Abstract
Depending upon the properties of their compact remnants and the physics included in the models, simulations of neutron star mergers can produce a broad range of ejecta properties. The ...characteristics of this ejecta, in turn, define the kilonova emission. To explore the effect of ejecta properties, we present a grid of two-component 2D axisymmetric kilonova simulations that vary mass, velocity, morphology, and composition. The masses and velocities of each component vary, respectively, from 0.001 to 0.1
M
⊙
and 0.05 to 0.3
c
, covering much of the range of results from the neutron star merger literature. The set of 900 models is constrained to have a toroidal low electron fraction (
Y
e
) ejecta with a robust
r
-process composition and either a spherical or lobed high-
Y
e
ejecta with two possible compositions. We simulate these models with the Monte Carlo radiative transfer code
SuperNu
using a full suite of lanthanide and fourth-row element opacities. We examine the trends of these models with parameter variation, show how they can be used with statistical tools, and compare the model light curves and spectra to those of AT2017gfo, the electromagnetic counterpart of GW170817.
More than 20 precataclysmic variable (pre-CV) systems have now been discovered with very short orbital periods ranging from 250 minutes down to 68 minutes. A pre-CV consists of a white dwarf (WD) or ...hot subdwarf primary and a low-mass companion star, where the companion star has successfully ejected the common envelope (CE) of the primary progenitor, but mass transfer from the companion star to the primary has not yet commenced. In this short-period range, a substantial fraction of the companion stars are likely to be either brown dwarfs with masses 0.07 M or stars at the bottom of the main sequence (MS; 0.1 M ). The discovery of these short-period pre-CVs raises the question, what is the shortest possible orbital period of such systems? We ran 500 brown dwarf/low-mass MS models with Modules for Experiments in Stellar Astrophysics that cover the mass range from 0.002 to 0.1 M . We find that the shortest possible orbital period is 40 minutes, with a corresponding brown dwarf mass of 0.07 M for an age equal to a Hubble time. We discuss the past evolution of these systems through the CE and suggest that many of the systems with present-day WD primaries may have exited the CE with the primary as a helium-burning hot subdwarf. We also characterize the future evolution of the observed systems, which includes a phase as CVs below the conventional period minimum.
The gamma-exponentiated exponential distribution Ristić, Miroslav M.; Balakrishnan, Narayanaswamy
Journal of statistical computation and simulation,
08/2012, Letnik:
82, Številka:
8
Journal Article
Recenzirano
In this paper, we introduce a new distribution generated by gamma random variables. We show that this distribution includes as a special case the distribution of the lower record value from a ...sequence of i.i.d. random variables from a population with the exponentiated (generalized) exponential distribution. The properties of this distribution are derived and the estimation of the model parameters is discussed. Some applications to real data sets are finally presented for illustration.
Glass samples with composition xFe2O3・yAl2O3・(100-x-y)SiO2 abbreviated as xFyAS for photo-Fenton catalyst were prepared by a sol-gel method and heat-treated at 1000 °C for 100 min. It was found that ...when alumina was added to the Fe2O3 + SiO2 glass matrix, the photo-Fenton activity tested with methylene blue degradation increased, so did the photoactivity with visible light. From Mössbauer and XRD results, it was noticed that hercynite phase appeared that showed higher photoactivity even for the samples having lower hematite content and that the Fe+3 (Td) content increased with Al2O3 content. In these samples, the more Fe+3 (Td) found, the more effective was the photo-Fenton degradation.
•Sol-gel synthesized and heated 30FyAS, 40FyAS and 50FyAS samples with ‘y’ of 10, 15, and 20 resulted in the precipitation of hematite and hercynite (FeAl2O4) with photocatalytic properties.•As for the photo-Fenton degradation ability by adding H2O2, the best sample was 40F20AS yielding the highest first-order rate constant of 8.61 × 10−2 min−1.•These results indicate that Fe3+ ions also show photo-Fenton catalytic abilities and light-scattering ability caused by the introduction of Al2O3 is effective for the visible light photocatalytic activity.
Objectives
To evaluate the influence of irradiation time on degree of conversion (DC) and microhardness of high-viscosity bulk-fill resin composites in depths up to 6 mm.
Materials and methods
Four ...bulk-fill materials (Tetric EvoCeram Bulk Fill—TECBF; x-tra fil—XF; QuixFil—QF; SonicFill—SF) and one conventional nano-hybrid resin composite (Tetric EvoCeram—TEC) were irradiated for 10, 20, or 30 s at 1,170 mW/cm
2
. DC and Knoop microhardness (KHN) were recorded after 24-h dark storage at five depths: 0.1, 2, 4, 5, and 6 mm. Data were statistically analyzed using ANOVA and Bonferroni’s post-hoc test (
α
= 0.05).
Results
With increasing bulk thickness, DC and KHN significantly decreased for TEC. TECBF and SF showed a significant decrease in DC and KHN at 4-mm depth after 10-s irradiation, but no decrease in DC after 30-s irradiation (
p
> 0.05). XF and QF demonstrated no significant DC decrease at depths up to 6 mm after irradiation of at least 20 s. At 4-mm depth, all materials tested achieved at least 80 % of their maximum DC value, irrespective of irradiation time. However, at the same depth (4 mm), only XF and QF irradiated for 30 s achieved at least 80 % of their maximum KHN value.
Conclusions
Regarding DC, the tested bulk-fill resin composites can be safely used up to at least 4-mm incremental thickness. However, with respect to hardness, only XF and QF achieved acceptable results at 4-mm depth with 30 s of irradiation.
Clinical relevance
Minimum irradiation times stated by the manufacturers cannot be recommended for placement of high-viscosity bulk-fill materials in 4-mm increments.
In this study, a new one-parameter discrete distribution obtained by compounding the Poisson and xgamma distributions is proposed. Some statistical properties of the new distribution are obtained ...including moments and probability and moment generating functions. Two methods are used for the estimation of the unknown parameter: the maximum likelihood method and the method of moments. Additionally, the count regression model and integer-valued autoregressive process of the proposed distribution are introduced. Some possible applications of the introduced models are considered and discussed.
Air quality biomonitoring using plant leaves has been widely applied to assess the effects of atmospheric pollution. Although practiced for many years, it has not given completely satisfactory data, ...due to different and even opposing results. This study comprises an investigation on the content of some trace elements (Al, As, Ba, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Cd, Pb) in leaves of four tree species common for the urban area of Belgrade (Serbia). The assay took place in July 2009 when the selected trees (
Acer platanoides,
Aesculus hippocastanum,
Betula pendula,
Tilia cordata) were in the maximum of physiological activity during the vegetation season. Among the investigated species, leaves of
A. platanoides contained the highest concentrations of the measured elements. The assumption that a large green area in the Belgrade city periphery would be a suitable control site appeared to be disputable due to the substantial load of the elements obtained in the leaves. It was shown that even a short rinse with bidistilled water (3–5
s), applied twice to the leaves prior to chemical analysis, led to a significant decrease of some element concentrations (most pronounced for Al, Fe and Pb in all species, but also evident for Cu, Cr, Co and Zn for some of them). However, by washing leaves, the representativeness of leaf samples per studied site could be improved due to removal of some superficial loosely adhered impurities and so diminished large variability of element concentrations among leaf subsamples providing more representative information on the element content in leaves per site, and the area, respectively.
We analyzed the prevalence and predisposing factors for the overall rejection rate after retrieval of 267 fresh femoral head allografts over the past 7 years. The present study aimed to assess the ...quality system of institutional bone banking that can provide high-standard allografts with a low infection rate. Retrospective analysis of bone banking from June 2013 to December 2019 was conducted on 267 donors and 153 recipients. Of the 267 donated femoral heads, 74 were rejected, giving an overall rejection rate of 27.71%. The leading cause of allograft rejection was the inability to perform serology tests due to donor death; the absence of serological tests itself, and the donor refusal to perform the serology 6-month retest in 42 donors (15.72%). At retrieval, 12 allografts were positive, giving an overall contamination rate of 4.49%. Seven (2.62%) of the 267 allografts failed the blood screening tests. Thirteen allografts (4.86%) were discarded because of suspected damage to the packaging or disuse during surgery. An infection rate of 1.30% was found following transplantation. Over the past 7 years of bone banking, our results show that the overall rejection rate and the allograft-related infection rate correlate with international standards. The leading cause of allograft rejection was the inability to perform serology tests due to donor death and their refusal to perform the serology retests. Besides stringent aseptic allograft handling, donor motivation to participate in bone banking is extremely important for its efficient functioning.
A new stationary first-order integer-valued autoregressive process with geometric marginal distributions is introduced based on negative binomial thinning. Some properties of the process are ...established. Estimators of the parameters of the process are obtained using the methods of conditional least squares, Yule–Walker and maximum likelihood. Also, the asymptotic properties of the estimators are derived involving their distributions. Some numerical results of the estimators are presented with a discussion to the obtained results. Real data are used and a possible application is discussed.
Aims
In the present work, the Libyan wild‐growing Thymus capitatus essential oil (EO) was evaluated for its biological properties.
Methods and Results
Carvacrol (68·19%) and thymol (12·29%) were ...found to be the main compounds of the oil. Antioxidant properties, determined by 2,2‐diphenylpicrylhydrazyl (DPPH) assay, revealed that IC50 values were 119, 403 and 105 μg ml−1 for oil, thymol and carvacrol respectively. Microdilution method showed strong antibacterial and especially antifungal potential. Tetrazolium (MTT) colorimetric assay indicated moderate cytotoxicity towards human cell lines MRC‐5, HCT 116 and HT‐29 (IC50 = 30–150 μg ml−1). In adhesion‐inhibition assay oil and main compounds reduced adhesion of Escherichia coli and Listeria monocytogenes on colon cells HT‐29 (51 and 39% of inhibition against L. monocytogenes and E. coli respectively).
Conclusions
Essential oil of Th. capitatus showed moderate cytotoxic activity, together with excellent antimicrobial effect, in particular against fungi, and significant potential to reduce pathogen colonization in colon.
Significance and Impact of the Study
This is the first report that EO of Th. capitatus could protect against colonization of pathogens to colon epithelium. Thymus capitatus from Libya should be recognized as possible new source of natural antioxidants, antimicrobials as well as possible source of new chemotherapeutics.
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