-plane fracture and slip The strength Increased with decreasing temperature, increasing strain rate up to 5 × 10−3s−1 and increasing confining pressure at the lower temperatures. The strength at 5 × 10−2s−1 was lower than at 5 × 10−3s−1 probably because extension and interaction of microcracks is enhanced at the higher rate. For higher confining pressures at −1°C, the strength decreased due to freezing-point depression. The ice from the different sources exhibited different mean uniaxial compressive strengths. The mean number of air bubbles per unit volume correlated with the mean uniaxial compressive strengths and this may be the dominant factor distinguishing the strengths of the various ice types.

A series of 40 impact tests was conducted an large right-circular cylinders (68.5 cm diameter and 25.7 cm thickness) of iceberg ice collected from an iceberg in Labrador. Temperature profiles were also obtained for the iceberg and the profiles exhibited differences associated with the probe location. Temperatures as low as –15°C were measured at penetration depths of about 8 m. The impact specimens were confined at the perimeter and base by a rigid metallic ring and plate. A spherically terminated impactor, with center-mounted pressure transducer, was dropped on to the flat top surface of specimens from various heights and with various added masses. Impact velocity varied from 1.8 to 3.9 m s−1; impactor mass varied from 155 to 510 kg and the ice-specimen temperature varied from –0.5° to –14.5°C. Peak center pressures averaged from about 25 MPa at the highest temperature to about 41 MPa at the lowest temperature, with the highest recorded pressure being 50 M Pa. Crater volume increased with increasing impact energy, as expected; however, the specific energy of the ejected material was found to decrease as the energy of impact and crater volume increased. A mechanism for this observed behaviour is proposed.

Indentation experiments have been performed on fresh-water ice at -9°C using an apparatus which permitted visual observation of the contact zone at the ice/indentor interface by viewing through the specimens. Analysis of the video records and test data indicated that at least 50% of the energy dissipated during the process of indentation was consumed by pressure melting and heat generation through the rapid viscous flow of the liquid. The thickness of the liquid layer was estimated to be 16/μm and the contact pressure in the melting zone was at least 90 MPa. Video records of small-scale impact tests on ice indicated that the same process of pressure melting and extrusion was taking place.

Numerous natural processes are contingent on microorganisms’ ability to swim through fluids with non-Newtonian rheology. Here, we use the model organism Caenorhabditis elegans and tracking methods to experimentally investigate the dynamics of undulatory swimming in shear-thinning fluids. Theory and simulation have proposed that the cost of swimming, or mechanical power, should be lower in a shear-thinning fluid compared to a Newtonian fluid of the same zero-shear viscosity. We aim to provide an experimental investigation into the cost of swimming in a shear-thinning fluid from (i) an estimate of the mechanical power of the swimmer and (ii) the viscous dissipation rate of the flow field, which should yield equivalent results for a self-propelled low Reynolds number swimmer. We find the cost of swimming in shear-thinning fluids is less than or equal to the cost of swimming in Newtonian fluids of the same zero-shear viscosity; furthermore, the cost of swimming in shear-thinning fluids scales with a fluid’s effective viscosity and can be predicted using fluid rheology and simple swimming kinematics. Our results agree reasonably well with previous theoretical predictions and provide a framework for understanding the cost of swimming in generalized Newtonian fluids.

The swimming behaviour of micro-organisms can be strongly influenced by the rheology of their fluid environment. In this article, we experimentally investigate the effects of shear-thinning (ST) viscosity on the swimming behaviour of an undulatory swimmer, the nematode Caenorhabditis elegans. Tracking methods are used to measure the swimmer’s kinematic data (including propulsion speed) and velocity fields. We find that ST viscosity modifies the velocity fields produced by the swimming nematode but does not modify the nematode’s speed and beating kinematics. Velocimetry data show significant enhancement in local vorticity and circulation and an increase in fluid velocity near the nematode’s tail. These findings are compared with recent theoretical and numerical results.

The Dominion Radio Astrophysical Observatory (DRAO) is carrying out a survey as part of an international collaboration to image the northe, at a common resolution, in emission from all major constituents of the interstellar medium; the neutral atomic gas, the molecular gas, the ionised gas, dust and relativistic plasma. For many of these constituents the angular resolution of the images (1 arcmin) will be more than a factor of 10 better than any previous studies. The aim is to produce a publicly-available database of high resolution, high-dynamic range images of the Galaxy for multi-phase studies of the physical states and processes in the interstellar medium. We will sketch the main scientific motivations as well as describe some preliminary results from the Canadian Galactic Plane Survey/Releve Canadien du Plan Galactique (CGPS/RCPG).

Disruptive boys in kindergarten, selected from teacher ratings in a large study, were each followed up for four successive years. There was considerable continuity of the boys' fighting, despite a declining prevalence in fighting over the years. High oppositional behavior in one year did not consistently predict fighting in the next year. A history of fighting was associated with being held back in grade. Boys were assigned to fighting evolution status on the basis of their fighting scores over the four years: stable high fighters, desisting high fighters, and variable/initiating high fighters. Stable high fighters, unlike desisting high fighters, scored high on nonaggressive antisocial acts at the end of the four years. For some boys, cessation of fighting was associated with later nonaggressive antisocial behavior. Fighting evolution status was examined further in relationship to anxiety, hyperactivity/inattentiveness, and prosocial behaviors. At age 9, stable high fighters, and to a lesser extent variable/initiating high fighters, were more likely to come from single parent families than desisting high fighters. The results are discussed in the context of the development of conduct problems in children.