361 research outputs found
Influence of luminance and resolution on the perceived quality of black-and-white images on soft displays
The perceived quality of an image displayed on a computer monitor depends on a number of different factors that can affect viewers' preferences. Two of these are the luminance of the monitor display and the resolution of the image. The effect of luminance is of interest for applications such as on-line access of images where the computer displays used for viewing these images could have different luminance settings. A relationship between cathode-ray tube (CRT) display luminance and resolution has been shown in previous studies. It was therefore interesting to investigate whether there is a relationship between image resolution and CRT display luminance on perceived image quality. Image resolution is related to the image file size, which is an important factor for applications such as on-line access of images. This work used a CRT display to study the effect of the above-mentioned factors on the perceived quality of the displayed image. Three sets of black-and-white images, each set with a different resolution, were presented to observers at three brightness settings of the computer monitor. Results are discussed regarding the effect of monitor display luminance and image resolution on perceived image quality and the interaction between them. Evaluation of results is further extended to the influence of the different backgrounds of the images. The scene content of the images was also shown to affect the viewers' judgement
Effect of Plasma Composition on the Interpretation of Faraday Rotation
Faraday rotation (FR) is widely used to infer the orientation and strength of
magnetic fields in astrophysical plasmas. Although the absence of
electron-positron pairs is a plausible assumption in many astrophysical
environments, the magnetospheres of pulsars and black holes and their
associated jets may involve a significant pair plasma fraction. This motivates
being mindful of the effect of positrons on FR. Here we derive and interpret
exact expressions of FR for a neutral plasma of arbitrary composition. We focus
on electron-ion-positron plasmas in which charge neutrality is maintained by an
arbitrary combination of ions and positrons. Because a pure electron-positron
plasma has zero FR, the greater the fraction of positrons the higher the field
strength required to account for the same FR. We first obtain general formulae
and then specifically consider parameters relevant to active galctic nuclei
(AGN) jets to illustrate the significant differences in field strengths that FR
measurements from radio frequency measurements. Complementarily, using galaxy
cluster core plasmas as examples, we discuss how plasma composition can be
constrained if independent measurements of the field strength and number
density are available and combined with FR.Comment: Submitted to MNRA
Just noticeable gamma differences and acceptability of sRGB images displayed on a CRT monitor
The standard RGB colour space (sRGB) has been proposed as a means for
obtaining accurate reproduction of colour and tone for images displayed across the Internet, provided that they are viewed under the reference display and viewing conditions defined in the standard. It has been found, however, that typical display and viewing conditions when accessing online images vary and therefore deviate from the reference sRGB conditions. One of the parameters that may affect the perceived quality of online images is the gamma setting of the display. In this work psychophysical experiments were conducted to determine the imperceptibility and acceptability of gamma differences of sRGB images when they are viewed on cathode ray tube displays. These experiments were carried out under both controlled and uncontrolled display and viewing conditions. The results of these experiments are presented and discussed, including the estimated points of subjective equality and the just noticeable difference of gamma values
Multifrequency VLBA Monitoring of 3C 273 during the INTEGRAL Campaign in 2003 - I. Kinematics of the Parsec Scale Jet from 43 GHz Data
In this first of a series of papers describing polarimetric multifrequency
Very Long Baseline Array (VLBA) monitoring of 3C 273 during a simultaneous
campaign with the INTEGRAL gamma-ray satellite in 2003, we present 5 Stokes I
images and source models at 7 mm. We show that a part of the inner jet (1-2
milliarcseconds from the core) is resolved in a direction transverse to the
flow, and we analyse the kinematics of the jet within the first 10 mas. Based
on the VLBA data and simultaneous single-dish flux density monitoring, we
determine an accurate value for the Doppler factor of the parsec scale jet, and
using this value with observed proper motions, we calculate the Lorentz factors
and the viewing angles for the emission components in the jet. Our data
indicates a significant velocity gradient across the jet with the components
travelling near the southern edge being faster than the components with more
northern path. We discuss our observations in the light of jet precession model
and growing plasma instabilities.Comment: Accepted for publication in Astronomy & Astrophysics, 16 pages, 15
figure
Adequacy of Maternal Iron Status Protects against Behavioral, Neuroanatomical, and Growth Deficits in Fetal Alcohol Spectrum Disorders
Fetal alcohol spectrum disorders (FASD) are the leading non-genetic cause of neurodevelopmental disability in children. Although alcohol is clearly teratogenic, environmental factors such as gravidity and socioeconomic status significantly modify individual FASD risk despite equivalent alcohol intake. An explanation for this variability could inform FASD prevention. Here we show that the most common nutritional deficiency of pregnancy, iron deficiency without anemia (ID), is a potent and synergistic modifier of FASD risk. Using an established rat model of third trimester-equivalent binge drinking, we show that ID significantly interacts with alcohol to impair postnatal somatic growth, associative learning, and white matter formation, as compared with either insult separately. For the associative learning and myelination deficits, the ID-alcohol interaction was synergistic and the deficits persisted even after the offsprings’ iron status had normalized. Importantly, the observed deficits in the ID-alcohol animals comprise key diagnostic criteria of FASD. Other neurobehaviors were normal, showing the ID-alcohol interaction was selective and did not reflect a generalized malnutrition. Importantly ID worsened FASD outcome even though the mothers lacked overt anemia; thus diagnostics that emphasize hematological markers will not identify pregnancies at-risk. This is the first direct demonstration that, as suggested by clinical studies, maternal iron status has a unique influence upon FASD outcome. While alcohol is unquestionably teratogenic, this ID-alcohol interaction likely represents a significant portion of FASD diagnoses because ID is more common in alcohol-abusing pregnancies than generally appreciated. Iron status may also underlie the associations between FASD and parity or socioeconomic status. We propose that increased attention to normalizing maternal iron status will substantially improve FASD outcome, even if maternal alcohol abuse continues. These findings offer novel insights into how alcohol damages the developing brain
Support with caveats: advocates’ views of the Theory of Formal Discipline as a reason for the study of advanced mathematics
The Theory of Formal Discipline (TFD) suggests that studying mathematics improves general thinking skills. Empirical evidence for the TFD is sparse, yet it is cited in policy reports as a justification for the importance of mathematics in school curricula. The study reported in this article investigated the extent to which influential UK advocates for mathematics agree with the TFD and their views on the arguments and evidence that surround it. Quantitative and qualitative analysis of data from structured interviews revealed four themes: broad endorsement of the TFD; reference to supportive employment data; the possibilities that mathematics education might not always effectively develop reasoning and that study of other subjects might have similar effects; and concerns about causality and the extent of the evidence base. We conclude that advocates broadly support the TFD despite being aware of its limitations
Resonant Kelvin-Helmholtz modes in sheared relativistic flows
Qualitatively new aspects of the (linear and non-linear) stability of sheared
relativistic (slab) jets are analyzed. The linear problem has been solved for a
wide range of jet models well inside the ultrarelativistic domain (flow Lorentz
factors up to 20; specific internal energies ). As a distinct
feature of our work, we have combined the analytical linear approach with
high-resolution relativistic hydrodynamical simulations, which has allowed us
i) to identify, in the linear regime, resonant modes specific to the
relativistic shear layer ii) to confirm the result of the linear analysis with
numerical simulations and, iii) more interestingly, to follow the instability
development through the non-linear regime. We find that very high-order
reflection modes with dominant growth rates can modify the global, long-term
stability of the relativistic flow. We discuss the dependence of these resonant
modes on the jet flow Lorentz factor and specific internal energy, and on the
shear layer thickness. The results could have potential applications in the
field of extragalactic relativistic jets.Comment: Accepted for publication in Physical Review E. For better quality
images, please check
http://www.mpifr-bonn.mpg.de/staff/mperucho/Research.htm
Firearm Safety, Gun Violence and Chicago Families: Voices of Child Health in Chicago Report
Chicago has seen continuing firearm violence, with over 2,000 shooting victims so far in 2021. The epidemic of firearm violence impacts children across the state, as it remains the number one cause of death in children and youth across Illinois. In some of our previous reports, Chicago parents identified gun violence as their top social concern for kids in the city, and in recent years, they reported it was the main social problem getting worse the fastest for Chicago youth. In this month's Voices of Child Health in Chicago Report, we focus on the importance of firearm safety and parents' concerns about gun violence in the city. We asked 1,505 Chicago parents from all 77 community areas in the city about their experiences with firearm safety as well as other gun violence prevention and concern-related questions.
Faraday rotation in the MOJAVE blazars: 3C 273 a case study
Radio polarimetric observations of Active Galactic Nuclei can reveal the
magnetic field structure in the parsec-scale jets of these sources. We have
observed the gamma-ray blazar 3C 273 as part of our multi-frequency survey with
the Very Long Baseline Array to study Faraday rotation in a large sample of
jets. Our observations re-confirm the transverse rotation measure gradient in
3C 273. For the first time the gradient is seen to cross zero which is further
indication for a helical magnetic field and spine-sheath structure in the jet.
We believe the difference to previous epochs is due to a different part of the
jet being illuminated in our observations.Comment: 6 pages, 3 figures. To appear in the proceedings of "Beamed and
Unbeamed Gamma-rays from Galaxies", held in Muonio, Finland, April 11-15,
2011. Journal of Physics: Conference Serie
Assessment and Revision of Clinical Pharmacy Practice Internet Websites
Background:
Health care professionals, trainees, and patients use the Internet extensively. Editable Web sites may contain inaccurate, incomplete, and/or outdated information that may mislead the public’s perception of the topic.
Objective:
To evaluate the editable, online descriptions of clinical pharmacy and pharmacist and attempt to improve their accuracy.
Methods:
The authors identified key areas within clinical pharmacy to evaluate for accuracy and appropriateness on the Internet. Current descriptions that were reviewed on public domain Web sites included: (1) clinical pharmacy and the clinical pharmacist, (2) pharmacy education, (3) clinical pharmacy and development and provision for reimbursement, (4) clinical pharmacists and advanced specialty certifications/training opportunities, (5) pharmacists and advocacy, and (6) clinical pharmacists and interdisciplinary/interprofessional content. The authors assessed each content area to determine accuracy and prioritized the need for updating, when applicable, to achieve consistency in descriptions and relevancy. The authors found that Wikipedia, a public domain that allows users to update, was consistently the most common Web site produced in search results.
Results:
The authors’ evaluation resulted in the creation or revision of 14 Wikipedia Web pages. However, rejection of 3 proposed newly created Web pages affected the authors’ ability to address identified content areas with deficiencies and/or inaccuracies.
Conclusions:
Through assessing and updating editable Web sites, the authors strengthened the online representation of clinical pharmacy in a clear, cohesive, and accurate manner. However, ongoing assessments of the Internet are continually needed to ensure accuracy and appropriateness
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