摘要:本文主要研究注册土地的第三方权利的性质,是一篇留学生第三方权利的相关作业,美国在第二次世界大战的后期开发了代号为曼哈顿计划的原子弹,放射性碳年代测定法是这一和平项目的延伸。
y), radiocarbon dating was a revolution in archaeology, and heralded in a new scientific approach to the field. Therefore, and justifiably, Libby received the Nobel Prize for Chemistry in 1960 (AMA 2005: 39-41; Libby 1955).
Dendrochronology:
Dendrochronology is a method used for dating objects by way of tree ring growth. Annually a tree adds a layer of outer bark to its trunk and bows, thereby producing the annual rings seen when examination is made of a cross section. Samples gathered from other trees with an unknown age, can be studied for comparisons with samples from trees with a known timeframe of growth. Climatic variants in a selected geographic region, maybe traced by the study of older trees that are still alive. (Brothwell and Pollard 2001).
Using this method, we can look even further back in time by taking note where the rings (match) or they overlap. A quantity of tree ring samples must be assessed and cross-dated from any chosen site, to avoid the likelihood of the collected data displaying a missing or an extra ring; this process is repeated until no discrepancy appears. To remove these individual variables in tree ring growth, archaeologists take the average of the tree ring widths from numerous tree samples, to build up a
history of tree rings. This tree ring data, at present, extends back in time to almost 9,000 BP; tree rings are one of the most precise ways to date ancient objects and structures (Brothwell and Pollard 2001).
Radiometric Dating - Uranium Series Dating:
In 1956, uranium-thorium dating was first used to date fossil bones, this dating technique has been used successfully on teeth, wood, marine sediment, coral, bone, peat, wood, and stone, timeframe 500,000 BP (
Science Encyclopedia 2010).
Uranium-thorium dating is a dating method that uses (‘the radioactive half-life of uranium-238, and thorium-230’) (Pitman 2008). Uranium-238 has a half-life of 4,470,000,000 years; thorium-230 has half-life of only 75,380 years, so when a comparison is made between the uranium and thorium, an accurate judgment of the age of an article can be obtained (Pitman 2008; Greene 2002: 169 -170; Bahn 2008:150-152).
There are three other dating techniques that maybe used with this dating method, Isotope Dilution Mass Spectrometry, Ion Mass Spectrometry, and Thermal Ionization Mass Spectrometry. With these dating techniques, there is also the added benefit of using smaller material sizes less than 20 grams, and bone samples 3-5 grams, for a precise date. Each process uses an element specific chemical resin to separate the uranium and thorium and to remove metals (Science Encyclopedia 2010; Pitman 2008; Greene 2002:169-170; Bahn 2008:150-152).
There is one problem associated with uranium-thorium dating; the materials to be dated must have taken up uranium-238 and nil thorium; then, (instantaneously contained), by compaction, or solidification, so the material cannot absorb anymore (Science Encyclopedia 2010).
Fission Track Dating:
R.Wallace, R. Fleischer, and P. Price, of the General Electric Research Laboratory, discovered the idea of etching in 1960. This method works best on glass, (fabricated or natural), pottery, tiles, and any stone used in a hearth. It is possible to determine dates as far back as 300,000 BP using this method (Walk
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