Approaches for reduction of the temperature bias on radon detectors packed in anti-thoron polymer membranes.

Passive and active detectors used for radon (222Rn) measurements can be influenced by thoron (220Rn). Polyethylene membranes are very appropriate diffusion barriers for anti-thoron protection of such detectors. However, if not properly chosen, these membranes may not reduce efficiently the thoron influence or could introduce temperature bias in the radon sensitivity of the detectors. In this work three approaches are proposed dealing with the thoron influence and the temperature bias introduced by packing in polymer membranes. The approaches exploit a model of the radon and thoron diffusion transport through the membranes and the already known diffusion properties of the membranes to estimate the thoron influence and the temperature bias and to take them into account. The approaches are experimentally verified. It is shown that, in some cases, with the proper choice of membrane the thoron influence could be reduced down to few percents introducing only a few percents temperature bias. Additionally, in the cases when temperature bias is significant and cannot be avoided (the thoron bias in that cases is shown to be below 1%), the proposed approaches allow to estimate and to correct that bias.

[First results of clinical diagnostic analysis of post-COVID peripheral neuropathy]. / Pervye rezul'taty kliniko-diagnosticheskogo analiza postkovidnoi perifericheskoi nevropatii.

This analysis of ocular manifestations of the COVID-19 that can occur both in the acute and the post-COVID period focuses on pathological changes associated with hypercoagulation: thrombosis of the central retinal vein, occlusion of the central retinal artery, and decreased peripapillary perfusion. Potential changes in corneal nerve fibers (CNF) associated with coronavirus infection remain poorly understood. Meanwhile, previous studies have shown the possibility of using CNF as biomarkers of polyneuropathy (PNP). PURPOSE: To study clinical and diagnostic features of post-COVID PNP. MATERIAL AND METHODS: We examined 9 female patients aged 32 to 51 years who had suffered an infection caused by SARS-CoV-2 of varying severity. The patients were divided into two groups: the first consisted of 6 patients with clinical manifestations of PNP in the form of neuropathic pain, the second - 3 patients without clinical manifestations. Patients of group 1 underwent comprehensive examination including neurological examination, confocal microscopy of the cornea (in vivo CM), electroneuromyography (ENMG) of the nerves of the upper and lower extremities, quantitative sensory testing in the zone of painful sensations, while patients of group 2 only underwent in vivo CM. RESULTS: All patients of the first group, within 5-40 days after the onset of infection caused by SARS-CoV-2, exhibited symptoms of damage to various parts of the nervous system (peripheral nerves, thoracic spinal roots, trigeminal nerve). The main - and in most cases the only - symptom of the disease was neuropathic pain syndrome. In Guillain-Barré syndrome, for the first time using in vivo CM, the following changes were revealed: enlargement of in Langerhans cells, shortening of CNF and their processes, presence of neuromas. CONCLUSION: The standard neurological examination of patients with post-COVID neuropathy should be supplemented with special diagnostic methods for assessment of structural and functional state of the peripheral nerves. The in vivo CM method is capable of non-invasive assessment of changes in thin CNF and, with accumulation of empirical data, can be included in the algorithm for diagnosing post-COVID PNP.

Methods for the experimental study of 220Rn homogeneity in calibration chambers.

This work presents two experimental methods for the evaluation of 220Rn homogeneity in calibration chambers. The first method is based on LSC of the 220Rn decay products captured in silica aerogel. The second method is based on application of solid state nuclear track detectors facing the air of the calibration chambers. The performances of the two methods are evaluated by dedicated experiments. The repeatability of the LSC-based method, estimated as relative standard deviation of the LSC measurements of ten silica aerogel samplers exposed under the same conditions is found to be 1.6%. Both methods are applied to study thoron homogeneity in the commercially available 50 L AlphaGuard emanation and calibration container, which was empty and its fan was turned on. It was found that the 220Rn distribution in this case is homogeneous within 10%. Both methods are also applied to test the thoron homogeneity in the BACCARA chamber at IRSN during a thoron calibration exercise. The results show that, at the centre of the chamber where the inputs of the sampling systems of the radon/thoron detectors were put close to each other, the thoron inhomogeneity is less than 10%. However, regions of higher thoron concentrations are clearly identified near the walls and the upper part of the chamber, with 220Rn concentrations being up to 60% higher compared to the concentration at the reference point. These results highlight the importance of the control and assessment of thoron homogeneity in thoron calibrations and in the cases when radon monitors are checked for thoron influence.

Identifying radon priority areas and dwellings with radon exceedances in Bulgaria using stored CD/DVDs.

The implementation of the 2013/59/EURATOM directive in the part related to radon exposure imposes challenges for radon measurement methodology and radon survey design. Among them is the need to have estimates (preferably direct) of the annual average radon concentrations, which can be directly compared to the recommended reference levels. On this basis, the surveys should make possible the identification of dwellings with indoor radon above the reference levels and "radon priority areas" where significant proportion of the dwellings falls in this category. The performance of the CD/DVD method for radon measurements as a tool to address these issues is presented. A recent large scale field study based on the CD/DVD method that was carried out in the suburb area of Sofia, Bulgaria is described. Part of the studied area was affected in the past by the uranium mining and milling industry. In total 462 disks (CDs and DVDs) taken from 335 private dwellings from 10 districts in the region were analyzed. The results revealed the large heterogeneity in radon distribution in the area, with the percentage of dwellings with a 222Rn level above 300 Bq m-3 ranking from about 7% to 74%. The district of Yana, for which this percent was 74, was identified as the area of highest radon priority in the region. The paper also discusses how prompt identification of dwellings with radon above the reference level by CD/DVDs can be incorporated within an integrated approach to the radon problem. Within this approach the radon hazard is identified shortly after the stakeholder's decision to test, which allows fast solution of the problem without waiting the long (and usually demotivating) one-year period needed for direct results by the commonly used prospective methods.

Unperturbed, high spatial resolution measurement of Radon-222 in soil-gas depth profile.

This work presents a method for measuring the depth distribution of 222Rn activity in soil gas. The method is based on the capacity of polycarbonates to absorb 222Rn and on the possibility of performing sensitive measurements of 222Rn absorbed by the polycarbonates via liquid scintillation counting (LSC). The method is the following: cylindrical holes are drilled along a metal rod and Makrofol® N polycarbonate foils enclosed in polyethylene envelopes are placed in each hole. The rod is driven into the soil and kept for a certain time. As long as the rod is in the soil, the polycarbonate foils are exposed to the 222Rn concentration at their depth. At the end of the exposure the rod is pulled out and the foils are transferred to liquid scintillation (LS) vials filled with liquid scintillator. The 222Rn absorbed in the foils is then measured with a LS analyzer. The rod with the polycarbonate foils acts as a passive probe which senses the 222Rn concentration at different depths beneath the ground surface. The achievable minimum detectable 222Rn activity concentration with the equipment and conditions used in this study is around 12.5 kBq/m3. It can easily be lowered below 1 kBq/m3 if larger foils and low-background LS analyzers are used. Since the method does not require air sampling the depth distribution of 222Rn in the soil is unperturbed by the sampling. The spatial distribution and the maximum measurement depth are set by the distance between the holes and the depth to which the rod can be fixed into the ground. Results from in situ applications of the method in terrains with high 222Rn in soil-gas are reported, which demonstrate the feasibility and the usefulness of the proposed approach.

RADON-222 IN SOIL-GAS MEASUREMENTS BY COMPACT DISCS. COMPARISON TO DIFFUSION CHAMBER MEASUREMENTS.

This work presents the results from simultaneous measurements of 222Rn in soil-gas by compact discs (CDs) and diffusion chambers. The measurements were performed in three terrains with high, medium and low 222Rn-in-soil-gas concentrations. Good correlations between the CD measurements and the reference diffusion chamber measurements are observed. The results indicate that it is important to apply temperature correction in the CD measurements, in order to account for the actual temperature during the exposure of the CDs in the soil.

Balloon-expandable stents for recoarctation of the aorta in small children. Two centre experience.

BACKGROUND: In young patients with native aortic coarctation (CoA), the management of choice is surgery. However, in re-coarctation (re-CoA) surgery is associated with increased morbidity and even mortality. Some children with native CoA present relative contraindications for surgery. METHODS: From 2006 to 2017, thirty-four patients (male n = 20; 59%) from two centres with re-CoA (31) and native CoA (3) were managed by stent implantation with premounted balloon expandable stents. Inclusion criteria were age < 3 years and >1 month, weight < 16 kg. Median age was 6,5 months (min. 1; max. 34 months), median weight 6,2 kg (min. 3,7; max. 16 kg). Thirteen patients (38%) had Re-CoA and hypoplastic left heart syndrome (HLHS). In three patients (9%) the native CoA was stented due to contraindications for surgical treatment. RESULTS: All procedures were successful. The median peak invasive systolic pressure gradient declined from 31 mm Hg (max. 118; min. 4) to 0 mm Hg (max. 32; min.-7) (p < 0.001). The median minimal diameter of the narrowed segment of aorta increased from 3 mm (max. 6,9; min. 1,0) to 7 mm (max. 11,5; min. 3,5) (p < 0.001). There were no serious complications. The median follow-up time was 12,5 months (max. 88; min. 0 month). During this time ten patients (29%) required re-dilatation and two of them re-stenting. CONCLUSION: Percutaneous stent implantation for Re-CoA and in selected patients for native CoA can be performed successfully in very young patients with a good immediate hemodynamical result. However, repeated stent angioplasties and further on interventional 'opening' of the stent is necessary to augment the aorta to adult size.

Diffusion lengths and partition coefficients of 131mXe and 85Kr in Makrofol N and Makrofol DE polycarbonates.

This work presents the results of an experimental study of the Makrofol® N and Makrofol® DE polycarbonate foils absorption properties of 85Kr and 131mXe. The diffusion lengths of 85Kr and 131mXe in both types of foils are determined. The partition coefficients of 85Kr from air and water and that of 131mXe from air in Makrofol® N are determined. The partition coefficients of 85Kr from water and 131mXe from air in Makrofol® DE are also determined. The parameters are determined for T = 22°C and allow for the full characterization of sorption and desorption of 85Kr and 131mXe in the foils at this temperature. The results from this study highlight the remarkable absorption ability of Makrofol® and especially of the Makrofol® N foil and show that it surpasses the Makrofol DE® foil not only as a Rn absorber, but also as Kr and Xe absorber.

Laboratory facility to create reference radon + thoron atmosphere under dynamic exposure conditions.

Radon (222Rn) and thoron (220Rn) levels in the environment are typically subject to significant random and systematic variations. Creation in the laboratory of reproducible and controlled exposure conditions close to that in the real environment can be useful for testing 222Rn and 220Rn detectors and for research. In this report the design and performance of a novel laboratory facility with such functionality is presented. The facility allows the exposure of detectors under controlled dynamic as well as static activity concentrations of 222Rn and 220Rn (pure and mixed) and temperature. The temperature is measured and regulated within -15 °C ÷ +60 °C by a dedicated programmable thermostat. Different reference activity concentrations in the exposure vessel are made by regulating the flow-rate of the air that flushes 222Rn/220Rn activity from the sources towards the exposure vessel. Reference atmospheres that contain 222Rn, 220Rn or a specified ratio of the two can be created. Pilot experiments that demonstrate the feasibility of the approach are presented. They include follow-up of a pre-defined temperature profile (in the range -5 °C ÷ +35 °C), test of the correspondence between planned and measured 222Rn and 220Rn activity concentrations, follow-up of a pre-defined dynamic profile of 220Rn concentrations and test of the possibility to create mixed 220Rn/222Rn atmospheres (experimentally checked for ratio of the activity concentrations from 0.27 to 4.5). The results from the experimental tests are in agreement with the values obtained by the developed theoretical model. The proposed approach can be used to plan and create stationary and dynamic reference exposure conditions that are close to the real exposure regimes in the environment.

Determination of (222)Rn absorption properties of polycarbonate foils by liquid scintillation counting. Application to (222)Rn measurements.

This work demonstrates that a Liquid Scintillation Counting (LSC) technique using a Triple to Double Coincidence Ratio counter with extending dead-time is very appropriate for the accurate measurement of (222)Rn activity absorbed in thin polycarbonate foils. It is demonstrated that using a toluene-based LS cocktail, which dissolves polycarbonates, the (222)Rn activity absorbed in thin Makrofol N foil can be determined with a relative standard uncertainty of about 0.7%. A LSC-based application of the methodology for determination of the diffusion length of (222)Rn in thin polycarbonate foils is proposed and the diffusion length of (222)Rn in Makrofol N (38.9±1.3µm) and the partition coefficient of (222)Rn in Makrofol N from air (112±12, at 20°C) and from water (272±17, at 21°C) are determined. Calibration of commercial LS spectrometers for (222)Rn measurements by LSC of thin polycarbonate foils is performed and the minimum detectable activities by this technique are estimated.

Influence of the type of CD case on the track density distribution in CDs exposed to thoron.

A novel approach for retrospective thoron (Rn-220) measurements in buildings was recently proposed. It employs CDs/DVDs as detectors, in which the alpha-tracks formed by thoron's progeny Po-212 are analyzed. Compact disks and DVDs that had been stored in their cases are suitable, because the case provides a fixed and reproducible geometry of the Po-212 source. Since the measurement and calibration procedures involve analysis of different pieces of the disk, it is important to test the homogeneity of the track density over the disk area. This report presents results of such a study, in which disks in different containers were exposed to thoron. In almost all disks, the track density was inhomogeneous, increasing significantly near the holes in the container through which thoron could enter. However, as demonstrated, in disks regularly used and randomly rotated in their containers, the track density is expected to homogenize. It is concluded that the homogeneity of the tracks should be tested in disks exposed to thoron in homes and should be estimated or compensated in calibration exposures.

Long-term consequences of anesthetic technique after cancer surgery.

UNLABELLED: The main treatment for most types of malignant tumors is their surgical removal. During the past years there has been a growing interest in the anesthesia effects on long-term surgery results in connection with cancer. Modern clinical and laboratory data indicate that the anesthetic technique may play a role in tumor dissemination and recurrence. The purpose of this study is to review the available literature data on the anesthetic techniques applied in oncology surgery, long-term consequences of anesthesia/analgesia and their relation to tumor progression. MATERIAL AND METHODS: We have reviewed the specialized medical literature and have analyzed the effects of anesthesia/analgesia on long-term results of surgical treatment--incidence of local recurrence, metastases and patients' survival. RESULTS: The hypothesis about the influence of the anesthesia type on long-term results after cancer surgery is generated. The use of anesthetics and analgesics with low potential for immunosuppression may reduce the relapse. This is a useful approach for patients with cancer. IN CONCLUSION: Further randomized controlled trials are required for extensive research of this problem.

A high-sensitivity method for the measurement of 222Rn based on liquid scintillation counting of polycarbonate powder.

This work describes a technique for the measurement of 222Rn by absorption in polycarbonate (PC) powder and liquid scintillation counting (LSC). The work is an improvement of the recently proposed method for 222Rn measurements by LSC of exposed PC grains. It is demonstrated that the use of PC powder as a 222Rn sampler improves 13.6 times the sampling efficiency and leads to 6.5 times smaller minimmal detectable activity concentrations (MDAC) compared with the PC grains used so far. For a 40-h exposure of 7.4-g PC powder to 222Rn in air, the MDAC with a RackBeta 1219 LS counter is 62 Bq m(-3) (assuming a 8-h sample counting time and 24-h background time). For the same conditions the estimated 222Rn MDAC with a Quantulus 1220 LS counter is 20 Bq m(-3). The proposed technique is suitable for radon in air and radon in soil-gas measurements.

Liquid scintillation counting of polycarbonates: a sensitive technique for measurement of activity concentration of some radioactive noble gases.

This work explores the application of the liquid scintillation counting of polycarbonates for measurement of the activity concentration of radioactive noble gases. Results from experimental studies of the method are presented. Potential applications in the monitoring of radioactive noble gases are discussed.

[Hypotension and hydration during spinal anesthesia for caesarean section].

Spinal anesthesia is the technique of choice for elective cesarean section. It is easily achievable, fast and reliable technique. Maternal hypotension is a complication of spinal anesthesia, which is associated with adverse effects on both the mother and the fetus. Thus, the aim of the anesthesiologists should be to treat maternal hypotension quickly and efficaciously, or better yet, to actively prevent it. In current practice the application of vasopressors to maintain arteriolar tone is the most widely used strategy for the prevention of hypotension induced by spinal anesthesia. Other methods such as left tilt of the operating table, decreasing aortocaval compression and hydration are also routinely applied. Possible four different methods of intravascular hydration: (1) crystalloid preloading, (2) colloid preloading, (3) crystalloid co loading, and (4) colloid co loading.

[Multipurpose treatment of vaginal infections].

Untreated bacterial vaginosis is related with many complications for non-pregnant women in reproductive age, most common from them are vaginal discharge and postoperative infections. The aim of our investigation was to compare the effectiveness of two therapeutic regimes which consist in Macmiror/Macmiror Complex alone and in combination with Feminella Vagi C for treatment of bacterial vaginosis (BV) and/or mycotic infection. 117 non-pregnant women with symptoms of vaginal infection were prospectively enrolled into two groups according their treatment. First group consist 66 women treated with Macmiror tablets and vaginal capsules followed with local application of Feminella Vagi C, the second group consist 54 women treated with Macmiror tablets and vaginal capsules only. The impact of treatment on clinical symptoms was observed at the end of medication and 20 days after it. Microbiological testing was repeated 20 days after treatment. Over than 80% (78.6 divided by 86.7%) of the cases with vaginal infection (BV and mycotic one) were successfully treated with Macmiror/Macmiror Complex. Supplement treatment with Feminella Vagi C lead to higher percentage of clinically recovery (86.7% vs 84.6%), better microbiological cleaning (86.7% vs 82.1%) and longer effect of treatment. Used medication showed higher efficacy against BV than to fungal infection. According obtained results we may conclude that bacterial vaginosis was better treated with multipurpose treatment (Nifuratel, Nistatin and vit. C) than with Macmiror alone.

Logistic of surveys of retrospective radon concentrations by home-stored CDs/DVDs.

Recently, a method for rather precise retrospective (222)Rn measurements, based on home-stored compact disks (CDs)/DVDs, has demonstrated a promising potential for wide application. In Bulgaria, pilot surveys have been initiated based on voluntarily provided CDs/DVDs. The results showed that large-scale surveys could be efficiently organised. However, several problems were identified and are discussed in the report. The first is the relatively small proportion of participants (30-50 %) that actually provided disks. Other addressed topics include the compatibility between results of different disks from one place, the accuracy of dating CDs/DVDs and the possibility for individual a posteriori calibration of each disk. The possibility to follow year-to-year variations by disks of different age is also discussed.

Determination of the diffusion coefficient and solubility of radon in plastics.

This paper describes a method for determination of the diffusion coefficient and the solubility of radon in plastics. The method is based on the absorption and desorption of radon in plastics. Firstly, plastic specimens are exposed for controlled time to referent (222)Rn concentrations. After exposure, the activity of the specimens is followed by HPGe gamma spectrometry. Using the mathematical algorithm described in this report and the decrease of activity as a function of time, the diffusion coefficient can be determined. In addition, if the referent (222)Rn concentration during the exposure is known, the solubility of radon can be determined. The algorithm has been experimentally applied for different plastics. The results show that this approach allows the specified quantities to be determined with a rather high accuracy-depending on the quality of the counting equipment, it can be better than 10 %.

[Congenital rhabdomyoma--prenatal diagnosis with three-dimensional ultrasound of two cases with different pregnancy outcome].

Congenital rhabdomyoma is the most common benign tumor of the fetal heart. Usually it occurs as a single or multiple lesions located within the ventricles and it is often associated with tuberous sclerosis after birth. We present two cases of congenital rhabdomyoma diagnosed in the third trimester with three-dimensional (3D) ultrasound. Both cases had different pregnancy outcome.