Reduction Of Relative Intensity Research Articles

Influence of ball-in-play time on the activity profiles of rugby league match-play.

Most investigations of the activity profiles of rugby league match-play have reported the physical demands across the entire match irrespective of stoppages in play. This study investigated the activity profiles of rugby league match-play, accounting for time when the ball was "in" and "out-of-play." One-hundred four players (mean age, 24.0 ± 3.0 years) from 11 semiprofessional rugby league teams underwent global positioning system analysis during 22 matches. Matches were coded for activity and recovery cycles. Time when the ball was continuously in play was considered activity, whereas any stoppages during the match (e.g., for scrums, penalties, line drop-outs, and tries) were considered recovery. The relative distance (125.1 ± 16.1 m·min vs. 86.7 ± 9.8 m·min), low-speed activity (115.3 ± 15.7 m·min vs. 81.7 ± 9.8 m·min), and high-speed running (9.5 ± 2.9 m·min vs. 5.0 ± 1.8 m·min) demands were significantly (p < 0.0001) higher when accounting for ball-in-play time. The frequency of collisions (0.67 ± 0.28 per minute vs. 0.41 ± 0.17 per minute) and repeated high-intensity effort (RHIE) bouts (1 every 6.1 ± 4.7 minutes vs. 1 every 10.7 ± 8.3 minutes) were also higher when stoppage time was excluded. Large negative correlations (p ≤ 0.001) were found between total ball-in-play time and relative measures of total distance (r = -0.67) and low-speed activity (r = -0.60). These results demonstrate the greater movement, contact, and RHIE demands when rugby league time-motion data are expressed relative to ball-in-play time. Furthermore, the reduction in relative intensity with longer total ball-in-play time suggests that during prolonged passages of play, players adopt a pacing strategy to maintain high-intensity performance and manage fatigue.

Influence of blocked polyisocyanate on the mechanical, thermal and interfacial properties of bamboo/hydroxyl-terminated polyurethane composites

In this study, chemical modification of bamboo powder (BP)/hydroxyl-terminated polyurethane (HPU) composites obtained by hot press was investigated using blocked polyisocyanate synthesized from reaction of isophorone diisocyanate with 1,1,1-trimethylolpropane (TMP) followed by addition of methyl ethyl ketoxime (MEKO). The modified surface of MEKO-blocked polyisocyanate (M-bp)-treated BP/HPU composites was identified by Fourier transform infrared spectroscopy from the appearance of CO bands absorbance and the reduction in relative intensity of OH, with respect to bamboo. The effects of M-bp as a cross-linker on the properties of the products were studied. Mechanical testing results showed that the tensile and flexural properties of the composites were improved by addition of such a cross-linker. The morphology analysis revealed that the M-bp-modified composites exhibited better compatibility and homogeneous morphologies in comparison with the unmodified composites. Moreover, the thermogravimetric analysis demonstrated that thermal resistance of the composites was enhanced by addition of M-bp. The moisture absorption characteristics of the products were also studied and discussed, because it is a major influencing factor for natural fibre composites. The results showed that better water resistance of modified composites was obtained due to stronger interfacial adhesion. Based on the findings in this work, they all indicated that the chemical modification occurred by the cross-linking effect of M-bp, which induced the strong bonds among the composite components.

Preparation of Mg-Vermiculite Nanoparticles Using Potassium Persulfate Treatment

Delamination/exfoliation process of the Mg-vermiculite (Letovice, Czech Republic), particles with size less than 5 microm, was studied after potassium persulfate treatment and compared with known method utilized hydrogen peroxide treatment. X-ray powder diffraction (XRPD) patterns showed that treatment of Mg-vermiculite with different molar concentration of potassium persulfate: c = 0.02, 0.04, and 0.08 mol x dm(-3) at the temperature 60 degrees C for 2 hr caused reduction of relative intensity (I(rel.)) of the basal 001 diffraction to the 15%, 9%, and 4%, respectively, compared to intensity of 001 diffraction of untreated Mg-vermiculite (I(rel.) = 100%). On the other hand I(rel.) of the 001 diffraction of Mg-vermiculite after treatment with 30% and 50% (c = 9.8 and 17.4 mol x dm(-3)) hydrogen peroxide at the 60 degrees C for 2 hr decreased only to I(rel.) = 36% and 32%, respectively. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) verified effect of potassium persulfate treatment on structure degradation which is connected with higher degree of delamination/exfoliation of the particles and their cracking into nano-sized particles.

The UV environment of the Beagle 2 landing site: detailed investigations and detection of atmospheric state

December 25th 2003 will see the Beagle 2 lander arrive at the surface of Mars in the Isidis region, allowing for the first time in situ measurements of ultraviolet (UV) flux directly from the surface of Mars through the use of a sensor designed as part of a miniaturised environmental package. The expected conditions the sensor will experience are studied here, and the detection signatures for phenomenon such as dust devils, H 2O clouds ands near-surface fogs are presented. The beginning and end of mission surface fluxes show little variation, though the period towards mid-nominal mission does experience a maximum in total daily dose levels. Diurnal profiles are calculated highlighting the effects of increased scattering towards shorter wavelengths. A possible dust storm scenario is presented, and the effect upon component UV fluxes is shown to reverse the relative contributions of direct and diffuse components of the total UV flux. The presence of cloud formation above the landing site will be detectable though the observation of elevated diffuse/direct flux ratios. Near-surface morning fogs show a characteristic ‘dip’ in the morning profile when compared to clear mornings, allowing their detection on cloud-free mornings through post-event analysis of long term data. Predicted Phobos eclipses are investigated at each of the sensor centre wavelengths, and show greatest reduction in relative intensity at short wavelengths. Observations of near-miss eclipse events will also be possible, through monitoring of the diffuse UV flux. Dust devil encounters are shown to create a double minima lightcurve, with the depth of the minima dependent upon the total dust loading of the vortex. The effects of these changing conditions on DNA-weighted irradiances are investigated. Possible dust storms provide the greatest increase in biological protection, whereas expected cloud formations at the Beagle 2 site are found to offer negligible protection. Within just five minutes of landing >95% of any Bacillus subtilis-like bacteria present on the surface of the craft will have lost viability.

Effect of hydrogenation on Al-related photoluminescence in 6H–SiC

Interaction of hydrogen with Al acceptors in SiC is investigated using low-temperature photoluminescence (PL) spectroscopy. Hydrogenation is performed in hydrogen plasma using a standard inductively coupled plasma etching system. Appearance of H-related PL peaks after hydrogenation is accompanied with a significant reduction in relative intensity of Al bound exciton (Al–BE) PL. A gradual quenching of the remaining Al–BE photoluminescence is observed in hydrogenated samples under excitation with above band gap light, resulting in a complete disappearance of Al–BE PL emission. High-temperature annealing completely restores the shape of the PL spectrum to its prehydrogenation form.