Joseph Priestley was an 18th-century English Separatist theologian, natural philosopher, innovative grammarian, multi-subject educator, liberal political theorist who published over 150 works. He has been credited with the discovery of oxygen, having isolated it in its gaseous state, although Carl Wilhelm Scheele and Antoine Lavoisier have strong claims to the discovery. During his lifetime, Priestley's considerable scientific reputation rested on his invention of carbonated water, his writings on electricity, his discovery of several "airs", the most famous being what Priestley dubbed "dephlogisticated air". However, Priestley's determination to defend phlogiston theory and to reject what would become the chemical revolution left him isolated within the scientific community. Priestley's science was integral to his theology, he tried to fuse Enlightenment rationalism with Christian theism. In his metaphysical texts, Priestley attempted to combine theism and determinism, a project, called "audacious and original".
He believed that a proper understanding of the natural world would promote human progress and bring about the Christian millennium. Priestley, who believed in the free and open exchange of ideas, advocated toleration and equal rights for religious Dissenters, which led him to help found Unitarianism in England; the controversial nature of Priestley's publications, combined with his outspoken support of the French Revolution, aroused public and governmental suspicion. He spent his last ten years in Pennsylvania. A scholar and teacher throughout his life, Priestley made significant contributions to pedagogy, including the publication of a seminal work on English grammar and books on history, he prepared some of the most influential early timelines; these educational writings were among Priestley's most popular works. It was his metaphysical works, that had the most lasting influence, being considered primary sources for utilitarianism by philosophers such as Jeremy Bentham, John Stuart Mill, Herbert Spencer.
Priestley was born to an established English Dissenting family in Birstall, near Batley in the West Riding of Yorkshire. He was the oldest of six children born to a finisher of cloth. To ease his mother's burdens, Priestley was sent to live with his grandfather around the age of one, he returned home, five years after his mother died. When his father remarried in 1741, Priestley went to live with his aunt and uncle, the wealthy and childless Sarah and John Keighley, 3 miles from Fieldhead; because Priestley was precocious—at the age of four he could flawlessly recite all 107 questions and answers of the Westminster Shorter Catechism—his aunt sought the best education for the boy, intending him for the ministry. During his youth, Priestley attended local schools where he learned Greek and Hebrew. Around 1749, Priestley became ill and believed he was dying. Raised as a devout Calvinist, he believed a conversion experience was necessary for salvation, but doubted he had had one; this emotional distress led him to question his theological upbringing, causing him to reject election and to accept universal salvation.
As a result, the elders of his home church, the Independent Upper Chapel of Heckmondwike, refused him admission as a full member. Priestley's illness left him with a permanent stutter and he gave up any thoughts of entering the ministry at that time. In preparation for joining a relative in trade in Lisbon, he studied French and German in addition to Aramaic, Arabic, he was tutored by the Reverend George Haggerstone, who first introduced him to higher mathematics, natural philosophy and metaphysics through the works of Isaac Watts, Willem's Gravesande, John Locke. Priestley decided to return to his theological studies and, in 1752, matriculated at Daventry, a Dissenting academy; because he had read Priestley was allowed to skip the first two years of coursework. He continued his intense study. Abhorring dogma and religious mysticism, Rational Dissenters emphasised the rational analysis of the natural world and the Bible. Priestley wrote that the book that influenced him the most, save the Bible, was David Hartley's Observations on Man.
Hartley's psychological and theological treatise postulated a material theory of mind. Hartley aimed to construct a Christian philosophy in which both religious and moral "facts" could be scientifically proven, a goal that would occupy Priestley for his entire life. In his third year at Daventry, Priestley committed himself to the ministry, which he described as "the noblest of all professions". Robert Schofield, Priestley's major modern biographer, describes his first "call" in 1755 to the Dissenting parish in Needham Market, Suffolk, as a "mistake" for both Priestley and the congregation. Priestley yearned for urban life and theological debate, whereas Needham Market was a small, rural town with a congregation wedded to tradition. Attendance and donations dropped when they discovered the extent of his heterodoxy. Although Priestley's aunt had promised her support if he became a minister, she refused any further assistance when she realised he was no longer a Calvinist. To earn extra money, Priestley proposed opening a school
In physics, Knudsen diffusion, named after Martin Knudsen, is a means of diffusion that occurs when the scale length of a system is comparable to or smaller than the mean free path of the particles involved. An example of this is in a long pore with a narrow diameter because molecules collide with the pore wall. Consider the diffusion of gas molecules through small capillary pores. If the pore diameter is smaller than the mean free path of the diffusing gas molecules and the density of the gas is low, the gas molecules collide with the pore walls more than with each other; this process is known as Knudsen diffusion. The Knudsen number is a good measure of the relative importance of Knudsen diffusion. A Knudsen number much greater than one indicates. In practice, Knudsen diffusion applies only to gases because the mean free path for molecules in the liquid state is small near the diameter of the molecule itself; the diffusivity for Knudsen diffusion is obtained from the self-diffusion coefficient derived from the kinetic theory of gases: D A A ∗ = λ u 3 = λ 3 8 R T π M A For Knudsen diffusion, path length λ is replaced with pore diameter d, as species A is now more to collide with the pore wall as opposed with another molecule.
The Knudsen diffusivity for diffusing species A, D K A is thus D K A = d u 3 = d 3 8 R T π M A, where R is the gas constant, molecular mass M A is expressed in units of kg/mol, temperature T. Knudsen diffusivity D K A thus depends on the pore diameter, species molecular mass and temperature. Expressed as a molecular flux, Knudsen diffusion follows the equation for Fick's first law of diffusion: J K = ∇ n D K A Here, J K is the molecular flux in mol/m²·s, n is the molar concentration in m o l / m 3; the diffusive flux is driven by a concentration gradient, which in most cases is embodied as a pressure gradient. If we assume that Δ P is much less than P a v e, the average absolute pressure in the system we can express the Knudsen flux as a volumetric flow rate as follows: Q K = Δ P d 3 6 l P a v e 2 π R T M A,where Q K is the volumetric flowrate in m 3 / s. If the pore is short, entrance effects can reduce to net flux through the pore. In this case, the law of effusion can be used to calculate the excess resistance due to entrance effects rather by substituting an effective length l e = l + 4 3 d in for l.
The Knudsen process is significant only at low pressure and small pore diameter. However there may be instances where both Knudsen diffusion and molecular diffusion D A B are important; the effective diffusivity of species A in a binary mixture of A and B, D A e is determined by 1 D A e = 1 − α y a D A B + 1 D K
Martin Kunert is a feature film and television writer and producer. In 2004, Kunert conceived and directed the documentary Voices of Iraq, made by sending 150 DV cameras to Iraqis to film their own lives. MovieMaker Magazine hailed the film as "truly a groundbreaking film…both in terms of its content and the process behind its production."Previously, Kunert created and executive produced MTV's Fear, the first reality show to have contestants film themselves. Kunert created the show's frightening ambiance, developed the oft-mimicked visual and musical style and streamlined the show's editing process, where on a weekly basis, over 250 hours of contestant generated video was edited into 45-minute episodes. MTV's Fear spawned TV specials, fan clubs, DVDs, numerous copycat television shows, including NBC's Fear Factor and VH1's Celebrity Paranormal Project. Kunert has directed television and feature films, including the cult favorite Campfire Tales for New Line Cinema and Rogue Force for Miramax.
His screenplays include Warner Bros.' Dodging Bullets for Will Smith and Halle Berry, Paramount's The Brazilian, 20th Century Fox's Hindenburg for Jan de Bont. He created and executive produced "HRT" for CBS and Columbia TriStar and "Catch" for CBS. With Doug Liman, Kunert reinvented "CHiPs" for NBC and Warner Bros.. He created the reality show "Mayor" for Columbia TriStar. In 2002, NBC/StudiosUSA signed Kunert to an exclusive writing/directing/producing contract, he wrote and executive produced "Witch Doctor", a TV pilot for Beacon TV and ABC television studios in 2008. In 2011, DirecTV, Panasonic got together to finance an experimental 3D film for Kunert to direct and shoot on Panasonic's new 3D camera systems; as part of it, Technicolor trained Kunert extensively on how to make clean, non-headache inducing, 3D motion images. DirecTV will distribute the 3D film internationally. Kunert is a graduate of New York University's film school, he is a member of Writers Guild of America. He was born in Warsaw and grew up in Westfield, New Jersey before attending the New York Military Academy.
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