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Polarimetric studies of pulsars at low radio frequencies provide important observational insights into the pulsar emission mechanism and beam models, and probe the properties of the magneto-ionic interstellar medium (ISM). Aperture arrays are the main form of next-generation low-frequency telescopes, including the Murchison Widefield Array (MWA). These require a distinctly different approach to data processing (e.g. calibration and beamforming) compared to traditional dish antennas. As the second paper of this series, we present a verification of the MWA’s pulsar polarimetry capability, using two bright southern pulsars, PSRs J0742–2822 and J1752–2806. Our observations simultaneously cover multiple frequencies (76–313 MHz) and were taken at multiple zenith angles (ZA) during a single night for each pulsar. We show that the MWA can be reliably calibrated for ZA ≲45° and frequencies ≲270 MHz. We present the polarimetric profiles for PSRs J0742–2822 and J1752–2806 at frequencies lower than 300 MHz for the first time, along with an analysis of the linear polarisation degree and pulse profile evolution with frequency. For PSR J0742–2822, the measured degree of linear polarisation shows a rapid decrease at low frequencies, in contrast with the generally expected trend, which can be attributed to depolarisation effects from small-scale, turbulent, magneto-ionic ISM components. This effect has not been widely explored for pulsars in general and will be further investigated in future work.
The evolution of glaciers and ice sheets depends on processes in the subglacial environment. Shear seismicity along the ice–bed interface provides a window into these processes. Such seismicity requires a rapid loss of strength that is typically ascribed to rate-weakening friction, i.e., decreasing friction with sliding or sliding rate. Many friction experiments have investigated glacial materials at the temperate conditions typical of fast flowing glacier beds. To our knowledge, however, these studies have all found rate-strengthening friction. Here, we investigate the possibility that rate-weakening rock-on-rock friction between sediments frozen to the bottom of the glacier and the underlying water-saturated sediments or bedrock may be responsible for subglacial shear seismicity along temperate glacier beds. We test this ‘entrainment-seismicity hypothesis’ using targeted laboratory experiments and simple models of glacier sliding, seismicity and sediment entrainment. These models suggest that sediment entrainment may be a necessary but not sufficient condition for the occurrence of basal shear seismicity. We propose that stagnation at the Whillans Ice Stream, West Antarctica may be caused by the growth of a frozen fringe of entrained sediment in the ice stream margins. Our results suggest that basal shear seismicity may indicate geomorphic activity.
Glacier sliding over small obstacles relies on melting on their upstream sides and refreezing downstream. Previous treatments have appealed to ‘pressure melting’ as the cause of the spatial variations in melting temperature that drive this regelation process. However, we show that typical liquid pressure variations across small obstacles are negligible and therefore variations in ice pressure closely approximate variations in effective stress. For a given change in effective stress, the equilibrium melting temperature changes by an order of magnitude more than when the pressure of ice and liquid both change by an equal amount. In consequence, the temperature gradients that drive heat flow across small obstacles are larger than previously recognized and the rate of regelation is faster. Under typical conditions, the transition wavelength at which ice deformation and regelation contribute equally is of m-scale, several times longer than previous predictions, which have been reported to underestimate field inferences.
Infections due to Campylobacter, Escherichia coli and Salmonella pose a significant health burden in Canada, resulting in major costs to the health care system and economic impacts due to lost productivity resulting from illness. Recent literature suggests that climate may play a role in the prevalence of these pathogens along the food chain. This study used integrated surveillance data to examine associations between weather variables, serving as a proxy for climate, in agricultural areas and Campylobacter, generic E. coli and Salmonella contamination on samples of beef, poultry and swine meat products in Canada. Various temperature metrics (average, maximum and variability) were correlated with Campylobacter prevalence along the food chain. The prevalence of E. coli and Salmonella was correlated with both precipitation and temperatures metrics; however, analysis for E. coli was limited to beef and swine meats at retail settings, because prevalence in other combinations approached 100%, which obviated further analysis. Campylobacter contamination in poultry and swine at abattoir and retail settings demonstrated a seasonal trend, with increased prevalence generally from June or July through November, compared to the baseline month of December. Based on these analyses, Campylobacter is the most likely foodborne bacteria studied whose occurrence in meat products is affected by climatic changes in Canada. An exploratory analysis of data at the provincial scale, using Ontario as an example, revealed similar directional relationships between climate and bacterial prevalence.
Studies were conducted to determine the tolerance of sweetpotato and Palmer amaranth control to a premix of flumioxazin and pyroxasulfone pretransplant (PREtr) followed by (fb) irrigation. Greenhouse studies were conducted in a factorial arrangement of four herbicide rates (flumioxazin/pyroxasulfone PREtr at 105/133 and 57/72 g ai ha–1, S-metolachlor PREtr 803 g ai ha–1, nontreated) by three irrigation timings [2, 5, and 14 d after transplanting (DAP)]. Field studies were conducted in a factorial arrangement of seven herbicide treatments (flumioxazin/pyroxasulfone PREtr at 40/51, 57/72, 63/80, and 105/133 g ha–1, 107 g ha–1 flumioxazin PREtr fb 803 g ha–1S-metolachlor 7 to 10 DAP, and season-long weedy and weed-free checks) by three 1.9-cm irrigation timings (0 to 2, 3 to 5, or 14 DAP). In greenhouse studies, flumioxazin/pyroxasulfone reduced sweetpotato vine length and shoot and storage root fresh biomass compared to the nontreated check and S-metolachlor. Irrigation timing had no influence on vine length and root fresh biomass. In field studies, Palmer amaranth control was≥91% season-long regardless of flumioxazin/pyroxasulfone rate or irrigation timing. At 38 DAP, sweetpotato injury was≤37 and≤9% at locations 1 and 2, respectively. Visual estimates of sweetpotato injury from flumioxazin/pyroxasulfone were greater when irrigation timing was delayed 3 to 5 or 14 DAP (22 and 20%, respectively) compared to 0 to 2 DAP (7%) at location 1 but similar at location 2. Irrigation timing did not influence no.1, jumbo, or marketable yields or root length-to-width ratio. With the exception of 105/133 g ha–1, all rates of flumioxazin/pyroxasulfone resulted in marketable sweetpotato yield and root length-to-width ratio similar to flumioxazin fb S-metolachlor or the weed-free checks. In conclusion, flumioxazin/pyroxasulfone PREtr at 40/51, 57/72, and 63/80 g ha–1 has potential for use in sweetpotato for Palmer amaranth control without causing significant crop injury and yield reduction.
Ice rheology governs how glaciers flow and respond to environmental change. The rheology of glacier ice evolves in response to a variety of mechanisms, including damage, heating, melting and the development of crystalline fabric. The relative contributions of these rheological mechanisms are not well understood. Using remotely sensed data and physical models, we decouple the influence of each of the aforementioned mechanisms along the margins of Rutford Ice Stream, a laterally confined outlet glacier in West Antarctica. We show that fabric is an important control on ice rheology in the shear margins, with an inferred softening effect consistent with a single-maximum fabric. Fabric evolves to steady state near the onset of streaming flow, and ice progressively softens downstream almost exclusively due to shear heating. The rate of heating is sensitive to local shear strain rates, which respond to local changes in bed topography as ice is squeezed through the basal trough. The impact of shear heating on the downstream evolution of ice rheology in a laterally confined glacier suggests that the thermoviscous feedback – wherein faster ice flow leads to higher rates of shear heating, further softening the ice – is a fundamental control on glacier dynamics.
Introduction: Aligning health systems appropriately to the needs of the elderly is an urgent global priority, according to the WHO. In Canada, ED length of stay has risen 16% for elderly patients in the last year. Agitation requiring chemical restraint is a common, high-risk problem for elderly in the ED. Improving outcomes in this heterogeneous population remain difficult due to inability to effectively identify and evaluate delirium, frailty, multi-morbidity, and incompatibility with the ED system. A data-driven approach to complex health problems is a recognized emerging tool for healthcare innovation. New opportunities for targeted quality improvement in the ED will be uncovered by identifying the clinical characteristics of elderly patients with agitation, and the system process factors that influence their outcomes. Methods: We studied 400 patients in a case-control study at two tertiary-care EDs over five years. Patients were randomly selected if age was greater than 75 years. 200 cases of patients who received an intravenous dose of haloperidol, midazolam and/or lorazepam were selected as a surrogate data marker for having agitation. Controls were randomly matched by age and ED diagnosis. Standardized clinical, systems and process variables were collected. We conducted a univariate analysis. Results: Elderly given intravenous medications for agitation had increased mortality (OR 3.8 CI: 1.6-10.7, p<0.001) and ED length of stay (27 vs. 15 hours, p<0.001). No statistical significance was found in clinical characteristics, CTAS scores, PRISMA7 frailty scores nor sentinel or return visits. There was no statistical difference in median hospital length of stay (8 vs. 6 days, p<0.70). No differences were found in median time from ED physician seeing a patient to first consultant request (73 vs. 83 mins, p=0.75). The largest time intervals contributing to ED length of stay were from first consultant request to hospital request (15 vs. 12 hours, p=0.056) and hospitalization delay (13 vs. 7 hours, p=0.45). Conclusion: Identification of high-risk elderly patients for targeted intervention through a data-driven approach is feasible and informative. Traditional clinical characteristics remain unhelpful in identifying and evaluating outcomes in elderly with agitation. We have identified a process factor that is clinically relevant and pragmatic to evaluate in our ED system. Future research focused on optimizing systems process factors to improve quality of elderly care should be prioritized.
Risk populations for HIV infections tend to neglect condom use, making alternative preventive approaches necessary. Accordingly, we modelled the risk of sexual HIV transmission for condom use vs. use of rapid diagnostic test (RDT) systems with subsequent exclusion of potential sexual partners with a correctly or falsely positive test from unprotected sex with and without the use of HIV pre-exposure prophylaxis (PrEP) in a bio-statistical approach. We combined a previously described model of transmission risk for HIV-exposed individuals with a newly suggested model of risk of HIV exposure for sexually active HIV-negative individuals. The model was adapted for several stages of infection and different strategies of HIV infection prevention.
HIV prevention with RDTs can reduce the transmission risk by up to 97% compared with having sex without any prevention and up to 80% compared with condom use. Nevertheless, RDT-based prevention strategies demonstrate a lack of protection in several stages of infection; in particular, RNA-based RDT systems may fail under treatment. RDT-based pre-screening of potential sex partners prior to unprotected sexual contacts substantially reduces HIV transmission risk. Combination of different prevention strategies is advisable for high-risk groups.
Characterisation of genetic diversity in a large number of European pig populations has been undertaken with EC support. The populations sampled included local (rare) breeds, national varieties of the major international breeds, commercial lines and the Chinese Meishan breed. A second phase of the project will sample a further 50 Chinese breeds. Neutral genetic markers (AFLP and microsatellites), with individual or bulk typing, were used and compared.
DNA from 59 European pig populations was extracted on samples of about 50 individuals per population. Individuals were typed for 50 microsatellites and for 148 AFLP bands. A subset of 25 populations was typed for 20 microsatellites on pools of DNA. Allele frequencies were estimated by direct allele counting for the co-dominant markers. Frequencies of AFLP negative alleles (absent bands) were obtained by taking the square root of absent band frequencies. Within-breed variability was summarised using standard statistics: expected and observed heterozygosity, mean observed and effective numbers of alleles, and F statistics. Between-breed diversity analysis was based on a bootstrapped Neighbor-Joining (NJ) tree derived from Reynolds distances (DR). The standard distance of Nei (DS) was also calculated.
Transmission of acute respiratory infections (ARI) and acute gastroenteritis (AGE) often occurs in households. The aim of this study was to assess which proportion of ARI and AGE is introduced and transmitted by children in German households with children attending child care. We recruited families with children aged 0–6 years in Braunschweig (Germany), for a 4 months prospective cohort study in the winter period 2014/2015. Every household member was included in a health diary and used nasal swabs for pathogen identification in case of ARI. We defined a transmission if two persons had overlapping periods with symptoms and used additional definitions for sensitivity analyses. In total, 77 households participated with 282 persons. We observed 277 transmission events for ARI and 23 for AGE. In most cases, the first infected person in a household was a child (ARI: 63%, AGE: 53%), and the risk of within-household transmission was two times higher when the index case was a child. In 26 ARI-transmission events, pathogens were detected for both cases; hereof in 35% (95% confidence interval (17–56%)) the pathogens were different. Thus, symptomatic infections in household members, apparently linked in time, were in 2/3 associated with the same pathogens.
The Murchison Widefield Array, and its recently developed Voltage Capture System, facilitates extending the low-frequency range of pulsar observations at high-time and -frequency resolution in the Southern Hemisphere, providing further information about pulsars and the ISM. We present the results of an initial time-resolved census of known pulsars using the Murchison Widefield Array. To significantly reduce the processing load, we incoherently sum the detected powers from the 128 Murchison Widefield Array tiles, which yields ~10% of the attainable sensitivity of the coherent sum. This preserves the large field-of-view (~450 deg2 at 185 MHz), allowing multiple pulsars to be observed simultaneously. We developed a WIde-field Pulsar Pipeline that processes the data from each observation and automatically folds every known pulsar located within the beam. We have detected 50 pulsars to date, 6 of which are millisecond pulsars. This is consistent with our expectation, given the telescope sensitivity and the sky coverage of the processed data (~17 000 deg2). For 10 pulsars, we present the lowest frequency detections published. For a subset of the pulsars, we present multi-frequency pulse profiles by combining our data with published profiles from other telescopes. Since the Murchison Widefield Array is a low-frequency precursor to the Square Kilometre Array, we use our census results to forecast that a survey using the low-frequency component of the Square Kilometre Array Phase 1 can potentially detect around 9 400 pulsars.
The molecular, neurobiological, and physical health impacts of child maltreatment are well established, yet mechanistic pathways remain inadequately defined. Telomere length (TL) decline is an emerging molecular indicator of stress exposure with definitive links to negative health outcomes in maltreated individuals. The multiple confounders endemic to human maltreatment research impede the identification of causal pathways. This study leverages a unique randomized, cross-foster, study design in a naturalistic translational nonhuman primate model of infant maltreatment. At birth, newborn macaques were randomly assigned to either a maltreating or a competent control mother, balancing for sex, biological mother parenting history, and social rank. Offspring TL was measured longitudinally across the first 6 months of life (infancy) from peripheral blood. Hair cortisol accumulation was also determined at 6, 12, and 18 months of age. TL decline was greater in animals randomized to maltreatment, but also interacted with biological mother group. Shorter TL at 6 months was associated with higher mean cortisol levels through 18 months (juvenile period) when controlling for relevant covariates. These results suggest that even under the equivalent social, nutritional, and environmental conditions feasible in naturalistic translational nonhuman primate models, early adverse caregiving results in lasting molecular scars that foreshadow elevated health risk and physiologic dysregulation.
The SKA and its pathfinders will enable studies of H i emission at higher redshifts than ever before. In moving beyond the local Universe, this will require the use of cosmologically appropriate formulae that have traditionally been simplified to their low-redshift approximations. In this paper, we summarise some of the most important relations for tracing H i emission in the SKA era, and present an online calculator to assist in the planning and analysis of observations (http://hifi.icrar.org).
Little is known about violence against children in refugee camps and settlements, and the evidence-base concerning mental health outcomes of youth in refugee settings in low and middle-income countries is similarly small. Evidence is needed to understand patterns of violence against children in refugee camps, and associations with adverse mental health outcomes.
Surveys were conducted with adolescent refugees (aged 13–17) in two refugee contexts – Kiziba Camp, Rwanda (n = 129) (refugees from Democratic Republic of Congo) and Adjumani and Kiryandongo refugee settlements, Uganda (n = 471) (refugees from South Sudan). Latent Class Analysis was utilized to identify classes of violence exposure (including exposure to witnessing household violence, verbal abuse, physical violence and sexual violence). Logistic regressions explored the association between latent class of violence exposure and symptoms of depression and anxiety.
In Rwanda, a two-class solution was identified, with Class 1 (n = 33) representing high levels of exposure to violence and Class 2 (n = 96) representing low levels of exposure. In Uganda, a three-class solution was identified: Class 1 (high violence; n = 53), Class 2 (low violence, n = 100) and Class 3 (no violence, n = 317). Logistic regression analyses indicated that latent violence class was associated with increased odds of high anxiety symptoms in Rwanda (AOR 3.56, 95% CI 1.16–0.95), and high v. no violence class was associated with depression (AOR 3.97, 95% CI 1.07–7.61) and anxiety symptoms (AOR 2.04, 95% CI 1.05–3.96) in Uganda.
The present results support the existing evidence-base concerning the association between violence and adverse mental health outcomes, while identifying differences in patterns and associations between refugee youth in two different contexts.