| 1. |
- Stenberg, Pontus, 1984-, et al.
(författare)
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Matching precursor kinetics to afford a more robust CVD chemistry: a case study of the C chemistry for silicon carbide using SiF4 as Si precursor
- 2017
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 5, s. 5818-5823
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Tidskriftsartikel (refereegranskat)abstract
- Chemical Vapor Deposition (CVD) is one of the technology platforms forming the backbone of the semiconductor industry and is vital in the production of electronic devices. To upscale a CVD process from the lab to the fab, large area uniformity and high run-to-run reproducibility are needed. We show by a combination of experiments and gas phase kinetics modeling that the combinations of Si and C precursors with the most well-matched gas phase chemistry kinetics gives the largest area of of homoepitaxial growth of SiC. Comparing CH4, C2H4 and C3H8 as carbon precursors to the SiF4 silicon precursor, CH4 with the slowest kinetics renders the most robust CVD chemistry with large area epitaxial growth and low temperature sensitivity. We further show by quantum chemical modeling how the surface chemistry is impeded by the presence of F in the system which limits the amount of available surface sites for the C to adsorb.
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| 2. |
- Atakan, Aylin, et al.
(författare)
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Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
- 2018
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 362, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- Time evolution of catalytic CO2 hydrogenation to methanol and dimethyl ether (DME) has been investigated in a high-temperature high-pressure reaction chamber where products accumulate over time. The employed catalysts are based on a nano-assembly composed of Cu nanoparticles infiltrated into a Zr doped SiOx mesoporous framework (SBA-15): Cu-Zr-SBA-15. The CO2 conversion was recorded as a function of time by gas chromatography-mass spectrometry (GC-MS) and the molecular activity on the catalyst’s surface was examined by diffuse reflectance in-situ Fourier transform infrared spectroscopy (DRIFTS). The experimental results showed that after 14 days a CO2 conversion of 25% to methanol and DME was reached when a DME selective catalyst was used which was also illustrated by thermodynamic equilibrium calculations. With higher Zr content in the catalyst, greater selectivity for methanol and a total 9.5% conversion to methanol and DME was observed, yielding also CO as an additional product. The time evolution profiles indicated that DME is formed directly from methoxy groups in this reaction system. Both DME and methanol selective systems show the thermodynamically highest possible conversion.
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| 3. |
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| 4. |
- Erdtman, Edvin, 1981-
(författare)
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5-Aminolevulinic acid and derivatives thereof : properties, lipid permeability and enzymatic reactions
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Erdtman, Edvin, 1981-
(författare)
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A theoretical study of 5-Aminolevulinic acid and its esters : properties and lipid permeability
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 5-aminolevulinic acid (5ALA) is a widely used prodrug in Photodynamic therapy (PDT). The target molecule in 5ALA-PDT is Protoporphyrin IX (PpIX), which is synthesized endogenously via the heme pathway in the cell. In this thesis; the structural and energetic properties of 5ALA, its methyl-, ethyl- and hexyl esters, four different 5ALA enols, and hydrated 5ALA have been investigated using Quantum Mechanical (QM) first principles calculations. The vacuum proton affinity (PA) of 5ALA is found to be in good agreement with other similar compounds. The keto-enol tautomerization mechanism of 5ALA has been studied, and a self-catalysis mechanism has been proposed to be the most probable. Molecular Dynamics (MD) simulations of a lipid bilayer have been performed to study the membrane permeability of 5ALA and its esters. In the simulations the molecules were inserted in the middle of the membrane, equilibrated, and then simulated in 20 ns. It has been found that there are some differences in penetration between the molecules studied. The methyl ester of 5ALA is diverging from the others by having its barrier not in the middle of the membrane, as the others have.
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| 6. |
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| 7. |
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| 8. |
- Erdtman, Edvin, 1981-, et al.
(författare)
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Simulation of α- and β-PVDF melting mechanisms
- 2012
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Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 53:14, s. 2919-2926
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) simulations have been used to study the melting of α- and β-poly (vinylidene fluoride) (α- and β-PVDF). It is seen that melting at the ends of the polymer chains precedes melting of the bulk crystal structure. Melting of α-PVDF initially occurs via transitions between the two gauche dihedral angles (G ↔ G′) followed by transitions between trans and gauche dihedral angles (T ↔ G/G′). Melting of β-PVDF initially occurs via T → G/G′ transitions and via transitions of complete β- (TTTT) to α- (TGTG') quartets. The melting point of β-PVDF is higher than that of α-PVDF, and the simulated melting points of both phases depend on the length of the polymer chains used in the simulations. Since melting starts at the chain ends, it is important to include these in the simulations, and simulations of infinitely long chains yield melting points far larger than the experimental values (at least for periodic cells of the size used in this work), especially for β-PVDF. The simulated heats of fusion are in agreement with available experimental data.
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| 9. |
- Erdtman, Edvin, 1981-, et al.
(författare)
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Simulations of the thermodynamics and kinetics of NH3 at the RuO2 (110) surface
- 2017
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Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 656, s. 77-85
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Tidskriftsartikel (refereegranskat)abstract
- Ruthenium(IV)oxide (RuO2) is a material used for various purposes. It acts as a catalytic agent in several reactions, for example oxidation of carbon monoxide. Furthermore, it is used as gate material in gas sensors. In this work theoretical and computational studies were made on adsorbed molecules on RuO2 (110) surface, in order to follow the chemistry on the molecular level. Density functional theory calculations of the reactions on the surface have been performed. The calculated reaction and activation energies have been used as input for thermodynamic and kinetics calculations. A surface phase diagram was calculated, presenting the equilibrium composition of the surface at different temperature and gas compositions. The kinetics results are in line with the experimental studies of gas sensors, where water has been produced on the surface, and hydrogen is found at the surface which is responsible for the sensor response.
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| 10. |
- Nählinder, Johanna, 1973-
(creator_code:cre_t, redaktör/utgivare)
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Survival guide 2.0 : Hjälp! Jag får inte tag i artikeln jag letar efter!
- 2021
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Annan publikation (populärvet., debatt m.m.)abstract
- En infografic som visar hur en användare kan hitta artiklar och innehåller följande:Välkommen till Survival Guide 2.0! Sedan vi gjorde första versionen av Survival Guide 2017 har mycket hänt. Idag är det till exempel mycket vanligare att artiklar publiceras med öppen tillgång (open access) och inte kräver biblioteksprenumerationer. För de tillfällen då det trots allt är svårt att hitta en viss artikel finns Survival Guide.Unpaywall går att installera som plug-in i din webbläsare. Den hjälper dig att snabbt hitta open access-versioner av publikationer. Andra liknande tjänster är Google Scholar Button och Open Access Button.Via ResearchGate, och i viss mån LinkedIn, kan man ladda ner och efterfråga artiklar och få kontakt med författare.UniSearch: UBs sökmotor ger direkt tillgång till resurser som biblioteket prenumererar på (inklusive e-böcker som är svårt att kommer åt annars) och även fritt tillgängligt innehåll. Missa inte PubMedCentral!Mejla direkt till författaren! Förmodligen är hen intresserad av att bli läst och citerad.Undersök om artikeln du letar efter finns som preprint. Inom vissa områden finns många artiklar som icke granskade manus, så kallade preprints. Se Wikipedia uppslagsord ”list of preprint repositories” för adresser till preprintservrar.Fjärrlån är gratis för dig som forskar eller studerar vid LiU. Du kan ofta mycket snabbt få artiklar.
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