New biosourced AA and AB monomers from 1,4:3,6-dianhydrohexitols,Isosorbide, Isomannide,and Isoidide

In the present work, we propose the synthesis of a new family of sugar derived 1,4:3,6-dianhydrohexitol based AA/AB-type monomers. Unprecedented diacids based on Isomannide and Isoidide were elaborated with high yields and showed interestingly high melting point ranges (240–375 °C). Optimization of reaction conditions (temperature, time of reaction, and reactant ratios) has been investigated to synthesize the key intermediate of a set of AB monomers with acid, ester, and acid chloride functionalities. Isosorbide based ether benzoic acid AB monomer was polymerized and characterized by NMR and DSC techniques. The results show a semicrystalline behavior of the obtained polymer thanks to the controlled stereoregular arrangement of the AB starting monomer.     

Continuous-fiber reinforced composites: A new generation

The mechanical and physical properties of aluminum-matrix composites reinforced with high-performance continuous alumina fibers are reviewed and compared with those of other structural materials. Continuous-fiber reinforced aluminum-matrix compositesoffer outstanding improvements in specific strength and specific stiffness over conventional alloys and particulate composites. Thelongitudinal tensile strength of an aluminum matrix reinforced with 55–65 vol.% alumina fibers is in the range ofl.4-1.9 GPa, the longitudinal Young's modulus is 220–240 GPa, and the density is 3.2-3.4 g/cm3. The mechanisms of strengthening and fracture under longitudinal, transverse, and shear loading are reviewed. Examples of applications are presented that are representative of the range of product forms being developed.     

Evidence that a transient enhancement of endogenous hematopoiesis contributes significantly to the favorable outcome following interleukin 1 pretreatment and allogeneic bone marrow transplantation

The administration of IL-1, a potent radioprotective cytokine, before allogeneic BMT is associated with an early transient increase of circulating granulocytes, successful engraftment, and accelerated multilineage hematopoietic recovery. We have examined the effects of IL-1 alpha pretreatment on the engraftment of an allogeneic BMT unable to sustain survival by itself after a lethal irradiation: (1) transplantation of a limited amount of marrow cells and (2) transplantation several days after irradiation. IL-1 was unable to allow the engraftment of an early quantitatively inadequate BMT. However, delayed BMT with limited amounts of marrow cells was associated with engraftment in IL-1 pretreated recipients. Engraftment of a late (day 12) BMT in these IL-1-pretreated mice was comparable to the engraftment of a similar day 12 allogeneic BMT in non-IL-1-pretreated mice rescued from the lethal irradiation by an early (day 1) syngeneic graft. These findings demonstrate that IL-1 pretreatment can result in a dissociation between BMT-induced survival and engraftment and suggest that the favorable effects of IL-1 pretreatment in an allogeneic BMT setting are mainly mediated through a transient enhancement of endogenous hematopoiesis and not through a direct effect on the allogeneic stem cells present in the marrow graft.     

Peri-ano-rectal cysts and tumours of vestigial origin in the adult (author''s transl)

Although the annular dark field detector in the STEM collects a large fraction of the elastically scattered electrons, it does not use all the information carried by these electrons because it ignores the distribution of electrons over its surface. This information can be obtained by dividing the detector into sections. This paper calculates the number of electrons scattered by a single atom onto each side of an annular dark field detector split in half by a line passing through its center. This scattering problem is unusual becuase the incident wave is not a plane wave in the STEM. The sum and difference signals are calculated for a single atom from its scattering amplitude for a STEM limited by primary or secondary spherical aberration operating at 10 kV, 70kV, or 100 kV. All the cases calculated show that a single thorium atom should give an observable difference signal which is very sensitive to the focal conditions of the STEM.     

The rate of formation of the hydrates of F-31(CH2ClF) and F-142b(CH3CClF2) in a stirred tank reactor

The kinetics of formation of the hydrates of F-31 and F-142b have been measured separately in a continuous-stirred tank reactor of 3700 cc volume. Rates of formation vary from 0.6 to 3 wt%/min with the ΔT ranging from 0.25 to 0.9°C and the agitation rate varying between 1 and 46 watts/liter. All data were taken in NaCl solutions of near 6% by weight.F-31(CH₂ClF) hydrate appears to be an excellent choice for use in the hydrate process for desalting. Its formation conditions in pure water are 17.9°C and 2.8 atm absolute, the rates of formation are high, and the crystals formed are rough spheres of mean diameters of 200 to 250 microns.     

Direct Calorimetric Measurement of Enthalpies of Phase Transitions at 2000°–2400°C in Yttria and Zirconia

High-temperature differential thermal analysis provided data on phase transitions in zirconia and yttria. The tetragonal form of ZrO₂ transforms to the cubic fluorite structure at 2311°±15°C with an enthalpy of 3.4±3.1 kJ/mol. Cubic C-type Y₂O₃ transforms, probably to the fluorite structure, at 2308°±15°C with Δ H =47.7±3.0 kJ/mol. This high-temperature polymorph melts at 2382°±15°C with an enthalpy of fusion of 35.6±3.0 kJ/mol.     

Multi Modal Dynamic Linear Viscoelastic Back Analysis for Asphalt Mixes

In this paper, an investigation was performed to determine the accuracy of a simplified viscoelastic back analysis to interpret dynamic loading tests on asphalt mixes (AM). First, quasi-static cyclic tension–compression lab tests were performed on different AM to fit the 3 dimensional 2S2P1D linear viscoelastic (LVE) model. Considering these tests on very different types of AM, a LVE material with “averaged” viscoelastic properties was obtained. Then, these “averaged” viscoelastic properties were considered to perform finite elements method numerical simulations of dynamic loading tests on a cylinder. The simulations were performed at ten different temperatures from \(-\,40\) to 50 \({^\circ }\)C. The longitudinal, flexural and torsional modes of vibration are studied. The complex Young’s modulus and complex Poisson’s ratio were first obtained using the viscoelastic 2S2P1D model at the first resonance frequency for the three studied modes of vibration. Then, a combined viscoelastic back analysis, which has the advantage of simplicity, was used to determine the elastic equivalent properties and the phase angle of the material. The results obtained directly with the 2S2P1D model and the results from the combined viscoelastic back analysis results regarding both the Young’s modulus and the Poisson’s ratio are discussed in the paper.     

Optimizing widths with PSO for center selection of Gaussian radial basis function networks

The radial basis function （RBF） centers play different roles in determining the classification capa- bility of a Gaussian radial basis function neural network （GRBFNN） and should hold different width values. However, it is very hard and time-consuming to optimize the centers and widths at the same time. In this paper, we introduce a new insight into this problem. We explore the impact of the definition of widths on the selection of the centers, propose an optimization algorithm of the RBF widths in order to select proper centers from the center candidate pool, and improve the classification performance of the GRBFNN. The design of the objective function of the optimization algorithm is based on the local mapping capability of each Gaussian RBF. Further, in the design of the objective function, we also handle the imbalanced problem which may occur even when different local regions have the same number of examples. Finally, the recursive orthogonal least square （ROLS） and genetic algorithm （GA）, which are usually adopted to optimize the RBF centers, are separately used to select the centers from the center candidates with the initialized widths, in order to testify the validity of our proposed width initialization strategy on the selection of centers. Our experimental results show that, compared with the heuristic width setting method, the width optimization strategy makes the selected cen- ters more appropriate, and improves the classification performance of the GRBFNN. Moreover, the GRBFNN constructed by our method can attain better classification performance than the RBF LS-SVM, which is a state-of-the-art classifier.     

Solution structure of human corticotropin releasing factor by 1H NMR and distance geometry with restrained molecular dynamics

The structure of human corticotropin releasing factor (hCRF)has been determined by proton nuclear magnetic resonance (¹HNMR) in a mixed-solvent system of 66% trifluoroethanol/34% H₂Oat pH 3.8 and 37°C. Nearly complete resonance assignmentwas achieved by using standard two-dimensional methods. Distancerestraints for structure calculations were obtained by qualitativeanalysis of intra- and interresidue nuclear Overhauser effects.Structures were obtained from the distance restraints by distancegeometry, followed by refinement using molecular dynamics andwere completed with amide hydrogen exchange data. The structureof hCRF in this solvent comprises an extended N-terminal tetrapeptideconnected to a well-defined -helix between residues 6 and 36.The first half of the -helix (residues 6–20) is clearlyamphipathic. The five carboxy-terminal residues are predominantlydisordered.