Self-bound models of compact stars and recent mass-radius measurements

The exact composition of a specific class of compact stars, historically referred to as "neutron stars", is still quite unknown. Possibilities ranging from hadronic to quark degrees of freedom, including self-bound versions of the latter have been proposed. We specifically address the suitability of strange star models (including pairing interactions) in this work, in the light of new measurements available for four compact stars. The analysis shows that these data might be explained by such an exotic equation of state, actually selecting a small window in parameter space, but still new precise measurements and also further theoretical developments are needed to settle the subject.Comment: To appear in PR

The amplitude of the kilohertz quasi-periodic oscillations in 4U 1636-53 in the frequency-energy space

We present for the neutron-star low-mass X-ray binary 4U 1636$-$53, and for the first time for any source of kilohertz quasi-periodic oscillations (kHz QPOs), the two-dimensional behaviour of the fractional rms amplitude of the kHz QPOs in the parameter space defined by QPO frequency and photon energy. We find that the rms amplitude of the lower kHz QPO increases with energy up to $\sim12$ keV and then decreases at higher energies, while the rms amplitude of the upper kHz QPO either continues increasing or levels off at high energies. The rms amplitude of the lower kHz QPO increases and then decreases with frequency, peaking at $\sim 760$ Hz, while the amplitude of the upper kHz QPO decreases with frequency, with a local maximum at around $\sim 770$ Hz, and is consistent with becoming zero at the same QPO frequency, $\sim1400$ Hz, in all energy bands, thus constraining the neutron-star mass at $M_{NS} \leq 1.6 M_{\odot}$, under the assumption that this QPO reflects the Keplerian frequency at the inner edge of the accretion disc. We show that the slope of the rms energy spectrum is connected to the changing properties of the kHz QPOs in different energy bands as its frequencies change. Finally, we discuss a possible mechanism responsible for the radiative properties of the kHz QPOs and, based on a model in which the QPO arises from oscillations in a Comptonising cloud of hot electrons, we show that the properties of the kHz QPOs can constrain the thermodynamic properties of the inner accretion flow

Entropy, complexity and disequilibrium in compact stars

We used the statistical measurements of information entropy, disequilibrium and complexity to infer a hierarchy of equations of state for two types of compact stars from the broad class of neutron stars, namely, with hadronic composition and with strange quark composition. Our results show that, since order costs energy. Nature would favor the exotic strange stars even though the question of how to form the strange stars cannot be answered within this approach. (C) 2012 Elsevier B.V. All rights reserved.CAPESFAPESPCNPq Agency (Brazil

Pulgão Melanaphis sorghi (Theobald, 1904) (Hemiptera: Aphididae) na cultura do sorgo: análise do cenário brasileiro.

From the 2018/2019 agricultural season, reports of the occurrence of a new pest in the sorghum crop began in Minas Gerais and São Paulo, where abundant infestations of the aphid Melanaphis sorghi (Theobald, 1904) (Hemiptera: Aphididae) in crops with negative impacts on the yield of grains, causing losses to producers. Thus, this work aimed to evaluate the occurrence and scenario of the infestation of this pest in the sorghum crop in the country, aiming to understand its dynamics and support strategies for its management. As a data collection technique, a controlled electronic control was used, made available through the google forms digital platform, for 90 days, to the various actors of agribusiness, linked to the sorghum culture of different extracts of producers, throughout the country. Containing 14 questions related to knowledge of the crop, cultivated area, use of agrochemicals and occurrence of the pest. The greatest losses observed reached values of up to 20% of production. Of the total number of preparations, 64% used some chemical product, 42% using it with their own knowledge, 29% using it under the prescription/recommendation of a professional and 29% did not use pesticides. There was wide dissemination of the sorghum aphid in sorghum crops in the country, which implies necessary control measures in order to reduce losses, according to the profile of the evaluated producers

Resistance of sorghum hybrids to sorghum aphid.

ABSTRACT - The aphid Melanaphis sorghi (Theobald) (Hemiptera: Aphididae), which infest the sorghum crop, has been an economically important pest which have been causing severe damage to sorghum crops in Brazil since 2019. These species have been observed mainly at the end of vegetative stage and beginning of reproductive stage of plants. Their high reproductive rate on sorghum raises concerns about these pests. Therefore, the present study aimed to estimate the life expectancy and fertility tables of Melanaphis sorghi fed on 15 hybrids of grain sorghum, in order to know the resistance characteristics of these materials and understand how plant resistance can help manage this insect. This study was carried out in a laboratory at 26±2 ºC and 60±10% R.H (relative humidity). Fifty insects were kept in each hybrid, each insect was considered one repetition. According to biological parameters and fertility life table, hybrids BRS373, DKB590 and 50A10 were less suitable for the sugarcane aphid multiplication. Thus, these hybrids could be useful to manage this pest, since the population growth speed is one of the worst problems for the implementation of cropping systems. Genotypes AG1090, MSK327 and XGN1305 favored the development of this pest and, when chosen within a cropping system, other management strategies should be considered. RESUMO - O pulgão Melanaphis sorghi (Theobald) (Hemiptera: Aphididae), que infesta a cultura do sorgo, tem sido uma praga economicamente importante que vem causando sérios danos às lavouras de sorgo no Brasil desde 2019. As infestações têm sido observadas principalmente no final do estádio vegetativo e início do período reprodutivo das plantas. A alta taxa de reprodução destes insetos no sorgo aumenta a preocupação com a praga. Nesse sentido, o presente estudo teve por objetivo estimar as tabelas de esperança de vida e fertilidade para Melanaphis sorghi, alimentados com quinze híbridos de sorgo granífero, afim de conhecer as características de resistência desses materiais e entender como a resistência de plantas pode ajudar no manejo do inseto. O estudo foi conduzido em laboratório com temperatura de 26±2ºC e UR (Umidade Relativa) de 60±10%, foram mantidos 50 insetos em cada hibrido, cada inseto, considerado uma repetição. Com as estimativas dos parâmetros biológicos e mediante tabela de vida de fertilidade, verificamos que os híbridos BRS373, DKB590 e 50A10 foram menos adequados para a multiplicação da praga o que poderia ser considerado melhor para uso em sistemas de manejo da praga, uma vez que a velocidade de crescimento populacional pode ser vista como um dos piores problemas para implementação do sistema de manejo. Os genótipos AG1090, MSK327 e XGN1305 favoreceram o desenvolvimento da praga e, ao ser escolhido dentro do sistema de produção devem ser considerados outras estratégias de manejo

Manejo do pulgão da cana-de-açúcar (Melanaphis sacchari/sorghi) na cultura do sorgo.

O objetivo do presente documento é sumarizar informações sobre identificação, reprodução, monitoramento e dano causado, para auxiliar produtores e técnicos na tomada de decisão no manejo do inseto.bitstream/item/222934/1/COT-249.pd