Second-order Regression Analysis Research Articles

PERFORMANCE ANALYSIS OF AISI 4340 HARDENED STEEL IN DUAL JET MQL TURNING SYSTEM: A COMPARISON STUDY BETWEEN CVD AND PVD-COATED CARBIDE TOOLS

The hard part turning process used to finish the cylindrical surfaces has some critical machining responses like tool wear with the lower quality of the machined surfaces. Minimum quantity lubrication (MQL)-based machining environment is currently considered an advanced cooling and lubrication technique. Cutting speed, feed rate, and cutting depth are considered input parameters, and the TaguchiL27 orthogonal array (OA) has been adopted as the design of the experiment. In this context, average surface roughness ([Formula: see text]), tool flank wear (VBc), cutting temperature ([Formula: see text]C), and chip morphology have been selected as measured outputs. To improve the machining performance of hardened steel, a sustainable MQL ([Formula: see text] directions) cooling system has been employed at the cutting zone. Iron–aluminum LRT 30 was considered as the base fluid for the hard turning of AISI 4340 steel by PVD (AlTiN) and CVD (TiN/TiCN/Al2O3) coating cutting inserts. The primary effects of process parameters and their influences on the measured outputs have been discussed. The dual jet MQL-based hard turning was performed at three levels of cutting speeds (80, 170, and 260[Formula: see text]m/min), feed rate (0.5, 0.1, and 0.15[Formula: see text]mm/rev), and cutting depth (0.2, 0.3, and 0.4[Formula: see text]mm) with an air pressure of 5[Formula: see text]bar and mist flow rate 50[Formula: see text]ml/h. The findings showed that PVD-coated carbide tools outperformed CVD-coated tools. The model of the measured outputs of both tools has been developed using second-order regression analysis. Utilizing ANOVA analysis, all the predictive models were observed to be significant and acceptable with larger than 90% of [Formula: see text] value.

Dietary condensed tannin supplementation improves growth performance and feed utilization of juvenile Largemouth bass (Micropterus salmoides) through positively regulating serum lipids and intestinal health

Considering the diverse biological activities of condensed tannin (CT), the study aimed to evaluate the effect of CT on growth performance and intestinal health in juvenile largemouth bass (Micropterus salmoides) through a 56-day feeding trial. Largemouth bass (5.99 ± 0.03 g) were fed a basic diet supplemented with different levels of CT: 0 g/kg (the control group, CG), 0.60 g/kg (the T0.6 group), 1.50 g/kg (the T1.5 group), 3.75 g/kg (the T3.75 group), and 9.38 g/kg (the T9.38 group). The results indicated that dietary supplementation of CT at 3.75 g/kg promoted growth performance, feed conversion ratio, the apparent digestibility coefficients (ADCs) of crude protein and crude lipid, the crude protein of whole-body, the intestinal antioxidant capacity, and intestinal immune response, as well as the development of intestinal villi (P < 0.05), while the fish fed with 9.38 g/kg CT exhibited the opposite trend. Further, dietary CT (3.75 g/kg) decreased crude lipid in the whole-body compared to the CG (P < 0.05). Dietary CT (3.75 g/kg) altered the microbial community, the relative abundance of Bacillus and Lysinibacillus were increased compared to the CG. Additionally, the serum metabolome results revealed a negative correlation between Lysinibacillus abundance and lipid metabolites in the serum. These findings suggested that supplementing the diet with 3.75 g/kg CT promoted the growth performance, feed utilization, and intestinal health of largemouth bass. The optimum CT level was 4.15 g/kg based on second-order polynomial regression analyses of weight gain rate.

Dietary supplementation of ornithine improved the growth, immune response and acute NH3 stress tolerance of Pacific white shrimp, Penaeus vannamei

Ornithine is an arginine family amino acid and is not incorporated into protein. This study evaluated its role in growth, immune response and acute NH3 stress tolerance of Penaeus vannamei. Six diets with graded levels (0.6, 0.9, 1.2, 1.5, 1.8, 2.1 g kg−1) of L-ornithine were formulated, and fed the shrimp for 8 weeks. The growth of shrimp was significantly improved with the dietary ornithine levels increased from 0.6 to 1.5 g kg−1. Feed efficiency, protein efficiency ratio and protein productive value showed a similar trend to the growth performance of shrimp. Whole body protein and muscle lipid of shrimp were significantly increased in shrimp fed 1.8 g kg−1 ornithine compared to those fed 0.6 g kg−1 ornithine. The contents of several amino acids were increased with the dietary ornithine increased to 1.5 g kg−1. Elevated levels of ornithine increased the Nitric Oxide (NO) content and suppressed arginase activity in the hemolymph. The relative mRNA expression of superoxide dismutase, heat shock protein 70, dorsal and caspase 3 were increased with the dietary addition of ornithine, while the mRNA level of arginase was decreased with the increasing dietary ornithine levels. After 9 h acute NH3 stress, mortality of shrimp reduced with the increasing dietary ornithine levels. The relative mRNA levels of superoxide dismutase, heat shock protein 70, dorsal and catalase were increased with the dietary addition of ornithine after the acute NH3 stress. The second-order regression analysis of weight gain and survival after acute stress revealed that the suitable ornithine content in the shrimp diet was 1.4–1.5 g kg−1.

Recovery of oil viscosity values according to its additive parameters

Considering the complexity of mixtures formed within extensive and intricate pipeline networks, determining the viscosity of mixtures through a computational method that utilizes parameters conducive to additivity is advantageous. These parameters may include the density and component composition, as well as corresponding derivatives, such as the content of paraffins, resins, asphaltenes, and fractional composition. This study explored the relationship between the viscosity and these parameters. A linear regression model for estimating the logarithm of the viscosity was developed, where significant regression coefficients were identified, and the prediction error was assessed through cross-validation. A similar approach was adopted for the second-order regression analysis. This analysis incorporated linear regression including parameters pertaining to the fractional composition. Formulas for calculating the viscosity based on the identified properties were derived and the respective errors were evaluated. Keywords: oil; viscosity; Arrhenius formula; cross-validation; paraffin; resins; asphaltenes; database.

Substantiation of the technology of treatment of flushing water of water treatment facilities with subsequent return to the technological cycle

The paper lists the existing technological schemes for the purification of flushing water of water treatment facilities; shows the results of a multifactorial central composite planning experiment with the obtained second-order correlation and regression analysis equations describing the dependence of the residual content of suspended solids on the initial content, sedimentation duration, coagulant dose when using various reagents; the recommended technological scheme for the purification of flushing water with technological calculation of the main structure.

Protective effect of dietary dandelion (Taraxacum officinale) extract on common carp under acute ammonia stress

This study examined the remedial effect of dandelion extract (DE) on acute ammonia stress in common carp. The experiment involved supplementing the common carp diet with five DE dozes, including 0 (control), 2%, 4%, 6%, and 8% DE to the basic feed for 56 days. Then, all the fish were exposed to semile thal ammonia stress (1.65 mg/L) for 96 h, followed by detections the indexes of mortality, blood biochemistry, antioxidation, immunity, stress, and inflammation. The results showed that dietary DE increased the serum protein content and antioxidant enzyme activity of common carp ( P < 0.05). However, DE did not significantly affect the contents of stress hormone, HSP70 and HSP90 (p > 0.05). Exposure to ammonia significantly decreased the activities of immune and antioxidant enzymes in the control group. The serum protein content and immune enzyme activity of each DE group were significantly higher than the control group. After ammonia exposure, IL-1β, IL-6, IL-8, TNF-α, and IFN-γ activities in DE groups were significantly lower then the Ctrl group，and IL-10 and antioxidant enzyme activities in 4% DE, 6% DE, and 8% DE groups was significantly higher compared to the Ctrl ( P < 0.05). Ammonia stress caused pathological damage to the liver tissue in control, 2% DE, 4% DE, and 8% DE groups, but the liver tissue of the 6% DE group showed normal tissue characteristics. Therefore, DE has a protective effect on common carp under acute ammonia exposure. Optimal doses of DE can improve the survival rate, antioxidant capacity, and nonspecific immunity, while can reduce the stress and inflammatory reaction of common carp caused by acute ammonia exposure. The second-order multiple regression analysis of TP, COR, LZM, T-AOC, mortality, and immune protection after ammonia stress showed 4.62–6.82% as the optimal level of dietary DE supplementation for carp under acute ammonia stress.

Optimizing the ECAP processing parameters of pure Cu through experimental, finite element, and response surface approaches

Abstract The main aim of the current work is to investigate the effect of equal channel angular pressing (ECAP) processing parameters, namely, number of passes, ECAP die angle, route type, and processing temperature on the mechanical and electrical properties of pure copper (Cu). The finite element method was used to simulate the homogeneity of stress and plastic strain distribution during ECAP processing. The response surface methodology (RSM) was used to identify the optimum ECAP processing parameters by analyzing the impact of ECAP conditions on responses. A second-order regression model and analysis of variance were created to analyze the ECAP condition of optimum responses. A genetic algorithm (GA) was also applied to optimize the ECAP condition. Finally, a hybrid RSM–GA was created to improve the optimization of ECAP responses and corresponding conditions evaluated using GA. The developed models were validated and compared with the experimental findings to prove that they are reliable as predictive tools. The optimization findings revealed that route Bc was more effective in improving the hardness, yield stress, ductility, and impact energy whereas route A was more effective in improving the ultimate tensile strength and the electrical conductivity of the Cu billets. Furthermore, the optimum die angle, number of passes, and processing temperature for the mechanical and electrical properties were also identified individually.

Functional and phylogenetic analyses of tadpole community assembly in temperate montane streams

Understanding the spatial patterns and the maintenance of biodiversity is a central target in ecology and biogeography, which provide important insights into community assembly processes. Mountain ecosystems provide informative systems for examining how biodiversity is distributed and identifying the mechanisms underlying those patterns. However, most of the existed studies only focused on plants, birds, and microbes, while little attention has been paid on amphibians, especially tadpoles. In the present study, we explored the elevational patterns of multiple facets of tadpole diversity and the community assembly mechanisms in temperate montane streams of Mount Emei, China. The taxonomic, functional, and phylogenetic diversity of tadpole assemblages in montane streams were quantified. Their elevational patterns were investigated using first and second-order polynomial regression analyses. The microhabitat determinants of these patterns were assessed by ordinary least squares models and hierarchical partitioning analyses. The phylogenetic tree of tadpoles and the Eucliden distance of traits between tadpoles were constructed. They were subsequently used to calculate the standardized effect size of mean pairwise phylogenetic and functional distances, and to speculate the tadpole assembly rules. Our results indicated that the Faith’s PD and the standardized effect size of Faith’s PD had hump-shaped responses to elevation, while the relationships between elevation and observed taxonomic diversity, observed functional diversity, and the standardized effect size of functional diversity were not significant. Interestingly, these patterns were determined by microhabitat variables, such as water conductivity, river width, water depth, and substrate type. Mean pairwise phylogenetic distance also showed hump-shaped correlations with the elevational gradient. Tadpole functional and phylogenetic structures were more clustered in low and high elevational streams, suggesting that environmental filtering was the main driver. At mid-elevations, functional and phylogenetic structures were overdispersal, indicating that limiting similarity plays a dominant role in shaping the tadpole assemblages.

Optimization of the main parameters of the diesel engine during its operation on the multicomponent biofuel composition

BACKGROUND: When conducting experimental studies aimed at finding optimal parameters of the diesel engine operating mode, as well as other objects, the issue of reducing the volume of the experiment becomes acute. The use of modern methods of planning, obtaining, processing and analyzing experimental data allows to reduce significantly the number of experiments conducted without notable loss of the reliability of the data obtained.&#x0D; AIMS: The aim of this study is to determine the optimal operating characteristics of the diesel engine, which uses the multi-component bio-fuel composition.&#x0D; METHODS: In order to determine the optimal values of the main parameters, affecting the effective indicators of the 4ChN 11.0/12.5 diesel engine when operating on the multicomponent biofuel composition and a mathematical description of their relationship, a second-order three-factor Box Benken plan was implemented. These factors are effective load, crankshaft rotational speed, and fuel injection advance angle. The diesel engine operation studies were performed on the most stable mixture of the multicomponent biofuel composition, including the following ingredients, wt %: rapeseed oil 34.5; ethanol 31.0; diesel fuel 34.5. The search of a compromise solution for the optimal combination of the levels of studied factors was performed with the method of superimposing of bidimensional sections of the response surfaces of the effective efficiency factor and the specific effective fuel consumption.&#x0D; RESULTS: Adequate models of second-order regression analysis of changes in effective efficiency factor and specific effective fuel consumption have been obtained. The factor space is described and grapho-analytical studies are carried out. The analysis of regression models and bidimensional sections of response surfaces allowed to determine the optimal values of the studied factors. The method for determining the optimal load and speed ranges of the diesel engine operation, using the multicomponent biofuel composition, has been optimized due to the application of the experimental plan and the description of the factor space by mathematical models, while number of experiments was reduced.&#x0D; CONCLUSIONS: The optimal area of the combination of the factors is in the range of varying the rotational speed of the diesel engine crankshaft n=1400...1550 rpm and the effective load Pe=0.68...0.85 MPa at the fuel injection advance angle Ѳinj=23.5 degrees to TDC. Considering the variable nature of the load and speed modes of a diesel engine in a real operation environment, the obtained data are of practical interest.

Optimization of the Physical, Optical and Mechanical Properties of Composite Edible Films of Gelatin, Whey Protein and Chitosan.

The aim of this work was to evaluate the effect of the concentration of gelatin (G) (3–6 g), whey protein (W) (2.5–7.5 g) and chitosan (C) (0.5–2.5 g) on the physical, optical and mechanical properties of composite edible films (CEFs) using the response surface methodology (RSM), as well as optimizing the formulation for the packaging of foods. The results of the study were evaluated via first- and second-order multiple regression analysis to obtain the determination coefficient values with a good fit (R ˃ 0.90) for each of the response variables, except for the values of solubility and b*. The individual linear effect of the independent variables (the concentrations of gelatin, whey protein and chitosan) significantly affected (p ≤ 0.05) the water vapor permeability (WVP), strength and solubility of the edible films. The WVP of the edible films varied from 0.90 to 1.62 × 10−11 g.m/Pa.s.m2, the resistance to traction varied from 0.47 MPa to 3.03 MPa and the solubility varied from 51.06% to 87%. The optimized values indicated that the CEF prepared with a quantity of 4 g, 5 g and 3 g of gelatin, whey protein and chitosan, respectively, provided the CEF with a smooth, continuous and transparent surface, with L values that resulted in a light-yellow hue, a lower WVP, a maximum strength (resistance to traction) and a lower solubility. The results revealed that the optimized formulation of the CEF of G–W–C allowed a good validation of the prediction model and could be applied, in an effective manner, to the food packaging industry, which could help in mitigating the environmental issues associated with synthetic packaging materials.

Effects of dietary arginine levels on growth, immune function of physical barriers and serum parameters of spotted seabass (Lateolabrax maculatus) reared at different water temperatures

A growth experiment was conducted to investigate the effects of dietary arginine levels on growth, immune function of physical barriers and serum parameters of spotted seabass (Lateolabrax maculatus) reared at different water temperatures (27°C and 33°C). Six iso‑nitrogenous and iso‑lipid diets were formulated with 1.16%, 1.65%, 2.04%, 2.44%, 2.98% and 3.36% arginine, respectively. Growth of fish reared at 27°C was significantly higher than that of fish reared at 33°C (P < 0.05). Weight gain (WG) increased first and then decreased with the increase of arginine levels, and the maximum value was obtained in fish fed the diet with 2.04% arginine at 27°C or 33°C. As for immune function of physical barriers, activities of antioxidant enzymes (GPx and SOD) and expression of genes related to tight junction (ZO-1, Occludin and Claudin b) were significantly higher in the gills of fish reared at 27°C than those of fish reared at 33°C (P < 0.05). Furthermore, activities of GPx and SOD and the mRNA expression of ZO-1, Occludin and Claudin b reached the maximum values in the gills of fish fed the diet with 2.44% or 2.04% arginine at 27°C among all treatments. The mRNA expression of MAPK p38 and MyD88 and contents of pro-inflammatory cytokines (IL-1β, IL-6 and TNFα) were significantly lower in the intestine of fish reared at 27°C than those of fish reared at 33°C (P < 0.05). Regardless of water temperature, contents of IL-1β, IL-6 and TNFα as well as the mRNA expression of MAPK p38 and MyD88 reached the minimum values in the intestine of fish fed the diet with 2.04% or 2.44% arginine at 27°C among all treatments. As for serum parameters, the activity of iNOS as well as contents of NO, complements 3 and 4 were significantly higher in fish reared at 27°C than those of fish reared at 33°C (P < 0.05). Regardless of water temperature, serum activities of TNOS and iNOS reached the maximum values in fish fed the diet with 2.04% or 2.44% arginine among different arginine supplementation groups. The activity of lysozyme reached the maximum value in fish fed the diet with 2.04% arginine level at 27°C among all treatments. Those results showed that a water temperature of 33°C decreased growth, immune function of physical barriers and serum parameters of fish. Growth and immunity were maximized when the arginine requirement of spotted seabass was met. Second-order polynomial regression analyses of WG and lysozyme activity showed that the arginine requirement of spotted seabass was 2.47% and 2.53% of the dry diet (5.49% and 5.62% of dietary protein) at 27°C as well as 2.40% and 2.37% of the dry diet (5.33% and 5.27% of dietary protein) at 33°C, respectively.

Evaluation of Bacillus pumillus SE5 fermented soybean meal as a fish meal replacer in spotted seabass (Lateolabrax maculatus) feed

The impacts of fish meal (FM) substitution with Bacillus pumillus SE5 fermented soybean meal (FSM) were investigated in spotted seabass juveniles. A diet containing 35% FM was considered as the basal diet, then 20, 40, 60 and 80% of FM was replaced with FSM (FM, FSM20, FSM40, FSM60 and FSM80 diets). The experimental diets were fed to three replicate groups of fish (14.3 ± 0.35 g) for eight weeks. The results showed linear and quadratic decrease of growth performance by increasing FM replacement level (P < 0.05). Feed consumption decreased linearly, and feed efficiency decreased linearly and quadratically by increasing FSM level. Furthermore, negative linear and quadratic trends were observed between FSM levels and protein efficiency ratio, and digestibility of protein, calcium and phosphorous. Serum total protein, cholesterol and triglyceride concentrations and alkaline phosphatase activity decreased linearly by increasing FSM level, and a linear increase was observed for alanine aminotransferase activity. Serum superoxide dismutase and lysozyme activities decreased linearly and quadratically with increasing FSM level while an opposite trend was observed for serum malondialdehyde concentration. Significant negative linear and quadratic trends were observed between FSM levels and intestinal protease and lipase activities. Increasing FSM level led to linear decrease of foregut villus height, and linear and quadratic decrease of villus and muscular thicknesses. Increasing FSM level led to linear increase of serum D-lactate concentration, and linear and quadratic enhancement of diamine oxidase activity. Expression of intestinal HSP70, IL-1β and TNF-α increased linearly and quadratically with increment of FSM level. The optimum replacement level of FM with the FSM was estimated to be in the range of 26.9–37.1% by broken-line and second-order polynomial regression analyses based on weight gain, feed efficiency, and lysozyme and superoxide dismutase activities.

Performance in 100-km Ultramarathoners-At Which Age, It Reaches Its Peak?

Nikolaidis, PT and Knechtle, B. Performance in 100-km ultramarathoners-At which age, it reaches its peak? J Strength Cond Res 34(5): 1409-1415, 2020-The number of those participating in 100-km ultramarathon has increased over the past years; however, we have limited knowledge about performance trends in this sport, and particularly, the effect of age. The aim of this study was to analyze the age when women and men runners achieve their peak performance considering 1- and 5-year age group intervals, and examining all or the fastest (i.e., top 10) participants in each age group. We analyzed 370,051 athletes (i.e., 44,601 women and 325,450 men) who finished a 100-km ultramarathon between 1959 and 2016, and studied the age of peak performance using a second-order nonlinear regression analysis. The age of peak performance was 40-44 years in women and 45-49 years in men when all finishers were analyzed, whereas it was 30-34 years in women and 35-39 years in men when the top 10 finishers were considered in 5-year age groups. When we analyzed finishers in 1-year age groups, we found the age of peak performance at 41 years in women and 45 years in men considering all finishers, and at 39 years in women and 41 years in men considering the top 10 finishers. In conclusion, the age of peak performance was younger in women than in men, which might reflect the overall younger age of women participants than men. Compared with previous studies, we observed the peak performance at an age older by ∼10 years, which could be attributed to an increase of finishers' age across calendar years. Because the knowledge of the age of peak performance is unique for each sport, coaches and fitness trainers might benefit from the findings of this study in the long-term training of their athletes.

Optimal dietary curcumin improved growth performance, and modulated innate immunity, antioxidant capacity and related genes expression of NF-κB and Nrf2 signaling pathways in grass carp (Ctenopharyngodon idella) after infection with Aeromonas hydrophila

This study investigated the effects of dietary curcumin on growth performance, non-specific immunity, antioxidant capacity and related genes expression of NF-κB and Nrf2 signaling pathways in grass carp (Ctenopharyngodon idella). A total of 525 juvenile grass carps with mean initial body weight of (5.30 ± 0.10) g were randomly distributed into five groups with three replicates each, fed five diets containing graded levels of curcumin (0, 196.11, 393.67, 591.46 and 788.52 mg/kg diet) for 60 days. After feeding trial, fifteen fish per tank were challenged with Aeromonas hydrophila and the mortalities were recorded for 7 days. The results showed that optimal dietary curcumin (393.67 mg/kg diet) improved the weight gain (WG) and specific growth rate (SGR) of juvenile grass carp, reduced feed conversion ratio (FCR) and the mortalities after challenge (P < 0.05). Moreover, optimal dietary curcumin increased the activities of lysozyme (LYZ) and acid phosphatase (ACP), and complement 3 (C3) and C4 levels, decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in serum of grass carp after injection with A. hydrophila (P < 0.05). Meanwhile, optimal dietary curcumin up-regulated the mRNA levels of LYZ, C3 and antimicrobial peptides [hepcidin, liver-expressed antimicrobial peptide-2 (LEAP-2), β-defensin], and anti-inflammatory cytokines of interleukin-10 (IL-10) and transforming growth factor β1 (TGF-β1), and inhibitor of κBα (IκBα), whereas down-regulated pro-inflammatory cytokines of tumor necrosis factor-α (TNF-α), IL-1β, IL-6 and IL-8, and nuclear factor kappa B p65 (NF-κB p65), IκB kinases (IKKα, IKKβ and IKKγ) mRNA levels in the liver and blood of grass carp after injection with A. hydrophila (P < 0.05). In addition, optimal dietary curcumin increased the reduced glutathione (GSH) content and activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR), reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels in the liver of grass carp after injection with A. hydrophila (P < 0.05). Meanwhile, optimal dietary curcumin up-regulated the mRNA levels of these antioxidant enzymes and nuclear factor erythroid 2-related factor 2 (Nrf2), whereas down-regulated Kelch-like ECH-associated protein (Keap) 1a and Keap 1b mRNA levels (P < 0.05) in the liver and blood of grass carp after injection with A. hydrophila. Thus, optimal dietary curcumin supplementation could promote growth of juvenile grass carp, reduce FCR, and enhance disease resistance, innate immunity and antioxidant capacity of fish, attenuating inflammatory response. However, dietary excessive curcumin had negative effect on fish. Based on second-order regression analysis between dietary curcumin contents and weight gain, the optimum requirement of dietary curcumin in juvenile grass carp was determined to be 438.20 mg/kg diet.

Modeling and optimization of face milling process parameters for AISI 4140 steel

In this study, the effect of cutting parameters such as the depth of cut, feed rate, cutting speed and the number of inserts on surface roughness were investigated in the milling of the AISI 4140 steel. The optimal control factors for surface quality were detected by using the Taguchi technique. Experimental trials were designed according to the Taguchi L18 (21x33) orthogonal array. The statistical effects of control factors on surface roughness have been established by using the analysis of variance (ANOVA). Optimal cutting parameters were obtained by using the S/N ratio values. The ANOVA results showed that the effective factors were the number of inserts and the feed rate on surface roughness. However, the depth of cut and the cutting speed showed an insignificant effect. Additionally, the First-order and Second-order regression analysis were conducted to estimate the performance characteristics of the experiment. The acquired regression equation results matched with the surface roughness measurement results. The optimal performance characteristics were obtained as a 0.5 mm depth of cut, 0.08 mm/rev feed rate, 325 m/min cutting speed and 1 number of inserts by using the Taguchi method. Additionally, the confirmation test results indicated that the Taguchi method was very prosperous in the optimization of the machining parameters to obtain the minimum surface roughness in the milling of the AISI 4140 steel.

Edible coating based on modified corn starch/tomato powder: Effect on the quality of dough bread

The ascorbic acid modified starch coating solutions were developed based on the Central Compound Rotational Design (CCRD) and the variables were ascorbic acid and tomato powder. The dough was immersed in the coating solution to be analyzed for maximum expansion factor, bread crumb and crust color, specific volume, crumb image and Scanning Electron Microscopy (SEM). The results show that the corn starch with ascorbic also contributed to the expansion of the bread. The crust browning index decreased when the levels of ascorbic acid increase up to 1.6%, correlated with 4.0% of tomato powder; the best specific volume results for the breads samples were run 7 (4.25 cm3/g) and run 2 (3.84 cm3/g). In the data obtained, the inclusion of up to 7.5% of tomato powder in the solutions presented a browning index of crumb superior compared with others samples promoting a good quality bread. The use of ascorbic acid in the modification of the starch contributed to the increase of the specific volume of bread. The results were analyzed by second-order multivariate regression analysis and ANOVA with Tukey test at a significance level of 5% (p ≤ 0.05).

Dietary arachidonic acid promotes growth, improves immunity, and regulates the expression of immune-related signaling molecules in Macrobrachium nipponense (De Haan)

Arachidonic acid (ARA) is involved in the growth and regulation of immunity in fish. Little research has focused on ARA in crustaceans. This study was an 8-week feeding experiment investigating the effects of dietary ARA on growth, antioxidative indices, and immune characteristics of the juvenile oriental river prawn (Macrobrachium nipponense). An ARA-enriched oil was supplemented into the basal diet to formulate six isonitrogenous and isoenergetic diets containing 0.02% (the control group), 0.28%, 0.54%, 0.86%, 1.22%, and 1.54% ARA dry weight. Diets were fed to juvenile prawns (mean weight: 0.104±0.002g) twice daily to apparent satiation in three replicates. Weight gain and specific growth rate of M. nipponense significantly increased with increasing dietary levels of ARA from 0.02% to 0.86% and thereafter declined. Hepatopancreas super oxide dismutase and catalase activities significantly increased with supplementation with ARA, particularly in prawns fed 1.22% and 1.54% ARA. The malondialdehyde level in prawns fed 1.54% ARA also significantly increased, and was higher than that of prawns fed ARA from 0.02% to 0.86%. Serum lysozyme activity was significantly greater in prawns fed 0.86% ARA compared with the other groups. mRNA expression of toll-like receptor signaling pathway-related genes was promoted by a dietary ARA level from 0.54% to 0.86% but inhibited with the higher ARA levels (1.22–1.54%). The mortality percentage increased after challenge with live Aeromonas hydrophila. The mortality percentage of prawns fed 1.54% ARA was significantly higher than that of prawns fed 0.28–1.22% ARA. The results suggest that the optimal dietary ARA requirement for juvenile M. nipponense is 0.82% (dry weight) based on second-order regression analysis of weight gain vs. dietary ARA level, and that 0.86% ARA could significantly enhance non-specific immunity of M. nipponense; however, too high a level of ARA will affect the health status of this prawn.

Dietary histidine requirement of Nile tilapia juveniles based on growth performance, expression of muscle-growth-related genes and haematological responses

A 100-day feeding trial was carried out to determine the dietary histidine requirement of Nile tilapia juveniles based on growth performance, muscle development, expression of muscle-growth-related genes, biochemical and hematological responses. Nile tilapia juveniles (4.84±0.04g) were fed six extruded practical isonitrogenous (265.7g of crude protein kg−1) and isoenergetic (17.3MJ of gross energy kg−1) diets containing graded levels of histidine (4.2, 5.4, 7.1, 8.9, 9.8 and 11.5gkg−1 dry diet). The feeding trial was conducted in a flow-through system (1.5Lmin−1) at 28°C water temperature, and triplicate groups of fish were hand-fed each diet four times a day until apparent satiation. Final weight, weight gain, feed conversion ratio, protein efficiency ratio and net protein utilization were optimized in fish fed 8.9g of histidine kg−1. Whole-body protein content was enhanced in fish fed 7.1 and 9.8g of histidine kg−1 compared to fish fed 11.5g of histidine kg−1. Active hypertrophic growth process was observed in fish fed 8.9g of histidine kg−1, as confirmed by lower frequency of occurrence of muscle fibers <20µm diameter and higher frequency of occurrence of muscle fibers >50 µm diameter, compared to fish fed 5.4g of histidine kg−1. Fish fed 9.8g of histidine kg−1 showed the highest expression level of MyoD. However, myogenin expression was higher in fish fed 9.8 and 11.5g of histidine kg−1 compared to fish fed 4.2 to 7.1g of histidine kg−1. Myostatin expression was similar among fish from all treatments. Biochemical and haematological responses were not affected in fish fed graded levels of histidine. Based on second-order regression analysis, the dietary histidine requirement for maximum WG of Nile tilapia juveniles was estimated to be 8.2gkg−1, corresponding to 3.1% of crude protein. Statement of RelevanceHistidine is a limiting amino acid in Nile tilapia diets.

Dietary lysine requirement to enhance muscle development and fillet yield of finishing Nile tilapia

The dietary lysine requirement has not been established for finishing Nile tilapia despite being considered the first limiting essential amino acid in many cereal grain ingredients. A feeding trial was designed to determine the dietary lysine requirement using 600 fish (274.9±3.3g) distributed into 15, 1.2m3 net cages in a completely randomized design with five treatments and three replicates. Five extruded isoproteic (251.2g of crude protein kg−1) and isoenergetic diets (13.1MJ of digestible energy kg−1) containing 11.1, 12.5, 13.9, 15.1 and 16.4glysinekg−1 were prepared. Fish were hand fed four times a day until apparent satiety. Fish fed 15.1glysinekg−1 exhibited improved final body weight and daily weight gain compared to fish fed 11.1glysinekg−1. Fillet weight and fillet yield of finishing Nile tilapia were significantly affected by dietary lysine levels and optimized at 15.1glysinekg−1 compared to fish fed the other treatments. Whole-body and fillet compositions of fish were unresponsive to dietary lysine levels. Whole-body lysine, tryptophan, alanine, aspartic acid and tyrosine retention was significantly affected by dietary lysine levels. Although the recruitment of new fibers by hyperplasia continues in adult Nile tilapia, the predominance of muscle growth was by hypertrophy as observed in fish from all treatments. Based on second-order regression analysis, the dietary lysine requirement for maximum fillet yield of finishing Nile tilapia was estimated at 14.6gkg−1, corresponding to 5.8% of dietary protein. Statement of relevanceFirst mention of lysine requirements of large Nile tilapia

Dietary threonine requirement to optimize protein retention and fillet production of fast-growing Nile tilapia

Threonine is the third-limiting essential amino acid in diets based on cereal ingredients. A 4-week trial was conducted to determine the threonine requirement of large Nile tilapia based on fish growth, feed efficiency, body composition, protein and amino acid retention. Six hundred fish (563.3 ± 15.1 g) were distributed into twenty 1.2-m3 cages. Five diets containing 288 g kg−1 of crude protein, 12.7 MJ kg−1 of digestible energy and 8.9, 10.5, 12.2, 13.7 and 15.4 g kg−1 of threonine were elaborated. Fish were hand-fed five times a day to extruded diets. Significantly, differences in growth performance and amino acids retention among the treatments were observed. Fish fed 10.5 g kg−1 of threonine showed higher daily weight gain, gutted weight and fillet weight (P < 0.05) compared to fish fed with other experimental diets. Diets containing 8.9–15.4 g kg−1 of threonine did not affect whole body and muscle proximate composition. Based on second-order regression analysis, the dietary threonine requirement estimated based on final gain, fillet weight and fillet yield was 12, 12.1 and 11.5 g kg−1 diet, respectively. The dietary threonine requirement for maximum fillet yield of Nile tilapia was estimated to be 11.5 g kg−1.