Membrane potential measurements on cellulose acetate membranes

Membrane potentials and apparent transport numbers of the cation are reported for cured cellulose acetate membranes bounded by HCl, NaCl, KCl and MgCl₂ solutions, using Ag/AgCl electrodes and a flow-cell method. Membranes cured at 70°, 80° and 90° are used. Bounding solution concentrations vary from 0.005 to 0.05 M at the high concentration side (bounding the dense side of the membrane), and are kept constant at 0.002 M for the low concentration solution. In the KCl 90° membrane case the low concentration solution is varied as well, from 0.0001 to 0.002 M. Results show that cured cellulose acetate membranes are permselective towards univalent cations. This is interpreted as resulting from a low cation-exchange capacity of the dense layer of the cured membrane. The permselectivity increases with increased curing temperature. Addition of a non-electrolyte to the low concentration side reverses the osmotic flow and leads to higher apparent transport numbers of the cation. It is concluded that diffusion in small pores contributes significantly to the transport of ionic solutes through uncompacted membranes.     

Heelstrike and the pathomechanics of osteoarthrosis: a pilot gait study

Involvement of mechanical factors in osteoarthrosis (OA) has been well documented. For OA of the human lower limb, the impulse imparted at heelstrike has been suggested as a pathogenic factor. It has also been reported that there is a large amount of variation in the level of impulse experienced by different individuals, and it is suggested that those who experience large impulses are at a greater risk of developing OA. The current study investigated gait patterns of 12 normal subjects to establish the gait determinants responsible for producing large impulses at heelstrike. The results suggest that subtle variations in the early part of the swing phase pattern are responsible for large differences in the impulse experienced at heelstrike; the usually reported gait variables mask these variations.     

Familial aggregation of urinary kallikrein concentration in childhood: relation to blood pressure, race and urinary electrolytes

Biochemical alterations that have been correlated with elevated blood pressure have not received extensive epidemiologic study because of the technical difficulties involved. Because the excretion of urinary kallikrein is reduced significantly in adult hypertensives, we have studied urinary kallikrein in a cohort of children in whom familial aggregation of blood pressure has been demonstrated. Casual specimens of urine were obtained in household surveys, and urinary concentration of kallikrein was determined in 601 children aged 5-18 years. The children were from 163 families, whose members also had their blood pressures measured. Familial aggregation of urinary kallikrein concentration was found by analysis of variance (F=3.45, p less than 0.001) even in these casual specimens and was demonstrable for black and white children analyzed separately. Urinary kallikrein concentration was significantly lower in black children than in white children (p less than 0.001) and was positively correlated with urinary creatinine and urinary potassium and inversely related to urinary sodium concentrations. Urinary kallikrein concentration also was being altered by season (being lowest in the summer) and by time of day (being highest in the morning). Families with the lowest mean kallikrein concentrations tended to have higher blood pressures than did families with the highest mean kallikrein concentrations, although the effect is small and subject to many variables.     

Comparative loss analysis and efficiency performance of resonance-based PDP sustain drivers

Sustain drivers based on the LC resonant operation have a significant influence on the entire circuit efficiency and cost of plasma display panels (PDPs). Although circuit efficiency of PDP drivers is extremely important, theoretical loss analysis and comparative studies of the sustain drivers have been missed in the literature, despite a variety of developed PDP sustain drivers. This paper presents in detail theoretical analyses and systematic comparisons of semiconductor losses in the PDP sustain drivers, including the inevitable conduction losses by the displacement currents, the undesirable extra conduction losses, the switching losses by the forced current commutations and the switching losses by the step voltage changes. Based on derived theoretical analysis and comparative features, sustain drivers are evaluated in terms of PDP operating speed as well as circuits’ efficiency.     

Design of Strain‐Limiting Substrate Materials for Stretchable and Flexible Electronics

Recently developed classes of electronics for biomedical applications exploit substrates that offer low elastic modulus and high stretchability, to allow intimate, mechanically biocompatible integration with soft biological tissues. A challenge is that such substrates do not generally offer protection of the electronics from high peak strains that can occur upon large‐scale deformation, thereby creating a potential for device failure. The results presented here establish a simple route to compliant substrates with strain‐limiting mechanics based on approaches that complement those of recently described alternatives. Here, a thin film or mesh of a high modulus material transferred onto a prestrained compliant substrate transforms into wrinkled geometry upon release of the prestrain. The structure formed by this process offers a low elastic modulus at small strain due to the small effective stiffness of the wrinkled film or mesh; it has a high tangent modulus (e.g., >1000 times the elastic modulus) at large strain, as the wrinkles disappear and the film/mesh returns to a flat geometry. This bilinear stress–strain behavior has an extremely sharp transition point, defined by the magnitude of the prestrain. A theoretical model yields analytical expressions for the elastic and tangent moduli and the transition strain of the bilinear stress–strain relation, with quantitative correspondence to finite element analysis and experiments.     

Ferromagnetic,Folded Electrode Composite as a Soft Interface to the Skin for Long‐Term Electrophysiological Recording

A class of ferromagnetic, folded, soft composite material for skin‐interfaced electrodes with releasable interfaces to stretchable, wireless electronic measurement systems is introduced. These electrodes establish intimate, adhesive contacts to the skin, in dimensionally stable formats compatible with multiple days of continuous operation, with several key advantages over conventional hydrogel‐based alternatives. The reported studies focus on aspects ranging from ferromagnetic and mechanical behavior of the materials systems, to electrical properties associated with their skin interface, to system‐level integration for advanced electrophysiological monitoring applications. The work combines experimental measurement and theoretical modeling to establish the key design considerations. These concepts have potential uses across a diverse set of skin‐integrated electronic technologies.     

Modulation of magnetoelectric coupling through systematically engineered spin canting in nickel–zinc ferrite

A nickel–zinc ferrite system, which is one of the well-known versatile soft-ferromagnetic oxides, was investigated in terms of magnetoelectric (ME) coupling at room temperature. Herein, we demonstrated that spin canting is manipulated through a composition-induced structural transition from an inverse to a normal spinel structure, leading to modulation in the ME coupling. The ME coefficient was maximized at 60 at.% Zn substitution with a value of 0.1 mV/(Oe·cm), denoting ∼70% enhancement compared to that of the pure nickel ferrite. It was revealed that the interspin angle is enhanced along the octahedral site at up to ∼60 at.% Zn substitution, consistent with the composition level at the culmination of the ME coupling, evidenced by X-ray diffraction profiles and magnetic hysteresis loops combined with density functional theory calculations. Given that this approach is based on a tractable fabrication method, this study is expected to be widely used in modulation of the ME coupling in spinel-structured oxides.     

Effects of Annealing Treatment Prior to Cold Rolling on the Edge Cracking Phenomenon of Ferritic Lightweight Steel

Effects of annealing treatment from 923 K to 1023 K (650 °C to 750 °C) prior to cold rolling on the edge cracking phenomenon of a ferritic lightweight steel were investigated. The edge cracking was severely found in the hot-rolled and 923 K (650 °C)-annealed steels after cold rolling, whereas it hardly occurred in the 1023 K (750 °C)-annealed steel. As the annealing temperature increased, lamellar κ-carbides were dissolved and coarsened, and most of the κ-carbides continuously formed along boundaries between ferrite and κ-carbide bands disappeared. Microstructural observation of the deformed region of tensile specimens revealed that the removal of band boundary κ-carbides reduced the difference in tensile elongation along the longitudinal direction (LD) and transverse direction (TD), which consequently led to the reduction in edge cracking. The 1023 K (750 °C)-annealed steel showed fine ferrite grain size, weak texture, and decomposed band structure after subsequent cold rolling and intercritical annealing, because κ-carbides actively worked as nucleation sites of ferrite and austenite. The present annealing treatment prior to cold rolling, which was originally adopted to prevent edge cracking, also beneficially modified the final microstructure of lightweight steel.