Some 52 stellar systems beyond our own, the Solar System lie within 5.0 parsecs of the Sun. These systems contain a total of 63 stars, of which 50 are red dwarfs, by far the most common type of star in the Milky Way. Much more massive stars, such as our own, make up the remaining 13. In addition to these "true" stars, scientists have identified 11 brown dwarfs, four white dwarfs. Despite the relative proximity of these 78 objects to Earth, only nine are bright enough in visible light to reach or exceed the dimmest brightness to be visible to the naked eye from Earth, 6.5 apparent magnitude. All of these objects are moving in the Local Bubble, a region within the Orion–Cygnus Arm of the Milky Way. Based on results from the Gaia telescope's second data release from April 2018, an estimated 694 stars will approach the Solar System to less than 5 parsecs in the next 15 million years. Of these, 26 have a good probability to come within another 7 within 0.5 parsecs. This number is much higher, due to the sheer number of stars needed to be surveyed.
The closest encounter to the Sun so far predicted is the low-mass orange dwarf star Gliese 710 / HIP 89825 with 60% the mass of the Sun. It is predicted to pass 19,300 ± 3,200 astronomical units from the Sun in 1.280+0.041−0.039 million years from the present, close enough to disturb our Solar System's Oort cloud. The easiest way to determine stellar distance to the Sun for objects at these distances is parallax, which measures how much stars appear to move against background objects over the course of Earth's orbit around the Sun; as a parsec is defined by the distance of an object that would appear to move one second of arc against background objects, stars less than 5 parsecs away will have measured parallaxes of over 0.2 arcseconds, or 200 milliarcseconds. Determining past and future positions relies on accurate astrometric measurements of their parallax and total proper motions, along with spectroscopically determined radial velocities. Both of these measurements are subject to increasing and significant errors over long time spans over the several thousand-year time spans it takes for stars to noticeably move relative to each other.
The classes of the stars and brown dwarfs are shown in the color of their spectral types. Many brown dwarfs are not listed by visual magnitude but are listed by near-infrared J band apparent magnitude due to how dim they are in visible color bands. Absolute magnitude is a measurement at a 10-parsec distance across imaginary empty space devoid of all its sparse dust and gas; some of the parallaxes and resultant distances are rough measurements. Over long periods of time, the slow independent motion of stars change in both relative position and in their distance from the observer; this can cause other distant stars to fall within a stated range, which may be calculated and predicted using accurate astrometric measurements of parallax and total proper motions, along with spectroscopically determined radial velocities. Although predictions can be extrapolated back into the past or forward into the future, they are subject to increasing significant cumulative errors over long periods. Inaccuracies of these measured parameters make determining the true minimum distances of any encountering stars or brown dwarfs difficult.
One of the first stars known to approach the Sun close is Gliese 710. The star, whose mass is half that of the Sun, is 62 light-years from the Solar System, it was first noticed in 1999 using data from the Hipparcos satellite, was estimated to pass less than 1.3 light-years from the Sun in 1.4 million years. With the release of Gaia's observations of the star, it has since been refined to a much closer 0.178 light-years, close enough to disturb objects in the Oort cloud, which extends out to 1.2 light-years from the Sun. The second-closest object known to approach the Sun was only discovered in 2018 after Gaia's second data release, known as 2MASS J0610-4246, its approach has not been described due to it being a distant binary star with a red dwarf, but certainly passed less than 1 light-year from the Solar System 1.16 million years ago. "The 100 nearest star systems", Research Consortium on Nearby Stars "NStars database". Northern Arizona University. Archived from the original on October 30, 2005.
Retrieved October 24, 2005. Nemiroff, R.. "Map of the 25 nearest star systems". Astronomy Picture of the Day. NASA. Retrieved 2005-10-24. "Notable Nearby Stars". SolStation. Retrieved 2005-10-24. "Cool stars in the solar Neighbourhood". D. Montes, UCM. Retrieved 2005-11-14; the dynamics of the closest stars Takeda, G.. Ford.
The Tongan Passport is an international travel document, issued to Tongan citizens. In 2017, Tongan citizens holding regular Tongan passports had visa-free or visa on arrival access to 111 countries and territories, ranking the Tongan passport 47th in the world according to the Visa Restrictions Index. Tonga signed a mutual visa waiver agreement with Schengen Area countries on 20 November 2015. Tongan Protected Person passports are sold by the King of Tonga to persons who are not a Tongan citizen. Tongan Protected Person passport holders can not settle in Tonga on this passport; those holders are refugees, stateless persons, individuals who for political reasons do not have access to any other passport-issuing authority. Some countries/regions, e.g. Hong Kong, do not recognize the Tongan Protected Person passport as a legitimate travel document, refuse entry to the holder attempting to enter on this passport. Visa requirements for Tongan citizens
La'Reonte Wright, known professionally as Dizzy Wright, is an American rapper and songwriter. In December 2011, Wright signed Funk Volume. After signing he released his debut studio album SmokeOut Conversations in April 2012, he followed that with The First Agreement in December of that year, a mixtape The Golden Age in August 2013. Following touring with Hopsin in early 2014, Dizzy Wright released State of Mind, an EP that would peak at number 54 on the Billboard 200. On May 22, 2015, he released his second studio album The Growing Process which peaked at number 47 on the Billboard 200. Wright looked up to Bone Thugs-n-Harmony, of which his uncles Layzie Bone and Flesh-N-Bone are members. At the age of four he moved with his mom and siblings to Nevada, he began rapping at just 8 years old with the group DaFuture which included his brother and a close friend. His mother wrote his raps at the time and was a concert promoter so he was exposed to the music industry early doing youth reporting at major awards shows like the BET Awards and interviewing Tyrese, St. Lunatics and Boyz II Men.
He credits this for being the reason he wants to stay away from major record labels and stick to independent labels. In seventh grade Wright lived in a homeless shelter with his family for five months. Throughout the rest of high school he lived in Georgia and California before moving back to Las Vegas when he was in twelfth grade. In 2010, Wright took part in and won the Sheikh Music Rip the Mic competition, which impressed record label Funk Volume. In 2010, he appeared on 106 & Park's Wild Out Wednesday, as Dizzy D Flashy. In 2011, Dizzy Wright released his mixtape, titled Soul Searchin' Next Level, which would be a final release under Bluestar Records. In 2012, Wright signed to rapper Hopsin's independent record label Funk Volume. Wright's debut studio album, Smokeout Conversations, was released on April 20, 2012, in honor of the annual marijuana type-of "holiday" under Funk Volume; the album included the single "Can't Trust Em", peaked at number 42 on the US Top R&B/Hip-Hop Albums and number eight on the US Heatseekers Albums charts.
Months Wright released a reloaded version of a mixtape, titled Free SmokeOut Conversations, downloaded over 170,000 times. This mixtape features guest appearances from a fellow rapper and his label-mate Hopsin, SwizZz, it contains his single "Independent Living". Not withstanding the original plan to release the mixtape prior to the album, but instead Dizzy released the album; the album's success allowed him to perform on a national 30-day headlining tour following its release. He capped off the year performing on the Funk Volume Tour 2012 with Hopsin, SwizZz and Jarren Benton. On December 3, 2012, Dizzy released; the EP was named after Don Miguel Ruiz's book The Four Agreements. Its lead single, "Fly High", was released; the EP debuted at number 41 on the Top R&B/Hip Hop Albums chart and number 25 on the Top Rap Albums charts. Wright had hinted at the releases of more chapters in the series. On March 11, 2013, Wright released the first song from his upcoming mixtape, titled "Maintain" featuring fellow rapper Joey Bada$$.
On March 26, it was announced that Wright would be included in XXL's Freshman Class of 2013 due to getting the "Peoples Choice" vote. Three days he would release the music video for a new song titled, "Still Movin'" which featured cameos from his Funk Volume label mates, followed by "Killem Wit Kindness" a few days later; these songs were the second and third releases from his upcoming mixtape, shortly announced to be titled, The Golden Age. Guest appearances on the mixtape included Wyclef Jean, Joey Bada$$, Jarren Benton, SwizZz, Kid Ink and Honey Cocaine among others. Along with production from DJ Hoppa, Kato, 6ix, Cardo; the mixtape was released for free, for purchase on iTunes on August 19, 2013. Due to its retail release, the mixtape debuted on the Top R&B/Hip-Hop Albums chart at number 39 becoming his highest charting project at the time. Wright announced plans to drop The Second Agreement EP, his second studio album after the release of the mixtape. On December 18, 2013, he was named a runner-up for "Rising Star of the Year" by HipHopDX.
Starting 2014, Wright begun touring with Hopsin on the Knock Madness world tour. He was featured on Knock Madness, on the song "Who's There?" featuring label mate Jarren Benton. On February 16, 2014, Dizzy Wright announced he would be releasing State of Mind, a new EP during March 2014. In an interview with XXL the following month, Dizzy Wright said State of Mind had no current release date and confirmed his second studio album would be released during 2014. However, on April 8, Wright revealed the cover artwork and release date of April 15, 2014 for the EP. State of Mind debuted at number 54 on the US Billboard 200 chart. In July 2014, Dizzy Wright revealed that his second studio album would be released in early 2015, with a guest appearance to come from Bone Thugs-n-Harmony. In an interview with Mr. Wavvy released on June 24, 2015, Wright confirmed that a project with Logic is in the works; the rapper went on to confirm that the two have 4-5 songs recorded for it. In February 2015, Wright released a collaborative mixtape with Mark Battles titled, Lost In Reality.
On May 26, 2015, Wright released his second studio album, The Growing Process, released through Funk Volume and distributed by Warner Bros. The album peaked at number 47 on the Billboard 200 chart. In January 2016, Funk Volume disbanded. On February 5, 2016, Wright released his first project post-Funk Volume titled and Good Vibes. On July 2, Wright r
Edith Abbott was an American economist, social worker and author. Abbott was born in Nebraska. Abbott was a pioneer in the profession of social work with an educational background in economics, she was a leading activist in social reform with the ideals that humanitarianism needed to be embedded in education. Abbott was in charge of implementing social work studies to the graduate level. Though she was met with resistance on her work with social reform at the University of Chicago, she was successful and was elected as the school's dean in 1924, making her the first female dean in the United States. Abbott was foremost an educator and saw her work as a combination of legal studies and humanitarian work which shows in her social security legislation, she is known as an economist. Her younger sister was Grace Abbott. Social work will never become a profession—except through the professional schools The Edith Abbott Memorial Library, in Grand Island, Nebraska, is named after her. Edith was born September 1876 in Grand Island, Nebraska.
Her father, Othman Abbott, was Nebraska's first Lieutenant Governor. Her mother, Elizabeth Griffin, was an suffrage leader. Both parents instilled values of women's rights and social reform into Edith and her sister Grace, inspiring their future work. Grace Abbott had many accomplishments working as a social worker, child labor legislation reformer, chief of the United States Children's Bureau working with Edith on many different professional projects during their careers. In 1893, Abbott graduated from a girls' boarding school in Omaha. However, her family could not afford to send her to college due to a drought which struck Nebraska and led to an economic depression. Instead of going to college Abbott began to teach high school in Grand Island, Nebraska. Determined to receive a college education, Abbott took correspondence courses and night classes until she was able to afford to enroll. Abbott enrolled at the University of Nebraska, receiving her degree in 1901, she continued to teach for two more years and was awarded a fellowship to the University of Chicago.
While at the University of Chicago working on her doctorate, she met Professor Sophonisba Breckinridge. She earned her doctorate in political economy in 1905. Abbott and Breckinridge would publish multiple studies while at the Chicago School of Civics and Philanthropy. In 1905, Abbott graduated, receiving her Ph. D. in economics. In 1906, Abbott received a Carnegie Fellowship and continued her studies at University College London, the London School of Economics, she learned from social reformers Sidney Webb and Beatrice Webb, who championed new approaches to dealing with poverty. The Webbs influenced the direction of Abbott's career; the Webbs were in favour of repealing the British "poor laws"—which they viewed as demeaning to people in poverty—and they supported establishing programs to eliminate poverty. While studying in London, Abbott lived part of the time in a social reformers' settlement in a poverty-stricken area of the East End, where she gained experience in social work. Abbott returned to the United States in 1907 after her years studying in London, took a job teaching economics at Wellesley College.
Though her job at Wellesley was regarded for a woman with a Ph. D at the time, she desired to return to Chicago, she got her chance in 1908 when Sophonisba Breckinridge Director of Social Research at the independent Chicago School of Civics and Philanthropy, offered her a job teaching statistics in the Department of Social Investigation. Abbott moved into Jane Addams's Hull House with her sister, when she moved back to Chicago. At that time, Hull House was renowned as a mecca for educated women, for its vibrant community of residing revolutionary thinkers. Grace and Edith Abbott became great additions to the reform-minded community as they contributed through their commitment to social reform advocacy and scholarship of statistical research; the long-lasting professional partnership between Abbott and Breckinridge first started during their years together at the School of Civics and Philanthropy. They shared a common interest in detailed statistical investigations of contemporary social problems which they believed they could use to spark reform advocacy.
As a result of her experience in statistical research, following a crime wave in Chicago in 1914 Abbott was commissioned to investigate statistics on crime and criminals in the city. This led to a ground-breaking report titled "Statistics Relating to Crime in Chicago", published in 1915. During the first 12 years of their collaboration at the Department of Social Investigation and Breckinridge jointly produced'The Housing Problem in Chicago', which consisted of ten articles in the American Journal of Sociology reporting the results of their major survey of tenement conditions in Chicago.. In 1927, in dedication to the "scientific and professional interests of social work", Abbott and Breckinridge jointly established the distinguished academic journal, Social Service Review, published by the University of Chicago Press. With the joint efforts of Abbott and Breckinridge, in 1920, the University of Chicago's Board of Trustees voted to rename the School the University of Chicago Graduat
Asynchronous muscles are muscles in which there is no one-to-one relationship between electrical stimulation and mechanical contraction. These muscles have convergently evolved 7-10 times. Unlike their synchronous counterparts that contract once per neural signal, mechanical oscillations trigger force production in asynchronous muscles; the rate of mechanical contraction is an order of magnitude greater than electrical signals. Although they achieve greater force output and higher efficiency at high frequencies, they have limited applications because of their dependence on mechanical stretch; the exact molecular mechanisms used by asynchronous muscles are unknown, but it is believed that asynchronous muscles have no unique molecular structures as compared to their synchronous counterparts. A study investigating the asynchronous power muscles in bumblebees with X-ray diffraction videos showed that actin and myosin alone are sufficient for generating asynchronous behavior; this finding helps explain.
More recent work using similar X-ray diffraction techniques in Lethocerus discovered that troponin bridges may play a critical role in stretch activation. As the muscle is stretched, these bridges move tropomyosin to reveal myosin-actin binding sites; the muscle can only produce force. Several changes to asynchronous muscles' macroscopic structure provide it with high force production and efficiency at high contraction frequencies. A critical adaptation is that asynchronous muscles maintain a tonic level of calcium instead of cycling calcium between contractions; this is evident in their long twitch duration. This is due to spare sarcoplasmic reticulum; because of requirements for high force production and myofibril diameters are increased and the large amount of ATP necessary leads to high mitochondria densities. In Cotinus mutabilis, asynchronous muscles are composed of 58.1% myofibril, 36.7% mitochondria, 1.6% sarcoplasmic reticulum. In comparison, synchronous muscles in Schistocerca americana are composed of 65% myofibril, 23.5% mitochondria and 9.6% sarcoplasmic reticulum.
Although synchronous muscle has a higher percentage of myofibril, the cross-sectional area of asynchronous myofibril is 3.7 µm2 as opposed to 0.82 µm2 in synchronous muscle for the described species. The defining characteristic of asynchronous muscles is that there is no direct relationship between neural activation and muscle contraction; the number of muscle contractions is an order of magnitude greater than the number of action potentials sent to the muscle. Instead of directly controlling force generation, neural signals maintain above a threshold for stretch-activation to occur. For asynchronous muscles, neural inputs are thought of as an "on-off" switch while mechanical stimulus leads to individual muscle contractions. However, recent studies using genetically engineered Drosophila revealed correlations between and force production. Further work has shown bilateral calcium asymmetries in Drosophila; these results indicate that there is some level of neural control beyond a simple "on" or "off" state.
Delayed stretch activation and delayed shortening deactivation allow asynchronous muscles to generate positive work under cyclic oscillations. When the muscle shortens, force drops and continues dropping when the muscle length remains constant; when the muscle lengthens, force increases and continues increasing after the muscle length remains constant. Because of these delays, the work produced by the muscle during shortening is greater than the work absorbed during lengthening, therefore producing positive work. In contrast, synchronous muscles absorb work under similar conditions. Both types of muscles consume ATP to produce work. Long twitch duration is a functional consequence of the macroscopic properties of asynchronous muscle; because asynchronous muscle can generate power without cycling calcium between contractions, the required rate of calcium regulation is slower. In addition to the reduction in sarcoplasmic reticulum large myofibril diameters lead to increased diffusion times of Ca2+.
Under isometric twitch experiments, asynchronous muscle in Cotinus mutabilis were found to have a twitch duration of 125 ms. In the same study, synchronous muscle in Schistocerca americana had a twitch duration of 40 ms. Therefore, asynchronous muscles respond to neural stimulus. In the case of insect flight, electrical stimulation alone is too slow for muscle control. For Cotinus mutabilis, the twitch duration is ten times as long as a wingbeat period. Asynchronous muscles produce work when they undergo mechanical oscillations provided there is sufficient Ca2+; this can be achieved in one of two ways. First, two antagonistic muscles can be configured with elastic structures such that the contraction of one muscle stretches the other, causing it to activate and vice versa; this configuration is found in the power muscles of flying insects. Second, a single asynchronous muscle can deform an elastic element which stretches the muscle and causes the muscle to contract again; this setup is used by Drosophila to oscillate mechanosensory organs known as halteres.
As long as neural stimulus turn the muscles "on," both systems will continue to oscillate. These systems can be thought of as resonant systems, for which the oscillation frequency is dependent on the elasticity and force applied to the system. In a simplified case, this can be thought of as a linearly damped harmonic oscillator, for which the damped resonant frequency is The damping ratio, ζ, is dependent on c, the damping coefficient, m, the mass of
Acacia lasiocarpa known as Panjang or Pajang or glow wattle, is a shrub of the genus Acacia and the subgenus Pulchellae, endemic to Western Australia. The shrub grows to a height of 0.15 to 0.5 metres and 1 m across. The branchlets are covered in spines; the pinnae occur in pairs and have a length of 1 to 10 millimetres with two to eight pairs of pinnules that are 1 to 5 mm long and 0.5 to 1 mm wide. The foliage is lime green in colour, it produces yellow flowers. The rudimentary inflorescences have globular flowerheads containing 16 to 50 golden flowers. Following flowering flat or undulate brown seed pods form that are 10 to 40 mm in length and 3 to 5 mm wide; the sometimes mottled seeds inside have an oblong to elliptic or circular shape and are 1.5 to 2.5 mm in length. The species was first formally described by the botanist George Bentham in 1837 as part of the Bentham, Stephan Endlicher, Eduard Fenzl and Heinrich Wilhelm Schott work Enumeratio plantarum quas in Novae Hollandiae ora austro-occidentali ad fluvium Cygnorum et in Sinu Regis Georgii collegit Carolus liber baro de Hügel.
It was reclassified as Racosperma lasiocarpum in 2003 but transferred back to the genus Acacia in 2006. There are three varieties: Acacia lasiocarpa var. bracteolata Acacia lasiocarpa var. lasiocarpa Acacia lasiocarpa var. sedifolia It is native to an area in the Wheatbelt, Goldfields-Esperance and Great Southern regions of Western Australia with the bulk of the population found south west of a line from Kalbarri to Esperance. The plant is found in a range of habitat including in seasonally damp areas, in and around swamps, on flats and coastal dunes an can grow in a variety of soils. List of Acacia species