Commensurability classes of hyperbolic Coxeter groups

AbstractIn this paper, we classify all the hyperbolic Coxeter n-simplex reflection groups up to wide-commensurability for all n⩾3. We also determine all the subgroup relationships among the groups

Trends and ethnic disparities in oral and oro-pharyngeal cancers in South Africa, 1992-2001

OBJECTIVE: To describe trends in the epidemiology of oral and of oro-pharyngeal (OAP) cancers in South Africa for the latest period available. METHODS: Data were obtained from the South African pathology- based National Cancer Registry. All new cases of OAP cancers diagnosed and confirmed histologically from 1992 to 2001 are included for the ICD-10 sites C00 to C14, excluding those involving the major salivary glands (C07- C08) and the nasopharynx (C11). OAP cancer incidence is reported by demographics (gender, age, race/ethnicity) and the anatomical sites involved. The analysis on anatomical sites was restricted to squamous cell carcinomas. RESULTS: Overall, males had a much higher OAP cancer incidence rate (world age-Standardised incidence rate [ASIR]= 7.01/100 000 per year) than females (ASIR=1.99). However, among Asian/Indian South Africans, OAP cancer incidence was higher among females (ASIR=4.60) than among males (ASIR=3.80). OAP cancer, excluding those involving the lip, was highest among Coloureds (ASIR=5.72) and lowest among Blacks (ASIR=3.16). OAP cancer incidence was stable overall, but incidence rates increased significantly among Coloured South Africans over the period under review (p≤0.05). Cancer specifically involving the oro-pharyngeal was most common among Coloureds and showed an increasing trend during the period under review. CONCLUSIONS: Variations in the incidence of OAP cancers by gender, race/ethnicity and anatomic site indicate a need for culturally-targeted reductions in major risk factors, including promoting tobacco cessation and prevention of risky alcohol use. The implications of the role of the human papillomavirus (HPV) in the prevention of squamous cell carcinomas involving the oro-pharyngeal in South Africa require further investigation.The authors thank Patricia Kellet for her valuable support in extracting the data and the National Cancer Registry for making the data available.http://www.sada.co.zaam2013ay201

Surface-specific caries preventive effect of an intervention comprising fissure sealant, povidone-iodine and fluoride varnish in a remote Indigenous community in Australia

This study evaluates the effect of a topical intervention comprising of fissure sealant, povidone-iodine, and fluoride varnish in preventing caries on occlusal, approximal, and smooth surfaces. This three-year clinical trial was conducted in a remote Indigenous community of Australia. All schoolchildren (age range: 4-17) were invited to participate; those with parental consents to receive three-annual epidemiological examinations and interventions constituted the experimental group, while those with consents for only the epidemiological examination formed a comparison group. The intervention group received an annual application of fissure sealant, povidone-iodine and fluoride varnish for two consecutive years along with the restoration of any cavitated lesions, while the comparison group did not receive any intervention except for the usual care that included emergency treatment and restorations. Incipient and advanced caries were recorded in the permanent dentition while data on confounding variables were collected through questionnaires. Caries increment and progression were the outcome variables. A total of 408 children participated in the baseline examination, 208 finished the study. After adjusting for confounders, the prevented fraction (PF) on occlusal surfaces for advanced caries in the experimental group was 76.1% (mean difference- -0.35, 95% CI: -0.67-0.04), while the PF for progression from incipient to advanced caries was 100%(mean difference- -0.30, 95% CI: -0.52-0.09). The mean number of smooth surfaces that progressed from incipient to advanced caries in the comparison group was more than twice that of the experimental group, the mean difference was -0.25 (95% CI: -0.46--0.03) with a PF of 61%. The intervention was only effective in preventing advanced caries on occlusal surfaces and in halting the progression of caries on occlusal and smooth surfaces but not on approximal caries.Santosh K. Tadakamadla , Ratilal Lalloo, Jeroen Kroon and Newell W. Johnso

Carious lesions in permanent dentitions are reduced in remote Indigenous Australian children taking part in a non-randomised preventive trial

We tested the effect of an annual caries preventive intervention, delivered by a fly-in/fly-out oral health professional team, with Indigenous children residing in a remote Australian community. Around 600 Indigenous children aged 5 to 17 years were invited to participate at baseline, of who 408 had caregiver consent. One hundred and ninety-six consented to the epidemiological examination and intervention (Intervention group) and 212 consented to the epidemiological examination only (Comparison group). The intervention, which occurred annually, comprised placement of fissure sealants on suitable teeth, and application of povidone-iodine and fluoride varnish to the whole dentition, following completion of any necessary restorative dental treatment. Standard diet and oral hygiene advice were provided. Caries increment (number of tooth surfaces with new dental caries) in both deciduous and permanent dentitions was measured at the 2-year follow-up. Comparison group children had significantly higher number of new surfaces with advanced caries in the permanent dentition than the Intervention group (IRR = 1.61; 95% CI: 1.02-2.54; p = 0.04); with a preventive fraction of 43%. The effect of intervention remained significant with children in the Comparison group developing significantly more advanced caries lesions in the permanent dentition than the Intervention group children in the adjusted multivariable analysis (IRR = 2.21; 95% CI: 1.03-4.71). Indigenous children exposed to the intervention had less increment in advanced dental caries in the permanent dentition than those not exposed to the intervention.Ratilal Lalloo, Santosh K. Tadakamadla, Jeroen Kroon, Lisa M. Jamieson, Robert S. Ware, Newell W. Johnso

Response of salivary microbiota to caries preventive treatment in Aboriginal and Torres Strait Islander children

A once-annual caries preventive (Intervention) treatment was offered to Aboriginal and Torres Strait Islander schoolchildren—a population with disproportionately poorer oral health than non-Indigenous Australian children—in the Northern Peninsula Area (NPA) of Far North Queensland (FNQ), which significantly improved their oral health. Here, we examine the salivary microbiota of these children (mean age = 10 ± 2.96 years; n = 103), reconstructing the bacterial community composition with high-throughput sequencing of the V4 region of bacterial 16S rRNA gene. Microbial communities of children who received the Intervention had lower taxonomic diversity than those who did not receive treatment (Shannon, p < 0.05). Moreover, the Intervention resulted in further decreased microbial diversity in children with active carious lesions existing at the time of saliva collection. Microbial species associated with caries were detected; Lactobacillus salivarius, Lactobacillus reuteri, Lactobacillus gasseri, Prevotella multisaccharivorax, Parascardovia denticolens, and Mitsuokella HMT 131 were significantly increased (p < 0.05) in children with severe caries, especially in children who did not receive the Intervention. These insights into microbial associations and community differences prompt future considerations to the mechanisms behind caries-preventive therapy induced change; important for understanding the long-term implications of like treatment to improve oral health disparities within Australia.Emily Skelly, Newell W. Johnson, Kostas Kapellas, Jeroen Kroon, Ratilal Lalloo and Laura Weyric

Biocultural Drivers of Salivary Microbiota in Australian Aboriginal and Torres Strait Islander Children

Published: 18 March 2021.Australian Aboriginal and Torres Strait Islander children experience unacceptably high rates of dental caries compared to their non-Indigenous Australian counterparts. Dental caries significantly impacts the quality of life of children and their families, particularly in remote communities. While many socioeconomic and lifestyle factors impact caries risk, the central role of the oral microbiota in mediating dental caries has not been extensively investigated in these communities. Here, we examine factors that shape diversity and composition of the salivary microbiota in Aboriginal and Torres Strait Islander children and adolescents living in the remote Northern Peninsula Area (NPA) of Far North Queensland. We employed 16S ribosomal RNA amplicon sequencing to profile bacteria present in saliva collected from 205 individuals aged 4–17 years from the NPA. Higher average microbial diversity was generally linked to increased age and salivary pH, less frequent toothbrushing, and proxies for lower socioeconomic status (SES). Differences inmicrobial composition were significantly related to age, salivary pH, SES proxies, and active dental caries. Notably, a feature classified as Streptococcus sobrinus increased in abundance in children who reported less frequent tooth brushing. A specific Veillonella feature was associated with caries presence, while features classified as Actinobacillus/Haemophilus and Leptotrichia were associated with absence of caries; a Lactobacillus gasseri feature increased in abundance in severe caries. Finally, we statistically assessed the interplay between dental caries and caries risk factors in shaping the oral microbiota. These data provide a detailed understanding of biological, behavioral, and socioeconomic factors that shape the oral microbiota and may underpin caries development in this group. This information can be used in the future to improve tailored caries prevention and management optionsMatilda Handsley-Davis, Emily Skelly, Newell W. Johnson, Kostas Kapellas, Ratilal Lalloo, Jeroen Kroon, and Laura S. Weyric

Resonant transmission through an open quantum dot

We have measured the low-temperature transport properties of a quantum dot formed in a one-dimensional channel. In zero magnetic field this device shows quantized ballistic conductance plateaus with resonant tunneling peaks in each transition region between plateaus. Studies of this structure as a function of applied perpendicular magnetic field and source-drain bias indicate that resonant structure deriving from tightly bound states is split by Coulomb charging at zero magnetic field.Comment: To be published in Phys. Rev. B (1997). 8 LaTex pages with 5 figure

Stress response inside perturbed particle assemblies

The effect of structural disorder on the stress response inside three dimensional particle assemblies is studied using computer simulations of frictionless sphere packings. Upon applying a localised, perturbative force within the packings, the resulting {\it Green's} function response is mapped inside the different assemblies, thus providing an explicit view as to how the imposed perturbation is transmitted through the packing. In weakly disordered arrays, the resulting transmission of forces is of the double-peak variety, but with peak widths scaling linearly with distance from the source of the perturbation. This behaviour is consistent with an anisotropic elasticity response profile. Increasing the disorder distorts the response function until a single-peak response is obtained for fully disordered packings consistent with an isotropic description.Comment: 8 pages, 7 figure captions To appear in Granular Matte

Academic freedom: in justification of a universal ideal

This paper examines the justification for, and benefits of, academic freedom to academics, students, universities and the world at large. The paper surveys the development of the concept of academic freedom within Europe, more especially the impact of the reforms at the University of Berlin instigated by Wilhelm von Humboldt. Following from this, the paper examines the reasons why the various facets of academic freedom are important and why the principle should continue to be supported

Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV

We report the results of a study of color coherence effects in ppbar collisions based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8 TeV. Initial-to-final state color interference effects are studied by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters