An examination of atmospheric lids during COPS

Copyright @ 2009 E.Schweizerbart Science PublishersThe understanding of the nature, origin and prevalence of atmospheric lids is low. There is, therefore, an opportunity to contribute significantly to this area of meteorology - this is the goal of this work. The context for this paper is the Convective and Orographically-induced Precipitation Study (COPS). The COPS observational campaign, which was undertaken in 2007, was based around the Black Forest region with the aim of improving precipitation forecasts in low mountainous regions. However, the project also represents a great data archive with which to analyse isolated features, such as atmospheric lids. In short, lids play a vital role in the development of convective storms. For example, evidence from the Convective Storm Initiation Project (CSIP), which was run in the UK in 2005, has shown that lids are important not only in determining whether a storm occurs but also when and where they develop and how intense they are – sometimes, counterintuitively, they appear to increase the intensity. This extended abstract is intended as a brief overview of the previous literature on lids in order to place the work presented at ICAM-2009 in the wider scientific context.This work is funded by the Natural Environment Research Council (NERC)

Dielectric Breakdown Strength of Polyethylene Nanocomposites

The term “nanometric dielectrics” or simply “nanodielectrics” was introduced in 1994 when Lewis [1] anticipated the potential property changes that would benefit electrical insulation due to nano-sized inclusion. Such materials, containing homogenous dispersion of small amount (normally less than 10wt%) of nanoparticles (with at least one dimension in nanometre range) in host matrix, are of specific dielectric interest. Although much effort has been put forth to investigate the potential dielectric benefit of such newly emerging materials, many uncertainties remain unanswered, and much remains to be explored [2]. Current experimental work is to investigate the preparation of nanodielectrics via solution blending approach. Polyethylene blend composed of 20wt% of high density polyethylene (HDPE) in low density polyethylene (LDPE) is proposed as the base polymer, with varying content of nanosilica (between 0wt% and 10wt%) as the fillers. Although expensive, solution blending method, when compared with melt compounding method, is expected to provide better dispersion of nanoparticles in polymers, thus providing qualitative data in understanding the behaviour of nanodielectrics [3]. Upon successful preparation of polyethylene nanocomposites, breakdown strength based on ASTM Standard D149-87 is to be conducted to determine the feasibility of such dielectric materials in engineering point of view. Figure 1 illustrates the schematic diagram of the breakdown test configuration. The samples are placed between two 6.3mm diameter steel ball bearings immersed in silicone fluid. AC voltage at a preset ramp rate will be applied until the samples fail and the values of breakdown voltages will be recorded and analysed using two-parameter Weibull distribution. Based upon top-down research approach, the underlying physics and chemistry associated with dielectric property changes will then be explored

Towards Recyclable Insulation Materials for High Voltage Cables

The preferred material for modern extruded high voltage transmission cables is cross-linked polyethylene (XLPE). This material has excellent thermo-mechanical and dielectric properties, however it is not easily recycled at end of use, raising questions as to its long term sustainability [1]. Therefore research work at Southampton has sought to identify suitable recyclable alternatives to XLPE. Such candidate materials need to have low temperature flexibility and high temperature mechanical stability combined with a sufficiently high electrical breakdown strength

Electrical Treeing in Silicone Rubber

Electrical treeing has been widely studied in a range of polymeric materials. In these investigations, the morphology and PD patterns associated with the growth of electrical trees in a model transparent silicone rubber were investigated using a new system recently developed at Southampton. With increasing voltage the trees became more complex in appearance but nevertheless grow more rapidly. As the tree evolves the PD pattern becomes more intense which may provide a method of monitoring the extent of treeing in opaque samples. Raman studies indicate that treeing and breakdown channels are hollow, carbonaceous entities, a finding consistent with other studies

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

Somatosympathetic Vasoconstrictor Reflexes in Human Spinal Cord Injury: Responses to Innocuous and Noxious Sensory Stimulation below Lesion

It is known that the sudden increases in blood pressure associated with autonomic dysreflexia in people with spinal cord injury (SCI) are due to a spinally mediated reflex activation of sympathetic vasoconstrictor neurons supplying skeletal muscle and the gut. Apart from visceral inputs, such as those originating from a distended bladder, there is a prevailing opinion that autonomic dysreflexia can be triggered by noxious stimulation below the lesion. However, do noxious inputs really cause an increase in blood pressure in SCI? Using microelectrodes inserted into a peripheral nerve to record sympathetic nerve activity we had previously shown that selective stimulation of small-diameter afferents in muscle or skin, induced by bolus injection of hypertonic saline into the tibialis anterior muscle or the overlying skin, evokes a sustained increase in muscle sympathetic nerve activity and blood pressure and a transient increase in skin sympathetic nerve activity and decrease in skin blood flow in able-bodied subjects. We postulated that these sympathetic responses would be exaggerated in SCI, with a purely noxious stimulus causing long-lasting increases in blood pressure and long-lasting decreases in skin blood flow. Surprisingly, though, we found that intramuscular or subcutaneous injection of hypertonic saline into the leg caused negligible changes in these parameters. Conversely, weak electrical stimulation over the abdominal wall, which in able-bodied subjects is not painful and activates large-diameter cutaneous afferents, caused a marked increase in blood pressure in SCI but not in able-bodied subjects. This suggests that it is activation of large-diameter somatic afferents, not small-diameter afferents, that triggers increases in sympathetic outflow in SCI. Whether the responses to activation of large-diameter afferents reflect plastic changes in the spinal cord in SCI is unknown