Assessment of air pollution origin based on year-long parallel measurement of PM2.5 and PM10 at two suburban sites in Prague, Czech Republic.

From 2nd April 2008 to 28th March 2009, a total 248 daily samples of the PM2.5 and PM10 were collected every sixth day parallel at two suburban sites (Libus and Suchdol) located at the two opposite sides (south and north, respectively) of Prague, Czech Republic. The PM2.5 samples were analyzed for ions by ion chromatography (IC), organic and elemental carbon (OC and EC) by OC/EC analyzer and PM10 samples also for 56 elements by inductively coupled plasma-mass spectrometry (ICP-MS). The average annual PM2.5 and PM10 was 24.4 ±â€¯13.0 µg m-3 and 26.7 ±â€¯15.1 µg m-3, respectively, in Prague-Libus, and 25.1 ±â€¯22.1 µg m-3 and 27.1 ±â€¯23.2 µg m-3, respectively, in Prague-Suchdol. Since the species forming large part of the aerosol mass were strongly correlated (Spearman's rank correlation coefficient rs > 0.80), the variability of PM2.5 and PM10 concentration was mainly driven by the local meteorology or regional and/or long range transport. PM10 mass closure was calculated based on analytical results with the average percentage of recalculated mass of 77 ±â€¯19% in Prague-Libus and 86 ±â€¯16% in Prague-Suchdol. The most abundant groups in PM10 at both sites during the four seasons were OM (Prague-Libus 34% and Prague-Suchdol 37%) and SIA (Prague-Libus 30% and Prague-Suchdol 34%). The Positive Matrix Factorization (PMF) was applied to the chemical composition of PM10 from both sites (124 samples) together to determine its sources. The nine factors were assigned as: mixed factor secondary sulphate and biomass burning, secondary sulphate, traffic, secondary nitrate, road dust, residential heating, aged sea salt, industry and mixed factor road salt along with aged sea salt. According to the polar plots and ventilation index (VI) east/west classification analysis the sources were separated based on origin to four categories local, urban agglomeration, regional and long range transport (LRT). The mixed source secondary sulphate and biomass burning, residential heating and industry were common sources of local origin at both sites. Prague-Suchdol was influenced by traffic related pollution from the urban agglomeration more than Prague-Libus where the traffic and road dust/salt were of local origin. The regional pollution by secondary sulphates and nitrate was also relevant at both sites along with long range transport of sea salt from North Atlantic Ocean, Norwegian Sea and North Sea. The contribution of the local sources to PM10 was significant mainly at Prague-Libus site. However, the sources of regional origin were also important and influence of urban agglomeration pollution to PM10 is not negligible as well.

Facial approximation of Tycho Brahe's partial skull based on estimated data with TIVMI-AFA3D.

The virtual approach in physical and forensic anthropology is increasingly used to further analyze human remains, but also to propose new didactic means for visualization and dissemination of scientific results. Computerized facial approximation (FA) offers an alternative to manual methods, but usually requires a complete facial skeleton to allow for the estimation of the facial appearance of an individual. This paper presents the case of Tycho Brahe, Danish astronomer born during the XVIth century, whose remains were reanalyzed at the occasion of a short exhumation in 2010. Cranial remains of Brahe were poorly preserved, with only a partial facial skeleton, and virtual anthropology tools were used to estimate the missing parts of his skull. This 3D restoration was followed by a FA using TIVMI-AFA3D, subsequently textured with graphic tools. The result provided an interesting estimate that was compared with portraits of the astronomer. The impact of the missing data estimation was investigated by performing FAs on 10 complete test subjects and the same 10 subjects after cropping and estimating 50% of the landmarks (reproducing the preservation state of Tycho Brahe's cranial remains). The comparison between the FA based on the complete and incomplete skulls of the same subject produced a visual assessment of the estimation impact on FAs which is relatively low. This procedure is an alternative to manual methods and offers a reproducible estimate of a face based on incomplete cranial remains. Although the case report concerns a historical individual, the robust automatic estimation of missing landmarks followed by a FA has value for forensic caseworks as a support to the identification process.

Rich table but short life: Diffuse idiopathic skeletal hyperostosis in Danish astronomer Tycho Brahe (1546-1601) and its possible consequences.

The exhumation of Danish astronomer Tycho Brahe (1546-1601) was performed in 2010 to verify speculative views on the cause of his death. Previous analyses of skeletal and hair remains recovered from his grave refuted the presumption that he died from poisoning. These studies also outlined the possibility that he actually died from an acute illness, echoing the rather vague and inaccurate testimony of some historical records. We performed a detailed paleopathological analysis of Tycho Brahe's skeletal remains, along with a reconstruction of his diet based on carbon and nitrogen stable isotopes analysis and an estimate of his physical status (relative body fat) based on medullar and cortical dimensions of the femoral shaft. The astronomer's remains exhibit bone changes indicative of diffuse idiopathic skeletal hyperostosis (DISH). The study further allows us to classify him as obese (100% reliability according to our decision tree designed from Danish males), and points out his rich diet (high input of animal protein and/or marine resources) and high social status. Comorbidities of DISH and obesity are reviewed, and their influence on health status is discussed. We further consider some conditions associated with metabolic syndrome as possible causes of Tycho Brahe's final symptoms (urinary retention, renal failure and coma), including diabetes, alcoholic ketoacidosis and benign prostatic hypertrophy. Although a definite and specific diagnosis cannot be established, our study points to today's civilization diseases often associated with DISH and metabolic syndrome as the possible cause of death of Tycho Brahe.

On airborne nano/micro-sized wear particles released from low-metallic automotive brakes.

The paper addresses the wear particles released from commercially available "low-metallic" automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10 nm and 20 µm were released into the air. The numbers of nanoparticles (< 100 nm) were by three orders of magnitude larger when compared to the microparticles. A significant release of nanoparticles was measured when the average temperature of the rotor reached 300°C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles.

Homogeneous nucleation rate measurements in supersaturated water vapor.

The rate of homogeneous nucleation in supersaturated vapors of water was studied experimentally using a thermal diffusion cloud chamber. Helium was used as a carrier gas. Our study covers a range of nucleation rates from 3x10(-1) to 3x10(2) cm(-3) s(-1) at four isotherms: 290, 300, 310, and 320 K. The molecular content of critical clusters was estimated from the slopes of experimental data. The measured isothermal dependencies of nucleation rate of water on saturation ratio were compared with the prediction of the classical theory of homogeneous nucleation, the empirical prediction of Wolk et al. [J. Chem. Phys. 117, 10 (2002)], the scaled model of Hale [Phys. Rev. A 33, 4156 (1986)], and the former nucleation onset data.

The carrier gas pressure effect in a laminar flow diffusion chamber, homogeneous nucleation of n-butanol in helium.

Homogeneous nucleation rate isotherms of n-butanol+helium were measured in a laminar flow diffusion chamber at total pressures ranging from 50 to 210 kPa to investigate the effect of carrier gas pressure on nucleation. Nucleation temperatures ranged from 265 to 280 K and the measured nucleation rates were between 10(2) and 10(6) cm(-3) s(-1). The measured nucleation rates decreased as a function of increasing pressure. The pressure effect was strongest at pressures below 100 kPa. This negative carrier gas effect was also temperature dependent. At nucleation temperature of 280 K and at the same saturation ratio, the maximum deviation between nucleation rates measured at 50 and 210 kPa was about three orders of magnitude. At nucleation temperature of 265 K, the effect was negligible. Qualitatively the results resemble those measured in a thermal diffusion cloud chamber. Also the slopes of the isothermal nucleation rates as a function of saturation ratio were different as a function of total pressure, 50 kPa isotherms yielded the steepest slopes, and 210 kPa isotherms the shallowest slopes. Several sources of inaccuracies were considered in the interpretation of the results: uncertainties in the transport properties, nonideal behavior of the vapor-carrier gas mixture, and shortcomings of the used mathematical model. Operation characteristics of the laminar flow diffusion chamber at both under-and over-pressure were determined to verify a correct and stable operation of the device. We conclude that a negative carrier gas pressure effect is seen in the laminar flow diffusion chamber and it cannot be totally explained with the aforementioned reasons.