Design of Multiple Impeller Stirred Tanks for the Mixing of Highly Viscous Fluids Using CFD

The effect of multiple Intermig impeller configuration on hydrodynamics and mixing performance in a stirred tank has been investigated using computational fluid dynamics. Connection between impeller stages and compartmentalisation has been assessed using Lagrangian particle tracking. The results show that by a rotating Intermig impeller by 45° respect to its neighbours, instead of a 90° rotation as recommended by manufacturers, enables a larger range of operating conditions, i.e. lower Reynolds number flows, to be handled. Furthermore by slightly decreasing the distance between the lower two impellers, fluid exchange between the impellers is ensured down to Re = 27

Multi-Scale Fluctuations in Non-Equilibrium Systems: Statistical Physics and Biological Application

Understanding how fluctuations continuously propagate across spatial scales is fundamental for our understanding of inanimate matter. This is exemplified by self-similar fluctuations in critical phenomena and the propagation of energy fluctuations described by the Kolmogorov-Law in turbulence. Our understanding is based on powerful theoretical frameworks that integrate fluctuations on intermediary scales, as in renormalisation group or coupled mode theory. In striking contrast to typical inanimate systems, living matter is typically organised into a hierarchy of processes on a discrete set of spatial scales: from biochemical processes embedded in dynamic subcellular compartments to cells giving rise to tissues. Therefore, the understanding of living matter requires novel theories that predict the interplay of fluctuations on multiple scales of biological organisation and the ensuing emergent degrees of freedom. In this thesis, we derive a general theory of the multi-scale propagation of fluctuations in non-equilibrium systems and show that such processes underlie the regulation of cellular behaviour. Specifically, we draw on paradigmatic systems comprising stochastic many-particle systems undergoing dynamic compartmentalisation. We first derive a theory for emergent degrees of freedom in open systems, where the total mass is not conserved. We show that the compartment dynamics give rise to the localisation of probability densities in phase space resembling quasi-particle behaviour. This emergent quasi-particle exhibits fundamentally different response kinetics and steady states compared to systems lacking compartment dynamics. In order to investigate a potential biological function of such quasi-particle dynamics, we then apply this theory to the regulation of cell death. We derive a model describing the subcellular processes that regulate cell death and show that the quasi-particle dynamics gives rise to a kinetic low-pass filter which suppresses the response of the cell to fast fluituations in cellular stress signals. We test our predictions experimentally by quantifying cell death in cell cultures subject to stress stimuli varying in strength and duration. In closed systems, where the total mass is conserved, the effect of dynamic compartmentalisation depends on details of the kinetics on the scale of the stochastic many-particle dynamics. Using a second quantisation approach, we derive a commutator relation between the kinetic operators and the change in total entropy. Drawing on this, we show that the compartment dynamics alters the total entropy if the kinetics of the stochastic many-particle dynamics violate detailed balance. We apply this mechanism to the activation of cellular immune responses to RNA-virus infections. We show that dynamic compartmentalisation in closed systems gives rise to giant density fluctuations. This facilitates the emergence of gelation under conditions that violate theoretical gelation criteria in the absence of compartment dynamics. We show that such multi-scale gelation of protein complexes on the membranes of dynamic mitochondria governs the innate immune response. Taken together, we provide a general theory describing the multi-scale propagation of fluctuations in biological systems. Our work pioneers the development of a statistical physics of such systems and highlights emergent degrees of freedom spanning different scales of biological organisation. By demonstrating that cells manipulate how fluctuations propagate across these scales, our work motivates a rethinking of how the behaviour of cells is regulated

Ethical human resource management: a critical analysis

In modern day, Human Resource Management (HRM) is seen as a mere variant of management control aiming intentionally to ‘colonize’ the identity of the individual employee which points to the contradictions between the idealised HRM theories and its practice commonly referred to as the difference between rhetoric and reality. These critical analyses suggest that HRM reflects a historical shift in the way work is defined and managed and research has to be undertaken on how morality and ethics may be represented in the discourse, lived experiences, practice and broader context of HR professionals. The HR function will continue to face challenges in balancing business imperatives and ethical values but as long as the corporate and HR leadership remains committed, no challenge may be insurmountable

Exploring pig trade patterns to inform the design of risk-based disease surveillance and control strategies

An understanding of the patterns of animal contact networks provides essential information for the design of risk-based animal disease surveillance and control strategies. This study characterises pig movements throughout England and Wales between 2009 and 2013 with a view to characterising spatial and temporal patterns, network topology and trade communities. Data were extracted from the Animal and Plant Health Agency (APHA)’s RADAR (Rapid Analysis and Detection of Animal-related Risks) database, and analysed using descriptive and network approaches. A total of 61,937,855 pigs were moved through 872,493 movements of batches in England and Wales during the 5-year study period. Results show that the network exhibited scale-free and small-world topologies, indicating the potential for diseases to quickly spread within the pig industry. The findings also provide suggestions for how risk-based surveillance strategies could be optimised in the country by taking account of highly connected holdings, geographical regions and time periods with the greatest number of movements and pigs moved, as these are likely to be at higher risk for disease introduction. This study is also the first attempt to identify trade communities in the country, information which could be used to facilitate the pig trade and maintain disease-free status across the country in the event of an outbreak

Exploring Knowledge Leakage Risk in Knowledge-Intensive Organisations: behavioural aspects and key controls

Knowledge leakage poses a critical risk to the competitive advantage of knowledge-intensive organisations. Although knowledge leakage is a human-centric security issue, little is known about leakage resulting from individual behaviour and the protective strategies and controls that could be effective in mitigating leakage risk. Therefore, this research explores the perspectives of security practitioners on the key factors that influence knowledge leakage risk in the context of knowledge-intensive organisations. We conduct two focus groups to explore these perspectives. The research highlights three types of behavioural controls that mitigate the risk of knowledge leakage: human resource management practices, knowledge security training and awareness practices, and compartmentalisation practices

Population Balance Modelling and Experimental Studies of Emulsion Polymerisation

Emulsion polymerisation is a process of considerable technological and industrial significance. The process presents many challenges in respect to design, optimisation and multi-objective distribution control. The quality of latex is determined by the final product properties, Le. viscosity, mechanical strength and film-forming ability, which are in turn a function of the latex attributes of PSD and MWD. This motivates an inferential control scheme utilising these distributions. This research addresses model development and controllability analysis towards model-based control. A population balance model for PSD and MWD is developed. The PSD information is incorporated via a one-dimensional population distribution of the polymer particles with respect to their size, in conjunction with a population distribution of the total live polymer radicals/particle. MWD information is incorporated via one-dimensional population distributions of the live radicals and dead polymer chains with respect to their length (in different sized particles). The model solution is facilitated by a number of algorithmic developments, including a decomposition algorithm coupled with a multi-level discretisation for PSD and the application of the method of moments for MWD. This model is compared to extensive experimental data for its validation. Improvements in the form of a twodimensional version of this model enable better prediction of compartmentalisation and hence the growth rates, thereby improving model match with experiments. This work presents a study into the simultaneous controllability of PSD and MWD, assessed through an experimental sensitivity analysis on the main process manipulations: initiator, eTA, monomer and surfactant. The work analyses the practical limitations on the attainability of PSD and MWD. The range of experiments carried out clearly indicates the operation of individual mechanisms in the simultaneous formation of PSD and MWD.Imperial Users onl

Mirrors of Prison Life - From Compartmentalised Practice towards Boundary Crossing Expertise

Peer reviewe

Quantum scale biomimicry of low dimensional growth: An unusual complex amorphous precursor route to TiO2 band confinement by shape adaptive biopolymer-like flexibility for energy applications

Crystallization via an amorphous pathway is often preferred by biologically driven processes enabling living species to better regulate activation energies to crystal formation that are intrinsically linked to shape and size of dynamically evolving morphologies. Templated ordering of 3-dimensional space around amorphous embedded non-equilibrium phases at heterogeneous polymer-metal interfaces signify important routes for the genesis of low-dimensional materials under stress-induced polymer confinement. We report the surface induced catalytic loss of P=O ligands to bond activated aromatization of C-C C=C and Ti=N resulting in confinement of porphyrin-TiO(2 )within polymer nanocages via particle attachment. Restricted growth nucleation of TiO2 to the quantum scale (˂= 2 nm) is synthetically assisted by nitrogen, phosphine and hydrocarbon polymer chemistry via self-assembly. Here, the amorphous arrest phase of TiO, is reminiscent of biogenic amorphous crystal growth patterns and polymer coordination has both a chemical and biomimetic significance arising from quantum scale confinement which is atomically challenging. The relative ease in adaptability of non-equilibrium phases renders host structures more shape compliant to congruent guests increasing the possibility of geometrical confinement. Here, we provide evidence for synthetic biomimicry akin to bio-polymerization mechanisms to steer disorder-to-order transitions via solvent plasticization-like behaviour. This challenges the rationale of quantum driven confinement processes by conventional processes. Further, we show the change in optoelectronic properties under quantum confinement is intrinsically related to size that affects their optical absorption band energy range in DSSC.This work was supported by the National Research Foundation of Korea (NRF) grant funded by Korea government (MEST) NRF-2012R1A1A2008196, NRF 2012R1A2A2A01047189, NRF 2017R1A2B4008801, 2016R1D1A1A02936936, (NRF-2018R1A4A1059976, NRF-2018R1A2A1A13078704) and NRF Basic Research Programme in Science and Engineering by the Ministry of Education (No. 2017R1D1A1B03036226) and by the INDO-KOREA JNC program of the National Research Foundation of Korea Grant No. 2017K1A3A1A68. We thank BMSI (A*STAR) and NSCC for support. SJF is funded by grant IAF25 PPH17/01/a0/009 funded by A* STAR/NRF/EDB. CSV is the founder of a spinoff biotech Sinopsee Therapeutics. The current work has no conflicting interests with the company. We would like to express our very great appreciation to Ms. Hyoseon Kim for her technical expertise during HRTEM imaging