The Compelling Case for Indentation as a Functional Exploratory and Characterization Tool

The utility of indentation testing for characterizing a wide range of mechanical properties of brittle materials is highlighted in light of recent articles questioning its validity, specifically in relation to the measurement of toughness. Contrary to assertion by some critics, indentation fracture theory is fundamentally founded in Griffith–Irwin fracture mechanics, based on model crack systems evolving within inhomogeneous but well‐documented elastic and elastic–plastic contact stress fields. Notwithstanding some numerical uncertainty in associated stress intensity factor relations, the technique remains an unrivalled quick, convenient and economical means for comparative, site‐specific toughness evaluation. Most importantly, indentation patterns are unique fingerprints of mechanical behavior and thereby afford a powerful functional tool for exploring the richness of material diversity. At the same time, it is cautioned that unconditional usage without due attention to the conformation of the indentation patterns can lead to overstated toughness values. Limitations of an alternative, more engineering approach to fracture evaluation, that of propagating a precrack through a “standard” machined specimen, are also outlined. Misconceptions in the critical literature concerning the fundamental nature of crack equilibrium and stability within contact and other inhomogeneous stress fields are discussed.     

Comparison of PIV and PDA droplet velocity measurement techniques on two high-pressure water mist nozzles

The need for reliable measurement of droplet velocities and droplet size has increased with the more widespread use of water mist systems. Two optical measuring techniques have been investigated, Particle Image Velocimetry (PIV) and phase Doppler anemometry (PDA). Measurements have been performed on two high-pressure nozzles, a hollow cone nozzle and a full cone nozzle. Both methods performed well close to the nozzle and further away from the nozzle. In the intermediate region the results obtained with PIV are biased against the larger droplets. The two methods complement each other, PIV giving the instantaneous velocity field and PDA giving both the droplet velocity and droplet size at a point. The measurement indicates that higher throw length can be archived with a full cone nozzle compared to the hollow cone nozzle, if both nozzles have the same cone angle and flow rate.     

Epistemological beliefs, interest, and gender as predictors of Internet-based learning activities

We examined the contribution of epistemological beliefs, individual interest, and gender to self-reports of Internet-based learning activities in a sample of 80 Norwegian student teachers in an innovative pedagogical context with special emphasis on the use of information and communication technologies. Epistemological beliefs and individual interest were measured in the autumn term of the first year of the teacher education program, and learning activities were measured in the autumn term of the second year. The results indicated that epistemological beliefs about the speed of knowledge acquisition predicted Internet-search activities, with students who believed that learning occurs quickly or not at all being less likely to realize that managing the wealth of information found on the Internet and critically evaluating Web-based resources is a difficult and often time-consuming task. In addition, students who held the naive epistemological belief that knowledge is given and stable were less likely to engage in discussion and communication about subject content on the Internet, with such Internet-based communication also predicted by students’ interest in their field of study. Epistemological beliefs predicting Internet-communication activities were also found to predict self-reported use of strategies when learning from conventional printed texts. Finally, males reported higher levels of participation in Internet-based communication activities than females, and females reported higher levels of strategy use when learning from conventional printed texts than males.     

Knobology in use: an experimental evaluation of ergonomics recommendations

The scientific basis for ergonomics recommendations for controls has usually not been related to active goal-directed use. The present experiment tests how different knob sizes and torques affect operator performance. The task employed is to control a pointer by the use of a control knob, and is as such an experimentally defined goal-directed task relevant to machine systems in general. Duration of use, error associated with use (overshooting of the goal area) and movement reproduction were used as performance measures. Significant differences between knob sizes were found for movement reproduction. High torques led to less overshooting as opposed to low torques. The results from duration of use showed a tendency that the differences between knob sizes were reduced from the first iteration to the second iteration. The present results indicate that the ergonomically recommended ranges of knob sizes might differently affect operator performance.     

Control situations in high-speed craft operation

The control situation framework presented by Petersen (Cogn Technol Work 6(4):266–274, 2004) is elaborated upon in the context of military high-speed craft navigation. An observational study was done on a military navigational exercise in Indre Folda, a stretch of particularly demanding confined waters in Norway. The concept of control strategies is presented as a term related to how navigators choose to take out the control possibilities present in the system. Control actions are viewed as actions that fix the control demands and control possibilities over longer time-scales. Control strategies are different from control actions in that they continuously alter the control demands and control possibilities through its execution.     

Modulation by presynaptic beta-adrenoceptors of noradrenaline release from sympathetic nerves in human dental pulp

BACKGROUND: Severe and therapy-resistant pruritus is the most prominent feature of macular (MA) and lichen (LA) amyloidosis that leads to further amyloid deposition by recurrent frictional trauma to the epidermis. Of the various therapeutic modalities with variable success, the most encouraging and beneficial effect has been observed with topical dimethyl sulfoxide (DMSO) therapy. In a previous study, we achieved marked clinical improvement in nine of 10 patients in a daily treatment regimen over 6-20 weeks, but relapses occurred in the post-treatment follow-up period. The aims of this study are to investigate whether the patients would benefit from intermittent therapy and to determine the optimal application interval of DMSO to maintain the relief of symptoms. METHODS: Thirteen patients with histopathologically verified cutaneous amyloidosis (five MA, two LA and six biphasic) were enrolled in the study. They were treated once daily with a 50 or 100% DMSO solution until pruritus disappeared. Then, DMSO was applied at increasing intervals until the widest effective application interval for maintenance of relief was reached. Patients were regularly followed-up by a scoring system for pruritus, papules, and pigmentation, control biopsies, photographs, blood biochemistry, and side-effects. RESULTS: The mean time required for the disappearance of pruritus was 4.1 weeks. Remarkable flattening of the papules was achieved after an average therapy period of 9 weeks. After a total therapy period of 6.5 months, a nearly 50% remission in pigmentation and >70% flattening of papules were achieved. The widest effective DMSO application interval was 8.6 days. The side-effects of therapy were contact urticaria, desquamation, burning sensation, and garlic-like breath odor, which were more prominent with the higher concentration of DMSO. In interval therapy, side-effects were tolerated more easily than in daily therapy. No reduction of amyloid deposits was revealed in control biopsies. CONCLUSIONS: Locally applied DMSO can break the vicious "pruritus-amyloid deposition-pruritus" cycle in patients with MA and LA. In addition to its daily use, interval therapy seems to maintain this effect and enables patients to tolerate side-effects more easily.