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Educación química
versión impresa ISSN 0187-893X
Educ. quím vol.22 no.4 Ciudad de México oct. 2011
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John Henry Poynting
Jaime Wisniak*
* Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel 84105. Correo electrónico: wisniak@bgu.ac.il
Recepción: 2 de agosto de 2010.
Aceptación: 5 de septiembre de 2010.
John Henry Poynting (1852-1914) is known for his work related to the determination of the effect of pressure on the changes of phase and osmotic pressure (the Poynting effect), the determination of the constant of gravity and the mean density of the Earth, the pressure exerted by radiation, the transfer of energy in an electromagnetic field, and the connection between electric current and the electric and magnetic inductions in the surrounding field (the Poynting vector).
Keywords: Phase changes, Poynting effect, density of Earth, radiation, Poynting vector.
John Henry Poynting (1852-1914) es conocido por sus trabajos relacionados con la determinación del efecto de la presión sobre los cambios de fase y la presión osmótica (efecto Poynting); la determinación de la constante de la gravedad y la densidad media de la Tierra; la presión ejercida por la radiación; la transferencia de energía en un campo electromagnético, y la conexión entre la corriente eléctrica y la inducción eléctrica y magnética en el campo de alrededor (el vector de Poynting).
Life and career (Shakespear, 1920; Falconer, 1999; Larmor, 1914; Lodge, 1914)
John Henry Poynting was born on September 9, 1852, at Monton, near Manchester, the youngest son of the Reverend Thomas Elford Poynting (1830-1878), Unitarian Minister of Monton. He received his first education at the school run by his father, and then, from 1867-1872, he attended Owens College, Manchester, after gaining a Dalton Entrance Exhibition in Mathematics. In due time Charles would follow the steps of his father and become Unitarian Minister at Fallowfield, near Manchester. His second brother, Frank Poynting (1848-1897), became a well-known ornithologist who studied the eggs of British birds.
At that time Owens had not the authority of granting degrees and most of the students prepared for the external examinations of the University of London. Poynting took second place at the London Matriculation exam in 1869, obtained Second Class Honors in both Physics and Mathematics in the First B.Sc. examination in 1871, and took the B.Sc. degree in 1872. In the same he was awarded an entrance scholarship to Trinity College, Cambridge. At Trinity he studied mathematics with Edward John Routh (1831-1907) and obtained his Major Scholarship in due course. He joined the Second Trinity Boat Club and rowed in the first boat in 1875. He took his degree in the Mathematical Tripos of 1876 as Third Wrangler (i.e., third in his year), tied with another student by the name of Trimmer, of Trinity College (Thomson, 1914).
After graduation Poynting returned for a short time to Owens College as a demonstrator in the Physical Laboratory under Balfour Stewart (1828-1887), who had succeeded Jack as Professor of Natural Philosophy shortly before Poynting's departure for Cambridge. While at Owens he began a lifelong friendship with his fellow student Joseph John Thomson (1856-1940, 1906 Nobel Prize for Physics for his discovery of the electron). In 1887 Cambridge awarded him his doctoral degree.
In 1878 Poynting received a Fellowship to continue his studies at Trinity College; there, in the Cavendish Laboratory under Clerk Maxwell, he begun his experiments on the mean density of the Earth, which were to occupy much of his time for the next 10 years and be the subject of his doctoral dissertation. He stayed at Cambridge until 1880 when he was appointed to the Chair of Physics in Mason College, Birmingham, which had just been founded; he held this post until his death (Thomson, 1914). In the same year he married Maria A. Cropper, daughter of John Cropper, Unitarian Minister of Stand, near Manchester, with whom he had three children.
Poynting was one of the prime movers in the development of Mason College into the University of Birmingham in 1900 and was largely responsible for the planning and organization of the new technological departments and their buildings (Thomson, 1914). In 1900 Poynting was elected Dean of the Faculty of Science (Lodge, 1914).
Poynting carried out all this despite continual poor health, showing the first signs of diabetes. In the 1880s he and his family moved to Alvechurch, near Birmingham, where Poynting took up farming in his spare time, an activity that did not prove to be profitable. In the spring of 1912 a severe attack of influenza was followed by a recrudescence of diabetes and he was ordered to take a long rest, which kept him away from Birmingham for two terms. Another attack of influenza in the spring of 1914 brought on a very severe attack of diabetes and led to his death on March 30, 1914 (Lodge, 1914; Thomson, 1914).
While at Owens Poynting published his first memoir (Poynting, 1877), which was not exactly of an academic nature; it dealt with an analysis of the statistics for drunkenness in England and Wales, which Chamberlain had published in February of 1877. According to the latter, the data was contrary to the proposition that the multiplication of public houses (pubs) had a tendency to diminish intemperance. Poynting grouped the data as a histogram and obtained the opposite result: the number of apprehensions for drunkenness increased considerably as the number of public housed decreased in proportion to the population. His method of analysis seemed more justified because instead of considering the information on a town-by-town basis, he grouped the towns having more or less the same number of pubs and plotted the average of apprehensions of each group against their number of public houses. In this way he neutralized the effect of more or less stringent police regulations and other circumstances peculiar to individual towns. This work, done in collaboration with John Dendy (1827-1894) and forming part of a report to the Select Committee of the House of Lords on Intemperance, concluded among other things, that there was a marked geographical distribution of drunkenness, northern England being decidedly more drunken than southern England, and that there appeared to be a direct relation between the rate of increase of population and the rate of drunkenness (Poynting and Dendy, 1878).
Another publication in the area of statistics was related to the fluctuations in the price of wheat and in the cotton and silk imports into Great Britain and the possible relations between this phenomenon and common meteorological causes (Poynting, 1884a).
Poynting's well-known works on the use of a common balance for determining the mean density of the Earth and the gravity constant were also started during 1877 in Owens. The gravitational experiments were moved first to Cambridge, and then to Mason College. The results of this work gained him Cambridge University's Adams Prize.
Poynting's memoir on the transfer of energy (Poynting, 1884b) aroused universal attention. The paths by which energy travels from an electromotive source to various parts of a circuit were displayed, and their intricacies unraveled. These papers are the basis of the fundamental generalization connecting mechanical motion with electric and magnetic forces, which is known as Poynting's Theorem (Lodge, 1914).
Poynting's work on radiation and radiation pressure (Poynting, 1903a, 1904ab, 1905, 1910a) analyzing and proving the tangential pressure of radiation; shows, both theoretically and experimentally, that a beam of light behaves essentially as a stream of momentum, and produces all the mechanical results which may thus be expected, in spite of being extremely small. His results allow a way to determine the absolute temperatures of the Sun and the planets, and of other masses in space (Lodge, 1914).
Poynting also took great interest in the philosophical aspects of physical science, and Ward acknowledges his help in connection with the publication of the Gifford Lectures delivered before the University of Aberdeen in the years 18961898, entitled Naturalism and Agnosticism (Ward, 1899). Poynting was strongly inclined to limit the realm of science to description and to regard a law of nature as nothing but a formulation of observed correspondences. He wished to abolish the idea of cause in physics.
Some of Poynting's philosophic views were exposed in his Presidential Address to Section A of the British Association for 1899 (Poynting, 1899): "Concurrently with the change in our conception of physical law has come a change in our conception of physical explanation [...] we have explained anything when we know the cause of it, or when we have found out the reason why [.] We explain an event not when we know why it happened, but when we show how it is like something else happening elsewhere or other when, w2hen in fact, we can include it's a case described by some law already set forth. In explanation we do not account for the event, but we improve our account of it by likening to what we already know [...] the physicist is examining the garment of Nature, learning of how many, or rather of how few different kinds of thread it is woven, finding how each separate thread enters into the pattern, and seeking from the pattern woven in the past to know the pattern yet to come [...] We stand in front of Nature's loom as we watch the weaving of the garment; while we follow a particular thread in the pattern it suddenly disappears, and a thread of different color takes its place. Is this a new thread or is merely the old thread turned around and presenting a new face to us? So as we watch the weaving of the garment in Nature, we resolve it in imagination into threads of ether spangled over with beads of matter. We look still closer, and the beads of matter vanish; they are mere knots, and loops in the threads of ether [...] Do we, or do we not, as a matter of fact, make any attempt to apply the physical method to describe and explain those motions of matter which on the psychical view we term voluntary?
Poynting was awarded much recognition as a result of his brilliant research in many areas, and his public activities. He was elected a Fellow of the Royal Society (1888); he received the 1893 Adams Prize from the University of Cambridge, the 1903 Hopkins Prize of the Cambridge Philosophical Society, and in 1905 a medal from the Royal Society "for his researches in physical science, especially in connection with the constant of gravitation and theories of electro-dynamics and radiation." Poynting served on the Council of the Royal Society from 1909 to 1911 and as its Vice-President in the period 1910-11. He was President of Section A at the 1899 meeting in Dover of the British Association for the Advancement of Science; he also served as President of the Physical Society in 1909-1911. In addition to the effort involved in twice planning and equipping a new physics laboratory, preparing lectures and doing research, he found time to serve as a Justice of the Peace, Chairman of the Birmingham Horticultural Society, and as member of the licensing committee, the Gassiot Committee of the Royal Society, and on the Sights Test Committee of the Board of Trade (Thomson, 1914).
Scientific contribution
Poynting is remembered particularly for the equation he developed to describe the variation of the vapor pressure with the external pressure (the Poynting effect) and the Poynting vector, which he formulated in 1884 to describe the flow of energy in an electromagnetic field.
In addition to over 100 papers published in several scientific journals Poynting wrote The Mean Density of the Earth (Poynting, 1894; the Adams Prize Essay for 1893), The Pressure of Light (Poynting, 1910b; "Romance of Science" Series) and The Earth (Poynting, 1913). To the Text Book of Physics written in conjunction with Thomson (Poynting and Thomson, 1914) he contributed the whole of the volumes on Sound and Heat and of the first volume of Electricity and Magnetism and the chapters on Gravitation in the Properties of Matter.
Poynting's papers may be divided into four groups: (a) on the change of state, (b) studies on gravitational attraction, (c) on the transfer of energy in the electromagnetic field, and (d) on the pressure of light. The content of these papers is briefly discussed below.
Change of state
In the introduction to his first paper on the subject (Poynting, 1881a) Poynting summarized the findings of Thomson on the effect of the curvature of a liquid surface on its vapor pressure (Thomson, 1872). According to Thomson, when a liquid rises in a capillary tube so that its surface is concave upwards, then its vapor pressure is less than at the plane surface. If the liquid falls in the tube so that its surface is now convex, then its vapor pressure is larger than at the plane surface. Thomson derived the following equation to express these results:
where p and p' are the vapor pressures over the plane surface and over the curved surface of the meniscus, pL and pV the densities of the liquid and vapor respectively, σ the surface tension of the liquid, and r the radius of curvature of the curved surface. In equation (1) the term 2σ/p represents the difference in pressure between the upper and the lower part of the meniscus. Since pL>>pV the sign of (p - p/) will depend on the sign of r. For non-wetting liquids such as mercury, r > 0 and consequently, the vapor pressure of a drop will increase above that over a plane surface, inversely proportional to the decrease in the radius of the drop. For example, for mercury drops with r = 10-7 cm, the increase in vapor pressure is 100 percent.
Poynting proceed to show that the same equation was applicable to both the solid and the liquid state, making Thomson's result more general. His starting point was the accepted assumption that the maximum vapor pressure of a substance at a given temperature is an indication of the number of molecules escaping from its free surface. Two different phases will then be in the equilibrium when the escaping tendency of the molecules is the same for the two phases. To explain the fact that the melting point of a substance is affected by pressure it becomes necessary to assume that the pressure alters the vapor pressure, and therefore the rate of escape of the molecules, and that this alteration is different for the two states. Equality of the vapor pressures will now occur at the new melting point. Pressure increases the number of molecules escaping from the surface of the two phases in contact, but the increase is greater in the less dense state. For the particular case of ice + water, ice is the dense state and below 0°C it has the less vapor pressure. Hence a sufficiently great increase of pressure, while increasing both vapor pressures, can make that of ice overtake that of water and lower the melting point.
Suppose now that only one of the states (ice) is subjected to an increase in pressure. In this situation the new pressure will increase the rate at which molecules escape from the ice into the water but will not affect the rate of escape of water molecules into the ice. Assuming the applied pressure δP to be represented by 2σ/r and substituting in equation (1) we get
In a second paper on the subject (Poynting, 1881b) Poynt-ing extended his analysis to the evaporation of a liquid. In this situation the effect of surface tension on vapor pressure originates from the hydrostatic pressure 2σ/r produced on the surface, hence the vapor pressure over a flat surface should increase when the pressure on the liquid in increased, for example, by addition of an inert gas into a vessel containing liquid in equilibrium with its vapor. Poynting derived an expression for the variation of the vapor pressure of the liquid with the external pressure by analyzing the following isothermal cycle: (a) evaporation of one gram of liquid under the total pressure p + P, (b) expansion of the vapor produced to the pressure p assuming ideal behavior, (c) condensation of the vapor at pressure p, and (d) closing the cycle by compressing the liquid formed back to the original pressure p + P. Let v, v', V, and V be the corresponding volumes of the liquid and vapor respectively, and a the isothermal compressibility of the liquid. According to the First law of thermodynamics the total work done by the cycle is zero, that is
Equation (3) can be simplified significantly using the facts that PV = p'Vand that terms containing ap are negligible, to yield
Hence if P is no very great
the same result as equation (2), obtained by a different process.
All the assumptions regarding the ideality of the gas phase may be removed by considering the modern term of fugacity, f, instead of the pressure. We know that (Smith, 2006):
Separating variables and integrating at constant temperature between vapor pressure p10 and any external pressure P, we get
Assuming the liquid to be incompressible, the expression for the Poynting effect becomes
where p10 is now the vapor pressure of the component at temperature T. Nowadays, equations (8) and (9) expressing the effect of the external pressure on the vapor pressure of a liquid are called the Poynting effect. These equations convert the fugacity of a pure saturated liquid from the vapor pressure to the system pressure at the same temperature. Calculation of the Poynting effect plays an important role in the analysis of vapor-liquid equilibrium.
Osmotic pressure
According to Poynting (Poynting, 1896ab), the phenomena of liquid viscosity, diffusion, and surface evaporation may be analyzed by imagining the liquid to be a solid structure, inasmuch as the molecules cohere and resist strain of any kind1 Anyhow, it is clear that the amount of kinetic and potential energy of the molecules puts this structure not far from instability. In a mass of connected molecules irregularly distributed and irregularly vibrating, concentrations of energy must occur and at the points of concentration individual molecules may receive enough energy to free themselves from their immediate surroundings. The near unstable solid structure is thus continually breaking down and renewing itself. If the breaking down of the structure takes place near the surface of the liquid some of the moving molecules have a velocity vector that allows them to escape the liquid and become part of the gas space. Based on these ideas, Poynting coined the term mobility to quantify the number of free or mobilized molecules crossing a square centimeter per second of liquid, where by free or mobilized molecules he meant those that were changing their surroundings and forming new connections. When the square centimeter is located on the surface of the liquid, the upward mobility corresponds to the rate of vaporization and the downward mobility of the vapor is the rate of condensation; when both mobilities are equal the pressure on the system becomes the vapor pressure.
Assume now a closed chamber maintained at constant temperature and holding two partly filled deep vessels, one containing pure solvent and the other a dilute solution of a non-volatile salt. As a result of the difference in vapor pressures, the pure solvent will distill over into the solution and will continue to do so until the difference in level in the two vessels is such that each surface is in equilibrium with the vapor at its level. The hydrostatic pressure in the solution at the level of the surface of the pure solvent will then be the osmotic pressure.
These remarks may be used to explain in general terms the rise that takes place when a semi-permeable vessel containing a solution is placed inside another vessel containing pure solvent. The molecules of the solvent began entering the membrane from both sides but since the vapor pressure over the pure solvent is larger than that over the solution, the mobility or number of molecules set free from the pure solvent is greater than the number set free from the solution. According to Poynting, the membrane continues to absorb the solvent from both sources until it becomes saturated, that is, it returns as many molecules as it receives. The membrane is receiving more molecules from the pure solvent side, and therefore when saturated for that side it is supersaturated for the other. Consequently more molecules are sent into the solution than are received from it, and the volume of the solution grows until the growing hydraulic pressure so much increases the mobility that it becomes identical on both sides of the membrane (Poynting, 1896a).
Poynting now applies the same idea to the change of melting point in a solution. In the solid the mobility is unchanged but that of the solution is lowered by the fraction PpV/ P°pL, where P is the osmotic pressure and P° the vapor pressure of the pure solvent. To find the new melting point it is necessary to find the temperature dθ below the normal melting point at which this is equal to the difference between the liquid and solid mobilities. Taking the pressure to represent mobilities Poynting derives the relation
where L is the heat of change of phase.
Poynting now assumes an unusual mechanism to explain the decrease in vapor pressure caused by the solute: he imagines that the latter probably combines with the solvent to form unstable molecular aggregates, which continuously interchange constituents so that when located near the surface they compete with the non associated molecules to capture the vapor molecules hitting the surface. This capture is done by pure solvent molecules or by the complex molecules exchanging their attached solvent molecules for the ones arriving from the vapor phase. Poynting's view differs from the one accepted today where it is said that in a solution the fraction of the free surface of the liquid available for the solvent molecules to escape is proportional to the mole fraction of the solvent, but the return surface for the vapor molecules is the total surface.
The trapping-exchange phenomenon may be quantified as follows: Assume that each molecule of salt associates with a molecules of the solvent in such a way that it prevents them from evaporating. The solution may be considered as solvent having a number of the molecules forming aggregates that are inactive as regards evaporation but active in effective condensation. If N is the number of solvent molecules per liter and n the number of solute molecules added, then the number of molecules of free solvent left is (N- an). In other words, the solution contains (N - an) molecules active for evaporation, while there is still N for condensation. As a result, the vapor pressure has decreased in the ratio (N - an)/N and
Assuming that a = 1, we have
which is the result obtained by van't Hoff for the value of the osmotic pressure (van't Hoff, 1887).
Poynting closed his paper with the remark that although his was a crude model, it showed that it was not necessary to ascribe osmotic pressure to dissociation but rather to association or some of the processes operative in solutions (Poynting, 1896a).
Gravitational attraction and the density of the Earth
The works for which Poynting is best known in the area of physics are his determination of the Newtonian constant of gravitation and the average density of the Earth by a very accurate use of an ordinary balance with an adjustable mass under one or other of the arms, a determination which is popularly known as weighing the Earth. These experiments were begun Cambridge in 1878 and only after twelve years they gave results which satisfied him. In his final memoir about the experiments to the Royal Society in 1891 (Poynt-ing, 1892) Poynting gave the measurement of G, the gravitational constant, as the first aim of the experiment, and then went on to discuss the use of the results to measure the mass of the Earth (Falconer, 1999).
Newton's theory of gravitation explained the motion of terrestrial objects and celestial bodies by postulating that pairs of massive objects attracted each other with a force proportional to the product of the two masses and inversely proportional to the square of the distance between them. In his book Principia (Newton, 1687) Newton reported the relative densities of the Sun, Jupiter, Saturn, and the Earth as 100, 94.5, 67, and 400, respectively, so that if the density of the Earth were known the densities of the Sun and the two planets could be calculated. On the basis of the known density of rocks at the surface of the Earth and rocks from mines, Newton guessed that the average density of the Earth is 5 to 6 times the density of water (Newton, 1687). After Newton, and at different times, British and French scientists attempted to weight the Earth by observing the gravitational force on a test mass from a nearly large mountain. The experimental procedure involved measuring the line of a pendulum hung near a mountain and comparing it to the line expected if the mountain was not there. These effects were hampered, however, by a very imperfect knowledge of the composition and average density of the rock composing the mountain (Wisniak, 2004).
The determination of the structure and composition of the interior of the Earth was one of the many subjects that interested Henry Cavendish (1731-1810). In an exchange of letters with his friend John Mitchell (1724-1793) they discussed the possibility of devising an experiment to weigh the Earth. Mitchell suggested an arrangement similar to the one used by Charles Coulomb (1736-1806) for measuring the electrical force between small charged metal spheres; that is, using a torsion balance to detect the very small gravitational attraction between metal spheres. Mitchell built a first prototype of the equipment but died (1793) before he was able to conduct the experiments. Cavendish rebuilt the apparatus into a balance constructed from a 6-foot wooden rod suspended at his middle point by a long metal fibre and carrying two 2-inch diameter lead spheres at each extremity. Two 350-pound lead spheres, brought close to the enclosure housing the rod, provided the attraction effect. This arrangement set up vibrations between the attractive force and the torsion of the wire and equilibrium was determined between the turning moment and the moment of torsion (Wisniak, 2004). Cavendish made seventeen experiments and concluded that the density of the Earth should be 5.48 greater than that of water (Cavendish, 1798). In 1841 Francis Baily (1774-1844) reviewed Cavendish's calculations and found a small mistake of simple arithmetic that decreased the expected density of the Earth from 5.48 to 5.45 (Berry, 1960). Between 1894 and 1896, Charles Vernon Boys (1855-1944), while repeating Cavendish's experiments, made the discovery that the sensitiveness of the apparatus could be greatly increased by reducing its dimensions (Boys, 1896). He reported the density of the Earth as 5.527 times the density of water.
Poynting's approach to the problem was similar to that of Cavendish, except that he substituted the torsion balance by a common one (Poynting, 1879). In his words: "In using the common balance to find the attraction between two masses, perhaps the most direct mode of proceeding would consist in suspending a mass from one arm of a balance by a long wire and counterpoising it in the other pan. Then bringing under it a known mass, its weight would be slightly increased by the attraction of this mass [...]" (Poynting, 1892). The balance used in the later experiments was built specially by Ludwig Oertling (1818-1893) and had a beam 123 cm long (note the extremely large size of the balances used by Cavendish and Poynting). With a balance of this size overcoming the difficulties arising from air currents proved to be quite an experimental challenge.
The mechanic principles of Poynting's method are straightforward. Consider a balance with two equal masses MA and MB; both are equally attracted to the Earth with a force
where FA, FB are the forces on MA and MB respectively. ME and R are the mass and the radius of the Earth, respectively, and G is the universal gravitational constant (Falconer, 1999). As Poynting writes: "To determine G we must measure GMAMB/R2 in some situation in which both MA and MB are known, whether they be a mountain and a plumb-bob, or two spheres of known mass and dimensions [.]" (Poynting, 1892).
Now, if a large extra mass M is put under MA at a distance r, then the additional force attracts MA down by the amount
while the force on MB remains constant. Hence the balance tilts, giving a measure of
Since M, MA, r, and (), are known, G can be evaluated and from it, the mean density of the Earth can be calculated from the expression:
where A is the density and V the volume of the Earth considered as a sphere of radius R. Hence A = gRs/GV (Falconer, 1999).
The experiments were much more complex than the theoretical equations suggest. Allowance had to be made for the attraction between M and MA before M was moved into position, for the attraction of the beam and of MB to M, and methods devised for measuring or canceling these. The apparatus was operated from a distance sufficient to prevent disturbances caused by the attraction and temperature effects of the body of the operator. A hole in the wall of the balance room permitted the experimenter to observe the setup with the help of a telescope (Falconer, 1999).
Traditionally, the common balance was considered unsuitable for measuring such small forces, first because of the greater disturbance produced by changes of temperature, such as convection currents and unequal expansion of the arms of the balance, and second because of the errors arising from raising the beam between each weighing, resulting in varying flexure of the beam and in constancy of the points of contact of the knife edges and planes (Poynting, 1879). Poynt-ing later picturesquely summed up the sensitivity and accuracy of his experiment (Poynting 1894ab): "Imagine a balance large enough to contain on one pan the whole population of the British Islands and that all the population were placed there but one medium-sized boy. Then the increase in weight, which had to be measured, was equivalent to measuring the increase due to putting that boy on with the rest. The accuracy of measurement was equivalent to observing from the increase in weight whether or no he had taken off one of his boots before stepping on to the pan" (Falconer, 1999).
Poynting reasoned that if the attraction between two spheres was different according to whether their axes were parallel or crossed, then there would be a directive action on one sphere in the field of the other. He and P. L. Gray attempted to detect such directive action by rotating one sphere and attempting to force rotational oscillations of the other (Poynting and Gray, 1899). They found no significant oscillations within the limits of accuracy of the experiment. Poynt-ing and Percy Phillips also did careful experiments (Poynting and Phillips, 1905) to determine if a change of temperature had any effect on weight. The results were negative, between 150° and 100°C, the change was smaller than one part in 109 and between 16.6° and -186°C it was smaller than one part in 1010 per 10°C.
Poynting's final results for the mean density of the Earth and the gravitational constant were 5.4934 times the density of water and 6.6984 x 10-8 dynes cm2 g-2, respectively (Poynt-ing, 1892). The present accepted value of the average mean density of the Earth is 5.52 times the density of water (Wisniak, 2004).
Poynting reported the results of his experiments to Trinity College, Cambridge, as a fellowship dissertation and Clerk Maxwell acted as referee (Falconer, 1999).
In his1900 address to the Royal Institution on recent studies in gravitation (Poynting, 1900) Poynting closed his lecture with the following remarks: "So while the experiments to determine g are converging on the same value, the attempts to show that under certain conditions it may not be constant, have resulted so far in failure all along the line. No attack on gravitation has succeeded in showing that it is related to anything but the masses of the attracting and the attracted bodies. It appears to have no relation to physical or chemical composition of the acting masses or to the intervening medium [...] But gravitation still stands alone. The isolation, which Faraday sought to break down, is still incomplete. We at least know something in knowing what qualities gravitation does not possess, and when the time shall come for explanation, all these laborious, and at first sight, useless experiments will take their place in the foundation on which that explanation will be built" (Poynting, 1900).
Transfer of energy in the electromagnetic field
The researches by which Poynting is most widely known are those published in his papers for the period 1885-1887 (Poynting, 1884b, 1885, 1887). The subject is described in the introduction to his first paper: "A space containing electric currents may be regarded as a field where energy is transformed at certain points into the electric and magnetic kinds by means of batteries, dynamos, thermoelectric actions, and so on, while in other parts of the field this energy is again transformed into heat, work done by electromagnetic forces, or any form of energy yielded by currents [...] the existence of induced currents and of electromagnetic actions at a distance has led [...] to look upon the medium surrounding the conductor as playing a very important part in the development of the phenomena. If we believe in the continuity of the motion of energy [.] we are forced to conclude that the surrounding medium contains at least part of the energy, and that it is capable of transferring it from point to point [.] How does the energy about an electric current pass from point to point [...] according to what law does it travel from [.] where it is recognizable as electric and magnetic to the parts where it is changed into heat or other forms? The aim of this paper is to prove that there is a general law for the transfer of energy, according to which it moves at any point perpendicularly to the plane containing the lines of electric and magnetic force, and that the amount crossing unit of area per second of this plane is equal to the product of the two forces multiplied by the sine of the angle between them divided by 4π, while the direction of the flow of energy is that in which a right-handed screw would move if turned round from the positive direction of the electromotive to the positive direction of the magnetic intensity" (Poynting, 1884b).
Poynting goes on to the full mathematical proof of his law and uses the equation of the electromagnetic field to show that the rate of increase in the energy inside a closed surface is equal to:
where dS is an element of the closed surface, l, m, n the direction cosines of the normal to the surface; P, Q, R the components of the electromotive intensity, and α, ß, γ, those of the magnetic force. The first two terms of Poynting's final equation express the gain per unit time in electric and magnetic energies, the third term, the work done per unit time of the electromagnetic forces, and the fourth one, the energy transformed by the conductor into heat, chemical energy, and so on. Equation (18) may be regarded as showing that the energy comes through the bounding force, the components of flux being (Rß - Qγ) / 4π, (pγ - Rα) / 4π, and (Qα - Pß ) / 4π, and that each element is contributing the indicated amount (Poynting, 1884b).
The vector having these components is now universally known as Poynting's vector; it is at right angles to both the electric and magnetic forces and is proportional to the product of these forces and the sine of the angle between them. Thus when we can draw equipotential surfaces for both the electric and magnetic forces the energy flows along the lines of intersection of the two sets of surfaces.
In modern vector terms:
where the vector →S is the rate of energy transport per unit area in the direction of the propagation of the wave, vectors →H and →B the magnetic field and the magnetic field flux density, respectively, vector →E the electric field normal to →B, and 1 / µ0 the permeability of the free space.
Poynting illustrated his theorem by applying it to a constant current flowing along a straight wire, a condenser discharged by short-circuiting the plates by a wire of great resistance, a voltaic battery, and a thermo-electric circuit. His results indicated that in the case of a wire, none of the energy travels along the wire but comes in from the non-conducting medium surrounding the wire, and that as soon as it enters it begins to be transformed into heat. The amount of energy crossing successive layers of the wire decreases systematically until the time when it reaches the center of the wire. At the axis there is no magnetic force and no energy passing, it has all been transformed into heat (Poynting, 1884b).
Before the publication of this paper the general opinion was that the energy was transferred along the wire much in the same way as hydraulic power is carried through a pipe. On Poynting's view the energy flows out from the space between the plates and then converges sideways into the wire, where it is converted into heat. In Poynting's words: "A current in a conductor is rather to be regarded as consisting essentially of a convergence of electric and magnetic energy from the medium upon the conductor and its transformation there into other forms. The current [.] consists essentially of a divergence of energy from the conductor into the medium [.] This mode of regarding the relations of the various parts of the circuit is [.] very different from that usually given, but it seems to me to give us a better account of the known facts" (Poynting, 1884b). In the second paper Poynting takes the view that the electromagnetic field consists of distributions of lines of electric and magnetic force and discusses the question of the transfer of energy from the point of view of the movement of these lines.
Poynting's vector occurs as a quantity of fundamental importance in many theories of electromagnetic action in which the subject is approached from a point of view somewhat different from the one described above. It appears, for example, as a measure of the momentum per unit volume when the electromagnetic field is regarded as a mechanical system and the properties of the field as the result of the laws of motion of such a system. It appears, too, when we regard magnetic force as the result of the motion of tubes of electric force, the direction of motion of these tubes being parallel to Poynting's vector (Thomson, 1914).
Pressure of Light
Poynting published a well-known paper on the theory of the subject (Poynting, 1903ab). In the first part of it he discussed the application of the fourth-power law of radiation (Stefan's law) to determine the temperature of planets such as Mercury, Venus, Mars, and Neptune. Among some of the interesting results he arrived at was that since the temperature of the Sun lies between 6000 Å and 7000 Å, then the effective temperature of space must be 10 Å; and that the average temperature of Mars is about 235 K, not different from the freezing point of mercury, that is, so low that life, as we know it, would be impossible on its surface.
The second part of the paper (Poynting, 1903b) discusses and calculates the pressure exerted by radiation against a surface on which it falls. His results indicate, for example, that a full absorber exposed normally to the solar radiation at the distance of the Earth, is subject to a pressure of 5.8 x 10-5 dyne ■ cm-2. He then calculated the repulsive force between two hot spheres, arising from the radiation from the one tending to repel the other and showed that if the bodies were in radiation equilibrium with the Sun at the distance of the Earth from it, the repulsive effect would be greater than the gravitational attraction between them if their radii are less than 19.6 cm, if their density were that of water; if they were made of lead the corresponding radius would be 1.78 cm.
There is a remarkable effect of size on the relation between the radiation pressure and the gravitational pull, the first one acts on the surface and is thus proportional to it, the second penetrates the surface and pulls every particle of matter throughout the entire volume. Poynting's calculations indicate that the radiation pressure on a minuscule speck of dust of 1 /40,000 cm radius and density equal to that of the Earth, balances exactly the pull of gravity and it would be neither attracted nor repelled by the Sun. This effect should be taken into account in the motion of Saturn's rings if these consisted of very small particles: it is perfectly possible that the effect of radiation might make them repel instead of attract each other. Each particles in the ring, having about 2.5 cm diameter, would neither attract nor repel each other, and each would move in circles around the planet as if the rest were absent (Poynting, 1905, 1906, 1909, 1910ab). At the end of the paper Poynting analyzes the effect produced by radiation on the orbits of small bodies around the Sun and shows that this would ultimately cause them to fall into that body. To quote his own words: "Thus the Sun is ever at work keeping the space round him free from dust, if the particles are very minute he drives them forth into outer space, if they are larger, he draws them in. It is just possible that we have evidence of this drawing in, in the zodiacal light, that vast dust-like ring which stretches from the Sun outwards far beyond the orbit of the Earth, and is at once the largest and the most mysterious member of the solar system (Poynting, 1906).
This idea was later developed by the American physicist Howard Percy Robertson (1903-1961) and is now known as the Poynting-Robertson effect.
Berry, A. J., Henry Cavendish — His Life and Scientific Work, Hutchinson, London, 1960. [ Links ]
Boys, C. V., The Newtonian Constant of Gravitation, Proc. Royal Inst., 14, 353-377, 1896. [ Links ]
Cavendish, H., Experiments to Determine the Density of the Earth, Phil. Trans., 88, 469-526, 1798. [ Links ]
Falconer, I., A Purely Local Experiment - Poynting and the Mean Density of the Earth, Meas. Sci. Technol., 10, 525-530, 1999. [ Links ]
Larmor, J. Obituary Notice, Nature, 93, 138-144, 1914. [ Links ]
Lodge O. J., Obituary Notice, Phil. Mag., 27, 914-916, 1914. [ Links ]
Newton, I., Philosophiae Naturalis Principia Mathematica, (London), 1687, pp. 301-303, Book II, proposition XXIII. [ Links ]
Poynting, J. H., The Drunkenness Statistics of the Large Towns in England and Wales, Manchester Lit. Phil. Soc. Proc., 16, 211-218, 1887. [ Links ]
Poynting, J. H., On a Method of Using the Balance with Great Delicacy, and on its Employment to Determine the Mean-Density of the Earth, Proc. Roy. Soc, 28, 2-35, 1879. [ Links ]
Poynting, J. H., Change of State: Fusion and Solidification, Birmingham Phil. Soc. Proc., 2, 354-372, 1881a. [ Links ]
Poynting, J. H., Change of State: Solid-Liquid, Phil. Mag., 12, 32-48, 232, 1881b; [ Links ] Lond. Phys. Soc. Proc., 4, 271-288, 1881b. [ Links ]
Poynting, J. H., A Comparison of the Fluctuations in the Price of Wheat and in the Cotton and Silk Imports into Great Britain, Statistical Soc. J., January, 1884a. [ Links ]
Poynting, J. H., On the Transfer of Energy in the Electromagnetic Field, Phil. Trans. 175, 1884b, 343-361; [ Links ] Arch. Sc. Phys. Nat., 22, 1889, 214-230 (abstract); [ Links ] Physik. Rev., 1, 1892, 48-75. [ Links ]
Poynting, J. H., On the Connection Between Electric Current and Electric and Magnetic Inductions in the Surrounding Field, Phil. Trans., 176, 277-306, 1885; [ Links ] Proc. Roy. Soc., 38, 168-172, 1885 (abstract). [ Links ]
Poynting, J. H., The Electric Current and its Connection with the Surrounding Field, Birmingham Phil. Soc. Proc., 5, 337-353, 1887. [ Links ]
Poynting, J. H., On a Determination of the Mean Density of the Earth and the Gravitation Constant by Means of the Common Balance, Phil. Trans. A, 182, 565-656, 1892. [ Links ]
Poynting, J. H., The Mean Density of the Earth. An Essay to which the Adams Prize was adjudged in 1893 in the University of Cambridge. London: Griffin and Co., 1894. [ Links ]
Poynting, J. H., A History of the Methods of Weighing the Earth. Presidential Address Delivered to the Birmingham Philosophical Society, October 19, 1893, Birmingham Phil. Soc. Proc, 9, 1-23, 1894b. [ Links ]
Poynting, J. H., Osmotic Pressure, Phil. Mag., 42, 289-300, 1896a. [ Links ]
Poynting, J. H., Osmotic Pressure [Letter], Nature, 55, 33, 1896b. [ Links ]
Poynting, J. H., Presidential Address to the Mathematical and Physical Section of the British Association (Dover), 1899, Brit. Assoc. Report, 615-624, 1899. [ Links ]
Poynting, J. H., Recent Studies in Gravitation. Address: Royal Institution of Great Britain, February 23, 1900; Proc. Roy. Inst., 16, 278-294, 1900-1902; [ Links ] Nature, 62, 403-408, 1900; [ Links ] Smithsonian Inst. Report, 199-214, 1901; [ Links ] Scientific. Amer. Sup. New York, 55, 22856-22858, 1903. [ Links ]
Poynting, J. H., The Pressure of Light, The Inquirer, 195-196, 1903a. [ Links ]
Poynting, J. H., Radiation in the Solar System: It's Effect on Temperatures and its Pressure on Small Bodies, Phil. Trans. A, 202, 525-552, 1903b. [ Links ] Correction by Sir J. Larmor: this volume, p. 734; Arch. Sc. Phys. Nat., 17, 390-400, 1904 (abstract); [ Links ] Monthly Weather Report-Washington, D.C. U.S. Dept-Agric. 32, 508-511, 1905. [ Links ]
Poynting, J. H., Radiation in the Solar System. Afternoon Address delivered at the Cambridge Meeting of the British Association, August 23, 1904; Nature, 70, 512-515, 1904a; [ Links ] Smithsonian Inst. Report, 185-193, 1904a; [ Links ] Jahrbuch Radio-aktivitat Elektronik, 2, 412-55, 1905; [ Links ] Fiz. Obozr. Varsava, 5, 253-263, 1904a. [ Links ]
Poynting, J. H., Radiation-Pressure [Letter in correction to address delivered at the meeting of the British Association, 1904]; Nature, 71, 200-201, 1904b. [ Links ]
Poynting, J. H., Radiation-Pressure. Presidential Address to the Physical Society of London, February 10, 1905; Phil. Mag. 9, 393-406, 1905; [ Links ] Lond. Phys. Soc. Proc, 19, 475-490, 1905; [ Links ] Nature, 71, 376-377, 1905 (abstract); [ Links ] Electrician, 54, 706-707, 1905. [ Links ]
Poynting, J. H., Some Astronomical Consequences of the Pressure of Light. Discourse delivered at the Royal Institution of Great Britain on May 11, 1906; Nature, 75, 90-93, 1906; [ Links ] Roy. Inst. Proc., 18, 339-341, 1906-1909 (abstract); [ Links ] Pop. Astr., Northfield, Minn., 15, 626-629, 1907. [ Links ]
Poynting, J. H., Quelques Expériences sur la Pression de la Lumière. Address to the French Physical Society, March 31, 1910b; Bull. Soc. Fr. Physique, 1, 1910a. [ Links ]
Poynting, J. H., The Pressure of Light, Romance of Science Series. Society for Promoting Christian Knowledge. London, 1910b. [ Links ]
Poynting, J. H., The Earth: Its Shape, Size, Weight and Spin, The Cambridge Manuals of Science and Literature, Cambridge Univ. Press, 1913. [ Links ]
Poynting, J. H., Barlow, G., Preliminary Note on the Pressure of Radiation against the Source: The Recoil from Light, Brit. Assoc. Rep., 385, 1909. [ Links ]
Poynting, J. H., Barlow, G., Bakerian Lecture, 1910. The Pressure of Light against the Source: The Recoil from Light, Proc. Roy. Soc. A, 83, 534-546, 1910a; [ Links ] Nature, 84, 139-142, 1910 (abstract). [ Links ]
Poynting, J. H., Dendy, J., The Geographical Distribution of Drunkenness in England and Wales, Jun.; Fourth Report from the Select Committee of the House of Lords on Intemperance, 1878. Appendix R, 580-591. [ Links ]
Poynting, J. H., Gray, P. L., An Experiment in Search of a Directive Action of one Quartz Crystal on Another, Phil. Trans. A, 192, 245-256, 1899; [ Links ] Roy. Soc. Proc., 64, 121-122, 1898 (abstract). [ Links ]
Poynting, J. H., Phillips, P., An Experiment with the Balance to Find if Change of Temperature has any Effect upon Weight., Proc. Roy. Soc. A, 76, 445-457, 1905. [ Links ]
Poynting, J. H., Thomson, J. J., A Textbook of Physics, Vol. II. Sound. 1st edition, 1899; [ Links ] Vol. I. Properties of Matter. 1st edition, 1902; Vol. III. Heat. 1st edition, 1904; Vol. IV. Electricity and Magnetism. Parts I and II. Static Electricity and Magnetism. 1st edition, Griffin and Co., London, 1914.
Renon, H., Prausnitz, J. M., Local Compositions in Thermodynamics Excess Functions for Liquid Mixtures, AIChE J., 14, 135-144, 1968. [ Links ]
Shakespear, G. A., Barlow, G., editors, Collected Scientific Papers of John Henry Poynting. Cambridge: Cambridge Univ. Press, 1920. [ Links ]
Smith, J. M., Van Ness, H. C., Abbott, M. M., Introduction to Chemical Engineering Thermodynamics, 7th edition, McGraw-Hill, New York, 2006. [ Links ]
Thomson, W., On the Equilibrium of Vapour at a Curved Surface of Liquid, Phil. Mag., 42, 448-452, 1871; [ Links ] Proc. Edinburgh Roy. Soc., 7, 63-68, 1872. [ Links ]
Thomson, J. J., Obituary Notice, Proc. Roy. Soc. A, 92, 1914. [ Links ]
Van't Hoff, J. H., Die Rolle des Osmotischen Druckes in der Analogie Zwischen Lösungen und Gases, Zeit. Phys. Chem., 1, 481-508, 1887. [ Links ]
Ward, J., Naturalism and agnosticism; Gifford lectures delivered before the University of Aberdeen in the years 1896-1898. London: Macmillan Company, 1899. [ Links ]
Wisniak, J., Henry Cavendish, Educ. quim., 15, 60-70, 2004. [ Links ]
1 Poynting is advancing here a viewpoint accepted in the modern interpretation of solutions. The molecules in the liquid are, in general, not distributed at random but according to a certain internal structure created by the physical and chemical forces present. One classical model for the latter is Renon's Non-Random Two-Liquid (NRTL) model for explaining liquid-liquid and vapor-liquid equilibrium (Renon and Prausnitz, 1968).
Circuito interior s/n, Ciudad Universitaria, A.P. 70-197, Ciudad de México, Ciudad de México, MX, 04510, (52-55)5622-3439
martina@unam.mx


Those chilly fall days are here and it's time to dust off the slow-cooker! Spicy pulled pork is always a favorite of ours to make because before you even open the front door you can smell the delicious aroma of a slow-cooked pork loin marinating in a spicy barbecue tequila sauce and an array of spices. I paired ours with a sweet and tangy apple salsa that provides the perfect crunch and sweetness to compliment the tender, spicy, slow-cooked pork. It makes enough for a large group or perfect to make at the beginning of the week and take the leftovers for lunch.
(1.) Combine salt, chili powder, cumin, oregano, garlic powder, cayenne pepper, and black pepper in a small back, seal, and shake to mix. (2.) Place pork loin on a plate and sprinkle dry rub seasoning over the pork. Turn to coat evenly in mixture and then place in the slow-cooker. (3.) In a medium sized bowl stir together BBQ sauce, brown sugar, tequila, and lime juice. (4.) Pour over pork loin, cover, and cook on low for 6-8 hours or on high for 4-6 hours. When pork is finished cooking, shred with two forks.
Combine salsa ingredients in a medium sized bowl and stir to mix.
Add a few spoonfuls of the pulled pork to a tortilla shell, top with shredded cheese and other toppings, a few spoonfuls of apple salsa, and serve!
Well, I ran right out and tried this recipe on Sunday and all I can say as I heard angels singing is "Perfection"! The only thing I did differently from your recipe is to use 1/2 tsp cayenne instead of the full tsp because I have a 13 y/o that thinks ketchup is spicy. No complaints from him about the spiciness, and I felt the flavors worked really well together. Thank you so much for this recipe. I'll be making this often!
That's great to hear Bruce! I'm so happy the whole family enjoyed it!
Oh man, I gotta utilize my crock-pot more often! ^_^ And what an interesting mix of flavors going on here – I've never heard of apple salsa before!
Pork and apples are always a great combo! I think you'll love it!


text:
Boston Man Pleads Guilty to Charges in Commercial Child Pornography Website Case
WEBWIRE – Tuesday, May 15, 2007
WASHINGTON – A Boston man has pleaded guilty to one count of conspiracy to sell, transport, reproduce, distribute and receive child pornography, and one count of money laundering, Assistant Attorney General Alice S. Fisher of the Criminal Division and U.S. Attorney John L. Brownlee of the Western District of Virginia announced today.
Aaron Campbell Brown entered the plea today before U.S. District Court Judge Samuel G. Wilson at the federal court in Roanoke, Va. Brown pleaded guilty to two counts from a superseding indictment returned on March 28, 2007. The remaining counts, including allegations of conspiracy to produce and advertise child pornography; conspiracy to produce child pornography for importation into the United States; transportation, receipt, distribution, and sale of child pornography; and other money laundering counts, were dismissed.
In his guilty plea, Brown admitted that the conspiracy spanned more than five years and involved a number of commercial child pornography websites. These Web sites included mexicofriends.com and justinsfriends.com, which were created, developed, hosted, and operated by co-conspirators Brown, Gregory John Mitchel, Timothy Ryan Richards and a cooperating witness. The mexicofriends.com and justinsfriends.com Web sites contained child pornography and offered memberships to the Web sites for a subscription fee. Through his company NEOVA.NET, Brown provided services and other support to the mexicofriends.com and justinsfriends.com Web sites, including Web site hosting, technical assistance, and customer payment processing. For example, Brown would assist subscribers to the these Web sites in many ways, including not only processing their credit card transactions, but also trouble-shooting access to the child pornography Web sites. He would also field complaints about the nature of the images. Brown disbursed the proceeds generated from the sale of subscriptions to the mexicofriends.com and justinsfriends.com Web sites to himself, Mitchel, Richards and the cooperating witness.
"One of the highest priorities of the U.S. Attorney's Office is to protect our children from predators. Mr. Brown was involved not only in exploiting these children, but also in making money from this horrible crime. We hope this case sends a message that we will aggressively pursue anyone who is involved in the exploitation of our children," said U.S. Attorney John L. Brownlee.
As part of his plea agreement, Brown faces a sentence between 108 and 135 months in prison, a fine of $250,000, and a period of supervised release up to the remainder of his life following his release from prison. On July 14, 2006, Mitchel was sentenced to 150 years in prison by the U.S. District Court for the Western District of Virginia for his participation in child pornography offenses. On Oct. 26, 2006, Richards was convicted on 10 counts of child pornography offenses in the Middle District of Tennessee; he faces a minimum of 15 years in prison at his sentencing on Aug. 19, 2007.
The case is being prosecuted by Assistant U.S. Attorney Joseph W. H. Mott of the United States Attorney's Office for the Western District of Virginia, Deputy Chief Sherri A. Stephan of the Criminal Division's Child Exploitation and Obscenity Section, and Trial Attorney Bonnie L. Kane of the Child Exploitation and Obscenity Section. The case is being investigated by the Federal Bureau of Investigation. Computer forensics analysis was provided by Assistant to the Chief for Computer Forensics and Investigations James M. Fottrell and Computer Forensics Specialist Kristi Witsman of the Child Exploitation and Obscenity Section's High Technology Investigative Unit.
Class Actions / Lawsuits
Multimedia / Online / Internet
Youth / Children

redpajama_set_name: RedPajamaCommonCrawl


text:
package net.techreadiness.security;

import java.util.HashSet;
import java.util.Set;

public class PermissionCodeSetImpl implements PermissionCodeSet {

	Set<PermissionCode> permissionCodes = new HashSet<>();

	public PermissionCodeSetImpl() {
	}

	public PermissionCodeSetImpl(PermissionCode permissionCode) {
		permissionCodes.add(permissionCode);
	}

	@Override
	public boolean add(PermissionCode permissionCode) {
		return permissionCodes.add(permissionCode);
	}

	@Override
	public int size() {
		return permissionCodes.size();
	}

	@Override
	public PermissionCode[] toArray() {
		return permissionCodes.toArray(new PermissionCode[0]);
	}

	@Override
	public Set<PermissionCode> getPermissionCodes() {
		return permissionCodes;
	}

	@Override
	public void setPermissionCodes(Set<PermissionCode> permissionCodes) {
		this.permissionCodes = permissionCodes;

	}

}

redpajama_set_name: RedPajamaGithub


text:
namespace Microsoft.Azure.Management.DataFactory.Models
{
    using Microsoft.Azure;
    using Microsoft.Azure.Management;
    using Microsoft.Azure.Management.DataFactory;
    using Microsoft.Rest;
    using Microsoft.Rest.Serialization;
    using Newtonsoft.Json;
    using System.Collections;
    using System.Collections.Generic;
    using System.Linq;

    /// <summary>
    /// The MongoDB database dataset.
    /// </summary>
    [Newtonsoft.Json.JsonObject("MongoDbCollection")]
    [Rest.Serialization.JsonTransformation]
    public partial class MongoDbCollectionDataset : Dataset
    {
        /// <summary>
        /// Initializes a new instance of the MongoDbCollectionDataset class.
        /// </summary>
        public MongoDbCollectionDataset()
        {
          CustomInit();
        }

        /// <summary>
        /// Initializes a new instance of the MongoDbCollectionDataset class.
        /// </summary>
        /// <param name="linkedServiceName">Linked service reference.</param>
        /// <param name="collectionName">The table name of the MongoDB
        /// database. Type: string (or Expression with resultType
        /// string).</param>
        /// <param name="description">Dataset description.</param>
        /// <param name="structure">Columns that define the structure of the
        /// dataset. Type: array (or Expression with resultType array),
        /// itemType: DatasetDataElement.</param>
        /// <param name="parameters">Parameters for dataset.</param>
        public MongoDbCollectionDataset(LinkedServiceReference linkedServiceName, object collectionName, string description = default(string), object structure = default(object), IDictionary<string, ParameterSpecification> parameters = default(IDictionary<string, ParameterSpecification>))
            : base(linkedServiceName, description, structure, parameters)
        {
            LinkedServiceName = new LinkedServiceReference();
            CollectionName = collectionName;
            CustomInit();
        }

        /// <summary>
        /// An initialization method that performs custom operations like setting defaults
        /// </summary>
        partial void CustomInit();

        /// <summary>
        /// Gets or sets the table name of the MongoDB database. Type: string
        /// (or Expression with resultType string).
        /// </summary>
        [JsonProperty(PropertyName = "typeProperties.collectionName")]
        public object CollectionName { get; set; }

        /// <summary>
        /// Validate the object.
        /// </summary>
        /// <exception cref="ValidationException">
        /// Thrown if validation fails
        /// </exception>
        public override void Validate()
        {
            base.Validate();
            if (CollectionName == null)
            {
                throw new ValidationException(ValidationRules.CannotBeNull, "CollectionName");
            }
        }
    }
}


text:
Compromise: On the road to Fiesta – Part 1
Driven to Write looks in depth at the Fiesta's development.
Lest it should pass un-noticed, January 2017 is the fortieth anniversary of the Ford Fiesta's launch in the UK. Production at Ford Germany's Saarlouis factory began in July 1976, with the core Almusafes plant coming on stream in October 1976, so the lucky continentals were introduced to the car a few months earlier.
To mark the occasion, I found myself re-reading Edouard Seidler's "Let's call it Fiesta", the story of the Fiesta Mk.I, along with some other publications from around the time. The "auto-biography" was launched at the same time as the car, so there is no hindsight – Ford were entering unknown territory; a new market sector, their first transverse-engined car, and a huge new production facility in a country in which they had no previous presence.
Edouard Seidler was a giant of European journalism, a safe choice of author, and the big name needed to ensure that the book's market extended beyond hard-core car enthusiasts.
It is very much the book Ford wanted to have written. Ford's people are portrayed as capable, resourceful, and hard-working, but also strong on human character. The decision-making and change control processes are shown to be effective and robust in the face of evolving priorities and missed targets. I would characterise it as a book about management, rather than design and engineering. There is a mildly irritating tendency towards melodrama; less than convincing fly-on-the-wall reportage of moments of high intrigue.
Appropriately to this month's theme, Seidler states that the development process of a new car is:
"an infinite succession of compromises, a process of evolving priorities"
This is a general remark, rather than being specific to the Fiesta. However the compromises which informed the development of the Fiesta are intriguing, as a huge, technically conservative American multinational adapts to European thinking, while pragmatically applying its own systems and processes.
Even with the passage of four decades, I'd commend the book to anyone interested in the management aspect, but there are also some curious "might have beens", and "nearly happeneds". Later on, I'll look at some of the engineering compromises, from the days when Fiesta was "Project Bobcat", but as amuse-bouches, here are some detours on the long road to Fiesta.
The world car that wasn't
This three-box proposal came from Dearborn, at a point where large scale sales were contemplated not only in North America, but also in Brazil and Argentina. That 'toothy' grille has a Japanese look to it, possibly intentionally, as Far Eastern small car imports were making huge inroads into the United States at the time of the Bobcat development.
Source: Edita
And no, Giorgetto, they haven't…
Elsewhere, there's an unexplained European four door saloon proposal:
It's a neat little thing, which is never mentioned in the text. There never seems to be an intention to make a five-door Fiesta Mk.I, despite Spain being keen on such things – SEAT made four-door 600s, 850s, and 127s. Could Ford have been contemplating a rival to FASA-Renault's four-door-and-boot 5-based 7?
Source: autovia-media
There was very nearly a two door Fiesta
In the 1970s, the hatch was far from being a "holy writ" to small car design. A two-box with boot Fiesta was in the plan from its early stages, when it was expected that the hatchback would only be taken up by 40% of customers. In August 1974, a decision was taken to sell the two door cars only in Spain and Italy, and to standardise the fold down rear seat back across both bodystyles. At the end of October 1974, two door Bobcats were excised from the planned production schedule at Saarlouis. A few months later the two door was dropped completely from the production plan.
Here's how it might have looked, with added Bill Bourke – President of Ford Europe at the time of the Bobcat project, he was promoted to Head of North American Operations before it went on sale.
We might regret the loss of a lighter, more rigid, potential rally weapon, but Ford clearly saw the way market sentiment was going, and took the decision to rationalise production to a single bodystyle.
Note also the Renault 5-style bumper 'shields'. The mean-spirited would say that an interesting feature was lost through timidity and parsimony during the design development process. We should be more understanding. The technology was new, and largely untested in its colour matched form. A Renault 5/15/17 -like button and recess door release arrangement also appears, production cars had a more conventional recessed flap handle.
I'd put this down not to compromise, but a strong will for their new supermini to look and feel like a true Ford, rather than a synthesis of the European competitors with which it shared its dimensions and elements of engineering principles.
Author Robertas ParazitasPosted on 24 Jan 2017 5 Mar 2017 Categories Ford Europe, Ford North America, Marques, Monthly Themes, The IndustryTags 1976 Ford Fiesta, 1977 Ford Fiesta, Class of '76
8 thoughts on "Compromise: On the road to Fiesta – Part 1"
Am I alone in thinking that the unknown white small saloon looks better than the Fiesta? That drooping window line is execrable. Everything else on the car is straight and that curve shouts out. It made sense on Tjaarda´s car. In the context it ended up in it jars.
Another 'compromise' in the transition from Bobcat to Festie was the drip rail treatment. Both prototypes appear to have roof mounted body seams, possibly ahead of their time and most likely too expensive a solution for a car as inexpensive as this was intended to be. In fact, even the Sierra had the same old fashioned roof gutters, although the Sapphire saloon facelift did not.
Good observation. So who did introduce that? Is it possible the model didn´t have them because they were taken as a given at that point. The gutters are a flange made of two sheets of metal pressed and folded (as far as I know). They´d be fidly to make as details on a model.
Still and all the white saloon prototype has a lot going for it. There is some of the 1974 Escort in their but done far better (there´s a car I don´t care for, rare as they now are).
Another thing. That saloon concept has some noticeable Harris Mann DNA, wouldn't you say?
Which one? The blue Dearborn car looks very like the Maxi saloon which very nearly made it to production (easily found on The World's Most Plagiarised Car Website). Roy Haynes joined BMC in 1967, The Mann followed him very shortly afterwards.
Which is all rather puzzling, except that the Ford vibrations lived on through the Maxi, Mini Clubman, X6 Tasman/Kimberley, and Allegro, fading only with the ADO71 and TR7.
The blue car: I see a lot of Allegro in it although I can understand why you mention the three volume Maxi. Perhaps when I say Mann, I mean Heynes, since he would have been in a position to influence its shape during his short tenure at BLMC. The Ford concept is less rotund in the flanks and perhaps offers a vision of how an alternative Allegro could have looked. (With some of the air let out). I doubt there was any influence here given the timeline and direction of travel, but it's interesting nonetheless…
The white one would have made an excellent Fiat.
8 Feb 2017 at 15:50
Never knew Ford was considering 2/4-door Fiesta saloons with a mk2 Escort / mk3 Cortina style rear, wonder how much longer it is compared to the existing mk1/2 Fiesta in saloon and theoretical 5-door hatchback forms?
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text:
Mags and Julie Go on a Road Trip (2020)
Mags and Julie Go On A Road Trip is a heartfelt, laugh out loud buddy movie, written and directed by actress Ryann Liebl. This film, in the vein of Bridesmaids mixed with Grumpy Old Men, takes the audience on a journey of what it means to be a woman and balance life.
Director: Ryann Liebl
Actors: Angie Campbell, Elisabeth Donaldson, Luis Rico, Sammy Ketcham
Keywords:Mags and Julie Go on a Road Trip 123movies Mags and Julie Go on a Road Trip Gomovies Mags and Julie Go on a Road Trip Yesmovies
Ricki and the Flash (2015)
Meryl Streep stars as Ricki Rendazzo, a guitar heroine who made a world of mistakes as she followed her dreams of rock-and-roll stardom. Returning home, Ricki gets a shot at…
Genre: Comedy, Drama, Music
On the 12th Date of Christmas (2020)
Two seemingly incompatible game designers team up to create a romantic, city-wide scavenger hunt themed for the "12 Days of Christmas."
You Choose! (2017)
Even at the age of 40, Juliette is used to other people making decisions for her. When she meets two guys she likes, she has to finally make her own…
Country: France, Belgium
Love, Rosie (2014)
Since the moment they met at age 5, Rosie and Alex have been best friends, facing the highs and lows of growing up side by side. A fleeting shared moment,…
A DEA agent and an undercover Naval Intelligence officer who have been tasked with investigating one another find they have been set up by the mob — the very organization…
Genre: Action, Comedy, Thriller
The Last: Naruto the Movie (2014)
Two years after the events of the Fourth Great Ninja War, the moon that Hagoromo Otsutsuki created long ago to seal away the Gedo Statue begins to descend towards the…
Genre: Action, Adventure, Animation, Comedy, Romance
Set in 1879 Paris. An orphan girl dreams of becoming a ballerina and flees her rural Brittany for Paris, where she passes for someone else and accedes to the position…
Genre: Adventure, Animation, Comedy, Family, Music
The Turkey Bowl (2019)
A 30-something urbanite is pulled back to his rural hometown by his high school buddies on Thanksgiving to finish The Turkey Bowl – an epic football game against their cross…
The Dead Don't Die (2019)
In a small peaceful town, zombies suddenly rise to terrorize the town. Now three bespectacled police officers and a strange Scottish morgue expert must band together to defeat the undead.
Country: USA, Sweden, South Africa
Genre: Comedy, Fantasy, Horror, Sci-Fi
The Sleepover (2020)
Two siblings who discover their seemingly normal mom is a former thief in witness protection. Mom is forced to pull one last job, and the kids team up to rescue…
Genre: Action, Adventure, Comedy, Family
A Taste of Christmas (2020)
When Natalie (Anni Krueger) learns her cousin Francesca (Nia Vardalos) must cancel the Christmas Eve opening of her new Italian restaurant, Natalie's heart goes out to all of the guests…
So Much Love to Give (2020)
A bigamist with one family in Buenos Aires and the other in Mar del Plata sees his life turned upside down when his wives discover what he has hidden from…


Thread: Is this going to affect the flow in the next few months?
What MAY affect AA hiring this Summer and thus the flow is higher then normal training logjams and lack of check airman. Staffing is reportedly at critical levels in many statutes and it's only April. Summer could be insane just trying to cover the schedule. The present staffing woes are already with the Max grounded thus the daily diet of 115 flight cancellations doesn't seem to be providing much relief.
The Summer flow classes are always smaller than the balance of the year. This is due to the exact reasons you mentioned, except this summer will be no different than last.
Good! That means all Protected Pilots still on schedule to go by October 2019.
No they won't. Between the MD80s parking and the Max being grounded, the PPs are about to get hosed. But you already knew that.
Yes, I'm aware of training variations and actually December has traditionally been among the slowest months. As for this Summer, no one can predict that with certainty, yourself included. That being said, despite the fact they are trying to get people through training early, staffing is likely to be far worse then now which is already critical based on reserve usage and premium and OG usage. Summer vacations will be full and sick calls likely way up due to scheduling abuse. Word is fatigue calls have spiked as well.
Obviously, you are far more optimistic then me.
agreed on all points. Exception, I don't have to FTG info.
Word from over there is that a large percentage of long time 80 drivers are needing a lot of extra time in the training cycle when transitioning to the Bus. The extra sim slots have to be found and numerous folks have literally been sent home for weeks. This has basically put them back at square one and requires yet more time.
None of this bull**** spouted on this very brief thread will affect the flow. Flow continues unimpeded and WILL continue unimpeded.
My pre response to the biggest blockhead who has ever walked the planet. I'll go ahead and respond for him and then my rebuttal is linked below.
"Ummm, bad times ahead for AA and Envoy, ummm better have your life rafts to get away from the good ship AA, ummmm (Buzzwords) far worse, word is failure on the horizon, deficient, declining. I THINK YOU GET THE ******** PICTURE!
A conversation with ones self.
Is there a doctor in the house.
No doubt attempting to self-medicate with alcohol again...…..and failing.
A large percentage of the handful who bid out of the 80? The vast majority of 80 pilots are waiting for displacement, which has yet to happen.
Just like I said...2021 keeps getting closer.
But will there be a furlough at aa?
AA Furlough from the top should take care of most scenarios. Cut the Head off the Snake, even more aimless drifting.
All should note that even in "most scenarios", why hire if you need to or are contracting at the rate of attrition ? I agree that an AA furlough is likely only under the most serious of situations and thus unlikely, but many scenarios result in AA contraction which means no flow for a period of time that could be months or possibly years depending. I also means during the same period, stagnation occurs and for those commuting until they get their home domicile on reserve and/or both, that's not so good. Slow upgrades too. At least AA's training costs drop as most of that action would occur in Group II and Group IV would likely be fairly stable.


My 'readers' are probably sick of this.
The makers of Zenit, arguably the best, most cost-effective choice for amateur film SLR cameras, is now going digital (I've already posted here the supposed end of the Zenit line).
What you see above are obviously concept models. This privileged info is courtesy of the Zenit Camera Group.
The beauty of the analog Zenits is being ultimately mechanical, that even non-working metered ones can work perfectly in manual mode, when properly calibrated. Essentially, this is the reason why Zenit fanatics use their 50-or-so year old units because they simply work, despite any age. It will be interesting to see the actual digital output the Russians will manufacture, wholeheartedly considering electornics isn't really their major strength.
Also, camera price will be an issue. Being able to catch a classic Zenit for $10-20 on eBay makes anyone interested in grabbing more than one of these FSU (Former Soviet Union) relics. However, if these digicams are priced slightly lower than the Canon's and the Nikon's, I'm afraid they will just remain a novelty, and for serious collectors only.
Finally, I am hoping they give it an M42 screwmount.
PS: According to the guys at ZCG, the digital path Zenit is planning may not at all be realized, mainly considering that it will be a very expensive undertaking. Bummer.
Oh, and for the Lomo suckered-in guys out there, there is also news that the camera factories that make your insanely overpriced cameras are up for sale.
It would indeed be intersting to see a digital Zenit.
I agree with you about what their fate is likely to be. Znit propably hasn't enough knowledge to produce its own camera sensor. Buing it from another company would dramatically increase the price. Pentax is cheaper than canon or nikon. Does Zenit really have a chance?


Isn't that a line from The Matrix? Isn't this whole franchise essentially just another build of The Matrix with realism sub-routines to prevent Neo John Wick from stopping bullets?
Sorry, I won't spoil your gun-fu.
Ian McShane is back as Winston, the proprietor The Continental Hotel, a sort of neutral ground for assassins. So are both Lawrence Fishburne as the Bowery King and Lance Reddick as the concierge at the Continental.
A couple of new female characters include Angelica Huston as The Director of something called The High Table, as well as Halle Berry who plays a ghost from John Wick's past.
Hiroyuki Sanada, who brought some gravitas to Sunshine and The Wolverine.
John Wick: Chapter 3 — Parabellum puts everything inside the circle on May 17th.


A tropical oceanview masterpiece located in the Pacific of Costa Rica enjoy a complete experience surrounded by jungle and amazing views of the Pacific. It comes fully furnished with infinity pool facing the amazing landscape of the ocean and the unique forest. The area lends itself to the perfect location to fit everything in from whitewater rafting adventures, surf classes, rappeling waterfalls, ziplines, fine dining and much more.


Abstract - Bees (a.k.a. Apoidea Anthophila) are among the main pollinators in most ecosystems. The yearly value of the ecological services provided worldwide by pollinators reaches more than € 150 billion. As in many other groups, the erosion of bee diversity is now a well-assessed reality. However, quantification of the phenomenon, including the assessment of its extent and severity has been lacking for a long time. In the West-Palaearctic, the decrease in wild bees has been highlighted in several studies over the last few decades. Specifically, the plight of a few populations of bees in Europe has been measured and assessed. In this paper, we review the state of the knowledge of bee diversity in the West-Palaearctic. We present the available resources usable for estimation of the extinction risk in West-Palaearctic bees. We also point out the work that is needed to outline a holistic picture of West-Palaearctic bee diversity. We conclude by suggesting that former initiatives should be integral in developing the framework of a subregion-wide monitoring program for bees.


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http://www.truthtalklive.com/ Truth Talk Live Stu Epperson, Jr.


Tape your agility obstacles any way you choose! The more tape the better visibility for you dogs. Available in black, white, yellow, blue, read or green. Each roll has 6 feet of tape. Specify color when ordering.
Need more pvc tape? Buy our prepackaged tape. Two rolls each of red, blue, yellow, green and white. Each roll has 6 feet of tape on it.


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A parameter called electrochemical skin conductance is linked to disease severity in patients with familial amyloid polyneuropathy (FAP), potentially supporting the use of a device called Sudoscan to assess the clinical evolution of the disease, according to researchers.
Their study, "The value of electrochemical skin conductance measurement using Sudoscan in the assessment of patients with familial amyloid polyneuropathy," was published in the journal Clinical Neurophysiology.
FAP is a rare, inherited, and progressive disease characterized by nerve lesions due to the accumulation of amyloid fibers. The disease is caused by mutations in the TTR gene.
Recently, a new device called Sudoscan, developed by Paris-based Impeto Medical, was introduced into clinical practice to evaluate damages to peripheral nerves in patients with diabetes.
Sudoscan applies a small electrical stimulus to the skin of the hands and palms, leading to the production of a current, the electrochemical skin conductance (ESC). Decreases in ESC reflect loss or damages to small nerve fibers.
Now, researchers in France used Sudoscan to measure ESC in the hands and feet of 126 FAP patients with the Val30Met mutation (65 patients), the most common of more than 100 point mutations identified worldwide, and without the Val30Met (61) TTR mutation.
The 52 women and 74 men were ages 25 to 81 and ranged from asymptomatic FAP to mild and advanced stages of the disease.
The ESC measurements did not differ between the two subgroups of patients with Val30Met or non-Val30Met mutation.
Lower ESC measures were found in 24% of clinically asymptomatic patients, increasing to 65% of patients with moderate TTR-FAP, and 92% of patients with advanced TTR-FAP.
Accordingly, the results showed a good correlation between the ESC values and the clinical parameters used to assess the severity of the disease. These included the neuropathy impairment score, the modified Polyneuropathy Disability Score, the Karnofsky Performance Status, and body mass index (BMI), a measure of body fat.
The neuropathy impairment score is a comprehensive measure assessing motor and sensory function, as well as tendon reflexes. The Karnofsky Performance Status reflects the global health of the patient, and the polyneuropathy disability score evaluates patients' walking abilities.
Overall, these results suggest that measuring ESC via Sudoscan can be used to assess the severity of TTR-FAP.
Also, "the clinical importance of measuring ESC could be to first to provide an early marker of the onset of the disease and then a biomarker of its evolution (including in patients with advanced neuropathy)," researchers wrote.
"Thus, Sudoscan could be useful for treatment decisions, whatever the type of TTR variant, even in non-Val30Met- patients," they concluded.
Tagged electrochemical skin conductance, neuropathy impairment score, severity, Sudoscan, Val30Met mutation.