Environmental radioactivity studies at the Nuclear Engineering Laboratory of the National Technical University of Athens

2021 ◽  
Author(s):  
Marios Anagnostakis
Keyword(s):  
Activity Ratio ◽  
Natural Radionuclides ◽  
High Volume ◽  
Environmental Radioactivity ◽  
Low Energy ◽  
Nuclear Engineering ◽  
Radioactive Equilibrium ◽  
Chernobyl Fallout ◽  
Fallout Radionuclides ◽  
The Mean

<p>The Nuclear Engineering Laboratory of the National Technical University of Athens (NEL-NTUA) is among the oldest laboratories conducting radioactivity mesurements in Greece, founded in the early sixties. One of the main activities at NEL-NTUA is environmental radioactivity studies, mainly based on gamma spectroscopic analysis. For this purpose NEL-NTUA is equipped with a variety of Germanium detectors for in-vitro and in-situ measurements. Starting back in the early eighties, environmental radioactivity studies at NEL-NTUA were significantly boosted after the Chernobyl accident in 1986  when they focused on the Chernobyl fallout radionuclides, as well as some natural radionuclides typically determined in environmental studies, namely <sup>232</sup>Th, <sup>226</sup>Ra and <sup>40</sup>K. As a result of these studies maps of nine Chernobyl fallout radionuclides and the three natural radionuclides in continental Greece surface soils were produced. </p><p>Since natural radioactivity in soil is in most cases relatively low, high volume samples had to be analyzed. Over the years, the acquisition of detectors capable of detecting low energy photons (LEGe) along with the development of techniques to correct for self-absorption of low energy photons within the sample, allowed for the accurately determination of radionuclides emitting such photons, like <sup>234</sup>Th (63.29keV), <sup>210</sup>Pb (46.52keV) and <sup>241</sup>Am (59.54keV). These newer studies showed that a significant disruption of radioactive equilibrium in surface soil between <sup>226</sup>Ra and <sup>210</sup>Pb is very common, while radioactive equilibrium disruption between <sup>238</sup>U and <sup>226</sup>Ra is common as well. It is interesting to notice that the mean activity ratio <sup>210</sup>Pb/<sup>226</sup>Ra as obtained from ~300 sample measurements is of the order of ~4, while the mean activity ratio<sup> 226</sup>Ra/<sup>238</sup>U was estimated to be around one. A mapping of radioactive equilibrium disruption that followed provided interesting results.</p><p>In the years to follow studies focused on the vertical distribution of natural (<sup>210</sup>Pb) and artificial (<sup>137</sup>Cs) radionuclides in soil and sea sediments and the study of radionuclides fractionation in soil as well as NORM. Both types of studies require the analysis of small volume samples – of the order of 20-50g or even less. Therefore, the development of techniques for sampling of soil vertical profile and the accurate analysis of small samples was of great importance. These analyses require high efficiency detectors, such as XtRa detectors, background reduction techniques, such as Compton Suppression Systems, optimized sample geometries for higher full energy peak efficiency. Sophisticated techniques for background determination and subtraction, in order to obtain accurate results for natural radionuclides which are often detected in the background, are also required.</p><p>Another field of research at NEL-NTUA is the development and improvement of techniques for monitoring of <sup>222</sup>Rn daughters outdoors using on-line detector systems, as well as for monitoring of natural and artificial radionuclides in atmospheric precipitations and aerosols (<sup>7</sup>Be, <sup>210</sup>Pb, <sup>22</sup>Na) using high volume air samplers.</p><p>Aim of this work is to present the research conducted at NEL-NTUA over the years with regard to the environmental radioactivity, as well as the current activities in the field and those planned for the future.</p>

scholarly journals Asymptotic expansion of low-energy excitations for weakly interacting bosons

2021 ◽  
Vol 9 ◽  
Author(s):  
Lea Boßmann ◽  
Sören Petrat ◽  
Robert Seiringer
Keyword(s):  
Asymptotic Expansion ◽  
Coulomb Potential ◽  
Mean Field ◽  
Low Energy ◽  
Energy Eigenstates ◽  
Bogoliubov Theory ◽  
Weakly Interacting ◽  
Repulsive Coulomb ◽  
The Mean

Abstract We consider a system of N bosons in the mean-field scaling regime for a class of interactions including the repulsive Coulomb potential. We derive an asymptotic expansion of the low-energy eigenstates and the corresponding energies, which provides corrections to Bogoliubov theory to any order in $1/N$ .

scholarly journals Minimally invasive distal pancreatectomy: a case-matched cost-analysis between robot-assisted surgery and direct manual laparoscopy

2021 ◽  
Author(s):  
Gregorio Di Franco ◽  
Andrea Peri ◽  
Valentina Lorenzoni ◽  
Matteo Palmeri ◽  
Niccolò Furbetta ◽  
...  
Keyword(s):  
Minimally Invasive ◽  
Cost Analysis ◽  
Distal Pancreatectomy ◽  
Length Of Hospital Stay ◽  
High Volume ◽  
Fixed Costs ◽  
Spleen Preservation ◽  
Robotic Assisted Surgery ◽  
The Mean ◽  
Complications Rate

Abstract Background Few studies have reported a structured cost analysis of robotic distal pancreatectomy (RDP), and none have compared the relative costs between the robotic-assisted surgery (RAS) and the direct manual laparoscopy (DML) in this setting. The aim of the present study is to address this issue by comparing surgical outcomes and costs of RDP and laparoscopic distal pancreatectomies (LDP). Methods Eighty-eight RDP and 47 LDP performed between January 2008 and January 2020 were retrospectively analyzed. Three comparable groups of 35 patients each (Si-RDP-group, Xi-RDP group, LDP-group) were obtained matching 1:1 the RDP-groups with the LDP-group. Overall costs, including overall variable costs (OVC) and fixed costs were compared using generalized linear regression model adjusting for covariates. Results The conversion rate was significantly lower in the Si-RDP-group and Xi-RDP-group: 2.9% and 0%, respectively, versus 14.3% in the LDP-group (p = 0.045). Although not statistically significant, the mean operative time was lower in Xi-RDP-group: 226 min versus 262 min for Si-RDP-group and 247 min for LDP-group. The overall post-operative complications rate and the length of hospital stay (LOS) were not significantly different between the three groups. In LDP-group, the LOS of converted cases was significantly longer: 15.6 versus 9.8 days (p = 0.039). Overall costs of LDP-group were significantly lower than RDP-groups, (p < 0.001). At multivariate analysis OVC resulted no longer statistically significantly different between LDP-group and Xi-RDP-group (p = 0.099), and between LDP-group and the RDP-groups when the spleen preservation was indicated (p = 0.115 and p = 0.261 for Si-RDP-group and Xi-RDP-group, respectively). Conclusions RAS is more expensive than DML for DP because of higher acquisition and maintenance costs. The flattening of these differences considering only the variable costs, in a high-volume multidisciplinary center for RAS, suggests a possible optimization of the costs in this setting. RAS might be particularly indicated for minimally invasive DP when the spleen preservation is scheduled.

The underrepresentation of female participants in studies assessing the impact of high-dose exercise on cardiovascular outcomes: a scoping review

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
S Pallikadavath ◽  
R Patel ◽  
CL Kemp ◽  
M Hafejee ◽  
N Peckham ◽  
...  
Keyword(s):  
Scoping Review ◽  
High Volume ◽  
Cardiovascular Outcomes ◽  
High Dose ◽  
Funding Sources ◽  
Review Protocol ◽  
The Mean ◽  
The Impact ◽  
Over Time ◽  
Funding Acknowledgements

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Cardiovascular adaptations as a result of exercise conducted at high-intensity and high-volume are often termed the ‘Athlete’s heart’. Studies have shown that these cardiovascular adaptations vary between sexes. It is important that both sexes are well represented in this literature. However, many studies assessing the impact of high-dose exercise on cardiovascular outcomes under-recruit female participants. Purpose This scoping review aimed to evaluate the representation of females in studies assessing the impact of high-dose exercise on cardiovascular outcomes and demonstrate how this has changed over time. Methods The scoping review protocol as outlined by Arksey and O’Malley was used. OVID and EMBASE databases were searched and studies independently reviewed by two reviewers. Studies must have investigated the effects of high-dose exercise on cardiovascular outcomes. To assess how the recruitment of females has changed over time, two methods were used. One, the median study date was used to categorise studies into two groups. Two, studies were divided into deciles to form ten equal groups over the study period. Mean percentage of female recruitment and percentage of studies that failed to include females were calculated. Results Overall, 250 studies were included. Over half the studies (50.8%, n = 127) did not include female participants. Only 3.2% (n = 8) did not include male participants. Overall, mean percentage recruitment was 18.2%. The mean percentage of recruitment was 14.5% before 2011 and 21.8% after 2011. The most recent decile of studies demonstrated the highest mean percentage of female recruitment (29.3%) and lowest number of studies that did not include female participants (26.9%). Conclusion Female participants are significantly underrepresented in studies assessing cardiovascular outcomes caused by high-dose exercise. The most recent studies show that female recruitment may be improving, however, this still falls significantly short for equal representation. Risk factors, progression and management of cardiovascular diseases vary between sexes, hence, translating findings from male dominated data is not appropriate. Future investigators should aim to establish barriers and strategies to optimise fair recruitment. Mean percentage females recruited per study (%) Percentage studies that do not include women (%) Overall (n = 250) 18.2 50.8 (n = 127) Studies before 2011 (n = 121) 14.5 59.5 (n = 72) Studies after 2011 (n = 129) 21.8 42.6 (n = 55) Table 1: Female recruitment characteristics. The year 2011 (median study year) was chosen as this divides all included studies into two equal groups.

Insight into the Formation of Ultrafine Nanostructures in Bulk Amorphous Zr54.5 Ti7.5Al10Cu20Ni8

2001 ◽  
Vol 703 ◽  
Author(s):  
André Heinemann ◽  
Helmut Hermann ◽  
Albrecht Wiedenmann ◽  
Norbert Mattern ◽  
Uta Kühn ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Volume Fraction ◽  
High Volume ◽  
High Resolution Electron Microscopy ◽  
Scattering Data ◽  
Scanning Calorimetry ◽  
Enhanced Diffusion ◽  
Resolution Electron ◽  
The Mean ◽  
Interparticle Interference

ABSTRACTBulk amorphous Zr54.5 Ti7.5Al10Cu20Ni8 is investigated by means of smal-angle neutron scattering (SANS), differential-scanning calorimetry (DSC), high-resolution electron microscopy (HREM) and other methods. The formation of ultrafine nanostructures in the glassy phase is observed and explained by a new model. Structura fluctuations of randomly distributed partialy ordered domains grow during annealing just below the glass transition temperature by local re-ordering. During anneaing the DSC gives evidence for a increasing volume fraction of the localy ordered domains. At high volume fractions of impinging domains a percolation threshold on the interconnected domain boundaries occurs and enhanced diffusion becomes possible. At that stage SANS measurements lead to satistically significant scattering data. The SANS signals are anayzed in terms of a model taking into account spherica particles surrounded by diffusion zones and interparticle interference effects. The mean radius of the nanocrystaline particles is determined to 1 nm and the mean thickness of the depletion zone is 2 nm. The upper limit for the volume fraction after annealing at 653 K for 4hours is about 20 %. Electron microscopy confirms the size and shows that the particle are crystaline.

Gamma-Ray Spectrum Analysis of Chang’E-1 for Lunar Detection

2010 ◽  
Vol 133 (5) ◽  
Author(s):  
Xu HongKun ◽  
Fang Fang ◽  
Ni Shijun ◽  
He Jianfeng ◽  
You Lei
Keyword(s):  
Spectral Characteristic ◽  
Spectrum Analysis ◽  
Gamma Ray ◽  
Low Energy ◽  
Elemental Abundance ◽  
Nuclear Engineering ◽  
Gamma Ray Spectrometer ◽  
Lunar Prospector ◽  
Spectrometer Data ◽  
Wavelet Methods

Gamma-ray spectrum analysis was essential for radioactive environmental monitoring, and it had been widely used in many areas of nuclear engineering. However, for the low-energy region of gamma-ray spectrum, weak peaks were contained in the fast-decreasing background, so it was difficult to extract characteristic information from original spectra. In order to get a better analytic result based on wavelet methods in frequency domain, we had processed the gamma-ray spectrometer data of Chang’E-1 and well extracted some useful information of spectral characteristic peaks. Then, we preliminarily mapped the distribution of net peak counts for potassium on lunar surface, which indirectly reflected the distribution of elemental abundance. At last, we compared our analytic result with that of Apollo and Lunar Prospector and found some consistencies and differences.

scholarly journals Specific Activities of Natural Radionuclides and Annual Effective Dose Due to the Intake of Some Types of Children Powdered Milk Available in Baghdad Markets

2017 ◽  
Vol 14 (3) ◽  
pp. 619-624
Author(s):  
Baghdad Science Journal
Keyword(s):  
Effective Dose ◽  
Sodium Iodide ◽  
Specific Activity ◽  
Annual Effective Dose ◽  
Natural Radionuclides ◽  
Mean Value ◽  
Powdered Milk ◽  
Effective Doses ◽  
The Mean ◽  
Specific Activities

In this research the specific activity of natural radionuclides 226Ra, 232Th and 40K were determined by sodium iodide enhanced by thallium NaI(TI) detector and assessed the annual effective dose in Dielac 1 and 2 and Nactalia 1 and 2 for children of less than 1 year which are available in Baghdad markets. The specific activity of 40K has the greater value in all the types which is in the range of allowed levels globally that suggested by UNSCEAR. The mean value of annual effective doses were 2.92, 4.005 and 1.6325 mSv/y for 226Ra, 232Th and 40K respectively.

scholarly journals Coupled amidolytic assay for factor VII: its use with a clotting assay to determine the activity state of factor VII

Blood ◽  
1978 ◽  
Vol 52 (5) ◽  
pp. 978-988 ◽  
Author(s):  
U Seligsohn ◽  
B Osterud ◽  
SI Rapaport
Keyword(s):  
Healthy Subjects ◽  
Activity Ratio ◽  
Factor Xa ◽  
Factor Vii ◽  
Test Material ◽  
Chromogenic Substrate ◽  
Factor X ◽  
Transfusion Therapy ◽  
The Mean ◽  
Activity State

Abstract A coupled amidolytic assay for factor VII (VII) has been developed that when used with a clotting assay for VII enables detection of activated VII. In the assay, VII in a test material determines generation of factor Xa in a mixture of purified factor X, tissue factor, and calcium; factor Xa is measured with a chromogenic substrate. Factor VII activity in the coupled amidolytic assay (VIIam) correlated well with VII activity in a one-stage clotting assay (VIIc) in 57 healthy subjects, 5 patients with hereditary VII deficiency, and 11 patients with liver disease. Activation of plasma VII by kaolin, clotting, or cold strikingly increased VIIc but not VIIam levels. Thus the ratio VIIc/VIIam (VII activity ratio) is a measure of VII activation. In 27 warfarin-treated patients the mean VII activity ratio was significantly decreased, reflecting a greater decline in VIIc than in VIIam. This probably stems from partially carboxylated VII being able to act during the 3-min incubation of the amidolytic assay but unable to act rapidly enough to affect the clotting assay. Measurement of VIIc/VIIam should enable evaluation of the activity state of VII in thrombotic disorders and in components for transfusion therapy.

scholarly journals The Development of Heterotopic Ossification Following Ankle Fracture Syndesmotic Screw Fixation

2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0044
Author(s):  
Benjamin R. Williams ◽  
Paul M. Lafferty
Keyword(s):  
Risk Factors ◽  
Heterotopic Ossification ◽  
Ankle Fracture ◽  
Screw Fixation ◽  
Low Energy ◽  
Ankle Fractures ◽  
Factors Associated ◽  
Syndesmotic Screw ◽  
The Mean

Category: Ankle, Trauma Introduction/Purpose: Syndesmotic fixation with screws is commonly used for ankle fractures with syndesmotic disruption. Few studies have reported the development of heterotopic ossification (HO) within the syndesmosis following ankle injuries, which may lead to abnormal joint kinematics and even joint synostosis. However, there is little data on the prevalence and on the risk factors associated with the development of HO. The purpose of this study is to determine the (1) prevalence and (2) risk factors associated with the development of HO within the distal tibiofibular syndesmosis following ankle fractures requiring syndesmotic fixation. We hypothesized that screws within the syndesmosis articulation and broken screws would be associated with a higher incidence of HO than extraarticular and intact screws, respectively. Methods: A retrospective review was conducted for patients who sustained an ankle fracture with syndesmotic disruption. Inclusion criteria: age between 18 and 65 years old, a closed ankle fracture treated operatively with syndesmotic screw fixation. Exclusion criteria: additional lower extremity injury, history of prior ankle fracture, lack of radiographic follow-up and fixation other than 1 or 2 syndesmosis screws. Medical records were reviewed for: age, sex, high or low energy injury mechanism, smoking status, diabetes, BMI, perioperative complications, and further procedures. Fractures were classified by Lauge-Hansen and Weber systems. Immediate postoperative radiographs were reviewed for the number of syndesmotic screws, whether screws were intraarticular or extraarticular and the number of cortices each screw crossed. Final postoperative radiographs were reviewed for retention or screw removal and the presence of HO. The presence of HO was defined as new or increased bone formation within the syndesmosis compared to immediate postoperative radiographs. Results: Included were 264 patients, mean radiographic follow-up of 10.5+/-10.2 months. The mean age was 39.2+/-12.6 years (38.7% female) with a mean BMI of 32.1+/-7.8. Current smokers made up 39.4% of patients and 10.6% were diabetic. The mean time to fracture fixation was 12.6+/-3.2 days and 198 patients (75%) had a low energy injury. There was no significant difference in HO formation for demographics, injury mechanism or time to fixation. Overall, HO developed in 160 patients (60.6%). There was no difference, additionally for fracture pattern, number screws or fixation construct (Table 1). HO developed in 92% of broken, 75% of loose and 44% of intact screws (P<0.001). Screws were removed in 107 patients (40.5%) with no difference in HO formation compared to patients with intact screws. Conclusion: Heterotopic ossification is commonplace following screw fixation for syndesmotic injuries with a prevalence of 60.6%. Broken screws and loosened screws are a significant risk factor for the development of HO. However, no other risk factors in this study were found to be associated with the development of HO, including intraarticular syndesmotic screw placement. Patients should be counseled on the prevalence although further research is needed to determine the effect on ankle motion and progression of post-traumatic osteoarthritis.

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