An efficient synthesis of highly functionalized chiral lactams

A new method was developed to synthesize highly functionalized lactams via a one pot reductive amination/lactam formation reaction. This methodology is amenable for parallel synthesis and was used to prepare a large number of lactam analogs in a library format with good ee (de) retention.     

La3Ni2O6: a new double T'-type nickelate with infinite Ni1+/2+O2 layers

New mixed-valent, Ni1+/Ni2+, metastable nickelate, La3Ni2O6, was synthesized by low-temperature reduction of La3Ni2O7 with CaH2. The crystal structure of La3Ni2O6 (space group: I4/mmm, a = 3.9686(1) A and c = 19.3154(6) A) was determined from powder neutron diffraction data by Rietveld analysis. The structure can be described as an intergrowth of LaO2 fluorite and double infinite layer (LaNiO2)2 blocks and represents the n = 2 homologue of the T'-type series Lan+1NinO2n+2. Such double T'-type structural arrangement has never been observed before. The 3d9/3d8 electronic configuration of Ni1+/Ni2+ and the presence of NiO2 infinite layers resemble electronic and structural features of the superconducting cuprates. X-ray absorption spectroscopy supports the 1+/2+ oxidation state and planar coordination of Ni in agreement with the structure determination.     

The Galerkin method as applied to problems in viscoelasticity

This paper establishes the convergence of the continuous-time Galerkin technique as applied to quasi-static, linear viscoelasticity.     

Effect of loading variables on the acoustic emissions of fatigue-crack growth

A series of experiments has been conducted to determine the effect of loading variables such as cyclic frequency, load ratio, and material on acoustic emission from fatigue-crack propagation. It is shown that the applied-stress intensity range (ΔK) is the controlling parameter for all materials studied while the other parameters have lesser effects. Two potential methods for engineering application of acoustic emission during fatigue loading are described.     

Application of holographic interferometry to predict long-time torsional relaxation

The objective of the work described in this paper was to develop techniques to predict long-term relaxation in torsional springs based on short-time data. The torsional springs examined in this study were torsion bars fabricated from 300M steel (280–300-ksi tensile strength). A holographic technique was utilized to perform very precise measurements of relaxation in torsion bars. The technique utilizes real-time holographic interferometry and was capable of resolving relaxation (torque losses) as small as. 01 in.-lb for a bar initially torqued to 825 in.-lb. The holographically determined torque-logs data were used to develop a model to estimate the relaxation behavior of the torsion bars. The model determined to best fit the data is described by: ΔT=0.32(t+50)^0.4?qt ^?1 wheret = time in hours ΔT = total change in torque (in.-lb) The model was developed to fit the holographic data from 0 to 5000 h. Excellent agreement between the torque-loss rate predicted by the model and that actually measured holographically at 10,000 h was obtained. This further indicates that long-time relaxation behavior of the torsion bars can be accurately predicted from short-time tests. Using the model, it is now a simple matter to holographically measure and evaluate the relaxation of other lots of torsion bars to predict their long-time relaxation behavior. The measurement period can be as short as 100 h to show the comparison with baseline data. The long-time prediction can be compared with the acceptable engineering-energy requirements to determine suitability for service.     

A localized hybrid method of stress analysis: A combination of moiré interferometry and FEM

A method of combining moiré interferometry and the finite-element method to effect localized stress analysis is presented. The displacement data from local regions of interest in the optical experiment are used as boundary conditions for the finite-element stress analysis. The stability of the method is examined with data from simple numerical models one of which corresponded to the stress analysis of a pin-loaded plate with friction. These studies show that the method requires the sensivity of moiré interferometry for successful implementation, i.e., displacement data accuracy within 0.1 μm or 4 μin. This localized hybrid method of stress analysis provides a powerful and efficient method for the reduction of experimental data.     

Linear and non-linear nature of the flow of polypropylene filled with ferrite particles: from low to concentrated composites

The flow behavior of a filled suspension consisting of ferrite particles suspended in a polypropylene matrix with and without the addition of a commercial dispersant (Solplus DP310) was studied. The composites were filled with 10, 20, 30, and 40 vol.%. Both capillary and parallel disk rotational flows were employed. On the one hand, dynamic results confirm general trends found for highly concentrated systems. The higher is the filler level, the lower is the linear viscoelastic domain. When adding the dispersant agent, it was shown a larger linear viscoelastic domain, lower moduli values and thus, lower viscosity. Also, the critical strain, G′ and G′′ showed a power law dependency on the volume fraction. On the other hand, the capillary results showed no dependency of the flow properties on the die. Thus, no slip of the suspension at the wall was observed. Actually, this experimental finding elucidated that the significant decrease on viscosity produced by the addition of the dispersant agent at 40 vol.% is principally due to lubricant effects and not at all to slip contributions. The results also reveal three distinct flow regimes. Low, moderate, and high shear rates lead to different microstructure under flow.