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The effects of stocking density and environmental conditions on performance, economic profit, carcase characteristics, immunity, and blood plasma parameters of Cobb 500 strain of broiler chickens were evaluated. The 4 climate regions (mild and humid, semi-arid, alpine, hot and dry) and 4 densities (10, 15, 17 and 20 chicks/m 2 ) were carried out as a completely randomised design with 4 Â 4 factorial arrangement of treatments. The corn and soybean based diets were formulated according to the nutrition requirements guide of the Cobb 500 for starter and grower periods. The amount and the composition of the diet were the same for all experimental groups. Growth performance and feed intake were measured weekly. After the injection of sheep red blood cell at 15 and 35 days, blood samples were taken at 24 and 42 days, respectively, to study the immunity of broiler chickens. At the end of the experiment, 3 birds were slaughtered from each experimental unit for measuring the weights of carcase, abdominal fat, gastrointestinal organs (the total weight of gastrointestinal tract and caeca, and liver) and blood parameters. The interaction effects of stocking density and climate region on feed conversion ratio (in starter period), survival rate, cost, profit, cholesterol, triglyceride, high density lipoproteins (HDL), HDL/low density lipoproteins (LDL) ratio, and liver enzymes aspartate aminotranferases (AST), also known as serum glutamic oxaloacetic transaminase (SGOT), and alanine aminotranferase (ALT) were significant (p < .05). Climate and density each had a significant effect on production index (p < .05). The highest production index was obtained in alpine climate. Moreover, the density of 10 chicks/m 2 showed the highest production index. The results showed that rearing Cobb strain chickens in hot and dry climate and at the density of 17 chicks/m 2 had the most economic benefit. Based on the results of this study to achieve the highest profit in different climates, a density of 17 chicks/m 2 (0.633 ft 2 per bird) is recommended for Cobb 500 strain chickens. HIGHLIGHTSNutritional efficiency changes by environmental factors such as climate and stocking density. Obtain sufficient information to combined effect of stocking density and climate on the performance of Cobb 500 broiler chickens. The most reached profit was in the dry climate at a density of 17 chicks/m 2 compared to other climates and densities.

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Direct CO dissociation is seen the main path of the first step in the Fischer-Tropsch Synthesis (FTS) on the reactive iron surfaces. Cu/Fe alloy film is addressed with various applications over face-centered-cubic (fcc)-Cu and body-centered-cubic (bcc)-Fe in the FTS, i.e. preventing iron carbide formation (through direct CO dissociation) by moderating the surface reactivity and facilitating the reduction of iron surfaces, respectively. In this study by density functional theory, the stable configurations of CO molecule on various Cu/Fe alloys over fcc-Cu(100) and bcc-Fe(100) surfaces with different CO coverage (25% and 50%) have been evaluated. Our results showed that the ensemble effect plays a fundamental role to CO adsorption energy on the surface alloys over bcc-Fe(100); on the other hand, the ligand effect determines the CO stability on the fcc-Cu(100) surface alloys. CO dissociation barrier was also calculated on the surface alloys that showed although the CO dissociation process is thermodynamically possible on the more reactive surface alloys, but according to their high barrier, CO dissociation does not occur directly on these surfaces.