Record of Past Contact Between Altered Rocks and Radioactive Solutions Through Radiation-Induced Defects in Kaolinite

1990 ◽  
Vol 212 ◽  
Author(s):  
Philippe Ildefonse ◽  
Jean-Pierre Muller ◽  
Blandine Clozel ◽  
George Calas
Keyword(s):  
Ion Beam ◽  
X Rays ◽  
Paramagnetic Defect ◽  
Paramagnetic Resonance ◽  
Defect Centers ◽  
Different Types ◽  
Natural Analogues ◽  
Cumulative Radiation Dose ◽  
And Migration ◽  
Induced Defects

ABSTRACTA U-deposit located in hydrothermally altered tuff in Mexico, and two tropical weathering systems from Brazil and Cameroon were studied as natural analogues of radionuclide release and migration in the geosphere. In these alteration systems, kaolinite is the main secondary phyllosilicate associated with variable amounts of iron oxides. Defect centers are detected in natural kaolinites by means of electron paramagnetic resonance. The origin of the paramagnetic defect centers (PDC) is from radionuclide irradiation. This interpretation is supported by laboratory experiments on kaolinite using four different types of radiation: x-rays, γ-rays, and He+ and Pb2+ ion beam implantations. Several types of PDC (designated A-, A‵- and B-centers) are clearly identified and can be distinguished with respect to their relative stability. The A-center is stable over geological periods (on the order of 109 years) at surface temperatures. Moreover, it is shown that PDC’s in kaolinites reflect the cumulative radiation dose.PDC’s in kaolinite have been used to trace radionuclide migration in the three natural alteration systems studied. The kaolinites investigated show a significant concentration of PDC’s which corresponds to background natural irradiation. The different types of PDC detected may record successive irradiations of kaolinite directly linked to geochemical conditions prevailing during and after kaolinite growth. Because of their different thermal stability, these different PDC–s may be considered to have formed at different time periods. This makes a unique tool for tracing the dynamics of the transfer of radionuclides and allows the use of kaolinite as an in-situ dosimeter. Because some of the geological settings chosen for nuclear wastes are located in kaolinite-bearing strata, PDC dosimetry could be used in a safety assessment of these wastes.

Investigation of Damage Induced by Low Energy Focused Ion Beam Irradiation in GaAs

1993 ◽  
Vol 316 ◽  
Author(s):  
Toshihiko Kosugi ◽  
Yoshihiko Yuba ◽  
Kenji Gamo
Keyword(s):  
Focused Ion Beam ◽  
Deep Level ◽  
Ion Beam ◽  
High Energy ◽  
Low Energy ◽  
Defect Migration ◽  
Defect Centers ◽  
Energy Irradiation ◽  
Transient Spectroscopy ◽  
Induced Defects

ABSTRACTDefects induced by Ga focused ion beam (FIB) irradiation at an energy between 0.1 and IkeV have been characterized by means of deep level transient spectroscopy (DLTS) and related capacitance measurements. Seven different kinds of defect centers were resolved and two centers at 0.33 and O.56eV below the conduction band were dominant in the 100eV Ga implanted sample at doses up to 1015/cm2. Induced defect centers were observed to distribute over the region far beyond the theoretical ion range, which resulted from defect migration during the irradiation. Low energy irradiation induced defects were readily annealed out during low temperature heat treatment in contrast to those induced by high energy irradiations.

The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

1985 ◽  
Vol 43 ◽  
pp. 154-157
Author(s):  
A.J. Tousimis
Keyword(s):  
Ion Beam ◽  
Depth Resolution ◽  
Sample Surface ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Electrons And Ions ◽  
Spatial Depth ◽  
Minimum Surface Area ◽  
Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

scholarly journals Immunomodulatory Effects of Radiotherapy

2020 ◽  
Vol 21 (21) ◽  
pp. 8151
Author(s):  
Sharda Kumari ◽  
Shibani Mukherjee ◽  
Debapriya Sinha ◽  
Salim Abdisalaam ◽  
Sunil Krishnan ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Carbon Particle ◽  
Dna Lesions ◽  
X Rays ◽  
Adaptive Immune ◽  
High Let Radiation ◽  
Different Types ◽  
High Let ◽  
Radiation Induced ◽  
Tumor Death

Radiation therapy (RT), an integral component of curative treatment for many malignancies, can be administered via an increasing array of techniques. In this review, we summarize the properties and application of different types of RT, specifically, conventional therapy with x-rays, stereotactic body RT, and proton and carbon particle therapies. We highlight how low-linear energy transfer (LET) radiation induces simple DNA lesions that are efficiently repaired by cells, whereas high-LET radiation causes complex DNA lesions that are difficult to repair and that ultimately enhance cancer cell killing. Additionally, we discuss the immunogenicity of radiation-induced tumor death, elucidate the molecular mechanisms by which radiation mounts innate and adaptive immune responses and explore strategies by which we can increase the efficacy of these mechanisms. Understanding the mechanisms by which RT modulates immune signaling and the key players involved in modulating the RT-mediated immune response will help to improve therapeutic efficacy and to identify novel immunomodulatory drugs that will benefit cancer patients undergoing targeted RT.

scholarly journals Targeting the hallmarks of cancer: the effects of silibinin on proliferation, cell death, angiogenesis, and migration in colorectal cancer

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Saba Sameri ◽  
Chiman Mohammadi ◽  
Mehrnaz Mehrabani ◽  
Rezvan Najafi
Keyword(s):  
Annexin V ◽  
Anticancer Activities ◽  
Scratch Assay ◽  
Anti Cancer ◽  
Different Types ◽  
Colon Cell ◽  
Colon Cell Line ◽  
And Migration ◽  
Induced Apoptosis ◽  
Colony Forming Assay

Abstract Background Silibinin, as a chemopreventive agent, has shown anti-cancer efficacy against different types of cancers. In the present study, we investigated the anti-cancer activities of silibinin on CT26 mouse colon cell line. Methods CT26 cells were treated with different concentrations of silibinin. To examine the cytotoxic effect of silibinin on proliferation, apoptosis, autophagy, angiogenesis, and migration, MTT, colony-forming assay, Annexin V/PI flow cytometry, RT-qPCR, and Scratch assay were used. Results Silibinin was found to significantly reduce CT26 cells survival. Furthermore, silibinin strongly induced apoptosis and autophagy by up-regulating the expression of Bax, Caspase-3, Atg5, Atg7 and BECN1 and down-regulating Bcl-2. Silibinin considerably down-regulated the expression of COX-2, HIF-1α, VEGF, Ang-2, and Ang-4 as well as the expression of MMP-2, MMP-9, CCR-2 and CXCR-4. Conclusions The present study revealed that silibinin shows anticancer activities by targeting proliferation, cell survival, angiogenesis, and migration of CT26 cells.

scholarly journals New Polyporphyrin Arrays with Controlled Fluorescence Obtained by Diaxial Sn(IV)-Porphyrin Phenolates Chelation with Cu2+ Cation

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 829
Author(s):  
Galina M. Mamardashvili ◽  
Dmitriy A. Lazovskiy ◽  
Ilya A. Khodov ◽  
Artem E. Efimov ◽  
Nugzar Z. Mamardashvili
Keyword(s):  
Chemical Species ◽  
Ultra Violet ◽  
X Rays ◽  
Structure And Properties ◽  
Paramagnetic Resonance ◽  
1H Nuclear Magnetic Resonance ◽  
Infra Red ◽  
Connection Type ◽  
Chelation Reaction ◽  
Electron Paramagnetic

New coordination oligomers and polymers of Sn(IV)-tetra(4-sulfonatophenyl)porphyrin have been constructed by the chelation reaction of its diaxialphenolates with Cu2+. The structure and properties of the synthesized polyporphyrin arrays were investigated by 1H Nuclear Magnetic Resonance (1H NMR), Infra Red (IR), Ultra Violet - Visible (UV-Vis) and fluorescence spectroscopy, mass spectrometry, Powder X-Rays Diffraction (PXRD), Electron Paramagnetic Resonance (EPR), thermal gravimetric, elemental analysis, and quantum chemical calculations. The results show that the diaxial coordination of bidentate organic ligands (L-tyrazine and diaminohydroquinone) leads to the quenching of the tetrapyrrole chromophore fluorescence, while the chelation of the porphyrinate diaxial complexes with Cu2+ is accompanied by an increase in the fluorescence in the organo-inorganic hybrid polymers formed. The obtained results are of particular interest to those involved in creating new ‘chemo-responsive’ (i.e., selectively interacting with other chemical species as receptors, sensors, or photocatalysts) materials, the optoelectronic properties of which can be controlled by varying the number and connection type of monomeric fragments in the polyporphyrin arrays.

Hyaluronic Acid Hydrogel Particles Obtained Using Liposomes as Templates

2021 ◽  
Vol 7 (1) ◽  
pp. 7
Author(s):  
Irene Abelenda Núñez ◽  
Ramón G. Rubio ◽  
Francisco Ortega ◽  
Eduardo Guzmán
Keyword(s):  
Cell Proliferation ◽  
Cross Linking ◽  
Hydrogel Particles ◽  
Cell Proliferation And Migration ◽  
Different Types ◽  
And Migration ◽  
Tissue Matrix ◽  
Hyaluronic Acid Hydrogel ◽  
3D Networks ◽  
Proliferation And Migration

Hydrogels (HG) are 3D networks of hydrophilic macromolecules linked by different “cross-linking points”, which have as a main advantage their capacity for the adsorption of large amounts of water without any apparent dissolution. This allows hydrogels to undergo reversible swelling–shrinking processes upon the modification of the environmental conditions (pH, ionic strength or temperature). This stimuli-responsiveness and their ability for entrapping in their interior different types of molecules makes hydrogels suitable platforms for drug delivery applications. Furthermore, HGs exhibit certain similarities to the extracellular tissue matrix and can be used as a support for cell proliferation and migration.

Interaction and Migration Properties of Ion Beam Induced Point Defects in Crystalline Silicon: Basic Research and Technological Relevance

1997 ◽  
Vol 153-155 ◽  
pp. 137-158 ◽  
Author(s):  
Emanuele Rimini ◽  
Salvatore Coffa ◽  
Sebania Libertino ◽  
G. Mannino ◽  
F. Priolo ◽  
...  
Keyword(s):  
Point Defects ◽  
Crystalline Silicon ◽  
Ion Beam ◽  
Basic Research ◽  
And Migration
Sign in / Sign up

Export Citation Format

Share Document