Parabolic movement primitives and cortical states: merging optimality with geometric invariance

Previous studies have suggested that several types of rules govern the generation of complex arm movements. One class of rules consists of optimizing an objective function (e.g., maximizing motion smoothness). Another class consists of geometric and kinematic constraints, for instance the coupling between speed and curvature during drawing movements as expressed by the two-thirds power law. It has also been suggested that complex movements are composed of simpler elements or primitives. However, the ability to unify the different rules has remained an open problem. We address this issue by identifying movement paths whose generation according to the two-thirds power law yields maximally smooth trajectories. Using equi-affine differential geometry we derive a mathematical condition which these paths must obey. Among all possible solutions only parabolic paths minimize hand jerk, obey the two-thirds power law and are invariant under equi-affine transformations (which preserve the fit to the two-thirds power law). Affine transformations can be used to generate any parabolic stroke from an arbitrary parabolic template, and a few parabolic strokes may be concatenated to compactly form a complex path. To test the possibility that parabolic elements are used to generate planar movements, we analyze monkeys’ scribbling trajectories. Practiced scribbles are well approximated by long parabolic strokes. Of the motor cortical neurons recorded during scribbling more were related to equi-affine than to Euclidean speed. Unsupervised segmentation of simulta- neously recorded multiple neuron activity yields states related to distinct parabolic elements. We thus suggest that the cortical representation of movements is state-dependent and that parabolic elements are building blocks used by the motor system to generate complex movements.     

Stochastic identification of bioreactor process exhibiting input multiplicity

Bioreactor systems involve complex biochemical reactions, which make the systems highly non-linear in nature. Developing model based controllers for such processes require mathematical representations, which are simple, yet capable of capturing the non-linear process characteristics. Continuous bioreactor falls under the class of non-linear systems that exhibit input multiplicity in the optimal operating region, i.e., the operating region where identical outputs are obtained for multiple inputs. Linear modeling techniques are not useful for the referred class of systems for obvious reasons. Even for non-linear modeling techniques, the real bottleneck is to capture the bell-shaped parabolic structure of steady state characteristics exhibited by these systems. The stochastic approach of modeling, which is based on process input/output time-series data, is very useful for this purpose. The aim of this paper is to address the stochastic modeling issues related to bioreactor processes. In this work, three efficient modeling techniques have been studied, viz. block oriented NARMAX structure (Pearson and Pottmann in J Process Control 10:301-315, 2000), Bootstrap structure detection for NARMAX model (Kukreja et al. in Int J Control 77(2):132-143, 2004) and Wavelet-NARMAX model (Billings and Wei in Int J Syst Sci 36(3):137-152, 2005).     

Global dynamics of a ratio-dependent predator-prey system

Recently, ratio-dependent predator-prey systems have been regarded by some researchers to be more appropriate for predator-prey interactions where predation involves serious searching processes. However, such models have set up a challenging issue regarding their dynamics near the origin since these models are not well-defined there. In this paper, the qualitative behavior of a class of ratio-dependent predator-prey system at the origin in the interior of the first quadrant is studied. It is shown that the origin is indeed a critical point of higher order. There can exist numerous kinds of topological structures in a neighborhood of the origin including the parabolic orbits, the elliptic orbits, the hyperbolic orbits, and any combination of them. These structures have important implications for the global behavior of the model. Global qualitative analysis of the model depending on all parameters is carried out, and conditions of existence and non-existence of limit cycles for the model are given. Computer simulations are presented to illustrate the conclusions.     

Bifurcations of nonlinear reaction-diffusion systems in prolate spheroids

Spontaneous pattern formation may arise in biological systems as primary and secondary bifurcations to nonlinear parabolic partial differential equations describing chemical reaction-diffusion systems subject to zero flux boundary conditions. Prepatterns are investigated, which arise in the three dimensional region of a prolate spheroid (elongated sphere). Pattern sequences and selection rules are established numerically. The results confirm previously recorded results of the spherical region upon which a prepattern theory of mitosis and cytokinesis is based. New results described here establish the emerging patterns as reliable prepatterns ensuring bipolarity during elongation of biological cells, as seen in anaphase of the process of mitosis.     

Application of LCSA to used cooking oil waste management

Purpose

Used cooking oil (UCO) is a domestic waste generated as the result of cooking and frying food with vegetable oil. The purpose of this study is to compare the sustainability of three domestic UCO collection systems: through schools (SCH), door-to-door (DTD), and through urban collection centres (UCC), to determine which systems should be promoted for the collection of UCO in cities in Mediterranean countries.

Methods

The present paper uses the recent life cycle sustainability assessment (LCSA) methodology. LCSA is the combination of life cycle assessment (LCA), life cycle costing, and social life cycle assessment (S-LCA).

Results and discussion

Of the three UCO collection systems compared, the results show that UCC presents the best values for sustainability assessment, followed by DTD and finally SCH system, although there are no substantial differences between DTD and SCH. UCC has the best environmental and economic performance but not for social component. DTD and SCH present suitable values for social performance but not for the environmental and economic components.

Conclusions

The environmental component improves when the collection points are near to citizens’ homes. Depending on the vehicle used in the collection process, the management costs and efficiency can improve. UCO collection systems that carry out different kind of waste (such as UCC) are more sustainable than those that collect only one type of waste. Regarding the methodology used in this paper, the sustainability assessment proposed is suitable for use in decision making to analyse processes, products or services, even so in social assessment an approach is needed to quantify the indicators. Defining units for sustainability quantification is a difficult task because not all social indicators are quantifiable and comparable; some need to be adapted, raising the subjectivity of the analysis. Research into S-LCA and LCSA is recent; more research is needed in order to improve the methodology.     

非线性种群反应扩散系统的奇摄动

研究了一类具有非线性种群反应扩散系统奇摄动问题,在适当的条件下,利用微分不等式理论,讨论了问题解的存在性和渐近性态．     

Potential emission savings from refrigeration and air conditioning systems by using low GWP refrigerants

Purpose

Refrigeration and air conditioning systems have high, negative environmental impacts due to refrigerant charge leaks from the system and their corresponding high global warming potential. Thus, many efforts are in progress to obtain suitable low GWP alternative refrigerants and more environmentally friendly systems for the future. The system’s life cycle climate performance (LCCP) is a widespread metric proposed for the evaluation of the system’s environmental impact.

Methods

In this paper, the potential emission reductions in the commercial refrigeration and residential air conditioning systems, made possible by shifting towards more environmentally friendly refrigerants in the US, are presented. First, the current LCCP of the most common commercial refrigeration and residential air conditioning systems is calculated. Then, the LCCP of the baseline systems, when using the potential low GWP alternative refrigerants, is presented. This helps to determine the systems which have the highest potential for emission reductions.

Results and discussion

By shifting from the baseline refrigerants, R-404A and R-410A, to the suggested low GWP refrigerants, N-40 and L-41a, in the commercial refrigeration and residential HVAC systems, respectively, a combined drop of 30.43 % in the total emissions (i.e., total equivalent mass of emissions in kg CO_2eq) is obtained. This results from a 50.5 and 28.01 % drop in total emissions from supermarket refrigeration systems and residential air conditioning, respectively.

Conclusions

Shifting to lower GWP refrigerants in the refrigeration and air conditioning systems helps to reduce the total emissions and negative environmental impacts of these systems. Shifting to a secondary circuit commercial refrigeration system using N-40/L-40 and residential air conditioning and heat pump systems using L-41a helps in reducing the total emissions.

     

Towards Real-Time Fault-Tolerant CORBA Middleware

An increasing number of applications are being developed using Distributed Object Computing (DOC) middleware, such as CORBA. Many of these applications require the underlying middleware, operating systems, and networks to provide dependable end-to-end Quality of Service (QoS) support to enhance their efficiency, predictability, scalability, and reliability. The Object Management Group (OMG), which standardizes CORBA, has addressed many of these application requirements individually in the Real-Time CORBA (RT-CORBA) and Fault-Tolerant CORBA (FT-CORBA) specifications. Though the implementations of RT-CORBA are suitable for mission-critical commercial or military distributed Real-Time and Embedded (DRE) systems, the usage of FT-CORBA with RT-CORBA implementations are not yet suitable for systems that have stringent simultaneous dependability and predictability requirements.This paper provides three contributions to the study and evaluation of dependable CORBA middleware for performance-sensitive DRE systems. First, we provide an overview of FT-CORBA and illustrate the sources of unpredictability associated with conventional FT-CORBA implementations. Second, we discuss the QoS requirements of an important class of mission-critical DRE systems to show how these requirements are not well served by FT-CORBA today. Finally, we empirically evaluate new dependability strategies for FT-CORBA that can help make the use of DOC middleware for mission-critical DRE systems a reality.     

Automatic non-proliferative diabetic retinopathy screening system based on color fundus image

Background

Non-proliferative diabetic retinopathy is the early stage of diabetic retinopathy. Automatic detection of non-proliferative diabetic retinopathy is significant for clinical diagnosis, early screening and course progression of patients.

Methods

This paper introduces the design and implementation of an automatic system for screening non-proliferative diabetic retinopathy based on color fundus images. Firstly, the fundus structures, including blood vessels, optic disc and macula, are extracted and located, respectively. In particular, a new optic disc localization method using parabolic fitting is proposed based on the physiological structure characteristics of optic disc and blood vessels. Then, early lesions, such as microaneurysms, hemorrhages and hard exudates, are detected based on their respective characteristics. An equivalent optical model simulating human eyes is designed based on the anatomical structure of retina. Main structures and early lesions are reconstructed in the 3D space for better visualization. Finally, the severity of each image is evaluated based on the international criteria of diabetic retinopathy.

Results

The system has been tested on public databases and images from hospitals. Experimental results demonstrate that the proposed system achieves high accuracy for main structures and early lesions detection. The results of severity classification for non-proliferative diabetic retinopathy are also accurate and suitable.

Conclusions

Our system can assist ophthalmologists for clinical diagnosis, automatic screening and course progression of patients.

     

Pore canal shape related to molecular architecture of arthropod cuticle

The rotating structure of pore canals is interpreted in terms of the Bouligand model of rotating layers of chitin-protein microfibrils, and the daily growth layer system in insects. Crustacean and arachnid examples are also used. Pore canals are flattened into ribbons by neighbouring microfibrils. The ribbons run straight when traversing layers with preferred microfibril orientation, but rotate in phase through lamellate layers in which the layers of microfibrils also rotate. Oblique sections of models show that the parabolic artefact derived from microfibrils, and the parabolic arcs of pore canals seen as crescents in section, only superimpose, as they do in actual sections, when both systems have the same sense of rotation. Pore canal rotation may be determined by chitin-protein architecture.     

Additional Circular Systematic Sampling Methods

Several systematic sampling methods have been used to estimate the population mean when size of the population is a multiple of sample size. Among these, only few methods have been extended and used to estimate mean of the population when its size is not a multiple of sample size. In this paper, new methods called balanced circular systematic sampling and centered circular systematic sampling are introduced by extending balanced systematic sampling method and centered systematic sampling method respectively. These methods are compared with circular systematic sampling using average variance of corrected sample means for populations exhibiting approximate linear and parabolic trends. The suggested methods are found suitable to estimate the population mean.     

Roles for asparagine endopeptidase in class II MHC-restricted antigen processing

The adaptive immune response depends on the creation of suitable peptides from foreign antigens for display on MHC molecules to T lymphocytes. Similarly, MHC-restricted display of peptides derived from self proteins results in the elimination of many potentially autoreactive T cells. Different proteolytic systems are used to generate the peptides that are displayed as T cell epitopes on class I compared with class II MHC molecules. In the case of class II MHC molecules, the proteases that reside within the endosome/lysosome system of antigen-presenting cells are responsible; surprisingly, however, there are relatively few data on which enzymes are involved. Recently we have asked whether proteolysis is required simply in a generic sense, or whether the action of particular enzymes is needed to generate specific class II MHC-associated T cell epitopes. Using the recently identified mammalian asparagine endopeptidase as an example, we review recent evidence that individual enzymes can make clear and non-redundant contributions to MHC-restricted peptide display.     

Consequential and attributional environmental assessment of biofuels: implications of modelling choices on climate change mitigation strategies

Purpose

The study aims to assess climate change mitigation potentials when using biomass-based fuels to replace fossil energy under consequential and attributional modelling approaches. The objectives are also to determine policy implications and to recommend the specific contexts suitable for each modelling choice by using specific illustrative cases on biofuels.

Methods

Consequential and attributional modelling approaches are chosen for life cycle greenhouse gas emission assessment of several bioenergy options. The assessed functional unit is 1 MJ of energy from molasses-based ethanol, palm-based biodiesel and electricity production from rice straw. The fossil fuel comparators are gasoline (for molasses-based ethanol), diesel (for palm-based biodiesel) and coal and gas (for rice straw). The substituted and substituting product systems are modelled under the global and national markets depending on the market delimitation of each product.

Results and discussion

The climate change mitigation potentials when using different approaches are dissimilar, because the affected product systems being included in the analysis are not the same. The palm biodiesel could reduce greenhouse gas emissions. The molasses-based ethanol and rice straw-based electricity may or may not mitigate the climate change, since it depends on the methodological choices as well as the baseline situations of the product systems being investigated. The main characteristics of consequential modelling as additionality and the inclusion of only actually affected processes under market-based mechanisms while those of attributional modelling as specification and attribution/allocation have limitations. The limitations lead to potential risks on unintended and undesirable consequences (for the attributional model), unfairness and sub-optimisation (for the consequential model) in policy recommendations.

Conclusions

This research clearly illustrates how certain modelling choices affect the climate change mitigation potentials of biomass-based fuels in comparison with fossil energy. Specific questions and conditions which could be more suitable for each modelling choice are addressed. The attributional modelling is more suitable for national environmental taxation and emission labelling/accounting for import-export, while the consequential modelling is more appropriate for new production development and eco-design. Due to the potential environmental risks arising from the modelling limitations, the consideration of both the widely applied approaches could support decisions more comprehensively.

     

A relational theory of biological systems

The relational phenomena exhibited by metabolizing systems may be considered as special cases of those exhibited by a more general class of systems. This class is specified, and some of tis properties developed. An attempt is then made to apply these properties to a theory of metabolism by suitable specialization. A number of biologically significant theorems are obtained which apply directly to the theory of the free-living single cell. Among the results obtained are the following: On the basis of our model, there must always exist a component of the system which cannot be replaced or repaired by the system in the event of its inhibition or destruction. Under certain conditions, a metabolizing system possesses a component the inhibition of which will completely terminate the metabolic activity of the system. Furthermore a number of other diverse phenomena, such as the effects of a deficient environment, encystment phenomena, and even an indication of why a metabolizing system which represents a cell should possess a nucleus, follow in a straightforward fashion from our model.     

Practical aspects of the mathematical modeling of fermentation processes as a method of description,simulation, identification and optimization

Most mathematical models for describing the physiological state in fermentations lead to solutions of the so-called “stiff differential systems” during simulation on a digital computer There is no suitable conventional software for solving these systems As a result of a relatively extensive screening of suitable methods for the solution of “stiff” differential systems (about 200 methods) it may be concluded that the semiimplicit RUNGE -KUTTA -formulas of the ROSENBROCK type, which constitute a part of the collection of programmes STIFFSOLVER-80, are optimal for the simulation of fermentation processes For determining kinetic parameters from integral data the authors use the system of programmes BIOKIN Their practical application is discussed for 3 examples:

• 1 Growth of the yeast Saccharomyces cerevisiae and changes in the content of specific compounds (proteins and ergosterol)
• 2 Quantitative evaluation of “;direct oxygen transfer” in the submerged culture.
• 3 Biosynthesis of a new antibiotic substance mucidin

.     

Evidence of short-term adaptation to microgravity of neuromuscular synergy during a whole body movement

Human, like any other animal systems, moves in the terrestrial gravity field and must learn gravity-related motor strategies during his ontogenetic development. Considering continuous gravity action upon body segments, movement involves particular muscle activation patterns depending on body orientation to gravity. Gravitational-altered environments provided by parabolic flight or orbital space mission offer a great opportunity to investigate how gravity is taken into account in posture and movement planning. Indeed, in a context where the mechanical constraints are modified, movement execution involves that new muscular activity have to be produced. Almost, only few studies in microgravity environment are included electromyographic analysis and this parameter is generally used only to confirm modification of the muscular activation patterns. This study is focused to analyse the adaptation capacity of the brain to a modified gravitational environment. In this aim, EMG activity have been recorded during a whole body movement execution in both normo- and microgravity environment during parabolic flight. This procedure allowed us to analyse the EMG patterns recorded during the very first moments of weightlessness. In this study are reported the results of this analyse.     

Hopf bifurcation and transition to chaos in Lotka-Volterra equation

It is shown that in a suitable class of Lotka-Volterra systems it is possible to characterize the centre-critical case of the Hopf bifurcation of the multipopulation equilibrium. Moreover, for three populations, it is shown that, in the non-critical case, Hopf bifurcation is supercritical. Numerical evidence of transition to chaotic dynamics, via period-doubling cascades, from the limit cycle is reported.     

A comparison of different focus functions for use in autofocus algorithms

A number of functions for the autofocusing of microscopes and other optical instruments are to be found in the literature. In this article we compare 11 of them to determine, in an objective manner, which functions are most suitable for implementation with real-time video acquisition systems. Three different images, each representing a typical class of image, are used in the comparison. Among the best focus functions found in our study are the squared magnitude gradient, the squared Laplacian, and the normalized image standard deviation.     

具有抛物线解的Kolmogorov三次系统的极限环的存在性问题

本文证明了具有既不与两坐标轴相切,又不通过原点的抛物线解的Kolmogorov三次系统可以存在极限环．     

Appendix to the sulfur-cyanolysis sites of serum albumin: metabolite competition studies. Tight-binding inhibitions that yield atypical Henderson plots

Ordinary tight-binding inhibition in steady-state enzyme systems is conveniently evaluated by means of the Henderson plot. This is a linear plotting form that has an ordinate intercept equal to the total enzyme concentration. However, there are two experimental situations that yield deviations from the common Henderson plot form. These are inhibitor binding in a separate, noninhibitory mode that depletes the concentration of free inhibitor, and partial inhibition, i.e., the retention of partial activity by the enzyme-inhibitor complex. Noninhibitory depletion results in Henderson plots with elevated ordinate intercepts. Competitive partial inhibition yields a characteristic pattern of parabolic Henderson plots.