Moment arms and lengths of human upper limb muscles as functions of joint angles

Modeling of musculoskeletal structures requires accurate data on anatomical parameters such as muscle lengths (MLs), moment arms (MAs) and those describing the upper limb position. Using a geometrical model of planar arm movements with three degrees of freedom, we present, in an analytical form, the available information on the relationship between MAs and MLs and joint angles for thirteen human upper limb muscles. The degrees of freedom included are shoulder flexion/extension, elbow flexion/extension, and either wrist flexion/extension (the forearm in supination) or radial/ulnar deviation (the forearm in mid-pronation). Previously published MA/angle curves were approximated by polynomials. ML/angle curves were obtained by combining the constant values of MLs (defined by the distance between the origin and insertion points for a specific upper limb position) with a variable part obtained by multiplying the MA (joint radius) and the joint angle. The MAs of the prime wrist movers in radial/ulnar deviation were linear functions of the joint angle (R2 > or = 0.9954), while quadratic polynomials accurately described their MAs during wrist flexion/extensions. The relationship between MAs and the elbow angle was described by 2nd, 3rd or 5th-order polynomials (R2 > or = 0.9904), with a lesser quality of fit for the anconeus (R2 = 0.9349). In the full range of angular displacements, the length of wrist, elbow and shoulder muscles can change by 8.5, 55 and 200%, respectively.     

Investigating the thermal-plasma processing of advanced materials

Due to several inherent advantages, plasma processing technology may become a very useful tool in the production of new materials. An increasing research effort based on experimental as well as theoretical investigations has been invested in this area for the synthesis of advanced materials. In describing the thermal-plasma processing technique, this article employs examples from research at the Plasma Processing Laboratory at the University of Idaho.     

A discontinuous buffer system increasing resolution and reproducibility in DNA sequencing on high voltage horizontal ultrathin-layer electrophoresis

A novel discontinuous buffer system for DNA sequencing based on horizontal ultrathin-layer gel electrophoresis is described. The optimized system, named unbuffered stacking gel/discontinuous borate EDTA-buffer system, is composed of a 0.5 mm thick stacking gel, where standard sequencing reactions (1 microL volume) are easily loaded, and a 50 microns ultrathin running gel, where DNA fragments are separated. The novel discontinuous buffer system allows for sample concentration and efficient injection from the stacking gel into the capillary slab gel. Increased resolution, assessed by autoradiography, can be achieved within 25 min running time already over a 10.1 cm distance from the gel slot compared to the conventional gel system. An advantage of the new system is the capacity to resolve compressions in GC-rich regions, usually causing migrating artifacts in standard gels. The described system affords a major improvement in speed, resolution and reproducibility in DNA sequencing.     

Minimum-phase filter design from linear-phase startpoint viabalanced model truncation

A new practical design approach for minimum-phase FIR or IIR filters, setting out from a high dimensionality FIR linear-phase prototype is described. The novelty of this technique lies in overcoming the inherent problem of finding the roots of a high order polynomial with repeated and/or very closely clustered roots     

New method for assessing the global quality of energy systems

Comparisons of various energy systems are often made from partial, limited standpoints that do not take into due consideration the numerous factors involved in such systems. A more complete assessment of the global quality of energy systems must consider a wider range of characteristics, such as: conversion and transportation yields, energy potential, added value, risk of accidents during conversion and transportation, coefficients of transportability and storability, and polluting emissions (carbon monoxide, carbon dioxide, sulphur and nitrogen oxides, unburnt hydrocarbons, dust, radionuclides and dispersed heat).

This paper not only identifies and quantifies the parameters that allow the above qualities to be expressed, but also defines a tree-structured energy-quality index system which starts from the parameters identified and makes it possible to obtain a global summary index, through various intermediate levels of aggregation.

Our objective is to make an instrument available to professionals (engineers, policymakers and energy managers) which allows them to concentrate their attention each time, according to the specific needs in question, on particular aspects of the quality of the energy, or to obtain numerical indicators that briefly express quality in the broadest sense.

In addition, a sample application of the proposed method is presented, using data gathered mainly from the literature on alternative systems for power production and space heating by fossil fuels.     

Influence of interfacial microcracks on the elastic properties of composites

A model is established to quantify the influence of interfacial microcracks on the elastic properties of a particulate composite using a combination of theoretical and finite element analysis. A unique way to construct physical models which could accommodate both crack size and crack density is proposed. Based on energy principles, the influence of a dilute concentration of interfacial microcracks is first studied. The case of a finite concentration of microcracks is solved subsequently by combining the dilute concentration solutions and the differential scheme. Both cases agreed well with existing composite theories for the limiting condition of complete decohesion. The final model predicts the effective elastic properties as functions of both crack size and microcrack density.     

Diffusion bonding of ferritic oxide dispersion strengthened alloys to austenitic superalloys

The superior high temperature mechanical strength and oxidation resistance of ferritic oxide dispersion strengthened (ODS) tubular alloys are compromised by the difficulties encountered in joining. Conventional fusion welding techniques generate a weld fusion zone which is devoid of the mechanical strength exhibited by the base material. Therefore, more sophisticated solid state joining techniques, such as diffusion bonding, must be employed when joining ODS materials. This paper describes a series of solid state diffusion bonding experiments carried out between two tubular ferritic ODS alloys and two high temperature austenitic alloys. Careful control of bonding conditions produced pressure retaining joints between one of the tubular ODS alloys and both austenitic alloys. The successful joint design was incorporated into the manufacture of a tubular creep component, which enabled a series of internally pressurized creep tests to be carried out. The microstructure developed at the bond interface of each of the four separate material couples is described and the high temperature performance of the pressure retaining joints is discussed.     

Behavior of a vibrating wire near the liquid3He-vacuum interface and in a saturated3He-4He mixture

In this paper we describe the effect of the vicinity of a liquid³He-vacuum interface on the behavior of a vibrating wire viscometer. It was found that in the fluid near the liquid interface the quality factor is lower than in the bulk liquid. We further report on the observation of a doubling of the resonance peak of the wire in a saturated³He-⁴He mixture. The frequencies and amplitudes of the two peaks strongly depend on the distance between the phase boundary and the vibrating wire; the temperature and the velocity of the phase boundary have no significant influence on the peak frequencies. The observed peak doubling is attributed to the coupling of the vibrating wire with a standing second-sound wave in the dilute phase where the volume of the dilute phase can be regarded as a resonating cavity for second sound.