1,721,002 research outputs found
Seroprevalence and determinants of herpes simplex type 2 infection in an STD clinic in Milan, Italy
No full textA number of studies have shown that the seroprevalence of herpes simplex virus type 2 (HSV-2) is higher among persons attending clinics for sexually transmitted diseases (STD) than among the general population. The HSV-2 seroprevalence among STD patients, however, varies greatly among studies, possibly reflecting differences in the baseline prevalence of the infection among different general populations or in the distribution of risk factors. A cross-sectional study was carried out to determine the seroprevalence of and the risk factors for HSV-2 infection among 776 HIV-negative persons attending an STD clinic in Milan, Italy. All samples were tested with a commercial HSV type-2 specific gG ELISA test. The HSV-2 seroprevalence was 29.5% (95% Cl: 26.3-32.7%). The seroprevalence increased with age, yet it did not differ by gender. Among persons with a current STD, the seroprevalence was 44.3%. At the multivariate analysis, older age was independently associated with HSV-2 infection. A self-reported history of genital herpes was predictive of HSV-2 infection. The agreement between history of genital herpes and HSV-2 seroprevalence was poor, however, stressing that in clinical practice, caution should be used in interpreting the presence or absence of a history of genital herpes as an indicator of the presence or absence of HSV-2 infection. Our data show that HSV-2 seroprevalence among persons attending an STD clinic in Italy is high; thus serological screening for HSV-2 might be advisable for STD patients
Dynamic Multilevel Methods for Simulation of Multiphase Flow in Heterogeneous Porous Media
No full textReservoir Engineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Multilevel Multiscale Method for Embedded Discrete Fracture Modeling Approach (F-MLMS)
No full textAccurate numerical simulations of multiphase flow in fractured porous media require high resolution grids to explicitly capture the effect of fractures on the flow field without using excessively up-scaled quantities (e.g., modified rock permeabilities). For field-scale applications, as the consequence of large-scale domains and many explicit fractures, the size of the (non)linear systems becomes out of the scope of the classical numerical methods. Thus, various advanced numerical methods have been introduced to reduce this computational challenge. The Embedded Discrete Fracture Model (EDFM) which employs sets of independent grids for the rock matrix and the fractures (represented as lower dimensional domains). By employing two separate grids, coupled by a transfer function, EDFM allows to avoid adapting the matrix grid to accommodate the presence of fractures. Therefore, computational complexities with respect to the fracture geometries are significantly reduced. Even after employing EDFM, the size of the systems for real-field applications is still too large to be solved accurately with classical solvers. This challenge motivates the development of Multiscale Finite Volume (MSFV) method, which is the focus of this work, as well. The MSFV method efficiently solves the pressure (flow) equations by solving it at a coarser resolution, while honoring the fine-scale heterogeneous data. Recently, an efficient MSFV method for EDFM approach (F-AMS) was developed and tested for many cases of practical interests. Even though the F-AMS was found efficient for many scenarios, its applicability is limited to only the use of 2 levels of grids (fine and coarse). For real-field applications, where there exist several millions (or billions) degrees of freedom, the construction of only 1 level of coarse grid resolution may not be sufficient. Of high interest to the community is the development of a multiscale method which allows for arbitrary number of accurate coarse resolutions. In this work, for the first time in the multiscale community, a novel multilevel multiscale finite volume method for fractured porous media (F-MLMS) is developed. F-MLMS is successfully applied to a set of synthetic 2D test cases and its performance is carefully studied. Employing a multilevel strategy becomes crucial for field-scale applications, where a single level of coarsening is not enough to reduce significantly the size of the linear systems to be solved. The use of two independent grids allows to employ different coarsening strategies for the two media. Consequently, F-MLMS represents an important step forward for the application of multiscale methods to naturally and induced fractured reservoirs, with complex fracture networks.Civil Engineering and GeosciencesGeoscience & EngineeringPetroleum Engineering and Geo-science
Efficient and accurate simulation of nonlinearly coupled multiphase flow in porous media
No full textIn this work, the non-linear behaviour of saturation transport equations in sequential implicit simulation strategy for multi-phase, immiscible and incompressible displacements are investigated. In reservoir simulation, use of explicit time schemes can lead to severe time-step size restrictions, specially when strong nonlinear terms exist. For highly heterogeneous formations, when a global time step needs to be taken, the CFL numbers can vary by orders of magnitude through the entire domain. In such cases, explicit schemes are not practical, and implicit time schemes are typically followed. The transport equation which describe the fluid flow in porous media in space and time are often highly non-linear and tightly coupled with the flow (pressure) equation. Characterized by S-shaped flux functions, they can also be non-monotone in presence of strong buoyancy (and capillary) forces. Through the phase velocities, which depend on pressure, the transport equation is strongly coupled to pressures equation. In presence of strong capillarity, the pressure solution also depends on the slope of capillary function, which is a function of saturation. An industry standard procedure is to use Newton method to first linearize these coupled governing equations, and iteratively reach a converged solution. To study the nonlinearity within the transport equation, first, a two-dimensional twophase simulator based on all types of Implicit Pressure Explicit Saturation (IMPES), Sequential Implicit, and Fully Implicit strategies are developed. Both capillary and gravitational effects are being considered. As to extend the stability limits of the sequential implicit strategy, flux correction method is investigated and implemented in the transport equation. All cases of viscous, buoyancy and capillary dominated flows are studied, where, in the cases of strong nonlinearities, non-convergence and severe time-step restrictions have been observed. Stability analysis of the flux functions in buoyancy and capillary dominated flows is performed along with a time-step control strategy, which is shown to result in unconditional convergence irrespective of the time-step size selection. Finally, application of flux correction strategies to EOR processes, where foam flows through the rock formation, is presented. Such a study has never been performed in the literature.Section for Petroleum EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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