Derived categories and K-groups of singular varieties

This thesis consists of three parts and is a collection of papers written by the author of this text during his postgraduate studies, together with an Appendix chapter. The first chapter is based on [98] and is in collaboration with Evgeny Shinder. It discusses the K-groups K_1, K_0 and K_{−n} of the singularity category of isolated quotient singularities. The second chapter is based on [73] and is joint with Martin Kalck and Evgeny Shinder. It introduces Kawamata type semiorthogonal decompositions for singular varieties and obstructions for such decompositions are studied, mainly for the case of nodal threefolds. Each of these two chapters can be read independently. The third chapter is an Appendix to the first chapter and explains in more detail how the main technical result in chapter one is proven, on which the main theorems rely on

New Vibration Online Journal Will Get Us Back to Basics

This is the final version of the article. Available from MDPI via the DOI in this record.When Vibration approached me to be its founding Editor-in-Chief, it was explained to me that the key selling points of this new online journal would be as follows [...

Efficacious control of cytomegalovirus infection after long-term depletion of CD8+ T lymphocytes

Although the relative contribution of different immune effector functions to clearing tissues of cytomegalovirus is controversial, the contribution of CD8+ T lymphocytes has generally been accepted as essential. In this report, we show that under certain conditions the CD8+ T-lymphocyte subset can be dispensable for clearance of cytomegalovirus. Mice depleted of the CD8+ T-lymphocyte subset eliminated infectious virus with a clearance kinetics similar to that of normal mice. Adoptive transfer studies revealed that the limitation of virus spread required the cooperation between the CD4+ subset and other cells. Comparison between protective functions generated in fully immunocompetent and in CD8- mice demonstrated that elimination of the CD8+ subset before infection altered the quality of the antiviral immune response. The compensatory protective activity gained by CD4+ cells in CD8- mice was absent in normal mice recovering from virus infection

Gamma interferon-dependent clearance of cytomegalovirus infection in salivary glands

Cytomegalovirus (CMV), similar to other members of the Herpesviridae family, can establish both persistent and latent infections. Each of the CMVs that are found in many animal species replicates in the salivary gland, and oral secretion represents a source of horizontal transmission. Locally restricted replication characterizes the immunocompetent individual, whereas in the immunocompromised host, protean disease manifestations occur due to virus dissemination. The virus is cleared by immune surveillance, and CD8+ T lymphocytes play a major role. Remarkably, certain cell types of salivary gland tissues are exempt from CD8+ T-lymphocyte control of murine CMV infection and require the activity of CD4+ T lymphocytes. The results presented here suggest that this activity is a function of Th1 cells. Neutralization of endogenous gamma interferon abrogated the antiviral activity of Th1 cells but not that of CD8+ T lymphocytes in other tissues. Neutralization of endogenous gamma interferon did not interfere with the induction of the cellular and humoral immune response but acted during the effector phase. Recombinant gamma interferon could not replace the function of Th1 cells in vivo and had limited direct antiviral activity in vitro. The results therefore suggest that gamma interferon represents one, but not the only, essential factor involved in salivary gland clearance, establishment of CMV latency, and, eventually, the control of horizontal transmission

Effect of Walking people on Dynamic Properties of Floors

This is the final version of the article. Available from Elsevier via the DOI in this record.X International Conference on Structural Dynamics, EURODYN 2017Despite the intensive research that has focused on the dynamic interaction between walking people and slender footbridges, this phenomenon has never been investigated for floor structures. For lightweight floors having mass of 150 kg/m2 or less, where they have relatively low modal masses and damping ratios, this interaction is expected to be more effective than that for normal floors. Such phenomenon, if proven to exist for floors, could explain one of the reasons behind the discrepancy between the measured vibration response of floors due to human walking and the corresponding predicted responses using the currently available models which neglect human-structure interaction for walking humans. This paper presents the first attempt to investigate the effect of walking people on the dynamic properties of floors. It is based on several experimental tests for groups of people walking on a full-scale but slender laboratory floor structure. For each experiment, a modal test was carried out to identify the dynamic properties of the tested floor. The results showed a significant increase in modal damping for the first vibration mode, while higher modes exhibited less damping increase. A slight increase was also noticed in the natural frequency of the observed modes. These changes in the modal properties are in line with previous observations of the effects of walking people on footbridges. The results presented in this paper can pave the way for future research to model the interaction between walking people and the supporting floor structures in the context of their vibration serviceability.The authors are grateful for the College of Engineering, Mathematics and Physical Sciences in the University of Exeter for the financial support they provided for the first author and his PhD program. The authors would also like to acknowledge the financial support provided by the UK Engineering and Physical Sciences Research Council (EPSRC) for grant reference EP/K03877X/1 ('Modelling complex and partially identified engineering problems - Application to the individualised multiscale simulation of the musculoskeletal system')

The dynamic stiffening effects of non-structural partitions in building floors

PublishedIt is commonly known that full-height non-structural partitions of a fitted out floor structure affect its dynamic properties, with increase in floor mass and modal damping being commonly quoted in floor design guidelines. As a consequence, it is generally accepted that the non-structural elements usually reduce the response of floors to walking excitation. There is very little understanding of the effects of full-height partitions on the stiffness of building floors and this effect is generally not taken into account in floor design guidelines. This paper is therefore focused on establishing experimentally the effects of full-height non-structural partitions on dynamic stiffness of a full-scale real-life composite building floor. Modal testing data are presented for three construction phases of the floor: from a completely bare floor via partially to fully-fitted floor. The effects of the partitions are shown by comparing the measured frequency response functions (FRFs) at the same location for different construction phases and the estimated key modal properties of the floor corresponding to these phases. This kind of multi-phase measurements on a real-life floor structure during construction is very rare due to its logistical complexity and long-time required to gather data through all of the phases. It is shown that the partitions significantly affect measured FRFs by increasing damping, and in particular, floor stiffness. It is also shown that the mode shapes are changed by the partitions. The magnitude of the changes is quantified experimentally which is one of the first attempts to do this on a real-life floor structure using high-quality FRF measurements. © The Society for Experimental Mechanics, Inc. 2013

Simulation of people’s movements on floors using social force model

This is the author accepted manuscript. The final version is available via the link in this recordVibration serviceability assessment of floors has been traditionally based on a scenario of a single person walking along a path which will generate maximum vibration level. This is due to the difficulty of predicting the real positions and paths of the walking people. With such a design scenario, it is possible to obtain calculated responses, which could be both over- or underestimated, depending on the specifics. This could be due to considering only one person walking along one walking path in the simulations. This aspect in the design guidelines could be improved if realistic modelling of people’s movements is utilised. Hence, this paper examines the performance of the social force model to simulate the behaviour of people’s movements on floors. This method has been widely used to model a crowd of people in evacuation and panic situations. However, it has been reported in the literature that this approach could be used to model people’s movements in normal situations as well. The simulation carried out in this paper focuses on the interaction between walking people themselves and between walking people and the surrounding boundaries in typical office floors. The results show that reasonable and realistic behaviour of the floor occupants could be obtained using the social force model. Furthermore, utilising the ‘heatmap’ can help the designers to visualise and obtain information about the proportion of time spent by walking individuals at various points on the floor. This approach can be adopted in a more realistic procedure for the vibration serviceability assessment of floorsEngineering and Physical Sciences Research Council (EPSRC)University of Exete

Estimation of tri-axial walking ground reaction forces of left and right foot from total forces in real-life environments

This is the final version of the article. Available from MDPI via the DOI in this record.Continuous monitoring of natural human gait in real-life environments is essential in many applications including disease monitoring, rehabilitation, and professional sports. Wearable inertial measurement units are successfully used to measure body kinematics in real-life environments and to estimate total walking ground reaction forces GRF(t) using equations of motion. However, for inverse dynamics and clinical gait analysis, the GRF(t) of each foot is required separately. Using an experimental dataset of 1243 tri-axial separate-foot GRF(t) time histories measured by the authors across eight years, this study proposes the ‘Twin Polynomial Method’ (TPM) to estimate the tri-axial left and right foot GRF(t) signals from the total GRF(t) signals. For each gait cycle, TPM fits polynomials of degree five, eight, and nine to the known single-support part of the left and right foot vertical, anterior-posterior, and medial-lateral GRF(t) signals, respectively, to extrapolate the unknown double-support parts of the corresponding GRF(t) signals. Validation of the proposed method both with force plate measurements (gold standard) in the laboratory, and in real-life environment showed a peak-to-peak normalized root mean square error of less than 2.5%, 6.5% and 7.5% for the estimated GRF(t) signals in the vertical, anterior-posterior and medial-lateral directions, respectively. These values show considerable improvement compared with the currently available GRF(t) decomposition methods in the literature.The authors acknowledge the financial support provided by the UK Engineering and Physical Sciences Research Council (EPSRC) for the following research grants: Frontier Engineering Grant EP/K03877X/1 (Modelling complex and partially identified engineering problems: Application to the individualized multiscale simulation of the musculoskeletal system); and Platform Grant EP/G061130/2 (Dynamic performance of large civil engineering structures: an integrated approach to management, design and assessment)