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Simple Equation (simple + equation)
Selected AbstractsInitial stiffness of reinforced concrete structural walls with irregular openingsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2010Bing Li Abstract Reinforced concrete (RC) structural walls with openings are the primary lateral-load-carrying elements utilized in many structures designed to resist earthquakes. A review of the technical literature shows that there is a considerable amount of uncertainty with regards to the elastic stiffness of these structures when subjected to seismic excitations. Current design practices often employ a stiffness reduction factor to deal with this uncertainty. In an attempt to develop additional information regarding the stiffness of these structures, this paper discusses an approach to determine the initial stiffness of RC structural walls with irregular openings and low aspect ratios. This approach would consider the effect of both flexural and shear deformations. As a part of this study, an analytical approach to determine stiffness was also developed and validated by comparing theoretical and experimental results obtained from six RC shear walls with irregular openings. Simple equations for assessing initial stiffness of RC structural walls with irregular openings are then proposed, based on these parametric case studies. Copyright © 2009 John Wiley & Sons, Ltd. [source] RHEOLOGICAL BEHAVIOUR OF CLARIFIED MANGO JUICE CONCENTRATESJOURNAL OF TEXTURE STUDIES, Issue 3 2000NGASEPPAM IBOYAIMA SINGH ABSTRACT The rheological behaviour of clarified mango juice was measured at temperatures 15,85C and concentrations 15,66 °Brix, using a rotoviscometer. Mango juice free of pectin and pulp behaves as a Newtonian fluid. The effect of temperature can be described by an Arrhenius-type equation. The activation energy for viscous flow was in the range of 1.64,8.44 kcal/g-mol, depending on the concentration. The effect of concentration was modelled better by an exponential relationship than a power-law relationship. Simple equations are proposed for describing the combined effect of temperature and soluble solids content on the juice viscosity. [source] Examples of fire engineering design for steel members, using a standard curve versus a new parametric curveFIRE AND MATERIALS, Issue 2-4 2004C. R. Barnett Abstract This paper presents examples of the differences that can occur when a standard time-temperature curve and a parametric time-temperature curve are used to determine temperatures likely to be reached by uninsulated and insulated steel members during a fire. For low and moderate structural fire severity situations, determination of the adequacy of a steel member by comparing the temperature reached in a ,design fire' with the limiting temperature based on the member heat sink characteristics, extent of insulation and utilization factor is becoming increasingly common fire engineering design practice. For this it is important to have an accurate and widely applicable parametric fire model as is practicable. The standard time-temperature curve used in the examples is the ISO 834 curve. The two parametric time-temperature curves used in the paper are the Eurocode parametric curve and a recently developed one termed the ,BFD curve'. The latter has been found to fit the results of a wide range of actual fire tests more closely than do existing parametric curves and is mathematically simpler in form. The shape of the BFD curve and the parameters used to define it bear a strong relationship to both the pyrolysis coefficient (R/Avhv0.5) and the opening factor, F02. The curve also models the development of fire without the need for time shifts. It uses a single and relatively simple equation to generate the temperature of both the growth and decay phases of a fire in a building and only three factors are required to derive the curve. These factors are (i) the maximum gas temperature, (ii) the time at which this maximum temperature occurs, and (iii) a shape constant for the curve. If desired, the shape constant can be different on the growth and the decay sides to model a very wide range of natural fire conditions and test results. This paper presents an overview of the background to the BFD curve. It then illustrates its use in a simple fire engineering design application, where the adequacy of a steel beam is checked using the Eurocode parametric curve and the BFD curve to represent the fire. Copyright © 2004 John Wiley & Sons, Ltd. [source] Travel Time to a Well Pumping an Unconfined Aquifer without RechargeGROUND WATER, Issue 4 2006Robert P. Chapuis A solution is given for the travel time to a well pumping an ideal, horizontal unconfined aquifer, under steady-state conditions, when recharge from infiltration is negligible. Three forms of the solution are provided: a closed-form solution, an integral to be calculated in a worksheet, and a simple equation. The three forms of the solution give travel times nearly identical to those obtained using a finite-element code for saturated and unsaturated flow and particle tracking. [source] Predicting river water temperatures using the equilibrium temperature concept with application on Miramichi River catchments (New Brunswick, Canada)HYDROLOGICAL PROCESSES, Issue 11 2005Daniel Caissie Abstract Water temperature influences most of the physical, chemical and biological properties of rivers. It plays an important role in the distribution of fish and the growth rates of many aquatic organisms. Therefore, a better understanding of the thermal regime of rivers is essential for the management of important fisheries resources. This study deals with the modelling of river water temperature using a new and simplified model based on the equilibrium temperature concept. The equilibrium temperature concept is an approach where the net heat flux at the water surface can be expressed by a simple equation with fewer meteorological parameters than required with traditional models. This new water temperature model was applied on two watercourses of different size and thermal characteristics, but within a similar meteorological region, i.e., the Little Southwest Miramichi River and Catamaran Brook (New Brunswick, Canada). A study of the long-term thermal characteristics of these two rivers revealed that the greatest differences in water temperatures occurred during mid-summer peak temperatures. Data from 1992 to 1994 were used for the model calibration, while data from 1995 to 1999 were used for the model validation. Results showed a slightly better agreement between observed and predicted water temperatures for Catamaran Brook during the calibration period, with a root-mean-square error (RMSE) of 1·10 °C (Nash coefficient, NTD = 0·95) compared to 1·45 °C for the Little Southwest Miramichi River (NTD = 0·94). During the validation period, RMSEs were calculated at 1·31 °C for Catamaran Brook and 1·55 °C for the Little Southwest Miramichi River. Poorer model performances were generally observed early in the season (e.g., spring) for both rivers due to the influence of snowmelt conditions, while late summer to autumn modelling performances showed better results. Copyright © 2005 John Wiley & Sons, Ltd. [source] Quantitative relation between shear history and rheological properties of LDPEADVANCES IN POLYMER TECHNOLOGY, Issue 4 2001Masayuki Yamaguchi The role of the applied processing equipment shear history on the rheological properties of low-density polyethylene was studied in detail. It was found that the shear history depresses the melt strength and the oscillatory shear modulus, especially the storage modulus in low frequency region. This phenomenon is not caused by lowering of the molecular weight, which remained the same as the original, for all shear history samples, indicating absence of mechanical/thermal degradation during processing. Furthermore, annealing the melt processed samples enhances both the melt strength and the oscillatory modulus to the values of the original, unsheared sample. Finally we applied shear history in a cone-and-plate rheometer and found that the growth curve of the storage modulus, which can be expressed by a simple equation, is determined by both the duration of the flow and the magnitude of the applied shear stress. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 261,269, 2001 [source] Formation process of three-dimensional arrays from silica spheresAICHE JOURNAL, Issue 5 2003Keiji Ishikawa Elucidating the formation process of 3-D arrays from submicrometer-sized particles is a key to creating an optimal fabrication process of photonic crystals. In this research, the spontaneous sedimentation of silica spheres is imaged by in situ confocal laser scanning microscopy, and the dynamics is studied. When the pH is 7.0 and 10, the rate of the formation process of a hexagonal structure is attributed to the transport of spheres in the early stage of precipitation, and can be reproduced by a simple equation for Langmuir-type adsorption, ignoring the desorption part. In a later stage, however, the rate becomes smaller. In the first layer, even after drying, the nearest two spheres are separated, while maintaining a hexagonal structure. From the results, the formation process of three-dimensional arrays from silica spheres is illustrated. [source] A RAPID METHOD OF QUANTIFYING THE RESOLUTION LIMITS OF HEAT-FLOW ESTIMATES IN BASIN MODELSJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2008A. Beha Deterministic forward models are commonly used to quantify the processes accompanying basin evolution. Here, we describe a workflow for the rapid calibration of palaeo heat-flow behaviour. The method determines the heat-flow history which best matches the observed data, such as vitrinite reflectance, which is used to indicate the thermal maturity of a sedimentary rock. A limiting factor in determining the heat-flow history is the ability of the algorithm used in the software for the maturity calculation to resolve information inherent in the measured data. Thermal maturation is controlled by the temperature gradient in the basin over time and is therefore greatly affected by maximum burial depth. Calibration, i.e. finding the thermal history model which best fits the observed data (e.g. vitrinite reflectance), can be a time-consuming exercise. To shorten this process, a simple pseudo-inverse model is used to convert the complex thermal behaviour obtained from a basin simulator into more simple behaviour, using a relatively simple equation. By comparing the calculated "simple" maturation trend with the observed data points using the suggested workflow, it becomes relatively straightforward to evaluate the range within which a best-fit model will be found. Reverse mapping from the simple model to the complex behaviour results in precise values for the heat-flow which can then be applied to the basin model. The goodness-of-fit between the modelled and observed data can be represented by the Mean Squared Residual (MSR) during the calibration process. This parameter shows the mean squared difference between all measured data and the respective predicted maturities. A minimum MSR value indicates the "best fit". Case studies are presented of two wells in the Horn Graben, Danish North Sea. In both wells calibrating the basin model using a constant heat-flow over time is not justified, and a more complex thermal history must be considered. The pseudo-inverse method was therefore applied iteratively to investigate more complex heat-flow histories. Neither in the observed maturity data nor in the recorded stratigraphy was there evidence for erosion which would have influenced the present-day thermal maturity pattern, and heat-flow and time were therefore the only variables investigated. The aim was to determine the simplest "best-fit" heat-flow history which could be resolved at the maximum resolution given by the measured maturity data. The conclusion was that basin models in which the predicted maturity of sedimentary rocks is calibrated solely against observed vitrinite reflectance data cannot provide information on the timing of anomalies in the heat-flow history. The pseudo inverse method, however, allowed the simplest heat-flow history that best fits the observed data to be found. [source] A convenient method for estimating the quantity of drug eliminated by the routes other than hepatic metabolism and renal excretion and the fraction of drug that reaches the "first pass" after oral administrationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2006Leonid M. Berezhkovskiy Abstract The comparison of routine pharmacokinetic data obtained after intravenous and oral drug administration allows to figure out that some quantity of drug, which reached the systemic circulation, was eliminated from the body by routes other than hepatic metabolism and renal excretion. This quantity is equal or exceeds the certain minimum value, which can be calculated from a simple equation obtained in the article. If the minimum value is equal to zero, then the maximum possible fraction of orally administered drug, that is, absorbed into the gut wall and gets through it unchanged, can be calculated. The examples considered indicate that the quantity of drug eliminated not by liver metabolism or kidney excretion could be quite substantial (exceeds half of the dose that reached the circulation). © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:828,833, 2006 [source] Prediction of human pharmacokinetics , improving microsome-based predictions of hepatic metabolic clearanceJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2007Urban Fagerholm Physiologically based methods generally perform poorly in predicting in-vivo hepatic CL (CLH) from intrinsic clearance (CLint) in microsomes in-vitro and unbound fraction in blood (fu,bl). Various strategies to improve the predictability have been developed, and inclusion of an empirical scaling factor (SF) seems to give the best results. This investigation was undertaken to evaluate this methodology and to find ways to improve it further. The work was based on a diverse data set taken from Ito and Houston (2005). Another objective was to evaluate whether rationalization of CLH predictions can be made by replacing blood/plasma-concentration ratio (Cbl/Cpl) measurements with SFs. There were apparently no or weak correlations between prediction errors and lipophilicity, permeability (compounds with low permeability missing in the data set) and main metabolizing CYP450s. The use of CLint class (high/low) and drug class (acid/base/neutral) SFs (the CD-SF method) gives improved and reasonable predictions: 1.3-fold median error (an accurate prediction has a 1-fold error), 76% within 2-fold-error, and a median absolute rank ordering error of 2 for CLH (n = 29). This approach is better than the method with a single SF. Mean (P < 0.05) and median errors, fraction within certain error ranges, higher percentage with most accurate predictions, and ranking were all better, and 76% of predictions were more accurate with this new method. Results are particularly good for bases, which generally have higher CLH and the potential to be incorrectly selected/rejected as candidate drugs. Reasonable predictions of fu,bl can be made from plasma fu (fu,pl) and empirical blood cell binding SFs (B-SFs; 1 for low fu,pl acids; 0.62 for other substances). Mean and median fu,bl prediction errors are negligible. The use of the CD-SF method with predicted fu,bl (the BCD-SF method) also gives improved and reasonable results (1.4-fold median error; 66% within 2-fold-error; median absolute rank ordering error = 1). This new empirical approach seems sufficiently good for use during the early screening; it gives reasonable estimates of CLH and good ranking, which allows replacement of Cbl/Cpl measurements by a simple equation. [source] Effect of temperature on the chromatographic retention of ionizable compounds.JOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2008Abstract We propose a general simple equation for accurately predicting the retention factors of ionizable compounds upon simultaneous changes in mobile phase pH and column temperature at a given hydroorganic solvent composition. Only four independent experiments provide the input data: retention factors measured in two pH buffered mobile phases at extreme acidic and basic pH values (e. g., at least ± 2 pH units far from the analyte pKa) and at two column temperatures. The equations, derived from the basic thermodynamics of the acid,base equilibria, additionally require the knowledge of the solute pKa and enthalpies of acid,base dissociation of both the solute and the buffer components in the hydroorganic solvent mixture. The performance of the predictive model is corroborated with the comparison between theoretical and experimental retention factors of several weak acids and bases of important pharmacological activity, in mobile phases containing different buffer solutions prepared in 25% w/w ACN in water and at several temperatures. [source] RHEOLOGICAL BEHAVIOR OF POMEGRANATE (PUNICA GRANATUM L.) JUICE AND CONCENTRATEJOURNAL OF TEXTURE STUDIES, Issue 1 2005N ALTAN ABSTRACT The rheological behavior of pomegranate juice (Punica granatum L.), prepared from fresh pomegranates, was studied as a function of solids concentration in the range 17.5,75°Brix at 10,55C, using a controlled stress rheometer. Concentration methods did not influence flow behavior. There were no significant differences (P > 0.05) between viscosity and activation energy values for the pomegranate juices concentrated by different methods. The juices exhibited Newtonian behavior regardless of the concentration method. The effect of temperature was described by an Arrhenius-type equation with an activation energy in the range 5.34,32.2 kJ/mol depending on concentration. An exponential model described better the effect of the soluble solids on the viscosity and Eavalues. A simple equation was proposed for describing the combined effect of temperature and soluble solids content on the juice viscosity. [source] Equivalence of weak Dirichlet's principle, the method of weak solutions and Perron's method towards classical solutions of Dirichlet's problem for harmonic functionsMATHEMATISCHE NACHRICHTEN, Issue 4 2006Christian G. Simader Abstract For boundary data , , W1,2(G ) (where G , ,N is a bounded domain) it is an easy exercise to prove the existence of weak L2 -solutions to the Dirichlet problem ",u = 0 in G, u |,G = , |,G". By means of Weyl's Lemma it is readily seen that there is , , C,(G ), ,, = 0 and , = u a.e. in G . On the contrary it seems to be a complicated task even for this simple equation to prove continuity of , up to the boundary in a suitable domain if , , W1,2(G ) , C0(). The purpose of this paper is to present an elementary proof of that fact in (classical) Dirichlet domains. Here the method of weak solutions (resp. Dirichlet's principle) is equivalent to the classical approaches (Poincaré's "sweeping-out method", Perron's method). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Gas-phase tautomerism in 1-phenylazonaphthalene-4-ol: verification of the responses of individual tautomersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2009Daniela Nedeltcheva Gas-phase tautomerism in 1-phenylazonaphthalene-4-ol (1) was studied by using electron ionization (EI) mass spectrometry on the basis of the fragmentations of the model enol and keto tautomers, where the movable proton is replaced by a methyl group. These fixed tautomers were obtained as an easy separable mixture by simple methylation of the cheap and easily accessible diazene (1). It was found that their EI mass spectral fragmentations are in full congruence with the already published theoretical predictions. The relative energies required for bond cleavage in 1 and its fixed tautomers were estimated by stepwise increasing of the electron energy of the ion source of the mass spectrometer. A simple equation for the approximate estimation of the molar fractions of the individual tautomers was suggested. It was shown that the enol form is dominant in the temperature range of 200,300°C. Copyright © 2009 John Wiley & Sons, Ltd. [source] Estimation of gas hold-up in aerated vesselsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2000Alessandro Paglianti Abstract An attempt to produce a simple equation for gas hold-up in stirred tank reactors has been made. This new semi-empirical equation, based on the mass balance for the gas phase, predicts the observed effem due to the tank and impeller diameters and physical properties reasonably well. It can be used both for tanks working with a single Rushton impeller as well as with multiple Rushton impeller systems. The equation has been validated using both data found in literature and from our experiments. On a tenté de produire une équation simple pour la rétention de gaz dans des réacteurs à réservoir agité. Cette nouvelle équation semi-empirique, reposant sur le bilan massique de la phase gazeuse, prédit raisonnablement bien les effets observés dus aux diamètres et aux propriétés physiques du réservoir et de la turbine. Celle-ci peut çtre utilisée aussi bien pour les réservoirs munis d'une turbine Rushton unique que pour des systèmes munis de plusieurs turbines Rushton. L'équation a été validée à l'aide de données provenant de la littérature scientifique ainsi que de nos expériences. [source] Kinetic Study of the Conversion of Different Substrates to Lactic Acid Using Lactobacillus bulgaricusBIOTECHNOLOGY PROGRESS, Issue 3 2000Concepción N. Burgos-Rubio Lactic acid fermentation includes several reactions in association with the microorganism growth. A kinetic study was performed of the conversion of multiple substrates to lactic acid using Lactobacillusbulgaricus. Batch experiments were performed to study the effect of different substrates (lactose, glucose, and galactose) on the overall bioreaction rate. During the first hours of fermentation, glucose and galactose accumulated in the medium and the rate of hydrolysis of lactose to glucose and galactose was faster than the convesion of these substrates. Once the microorganism built the necessary enzymes for the substrate conversion to lactic acid, the conversion rate was higher for glucose than for galactose. The inoculum preparation was performed in such a way that healthy young cells were obtained. By using this inoculum, shorter fermentation times with very little lag phase were observed. The consumption patterns of the different substrates converted to lactic acid were studied to determine which substrate controls the overall reaction for lactic acid production. A mathematical model (unstructured Monod type) was developed to describe microorganism growth and lactic acid production. A good fit with a simple equation was obtained. It was found experimentally that the approximate ratio of cell to substrate was 1 to 10, the growth yield coefficient (YXS) was 0.10 g cell/g substrate, the product yield (YPS) was 0.90 g lactic acid/g substrate, and the , parameter in the Luedeking-Piret equation was 9. The Monod kinetic parameters were obtained. The saturation constant (KS) was 3.36 g/L, and the specific growth rate (,m ) was 1.14 l/h. [source] ORIGINAL ARTICLE: Probability of emergence of antimalarial resistance in different stages of the parasite life cycleEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 1 2009Wirichada Pongtavornpinyo Abstract Understanding the evolution of drug resistance in malaria is a central area of study at the intersection of evolution and medicine. Antimalarial drug resistance is a major threat to malaria control and directly related to trends in malaria attributable mortality. Artemisinin combination therapies (ACT) are now recommended worldwide as first line treatment for uncomplicated malaria, and losing them to resistance would be a disaster for malaria control. Understanding the emergence and spread of antimalarial drug resistance in the context of different scenarios of antimalarial drug use is essential for the development of strategies protecting ACTs. In this study, we review the basic mechanisms of resistance emergence and describe several simple equations that can be used to estimate the probabilities of de novo resistance mutations at three stages of the parasite life cycle: sporozoite, hepatic merozoite and asexual blood stages; we discuss the factors that affect parasite survival in a single host in the context of different levels of antimalarial drug use, immunity and parasitaemia. We show that in the absence of drug effects, and despite very different parasite numbers, the probability of resistance emerging at each stage is very low and similar in all stages (for example per-infection probability of 10,10,10,9 if the per-parasite chance of mutation is 10,10 per asexual division). However, under the selective pressure provided by antimalarial treatment and particularly in the presence of hyperparasitaemia, the probability of resistance emerging in the blood stage of the parasite can be approximately five orders of magnitude higher than in the absence of drugs. Detailed models built upon these basic methods should allow us to assess the relative probabilities of resistance emergence in the different phases of the parasite life cycle. [source] Can the Earth's dynamo run on heat alone?GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2003David Gubbins SUMMARY The power required to drive the geodynamo places significant constraints on the heat passing across the core,mantle boundary and the Earth's thermal history. Calculations to date have been limited by inaccuracies in the properties of liquid iron mixtures at core pressures and temperatures. Here we re-examine the problem of core energetics in the light of new first-principles calculations for the properties of liquid iron. There is disagreement on the fate of gravitational energy released by contraction on cooling. We show that only a small fraction of this energy, that associated with heating resulting from changes in pressure, is available to drive convection and the dynamo. This leaves two very simple equations in the cooling rate and radioactive heating, one yielding the heat flux out of the core and the other the entropy gain of electrical and thermal dissipation, the two main dissipative processes. This paper is restricted to thermal convection in a pure iron core; compositional convection in a liquid iron mixture is considered in a companion paper. We show that heat sources alone are unlikely to be adequate to power the geodynamo because they require a rapid secular cooling rate, which implies a very young inner core, or a combination of cooling and substantial radioactive heating, which requires a very large heat flux across the core,mantle boundary. A simple calculation with no inner core shows even higher heat fluxes are required in the absence of latent heat before the inner core formed. [source] Does corneal polarisation vary with corneal astigmatism?OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2002A. Mamoojee Purpose:, To assess the correlation between the axis of corneal astigmatism and/or corneal thickness with that of corneal birefringence in a small group of observers using a subjective polarimeter and a corneal topographer. Methods:, The corneal polarisation axis and corneal astigmatism directions were measured in 11 subjects, providing data for 22 eyes. One kerataconic subject was included in the sample. The study utilised subjective ellipsometry using an instrument engineered at Imperial College, London to determine the corneal polarisation axis. An Orbscan (Bausch & Lomb, Rochester, NY, USA) corneal topographer was used to measure corneal astigmatism and corneal thickness. Results:, It was found that the angle of corneal polarisation axis and the steepest direction of corneal astigmatism were correlated. The correlation coefficient for the RE was ,0.49, whilst that for LE was 0.43. A similar relationship was found for the flat axis of the cornea. Conclusions:, There was a fair correlation between the corneal polarisation direction and both the flat and steep axis of corneal astigmatism. It was also found, in agreement with other studies, that corneal polarisation axis in either eye was symmetrical about the nose, as was corneal astigmatism. The kerataconic cornea followed the trend observed, although nothing conclusive can be stated. A relationship between the corneal polarisation axis and corneal thickness was not established. Analysis of the data provided us with simple equations, which could help to predict a polarisation axis for a known direction of corneal astigmatism. [source] On the 13C/12C isotopic signal of day and night respiration at the mesocosm levelPLANT CELL & ENVIRONMENT, Issue 6 2010GUILLAUME TCHERKEZ ABSTRACT While there is currently intense effort to examine the 13C signal of CO2 evolved in the dark, less is known on the isotope composition of day-respired CO2. This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure ci/ca effect) from respiratory effect (production of CO2 with a different ,13C value from that of net-fixed CO2) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO2]. We show that whole mesocosm-respired CO2 is slightly 13C depleted in the light at the mesocosm level (by 0.2,0.8,), while it is slightly 13C enriched in darkness (by 1.5,3.2,). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the 13C abundance in day- and night-evolved CO2. We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO2 production may change, thereby explaining the different 12C/13C respiratory fractionations in the light and in the dark. [source] | |||||||||||||||||||||||||