1,720,971 research outputs found
Three-dimensional numerical analysis of steady state pumping tests in heterogeneous confined aquifers
No full textWe study three-dimensional steady state flow field generated by a fully penetrating well extracting a constant water discharge from a confined aquifer of constant thickness. The hydraulic conductivity K is modeled as an axisymmetric, stationary random space function, and the flow equation is solved by using the seven-node finite volume numerical scheme. In view of application in aquifer characterization we analyze how the equivalent conductivity K-eq varies as a function of the distance from the extraction well. The numerical simulations showed that the boundary condition at the well exerts a large impact on K-eq and that the first-order solution in sigma(Y)2 obtained by Indelman et al. (1996) is valid up to sigma(2)(Y) = 0.5. For higher values of sigma(2)(Y) the first-order solution overestimates K-eq with differences that for a given sigma(2)(Y), reduce progressively as the formation becomes more anisotropic. A simple inverse procedure based on K-eq, obtained through cross-well interference, is finally proposed and tested with the objective of estimating the parameters of the geostatistical model of variability of the hydraulic conductivity. A few parametric examples showed that a suitable interpretation of pumping tests can be used to safely estimate parameters such as the geometric mean of the hydraulic conductivity, its variance, and, although with larger uncertainty, the horizontal integral scale, while the inference of the anisotropy ratio is highly uncertain and error prone
A Simple Method for Quantitative Assessment of Suction Drains
No full textAbstract: Suction drains are widely used in surgical practice, but a consensus is yet to be found around their use in plastic surgery. Nowadays, patients are frequently discharged from hospitals with drains still in place. Soft drains are easier to manage at home because of the reduced weight and size. The content can be disposed of when the container is full, but volume assessment is only possible when the reservoir is inflated. Evaluating the total drained volume alone is a flawed assessment method, as it might lead to erroneously decide whether a drain should be kept or removed. What we should use as a reference instead is the output quantity from the last 24 h. We can precisely determine the amount of collected material on a daily basis by closing the clip of the tubing, opening the exit valve to inflate the container, measuring and then emptying the container. However, this whole process can be complicated and put the sterile environment at risk of contamination, which is why it cannot be performed by the patient at home. We ask our patients to weigh the container daily using a kitchen scale and to write down the obtained values. When the patient returns for a postoperative checkup, they can report their measurements, thus making it easier for the surgeon to decide whether to remove the drain or not. We believe that this simple method can be safely implemented to track drains in the postoperative period after the patient is discharged. Level of Evidence V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266
The superficial vein-only DIEP flap
No full textWe read with interest this retrospective investigation by Nigro et al.,1 although we find that the conclusion is insufficiently supported. While discussing the results, the authors mention that “these values are not significantly different”; they refer to a statistical analysis by means of the t test, but do not present any P values
EFFECTIVE CONDUCTIVITY OF RANDOM MULTIPHASE 2D MEDIA WITH POLYDISPERSE CIRCULAR INCLUSIONS RID A-2321-2010
No full textThe effective conductivity Kef of porous formations of spatially variable permeability K is determined for media of random two-dimensional and isotropic structures. The medium is modeled as an ensemble of multiphase circular inclusions of different Y = ln K, characterized by a pdf f(Y), and of different radii R (polydisperse medium), of pdf f(R vertical bar Y), which are implanted in a matrix of K = K(0). A large number of inclusions are embedded in a large circle, to allow for exchange of space and ensemble averaging. For symmetrical pdf f(Y) = f(-Y) and symmetrical f(R vertical bar Y), the Matheron exact relationship K(ef) = KG (the geometric mean) applies. The main aim of the article is to determine the deviation of K(ef) from K(G) for symmetrical f(Y) but nonsymmetrical f(R vertical bar Y). This is related to recent studies on the effect on Kef of connectivity of spatial domains of different K classes. The problem is solved numerically by an accurate and efficient iterative procedure and by a novel, approximate, analytical method. The two procedures are illustrated and compared for the configuration of two phases of conductivities K(1), K(2), of equal volume fractions, of different radii R(1) and R(2), respectively, within a matrix of K(0) = K(G) = (K(1) K(2))(1/2). Even for very high heterogeneity (K(1)/K(2) = 1000) it is found that the effect of variable R is relatively modest and it manifests mainly at the largest attainable volume fraction. The simple analytical approximation, valid for moderate volume fractions, is applied to investigation of K(ef) for normal f(Y), and for two values of R, for Y 0 and Y > 0, respectively. The results are of interest for similar heterogeneous media and for other physical processes governed by linear relationships between the flux and the driving potential gradient
Limitations of estimating BIA-ALCL incidence risk using implant sales data and the Italian National Breast Implant Registry
No full textattempt to determine the BIA-ALCL
incidence risk (IR), however, the described methods raise
major concerns. The authors’ first aim is to provide a new
reliable method to estimate the Breast Implanted Population (BIP). To do so, they use an indirect method based on
four variables: number of Breast Implants (BI) sold/
year; purpose (aesthetic/reconstructive); number of
implanted patients stratified by purpose; time to
revision
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
- …
