Mathematical and statistical methods, Research methods, Plant structure, PLANT PRODUCTS, MECHANICAL PROPERTIES, ELASTICITY, STRENGTH, MEASUREMENT, MEASURING INSTRUMENTS, METHODS, MATHEMATICAL MODELS, MATHEMATICS, STATISTICAL METHODS, PRODUIT VEGETAL, PROPRIETE MECANIQUE, ELASTICITE, RESISTANCE MECANIQUE, MESURE, INSTRUMENT DE MESURE, METHODE, MODELE MATHEMATIQUE, MATHEMATIQUE, METHODE STATISTIQUE, PRODUCTOS DE ORIGEN VEGETAL, PROPIEDADES MECANICAS, ELASTICIDAD, RESISTENCIA MECANICA, MEDICION, INSTRUMENTOS DE MEDICION, METODOS, MODELOS MATEMATICOS, MATEMATICAS, and METODOS ESTADISTICOS

Summaries (En, Pl)
1 fig., 1 table; 5 ref.
Plant materials of high moisture content and viscoelastic behaviour may be described by generalized Maxwell model. Using this model and making relaxation test consisted in axial squeezing of cylindrical samples at determined speed and deformation extent, the viscoelastic qualities of plant material may be determined. An experimental stand was developed and equipped with force sensor and software for gathering and analysis of measurement data. Actual sample deformation was used for calculation that in the experiment was smaller by the bend of force sensor and constituted a systematic measurement error. Instantaneous sensor bend was determined from force applied and linear sensor characteristics. As a result of numerical computations corrected models' parameters were obtained at 2% systematic error

Soil chemistry and physics, Mathematical and statistical methods, INFILTRATION, SIMULATION MODELS, MATHEMATICAL MODELS, EVALUATION, MEASUREMENT, STATISTICAL METHODS, MATHEMATICS, CLAY SOILS, LOAM SOILS, SANDY SOILS, MODELE DE SIMULATION, MODELE MATHEMATIQUE, MESURE, METHODE STATISTIQUE, MATHEMATIQUE, SOL ARGILEUX, SOL SABLOLIMONEUX, SOL SABLEUX, INFILTRACION, MODELOS DE SIMULACION, MODELOS MATEMATICOS, EVALUACION, MEDICION, METODOS ESTADISTICOS, MATEMATICAS, SUELO ARCILLOSO, SUELO FRANCO, SUELO ARENOSO, ERRORS, and MONTE CARLO METHOD

references
Water infiltration is a driving force influencing crop growth, soil erosion, and chemical leaching processes. Knowledge of the relative precision and accuracy of infiltration models is needed for best characterization of the infiltration parameters. The two-parameter Green-Ampt and Philip, three-parameter Horton, Mezencev, Swartzendruber, and Parlange et al., and four-parameter Barry et al. infiltration models were compared for their precision and accuracy of estimated parameter confidence intervals using simulated infiltration reference data. To account for potential levels of uncertainty, three levels of measurement error were included using a Monte Carlo analysis. Reference data were generated for a clay and a sandy loam soil using an adaptive-grid finite-element code. Results show that extending the measurement period provided parameter estimates with higher confidence, a more precise estimate of that confidence, and better defined minima in the objective function. The empirical Horton model resulted in the worst fits due to model bias, which also prevented estimation of parameter uncertainty for this model. The semianalytical Swartzendruber and the physically based Parlange et al. and Barry et al. models provided the best fits. Considering all selected criteria, the Swartzendruber model was a reasonable compromise under the conditions imposed in this study

Forestry production, Mathematical and statistical methods, Cropping patterns and systems, FOREST TREES, MATHEMATICAL MODELS, STATISTICAL METHODS, MULTIPURPOSE TREES, EUCALYPTUS SALIGNA, VOLUME, MEASUREMENT, MATHEMATICS, CAMEROON, ARBRE FORESTIER, MODELE MATHEMATIQUE, METHODE STATISTIQUE, ARBRE A BUTS MULTIPLES, MESURE, MATHEMATIQUE, CAMEROUN, ARBOLES FORESTALES, MODELOS MATEMATICOS, METODOS ESTADISTICOS, ARBOLES DE PROPOSITO MULTIPLE, VOLUMEN, MEDICION, MATEMATICAS, CAMERUN, VALIDATION, and EQUATIONS

29 ref.

Mathematical and statistical methods, Agricultural machinery and equipment, PLANT PROTECTION, AIRCRAFT, SPRAYERS, NOZZLES, LOW VOLUME SPRAYING, AERIAL APPLICATION, SPRAY DRIFT, MATHEMATICAL MODELS, FLUID FLOW, RHEOLOGICAL PROPERTIES, FLUID MECHANICS, DISPERSIONS, DIMENSIONS, MEASUREMENT, MATHEMATICS, PROTECTION DES PLANTES, AERONEF, PULVERISATEUR, BUSE, PULVERISATION A BAS VOLUME, EPANDAGE AERIEN, DERIVE DES PRODUITS PULVERISES, MODELE MATHEMATIQUE, ECOULEMENT DE FLUIDE, PROPRIETE RHEOLOGIQUE, MECANIQUE DES FLUIDES, ETAT DISPERSE, DIMENSION, MESURE, MATHEMATIQUE, PROTECCION DE LAS PLANTAS, AERONAVES, PULVERIZADORES, TOBERAS, PULVERIZACION A DOSIS REDUCIDA, APLICACION AEREA, DERIVA DE PULVERIZACION, MODELOS MATEMATICOS, FLUJO, PROPIEDADES REOLOGICAS, MECANICA DE FLUIDOS, DISPERSION, MEDICION, and MATEMATICAS

Summary (En)
3 fig., 1 table; 13 ref.
An analysis was presented in order to bring closer obtained results based on a "free model" of theoretical off-target drift function of airborne spraying to experimental data obtained with the use of an agricultural flight An-2R and helicopter Mi-2R. The correlation coefficients were obtained, being the function of droplets diameter, that included in the mass distribution equations allowed to form semi-empirical equation closer to real distribution

Agricultural machinery and equipment, Mathematical and statistical methods, RAPESEED, HUSKING, EQUIPMENT, EQUIPMENT PARTS, PROCESS CONTROL, MECHANICAL PROPERTIES, MOVEMENT, VELOCITY, MEASUREMENT, MATHEMATICAL MODELS, SIMULATION, MATHEMATICS, GRAINE DE COLZA, MONDAGE, MATERIEL, ELEMENT DE MATERIEL, CONTROLE DE FABRICATION, PROPRIETE MECANIQUE, MOUVEMENT, VITESSE, MESURE, MODELE MATHEMATIQUE, MATHEMATIQUE, SEMILLA DE COLZA, MONDADO, EQUIPO, ELEMENTOS DE MAQUINARIA, CONTROL DE FABRICACION, PROPIEDADES MECANICAS, MOVIMIENTO, VELOCIDAD, MEDICION, MODELOS MATEMATICOS, SIMULACION, and MATEMATICAS

Summary (En)
9 fig.; 7 ref.
Distributions of the velocities of rape seed impacts towards working elements of a disc huller during hulling process, were analysed. Mathematical relationships for the velocities and angles of seed rebound from rotor blades, grooves of top cover and the surfaces between blades and grooves, were derived. The analysis made possible to select the inclination angles of working surfaces in rotor blades and top cover grooves optimizing the impact velocities and numbers of seed rebounds from the working components and thus to improve the effectiveness of disc huller operation

Mathematical and statistical methods, Food processing and preservation, MATHEMATICAL MODELS, MATHEMATICS, COMPUTER APPLICATIONS, ONIONS, CUTTING, HOT AIR DRYING, CONVECTION, THERMAL PROPERTIES, SPECIFIC HEAT, MOISTURE CONTENT, TEMPERATURE, DURATION, MEASUREMENT, EXPERIMENTATION, MODELE MATHEMATIQUE, MATHEMATIQUE, APPLICATION DES ORDINATEURS, OIGNON, DECOUPAGE, SECHAGE PAR AIR CHAUD, PROPRIETE THERMIQUE, CHALEUR SPECIFIQUE, TENEUR EN EAU, DUREE, MESURE, MODELOS MATEMATICOS, MATEMATICAS, APLICACIONES DEL ORDENADOR, CEBOLLA, CORTE, SECADO POR AIRE CALIENTE, CONVECCION, PROPIEDADES TERMICAS, CALOR ESPECIFICO, CONTENIDO DE HUMEDAD, TEMPERATURA, DURACION, MEDICION, and EXPERIMENTACION

Summary (En)
2 fig., 1 table; 4 ref.
At convection drying of vegetables the temperature of dried material changes from wet thermometer value to the temperature of drying agent. Assuming that this period is dominated by internal mass exchange and considering temperature variations in dried object, enabled the elaboration of a new model of moisture content changes in dried material. The model relates moisture content to time, temperature and other parameters of the process. Logical and empirical verification, including measurements of drying kinetics of the onion slices, confirmed the correctness of model computations in studied phase of onion drying

Mathematical and statistical methods, Food processing and preservation, MATHEMATICAL MODELS, COMPUTER APPLICATIONS, PUMPKINS, MOISTURE CONTENT, CUTTING, DRYING, CONVECTION, METHODS, EVALUATION, LABORATORY EXPERIMENTATION, MEASUREMENT, MATHEMATICS, MODELE MATHEMATIQUE, APPLICATION DES ORDINATEURS, CITROUILLE, TENEUR EN EAU, DECOUPAGE, SECHAGE, METHODE, EXPERIMENTATION EN LABORATOIRE, MESURE, MATHEMATIQUE, MODELOS MATEMATICOS, APLICACIONES DEL ORDENADOR, CALABAZA (CUCURBITA), CONTENIDO DE HUMEDAD, CORTE, SECADO, CONVECCION, METODOS, EVALUACION, EXPERIMENTACION EN LABORATORIO, MEDICION, and MATEMATICAS

Summaries (En, Pl)
4 fig., 3 tables; 6 ref.
A model of the first period of drying pumpkin, including its volumetric shrinkage, was verified. The basis to computation were the results of measuring kinetics of drying pumpkin slices (4x20x35 mm) under free convection at five drying air temperatures (40, 50, 60, 70, 80 deg C). The volumetric changes of pumpkin particles, dried under free convection at the temperature 80 deg C, were also considered

Plant physiology and biochemistry, Mathematical and statistical methods, TRITICUM AESTIVUM, LEAVES, PHOTOSYNTHESIS, CARBON DIOXIDE ENRICHMENT, RUBISCO, ENZYMIC ACTIVITY, MEASUREMENT, CHEMICAL REACTIONS, RESPIRATION RATE, LIGHT, NITROGEN CONTENT, GROWTH, MATHEMATICAL MODELS, MATHEMATICS, FEUILLE, PHOTOSYNTHESE, ENRICHISSEMENT EN GAZ CARBONIQUE, ACTIVITE ENZYMATIQUE, MESURE, REACTION CHIMIQUE, TAUX DE RESPIRATION, LUMIERE, TENEUR EN AZOTE, CROISSANCE, MODELE MATHEMATIQUE, MATHEMATIQUE, HOJAS, FOTOSINTESIS, ENRIQUECIMIENTO EN GAS CARBONICO, ACTIVIDAD ENZIMATICA, MEDICION, REACCIONES QUIMICAS, TASA DE RESPIRACION, LUZ, CONTENIDO DE NITROGENO, CRECIMIENTO, MODELOS MATEMATICOS, MATEMATICAS, RIBULOSE-BISPHOSPHATE CARBOXYLASE, CARBOXYLATION, NET ASSIMILATION RATE, and EQUATIONS

references
Wheat (Triticum aestivum L.) was grown under CO2 partial pressures of 36 and 70 Pa with two N-application regimes. Responses of photosynthesis to varying CO2 partial pressure were fitted to estimate the maximal carboxylation rate and the nonphotorespiratory respiration rate in flag and preceding leaves. The maximal carboxylation rate was proportional to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content, and the light-saturated photosynthetic rate at 70 Pa CO2 was proportional to the thylakoid ATP-synthase content. Potential photosynthetic rates at 70 Pa CO2 were calculated and compared with the observed values to estimate excess investment in Rubisco. The excess was greater in leaves grown with high N application than in those grown with low N application and declined as the leaves senesced. The fraction of Rubisco that was estimated to be in excess was strongly dependent on leaf N content, increasing from approximately 5% in leaves with 1 g N m(-2) to approximately 40% in leaves with 2 g N m(-2). Growth at elevated CO2 usually decreased the excess somewhat but only as a consequence of a general reduction in leaf N, since relationships between the amount of components and N content were unaffected by CO2. We conclude that there is scope for improving the N-use efficiency of C3 crop species under elevated CO2 conditions

Plant physiology and biochemistry, Mathematical and statistical methods, Plant structure, BASIDIOMYCOTINA, FUNGAL SPORES, SPORES, SECRETION, CHEMICAL COMPOSITION, MANNITOL, MONOSACCHARIDES, SURFACE TENSION, MEASUREMENT, VELOCITY, MATHEMATICAL MODELS, MATHEMATICS, DEVELOPMENTAL STAGES, PLANT ANATOMY, ULTRASTRUCTURE, CELL STRUCTURE, SPORE FONGIQUE, SPORE, COMPOSITION CHIMIQUE, MONOSACCHARIDE, TENSION SUPERFICIELLE, MESURE, VITESSE, MODELE MATHEMATIQUE, MATHEMATIQUE, STADE DE DEVELOPPEMENT, ANATOMIE VEGETALE, STRUCTURE CELLULAIRE, ESPORAS FUNGICAS, ESPORAS, SECRECION, COMPOSICION QUIMICA, MANITOL, MONOSACARIDOS, TENSION DE LA SUPERFICIE, MEDICION, VELOCIDAD, MODELOS MATEMATICOS, MATEMATICAS, ETAPAS DE DESARROLLO, ANATOMIA DE LA PLANTA, ULTRAESTRUCTURA, ESTRUCTURA CELULAR, BIOMECHANICS, BASIDIOSPORES, HEXOSES, and EQUATIONS

references

Plant physiology and biochemistry, Mathematical and statistical methods, Plant ecology, PLANTS, GROWTH, MEASUREMENT, MATHEMATICS, STAND CHARACTERISTICS, POPULATION DENSITY, BIOMASS, MATHEMATICAL MODELS, STEMS, WIDTH, HEIGHT, PLANTE, CROISSANCE, MESURE, MATHEMATIQUE, CARACTERISTIQUE DU PEUPLEMENT, DENSITE DE POPULATION, BIOMASSE, MODELE MATHEMATIQUE, TIGE, LARGEUR, HAUTEUR, PLANTAS, CRECIMIENTO, MEDICION, MATEMATICAS, CARACTERISTICAS DEL RODAL, DENSIDAD DE LA POBLACION, BIOMASA, MODELOS MATEMATICOS, TALLO, ANCHURA, ALTURA, STAND MASS, ALLOMETRY, STAND DENSITY, and FOLIAGE

references
We present an a priori theoretical framework for the interspecific allometric relationship between stand mass and plant population density. Our model predicts a slope of -1/3 between the logarithm of stand mass and the logarithm of stand density, thus conflicting with a previously assumed slope of -1/2. Our model rests on a heuristic separation of resource-limited living mass and structural mass in the plant body. We point out that because of similar resource requirements among plants of different sizes, a nonzero plant mass-density slope is primarily defined by structural mass. Specifically, the slope is a result of (i) the physical size-dependent relationship between stem width and height, (ii) foliage-dependent demands of conductance, and (iii) the cumulative nature of structural mass. The data support our model, both when the potential sampling bias of taxonomic relatedness is accounted for and when it is not. Independent contrasts analyses show that observed relationships among variables are not significantly different from the assumptions made to build the model or from its a priori predictions. We note that the dependence of the plant mass-density slope on the functions of structural mass provides a cause for the difference from the zero slope found in the animal population mass-density relationship; for the most part, animals do not have a comparable cumulative tissue type

Plant physiology and biochemistry, Fisheries and aquaculture - General aspects, Mathematical and statistical methods, CHLOROPHYCEAE, CYTOPLASM, CELL MEMBRANES, CALCIUM, ION EXCHANGE, CATIONS, STRONTIUM, MEASUREMENT, BIOCHEMICAL PATHWAYS, MATHEMATICAL MODELS, MATHEMATICS, CYTOPLASME, MEMBRANE CELLULAIRE, ECHANGE D'ION, CATION, MESURE, VOIE BIOCHIMIQUE DU METABOLISME, MODELE MATHEMATIQUE, MATHEMATIQUE, CITOPLASMA, MEMBRANAS CELULARES, CALCIO, INTERCAMBIO IONICO, CATIONES, ESTRONCIO, MEDICION, VIA BIOQUIMICA DEL METABOLISMO, MODELOS MATEMATICOS, MATEMATICAS, EREMOSPHAERA VIRIDIS, CHLOROPHYTA, CYTOSOL, PLASMA MEMBRANES, INDUCTION, MEMBRANE POTENTIAL, THEORY, and EQUATIONS

references
The divalent cation Sr2+ induced repetitive transient spikes of the cytosolic Ca2+ activity [Ca2+]cy and parallel repetitive transient hyperpolarizations of the plasma membrane in the unicellular green alga Eremosphaera viridis. [Ca2+]cy measurements, membrane potential measurements, and cation analysis of the cells were used to elucidate the mechanism of Sr2+ -induced [Ca2+]cy oscillations. Sr2+ was effectively and rapidly compartmentalized within the cell, probably into the vacuole. The [Ca2+]cy oscillations cause membrane potential oscillations, and not the reverse. The endoplasmic reticulum (ER) Ca2+ -ATPase blockers 2,5-di-tert-butylhydroquinone and cyclopiazonic acid inhibited Sr2+ -induced repetitive [Ca2+]cy spikes, whereas the compartmentalization of Sr2+ was not influenced. A repetitive Ca2+ release and Ca2+ re-uptake by the ER probably generated repetitive [Ca2+]cy spikes in E. viridis in the presence of Sr2+. The inhibitory effect of ruthenium red and ryanodine indicated that the Sr2+ -induced Ca2+ release from the ER was mediated by a ryanodine/cyclic ADP-ribose type of Ca2+ channel. The blockage of Sr2+ -induced repetitive [Ca2+]cy spikes by La3+ or Gd3+ indicated the necessity of a certain influx of divalent cations for sustained [Ca2+]cy oscillations. Based on these data we present a mathematical model that describes the baseline spiking [Ca2+]cy oscillations in E. viridis

Plant physiology and biochemistry, Mathematical and statistical methods, TRITICUM AESTIVUM, THLASPI, ROOTS, CYTOPLASM, CADMIUM, CALCIUM, POTASSIUM, ZINC, MAGNESIUM, IONS, MEASUREMENT, PH, ELECTRODES, MATHEMATICAL MODELS, MATHEMATICS, BIOREMEDIATION, THLASPI CAERULESCENS, THLASPI ARVENSE, ION UPTAKE, ION TRANSPORT, and EQUATIONS

references
A Cd2+-selective vibrating microelectrode was constructed using a neutral carrier-based Cd ionophore to investigate ion-transport processes along the roots of wheat (Triticum aestivum L.) and two species of Thlaspi, one a Zn/Cd hyperaccumulator and the other a related nonaccumulator. In simple Cd(NO3)2 solutions, the electrode exhibited a Nernstian response in solutions with Cd2+ activities as low as 50 nM. Addition of Ca2+ to the calibration solutions did not influence the slope of the calibration curve but reduced the detection limit to a solution activity of 1 micromolar Cd2+. Addition of high concentrations of K+ and Mg2+ to the calibration solution to mimic the ionic composition of the cytoplasm affected neither the slope nor the sensitivity of the electrode, demonstrating the pH-insensitive electrode's potential for intracellular investigations. The electrode was assayed for selectivity and was shown to be at least 1000 times more selective for Cd2+ than for any of those potentially interfering ions tested. Flux measurements along the roots of the two Thlaspi species showed no differences in the pattern or the magnitude of Cd2+ uptake within the time frame considered. The Cd2+-selective microelectrode will permit detailed investigations of heavy-metal ion transport in plant roots, especially in the area of phytoremediation

Plant physiology and biochemistry, Mathematical and statistical methods, ARABIDOPSIS THALIANA, ROOTS, GROWTH, CELLS, GROWTH RATE, CELL DIVISION, LENGTH, MEASUREMENT, EPIDERMIS, MERISTEMS, MATHEMATICAL MODELS, MATHEMATICS, TRICHOBLASTS, ATRICHOBLASTS, LOCALIZATION, and EQUATIONS

references
To investigate the relation between cell division and expansion in the regulation of organ growth rate, we used Arabidopsis thaliana primary roots grown vertically at 20 degrees C with an elongation rate that increased steadily during the first 14 d after germination. We measured spatial profiles of longitudinal velocity and cell length and calculated parameters of cell expansion and division, including rates of local cell production (cells mm-1 h-1) and cell division (cells cell-1 h-1). Data were obtained for the root cortex and also for the two types of epidermal cell, trichoblasts and atrichoblasts. Accelerating root elongation was caused by an increasingly longer growth zone, while maximal strain rates remained unchanged. The enlargement of the growth zone and, hence, the accelerating root elongation rate, were accompanied by a nearly proportionally increased cell production. This increased production was caused by increasingly numerous dividing cells, whereas their rates of division remained approximately constant. Additionally, the spatial profile of cell division rate was essentially constant. The meristem was longer than generally assumed, extending well into the region where cells elongated rapidly. In the two epidermal cell types, meristem length and cell division rate were both very similar to that of cortical cells, and differences in cell length between the two epidermal cell types originated at the apex of the meristem. These results highlight the importance of controlling the number of dividing cells, both to generate tissues with different cell lengths and to regulate the rate of organ enlargement

Soil chemistry and physics, Mathematical and statistical methods, SOIL TESTING, SOIL WATER CONTENT, SOIL WATER POTENTIAL, SOIL WATER RETENTION, INFILTRATION, SOIL CHEMICOPHYSICAL PROPERTIES, MEASUREMENT, MEASURING INSTRUMENTS, ANALYTICAL METHODS, MATHEMATICAL MODELS, MATHEMATICS, SORPTIVITY, MATRIC POTENTIAL, SATURATED HYDRAULIC CONDUCTIVITY, ESTIMATION, DETERMINATION, and CALCULATION

references
Tension infiltrometers have become a popular instrument for field determination of soil hydraulic properties. To develop and test different models for parameter estimation based on tension infiltrometer measurement, we obtained simultaneous measurements of transient tension infiltration rate, soil water content, and tension using small time domain reflectometry (TDR) probes and tensiometers installed at fixed locations relative to the infiltrometer disk. Infiltration was made with 10- and 20-cm-diam. disks under 1 and 5 cm of water supply tensions. The soil is an Arlington fine sandy loam (coarse-loamy, mixed, thermic Haplic Durixeralf). Wooding's steady-state approximate solution for water flow from a surface circular pond was used to estimate the saturated hydraulic conductivity (K(s)) and an empirical parameter (alpha G) used in Gardner's exponential hydraulic conductivity function. These two parameters (i.e., K(s) and alpha G) were then independently estimated using an integral form of the steady-state Darcy-Buckingham flux law. A sorptivity method was also proposed as an alternative to Wooding's steady-state approach. Calculated K(s) and alpha G with the Darcy-Buckingham flux law method was in good agreement with estimates using Wooding's steady-state approximation. The sorptivity method produced K(s) estimates that were statistically similar to those obtained with Wooding's method. The K(h) inferred from measured theta(h) underestimated the conductivity close to saturation compared with estimates obtained from the infiltrometer measurements

Plant physiology and biochemistry, Fisheries and aquaculture - General aspects, Mathematical and statistical methods, CYANOPHYTA, PHOTOSYSTEMS, LIGHT, DARKNESS, NITROGEN FIXATION, BIOLOGICAL RHYTHMS, OXYGEN, GAS EXCHANGE, MEASUREMENT, NITROGENASE, ENZYMIC ACTIVITY, OXIDATION, SPECTROMETRY, MATHEMATICAL MODELS, MATHEMATICS, CYANOBACTERIA, REGULATION, FLUORESCENCE EMISSION SPECTROSCOPY, and EQUATIONS

references
The unicellular, diazotrophic cyanobacterium Cyanothece sp. ATCC 51142 demonstrated important modifications to photosystem II (PSII) centers when grown under light/dark N2-fixing conditions. The properties of PSII were studied throughout the diurnal cycle using O2-flash-yield and pulse-amplitude-modulated fluorescence techniques. Nonphotochemical quenching (q(N)) of PSII increased during N2 fixation and persisted after treatments known to induce transitions to state 1. The q(N) was high in cells grown in the dark, and then disappeared progressively during the first 4 h of light growth. The photoactivation probability, epsilon, demonstrated interesting oscillations, with peaks near 3 h of darkness and 4 and 10 h of light. Experiments and calculations of the S-state distribution indicated that PSII displays a high level of heterogeneity, especially as the cells prepare for N2 fixation. We conclude that the oxidizing side of PSII is strongly affected during the period before and after the peak of nitrogenase activity; changes include a lowered capacity for O2 evolution, altered dark stability of PSII centers, and substantial changes in q(N)

Food composition, Feed composition, Mathematical and statistical methods, WHEATS, GRAIN, DIELECTRIC PROPERTIES, MEASUREMENT, RADIATION, SENSORS, DESIGN, MATHEMATICS, MATHEMATICAL MODELS, BLE, PROPRIETE DIELECTRIQUE, MESURE, CAPTEUR, CONCEPTION, MATHEMATIQUE, MODELE MATHEMATIQUE, TRIGO, GRANOS, PROPIEDADES DIELECTRICAS, MEDICION, RADIACION, SENSORES, DISENO, MATEMATICAS, MODELOS MATEMATICOS, RADIO WAVES, FREQUENCY, and EQUATIONS

references
A system for measuring the dielectric properties of cereal grains from 1 to 350 MHz with a coaxial sample holder is presented. Several polar alcohols were used to calibrate and verify permittivity measurements obtained with a signal-flow graph model from the full two-port S-parameter measurements. At the lowest frequencies (1-25 MHz), where the phase measurements are less accurate, a lumped parameter model was used for the dielectric loss factor measurements. The system was calibrated with measurements on air and decanol and verified with measurements on octanol, hexanol, and pentanol. The standard error for the polar alcohols used for verification was 2.3% for the dielectric constant and 7.6% for the dielectric loss factor. Although measurements were taken on static samples, the sample holder is designed to accommodate flowing grain. Dielectric properties measurements at 25 degrees C were taken on four hard red winter wheat cultivars ranging in moisture content from about 9% to 21% with bulk densities varying from 0.66 to 0.83 g/cm3. Most of the data agreed with measurements reported in the literature

Physiology of human nutrition, Mathematical and statistical methods, RATS, BLOOD SUGAR, GLUCOSE, BODY FLUIDS, INSULIN, INJECTION, ELECTRODES, MEASUREMENT, SENSORS, MATHEMATICS, MATHEMATICAL MODELS, RAT, SUCRE DU SANG, LIQUIDE BIOLOGIQUE, INSULINE, ELECTRODE, MESURE, CAPTEUR, MATHEMATIQUE, MODELE MATHEMATIQUE, RATA, AZUCAR EN SANGRE, GLUCOSA, LIQUIDOS CORPORALES, INSULINA, INYECCION, ELECTRODOS, MEDICION, SENSORES, MATEMATICAS, MODELOS MATEMATICOS, SUBCUTANEOUS FLUID, and INTRAVENOUS INJECTION

references
The kinetics of the fall in subcutaneous fluid glucose concentration in anesthetized rats (n = 7) after intravenous injection of insulin (0.5 units/kg) was studied by using 5 x 10(-4) cm2 active area, 150-sec 10-90% response time, amperometric glucose sensors. The onset of the decline in the subcutaneous glucose concentration was delayed and statistically different (P 0.001) from that in blood (8.9 +/- 2.1 min vs. 3.3 +/- 0.5 min). Similarly, the rate of drop in glucose concentration between 6 and 20 min after the insulin injection was different for subcutaneous tissue (3.9 +/- 1.3 mg.dl-1 min-1) and blood (6.8 +/- 2.0 mg.dl-1.min-1) (P

Agricultural structures, Mathematical and statistical methods, ANIMAL HOUSING, LIVESTOCK, STOCKING DENSITY, MICROCLIMATE, ENVIRONMENT, ANIMAL FEEDING, WASTE GASES, AMMONIA, WATER VAPOUR, MATHEMATICAL MODELS, COMPUTER APPLICATIONS, SIMULATION, METHODS, MATHEMATICS, MEASUREMENT, EXPERIMENTATION, LOGEMENT DES ANIMAUX, BETAIL, TAUX DE CHARGE, MICROCLIMAT, ENVIRONNEMENT, ALIMENTATION DES ANIMAUX, EFFLUENT GAZEUX, AMMONIAC, VAPEUR D'EAU, MODELE MATHEMATIQUE, APPLICATION DES ORDINATEURS, METHODE, MATHEMATIQUE, MESURE, ALOJAMIENTO DE ANIMALES, GANADO, CARGA GANADERA, MICROCLIMA, MEDIO AMBIENTE, ALIMENTACION DE LOS ANIMALES, GAS RESIDUAL, AMONIACO, VAPOR DE AGUA, MODELOS MATEMATICOS, APLICACIONES DEL ORDENADOR, SIMULACION, METODOS, MATEMATICAS, MEDICION, and EXPERIMENTACION

Summaries (En, Pl)
6 fig., 2 tables; 6 ref.
Comprehensive interpretation of animal raising process with reference to the emission of noxious gases was presented. It dealt with the object identification by means of regression analysis and proposed a general conception of control. A complete identification algorithm was defined and tentatively applied to control on a "real" experimental stand. The algorithm identifying animal raising system in respect of ammonia emission, verified under conditions of stand experiment, is an attempt to present the phenomenon in form enabling its computer simulation. The results of experiment were given and interpretation of the process in aspect of computer simulation was suggested

Soil chemistry and physics, Mathematical and statistical methods, SOIL TESTING, SOIL WATER, WATER, FLOW RATE, SOIL CHEMICOPHYSICAL PROPERTIES, INFILTRATION, MEASUREMENT, MEASURING INSTRUMENTS, MATHEMATICS, MATHEMATICAL MODELS, ANALYSE DE SOL, EAU DU SOL, EAU, DEBIT, PROPRIETE PHYSICOCHIMIQUE DU SOL, MESURE, INSTRUMENT DE MESURE, MATHEMATIQUE, MODELE MATHEMATIQUE, ANALISIS DEL SUELO, AGUA DEL SUELO, AGUA, GASTO, PROPIEDADES FISICO-QUIMICAS SUELO, INFILTRACION, MEDICION, INSTRUMENTOS DE MEDICION, MATEMATICAS, MODELOS MATEMATICOS, SOIL SORPTIVITY, SOIL HYDRAULIC PROPERTIES, HYDRAULIC CONDUCTIVITY, DETERMINATION, EQUATIONS, and CALCULATION

references
The disk infiltrometer is becoming a widely used device for determining soil hydraulic properties in the field. To describe the infiltration process from the disk infiltrometer, a two-term equation was developed. The first and second terms characterize water flow out of the disk due to capillary forces and gravity, respectively. The parameter of the first term in the equation was a product of a nondimensional coefficient and soil sorptivity. The parameter of the second term was a product of another nondimensional coefficient and soil hydraulic conductivity. Time-dependent relationships were obtained from numerical models to determine the coefficients based on physical parameters of the infiltrometer, such as the radius and tension used; and soil retention parameters. The cumulative infiltration and steadystate infiltration rate calculated using the two-term equation were in excellent agreement with numerically simulated results for various soils, and radii and tensions of disk infiltrometers. Absolute relative errors of predicted infiltration were 5% for soils ranging from clay to sand. The infiltration solution is an accurate, yet simple approach to estimate fluxes from an axisymmetric source. It can also be applied to estimate soil sorptivity and hydraulic conductivity using inverse methods

Plant physiology and biochemistry, Plant genetics and breeding, Mathematical and statistical methods, COMPOSITAE, LEAVES, PHOTOSYSTEMS, LIGHT, OXIDOREDUCTIONS, ATP, CARBON DIOXIDE, GAS EXCHANGE, MEASUREMENT, PROTEINS, CHEMICAL COMPOSITION, PROTEIN CONTENT, RUBISCO, ENZYMIC ACTIVITY, GENE EXPRESSION, TRANSGENIC PLANTS, GENETIC VARIATION, MATHEMATICAL MODELS, MATHEMATICS, FEUILLE, PHOTOSYSTEME, LUMIERE, OXYDOREDUCTION, DIOXYDE DE CARBONE, ECHANGE GAZEUX, MESURE, PROTEINE, COMPOSITION CHIMIQUE, TENEUR EN PROTEINES, ACTIVITE ENZYMATIQUE, EXPRESSION DES GENES, PLANTE TRANSGENIQUE, VARIATION GENETIQUE, MODELE MATHEMATIQUE, MATHEMATIQUE, HOJAS, FOTOSISTEMAS, LUZ, OXIRREDUCION, DIOXIDO DE CARBONO, INTERCAMBIO DE GASES, MEDICION, PROTEINAS, COMPOSICION QUIMICA, CONTENIDO PROTEICO, ACTIVIDAD ENZIMATICA, EXPRESION GENICA, PLANTAS TRANSGENICAS, VARIACION GENETICA, MODELOS MATEMATICOS, MATEMATICAS, PHOTOSYSTEM I, PHOTOSYSTEM II, NET ASSIMILATION RATE, LIGHT INTENSITY, ELECTRON TRANSFER, RIBULOSE-BISPHOSPHATE CARBOXYLASE, WILD STRAINS, and EQUATIONS

references
It was previously shown with concurrent measurements of gas exchange and carbon isotope discrimination that the reduction of ribulose-1,5-bisphosphate carboxylase/oxygenase by an antisense gene construct in transgenic Flaveria bidentis (a C4 species) leads to reduced CO2 assimilation rates, increased bundle-sheath CO2 concentration, and leakiness (defined as the ratio of CO2 leakage to the rate of C4 acid decarboxylation; S. von Caemmerer, A. Millegate, G.D. Farquhar, R.T. Furbank [1997] Plant Physiol 113: 469-477). Increased leakiness in the transformants should result in an increased ATP requirement per mole of CO2 fixed and a change in the ATP-to-NADPH demand. To investigate this, we compared measurements of the quantum yield of photosystem I and II (phi(PSI) and phi(PSII)) with the quantum yield of CO2 fixation (phi(CO2)) in control and transgenic F. bidentis plants in various conditions. Both phi(PSI)/phi(CO2) and phi(PSII)/phi(CO2) increased with a decrease in ribulose-1,5-bisphosphate carboxylase/oxygenase content, confirming an increase in leakiness. In the wild type the ratio of phi(PSI) to phi (PSII) was constant at different irradiances but increased with irradiance in the transformants, suggesting that cyclic electron transport may be higher in the transformants. To evaluate the relative contribution of cyclic or linear electron transport to extra ATP generation, we developed a model that links leakiness, ATP/NADP requirements, and quantum yields. Despite some uncertainties in the light distribution between photosystem I and II, we conclude from the increase of phi(PSII)/phi (CO2) in the transformants that cyclic electron transport is not solely responsible for ATP generation without NADPH production