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At least 559 records · Page 31Linked to original sources
PubMed1999

Energy spectrum of iron nuclei measured inside the MIR space craft using CR-39 track detectors.

We have exposed stacks of CR-39 plastic nuclear track detectors inside the MIR space craft during the EUROMIR95 space mission for almost 6 months. Over this long period a large number of tracks of high LET events was accumulated in the detector foils. The etching and measuring conditions for this experiment were optimized to detect tracks of stopping iron nuclei. We found 185 stopping iron nuclei inside the stack and identified their trajectories through the material of the experiment. Based on the energy-range relation the energy at the surface of the stack was determined. These particles allow the determination of the low energy part of the spectrum of iron nuclei behind shielding material inside the MIR station.

Cosmic Radiation↗
PubMed2000

Analysis of MIR-18 results for physical and biological dosimetry: radiation shielding effectiveness in LEO.

We compare models of radiation transport and biological response to physical and biological dosimetry results from astronauts on the Mir space station. Transport models are shown to be in good agreement with physical measurements and indicate that the ratio of equivalent dose from the Galactic Cosmic Rays (GCR) to protons is about 3/2:1 and that this ratio will increase for exposures to internal organs. Two biological response models are used to compare to the Mir biodosimetry for chromosome aberration in lymphocyte cells; a track-structure model and the linear-quadratic model with linear energy transfer (LET) dependent weighting coefficients. These models are fit to in vitro data for aberration formation in human lymphocytes by photons and charged particles. Both models are found to be in reasonable agreement with data for aberrations in lymphocytes of Mir crew members: however there are differences between the use of LET dependent weighting factors and track structure models for assigning radiation quality factors. The major difference in the models is the increased effectiveness predicted by the track model for low charge and energy ions with LET near 10 keV/micrometers. The results of our calculations indicate that aluminum shielding, although providing important mitigation of the effects of trapped radiation, provides no protective effect from the galactic cosmic rays (GCR) in low-earth orbit (LEO) using either equivalent dose or the number of chromosome aberrations as a measure until about 100 g/cm 2 of material is used.

Chromosome Aberrations↗
PubMed1999

Cytogenetic analysis of peripheral blood lymphocytes of occupational workers exposed to low levels of ionising radiation.

The incidence of chromosomal aberrations was analysed in peripheral blood lymphocytes of occupationally exposed people having cumulative doses of 500 mSv. The exposed individuals showed higher frequencies of dicentrics as well as acentrics than normal controls. Absorbed radiation dose was calculated by using in vitro dose response curve established for Cobalt-60 gamma rays. In the control constituting 17 healthy individuals, two dicentrics were detected among 3700 metaphases analysed. In the exposed group 27 dicentrics and one centric ring was detected among 8400 metaphases analysed. Due to small number of dicentrics scored in each individual, the dose estimate suffers from a large statistical uncertainty. The collective dose was found to be 1.89 Gy. This is in good agreement with the corrected physical doses, assuming a mean life of 10 years for the disappearance of lymphocytes. The physical doses accumulated during the last 10 years of occupation were also in good agreement with the biological dose estimate.

Adult↗
PubMed2006

Preliminary investigation of proton and helium ion radiation effects on fluorescent dyes for use in astrobiology applications.

The Specific Molecular Identification of Life Experiment (SMILE) instrument (Sims et al. Planet. Space Science 2005, 53, 781-791) proposes to use specific molecular receptors for the detection of organic biomarkers on future astrobiology missions (e.g., to Mars). Such receptors will be used in assays with fluorescently labeled assay reagents. A key uncertainty of this approach is whether the fluorescent labels used in the system will survive exposure to levels of solar and galactic particle radiation encountered during a flight to Mars. Therefore, two fluorescent dyes (fluorescein and Alexa Fluor 633) have been exposed to low-energy proton and alpha radiation with total fluences comparable or exceeding that expected during an unshielded cruise to Mars. The results of these initial experiments are presented, which show that both dyes retain their fluorescent properties after irradiation. No significant alteration in the absorption and emission wavelengths or the quantum yields of the dyes with either radiation exposure was found. These results suggest other structurally similar fluorophores will likely retain their fluorescent properties after exposure to similar levels of proton and alpha radiation. However, more extensive radiation fluorophore testing is needed before their suitability for astrobiology missions to Mars can be fully confirmed.

Absorption↗
PubMed2006

First derivation of predicted-no-effect values for freshwater and terrestrial ecosystems exposed to radioactive substances.

The FASSET Radiation Effects Database (FRED) constitutes a unique structured resource of the biological effects of ionizing radiation on non-human species mainly from temperate ecosystems, encompassing 26,000 primary data entries. Quality-assessed data were extracted from FRED and dose-effect relationships were constructed to provide estimates of ED50 and EDR10. These estimates are Doses (or Dose Rates) related to the percent change in the average level of the endpoint for a particular effect (50% or 10% for acute or chronic exposure regimes, respectively). Acute and chronic Species Sensitivity Distributions (SSDs) were built on the basis of these data sets, and the Assessment Factor Method (AFM) was applied when data were too scarce. The Hazardous Dose corresponding to 5% of species acutely affected at the 50% effect level varied from 1 to 5.5 Gy according to the ecosystem. For chronic gamma external irradiation exposure, no-effect values varied from 10 microGy/h for freshwaters through application of the AFM to 67 microGy/h for terrestrial ecosystems, corresponding to the 5th percentile of the non-weighted SSD (vs 229 microGy/h when trophic weights are applied). These values are higher by ca. x50 to x100 than the upper bound of natural background, and lower than dose rates triggering effects at individual levels on contaminated sites.

Amphibians↗
PubMed2003

Investigation of the photochemical properties and in vitro phototoxic potential of bumetanide.

The photophysical and photochemical properties of bumetanide, a sulfonamide diuretic drug, have been investigated and the photodegradation of the drug on exposure to UV-B and UV-A radiation monitored by fluorimetric and chromatographic (HPLC) methods. The main photoproducts were isolated by solid-phase extraction and liquid chromatographic procedures, and their structure elucidated by 1H-NMR and mass spectrometry. Bumetanide generates only extremely small quantities of singlet oxygen (1O2) upon irradiation in the presence of oxygen. The in vitro 3T3 N RU phototoxicity test yielded no evidence of phototoxic action.

Animals↗
PubMed2002

[18F-fluorodeoxyglucose positron emission tomography in colorectal cancer: value in primary staging and follow-up].

Positron emission tomography using 18F-fluorodeoxyglucose (FDG-PET) is a encouraging imaging technique allowing a highly sensitive whole-body search for malignant foci detected by their increased glucose metabolism compared with benign tissues. Several studies are now available that indicate its added value for diagnosis and staging of colorectal cancer. In all, patient management seems to be changed in 20-30% of patients who undergo Fluorodeoxyglucose positron emission tomography in addition to standard staging procedures. Fluorodeoxyglucose positron emission tomography is also useful in monitoring radiation therapy and chemotherapy. Regarding preoperative staging of primary colorectal cancer the literature is very limited.

Colorectal Neoplasms↗
PubMed2004

Review of radiation issues for computed tomography.

Over the past three decades, computed tomography (CT) has proven to be central in imaging evaluation. Multidetector technology continues to drive practice patterns by combining fast scanning with high quality data sets. This has resulted in new applications as well as improved use in traditional applications. With this recognition has also come the realization that there are potential costs of CT. One major cost is the radiation dose. Therefore, in order to begin to assess benefits (which are relatively familiar to radiologists) versus costs (which are less familiar), the issues related to CT radiation need to be addressed. Familiarity with measures of CT radiation and the actual doses delivered by CT are important issues as they provide a basis for understanding the potential cancer risks from CT radiation. Moreover, these justify development of strategies to minimize radiation dose. Strategies include obtaining only necessary CT examinations and adjusting the examinations based on scan indication, region examined, and patient size. These strategies must also be combined with efforts by manufacturers in development and implementation of technology aimed at radiation dose management, as well as efforts in research, education, and CT standards and regulation. This article reviews the subject of radiation dose with multidetector CT technology, including measures of CT radiation, the dose that can result from CT examinations, the risks of this amount of radiation, and strategies for minimizing CT radiation dose.

Humans↗
PubMed1976

[Radiation burden from X-ray diagnosis and new technological developments (author's transl)].

Radiation exposure of the population is expressed nowadays in terms of genetically significant dose and its individual components are compared. The calculations necessary for the present considerations have been carried out. As a basis for evaluating radiation protection, the natural sources of radiation and therir variations are used. The dose of 110 mrem/a for the population of the Federal Republic is subject os considerable variations. Artificially produced radiation contributes a total of 60 mrem/a to the exposure. Of this, most is contributed by medical sources with 50 mrem/a, second is exposure due to atom bomb research. Other sources of radiation, such as occupational exposure, its use in research and technology, and use of nuclear technology, contribute little to total exposure, each producing about 1 mrem/a. The data provided is supported by numerical evidence.

Adolescent↗
PubMed2004

Radiation hazard during a manned mission to Mars.

The radiation hazard of interplanetary flights is currently one of the major obstacles to manned missions to Mars. Highly energetic, heavy-charged particles from galactic cosmic radiation can not be sufficiently shielded in space vehicles. The long-term radiation effects to humans of these particles are largely unknown. In addition, unpredictable storms of solar particles may expose the crew to doses that lead to acute radiation effects. A manned flight to Mars currently seems to be a high-risk adventure. This article provides an overview on the radiation sources and risks for a crew on a manned flight to Mars, as currently estimated by scientists of the US National Administration for Space and Aeronautics (NASA) and the Space Studies Board (SSB) of the US National Research Council.

Earth, Planet↗