The effect of root architecture on the shearing resistance of root-permeated soils

This paper aims to investigate the effect of the root architecture on the shear strength increment provided by plant roots in the soil. In situ shear tests were conducted for this purpose. Five plant species – Hibiscus tiliaceus L. (Linden hibiscus), Mallotus japonicus (Thunb.) Muell.-Arg. (Japanese Mallotus), Sapium sebiferum (L.) Roxb. (Chinese tallow tree), Casuarina equisetifolia L. (ironwood), and Leucaena leucocephala (Lam.) (white popinac) – were used in this study. Tensile tests on roots of various diameters and surveys on the root system structure were carried out for each of the plant species tested. The shear strength increments (ΔS) provided by the roots of Linden hibiscus, Japanese Mallotus, Chinese tallow tree, ironwood, and white popinac were 0.34t_R, 0.462t_R, 0.688t_R, 0.3t_R, and 0.87t_R, respectively, when t_R was estimated on the basis of the tensile root strength crossing through the shear plane. The shear strength increment provided by plant roots with conspicuous oblique and vertical roots was greater than that of root structures in which lateral roots were dominant. In comparison with other types of root architecture, the R-type root architecture was found to be the most effective root system against shear failure in the soil. Its shear strength increment was slightly greater than that with the V-type root architecture, followed by the VH-type root architecture. The shear strength increment provided by plants with the H-type root architecture was less effective than that contributed by plant species with other types of root architecture.     

A rapid gravimetric method for estimating calcium carbonate in soils

Summary A simple gravimetric procedure is offered for determining carbonates in soil.     

A theoretical model for estimating the margination constant of leukocytes

Background  

Blood leukocytes constitute two interchangeable sub-populations, the marginated and circulating pools. These two sub-compartments are found in normal conditions and are potentially affected by non-normal situations, either pathological or physiological. The dynamics between the compartments is governed by rate constants of margination (M) and return to circulation (R). Therefore, estimates of M and R may prove of great importance to a deeper understanding of many conditions. However, there has been a lack of formalism in order to approach such estimates. The few attempts to furnish an estimation of M and R neither rely on clearly stated models that precisely say which rate constant is under estimation nor recognize which factors may influence the estimation.     

A comparison of the parameter estimating procedures for the Michaelis-Menten model

The performance of four parameter estimating procedures for the estimation of the adjustable parameters in the Michaelis-Menten model, the maximum initial rate Vmax, and the Michaelis-Menten constant Km, including Lineweaver & Burk transformation (L-B), Eadie & Hofstee transformation (E-H), Eisenthal & Cornish-Bowden transformation (ECB), and Hsu & Tseng random search (H-T) is compared. The analysis of the simulated data reveals the followings: (i) Vmax can be estimated more precisely than Km. (ii) The sum of square errors, from the smallest to the largest, follows the sequence H-T, E-H, ECB, L-B. (iii) Considering the sum of square errors, relative error, and computing time, the overall performance follows the sequence H-T, L-B, E-H, ECB, from the best to the worst. (iv) The performance of E-H and ECB are on the same level. (v) L-B and E-H are appropriate for pricesly measured data. H-T should be adopted for data whose error level are high. (vi) Increasing the number of data points has a positive effect on the performance of H-T, and a negative effect on the performance of L-B, E-H, and ECB.     

A method for estimating the diffusion resistance of the unstirred layer of microorganisms

A general enzyme-mediated flux equation which incorporates diffusion resistance was derived. By fitting the model to phosphate flux data from a blue-green alga, Anacystis nidulans, diffusion resistance, the half-saturation constant and maximal uptake velocity were estimated. Diffusion resistance for this organism was estimated to be 29 s / cm with a relative precision of about 10%. The parameters were also estimated by graphical analysis of a Woolf plot, but this method was less precise and tended to yield biased estimates.     

A model for estimating the extent of variegation in mosaic tissues

A method is described which allows the size of patches of like cells in mosaic tissues to be estimated from the frequency with which small samples taken from the tissue contain both of the mosaic cell types. The mosaic patches are represented as close-packed geometric figures arranged in twoor three-dimensional tissues. Small samples drawn at random from these tissues will include portions of one or more patches; only those samples which include portions of two or more dissimilar patches (mixed samples) will contain both cell types. The expected frequency of mixed samples is calculated as a function of the shape of the mosaic patches, the frequency of the two mosaic cell types and the sample to patch size ratio. This expected frequency is not strongly dependent on patch shape for triangular, square and hexagonal patches in two dimensions or for cubic and orthotetrakaidekahedral patches in three dimensions. Elongation of square patches along one axis or of cubic patches along one or two axes results in slight increases in the expected frequency of mixed samples for given sample to patch size ratio.     

A test of a model for estimating production in the sea

Primary productivity was measured in the sea off the coasts of Florida and Georgia with the radiocarbon method at four stations during March, 1971. Integral photosynthesis per square meter surface was determined with a mathematical model from empirical data gathered from in situ and shipboard incubation experiments. The mathematical model provided shipboard incubators to be used to estimate primary production rates while overcoming the problem of relating light quality and quantity simulated by the incubators to that found in the euphotic zone. The use of shipboard incubation can allow for measurements to be made on a moving vessel, more stations visited per day and water samples incubated at a constant light intensity. Primary productivity at the four sampling stations ranged from 0.026 to 0.042 mg C/M² hr.     

A new method for estimating gross phosphorus mineralization and immobilization rates in soils

Phosphorus availability in soils is controlled by both the sizes of P pools and the transformation rates among these pools. Rates of gross P mineralization and immobilization are poorly known due to the limitations of available analytical techniques. We developed a new method to estimate P transformation rates in three forest soils and one grassland soil representing an Alfisol, an Ultisol, and Andisol, and a Mollisol. Three treatments were applied to each soil in order to separate the processes of mineral P solubilization, organic P mineralization, and solution P immobilization. One set of soils was retained as control, a second set was irradiated with -rays to stop microbial immobilization, and a third was irradiated and then autoclaved, also stop phosphatase activity. All three sets of samples were then incubated with anion exchange resin bags under aerobic conditions. Differences in resin P among the three treatments were used to estimate gross P mineralization and immobilization rates. Autoclaving did not affect resin-extractable P in any of the soils. Radiation did not alter resin-extractable P in the forest soils but increased resin-extractable P in the grassland soil. This increase was corrected in the calculation of potential P transformation rates. Effects of radiation on phosphatase activity varied with soils but was within 30% of the original values. Rates of P gross mineralization and immobilization ranged from 0.6–3.8 and 0–4.3 mg kg-soil^-1 d^-1, respectively, for the four soils. The net rates of solubilization of mineral P in the grassland soil were 7–10 times higher than the rates in forest soils. Mineralization of organic P contributed from 20–60% of total available P in the acid forest soils compared with 6% in the grassland soil, suggesting that the P mineralization processes are more important in controlling P availability in these forest ecosystems. This new method does not require an assumption of equilibrium among P pools, and is safer and simpler in operation than isotopic techniques.     

A model for estimating the medium properties of Avicel to ethanol conversion

Simultaneous saccharification and fermentation received an increasing level of attention over recent decades, with the primary focus on the development of improved enzyme and organism performance. Little literature is available on the effects of the various fermentation components on the apparent dynamic viscosity of the fermentation broth for use in reactor design and analysis. This work investigates density and settling properties of Avicel PH-101 particles and the effects of base medium composition, yeast concentration and cellulose particles on the apparent dynamic viscosity of the fermentation mixture. Dynamic viscosity measurements were obtained using a rotational viscometer equipped with a DG 26.7 double gap concentric cylinder measuring system. Results indicated that Avicel particles experience a greater drag force compared to similar sized spherical particles and have a measured density of 1,605.7 kg m^?3. The Ostwäld-de Waele formulation was used to describe the dynamic viscosity of the particles due to it shear-thinning nature. Correlation between the predicted particle effects and experimental results deviated with a root mean square error of 8.46 %.     

A real-time computational model for estimating kinematics of ankle ligaments

Background: An accurate assessment of ankle ligament kinematics is crucial in understanding the injury mechanisms and can help to improve the treatment of an injured ankle, especially when used in conjunction with robot-assisted therapy. A number of computational models have been developed and validated for assessing the kinematics of ankle ligaments. However, few of them can do real-time assessment to allow for an input into robotic rehabilitation programs. Method: An ankle computational model was proposed and validated to quantify the kinematics of ankle ligaments as the foot moves in real-time. This model consists of three bone segments with three rotational degrees of freedom (DOFs) and 12 ankle ligaments. This model uses inputs for three position variables that can be measured from sensors in many ankle robotic devices that detect postures within the foot–ankle environment and outputs the kinematics of ankle ligaments. Validation of this model in terms of ligament length and strain was conducted by comparing it with published data on cadaver anatomy and magnetic resonance imaging. Results: The model based on ligament lengths and strains is in concurrence with those from the published studies but is sensitive to ligament attachment positions. Conclusions: This ankle computational model has the potential to be used in robot-assisted therapy for real-time assessment of ligament kinematics. The results provide information regarding the quantification of kinematics associated with ankle ligaments related to the disability level and can be used for optimizing the robotic training trajectory.     

A concentric layer model for estimating the energy expenditure of the left ventricle

The energy cost of the left ventricle is quantitatively analyzed on the basis of the following assumptions: (1) The left ventricle is assumed to be an isotropic, homogeneous elastic, thick, spherical shell. (2) The ventricular wall is made up of a finite number of thin concentric shells. (3) The energetics of the left ventricle is in accordance with the second law of thermodynamics. An expression for the work done during ventricular contraction is derived according to the definition of physical work. The energy liberation during isovolumic contraction is formulated parallel to the concepts of heat production in skeletal muscle during isometric contraction. This expression gives the total work done per stroke in terms of mean systolic pressure, end diastolic volume, stroke volume and wall thickness during diastolic phase. Supported by a research fellowship and research grant from the Canadian Heart Foundation.     

A maximum pseudo-likelihood approach for estimating species trees under the coalescent model

Background  

Several phylogenetic approaches have been developed to estimate species trees from collections of gene trees. However, maximum likelihood approaches for estimating species trees under the coalescent model are limited. Although the likelihood of a species tree under the multispecies coalescent model has already been derived by Rannala and Yang, it can be shown that the maximum likelihood estimate (MLE) of the species tree (topology, branch lengths, and population sizes) from gene trees under this formula does not exist. In this paper, we develop a pseudo-likelihood function of the species tree to obtain maximum pseudo-likelihood estimates (MPE) of species trees, with branch lengths of the species tree in coalescent units.     

A model for estimating infection levels of anthracnose disease of mango

Anthracnose disease of mango caused by Colletotrichum gloeosporioides var. minor, spreads by water-borne conidia from vegetative parts of the tree to attack inflorescences and prevent fruit set. An analysis of data from laboratory studies demonstrated that infection by conidia during wet periods was related both to the temperature and to the duration of the wet period. A model was used to estimate infection levels of anthracnose disease in two mango orchards over three seasons. The number of infection periods recorded and the estimated percentage of conidia forming appressoria in these periods matched disease development during flush growth and flowering. In 1980, only two infection periods were detected during flowering in one of these orchards and blossom blight did not prevent fruit set. In 1981 and 1982 however, higher estimated levels of infection were recorded more frequently during the same time and severe blossom blight developed. A second orchard, situated in an area less favourable to disease, was also monitored during 1982. Nine infection periods were recorded during flowering in this orchard compared to 14 in the first. A moderate level of blossom blight developed in this orchard.     

A model for estimating corneal stiffness using an indenter.

A finite element model that simulates indentation of the cornea was generated to examine the feasibility of using indentation data to determine mechanical properties. A layered model which included geometric nonlinearities was necessary to characterize the indentation process. Results indicate that a secant modulus could be determined by measuring indenter force and contact area.     

Quantitative genetic tools for insecticide resistance risk assessment: estimating the heritability of resistance

Quantitative genetic studies of resistance can provide estimates of genetic parameters not available with other types of genetic analyses. Three methods are discussed for estimating the amount of additive genetic variation in resistance to individual insecticides and subsequent estimation of the heritability (h2) of resistance. Sibling analysis and offspring-parent regression permit direct estimates of h2 by comparing the resistance phenotypes of individuals of known relatedness. Threshold trait analyses, performed on data from selection experiments, provide estimates of realized heritability. Procedures are outlined for predicting changes in resistance to insecticides based on h2 estimates. Quantitative genetic theory is examined as it relates to resistance and resistance as a quantitative trait; quantitative genetic methods also are unique in providing estimates of genetic correlations between traits. Comments are included on estimates of genetic correlation between resistance and phenotypic traits (e.g., development time) and how they may be used to predict changes in the genetic aspects of phenology that result from insecticide applications (i.e., to predict how the reproductive capacity of future generations will differ from that of the treated generation).     

A model system for evaluating shear in the design of stirred fermentors

A model system, utilizing shear-sensitive protozoa, has been developed for characterizing the disruptive forces in agitated systems. The model system gives a measure of the maximum shear stresses in the apparatus being tested, and is particularly useful when tissue fragility is a factor in fermentor design. The time dependency of protozoan disruption is shown and discussed. Breakdown data in conventional stirred vessels and a laminar shear device are presented and discussed.     

A hierarchical statistical model for estimating population properties of quantitative genes

Background  

Earlier methods for detecting major genes responsible for a quantitative trait rely critically upon a well-structured pedigree in which the segregation pattern of genes exactly follow Mendelian inheritance laws. However, for many outcrossing species, such pedigrees are not available and genes also display population properties.