Size distribution and sites of origin of droplets expelled during expiratory activities

A new Expiratory Droplet Investigation System (EDIS) was used to conduct the most comprehensive program of study to date, of the dilution corrected droplet size distributions produced during different respiratory activities.----- Distinct physiological processes were responsible for specific size distribution modes. The majority of particles for all activities were produced in one or more modes, with diameters below 0.8 µm. That mode occurred during all respiratory activities, including normal breathing. A second mode at 1.8 µm was produced during all activities, but at lower concentrations.----- Speech produced particles in modes near 3.5 µm and 5 µm. The modes became most pronounced during continuous vocalization, suggesting that the aerosolization of secretions lubricating the vocal chords is a major source of droplets in terms of number.----- Non-eqilibrium droplet evaporation was not detectable for particles between 0.5 and 20 μm implying that evaporation to the equilibrium droplet size occurred within 0.8 s.

Students' attitudes and perceptions to online tutorials

The purpose of education is to facilitate learning. Online learning methods have grown substantially with students demanding increased flexibility. Many studies document positive learning outcomes, but do students understand this mode of learning? In this study a survey was conducted to determine student's att itudes and perceptions of online tutorials, because perceptions of learning environments vary.

Orals ain't orals : how instruction and assessment practices affect delivery choices with prepared student oral presentations.

Despite an ostensibly technology-driven society, the ability to communicate orally is still seen as an essential ability for students at school and university, as it is for graduates in the workplace. The need to develop effective oral communication skills is often tied to future work-related tasks. One tangible way that educators have assessed proficiency in this area is through prepared oral presentations. While some use the terms oral communication and oral presentation interchangeably, other writers question the role more formal presentations play in the overall development of oral communication skills. Adding to the discussion, this paper is part of a larger study examining the knowledge and skills students bring into the academy from previous educational experiences. The study examines some of the teaching and assessment methods used in secondary schools to develop oral communication skills through the use of formal oral presentations. Specifically, it will look at assessment models and how these are used as a form of instruction as well as how they contribute to an accurate evaluation of student abilities. The purpose of this paper is to explore key terms and identify tensions between expectations and practice. Placing the emphasis on the ‘oral’ aspect of this form of communication this paper will particularly look at the ‘delivery’ element of the process.

International epidemiology of prostate cancer : geographical distribution and secular trends

This review outlines current international patterns in prostate cancer incidence and mortality rates and survival, including recent trends and a discussion of the possible impact of prostate-specific antigen (PSA) testing on the observed data. Internationally, prostate cancer is the second most common cancer diagnosed among men (behind lung cancer), and is the sixth most common cause of cancer death among men. Prostate cancer is particularly prevalent in developed countries such as the United States and the Scandinavian countries, with about a six-fold difference between high-incidence and low-incidence countries. Interpretation of trends in incidence and survival are complicated by the increasing impact of PSA testing, particularly in more developed countries. As Western influences become more pronounced in less developed countries, prostate cancer incidence rates in those countries are tending to increase, even though the prevalence of PSA testing is relatively low. Larger proportions of younger men are being diagnosed with prostate cancer and living longer following diagnosis of prostate cancer, which has many implications for health systems. Decreasing mortality rates are becoming widespread among more developed countries, although it is not clear whether this is due to earlier diagnosis (PSA testing), improved treatment, or some combination of these or other factors.

Initial steps in optimal planning of a distribution system

This paper reports the initial steps of research on planning of rural networks for MV and LV. In this paper, two different cases are studied. In the first case, 100 loads are distributed uniformly on a 100 km transmission line in a distribution network and in the second case, the load structure become closer to the rural situation. In case 2, 21 loads are located in a distribution system so that their distance is increasing, distance between load 1 and 2 is 3 km, between 2 and 3 is 6 km, etc). These two models to some extent represent the distribution system in urban and rural areas, respectively. The objective function for the design of the optimal system consists of three main parts: cost of transformers, and MV and LV conductors. The bus voltage is expressed as a constraint and should be maintained within a standard level, rising or falling by no more than 5%.