Toluene depletion in produced oil contributes to souring control in a field subjected to nitrate injection

Souring in the Medicine Hat Glauconitic C field, which has a low bottom-hole temperature (30 °C), results from the presence of 0.8 mM sulfate in the injection water. Inclusion of 2 mM nitrate to decrease souring results in zones of nitrate-reduction, sulfate-reduction, and methanogenesis along the injection water flow path. Microbial community analysis by pyrosequencing indicated dominant community members in each of these zones. Nitrate breakthrough was observed in 2-PW, a major water- and sulfide-producing well, after 4 years of injection. Sulfide concentrations at four other production wells (PWs) also reached zero, causing the average sulfide concentration in 14 PWs to decrease significantly. Interestingly, oil produced by 2-PW was depleted of toluene, the preferred electron donor for nitrate reduction. 2-PW and other PWs with zero sulfide produced 95% water and 5% oil. At 2 mM nitrate and 5 mM toluene, respectively, this represents an excess of electron acceptor over electron donor. Hence, continuous nitrate injection can change the composition of produced oil and nitrate breakthrough is expected first in PWs with a low oil to water ratio, because oil from these wells is treated on average with more nitrate than is oil from PWs with a high oil to water ratio.     

Beta glucan: a valuable functional ingredient in foods

β-Glucan is a valuable functional ingredient and various extraction techniques are available for its extraction. Choice of an appropriate extraction technique is important as it may affect the quality, structure, rheological properties, molecular weight, and other functional properties of the extracted β-glucan. These properties lead to the use of β-glucan into various food systems and have important implications in human health. This review focuses on the extraction, synthesis, structure, molecular weight, and rheology of β-glucan. Furthermore, health implications and utilization of β-glucan in food products is also discussed.     

Detection of methicillin-resistant coagulase-negative staphylococci and PVL/mecA genes in cefoxitin-susceptible Staphylococcus aureus (t044/ST80) from unpasteurized milk sold in stores in Djelfa,Algeria

This study was designed to determine antimicrobial resistance phenotypes and genotypes and virulence factors in Staphylococcus aureus and coagulase-negative staphylococci (CNS) in unpasteurized milk sold in Djelfa, Algeria. Eighty-two unpasteurized cow milk samples were randomly obtained from 82 retail stores in Djelfa and tested to detect staphylococci. Species were identified by biochemical tests and MALDI-TOF. Antimicrobial resistance phenotypes and genotypes were determined by disk diffusion test, PCR, and sequencing. The Staph. aureus isolates were subjected to spa typing, multilocus sequence typing, and detection of virulence genes and the scn gene by PCR and sequencing. Forty-five (54.9%) milk samples were contaminated by staphylococci and 45 isolates were recovered: 10 Staph. aureus (12.2% of total samples) and 35 CNS (42.7%). Resistance to penicillin (blaZ), tetracycline (tetL/tetK), and erythromycin (ermB/msrA/ermC) were the most common phenotypes (genotypes). Three CNS were methicillin-resistant and all were mecA-positive. The Staph. aureus isolates were ascribed to the following lineages [spa type/sequence type/associated clonal complex (number of isolates)]: t267/ST479/CC479 (n = 6), t1510/ST5651/CC45 (n = 1), t359/ST97/CC97/ (n = 1), t346/ST15/CC15 (n = 1), and t044/ST80 (n = 1). The mecA gene was detected in the cefoxitin-susceptible t044/ST80 isolate and co-harbored the lukF/lukS-PV and scn genes. The detection of mecA-PVL-positive Staph. aureus, methicillin-resistant CNS, and multidrug-resistant staphylococcal species indicates a potentially serious health issue and reveals that unpasteurized milk sold in Djelfa city could be a potential vehicle for pathogenic and antimicrobial-resistant staphylococci.     

Cheddar Cheese Ripening and Flavor Characterization: A Review

Cheddar cheese is a biochemically dynamic product that undergoes significant changes during ripening. Freshly made curds of various cheese varieties have bland and largely similar flavors and aroma and, during ripening, flavoring compounds are produced that are characteristic of each variety. The biochemical changes occurring during ripening are grouped into primary events including glycolysis, lipolysis, and proteolysis followed by secondary biochemical changes such as metabolism of fatty acids and amino acids which are important for the production of secondary metabolites, including a number of compounds necessary for flavor development. A key feature of cheese manufacture is the metabolism of lactose to lactate by selected cultures of lactic acid bacteria. The rate and extent of acidification influence the initial texture of the curd by controlling the rate of demineralization. The degree of lipolysis in cheese depends on the variety of cheese and may vary from slight to extensive; however, proteolysis is the most complex of the primary events during cheese ripening, especially in Cheddar-type cheese.     

Nutritional characterization of high protein and high lysine barley lines

Six high protein and high lysine barley lines were derived from four crosses involving high protein andlor high lysine donors, ie Riso 1508 and SV 73608 (Hiproly×Mona⁵), with well adapted local strains V 5681 and V 4342. The trial was grown at the Wheat Research Institute, Faisalabad, Pakistan. The lines were chemically and nutritionally characterized and the results were compared with the parents. The biological value, net protein utilization and lysine contents were higher in all the derived lines than in their local parents, ie V 5681 and V 4342. The increased lysine levels in the lines B 82503 and B 82507 may be a consequence of the reduction of prolamin fractions with simultaneous increases in salt soluble fractions. In all the lines, lysine and nutritional quality increase were a reflection of high protein andlor high lysine parents. The line B 82503 had grain yield comparable to its local parent V 5681 but it was superior in lysine and some nutritional attributes to its high lysine donor parent Riso 1508. In some lines, lysine improvement was achieued without impairing grain yield.     

Characterization and physiochemical studies of crosslinked thiolated polyvinyl alcohol hydrogels

Modification and crosslinking of polyvinyl alcohol (PVA) by thiolation using thioglycolic acid (TGlA) and various crosslinkers were carried out. The crosslinked thiolated PVA (TPVA) hydrogels were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infra red spectroscopy coupled with thermal analysis (TG-FTIR) techniques. The crosslinking of the resultant material was carried out using three crosslinker sodium trimetaphosphate (STMP), glyoxal and boric acid. The influence of esterification and crosslinking on the physical and chemical properties of the material was studied. XRD showed that after crosslinking the crystallinity of TPVA hydrogels decreased. These results were further substantiated by DSC observations. The thermal stability of the TPVA hydrogels is enhanced. A significant variation in the initial decomposition temperature was observed with respect to different STMP crosslinked samples having varying TGlA concentration and different crosslinkers. The coupled TG-FTIR studies of crosslinked samples at different temperatures show that the evolution of sulfur-containing gases (carbon disulfide and carbon monosulfide) is being prominent for this material.     

Design of dual-band bandpass coplanar waveguide filter

Several recent applications in communications require filters that can operate in two or more frequency bands. The aim of this article is to exploit the advantages of coplanar waveguides (CPWs) to design a dual-band bandpass coplanar waveguide filter (DBBPF). Starting from the prototype of a two pole Chebyshev low pass filter, two frequency transformations are applied to generate the DBBPF's lumped equivalent circuit. These circuits are then implemented using compact CPW series-connected resonators patterned in the centre conductor. The designed filter operates at the two frequency bands centred at 1.7 GHz and 2.7 GHz. Measured results are obtained and compared to HFSS-simulated results with very good agreement.     

Heat transfer in a conical cylinder with porous medium

In this paper, numerical study of heat transfer in a conical annular cylinder fixed with saturated porous medium is presented. The heat transfer is assumed to take place by natural convection and radiation. The inner surface of conical cylinder is maintained at uniform wall temperature. The governing partial differential equations are non-dimensionalised using suitable non-dimensional parameters and then solved by using finite element method. The porous medium is divided using triangular elements with uneven element size. A computer software is used to solve the coupled momentum and energy equations in an iterative manner. The results are discussed for various values of geometric and physical parameters of porous medium with emphasis on cone angle of the cylinder. It is seen that the cone angle plays a vital role in heat transfer from the hot surface to porous medium.