Effect of salt on the compression of polyelectrolyte brushes in a theta solvent

Classical strong-stretching theory (SST) predicts that, as opposing polyelectrolyte brushes are compressed together in a salt-free theta solvent, they contract so as to maintain a finite polymer-free gap, which offers a potential explanation for the ultra-low frictional forces observed in experiments even with the application of large normal forces. However, the SST ignores chain fluctuations, which would tend to close the gap resulting in physical contact and in turn significant friction. In a preceding study, we examined the effect of fluctuations using self-consistent field theory (SCFT) and illustrated that high normal forces can still be applied before the gap is destroyed. We now look at the effect of adding salt. It is found to reduce the long-range interaction between the brushes but has little effect on the short-range part, provided the concentration does not enter the salted-brush regime. Consequently, the maximum normal force between two planar brushes at the point of contact is remarkably unaffected by salt. For the crossed-cylinder geometry commonly used in experiments, however, there is a gradual reduction because in this case the long-range part of the interaction contributes to the maximum normal force.

A review of vertebroplasty for osteoporotic and malignant vertebral compression fractures

Vertebral compression fractures are a common clinical problem and the incidence of them will increase with the ageing population. Traditionally management has been conservative; however, there has been a growing trend towards vertebroplasty as an alternative therapy in patients with persisting severe pain. NICE produced guidance in 2003 recommending the procedure after 4 weeks of conservative management. Recent high-quality studies have been contradictory and there is currently a debate surrounding the role of the procedure with no agreement in the literature. We examine the evidence in both osteoporotic and malignant vertebral compression fractures; we also describe the benefits and side effects, alternative treatment options and the cost of the procedure. Finally, we recommend when vertebroplasty is most appropriately used based on the best available evidence.

Les variations formelles d'un moule stylistique: rubrique, texte et image à la charnière du Merlin et de sa Suite Vulgate

Le passage du Merlin propre à sa Suite Vulgate, espace de suture entre le texte et sa continuation est dans la tradition manuscrite l'objet de variances et de déplacements. A la paix annoncée à la fin du Merlin succède en effet le conflit qui oppose le jeune roi Arthur à ses barons. Les passages de rubrication et d'entrelacement sont le lieu privilégié de variations formelles gommées par l'adoption et la reprise de moules stylistiques attendus. Ceux-ci exhibent tout en les masquant de subtiles divergences relevant de partis pris à la fois narratifs, interprétatifs et idéologiques.

Le rêve du roi Flualis : mise en texte et mise en image d'enjeux épiques et hagiographiques dans le Roman de Merlin

L'illustration de la plupart des manuscrits de la Suite Vulgate met l'accent sur l'intervention prophétique de Merlin et sur l'accomplissement des désastres qu'il annonce au roi de Jérusalem Flualis, replaçant l'épisode dans une série de passages où Merlin fait la démonstration de ses pouvoirs surnaturels et de sa capacité à interpréter les songes. Pourtant, dans un petit groupe d'ouvrages, l'illustration se focalise sur la conversion ultime de Flualis et de sa femme, insistant sur le caractère exemplaire et édifiant d'un épisode qui propose une résolution des relations entre païens et chrétiens différente de celles habituellement mises en scène dans l'univers à coloration épique de la continuation.

An approximate dynamic programming approach for improving accuracy of lossy data compression by Bloom filters

Bloom filters are a data structure for storing data in a compressed form. They offer excellent space and time efficiency at the cost of some loss of accuracy (so-called lossy compression). This work presents a yes-no Bloom filter, which as a data structure consisting of two parts: the yes-filter which is a standard Bloom filter and the no-filter which is another Bloom filter whose purpose is to represent those objects that were recognised incorrectly by the yes-filter (that is, to recognise the false positives of the yes-filter). By querying the no-filter after an object has been recognised by the yes-filter, we get a chance of rejecting it, which improves the accuracy of data recognition in comparison with the standard Bloom filter of the same total length. A further increase in accuracy is possible if one chooses objects to include in the no-filter so that the no-filter recognises as many as possible false positives but no true positives, thus producing the most accurate yes-no Bloom filter among all yes-no Bloom filters. This paper studies how optimization techniques can be used to maximize the number of false positives recognised by the no-filter, with the constraint being that it should recognise no true positives. To achieve this aim, an Integer Linear Program (ILP) is proposed for the optimal selection of false positives. In practice the problem size is normally large leading to intractable optimal solution. Considering the similarity of the ILP with the Multidimensional Knapsack Problem, an Approximate Dynamic Programming (ADP) model is developed making use of a reduced ILP for the value function approximation. Numerical results show the ADP model works best comparing with a number of heuristics as well as the CPLEX built-in solver (B&B), and this is what can be recommended for use in yes-no Bloom filters. In a wider context of the study of lossy compression algorithms, our researchis an example showing how the arsenal of optimization methods can be applied to improving the accuracy of compressed data.

Endogenous wage compression and aggregation boundaries in a model of hierarchical human capital

en_US

Extrinsic compression of popliteal artery in asymptomatic athlete and non-athlete individuals - A comparative study using duplex scan (color duplex sonography)

Aim. Extrinsic compression of the popliteal artery and absence of surrounding anatomical abnormalities characterize the functional popliteal artery entrapment syndrome (PAES). The diagnosis is confirmed to individuals who have typical symptoms of popliteal entrapment and occlusion or important stenosis of the popliteal artery with color duplex sonography (CDS), magnetic resonance imaging (MRI) or arteriography during active plantar flexion-extension maneuvers. However, variable result findings in normal asymptomatic subjects have raised doubts as to the validity of these tests. The purpose of this study was to compare the frequency of popliteal artery compression in 2 groups of asymptomatic subjects, athletes and non-athletes.Methods. Forty-two individuals were studied. Twenty-one subjects were indoor soccer players, and 21 were sedentary individuals. Physical activity was evaluated through questionnaires, anthropometric measurements, and cardiopulmonary exercise test. Evaluation of popliteal artery compression was performed in lower limbs with CDS, ankle-brachial index (ABI) measurements and continuous wave Doppler of the posterior tibial artery.Results. The athletes studied fulfilled the criteria of high level of physical activity whereas sedentary subjects met the criteria of low level of activity. Popliteal artery compression was observed with CDS in 6 (14.2%) studied subjects; 2 of whom (4.7%) were athletes and 4 (9.5%) were non-athletes. This difference was not statistically significant (p=0.21). Doppler of the tibial arteries and ABI measurements gave good specificity and sensibility in the identification of popliteal artery compression.Conclusion. The frequency of popliteal artery compression during maneuvers in normal subjects was 14.2% irrespective of whether or not they performed regular physical activities. Both Doppler and ABI showed good agreement with CDS and should be considered in screening popliteal arteries in individuals suspected of PAES.

Histomorphometric evaluation of periodontal compression and tension sides during orthodontic tooth movement in rats

OBJECTIVE: The purpose of this study was to evaluate the thickness of the periodontal ligament of rat molars during orthodontic tooth movement (OTM). METHODS: Thirty Wistar rats were divided into three groups of 10 animals each: GI, GII and GIII and the mice were euthanized at 7, 14 and 21 days, respectively. Experimental subjects were compared to their respective controls by the Mann-Whitney test. Comparison of values between compression and tension sides were performed during the same and different time periods through Analysis of Variance (ANOVA), Kruskal-Wallis test and, subsequently, Tukey's test. RESULTS: Groups GI and GII showed decreased PDL size in the apical regions of the mesiobuccal root and in the cervical region of the distobuccal root. There was also an increased PDL in the cervical regions of the mesiobuccal root, apical region of the distobuccal root and middle region of both roots. CONCLUSION: The reduction and increase in PDL size were seen in the same root, which characterizes tooth inclination. The apical, middle and cervical regions were compared with one another in each time period and at three times: 7, 14 and 21 days. They were also compared in each region, confirming a tipping movement in GI and GII and a gradual decreased intensity between GI to GII, reaching normal dimension in GIII.