667 results on '"Shorten, Robert"'
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652. Konsensus in Multi-Agenten-Systemen
- Author
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Parada Contzen, Miguel, Raisch, Jörg, Technische Universität Berlin, Shorten, Robert, and Schiffer, Johannes
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ddc:620 - Abstract
During the last decade, the problem of consensus in multiagents systems has been studied with special emphasis on graph theoretical methods. Consensus can be regarded as a control objective in which is sought that all systems, or agents, in a network have an equivalent output value. This is achieved through a given control strategy usually referred to as consensus algorithm. The motivation to study such an objective comes from different areas, such as engineering, and social and natural sciences. In the control engineering field, important application examples are formation control of swarms of mobile robots and distributed electric generation. Most of the work in this area is done for agents with single or double integrator dynamics and algorithms derived as the Laplacian matrix of undirected graphs. That is, consensus is often studied as a property of particular networks and particular algorithms. In this thesis, we tackle the problem from a Control Theory perspective in an attempt to augment the class of systems that can be studied. For that we translate the consensus problem from its classical formulation for integrator systems into a general continuous time stability problem. From here, different algorithmic strategies under several dynamical assumptions of the agents can be studied through well known control theoretical tools -- as Lyapunov's theory, linear matrix inequalities (LMI), or robust control -- along with graph theoretical concepts. In particular, in this work we study consensus of agents with arbitrary linear dynamics under the influence of linear algorithms not necessarily derived from graphs. Furthermore, we include the possibility that the agents are disturbed by several factors as external signals, parameter uncertainties, switching dynamics, or communication failure. The theoretical analysis is also applied to the problem of power sharing in electric grids and to the analysis of distributed formation control. Im Laufe der letzten zehn Jahre wurde das Problem des Konsenses in Multi-Agenten-Systemen mit besonderem Augenmerk auf graphen-theoretische Methoden erforscht. Ein Konsens kann als ein Regelungsziel interpretiert werden, in welchem alle Systeme, oder Agenten, in einem Netzwerk identische Ausgangswerte anstreben. Dies wird durch eine Regelungsstrategie erreicht, die man üblicherweise als Konsens Algorithm bezeichnet. Motiviert wird diese Regelungsstrategie aus verschiedenen Bereichen, wie den Ingenieurwissenschaften und den Sozial- und Naturwissenschaften. Wichtige Beispiele im Bereich der Regelungstechnik sind die Formationsregelung in Schwärmen von mobilen Robotern oder die verteilte Energieerzeugung. Die Mehrheit der Werke in diesem Bereich konzentriert sich auf Agenten mit Einfach- oder Doppel-Integratordynamiken, sowie Algorithmen abgeleitet aus der Laplacian-Matrix von ungerichteten Graphen. In anderen Worten, der Konsens wird oft als eine Eigenschaft besonderer Netzwerke und Algorithmen erforscht. In dieser Dissertation wird das Problem des Konsenses aus einer regelungs-theoretischen Perspektive betrachtet. Dies wird durch die Übersetzung des Konsens-Problems aus seiner klassischen Formulierung für Integratorensysteme zu einem zeitkontinuierlichen Stabilität-Problem bewerkstelligt. Basierend auf bekannten Methoden der Regelungstechnik (zum Beispiel, auf Lyapunovs Theorie, den linearen Matrixungleichungen (LMI), oder der Robustregelung) und graph-theoretische Ideen werden unterschiedliche algorithmische Strategien und mehrere Arten von dynamischen Agenten behandelt. Im Besonderen wird in dieser Arbeit der Konsens von Agenten mit willkürlichen linearen Dynamiken betrachtet. Dies ist eine Erweiterung zu den klassischen Einfach- und Doppelt-Integratoren Dynamiken. Desweiteren betrachten wir Algorithmen, die nicht unbedingt von Graphen abgeleitet sind. Es wird weiterhin das Verhalten der Agenten unter dem Einfluss von Störungen untersucht. Dies beinhaltet zum Beispiel externe Störungssignale, parametrische Unsicherheiten, geschaltete Dynamiken oder Kommunikationfehler. Die Anwendbarkeit der hier erlangten theoretischen Ergebnisse wird am Beispiel der Formationsregelung und der Stabilisierung verteilter Energiesysteme demonstriert.
- Published
- 2017
653. Regelungssysteme für ITS Anwendungen in Smart Cities
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Häusler, Florian, Raisch, Jörg, Technische Universität Berlin, Shorten, Robert, and Taiber, Joachim
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ddc:005 ,ddc:620 - Abstract
This thesis introduces new applications from the domain of Intelligent Transportation Systems to address some of the central challenges of urban road traffic. All applications exploit the potential of recent developments in the automotive field, in particular vehicular networks, new kinds of vehicles such as electric and full hybrid vehicles and results from networked control theory. By setting up a feedback loop around a large number of vehicles applications are able to address general road traffic problems in a very direct way - in a way which is not possible by per-vehicle measures. Domain-specific requirements (e.g. preserve drivers' privacy) are considered in the design of each application and its underlying control and optimization algorithm. It is shown that multiple problems can be approached with a simple system architecture: On the one hand, there is a central infrastructure, which has access to general, system-wide information such as air pollution levels, traffic flow information, etc. On the other hand, there are vehicles - in particular full hybrids - which are equipped with advanced communication technology. Communication technology integrates both parts into a feedback control loop. It is shown that in many cases it is sufficient that the infrastructure broadcasts minimal information such that vehicles act in a collaborative way. The introduced applications address the problem of air pollution in urban environments, optimize emission in a fleet, target the problem of supply variations in electric grids with hybrid vehicles, provide balancing solutions for electric vehicle charging stations and aim at utilizing given parking spaces in a more efficient way. The performance is discussed with help of extensive simulations. (Limited) mathematical analyses for algorithmic approaches are included or cited. It is considered that proposed applications might recommend behaviour which does not optimize individual utilities - while they do optimize other aspects such as the total utility of all users. Thus, the question of user acceptance is crucial. In this sense, selected user acceptance tests and surveys have been performed. Furthermore a technical platform is introduced which provides the possibility to test collaborative applications in the field (including user acceptance) without requiring a large number of vehicles. Die Dissertation beschreibt neue Anwendungen im Bereich Intelligent Transportation Systems, um zentralen Problemen des urbanen Straßenverkehrs zu begegnen. Die hier betrachteten Probleme können nur gelöst werden, wenn Fahrzeuge miteinander kooperieren und ihr Verhalten aufeinander abstimmen. Die entwickelten Lösungsansätze verbindet, dass sie die Möglichkeiten ausnutzen, die mit der Entwicklung neuer Fahrzeugtypen - insbesondere Elektrohybridfahrzeugen - und ihrer zunehmenden Vernetzung einhergehen. Dabei entsteht ein dem Internet verwandtes Systemumfeld auf das Ansätze aus dem Bereich Netzwerksteuerung mit wenigen Anpassungen übertragen werden können. Indem eine große Zahl von Fahrzeugen in einen übergeordneten Regelkreis integriert werden, können grundsätzliche Verkehrsprobleme in Smart Cities auf eine sehr direkte Art adressiert werden - viel direkter als es mit fahrzeugindividuellen, nicht-kooperativen Ansätzen möglich ist. Es wird gezeigt, dass dabei relevante, domänenspezifische Anforderungen (z.B. Sicherung der Privatsphäre) berücksichtigt werden können. Dabei kann eine einfache Systemarchitektur genutzt werden: Auf der einen Seite steht eine zentrale Infrastruktur (z.B. Verkehrsmanagementzentrale), die auf entsprechende Informationen Zugriff hat (z.B. Luftbelastung, Verkehrsflussinformationen). Auf der anderen Seite stehen mit Kommunikationstechnologie ausgestatteten Fahrzeuge. Die entwickelten Anwendungen belegen, dass es in vielen Fällen ausreicht, einfache Informationen via Broadcasts durch die zentrale Infrastruktur zu verbreiten, so dass sich ein abgestimmtes, kollaboratives Verhalten der Fahrzeuge einstellt. Auf diese Weise können mehrere Probleme im urbanen Verkehr adressiert werden. Dazu zählen die lokale Luftbelastung in städtischen Räumen, die Optimierung der Emission einer Fahrzeugflotte, Schwankungen im Stromangebot in Elektrizitätsnetzen und die ineffiziente Nutzung von Parkplätzen und Ladesäulen für Elektrofahrzeuge. Alle Anwendungen werden mit Hilfe von umfangreichen Simulation validiert. Auf erweiternde mathematische Diskussionen und Herleitungen wird an entsprechender Stelle auf jeweilige Publikationen verwiesen. Da die vorgestellten Lösungsansätze den systemweiten und nicht notwendigerweise den individuellen Nutzen von Teilnehmern optimiert, ist die Nutzerakzeptanz kritisch. Zu ausgewählten Anwendungen werden daher die Ergebnisse von Akzeptanzstudien vorgestellt. In diesem Zusammenhang wurde zudem eine technische Plattform entwickelt, die es ermöglicht kooperative Anwendungen im Feld zu testen, ohne auf eine große Anzahl von Fahrzeugen zurückgreifen zu müssen.
- Published
- 2016
654. Contributions to the Control of Hybrid and Switched Linear Systems
- Author
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Kouhi Anbaran, Yashar, Raisch, Jörg, Technische Universität Berlin, Fakultät IV - Elektrotechnik und Informatik, Shorten, Robert, and Curran, Paul
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ddc:000 - Abstract
Hybride lineare Systeme sind eine Klasse von hybriden Systemen, bei denen die kontinuierliche Zeitentwicklung durch einen Satz von linearen Differentialgleichungen erster Ordnung, und die Sprungdynamik durch einen Satz von linearen Differenzengleichungen erster Ordnung beschrieben werden. Geschaltete lineare Systeme sind eine Unterklasse von hybriden linearen Systemen mit einer stetigen Zeitentwicklung der Systemzustände. Aufgrund der großen Anzahl physikalischer Anwendungen erfuhr die Regelung von hybriden und geschalteten linearen Systemen in den letzten Jahren beträchtliche Aufmerksamkeit. Diese Dissertation stellt neue Beiträge zur Regelung solcher Systeme vor und erweitert einige vorhandene Ergebnisse in diesem Bereich. Diese Arbeit konzentriert sich auf verschiedene Aspekte der Stabilität und Stabilisierung geschalteter linearer Systeme sowie der optimalen Regelung hybrider linearer Systeme. Der größte Teil dieser Arbeit betrifft die Stabilität und Stabilisierung von geschalteten linearen Systemen. Die Darstellung der Ergebnisse bezieht sich in erster Linie auf Bedingungen für die Stabilität autonomer geschalteter linearer Systeme. Stabilisierungsverfahren zielen dann auf den Entwurf einer lokalen Zustandsrückführung für jeden Modus eines geregelten geschalteten linearen Systems, um die Stabilitätskriterien für die Modi des geschlossenen Regelkreises zu befriedigen. Teile dieser Ergebnisse beruhen auf dem Konzept gemeinsamer linker Eigenvektoren und der Zuweisung linker Eigenstruktur. Zu diesem Zweck werden mehrere Verfahren zur Zuweisung der Eigenstruktur von linearen Systemen entwickelt. Anschließend werden diese Techniken zur Charakterisierung exponentieller Stabilität und zur Stabilisierung einer Klasse von geschalteten linearen Systemen mit zustandsabhängigem Schalten unter bestimmten Einschränkungen bezüglich der Schaltmannigfaltigkeiten eingesetzt. Darüber hinaus werden sie zur quadratischen Stabilisierung einer Klasse von beliebig schaltenden linearen Systemen eingesetzt, in der die Dynamikmatrizen des offenen Kreises einen invarianten Untervektorraum gemeinsam haben, der mit einer gemeinsamen quadratischen Lyapunov-Funktion assoziiert werden kann. Ein weiterer Stabilitätsansatz nutzt das Kalman-Yakubovic-Popov-Lemma, um quadratische Stabilität einer Klasse von geschalteten linearen Systemen zu zeigen. Diese Klasse wird von beliebigem Schalten zwischen zwei Modi gekennzeichnet, für welche die Differenz der Dynamikmatrizen von Rang $m \geq 1$ ist, und mit denen eine symmetrische Übertragungsfunktionsmatrix assoziiert werden kann. Diese Ergebnisse erweitern vorhandene Ergebnisse zur quadratischen Stabilität geschalteter linearer Systeme, bei denen die Differenz der Dynamikmatrizen Rang 1 aufweist. Die Dissertation befasst sich auch mit der linear quadratischen Regelung von hybriden linearen Systemen. Hierbei sind die Kostenfunktionen quadratisch, der Zeithorizont und die Anzahl und Reihenfolge des Schaltens gegeben. Einschränkungen sind durch lineare (Un-) Gleichungen im Zustandsraum gegeben. Die Zeitpunkte des Schaltens zwischen unterschiedlichen Dynamiken können entweder vorgegeben oder frei sein. Ein Parametrierungsverfahren in Bezug auf Ausgangs- und Endpunkte der einzelnen Intervalle eines generalisierten Zeitbereichs wird verwendet. Numerische Lösungen werden für solche Aufgaben vorgeschlagen. Hybrid linear systems are a class of hybrid systems where the continuous time evolution is governed by a set of first order linear ordinary differential equations and the jump dynamics are described by a set of first order linear difference equations. Switched linear systems are a subclass of hybrid linear systems with a continuous evolution of the system states. Due to the large number of physical applications, control of hybrid and switched linear systems has received considerable attention over the past years. This dissertation provides novel contributions to the control of such systems and extends some existing results in this area. This work focuses on different problems regarding stability and stabilization of switched linear systems and optimal control of hybrid linear systems. The major part of this thesis concerns stability and stabilization of switched linear systems. The results are primarily presented in terms of conditions for stability of autonomous switched systems. Then, stabilization methods aim at designing a local state feedback for each mode of a controlled switched system to satisfy the stability criteria for the closed loop system modes. Parts of these results rely on the concept of common left eigenvectors and left eigenstructure assignment. To this end, several techniques for eigenstructure assignment in the context of linear systems are developed. Afterwards, these techniques are employed for characterizing exponential stability and for stabilization of a class of switched linear systems with state dependent switching and certain restrictions on the switching manifolds. In addition, they are used for quadratic stabilization of a class of controlled switched linear systems with arbitrary switching signals where the open loop constituent matrices share an invariant subspace to which a common quadratic Lyapunov function can be associated. Another stability approach makes use of the Kalman-Yakubovic-Popov lemma to demonstrate quadratic stability of a class of switched linear systems. This class is characterized by arbitrary switching between two modes, where the difference of the constitute matrices is of rank $m\geq 1$, and to which a symmetric transfer function matrix can be associated. These results extend existing results in quadratic stability of rank-1 difference switched linear systems. The thesis also addresses problems in linear quadratic control of hybrid linear systems. In these problems, cost functions are quadratic, the final time and the number and sequence of switches are given. Constraints are specified by linear (in-)equalities in the state space. Switching between different dynamics may either occur at fixed or free time instances. A parameterization method with respect to initial and end points of each interval in a generalized time domain is employed. Numerical solutions for such problems are suggested.
- Published
- 2014
655. Stability and Controllability of Double Integrator Consensus Systems in Heterogeneous Networks
- Author
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Goldin, Darina, Technische Universität Berlin, Fakultät IV - Elektrotechnik und Informatik, Raisch, Jörg, Shorten, Robert, and Stanczak, Slawomir
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Leader-Follower Systeme ,Consensus controllability ,Doppelintegratorkonsens ,Double integrator consensus ,Consensus ,620 Ingenieurwissenschaften und zugeordnete Tätigkeiten ,Networked systems ,Steuerbarkeit von Konsenssystemen ,ddc:620 ,Konsens ,Vernetzte Systeme ,Leader-follower systems - Abstract
Ein Konsensussystem besteht aus einer Menge von kommunizierenden Agenten, die sich mittels ausschließlich lokaler Kommunikation auf eine Variable einigen. Einige denkbare Anwendungen für Konsensussysteme sind beispielsweise elektrische Netzwerke (so genannte "smart grids"), drahtlose Sensornetzwerke, soziale Netzwerke, und viele Anwendungen aus dem Bereich unbemannte Flugmaschinen, wie etwa Überwachung, Kartographie und Beobachtung von Ökosystemen. Wenn die Agenten, aus denen das Netzwerk besteht, eine Doppelintegratordynamik besitzen, so spricht man vom Doppelintegratorkonsensussystem. Diese Arbeit beschäftigt sich mit einem Doppelintegratorkonsensussystem in kontinuierlicher Zeit. Es wird angenommen, dass die Agenten ihre Position und Geschwindigkeit entlang von gewichteten Kommunikationsnetzwerken übermitteln können, die verschieden sein dürfen und mittels gewichteter gerichteter Graphen modelliert werden. Das mathematische Modell des Systems hat die Form \begin{equation}\ddot x(t)=-L_xx(t)-\beta L_{\dot x}\dot x(t),\tag{S1}\label{abs:3}\end{equation} wobei $x:\mathbb R^+\rightarrow\mathbb R^n$ und $\dot x:\mathbb R^+\rightarrow \mathbb R^n$ die gesammelten Positionen und Geschwindigkeiten der Agenten repräsentieren, $L_x$ und $L_{\dot x}$ die Laplacematrizen der Kommunikationsgraphen sind und $\beta\in\mathbb R^+\setminus\{0\}$ ein Verstärkungsfaktor ist. Für solche Systeme wird in dieser Arbeit ein Stabilitätskonzept hergeleitet. Das System \ref{abs:3} wird konsensusstabil genannt, wenn alle Geschwindigkeitsunterschiede im System mit laufender Zeit null werden. Es wird asymptotisch konsensusstabil genannt, wenn alle Positionsunterschiede mit laufender Zeit null werden. Die üblicherweise in der Literatur getätigte Annahme, dass die Kommunikationsnetzwerke gleich, also homogen für beide Informationsflüsse sind, ist in vielen Fällen zu stark. Daher wird in dieser Arbeit die Annahme getroffen, dass die Kommunikationsnetzwerke unterschiedlich und unter Umständen sogar nicht verbunden sein können. Notwendige und hinreichende Bedingungen für Konsensusstabilität und asymptotische Konsensusstabilität werden für den Spezialfall hergeleitet, dass die Kommunikationsgraphen gewichtet und ungerichtet sind. Diese Bedingungen werden anschließend auf einige Fälle erweitert, in denen die Graphen gewichtet und gerichtet sind. Zudem betrachten wir die Konvergenzgeschwindigkeit und -wert des Systems. Im Anschluß an die Stabilitätsanalyse wird aufgezeigt, wie das autonome Konsensusystem \ref{abs:3} in ein Regelsystem überführt werden kann, indem ein Teil der Agenten mit einem externen Regler versehen wird. Es ergibt sich das System \begin{equation} \ddot x(t)=-A_x^fx(t)-A_{\dot x}^f\dot x(t)+Bu(t),\tag{S2}\label{abs:4} \end{equation} wobei $x:\mathbb R^+\rightarrow \mathbb R^{n_f}$ und $\dot x:\mathbb R^+\rightarrow \mathbb R^{n_f}$ die Zustände der zu regelnden, ``folgenden'' Agenten sind, $u:\mathbb R^+\rightarrow \mathbb R^{n_l}$ die Stellgröße ist, die von den ``führenden'' Agenten übermittelt wird, $n_f+n_l=n$, und die Matrizen $A_x^f,A_{\dot x}^f\in\mathbb R^{n_f\times n_f}$, $B\in\mathbb R^{n_f\times n_l}$ aus den Laplacematrizen $L_x$, $L_{\dot x}$ hergeleitet werden. Dieses Netzwerk wird als ein so genanntes "leader-follower" Netzwerk bezeichnet. Es wird auf Steuerbarkeit hin untersucht. Notwendige Bedingungen für die Steuerbarkeit von \ref{abs:4} werden sowohl auf graphenteoretischer als auch auf algebraischer Ebene hergeleitet. Es wird aufgezeigt, dass die graphtheoretischen Bedingungen stark von den in den Graphen vorhandenen Symmetrien abhängen., A consensus system is a set of communicating agents that agree on a variable of interest using only local communication. Some possible uses for consensus systems include smart grids, wireless sensor networks, social networks and various applications of unmanned aerial vehicles such as surveillance, mapping and environmental monitoring. If the agents have double integrator dynamics, then the consensus system is called a double integrator consensus system. In this thesis a double integrator consensus system in continuous time is studied. The agents are assumed to be communicating their position and velocity information along some possibly different, weigh\-ted directed communication networks that are modeled by weighted directed graphs. The mathematical model of the system has the form \begin{equation}\ddot x(t)=-L_xx(t)-\beta L_{\dot x}\dot x(t),\tag{S1}\label{abs:1}\end{equation} where $x:\mathbb R^+\rightarrow\mathbb R^n$ and $\dot x:\mathbb R^+\rightarrow \mathbb R^n$ are the collected positions and velocities of the agents, $L_x$ and $L_{\dot x}$ are the Laplacians of the communication graphs and $\beta\in\mathbb R^+\setminus\{0\}$ is a gain. A stability concept for such systems is derived in the thesis. The system \ref{abs:1} is said to be consensus stable if all of its velocity differences approach zero in time, and asymptotically consensus stable, if all of its position differences tend to zero. The standard assumption made in the literature, that the communication networks are the same, i.e. homogeneous, for both information, is too strong in many cases. Thus, the algorithm is investigated under the assumption that the communication graphs may be different and possibly even disconnected. Necessary and sufficient conditions for consensus stability and asymptotic consensus stability are presented in the special case that the communication graphs are weighted and undirected. These conditions are subsequently relaxed to some cases of weighted directed graphs. Moreover, we consider the convergence rate of the system and the final convergence value. Following the stability analysis, it is shown how the autonomous consensus system \ref{abs:1} can be transformed into a control system by introducing an external control input to a subset of the agents. The resulting system is given by \begin{equation} \ddot x(t)=-A_x^fx(t)-A_{\dot x}^f\dot x(t)+Bu(t),\tag{S2}\label{abs:2} \end{equation} where $x:\mathbb R^+\rightarrow \mathbb R^{n_f}$ and $\dot x:\mathbb R^+\rightarrow \mathbb R^{n_f}$ are the states of the controlled, ``follower'' agents, $u:\mathbb R^+\rightarrow \mathbb R^{n_l}$ is the control input provided by the ``leader'' agents, $n_f+n_l=n$, and the matrices $A_x^f,A_{\dot x}^f\in\mathbb R^{n_f\times n_f}$, $B\in\mathbb R^{n_f\times n_l}$ are obtained from the Laplacian matrices $L_x$, $L_{\dot x}$. This network is called a leader-follower network and its controllability is investigated. Necessary conditions for controllability of the system \ref{abs:2} are given on both algebraic and graph-theoretic levels. It is made apparent that the graph-theoretic conditions are highly dependent on the underlying graph symmetries.
- Published
- 2013
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656. Diagnostic stewardship in infectious diseases: a scoping review.
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Shorten R, Pickering K, Goolden C, Harris C, Clegg A, and J H
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- Humans, Anti-Bacterial Agents therapeutic use, Antimicrobial Stewardship, Communicable Diseases diagnosis
- Abstract
Introduction. The term 'diagnostic stewardship' is relatively new, with a recent surge in its use within the literature. Despite its increasing popularity, a precise definition remains elusive. Various attempts have been made to define it, with some viewing it as an integral part of antimicrobial stewardship. The World Health Organization offers a broad definition, emphasizing the importance of timely, accurate diagnostics. However, inconsistencies in the use of this term still persist, necessitating further clarification. Gap Statement. There are currently inconsistencies in the definition of diagnostic stewardship used within the academic literature. Aim. This scoping review aims to categorize the use of diagnostic stewardship approaches and define this approach by identifying common characteristics and factors of its use within the literature. Methodology. This scoping review undertook a multi-database search from date of inception until October 2022. Any observational or experimental study where the authors define the intervention to be diagnostic stewardship from any clinical area was included. Screening of all papers was undertaken by a single reviewer with 10% verification by a second reviewer. Data extraction was undertaken by a single reviewer using a pre-piloted form. Given the wide variation in study design and intervention outcomes, a narrative synthesis approach was applied. Studies were clustered around common diagnostic stewardship interventions where appropriate. Results. After duplicate removal, a total of 1310 citations were identified, of which, after full-paper screening, 105 studies were included in this scoping review. The classification of an intervention as taking a diagnostic stewardship approach is a relatively recent development, with the first publication in this field dating back to 2017. The majority of research in this area has been conducted within the USA, with very few studies undertaken outside this region. Visual inspection of the citation map reveals that the current evidence base is interconnected, with frequent references to each other's work. The interventions commonly adopt a restrictive approach, utilizing hard and soft stops within the pre-analytical phase to restrict access to testing. Upon closer examination of the outcomes, it becomes evident that there is a predominant focus on reducing the number of tests rather than enhancing the current test protocol. This is further reflected in the limited number of studies that report on test performance (including protocol improvements, specificity and sensitivity). Conclusion. Diagnostic stewardship seems to have deviated from its intended course, morphing into a rather rudimentary instrument wielded not to enhance but to constrict the scope of testing. Despite the World Health Organization's advocacy for an ideology that promotes a more comprehensive approach to quality improvement, it may be more appropriate to consider alternative regional narratives when categorizing these types of quality improvement interventions.
- Published
- 2024
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657. A smart mask to enforce social contracts based on IOTA Tangle.
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Zhao L, Ferraro P, and Shorten R
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- Humans, Computer Simulation, Monte Carlo Method, COVID-19
- Abstract
In this paper we present the design for a smart-mask to mitigate the impact of an airborne virus such as COVID-19. The design utilises recent results from feedback control theory over a distributed ledger that have been developed to enforce compliance in a pseudo-anonymous manner. The design is based on the use of the IOTA distributed ledger. A hardware-in-the-loop simulation based on indoor positioning, paired with Monte-Carlo simulations, is developed to demonstrate the efficacy of the designed prototype., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Zhao et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)
- Published
- 2024
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658. Does comorbidity index predict OPAT readmission?
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Stubbs RD, Shorten RJ, Benedetto V, and Muir A
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Objectives: To determine if the Charlson comorbidity index (CCI) is an accurate predictor of unplanned readmissions for patients using outpatient parenteral antimicrobial therapy (OPAT) services., Methods: Retrospective analysis of patients >16 years of age who had received OPAT at Lancashire Teaching Hospitals between 2019 and 2021. The number of unplanned hospitalizations was measured and categorized as OPAT related or non-OPAT related. The CCI for each patient group was calculated using an online tool, and logistic regression was used to assess the association between risk factors and risk of being readmitted., Results: The cohort consisted of 741 patients. Unplanned readmission was seen in 112 patients (15.1%). The mean CCI score for patients with OPAT-related readmissions was 4.22, 0.92 higher than the mean for patients who were not readmitted (3.30). The mean CCI score for patients with non-OPAT-related readmissions was higher still at 4.89. The logistic regression showed that increased CCI, age, male gender and home location compared with clinic were associated with increased odds of readmission, although these effects did not meet statistical significance., Conclusions: These results suggest that a higher CCI score is associated with a non-statistically significant increased risk of unplanned hospitalization. We concluded that the CCI may therefore be used in future decision-making regarding the acceptance of patients to OPAT and requires further investigation., (© The Author(s) 2023. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy.)
- Published
- 2023
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659. Seroprevalence of SARS-CoV-2 infection in healthcare workers in a large teaching hospital in the North West of England: a period prevalence survey.
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Shorten RJ, Haslam S, Hurley MA, Rowbottom A, Myers M, Wilkinson P, and Orr D
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- COVID-19 blood, England epidemiology, Hospitals, Teaching, Humans, Prevalence, Retrospective Studies, COVID-19 diagnosis, Health Personnel statistics & numerical data, Seroepidemiologic Studies
- Abstract
Objectives: Since its emergence in late 2019, SARS-CoV-2 has caused a global pandemic that has significantly challenged healthcare systems. Healthcare workers have previously been shown to have experienced higher rates of infection than the general population. We aimed to assess the extent of infection in staff working in our healthcare setting., Design: A retrospective analysis of antibody results, compared with staff demographic data, and exposure to patients with COVID-19 infection., Setting: A large teaching hospital in the North West of England., Participants: 4474 staff in diverse clinical and non-patient facing roles who volunteered for SARS-CoV-2 antibody testing by the Roche Elecsys assay between 29 May and 4 July 2020., Results: Seroprevalence was 17.4%. Higher rates were seen in Asian/Asian British (OR 1.61, 95% CI 1.27 to 2.04) and Black/Black British (OR 2.08, 95% CI 1.25 to 3.45) staff. Staff working in any clinical location were more likely to be seropositive (OR 2.68, 95% 2.27 to 3.15). Staff were at an increased risk of seropositivity as the 'per 100 COVID-19 bed-days change' increased in the clinical area in which they worked (OR 1.12, 95% 1.10 to 1.14). Staff working in critical care were no more likely to have detectable antibodies than staff working in non-clinical areas. Symptoms compatible with COVID-19 were reported in 41.8% and antibodies were detected in 30.7% of these individuals. In staff who reported no symptoms, antibodies were detected in 7.7%. In all staff who had detectable antibodies, 25.2% reported no symptoms., Conclusions: Staff working in clinical areas where patients with COVID-19 were nursed were more likely to have detectable antibodies. The relationship between seropositivity in healthcare workers and the increase in 'per 100 COVID-19 bed-days' of the area in which they worked, although statistically significant, was weak, suggesting other contributing factors to the risk profile. Of staff with detectable antibodies and therefore evidence of prior infection, a quarter self-reported that they had experienced no compatible symptoms. This has implications for potential unrecorded transmission in both staff and patients., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)
- Published
- 2021
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660. An unusual presentation of Legionella pneumonia in a returning traveller.
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Shorten RJ, Norman J, and Sweeney LC
- Subjects
- Aspergillosis microbiology, Greece, Humans, Leukemia, Hairy Cell microbiology, Male, Middle Aged, United Kingdom, Aspergillus, Legionella pneumophila, Legionnaires' Disease microbiology, Pneumonia microbiology, Travel-Related Illness
- Abstract
A male patient in his mid-60s presented with a severe pneumonia following return to the UK after travel to Crete. He was diagnosed with Legionnaire's disease (caused by an uncommon serogroup of Legionella pneumophila ). He was pancytopenic on admission, and during a long stay on critical care he was diagnosed with a disseminated Aspergillus infection. Bone marrow aspiration revealed an underlying hairy cell leukaemia that undoubtedly contributed to his acute presentation and subsequent invasive fungal infection., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.)
- Published
- 2019
- Full Text
- View/download PDF
661. A sputum sample processing method for community and mobile tuberculosis diagnosis using the Xpert MTB/RIF assay.
- Author
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Gliddon HD, Shorten RJ, Hayward AC, and Story A
- Abstract
The Xpert MTB/RIF assay can rapidly diagnose tuberculosis, but sputum samples cannot be safely processed unless in a lab. The septum sample pot allows safe handling of sputum and has allowed a mobile TB unit to run the assay in community settings. http://ow.ly/HOA130mS6LG., Competing Interests: Conflict of interest: H.D. Gliddon has nothing to disclose. Conflict of interest: R.J. Shorten reports personal fees from Cepheid (sponsored attendance at an international conference in 2016), outside the submitted work. Conflict of interest: A.C. Hayward has nothing to disclose. Conflict of interest: A. Story has nothing to disclose.
- Published
- 2019
- Full Text
- View/download PDF
662. Ebola Virus Disease: An Update on Epidemiology, Symptoms, Laboratory Findings, Diagnostic Issues, and Infection Prevention and Control Issues for Laboratory Professionals.
- Author
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Brown CS, Mepham S, and Shorten RJ
- Subjects
- Algorithms, Disease Outbreaks, Humans, Clinical Laboratory Techniques, Hemorrhagic Fever, Ebola diagnosis, Hemorrhagic Fever, Ebola epidemiology, Hemorrhagic Fever, Ebola prevention & control, Laboratories
- Abstract
The 2014 to 2016 Ebola virus disease (EVD), through the sheer size of the outbreak and combined experience within both resource-rich and resource-poor settings, allowed for more information to be gained about the clinical and pathologic features of EVD. This review highlights the range of aspects of EVD that the authors find are relevant to laboratory medicine, including the need for robust prediagnostic and laboratory processing algorithms to inform sampling of suspect patients, the vast majority of whom, in resource-rich settings, will have another diagnosis., (Copyright © 2017 Elsevier Inc. All rights reserved.)
- Published
- 2017
- Full Text
- View/download PDF
663. The risk of transmission of a viral haemorrhagic fever infection in a United Kingdom laboratory.
- Author
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Shorten RJ and Wilson-Davies E
- Subjects
- Hemorrhagic Fevers, Viral prevention & control, Hemorrhagic Fevers, Viral virology, Humans, Infection Control methods, Laboratory Infection prevention & control, Laboratory Infection virology, Risk Factors, Travel, United Kingdom, Virus Attachment, Virus Internalization, Hemorrhagic Fevers, Viral transmission, Laboratory Infection transmission, Occupational Exposure
- Published
- 2017
- Full Text
- View/download PDF
664. Diagnostics in Ebola Virus Disease in Resource-Rich and Resource-Limited Settings.
- Author
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Shorten RJ, Brown CS, Jacobs M, Rattenbury S, Simpson AJ, and Mepham S
- Subjects
- Africa, Western epidemiology, Ebolavirus genetics, Ebolavirus physiology, Hemorrhagic Fever, Ebola epidemiology, Hemorrhagic Fever, Ebola virology, Humans, Travel, Ebolavirus isolation & purification, Hemorrhagic Fever, Ebola diagnosis
- Abstract
The Ebola virus disease (EVD) outbreak in West Africa was unprecedented in scale and location. Limited access to both diagnostic and supportive pathology assays in both resource-rich and resource-limited settings had a detrimental effect on the identification and isolation of cases as well as individual patient management. Limited access to such assays in resource-rich settings resulted in delays in differentiating EVD from other illnesses in returning travellers, in turn utilising valuable resources until a diagnosis could be made. This had a much greater impact in West Africa, where it contributed to the initial failure to contain the outbreak. This review explores diagnostic assays of use in EVD in both resource-rich and resource-limited settings, including their respective limitations, and some novel assays and approaches that may be of use in future outbreaks., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2016
- Full Text
- View/download PDF
665. Rapid Whole-Genome Sequencing of Mycobacterium tuberculosis Isolates Directly from Clinical Samples.
- Author
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Brown AC, Bryant JM, Einer-Jensen K, Holdstock J, Houniet DT, Chan JZ, Depledge DP, Nikolayevskyy V, Broda A, Stone MJ, Christiansen MT, Williams R, McAndrew MB, Tutill H, Brown J, Melzer M, Rosmarin C, McHugh TD, Shorten RJ, Drobniewski F, Speight G, and Breuer J
- Subjects
- Humans, Lithuania, Mycobacterium tuberculosis drug effects, Mycobacterium tuberculosis isolation & purification, Sequence Analysis, DNA methods, Time Factors, Tuberculosis, Pulmonary diagnosis, United Kingdom, Bacteriological Techniques methods, Drug Resistance, Bacterial, Genotyping Techniques methods, Mycobacterium tuberculosis genetics, Specimen Handling methods, Sputum microbiology, Tuberculosis, Pulmonary microbiology
- Abstract
The rapid identification of antimicrobial resistance is essential for effective treatment of highly resistant Mycobacterium tuberculosis. Whole-genome sequencing provides comprehensive data on resistance mutations and strain typing for monitoring transmission, but unlike for conventional molecular tests, this has previously been achievable only from cultures of M. tuberculosis. Here we describe a method utilizing biotinylated RNA baits designed specifically for M. tuberculosis DNA to capture full M. tuberculosis genomes directly from infected sputum samples, allowing whole-genome sequencing without the requirement of culture. This was carried out on 24 smear-positive sputum samples, collected from the United Kingdom and Lithuania where a matched culture sample was available, and 2 samples that had failed to grow in culture. M. tuberculosis sequencing data were obtained directly from all 24 smear-positive culture-positive sputa, of which 20 were of high quality (>20× depth and >90% of the genome covered). Results were compared with those of conventional molecular and culture-based methods, and high levels of concordance between phenotypical resistance and predicted resistance based on genotype were observed. High-quality sequence data were obtained from one smear-positive culture-negative case. This study demonstrated for the first time the successful and accurate sequencing of M. tuberculosis genomes directly from uncultured sputa. Identification of known resistance mutations within a week of sample receipt offers the prospect for personalized rather than empirical treatment of drug-resistant tuberculosis, including the use of antimicrobial-sparing regimens, leading to improved outcomes., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)
- Published
- 2015
- Full Text
- View/download PDF
666. Person-Specific Standardized Vulnerability Assessment in Health and Social Care.
- Author
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Deleris LA, Aonghusa PM, and Shorten R
- Subjects
- Delivery of Health Care standards, Ireland, Risk Assessment standards, Comprehensive Health Care standards, Models, Organizational, Patient-Centered Care standards, Practice Guidelines as Topic, Social Work standards, Vulnerable Populations classification
- Abstract
We describe an integrated person-specific standardized vulnerability assessment model designed to facilitate patient management in health and social care. Such a system is not meant to replace existing health and social assessment models but rather to complement them by providing a holistic picture of the vulnerabilities faced by a given patient. In fact, it should be seen as a screening tool for health and social care workers. One key aspect of the modeling framework is the ability to provide personalized yet standardized multi-dimensional assessments of risk based on incomplete information about the patient status, as is the case in screening situations. Specifically, we integrate a Markov chain model describing the evolution of patients in and out of vulnerable states over time with a Bayesian network that serves to customize the dynamic model. We present an application in the context of elder care.
- Published
- 2015
667. A Rapid and Sensitive Diagnostic Screening Assay for Detection of Mycobacteria Including Mycobacterium tuberculosis Directly from Sputum without Extraction.
- Author
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Cross LJ, Anscombe C, McHugh TD, Abubakar I, Shorten RJ, Thorne N, and Arnold C
- Abstract
We report a novel approach utilising a real-time PCR screening assay targeting a 53 bp tandemly repeated element present at various loci within the Mycobacterium tuberculosis (Mtb) genome. Positive samples were identified within a discriminatory melting curve range of 90-94°C, with results obtained in under one hour directly from decontaminated sputum samples without extraction. A panel of 89 smear-positive sputa were used for analytical validation of the assay with 100% concordance, with sensitivity matching that of culture. Cross reactivity was detected within a narrow range of mycobacteria other than tuberculosis (MOTT) (five sputa, three in silico), with the highest sensitivity within M. avium complex (MAC). A year-long head to head evaluation of the test with the GeneXpert platform was carried out with 104 consecutive samples at the Royal Free Hospital, UK. Receiver operating characteristics (ROC) analysis of the data revealed that the two tests are approximately equivalent in sensitivity, with the area under the curve being 0.85 and 0.80 for the GeneXpert and our assay, respectively, indicating that the test would be a cost effective screen prior to GeneXpert testing.
- Published
- 2015
- Full Text
- View/download PDF
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