20,963 research outputs found
Skeletal status and soft tissue composition in astronauts. Tissue and fluid changes by radionuclide absorptiometry in vivo
A device has been constructed and tested which provides immediate readout of bone mineral content and bone width from absorptiometric scans with low energy radionuclides. The basis of this analog system is a logarithmic converter-integrator coupled with a precision linear ratemeter. The system provided accurate and reliable results on standards and ashed bone sections. Clinical measurements were made on about 100 patients with the direct readout system, and these were highly correlated with the results from digital scan data on the same patients. The direct readout system has been used successfully in field studies and surveys as well as for clinical observations
WASP-1: A lithium- and metal-rich star with an oversized planet
In this paper we present our results of a comprehensive spectroscopicanalysis
of WASP-1, the host star to the exoplanet WASP-1b. We derive T_eff = 6110 +/-
45 K, log g = 4.28 +/- 0.15, and [M/H] = 0.23 +/- 0.08, and also a high
abundance of lithium, log n(Li) = 2.91 +/- 0.05. These parameters suggests an
age for the system of 1-3 Gyr and a stellar mass of 1.25-1.35 M_sun. This means
that WASP-1 has properties very similar to those of HD 149026, the host star
for the highest density planet yet detected. Moreover, their planets orbit at
comparable distances and receive comparable irradiating fluxes from their host
stars. However, despite the similarity of WASP-1 with HD 149026, their planets
have strongly different densities. This suggests that gas-giant planet density
is not a simple function of host-star metallicity or of radiation environment
at ages of ~2 Gyr.Comment: Accepted for publication in MNRAS. 6 pages, 4 figure
Average motion of emerging solar active region polarities I: Two phases of emergence
Our goal is to constrain models of active region formation by tracking the
average motion of active region polarity pairs as they emerge onto the surface.
We measured the motion of the two main opposite polarities in 153 emerging
active regions (EARs) using line-of-sight magnetic field observations from the
Solar Dynamics Observatory Helioseismic Emerging Active Region (SDO/HEAR)
survey (Schunker et al. 2016). We first measured the position of each of the
polarities eight hours after emergence and tracked their location forwards and
backwards in time. We find that, on average, the polarities emerge with an
east-west orientation and the separation speed between the polarities
increases. At about 0.1 days after emergence, the average separation speed
reaches a peak value of 229 +/- 11 m/s, and then starts to decrease, and about
2.5 days after emergence the polarities stop separating. We also find that the
separation and the separation speed in the east-west direction are
systematically larger for active regions with higher flux. Our results reveal
two phases of the emergence process defined by the rate of change of the
separation speed as the polarities move apart. Phase 1 begins when the opposite
polarity pairs first appear at the surface, with an east-west alignment and an
increasing separation speed. We define Phase 2 to begin when the separation
speed starts to decrease, and ends when the polarities have stopped separating.
This is consistent with the picture of Chen, Rempel, & Fan (2017): the peak of
a flux tube breaks through the surface during Phase 1. During Phase 2 the
magnetic field lines are straightened by magnetic tension, so that the
polarities continue to move apart, until they eventually lie directly above
their anchored subsurface footpoints.Comment: accepted A&
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Picoliter-volume inkjet printing into planar microdevice reservoirs for low-waste, high-capacity drug loading.
Oral delivery of therapeutics is the preferred route for systemic drug administration due to ease of access and improved patient compliance. However, many therapeutics suffer from low oral bioavailability due to low pH and enzymatic conditions, poor cellular permeability, and low residence time. Microfabrication techniques have been used to create planar, asymmetric microdevices for oral drug delivery to address these limitations. The geometry of these microdevices facilitates prolonged drug exposure with unidirectional release of drug toward gastrointestinal epithelium. While these devices have significantly enhanced drug permeability in vitro and in vivo, loading drug into the micron-scale reservoirs of the devices in a low-waste, high-capacity manner remains challenging. Here, we use picoliter-volume inkjet printing to load topotecan and insulin into planar microdevices efficiently. Following a simple surface functionalization step, drug solution can be spotted into the microdevice reservoir. We show that relatively high capacities of both topotecan and insulin can be loaded into microdevices in a rapid, automated process with little to no drug waste
Twenty Years of Timing SS433
We present observations of the optical ``moving lines'' in spectra of the
Galactic relativistic jet source SS433 spread over a twenty year baseline from
1979 to 1999. The red/blue-shifts of the lines reveal the apparent precession
of the jet axis in SS433, and we present a new determination of the precession
parameters based on these data. We investigate the amplitude and nature of
time- and phase-dependent deviations from the kinematic model for the jet
precession, including an upper limit on any precessional period derivative of
. We also dicuss the implications of these results
for the origins of the relativistic jets in SS433.Comment: 21 pages, including 9 figures. To appear in the Astrophysical Journa
The Angular Momentum Evolution of Very Low Mass Stars
We present theoretical models of the angular momentum evolution of very low
mass stars (0.1 - 0.5 M_sun) and solar analogues (0.6 - 1.1 M_sun). We
investigate the effect of rotation on the effective temperature and luminosity
of these stars. We find that the decrease in T_eff and L can be significant at
the higher end of our mass range, but becomes negligible below 0.4 M_sun.
Formulae for relating T_eff to mass and v_rot are presented.
We compare our models to rotational data from young open clusters of
different ages to infer the rotational history of low mass stars, and the
dependence of initial conditions and rotational evolution on mass. We find that
the qualitative conclusions for stars below 0.6 M_sun do not depend on the
assumptions about internal angular momentum transport, which makes these low
mass stars ideal candidates for the study of the angular momentum loss law and
distribution of initial conditions. We find that neither models with solid body
nor differential rotation can simultaneously reproduce the observed stellar
spin down in the 0.6 to 1.1 M_sun mass range and for stars between 0.1 and 0.6
M_sun. The most likely explanation is that the saturation threshold drops more
steeply at low masses than would be predicted with a simple Rossby scaling. In
young clusters there is a systematic increase in the mean rotation rate with
decreased temperature below 3500 K (0.4 M_sun). This suggests either
inefficient angular momentum loss or mass-dependent initial conditions for
stars near the fully convective boundary. (abridged)Comment: To appear in the May 10, 2000 Ap
Capturing the moment : understanding embodied interactions in early primary physical education
Background: Several studies demonstrate the benefits of understanding explicit and tacit embodied interactions in physical education (PE). However, there is little research that explores the embodied interactions that occur in early primary PE classes (years 1 and 2), where children (are socialized to) embody various body values, attitudes and stigma. We adopted a micro-sociological approach to examine the embodied interactions of a group of early primary school children. The study provides new insight into how primary age children embody the world around them in their PE interactions and the impact this embodiment has on them and on their peers. Purpose: Using a micro-sociological approach, the aim of this study was to examine the embodied interactions of a group of year 1 and 2 children (ages 6–8) in PE classes. Participants and settings: The study was conducted at a public primary school in Australia over a six-month period. The lessons were filmed by the lead author, yielding a total of 12 h and 21 min of footage. Observer XT, a systematic observation programme, was utilized to aid in the coding, management and analysis of observational data, allowing for the creation of multiple coding schemes. Findings: The findings highlighted two distinct themes. First, competition, which involved the constant comparison of performance between the children. Second, skill mastery, which involved the children engaging in acts that displayed their advanced understanding of how to perform certain skills. While the emphasis on competition and skill mastery has been echoed across PE literature, this study showed how those with the most cultural resources (sport experience and physical capital) were able to embody these goals to produce high levels of emotional energy during Interactional Rituals. The findings also indicated the pedagogical implications of these micro-moments. The implementation of an approach characterized by a lack of differentiation and minimal teacher intervention created an environment ripe for embodied engagement in competition and skill mastery. Implications: The micro-sociological approach provided a unique insight into how primary age children are embodying the world around them in their PE interactions and the impact this embodiment is having on themselves and their peers. This approach also provides insight into the pedagogical implications of this embodiment, and highlights the need for more creative and/or student-centred pedagogies in primary PE. © 2020 Association for Physical Education
Stoichiometry control of sputtered CuCl thin films: Influence on ultraviolet emission properties
We demonstrate that the chemical composition of the sputtered CuCl thin films could be finely controlled by adjusting the bias to the substrate. The films deposited without any intentional bias were Cl rich (CuCl1+x), a bias of −22 V yielded stoichiometric CuCl, and a further increase in the negative bias resulted in Cl deficient films (CuCl1−x). The crystalline and optical properties were found to be associated with the chemical composition. Cl rich films showed a deep level green emission at around 515 nm in addition to ultraviolet (UV) excitonic emission. The stoichiometric films have higher optical quality, exhibiting a sharp UV emission at around 385 nm at room temperature, compared to nonstoichiometric samples. Visible luminescence related to deep level defects was not observed in the stoichiometric films. Changes in energy of the flux from the target and the subsequent ion bombardment on the substrate surface are correlated with the variations in chemical composition and their impact on the film microstructure and UV emission
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