A comparison of the Schumacher with other functions for describing growth in pigs

This study was undertaken to introduce the Schumacher equation and compare it with established functions for describing growth in pigs. The relationship between live weight (LW) and cumulative feed intake was also investigated. A database was constructed from three independent trials in which LW, age and intake were measured from birth to 937 days. Three growth functions were used for analysis of growth versus age: Gompertz, Schumacher and Weibull; and the Richards and monomolecular equations were used for analysis of cumulative feed intake versus LW. The growth functions have different points of inflexion. Liveweight at inflexion is W_f/e for the Gompertz, where W_f is the final weight, W_f/e² for the Schumacher, and W_f − (W_f − W₀) exp[−(n − 1)/n] for the Weibull, where W₀ is initial body weight and n is a shape parameter. Meta-analysis of the data using mixed model and nonlinear regression procedures was conducted to identify the most appropriate growth function. Functions were compared using F-tests or Bayesian Information Criteria, which give a value based on best fit and number of parameters in the model. The three equations were fitted to five individual pig growth profiles and to the composite data. Although the Weibull had a lower residual mean square, it did not significantly improve the fit compared to the simpler models and appears to be over-parameterised. The results suggest that model selection should be based on the type and amount of data available for analysis. Residuals plot showed that Schumacher and Weibull better predict the initial growth phase, however, all models showed largest magnitude of residuals towards the end of the growth profile. The monomolecular equation was most appropriate for describing LW against cumulative feed intake and may be used to formulate diets based on the efficiency of conversion of feed to LW at various stages of the animal's life span.     

Evaluation of surface hydrophobicity of immobilized protein with a surface plasmon resonance sensor

Immobilization is widely used to isolate agglutinative and associative proteins with large hydrophobic surfaces. Surface hydrophobicities of immobilized proteins were quantified by measuring the adsorption amounts of Triton X-100 as a hydrophobic probe with a biosensor that utilizes the phenomena of surface plasmon resonance (SPR). We measured SPR signal changes derived from adsorption of Triton X-100 to five kinds proteins and calculated the monolayer adsorption capacity using the Brunauer-Emmett-Teller equation, partly modified with a term for correcting an influence of the net charge of immobilized protein. SPR signal changes obtained by this method correlated with the values of surface hydrophobicities obtained by conventional assay using a hydrophobic probe. Thus this measuring method using an SPR sensor and Triton X-100 is expected to be a tool for quantifying surface hydrophobicities of immobilized proteins.     

The structural error-in-equation model to evaluate individual bioequivalence

Individual bioequivalence is assessed using an extension of the classical structural equation model, known as the error-in-equation model. This procedure estimates the relationship between individual means, as well as the variance-covariance parameters, of the bioavailabilities measurement model, by considering individual means related through a straight line with a random term, whereas the classical structural equation considers a deterministic linear relationship. We discuss the implications of this approach in terms of the bioavailabilities measurement model and how to test the overall hypothesis of individual bioequivalence. Both models are compared in a simulation study and a case example is presented.     

Permeation mechanism of a two-state potassium channel

A two-state hopping model was proposed to study the permeation of ion channel. The Nernst equation in equilibrium and the Michaelis-Menten relation in steady state were derived from the two-state kinetic model. The current-voltage relationship obtained in the symmetrical solutions case was linear when the applied potential was less than 100 mV, which met Ohm’s law. The conductance-concentration relationship exhibited the saturation property. Moreover, the characteristic time reaching the steady state of the KcsA channel was also discussed. Translated from Acta Biophysica Sinica, 2005, 21(4): 289–294 [译自: 生物物理学报]     

Fluorescence polarization assay and inhibitor design for MDM2/p53 interaction

MDM2 is an important negative regulator of the tumor suppressor protein p53 which regulates the expression of many genes including MDM2. The delicate balance of this autoregulatory loop is crucial for the maintenance of the genome and control of the cell cycle and apoptosis. MDM2 hyperactivity, due to amplification/overexpression or mutational inactivation of the ARF locus, inhibits the function of wild-type p53 and can lead to the development of a wide variety of cancers. Thus, the development of anti-MDM2 therapies may restore normal p53 function in tumor cells and induce growth suppression and apoptosis. We report here a novel high-throughput fluorescence polarization binding assay and its application in rank ordering small-molecule inhibitors that block the binding of MDM2 to a p53-derived fluorescent peptide.     

Shifts and disruptions in resource-use trait syndromes during the evolution of herbaceous crops

Trait-based ecology predicts that evolution in high-resource agricultural environments should select for suites of traits that enable fast resource acquisition and rapid canopy closure. However, crop breeding targets specific agronomic attributes rather than broad trait syndromes. Breeding for specific traits, together with evolution in high-resource environments, might lead to reduced phenotypic integration, according to predictions from the ecological literature. We provide the first comprehensive test of these hypotheses, based on a trait-screening programme of 30 herbaceous crops and their wild progenitors. During crop evolution plants became larger, which enabled them to compete more effectively for light, but they had poorly integrated phenotypes. In a subset of six herbaceous crop species investigated in greater depth, competitiveness for light increased during early plant domestication, whereas diminished phenotypic integration occurred later during crop improvement. Mass-specific leaf and root traits relevant to resource-use strategies (e.g. specific leaf area or tissue density of fine roots) changed during crop evolution, but in diverse and contrasting directions and magnitudes, depending on the crop species. Reductions in phenotypic integration and overinvestment in traits involved in competition for light may affect the chances of upgrading modern herbaceous crops to face current climatic and food security challenges.     

Acceleration Workspace of Cooperating Multi-Finger Robot Systems

We present a mathematical method for acceleration workspace analysis of cooperating multi-finger robot systems using a model of point-contact with friction. A new unified formulation from dynamic equations of cooperating multi-finger robots is derived considering the force and acceleration relationships between the fingers and the object to be handled. From the dynamic equation, maximum translational and rotational acceleration bounds of an object are calculated under given constraints of contact conditions, configurations of fingers, and bounds on the torques of joint actuators for each finger. Here, the rotational acceleration bounds can be applied as an important manipulability index when the multi-finger robot grasps an object. To verify the proposed method, we used a set of case studies with a simple multi-finger mechanism system. The achievable acceleration boundary in task space can be obtained successfully with the proposed method and the acceleration boundary depends on the configurations of fingers.     

Evaluation of viscosities of aqueous two-phase systems containing protein

The dynamic viscosities of aqueous polyethylene glycol, aqueous bovine serum albumin, and polyethylene glycol-bovine serum albumin-water solutions were measured at temperatures of 15, 20, 25, 30 and 35 degree C. To estimate the viscosity values of polyethylene glycol-bovine serum albumin-water solutions, a one parameter Grunberg-like model which was satisfactorily used earlier by the present author for polyethylene glycol-dextran-water solutions was employed. The disposable parameter a for our temperature range was estimated as 3.71. The relative errors varying from 0.29 to 18.98 in absolute value indicates that the Grunberg-like model works perfectly for polymer-protein solutions as well.     

土壤侵蚀预报模型中的植被覆盖与管理因子研究进展

植被覆盖和土地管理措施是土支离破碎中侵蚀的主要抑制因素之一,通用土壤流失方程（USLE）中的植被覆盖与田间管理因子（C）是评价这种抑制作用的有效指标,并被广泛采用和深入研究。我国在这方面的研究还不能满足土壤侵蚀预报和水土保持规划的要求,在系统回顾该因子的研究历史的基础上,介绍了USLE和RUSLE中C因子估计方法及其不断改进和完善的过程,并概述了中国的覆盖与田间管理因子的研究进展。此外,总结国内在（C）因子估计值以及植被覆盖度,地面覆盖物和植被根系对土壤侵蚀的影响等方面研究成果,分析了目前我国覆盖与田间管理因子研究中存在的3个方面问题,并提出了前景展望。