Reporting mathematics

We have analyzed several mathematical models that describe inhibition of the factor VIIa–tissue factor complex (VIIa–TF) by tissue factor pathway inhibitor (TFPI). At the core of these models is a common mechanism of TFPI action suggesting that only the Xa–TFPI complex is the inhibitor of the extrinsic tenase activity. However, the model based on this hypothesis could not explain well all the available experimental data. Here, we show that a good quantitative description of all experimental data could be achieved in a model that contains two more assumptions....

16p research12 01-06-2013 37 6   Download

This review provides a comparative overview of recent developments in the modelling of cellular calcium oscilla-tions. A large variety of mathematical models have been developed for this wide-spread phenomenon in intra- and intercellular signalling. From these, a general model is extracted that involves six types of concentration variables: inositol 1,4,5-trisphosphate (IP3), cytoplasmic, endoplasmic reticulum and mitochondrial calcium, the occupied binding sites of calcium buffers, and the fraction of active IP3 receptor calciumrelease channels....

23p research12 29-04-2013 27 3   Download

Metabolite channelling, the process in which consecutive enzymes have confined substrate transfer in metabolic pathways, has been proposed as a biochemical mechanism that has evolved because it enhances catalytic rates and protects unstable intermediates. Results from experiments on the synthesis of radioactive urea [Cheung, C., Cohen, N.S. & Raijman, L (1989)J. Biol. Chem.264, 4038–4044] have been interpreted as implying channelling of arginine between argininosuccinate lyase and arginase in permeabi-lized hepatocytes. ...

9p tumor12 20-04-2013 35 1   Download

We report that autonomous oscillations, which usually happen in aerobic glucose-limited continuous cultures of yeast at low dilution rate, were also observed in trehalose discontinuous cultures ofSaccharomyces cerevisiae. This unexpected oscillatory behaviour was therefore examined using fast Fourier transformation of online gas measurements. This robust mathemat-ical analysis underlined the existence of two types of oscillation.

11p awards 06-04-2013 36 2   Download

A mathematical description was made of an autocatalytic zymogen activa-tion mechanism involving both intra- and intermolecular routes. The reversible formation of an active intermediary enzyme–zymogen complex was included in the intermolecular activation route, thus allowing a Micha-elis–Menten constant to be defined for the activation of the zymogen towards the active enzyme.

12p awards 05-04-2013 33 4   Download

The control properties of biochemical pathways can be described by control coefficients and elasticities, as defined in the framework of metabolic control analysis. The determination of these parameters using the traditional metabolic control analysis relationships is, however, lim-ited by experimental difficulties (e.g. realizing and meas-uring small changes in biological systems) and lack of appropriate mathematical procedures (e.g. when the more practical large changes are made).

12p dell39 03-04-2013 64 3   Download

Systems biology and its usage of mathematical modeling to analyse biologi-cal data is rapidly becoming an established approach to biology. A crucial advantage of this approach is that more information can be extracted from observations of intricate dynamics, which allows nontrivial complex expla-nations to be evaluated and compared.

20p vinaphone15 27-02-2013 22 1   Download

Experimental design has a long tradition in statistics, engineering and life sciences, dating back to the beginning of the last century when optimal designs for industrial and agricultural trials were considered. In cell biol-ogy, the use of mathematical modeling approaches raises new demands on experimental planning.

17p vinaphone15 27-02-2013 40 3   Download

The phosphotransferase system inEscherichia coliis a transport and sen-sory system and, in this function, is one of the key players of catabolite repression. Mathematical modelling of signal transduction and gene expres-sion of the enzymes involved in the transport of carbohydrates is a promis-ing approach in biotechnology, as it offers the possibility to achieve higher production rates of desired components.

9p vinaphone15 27-02-2013 36 2   Download

Parasitic nematodes can downregulate the immune response of their hosts through the induction of immunoregulatory cytokines such as interleukin-10 (IL-10). To define the underlying mechanisms, we measuredin vitro the production of IL-10 in macrophages in response to cystatin fromAcantho-cheilonema viteae, an immunomodulatory protein of filarial nematodes, and developed mathematical models of IL-10 regulation.

16p viettel02 22-02-2013 38 3   Download

Multisite phosphorylation is an important mechanism for fine-tuned regula-tion of protein function. Mathematical models developed over recent years have contributed to elucidation of the functional consequences of a variety of molecular mechanisms involved in processing of the phosphorylation sites.

22p viettel02 22-02-2013 31 4   Download

In the present study, we investigated lipid biosynthesis in the bacterium Escherichia coliby mathematical modeling. In particular, we studied the interaction between the subsystems producing unsaturated and saturated fatty acids, phospholipids, lipid A, and cardiolipin.

12p mobifone23 18-01-2013 48 5   Download

Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is the key enzyme of the Calvin cycle, catalyzing the fixation of inorganic carbon dioxide to organic sugars. Unlike most enzymes, RuBisCO is extremely slow, substrate unspecific, and catalyzes undesired side-reactions, which are considered to be responsible for the slow deactivation observed in vitro, a phenomenon known as fallover.

20p mobifone23 18-01-2013 29 4   Download

Suppose that G is a locally compact abelian group, and write M(G) for the algebra of bounded, regular, complex-valued measures under convolution. A measure µ ∈ M(G) is said to be idempotent if µ ∗ µ = µ, or alternatively if µ takes only the values 0 and 1. The Cohen-Helson-Rudin idempotent theorem states that a measure µ is idempotent if and only if the set {γ ∈ G : µ(γ) = 1} belongs to the coset ring of G, 1. Introduction Let

31p dontetvui 17-01-2013 73 8   Download

We construct an exhaustive submeasure that is not equivalent to a measure. This solves problems of J. von Neumann (1937) and D. Maharam (1947). Contents 1. Introduction 2. Roberts 3. Farah 4. The construction 5. The main estimate 6. Exhaustivity 7. Proof of Theorems 1.2 to 1.4 References 1. Introduction Consider a Boolean algebra B of sets.

30p dontetvui 17-01-2013 75 11   Download

A quantitative sharp form of the classical isoperimetric inequality is proved, thus giving a positive answer to a conjecture by Hall. 1. Introduction The classical isoperimetric inequality states that if E is a Borel set in Rn , n ≥ 2, with finite Lebesgue measure |E|, then the ball with the same volume has a lower perimeter, or, equivalently, that (1.1) 1/n nωn |E|(n−1)/n ≤ P (E) . Here P (E) denotes the distributional perimeter of E (which coincides with the classical (n − 1)-dimensional measure of ∂E when E has a smooth boundary) and ωn is the measure of the...

41p dontetvui 17-01-2013 65 8   Download

The goal of this paper is to describe all closed, aspherical Riemannian manifolds M whose universal covers M have a nontrivial amount of symmetry. By this we mean that Isom(M ) is not discrete. By the well-known theorem of Myers-Steenrod [MS], this condition is equivalent to [Isom(M ) : π1 (M )] = ∞. Also note that if any cover of M has a nondiscrete isometry group, then so does its universal cover M . Our description of such M is given in Theorem 1.2 below. The proof of this theorem uses methods from Lie theory, harmonic maps,...

27p dontetvui 17-01-2013 54 7   Download

In this paper we give a new proof for the classification result in [3]. We show that isoparametric hypersurfaces with four distinct principal curvatures in spheres are of Clifford type provided that the multiplicities m1 , m2 of the principal curvatures satisfy m2 ≥ 2m1 − 1. This inequality is satisfied for all but five possible pairs (m1 , m2 ) with m1 ≤ m2 .

15p dontetvui 17-01-2013 64 7   Download

The existence problem is solved, and global pointwise estimates of solutions are obtained for quasilinear and Hessian equations of Lane-Emden type, including the following two model problems: −∆p u = uq + µ, Fk [−u] = uq + µ, u ≥ 0, on Rn , or on a bounded domain Ω ⊂ Rn . Here ∆p is the p-Laplacian defined by ∆p u = div ( u| u|p−2 ), and Fk [u] is the k-Hessian defined as the sum of k × k principal minors of the Hessian matrix D2 u (k = 1, 2, . . . ,...

58p dontetvui 17-01-2013 58 10   Download

In this paper we describe the propagation of C ∞ and Sobolev singularities for the wave equation on C ∞ manifolds with corners M equipped with a Rie2 1 mannian metric g. That is, for X = M × Rt , P = Dt − ∆M , and u ∈ Hloc (X) solving P u = 0 with homogeneous Dirichlet or Neumann boundary conditions, we show that WFb (u) is a union of maximally extended generalized broken bicharacteristics. This result is a C ∞ counterpart of Lebeau’s results for the propagation of analytic singularities on real analytic manifolds with...

65p dontetvui 17-01-2013 55 8   Download