SACM - Spain
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14154/68029
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Item Restricted رسالة دكتوراه ( قدرة الجماعات الارهابية على استخدام مواقع التواصل في السعودية لتنجيد الشباب ونشر الايدلوجيا المتطرفة - دراسة تحليلية لبناء السرديات الجهادية في تويتر - )(Universidad De Alcala, 2024) Alghamdi, Saleh Saeed; Pertu, Julian LaThe rise of jihadi discourse on Twitter (now known as X) has represented an issue of increasing concern with its influence on online audiences and sociey. Despite counter strategies and global initiatives to curb extremist discourse and online radicalisation the influence of jihadi narratives on social media and Twitter remains a pervasive threat. The widespread adoption of social media and Twitter in Saudia and as a major power in the Middle East, Saudia Arabia has been the target of jihadi discourse and susceptible to extremist influence with far reaching regional and global implications. Given the rise and dissemination of jihadi discourse on Twitter relating to or emanating from Saudi Arabia this research investigates the ability of extremist groups to spread their ideologies through the social media platforms in Saudi Arabia on Twitter in the period 2015-2106. A systematic grounded discourse analysis of Twitter data was employed to comprehensively examine jihadi discourse on the platform. The findings reveal a deliberate and diverse narrative structure that integrates ideological, historical, religious, and socio-political elements, enhancing its persuasive power through strategic framing techniques. The communication strategies on Twitter, including rapid dissemination, amplification, and the use of multimedia, significantly enhance the discourse’s influence. This discourse shapes perceptions, behaviors, and identities, creating strong emotional and cognitive impacts. In Saudi Arabia, Twitter's role in propagating jihadi narratives is particularly impactful, linking messages to current events and leveraging multimedia to resonate with the audience, thereby posing a persistent threat to societal stability. This contributes a novel strategic framework for analysing online extremist communication that extends theory and supports policy guidance to counter online extremism by analysing jihadi discourse's persuasive power and influence on Twitter.29 0Item Restricted Cloud Cybersecurity(Universidad de Al cala, 2024) Bokhari, Nabil; Herraiz, Martinez; Javier, JoseThe rapid evolution of cloud computing has revolutionized modern business operations, from hosting applications to storing data in high-security environments. Competitive businesses are leveraging cloud computing solutions to maximize the benefits, including cost-effectiveness, flexibility, and scalability. Cloud computing enables enterprises to access on-demand and scalable computing resources, specifically computational power and vast data storage. Despite the immense benefits, the security of data transmitted and stored in a cloud computing environment is vulnerable to multiple cybersecurity attacks, including data manipulation, loss, and theft. The study aims to develop a security model for enhanced data privacy and security in the cloud by leveraging a hybrid of cryptographic algorithms and steganography image-based techniques. The security model innovatively combines Advanced Encryption Standard (AES), Rivest Shamir Adleman (RSA), and the Least Significant Bit (LSB) technique to enhance data privacy and security of data in motion in a cloud computing environment. The three-step security model was designed, developed, and evaluated using the Design Science Research (DSR) methodology. The model secures data through cryptographic algorithms, adds an extra security layer using steganography, and implements backup and data recovery. The methodology was selected because of its practicality and philosophical underpinnings on addressing contemporary challenges by developing novel and relevant artifacts using scientifically rigorous procedures. The findings show that a hybrid of cryptography and steganography provides unbeatable security for data in a cloud computing environment. Implementing the security model will enhance data privacy and security in the cloud by revolutionizing how data is encrypted and decrypted. In the future, the integration of Machine Learning and Artificial Intelligence methodologies and algorithms will quadruple the effectiveness and robustness of this data security model for the cloud.11 0Item Restricted Effects of Retargeting on Post-Purchase Behavior in the Tourism Industry(Universitat Autònoma de Barcelona, 2024-07) Alghanayem, Haitham; Lopez-Sintas, Jordi; Lamberti, GiuseppeThis study examines the impact of digital retargeting strategies on consumers' post-purchase behavior within the e-tourism sector, specifically how these practices affect consumers' purchasing experiences, including satisfaction and repurchase intentions. This study provides an in-depth analysis of consumer reactions to retargeting ads in Saudi Arabia and Spain, offering valuable insights into the effectiveness of these marketing strategies in diverse global settings. This research uses a quantitative approach to analyze survey data from e-tourism consumers in Saudi Arabia and Spain who received retargeting ads after booking. Applying the Expectation Confirmation Theory, the study explores the relationship between such ads and consumers' expectations confirmation, satisfaction, and future purchasing plans. Additionally, it investigates the role of cultural values and how varying levels of trust in technology and digital skills influence the impact of retargeting ads. The findings reveal that post-purchase retargeting ads can negatively affect consumer expectation confirmation by altering their initial expectations, reducing their satisfaction, and repurchase intentions. This is particularly true for consumers with higher digital skills and trust in technology, who tend to scrutinize advertising practices more critically. Furthermore, even though the results were very similar across users from Spain and Saudi Arabia, individual cultural values play a crucial role in shaping the effectiveness of retargeting campaigns. The research advocates for a more personalized and culturally sensitive approach to retargeting in the e-tourism industry. These findings enrich the academic discussion on digital marketing strategies and offer strategic recommendations for marketers seeking to optimize engagement in culturally diverse markets.5 0Item Restricted Do the US Federal Reserve System Instruments Still Influence the Global Economy?(Esade Ramon Illul, 2023) Ferak, Rakan Ramiz; Garroum, GabrielThe Federal Reserve System (Fed) of the United States is a strong economic organization that substantially affects economies worldwide. The Federal Reserve has many tools at its disposal, including monetary policy instruments, such as interest rate changes and quantitative easing, and regulatory functions, such as monitoring banks and fostering financial stability. This plays the role of setting the currency exchange rate in the financial market. However, as the interconnectedness and complexity of the global economy have increased, doubts have been raised by economists and policymakers concerning the efficacy of the Fed's tools in tackling the issues faced by the global economy (Fischer, 2015). In this thesis, the geo-economic consequences of the Fed's instruments are analyzed, and an investigation is conducted to determine whether these instruments are still effective in the present state of the global economy. Through a mixed methods literature review, which aims to discern and synthesize existing narratives on this topic, this thesis aims to provide a comprehensive understanding of the Federal Reserve's role in the global economy and the effectiveness of its instruments by analyzing the historical context of the Fed's instruments, an evaluation of their impact on the economies of the United States and the global economy, and an examination of current economic trends and challenges. This thesis seeks to contribute to ongoing discussions on the role of the Federal Reserve System through its policies, influence on the USD, and its effect on international economies.20 0Item Restricted Metagenomic Exploration of the Effects of Depth and Temperature on the Microbiome Structure and Function of the Gorgonian Eunicella singularis and the Cold Water Scleractinia Desmophyllum pertusum(University of Barcelona, 2024) Binsarhan, Mohammad; Logares, Ramiro; Calafat, AntonioCorals play an essential role in marine environments and their morphological structure provides microbes with different habitat types. In turn, the microbes provide corals with important compounds that contribute to coral fitness and health. Corals have been suggested to hold distinct microbes within the anatomical layer, such as the Skeleton, Surface mucus layer (SML), Tissue, and Gastric cavity. Furthermore, many factors can influence the structure and function of the microbiome, making it more challenging to understand. Coral age, taxonomy, disease, depth zones, and many other abiotic factors could shape coral microbiomes and are responsible for their stability. Disturbances in the relationship's stability between coral hosts and their associated microbes increase the chance of coral infections and bleaching, leading to mortality. Therefore, studying the influence of each factor on the microbiome could lead to a better understanding of the nature and dynamics of this complex system. However, many questions remain regarding how microbes are acquired and function in corals. In this thesis, we explored the coral microbiome and its relationship with two abiotic variables, depth and temperature. High-throughput meta-omics approaches have been used to investigate coral microbiomes. Some limitations may hinder the full benefits of meta-omics; however, these powerful tools open doors for understanding the coral microbiome. Our comprehensive analysis of the Mediterranean Eunicella singularis microbiome revealed significant differences between shallow and mesophotic colonies at both taxonomic and functional levels. While shallow water colonies prominently featured Symbiodinium, essential for coral energy production through photosynthesis, its absence in the mesophotic zone indicates a shift in microbial community structure. In deeper environments, the microbial community exhibited higher abundances of functional genes related to carbohydrate, energy, amino acid, cofactor, and vitamin metabolism. This potentially allows the microbiome to utilize carbon and nitrogen from various sources, such as glutathione, steroids, fatty acids, and aromatic hydrocarbons, which might help sustain coral nutrition through enhanced nutrient availability. Additionally, Metagenome-Assembled Genomes (MAGs) analysis identified microbiome taxa, such as DT-91 (Order Pseudomonadales) and Endozoicomonas, involved in nutrient recycling, vitamin production, and secretion systems, highlighting their role in microbiome fitness. These findings underscore potential microbial adaptation mechanisms to environmental conditions, emphasizing their potential role in facilitating coral resilience and adaptation to different contexts. Further investigations are needed to determine whether these genes are actively expressed in the microbial community and to assess the extent of their influence on both the coral's health and its associated microbiome. Our study of the potential influence of prolonged thermal stress on the cold-water coral D. pertusum revealed a significant impact on the microbiome structure at both taxonomic and functional levels. Metagenomic analyses supported previous research, showing an increase in Rhodobacterales under thermal stress conditions. Moreover, our analyses indicated an increase in the carbon metabolic genes, such as methylotrophy and glycoside hydrolase enzymes, which may destabilize the microbiome and promote the growth of opportunistic pathogenic organisms. Indeed, we found an increase in pathogenic marker genes within the D. pertusum microbiome as temperature increased. Interestingly, the microbial taxa associated with these markers, such as those related to type 1 and 3 secretion systems, also increased in abundance in thermally stressed microbiomes. Additionally, we observed an increase in genes associated with diazotrophic activity, including denitrification and nitrification, which could disrupt the nitrogen cycle balance between the coral and its microbiome, potentially increasing the susceptibility to diseases and mortality. Together, these findings underscore the influence of increasing temperature on the taxonomic and functional structure of the cold-water coral microbiome. However, further research is required to investigate the gene expression profiles associated with formaldehyde assimilation, denitrification, and nitrification. Examining the expression levels of these metabolic pathways would provide deeper insights into their activity and regulation, contributing to a more comprehensive understanding of their roles in the microbiome's response to environmental stressors such as temperature increase.1 0Item Restricted A Sectorial Analysis of Municipal Water Consumption and Management(Universitat Politecnica De Valencia, 2023-11-15) Alhudaithi, Musaad Abdulaziz; Arregui de la Cruz, Francisco; Cobacho Jordan, RicardoThe Kingdom of Saudi Arabia is undergoing substantial economic, industrial, commercial, and population growth. This growth, in turn, leads to increased water demand in the region. In addition to population growth, industrialization and modernization have placed increasing pressure on KSA’s water infrastructure. There is an urgent need to increase the water capacity to meet the projected demand and maintain the water systems' security and reliability. Therefore, it is imperative to find solutions that improve the efficiency of the Kingdom’s water system. A key element in this effort is understanding and classifying how water is consumed with its micro-components within various segments. The thesis aims to collect precise knowledge about municipal water consumption patterns and trends to understand water consumption patterns and consumer behaviors better and develop preliminary estimates and assumptions. This will drive the municipal water demand model in KSA to be capable of dealing with different scenarios and constraints. The development of the municipal water demand model highlighted the need for reliable statistical and water billing data. These form the starting point of the forecast and need to be available at a high enough resolution. The model provides a framework for the required data to be built on further. The analysis results will also determine the drivers and categories used in the model. The model focuses on the non-Residential water demand. Still, separate forecasts are included for the residential category to enable the extrapolation of the results and downward analysis for a more accurate and cost-effective bottom-up approach to forecasting and an overall better understanding of the population’s water consumption behaviors.2 0Item Restricted Terminología ecuestre en el diccionario al-Muẖaṣṣaṣ de Ibn Sīda(Universidad de Salamanca, 2024-02-28) Alqahtani, Ahmad Salman; Perez, Buendia PedroThis Ph.D. Thesis provides a thorough translation and analysis of the hippological vocabulary contained in the al-Muẖaṣṣaṣ dictionary of the Andalusian scholar Ibn Sīda (11th century), one of the most famous lexicographers of Arabic literature. The al-Muẖaṣṣaṣ dictionary stands out as the first great onomasiological dictionary of the Arabic literary-lexicographic tradition, as well as the most complete. It devotes an entire section to the vocabulary related to hippology, the Kitāb al-ẖayl or Book of Horses, a discipline in whose study medieval Arabic culture reached a remarkable dimension. In addition to the study and terminological translation of this broad hippological corpus, this research is interested in the author's life and work, examines in detail the structure and content of the al-Muẖaṣṣaṣ dictionary, and offers an overview of Arabic lexicography that allows readers and researchers to get closer to the nature of the work. It also takes stock of the situation of Arabic-Spanish terminology, as well as a conceptual system and lexicographical and lexicological study of Kitāb al-ẖayl. Finally, three glossaries (Arabic, Arabic-Spanish, and of concepts) are prepared to facilitate consultation and access to the corpus under study. This analysis covers philological questions (translation, etymologies, influences and transfers into Spanish, references in other medieval Arabic dictionaries), as well as zoological and cultural, due to the contamination existing in all medieval traditions between the scientific, the literary and the paradoxical.34 0Item Restricted Assessment of bone loss adjacent to lower second molar in case of third molar impaction and other findings using Orthopantomography (OPG)(University of Barcelona, 2024-03-13) Assiri, Hassan; López-López, José; Estrugo-Devesa, AlbertIntroducción: la impactación dental es una situación patológica en la que un diente se incluye total o parcialmente en el hueso de la mandíbula o del maxilar. Diferentes dientes son notablemente propensos a los fenómenos de impactación, incluyendo el canino y el tercer molar superior, el tercer molar y el canino inferior. Sin embargo, el tercer molar inferior se considera el diente impactado más común, representando el 98% en comparación con otros dientes impactados. Por lo general, entra en erupción entre los 17 y 24 años. La prevalencia global de impactación del tercer molar inferior se estima en torno al 24%, sin predilección de género entre hombres y mujeres. Hay factores que hacen que un diente no erupcione en el tiempo esperado, incluida la falta de espacio, los gérmenes dentales mal posicionados, la vía de erupción anormal y las alteraciones del desarrollo de la mandíbula. La impactación del tercer molar mandibular tiene muchas complicaciones en el tejido blando adyacente y en el segundo molar. Así, la pericoronaritis es una de las consecuencias causadas por la impactación, que se manifiesta como inflamación del tejido gingival que la recubre. Otras complicaciones incluyen la caries distal, la pérdida ósea adyacente al segundo molar, formación quística y cambios neoplásicos. Las diferentes posiciones de los terceros molares mandibulares impactados pueden complicar el mantenimiento de la higiene oral y la placa control. Por lo tanto, el periodonto manifiesta la formación de bolsas que facilitan la perdida oseas en la cara distal del segundo molar. Además, el tercer molar mandibular está ubicado cerca del canal mandibular inferior el cual contiene el nervio alveolar inferior, la arteria y la vena correspondiente. La extracción quirúrgica de dicho diente puede ejercer un riesgo de lesión nerviosa que conduzca a disestesia o a parestesia. Además, el procedimiento de extracción del tercer molar puede ejercer una presión sobre el hueso que puede conducir a la fractura del ángulo de la mandíbula. Finalmente, la extracción puede afectar al 2º molar inferior. Por lo tanto, los procedimientos clínicos y diagnósticos son esenciales para abordar la posición del diente impactado, la patología asociada, la proximidad al canal nervioso y la decisión de intervención. La ortopantomografía (OPG) es una técnica de diagnóstico por la imagen utilizada rutinariamente en el consultorio dental, que representa al maxilar y la mandíbula en una sola imagen. Tiene la ventaja de exponer los cambios dentales y óseos en la cavidad oral, incluidos los dientes impactados. Entre las ventajas de la OPG, se encuentran su rapidez y facilida, en especial el 2º molar y el canal dentro de realización, mejor cooperación y aceptación del paciente, cobertura completa de las arcadas dentales y estructuras relacionadas (se pueden ver más estructuras anatómicas en una película panorámica que en una serie completa de radiografías intraorales), simplicidad y baja exposición a la radiación para el paciente, en comparación con la herramienta de imagen más avanzada, la tomografía computarizada de haz cónico (CBCT). Como la impactación del tercer molar es una de las patologías dentales que los odontólogos ven con frecuencia, la determinación de la posición y la relación con las estructuras cercanas, en especial el 2º molar y el canal dentario inferior, se puede predecir utilizando OPG. Hipótesis: La impactación del tercer molar causa pérdida ósea distal al segundo molar, por lo tanto, habrá ganancia ósea distal al segundo molar después de la extracción del tercer molar. molar impactado. Hipótesis nula: la impactación del tercer molar causa pérdida ósea distal al segundo molar, sin embargo, no habrá ganancia ósea distal al segundo molar después de la extracción dental del tercer molar impactado. Objetivo: determinar la pérdida ósea distal del segundo molar inferior asociada a impactación del tercer molar y analizar su evolución tras la extracción del tercer molar. Metodología: el estudio es retrospectivo de casos y controles de pacientes que visitan el Hospital Dental de la Universidad de Barcelona (HOUB). Las radiografías de los pacientes se obtuvieron desde junio 2018 hasta Agosto de 2022, y se dividieron en dos grupos: un grupo de estudio (SG) y un grupo de control (GC). El grupo de estudio contiene las imágenes de los pacientes en los que se mide el nivel óseo distal al segundo molar antes y después de la extracción del tercer molar impactado mandibular, mientras que el grupo control incluye las imágenes de pacientes que no realizan la exodoncia de sus terceros molares mandibulares impactados, en los que el nivel óseo se mide dos veces en un período de al menos 3-6 meses. Pérdida ósea distal al segundo molar se midió en ambos grupos y se comparó. Las mediciones se realizan utilizando la herramienta asociada al dispositivo de radiografía panorámica [DICOM]. Las variables analizadas son cualitativas según frecuencia y porcentajes y de las cuantitativas según medidas de tendencia central y de dispersión. Las variables cuantitativas, dependiendo de su distribución de normalidad, se estudian según la prueba de Kolmogórov-Smirnov (p<0,05), y se definieron según la media y desviación estándar. Resultados: La muestra está constituida 80 pacientes y (160) OPGs 40 pacientes por dos grupos; el grupo de estudio y el grupo control. La edad media de los pacientes por grupo estudio es 35.5 años y una desviación estándar de 15.45. De ellos 62.5% son mujeres y 37.5% son varones. Por otro lado, la edad media de los pacientes por grupo control es 33.47 años y desviación estándar 16.49. De ellos 55% son mujeres y 45% son varones. Estadísticamente, nuestros hallazgos no ilustran diferencias significativas entre ninguno de los grupos con respecto a la edad (p-valor 0.57), las categorías de grupos deedad (pvalor 0.43) y el sexo (p-valor 0.36). Obviamente la mayoría de los pacientes acudieron al hospital para la extracción del tercer molar mandibular impactado (IMTM). La mayoría de los pacientes de los dos grupos son no fumadores 73% y 75%del grupo estudio y grupo control respectivamente. La IMTM bilateral es la más frecuente entre otros procedimientos, representando el 73% del grupo de estudio y el 75% del grupo control y no hay diferencias entre ambos grupos (valor de p 0.509). Respecto de la clasificación de Winter, la impactación vertical es más frecuente en comparación de las otras. Según la medida de la perdida ósea, las mediciones del nivelóseo se calcularon e informaron en términos de media y desviación estándar entre el grupo de estudio y el grupo control, como un total, independientemente de los lados. Por lo tanto, nuestro análisis ha revelado que la media y la desviación estándar en el grupo de estudio antes de la extracción fue de 3,00 ± 1,68 mm. Por otro lado, la mediay la desviación estándar de las mediciones después de la extracción fue de 2,63 ± 1,75mm y hay diferencia estadísticamente significativa a favor de la ganancia ósea en el grupo de estudio (valor de p 0,0001). En cuanto al grupo control, la media y la desviación estándar en la radiografía basal fue de 2,73 ± 1,75 mm, mientras que despuésde la segunda radiografía se encontró que era de 3,01 ± 1,98 mm. El análisis estadístico reveló diferencias significativas a favor de la pérdida ósea (valor de p 0,001). En relación con el análisis univariado de los cambios en el estado óseo, el grupo de estudio,en el que se extrae el IMTM, muestra una ganancia ósea significativa en comparación con los controles que no extrajeron el tercer molar, con una diferencia estadísticamentesignificativa (FEE 0,73, DE 0,21, valor de p 0,0001). Con respecto al modelo multivariante ajustado, la asociación se mantiene y es independiente de los factores de confusión (efecto fijo 0,79, error de desviación 0,26, valor p 0,003) que también es estadísticamente significativo. Conclusión: Podemos concluir de nuestro estudio que el hueso distal al segundo molar en caso de extracción generalmente conducirá a la ganancia ósea y el cambio es estadísticamente significativo, mientras que en caso de no extracción de la impactación resultaría en pérdida ósea. La radiografía panorámica, aunque no es reproducible en la cuantificación del cambio óseo en milímetros, sigue siendo una herramienta valiosa en la identificación de los cambios óseos si permiten valores mejores o pérdida ósea.5 0Item Restricted GEOMETRICAL FRUSTRATED MAGNETIC MATERIALS(Universidad Complutense De Madrid, 2024-02-14) Alshalawi, Dhoha; de la Presa Muñoz de Toro, Patricia Marcela; Alonso Rodriguez, José MariaThis thesis delves into the intriguing Quantum Spin Liquid (QSL) and Spin Glass (SG) systems. It aims to unravel their unique properties and gain insights into their potential applications. Both QSL and SG systems exhibit high degrees of frustration at low temperatures and lack of long-range order. QSL maintains continuous fluctuation, while SG systems freeze at a glassy point. This study’s findings could help connect theoretical aspects and understand the unique magnetic behaviors of these systems, which differ from known magnetic interactions. Two primary materials, Ca10Cr7O28 and LaFeO3, are the central focus of this research. These materials are attractive due to the advancement of quantum and magnetism applications, including data storage, sensors, and quantum computing. Additionally, the study explores exchange bias interactions in nanoparticle materials at low temperatures, specifically the core/shell effects. The overarching goal is to contribute to understanding both systems' magnetic geometrical fluctuation in low temperatures. The investigation employs various experimental methods and equipment, encompassing structural, thermal, chemical, and magnetic measurements for both bulk and nanoparticle properties. Impurity-free materials let us to go deep into the intrinsic physical properties of these systems. The Ca10Cr7O28 emerges as a potential QSL material governed by a two-dimensional antiferromagnetic Heisenberg Hamiltonian interaction. Previous synthesis attempts suffered from incorrect precursor ratios, resulting in materials with certain degree of impurities, that can affect the analysis of the physical properties. This study successfully identifies the correct ratio (CaO: Cr2O3≈ 2.85:1) for the pure Ca10Cr7O28 sample. The research not only determines the correct synthesis ratio for pure Ca10Cr7O28 but also offers valuable insights into the impact of impurities on the crystal structure. The crystal structure, determined through X-ray diffraction (XRD) analysis, reveals a trigonal structure with Cr5+ ions arranged in two-dimensional Kagome layers and three-dimensional Zigzag chains. The Rietveld method verifies these proposed crystal structures by calculating the compound's atomic distances. The study extends to low temperatures, demonstrating structural distortions as temperature varies. These results were confirmed using neutron diffraction (ND), including calculating atomic distances between Cr-O. The study explores the impact of temperature on atomic distances and volume values. Comparing the pure with impure samples helps clarify the influence of impurities (CaO and Cr2O3) on crystal structure. This analysis highlights increased distortion in the crystal structure due to impurities, as confirmed through XRD measurements. High-resolution transmission electron microscopy (HRTEM) images were carried out in this study that resolved the role of the impurities and, at the same time, to determine a twins-free structure despite the large dimension of the crystals. The Bond Valence Sum (BVS) calculation method establishes, with ND data, the oxidation state of the compound and confirms the proposed formula of Ca10(Cr6+)1 (Cr5+)6 O28. The material Ca10Cr7O28 exhibits quantum spin liquid behavior, as evidenced by the disappearance of paramagnetic behavior at low temperatures, a lack of remanence and coercivity, and the calculation of Curie temperature. Specific heat measurements confirm short-range magnetic ordering below 3 K, with entropy showing an inverse relationship with an applied magnetic field. Besides, magnetic long-range order emerges below 35 mK. The study extends to LaFeO3, a material displaying antiferromagnetic properties with spin canting at high temperatures. The sol-gel synthesis allows for the variation of particle size, thus enabling the investigation of magnetic frustration as a function of size. HRTEM analysis reveals changes in FeO6 octahedral distortion and the disappearance of spin canting as particle size decreases. Smaller particles exhibit spin-glass behavior at the surface while maintaining an antiferromagnetic core. This creates a core/shell magnetic structure with a significant exchange bias effect. This thesis comprehensively explores Quantum Spin Liquid and Spin Glass systems, highlighting their distinctive properties and behaviors. Additionally, the study reveals the emergence of quantum spin liquid and spin-glass behavior in different materials. This is opening new insight for understanding and potential applications in the future and understanding the related theories.37 0Item Restricted High throughput determination of relevant physicochemical parameters in the drug discovery and HPLC processes. Microfluidic devices(University of Barcelona, 2024-02-08) Albishri, Abdulkarim Khalaf; Pascual, Martí Rosés; Canyelles, Joan Marc CabotDetermining the acidity (pKa) and lipophilicity (log Po/w) of organic compounds is fundamental in analytical chemistry fields, with potential relevance in drug development, material science, analytical separation, and environmental research. A precise estimation of these physicochemical parameters is important for estimating compound behavior and distribution in different biological and chemical systems. Fast determination of pKa of very insoluble drugs has become an essential tool in drug development as it frequently creates compounds that are highly lipophilic and sparingly soluble in water. Also, studying the pharmacokinetics and pharmacodynamics of a proposed drug involves a thorough knowledge of its ionization state and hydrophobicity. In the first part of the thesis, a high-throughput internal standard capillary electrophoresis (IS-CE) method was established to determine the pKa of ISs at different concentrations of methanol and acetonitrile from 0 to 90% (v/v). IS-CE is a pKa determination method based on the use of a known pKa reference compound as an internal standard (IS), whose nature and pKa value are similar to those one of the analytes. Internal standard mobility is measured under the same conditions as analyte mobility when injected at the same time, hence any change in experimental conditions influences both analyte and IS equally. Whereas the traditional CE approach needs potentiometric measurement of the pH of the buffers used, IS-CE uses IS to calculate the true pH in our electrophoretic system and reduces measurement mistakes. Herein, the acid and base scales of methanol-water mixtures and acetonitrile-water mixtures were properly anchored to the potentiometrically obtained pKa values of reference compounds to get absolute pKa scales. As a consequence, a set of 46 acid-base compounds with changing structures were proposed as internal standards for consistent pKa measurements in methanol-water and acetonitrile-water mixtures buffers using capillary electrophoresis. The determined ISs reference set facilitates the determination of analytes pKa and measurement of buffer pH in the range 4-11.5 (in water) for any methanol-water and acetonitrile-water composition. Secondly, to prove its feasibility, the IS-CE approach was successfully used to determine the aqueous pKa in methanol-aqueous buffer compositions up to 40% of methanol in volume. The Yasuda-Shedlovsky extrapolation method was utilized to determine seven drugs of different chemical nature with intrinsic water solubilities lower than 10−6 M. The results were successfully compared to literature ones obtained by other approaches. It is concluded then that the IS-CE methodolgy permits the measurement of aqueous pKa values using lower ratios of methanol than the classical method, becoming then more accurate in the extrapolation procedure than other reference methods. Finally, since methanol-water and acetonitrile-water mixtures are solvents of interest in liquid chromatographic separations because of their use as the mobile phase, the IS-CE method was also applied to measure the pKa of eight organic bases in methanol-water and acetonitrile-water mixtures (0-90%,v/v), which are usually used as test compounds in HPLC column evaluation. As a result of this work, the IS-CE method was proven to be a fast and simple approach for determining the pH of the buffer and the pKa of analytes in typical HPLC systems (RPLC, HILIC) in both methanol-water mixtures and acetonitrile-water mixtures. The degree of ionization of the analytes may be easily determined using them, making it easier to choose the mobile phase composition and thus enhance analytical separations. In the second part of the thesis, a new approach based on microfluidics was developed to determine the octanol-water partition. The octanol-water partition coefficient is crucial in pharmaceutical and biological sciences as it is a vital metric in predicting chemical distribution and behavior in biological systems. However, the current techniques are time consuming and requires high amounts of solvents. From the need to develop a quicker, more cost-effective, and more sustainable method, microfluidics has raised as a powerful miniaturized analytical tool. As a first step, a design with a perpendicular configuration of the channels was developed using direct 3D printed microfluidics. A gravitational perfusion system was implemented to create a spontaneous flow within the octanol and water channels without the need for external pump. The movement of octanol and water phases was successfully validated using fluorescent dyes. After that, the intensity of the fluorescent dye was used to evaluate the partition dynamics in static and dynamic conditions. The results prove that the proposed design with this microfluidic methodology allows the evaluation of molecule partition, achieving high efficiency partition and reaching the equilibrium of O/W partition faster than conventional techniques. Later, the design was adapted to a parallel configuration of the channels to be compatible with up-scalable manufacturing techniques and parallelize it for up to 56 simultaneous determinations in a single platform. Finally, both the perpendicular and parallel designs were validated using several drugs with well standardize log Po/w values that cover a wide range of lipophilicity. The microfluidic device was coupled with HPLC to determine their partition coefficients from the peak areas of the compounds in octanol and in water after partition. Good agreement with the literature values was achieved, showing the capability of microfluidic chips for precise and accurate prediction of the partition coefficient. Finally, the progress of a cost-effective and consistent method for predicting partition coefficient via microfluidic chips demonstrated a great advancement in the field of analytical chemistry, with powerful applications in drug discovery and other related fields. The results gotten from this investigation offer an establishment for additional research and advance of this approach. To summarize, estimating pKa and log Po/w values is vital in analytical chemistry, with capacity applications in drug development, material science, and environmental research. A precise estimation of these physicochemical parameters is important for predicting compound performance and distribution in diverse biological and chemical systems. The use of innovative analytical techniques for verifying pKa values, like the IS-CE method for pKa and microfluidics for measuring log Po/w, represents valuable advances in the field of analytical chemistry. These methods provide low-reagent-consumption, cost-effective, and reliable determination for evaluating these parameters, for high-throughput analysis.11 0