I kemi måste elever ofta balansera reaktionsformler. Under århundradenas lopp har det utvecklats olika modeller inom området reduktions- och oxidationsreaktioner och på gymnasiet idag används framförallt två metoder för balansering av dessa reaktioner, elektronövergångsmetoden och oxidationstalsmetoden.

Syftet med denna studie var att undersöka om det förekommer några missuppfattningar eller svårigheter hos elever gällande elektronövergångsmetoden och oxidationstalsmetoden, samt att få en uppfattning om hur vanligt förekommande eventuella missuppfattningar är. Till hjälp användes ett frågeformulär med uppgifter av öppen karaktär där eleverna skulle balansera olika redoxreaktioner, samt besvara frågor som har med de två metoderna att göra. Elevernas svar kategoriserades och frekvensen räknades fram för varje svarskategori. Denna studie har alltså både kvalitativa och kvantitativa inslag.

Resultatet visar att elever föredrar att använda oxidationstalsmetoden framför elektronövergångsmetoden, när de får chansen att välja. Dock definierar majoriteten av eleverna oxidation och reduktion utifrån elektronövergångsmetoden. Det uppstår missförstånd och svårigheter med båda metoderna. En del av svårigheterna kommer av att eleverna blandar ihop elektronövergångsmetoden och oxidationstalsmetoden. Vid balansering med oxidationstalsmetoden ligger svårigheterna framförallt kring balanseringen av laddningarna.

Evaluation of the wet etching properties of several different thin film oxidesgrown by physical vapour deposition was performed in this work. MgO, Al₂O₃,SiO₂, TiO₂, HfO₂ ZrO₂ and Y₂O₃ were coated on two types of substrates; Si andborosilicate glass and etching tests were performed in different etchingsolutions. MgF₂ thin films have also been evaluated.

Important aspects of the choice of the thin films was taken into account in orderto match to good optical properties such as refractive index (n), extinction coefficient (k) and optical thickness (TP) as well as good chemical properties in the wet etching process.

A description is made of the physics of optical filters and how a combination of different oxides stacked onto each other can create interference filters.

A description of the manufacturing process of the thin films where physical vapour deposition (PVD) was used is presented.

Thermal shift of the optical spectra caused by porous coatings was investigated and analyses of the thin films by ellipsometry, surface profilometry and transmission spectrophotometry have been performed.

The wet etching properties were evaluated by monitoring the transmission insituon transparent borosilicate glass substrates. A method of how to measure the wet etching rate for different thin films is described.

A computer software was used to calculate the Pourbaix diagrams in order to understand the chemical behaviour of the etching solutions. The pH can have a significant impact on the etching behaviour.

In case of TiO₂, it can be dissolved in an alkaline solution of H₂O₂. The catalytically process behind this is evaluated. Etching rate for both Y₂O₃ andSiO₂ were matched by adjusting the etchant concentration as a case example.

The group IVB oxides are difficult to etch. The catalytic etching of TiO₂ with peroxide is slow but detectable. Al₂O₃, Y₂O₃ and MgO are reasonably easy to etch but have too low refractive indices to be useful in multilayer optical filters. The In-situ etching instrument was found to be very useful for measuring etching rates.

Metallic implants are widely used in applications associated with bone. A major drawback of using metals is their elastic modulus which is higher than that of bone resulting in stress shielding and premature failure of the implant. The employment of biomaterials with a porous structure has the potential to lower the modulus and promote osseointegration. The present work investigates the microstructure formation and the resulting elastic modulus of a new Ti-Si-Zr alloy. The sintering procedure involves the use of both mechanically alloyed Ti-Si powder and TiH2 to activate sintering with the TiH2 also serving as a pore precursor. The procedure is designed to promote bonding but not consolidation. The influence of sintering temperature, heating rate, as well as the amount and size of the TiH2 on the phases formed and porosity was investigated. It was observed that the use of TiH2 increased the degree of porosity whilst the size of TiH2 particles could be used to control the pore size. The results showed that when using small TiH2 particles, the elastic modulus was strongly dependent on the fraction of TiH2. When large TiH2 particles were used, the porosity had no significant influence on the elastic modulus. The variation in behavior could be attributed to differences in microstructure. To control the bulk modulus it is essential to understand the differences in the microstructure formation mechanisms between these two cases. (C) 2014 Elsevier B.V. All rights reserved.

Recently, a new type of ultrasound contrast agent that consists of air-filled microbubbles stabilized with a shell of polyvinyl alcohol was developed. When superparamagnetic nanoparticles of iron oxide are incorporated in the polymer shell, a multimodal contrast agent can be obtained. The biodistribution and elimination pathways of the polyvinyl alcohol microbubbles are essential to investigate, which is limited with today's techniques. The aim of the present study was, therefore, to develop a method for qualitative and quantitative analysis of microbubbles in biological samples using capillary electrophoresis with ultraviolet detection. The analysis parameters were optimized to a wavelength at 260 nm and pH of the background electrolyte ranging between 11.9 and 12. Studies with high-intensity ultrasonication degraded microbubbles in water showed that degraded products and intact microbubbles could be distinguished, thus it was possible to quantify the intact microbubbles solely. Analysis of human blood plasma spiked with either plain microbubbles or microbubbles with nanoparticles demonstrated that it is possible to separate them from biological components like proteins in these kinds of samples.

Highly purified mitochondria were isolated from green 7-day-old rice leaves. The mitochondria were sonicated and the matrix fraction isolated as the 100,000g supernatant. Part of the matrix fraction was left untreated while the other part was subjected to a mild oxidative treatment (0.5 mM H₂O₂ + 0.2 mM CuSO₄ for 10 min at room temperature). The oxidised proteins in both samples were tagged with dinitrophenylhydrazine (DNP), which forms a covalent bond with carbonyl groups. The DNP-tagged proteins were immunoprecipitated using anti-DNP antibodies and digested with trypsin. The mixture of peptides was analysed by nano-HPLC coupled online to an ESI-Quad-TOF mass spectrometer. The peptides were separated by stepwise ion exchange chromatography followed by reverse phase chromatography (2D-LC), and analysed by MS/MS. Proteins were identified by un-interpreted fragment ion database searches. Using this approach we identified 20 oxidised proteins in the control sample and a further 32 in the oxidised sample. Western blots of 2D-gels of the same samples prior to immunoprecipitation verified that the oxidation treatment increases protein oxidation also for specific proteins. Likewise Western blots showed that neither the isolation of mitochondria nor their subfractionation introduced carbonyl groups. We therefore conclude that a number of proteins are oxidised in the matrix of rice leaf mitochondria in vivo and further identify a group of proteins that are particularly susceptible to mild oxidation in vitro.

Highlights Molybdenum single crystals and wires exhibit large pseudocapacitances in cyanide solution. Gold deposition takes place after partial reduction of the thin surface oxide. The partially reduced surface oxide may assist gold deposition prior to electrodeposition. Adsorbed intermediates are involved both in the deposition and dissolution of gold. The chemical adhesion of gold on molybdenum is weak and physical binding is a prerequisite.

Materiens partikelnatur anses vara en av de allra mest grundläggande teorierna i den naturvetenskapliga världen. Undervisning kring denna teori är omdiskuterad i forskning, inte minst vad gäller begreppsanvändning. Mer allmänna begrepp som ”partikel” kan användas i undervisningen, men det kan också vara nödvändigt att differentiera mellan olika begrepp, som atomer, molekyler eller elektroner beroende på vilket fenomen som beskrivs. Den här studien ämnar analysera läromedlet NTA och dess begreppsanvändning i relation till materiens partikelnatur. Det görs genom en enkel kvantitativ analys och kvalitativ innehållsanalys. Studien visar att NTA-materialets olika delar använder partikelbegrepp på ett konsekvent sätt, men att mellan delarna är det stora skillnader. I vissa delar används ett begrepp men i ett annat används ett annat begrepp för att beskriva samma sak. Användningen av begrepp relateras till teorier om begreppsförståelse i grundskoleåldrar. Det diskuteras också kring vad skillnaderna i begreppsanvändning kan bero på och vad detta innebär för användandet av NTA som läromedel.