A new method for calculating saddle seat height with an emphasis on optimal posture based on trigonometric relations

Introduction. Based on the literature, the ergonomic saddle chair provides the most appropriate posture for users. Determination of the seat height is critical to establish the proper posture, carried out using various methods of anthropometry. This study aimed to develop a simple and applied method for determining the saddle seat height with an emphasis on appropriate posture. Methods. In this study, anthropometric dimensions including weight, body height, popliteal height and seat height at 135° knee angle in 150 male and female dentists were measured. In the laboratory, to determine the ‘acetabuloischial number’, 25 male and female natural hip bones were measured. The mean saddle-chair height with knee angle of 135° was then compared by two different methods, field measurement and the new calculation method. Results. The results showed a strong correlation between data gathered from the two different methods, the field measurement and the new calculation method (98%), and Cronbach’s α from the intraclass correlation was equal to 0.994 (p?<?0.05). This indicated that the two methods produced similar results. Conclusion. The new method can be applied to calculate the optimal height of the saddle seat based on body height and popliteal height.     

Evaluation of dilute hydrochloric acid and acid ammonium oxalate as extractants for some heavy metals from Nile River sediments

The suitability of a 0.5 M HCl solution for extraction of Fe, Mn, Cd, Co, Cu, Pb, and Zn from Nile River sediments was evaluated by comparing its effectiveness with that of conventional acid ammonium oxalate (Tamm's solution) and aqua regia extraction solutions. The present study has shown that although the extraction data indicate that both 0.5 M HCl and acid ammonium oxalate solutions are able to extract heavy metals simultaneously from the adsorbed, organic, and precipitated phases of Nile sediments, the 0.5 M HCl solution is preferred. It provides a rapid, reliable, and inexpensive method of measuring environmentally mobile metal concentrations in the aquatic sediments. From an analytical chemistry point of view, the 0.5 M HCl extracts do not clog the atomizer of the spectrophotometer. Extraction with dilute HCl solution obviates the need to use chemicals, some of which are toxic or not available readily as a high-purity grade. A standard extraction method should be relatively simple, to conduct a routine analysis of large numbers of sediment samples, yet at the same time it should provide sufficient information for assessment of the environmental impact of particulate metals. Therefore, extraction with 0.5 M HCl solution is very suitable for heavy-metal pollution monitoring in the Nile River     

Toxic responses of different organs following occupational exposure to sub-threshold limit value levels of paving asphalt fumes

The main purpose of this study was to ascertain whether occupational exposure to asphalt fumes, under normal working conditions, is associated with any hepatotoxic, nephrotoxic, or hematotoxic response. This was a cross-sectional study in which 210 subjects (80 exposed and 130 reference subjects) were investigated. Using standard methods, atmospheric concentrations of total particulate and benzene-soluble fractions of asphalt fumes were measured. Additionally, urine and blood samples were taken from subjects for complete blood count, white blood cell differential test, urinalysis, and routine biochemical tests of kidney and liver function. Both groups were similar as far as their demographic variables and smoking habits were concerned. The levels of exposure to total particulate and benzene-soluble fractions were estimated to be 0.9?±?0.2 and 0.32?±?0.09 mg m^?3, respectively (mean?±?SD), both of which being lower than the existing threshold limit values. Statistically, significant associations between exposure to asphalt fumes and changes in most liver and kidney function tests and complete blood count parameters provided circumstantial evidence in favor of the notion that exposure to sub-threshold limit value levels of total particulate and benzene-soluble fractions is associated with early liver and kidney dysfunction as well as hematological disorders.     

Factors affecting incentive dependency of residents to participate in e-waste recycling: a case study on adoption of e-waste reverse supply chain in Iran

Modern societies face a dilemma called electronic waste (e-waste). This waste, which may contaminate the soil or cause unwanted impacts on human health when treated improperly, is one of the fastest growing waste streams in developed as well as developing countries and has brought great environmental impacts. Developing countries like Iran also face this modern waste management challenge. In order for more appropriate disposal or, if possible, recycling of this waste, more attention has been paid to reverse logistics as the most appropriate way to manage them. The first and most important action to address e-waste and implementation of reverse logistics is to persuade residents to bring back their obsolete electronic products. This paper attempts to understand significant factors affecting residents’ incentive dependency to participate in e-waste recycling program. Socioeconomic and demographic information of different residents is discussed by means of logistic regression for the first time in Iran. The results show that about 58.7 % of residents will participate even if no incentive is given. Household income, household size, education, e-waste concern level, and marital status are the significant factors affecting the incentive dependency of respondents.     

Assessment of metals in soil extracts and their uptake and movement within Tamarix nilotica at Lake Nasser banks, Egypt

This study aims to determine heavy-metal levels in soil from the banks of Lake Nasser, the ability of Tamarix nilotica to accumulate such metals from soil and hence its potential for phytoextraction. Soil and Tamarix samples were collected from the banks of four bights around Lake Nasser and analysed for Fe, Mn, Ca, Mg, Cr, Cu, Ni, Zn, Cd and Pb by atomic absorption spectrometry, whereas Na and K were measured by atomic emission spectrophotometry. Three different methods of extraction were used for the soil samples. Lead, copper and zinc were equally distributed between the exchangeable phase and Fe/Mn oxide-bound form, while other measured metals were mainly present in the Fe/Mn oxide fraction. With the exception of iron, all metals studied showed total concentrations within the geochemical background values. T. nilotica exhibited elevated concentrations of Na (36.2-48.5 mg g^-1) and K (2.74-4.33 mg g^-1) in stems, and relatively high concentrations of Pb, Cd and Co (0.39-1.03 µg g^-1, 0.24-1.3 µg g^-1 and 1.94-5.3 µg g^-1, respectively) are found in plant leaves. Bioaccumulation factors of Na and K (9.3 and 12.63, respectively) were high in T. nilotica stems. While the bioaccumulation of Pb, Cd, Co and Ni (2870.1, 2035.4, 10.5 and 5313.2, respectively) was high in plant leaves, Fe, Mn, Ca and Mg were accumulated relatively equally in plant stems and leaves. T. nilotica was found to secrete high amounts of Na, Ca and K, in addition to small amounts of all accumulated metals except Cd and Cu. These secreted metals appeared as salt crystals (67.5% Na; 25.8% Ca; 5% Mg; 1.5% K and 0.16% trace and minor elements) on the plant surface. The concentrations of all the metals studied in T. nilotica were higher than in the salt crystals. Statistical analysis of the database suggests bioaccumulation of these metals from soil to T. nilotica. This reflects the importance of using T. nilotica as a model in the phytoremediation process as an established environmental clean-up technology.     

Evaluation Of Ground Water Quality In Dakhla Oasis (Egyptian Western Desert)

Chemical analyses of ground water and soil samples at Zakhera Village (Dakhla Oasis, Egyptian Western Desert) were carried out on ten artesian wells. The interrelationships between the major and minor ions' behaviour and the prevailing geological and environmental conditions were examined. Ground water quality varies widely, even at short distances, depending on hydrogeological conditions, pumping period, depth of aquifer, type of soil, and human activities. Significant differences of the flux coefficient values for metals and non-metals were observed as a result of the redox status of their environment and adsorption phenomena. Water quality index (WQI), and saturation index (SI) indicated the suitability of these samples for different uses.     

Effect of fertilizer application on soil heavy metal concentration

A large amount of chemicals is annually applied at the agricultural soils as fertilizers and pesticides. Such applications may result in the increase of heavy metals particularly Cd, Pb, and As. The objective of this study was to investigate the variability of chemical applications on Cd, Pb, and As concentrations of wheat-cultivated soils. Consequently, a study area was designed and was divided into four subareas (A, B, C, and D). The soil sampling was carried out in 40 points of cultivated durum wheat during the 2006–2007 periods. The samples were taken to the laboratory to measure their heavy metal concentration, soil texture, pH, electrical conductivity, cationic exchange capacity, organic matter, and carbonate contents. The result indicated that Cd, Pb, and As concentrations were increased in the cultivated soils due to fertilizer application. Although the statistical analysis indicates that these heavy metals increased significantly (P value < 0.05), the lead and arsenic concentrations were increased dramatically compared to Cd concentration. This can be related to overapplication of fertilizers as well as the pesticides that are used to replant plant pests, herbs, and rats.