14,838 research outputs found
Does the taste matter? Taste and medicinal perceptions associated with five selected herbal drugs among three ethnic groups in West Yorkshire, Northern England
In recent years, diverse scholars have addressed the issue of the chemosensory perceptions associated with traditional medicines, nevertheless there is still a distinct lack of studies grounded in the social sciences and conducted from a cross-cultural, comparative perspective. In this urban ethnobotanical field study, 254 informants belonging to the Gujarati, Kashmiri and English ethnic groups and living in Western Yorkshire in Northern England were interviewed about the relationship between taste and medicinal perceptions of five herbal drugs, which were selected during a preliminary study. The herbal drugs included cinnamon (the dried bark of Cinnamomum verum, Lauraceae), mint (the leaves of Mentha spp., Lamiaceae), garlic (the bulbs of Allium sativum, Alliaceae), ginger (the rhizome of Zingiber officinale, Zingiberaceae), and cloves (the dried flower buds of Syzygium aromaticum, Myrtaceae).
The main cross-cultural differences in taste perceptions regarded the perception the perception of the spicy taste of ginger, garlic, and cinnamon, of the bitter taste of ginger, the sweet taste of mint, and of the sour taste of garlic.
The part of the study of how the five selected herbal drugs are perceived medicinally showed that TK (Traditional Knowledge) is widespread among Kashmiris, but not so prevalent among the Gujarati and especially the English samples. Among Kashmiris, ginger was frequently considered to be helpful for healing infections and muscular-skeletal and digestive disorders, mint was chosen for healing digestive and respiratory troubles, garlic for blood system disorders, and cinnamon was perceived to be efficacious for infectious diseases.
Among the Gujarati and Kashmiri groups there was evidence of a strong link between the bitter and spicy tastes of ginger, garlic, cloves, and cinnamon and their perceived medicinal properties, whereas there was a far less obvious link between the sweet taste of mint and cinnamon and their perceived medicinal properties, although the link did exist among some members of the Gujarati group.
Data presented in this study show how that links between taste perceptions and medicinal uses of herbal drugs may be understood as bio-cultural phenomena rooted in human physiology, but also constructed through individual experiences and culture, and that these links can therefore be quite different across diverse cultures
Starspot-induced optical and infrared radial velocity variability in T Tauri star Hubble 4
We report optical (6150 Ang) and K-band (2.3 micron) radial velocities
obtained over two years for the pre-main sequence weak-lined T Tauri star
Hubble I 4. We detect periodic and near-sinusoidal radial velocity variations
at both wavelengths, with a semi-amplitude of 1395\pm94 m/s in the optical and
365\pm80 m/s in the infrared. The lower velocity amplitude at the longer
wavelength, combined with bisector analysis and spot modeling, indicates that
there are large, cool spots on the stellar surface that are causing the radial
velocity modulation. The radial velocities maintain phase coherence over
hundreds of days suggesting that the starspots are long-lived. This is one of
the first active stars where the spot-induced velocity modulation has been
resolved in the infrared.Comment: Accepted for publication in The Astrophysical Journa
Accretion-powered Stellar Winds as a Solution to the Stellar Angular Momentum Problem
We compare the angular momentum extracted by a wind from a pre-main-sequence
star to the torques arising from the interaction between the star and its
Keplerian accretion disk. We find that the wind alone can counteract the
spin-up torque from mass accretion, solving the mystery of why accreting
pre-main-sequence stars are observed to spin at less than 10% of break-up
speed, provided that the mass outflow rate in the stellar winds is ~10% of the
accretion rate. We suggest that such massive winds will be driven by some
fraction of the accretion power. For observationally constrained
typical parameters of classical T-Tauri stars, needs to be between a
few and a few tens of percent. In this scenario, efficient braking of the star
will terminate simultaneously with accretion, as is usually assumed to explain
the rotation velocities of stars in young clusters.Comment: Accepted by ApJ Letter
The Angular Momentum Evolution of 0.1-10 Msun Stars From the Birthline to the Main Sequence
(Abridged) Projected rotational velocities (vsini) have been measured for a
sample of 145 stars with masses between 0.4 and >10 Msun (median mass 2.1 Msun)
located in the Orion star-forming complex. These measurements have been
supplemented with data from the literature for Orion stars with masses as low
as 0.1 Msun. The primary finding from analysis of these data is that the upper
envelope of the observed values of angular momentum per unit mass (J/M) varies
as M^0.25 for stars on convective tracks having masses in the range ~0.1 to ~3
Msun. This power law extends smoothly into the domain of more massive stars (3
to 10 Msun), which in Orion are already on the ZAMS. This result stands in
sharp contrast to the properties of main sequence stars, which show a break in
the power law and a sharp decline in J/M with decreasing mass for stars with M
<2 Msun. A second result of our study is that this break is seen already among
the PMS stars in our Orion sample that are on radiative tracks, even though
these stars are only a few million years old. A comparison of rotation rates
seen for stars on either side of the convective-radiative boundary shows that
stars do not rotate as solid bodies during the transition from convective to
radiative tracks.Comment: to appear in Ap
El Niño and the delayed action oscillator
We study the dynamics of the El Niño phenomenon using the mathematical model of delayedaction oscillator (DAO). Topics such as the influence of the annual cycle, global warming, stochastic influences due to weather conditions and even off-equatorial heat-sinks can all be discussed using only modest analytical and numerical resources. Thus the DAO allows for a pedagogical introduction to the science of El Niño and La Niña while at the same time avoiding the need for large-scale computing resources normally associated with much more sophisticated coupled atmosphere-ocean general circulation models. It is an approach which is ideally suited for student projects both at high school and undergraduate level
Precision radial velocities with CSHELL
Radial velocity identification of extrasolar planets has historically been
dominated by optical surveys. Interest in expanding exoplanet searches to M
dwarfs and young stars, however, has motivated a push to improve the precision
of near infrared radial velocity techniques. We present our methodology for
achieving 58 m/s precision in the K band on the M0 dwarf GJ 281 using the
CSHELL spectrograph at the 3-meter NASA IRTF. We also demonstrate our ability
to recover the known 4 Mjup exoplanet Gl 86 b and discuss the implications for
success in detecting planets around 1-3 Myr old T Tauri stars.Comment: 31 pages, 3 figures, 2 tables, accepted for publication in Ap
Stationarity, soft ergodicity, and entropy in relativistic systems
Recent molecular dynamics simulations show that a dilute relativistic gas
equilibrates to a Juettner velocity distribution if ensemble velocities are
measured simultaneously in the observer frame. The analysis of relativistic
Brownian motion processes, on the other hand, implies that stationary
one-particle distributions can differ depending on the underlying
time-parameterizations. Using molecular dynamics simulations, we demonstrate
how this relativistic phenomenon can be understood within a deterministic model
system. We show that, depending on the time-parameterization, one can
distinguish different types of soft ergodicity on the level of the one-particle
distributions. Our analysis further reveals a close connection between time
parameters and entropy in special relativity. A combination of different
time-parameterizations can potentially be useful in simulations that combine
molecular dynamics algorithms with randomized particle creation, annihilation,
or decay processes.Comment: 4 page
Magnetic fields and accretion flows on the classical T Tauri star V2129 Oph
From observations collected with the ESPaDOnS spectropolarimeter, we report
the discovery of magnetic fields at the surface of the mildly accreting
classical T Tauri star V2129 Oph. Zeeman signatures are detected, both in
photospheric lines and in the emission lines formed at the base of the
accretion funnels linking the disc to the protostar, and monitored over the
whole rotation cycle of V2129 Oph. We observe that rotational modulation
dominates the temporal variations of both unpolarized and circularly polarized
line profiles. We reconstruct the large-scale magnetic topology at the surface
of V2129 Oph from both sets of Zeeman signatures simultaneously. We find it to
be rather complex, with a dominant octupolar component and a weak dipole of
strengths 1.2 and 0.35 kG, respectively, both slightly tilted with respect to
the rotation axis. The large-scale field is anchored in a pair of 2-kG unipolar
radial field spots located at high latitudes and coinciding with cool dark
polar spots at photospheric level. This large-scale field geometry is unusually
complex compared to those of non-accreting cool active subgiants with moderate
rotation rates. As an illustration, we provide a first attempt at modelling the
magnetospheric topology and accretion funnels of V2129 Oph using field
extrapolation. We find that the magnetosphere of V2129 Oph must extend to about
7R* to ensure that the footpoints of accretion funnels coincide with the
high-latitude accretion spots on the stellar surface. It suggests that the
stellar magnetic field succeeds in coupling to the accretion disc as far out as
the corotation radius, and could possibly explain the slow rotation of V2129
Oph. The magnetospheric geometry we derive produces X-ray coronal fluxes
typical of those observed in cTTSs.Comment: MNRAS, in press (18 pages, 17 figures
Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. I. The Complex Behavior of the M8.5 Dwarf TVLM513-46546
[Abridged] We present the first simultaneous radio, X-ray, ultraviolet, and
optical spectroscopic observations of the M8.5 dwarf TVLM513-46546, with a
duration of 9 hours. These observations are part of a program to study the
origin of magnetic activity in ultracool dwarfs, and its impact on
chromospheric and coronal emission. Here we detect steady quiescent radio
emission superposed with multiple short-duration, highly polarized flares;
there is no evidence for periodic bursts previously reported for this object,
indicating their transient nature. We also detect soft X-ray emission, with
L_X/L_bol~10^-4.9, the faintest to date for any object later than M5, and a
possible weak X-ray flare. TVLM513-46546 continues the trend of severe
violation of the radio/X-ray correlation in ultracool dwarfs, by nearly 4
orders of magnitude. From the optical spectroscopy we find that the Balmer line
luminosity exceeds the X-ray luminosity by a factor of a few, suggesting that,
unlike in early M dwarfs, chromospheric heating may not be due to coronal X-ray
emission. More importantly, we detect a sinusoidal H-alpha light curve with a
period of 2 hr, matching the rotation period of TVLM513-46546. This is the
first known example of such Balmer line behavior, which points to a co-rotating
chromospheric hot spot or an extended magnetic structure, with a covering
fraction of about 50%. This feature may be transitory based on the apparent
decline in light curve peak during the four observed maxima. From the radio
data we infer a large scale steady magnetic field of ~100 G, in good agreement
with the value required for confinement of the X-ray emitting plasma. The radio
flares, on the other hand, are produced in a component of the field with a
strength of ~3 kG and a likely multi-polar configuration.Comment: 13 pages, 4 figure
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