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Generalized Baumslag-Solitar groups are a class of combinatorially interesting groups. Their group theory is also closely associated to a the topology of a class of 2-dimensional spaces. These 2-dimensional spaces are Seifert fibred. We develop the basic topology of these fibrations and derive some of the most immediate group theoretic consequences of this topology.
This survey article has two components. The first part gives a gentle introduction to Serres notion of $G$-complete reducibility, where $G$ is a connected reductive algebraic group defined over an algebraically closed field. The second part concerns consequences of this theory when $G$ is simple of exceptional type, specifically its role in elucidating the subgroup structure of $G$. The latter subject has a history going back about sixty years. We give an overview of what is known, up to the present day. We also take the opportunity to offer several corrections to the literature.
Every four years leading researchers gather to survey the latest developments in all aspects of group theory. Since 1981, the proceedings of these meetings have provided a regular snapshot of the state of the art in group theory and helped to shape the direction of research in the field. This volume contains selected papers from the 2022 meeting held in Newcastle. It includes substantial survey articles from the invited speakers, namely the mini course presenters Michel Brion, Fanny Kassel and Pham Huu Tiep; and the invited one-hour speakers Bettina Eick, Scott Harper and Simon Smith. It features these alongside contributed survey articles, including some new results, to provide an outstanding resource for graduate students and researchers.
A survey of academic medical-center hospital epidemiologists indicated substantial deviation from Centers for Disease Control and Prevention guidance regarding healthcare providers (HCPs) recovering from coronavirus disease 2019 (COVID-19) returning to work. Many hospitals continue to operate under contingency status and have HCPs return to work earlier than recommended.
The radio signal transmitted by the Mars Express (MEX) spacecraft was observed regularly between the years 2013–2020 at X-band (8.42 GHz) using the European Very Long Baseline Interferometry (EVN) network and University of Tasmania’s telescopes. We present a method to describe the solar wind parameters by quantifying the effects of plasma on our radio signal. In doing so, we identify all the uncompensated effects on the radio signal and see which coronal processes drive them. From a technical standpoint, quantifying the effect of the plasma on the radio signal helps phase referencing for precision spacecraft tracking. The phase fluctuation of the signal was determined for Mars’ orbit for solar elongation angles from 0 to 180 deg. The calculated phase residuals allow determination of the phase power spectrum. The total electron content of the solar plasma along the line of sight is calculated by removing effects from mechanical and ionospheric noises. The spectral index was determined as $-2.43 \pm 0.11$ which is in agreement with Kolmogorov’s turbulence. The theoretical models are consistent with observations at lower solar elongations however at higher solar elongation ($>$160 deg) we see the observed values to be higher. This can be caused when the uplink and downlink signals are positively correlated as a result of passing through identical plasma sheets.
A 43-year-old woman presented with a 3-week history of globus sensation and malaise. A computed tomography scan of her neck showed a large right paratracheal abscess secondary to an infected tracheal diverticulum. The patient was admitted under the ENT surgical team, and underwent incision and drainage of the abscess. There were no post-operative complications and she was discharged home after 2 days, on oral antibiotics.
Conclusion
This case demonstrates that a tracheal diverticulum may become infected and present as a cervical abscess. To our knowledge, this is the fourth reported case in the international literature of abscess formation related to an infected tracheal diverticulum.
The southwestern Cape of South Africa is a particularly dynamic region in terms of long-term climate change. We analysed fossil pollen from a 25,000 year sediment core taken from a near-coastal wetland at Pearly Beach that revealed that distinct changes in vegetation composition occurred along the southwestern Cape coast. From these changes, considerable variability in temperature and moisture availability are inferred. Consistent with indications from elsewhere in southwestern Africa, variability in Atlantic Meridional Overturning Circulation (AMOC) was identified as a strong determinant of regional climate change. At Pearly Beach, this resulted in phases of relatively drier conditions (~24–22.5 cal ka BP and ~22–18 cal ka BP) demarcated by brief phases of increased humidity from ~24.5–24 cal ka BP and 22.5–22 cal ka BP. During glacial Termination I (~19–11.7 ka), a marked increase in coastal thicket pollen from ~18.5 to 15.0 cal ka BP indicates a substantial increase in moisture availability, coincident, and likely associated with, a slowing AMOC and a buildup of heat in the southern Atlantic. With clear links to glacial and deglacial Earth system dynamics and perturbations, the Pearly Beach record represents an important new contribution to a growing body of data, providing insights into the patterns and mechanisms of southwestern African climate change.
Since 2009, mid-upper arm circumference (MUAC) has become an accepted measure for screening children for acute malnutrition and determining eligibility for services to manage acute malnutrition. Use of MUAC has increased the reach and enhanced the quality of community-based management of acute malnutrition services. Increasingly, MUAC is also used to assess nutritional status and eligibility for nutrition support among adolescents and adults, including pregnant and lactating women and HIV and TB clients. However, globally recognised cut-offs have not been established to classify malnutrition among adults using MUAC. Therefore, different countries and programmes use different MUAC cut-offs to determine eligibility for programme services. Patient monitoring guidelines provided by WHO for country adaptation to support the integrated management of adult illness do not include MUAC, in part because guidance does not exist about what MUAC cut-off should trigger further action.
Every four years leading researchers gather to survey the latest developments in all aspects of group theory. Initially held in St Andrews, these meetings have become the premier forum for group theory across the whole of the UK. Since 1981, the proceedings of 'Groups St Andrews' have provided a regular snapshot of the state-of-the-art in group theory and helped to shape the direction of research in the field. This volume contains papers from the 2017 meeting held in Birmingham. It includes expository articles from the invited speakers, and further surveys contributed by the participants. Topics include: generation of finite simple groups, block theory, fusion systems, algebraic groups, one-relator groups, geometric group theory, and Beauville groups.
This paper analyses a series of high-quality continuous records from southeastern Africa to study the spatiotemporal patterning of Holocene hydroclimatic anomalies in the region. Results indicate dominant frequencies of variability at millennial time scales, and a series of anomalies broadly common to all records. Of particular interest, data from the southern Cape coast exhibit periods of wetter/drier conditions that are out of phase with the sites less than 150 km away in the adjacent interior, but in phase with sites in tropical regions over 1000 km to the northeast. To explain such spatial patterns and gradients, we propose that the Agulhas Current may be a critical vector by which tropical climatic signals are propagated along the littoral zone, exerting a dominant, highly localized influence on near-coastal environmental conditions. Limitations in the data available do not allow for a detailed examination of the climatic dynamics related to these phenomena, but this paper highlights a series of avenues for future research to clarify the spatial extent and stability of the patterns observed.
The study objective was to determine the prevalence of Staphylococcus aureus colonisation in the nares and oropharynx of healthy persons and identify any risk factors associated with such S. aureus colonisation. In total 263 participants (177 adults and 86 minors) comprising 95 families were enrolled in a year-long prospective cohort study from one urban and one rural county in eastern Iowa, USA, through local newspaper advertisements and email lists and through the Keokuk Rural Health Study. Potential risk factors including demographic factors, medical history, farming and healthcare exposure were assessed. Among the participants, 25.4% of adults and 36.1% minors carried S. aureus in their nares and 37.9% of adults carried it in their oropharynx. The overall prevalence was 44.1% among adults and 36.1% for minors. Having at least one positive environmental site for S. aureus in the family home was associated with colonisation (prevalence ratio: 1.34, 95% CI: 1.07–1.66). The sensitivity of the oropharyngeal cultures was greater than that of the nares cultures (86.1% compared with 58.2%, respectively). In conclusion, the nares and oropharynx are both important colonisation sites for healthy community members and the presence of S. aureus in the home environment is associated with an increased probability of colonisation.
We compared the impact of a commercial chlorination product (brand name Air RahMat) in stored drinking water to traditional boiling practices in Indonesia. We conducted a baseline survey of all households with children <5 years in four communities, made 11 subsequent weekly home visits to assess acceptability and use of water treatment methods, measured Escherichia coli concentration in stored water, and determined diarrhoea prevalence among children <5 years. Of 281 households surveyed, boiling (83%) and Air RahMat (7%) were the principal water treatment methods. Multivariable log-binomial regression analyses showed lower risk of E. coli in stored water treated with Air RahMat than boiling (risk ratio (RR) 0·75, 95% confidence interval (CI) 0·56–1·00). The risk of diarrhoea in children <5 years was lower among households using Air RahMat (RR 0·43, 95% CI 0·19–0·97) than boiling, and higher in households with E. coli concentrations of 1–1000 MPN/100 ml (RR 1·54, 95% CI 1·04–2·28) or >1000 MPN/100 ml (RR 1·86, 95% CI 1·09–3·19) in stored water than in households without detectable E. coli. Although results suggested that Air RahMat water treatment was associated with lower E. coli contamination and diarrhoeal rates among children <5 years than water treatment by boiling, Air RahMat use remained low.
Studies determined the effect of sodium bisulfate (NaHSO4) on the phytotoxicity, retention, uptake, and translocation of the suspension concentrate formulation of imazamethabenz in wild oats. NaHSO4 completely solubilized this herbicide formulation when added in an equimolar concentration and did not affect herbicidal activity at NaHSO4 concentrations below 28 mM when used in a carrier volume of 100 L ha−1. NaHSO4 improved phytotoxicity at a carrier volume of 33 L ha−1. NaHSO4 at 28 mM increased the efficacy of imazamethabenz applied as individual drops on growth chamber-grown wild oats. The herbicide retention was not changed but foliar absorption and acropetal translocation were increased, while basipetal translocation was decreased. The increase in phytotoxicity of imazamethabenz with NaHSO4 was related to absorption of imazamethabenz by the target plants.
We present results from a multiwavelength study of the blazar PKS 1954–388 at radio, UV, X-ray, and gamma-ray energies. A RadioAstron observation at 1.66 GHz in June 2012 resulted in the detection of interferometric fringes on baselines of 6.2 Earth-diameters. This suggests a source frame brightness temperature of greater than 2 × 1012 K, well in excess of both equipartition and inverse Compton limits and implying the existence of Doppler boosting in the core. An 8.4-GHz TANAMI VLBI image, made less than a month after the RadioAstron observations, is consistent with a previously reported superluminal motion for a jet component. Flux density monitoring with the Australia Telescope Compact Array confirms previous evidence for long-term variability that increases with observing frequency. A search for more rapid variability revealed no evidence for significant day-scale flux density variation. The ATCA light-curve reveals a strong radio flare beginning in late 2013, which peaks higher, and earlier, at higher frequencies. Comparison with the Fermi gamma-ray light-curve indicates this followed ~ 9 months after the start of a prolonged gamma-ray high-state—a radio lag comparable to that seen in other blazars. The multiwavelength data are combined to derive a Spectral Energy Distribution, which is fitted by a one-zone synchrotron-self-Compton (SSC) model with the addition of external Compton (EC) emission.