Closed System Method Research Articles

Predicting the Respiration Rate of Papaya (<i>Carica papaya </i>L.) Using Different Models

The modellings of the respiration rate of papaya by using enzyme kinetics, chemical kinetics and artificial neural network (ANN) were developed respectively, and all the models were parameterized with experimental data obtained at temperatures of 8, 18 and 28 °C by the closed system method for comparison. The ANN model was thought to be the best after being evaluated by the mean absolute percentage error (MAPE) and the two-tailed Pearson correlation coefficientr. The study demonstrated that the ANN model and the chemical kinetic model can be applied to the prediction of papaya’s respiration rate.

Comparative analysis and geological significance of kerogen isolated using open-system (palynological) versus chemically and volumetrically conservative closed-system methods

Characterization of kerogen, the insoluble organic fraction of sedimentary rocks, is of key importance in investigations of the geochemistry of ancient depositional systems, paleo climates, basin thermal history, and petroleum generation systematics. Furthermore, exploitation of organic-rich oil shales as unconventional petroleum resources requires understanding of the physical chemistry of the kerogen conversion reactions and the coking behavior. These issues can be effectively addressed only if pure, representative kerogen is obtained from the rock matrix using chemically and volumetrically conservative methods that preclude losses, alteration, or fractionation of the organic matter. Isolation of representative and pure kerogen concentrates from the rock matrix is difficult. Many methods have been used over the years with various degrees of success. Most are based on traditional palynological processing approaches in open systems that commonly yield fractionated products, generally contaminated with pyrite and insoluble neo-fluorides. A few are based on complex sealed-system procedures that purport to conserve the entire kerogen with no fractionation, no alteration and no contamination. This study focuses on a comparative analysis of kerogens isolated with the conventional open-system approach (HCl/HF/heavy liquid separation) and kerogens concentrated with a fully automated, conservative, closed-system method (HCl/HF/CrCl 2) under an inert N 2 atmosphere. Source-rock samples of various richness, kerogen types, ages, depositional environments, lithologies and thermal histories were selected for kerogen isolation using the two approaches. Kerogen recovery efficiency, progress of the processes and quality of the isolated kerogens were monitored via mass balance calculations, organic elemental analysis and X-ray diffraction analysis. The inherent inadequacy in the open-system approach for geochemical research and the improved features of the chemically and volumetrically conservative method are documented.

MODELING OF RESPIRATION RATE OF SAPOTA FRUIT UNDER AEROBIC CONDITIONS

ABSTRACT Accurate measurement of respiration rate is an important aspect to the success of design and operational features of techniques like controlled and modified atmosphere storage. Two different models based on regression analysis and enzyme kinetics were developed with the help of respiration data generated at temperatures of 0, 5, 10, 15, 20, 25 and 30C for sapota fruit using a closed system method. Temperature was found to influence the model parameters. In the model based on enzyme kinetics, the dependence of respiration rate on O2 and CO2 was found to follow the uncompetitive inhibition. The developed models were tested for its validity at 12C. The models showed good agreement with the experimentally estimated respiration rate, although the model based on enzymatic kinetic with Arrhenius‐type temperature dependence was found to have a closer agreement than the other model studied. The levels of agreement between the respiration rates of sapota at 12C predicted by regression analysis and that obtained through experiments were 18.44 and 22.18% for O2 consumption and CO2 evolution, respectively, while those for the model based on enzyme kinetics were found to be 16.79 and 12.12%.PRACTICAL APPLICATIONSManipulation of respiration rate is the underlying principle behind storage techniques like controlled atmosphere (CA) storage and modified atmosphere packaging (MAP). However, besides being specific to horticultural parameters, respiration rate is also dependent on factors like storage temperature and composition of storage atmosphere. Hence, a mathematical approach to predict the respiration rate under given conditions would be an immense help in both design and process control of such storage systems. For example, predictive models for respiration rate would aid in the selection of packaging material of appropriate permeability for MAP. Also, it would help in protocols for the control of gas compositions in CA systems. In this study, mathematical models have been developed and tested to predict the respiration rate of sapota (cv. Calcutta).

Modelling the respiration rate of guava (Psidium guajava L.) fruit using enzyme kinetics, chemical kinetics and artificial neural network

The respiration rate prediction of fresh produce is crucial for designing and operating postharvest storage systems. This paper constructs and evaluates respiration models of guava fruit by using not only the enzyme, chemical kinetics but also artificial neural network (ANN) with the experimental data obtained from 5, 10, 15, 20, 25 and 30 °C (for constructing) as well as 12 and 22 °C (for evaluating) by closed system method. All of the developed models showed good agreement with actual observations. As regards fidelity the ANN model with topologic structure of 3 × 9×1 trained by the Levenberg–Marquardt algorithm, evaluation results were such that the mean absolute percentage error (MAPE) and the two-tailed Pearson correlation coefficient (r) were 5.31 and 0.997 for 12 °C, 4.85 and 0.995 for 22 °C, had superiority over the two other models. The results indicate that the ANN approach is a more precise method, and can be used for predicting the respiration rate of guava fruit.

Modeling of Respiration Rate of Litchi Fruit under Aerobic Conditions

Respiration of the produce and permeation of gas through the packaging films are the processes involved in creating a modified atmosphere inside a package that will extend shelf life of agricultural perishables. Thus modeling respiration rate of the selected produce is crucial to the design of a successful modified atmosphere packaging system. Two different models based on regression analysis and enzyme kinetics were developed with the help of respiration data generated at temperatures 0, 5, 10, 15, 20, 25, and 30 °C for litchi fruit using the closed system method. Temperature was found to influence the model parameters. In the model, based on enzyme kinetics, the dependence of respiration rate on O2 and CO2 was found to follow the uncompetitive inhibition. The enzyme kinetic model parameters, calculated from the respiration rate at different O2 and CO2 concentration were used to fit the Arrhenius equation against different storage temperature. The regression coefficients values were used for the prediction of respiration rate using regression model. The activation energy and respiration pre-exponential factor were used to predict the model parameters of enzyme kinetics at any storage temperature. The developed models were tested for its validity at 2 °C. The models showed good agreement with the experimentally estimated respiration rate.

Modelling the respiration rate of green mature mango under aerobic conditions

Accurate measurement of respiration rate is an important aspect in designing and operating systems such as controlled and modified atmosphere storage. Models based on regression analysis and enzyme kinetics were developed with the help of respiration data generated at temperatures 5, 10, 15, 20, 25 and 30 °C for green mature mango fruit using the closed system method. A model based on second-order polynomial regression, simultaneously incorporating the factors influencing respiration, such as temperature, O2 consumption, CO2 evolution and storage time, was proposed. All the developed models were tested for their validity at 12 °C. All showed good agreement with the experimentally estimated respiration rate, although models based on enzymatic kinetic with Arrhenius-type temperature dependence and three-parameter second-order polynomial regression were found to have a closer agreement than the other models studied.

Respiration rate of banana fruit under aerobic conditions at different storage temperatures

The underlying principle behind storage techniques like controlled atmosphere storage and modified atmosphere packaging involves manipulation of respiration rate of the stored produce. However, since respiration rate is dependent on factors like storage temperature and composition of storage atmosphere, a mathematical approach to predict the respiration rate under given conditions would be an immense help in both design and process control of such storage systems. Experimental data were generated at temperatures 10, 15, 20, 25 and 30 °C for banana fruit using the closed system method. The generated data were used to develop two different models based on regression analysis and enzyme kinetics, respectively. Both models were tested for its validity at 12 °C. The models showed good agreement with the experimentally estimated respiration rate, though the model based on enzymatic kinetic with Arrhenius type temperature dependence was found to have a closer agreement than the other model studied.

Formation mechanism of defect metal hydrides containing superabundant vacancies

The formation of defect hydrides containing a large number of M-atomvacancies (superabundant vacancies; SAVs) was studied in bccNbHx and in thefcc phase of FeHx, CoHx, NiHx and PdHx, by resistivity and XRD measurements under different conditions of hydrogen pressure andtemperature, with/without allowing for exchange of hydrogen with environment(open-/closed-system methods). Two distinctly different behaviors were observed: in metalswith small formation energy of Vac–H clusters, both H and vacancies enter abundantly intothe M-lattice to form the ultimate defect-ordered structure, whereas in metalswith relatively large formation energies, vacancy concentrations remain relativelysmall. This general trend was examined by Monte Carlo simulations based on alattice–gas model. The result showed the occurrence of two distinct phases in thevacancy distribution caused by the combined action of the long-range elasticinteraction and local Vac–H interactions, in accordance with the observation.Conditions for the occurrence of these ‘vacancy-rich’ and ‘vacancy-poor’ states areexamined.

Temperature- and body mass-related variation in cyclic gas exchange characteristics and metabolic rate of seven weevil species: Broader implications

The influence of temperature on metabolic rate and characteristics of the gas exchange patterns of flightless, sub-Antarctic Ectemnorhinus-group species from Heard and Marion islands was investigated. All of the species showed cyclic gas exchange with no Flutter period, indicating that these species are not characterized by discontinuous gas exchange cycles. Metabolic rate estimates were substantially lower in this study than in a previous one of a subset of the species, demonstrating that open-system respirometry methods provide more representative estimates of standard metabolic rate than do many closed-system methods. We recommend that the latter, and especially constant-pressure methods, either be abandoned for estimates of standard metabolic rate in insects, or have their outputs subject to careful scrutiny, given the wide availability of the former. V˙CO 2 increase with an increase in temperature (range: 0–15 °C) was modulated by an increase in cycle frequency, but typically not by an increase in burst volume. Previous investigations of temperature-related changes in cyclic gas exchange (both cyclic and discontinuous) in several other insect species were therefore substantiated. Interspecific mass-scaling of metabolic rate (ca. 0.466–0.573, excluding and including phylogenetic non-independence, respectively) produced an exponent lower than 0.75 (but not distinguishable from it or from 0.67). The increase of metabolic rate with mass was modulated by an increase in burst volume and not by a change in cycle frequency, in keeping with investigations of species showing discontinuous gas exchange. These findings are discussed in the context of the emerging macrophysiological metabolic theory of ecology.

The Anaerobic Compensation Point for Fresh-cut Watermelon and Implications for Postprocess Handling

The influence of temperature and O2 concentration on respiration and shelf life of fresh-cut watermelon was investigated. Product stored at selected temperatures from 1 to 30 °C showed increasing respiration and reduced shelf life with increasing temperature. Oxygen depletion and CO2 evolution were measured using a closed system method and rates of O2 consumption and CO2 production were computed. A mathematical model found to predict the CO2 production as function of temperature and O2 showed an elevated rate of CO2 production at about 14% O2 or lower. A modified atmosphere trial that compared product stored at 7 to 9 °C in air with product at either 14% or 8% O2 revealed increased respiration in the latter treatments, suggesting a relatively high anaerobic compensation point (ACP) at >14% O2. Our results suggest limited applicability of modified atmosphere packaging (MAP) for this product. Fresh-cut watermelon had extended shelf life and reduced respiration rate when stored at 1 to 3 °C and in >14% O2 atmospheres.

Determination of Cr in certified reference material HISS-1, marine sediment, by cold plasma isotope dilution ICP-MS and INAA: comparison of microwave versus closed (Carius) tube digestion

The recovery of Cr from National Research Council Canada (NRCC) certified reference material HISS-1 sediment was investigated by non-destructive instrumental neutron activation analysis (INAA) and isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) after two different chemical treatments: (1) microwave dissolution using HNO3, HF, and HClO4, followed by reflux with concentrated HClO4, and (2) a closed system method using sealed Carius tube digestion with HNO3 and HCl at high temperature (240 °C) and high pressure (1 × 107 Pa, ∼100 atm). The first chemical treatment gave recoveries of only ∼50% in agreement with observations of Yang et al. of NRCC. Samples digested in Carius tubes gave recoveries that ranged from 79 to 110% which may reflect heterogeneity in the samples rather than differing recoveries. This is supported by the excellent agreement of the mean value determined by INAA of 31.4 ± 4.5 µg g−1, and the mean value of 28.1 ± 3.9 µg g−1 by Carius tube digestion and the observation that these standard deviations are essentially equal and much larger than the measurement precisions. The results from this study are also in excellent agreement with the certified value of 30.0 ± 6.8 µg g−1. This preliminary study demonstrates that chemical treatment of this sediment with HNO3 and HCl acids in closed system Carius tubes is an efficient and capable preparation method for the determination of Cr in silicate materials which typically contain refractory Cr-bearing minerals. This study also demonstrates the unique advantage of using two independent methods for the determination of Cr in a complex matrix which has a high potential for low chemical recovery.

PH—Postharvest Technology: Enzyme Kinetics Based Modelling of Respiration Rate for Apple

A respiration rate model, based on enzyme kinetics and the Arrhenius equation, was proposed for predicting respiration rates of fresh apple as a function of O2and CO2concentration and storage temperature. Several experiments were conducted at different storage temperatures for generating respiration data by using a closed system method of respiration measurement. In this model, the dependence of respiration rate on O2and CO2was found to follow the uncompetitive inhibition. The enzyme kinetic model parameters, calculated from the respiration rate at different O2and CO2concentrations, were used to fit the Arrhenius equation against different storage temperatures. The activation energy and respiration pre-exponential factor could be used to predict the model parameters of enzyme kinetics at any storage temperature between 0 and 30°C. Respiration rates of apple predicted by the proposed model were found in good agreement with those obtained experimentally.

Respiration Rate of Sweet Cherries: ‘Burlat’, ‘Sunburst’ and ‘Sweetheart’ Cultivars

ABSTRACT: Oxygen depletion and CO2 formation were measured using a closed system method at various temperatures. No CO2 inhibition effect was observed. Respiration rates were related to O2 concentration by a simple Michaelis‐Menten equation. Lineweaver‐Burk plots of respiratory rate versus O2 concentration were nonlinear over the whole O2 concentration range explored. However, this type of analysis allowed us to differentiate two O2 concentration intervals (above and below 10%) in which the double reciprocal plots are linear. Respiration rates decreased with decreasing temperature following the Arrhenius law. The Michaelis‐Menten equation constants Vm and Km for the 3 cultivars at 2, 5, and 20°C are tabulated.

Respiration Rates of Live Clams (Mercenaria mercenaria; Hard Clams) in Modified Atmospheres at Various Temperatures

ABSTRACT Respiration rates of live clams were measured as a function of O2 and CO2 at 5, 15 and 25°C using the closed system method. The respiration rates were found to increase with increasing CO2 and decreasing 02-this respiratory behavior was opposite to that of fresh produce. The respiration rates followed the Arrhenius relationship, with activation energies ranging from 35.6 to 41.0 kj/ mole, which were little affected by O2 and CO2 and were lower than those of some fruits. The respiratory quotients were between 1.4 to 1.9. Some practical implications of the findings on modified atmosphere storage and packaging of live clams as well as further research needs are discussed.

Modified atmosphere packaging for green chili peppers

Modified atmosphere packages were designed and used for the packaging of green chili peppers. Respiration of green peppers at 10°C was characterized by the closed-system method as a function of O2 and CO2 concentrations, and was incorporated into mass balance equations of O2 and CO2 gases in order to predict the gas composition inside the package over time. From the prediction of atmospheres inside packages constructed of the available plastic films, three retail packages (110-g peppers) were designed and studied experimentally for their ability to modify the package atmosphere and to retain quality (moisture, ascorbic acid and chlorophyll). Pepper packages using 25 μm low-density polyethylene and 30 μm cast polypropylene could attain modified atmosphere close to the optimal gas concentrations (3% O2 and 5% CO2), and therefore provided better quality retention compared with unpackaged controls.

Respiration Rate of Blueberry in Modified Atmosphere at Various Temperatures

Respiration rates of three blueberry (Vaccinium corymbosum L.) cultivars (Coville, Blueray, and Jersey) were measured as a function of O2, CO2, and temperature using the closed system method. The data conformed well to a recently proposed Michaelis-Menten type respiration (r) model (r = Vm [O2]/{Km + (1 + [CO2]/Ki)[O2]}), where Vm was maximum respiration rate, Km was Michaelis-Menten constant, and Ki was inhibition constant. The model predictions were used to examine the behavior of respiration rates. In general, the respiration rates decreased with increasing CO2, but were little affected by changes in O2. `Coville' blueberries had the highest respiration rate, followed by `Blueray' and `Jersey'. The temperature dependence of the respiration rates followed the Arrhenius relationship.

Closed-System Analysis of Tritium in Palladium

A closed-system procedure for the analysis of tritium in palladium has been developed that has a sensitivity and accuracy of 5 × 107 tritium atoms, corresponding to one tritium atom per 1013 palladium atoms for a typical 0.1-g palladium sample. The technique involves palladium dissolution in acid, distillation of the tritiated water, and catalytic oxidation of tritium gas to tritiated water, followed by liquid scintillation counting. This technique is not subject to false tritium findings from a variety of chemical factors or environmental influences that may affect the results of open-system analytical procedures. The closed-system procedure has been applied to nearly 100 as-manufactured palladium wire samples of various lots and sizes from two different sources. None of these samples show any tritium contamination within the detection limit of 5 × 107 tritium atoms. By comparison, others, employing an open-system procedure, have reported tritium contamination in as-manufactured palladium 10000 times larger than the values obtained by this closed system method.

APPLICATION of an ENZYME KINETICS BASED RESPIRATION MODEL to CLOSED SYSTEM EXPERIMENTS FOR FRESH PRODUCE

ABSTRACTAn approach was developed to use a respiration model, based on enzyme kinetics principle, along with the closed system method for generating respiration rates of fresh produce as a function of O2 and CO2 concentrations. to verify this approach, experiments were conducted to measure the respiration rates of cut broccoli contained in closed jars at 0, 7, 13 and 24C. the respiration model was found to fit the experimental data very well, and the model parameters were estimated using multiple linear regression analysis. Another experiment was also conducted with a permeable package containing cut broccoli at 13C, and the experimental respiration rates were found to compare well with those predicted using the model parameter values estimated above.

Carcinogenicity tests with rainbow trout embryos: a review

Methods of exposure and results of laboratory carcinogenicity tests using rainbow trout are reviewed. Although the rainbow trout has had significant use as a model of aflatoxin-induced liver cancer, the species has not yet been widely used as a bioassay species for carcinogen testing. The observation that rainbow trout embryos were susceptible to carcinogen exposure by immersion in aqueous solutions of test agents was discovered in research with aflatoxin. The aqueous exposure method had numerous advantages, but did not work well with some chemicals. Subsequently, closed system methods of micro-injection into the perivitelline space and the yolk-sac have also been developed which can be used to obviate the limited permeability of the chorion to some chemicals. An additional method of exposure involves topical application of a dimethylsulfoxide containing carcinogen solution onto the egg surface. Results to date suggest that carcinogen tests using rainbow trout embryos will detect most direct-acting alkylating agents such as dimethylnitrosamine, N-methyl-N′-nitro-N-nitrosoguanidine, methylnitrosourea, etc. and some agents requiring metabolic activation, such as aflatoxin B 1 and benzo( a)pyrene, but the range of the rainbow trout embryo assay to a broad range of chemicals has not been fully studied. Limited data from one laboratory suggest that rainbow trout may lack the ability to activate aromatic amines such as 2-acetamidofluorine, 2-naphthylamine, and 4-aminobiphenyl to carcinogenic metabolites. Methods of exposure useful for carcinogenicity testing may also be applicable to teratology and ecotoxicology.

Lipid metabolism, cerebral metabolic rate, and some related enzyme activities after brain infarction in rats.

Multiple infarcts were produced in cerebral hemispheres of rats by injecting calibrated 50-micron microspheres into the left internal carotid artery, and alterations in lipid and energy metabolism were evaluated 24 hours later in the embolized hemisphere. Total phospholipid content was decreased by 26%, but the different classes of phospholipids were not equally affected. Phosphatidylinositol and phosphatidylserine levels were decreased by about 40% and phosphatidylcholine and phosphatidylethanolamine by 25%, while sphingomyelin level remained unchanged. There was a 3.2-fold increase in total free fatty acid content with a relatively larger rise in polyunsaturated free fatty acids 20:4 and 22:6 (20-fold increase). Determination of enzyme activities showed decreases in Na+,K+-ATPase (-21%) and hexokinase (-14%) but no changes in phosphofructokinase and pyruvate kinase. Study of energy metabolism using the closed system method of Lowry et al showed a significant depression (-36%) of the cerebral metabolic rate. Taken together, these data suggest a relation between lipid alterations and dysfunction of energy metabolism. Phospholipid degradation with subsequent free fatty acid release and alteration in membrane-bound enzymes may have a direct effect on metabolic machinery and may slow cerebral metabolic rate.