Fish Community Structure and Food Web Dynamics in Low Rainfall Mangrove and Non-mangrove Ecosystems (Persian Gulf)

Mangroves are considered as an important source of nutrition to aquatic consumers, which, in return, sustain the fish population. However, there is still controversy about the importance of mangroves to fish communities, and furthermore, not all mangroves fulfill every function ascribed to them. The Persian Gulf presents the northernmost mangroves in the Indo-Pacific region, thriving under extreme environmental conditions such as very low rainfall and high salinities. Very few studies have addressed fish distribution patterns of mangroves in this arid region. The main objective of this study is to describe and compare the fish community structure and food web dynamics of mangrove and non-mangrove intertidal creeks in a low-rainfall system in Qeshm Island, Persian Gulf, Northern Indian Ocean (26.8°N, 55.75°E). Therefore, this thesis addresses temporal changes in mangrove fish assemblages related to the tidal and diel cycles in the meso-tidal mangrove of Qeshm Island. Also, the food webâ s dynamics were studied to determine the role of mangroves in fish food webs. Moreover, due to the arid climate along the northern Indian Ocean, many neighboring creeks are devoid of mangroves but still provide habitat for fish. This provided the necessary conditions for a natural experiment to compare fish assemblage structures and trophic diversity between creeks that are mangrove lined, and creeks without mangroves across seasons. For that, fish were collected with respect to the different combinations of tidal amplitude (and lunar phase) and day light conditions as well as seasons (winter, summer). Also, various potential food sources were collected for à ´13C and à ´15N measurements from both habitats across seasons. The findings show the impact of environmental variables (e.g. tide and temperature) in structuring fish assemblages in Qeshm intertidal creeks. The interaction between tide and time of day emerged as an important factor in organizing mangrove fish assemblages in this meso-tidal arid region. The highest fish biomass, abundance, and diversity were observed during spring tide night. High inundation during spring tides coinciding with the darkness provided the most favorable conditions for fish. When mangrove fish communities were compared with the non-mangroves, seasonality appeared as a more important factor than habitat. Extreme summer water temperatures (>33°C) likely limit the fish abundances and biomass. Fish assemblages of mangrove and non-mangrove intertidal creeks were equally diverse and dominated by the same fish families (e.g. Mugilidae). Small-sized fish dominated catches in both habitats. Also, there were no consistent differences in fish abundance and biomass for mangrove vs. non-mangrove fish collections. Community trophic diversity, measured with size-corrected standard ellipse areas (SEAc), also showed no significant difference across habitats. Instead, strong seasonal patterns were observed for the food sources and fish communities isotopic niche sizes. These findings demonstrate that the structuring effect of seasonality is more important than habitat in determining the fish distribution patterns in this region. Mangrove-derived organic matter contributed to a maximum of 36% to the fish tissue, whereas organic matter produced by microphytobenthos and plankton plays a major role in the diets of the most abundant fish species, with contributions of 64 - 100%. Thus, the fish food webâ s support of mangrove and non-mangrove intertidal creeks seems to be energetically driven by pelagic and benthic food pathways in this study area. Furthermore, the dominance of detritivores in both mangrove and non-mangrove intertidal creeks suggests the importance of benthic food webs in the intertidal creeks at Qeshm Island. The outcomes of this dissertation contribute to the global understanding of the importance of mangrove and non-mangrove intertidal creeks for fish food webs and fisheries support in a low-rainfall coastal ecosystem. The findings imply some potentially interesting consequences on habitat conservation and indicate that the abundance of small fish is not always higher in complex vegetation. Like mangrove creeks, the bare creeks are utilized by a wide variety of fish, suggesting greater attention should be drawn to these habitats

Numerical Analysis of Soil Behavior and Stone Columns Effects on the Railway Track

Railway systems are highly competitive compared with other means of transportation because of their distinct advantages in speed, convenience and safety. Therefore, the demand for railway transportation is increasing around the world. Constructing railway tracks and related engineering structures in areas with loose or soft cohesive subgrade usually leads to problems, such as excessive settlement, deformation and instability. Several remedies have been proposed to avoid or reduce such problems, including the replacement of soft soil and the construction of piles or stone columns. This thesis aims to expand the geotechnical knowledge of how to improve subgrade ballasted railway tracks, using stone columns and numerical modeling for the railway infrastructure. Three aspects are considered: i) railway track dynamics modeling and validation by field measurements, ii) modeling and parametric studies on stone columns, and iii) studies on the linear and non-linear behavior of stone columns under the dynamic load of trains. The first step of this research was to develop a reliable numerical model of a railway track. The finite element method in a time domain was used for either a 2D plane strain or 3D analysis. Individual methods for modeling a train load in 2D and 3D were implemented and are discussed in this thesis. The developed loading method was validated with three different railway tracks using obtained vibration measurements. Later, these numerical models were used to analyze the influence of stone column length and train speed in the stress field. The performance of the treated ground depends on various parameters, such as the strength of stone columns, spacing, length and diameter of the columns. Therefore, the second step was devoted to a parameter study of stone columns as a unit cell with an axisymmetric condition. The results showed that even short stone columns were effective for settlement reduction, and area of replacement was the main influential parameter in their performance. The third part of this thesis focuses on a hypothetical railway-track response to the passage of various train speeds and the influence of stone-column length. The stress-strain response of subgrade is analyzed under either an elastic–perfectly plastic or advanced constitutive model. The non-linear soil response in the finite element method and the impact of train speed and stone column length on railway tracks are also evaluated. Moreover, the reductions of induced vibration – in both a horizontal and a vertical direction – after improvement are investigated

Workforce fatigue model and its relationship with workforce productivity

Earlier studies have shown that attention to ergonomic factors such as suitable work design and planning, appropriate workplace design and facilities, and suitable machine and human design can help to boost workforce productivity, enhance work safety, increase nervous and physical well-being and fulfil job satisfaction. Ergonomic studies can assist managers in planning to reduce fatigue and increase workforce productivity. A review of the models of ergonomics shows that there is a need to conduct further research to gain a more comprehensive fatigue model. This research aims to propose a workforce fatigue model and investigate its relationship with workforce productivity, and the relationships among the variables and mediating variables with the physical and nervous abilities. The main research question is whether there is a significant relationship between the workforce fatigue model and workforce productivity. By adding forgetfulness and retraining as dependent variables and several mediating variables, this model enhances its precision and sensitivity. The service companies in Iran contribute 51.5 % to the economy of the country. From this percentage, the telecommunication service industry holds 12.8%. As a case study, the researcher decided to select a few telecommunication companies, which make up the biggest branches of the telecommunication companies of Iran. To achieve the research objectives, initially interviews were conducted with thirty experts in this area. Answers and responses from the questions about the fatigue model and the degree of its impact on productivity were used to test the performance and validity of the model. The interview results were analysed and the degree of effectiveness of each variable on the conceptual model was measured. Accordingly, a point was assigned to each variable. It was decided to include the main variables and mediating variables with the highest point in the final model. Based on the findings from the interviews, questionnaires were designed and distributed among the eligible study workforce of the companies. Four hundred and fifty respondents were selected as the sample size, among eight hundred workers, from whom information required for the analysis of the model was collected. The survey data collected from the respondents were processed using a Chi-Square Test, Kolmogorov-Smimov Z Test, One Sample TTest, and Cronbach’s alpha. The result showed a strong significant relationship (pvalue was less than 5%) between the workforce fatigue model and workforce productivity and this model provides higher efficiency and accuracy in assisting the company managers in their decision making in work planning and design. The findings from the case service companies greatly improve workforce productivity through reducing risks due to fatigue in the work environment

Protective effect of aqueous and ethanoic extracts o Achillea Wilhelmsii on oxidative stress induced by trivalent arsenic

Introduction: Arsenic (As3+) is a toxic metalloid and a potent environmental toxicant that has been reported to cause severe liver injury. Long-term exposure to arsenic through food and contaminated water can result in a chronic As3+ poisoning. One of the main hypotheses about the mechanism of As3+ toxicity is oxidative stress so that As3+  toxicity which may be due to direct reaction of reactive oxygen species with cell biomolecules, causing damages to lipids, proteins, and DNA, hence leading to cell death. In the present study, the protective role of hydro alcoholic and aqueous extract of Achillea wilhelmssi (A. Wilhelmsii) against liver injury induced by As3+ toxicity. Methods and Results: Hepatocytes were obtained by collagenase perfusion of the liver and their viability was assessed by the trypan blue (0.2% w/v) exclusion test. Cytotoxicity was associated with reactive oxygen species (ROS) formation, lipid peroxidation and loss of mitochondrial membrane potential which were prevented by antioxidants and ROS scavengers (DMSO, mannitol), mitochondrial permeability transition (MPT) pore sealing agent (carnitine) and the ATP generator (L-glutamine),  Lysosomal protective agent and glutathione discharge. We used aqueous and hydroalcoholic extracts of Achillea wilhelmssi with concentrations 25μg/ml, 50μg/ml and 100μg/ml for 3h to evaluate the protective effect of these extracts on the As3 –induced oxidative stress in isolated rat hepatocytes. Also the protective and antioxidant effects of Quercetin and Gallic acid polyphenols in the A. Wilhelmsii have been investigated as control. According to the results, the concentration of As3+, which can cause death of 50% of cells, is equivalent to 50 μM, that could significantly increase cell death, ROS production, lipid peroxidation induction and mitochondrial membrane slump compared to the control group (p <0.05). Achillea wilhelmssi extract could significantly decrease produce ROS, lipid peroxide and loss of mitochondrial membrane decline. Conclusions: In the present study, result showed the hepatoprotective role of hydroalcoholic and aqueous extract of Achillea wilhelmssi against liver injury induced by arsenic in rats had been studied by determining their effects on decrease produce ROS, lipid peroxide and loss of mitochondrial membrane decline. Because of existence large amounts of flavonoids and polyphenols, including quetitintin and Gallic acid in A. Wilhelmsii can hepatoprotective effects be attributed to these compounds

Effects of mitomycin-C on tear film function following photorefractive keratectomy for mild-to-moderate myopia

Background: Mitomycin C (MMC) is used to prevent corneal opacity after photorefractive keratectomy (PRK). This study sought to determine the effect of MMC on tear film function after PRK in eyes with mild-to-moderate myopia.Methods: This prospective, contralateral eye comparison was conducted on 30 eyes of 15 patients with low-to-moderate myopia referred to Alzahra Eye Hospital, Zahedan, Iran. The eyes of the control group underwent PRK with a balanced salt solution, while the fellow eyes in the intervention group underwent PRK with 0.02% MMC for 25 s. The tear breakup time test (TBUT) and basic Schirmer test results of eyes in the control and intervention groups were compared at baseline and 1, 3, and 6 months postoperatively. Tear osmolarity was recorded and compared at baseline and 3 months postoperatively. Results: The mean ± standard deviation (SD) age of participants was 27.53 ± 7.04 years. No statistically significant differences were observed in the means ± SDs for tear osmolarity, TBUT, and basic Schirmer test values (all P > 0.05) between MMC-treated eyes and untreated fellow eyes at baseline and during postoperative follow-up. The means ± SDs for tear osmolarity, TBUT, and basic Schirmer test results were comparable in both groups between the baseline and postoperative follow-ups (all P > 0.05). Conclusions: Single application of a standard dose of MMC (0.02%) for 25 s in PRK did not change tear stability, tear production, or variation in tear dynamics up to 6 months postoperatively in eyes with low-to-moderate myopia. Future longitudinal studies with a longer follow-up and a larger sample size are warranted to confirm our findings