Power geometry in nonlinear partial differential equations

Power Geometry (PG) is a new calculus developing the differential calculus and aimed at nonlinear problems. The main concept of PG is the study of nonlinear problems in logarithms of original coordinates. Then many relations nonlinear in the original coordinates become linear. The algorithms of PG are based on these linear relations. They allow to simplify equations, to resolve their singularities (including singular perturbations), to isolate their first approximations, and to find asymptotic forms and asymptotic expansions of their solutions. In particular, they give simple methods to identify the equations and systems as quasihomogeneous, and then to introduce for them self-similar coordinates. As an application, we consider the stationary spatial axially symmetric flow of the viscous compressible heat conducting gas around a semi-infinite needle. Other application: finding blow-up solutions

Expansions of solutions to the equation P₁² by algorithms of power geometry

Algorithms of Power Geometry allow to find all power expansions of solutions to ordinary differential equations of a rather general type. Among these, there are Painlev´e equations and their generalizations. In the article we demonstrate how to find by these algorithms all power expansions of solutions to the equation P₁² at the points z = 0 and z = ∞. Two levels of the exponential additions to the expansions of solutions near z = ∞ are computed. We also describe an algorithm of computation of a basis of a minimal lattice containing a given set

Inflation and Holography in String Theory

The encoding of an inflating patch of space-time in terms of a dual theory is discussed. Following Bousso's interpretation of the holographic principle, we find that those are generically described not by states in the dual theory but by density matrices. We try to implement this idea on simple deformations of the AdS/CFT examples, and an argument is given as to why inflation is so elusive to string theory.Comment: 15 pages, LaTeX, 2 figures. Uses psbox.te

Screening for head and neck second primary tumors in patients with esophageal squamous cell cancer: A systematic review and meta-analysis

Background: Esophageal squamous cell carcinomas (ESCCs) are often accompanied by head and neck second primary tumors (HNSPTs). The prognosis of patients with an additional HNSPT is worse compared with patients with only ESCC. Therefore, early detection of HNSPTs may improve the overall outcome of patients with ESCC. The purpose of this study was to investigate the yield of endoscopic screening for HNSPTs in patients with primary ESCC. Methods: We conducted a systematic literature search of all available databases. Studies were included if ESCC patients were endoscopically screened for HNSPT. The primary outcome was the pooled prevalence of HNSPTs. Results: Twelve studies, all performed in Japan, were included in this systematic review with a total of 6483 patients. The pooled prevalence of HNSPTs was 6.7% (95% confidence interval: 4.9–8.4). The overall heterogeneity was high across the studies (I 2 ¼ 89.0%, p < 0.001). Most HNSPTs were low stage (85.3%) and located in the hypopharynx (60.3%). The proportion of synchronous (48.2%) and metachronous (51.8%) HNSPTs was comparable. Conclusion: Based on our results, HNSPT screening could be considered in patients with primary ESCC. All studies were performed in Japan; it is therefore not clear whether this consideration applies to the Western world

Reflection of electrons from a domain wall in magnetic nanojunctions

Electronic transport through thin and laterally constrained domain walls in ferromagnetic nanojunctions is analyzed theoretically. The description is formulated in the basis of scattering states. The resistance of the domain wall is calculated in the regime of strong electron reflection from the wall. It is shown that the corresponding magnetoresistance can be large, which is in a qualitative agreement with recent experimental observations. We also calculate the spin current flowing through the wall and the spin polarization of electron gas due to reflections from the domain wall.Comment: 7 pages, 4 figure

"Spice", "Kryptonite", "Black Mamba": An overview of brand names and marketing stragtegies of Novel Psychoactive Substances on the Web

Novel Psychoactive Substances (NPSs) are often sold online as “legal” and “safer” alternatives to International Controlled Drugs (ICDs) with captivating marketing strategies. Our aim was to review and summarize such strategies in terms of the appearance of the products, the brand names, and the latest trends in the illicit online marketplaces. Methods: Scientific data were searched in PsychInfo and Pubmed databases; results were integrated with an extensive monitoring of Internet (websites, online shops, chat rooms, fora, social networks) and media sources in nine languages (English, French, Farsi, Portuguese, Arabic, Russian, Spanish, and Chinese simplified/traditional) available from secure databases of the Global Public Health Intelligence Network. Results: Evolving strategies for the online diffusion and the retail of NPSs have been identified, including discounts and periodic offers on chosen products. Advertisements and new brand names have been designed to attract customers, especially young people. An increased number of retailers have been recorded as well as new Web platforms and privacy systems. Discussion: NPSs represent an unprecedented challenge in the field of public health with social, cultural, legal, and political implications.Web monitoring activities are essential for mapping the diffusion of NPSs and for supporting innovative Web-based prevention programmes.Peer reviewedSubmitted Versio

Face and construct validity of a novel mechanical ERCP simulator

__Background__ and study aims Simulation-based training has become an important pillar in competence-based medicine. However, limited data are available on use of simulators in training for endoscopic retrograde cholangiopancreatography (ERCP). We aimed to determine the face and construct validity of the Boškoski-Costamagna mechanical ERCP Trainer, and to assess its didactic value, as judged by experts. Methods Participants were divided into four groups based on ERCP lifetime experience: novices, intermediate, experienced, and experts. Participants performed several standardized assignments on the simulator. Outcome parameters included times to complete the procedure, ability to cannulate both ducts, number of attempts to cannulate the common bile duct and pancreatic duct, number of inadvertent pancreatic duct cannulations, successful stent placement, and successful stone extraction. All experts filled out a questionnaire on the simulator’s realism and didactic value. Results Novices (n = 11) completed the total procedure in 21:09 (min:sec), intermediates (n = 5) in 10:58, experienced (n = 8) in 06:42 and experts (n = 22) in 06:05. Experts were significantly faster than novices (Kruskal-Wallis test P < 0.000). Experts rated the realism of the simulator 7.12 on a 10-point Likert scale. The simulator’s potential as a tool for training novices was rated 3.91 on a four-point Likert scale, and there was a high agreement among experts to include the simulator in the training of novice endoscopists (3.86 on a four-point Likert scale). Conclusions The novel Boškoski-Costamagna ERCP simulator demonstrates good face and construct validity. ERCP experts highly agree on the didactic value and added value of this simulator in the training curriculum for novice endoscopists

A rapid staining technique for the detection of the initiation of germination of bacterial spores

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75645/1/j.1472-765x.2002.01047.x.pd

Face validity of a synthetic papilla designed for biliary sphincterotomy training

Background and study aims Endoscopic retrograde cholangiopancreatography (ERCP) is considered one of the most technically demanding endoscopic procedures. Still, limited data are available on simulators in ERCP training. Recently, the Boškoski-Costamagna ERCP Trainer was validated as a realistic training model by our study group. As an extension to this model, a novel synthetic papilla has been designed allowing to train biliary sphincterotomy. We aimed to determine the face validity of this synthetic papilla and its didactic value for training sphincterotomy. Methods Expert participants, each with more a than 2500 ERCPs lifetime experience, were invited to perform a biliary sphincterotomy and fill out a questionnaire on the realism of the procedure and the didactic value. Results A total of 40 ERCP experts were included, originating from 16 different countries. Experts’ opinion on realism of performing a biliary sphincterotomy was rated with a median of 7 on a 10-point Likert scale, resemblance of the performed maneuvers 8 and tactile feedback 7. When asked if the cutting was perceived as realistic, experts rated a 6 and the cutting result was rated 8. Th

Effectiveness of topical budesonide in preventing esophageal strictures after endoscopic resection of esophageal cancer

Background and study aims A disadvantage of endoscopic resection (ER) of early esophageal cancer (EC) is the high stricture rate after resection. A risk factor for stricture development is a mucosal defect after ER of ≥ 75 % of the esophageal circumference. Stricture rates up to 94 % have been reported in these patients. The aim of this stu