A study was conducted involving a group of 290 medical and dental students to directly compare perceived stress levels encountered during their education. A modified questionnaire based on Garbee et al.'s Dental Environmental Stress survey was provided to the students by either email or paper. The purpose of the investigation was to determine if the sources of stress reported by medical and dental students, both male and female, were due to common factors. A multivariate statistical analysis was also conducted to measure stress differences by year in school. Through factor analysis, the survey question responses were grouped into five causal categories: academic performance, faculty relations, patient and clinic responsibilities, personal life issues, and professional identity. The overall findings show that dental students had greater levels of stress than medical students in three of the five categories. The only category in which medical students demonstrated greater stress levels than dental students was in professional identity. Measures of comparative levels of stress between male and female students for either profession did not demonstrate any significant differences. Stress levels related to clinical work varied significantly between the type of professional student and his or her year in school.Mr. Murphy is an Ed.D. candidate

One of the most serious challenges that dental educators face today is improving the level of student satisfaction with the curriculum and learning environment. To determine whether a particular teaching method might enhance student satisfaction with the learning process, a learning preference survey linked to sensory modalities was given to students in the four classes of the Temple University School of Dentistry. New Zealand educator Neil Fleming developed the survey called VARK (an acronym for Visual, Aural, Read/Write, and Kinesthetic) in 1998. The purpose of this study was to measure the distribution of learning preference mean scores of the dental students and note any significant differences among classes, gender, and a sample population determined using 31,243 participants on the VARK website. Results clearly demonstrate that the dominant preference distributions for the two populations (dental student and sample population) are different. In particular, the proportions of learners who selected visual or kinesthetic are significantly different for the two populations, while the proportions of learners who selected aural or read/write are not significantly different. Dental students prefer visual learning at a higher percentage and kinesthetic learning at a lower percentage than the sample population measured in the VARK website. Inter-class differences varied, and gender differences were not significant. The distribution of dental student scores shows a preference for instructors who use strong visual presentations and facilitate note-taking during lectures. Dental educators should be aware of these differences in order to explore opportunities for making the educational experience more productive and enjoyable.

Improvement in CHD risk factors over time unrelated to education or income suggests that population-wide factors such as improved health knowledge, availability of healthy food items, hypertension treatment, and restrictions on cigarette smoking are operating beneficially in all SES groups. Although the SES gradient in risk factors is not increasing, it remains substantial and indicates directions for future prevention efforts.

We have described a one-step, high-yield, nondestructive purification and processing method for multiwalled carbon nanotube (MWNT) containing soot using a conjugated organic polymer host. This host selectively suspends nanotubes relative to impurities. The fraction of available MWNTs suspended can be measured using electron paramagnetic resonance (EPR) and rises with increasing polymer mass before saturating at approximately 50% by mass for a soot to polymer mass ratio of 1:5. Thermogravimetric analysis can then be used to calculate the mass of nanotubes suspended and hence the purity of the original soot. Furthermore, this allows the calculation of numerical constants relating the EPR signal intensity to the nanotube mass, allowing the routine calculation of nanotube content. Finally the host polymer was removed by filtration, giving 91% pure nanotube material. In this case a yield of 17% pristine nanotubes was reclaimed from the soot. Full optimization of this process could lead to yields of up to 40%.

Electron field emission measurements have been made on multiwall arc discharge carbon nanotubes embedded in a conjugated polymer host. Electron emission at low nanotube content is observed and attributed to an enhancement of the applied electric field at the polymer/nanotube/vacuum interface where the electron supply through the film is attributed to fluctuation induced tunneling in a disordered percolation network. A high network resistance is attributed to a polymer coating surrounding each nanotube, resulting in high resistance nanotube-polymer-nanotube tunnel junctions. The potential use of carbon nanotube-polymer composites for field emission based displays is also discussed. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.2158023͔Electron field emission based displays ͑FEDs͒ are highly attractive from a technological viewpoint for the next generation of displays. 1 Considerable research is currently being undertaken to find alternative cathode materials that emit electrons at relatively low applied electric fields. The discovery 2 of carbon nanotubes ͑CNTs͒ inevitably led to the use of CNTs as potential electron sources 3 and the subsequent development of a prototype FED. 4 In addition, electron emission from carbon nanofibers grown on low temperature substrates has also been demonstrated. 5 Optimizing emission from CNTs is an important technological goal due to the relatively high current production costs of nanotubes. To that end, the previous report of emission from CNTs, with mass fractions of 11%-33% embedded in a polystyrene matrix, is therefore important since the use of a composite structure potentially allows a lower concentration of nanotubes to be used. 6 The concept of an emitter based material embedded in a host matrix can be originally traced back to the pioneering work of Latham. 7 This approach has been recently revived by the incorporation of conductive graphitic particles into a nonconductive epoxy matrix to form metal-insulator-metalinsulator-vacuum cathodes. 8 In these electrically inhomogeneous cathodes, tailoring the concentration of the conductive phase, as a means to control charge transport, is an important issue. For flat metals, while there is an abundance of electrons, the absence of a surface geometric enhancement factor coupled with a high surface potential barrier ͑work function͒ results in the need for a high electric field ͑Ͼ200 V / m͒ to be applied for emission. In DLC films, emission has been described in terms of transport of electrons by hopping between conductive sp 2 clusters. 9 From these examples, it is evident that charge transport and emission of electrons are intrinsically linked. In this letter we report on the field emission characteristics of multiwall carbon nanotube-conjugated polymer composites as a function of nanotube loading. We show how the threshold field for emission decreases with nanotube loading and the transport of charge through a disordered percolation network.Composite solutions of conjugated polymer poly͑m-phenylenevinylene-co-2,5-diocty...

The fabrication of a polymer and carbon nanostructure composite material is reported. A comprehensive material investigation of this stable dispersed system is presented. The fabrication technique and characterization steps are described where it was found that multiwalled carbon nanotubes and other clearly defined carbon nanostructures were stably dispersed in the polymer matrix. The properties of the material are investigated to characterize the carbon phases present. Experimental measurements of optical limiting of nanosecond laser pulses by a range of these composite materials in solution are reported. These composites were varied according to carbon nanostructure mass content. The experiments were performed using an open aperture z-scan apparatus with 6 ns Gaussian pulses at 532 nm from a frequency-doubled Q-switched Nd:YAG laser. Saturation of the optical limiting was reached at carbon nanostructure mass percentages in excess of 3.8%, relative to the polymer mass. Mechanistic implications of the optical limiting are investigated via angular dependent scattering measurements.

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