Flatness-based control of PER protein oscillations in a drosophila model

Rhythms, and specially circadian rhythms governed by an oscillating set of genes called the central clock, and their incidence on therapeutics, have become an important concern in biology and medicine. Restoration of altered rhythms for therapeutic purpose can be viewed as an open-loop control problem. We study in this paper a nonlinear oscillator modeling the central clock mechanism through the synthesis cycle of PER protein for fruit fly Drosophila. Its particularly robust bifurcation structure makes it representative for a wide number of oscillating biological systems. We show how classical flatness-based motion planning techniques allow for fast design of chronomodulated injection schemes achieving circadian rhythm restoration.     

Thermal and fire degradation of recycled and polluted polypropylene‐based materials

In this study, the effect of processing cycles and two pollutants (engine oil (HM) and ethylene glycol (EG)) on the thermal and rheological properties of polypropylene‐based materials (108MF97 and 7510) has been studied. It was investigated if polymers coming from bumper face bar could keep their properties and can be reused after recycling. The different results demonstrate that the two polymers that were polluted and recycled do not show any decrease of their intrinsic properties. Moreover, for one of the two polymers (108MF97), the presence of engine oil enables to increase the thermal stability and reaction to fire. Finally, it appears that the reuse of such polymers is possible. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Comment on 'Therapeutic application of metallic nanoparticles combined with particle-induced x-ray emission effect'

A recent paper (Kim et al 2010 Nanotechnology 21 425102) presented results on the combination of irradiation by atomic ions of cells loaded by particles made of heavy atoms. They propose that the projectile induced x-rays emission (PIXE) mechanism has an important contribution to the enhancement of the cell death rate. Experiments made in our group to study the effects of such a combination have shown that the Auger effect induced in the high-Z atoms and the following induction of surrounding water radiolysis has an important contribution to the enhancement of the cell death rate. In the light of our studies we propose an alternative interpretation of the results presented in the paper by Kim et al.     

Tensile and bending behaviour of a strain hardening cement-based composite: Experimental and numerical analysis

IFSTTAR has developed a Multi-Scale Cement Based Composite (MSCC). This composite material is strain hardening in tension and exhibits ultra-high strengths as well in both compression and tension. The main research objectives for the present paper are the determination of the strain hardening properties of the material: using a newly developed tensile test in conjunction with a finite-element-based inverse analysis, the input parameters of an (adapted) numerical model can be identified. Therefore, numerical simulations can be performed to describe the bending behaviour of a thin slab having a thickness representative of the corresponding industrial application.The main conclusions of this study are:

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The studied material clearly exhibits strain hardening in tension with a uniaxial tensile strength of about 20 MPa and a modulus of rupture of about 50 MPa.

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Elasto-plastic behaviour with strain hardening is a relevant mechanical model (for the studied material) for designing (by the finite element method) structural elements behaving principally in bending.

     

The determination of viable counts in probiotic cultures microencapsulated by spray-coating

An assessment of various methods to determine viable counts (CFU) in freeze-dried and dried microencapsulated (ME) probiotic cultures was carried out. Microencapsulation was done by spray-coating of dried Lactobacillus rhamnosus R0011 or Bifidobacterium longum ATCC 15708 cultures with fat. Rehydration of the ME powders was incomplete when they were added to water and gently agitated. As a result analytical methods based on vortexing of rehydrated ME cultures and which did not incorporate a high-shear homogenization (HSH) step underestimated the viable counts. The CFU of ME cultures were identical when methods using either blender or generator probes high-shear homogenization (HSH) were carried out. Furthermore HSH reduced the variability of the CFU results of both free-cell and ME cultures by a factor of three. The addition of an emulsifier (Tween 80) in the rehydrating medium to dissolve fat did not improve CFU counts when generator probes were used for HSH. The presence of fat in the ME product, or when added to the rehydration medium, improved CFU counts of B. longum but not of L. rhamnosus.     

Dendrite fragmentation and columnar-to-equiaxed transition during directional solidification at lower growth speed under a strong magnetic field

The effects of strong magnetic fields on the columnar-to-equiaxed transition (CET) have been investigated experimentally. Six alloys have been directionally solidified at low growth speeds (1–10 μm s^?1) under magnetic fields up to 10 T. Experimental results show that the application of a strong magnetic field causes a dendrite fragmentation and then the CET. The thermoelectric magnetic force acting on cells/dendrites and equiaxed grains in the mushy zone has been studied numerically. Numerical results reveal that the value of the thermoelectric magnetic force increases as the magnetic field intensity and the temperature gradient increase. A torque is created on cells/dendrites and equiaxed grains. This torque breaks cells/dendrites and drives the rotation of equiaxed grains. The rotation of equiaxed grains in the mushy zone will further destroy cells/dendrites. Thus, with the increase of the magnetic field intensity and the temperature gradient, the volume fraction of equiaxed grains in front of columnar dendrites increases. When the magnetic field intensity and the temperature gradient reach a critical value, the growth of columnar dendrites is blocked and the CET then occurs. The present work may initiate a new method of inducing the CET via an applied strong magnetic field during directional solidification.     

A New Variant Selection Criterion for Twin Variants in Titanium Alloys (Part 2)

A new selection criterion to explain the activation of the twinning variant is proposed. This criterion is based on the calculation of the deformation energy to create a primary twin. The calculation takes into account the effect of the grain size using a Hall–Petch type relation. This criterion allows to obtain a very good prediction for the twin family selection and twin variant selection. The calculations are compared with the experimental results obtained on T40 (ASTM grade 2) deformed by Channel Die compression.     

The role of activity restriction in poststroke depressive symptoms.

Objective: Little is known about the determinants of poststroke depression. The Activity Restriction Model of Depressed Affect (ARMDA) may be helpful in understanding poststroke depression but has never been tested in that context. The goal of this study was to examine the relation between activity restriction and depressive symptoms in stroke survivors during the period following discharge from the hospital. Method: Participants (N = 197) were assessed on three occasions: (1) time 1 (T1), 3 weeks following discharge; (2) time 2 (T2), 3 months after discharge; and (3) time 3 (T3), 6 months after discharge. Results: Although both stroke severity and activity restriction were significantly related to depressive symptoms, the relation between stroke severity and depression was no longer significant after controlling for activity restriction. Moreover, restrictions in daily activities and social roles were both related to depressive symptoms, but these relations were found to vary during the course of the period following discharge. Conclusions: These findings support the ARMDA and have practical implications for the prevention of poststroke depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)