8,370 research outputs found
Quantifying anhedonia-like symptoms in marmosets using appetitive Pavlovian conditioning.
Blunted reward responsivity is associated with anhedonia in humans and is a core feature of depression. This protocol describes how to train the common marmoset, Callithrix jacchus, on an appetitive Pavlovian conditioning paradigm to measure behavioral and cardiovascular correlates of anticipatory and consummatory phases of reward processing. We describe how to use intracerebral infusions to manipulate brain regions whose activity is relevant to impaired reward processing in depression and how the paradigm can be used to test antidepressant efficacy. For complete details on the use and execution of this protocol, please refer to Alexander et al. (2019)
Dissipation Rate of Turbulent Kinetic Energy in Diel Vertical Migrations: Comparison of ANSYS Fluent Model to Measurements
Recent studies suggest that diel vertical migrations of zooplankton may have an impact on ocean mixing, though details are not completely clear. A strong sound scattering layer of zooplankton undergoing diel vertical migrations was observed in Saanich Inlet, British Colombia, Canada by Kunze et al. (2006). In this study, a shipboard 200- kHz echosounder was used to track vertical motion of the sound scattering layer, and microstructure profiles were collected to observe turbulence. An increase of dissipation rate of turbulent kinetic energy by four to five orders of magnitude was measured during diel vertical migrations of zooplankton in one case (but not observed during other cases). A strong sound scattering layer undergoing diel vertical migration was also observed in the Straits of Florida via a bottom mounted acoustic Doppler current profiler at 244 m isobath. A 3-D non-hydrostatic computational fluid dynamics model with Lagrangian particle injections (a proxy for migrating zooplankton) via a discrete phase model was used to simulate the effect of diel vertical migrations on the turbulence for both Saanich Inlet and the Straits of Florida. The model was initialized with idealized (but based on observation) density and velocity profiles. Particles, with buoyancy adjusted to serve as a proxy for vertically swimming zooplankton, were injected to simulate diel vertical migration cycles. Results of models run with extreme concentrations of particles showed an increase in dissipation rate of turbulent kinetic energy of approximately five orders of magnitude over background turbulence during migration of particles in both Saanich Inlet and the Straits of Florida cases (though direct relation of the turbulence produced by buoyant particles and swimming organisms isn’t straightforward). This increase was quantitatively consistent, with turbulence measurements by Kunze et al. (2006). When 10 times fewer particles were injected into the model, the effect on dissipation rate of turbulent kinetic energy was an order of magnitude smaller than that from the extreme concentration. At a concentration of particles 100 times smaller than the extreme concentration, there was no longer an observable effect. In the Straits of Florida, direct turbulence measurements were not available to make a quantitative comparison. However, a small, but statistically significant decrease in northward current velocity profiles during migration times were observed after averaging these profiles over 11 months. A small decrease of current velocity connected to the vertical migrations of particles was reproduced in the Straits of Florida model case. The deviations in the velocity profiles can be explained by the increase in turbulent mixing during vertical migration periods
Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond
In this report we summarize the many dark matter searches currently being
pursued through four complementary approaches: direct detection, indirect
detection, collider experiments, and astrophysical probes. The essential
features of broad classes of experiments are described, each with their own
strengths and weaknesses. The complementarity of the different dark matter
searches is discussed qualitatively and illustrated quantitatively in two
simple theoretical frameworks. Our primary conclusion is that the diversity of
possible dark matter candidates requires a balanced program drawing from all
four approaches.Comment: Report prepared for the Community Summer Study (Snowmass) 2013, on
behalf of Cosmic Frontier Working Groups 1-4 (CF1: WIMP Dark Matter Direct
Detection, CF2: WIMP Dark Matter Indirect Detection, CF3: Non-WIMP Dark
Matter, and CF4: Dark Matter Complementarity); published versio
Bone Mineral Density and Osteoporosis after Preterm Birth: The Role of Early Life Factors and Nutrition
The effects of preterm birth and perinatal events on bone health in later life remain largely unknown. Bone mineral density (BMD) and osteoporosis risk may be programmed by early life factors. We summarise the existing literature relating to the effects of prematurity on adult BMD and the Developmental Origins of Health and Disease hypothesis and programming of bone growth. Metabolic bone disease of prematurity and the influence of epigenetics on bone metabolism are discussed and current evidence regarding the effects of breastfeeding and aluminium exposure on bone metabolism is summarised. This review highlights the need for further research into modifiable early life factors and their effect on long-term bone health after preterm birth
Macroinvertebrate responses to flow and stream temperature variability across regulated and non-regulated rivers
Asteroseismological constraints on the pulsating planetary nebula nucleus (PG1159-type) RX J2117.1+3412
We present asteroseismological inferences on RX J2117.1+3412, the hottest
known pulsating PG1159 star. Our results are based on full PG1159 evolutionary
models recently presented by Miller Bertolami & Althaus (2006). We performed
extensive computations of adiabatic g-mode pulsation periods on PG1159
evolutionary models with stellar masses ranging from 0.530 to 0.741 Mo. PG1159
stellar models are extracted from the complete evolution of progenitor stars
started from the ZAMS, through the thermally pulsing AGB and born-again phases
to the domain of the PG 1159 stars. We constrained the stellar mass of RX
J2117.1+3412 by comparing the observed period spacing with the asymptotic
period spacing and with the average of the computed period spacings. We also
employed the individual observed periods to find a representative seismological
model. We derive a stellar mass of 0.56-0.57 Mo from the period spacing data
alone. In addition, we found a best-fit model representative for RX
J2117.1+3412 with an effective temperature of 163,400 K, a stellar mass of
0.565 Mo, and a surface gravity log g= 6.61. The derived stellar luminosity and
radius are log(L/Lo)= 3.36 and log(R/Ro)= -1.23, respectively, and the He-rich
envelope thickness is Menv= 0.02 Mo. We derive a seismic distance of 452 pc and
a linear size of the planetary nebula of 1.72 pc. These inferences seem to
solve the discrepancy between the RX J2117.1+3412 evolutionary timescale and
the size of the nebula. All of the seismological tools we use concur to the
conclusion that RX J2117.1+3412 must have a stellar mass of 0.565 Mo much in
agreement with recent asteroseismology studies and in clear conflict with the
predictions of spectroscopy plus evolutionary tracks.Comment: 10 pages, 6 figures, 2 tables. Accepted for publication in Astronomy
and Astrophysics. Erratum available as a separate fil
Evidence for a Long-Standing Top-Heavy IMF in the Central Parsec of the Galaxy
We classify 329 late-type giants within 1 parsec of Sgr A*, using the
adaptive optics integral field spectrometer SINFONI on the VLT. These
observations represent the deepest spectroscopic data set so far obtained for
the Galactic Center, reaching a 50% completeness threshold at the approximate
magnitude of the helium-burning red clump (Ks ~ 15.5 mag.). Combining our
spectroscopic results with NaCo H and Ks photometry, we construct an observed
Hertzsprung-Russell diagram, which we quantitatively compare to theoretical
distributions of various star formation histories of the inner Galaxy, using a
chi-squared analysis. Our best-fit model corresponds to continuous star
formation over the last 12 Gyr with a top-heavy initial mass function (IMF).
The similarity of this IMF to the IMF observed for the most recent epoch of
star formation is intriguing and perhaps suggests a connection between recent
star formation and the stars formed throughout the history of the Galactic
Center.Comment: 18 pages, 10 figures, Accepted to ApJ: 15 July 200
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