An economic case for providing free access to antiretroviral therapy for HIV-positive people in South Australia

Background As financial constraints can be a barrier to accessing HIV antiretroviral therapy (ART), we argue for the removal of copayment requirements from HIV medications in South Australia. Methods Using a simple mathematical model informed by available behavioural and biological data and reflecting the HIV epidemiology in South Australia, we calculated the expected number of new HIV transmissions caused by persons who are not currently on ART compared with transmissions for people on ART. The extra financial investment required to cover the copayments to prevent an HIV infection was compared with the treatment costs saved due to averting HIV infections. Results It was estimated that one HIV infection is prevented per year for every 31.4 persons (median, 24.0–42.7 interquartile range (IQR)) who receive treatment. By considering the incremental change in costs and outcomes of a change in program from the current status quo, it would cost the health sector $17 860 per infection averted (median, $13 651–24 287 IQR) if ART is provided as a three-dose, three-drug combination without requirements for user-pay copayments. Conclusions The costs of removing copayment fees for ART are less than the costs of treating extra HIV infections that would result under current conditions. Removing the copayment requirement for HIV medication would be cost-effective from a governmental perspective.

Exploring diarrhoea, enteral nutrition and intestinal microbial flora relationships in critically ill patients

Diarrhoea is a common complication observed in critically ill patients. Relationships between diarrhoea, enteral nutrition and aerobic intestinal microflora have been disconnectedly examined in this patient cohort. This research used a two-study, observational design to examine these associations. Higher diarrhoea incidence rates were observed when patients received enteral tube feeding, had abnormal serum blood results, received multiple medications and had aerobic microflora dysbiosis. Further, significant aerobic intestinal microflora changes were observed over time in patients who experienced diarrhoea. These results establish a platform for further work to improve the intestinal health of critically ill patients.

Visual predictive control of spiral motion

This paper deals with constrained image-based visual servoing of circular and conical spiral motion about an unknown object approximating a single image point feature. Effective visual control of such trajectories has many applications for small unmanned aerial vehicles, including surveillance and inspection, forced landing (homing), and collision avoidance. A spherical camera model is used to derive a novel visual-predictive controller (VPC) using stability-based design methods for general nonlinear model-predictive control. In particular, a quasi-infinite horizon visual-predictive control scheme is derived. A terminal region, which is used as a constraint in the controller structure, can be used to guide appropriate reference image features for spiral tracking with respect to nominal stability and feasibility. Robustness properties are also discussed with respect to parameter uncertainty and additive noise. A comparison with competing visual-predictive control schemes is made, and some experimental results using a small quad rotor platform are given.

Force controlled hexapod walking

This thesis is a study on controlling methods for six-legged robots. The study is based on mathematical modeling and simulation. A new joint controller is proposed and tested in simulation that uses joint angles and leg reaction force as inputs to generate a torque, and a method to optimise this controller is formulated and validated. Simulation shows that hexapod can walk on flat ground based on PID controllers with just four target configurations and a set of leg coordination rules, which provided the basis for the design of the new controller.

Delivering crushed tablets using thickened fluids : is drug diffusion into gastric fluids restricted?

Solid medications are often crushed and mixed with food or thickened water to aid drug delivery for those who cannot or prefer not to swallow whole tablets or capsules. Dysphagic patients have the added problem of being unable to safely swallow thin fluids so water thickened with polysaccharides is used to deliver crushed medications and ensure safe swallowing. It is postulated that these polysaccharide systems may restrict drug release by reducing the diffusion of the drug into gastric fluids. METHODS By using a vertical diffusion cell separated with a synthetic membrane, the diffusion of a model drug (atenolol) was studied from a donor system containing the drug dispersed into thickened water with xanthan gum (concentration range from 0.005%-2.2%) into a receptor system containing simulated gastric fluid (SGF) at 37°C. The amount of drug transferred was measured over 8 hours and diffusion coefficients estimated using the Higuchi model approach. RESULTS Atenolol diffusion decreased with increasing xanthan gum concentration up to 1.0%, above which diffusion remained around 300 μ2s-1. The rheological measurements captured the influence of the structure and conformation of the polysaccharide in water on the movement and availability of the drug in SGF. DISCUSSION Dose form administration for dysphagic patients’ needs special attention from general practitioners, pharmacist and patients. Improving drug release of crushed tablets from thickening agents requires a reduction in the diffusion pathway (e.g. by decreasing drop size radius). This approach could make the drug available in SGF in a short time without compromising the mechanical aspects of thickening agents that guarantee safe swallowing.

Delivering crushed paracetamol tablets using thickened fluids : does it alter the pharmacokinetics?

Dysphagia, often associated with conditions such as stroke, Parkinson’s disease, multiple sclerosis, and dementia, causes patients to have difficulty with swallowing food and/or liquids. These patients require their fluids to be thickened using gum-based thickening powders in order to facilitate safe swallowing. These thickened fluids are also used as a vehicle for delivery of crushed medicines. Our in vitro measurements suggest that thickened fluids can delay and reduce the dissolution of a number of medications. This study was conducted to assess the impact of the use of thickened fluids on the clinical pharmacokinetics of oral paracetamol. METHODS 20 Healthy volunteers were administered a single oral dose (1g) of paracetamol as either whole tablets, crushed with water, crushed with semi-solid jam, or crushed with thickened fluid according to a randomised, crossover design. Saliva samples were collected periodically over 8 hr and paracetamol concentration analysed by HPLC-UV. Non-compartmental pharmacokinetic analysis was conducted using Winnonlin®. RESULTS The mean peak concentration (Cmax) of paracetamol ranged between 5.62 – 8.00 μg/mL. Comparison between the crushed paracetamol with thickened water (Level 900) and other treatment options (whole, crushed with water, and crushed with jam) showed there was a significant difference in Cmax at 90% CI (p < 0.05). Also, whole tablet had a significant difference in Cmax between crushed with water and crushed with jam. There was no significant difference in AUC irrespective of the treatment. DISCUSSION The use of thickened water resulted in alteration in the absorption kinetics of paracetamol. Given this interaction, co-administration with thickened fluids may have important clinical implications for medications with a narrow therapeutic index.

Potentially inappropriate prescribing in older patients discharged from acute care hospitals to residential aged care facilities

Background The frequency of prescribing potentially inappropriate medications (PIMs) in older patients remains high despite evidence of adverse outcomes from their use. Little is known about whether admission to hospital has any effect on appropriateness of prescribing. Objectives This study aimed to identify the prevalence and nature of PIMs and explore the association of risk factors for receiving a PIM. Methods This was a prospective study of 206 patients discharged to residential aged care facilities (RACFs) from acute care. All patients were aged at least 70 years and were admitted between July 2005 and May 2010; their admission and discharge medications were evaluated. Results Mean patient age was 84.8 ± 6.7 years; the majority (57%) were older than 85 years and mean (SD) Frailty Index was 0.42 (0.15). At least one PIM was identified in 112 (54.4%) patients on admission and 102 (49.5%) patients on discharge. Of all medications prescribed at admission (1728), 10.8% were PIMs and at discharge of 1759 medications, 9.6% were PIMs. Of total 187 PIMs on admission, 56 (30%) were stopped and 131 were continued; 32 new PIMs were introduced. Of the potential risk factors considered, in-hospital cognitive decline and frailty status were the only significant predictors of PIMs. Conclusion Although, admission to hospital is an opportunity to review the indications for specific medications, a high prevalence of inappropriate drug use was observed. The only associations with PIM use were the frailty status and in-hospital cognitive decline. Additional studies are needed to further evaluate this association.

Modeling and control of a CLC resonant dual active bridge

This paper proposes a linear large signal state-space model for a phase controlled CLC (Capacitor Inductor Capacitor) Resonant Dual Active Bridge (RDAB). The proposed model is useful for fast simulation and for the estimation of state variables under large signal variation. The model is also useful for control design because the slow changing dynamics of the dq variables are relatively easy to control. Simulation results of the proposed model are presented and compared to the simulated circuit model to demonstrate the proposed model's accuracy. This proposed model was used for the design of a Proportional-Integral (PI) controller and it has been implemented in the circuit simulation to show the proposed models usefulness in control design.

An efficiency optimization scheme for bidirectional inductive power transfer systems

Unidirectional inductive power transfer (UIPT) systems allow loads to consume power while bidirectional IPT (BIPT) systems are more suitable for loads requiring two way power flow such as vehicle to grid (V2G) applications with electric vehicles (EVs). Many attempts have been made to improve the performance of BIPT systems. In a typical BIPT system, the output power is control using the pickup converter phase shift angle (PSA) while the primary converter regulates the input current. This paper proposes an optimized phase shift modulation strategy to minimize the coil losses of a series – series (SS) compensated BIPT system. In addition, a comprehensive study on the impact of power converters on the overall efficiency of the system is also presented. A closed loop controller is proposed to optimize the overall efficiency of the BIPT system. Theoretical results are presented in comparison to both simulations and measurements of a 0.5 kW prototype to show the benefits of the proposed concept. Results convincingly demonstrate the applicability of the proposed system offering high efficiency over a wide range of output power.

Orexin/hypocretin role in reward: implications for opioid and other addictions

Addiction is a devastating disorder that affects 15.3 million people worldwide. While prevalent, few effective treatments exist. Orexin receptors have been proposed as a potential target for anti-craving medications. Orexins, also known as hypocretins, are neuropeptides produced in neurons of the lateral and dorsomedial hypothalamus and perifornical area, which project widely throughout the brain. The absence of orexins in rodents and humans leads to narcolepsy. However, orexins also have an established role in reward seeking. This review will discuss some of the original studies describing the roles of the orexins in reward seeking as well as specific works that were presented at the 2013 International Narcotics Research Conference. Orexin signalling can promote drug-induced plasticity of glutamatergic synapses onto dopamine neurons of the ventral tegmental area (VTA), a brain region implicated in motivated behaviour. Additional evidence suggests that orexin signalling can also promote drug seeking by initiating an endocannabinoid-mediated synaptic depression of GABAergic inputs to the VTA, and thereby disinhibiting dopaminergic neurons. Orexin neurons co-express the inhibitory opioid peptide dynorphin. It has been proposed that orexin in the VTA may not mediate reward per se, but rather occludes the ‘anti-reward’ effects of dynorphin. Finally, orexin signalling in the prefrontal cortex and the central amygdala is implicated in reinstatement of reward seeking. This review will highlight recent work describing the role of orexin signalling in cellular processes underlying addiction-related behaviours and propose novel hypotheses for the mechanisms by which orexin signalling may impart drug seeking.

Potentially inappropriate prescribing in older patients admitted to acute care hospitals and discharged to residential aged care facilities

Background The frequency of prescribing potentially inappropriate medications (PIMs) in older patients remains high regardless of the evidence of adverse outcomes from their use. This study aims to identify the prevalence and nature of PIMs at admission to acute care and at discharge to residential aged care facilities (RACFs) using the recently updated Beers’ Criteria. We also aim to identify if polypharmacy, age, gender and the frailty status of patients are independent risk factors for receiving a PIM. Methods This was a retrospective study of 206 patients discharged to RACFs from acute care. All patients were aged at least70 years and were admitted between July 2005 and May 2010; their admission and discharge medications were evaluated. Frailty status was measured as the Frailty Index (FI), adding each individual’s deficits and dividing by the total number of deficits considered, with FI 0.25 used as the cut-off between “fit” and “frail”. Results Mean patient age was 84.8 ± 6.7 years; the majority (57%) were older than 85 years and approximately 90% were frail. Patients were prescribed a mean of 7.2 regular medications at admission and 8.1 on discharge. At least one PIM was identified in 112 (54.4%) patients on admission and 102 (49.5%) patients on discharge. Of all medications prescribed at admission (1728), 10.8% were PIMs and at discharge of 1759 medications, 9.6% were PIMs. Of the total 187 PIMs on admission, 56 (30%) were stopped, and 131 were continued; 32 new PIMs were introduced. Commonly prescribed PIMs at both admission and discharge were central nervous system, cardiovascular and gastrointestinal drugs and analgesics. Of the potential risk factors, frailty status was the only significant predictor of PIMs at both admission and discharge (p = 0.016). Conclusion A high prevalence of unnecessary drug use was observed in frail older patients on admission to acute care hospitals and on discharge to RACFs. The only association with PIM use was the frailty status of patients. Further studies are needed to further evaluate this association.

Design & performance of a networked ad-hoc acoustic communications system using inexpensive commercial CDMA modems

We present a new approach for creating and implementing an ad-hoc underwater acoustic sensor network based on connecting a small processor to the serial port of a commercial CDMA acoustic modem. The processor acts as a "node controller" providing the networking layer that the modems lack. The ad-hoc networking protocol is based on a modified dynamic source routing (DSR) approach and can be configured for maximising information throughput or minimising energy expenditure. The system was developed in simulation and then evaluated during field trials using a 10 node deployment. Experimental results show reliable multi-hop networking under a variety of network configurations, with the added ability to determine internode ranges to within 1.5 m for localisation.

Eigenvalue Analysis of a DFIG Based Wind Power System under Different Modes of Operations

This chapter discussed the various modes of operation of the Doubly Fed Induction Generator (DFIG) based wind farm system. The impact of a auxiliary damping controller on the different modes of operation for the DFIG based wind generation system is investigated. The co-ordinated tuning of the damping controller to enhance the damping of the oscillatory modes using Bacteria Foraging (BF) technique is presented. The results from eigenvalue analysis are presented to elucidate the effectiveness of the tuned damping controller in the DFIG system under Super/Sub-synchronous speed of operation. The robustness issue of the damping controller is also investigated.

Doubly Fed Induction Generators : Overview and Intelligent Control Strategies for Wind Energy Conversion Systems

Adjustable speed induction generators, especially the Doubly-Fed Induction Generators (DFIG) are becoming increasingly popular due to its various advantages over fixed speed generator systems. A DFIG in a wind turbine has ability to generate maximum power with varying rotational speed, ability to control active and reactive by integration of electronic power converters such as the back-to-back converter, low rotor power rating resulting in low cost converter components, etc, DFIG have become very popular in large wind power conversion systems. This chapter presents an extensive literature survey over the past 25 years on the different aspects of DFIG. Application of H8 Controller for enhanced DFIG-WT performance in terms of robust stability and reference tracking to reduce mechanical stress and vibrations is also demonstrated in the chapter.

Tracking control of a class of Hamiltonian mechanical systems with disturbances

This paper presents a trajectory-tracking control strategy for a class of mechanical systems in Hamiltonian form. The class is characterised by a simplectic interconnection arising from the use of generalised coordinates and full actuation. The tracking error dynamic is modelled as a port-Hamiltonian Systems (PHS). The control action is designed to take the error dynamics into a desired closed-loop PHS characterised by a constant mass matrix and a potential energy with a minimum at the origin. A transformation of the momentum and a feedback control is exploited to obtain a constant generalised mass matrix in closed loop. The stability of the close-loop system is shown using the close-loop Hamiltonian as a Lyapunov function. The paper also considers the addition of integral action to design a robust controller that ensures tracking in spite of disturbances. As a case study, the proposed control design methodology is applied to a fully actuated robotic manipulator.