Low Volume Load Research Articles

Effect of muscle oxygenation during resistance exercise on anabolic hormone response.

The mechanisms that underlie the affect of acute program variables on muscle growth and strength development for strength/power athletes have been of great interest. This investigation examined the affects of two different resistance exercise protocols on muscle oxygenation, and the anabolic hormonal response to such exercise. Eleven experienced resistance-trained male athletes performed four sets of the squat exercise using either a low-intensity, high-volume (LI; 15 repetitions at 60% one-repetition maximum [1-RM]) or high-intensity, low-volume (HI; 4 repetitions at 90% 1-RM) load. Venous blood samples were obtained before (Pre), immediate (IP), 20- (20P), and 40-min (40P) postexercise. Continuous-wave near-infrared spectroscopy was used to measure oxygen desaturation during exercise. No differences in muscle deoxygenation were seen between LI and HI. However, time-dependent postexercise reoxygenation was significantly different between the two exercise sessions (35.3 +/- 17.4 s vs 24.5 +/- 14.3 s in LI and HI, respectively). Testosterone and growth hormone (GH) concentrations were significantly elevated from Pre at IP, 20P, and 40P in both LI and HI. GH concentrations were higher (P<0.05) for LI than at HI at 20P and 40P. Muscle oxygen recovery kinetics appeared to be influenced by differences in the intensity and volume of exercise, and delayed reoxygenation appears to affect the GH response to exercise.

Energy accumulation in nanoparticle collision and coalescence processes

During coalescence, the surface area of the particle decreases, resulting in a heat release associated with the resulting lower surface energy. In a growth process particle heating competes with heat transfer by conduction to the cooler carrier gas and radiation. This temperature increase can be extremely important and should be accounted for when modeling collision/coalescence processes. The heat release associated with particle coalescence may reduce the coalescence time by as much as a few orders of magnitude. In addition, under some conditions there is insufficient time for the particles to cool to the gas temperature before another collision event takes place. Two such cases are investigated in this paper: (1) low pressure growth of Si nanoparticles and (2) high volume loading growth of TiO 2 nanoparticles. It is shown that accounting for energy release and heat transfer effects have a dramatic effect on primary particle formation and the onset of aggregate formation. The results of the work indicate that to grow the largest primary particles one should operate at low pressures and/or high volume loadings.

COAL FLY ASH-AND COPPER SMELTER DUST-INDUCED MODULATION OF EX VIVO PRODUCTION OF TUMOR NECROSIS FACTOR-ALPHA BY MURINE MACROPHAGES: EFFECTS OF METALS AND OVERLOAD

The objective of this study was to assess the effect of two arsenic-containing particles, coal fly ash (FA) and copper smelter dust (CU), on lung integrity and on the ex vivo release of tumor necrosis factor alpha (TNF- ) by alveolar phagocytes. Particle effects were compared in nonoverload condition on the basis of a low but identical volume load and arsenic content intratracheally instilled in the mouse lung (273 nl/mouse and 186 ng arsenic/mouse; FAL and CUL groups). Other mice received 600 ng arsenic/mouse in amounts of particles leading to different volume loads (FAH and CUH groups: 880 and 273 nl/mouse, respectively). Animals were sacrificed at 1, 6, 30, or 120 d (FAL and CUL groups) or at 6 and 120 d posttreatment (FAH and CUH groups). Biochemical markers and inflammatory cell number and type were analyzed in bronchoalveolar lavage, ex vivo TNF- production by alveolar phagocytes was assessed, and measurement of arsenic lung content and histopathological examinations were performed. Our results show that coal fly ash and copper smelter dust bear distinct inflammatory properties. At the end of the observation period (d 120), the high CU dose (CUH ) produced a fibrotic reaction whereas the high dose of FA particles (FAH ) generated a delayed and persistent lung inflammatory reaction associated with lymphoid noduli. Marked differences in TNFproduction were observed within the CU and FA groups. CU particles, conceivably through their metal content, decreased TNF-production by alveolar phagocytes. Due to their low arsenic content, considerably higher FA particle doses needed to be administered to produce an inhibition of TNF-production. Since high doses of FA (FAH) caused an overload condition, our results do not allow us to decide whether FA-mediated TNF reduction is due to the load administered or to the metallic content.

High Frequency Permeability of Mn-Zn Ferrite and its Composite Materials

Complex permeability spectra (μ*=μ'-iμ) in Mn-Zn ferrite and its composite materials have been studied. In sintered ferrite, resonance-type frequency dispersion was observed at room temperature but decrement of μ' is steeper than that of ordinary resonance. As the temperature is decreased, onset frequency of dispersion shifts higher and dispersion character changes to relaxation-type. In ferrite composite materials, relaxation characters were also observed at low volume loading samples. Since Mn-Zn ferrite has relatively high electrical conductivity at room temperature, high frequency permeability is suppressed by eddy current. However, lowering of temperature and reduction of ferrite content result in the decrease of eddy current; magnetic resonance such as relaxation-type spin rotational one appears in high frequency region.

The permeability tensor of composite consisting of magnetic particles

The demagnetizing energy of spheroidal magnetic particles dispersed in cubic lattices has been calculated. The demagnetizing energy contains contributions from the demagnetizing self-energy and magnetostatic coupling energy between particles. The total demagnetizing energy can be conveniently expressed in terms of three demagnetizing factors whose sum equals unity. For low volume loading of particles the self-energy contribution is the dominant one, which is insensitive to particle coordinations and can be approximated by that of an isolated particle. However, when particle loading increases appreciably, significant differences arise for different particle lattices (sc, bcc, and fcc). One advantage of our formulation is that the permeability tensor of the composite can then be calculated for either a magnetic nonsaturated or saturated state of the particle. In contrast to conductivity calculations at the percolation limit there is no divergence of the permeability.

The environmental response of hybrid composites

Hybrid composite specimens containing a total of 60 or 75 vol % of unidirectional fibre were prepared from HT S-carbon fibre and E-glass fibre, HT S-carbon fibre and Kevlar 49 fibre, and E-glass fibre and Kevlar 49 fibre with a standard anhydride cured epoxide resin. The specimens were divided into four groups and subjected to the following environments: (A) room temperature and humidity; (B) soaked in water for 300 h at 95° C and then oven dried at 60° C to a constant weight; (C) thermally cycled 100 times between −196 and 95° C; (D) cycled 35 times between −196 and water at 95° C. The flexural properties of the samples were measured at room temperature after exposure. The modulus of the hybrid materials was not significantly affected by any of the treatments, although thermal cycling with or without water caused a large decrease in the modulus of all Kevlar fibre/resin and to a lesser extent all glass fibre specimens. The flexural strength of the unexposed carbon fibre/glass fibre and glass fibre/Kevlar fibre hybrids showed a positive deviation from the rule of mixtures behaviour at low volume loadings of the lower extension fibre. Wet thermal cycling or soaking in water caused a substantial reduction in the flexural strength of glass fibre/Kevlar fibre specimens. The interlaminar shear strength of all three fibre combinations was not affected by dry thermal cycling, but the effects of soaking in water and especially thermal cycling with water exposure were significant and irreversible.

Effect of hydration state on cardiac function in patients on chronic haemodialysis.

Haemodynamic studies were performed at rest and during exercise in five chronic haemodialysis patients at two different states of hydration, called "normal hydration" and "over-hydration" (mean change in body weight 2.9 kg). Apart from an increase in mean aortic pressure and cardiac index there were no signs of cardiac dysfunction at rest at normal hydration. On exercise the mean pulmonary artery and wedge pressure increased significantly while cardiac output doubled. Overhydration caused considerable increases in right and left sided heart pressures at rest, without any increase in cardiac index. These changes became more pronounced during exercise. Anaemia and arteriovenous shunting make dialysis patients very sensitive to volume load. Extreme anaemia should be avoided, and keeping dialysis patients in a state of low volume load should be given high priority.

Effects of indomethacin on central, renal and coronary hemodynamics. An experimental study in swine with unilateral ureteral obstruction.

The circulatory effects of intravenously administered indomethacin, a potent prostaglandin synthesis inhibitor (0.8 mg/kg bw) were investigated in pigs with unilateral ureteral obstruction. The drug induced a marked but transient increase in systemic arterial pressure (+53%, p less than 0.02) and pulmonary arterial (+81%, p less than 0.02) pressure without any changes in left or right sided filling pressures, cardiac output or heart rate. Coronary blood flow remained unchanged and renal venous blood flow decreased (-26%, p less than 0.02). Renal pelvic pressure decreased (-20%, p less than 0.02). Thus systemic (SVR), pulmonary (PVR) and coronary vascular resistance (CVR) and renal vascular resistance (RVR) on the obstructed side increased (SVR + 73%, p less than 0.02; PVR + 140%, p less than 0.02; CVR + 53%, p less than 0.02 and RVR + 107%, p less than 0.02 respectively). Even if one takes into consideration other factors than ureteral obstruction contributing to these reactions, e.g. low volume load, anaesthesia, surgical trauma and species differences, care is advised in treating patients with coronary artery disease or obstructive lung disease with indomethacin.

Dispersion strengthened aluminum-4 pct magnesium alloy made by mechanical alloying

Mechanical alloying is a unique high energy milling process for producing metal powders with a controlled microstructure. When applied to aluminum based alloys, a uniform, equiaxed fine dispersion of oxygen- and carbon-based particles is obtained. In addition, a very fine grain structure, pinned by the dispersoid, is generated. Relatively low volume loadings of dispersoid may be employed to achieve attractive combinations of properties including ambient temperature tensile strength, corrosion resistance and stress corrosion cracking resistance. The development of a dispersion strengthened aluminum-4 pct magnesium alloy is discussed.

Fabrication, morphology, and dynamic mechanical properties of a model composite system containing in situ-grown filler

Abstract The technique of in situ crystallization was utilized to fabricate a model composite system in which the filler morphology is variable under constant interface conditions. A butadiene-acrylonitrile copolymer was chosen as the matrix from which acetanilide was crystallized in two distinctly different crystal morphologies for filler volume loadings up to 0.35. At the same volume fraction filler, the shape of the relative modulus-filler loading curve is sensitive to the filler crystallization temperature and, thus, to the filler size and shape. For a given crystallization temperature (25°C), the data in the low-volume loading region (>0.2) can be represented reasonably well with the Mooney equation which indirectly yields a filler aspect ratio in agreement with scanning electron micrographs. When the observed morphological parameters are utilized for the entire filler loading range, the 25°C data are best predicted by the Halpin-Tsai equation in conjunction with lamination theory. In general, filler...

The Reinforcing Action and Other Properties of Titanium Fillers in Rubber Stocks

Abstract (1) The reinforcing properties of a high-grade titanium white, containing 74 per cent barium sulfate in intimate combination with the oxide, are slightly better than those of “White Seal” zinc oxide in mixes vulcanized with diphenylguanidine. (2) Titanium dioxide is generally inferior to titanium white as a reinforcing agent, and at high loadings gave poor tensile properties, especially in compounds accelerated with mercaptobenzothiazole. (3) The titanium fillers are incapable of behaving as activators of organic accelerators, as zinc oxide does, and from 3 to 5 per cent of zinc oxide is required in the majority of titanium stocks containing organic accelerators. (4) The aging properties of compounds reinforced with titanium fillers are generally similar to those conferred by zinc oxide, but are inferior to the latter at low volume loadings. (5) Better pigmentary and water-resisting properties are conferred by titanium dioxide than by titanium white, and both these fillers are superior to zinc oxide in these respects.