Evaluation of the wettability of mortar component granular materials through contact angle measurements

The wettability of granular materials has a direct effect on the workability of pastes, mortars and concretes containing such materials. Given this, the wetting behaviour of two Portland cements, two mineral admixtures (limestone filler and silica fume) and different sand types (siliceous, limestone and granite) was evaluated through the measurement of the contact angle between these materials and water. The results show that all the materials possess high wettability. A chemical agent, dichlorodimethylsilane, was used to modify the surface properties of a 0–1 mm siliceous sand, making it more hydrophobic and, therefore, unable to be spontaneously wetted by water. The properties of a mortar produced with the silane-treated sand were evaluated, showing improvements on workability as a result of the chemical treatment.     

Experiences in Barcelona with the use of fibres in segmental linings

This paper presents the most outstanding experiences regarding the use of fibres as the main reinforcement in precast segmental linings in the metropolitan area of Barcelona. It is known that the addition of structural fibres improves, on the one hand, the mechanical behaviour of the structure during its construction, especially in cases such as the thrust of the jacks, and on the other hand it leads to a reduction of the global costs by reducing the conventional passive reinforcement. The aim of this paper consists in presenting three real experiences that are representative of the application of FRC in urban tunnels and a design methodology to take into account the structural contribution of the fibres. Two particular cases of the application of this design method are presented. In the first case, the use of 25 kg/m³ of fibres has led to a reduction of 70% of the conventional reinforcement initially proposed in the project. In the second one, which was planned to employ fibres but without considering its structural contribution, the parametric study reflected the possibility of reducing up to a 38% of the rebars adding 25 kg/m³ of steel fibres in the concrete mixture. In light of good results, construction companies in Spain have become aware of the advantages of using fibres in these structures and have carried out experimental stretches. This attitude has also been influenced by the approval of the new Spanish Code, which includes the FRC as a construction material with design purposes.     

Characterization of presynaptic proteins involved in synaptic vesicle exocytosis in the nervous system of Torpedo marmorata

Synaptobrevin, SNAP-25 and syntaxin (SNAP receptor proteins) are molecular components that play a key role in the exocytotic machinery of synaptic vesicles. Their presence, distribution and interactions are reported in central and peripheral nervous systems of the electric fish Torpedo marmorata. These three proteins form a protein complex in all the nervous system regions tested, including the electric lobe and the electric organ which is innervated by pure cholinergic nerve terminals. Immunoblot analysis revealed a double protein pattern of SNAP-25 in the anterior brain and cerebellum, although a single protein band corresponding to SNAP-25 was observed in the electromotor system. Moreover, SNAP-25 showed a differential distribution in the electromotor system. It was present along nerve fibres and terminals that innervated the electric organ but it was not detected in nerve terminals at the electric lobe. Immunoisolation experiments using anti-synaptobrevin antibodies showed a tissue-specific co-existence of SNAP-25 and syntaxin with synaptobrevin in the immunoisolated organelles. In conclusion, the molecular components of the exocytotic machinery are shown to be conserved in Torpedo, although some differences mainly on SNAP-25, suggest a potential diversity in the regulation of neurosecretion.     

Implementation of energy sustainability concepts during the comminution process of the Punta Gorda nickel ore plant (Cuba)

This paper presents an analysis of the potential benefits of implementing energy sustainability concepts during comminution processes. The work is based on the classical comminution theory and on the theoretical postulates of the multi-component grinding. The assessment of the Punta Gorda grinding plant is presented as a case study. It applies factorial method from the Energy Management System perspective.     

MMP1 and MMP11 Expression in Peripheral Blood Mononuclear Cells upon Their Interaction with Breast Cancer Cells and Fibroblasts

Tumor-infiltrating immune cells phenotype is associated with tumor progression. However, little is known about the phenotype of the peripheral blood mononuclear cells (PBMC) from breast cancer patients. We investigated MMP1 and MMP11 expression in PBMC from breast cancer patients and we analyzed gene expression changes upon their interaction with cancer cells and cancer-associated fibroblasts (CAF). We measured the impact of PBMC on proinflammatory gene expression in breast cancer cells, normal fibroblast (NF), and CAF and the impact on proliferation and invasiveness capacity of breast cancer cells. Gene expression of MMP1 and MMP11 in PBMC from breast cancer patients (n = 54) and control (n = 28); expression of IL1A, IL6, IL17, IFNβ, and NFĸB in breast cancer cell lines (MCF-7 and MDA-MB-231); and, additionally, IL10 and MMP11 in CAF and NF were analyzed by qRT-PCR before and after co-culture. Our results show the existence of a subpopulation of breast cancer patients (25.9%) with very high levels of MMP11 gene expression in PBMC. Also, gene expression of MMP1 and MMP11 increases in PBMC after co-culture with breast cancer cell lines, NF or CAF. PBMC from healthy or breast cancer patients induce an increased proliferation rate on MCF-7 and an increased invasiveness capacity of MDA-MB-231. Finally, we show a differential expression profile of inflammatory genes in NF and CAF when co-cultured with control or breast cancer PBMC. We have observed that MMPs’ expression in PBMC is regulated by the microenvironment, while the expression of inflammatory genes in NF or CAF is differentially regulated by PBMC. These findings confirm the importance of the crosstalk between stromal cells and suggest that PBMC would play a role in promoting aggressive tumor behavior.     

Meso-structural study of concrete fracture using interface elements. I: numerical model and tensile behavior

A recently developed FE-based mesostructural model for the mechanical behavior of heterogeneous quasi-brittle materials is used systematically to analyze concrete specimens in 2D. The numerical model is based on the use of zero-thickness interface elements equipped with a normal-shear traction-separation constitutive law representing non-linear fracture, which may be considered a mixed-mode generalization of Hillerborg’s “Fictitious Crack Model.” Specimens with 4 × 4 and 6 × 6 arrays of aggregates are discretized into finite elements. Interface elements are inserted along the main lines in the mesh, representing potential crack lines. The calculations presented in this paper consist of uniaxial tension loading, and the continuum elements themselves are assumed to behave as linear elastic. In this way, the influence of various aspects of the heterogeneous geometry and interface parameters on the overall specimen response has been investigated. These aspects are aggregate volume fraction, type of arrangement and geometry, interface layout, and values of the crack model parameters chosen for both the aggregate-aggregate and matrix-aggregate interfaces. The results show a good qualitative agreement with experimental observations and illustrate the capabilities of the model. In the companion second part of the paper, the model is used to represent other loading states such as uniaxial compression, Brazilian test, or biaxial loading.     

Catalytic conversion of low-density polyethylene using a continuous screw kiln reactor

Both thermal and catalytic cracking of low-density polyethylene (LDPE) have been investigated using a screw kiln reactor. Thermal degradation gives rise to a broad product distribution, whereas catalytic cracking over Al-MCM-41 leads mainly to hydrocarbons within the gasoline range (C₅–C₁₂) with selectivities up to 80%. The increase of the screw speed between 3 and 15 rpm in the catalytic experiments allows the plastic feed rate to be varied in the range 20–41 g h⁻¹. The changes observed in the TOF values when varying the screw speed point out a decrease of the activity per site with increasing residence times, which may be due to the catalyst deactivation or to a contribution of the degradative extrusion at higher screw speeds. Likewise, a certain increase in the selectivity towards the gasoline fraction is observed at short residence times. On the other hand, PIONA analyses indicate that, regardless of the screw speed, the main components of the gasoline are olefins (50%) and isoparaffins (20%), whereas the aromatic content is always below 6%, with a proportion of benzene lower than 0.1%.     

Ellipsometric measurements on tantalum and tantalum oxide films and variation of the optical constants with structure

The optical constants n and k for films of tantalum and naturally grown tantalum oxide were determined at wavelengths of 4960 Å, 5487 Å and 6049 Å using an ellipsometer at two angles of incidence. The tantalum films were prepared at a pressure equal to or less than 2 × 10^-8 Torr during evaporation. Values are compared with those of other workers. Optical observations on films with mixed b.c.c. and f.c.c. structures (as determined from X-ray measurements) indicate the presence of a b.c.c. and f.c.c. mixture throughout; this is contrary to previous suggestions by other workers that the f.c.c. phase was present in very thin films only and was converted to b.c.c. in thick films.