Atom Probe Tomography Investigations of Biologically Relevant Nanoparticles

The study of materials at the nanoscale is essential in many scientific disciplines. For example, in materials science the size of the building blocks of a material is directly linked to its properties. New materials are constantly being developed having features at the nanoscale, for example nanoparticles that are used in fields such as catalysis, electronics, and medicine. In biology, many features exist which have nanosized structures including proteins. The 3D secondary structure of proteins is directly linked to their functions; hence structure determination of proteins is of high interest to gain information of biological processes that serves the development of future medicines.Due to the importance of nanostructures, many methods for their investigation have been developed such as X-ray diffraction, electron microscopy, and atom probe tomography. These methods rely on different probes and are thus often considered complementary as they provide different information. For the same reason, they put different constraints or limitations on the materials studied.In this work, two novel methods for studying nanoparticles of biological relevance, gold nanoparticles and hydroxyapatite nanoparticles, have been developed for analysis using atom probe tomography.Gold nanoparticles are popularly used as markers for biomolecules and to immobilize biomolecules on surfaces with retained function and activity. Several methods have been developed in the last decade to study nanoparticles using atom probe tomography, generally involving forming a metal matrix embedding the particles in a material from which a specimen can be made. In this thesis, an alternative approach utilizing a silica matrix made by a sol-gel method used to embed a gold nanoparticle covered surface is presented. This silica-based method provides an environment for the particles that is similar to an aqueous environment.Nanoparticles of hydroxyapatite, a mineral that is found in bone and teeth, are commonly used as biomaterials, for example as coatings to improve the performance of surgical implants. In this thesis, hydroxyapatite nanoparticles immobilized onto titanium are examined. The analysed surfaces were sputter coated with chromium, forming a matrix that allows for correlative transmission electron microscopy and atom probe tomography analysis. It is shown that calcium and phosphorous integrated into the surface oxide of the titanium, revealing detailed insights on immobilization of the nanoparticles on the surface. This integration resembles the osseointegration of bone when compared to similar titanium implants being introduced to the human body

Compacting of bark at different temperatures and pressures : change of bark density at different temperatures and pressure

Bark är en restprodukt från skogsindustrierna som framförallt används för värme- och elproduktion. Fukthalten är normalt sett högre i bark än i stamved, vilket medför ett lägre effektivt värmevärde och en sämre bränslekvalitet. Den vanligaste metoden för att minska fukthalten och därigenom höja bränslekvaliteten är att lagra bark. Lagring av sönderdelade biobränslen medför risker kopplade till värmeutveckling, så som substans- och energiförluster. Processerna under lagring är väldokumenterade, men en aspekt som tidigare inte undersökts är hur bark kompakteras vid olika temperaturer och tryck. Detta kan i sin tur påverka permeabiliteten i stackar under lagring. Genom att undersöka kompaktering vid olika temperaturer och tryck går det att beräkna fram en teoretisk modell på hur aktiviteten i stacken varit. Syftet med denna studie var att undersöka hur bark kompakteras vid olika temperaturer och tryck som uppstår i en stack under lagring. Syftet var även att utvärdera metoderna för att uppskatta substansförlusterna med metoden att använda nätpåsar med en mindre del av materialet jämfört med att väga allt material i torr ton. För att undersöka kompaktering vid olika temperaturer genomfördes laboratorieförsök i 0˚C, 30˚C och 50˚C. Barken som användes vid försöket var från tall (Pinus Sylvestris). Resultatet från studien visade att bark kompakterades till olika grad beroende på temperatur och tryckbelastning. Olika temperaturer och tryck gav olika kompakteringsgradienter. Kompakteringsgraden var högst vid 50 ˚C och lägst vid 0˚C. Skillnaden mellan de olika metoderna för att beräkna substansförluster var liten. Från studien kan det konstateras att bark kompakteras olika mycket beroende på temperatur och tryck. Metoden att väga allt material i torr ton är i princip lika bra som att använda nätpåsar.Bark is a residual product from the forest industry, which is primarily used for heat and electricity production. The moisture content is normally higher in bark than in logs, which results in lower effective heat value and poor fuel quality. The most common method of reducing moisture content and thereby increasing fuel quality is to store bark. Storage of decomposed biofuels entails risks associated with heat generation such as loss of substance and energy. The processes during storage are well documented but one aspect that has not previously been investigated is how bark is compacted at different temperatures and pressures. This in turn, can affect the permeability of stacks during storage. By investigating compaction at different temperatures and pressures, it´s possible to calculate a theoretical model of the activity in the stack. The purpose of this study was to investigate how bark is compacted at different temperatures and pressures that occur in a stack during storage. The purpose was also to evaluate the methods for estimating the loss of substance with the method of having net bags with a smaller amount of material compared to weighing all material in dry tone. The laboratory experiments were performed at 0˚C, 30˚C and 50˚C to investigate compaction at different temperatures. The bark used in the experiment was from scots pine (Pinus Sylvestris). The results from the study showed that bark was compacted differently at different temperatures and pressure. Different temperatures pressures gave different compaction grade. The compaction rate was highest at 50˚C and lowest at 0˚C. The difference between the different methods for calculating the loss of substance was minimal. From the study it can be found that bark is compacted very much depending on the temperature and pressure. The method of weighing all material in dry tone is equally as good as using mesh bags

Acoustic shape optimization using energy stable curvilinear finite differences

A gradient-based method for shape optimization problems constrained by the acoustic wave equation is presented. The method makes use of high-order accurate finite differences with summation-by-parts properties on multiblock curvilinear grids to discretize in space. Representing the design domain through a coordinate mapping from a reference domain, the design shape is obtained by inversion of the discretized coordinate map. The adjoint state framework is employed to efficiently compute the gradient of the loss functional. Using the summation-by-parts properties of the finite difference discretization, we prove stability and dual consistency for the semi-discrete forward and adjoint problems. Numerical experiments verify the accuracy of the finite difference scheme and demonstrate the capabilities of the shape optimization method on two model problems with real-world relevance

The density difference between tissue and neural probes is a key factor for glial scarring.

A key to successful chronic neural interfacing is to achieve minimal glial scarring surrounding the implants, as the astrocytes and microglia may functionally insulate the interface. A possible explanation for the development of these reactions is mechanical forces arising between the implants and the brain. Here, we show that the difference between the density of neural probes and that of the tissue, and the resulting inertial forces, are key factors for the development of the glial scar. Two probes of similar size, shape, surface structure and elastic modulus but differing greatly in density were implanted into the rat brain. After six weeks, significantly lower astrocytic and microglial reactions were found surrounding the low-density probes, approaching no reaction at all. This provides a major key to design fully biocompatible neural interfaces and a new platform for in vivo assays of tissue reactions to probes with differing materials, surface structures, and shapes

Atomically Resolved Interfacial Analysis of Bone-Like Hydroxyapatite Nanoparticles on Titanium

Titanium is commonly used for medical devices, including osseointegrating implants, owing to its biocompatibility and mechanical properties. Nanostructuring titanium implants is known to enhance the healing process by promoting bone growth on the implant surface. Hydroxyapatite nanoparticles, resembling natural bone mineral, have been used to further improve osseointegration. While previous studies have investigated the osseointegration of titanium implants using atom probe tomography, limited research has focused on the attachment of synthetic hydroxyapatite to titanium. Herein, electron microscopy and atom probe tomography are used to reveal the assembly of synthetic hydroxyapatite nanoparticles in the titanium oxide surface. By sputter coating with chromium, a suitable matrix is formed for detailed interfacial analysis. The results demonstrate the diffusion of calcium, phosphorus, and carbon from hydroxyapatite nanoparticles into the titanium oxide surface. Titanium is commonly used for medical devices, owing to its biocompatibility and mechanical properties. Nanostructuring titanium implants with hydroxyapatite nanoparticles, resembling natural bone mineral, enhances the healing process by promoting bone growth on the implant surface. Herein, atom probe tomography reveals the assembly of synthetic hydroxyapatite nanoparticles in the titanium oxide surface.image & COPY; 2023 WILEY-VCH Gmb

Svarta, vita eller gråa får? - Den samtida debatten om lobbyism i Sverige.

Uppsatsen syftar kartlägga och analysera den samtida offentliga debatten om lobbyism i Sverige. Detta görs utifrån tre teorier om demokratiska idealtyper: Tunn, snabb och stark demokrati. Dessa används sedan som verktyg för att analysera debatten. Uppsatsen ämnar fylla ett tomrum i svensk forskning om lobbyism, då den forskning som tidigare gjorts inte direkt undersöker bortom maktens korridorer. Hur ser debatten egentligen ut? Är lobbyister onda, eller är de en naturlig del av en moderniserad beslutsprocess som gynnar alla? Det finns lika många åsikter i frågan, som det finns fiskar i havet. Genom studien hoppas vi bringa klarhet i debatten, och med det bidra till samtalet om lobbyism och dess roll i det demokratiska Sverige. Materialet hämtas från artiklar från dags-och kvällstidningar. Det visar sig att tvetydighet råder, och att frågan väcker känslor och tänder även eld på ideologisk ved. En sak står dock klart. De flesta artiklar i materialet förespråkar reglering. För nu handlar det om anpassning, då fenomenet lobbyism verkar vara här för att stanna

Questionnaire survey and knowledge analysis of Swedish forestry for dissemination of knowledge along a hiking trail in Skinnskatteberg municipality

Den svenska skogen har en potential att bidra med lösningar för framtiden. För att möta framtida behov har regeringen beslutat om ett nationellt skogsprogram med fem fokusområden. Ett kunskapskliv för hållbart brukande och bevarande av skogen är ett fokusområde där målet är att utveckla och bredda kunskapen kring skogen och trakthyggesbruket i svenskt skogsbruk. Men hur kunskapsnivå hos allmänheten om skog och det svenska trakthyggesbruket ser ut idag finns det begränsad vetskap om, speciellt bland invånare i områden där omfattande skogsbruk bedrivs. Syftet med kandidatarbetet var att undersöka vilken kunskapsnivå invånare med koppling till Skinnskattebergs kommun har gällande svenskt skogsbruk. Ett delsyfte var att skapa och sprida information längs en vandringsled i Skinnskattebergs kommun om natur, svenskt skogsbruk och trakthyggesbrukets olika skogsbruksåtgärder. En enkät skapades med en större mängd frågor med främst förutbestämda svarsalternativ. Frågorna delades in i tre områden, bakgrundsfrågor, kunskapsfrågor och vidare intresse. Litteraturstudie genomfördes om svenskt skogsbruk, litteraturen sammanställdes och simplifierades. Förslag på skyltmaterial skapades. Informationsplatser identifierades där skyltmaterialet ämnas distribueras. Resultatet visade att av de 261 svarande på enkäten fick dessa ett medel på 75 procent antal rätt på kunskapsfrågorna. Hos respondenterna kunde det ses en svag trend med stigande kunskap med en ökad ålder, dock var denna trend inte signifikant mellan de olika åldersgrupperna. Majoriteten av respondenterna angav att de vistas i skogen på fritiden, endast sju av de 261 respondenterna angav att de inte vistas i skogen på fritiden. I studien identifierade vi en potential att informera ytterligare kring skog och trakthyggesbruk i svenskt skogsbruk. Målet blev att skapa ett underlag till skyltar om skog och olika åtgärder i trakthyggesbruket. Hur skog och skogsbruk uppfattas av personer kan variera från region till region och därför ser vi ett behov av ytterligare undersökningar.The Swedish forest has the potential to contribute with many solutions to future problems. To meet the future demands, the Swedish government has decided on a national forest program with five focus areas. One of these focus areas, Increased knowledge for sustainable use and conservation of the forest, has the goal to develop and broaden knowledge about the forest and clearcutting in Swedish forestry. There is limited understanding about what level of knowledge there is in the general public about forests and clearcutting in Swedish forestry. This is especially true regarding residents in areas where extensive forestry is conducted. The objective of this study was to investigate what level of knowledge the residents in Skinnskatteberg municipality have regarding Swedish forestry. A secondary objective was to create and disperse information along a hiking trail in Skinnskatteberg municipality about nature, the Swedish clearcutting system and the different silvicultural measures. A survey was created with eleven mainly multiple-choice questions. The questions were split in to three categories, background questions, knowledge questions and further interest. A literature study was conducted on Swedish forestry. The material was compiled and analyzed. The data was used to help formulate signs along a hiking trail. Information places were identified where the sign material is intended to be located. The results showed that of the 261 respondents to the survey, respondents answered on average 75 percent correctly among the knowledge questions. Among the respondents, a weak trend could be seen of increasing knowledge with increasing age. However, this trend was not significant between the different age groups in the survey. A majority of the respondents stated that they recreate in forests during their leisure time. Only seven of the 261 respondents stated that they do not recreate in the forest in their free time. Using the results from the survey, we identified a potential for further information about forests and the clearcutting system in Swedish forestry. The goal became to create baseline knowledge for the signs about forests and the Swedish clearcutting system and the different silvicultural measures that commonly occur. Because forests and forestry are viewed differently by people in different regions of Sweden (eg. urban vs rural Sweden,), we conclude that there is a need for similar research elsewhere in Sweden as well

Solution-Spinning of a Collection of Micro- and Nanocarrier-Functionalized Polysaccharide Fibers

Continuous polysaccharide fibers and nonwovens—based on cellulose, hydroxypropyl cellulose, chitosan, or alginate—containing biopolymeric microcapsules (MC) or mesoporous silica nanoparticles (MSN) are prepared using a wet-spinning or solution blowing technique. The MCs are homogeneously distributed in the fiber matrices whereas the MSNs form discrete micron-sized aggregates as demonstrated using scanning electron-, fluorescence-, and confocal microscopy. By encapsulating the model compound pyrene, it is shown that 95% of the substance remains in the fiber during the formation process as compared to only 7% for the nonencapsulated substance. The material comprising the MC has a strong impact on the release behavior of the encapsulated pyrene as investigated using methanol extraction. MCs based on poly(l-lactic acid) prove to be practically impermeable with no pyrene released in contrast to MCs based on poly(lactic-co-glycolic acid) which allow for diffusion of pyrene through the MC and fiber as visualized using fluorescence microscopy

Factors influencing stoichiometry and stability of polyoxometalate - peptide complexes

In the pursuit of understanding the factors guiding interactions between polyoxometalates (POMs) and biomolecules, several complexes between Keggin phosphomolybdate and diglycine have been produced at different acidity and salinity conditions, leading to difference in stoichiometry and in crystal structure. Principal factors determining how the POM and dipeptide interact appear to be pH, ionic strength of the medium, and the molar ratio of POM to peptide. An important effect turned out to be even the structure-directing role of the sodium cations coordinating carbonyl functions of the peptide bond. Given the interest in applying POMs in biological systems, these factors are highly relevant to consider. In the view of recent interest in using POMs as nano catalysts in peptide hydrolysis also the potential Keggin POM transformation in phosphate buffered saline medium was investigated leading to insight that nanoparticles of zirconium phosphate (ZrP) can be actual catalysts for breakdown of the peptide bond