The cosmic merger rate of neutron stars and black holes

Six gravitational wave detections have been reported so far, providing crucial insights on the merger rate of double compact objects. We investigate the cosmic merger rate of double neutron stars (DNSs), neutron star-black hole binaries (NSBHs) and black hole binaries (BHBs) by means of population-synthesis simulations coupled with the Illustris cosmological simulation. We have performed six different simulations, considering different assumptions for the efficiency of common envelope (CE) ejection and exploring two distributions for the supernova (SN) kicks. The current BHB merger rate derived from our simulations spans from $\sim{}150$ to $\sim{}240$ Gpc$^{-3}$ yr$^{-1}$ and is only mildly dependent on CE efficiency. In contrast, the current merger rates of DNSs (ranging from $\sim{}20$ to $\sim{}600$ Gpc$^{-3}$ yr$^{-1}$) and NSBHs (ranging from $\sim{}10$ to $\sim{}100$ Gpc$^{-3}$ yr$^{-1}$) strongly depend on the assumptions on CE and natal kicks. The merger rate of DNSs is consistent with the one inferred from the detection of GW170817 only if a high efficiency of CE ejection and low SN kicks (drawn from a Maxwellian distribution with one dimensional root mean square $\sigma{}=15$ km s$^{-1}$) are assumed.Comment: 9 pages, 6 figures, 2 tables, accepted for publication in MNRA

SUSTAINABLE HRM: ORGANIZATIONAL PRACTICES TO ATTRACT EMPLOYEES IN THE WAR FOR TALENT

openIn a changing and increasingly complex labor market, affected by growing expectations in terms of sustainability, an aging and fragmented workforce and a worrying scarcity of skilled employees, Sustainable HRM has emerged as an approach to managing people inside firms. Through the adoption of Sustainable HRM practices organizations are in fact able to not simply comply with stakeholders expectations, but possibly exploit them as a strategic tool to gain competitiveness in face of changing markets. It therefore becomes relevant to analyze which practices in particular can influence attractiveness of employers and serve as a competitive advantage in talents’ attraction, from a Sustainable HRM point of view. Accordingly, the scope of this thesis is to conduct a survey, with the guide of what literature indicates as the most relevant activities relating to Sustainable HRM that firms apply, to analyze what are the preferences of individuals pertaining to these matters. So as to identify which are the factors that can characterize an employer as appealing for the labor market. The methodology consists in creating a framework of reference of practices drawing these from literature. Further selecting then among these practices to develop a survey to study the preferences of individuals among different dimensions of sustainability, specifically comparing social and environmental practices, different bundles (the attraction, maintenance or development ones) and different characteristics of values of individuals. Ultimately building up our understanding on what may affect such preferences and inquire whether Sustainable HRM can ultimately represent a tool for talents’ attraction by corporations.

Teaching every body: A critical analysis of school programming on body image

Body dissatisfaction in children grows into harmful practices as they age. Schools provide education and programming to promote body satisfaction and positive body image in adolescents, but these teachings can be improved. This paper analyzes educational stakeholders’ services on body image through a critical lens while suggesting solutions to improve lessons, courses, and programming. Through braiding internal lessons with external programs, schools can fight against the potential risks of negative body image on adolescents. The literature review highlights the need for early education on body image and the importance of caregiver intervention. A critical review of the teacher and student dynamic introduces the opportunity that teachers as caregivers have to promote positive body image. Next, this paper discusses external intervention programs and the effectiveness of gender-specific programming while remaining critical of a lack of male-focused programs. This paper then discusses how teachers have more opportunities to hold open discussions for students to learn and share. Lastly, this paper describes how physical education classes can be modified to promote feelings of attractiveness and positivity while correcting misconceptions regarding exercising and gender. These changes to school programming will promote positive body image in students and open up classroom conversations

The High Mass X-ray Binaries in star-forming galaxies

The high mass X-ray binaries (HMXBs) provide an exciting framework to investigate the evolution of massive stars and the processes behind binary evolution. HMXBs have shown to be good tracers of recent star formation in galaxies and might be important feedback sources at early stages of the Universe. Furthermore, HMXBs are likely the progenitors of gravitational wave sources (BH--BH or BH--NS binaries that may merge producing gravitational waves). In this work, we investigate the nature and properties of HMXB population in star-forming galaxies. We combine the results from the population synthesis model MOBSE (Giacobbo et al. 2018) together with galaxy catalogs from EAGLE simulation (Schaye et al. 2015). Therefore, this method describes the HMXBs within their host galaxies in a self-consistent way. We compute the X-ray luminosity function (XLF) of HMXBs in star-forming galaxies, showing that this methodology matches the main features of the observed XLF.Comment: 4 pages, 2 figures. To appear in Proc. IAUS 346: High-mass X-ray binaries: illuminating the passage from massive binaries to merging compact object

Social stress: the good, the bad, and the neurotrophic factor:understanding the brain through PET imaging and molecular biology

The growing burden of social pressure is reflected by the increasing number of stress-associated health issues around the globe. One example of a stress-related health issue is depressive disorder. Depression is considered a major global health issue, affecting every cultural, economic and age group. The work described in this thesis aimed to investigate how different social stimuli –beneficial or harmful – can affect the brain. In this context, we mimicked different environments that are usually observed in humans in animal models, which allowed us to investigate how the brain of the animal physiologically responds to different social stressors, focusing especially on memory, inflammation of the brain, and a protein involved in proper functioning and survival of brain cells: the brain-derived neurotrophic factor (BDNF).In this thesis, we describe that social environment is able to increase or decrease BDNF levels in the hippocampus, when animals were exposed for a long time to beneficial or harmful social interactions, respectively. However, when animals were exposed to acute social and physical stress, there was no effect on BDNF concentration. We also found that animals submitted to harmful social stress showed transient effects on behavior, which had normalized after two weeks. Brain inflammation, as observed by positron emission tomography, was also normalized after two weeks. We concluded that the effect of short social stress exposure was temporary, showing an effect after a few days, but normalizing a few weeks after exposure to the stressor, but long exposue to social stimuli can induce lasting modification of brain functioning

Removal of quinoline from oily wastewater using biochars prepared from compost

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáThe petrochemical industry is one of the main sources of aquatic pollution, because when its waste is discarded in water resources, the generation of oily wastewater is dangerous to the ecosystem and to human health. Due to the diversified origin of these waters they present an extremely varied composition and they are difficult to treat. Thus, this dissertation aims to evaluate the removal of quinoline, a compound derived from the petrochemical industry, through an adsorption process. A solution of quinoline solubilized in 2,2,4-trimethylpentane was used as pollutant solution. Three different types of activated carbons prepared from precursor mixtures of compost originated from urban solid waste and glycerol were used as adsorbents and their adsorption capacity was tested. The adsorption kinetics of quinoline reveal that the adsorption is very fast in the first 30 minutes and that this process is more efficient at low concentrations. The kinetic data for the three activated carbons were successfully fitted to the pseudo-second order model. The equilibrium data were better adjusted to the Freundlich model, revealing the adsorption process physisorption character. The maximum adsorption capacity obtained by the Langmuir model was 3.376 mg.g-1. The results show that activated carbons with ratios of compost:glycerol of 1:3 (C1G3) and 2:2 (C2G2) were the best adsorbents.A indústria petroquímica é uma das principais fontes de poluição aquática, pois quando os seus resíduos são descartados nos recursos hídricos ocorre a geração de águas residuais oleosas que são perigosas para o ecossistema e para a saúde humana. Devido à origem diversificada destas águas elas apresentam uma composição extremamente variada e de difícil tratamento. Assim, esta dissertação teve como objetivo avaliar a remoção de quinolina, um composto derivado da indústria petroquímica, por meio de um processo de adsorção. Uma solução de quinolina solubilizada em 2,2,4-trimetilpentano foi utilizado como solução poluente. Foram utilizados como adsorvente três tipos diferentes de carvão ativado preparados a partir de misturas de resíduos sólidos urbanos e glicerol, avaliando-se a sua capacidade de adsorção. A cinética de adsorção da quinolina revelou que nos primeiros 30 minutos a adsorção é muito rápida e que este processo é mais eficiente em concentrações baixas. Os dados cinéticos para os três carvões ativados foram ajustados com sucesso ao modelo de pseudo-segunda ordem. Os dados de equilíbrio foram mais bem ajustados ao modelo de Freundlich, revelando o caráter de fisissorção do processo de adsorção. A capacidade de adsorção máxima, obtida através do modelo de Langmuir, foi de 3.376 mg.g-1. Os resultados mostram que os carvões ativados preparados com razões composto:glicerol de 1:3 (C1G3) e 2:2 (C2G2) foram os melhores adsorventes

The progenitors of compact-object binaries: impact of metallicity, common envelope and natal kicks

Six gravitational wave events have been reported by the LIGO-Virgo collaboration (LVC), five of them associated with black hole binary (BHB) mergers and one with a double neutron star (DNS) merger, while the coalescence of a black hole-neutron star (BHNS) binary is still missing. We investigate the progenitors of double compact object binaries with our population-synthesis code MOBSE. MOBSE includes advanced prescriptions for mass loss by stellar winds (depending on metallicity and on the Eddington ratio) and a formalism for core-collapse, electron-capture and (pulsational) pair instability supernovae. We investigate the impact of progenitor's metallicity, of the common-envelope parameter $\alpha{}$ and of the natal kicks on the properties of DNSs, BHNSs and BHBs. We find that neutron-star (NS) masses in DNSs span from 1.1 to 2.0 M$_\odot$, with a preference for light NSs, while NSs in merging BHNSs have mostly large masses ($1.3-2.0$ M$_\odot$). BHs in merging BHNSs are preferentially low mass ($5-15$ M$_\odot$). BH masses in merging BHBs strongly depend on the progenitor's metallicity and span from $\sim{}5$ to $\sim{}45$ M$_\odot$. The local merger rate density of both BHNSs and BHBs derived from our simulations is consistent with the values reported by the LVC in all our simulations. In contrast, the local merger rate density of DNSs matches the value inferred from the LVC only if low natal kicks are assumed. This result adds another piece to the intricate puzzle of natal kicks and DNS formation.Comment: 22 pages, 15 figures, 2 tables, published in MNRAS, We corrected a bug in the script for producing table 2 and figure 1

The impact of electron-capture supernovae on merging double neutron stars

Natal kicks are one of the most debated issues about double neutron star (DNS) formation. Several observational and theoretical results suggest that some DNSs have formed with low natal kicks ($\lesssim{}50$ km s$^{-1}$), which might be attributed to electron-capture supernovae (ECSNe). We investigate the impact of ECSNe on the formation of DNSs by means of population synthesis simulations. In particular, we assume a Maxwellian velocity distribution for the natal kick induced by ECSNe with one dimensional root-mean-square $\sigma_{\rm ECSN} = 0,7,15,26,265$ km s$^{-1}$. The total number of DNSs scales inversely with $\sigma_{\rm ECSN}$ and the number of DNS mergers is higher for relatively low kicks. This effect is particularly strong if we assume low efficiency of common-envelope ejection (described by the parameter $\alpha=1$), while it is only mild for high efficiency of common-envelope ejection ($\alpha{}=5$). In most simulations, more than 50 per cent of the progenitors of merging DNSs undergo at least one ECSN and the ECSN is almost always the first SN occurring in the binary system. Finally, we have considered the extreme case in which all neutron stars receive a low natal kick ($\lesssim{}50$~km~s$^{-1}$). In this case, the number of DNSs increases by a factor of ten and the percentage of merging DNSs which went through an ECSN is significantly suppressed ($<40$ per cent).Comment: 11 pages, 7 figures, 1 tables, to appear in MNRA