Bulletin No. 5: Estimating the number of heroin users in Australia

Estimating the prevalence of drug use is one of the key focal areas of alcohol and drug epidemiology. Estimation of the extent of alcohol and drug use in the Australian community has primarily been undertaken using surveys of the general population. Nevertheless, it is widely understood that prevalence estimates derived from general population surveys underestimate the true extent of drug use in the community for drugs of low use prevalence (e.g. heroin) because of issues around sampling (e.g. response rates and the extent to which crucial samples such as the homeless are missed in household surveys) and the truthfulness of responses to questions concerning illegal or hidden behaviours. In response, epidemiologists have applied specialised statistical techniques to the analysis of data sources on the extent of drug-related harm (e.g. Opioid overdose deaths) to produce estimates of the extent of problematic drug use in the Australian community. Prevalence estimation using secondary data sources has generally been undertaken only in relation to heroin use in Australia. This work has used a variety of techniques (e.g. capture-recapture, back-projection, multiplier) in accordance with a general consensus that has emerged around the application of such techniques to the estimation of problematic drug use. In applying these methods Australian work has developed multiple estimates using available statistical estimation tools with convergence among estimates used as the source of the most parsimonious estimate (e.g. the median of the estimates derived). While this approach is appealing, the resultant ‘best’ estimates are derived primarily from the application of simple mortality multipliers (e.g. 1% annual mortality rate for heroin users) to the number of opioid overdose deaths occurring in specific Australian jurisdictions (generally NSW). The problem of this multiplier approach is highlighted by the effect of the heroin shortage in Australia. The aim of this component of the DPMP was to develop plausible estimates of the prevalence of heroin use in Melbourne with a view to informing various elements of DPMP projects. The work was also designed to provide a method for estimating the extent of injecting drug use more widely (specifically through application to amphetamines). It was funded by a Travelling Scholarship from the Victorian Premier’s Drug Prevention Council awarded to Paul Dietze

Bulletin No. 6: Illicit drugs in Australia: What do we know about the role of price?

There has been an increasing awareness of the importance of using price information to understand illicit drug markets. Internationally, researchers have found relationships between illicit drug prices and other market characteristics such as the numbers of drug users, the proportion of arrestees testing positive to drugs and the number of drug-related emergency department incidents. This work aimed to assess whether the Australian heroin market shares the same basic characteristics (e.g. real prices falling over time, significant price variability) as other illicit drug markets where more price analysis has been done; and begin to explore the relationship between price and harm. It is hard to measure how much heroin is being consumed with any precision, making it extremely difficult to understand the relationship between drug use and the harmful consequences that result from use. On the other hand other market characteristics, such as price, can be better measured. If there are relationships between price (as an indirect measure of consumption) and harms, we can use price (and potentially other market data) to assess harms and policy responses

CEP-stable Tunable THz-Emission Originating from Laser-Waveform-Controlled Sub-Cycle Plasma-Electron Bursts

We study THz-emission from a plasma driven by an incommensurate-frequency two-colour laser field. A semi-classical transient electron current model is derived from a fully quantum-mechanical description of the emission process in terms of sub-cycle field-ionization followed by continuum-continuum electron transitions. For the experiment, a CEP-locked laser and a near-degenerate optical parametric amplifier are used to produce two-colour pulses that consist of the fundamental and its near-half frequency. By choosing two incommensurate frequencies, the frequency of the CEP-stable THz-emission can be continuously tuned into the mid-IR range. This measured frequency dependence of the THz-emission is found to be consistent with the semi-classical transient electron current model, similar to the Brunel mechanism of harmonic generation

Sub-daily Statistical Downscaling of Meteorological Variables Using Neural Networks

AbstractA new open source neural network temporal downscaling model is described and tested using CRU-NCEP reanal ysis and CCSM3 climate model output. We downscaled multiple meteorological variables in tandem from monthly to sub-daily time steps while also retaining consistent correlations between variables. We found that our feed forward, error backpropagation approach produced synthetic 6 hourly meteorology with biases no greater than 0.6% across all variables and variance that was accurate within 1% for all variables except atmospheric pressure, wind speed, and precipitation. Correlations between downscaled output and the expected (original) monthly means exceeded 0.99 for all variables, which indicates that this approach would work well for generating atmospheric forcing data consistent with mass and energy conserved GCM output. Our neural network approach performed well for variables that had correlations to other variables of about 0.3 and better and its skill was increased by downscaling multiple correlated variables together. Poor replication of precipitation intensity however required further post-processing in order to obtain the expected probability distribution. The concurrence of precipitation events with expected changes in sub ordinate variables (e.g., less incident shortwave radiation during precipitation events) were nearly as consistent in the downscaled data as in the training data with probabilities that differed by no more than 6%. Our downscaling approach requires training data at the target time step and relies on a weak assumption that climate variability in the extrapolated data is similar to variability in the training data

The morphological and clinical relevance of mandibular and maxillary bone structures for implantation

Tooth loss, which interrupts the biocybernetic feedback circuit of the masticatory system, changes the structures of the jaw bone: such changes are termed "inactivity atrophy". The mandible is subject to vertical atrophy and the maxilla is primarily subject to horizontal atrophy. The mandible possesses more compact bone, the maxilla more spongy; the resorption directions also differ (mandible: towards the oral aspect; maxilla: towards the vestibular). An implant helps to restore the biocybernetic feedback system. The amount of available bone, bone structure, and topographic conditions are crucial factors influencing implant success. Osseointegration is performed at an early stage (which includes bleeding, granulation tissue, foreign-body recognition, interactions) and at a late stage (so-called osseous bridging, development of fibrous and lamellar bone)

The use of ceramic drills on a zirconium oxide basis in bone preparation

The favourable mechanical properties and high biocompatibility of the newly developed mixed ceramics composed of zirconium oxide and aluminium oxide have continuously extended the scope of their application. Rotating instruments on a zirconium oxide basis are regarded as superior to metal burs in dentoalveolar surgery in terms of favourable temperature effects on the surrounding bone tissue and the economic advantage that they wear slowly, enabling them to be used repeatedly. In this study ten round burs made of zirconium oxide and aluminium oxide mixed ceramics were used for typical dental-alveolar preparation types on an explanted pig jaw. Prior to the first and following the tenth application a scanning electron microscopic (SEM) analysis of possible wear signs was conducted. However, this revealed no evidence of wear or resulting loss of sharpness

Bacterial colonisation of interior implant threads with and without sealing

Premature loss of dental implants is due, apart from mechanical factors, to germrelated inflammation. Gaps and hollow spaces within the implant system, for example the gap between implant and abutment in the two-part implant system, may provide a bacterial reservoir causing or maintaining inflammation. The bacterial spectrum involved is similar to that found in periodontitis. This in vitro study aimed to scrutinise the capability of Porphyromonas gingivalis (DSM 20709), the bacterium blamed for inducing peri-implantitis, to pass the implant/abutment gap in titanium implant systems used for orthodontic anchorage and to remain vital in the interior. Additionally, the in vitro effectiveness of gutta percha for gap sealing was examined. Twelve titanium implants (Straumann ®, diameter: 3.3 mm, length 5.5 mm) were provided with abutments at a defined torque (20 Ncm), six of which were sealed with gutta percha before screwing in the abutment. Subsequently the implants were placed in a nutrient solution (thioglycolate boullion with haemin-menadione solution) that contained Porphyromonas gingivalis. Microbiological specimens were sampled from the implant interiors after 24 and 72 hours and analysed using culture methods. There was evidence that penetration of the periodontal pathogen Porphyromonas gingivalis to the implant interior may occur as early as after 24 hours. Microbes were also detected in the interior of implants sealed with gutta percha. The abutment/implant interface in vitro provides a microbiological leakage for the prospective peri-implantitis-inducing bacterium Porphyromonas gingivalis. Survival of the bacterium is possible in the interior, so that development of a bacterial reservoir is assumed. This in vitro trial produced no evidence that sealing with gutta percha is an effective means to prevent secondary bacterial colonisation in the implant interior

Histological and fluorescence microscopic examination of the bone/implant interface in orthodontic miniscrews (Mondeal®)

The temporary nature of orthodontic implants demands optimisation of size and design in order to minimise damage and risk to the patient. Slender and shorter miniscrews offer the advantage over conventional implants of easier and more ubiquitous positioning with minimised risk of injury to neighbouring anatomical structures such as tooth roots, nerves or vessels. The question is raised, however, as to what extent these advantages are gained at the price of diminished stability or a more unfavourable bone interface. In order to evaluate the screw/bone interface, 14 orthodontic miniscrews (Mondeal Medical Systems, diameter: 1.5 mm, length: 9 mm) were inserted into the right and left mandibles of 7 pigs (Sus scrofa domestica). Bone fluorochromes were administered in a defined order for polychrome sequencing. The samples gathered after 70 days were analysed using histological techniques and fluorescence microscopy. The lower part of the self-tapping thread displayed undisturbed bone apposition. Fluorescence microscopy revealed remodelling and bone apposition within the thread grooves