2,334 research outputs found
A SURVEY OF CANNABIS CONSUMPTION AND IMPLICATIONS OF AN EXPERIMENTAL POLICY MANIPULATION AMONG YOUNG ADULTS
The purpose of this online cross-sectional study was to identify cannabis user profiles by administration method and examine how differential cannabis policies influence intentions among young adults. Participants were assigned randomly to one of three hypothetical cannabis policy conditions (recreationally legal; medically legal; illegal). Within conditions, participants completed measures regarding cannabis use, including administration methods, cannabis attitudes, norms, perceived behavioral control, self-efficacy, and intentions. Latent class analysis (LCA) was used to determine sub-groups of past 30-day cannabis users by administration method followed by sub-group comparisons. Condition effects on intentions and associated variables were examined using ANCOVA. Four classes (Low-Blunt, Low-Bong, Mod-Poly, High-Poly) differing in demographics and tobacco use were identified. Recreationally and medically legal policy conditions resulted in more favorable cannabis attitudes, higher selfefficacy, and higher intentions to use compared to the illegal policy condition. Results inform cannabis intervention efforts and longitudinal research on the effects of cannabis policy changes
A Chandra observation of GRO J1744-28: the bursting pulsar in quiescence
We present a Chandra/ACIS-I observation of GRO J1744-28. We detected a source
at a position of R.A = 17h 44m 33.09s and Dec. = -28degr 44' 27.0'' (J2000.0;
with a 1sigma error of ~0.8 arcseconds), consistent with both ROSAT and
interplanetary network localizations of GRO J1744-28 when it was in outburst.
This makes it likely that we have detected the quiescent X-ray counterpart of
GRO J1744-28. Our Chandra position demonstrates that the previously proposed
infrared counterpart is not related to GRO J1744-28. The 0.5-10 keV luminosity
of the source is 2 - 4 x 10^{33} erg/s (assuming the source is near the
Galactic center at a distance of 8 kpc). We discuss our results in the context
of the quiescent X-ray emission of pulsating and non-pulsating neutron star
X-ray transients.Comment: Accepted for publication in ApJ Letters, 20 February 200
Near-infrared Observations of Nova V574 Puppis (2004)
We present results obtained from extensive near-infrared spectroscopic and
photometric observations of nova V574 Pup during its 2004 outburst. The
observations were obtained over four months, starting from 2004 November 25
(four days after the nova outburst) to 2005 March 20. The near-IR JHK light
curve is presented - no evidence is seen from it for dust formation to have
occurred during our observations. In the early decline phase, the JHK spectra
of the nova are dominated by emission lines of hydrogen Brackett and Paschen
series, OI, CI and HeI. We also detect the fairly uncommon Fe II line at 1.6872
micron in the early part of our observations. The strengths of the HeI lines at
1.0830 micron and 2.0585 micron are found to become very strong towards the end
of the observations indicating a progression towards higher excitation
conditions in the nova ejecta. The width of the emission lines do not show any
significant change during the course of our observations. The slope of the
continuum spectrum was found to have a lambda^{-2.75} dependence in the early
stages which gradually becomes flatter with time and changes to a free-free
spectral dependence towards the later stages. Recombination analysis of the HI
lines shows deviations from Case B conditions during the initial stages.
However, towards the end of our observations, the line strengths are well
simulated with case B model values with electron density n_e = 10^{9-10}
cm^{-3} and a temperature equal to 10^4 K. Based on our distance estimate to
the nova of 5.5 kpc and the observed free-free continuum emission in the later
part of the observations, we estimate the ionized mass of the ejecta to be
between 10^{-5} and 10^{-6} solar-mass.Comment: 10 pages, 8 figures, Accepted for publication in MNRA
The Complex Phase Lag Behavior of the 3-12 Hz Quasi-Periodic Oscillations during the Very High State of XTE J1550-564
We present a study of the complex phase lag behavior of the low-frequency
(<20 Hz) quasi-periodic oscillations (QPOs) in the X-ray transient and
black-hole candidate XTE J1550-564 during its very high state. We distinguish
two different types of low-frequency QPOs, based on their coherence and
harmonic content. The first type is characterized by a 6 Hz QPO with a Q (the
QPO frequency divided by the QPO width) of <3 and with a harmonic at 12 Hz. The
second type of QPO is characterized by a 6 Hz QPO with a Q value of >6 and with
harmonics at 3, 12, 18, and possibly at 9 Hz. Not only the Q values and the
harmonic content of the two types are different, but also their phase lag
behavior. For the first type of QPO, the low energy photons (<5 keV) of both
the 6 Hz QPO and its harmonic at 12 Hz lag the hard energy photons (>5 keV) by
as much as 1.3 radian. The phase lags of the second type of QPO are more
complex. The soft photons (<5 keV) of the 3 and the 12 Hz QPOs lag the hard
photons (>5 keV) by as much as 1.0 radian. However, the soft photons of the 6
Hz QPO precede the hard ones by as much as 0.6 radian. This means that
different harmonics of this type of QPO have different signs for their phase
lags. This unusual behavior is hard to explain when the lags are due to
light-travel-time differences between the photons at different energies, e.g.,
in a Comptonizing region surrounding the area where the QPOs are formed.Comment: Accepted for publication in ApJ Letters, 29 September 199
Near-Infrared H and K band studies of the 2006 outburst of the recurrent nova RS Ophiuchi
We present near-IR photo-spectroscopy in the H and K bands of the 2006
outburst of the recurrent nova RS Ophiuchi (RS Oph). The observations cover the
period between 1 to 94 days after the eruption. The near IR light curve and an
extensive set of spectra are presented, lines identified and the general
characteristics of the spectra discussed. Analysis of the HI line profiles show
the presence of broad wings on both flanks of a strong central component
indicating the presence of a bipolar velocity flow in the ejecta. Such a flow
is kinematically consistent with the bipolar structure that the object displays
in high-resolution spatial images. We discuss the behaviour and origin of the
Fe II lines at 1.6872 and 1.7414 micron and show that Lyman alpha and Lyman
continuum fluorescence are viable mechanisms to excite these lines. We draw
upon the result, that collisional excitation can also contribute in exciting
and significantly enhancing the strength of these Fe II lines, to propose that
these lines originate from a site of high particle density. Such a likely site
could be the high-density, low temperature contact surface that should exist in
the shockfront in between the shocked ejecta and red giant wind. Recombination
analysis of the HI lines indicate deviations from Case B conditions during most
of the span of our observations indicating optical depth effects. It appears
likely that the breakout of the shockfront had not yet occured till the end of
our observations. An analysis is made of the temporal evolution of the [Si VI]
1.9641 micron coronal line and another coronal line at 2.0894 micron which is
attributed to [Mn XIV]. Assuming collisional effects to dominate in the hot
coronal gas, estimates are made of the ion temperature in the gas.Comment: Accepted in MNRAS. Accepted version with inclusion of additional
analysi
Flight prototype CO2 and humidity control system
A regenerable CO2 and humidity control system is presently being developed for potential use on the space shuttle as an alternative to the baseline lithium hydroxide system. The system utilizes a sorbent material (designated HS-C) to adsorb CO2 and water vapor from the cabin atmosphere and desorb the CO2 and water vapor overboard when exposed to a space vacuum. Continuous operation is achieved by utilizing two beds which are alternately cycled between adsorption and desorption. A shuttle vehicle integration study showed that the HS-C system offers substantial weight advantages compared to the baseline shuttle orbiter expendable lithium hydroxide CO2 removal system for extended missions beyond the nominal design of four men for seven days. This study defined a system packaging envelope in the area presently occupied by the LiOH cartridges
Quiescent X-Ray/Optical Counterparts of the Black Hole Transient H 1705-250
We report the result of a new Chandra observation of the black hole X-ray
transient H 1705-250 in quiescence. H 1705-250 was barely detected in the new
50 ks Chandra observation. With 5 detected counts, we estimate the source
quiescent luminosity to be Lx~9.1e30 erg/s in the 0.5-10 keV band (adopting a
distance of 8.6 kpc). This value is in line with the quiescent luminosities
found among other black hole X-ray binaries with similar orbital periods. By
using images taken with the Faulkes Telescope North, we derive a refined
position of H 1705-250. We also present the long-term lightcurve of the optical
counterpart from 2006 to 2012, and show evidence for variability in quiescence.Comment: 5 pages, 2 figures; Accepted for publication in MNRA
Nonmesonic decay of the Lambda-hyperon in hypernuclei produced by p+Au collisions
The lifetime of the Lambda-hyperon for the nonmesonic decay Lambda N ---> N N
has been determined by a measurement at COSY Juelich of the delayed fission of
heavy hypernuclei produced in proton - Au collisions at T_p=1.9 GeV. It is
found that heavy hypernuclei with mass numbers A= 180 +- 5 and atomic numbers
Z= 74 +-2 fission with a lifetime
130ps +- 13ps (stat.) +- 15ps (syst.) . This value together with the results
obtained for other heavy hypernuclei in previous investigations indicates (on
the confidence level of 0.9) a violation of the phenomenological Delta I = 1/2
rule for Lambda N ---> NN transitions as known from the weak mesonic decays of
kaons and hyperons. PACS:
{13.30.-a}{Decays of baryons}
{13.75.Ev}{Hyperon-nucleon interaction}
{21.80}{Hypernuclei}
{25.80.Pw}{Hyperon-induced reactions}Comment: 3 pages, 2 Postscript figures, uses svepj.clo and svjour.cls.
submitted to European Physical Journal
A XMM-Newton observation during the 2000 outburst of SAX J1808.4-3658
I present a XMM-Newton observation of the accretion driven millisecond X-ray
pulsar SAX J1808.4-3658 during its 2000 outburst. The source was conclusively
detected, albeit at a level of only ~2 x 10^{32} erg/s. The source spectrum
could be fitted with a power-law model (with a photon index of ~2.2), a neutron
star atmosphere model (with a temperature of ~0.2 keV), or with a combination
of a thermal (either a black-body or an atmosphere model) and a power-law
component. During a XMM-Newton observation taken approximately one year later,
the source was in quiescence and its luminosity was a factor of ~4 lower. It is
possible that the source spectrum during the 2000 outburst was softer than its
quiescent 2001 spectrum, however, the statistics of the data do not allow to
make a firm conclusion. The results obtained are discussed in the context of
the 2000 outburst of SAX J1808.4-3658 and the quiescent properties of the
source.Comment: Accepted for publication in ApJ, 15 January 200
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