The ongoing COVID-19 epidemics poses a particular challenge to low and middle income countries, making some of them consider the strategy of "vertical confinement". In this strategy, contact is ...reduced only to specific groups (e.g. age groups) that are at increased risk of severe disease following SARS-CoV-2 infection. We aim to assess the feasibility of this scenario as an exit strategy for the current lockdown in terms of its ability to keep the number of cases under the health care system capacity. We developed a modified SEIR model, including confinement, asymptomatic transmission, quarantine and hospitalization. The population is subdivided into 9 age groups, resulting in a system of 72 coupled nonlinear differential equations. The rate of transmission is dynamic and derived from the observed delayed fatality rate; the parameters of the epidemics are derived with a Markov chain Monte Carlo algorithm. We used Brazil as an example of middle income country, but the results are easily generalizable to other countries considering a similar strategy. We find that starting from 60% horizontal confinement, an exit strategy on May 1st of confinement of individuals older than 60 years old and full release of the younger population results in 400 000 hospitalizations, 50 000 ICU cases, and 120 000 deaths in the 50-60 years old age group alone. Sensitivity analysis shows the 95% confidence interval brackets a order of magnitude in cases or three weeks in time. The health care system avoids collapse if the 50-60 years old are also confined, but our model assumes an idealized lockdown where the confined are perfectly insulated from contamination, so our numbers are a conservative lower bound. Our results discourage confinement by age as an exit strategy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
An
α
Ω dynamo, combining shear and cyclonic convection in the tachocline, is believed to generate the solar cycle. However, this model cannot explain cycles in fast rotators (with minimal ...shear) or in fully convective stars (no tachocline); an analysis of these stars could therefore provide key insights into how these cycles work. We reexamine ASAS data for 15 M dwarfs, 11 of which are presumed fully convective; the addition of newer ASAS-SN data confirms cycles in roughly 12 of them, while presenting new or revised rotation periods for 5 stars. The amplitudes and periods of these cycles follow
A
cyc
∝
P
cyc
0.94
±
0.11
, with
P
cyc
/
P
rot
∝
Ro
−1.02±0.06
(where
Ro
is the Rossby number), very similar to
P
cyc
/
P
rot
∝
Ro
−0.81±0.17
that we find for 40 previously studied FGK stars, although
P
cyc
/
P
rot
and
α
are a factor of ∼20 smaller in the M stars. The very different
P
cyc
/
P
rot
–
Ro
relation seen here compared to previous work suggests that two types of dynamo, with opposite
Ro
dependences, operate in cool stars. Initially, a (likely
α
2
or
α
2
Ω) dynamo operates throughout the convective zone in mid- to late-M and fast-rotating FGK stars, but once magnetic breaking decouples the core and convective envelope, a tachocline
α
Ω dynamo begins and eventually dominates in older FGK stars. A change in
α
in the tachocline dynamo generates the fundamentally different
P
cyc
/
P
rot
–
Ro
relation.
The COVID-19 pandemic was severely aggravated in Brazil due to its politicization by the country’s federal government. However, the impact of diffuse political forces on the fatality of an epidemic ...is notoriously difficult to quantify. Here we introduce a method to measure this effect in the Brazilian case, based on the inhomogeneous distribution throughout the national territory of political support for the federal government. This political support is quantified by the voting rates in the last general election in Brazil. This data is correlated with the fatality rates by COVID-19 in each Brazilian state as the number of deaths grows over time. We show that the correlation between fatality rate and political support grows as the government’s misinformation campaign is developed. This led to the dominance of such political factor for the pandemic impact in Brazil in 2021. Once this dominance is established, this correlation allows for an estimation of the total number of deaths due to political influence as 350±70 thousand up to the end of 2021, corresponding to (57±11)% of the total number of deaths.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We study with unprecedented detail the chemical composition and stellar parameters of the solar twin 18 Sco in a strictly differential sense relative to the Sun. Our study is mainly based on ...high-resolution (R ~ 110,000), high signal-to-noise ratio (800-1,000) Very Large Telescope UVES spectra, which allow us to achieve a precision of about 0.005 dex in differential abundances. The effective temperature and surface gravity of 18 Sco are T sub(eff) = 5823 + or - 6 K and log g = 4.45 + or - 0.02 dex, i.e., 18 Sco is 46 + or - 6 K hotter than the Sun and log g is 0.01 + or - 0.02 dex higher. Its metallicity is Fe/H = 0.054 + or - 0.005 dex, and its microturbulence velocity is +0.02 + or - 0.01 km s super(-1) higher than solar. Our precise stellar parameters and differential isochrone analysis show that 18 Sco has a mass of 1.04 + or - 0.02 M sub(odot) and that it is ~1.6 Gyr younger than the Sun. We use precise High Accuracy Radial velocity Planet Searcher (HARPS) radial velocities to search for planets, but none are detected. The chemical abundance pattern of 18 Sco displays a clear trend with condensation temperature, thus showing higher abundances of refractories in 18 Sco than in the Sun. Intriguingly, there are enhancements in the neutron-capture elements relative to the Sun. Despite the small element-to-element abundance differences among nearby n-capture elements (~0.02 dex), we successfully reproduce the r-process pattern in the Solar System. This is independent evidence for the universality of the r process. Our results have important implications for chemical tagging in our Galaxy and nucleosynthesis in general.
We present the first detailed chemical abundance analysis of the old 8.2 Gyr solar twin, HIP 102152. We derive differential abundances of 21 elements relative to the Sun with precisions as high as ...0.004 dex (<, ~1%), using ultra high-resolution (R = 110,000), high S/N UVES spectra obtained on the 8.2 m Very Large Telescope. Our determined metallicity of HIP 102152 is Fe/H = -0.013 + or - 0.004. The atmospheric parameters of the star were determined to be 54 K cooler than the Sun, 0.09 dex lower in surface gravity, and a microturbulence identical to our derived solar value. Elemental abundance ratios examined versus dust condensation temperature reveal a solar abundance pattern for this star, in contrast to most solar twins. The abundance pattern of HIP 102152 appears to be the most similar to solar of any known solar twin. Abundances of the younger, 2.9 Gyr solar twin, 18 Sco, were also determined from UVES spectra to serve as a comparison for HIP 102152. The solar chemical pattern of HIP 102152 makes it a potential candidate to host terrestrial planets, which is reinforced by the lack of giant planets in its terrestrial planet region. The following non-local thermodynamic equilibrium Li abundances were obtained for HIP 102152, 18 Sco, and the Sun: log epsilon (Li) = 0.48 + or - 0.07, 1.62 + or - 0.02, and 1.07 + or - 0.02, respectively. The Li abundance of HIP 102152 is the lowest reported to date for a solar twin, and allows us to consider an emerging, tightly constrained Li-age trend for solar twin stars.
The Solar Twin Planet Search dos Santos, Leonardo A.; Meléndez, Jorge; Nascimento, José-Dias do ...
Astronomy and astrophysics (Berlin),
8/2016, Letnik:
592
Journal Article
Motivated by the desire to measure beryllium abundances in red giant stars, we have constructed a new line list for synthesizing spectra in the near-ultraviolet. Using the Sun, Arcturus, and Pollux ...as benchmark stars, we explore potential sources of missing continuous opacity and line absorption. Despite the inclusion of new sources of continuous opacity, fitting the ultraviolet OH lines in the solar spectrum still requires artificially inflating the continuous opacity. The red giants also require the addition of a line of unknown origin in the blue wing of the Be line at λ3131.065 , and we find a good match can be made by adopting a Ti ii line with low excitation potential. The inclusion of this line does not affect the measurement of the solar Be abundance. Because the fits to all of the benchmark stars require tuning the properties of known spectral lines and including both an unknown source of additional continuous opacity and spectral lines of unknown origin, we argue that the absolute abundances of Be in stars should be interpreted with caution. Therefore, the question of whether the solar Be abundance is depleted may not yet be resolved, although our model favors minimal Be depletion in the Sun.
Abstract
In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the ...High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.
Candida albicans is a major cause of human infections, ranging from relatively simple to treat skin and mucosal diseases to systemic life-threatening invasive candidiasis. Fungal infections treatment ...faces three major challenges: the limited number of therapeutic options, the toxicity of the available drugs, and the rise of antifungal resistance. In this study, we demonstrate the antifungal activity and mechanism of action of peptides ToAP2 and NDBP-5.7 against planktonic cells and biofilms of C. albicans. Both peptides were active against C. albicans cells; however, ToAP2 was more active and produced more pronounced effects on fungal cells. Both peptides affected C. albicans membrane permeability and produced changes in fungal cell morphology, such as deformations in the cell wall and disruption of ultracellular organization. Both peptides showed synergism with amphotericin B, while ToAP2 also presents a synergic effect with fluconazole. Besides, ToAP2 (6.25 µM.) was able to inhibit filamentation after 24 h of treatment and was active against both the early phase and mature biofilms of C. albicans. Finally, ToAP2 was protective in a Galleria mellonella model of infection. Altogether these results point to the therapeutic potential of ToAP2 and other antimicrobial peptides in the development of new therapies for C. albicans infections.
Li abundances for solar twins in the open cluster M67 Carlos, Marília; Meléndez, Jorge; do Nascimento, José-Dias ...
Monthly notices of the Royal Astronomical Society,
02/2020, Letnik:
492, Številka:
1
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We determine lithium (Li) abundances for solar twins in the M67 open cluster to add valuable information about the correlation between Li depletion and stellar age and, then, better ...understand stellar structure and evolution. We use high resolution and good signal-to-noise ratio spectra to characterize Li depletion in three solar twins from M67, using spectral synthesis in the region of the asymmetric 6707.75 Å Li i feature. The mean Li abundance value of A(Li) = 1.6 ± 0.2 dex for our sample of M67 solar twins (our three stars plus a fourth solar twin from a previous analysis in the literature) presents Li abundance expected for its age. Also, the scatter estimated from the standard deviation of the Li abundances in this work is similar to the typical scatter found in a sample of field solar twins presented in the literature.
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