Various Types Of Radiation Research Articles

Effects of Radiation and Thermal Cycling on Teflon ® FEP

Surfaces of the aluminized Teflon® FEP (fluorinated ethylene propylene) multilayer thermal insulation on the Hubble Space Telescope (HST) were found to be cracked and curled in some areas at the time of the second servicing mission (SM2) in February 1997, 6.8 years after HST was deployed in low Earth orbit (LEO). In an effort to understand what elements of the space environment might cause such damage, pristine second-surface aluminized Teflon® FEP was tested for durability to various types of radiation, to thermal cycling and to radiation followed by thermal cycling. Types of radiation included synchrotron vacuum ultraviolet and soft x-ray radiation, simulated solar flare x-ray radiation, electrons and protons. Thermal cycling was conducted in various temperature ranges to simulate HST orbital conditions for Teflon® FEP. Resultsoftensiletestingoftheexposedspecimensshowedthatexposuretohighfluencesofradiation caused degradation in tensile properties of FEP. However, exposure to radiation alone in exposures comparable to those experienced by HST did not produce reduction in ultimate tensile strength and elongation of Teflon® similar to that observed for HST-retrieved aluminized Teflon®. Synergism of radiation exposure and thermal cycling was evident in the results of three experiments: thermal cycling following electron and proton irradiation, thermal cycling following x-ray exposure, and additional thermal cycling of a sample retrieved from HST. However, irradiation and thermal cycling with comparable HST SM2 exposure conditions did not produce the degradation observed in the FEP material retrieved during HST SM2.

Perspective: National Cancer Institute summary report about estimated exposures and thyroid doses received from iodine 131 in fallout after Nevada atmospheric nuclear bomb tests.

Environmental 131I contamination from atmospheric nuclear bomb tests conducted at the NTS from 1951 to 1958 exposed Americans nationwide to a cumulative average dose of 1 to 4 rad to the thyroid gland. By comparison, 10 years of exposure to natural background sources of thyroid radiation results in a cumulative dose of 1 rad. Americans living in certain high-deposition areas received an average cumulative thyroid dose of as much as 16 rad. Individual dose rates vary considerably as a function of age at the time of exposure, site of residence, and dietary habits with respect to milk consumption. The individual cumulative thyroid dose for persons born between 1945 and 1958 may be significantly higher than the reported averages for their locale. The NCI report contains voluminous data tables permitting detailed calculations of individual dose. Additionally, color-coded dose maps allow one to approximate individual dose conveniently. Translation of cumulative thyroid dose attributable to 131I to predictions of increased rates of thyroid cancer appears problematic and is the subject of further study. In contrast to studies of patients receiving external thyroid irradiation, existing studies of patients treated with 131I for diagnostic and therapeutic medical purposes do not document increased rates of thyroid cancer. An Institute of Medicine task force is expected to issue a report on this subject in September 1998. This review also briefly summarizes the evaluation, diagnosis, and treatment of patients with papillary and follicular thyroid cancers. Data from 53,856 patients with thyroid cancer accessioned to the NCDB from 1985 to 1995 document extremely high survival rates for patients in the United States with papillary and follicular thyroid cancer.

Photon statistics of various radiation sources

Recent successful experimental demonstrations of the self-amplified spontaneous emission (SASE) in the infra-red region of the spectrum and project proposals for the production of XUV/X-ray SASE radiation have revitalized the interest in the statistical properties of FEL radiation. In this paper, after a review of photon statistics is given, those from various types of radiation including non-classical light are compared. Predicted photon statistics (or lack thereof) from a FEL oscillator, an amplifier, coherent spontaneous emission (CSE), SASE and high-gain harmonic generation (HGHG) are summarized. Different schemes of experimental methods to measure photon statistics are examined, and the experiment carried out at the National Synchroton Light Source (NSLS) to measure the photon statistics of wiggler spontaneous emission is described.

Double helical and double toroidal spiral fields

Toroidal spiral field theory, proposed earlier by the author, is utilized to present the double helical and double toroidal spiral fields as the basic substances of nature. Both fields exist at discrete energy levels and transform one into the other. Double helical spiral fields are formed during polarization of adjacent ‘field strings’ that propagate along the straight lines at ‘ultimate spiral field velocity’. These fields form various types of radiation as long as their energy exceeds a predetermined lowest level, below which they transform into depolarized and massless ‘field rings’. Polarization of the field rings leads to creation of double toroidal spiral fields that form various sub-atomic particles. The mass and electric charge of the spiral fields are defined by their geometry. The features of the spiral fields follow from application of novel relativistic relationships according to which both the mass and electric charge decrease with increase in velocity and become equal to zero at the velocity equal to the ultimate spiral field velocity.

Molecular basis of DNA repair mechanisms and syndromes.

Numerous chemical agents and various types of radiation (e.g. UV-light, X-rays) induce a wide range of lesions in DNA. Such damage can lead to changes in the nucleotide sequence varying from point mutations to gross chromosomal aberrations which can alter the expression or functioning of genes implicated in regulation of cell proliferation and differentiation, thereby forwarding the cell in the multistep process of carcinogenesis. To prevent these and other deleterious consequences of DNA injury, all living organisms are equipped with a complex network of DNA repair systems. One of the best studied repair processes is the nucleotide excision repair (NER) pathway which removes a wide diversity of DNA lesions including cyclobutane pyrimidine dimers and (6–4) photoproducts as well as chemical adducts and cross-links. In most — if not all — organisms two NER subpathways operate. One deals with the rapid and efficient removal of lesions that block transcription and thus need to be eliminated urgently (transcription-coupled repair, TCR). The other accomplishes the slower and less efficient global genome repair (GGR) of bulk DNA, including the nontranscribed strand of active genes.

The late effects on bone marrows in mice after total body irradiation by p(35) be fast neutrons and γ rays

Purpose: To understand the late effects on bone marrow after widefield or total body irrdiation with various types of radiation. Materials and Methods: Total body irradiation with single dose of P(35) Be fast Neutrons and γ rays respectively have been used in this study. Kunming strain mice were irradiated by fast neutrons produced by bombardment of beryllium target with 35MeV protons and the dose rate was 0.12 to 0.14 Gy/min. Nine dose levels were used in fast neutrons irradiation from 0.20 to 3.50Gy. The dose rate of 68 Co γ rays was 0.60Gy/min and irradiation was in the range of 0.25 to 9.00Gy. Sixteen dose points were studied. All animals without anesthesia were irradiated whole body with single doses by fast neutrons and T rays respectively. One group without irradiation was regarded as control group. 90 days after irradiation all animals were sacrificed. The nucleated cells of bone marrow and the peripheral blood cells including WBC and lymphocytes were counted. Results: Our study shows that the number of nucleated cells of bone marrow in both fast neutrons and ray gronps decreased with increase of the doses. There are significant differences between irradiated groups and zero line (control group) and the slopes are -1.41 ± 0.55 (p=0.038) and -0.98 ± 0.24(p=0.0015) for fast neutrons and γ rays respectively. There is no significant difference between the two kinds of radiation (P>0.05). The late effects on peripheral blood cells (WBC and iymphocytes) in mice after irradiation with single doses of neutrons and rays were significantly lower than unirradiated group (P Conclusions: Total body irradiation with neutrons or γ rays can suppress marrow in mice in the long-term, and is more obvious with increase of doses. There is no significant difference between neutrons and γ rays for the late effects studied.

Effect of thermal treatment and radiation on ( N, N-dimethylaminopropyl) acrylamide copolymers in the solid state

The effect of various types of radiation (gamma radiation, electron-beam, and UV) exposure on ( N, N-dimethylaminopropyl) acrylamide copolymers in the solid state has been investigated. The influence of methyl methacrylate and styrene as comonomers in the copolymer chain has also been studied. Radiation leads to crosslinking rather than chain-scission on poly(DMAPAM-co-MMA). Poly(DMA-PAM-co-St) were more resistant to crosslinking by radiation. It was found that the crosslinking reaction is due to the DMAPAM units. Thermal treatment of these copolymers in the solid state also leads to crosslinking through DMAPAM units.

Lesion spectra: radiation signatures and biological gateways.

We describe an integrative approach to the modeling of biophysical radiation effects. The model takes aim at practical applications of the knowledge provided by molecular studies of radiation-matter interactions in DNA. The central proposition is the idea that the distribution of molecular lesions (i.e., a molecular lesion spectrum, MLS) generated in DNA by exposure to a particular radiation is a characteristic of that causal radiation (i.e., is a radiation signature, RS). We have found that adaptive neural networks (ANN's) provide an efficient way to validate that proposition and that ANN's are also likely to be invaluable in any attempt to correlate cancers with radiation types (i.e., with RS's), to use RS's for evaluating individual carcinogenic susceptibilities, and to develop a low-dose personalized monitoring capability. Although efforts to identify products of radiation that are specific to radiation type and to link those with biological responses are almost a century old, the RS concept has provided the first quantitative confirmation of such causal relations. That is, RS's and radiation markers have been identified for various types of radiation, electromagnetic (EM) and particulate, and these signatures and markers may constitute a new way for fast radiation exposure estimates, risk assessment, and cumulative low-dose evaluation. In this work, while we will present a short review of the concepts and methods related to both RS's and markers, almost the entire effort will relate to the modeling and interpretation of RS's using ANN processing.

A comparison of the effects of neutron and other irradiation sources on the dynamic property changes of ceramic insulators

The interaction of various types of radiation with matter is briefly reviewed with particular emphasis on those effects peculiar to polyatomic ceramic insulators. A comparison is made between neutron and other energetic particles on the swelling behavior of alumina (A1 2O 3), which is the strongest candidate ceramic for fusion reactor applications. Special attention focussed on the dynamic effects of irradiation, such as radiation induced conductivity, radiation enhanced electrical degradation and dielectric loss.

Human nucleotide excision repair syndromes: Molecular clues to unexpected intricacies

INTRODUCTION THE DEVELOPMENT and maintenance of life has critically depended on the evolution of mechanisms that ensure genetic integrity and stability. DNA, the vital carrier of genetic information, is continually subjected to undesired chemical alterations. Numerous environmental or endogenous compounds and various types of radiation, such as X-rays and ultra-violet (UV) light, induce a wide variety of lesions in the bases, sugars or phosphates that make up the DNA. Obviously, such lesions (adducts, crosslinks, breaks, etc.) interfere with the proper functioning of the genome. An intricate network of DNA repair systems constitutes the main barrier protecting against the deleterious consequences of DNA injury. This is illustrated by the phenotype of inherited defects in one of these repair pathways. Such disorders are invariably associated with a characteristic hypersensitivity to a specific class of genotoxic agent. In addition, the DNA lesions that persist lead to cellular malfunction and to enhanced mutagenesis, due to the increased probability that errors occur upon replication of a damaged template. Somatic mutagenesis is the initiator of multistep carcinogenesis. Rare inborn disorders with hallmarks characteristic of repair defects comprise the class of chromosomal instability syndromes. Well-known examples are Fanconi’s anaemia, ataxia telangiectasia and Bloom’s syndrome, all of which display different manifestations of cancer predisposition and increased sensitivity to specific mutagens. The prototype disorder of this type is, however, xeroderma pigmentosum (XP), in which a defect in the nucleotide excision repair pathway underlies the pronounced predisposition to skin cancer and characteristic photosensitivity. The molecular mechanism and biological relevance of this repair system constitutes the topic of this chapter. For a comprehensive review of DNA damage and the intricate network of DNA repair systems in general, the interested reader is referred to Friedberg PI. Nucleotide excision repair (henceforth abbreviated as NER) is one of the most versatile cellular repair mechanisms. This universal system eliminates a remarkably diverse array of structurally unrelated lesions, that range from W-induced photoproducts (cyclobutane pyrimidine dimers and 6-4 photoproducts) to bulky and small chemical adducts as well as intra-strand crosslinks. In this light, it is not surprising that the NER process entails multiple steps, and involves the concerted action of a number of proteins. The details of the reaction mechanism are best understood in the case of the UvrABC system in the

Model of mammalian cell reproductive death. I. Basic assumptions and general equations.

A systemic model describing the major radiobiological effects of various types of radiation is proposed. The model base lines were substantiated, and general mathematical equations for cell survival developed. The model takes into consideration such physical and biological factors as linear energy transfer, ion track structure, and structural and functional organization of interphase chromatin. This paper presents the basic assumptions made and general equations for the cell killing.

Thermoluminescent Response of LiF:Mg,Ti (TLD-100) as a Function of Irradiation Temperature for Various Types of Radiation

The thermoluminescent (TL) response of LiF:Mg,Ti (TLD-100) as a function of irradiation temperature (Tirr) was studied for different types of radiation such as 60Co gamma rays, 241Am gamma rays, positive pions (p+) and moderated PuBe neutrons. It was found that the TL response increases as the Tirr rises up to 120 oC and then decreases in a manner which is LET dependent.

Vacuum photolysis of poly(phenylene ether) at short and long wavelengths

The vacuum photolysis of poly(phenylene ether) (PPE) under various types of radiation (254–365 nm) is reported. The photolysis observed in PPE in the solid state is characterized using FTIR analysis as a complement to UV spectroscopy. The primary photolytic process implies scission of the ether bond leading to the formation of phenoxy and phenyl radicals. Subsequently, benzyl radicals are formed. Photolysis products are identified as phenolic and quinone-methide structures and are responsible for yellowing of irradiated films.

Some Properties of the Microdosimetric Quality Factor

Some individual and general properties of the quality factor Q, defined in ICRU Report 40, were studied by analysis of microdosimetric spectra for various types of radiation. By analysis of an individual lineal energy spectrum, we may assess the role of partial factors in the resultant value of Q. The general analysis applicable to any lineal energy spectrum enables simple estimates of Q. The upper limit of the quality factor can be determined from the dose-mean lineal energy. An approximate estimate of the quality factor can easily be made.

Circuit related issues due to radiation in hostile environments

Various types of radiation in hostile environments cause transient and permanent changes in the devices used in complex integrated circuits. The failure of a particular IC is a function not only of the basic material and device parameter changes but also of the circuit environment in which the device is located. Circuit techniques have been developed which minimize the detrimental effects of radiation on certain types of circuits. In other cases, circuit techniques are not very effective in minimizing radiation effects. This work discusses selected issues related to the interactions between device radiation effects and circuit performance or circuit failure in a hostile radiation environment. This is not meant to be a comprehensive study of circuit effects but rather several examples are selected to illustrate the issues involved in designing circuits to operate in hostile radiation environments.

Giant balloon to ply Antarctic skies

During the last two weeks of December 1989 the biggest balloon ever is scheduled to fly around the continent of Antarctica. The mission is to prove that it is possible and to seek out information on various types of radiation. Reprinted by permission from the National pages of the 18 Dec. 1989 issue of The New York Times.

Low energy charged particle nuclear reaction studies with SSNTDs

In experimental nuclear reaction studies the most general requirement is to measure the yield and the spatial distribution of the reaction products, while their energy and type are simultaneously determined, frequently in the presence of a high background due to various types of radiation. Especially in studying low-yield nuclear processes, high efficiency and long-term stability of the applied spectroscopic method are highly desirable. In such situations, various nuclear track detection methods can be used very advantageously and successfully. Some of these methods are briefly discussed and examples are presented from our results concerning the application of nuclear track spectroscopy to different low-energy nuclear reaction studies, angular distribution and excitation function measurements.

Radiation biology in space: A critical review

A short summary of the results of radiobiological studies in space or on respective particles on ground will be given. Among the various types of radiation in space, the effect of heavy ions with high energy (HZE-particles) are most essential. Thus, radiobiology in space concerns mostly to the effect of these particles, in cells and in whole organism. Cell death, mutation and malignant transformation are the relevant endpoints, with can be studied on ground with heavy ions of different energy with suitable accelerators or in space, especially by the BIOSTACK concept. In space, however, the effect of microgravity has to be considered as well and there are hints, that under weightlessness the biological effect of radiation may be enhanced. There are still open questions to be answered concerning radioprotection of man in space. Further experiments are necessary.

Determination of the Recombination Index of Quality for Neutrons and Charged Particles Employing High Pressure Ionisation Chambers

Abstract The concept of the recombination index of quality (RIQ) is based on the degree of initial recombination and was introduced to provide a measurable quantity of radiation quality. The RIQR values can be determined employing a high pressure ionisation chamber operated under saturation conditions and at a suitable collecting potential, UR. Experiments were performed with various types of radiation including monoenergetic neutrons with energies of 0.9, 2.1, 5.5 and 14 MeV, polyenergetic neutrons (Pu-Be and 252Cf with different filters), high energy protons and alpha particles from natural uranium. To obtain RIQ values for neutrons alone, the photon component of the total absorbed dose was determined using the twin chamber technique and the photon component was subtracted from the total RIQ. It is shown that RIQ4 values can estimate with good accuracy the quality factor values (ICRP 1973). RIQ1 (or RIQ0.5/1 determined from measurements at saturation and two voltages) can be used for estimation of QF values recently proposed by ICRU. The expected independence of RIQ4 on filling gas pressure was confirmed experimentally for a Pu-Be source.

Basic radiobiology.

Experimental studies of the biological effects of radiation were started soon after the discoveries of x-rays in 1895, but there is still much that is not known. This article includes some research objectives that are essentially pragmatic in nature, intended to support and improve the current practice of radiotherapy, but the central thrust is the understanding of the mechanisms involved in the biological effects of radiation at the cellular and molecular levels. The article was written by a consortium of scientists and suffers inevitably from the drawback that writing styles are inconsistent, and coverage is not uniform. However, it benefits from the enormous advantage that it reflects the accumulated wisdom and judgment of more than a dozen scientists who, in their own areas of expertise, are recognized as being at the cutting edge of radiation research. The niceties of style and syntax are sacrificed in favor of the quality of the science and the maturity of judgment. The study of DNA damage as a mechanism for cell injury in early- and late-responding tissues, as well as a comparison of DNA damage that leads to lethality, as opposed to transformation and mutagenesis, are key items. The study of cell lethality with cells in culture led to the identification of repair, both sublethal and potentially lethal, as well as the dose-rate effect, and has had a considerable impact on radiotherapy. Future studies should focus on understanding the factors that determine radiosensitivity/radioresistance. A variety of approaches are available, including the study of genetically deficient cell lines from cancer-prone individuals. A parallel approach is the application of the techniques of molecular biology to clone the repair genes in mammalian cells, and to understand genetic defects that alter gene regulation, or to regulate biochemical factors in the cell. Substantial progress has been made in developing in vitro assays for mutagenesis, particularly using hybrids of rodent and human cells. Better methods are needed to study the effects of mutation on gene expression, and sensitive systems are needed that can detect low doses of radiation. Assays of oncogenic transformation, the in vitro counterpart of carcinogenesis, have been used to investigate the oncogenic potential of various types of radiation and chemotherapy agents. Key topics in future will include the investigation of supra-additivity between different agents, the identification and characterization of oncogenes that may be activated by radiation, the development of quantitative assays based on human cells, and further studies involving cell-to-cell communication.(ABSTRACT TRUNCATED AT 250 WORDS)