Understanding the impact of Lumbar Disc Degeneration (LDD) and recurrent pain

Introduction: Some people with Lumbar Disc Degeneration (LDD) experience recurrent low back pain (LBP) and others do not and it is unclear why. This thesis investigates the biomechanical differences between those with LDD and LBP and those without through the examination of intrinsic lumbar spine shape, postural adjustments and kinematic strategies. Methods: Patients and healthy controls were recruited and consented to our cross-sectional cohort (ethical approval reference13/LO/0793). T2 weighted images (L1-S1, 3T MRI) were acquired and groups identified based upon LDD grade (Modified Pfirrmann grading) and the presence of LBP. Intrinsic lumbar spine shape was investigated using Statistical Shape Modelling (SSM). Postural and kinematic strategies were examined during gait, sit-to-stand and bespoke perturbation tasks using surface electromyography (eight bilateral trunk and lower limb muscles) and a novel marker set, the ‘Imperial Spine’ (three segmented spine and bilateral lower limbs). Participant pain (NRS), depression and anxiety (HADS), quality of life (SF-36), disability (ODI) and total STarT Back scores (SBT) were recorded. Results: Intrinsic lumbar shape was significantly different between groups; the ‘LDD pain’ group had larger antero-posterior vertebral diameters (p=0.05) and a more even lumbar curvature with smaller L5/S1 intervertebral disc spaces (p=0.01) than the ‘no LDD no pain’ group. Significant differences in postural and kinematic strategy were observed between ‘LDD pain’ and ‘LDD no pain’ groups, particularly during the postural perturbation task (p=0.049-0.001). Depression, anxiety, disability and SBT scores were significantly higher and quality of life lower for the ‘LDD pain’ group when compared with the ‘LDD no pain’ group (p≤0.0001). Conclusions: This study provides new evidence that intrinsic lumbar shape is associated with LDD and LBP in adults. People with LDD and LBP use different postural and kinematic strategies and have different psychosocial profiles to those without LBP. Future management will need to reflect these biomechanical and psychosocial components.Open Acces

Mobile Augmented Reality: User Interfaces, Frameworks, and Intelligence

Mobile Augmented Reality (MAR) integrates computer-generated virtual objects with physical environments for mobile devices. MAR systems enable users to interact with MAR devices, such as smartphones and head-worn wearables, and perform seamless transitions from the physical world to a mixed world with digital entities. These MAR systems support user experiences using MAR devices to provide universal access to digital content. Over the past 20 years, several MAR systems have been developed, however, the studies and design of MAR frameworks have not yet been systematically reviewed from the perspective of user-centric design. This article presents the first effort of surveying existing MAR frameworks (count: 37) and further discuss the latest studies on MAR through a top-down approach: (1) MAR applications; (2) MAR visualisation techniques adaptive to user mobility and contexts; (3) systematic evaluation of MAR frameworks, including supported platforms and corresponding features such as tracking, feature extraction, and sensing capabilities; and (4) underlying machine learning approaches supporting intelligent operations within MAR systems. Finally, we summarise the development of emerging research fields and the current state-of-the-art, and discuss the important open challenges and possible theoretical and technical directions. This survey aims to benefit both researchers and MAR system developers alike.Peer reviewe

Detection of satellite remnants in the Galactic Halo with Gaia III. Detection limits for Ultra Faint Dwarf Galaxies

We present a method to identify Ultra Faint Dwarf Galaxy (UFDG) candidates in the halo of the Milky Way using the future Gaia catalogue and we explore its detection limits and completeness. The method is based on the Wavelet Transform and searches for over-densities in the combined space of sky coordinates and proper motions, using kinematics in the search for the first time. We test the method with a Gaia mock catalogue that has the Gaia Universe Model Snapshot (GUMS) as a background, and use a library of around 30 000 UFDGs simulated as Plummer spheres with a single stellar population. For the UFDGs we use a wide range of structural and orbital parameters that go beyond the range spanned by real systems, where some UFDGs may remain undetected. We characterize the detection limits as function of the number of observable stars by Gaia in the UFDGs with respect to that of the background and their apparent sizes in the sky and proper motion planes. We find that the addition of proper motions in the search improves considerably the detections compared to a photometric survey at the same magnitude limit. Our experiments suggest that Gaia will be able to detect UFDGs that are similar to some of the known UFDGs even if the limit of Gaia is around 2 magnitudes brighter than that of SDSS, with the advantage of having a full-sky catalogue. We also see that Gaia could even find some UFDGs that have lower surface brightness than the SDSS limit.Comment: Accepted for publication in MNRA

An end-to-end review of gaze estimation and its interactive applications on handheld mobile devices

In recent years we have witnessed an increasing number of interactive systems on handheld mobile devices which utilise gaze as a single or complementary interaction modality. This trend is driven by the enhanced computational power of these devices, higher resolution and capacity of their cameras, and improved gaze estimation accuracy obtained from advanced machine learning techniques, especially in deep learning. As the literature is fast progressing, there is a pressing need to review the state of the art, delineate the boundary, and identify the key research challenges and opportunities in gaze estimation and interaction. This paper aims to serve this purpose by presenting an end-to-end holistic view in this area, from gaze capturing sensors, to gaze estimation workflows, to deep learning techniques, and to gaze interactive applications.PostprintPeer reviewe

Engaged decision making:From team knowledge to team decisions

In the knowledge economy, teams play a central role in decisions made within and across organisations. The reason why teams with diverse compositions are often used is arguably their ability to develop solutions that none of their members could have produced alone. Systems design, strategy and policy development, risk management, and innovation are just a few of the areas that call for team decisions. Unfortunately, a considerable number of behavioural research studies show that teamwork is fraught with difficulties. Teams often underestimate their fallibility, struggle with conflict, or are unable to share and integrate critical information effectively. Indeed, the evidence shows that two out of three teams do not achieve their goals and half of organisational decisions – many of which are team decisions – fail.In this book, the authors draw from research in psychology, decision and systems sciences – as well as their own research and consulting work that spans more than 20 years – to show how designed interventions can enable team decision making to become rigorous, transparent, and defensible. They cover theory and practice regarding the design, delivery, and evaluation of interventions to support team decision making in situations of varied complexity. Written as an applied resource for researchers and advanced students in particular, this book offers a guide to proven interventions that enhance the process of making team decisions and increase the chances of superior team results

Engaged decision making:From team knowledge to team decisions

In the knowledge economy, teams play a central role in decisions made within and across organisations. The reason why teams with diverse compositions are often used is arguably their ability to develop solutions that none of their members could have produced alone. Systems design, strategy and policy development, risk management, and innovation are just a few of the areas that call for team decisions. Unfortunately, a considerable number of behavioural research studies show that teamwork is fraught with difficulties. Teams often underestimate their fallibility, struggle with conflict, or are unable to share and integrate critical information effectively. Indeed, the evidence shows that two out of three teams do not achieve their goals and half of organisational decisions – many of which are team decisions – fail.In this book, the authors draw from research in psychology, decision and systems sciences – as well as their own research and consulting work that spans more than 20 years – to show how designed interventions can enable team decision making to become rigorous, transparent, and defensible. They cover theory and practice regarding the design, delivery, and evaluation of interventions to support team decision making in situations of varied complexity. Written as an applied resource for researchers and advanced students in particular, this book offers a guide to proven interventions that enhance the process of making team decisions and increase the chances of superior team results

Vibrational and Anion Photoelectron Spectroscopy of Transition Metal Clusters

The understanding of chemical bonding and of the resulting atomic arrangements is a central topic in molecular physics. The bonding mechanisms of transition metal atoms still constitute a challenge in their theoretical description due to the massive number of valence electrons. Moreover, small transition metal clusters and their complexes may serve as models for catalytic systems of interest for science and technology. The goal of this thesis is the characterization of the geometric and electronic structures of isolated transition metal clusters in the gas phase and, consequently, a better understanding of their bonding nature. The first part of the thesis encompasses experimental results and conclusions for the anionic platinum trimer (Pt3-) and the tantalum nitride anion (TaN-). The data is obtained through anion photoelectron spectroscopy via velocity map imaging (VMI), which permits the simultaneous measurement of photoelectron spectra and photoelectron angular distributions (PADs). The study on TaN- reports the first photoelectron spectra of this diatomic molecule. The spectroscopic assignments, carried out with the support of previous theoretical and experimental works, provide measurements of the adiabatic electron affinity (EAad) and of the vibrational frequencies of the anion and the neutral molecule. In addition, the analysis of the PADs reveals the existence of two core excited shape resonances and disentangles the hybridization of a key molecular orbital. In the study of Pt3-, the experiment is performed in the slow electron velocity map imaging (SEVI) mode to resolve the low-frequency vibrational structure, characteristic of metal clusters. A plethora of information is obtained with the support of density functional theory (DFT) calculations, which includes the presence of two isomeric forms (triangular and linear) and hints at pseudo Jahn-Teller and Jahn-Teller effects. Some of the PADs reveal an oscillatory energetic dependence that, according to the quantum analogy established by Fano with the Young’s double slit experiment, is interpreted as interferometric efects in the linear isomer. In the second part of the thesis, the characterizations of CoArn+ (n=3 to 6), Con-mMnmArx+ (n=3 to 14; m=0 to 2) and saturated cationic Ru cluster carbonyls Run(CO)m+ (n=1 to 8) via (far-)infrared multiple photon dissociation (IRMPD) spectroscopy, more suitable to obtain structural information on the studied complexes, are reported. The investigation on CoArn+ readdresses the question on the nature of the interaction between the metal cation and the rare gas atom by proposing some amount of covalency in the bonding. Motivated by the role of ruthenium as catalyst for CO methanation in the Fischer-Tropsch process, the composition and structures of saturated cationic ruthenium carbonyls are studied. Their IR spectra are obtained in the range of the C-O stretches, Ru-CO stretches and deformation modes. Structural assignment is achieved with the aim of DFT calculations and the results corroborate former predictions. Finally, IR spectra of Con-mMnmArx+ are presented and discussed in comparison to those of pure cobalt clusters with the purpose of motivating future theoretical studies that may solve the puzzling structures of these binary metal clusters.Das Verständnis der chemischen Bindung und der daraus folgenden räumlichen Anordnungen von Atomen ist ein zentrales Thema der Molekülphysik. Die große Zahl der Valenzelektronen von Übergangsmetall-Atomen stellt auch heute noch eine Herausforderung für die theoretische Beschreibung ihrer Bindungsmechanismen dar. Gleichwohl können kleine Übergangsmetallcluster und ihre Komplexe als Modelle für katalytische Systeme von Relevanz in Wissenschaft und Technik dienen. Das Ziel dieser Arbeit ist die Charakterisierung der geometrischen und elektronischen Strukturen von isolierten Übergangsmetallclustern in der Gasphase und damit ein besseres Verständnis für das Wesen ihrer chemischen Bindung. Der erste Teil dieser Arbeit beinhaltet experimentelle Ergebnisse und darauf beruhende Schlussfolgerungen für das Anion des Platintrimers (Pt3-)und das Tantalnitrid-Anion (TaN-). Die Daten basieren auf Anionen-Photoelek- tronenspektroskopie mittels velocity map imaging (VMI), einer Technik, die die gleichzeitige Messung der Photoelektronenspektren und der Winkelverteil- ung der Photoelektronen ermöglicht. Für das zweiatomige Molekül TaN- wurde das Photoelektronenspektrum erstmalig bestimmt. Die spektroskopische Zuordnung gelang unter Zuhilfenahme vorhergehender theoretischer und experimenteller Arbeiten und liefert Werte für die adiabatische Elektronenaffinität (EAad) sowie die Schwingungsfrequenzen des Anions und des neutralen Moleküls. Weiterhin lässt die Untersuchung der Winkelverteilung auf das Vorliegen von zwei rumpfangeregten Formresonanzen (engl. core excited shape resonances) schließen und erlaubt die Analyse der Hybridisierung eines wichtigen Molekülorbitals. Die experimentelle Untersuchung von Pt3- erfolgte im SEVI-Modus (von engl. slow electron velocity map imaging), um die Schwingungsstruktur bei den für Metallclustern charakteristischen niedrigen Frequenzen aufzulösen. Die große Menge an experimentellen Daten erlaubt, unterstützt durch Dichtefunktionaltheorie(DFT)-Rechnungen, den Nachweis von zwei isomeren Formen (linear und gewinkelt) und liefert Hinweise auf den Einfluss von Jahn-Teller- und Pseudo-Jahn-Teller-Effekten. Einige Winkelverteilungen zeigen eine oszillierende Energieabhängigkeit, die, entsprechend der von Fano beschriebenen Quanten-Analogie zu Youngs Doppelspaltexperiment, als Interferenzeffekt im linearen Isomer gedeutet werden kann. Der zweite Teil der Arbeit widmet sich der Charakterisierung von CoArn+ (n=3 to 6), Con-mMnmArx+ (n=3 to 14; m=0 to 2) und gesättigten kationischen Rutheniumcluster-Carbonylen Rum(CO)m+ (n=1 to 8) mittels (Fern-)Infrarot Mehrphotonendissoziations-(IRMPD)-Spektroskopie, welche besonders geeignet ist, Strukturinfomationen für diese Komplexe zu erlangen. Die Untersuchung von CoArn+ widmet sich der Frage nach der Art der Wechselwirkung zwischen Metallkation und Edelgasatom und lässt auf einen kovalenten Anteil an der Bindung schließen. Motiviert durch die Funktion von Ruthenium als Katalysator bei der CO-Methanisierung in der Fischer-Tropsch-Synthese wurden Zusammensetzung und Struktur von gesättigten kationischen Rutheniumcarbonylen untersucht. Deren IR-Spektren wurden im Bereich der C-O Streckschwingung sowie der Ru-CO Streck- und Deformationsmoden bestimmt. Die Zuordnung der Strukturen gelang mit Hilfe von DFT-Rechnungen und bestätigt frühere Vorhersagen. Schließlich werden die IR-Spektren von Con-mMnmArx+ vorgestellt und, im Vergleich zu denen der reinen Cobaltcluster, diskutiert. Diese Daten stehen als Motivation für zukünftige theoretische Untersuchungen, die das Rätsel um die Strukturen dieser binären Metallcluster lösen könnten

Design of ships and offshore structures: a probabilistic approach for multi-year ice and iceberg impact loads for decision-making with uncertainty

Ice is a complex material that exhibits different failure properties depending on the loading rate, temperature and salinity. Under fast loading rates such as a ship ramming a multi-year (MY) ice, it fails as a brittle fracturing material. Fracture and spalling processes nonsimultaneously reshape the contact zone resulting in concentrated forces on localized contact areas. These localized High Pressure Zones (HPZs) are highly variable in time and space. The relationship between local and global processes is that the sum of n HPZs forces transferred into the structure at any point in time is the total global force transmitted to the structure. As with other fracturing materials, an inherent scale effect exists. Global pressures result from the sum of n HPZ forces averaged over the nominal contact area (e.g. the imprint of a ship’s bow into the ice without correction for spalling effects). The maximum global force will generally occur at the end of a ram at the maximum nominal contact area. Due to the random occurrence of natural flaws in the ice, pressures will vary as fractures occur, continually changing the contact face. A global scale effect exists such that pressures on larger contact areas, including zones of low and zero pressure, average out to be smaller. Unlike global pressures, maximum local pressures may occur on any panel and at any point through the ram duration. Modeling exposure is important as design pressures will increase for increasing number of interaction events as well as increased penetration or duration. The scale effect for local pressures within the nominal contact area is more demanding than for global pressures such that pressures on smaller areas are considerably higher. While this is expected, given confinement can suppress damage and limit fracturing events, a force limit exists where microstructural damage occurs, softening the ice and causing HPZs to fail. Local pressures on varying panel areas were studied based on spatial HPZ density and HPZ force. Building on earlier HPZ analysis using Louis S. St. Laurent data, in this thesis HPZ density and forces were derived from analysis of four Polar Sea data sets. The occurrence and intensity of HPZs on panel areas were simulated using a Poisson Process and an exponential distribution for HPZ force. The influence of modeling HPZ cutoff force on HPZ density, HPZ force distribution as well as local pressure parameters were studied and appropriate combinations recommended. Building on the Polar Sea HPZ analysis, a new model was developed for this thesis that considers HPZ occurrence in time through a ramming event, modeling HPZ rate. This was further enhanced by correlating HPZ rate with ship speed. Such a model allows the designer to determine baseline ‘parent’ local pressure design parameters based on vessel size and expected operational speed. The faster a ship operates through an ice regime, the greater the HPZ rate. Larger and faster ships will penetrate further, having longer interaction durations and hence a greater number of HPZs forming (unless, for example, the ship passes through a ridge). For design, we are interested in the maximum local pressure on a single panel area through the ram duration. Rates too will vary along the vessel being greater on the bow and least from mid-body to stern. For fixed structures designed for iceberg impacts, rate and duration based on iceberg size and drift can be used to model exposure in time. For floaters, modeling HPZ formation in time provides a means to estimate dynamic global forces and mooring loads illustrating benefit of compliance effects. Modeling of HPZ occurrence over a panel area is also very attractive for structure response analysis. The random placement of n HPZs over a structural panel gives a better basis to model stress localization, which is very important for limit states design. A preliminary review of the IACS Polar Class rules was carried out in this thesis. Global impact forces are estimated using a kinetic energy collision model. Consideration for modeling ice crushing strength assumes a pressure-area relationship that is proportional to A⁻⁰·¹ which is not consistent with experimental results demonstrating a scale effect proportional to A⁻⁰·⁴. The resultant design formulation models excessive semi-local pressures increasing with increasing semi-local contact area. While the intent is to model increasing pressures locally with increasing vessel displacement and subsequent penetration and contact area, justification for this trend suggests that there is no reason for traditional pressure area scale effects to exist and that with confinement, fracturing processes will be limited. But fracturing processes exist at all scales. The occurrence and behavior of HPZs either lead to very large stress localization that enhances fracture events or they undergo microstructure damage that softens the ice at the structure interface. While the design trend in the Polar Class rules may be okay, the background ice mechanics can be improved. An alternative collision model is developed in this thesis with an ice strength model based on data and an exposure algorithm to model pressures increasing locally with larger displacement vessels. In the mid 1990s as part of the Arctic Shipping Pollution Prevention Regulations (ASPPR) proposal reviews, a probabilistic time-step ship ram model was developed to estimate impact forces. Consistent with the ASPPR work, exposure based on annual number of collisions was mapped to each Polar Class (e.g. PC1, PC2, PC3 can expect on the order of 10000, 1000, 100 rams per year respectively). Using the MV Arctic as a test case and exercising extremal analysis, impact forces were estimated for each Polar Class. Characteristic 10⁻² global forces were compared with Polar Class rule estimates. Probabilistic local pressures were also compared with rule based estimates. Assuming impacts with MY ice, preliminary results show that plating design pressures may be reasonable, with recommendation for adjustment to the Polar Class 1 coefficients to reduce conservatism, and possible increases for lower classes. Analysis should be extended to other vessels and operating conditions. A probabilistic methodology for design of ships based on the principles of safety and consequences is important and necessary both for design and safety validation. Such approaches can consider the class of the vessel on the basis of expected number of annual interactions with extreme ice features. An example illustration of a design based on an arctic shipping route, ice conditions, design strategy, risk mitigation via detection and avoidance and resultant local pressures on the hull for structural design

Simulazioni della Coalescenza di Stelle di Neutroni Binarie nell'Era dell'Astrofisica Multimessaggera

The recent ground-breaking detection of gravitational waves (GW) from the merger of two neutron stars (NS), known as the GW170817 event, along with the observations of electromagnetic counterparts across the entire spectrum including a short gamma-ray burst (SGRB) and a radioactively powered kilonova, has given birth to the era of multimessenger astrophysics with GW sources. In order to probe the underlying physical mechanisms at play in such systems, it is necessary to employ fully general relativistic magnetohydrodynamic (GRMHD) simulations, including effects of magnetic fields and neutrino emission/reabsorption for a more realistic description. In the first part of this Thesis, we introduce our newly-developed GRMHD code Spritz, that solves the GRMHD equations in 3D Cartesian coordinates and on a dynamical spacetime. We present its salient features including the staggered formulation of the vector potential as well as support for any arbitrary equation of state (EOS), followed by a series of tests for code validation. We then describe the implementation of an approximate neutrino leakage scheme in Spritz, shedding some light on the involved equations, physical assumptions, and implemented numerical methods including higher order schemes, along with a large battery of general relativistic tests performed with and without magnetic fields and/or neutrino leakage. Since flux-conserving GRMHD codes like Spritz depend upon a technical algorithm to recover the fundamental `primitive' variables from the evolved `conserved' ones, which is often error-prone, we propose a new robust, accurate and efficient conservative-to-primitive variable recovery scheme named `RePrimAnd', along with the proof of existence of a solution and its uniqueness. As a next natural step, we implemented this scheme in Spritz, and performed a number of demanding GRMHD tests including critical cases like a NS collapse to a black hole (BH) as well as the evolution of a BH-accretion disk system. The second part of the thesis focusses instead on the application of GRMHD codes to perform magnetized BNS merger simulations. In particular, using the WhiskyMHD code, we present a detailed study of BNS merger simulations forming a long-lived NS remnant and including long post-merger evolution. Exploring this `magnetar scenario' allows us to address some of the open questions in the context of the SGRB and accompanying kilonova of the GW170817 event. Finally, we also discuss the results of the first magnetized BNS merger simulation performed with Spritz and the RePrimAnd scheme, concluding with an outlook on the next steps.The recent ground-breaking detection of gravitational waves (GW) from the merger of two neutron stars (NS), known as the GW170817 event, along with the observations of electromagnetic counterparts across the entire spectrum including a short gamma-ray burst (SGRB) and a radioactively powered kilonova, has given birth to the era of multimessenger astrophysics with GW sources. In order to probe the underlying physical mechanisms at play in such systems, it is necessary to employ fully general relativistic magnetohydrodynamic (GRMHD) simulations, including effects of magnetic fields and neutrino emission/reabsorption for a more realistic description. In the first part of this Thesis, we introduce our newly-developed GRMHD code Spritz, that solves the GRMHD equations in 3D Cartesian coordinates and on a dynamical spacetime. We present its salient features including the staggered formulation of the vector potential as well as support for any arbitrary equation of state (EOS), followed by a series of tests for code validation. We then describe the implementation of an approximate neutrino leakage scheme in Spritz, shedding some light on the involved equations, physical assumptions, and implemented numerical methods including higher order schemes, along with a large battery of general relativistic tests performed with and without magnetic fields and/or neutrino leakage. Since flux-conserving GRMHD codes like Spritz depend upon a technical algorithm to recover the fundamental `primitive' variables from the evolved `conserved' ones, which is often error-prone, we propose a new robust, accurate and efficient conservative-to-primitive variable recovery scheme named `RePrimAnd', along with the proof of existence of a solution and its uniqueness. As a next natural step, we implemented this scheme in Spritz, and performed a number of demanding GRMHD tests including critical cases like a NS collapse to a black hole (BH) as well as the evolution of a BH-accretion disk system. The second part of the thesis focusses instead on the application of GRMHD codes to perform magnetized BNS merger simulations. In particular, using the WhiskyMHD code, we present a detailed study of BNS merger simulations forming a long-lived NS remnant and including long post-merger evolution. Exploring this `magnetar scenario' allows us to address some of the open questions in the context of the SGRB and accompanying kilonova of the GW170817 event. Finally, we also discuss the results of the first magnetized BNS merger simulation performed with Spritz and the RePrimAnd scheme, concluding with an outlook on the next steps

Modeling the Interactions of Anticancer Compounds with DNA and Lipid Membranes

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química. Fecha de Lectura: 15-07-202