Revealing the secrets of composite helmets of ancient Japanese tradition

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Belief Propagation and Loop Series on Planar Graphs

We discuss a generic model of Bayesian inference with binary variables defined on edges of a planar graph. The Loop Calculus approach of [1, 2] is used to evaluate the resulting series expansion for the partition function. We show that, for planar graphs, truncating the series at single-connected loops reduces, via a map reminiscent of the Fisher transformation [3], to evaluating the partition function of the dimer matching model on an auxiliary planar graph. Thus, the truncated series can be easily re-summed, using the Pfaffian formula of Kasteleyn [4]. This allows to identify a big class of computationally tractable planar models reducible to a dimer model via the Belief Propagation (gauge) transformation. The Pfaffian representation can also be extended to the full Loop Series, in which case the expansion becomes a sum of Pfaffian contributions, each associated with dimer matchings on an extension to a subgraph of the original graph. Algorithmic consequences of the Pfaffian representation, as well as relations to quantum and non-planar models, are discussed.Comment: Accepted for publication in Journal of Statistical Mechanics: theory and experimen

Corneal Penetration of Polyhexamethylene Biguanide and Chlorhexidine Digluconate

Objective: Cationic antiseptics, such as polyhexamethylene biguanide (PHMB) and chlorhexidine digluconate (CHG), are widely used for the topical treatment of Acanthamoeba keratitis. The aim of this study was to investigate the corneal penetration of PHMB and CHG topically administered as eye drops and to study the effect of PHMB and CHG on the epithelial barrier function. Methods: The penetration was evaluated in vitro in rabbit corneas clamped in artificial perfusion chambers. Two different preparations of PHMB 0.02% (Cosmocil and Lavasept) and CHG 0.02% eye drops were administered twice each hour for up to 8 hours to the rabbit corneas with and without epithelium. The amount of drug penetrating into the anterior chamber was measured using capillary electrophoresis with contactless conductivity detection. The integrity of the epithelial barrier function was evaluated by adding fluorescein to the PHMB or CHG eye drops. The fluorescence of the anterior chamber perfusate was measured continuously throughout the experiment. Corneas treated with fluorescein alone (in either NaCl 0.9% or benzalkoniumchloride (BAC) eye drops) served as controls. Results: Neither PHMB nor CHG were detectable at any time in the anterior chamber perfusate of either the corneas with or without epithelium. PHMB and CHG treatment resulted in a minimal increase of fluorescein penetration as compared to the controls treated with 0.9% NaCl/0.05% fluorescein eye drops indicating a slight disruption of the epithelial barrier function caused by the biguanides. In contrast fluorescein penetration was much further enhanced when BAC 0.01% control eye drops were administered. Conclusion: This study showed that neither PHMB nor CHG readily penetrated through the cornea to the anterior chamber, which may explain why treatment of Acanthamoeba keratitis requires many months of sustained topical drug administration. PHMB and CHG had little effect on the epithelial barrier function compared to BAC, which is widely used as a preservative in eye drops

Multicentre multi-device hybrid imaging study of coronary artery disease: results from the EValuation of INtegrated Cardiac Imaging for the Detection and Characterization of Ischaemic Heart Disease (EVINCI) hybrid imaging population

Hybrid imaging provides a non-invasive assessment of coronary anatomy and myocardial perfusion. We sought to evaluate the added clinical value of hybrid imaging in a multicentre, multivendor setting. Fourteen centres enrolled 252 patients with stable angina and intermediate (20-90%) pre-test likelihood of coronary artery disease (CAD) who underwent myocardial perfusion scintigraphy (MPS), computed tomography coronary angiography (CTCA), and quantitative coronary angiography (QCA) with fractional flow reserve (FFR). Hybrid MPS/CTCA images were obtained by 3D image fusion. Blinded core-lab analyses were performed for CTCA, MPS, QCA, and hybrid data sets. Haemodynamically significant CAD was ruled-in non-invasively in the presence of a matched finding (myocardial perfusion defect co-localized with stenosed coronary artery) and ruled-out with normal findings (both CTCA and MPS normal). Overall prevalence of significant CAD on QCA (>70% stenosis or 30-70% with FFR ≤0.80) was 37%. Of 1004 pathological myocardial segments on MPS, 246 (25%) were reclassified from their standard coronary distribution to another territory by hybrid imaging. In this respect, in 45/252 (18%) patients, hybrid imaging reassigned an entire perfusion defect to another coronary territory, changing the final diagnosis in 42% of the cases. Hybrid imaging allowed non-invasive CAD rule-out in 41%, and rule-in in 24% of patients, with a negative and positive predictive value of 88 and 87%, respectively. In patients at intermediate risk of CAD, hybrid imaging allows non-invasive co-localization of myocardial perfusion defects and subtending coronary arteries, impacting clinical decision-making in almost one every five subjects