Statistical Uncertainties in Temperature Diagnostics for Hot Coronal Plasma Using the ASCA SIS

Statistical uncertainties in determining the temperatures of hot (0.5 keV to 10 keV) coronal plasmas are investigated. The statistical precision of various spectral temperature diagnostics is established by analyzing synthetic ASCA Solid-state Imaging Spectrometer (SIS) CCD spectra. The diagnostics considered are the ratio of hydrogen-like to helium-like line complexes of $Z\ge14$ elements, line-free portions of the continuum, and the entire spectrum. While fits to the entire spectrum yield the highest statistical precision, it is argued that fits to the line-free continuum are less susceptible to atomic data uncertainties but lead to a modest increase in statistical uncertainty over full spectral fits. Temperatures deduced from line ratios can have similar accuracy but only over a narrow range of temperatures. Convenient estimates of statistical accuracies for the various temperature diagnostics are provided which may be used in planning ASCA SIS observations.Comment: postscript file of 8 pages+3 figures; 4 files tarred, compressed and uuencoded. To appear in the Astrophysical Journal Letters; contents copyright 1994 American Astronomical Societ

A COMPARATIVE CORRELATIONAL STUDY OF GRADES SIX TO EIGHT STUDENTS’ PERCEPTUAL LEARNING STYLE PREFERENCE AND THEIR LEARNING ACHIEVEMENT AT PAN-ASIA INTERNATIONAL SCHOOL, THAILAND

The purpose of this study was to investigate the perceptual learning styles of the grades six to eight middle school students in Pan-Asia International School located in Bangkok, Thailand. This study was also to determine the preferred learning styles of the students and compare those learning styles with the students’ learning achievement. The research was conducted from December 14 to 16, 2015 in the first semester of the 2015-2016 academic school year at Pan-Asia International School. In this study, Reid’s Perceptual Learning Styles Questionnaire was used as the primary source of data collection. The data collected from the questionnaire was analyzed by Percentage & Frequency, Means & Standard Deviations, One Way ANOVA and Pearson Product – Moment Correlation Coefficient. This study found that the participants preferred group learning style followed by mixed, kinesthetic, individual & auditory, tactile and visual learning styles. There was no significant difference between the grade six to eight middle school students’ learning achievement, according to their most preferred learning style. The results of this study demonstrated that the grades six to eight middle school students did favor group projects as their most preferred learning style. There was no relationship between learning styles and learning achievement. Teachers should be aware of what learning styles are and how students are predetermined to prefer their own unique learning styles. Any teacher has their own methods of classroom instruction. Some teachers are aware of learning styles and can use learning styles to help with classroom engagement and higher student learning achievement. It is recommended that Pan-Asia International School uses current data to plan future professional development and school-wide changes in teacher instruction to help create a learning environment that best supports students’ learning styles

Driver vs. manager perceptions of commonly used safety practices in commercial motor vehicle operations

This research investigated the perceptions of Commercial Motor Vehicle Operators and Safety Professionals regarding 35 commonly implemented practices used to improve operating safety. Several differences were found in how drivers of different backgrounds rated various practices, and between the drivers and safety managers. These differences were found to be persistent even when combined with measures of safety performance and experience. Managers tended to overvalue (relative to drivers) practices related to hiring, while drivers tended to overvalue (relative to managers) practices related to company support and reward systems. Motor Carriers, insurers, and regulators could consider areas of agreement with respect to high value practices as actionable for increased investment of resources. At the same time, resources allocated toward areas of low perceived value could be reduced

Safety attitudes and behavioral intentions of municipal waste disposal drivers

The Theory of Planned Behavior was used to study factors useful for predicting Behavioral Intentions to commit unsafe acts while driving for commercial drivers working for municipal waste management operations centers. The Theory of Planned Behavior was found to be moderately effective in predicting behavioral intentions, particularly through the constructs of Attitude and Perceived Control. Driver perceptions of safety climate, self-assessed personal safety performance, risk aversion, and attitudes toward behavioral factors associated with engaging in risky behaviors while operating motor vehicles were studied. Risk aversion and driver perception of their own safety performance were also useful predictors of intention

Discovery of a 3.6-hr Eclipsing Luminous X-Ray Binary in the Galaxy NGC 4214

We report the discovery of an eclipsing X-ray binary with a 3.62-hr period within 24" of the center of the dwarf starburst galaxy NGC 4214. The orbital period places interesting constraints on the nature of the binary, and allows for a few very different interpretations. The most likely possibility is that the source lies within NGC 4214 and has an X-ray luminosity of up to 7 e38 ergs/s. In this case the binary may well be comprised of a naked He-burning donor star with a neutron-star accretor, though a stellar-mass black-hole accretor cannot be completely excluded. There is no obvious evidence for a strong stellar wind in the X-ray orbital light curve that would be expected from a massive He star; thus, the mass of the He star should be <3-4 solar masses. If correct, this would represent a new class of very luminous X-ray binary -- perhaps related to Cyg X-3. Other less likely possibilities include a conventional low-mass X-ray binary that somehow manages to produce such a high X-ray luminosity and is apparently persistent over an interval of years; or a foreground AM Her binary of much lower luminosity that fortuitously lies in the direction of NGC 4214. Any model for this system must accommodate the lack of an optical counterpart down to a limiting magnitude of 22.6 in the visible.Comment: 7 pages, ApJ accepted versio

Amygdala reactivity predicts adolescent antisocial behavior but not callous-unemotional traits.

Recent neuroimaging studies have suggested divergent relationships between antisocial behavior (AB) and callous-unemotional (CU) traits and amygdala reactivity to fearful and angry facial expressions in adolescents. However, little work has examined if these findings extend to dimensional measures of behavior in ethnically diverse, non-clinical samples, or if participant sex, ethnicity, pubertal stage, and age moderate associations. We examined links between amygdala reactivity and dimensions of AB and CU traits in 220 Hispanic and non-Hispanic Caucasian adolescents (age 11-15; 49.5% female; 38.2% Hispanic), half of whom had a family history for depression and thus were at relatively elevated risk for late starting, emotionally dysregulated AB. We found that AB was significantly related to increased right amygdala reactivity to angry facial expressions independent of sex, ethnicity, pubertal stage, age, and familial risk status for depression. CU traits were not related to fear- or anger-related amygdala reactivity. The present study further demonstrates that AB is related to increased amygdala reactivity to interpersonal threat cues in adolescents, and that this relationship generalizes across sex, ethnicity, pubertal stage, age, and familial risk status for depression

Chandra Contaminant Migration Model

High volatility cleans OBFs and low volatility produces a high build-up at OBF centers; only a narrow (factor of 2 or less) volatility range produces the observed spatial pattern. Simulations predict less accumulation above outer S-array CCDs; this may explain, in part, gratings/imaging C/MnL discrepancies. Simulations produce a change in center accumulation due solely to DH heater ON/OFF temperature change; but a 2nd contaminant and perhaps a change in source rate is also required. Emissivity E may depend on thickness; another model parameter. Additional physics, e.g., surface migration, is not warranted at this time. At t approx. 14 yrs, model produced 0.22 grams of contaminant, 0.085 grams remaining within ACIS cavity; 7 percent (6mg) on OBFs

On the Short-Period Eclipsing High-Mass X-ray Binary in NGC 4214

We present the results of our study of the luminous (L_{X} ~ 10^{39} erg/s) X-ray binary CXOU J121538.2+361921 in NGC 4214, the high mass X-ray binary with the shortest known orbital period. Using Chandra data, we confirm the ~13,000 s (3.6 hr) eclipse period, and an eclipse duration of ~2000 s. From this, we estimate a mass ratio M_2/M_1 >~ 3 and a stellar density of about 6 g cm^{-3}, which implies that the donor must be a Wolf-Rayet or a stripped Helium star. The eclipse egress is consistently much slower than the ingress. This can be explained by denser gas located either in front of the compact object (as expected for a bow shock) or trailing the donor star (as expected for a shadow wind, launched from the shaded side of the donor). There is no change in X-ray spectral shape with changing flux during the egress, which suggests either variable partial covering of the X-ray source by opaque clumps or, more likely, a grey opacity dominated by electron scattering in a highly ionized medium. We identify the optical counterpart from Hubble images. Photometry blueward of ~5500 Ang indicates a bright (M_{B} = -3.6 +/- 0.3 mag, for a range of plausible extinctions), hot (T = 90,000 +/- 30,000 K) emitter, consistent with the Wolf-Rayet scenario. There is also a bright (M_{I} ~ -5.2 mag), cool (T = 2700 +/- 300 K) component consistent with an irradiated circumbinary disk or with a chance projection of an unrelated asymptotic giant branch star along the same line of sight.Comment: 20 pages, 4 MB, accepted for publication in Ap