490 research outputs found
Optical Coherence Tomography Features of Active and Inactive Retinal Neovascularization in Proliferative Diabetic Retinopathy
PURPOSE: To describe spectral domain-optical coherence tomography features of retinal neovascularization in proliferative diabetic retinopathy and thus to identify novel signs of new vessel activity.
METHODS: Retrospective, cross-sectional study. Data were collected over a 9-month period. Spectral domain optical coherence tomography scans were performed over areas of new vessel complexes (NVC) in both the disk and elsewhere, and were qualitatively graded by two masked observers. New vessel complexes activity was determined using clinical and angiographic criteria and correlated with spectral domain optical coherence tomography features.
RESULTS: Forty-three eyes of 30 patients with proliferative diabetic retinopathy were included. Sixty-one NVC lesions (neovascularization of the disk—37.7%, neovascularization elsewhere—62.3%) were captured by spectral domain-optical coherence tomography and analyzed. Among them, 63.9% were classified as active and 36.1% as quiescent. Five distinctive features were identified as significantly different between active and quiescent NVC: the presence of vitreous hyperreflective dots in active NVC (P = 0.002) and the presence of epiretinal membrane (P = 0.04), inner retinal tissue contracture (P = 0.03), vitreous invasion (P = 0.02), and protrusion towards vitreous (P = 0.002) in quiescent NVC.
CONCLUSION: In this exploratory study, the presence of vitreous hyperreflective dots, epiretinal membrane, inner retinal tissue contracture, vitreous invasion, and vitreous protrusion were identified as distinct signs of disease activity. Such parameters may be useful as a noninvasive imaging modality in eyes undergoing treatment for proliferative diabetic retinopathy
Protention and retention in biological systems
This paper proposes an abstract mathematical frame for describing some
features of cognitive and biological time. We focus here on the so called
"extended present" as a result of protentional and retentional activities
(memory and anticipation). Memory, as retention, is treated in some physical
theories (relaxation phenomena, which will inspire our approach), while
protention (or anticipation) seems outside the scope of physics. We then
suggest a simple functional representation of biological protention. This
allows us to introduce the abstract notion of "biological inertia".Comment: This paper was made possible only as part of an extended
collaboration with Francis Bailly (see references), a dear friend and
"ma\^itre \'a penser", who contributed to the key ideas. Francis passed away
in february 2008: we continue here our inspiring discussions and joint wor
Accurate masses and radii of normal stars: modern results and applications
This paper presents and discusses a critical compilation of accurate,
fundamental determinations of stellar masses and radii. We have identified 95
detached binary systems containing 190 stars (94 eclipsing systems, and alpha
Centauri) that satisfy our criterion that the mass and radius of both stars be
known to 3% or better. To these we add interstellar reddening, effective
temperature, metal abundance, rotational velocity and apsidal motion
determinations when available, and we compute a number of other physical
parameters, notably luminosity and distance. We discuss the use of this
information for testing models of stellar evolution. The amount and quality of
the data also allow us to analyse the tidal evolution of the systems in
considerable depth, testing prescriptions of rotational synchronisation and
orbital circularisation in greater detail than possible before. The new data
also enable us to derive empirical calibrations of M and R for single (post-)
main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff),
log g and [Fe/H] yield M and R with errors of 6% and 3%, respectively.
Excellent agreement is found with independent determinations for host stars of
transiting extrasolar planets, and good agreement with determinations of M and
R from stellar models as constrained by trigonometric parallaxes and
spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23
interferometric binaries with masses known to better than 3%, but without
fundamental radius determinations (except alpha Aur). We discuss the prospects
for improving these and other stellar parameters in the near future.Comment: 56 pages including figures and tables. To appear in The Astronomy and
Astrophysics Review. Ascii versions of the tables will appear in the online
version of the articl
Globally convergent evolution strategies for constrained optimization
International audienceIn this paper we propose, analyze, and test algorithms for constrained optimization when no use of derivatives of the objective function is made. The proposed methodology is built upon the globally convergent evolution strategies previously introduced by the authors for unconstrained optimization. Two approaches are encompassed to handle the constraints. In a first approach, feasibility is first enforced by a barrier function and the objective function is then evaluated directly at the feasible generated points. A second approach projects first all the generated points onto the feasible domain before evaluating the objective function.The resulting algorithms enjoy favorable global convergence properties (convergence to stationarity from arbitrary starting points), regardless of the linearity of the constraints.The algorithmic implementation (i) includes a step where previously evaluated points are used to accelerate the search (by minimizing quadratic models) and (ii) addresses the particular cases of bounds on the variables and linear constraints. Our solver is compared to others, and the numerical results confirm its competitiveness in terms of efficiency and robustness
Belongingness in early secondary school: Key factors that primary and secondary schools need to consider
© 2015 Vaz et al. It is unknown if, and how, students redefine their sense of school belongingness after negotiating the transition to secondary school. The current study used longitudinal data from 266 students with, and without, disabilities who negotiated the transition from 52 primary schools to 152 secondary schools. The study presents the 13 most significant personal student and contextual factors associated with belongingness in the first year of secondary school. Student perception of school belongingness was found to be stable across the transition. No variability in school belongingness due to gender, disability or household-socio-economic status (SES) was noted. Primary school belongingness accounted for 22% of the variability in secondary school belongingness. Several personal student factors (competence, coping skills) and school factors (low-level classroom task-goal orientation), which influenced belongingness in primary school, continued to influence belongingness in secondary school. In secondary school, effort-goal orientation of the student and perception of their school's tolerance to disability were each associated with perception of school belongingness. Family factors did not influence belongingness in secondary school. Findings of the current study highlight the need for primary schools to foster belongingness among their students at an early age, and transfer students' belongingness profiles as part of the handover documentation. Most of the factors that influenced school belongingness before and after the transition to secondary are amenable to change
Antimicrobial activity and bioactive compounds of portuguese wild edible mushrooms methanolic extracts
The antimicrobial properties of phenolic extracts of Portuguese wild edible mushroom species (Lactarius deliciosus,
Sarcodon imbricatus and Tricholoma portentosum)
against pathogens were investigated. The minimal inhibitory
concentrations (MICs) were evaluated for the entire mushroom,
the cap and the stipe, separately; the portion of the
mushroom used proved to be influenced in the results obtained,
which are directly correlated with the content of total
phenols and flavonoids in the extracts. The growth of Grampositive
bacteria (Bacillus cereus, B. subtilis,) was well inhibited
by these mushrooms, while Escherichia coli (Gramnegative
bacteria) was resistant. The study on the antifungal
effect of these mushrooms revealed that Candida albicans
and Cryptococcus neoformans were differently inhibited for
the mushrooms used
Depression in medical students: insights from a longitudinal study
Background: Factors associated with depression of medical students are poorly understood. The purpose of this study is to determine the prevalence of depression in medical students, its change during the course, if depression persists for affected students, what are the factors associated with depression and how these factors change over time.
Methods: A prospective, longitudinal observational study was conducted at the Medical School of the University of Minho, Portugal, between academic years 2009-2010 to 2012-2013. We included students who maintained their participation by annually completing a questionnaire including Beck Depression Inventory (BDI). Anxiety and burnout were assessed using the State Trait Anxiety Inventory and Maslach Burnout Inventory. Surveys on socio-demographic variables were applied to evaluate potential predictors, personal and academic characteristics and perceived difficulties. ANOVA with multiple comparisons were used to compare means of BDI score. The medical students were organized into subgroups by K-means cluster analyses. ANOVA mixed-design repeated measurement was performed to assess a possible interaction between variables associated with depression.
Results: The response rate was 84, 92, 88 and 81% for academic years 2009-2010, 2010-2011,2011-2012 and 2012/2013, respectively. Two hundred thirty-eight medical students were evaluated longitudinally. For depression the prevalence ranged from 21.5 to 12.7% (academic years 2009/2010 and 2012/2013). BDI scores decreased during medical school. 19.7% of students recorded sustained high BDI over time. These students had high levels of trait-anxiety and choose medicine for anticipated income and prestige, reported more relationship issues, cynicism, and decreased satisfaction with social activities. Students with high BDI scores at initial evaluation with low levels of trait-anxiety and a primary interest in medicine as a career tended to improve their mood and reported reduced burnout, low perceived learning problems and increased satisfaction with social activities at last evaluation. No difference was detected between men and women in the median BDI score over time.
Conclusions: Our findings suggest that personal factors (anxiety traits, medicine choice factors, relationship patterns and academic burnout) are relevant for persistence of high levels of BDI during medical training. Medical schools need to identity students who experience depression and support then, as early as possible, particularly when depression has been present over time.info:eu-repo/semantics/publishedVersio
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The HOSTS Survey for Exozodiacal Dust: Preliminary results and future prospects
[abridged] The presence of large amounts of dust in the habitable zones of
nearby stars is a significant obstacle for future exo-Earth imaging missions.
We executed an N band nulling interferometric survey to determine the typical
amount of such exozodiacal dust around a sample of nearby main sequence stars.
The majority of our data have been analyzed and we present here an update of
our ongoing work. We find seven new N band excesses in addition to the high
confidence confirmation of three that were previously known. We find the first
detections around Sun-like stars and around stars without previously known
circumstellar dust. Our overall detection rate is 23%. The inferred occurrence
rate is comparable for early type and Sun-like stars, but decreases from 71%
[+11%/-20%] for stars with previously detected mid- to far-infrared excess to
11% [+9%/-4%] for stars without such excess, confirming earlier results at high
confidence. For completed observations on individual stars, our sensitivity is
five to ten times better than previous results. Assuming a lognormal luminosity
function of the dust, we find upper limits on the median dust level around all
stars without previously known mid to far infrared excess of 11.5 zodis at 95%
confidence level. The corresponding upper limit for Sun-like stars is 16 zodis.
An LBTI vetted target list of Sun-like stars for exo-Earth imaging would have a
corresponding limit of 7.5 zodis. We provide important new insights into the
occurrence rate and typical levels of habitable zone dust around main sequence
stars. Exploiting the full range of capabilities of the LBTI provides a
critical opportunity for the detailed characterization of a sample of
exozodiacal dust disks to understand the origin, distribution, and properties
of the dust.GMK is supported by the Royal Society as a Royal Society University Research Fellow. AS is partially supported by funding from the Center for Exoplanets and Habitable Worlds. The Center for Exoplanets and
Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. JMS is supported by NASA through Hubble Fellowship grant HSTHF2-51398.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555
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