Environmental life cycle assessment of permeable reactive barriers: effects of construction methods, reactive materials and groundwater constituents

The effects of the construction methods, materials of reactive media and groundwater constituents on the environmental impacts of a permeable reactive barrier (PRB) were evaluated using life cycle assessment (LCA). The PRB is assumed to be installed at a simulated site contaminated by either Cr(VI) alone or Cr(VI) and As(V). Results show that the trench-based construction method can reduce the environmental impacts of the remediation remarkably compared to the caisson-based method due to less construction material consumption by the funnel. Compared to using the zerovalent iron (Fe(0)) and quartz sand mixture, the use of the Fe(0) and iron oxide-coated sand (IOCS) mixture can reduce the environmental impacts. In the presence of natural organic matter (NOM) in groundwater, the environmental impacts generated by the reactive media were significantly increased because of the higher usage of Fe(0). The environmental impacts are lower by using the Fe(0) and IOCS mixture in the groundwater with NOM, compared with using the Fe(0) and quartz sand mixture. Since IOCS can enhance the removal efficiency of Cr(VI) and As(V), the usage of the Fe(0) can be reduced, which in turn reduces the impacts induced by the reactive media.     

Butyric acid and tributyrin induce apoptosis in human hepatic tumour cells

The anti-colon cancer effect of dietary fibre results in part from its fermentation into the short-chain fatty acid butyric acid (BA) by intestinal microflora. BA has potent anti-colon cancer properties owing to its ability to induce apoptosis in colon cancer cells. The colon is not the only location where BA may reach high concentrations, because dietary BA is rapidly absorbed and transported to the liver. We have investigated whether BA could induce apoptosis in transformed human liver (Hep G2) cells. Hep G2 cells treated with BA displayed acetylated histones, increased DNA fragmentation and morphological features consistent with apoptosis. These biochemical features of BA-treated liver cells are identical to those of BA-treated colon cells. In addition, we investigated whether BA present in tributyrin, a triacylglycerol more compatible for inclusion into colloidal lipid structures than BA, could also induce apoptosis in Hep G2 cells. Tributyrin induced DNA fragmentation and morphological features characteristic of apoptotic cells in Hep G2 cells. These results are a significant advance towards delivering BA via colloidal lipid particles to cancerous sites in vivo. This study showed that BA and tributyrin are potent apoptotic agents, and we suggest that sources of dietary BA, such as milk fat, may provide anti-liver cancer properties.     

Preparation and characteristics of fine-grained ferroelectric glass-ceramic composites via a modified hybrid route at low temperature sintering

Dense, homogeneous and fully developed fine-grained ferroelectric Pb(Zr_0.53Ti_0.47)O₃?Cbased glass-ceramics have been successfully prepared at a low-sintering temperature of 850?C900°C by a modified hybrid process in air. The influence of the PbO-B₂O₃-SiO₂ (abbreviated as PBS) glass-gel content on the microstructure, dielectric, and ferroelectric properties of such glass-ceramics has been investigated. The temperature dependence of the dielectric constant indicated that the fine-grained Pb(Zr_0.53Ti_0.47)O₃ (abbreviated as PZT(53/47)) based glass-ceramic shows the characteristic dispersion at the Curie point. Ferroelectric hysteresis loop analyses have been performed to manifest the ferroelectric nature of the highly crystallized PZT(53/47) phase prepared by this modified novel hybrid process despite containing higher wt% glass-gel contents. The best dielectric and ferroelectric properties in a typical sample with 5% by weight of glass-gel content were found to have dielectric constant and loss tangent of 920 and 0.02 at 1 kHz, respectively. The saturation polarization (P _s ), and remanent polarization (P _r ) as well as the coercive field (E _c ) are 21.9 ??C/cm², 10.8 ??C/cm² and 2.19 kV/mm, respectively.     

Assessment of the stability of isolated vibratory building services systems and the use of inertia blocks

Inertia blocks are commonly used by engineers to stabilize vibration-isolated building services equipment. However, no comprehensive guidelines for the selection of inertia blocks or indices for assessing the effect of inertia blocks on the stability of the vibratory system are available. In this paper, the level of “power transmissibility” is used to assess the performance of vibration isolators, and the level of the “vibration velocity transmissibility” of the supporting floor structure, the “mounted vibration velocity”, and the “mounted rotational velocity level” of the vibratory machine are proposed to assess the stability of the vibratory system with various inertia blocks. The results primarily indicate that the use of an inertia block does not affect the performance of vibration isolation. Instead, it decreases the vibration velocity and rotational velocity of the isolated vibratory machine; so it can increase the stability of the vibratory system regardless of whether the machine has slightly or highly uneven mass distribution. The results reveal that, for the machine with highly uneven mass distribution, the degree of an larger inertia block is required to enhance the stability of the isolated vibratory system. Therefore, in addition to proposing indices for assessing the stability of the vibratory system, this paper also provides an insight into the selection of the inertia block based on the mass distribution of an isolated vibratory machine.     

Finite element analysis of buckling and post-buckling behaviors of arches with geometric imperfections

The buckling and post-buckling behavior of arches is very sensitive to their geometric imperfections. The purpose of this paper is to develop a refined curved finite element that might accurately represent the actual geometry of arches so that the imperfection effects on their buckling behavior could be properly investigated. For an arch with known geometric imperfections, the element stiffness matrix is precisely formulated in terms of Lagrangian variables for a perfect arch from a general incremental variational principle. In general, the element stiffness matrix contains Lagrangian strain, first and second order incremental strain and imperfection terms. For any general planar imperfect arch with a variable curvature, the element stiffness matrix is evaluated by numerical integration; however, for a nominally circular arch, it can be represented in closed form. Numerical results in terms of load-deformation curves are presented for a number of circular arches with and without imperfections and compared with existing solutions.     

Effective elastic properties for lower limb soft tissues from manual indentation experiment.

Quantitative assessment of the biomechanical properties of limb soft tissues has become more important during the last decade because of the introduction of computer-aided design and computer-aided manufacturing (CAD/CAM) and finite element analysis to the prosthetic socket design. Because of the lack of a clinically easy-to-use apparatus, the site and posture dependences of the material properties of lower limb soft tissues have not been fully reported in the literature. In this study, an ultrasound indentation system with a pen-size hand-held probe developed earlier by the authors was used to obtain the indentation responses of lower limb soft tissues. Indentation tests were conducted on normal young subjects with four females and four males at four sites with three body postures. A linear elastic indentation solution was used to extract the effective Young's modulus from the indentation responses. The determined modulus ranged from 10.4 to 89.2 kPa for the soft tissues tested. These results were in a similar range as those reported in the literature. The thickness of the lower limb soft tissues varied slightly with body posture changes. The Young's modulus determined was demonstrated to be significantly dependent on site, posture, subject and gender. The overall mean modulus of male subjects was 40% larger than that of female subjects. No significant correlation was established between the effective Young's modulus and the thickness of entire soft tissue layers.