Performance analysis of polling systems with retrials and glue periods

We consider gated polling systems with two special features: (i) retrials, and (ii) glue or reservation periods. When a type-$i$ customer arrives, or retries, during a glue period of station $i$, it will be served in the next visit period of the server to that station. Customers arriving at station $i$ in any other period join the orbit of that station and retry after an exponentially distributed time. Such polling systems can be used to study the performance of certain switches in optical communication systems. For the case of exponentially distributed glue periods, we present an algorithm to obtain the moments of the number of customers in each station. For generally distributed glue periods, we consider the distribution of the total workload in the system, using it to derive a pseudo conservation law which in its turn is used to obtain accurate approximations of the individual mean waiting times. We also consider the problem of choosing the lengths of the glue periods, under a constraint on the total glue period per cycle, so as to minimize a weighted sum of the mean waiting times

P202 Crohn’s disease extent and small bowel inflammatory activity: Results of a small bowel capsule endoscopy study

Abstract Background Small bowel capsule endoscopy (SBCE) enables the direct visualisation of the entire small bowel (SB) mucosa and the application of the Lewis score allows the reliable assessment of the SB mucosal inflammatory activity in Crohn’s disease (CD) patients. The study aim was to investigate the association of disease location, extent and inflammatory activity in CD patients with the use of SBCE Methods Retrospective study of 80 consecutive patients with an established CD that underwent SBCE in the Gastroenterology Department of the University Hospital of Ioannina between January 2007 and October 2019, for the evaluation of disease extent and disease activity. Results Fifty-one patients had evidence of endoscopic disease activity. In 30 of these patients (58.8%), the disease was located in the ileum and proximal SB, whereas in 20 patients (39.2%) the disease was located solely in the terminal ileum. In one patient (2%) treated with adalimumab, the disease was located solely in the jejunum. Eight patients (15.7%) had evidence of disease activity in the upper GI. All patients with upper GI disease activity demonstrated proximal SB disease involvement. The median Lewis score in patients with proximal CD was 1350 (mean 1666.3; Std 1343) median) against 458 (mean 1548,6; Std 1751) in patients with disease located in the ileum (p = 0.10). Conclusion In our study, proximal small bowel disease involvement was present in &amp;gt;50% of CD patients. Upper GI involvement was associated with extensive SB disease. Patients with proximal SB CD demonstrated a higher median Lewis score compared with those with CD located solely in the terminal ileum. </jats:sec

A queueing system with linear repeated attempts, bernoulli schedule and feedback

Embedded Markov chain, ergodicity, steady-state distribution, stochastic decomposition, Bernoulli feedback, 60K25,

The Inflammatory Bowel Disease—Disk Tool for Assessing Disability in Inflammatory Bowel Disease Patients: Validation of the Greek Version

Background: The Inflammatory Bowel Disease-Disk (IBD-Disk) is a physician-administered tool that evaluates the functional status of patients with Inflammatory Bowel Disease (IBD). The aim of our study was to validate the content of the IBD-Disk in a Greek cohort of IBD patients. Methods: Two questionnaires [the IBD Disk and the IBD-Disability Index (IBD-DI)] were translated into Greek and administered to IBD patients at baseline visit, after 4 weeks and 6 months. Validation of the IBD Disk included measuring of concurrent validity, reproducibility, and internal consistency. Results: A total of 300 patients were included at baseline and 269 at follow-up. There was a good correlation between the total scores of the IBD-Disk and IBD-DI at baseline (Pearson correlation 0.87, p &lt; 0.001). Reproducibility of the total IBD-Disk score was very good [intra-class correlation coefficient (ICC), 95% confidence interval (CI) 0.89 (0.86–0.91)]. Cronbach’s coefficient alpha for all items achieved 0.90 (95%CI 0.88–0.92), demonstrating a very good homogeneity of the IBD-Disk items. Female gender and extraintestinal manifestations were significantly associated with a higher IBD-Disk total score. Conclusions: The Greek version of the IBD-Disk proved to be a reliable and valid tool in detecting and assessing IBD-related disability in a Greek cohort of IBD patients. © 2023 by the authors