Functional materials synthesis by surface-supported chemistry

96 p.La química orgánica es un campo de investigación extremadamente maduro cuyos continuos avances han ido permitiendo la generación de materiales cada vez más refinados, caracterizados por fascinantes propiedades físicas y químicas. La aplicación de tales compuestos orgánicos nanoestructurados ha ido generando importantes impulsos al campo de la nanociencia. En los últimos 15 años se está desarrollando una nueva alternativa a la química convencional: la síntesis en superficies (¿on-surface synthesis¿, OSS) bajo condiciones de ultra alto vacío. Este nuevo planteamiento ha abierto nuevas puertas para la formación de nanoestructuras de carbono que no están al alcance de los métodos convencionales. Su aplicación para la síntesis de materiales orgánicos de baja dimensionalidad y con precisión atómica está mostrando un crecimiento en auge y tiene un enorme potencial para aplicaciones que incluyen nuevas tecnologías cuánticas.En esta tesis, este novedoso enfoque se aplica al crecimiento de diferentes tipos de materiales, seguido de una caracterización integral de las propiedades estructurales, químicas y electrónicas de los productos intermedios y finales. Para tal fin se ha utilizado principalmente la microscopía túnel de barrido a baja temperatura (4,3 K) en varios modos de medición, complementados con cálculos teóricos (DFT y métodos de partículas de sonda). En concreto se han estudiado los siguientes sistemas:(i) Química metal-orgánica, en la que se muestra la manera de controlar la estructura de enlace de tiolatos de oro y su estereoespecíficidad variando los parámetros de reacción en la superficie (recubrimiento y temperatura del sustrato).(ii) Química basada en pirenos. Usando moléculas de pireno funcionalizadas con alquinos, se investiga el efecto de los complejos metal-orgánicos descritos anteriormente en las reacciones de acoplamiento de alquinos. Los complejos metal-orgánicos no solo modifican el resultado de la reacción, sino que también reducen el umbral de la temperatura de activación, siendo por tanto un excelente ejemplo de síntesis en superficie de segundo orden (es decir, OSS del catalizador para dirigir nuevas reacciones de OSS). De otro lado, también se han utilizado pirenos funcionalizados con dos tipos de grupos funcionales distintos, como son los alquinos y átomos de Br. La presencia de ambos grupos funcionales permite nuevo abanico de reacciones que incluyen el tanto el acoplamiento de alquinos o el acoplamiento cruzado. El análisis de los productos resultantes y su abundancia tras tratamientos de calentamiento muestran una dominancia del acoplamiento de Glaser (acoplamiento de alquinos con pérdida de hidrógeno) como reacción inicial. Sin embargo, al utilizar un precursor no halogenado se observa una prevalencia de un acoplamiento sin pérdida de hidrógeno y una total ausencia de acoplamiento Glaser, evidenciando el papel crítico del Br en la reactividad de alquinos. Es importante destacar también que una comparación sistemática de las propiedades electrónicas de las diferentes estructuras de los productos ha permitido trazar importantes relaciones entre la estructura y las propiedades de los diversos tipos de acoplamientos entre pirenos.(iii) Química basada en aceno. Se ha estudiado la síntesis de acenos de gran tamaño, en concreto de heptaceno sobre Ag(001), a partir de precursores moleculares de tetrahidroheptaceno con y sin funcionalización adicional por átomos de Br. Se ha encontrado una variedad de productos intermedios que a menudo resultan de eventos de migración de hidrógeno. Sin embargo, el heptaceno es el producto final de los dos precursores y muestra un orbital LUMO completamente cargado. Centrándonos en los intermedios, se observa cómo dos átomos de carbono con hibridación sp3 en el segundo anillo de dihidroheptaceno son suficientes para causar el auto-desacoplamiento electrónico de la molécula y el sustrato. Se han investigado asimismo las señales magnéticas, evidenciadas en resonancias Kondo, asociadas a determinados escenarios de carga. Finalmente, utilizando precursores basados en acenos se ha explorado el impacto del sustrato en las reacciones de acoplamiento. En concreto se han utilizado superficies de Au(111) y Au(110), así como precursores de antraceno funcionalizados con halógenos y metilos. Sobre Au(111), una superficie atómicamente plana, se encuentran cinco tipos de productos covalentes, siendo el starphene con simetría de eje ternario el producto dominante. Por contra, sobre la superficie reconstruida de Au(110) 2×1, su simetría uniaxial promueve la formación de polímeros lineales no benzenoides.Esta tesis contribuye al campo de la ciencia de superficies, mostrando la posibilidad de sintetizar una variedad de nanomateriales novedosos basados en carbono mediante la síntesis en superficie, así como mediante la caracterización detallada sus propiedades. La comprensión de las propiedades físico-químicas de estos materiales avanzados es un paso de gran relevancia hacia sus futuras aplicaciones.The mature research field of conventional solution-based chemistry has allowed for a continuous generation of increasingly refined materials with amazing physical and chemical properties. This has contributed to great advances in the field of organic nanomaterials. The development of the recently revealed surface-supported synthesis under ultrahigh vacuum conditions has opened new doors for the formation of defect-free low-dimensional carbon nanostructures that are not achievable by conventional means. This new field, typically termed on-surface synthesis (OSS), is lately showing a booming growth that resonates with almost all the requirements for promising quantum size materials with tunable physicochemical properties.In this thesis, this novel approach is applied for the growth of a variety of materials, followed by a comprehensive characterization of the structural, chemical and electronic properties of the intermediates and end-products. This is achieved mainly by scanning tunneling microscopy operating at low temperature (4.3 K) in various measurement modes, assisted by theoretical calculations (DFT and probe particle methods). In particular, the following systems have been studied:(i) Metal-organic chemistry, in which the stereospecific coupling motif of gold thiolates is found to be controllable by varying the on-surface reaction parameters (i.e. coverage and substrate temperature).(ii) Pyrene-based chemistry. With alkyne-functionalized pyrene molecules, the impact of the presence of metal-organic complexes on alkyne coupling reactions is investigated. The complexes do not only modify the reaction outcome, but also reduce its activation temperature threshold, becoming an excellent example of second-order on-surface synthesis (i.e. OSS of catalyst to steer following OSS reactions). Secondly, pyrenes are used that are functionalized with alkynes and also Br atoms, allowing for alkyne homo- and cross-coupling reactions. The resulting products and their relative abundance are explored thoroughly after different annealing steps, revealing a dominant Glaser-coupling product upon heating. The absence of the latter when using non-halogenated precursor evidenced the role of Br in this coupling reaction. Importantly, a systematic comparison of the electronic properties of the different product structures has allowed drawing important structure-property relations with regard to the various inter-pyrene coupling motifs.(iii) Acene-based chemistry. The synthesis of higher acenes is studied, in particular heptacene on Ag(001), starting from tetrahydroheptacene molecular precursors with and without additional functionalization by Br atoms. A variety of stable reaction intermediates is found, often resulting from hydrogen migration events. However, heptacene is the end-product from the two precursors and displays a fully charged LUMO orbital. Focusing on the intermediates, two sp3-hybridized carbon atoms present at the second ring of dihydroheptacene are shown as sufficient self-decoupling factors. Magnetic Kondo fingerprints associated to specific charging scenarios are investigated. Finally, the impact of the surface structure on coupling reactions with acene-based precursors is then explored. More specifically, Au(111) and Au(110) surfaces, as well as anthracene precursors functionalized with halogen and methyls are used with this aim. On Au(111), the atomically flat surface, five covalent coupling motifs are found, with the 3-fold symmetric starphene showing the highest occurrence upon annealing. In contrast, on Au(110), being a 2×1 reconstructed surface, the uniaxial symmetry of the surface promotes the formation of mainly linear non-benzenoid polymers along the grooves of this substrate.This thesis contributes to the surface science field by showing the possibility to synthesize a variety of novel carbon-based nanomaterials using on-surface synthesis methods. The second main contribution is the detailed characterization of the produced materials using surface-sensitive techniques assisted by theoretical calculations. A deep understanding of the physicochemical properties of these materials is a crucial step forward towards their ultimately progressing applications.CFM; CSI

Functional materials synthesis by surface-supported chemistry

96 p.La química orgánica es un campo de investigación extremadamente maduro cuyos continuos avances han ido permitiendo la generación de materiales cada vez más refinados, caracterizados por fascinantes propiedades físicas y químicas. La aplicación de tales compuestos orgánicos nanoestructurados ha ido generando importantes impulsos al campo de la nanociencia. En los últimos 15 años se está desarrollando una nueva alternativa a la química convencional: la síntesis en superficies (¿on-surface synthesis¿, OSS) bajo condiciones de ultra alto vacío. Este nuevo planteamiento ha abierto nuevas puertas para la formación de nanoestructuras de carbono que no están al alcance de los métodos convencionales. Su aplicación para la síntesis de materiales orgánicos de baja dimensionalidad y con precisión atómica está mostrando un crecimiento en auge y tiene un enorme potencial para aplicaciones que incluyen nuevas tecnologías cuánticas.En esta tesis, este novedoso enfoque se aplica al crecimiento de diferentes tipos de materiales, seguido de una caracterización integral de las propiedades estructurales, químicas y electrónicas de los productos intermedios y finales. Para tal fin se ha utilizado principalmente la microscopía túnel de barrido a baja temperatura (4,3 K) en varios modos de medición, complementados con cálculos teóricos (DFT y métodos de partículas de sonda). En concreto se han estudiado los siguientes sistemas:(i) Química metal-orgánica, en la que se muestra la manera de controlar la estructura de enlace de tiolatos de oro y su estereoespecíficidad variando los parámetros de reacción en la superficie (recubrimiento y temperatura del sustrato).(ii) Química basada en pirenos. Usando moléculas de pireno funcionalizadas con alquinos, se investiga el efecto de los complejos metal-orgánicos descritos anteriormente en las reacciones de acoplamiento de alquinos. Los complejos metal-orgánicos no solo modifican el resultado de la reacción, sino que también reducen el umbral de la temperatura de activación, siendo por tanto un excelente ejemplo de síntesis en superficie de segundo orden (es decir, OSS del catalizador para dirigir nuevas reacciones de OSS). De otro lado, también se han utilizado pirenos funcionalizados con dos tipos de grupos funcionales distintos, como son los alquinos y átomos de Br. La presencia de ambos grupos funcionales permite nuevo abanico de reacciones que incluyen el tanto el acoplamiento de alquinos o el acoplamiento cruzado. El análisis de los productos resultantes y su abundancia tras tratamientos de calentamiento muestran una dominancia del acoplamiento de Glaser (acoplamiento de alquinos con pérdida de hidrógeno) como reacción inicial. Sin embargo, al utilizar un precursor no halogenado se observa una prevalencia de un acoplamiento sin pérdida de hidrógeno y una total ausencia de acoplamiento Glaser, evidenciando el papel crítico del Br en la reactividad de alquinos. Es importante destacar también que una comparación sistemática de las propiedades electrónicas de las diferentes estructuras de los productos ha permitido trazar importantes relaciones entre la estructura y las propiedades de los diversos tipos de acoplamientos entre pirenos.(iii) Química basada en aceno. Se ha estudiado la síntesis de acenos de gran tamaño, en concreto de heptaceno sobre Ag(001), a partir de precursores moleculares de tetrahidroheptaceno con y sin funcionalización adicional por átomos de Br. Se ha encontrado una variedad de productos intermedios que a menudo resultan de eventos de migración de hidrógeno. Sin embargo, el heptaceno es el producto final de los dos precursores y muestra un orbital LUMO completamente cargado. Centrándonos en los intermedios, se observa cómo dos átomos de carbono con hibridación sp3 en el segundo anillo de dihidroheptaceno son suficientes para causar el auto-desacoplamiento electrónico de la molécula y el sustrato. Se han investigado asimismo las señales magnéticas, evidenciadas en resonancias Kondo, asociadas a determinados escenarios de carga. Finalmente, utilizando precursores basados en acenos se ha explorado el impacto del sustrato en las reacciones de acoplamiento. En concreto se han utilizado superficies de Au(111) y Au(110), así como precursores de antraceno funcionalizados con halógenos y metilos. Sobre Au(111), una superficie atómicamente plana, se encuentran cinco tipos de productos covalentes, siendo el starphene con simetría de eje ternario el producto dominante. Por contra, sobre la superficie reconstruida de Au(110) 2×1, su simetría uniaxial promueve la formación de polímeros lineales no benzenoides.Esta tesis contribuye al campo de la ciencia de superficies, mostrando la posibilidad de sintetizar una variedad de nanomateriales novedosos basados en carbono mediante la síntesis en superficie, así como mediante la caracterización detallada sus propiedades. La comprensión de las propiedades físico-químicas de estos materiales avanzados es un paso de gran relevancia hacia sus futuras aplicaciones.The mature research field of conventional solution-based chemistry has allowed for a continuous generation of increasingly refined materials with amazing physical and chemical properties. This has contributed to great advances in the field of organic nanomaterials. The development of the recently revealed surface-supported synthesis under ultrahigh vacuum conditions has opened new doors for the formation of defect-free low-dimensional carbon nanostructures that are not achievable by conventional means. This new field, typically termed on-surface synthesis (OSS), is lately showing a booming growth that resonates with almost all the requirements for promising quantum size materials with tunable physicochemical properties.In this thesis, this novel approach is applied for the growth of a variety of materials, followed by a comprehensive characterization of the structural, chemical and electronic properties of the intermediates and end-products. This is achieved mainly by scanning tunneling microscopy operating at low temperature (4.3 K) in various measurement modes, assisted by theoretical calculations (DFT and probe particle methods). In particular, the following systems have been studied:(i) Metal-organic chemistry, in which the stereospecific coupling motif of gold thiolates is found to be controllable by varying the on-surface reaction parameters (i.e. coverage and substrate temperature).(ii) Pyrene-based chemistry. With alkyne-functionalized pyrene molecules, the impact of the presence of metal-organic complexes on alkyne coupling reactions is investigated. The complexes do not only modify the reaction outcome, but also reduce its activation temperature threshold, becoming an excellent example of second-order on-surface synthesis (i.e. OSS of catalyst to steer following OSS reactions). Secondly, pyrenes are used that are functionalized with alkynes and also Br atoms, allowing for alkyne homo- and cross-coupling reactions. The resulting products and their relative abundance are explored thoroughly after different annealing steps, revealing a dominant Glaser-coupling product upon heating. The absence of the latter when using non-halogenated precursor evidenced the role of Br in this coupling reaction. Importantly, a systematic comparison of the electronic properties of the different product structures has allowed drawing important structure-property relations with regard to the various inter-pyrene coupling motifs.(iii) Acene-based chemistry. The synthesis of higher acenes is studied, in particular heptacene on Ag(001), starting from tetrahydroheptacene molecular precursors with and without additional functionalization by Br atoms. A variety of stable reaction intermediates is found, often resulting from hydrogen migration events. However, heptacene is the end-product from the two precursors and displays a fully charged LUMO orbital. Focusing on the intermediates, two sp3-hybridized carbon atoms present at the second ring of dihydroheptacene are shown as sufficient self-decoupling factors. Magnetic Kondo fingerprints associated to specific charging scenarios are investigated. Finally, the impact of the surface structure on coupling reactions with acene-based precursors is then explored. More specifically, Au(111) and Au(110) surfaces, as well as anthracene precursors functionalized with halogen and methyls are used with this aim. On Au(111), the atomically flat surface, five covalent coupling motifs are found, with the 3-fold symmetric starphene showing the highest occurrence upon annealing. In contrast, on Au(110), being a 2×1 reconstructed surface, the uniaxial symmetry of the surface promotes the formation of mainly linear non-benzenoid polymers along the grooves of this substrate.This thesis contributes to the surface science field by showing the possibility to synthesize a variety of novel carbon-based nanomaterials using on-surface synthesis methods. The second main contribution is the detailed characterization of the produced materials using surface-sensitive techniques assisted by theoretical calculations. A deep understanding of the physicochemical properties of these materials is a crucial step forward towards their ultimately progressing applications.CFM; CSI

On Cohomology Groups of Four-Dimensional Nilpotent Associative Algebras

تعد دراسة الزمر الكوهومولوجية واحدة من أكثر البحوث المكثفة والمثيرة  والتي قد  نشأت من التبولوجيا الجبرية. حيث يعتبرالبعد للزمر الكوهومولوجية على وجه الخصوص ثابت في غاية الفائدة ويلعب دورآ هامآ في التصنيف الهندسي للجبر التجميعي. هذا العمل يركز على تطبيقات الزمر الكوهومولوجية ذات الابعاد المنخفضة. في هذا الخصوص, الزمر الكوهومولوجية المنخفضة للجبر التجميعي عديم القوى ذات البعد الرابع تم وصفهاعلى شكل مصفوفة.The study of cohomology groups is one of the most intensive and exciting researches that arises from algebraic topology. Particularly, the dimension of cohomology groups is a highly useful invariant which plays a rigorous role in the geometric classification of associative algebras. This work focuses on the applications of low dimensional cohomology groups. In this regards, the cohomology groups of degree zero and degree one of nilpotent associative algebras in dimension four are described in matrix form

Numerical solution for the time-Fractional Diffusion-wave Equations by using Sinc-Legendre Collocation Method

In this paper the numerical solution of fractional diffusion wave equation is proposed. The fractional derivative will be in the Caputo sense. The proposed method will be based on shifted Legendre collocation scheme and sinc function approximation for time and space respectively. The problem is reduced to the problem into a system of algebraic equations after implementing this method. For demonstrating the validity and applicability of the proposed numerical scheme some examples are presented. Keywords: Fractional diffusion equation, Sinc functions, shifted Legendre  polynomials, Collocation method

Antimalarial Activity of Certain Sudanese Medicinal Plants Used in Folk –Medicine

Ten indigenous plants of common use in Sudanese folk-medicine, vitro for antimalarial activity against Plasmoclium were examined in falciparum, the major human malaria parasite. All plant samples displayed various antimalarial activity. Three plant extracts caused 100% inhibition of the parasite growth at a concentration ≤ 500 g/ml. The most active extracts that produced 100% inhibition of the parasite growth at a concentration ≤ 50 g/ml were obtained from the seeds of Nigella sativa and the whole plant of Aristolochia bracteolata. These two plants were phytochemically screened for their active constituents and both showed the presence of sterols, alkaloids and tannins

A Business Processes Reference Model for Course Document Management for Supporting Accreditation

A reference model is a fundamental starting point for the development of new information systems. Reference models are also called universal models, generic models, or model patterns. In order to obtain a higher learning programme accreditation, most of the educational institutions such as private and public universities have to clearly demonstrate that the programmes offered by them meet the quality standards established by the accreditation body. However, there is no complete and effective reference model for the business process of managing courses' document in order to support accreditation. Therefore, this master's thesis is an attempting to design a reference model, which will be as a general reference model for the business processes of managing document of courses in higher educational institutions and universities in order to obtain accreditation. As the processes to obtain the accreditation is almost similar in most universities and higher educational institutions around world, this study tries to design general business processes reference model to these process that can be as a reference for any education institutions to model its own model since the specific model is a partial model of the reference model. Moreover based on this reference model, the requirements model for Universiti Utara Malaysia (UUM)was designed and implemented as web-based system for Courses' document management supporting Accreditation. In addition to this, the purposed reference model covers all processes that are used in most universities and higher educational institutions to store, retrieve and organise the information of the courses. The methodology of this study is the general design research methodology that contained; awareness of problem, suggestion, development, evaluation, and conclusion. To evaluate the system that was designed and implemented based on the reference model, two methods was used. The first one is black box testing to ensure that the functionality specified in the requirement specification works. The other method is the questionnaire to evaluate the usability of the systems in terms of usefulness. The summary of evaluation results emphasises that this system provides an enhancement and improvement to the performance of the users to accomplish their tasks, and enables the users to complete their tasks quickly

Novel use of ear sockets as points of traction in partial foetotomy in Bunaji cows

Dystocia was managed in 4½-, 3- and 3½-year-old Bunaji and Bunaji-Friesian cross cows at the University farm, a Fulani camp and an Institutional farm, respectively. Clinical examination showed normal vital parameters, straining, well relaxed perineum, oedematous vulva, fully engorged mammary glands and extended foetal fore-limbs. Vaginal exploration revealed fully relaxed cervices, dead foetuses in anterior longitudinal presentation and dorso-sacral positions. The necks and heads were flexed laterally and dorsally. Dystocia of foetal causes due to postural abnormalities (lateral and dorsal flexion of the neck) were diagnosed. Amputations of fore-limbs of the foetuses at the point of the shoulders using ThygesenM® foetotome and obstetrical wire were done. A crutch-repeller placed between the neck and the stump of shoulder of the amputated fore-limb was then used to repel the foetuses into the uteri to achieve extension of the neck. Extension of the flexed necks and heads was achieved by the use of three-point traction on the heads and repulsion concurrently. Traction was used to deliver the dead foetuses while guarding the points of amputation in the birth canals. It was concluded that the ear socket can be used as a new point of traction along with or in place of the eye socket in partial foetotomy for relieving dystocia with non-viable foetus in Bunaji cows.Keywords: Bunaji cow, Dystocia, Ear, Foetotomy, Obstetrical-wire, Tractio

Transferring Axial Molecular Chirality Through a Sequence of On-Surface Reactions

Fine management of chiral processes on solid surfaces has progressed over the years, yet still faces the need for the controlled and selective production of advanced chiral materials. Here, we report on the use of enantiomerically enriched molecular building blocks to demonstrate the transmission of their intrinsic chirality along a sequence of on-surface reactions. Triggered by thermal annealing, the on-surface reac-tions induced in this experiment involve firstly the coupling of the chiral reactants into chiral polymers and subsequently their transformation into planar prochiral graphene nanoribbons. Our study reveals that the axial chirality of the reactant is not only transferred to the polymers, but also to the planar chirality of the graphene nanoribbon end products. Such chirality transfer consequently allows, starting from ad-equate enantioenriched reactants, for the controlled production of chiral and prochiral organic nanoarchi-tectures with pre-defined handedness

New connection formulae for the q-orthogonal polynomials via a series expansion of the q-exponential

Using a realization of the q-exponential function as an infinite multiplicative sereis of the ordinary exponential functions we obtain new nonlinear connection formulae of the q-orthogonal polynomials such as q-Hermite, q-Laguerre and q-Gegenbauer polynomials in terms of their respective classical analogs.Comment: 14 page