Recent progress in exact geometric computation

AbstractComputational geometry has produced an impressive wealth of efficient algorithms. The robust implementation of these algorithms remains a major issue. Among the many proposed approaches for solving numerical non-robustness, Exact Geometric Computation (EGC) has emerged as one of the most successful. This survey describes recent progress in EGC research in three key areas: constructive zero bounds, approximate expression evaluation and numerical filters

Photo-induced reduction of graphene oxide coating on optical waveguide and consequent optical intermodulation

Increased absorption of transverse-magnetic (TM) - polarised light by a graphene-oxide (GO) coated polymer waveguide has been observed in the presence of transverse-electric (TE) - polarised light. The GO-coated waveguide exhibits very strong photo-absorption of TE-polarised light - and acts as a TM-pass waveguide polariser. The absorbed TE-polarised light causes a significant temperature increase in the GO film and induces thermal reduction of the GO, resulting in an increase in optical-frequency conductivity and consequently increased optical propagation loss. This behaviour in a GO-coated waveguide gives the action of an inverted optical switch/modulator. By varying the incident TE-polarised light power, a maximum modulation efficiency of 72% was measured, with application of an incident optical power level of 57 mW. The GO-coated waveguide was able to respond clearly to modulated TE-polarised light with a pulse duration of as little as 100 μs. In addition, no wavelength dependence was observed in the response of either the modulation (TE-polarised light) or the signal (TM-polarised light)

Is the high cu tolerance of trichoderma atroviride isolated from the cu-polluted sediment due to adaptation?: an in vitro toxicological study

The tolerance of Cu by Trichoderma atroviride, a tolerant fungus isolated from the drainage surface sediment of the Serdang Industrial Area was investigated under in vitro conditions. Only this fungus species can tolerate up to 600 mg/L of Cu on solid medium Potato Dextrose Agar based on the isolation of the most tolerant fungus from the polluted sediment. Toxicity test performed on T. atroviride, showed a maximum tolerance at 300 mg/L of Cu concentration when grown in liquid medium Potato Dextrose Broth (PDB). The EC50 value of the isolate was 287.73 mg/L of Cu concentration in PDB. The Cu concentration in the drainage surface sediment, where the T. atroviride was isolated from, was 347.64 μg/g while the geochemical distributions of the non-resistant and resistant fractions of Cu were 99.6 and 0.4%, respectively. The sediment data indicated that the drainage had greatly received anthropogenic Cu from the nearby industries which are involved in the manufacturing of plastics and electronic products. The present findings indicate that the high Cu tolerance showed by T. atroviride could be due to the well adaptation of the fungus to the Cu polluted sediment. Therefore, T. atroviride could be a potential bioremediator of Cu pollution in the freshwater ecosystem

Synergistic and antagonistic effects of Zinc Bioaccumulation with lead and antioxidant activities in centella asiatica

This study was carried out by using Centella asiatica grown using a hydroponic system under laboratory conditions to study synergistic and antagonistic effects of Zn bioaccumulation with added Pb and the changes in antioxidant activities in leaves and roots of C. asiatica. The antioxidant activities included superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX). The treatments Zn (2 ppm) + Pb (0.4 ppm) and Zn (4 ppm) + Pb (0.6 ppm) increased the accumulation of Zn in leaves by 14.06 and 16.84%, respectively, but decreased by 7.36% uptake in roots (Zn 4 ppm + Pb 0.6 ppm). This showed that Pb and Zn acted synergistically to Zn accumulation in leaves but antagonistically in roots. CAT and SOD activities in leaves were increased when Zn was added together with Pb. In roots, CAT, APX and SOD activities were increased but GPX was decreased. Owing to their sensitivities to Zn with Pb, SOD and CAT could be used as biomarkers to monitor the toxicity of Pb and Zn exposure in the leaves and roots of C. asiatica

Selective Laser Melting of Pure Tin: Microstructure Study

Selective Laser Melting (SLM) of pure tin was examined and 3D samples were successfully fabricated. High relative density of 99.9 % was achieved. Microstructure study was carried out via a combination of X-ray diffraction (XRD), light microscopy (LOM) and electron backscatter diffraction (EBSD). Under LOM, columnar structures, some spanning the entire height of the sample, are observed in the vertical plane. This study also examines the variation of relative density against process parameters such as hatch spacing and the input volumetric energy density for the SLM of tin.Mechanical Engineerin

Effects of metal-contaminated soils on the accumulation of heavy metals in different parts of centella asiatica: a laboratory study

Centella asiatica is widely used as a medicinal plant in Malaysia and other parts of the world. In the present study, the growth and uptake of heavy metal by C. asiatica were determined based on the plant exposure to different treatment of metal-contaminated soils under laboratory conditions. Heavy metals uptake in different parts of the plants namely roots, stems and leaves were determined. In general, it was found that the metal uptake capacity followed the order: roots > stems > leaves. Since a close positive relationship was established between the concentrations of metal accumulated in different parts of the plant and the metal levels in the most contaminated soil, C. asiatica has the potential of being used as a biomonitoring plant for heavy metal pollution in the polluted soils

Muddy sediments acting as sinks of Cu and Zn : evidence from a laboratory experimental study by using cockle Anadara granosa plus muddy sediments.

Previous studies showed that red-blood cockle Anadara granosa was able to accumulate Cd and Cu to a significant high level in their tissues (Mat et al., 1994a, 1994b; Chan et al., 2002). However, little is known on the distribution of Cu and Zn in the soft tissues of A. granosa in the presence of muddy sediments, under laboratory conditions. In this study, sediment samples were analyzed because sediments have advantages to assess anthropogenic impacts on aquatic environments (Bryan & Langston, 1992). Sediment plays a major role in the transport and storage of metals (Salomons et al., 1987) and it can be used to identify sources of pollutants both spatially and temporally (Zwolsman et al., 1996; Birch et al., 2001). Furthermore, sediments can be used to locate the main sinks for heavy metals since these elements are persistent in the marine environment (Nriagu 1978; Hickey et al., 1995). However, understanding the ‘sediments can locate the main sinks for heavy metals’ is sometimes difficult and very much dependent on how a researcher define it and again it is based on the researcher’s comprehension. To understand that the sediment acts as a sink of heavy metals also needs evidence that can be provided through experimental studies based on proper experimental design

Correlates of elevational specialisation in Southeast Asian tropical birds

The understanding of elevational selectivity in extremely rich tropical biotas is critical to the study of accelerating human-mediated environmental changes (e.g., deforestation and global climate warming). This paper explores the characteristics of Southeast Asian birds that are altitudinal specialists (i.e., lowland specialists and montane specialists) by assessing the relative importance of various species traits (e.g., breeding phenology and clutch size) in determining the altitudinal specialisation of these tropical birds. After controlling for phylogeny, we found that habitat specificity, breeding phenology, and clutch size were significant correlates of lowland specialisation. The most parsimonious model predicting lowland specialisation included the first of these only. Breeding phenology was the significant phylogeny-independent correlate of montane specialisation. Thus, species were confined to altitudinal niches by different constraints. By analysing the altitudinal distribution of Southeast Asian birds, we provide insights on why altitudinal confinement exists in lowland and montane specialists. Understanding such constraints may be important for the conservation of tropical birds

Tolerance of High Inorganic Mercury of Perna Viridis : Laboratory Studies of Its Accumulation, Depuration and Distribution

The tolerance of Perna Viridis to a high inorganic mercury (Hg) exposure was determined based on its accumulation, depuration and distribution. The Hg accumulation of the mussel was conducted for a 4-day semi-static exposure at a \u2018very\u2019 high Hg concentration (100 \u3bcg/L). None of the mussels died after the experimental period, indicating that the elevated level of inorganic Hg exposure was not toxic to P. viridis. Following the 4-day exposure, the Hg concentrations were higher in the gill and byssus than in the mantle, foot, gonad and muscle (with bioconcentration factor values being between 13 and 625). The Hg distribution among the different soft tissues after 11 days of depuration was almost similar with that after Hg exposure. The high Hg levels found in the byssus and different soft tissues after the depuration indicated that Hg accumulated in the different ST was tightly bound to metallothionein and it was not easily mobilized. The Hg distribution in the byssus and in the different soft tissues could be due to their differing capacities for Hg accumulation and depuration. Since the soft tissues of P. viridis can accumulate inorganic Hg in high concentrations after exposing to a \u2018very\u2019 high level of inorganic Hg, it has a high bioaccumulative capability and a high tolerance to inorganic Hg. The mussel byssus was found to have the highest depuration rate coefficient, indicating that it could act as one of the excretion routes for Hg and it can be proposed as a sensitive biomonitoring material for Hg. The fecal materials released by the mussel had elevated levels of Hg, indicating that the mussels acted as a Hg retention mechanism in the coastal ecosystem

Thomas Decomposition of Algebraic and Differential Systems

In this paper we consider disjoint decomposition of algebraic and non-linear partial differential systems of equations and inequations into so-called simple subsystems. We exploit Thomas decomposition ideas and develop them into a new algorithm. For algebraic systems simplicity means triangularity, squarefreeness and non-vanishing initials. For differential systems the algorithm provides not only algebraic simplicity but also involutivity. The algorithm has been implemented in Maple