Search results for "Matrix"
showing 10 items of 3205 documents
Digital generation of multivariate wind field processes
2001
Abstract A very efficient procedure for the generation of multivariate wind velocity stochastic processes by wave superposition as well as autoregressive time series is proposed in this paper. The procedure starts by decomposing the wind velocity field into a summation of fully coherent independent vector processes using the frequency dependent eigenvectors of the Power Spectral Density matrix. It is shown that the application of the method allows to show some very interesting physical properties that allow to reduce drastically the computational effort. Moreover, using a standard finite element procedure for approximating the frequency dependent eigenvectors, the generation procedure requi…
An empirical analysis of growth volatility: A Markov chain approach
2005
This paper studies the determinants of growth rate volatility, focusing on the effect of level of GDP, structural change and the size of economy. First we provide a graphical analysis based on nonparametric techniques, then a quantitative analysis which follows the distribution dynamics approach. Growth volatility appears to (i) decrease with per capita GDP, (ii) increase with the share of the agricultural sector on GDP and, (iii) decrease with the size of the economy, measured by a combination of total GDP and trade openness. However, we show that the explanatory power of per capita GDP tends to vanish when we control for the size of the economy. © 2005 Springer-Verlag Berlin Heidelberg.
Vulnerability matrix of the food system : operationalizing vulnerability and addressing food security
2016
Food security is the major desired outcome of any food system, but its realization may be prevented by vulnerabilities in a food system. By shifting the focus of their vulnerability analysis from the discrete components of the food system to the food system as a whole, the authors of this article were able to develop a qualitative food system vulnerability matrix. The objective of the research was to make the concept of food system vulnerability operational by identifying vulnerability drivers, vulnerable systems and vulnerable subclasses in light of food security. The vulnerability matrix was set up with five classes of vulnerable systems (‘Vulnerability of what?’) on the horizontal axis a…
Mutation of a critical tryptophan to lysine in avidin or streptavidin may explain why sea urchin fibropellin adopts an avidin-like domain
1999
Sea urchin fibropellins are epidermal growth factor homologues that harbor a C-terminal domain, similar in sequence to hen egg-white avidin and bacterial streptavidin. The fibropellin sequence was used as a conceptual template for mutation of designated conserved tryptophan residues in the biotin-binding sites of the tetrameric proteins, avidin and streptavidin. Three different mutations of avidin, Trp-110-Lys, Trp-70-Arg and the double mutant, were expressed in a baculovirus-infected insect cell system. A mutant of streptavidin, Trp-120-Lys, was similarly expressed. The homologous tryptophan to lysine (W--K) mutations of avidin and streptavidin were both capable of binding biotin and bioti…
Quasi-Ductile Behaviour of Carbon-Reinforced Carbon
1991
Firstly a brief review of the problem of a “ductilization” of ceramic materials by endless-fiber reinforcement is given. The problems, especially the influence of the frictional stress in the fiber-matrix interface, are pointed out for the unidirectionally reinforced ceramic matrix composite (CMC) system LAS/SiC, which is well documented in the literature.
Poly(γ-Glutamic Acid) as an Exogenous Promoter of Chondrogenic Differentiation of Human Mesenchymal Stem/Stromal Cells
2015
Cartilage damage and/or aging effects can cause constant pain, which limits the patient's quality of life. Although different strategies have been proposed to enhance the limited regenerative capacity of cartilage tissue, the full production of native and functional cartilaginous extracellular matrix (ECM) has not yet been achieved. Poly(γ-glutamic acid) (γ-PGA), a naturally occurring polyamino acid, biodegradable into glutamate residues, has been explored for tissue regeneration. In this work, γ-PGA's ability to support the production of cartilaginous ECM by human bone marrow mesenchymal stem/stromal cells (MSCs) and nasal chondrocytes (NCs) was investigated. MSC and NC pellets were cultur…
Novel Immunomodulatory Markers Expressed by Human WJ-MSC: an Updated Review in Regenerative and Reparative Medicine.
2012
Mesenchymal (stromal) stem cells (MSC) are a broad class of stromal populations which are able to differentiate towards mature cell types, and do express molecules involved in immune modulation, tolerance induction and inflammation dampening. MSC can be virtually isolated from each adult organ, as well as from foetus-associated perinatal tissues. In particular, Wharton's jelly-derived MSC (WJ-MSC) bear all of these key properties, together with their ease of sourcing and lack of ethical issues. Cellular therapy is a key technique in regenerative medicine approaches, in particular for the treatment of diseases in which physiological processes of cellular repopulation are blocked by the under…
Growth Volatility Indices
2006
We study the determinants of growth rate volatility in a multisector economy where sectors are heterogeneous in their individual volatility. We propose a model where aggregate volatility is explained by structural change and the size of the economy. We present a first attempt to test these predictions measuring growth volatility by indices based on Markov transition matrices. Growth volatility appears to (i) decrease with total GDP and (ii) increase with the share of the agricultural sector on GDP, although some nonlinearities appear. Trade openness, which we relate to the size of the economy, also plays a role. In accordance with our model, the explanatory power of per capita GDP, a releva…
A Concept for Quantitative Comparison of Mathematical and Natural Language and its possible Effect on Learning
2017
Starting with the question whether there is a connection between the mathematical capabilities of a person and his or her mother tongue, we introduce a new modeling approach to quantitatively compare natural languages with mathematical language. The question arises from educational assessment studies that indicate such a relation. Texts written in natural languages can be deconstructed into a dependence graph, in simple cases a dependence tree. The same kind of deconstruction is also possible for mathematical texts. This gives an idea of how to quantitatively compare mathematical and natural language. To that end, we develop algorithms to define the distance between graphs. In this paper, w…
Influence of the composition and the structure of different media on the release of aroma compounds
2004
International audience; The release of 2-nonanone and hexenol (hex-4-en-3-ol) was studied in model media with different structures and compositions: water, a gel of $\beta$-lactoglobulin, gelified or non-gelified emulsions (5.0% Miglyol, 6.9% $\beta$-lactoglobulin; the gelation was realized by heating) and milk. The aroma compounds were analyzed by gas chromatography. A strong influence of the nature of the volatile compound on its behavior towards the food matrix was observed: in the case of 2-nonanone, a hydrophobic compound (log P = 2.9) with a relatively high vapor-water partition coefficient (Kmol = 33.6), the release was greatly influenced by the composition and the structure of the m…