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。
m-40 is a common element found in many types of mica, clay minerals, rock and volcanic materials, samples of these materials are irradiated with neutrons to convert potassium-40 to argon-40. Argon-40 is not contained in rock or volcanic materials, while in its molten form, but starts to accumulate when the rock recrystallises. The time since re-crystallisation is calculated by measuring the percentage of argon-40 accumulated, to the amount of potassium-40 remaining. With a half-life of about 1.3 billion years, the potassium-40 radiometric dating method is utilized to calculate the definite (absolute) age, of samples dated between 100,000 and 2 billion BP (Bahn 2008: 159-160; Greene 2002: 159-168).
Amino-Acid Racemisation:
Peter Hare joined the scientific staff of the Geophysical Laboratory, Carnegie Institution of Washington, in 1963, where he set up his fist instrument for measuring Amino Acid. Hare released his first paper on the
methodology of amino acid analysis, in 1966 (Pitman 2010 Bahn 2008:160-161; Greene 2002:174).
Amino-Acid Racemisation is a dating method for archaeological and geological substances, that uses the rate of exchange of an amino acid to its mirror image, as an estimate of the passing of time. Therefore, as amino acids are the building blocks of proteins, this method is only applied to archaeological materials that still contain indigenous proteins. Residual protein is common in many excavated parts such as, tooth, bone, or shell, and in similar fossilized material as old as 100,000 BP. These change over time into useful proteins, which are the polymers of natural amino acids, these amino acid residues are linked together through peptide bonds (Pitman 2010; Bahn 2008: 160-161; Greene 2002:174).
With time, all of the protein originally in the live creature degrades in one way or or another (e.g., by chemical or microbial action), but primary is its reaction with water, this hydrolysis cleaves the peptide bonds giving off smaller fragments of proteins, and eventually, amino acids. In archaeological time scales, such hydrolysis (and other degradation mechanisms), is quite commonly slow enough to leave residual intact protein, which is the source for dating work (Pitman 2010; Bahn 2008: 160-161; Greene 2002:174).
Argo – Argon Dating:
In 1965, American geologist Craig Merrihue and Grenville Turner discovered argon-39, which is a derivative of potassium-39; their first paper presenting their results followed in 1966; in 1968, John Mitchell further developed and improved the method (Bahn 2008:149-150; Pitman 2008; Greene 2002:168 - 169).
As in potassium–argon dating, samples are also irradiated with neutrons to change potassium-39, to argon-39; the percentage of potassium-39, to Argon-39, provides a measure for the age of the sample. Due to refinements and improvements in equipment, the Argon-argon technique can now be used with milligram samples, instead of larger quantities of rock as needed in potassium-argon dating (Bahn 2008: 149-150; Pitman 2008; Greene 2002:168-169).
Argon-argon dating allows the correlation with other airborne isotopes, to tell if there is any variation caused by non-atmospheric argon, (e.g. contamination from argon already in the rocks). With the argon-argon dating method, it is possible to date even younger samples, as young as 1,000 BP with 10% a
本论文由英语论文网提供整理,提供论文代写,英语论文代写,代写论文,代写英语论文,代写留学生论文,代写英文论文,留学生论文代写相关核心关键词搜索。