Mercury Accumulation in Marine Sediments: A Comparison of an Upwelling Area and Two Large River Mouths

Understanding marine mercury (Hg) biogeochemistry is crucial, as the consumption of Hg-enriched ocean fish is the most important pathway of Hg uptake in humans. Although ocean sediments are seen as the ultimate Hg sink, marine sediment studies on Hg accumulation are still rare. In this context, studying Hg behavior in the marine environment, especially in upwelling environments, is of particular interest due to its importance in these great upwelling regions for the global fishery. There are contradictory statements about the fate of Hg in upwelling regions. Some studies have suggested high biotic reduction of oxidized Hg and gaseous elemental mercury evasion to the atmosphere. More recent work has suggested that in upwelling regions, where productivity is high, evasion of gaseous elemental mercury is diminished due to scavenging and sedimentation of Hg by organic particles. In this study, we compared Hg concentrations and accumulation rates in the past ∼4,300 and 19,400 years derived from sediment cores collected in the Peruvian upwelling region (Peru Margin) and compared them with those of two other cores collected from the sediment fan of the Amazon and a core from the Congo Basin, which is influenced by both seasonal coastal upwelling and discharge from the river. Median Hg concentrations were higher at the Peru Margin (90.7 μg kg–1) and in the Congo Basin (93.4 μg kg–1) than in the Amazon Fan (35.8 μg kg–1). The average Hg accumulation rates in sediments from the Peru Margin (178 μg m–2 yr–1) were factors of ∼4 and ∼39 times higher than those from the Congo Basin (46.7 μg m–2 yr–1) and Amazon Fan (4.52 μg m–2 yr–1), respectively. Principal component analysis (PCA) of the geochemical data set reveals that Amazon Fan sediments are strongly influenced by the deposition of terrestrial material, which is of less importance in the Congo Basin and of minor importance in Peru Margin sediments. Accordingly, Hg export to sediments in upwelling areas largely surpasses that in fans of large rivers that drain large terrestrial catchments. The high Hg accumulation rates in the sediments from the upwelling area and the minor influence of terrestrial Hg fluxes there suggest that atmospheric-derived Hg in upwelling areas is effectively exported to the sediments through scavenging by organic particles

Corrosion inhibition of carbon steel in acidic solution by Alizarin yellow GG (AYGG)

Published September 04, 2014Alizarin yellow GG (AYGG) is a natural dye used as a corrosion inhibitor. The inhibitive action of this compound against corrosion of carbon steel in hydrochloric acid solution (1M concentration), has been tested using the weight loss measurements and electrochemical measurements techniques. The results indicates this compound is a good inhibitor for carbon steel in hydrochloric acid solution, and the inhibition efficiency increased as the concentration of this compound increased. Also the results revealed as the temperature increased, efficiency and corrosion activation energies are increased. On the basis of the experimentally determined activation energy values, the addition of this compound can be considered chemisorption adsorbed.Sadeq Hooshmand Zaferani and Mohammad Reza Shishesa

Failure Analysis of Corrosion Case Histories

Sadeq Hooshmand Zaferan

The application of finite element analysis as a new approach in corrosion and integrity assessment programs

Published: February 02, 2017Structural integrity assessment procedures are interesting areas in many industrial plants, e.g., oil and gas, and petrochemical for ensuring the safety and economy of an operating sector. The remaining strength of components (e.g. pipelines, risers) with corrosion defects is a prevalent project in the oil and gas industry, and it has been investigated for years via using experimental, numerical and analytical methods. Obtaining the stress distribution in the vicinity of corrosion defects is a decisive phase in understanding the structural integrity of corroded components under high internal pressure. In the corrosion based management programs, finite element analysis (FEA) can provide valuable results in the integrity assessment. Also, FEA can be applied to corrosion monitoring of structures by considering different parameters such as protecting current distribution, electrochemical potential grid and coating degradation. This research discusses the application of FEA in the corrosion and integrity assessment process based on three areas including, in-service performance of corroded parts, repairing methods and corrosion monitoring techniques.Sadeq Hooshmand Zaferan

Improvement of Thermoelectric Properties Through Manipulation of their Microstructure: the Effect of Graphene Reinforcement

Environmental changes and extreme climate-related events are mainly attributed to greenhouse gas (GHG) emissions and are becoming a growing concern. The reported scientific evidence, highlighting such interrelationships, has convinced researchers to look for clean energy sources and improve operational efficiencies, and capture and convert the waste heat into electricity. Since almost two-thirds of energy is converted to heat and wasted, the recovery of waste heat will boost savings in fossil fuel consumption as an abundant source of energy. In this regard, thermoelectric (TE) compounds can be employed to convert the waste heat into electricity, thereby increasing the efficiencies of energy generating operations. Such an approach is even applicable to renewable energy (RE) sources. However, the applications of the thermoelectric converters necessitate the development of advanced, efficient thermoelectric materials with a high level of thermomechanical stability. This doctoral research project aims to develop and modify thermoelectric compounds by manipulating their microstructure and improving their mechanical properties by reinforcement with graphene nanoplates (GNPs). To the best of our knowledge, there is no specific report in the open literature to determine the reinforcing effects of graphene nanofillers (e.g., GNPs) on thermoelectric products. There is a lack of a comprehensive assessment in the scientific and industrial communities in evaluating the advantages and drawbacks of GNPs, as the reinforcing agent on TE compounds. In this dissertation, to assess the performance of the GNPs, three potential thermoelectric compounds, namely MnTe, CoVSn, and CuSbTe2, have been investigated. These designated compounds address the requirements for covering an extended working temperature range from low to high, examining various crystal structures (e.g., Chalcogenides and half-Heusler), and developing environmentally-friendly (i.e., lead-free) TE products. The bulk samples with the addition of small quantities of GNPs (0.25, 0.5, 0.75, and 1 wt. %) were synthesized using powder metallurgy and fabricated by spark plasma sintering (SPS). The thermoelectric factors, magnetic behavior, microstructure, and mechanical properties of the samples were evaluated and analyzed. Grain growth inhibition is the main consequence of the reinforcing GNPs, which results in an enhancement in the thermoelectric and mechanical characteristics of the nominated TE products. Scattering of electrical carriers and phonons due to the precipitation of the reinforcing GNPs in the matrix, thus providing a higher density of microstructural boundaries, improves the thermoelectric properties. Furthermore, microstructural manipulation, such as crystal/particle size reduction caused by the segregation of the reinforcing GNPs as a second phase in the matrix, enhances the mechanical characteristics of TE compounds, for example, the fracture toughness () and hardness.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 202

Knowledge and attitude towards HIV/AIDS among Iranian students

BACKGROUND: Young people are of particular importance in state policies against Acquired Immunodeficiency Syndrome (AIDS). We intended to assess the knowledge and attitude of high school students regarding AIDS in Iran. METHODS: Through a cluster-sampling, 4641 students from 52 high schools in Tehran were assessed by anonymous questionnaires in February 2002. RESULTS: The students identified television as their most important source of information about AIDS. Only a few students answered all the knowledge questions correctly, and there were many misconceptions about the routes of transmission. Mosquito bites (33%), public swimming pools (21%), and public toilets (20%) were incorrectly identified as routes of transmission. 46% believed that Human Immunodeficiency Virus positive (HIV positive) students should not attend ordinary schools. Most of the students wanted to know more about AIDS. In this study knowledge level was associated with students' attitudes and discipline (p < 0.001). CONCLUSION: Although the knowledge level seems to be moderately high, misconceptions about the routes of transmission were common. There was a substantial intolerant attitude towards AIDS and HIV positive patients. We recommend that strategies for AIDS risk reduction in adolescents be developed in Iranian high schools

Spatial and temporal patterns of benthic macrofauna in Gorgan Bay, south Caspian Sea, Iran

We quantified the distribution, abundance and assemblage structure of macrofauna at 22 stations in Gorgan Bay, seasonally in 2012-2013. Also, depth, temperature, salinity, DO, TOM and sediment particle size were measured in each station. The highest concentration of TOM was measured near the western littoral zone (10.22) while the mouth part and north-eastern area was characterized by the lowest values (2.65 % and 4.69). A total of 31658 individuals belonging to 12 families and 14 species were identified. Polychaeta with 3 species was the most dominant group in terms of abundance. The four most abundant taxa making up 85% of all specimens were Streblospio gynobranchiata, Tubificidae, Hediste diversicolor and Abra segmentum. The maximum density (7,893 ind/m^2) was obtained at station 1 while the minimum (1,777 ind/m^2) was observed at station 16. The western area was characterized by the highest species diversity (H', 1.94) and the stations 10, 8 and 7 were characterized by the lowest diversity indices (H', 0.72, 0.77 and 0.87, respectively). The PCA showed that water parameters with more temporary variations had a greater significance in explaining the system variability, and a not marked but evident difference between the two parts of Gorgan Bay was observed and supported by nmMDS test. So Gorgan Bay presents transitional macrobenthic assemblages that are spatially distributed along substrate gradients but it seems that the coastal ecosystem of the south Caspian Sea and mouth-eastern part of Gorgan Bay is very dynamic and some species are forming a metapopulation toward western sites

Anterior subcutaneous transposition of ulnar nerve with fascial flap and complete excision of medial intermuscular septum in cubital tunnel syndrome: A prospective patient cohort

Objective: Regarding the frequency of cubital tunnel syndrome, varieties of treatment modalities, and ambiguity of anterior subcutaneous transposition of ulnar nerve method, we aimed to evaluate the efficacy of this procedure in patients with cubital tunnel syndrome referred to Taleghani hospital between 2006 and 2009. Methods: This study was a case series including all referred patients with definite diagnosis of cubital tunnel syndrome, treated by anterior subcutaneous transposition. Treatment results were measured according to modified Bishop rating system, and were ranked into excellent, good, fair, and poor. Variables such as gender, age (less/more than 45 years), causation, and initial severity, determined by Dellon criteria preoperatively, were analyzed by Fisher’s exact test. Results: This study was performed on 26 eligible cases including 29 elbows, 38% males and 62.1% females, with mean age of 44.5 years (ranging 23–72 years). In a 12 months follow-up post-operatively, 62% showed excellent, 20.7% good, and 17.3% fair, with no poor result. In a 1–12 months follow-up post-operatively, results showed improvement, and initial severity and old age were demonstrated to significantly affect treatment results (P < 0.07). Conclusion: Though considered standard of care, the present study suggests that criteria for surgical techniques of ulnar nerve decompression, e.g. simple decompression vs. more extensive repair as in the present cohort, should be revised by controlled prospective studie