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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

WOOD-POLYMER ALLOYS -- SOME FUNDAMENTAL CONSIDERATIONS

Ross, L. 10 1900 (has links)
<p>An experimental investigation of graft copolymerization of styrene in wood was performed utilizing (1) Cobalt-60 radiation initiation, 2) impregnating solutions of styrene, methanol and water and (3) heat during the irradiation period. It was found that heating did not increase the grafting efficiency of the system. The grafting process was found to be dependent upon (1) the method of impregnation, (2) the density of the wood and (3) the amount of swelling agents in the impregnating solution. Wood treated with styrene and swelling agents was weakened in all mechanical properties except the maximum crushing strength and properties associated with compression. In genaral, wood treated with pure styrene was strengthened. It is felt that the use of radiation in the formation of wood-plastic composites is commercially unjustified.</p> / Master of Engineering (ME)
2

In Vitro Starch Digestion for Analysis of Healthy Carbohydrates

Ngo, Carolin January 2018 (has links)
The health impact of carbohydrates is often debated in questions regarding nutrition and health. One reason is that intake of carbohydrates affect the blood glucose level to different extent depending on the characteristics of the carbohydrate. Starch is the most common carbohydrate and it can be categorized as rapidly digested starch (RDS), slowly digested starch (SDS) and resistant starch (RS) where the speed parameter refers to how easily enzymes hydrolyze the starch is and thus how fast the blood glucose level is affected. However, RS does not affect the blood glucose level but instead becomes substrate for microbial fermentation of the gut microbiota. Long term consumption of resistant starch decreases the risk of intestinal diseases. The aim of this project was therefore to investigate different in vitro methods for determination of RS content in samples. The impact which particle size and extrusion have on the amount of RS were investigated since the factors can increase or decrease the amount of RS. Sorghum and cowpea were of interest to analyze since the crops are important nutrient sources in both Africa and Asia. Two methods were investigated for determination of RS content where the method developed by Megazyme International Ireland Ltd. was more stable than the method developed by Goñi et al. Modifications of the Megazyme method were performed in order to obtain more reliable values which was achieved when enzymes from Sigma-Aldrich were used. Samples of sorghum of the particle sizes 125 µm and 250 µm resulted in values ranging between 11.44 – 11.94 g RS/100 g sample and 8.49 – 9.02 g RS/100 g sample after extrusion was performed. Samples of the larger particle size resulted in lower amount of RS, most likely due to starch-protein associations. Cowpea resulted in 11.05 g RS/100 g sample and 9.20 g RS/100 g sample before and after extrusion. Determination of the amylose and amylopectin ratio showed that sorghum contained 53.3 – 59.3 % (w/w) amylose and cowpea 53.2 % (w/w) amylose. A ratio favoring amylose also favors the formation of RS. However, the particle size has larger impact on the RS content than the amylose content and sorghum of particle size 125 µm was shown to be the healthiest regarding amount of RS. Cowpea showed the lowest amount of amylose yet the highest amount of RS among the extrudates and the lowest set back value of -0.5 which leads to an assumption towards unstable methods. Further development of the methods should be carried out in forms of modifications. Optimization of treatments regarding sorghum of particle size 125 µm should be continued in order to obtain even higher RS content.
3

Heterogenization of a Cobalt Porphyrin Catalyst Investigated by Scanning Probe Microscopy and X-Ray Photoelectron Spectroscopy: The Effect on Catalysis of Oxidation Reactions

Ledung, Greger January 2008 (has links)
<p>Construction of advanced materials through self-assembly on the molecular level is an important route to achieve novel functionality. Self-assembly of thiols onto gold has during the last decades shown greate promise in the creation of functional nanomaterials, such as sensors or catalysts, but for many applications silicon should be a better substrate since it offers semiconducting properties and better processing abilities in addition to being cheaper. This work describes an efficient novel method to incorporate reactive disulfide bonds onto a silica surface under mild reaction conditions. The reactive thiol groups introduced onto the silica surface will be oxidized but is then converted into highly reactive thiopyridyl groups, which can easily be utilized for further organic synthesis involving thiol-containing molecules. </p><p>Cobalt tetraarylporphyrins with thioacetate-functionalized carbon chains on the aryl groups were synthesized (CoTPP-L) and were used as a model system for investigating catalytic activity in homogeneous and heterogeneous oxidation catalysis. For heterogeneous catalysis CoTPP-L was immobilized onto gold surfaces through thiol-gold self-assembly, and onto silica surfaces by the above mentioned disulfide exchange method.</p><p>The properties of the molecular layers were characterized on the molecular level by means of X-ray photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). The immobilization on gold surfaces took place through the formation of multiple thiolate bonds and it could be controlled by varying the preparation scheme. More thiolate bonds form if the thioacetyl protective groups of the thiol linkers are cleaved off prior to immobilization. The CoTPP-L molecules were in all cases found to form stable disordered monolayers on gold surfaces. On silica surfaces the CoTPP-L forms patchwise multilayers. </p><p>The catalytic performance of the heterogenized systems (CoTPP-L immobilized onto gold or silicon wafers) was evaluated and it was found that the strong inactivation observed for their homogeneous congener was avoided. As a result, the turnover number per molecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneous catalyst. It is thus demonstrated that the performance of these catalysts can be dramatically improved if the catalyst arrangement can be controlled on the molecular level. Work is ongoing to extend the system to high surface area materials.</p>
4

Heterogenization of a Cobalt Porphyrin Catalyst Investigated by Scanning Probe Microscopy and X-Ray Photoelectron Spectroscopy: The Effect on Catalysis of Oxidation Reactions

Ledung, Greger January 2008 (has links)
Construction of advanced materials through self-assembly on the molecular level is an important route to achieve novel functionality. Self-assembly of thiols onto gold has during the last decades shown greate promise in the creation of functional nanomaterials, such as sensors or catalysts, but for many applications silicon should be a better substrate since it offers semiconducting properties and better processing abilities in addition to being cheaper. This work describes an efficient novel method to incorporate reactive disulfide bonds onto a silica surface under mild reaction conditions. The reactive thiol groups introduced onto the silica surface will be oxidized but is then converted into highly reactive thiopyridyl groups, which can easily be utilized for further organic synthesis involving thiol-containing molecules. Cobalt tetraarylporphyrins with thioacetate-functionalized carbon chains on the aryl groups were synthesized (CoTPP-L) and were used as a model system for investigating catalytic activity in homogeneous and heterogeneous oxidation catalysis. For heterogeneous catalysis CoTPP-L was immobilized onto gold surfaces through thiol-gold self-assembly, and onto silica surfaces by the above mentioned disulfide exchange method. The properties of the molecular layers were characterized on the molecular level by means of X-ray photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). The immobilization on gold surfaces took place through the formation of multiple thiolate bonds and it could be controlled by varying the preparation scheme. More thiolate bonds form if the thioacetyl protective groups of the thiol linkers are cleaved off prior to immobilization. The CoTPP-L molecules were in all cases found to form stable disordered monolayers on gold surfaces. On silica surfaces the CoTPP-L forms patchwise multilayers. The catalytic performance of the heterogenized systems (CoTPP-L immobilized onto gold or silicon wafers) was evaluated and it was found that the strong inactivation observed for their homogeneous congener was avoided. As a result, the turnover number per molecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneous catalyst. It is thus demonstrated that the performance of these catalysts can be dramatically improved if the catalyst arrangement can be controlled on the molecular level. Work is ongoing to extend the system to high surface area materials.
5

Hydrogen-rich materials as auxiliary reducing agents in the blast furnace

Sideris, Dimitrios January 2018 (has links)
No description available.
6

Freeze-drying of protein pharmaceuticalin vials with different character

Falk, Julia January 2019 (has links)
Freeze-drying of protein pharmaceuticals is a procedure frequentlyused to obtain stability of the active pharmaceutical ingredientduring distribution and storage. It can be performed in pre-filledsyringes, with a lubricous coating of silicone on the inside, toenable the piston moving. The coating changes the environmentpotentially affecting the features of the freeze-dried cake sincethe wetting behavior and adhesion to the inner wall is affected.This project aimed to investigate the effect of the siliconizationof the cakes. Three different formulations were freeze-dried in nonsiliconized(NS) and siliconized vials using differentsiliconization protocols. Analysis was done using differentialscanning calorimetry (DSC), thermal gravimetric analysis (TGA),scanning electron microscopy (SEM), X-ray photoelectron spectroscopy(XPS) and an embedding method, intended to give information aboutthe cake’s shrinkage, cracking and pore-structure. The water contentin the bottom of the cakes was consistently higher than in the top,a difference decreasing over time. Increased surface hydrophobicitylead to increased shrinkage of the cake’s volume and a decrease infogging. The bottom of the protein cake in the vial siliconized witha commercial silicone emulsion consisted of pores with regularlyequal pore size and thick pore walls, a structure not seen in anyother cake. All cakes in the silicone emulsion siliconized vials hadlower water content than the cakes in the vials using the othersiliconization method. The XPS-analysis showed that the cakes in theemulsion siliconized vials contained silicon, indicating an excessof silicone when siliconizing and/or an unstable coating.
7

An Investigation of Aspects Affecting Availability and Grading of High-Risk Antibiotics in Sweden. : Group 2

Fridberg, Andrea, Leding, Albin, Lundahl, Hanna, Rydin, Hannah, Sjölund, Hanna January 2019 (has links)
The Public Health Agency of Sweden published a report in 2017 listing 34 antibiotics that risk disappearing from the Swedish market, all with significant value to the Swedish healthcare. The aim of this report was to investigate the availability risk, why these risks occur and identify potential patterns. Ten different aspects were developed with different impact on the availability to establish the grade of availability risk for each of the analysed antibiotics. The antibiotics were compiled in a table and were graded as low, medium or high risk. The results showed that nine of the antibiotics have a high risk of disappearing from the Swedish market while ten respectively 20 were graded as medium and low risk. Patterns were found regarding the difference in formulations and the economic aspects.
8

Quantification of circulating CD19 CAR-T cells in peripheral blood for implementation in routine diagnostics

Sjölund, Hanna January 2021 (has links)
No description available.
9

Computational Cyclic Voltammetry of Supercapacitors

Pettersson, Albert January 2022 (has links)
As the demand on electrochemical energy storage devices grows, more complex technologies are required, hence an improved knowledge on the microscopical level is needed. This can be achieved by using computational tools, in particular molecular simulations. Recent studies have shown that the commonly used electrode model fails to describe non perfect conductors simulated with molecular dynamics. The extended version of the polarizable electrode model, i.e., the Thomas-Fermi model includes a term to describe the characteristic screening length of the electrode material, hence the metalicity can be tuned. Herein, supercapacitors with electrodes described by the Thomas-Fermi model with a graphite like structure and an ionic liquid as the electrolyte are investigated. By performing cyclic voltammetry, it is found that the scan rate has less impact on the capacitance when the screening length is large and vice versa that the capacitance is little affected by the screening length at high scan rates. A comparison with a previous study made with an aqueous sodium chloride solution as the electrolyte shows that ionic liquids and aqueous sodium chloride are affected similarly by the metalicity of the electrode, although the ionc liquid is found to have a slower dynamics compared to aqueous sodium chloride.
10

Recovery of Phosphorus from Incineration of Sewage Sludge / Återvinning av fosfor från förbränning av avloppsslam

Bhasin, Aditi January 2017 (has links)
The primary source of phosphorus, phosphate rock, is a non-renewable resource which is expected to get exhausted in the next 50 – 100 years. Sewage sludge in Sweden constitutes 25% of the annual phosphorus in the country, making it a potentially significant source for phosphorus recovery. The aim of this project was to identify the potential for phosphorus recovery from incineration of dewatered and digested sewage sludge in Fortum Värme’s power plants in Stockholm. The study was limited to two boilers located at Bristaverket, Stockholm - boiler B1, a bio-fired fluidized bed boiler and boiler B2, a waste-fired grate incinerator. A theoretical analysis for boiler B1 showed that it is possible to reach a concentration of 4.6% phosphorus in fly ash if sludge and recycled wood fuel are mixed in the ratio 48:52. A test program was executed in boiler B2 to burn up to 12.5% sludge with a mixture of household waste and industrial waste. A total of 755 tons of sludge was used over a period of three weeks during the test in boiler B2. The test was successful in terms of combustion and emissions. There was no increase in the emissions of nitrogen oxides, sulphur dioxide and hydrochloric acid in the flue gas. Mercury emissions in the chimney increased with an increase in the share of sludge, nevertheless, the emission level was below the limit set by the Swedish Environmental Protection Agency. Decrease in the amount of unburnt materials in bottom ash and in the emission of carbon monoxide showed that the burning of fuel was more efficient with input of sludge. The maximum phosphorus concentration was 0.7% in both bottom ash and fly ash from boiler B2 and occurred at an input of 12.5% sludge. This concentration is close to the expected theoretical value, however it is not expected to be feasible to recover phosphorus at such a low concentration. The ashes were sent to Fortum Waste Solutions and Ragn-Sells for recovery of phosphorus, however the results are not included in this report due to time constraints for thesis study. In order to increase the concentration of phosphorus in the ashes, a system approach is recommended, for instance, recirculation of bottom ash into the incinerator. / Den primära källan till fosfor, fosforit, är en icke-förnybar resurs som är begränsad och förväntas bli förbrukad under de kommande 50-100 åren. Avloppsslam i Sverige innehåller 25% av det årliga fosforflödet, därmed är det en potentiellt viktig källa för fosforåtervinning. Syftet med detta projekt var att identifiera potentialen för fosforåtervinning från förbränning av rötat och avvattnat avloppsslam i Fortum Värmes kraftvärmeverk i Stockholm. Projektet avgränsades till fokus på två pannor i Bristaverket: panna B1, en bioeldad fluidiserad bäddpanna och panna B2, en avfallseldad rosterpanna. En teoretisk analys av panna B1 visade att det är möjligt att uppnå en koncentration på 4,6% fosfor i flygaska om slam och RT-flis blandas med förhållandet 48:52. Ett test program genomfördes på panna B2 för att förbränna uppe till 12,5% slam med en blandning av hushållsavfall och grovkross. Totalt användes 755 ton slam under en period av tre veckor då testet genomfördes i panna B2. Det var ett lyckat test med avseende på förbränning och utsläpp. Ingen ökning av kväveoxider, svaveldioxid och saltsyra i rökgasen observerades vid utsläppen. Kvicksilverutsläppet i skorstenen ökade med en ökad andel slam, dock var utsläppsnivån under den gränsen som är fastställd av Naturvårdsverket. Minskning av oförbrända material i bottenaska och i utsläpp av kolmonoxid visade att förbränningen av bränsle är effektivare med inmatning av slam. Den maximala fosforkoncentrationen var 0,7% i både bottenaska och flygaska från panna B2 vid ett intag av 12,5% slam. Denna koncentration ligger nära det förväntade teoretiska värdet, men det anses inte vara rimligt att återvinna fosfor vid en sådan låg koncentration ut ett ekonomist perspektiv. Askan skickades till Fortum Waste Solutions och Ragn-Sells för återvinning av fosfor, men resultatet redovisas inte i denna rapport på grund av tidsbegränsningen av detta examensarbete. För att öka koncentrationen av fosfor i askan rekommenderas en systeminriktning, till exempel recirkulation av bottenaska i pannan.

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