Environmental risk index: A tool to assess the safety of dams for leachate

Dams for leachate store very toxic substances that contain a large amount of organic material and, probably, heavy metals; they therefore constitute an important threat to the environment. Existing models of environmental risk assessment for landfills do not take into consideration the specific risk that leachate dams may represent for the environment. In this paper a methodology to improve the environmental safety is presented according to the parameters used in their construction and management. In order to do that, the following characteristics of the dam must be known: (1) geotechnical stability, (2) erosion of downstream slope, (3) type of sealing of the dam, (4) overtopping probability, (5) volume of leachate stored inside the dam and (6) pollution load of leachate. Once these parameters have been calculated, they are transformed by means of rating curves into homogeneous units, so as to make it possible to operate between them. From the study and analysis of these parameters an environmental risk index for a dam for leachate can be calculated. If the environmental risk index exceeds an established value then it involves a dam for leachate with high environmental risk, therefore preventive measures in its design, construction and management would be necessary.     

Squamous cell carcinoma and infection in a solitary hepatic cyst

A case of mediastinal cavernous hemangioma was reported. An abnormal shadow on the chest X-ray film was pointed out in a 55-year-old male. CT scan and MRI revealed a right posterior mediastinal tumor but did not aid in the final diagnosis. We underwent extirpation of the tumor through thoracoscope and confirmed to be a cavernous hemangioma histologically. No major vascular connections between the tumor and major vessels were found. It was useful of thoracoscopic surgery in this case.     

Tragfähigkeit von Lochleibungsverbindungen vorgespannter Glasscheiben zur Ausbildung von Anschlüssen im Konstruktiven Glasbau

Strength of bearing connections in toughened glass plates for the structural use. In steel structures due to their “infinite'” ductility the bearing connections are standard components of joints. Their design rules are based on simple engineering models. However if analogous bearing connections are subject of glazing structures the requirements on the materials' ductility cannot be met. Therefore interlayers out of mortar etc. in the hole surrounding the bolt have to be introduced such that a ductile load deformation behaviour can be reached reducing stress peaks and avoiding steel‐glass‐contact. On this basis design rules are to be established to predict the load carrying capacity of bolts in glass bearings. The following investigations describe the experimental and theoretical works to derive an engineering model for this purpose.     

Synthesis of titanium dioxide nanoparticles by reactive DC magnetron sputtering

Nanometer-sized titanium dioxide (TiO₂) particles were prepared on carbon substrates by reactive direct-current magnetron sputtering. By performing measurements with high resolution electron microscopes, the mean nanoparticle diameter and the coverage fraction of the substrate by the nanoparticles (NPs) were measured at 19 nm and 30%, respectively. Moreover, electron diffraction analysis showed that the TiO₂ NPs' crystalline structure on the carbon substrate was a mixture of anatase and rutile. Finally, we provided information on the TiO₂ initial growth stage: crystalline NPs were formed after deposition of amorphous nanoparticles on the substrate and heating.     

Efficiency of different shear devices on flocculation

Various types of coagulation devices have been used to study aggregation, with the goal of understanding aggregation dynamics in natural and engineered systems. Three different devices were investigated here (paddle mixer, oscillating grid and Couette) to examine the effect of different laboratory devices on the particle size spectra over a wide range of shear range values (G=4-102 s(-1)) at four different initial volume concentrations (phi0=2 x 10(-5), 4 x 10(-5), 8 x 10(-5) and 10 x 10(-5)). For each device there was maximum aggregate size produced at each shear rate, with three distinct zones observed depending on the magnitude of G. At low shear rates (G<20s(-1)), mean particle diameter increased with G, showing that aggregation dominated over breakup. At intermediate shear rates (20s(-1)30s(-1)), the dominant effect of breakup was shown through reduced maximum floc sizes with increasing shear rates. Fractal dimensions of aggregates from the paddle mixer and oscillating grid, calculated using cumulative size spectra and assuming pseudo-steady-state conditions, were typical of aggregates formed by reaction-limited conditions or those compacted by aggregate reformation (D=2.2+/-0.2). Fractal dimensions for the Couette flow device were extremely low and less than unity (D=0.9+/-0.2), indicating that this method of calculating D could not be used for conditions produced in this device. The paddle mixer and the oscillating grid produced almost identical maximum diameters of the suspension under pseudo-steady-state conditions for all initial volume fractions, but the Couette device consistently produced larger diameter flocs at the same average shear rates and the maximum size of the aggregates increased with the volume concentration. These results indicate that even at low shear rates aggregate formation was influenced by breakup. It is therefore concluded that the Couette device is the most useful method for forming aggregates that are least influenced by breakup processes during aggregate formation.     

Experimental analysis of coagulation of particles under low-shear flow

The aggregation and breakup of particle flocs were investigated by monitoring the size distribution of a suspension of aggregates, with diameter d(o), under shear flow created by two mixing systems. The aggregation behavior was studied in 63 experiments under various conditions of induced shear rate and particle volume concentration for particle aggregates smaller than the Kolmogorov scale. Despite small shear rates being characteristics of natural systems, only experiments with comparatively high shear rates have been conducted to date. Because of this reason, in this study, the shear rates were chosen to mimic those found in natural systems. In the first set of experiments the aggregate size, d, was analyzed by changing the mean shear, G (ranging from 0.70 to 27.36 s(-1)) created in a tank with a grid oscillating through the whole suspension volume. In the second set of experiments, a spherical flask was placed in an orbital shaking table where G ranged from 0.45 to 2.40s(-1). In all the cases there was an increase of d at increasing G . The dependence on d was found to be identical for the particle volume concentrations investigated, phi=0.2,0.8,2,4,6,8 and 10 x 10(-5), with the stable aggregate size shifting towards aggregate growth as particle volume concentration increased. These results demonstrate that shear provided a means to keep the particle number count high for collisions to occur but it is small enough that the aggregation-breakup balance is dominated by aggregation.     

Isothermal crystallization of poly(ethylene-terephthalate) of low molecular weight by differential scanning calorimetry: 1. Crystallization kinetics

The isothermal crystallization of poly(ethylene-terephthalate) (PETP) fractions, from the melt, was investigated using differential scanning calorimetry (d.s.c.). The molecular weight range of the fractions was from 5300–11750. Crystallization temperatures were from 498–513 K. The dependence of molecular weight and undercooling on several crystallization parameters has been observed. Either maxima or minima appear at a molecular weight of about 9000, depending on the crystallization temperature. The activation energy values point to the possibility of different mechanisms of crystallization according to the chain length. A folded chain process for the higher $\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$ chains and an extended chain mechanism for the lower $\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$ chains. The values of the Avrami equation exponent n vary from 2–4 depending on the crystallization temperature; non-integer values are indicative of heterogeneous nucleation. The rate constant K depends on T_c and $\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$, showing maxima related to the T_c used. The plot of log K either vs. (ΔT)^?1 and (ΔT)^?2 or $\text{T}{}_{\mathrm{<mtext>m</mtext>}}\text{T(ΔT)}$ and $\text{T}{}^2{}_{\mathrm{<mtext>m</mtext>}}\text{T(ΔT)}{}^2$ is linear in every case.     

Environmental performance of ceramic tiles: Improvement proposals

Ceramic tile is one of the most widely used materials in construction. Due to the increased demand for environmentally responsible construction and the ever more restrictive environmental requirements derived from the legislation, there is a need for a tool to enable the environmental behaviour of such material to be evaluated. By the application of the life cycle assessment (LCA) methodology, this study is focused on calculating indicators capable of measuring the environmental behaviour of ceramic tiles. Taking the production of 1 m² of ceramic as a functional unit, the aim was to perform a life cycle inventory that covers all the stages from mining the red clay and atomising it to glaze manufacture and the production of the ceramic tiles and their delivery to customers. Next, the stages/materials/processes that have the greatest impact were identified, and a series of improvements were proposed with a view to enhancing the energetic efficiency of the firing process and minimising the emissions into the atmosphere, while at the same time reducing the noise pollution resulting from the pressing process. The environmental and economic feasibility of such a improvements was also studied.