Atmospheric residence time of 210Pb determined from the activity ratios with its daughter radionuclides 210Bi and 210Po

The residence time of 210Pb created in the atmosphere by the decay of gaseous 222Rn is a key parameter controlling its distribution and fallout onto the landscape. These in turn are key parameters governing the use of this natural radionuclide for dating and interpreting environmental records stored in natural archives such as lake sediments. One of the principal methods for estimating the atmospheric residence time is through measurements of the activities of the daughter radionuclides 210Bi and 210Po, and in particular the 210Bi/210Pb and 210Po/210Pb activity ratios. Calculations used in early empirical studies assumed that these were governed by a simple series of equilibrium equations. This approach does however have two failings; it takes no account of the effect of global circulation on spatial variations in the activity ratios, and no allowance is made for the impact of transport processes across the tropopause. This paper presents a simple model for calculating the distributions of 210Pb, 210Bi and 210Po at northern mid-latitudes (30°-65°N), a region containing almost all the available empirical data. By comparing modelled 210Bi/210Pb activity ratios with empirical data a best estimate for the tropospheric residence time of around 10 days is obtained. This is significantly longer than earlier estimates of between 4 and 7 days. The process whereby 210Pb is transported into the stratosphere when tropospheric concentrations are high and returned from it when they are low, significantly increases the effective residence time in the atmosphere as a whole. The effect of this is to significantly enhance the long range transport of 210Pb from its source locations. The impact is illustrated by calculations showing the distribution of 210Pb fallout versus longitude at northern mid-latitudes

The transport and mass balance of fallout radionuclides in Brotherswater, Cumbria (UK)

This paper investigates the role of intervening transport processes on lake sediment records of the atmospherically deposited radionuclides 210Pb and 137Cs. Brotherswater is of particular interest to this issue in that its large catchment/lake area ratio and short water residence time are likely to amplify the influence of these processes, both from the catchment and through the water column. Brotherswater is also unique in being the site of two earlier multicore studies that, together with the present study, span a period of 4 decades. Measurements of fallout radionuclides were made on soil cores, suspended sediments and sediment cores, and the results combined with those from earlier studies to construct mass balances for 210Pb and 137Cs in Brotherswater. The results showed that catchment inputs accounted for 63% of 210Pb entering the lake. Further, just 47% of 210Pb entering the water column was delivered to the sediment record. For comparison, in an earlier study at nearby Blelham Tarn with a relatively smaller catchment but longer water residence time it was shown that 47% of 210Pb inputs were delivered via the catchment, 75% of which were delivered to the sediment record. Results from both sites suggest that 210Pb is predominantly transported on fine particulates with a mean particle size of 3–4 μm. Their relatively slow removal from the water column allows them to be transported relatively uniformly throughout the lake and may help account for the fact that simple 210Pb dating models are relatively reliable in spite of the complexities of the transport processes. Mass balance calculations for 137Cs are more complicated because of the variable fallout record. Measurements of 137Cs in the input stream and water column showed that catchment inputs are still significant 30 years after the last significant fallout (Chernobyl). Modelled results showed that catchment inputs delayed the date of peak inputs of weapons test fallout to the lake though by no more than 2 years. Although the results presented here are primarily concerned with fallout radionuclides and their reliability for dating, they also have implications for the use of sediment archives in reconstructing historical records of other atmospherically deposited substances such as trace metals or persistent organic pollutants

Towards a graph theoretical approach to study gender lateralization effect in mathematical thinking

Gender differences in mathematical thinking is a common concern of scientists from different research fields. Both parents and teachers report that males seem to perform better in complex mathematics compared to females. This study comes to shed light in the different organization of the underlying functional networks, in order to investigate the aforementioned observation, without supporting or rejecting this statement. In this sense, it is generally accepted that females use their both hemispheres to accomplish a certain task, while males use mostly the hemisphere which is properly suited. For the purposes of the current analysis, electroencephalographic recordings were collected from 11 males and 11 females, during a difficult mathematical task. Then a previously proposed model was used in order to pass from the sensor level to the cortical one, in order to examine the networks formed among the cortical dipoles. Mutual information was employed to form the graphs represeting the functional connectivity among the different dipoles, while the density, the global and the local efficiencies were further examined. The results suggest that females use their both hemisphere to solve the complex mathematical task while males use mostly their left hemisphere which is the responsible one for the mathematical thinking

3D vocal power Doppler sonography for the estimation of tumor volume and vascularization in stage IB1 cervical cancer

Purpose: To evaluate the tumor’s volume and intratumoral vascularization with 3D vocal power Doppler ultrasound in patients with stage 1B1 cervical cancer. Methods: This was a prospective study on patients with cervical cancer and stage 1B1 disease, which took place between 2012 and 2015. All women had an initial 2D ultrasound examination for the estimation of the tumor volume. Following this, 3D volumes of the cervix were acquired and were further analyzed using the Virtual Organ Computer Aided Analysis (VOCAL) program. In the selected volume, the vascular pattern (linear or complex vascularization) was also examined. The ultrasonographic findings were compared to the histological ones following surgery. Results: Twenty-seven patients were included. The average cervical tumor volume measured by the 2D ultrasound and 3D VOCAL-PD were 3.14 and 3.08 cm3, respectively. Both 2D and 3D VOCAL-PD overestimated the tumor staging. Further analysis showed a statistically significant superiority of 2D ultrasound over 3D VOCAL-PD for tumors equal or smaller than 2.5 cm3 with linear vascularity (p < 0.001), while for tumors of larger volume with complex vascularization, a statistically significant superiority of 3D VOCAL-PD was confirmed (p < 0.001). Conclusions: 3-D VOCAL-PD is extremely accurate and superior to 2D ultrasound for the estimation of tumor volume and vascularization when it is more than 2.5 cm3 and has a complex vascularization in patients with stage 1B1 cervical cancer. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature

Detecting neurophysiological alterations during Mild Cognitive Impairment and Dementia using wavelet-based energy computation and a Mahalanobis Distance classifier

Recently, a transitional stage, called Mild Cognitive Impairment (MCI) has been identified. Early MCI detection is of crucial importance for preventing dementia onset. The aim of this study is to provide a classification framework able to discriminate subtle alterations due to neurodegenerative processes. Primary attention was given at the MCI stage. Therefore two MCI groups were formed according the patient's performance in the Montreal Cognitive Assessment (MoCA) test; a group of 39 patient with a low cognitive decline (MCI-1; MoCA ≥ 25), and a group of 31 patients with moderate cognitive decline group (MCI-2; MoCA < 25). In addition, we tested 17 healthy control participants, and 14 mild demented patients. Participants underwent a full neuropsychologic examination. Application of the Independent Component Analysis (ICA) and visual inspection of EEG data during resting state condition with eyes closed was initially adopted for noise rejection. Then, the energy for each frequency band was computed through discrete wavelet transform (DWT). These spectral components for 57 electrodes served as an input to a classification system employing Mahalanobis Distance. Classification results (84.16% overall accuracy) demonstrated the system's robustness and reliability. Discrimination reached 82.35% for healthy controls, 92.31% for MCI-1, 74.19% for MCI-2 and 85.71% for mild demented patients. The classification system is proposed in order to supplement the neuropsychologic examination and to correlate subtle cognitive deficits revealed by MoCA with modified neurophysiological patterns, providing thus a better understanding to the progression of neurodegenerative mechanisms