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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.
191

5-Aminolevulinic acid and derivatives thereof : properties, lipid permeability and enzymatic reactions

Erdtman, Edvin January 2010 (has links)
5-aminolevulinic acid (5-ALA) and derivatives thereof are widely usedprodrugs in treatment of pre-malignant skin diseases of the cancer treatmentmethod photodynamic therapy (PDT). The target molecule in 5-ALAPDTis protoporphyrin IX (PpIX), which is synthesized endogenously from5-ALA via the heme pathway in the cell. This thesis is focused on 5-ALA,which is studied in different perspectives and with a variety of computationalmethods. The structural and energetic properties of 5-ALA, itsmethyl-, ethyl- and hexyl esters, four different 5-ALA enols, and hydrated5-ALA have been investigated using Quantum Mechanical (QM) first principlesdensity functional theory (DFT) calculations. 5-ALA is found to bemore stable than its isomers and the hydrolysations of the esters are morespontaneous for longer 5-ALA ester chains than shorter. The keto-enoltautomerization mechanism of 5-ALA has been studied, and a self-catalysismechanism has been proposed to be the most probable. Molecular Dynamics(MD) simulations of a lipid bilayer have been performed to study themembrane permeability of 5-ALA and its esters. The methyl ester of 5-ALAwas found to have the highest permeability constant (PMe-5-ALA = 52.8 cm/s).The mechanism of the two heme pathway enzymes; Porphobilinogen synthase(PBGS) and Uroporphyrinogen III decarboxylase (UROD), have beenstudied by DFT calculations and QM/MM methodology. The rate-limitingstep is found to have a barrier of 19.4 kcal/mol for PBGS and 13.7kcal/mol for the first decarboxylation step in UROD. Generally, the resultsare in good agreement with experimental results available to date.
192

Naturvetenskap och estetik i förskolan : fysikaliska förändringar och upptäckande av vätskor med barn i förskolan / Natural science and aesthetics in pre-school : physical changes and detection of fluids with children in pre-school

Holm, Sandra, Jönsson Ahlbin, Mimmie January 2020 (has links)
Det här examensarbetet fokuserar på hur man kan kombinera två innehållsaspekter i undervisning med barn i förskolan. Innehållet som bearbetas är naturvetenskap och estetik. Naturvetenskapsdelen i arbetet innefattar kemiska reaktioner och den estetiska delen innefattar drama. Dramat kommer att användas som ett verktyg för att lära om naturvetenskap med fokus på kemiska reaktioner. Studiens insamlingsmetod innefattar filmning och ljudinspelning. Resultatet i studien visar att barnens perspektiv blir synligt genom att barnen får berätta sina tankar om kemiska vätskor. Studiens resultat visar även att ett intresse har väckts bland barnen kring kemiska vätskor och detta lägger en grund för förskollärare att arbeta vidare med och utgå från barnens intresse.
193

Visualization, modeling and consequences of residual stresses in glass frit sealing of a UV light source

Hurtigh Grabe, Vilma January 2023 (has links)
PureFize Technologies AB develops and manufactures a broadband ultraviolet (UVC) light technology device that is mercury-free and based on nanotechnology, using the principle of field emission. The light source is made of Ti and glass, which are hermetically bonded, using a low-temperature glass frit, at elevated temperatures. The bonding procedure will induce stresses in the device originating from the mismatch of the coefficient of thermal expansion (CTE) between the materials. Brittle materials, as glass, withstands tensile stresses poorly. Therefore, the stress magnitude and distribution needs to be understood.  This work develops a quality inspection method for the glass bond and internal stresses, as well as stress simulations of the device, to be used in production at the company. The glass bond width and the internal stresses in the device were classified and analyzed by light optical microscopy and by polarised light optical microscopy. The optical analysis was followed by pressure tests of the devices using a chamber that allowed for pressurized air up to 7 bar. In parallell with the experimental work, stress and deformation simulations of the device using the finite element method (FEM) was made. Data collected from the inspections and pressure tests were compiled and analyzed, showing clear connections between the glass bond quality and the device's ability to withstand external pressure. A narrow glass bond could withstand external pressure poorly, whereas a wide glass bond could withstand external pressure well. Correlations could be made both between the glass bond appearance and the stress patterns, as well as between the FEM simulations and the stress patterns in the device. It is clear that the stresses induced in the device after bonding originates from the CTE mismatch of the bonded components when cooling it from the bonding temperature to room temperature. The pressure testing method proved to be an efficient way of verifying the maximum pressure capacity of the devices.  The knowledge from this thesis can be used when further investigating induced stresses from glas frit bonding.
194

The Binding Mechanism of Carbapenems in the Class A beta-lactamase IMI-1 : A Molecular Dynamics Study of Ligand Stability

Lindahl, Isabell January 2022 (has links)
Antibiotic resistance is a global and accelerating matter. Over time, the bacteria have evolved several defense mechanisms against the antibiotics. One of the defense mechanisms is that the bacteria can produce enzymes with the ability to hydrolyze the characteristic b-lactam ring of the antibiotics. These enzymes are called b-lactamases. There are three different generations of antibiotics clinically available, and b-lactamases have co-evolved with the antibiotics over the generations. The third generation of antibiotics are called the carbapenems and b-lactamases which hydrolyze carbapenems are called carbapenemases. Carbapenemases are promiscuous, which means that they hydrolyze a variety of antibiotics. The b-lactamase IMI-1 is an imipenem-hydrolyzing enzyme and imipenem is a carbapenem, hence IMI-1 is a carbapenemase. In this project, IMI-1 was investigated in complex with the carbapenems imipenem, meropenem and biapenem using computational methods. More specifically, a homology model of IMI-1 was generated and the carbapenems were docked into the model. The system was then used for MD simulations where the important molecular interactions were identified, and the binding free energies were calculated using the LIE method. The results indicate that IMI-1 has flexible loops that enables an open and a closed conformation of IMI- 1. All three carbapenems were docked and simulated in both conformations of IMI-1. The results indicate that open and closed conformations confirms the promiscuity of carbapenemases since the flexibility enables various initial binding mechanisms. in other words, the hydrolysis may occur so quickly that the binding does not have much bearing of the activity of the enzyme. Furthermore, the calculated binding free energies indicate that IMI-1 is optimized for the catalytic process rather than the binding affinity. In conclusion, IMI-1 and similar systems requires further research using computational methods to counteract antibiotic resistance based on knowledge.
195

Molecular insight into ion interactions at charged interfaces exposing sulfonate headgroups / Molekylär insikt i joninteraktioner vid laddade gränssnitt som exponerar huvudgrupper för sulfonat

Widehammar, Hugo January 2021 (has links)
Hur elektrolytlösningar interagerar med laddade ytor är viktigt för många fenomen. I detta arbete undersöktes samspelet mellan flera joner med en negativt laddad yta som exponerade sulfonat funktionella grupper mot lösning. Särskild vikt lades på deprotoneringsbeteendet vid ytan. Samspelet mellan olika joner och sulfonatgruppen hade inte tidigare beaktats ur ett molekylärt perspektiv. Här användes ett Langmuir-monolager bestående av dokosan-1-sulfonsyra deponerat på olika elektrolytlösningar som modellsystem. För att studera molekylära interaktioner mellan ytan och elektrolyterna användes Vibrational Sum Frequency Spectroscopy (VSFS). Denna inneboende ytkänsliga teknik gör det möjligt att observera små förändringar i vibrationsenergier i sulfonagruppen vid kontakt med olika joner, här hydronium, litium, natrium och cesium. Ett av huvudsyftena med detta arbete var att jämföra de experimentellt bestämda parametrarna med teoretiska modeller av det elektriska dubbelskiktet vid laddade gränssnitt, såsom Gouy-Chapman-teorin och andra mer avancerade Poisson-Boltzmann-baserade modeller, för att utforska deras lämplighet och gränser av giltighet. Docosan-1-sulfonsyra packades snyggt i monolager, med packningstätheten ökande med starkare jonstyrka I underfasen. Två toppar i vibrationsspektra sågs för sulfonatgruppen, den symmetriska och asymmetriska sträckningen vid 1048 cm-1 respektive 1150 cm-1. Dessa band sågs blåskiftas vid bindning av litium- och natriummotjoner. Amplituden för den symmetriska sträckningen kunde kopplas direkt till mängden laddade arter. Den teoretiska Gouy-Chapman-modellen var tillräcklig att användas för relativt låga ytpotentialer (<|150mV|). För högre potentialer var motjonens storlek nödvändig att inkludera i modellen för mer exakta förutsägelser. Sulfonsyrans surhetsgrad uppmättes till att vara pKa=-1.8±0.4 och bindningskonstanterna för olika hårda joner till den sulfonatfunktionella gruppen uppskattades vara pKLi=0 och pKNa=-0.7. Däremot binder den mjuka jonen, cesium, inte till sulfonatgruppen. Implikationen är att sulfonatgruppen bör betraktas som en hård jon I enlighet med Collins lag om matchande vattenaffiniteter. / How electrolyte solutions interact with charged surfaces is essential for many phenomena in physics, chemistry and biology. In this work, the interactions of several ions with a negatively charged surface exposing sulfonate functional groups to solution were investigated. Specific emphasis was made on the deprotonation behaviour at the surface. The interplay between different ions and the sulfonate moiety had not been previously considered from a molecular perspective.  Here, a Langmuir monolayer consisting of docosane-1-sulfonic acid deposited on top of different electrolyte solutions was used as model system. To study the molecular interactions between the surface and the electrolytes, Vibrational Sum Frequency Spectroscopy (VSFS) was used. This intrinsically surface sensitive technique allows observing small changes in vibrational energies of the sulfonate functional group when in contact with different ionic species, here hydronium, lithium, sodium and cesium. One of the main objectives of this work was to compare the experimentally determined parameters with theoretical models of the electric double layer at charged interfaces, such as the Gouy-Chapman theory and other more advanced Poisson-Boltzmann based models, to explore their suitability and limits of validity. Docosane-1-sulfonic acid packed nicely into monolayers, with the packing density increasing with stronger ionic strength in the subphase. Two peaks in the vibrational spectra were seen for the sulfonate functional group, the symmetric and asymmetric stretch at 1048 cm-1 and 1150 cm-1, respectively. These bands were seen to blue-shift upon binding of lithium and sodium counterions. The amplitude of the symmetric stretch could be directly linked to the amount of charged species. The Gouy-Chapman theoretical model was adequate to use for relative low surface potentials (<|150mV|). For higher potentials, the size of the counterion was necessary to include in the model for more accurate predictions. The acidity of the sulfonic acid was measured to be pKa=-1.8±0.4 and the binding constants for different hard ions to the sulfonate functional group were estimated to be pKLi=0 and pKNa=-0.7. In contrast, the soft ion, cesium, does not bind to the sulfonate. The implication is that the sulfonate moiety should be considered a hard ion in accordance with Collins law of matching water affinities.
196

Aggregation mechanisms of proteins in liquid formulations / Aggregationsmekanismer av proteiner i vätskeformuleringar

Hamrin, Amanda January 2022 (has links)
Biologiska läkemedel har under det senaste århundradet utökats, och under de senaste 25 åren så har proportionen av godkända biologiska läkemedel har ökat för behandlingen av sjukdomar, vaccin, och diagnostik. Det finns flera olika mekanismer för protein aggregering, och en av dessa är seeding, vilket innebär aggregering inducerat av tillsatta aggregat eller förekomsten av strukturförändringar i proteinet. I detta examensarbete har två terapeutiska proteiner, Somatropin och en monoklonal antikropp, studerats i form av aggregering. Denna studie har utförts genom att värma en del av proteinlösningen för att bilda aggregat och strukturförändrat protein, och sedan blanda detta med nativt protein till olika volymprocent. Dessa lösningar förvarades i olika temperaturer, 4°C, RT och 40°C för att undersöka temperaturberoendet. Med Dynamic Light Scattering (DLS) mättes storleksfördelningen och medelstorleken på proteinet, vilket visade att de seedade proverna ökade i medelstorlek med tiden. Detta indikerar att seedingen inducerade aggregering med tiden. / Biological pharmaceuticals have expanded their use over the last decade, and during the recent 25 years, the proportion of approved biologics has increased for the treatment of diseases, vaccines, and diagnostics. There are several aggregation mechanisms, and one is seeding, i.e., aggregation induced by pre-formed aggregates or the presence of conformational changed proteins. In this master thesis, two therapeutic proteins, Somatropin and one monoclonal antibody have been studied in terms of aggregation. The study has been performed by heating a part of a protein solution to induce aggregation and mixing this with native protein in different volume percentages. These were stored in different temperatures, 4°C, RT, and 40°C, to investigate the temperature dependence. With Dynamic light scattering (DLS), the size distribution and the average-sized particles were measured. This showed that there was a growth of average size in the seeded samples with time. This indicates that the seeding induced aggregation with time.
197

Drug Design of β-Lactamase Inhibitors of the DBO-scaffold against OXA-48 : A Molecular Dynamics Study of Ligand Stability in the Michaelis Complex

Liljeholm, Linda January 2022 (has links)
The emergence of β-lactamase-mediated antibiotic resistance is one of the biggest threats in modern times. Combined with the discovery void of new forms of antibiotics, this sets the course toward a future where the efficacy of present-day health care will be jeopardized. To hinder the spread of β-lactamase-mediated antibiotic resistance, the development of the drug class β-lactamase inhibitors has been prioritized. The foremost candidate for development of this drug class, that has wide-spectrum inhibition of β-lactamases, is the clinically available avibactam of the diazabicyclooctane-scaffold (i.e., DBO-scaffold). However, the clinical applications of this inhibitor have been limited against one of the more rapidly spreading β-lactamases; OXA-48. In order to bolster the drug development of β-lactamase inhibitors of the DBO-scaffold, with good inhibitory activity toward OXA-48, DBO-ligands with different structure elements were analyzed for stability of the Michaelis Complex in the OXA-48 binding site using molecular dynamic simulations. The results indicate that elongation of the chain to the anionic group of the ligand combined with the addition of a methyl group to the DBO-ring was stabilizing for the productive position between the backbone hydrogens of Y211 and S70. The binding affinity was also estimated using the Linear Interaction Energy method, and an offset parameter of γ ≈ -19 kcal/mol was found and could represent the entropic differences of a flexible ligand-protein system. The results of this study may also indicate that the ligand stability of the Michaelis Complex is of minor consequence to the inhibition mechanism as a whole compared to the reaction rate.
198

Synthesis and characterization of novel hybrid organic-inorganic materials / Syntes och karakterisering av nya hybrida organiska-oorganiska material

Blomdahl, Emil January 2021 (has links)
Efterfrågan på bättre och mer hållbart material ökar. Mer effektivt material kommer att behövas för att möta den ökande, globala efterfrågan. Hybrida organiska-oorganiska material är en typ av material som har varit av stort intresse nyligen, och kan beskrivas som en typ av material som består av både organiska och oorganiska komponenter. Denna avhandling har fokuserat på hybrida organiska-oorganiska material inspirerade av den klassiska perovskitstrukturen ABX3, där komponent A är en organisk katjon, komponent B är en divalent metalkatjon och komponent X är en anjon. Hybrida organiska-oorganiska material som är utgår från den klassiska perovskitstrukturen kan ha olika funktionella egenskaper och en bred variation av tänkbara applikationer. Några exempel på dessa egenskaper och möjliga applikationer inkluderar god fotokonduktivitet för solceller, utmärkt emissionsegenskaper för ljusdioder och justerbara dielektriska egenskaper för elektroniska växlar och sensorer.  De fysiska egenskaperna av det hybrida organiska-oorganiska materialet beror på kristallstrukturen av materialet, som i sig bestäms av valet av komponenter. På grund av de många möjligheter av organiska och oorganiska komponenter så finns det möjlighet att syntetisera helt nya hybrida organiska-oorganiska föreningar som kan ha nya eller förbättrade fysiska egenskaper.  Nuvarande hybrida organiska-oorganiska material som utgår från perovskitstrukturen använder huvudsakligen bly som divalent metalkatjon, och det beror på att den ger den bästa funktionella effekten. Blys toxicitet är dock en stor nackdel för nuvarande blybaserade hybrid oorganiska material. Möjligheten att ersätta bly med en annan divalent metall har undersökts under detta projekt. I denna avhandling så har den organiska katjonen cyclohexylammonium (CHA) varit i fokus som den organiska komponenten. Målet med detta examensarbete var att designa, syntetisera och karakterisera nytt hybrid organisk-oorganiskt material. De hybrida organiska-oorganiska föreningarna CHAZnBr3 och (CHA)2ZnBr4 syntetiserades för den första gången, så vitt författaren vet, och kommer vara i fokus i denna avhandling. De två nya hybrida organiska-oorganiska föreningarna blev strukturellt karakteriserade med X-ray Diffraction (XRD) och termiskt karakteriserade med Thermal Gravimetric Analysis (TGA) och Differential Scanning Calorimetry (DSC).  Den första föreningen, CHAZnBr3, kunde bestämmas att vara ortorombisk vid 298 K. Föreningen bestämdes vara termisk stabil upp till 490 K, och genomgår en fasövergång vid 445 K. Den andra föreningen, (CHA)2ZnBr4, kunde inte bestämmas strukturellt vid varken 100 K eller 298 K. Föreningen bestämdes vara termisk stabil upp till 490 K, och genomgår en fasövergång vid 230 K. Ytterligare karakterisering krävs för att bättre förstå egenskaperna hos dessa föreningar och deras möjliga användningsområden. / The demand for better and more sustainable material is increasing. More efficient materials will be needed to meet the growing global need. Hybrid organic-inorganic materials are one type of materials that have been of great interest recently, which can be described as a class of materials that mix organic and inorganic components. This thesis focused on hybrid organic-inorganic materials inspired by the classical perovskite crystal structure ABX3, where component A is an organic cation, component B is a divalent metal cation and component X is an anion. Hybrid organic-inorganic materials based on the classical perovskite structure may have various functional properties and may have a broad range of potential applications. Some examples of those properties as well as some and possible applications include good photoconductivity and power conversion efficiency for photovoltaic devices, excellent emission properties for light emitting diodes and tunable dielectric properties for electronic switches and sensors.  The physical properties of the hybrid organic-inorganic material are determined by the crystal structure of the material, which in turn will be decided by the choice of components. With the many possible choices for organic and inorganic components, there is an opportunity to synthesize completely new hybrid organic-inorganic compounds that may display new or superior physical properties. Current hybrid organic-inorganic materials based on the perovskite crystal structure mainly use lead as the divalent metal, since it currently gives the best performance. The toxicity of lead is a major drawback for current lead-based hybrid organic-inorganic materials. The possibility to replace lead with another divalent metal has been explored during this project. For this thesis, the organic cation cyclohexylammonium (CHA) has been of focus as the organic component. The aim of this thesis was to design, synthesize and characterize novel hybrid organic-inorganic compounds. The hybrid organic-inorganic compounds CHAZnBr3 and (CHA)2ZnBr4 were synthesized for the first time, to the best of our knowledge, and will be the focus of this thesis. The two new hybrid organic-inorganic compounds were structurally characterized by X-ray Diffraction (XRD) and thermally characterized by Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC).  The first compound, CHAZnBr3, could be determined to be orthorhombic at 298 K. The compound was found to be thermally stable up 490 K, and to undergo a phase transition at 445 K.  The second compound, (CHA)2ZnBr4, could not be fully structurally solved at either 100 K or 298 K. The compound was found to be thermally stable up to 490 K, and to undergo a phase transition at 230 K.  Further characterization will be needed to better understand the properties of these two compounds and their possible applications.
199

Ion specific effects in polymer conformation / Jonspecifika effekter i polymerkonformation

Svanholm, Lovisa, Köttö, Anna, Deuda Lundkvist, Samuel January 2021 (has links)
It is well known that ions affect polymers in specific ways not solely based on electric charge, usually referred to as the Hoffmeister effect or ion specific effects. Poly(N-isopropylacrylamid) (PNIPAM) is a thermosensitive polymer with a LCST at 32℃. PNIPAM is a well studied polymer due to its similarities with denaturation of proteins in aqueous solutions. Utilizing diffusion NMR this report studied the effect different Hoffmeister anion concentrations have on the configuration of pre-transitional PNIPAM. A fractionation process was developed for PNIPAM, yielding a product of about 87 000 g/mol, used for diffusion measurements. Diffusion coefficients for PNIPAM in saline solutions ranging from 0 to 800 mM were measured for NaCl, NaClO4, NaSCN and NaI. Diffusion coefficients for PNIPAM were also measured at some concentrations of NaF, Na2SO4 and Na2CO3. Hydrodynamic radius was calculated from the diffusion coefficients. The report found a pre-transitional chain collapse of PNIPAM which increased with ionic concentrations of NaCl, NaClO4, NaSCN, NaF and Na2CO3, but not for NaI and Na2SO4. At 800 mM the hydrodynamic radius decreased with 9% for NaCl, 13% for NaClO4 and 5% for NaSCN. The hydrodynamic radius decreased with 19% at 300 mM Na2CO3 and with 10% at 400 mM NaF. There was a significant decrease in hydrodynamic radius for high concentrations of NaCl and NaClO4 but exact decrease needs to be replicated to validate the findings due to an unexpected large decrease in hydrodynamic radius already at 50 mM. Values for NaF and Na2CO3 should be replicated with internal standard to accomodate for possible precipitation of the longer polymer chains within the fraction.
200

A Quantum Chemical Investigation of Chemical Vapour Deposition of Fe using Ferrocene and Plasma Electrons

Andersson, Felicia January 2023 (has links)
Thin films provide a remarkable asset, as depositing a thin surface layer can completely alter a material’s characteristics and provide new, inexpensive, and valuable properties. In 2020, a new Chemical Vapour Deposition (CVD) approach was developed at Linköping University, using plasma electrons as reducing agents for the deposition of metallic thin films. To understand the CVD approach, comprehension of the deposition chemistry is crucial. In this thesis, I have performed a theoretical examination of the gas phase and surface chemistry of ferrocene in the recently developed CVD method to form metallic iron thin films, using plasma electrons as reducing agents. Results show that ferrocene anion formation and dissociation are probable in the gas phase, depending on the energy of the plasma electrons. It gets successively easier to dissociate the complex after gaining electrons. The most probable gas phase species leading to film formation was determined as FeCp2-, FeCp, and Cp− under the normal deposition parameters. An electron energy above 220 kJ/mol would suffice for ion formation and dissociation to form FeCp and Cp− fragments. On the surface, ferrocene’s vertical and horizontal adsorption is equally probable, with energies around -72 kJ/mol. Cp, Fe, and FeCp with Fe facing towards the surface interacts stronger with the surface than ferrocene, with adsorption energies of -179, -279 kJ/mol, and -284 kJ/mol. FeCp with Fe facing up from the surface had adsorption energy of -23 kJ/mol. As the surface bonding of Fe and FeCp with Fe facing the surface is stronger than for the other species, this poses a possible way of tuning the CVD method to limit carbon impurities. By providing above 180 kJ/mol energy, for example in the form of heating the substrate, the unwanted species FeCp2, Cp, and FeCp with the ring facing downwards would desorb from the surface, leaving the Fe and FeCp fragments with iron facing towards the surface still adsorbed. This poses a possible way of reducing carbon impurities.

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