Attitude-referenced radiometer study. Part 2: Primary calibration system

A primary calibration system, PCS, for infrared radiometers has been developed, built, and tested. The system allows radiometers to be calibrated with less than 1 percent error for use in earth coverage horizon measurements, earth resources surveys, and synoptic meteorological measurement. The final design, fabrication and test of the PCS are reported. A detailed description of the PCS construction is presented, along with the results of a complete series of functional tests. Test to verify the source thermal characteristics, collimator reflectance, and output beam characteristics are described and their results presented

Searching for additional heating - [OII] emission in the diffuse ionized gas of NGC891, NGC4631 and NGC3079

We present spectroscopic data of ionized gas in the disk--halo regions of three edge-on galaxies, NGC 891, NGC 4631 and NGC 3079, covering a wavelength range from [\ion{O}{2}] $\lambda$3727\AA to [\ion{S}{2}] $\lambda$6716.4\AA. The inclusion of the [\ion{O}{2}] emission provides new constraints on the properties of the diffuse ionized gas (DIG), in particular, the origin of the observed spatial variations in the line intensity ratios. We used three different methods to derive electron temperatures, abundances and ionization fractions along the slit. The increase in the [\ion{O}{2}]/H$\alpha$ line ratio towards the halo in all three galaxies requires an increase either in electron temperature or in oxygen abundance. Keeping the oxygen abundance constant yields the most reasonable results for temperature, abundances, and ionization fractions. Since a constant oxygen abundance seems to require an increase in temperature towards the halo, we conclude that gradients in the electron temperature play a significant role in the observed variations in the optical line ratios from extraplanar DIG in these three spiral galaxies.Comment: 43 pages, 29 figure

Computer Self-Efficacy, Digital Learners, and Completion Rates in the California Community College System

The importance of online learning in higher education has increased considerably over the last two decades. As a result, online learning has become an important area of research. The purpose of the study was to examine if higher levels of computer self-efficacy (CSE) contributed to online course completion among online California community college students. Guided by Bandura’s (1977) work on self-efficacy and the work of Compeau and Higgins (1995) and Howard (2014) on computer self-efficacy, this study revealed that there is no relationship between high levels of CSE and successful completion of the course. A judgement sample was used to select five online sections from a northern California community college in which 122 students participated. These students completed a Computer User Self-efficacy questionnaire which consisted of 12 questions on a six-point Likert scale as well as three questions regarding their perceived use of computers. Spearman’s Correlation Coefficient was conducted to see if a relationship existed between high levels of computer self-efficacy and course grades. The results showed that there was no statistically significant relationship between high levels of computer self-efficacy and course grades. The implication of this study suggests that computer self-efficacy may not be an important factor for today’s digital learner

Computer Self-Efficacy, Digital Learners, and Completion Rates in the California Community College System

The importance of online learning in higher education has increased considerably over the last two decades. As a result, online learning has become an important area of research. The purpose of the study was to examine if higher levels of computer self-efficacy (CSE) contributed to online course completion among online California community college students. Guided by Bandura’s (1977) work on self-efficacy and the work of Compeau and Higgins (1995) and Howard (2014) on computer self-efficacy, this study revealed that there is no relationship between high levels of CSE and successful completion of the course. A judgement sample was used to select five online sections from a northern California community college in which 122 students participated. These students completed a Computer User Self-efficacy questionnaire which consisted of 12 questions on a six-point Likert scale as well as three questions regarding their perceived use of computers. Spearman’s Correlation Coefficient was conducted to see if a relationship existed between high levels of computer self-efficacy and course grades. The results showed that there was no statistically significant relationship between high levels of computer self-efficacy and course grades. The implication of this study suggests that computer self-efficacy may not be an important factor for today’s digital learner

Catching GRBs with atmospheric Cherenkov telescopes

Fermi has shown GRBs to be a source of >10 GeV photons. We present an estimate of the detection rate of GRBs with a next generation Cherenkov telescope. Our predictions are based on the observed properties of GRBs detected by Fermi, combined with the spectral properties and redshift determinations for the bursts population by instruments operating at lower energies. While detection of VHE emission from GRBs has eluded ground-based instruments thus far, our results suggest that ground-based detection may be within reach of the proposed Cherenkov Telescope Array (CTA), albeit with a low rate, 0.25 - 0.5/yr. Such a detection would help constrain the emission mechanism of gamma-ray emission from GRBs. Photons at these energies from distant GRBs are affected by the UV-optical background light, and a ground-based detection could also provide a valuable probe of the Extragalactic Background Light (EBL) in place at high redshift.Comment: 4 pages, 3 figures, to appear in the Proceedings of "Gamma Ray Bursts 2010", held Nov. 1-4, 2010 in Annapolis, M

Word Adjacency Graph Modeling: Separating Signal From Noise in Big Data

There is a need to develop methods to analyze Big Data to inform patient-centered interventions for better health outcomes. The purpose of this study was to develop and test a method to explore Big Data to describe salient health concerns of people with epilepsy. Specifically, we used Word Adjacency Graph modeling to explore a data set containing 1.9 billion anonymous text queries submitted to the ChaCha question and answer service to (a) detect clusters of epilepsy-related topics, and (b) visualize the range of epilepsy-related topics and their mutual proximity to uncover the breadth and depth of particular topics and groups of users. Applied to a large, complex data set, this method successfully identified clusters of epilepsy-related topics while allowing for separation of potentially non-relevant topics. The method can be used to identify patient-driven research questions from large social media data sets and results can inform the development of patient-centered interventions

Exploring the phase diagram of the two-impurity Kondo problem

A system of two exchange-coupled Kondo impurities in a magnetic field gives rise to a rich phase space hosting a multitude of correlated phenomena. Magnetic atoms on surfaces probed through scanning tunnelling microscopy provide an excellent platform to investigate coupled impurities, but typical high Kondo temperatures prevent field-dependent studies from being performed, rendering large parts of the phase space inaccessible. We present an integral study of pairs of Co atoms on insulating Cu2N/Cu(100), which each have a Kondo temperature of only 2.6 K. In order to cover the different regions of the phase space, the pairs are designed to have interaction strengths similar to the Kondo temperature. By applying a sufficiently strong magnetic field, we are able to access a new phase in which the two coupled impurities are simultaneously screened. Comparison of differential conductance spectra taken on the atoms to simulated curves, calculated using a third order transport model, allows us to independently determine the degree of Kondo screening in each phase.Comment: paper: 14 pages, 4 figures; supplementary: 3 pages, 1 figure, 1 tabl