A New Sub-Period-Minimum Cataclysmic Variable With Partial Hydrogen Depletion And Evidence Of Spiral Disk Structure

We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (=SBS 1108+574), a recently discovered SU UMa-type dwarf nova whose 55 minute orbital period is well below the cataclysmic variable (CV) period minimum of similar to 78 minutes. In contrast with most other known CVs, its spectrum features He I emission of comparable strength to the Balmer lines, implying a hydrogen abundance less than 0.1 of long-period CVs-but still at least 10 times higher than that in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in CSS 120422 began near the end of the donor star's main-sequence lifetime, meaning that this CV is a strong candidate progenitor of an AM CVn system as described by Podsiadlowski et al. Moreover, a Doppler tomogram of the Ha line reveals two distinct regions of enhanced emission. While one is the result of the stream-disk impact, the other is probably attributable to spiral disk structure generated when material in the outer disk achieves a 2:1 orbital resonance with respect to the donor.NSF AST-1211196, AST-9987045Department of Physics at the University of Notre DameNSF Telescope System Instrumentation Program (TSIP)Ohio Board of RegentsOhio State University Office of ResearchAstronom

Aflatoxin B1 in Corn Silage

Nineteen piles and bunk silos of corn silage were sampled in late fall of 1976 and early spring of 1977. These samples were assayed for aflatoxin Bl, a potent mycotoxin, using a newly developed procedure. No aflatoxin Bl (<5 ug/kg) was detected in any of the 270 samples of corn silage

Expression, Purification, and Analysis of Unknown Translation Factors from Escherichia coli: A Synthesis Approach

New approaches are currently being developed to expose biochemistry and molecular biology undergraduates to a more interactive learning environment. Here, we propose a unique project-based laboratory module, which incorporates exposure to biophysical chemistry approaches to address problems in protein chemistry. Each of the experiments described herein contributes to the stepwise process of isolating, identifying, and analyzing a protein involved in a central biological process, prokaryotic translation. Students are provided with expression plasmids that harbor an unknown translation factor, and it is their charge to complete a series of experiments that will allow them to develop hypotheses for discovering the identity of their unknown (from a list of potential candidates). Subsequent to the identification of their unknown translation factor, a series of protein unfolding exercises are performed employing circular dichroism and fluorescence spectroscopies, allowing students to directly calculate thermodynamic parameters centered around determining the equilibrium constant for unfolding as a function of denaturant (temperature or chemical). The conclusion of this multi-part laboratory exercise consists of both oral and written presentations, emphasizing synthesis of the roles of each translation factor during the stepwise process of translation

Differences in oxygen uptake but equivalent energy expenditure between a brief bout of cycling and running

BACKGROUND: We examined aerobic and anaerobic exercise energy expenditure and excess post-exercise oxygen consumption (EPOC) between a 250 Watt, 1-minute bout of cycling and uphill treadmill running. METHODS: Fourteen active to well-trained subjects volunteered for the investigation (VO(2 )max: 57.0 ± 12.9 ml·kg·min(-1 )cycle; 59.3 ± 13.7 ml·kg·min(-1 )run; p = 0.44). Anaerobic energy expenditure was estimated from △blood lactate. Statistical analysis was completed using a paired t-test (mean ± SD). RESULTS: Perceived exertion did not differ between exercise bouts (14.0 ± 2.3 cycle; 13.2 ± 2.1 run; p = 0.29). Exercise oxygen uptake was significantly greater for running (41.4 ± 6.9 kJ) compared to cycling (31.7 ± 7.7 kJ) (p = 0.0001). EPOC was not different between cycling and running (p = 0.21) so that exercise oxygen uptake + EPOC was greater for running (103.0 ± 13.5 kJ) as compared to cycling (85.4 ± 20.2 kJ; p = 0.008). Anaerobic energy expenditure was significantly greater for cycling (32.7 ± 8.9 kJ) versus running (22.5 ± 11.1 kJ) (p = 0.009). Aerobic + anaerobic exercise energy expenditure (cycle 64.3 ± 12.2 kJ; run 63.9 ± 10.1 kJ) (p = 0.90) and total energy expenditure (including EPOC; cycle 118.0 ± 21.8 kJ; run 125.4 ± 19.1 kJ; p = 0.36) were similar for cycling and running. CONCLUSION: Oxygen-only measures reveal discrepancy in energy expenditure between cycling and uphill running. Measurements of exercise oxygen uptake, △blood lactate and a modified EPOC promote the hypothesis of a similarity in exercise and total energy expenditure between 1-minute work-equivalent bouts of cycling and uphill running