Ko Values Research Articles

Effect of potassium fertilizers on quantity‐intensity parameters in some argentine soils

The parameters obtained from the quantity‐intensity (Q/I) isotherms have been used by several authors as criteria to estimate the immediate availability of labile potassium (K) in a soil. The aim of this work was to study how these parameters have been modified in four agricultural soils in Argentina by the addition of K (0 to 936 kg K2O ha‐1) in an incubation trial simulating K fertilizers application. In two of the soils, the increase in the labile forms of K was proportional to the amount of added K and the recovery percentages were high. In the other soils, a contrasting behavior was found. This difference might be due to different fixing capacity of the soils, which was related to the clay content and mineralogical composition of this fraction. The slopes of the Q/I curves for each soil indicate that the potential buffer capacity (PBC) was similar for the different treatments over the range of K added. The addition of K produced proportional increases in ARe and ?Ko values. This could be attributed to the presence of non saturated planar sites at the highest rates of K applied.

Carbanion Stabilization by Adjacent Sulfur: Polarizability, Resonance, or Negative Hyperconjugation? Experimental Distinction Based on Intrinsic Rate Constants of Proton Transfer from (Phenylthio)nitromethane and 1-Nitro-2-phenylethane

(Phenylthio)nitromethane, PhSCH2NO2, is about as acidic as PhCH2NO2 and about 4 pKa-units more acidic than CH3NO2 in water or aqueous DMSO, showing the well-known acidifying effect of thio substituents in the α-position of carbon acids. Over the years various interpretations have been offered for the acidifying effect of sulfur groups: d−p π-resonance, polarizability, and negative hyperconjugation. Assuming that the nature of the factors that potentially stabilize the transition state of the proton transfer from the carbon acid are the same as those that potentially stabilize the carbanion, we show that a distinction between these interpretations can be based on the effect of the phenylthio group on the intrinsic rate constants (ko) of proton transfer. Such intrinsic rate constants were determined for the deprotonation of PhSCH2NO2 and PhCH2CH2NO2 by amines in water and 90% DMSO−10% water; in both solvents ko for PhSCH2NO2 was found to be substantially higher than for PhCH2CH2NO2 as well as for other nitroalkanes reported previously. Based on a detailed analysis of how various factors such as resonance, inductive effects, polarizability, and positive and negative hyperconjugation affect the intrinsic rate constants for proton transfer, it is concluded that the high ko values for PhSCH2NO2 result from a combination of the inductive and polarizability effect of the PhS group and that d−p π-resonance and negative hyperconjugation play a minor role if any.

Study on the Estimation Methods for Infiltration Capacity of Field Soils Based on the Falling Head Tests Using Borehole

This paper discussed the estimation methods for saturated hydraulic conductivities (ko) of soils under various initial conditions, using borehole falling head tests (FHT). Parameters relating to soil properties were determined by soil tests and preliminary analyses. In addition, an empirical formula specifying the initial condition of the surface soil layer was introduced on the basis of the field data observed by tensiometers. As a result, ko values evaluated from FHT carried out for the dry soils are in good agreement with the values obtained by constant head tests.

The coefficient of earth pressure at rest: Reply

In particular, the vhlues ca1dulated'~ith [2] are 3.4% less than the average meas~ired value. If [3] iskused, the differences are equal to 2.4%, whereas if [4] is used the calculated and measured KO values practically coincide. For the tested pressure range, the maximum percentage differences (positive and (or) negative) between the calculated and measured values have come out as + 16% and 11%.

Consolidation, Pre- and Post-Peak Shearing Responses from Internally Instrumented Biaxial Compression Device

Abstract An internally instrumented, servo-controlled biaxial compression device is described for evaluating shear band formation in soils. Internally measured vertical and lateral soil displacements as well as lateral deformations of a very low friction bottom sled allow one to observe the progressive development of shear bands in a specimen. Anisotropically consolidated specimens of relatively insensitive, soft Chicago glacial clay were sheared under undrained conditions. Differences in responses based on the internal and globally derived stress and strain quantities illustrate the uniformities which are attained during both consolidation and shear. Small, outward lateral displacements were observed during K0 consolidation, which was based on globally observed axial and volumetric strains; yet, observed Ko values were similar to those measured by other means. Observed lateral deformations during undrained shear and bottom sled movements showed the progressive development of a shear band in all tests. Nonuniformity of the deformations arose after attaining a peak shear stress. The globally observed strain-softening response was both constitutive and geometric in nature.

Static and dynamic model for 1-naphthol fluorescence quenching by carbon tetrachloride in dioxane—acetonitrile mixtures

The quenching of 1-naphthol fluorescence by carbon tetrachloride (CCl4) has been studied in different solvent mixtures of acetonitrile and dioxane at room temperature. The quenching is found to be appreciable and a positive deviation from linearity was observed in the Stern-Volmer plot in all the solvent mixtures even at moderate CCl4 concentrations (0.1 M or less). This could be explained satisfactorily by a static-dynamic model. The static quenching constant Ko values indicate that the ground-state complex is weak and independent of solvent polarity, whereas the dynamic quenching constant Ksv depends on the solvent polarity.

Purification and Subsite Affinities ofexo-lnulinase fromPenicillium trzebinskii

An exo-inulinase was highly purified from the culture broth of Penicillium trzebinskii by anion exchange, hydrophobic, and gel filtration chromatographies. The enzyme was homogeneous by disc electrophoresis. The molecular weight was 8.7 × 104, and the isoelectric point was pH 4.3. The enzyme hydrolyzed not only inulin and sucrose but also inulooligosaccharides [1F(1-β-D-fructofuranosyl)n-1fructose, Fn (n= 2—5)] and fructooligosaccharides [1F(1-β-D-fructofuranosyl)n-1 sucrose, GFn, (n = 2—8)] liberating the nonreducing terminal fructose of the substrates. The substrate specificity was investigated. The Km (mM) and ko (sec−1were: inulin, 0.042 and 159; sucrose, 6.5 and 169; F2, 2.1 and 62.8; F3, 0.40 and 126; F4, 0.47 and 171; and F5, 0.47 and 131, respectively. Dependence of Km and ko values on the degree of polymerization of substrates was observed. The subsite affinities in the active site were 1.05, 4.57, 1.45, 0.09, and — 0.16kcal/mol for subsite 1, 2, 3, 4, and 5, respectively.

Kinetics and mechanism of dissociation of copper(II) complexes of biguanide and someN 1-substituted biguanides in aqueous acetate buffer media

The kinetics fo dissociation of thebis complexes [Cu(LH)2]2+ formed by CuII with biguanide andN 1-substituted methyl, phenyl, dimethyl and diethyl biguanides into the mono biguanide complexes in aqueous NaOAc-HOAc buffer media have been studied by stopped-flow spectrophotometry. The results, under pseudo-first-order conditions, indicate kobs=ko+kH[H+]. For the different complexes ko values are comparable, but kH values differ appreciably; log kH versus log K d H is linear withca. unit slope K d H being the equilibrium constant for the process: $$[{\text{Cu(LH)}}_{\text{2}} ]^{2 + } + 2{\text{H}}_{\text{2}} {\text{O}} + {\text{H}}^{\text{ + }} \rightleftharpoons [{\text{Cu(LH)(H}}_{\text{2}} {\text{O)}}_{\text{2}} ]^{2 + } + {\text{LH}}_{\text{2}}^{\text{ + }}$$ Based on these observations and from consideration of ΔH‡ and ΔS‡ values, we propose and associative mechanism, with significant bond formation by the incoming H2O in the Ko path, and a dissociative mechanism for the kH path.

Evaluating Ko in Champlain clays with hydraulic fracture tests

Hydraulic fracture tests using piezometer tips 10–500 mm long were performed in Champlain clays at five different sites with overconsolidation ratios (OCR) varying from 1.6 to 4.8. Before the test, the piezometer fluid was replaced by a methylene blue solution (10 g/L) to dye the fissures resulting from the test. After the hydraulic fracture, the soil around the piezometer tips was recovered by means of a large-diameter sampler. For 300 and 500 mm long piezometers, the fissure pattern was radial and vertical, even in deposits with an OCR above unity, confirming that hydraulic fracturing is related to the total stress acting on the cavity walls. The results for the five sites define for the Champlain clay deposits a Ko–OCR relationship that gives higher Ko values than generally proposed in the literature. Key words: hydraulic fracture, piezometer tip, sensitive clay, fissure, stress ratio Ko, overconsolidation.

Studies of some material constants of a SmC* ferroelectric liquid crystal mixture

Abstract The material constants, (1) the tilt angle (θ), (2) the helical pitch (Zo), (3) the spontaneous polarization (Ps), (4) the critical fields (Ec) to unwind the helix and (5) the switching time of ferroelectric liquid crystal mixture, FCS 101, in its SmC* phase have been studied. Our experimental data show that Ps∝ t0.5 and θ ∝ t0.3 at lower temperatures, where, t = (Tc−T)/Tc . The dependence of both the critical fields Ec and E'c on temperature are obtained experimentally. Ec , ΔE'c show the temperature relation as (Tc − T)0.53±0.04 and (Tc − T)0.59±0.01 respectively. The ratio of these critical fields, 0.71, is found to be temperature independent. The switching time is found to be of the same order (≃ 2 ms) as electro-optic response time. The agreement between the experimental and calculated P ko values is found to be poor. This discrepancy shows the inadequency of the theory so far developed. The differences between the real and ideal situations are discussed.

Soil Hydrology in Lodgepole Pine Ecosystems in Southeastern Wyoming

AbstractThe rates and pathways of water movement through the soil were examined in several lodgepole pine (Pinus contorta ssp. latifolia) forests in southeastern Wyoming to improve our understanding of the dynamics of solute flux in forest ecosystems. We employed internal drainage and tracer pulse methods to determine hydraulic conductivity, and we examined snowmelt infiltration and drainage water chemistry on contrasting soils supporting lodgepole pine forests. Saturated hydraulic conductivity (Ko) values were lognormally distributed for 27 plots at each of two sites examined. The median value was significantly higher at a site on a gravelly, loamy‐sand (median Ko = 1.20 cm/h) than on a bouldery, sandy‐loam (Ko = 0.49). At these sites the high range in both Ko values and in the transit time for a Cl‐ pulse were suggestive of highly variable water flow pathways through the soil. Early in the spring snowmelt period much of the infiltrating water circumvented the soil matrix, probably flowing around entrapped air pockets and through macropores. Although large systematic differences in chemistry were not observed between soil solutions collected with tension and tensionless lysimeters, saturated flow (collected as drips from the ceiling of soil tunnels) contained about three times lower cation concentrations than the lysimeter solutions. To obtain more accurate estimates of nutrient leaching from the tree rooting zone better quantification of the chemistry of percolating soil water is needed.

Characterization of high affinity receptor sites for atrial natriuretic factor in anterior pituitary gland: Evidence for the existence of two receptor forms

The present study shows that in rat anterior pituitary tissue atrial natriuretic factor (ANF) binds to two distinct receptor forms, with apparent molecular weights of about 166K and 58K. Binding assays carried out with (125I)-ANF revealed specific and high affinity non-interacting binding sites, with Ko values of 1-1.7 nM and a density of 10-15,000 sites/cell. rANF fragments (5-25), (5-27) and (5-28) exhibited apparent equipotency in displacing tracer binding, while fragment (13-28) and various other peptides were ineffective. ANF (5-25) was about 100-times less potent than ANF (8-33) in stimulating half-maximum pituitary cGMP production. These data indicate the presence of multiple binding sites for ANF in the pituitary gland and suggest that only part of these sites may be coupled to activation of guanylate cyclase.

Purification and properties of Bacillus acidopullulyticus pullulanase.

Two active forms (F1 and F2) of Bacillus acidopullulyticus pullulanase (EC 3.2.1.41 pullulan 6-glucanohydrolase) from Promozyme 200L (Novo Industri A/S) were purified using 50% (v/v) acetone precipitation and chromatographies on CM-Toyopearl 650S, Toyopearl HW-55S, and Butyl-Toyopearl 650S columns. The FI and F2 forms showed single bands in polyacrylamide gel electrophoresis with or without sodium dodecyl sulfate. The optimum pHs and specific activities of F1 and F2 were about 5.0 and 200 ∼ 220 units/mg, respectively. The molecular weights of F1 and F2 were estimated as 115,000 and 116,000, and their isoelectric points were 5.0 and 5.2. The values of F1 and F2 for pullulan were the same, 2.5 mm glucose equivalents, and their ko values were calculated as 2.9 × 103 and 3.6 × 103 s−1, respectively, from the Lineweaver-Burk plots. These Ko values of F and F2 for pullulan are larger than that (2.9 × 102 sec−1 of Klebsiella pneumoniae pullulanase. The activities of F1 and F2 on glycogen β-limit dextrins were 26...

Acetylcholine receptor: channel-opening kinetics evaluated by rapid chemical kinetic and single-channel current measurements

A combination of rapid chemical kinetic (quench-flow) and single-channel current measurements was used to evaluate kinetic parameters governing the opening of acetylcholine-receptor channels in the electric organ (electroplax) of Electrophorus electricus. Chemical kinetic measurements made on membrane vesicles, prepared from the E. electricus electroplax, using carbamoylcholine (200 microM-20 mM) at 12 degrees C, pH 7.0, and in the absence of a transmembrane voltage, yielded values for K1 (dissociation constant for receptor activation), phi (channel closing equilibrium constant), J (specific reaction rate for ion flux), and alpha max (maximum inactivation rate constant) of 1 mM, 3.4, 4 x 10(7) M-1 s-1, and 12 s-1, respectively. The single-channel current recordings were made with cells also from the E. electricus electroplax, at the same temperature and pH as the chemical kinetic measurements, using carbamoylcholine (50 microM-2 mM), acetylcholine (500 nM), or suberyldicholine (20 nM). Single-channel current measurements indicated the presence of a single, unique open-channel state of the E. electricus receptor, in concurrence with previous, less extensive measurements. The rate constant for channel closing (kc) obtained from the mean open time of the receptor channel is 1,100 s-1 for carbamoylcholine, 1,200 s-1 for acetylcholine, and 360 s-1 for suberyldicholine at zero membrane potential; and it decreases e-fold for an 80 mV decrease in transmembrane voltage in each case. The decrease in mean open times of the receptor channel that is associated with increasing the carbamoylcholine concentration is interpreted to be due to carbamoylcholine binding to the regulatory (inhibitory) site on the receptor. An analysis of data obtained with carbamoylcholine showed that the closed times within a burst of channel activity fit a two-exponential distribution, with a concentration-independent time constant considered to be the time constant for carbamoylcholine to dissociate from the regulatory site, and a carbamoylcholine concentration-dependent, but voltage-independent, time constant interpreted to represent the rate constant for channel opening (k0). An analysis of the mean closed time data on the basis of the minimum model gives values for K1 and k0 of 0.6 mM and 440 s-1, respectively, with carbamoylcholine as the activating ligand. The values obtained for K1, phi (= kc/k0), J, and alpha from the single-channel current measurements using electroplax are in good agreement with the values obtained from the chemical kinetic measurements using receptor-rich vesicles prepared from the same cells. These results confirm the assumed basic agreement between two entirely different methodologies and underlie the strategy of using the two techniques to obtain complementary information in time and ligand-concentration regions where only one or the other technique can be used. This agreement between results allows estimates to be made of the ko values, for both acetylcholine and suberyldicholine, from the phi values obtained from the chemical kinetic measurements and the kc values obtained in single-channel current measurements.

Small artery occlusion: A theoretical approach to the definition of coronary architecture and resistance by a branching tree model

The aim of this study was to evaluate the theoretical possibility of assessing the architecture of the coronary small artery circulation in vivo by the analysis of the increments in the total resistance of the vascular system caused by the progressive occlusion of the terminal vessels as would be possible in animal experiments by microsphere embolization. Different distributions of the resistance values of all the vessels have been obtained in branching tree models by means of only two parameters: (a) the resistance ratio between daughter and parent vessels at each branching site ( KO); and (b) the resistance ratio between the two daughter vessels at each branching site ( KV). Simulation of branching tree occlusion has been performed under two main conditions of resistance distribution: (1) symmetric resistance distribution, characterized by equal KO values at each branching site of the same level and by KV = 1, that is, equal resistance values for the vessel of the same level; and (2) asymmetric resistance distribution in dichotomous branching trees, wherein all the vessels may have different values of resistance; the variability in these values has however been restricted on the basis of physiological considerations. The analysis of the function of the total resistance vs the number of occluded vessels, obtained by a simulated progressive occlusion of the terminal vessels in these two systems, gives the following results: (1) in a symmetric branching tree, discontinuities are present in the occlusion function which permit identification of both the architecture and the resistance value of each single vessel of any unknown vascular tree; and (2) in the asymmetric model, the function does not allow a direct definition of the branching architecture and the values of resistance of each vessel; however, also in this case, any branching tree can be analyzed by means of a nonlinear optimization procedure which produces an equivalent symmetric branching tree. We conclude that, theoretically, the analysis of the occlusion function represents a valuable indirect approach to the quantitative study of the coronary microcirculation as well as of other vascular districts under steady flow conditions.

The diffusion and electrogenic components of the membrane potential of hypoxic myocardium.

The diffusion and electrogenic components of the resting potential of hypoxic ventricular muscle were separated by inhibition of the sodium pump with 10(-4) M ouabain. The response to varying external K concentrations (Ko) was studied. Arterially perfused rabbit hearts were submitted to 60 min hypoxia in Krebs solution containing 5 mM K throughout or to different external K concentrations during the last 20 min of hypoxia. For K concentrations between 1.5 and 10 mM, hypoxia did not change the resting potential except for a slight hyperpolarization in 7.5 mM K. The diffusion component of the resting potential did not differ from the resting potential at Ko less than 5 mM. An electrogenic potential of -3 to -6 mV was detectable at Ko values between 5 and 10 mM. The internal K concentration, Ki, was estimated from extrapolations to zero potential of the relation resting potential vs. Ko in normoxic and hypoxic hearts. These experiments revealed a decline of Ki of 16 mM with hypoxia. The variation of the diffusion potential with external K was fitted by a PNa:PK ratio five times lower than in normoxia. It has been concluded that an increase in K permeability and the persistence of electrogenic Na extrusion during hypoxia of rather short duration prevent membrane depolarization despite the myocardial K loss.

Ion mobility detection after supercritical fluid chromatography

AbstractUsing a unidirectional flow ion mobility detector, non‐selective detection, tunable selective detection, and complete Fourier transformed ion mobility spectra were successfully obtained after supercritical fluid chromatography on compounds with higher molecular weights than have been previously investigated. In the most selective mode, single oligomers from polymeric material could be independently detected. Using the Fourier transform capabilities of this instrument, complete ion mobility spectra for each oligomer could be obtained in a single chromatographic separation. The collection of individual ion mobility spectra of the components of polymeric material has not been possible prior to the technique described in this paper. Only complex ion mobility spectra of polymeric mixtures are available in the literature. The spectra obtained in this study are all simple, uncomplicated spectra consisting of only one or two product ion peaks. Ko values reported in this work range from 0.633 to 1.61, which are some of the lowest values ever reported in ion mobility spectrometry.With the unidirectional flow design of the detector, the supercritical fluid mobile phase, carbon dioxide, was efficiently eliminated from the detector so that the ion mobility spectrometer could be operated in its normal manner. The fact that CO2 did not interfere with normal ion mobility operation indicates that other supercritical fluids may also be compatible with this sensitive and versatile detection method.

Evaluation of Simplified Methods for Determining Unsaturated Hydraulic Conductivity of Layered Soils

AbstractThe simplified field method of L.R. Ahuja et al. (1980) for determining hydraulic conductivity as a function of soil water suction, K(S), and the simplified field method of P.L. Libardi et al. (1980) for determining hydraulic conductivity as a function of soil water content, K(θ), were compared with the instantaneous profile method, to evaluate their suitability for estimating hydraulic conductivity of layered soil. The Ahuja method worked well on coarse and fine‐textured soils and complex soil profiles with stratification. The Libardi method worked well on coarse and fine‐textured, homogeneous materials and homogeneous parent materials underlying stratified soil materials. A calculated matching value (Ko) was used with the Libardi method. Within layered soil materials slopes of the K(θ) curves, calculated with the Libardi method, were adequate; however, calculated Ko values were often inadequate. Fit of calculated values with measured values of hydraulic conductivity could have been improved by using field‐determined Ko values.

Subsite affinity of a glucoamylase from Aspergillus saitoi.

In order to investigate the subsite structure of the glucoamylase from Asp. saitoi, kinetic parameters (Km and ko values) of the enzyme for various sizes of maltooligosaccharide substrates were measured. The subsite affinities of this enzyme were calculated from the kinetic parameters and compared with those of the Rhizopus sp. glucoamylase, which differs from the Asp. saitoi glucoamylase in molecular weight, pI and of course, origin. The characteristic features of the subsite affinities of glucoamylase from Rhizopus, reported by Hiromi and his colleagues [Agric. Biol. Chem., 47, 573 (1983); Biochim. Biophys. Acta, 302, 362 (1973)], were retained in the glucoamylase from Asp. saitoi. However, the kint value for the glucoamylase from Asp. saitoi was about half of that for the enzyme from Rhizopus sp.

Effect of orally administered hydrocortisone on the rate of aqueous flow in man.

We studied the possible influence on the rate of aqueous flow of peroral hydrocortisone in 8 normal eyes of 8 normal subjects by means of fluorophotometry. In the control period, the mean value of ko obtained was 0.011 +/- 0.0023 min, where ko was the loss coefficient from the anterior chamber. On another day (hydrocortisone trial period), fluorophotometry was again performed after giving a dose of oral hydrocortisone (80 mg) and the mean value of ko obtained was 0.020 +/- 0.0027/min. The mean difference in ko values between the control period and the hydrocortisone trial period was significant (P less than 0.001). An increased rate of aqueous flow after giving a dose of oral hydrocortisone was demonstrated.