Search results for "Sampling"
showing 10 items of 788 documents
Exact simulation of first exit times for one-dimensional diffusion processes
2019
International audience; The simulation of exit times for diffusion processes is a challenging task since it concerns many applications in different fields like mathematical finance, neuroscience, reliability horizontal ellipsis The usual procedure is to use discretization schemes which unfortunately introduce some error in the target distribution. Our aim is to present a new algorithm which simulates exactly the exit time for one-dimensional diffusions. This acceptance-rejection algorithm requires to simulate exactly the exit time of the Brownian motion on one side and the Brownian position at a given time, constrained not to have exit before, on the other side. Crucial tools in this study …
Potencialidades de Google Maps en la investigación social aplicada
2019
In recent years, Google has devoted resources to build a complete map of the world. They constantly scan the territory, collecting a large amount of data that provides updated and complete geographic information. This allows us to have an interoperable map that provides the end user with a search tool, not only of routes but also of shops, equipment and any type of geo-referenced information. In addition, Google Maps provides a series of Application Programming Interface (API), which provides a library of set of subroutines, functions and procedures (in object-oriented programming) that can be used by other software to automate the extraction of information of the Google platform. These fre…
Estrogen levels in premenopausal (prem) patients (pts) with hormone-receptor positive (HR+) early breast cancer (BC) receiving adjuvant triptorelin (…
2014
585 Background: Optimal endocrine therapy for prem pts with early HR+ BC may depend on complete estrogen suppression with GnRH-A, and is crucial for those receiving concurrent aromatase inhibitors (AI). SOFT-EST is a prospective substudy of the phase III SOFT trial. Aims of SOFT-EST are to describe estradiol (E2), estrone (E1) and estrone sulphate (E1S) during monthly Trip + E or T and to assess if there is a group in E+Trip with suboptimal estrogen suppression (SES). Methods: All pts enrolled in SOFT from selected centers who consented, selected Trip as ovarian function suppression method and were randomized to E+Trip or T+Trip were enrolled in SOFT-EST until reaching the accrual goal (E=9…
Positivity rates and performances of immunochemical faecal occult blood tests at different cut-off levels within a colorectal cancer screening progra…
2012
Abstract Background Immunochemical faecal occult blood tests have greater sensitivity for colorectal cancer screening than guaiac-based tests; however the number of positive tests required is still under discussion. Methods A direct comparison of Hemoccult II with two immunochemical quantitative tests (OC-Sensor and FOB-Gold) using a 2-sample strategy was performed in over 30,000 patients undergoing colorectal cancer screening in France. Results Positivity ratio between immunochemical tests and Hemoccult II varied between 2.2 (OC-Sensor) and 2.4 (FOB-Gold) for the lowest cut-off value and 1.5–1.4 for the highest cut-off value. The positive predictive value for colorectal cancer was similar …
Ausgeprägte Virilisierung in der Postmenopause - eine Falldarstellung
2005
Severe postmenopausal virilization is a rare event in clinical practice. To evaluate ovarian or adrenal hyperandrogenism endocrine tests and imaging are useful diagnostic tools. We report a case of a postmenopausal woman with hirsutism and androgenetic alopecia. A malignant cause for the present disorder could be excluded by imaging. Selective venous sampling was administered with increased testosterone level of the right adrenal vein. Right adrenalectomy and right oophorctomy was recommended.
Can antepartum computerized cardiotocography predict the evolution of intrapartum acid-base status in normal fetuses?
2004
Background. To study the relationship between antepartum computerized cardiotocography (cCTG) and the evolution of intrapartum fetal acid-base balance in a low-risk population. Methods. Forty-nine healthy fetuses were prospectively followed up by antepartum cCTG (Oxford System 8002), fetal scalp blood sampling at the onset of the active phase of dilatation (3 cm) and at the beginning of the second stage of labor (10 cm) and study of acid-base status at birth in the umbilical cord. Correlation studies and linear regression analysis were performed. Results. Normal prelabor cCTG was followed by normal fetal acid-base balance in the different study periods. No relationship was found between cCT…
Enhanced sampling in simulations of dense systems
2002
In the simulations of a variety of systems we encounter the problem of large relaxation times due to the dense packing of the systems constituents. We propose an algorithm to overcome this slowing down by temporarily allowing the constituents of a 3d systems to escape into a 4th space coordinate. The idea will be exemplified for the problem of a homopolymer collapse.
Drivers for human papillomavirus vaccination in Valencia (Spain)
2018
Objective: To describe the drivers associated with HPV vaccination in adolescent girls and their parent's opinion on the vaccine. Methods: We conducted an observational and cross-sectional study on adolescent girls and their parents in Valencia (Spain), between September 2011 and June 2012. A consultation was made at a random sample of schools of the 14-year-old girls that should have received the vaccine in the free vaccination programme. We ran a personal survey on knowledge and attitudes regarding HPV infection and the vaccine. A binary logistic regression model was performed to determine which factors were most associated with vaccination. Results: The survey was run on a binomial of 1,…
Avoiding Boundary Effects in Wang-Landau Sampling
2003
A simple modification of the ``Wang-Landau sampling'' algorithm removes the systematic error that occurs at the boundary of the range of energy over which the random walk takes place in the original algorithm.
Physical and hydraulic characterization of a clay soil at the plot scale
2010
Summary The soil physical and hydraulic properties have to be determined for interpreting and simulating many hydrological processes. An investigation was carried out to determine the physical and hydraulic characteristics of a clay soil at the plot scale. An intensive sampling of the surface soil layer of two plots of 4 × 11 m2 was carried out by measuring, for each plot, dry soil bulk density, ρb, and antecedent soil water content, θi, at 88 sampling points and field-saturated soil hydraulic conductivity, Kfs, at 176 sampling points. A wide range of Kfs values (0.7–5107 mm h−1) were measured by the Simplified Falling Head (SFH) technique. For each variable, the two plots yielded very simi…