Noise-enabled precision measurements of a Duffing nanomechanical resonator

We report quantitative experimental measurements of the nonlinear response of a radiofrequency mechanical resonator, with very high quality factor, driven by a large swept-frequency force. We directly measure the noise-free transition dynamics between the two basins of attraction that appear in the nonlinear regime, and find good agreement with those predicted by the one-dimensional Duffing equation of motion. We then measure the response of the transition rates to controlled levels of white noise, and extract the activation energy from each basin. The measurements of the noise-induced transitions allow us to obtain precise values for the critical frequencies, the natural resonance frequency, and the cubic nonlinear parameter in the Duffing oscillator, with direct applications to high sensitivity parametric sensors based on these resonators.Comment: 5 pages, 5 figure

A study of the ontogeny of the molar dentition of some microchiroptera with special reference to the development of occlusal

The functioning of the molar teeth depends upon a correct relationship between the cusps of the two jaws. This is perhaps less evident in man owing to the flatness of the molar crowns; accordingly, an animal with pointed, interlocking cusps was studied - the insectivous bat Hipposideros beatus. The purpose of the work was to find the growth processes involved to ensure a correct mutual positioning of the erupted teeth in an animal where normal occlusion is essential. So that with a knowledge of normal occlusion, factors causing malocclusion may be better understood. Graphic and wax-plate reconstructions were made of the teeth and jaws in a series of H. beatus embryos. The methods of reconstructing this difficult material are described in Chapter II. In Chapter III the adult dentition and the occlusal relations of the teeth are described. The latter aided by a slow-motion cinematograph study of the chewing action in a British bat. Chapter IV is concerned with the growth and calcification of the tooth germs. Chapter V is concerned with the movements of the tooth germs during ontogeny. In both these chapters the growth of the upper toothrow is compared with the growth of the lower toothrow. It is found that the intrinsic growth of the tooth germs is such, that at all stages, models of teeth, that will later occlude, will fit if put together. However the teeth do not occupy their correct positions relative to each other until eruption. To attain these positions complicated growth movements take place. These movements, and a possible explanation for them are described. Eruption appears to be the terminal phase of these growth movements. The results of the investigation are discussed in Chapter VI.<p

Large-Scale Integration of Nanoelectromechanical Systems for Gas Sensing Applications

We have developed arrays of nanomechanical systems (NEMS) by large-scale integration, comprising thousands of individual nanoresonators with densities of up to 6 million NEMS per square centimeter. The individual NEMS devices are electrically coupled using a combined series-parallel configuration that is extremely robust with respect to lithographical defects and mechanical or electrostatic-discharge damage. Given the large number of connected nanoresonators, the arrays are able to handle extremely high input powers (>1 W per array, corresponding to <1 mW per nanoresonator) without excessive heating or deterioration of resonance response. We demonstrate the utility of integrated NEMS arrays as high-performance chemical vapor sensors, detecting a part-per-billion concentration of a chemical warfare simulant within only a 2 s exposure period

Using teacher action research to promote constructivist learning environments in South Africa

The primary focus was to assist South African teachers to become reflective practitioners in their daily mathematics classroom teaching. The study involved a combination of quantitative and qualitative research methods. Quantitative data were collected using the Constructivist Learning Environment Survey (CLES) to assess learners' perceptions of the emphasis on constructivism in the classroom environment. In the first phase of the study, the CLES was administered to 1 864 learners in 43 classes and analysed to determine whether the CLES is valid and reliable for use in South Africa. As well, descriptive analysis was used to generate graphical profiles of learners' perceptions of the actual and preferred learning environment for each class. During the second 12-week intervention phase, two teachers used the profiles to assist them to develop strategies aimed at improving the constructivist orientation of their classroom learning environments. The teachers implemented strategies and maintained a daily journal as a means of reflecting on their teaching practices. At the end of the 12 weeks, the CLES was re-administered to learners to determine whether their learners' perceptions of the constructivist emphasis in their classroom learning environments had changed. South African Journal of Education Vol.24(4) 2004: 245-25

Homogeneous and heterogeneous distributed classification for pocket data mining

Pocket Data Mining (PDM) describes the full process of analysing data streams in mobile ad hoc distributed environments. Advances in mobile devices like smart phones and tablet computers have made it possible for a wide range of applications to run in such an environment. In this paper, we propose the adoption of data stream classification techniques for PDM. Evident by a thorough experimental study, it has been proved that running heterogeneous/different, or homogeneous/similar data stream classification techniques over vertically partitioned data (data partitioned according to the feature space) results in comparable performance to batch and centralised learning techniques

Synchrotron powder diffraction study of cements pastes

&nbsp;Knowledge of the degree of hydration of cement pastes is critical for determining properties such as the durability of&nbsp;concrete. As part of an integrated study on the prediction of chloride ingress in reinforced concrete, synchrotron Xray&nbsp;powder diffraction was used to estimate the degree of hydration of cement pastes. While for the past 20 years the&nbsp;composition of Portland cement has been determined by Rietveld analysis of X-ray diffraction, nevertheless there are&nbsp;a number of factors, including the amorphous content of the cement and relative proportion of mineral polymorphs&nbsp;present in the initial clinker, whose impact on the analysis are still not completely understood. Analysis of the&nbsp;resulting diffraction patterns indicated enhanced identification of polymorphs of alite, belite, ferrite and aluminate,&nbsp;which are present in the initial unhydrated cement and clinker, as well as improved quantification of hydrated&nbsp;crystalline phases such as calcium hydroxide and ettringite, which are key phases determining the speed of the&nbsp;chemical reactions in cement. In this paper we describe the experience that we have gained in the determination of&nbsp;the degree of hydration of cement pastes. We detail the standards and precautions that we took to characterize&nbsp;production cements and their hydration products

Evaluation of Outcomes for Psychosis and Epilepsy Treatment Delivered by Primary Health Care Workers in Nepal: A Cohort Study.

Background: Most evaluations of task-shifting have focused on common mental disorders. Much less work has been done on severe mental neurological and substance use (MNS) disorders, such as chronic psychosis and epilepsy. Given the high burden associated with severe MNS and the lack of mental health professionals in low and middle income countries, evaluations on the impact of task-shifting for these disorders are important. Methods: In a rural district of Nepal, a community mental health program, based on World Health Organization\u27s Mental Health Gap Action Programme guidelines, was evaluated using a cohort study design. People with epilepsy and psychotic disorders were interviewed at treatment initiation and at 12-month follow-up. We also compared a group that was offered a comprehensive package of care (medication combined with psychosocial interventions, such as counselling and peer support groups) to a group that received medication only. Results: One-hundred nineteen persons were enrolled in the epilepsy cohort (EC) and 85 in the psychosis cohort (PC). The patients were enrolled in either the comprehensive package (n = 157) or medication only (n = 47). There was significant improvement (P \u3c 0.0001) in psychosis symptoms (PC: Z = 6.78, r = 0.80) and depressive symptoms (EC: Z = 7.43, r = 0.73; PC: Z = 6.02, r = 0.70), seizures (EC: Z = 6.78), functional disability (EC: Z = 6.38, r = 0.67; PC: Z = 4.60, r = 0.57), family and caregiver burden (EC: Z = 8.09, r = 0.85; PC: Z = 6.81, r = 0.84), and social behaviour (PC: Z = 5.94, r = 0.84). There was greater risk reduction for recent seizures among people with epilepsy in the comprehensive treatment package vs. medication only (risk ratio = 0.52, 95% CI 0.29-0.95; P = 0.03); no other significant differences were observed between treatment arms. Conclusions: A community mental health program in Nepal, implemented by non-specialists, resulted in moderate to large effects among people with epilepsy or psychosis. A comprehensive package of care, including counselling and patient support groups, appears to offer added clinical benefits for patients with epilepsy. For people with psychosis, the basic package of care (i.e., psychotropic medications) performed similar to the comprehensive package, suggesting a less resource-intensive package may offer comparable results

Siren songs or path to salvation? Interpreting the visions of web technology at a UK regional newspaper in crisis, 2006-11

A 5-year case study of an established regional newspaper in Britain investigates journalists about their perceptions of convergence in digital technologies. This research is the first ethnographic longitudinal case study of a UK regional newspaper. Although conforming to some trends observed in the wider field of scholarship, the analysis adds to skepticism about any linear or directional views of innovation and adoption: the Northern Echo newspaper journalists were observed to have revised their opinions of optimum Web practices, and sometimes radically reversed policies. Technology is seen in the period as a fluid, amorphous entity. Central corporate authority appeared to diminish in the period as part of a wider reduction in formalism. Questioning functionalist notions of the market, the study suggests cause and effect models of change are often subverted by contradictory perceptions of particular actions. Meanwhile, during technological evolution, the ‘professional imagination’ can be understood as strongly reflecting the parent print culture and its routines, despite pioneering a new convergence partnership with an independent television company