Manual dexterity of older Mexican American adults: a cross-sectional pilot experimental investigation

This paper reports results from an experimental pilot study performed to quantify the manual dexterity of older Mexican American adults. The Purdue pegboard test, a two-arm coordination test, and a hand-tool dexterity test were used in this study. To enable cross-sectional comparisons of manual dexterity measures of older Mexican American adults with young Mexican American adults, these tests were administered to 18 older Mexican American adults aged 63–85 (mean age: 71.3 years, SD: 7.0 years), recruited from senior recreation centers in El Paso, and eighteen young adults aged 21–32 (mean age: 25.6 years, SD: 3.8 years) recruited from the student body at the University of Texas at El Paso. For the Purdue pegboard test, the number of pegs placed in 30 s using the preferred hand, the non-preferred hand, and both hands were first individually monitored. Then, scores on an assembly task using the Purdue pegboard were obtained. For the two-arm coordination test, participants were required to trace a star pattern with a stylus using both hands. The time for task completion and the number of errors made during task performance were monitored. For the hand-tool dexterity test, participants were required to use common hand tools and remove nuts and bolts from one side of a wooden upright, and to assemble nuts and bolts in the corresponding holes on the other side of the upright. The time taken for task completion was recorded. Since modified Levene's test showed equality of variances, two sample t-tests, comparing the mean responses of older adults with the mean responses of young adults for each individual test, were conducted. Results indicate that responses for the older adults were statistically significant different (p<0.001) from young adults for all Purdue pegboard tasks. On the average, older adults performed significantly slower (p<0.001) than young adults on the two-arm coordination test, and committed more errors before task completion (p<0.05). Older adults also took longer to complete the hand-tool dexterity task compared to their younger counterparts (p<0.05). In addition to the t-tests, manual dexterity performance measures from older adults were regressed with age to determine the cross-sectional age effects on manual dexterity measures. Results indicate that all Purdue pegboard performance measures were significantly affected by age (p<0.05). The time to complete the two-arm coordination test was significantly linearly related to age (p<0.05). However, the number of errors committed by older adults in the performance of the two-arm coordination test was not significantly linearly related to age. Time to complete the hand-tool dexterity was also significantly linearly related to age (p<0.05). Accommodating age-related changes in manual dexterity is important for job design in industry, especially in industries employing older adults requiring significant assembly and hand-tool use.

Relevance to industry

Given the aging of the industrial workforce, it is important to understand how manual dexterity is affected by age, so that jobs requiring significant manual dexterity for task initiation, task performance and task completion are designed to fit older adult dexterity levels.     

Efficient procedure for computing fields created by current modes

An efficient method for computing the fields of large scatterers is presented. The current is expanded in terms of modes defined as complex exponential functions. The modes are represented efficiently by means of spline functions. Analytical expressions have been obtained to compute efficiently the fields due to the current modes.     

Improving manufacturing by cost-effective process modeling

Computer-aided engineering tools are routinely used to simulate forging and heat-treatment operations and to perform thermal and stress analyses. This review gives a few examples of the current uses of process modeling tools and outlines some developing capabilities and near-term applications.     

A Simple Experimental Technique to Measure Tortuosity in Packed Beds

In this article, a simple and inexpensive experimental technique easy to build in laboratory, for the measurement of tortuosity of a packed bed of inert particles, is described. Experimental values of the tortuosity were obtained with four different packed beds of sand. The experimental results obtained are in good agreement with the theoretical values of tortuosity in a porous media; and the data reported showed the tortuosity to increase with decrease in the void fraction of the packed bed as expected.     

Molecular Diffusion Coefficients of Organic Compounds in Water at Different Temperatures

Molecular (or tracer) diffusion coefficient data were obtained for 2-naphthol, benzoic acid, salicylic acid, camphor, and cinnamic acid in water at temperatures that differ significantly from ambient value. Experimental values were determined for the dissolution of 2-naphthol in water at 283 to 368 K, of benzoic acid in water at 283 to 338 K, of salicylic acid in water at 283 to 343 K, of camphor in water at 283 to 318 K, and of cinnamic acid in water at 283 to 318 K. Empirical correlations are presented for the prediction of molecular diffusion coefficient over the entire range of temperatures studied, and they are shown to predict the obtained data with very good accuracy.     

Modelling the kinetics of antigen-antibody reactions at particle enhanced optical immunoassays

Functionalized latexes coated by antibodies are used in diagnostic tests for the detection of antigens in biological fluids. A simple kinetic model is presented which is related to the optical monitoring of the formation of specific complexes between antigen and antibody amplified by latex beads. The antibodies are chemically coupled onto chloromethylstyrene (CMST) particles. The kinetic model is able to describe the immunoprecipitin curves of immunolatex beads. The number of fitting parameters is relatively reduced (only three), and the meaning of these parameters can be interpreted in terms of the chemical equilibrium constant, the percentage of active IgG on the latex beads, and optical response. The model explains very well the optical response of immunolatex prepared by covalent coupling of antibodies on polymer carriers.     

Crystallinity and thermal properties of ethylene-1-decene copolymers

Summary Three copolymers of ethylene and 1-decene, covering a wide range of compositions, have been synthesized with a MgCl₂-supported Ziegler-Natta catalyst. The analysis by DSC and X-ray shows a great degree of heterogeneity in these copolymers and appreciable levels of crystallinity, corresponding to the orthorhombic lattice of polyethylene, are present even for very high 1-decene contents.     

Impact of agriculture on soil consumption of atmospheric CH4 and a comparison of CH4 and N2O flux in subarctic, temperate and tropical grasslands

Increasing concentrations of methane (CH₄) in the atmosphere are projected to account for about 25% of the net radiative forcing. Biospheric emissions of CH₄ to the atmosphere total approximately 400 Tg C y^-1. An estimated 300 Tg of CH₄-C y^-1 is oxidized in the atmosphere by hydroxyl radicals while about 40 Tg y^-1 remains in the atmosphere. Approximately 40 Tg y^-1 of the atmospheric burden is oxidized in aerobic soils. Research efforts during the past several years have focused on quantifying CH₄ sources while relatively less effort has been directed toward quantifying and understanding the soil sink for atmospheric CH₄. Recent research has demonstrated that land use change, including agricultural use of native forest and grassland systems has decreased the soil sink for atmospheric methane. Some agricultural systems consume atmospheric CH₄ at rates less than 10% of those found in comparable undisturbed soils. While it has been necessary to change land use practices over the past centuries to meet the required production of food and fiber, we need to recognize and account for impacts of land use change on the biogeochemical nutrient cycles in the biosphere. Changes that have ensued in these cycles have and will impact the atmospheric concentrations of CH₄ and N₂O. Since CH₄ and N₂O production and consumption are accomplished by a variety of soil microorganisms, the influence of changing agricultural, forest, and, demographic patterns has been large. Existing management and technological practices may already exist to limit the effect of land use change and agriculture on trace gas fluxes. It is therefore important to understand how management and land use affect trace gas fluxes and to observe the effect of new technology on them. This paper describes the role of aerobic soils in the global CH₄ budget and the impact of agriculture on this soil CH₄ sink. Examples from field studies made across subarctic, temperate and tropical climate gradients in grasslands are used to demonstrate the influence of nutrient cycle perturbations on the soil consumption of atmospheric CH₄ and in increased N₂O emissions. This revised version was published online in August 2006 with corrections to the Cover Date.     

A geometric solution to the largest-free-sphere problem in zeolite frameworks

We have applied Delaunay triangulation to models of the known zeolite frameworks. We show that this well-established technique from computational geometry provides for each framework; (i) the location and shape of the open pores and channels, (ii) the diameter of the largest possible included sphere, and indirectly (iii) the diameter of the largest-free-sphere that can diffuse through the framework by at least one lattice translation. Since Delaunay triangulation naturally locates the empty spaces within a set of points, it provides a powerful computer-automated tool for determining the physical characteristics of pores and channels of zeolite frameworks. Such tools will further enhance the usefulness of large databases of hypothetical framework materials.

Here, we tabulate results for the 165 zeolite frameworks that are presently listed in the Atlas of Zeolite Frameworks. Of the known zeolites, refined as pure silicates, the largest included sphere occurs in the TSC framework, with a diameter of 16.39 Å. The largest-free-sphere has a diameter of 11.33 Å, for diffusion along the [0 0 1] direction in the VFI framework.     

The influence of gun transverse speed on electrochemical behaviour of thermally sprayed Cr3C2-NiCr coatings in 0.5 M H2SO4 solution

In the present study, different types of 75% Cr₃C₂-25% NiCr coatings were applied on a steel substrate by means of high velocity oxygen fuel spraying (HVOF), and studied using ac and dc electrochemical measurements in an aerated and unstirred 0.5 M H₂SO₄ solution. Structural characterization was determined before and after electrochemical tests. Differences between all sprayed systems are related to the gun transverse speed and number of deposited layers, which strongly affected the electrochemical characteristics of the coated steels. The coating obtained with a higher torch speed showed better resistance against corrosion. The electrochemical impedance results were analyzed using an equivalent circuit where porosity of the coatings and substrate oxidation were considered.