BEIR VII develops the most up-to-date and comprehensive risk estimates for cancer and other health effects from exposure to low-level ionizing radiation. It is among the first reports of its kind to ...include detailed estimates for cancer incidence in addition to cancer mortality. In general, BEIR VII supports previously reported risk estimates for cancer and leukemia, but the availability of new and more extensive data have strengthened confidence in these estimates. A comprehensive review of available biological and biophysical data supports a "linear-no-threshold" (LNT) risk model?that the risk of cancer proceeds in a linear fashion at lower doses without a threshold and that the smallest dose has the potential to cause a small increase in risk to humans. The report is from the Board on Radiation Research Effects that is now part of the newly formed Nuclear and Radiation Studies Board.
Purpose:
TheGEANT4 general-purpose Monte Carlo simulation toolkit is able to simulate physical interaction processes of electrons, hydrogen and helium atoms with charge states (
H
0
,
H
+
) and (
He
...0
,
He
+
,
He
2
+
), respectively, in liquid water, the main component of biological systems, down to the electron volt regime and the submicrometer scale, providing GEANT4 users with the so-called “GEANT4-DNA” physics models suitable for microdosimetry simulation applications. The corresponding software has been recently re-engineered in order to provide GEANT4 users with a coherent and unique approach to the simulation of electromagnetic interactions within the GEANT4 toolkit framework (since GEANT4 version 9.3 beta). This work presents a quantitative comparison of these physics models with a collection of experimental data in water collected from the literature.
Methods:
An evaluation of the closeness between the total and differential cross section models available in theGEANT4 toolkit for microdosimetry and experimental reference data is performed using a dedicated statistical toolkit that includes the Kolmogorov–Smirnov statistical test. The authors used experimental data acquired in water vapor as direct measurements in the liquid phase are not yet available in the literature. Comparisons with several recommendations are also presented.
Results:
The authors have assessed the compatibility of experimental data withGEANT4 microdosimetry models by means of quantitative methods. The results show that microdosimetric measurements in liquid water are necessary to assess quantitatively the validity of the software implementation for the liquid water phase. Nevertheless, a comparison with existing experimental data in water vapor provides a qualitative appreciation of the plausibility of the simulation models. The existing reference data themselves should undergo a critical interpretation and selection, as some of the series exhibit significant deviations from each other.
Conclusions:
TheGEANT4-DNA physics models available in the GEANT4 toolkit have been compared in this article to available experimental data in the water vapor phase as well as to several published recommendations on the mass stopping power. These models represent a first step in the extension of the GEANT4 Monte Carlo toolkit to the simulation of biological effects of ionizing radiation.
There is a persistent risk of a large-scale malicious or accidental exposure to ionizing radiation that may affect a large number of people. Exposure will consist of both a photon and neutron ...component, which will vary in magnitude between individuals and is likely to have profound impacts on radiation-induced diseases. To mitigate these potential disasters, there exists a need for novel biodosimetry approaches that can estimate the radiation dose absorbed by each person based on biofluid samples, and predict delayed effects. Integration of several radiation-responsive biomarker types (transcripts, metabolites, blood cell counts) by machine learning (ML) can improve biodosimetry. Here we integrated data from mice exposed to various neutron + photon mixtures, total 3 Gy dose, using multiple ML algorithms to select the strongest biomarker combinations and reconstruct radiation exposure magnitude and composition. We obtained promising results, such as receiver operating characteristic curve area of 0.904 (95% CI: 0.821, 0.969) for classifying samples exposed to ≥ 10% neutrons vs. < 10% neutrons, and R
of 0.964 for reconstructing photon-equivalent dose (weighted by neutron relative biological effectiveness) for neutron + photon mixtures. These findings demonstrate the potential of combining various -omic biomarkers for novel biodosimetry.
Abstract
We analyze new far-ultraviolet spectra of 13 quasars from the
COS-Halos survey that cover the H
i
Lyman limit of 14 circumgalactic medium (CGM) systems. These data yield precise estimates or ...more constraining limits than previous COS-Halos measurements on the H
i
column densities
. We then apply a Monte-Carlo Markov chain approach on 32 systems from COS-Halos to estimate the metallicity of the cool (
K) CGM gas that gives rise to low-ionization state metal lines, under the assumption of photoionization equilibrium with the extragalactic UV background. The principle results are: (1) the CGM of field
L
* galaxies exhibits a declining H
i
surface density with impact parameter
(at
confidence), (2) the transmission of ionizing radiation through CGM gas alone is 70 ± 7%; (3) the metallicity distribution function of the cool CGM is unimodal with a median of
and a 95% interval
to
; the incidence of metal-poor (
) gas is low, implying any such gas discovered along quasar sightlines is typically unrelated to
L
* galaxies; (4) we find an unexpected increase in gas metallicity with declining
(at
confidence) and, therefore, also with increasing
; the high metallicity at large radii implies early enrichment; and (5) a non-parametric estimate of the cool CGM gas mass is
, which together with new mass estimates for the hot CGM may resolve the galactic missing baryons problem. Future analyses of halo gas should focus on the underlying astrophysics governing the CGM, rather than processes that simply expel the medium from the halo.
This study explored the feasibility to produce .sup.198Au in the Isfahan miniature neutron source reactor (MNSR). To estimate production level, we used the MCNP simulation method, validated through ...empirical data. Role of different irradiation and cooling periods to maximize the produced yield was also studied. The results of our study showed that after 30 cycles, the maximum production was 812.3 mCi g.sup.-1 in the maximum flux and irradiation time. However, after the 15th cycle it reached its maximum production of 90% (740.3 mCi g.sup.-1). Also, the role of irradiation and cooling periods in the optimum fuel management was shown. Our results showed that producing .sup.198Au is feasible in MNSRs.
The cardiovascular system effects of environmental low-dose radiation exposure on radiation practitioners remain uncertain and require further investigation. The aim of this study was to initially ...investigate and explore the mechanisms by which low-dose radiation may contribute to atherosclerosis through a multi-omics joint comprehensive basic experiment.
We used WGCNA and differential analyses to identify shared genes and potential pathways between radiation injury and atherosclerosis sequencing datasets, as well as tissue transcriptome immune infiltration level extrapolation and single-cell transcriptome data correction using the CIBERSORT deconvolution algorithm. Animal models were constructed by combining a high-fat diet with 5 Gy γ-ray whole-body low-dose ionizing radiation. The detection of NETs release was validated by enzyme-linked immunosorbent assay.
Analysis reveals shared genes in both datasets of post-irradiation and atherosclerosis, suggesting that immune system neutrophils may be a key node connecting radiation to atherosclerosis. NETs released by neutrophil death can influence the development of atherosclerosis. Animal experiments showed that the number of neutrophils decreased (P < 0.05) and the concentration of NETs reduced after low-dose radiation compared with the control group, and the concentration of NETs significantly increased (P < 0.05) in the HF group. Endothelial plaques were significantly increased in the high-fat feed group and significantly decreased in the low-dose radiation group compared with the control group.
Long-term low-dose ionizing radiation exposure stimulates neutrophils and inhibits their production of NETs, resulting in inhibition of atherosclerosis.
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•HDIR may affect the progression of atherosclerosis via neutrophils.•LDIR does not affect atherosclerosis by promoting the release of NETs.•The development of advanced cardiovascular disease is not necessarily affected by early IR.
Radiation exposure to lungs during nuclear catastrophes or radiotherapy poses long-term side effects and can induce pulmonary injury sufficient for causing death. The strategies for preventing or ...reversing radiation-induced lung injuries have not been yet developed. Quercetin-3-Rutinoside (Q-3-R), a polyphenolic bioflavonoid, has shown multifaceted pharmacological applications due to its high antioxidant and anti-inflammatory properties.
In the current study, the potential of Q-3-R against radiation-induced lung pneumonitis/fibrosis and the possible underlying mechanism was investigated.
To evaluate the effect of Q-3-R against lung damage, C57Bl/6 mice were administered with Q-3-R (10 mg/kg b.wt.) and irradiated with a single dose of gamma radiation (12 Gy) at thoracic region.
16 weeks after irradiation lung damage was seen by histopathological studies and staining for collagen deposition. Expression of Nuclear factor kappa-B (NF-κB), transforming growth factor-β1 (TGF-β1), Smad3, intercellular adhesion molecule 1 (ICAM-1), α-smooth muscle actin protein (α-SMA), Aquaporin 5 (AQP 5), Interleukins (IL-6, IL-18, IL-1β), tumor necrosis factor-α (TNF-α) and caspase-3 was evaluated by immunohistochemistry/western blot/Elisa. Reactive oxygen species (ROS)/ Nitric oxide (NO) scavenging potential of Q-3-R and inhibition of cell death in irradiated lungs were also assessed.
Mice showed signs of pneumonitis and fibrotic changes in lungs following radiation treatment. A dramatic increase in inflammatory cells and cytokines contributing to lung disease pathogenesis was observed. Furthermore, expression of NF-κB, TGF-β1, Smad3, ICAM-1, AQP5and α-SMA was found markedly up-regulated. However, pretreatment of Q-3-R significantly attenuated radiation-induced pneumonitis and fibrosis. Histological examination revealed less structural and fibrotic changes with down-regulation of AQP 5, ICAM-1, α-SMA and caspase-3 in Q-3-R pretreated irradiated groups. The formulation significantly relieved lung injury by suppressing inflammatory and pro-fibrotic cytokines such as IL-6, IL-18, IL-1β, TNF-α and TGF-β1 via inhibition of NF-κB. Q-3-R also curtailed radiation-induced ROS/NO generation and minimized DNA damage in the irradiated lungs.
The findings from the current study clearly demonstrate that Q-3-R provides radioprotection to the lungs by regulating NF-κB/TGF-β1 signaling, scavenging free radicals, preventing perivascular infiltration and prolonged inflammatory cascade which could otherwise lead to chronic radiation fibrosis. Q-3-R can be proved as a potential therapeutic agent for alleviating radiation-induced lung injury in case of planned or unplanned radiation exposure scenario.
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Abstract
We present a detailed study of the rest-optical (3600–7000 Å) nebular spectra of ∼380 star-forming galaxies at
, obtained with Keck/Multi-object Spectrometer for Infrared Exploration ...(MOSFIRE) as part of the Keck Baryonic Structure Survey (KBSS). The KBSS-MOSFIRE sample is representative of star-forming galaxies at these redshifts, with stellar masses
and star formation rates SFR = 3–1000
yr
−1
. We focus on robust measurements of many strong diagnostic emission lines for individual galaxies: O
ii
λλ
3727, 3729, Ne
iii
λ
3869, H
β
, O
iii
4960, 5008, N
ii
λλ
6549, 6585, H
α
, and S
ii
λλ
6718, 6732. Comparisons with observations of typical local galaxies from the Sloan Digital Sky Survey and between subsamples of KBSS-MOSFIRE show that high-redshift galaxies exhibit a number of significant differences in addition to the well-known offset in log(O
iii
/H
β
) and log(N
ii
/H
α
). We argue that the primary difference between H
ii
regions in
galaxies and those at
is an enhancement in the degree of nebular excitation, as measured by O
iii
/H
β
and
(O
iii
+O
ii
)/H
β
. At the same time, KBSS-MOSFIRE galaxies are ∼10 times more massive than
galaxies with similar ionizing spectra and have higher N/O (likely accompanied by higher O/H) at fixed excitation. These results indicate the presence of harder ionizing radiation fields at fixed N/O and O/H relative to typical
galaxies, consistent with Fe-poor stellar population models that include massive binaries, and highlight a population of massive, high-specific star formation rate galaxies at high redshift with systematically different star formation histories than galaxies of similar stellar mass today.
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