まとめ
モノ・レイク モノ・レイク
科学分野:
- 環境化学 環境化学
- 放射化学は放射化学である.
- 地質化学 地質化学
背景:
- 自然に発生するウランとトリウムの腐敗系放射性同位体と降下物プルトニウムは,モノ湖の水柱に高濃度を示しています.
- モノ湖は,天然のアルカリと塩水の環境で特徴付けられています.
研究 の 目的:
- モノ湖における放射性同位体の溶解性と分布を制御する要因を調査する.
- アルカリ,塩水におけるアクティニド元素の複合化行動を理解する.
- 水柱から堆積物へのトリウムの除去と放出率を測定する.
主な方法:
- 水柱における放射性同位体濃度の分析.
- 炭酸イオンによるアクチニド元素の複合性の評価.
- トリウム,ラジウム,ウランの同位体に対する子/親活動比の評価.
主要な成果:
- モノ湖の水には,異常に高い濃度のウラン,トリウム,プルトニウム放射性同位体が見られた.
- 炭酸塩の複合化により,アクティニド元素の溶解性 (酸化状態IV-VI) が向上する.
- ストロンチウム-90は水柱から大部分除去され,おそらくカルシウム炭酸との共同降水によって除去された.
- トリウムの沈殿物への除去は1ヶ月以上の時間スケールで発生し,水への脱吸収には数年未満が必要です.
結論:
- 炭酸塩の複合化は,モノ湖のアクティニドの溶解度が高い要因の1つである.
- 異なる除去メカニズムは,さまざまな放射性同位体に影響し,ストロンチウム-90は効率的に除去されます.
- トリウムは,比較的急速な吸収解消運動で,堆積物の中にかなりの滞在時間を示しています.
関連する概念動画
Nuclear Stability
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together in the...
To hold positively charged protons together in the...
Nuclear Fission
Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger binding energies per nucleon—that is, mass numbers and binding energies per nucleon that are closer to the “peak” of the binding energy graph near 56. Sometimes neutrons are also produced. This decomposition of a large nucleus into smaller pieces is called fission. The breaking is rather random with the formation of a large number of different...
Nuclear Transmutation
Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed protons being...
Nuclear Localization Signals and Import
Proteins targeted to the nucleus carry short stretches of amino acid sequences called the nuclear localization signal or NLS. Classical nuclear localization signals are of two types: monopartite and bipartite NLS. Monopartite classical NLS (cNLS) consists of a single cluster of 4-8 amino acids. Bipartite cNLS consists of two clusters of 2-3 amino acids and a 9-12 residue long proline-rich linker bridging the two clusters. Signal clusters are rich in positively charged amino acids such as...
Nuclear Export
The nucleus restricts several proteins within and allows others to pass. The restricted proteins possess a nuclear retention sequence or NRS, anchoring them to the nuclear lamins and preventing their transport to the cytosol. The non-restricted proteins, after their synthesis, are transported to their site of action, such as the cytosol or other organelles, with the help of nuclear export signals or NES.
NES are of three types- the canonical 10-residue long leucine-rich signal and other...
NES are of three types- the canonical 10-residue long leucine-rich signal and other...
Other Nuclides: 31P, 19F, 15N NMR
Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...

![Automated Radiochemical Synthesis of [18F]3F4AP: A Novel PET Tracer for Imaging Demyelinating Diseases](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F55537.jpg&w=3840&q=50)
