60,907 research outputs found
On the rotation of ONC stars in the Tsallis formalism context
The theoretical distribution function of the projected rotational velocity is
derived in the context of the Tsallis formalism. The distribution is used to
estimate the average for a stellar sample from the Orion Nebula Cloud
(ONC), producing an excellent result when compared with observational data. In
addition, the value of the parameter q obtained from the distribution of
observed rotations reinforces the idea that there is a relation between this
parameter and the age of the cluster.Comment: 6 pages, 2 figure
Strong evidences for a nonextensive behavior of the rotation period in Open Clusters
Time-dependent nonextensivity in a stellar astrophysical scenario combines
nonextensive entropic indices derived from the modified Kawaler's
parametrization, and , obtained from rotational velocity distribution. These
's are related through a heuristic single relation given by , where is the cluster age. In a nonextensive
scenario, these indices are quantities that measure the degree of
nonextensivity present in the system. Recent studies reveal that the index
is correlated to the formation rate of high-energy tails present in the
distribution of rotation velocity. On the other hand, the index is
determined by the stellar rotation-age relationship. This depends on the
magnetic field configuration through the expression , where
and denote the saturation level of the star magnetic field and its
topology, respectively. In the present study, we show that the connection
is also consistent with 548 rotation period data for single
main-sequence stars in 11 Open Clusters aged less than 1 Gyr. The value of
2.5 from our unsaturated model shows that the mean magnetic field
topology of these stars is slightly more complex than a purely radial field.
Our results also suggest that stellar rotational braking behavior affects the
degree of anti-correlation between and cluster age . Finally, we suggest
that stellar magnetic braking can be scaled by the entropic index .Comment: 6 pages and 2 figures, accepted to EPL on October 17, 201
A nonextensive insight to the stellar initial mass function
the present paper, we propose that the stellar initial mass distributions as
known as IMF are best fitted by -Weibulls that emerge within nonextensive
statistical mechanics. As a result, we show that the Salpeter's slope of
2.35 is replaced when a -Weibull distribution is used. Our results
point out that the nonextensive entropic index represents a new approach
for understanding the process of the star-forming and evolution of massive
stars.Comment: 5 pages, 2 figures, Accepted to EP
Growth of seven perennial plant species adapted to the Brazilian Semi-Arid.
Growth of seven perennial plant species adapted to the Brazilian Semi-Arid. Abstract - Measuring plant height (y) and canopy diameter (x) in trees may not be an easy task, but stem diameter (z) can be more easily evaluated. This work's objective was two-fold: evaluate the growth of species adapted to the Brazilian Semi-Arid Region in the first two years of age, and obtain linear equations to estimate y and x from z, in those species. A random block design with four replications was employed. The values for x, z, and y were measured biannually from October/2003 to March/2005. Prosopis juliflora and Mimosa caesalpiniaefolia showed the highest stem diameter and plant height values, respectively, and both showed the highest canopy diameter. In the equations to estimate plant height from the stem diameter the value of the coefficient of determination (R2) ranged from 0.76 (Tamarindus indica and Leucaena leucocephala) to 0.92 (Prosopis juliflora and Azadirachta indica). In the equations that allowed to estimate the crown diameter from the stem diameter the R2 value ranged from 0.70 (Leucaena leucocephala) to 0.92 (Azadirachta indica). Crescimento de sete espĂ©cies vegetais perenes adaptadas ao Semi-Ărido brasileiro. Resumo - A mensuração da altura da planta (y) e do diĂąmetro da copa (x) em ĂĄrvores pode nĂŁo ser tarefa fĂĄcil, mas o diĂąmetro do caule (z) pode ser avaliado mais facilmente. Este trabalho teve por objetivos avaliar o crescimento de espĂ©cies adaptadas ao Semi-Ărido brasileiro, nos primeiros dois anos de idade, e obter equaçÔes lineares para estimar y e x a partir de z, nessas espĂ©cies. Utilizou-se o delineamento de blocos ao acaso com quatro repetiçÔes. Os valores de x, z e y foram medidos semestralmente de outubro/2003 a março/2005. Prosopis juliflora e Mimosa caesalpiniaefolia apresentaram os maiores diĂąmetros do caule e altura da planta, respectivamente, e ambas apresentaram o maior diĂąmetro da copa. Nas equaçÔes para estimar a altura da planta a partir do diĂąmetro do caule, o valor do coeficiente de determinação (R2) variou de 0,76 (Tamarindus indica and Leucaena leucocephala) a 0,92 (Prosopis juliflora and Azadirachta indica). Nas equaçÔes que permitiram estimar o diĂąmetro da copa a partir do diĂąmetro do caule, o valor de R2 variou de 0,70 (Leucaena leucocephala) a 0,92 (Azadirachta indica)
Displaying desire and distinction in housing
The article discusses the significance of cultural capital for the understanding of the field of housing in contemporary Britain. It explores the relationship between housing and the position of individuals in social space mapped out by means of a multiple correspondence analysis. It considers the material aspects of housing and the changing contexts that are linked to the creation and display of desire for social position and distinction expressed in talk about home decoration as personal expression and individuals' ideas of a `dream house'. It is based on an empirical investigation of taste and lifestyle using nationally representative survey data and qualitative interviews. The article shows both that personal resources and the imagination of home are linked to levels of cultural capital, and that rich methods of investigation are required to grasp the significance of these normally invisible assets to broaden the academic understanding of the field of housing in contemporary culture
Transverse self-modulation of ultra-relativistic lepton beams in the plasma wakefield accelerator
The transverse self-modulation of ultra-relativistic, long lepton bunches in
high-density plasmas is explored through full-scale particle-in-cell
simulations. We demonstrate that long SLAC-type electron and positron bunches
can become strongly self-modulated over centimeter distances, leading to wake
excitation in the blowout regime with accelerating fields in excess of 20 GV/m.
We show that particles energy variations exceeding 10 GeV can occur in
meter-long plasmas. We find that the self-modulation of positively and
negatively charged bunches differ when the blowout is reached. Seeding the
self-modulation instability suppresses the competing hosing instability. This
work reveals that a proof-of-principle experiment to test the physics of bunch
self-modulation can be performed with available lepton bunches and with
existing experimental apparatus and diagnostics.Comment: 8 pages, 8 figures, accepted for publication in Physics of Plasma
Higher education systems and institutions, Guinea Bissau
The Republic of Guinea-Bissau is a small country (approximately 36,125 square kilometers) on the west coast of Africa, bordered by Senegal to the north and the Republic of Guinea-Conakry to the southeast. With a population estimated at around 1.9 million inhabitants, it is one of the poorest countries in the world, ranking 178th of the 189 countries listed in the Human Development Index of 2019. The populationâs life expectancy is 57 years, the adult literacy rate is 46%, and the most recent figures on expenditure on education reveal that, in 2013, only 2.13% of its GDP was allocated to the different levels of the education system. Even though Portuguese is the official language, the majority of the population speaks Creole. Constant political instability contributes to the countryâs economic difficulties.
Guinea-Bissau gained its independence from Portugal in 1974 after a destructive war and PAIGC, the political party resulting from the main independence...info:eu-repo/semantics/acceptedVersio
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