Studies on slag deposit formation in pulverized coal combustors. 1. Results on the wetting and adherence of synthetic coal ash drops on steel

As part of a study of slag deposit formation in pulverized-coal-fired boilers, apparent contact angles and adhesion strengths of molten mineral drops contacted with cooler oxidized steel substrates have been investigated. High-speed photography indicated that freezing of the interface between the molten drop and metal surface occurred in milliseconds. Adherence occurred between an oxide film on the metal and the drop, adherence was weak on stainless steels, and particles of oxide film were broken away from the substrate when the drops were sheared off. Higher substrate temperatures gave increased adhesion, with a larger area of strong interaction between the oxide and the drop interface and less area of weak interaction. Addition of compounds to lower the liquidus temperature of the drop gave increased adherence. Pyrite drops were converted to mainly pyrrhotite on melting and showed a high degree of wetting and adherence to the oxidized steel even at low temperatures.     

Analysis of pulverized coal particles (10–100 μm) for Fe, S, Ca, Si and Al on a particle-by-particle basis

A computer controlled scanning electron microscope fitted with soft X-ray fluorescence analysed thousands of pulverized coal particles in the size range 10 to 100 μm for amounts of Al, Si, Ca, S and Fe in each of the particles. Two coals were used, namely, subbituminous C, Comanche-Wyoming and subbituminous B, Rosebud-Montana. In pulverized coal combustion Rosebud coal has a bad slagging record not predictable from conventional slagging indices based on the elemental analyses of the total coal ash. The coal particles were placed into one of four groups: little mineral matter; low melting point inorganic composition; high melting point compositions; and large amounts of iron or pyrite. On this basis, Rosebud coal had 47% of its mineral matter in groups likely to cause slagging compared with 12% for Comanche coal, in agreement with the slagging record. It is concluded that although the particle-by-particle analysis technique used here is in a crude state of development, it can give a correct indication of the possible slagging behaviour of a pulverized coal in cases where conventional slagging indices based on the analysis of the total mean coal ash fail to give the correct indication.     

Concentration and Exposure Assessment of Mercury in Commercial Fish and Other Seafood Marketed in Oman

The results of this study present analytical data of the mercury levels in several fish and shellfish species to create awareness among individuals of the risks associated with consuming fish contaminated with mercury. Mercury concentrations varied from a mean of 0.02 mg/kg in Indian mackerel to 0.19 mg/kg in shark in both fresh and frozen fish, from 0.02 mg/kg in sardines to 0.18 mg/kg in skipjack tuna in canned fish, and from 0.02 mg/kg in Indian mackerel to 0.79 mg/kg in shark in dried fish. Shellfish contained a slightly higher amount of mercury than fresh or frozen fish with a mean of 0.09 mg/kg. Trophic position, followed by habitat, was the most important factors for variability in mercury concentrations in fish and shellfish. The maximum safe weekly intake (MSWI) values of mercury were significantly higher for herbivores than for carnivores. The MSWI value for total mercury in the case of consuming most (72%) fish species was more than 5 kg; however, the MSWI value was never more than 5 kg in most (66%) shellfish species. Risks were identified upon consumption of 120 g of dried shark when exceeding the provisional tolerable weekly intake threshold (1.6 μg/kg) for methylmercury. Therefore, fish‐eating populations should reduce the quantity of dried shark to efficiently diminish the exposure to mercury.     

Survival of bacteria in less than thorough cooked,brine-injected steaks

Bacteria that may include enteric pathogens are introduced into muscle tissues when they are injected with brine. Consequently, steaks of such non-intact, non-comminuted tissues should be cooked to temperatures sufficient to render them microbiologically safe. Studies were conducted to identify the minimum safe temperature for cooking those meats. Suspensions of Escherichia coli and Listeria innocua at numbers about 8 log cfu/ml, in broth or in brines containing 2% or 5% of each of NaCl and sodium tripolyphosphate that were not supplemented or were supplemented with 2% soy protein or 2% emulsified sunflower oil were injected into the centres of 3 cm thick steaks. Groups of four steaks injected with each type of suspension were cooked to temperatures at the centres of 50, 55, 60, 65 or 70 °C. Bacteria were recovered from samples from the centres of steaks, on agars that did or did not allow resuscitation of injured cells of each organism. The results indicated that E. coli but not L. innocua was injured by the brines; that supplementing brines with protein or oil did not protect the organisms from injury or inactivation by heating; and that cooking to a central temperature > 60 ? 65 °C was sufficient to inactivate all bacteria in the meat. The centres of steaks were subsequently injected with 0.1 ml portions of five strain cocktails of E. coli O157:H7 or Listeria monocytogenes in broth containing a dye and the bacteria at numbers >8 log cfu/ml. Steaks were cooked to temperatures of 63, 64 or 65 °C, with holding for 0, 1 or 2 min after cooking before excision of all the dyed tissue from each steak and enumeration of bacteria from the tissue on resuscitating media. The results indicated that cooking to 65 °C without holding would be sufficient to reduce numbers of E. coli O157:H7 or L. monocytogenes in non-intact, non-comminuted steaks by ?7 log units.     

Fatty Acid Profile and Selected Chemical Contaminants in Yellowfin Tuna From the Arabian Sea

Fresh yellowfin tuna (n = 110) collected for a period of one year was analyzed for chemical composition, fatty acids, nutrients, and toxic metals. The mean values of investigated minerals were 892, 2834, 0.81, 6.61, 0.38, 11.0, 0.94, 0.59, 0.71, 0.53, and 0.29 mg kg^–1 for Na, K, Cu, Zn, Mn, Fe, Ni, Co, Cr, Sr, and V, respectively. Average Cd, Pb and Hg levels were 0.016, 0.029 and 0.137 mg kg^?1, respectively. The average concentrations of saturated, monounsaturated, and polyunsaturated fatty acids were 196.56, 84.8, and 218 mg 100g^–1, respectively. Yellowfin tuna contained higher DHA (148.2 mg 100g^–1) than EPA (29.3 mg 100 g^–1). A meal with 100 g of this species provides 48.6 and 71.05% of the required daily level of protein and EPA+DHA, respectively. Yellowfin tuna showed low thrombogenic (0.27) and atherogenic (0.43) potential and the value obtained for h/H index (1.97) indicates that regular intake of yellowfin tuna may bring hypocholesterolemic effect. All contaminants in the studied fish were either undetectable or present at very low levels when compared to the United States Food and Drug Administration (USFDA), Food and Agriculture Organization/World Health Organization (FAO/WHO), and European Union regulatory standards and yellowfin tuna would be one of the best options for people who frequently consume tuna fish to get sufficient EPA+DHA and essential elements.     

Histamine levels in commercially important fresh and processed fish of Oman with reference to international standards

Histamine was investigated in fresh (378), frozen (441), canned (290) and dried (24) fish samples of scombroid and non-scombroid species of Oman using a high performance liquid chromatography with a fluorescence detector. Of the 1133 fish samples tested, histamine was detected in 551 samples with a detection rate of about 41.8% among fresh fish, 61.0% of frozen fish, 78.9% of canned fish and 91.6% of dried fish samples and the mean histamine levels were 2.6, 5.8, 3.1 and 104 mg kg⁻¹, respectively. A total of 3.7% and 0.79% of the total samples exceeded the FDA and EU regulatory limits for histamine. Imported dried anchovies contained high histamine levels. The study confirms that post catching and commercialisation practices of seafood are adequate, warranting good quality fish and may not cause histamine risk to consumer in terms of human diet. While necessary monitoring may be done for imported dried fish products.     

The effects on the microbiological condition of product of carcass dressing, cooling, and portioning processes at a poultry packing plant

The log mean numbers of aerobes, coliforms, Escherichia coli and presumptive staphylococci plus listerias on chicken carcasses and carcass portions at various stages of processing at a poultry packing plant were estimated from the numbers of those bacteria recovered from groups of 25 randomly selected product units. The fractions of listerias in the presumptive staphylococci plus listerias groups of organisms were also estimated. Samples were obtained from carcasses by excising a strip of skin measuring approximately 5 x 2 cm(2) from a randomly selected site on each selected carcass, or by rinsing each selected carcass portion. The log mean numbers of aerobes, coliforms, E. coli and presumptive staphylococci plus listerias on carcasses after scalding at 58 degrees C and plucking were about 4.4, 2.5, 2.2 and 1.4 log cfu/cm(2), respectively. The numbers of bacteria on eviscerated carcasses were similar. After the series of operations for removing the crop, lungs, kidneys and neck, the numbers of aerobes were about 1 log unit less than on eviscerated carcasses, but the numbers of the other bacteria were not substantially reduced. After cooling in water, the numbers of coliforms and E. coli were about 1 log unit less and the numbers of presumptive staphylococci plus listerias were about 0.5 log unit less than the numbers on dressed carcasses, but the numbers of aerobes were not reduced. The numbers of aerobes were 1 log unit more on boneless breasts, and 0.5 log units more on skin-on thighs and breasts that had been tumbled with brine than on cooled carcasses; and presumptive staphylococci plus listerias were 0.5 log unit more on thighs than on cooled carcasses. Otherwise the numbers of bacteria on the product were not substantially affected by processing. Listerias were <20% of the presumptive staphylococci plus listerias group of organisms recovered from product at each point in the process except after breasts were tumbled with brine, when >40% of the organisms were listerias.     

Studies on slag deposit formation in pulverized-coal combustors. 3. Preliminary hypothesis for the sticking behaviour of slag drops on steels

A mechanism is postulated to explain the effects of drop composition and substrate temperature on the adherence of molten synthetic coal ash drops to steel substrates. For a strong bond to form between the drop and the oxide film on the substrate, it is necessary to form an interfacial region consisting of both iron oxide and slag. Depth profile analysis by ion beam spectrochemical analysis indicates that the thickness of this interfacial region is 1–3 μm. The formation of this region is expected to be assisted by long times of contact of liquid slag with the substrate. A heat transfer calculation indicates that high substrate temperature and lower solidus temperature greatly increased the time to completely solidify a 2 μm thick interface.     

Studies on slag deposit formation in pulverized coal combustors. 2. Results on the wetting and adhesion of synthetic ash drops on different steel substrates

A simple sticking apparatus has been further developed to study the comparative wetting and adhesion properties of a synthetic coal ash slag on boiler steels. Both the wetting and adhesion behaviour appears to be affected by the physical nature of the oxide layer on the steel surface (i.e., thickness and microporosity). The adhesion force is also found to be a function of the chemical nature of the surface oxide layer on the steel (i.e., whether the layer is predominantly ferrous (FeO) or ferric (Fe₂O₃) oxide). The presence of a sodium salt (either sulfate or carbonate) on the steel surface enhances both the wetting and adhesion properties by dissolution in the molten drop creating a less viscous glass with a lower liquidus temperature at the drop-surface interface. At this time it is difficult to establish whether the bonding between the slag and steel oxide layer is mechanical, chemical, or a combination of both.     

Functional Characterization of the MYO6 Variant p.E60Q in Non-Syndromic Hearing Loss Patients

Hereditary hearing loss (HHL) is a common genetic disorder accounting for at least 60% of pre-lingual deafness in children, of which 70% is inherited in an autosomal recessive pattern. The long tradition of consanguinity among the Qatari population has increased the prevalence of HHL, which negatively impacts the quality of life. Here, we functionally validated the pathogenicity of the c.178G>C, p.E60Q mutation in the MYO6 gene, which was detected previously in a Qatari HHL family, using cellular and animal models. In vitro analysis was conducted in HeLa cells transiently transfected with plasmids carrying MYO6^WT or MYO6^p.E60Q, and a zebrafish model was generated to characterize the in vivo phenotype. Cells transfected with MYO6^WT showed higher expression of MYO6 in the plasma membrane and increased ATPase activity. Modeling the human MYO6 variants in zebrafish resulted in severe otic defects. At 72 h post-injection, MYO6^p.E60Q embryos demonstrated alterations in the sizes of the saccule and utricle. Additionally, zebrafish with MYO6^p.E60Q displayed super-coiled and bent hair bundles in otic hair cells when compared to control and MYO6^WT embryos. In conclusion, our cellular and animal models add support to the in silico prediction that the p.E60Q missense variant is pathogenic and damaging to the protein. Since the c.178G>C MYO6 variant has a 0.5% allele frequency in the Qatari population, about 400 times higher than in other populations, it could contribute to explaining the high prevalence of hearing impairment in Qatar.