447 research outputs found
Inferring individual attributes from search engine queries and auxiliary information
Internet data has surfaced as a primary source for investigation of different
aspects of human behavior. A crucial step in such studies is finding a suitable
cohort (i.e., a set of users) that shares a common trait of interest to
researchers. However, direct identification of users sharing this trait is
often impossible, as the data available to researchers is usually anonymized to
preserve user privacy. To facilitate research on specific topics of interest,
especially in medicine, we introduce an algorithm for identifying a trait of
interest in anonymous users. We illustrate how a small set of labeled examples,
together with statistical information about the entire population, can be
aggregated to obtain labels on unseen examples. We validate our approach using
labeled data from the political domain.
We provide two applications of the proposed algorithm to the medical domain.
In the first, we demonstrate how to identify users whose search patterns
indicate they might be suffering from certain types of cancer. In the second,
we detail an algorithm to predict the distribution of diseases given their
incidence in a subset of the population at study, making it possible to predict
disease spread from partial epidemiological data
Cross-cultural Research
Edited by Matthias R. Mehl, Tamlin S. Conner</p
Concerns of Female Adolescents About Menarche and First Sexual Intercourse: Mixed Methods Analysis of Social Media Questions
Background: Adolescents use social media for information on medical and social aspects of maturation.
Objective: The aim of this study was to investigate the concerns and information needs of adolescents regarding menarche and first sexual intercourse.
Methods: Questions about menarche or first sexual intercourse were obtained from Yahoo Answers, a community-based social media question-and-answer website. A total of 1226 questions were analyzed. We focused on 123 question pairs made by users who asked questions on both topics and reported their ages at each. Quantitative and qualitative analyses were performed on these question pairs.
Results: Qualitative analysis identified uncertainty as a significant theme for both menarche and first intercourse. Quantitative analysis showed that uncertainty was expressed in 26% (13/50) of menarche questions and 14% (7/50) of intercourse questions. Lack of communication was expressed in 4% (2/50) of menarche questions, compared with 8% (4/50) of intercourse questions. Ages at menarche and at first sexual intercourse were correlated, with women reporting menarche at the age of 13 years or younger being 2.6 times more likely to experience first sexual intercourse before the age of 16 years (PP=.002).
Conclusions: The questions of adolescents on the topics of menarche and first sexual intercourse express anxiety and uncertainty and are associated with a lack of information and deficient communication with parents. The more normative and expected a behavior, the less these factors appear. Therefore, parents and educators should, to the extent possible, improve communication around these topics, especially when they occur at less typical ages
Generation of Large-Scale Vorticity in a Homogeneous Turbulence with a Mean Velocity Shear
An effect of a mean velocity shear on a turbulence and on the effective force
which is determined by the gradient of Reynolds stresses is studied. Generation
of a mean vorticity in a homogeneous incompressible turbulent flow with an
imposed mean velocity shear due to an excitation of a large-scale instability
is found. The instability is caused by a combined effect of the large-scale
shear motions (''skew-induced" deflection of equilibrium mean vorticity) and
''Reynolds stress-induced" generation of perturbations of mean vorticity.
Spatial characteristics, such as the minimum size of the growing perturbations
and the size of perturbations with the maximum growth rate, are determined.
This instability and the dynamics of the mean vorticity are associated with the
Prandtl's turbulent secondary flows. This instability is similar to the
mean-field magnetic dynamo instability. Astrophysical applications of the
obtained results are discussed.Comment: 8 pages, 3 figures, REVTEX4, submitted to Phys. Rev.
Large-scale instability in a sheared nonhelical turbulence: formation of vortical structures
We study a large-scale instability in a sheared nonhelical turbulence that
causes generation of large-scale vorticity. Three types of the background
large-scale flows are considered, i.e., the Couette and Poiseuille flows in a
small-scale homogeneous turbulence, and the "log-linear" velocity shear in an
inhomogeneous turbulence. It is known that laminar plane Couette flow and
antisymmetric mode of laminar plane Poiseuille flow are stable with respect to
small perturbations for any Reynolds numbers. We demonstrate that in a
small-scale turbulence under certain conditions the large-scale Couette and
Poiseuille flows are unstable due to the large-scale instability. This
instability causes formation of large-scale vortical structures stretched along
the mean sheared velocity. The growth rate of the large-scale instability for
the "log-linear" velocity shear is much larger than that for the Couette and
Poiseuille background flows. We have found a turbulent analogue of the
Tollmien-Schlichting waves in a small-scale sheared turbulence. A mechanism of
excitation of turbulent Tollmien-Schlichting waves is associated with a
combined effect of the turbulent Reynolds stress-induced generation of
perturbations of the mean vorticity and the background sheared motions. These
waves can be excited even in a plane Couette flow imposed on a small-scale
turbulence when perturbations of mean velocity depend on three spatial
coordinates. The energy of these waves is supplied by the small-scale sheared
turbulence.Comment: 12 pages, 14 figures, Phys. Rev. E, in pres
The Incompatibility of Materialism and the Desire for Children: Psychological Insights into the Fertility Discrepancy Among Modern Countries
Singapore Management University Office of Researc
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