The Role Played by Acetyl Group Distribution Patterns in Substituted Starch Toward Enzymatic De-acetylation and Chain Fragmentation

The nature and distribution of the acetylated groups were evaluated by ¹³C-NMR and ¹H-NMR. The starch substrate with a DS of 1.5 comprises only two patterns: -(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose. The starch with a DS of 3.0 also comprises two patterns: 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose; whereas starch (DS = 1.9) contains 4 patterns: 2,3,6-tri-O-acetyl--(14)-d-glucopyranose, 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose terminal, 2,6-di-O-acetyl--(14)-d-glucopyranose, and 3,6-di-O-acetyl--(14)-d-glucopyranose. Using esterase from Viscozyme, it has been possible to hydrolyze up to 7% of the DS 3.0 starch. An -amylase (Fungamyl 800) was then added to these acetylesterases. With a 2.4 FAU/mL fraction of -amylase and 2.4 U/mL from the Viscozyme's acetylesterase, 28% of the acetylated end groups were hydrolyzed for the starch substrates with DS 3.0. Moreover, a synergic action between -amylase and acetylesterase was noticed, allowing fragmentation of 32% for DS 1.5, 30% for DS 1.9, and 11% for DS 3.0.     

Heavy metal contamination from mining sites in South Morocco: 1. Use of a biotest to assess metal toxicity of tailings and soils

Our work was conducted to investigate the heavy metal toxicity of tailings and soils collected from five metal mines located in the south of Morocco. We used the MetPAD biotest Kit which detects the toxicity specifically due to the heavy metals in environmental samples. This biotest initially developed to assess the toxicity of aquatic samples was adapted to the heterogeneous physico-chemical conditions of anthropogenic soils. Contrasted industrial soils were collected from four abandoned mines (A, B, C and E) and one mine (D) still active. The toxicity test was run concurrently with chemical analyses on the aqueous extracts of tailings materials and soils in order to assess the potential availability of heavy metals. Soil pH was variable, ranging from very acidic (pH 2.6) to alkaline values (pH 8.0-8.8). The tailings from polymetallic mines (B and D) contained very high concentrations of Zn (38,000-108,000 mg kg(-1)), Pb (20,412-30,100 mg kg(-1)), Cu (2,019-8,635 mg kg(-1)) and Cd (148-228 mg kg(-1)). Water-extractable metal concentrations (i.e., soil extracts) were much lower but were highly toxic as shown by the MetPAD test, except for soils from mines A, E and site C3 from mine C. The soil extracts from mine D were the most toxic amongst all the soils tested. On this site, the toxicity of soil water extracts was mainly due to high concentrations of Zn (785-1,753 mg l(-1)), Cu (1.8-82 mg l(-1)) and Cd (2.0-2.7 mg l(-1)). The general trend observed was an increase in metal toxicity measured by the biotest with increasing available metal contents in tailings materials and soils. Therefore, the MetPAD test can be used as a rapid and sensitive predictive tool to assess the heavy metal availability in soils highly contaminated by mining activities.     

Energy Expenditure in Egypt: Empirical Evidence Based on a Quantile Regression Approach

Environmental Modeling & Assessment - This paper investigates the key factors affecting household energy expenditure in Egypt. Based upon the latest 2015 Egyptian HIECS Survey, we develop a...     

Innovative design of an LDPE reactor bay against gas explosion using a risk-based approach coupled with high fidelity computer tools

High pressure tubular reactors for the production of Low Density Polyethylene (LDPE) are, for safety reasons, enclosed in a protective bay open towards the sky. They are becoming longer and larger due to production capacity increases. TECHNIP has historically designed these reactor bays based on Licensor information, which include more or less empirical correlations. Further capacity developments require the design of these concrete enclosures to be challenged. With this in mind, the present study shows the interest of implementing an innovative methodology based upon a risk-based approach to define new design criteria for the enclosure walls. The method, which combines both risk analysis with computational fluid dynamics modelling (3D CFD) and non-linear finite element analysis (NLFEA) tools, allows a clear determination of the design overpressure loads applied on walls and offers an optimisation of the concrete wall thickness. The CFD study also leads to a better understanding of the ventilation and efficiency of safety systems (gas detection, depressurisation) with possibility for improvement of the hazardous area classification rating.     

Combustion characteristics of spent catalyst and paper sludge in an internally circulating fluidized-bed combustor

Combustion of spent vacuum residue hydrodesulfurization catalyst and incineration of paper sludge were carried out in thermo-gravimetric analyzer and an internally circulating fluidized-bed (ICFB) reactor. From the thermo-gravimetric analyzer-differential thermo-gravimetric curves, the pre-exponential factors and activation energies are determined at the divided temperature regions, and the thermo-gravimetric analysis patterns can be predicted by the kinetic equations. The effects of bed temperature, gas velocity in the draft tube and annulus, solid circulation rate, and waste feed rate on combustion efficiency of the wastes have been determined in an ICFB from the experiments and the model studies. The ICFB combustor exhibits uniform temperature distribution along the bed height with high combustion efficiency (>90%). The combustion efficiency increases with increasing reaction temperature, gas velocity in the annulus region, and solid circulation rate and decreases with increasing waste feed rate and gas velocity in the draft tube. The simulated data from the kinetic equation and the hydrodynamic models predict the experimental data reasonably well.     

Combustion Characteristics of Spent Catalyst and Paper Sludge in an Internally Circulating Fluidized-Bed Combustor

Abstract

Combustion of spent vacuum residue hydrodesulfurization catalyst and incineration of paper sludge were carried out in thermo-gravimetric analyzer and an internally circulating fluidized-bed (ICFB) reactor. From the thermogravimetric analyzer-differential thermo-gravimetric curves, the pre-exponential factors and activation energies are determined at the divided temperature regions, and the thermo-gravimetric analysis patterns can be predicted by the kinetic equations. The effects of bed temperature, gas velocity in the draft tube and annulus, solid circulation rate, and waste feed rate on combustion efficiency of the wastes have been determined in an ICFB from the experiments and the model studies. The ICFB combustor exhibits uniform temperature distribution along the bed height with high combustion efficiency (>90%). The combustion efficiency increases with increasing reaction temperature, gas velocity in the annulus region, and solid circulation rate and decreases with increasing waste feed rate and gas velocity in the draft tube. The simulated data from the kinetic equation and the hydrodynamic models predict the experimental data reasonably well.     

Restoration ecology of riverine wetlands: II. An example in a former channel of the Rhône River

Riverine wetlands, which provide numerous valuable functions, are disappearing in floodplains of a channelized European river. A restoration project has been proposed by scientists to restore a former braided channel of the Rhône River by the removal of fine organic sediments in order to enhance groundwater supply. A precise and intensive prerestoration monitoring program during one year (including comparison with a reference channel) has taken into account several variables and ecological performance indicators measured at various spatial and temporal scales. Three restoration techniques were then suggested, taking into account two characteristics of ecosystem functions for increasing restoration success and self-sustainability: (1) the riparian forest as well as the shores must be preserved or disturbed as little as possible; and (2) the upstream alluvial plug must be preserved to prevent direct supply of nutrientrich water from the Rhône River. Among the three restoration options proposed, it was not possible to carry out the less ecologically disturbing one as it was considered too expensive, time consuming, and difficult to realize. A precise and intensive postrestoration monitoring program, conducted over two years, demonstrated restoration success but also unpredicted problems, such as a locally thick layer of fine organic sediment. As long as a self-sustainable state is not achieved, this monitoring should be continued. Afterwards, a less precise and less intensive long-term monitoring should enable the detection of future events that may influence ecosystem changes.     

Towards a constructivist program in safety

This paper delves into the relationship between safety and constructivism. In the past 30 years, the constructivist discourse has become very popular but also controversial as it challenges some key categories associated with modernity, such as reason, objectivity, truth and reality. In the safety literature, several works advocate its use. This paper has three objectives. The first one is to reveal the existence of a constructivist discourse in the field of safety. It does this by bringing together scattered pieces of works from different authors who endorse and apply to various topics a position labelled as constructivist. However, and that is the paper’s second objective; it demonstrates that there is not only one constructivism, but several. In order to ground this contention, the paper proceeds with a multidisciplinary and historical approach. It is then argued that it is more appropriate not to conflate this diversity of constructivisms. The paper looks for a solution to this problem by providing a classification based on two groups of parameters: mild/strong and cognitive/social, defining four types. This step serves the third objective which consists in initiating a multifaceted constructivist program in safety composed of heterogeneous but related empirical and theoretical areas of investigations.     

Effect of biogeographic history on population vulnerability in European amphibians

The genetic diversity of populations, which contributes greatly to their adaptive potential, is negatively affected by anthropogenic habitat fragmentation and destruction. However, continental‐scale losses of genetic diversity also resulted from the population expansions that followed the end of the last glaciation, an element that is rarely considered in a conservation context. We addressed this issue in a meta‐analysis in which we compared the spatial patterns of vulnerability of 18 widespread European amphibians in light of phylogeographic histories (glacial refugia and postglacial routes) and anthropogenic disturbances. Conservation statuses significantly worsened with distances from refugia, particularly in the context of industrial agriculture; human population density also had a negative effect. These findings suggest that features associated with the loss of genetic diversity in post‐glacial amphibian populations (such as enhanced fixation load or depressed adaptive potential) may increase their susceptibility to current threats (e.g., habitat fragmentation and pesticide use). We propose that the phylogeographic status of populations (i.e., refugial vs. post‐glacial) should be considered in conservation assessments for regional and national red lists.     

Sex differences in mass loss rate and growth efficiency in Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island

We investigated the relationship between the mass gained by a pup during a period of maternal attendance (as an index of milk intake) and the duration of the preceding foraging trip in relation to the mass-specific rate of mass loss during fasting periods and the growth rate of Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island. We found that (1) serially weighed male pups grew significantly faster than females pups and that (2) fasting female pups lost mass at a significantly higher rate (2.55% day⁻¹) than male pups (2.12% day⁻¹) of the same mass; (3) during periods of maternal attendance, there were no intersexual differences in the amount of mass gained by pups of the same size, hence (4) female pups required a higher daily mass gain to grow at the same rate as male pups. Our results show that intersexual differences in growth rate may be accounted for by intersexual differences in mass-specific rate of mass loss, because females lost 0.42% more of their total mass per day (i.e. 4.2 g kg⁻¹ day⁻¹) compared with male pups of the same body mass. Despite intersexual differences in growth rates, our results indicate equality of maternal expenditure between the sexes. Intersexual differences in the rate of mass loss may be due to differences in the metabolic rate, activity level and/or body composition of male and female pups. Received: 19 August 1998 / Received in revised form: 19 April 1999 / Accepted: 19 April 1999