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Saturn has long been the only giant planet in our solar system without any known Trojan members. In this paper, with serendipitous archival observations and refined orbit determination, we report that 2019 UO\\(_{14}\\) is a Trojan of the gas giant. However, the object is only a transient Trojan currently librating around the leading Lagrange point \\(L_4\\) of the Sun-Saturn system in a period of \\(\\sim\\!0.7\\) kyr. Our N-body numerical simulation shows that 2019 UO\\(_{14}\\) was likely captured as a Centaur and became trapped around \\(L_4\\) \\(\\sim\\!2\\) kyr ago from a horseshoe coorbital. The current Trojan state will be maintained for another millennium or thereabouts before transitioning back to a horseshoe state. Additionally, we characterize the physical properties of 2019 UO\\(_{14}\\). Assuming a linear phase slope of \\(0.06 \\pm 0.01\\) mag/deg, the mean \\(r\\)-band absolute magnitude of the object was determined to be \\(H_r = 13.11 \\pm 0.07\\), with its color measured to be consistent with those of Jupiter and Neptune Trojans and not statistically different from Centaurs. Although the short-lived Saturn Trojan exhibited no compelling evidence of activity in the observations, we favour the possibility that it could be an active Trojan. If confirmed, 2019 UO\\(_{14}\\) would be marked as the first active Trojan in our solar system. We conservatively determine the optical depth of dust within our photometric aperture to be \\(\\lesssim\\!10^{-7}\\), corresponding to a dust mass-loss rate to be \\(\\lesssim\\!1\\) kg s\\(^{-1}\\), provided that the physical properties of dust grains resemble Centaur 29P/Schwassmann-Wachmann 1.

We present the Citizen Science program Active Asteroids and describe discoveries stemming from our ongoing project. Our NASA Partner program is hosted on the Zooniverse online platform and launched on 2021 August 31, with the goal of engaging the community in the search for active asteroids -- asteroids with comet-like tails or comae. We also set out to identify other unusual active solar system objects, such as active Centaurs, active quasi-Hilda asteroids, and Jupiter-family comets (JFCs). Active objects are rare in large part because they are difficult to identify, so we ask volunteers to assist us in searching for active bodies in our collection of millions of images of known minor planets. We produced these cutout images with our project pipeline that makes use of publicly available Dark Energy Camera (DECam) data. Since the project launch, roughly 8,300 volunteers have scrutinized some 430,000 images to great effect, which we describe in this work. In total we have identified previously unknown activity on 15 asteroids, plus one Centaur, that were thought to be asteroidal (i.e., inactive). Of the asteroids, we classify four as active quasi-Hilda asteroids, seven as JFCs, and four as active asteroids, consisting of one Main-belt comet (MBC) and three MBC candidates. We also include our findings concerning known active objects that our program facilitated, an unanticipated avenue of scientific discovery. These include discovering activity occurring during an orbital epoch for which objects were not known to be active, and the reclassification of objects based on our dynamical analyses.

We report statistically significant detections of non-radial nongravitational accelerations based on astrometric data in the photometrically inactive objects 1998 KY\\(_{26}\\), 2005 VL\\(_1\\), 2016 NJ\\(_{33}\\), 2010 VL\\(_{65}\\), 2016 RH\\(_{120}\\), and 2010 RF\\(_{12}\\). The magnitudes of the nongravitational accelerations are greater than those typically induced by the Yarkovsky effect and there is no radiation-based, non-radial effect that can be so large. Therefore, we hypothesize that the accelerations are driven by outgassing, and calculate implied H\\(_2\\)O production rates for each object. We attempt to reconcile outgassing induced acceleration with the lack of visible comae or photometric activity via the absence of surface dust and low levels of gas production. Although these objects are small and some are rapidly rotating, surface cohesive forces are stronger than the rotational forces and rapid rotation alone cannot explain the lack of surface debris. It is possible that surface dust was removed previously, perhaps via outgassing activity that increased the rotation rates to their present day value. We calculate dust production rates of order \\(\\sim10^{-4}\\) g s\\(^{-1}\\) in each object assuming that the nuclei are bare, within the upper limits of dust production from a sample stacked image of 1998 KY\\(_{26}\\) of \\(\\dot{M}_{\\rm Dust}<0.2\\) g s\\(^{-1}\\). This production corresponds to brightness variations of order \\(\\sim0.0025\\%\\), which are undetectable in extant photometric data. We assess the future observability of each of these targets, and find that the orbit of 1998 KY\\(_{26}\\) -- which is also the target for the extended Hayabusa2 mission -- exhibits favorable viewing geometry before 2025.

A complete accounting of nearby objects -- from the highest-mass white dwarf progenitors down to low-mass brown dwarfs -- is now possible, thanks to an almost complete set of trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census of objects within a Sun-centered sphere of 20-pc radius and check published literature to decompose each binary or higher-order system into its separate components. The result is a volume-limited census of \\(\\sim\\)3,600 individual star formation products useful in measuring the initial mass function across the stellar (\\(<8 M_\\odot\\)) and substellar (\\(\\gtrsim 5 M_{Jup}\\)) regimes. Comparing our resulting initial mass function to previous measurements shows good agreement above 0.8\\(M_\\odot\\) and a divergence at lower masses. Our 20-pc space densities are best fit with a quadripartite power law, \\(\\xi(M) = dN/dM \\propto M^{-\\alpha}\\) with long-established values of \\(\\alpha = 2.3\\) at high masses (\\(0.55 < M < 8.00 M_\\odot\\)) and \\(\\alpha = 1.3\\) at intermediate masses (\\(0.22 < M < 0.55 M_\\odot\\)), but at lower masses we find \\(\\alpha = 0.25\\) for \\(0.05 < M <0.22 M_\\odot\\) and \\(\\alpha = 0.6\\) for \\(0.01 < M < 0.05 M_\\odot\\). This implies that the rate of production as a function of decreasing mass diminishes in the low-mass star/high-mass brown dwarf regime before increasing again in the low-mass brown dwarf regime. Correcting for completeness, we find a star to brown dwarf number ratio of, currently, 4:1, and an average mass per object of 0.41 \\(M_\\odot\\).

Understanding the level and characteristics of protection from past SARS-CoV-2 infection against subsequent re-infection, symptomatic COVID-19 disease, and severe disease is essential for predicting future potential disease burden, for designing policies that restrict travel or access to venues where there is a high risk of transmission, and for informing choices about when to receive vaccine doses. We aimed to systematically synthesise studies to estimate protection from past infection by variant, and where data allow, by time since infection. In this systematic review and meta-analysis, we identified, reviewed, and extracted from the scientific literature retrospective and prospective cohort studies and test-negative case-control studies published from inception up to Sept 31, 2022, that estimated the reduction in risk of COVID-19 among individuals with a past SARS-CoV-2 infection in comparison to those without a previous infection. We meta-analysed the effectiveness of past infection by outcome (infection, symptomatic disease, and severe disease), variant, and time since infection. We ran a Bayesian meta-regression to estimate the pooled estimates of protection. Risk-of-bias assessment was evaluated using the National Institutes of Health quality-assessment tools. The systematic review was PRISMA compliant and was registered with PROSPERO (number CRD42022303850). We identified a total of 65 studies from 19 different countries. Our meta-analyses showed that protection from past infection and any symptomatic disease was high for ancestral, alpha, beta, and delta variants, but was substantially lower for the omicron BA.1 variant. Pooled effectiveness against re-infection by the omicron BA.1 variant was 45·3% (95% uncertainty interval [UI] 17·3–76·1) and 44·0% (26·5–65·0) against omicron BA.1 symptomatic disease. Mean pooled effectiveness was greater than 78% against severe disease (hospitalisation and death) for all variants, including omicron BA.1. Protection from re-infection from ancestral, alpha, and delta variants declined over time but remained at 78·6% (49·8–93·6) at 40 weeks. Protection against re-infection by the omicron BA.1 variant declined more rapidly and was estimated at 36·1% (24·4–51·3) at 40 weeks. On the other hand, protection against severe disease remained high for all variants, with 90·2% (69·7–97·5) for ancestral, alpha, and delta variants, and 88·9% (84·7–90·9) for omicron BA.1 at 40 weeks. Protection from past infection against re-infection from pre-omicron variants was very high and remained high even after 40 weeks. Protection was substantially lower for the omicron BA.1 variant and declined more rapidly over time than protection against previous variants. Protection from severe disease was high for all variants. The immunity conferred by past infection should be weighed alongside protection from vaccination when assessing future disease burden from COVID-19, providing guidance on when individuals should be vaccinated, and designing policies that mandate vaccination for workers or restrict access, on the basis of immune status, to settings where the risk of transmission is high, such as travel and high-occupancy indoor settings. Bill & Melinda Gates Foundation, J Stanton, T Gillespie, and J and E Nordstrom.

Background There is limited information on surgical site infections (SSI) and the related antibiotic resistance needed to guide their management and prevention in Sierra Leone. In this study, we aimed to establish the incidence and risk factors of SSI and the related antibiotic resistance among adults attending a tertiary hospital, and a secondary health facility in Freetown, Sierra Leone. Methods This is a prospective cohort study designed to collect data from adult (18 years or older) patients who attended elective and emergency surgeries at two hospitals in Freetown between February and July, 2021. Data analysis was done using STATA version 16. Results Of 338 patients, 245 (72.5%) and 93 (27.5%) had their surgeries at the tertiary and secondary hospitals, respectively. Many were males 192 (56.8%), less than 35 years 164 (48.5%), and 39 (11.5%) developed an SSI. Of the 39 patients who acquired an SSI, 7 (17.9%) and 32 (82.1%) had their surgeries at the secondary and tertiary hospitals, respectively. The incidence of SSI is higher in contaminated 17 (43.6%) than in clean-contaminated 12 (30.8%) and clean 10 (25.6%) wounds. Wound swabs were collected in 29 (74.4%) patients, of which 18 (62.1%) had bacterial growth. In total, 49 isolates of 14 different bacteria including gram-negative 41 (83.7%) and gram-positive 8 (16.3%) isolates were identified. Of these, 32 (65.3%) were Enterobacteriaceae , 9 (18.4%) were Non-fermenting gram-negative bacilli and 10 (12.2%) were Enterococci . The most common isolates were Escherichia coli (12, 24.5%), Klebsiella pneumoniae (10, 20.4%), Acinetobacter baumannii ( 5, 10.2%), Klebsiella oxytoca (4, 8.2%) and Enterococcus faecalis (4, 8.2%). The Enterobacteriaceae were either resistance to carbapenems (4, 8.2%) or were extended-spectrum beta-lactamase (ESBL) producing organisms (29, 59.2%). Male sex [ p  = 0.031], an ASA score ≥ 2 [ p  = 0.020), administration of general anaesthesia [ p  = 0.018] and elevated fasting glucose [ p  = 0.033] were predictive of SSI. Conclusion The incidence of SSI in this study is comparable to other low- and middle-income countries, but a substantial proportion of these postoperative wounds have an ESBL-producing Enterobacteriaceae . Therefore, routine surveillance of SSI and related antibiotic resistance is required in resource-limited settings.

Background Although one of the main drivers of antimicrobial resistance is inappropriate antibiotic prescribing, there are limited resources to support the surveillance of antibiotic consumption in low-income countries. In this study, we aimed to assess antibiotic use and consumption among medical patients of two hospitals in different geographic regions of Sierra Leone. Methods This is a cross-sectional study of adult (18 years or older) patients receiving medical care at two hospitals (34 Military Hospital-MH and Makeni Government Hospital-MGH) between March 2021 and October 2021. After admission to the medical or intensive care unit, patients were sequentially recruited by a nurse from each hospital. Demographic and clinical characteristics and information on the dose of antibiotics, their routes, and frequency of administration and duration were collected using a questionnaire adapted from previous studies and encrypted in EpiCollect software (Epic, Verona WI). A physician reviews and verifies each completed questionnaire. Data analysis was done using STATA version 16. Results The mean age of the 468 patients evaluated in this study was 48.6 years. The majority were women (241, 51.7%) and treated at MGH (245, 52.0%). Clinical diagnosis of bacterial infection was made in only 180 (38.5%) patients. Regardless of the diagnosis, most (442, 94.9%) patients received at least one antibiotic. Of a total 813 doses of antibiotics prescribed by the two hospitals, 424 (52.2%) were administered in MH. Overall, antibiotic consumption was 66.9 defined daily doses (DDDs) per 100 bed-days, with ceftriaxone being the most commonly used antibiotic (277, 34.1%). The ACCESS and WATCH antibiotics accounted for 18.9 DDDs per 100 bed-days (28.2%) and 48.0 DDDs per 100 bed-days (71.7%), respectively. None of the patients were prescribed a RESERVE antibiotics. The antibiotic consumption was lower in MH (61.3 DDDs per 100 bed-days) than MGH (76.5 DDDs per 100 bed-days). Conclusion Antibiotic consumption was highest with ceftriaxone, followed by levofloxacin and metronidazole. Given the high rate of consumption of antibiotics in the WATCH category of the AWaRe classification, there is a need to initiate surveillance of antibiotic consumption and establish hospital-based antibiotic stewardship in these settings.

Objective Catheter-associated urinary tract infections (CAUTI) are common worldwide, but due to limited resources, its actual burden in low-income countries is unknown. Currently, there are gaps in knowledge about CAUTI due to lack of surveillance activities in Sierra Leone. In this prospective cohort study, we aimed to determine the incidence of CAUTI and associated antibiotic resistance in two tertiary hospitals in different regions of Sierra Leone. Results The mean age of the 459 recruited patients was 48.8 years. The majority were females (236, 51.3%). Amongst the 196 (42.6%) catheterized patients, 29 (14.8%) developed CAUTI. Bacterial growth was reported in 32 (84%) patients. Escherichia coli (14, 23.7%), Klebsiella pneumoniae (10, 17.0%), and Klebsiella oxytoca (8, 13.6%) were the most common isolates. Most isolates were ESBL-producing Enterobacteriaceae (33, 56%) and WHO Priority 1 (Critical) pathogens (38, 71%). Resistance of K. pneumoniae, K. oxytoca, E. coli , and Proteus mirabilis was higher with the third-generation cephalosporins and penicillins but lower with carbapenems, piperacillin-tazobactam and amikacin. To reduce the high incidence of CAUTI and multi-drug resistance organisms, urgent action is needed to strengthen the microbiology diagnostic services and develop and implement catheter bundles that provide clear guidance for catheter insertion, care and removal.

(AlCrTiZrMox)N coatings with varying Mo content were successfully prepared using a multi-target co-deposition magnetron sputtering system. The results reveal that the Mo content significantly affects the microstructure, hardness, fracture toughness, and tribological behavior of the coatings. As the Mo content in the coatings increases gradually, the preferred orientation changes from (200) to (111). The coatings consistently exhibit a distinct columnar structure. Additionally, the hardness of the coatings increases from 24.39 to 30.24 GPa, along with an increase in fracture toughness. The friction coefficient is reduced from 0.72 to 0.26, and the wear rate is reduced by 10 times. During the friction process, the inter-column regions of the coatings are initially damaged, causing the wear track to exhibit a wavy pattern. Greater frictional heat is generated at the crest of the wave, resulting in the formation of a MoO2 lubricating layer. The friction reaction helps to reduce the shear force during friction, demonstrating the lower friction coefficient of the (AlCrTiZrMox)N coatings. Both the hardness and fracture toughness work together to reduce the wear rate, and the (AlCrTiZrMox)N coatings show excellent wear resistance. Most notably, although the columnar structure plays a negative role in the hardness, it contributes greatly to the wear resistance.

Electrical contact materials are increasingly widely used, but the existing electric contact lubricants still have lots of room for improvement, such as anti-wear performance and lubrication life. Due to the excellent electrical and lubrication properties, graphene shows great potential in lubricating the sliding electrical contact interface, but there is a lack of relevant research. Some researchers have studied the lubrication performance of graphene between the gold-coated/TiN-coated friction pair at an ultra-low current. However, the lubrication performance of graphene on more widely used electrical contact materials such as copper and its alloys under larger and more commonly used current or voltage conditions has not been reported. In this paper, we study the lubrication performance of graphene in the copper and its alloys sliding electrical contact interface under usual parameters, which is explored through four aspects: different substrates—copper and brass, different test methods—constant voltage and constant current, different normal loads and durability test. The experiments demonstrate that graphene can significantly reduce the friction and wear on brass and copper under the above test methods and parameters, with low contact resistance at the same time. Our work is expected to provide a new lubricant for electrical contact materials and contribute to enriching the tribological theory of graphene.