8,528 research outputs found
The Design, Implementation, and Assessment of a New Capstone Course Aimed at Science Education Majors
This paper rationalizes the selection of the concept of energy as the central theme of a new capstone course aimed at science education majors. It describes the goals of the course and the activities that preceded the course design and led to the selection of the topics, of the educational materials, and of the teaching methodologies. It presents a sequential description of the manner in which the conceptual knowledge of energy was to be developed. The specific experiments, interactive demonstrations and other educational materials utilized for the conceptual development of the concept of energy in context are described and referenced. The course objectives are described, as well as the instruments utilized to assess student learning. It also presents the activities utilized to assess the course, in addition to the modifications made to the course syllabus based on this assessment
Investigations of Protostellar Outflow Launching and Gas Entrainment: Hydrodynamic Simulations and Molecular Emission
We investigate protostellar outflow evolution, gas entrainment, and star
formation efficiency using radiation-hydrodynamic simulations of isolated,
turbulent low-mass cores. We adopt an X-wind launching model, in which the
outflow rate is coupled to the instantaneous protostellar accretion rate and
evolution. We vary the outflow collimation angle from =0.01-0.1 and
find that even well collimated outflows effectively sweep up and entrain
significant core mass. The Stage 0 lifetime ranges from 0.14-0.19 Myr, which is
similar to the observed Class 0 lifetime. The star formation efficiency of the
cores spans 0.41-0.51. In all cases, the outflows drive strong turbulence in
the surrounding material. Although the initial core turbulence is purely
solenoidal by construction, the simulations converge to approximate
equipartition between solenoidal and compressive motions due to a combination
of outflow driving and collapse. When compared to a simulation of a cluster of
protostars, which is not gravitationally centrally condensed, we find that the
outflows drive motions that are mainly solenoidal. The final turbulent velocity
dispersion is about twice the initial value of the cores, indicating that an
individual outflow is easily able to replenish turbulent motions on sub-parsec
scales. We post-process the simulations to produce synthetic molecular line
emission maps of CO, CO, and CO and evaluate how well
these tracers reproduce the underlying mass and velocity structure.Comment: Accepted to ApJ, 17 pages, 15 figure
A Precise Dispenser Design for Canine Cognition Research
Some forms of canine cognition research require a dispenser that can accurately dispense precise quantities of treats. When using off-the-shelf or retrofitted dispensers, there is no guarantee that a precise number of treats will be dispensed. Often, they will over-dispense treats, which may not be acceptable for some tasks. Here we describe a 3D-printed precise treat dispenser with a 59-treat capacity driven by a stepper motor drive and controlled by an integrated Raspberry Pi. The dispenser can be built for less than 200 USD and is fully 3D printable. While off-the-shelf dispensers can result in an error rate of 20–30%, the precision dispenser produces a 4% error rate. This lower error rate and the integrated Raspberry Pi allows for new possibilities for using treat dispensers across a range of canine research questions
An Extinction Study of the Taurus Dark Cloud Complex
We present a study of the detailed distribution of extinction in a region of
the Taurus dark cloud complex. Our study uses new BVR images of the region,
spectral classification data for 95 stars, and IRAS Sky Survey Atlas (ISSA) 60
and 100 micron images. We study the extinction of the region in four different
ways, and we present the first inter-comparison of all these methods, which
are: 1) using the color excess of background stars for which spectral types are
known; 2) using the ISSA 60 and 100 micron images; 3) using star counts; and 4)
using an optical (V and R) version of the average color excess method used by
Lada et al. (1994). We find that all four methods give generally similar
results, with important exceptions. To study the structure in the dust
distribution, we compare the ISSA extinction and the extinction measured for
individual stars. From the comparison, we conclude that in the relatively low
extinction regions studied, with 0.9 < A_V < 3.0 mag (away from filamentary
dark clouds and IRAS cores), there are no fluctuations in the dust column
density greater than 45% (at the 99.7% confidence level), on scales smaller
than 0.2 pc. We also report the discovery of a previously unknown stellar
cluster behind the Taurus dark cloud near R.A 4h19m00s, Dec. 27:30:00 (B1950)Comment: 49 pages (which include 6 pages of tables and 6 pages of figures
Structure and permeability of ion-channels by integrated AFM and waveguide TIRF microscopy.
Membrane ion channels regulate key cellular functions and their activity is dependent on their 3D structure. Atomic force microscopy (AFM) images 3D structure of membrane channels placed on a solid substrate. Solid substrate prevents molecular transport through ion channels thus hindering any direct structure-function relationship analysis. Here we designed a ~70 nm nanopore to suspend a membrane, allowing fluidic access to both sides. We used these nanopores with AFM and total internal reflection fluorescence microscopy (TIRFM) for high resolution imaging and molecular transport measurement. Significantly, membranes over the nanopore were stable for repeated AFM imaging. We studied structure-activity relationship of gap junction hemichannels reconstituted in lipid bilayers. Individual hemichannels in the membrane overlying the nanopore were resolved and transport of hemichannel-permeant LY dye was visualized when the hemichannel was opened by lowering calcium in the medium. This integrated technique will allow direct structure-permeability relationship of many ion channels and receptors
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