Pollution, Organization, administration and management of agricultural enterprises or farms, Mathematical and statistical methods, USA, GROUNDWATER POLLUTION, PESTICIDES, AGRICULTURAL SECTOR, STATISTICAL METHODS, PRODUCTIVITY, MEASUREMENT, PRODUCTION FUNCTIONS, MATHEMATICS, ETATS UNIS, POLLUTION DE L'EAU SOUTERRAINE, PESTICIDE, SECTEUR AGRICOLE, METHODE STATISTIQUE, PRODUCTIVITE, MESURE, FONCTION DE PRODUCTION, MATHEMATIQUE, EUA, POLUCION DE AGUAS SUBTERRANEAS, PLAGUICIDAS, SECTOR AGRARIO, METODOS ESTADISTICOS, PRODUCTIVIDAD, MEDICION, FUNCIONES DE LA PRODUCCION, MATEMATICAS, FACTOR ANALYSIS, and EQUATIONS

references. Paper presented at the ASSA winter meeting held January 3-5, 1998, Chicago, Illinois. Discussions by V.K. Smith, p. 591-594, and R.D. Weaver, p. 595-599

Food composition, Feed composition, Mathematical and statistical methods, WHEATS, GRAIN, MOISTURE CONTENT, MEASUREMENT, DIELECTRIC PROPERTIES, DENSITY, RADIATION, SPECTROMETRY, MATHEMATICS, STATISTICAL METHODS, BLE, TENEUR EN EAU, MESURE, PROPRIETE DIELECTRIQUE, DENSITE, SPECTROMETRIE, MATHEMATIQUE, METHODE STATISTIQUE, TRIGO, GRANOS, CONTENIDO DE HUMEDAD, MEDICION, PROPIEDADES DIELECTRICAS, DENSIDAD, RADIACION, ESPECTROMETRIA, MATEMATICAS, METODOS ESTADISTICOS, DENSITY-INDEPENDENT MEASUREMENT, BULK DENSITY, RADIO WAVES, SPECTRAL ANALYSIS, ACCURACY, EQUATIONS, MULTIVARIATE ANALYSIS, and PRINCIPAL COMPONENT ANALYSIS

references
A technique is presented for rapidly determining the moisture content of hard red winter wheat, Triticum aestivum L., independent of grain bulk density. Complex admittance measurements from 1 to 110 MHz on bulk wheat samples were collected for predicting moisture contents ranging from about 9% to 20%, wet basis, in samples with densities ranging from 0.620 to 0.790 g/cm3. The data were transformed to density-independent function (DIF) values, and multivariate analysis was used to eliminate spectral and statistical outliers. Principal component analysis was also used to determine the optimum frequencies for predicting moisture content with the DIF values. Partial least-squares regression was then used to develop a calibration based on measurements at three frequencies of about 2, 25, and 80 MHz. Calibration was performed with 47 wheat samples representing six cultivars harvested in 1991 and 1992 with a standard error of cross validation of 0.34% moisture content, and validation was tested on 146 different samples from the same cultivars. Predicted moisture contents compared well with values determined by air oven drying with a standard error of performance of 0.39% moisture content and a bias of +0.03%

Processing of forest products, Mathematical and statistical methods, PAPER, ELASTICITY, MOISTURE CONTENT, WATER, HYDROGEN, FORECASTING, MEASUREMENT, STATISTICAL METHODS, MATHEMATICS, PAPIER, ELASTICITE, TENEUR EN EAU, EAU, HYDROGENE, TECHNIQUE DE PREVISION, MESURE, METHODE STATISTIQUE, MATHEMATIQUE, PAPEL, ELASTICIDAD, CONTENIDO DE HUMEDAD, AGUA, HIDROGENO, TECNICAS DE PREDICCION, MEDICION, METODOS ESTADISTICOS, MATEMATICAS, MODULUS OF ELASTICITY, PROBABILITY, EQUATIONS, and REGRESSION ANALYSIS

references

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.

Water resources and management, Mathematical and statistical methods, MATHEMATICS, IRRIGATION, MEASUREMENT, RISK, ROADS, RIVERS, TROPICAL ZONES, MATHEMATIQUE, MESURE, RISQUE, ROUTE, COURS D'EAU, ZONE TROPICALE, MATEMATICAS, RIEGO, MEDICION, RIESGO, CARRETERAS, CURSOS DE AGUA, ZONA TROPICAL, EQUATIONS, and RISK ASSESSMENT

41 ref.

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

Food composition, Handling, transport, storage and protection of fisheries and aquacultural products, MACKEREL, ANIMAL TISSUES, MUSCLES, ANTIOXIDANTS, GLUTATHIONE, ASCORBIC ACID, TOCOPHEROLS, QUINONES, STORAGE LOSSES, FOODS, FROZEN STORAGE, DURATION, LIPID PEROXIDATION, QUALITY, MEASUREMENT, ORGANOLEPTIC ANALYSIS, STATISTICAL METHODS, MATHEMATICS, MAQUEREAU, TISSU ANIMAL, MUSCLE, ANTIOXYDANT, GLUTATHION, ACIDE ASCORBIQUE, TOCOPHEROL, QUINONE, PERTE AU STOCKAGE, PRODUIT ALIMENTAIRE, STOCKAGE CONGELE, DUREE, PEROXYDATION DES LIPIDES, QUALITE, MESURE, ANALYSE ORGANOLEPTIQUE, METHODE STATISTIQUE, MATHEMATIQUE, CABALLA, TEJIDOS ANIMALES, MUSCULOS, ANTIOXIDANTES, GLUTATION, ACIDO ASCORBICO, TOCOFEROLES, QUINONAS, PERDIDAS POR ALMACENAMIENTO, ALIMENTOS, ALMACENAMIENTO CONGELADO, DURACION, PEROXIDACION LIPIDICA, CALIDAD, MEDICION, ANALISIS ORGANOLEPTICO, METODOS ESTADISTICOS, MATEMATICAS, LIGHT MUSCLE, WATER-SOLUBLE ANTIOXIDANTS, LIPID-SOLUBLE ANTIOXIDANTS, UBIQUINONE-10, UBIQUINOL-10, THIOBARBITURIC ACID REACTIVE SUBSTANCES (TBARS), STORAGE TIME, UBIQUINONES, REGRESSION ANALYSIS, and EQUATIONS

references
The loss of water- and lipid-soluble antioxidants of mackerel light and dark muscle was determined as a function of time of storage on ice to provide clues as to mechanisms of oxidation and to assess the use of antioxidants to measure and predict quality. Glutathione and ascorbate decreased faster initially than alpha-tocopherol and ubiquinone in both light and dark muscle of mackerel; in dark muscle, the rate of loss of ubiquinol was comparable to the loss of the water-soluble antioxidants. Antioxidants decreased more rapidly initially in dark muscle than in light muscle. Rates of sensory quality loss in the light and dark muscles were similar except that initial loss of quality in the dark muscle was greater than that in the light. Regression equations showed good relationships of tocopherol, ubiquinone-10, and TBARS in light and dark muscle with storage time. Ascorbate and glutathione gave the best correlation values with sensory scores for light muscle, while a good relationship was seen in dark muscle between sensory score and reduced or oxidized CoQ, ascorbate, and glutathione. The kinetic data suggest an important role of mitochondria in lipid oxidation in mackerel dark muscle

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

Water resources and management, Mathematical and statistical methods, NORTH DAKOTA, SOIL PARENT MATERIALS, GROUNDWATER, GROUNDWATER TABLE, STORAGE, MEASUREMENT, TESTING, MATHEMATICS, DAKOTA DU NORD, ROCHE MERE, EAU SOUTERRAINE, NAPPE SOUTERRAINE, STOCKAGE, MESURE, TESTAGE, MATHEMATIQUE, DAKOTA DEL NORTE, ELEMENTO PRIMARIO DEL SUELO, AGUAS SUBTERRANEAS, CAPA FREATICA, ALMACENAMIENTO, MEDICION, ENSAYO, MATEMATICAS, CONSOLIDATION TESTS, AQUIFERS, and EQUATIONS

references
Specific storage (S(s)) was calculated for 107 glacial till core samples collected in 1962 from 93 drilling sites at U.S. Air Force Intercontinental Ballistic Missile launch and launch control facilities located in North Dakota. Core sample depths ranged from 8 to 26 m. Consolidation tests were performed on the till samples using a floating ring consolidometer. The coefficient of volume change (m(v)), which is defined as the volume change per unit volume per unit increase in effective stress, was calculated for this study using previously reported consolidation test data. S(s) calculated for the 107 till samples ranged from 2.0 X 10-4 m-1 to 1.1 X 10-3 m-1, with a mean value of 5.6 X 0-4 m-1. Till is easily compressible and, as a result, S(s) is not constant, but rather a function of loading. With increased depth, effective stress increases and S(s) decreases. Based on data from 107 till cores in this study, the relationship between effective stress and S(s) is described by: S(s)=0.049 effective stress-0.84, (r2=0.60, p0.0001), where effective stress

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

Soil chemistry and physics, Mathematical and statistical methods, IOWA, INFILTRATION, TEXTURAL SOIL TYPES, GLACIAL TILL SOILS, CULTURAL SOIL TYPES, SOIL COMPACTION, FARMLAND, MEASUREMENT, MEASURING INSTRUMENTS, MATHEMATICS, TYPE DE SOL TEXTURAL, SOL DE TILL GLACIAIRE, TYPE DE SOL DE CULTURE, COMPACTAGE DU SOL, TERRE AGRICOLE, MESURE, INSTRUMENT DE MESURE, MATHEMATIQUE, INFILTRACION, TIPOS TEXTURALES DE SUELOS, SUELO DE ALUVION GLACIAL, TIPOS DE SUELOS CULTIVABLES, COMPACTACION DEL SUELO, TIERRAS AGRICOLAS, MEDICION, INSTRUMENTOS DE MEDICION, MATEMATICAS, SOIL WATER PRESSURE HEAD, VADOSE ZONE, WHEEL TRACK INTERROWS, NO-TRACK INTERROWS, UNSATURATED HYDRAULIC CONDUCTIVITY, MAIZE SOILS, SPATIAL VARIATION, and EQUATIONS

references
A function relating unsaturated soil hydraulic conductivity K and soil water pressure head h is most important for understanding water flow and chemical transport in the vadose zone. Furthermore, the K(h) function near saturation is critical for describing flow in macropores and other structural voids. The usefulness of similar media scaling and functional normalization to describe the near-saturated hydraulic conductivity function K(h) measured in situ at 296 spatial locations across a heterogeneous agricultural field was tested. Disc (ponded and tension) infiltrometers were used to measure K(h) at different field positions (corn row, no traffic interrow, and traffic interrow) cutting across different soil types (Nicollet and Clarion loam derived from glacial till material). The K(h) data ranged several orders of magnitude for different field positions and soil types and were found to be statistically different between different field positions. Using a Gardner type K(h) function, relative hydraulic conductivity values, and a hybrid of similar media scaling and functional normalization concepts, all disc infiltrometer data sets were coalesced to a single reference curve. Poor to moderately correlated K and h scale factors did not show any significant spatial structure across the field. A novel finding is that saturated hydraulic conductivities (Ksat) could be successfully used as the scale factor for the near-saturated K(h) functions (e.g., 0-15 cm soil water tension) under all field positions and soil types at the experimental field

Pollution, Mathematical and statistical methods, EPTC, VOLATILIZATION, TEMPERATURE, SOIL SOLUTION, MEASUREMENT, ANALYTICAL METHODS, MATHEMATICS, BATCH AIR STRIPPING TECHNIQUE, and EQUATIONS

references
Many pesticides are susceptible to volatilization, which may result in decreased pest control and off-site deposition that may cause adverse environmental impacts. Prediction of such losses requires knowledge of pesticide partition coefficients, including Henry's constant (H(c)); however accurate data are lacking. In this experiment, the batch air stripping technique was used to determine H(c) for EPTC (S-ethyl N,N-di-n-propylthiocarbamate). At 25 degrees C, measured H(c) in pure water was 0.0107, 11 times greater than indirectly estimated values reported in the literature. The measured heat of volatilization for EPTC, used to describe the temperature dependence of H(c), was 37.12 kJ mol-1. H(c) measured with soil extract was 7 times greater than that measured in pure water, presumably due to effects of dissolved salts and organic acids

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

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

Soil chemistry and physics, Mathematical and statistical methods, INFILTRATION, AIR, TEXTURAL SOIL TYPES, SOIL WATER MOVEMENT, AIR FLOW, WATER, FLOW RATE, SOIL MORPHOLOGICAL FEATURES, MEASUREMENT, MATHEMATICS, TYPE DE SOL TEXTURAL, MOUVEMENT DE L'EAU DANS LE SOL, FLUX D'AIR, EAU, DEBIT, TRAIT MORPHOLOGIQUE DU SOL, MESURE, MATHEMATIQUE, INFILTRACION, AIRE, TIPOS TEXTURALES DE SUELOS, MOVIMIENTO DEL AGUA EN EL SUELO, FLUJO DE AIRE, AGUA, GASTO, CARACTERISTICAS MORFOLOGICAS SUELO, MEDICION, MATEMATICAS, LOAMY SAND SOILS, WATER PRESSURE, AIR DRAINING, AIR CONFINING, SOIL WATER INFLOW, SOIL AIR OUTFLOW, WETTING FRONT, SURFACE LAYERS, HYDRAULIC CONDUCTIVITY, and EQUATIONS

references
Experiments were conducted to quantify the effects of entrapped air on water infiltration into a loamy sand. Transparent three-dimensional (3-D) and 2-D columns were used for experiments carried out for two infiltration conditions: (1) when air was free to move ahead of the wetting front and leave the bottom of the column (air draining) and (2) when air was confined ahead of the wetting front and hence could escape only through the soil surface (air confining). The measurement setup was composed of a tension-pressure infiltrometer, an air flowmeter, water manometers, and video-picture cameras. We applied both positive and negative water pressures at the soil surface and measured the simultaneous changes in the rates of water inflow and air outflow; the air pressure ahead of the wetting front, and the dynamic behavior and advance of the wetting front. The air pressure ahead of the wetting front for the air-confining condition was generally found to increase with time rather than reaching a constant level, as observed in other studies by other researchers. The air pressure fluctuated locally because of air escaping from the soil surface. On the basis of an analysis of the results we present two empirical equations to predict the maximum air pressure at which air begins to erupt from the soil surface and to predict the minimum air pressure at which air eruption stops. We found that the infiltration rate was always equal to, and controlled by, the rate of air outflow. The infiltration rate varied inversely with the air pressure ahead of the wetting front and with the ponding depth at the soil surface. The infiltration rate fluctuated with time rather than undergoing changes in a three-stage process, as is often characterized in the literature. The volume of residual entrapped air in the air-confining condition increased 7% on average, and the infiltration rate decreased threefold to tenfold as compared to the air-draining condition. Finally, it was shown that the air-co

Veterinary science and hygiene, Mathematical and statistical methods, DOGS, BLADDER, VOLUME, MEASUREMENT, ULTRASONICS, ECHOGRAPHY, DIMENSIONS, MATHEMATICS, CHIEN, VESSIE, MESURE, ULTRASON, ECHOGRAPHIE, DIMENSION, MATHEMATIQUE, PERRO, VEJIGA, VOLUMEN, MEDICION, ULTRASONIDO, ECOGRAFIA, MATEMATICAS, ULTRASONOGRAPHY, ACCURACY, EQUATIONS, and ESTIMATION

references

Meteorology and climatology, Plant physiology and biochemistry, Mathematical and statistical methods, MATHEMATICS, MEASUREMENT, CROPS, EVAPOTRANSPIRATION, MATHEMATIQUE, MESURE, PLANTE DE CULTURE, MATEMATICAS, MEDICION, CULTIVOS, EVAPOTRANSPIRACION, EQUATIONS, and DETERMINATION

23 ref.

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