Maximal Abelian Sets of Roots

In this work we let Φ be an irreducible root system, with Coxeter group W. We consider subsets of Φ which are abelian, meaning that no two roots in the set have sum in Φ∪{0}. We classify all maximal abelian sets (i.e., abelian sets properly contained in no other) up to the action of W: for each W-orbit of maximal abelian sets we provide an explicit representative X, identify the (setwise) stabilizer W_X of X in W, and decompose X into W_X-orbits. Abelian sets of roots are closely related to abelian unipotent subgroups of simple algebraic groups, and thus to abelian p-subgroups of finite groups of Lie type over fields of characteristic p. Parts of the work presented here have been used to confirm the p-rank of E_8(p^n), and (somewhat unexpectedly) to obtain for the first time the 2-ranks of the Monster and Baby Monster sporadic groups, together with the double cover of the latter. Root systems of classical type are dealt with quickly here; the vast majority of the present work concerns those of exceptional type. In these root systems we introduce the notion of a radical set; such a set corresponds to a subgroup of a simple algebraic group lying in the unipotent radical of a certain maximal parabolic subgroup. The classification of radical maximal abelian sets for the larger root systems of exceptional type presents an interesting challenge; it is accomplished by converting the problem to that of classifying certain graphs modulo a particular equivalence relation

Collaboration and teamwork: immersion and presence in an online learning environment

In the world of OTIS, an online Internet School for occupational therapists, students from four European countries were encouraged to work collaboratively through problem-based learning by interacting with each other in a virtual semi-immersive environment. This paper describes, often in their own words, the experience of European occupational therapy students working together across national and cultural boundaries. Collaboration and teamwork were facilitated exclusively through an online environment, since the students never met each other physically during the OTIS pilot course. The aim of the paper is to explore the observations that here was little interaction between students from different tutorial groups and virtual teamwork developed in each of the cross-cultural tutorial groups. Synchronous data from the students was captured during tutorial sessions and peer-booked meetings and analysed using the qualitative constructs of ‘immersion’, ‘presence’ and ‘reflection in learning’. The findings indicate that ‘immersion’ was experienced only to a certain extent. However, both ‘presence’ and shared presence were found by the students, within their tutorial groups, to help collaboration and teamwork. Other evidence suggests that communities of interest were established. Further study is proposed to support group work in an online learning environment. It is possible to conclude that collaborative systems can be designed, which encourage students to build trust and teamwork in a cross cultural online learning environment.</p

Ovarian metabolism of xenobiotics

At birth, the mammalian ovary contains a finite number of primordial follicles, which once depleted, cannot be replaced. Xenobiotic exposures can destroy primordial follicles resulting in premature ovarian failure and, consequently, early entry into menopause. A number of chemical classes can induce premature ovarian failure, including environmental, chemotherapeutic and industrial exposures. While our knowledge on the mechanistic events that occur in the ovary with chemical exposures is increasing, our understanding of the ovary\u27s capacity to metabolize such compounds is less established. This review will focus on three chemicals for which information on ovarian metabolism is known: trichloroethylene, 7,12-dimethylbenz[a]anthracene and 4- vinylcyclohexene. The current state of understanding of ovarian bioactivation and detoxification processes for each will be described

Flavan-3-ol-methylxanthine interactions: Modulation of flavan-3-ol bioavailability in volunteers with a functional colon and an ileostomy

Flavan-3-ols, including the flavan-3-ol monomer (-)-epicatechin, are dietary bioactives known to mediate beneficial cardiovascular effects in humans. Recent studies showed that flavan-3-ols could interact with methylxanthines, evidenced by an increase in flavan-3-ol bioavailability with a concomitant increase in flavan-3-ol intake-mediated vascular effects. This study aimed at elucidating flavan-3-ol-methylxanthine interactions in humans in vivo by evaluating the specific contributions of theobromine and caffeine on flavan-3-ol bioavailability. In ileostomists, the effect of methylxanthines on the efflux of flavan-3-ol metabolites in the small intestine was assessed, a parameter important to an understanding of the pharmacokinetics of flavan-3-ols in humans. In a randomized, controlled, triple cross-over study in volunteers with a functional colon (n = 10), co-ingestion of flavan-3-ols and cocoa methylxanthines, mainly represented by theobromine, increased peak circulatory levels (C ) of flavan-3-ols metabolites (+21 ± 8%; p &lt; 0.05). Conversely, caffeine did not mediate a statistically significant effect on flavan-3-ol bioavailability (C = +10 ± 8%, p = n.s.). In a subsequent randomized, controlled, double cross-over study in ileostomists (n = 10), cocoa methylxanthines did not affect circulatory levels of flavan-3-ol metabolites, suggesting potential differences in flavan-3-ol bioavailability compared to volunteers with a functional colon. The main metabolite in ileal fluid was (-)-epicatechin-3'-sulfate, however, no differences in flavan-3-ol metabolites in ileal fluid were observed after flavan-3-ol intake with and without cocoa methylxanthines. Taken together, these results demonstrate a differential effect of caffeine and theobromine in modulating flavan-3-ol bioavailability when these bioactives are co-ingested. These findings should be considered when comparing the effects mediated by the intake of flavan-3-ol-containing foods and beverages and the amount and type of methylxanthines present in the ingested matrixes. Ultimately, these insights will be of value to further optimize current dietary recommendations for flavan-3-ol intake. CLINICAL TRIAL REGISTRATION NUMBER: This work was registered at clinicaltrials.gov as NCT03526107 (study part 1, volunteers with functional colon) and NCT03765606 (study part 2, volunteers with an ileostomy). [Abstract copyright: Copyright © 2023 Elsevier Inc. All rights reserved.

Intergroup struggles over victimhood in violent conflict: The victim-perpetrator paradigm

Most groups in violent, intergroup conflict perceive themselves to be the primary or sole victims of that conflict. This often results in contention over who may claim victim status and complicates a central aim of post-conflict processes, which is to acknowledge and address harms experienced by the victims. Drawing from victimology scholarship and intergroup relations theory, this article proposes the victim-perpetrator paradigm as a framework to analyse how, why and to what end groups in conflict construct and maintain their claims to the moral status of victim. This interdisciplinary paradigm builds on the knowledge that groups utilise the ‘ideal victim’ construction to exemplify their own innocence and blamelessness in contrast to the wickedness of the perpetrator, setting the two categories as separate and mutually exclusive even where experiences of violence have been complex. Additionally, this construction provides for a core intergroup need to achieve positive social identity, which groups may enhance by demonstrating a maximum differentiation between the in-group as victims and those out-groups identified as perpetrators. The paradigm contributes greater knowledge on the social roots of victim contention in conflict, as well as how groups legitimise their violence against out-groups during and after conflict

Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy

Background A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets. Methods Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis. Results A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001). Conclusion We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty