The impact of bromide on the formation of neutral and acidic disinfection by-products (DBPs) in Mediterranean chlorinated drinking water

By using the Grob closed loop stripping analysis technique a wide variety of disinfection by-products (DBPs) was determined, in finished drinking water of 15 important cities of Greece distributed in the southern, northern, west continental land and in the islands of Aegean and Ionian Seas. Trihalomethanes, haloacetonitriles, haloacetic acids, chloropicrin, halogenated ketons and chloral hydrate were the main DBPs determined. In chlorinated drinking water of coastal cities brominated DBPs were most abundant than their chlorinated homologues due to the higher bromide concentration in raw waters of these areas. Factor analysis with principal component extraction of the results demonstrated a clear differentiation between the examined drinking waters on the basis of their DBPs content and vicinity to the sea.     

Structural features of ball-milled nanostructured K2Bi8Se13 thermoelectric material

In this work, K₂Bi₈Se₁₃ material was ball-milled in order to develop nanostructures through the modification of structural features. Structural changes during ball-milling were followed by powder X-ray diffraction measurements, Scanning Electron Microscope images and High Resolution and conventional Transmission Electron Microscopy studies. Powder X-ray diffraction patterns presented a significant broadening in the peak patterns with the increase of the ball-milling time that was attributed to the formation of nanocrystalline as well as amorphous material. TEM studies showed the formation of K₂Bi₈Se₁₃ nanostructured material consisting of nanocrystals that were surrounded by an amorphous matrix. Preliminary measurements of thermoelectric properties have shown that Seebeck coefficient is increased in ball-milled samples where as thermal conductivity is decreased. Sintering process that was applied on the ball-milled material leads to its recrystallization and the growth of grains.     

Comparing Doping Methodologies in Mg2Si/AgMg System

Morphological and optical characterizations for the Mg₂Si samples doped with Ag are presented. Two different doping methodologies with silver, namely in situ and ex situ doping, were studied for the case of Mg₂Si of self-propagating high-temperature synthesis. Electron microscopy measurements in both scanning and transmission configurations verified the presence of AgMg precipitates embedded in the Mg₂Si matrix and similar results were also yielded by FTIR spectroscopy. Finally, the dependence of silver content in both forms of dopant and inter-metallic constituent is studied upon doping technology.     

Bending resistance of composite slabs made with thin-walled steel sheeting with indentations or embossments

The paper studies the behaviour of thin-walled steel sheeting with embossments. The study aims to determine the contribution of the embossed areas of the steel sheeting to the total strength in pure tension and in pure bending. For this study, various three-dimensional finite element models are constructed, which take accurately into account the nonlinear response of the problem. The study concludes that there is a strong relation between the area of the embossment region that can be considered as active and the ratio between the depth of the embossment and the thickness of the profile.     

Emerging contaminants in car interiors: evaluating the impact of airborne PBDEs and PBDD/Fs

Air samples from automobile cabins were collected and analyzed for polybrominated diphenyl ethers (PBDEs), polybrominated dibenzofurans (PBDFs), and polybrominated dibenzo-p-dioxins (PBDDs). The concentration of total PBDEs (sigmaPBDE; sum of 19 congeners) varied from 0.4 to 2644 pg m(-3), with a median of 201 pg m(-3), while BDE 47, 99, and 209 collectively accounted for 70 +/- 30% of sigmaPBDE concentrations. Multiple linear regression analysis revealed that sigmaPBDE concentration was significantly influenced by vehicle's age and interior temperature. More specifically, sigmaPBDE decreased over time and increased with the rise of temperature. The daily inhalation intake of PBDEs during commuting was estimated to range from 0.5 to 2909 pg day(-1) (median 221 pg day(-1)) and contributed 29% of the overall daily exposure to PBDEs via inhalation. When excluding BDE 209, a lower contribution was calculated for this source (18%), but this was still comparable with residential exposure (22%). The levels of PBDD/Fs were generally below the limits of detection and only in one case were hepta-BDFs positively detected at a concentration of 61 pg m(-3). This study demonstrates that car interiors, especially when new, contain high levels of airborne PBDEs and represent a potential route of human exposure via inhalation.     

Light scattering by aggregated red blood cells

In low flow rates, red blood cells (RBCs) fasten together along their axis of symmetry and form a so-called rouleaux. The scattering of He-Ne laser light by a rouleau consisting of n (2 < or = n < or = 8) average-sized RBCs is investigated. The interaction problem is treated numerically by means of an advanced axisymmetric boundary element--fast Fourier transform methodology. The scattering problem of one RBC was solved first, and the results showed that the influence of the RBC's membrane on the scattering patterns is negligible. Thus the rouleau is modeled as an axisymmetric, homogeneous, low-contrast dielectric cylinder, on the surface of which appears, owing to aggregated RBCs, a periodic roughness along the direction of symmetry. The direction of the incident laser light is considered to be perpendicular to the scatterer's axis of symmetry. The differential scattering cross sections in both perpendicular and parallel scattering planes and for all the scattering angles are calculated and presented in detail.     

Direct evidence for destruction of polychlorobiphenyls by OH radicals in the subtropical troposphere

Although laboratory studies have indicated that OH radicals readily oxidize polychorobiphenyls (PCBs) in the gas-phase, this mechanism has never been positively demonstrated under real atmospheric conditions. By applying elaborated sampling and analytical techniques we achieved for the first time simultaneously a field study of the diurnal atmospheric cycle of OH radical and PCBs in a remote site of eastern Mediterranean. In all cases, the concentration of sigmaPCB (sum of 27 congeners) showed a characteristic depletion during daytime, while the concentration of OH radicals was at the maximum levels. By assuming that the depletion of PCBs was caused solely by the destruction from OH radicals, PCB-OH rate constants (KOH) of different PCB congeners were determined from field data by applying the relative rate method. Our field-determined KOH values were notably coherent with those previously measured in laboratory experiments. In all measurement periods, the KOH values consistently decreased in sequence for those compounds showing an increasing degree of chlorination on the biphenyl group. By taking into account KOH values and latitude-dependent concentration of OH radicals, it was estimated that, near to tropical and subtropical regions, the atmospheric lifetimes of PCBs 8 and 110 should be substantially low (10 and 20 days, respectively). A significant fraction of PCBs should be destroyed during their residence over tropical/subtropical regions, due to the intensive destruction by OH.     

A new LBIE method for solving elastodynamic problems

A new local boundary integral equation (LBIE) method for the solution of elastodynamic problems in both frequency and time domain is proposed. Non-uniformly distributed points covering the analyzed domain are used for the interpolation of the involved fields. The key-point of the proposed methodology is that the support domain of each point is divided into parts with the aid of cells formed by connecting the point of interest with the nearby points. Then an efficient radial basis functions (RBF) interpolation scheme is exploited for the representation of displacements in each cell, while on the intersections between the local domains and the global boundary, tractions are treated as independent variables via conventional boundary elements. For each point the corresponding LBIE is written in terms of displacements only, since on the boundary of support domains tractions are eliminated with the aid of the elastostatic companion solution. The integration in support domains is performed easily and with high accuracy, while due to cells the extension of the method to three dimensions is straightforward. Transient solutions are obtained after inversion of frequency domain results with the inverse fast Fourier transform (FFT). Two representative numerical examples that demonstrate the accuracy of the proposed methodology are provided.     

Polycyclic aromatic hydrocarbons in the atmosphere of the eastern Mediterranean

Atmospheric processes governing the fate of the polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of the Eastern Mediterranean were studied for a two-year period (2000-2001). Atmospheric samples were collected off-shore over the Eastern Mediterranean Sea as well as at a background station in Northeastern Crete, Greece. PAH total concentration varied from 4.1 to 57.2 ng m(-3), with >90% in the gas phase. Gas-to-particle distribution of PAHs was correlated (R2 0.75-0.98, p < 0.001) with their subcooled vapor pressure. Seasonal changes in the total concentration of PAHs were not observed, while the origin of air mass was the dominant factor determining their atmospheric concentration levels. Air masses, originating from central and eastern Europe, were associated with the highest PAH concentrations. Gas-to-particle distribution of sigmaPAHs correlated well (R2 0.75-0.98, p < 0.001) with their subcooled vapor pressure. Tropospheric ozone concentration correlated with the vapor-phase PAH concentration (p < 0.001) but less (p < 0.01) with the particulate PAH concentration. Distribution of volatile PAHs over the Eastern Mediterranean basin was uniform. Conversely, particulate PAH concentrations were higher at sampling sites located close to urban centers. Calculated relative removal rates of PAHs associated with particles were significantly higher than those of volatile members.