•Facilitating the exchange of knowledge between the areas of statistics, geodesy, meteorology, engineering, economics, image processing, astronomy, etc...•These estimators can adapt their shape by ...varying some parameters so that the estimator obtains characteristics of monotonous, soft-redescending or hardredescending estimators.•For many robust estimators, specifically, those classified as redescending, there is a need for global-type optimization methods, since their structure are non-convex.•Tuning constants of all these estimators, for 90%, 95%, 98%, and 99% relative efficiency levels regarding the Normal distribution.
Regression analysis constitutes an important tool for investigating the effect of explanatory variables on response variables. When outliers and bias errors are present, the weighted least squares estimator can perform poorly. For this reason, alternative robust techniques have been studied in several areas of science. However, often these different scientific communities are disconnected from each other, culminating in the scarcity of knowledge exchange among these areas. Thus, this paper presents a review on robust M-estimators in various knowledge areas. 50 (48 robust) M-estimators are illustrated, including the Weighted Least Squares estimator (non-robust), the Contaminated Normal estimator (quasi-robust), the Huber estimator (monotone), the Correntropy estimator (soft-redescending), the Smith estimator (hard-redescending), and the adaptive Barron and Generalized T-distribution. The mathematical functions that describe the estimators and their respective graphical forms are presented. The tuning constants of all these estimators, for 90%, 95%, 98%, and 99% relative efficiency levels in respect to the Normal distribution are also presented.
•Detecting and quantifying olive oil adulteration by Raman spectroscopy.•Appling an exponential equation for quantification the adulteration of olive oil with rapeseed oil or corn oil.•Proposing a ...new method to analyse adulteration of foods based on Raman spectroscopy and exponential equation.
This study presents a method to determine adulteration of olive oil (obtained from Olea europea, i.e. olives) with rapeseed oil (obtained from Brassica napus) or with corn oil (also named maize oil, obtained from Zea mays, i.e. maize) using Raman spectroscopy and a mathematical method based on exponential equation fit. The samples were prepared by mixing olive oil with volume fractions (0–100%) of rapeseed or corn oil. The oils were differentiated spectroscopically using intensity ratio for specific Raman peaks; Raman spectroscopy is able to detect changes within a liquid molecular environment without the need for sample treatment. It was possible to determine rapeseed or corn oil volume fractions added into the olive oil using the method proposed. Thus, the potential of Raman spectroscopy as a technique for determining adulteration of olive oil was corroborated clearly, opening the potential to investigate adulteration of other liquid foods, without any need for sample preparation.
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.
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.
The ground beetle, Neoaulacoryssus speciosus (Coleoptera: Carabidae) is of high relevance to field because it has been recorded as a pest of seeds and young plants of vegetables and other crops and a ...predator in agricultural crops, forest and weeds in Brazil. However, natural habitat changes are increasing agriculture and forest insect outbreaks in urban areas. A N. speciosus population outbreak occurred in October and November 2018 simultaneously in 12 neighboring municipalities at the beginning of the rainy season in the northern region of Minas Gerais State, Brazil. The objectives of this study were to report a sudden and simultaneous population outbreak of N. speciosus and to describe the factors of habitat change that could have contributed to this invasion in 12 municipalities in the northern region of Minas Gerais State in the Caatinga biome of Brazil. In addition, female and male genitals were described and illustrated, the scientific classification revised and common names of N. speciosus listed. Thousands of males and females of N. speciosus agglomerated in shady, humid places during the day and night for about 15 days. Neoaulacoryssus speciosus has been identified and illustrated, its scientific classification revised and four common names listed for this species.
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.
Poly(methyl methacrylate) (PMMA) is a very versatile polymer which is used as a glass substitute or as an economical alternative to polycarbonate for many types of important applications, due to its ...particular physical properties. In this study we deal with the Raman spectroscopic characterization of the glass transition of PMMA, the value of the glass transition temperature being generally a decisive parameter for determining the application of polymers. The information obtained by two-dimensional correlation spectroscopy (2DCOS) analysis and perturbation-correlation moving-windows spectroscopy (PCMW2D) analysis of the temperature dependent depolarized Raman spectra enabled us to recognize that the glass transition of PMMA is ruled by intermolecular interactions which influence the vibrational modes of the molecular groups associated with
ν
(C&z.dbd;O),
δ
a
(C-H) of α-CH
3
and/or O-CH
3
,
ν
(C-O-C),
ν
(C-COO), and
ν
(C-C-O). This information was employed for the temperature dependent study of the Raman shift and of the full width at half maximum of the Raman peaks obtained through anisotropic and isotropic Raman spectra, of the depolarization ratio, of the Raman spectroscopic noncoincidence effect, and of the Raman peak intensities represented by Arrhenius-type plots, all results supporting the outcomes of this work. The comparison with results obtained by differential scanning calorimetry and with published results in molecular dynamics studies was also part of this work. As the main result, one can highlight the peak associated with the
ν
(C-O-C) stretching mode at around 812 cm
−1
as the one which presents the better outcome for explaining the glass transition from the molecular point of view.
Poly(methyl methacrylate) (PMMA) is a very versatile polymer which is used as a glass substitute or as an economical alternative to polycarbonate for many types of important applications, due to its particular physical properties.
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.
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.
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.
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