Dark matter effects on hybrid star properties Lenzi, C. H.; Dutra, M.; Lourenço, O. ...
European physical journal. C, Particles and fields,
03/2023, Letnik:
83, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In the present work, we investigate the effects of dark matter (DM) on hybrid star properties. We assume that dark matter is mixed with both hadronic and quark matter and interacts with them through ...the exchange of a Higgs boson. The hybrid star properties are obtained from equations of state calculated with a Maxwell prescription. For the hadronic matter, we use the NL3* parameter set, and for the quark matter, the MIT bag model with a vector interaction. We see that dark matter does not influence the phase transition points (pressure and chemical potential) but shifts the discontinuity on the energy density, which ultimately reduces the minimum mass star that contains a quark core. Moreover, it changes considerably the star family mass-radius diagrams and moves the merger polarizability curves inside the confidence lines. Another interesting feature is the influence of DM in the quark core of the hybrid stars constructed. Our results show an increase of the core radius for higher values of the dark particle Fermi momentum.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
ABSTRACT
The presence of nuclear pasta is expected to modify the transport properties in the mantle of neutron stars. The non-spherical geometry of the pasta nuclear clusters leads to anisotropies in ...the collision frequencies, impacting the thermal and electrical conductivity. We derive analytical expressions for the anisotropic collision frequencies using the Boltzmann equation in the relaxation time approximation. The average parallel, perpendicular, and Hall electrical conductivities are computed in the high-temperature regime above crustal melting, considering incoherent elastic electron-pasta scattering and randomly oriented pasta structures. Numerical values are obtained at different densities and temperatures by using the Indiana University–Florida State University (IUFSU) parametrization of the non-linear Walecka model to determine the crustal structure. We find that the anisotropy of the collision frequencies grows with the length of the pasta structures and, independently of the magnetic field, the presence of rod and slab phases decreases the conductivity by more than one order of magnitude. Our numerical results indicate that, even if the pasta structures might survive above the crustal melting point, no strong anisotropies are to be expected in the conduction properties in this temperature regime, even in the presence of a very high magnetic field.
MLL-rearranged acute lymphoblastic leukemia (ALL) in infants (<1 year) is the most aggressive type of childhood leukemia. To develop more suitable treatment strategies, a firm understanding of the ...biology underlying this disease is of utmost importance. MLL-rearranged ALL displays a unique gene expression profile, partly explained by erroneous histone modifications. We recently showed that t(4;11)-positive infant ALL is also characterized by pronounced promoter CpG hypermethylation. In this study, we investigated whether this widespread hypermethylation also affected microRNA (miRNA) expression. We identified 11 miRNAs that were downregulated in t(4;11)-positive infant ALL as a consequence of CpG hypermethylation. Seven of these miRNAs were re-activated after exposure to the de-methylating agent Zebularine. Interestingly, five of these miRNAs are associated either with MLL or MLL fusions, and for miR-152 we found both MLL and DNA methyltransferase 1 (DNMT1) as potential targeted genes. Finally, a high degree of methylation of the miR-152 CpG island was strongly correlated with a poor clinical outcome. Our data suggests that inhibitors of methylation have a potential beyond re-expression of hypermethylated protein-coding genes in t(4;11)-positive infant ALL. In this study, we provide additional evidence that they should be tested for their efficacy in MLL-rearranged infant ALL in in vivo models.
Caryocar coriaceum Wittm. fruit pulp fixed oil (CCFO) has been widely employed by communities from Brazil Northeastern in the treatment of skin inflammation, respiratory affections, wound healing and ...muscle pain. In this study, we evaluated the topical effect of CCFO against different irritant agents
in vivo, in order to verify its antiedematous effect as well to unravel its tentative mechanisms of action.
CCFO was obtained from
Caryocar coriaceum fruits using ethyl acetate as solvent. Ear edema provoked by the application of Croton oil (single and multiple applications), arachidonic acid (AA), capsaicin, phenol and histamine to Swiss mice was used to evaluate the topical anti-inflammatory effect of CCFO. Histological analysis from mice ears sensitized with Croton oil and AA single application was also performed.
Crude CCFO (20
μL/ear) demonstrated significant topical antiedematous effect against Croton oil single (inhibition of 32.0%;
P
<
0.05) and multiple (41.4% after 9 days,
P
<
0.001) applications, AA (inhibition of 49.7%;
P
<
0.01) and phenol (inhibition of 38.8%;
P
<
0.001). In contrast, CCFO did not antagonize the edema caused by topical treatment with capsaicin and histamine when compared to control group (
P
>
0.05). Histological analysis also revealed that CCFO was able to reduce the edema and the influx of inflammatory cells in mice ears sensitized with Croton oil and AA.
CCFO exhibited a similar profile of topical anti-inflammatory activity to that of drugs that classically modulate the production of arachidonic acid metabolites. The study also indicates the potential application of CCFO as an important herbal medicine to be used against skin inflammatory diseases.
ABSTRACT
Using a density-dependent quark model and a relativistic model within the mean-field approximation for hadrons with density-dependent meson-baryon couplings, we construct, for the first ...time, models that describe hybrid neutron stars consisting of nucleons and exotic baryons (hyperons and Δ-resonances). We do the study using a Maxwell construction. The quark-hadron phase transition in the stellar matter is determined through the structure, composition, and properties of the hybrid neutron star matter. The macroscopic properties of the star are determined, and the results for these particular models are found to be compatible with recent observational astrophysical data.
We study the statistics of 61 measured masses of neutron stars (NSs) in binary pulsar systems, including 18 double NS (DNS) systems, 26 radio pulsars (10 in our Galaxy) with white dwarf (WD) ...companions, 3 NSs with main-sequence companions, 13 NSs in X-ray binaries, and one undetermined system. We derive a mean value of M = 1.46 ± 0.30 M⊙. When the 46 NSs with measured spin periods are divided into two groups at 20 milliseconds, i.e., the millisecond pulsar (MSP) group and others, we find that their mass averages are, respectively, M = 1.57 ± 0.35 M⊙ and M = 1.37 ± 0.23 M⊙. In the framework of the pulsar recycling hypothesis, this suggests that an accretion of approximately ~0.2 M⊙ is sufficient to spin up a neutron star and place it in the millisecond pulsar group. Based on these estimates, an approximate empirical relation between the accreting mass (ΔM) of recycled pulsar and its spin period is proposed as ΔM = 0.43 (M⊙)(P/1 ms) − 2/3. If we focus only on the DNS, the mass average of all 18 DNSs is 1.32 ± 0.14 M⊙, and the mass averages of the recycled DNSs and the non-recycled NS companions are, respectively, 1.38 ± 0.12 M⊙ and 1.25 ± 0.13 M⊙. This is consistent with the hypothesis that the masses of both NSs in DNS system have been affected by accretion. The mass average of MSPs is higher than the Chandrasekhar limit 1.44 M⊙, which may imply that most of binary MSPs form via the standard scenario by accretion recycling. If we were to assume that the mass of a MSP formed by the accretion induced collapse (AIC) of a white dwarf must be less than 1.35 M⊙, then the portion of the binary MSPs involved in the AICs would not be higher than 20%, which imposes a constraint on the AIC origin of MSPs. With accreting mass from the companion, the nuclear matter composition of MSP may experience a transition from the “soft” equation of state (EOS) to a “stiff” EOS or even neutron to quark matter.
Stability windows for proto-quark stars Dexheimer, V.; Torres, J. R.; Menezes, D. P.
European physical journal. C, Particles and fields,
09/2013, Letnik:
73, Številka:
9
Journal Article
Recenzirano
Odprti dostop
We investigate the existence of possible stable strange matter and related stability windows at finite temperature for different models that are generally applied to describe quark stars, namely, the ...quark-mass density dependent model, the MIT bag model and the Nambu–Jona-Lasinio model. We emphasize that, although the limits for stable strange matter depend on a comparison with the ground state of
56
Fe, which is a zero temperature state, the quantity that has to be used in the search for strange matter in proto-quark stars is the free energy and we analyze stability windows up to temperatures of the order of 40 MeV. The effects of strong magnetic fields on stability windows are computed and the resulting mass-radius relations for different stages of the proto-quark star are analyzed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Exotic baryons in hot neutron stars Issifu, A; Marquez, K D; Pelicer, M R ...
Monthly Notices of the Royal Astronomical Society,
05/2023, Letnik:
522, Številka:
3
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We study the nuclear isentropic equation of state for a stellar matter composed of nucleons, hyperons, and Δ-resonances. We investigate different snapshots of the evolution of a neutron ...star, from its birth as a lepton-rich proto-neutron star in the aftermath of a supernova explosion to a lepton-poor regime when the star starts cooling to a catalysed configuration. We use a relativistic model within the mean-field approximation to describe the hot stellar matter and adopt density-dependent couplings adjusted by the DDME2 parameterization. We use baryon–meson couplings for the spin-1/2 baryonic octet and spin-3/2 decuplet determined in a unified manner relying on SU(6) and SU(3) symmetry arguments. We observe that Λ is the dominant exotic particle in the star at different entropies for both neutrino-free and neutrino-trapped stellar matter. For a fixed entropy, the inclusion of new particles (hyperons and/or delta resonances) in the stellar matter decreases the temperature. Also, an increase in entropy per baryon (1–2) with decreasing lepton number density (0.4–0.2) leads to an increase in stellar radii and a decrease in its mass due to neutrino diffusion. In the neutrino transparent matter, the radii decrease from entropy per baryon 2 to $T\, =\, 0$ without a significant change in stellar mass.
We analyze different stages of magnetized quark star evolution incorporating baryon number conservation and using an anisotropic energy-momentum tensor. The first stages of the evolution are ...simulated through the inclusion of trapped neutrinos and fixed entropy per particle, while in the last stage the star is taken to be deleptonized and cold. We find that, although strong magnetic fields modify quark star masses, the evolution of isolated stars needs to be constrained by fixed baryon number, which necessarily lowers the possible star masses. Moreover, magnetic field effects, measured by the difference between the parallel and perpendicular pressures, are more pronounced in the beginning of the star evolution, when there is a larger number of charged leptons and up quarks. We also show that having a spatially varying magnetic field allows for larger magnetic fields to be supported.
Abstract Biochar has been used to reuse the agro-industrial wastes and improve soil quality. Several studies have been carried out to show the impact of biochar on physical and chemical soil ...attributes. However, there are still gaps regarding the effects on as microbial biomass and enzymatic activities that are important to determine sensitive indicators to evaluate changes in management practices. The objective of this study was to assess the effect of two biochars on the chemical, microbial biomass carbon, and the enzymatic activities in an Entisol cultivated with bean. We evaluate two types of coffee biochar: ground and husks, four doses (4, 8, 12, and 16 Mg ha-1) and control. All treatments received organic fertilization with cow manure. Husks biochar increase the soil pH, Ca, and K, also contributing to the reduction of toxic aluminum contents and raising the concentrations of P labile. The treatments that received ground biochar showed higher soil organic carbon, microbial biomass, β-glucosidase, and fluorescein diacetate. Biochar produced from coffee residues increased sandy soil quality. We showed the first report on the beneficial impact of coffee biochar on enzymatic and microbiological quality of sandy soil cultivated with the bean.
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