We present a new self-consistent and versatile method that derives photo-spheric radius and temperature variations of Type II-Plateau supernovae based on their expansion velocities and photo-metric ...measurements. We apply the method to a sample of 26 well-observed, nearby supernovae with published light curves and velocities. We simultaneously fit ~230 velocity and ~6800 mag measurements distributed over 21 photometric pass-bands spanning wavelengths from 0.19 to 2.2 mu m. We compare our model to the theoretical dilution factors and find good agreement for the B and V filters. Our results differ from the theory when the I, J, H, or K bands are included. We investigate the reddening law toward our supernovae and find reasonable agreement with standard RV ~ 3.1 reddening law in UBVRI bands. Results for other bands are inconclusive. We make our fitting code publicly available.
ABSTRACT Hydrogen-rich Type II-Plateau supernovae (SNe) exhibit correlations between the plateau luminosity , the nickel mass , the explosion energy , and the ejecta mass . Using our global, ...self-consistent, multi-band model of nearby well-observed SNe, we find that the covariances of these quantities are strong and that the confidence ellipsoids are oriented in the direction of the correlations, which reduces their significance. By proper treatment of the covariance matrix of the model, we discover a significant intrinsic width to the correlations between , and , where the uncertainties due to the distance and the extinction dominate. For fixed , the spread in is about 0.25 dex, which we attribute to the differences in the progenitor internal structure. We argue that the effects of incomplete γ-ray trapping are not important in our sample. Similarly, the physics of the Type II-Plateau SN light curves leads to inherently degenerate estimates of and , which makes their observed correlation weak. Ignoring the covariances of SN parameters or the intrinsic width of the correlations causes significant biases in the slopes of the fitted relations. Our results imply that Type II-Plateau SN explosions are not described by a single physical parameter or a simple one-dimensional trajectory through the parameter space, but instead reflect the diversity of the core and surface properties of their progenitors. We discuss the implications for the physics of the explosion mechanism and possible future observational constraints.
Poor information privacy practices have been identified in health apps. Medical app accreditation programs offer a mechanism for assuring the quality of apps; however, little is known about their ...ability to control information privacy risks. We aimed to assess the extent to which already-certified apps complied with data protection principles mandated by the largest national accreditation program.
Cross-sectional, systematic, 6-month assessment of 79 apps certified as clinically safe and trustworthy by the UK NHS Health Apps Library. Protocol-based testing was used to characterize personal information collection, local-device storage and information transmission. Observed information handling practices were compared against privacy policy commitments.
The study revealed that 89% (n = 70/79) of apps transmitted information to online services. No app encrypted personal information stored locally. Furthermore, 66% (23/35) of apps sending identifying information over the Internet did not use encryption and 20% (7/35) did not have a privacy policy. Overall, 67% (53/79) of apps had some form of privacy policy. No app collected or transmitted information that a policy explicitly stated it would not; however, 78% (38/49) of information-transmitting apps with a policy did not describe the nature of personal information included in transmissions. Four apps sent both identifying and health information without encryption. Although the study was not designed to examine data handling after transmission to online services, security problems appeared to place users at risk of data theft in two cases.
Systematic gaps in compliance with data protection principles in accredited health apps question whether certification programs relying substantially on developer disclosures can provide a trusted resource for patients and clinicians. Accreditation programs should, as a minimum, provide consistent and reliable warnings about possible threats and, ideally, require publishers to rectify vulnerabilities before apps are released.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The prevalence of diabetes is on a steady increase worldwide and it is now identified as one of the main threats to human health in the 21st century. In Nigeria, the use of herbal medicine alone or ...alongside prescription drugs for its management is quite common. We hereby carry out a review of medicinal plants traditionally used for diabetes management in Nigeria. Based on the available evidence on the species׳ pharmacology and safety, we highlight ways in which their therapeutic potential can be properly harnessed for possible integration into the country׳s healthcare system.
Ethnobotanical information was obtained from a literature search of electronic databases such as Google Scholar, Pubmed and Scopus up to 2013 for publications on medicinal plants used in diabetes management, in which the place of use and/or sample collection was identified as Nigeria. ‘Diabetes’ and ‘Nigeria’ were used as keywords for the primary searches; and then ‘Plant name – accepted or synonyms’, ‘Constituents’, ‘Drug interaction’ and/or ‘Toxicity’ for the secondary searches.
The hypoglycemic effect of over a hundred out of the 115 plants reviewed in this paper is backed by preclinical experimental evidence, either in vivo or in vitro. One-third of the plants have been studied for their mechanism of action, while isolation of the bioactive constituent(s) has been accomplished for twenty three plants.
Some plants showed specific organ toxicity, mostly nephrotoxic or hepatotoxic, with direct effects on the levels of some liver function enzymes. Twenty eight plants have been identified as in vitro modulators of P-glycoprotein and/or one or more of the cytochrome P450 enzymes, while eleven plants altered the levels of phase 2 metabolic enzymes, chiefly glutathione, with the potential to alter the pharmacokinetics of co-administered drugs.
This review, therefore, provides a useful resource to enable a thorough assessment of the profile of plants used in diabetes management so as to ensure a more rational use. By anticipating potential toxicities or possible herb–drug interactions, significant risks which would otherwise represent a burden on the country׳s healthcare system can be avoided.
Display omitted
Context.
The peculiar supernova (SN) 2009ip was an ambiguous event that placed many questions on its true origin. Here, we present very late-time spectroscopic and photometric observations of SN ...2009ip, obtained 9 years (3274 days) after the 2012B outburst.
Aims.
We analyze the H
α
emission still present in the very late-time spectrum of SN 2009ip. We also obtain photometric measurements in
r
,
g
and
i
bands.
Methods.
We obtain observations of SN 2009ip on 2021 September 10 with the IMACS instrument at the 6.5 m
Magellan Baade
Telescope, located at the Las Campanas Observatory.
Results.
SN 2009ip was detected in
r
,
g
and
i
bands, with an absolute magnitude in
r
band of ∼ − 8.66 mag. We show that the source faded significantly since the last observations in these bands. We further show that the very late-time spectrum contains a persistent H
α
emission, although no other emission lines were detected. We measure a full width at half maximum of 930 ± 40 km s
−1
and luminosity of ∼ 8.0 × 10
37
erg s
−1
for the H
α
emission. The luminosity decreased relatively slowly in comparison to the last observations and its fading rate is very similar to other long-living interacting transients, such as SN 2005ip. Finally, we conclude that although these properties could be consistent with a non-regular core-collapse SN, they could also be explained by non-terminal explosion scenarios.
The recent supernova (SN) known as SN 2009ip had dramatic precursor eruptions followed by an even brighter explosion in 2012. Its pre-2012 observations make it the best documented SN progenitor in ...history, but have fuelled debate about the nature of its 2012 explosion – whether it was a true SN or some type of violent non-terminal event. Both could power shock interaction with circumstellar material (CSM), but only a core-collapse SN provides a self-consistent explanation. The persistent broad emission lines in the spectrum require a relatively large ejecta mass, and a corresponding kinetic energy of at least 1051 erg, while the faint 2012a event is consistent with published models of core-collapse SNe from compact (∼60 R⊙) blue supergiants. The light curves of SN 2009ip and another Type IIn, SN 2010mc, were nearly identical; we demonstrate that their spectra match as well, and that both are standard SNe IIn. Our observations contradict the recent claim that the late-time spectrum of SN 2009ip is returning to its progenitor's luminous blue variable-like state, and we show the that late-time spectra of SN 2009ip closely resemble the spectra of SN 1987A. Moreover, SN 2009ip's changing Hα equivalent width after explosion matches behaviour typically seen in core-collapse SNe IIn. Several key facts about SN 2009ip and SN 2010mc argue strongly in favour of a core-collapse interpretation, and make a non-terminal 1050 erg event implausible. The most straightforward and self-consistent interpretation is that SN 2009ip was an initially faint core-collapse explosion of a blue supergiant that produced about half as much 56Ni as SN 1987A, with most of the peak luminosity from CSM interaction.
We discover clear doubly peaked line profiles in 3 out of ∼20 Type Ia supernovae (SNe Ia) with high-quality nebular-phase spectra. The profiles are consistently present in three separated Co/Fe ...emission features. The two peaks are respectively blueshifted and redshifted relative to the host galaxies and are separated by ∼5000 km s−1. The doubly peaked profiles directly reflect a bimodal velocity distribution of the radioactive 56Ni in the ejecta that powers the emission of these SNe. Due to their random orientations, only a fraction of SNe with intrinsically bimodal velocity distributions will appear as doubly peaked spectra. Therefore, SNe with intrinsic bimodality are likely common, especially among the SNe in the low-luminosity part on the Phillips relation (Δm
15(B) ≳ 1.3; ∼ 40 per cent of all SNe Ia). Such bimodality is naturally expected from direct collisions of white dwarfs (WDs) due to the detonation of both WDs and is demonstrated in a 3D 0.64–0.64M⊙ WD collision simulation. In the future, with a large sample of nebular spectra and a comprehensive set of numerical simulations, the collision model can be unambiguously tested as the primary channel for SNe Ia, and the distribution of nebular line profiles will either be a smoking gun or rule it out.
The single-degenerate scenario for Type Ia supernovae should yield metal-rich ejecta that enclose some stripped material from the non-degenerate H-rich companion star. We present a large grid of ...non-local thermodynamic equilibrium steady-state radiative transfer calculations for such hybrid ejecta and provide analytical fits for the H
α
luminosity and equivalent width. Our set of models covers a range of masses for
56
Ni and the ejecta, for the stripped material (
M
st
), and post-explosion epochs from 100 to 300 d. The brightness contrast between stripped material and metal-rich ejecta challenges the detection of H
I
and He
I
lines prior to ~100 d. Intrinsic and extrinsic optical depth effects also influence the radiation emanating from the stripped material. This inner denser region is marginally thick in the continuum and optically thick in all Balmer lines. The overlying metal-rich ejecta blanket the inner regions, completely below about 5000 Å, and more sparsely at longer wavelengths. As a consequence, H
β
should not be observed for all values of
M
st
up to at least 300 days, while H
α
should be observed after ~100 d for all
M
st
≥ 0.01
M
⊙
. Observational non-detections capable of limiting the H
α
equivalent width to <1 Å set a formal upper limit of
M
st
< 0.001
M
⊙
. This contrasts with the case of circumstellar-material (CSM) interaction, not subject to external blanketing, which should produce H
α
and H
β
lines with a strength dependent primarily on CSM density. We confirm previous analyses that suggest low values of order 0.001
M
⊙
for
M
st
to explain the observations of the two Type Ia supernovae with nebular-phase H
α
detection, in conflict with the much greater stripped mass predicted by hydrodynamical simulations for the single-degenerate scenario. A more likely solution is the double-degenerate scenario, together with CSM interaction, or enclosed material from a tertiary star in a triple system or from a giant planet.
In the last decades, astrocytes have emerged as important regulatory cells actively involved in brain function by exchanging signaling with neurons. The endocannabinoid (eCB) signaling is widely ...present in many brain areas, being crucially involved in multiple brain functions and animal behaviors. The present review presents and discusses current evidence demonstrating that astrocytes sense eCBs released during neuronal activity and subsequently release gliotransmitters that regulate synaptic transmission and plasticity. The eCB signaling to astrocytes and the synaptic regulation mediated by astrocytes activated by eCBs are complex phenomena that exhibit exquisite spatial and temporal properties, a wide variety of downstream signaling mechanisms, and a large diversity of functional synaptic outcomes. Studies investigating this topic have revealed novel regulatory processes of synaptic function, like the lateral regulation of synaptic transmission and the active involvement of astrocytes in the spike‐timing dependent plasticity, originally thought to be exclusively mediated by the coincident activity of pre‐ and postsynaptic neurons, following Hebbian rules for associative learning. Finally, the critical influence of astrocyte‐mediated eCB signaling on animal behavior is also discussed.
Main Points
Astrocytes sense eCB signaling via CB1R activation and respond to eCB released during neuronal activity regulating synaptic plasticity.
The eCB signaling is widely expressed in many brain areas being crucial in many brain functions and animal behaviors.
We test the hypothesis that metal-poor globular clusters form within disk galaxies at redshifts image. We calculate the orbits of model clusters in the time-variable gravitational potential of a ...Milky Way-sized galaxy, using the outputs of a cosmological N-body simulation. We find that at present the orbits are isotropic in the inner 50 kpc of the Galaxy and preferentially radial at larger distances. All clusters located outside 10 kpc from the center formed in satellite galaxies, some of which are now tidally disrupted and some of which survive as dwarf galaxies. Mergers of the progenitors lead to a spheroidal spatial distribution of model clusters, although it is more extended than that of Galactic metal-poor clusters and has a somewhat shallower power-law slope of the number density profile, image. The combination of two-body relaxation, tidal shocks, and stellar evolution drives the evolution of the cluster mass function from an initial power law to a peaked distribution, in agreement with observations. However, not all initial conditions and not all evolution scenarios are consistent with the observed mass function of the Galactic globular clusters. We find that our best-fitting models require the average cluster density, image, to be constant initially for clusters of all mass and to remain constant with time. However, these models do not explain the observed decrease of the mean density with galactocentric distance. Both synchronous formation of all clusters at a single epoch and continuous formation over a span of 1.6 Gyr (between image and 3) are consistent with the data. For both formation scenarios, we provide online catalogs of the main physical properties of model clusters.
PDF
