The Role of Thyroid Hormone in the Ventromedial Nucleus of the Hypothalamus

The hypothalamic arcuate and paraventricular nuclei play important roles in the neuroendocrine regulation of systemic thyroid hormone homeostasis. However, the roles of other hypothalamic regions are poorly understood. Triiodothyronine (T3) is the active form of thyroid hormone. T3 administration to the hypothalamic ventromedial nucleus (VMN) of rats stimulates feeding, although the mechanism remains unclear. Activation and inactivation of thyroid hormones is mediated by the iodothyonine deiodinases, where D2 is the activating enzyme and D3 the inactivating enzyme. Recombinant adeno-associated virus (rAAV) vectors were designed to modulate the local activity of thyroid hormones by over-expressing D2 (rAAV-D2) or D3 (rAAV-D3). Two initial investigations were carried out employing these viruses in vivo. Initially, rats received bilateral injections of either rAAV-D2 or rAAV-GFP into the VMN. Cumulative food intake and body weight were unaffected, despite a significant increase D2 enzyme activity. However, fasted rAAV-D2 treated rats consumed significantly more food than controls over the initial 2 hours of refeeding following a 12 fast. In the second investigation, rats received bilateral injections of either rAAV-D3 or rAAV-GFP into the VMN. Hypothalamic D3 mRNA and brown adipose tissue activity were both significantly increased in the rAAV-D3 group, which was not associated with any change in systemic thyroid hormone levels. This suggested that sympathetic activity had been increased, independent of peripheral thyroid status. In a final investigation, rats were challenged with a high fat diet (HFD) 17 days after iVMN injection of either rAAV-D3 or rAAV-GFP. The rAAV-D3 treated group gained significantly more weight and consumed significantly more energy than controls, per day of HFD treatment. The increased HFD consumption was matched with a significant increase in hypothalamic fatty acid synthase mRNA. This thesis highlights putative mechanisms by which thyroid hormones affect peripheral metabolism and appetite via the VMN, through interplay with neuronal fatty acid homeostasis

Symbolic energy estimation model with optimum start algorithm implementation

The drive to reduce carbon emissions and energy utilisation, directly associated with dwellings and to achieve a zero carbon home, suggests that the assessment of energy ratings will have an increasingly prioritised role in the built environment. Created by the Building Research Establishment (BRE), the Standard Assessment Procedure (SAP) is the UK Government’s recommended method of assessing the energy ratings of dwellings. This paper describes a new, simplified dynamic method (hence known as IDEAS – Inverse Dynamics based Energy Analysis and Simulation) of assessing the controllability of a building and its servicing systems. The IDEAS method produces results that are comparable to SAP. An Optimum Start algorithm is explored in this paper to allow heating systems of different responsiveness and size to be integrated into the IDEAS framework. Results suggest that this design approach could enhance the SAP Methodology by the addition of advanced systems controllability and dynamic values

Modelling and simulation of advanced non-linear autopilot designs

This paper presents the simulation in ESL of a non-linear 6 degree-of-freedom missile model with an advanced, non-linear, multivariable autopilot designed using Rate Actuated Inverse Dynamics (RAID) methods. High performance control of non-linear systems requires the design of advanced, non-linear control systems, such as those used in autopilot design. Traditional linear control system design and analysis techniques are not sufficient for non-linear systems and current non-linear analysis methods are extremely limited. Therefore, the only method available to fully assess the performance of non-linear controller designs is simulation of the non-linear system. For this reason it is an essential part of the analysis and design process of these types of controllers. Non-linear dynamics can be continuous or discontinuous, the aerodynamics of a missile are non-linear but since they are continuous they do not represent a simulation challenge. However, there are multiple sets of discontinuous dynamics present in both the missile control surface model and the autopilot which can lead to multiple discontinuities being reached simultaneously, providing a challenging modeling exercise. The paper demonstrates how this kind of behavior can be successfully modeled and simulated within ESL using a simple switching logic

A holistic analysis method to assess the controllability of commercial buildings and their systems

This paper describes a novel design process for advanced MIMO (multiple inputs and multiple outputs) control system design and simulation for buildings. The paper describes the knowledge transfer from high technology disciplines such as aerospace flight control systems and the space industry to establish a three-step modelling and design process. In step 1, simplified, but holistic nonlinear and linearised dynamic models of the building and its systems is derived. This model is used to analyse the controllability of the building. In step 2, further synthesis of this model leads to the correct topology of the control system design. This is proved through the use of simulation using the simple building model. In step 3, the controller design is proved using a fully detailed building simulation such as ESP-r that acts as a type of virtual prototype of the building. The conclusions show that this design approach can help in the design of superior and more complex control systems especially for buildings designed with a Climate Adaptive Building (CAB) philosophy where many control inputs and outputs are used to control the building's temperature, concentration of CO2, humidity and lighting levels

Beyond Power over Ethernet : the development of Digital Energy Networks for buildings

Alternating current power distribution using analogue control and safety devices has been the dominant process of power distribution within our buildings since the electricity industry began in the late 19th century. However, with advances in digital technology, the seeds of change have been growing over the last decade. Now, with the simultaneous dramatic fall in power requirements of digital devices and corresponding rise in capability of Power over Ethernet, an entire desktop environment can be powered by a single direct current (dc) Ethernet cable. Going beyond this, it will soon be possible to power entire office buildings using dc networks. This means the logic of “one-size fits all” from the existing ac system is no longer relevant and instead there is an opportunity to redesign the power topology to be appropriate for different applications, devices and end-users throughout the building. This paper proposes a 3-tier classification system for the topology of direct current microgrids in commercial buildings – called a Digital Energy Network or DEN. The first tier is power distribution at a full building level (otherwise known as the microgrid); the second tier is power distribution at a room level (the nanogrid); and the third tier is power distribution at a desktop or appliance level (the picogrid). An important aspect of this classification system is how the design focus changes for each grid. For example; a key driver of the picogrid is the usability of the network – high data rates, and low power requirements; however, in the microgrid, the main driver is high power and efficiency at low cost

Robust control of room temperature and relative humidity using advanced nonlinear inverse dynamics and evolutionary optimisation

A robust controller is developed, using advanced nonlinear inverse dynamics (NID) controller design and genetic algorithm optimisation, for room temperature control. The performance is evaluated through application to a single zone dynamic building model. The proposed controller produces superior performance when compared to the NID controller optimised with a simple optimisation algorithm, and classical PID control commonly used in the buildings industry. An improved level of thermal comfort is achieved, due to fast and accurate tracking of the setpoints, and energy consumption is shown to be reduced, which in turn means carbon emissions are reduced

Trends in office internal gains and the impact on space heating and cooling demands

Internal gains from occupants, equipment and lighting contribute a significant proportion of the heat gains in an office space. Looking at trends in Generation-Y, it appears there are two diverging paths for future ICT demand: one where energy demand is carefully regulated and the other where productivity enhancers such as multiple monitors and media walls causes an explosion of energy demand within the space. These internal gains scenarios were simulated on a variety of different building archetypes to test their influence on the space heating and cooling demand. It was demonstrated that in offices with a high quality facade, internal gains are the dominant factor. As a case study, it was shown that natural ventilation is only possible when the ICT demand is carefully regulated

Non-linear autopilot design using the philosophy of variable transient response

The novel non-linear controller design methodology of Variable Transient Response (VTR) is presented in this research. The performance of VTR is compared to that of successful non-linear controller designs (such as Robust Inverse Dynamics Estimation and a traditional autopilot design) by application to a non-linear missile model. The simulated results of this application demonstrate that the inclusion of VTR into the RIDE design results in a 50% improvement in response time and 100% improvement in settling time whilst achieving stable and accurate tracking of a command input. Analysis demonstrates that VTR dynamically alters the system's damping, resulting in a non-linear response. The system stability is analysed during actuator saturation using non-linear stability criteria. The results of this analysis show that the inclusion of VTR into the RIDE design does not compromise non-linear system stability

Enhancement of the UK Standard Assessment Procedure (SAP) solar water heating prediction algorithm using parametric dynamical thermal simulations

SAP is the UK Government’s method for calculation of a dwelling’s energy efficiency and carbon dioxide emissions. This paper presents a method of informing the SAP procedure regarding evaluation of the advantage given to SAP ratings by installation of typical domestic Solar Domestic Hot Water (SDHW) systems. Comparable SDHW systems were simulated using the dynamic thermal simulation package TRNSYS and results were translated into empirical relations in a form that could be input into the SAP calculation procedure. Findings were compared against the current SAP algorithm and differences explained. Results suggest that calculation variances can exist between the SAP methodology and detailed dynamic thermal simulation methods. This is especially true for higher performance systems that can deviate greatly from default efficiency parameters. This might be due to SAP algorithms being historically based on older systems that have lower efficiencies. An enhancement to the existing SAP algorithm is suggested

A simplified dynamic systems approach for the energy rating of dwellings

The drive to reduce carbon emissions and energy utilisation, directly associated with dwellings and to achieve a zero carbon home, suggests that the assessment of energy ratings will have an increasingly prioritised role in the built environment. Created by the Building Research Establishment (BRE), the Standard Assessment Procedure (SAP) is the UK Government’s recommended method of assessing the energy ratings of dwellings. This paper describes a new, simplified dynamic method (hence known as IDEAS – Inverse Dynamics based Energy Analysis and Simulation) of assessing the controllability of a building and its servicing systems. The IDEAS method produces SAP Comparable results. Results suggest this design approach could enhance the SAP Methodology by the addition of advanced systems controllability and dynamic values