Magneto-Resistance Investigations on the In-situ Synthesized Stainless Steel Sheathed MgB2 Tapes

We report the measurement of magnetoresistance in MgB₂ tapes with a varying magnetic field applied perpendicular to the tape surface. Scaling functions for excess conductance suggested by Ullah and Dorsey have been used to analyze the scaling behavior of the resistivity in MgB₂ tapes just above their critical region. The fluctuations in the magnetoresistance, R(T,H), behavior is found to follow 3D scaling for the MgB₂ tape. From the slope of the upper critical field, H _C2 vs. T curve, it is ～68 Å. The zero temperature H _C2 that was found following the WHH model was ～5 T, whereas, from linear extrapolation of H _C2 versus T yield a value of H _C2(0)～24.5 T.     

A dysfunctional desmin mutation in a patient with severe generalized myopathy

Mice lacking desmin produce muscle fibers with Z disks and normal sarcomeric organization. However, the muscles are mechanically fragile and degenerate upon repeated contractions. We report here a human patient with severe generalized myopathy and aberrant intrasarcoplasmic accumulation of desmin intermediate filaments. Muscle tissue from this patient lacks the wild-type desmin allele and has a desmin gene mutation encoding a 7-aa deletion within the coiled-coil segment of the protein. We show that recombinant desmin harboring this deletion cannot form proper desmin intermediate filament networks in cultured cells, nor is it able to assemble into 10-nm filaments in vitro. These findings provide direct evidence that a mutation in desmin can cause human myopathies.     

Homotopy Perturbation Method for Thermal Stresses in an Annular Fin with Variable Thermal Conductivity

An approximate analytical solution method for thermal stresses in an annular fin with variable thermal conductivity is presented. Homotopy perturbation method (HPM) is employed to estimate the non-dimensional temperature field by solving nonlinear heat conduction equation. The closed-form solutions for the thermal stresses are formulated using the classical thermoelasticity theory coupled with HPM solution for temperature field. The plane state of stress conditions are considered in this study. The effects of thermal parameters such as variable thermal conductivity parameter (β), thermogeometric parameter (K), and the non-dimensional coefficient of thermal expansion (χ) on the temperature field and stress field are studied. The results for temperature field and stress field obtained from HPM-based solution are found to be in very close agreement with the results available in literature. Furthermore, the HPM solution is found to be very efficient and handles nonlinear heat transfer equation with greater convenience.     

Determination of lubricant film thickness on a particulate disksurface by atomic force microscopy

The ability of the atomic force microscope (AFM) to measure the lubricant film thickness on the surface of particulate disks is demonstrated, and experimental results are presented. AFM measure the thickness of the lubricant film at a particular location on the disk surface with a lateral resolution of the order of the AFM tip radius, ~1000 Å. For an unused disk, 50-70 Å of lubricant thickness is found. After the disk has been in use for several years, the lubricant thickness decreases to 35-55 Å. In both cases, the lubricant is uniformly distributed on the disk surface, although somewhat more uniformly on the used disk. For all types of disks studied, most of the lubricant resides below the disk surface, presumably in the medium's porosity, with only a molecular thin film of lubricant on the surface     

Adhesion and friction properties of hydrogenated amorphous carbon films measured by atomic force microscopy

Atomic force microscopy has been used to measure adhesion and friction forces at the interface between an oxidized metal probe tip and amorphous carbon films of varying hydrogen contents (12.3–39.0 atomic percent hydrogen). The interface of an oxide surface and a hard carbon coating models the unlubricated head-disk interface of current hard disk products. Adhesion forces normalized by the radius of curvature of the contacting tip range from 1.09 to 8.53 N/m. Coefficients of friction values, measured as the slope of the friction versus load plot, range from 0.33 to 0.87. A trend of increasing adhesion forces and coefficients of friction is observed for increasing hydrogen content in the films. We attribute the increase in adhesion and friction to increases in the surface free energy of the carbon films with the incorporation of hydrogen.     

Tribological Performance of UHMWPE and PFPE Coated Films on Aluminium Surface

A thin layer of Ultra High Molecular Weight Polyethylene (UHMWPE) or UHMWPE + PFPE is coated onto cylindrical aluminium (Al) pin (4.6 mm diametre) surface with the aim of providing wear resistant coating on this soft and tribologically poor metal. The coefficient of friction and wear life of the coated samples are investigated on a pin-on-disk tribometre under different normal loads (394–622 g) and two sliding speeds (0.1 and 0.31 m/s) against uncoated Al disk as the counterface. Both coatings provide coefficient of friction values in the range of 0.02–0.2 as compared to 0.4–1.0 for uncoated Al. There is tremendous improvement in the wear life of the pin, with UHMWPE + PFPE film giving wear life approximately twice to thrice higher than that with only UHMWPE film. A thin polymer film is transferred to the disk surface during sliding providing very long-term wear life (continuous low coefficient of friction) despite visual removal of the film from the pin surface. The present films will have applications in gears and bearings as solid or boundary lubricants for automotive and aerospace component.     

Multi-objective mixed integer programming and an application in a pharmaceutical supply chain

Multi-objective integer linear and/or mixed integer linear programming (MOILP/MOMILP) are very useful for many areas of application as any model that incorporates discrete phenomena requires the consideration of integer variables. However, the research on the methods for the general multi-objective integer/mixed integer model has been scant when compared to multi-objective linear programming with continuous variables. In this paper, an MOMILP is proposed, which integrates various conflicting objectives. We give importance to the imprecise nature of some of the critical factors used in the modelling that can influence the effectiveness of the model. The uncertainty and the hesitation arising from estimating such imprecise parameters are represented by intuitionistic fuzzy numbers. The MOMILP model with intuitionistic fuzzy parameters is first converted into a crisp MOMILP model, using appropriate defuzzification strategies. Thereafter, the MOMILP is transformed into a single objective problem to yield a compromise solution with an acceptable degree of satisfaction, using suitable scalarisation techniques such as the gamma-connective technique and the minimum bounded sum operator technique. The proposed solution method is applied to several test problems and a multi-objective pharmaceutical supply chain management model with self generated random data.     

Bonding and tribological properties of perfluorinated lubricantsand hydrogenated amorphous carbon films

Molecular properties of perfluorinated lubricants and amorphous carbon films relevant to the tribological performance of hard disk drives have been measured. The bonding of water and model perfluorinated lubricants to amorphous carbon surfaces has been studied by thermal desorption spectroscopy. Binding energies consistent with a physisorbed state are found for each of these small molecules. Binding energies are found to increase with increasing molecular weight and polarity of the adsorbate as well as increasing surface free energy of the carbon film. Adhesion forces and coefficients of friction have been measured with atomic force microscopy at hydrogenated amorphous carbon surfaces as a function of hydrogen content. An increase in both adhesion and friction forces is observed with increasing hydrogen contents and is attributed to changes in the surface free energy of the carbon films     

Computation of sensitivity of periodically excited dynamical systems

An analytical treatment is presented for bonded contact of a rigid disk inclusion embedded in a penny-shaped crack in a transversely isotropic full-space. Theoretical analysis is carried out using a complete potential function method, and with the aid of Hankel transforms. Boundary conditions propel the problem toward a set of triple integral equations, which are solved analytically and then reduced to a pair of Fredholm integral equations of the second kind. Furthermore, the results are evaluated and presented graphically using numerical schemes, and comparison is made with well-known classical solutions in transversely isotropic and isotropic media. This can be obtained as special cases for the problem to reveal the efficacy of the proposed method. Eventually, it can be seen that not only the presence of the crack around the disk inclusion decreases the axial stiffness, but also the extension of its length also reduces the fracture parameter, stress intensity factor, for different degrees of material anisotropy.