Radionuclides are widely used to perform geochronologic investigations of the trace sediment deposition process in aquatic environments on different temporal scales. This study presents the ...activities of radionuclides to select a reasonable geochronologic dating method and study the sediment depositional environment in Lake Qinghai on the Qinghai-Tibet Plateau. The range of activities (Bq.kg−1) of 137Cs, 226Ra, 238U, 228Ra, 228Th, and 40K were 2–103, 24–49, 33–156, 20–49, 30–50, and 403–664, respectively. The sedimentation flux was calculated as 1.66 × 106 ton.a−1 based on the summary sedimentation rate in Lake Qinghai, and the sediment contributions from rivers, authigenic carbonates, lacustrine organisms, and atmospheric deposition were 45.18%, 22.44%, 3.02%, and 29.36%, respectively. The decreased 226Ra/238U radioactivity ratios from the catchment to the lake centre indicated that the removal of uranium relative to its daughter products occurs during erosion processes. The positive 228Thex (excess 228Th) values in the upper 1 cm of the sediment suggested that the sediment in the top 1 cm have been resuspended, mixed and/or transported. The distribution of 137Cs in the sediments indicated that the maximum activity of 137Cs in the sediments corresponds to the 1963 peak in the global fallout from atmospheric nuclear weapons testing; moreover, the 1986 Chernobyl accident signal was difficult to identify. The use of 137Cs as a chronologic tool must be performed carefully due to its migration process in sediments.
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•The vertical distribution of radionuclides was investigated.•Sedimentary depositional flux is 1.66 × 106 ton.a−1 in Lake Qinghai.•Sediment have been resuspended or/and mixed in the top 1 cm by the 228Thex result.•The diffusion of 137Cs in the sediment column was significant.
Purpose: To derive a nomogram for
Cs
131
prostate seed implant. Method and Materials: Adopting the isotropic point source model from TG43, the integral dose delivered by a single source is
E
= 4π∫
r
...2
ΛΦ
an
S
k
g
(
r
)/
r
2
dr
, where g(r) is the radial dose function, given as
0.0002
r
4
+0.0049
r
3
−0.0397
r
2
+0.0041
r
+1.0322
(1). Let N be the number of sources implanted, the total integral dose will be NE. Defining F is the fraction factor for energy absorbed by the prostate, and then energy absorbed inside the prostate will be NEF. Assuming the prostate is spherical and radioactivity is uniformly distributed, fraction factor F with energy 30 keV (
Cs
131
's average energy) has been calculated by Monte Carlo technique (2). The integral dose inside the prostate will be the volume of the prostate (V) times the mean dose (Dmean). The mean dose in the uniformly distributed sphere is calculated using numerical integration (3) to be 1.76 times of prescribed dose (D). By equating
NEF
=
V
D
mean
=1.76
DV
, the nomogram is obtained. Results: The nomogram (total activity =0.1128DV0.6727) is used to compare with clinical data provided by IsoRay (Richland, WA). The agreement is within 10% for monotherapy cases and within 12% for boost cases with regular gland sizes (25 to 60 cc). With gland sizes range from 30 to 60 cc, the agreement improves to 7% for monotherapy cases. Conclusion: Assuming radioactivity is uniformly distributed inside the spherical prostate, we have derived a nomogram for
Cs
131
seeds used in prostate implant. Compared with clinical data, our nomogram shows good agreement for regular size glands. The agreement is improved in monotherapy for large size glands (30 to 60 cc).
Cluster decay half-lives of actinides ranging from 221Fr to 242Cm are studied with a model where MGLDM (Modified Generalized Liquid Drop Model) includes pre-formation factor which depends on size of ...cluster and daughter nucleus and also on iso-spin parameter. Theoretical prediction could replicate experimental values with a standard deviation of about 0.569. Also we checked the applicability of our model in the case of alpha decay and obtained exactly matching results. Then we make prediction of half-lives of several clusters which are not detected experimentally so far so that this will be very helpful for future investigation in this field.
On January 1940, Eve Curie was pictured at the Portuguese Institute of Oncology (IPO). The shot would be reproduced in IPO’s Bulletin, a monthly journal of anti-cancer propaganda directed to the ...general public. Addressing Eve’s photograph as a picture, endowed with epistemic value, I seek to understand how it became an important tool for Portuguese anti-cancer campaigns. A second picture is considered – that of Marie Curie receiving her ‘gram’ of radium at the White House (1921) – to show the role that both mother and daughter played in the construction of radioactivity’s ambiguous public image. This paper tries to analyze how the public reproduction of the younger Curie’s photograph at IPO’s Radium Pavilion, the first European facility that followed the safety guidelines of the International Congress of Radiology of 1928, attempted to dismiss public fears over radioactive contamination. Portuguese anti-cancer campaigns needed to gain public support, not only regarding cancer, but also radioactivity, for the latter needed to be trusted if it was to be applied in time to its potential beneficiaries.
Context. Galactic cosmic rays (CRs) are a ubiquitous source of ionisation of the interstellar gas, competing with UV and X-ray photons as well as natural radioactivity in determining the fractional ...abundance of electrons, ions, and charged dust grains in molecular clouds and circumstellar discs. Aims. We model the propagation of various components of Galactic CRs versus the column density of the gas. Our study is focussed on the propagation at high densities, above a few g cm−2, especially relevant for the inner regions of collapsing clouds and circumstellar discs. Methods. The propagation of primary and secondary CR particles (protons and heavier nuclei, electrons, positrons, and photons) is computed in the continuous slowing down approximation, diffusion approximation, or catastrophic approximation by adopting a matching procedure for the various transport regimes. A choice of the proper regime depends on the nature of the dominant loss process modelled as continuous or catastrophic. Results. The CR ionisation rate is determined by CR protons and their secondary electrons below ≈130 g cm−2 and by electron-positron pairs created by photon decay above ≈600 g cm−2. We show that a proper description of the particle transport is essential to compute the ionisation rate in the latter case, since the electron and positron differential fluxes depend sensitively on the fluxes of both protons and photons. Conclusions. Our results show that the CR ionisation rate in high-density environments, such as the inner parts of collapsing molecular clouds or the mid-plane of circumstellar discs, is higher than previously assumed. It does not decline exponentially with increasing column density, but follows a more complex behaviour because of the interplay of the different processes governing the generation and propagation of secondary particles.
The sensitive detection and tracing of UO22+ in both complex water environments and cells are of great significance for environmental protection and life health. In this study, three flavonoid ...fluorescence sensors, including Ph-A, Ph-B, and Ph-C, were designed and prepared for the intracellular and aqueous solution detection of UO22+. The systematic structure and property relationship observation demonstrated that Ph-A with aldehyde groups achieved better detection stability and recognition effects compared with conventional molecules with carbonyl groups. Ph-A can be aggregated into nanoparticles in water. Based on the ESIPT mechanism, Ph-A can emit bright fluorescence in water, which can be further quenched by UO22+. Besides, Ph-A exhibited excellent selectivity and sensitivity, with the detection limit reaching as low as 1.17×10−8 mol/L. In addition, Ph-A and its fluorescent test strips presented high accuracy and perfect recovery in complex water sample tests, and they can be used for the on-site visual detection of UO22+ in low concentrations. More meaningfully, the sensor could penetrate through the cell membrane and localize in the lysosome, and the UO22+ in the lysosome was traced for the first time. The findings are expected to extend the advanced fluorescent sensor to the fields of environmental monitoring and targeted decorporation drug development.
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•Ph-A enables the tracing and detection of UO22+ in lysosomes for the first time.•Ph-A shows excellent selectivity, sensitivity, and stability for UO22+ detection.•The test strip prepared by Ph-A can realize the visual on-site detection low concentrations of UO22+.•Ph-A was successfully used for the detection of UO22+ in complex water samples.
Abstract Health effects of radon, most notably lung cancer, have been investigated for several decades. Therefore, indoor radon monitoring is a great way to consider the problem of natural ...radioactivity but also a way to insert phenomenological elements into physics education useful in understanding the crisis of classical physics and for introducing modern physics. The RadioLab project allowed to explore the possibility of a rapid introduction of elements of modern physics for younger students.
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