Enumeration of distinct mechanically stable disk packings in small systems

We create mechanically stable (MS) packings of bidisperse disks using an algorithm in which we successively grow or shrink soft repulsive disks followed by energy minimization until the overlaps are vanishingly small. We focus on small systems because this enables us to enumerate nearly all distinct MS packings. We measure the probability to obtain a MS packing at packing fraction $\phi$ and find several notable results. First, the probability is highly nonuniform. When averaged over narrow packing fraction intervals, the most probable MS packing occurs at the highest $\phi$ and the probability decays exponentially with decreasing $\phi$. Even more striking, within each packing-fraction interval, the probability can vary by many orders of magnitude. By using two different packing-generation protocols, we show that these results are robust and the packing frequencies do not change qualitatively with different protocols.Comment: 4 pages, 3 figures, Conference Proceedings for X International Workshop on Disordered System

Diffusion of peroxides through dentine in vitro with and without prior use of a desensitizing varnish

Different bleaching regimens are used in dentistry possibly penetrating the dentine and affecting the pulp. The aim of the present study was to investigate peroxide diffusion through dentine pre-treated with a desensitizing varnish (Vivasens®) in a standardized in vitro setup during application of different bleaching materials. The penetration was tested using 1.3-mm-thick bovine dentine slabs. The following bleaching materials were tested with and without prior application of the desensitizing varnish on the external side of the dentine slabs: Vivastyle, Whitestrips, Simply White, Opalescence (external bleaching), and sodium perborate (internal bleaching, only tested without varnish; n = 8 samples per subgroup). The penetration of peroxides was measured photometrically using 4-aminoantipyrin as a substrate, the penetration of peroxides was monitored over 240 min. All bleaching agents yielded a diffusion of peroxides through the dentine, the kinetics of penetration were approximately linear for all materials tested. The significantly highest diffusion of peroxides was observed with Opalescence, the lowest with sodium perborate. The adoption of the desensitizing varnish reduced the diffusion of peroxides significantly for all external bleaching materials. Peroxides penetrated the dentine during application of bleaching materials; the penetration of peroxides can be reduced by application of a desensitizing agent

Maximizing the general success of cecal intubation during propofol sedation in a multi-endoscopist academic centre

<p>Abstract</p> <p>Background</p> <p>Achieving the target of 95% colonoscopy completion rate at centres conducting colorectal screening programs is an important issue. Large centres and teaching hospitals employing endoscopists with different levels of training and expertise risk achieving worse results. Deep sedation with propofol in routine colonoscopy could maximize the results of cecal intubation.</p> <p>Methods</p> <p>The present study on the experience of a single centre focused on estimating the overall completion rate of colonoscopies performed under routine propofol sedation at a large teaching hospital with many operators involved, and on assessing the factors that influence the success rate of the procedure and how to improve this performance, analyzing the aspects relating to using of deep sedation. Twenty-one endoscopists, classified by their level of specialization in colonoscopic practice, performed 1381 colonoscopies under deep sedation. All actions needed for the anaesthesiologist to restore adequate oxygenation or hemodynamics, even for transient changes, were recorded.</p> <p>Results</p> <p>The "crude" overall completion rate was 93.3%. This finding shows that with routine deep sedation, the colonoscopy completion rate nears, but still does not reach, the target performance for colonoscopic screening programs, at centers where colonoscopists of difference experience are employed in such programs.</p> <p>Factors interfering with cecal intubation were: inadequate colon cleansing, endoscopists' expertise in colonoscopic practice, patients' body weight under 60 kg or age over 71 years, and the need for active intervention by the anaesthesiologist. The most favourable situation - a patient less than 71 years old with a body weight over 60 kg, an adequate bowel preparation, a "highly experienced specialist" performing the test, and no need for active anaesthesiological intervention during the procedure - coincided with a 98.8% probability of the colonoscopy being completed.</p> <p>Conclusions</p> <p>With routine deep sedation, the colonoscopy completion rate nears the target performance for colonoscopic screening programs, at centers where colonoscopists of difference experience are employed in such programs. Organizing the daily workload to prevent negative factors affecting the success rate from occurring in combination may enable up to 85% of incomplete procedures to be converted into successful colonoscopies.</p