Search results for "Activation"

Measurement of long-lived radionuclide activity induced in target components of a cyclotron used for [18F ]-[FDG] production

2019

The evaluation of high activity induced in target components in using a medical cyclotron to produce positron-emitting radionuclides for PET (Positron Emission Tomography) diagnostic studies is one of important issue and involves radiation protection concepts when operators are engaged in maintenance and/or substitution of a target or its components. Most of replaced target components are generally classified and stored in a Pb-shielded container in order to wait for their radioactive decay. However, after some years, it can be necessary to start with the removal of the oldest parts, for a temporary storage of the fresh activated ones. The feasibility of these operations and the waste final…

Iron-Catalyzed C–O Bond Activation: Opportunity for Sustainable Catalysis

2017

Oxygen-based electrophiles have emerged as some of the most valuable cross-coupling partners in organic synthesis due to several major strategic and environmental benefits such as abundance and potential to avoid toxic halide waste. In this context, iron-catalyzed C–O activation/cross-coupling holds particular promise to achieve sustainable catalytic protocols due to its natural abundance, inherent low toxicity, an excellent economic and ecological profile. Recently, tremendous progress has been achieved in the development of new methods for functional group tolerant iron-catalyzed cross-coupling reactions by selective C–O cleavage. These methods establish highly attractive alternatives to …

Sex-Specific Relationship Between Parathyroid Hormone and Platelet Indices in Phenotypes of Heart Failure—Results From the MyoVasc Study

2021

Background: Heart failure (HF) is a multifactorial syndrome with pathophysiological complexities still not fully understood. Higher mean platelet volume (MPV), a potential marker of platelet activation, and high concentrations of parathyroid hormone (PTH) have been implicated in the pathogenesis of HF.Aim: This study aims to investigate sex-specifically the association between PTH concentrations and platelet indices in phenotypes of HF.Methods and Results: PTH and platelet indices (MPV and platelet count) were available in 1,896 participants from the MyoVasc study in Mainz, Germany. Multivariable linear regression models, adjusted for age, sex, season, vitamin D status, cardiovascular risk …

Catalytic effect of transition metals (copper, iron, and nickel) on the foaming and properties of sugar-based carbon foams

2019

Abstract Recently, bio-based carbon foams have gained much interest in many chemical industry fields because of their unique structure and properties. This study provides new information on the effects of catalytic metals (iron, nickel, and copper) on the foaming process. Specifically, the effects of these catalysts on the density, foam growth, and cell size and then further on the pore size distribution and specific surface areas after the physical activation are considered. Furthermore, some of the activated sugar foams were used in adsorption tests using methylene blue as adsorbent. Results showed that the highest effect on foam density was obtained using the iron catalyst in the foaming…

Activated carbon from hydrolysis lignin: Effect of activation method on carbon properties

2022

This study presents the effects of different activation methods to produce activated carbon from the hydrolysis lignin. Pretreatment of the feedstock with common mineral acids (HCL, HNO3, and H3PO4), different steam rates for physical activation, and different chemical activating agents (ZnCl2, Na2CO3, and KOH) for chemical activation were investigated. The pretreated biomass was carbonized and activated in one-stage process and the surface characteristics, such as total pore volume, pore size distribution and specific surface area, were investigated. The results showed that the activated carbon surface properties were not greatly affected by acid pretreatment. Brunauer-Emmett-Teller (BET) …

Linkage between inflammation, endothelial activation and renal function in kidney transplantation.

2006

Allosteric regulation by Mg2+ of the vacuolar H(+)-PPase from Acer pseudoplatanus cells. Ca2+/Mg2+ interactions.

1996

The tonoplast H(+)-PPase was previously characterized in Acer pseudoplatanus cells (Pugin et al (1991) Plant Sci 73, 23-34; Fraichard et al (1993) Plant Physiol Biochem 31, 349-359). Tonoplast vesicles were obtained from vacuoles isolated from protoplasts of A pseudoplatanus suspension cultures and used to study kinetic effects of Mg2+ and Ca2+ on PPi hydrolysis. The concentrations of ionic species (free Mg2+, free PPi, and MgPPi complexes) were calculated with apparent dissociation constants of 55.3 microM for MgPPi and 59.6 microM for CaPPi. Our results indicated that the substrate of the tonoplast PPase was a MgPPi complex and that free Mg2+ was essential for PPi hydrolysis. With fixed f…

Decomposition of nitrous oxide upon nickel oxide-magnesium oxide solid solutions

1966

The decomposition of N 2 O has been studied over MgO catalysts, doped with NiO and NiO + Li 2 O from 1 to 10% (atomic). For pure MgO, activity is low, but is enhanced by addition of Ni 2+ ions. The apparent activation energy is reduced from 35 kcal/mole for pure MgO, to about 18 kcal/mole. Oxygen acts as a poison, and it is chemisorbed on the catalyst. The presence of lithium greatly increases the apparent activation energy. The results are interpreted in terms of oxygen chemisorption and of its influence on the course of the reaction.

Electrothermal Atomic Absorption Determination of Chromium in Sediments

1999

Abstract An electrothermal atomic absorption spectrometric method has been developed to determine total chromium concentration in natural sediment samples. Samples were mineralized by dry ashing at 550°C and fused at 1100°C for 30 min with lithium metaborate. Dissolved samples were injected in graphite tubes, mineralized at 1100°C, and atomized at 2600°C. Standard addition calibration made unnecessary the use of chemical modifiers. The method provided a limit of detection from 23 to 45 ng liter −1 . The relative standard deviation for chromium determination was between 3 and 14%. Results obtained for a standard reference material agree well with the certified value. A series of natural samp…

Validation of a method for neutron dosimetry and spectrometry using neutron activation of metal discs

2009

A technique for neutron dosimetry and spectrometry based on neutron activation of different metal discs has been studied. After exposure to a neutron field, the radionuclides produced in the discs are detected using low-level gamma-ray spectrometry and the neutron spectrum is obtained using a spectrum unfolding technique. In order to validate the method, irradiation was performed in a well-characterised (252)Cf neutron reference field. Furthermore, the detector was used to determine the neutron fluence rate and spectrum at a storage place for MOX nuclear fuel. The results of the two measurements are reported and discussed.