Development and characterization of Sulfur dioxide gas analyzer

Sulfur dioxide (SO2) is considered one of the main contaminants in air because of its major contribution to acid rain and due to the major health concerns associated with exposure to high concentrations of SO2. Hence, there has been a great interest in the determination of SO2 because of continuous monitoring its impacts on the environment and public health. However, limited reports targeted SO2 in gas streams. Therefore, the primary objective of the present work was to develop affordable gas analyzer for continuous monitoring of SO2 in gas streams. The principle of operation of the described analyzer was based on a gas diffusion scrubber (in the form of hollow fiber membrane module, HFMM) as a prior gas sampling unit which allowed the contact between the gas stream and a selected carrier solution. SO2, present in the gas stream diffuses to and dissolves in the flowing carrier solution. The concomitant changes of the carrier solution can be measured by means of a suitable flow-through detector placed downstream to produce analytical signal for the quantification of SO2 in the gas stream. The selected detectors were limited to electrochemical detectors because of their simplicity and they do not usually require additional reagents or prior derivatization reactions. With regards to the chemical properties of SO2, pH, conductivity and amperometric detectors were selected as potential detectors for the construction of SO2 gas analyzers. The first detector evaluated in the current project was based on potentiometric pH measurements. The obtained optimum experimental conditions for S02 detection were 0.1 M potassium oxalate buffer as carrier solution at flow rate 1.5 mL/min, gas flow rate 250 mL/min, using flat-bottom pH glass electrode and HFMM consisting of 60 PP fibers. Under the optimized conditions, a Nernestian slope up to 10000 ppm with a detection limit of 1.0 ppm SO2 was obtained. The response time varied from 20 to 200 seconds whereas the recovery time was 600 seconds when SO2 concentration decreased from 1000 ppm to zero. The pH-detector showed excellent selectivity. CO2 up to 500 folds did not exert significant interference and H2S up to 5 folds greater than that of SO2 was tolerated. The second described detector was based on conductivity detection. The obtained optimum experimental conditions for S02 detection were 1.0 mM H2O2 as carrier solution at flow rate 2.0 mL/min, gas flow rate 200 mL/min, using commercial conductivity probe and HFMM consisting of 60 PP fibers. The favorable performance characteristics of the proposed SO2 analyzer was successfully applied in monitoring real experiment of removing SO2 from a gas stream. The optimized detector gave linear range up to 2500 ppm, a detection limit of 16 ppm for SO2 in nitrogen and 115 to 180 seconds for recovery time. In addition the conductometric detector showed no interference of CO2 up to 100 folds greater than that of SO2. The third detector was based on a novel amperometric detection. The utilized electrode was based on an organic conducting salt (OCS) based on tetrathiafulvalenetetracyanoquinodimethane [TTF-TCNQ] complex. The TTF-TCNQ was mixed with silicone oil in 1:1.25 ratio. The formed paste was packed in Teflon cavity (12 mm in diameter). The obtained optimum experimental conditions for SO2 detection were 0.2 M potassium phosphate buffer pH 6.5 as carrier buffer at flow rate 5.0 mL/min, using commercial HFMM mini-module. The TTF-TCNQ electrode was polarized at 0.24 V vs. SCE. The obtained amperometric response was linear up to 500 ppm and can detect as small as 10 ppm of SO2 and showed no interference at very high levels of CO2 (3900 folds). The advantages of the developed SO2 gas analyzers were manifold which include (i) the obtained performance characteristics of the described SO2 analyzer can be tuned for certain application requirements such as high sensitivity, wide linearity range, high selectivity towards a particular interfering gas, etc. (ii) low construction and operational cost, (iii) no special disposal required for the waste carrier, (iv) favorable response characteristics such as fast response, excellent reproducibility and signal stability, (v) the entire analyzer construction can be miniaturized to provide low-cost portable unit for industrial and/or environmental monitoring. This latter advantage presents some potential for commercialization of the described analyzer

Overview on Mediterranean Shark’s Fisheries: Impact on the Biodiversity

Bibliographic analysis shows that the Mediterranean Sea is a hot spot for cartilaginous species biodiversity, including sharks, rays, and chimaeras; 49 sharks and 36 rays were recorded in this region. However, they are by far the most endangered group of marine fish in the Mediterranean Sea. The IUCN Red List shows clearly the vulnerability of elasmobranchs and the lack of data; 39 species (53% of 73 assessed species) are critically endangered, endangered, or vulnerable. The biological characteristics of elasmobranchs (low fecundity, late maturity, and slow growth) make them more vulnerable to fishing pressure than most teleost fish. Overfishing, the wide use of nonselective fishing practices, and habitat degradation are leading to dramatic declines of these species in the Mediterranean Sea. In general, elasmobranchs are not targeted but are caught incidentally. In many fisheries, they are, however, often landed and marketed. A decline in cartilaginous fish species landings has been observed while fishing effort has generally increased. Better understanding of the composition of incidental and targeted catches of sharks by commercial fisheries are fundamentally important for the conservation of these populations. Moreover, problems encountered by elasmobranchs in the area are highlighted, and conservation measures are suggested

How Nestle Applied Shared Value Creation in Agriculture Sector to achieve Sustainable Agriculture and Make more Profit «Nestle Model»

This paper explains how Nestlé used the shared value concept to make agriculture more sustainable and achieve more profit by creating business value. Based on qualitative research, we use a case study approach to investigate the idea of shared value in achieving sustainable agriculture. We analyzed Nestlé programs in three areas: rural development, environmental sustainability and the Water field. We found that applying the shared value concept by nestle make agriculture more sustainable and leads to business value

First record of three species of "Pythium" from Moroccan waters

First record of three species of Pythium from Moroccan waters. Species of Pythium, including P.torulosum, P.catenulatum and P. "Group F", isolated from dam near Rabat city (capital of Morocco) in northern Africa, are described. Taxonomic and morphological details of the fungi are discussed. This work is the first report of these species from Moroccan waters.Primeras citas de tres especies de Pythium para Marruecos. Se describen especies de Pythium, incluyendo P. torulosum, P. catenulatum y P. "Group F", aislados cerca de la ciudad de Rabat (Marruecos) en el norte de Africa. Se discuten detalles taxonómicos y morfológicos del hongo. Este trabajo es la primera refencia de estas especies en aguas de Marruecos

Embryoid induction and plantlet regeneration from leaf segments of sugarcane (Saccharum officinarum L.)

     Sugarcane (Saccharum officinarum L.) is an economically important crop in Sudan for domestic consumption and export. It is the first and essential source for production of high purity sugar. Tissue culture techniques can be used for in vitro conservation of sugarcane (Taylor and Dukic, 1993) and mass propagation of elite cultivars of crop species. Moreover, it was used for production of pathogen-free planting material from infected mother plants. Variability induced in vitro can furnish a base for improvement of vegetatively propagated crops including sugarcane. Different tissue culture techniques were applied successfully to sugarcane propagation and plant regeneration through organogenesis of shoot meristem (Nadar and Heinz, 1977; Ho and Vasil, 1983a), cell suspension cultures (Ho and Vasil, 1983b, Aftab et al., 1996) and protoplast cultures ( Liu, 1994). Cell suspen - Sion cultures were also used for cytological, pathological (Peros and Lombard, 1992), biochemical and physiological investigations of sugarcane (Heinz et al., 1977).      This study was initiated, during 1998-2000, to investigate the effect of 2,4-D on induction of embryogenic callus from leaf explants of sugarcane and regeneration of somatic embryos on different concen-trations of Murashige and Skoog (1962) medium (MS)

Sous le signe indien ou le pessimisme littéraire : poétique du fatalisme et du déterminisme dans Douleur exquise de Salah Oudina

La littérature algérienne francophone postmoderne suggère de nouvelles thématiques qui appréhendent des réflexions sur l’existence dans son rapport à l’expérience humaine. En dépit de la prévalence de la science à l’époque contemporaine, certaines croyances et superstitions ont su traverser le temps et trouver refuge dans les esprits fatalistes, nourries de désespoir et de défaitisme. Le roman algérien de langue française Douleur exquise de Salah Oudina dépeint un cadre général de déception et d’affliction dans le rapport conflictuel de l’homme à Dieu et nous propose de pénétrer dans l’esprit fataliste et l’attitude défaitiste du protagoniste dans sa tentative de trouver des réponses à des questions d’existence et de providence. Nous tenterons dès lors de procéder à une étude analytique des différentes manifestations du fatalisme et du déterminisme dans l’œuvre à travers une thématique éclatée qui raconte le parcours d’un antihéros, dans une certaine ambiance pessimiste et prospective. Le déterminisme psychique du personnage sera projeté sur une société ambivalente et à l’échec pour ainsi tenter de reconstruire le chaos d’un monde qui fonce vers l’abîme. Nous analyserons les signes du fatum y compris le retour au mythe des ancêtres à l’origine de la malédiction ainsi que la manière dont le narrateur déjoue, par le biais de la mise en abyme, le sort du protagoniste et propose la reconstitution d’une société dystopique dans son ultime tentative de regagner l’optimisme souhaité et de contourner le destin