Status of the European indoor radon map

Since 2006 a European map of indoor radon (Rn) concentration is in the making. So far 20 countries have contributed with national data, allowing a fair coverage of parts of Europe. This paper presents the current (September 2010) state of the map, discusses its rationale, presents some statistical findings and addresses a few problems which arose during the work. It also briefly presents the European Atlas of Natural Radiation project, of which the Rn map will be part, and further, planned maps of environmental natural radioactivity.     

Au-Sn SLID Bonding: A Reliable HT Interconnect and Die Attach Technology

Au-Sn solid–liquid interdiffusion (SLID) bonding is an established reliable high temperature (HT) die attach and interconnect technology. This article presents the life cycle of an optimized HT Au-Sn SLID bond, from fabrication, via thermal treatment, to mechanical rupture. The layered structure of a strong and uniform virgin bond was identified by X-ray diffraction to be Au/ζ (Au_0.85Sn_0.15)/Au. During HT exposure, it was transformed to Au/β (Au_1.8Sn_0.2)/Au. After HT exposure, the die shear strength was reduced by 50 pct, from 14 Pa to 70 MPa, which is still remarkably high. Fractographic studies revealed a change in fracture mode; it was changed from a combination of adhesive Au/Ni and cohesive SiC fracture to a cohesive β-phase fracture. Design rules for high quality Au-Sn SLID bonds are given.     

Radon in indoor air of primary schools: a systematic survey to evaluate factors affecting radon concentration levels and their variability

In order to optimize the design of a national survey aimed to evaluate radon exposure of children in schools in Serbia, a pilot study was carried out in all the 334 primary schools of 13 municipalities of Southern Serbia. Based on data from passive measurements, rooms with annual radon concentration >300 Bq/m³ were found in 5% of schools. The mean annual radon concentration weighted with the number of pupils is 73 Bq/m³, 39% lower than the unweighted 119 Bq/m³ average concentration. The actual average concentration when children are in classrooms could be substantially lower. Variability between schools (CV = 65%), between floors (CV = 24%) and between rooms at the same floor (CV = 21%) was analyzed. The impact of school location, floor, and room usage on radon concentration was also assessed (with similar results) by univariate and multivariate analyses. On average, radon concentration in schools within towns is a factor of 0.60 lower than in villages and at higher floors is a factor of 0.68 lower than ground floor. Results can be useful for other countries with similar soil and building characteristics.     

Au-Sn SLID Bonding—Properties and Possibilities

Au-Sn solid–liquid interdiffusion (SLID) bonding is a novel and promising interconnect technology for high-temperature applications. This article gives a review over previously published work on Au-Sn SLID bonding. An overview of the crystal phases and the thermomechanical properties of the Au-Sn phases relevant for Au-Sn SLID bonding is given. A summary of the bonding conditions used during Au-Sn SLID bonding is presented together with results from reliability tests. Additional challenges, possibilities, and recommendations for how a reliable high-temperature Au-Sn SLID bonding should be constructed are also discussed.     

Toxicity of synthetic naphthenic acids and mixtures of these to fish liver cells

Environmental concerns have been raised over the toxicity of crude naphthenic acids (NA) originating from oil exploration activities offshore, oil sands exploitation onshore, and use of refined NA as wood preservatives, tire additives, and in various other applications. The NA exist in highly complex mixtures, so the toxic effects of the individual acids are rarely known. The present study investigated the relationships between the chemical structures of a range of synthetic alicyclic and aromatic acids and their acute toxicities both as single chemicals and as complex mixtures in a primary culture of rainbow trout (Oncorhynchus mykiss) hepatocytes. The combined toxicity of multicomponent mixtures of these NA was assessed using the concept of concentration addition (CA) and independent action (IA) prediction. All of the acids tested were moderately toxic, with EC(50) values in the range 108-405 μM (24-89 mg L(-1)) and 188-656 μM (43-148 mg L(-1)) when assessed by effects on metabolic inhibition or loss of membrane integrity, respectively. Binary and 6-compound mixture of NA caused combined toxicity according to the concept of additivity, although slight deviations from additivity were observed at a few mixture concentrations. Single NA and mixtures of NA with similar structures to those tested herein probably contribute to the toxicity of complex natural mixtures of NA. Toxicity tests on three commercial NA mixtures showed that these exhibited highly variable toxicities themselves probably reflecting their chemical heterogeneity.     

Assessment of long-term radon concentration measurement precision in field conditions (Serbian Schools) for a survey carried out by an international collaboration

In an international collaboration, a long-term radon concentration survey was carried out in schools of Southern Serbia with radon detectors prepared, etched and read-out in Italy. In such surveys it is necessary to evaluate measurement precision in field conditions, and to check whether quality assurance protocols were effective in keeping uncertainties under control, despite the complex organisation of measurements. In the first stage of the survey, which involves only some of the total number of municipalities, paired detectors were exposed in each monitored room in order to experimentally assess measurement precision. Paired passive devices (containing CR-39 detectors) were exposed for two consecutive 6-month periods. Two different measurement systems were used to read out CR-39s of the first and second period, respectively. The median of the coefficient of variation (CV) of the measured exposures was 8 % for 232 paired devices of the first 6-month period and 4 % for 242 paired devices of the second 6-month period, respectively. This difference was mainly due to a different track count repeatability of the two read-out systems, which was 4 and 1 %, respectively, as the median value of CV of repeated countings. The in-field measured precision results are very similar to the precision assessed in calibration conditions and are much lower than the room-to-room variation of radon concentration in the monitored schools. Moreover, a quality assurance protocol was followed to reduce extra-exposures during detector transport from Rome to schools measured and back.     

Inhibition of meizothrombin and meizothrombin(desF1) by heparin cofactor II

Meizothrombin and meizothrombin(desF1) are intermediates formed during the conversion of prothrombin to thrombin by factor Xa, factor Va, phospholipids, and Ca2+ (prothrombinase). These intermediates are active toward synthetic peptide substrates but have limited ability to interact with platelets or macromolecular substrates such as fibrinogen. Meizothrombin and meizothrombin(desF1) activate protein C, however, and may exert primarily an anticoagulant effect. In this study, we investigated the inhibition of meizothrombin and meizothrombin(desF1) by two glycosaminoglycan-dependent protease inhibitors, heparin cofactor II (HCII) and antithrombin (AT). Purified recombinant meizothrombin and meizothrombin(desF1) were inhibited by HCII in the presence of dermatan sulfate with maximal second-order rate constants of 8 x 10(6) M-1.min-1 and 1.8 x 10(7) M-1.min-1, respectively, but were inhibited less than one-tenth as fast by AT in the presence of heparin. Similarly, the products of the prothrombinase reaction were inhibited in situ more effectively by HCII than by AT. When HCII and dermatan sulfate were present continuously during the prothrombinase reaction, meizothrombin was trapped as a sodium dodecyl sulfate-stable complex with HCII and no amidolytic activity could be detected with a thrombin substrate. Our findings indicate that HCII is an effective inhibitor of meizothrombin and meizothrombin(desF1) and, therefore, might regulate the anticoagulant activity of these proteases.     

Speciation of lead, copper, zinc and antimony in water draining a shooting range—Time dependant metal accumulation and biomarker responses in brown trout (Salmo trutta L.)

The speciation of Pb, Cu, Zn and Sb in a shooting range run-off stream were studied during a period of 23 days. In addition, metal accumulation in gills and liver, red blood cell ALA-D activity, hepatic metallothionine (Cd/Zn-MT) and oxidative stress index (GSSG/ tGSH levels) in brown trout (Salmo trutta L.) exposed to the stream were investigated. Fish, contained in cages, were exposed and sampled after 0, 2, 4, 7, 9, 11 and 23 days of exposure. Trace metals in the water were fractionated in situ according to size (nominal molecular mass) and charge properties. During the experimental period an episode with higher runoff occurred resulting in increased levels of metals in the stream. Pb and Cu were mainly found as high molecular mass species, while Zn and Sb were mostly present as low molecular mass species. Pb, Cu and Sb accumulated on gills, in addition to Al origination from natural sources in the catchment. Pb, Cu and Sb were also detected at elevated concentration in the liver. Blood glucose and plasma Na and Cl levels were significantly altered during the exposure period, and are attributed to elevated concentrations of Pb, Cu and Al. A significant suppression of ALA-D was detected after 11 days. Significant differences were detected in Cd/Zn-MT and oxidative stress (tGSH/GSSG) responses at Day 4. For Pb the results show a clear link between the HMM (high molecular mass) positively charged Pb species, followed by accumulation on gills and liver and a suppression in ALA-D. Thus, high flow episodes can remobilise metals from the catchment, inducing stress to aquatic organisms.