Low-activity Samples Research Articles

Validating plutonium-239+240 as a novel soil redistribution tracer – a comparison to measured sediment yield

Abstract. Quantifying soil redistribution rates is a global challenge addressed with direct sediment measurements (e.g. traps), models, and isotopic, geochemical, and radionuclide tracers. The isotope of plutonium, namely 239+240Pu, is a relatively new soil redistribution tracer in this challenge. Direct validation of 239+240Pu as a soil redistribution tracer is, however, still missing. We used a unique sediment yield time series in southern Italy, reaching back to the initial fallout of 239+240Pu to verify 239+240Pu as a soil redistribution tracer. Distributed soil samples (n=55) were collected in the catchment, and at undisturbed reference sites (n=22), 239+240Pu was extracted, measured with inductively coupled plasma mass spectrometry (ICP-MS), and converted to soil redistribution rates. Finally, we used a generalized additive model (GAM) to regionalize soil redistribution estimates for the catchment. For the catchment sites, mean 239+240Pu inventories were significantly reduced (16.8 ± 10.2 Bq m−2) compared to the reference inventory (40.5 ± 3.5 Bq m−2), indicating the dominance of erosion. Converting these inventory losses into soil erosion rates resulted in an average soil loss of 22.2 ± SD 7.2 t ha−1 yr−1. The uncertainties of the approach stemmed mainly from the high measurement uncertainties of some low-activity samples where samples have been bulked over depth. Therefore, we recommend taking incremental soil samples and extracting larger soil volumes (∼ 20 g). The geographic coordinates and the flow accumulation best described the spatial pattern of erosion rates in the GAM model. Using those predictors to upscale Pu-derived soil redistribution rates for the entire catchment resulted in an average on-site loss of 20.7 t ha−1 yr−1, which corresponds very well to the long-term average sediment yield of 18.7 t ha−1 yr−1 measured at the catchment outlet and to 137Cs-derived soil redistribution rates. Overall, this comparison of Pu-derived soil redistribution rates with measured sediment yield data validates 239+240Pu as a suitable retrospective soil redistribution tracer.

Development of a wide-field EMCCD camera-based alpha-particle imaging system

We demonstrate a wide-field alpha-particle imaging system based on the detection of alpha-induced scintillation light from ZnS:Ag screen using an EMCCD camera. We develop an efficient image processing algorithm to remove cosmic and thermal noise and to locate alpha particle interactions in EMCCD images. This algorithm is particularly suited to imaging low-activity samples where long image acquisition periods entail a large number of frames with no detected alpha particle. Our system has a relative counting efficiency of ∼50 % compared to a PMT-based alpha counter. It can detect alpha particles at a resolution of <480 µm over an imaging area of ∼45 × 45 mm. We demonstrate the performance of this system by imaging a granite sample. Correlation between the resulting alpha image and the micro XRF-determined element map demonstrates that most of the alpha activity in our sample is held in dark-coloured Ba-rich veins and inclusions at mineral grain boundaries.

Background shielding by dense samples in low-level gamma spectrometry

In low activity gamma spectrometric measurements of large, dense samples, the bulk sample material shields the HPGe crystal from external background sources. If not accounted for in studies that utilise background-subtraction methods, this effect may result in systematic errors in the sample activity and detection limit estimation. We introduce a Monte Carlo based method to minimise the impact of this effect on sample gamma spectra. It is validated using simulated detector backgrounds and applied to a measurement of low-activity Gd2SO43⋅8H2O. One main prerequisite for the correct application of this method is to know in advance the nuclides which contribute to the detector background spectrum and their spatial distribution. With a thorough understanding of the detector backgrounds, the method improves the accuracy of sensitive low-background measurements of low-activity samples. Even without knowing the background sources and their distribution, conservative results may still be presented that account for the potential systematic errors introduced by this background shielding effect.

Radiochemical separation and purification of non-carrier-added silicon-32

Abstract 32Si (T 1/2 = 153(19) y) is an extremely rare, naturally-occurring isotope that has been considered as a geochronometer suitable for radiometric dating over the time span from 100 to 1000 years ago – a time span that has proved rather difficult to explore in this manner. Past attempts to determine the 32Si half-life have resulted in a wide range of values possessing significant uncertainties because only low-activity samples could be made available for such measurements. Utilizing the 590 MeV ring cyclotron at PSI, megabecquerel quantities of 32Si have been produced by exposing metallic vanadium discs to high-energy protons in order to induce spallation. A radiochemical separation procedure has been successfully developed and applied to the irradiated discs as part of the SINCHRON project, based on a combination of ion-exchange and extraction resins. The process was shown to be reliable and robust with a high chemical yield. Radiochemically pure 32Si solutions with activity concentrations of up to several kBq/g can be produced to perform individual measurements (AMS, ICP-MS, LSC) for various studies. Thus, a careful redetermination of the 32Si half-life has become feasible to begin the first steps toward the confident implementation of this radionuclide for geochronological purposes.

BATCH PROCESSING OF TREE-RING SAMPLES FOR RADIOCARBON ANALYSIS

ABSTRACTWe here present a comparison of methods for the pretreatment of a batch of tree rings for high-precision measurement of radiocarbon at the Aarhus AMS Centre (AARAMS), Aarhus University, Denmark. The aim was to develop an efficient and high-throughput method able to pretreat ca. 50 samples at a time. We tested two methods for extracting α-cellulose from wood to find the most optimal for our use. One method used acetic acid, the other used HCl acid for the delignification. The testing was conducted on background 14C samples, in order to assess the effect of the different pretreatment methods on low-activity samples. Furthermore, the extracted wood and cellulose fractions were analyzed using Fourier transform infrared (FTIR) spectroscopy, which showed a successful extraction of α-cellulose from the samples. Cellulose samples were pretreated at AARAMS, and the graphitization and radiocarbon analysis of these samples were done at both AARAMS and the radiocarbon dating laboratory at Lund University to compare the graphitization and AMS machine performance. No significant offset was found between the two sets of measurements. Based on these tests, the pretreatment of tree rings for high-precision radiocarbon analysis at AARAMS will henceforth use HCI for the delignification.

(Invited) Novel Approach of Efficient-Photocatalyst Design Based on Electron Trap-Distribution Analysis

How can we design solid photocatalysts? What is the decisive factor controlling photocatalytic activities?So-called band-structure model (BSM), electrons in a valence band (VB) of a photocatalyst is photoexcited into a conduction band (CB), leaving positive holes in VB, and electrons and holes reduce and oxidize, respectively, substrates adsorbed on the surface of the photocatalyst, does suggest preferable band positions for redox reaction uniquely decided only by crystalline structure. The other possible factors, e.g., particle size and surface structure, cannot be discussed within BSM.Recently, we have developed reversed double-beam photoacoustic spectroscopy (RDB-PAS) which enables measure energy-resolved density of electron traps (ERDT). Those electron traps (ETs) seem to be predominantly located on the surface of almost all the metal oxide particles and therefore they reflect macroscopic surface structure in ERDT patterns [1,2]. Using ERDT pattern along with the data of CB-bottom position (CBB), i.e., ERDT/CBB patterns, it has been shown that metal oxide powders and the other semiconducting materials such as carbon nitrides can be identified without using the other analytical data such as X-ray diffraction patterns or specific surface area, and similarity/differentness of a pair of metal-oxide samples can be quantitatively evaluated as a parameter, ζ, degree of coincidence of ERDT/CBB patterns [3].Three representative photocatalytic reactions, (a) hydrogen (H2) evolution from deaerated aqueous methanol (H2 system), (b) carbon-dioxide (CO2) evolution from aqueous acetic acid under aerobic conditions (CO2 system) and (c) oxygen (O2) evolution from aqueous silver fluoride (O2 system), were carried out with those titania samples, and the ratios of evaluated photocatalytic activities for pairs of titania samples (0 < ζ pc < 1) were compared with ζ. It was observed that the higher the value of ζ at > 0.6 is, the higher becomes ζ pc , i.e., the ERDT/CBB patterns reflect bulk/surface structures which govern overall photocatalytic activities of titania samples; ERDT/CBB patterns can identify these titania samples and this can be extended to the other metal oxides and semiconducting materials such as carbon nitride (C3N4).Then, reversed analysis has been made, i.e., those ERDT/CBB patterns were arranged in the order of photocatalytic activity from higher side to lower side. Interestingly, for CO2 and O2 systems, highest activity titania samples exhibited similar patterns in each system, while middle or low-activity samples did no similarity. One of the possible reasons is that photocatalytic activities are governed by many independent factors, which are all optimized in the highest activity samples, though activities can be much reduced only by one unfavorable factor. In the other words, we cannot expect to find titania samples of activity higher than those titania samples in CO2 and O2 systems. This assumption, however, may suggest that titania samples exhibiting superior photocatalytic activity in H2 system may be discovered, because they seem not to be optimized.[1] Nitta, A.; Takase, M.; Takashima, M.; Murakami, N.; Ohtani, B. Chem. Commun. 2016, 52, 12096-12099.[2] Nitta, A.; Takashima, M.; Murakami, N.; Takase, M.; Ohtani, B. Electrochim. Acta 2018, 264, 83-90.[3] Nitta, A.; Takashima, M.; Takase, M.; Ohtani, B. Catal. Today 2019, 321-322, 2-8.

Methods and Influencing Factors for the Simple and Rapid Identification of Depleted Uranium Weapon Use under Battlefield Conditions.

The purpose of this paper is to explore how to rapidly and easily identify depleted uranium (DU) samples under battlefield conditions and to study the factors that influence their measurement. The air-absorbed dose rate and surface contamination levels for DU samples of 2-330 g were measured using a patrol instrument and portable energy spectrometer. The results were analyzed in accordance with IAEA standards for judging radioactive substances. The energy spectra of 5-g quantities of DU samples were analyzed using a high-purity germanium gamma spectrometer, and the uranium content of 100 mg DU samples was determined with an inductively coupled plasma mass spectrometer to clarify the type and composition of the uranium. The same batches of DU samples were identified using a portable gamma-ray spectrometer. We added 0-5 g environmental soil powders at different proportions. After sealing, the spectra were collected with a detection distance of 1-5 cm for 10 min. The activities of U and U nuclides in the samples were detected with an NaI(TI) scintillation detector. The U and U mass abundances in samples were calculated from measured specific activities. The sample was determined to contain DU if the U to U ratio was below 0.00723. It is found that for detecting DU materials with a low activity, surface contamination level measurements are more effective than calculating the air-absorbed external irradiation dose rate. Hence, for low-activity samples suspected to be radioactive, a radiometer with a high sensitivity for surface contamination is recommended, and the optimal measurement distance is 1-3 cm. Under all detection conditions, U can be identified using a portable gamma spectrometer, whereas U can only be detected under certain conditions. If these nuclides can be detected simultaneously, a U to U ratio of below 0.00723 indicates the presence of DU. The main factors affecting this identification include the sample mass, sample purity, measurement distance, and measurement time. For the rapid identification of DU with a portable gamma-ray spectrometer, the mass of uranium in the sample must be more than 1 g, the measuring distance needs to be less than 1 cm, and the measuring time must be 1-10 min. It is feasible to use a portable gamma-ray spectrometer to rapidly identify the types and composition of nuclides in DU samples. The detection of U activity is a precondition for the identification of DU.

(Invited) Novel Approach of Efficient-Photocatalyst Design Based on Electron Trap-Distribution Analysis

How can we design solid photocatalysts? What is the decisive factor controlling photocatalytic activities? So-called band-structure model (BSM), electrons in a valence band (VB) of a photocatalyst is photoexcited into a conduction band (CB), leaving positive holes in VB, and electrons and holes reduce and oxidize, respectively, substrates adsorbed on the surface of the photocatalyst, does suggest preferable band positions for redox reaction uniquely decided only by crystalline structure. The other possible factors, e.g., particle size and surface structure, cannot be discussed within BSM.Recently, we have developed reversed double-beam photoacoustic spectroscopy (RDB-PAS) which enables measure energy-resolved density of electron traps (ERDT). Those electron traps (ETs) seem to be predominantly located on the surface of almost all the metal oxide particles and therefore they reflect macroscopic surface structure in ERDT patterns [1,2]. Using ERDT pattern along with the data of CB-bottom position (CBB), i.e., ERDT/CBB patterns, it has been shown that metal oxide powders and the other semiconducting materials such as carbon nitrides can be identified without using the other analytical data such as X-ray diffraction patterns or specific surface area, and similarity/differentness of a pair of metal-oxide samples can be quantitatively evaluated as a parameter, ζ, degree of coincidence of ERDT/CBB patterns [3].Three representative photocatalytic reactions, (a) hydrogen (H2) evolution from deaerated aqueous methanol (H2 system), (b) carbon-dioxide (CO2) evolution from aqueous acetic acid under aerobic conditions (CO2 system) and (c) oxygen (O2) evolution from aqueous silver fluoride (O2 system), were carried out with those titania samples, and the ratios of evaluated photocatalytic activities for pairs of titania samples (0 < ζ pc < 1) were compared with ζ. It was observed that the higher the value of ζ at > 0.6 is, the higher becomes ζ pc , i.e., the ERDT/CBB patterns reflect bulk/surface structures which govern overall photocatalytic activities of titania samples; ERDT/CBB patterns can identify these titania samples and this can be extended to the other metal oxides and semiconducting materials such as carbon nitride (C3N4).Then, reversed analysis has been made, i.e., those ERDT/CBB patterns were arranged in the order of photocatalytic activity from higher side to lower side. Interestingly, for CO2 and O2 systems, highest activity titania samples exhibited similar patterns in each system, while middle or low-activity samples did no similarity. One of the possible reasons is that photocatalytic activities are governed by many independent factors, which are all optimized in the highest activity samples, though activities can be much reduced only by one unfavorable factor. In the other words, we cannot expect to find titania samples of activity higher than those titania samples in CO2 and O2 systems. This assumption, however, may suggest that titania samples exhibiting superior photocatalytic activity in H2 system may be discovered, because they seem not to be optimized.[1] Nitta, A.; Takase, M.; Takashima, M.; Murakami, N.; Ohtani, B. Chem. Commun. 2016, 52, 12096-12099.[2] Nitta, A.; Takashima, M.; Murakami, N.; Takase, M.; Ohtani, B. Electrochim. Acta 2018, 264, 83-90.[3] Nitta, A.; Takashima, M.; Takase, M.; Ohtani, B. Catal. Today 2019, 321-322, 2-8.

Design of Heterogeneous Photocatalysis Based on Energy-Resolved Distribution of Electron Traps

How can we design solid photocatalysts? What is the decisive factor controlling photocatalytic activities? For at least more than 35 years, since photoinduced water splitting in an electrochemical system including titania single crystal and platinum electrodes has been discovered in 1972 [1], has been passed. So-called band-structure model (BSM), electrons in a valence band (VB) of a photocatalyst is photoexcited to a conduction band (CB), leaving positive holes in VB, and electrons and holes reduce and oxidize, respectively, substrates adsorbed on the surface of the photocatalyst, does suggest preferable band positions for redox reaction uniquely decided only by crystalline structure. Possible the other factors, e.g., particle size and surface structure, cannot be discussed within BSM. Recently, we have developed reversed double-beam photoacoustic spectroscopy (RDB-PAS) which enables measure energy-resolved density of electron traps (ERDT). Those electron traps (ETs) seem to be predominantly located on the surface of almost all the metal oxide particles, with exception of nickel oxide and therefore they reflect macroscopic surface structure in ERDT patterns [2,3]. Using ERDT pattern along with the data of CB-bottom position (CBB), i.e., ERDT/CBB patterns, it has been shown that metal oxide powders can be identified without using the other analytical data such as X-ray diffraction patterns or specific surface area, and similarity/differentness of a pair of metal-oxide samples can be quantitatively evaluated as a parameter, ζ, degree of coincidence of ERDT/CBB patterns[4]. Three representative photocatalytic reactions, (a) hydrogen (H2) evolution from deaerated aqueous methanol (H2 system), (b) carbon-dioxide (CO2) evolution from aqueous acetic acid under aerobic conditions (CO2 system) and (c) oxygen (O2) evolution from aqueous silver fluoride (O2 system), were carried out with those titania samples, and the ratios of evaluated photocatalytic activities for pairs of titania samples (0 < ζ pc < 1) were compared with z as shown in Fig. 1. It is clearly seen that the higher the value of ζ at > 0.6 is, the higher becomes ζ pc, i.e., the ERDT/CBB patterns reflect bulk/surface structures which govern overall photocatalytic activities of titania samples. Then reversed analysis has been made, i.e., those ERDT/CBB patterns were arranged in the order of photocatalytic activity from higher side to lower side. Interestingly, for CO2 and O2 systems, highest activity titania samples exhibited similar patterns in each system, while middle or low-activity samples did no similarity. One of the possible reasons is that photocatalytic activities are governed by many independent factors, which are all optimized in the highest activity samples, though activities can be much reduced only by one unfavorable factor. In the other words, we cannot expect to find titania samples of activity higher than those titania samples in CO2 and O2 systems. This assumption, however, may suggest that titania samples exhibiting superior photocatalytic activity in H2 system may be discovered, because they seem not to be optimized. [1] A. Fujishima, K Honda, Nature 238 (1972) 37. [2] A. Nitta, M. Takase, M. Takashima, N. Murakami, B. Ohtani, Chem. Commun. 52 (2016) 12096. [3] A. Nitta, M. Takashima, N. Murakami, M. Takase, B. Ohtani, Electrochim. Acta 254 (2018) 83. [4] A. Nitta, M. Takashima, M. Takase, B. Ohtani, Catal. Today in press (10.1016/j.cattod.2017.12.020). Figure 1

Detection efficiency of NaI(Tl) detector based on the fabricated calibration of HPGe detector

Determination of the full-energy peak efficiency of a detection system is significant in the activity calculation of the measured radioactive samples. In this work, we present an experimental method to determine the absolute efficiency calibration of a NaI(Tl) detector, considering that a standard source of interest is unavailable and by using the known specific activity of a standard sample measured using a HPGe detector. The efficiency of a gamma-ray spectrometer that consists of a coaxial HPGe detector is calculated using Canberra ISOCS/LabSOCS software and a fabricated calibration source. To validate our method, environmental samples (rock and soil samples) were analyzed on both the detectors. The obtained activity concentrations were checked by means of the IAEA proficiency test procedure. The performance criteria evaluation results were found to be ‘Acceptable’ for all the analytical determinations of all the radionuclides under study, except for the samples with low activity (<15 Bq kg−1 and <10 Bq kg−1 for 226Ra and 232Th, respectively). The precision of the low-activity samples was not considered ‘Acceptable’ as the results were slightly inaccurate; in this case, the results were considered as ‘Warning’ because the relative bias (RB) was less than the maximum acceptable bias (MAB).

Recognising Bone Loading Exercises In Older Adults Using Machine Learning

Machine learning has been used to accurately recognise physical activity patterns; however, classifiers for recognising targeted bone loading exercises have not been developed. PURPOSE: The purpose of this study was to determine the accuracy of machine learning models for classifying the intensity of exercises necessary for bone adaption in older adults. METHODS: Triaxial accelerometer data was collected from forty-four older participants (60-70 yrs) wearing a GCDC X16-1C accelerometer on their hip during three aerobics classes consisting of impact aerobic exercises performed at high and low intensities. Multi-class support vector machine (M-SVM) classifiers were trained in parallel for activity type detections where one classifier trained with low intensity activity samples and the other with high intensity samples. In a multi-view scoring manner, the classification confidence of these two learners was utilised for predicting the activity intensity. The leave-one-out cross-validation technique was used for assessment purpose. RESULTS: Overall recognition accuracy of the M-SVM classifier for detecting exercise intensity was 73%. For each aerobics class, the M-SVM classifier accurately recognised exercise intensity by 82%, 73% and 65%. CONCLUSIONS: Machine learning techniques such as M-SVM accurately recognised the intensity of bone promoting exercises from triaxial accelerometer data in community-dwelling older adults. First results of the developed classifier demonstrate significant potential of machine learning models for the evaluation of exercise adherence and performance in older adults.

Well-type NaI(Tl) detector efficiency using analytical technique and ANGLE 4 software based on radioactive point sources located out the well cavity

Well-type detectors play an important role in qualitative and quantitative analysis of low-activity samples, thanks to their pronouncedly high efficiency; this is particularly the case with scintillation detectors. In this work a theoretical approach to calculations of full-energy peak efficiencies of well-type detectors is elaborated. The approach is based on the concept of the effective solid angle and the efficiency transfer principle. In parallel, ANGLE 4 software was employed to the same aim, using point sources positioned on 2″ × 2″ NaI(Tl) detector axis outside the detector well cavity. The theoretically obtained and ANGLE 4 calculated efficiency values were compared to the measured ones. These comparisons supported/confirmed both the theoretical concept and ANGLE 4 Software validity in well-type scintillation detectors calibration.

Characterization of a double‐sided silicon strip detector autoradiography system

The most commonly used technology currently used for autoradiography is storage phosphor screens, which has many benefits such as a large field of view but lacks particle-counting detection of the time and energy of each detected radionuclide decay. A number of alternative designs, using either solid state or scintillator detectors, have been developed to address these issues. The aim of this study is to characterize the imaging performance of one such instrument, a double-sided silicon strip detector (DSSD) system for digital autoradiography. A novel aspect of this work is that the instrument, in contrast to previous prototype systems using the same detector type, provides the ability for user accessible imaging with higher throughput. Studies were performed to compare its spatial resolution to that of storage phosphor screens and test the implementation of multiradionuclide ex vivo imaging in a mouse preclinical animal study. Detector background counts were determined by measuring a nonradioactive sample slide for 52 h. Energy spectra and detection efficiency were measured for seven commonly used radionuclides under representative conditions for tissue imaging. System dead time was measured by imaging (18)F samples of at least 5 kBq and studying the changes in count rate over time. A line source of (58)Co was manufactured by irradiating a 10 μm nickel wire with fast neutrons in a research reactor. Samples of this wire were imaged in both the DSSD and storage phosphor screen systems and the full width at half maximum (FWHM) measured for the line profiles. Multiradionuclide imaging was employed in a two animal study to examine the intratumoral distribution of a (125)I-labeled monoclonal antibody and a (131)I-labeled engineered fragment (diabody) injected in the same mouse, both targeting carcinoembryonic antigen. Detector background was 1.81 × 10(-6) counts per second per 50 × 50 μm pixel. Energy spectra and detection efficiency were successfully measured for seven radionuclides. The system dead time was measured to be 59 μs, and FWHM for a (58)Co line source was 154 ± 14 μm for the DSSD system and 343 ± 15 μm for the storage phosphor system. Separation of the contributions from (125)I and (131)I was performed on autoradiography images of tumor sections. This study has shown that a DSSD system can be beneficially applied for digital autoradiography with simultaneous multiradionuclide imaging capability. The system has a low background signal, ability to image both low and high activity samples, and a good energy resolution.

Ultra-low-background gamma spectroscopy for the measurement of environmental samples

This paper presents an ultra-low-level gamma spectrometer designed to achieve the lowest possible limit of detection and the optimal sensitivity for low-activity samples in environmental research applications. The spectrometer is composed of high-purity germanium and is shielded by a combination of four layers of low-activity materials. The passive shield is surrounded by five plastic-scintillator-based veto detectors to employ the anticoincidence technique. Laboratory tests demonstrate that the background count rate in the range of 40–2,700 keV is 50(20) × 10−3 cps kg−1 Ge. The concept and performance of the system were also investigated using a Monte Carlo simulation method.

The CERN n_TOF Facility: Neutron Beams Performances for Cross Section Measurements

This paper presents the characteristics of the existing CERN n_TOF neutron beam facility (n_TOF-EAR1 with a flight path of 185 meters) and the future one (n_TOF EAR-2 with a flight path of 19 meters), which will operate in parallel from Summer 2014. The new neutron beam will provide a 25 times higher neutron flux delivered in 10 times shorter neutron pulses, thus offering more powerful capabilities for measuring small mass, low cross section and/or high activity samples.

EPHX1 gene polymorphisms among south Indian populations

Microsomal epoxide hydrolase is a smooth endoplasmic reticulum enzyme and is expressed relatively ubiquitously in most tissues and in many species. The microsomal epoxide hydrolase (mEH) encoded by EPHX1 is a biotransformation enzyme that metabolizes numerous reactive epoxide intermediates to more water-soluble trans-dihydrodiol derivatives. In the present study, we genotyped two SNPs of the EPHX1 gene [(Exon 3: Tyr113His; rs1051740) and (Exon 4: His139 Arg; rs2234922)], using TaqMan allelic discrimination among 212 individuals of six major south Indian populations, and compared with other available world populations data. Both polymorphisms followed Hardy-Weinberg equilibrium and were highly polymorphic in the studied populations. The haplotype based analysis revealed remarkable variation among the study populations. Linkage disequilibrium (LD) between Tyr113 His and His139Arg loci was not significant in any of the population studied. Calculation of LD in the 20kb up and downstream regions from Tyr113His and His 139Arg loci in HapMap populations revealed no significant LD between these markers in all the populations. Analysis of predicted EPHX1 activity status of all samples revealed that the prevalence of low activity samples is more than the intermediate and high activity samples in all populations studied. Screening of additional populations and computation of genetic distances between populations at SNP sites may help in understanding the population genetic and evolutionary aspects of this gene.

Contamination Analysis of Radioactive Samples in Focused Ion Beam Instruments

The use of Focused Ion Beam (FIB) instrument's to analyze and prepare samples that are radioactive requires attentiveness to the materials that are dislodged and free inside the chamber. Radioactive sputtered material must be understood even when observed at trace concentrations. Measurements using liquid scintillation counting and high purity germanium detectors were used to evaluate contamination on accessible surfaces inside a focused ion beam chamber that was used in the preparation of samples that were radioactive. The maximum removable contamination found was 0.27 0.4 Bq cm(-2), on the focused ion beam wall with 0.24 0.019 Bq cm(-2) on the door. Although these magnitudes of removable contamination are inconsequential for activation products, these same magnitudes of actinides, for example 239Pu, would represent 3.2% of an Annual Limit of Intake. This might be considered significant if one examines the relatively infrequent use of this device for the preparation of radioactive samples. Predicted activities of sputtered material were found using the software Transport of Ions in Matter, estimating that 0.003% of a radioactive samples activity is released into the FIB chamber. A used secondary electron detector's activity was measured to be 383.7 8.1 Bq. Preferential build-up of sputtered materials due to temperature or static charge gradients was considered. No temperature gradients were observed. Static charge gradients were measured inside the chamber varying between 0.057% below the mean to 34% higher than the mean. However, the magnitudes of contamination measured did not correlate to static charge gradients. Deposition in the chamber appears to have no mechanical cause but rather is sporadic however, measureable. Experience to date has been limited to samples of low activity; nevertheless, contamination inside the chamber was observed. Users should anticipate higher levels of readily dispersible radioactive contamination within the FIB as sample activity increases.

Identification of bioactive metabolites against adenosine A1 receptor using NMR-based metabolomics

Marine sponges are relatively less explored for their chemical features but highly anticipated resource for bioactive compounds. In this paper we report the screening of marine sponges crude extracts for their potential to bind the adenosine A1 receptor. Many samples showed very promising activity and in order to identify the active components, a metabolomics-chemometrics approach is employed. Nuclear magnetic resonance spectroscopy is used for the metabolic profiling of the marine sponges and partial least squares (PLS) and orthogonal PLS (OPLS) algorithms are used to correlate the metabolomics with bioactivity data. Using several two dimensional-NMR techniques, the resonances responsible for the separation of high activity samples from the medium and low activity samples were identified as associated to metabolites like halisulfate 1, halisulfate 3–5, and suvanine (1–5), all belongs to sesterterpenes class. The reference compounds for these metabolites are also tested for the activity, which endorse the findings of the applied methodology.

Semi-quantitative analysis of leaf surface contamination by radioactivity from the Fukushima Daiichi nuclear power plant accident using HPGe and imaging plate

After the nuclear power plant accident at Fukushima Daiichi on 11 March 2011, green-leaves from trees, dead-leaves and grass on ground were collected from March to June 2011 in Japan. Radioactive concentrations were measured by a high purity germanium detector. Five radionuclides including 129mTe, 132Te, 131I, 134Cs and 137Cs were detected. The fission product concentration of the dead-leaves was higher than those of the green-leaves in many cases. The highest concentration observed was found on the dead-leaves collected at Iwaki, 60 km far from Fukushima Daiichi. A total activity of 2,000 Bq g−1 was measured for all 5 radionuclides. Clear images of radioactivity of the highly contaminated leaves were obtained with an imaging plate (IP) after <24 h exposure time without using a shielded box. The photostimulated luminescence values (PSL) of leaves arranged on half size of IP were roughly in proportion to their activities except for the low activity samples. Semi-quantitative analysis was possible by using PSL values with a large region of interest of half size of IP, because the radioactivity released in the case of the nuclear power plant accident was uniform in the early days.

Continuous separation of Sr, Y and some actinides by mixed solvent anion exchange and determination of 89,90Sr, 238,239Pu and 241Am in soil and vegetation samples

Methodology for the determination of 89,90Sr, Am and Pu isotopes in complex samples is given. Methodology is based on simultaneous isolation of Sr, Y and actinides from samples by mixed solvent anion exchange chromatography, mutual separation of 89,90Sr and 90Y from actinides, mutual separation of Th, Pu and Am by extraction chromatography, quantitative determination of 89,90Sr by Cherenkov counting and quantitative determination of Pu and Am isotopes in soil and vegetation samples by alpha spectrometry. It is shown that Y and Sr can be efficiently separated from alkaline, alkaline earth and transition elements as well as from lanthanides and actinides on the column filed by strong base anion exchanger in nitrate form and 0.25 M HNO3 in mixture of ethanol and methanol as eluent. It is also shown that Pu, Am and Th strongly binds on the mentioned column, can be separated from number of elements and easily be eluted from column by water. After elution actinides were mutually separated on TRU column and electrodeposited on stainless steel disc. Examination of conditions of electrodeposition was shown that chloride-oxalate electrolyte with addition of DTPA in presence of sodium hydrogen sulphate in cell with cooling and rotating platinum anode enables deposition of actinides within 1 h by 0.8 A cm−2 current density. Obtained peaks FWHM for Pu, Am and Th isotopes are between 27 and 40 keV. Scanning electron microscopy picture and ED XRF analysis of electroplated discs showed that actinide deposition is followed by iron oxide formation on disc surface. The methodology was tested by determination of 89,90Sr, Am and Pu isotopes in ERA proficiency testing samples (low level activity samples). Obtained results shows that 89,90Sr, 241Am and 238,239Pu can be simultaneously separated on anion exchange column, 89,90Sr can be determined by Cherenkov counting with a satisfactory accuracy and limit of determination within 1–3 days after separation. 241Am and 238,239Pu can easily be separated on TRU column and determined after electrodeposition with acceptable accuracy within 1 day.