scholarly journals Zum Einbau von einigen Lanthaniden in Gd2Cl3 / Incorporation of Some Lanthanides into Gd2Cl3

1987 ◽  
Vol 42 (6) ◽  
pp. 666-668 ◽  
Author(s):  
A. Simon ◽  
Hj. Mattausch ◽  
N. B. Mikheev ◽  
C. Keller
Keyword(s):  
Electronic Configuration ◽  
Radioactive Isotopes ◽  
Redox Potentials ◽  
Crystallization Experiments

Abstract Co-crystallization experiments with radioactive isotopes of lanthanides (Ce, Nd, Eu, Gd, Tb, Dy, Tm, Yb) show that only Tb is incorporated by Gd2Cl3 in a significant amount. The results are discussed in terms of the electronic configuration of Ln2+ ions as well as redox potentials E°(Ln3+/Ln2+).

The Synthesis and Properties of Cobalt Cage Complexes With N3S3 Donor Sets

1993 ◽  
Vol 46 (5) ◽  
pp. 641 ◽  
Author(s):  
PA Lay ◽  
J Lydon ◽  
AWH Mau ◽  
P Osvath ◽  
AM Sargeson ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Visible Region ◽  
Diethyl Malonate ◽  
Electronic Configuration ◽  
Ester Group ◽  
Al Alloy ◽  
Redox Potentials ◽  
Effective Electron ◽  
Cage Complex ◽  
Spin Electronic

An understanding of how variations in the cage ligands modify the redox behaviour of cobalt(II)/(III) couples has led to rational syntheses of a series N3S3 donor cobalt cage complexes that have redox potentials and electron self-exchange rates appropriate for their use as electron carriers in systems devised for the photoreduction of water. Diazotization of [Co(NH3-capten)]Cl4 (NH3-capten = 8-ammonio-1-methyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6] icosane ) in nitric acid resulted in a mixture of five complexes: [Co(NO2-capten)]3+, [Co( Cl-capten )]3+ and [Co(HO- capten )]3+ (8-nitro-, 8-chloro- and 8-hydroxy-1-methyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6] icosanecobalt (III) respectively), in which the cage framework remained intact, together with two complexes with a contracted cap, [Co(ClCH2-abcapten)]3+ and [Co(HOCH2-abcapten)]3+, (8-chloromethyl- and 8-hydroxymethyl-1-methyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.5] nonadecanecobalt (III), respectively). Reductive elimination occurred with [Co( Cl-capten )]3+ in the presence of Zn or Ni/Al alloy to give the parent cage complex, [Co( capten )]3+ (1-methyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6] icosanecobalt (III)). When [Co(ten)]3+(4,4′,4″-ethylidynetris(3-thiabutan-1-amine)cobalt(III)) and an aqeuous solution of diethyl malonate and formaldehyde were reacted under basic conditions, the amide cage complex, [Co( EtOOC-oxocapten-H )]2+, (8-ethoxycarbonyl-1-methyl-3,13,16-trithia-6,10,19-triazabicyclo [6.6.6]icosan-7-onato(1-)cobalt(III)) was obtained. Hydrolysis of the ester group in base yielded the carboxylate derivative [Co(OOC- oxocapten - H)]+(8-carboxylate-1-methyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6]icosan-7-onato(1-)cobalt(III)). The complexes were characterized by microanalyses, 1H and 13C n.m.r. spectroscopy, and electrochemistry. The values of the cobalt(III)/(II) redox potentials change with the nature of the apical substituents in a similar manner to that observed for the analogous hexaamine cage complexes, but they are all more positive, and the cobalt(II) complexes are low spin. The N3S3 donor set stabilizes the lower oxidation state and the low-spin electronic configuration. All of these cage complexes are effective at quenching the lowest lying triplet excited state of the [ Ru ( bpy )3]2+ complex, with rate constants typically c. 109 dm3 mol-1s-1. [Co( EtOOC-oxocapten-H )]2+ quenches [ Ru*( bpy )3]2+ very efficiently and has a suitable redox potential for hydrogen production, but it is only moderately efficient as an electron-transfer agent in the photoreduction of water. It is apparent that the high molar absorption coefficients of these cage complexes in the visible region, the too positive redox potentials and competing energy transfer and/or back electron-transfer inhibit their ability to be used as effective electron-transfer agents in these reactions at pH c. 5. However, the molecules are inherently interesting and stable redox reagents which undergo rapid one-electron reactions.

Bioavailability of Vitamin B12

2010 ◽  
Vol 80 (45) ◽  
pp. 330-335 ◽  
Author(s):  
Lindsay Helen Allen
Keyword(s):  
Vitamin B12 ◽  
Vitamin B12 Deficiency ◽  
The Elderly ◽  
Radioactive Isotopes ◽  
Animal Source Foods ◽  
Dietary Requirements ◽  
In Vivo Labeling ◽  
B12 Deficiency ◽  
Vitamin B12 Malabsorption

Vitamin B12 deficiency is common in people of all ages who consume a low intake of animal-source foods, including populations in developing countries. It is also prevalent among the elderly, even in wealthier countries, due to their malabsorption of B12 from food. Several methods have been applied to diagnose vitamin B12 malabsorption, including Schilling’s test, which is now used rarely, but these do not quantify percent bioavailability. Most of the information on B12 bioavailability from foods was collected 40 to 50 years ago, using radioactive isotopes of cobalt to label the corrinoid ring. The data are sparse, and the level of radioactivity required for in vivo labeling of animal tissues can be prohibitive. A newer method under development uses a low dose of radioactivity as 14C-labeled B12, with measurement of the isotope excreted in urine and feces by accelerator mass spectrometry. This test has revealed that the unabsorbed vitamin is degraded in the intestine. The percent bioavailability is inversely proportional to the dose consumed due to saturation of the active absorption process, even within the range of usual intake from foods. This has important implications for the assessment and interpretation of bioavailability values, setting dietary requirements, and interpreting relationships between intake and status of the vitamin.

Using A Segmented Voltage Sweep Mode and A Gaussian Curve Fitting Method to Improve Heavy Metal Measurement System Performance

2012 ◽  
Vol 19 (2) ◽  
pp. 381-394
Author(s):  
José Pereira ◽  
Octavian Postolache ◽  
Pedro Girão
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Measurement System ◽  
Curve Fitting ◽  
System Performance ◽  
Redox Potentials ◽  
Voltage Sweep ◽  
Gaussian Curve ◽  
Fitting Method ◽  
Curve Fitting Method

Using A Segmented Voltage Sweep Mode and A Gaussian Curve Fitting Method to Improve Heavy Metal Measurement System PerformanceThis paper presents a voltammetric segmented voltage sweep mode that can be used to identify and measure heavy metals' concentrations. The proposed sweep mode covers a set of voltage ranges that are centered around the redox potentials of the metals that are under analysis. The heavy metal measurement system can take advantage of the historical database of measurements to identify the metals with higher concentrations in a given geographical area, and perform a segmented sweep around predefined voltage ranges or, alternatively, the system can perform a fast linear voltage sweep to identify the voltammetric current peaks and then perform a segmented voltage sweep around the set of voltages that are associated with the voltammetric current peaks. The paper also includes the presentation of two auto-calibration modes that can be used to improve system's reliability and proposes the usage of a Gaussian curve fitting of voltammetric data to identify heavy metals and to evaluate their concentrations. Several simulation and experimental results, that validate the theoretical expectations, are also presented in the paper.

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

EVALUATION OF NATURAL ION EXCHANGERS FOR THE REMOVAL OF RADIOACTIVE ISOTOPES FROM LIQUID EFFLUENTS

2002 ◽  
Vol 1 (4) ◽  
pp. 577-588
Author(s):  
Eveline Popovici ◽  
Igor Cretescu ◽  
Elena Botezatu ◽  
Gabriela Soreanu ◽  
Alina Mihaela Hanu ◽  
...  
Keyword(s):  
Radioactive Isotopes ◽  
Ion Exchangers

Superposition of Potential Chemical Polluants and Radioisotopes and Their Influence Upon the Environment and Living Organisms

2017 ◽  
Vol 68 (9) ◽  
pp. 2189-2195
Author(s):  
Valeriu V. Jinescu ◽  
Simona Eugenia Manea ◽  
George Jinescu ◽  
Vali Ifigenia Nicolof
Keyword(s):  
Solid Waste ◽  
Critical Energy ◽  
Radioactive Isotopes ◽  
Nuclear Facility ◽  
Chemical Pollutants ◽  
Living Organisms

Following the activities developed in a nuclear facility result gaseous and liquid radioactive effluents and radioactive solid waste. All these waste contain radioactive isotopes which are potentially pollutants for the environment. In the same time chemicals are, also, pollutants. According to the legislation, discharging of chemicals and radioactive liquid and gaseous effluents into the environment, should meet the requirements of the unrestricted discharge. However, what happens when several pollutants superpose: only chemical pollutants, or only radioactive pollutants, or chemical and radioactive pollutants? Such problems have been solved in this paper on the basis of the principle of critical energy.

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