42 resultados para Cleaning machinery and appliances

em University of Queensland eSpace - Australia


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Longwall shearers usually suffer from excessive pick and pickholder consumptions and severe wear of the backplate of the clearance ring section of shearer drums. In practice, most of the drums were seen to be withdrawn from the face due to the abovementioned problems, while vane picks and their holders were intact due to the improper lacing design of the clearance ring picks. However, few underground investigations and their results on the effect of lacing arrangement of clearance picks on the service life of shearer drums have been published. Nevertheless, the pick consumption characteristics of shearer drums were not investigated in detail, since these are fewer pick consumptions with shearers when compared to roadheaders. This paper is concerned with the comprehensive in situ trials on the effect of lacing of clearance ring picks on the lifespan of shearer drums, and the pick consumption characteristics of longwall shearers at Cayirhan Coal Mine in Turkey. The lifespan of shearer drums employed with shearers in this mine increased 70 per cent, while the consumption rate of clearance ring picks decreased three fold through using an alternative lacing for clearance picks, indicating the significance of utilizing proper design techniques for clearance ring picks for the service life of shearer drums. Statistical analyses carried out, using the raw pick consumption data, implied that the clearance ring picks experienced much higher loads than vane picks, revealing that special attention must be paid to designing clearance ring picks. An average maximum consumption value of 41 was determined for clearance ring picks, with corner-cutting picks having the most replacements, while it was 35 for vane picks, on three-day based pick replacements.

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Participation in at least 30 min of moderate intensity activity on most days is assumed to confer health benefits. This study accordingly determined whether the more vigorous household and garden tasks (sweeping, window cleaning, vacuuming and lawn mowing) are performed by middle-aged men at a moderate intensity of 3-6 metabolic equivalents (METs) in the laboratory and at home. Measured energy expenditure during self-perceived moderate-paced walking was used as a marker of exercise intensity. Energy expenditure was also predicted via indirect methods. Thirty-six males [Xmacr (SD): 40.0 (3.3) years; 179.5 (6.9) cm; 83.4 (14.0) kg] were measured for resting metabolic rate (RMR) and oxygen consumption (V.O-2) during the five activities using the Douglas bag method. Heart rate , respiratory frequency, CSA (Computer Science Applications) movement counts, Borg scale ratings of perceived exertion and Quetelet's index were also recorded as potential predictors of exercise intensity. Except for vacuuming in the laboratory, which was not significantly different from 3.0 METs (P=0.98), the MET means in the laboratory and home were all significantly greater than 3.0 (Pless than or equal to0.006). The sweeping and vacuuming MET means were significantly higher (P

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A number of recent studies have provided new insights into the complexity of the endocytic pathways originating at the plasma membrane of mammalian cells. Many of the molecules involved in clathrin coated pit internalization are now well understood but other pathways are less well defined. Caveolae appear to represent a low capacity but highly regulated pathway in a restricted set of tissues in vivo. A third pathway, which is both clathrin- and caveolae-independent, may constitute a specialized high capacity endocytic pathway for lipids and fluid. The relationship of this pathway, if any, to macropinocytosis or to the endocytic pathways of lower eukaryotes remains an interesting open question. Our understanding of the regulatory mechanisms and molecular components involved in this pathway are at a relatively primitive stage. In this review, we will consider some of the characteristics of different endocytic pathways in high and lower eukaryotes and consider some of the common themes in endocytosis. One theme which becomes apparent from comparison of these pathways is that apparently different pathways can share common molecular machinery and that pathways considered to be distinct actually represent similar basic pathways to which additional levels of regulatory complexity have been added. (c) 2005 Elsevier B.V. All rights reserved.

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The nuclear localization of a number of growth factors, cytokine ligands and their receptors has been reported in various cell lines and tissues. These include members of the fibroblast growth factor (FGF), epidermal growth factor and growth hormone families. Accordingly, a number of nuclear functions have begun to emerge for these protein families. The demonstration of functional interactions of these proteins with the nuclear import machinery has further supported their functions as nuclear signal transducers. Here, we review the membrane- trafficking machinery and pathways demonstrated to regulate this cell surface to nucleus-trafficking event and highlight the many remaining unanswered questions. We focus on the FGF family, which is providing many of the clues as to the process of this unusual phenomenon.

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Isoleucine, leucine and valine are synthesized via a common pathway in which the first reaction is catalysed by AHAS (acetohydroxyacid synthase; EC 2.2.1.6). This heterotetrameric enzyme is composed of a larger subunit that contains the catalytic machinery and a smaller subunit that plays a regulatory role. The RSU (regulatory subunit) enhances the activity of the CSU (catalytic sub unit) and mediates end-product inhibition by one or more of the branched-chain amino acids, usually valine. Fungal AHAS differs front that in other organisms in that the inhibition by valine is reversed by MgATP. The fungal AHAS RSU also differs from that in other organisms in that it contains a sequence insert. We suggest that this insert may form the MgATP-binding site and we have tested this hypothesis by mutating ten highly conserved amino acid residues of the yeast AHAS RSU. The modified subunits were tested for their ability to activate the yeast AHAS CSU, to confer sensitivity to valine inhibition and to mediate reversal of the inhibition by MgATP. All but one of the mutations resulted in substantial changes in the properties of the RSU. Unexpectedly, four of them gave a protein that required mgATP in order for strong stimulation of the CSU and valine inhibition to be observed. A model to explain this result is proposed. Five of the mutations abolished MgATP activation and are suggested to constitute the binding site for this modulator.