Approximation of the effective conductivity of ergodic media by periodization

 This paper is concerned with the approximation of the effective conductivity σ(A, μ) associated to an elliptic operator ∇ _xA (x,η)∇ _x where for xℝ ^d , d≥1, A(x,η) is a bounded elliptic random symmetric d×d matrix and η takes value in an ergodic probability space (X, μ). Writing A ^N (x, η) the periodization of A(x, η) on the torus T ^d _N of dimension d and side N we prove that for μ-almost all η

A subharmonic dynamical bifurcation during in vitro epileptiform activity

Epileptic seizures are considered to result from a sudden change in the synchronization of firing neurons in brain neural networks. We have used an in vitro model of status epilepticus (SE) to characterize dynamical regimes underlying the observed seizure-like activity. Time intervals between spikes or bursts were used as the variable to construct first-return interpeak or interburst interval plots, for studying neuronal population activity during the transition to seizure, as well as within seizures. Return maps constructed for a brief epoch before seizures were used for approximating the local system dynamics during that time window. Analysis of the first-return maps suggests that intermittency is a dynamical regime underlying the observed epileptic activity. This type of analysis may be useful for understanding the collective dynamics of neuronal populations in the normal and pathological brain.     

Computational simulation of variable magnetic force on heat characteristics of backward-facing step flow

Journal of Thermal Analysis and Calorimetry - The application of the nanofluid is highly increased due to its high heat rate in the attendance of the magnetic field. In current investigation, CFD...     

Entropy generation of nanomaterial through a tube considering swirl flow tools

Journal of Thermal Analysis and Calorimetry - The focus of the current investigation is on insertion of complex-shaped device for inducing swirl intensity. H2O-based copper oxide mixture was...     

Ferrofluid non-Darcy heat transfer involving second law analysis: an application of CVFEM

Journal of Thermal Analysis and Calorimetry - The non-Darcy heat transportation of the ferrofluid together with the entropy generation has been studied in a permeable zone under the role of...     

Dynamic half-Fourier single-shot turbo spin echo for assessment of deep venous thrombosis: initial observations

Objective

The objective of this study was to retrospectively analyze the value of dynamic half-Fourier single-shot turbo spin echo (HASTE) imaging in patients with suspected deep venous thrombosis (DVT).

Materials and Methods

Fifty-five veins in 24 patients were interrogated using a HASTE sequence with the patients relaxed and in various degrees of Valsalva. Veins were analyzed for changes in caliber (+CAL) and signal intensity (+SI) or in their absence (−CAL and −SI, respectively) and compared with the presence of thrombus on gadolinium-enhanced magnetic resonance imaging.

Results

There was no thrombus in veins with the +CAL, +SI pattern (n=40) (P<.01). Five of seven veins (71.4%) with the −CAL, −SI pattern had thrombus (P<.01). A qualitative change in CAL had a sensitivity of 100% and a specificity of 91% for the presence of thrombus. An increase of 1.5 mm in CAL had a sensitivity of 100% and a specificity of 93% for this diagnosis.

Conclusion

Dynamic HASTE imaging offers a physiological method to evaluate veins for deep venous thrombosis.     

A cutoff phenomenon in accelerated stochastic simulations of chemical kinetics via flow averaging (FLAVOR-SSA)

We present a simple algorithm for the simulation of stiff, discrete-space, continuous-time Markov processes. The algorithm is based on the concept of flow averaging for the integration of stiff ordinary and stochastic differential equations and ultimately leads to a straightforward variation of the the well-known stochastic simulation algorithm (SSA). The speedup that can be achieved by the present algorithm [flow averaging integrator SSA (FLAVOR-SSA)] over the classical SSA comes naturally at the expense of its accuracy. The error of the proposed method exhibits a cutoff phenomenon as a function of its speed-up, allowing for optimal tuning. Two numerical examples from chemical kinetics are provided to illustrate the efficiency of the method.     

Analytical techniques and bioactivity assays to compare the structure and function of filgrastim (granulocyte-colony stimulating factor) therapeutics from different manufacturers

The FDA has approved more than 100 protein and peptide drugs with hundreds more in the pipeline (Lanthier et al. in Nat Rev Drug Discov 7(9):733–737, 2008). Many of these originator biologic products are now coming off patent and are being manufactured by alternate methods than the innovator as follow-on drugs. Because changes to the production method often lead to subtle differences (e.g., degradation products, different posttranslational modifications or impurities) in the therapeutic (Schiestl et al. in Nat Biotechnol 29(4):310–312, 2011), there is a critical need to define techniques to test and insure the quality of these drugs. In addition, the emergence of protein therapeutics manufactured by unapproved methodologies presents an ongoing and growing regulatory challenge. In this work, high-resolution mass spectrometry was used to determine the presence or absence of posttranslational modifications for one FDA-approved and three foreign-sourced, unapproved filgrastim products. Circular dichroism (CD) was used to compare the secondary structure and probe the temperature stability of these products. Native 2D ¹H,¹⁵N-heteronuclear singular quantum coherence (HSQC) NMR test was applied to these samples to compare the higher-order structure of the four products. Finally, a cell proliferation assay was performed on the filgrastims to compare their bioactivity, and stressed filgrastim was tested in the bioassay to better understand the effects of changes in protein structure on activity. The results showed that orthogonal approaches are capable of characterizing the physiochemical properties of this protein drug and assessing the impact of structural changes on filgrastim purity and potency.     

Maillage simplicial d'un polyèdre arbitraire

Issues related to the existence of a triangulation of an arbitrary polyhedron are addressed. Given a boundary surface mesh (a set of triangular facets), the problem to decide whether or not a triangulation (with no internal points apart from the Steiner points) exists is reported to be NP-hard. In this paper, an algorithm to triangulate a general polyhedron is used which makes use of a classical Delaunay triangulation algorithm, a phase for recovering the missing boundary facets by means of facet partitioning and a final phase that makes it possible to remove the additional (non-Steiner) points previously defined so as to recover the initial boundary mesh thus resulting in a mesh of the given polyhedron. To cite this article: P.-L. George, H. Borouchaki, C. R. Acad. Sci. Paris, Ser. I 338 (2004).