Browsing by Author "Alharbi, Nouf"

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Electrospray Ion Beam Deposition And Preparation Of Model Molecular Solar Cells Surfaces
(2023) Alharbi, Nouf; O’Shea, James; Moriarty, Philip
Studying the fundamental science of surface science of dye-sensitised solar cells requires placing complex molecules on surfaces in an ultra-high vacuum. Since most dye molecules are fragile and non-volatile to be deposited by thermal evaporation or sublimation technique, electrospray deposition was therefore explored as an alternative method. This thesis aims to work on developing the electrospray deposition technique to obtain high-quality monolayers in situ in high vacuum environments. Image charge detection mass spectrometry (CDMS) has been used to measure the speed and charge distributions of molecular ions. Image charge drift tube measurements formed large clusters giving strong transient signals with a narrow velocity distribution of cluster sizes ranging from 300 ms−1 and 330 ms−1. The charge-to-speed relationship showed fitting with a 1/v2, meaning that all clusters have constant kinetic energy. In the case of the small clusters or individual molecular ions travelling through the drift tube, advanced electronics are required to see the weak signals hidden in the background noise. The electrostatic ion deflector experiments, highlighting the capabilities of bending the ion beam in order to work towards separating two components of the beam, showed the formation of large clusters in the beam. These clusters have required a higher voltage in order to be deflected by the same amount based on SIMION simulations and a smooth range of charge distributions. Small molecular ions are worth studying in the future - via the discovery of low voltage range since these deflection experiments have concentrated on the high voltage regime. In the second section, the XPS measurements of defocussing experiments showed an incapability of the Einzel lens to diverge the beam over a large area on the sample, especially when the SIMION simulation achieved this. As well as, the defocussing experiment using a long tube exhibited the success of the Einzel lens to spread the beam over the entire sample. In the last section, AFM and optical images displayed the deposition of graphene oxide successfully with heterogeneous deposition coverage across the surface. Dye-sensitisers adsorbed onto rutile TiO2 (110) were deposited in situ in UHV using electrospray deposition. Adsorption geometries and determining the dispersion of these molecules with this titanium surface were investigated using X-ray photoemission spectroscopy (XPS). The results of O 1s photoemission in the monolayer coverages showed that dye complexes bind onto TiO2 (110) by deprotonation of the carboxylic acid and phosphonic acid groups so that their oxygen atoms bond to titanium atoms of the substrate. Photoemission of C 1s, together with N 1s, indicated that the molecule is intact on the surface.
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Innovative 3D Tri-Culture Systems for Advanced in vitro Tissue Interface Engineering
(University of Edinburgh, 2024-08-08) Alharbi, Nouf; Paxton, Jennifer
3D tissue engineering has enhanced the study of complex structures like the tendon-to-bone interface; it consists of tendons, uncalcified fibrocaltogenous and calcified fibrocartigoues, and bone cells. The unique gradual arrangement allows for smooth transfers of mechanical force during mobility without compromising anatomical integrity. In vitro, studies require complex models to imitate such an environment. This study investigates the fabrication of a novel design with two compartments for different cell-encapsulating hydrogels, separated by a 2mm gap. The gap can be left empty, filled with hydrogel, or populated with a third cell type to suit various experimental needs. A 3D-printed resin lid with six inferiorly projected positive rectangular impressions was designed to fit 6-well plates using computer-aided design software. 7ml polydimethylsiloxane (PDMS) mixture was cast inside each well around the rectangular shapes, leaving six cured elastomeric rectangular wells, which were extracted and mounted on a glass slide utilising PDMS crosslinker as a bonding agent. Additionally, a 35mm plate's lid was utilised as a cover. The system's integrity was tested with a manual peeling test and daily microscopic observation. Fluorescent confocal microscopy assessed Compartmentalization by individually labelling osteoblast and fibroblast rat cells before encapsulating them separately in fibrin gel and cell viability, which was assessed using Calcein AM and Propidium Iodide staining. The well-on-glass slide system successfully fabricated and passed integrity and sterility tests with the ability of containing up to 7.14 ml working solution, it also supported more than 98% of cell viability at day 7, proliferation, while both cells miniating their 3D form with in the fibrin gel up to day 10 of the experiment. In conclusion, our novel 3D cell culture system promises more in-depth investigations of cellular behaviours, migration and differentiation in the formation of tissue interfaces. To aid in advancing our understanding of more complex anatomical structures such as interfaces through in vitro studies to ultimately, advance the clinical application.
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THE PRODUCTION EFFECT IN CHILDREN LEARNING MODERN STANDARD ARABIC VOCABULARY AS AN ADDITIONAL LANGUAGE
(University of Birmingham, 2024-08) Alharbi, Nouf; Carrol, Gareth; Littlemore, Jeannette
This thesis investigates the production effect (PE), a phenomenon where actively producing words (reading aloud, writing) leads to better learning compared to passive exposure (reading silently). While extensively studied in adults, the PE's impact on children's foreign language acquisition remains unclear. This research explores the influence of the PE on noun acquisition in child learners of Modern Standard Arabic (MSA). A pilot study was conducted to examine the Production Effect (PE) in 72 English-speaking children with basic knowledge of Modern Standard Arabic (MSA). Participants engaged in an online MSA word-learning task under two conditions: listening only and listening then repeating. Testing occurred immediately, 24 hours, and nine weeks after learning. Results indicated minimal accuracy differences between the conditions, suggesting no significant production effect. However, cross-linguistic similarities between English and Arabic influenced response times, with faster responses for similar words, highlighting the role of linguistic overlap in L2 vocabulary acquisition. Experiment 1 explored the PE using a larger set of 64 MSA words while controlling for age and language background. Participants (6-year-old bilingual children) learned new words in either listen-only or repeat conditions. Testing occurred immediately, one week later, and two weeks later. Delayed tests revealed an overall improvement in performance across both groups. However, the experiment did show a significant effect of production. Experiment 2 expanded the investigation by including a writing condition alongside listening and repeating. This experiment focused on 8-year-old bilingual children. Testing was conducted immediately after learning, one week later, and two weeks later. The writing condition significantly enhanced retention and recall, particularly in delayed tests. These findings suggest that the PE's learning effects on children's MSA word acquisition are moderated by various factors, including age of the learners, the specific learning materials and the length of time between learning and testing. Overall, this thesis contributes to understanding the PE in children's additional language learning. The results highlight the potential benefits of writing as a production mechanism in enhancing vocabulary learning in MSA children. The research also identifies factors influencing the effectiveness of the PE, paving the way for further investigation in the field of learning mechanisms and the development of more effective pedagogical approaches.
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