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Determination Coefficient (determination + coefficient)
Selected AbstractsDaily pan evaporation modelling using multi-layer perceptrons and radial basis neural networksHYDROLOGICAL PROCESSES, Issue 2 2009Özgür Ki Abstract This paper reports on investigations of the abilities of three different artificial neural network (ANN) techniques, multi-layer perceptrons (MLP), radial basis neural networks (RBNN) and generalized regression neural networks (GRNN) to estimate daily pan evaporation. Different MLP models comprising various combinations of daily climatic variables, that is, air temperature, solar radiation, wind speed, pressure and humidity were developed to evaluate the effect of each of these variables on pan evaporation. The MLP estimates are compared with those of the RBNN and GRNN techniques. The Stephens-Stewart (SS) method is also considered for the comparison. The performances of the models are evaluated using root mean square errors (RMSE), mean absolute error (MAE) and determination coefficient (R2) statistics. Based on the comparisons, it was found that the MLP and RBNN computing techniques could be employed successfully to model the evaporation process using the available climatic data. The GRNN was found to perform better than the SS method. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fibres in the dough influencing freezing and thawing kineticsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2010Jelena Filipovic Summary Three types of commercial fibres were incorporated into the dough formula at the level of 0%, 5% and 10%. Dough freezing/thawing kinetics was determined at ,18 °C and +30 °C, respectively. Fibres type and quantity are influencing the slope of freezing curve not the trend of the freezing curve. Related to the control the presence of fibres in dough prevents the formation of the solid phase. Freezing/thawing process of dough is defined by the Fourier's equation and tested with three approximations. Experimental data correspond the best to unsteady temperature profile, with introduced value of t2 referring to the phase transformation, proved by determination coefficient. At freezing/thawing the highest determination coefficient is experienced with 10% of inulin GR (0.966 and 0.991), and the lowest with 10% of fibrex (0.939 and 0.972). Pertinent data point at the possibility of mathematical interpretation of freezing/thawing processes that is of a particular interest for the bakery practice. [source] Rheological study of ternary mixtures and pectic gels of red fruit pulpsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2007Charles Windson Isidoro Haminiuk Summary In this work, the rheological behaviour of ternary mixtures of strawberry, blackberry and raspberry pulps in steady shear was studied using the response surface methodology. In addition, the rheology of pectic gels extracted from these pulps was investigated by means of oscillatory shear tests. The flow curves were adequately described by the rheological model of Herschel,Bulkley. All the formulations analysed exhibited shear-thinning behaviour. The rheological responses were influenced by the difference in pulp proportions and also by the temperatures (20 and 60 °C). The quadratic and cubic models used to fit the response were considered suitable owing to the higher values of determination coefficient (R2). The pectic gels from strawberry, blackberry and raspberry showed a strong gel character, with strawberry presenting the stronger gel, which was confirmed by the Cox,Merz experiment, degree of esterification and average molecular weight data. [source] Experimental and neural model analysis of styrene removal from polluted air in a biofilterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2009Eldon R. Rene Abstract BACKGROUND: Biofilters are efficient systems for treating malodorous emissions. The mechanism involved during pollutant transfer and subsequent biotransformation within a biofilm is a complex process. The use of artificial neural networks to model the performance of biofilters using easily measurable state variables appears to be an effective alternative to conventional phenomenological modelling. RESULTS: An artificial neural network model was used to predict the extent of styrene removal in a perlite-biofilter inoculated with a mixed microbial culture. After a 43 day biofilter acclimation period, styrene removal experiments were carried out by subjecting the bioreactor to different flow rates (0.15,0.9 m3 h,1) and concentrations (0.5,17.2 g m,3), that correspond to inlet loading rates up to 1390 g m,3 h,1. During the different phases of continuous biofilter operation, greater than 92% styrene removal was achievable for loading rates up to 250 g m,3 h,1. A back propagation neural network algorithm was applied to model and predict the removal efficiency (%) of this process using inlet concentration (g m,3) and unit flow (h,1) as input variables. The data points were divided into training (115 × 3) and testing set (42 × 3). The most reliable condition for the network was selected by a trial and error approach and by estimating the determination coefficient (R2) value (0.98) achieved during prediction of the testing set. CONCLUSION: The results showed that a simple neural network based model with a topology of 2,4,1 was able to efficiently predict the styrene removal performance in the biofilter. Through sensitivity analysis, the most influential input parameter affecting styrene removal was ascertained to be the flow rate. Copyright © 2009 Society of Chemical Industry [source] Texture Changes During the Ripening of Port Salut Argentino Cheese in 2 Sampling ZonesJOURNAL OF FOOD SCIENCE, Issue 5 2002R.A. Verdini ABSTRACT: Texture changes during ripening of Port Salut Argentino cheese for different sampling zones were studied. Compression relaxation tests were performed and results were analyzed using both Maxwellian and Peleg's models. Elastic equilibrium modulus obtained from the Maxwellian model decreased from 1.22 to 0.11 104Pa during ripening. The constants derived from Peleg's model, k1 and k2, diminished with ripening time from 1.18 to 0.71 min and from 1.27 to 1.12, respectively. Asymptotic equilibrium modulus from Peleg's model decreased from 0.95 to 0.07 104Pa during ripening. Rate parameters derived from a 1st order kinetics applied to both equilibrium moduli showed that the decrease was faster in the external zone (0.0846 d,1) than in the central zone (0.0368 d,1). The correlation between equilibrium moduli, salt concentration, moisture content, and maturation indexes was obtained with a determination coefficient of 0.76. [source] Quantitative determination of haloperidol in tablets by high performance thin-layer chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 5 2007Sigrid Mennickent Abstract A densitometric high performance thin-layer chromatography (HPTLC) method was developed and validated for the quantitative analysis of haloperidol in tablets. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone/chloroform/n -butanol/acetic acid glacial/water (5:10:10:2.5:2.5 v/v/v/v/v) as the mobile phase. Quantitative analysis was carried out at a wavelength of 254 nm. The method was linear in the 10,100 ng/,L range, with a determination coefficient of 0.999. The coefficients of variation for precision were not higher than 2.35%. The detection limit was 0.89 ng/,L, and the quantification limit was 2.71 ng/,L. The accuracy ranged from 97.76 to 100.33%, with a CV not higher than 4.50%. This method was successfully applied to quantify haloperidol in real pharmaceutical samples, including the comparison with HPLC measurements. The method was fast, specific, with a good precision and accuracy for the quantitative determination of haloperidol in tablets. [source] Abundance of stable flies on heifers treated for control of horn flies with organophosphate impregnated ear tagsMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2004A. A. Guglielmone Abstract., Ear tags containing 40% organophosphate insecticides (diazinon or diazinon plus chlorpyrifos-ethyl) were applied to control Haematobia irritans (L.) (Diptera: Muscidae) in treated (TG01 and TG02) and untreated (UG01 and UG02) groups of Holstein heifers born in 2001 and 2002, respectively. Control and treated groups were assessed for the abundance of Stomoxys calcitrans (L.) (Diptera: Muscidae) from August 2001 to April 2002 and again from August 2002 to April 2003. The treatment had a high efficacy for control of horn flies (maximum median number per heifer of TG01 and TG02 = 5) but a low effect on the abundance of stable flies. The total numbers of S. calcitrans were 1251 (42.9% of the total) and 1668 (57.1%) for TG01 and UG01, and 1423 (48.8%) and 1494 (51.2%) in TG02 and UG02, respectively. No significant difference in stable fly burden was found in 55 of the 76 weeks evaluated. A unimodal peak of abundance in the spring was found during the first fly season, and a bimodal abundance, with peaks in the spring and autumn, during the second season. No strong associations between horn fly and stable fly burdens was found in individuals of the CG01 (correlation coefficient = 0.13, P > 0.05) or CG02 (correlation coefficient = 0.538, P < 0.05, determination coefficient = 0.289). [source] Pharmacokinetic study of p -coumaric acid in mouse after oral administration of extract of Ananas comosus L. leavesBIOMEDICAL CHROMATOGRAPHY, Issue 9 2006Zhen Meng Abstract Quantification of p- coumaric acid in mouse plasma following oral administration of Ananas comosus L. leaves was achieved by reversed-phase high-performance liquid chromatography using a mobile phase of water,acetonitrile (82:18, v/v) and UV detection at 310 nm. The method was linear (determination coefficient, r2 = 0.9997) within the tested range (0.04,1.28 µg/mL). Intra- and inter-day precision coefficients of variation and accuracy bias were acceptable (maximal CV value was 4.06% for intra-day and 4.19% for inter-day) over the entire range. The recoveries were 90.63, 97.98 and 100.01% for concentrations of 0.04, 0.32 and 1.28 µg/mL, respectively. This is a very rapid, sensitive and economical way to determine p- coumaric acid concentration in mouse plasma after oral administration of A. comosus leaves. The concentration,time curve was fitted to the one-compartment model. This is the first time that p- coumaric acid extracted from A. comosus leaves was detected by HPLC-UV method and its pharmacokinetic characteristic was comprehensively studied. Copyright © 2006 John Wiley & Sons, Ltd. [source] On-line size measurement of yeast aggregates using image analysisBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2001Sandrine Mas Abstract Alcohol fermentation productivity can be strongly improved using a flocculation-based yeast recycle. However, the efficiency of the biomass retention system depends strongly on the yeast particle size. Accordingly, the monitoring and control of yeast floc diameter are of primary importance. The on-line measurement of mean floc diameter has been achieved using on-line image analysis, based on the evaluation of image texture. The texture analysis method consisted in the building of a co-occurrence matrix from which the so-called "Energy parameter" was extracted. While image texture is usually used for classification purposes, it has been used here as a quantitative descriptor: a correlation has been found between this statistical image feature and off-line manual floc-size determinations. In the floc-size range investigated (|bu 0.5,4.3 mm), the evaluated mean diameter was in good agreement with the actual particle size, with a determination coefficient equal to 0.980. In contrast with manual measurements, slow and tedious, this method gave the value of the mean particle diameter in real-time, without sampling. This novel tool has been used to investigate the behavior of yeast aggregates as a function of fermentation conditions. While biomass concentration was kept constant, step increases of the feed rate led to a decrease of the mean floc diameter. Image analysis showed that the particle-size reduction could occur within a few minutes after modification of the medium dilution rate, demonstrating the disruptive effect of the CO2 efflux. The kinetic of aggregate formation was dependent on the gas-phase composition. Instead of recycling fermentation gas, sparging the fermentor with nitrogen, to reduce dissolved CO2 concentration, increased the rate of floc-size growth. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 91,98, 2001. [source] Winter diatom blooms in a regulated river in South Korea: explanations based on evolutionary computationFRESHWATER BIOLOGY, Issue 10 2007DONG-KYUN KIM Summary 1. An ecological model was developed using genetic programming (GP) to predict the time-series dynamics of the diatom, Stephanodiscus hantzschii for the lower Nakdong River, South Korea. Eight years of weekly data showed the river to be hypertrophic (chl. a, 45.1 ± 4.19 ,g L,1, mean ± SE, n = 427), and S. hantzschii annually formed blooms during the winter to spring flow period (late November to March). 2. A simple non-linear equation was created to produce a 3-day sequential forecast of the species biovolume, by means of time series optimization genetic programming (TSOGP). Training data were used in conjunction with a GP algorithm utilizing 7 years of limnological variables (1995,2001). The model was validated by comparing its output with measurements for a specific year with severe blooms (1994). The model accurately predicted timing of the blooms although it slightly underestimated biovolume (training r2 = 0.70, test r2 = 0.78). The model consisted of the following variables: dam discharge and storage, water temperature, Secchi transparency, dissolved oxygen (DO), pH, evaporation and silica concentration. 3. The application of a five-way cross-validation test suggested that GP was capable of developing models whose input variables were similar, although the data are randomly used for training. The similarity of input variable selection was approximately 51% between the best model and the top 20 candidate models out of 150 in total (based on both Root Mean Squared Error and the determination coefficients for the test data). 4. Genetic programming was able to determine the ecological importance of different environmental variables affecting the diatoms. A series of sensitivity analyses showed that water temperature was the most sensitive parameter. In addition, the optimal equation was sensitive to DO, Secchi transparency, dam discharge and silica concentration. The analyses thus identified likely causes of the proliferation of diatoms in ,river-reservoir hybrids' (i.e. rivers which have the characteristics of a reservoir during the dry season). This result provides specific information about the bloom of S. hantzschii in river systems, as well as the applicability of inductive methods, such as evolutionary computation to river-reservoir hybrid systems. [source] Steady and dynamic shear rheology of glutinous rice flour dispersionsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2006Byoungseung Yoo Summary The steady and dynamic shear rheological properties of Korean glutinous rice flour dispersions were evaluated at different concentrations (4, 5, 6, 7 and 8%). Glutinous rice flour dispersions at 25 °C showed a shear-thinning behaviour (n = 0.487,0.522) with low magnitudes of Casson yield stresses (,oc = 0.056,0.339 Pa). The magnitudes of ,oc, consistency index (K) and apparent viscosity (,a,100) increased with the increase in concentration. The power law model was found to be more suitable than the exponential model in expressing the relationship between concentration and apparent viscosity. The apparent viscosity over the temperature range of 25,70 °C obeyed the Arrhenius temperature relationship, with high determination coefficients (R2 = 0.982,0.998), indicating that the magnitudes of activation energies (Ea) were in the range of 9.05,11.89 kJ mol,1. A single equation, combining the effects of temperature and concentration on ,a,100, was used to describe the flow behaviour of glutinous rice flour dispersions. Magnitudes of storage (G,) and loss (G,,) moduli increased with the increase in concentration and frequency. Magnitudes of G, were higher than those of G,, over most of the frequency range. [source] QSAR analysis of interstudy variable skin permeability based on the "latent membrane permeability" conceptJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2003Shin-Ichi Fujiwara Abstract A number of QSAR models for skin permeability have been proposed, but these models lack consistency due to interspecies and interlaboratory differences. This study was initiated to extract an essential QSAR from the multiplicity of data sets of skin permeability by using a novel statistical approach. Ten data sets were collected from the literature, which include a total of 111 permeability coefficients in human, hairless mouse, or hairless rat skin for 94 structurally diverse compounds. Following a Potts and Guy's approach, the octanol/water partition coefficient and molecular weight were chosen as molecular descriptors. All of the data sets were analyzed simultaneously, assuming that all of the sets share a latent, common factor as far as the structure/permeability relationship is concerned. Despite the fact that the degree-of-freedom for the present analysis was limited compared with that for individual regression analyses, the determination coefficients (R2) were high enough for all the 10 data sets, with an average R2 of 0.815 (average R2,=,0.825 for individual analyses). Thus, skin permeability of compounds can be well explained from the log P and M.W., where the ratio of the contribution to skin permeability was approximately 1:1. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1939,1946, 2003 [source] The utility of ultra-performance liquid chromatography/electrospray ionisation time-of-flight mass spectrometry for multi-residue determination of pesticides in strawberryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2008Michael J. Taylor The utility of ultra-performance liquid chromatography/orthogonal-acceleration time-of flight mass spectrometry (UPLC/TOFMS) for the rapid qualitative and quantitative analysis of 100 pesticides targeted in strawberry was assessed by comparing results with those obtained using a validated in-house UPLC tandem mass spectrometry (MS/MS) multi-residue method. Crude extracts from retail strawberry samples received as part of the 2007 annual UK pesticide residues in food surveillance programme were screened for the presence of pesticide residues using UPLC/TOFMS. Accurate mass measurement of positive and negative ions allowed their extraction following ,full mass range data acquisition' with negligible interference from background or co-eluting species observed during UPLC gradient separation (in a cycle time of just 6.5,min per run). Extracted ion data was used to construct calibration curves and to detect and identify any incurred residues (i.e. pesticides incorporated in or on the test material following application during cultivation, harvest and storage). Calibration using matrix-matched standards was performed over a narrow concentration range of 0.005,0.04,mg,kg,1 with determination coefficients (r2) ,0.99 for all analytes with the exception of malathion/fenarimol/fludioxanil (r2,=,0.98), quassia/pymetrazine (r2,=,0.97) and fenthion sulfone (r2,=,0.95). Residues found in selected samples ranged from 0.025,0.28,mg,kg,1 and were in excellent agreement with results obtained using UPLC/MS/MS. Mass measurement accuracies of ,5,ppm were achieved consistently throughout the separation, mass range and concentration range of interest thus providing the opportunity to obtain discrete elemental compositions of target ions. © Crown copyright 2008. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] | |||||||||||||