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Factorial Design (factorial + design)
Kinds of Factorial Design Terms modified by Factorial Design Selected AbstractsFactorial design of nanosized polyisoprene synthesis via differential microemulsion polymerizationPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2010Bunthita Suppaibulsuk Abstract The synthesis of nanosized polyisoprene latex was carried out by differential microemulsion polymerization using 2, 2,-Azoisobutyronitrile (AIBN) initiator system under various reaction conditions. A fractional factorial experimental design was applied to study the effects of reaction variables: amount of initiator and surfactant, monomer-to-water ratio, reaction temperature, and stirring speed on rubber particle size and monomer conversion. The analysis of the results from the design showed the main effects on the observed response and the amount of initiator, reaction temperature and stirring speed in the range of the test had significant effects on polyisoprene particle size. The significant effects on monomer conversion were reaction temperature, stirring speed, and interaction between reaction temperature and stirring speed in the range of the test. The optimum conditions gave highest monomer conversion of 90% and average particle size of polyisoprene of 27,nm. The nanosized polyisoprene was also characterized by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. Copyright © 2009 John Wiley & Sons, Ltd. [source] High-throughput screening techniques for rapid PEG-based precipitation of IgG4 mAb from clarified cell culture supernatantBIOTECHNOLOGY PROGRESS, Issue 3 2010Carol Knevelman Abstract Locating optimal protein precipitation conditions for complex biological feed materials is problematic. This article describes the application of a series of high-throughput platforms for the rapid identification and selection of conditions for the precipitation of an IgG4 monoclonal antibody (mAb) from a complex feedstock using only microliter quantities of material. The approach uses 96-microwell filter plates combined with high-throughput analytical methods and a method for well volume determination for product quantification. The low material, time and resource requirements facilitated the use of a full factorial Design of Experiments (DoE) for the rapid investigation into how critical parameters impact the IgG4 precipitation. To aid the DoE, a set of preliminary range-finding studies were conducted first. Data collected through this approach describing Polyethylene Glycol (PEG) precipitation of the IgG4 as a function of mAb concentration, precipitant concentration, and pH are presented. Response surface diagrams were used to explore interactions between parameters and to inform selection of the most favorable conditions for maximum yield and purification. PEG concentrations required for maximum yield and purity were dependant on the IgG4 concentration; however, concentrations of 14 to 20% w/v, pH 6.5, gave optimal levels of yield and purity. Application of the high-throughput approach enabled 1,155 conditions to be examined with less than 1 g of material. The level of insights gained over such a short time frame is indicative of the power of microwell experimentation in allowing the rapid identification of appropriate processing conditions for key bioprocess operations. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Uncertainty and Sensitivity Analysis of Damage Identification Results Obtained Using Finite Element Model UpdatingCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2009Babak Moaveni The shake table tests were designed so as to damage the building progressively through several historical seismic motions reproduced on the shake table. A sensitivity-based finite element (FE) model updating method was used to identify damage in the building. The estimation uncertainty in the damage identification results was observed to be significant, which motivated the authors to perform, through numerical simulation, an uncertainty analysis on a set of damage identification results. This study investigates systematically the performance of FE model updating for damage identification. The damaged structure is simulated numerically through a change in stiffness in selected regions of a FE model of the shear wall test structure. The uncertainty of the identified damage (location and extent) due to variability of five input factors is quantified through analysis-of-variance (ANOVA) and meta-modeling. These five input factors are: (1,3) level of uncertainty in the (identified) modal parameters of each of the first three longitudinal modes, (4) spatial density of measurements (number of sensors), and (5) mesh size in the FE model used in the FE model updating procedure (a type of modeling error). A full factorial design of experiments is considered for these five input factors. In addition to ANOVA and meta-modeling, this study investigates the one-at-a-time sensitivity analysis of the identified damage to the level of uncertainty in the identified modal parameters of the first three longitudinal modes. The results of this investigation demonstrate that the level of confidence in the damage identification results obtained through FE model updating, is a function of not only the level of uncertainty in the identified modal parameters, but also choices made in the design of experiments (e.g., spatial density of measurements) and modeling errors (e.g., mesh size). Therefore, the experiments can be designed so that the more influential input factors (to the total uncertainty/variability of the damage identification results) are set at optimum levels so as to yield more accurate damage identification results. [source] Prediction of gas-phase 13C nuclear magnetic shielding constants using ONIOM and optimally selected basis functionsCONCEPTS IN MAGNETIC RESONANCE, Issue 6 2008M. Tafazzoli Abstract The wave functions for calculating gas-phase 13C nuclear magnetic shielding constants of 22 molecules have been optimally selected using factorial design as a multivariate technique. GIAO and CSGT methods were used for computation of shielding constants. Different wave functions for different types of carbons were recommended. A wave function as the best level of the theory is proposed for almost similar carbons. ONIOM approach for molecules with different types of carbons is applied. The results of GIAO method using the proposed wave function are in very good agreement with the experimental values. An additional series (21 carbons) were used as test sets and their results confirmed the validity of the approaches. © 2008 Wiley Periodicals, Inc.Concepts Magn Reson Part A 32A: 449,461, 2008. [source] Gender-specific disruptions in emotion processing in younger adults with depression,DEPRESSION AND ANXIETY, Issue 2 2009Sara L. Wright Ph.D. Abstract Background: One of the principal theories regarding the biological basis of major depressive disorder (MDD) implicates a dysregulation of emotion-processing circuitry. Gender differences in how emotions are processed and relative experience with emotion processing might help to explain some of the disparities in the prevalence of MDD between women and men. This study sought to explore how gender and depression status relate to emotion processing. Methods: This study employed a 2 (MDD status) × 2 (gender) factorial design to explore differences in classifications of posed facial emotional expressions (N=151). Results: For errors, there was an interaction between gender and depression status. Women with MDD made more errors than did nondepressed women and men with MDD, particularly for fearful and sad stimuli (Ps <.02), which they were likely to misinterpret as angry (Ps <.04). There was also an interaction of diagnosis and gender for response cost for negative stimuli, with significantly greater interference from negative faces present in women with MDD compared to nondepressed women (P=.01). Men with MDD, conversely, performed similarly to control men (P=.61). Conclusions: These results provide novel and intriguing evidence that depression in younger adults (<35 years) differentially disrupts emotion processing in women as compared to men. This interaction could be driven by neurobiological and social learning mechanisms, or interactions between them, and may underlie differences in the prevalence of depression in women and men. Depression and Anxiety, 2009. Published 2008 Wiley-Liss, Inc. [source] Randomized controlled trial of physiotherapy in 56 children with cerebral palsy followed for 18 monthsDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 1 2001E Bower PhD MCSP Senior Research Fellow This study aimed to determine whether motor function and performance is better enhanced by intensive physiotherapy or collaborative goal-setting in children with cerebral palsy (CP). Participants were a convenience sample of 56 children with bilateral CP classified at level III or below on the Gross Motor Function Classification System (GMFCS), aged between 3 and 12 years. A 2 × 2 factorial design was used to compare the effects of routine amounts of physiotherapy with intensive amounts, and to compare the use of generalized aims set by the child's physiotherapist with the use of specific, measurable goals negotiated by the child's physiotherapist with each child, carer, and teacher. Following the six-month treatment period there was a further six-month period of observation. Changes in motor function and performance were assessed by a masked assessor using the Gross Motor Function Measure (GMFM) and the Gross Motor Performance Measure (GMPM) at three-month intervals. There was no statistically significant difference in the scores achieved between intensive and routine amounts of therapy or between aim-directed and goal-directed therapy in either function or performance. Inclusion of additional covariates of age and severity levels showed a trend towards a statistically significant difference in children receiving intensive therapy during the treatment period. This advantage declined over the subsequent six months during which therapy had reverted to its usual amount. Differences in goal-setting procedures did not produce any detectable effect on the acquisition of gross motor function or performance. [source] Time reproduction in finger tapping tasks by children with attention-deficit hyperactivity disorder and/or dyslexiaDYSLEXIA, Issue 4 2004Margaret C. Tiffin-Richards Abstract Aim: Deficits in timing and sequencing behaviour in children with dyslexia and with attention-deficit hyperactivity disorder have already been identified. However many studies have not controlled for comorbidity between dyslexia and ADHD. This study investigated timing performance of children with either dyslexia or ADHD, or ADHD + dyslexia or unaffected children using a finger-tapping paradigm. Method: Four groups of children (ADHD × Dyslexia) with a total of 68 children were compared using a four factorial design with two between-subject factors (ADHD (yes/no), dyslexia (yes/no)) and two within-subject factors, inter-stimulus interval (263, 500, 625, 750, 875 and 1000 ms) and tapping condition (free tapping, synchronous tapping, and unpaced tapping). In addition the complexity of rhythm reproduction pattern (unpaced tapping) was varied (simple/complex). Results: No significant differences were found either in the ability of the ADHD or the dyslexia groups to sustain a self-chosen free tapping rate or to generate a stable inter-response interval either by synchronising to a signal or in reproducing a given interval without the previous pacing signal. Response averages showed the expected asynchrony and variability. In rhythm pattern reproduction the groups did not differ significantly in their ability to reproduce rhythms. However, a significant two way interaction effect between dyslexia and complexity was apparent indicating that the difference in levels of performance for simple versus complex rhythms was more pronounced for dyslexia than for the two other groups. Conclusion: The results indicate that motor timing ability in the millisecond range below 1000 ms in children with ADHD and/or dyslexia is intact. The performance of the comorbid group was revealed to be similar to the performance of the single disorder groups, but both the dyslexic groups were relatively worse than either the ADHD-only or the unimpaired group at reproducing complex versus simple rhythms. Copyright © 2004 John Wiley & Sons, Ltd. [source] The effects of green tree retention and subsequent prescribed burning on ground beetles (Coleoptera: Carabidae) in boreal pine-dominated forestsECOGRAPHY, Issue 5 2006Petri Martikainen We studied how two methods to promote biodiversity in managed forests, i.e. green tree retention and prescribed fire, affect the assemblages of carabid beetles. Our experiment consisted of 24 study sites, each 3,5 ha in size, which had been prepared according to factorial design. Each of the eight treatment combinations determined by the two factors explored , tree retention level (0, 10, 50 m3/ha,1 and uncut controls) and prescribed use of fire (yes/no) , was replicated three times. We sampled carabids using pitfall traps one year after the treatments. Significantly more individuals were caught in most of the burned sites, but this difference was partially reflective of the trap-catches of Pterostichus adstrictus. The fire did not increase no. of P. adstrictus in the uncut sites as much as in the other sites. Species richness was significantly affected by both factors, being higher in the burned than in the unburned sites and in the harvested than in the unharvested sites. Many species were concentrated in the groups of retention trees in the burned sites, but only a few were in the unburned sites. The species turnover was greater in the burned than in the unburned sites, as indicated by the NMDS ordinations. Greater numbers of smaller sized species and proportion of brachypterous species were present in the burned sites. Fire-favored species, and also the majority of other species that prefer open habitats were more abundantly caught in the burned sites than in the unburned sites. Dead wood or logging waste around the traps did not correlate with the occurrence of species. We conclude that carabids are well adapted to disturbances, and that frequent use of prescribed fire is essential for the maintenance of natural assemblages of carabid beetles in the boreal forest. Small retention tree groups can not maintain assemblages of uncut forest, but they can be important by providing food, shelter and breeding sites for many species, particularly in the burned sites. [source] Wedged between bottom-up and top-down processes: aphids on tansyECOLOGICAL ENTOMOLOGY, Issue 1 2004Bernhard Stadler Abstract., 1. Many species of aphids exploit a single host-plant species and have to cope with changing environmental conditions. They often vary greatly in abundance even when feeding on the same host. In a field experiment, the bottom-up (plant quality/patch type frequency) and top-down (ant attendance/predation) effects on the abundance of four species of aphids feeding on tansy (Tanacetum vulgare) were tested using a full factorial design. In addition, a model was used to examine these patch characteristics for their relative effects on the population dynamics and abundance of different aphid species. 2. Aphid numbers changed significantly depending on the quality of the host plant and the presence/absence of attending ants. The obligate myrmecophile, Metopeurum fuscoviride, was abundant on high-quality plants, while on poor quality plants or on plants without attending ants these aphids did not survive until the end of the experiment. The facultative myrmecophiles, Aphis fabae and Brachycaudus cardui, and the unattended aphid species, Macrosiphoniella tanacetaria, all reached similar peak population densities, but M. tanacetaria did best in poor quality patches. 3. Natural enemies reduced aphid numbers, but those species feeding on high-quality plants survived longer than those on poor-quality plants, which existed only for a short period of time, especially when associated with ants. Losses due to migration of winged morphs and mortality caused by parasitoids were insignificant. 4. Varying the frequency of different patch types in a model indicates that different degrees of associations with ants are favoured in different environments. If the proportion of high-quality patches in a habitat is large, obligate myrmecophiles do best. On increasing the number of poor-quality patches, unattended species become more abundant. 5. The results suggest that, in spite of large species specific differences in growth rates, degree of myrmecophily or life cycle features, the temporal and spatial variability in top-down and bottom-up forces differentially affects aphid species and allows the simultaneous exploitation of a shared host-plant species. [source] Effects of atrazine and iridovirus infection on survival and life-history traits of the long-toed salamander (Ambystoma macrodactylum)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2006Diane Forson Abstract Environmental contaminants and emerging infectious diseases are implicated as factors contributing to global amphibian declines. However, few studies have tested the interaction of these factors. We exposed six-week-old, larval long-toed salamanders (Ambystoma macrodactylum) to Ambystoma tigrinum virus (ATV; 0 or 103.5 plaque-forming units/ml) and sublethal concentrations of atrazine (0, 1.84, 18.4, and 184 ,g/L) in a 4 × 2 factorial design for 30 d. We tested the effects of atrazine and virus on mass and snout-vent length (SVL) at metamorphosis and larval period as well as on rates of mortality and viral infectivity. We confirmed ATV transmission to A. macrodactylum via polymerase chain reaction, but infection rates were lower than expected, consistent with the theory predicting lower pathogen transmission to nonnative hosts. Larvae exposed to both atrazine and ATV had lower levels of mortality and ATV infectivity compared to larvae exposed to virus alone, suggesting atrazine may compromise virus efficacy. The highest atrazine level (184 ,g/L) accelerated metamorphosis and reduced mass and SVL at metamorphosis significantly relative to controls. Exposure to ATV also significantly reduced SVL at metamorphosis. The present study suggests moderate concentrations of atrazine may ameliorate effects of ATV on long-toed salamanders, whereas higher concentrations initiate metamorphosis at a smaller size, with potential negative consequences to fitness. [source] Effects of sublethal concentrations of atrazine and nitrate on metamorphosis of the African clawed frogENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2003Karen Brown Sullivan Abstract Tadpoles of the African clawed frog (Xenopus laevis) were exposed to sublethal concentrations of atrazine (0, 40, and 320 ,g/L) and nitrate (0, 37, and 292 mg/L) from feeding stage to metamorphosis. A 3 × 3 factorial design was used to identify both single and interactive effects. At metamorphosis, tadpole weight, snout,vent length (SVL), and hematocrit were determined. Mean mortality was greater in tanks receiving 320 ,g/L atrazine; nitrate had no effect on mortality. Significant differences for all mean traits at metamorphosis occurred among atrazine treatments; higher atrazine exposure increased time to metamorphosis and decreased weight, SVL, and hematocrit. Nitrate treatments were not significantly different. Significant interaction tests between atrazine and nitrate occurred for weight and SVL at metamorphosis; the specific type of interaction varied among treatments. Assuming an additive mixture model, at low atrazine (40 ,g/L), the addition of 37 mg/L nitrate produced SVL values less than expected (a synergistic effect) while the addition of 292 mg/L nitrate yielded SVL values greater than expected (an antagonistic effect). A similar response was noted for tadpoles in the 320-,g/L atrazine treatments. These results indicate that environmentally realistic concentrations of atrazine exert a negative impact on amphibian metamorphosis. Also, this study suggests that mixtures of agricultural chemicals, even if sublethal, may exert negative and not necessarily consistent mixture effects. [source] Increased toxicity to invertebrates associated with a mixture of atrazine and organophosphate insecticidesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2002Troy D. Anderson Abstract This study examined the joint toxicity of atrazine and three organophosphate (OP) insecticides (chlorpyrifos, methyl parathion, and diazinon) exposed to Hyalella azteca and Musca domestica. A factorial design was used to evaluate the toxicity of binary mixtures in which the lethal concentration/lethal dose (LC1/LD1, LC5/LD5, LC15/LD15, and LC50/LD50) of each OP was combined with atrazine concentrations of 0, 10, 40, 80, and 200 ,g/L for H. azteca and 0, 200, and 2,000 ng/mg for M. domestica. Atrazine concentrations (>40 ,g/L) in combination with each OP caused a significant increase in toxicity to H. azteca compared with the OPs dosed individually. Acetylcholinesterase (AChE) activity also was examined for the individual OPs with and without atrazine treatment. Atrazine in combination with each of the OPs resulted in a significant decrease in AChE activity compared with the OPs dosed individually. In addition, H. azteca that were pretreated with atrazine (>40 ,g/L) were much more sensitive to the OP insecticides compared with H. azteca that were not pretreated with atrazine before being tested. Topical exposure to atrazine concentrations did not significantly increase OP toxicity to M. domestica. The results of this study indicate the potential for increased toxicity in organisms exposed to environmental mixtures. [source] The Influence of Flowing Water on the Resource Pursuit-Risk Avoidance Tradeoff in the Crayfish Orconectes virilisETHOLOGY, Issue 4 2006Keith W. Pecor The influence of hydrodynamics on chemically mediated behavioral tradeoffs has received little attention. We tested the hypothesis that individuals of the crayfish Orconectes virilis would be more sensitive to chemical cues in flowing water than in still water. Orconectes virilis is a good subject for this test, because it is found in both still water (e.g. ponds), and flowing water (e.g. rivers). A factorial design was used, with two stimulus treatments and two habitat types. Crayfish were exposed to either food cue or food + alarm cue in either still water or flowing water in an artificial stream arena. Habitat use and activity were significantly influenced by stimulus treatment, with more time spent away from the stimulus source and less activity in the food + alarm treatment than in the food treatment. Neither habitat type nor the interaction of stimulus treatment and habitat type had a significant effect on the response variables. Given the natural history of O. virilis, we suggest that selection has favored the ability to equally utilize chemical cues in both still and flowing water. We acknowledge that different flow conditions may influence chemical ecology in this species and caution against the view that tests in flowing waters necessarily provide a more accurate approximation of natural responses. [source] Retail Store Lighting for Elderly Consumers: An Experimental ApproachFAMILY & CONSUMER SCIENCES RESEARCH JOURNAL, Issue 4 2007Nam-Kyu Park The study presents an investigation of the influence of the color of light on readability by figure to background value contrast, color perception, and overall room-light estimation for elderly consumers in an experimental setting representing a retail store. A factorial design with repeated measures was used to identify the impact of three independent variables: (a) lamp color temperatures, (b) lamp color-rendering properties, and (c) age of the participants. The results show that older adults perceived the higher color temperature light source as less cool than did younger adults. Older adults rated their level of comfort and preference higher than the younger participants under all lighting conditions. Regarding readability, higher color-rendering light sources provide better readability, and older adults have more difficulty with warmer lighting when value contrasts were reduced. Implications from this study can be applied to retail lighting techniques to attract elderly consumers. [source] Differential effects of elevated nutrient and sediment inputs on survival, growth and biomass of a common larval fish species (Dorosoma cepedianum)FRESHWATER BIOLOGY, Issue 3 2010MARÍA J. GONZÁLEZ Summary 1. Elevated allochthonous inputs of nutrients and sediments to aquatic ecosystems are associated with eutrophication and sedimentation. Reservoirs receive substantial subsidies of nutrients and sediments from catchments due to their large catchment : lake area ratios. We examined the effect of elevated subsidies of sediments and/or dissolved nutrients on the success (survival, growth, biomass and condition factor) of larval gizzard shad (Dorosoma cepedianum), a widespread and dominant omnivorous fish in reservoir ecosystems. 2. We simulated allochthonous agricultural subsides by manipulating dissolved nutrients and sediment inputs in a 2 × 2 factorial design in experimental mesocosms. We predicted that larval fish success would be greater under elevated nutrients. However, we propose two alternative hypotheses with respect to the overall effect of allochthonous sediment inputs. If sediment inputs negatively affect larval gizzard feeding success, larval success would be highest when only nutrients are added and lowest when only sediments are added (+N > +N+S , C > +S). If high turbidity enhances larval foraging activity (due to greater contrast between prey and background), we predict that larval success would be highest when both subsidy types (nutrients and sediment) are elevated, intermediate when either nutrients or sediments are added and the lowest when no subsidies are added (+N+S > +N , +S > C). 3. Our results indicate that elevated nutrient and sediment conditions enhanced larval gizzard shad biomass, but the overall nutrient addition effect was greater than the sediment addition effect (+N , +N+S > +S > C). We observed differential effects of nutrient and sediment inputs on larval survival, growth and condition factors. 4. The enhancement of fish biomass in elevated nutrients (+N, +N+S) relative to control conditions was associated with improved gizzard shad survival and not greater growth. The enhancement of fish biomass in the elevated sediment treatment (+S) relative to the control conditions was caused by an increase in survival that more than compensated for a negative effect of sediment addition on growth. 5. Our findings support the recommendation that reservoir management practices must consider the links between land use practices and food web dynamics. Our results suggest that reduction of subsidies of nutrients and sediments to productive reservoirs would decrease survival of larval gizzard shad due to lower food availability. [source] The effects of Daphnia on nutrient stoichiometry and filamentous cyanobacteria: a mesocosm experiment in a eutrophic lakeFRESHWATER BIOLOGY, Issue 7 2002M. J. PATERSON 1.,Stoichiometric theory predicts that the nitrogen : phosphorus (N : P) ratio of recycled nutrients should increase when P-rich zooplankton such as Daphnia become dominant. We used an enclosure study to test the hypothesis that an increased biomass of Daphnia will increase the relative availability of N versus P sufficiently to decrease the abundance of filamentous cyanobacteria. The experiment was conducted in artificially enriched Lake 227 (L227) in the Experimental Lakes Area (ELA), north-western Ontario, Canada. Previous studies in L227 have shown that the dominance of filamentous, N-fixing cyanobacteria is strongly affected by changes in the relative loading rates of N and P. 2.,We used a 2 × 2 factorial design with the addition or absence of D. pulicaria and high or low relative loading rates of N and P (+NH4, ,NH4) in small enclosures as treatment variables. If Daphnia can strongly affect filamentous cyanobacteria by altering N and P availability, these impacts should be greatest with low external N : P loading rates. The phytoplankton community of L227 was predominantly composed of filamentous Aphanizomenon spp. at the start of the experiment. 3.,Daphnia strongly reduced filamentous cyanobacterial density in all enclosures to which they were added. The addition of NH4 had only a small impact on algal community composition. Hence, we conclude that Daphnia did not cause reductions in cyanobacteria by altering the N : P ratio of available nutrients. 4.,Despite the lack of evidence that Daphnia affected filamentous cyanobacteria by altering the relative availability of N and P, we found changes in nutrient cycling consistent with other aspects of stoichiometric theory. In the presence of Daphnia, total P in the water column decreased because of an increase in P sedimentation. In contrast to P, a decrease in suspended particulate N was offset by an increase in dissolved N (especially NH4). Hence, dissolved and total N : P ratios in the water column increased with Daphnia as a result of differences in the fate of suspended particulate N versus P. There was minimal accumulation and storage of P in Daphnia biomass in the enclosures. 5.,Our experiment demonstrated that Daphnia can strongly limit filamentous cyanobacterial abundance and affect the biogeochemical cycling of nutrients. In our study, changes in nutrient cycling were apparently insufficient to cause the changes in phytoplankton community composition that we observed. Daphnia therefore limited filamentous cyanobacteria by other mechanisms. [source] Waterlogging and canopy interact to control species recruitment in floodplainsFUNCTIONAL ECOLOGY, Issue 4 2010Wiktor Kotowski Summary 1.,The extent to which seedling recruitment contributes to local functional diversity depends on the environmental filters operating in a plant community. Classical community assembly models assume that habitat constraints and competition act like hierarchical filters with habitat filtering as the dominant one. Alternative models assume a synergic interaction since responses to environmental stress and competition may impose physiological trade-offs in plants. 2.,River floodplains are an ideal system to test the relationship between habitat and competition filtering in community (re)assembly, as flooding causes changes in both habitat stress (waterlogging, resulting in anoxia and toxicity) and competition (dieback of vegetation) on one hand and acts as an effective seed dispersal vector on the other hand. 3.,We conducted a mesocosm experiment on early community assembly from a pool of 34 floodplain species covering a wetness gradient. Seed mixtures were sown in a full factorial design with water level, canopy and mowing as controlling factors. We measured the biomass of all species after one growing season and determined germination and seedling growth traits, both outside (response to waterlogging/no waterlogging) and in a growth-chamber (response to light/darkness). 4.,Species recruitment was analysed in relation to the controlling factors and measured functional traits using co-inertia analysis. Furthermore we analysed the effects of the controlling factors on several aspects of functional diversity. 5.,There was no establishment in grass sward, unless mowing was applied. Species-rich communities only developed when germination and early establishment phases occurred on waterlogged bare soil. High water level did not suppress establishment but reduced the total biomass and lowered inter-specific competition. The effect of mowing on species richness depended upon the interplay between waterlogging and canopy. 6.,Establishment success under canopy required seedling strategies to tolerate shade. The elimination of typical wetland specialists from oxic mesocosms was clearly an effect of their poorer and/or slower germination and lower competitive abilities in comparison to non-wetland plants, leading to their disappearance in this low-stress environment. 7.,Our results indicate that single stress factors can enhance species richness and functional diversity through limiting competition but a synergic interaction of different stresses can lead to reduced richness. [source] Combined effects of elevated temperatures and reduced leaf litter quality on the life-history parameters of a saprophagous macroarthropodGLOBAL CHANGE BIOLOGY, Issue 1 2009JEAN-FRANCOIS DAVID Abstract Because soil macroinvertebrates strongly modify decomposition processes, it is important to know how their abundance will respond to global change. We investigated in laboratory microcosms, the effects of elevated temperatures and reduced leaf litter quality on the life-history traits of a saprophagous macroarthropod (development time, growth, survival and reproduction). Millipedes (Polydesmus angustus) from an Atlantic temperate forest were reared throughout their life cycle (,16 months) under two temperature regimes differing on average by 3.3 °C; in a factorial design, they were fed either on Atlantic leaf litter or on Mediterranean leaf litter with a higher C : N ratio; humidity was consistently high. The components of the population growth rate (r) were affected positively by the temperature rise and negatively by the switch from Atlantic to Mediterranean leaf litter. When both treatments were combined, litter effects offset temperature effects. These results show that the short-term response of saprophagous macroarthropods to warming is positive but depends on the availability of high-quality litter, which is difficult to predict in the global change context. In a parallel experiment, conspecific millipedes from a Mediterranean population, which have evolved for a long time in a warmer climate and on poor-quality litter, were reared at elevated temperatures on Mediterranean leaf litter. All components of r were higher than in the Atlantic population under the same conditions. This suggests that in the longer term, macroarthropods can overcome detrimental trophic interactions. Based on our study and the literature, we conclude that for decades the positive effects of warming on saprophagous macrofauna should exceed the negative effects of changes in litter quality. The abundance of those organisms in temperate forests could increase, which is confirmed by latitudinal patterns in Europe. Studies aimed at predicting the impacts of global change on decomposition will need to consider interactions with soil macroinvertebrates. [source] Stress synergy between drought and a common environmental contaminant: studies with the collembolan Folsomia candidaGLOBAL CHANGE BIOLOGY, Issue 4 2001Rikke Højer Summary The term global change is used predominantly in connection with the global temperature increase and associated changes in weather patterns over the next century. In a broader sense it also covers other anthropogenic impacts on the environment such as habitat fragmentation and pollution. The individual effects of each of these stress types have been extensively studied in the biota. However, organisms will frequently encounter these stress types in combination rather than alone and there is little information available on the effects of stress combinations. Here an examination is made of the interaction between realistic levels of summer drought and a common contaminant of agricultural soil (4-nonylphenol, NP), on a widespread soil invertebrate, the collembolan Folsomia candida. These stress factors were tested individually and in combination using a full factorial design. This approach revealed the existence of highly significant Bliss type synergistic interaction between the two stress types. Thus, exposure to NP significantly reduced the drought tolerance of this organism and, reciprocally, the toxicity of NP (LC50) during realistic summer drought was more than doubled in comparison to the value obtained under optimal soil moisture conditions. Furthermore, it is shown that NP has a detrimental effect on the physiological mechanisms underlying this animal's drought tolerance, thus providing some explanation for the mechanisms involved in the synergy. It is argued that this type of synergy is unlikely to be confined to this particular combination of stresses and thus there is a need to study the interactions between dominant natural stresses and pollution. The most important implication of these results is that some of the effects of global climate changes can be predicted to be most severe in polluted areas. [source] Permutation tests for factorially designed neuroimaging experimentsHUMAN BRAIN MAPPING, Issue 3 2004John Suckling Abstract Permutation methods for analysis of functional neuroimaging data acquired as factorially designed experiments are described and validated. The F ratio was estimated for main effects and interactions at each voxel in standard space. Critical values corresponding to probability thresholds were derived from a null distribution sampled by appropriate permutation of observations. Spatially informed, cluster-level test statistics were generated by applying a preliminary probability threshold to the voxel F maps and then computing the sum of voxel statistics in each of the resulting three-dimensional clusters, i.e., cluster "mass." Using simulations comprising two between- or within-subject factors each with two or three levels, contaminated by Gaussian and non-normal noise, the voxel-wise permutation test was compared to the standard parametric F test and to the performance of the spatially informed statistic using receiver operating characteristic (ROC) curves. Validity of the permutation-testing algorithm and software is endorsed by almost identical performance of parametric and permutation tests of the voxel-level F statistic. Permutation testing of suprathreshold voxel cluster mass, however, was found to provide consistently superior sensitivity to detect simulated signals than either of the voxel-level tests. The methods are also illustrated by application to an experimental dataset designed to investigate effects of antidepressant drug treatment on brain activation by implicit sad facial affect perception in patients with major depression. Antidepressant drug effects in left amygdala and ventral striatum were detected by this software for an interaction between time (within-subject factor) and group (between-subject factor) in a representative two-way factorial design. Hum. Brain Mapping 22:193,205, 2004. © 2004 Wiley-Liss, Inc. [source] Availability and selection of arboreal termitaria as nest-sites by Orange-fronted Parakeets Aratinga canicularis in conserved and modified landscapes in MexicoIBIS, Issue 2 2009TANIA C. SANCHEZ-MARTINEZ Few studies have investigated the use of termitaria by nesting parrots, or how this may be affected by habitat transformation. We determined selection of termitaria by nesting Orange-fronted Parakeets Aratinga canicularis, and evaluated the effect of habitat transformation on the availability of termitaria nest-sites for Parakeets in the tropical dry forest of Western Mexico. Availability of termitaria was quantified in 24 survey plots in a factorial design of six 1-ha plots in each of conserved and modified, deciduous and semi-deciduous forest. Characteristics of termitaria were determined in survey plots, as well as 21 nest-termitaria used by Parakeets, and their nearest adjacent termitarium. There was an overall density of 1.6 termitaria/ha suitable for nesting by Parakeets, which did not differ between habitats, although only 8% of apparently suitable termitaria were occupied by nesting Parakeets. However, termitaria in conserved semi-deciduous forest were significantly higher above the ground, and termitaria in conserved deciduous forest were significantly smaller in volume. In the modified landscape, termitaria were significantly lower and their volume significantly larger than in conserved landscapes. Termitaria used by nesting parrots were at a significantly greater height above the ground than the nearest adjacent termitaria. Termitarium volume did not reliably predict the likelihood of nest-site selection, although Parakeets only used termitaria between 15 and 150 l. Parakeets nesting in modified habitats used termitaria at a significantly lower height than Parakeets nesting in conserved habitat. It is unclear whether this represents a decline in nest-site quality in modified habitats, which could affect reproductive success of Parakeet populations in fragmented landscapes. [source] A new approach to response surface development for detailed gas-phase and surface reaction kinetic model optimizationINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2004Scott G. Davis We propose a new method for constructing kinetic response surfaces used in the development and optimization of gas-phase and surface reaction kinetic models. The method, termed as the sensitivity analysis based (SAB) method, is based on a multivariate Taylor expansion of model response with respect to model parameters, neglecting terms higher than the second order. The expansion coefficients are obtained by a first-order local sensitivity analysis. Tests are made for gas-phase combustion reaction models. The results show that the response surface obtained with the SAB method is as accurate as the factorial design method traditionally used in reaction model optimization. The SAB method, however, presents significant computational savings compared to factorial design. The effect of including the partial and full third order terms was also examined and discussed. The SAB method is applied to optimization of a relatively complex surface reaction mechanism where large uncertainty in rate parameters exists. The example chosen is laser-induced fluorescence signal of OH desorption from a platinum foil in the water/oxygen reaction at low pressures. We introduce an iterative solution mapping and optimization approach for improved accuracy. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 94,106, 2004 [source] EVA: a better TCP version for resource-insufficient networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2002Jung-Shian Li Abstract TCP Vegas exhibits unfair congestion avoidance mechanism, which aggravates when there are insufficient network resources to accommodate buffer space of a pipe (bandwidth delay product). To remedy this shortcoming, we propose an Enhanced VegAs (EVA) that employs three auxiliary mechanisms: , revision, congestion detection and congestion tendency detection. A 2k factorial design with replications is used to study the effect of the three mechanisms. Our results show that TCP EVA achieves better performance than Vegas under various network conditions. Furthermore, congestion avoidance schemes, such as TCP EVA, perform much better than congestion control schemes, such as TCP Reno, in resource-insufficient networks. Copyright © 2002 John Wiley & Sons, Ltd. [source] Ranking factors of an investment in cogeneration: Sensitivity analysis ranking the technical and economical factorsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2001Gunnel Sundberg Abstract A deregulation of the electricity market in Europe will result in increased competition among the power-producing companies. They will therefore carefully estimate the financial risk in an investment in new power-producing capability. One part of the risk assessment is to perform a sensitivity analysis. This paper presents a sensitivity analysis using factorial design, resulting in an assessment of the most important technical and economical factors affecting an investment in a gas turbine combined cycle and a steam cycle fired by woodchips. The study is performed using a simulation model that optimizes the operation of existing power plants and potential new investments to fulfil the desired heat demand. The local utility system analysed is a Swedish district heating system with 655 GWh y,1 heat demand. The conclusion is that to understand which of the technical and economical factors affect the investment, it is not sufficient to investigate the parameters of the studied plant, but also the parameters related to the competing plants. Both the individual effects of the factors and the effect of their interaction should be investigated. For the energy system studied the price of natural gas, price of woodchips and investment cost have the major influence on the profitability of the investment. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synergistic effect of chemical preservatives with ethanol on the microbial shelf life of bread by factorial designINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2008George Katsinis Summary The shelf life, particularly the mould-free shelf life (MFSL) of bread, was evaluated either by adding a conventional chemical preservative or by spraying the surface of bread, in which a chemical preservative was added. As bread making is a complex process and bread is a multicomponent system, the investigation was based on statistical design experiments. Using first-order factorial designs, reliable models were constructed, revealing the effects of some common ingredients of bread (such as salt, sugar, glycerol, potassium sorbate, calcium propionate) and their interactions on the MFSL (optimisation parameter) with and without ethanol surface spraying. The effectiveness of preservation was ranked as potassium sorbate + ethanol > calcium propionate + ethanol > potassium sorbate > calcium propionate. Ethanol addition led to MFSL prolongation of 43.5% and 38.5% compared with MFSL of potassium sorbate and calcium propionate, respectively, when all the factors were fixed to their basic levels. [source] The effect of whey protein concentrates and hydrocolloids on the texture and colour characteristics of chicken sausagesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2006Silvina Andrès Summary The effects of fat reduction by increasing water content and the addition of whey protein and hydrocolloids on the instrumental texture profile, microstructure and water holding capacity of low-fat chicken sausages were analysed. Low-fat sausages were prepared with fresh breast chicken meat; in all formulations, a 3:7 ratio guar/xanthan gum was used. A factorial design with three levels of added fat (0%, 1.98% and 4.96%), two levels of whey protein concentrate (0.64% and 1.94%), and two levels of the hydrocolloids (0.13% and 0.32%) was applied. Samples were heat-processed (73 °C final internal temperature) and, after cooling, chemical composition of the sausages was determined and scanning electron microscopic images were obtained. Colour was measured with a tristimulus reflectance colorimeter. Texture profile analysis of sausages was performed and the results were related to sample formulations. Extra-lean products with a fat content lower than 0.5 g/100 g product showed very good quality attributes determined by a sensory panel. [source] Two-stage computing budget allocation approach for the response surface methodINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 6 2007J. Peng Abstract Response surface methodology (RSM) is one of the main statistical approaches to search for an input combination that optimizes the simulation output. In the early stages of RSM, an iterative steepest ascent search procedure is frequently used. In this paper, we attempt to improve this procedure by considering a more realistic case where there are computing budget constraints, and formulate a new computing budget allocation problem to look into the important issue of allocating computing budget to the design points in the local region of experimentation. We propose a two-stage computing budget allocation approach, which uses a limited budget to estimate the response surface in the first stage and then uses the rest of the budget to improve the lower bound of the estimated response at the center of the next design region in the second stage. Several numerical experiments are carried out to compare the two-stage approach with the regular factorial design, which allocates budget equally to each design point. The results show that our two-stage allocation outperforms the equal allocation, especially when the system noise is large. [source] Derivative Free Optimization in Higher DimensionINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 3 2001Shamsuddin Ahmed Non-linear optimizations that do not require explicit or implicit derivative information of an objective function are an alternate search strategy when the derivative of the objective function is not available. In factorial design, the number of trials for experimental identification method in Em is about (m+ 1). These (m+ 1) equally spaced points are allowed to form a geometry that is known as regular simplex. The simplex method is attributed to Spendley, Hext and Himsworth. The method is improved by maintaining a set of (m+ 1) points in m dimensional space to generate a non-regular simplex. This study suggests re-scaling the simplex in higher dimensions for a restart phase. The direction of search is also changed when the simplex degenerates. The performance of this derivative free search method is measured based on the number of function evaluations, number of restart attempts and improvements in function value. An algorithm that describes the improved method is presented and compared with the Nelder and Mead simplex method. The performance of this algorithm is also tested with artificial neural network (ANN) problem. The numbers of function evaluations are about 40 times less with the improved method against the Nelder and Mead (1965) method to train an ANN problem with 36 variables. [source] Comparison of Effect of Aerobic Cycle Training and Progressive Resistance Training on Walking Ability After Stroke: A Randomized Sham Exercise,Controlled StudyJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 6 2008Mi-Joung Lee PhD OBJECTIVES: To determine whether changes in strength or cardiorespiratory fitness after exercise training improve walking ability in individuals who have had a stroke. DESIGN: A sham exercise-controlled, randomized two-by-two factorial design, in which the two factors investigated were cycle training (AEROBIC) and resistance training (STRENGTH). SETTING: University exercise laboratory. PARTICIPANTS: Fifty-two individuals with a history of stroke (aged 63±9; time since stroke, 57±54 months). INTERVENTION: Participants undertook 30 exercise sessions over 10 to 12 weeks. Depending on group allocation, individuals underwent aerobic cycling plus sham progressive resistance training (PRT) (n=13), sham cycling plus PRT (n=13), aerobic cycling plus PRT (n=14), or sham cycling plus sham PRT (n=12). MEASUREMENTS: Primary outcomes were 6-minute walk distance, habitual and fast gait velocities, and stair climbing power. Secondary outcomes included measures of cardiorespiratory fitness; muscle strength, power, and endurance; and psychosocial attributes. RESULTS: Neither AEROBIC nor STRENGTH improved walking distance or gait velocity significantly more than sham exercise, although STRENGTH significantly improved participants' stair climbing power by 17% (P=.009), as well as their muscle strength, power, and endurance; cycling peak power output; and self-efficacy. Conversely, AEROBIC improved indicators of cardiorespiratory fitness only. Cycling plus PRT produced larger effects than either single modality for mobility and impairment outcomes. CONCLUSION: Single-modality exercises targeted at existing impairments do not optimally address the functional deficits of walking but do ameliorate the underlying impairments. The underlying cardiovascular and musculoskeletal impairments are significantly modifiable years after stroke with targeted robust exercise. [source] Effects of extrusion and supplementation of exogenous enzymes to diets containing Chinese storage brown rice on the carbohydrase activity in the digestive tract of pigletsJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 2 2010J. He Summary Two experiments were conducted to study the effects of extrusion of Chinese storage brown rice and of exogenous enzymes supplementation to diets containing Chinese storage brown rice on the carbohydrase activity in digestive tract of piglets. In Experiment 1, 96 weaned piglets [initially 6.95 ± 0.05 kg body weight (BW)] were used in a 2 × 2 factorial design, the animals were fed the diets containing extruded Chinese storage brown rice or non-treated Chinese storage brown rice and supplemented with or without exogenous enzymes. Each treatment had six replicate pens and four piglets in each pen. The results demonstrated that extrusion significantly increased (p < 0.05) the activity of duodenal maltase after 14 days of treatment and glucoamylase after 28 days of treatment, jejunal lactase, maltase, isomaltase, sucrase and ,-amylase after 28 days of treatment, and jejunal ,-amylase after 14 days of treatment; enzyme supplementation positively influenced (p < 0.05) the activity of pancreatic ,-amylase after 14 and 28 days of treatment, pancreatic glucoamylase after 28 days of treatment and ileal trehalase after 14 days of treatment. Similarly, interaction between extrusion and enzyme addition existed after 14 days of treatment on the activity of pancreatic ,-amylase and duodenal maltase and on the activity of duodenal glucoamylase and isomaltase, jejunal ,-amylase, lactase, maltase, isomaltase and jejunal ,-amylase after 28 days of treatment. In Experiment 2, six piglets (initially 21 ± 1.85 kg BW) fitted with ileal ,T'-cannulas in a 6 × 6 Latin Square Design were used to study the effects of extrusion and addition of exogenous enzymes on ileal carbohydrase activity and nutrients digestibility. The results showed that exogenous enzymes significantly (p < 0.05) increased ileal ,-amylase, glucoamylase and trehalase activity. The interaction between extrusion and enzyme supplementation had positive effect (p < 0.05) on the ileal lactase, cellobiase and sucrase activity. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||