Objectives/Goals: We describe the prevalence of individuals with household exposure to SARS-CoV-2, who subsequently report symptoms consistent with COVID-19, while having PCR results persistently negative for SARS-CoV-2 (S[+]/P[-]). We assess whether paired serology can assist in identifying the true infection status of such individuals. Methods/Study Population: In a multicenter household transmission study, index patients with SARS-CoV-2 were identified and enrolled together with their household contacts within 1 week of index’s illness onset. For 10 consecutive days, enrolled individuals provided daily symptom diaries and nasal specimens for polymerase chain reaction (PCR). Contacts were categorized into 4 groups based on presence of symptoms (S[+/-]) and PCR positivity (P[+/-]). Acute and convalescent blood specimens from these individuals (30 days apart) were subjected to quantitative serologic analysis for SARS-CoV-2 anti-nucleocapsid, spike, and receptor-binding domain antibodies. The antibody change in S[+]/P[-] individuals was assessed by thresholds derived from receiver operating characteristic (ROC) analysis of S[+]/P[+] (infected) versusS[-]/P[-] (uninfected). Results/Anticipated Results: Among 1,433 contacts, 67% had ≥1 SARS-CoV-2 PCR[+] result, while 33% remained PCR[-]. Among the latter, 55% (n = 263) reported symptoms for at least 1 day, most commonly congestion (63%), fatigue (63%), headache (62%), cough (59%), and sore throat (50%). A history of both previous infection and vaccination was present in 37% of S[+]/P[-] individuals, 38% of S[-]/P[-], and 21% of S[+]/P[+] (P<0.05). Vaccination alone was present in 37%, 41%, and 52%, respectively. ROC analyses of paired serologic testing of S[+]/P[+] (n = 354) vs. S[-]/P[-] (n = 103) individuals found anti-nucleocapsid data had the highest area under the curve (0.87). Based on the 30-day antibody change, 6.9% of S[+]/P[-] individuals demonstrated an increased convalescent antibody signal, although a similar seroresponse in 7.8% of the S[-]/P[-] group was observed. Discussion/Significance of Impact: Reporting respiratory symptoms was common among household contacts with persistent PCR[-] results. Paired serology analyses found similar seroresponses between S[+]/P[-] and S[-]/P[-] individuals. The symptomatic-but-PCR-negative phenomenon, while frequent, is unlikely attributable to true SARS-CoV-2 infections that go missed by PCR.

Turbulent mixing in a supercritical CO$_2$ shear layer is examined using both experimental and numerical methods. Boundary conditions are selected to focus on the rarely studied near-critical regime, where thermophysical properties vary nonlinearly with respect to temperature and pressure. Experimental results are obtained via Raman spectroscopy and shadowgraphy, while numerical results are obtained via direct numerical simulation. The shear layer growth rate is found to be 0.2. Additionally, density profiles indicate a relaxation of density gradients between the mixed fluid and heavy fluid as the flow evolves downstream, which runs counter to existing supercritical shear layer data in the literature. The computational results identify significant anisotropy in the turbulence in the shear layer, which is discussed in terms of the development of regions of high density gradient magnitude. The Reynolds-averaged enstrophy budget at various streamwise locations indicates no significant dilatational or baroclinic contribution within the shear layer.

Preventing neonatal calf diarrhea (NCD) and bovine respiratory disease (BRD) in cow–calf herds is essential to optimizing calfhood health. Disease control can prevent morbidity and mortality; however, evidence concerning the effectiveness of practices to achieve this is limited. The objective of this systematic review was to assess and summarize the evidence on the effectiveness of management practices to prevent calf morbidity and mortality from NCD and BRD in beef cow–calf herds. The population of interest was preweaned beef calves. The outcomes were calf morbidity and mortality caused by NCD and BRD. Only studies reporting naturally occurring diseases were included. Seventeen studies were deemed relevant, 6 studies of which were controlled trials or randomized controlled trials (RCTs), and 11 were observational studies. Most management practices had some evidence to support their use; however, the certainty of the findings was low to very low. Most of the practices were shown to impact both NCD and BRD. Yet, the different levels of consistency in the directionality of the findings suggest that some outcomes are more affected by some practices than others. More well-designed RCTs and cohort studies are required to provide reliable estimates to support recommended practices for cow–calf herds.

Calves sold at weaning are the main source of income for cow–calf operations, and their survival should be a priority. Given this, the effective use of management practices for pregnant dams and calves to prevent calf mortality is essential; however, decision-makers often do not have access to information about the effectiveness of many management practices. A systematic review was conducted to summarize the evidence of the effectiveness of biosecurity, vaccination, colostrum management, breeding and calving season management, and nutritional management practices for preventing preweaned beef calf mortality. The population of interest was preweaned beef calves from birth until at least 3 months of age. The outcome of interest was general preweaning calf mortality with stillbirths excluded. Eleven studies were deemed relevant. Ten were observational cross-sectional studies, and one was a randomized controlled trial (RCT). The practices that were statistically significantly associated with calf mortality were intervening with colostrum in case a calf had not nursed from its dam or was assisted at calving, timing and length of the calving season, and injecting selenium and vitamin E at birth. More well-executed RCTs and cohort studies are needed to provide evidence of effectiveness and help support implementation of recommended practices in herds.

This paper examines South–South security cooperation and regional organisations (ROs) in Africa. Much of the literature on peace and conflict in Africa has focused on ROs and the African Peace and Security Architecture (APSA). Guided by the mantra ‘African solutions to African problems’, these organisations have facilitated several instances of African-led security cooperation. Yet ROs have limited agency and capacity, are institutionally rigid, and are often donor-dependent. As a result, ad hoc security initiatives such as the G5 Sahel and Accra Initiative – our case studies – are on the rise. While such initiatives are better adapted to local context and feature higher levels of autonomy (relative to APSA), we critique this view by showing how donors pressure and trap African governments facing transnational security threats into ad hoc initiatives. These initiatives transform into ‘zombified’ security institutions that rarely live up to the elevated expectations of African and Western stakeholders. This creates a paradox for debates around African agency in security affairs: ad hoc initiatives lock African states into security frameworks that do not respond to their needs but also facilitate the pursuit of donor funding, reassert the national scale of sovereignty, and incentivise new forms of bilateral security cooperation.

The International Society for Twin Studies (ISTS) held its 19th scientific congress in Assisi, Italy, from September 26 to 28, 2024. This prestigious event, which was the seventh joint meeting with the World Congress on Twin Pregnancy, brought together researchers from various fields, including psychology, biology and medicine. Representatives from ICOMBO (the International Consortium of Multiple Birth Organisations), which supports multiple-birth families worldwide, were also in attendance. Many twin researchers consider this event to be the highlight of their professional year, as it brings together experts and parents alike to discuss the latest advancements in twin studies.

With wide-field phased array feed technology, the Australian Square Kilometre Array Pathfinder (ASKAP) is ideally suited to search for seemingly rare radio transient sources that are difficult to discover previous-generation narrow-field telescopes. The Commensal Real-time ASKAP Fast Transient (CRAFT) Survey Science Project has developed instrumentation to continuously search for fast radio transients (duration $\lesssim$ 1 s) with ASKAP, with a particular focus on finding and localising fast radio bursts (FRBs). Since 2018, the CRAFT survey has been searching for FRBs and other fast transients by incoherently adding the intensities received by individual ASKAP antennas, and then correcting for the impact of frequency dispersion on these short-duration signals in the resultant incoherent sum (ICS) in real time. This low-latency detection enables the triggering of voltage buffers, which facilitates the localisation of the transient source and the study of spectro-polarimetric properties at high time resolution. Here we report the sample of 43 FRBs discovered in this CRAFT/ICS survey to date. This includes 22 FRBs that had not previously been reported: 16 FRBs localised by ASKAP to $\lesssim 1$ arcsec and 6 FRBs localised to $\sim 10$ arcmin. Of the new arcsecond-localised FRBs, we have identified and characterised host galaxies (and measured redshifts) for 11. The median of all 30 measured host redshifts from the survey to date is $z=0.23$. We summarise results from the searches, in particular those contributing to our understanding of the burst progenitors and emission mechanisms, and on the use of bursts as probes of intervening media. We conclude by foreshadowing future FRB surveys with ASKAP using a coherent detection system that is currently being commissioned. This will increase the burst detection rate by a factor of approximately ten and also the distance to which ASKAP can localise FRBs.

If being asked to give to charity stimulates an emotional response, like empathy, that makes giving difficult to resist, a natural self-control mechanism might be to avoid being asked in the first place. We replicate a result from a field experiment that points to the role of empathy in giving. We conduct an experiment in a large superstore in which we solicit donations to charity and randomly allow shoppers the opportunity to avoid solicitation by using the other door. We find the rate of avoidance by store entrants to be 8.9 %. However, we also find that the avoidance effect disappears in very cold weather, suggesting that avoidance behavior is sensitive to its cost.

We examine the energy distribution of the fast radio burst (FRB) population using a well-defined sample of 63 FRBs from the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope, 28 of which are localised to a host galaxy. We apply the luminosity-volume ($V/V_{\mathrm{max}}$) test to examine the distribution of these transient sources, accounting for cosmological and instrumental effects, and determine the energy distribution for the sampled population over the redshift range $0.01 \lesssim z \lesssim 1.02$. We find the distribution between $10^{23}$ and $10^{26}$ J Hz$^{-1}$ to be consistent with both a pure power-law with differential slope $\gamma=-1.96 \pm 0.15$, and a Schechter function with $\gamma = -1.82 \pm 0.12$ and downturn energy $E_\mathrm{max} \sim 6.3 \, \times 10^{25}$ J Hz$^{-1}$. We identify systematic effects which currently limit our ability to probe the luminosity function outside this range and give a prescription for their treatment. Finally, we find that with the current dataset, we are unable to distinguish between the evolutionary and spectral models considered in this work.

Fast radio burst (FRB) science primarily revolves around two facets: the origin of these bursts and their use in cosmological studies. This work follows from previous redshift–dispersion measure (z–DM) analyses in which we model instrumental biases and simultaneously fit population parameters and cosmological parameters to the observed population of FRBs. This sheds light on both the progenitors of FRBs and cosmological questions. Previously, we have completed similar analyses with data from the Australian Square Kilometer Array Pathfinder (ASKAP) and the Murriyang (Parkes) Multibeam system. In this manuscript, we use 119 FRBs with 29 associated redshifts by additionally modelling the Deep Synoptic Array (DSA) and the Five-hundred-metre Aperture Spherical radio Telescope (FAST). We also invoke a Markov chain Monte Carlo (MCMC) sampler and implement uncertainty in the Galactic DM contributions. The latter leads to larger uncertainties in derived model parameters than previous estimates despite the additional data and indicate that precise measurements of DM$_\textrm{ISM}$ will be important in the future. We provide refined constraints on FRB population parameters and derive a new constraint on the minimum FRB energy of log $E_{\mathrm{min}}$(erg)=39.47$^{+0.54}_{-1.28}$ which is significantly higher than bursts detected from strong repeaters. This result likely indicates a low-energy turnover in the luminosity function or may alternatively suggest that strong repeaters have a different luminosity function to single bursts. We also predict that FAST will detect 25–41% of their FRBs at $z \gtrsim 2$ and DSA will detect 2–12% of their FRBs at $z \gtrsim 1$.

Weight loss results in obligatory reductions in energy expenditure (EE) due to loss of metabolically active fat-free mass (FFM). This is accompanied by adaptive reductions (i.e. adaptive thermogenesis) designed to restore energy balance while in an energy crisis. While the ‘3500-kcal rule’ is used to advise weight loss in clinical practice, the assumption that EE remains constant during energy restriction results in a large overestimation of weight loss. Thus, this work proposes a novel method of weight-loss prediction to more accurately account for the dynamic trajectory of EE. A mathematical model of weight loss was developed using ordinary differential equations relying on simple self-reported inputs of weight and energy intake to predict weight loss over a specified time. The model subdivides total daily EE into resting EE, physical activity EE, and diet-induced thermogenesis, modelling obligatory and adaptive changes in each compartment independently. The proposed model was tested and refined using commercial weight-loss data from participants enrolled on a very low-energy total-diet replacement programme (LighterLife UK, Essex). Mathematical modelling predicted post-intervention weight loss within 0.75% (1.07 kg) of that observed in females with overweight or obesity. Short-term weight loss was consistently underestimated, likely due to considerable FFM reductions reported on the onset of weight loss. The best model agreement was observed from 6 to 9 weeks where the predicted end-weight was within 0.35 kg of that observed. The proposed mathematical model simulated rapid weight loss with reasonable accuracy. Incorporated terms for energy partitioning and adaptive thermogenesis allow us to easily account for dynamic changes in EE, supporting the potential use of such a model in clinical practice.