Interface creation and stress dynamics in plasma-deposited silicon dioxide films

The stress in amorphous silicon dioxide filmgrown by plasma-assisted deposition was investigated both during and after film growth for continuously and intermittently depositedfilms. It is shown that an intermittent deposition leads to the creation of interfacial regions during film growth, but also causes dynamical structural change in already-deposited film which results in a significantly different stress-thickness profile measured after deposition.Film growth in the continuously depositedfilm was also monitored using an in situ laser reflection technique, and a strong change in stress was detected at about 145nm which was attributed to the onset of island coalescence

Downscaling of fracture energy during brittle creep experiments

We present mode 1 brittle creep fracture experiments along fracture surfaces that contain strength heterogeneities. Our observations provide a link between smooth macroscopic time-dependent failure and intermittent microscopic stress-dependent processes. We find the large-scale response of slow-propagating subcritical cracks to be well described by an Arrhenius law that relates the fracture speed to the energy release rate. At the microscopic scale, high-resolution optical imaging of the transparent material used (PMMA) allows detailed description of the fracture front. This reveals a local competition between subcritical and critical propagation (pseudo stick-slip front advances) independently of loading rates. Moreover, we show that the local geometry of the crack front is self-affine and the local crack front velocity is power law distributed. We estimate the local fracture energy distribution by combining high-resolution measurements of the crack front geometry and an elastic line fracture model. We show that the average local fracture energy is significantly larger than the value derived from a macroscopic energy balance. This suggests that homogenization of the fracture energy is not straightforward and should be taken cautiously. Finally, we discuss the implications of our results in the context of fault mechanics

Slow crack propagation through a disordered medium: Critical transition and dissipation

We show that the intermittent and self-similar fluctuations displayed by a slow crack during the propagation in a heterogeneous medium can be quantitatively described by an extension of a classical statistical model for fracture. The model yields the correct dynamical and morphological scaling, and allows to demonstrate that the scale invariance originates from the presence of a non-equilibrium, reversible, critical transition which in the presence of dissipation gives rise to self organized critical behaviour.Comment: 16 pages, 4 figures, to be published on EPL (http://epljournal.edpsciences.org/

Performance of the Ethiopian Somali goats during different watering regimes

Water is scarce in the semi-arid regions of Ethiopia and therefore goats are watered intermittently. This can result in dehydration and decreased animal performance. The aims of these studies were to investigate the mechanisms employed by the Ethiopian Somali goat to endure water scarcity and to generate information on milk yield and kid growth. All studies were conducted at the Errer Valley research station, eastern Ethiopia. The first study evaluated the effects of watering male goats once daily and every 2nd, 3rd and 4th day for 72 days at indoor conditions. The goats were fed hay ad libitum and were given 200 g of concentrates daily. In the second study, 14 does and their kids were studied 3 to 4 months after parturition in the hot dry season. They were randomly distributed to once daily or once every 4th day watering. The kids followed the does out on pasture. Every evening, the does were each given 300 g concentrates. The kids were offered 100 g of concentrate per head and day in-group. The third experiment evaluated drinking pattern and milk production of 12 goats during a rainy period. The does were randomly assigned to two feeding treatments starting 11 to 17 days after parturition and continuing for 72 days. Six goats were each given 250 g concentrates every evening and six goats were only grazing. The kids suckled morning and evening. One udder half was hand milked in the mornings. Plasma osmolality and vasopressin concentration increased to high levels on the 4th day of water deprivation in the males and initially in late lactating does. It shows that four days of water deprivation challenged water balance. The osmolality in every 4th day watered does increased less as the cycles continued, indicating that the goats economized on water. Intermittently watered does and kids spent more time in the shade and browsed watery plants. Rectal temperature increased daily by about 3.5°C in all does and by 2.5°C and 3.2°C in kids watered daily and every 4th day, respectively, during the hot dry period. Milk yield was about 22 % lower than in the group given water daily. Kids watered once every 4th day did not gain body weight as fast as those watered daily. Goats did not always drink when offered water during a rainy period. The milk yield was less than half a litre per day although good forage was available. Concentrate supplementation increased milk yield by 13%, but reduced fat percentage. Both does and kids increased their body weight during the rainy period. In conclusion, the Ethiopian Somali goat rapidly adjusts to water shortage and starts to economize on water when subjected to a prolonged period of intermittent watering. It is important that this unique adaptability is considered in breeding programs aimed at increasing the comparatively moderate milk production. Nevertheless, more than three days interval between watering during the hot dry season is not recommended since it may jeopardize animal performance and welfare

A biaxial apparatus for the study of heterogeneous and intermittent strains in granular materials

We present an experimental apparatus specifically designed to investigate the precursors of failure in granular materials. A sample of granular material is placed between a latex membrane and a glass plate. A confining effective pressure is applied by applying vacuum to the sample. Displacement-controlled compression is applied in the vertical direction, while the specimen deforms in plane strain. A Diffusing Wave Spectroscopy visualization setup gives access to the measurement of deformations near the glass plate. After describing the different parts of this experimental setup, we present a demonstration experiment where extremely small (of order $10^{-5}$) heterogeneous strains are measured during the loading process

Intermittent stick-slip dynamics during the peeling of an adhesive tape from a roller

We study experimentally the fracture dynamics during the peeling at a constant velocity of a roller adhesive tape mounted on a freely rotating pulley. Thanks to a high speed camera, we measure, in an intermediate range of peeling velocities, high frequency oscillations between phases of slow and rapid propagation of the peeling fracture. This so-called stick-slip regime is well known as the consequence of a decreasing fracture energy of the adhesive in a certain range of peeling velocity coupled to the elasticity of the peeled tape. Simultaneously with stick-slip, we observe low frequency oscillations of the adhesive roller angular velocity which are the consequence of a pendular instability of the roller submitted to the peeling force. The stick-slip dynamics is shown to become intermittent due to these slow pendular oscillations which produce a quasi-static oscillation of the peeling angle while keeping constant the peeling fracture velocity (averaged over each stick-slip cycle). The observed correlation between the mean peeling angle and the stick-slip amplitude questions the validity of the usually admitted independence with the peeling angle of the fracture energy of adhesives.Comment: Forthcoming in Physical Review

Effect of Wheelchair Running on Recovery of Blood Lactate and Physical Performance after High-Intensity Intermittent Exercise – An Experimental Trial

Background and Purpose: Repetitive sprint sport players perform high intensity exercise only for a small percentage of a total game and such periods are often instrumental in determining the eventual outcome. Recovery is a key factor for performance, and constant lack of recovery or insufficient recovery turns into overtraining which is detrimental in achieving peak performance. The purpose was to find out the effect of wheelchair running on the physical performance recovery after high-intensity intermittent exercise. Method: Ten sportsmen having the age range from 20 to 29, VO2max Ranges from 60.51 to 64.29 were randomly divided into experimental and control groups. After filling pre-participation questionnaire and 30-min of supine rest, Blood lactate and the field tests for the measurement of static balance, power, speed and agility were applied. The subjects were made to run in the treadmill and to increase the intensity to reach the Target Heart Rate (THR). After 1-min the subjects were given rest for 15-s and after that they started exercise again and thus the subjects completed several bouts of such exercises until exhaustion followed by either Passive rest or wheelchair running for the duration of 10 minutes. Parameters were measures after completed the exercise bout and after the recovery. Results: After the recovery in experimental group significant improvement found only in blood lactate (p<0.01) and no significant changes found in other parameters while in control group no significant changes found in all parameters. There was no significant difference found in all the parameters including blood lactate between the groups. Conclusion: Both wheelchair running and passive recovery are same in the efficiency of blood lactate removal and restoration of physical performance following intense intermittent exercise

Advanced reliability modeling of fault-tolerant computer-based systems

Two methodologies for the reliability assessment of fault tolerant digital computer based systems are discussed. The computer-aided reliability estimation 3 (CARE 3) and gate logic software simulation (GLOSS) are assessment technologies that were developed to mitigate a serious weakness in the design and evaluation process of ultrareliable digital systems. The weak link is based on the unavailability of a sufficiently powerful modeling technique for comparing the stochastic attributes of one system against others. Some of the more interesting attributes are reliability, system survival, safety, and mission success