On the role of power in the design of materials handling tasks

The safety and productivity of workers engaged in materials handling has been a topic of interest to industrial engineers and ergonomists for some time. One of the fundamental questions that has generated considerable research is that of how to define and measure material handling capacity. The potential role of human muscle power and the resultant capacity to exert power on an external load as a measure of materials handling capacity is explored. Aside from applied literature in the exercise and sports science disciplines supporting this notion, a more theoretical basis is provided by the muscle physiology and morphology literature. The further empirical investigation of power as a means of defining materials handling capacity is supported.     

Evaluation of the ability of power to predict low frequency lifting capacity

An experiment was conducted to examine the role that maximal lifting power has in predicting maximum acceptable weight of lift (MAWL) for a frequency of one lift per 8 h. The secondary aim of the study was to compare the ability of power to predict MAWL to previously used measures of capacity including two measures of isometric strength, five measures of isokinetic strength, and isoinertial capacity on an incremental lifting test. Twenty-five male subjects volunteered to participate in the experiment. The isometric tests involved maximum voluntary contractions for composite lifting strength at vertical heights of 15 and 75 cm. Peak isokinetic strength was measured at velocities of 0.1, 0.2, 0.4, 0.6 and 0.8 m s-1 using a modified CYBEX II isokinetic dynamometer. Isoinertial lifting capacity was measured on the X-factor incremental lifting machine and peak power was measured on the incremental lifting machine by having subjects lift a 25 kg load as quickly as possible. The results indicate that peak isoinertial power is significantly correlated with MAWL, and this correlation was higher than any of the correlations between the other predictor variables and MAWL. The relationships between the isokinetic strength measures and MAWL were stronger than the relationships between the isometric measures and MAWL. Overall, the results suggest that tests used to predict MAWL should be dynamic rather than static.     

Thrombopoietin and its receptor, c-mpl, are constitutively expressed by mouse liver endothelial cells: evidence of thrombopoietin as a growth factor for liver endothelial cells

Present data suggest that the primary site of thrombopoietin (TPO) mRNA is the liver. Previously, we reported that specific murine liver endothelial cells (LEC-1) located in the hepatic sinusoids support in vitro megakaryocytopoiesis from murine hematopoietic stem cells suggesting that these cells may be a source of TPO. We report here that TPO and its receptor, c-mpl, are coexpressed on cloned LEC-1. Enzyme-linked immunosorbent assay (ELISA), biological assay, and flow cytometry studies confirmed the expression of both TPO and its receptor, respectively, at the protein level. TPO activity was enhanced in supernatants from LEC-1 treated with tumor necrosis factor (TNF)-alpha and gamma-interferon (INF). Our results show that TPO through its receptor stimulated the growth of LEC-1 in vitro. These observations establish LEC-1 as a novel source of TPO in the liver. To our knowledge, this is the first report that liver endothelial cells express both TPO and its receptor, c-mpl, and our findings indicate that this cytokine constitutes a growth factor for liver endothelial cells in vitro.     

Micropatterning of Electrospun Polyurethane Fibers Through Control of Surface Topography

A novel technique was developed to control the deposition of electrospun polyurethane fibers using a silicone collector substrate patterned with soft lithography. This method can be used to control selective fiber deposition with broad pattern dimensions (50–500 µm) over a large area. The combination of ease of use, low cost, tunability, and generation of relatively large fiber mats available with this technique is expected to advance our ability to mimic the orientation and anisotropic properties of native tissues to generate improved tissue engineering scaffolds.

     

Enhancement of hematite bioreduction by natural organic matter

The effects of natural organic matter (NOM), ferrozine, and AQDS (anthraquinone-2,6-disulfonate) on the reduction of hematite (alpha-Fe2O3) by Shewanella putrefaciens CN32 were studied. It has been proposed that NOM enhances the reduction of Fe(III) by means of electron shuttling or by Fe(II) complexation. Previously both mechanisms were studied separately using "functional analogues" (AQDS for electron shuttling and ferrozine for complexation) and are presently compared with seven different NOMs. AQDS enhanced hematite reduction within the first 24 h of incubation, and this had been ascribed to electron shuttling. Most of the NOMs enhanced hematite reduction after 1 day of incubation indicating that these materials could also serve as electron shuttles. The effect of ferrozine was linear with concentration, and all of the NOMs exhibited this behavior. Fe(II) complexation only enhanced hematite reduction after sufficient Fe(II) had accumulated in the system. Fe(II) complexation appeared to alleviate a suppression of the hematite reduction rate caused by accumulation of Fe(II) in the system. Addition of Fe(II) to the hematite suspension, prior to inoculation with CN32, significantly inhibited hematite reduction and greatly diminished the effects of all of the organic materials, although some enhancement was observed due to addition of anthroquinone-2,6-disulfonate. These results demonstrate that NOM can enhance iron reduction by electron shuttling and by complexation mechanisms.     

Medication side effects in anxious patients: negative placebo responses?

Heart sounds produce an incessant noise during lung sounds recordings. This noise severely contaminates the breath sounds signal and interferes in the analysis of lung sounds. In this paper, the use of a wavelet transform domain filtering technique as an adaptive de-noising tool, implemented in lung sounds analysis, is presented. The multiresolution representations of the signal, produced by wavelet transform, are used for signal structure extraction. In addition, the use of hard thresholding in the wavelet transform domain results in a separation of the nonstationary part of the input signal (heart sounds) from the stationary one (lung sounds). Thus, the location of the heart sound noise (1st and 2nd heart sound peaks) is automatically detected, without requiring any noise reference signal. Experimental results have shown that the implementation of this wavelet-based filter in lung sound analysis results in an efficient reduction of the superimposed heart sound noise, producing an almost noise-free output signal. Due to its simplicity and its fast implementation the method can easily be used in clinical medicine.     

Core-Based SCB Fracture of Aligned First-Year Sea Ice (Phases III and IV)

This paper provides the results of two small-scale testing programs linked to large-scale field programs carried out by the writers and others. The large-scale in-situ sea ice testing program was part of the Office of Naval Research's (ONR's) Sea Ice Mechanics Initiative (SIMI). Three field trips to Barrow, Alaska, were completed to examine the seasonal evolution of the first-year sea ice growing on Elson Lagoon. Trips were made in November, March, and May, when significant changes in thickness and temperature profile were evident. The experiments were designed to determine the fracture behavior of sea ice in situ and make comparisons with small-scale lab tests. Due to the unique microstructure of the sea ice tested, it was necessary to complete small-scale (0.1 m) tests for comparative purposes. A detailed study of the ice fabric at the site revealed a very strong alignment of the c-axis. This prompted a study of the fracture properties parallel (hard-fail) and perpendicular (easy-fail) to the preferred c-axes orientation plane in both the largeand small-scale tests. The effects of c-axis alignment, temperature and microstructure on the fracture toughness and tensile strength are investigated.     

The influence of personal variables on work-related low-back disorders and implications for future research

Work-related low-back disorders (LBDs) continue to be one of the single largest sources of compensation costs. The relative contributions of personal, workplace, organizational, and environmental variables to the development and severity of LBDs are not completely understood. The inclusion of personal variables in epidemiologic studies of LBDs has been inconsistent, and different authors have different opinions concerning the importance of such variables. Personal variables either known or suspected to influence outcomes are discussed to elucidate the importance of these variables with respect to understanding LBDs and conducting epidemiological studies in industry. The authors suggest that age, gender, injury history, relative strength, smoking, and psychosocial variables be studied further, and that height, weight, pathologies, genetic factors, maximum oxygen uptake, and absolute strength are unlikely to produce significant effects in industrial populations.     

Fractographic examinations of fracture in polycrystalline S2 ice

Fractographic examinations were carried out on the fracture surfaces of both single-edge notched bend (SENB) and wedge-loaded compact tension (WLCT) specimens of S2 freshwater ice. Formvar solutions provided an effective means of making replicas that revealed various patterns of the fracture surfaces. The fracture modes consisted of both cleavage and brittle intergranular fracture, with cleavage fracture dominating. The cleavage planes of the S2 ice were mainly the {0 0 0 1} and {10¯1 1} planes under the experimental conditions for this study. Kinks forming new grain boundaries were found on the fracture surfaces of polycrystalline S2 ice for the first time. Kinking is regarded as a possible mechanism of plastic deformation for polycrystalline ice and to partially account for the high fracture energy of S2 ice found in this study.