Neuromuscular control of wingbeat kinematics in Anna's hummingbirds (Calypte anna)

Hummingbirds can maintain the highest wingbeat frequencies of any flying vertebrate – a feat accomplished by the large pectoral muscles that power the wing strokes. An unusual feature of these muscles is that they are activated by one or a few spikes per cycle as revealed by electromyogram recordings (EMGs). The relatively simple nature of this activation pattern provides an opportunity to understand how motor units are recruited to modulate limb kinematics. Hummingbirds made to fly in low-density air responded by moderately increasing wingbeat frequency and substantially increasing the wing stroke amplitude as compared with flight in normal air. There was little change in the number of spikes per EMG burst in the pectoralis major muscle between flight in normal and low-density heliox (mean=1.4 spikes cycle^(–1)). However the spike amplitude, which we take to be an indication of the number of active motor units, increased in concert with the wing stroke amplitude, 1.7 times the value in air. We also challenged the hummingbirds using transient load lifting to elicit maximum burst performance. During maximum load lifting, both wing stroke amplitude and wingbeat frequency increased substantially above those values during hovering flight. The number of spikes per EMG burst increased to a mean of 3.3 per cycle, and the maximum spike amplitude increased to approximately 1.6 times those values during flight in heliox. These results suggest that hummingbirds recruit additional motor units (spatial recruitment) to regulate wing stroke amplitude but that temporal recruitment is also required to maintain maximum stroke amplitude at the highest wingbeat frequencies

Time and Difficulty with Tasks and Illness Characteristics Among Caregivers of Individuals Receiving Daily Home Hemodialysis

poster abstractEnd Stage Renal Disease (ESRD) affected approximately 594,374 people in 2010. Patients receiving dialysis often need help with activities of daily living and tasks outside dialysis treatments. The burden of providing assistance and support for such patients can be overwhelming for caregivers, regardless of the modality. This study examined several factors that may be associated with time and difficulty of tasks experienced by caregivers of individuals receiving daily home hemodialysis (HHD). Examining relationships between caregivers age, caregiver income, length of time on dialysis, and patient co-morbidities with perceived time and difficulty with tasks may assist with focusing interventions within specific demographic groups. The purpose of this study is to examine these relationships. This study used existing data from a mixed-methods study. The original study examined needs, concerns, strategies, and advice of daily home hemodialysis caregivers. Participants included 16 caregivers, recruited from a large daily home hemodialysis program in a Mid-western city. There was no relationship between length of time the patient was receiving HHD and time or difficulty with tasks. There was no relationship between age of the caregiver and time or difficulty with tasks. There was no relationship between income and time or difficulty with tasks. There was no relationship between the number of patient comorbidities and time or difficulty with tasks. One important limitation of this study, and possibly the reason that no significant results were discovered, is the small sample size. This study was designed to look at possible factors that may increase perceived caregiver burden. Although there were no relationships found between selected demographic or clinical variables and perceived time expenditure and difficulty with tasks, future research should examine other variables such as relationship of caregiver to patient, caregiver health and comorbidities, and level of involvement of home dialysis staff

Evaluating “Not in Mama\u27s Kitchen” Second-Hand Smoke Campaign in Georgia

In 2003-2005, the Association of Black Cardiologists, Inc. initiated the Not in Mama’s Kitchen (NIMK) second-hand smoke (SHS) prevention campaign in Georgia as part of their effort to reduce exposure to SHS in African American communities statewide. This initiative was evaluated using baseline data from pledge cards as well as data from a self-administered mail survey of 1,000 campaign participants. 14,770 Georgians participated in NIMK, signing pledges to make their homes and cars smoke free. Majorities of those surveyed followed through with their pledge, banning tobacco use in their homes (76.1%) and cars (80.2%). The program was cited by 65.4% of respondents as being instrumental to their decision to ban smoking and by 81.6% as an important source of information on the dangers of SHS. Participants even became advocates, with 74.3% reporting talking to family and/or friends about the dangers of SHS and encouraging them to make their own homes smoke-free

On the Interpretation of Supernova Light Echo Profiles and Spectra

The light echo systems of historical supernovae in the Milky Way and local group galaxies provide an unprecedented opportunity to reveal the effects of asymmetry on observables, particularly optical spectra. Scattering dust at different locations on the light echo ellipsoid witnesses the supernova from different perspectives and the light consequently scattered towards Earth preserves the shape of line profile variations introduced by asymmetries in the supernova photosphere. However, the interpretation of supernova light echo spectra to date has not involved a detailed consideration of the effects of outburst duration and geometrical scattering modifications due to finite scattering dust filament dimension, inclination, and image point-spread function and spectrograph slit width. In this paper, we explore the implications of these factors and present a framework for future resolved supernova light echo spectra interpretation, and test it against Cas A and SN 1987A light echo spectra. We conclude that the full modeling of the dimensions and orientation of the scattering dust using the observed light echoes at two or more epochs is critical for the correct interpretation of light echo spectra. Indeed, without doing so one might falsely conclude that differences exist when none are actually present.Comment: 18 pages, 22 figures, accepted for publication in Ap

The Variable Stars and Blue Horizontal Branch of the Metal-Rich Globular Cluster NGC 6441

We present time-series VI photometry of the metal-rich ([Fe/H] = -0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost reaches of the cluster. The red clump slopes nearly parallel to the reddening vector. A component of this slope is due to differential reddening, but part is intrinsic. The blue horizontal branch stars are more centrally concentrated than the red clump stars. We have discovered about 50 new variable stars near NGC 6441, among them eight or more RR Lyrae stars which are very probably cluster members. Comprehensive period searches over the range 0.2-1.0 days yielded unusually long periods (0.5-0.9 days) for the fundamental pulsators compared with field RR Lyrae of the same metallicity. Three similar long-period RR Lyrae are known in other metal-rich globulars. With over ten examples in hand, it seems that a distinct sub-class of RR Lyrae is emerging. The observed properties of the horizontal branch stars are in reasonable agreement with recent models which invoke deep mixing to enhance the atmospheric helium abundance, while they conflict with models which assume high initial helium abundance. The light curves of the c-type RR Lyrae seem to have unusually long rise times and sharp minima. Reproducing these light curves in stellar pulsation models may provide another means of constraining the physical variables responsible for the anomalous blue horizontal branch extension and sloped red clump observed in NGC 6441.Comment: 30 pages plus 6 EPS and 6 JPEG figures; uses AAS TeX. Accepted by the Astronomical Journal. Minor changes include computing He abundance, modifications to Figs 1 and 8, and expansion on idea that blue HB stars may be produced in binarie

BIMA and Keck Imaging of the Radio Ring PKS 1830-211

We discuss BIMA (Berkeley Illinois Maryland Association) data and present new high quality optical and near-IR Keck images of the bright radio ring PKS 1830-211. Applying a powerful new deconvolution algorithm we have been able to identify both images of the radio source. In addition we recover an extended source in the optical, consistent with the expected location of the lensing galaxy. The source counterparts are very red, I-K=7, suggesting strong Galactic absorption with additional absorption by the lensing galaxy at z=0.885, and consistent with the detection of high redshift molecules in the lens.Comment: To be published in the ASP Conference Proceedings, 'Highly Redshifted Radio Lines', Greenbank, W

The ongoing pursuit of R Coronae Borealis stars: the ASAS-3 survey strikes again

CONTEXT: R Coronae Borealis stars( RCBs) are rare, hydrogen-deficient, carbon rich super giant variable stars that are likely the evolved merger products of pairs of CO and He white dwarfs. Only 55 RCB stars have been found in our galaxy and their distribution on the sky is weighted heavily by microlensing survey field positions. A less biased wide-area survey would enable us to test competing evolutionary scenarios, understand the population or populations that produce RCBs, and constrain their formation rate. AIMS: The ASAS-3 survey monitored the sky south of declination +28deg between 2000 and 2010 to a limiting magnitude of V = 14. We searched ASAS-3 for RCB variables using several different methods to ensure that the probability of RCB detection was as high as possible and to reduce selection biases based on luminosity, temperature, dust production activity and shell brightness. METHODS: Candidates whose light curves were visually inspected were pre-selected based on their infrared (IR) excesses due to warm dust in their circumstellar shells using the WISE and/or 2MASS catalogues. Criteria on light curve variability were also applied when necessary to minimise the number of objects. Initially, we searched for RCB stars among the ASAS-3 ACVS1.1 variable star catalogue, then among the entire ASAS-3 south source catalogue, and finally directly interrogated the light curve database for objects that were not catalogued in either of those. We then acquired spectra of 104 stars to determine their real nature using the SSO/WiFeS spectrograph. RESULTS: We report 21 newly discovered RCB stars and 2 new DY Per stars. Two previously suspected RCB candidates were also spectroscopically confirmed. Our methods allowed us to extend our detection efficiency to fainter magnitudes that would not have been easily accessible to discovery techniques based onlight curve variability. The overall detection efficiencyis about 90% for RCBs with maximum light brighter than V ∼13. CONCLUSIONS: With these new discoveries, 76 RCBs are now known in our Galaxy and 22 in the Magellanic Clouds. This growing sample is of great value to constrain the peculiar and disparate atmosphere composition of RCBs. Most importantly, we show that the spatial distribution and apparent magnitudes of Galactic RCB stars is consistent with RCBs being part of the Galactic bulge population.Department of HE and Training approved lis