13,026 research outputs found
The tropospheric gas composition of Jupiter's north equatorial belt (NH3, PH3, CH3D, GeH4, H2O) and the Jovian D/H isotropic ratio
The gas composition of the troposphere of Jupiter in the clearest regions of the North Equatorial Belt (NEB) was derived from the Voyager 1 IRIS data. The infrared spectrum for this homogeneous cloud free region was modeled to infer altitude profiles for NH3, PH3, GeH4 and H2O. The Profiles for NH3 and PH3 were found to be depleted in the upper troposphere but otherwise in agreement with their solar values at the 1 bar level. The mole fraction for CH3D was determined to be 3.5(+1.0 or -1.3) x 10 to the minus 7th power. The GeH4 mole fraction of 7+ or -2 x 10 to the minus 10th power at the 2 to 3 bar level is a factor of 10 lower than the solar value. The H2O mole fraction is approximately 1 x 0.00001 at the 2.5 bar level and is increasing to approximately 3 x 0.00001 at 4 bars where it is a factor of 30 lower than solar. Using IRIS infrared values for the mole fractions of CH3D and CH4 a value of D/H = 3.6(+1.0 or -1.4)x 0.00001 is derived. Assuming this Jovian D/H ratio is representative of the protosolar nebula, and correcting for chemical galactic evolution, yields a value of 5.5 - 9.0 x 0.00001 for the primordial D/H ratio and an upper limit of 1.8 to 2.4 x 10 to the minus 31st power cu cm for the present day baryon density
Tonic inhibition of accumbal spiny neurons by extrasynaptic 4 GABAA receptors modulates the actions of psychostimulants
Within the nucleus accumbens (NAc), synaptic GABAA receptors (GABAARs) mediate phasic inhibition of medium spiny neurons (MSNs) and influence behavioral responses to cocaine. We demonstrate that both dopamine D1- and D2-receptor-expressing MSNs (D-MSNs) additionally harbor extrasynaptic GABAARs incorporating α4, β, and δ subunits that mediate tonic inhibition, thereby influencing neuronal excitability. Both the selective δ-GABAAR agonist THIP and DS2, a selective positive allosteric modulator, greatly increased the tonic current of all MSNs from wild-type (WT), but not from δ−/− or α4−/− mice. Coupling dopamine and tonic inhibition, the acute activation of D1 receptors (by a selective agonist or indirectly by amphetamine) greatly enhanced tonic inhibition in D1-MSNs but not D2-MSNs. In contrast, prolonged D2 receptor activation modestly reduced the tonic conductance of D2-MSNs. Behaviorally, WT and constitutive α4−/− mice did not differ in their expression of cocaine-conditioned place preference (CPP). Importantly, however, mice with the α4 deletion specific to D1-expressing neurons (α4D1−/−) showed increased CPP. Furthermore, THIP administered systemically or directly into the NAc of WT, but not α4−/− or α4D1−/− mice, blocked cocaine enhancement of CPP. In comparison, α4D2−/− mice exhibited normal CPP, but no cocaine enhancement. In conclusion, dopamine modulation of GABAergic tonic inhibition of D1- and D2-MSNs provides an intrinsic mechanism to differentially affect their excitability in response to psychostimulants and thereby influence their ability to potentiate conditioned reward. Therefore, α4βδ GABAARs may represent a viable target for the development of novel therapeutics to better understand and influence addictive behaviors
Statistical mixing and aggregation in Feller diffusion
We consider Feller mean-reverting square-root diffusion, which has been
applied to model a wide variety of processes with linearly state-dependent
diffusion, such as stochastic volatility and interest rates in finance, and
neuronal and populations dynamics in natural sciences. We focus on the
statistical mixing (or superstatistical) process in which the parameter related
to the mean value can fluctuate - a plausible mechanism for the emergence of
heavy-tailed distributions. We obtain analytical results for the associated
probability density function (both stationary and time dependent), its
correlation structure and aggregation properties. Our results are applied to
explain the statistics of stock traded volume at different aggregation scales.Comment: 16 pages, 3 figures. To be published in Journal of Statistical
Mechanics: Theory and Experimen
Offenders' Crime Narratives across Different Types of Crimes
The current study explores the roles offenders see themselves playing during an offence and their relationship to different crime types. One hundred and twenty incarcerated offenders indicated the narrative roles they acted out whilst committing a specific crime they remembered well. The data were subjected to Smallest Space Analysis (SSA) and four
themes were identified: Hero, Professional, Revenger and Victim in line with the recent theoretical framework posited for Narrative Offence Roles (Youngs & Canter, 2012). Further analysis showed that different subsets of crimes were more like to be associated with different narrative offence roles. Hero and Professional were found to be associated with property offences (theft, burglary and shoplifting), drug offences and robbery and Revenger
and Victim were found to be associated with violence, sexual offences and murder. The theoretical implications for understanding crime on the basis of offenders' narrative roles as well as practical implications are discussed
The Rising Light Curves of Type Ia Supernovae
We present an analysis of the early, rising light curves of 18 Type Ia
supernovae (SNe Ia) discovered by the Palomar Transient Factory (PTF) and the
La Silla-QUEST variability survey (LSQ). We fit these early data flux using a
simple power-law to determine the time of first
light , and hence the rise-time from first light to
peak luminosity, and the exponent of the power-law rise (). We find a mean
uncorrected rise time of days, with individual SN rise-times
ranging from to days. The exponent n shows significant
departures from the simple 'fireball model' of (or ) usually assumed in the literature. With a mean value of , our data also show significant diversity from event to event. This
deviation has implications for the distribution of 56Ni throughout the SN
ejecta, with a higher index suggesting a lesser degree of 56Ni mixing. The
range of n found also confirms that the 56Ni distribution is not standard
throughout the population of SNe Ia, in agreement with earlier work measuring
such abundances through spectral modelling. We also show that the duration of
the very early light curve, before the luminosity has reached half of its
maximal value, does not correlate with the light curve shape or stretch used to
standardise SNe Ia in cosmological applications. This has implications for the
cosmological fitting of SN Ia light curves.Comment: 19 pages, 19 figures, accepted for publication in MNRA
A comparative study of Type II-P and II-L supernova rise times as exemplified by the case of LSQ13cuw
We report on our findings based on the analysis of observations of the Type
II-L supernova LSQ13cuw within the framework of currently accepted physical
predictions of core-collapse supernova explosions. LSQ13cuw was discovered
within a day of explosion, hitherto unprecedented for Type II-L supernovae.
This motivated a comparative study of Type II-P and II-L supernovae with
relatively well-constrained explosion epochs and rise times to maximum
(optical) light. From our sample of twenty such events, we find evidence of a
positive correlation between the duration of the rise and the peak brightness.
On average, SNe II-L tend to have brighter peak magnitudes and longer rise
times than SNe II-P. However, this difference is clearest only at the extreme
ends of the rise time versus peak brightness relation. Using two different
analytical models, we performed a parameter study to investigate the physical
parameters that control the rise time behaviour. In general, the models
qualitatively reproduce aspects of the observed trends. We find that the
brightness of the optical peak increases for larger progenitor radii and
explosion energies, and decreases for larger masses. The dependence of the rise
time on mass and explosion energy is smaller than the dependence on the
progenitor radius. We find no evidence that the progenitors of SNe II-L have
significantly smaller radii than those of SNe II-P.Comment: 19 pages, 10 figures, accepted by A&
The progenitor and early evolution of the Type IIb SN 2016gkg
We report initial observations and analysis on the Type IIb SN~2016gkg in the
nearby galaxy NGC~613. SN~2016gkg exhibited a clear double-peaked light curve
during its early evolution, as evidenced by our intensive photometric follow-up
campaign. SN~2016gkg shows strong similarities with other Type IIb SNe, in
particular with respect to the \he~emission features observed in both the
optical and near infrared. SN~2016gkg evolved faster than the prototypical
Type~IIb SN~1993J, with a decline similar to that of SN~2011dh after the first
peak. The analysis of archival {\it Hubble Space Telescope} images indicate a
pre-explosion source at SN~2016gkg's position, suggesting a progenitor star
with a mid F spectral type and initial mass \msun, depending on
the distance modulus adopted for NGC~613. Modeling the temperature evolution
within of explosion, we obtain a progenitor radius of
\rsun, smaller than that obtained from the analysis of the
pre-explosion images (\rsun).Comment: 7 pages, 5 figures. Submitted to ApJ Letter
Using late-time optical and near-infrared spectra to constrain Type Ia supernova explosion properties
The late-time spectra of Type Ia supernovae (SNe Ia) are powerful probes of
the underlying physics of their explosions. We investigate the late-time
optical and near-infrared spectra of seven SNe Ia obtained at the VLT with
XShooter at 200 d after explosion. At these epochs, the inner Fe-rich ejecta
can be studied. We use a line-fitting analysis to determine the relative line
fluxes, velocity shifts, and line widths of prominent features contributing to
the spectra ([Fe II], [Ni II], and [Co III]). By focussing on [Fe II] and [Ni
II] emission lines in the ~7000-7500 \AA\ region of the spectrum, we find that
the ratio of stable [Ni II] to mainly radioactively-produced [Fe II] for most
SNe Ia in the sample is consistent with Chandrasekhar-mass delayed-detonation
explosion models, as well as sub-Chandrasekhar mass explosions that have
metallicity values above solar. The mean measured Ni/Fe abundance of our sample
is consistent with the solar value. The more highly ionised [Co III] emission
lines are found to be more centrally located in the ejecta and have broader
lines than the [Fe II] and [Ni II] features. Our analysis also strengthens
previous results that SNe Ia with higher Si II velocities at maximum light
preferentially display blueshifted [Fe II] 7155 \AA\ lines at late times. Our
combined results lead us to speculate that the majority of normal SN Ia
explosions produce ejecta distributions that deviate significantly from
spherical symmetry.Comment: 17 pages, 12 figure, accepted for publication in MNRA
"How do pilates trained physiotherapists utilize and value pilates exercise for MSK conditions? A qualitative study"
Background
Pilates is a popular exercise therapy approach offering numerous benefits, including muscular strength, flexibility, control, and core stability. Pilates has been widely utilized in the prevention and rehabilitation of a variety of musculoskeletal disorders.
Objectives
The aim of this study was to explore the experiences and opinions of Pilates trained NHS and private practice physiotherapists in the UK, regarding the perceived benefits, risks, delivery and rationale for this exercise method.
Methods
This qualitative study used a self‐designed electronic survey to retrieve the views of 30 physiotherapists, who had undertaken formal Pilates Instruction training, recruited by a purposive and snowball sampling method. Questions were either multiple choice or open‐ended, examined via thematic analysis.
Results
Physiotherapists identified the most important benefits of Pilates as reduction in fear‐avoidance, improving bodily awareness and increasing muscular strength. Exercises that promote general movement were highlighted as being particularly useful, with a majority recommending daily practice for optimum benefit. Participants recognized lack of core strength as a key indicator, whereas others criticized excessive focus on this principle.
Conclusions
Physiotherapists identified a range of inter‐linked benefits and recognized that Pilates is hugely modifiable. Individualizing exercises can further encourage participation and negate the restriction of some health conditions. NHS and Private Practice Therapists utilize Pilates in a similar way, although rationales for its use may differ, as the justification for Pilates exercise may be evolving. Pilates appears a valuable methodology in the NHS, which can help patients engage with activity
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