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  • https://arxiv.org/abs/astro-ph/0011497
    Database of Geneva stellar evolution tracks and isochrones for UBVRIJHKLL'M, HST-WFPC2, Geneva and Washington photometric systems
    We have used an updated version of the empirically and semi-empirically calibrated BaSeL library of synthetic stellar spectra of Lejeune et al. (1997, 1998) and Westera et al. (1999) to calculate synthetic photometry in the UBVRIJHKLL'M, HST-WFPC2, Geneva, and Washington systems for the entire set of non-rotating Geneva stellar evolution models covering masses from 0.4-0.8 to 120-150 Msun and metallicities Z=0.0004 (1/50 Zsun) to 0.1 (5 Zsun). The results are provided in a database which includes all individual stellar tracks and the corresponding isochrones covering ages from 10^3 yr to 16--20 Gyr in time steps of Delta(log t)= 0.05 dex. The database also includes a new grid of stellar tracks of very metal-poor stars (Z=0.0004) from 0.8 - 150 Msun calculated with the Geneva stellar evolution code. The full database will be available in electronic form at the CDS (http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/(vol)/(page)) and at http://webast.ast.obs-mip.fr/stellar/.
    ARXIV.ORG
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  • https://arxiv.org/abs/2003.02326
    The Curious Case of the North Star: the continuing tension between evolution models and measurements of Polaris
    Polaris is the nearest Cepheid to us and as such holds a special place in our understanding of Cepheids in general and the Leavitt Law. In the past couple of decades, we have learned many new things about the star as a Cepheid and as the primary component of a multiple star system. As such, we are more precisely measuring the mass, radius and evolution of Polaris. However, as we learn more, it is becoming clear that we understand less. There is evidence that Polaris is much less massive than stellar evolution models suggest and that Polaris is a much younger star than its main sequence companion. In this work, we review some of the recent measurements and their connections with past studies. We then present new stellar evolution models and populations synthesis calculations to compare with the new mass measurements by Evans et al. (2018). We find that the mass discrepancy for Polaris is about 50%. We also find that there is a likely age discrepancy between Polaris and its companion, but that there is also a very small probability that the discrepancy is not real.
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  • https://simple.wikipedia.org/w/index.php?title=Stellar_evolution&oldid=9946517
    Stellar evolution
    Stellar evolution is the study of how a star changes over time. Stars can change very much between when they are first created and when they run out of energy. Because stars can produce light and heat for millions or billions of years, scientists study stellar evolution by studying many different stars in different stages of their life. The stages in a star's life are: protostar, main-sequence star, red giant and compact star: either white dwarf followed by black dwarf, neutron star or black hole. How a star is born A star starts its life as a cloud of dust and gas called a nebula. This is pulled together by gravity which causes it to heat up. It also starts to spin and to look like a ball. When it gets hot enough, it starts to release energy through nuclear fusion, changing hydrogen to helium. This makes it shine very brightly and become what astronomers think of as a main-sequence star. It may stay a main-sequence star, looking about the same, for billions of years. The details of a main-sequence star are based on its mass. The mass is often measured in terms of the Sun's mass, or a solar...
    SIMPLE.WIKIPEDIA.ORG
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  • https://ui.adsabs.harvard.edu/abs/2021ASPC..529...72N
    The Curious Case of the North Star: the Continuing Tension Between Evolution Models and Measurements of Polaris
    Polaris is the nearest Cepheid to us and as such holds a special place in our understanding of Cepheids in general and the Leavitt Law. In the past couple of decades, we have learned many new things about the star as a Cepheid and as the primary component of a multiple star system. As such, we are more precisely measuring the mass, radius and evolution of Polaris. However, as we learn more, it is becoming clear that we understand less. There is evidence that Polaris is much less massive than stellar evolution models suggest and that Polaris is a much younger star than its main sequence companion. In this work, we review some of the recent measurements and their connections with past studies. We then present new stellar evolution models and populations synthesis calculations to compare with the new mass measurements by Evans et al. (2018). We find that the mass discrepancy for Polaris is about 50%. We also find that there is a likely age discrepancy between Polaris and its companion, but that there is also a very small probability that the discrepancy is not real.
    UI.ADSABS.HARVARD.EDU
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  • https://www.thehealthsite.com/topics/coronavirus-evolution/
    coronavirus evolution : Top and Latest News, Articles, Videos and Photo About coronavirus evolution
    Get coronavirus evolution latest news, Article video and Photos on coronavirus evolution Explore latest health updates, news, information from TheHealthSite.com
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  • https://arxiv.org/abs/astro-ph/0402287
    Presupernova evolution of accreting white dwarfs with rotation
    We discuss the effects of rotation on the evolution of accreting carbon-oxygen white dwarfs, with the emphasis on possible consequences in Type Ia supernova (SN Ia) progenitors. Starting with a slowly rotating white dwarf, we simulate the accretion of matter and angular momentum from a quasi-Keplerian accretion disk. The role of the various rotationally induced hydrodynamic instabilities for the transport of angular momentum inside the white dwarf is investigated. We find that the dynamical shear instability is the most important one in the highly degenerate core. Our results imply that accreting white dwarfs rotate differentially throughout,with a shear rate close to the threshold value for the onset of the dynamical shear instability. As the latter depends on the temperature of the white dwarf, the thermal evolution of the white dwarf core is found to be relevant for the angular momentum redistribution. As found previously, significant rotation is shown to lead to carbon ignition masses well above 1.4 Msun. Our models suggest a wide range of white dwarf explosion masses, which could be responsible for some aspects of the diversity observed in SNe Ia. We analyze the potential role of the bar-mode and the r-mode instability in rapidly rotating white dwarfs, which may impose angular momentum loss by gravitational wave radiation. We discuss the consequences of the resulting spin-down for the fate of the white dwarf, and the possibility to detect the emitted gravitational waves at frequencies of 0.1 >... 1.0 Hz in nearby galaxies with LISA. Possible implications of fast and differentially rotating white dwarf cores for the flame propagation in exploding white dwarfs are also briefly discussed.
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  • https://arxiv.org/abs/0710.4003
    YREC: The Yale Rotating Stellar Evolution Code
    The stellar evolution code YREC is outlined with emphasis on its applications to helio- and asteroseismology. The procedure for calculating calibrated solar and stellar models is described. Other features of the code such as a non-local treatment of convective core overshoot, and the implementation of a parametrized description of turbulence in stellar models, are considered in some detail. The code has been extensively used for other astrophysical applications, some of which are briefly mentioned at the end of the paper.
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  • https://ui.adsabs.harvard.edu/abs/1998Geomo..22..325G
    New constraints on the evolution of Carolina Bays from ground-penetrating radar
    Ground-penetrating radar (GPR) data for the Savannah River Site (SRS) in the Upper Coastal Plain of South Carolina, combined with geological, archaeological, and ecological data place new constraints on the evolution of Carolina Bays. Extant SRS bay morphology formed mainly during the Holocene and did not involve migration of bays across the landscape. Multiple periods of bay-rim accretion with intervening intervals of erosion may characterize the longer-term evolution of the bays. Bay evolution, however, did not involve significant modification of the Upland Unit underlying the region. During fluctuating, but generally open water conditions, breaking waves along bay shorelines eroded and transported sediment which was subsequently exposed for deflation during periods of low water. Deflation and transport of sand into standing vegetation along the margin of the bay depression created a rim in the form of a parabolic dune lacking obvious internal stratification. Simultaneously, infilling occurred by shoreline erosion and transport from adjacent elevated surfaces. This, coupled with growth of emergent vegetation, resulted in decreased hydroperiod, wave energy, shoreline modification, and rim accretion. Transport of some rim sediments back into the bays via alluvial and colluvial activity created wedges of infilling sediment during waning stages of evolution. The apparent contradiction of bay orientation with respect to prevailing winds might reflect seasonal changes in water level and wind direction: southwesterly winds during spring high water causes NW-SE elongation of the bays, whereas northwesterly winds during lower water in the fall and winter account for nearshore deflation and rim accretion along the east-southeastern bay margins.
    UI.ADSABS.HARVARD.EDU
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  • https://arxiv.org/abs/1401.1809
    The Evolution of Protostars: Insights from Ten Years of Infrared Surveys with Spitzer and Herschel
    Stars form from the gravitational collapse of dense molecular cloud cores. In the protostellar phase, mass accretes from the core onto a protostar, likely through an accretion disk, and it is during this phase that the initial masses of stars and the initial conditions for planet formation are set. Over the past decade, new observational capabilities provided by the Spitzer Space Telescope and Herschel Space Observatory have enabled wide-field surveys of entire star-forming clouds with unprecedented sensitivity, resolution, and infrared wavelength coverage. We review resulting advances in the field, focusing both on the observations themselves and the constraints they place on theoretical models of star formation and protostellar evolution. We also emphasize open questions and outline new directions needed to further advance the field.
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  • https://arxiv.org/abs/1402.1177
    Revisiting the fundamental properties of Cepheid Polaris using detailed stellar evolution models
    Polaris the Cepheid has been observed for centuries, presenting surprises and changing our view of Cepheids and stellar astrophysics, in general. Specifically, understanding Polaris helps anchor the Cepheid Leavitt law, but the distance must be measured precisely. The recent debate regarding the distance to Polaris has raised questions about its role in calibrating the Leavitt law and even its evolutionary status. In this work, I present new stellar evolution models of Cepheids to compare with previously measured CNO abundances, period change and angular diameter. Based on the comparison, I show that Polaris cannot be evolving along the first crossing of the Cepheid instability strip and cannot have evolved from a rapidly-rotating main sequence star. As such, Polaris must also be at least 118 pc away and pulsates in the first overtone, disagreeing with the recent results of Turner et al. (2013).
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  • ary-algorithm/

    #include <iostream>
    #include <string>
    #include <vector>
    #include <algorithm>
    #include <random>
    #include <chrono>

    using namespace std;

    // random generator function:
    int myrandom (int i) { return std::rand()%i;}


    int main () {

    // seed the random number generator with a constant value:
    srand( unsigned (time(0)) );

    const string target = "Hello World!"; // target string we are trying to match

    const int populationSize = 500; // population size of our genetic algorithm

    vector<string> population; // vector to store our population of strings

    int generation = 0; // current generation number

    // create a random starting population of strings:

    for (int i=0; i<populationSize; i++) {

    string str;

    for (int j=0; j<target.length(); j++) {

    char c = 97 + rand() % 26; // generate a random lowercase character from 'a' to 'z'

    str += c;

    }

    population.push_back(str); // add the generated string to the population vector

    }

    while (true) { // loop until we find the target string

    cout << "Generation: " << generation++ << endl;

    for (int i=0; i<population.size(); i++) { // loop through each member of the population

    cout << "String: " << population[i] << "\t\tFitness: " << fitness(population[i]) << endl;

    if (population[i] == target) { // check if this member is equal to the target string

    cout << "Target Reached!" << endl;
    return 0; // exit program if target is reached

    }
    }

    vector<string> newPopulation;// create a new empty vector for our new generation of strings

    for (int i=0 ; i<population.size(); i++) {// loop through each member of the current population

    string parent1 = selection(population);// select two parents using tournament selection
    string parent2 = selection(population);

    vector<string> children = crossover(parent1, parent2);// perform crossover between parents and generate two children
    mutation(children[0]);// perform mutation on both children mutation(children[1]); newPopulation.push_back(children[0]);// add both children to the new generation's population newPopulation.push_back(children[1]); } population = newPopulation;// replace old generation's population with the new one } return 0;}

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  • Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive. During its life, a star will pass through several stages, fusing lighter elements into heavier ones in successive nuclear reactions. These reactions release energy, which allows the star to radiate light and heat into space. As it ages, a star will move through different stages, including main sequence, red giant, and white dwarf. In some cases, stars may even end their lives as supernovae or neutron stars.

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  • Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star. Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star, but as the preponderance of hydrogen gets used up, more and heavier elements are created by fusion processes in layers around the core. The outflow of energy from the core causes it to gradually expand and cool over time, thereby transforming it into a red giant. Stars with at least half to three-quarters of the mass of our Sun will expand further into a supergiant phase before running out of fuel and collapsing into an incredibly dense white dwarf. Stars with greater than three solar masses will continue to collapse until they become dense enough to begin thermonuclear fusion in their cores; these are known as supernovas. Finally, stars that are even more massive will be able to sustain nuclear fusion in their cores even after they collapse, forming neutron stars or black holes depending on their mass and rotation rate.

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  • Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive. During its life, a star will pass through several stages, such as protostar, main-sequence star, red giant and white dwarf. The more massive stars will also go through supernova and neutron star stages. As it ages, a star's temperature and luminosity will change, and it may also undergo pulsations and mass loss.

    By: ChatGPT AI
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  • Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive. During its life, a star will pass through several stages, such as a protostar, main-sequence star, red giant and white dwarf. During each stage, different nuclear reactions take place in the core of the star, causing it to heat up or cool down and change in luminosity and size. Eventually, all stars will end their lives by either exploding as supernovae or collapsing into black holes.

    By: ChatGPT AI
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  • Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive. During its life, a star will pass through various stages, such as protostar, main-sequence star, red giant, and white dwarf. The energy produced by stars comes from nuclear fusion reactions in which hydrogen is converted into helium. As a star ages, it will eventually exhaust its supply of hydrogen fuel and move on to other elements in its core. This process leads to changes in stellar structure and luminosity as well as the eventual death of the star.

    By: ChatGPT AI
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  • Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive. During its life, a star will pass through various stages, such as a protostar, main-sequence star, red giant, and white dwarf. Each stage is characterized by different properties such as luminosity and temperature. As a star ages, it will also undergo nuclear fusion reactions in its core that produce heavier elements from lighter ones. These heavier elements are then released into space when the star dies, enriching the interstellar medium with new material.

    By: ChatGPT AI
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  • Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive. During its life, a star will pass through several stages, such as a protostar, main-sequence star, red giant, and white dwarf. As it evolves, a star will undergo nuclear fusion in its core and produce energy in the form of radiation. This radiation will cause the star to expand and contract in size as it moves through different stages of its life cycle.

    By: ChatGPT AI
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  • -of-the-web

    The evolution of the web began in 1989 when Tim Berners-Lee proposed the idea of a global hypertext project. This was the first step towards creating the World Wide Web. In 1991, Berners-Lee and his team at CERN released the first web browser, which allowed users to navigate through documents that were linked together via hypertext. This was the beginning of what we know today as the internet.

    In 1993, Marc Andreessen released Mosaic, which was the first graphical web browser and allowed users to view images and videos on websites. This was a major breakthrough in web technology and led to a surge in internet usage.

    The late 1990s saw a number of important developments in web technology. Netscape Navigator became one of the most popular browsers and HTML 4 was released, which introduced new features such as tables and frames. Java applets also became popular during this time, allowing developers to create interactive websites with dynamic content.

    In 2000, Microsoft released Internet Explorer 6, which became one of the most widely used browsers for many years afterwards. The same year also saw the release of XML, which allowed developers to structure data more effectively than HTML.

    The early 2000s saw a number of important developments in web technology including AJAX (Asynchronous JavaScript And XML), which allowed for faster loading times on websites; CSS (Cascading Style Sheets), which allowed developers to separate content from design; and RSS (Really Simple Syndication), which made it easier for users to keep up with their favorite websites.

    The mid-2000s saw an explosion in social media usage with sites such as Myspace and Facebook becoming hugely popular amongst internet users. This period also saw an increase in mobile device usage with smartphones becoming commonplace by 2010. In response to this trend, responsive design techniques were developed that allowed websites to adapt their layout depending on the device they were being viewed on.

    Today, web technology is constantly evolving with new technologies such as HTML5 being developed all the time. Web development is now much more complex than it was when it first began but it has come a long way since 1989 when Tim Berners-Lee proposed his idea for a global hypertext project!

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  • The first known use of the word "evolution" in English was in 1679, when it was used by Thomas Browne in his book Religio Medici. The term had been used earlier by French philosopher and mathematician René Descartes (1596-1650) and German naturalist and physician Georges-Louis Leclerc, Comte de Buffon (1707-1788). In the 19th century, Charles Darwin popularized the concept of evolution through his work On the Origin of Species. Since then, evolutionary theory has been widely accepted as a scientific explanation for the diversity of life on Earth. Evolutionary biology is now a major field of study, with researchers exploring topics such as genetic drift, natural selection, speciation, and adaptation.

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  • Tom Hanks Evolution
    Tom Hanks Evolution 1980-2022 #Shorts.
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  • A new supercomputer simulation animates the evolution of the universe
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  • The Insane Evolution of the Woolly Rhino
    Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.
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