No description available.

As the demand for biogas increases, so does the amount of digestate produced. Digestate contains large amounts of nutrients and has been introduced in agriculture as an alternative plant nutrient. However, digestate can have a high content of heavy metals which over time increases in soil concentration and can have negative consequences for humans and the environment. Therefore, methods to remove the contaminants in digestate are necessary, while enabling resource recovery that reduces the demand for raw materials and promotes a circular society. In this study, a method was designed and tested that enables the extraction of heavy metals using the naturally sourced substances chitosan and apple cider vinegar. The quantitative part of the study has been carried out in the form of laboratory experiments with solutions of the heavy metals copper(ii)sulphate (CuSO4) and iron(iii)chloride (FeCl3), since the metals are easily analyzed in connection with their strong colors and reflect a typical behavior of heavy metals. The laboratory was divided into two phases where first the method was tested on aqueous solutions with heavy metals and then on biogas digestate. The qualitative part of the study consisted of two interviews with active actors in the field to gain a broader perspective and greater knowledge. The results show that apple cider vinegar and chitosan together enable the removal of heavy metals from polluted water.

Vi har skapat en ämnesorienterad länksamling för att undersöka om denna kan bidra till ett ökat engagemang och intresse för ämnet hos eleverna. 57 gymnasieelever i årskurs 1 och årskurs 2 på naturvetenskapliga programmet vid Pauliskolan i Malmö har använt länksamlingen under ett lektionspass och därefter besvarat en enkät. En väl genomarbetad och relevant länksamling innebär att eleverna undviker ett tidskrävande sökande med sökmotor och istället finner bra och förståelig information. Vår undersökning visar att mer än hälften av eleverna tror att de tar ett större ansvar för sina studier om de har tillgång till en ämnesorienterad länksamling. En majoritet av eleverna tror att de kommer att lägga ner mer tid på studierna om en länksamling finns tillgänglig i det aktuella ämnet. Resultatet visar att det finns god grund att tro att en länksamling ger upphov till ett ökat engagemang och motivation för studierna.

Sampling and sample introduction are two key steps in quantitative gas chromatography. In this thesis, a development of a previously described sampling technique as well as a novel concept for sample introduction in gas chromatography are presented. The thesis is based on two papers. Paper I describes a method for preparing physically mixed polymers for use as sorbent phases in open tubular trapping of gaseous analytes. The concept is based on mechanical disintegration and mixing of solid or liquid poly(ethylene glycol), PEG, into poly(dimethylsiloxane), PDMS, in a straightforward manner. The resulting mixture exhibits a higher affinity towards polar analytes, as compared to pure PDMS. Paper II describes a novel approach to liquid sample introduction with the split/splitless inlet, used in gas chromatography. Classical injection techniques struggle with discrimination of high boiling analytes and poor repeatability of the injected amount of analytes. The presented injection technique utilizes high voltage to obtain a spraying effect of the injected liquid. The spraying effect can be achieved with a cold needle, which is unprecedented for gas chromatographic injections. The cold needle spraying results in highly repeatable injections, free from discrimination of high boiling analytes. / QC 20101105

This licentiate thesis deals with quantum chemistry methods for large systems. In particular, the thesis focuses on the efficient construction of the Coulomb and exchange matrices which are important parts of the Fock matrix in Hartree--Fock calculations.The methods described are also applicable in Kohn--Sham Density FunctionalTheory calculations, where the Coulomb and exchange matrices areparts of the Kohn--Sham matrix. Screening techniques for reducing the computational complexity of bot Coulomb and exchange computations are discussed, as well as the fast multipole method, used for efficient computation of the Coulomb matrix. The thesis also discusses how sparsity in the matrices occurring in Hartree--Fock and Kohn--Sham Density Functional Theory calculations can be used to achieve more efficient storage of matrices as well as more efficient operations on them. As an example of a possible type of application, the thesis includes a theoretical study of Heisenberg exchange constants, using unrestricted Kohn--Sham Density Functional Theory calculations. / QC 20101123

Boron-carbon (BxC) thin films enriched in 10B are potential neutron converting layers for 10Bbased solid-state neutron detectors given the good neutron absorption cross-section of 10B atoms in the thin film. Chemical Vapour Deposition (CVD) of such films faces the challenge that the maximum temperature tolerated by the aluminium substrate is 660 °C and low temperature CVD routes for BxC films are thus needed. This thesis presents the use of two different organoboron precursors, triethylboron –B(C2H5)3 (TEB) and trimethylboron – B(CH3)3 (TMB) as single-source precursors for CVD of BxC thin films. The CVD behaviour of TEB in thermal CVD has been studied by both BxC thin film deposition and quantum chemical calculations of the gas phase chemistry at the corresponding CVD conditions. The calculations predict that the gas phase reactions are dominated by β-hydride eliminations of C2H4 to yield BH3. In addition, a complementary bimolecular reaction path based on H2-assisted C2H6 elimination to BH3 is also present at lower temperatures in the presence of hydrogen molecules. A temperature window of 600 – 1000 °C for deposition of X-ray amorphous BxC films with 2.5 ≤ x ≤ 4.5 is identified showing good film density (2.40 – 2.65 g/cm3) which is close to the bulk density of crystalline B4C, 2.52 g/cm3 and high hardness (29 – 39 GPa). The impurity level of H is lowered to < 1 at. % within the temperature window. Plasma chemical vapour deposition has been studied using TMB as single-source precursor in Ar plasma for investigating BxC thin film deposition at lower temperature than allowed by thermal CVD and further understanding of thin film deposition process. The effect of plasma power, total pressure, TMB and Ar gas flow on film composition and morphology are investigated. The highest B/C ratio of 1.9 is obtained at highest plasma power of 2400 W and TMB flow of 7 sccm. The H content in the films seems constant at 15±5 at. %. The B-C bond is dominant in the films with small amount of C-C and B-O bonds, which are likely due to the formation of amorphous carbon and surface oxidation, respectively. The film density is determined as 2.16±0.01 g/cm3 and the internal compressive stresses are measured to be <400 MPa.

No description available.

Informations och kommunikationsteknologier (IKT) används allt mer inomskolundervisningen. I detta studentinitierade utvecklingsprojekt har jag utvecklat ettwebbaserat frågesportsspel där eleverna kunde spela mot varandra. Syftet var att göralärandeprocessen mer lustfylld: “Playing is above all, a privileged learning experience”(Rosas et al., 2003). Den här studien innehåller ett försök till kvantitativ utvärdering aveffekten spelandet på de deltagande elevernas resultat på nationellt prov i kemi 1 med hjälp av Student's t-test. Jag noterar också att eleverna föreföll att ha roligt medan de spelade.

Med detta arbete vill jag undersöka kemilärares attityder till säkerheten gällande kemilaborationer. Jag vill få en inblick i hur arbetet fungerar i praktiken och vilka faktorer som har betydelse för säkerheten.För att studera lärarnas inställningar valde jag att utföra semistrukturerade intervjuer med hjälp av färdiga frågor. Denna metod ger möjlighet att med hjälp av följdfrågor få en rättvis bild av lärarnas åsikter samtidigt som det ger bra underlag för att jämföra mellan lärarna. Under laborationstid känner sig alla lärare ansvariga för säkerheten och har utarbetade säkerhetsrutiner. Lärarnas individuella inställningar till säkerhetsarbetet verkar vara beroende av hur mycket skolan de arbetar på har satsat på säkerhetsarbete. Erfarenhet och ämneskunskaper ger läraren trygghet i sin undervisning och stökiga elever kan ge en otrygg miljö både för lärare och elever. Oavsett hur säkerheten fungerar på skolorna så kände alla informanterna ett behov av tydliga och lättillgängliga regler och instruktioner till undervisande kemilärare. De skulle speciellt behövas vid nyanställningar. Från detta kan man dra slutsatsen att skolornas kemilärare över lag behöver veta vad som gäller på respektive skola samt de regler som gäller regionalt. En enkel lösning till detta är att ha ett häfte som delas ut till kemilärarna vid anställning. / With this thesis I intend to examine chemistry teachers’ attitudes towards safety concerning laboratory experiments within the subject. I want to get an insight in how laboratory experiments work in practice and what factors matter concerning safety.In order to study teachers’ attitudes I chose to implement semi structured interviews with ready made questions. This method gives the opportunity to, with the aid of resulting questions, receive a fair view of teachers’ opinions and at the same time it yields a good basis for comparison between the teachers.During laboratory experiments teachers feel responsible for safety and have safety routines worked out. Teachers’ individual attitudes towards safety seem to be dependent on how much the school in which they work prioritize safety. Experience and knowledge within the subject gives the teacher security in their teaching and unruly students can give both teacher and student an unsafe environment. But no matter how safety worked at the individual schools all informants felt a need of a legible and accessible rules and instructions for the chemistry teachers in their work. This was especially considered a necessity for newly employed teachers.From this we can draw the conclusion that schools’ chemistry teachers over all need to know what is common practise at their respective schools as well as what rules and regulations are regionally pertained.

Informations och kommunikationsteknologier (IKT) används allt mer inomskolundervisningen. I detta studentinitierade utvecklingsprojekt har jag utvecklat ettwebbaserat frågesportsspel där eleverna kunde spela mot varandra. Syftet var att göralärandeprocessen mer lustfylld: “Playing is above all, a privileged learning experience”(Rosas et al., 2003). Den här studien innehåller ett försök till kvantitativ utvärdering aveffekten spelandet på de deltagande elevernas resultat på nationellt prov i kemi 1 med hjälp av Student's t-test. Jag noterar också att eleverna föreföll att ha roligt medan de spelade.