| 1. |
- Baharudin, Zikri Abadi
(författare)
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Characterizations of ground flashes from tropic to northern region
- 2014
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- This thesis portrays new information concerning the cloud-to-ground (CG) lightning flashes or ground flashes produced by thunderclouds. It emphasizes the importance of characterizing lightning studies as the relationship between lightning mechanisms, and of incorporating the influence of geographical location, latitude and storm type. Sweden, Malaysia and USA were chosen as the main locations for field experiments in 2009 to 2011 to gather a significant number of negative and positive CG flashes. This work provided data on a total of 1792 CG lightning flashes (1685 negative and 107 positive ones) from a total of 53 thunderstorms by monitoring both the slow and the fast electric field and the narrowband radiation field at 3 and 30 MHz signals simultaneously. This thesis is comprised of: (i) the relationship of the Low Positive Charge Region (LPCR) and Preliminary Breakdown Pulse (PBP) trains to the occurrence of negative CG, (ii) slow field changes generated by preliminary breakdown processes in positive and negative ground flashes, and (iii) the occurrence of positive and negative ground flashes. It was revealed that the PBP train appeared have a higher strength in the in Sweden. The strength of the PBP train was caused by the LPCR; in contrast, weak PBP trains were characteristic in tropical countries constituting insignificant LPCR and needing little energy to break the “blocking” agent to allow the flash to propagate downward to the ground. The second contribution concerns the characteristics of the PBP train mentioned; this includes novel information for Malaysia. Further, it is stated that there are some different characteristics in the PBP trains in Johor, Malaysia and Florida, USA. The studies of slow field changes generated by preliminary breakdown processes clarifies unclear features concerning the starting position of slow field changes generated by preliminary breakdown processes in positive and negative ground flashes. It was found that the slow field changes did not occur before the initial process of the commencement of preliminary breakdown. Single-station electric field measurements incorporating narrowband radiation field measurement and high resolution transient recording (12 bits) with an accuracy of several nanoseconds, allows one to distinguish between the intracloud activities and the preceding processes of ground flashes. The results for the interstroke intervals, amplitude distribution of subsequent return-stroke (SRS) and the number of strokes per flash in the tropics, subtropics and northern regions were similar. Finally, a significant number of positive return-stroke (RS) electric fields provided statistically significant information on the characteristics of these strokes.
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| 2. |
- Dürr, Robin N.
(författare)
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Potential Electrocatalysts for Water Splitting Devices : A Journey Through the Opportunities and Challenges of Catalyst Classes
- 2022
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis work, different classes of catalysts and their suitability for integration into an electrolyzer cell has been investigated.Ruthenium based molecular catalysts have shown high activities and stabilities towards water oxidation in neutral pH. Especially the oligomeric catalysts exhibited a superior performance. The electrical conductivity of the electrode and the low loading of catalyst might impose limitations on reaching high current densities at reasonable potentials.Among the tested transition metal single atom catalysts, synthesized by pyrolyzing transition metal doped ZIF-8 structures, cobalt has shown the highest activity towards hydrogen evolution and a stable behaviour in acidic pH. The enhanced stability of single atomic sites compared to the corresponding nanoparticles was proposed. However, also for this class of catalyst, the low number of active sites seems to present a difficulty need to be overcome.With the novel method presented to fabricate a membrane electrode assembly, the usage of commonly used expensive membranes could possibly be avoided.Both nickel molybdate hydrate nanoparticle shapes have been proposed to transform in an electrochemical activation step into γ-NiOOH as active phase for the oxygen evolution reaction in alkaline pH. With the removal of molybdenum, a high electrochemical surface area with a large number of exposed nickel sites was indicated to be the origin behind the high catalytic activity of the nanoparticles. Molybdenum was suggested to only serve as structure and pore forming agent. Preliminary results indicated a higher activity for the rod structure towards the oxygen evolution reaction. An essential outcome is that it is uncertain if rods can be isolated synthesized on a nickel foam and hence the absence of the sheet structure should be verified, which could be done for example by selective molybdenum leaching combined with Raman spectroscopy. Furthermore, the two nanostructures are fundamentally different materials and characterized by various techniques.Among all different classes of catalysts investigated, the nanoparticle catalysts seem to be the most promising for a successful integration in a large scale electrolyzer cell for widespread use.
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| 3. |
- Galazka, Martyna A.
(författare)
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Social causality in motion : Visual bias and categorization of social interactions during the observation of chasing in infancy
- 2017
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Since the seminal work of Fritz Heider and Marienne Simmel (1944) the study of animacy perception, or the perception and attribution of life from the motion of simple geometrical shapes has intrigued researchers. The intrigue for psychologists and vision scientists then and today centered on the stark disconnect between the simplicity of the visual input and the universal richness of the resulting percept.Infant research in this domain has become critical in examining the ontological processes behind the formation of animated percepts. To date, little is known about how infants process these kinds of stimuli. While numerous habituation studies have shown sensitivity to animate motion in general, none to date has examined whether infants actually perceive animate displays as social interactions.The overarching goal of the present thesis is to answer this question and further augment knowledge about the mechanisms behind the formation of animated percepts in infancy. I, along with my collaborators, do so in three ways, in three separate studies. First, we examined visual attention during online observation of randomly moving geometrical shapes in adults and infants (Study I, using eye tracking). Second, we examine distribution of visual attention in infancy during online observation of non-contact causal interactions, focusing on the most ubiquitous, fitness relevant of interactions – chasing (Study II, using eye tracking). Third, we answer the question whether infants perceive social content in chasing displays by measuring the neural correlates in response to chasing (Study III, using EEG).The collective contribution of the present work is also three fold. First, it demonstrates that starting at the end of the first year of life, human visual system is sensitive to cues that efficiently predict an interaction. Second, at 5-months infants begins allocating attention differently across agents within interactions. Finally, attention to specific objects is not due to low-level saliency but the social nature of the interaction. Subsequently, I present the case that perception of social agents is fast, direct, and reflects the workings of a specialized learning mechanisms whose function is the detection of heat-seeking animates in motion.
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| 4. |
- Gu, Gucci Jijuan, 1984-
(författare)
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Proximity Ligation Assay for High Performance Protein Analysis in Medicine
- 2012
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- High quality reagents are preconditions for high performance protein analyses. But despite progress in some techniques, e.g. mass spectrometry, there is still a lack of affinity-based detection techniques with enhanced precision, specificity, and sensitivity. Building on the concept of multiple affinity recognition reactions and signal amplification, a proximity ligation assay (PLA) was developed as a molecular tool for analyzing proteins and their post-translational modification and interactions. PLA enhanced the analysis of protein expression levels and post-translational modifications in western blotting (Paper I), which had elevated sensitivity and specificity, and an ability to investigate protein phosphorylation.A general and straightforward method was established for the functionalization of affinity reagents through adding DNA strands to protein domains for protein analysis in medicine (Paper II). A method for protein domain-mediated conjugation was developed to simplify the use of recombinant affinity reagents, such as designed ankyrin repeat protein (DARPin), in DNA-mediated protein analyses.Alzheimer’s disease (AD) is characterized by progressive cognitive decline and memory impairment, and amyloid-beta plaques and neurofibrillary tangles (NFT) in the brain are clinical hallmarks of the disease. In order to understand the mechanisms underlying the formation of NFT, in situ PLA was used to explore the role of microtubule affinity related kinase 2 (MARK2) in phosphorylating tau protein during the pathological progress of AD (Paper III). The analyses of roles of MARK proteins 1-4 in phosphorylating tau protein in cells and in post-mortem human brains were performed in Paper IV.The focus of this thesis was the study of post-translational modifications and interactions of proteins in medicine. Procedures for high performance protein analysis in western blotting via proximity ligation were developed, and a functionalization method for recombinant affinity reagents in DNA-mediated protein analysis was established. These and other techniques were used to investigate the roles of tau-phosphorylating MARK family proteins in AD.
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| 5. |
- Innocenti, Paolo, 1981-
(författare)
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Sexual Conflict and Gene Expression in Drosophila melanogaster
- 2011
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Sexual conflict is broadly defined as a conflict between the evolutionary interests of the two sexes. Depending on the genetic architecture of the traits involved, it can occur at the level of male-female interactions or take the form of selection acting to change the mean of a shared trait against the sign of its genetic correlation. The aim of my thesis was to use genome-wide expression profiles in the model organism Drosophila melanogaster to provide novel insights in the study of sexual conflict. First, we studied the female post-mating response to partition transcriptional changes associated with reproduction from male-induced effects, which are known to be harmful to females. We found substantial changes in expression of metabolic pathways associated with the activation of reproduction, while male-specific effects were dominated by the onset of an immune response. Changes in female response under different mating strategies was studied using experimental evolution: we found that monogamous females suffered decreased fecundity and their gene expression profiles suggested an overall weaker response to mating. To identify sexually antagonistic genes, we used hemiclonal lines and associated their sex-specific fitness with genome-wide transcript abundance. We confirmed the presence of a negative covariance for fitness and identified a group of candidate genes experiencing sexually antagonistic selection. We then focused on mitochondria, which can enable the accumulation of deleterious mutations with sex-specific effects due to their maternal inheritance, and found few effects on nuclear gene expression in females but major effects in males, predominantly in male-specific tissues. Finally, we used published data to compare intraspecific and interspecific genetic variation for a set of transcripts, to test whether speciation occurs along lines of maximum genetic variance. In conclusion, gene expression techniques can generate useful results in the study of sexual conflict, particularly in association with phenotypic data or when integrated with published datasets.
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| 6. |
- Jaiteh, Mariama
(författare)
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New Paradigms in GPCR Drug Discovery : Structure Prediction and Design of Ligands with Tailored Properties
- 2020
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- G protein-coupled receptors (GPCRs) constitute a large superfamily of membrane proteins with key roles in cellular signaling. Upon activation by a ligand, GPCRs transduce signals from the extracellular to the intracellular environment. GPCRs are important drug targets and are associated with diseases such as central nervous system (CNS) disorders, cardiovascular diseases, cancer, and diabetes. Currently, 34% of FDA-approved drugs mediate their effects via modulation of GPCRs. Research during the past decades has resulted in a deeper understanding of GPCR structure and function. Moreover, recent breakthroughs in structural biology allowed the determination of several atomic resolution GPCR structures. New paradigms in GPCR pharmacology have also emerged that can lead to improved drugs. Together, these advances provide new avenues for structure-based drug discovery. The work in this thesis focused on how the large amount of structural data gathered over the last decades can be used to model GPCR targets for which no experimental structures are available, and the use of structure-based virtual screening (SBVS) campaigns to identify ligands with tailored pharmacological properties. In paper I, we investigated how template selection affects the virtual screening performance of homology models of the D2 dopamine receptor (D2R) and serotonin 5-HT2A receptor (5-HT2AR). In papers II and III, SBVS methods were used to identify dual inhibitors of the A2A adenosine receptor (A2AAR) and an enzyme, which could be relevant for treatment of Parkinson’s Disease, and functionally selective D2R ligands from a focused library. Finally, we also investigated how structural information can complement computational and biophysical methods to model and characterize the A2AAR-D2R heterodimer (paper IV).
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| 7. |
- Kaewmaraya, Thanayut, 1984-
(författare)
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First-Principles Studies of Materials Properties : Pressure-Induced Phase Transitions & Functional Materials
- 2015
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents the first-principles studies of materials properties within the framework of the density functional theory (DFT). The thesis constitutes three main parts, i. e., pressure-induced phase transitions in solids, data-storage and clean-energy materials.The first part focuses on the predictions of crystal structures and the determinations of electronic properties of Xe-H2, FeB4 and Co3O4. Pressurizing Xe-H2 compound yields the formation of H-rich Xe(H2)8, which can exhibit a metallic feature at comparatively lower pressure than pure hydrogen. Hard superconducting FeB4 gets transformed into a novel transparent phase under pressure owing to the enhanced overlap of atomic cores. Spinel Co3O4 undergoes the phase transition from a cubic to a monoclinic because of the charge transfer between cations via the increased 3d-3d interactions.The second part involves the study of structural and electronic properties of phase-change memory materials (PCMs), i. e., Ge2Sb2Te5 (GST) and Ga-doped In2O3. Van der Waals (vdW) interaction must be considered to obtain accurate crystal structure of layered GST. For Ga-doped In2O3 (GIO), the local structure of amorphous GIO is found to resemble that of amorphous In2O3, except the vicinity of doping atoms. The electronic property of a-GIO is metallic, which considerably differs from the semiconducting feature of the crystalline GIO. This emphasizes the contrast in the conductivity of the crystalline and amorphous upon phase switching of GIO.The third part associates with the search for clean-energy materials, viz., hydrogen production, hydrogen storage and green Mg-ion batteries. For hydrogen production, the role of intrinsic point defects to water adsorption on ZnO(10-10) surface is investigated. The findings show that the Zn and O defect-sites are energetically not favorable for the water adsorption and dissociation. For the purpose of storing hydrogen in a solid phase, silicene, doped by alkaline and alkaline earth metals, is investigated. We find that Li-doped and Na-doped silicene can attain the superior storage capacity. For cathode material of Mg-ion batteries, Mg2Mo6S8, the diffusivity of Mg ions occurs through an available channel in the bulk with the onset temperature of 200 K.
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| 8. |
- Li, Shiyu, 1991-
(författare)
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Engineering Surfaces of Solid-State Nanopores for Biomolecule Sensing
- 2021
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Nanopores have emerged as a special class of single-molecule analytical tool that offers immense potential for sensing and characterizing biomolecules such as nucleic acids and proteins. As an alternative to biological nanopores, solid-state nanopores present remarkable versatility due to their wide-range tunability in pore geometry and dimension as well as their excellent mechanical robustness and stability. However, being intrinsically incompatible with biomolecules, surfaces of inorganic solids need be modified to provide desired functionalities for real-life sensing purposes. In this thesis, we presented an exploration of various surface engineering strategies and an examination of several surface associated phenomena pertaining specifically to solid-state nanopores. Based on the parallel sensing concept using arrayed pores, optical readout is mainly employed throughout the whole study.For the surface engineering aspect, a list of approaches was explored. A versatile surface patterning strategy for immobilization of biomolecules was developed based on selective poly(vinylphosphonic acid) passivation and electron beam induced deposition technique. This scheme was then implemented on nanopore arrays for nanoparticle localization. In addition, vesicle rupture-based lipid bilayer coating was adapted to truncated-pyramidal nanopores, which was shown to be effective for the minimizing DNA-pore interaction. Further, HfO2 coating by means of atomic layer deposition was employed to prevent the erosion of Si-based pores and to shrink the pore diameter, which enabled reliable investigations of DNA clogging and DNA polymerase docking.For the surface associated phenomena, several findings were made. The lipid bilayer formation on truncated pyramidal nanopores via instantaneous rupture of individual vesicles was quantified based on combined ionic current monitoring and optical observation. The probability of pore clogging appeared to linearly increase with the length of DNA strands and applied bias voltage, which could be attributed a higher probability of knotting and/or folding of longer DNA strands and more frequent translocation events at higher voltage. A free-energy based analytical model was proposed to evaluate the DNA-pore interaction and to interpret observed clogging behavior. Finally, docking of DNA polymerase on nanopore arrays was demonstrated using label-free optical method based on Ca2+ indicator dyes, which may open the avenue to sequencing-by-synthesis enabled by the docked polymerase.
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| 9. |
- Neiß, Michael, 1977-
(författare)
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Förvandlingar i vikingatidens djurornamentik : Del 1 : En multiperspektivisk studie om figurknoppspännen av Birkatyp
- 2022
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- During the past 150 years, different generations of scholars have been approaching Scandinavian Animal Art with queries that were as multifaceted as the materials that they studied. The focal point of this study are Birka type brooches, which are best likened to interactive sculptures that change shape as the viewer changes perspective. Sculptural brooches do not only breathe new life into traditional research questions, but raise new ones that steer us into uncharted waters. Here, we make field observations which fall outside the established paradigms of archaeology. Following the parable of the six blind men who tried to come to terms with the unknown phenomenon ‘elephant’, this study approaches the sculptural brooch phenomenon from different angles, by combining different methods which have been developed within separate research disciplines such as archaeology, art history, cognitive science and philology. The methodological framework for my multi-method approach is informed GT, i.e. a variant of grounded theory which uses established theories to identify distinct patterns that previously went unnoticed. Contradictions that arise from the mix of methods are not seen as a hindrance, but as a generator for progress that gives rise to a new theory. By combining dynamic typology, Panofskyan hermeneutics and multimodal semiotics, my study on sculptural brooches uncovers hitherto unknown parallels between Animal Art and skaldic poetry in regards to context, cognition and imagery. As a result, one is inclined to look for a potential link between those distinct expressions of Viking Age culture. Did objects with Animal Art serve as points of reference for skaldic ekphrasis? Or was Animal Art a material anchor for the same conceptual blends that also transpired through skaldic poetry? The outcome is an empirically grounded theory which links the pictorial language of the smith to the verbal imagery of the skald, more precisely in the context of Old Norse íþrótt ideology.
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| 10. |
- Panda, Pritam Kumar, PhD Student, 1991-
(författare)
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GENOME2QUNOME : Interfacing Molecules with Nanomaterials
- 2023
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- The advent of technological furtherance in the biomedical sector and the renaissance of interdisciplinary science enable us to comprehend human lifestyle, and diseases at molecular and nanoscale levels. Lacking a shared theoretical foundation and terminological lexicon between various scientific domains might impede efforts to incorporate biological principles into nanoscience. In retrospect, it's possible to draw some instructive learnings from the fact that the development of contemporary nanoscience and biology was the consequence of the convergence of fields that had previously been kept separate. In this Ph.D. thesis, I have given the catchy moniker “GENOME2QUNOME” (an acronym for "Genetic organization of multicellular organisms and their enzymatic reaction 2 Quantum nanostructured materials for energy scavenging applications"), encompassing a combinatorial approach using computational methodologies in biophysics and nano/materials science. Structure-property correlations, a unifying paradigm based on understanding how nanomaterials behave and what qualities they exhibit at the molecular and nanoscale levels, are now widely acknowledged and are critical in the incorporation of bioinspired materials into nanoscience. Therefore, a unified framework have been elucidated in this thesis for the study of nanoscale materials ranging from 0D to 3D that may be useful in combining various strategies that characterize this interdisciplinary approach. This thesis is also a part of broader interdisciplinary research strategy aimed at depicting electronic transport in the nanoscale regime, elucidating interface mechanisms for contact electrification, and understanding the complex architectures of nanomaterials. The central hypothesis of this thesis is concentrated on the behavioral transition from the nanoscale regime to macromolecules, which is fascinating in real world scenario but theoretically challenging to bring it in reality or practice. To bridge this gap, I have made an attempt by integrating a wide range of computational methods, ranging from density functional theory (DFT) for systems with few atoms to classical dynamics dealing with billions of atoms.
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