Properties and Analysis of Thermally Aged Poly(ethylene oxide)

Recent studies have been performed into the use of polyethylene oxide (PEO) as a model system for observing the fundamental effects of adding micro and nano sized fillers to create polymeric composite systems. Many factors contribute to the successful creation of such a composite system, including dispersion of the filler and treatment of the material during creation. For example, while producing thin films of the materials for testing, high temperatures were used for short periods of time in open air to press the samples into small discs. It is well known that prolonged high temperature exposure can alter the chemistry and structure of polymeric materials and that small variations in the original chemistry, such as longer molecular weights or introduction of fillers, can reduce or possibly accelerate this 'ageing' effect. From these previous investigations many property changes were observed during addition of filler or variation of molecular weight, therefore to accurately attribute these changes to a cause the thermal ageing of the material should be observed. This investigation looks at the same 3 molecular weight PEO systems as those used in the previous investigations and analyses them for their vulnerability to thermal ageing. One thermally aged sample is then taken and tested alongside an unaged sample to observe the effects that the process has on the properties. This includes rheology in solution, differential scanning calorimetry (DSC), AC electrical breakdown, dielectric spectroscopy and Fourier transform infra-red (FTIR). By observing the property changes of aged samples it is possible to better understand the thermal ageing process occurring and possibly a way to reduce the effect, along with considering the effect with regard to the behaviour of the previously tested composite samples

Graded Lie algebras of maximal class IV

We describe the isomorphism classes of certain infinite-dimensional graded Lie algebras of maximal class, generated by an element of weight one and an element of weight two, over fields of odd characteristic.Comment: 38 pages. See also http://www-math.science.unitn.it/~caranti/ and http://users.ox.ac.uk/~vlee

Vertical distribution of clouds over Hampton, Virginia observed by lidar under the ECLIPS and FIRE ETO programs

Intensive cloud lidar observations have been made by NASA Langley Research Center during the two observation phases of the ECLIPS project. Less intensive but longer term observations have been conducted as part of the FIRE extended time observation (ETO) program since 1987. We present a preliminary analysis of the vertical distribution of clouds based on these observations. A mean cirrus thickness of just under 1 km has been observed with a mean altitude of about 80 percent of the tropopause height. Based on the lidar data, cirrus coverage was estimated to be just under 20 percent, representing roughly 50 percent of all clouds studied. Cirrus was observed to have less seasonal variation than lower clouds. Mid-level clouds are found to occur primarily in association with frontal activity

Rapid X-ray Variability of Seyfert 1 Galaxies

The rapid and seemingly random fluctuations in X-ray luminosity of Seyfert galaxies provided early support for the standard model in which Seyferts are powered by a supermassive black hole fed from an accretion disc. However, since EXOSAT there has been little opportunity to advance our understanding of the most rapid X-ray variability. Observations with XMM-Newton have changed this. We discuss some recent results obtained from XMM-Newton observations of Seyfert 1 galaxies. Particular attention will be given to the remarkable similarity found between the timing properties of Seyferts and black hole X-ray binaries, including the power spectrum and the cross spectrum (time delays and coherence), and their implications for the physical processes at work in Seyferts.Comment: To appear in From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender, and L. C. Ho (Dordrecht: Kluwer

Development of autoclave moldable addition-type polyimides

Chemistry and processing modifications of the poly(Diels Alder) polyimide (PDA) resin were performed to obtain structural composites suitable for 589 K (600 F) service. This work demonstrated that the PDA resin formulation is suitable for service at 589 K (600 F) for up to 125 hours when used in combination with Hercules HTS graphite fiber. Sandwich panels were autoclave molded using PDA/HTS skins and polyimide/glass honeycomb core. Excellent adhesion between honeycomb core and the facing skins was demonstrated. Fabrication ease was demonstrated by autoclave molding three-quarter scale YF-12 wing panels

Public perception of dentists' ability to manage a medical emergency

The importance of dentists to be able to manage a medical emergency in dental practice has been an established concept for many years, with medical emergency training being incorporated into dental undergraduate training programs as far as back as 1981. However, for far longer than this, dentists have held a professional role in the staffing of military field hospitals, providing emergency care to injured and ill members of the armed forces. Despite awareness of the importance of such skills, Australian studies have shown dentists often lack appropriate proficiencies and equipment for the effective and efficient management of medical crises that may arise as a part of routine dentistry. The only identified literature review on medical emergencies within dentistry recently found the majority of both students and graduate dentists were unable to correctly perform life support procedures3. This is a finding of concern when recent studies on the prevalence of medical emergencies in dentistry suggest that the incidence may be increasing, due to a myriad of factors. The populations of developed countries are generally getting older and consequently suffer from more acute and chronic conditions; notably, it has been argued that patients with multiple chronic diseases are more likely to suffer from a medical emergency. Simultaneously, a greater number of practitioners are utilising drugs such as sedatives compared to years past. These findings coincide with observations that dentists are being taught less clinical medical science than they have historically, and are further being seen as service providers to a consumerist public, rather than their trained role as health professionals. Although all schools of dentistry in Australia require their students to hold first aid and basic life support (BLS) certification, the requirements for practicing dentists to undergo ongoing training or medical emergency certification varies across countries and governing bodies. Australian dentists are not specifically required to undergo ongoing training in the management of medical emergencies, despite it being strongly recommended by the Australian Dental Association. Further, the public's expectation of dentists' competence in medical emergency management is likely much higher than what dentists may hold of themselves15, and reports on unpublished studies corroborate this suggestion. In the current military framework, Australian Defence Force (ADF) Dental Officers (DO) are often involved in the early triaging and stabilisation of injured members who have been evacuated to a role two facility but are not yet in receipt of advanced medical care. This too mandates a high level of knowledge and proficiency in emergency medical management. Given the special semi-autonomous status afforded to the self-regulation of dentistry there is a professional responsibility to meet or exceed public expectations, or such deficiencies may be legislatively mandated. To date, no published studies could be found examining the public's opinion of dentists' ability to manage a medical emergency in a dental setting, nor whether a patient's own medical status impacts on whether they visit a dentist because of concerns about a medical emergency. Based on this, the aim of this research is to quantify the public's attitudes towards dentists’ proficiency in a medical crisis

X-Ray Variability Coherence: How to Compute it, What it Means, and How it Constrains Models of Cyg X-1 and GX 339-4

We describe how the coherence function, a Fourier frequency-dependent measure of the linear correlation between time series measured simultaneously in two energy channels, can be used in conjunction with energy spectra, power spectra, and time delays between energy channels to constrain models of the spectrum and variability of x-ray binaries. Here we present a procedure for estimating the coherence function in the presence of counting noise. We apply this method to the black hole candidates Cyg X--1 and GX 339--4, and find that the near perfect coherence between low and high energy x-ray photons rules out a wide range of models that postulate: spatially extended fluctuating emission, thermal flares, and overlapping shot-noise.Comment: Latex file (emulateapj macro included, see comments at beginning of file), 1 eps figure. To be published in ApJ Letters, Jan. 1, 199

Binary evolution with LOFT

This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of very faint X-ray binaries, orbital period distribution of black hole X-ray binaries and neutron star spin up. For a summary, we refer to the paper.Comment: White Paper in Support of the Mission Concept of the Large Observatory for X-ray Timing. (v2 few typos corrected