Quantitative hydrogen and methane gas sensing via implementing AI based spectral analysis of plasma discharge

In this report we explore the feasibility of a quantitative gas detection system concept based on alternations in spectral emissions of a radio frequency power generated plasma in presence of a target gas. We then proceed with training a deep learning residual network computer vison model with the spectral data obtained from the plasma to be able to perform regressive calculation of the target gas content in the plasma. We explore this concept with hydrogen and methane gas present in the plasma at know quantities to evaluate the applicability of the concept as hydrogen or methane detection system. We will demonstrate that the system is well capable of quantitatively detecting either of the gases efficiently while it is challenging to estimate hydrogen content in presence of methane

Laser Diode Induced Lighting Modules

Laser diodes have the potential of becoming the light engines of future lighting technology since they have negligible efficiency droop factor, unlike light emitting diodes. This study demonstrates the possibility of laser diodes coupled to phosphor targets being used as a solid state lighting system with high power applications. It was revealed that white light emitting modules with efficiency of up to 217 lumens per watt based on laser diodes can currently be made and upon further development of laser diode technology and relevant phosphor materials there is room for further improvements. The report also demonstrates the ability of this technology to produce a tailored emission spectrum for a given specific requirement. Two test lamp prototypes were made using laser diodes and phosphor targets and their emission characteristics were investigatedBrunel University London & EPSRC grant No. EP/K504208/

Structural and Mechanistic insights into Centromere Specification and Kinetochore Regulation

Faithful transmission of the genome requires that chromosomes are accurately segregated between daughter cells in mitosis. Accurate chromosome segregation relies on proper specification of the site of kinetochore formation on each chromosome, in addition to dynamic regulation of the interactions of the kinetochore with the microtubule-based mitotic spindle. This thesis work focuses on two important contributors to accurate chromosome segregation: 1) centromere protein A (CENP-A), the histone H3 variant which epigenetically specifies the centromere which forms the platform onto which the kinetochore assembles and 2) the chromosomal passenger complex (CPC) which regulates kinetochore-microtubule interactions to ensure accurate genome partitioning between cells. In the first part of this work, we used a combination of in vitro, genomic sequencing, and novel bioinformatic approaches to probe the nature and structure of CENP-A nucleosomes at functional human centromeres. We found that CENP-A exists as part of a stable octameric nucleosome with loose superhelical DNA termini. CENP-A nucleosomes are very highly phased on the α-satellite monomers at normal centromeres and are also strongly positioned at naturally-occurring neocentromeres. In the second part of this work, we used cell biology-based approaches to uncover a novel mechanism to regulate kinetochore-microtubule interactions that was present only in healthy, diploid cells that had been previously overlooked in aneuploid cells. We found that Aurora B, the enzymatic kinase of the CPC, is enriched at the misaligned centromeres of healthy, diploid cells leading to an increased dynamic range of Aurora B substrate phosphorylation at misaligned versus properly aligned kinetochores. These findings suggest that in addition to Aurora B regulating kinetochore-microtubule interactions, the kinetochore also controls Aurora B recruitment to the inner centromere. We showed that this recruitment depends on both the activity of another mitotic kinase, Plk1, in addition to the activity of Aurora B itself. Altogether, this has led us to update the model by which the CPC regulates kinetochore-microtubule interactions on misaligned chromosomes. Taken together, the work presented from both parts of my thesis greatly enhance our understanding of how the kinetochore is specified and regulated to ensure fidelity in genome transmission during cell division

Deep learning analysis of plasma emissions: A potential system for monitoring methane and hydrogen in the pyrolysis processes

The estimation of methane and hydrogen production as output from a pyrolysis reaction is paramount to monitor the process and optimize its parameters. In this study, we propose a novel experimental approach for monitoring methane pyrolysis reactions aimed at hydrogen production by quantifying methane and hydrogen output from the system. While we appreciate the complexity of molecular outputs from methane hydrolysis process, our primary approach is a simplified model considering detection of hydrogen and methane only which involves three steps: continuous gas sampling, feeding of the sample into an argon plasma, and employing deep learning model to estimate of the methane and hydrogen concentration from the plasma spectral emission. While our model exhibits promising performance, there is still significant room for improvement in accuracy, especially regarding hydrogen quantification in the presence of methane and other hydrogen bearing molecules. These findings present exciting prospects, and we will discuss future steps necessary to advance this concept, which is currently in its early stages of development

Avanços na síntese e caracterização de nanocompositos multifuncionais de níquel/óxido de grafeno reduzido

Doutoramento em Engenharia MecânicaO grafeno é constituído por uma monocamada de átomos de carbono dispostos numa espécie de rede hexagonal perfeita. Devido às suas propriedades extraordinárias, este nanomaterial tem suscitado um grande interesse tanto no setor científico como no industrial. A este respeito, a investigação em torno do grafeno mostrou um aumento exponencial em áreas tão diferentes como a energia, biomedicina, eletrónica, entre outras. O óxido de grafeno (GO), um dos derivados de grafeno, foi considerado como um substrato interessante para o desenvolvimento de nanocompositos. Isto deve-se fundamentalmente à presença de grupos funcionais de oxigénio na superfície do grafeno, os quais proporcionam locais reativos para a nucleação e o crescimento de outras estruturas. O níquel (Ni) é um metal de transição muito abundante na terra, possui uma superfície brilhante comum à maioria dos metais e é dúctil e maleável possuindo propriedades magnéticas e catalíticas superiores, condutividade térmica e elétrica razoáveis sendo muito utilizado em diferentes aplicações. As nanopartículas (NPs) de Ni são utilizadas como catalisadores heterogéneos e receberam atenção notável devido ao seu baixo custo, reduzida toxicidade, baixa corrosão, entre outras características. Desta forma, a funcionalização do GO com NPs de Ni pode constituir uma nova família de nanocompósitos com propriedades sinérgicas. Esta tese está focada no controlo da síntese de nanocompósitos Ni/GO, uma vez que o tamanho, a morfologia e a dispersão de NPs de Ni no grafeno afetam as suas funcionalidades e estão em dependência direta com as metodologias de síntese. Em primeiro lugar, foi usado um método hidrotérmico de fácil implementação e execução num passo único. Foram estudados vários parâmetros de síntese, incluindo temperatura, tempo de reação e agente redutor. O controlo destes parâmetros influenciou efetivamente o tamanho das NPs de Ni, variando estas de 150 a 900 nm, a morfologia variou de forma esférica a formato em espiga e de partículas finas bem distribuídas para agregados. Em seguida, o controlo do tamanho das NPs de Ni para valores inferiores a 10 nm e com distribuição de tamanho reduzido no substrato foi conseguido através de um procedimento de síntese em dois passos com base num método solvotérmico seguido por tratamento térmico sob atmosfera redutora de H2. O tempo de reação mostrou ser um fator chave para controlar a distribuição e o tamanho das NPs de Ni simultaneamente com a redução do GO (rGO). O aquecimento em atmosfera de H2 foi crucial para formar as NPs de Ni metálicas cristalinas. A influência de um tratamento térmico adicional em atmosferas redutora e inerte sobre a estrutura do nanocompósito Ni/rGO foi também investigada. Diferentes nanocompósitos apresentaram boa estabilidade térmica sob H2 até à temperatura de 450 °C durante 2 horas. O tratamento a 900 °C sob o fluxo de árgon alterou a estrutura do Ni/rGO por formação de “sulcos” através da rede de carbono e coalescência das NPs de Ni com formação de partículas maiores. O estudo das propriedades eletrofisicas dos nanocompositos Ni/rGO mostrou que estas são dependentes do tamanho e estrutura das NPs de Ni nas folhas de rGO. Esta é uma potencial vantagem do método de síntese desenvolvido para o design de diferentes nanocompositos de Ni/rGO que poderão ser materiais favoráveis para aplicação em dispositivos eletrónicos integrados.Graphene, the world thinnest material made of carbon atoms in a dense honeycomb network has captured a great interest in both scientific and industry sectors due to its remarkable properties. In this regard, the graphene research is facing an incredible rise in different areas such as energy, biomedical, sensor and electronic applications, between others. Graphene oxide (GO), one of the graphene derivatives, has been considered as an interesting substrate to build nanocomposites. This is due to the presence of oxygen functionalities at the graphene surface which provides reactive sites for the nucleation and growth of other structures. Nickel (Ni) is a transition metal very abundant on earth, it has a shiny surface common to most metals and is both ductile and malleable possessing different properties such as superior magnetic and catalysis properties, a fairly good heat and electrical conductivity and is widely used in different areas of application. Ni nanoparticles (NPs) find use as heterogeneous catalyst and received noteworthy attention because of its inexpensive, non-toxic, low corrosion, waste minimization, between other characteristics. In this way, the functionalization of GO with Ni NPs can establish a new family of nanocomposites with synergic properties. This thesis is focused on the control of the synthesis of Ni/GO nanocomposites, since the size, morphology and dispersion of Ni NPs on graphene affect their functionalities and are in direct dependence with the synthesis methodologies. First, a facile one pot hydrothermal method was introduced and various synthesis parameters including temperature, reaction time and reducing agent were investigated. The control of these parameters effectively influenced the Ni size, ranging from 150 to 900 nm, the morphology from spherical to spiky shape and from well distributed fine particles to the big aggregation. Then, the control of the Ni NPs size to values of less than 10 nm with narrow size distribution on the substrate was achieved via a two-step synthesis procedure based on a solvothermal method followed by a heat treatment under H2 reducing atmosphere. The reaction time was shown to be a key factor to control the size and size distribution of Ni NPs simultaneously through the reduction of GO (rGO). Heating treatment under H2 was crucial to form the crystalized metallic Ni NPs. The influence of further thermal treatment under reducing and inert atmospheres on the structure of Ni/rGO nanocomposite was also investigated. Different nanocomposites showed a good thermal stability under H2 up to 450°C during 2 hours’ treatment. Higher temperature (900°C) under Argon flow changed the structure of Ni/rGO by formation of trenches through the carbon etching and coalescence of Ni NPs to form bigger particles. The study of the electrophysical properties of Ni/rGO showed that these properties are dependent on the size and structure of Ni NPs on rGO nanosheets. This is the potential advantage of the synthesis method developed for designing different matrix of Ni/rGO nanocomposites which could be a favorable material for integrated electronic devices application

Alternating current electroluminescent properties of zinc sulfide powders

In order to investigate the alternating current electroluminescent properties of zinc sulfide powders the following experiments were conducted: synthesis of zinc sulfide phosphors (comprised of zinc, sulfur and copper dopant); thermal shocking of phosphor materials (sudden cooling, using liquid nitrogen, of phosphor particles heated up to 500oC) and analysis of their alternating current electroluminescent properties as well as studies of particle crystal structures by synchrotron and conventional X-ray powder diffraction techniques. Inductively coupled plasma mass spectrometry was utilized to investigate the concentration of co-activator atoms within the zinc sulphide crystal lattice. Electroluminescent panels were prepared and the emission properties were evaluated theoretically in order to obtain a mathematical relationship between various parameters involved in the electroluminescent process. Thermal quenching of zinc sulfide phosphor alters its photoluminescent and electroluminescent properties. The dominant wavelength of the material alters from 504 nm to 517 nm. It appears that the blue centres are vulnerable to the thermal quenching procedure carried out as the blue emission deteriorates and the overall blue emission of the material is reduced due to the role that the interstitial Cu+ species play in this mechanism. The interstitial Cu+ is not as stable in its location within the lattice compared to substitutional Cu+ and hence a thermal shock is prone to effect its location or association with the surrounding atoms. The green emission centre, however, appears to be unaffected. Results obtained from layer by layer analysis of the material demonstrate that the surface of the phosphor particles contain most of the copper content (copper to zinc molar ratio of 0.08% in the surface compared to 0.06% at inner levels distributed within the lattice). The location of the outer copper layer may play a key role in the alternating current electroluminescence (ACEL) process; further experiments need to be conducted in order to prove the foregoing hypothesis. Irrespective of the amount of copper impurity (dopnat) initially added to the zinc sulphide precursor, prior to synthesis of the phosphor, during the high temperature firing of the material (above 700˚C) a considerable amount of the copper will be ejected from the lattice and be washed off in the latter steps of the synthesis process (where the newly synthesized phosphor is washed in concentrated ammonia solution); an initial copper content of 1.2% molar ratio is reduced to 0.154%; however, the duration of the high temperature firing is a key factor in the final amount of copper present within the lattice. XRPD experiments of a working ACEL device (i.e., when the AC field is applied across the electroluminescent phosphor) show that the diffraction lines all shift, but remain within the region where broad diffraction intensity is observed for a powder sample (i.e. random orientation). Indeed the sharp diffraction lines are observed to span across each broad diffraction area associated with the sphalerite phase. The panel exhibits a different diffraction pattern when the device is powered in an AC field compared to when it is not exposed to the field. This clearly indicates that the particles possess piezoelectric properties and the electric field causes strain on the crystal lattice. When considering the major drawbacks of ACEL technology, i.e. it’s short life time and degradation characteristics, defining a mathematical model of its emission degradation is a step towards understanding part of the mechanism of the ACEL process. Due to the various number of parameters involved in the phenomenon of electroluminescence (such as particle size, copper content and random distribution of crystal planes) and the fact that emissions arise from certain centres randomly distributed over each phosphor particle, mathematical models are only accurate when they are formulated in relation to the analysis of a particular batch of phosphor sample and used to prepare a particular panel. Hence, no overall mathematical formulation can be produced to measure the emission properties of various ACEL panels produced by different batches of zinc sulfide phosphors. The findings of this research indicate that sample preparation technique which involves addition of raw zinc sulfide to an already copper doped zinc sulfide causes an increase in the occurrence of nano p-n junctions species within the lattice where the cupper locations form the p-type and the n type is formed from the release of some sulfur atoms from zinc sulfide structure during the high temperature firing relative to the conventional phosphor preparation methods. Larger particles have a higher probability of contacting interstitial copper sites during firing and preparation as copper atoms tend to migrate out of the zinc sulfide lattice toward the surface. Hence larger particles (commercial phosphors) demonstrate better emission properties. Thermal quenching affects the interstitial copper sites more than the other luminescent centres formed of substitutional copper sites. Hence the lowered blue emission occurs. Due to the probability of high dispersion of Cu atoms within the ZnS lattice a useful mathematical model cannot easily be developed for an EL panel. EXAFS analysis cannot be fully relied up on in respect of the interstitial copper environment in these phosphors considering that a small fraction of the copper impurity in the phosphor exists at interstitial sites. However, the results from experiments using XANES confirm a change in the electronic configuration of Zn atoms when samples are quenched

Development of a Transparent Thermal Reflective Thin Film Coating for Accurate Separation of Food-Grade Plastics in Recycling Process via AI-Based Thermal Image Processing

This paper presents the development of a specific thin film coating designed to address the challenge of accurately separating food-grade plastics in the recycling process. The coating, created using a plasma sputtering process, is transparent to the visible spectrum of light while effectively reflecting infrared emissions above 1500 nm. Composed of a safe metal oxide formulation with a proprietary composition, the coating is applied to packaging labels. By employing thermal imaging and a computer vision AI model, the coated labels enable precise differentiation of plastics associated with food packaging in the initial stage of plastic recycling. The proposed system achieved a remarkable 100% accuracy in separating food-grade plastics from other types of plastics. This innovative approach holds great potential for enhancing the efficiency and effectiveness of plastic recycling processes, ensuring the recovery of food-grade plastics for future use

Evaluation of thermally stable phosphor screens for application in laser diode excited high brightness white light modules

A study on the preparation of thermally stable phosphor targets based on yttrium aluminum garnet doped with cerium (YAG:Ce) when excited by a high power laser diode is described. The luminous flux, chromaticity and radial spectral flux of the targets along with their thermal stability have been determined when exposed to laser powers of up to 5000 mW. This report presents successful high brightness light sources with adjustable emission properties achieved by utilizing thermally stable phosphor targets excited by high power laser diodes.Brunel University London, No. EP/K504208/

King Lear: A Negatively Capable Outsider

Negative capability, John Keats’s coined term, defines the ideal poet as being capable of being in uncertainties and mysteries without any irritable reaching after fact and reason. He insists that poets let the mind be a thoroughfare for all thoughts, by holding no fixed identity but metamorphic identities. Although Keats finds the ideal quality of a poet in Shakespeare the poet, it does not appear far from logical to investigate it in the characters of his plays, specifically king Lear, as he undergoes changes throughout the story and cuts across his enclosed self to enrich his receptivity to the actual vastness of life experience after he is estranged and labelled as an outsider in his erstwhile kingdom. In the present study I will employ the ongoing vigor of negative capability to take a step further ahead of its theoretically stipulated implications and investigate it on the character of king Lear

Artificial Neural Networks to Predict Sheet Resistance of Indium-Doped Zinc Oxide Thin Films Deposited via Plasma Deposition

We implemented deep learning models to examine the accuracy of predicting a single feature (sheet resistance) of thin films of indium-doped zinc oxide deposited via plasma sputter deposition by feeding the spectral data of the plasma to the deep learning models. We carried out 114 depositions to create a large enough dataset for use in training various artificial neural network models. We demonstrated that artificial neural networks could be implemented as a model that could predict the sheet resistance of the thin films as they were deposited, taking in only the spectral emission of the plasma as an input wi