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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Neutron scattering studies of water in biomolecules and biomaterials

Chan, Lok January 2012 (has links)
It is increasingly important to identify the nature of the interfacial water in biology in order to explain how biological functions and systems work. It is not simply a matter of which biomolecules are present in a cell, but also of how these biomolecules interact with one another. This body of work uses neutron scattering techniques to explain the nature of the vibrational dynamics of water interacting with biomolecules and systems that mimic the biological molecular crowding environment of a cell. Recent work in science has seen the synthesis of periodic mesoporous organosilicas with organic groups attached. In the first paper in this thesis, the use of one of these materials is highlighted to look at confined water, equivalent to the water found in a crowded cellular environment. Here it is shown that the properties of the water within the pores and water molecules around the surface were shown to be different and then identified as interfacial and bulk water respectively. In order to develop the investigation of interfacial water with biological matter, it seemed appropriate to start with the most basic molecules, amino acids. The second paper presents a complete survey of the 20 biologically important amino acids using one of the world's highest resolution neutron scattering spectrometer (TOSCA at ISIS, Rutherford Appleton Laboratory). Computer simulation of the experimental work through molecular dynamics, allows many vibrational modes to be assigned for the first time and correlated with the broader vibrational peaks previously observed for proteins. Comparison of the dry states with the hydrated states of amino acids, gives some insight into the sites within the amino acid side chains where water molecules are likely to bind. For serine this is the hydroxyl group in the side chain. The third paper focuses on IINS data of serine in more detail and discusses several low energy vibrational modes that have been assigned and for the first time, shows how the presence of water molecules changes the dynamic behaviour of librational and torsional modes differently. The combination of these studies allows a clearer picture of how water in biology interacts with biomolecules and of the importance of water to our existence.
252

Structure and connectivity of water molecules at the interfaces of nanoconfined systems / Structure et connectivité de molécules d’eau aux interfaces de systèmesnanoconfinants

Dalla bernardina, Simona 17 November 2015 (has links)
La compréhension des mécanismes d’absorption de l’eau, ainsi que l’arrangement moléculaire adopté par le réseau de molécules d’eau lors du confinement à l’échelle nanométrique, est crucial que ce soit pour l’optimisation de plusieurs applications, telles que la production d’énergie propre, la purification et le dessalement de l’eau, ou pour élucider certains processus complexes qui ont lieu dans les systèmes biologiques. Dans le cadre de cette thèse, l’hydratation contrôlée de trois systèmes poreux modèles suivie par spectroscopie infrarouge montre les effets de la nature des surfaces et des limitations stériques qui, en altérant les liaisons hydrogène établies entre les molécules d’eau, déclenche la formation de réseaux atypiques. La brillance de la source de rayonnement synchrotron infrarouge, exploitée par la ligne de lumière AILES au sein du synchrotron SOLEIL, a permis l’étude d’échantillons très absorbants en permettant de mettre en évidence la faible contribution de monocouches de molécules d’eau voire même de chaînes linéaires. L'effet d'une surface hydrophile sur la structure, la densité et la dynamique des molécules d'eau à l'interface a été étudié en mesurant l’absorbance d’une lamelle de Vycor poreux (pores d’environ 5 nm) à l’équilibre avec une pression de vapeur d'eau donnant lieu à la formation d’un réseau d’eau bi-dimensionnel. Les interactions fortes entre l’eau interfaciale et la surface hydrophile provoquent plusieurs transitions structurales du réseau d’eau expliquant ainsi les observations par d’autres techniques. Des similitudes et des différences surprenantes ont été observés entre l’hydratation d’une surface hydrophile et celle d’un système hydrophobe dans des conditions de confinement extrême : les nanotubes de carbone à paroi unique (SWCNTs) ayant un diamètre de quelques Angstrom. Nos mesures ont montré que l’établissement d’un réseau de molécules d’eau unique peut être à l’origine du déplacement rapide des molécules d’eau à l’intérieur des nanotubes de carbone. Enfin, l’étude des mécanismes d’adsorption de la membrane Nafion, membrane modèle dans les piles à combustible à membrane échangeuse de protons (PEMFCs), a permis de clarifier les processus en jeu lors de l’ionisation et la formation d’espèces protonique responsable de la remarquable conductivité ionique propre à cette famille de membranes.Cette méthodologie pourra être étendue à des systèmes plus complexes, tels que les réseaux de molécules d’eau dans les systèmes biologiques. / Understanding the water absorption mechanisms, and the molecular arrangement adopted by the water molecules upon confinement at the nanoscale is crucial both for technological applications, such as clean energy production, purification and desalination of water, and to unveil some of the complex processes occurring in biological systems.In this thesis, the controlled hydration of three porous model systems monitored by infrared spectroscopy shows the effects of surfaces forces and steric limitations that triggers the formation atypical networks by altering the hydrogen bonds established between water molecules. The brightness of the infrared synchrotron radiation source on the AILES beamline at synchrotron SOLEIL allowed to highlight the low contribution coming from water molecules arranged as monolayer or linear chains in highly infrared absorbent matrices. The effect of a hydrophilic surface on structure, density and dynamic of water molecules at interfaces was examined by measuring the absorbance of a porous Vycor slab (pores of about 5 nm) at equilibrium with the water vapor pressure needed to obtain a two-dimensional water network. The strong interfacial interactions between water and the hydrophilic surface cause several structural transitions on the water network elucidating the observations made by other techniques. Surprising similarities and differences are observed between the hydration of a hydrophilic surface and that of a hydrophobic system under extreme confinement: single-wall carbon nanotubes (SWCNTs) having a diameter of several Angstroms. Our measurements have shown that the arrangement of a peculiar water network may be the origin of the enhanced water flux in carbon nanotubes. Finally, the study of the adsorption mechanisms of the Nafion membrane, the benchmark electrolyte in proton exchange membrane fuel cells (PEMFCs), has shed new light on the processes involved in the ionization and the formation of protonic species, accountable for the remarkable ionic conductivity typical of these membranes.This approach may be also extended to more complex systems, such as water molecules networks in biological systems.
253

SumaqKay / SumaqKay

Díaz Chamorro, Roraima Lucia, Muriel Garriazo, Solanghe Alejandra Yovanna, Pacheco Huaringa, Alexsandra Margarita, Pairazamán Romero, Luis Ángel, Rodríguez Quispe, Angela Cristina 21 July 2020 (has links)
El mercado de cosmética e higiene personal ha tenido un crecimiento significativo en los últimos años en el país, esto debido a la demanda por productos como cosméticos, perfumes, maquillaje, preparaciones para la piel y geles capilares. Dichos productos son adquiridos principalmente por la población femenina, por lo que el segmento determinado son mujeres del NSE A y B que residen en Lima Metropolitana y que tienen preferencia por la compra vía online. Dentro del grupo de las preparaciones de la piel, se encuentran las cremas faciales, las cuales tienen diferentes composiciones y propiedades para la piel. No obstante, una de las controversias que gira en torno a estos tipos de productos es en base a la composición de estos, ya que existen marcas en el mercado que emplean elementos químicos, los cuales al usarse constantemente pueden, a largo plazo, generar problemas a la piel. Ante esto, se ha realizado el presente proyecto, el cual se basa en la comercialización de una crema facial limpiadora e hidratante a base de insumos naturales, entre ellos se destacan los vegetales como el espárrago y la espinaca, el aceite esencial de sándalo y el extracto de yogurt. Esta propuesta de cosmética natural brinda muchas propiedades beneficiosas para la piel, asimismo, genera un nivel de confianza y seguridad a los clientes al ser en base a insumos naturales. El modelo de negocio propuesto es atractivo, debido a que tiene una relación estrecha con la tendencia de lo natural, la cual es una de las tendencias que ha tenido un mayor impacto en los últimos años en la sociedad, asimismo, porque se ha identificado, durante la investigación realizada durante el proyecto, que existe una demanda insatisfecha por este tipo de productos en el rubro de la cosmética. / The cosmetics and personal hygiene market has had significant growth in recent years in the country, this due to the demand for products such as cosmetics, perfumes, makeup, skin preparations and hair gels. Said products are acquired mainly by the female population, so the specific segment is women from the NSE A and B who reside in Metropolitan Lima and who have a preference for online shopping. Within the group of skin preparations, are facial creams, which have different compositions and properties for the skin. However, one of the controversies that revolves around these types of products is based on their composition, since there are brands on the market that use chemical elements, which when used constantly can, in the long term, generate problems to the skin. Given this, the present project has been carried out, which is based on the commercialization of a cleansing and moisturizing facial cream based on natural inputs, including vegetables such as asparagus and spinach, sandalwood essential oil and yogurt extract. This proposal of natural cosmetics provides many beneficial properties for the skin, and also generates a level of confidence and security for customers, based on natural inputs. The proposed business model is attractive, because it has a close relationship with the natural trend, which is one of the trends that has had the greatest impact on society in recent years, also because it has been identified, during the research carried out during the project, there is an unmet demand for this type of product in the cosmetics sector." / Trabajo de investigación
254

Studium budičů anhydritových maltovin / Study of Exciters of Anhydrite Binders

Duda, Štěpán January 2018 (has links)
Presented diploma thesis is dealing with study of exciters of anhydrite binders. Theoretical part is dedicated to study of available domestic and foreign literature on a given topic. Attention is also paid to the study of the current research at the institute of THD. In the experimental part is developed a proposal of potential exciters of hydration on the basis of literature and according to the results of the research at the institute of THD. Next is proposed the methodological concept of the work. Testing of the monitored technological features follows. The study of the hydration process was recorded using XRD analysis and thermal analysis. Evaluation of the results was implemented by the mutual comparing of prepared recipes.
255

Studium vlastností synteticky připraveného thaumasitu / Study of the properties of thaumasite which was produced synthetically

Kábrtová, Denisa January 2018 (has links)
The thesis is focused on the optimization of the thaumasite preparation in the way of ternesite hydration and further comparison of this approach to the other methods. The thaumasite was prepared by three different methods for this purpose - according to Aguilera et al., Purnell and the hydration method of ternesite clinkers. Finally, the X-ray diffraction analysis was particularly used to evaluate the obtained properties and results.
256

Betonová konstrukce spodní stavby administrativního objektu / Concrete substructure of the administrative building

Neuschl, Marcel January 2019 (has links)
The theme of this diploma thesis is the design and assessment of a part of the underground load-bearing structure of the administrative center according to the source material. Emphasis is placed on the design, taking into account the waterproofness of the construction, the so-called white tank. This is ensured by the correct design of the concrete construction of the foundation slab and walls, taking into account the constructional details of the day and expansion joints, the concrete composition and the construction process.
257

Příprava modifikovaných trikalciumaluminátových fází a studium jejich hydratačních procesů / Preparation of modified tricalcium aluminate phases and study of their hydratation processes

Vávrová, Alžběta January 2019 (has links)
This diploma thesis deals with the preparation of modified tricalcium aluminate phases using sodium ions, and the study of their hydration processes and products. The X-ray diffraction analysis, isothermal calorimetry, laser diffraction, and scanning electron microscopy with energy dispersion analysis were used to solve this task. The preparation of modified tricalcium aluminate phases using high temperature methods has been described in the experimental section. Furthermore, the X-ray diffraction analysis was used to determine the purity of the prepared phases and the scanning electron microscopy with energy dispersion analysis was used to define the volume of sodium. Laser diffraction was used to measure a particle size distribution in the individual phases. Subsequently, hydration of the pure phases was performed in an isothermal calorimeter. It was followed by hydration of phases in the presence of different gypsum content and then in the presence of saturated portlandite solution. Hydration of some samples was stopped in order to better understand the hydration process. Hydration products were studied by X-ray diffraction analysis. The obtained results were compared with each other and the influence of sodium ions on both the structure of the prepared phases and the course of hydration and its products has been discussed. The effect of adding different volumes of gypsum and portlandite on the course of hydration of the individual phases was also compared.
258

Studium provzdušňovacích přísad v alkalicky aktivovaných materiálech / Study of air-entraining admixtures in alkali-activated materials

Kiripolský, Tomáš January 2020 (has links)
Air entraining admixtures are surfactants, that are commonly used in Portland cement materials, because they form and stabilize small air bubbles distributed in the binder, thereby changing the pore size distribution. The aim of these additives is to increase the durability of the cured binder, especially in climatic conditions, where it must withstand low temperatures, and simultaneously improving the workability in the plastic state. The effect of air entraining admixtures in alkali-activated slag was studied for certain properties. Air entraining admixtures were able to entrain the air in the alkali-activated matrix, they changed the pore size distribution, which resulted in a reduction in capillary pressure in the porous complex, and there was a reduction of shrinkage under autogenous conditions, respectively. The improvement of workability is certainly also positive, but on the other hand there has been a bad effect on flexural strength and compressive strength. The morphology of the air entrained binder was observed by scanning electron microscopy, and simultaneously the effect of air entrained admixtures on hydration was observed by isothermal calorimetry.
259

Tření a mazání kloubní chrupavky / Friction and lubrication of articular cartilage

Hilšer, Pavel January 2020 (has links)
The main goal of this diploma thesis is to determine the role of hyaluron acid and phospholipids on friction and lubrication of articular cartilage in regard to optimization of viscosupplements. This is carried out by measuring the coefficient of friction of the articular cartilage with several lubricants. Cartilage is lubricated particularly by a conventional viscosuplement, optimized viscosuplementation with phospholipids and model synovial fluid. In order to observe the function of those viscosuplements in the human body, both are mixed with the model synovial fluid, ubiquitous in human joints, in given ratio. Experiments revealed high friction when it comes to convectional viscosupplementation as opposed to low friction of the optimized viscosuplement with phospholipids. The same situation occurs when cartilage is lubricated with those viscosuplements mixed with model synovial fluid which might lead to development of a new, better, viscosupplementation based on hyaluron acid and phospholipids.
260

Studium hydratace RPC (Reactive Powder Concretes) v hydrotermálních podmínkách / The study of hydration of RPC (Reactive Powder Concretes) in hydrothermal condition

Dvořáková, Tereza January 2020 (has links)
The diploma thesis deals with the study of hydration of reactive powder concrete under hydrotermal conditions. The theoretical part describes the properties of materials and additives used for the preparation of mixtures. The following describes the principles and requiments for the materials for preparing the reactive powder concrete. The practical part is studied design method mix and the impact of materials to the consistency of paste. The effect of cample placement on flexural and compressive strength of the prepared mixtures was observed. The samples were stored under standart laboratory conditions and under hydrothermal conditions. The phase composition of the samples was monitored by X-ray diffraction analysis and the mocrostructure by scanning electron microscopy.

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