Order Exponential Model Research Articles

202 An Update on in Vitro and in Situ Experimental Techniques for Approximation of Ruminal Fiber Degradation

Abstract Measures of the quantity of chemical components are used to make certain assumptions about forage or feed quality. However, additional ruminal degradation kinetic measures are necessary for modern nutrient requirement models and more accurate estimates of intake and digestibility. The extent and rate of ruminal degradation is most easily and inexpensively measured with in vitro and in situ experimental techniques. This presentation is a summary of updates to these techniques in the last thirty years. The Daisy Incubator by ANKOM Technology has been marketed for over twenty-five years. This product resulted in standardization of materials and methods used to measure in vitro true digestibility. The biological component of the technique, ruminal fluid, is still a variable component since it is influenced by fistulated animal diet and collection and transport procedures. Despite several calls through review papers over the last thirty years, the in situ experimental technique is not standardized and there remains variation among laboratories and experiments. Animal species, ingredients and quantity of animal diet, grind size of the test material, bag pore size, ratio of the sample: surface area of bag, replications, sample treatment prior to incubation and after removal, incubation method, microbial contamination, bag washing, and even laboratory balance weigh method contribute to the variation among in situ experiments. Once in situ data is obtained, it is typically fitted to a first order exponential model and parameters estimated without determining if the model is the best fit. Perhaps understanding the reasons that standardization of in situ methodology have failed would facilitate ways to make standardization possible. In the meantime, careful in situ experimental technique results in measures that are valuable inputs into models for nutrient requirements, intake, and digestibility and an increase in knowledge about ruminal degradation kinetics, despite the inability to compare results across laboratories or experiments.

Productivity and Performance of U.S. Economic Growth: 1948-2015

This paper raises basic questions about the performance of economic growth. The paper is only about the United States and views the future from 2015-2015 while pretending that the financial crisis did not happen. The sample period for investigation in 1945-2015 the empirical analysis of this study employed annual secondary data, collected from different sources, which are time series data. Growth gradually accelerated after 1750, reached a peak in the middle of the 20th century, and has been slowing down since. Three influential factors of growth are less the labor force, technology, and capital. Growth of technology is the most influential and thus special attention should be given its advancement. A key idea to take away from this paper is that while a model that fit the current data well, it may weigh recent events to heavily, recessionary or exponential growth, the average between the most optimistic and pessimistic models may be the best bet. Technology makes up the greatest fraction of total production and changes in labor and capital would not affect the growth rate as much as technology can and it was projected that in 20 years, the GDP level could be anywhere from $19,138.8 using the polynomial model to $34,681.8 using the first order exponential model. The growth rate of GDP is at 2.07% as of 2015, but using the first order exponential model, it will slow down to 1.38% by 2035.

Behavior of the U.S. Economic Growth: An Empirical Analysis

The purpose of this paper is to measure behavior of the U.S. economic growth and views the future from 2015-2035 while pretending that the financial crisis did not happen. The sample period for investigation in 1945-2015 the empirical analysis of this study employed annual secondary time series data, collected from different sources. Three influential factors of growth are the labor force, technology, and capital, and our most important finding is that growth of technology is the highest influential among them and thus special attention should be given its advancement. The growth rate of GDP is at 2.07% as of 2015, but using the first order exponential model, it will slow down to 1.38% by 2035. The findings were conclusive in that total production was made up of 57.5% technology, 28.8% labor, and 12.8% capital. Technology makes up the greatest fraction of total production and changes in labor and capital would not affect the growth rate as much as technology can and it was projected that in 20 years, the GDP level could be anywhere from $19,138.8 using the polynomial model to $34,681.8 using the first order exponential model. The longest business cycle the U.S. has experienced was from 1989-2008, under which the economy had its longest stretch of better than experience performance. Growth gradually accelerated after 1950, reached a peak in the middle of the 20th century, and has been slowing down since. The most effective way to increase the growth rate is to increase the level of technology because the diminishing returns to labor and capital decrease the growth rate of GDP. A key idea to take away from this paper is that while a model fit the current data well, it may weigh recent events to heavily, recessionary or exponential growth, the average between the most optimistic and pessimistic models may be the best bet.

An Analytical Framework for the Study of Solid Body Cooling

This paper aims to study the cooling of a solid body. An analytical analysis of a solid body cooling in different regimes is presented, such as a simple first order exponential model, a modified exponential model, a generalized exponential model and the so-called regular temperature regime. The analysis also includes the influence of the dynamically changing relaxation time and we also present the solution of the nonlinear heat equation.

Nitrogen Mineralization from Animal Manures and Its Relation to Organic N Fractions

Laboratory aerobic incubation was conducted for 161 d to study N mineralization and the changes of organic N fractions of nine different manures (3 chicken manures, 3 pig manures and 3 cattle manures) from different farms/locations. Results indicated that significant (P<0.01 or P<0.001) difference existed in N mineralization between manures. The rapid N mineralization in manures occurred during 56 to 84 d of incubation. First order exponential model can be used to describe N mineralization from chicken manures and pig manures, while quadratic equation can predict mineralization of organic N from cattle manures. An average of 21, 19 and 13% added organic N from chicken manure, pig manure and cattle manure was mineralized during 161 d of incubation. Amino acid-N was the main source of N mineralization. The changes of amino acid-N together with ammonium N could explain significantly 97 and 96% of the variation in mineralized N from manured soils and manures. Amino acid-N and ammonium N are two main N fractions in determining N mineralization potential from manures. Amino acid-N contributed more to the mineralized N than ammonium N.

Modeling and simulation of landfill gas production from pretreated MSW landfill simulator

The cumulative landfill gas (LFG) production and its rate were simulated for pretreated municipal solid waste (MSW) landfill using four models namely first order exponential model, modified Gompertz model, single component combined growth and decay model and Gaussian function. Considering the behavior of the pretreated MSW landfill, a new multi component model was based on biochemical processes that occurring in landfilled pretreated MSW. The model was developed on the basis of single component combined growth and decay model using an anaerobic landfill simulator reactor which treats the pretreated MSW. It includes three components of the degradation i.e. quickly degradable, moderately degradable and slowly degradable. Moreover, the developed model was statistically analyzed for its goodness of fit. The results show that the multi components LFG production model is more suitable in comparison to the simulated models and can efficiently be used as a modeling tool for pretreated MSW landfills. The proposed model is likely to give assistance in sizing of LFG collection system, generates speedy results at lower cost, improves cost-benefit analysis and decreases LFG project risk. It also indicates the stabilization of the landfill and helps the managers in the reuse of the landfill space. The proposed model is limited to aerobically pretreated MSW landfill and also requires the values of delay times in LFG productions from moderately and slowly degradable fractions of pretreated MSW.

EFFECT OF NON-FIBER CARBOHYDRATES ON IN VITRO FIRST ORDER KINETICS DISAPPEARANCE OF CELLULOSE

Summary An in vitro experiment was conducted to determine the effect of supplemental non-fiber carbohydrate (NFC) on the disappearance kinetics of cellulose (Ce) by mixed ruminal microorganisms. Non-supplemented or NFC supplemented cellulose (467 mg NFC/g cellulose as sucrose (CeSu) or starch (CeSt) or a 1:1 mixture of sucrose + starch (CeSuSt)) were incubated for 24, 48, and 96 h at 39°C. After each incubation time, pH, ammonia-N concentration and cellulose disappearance were measured. The disappearance kinetics rate of all samples was determined using first order exponential model of D(t) = D(i).exp (-k. time) + I; where D(t) is potentially digestible fraction; D(i) is potentially digestible residues; k is digestion rate of cellulose (h -1 ) and I is indigestible fraction. In this experiment, inclusion of NFC to the rumen fluid medium resulted in a significant depression (P 0.05) on ammonia-N concentration.

The effect of frying conditions on moisture loss and oil uptake in yam slices (Dioscorea alata)

The effect of frying conditions on immersion on moisture loss and oil content were studied at different times in two yam varieties: Diamante 22 and Pico Botella. The experimental data adjusted itself to the first order exponential model for humidity transfer (r &gt; 0.9) for both cultivars. The humidity diffusion coefficient for the two varieties of yam fried at 140°, 160° and 180°C for 1 to 9 minutes were 8.11±0.76, 8.2±0.81, and 8.62 ±0.71*10-9 m2/s for the Diamante 22 variety, respectively, and 8.32±0.82, 8.38±0.78, 8.54±0.84*10-9 m2/s for the Pico de Botella variety. Activation energy was 24.43 kJ/mol for the Diamante 22 variety and 21.27 kJ/mol for the Pico de Botella variety. The results showed that there was higher oil absorption after 180 s and at 140°C while taking into account 0.377 kg water / kg solid moisture loss for Diamond 22 and 0.410 kg water / kg solid Pico de Botella at 180°C for 540 s.

Effect of frying conditions on moisture, fat, and density of papad

The moisture transfer mechanism by diffusion and uptake of frying oil was studied during deep fat frying of papads with an initial moisture content (IMC) 24.8% dry basis (db). The experimental data were found to fit well to a first order exponential model for moisture transfer (with a regression coefficient 0.99). The apparent moisture diffusivity of papad in the frying time range of 0–20 s at temperatures of 165, 175, 180 and 185 ± 1 °C were 2.83, 3.65, 3.87 and 5.03 × 10 −9 m 2 s −1, from which the activation energy (45 kJ mol −1) was calculated by using Arrhenius type equation. The optimum experimental frying parameters for maximum diametrical expansion (46.4%) were noted to be: oil temperature 185 ± 1 °C, moisture 1.2%db, oil absorption (47.3%db), density 377 kg m −3 for frying time of 20 s.

Efeito de sistemas de preparo e de cultura na dinâmica da matéria orgânica e na mitigação das emissões de CO2

Neste estudo, ajustou-se um modelo exponencial de primeira ordem aos dados de carbono orgânico (CO) e N total (NT) do solo, do 5º e 9º ano de um experimento instalado em um Podzólico Vermelho-Escuro, em Eldorado do Sul (RS). Determinaram-se os parâmetros da dinâmica da matéria orgânica e simularam-se os estoques de CO e NT do solo em três sistemas de preparo (convencional-PC, reduzido-PR e plantio direto-PD) e três sistemas de cultura (aveia/milho-A/M, aveia + ervilhaca/milho-A + E/M e aveia + ervilhaca/milho + caupi A + E/M + C). A taxa de decomposição da matéria orgânica do solo diminuiu de 0,054 ano-1, no sistema com lavração e gradagem (PC), para 0,039 ano-1, no solo escarificado (PR), e 0,029 ano-1, no solo não revolvido (PD). Estimou-se que os estoques de CO e NT do solo em 1990 (30,78 Mg ha-1 e 2.200 kg ha-1) diminuirão para 16,11 Mg ha-1 e 1.396 kg ha-1 na combinação PC - A/M. Por sua vez, no sistema PD - A + E/M + C, os estoques de CO e NT do solo em 1990 (32,52 Mg ha-1 e 2.690 Mg ha-1) tenderão a aumentar a estoques estáveis de 54,83 Mg ha-1 e 7.966 kg ha-1, respectivamente. Os sistemas de manejo sem revolvimento do solo e alto aporte de resíduos apresentaram efeito positivo na mitigação das emissões de CO2. Enquanto o sistema PC-A/M apresentou um efluxo líquido (emitido pelo solo &gt; fixado pelas culturas por fotossíntese) de 2,08 Mg CO2 ha-1 para atmosfera no ano de 1994, o sistema PD - A + E/M + C mostrou um influxo líquido (emitido pelo solo &lt; fixado pelas culturas) de CO2 de 1,79 Mg ha-1 ano-1. Atingidos os estoques estáveis de CO no solo estimados pelo modelo, o solo no sistema PD - A + E/M + C terá seqüestrado aproximadamente 142 Mg CO2 ha-1, em comparação ao sistema PC-A/M.

Breath-by-breath gas exchange kinetics during constant-load work.

In order to study respiratory transients during exercise, we examined breath-by-breath gas exchange kinetics during constant-load work. Five male subjects performed cycle ergometer tests which 6 min of constant-load work (150, 200, 250W) followed 50W base-line work. VCO2 and VO2 measured at the mouth ((VCO2)E, (VO2)E) and estimated at the alveolar level ((VCO2)A, (VO2)A) were computed breath-by-breath. The kinetic parameter (time constant) of first- and second-order exponential model was estimated using non-linear least-squares method. Our results demonstrated that a relative stability of PETO2, PETCO2, and R at their control values in the first phase. Independent of work intensities, breath-by-breath variation in gas exchange measured at the mouth was larger than those in gas exchange estimated at the alveolar level both at a non-steady state and a steady state. The time constants of (VO2)A and (VO2)E were varied with increase of work load intensity.

Respiratory response to sinusoidal work load in humans.

Present study was undertaken to elucidate possible distortion of phase response and amplitude response of various respiratory parameter such as VO2, VCO2 and VE to sinusoidal work load by comparing model analysis with manual analysis. Also, an attempt was made to determine whether there is any relationship between the characteristics of response of these parameters and the aerobic capacity of subjects. Six healthy male subjects were performed exercise on an electrically braked bicycle ergometer for 32 min. The work load was varied sinusoidally between 30 watts and 60% VO2max being under anaerobic threshold with periods from 1 to 16 min. These parameters were determined in breath-by-breath mode with a computer system and mass spectrometer. In model analysis, amplitude and phase responses were well described by first order exponential model, and strong correlations were observed between magnitude of phase response or time constant of amplitude response and aerobic capacity. Manual analysis revealed that respiratory responses to sinusoidal work load are not completely sinusoidal but somewhat distorted forming saw-tooth waves with steeper downslopes.

Predicting Colorado Potato Beetle ( Leptinotarsa decemlineata Say) 1 Density and Potato Yield Loss 2

Third order exponential models are fit to 7 sets of Leptinotarsa decemlineata (Say) larval incidence data. A. predictor algorithm is developed to mimic density-related amplitude and shape changes in incidence curves. Potato Yield is related to area under the predictor curves by a linear equation. Use of the predictor to project the entire incidence curve based on a few early counts is limited by precision of the count data. This can be enhanced by using coefficent of variation and sample mean to determine proper sample size. Limitations of adult manipulation techniques for establishing larval density gradients are also discussed.