In dieser Arbeit wurden die Möglichkeiten und Grenzen für Zirkulardichroismus-Messungen mit Synchrotronstrahlung untersucht. Dazu wurde ein Messaufbau für Zirkulardichroismus-Messungen an zwei Strahlrohren am Berliner Elektronenspeicherring für Synchrotronstrahlung eingesetzt, die für Messungen im Bereich des ultravioletten Lichts geeignet sind. Eigenschaften der Strahlrohre und des Messaufbau wurden in einigen wichtigen Punkten mit kommerziellen Zirkulardichroismus-Spektrometern verglichen. Der Schwerpunkt lag auf der Ausdehnung des zugänglichen Wellenlängenbereichs unterhalb von 180 nm zur Untersuchung des Zirkulardichroismus von Proteinen in diesem Bereich. In diesem Bereich ist es nicht nur die Lichtquelle sondern vor allem die Absorption des Lichts durch Wasser, die den Messbereich bei der Messung biologischer Proben in wässriger Lösung einschränkt. Es wurden Bedingungen gefunden, unter denen der Messbereich auf etwa 160 nm, in einigen Fällen bis auf 130 nm ausgedehnt werden konnte. Dazu musste die Pfadlänge deutlich reduziert werden und verschieden Probenküvetten wurden getestet. Der Einfluss der dabei auftretenden Spannungsdoppelbrechung in den Probenküvetten auf das Messsignal konnte mit einem alternativen Messaufbau deutlich reduziert werden. Systematische Fehler im Messsignal und auftretende Strahlenschäden begrenzen jedoch die Zuverlässigkeit der gemessenen Spektren. Bei Proteinfilmen schränkt die Absorption von Wasser den Messbereich kaum ein. Es wurden jedoch meist deutliche Unterschiede zwischen den Spektren von Proteinfilmen und den Spektren von Proteinen in wässriger Lösung festgestellt. Solange diese Unterschiede nicht minimiert werden können, stellen Proteinfilme keine praktikable Alternative zu Messungen in wässriger Lösung dar. / The possibilities and limitations for synchrotron radiation circular dichroism measurements were investigated in this thesis. Therefore an experimental setup to measure circular dichroism was used at two beamlines at the “Berliner Elektronenspeicherring für Synchrotronstrahlung”(BESSY), which were suitable in the ultraviolet range of light. Properties of the beamlines and the experimental setup were compared to those of commercial circular dichroism spectrometer in some important points. The focus was on the extension of the accessible wavelength range below 180 nm, with the aim to investigate the circular dichroism of proteins in that range. It is not only the light source that limits measurements with aqueous solutions in that range, but mainly the absorption of the light by water. Conditions were found under which the wavelength range was extended to about 160 nm, in some cases even to 130 nm. To achieve this, a significant reduction of the pathlength was necessary. Several sample cells were tested for their usability. The effect of birefringence within the sample cells on the circular dichroism signal could be reduced strongly with an alternative experimental setup. However systematic errors in the circular dichroism signal and appearing radiation damage of the proteins limits the reliability of the measured spectra. By using protein films, the light absorption by water is not a problem anymore. However, significant differences between the circular dichroism spectra of protein films and proteins in aqueous solution occurred in most of the cases. Unless these differences can be eliminated, measuring protein films is not an alternative to measurements in aqueous solution.

Capillary electrophoresis (CE) has a wide range of applications in the field of analytical chemistry. In general the most expensive part in a CE system is the detector due to the fact that the detector must have a high sensitivity for small detection volumes and low concentrations. Building portable instruments is one way to make the instruments cheaper and has the advantage that they can be used virtually everywhere. However, downscaling of CE instruments puts some extra demands on the detector. This report describes the design and building of two homemade light-emitting diode (LED) based detectors; a LEDabsorbance photometric detector (LED-AP) and a LED-induced fluorescence (LED-IF) detector. The main goal was to install them inside a portable CE and make a simple separation. The performance of the two detectors had to be evaluated before the main goal could be achieved. p-Nitrophenol was used to create a sensitivity graph for the LED-AP detector, calculating the upper linearity to 5.6 mM when the sensitivity had dropped 10 % caused by non-linearity. The sensitivity graph also showed that the detector had an effective pathlength of 74.2 µm and a stray light of 4.5 % for a 75 µm i.d fused-silica capillary. The LED-IF detector was evaluated by determining the limit of detection (LOD) for fluorescein, at a signal to noise ratio of 3. The LOD was 0.72 µM ± 0.01 µM when immersion oil was used to limit the light scattering from the optic fibres in to the capillary and 0.58 µM ±0.02 µM when silicone oil was used. Without doing any improvements only the LED-AP detector could be used in the portable CE. As a common application area for portable CE instruments is environmental analysis, indirect detection using p-nitrophenol as a probe for separating anions was done to test the system. All analytes were eluted in less than 4 minutes.

Research in the field of molecular neuroscience contributes a better perception of the events that trigger neurodegeneration. At the forefront of this work is the study of intracellular calcium as a consequence of mitochondrial dumping and NMDA receptor activation by glutamate. Increased intracellular calcium presages excitotoxicity with ultimate apoptosis of the cell. Among the many disorders involving this sequence is depression, a disorder that in and of itself is a risk factor for neurodegenerative disorders such as Alzheimer disease. The successful use of anti-depressants to alleviate the depressive state leads to the question about whether these pharmacological agents, as part of their effect to ameliorate depression, might have an effect on intracellular calcium. Until now, this has not been explored directly but such exploration was initiated with this thesis. As a model for astrocytes and neurons, two cell lines, C6 and SH-SY5Y were used. These were differentiated with all-trans retinoic acid into astrocyte-like and neuron-like cells. Graphic imaging of intracellular calcium by ratiometrics is not new, but what is new is using this technique to evaluate the effect of the antidepressants mirtazapine and citalopram on intracellular calcium fluxes induced by glutamate. Furthermore, comparing the ratiometric intracellular calcium flux in the presence of mirtazapine and citalopram to that of known NMDA blockers was also done for the first time. Also studied were the acute and chronic effects of mirtazapine and citalopram on cell viability. The antidepressant agents, mirtazapine and citalopram, were chosen for this study. Mirtazapine blocks the adrenergic and serotonergic inhibitory autoreceptors which results in the increased release of these neurotransmitters and increases their concentration in the synapse. And it also has been shown to have an anti-oxidant and a calcium modulatory effect. Citalopram has the highest degree of serotonin reuptake selectivity of all the selective serotonin reuptake inhibitors. The ratiometric studies found that mirtazapine and citalopram reduce the effect of glutamate-induced increase in relative [Ca2+]i by either a direct or indirect action on NMDA receptors. This effect is not similar to the NMDA blockers memantine and AP5. The supporting evidence is that CCCP, which normally releases calcium from mitochondria, has no effect in cells treated with acute mirtazapine or citalopram. This indicates that no calcium entered the cell – and subsequently none was taken up by mitochondria – in response to glutamate. However, these observations were with a limited number of cells and, therefore, these results will have to be verified by different techniques by different laboratories. In microplate studies, all drugs studied reduced cell viability but the mechanism behind this reduced viability remains to be determined. This may be due to mutations in enzymatic expression, uptake of drug through the cell membrane, or other perturbations. The reduction in cell viability induced by acute glutamate was attenuated by pretreatment with mirtazapine or citalopram. Moreover, chronic treatment of the cells with mirtazapine or citalopram for 10 weeks before acute treatment with glutamate either attenuated the effect on viability or reversed it. Based on this present study, mirtazapine and citalopram may be useful as neuroprotective agents to alleviate not only depression but also to reduce cell death in neurodegenerative diseases, trauma and stroke.

Alternative energy sources such as solar energy have attracted an extensive interest in the petroleum shortage era. Among solar cells, dye-sensitized solar cell (DSSC) attracts the attention of widespread research teams because of the easy-production process, low cost, and good photon-to-electron conversion efficiency. In this study, both UV and acid solution such as HCl are used to improve the efficiency of DSSC. The UV illumination can eliminate organic contaminates on TiO2 by photocatalysis and enhance the adsorption of dye molecules. Meanwhile, the coordination mode between TiO2 and dye could be changed and lower the electron transportation. If the HCl solution is used after UV illumination, the coordination mode can be preserved. Moreover, H+ from HCl can attract the COO¡Ð anchoring group of dye by electrostatic force. It further increases the adsorption of dye and improves the DSSC efficiency. The coordination mode was measured by Fourier-transform infrared spectrometer (FTIR). The internal resistance was measured by electrical impedance spectroscopy (EIS). The chemical properties were characterized by X-ray photoelectron spectroscopy (XPS). The light absorbance was measured by ultraviolet-visible spectroscopy (UV-Vis). The morphology was observed by field emission scanning electron microscope (FE-SEM). The performance of the cells was measured by a semiconductor device analyzer. In our results, the conversion efficiency was improved from 6.29% of untreated one to 6.71 and 7.39% for UV and UV + HCl treated ones.

A novel approach of using near infrared region (NIR) dyes is applied to elucidate the binding interaction between human serum albumin (HSA) and mangiferin (MGF). HSA is a blood carrier protein used for drug delivery, while mangiferin is a natural polyphenol found in mangoes that possesses numerous beneficial health properties. The NIR dyes are used as a probe to investigate MGF binding interaction with HSA via monitoring fluorescence of Trp-214 residue. Molecular modeling is used for docking and semi-empirical analysis. The investigation of the binding interaction between Trp-214 and MGF is significant, for it may offer broader pharmacological insight and applications for the polyphenol. Mangiferin in proposed to bind with a 2:1 stoichiometric ratio with HSA to the Trp-214 residue in subdomain IIA and another possible binding site to be determined in future studies. Spectral changes suggest a stabilized protein conformation upon mangiferin binding with the addition of NIR dye E-06 and MHI-06.

Halten löst organiskt material (DOC) har under de senaste 20 åren ökat i våra sjöar. Det har också skett förändringar i karaktären. DOC ställer till problem för vattenverk som använder ytvatten som dricksvattenkälla genom att det kan ge lukt, smak och färg till vattnet. Det ger också ett ökat behov av fällningskemikalier, större slambildning och större bildning av potentiellt skadliga desinfektionsprodukter. I och med förändringarna i halt och karaktär av DOC behöver nuvarande reningstekniker förbättras och nya tekniker utvecklas. I den här studien undersöktes två konventionella reningstekniker; fällning med järnklorid och fällning med aluminiumsulfat, samt två modernare tekniker; jonbyte med MIEX® och membranteknik. Sex olika vatten med extrema typer av DOC användes, såsom algogent vatten, avloppsvatten och myrvatten, för att få en stor spridning i SUVA (specifik UV254-absorbans). SUVA är kvoten mellan absorbansen vid 254 nm och DOC-halten och ger en indikation på fördelningen mellan alloktont och autoktont material. Analys av DOC, absorbans, fluorescensparametrar, anjoner och järn utfördes för att få en uppfattning av hur mycket och vilken typ av DOC som renades för respektive teknik. Membrantekniken hade generellt högre reducering av DOC än övriga reningstekniker. Genomgående renades alloktont material i högre utsträckning än autoktont material. Vatten med högt SUVA-värde (>3), alltså större andel alloktont material, var mer lättbehandlat än ett med lågt värde, men sambandet var inte linjärt. Algogent vatten renades dåligt med MIEX® och fällning men bättre med membran. Det fanns ett tydligt samband mellan absorbans (245 nm) och DOC-halt som gör det möjligt att med online-mätning av absorbans få fram tillräckligt noggranna värden på DOC-halter. / The amount of dissolved organic carbon (DOC) has risen in our lakes during the past 20 years and it has also changed in character. DOC causes problems for water treatment plants that are using surface water as a drinking water source. It gives the water odour, taste and colour. It also leads to a higher need of precipitation chemicals, more sludging, and larger formation of potentially harmful disinfection products. With the changes in both amount and character in DOC, current water treatment techniques need to be improved and new techniques developed. In this study, two conventional water treatment techniques; precipitation with iron chloride and precipitation with aluminium sulphate, and two more modern techniques; ion exchange with MIEX® and membrane filtration, were examined. Six waters with extreme types of DOC were used, including algogenic water, wastewater, and water from mire, in order to have a wide range of SUVA-values (specific UV254-absorbance). SUVA is the ratio between absorbance at 254 nm and the content of DOC. SUVA gives an indication about the distribution of allochthonous and autochthonous matter. In each water treatment technique analysis of DOC, absorbance, fluorescence parameters, anions, and iron were performed to gather information regarding how much and which type of DOC were reduced, in each water treatment technique. Membrane filtration had generally higher reduction of DOC compared to the other techniques. Allochthonous matter was reduced to a higher extent than autochthonous matter. Waters with a high value of SUVA (>3), which means a larger proportion of  allochthonous matter, was more easily treated than water with lower values, but the relation was not linear. DOC in algogenic water was poorly reduced with MIEX® and the precipitation techniques, but better reduced with the membrane filtration. There was a correlation between absorbance (254 nm) and the amount of DOC, which makes it possible to do online reading of absorbance and translate the values into amount of DOC.

Arctic regions are expected to be highly sensitive to climate change regarding the prediction of disproportionately large increases in surface temperatures and their related influence over the hydrological cycle and permafrost thaw. These modifications have the potential to impact biogeochemical cycles in these regions and in particular the mobilization of organic carbon into rivers. The most crucial period in arctic rivers hydrological cycle is the spring freshet that can account for most of the annual organic carbon transfers to the ocean in a very short window of time. The focus of this thesis was to monitor the dynamic of DOM in terms of quantity and quality along the hydrological cycle of the Yenisei river, through DOM characterization approaches to reveal seasonal variations in its composition, sources, age and degradation state. The first step was to make a review of the full range of existing DOM characterization approaches in worldwide river systems to identify the most widely used, the most relevant and reliable ones. Through the development of a DOM quality measurements database, we have been able to evaluate the geographical coverage of DOM characterization studies, to give estimates and ranges of values of the main reported DOM characterization variables and to observe global trends of DOM quality across latitudinal gradient. Second stage was to investigate DOC dynamic in the Yenisei river with regard to quantity and links with water chemistry and hydrology. We conducted sampling campaigns during three consecutive years (2014 to 2016), covering with a high sampling frequency the spring flood period to capture its very dynamic evolution. We reported DOC concentrations that followed the hydrograph with highest concentrations observed a few days before peak discharge. DOC concentration also responded to discharge variation (increase, likely due to higher precipitation) in early autumn. We reported average DOC flux over the three sampling years of about 4.53 Tg yr-1 which is within the range of values reported in the literature. We observed interannual variability with annual export estimates ranging from 5.45 Tg yr-1 in 2014 to 3.57 Tg yr-1 in 2016, likely driven by discharge amplitude. We confirmed the important role of spring freshet in DOC export with on average more than 65% occurring during this period (roughly May/June). Third point was to determine DOM quality combining characterization techniques. Combination of approaches helped to strengthen observations and cross validate interpretations. Most of the variables reported from the different characterization techniques confirmed one each other. The use of lignin biomarkers, optical properties and radiocarbon age of DOM allowed us to trace DOM main sources has primarily deriving from recently produced organic matter leached from boreal forest litter and top soil horizon during the spring flood and older organic matter derived from deeper soil horizons during low flow period.

Este trabalho estuda a propagação da luz no esmalte e dentina humanos, através da transmitância direta e absorbância no intervalo de comprimento de onda de 200 a 3200nm, e através da transmitância total no intervalo de onda de 380 a 760nm. Foram utilizadas secções de 30 molares humanos íntegros, que foram seccionados nos sentidos VL (vestíbulo – Lingual), MD (mésio distal) e OC (ocluso cervical). As espessuras utilizadas foram de 0,5mm e 0,25mm. Foram agrupados 5 dentes para cada sentido para cada espessura. Esmalte e dentina estavam presentes de maneira simultânea na mesma amostra. A absorbância foi calculada, a partir dos espectros de transmitância direta, aplicando-se a Lei e Beer-Lambert. Os espectros de transmitância total foram obtidos no espectro visível, e comparados, em média, com os espectros de transmitância direta no mesmo intervalo, para obter a energia difusa das amostras. Os espectros UV (Ultravioleta), VIS (Visível) e IV (Infravermelho), foram tratados separadamente para cada tecido e espessura. No infravermelho foram identificados os picos de transmitância e absorbância para ambos os tecidos. Os valores de transmitância e absorbância para cada faixa espectral foram tratados pela ANOVA, e os grupos comparados pelo teste de intervalo de confiança (95%). Os resultados mostraram que, as propriedades ópticas do esmalte e dentina diferem no que diz respeito as 3 faixas espectrais testadas. Os resultados também mostram que as propriedades ópticas são dependentes da espessura e do sentido de seccionamento dos dentes. A pesar das diferenças apresentadas entre os espectros, as curvas espectrais mostraram um padrão semelhante para todas as amostras de dentina e de esmalte, independente da espessura. Este comportamento possibilitou a identificação de picos comuns nos espectros estudados. / This research studies the propagation of light in the human enamel and dentine, through direct transmittance and absorbance in the 200 to 3200nm wavelength interval, and through total transmittance in the 380 to 760nm wavelength interval. The study employed sections of 30 human integral molars, which were sectioned in the VL directions (vestibule – Lingual), MD (mesio distal), and OC (occlusion cervical). The thicknesses used were from 0.5mm to 0.25mm. Five teeth were grouped in each direction for each thickness. Enamel and dentine were simultaneously present in the same sample. Absorbance was calculated from the direct transmittance specters, applying the Beer-Lambert Law. Total transmittance specters were obtained in the visible specter, and compared, on average, with the Total transmittance specters in the same interval, to obtain the diffuse energy of the samples. UV (Ultraviolet), VIS (Visible), and IV (Infrared) specters, were treated separately for each tissue and thickness. In infrared, the transmittance and absorbance peaks were identified for both tissues. The transmittance and absorbance spectral range were treated by ANOVA, and the groups compared by the confidence interval test (95%). The results showed that the optical properties of the enamel and dentine differ with regard to the three tested spectral ranges. The results also showed that the optical properties are dependent on the thickness and the direction of the sectioning of the teeth. Despite the differences found between the specters, the special curves showed a similar pattern for all samples of dentine and enamel, independently of the thickness. This behavior allowed the identification of common peaks in the specters under study.

Additive manufacturing offers a manufacturing technique to produce complex geometry prototypes at a rapid pace and low cost. These advantages advocate additive manufacturing for the design and production of cellular structures. Cellular structures are interesting because they contain a large amount of porosity (void space of air) to manifest a lightweight structure. Designs of cellular structures generate a periodic pattern; often of complex geometry, called a lattice. There has been a significant amount of research to maximize specific stiffness of lattice structures but little to evaluate low-stiffness lattices. Low-stiffness structures benefit energy absorbance through bending of the lattice. This research seeks to assess diamond lattices as low stiffness, bending structures. The research involves PA2200 (Nylon 12) laser sintered diamond lattices with experimental compression testing and direct FEA model comparison. A correction factor is applied for a design offset of laser sintered lattices. Once applied, the experimental and FEA data agree in validating the diamond lattice as a bending-dominated structure. Diamond lattices show a 4th order relationship between stiffness and parameters of thickness and unit cell length. For density, stiffness maintains a 2nd order relationship, as predicted by bending dominated structures. The resulting stiffness can be tuned over a stiffness range of four orders of magnitude. Further research shows the results for modifying the diamond lattice and scaling stiffness and density using other materials (like metals) to expand the range of stiffness and compare diamond lattices on material property charts. Lastly, the effective Poisson’s ratio varies from 0.5 to 0.4 depending on the (t/L) ratio.

During recent decades the brownification through leaching of organic carbon into Northern hemisphere water bodies has become apparent. This is considered a problem because of the implications it has on ecosystems and freshwater sources used for drinking water. It could be beneficial if wetlands can be used for reducing brownification but also detrimental if wetlands instead increase it as construction of wetlands is common practice for treating agricultural runoff in Sweden.  This study compares inlet and outlet absorbance in five wetlands in Kalmar County in Sweden and finds that one removes colour, two increases colour and two does not change the colour of the water at all. The study also compares absorbance values with variables concerning flow and temperature and concludes that a higher absorbance at inlet increases removal similar to how nutrient removal in wetlands work. Inlet absorbance is also dependent on flow with higher flow resulting in higher absorbance. Periods of no flow did not contribute to any changes in absorbance, but this could be because of a limited sample pool. Future recommendations for research include a more extensive look into periods of no flow and affecting variables to ensure wetlands do not contribute to brownification.