Simulation of Runoff Hydrograph on Soil Surfaces with Different Microtopography Using a Travel Time Method at the Plot Scale

In this study, a simple travel time-based runoff model was proposed to simulate a runoff hydrograph on soil surfaces with different microtopographies. Three main parameters, i.e., rainfall intensity (I), mean flow velocity (v _m) and ponding time of depression (t _p), were inputted into this model. The soil surface was divided into numerous grid cells, and the flow length of each grid cell (l _i) was then calculated from a digital elevation model (DEM). The flow velocity in each grid cell (v _i) was derived from the upstream flow accumulation area using v _m. The total flow travel time through each grid cell to the surface outlet was the sum of the sum of flow travel times along the flow path (i.e., the sum of l _i/v _i) and t _p. The runoff rate at the slope outlet for each respective travel time was estimated by finding the sum of the rain rate from all contributing cells for all time intervals. The results show positive agreement between the measured and predicted runoff hydrographs.     

CRITICAL INTENSITY AND FLASH DURATION FOR RESPONSE TO FLICKER: WITH ANAX LARVAE

Determinations of the flicker response curve (F – log I_m) with larvae of Anax junius (dragonfly) for various ratios t_L/t_D of light time to dark time in a flash cycle provide relations between t_L/t_D and the parameters of the probability integral fundamentally describing the F – log I function, including the variability of I. These relations are quantitatively of the same form as those found for this function in the sunfish, and are therefore non-specific. Their meaning for the theory of reaction to visual flicker is discussed. The asymmetry of the Anax curve, resulting from mechanical conditions affecting the reception of light by the arthropod eye, is (as predicted) reduced by relative lengthening of the fractional light time in a cycle.     

Half-time analysis of the integrated Michaelis equation. Simulation and use of the half-time plot and its direct linear variant in the analysis of some α-chymotrypsin-, papain- and fumarase-catalysed reactions

Substitution of half-time parameters in the integrated form of the Michaelis–Menten equation for any enzyme-catalysed reaction yields an equation that gives a linear relationship between the half-time of the reaction and the substrate concentration at that point of the reaction. The logarithmic term of the integrated equation becomes a constant as a result of the substitution, which means that the use of the half-time plot of the equation requires calculation only of half-time and substrate-concentration values at various stages of the reaction. The half-time method is both simple and exact, being analogous to an [S₀]/v_i against [S₀] plot. A direct linear form of the half-time plot has been devised that allows very simple estimation of Michaelis parameters and/or initial velocities from progress-curve data. This method involves no approximation and is statistically valid. Simulation studies have shown that linear-regression analysis of half-time plots provides unbiased estimates of the Michaelis parameters. Simulation of the effect of error in estimation of the product concentration at infinite time [P_∞] reveals that this is always a cause for concern, such errors being magnified approximately an order of magnitude in the estimate of the Michaelis constant. Both the half-time plot and the direct linear form have been applied to the analysis of a variety of experimental data. The method has been shown to produce excellent results provided certain simple rules are followed regarding criteria of experimental design. A set of rules has been formulated that, if followed, allows progress-curve data to be acquired and analysed in a reliable fashion. It is apparent that the use of modern spectrophotometers in carefully designed experiments allows the collection of data characterized by low noise and accurate [P_∞] estimates. [P_∞] values have been found, in the present work, to be precise to within ±0.2% and noise levels have always been below 0.1% (signal-to-noise ratio1000). As a result of the considerations above, it is concluded that there is little to be feared with regard to the analysis of enzyme kinetics using complete progress curves, despite the generally lukewarm recommendations to be found in the literature. The saving in time, materials and experimental effort amply justify analysis of enzyme kinetics by progress-curve methods. Half-time plots linear to ≥90% of reaction have been obtained for some α-chymotrypsin-, papain- and fumarase-catalysed reactions.     

Analysis of starch amylolysis using plots for first-order kinetics

Investigators often study product release from starches during prolonged incubations with α-amylase in vitro. The reaction time courses usually fit to a linear form of a first order rate equation, i.e., ln[(C_∞ − C_t)/C_∞] = −kt. This equation calls for an accurate estimate of C_∞, i.e., the concentration of product at the end of the reaction. Estimates of C_∞ from digestibility curves can be unreliable. The Guggenheim method does not require prior knowledge of C_∞ but seems not to have been applied to starch hydrolysis data. An alternative method is also available in which the logarithm of the slope (LOS) of a digestibility curve at various time points is plotted against time. This allows estimations of both k and C_∞ and can also reveal whether changes occur in digestion rate from rapid to slow as digestion proceeds. We describe the Guggenheim and LOS methods and provide examples of their application to starch digestibility data.     

THE IONIC ACTIVITY OF GELATIN

2.5 and 1.25 per cent gelatin have been titrated potentiometrically in the absence of salts and in the presence of two concentrations (0.0750 and 0.0375µ) of NaCl, MgCl₂, K₂SO₄, and MgSO₄. The data have been used to calculate values of ± S = v^z – (v – 1)^z, where v^z = v ² – (v ² – v) r_x/18. The maximum and minimum values of S with NaCl were used to calculate the mean distance (r_x) between like charges in gelatin. This is found to be 18 Å.u. or over (between acid or basic groups) which agrees with the probable value and the titration index dispersion. Thus the data with NaCl are shown to be normal and to obey the equation found to hold for simple weak electrolytes; namely, pK'' – pK = Sa See PDF for Equation where S is related to the valence and distance by the above equations. Using the NaCl data as a standard the deviations (ΔS) produced by the other salts are calculated and are found to agree quantitatively with the deviations calculated from equations derived for the simple weak electrolytes. This shows that in gelatin, as in the simple electrolytes, the deviations are related to the "apparent valences" (values which are a function of the true valence and the distance between the groups). The maximum "apparent valences" of gelatin are 2.4 for acid groups (in alkaline solution) and 1.8 for basic groups (in acid solution). These values correspond to the hypothetical condition of zero distance between the groups. They have no physical significance but have a practical utility first as mentioned above, and second in that they may be used in the unmodified Debye-Hückel equation to give the maximum effect of gelatin on the ionic strength. The true effect is probably even lower than these values would indicate. The data indicate that gelatin is a weak polyvalent ampholyte having distant groups and that the molecule has an arborescent structure with interstices permeated by molecules of the solvent and other solutes. The size and shape probably vary with the pH.     

Estimation of Growth Rate from the Mitotic Index

The growth rate of a eukaryotic population dividing at a constant rate can be estimated from the equation, t_m/g ln 2 = ln (1 + R), in which t_m is the time required for mitosis, g is the generation time, and R is the fraction of cells undergoing mitosis. Values for t_m and R can be determined by direct microscope examination of the population. The validity of the derived equation has been checked with an exponentially growing culture of a prokaryote, Escherichia coli, in which chloramphenicol was administered to inhibit protein synthesis. Cells having enough protein completed the division process whereas the rest of the population was inhibited. From the plot of the growth curve before and after administration of chloramphenicol, t_m and R were estimated. The calculated and actual growth rates were almost identical.     

Improvement in lipase-catalyzed methanolysis of triacylglycerols for biodiesel production using a solvent engineering method

A solvent engineering strategy was applied to the lipase-catalyzed methanolysis of triacylglycerols for biodiesel production. The effect of different pure organic solvents and co-solvent mixtures on the methanolysis was compared. The substrate conversions in the co-solvent mixtures were all higher than those of the corresponding pure organic solvents. Further study showed that addition of co-solvent decreased the values of |log P_interface − log P_substrate| and thus led to a faster reaction. The more the values of |log P_interface − log P_substrate| decreased, the faster the reaction proceeded and the higher the conversion attained. Different co-solvent ratio was further investigated. The co-solvent mixture of 25% t-pentanol:75% isooctane (v/v) was optimal, with which both the negative effects caused by excessive methanol and by-product glycerol could be eliminated. There was no obvious loss in lipase activity even after being repeatedly used for 60 cycles (720 h) with this co-solvent mixture as reaction medium. Other lipases and lipase combinations can also catalyze methanolysis in this co-solvent mixture. Furthermore, other vegetable oils were also explored for biodiesel production in this co-solvent mixture and it had been found that this co-solvent mixture media has extensive applicability.     

Ultrasound biomicroscopy for longitudinal studies of carotid plaque development in mice: validation with histological endpoints

Atherosclerosis is responsible for the death of thousands of Americans each year. The carotid constriction model of plaque development has recently been presented as a model for unstable plaque formation in mice. In this study we 1) validate ultrasound biomicroscopy (UBM) for the determination of carotid plaque size, percent stenosis, and plaque development in live animals, 2) determine the sensitivity of UBM in detecting changes in blood flow induced by carotid constriction and 3) test whether plaque formation can be predicted from blood flow parameters measured by UBM. Carotid plaques were induced by surgical constriction in Apo E−/− mice. Arteries were imaged bi-weekly by UBM, at which time PW-Doppler measurements of proximal blood flow, as well as plaque length and percent stenosis were determined. Histology was performed 9 weeks post surgery. When compared to whole mount post-mortem measurements, UBM accurately reported carotid plaque length. Percent stenosis, based on transverse B-mode UBM measurements, correlated well with that calculated from histological sections. PW-Doppler revealed that constriction reduced maximum systolic velocity (v_max) and duration of the systolic velocity peak (t_s/t_t). Pre-plaque (2 week post-surgery) PW-Doppler parameters (v_max and t_s/t_t) were correlated with plaque length at 9 weeks, and were predictive of plaque formation. Correlation of initiating PW-Doppler parameters (v_max and t_s/t_t) with resulting plaque length established the degree of flow disturbance required for subsequent plaque development and demonstrated its power for predicting plaque development.     

Estimation of viscosity from passage time of liquids flowing through a microchannel array

Recently, a microchannel flow analyzer (MC-FAN) has been used to study the flow properties of blood. However, the correlation between blood passage time measured by use of the MC-FAN and hemorheology has not been clarified. In this study, a simple model is proposed for estimation of liquid viscosity from the passage time t _p of liquids. The t _p data for physiological saline were well represented by the model. According to the model, the viscosity of Newtonian fluids was estimated reasonably well from the t _p data. For blood samples, although the viscosity $ \eta_{\text{mc}} $ estimated from t _p was shown to be smaller than the viscosity $ \eta_{{450{\text{s}}^{ - 1} }} $ measured by use of a rotatory viscometer at a shear rate of 450 s^?1, $ \eta_{\text{mc}} $ was correlated with $ \eta_{{450{\text{s}}^{ - 1} }} $ . An empirical equation for estimation of $ \eta_{{450{\text{s}}^{ - 1} }} $ from $ \eta_{\text{mc}} $ of blood samples is proposed.     

Specific features of the kinetics of H2-O2-O2(a 1Δ g ) mixtures: I. formation and quenching of electronically and vibrationally excited (A′) molecules in H2-O2-O2(A 1Δ g ) mixtures at a temperature of 300 K

Available data on the kinetic processes in H₂-O₂-O₂(a ¹Δ _g ) mixtures are analyzed theoretically, and the ranges in which the rate constants of these processes can vary are determined. The processes of energy transformation in an O₂(a ¹Δ _g )-H₂-H-HO₂ system in the approximations of the fast and slow (in comparison with the vibrational relaxation time of the HO₂ radical) quenching of the electronically excited state are considered. The experiments on the quenching of singlet delta oxygen (SDO) molecules O₂(a ¹Δ _g ) excited in a microwave discharge at a temperature of 300 K and pressure of 6 Torr in a lean hydrogen-oxygen mixture are simulated (by a lean fuel mixture is meant a mixture in which the ratio of the fuel to the oxidizer mass fraction is less than the stoichiometric ratio, which is 2: 1 for a hydrogen-oxygen mixture). It is shown that, over the experimental observation times, the SDO quenching frequency depends on the concentration of molecular hydrogen, the residual odd oxygen fraction in the gas flow, and the ratio between the rate constants of kinetic processes involving HO₂ and HO₂* radicals. Simulations of the microwave discharge and the transport of excited oxygen along the drift tube make it possible to determine the residual odd oxygen concentration in the gas flow. Recommendations on the choice of the rate constants for the O₂(a ¹Δ _g ) + HO₂)A″, v₃″ = 0) ? O₂ + HO₂*(A′, v₃′ = 1), HO₂*(A′v₃′ ≤ 1) + O₂(a ¹Δ _g ) → HO₂*(A′,v₃′ ≥ 6) + O₂, and HO₂*(A′,v₃′ ≤ 1) + O₂(a ¹Δ _g ) → H + O₂ + O₂ processes are given. It is shown that, in the case of slow quenching in a H₂-O₂-O₂(a ¹Δ _g ) mixture at a low temperature, the intensity of hydrogen oxidation is enhanced due to the reaction + HO₂*(A′,v₃′ ≤ 1) + O₂(¹Δ) → H + O₂ + O₂.     

Embryonic development of the European smelt Osmerus eperlanus eperlanus (L.) (Neva population)

The embryonic development of the European smelt Osmerus eperlanus eperlanus has been described. The whole period of the development has been subdivided into 6 subperiods. More than 80 stages may be described for all of these periods. The development of the European smelt embryo was studied in the 5 different regimes of a constant temperature in the range 9.5–18.3°C. The duration of different stages under different temperature regimes was expressed in the relative units of τ₀ (the time of a single cleavage) and τ_s (the time of formation of a single pair of somites). It was established that the τ_s value had proportionally changed by embryogenesis. Due to this fact, the duration of the stages was expressed only as τ_s. The dependency of the speed of the European smelt embryogenesis on temperature has been shown. This dependence was expressed using the standard interval τ_s and described using the equation log τ_s(t) = 3.22665?0.13876t + 0.00297t ², where t is the temperature.     

Cytogenetics of the South American DROSOPHILA MULLERI Complex: The MARTENSIS Cluster. More Interspecific Sharing of Inversions

Three Drosophila mulleri complex species have been found to be endemic to the cactus regions of northern South America. The three species are morphologically distinct, and no hybridization between species has been found in either the laboratory or nature. An analysis of their salivary gland chromosomes revealed that they evolved from a single cytological population, subspecies F of the ancestor of the D. mulleri complex, and comprise a cluster of sister species that are homozygous for inversions not found elsewhere. Within the martensis cluster are also found several inversions that are unique for these species, but have segregated out among the three species. Thus 2f² is found in martensis and starmeri, but not in uniseta, while 2t⁶, 3v and 3w are found in starmeri and uniseta, but not in martensis. This is analogous to the situation found within the remainder of the mulleri complex species, all the members of which share homozygosity for six other inversions. An interpretation of the cytological evolution of the martensis cluster is proposed.     

Effect of temperature on the embryonic development of the plaice, Pleuronectes Platessa L. (teleostei)

In normalyears, eggs and prolarvae of the plaice (Pleuronectes platessa L.) in the southern North Sea develop within the temperature range 6.0–8.5 °C, although the water may at times be some degrees colder or warmer than this. The effect of temperature, t °C, on the embryonic development time, D days, has been investigated within the tolerated range 2.8–10.5 °C. Various models to express the observed curvilinear relationship between t and D have been considered, that giving the closest fit to the data being (t−t₀)(D−D₀) = k or $\text{D =}\text{k}\text{(t−t}{}_0\text{)+D}{}_0$. A method is given for the calculation of constants k, D₀, and t₀. The relationship may also be expressed by the equation D = a(t−t₀)^b where a and b are constants, but t₀ must in this case be found by iteration. At investigated temperatures in the range 4.1–10.5 °C the smallest eggs in a batch from a single source hatched first. Within the tolerated range, hatching prolarvae were substantially smaller at 10.5 °C than at the other temperatures. During the period of prolarval yolk utilization, growth is slower at the high temperatures, so that median temperatures of 6.5–8.0 °C are most efficient in terms of the relationship between growth in length and yolk utilization. Toward the end of the yolk-sac phase, the rate of yolk utilization declines unless a suitable external food source (e.g., Artemia nauplii) is provided.     

Magnetic susceptibility equation for dinuclear high-spin cobalt(II) complexes considering the exchange interaction between two axially distorted octahedral cobalt(II) ions

A new magnetic susceptibility equation has been obtained for dinuclear high-spin cobalt(II) complexes considering the exchange interaction between two axially distorted octahedral cobalt(II) ions. A computational program has been developed, and the temperature dependencies of the magnetic susceptibility have been demonstrated. A characteristic χ_A versus T curve due to the zero-field splitting was shown when the distortion parameter v was positive.     

A rapid assay for the binding of actinomycin to DNA.

The theory of countercurrent distribution (CCD) was reviewed and extended. The separation function for the fundamental distribution of CCD was presented in the form n = t²(αk₁+β)²/αk₁(β?1)² where n is the number of transfers, t the abscissa of the standard normal distribution, α = v_m/v₈ the phase ratio, β = k₁/k₂≥ 1 the separation factor, and k₁ the partition coefficient of the more radidly moving component; n was found to be minimal on the condition αk₁ = β. The separation function for the single withdrawal of CCD was obtained in the form N = u + 1 = t²{(αk₁ + 1)^1/2 + [β(αk₁ + β)]^1/2}²/(β ? 1)²+ 1, where N is the number of partition units. From this equation it appears that N is minimal when αk₁ = 0. Compared with the former separation functions presented in the literature, these separation functions have the advantage of giving directly the relationships among the phase ratio, the absolute partition coefficient, the separation factor, the resolution degree, and the number of transfers or partition units required. In addition, the dependencies of the elution volumes and the widths of the elution curves on α, β, and the partition coefficients were considered mathematically by means of differential calculus. The elution volumes were found to have minima at certain αk₁ values. The standard deviations, on the contrary, did not have minima in respect to αk₁. The theory presented can be used for selecting proper operating conditions while separating chemical compounds.     

Effect of acyl chain length on selective biocatalytic deacylation on O-aryl glycosides and separation of anomers

It has been demonstrated that Lipozyme® TL IM (Thermomyces lanuginosus lipase immobilised on silica) can selectively deacylate the ester function involving the C-5′ hydroxyl group of α-anomers over the other acyl functions of anomeric mixture of peracylated O-aryl α,β-D-ribofuranoside. The analysis of results of biocatalytic deacylation reaction revealed that the reaction time decreases with the increase in the acyl chain length from C₁ to C₄. The unique selectivity of Lipozyme® TL IM has been harnessed for the separation of anomeric mixture of peracylated O-aryl α,β-D-ribofuranosides, The lipase mediated selective deacylation methodology has been used for the synthesis of O-aryl α-D-ribofuranosides and O-aryl β-D-ribofuranosides in pure forms, which can be used as chromogenic substrate for the detection of pathogenic microbial parasites containing glycosidases.     

THE KINETICS OF OSMOTIC SWELLING IN LIVING CELLS

The rate of swelling of unfertilized sea urchin eggs in hypotonic sea water was investigated. Analysis of curves leads to the following conclusions. 1. The rate of swelling follows the equation, See PDF for Equation where V _eq., V ₀, and V_t stand for volume at equilibrium, at first instant, and at time t, respectively, the other symbols having their usual significance. This equation is found to hold over a wide range of temperatures and osmotic pressures. This relation is the one expected in a diffusion process. 2. The rate of swelling is found to have a high temperature coefficient (Q ₁₀ = 2 to 3, or µ = 13,000 to 19,000). This deviation from the usual effect of temperature on diffusion processes is thought to be associated with changes in cell permeability to water. The possible influence of changes in viscosity is discussed. 3. The lower the osmotic pressure of the solution, the longer it takes for swelling of the cell. Thus at 15° in 80 per cent sea water, the velocity constant has a value of 0.072, in 20 per cent sea water, of 0.006.     

Relations between root length densities and root intersections with horizontal and vertical planes using root growth modelling in 3-dimensions

The root growth simulation model of Diggle (ROOTMAP; 1988) was modified to allow the numerical output of data on root intersections with horizontal and vertical planes. ROOTMAP was used to generate two three-dimensional model structures of fibrous root systems. The lateral roots were oriented randomly (geotropism index=0) but the main axes were positively gravitropic (geotropism index=0.6). The mean density of root intersections (n, cm^-2) with the sides of a series of 5×5×5 cm cubic volumes was related approximately linearly to the root length density (L_t cm^-2) within each volume by the equation L_t=2.3n (correlation coefficient, r=0.981). This compared with the relation of L_t=2n predicted theoretically for randomly oriented lines (Melhuish and Lang, 1968). Root length density was related to the intersection density by the equation L_t=2.43n_v (r=0.940) for the vertical faces and L_t=1.88n_h (r=0.984) for the horizontal faces. L_t/n_v was greater than L_t/n_h because of the preferential vertical orientation of the main root axes. The Melhuish and Lang (1968) equation does not generally give accurate prediction of root length density from field experiment data. Under field conditions, values have been reported in the ranges of 1.4 to 16 for L_t/n_h, and 3.8 to 9 for L_t/n_v. The most likely explanation for this difference is that only a small proportion (e.g. about 20–30%) of the actual number of roots are counted using the core-break and root mapping (including the trench wall) methods, due to the practical experimental difficulties of identifying individual fine roots under field conditions. Detailed experimental studies are needed to identify what portion of the root system is recorded using these field techniques (e.g. whether the main root axes are counted while the fine lateral roots remain undetected). Three-dimensional models of root growth provide a new method of studying the relations between L_t, n_v and n_h for root systems generated stochastically according to known geometrical rules. Using these models it will be possible to determine the effects of the degree of gravitropism and of root branching on the value and on the variability of L_t/n_h and L_t/n_v. The effectiveness of the statistical corrections that have been developed to correct for non-random root orientation can also be evaluated, as can the effects of sample position.     

Multiple liquid-liquid partition: II. Theory of Martin-Synge distribution (MSD)

The theory of Martin-Synge distribution (MSD) was refined, with special attention being focused upon the derivation of the separation functions. The separation function for the fundamental distribution of MSD was obtained in the form v = t²(αk₁ + 1)(αk₁ + β)[(αk₁ + 1)^1/2 + (αk₁ + β)^1/2]²/αk₁(β ? 1)², where ν is the number of aliquots v_m driven through the apparatus, t the abscissa of the standard normal distribution, α = v_m/v₈ the phase ratio, β = k₁/k₂≥ 1 the separation factor, and k₁ the partition coefficient of the more rapidly moving component; ν was shown to have minima at given αk₁ values. The separation function of the single withdrawal of MSD was presented in the form N = u + 1 = t²(2αk₁ + β + 1)²/(β ? 1)²+ 1, where N is the number of partition units; N is minimal when αk₁ = 0. The elution volumes and standard deviations of the two compounds to be separated were mathematically analyzed in a manner similar to that previously presented when dealing with the theory of counter-current distribution (CCD). As in CCD, the elution volumes in MSD were found to have minima at given αk₁ values. However, the standard deviations of the elution curves also have minima in respect to αk₁ in MSD, which is a different situation as compared to CCD. The selection of optimal operating conditions was found to be more critical in MSD than in CCD.