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Linear Effects (linear + effects)
Selected AbstractsOptimization of growth medium for the production of ,-amylase from Bacillus amyloliquefaciens using response surface methodologyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2006M Saban Tanyildizi Abstract The optimization of nutrient levels for the production of ,-amylase by Bacillus amyloliquefaciens was carried out using response surface methodology (RSM) based on the 23 factorial central composite design (CCD). This procedure limited the number of actual experiments performed while allowing for possible interactions between three components. RSM was adopted to derive a statistical model for the effect of starch, peptone and yeast extract (YE) on ,-amylase production. The P -value of the coefficient for linear effects of starch and YE concentration was <0.0001, suggesting that this was the principal experimental variable, having the greatest effect on the production of ,-amylase. The optimal combinations of media constituents for maximum ,-amylase production were determined as 12.61 g L,1 starch, 2.83 g L,1 peptone and 1.25 g L,1 YE. The optimization of the medium resulted not only in a 34% higher enzyme activity than unoptimized medium but also in a reduced amount of the required medium constituents. Copyright © 2006 Society of Chemical Industry [source] EFFECTS OF PROCESS VARIABLE CONDITIONS ON MINERAL AND CHEMICAL COMPOSITION OF EXTRUDED AFRICAN BREADFRUIT (TRECULIA AFRICANA DECNE) MIXTURESJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2009TITUS U. NWABUEZE ABSTRACT Five levels of African breadfruit (Treculia africana), corn and soybean mixtures (fc) in ratios of 40:5:55, 55:5:40, 70:5:25, 85:5:10 and 100:0:0, respectively, were hydrated to 15, 18, 21, 24 and 27% (fm) and extruded at 100, 120, 140, 160 and 180 rpm (ss) in a Brabender single-screw extruder. The objective was to study effects of process variable conditions on mineral and chemical composition of the mixtures. Models developed by response surface analysis were high (R2 = 0.7646,0.9732) for Na, Ca, Mg, protein, fat, fiber and carbohydrate, and showed no significant (P > 0.05) lack of fit. All process variables had significant (P , 0.05) linear effects on Mg, protein and carbohydrate, quadratic effects on fat, energy and Mg and cross-product effects on Ca, Mg, protein and carbohydrate, when fc interacted with either fm or ss. Optimum process variable conditions that gave the best mineral and chemical composition were obtained at 40:5:55(fc), 18% (fm) and 140 rpm (ss). PRACTICAL APPLICATIONS The potentials of African breadfruit as a nutrient resource and its position in the food cycle of the people in the subtropical African countries makes its blending with other local ingredients one important way of expanding the scope of its utilization. African breadfruit seeds provide a delicacy and a specialized meal when consumed alone or with shelled milk-corn. The versatility and acceptance of extrusion as a processing technology and its benefits over conventional methods and worldwide adaptability to a variety of crops, makes its application in this research appropriate. Optimization of process variable conditions affecting mineral and chemical composition of extruded and unextruded mixtures of African breadfruit, corn and soybean, using response surface analysis, was the thrust of the study. It is expected to produce an optimum process combination that could give the best mineral and chemical composition for a possible scale-up operation in African breadfruit seed processing enterprises. [source] Estimability of the linear effects in state space models with an unknown initial conditionJOURNAL OF TIME SERIES ANALYSIS, Issue 3 2010Rajesh Selukar In the case of state space models with an unknown initial condition, the diffuse Kalman smoother can be used to obtain smoothed state estimates. When the full initial state is not estimable because the available data are insufficient, some linear combinations of the states can still be estimable. This brief note provides a simple method to determine whether a linear combination of a state is estimable. [source] Simple means to improve the interpretability of regression coefficientsMETHODS IN ECOLOGY AND EVOLUTION, Issue 2 2010Holger Schielzeth Summary 1. Linear regression models are an important statistical tool in evolutionary and ecological studies. Unfortunately, these models often yield some uninterpretable estimates and hypothesis tests, especially when models contain interactions or polynomial terms. Furthermore, the standard errors for treatment groups, although often of interest for including in a publication, are not directly available in a standard linear model. 2. Centring and standardization of input variables are simple means to improve the interpretability of regression coefficients. Further, refitting the model with a slightly modified model structure allows extracting the appropriate standard errors for treatment groups directly from the model. 3. Centring will make main effects biologically interpretable even when involved in interactions and thus avoids the potential misinterpretation of main effects. This also applies to the estimation of linear effects in the presence of polynomials. Categorical input variables can also be centred and this sometimes assists interpretation. 4. Standardization (z -transformation) of input variables results in the estimation of standardized slopes or standardized partial regression coefficients. Standardized slopes are comparable in magnitude within models as well as between studies. They have some advantages over partial correlation coefficients and are often the more interesting standardized effect size. 5. The thoughtful removal of intercepts or main effects allows extracting treatment means or treatment slopes and their appropriate standard errors directly from a linear model. This provides a simple alternative to the more complicated calculation of standard errors from contrasts and main effects. 6. The simple methods presented here put the focus on parameter estimation (point estimates as well as confidence intervals) rather than on significance thresholds. They allow fitting complex, but meaningful models that can be concisely presented and interpreted. The presented methods can also be applied to generalised linear models (GLM) and linear mixed models. [source] Low- and high-level controlled processing in executive motor control tasks in 5,6-year-old children at risk of ADHDTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2003Ariane C. Kalff Background: The scant research on the characteristics of Attention-Deficit/Hyperactivity Disorder (ADHD) in kindergarten years curtails progress on early assessment of ADHD. Method: By screening a general population sample of 1317 five- to six-year-old children, four groups of children were selected. The performance of 30 children later diagnosed with ADHD was compared with 74 children later diagnosed with ,borderline ADHD' (children exhibiting all ADHD symptoms but without disruptions on two situations), 113 children later diagnosed with other psychopathology, and 126 healthy controls on computerised motor control tasks involving low- and high-level controlled processing. In addition, motor control was compared with movement speed. Results: The children at risk of ADHD were in general less accurate and more variable in their movements than the children with other psychopathology and healthy controls. Under conditions of high-level controlled processing, the children at risk of ADHD were disproportionately more inaccurate and had a more unstable performance with their preferred hand than the other children. In addition, linear effects were found, with the children at risk of ADHD having the worst performance, followed by the children with ,borderline ADHD', and then both groups of control children. No significant group differences were found in movement speed. Conclusions: The main findings are interpreted as evidence for a specific deficit in high-level controlled processing in young children at risk of ADHD, now found in a motor task, rather than a response task. Furthermore, the results support the notion that ADHD represents a dimensional trait. In addition, problems in movement control (the need to allocate attentional capacity) rather than problems in movement speed distinguish children at risk of ADHD from other children. The findings are interpreted as evidence that higher-order executive processes, such as self-control and self-regulation, are already affected early in the development of ADHD. [source] 8 Tb/s long haul transmission over low dispersion fibers using 100 Gb/s PDM-QPSK channels paired with coherent detectionBELL LABS TECHNICAL JOURNAL, Issue 4 2010Jérémie Renaudier 100Gb/s end-to-end broadband optical solutions are attractive to cope with the increasing demand for capacity. Polarization-division-multiplexed (PDM) quaternary-phase-shift-keying (QPSK) paired with coherent detection has been found to be promising for upgrading optical legacy systems based on 50GHz wavelength slots thanks to its high spectral efficiency (2bit/s/Hz) and its tolerance to linear effects. One of the major concerns for the deployment of such a solution is the transmission reach, mainly limited by nonlinear effects. This limitation can be exacerbated over non-zero dispersion shifted fiber (NZDSF) due to low local chromatic dispersion of the transmission fiber. The aim of this paper is first to report on the benefits brought by combining coherent detection techniques with advanced modulation formats as compared to conventional direct detection schemes for optical fiber communications. Digital signal processing paired with coherent detection is described to point out the efficiency of a coherent receiver to combat noise and to mitigate linear impairments. We then report on nonlinear tolerance of 100 Gb/s coherent PDM-QPSK through an 8 Tb/s transmission over a dispersion-managed link based on low dispersion fibers. © 2010 Alcatel-Lucent. [source] | ||||||||||