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Arkiv for kategorien ‘Kemi’

DINO 101: Some articles on the use of stable isotopes in dino research [da]

mandag den 9. september 2013

  • Shaena Montanari, Pennilyn Higgins, Mark A. Norell (2013). Dinosaur eggshell and tooth enamel geochemistry as an indicator of Mongolian Late Cretaceous paleoenvironments. Palaeogeography, Palaeoclimatology, Palaeoecology 370 158-166. http://www.sciencedirect.com/science/article/pii/S0031018212006736 [pdf]
  • Romain Amiot, Christophe Lécuyer, Eric Buffetaut, Gilles Escarguel, Frédéric Fluteau, François Martineau. (2006). Oxygen isotopes from biogenic apatites suggest widespread endothermy in Cretaceous dinosaurs. Earth and Planetary Science Letters 246 41–54 http://www.sciencedirect.com/science/article/pii/S0012821X06003050 [pdf]
  • Kathryn J. Stanton Thomas, Sandra J. Carlson. (2004). Microscale d18O and d13C isotopic analysis of an ontogenetic series of the hadrosaurid dinosaur Edmontosaurus: implications for physiology and ecology. Palaeogeography, Palaeoclimatology, Palaeoecology 206 257– 287 http://www.sciencedirect.com/science/article/pii/S0031018204000161 [pdf]
  • Robert A. Eagle, Thomas Tütken, Taylor S. Martin, Aradhna K. Tripati2,, Henry C. Fricke, Melissa Connely, Richard L. Cifelli, John M. Eiler. 2011. Dinosaur Body Temperatures Determined from Isotopic (13C-18O) Ordering in Fossil Biominerals. Science. Vol. 333 no. 6041 pp. 443-445 http://www.sciencemag.org/content/333/6041/443.abstract [pdf]

The periodic table as a spiral [da]

torsdag den 6. juni 2013

Another fascinating alternative version of the Periodic Table!

In May 1949, LIFE Magazine published a stunning series of images to accompany an issue dedicated largely to The Atom. You can check out the feature in its entirety here, but the reimagination of the periodic table of elements as a colorful spiral is easily one of the most striking graphics of the lot. [Click here to see it in hi-res]

The periodic table as a spiral
The periodic table as a spiral

Here in its entirety is the caption that accompanied the original graphic:

    The irregular spiral above is a systematic arrangement of the 92 natural elements, the four new elements so far created by man and eight more elements which is theoretically possible to create. It is called the periodic table of the elements. The sequence begins with hydrogen (at the center of the spiral), which is the first and simplest element. Under its name appears its chemical symbol (left), its atomic weight (right) and a larger numeral which gives the total number of electrons in its atom. It is on the basis of this number that the elements are arranged in sequence: after hydrogen, with its single electron, come helium with two, lithium with three, beryllium with four and so on around the spiral.

    The colors and construction of the table express another kind of relationship among the elements: the repetition, at regular intervals, of the chemical properties of the first few. Characteristics are thus repeated periodically in the progression form the simplest to the most complex. The table is so organized that elements whose chemistry is almost identical are grouped together in blocks of connected by solid arrows (all the inert gases–helium, neon, etc.–fall in the single gray block at the left). Broken arrows relate groups of elements which are similar in most respects but differ in a few of their properties. All related elements are given different shades of the same color. The key to this similarity among elements is found in the arrangement rather than the number of the electrons in their atoms. Only the electrons in the outer shell affect an atom's chemical nature. Therefore all elements whose atoms have identical outer shells are chemically related, regardless of the total umber of electrons which each of them may possess. For example, lithium, sodium and the other elements in the red segment at left all have one electron in their outer shells and are therefore similar though they differ in the total number of their electrons. Each complete circuit of the table starts with one of these elements and ends with an element in the adjacent gray segment whose atom's outer shell is complete.

    This table, like all attempts to reduce the basic phenomena of nature to a simple pattern, falls somewhat short of its objective. For one thing, there are variations in the sequence of elements which do not fit readily into its graphic form. For another, it is not so much a simplification as an orderly presentation which specifies the relationship between elements but leaves much about them to be explained... Yet in expressing this relationship the table reveals the extraordinary symmetry and order which underlie the universe.

Check out my earlier posts on the periodic table:

Added June 7th 2013: Just found a wonderful post on alternative periodic tables at chemistry-blog.com

An alternativ periodic table [da]

fredag den 14. december 2012

A periodic table showing the elements according to relative abundance

A periodic table showing the elements according to relative abundance