Nonperiodic Optical Flickering In Hz Herculis

NASA NGR 44-012-209NSF GP-25901, GP-41796Astronom

Tangible Teaching: The Effect of Physical Modeling on Community College Students’ Understanding of Conservation of Matter

Students’ weak understanding of conservation of matter is well documented; however, there is a paucity of research that provides science educators with actual examples of empirically proven curricula employing physical modeling that can be used in the chemistry classroom to teach this fundamental concept. An intervention (three sequential physical modeling activities) was developed and evaluated. The intervention was administered to two sections of a General Chemistry I course at a community college in the southeastern United States, and pre-test/post-test data using a published instrument were collected to evaluate the physical model’s effectiveness in developing students’ understanding of conservation of matter compared to traditional teaching approaches. Because cognitive ability is theorized to play a significant role in understanding abstract concepts such as conservation of matter, student logical thinking ability was also measured using the abbreviated Group Assessment of Logical Thinking (GALT). The results of a two-way mixed analysis of variance (2x2 ANOVA) revealed that statistically significant growth in understanding of conservation of matter and conceptual understanding occurred from pre-test to post-test for the treatment group only. In general, overall student understanding of conservation of matter was low with an average pre-test score of 39% and average post-test score of 47%. Initially, 87% of the students operated below the formal operational level, which decreased to 68% by the end of the study. The findings suggest that the physical model not only significantly enhanced students’ understanding of conservation of matter, but also develop their conceptual understanding

Self-consistent modelling of the polar thermosphere and ionosphere to magnetospheric convection and precipitation (invited review)

It has recently been demonstrated that the dramatic effects of plasma precipitation and convection on the composition and dynamics of the polar thermosphere and ionosphere include a number of strong interactive, or feedback, processes. To aid the evaluation of these feedback processes, a joint three dimensional time dependent global model of the Earth's thermosphere and ionosphere was developed in a collaboration between University College London and Sheffield University. This model includes self consistent coupling between the thermosphere and the ionosphere in the polar regions. Some of the major features in the polar ionosphere, which the initial simulations indicate are due to the strong coupling of ions and neutrals in the presence of strong electric fields and energetic electron precipitation are reviewed. The model is also able to simulate seasonal and Universal time variations in the polar thermosphere and ionospheric regions which are due to the variations of solar photoionization in specific geomagnetic regions such as the cusp and polar cap

A search for X-rays from UV Ceti flare stars

A search of MIT/OSO-7 data was made for evidence of X-ray emission from flares of UV Ceti flare stars. Observations from McDonald Observatory were used to identify the times of optical flares. The only instance of coincident coverage occurred on 1974 January 21 UT at 03:43:26 GMT for delta m(u)=0.86 flare of YZ CMi. No radio coverage of this particular event was obtained. Upper limits (3 sigma) of 0.8, 1.0, and 0.7 photons/sq cm-sec on the observed X-ray flux were set for the energy ranges greater than or approximately equal to 15, greater than or approximately equal to 3, and 1-10 keV, respectively

Brightness Distribution in Discrete Radio Sources III. The Structure of the Sources

The visibility functions of 195 radio sources are interpreted in terms of the structure of these sources. Of the 195 sources, 174 are known or presumed to be extragalactic. Seventy-five of these extragalactic sources are resolved with the interferometer spacings used, and complex structure is found in all but 13. In the sources showing complex structure, two similar components with nearly equal intensities are found in 15, 40 show two or more components of unequal intensities, while 7 appear to be a bright core surrounded by a halo. It is suggested that the majority of all extragalactic sources have complex structure. Data are also given on the brightness distributions in the 21 galactic sources observed. In contrast to the extragalactic sources, emission from the galactic sources is typically confined to a single region

Multifrequency Radio Observations of the Crab Pulsar

Previously unseen profile components of the Crab pulsar have been discovered in a study of the frequency-dependent behavior of its average pulse profile between 0.33 and 8.4 GHz. One new component, 36 degrees ahead of the main pulse at 1.4 GHz, is not coincident with the position of the precursor at lower frequencies. Two additional, flat-spectrum components appear after the interpulse between 1.4 and 8.4 GHz. The normal interpulse undergoes a transition in phase and spectrum by disappearing near 2.7 GHz, and reappearing 10 degrees earlier in phase at 4.8 and 8.4 GHz with a new spectral index. The radio frequency main disappears for frequencies above 4.8 GHz, even though it is seen at infrared, optical, and higher energies. The existence of the additional components at high frequency and the strange, frequency-dependent behavior is unlike anything seen in other pulsars, and cannot easily be explained by emission from a simple dipole field geometry.Comment: 13 pages. Source is single LaTeX file with 3 figures, using aaspp and epsf style files (included). To appear in The Astrophysical Journal, September 1996. Paper can also be found at http://www.ee.nmt.edu

A VLA Search for the Geminga Pulsar: A Bayesian Limit on a Scintillating Source

We derive an upper limit of 3 mJy (95% confidence) for the flux density at 317 MHz of the Geminga pulsar (J0633+1746). Our results are based on 7 hours of fast-sampled VLA data, which we averaged synchronously with the pulse period using a period model based on CGRO/EGRET gamma-ray data. Our limit accounts for the fact that this pulsar is most likely subject to interstellar scintillations on a timescale much shorter than our observing span. Our Bayesian method is quite general and can be applied to calculate the fluxes of other scintillated sources. We also present a Bayesian technique for calculating the flux in a pulsed signal of unknown width and phase. Comparing our upper limit of 3 mJy with the quoted flux density of Geminga at 102 MHz, we calculate a lower limit to its spectral index of 2.7. We discuss some possible reasons for Geminga's weakness at radio wavelengths, and the likelihood that many of the unidentified EGRET sources are also radio-quiet or radio-weak Geminga-like pulsars.Comment: 27 pages, including figures. Published in Ap

Microbiology and atmospheric processes: Biological, physical and chemical characterization of aerosol particles

The interest in bioaerosols has traditionally been linked to health hazards for humans, animals and plants. However, several components of bioaerosols exhibit physical properties of great significance for cloud processes, such as ice nucleation and cloud condensation. To gain a better understanding of their influence on climate, it is therefore important to determine the composition, concentration, seasonal fluctuation, regional diversity and evolution of bioaerosols. In this paper, we will review briefly the existing techniques for detection, quantification, physical and chemical analysis of biological particles, attempting to bridge physical, chemical and biological methods for analysis of biological particles and integrate them with aerosol sampling techniques. We will also explore some emerging spectroscopy techniques for bulk and single-particle analysis that have potential for in-situ physical and chemical analysis. Lastly, we will outline open questions and further desired capabilities (e. g., in-situ, sensitive, both broad and selective, on-line, time-resolved, rapid, versatile, cost-effective techniques) required prior to comprehensive understanding of chemical and physical characterization of bioaerosols

Examining how the Dark Triad moderates the relationship between workplace victimization and workplace behavior

This study will examine the relationship between workplace victimization and workplace behavior. Furthermore, this study will examine how the Dark Triad of personality affects that relationship. The study will be conducted as a Masters’ Thesis at Middle Tennessee State University. We propose that the there is a positive relationship between workplace victimization and counterproductive work behaviors (CWB) and a negative relationship between workplace victimization and occupational citizenship behaviors (OCB). We also propose that the Dark Triad (narcissism, Machiavellianism, and psychopathy) each positively moderate the relationship between workplace victimization and CWB. Data on each of these constructs will be collected from participants through Amazon’s Mechanical Turk. This study is intended to help gain an understanding of the range of negative effects that workplace victimization can have on both victims and organizations at large. This study will allow researchers and practitioners alike to understand the negative consequences of workplace mistreatment; also, it may motivate organizations to establish policies to protect their employees from harm