Radon in indoor air and water: design and development of experimental apparatuses and measurement protocols

Exposure to the decay products of radon (used in brief to refer to the isotope 222 of Rn) and thoron (used to refer to the isotope 220 of Rn) represents, on average, approximately half of the overall effective dose from natural sources suffered per year by the global population, i.e. 2.4 mSv per year. In particular, the UNSCEAR Report from 2008 reports effective doses due to radon and thoron inhalation of 1.15 mSv per year and 0.1 mSv per year, respectively. Due to the relatively low outdoor concentration, most of the exposure to radon occurs indoor where a wide variability exists in radon daughters concentration. Both temporal and spatial variability of the equilibrium factors surely reflects on radon progeny variability, but the latter is mainly caused by the difference in indoor radon concentration over time and from an indoor place to another. According to the cite{WHO2009}, indoor radon concentration depends on two main factors: typology of building construction and ventilation specifications and habits. Both of them affect the indoor radon concentration by influencing the relative contributions of the various radon sources. Several authors suggest that radon can enter building interiors: directly from soil due to radium-containing rocks still in the crust; via radon-carriers utilities such as water and, in principle, natural gas; indirectly from crustal materials no longer incorporated in crust but contained into building structure in the form of concrete, brick and the like. end{itemize} The relative contribution of each of these entry patterns obviously depends on specific circumstances, i.e. building characteristics (including building materials, construction typology and floor level), morphology and composition of the underlying soil, ventilation features, occupancy patterns and living habits of occupants. Council Directive 2013/59/EURATOM requires Member States to emph{consider} any source of radon ingress, whether from soil, building materials or water. This is required when preparing the national action plan to address long-term risks from radon exposure. In particular, regarding building materials, Member States are explicitly required to identify (and/or develop) strategy, including methods and tools, to identify building materials with significant radon exhalation rate. Pertaining to building materials, several measurements of radon exhalation rate have been reported on literature through the years (more references are available in the text). However, as firstly highlighted by Sahoo (in 2011), the difference between radon exhalation from samples and that from walls has not been investigated enough. As a result of this lack of knowledge, measurements of radon exhalation from building materials samples have been commonly used to assess the effective dose attributable to radon exhaled from walls in indoor environment even though different geometries and boundary conditions characterize the two scenarios. In fact, if the one dimensional (1-D) geometry better describes the radon flux from masonry surfaces, mainly walls, it is not suitable to the radon exhalation from a sample of building material, the latter better modelled as a three dimensional (3-D) phenomenon. At the present state of knowledge and technology, two main possibilities exist to provide reliable values of radon exhalation rate from a wall. The first is estimating the radon surface exhalation rate from a wall as related to that from a building material sample. This approach has been proposed by and recalled by Orabi (n 2018). It relies on the comparison between the 3-D model of the radon flux from the building material sample and the 1-D model used to assess flux from a wall made up by the same material. The 1-D model solution proposed by the authors -- firstly reported by and later recalled by -- is obtained under three main conditions: i) the diffusion is the only mechanism governing the radon transport, ii) the radon concentration inside the wall is an even function, symmetric with respect to the wall half thickness and iii) the room inner volume is much higher than the void wall volume. In other words, the solution is valid only when advective contribution is negligible and both wall surfaces are free to exhale into a radon-free space. As a matter of fact, the boundary conditions adopted by Sahoo and Orabi, despite being far from commonly verified, are not even declared at all. The resulting formulations can so lead to misleading predictions of radon surface flux from an existing wall. The issue just described is an evidence of the need to provide a systematic review of the differential equations describing the radon migration, as well as the corresponding solutions for any reasonable boundary conditions sets. This task has been accomplished by the Chapter 2 of this work. The aim is to provide the readers with a comprehensive description of how typical scenarios for radon transport are mathematically modelled as well as to clarify the assumptions underlying the solutions. In particular, the review has addressed either diffusive, advective and diffusive plus advective transport of radon through a slab, the latter containing radium sources or not, in different scenarios. The second possibility to provide reliable values of radon exhalation rate from a wall is in-situ measuring radon exhalation rate directly from the wall surface, i.e. through the so-called accumulation method described by ISO 11665-7. To the author knowledge, no published study exists of in-situ applications of the ISO method to vertical surfaces. This is mainly due to the several issues affecting the measuring apparatuses available on the market. Firstly, they are not specifically designed for vertical surfaces so they are not self-standing and equipped with a frame supporting the accumulation can. Secondly, they are not provided with sealing systems of any kind and the air exchanges between inside and outside the accumulation container, other than not being prevented, are not traceable at all. Besides, they are sold by the continuous radon monitor manufacturers, so the compatibility is assured only with a specific model of a specific detector. Furthermore, the analysis of the radon concentration registered to obtain exhalation rate value is a quite slow, multi-step and not automatized process completely up to the operator. Chapter 3 of this work deals with design, commissioning and realization of the first custom apparatus specifically conceived to in-situ measure the radon exhalation rate directly from walls vertical surfaces. The prototype, fully developed at the Laboratory of Radioactivity of the Italian National Institute of Health, is intended to solve such critical issues that have prevented similar apparatuses from being adopted by the radon experts: mechanically sustaining the accumulation can during the measurement without interfering with the measurements itself (i) and assuring the sealing of the chamber relative to the radon detector (ii) and the wall under investigation (iii). The prototype also aims to avoid the interfering effect of the chamber pressurization during the measurement and to reduce the effect of the back-diffusion on the accumulation process. The apparatus presented has been already successfully used in some surveys in large buildings to reconstruct the likely radon migration path through some surface flux measurements at different locations in different rooms. The apparatus has been designed for a specific continuous radon monitor model but the configuration can be adapted, with very few modifications, to other radon detectors. The choice comprehends the large number of low-cost detectors that entered, and are still entering, the market in the last few years. This quite recent and sudden entry into the market of a large number of different detectors for both professional and "domestic" purpose has turn a spotlight on the need of increasing the number of testing facilities and calibration apparatuses. These facilities should always rely on radon chambers that are designed to produce reference atmospheres whose radon activity concentration depends on the radium source employed and on the chamber volume. According to the current state of the art, radon chambers are characterized by significant costs as design, construction, commissioning, and maintenance are concerned. In particular, critical issues are i) materials used for the structure and the sealing, ii) fan system for concentration homogenization, iii) source-chamber interface circuit and iv) control instrumentation. Furthermore, industries, agencies or institutions managing a radon chamber need as many radium sources as the radon concentrations required by the different calibration protocols. Holding more than one source complicates the licensing requirements concerned with radioactive materials possession established by the national transpositions of the Council Directive 2013/59/Euratom. Chapter 4 of this work describes an innovative 0.1 m^3 radon chamber fully designed, built and tested at the laboratory of Radiation Protection of Sapienza -- University of Rome. It has been conceived as and easy-to-assemble, cheap and small facility dedicated to research on radon and calibrations services. The main innovation stands in the way radon activity concentration is varied and controlled within the chamber atmosphere: the system, in fact, may allow to establish a wide range of Rn concentrations through a single Ra source placed outside the control volume and by means of two air circulation circuits controlled by specific electric pumps remotely controlled and actuated. On view of this, the apparatus is intended to be suitable for several applications, such as: i) calibrating both passive and active radon detectors at different radon concentrations, ii) checking the response linearity of both passive and active radon detectors and iii) studying the dynamic response of the continuous radon monitors to sudden changes in radon concentration. Pertaining to the water as an indoor exposure source to radon, the Council Directive 2013/51 introduced several requirements to Member States about radon concentration in water, including: i) to adopt a parametric value above which the risk has to be evaluated and remedial actions have to be considered, and ii) to carry out representative surveys in order to identify water sources whose radon content might exceed such a parametric value. The implementation of the Council Directive has led to a considerable increase of radon concentration measurements in drinking waters. The Directive indicates for the method of analysis a minimum limit of detection (or detection limit, DL) of 10 Bq per L, i.e. 10% of the parametric value. Test methods satisfying such a limit are, mainly, gamma-ray spectrometry, liquid scintillation counting, and emanometry, whose achievable lowest detection limit are 10, 0.05 and 0.04 Bq per L, respectively. Findings from previous studies showed no statistically significant differences between results from the three different measuring techniques. The test method using emanometry, regulated by the international standard ISO 13164-3, has been used in several surveys thanks to its advantages: mainly, the possibility to use different detectors with low-to-moderate costs (i.e. 1-20 k€), the low achievable uncertainty (i.e. up to 5%), the suitability for in-situ measurements and the very short turnaround time. Chapter 5 of this work deals with the development of a specific quality assurance (QA) protocol for measurements of radon in water contemporary performed with different measuring chains by emanometry technique. This protocol is intended to allow increasing the number of measurements performed, i.e. samples analysed per day, considering that, for the emanometry test method, the water samples have to be analysed one at a time. The effectiveness of such a protocol has been evaluated by studying the results reproducibility and participating to an international proficiency test organized by the European Commission Joint Research Centre (JRC). The quality assurance protocol has been so adopted, with excellent results, during the first survey addressing the radon concentration in self-bottled mineral spring waters

Minimal flavor-changing Z′Z' models and muon g−2g-2 after the RK∗R_{K^*} measurement

There has been a steady interest in flavor anomalies and their global fits as ideal probes of new physics. If the anomalies are real, one promising explanation is a new $Z'$ gauge boson with flavor-changing coupling to bottom and strange quarks and a flavor-conserving coupling to muons and, possibly, electrons. We point out that direct production of such a $Z'$, emerging from the collision of $b$ and $s$ quarks, may offer a complementary window into these phenomena because collider searches already provide competitive constraints. On top of that, we analyse the same $Z'$ scenario in relation to another long-standing discrepancy between theory and experiment that concerns the anomalous magnetic moment of the muon. By scanning the allowed $Z'$ coupling strengths in the low-mass region, we assess the compatibility of the signals from LHCb with the $Z'$ searches in the high energy LHC data and the measurements of the anomalous magnetic moment of the involved leptons. We also argue that observations of the latter can break the degeneracy pattern in the Wilson coefficients $C_9$ and $C_{10}$ presented by LHCb data. The $Z'$ model we consider is compatible with the new measurement of $R_{K^*}$, therefore it can potentially account for the long-standing deviations observed in $B$-physics.Comment: 13 pages, 5 figures. Missing factors corrected in eqs. 2.7-2.9 with slight updates in fig.

Indoor Radon: Sources, Transport Mechanisms and Influencing Parameters

Population exposure to indoor radon has been proven to increase the risk of lung cancer, and it is considered a leading cause after tobacco smoking. Due to the relatively low outdoor activity concentration, most of the exposure to radon occurs indoors. Radon is generated mostly by the rocks that contain radium-226 either in the soil or in the building materials. Once generated, it enters the buildings directly, due to the activity concentration gradient, or indirectly via a radon carrier. The magnitude and the relative contribution of the entry patterns depend mainly on the building characteristics, the geology, and the living habits of occupants

Ultra high throughput sequencing excludes MDH1 as candidate gene for RP28-linked retinitis pigmentosa

PURPOSE: Mutations in IDH3B, an enzyme participating in the Krebs cycle, have recently been found to cause autosomal recessive retinitis pigmentosa (arRP). The MDH1 gene maps within the RP28 arRP linkage interval and encodes cytoplasmic malate dehydrogenase, an enzyme functionally related to IDH3B. As a proof of concept for candidate gene screening to be routinely performed by ultra high throughput sequencing (UHTs), we analyzed MDH1 in a patient from each of the two families described so far to show linkage between arRP and RP28. METHODS: With genomic long-range PCR, we amplified all introns and exons of the MDH1 gene (23.4 kb). PCR products were then sequenced by short-read UHTs with no further processing. Computer-based mapping of the reads and mutation detection were performed by three independent software packages. RESULTS: Despite the intrinsic complexity of human genome sequences, reads were easily mapped and analyzed, and all algorithms used provided the same results. The two patients were homozygous for all DNA variants identified in the region, which confirms previous linkage and homozygosity mapping results, but had different haplotypes, indicating genetic or allelic heterogeneity. None of the DNA changes detected could be associated with the disease. CONCLUSIONS: The MDH1 gene is not the cause of RP28-linked arRP. Our experimental strategy shows that long-range genomic PCR followed by UHTs provides an excellent system to perform a thorough screening of candidate genes for hereditary retinal degeneration

Surface exposure ages imply multiple low-amplitude Pleistocene variations in East Antarctic Ice Sheet, Ricker Hills, Victoria Land

One of the major issues in (palaeo-) climatology is the response of Antarctic ice sheets to global climate changes. Antarctic ice volume has varied in the past but the extent and timing of these fluctuations are not well known. In this study, we address the question of amplitude and timing of past Antarctic ice level changes by surface exposure dating using in situ produced cosmogenic nuclides (10Be and 21Ne). The study area lies in the Ricker Hills, a nunatak at the boundary of the East Antarctic Ice Sheet in southern Victoria Land. By determining exposure ages of erratic boulders from glacial drifts we directly date East Antarctic Ice Sheet variations. Erosion-corrected neon and beryllium exposure ages indicate that a major ice advance reaching elevations of about 500m above present ice levels occurred between 1.125 and 1.375 million years before present. Subsequent ice fluctuations were of lesser extent but timing is difficult as all erratic boulders from related deposits show complex exposure histories. Sample-specific erosion rates were on the order of 20-45cmMa-1 for a quartzite and 10-65cmMa-1 for a sandstone boulder and imply that the modern cold, arid climate has persisted since at least the early Pleistocen

Camera- and Viewpoint-Agnostic Evaluation of Axial Postural Abnormalities in People with Parkinson’s Disease through Augmented Human Pose Estimation

Axial postural abnormalities (aPA) are common features of Parkinson’s disease (PD) and manifest in over 20% of patients during the course of the disease. aPA form a spectrum of functional trunk misalignment, ranging from a typical Parkinsonian stooped posture to progressively greater degrees of spine deviation. Current research has not yet led to a sufficient understanding of pathophysiology and management of aPA in PD, partially due to lack of agreement on validated, user-friendly, automatic tools for measuring and analysing the differences in the degree of aPA, according to patients’ therapeutic conditions and tasks. In this context, human pose estimation (HPE) software based on deep learning could be a valid support as it automatically extrapolates spatial coordinates of the human skeleton keypoints from images or videos. Nevertheless, standard HPE platforms have two limitations that prevent their adoption in such a clinical practice. First, standard HPE keypoints are inconsistent with the keypoints needed to assess aPA (degrees and fulcrum). Second, aPA assessment either requires advanced RGB-D sensors or, when based on the processing of RGB images, they are most likely sensitive to the adopted camera and to the scene (e.g., sensor–subject distance, lighting, background–subject clothing contrast). This article presents a software that augments the human skeleton extrapolated by state-of-the-art HPE software from RGB pictures with exact bone points for posture evaluation through computer vision post-processing primitives. This article shows the software robustness and accuracy on the processing of 76 RGB images with different resolutions and sensor–subject distances from 55 PD patients with different degrees of anterior and lateral trunk flexion

Pseudoperoxidase activity, conformational stability and aggregation propensity of the His98Tyr myoglobin variant. Implications for the onset of myoglobinopathy.

The autosomal dominant striated muscle disease myoglobinopathy is due to the single point mutation His98Tyr in human myoglobin (MB) [Olivè et al. Nat. Comm, 2019, 10, 1396], the heme-protein responsible for binding, storage and controlled release of O2 in striated muscle. In order to understand the molecular bases of this disease, a comprehensive biochemical and biophysical study on wt MB and the variant H98Y has been performed. Although only small differences exist between the active site architectures of the two proteins, the mutant exhibits an (i) increased reactivity towards hydrogen peroxide, (ii) a higher tendency to form high-molecular weight aggregates and (iii) is more prone to heme bleaching, possibly as a consequence of the observed H2O2-induced formation of the Tyr98 radical close to the metal center. These effects add to the impaired oxygen binding capacity and faster heme dissociation of the H98Y variant compared to wt MB. As the above effects result from bond formation/cleavage events occurring at the distal and proximal heme sites, it appears that the molecular determinants of the disease are localized there. These findings set the bases for clarifying the onset of the cascade of chemical events that are responsible for the pathological symptoms of myoglobinopathy

Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance

Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the “OFF” state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability

Plasmodium falciparum liver stage antigen-1 is cross-linked by tissue transglutaminase

Background Plasmodium falciparum sporozoites injected by mosquitoes into the blood rapidly enter liver hepatocytes and undergo pre-erythrocytic developmental schizogony forming tens of thousands of merozoites per hepatocyte. Shortly after hepatocyte invasion, the parasite starts to produce Liver Stage Antigen-1 (LSA-1), which accumulates within the parasitophorous vacuole surrounding the mass of developing merozoites. The LSA-1 protein has been described as a flocculent mass, but its role in parasite development has not been determined. Methods Recombinant N-terminal, C-terminal or a construct containing both the N- and C- terminal regions flanking two 17 amino acid residue central repeat sequences (LSA-NRC) were subjected to in vitro modification by tissue transglutaminase-2 (TG2) to determine if cross-linking occurred. In addition, tissue sections of P. falciparum-infected human hepatocytes were probed with monoclonal antibodies to the isopeptide ε-(γ-glutamyl)lysine cross-bridge formed by TG2 enzymatic activity to determine if these antibodies co-localized with antibodies to LSA-1 in the growing liver schizonts. Results This study identified a substrate motif for (TG2) and a putative casein kinase 2 phosphorylation site within the central repeat region of LSA-1. The function of TG2 is the post-translational modification of proteins by the formation of a unique isopeptide ε-(γ-glutamyl)lysine cross-bridge between glutamine and lysine residues. When recombinant LSA-1 protein was crosslinked in vitro by purified TG2 in a calcium dependent reaction, a flocculent mass of protein was formed that was highly resistant to degradation. The cross-linking was not detectably affected by phosphorylation with plasmodial CK2 in vitro. Monoclonal antibodies specific to the very unique TG2 catalyzed ε- lysine cross-bridge co-localized with antibodies to LSA-1 in infected human hepatocytes providing visual evidence that LSA-1 was cross-linked in vivo. Conclusions While the role of LSA-1 is still unknown these results suggest that it becomes highly cross-linked which may aid in the protection of the parasite as it develo