The Effectiveness of Zn Leaching from EAFD Using Caustic Soda

Electric arc furnace dust (EAFD) is a toxic waste which is mainly rich in iron oxide, zinc, and lead. Hydrometallurgical extraction of zinc from Jordanian EAFD in alkaline medium was investigated; NaOH, NaHCO₃, and Na₂CO₃ were used as leaching agents. The pH values for the prepared solutions were 8.3, 8.2, and 12.55 for NaHCO₃, Na₂CO₃, and NaOH, respectively. The effect of NaOH concentration (1, 3, 5, 7, and 9 M), contact time (5 min to 3 h), temperature (20, 40, and 60), and solid-to-liquid ratio (SLR; 20, 40, 80, and 120 mg/ml) on the leachability of zinc from EAFD were tested. The initial EAFD and the resulting leach residues were characterized using X-ray diffraction (XRD) and X-ray fluorescence (XRF). EAFD contained 25.9% Zn, 18.0% Fe, and 3.2% Pb. A maximum zinc recovery of 92.9% was achieved using 6 M NaOH at 60 °C with solid loading of 20 g/L and 3 h leaching time. NaHCO₃ and Na₂CO₃ were not efficient leaching agents for Zn extraction since the recoveries were only 2.6 and 4.5%, respectively. Zn and Pb were depleted in the residues with an E-factor of 0.5–0.6 and 0.1–0.25, respectively. Iron was enriched in the residues; the E-factor was around 2. The EAFD contained mainly zincite, franklinite, and magnetite. After 3 h leaching, only traces of zincite exist in the residues, while sylvite and halite were completely dissolved.     

Effects of Silicon Application on Wheat Growth and Some Physiological Characteristics under Different Levels and Sources of Salinity

We investigated the effects of silicon (Si) and the levels and sources of salinity on the growth and some physiological properties of wheat (Triticum aestivum cv. Chamran) in a sandy loam soil under greenhouse conditions. Treatments comprised four Si levels (8, 50, 100 and 150 mg kg^?1 soil), four salinity levels (0.46, 4, 8 and 12 dS m^?1) and two salinity sources (sodium chloride (NaCl) and four-salt combination). Salts combination included NaCl, sodium sulfate (Na₂SO₄), calcium chloride (CaCl₂) and magnesium sulfate (MgSO₄) at a molar ratio of 4:2:2:1. The experiment was arranged as a completely randomized design in a factorial manner, with three replications. Increasing salinity level resulted in a significant decrease in shoot dry weight, chlorophyll content and catalase (CAT) activity, and it caused a marked increase in proline and glycine betaine (GB) concentrations and superoxide dismutase (SOD) enzyme activity. The stimulating effect on GB accumulation and SOD activity was more intense in NaCl-treated plants. However, the source of salinity had no significant effect on shoot dry weight, chlorophyll and proline concentrations, and CAT activity. Si application enhanced all the above-mentioned parameters, except for proline. The suppressing effect of salinity on shoot dry weight, chlorophyll concentration and CAT activity was alleviated by Si supplementation. The stimulating effects of Si fertilization on shoot dry weight and chlorophyll concentration became more pronounced at higher salinity levels. It could be concluded that a decrease in soil osmotic potential, nutrient imbalance and increasing reactive oxygen species (ROS) in salt-treated plants caused growth suppression, while Si supply decreased the deleterious effects of excess salt on wheat growth. Consequently, it appears that when wheat plants are to be grown in salt-affected soils, it is highly recommended to supply them with adequate available silicon (Si).     

Circadian rhythm of metabolic changes associated with summer heat stress in high-producing dairy cattle

The current study aimed to investigate the circadian rhythm of blood metabolic parameters associated with summer heat stress (HS) in dairy cows. Ten healthy lactating Holstein Friesian cows were followed during HS for three successive days at six different time points. Blood was sampled from each cow starting from 07:00 am; at 4-h intervals. Ambient air temperature and relative humidity were recorded, and temperature-humidity index (THI) was calculated as well. Respiration rate (RR) and rectal temperature (RT) were recorded for each cow at the time of blood sampling. Concentrations of glucose, non-esterified fatty acids (NEFA), total cholesterol (TC) and urea were measured in each blood sample. The THI values were >68 at all times of the day, and the highest values were recorded at 11:00 am, 03:00 pm and 07:00 pm (80.9, 83.7, and 80.8, respectively). All the cows showed a significantly higher RR and RT coinciding with higher THI values (93 ± 4 and 39.6 ± 0.1; 90.2 ± 3.4, and 40.1 ± 0.1; 87.6 ± 4.1, and 39.8 ± 0.1, respectively, P < 0.05). The concentrations of glucose were the lowest at 11:00 am and 03:00 pm (3.75 ± 0.1 and 3.44 ± 0.1 mmol/L, respectively, P < 0.05). Decreased glucose concentrations coincided with increased NEFA concentrations, (0.43 ± 0.01 and 0.56 ± 0.02 mmol/L, respectively, P < 0.05), and were highly negatively correlated (r = −0.50, P < 0.001). The highest urea and TC concentrations were registered at 11:00 am (6.11 ± 0.15 mmol/L and 109.9 ± 2.2 mg/dl, respectively) whereas the lowest urea and TC values were recorded at 03:00 am (4.97 ± 0.18 mmol/L and 99.5 ± 1.7 mg/dl, respectively, P < 0.05). The results of the present study indicate that there was a circadian variation in glucose, NEFA, urea, and TC resulting in the most unfavorable metabolic condition during the hottest moment of the day in dairy cattle. Earlier work revealed that HS-metabolic changes are reflected in the follicular fluid. The circadian changes observed in the present study associated with HS may imply that also the microenvironment of the oocyte is affected.     

Base cations ameliorate Zn toxicity but not Cu toxicity in sugar beet (Beta vulgaris)

Seedlings of sugar beet (Beta vulgaris) were grown in nutrient solutions containing a range of Cu and Zn concentrations. Based on measurements of shoot and root length and dry weight, copper was found to be already toxic at 10 μM, while Zn became toxic at 100 μM. At Cu and Zn levels found to induce a similar level of growth inhibiton, the influence of increasing the supply of K, Ca and Mg was investigated. Increasing the concentration of both Ca and Mg in the nutrient solution attenuated the degree of inhibition of root growth by Zn, but not Cu. Potassium did not affect the toxicity of either Cu or Zn. An increase in Ca decreased the level of both Cu and Zn in roots. Magnesium ameliorated the toxicity effects of Zn without effecting the Zn concentration in the roots. Treatment with Zn significantly decreased the concentration of Mg in the roots. An increased supply of Mg lowered the percentage decrease in root Mg concentration due to Zn toxicity. The maintenance of an adequate Mg level in the roots may be critical to prevent Zn induced inhibition of root growth.     

Vegetable oil blend as alternative lipid resources in diets for gilthead seabream, Sparus aurata

The recent decreasing worldwide supplies of marine oils have forced the aquaculture industry to investigate alternative lipid sources for use in marine fish feeds. The aim of this study was to determine the impact of dietary replacement of fish oil by vegetable oils on gilthead seabream (Sparus aurata) growth performance, nutritive utilization, body composition, and fatty acid profile as well as feed cost. Two dietary vegetable oil (VO) mix blends (VO1 and VO2) in which: sunflower (SO), cottonseed (CO) and linseed (LO) for VO1 or soybean oil (SBO) for VO2, were tested as 60% fish oil (FO) substitutes versus the 100% FO control or reference diet (FO). Three iso-proteic (46% CP) and iso-lipidic (18%) experimental diets were hand fed, twice a day, 6 days a week to apparent visual satiety to triplicate groups of seabream growers (average initial weight, 130.9 ± 3.44 g), until fish reached market size (300–400 g/fish) after 20 weeks at mean ambient temperature 27.0 ± 1.8°C. All experimental diets were well accepted by seabream growers regardless of the different lipid sources used, as overall mean feed intake (FI) and daily intake (DFI) were not significantly different (P > 0.05) among dietary treatments. In terms of growth performance, fish fed VO1 diet (with LO) exhibited a relatively lower, but significant (P < 0.05), total weight gain (WG) than fish fed all FO diet (FO). However, mean value of WG of fish fed either vegetable oil-tested diet was nonsignificantly different. Feeding seabream growers vegetable oil (VO) diets (VO1 or VO2) had no significant effect on specific growth rate (SGR), daily weight index (DWI), or feed conversion ratio (FCR) among dietary treatments. Consumption of VO for 20 weeks did not significantly alter the major nutrient composition of fish, but the muscle fatty acid (FA) profile was significantly altered compared to the reference FO diet. Comparatively reduced levels of eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA), as well as elevated levels of linoleic and linolenic acids (LA and LNA) compared with fish fed the FO were noticed. In terms of economics, 17 or 20% reduction in Kg feed cost was obtained for diets VO1 or VO2, respectively. In terms of growth performance and cost, VO2 diet showed slight relative superiority over VO1 diet. However, in terms of liver structure morphology, VO1 diet (with LO) has resulted in less fat-infiltration and altered hepatic cells than VO2 (with SBO). As these traits do not affect yield or the price paid for the fish, VO2 diet has therefore been considered better than VO1 as complementary lipid sources for gilthead seabream grower diets.     

Experimental study on compressive,flexural and fatigue behavior of warp-knitted spacer fabrics reinforced polyurethane cast elastomer composites

This paper reports an experimental study on compressive, flexural and fatigue behavior of polyurethane cast elastomers (PCE) reinforced with warp-knitted spacer fabrics (WKSF). It aims to investigate new applications for these fabrics as the reinforcements for elastomeric parts such as shoe soles, rubber floor coverings, vibration dampening and shock absorbing pads, etc. A series of polyester WKSF with different thickness, structure of outer layer fabric and spacer yarns density was prepared and converted to PCE reinforced WKSF using the hand molding method. All the samples, including the neat PCE, were subjected to static compression, flat and spherical compression, three-point bending and flexural fatigue tests. The results showed that reinforcing PCE with WKSF, considerably enhances its spherical compressive strength (concentrated loading), flexural strength and fatigue resistance. However, it deteriorates flat compressive strength (distributed loading) and recovery behavior after static compression loading. The effect of fiber weight fraction, thickness, structure of outer layer fabric and spacer yarns density on the mentioned properties of the composites was discussed in the paper.     

Mitigation of salt stress on tomato crop by using foliar spraying or fertigation of various products

Abstract

Among major constraints to crop production, salt stress affects the morphological structure and yield in crop plants. Nano-fertilizers, have made their hierarchy to supplement the traditional fertilizers in mitigating the effect of abiotic stress due to their slow release and efficiency. Three products were tested namely lithovit®-standard(LITHO), monopotassium-phosphate(MKP:0-52-34), and aspirin(ASP) on salt-stressed tomato crop. These products were applied through foliar spraying (foliar) or fertigation (ferti) on tomato plants irrigated with 4 saline solutions (4, 6, 8 and 10dS/m). Control plants were subjected to five salinity levels (0, 4, 6, 8 and 10dS/m) without any treatments. Results showed that increasing in salinity levels adversely affected all parameters in the control plants. The ameliorating effect of MKP-ferti was prominent in plant height, stem diameter, number of fruits, fruit weight and yield/plant at 4 and 6S/m. Whereas, the effect of salinity was mitigated by LITHO-foliar regarding flowers number and total chlorophyll content at all salinity level. Leaf N, P and K contents were accumulated higher when MKP-ferti was used whereas, Ca²⁺ and Mg²⁺ contents were accumulated higher in the plants treated with LITHO-foliar. The cellular leakage of electrolyte was reduced at 4, 6 and 10dS/m with MKP-ferti and at 8dS/m with LITHO-foliar application. Among the two methods of application, foliar spraying of LITHO and ASP, and fertigation of MKP improved plant performance more than their complementary methods of application. The better performance of MKP necessitates the use of phosphorous and potassium-based nano-fertilizers. It can reduce the production cost of vegetables using conventional fertilizers.     

Effects of participatory forest management on livelihood capitals of the community in Cox’s Bazar, Bangladesh

In Cox’s Bazar, Bangladesh, we surveyed 80 households to observe the effects of participatory forestry (PF) on the livelihood of local participants. We analyzed the effects on livelihood capitals to compare in two ways: (1) before and after participation, and (2) participants and non-participants. In Cox’s Bazar, there were some significant changes regarding income sources, but annual income was little changed after participation in participatory forestry. Literacy (about 10 % after participation) and mobile phone ownership (75 %) were significantly higher than before. Housing conditions were better (brick walls: 7.5 %; sun-grass roof: 70 %) than those of non-participants (brick walls: 0 %; sun-grass roof: 77.5 %). PF ensured legal rights on forest lands for participants, while non-participants were illegally living on public forestland. However, expenses were considerably higher than income; people were still struggling with poverty and many of them suffered from malnutrition. This ultimately put pressure on all capital. People had redistributed their available capital to cope with adversity, and there was a trend toward involvement in economic activities other than forests. Our study found that social capital was more influenced by PF more than other capitals. Due to the involvement with the PF program, people were feeling much more secure, women had elevated status, and social relationships became stronger.     

Depleting proteins from the growth medium of Mycoplasma capricolum unmasks bacterium-derived enzymatic activities

Mycoplasma constitutes a unique group of bacteria best characterized as lacking peptidoglycan and having one of the smallest genomes of all free-living prokaryotes. Members of this group also represent important pathogens of humans, animals, and plants. Our understanding of the interaction between these pathogens and their hosts is limited, partly due to our inadequate knowledge of the secreted enzymes and virulence factors of these pathogens. Analysis of secreted proteins of mycoplasma has been hampered by their fastidious growth requirements where protein-rich growth supplements are required. Simple ultrafiltration of the complete medium through a 10 kDa cut-off membrane successfully removed virtually all of the polypeptides in the medium and supported the growth of Mycoplasma capricolum (type California kid). This modification (AM medium) exposed the activities of a number of enzymes produced by this bacterium during growth including; acid and alkaline phosphatase, gelatinase, and β-lactamase activities. We also show that the spent culture medium contained hemolysin activity.