307 research outputs found
The catalytic removal of ammonia and nitrogen oxides from spacecabin atmospheres
Investigations were made on methods for the removal of ammonia and to a lesser extent nitrogen oxides in low concentrations from air. The catalytic oxidation of ammonia was studied over a temperature range of 250 F to 600 F and a concentration range 20 ppm to 500 ppm. Of the catalysts studied, 0.5 percent ruthenium supported on alumina was found to be superior. This material is active at temperatures as low as 250 F and was found to produce much less nitrous oxide than the other two active catalysts, platinum on alumina and Hopcalite. A quantitative design model was developed which will permit the performance of an oxidizer to be calculated. The ruthenium was found to be relatively insensitive to low concentrations of water and to oxygen concentration between 21 percent and 100 percent. Hydrogen sulfide was found to be a poison when injected in relatively large quantities. The adsorption of ammonia by copper sulfate treated silica gel was investigated at temperatures of 72 F and 100 F. A quantitative model was developed for predicting adsorption bed behavior
Removal of acid gases and oxides of nitrogen from space cabin atmospheres
Removal of acid gases and oxides of nitrogen from spacecraft cabin atmospheres at ambient temperature
Observation of anomalous spin-state segregation in a trapped ultra-cold vapor
We observe counter-intuitive spin segregation in an inhomogeneous sample of
ultra-cold, non-condensed Rubidium atoms in a magnetic trap. We use spatially
selective microwave spectroscopy to verify a model that accounts for the
differential forces on two internal spin states. In any simple understanding of
the cloud dynamics, the forces are far too small to account for the dramatic
transient spin polarizations observed. The underlying mechanism remains to be
elucidated.Comment: 5 pages, 3 figure
Internal state conversion in ultracold gases
We consider an ultracold gas of (non-condensed) bosons or fermions with two
internal states, and study the effect of a gradient of the transition frequency
between these states. When a RF pulse is applied to the sample,
exchange effects during collisions transfer the atoms into internal states
which depend on the direction of their velocity. This results, after a short
time, in a spatial separation between the two states. A kinetic equation is
solved analytically and numerically; the results agree well with the recent
observations of Lewandowski et al.Comment: Accepted version, to appear in PR
Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey
The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed
to locate quasars during the epoch of reionization. In this paper we present
the discovery of the first four CFHQS quasars at redshift greater than 6,
including the most distant known quasar, CFHQS J2329-0301 at z=6.43. We
describe the observational method used to identify the quasars and present
optical, infrared, and millimeter photometry and optical and near-infrared
spectroscopy. We investigate the dust properties of these quasars finding an
unusual dust extinction curve for one quasar and a high far-infrared luminosity
due to dust emission for another. The mean millimeter continuum flux for CFHQS
quasars is substantially lower than that for SDSS quasars at the same redshift,
likely due to a correlation with quasar UV luminosity. For two quasars with
sufficiently high signal-to-noise optical spectra, we use the spectra to
investigate the ionization state of hydrogen at z>5. For CFHQS J1509-1749 at
z=6.12, we find significant evolution (beyond a simple extrapolation of lower
redshift data) in the Gunn-Peterson optical depth at z>5.4. The line-of-sight
to this quasar has one of the highest known optical depths at z~5.8. An
analysis of the sizes of the highly-ionized near-zones in the spectra of two
quasars at z=6.12 and z=6.43 suggest the IGM surrounding these quasars was
substantially ionized before these quasars turned on. Together, these
observations point towards an extended reionization process, but we caution
that cosmic variance is still a major limitation in z>6 quasar observations.Comment: 15 pages, 9 figures, AJ, in press, minor changes to previous versio
The Architecture of the GW Ori Young Triple Star System and Its Disk: Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses
We present spatially and spectrally resolved Atacama Large
Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the
pre-main sequence hierarchical triple star system GW Ori. A forward-modeling of
the CO and CO =2-1 transitions permits a measurement of
the total stellar mass in this system, , and the
circum-triple disk inclination, . Optical spectra spanning
a 35 year period were used to derive new radial velocities and, coupled with a
spectroscopic disentangling technique, revealed that the A and B components of
GW Ori form a double-lined spectroscopic binary with a day
period; a tertiary companion orbits that inner pair with a day
period. Combining the results from the ALMA data and the optical spectra with
three epochs of astrometry in the literature, we constrain the individual
stellar masses in the system (,
, ) and
find strong evidence that at least one (and likely both) stellar orbital planes
are misaligned with the disk plane by as much as . A -band light
curve spanning 30 years reveals several new 30 day eclipse events
0.1-0.7~mag in depth and a 0.2 mag sinusoidal oscillation that is clearly
phased with the AB-C orbital period. Taken together, these features suggest
that the A-B pair may be partially obscured by material in the inner disk as
the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude
that stellar evolutionary models are consistent with our measurements of the
masses and basic photospheric properties if the GW Ori system is 1 Myr
old.Comment: 26 pages, 15 figures, accepted to Ap
Optical Confinement of a Bose-Einstein Condensate
Bose-Einstein condensates of sodium atoms have been confined in an optical
dipole trap using a single focused infrared laser beam. This eliminates the
restrictions of magnetic traps for further studies of atom lasers and
Bose-Einstein condensates. More than five million condensed atoms were
transferred into the optical trap. Densities of up to of Bose condensed atoms were obtained, allowing for a measurement of
the three-body decay rate constant for sodium condensates as . At lower densities, the observed 1/e
lifetime was more than 10 sec. Simultaneous confinement of Bose-Einstein
condensates in several hyperfine states was demonstrated.Comment: 5 pages, 4 figure
Health Product Risk Communication: Is the message getting through?
Risk communication is an important component of improving the health and safety of Canadians. For numerous departments and agencies at all levels of government, as well as public and private organizations, effective risk communication can protect Canadians from preventable hazards. The Minister of Health, on behalf of Health Canada (the Sponsor), asked the Council of Canadian Academies (the Council) to provide an evidence-based and authoritative assessment of the state of knowledge on measurement and evaluation of health risk communication. This assessment focuses on identifying tools, evaluation methods, gaps in the literature, and barriers and facilitators to carrying out successful communication and evaluation activities. Specifically, this assessment examines the following questions: How can the effectiveness of health risk communications be measured and evaluated? • What types of instruments/tools are currently available for health risk communication? • What methodological best practices can be used to evaluate the reach, use and benefit of health risk communication? • What research could be done to inform the measurement of the effectiveness of risk communications? • What are the existing barriers to effective risk communications and what best practices exist to address these challenges? To address the charge, the Council assembled a multi-disciplinary panel of 11 experts (the Panel) from Canada and abroad. The Panel’s composition reflected a balance of expertise, experience, and demonstrated leadership in academic, clinical, and regulatory fields. Each member served as an informed individual, rather than as a representative of a particular discipline, patron, organization, or region
Discovery of a New WZ Sagittae Type Cataclysmic Variable in the Kepler/K2 Data
We identify a new, bright transient in the Kepler/K2 Campaign 11 field. Its
light curve rises over seven magnitudes in a day and then declines three
magnitudes over a month before quickly fading another two magnitudes. The
transient was still detectable at the end of the campaign. The light curve is
consistent with a WZ~Sge type dwarf nova outburst. Early superhumps with a
period of 82 minutes are seen in the first 10 days and suggest that this is the
orbital period of the binary which is typical for the WZ~Sge class. Strong
superhump oscillations develop ten days after peak brightness with periods
ranging between 83 and 84 minutes. At 25 days after the peak brightness a bump
in the light curve appears to signal a subtle rebrightening phase implying that
this was an unusual type-A outburst. This is the only WZ~Sge type system
observed by Kepler/K2 during an outburst. The early rise of this outburst is
well-fit with a broken power law. In first 10 hours the system brightened
linearly and then transitioned to a steep rise with a power law index of 4.8.
Looking at archival Kepler/K2 data and new TESS observations, a linear rise in
the first several hours at the initiation of a superoutburst appears to be
common in SU~UMa stars.Comment: 11 pages, 14 figures, 2 tables, accepted to appear in the Monthly
Notices of the Royal Astronomical Societ
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On theory, technique and text: guidelines and suggestions on publishing international human resource management research
Publishing international human resource management (IHRM) research continues to be a challenge for seasoned as much as junior faculty. Quantitative and qualitative studies exploring HRM-related topics involving multiple countries or complex contextual factors raise issues of developing an appropriate research question, presenting multilevel methodologies, and making a contribution in which context stands central. In this Editorial, we reflect on such issues as discussed at the 2nd Global Conference on International Human Resource Management held at the Pennsylvania State University (USA) in 2015. Journal editors, reviewers and authors contribute to provide practical suggestions on the craft of getting published, including design of a study, developing a writing style, and dealing with journal feedback. Finally, we explore some myths and misperceptions around publishing IHRM research in high-ranking journals
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