Control strategies for integration of electric motor assist and functional electrical stimulation in paraplegic cycling: Utility for exercise testing and mobile cycling

AIM: The aim of this study was to investigate feedback control strategies for integration of electric motor assist and functional electrical stimulation (FES) for paraplegic cycling, with particular focus on development of a testbed for exercise testing in FES cycling, in which both cycling cadence and workrate are simultaneously well controlled and contemporary physiological measures of exercise performance derived. A second aim was to investigate the possible benefits of the approach for mobile, recreational cycling. METHODS: A recumbent tricycle with an auxiliary electric motor is used, which is adapted for paraplegic users, and instrumented for stimulation control. We propose a novel integrated control strategy which simultaneously provides feedback control of leg power output (via automatic adjustment of stimulation intensity) and cycling cadence (via electric motor control). Both loops are designed using system identification and analytical (model-based) feedback design methods. Ventilatory and pulmonary gas exchange response profiles are derived using a portable system for real-time breath-by-breath acquisition. RESULTS:We provide indicative results from one paraplegic subject in which a series of feedback-control tests illustrate accurate control of cycling cadence, leg power control, and external disturbance rejection. We also provide physiological response profiles from a submaximal exercise step test and a maximal incremental exercise test, as facilitated by the control strategy. CONCLUSION: The integrated control strategy is effective in facilitating exercise testing under conditions of well-controlled cadence and power output. Our control approach significantly extends the achievable workrate range and enhances exercise-test sensitivity for FES cycling, thus allowing a more stringent characterization of physiological response profiles and estimation of key parameters of aerobic function.We further conclude that the control approach can significantly improve the overall performance of mobile recreational cycling

Concept definition study for recovery of tumbling satellites. Volume 1: Executive summary, study results

The first assessment is made of the design requirements and conceptual definition of a front end kit to be transported on the currently defined Orbital Maneuvering Vehicle (OMV) and the Space Transportation System Shuttle Orbiter, to conduct remote, teleoperated recovery of disabled and noncontrollable, tumbling satellites. Previous studies did not quantify the dynamic characteristics of a tumbling satellite, nor did they appear to address the full spectrum of Tumbling Satellite Recovery systems requirements. Both of these aspects are investigated with useful results

Concept definition study for recovery of tumbling satellites. Volume 2: Supporting research and technology report

A number of areas of research and laboratory experiments were identified which could lead to development of a cost efficient remote, disable satellite recovery system. Estimates were planned of disabled satellite motion. A concept is defined as a Tumbling Satellite Recovery kit which includes a modular system, composed of a number of subsystem mechanisms that can be readily integrated into varying combinations. This would enable the user to quickly configure a tailored remote, disabled satellite recovery kit to meet a broad spectrum of potential scenarios. The capability was determined of U.S. Earth based satellite tracking facilities to adequately determine the orientation and motion rates of disabled satellites

Advanced orbit transfer vehicle propulsion system study

A reuseable orbit transfer vehicle concept was defined and subsequent recommendations for the design criteria of an advanced LO2/LH2 engine were presented. The major characteristics of the vehicle preliminary design include a low lift to drag aerocapture capability, main propulsion system failure criteria of fail operational/fail safe, and either two main engines with an attitude control system for backup or three main engines to meet the failure criteria. A maintenance and servicing approach was also established for the advanced vehicle and engine concepts. Design tradeoff study conclusions were based on the consideration of reliability, performance, life cycle costs, and mission flexibility

Is the Toxicity of Salvage Prostatectomy Related to the Primary Prostate Cancer Therapy Received?

PURPOSE: To compare the toxicity profile and oncological outcome of salvage radical prostatectomy (SRP) following focal therapy (FT) versus SRP after radiation therapies (RT) - external beam radiation therapy (EBRT) or brachytherapy (BT). MATERIALS AND METHODS: Data concerning all men undergoing SRP for recurrent prostate cancer after either FT, EBRT or BT were retrospectively collected from 4 high volume surgical centres. The primary outcome measure of the study was toxicity of SRP characterized by any 30-day post-operative Clavien-Dindo complication rate, 12-month continence rate and 12-month potency rate. The secondary outcome was oncological outcome after SRP including positive margin rate and 12-month biochemical recurrence (BCR) rate. BCR was estimated using Kaplan-Meier methods and significant differences were calculated using a log rank test. Median follow-up time was 29.5 months. RESULTS: Between April 2007 and September 2018, 185 patients underwent SRP of which 95 had SRP after FT and 90 had SRP after RT, either EBRT or BT. SRP after RT was associated with a significantly higher 30-day Clavien-Dindo I-IV complication rate (34% vs 5%, p<0.001). At 12 months following surgery, patients undergoing SRP after FT had significantly better continence (SRP after FT:83% pad-free vs RT:49%) while potency outcomes were similar (FT:14% vs RT:11%). Men undergoing SRP after RT had a significantly higher stage and grade of disease together with a higher positive surgical margin rate (37% vs 13%, p=0.001). 3-year BCR after FT was 35% compared to 32% after RT, p=0.76. In multivariable analysis, men undergoing SRP after FT experienced a higher risk of BCR (HR 0.36 [0.18-0.82], p<0.005). CONCLUSIONS: This multicentre study demonstrates the toxicity of SRP in terms of perioperative complications and long-term urinary continence recovery is dependent on initial primary prostate cancer therapy received with men undergoing SRP after FT experiencing lower postoperative complication rates and better urinary continence outcomes

Outcomes of the RAFT Trial: Robotic surgery After Focal Therapy

OBJECTIVES: To report toxicity of treatment observed in men participating in the Robotic surgery After Focal Therapy (RAFT) clinical trial. SUBJECTS/PATIENTS AND METHODS: Men were eligible for this prospective single group interventional study if they had histologically confirmed recurrent/residual prostate adenocarcinoma following primary FT. The short-form Expanded Prostate Cancer Index Composite (EPIC-26) measured prior to salvage robotic prostatectomy (S-RARP) and 3-monthly post-operatively together with Clavien-Dindo complications (I-IV). Secondary outcomes included biochemical recurrence-free survival (BCFS) following surgery and need for salvage treatment after surgery. This study is registered with ClinicalTrials.gov NCT03011606. RESULTS: 24 men were recruited between February 2016 and September 2018. 1 patient withdrew from the trial after consenting and before S-RARP. 23 men completed 12-month post S-RARP follow-up. Median EPIC-26 urinary continence scores initially deteriorated after 3 months (82.4 versus 100) but there was no statistically significant difference from baseline at 12 months (100 versus 100, p=0.31). Median lower urinary tract symptom scores improved after 12 months compared to baseline (93.8 versus 87.5, p=0.01). At 12 months, 19/23 (83%) were pad-free and 22/23 (96%) required 0/1 pads. Median sexual function subscale scores deteriorated and remained low at 12 months (22.2 versus 58.3, p<0.001). Utilising a minimally important difference of 9 points, at 12 months after surgery 17/23 (74%) reported urinary continence to be "better" or "not different" to pre-operative baseline. The corresponding figure for sexual function (utilising a minimally important difference of 12 points) was 7/23 (30%). There was no statistically significant difference on median bowel/hormonal subscale scores. Only a single patient had a post-operative complication (Clavien-Dindo Grade I). BCFS at 12 months after surgery was 82.6% (95% confidence interval [CI]: 60.1% - 93.1%] while 4/23 (17%) received salvage radiation. CONCLUSIONS: The RAFT clinical trial suggests toxicity of surgery after FT is low, with good urinary function outcomes, albeit sexual function deteriorated overall. Oncological outcomes at 12 months appear acceptable

Optimising mechanical separation of anaerobic digestate for total solids and nutrient removal

Publication history: Accepted - 16 June 2023; Published - 28 June 2023.Mechanical separation of anaerobic digestate has been identified as a method to reduce pollution risk to waterways by partitioning phosphorus in the solid fraction and reducing its application to land. Separators have adjustable parameters which affect separation efficiency, and hence the degree of phosphorous partitioning, but information on how these parameters affect separation performance is limited in the literature. Two well known technologies were investigated, decanter centrifuge and screw press, to determine the most efficient method of separation. Counterweight load and the use of an oscillator were adjusted for the screw press, while bowl speed, auger differential speed, feed rate and polymer addition were modified for the decanter centrifuge. Separation efficiency was determined for total solids, phosphorus, nitrogen, potassium, and carbon, and the total solids content of resulting fractions was measured. The decanter centrifuge had higher separation efficiency for phosphorus in all cases, ranging from 51% to 71.5%, while the screw press had a phosphorus separation efficiency ranging from 8.5% to 10.9% for digestate of ~5% solids (slurry/grass silage mix). Separation by decanter centrifuge partitioned up to 56% of nitrogen in the solid fraction leaving a reduced nitrogen content in the liquid fraction available for land spreading; this nitrogen would most likely need to be replaced by chemical fertiliser which would add to the cost of the system. The decanter centrifuge is better suited to cases where phosphorus recovery is the most important factor, while the screw press could be advantageous in cases where cost is a limiting factor.This project was supported by The Bryden Centre. The Bryden Centre project is supported by the European Union’s INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB). The views and opinions expressed in this paper do not necessarily reflect those of the European Commission or the Special EU Programmes Body (SEUPB). The work was also supported by Queen’s University Belfast and the Agri-Food and Biosciences Institute in Northern Ireland

An economic analysis of anaerobic digestate fuel pellet production: can digestate fuel pellets add value to existing operations?

Publication history: Accepted - 9 April 2021; Published online - 16 April 2021.Anaerobic digestion provides renewable energy through waste valorisation, but the digestate by-product is underutilised and presents a risk to water quality. Mechanical separation partitions phosphorous into the solid fraction and further processing into a fuel pellet can provide an additional source of energy and revenue. Previous economic analyses looked only at aspects of the system (e.g. operational costs solely) and the system requires further investigation to determine viability. In this paper, an economic assessment of digestate fuel pellet production at farm-scale anaerobic digestion plants was carried out. The significance of this work is to provide a comprehensive assessment of the energy, phosphorous, and economic balances involved in digestate fuel pellet production at existing anaerobic digestion plants. The aim of this paper is to determine the financial viability of digestate fuel pellet production with objectives to compare two mechanical separation technologies: screw press, and decanting centrifuge. Economies of scale hold true for digestate pellet production and the available digestate in typical UK farm-based anaerobic digestion plants ( 500 kWe) is insufficient for profitability, with pellet production costing from £176/t (decanting centrifuge) to £215/t (screw press), compared to a typical wood pellet sale price of £185/t. Increasing digestate quantity by collaboration of plant operators can reduce the cost of pellet production to between £95/t and £121/t, improving financial viability and increasing the profit per head of cattle by 9–20% on a typical dairy farm utilising anaerobic digestion. The system has potential to aid rural development while also protecting the environment and contributing to the diversification of energy supply.This project was supported by The Bryden Centre. The Bryden Centre project is supported by the European Union’s INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB). The views and opinions expressed in this paper do not necessarily reflect those of the European Commission or the Special EU Programmes Body (SEUPB). The work was also supported by Queen’s University Belfast and the Agri-Food and Biosciences Institute in Northern Ireland

Effect of anaerobic digestate fuel pellet production on Enterobacteriaceae and Salmonella persistence

Publication history: Accepted - 10 June 2022; Published online - 7 July 2022.Production of digestate pellets for fuel has been identified as a promising circular economy approach to provide renewable energy and additional income to farms, while at the same time presenting the potential to divert raw digestate from nutrient-saturated land and reduce the risk to water quality. Although previous research has investigated the feasibility of pellet production, there has been little focus on the bio-safety aspects of the system. Little is currently known about the persistence of bacteria present in the digestate and the potential impacts on human health for those handling this product. The aim of the present research was to determine the effect that each step in the pellet production process has on bacteria numbers: anaerobic digestion, mechanical separation, solid drying, and pelletisation. Enterobacteriaceae enumeration by colony count method was used to quantify bacteria, and the presence of Salmonella at each stage was determined. The Enterobacteriaceae count reduced with each stage, and the final pelletisation step reduced bacteria numbers to below detectable levels (<10 colony forming units/g). Salmonella was only detected in the starting slurry and absent from digestate onwards. Storage of the pellets under winter and simulated summer conditions showed no reactivation of Enterobacteriaceae over time. The pelletisation process produces a digestate product with Enterobacteriaceae counts below the maximum threshold (PAS110 specification) for transport off the source farm, but care must still be taken when handling digestate pellets as complete sterilisation has not been confirmed.This project was supported by The Bryden Centre. The Bryden Centre project is supported by the European Union's INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB). The work was also supported by Queen's University Belfast and the Agri-Food and Biosciences Institute in Northern Ireland