Cette thèse décrit comment la morphologie et le polymorphisme de membranes en fluorure de poly(vinylidène) (PVDF) préparées par séparation de phase induite par la vapeur d'eau (VIPS) et par un non-solvant liquide peuvent être ajustés par la température à laquelle le PVDF est dissous (Tdis) pour former la solution de coulée. Les résultats montrent que Tdis présente une transition, notée comme la température de dissolution critique (Tcri), à partir de laquelle la morphologie et le polymorphisme des membranes changent radicalement. Ce phénomène observé pour les trois solvants, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and N,M-dimethylformamide (DMF), et les non-solvants (eau et une série d'alcools) utilisés dans cette étude peut être considéré comme général. La cristallisation a lieu avant la démixtion L-L quelle que soit Tdis. Pour une Tdis supérieure à Tcri, les membranes se présentent sous forme de nodules (cristallite forme beta) dont la taille décroît lorsque Tdis diminue. Ce domaine a été dénommé "à grossissement libre" car les chaînes de polymère peuvent cristalliser librement pendant la séparation de phase. Pour une Tdis inférieure à Tcri, des membranes avec une structure bi-continue (cristallite forme alpha) sont obtenues. Ce domaine a été appelé "à grossissement empêché" dans la mesure où la séparation de phase s'accompagne d'une gélification. Nous avons démontré que la morphologie et le polymorphisme cristallin des membranes de PVDF peuvent ainsi être contrôlés par la Tdis et la vitesse d'échange avec le non-solvant. Ces résultats sont interprétés en termes d'auto germination et de compétition entre gélification, cristallisation et démixtion L-L. / This dissertation shows how the morphology and polymorphism of poly(vinylidene fluoride) (PVDF) membranes prepared by using vapor-induced phase separation (VIPS) and liquid-induced phase separation (LIPS) were tuned by varying the dissolution temperature at which PVDF was dissolved (Tdis) to form the casting solution. We observed a transition temperature denoted by critical dissolution temperature, Tcri, across which the morphology and polymorphism of membranes (obtained by VIPS) drastically changed. The phenomenon was considered as general, as a Tcri was observed for all the three solvents N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF) and the non-solvents, water and a series of alcohols, used in the present study. No matter which Tdis we used, polymer crystallization occurred prior to the L-L demixing. With Tdis above Tcri, the prepared membranes were composed of nodules (mainly in beta crystalline form) and the size of polymer domains decreased as the Tdis decreased. Because the polymer chains could freely coarsen to a large domain during the phase separation, we called the system free coarsening. With Tdis below Tcri, membranes with lacy (bi-continuous) structure (mainly in alpha crystalline form) were obtained. Because the polymer solution gelled during the phase separation, we called the system hindered coarsening. It was proven that PVDF membrane morphology and crystalline polymorphs can be monitored by Tdis and the solvent-nonsolvent exchange rate. These results were discussed in terms of self-seeding effect and competition between the gelation, crystallisation and L-L demixing.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Objective: This study aimed to evaluate surface microhardness changes in early, incipient, non-cavitated white-spot, enamel caries lesions treated with silver diamine fluoride (SDF) longitudinally. The utilization of silver nitrate and potassium fluoride test groups served as additional controls to assist in evaluating if the remineralization effects were due to the silver or fluoride component in SDF. Hypotheses: 1. SDF treatment will result in increased surface microhardness of early, incipient, non-cavitated white-spot, enamel caries lesions compared to all other tested interventions. 2. Specimen storage for 2-weeks in artificial saliva will result in greater surface rehardening in lesions treated with SDF compared to other tested interventions. Design: This laboratory study had 5 intervention groups (SDF, silver nitrate (AgNO3), potassium fluoride (KF), 5.0-percent sodium fluoride varnish (FV), deionized water (DI)) × 2-time intervals after intervention (immediate & delayed pH-cycling), resulting in 10 groups (n = 18). Early, incipient, non-cavitated white-spot, enamel caries lesions were created in bovine enamel and extent of demineralization was determined using Vickers surface microhardness (VHNlesion). Intervention treatments were applied. Half the specimens from each group underwent immediate 5-day pH-cycling and half were stored in an incubator with artificial saliva for two weeks before undergoing 5-day pH-cycling. After pH-cycling, lesion hardness was evaluated using VHNpost. Specimens were then exposed to a second demineralization challenge and lesion softening was evaluated using VHNsecdem. Surface rehardening was calculated: ΔVHN =VHNpost - VHNlesion. Surface softening was calculated: ΔVHNsecdem =VHNsecdem – VHNpost. Data was analyzed using two-way ANOVA. Results: Immediately cycled, SDF had significantly (p < .0001) greater remineralization than DI, AgNO3, and FV. All delayed cycling groups had significantly (p < .0001) greater remineralization than FV. Significantly greater remineralization was noted in delayed AgNO3 (p < .0001), DI (p = .0003), and FV (p = .0006) compared to immediately cycled. After the second demineralization challenge, FV had significantly less surface softening than AgNO3 (p = 0.0002), DI (p = 0.0003), KF (p = 0.0225), and SDF (p = 0.0388) intervention groups. No significant difference was found between the pH-cycle timings. Conclusion: Based on our findings, FV maybe better suitable than SDF to treat early, incipient, non-cavitated white-spot, enamel caries lesions. Longitudinally, SDF exhibited greater remineralization than both FV and DI groups, though not statistically significant. However, upon a second demineralization challenge, FV significantly outperformed SDF in preventing surface softening. / 2021-09-30

In Tanzania, approximately 76% of the drinking water supplies is dependent on groundwater sources. However, the groundwater in north Tanzania is susceptible to contamination by arsenic and fluoride. This study examines the spatial analysis of arsenic and fluoride mobilization in groundwater around Mount Meru, located in northern Tanzania. The study area covers approximately 1,450 Km2 around Mount Meru in Arusha region, Tanzania. The statistical analysis was performed in IBM SPSS Statistics version 28.0.0.0 to interpret data and unveil the correlation and trends between chemical elements in 11 springs and in 17 wells.  The geochemical modelling software, Visual MINTEQ ver.3.1. have been used to simulate chemical elements in springs and wells in the study area to predict the chemical species, saturation indices, and adsorption efficiency of arsenic to goethite and of fluoride to gibbsite. Moreover, the spatial analysis was done using ArcGIS Desktop 10.8.2 and Geoda 1.20.0.22 software to identify the hotspots areas and to connect spatial patterns of arsenic and fluoride distribution within the study area. The statistical analysis revealed a positive correlation between arsenic and pH in springs. The Na-Cl-HCO3 water type was found in springs, with increased F- concentration in groundwater. The results of geochemical modelling confirmed that more undersaturated values for F- minerals were observed in springs than in wells, which were likely influenced by the fluoride adsorption to gibbsite surface. It was observed that initial concentration and increase of adsorbent dose promoted adsorption efficiency of arsenic and fluoride on goethite and gibbsite, respectively, between pH 4 and pH 6. However, the increase in pH value hinders adsorption efficiency. Moreover, the highest adsorption efficiency was observed at adsorbent dose of 0.05 g/L of goethite for arsenic adsorption, and at adsorbent dose 6.6 g/L and 10 g/L of gibbsite for fluoride adsorption. The spatial analysis results showed that the concentration of fluoride was high in the northeast and eastern part of the study area, where the low elevation area is composed of Tertiary and Quaternary volcanic rocks and debris avalanche deposits. In contrast, the southwestern part of the study area had comparatively low fluoride concentrations, which could be attributed to the less permeable nature of the Tertiary and Quaternary unconsolidated soil. The geological map revealed that the study area is composed of pyroclastic rocks and basic igneous rocks, which predict the presence of fluoride rich minerals such as apatite and fluorapatite. The spatial distribution of arsenic and fluoride in springs and wells revealed that the hotspots groundwater sources such as S5, S6, S7and W3, W4, W5, W6 were in low elevated areas that accumulated from the mobilization of dissolved arsenic and fluoride species from high recharge altitude, groundwater interaction with arsenic and fluoride bearing minerals and agricultural areas. The findings of this study can be useful to the future researchers and local authorities to know about high risky sources of groundwater for better managing and mitigating the risks associated with arsenic and fluoride contamination in Mount Meru groundwater aquifers. / I Tanzania är cirka 76 % av dricksvatten försörjning beroende av grundvattenkällor. Grundvattnet i norra Tanzania är dock känsligt för kontaminering av arsenik och fluor. Denna studie undersöker den rumsliga analysen av arsenik- och fluoridmobilisering i grundvatten runt Mount Meru, beläget i norra Tanzania. Studieområdet omfattar cirka 1 450 km2 runt Mount Meru i Arusha-regionen, Tanzania. Den statistiska analysen utfördes i IBM SPSS Statistics version 28.0.0.0 för att tolka data och avslöja korrelationen och trenderna mellan kemiska grundämnen i 11 källor och i 17 brunnar. Programvaran för geokemisk modellering, Visual MINTEQ ver.3.1. har använts för att simulera kemiska element i källor och brunnar i studieområdet för att förutsäga de kemiska arterna, mättnadsindexen och adsorptionseffektiviteten för arsenik till goetit och av fluorid till gibbsit. Dessutom gjordes den rumsliga analysen med hjälp av mjukvaran ArcGIS Desktop 10.8.2 och Geoda 1.20.0.22 för att identifiera hotspot-områdena och för att koppla samman rumsliga mönster av arsenik- och fluoriddistribution inom studieområdet. Den statistiska analysen visade en positiv korrelation mellan arsenik och pH i fjädrar. Vattentypen Na-Cl-HCO3 hittades i källor, med ökad F- koncentration i grundvattnet. Resultaten av geokemiska modelleringar bekräftade att fler undermättade värden för F-mineraler observerades i källor än i brunnar, vilka troligen påverkades av fluoridadsorptionen till gibbsitytan. Det observerades att initial koncentration och ökning av adsorbentdos främjade adsorptionseffektiviteten av arsenik och fluorid på goetit respektive gibbsit mellan pH 4 och pH 6. Ökningen i pH-värde hindrar emellertid adsorptionseffektiviteten. Dessutom observerades den högsta adsorptionseffektiviteten vid adsorbentdosen på 0,05 g/L goetit för arsenikadsorption och vid adsorbentdosen 6,6 g/L och 10 g/L gibbsit för fluoridadsorption. De rumsliga analysresultaten visade att koncentrationen av fluorid var hög i den nordöstra och östra delen av studieområdet, där låghöjdsområdet är sammansatt av tertiära och kvartära vulkaniska bergarter och avfall av lavinavlagringar. Däremot hade den sydvästra delen av studieområdet jämförelsevis låga fluoridkoncentrationer, vilket kan tillskrivas den mindre permeabla naturen hos den tertiära och kvartära okonsoliderade marken. Den geologiska kartan avslöjade att studieområdet består av pyroklastiska bergarter och grundläggande magmatiska bergarter, som förutsäger närvaron av fluorrika mineraler som apatit och fluorapatit. Den rumsliga fördelningen av arsenik och fluor i källor och brunnar avslöjade att hotspots grundvattenkällor som S5, S6, S7 och W3, W4, W5, W6 låg i lågt upphöjda områden som ackumulerades från mobiliseringen av löst arsenik och fluorarter från hög uppladdning höjd över havet, grundvatteninteraktion med arsenik- och fluorhaltiga mineraler och jordbruksområden. Resultaten av denna studie kan vara användbara för framtida forskare och lokala myndigheter att veta om högriskfyllda grundvattenkällor för att bättre hantera och mildra riskerna förknippade med arsenik och fluoridkontamination i Mount Meru grundvattenakviferer.

Plasmonische Substrate stellen ein leistungsstarkes Werkzeug für analytische Anwendungen dar. Neue plasmonische Substrate werden entwickelt, um das Spektrum ihrer Anwendungen und die Nachweisgrenzen der analytischen Spektroskopie zu erweitern. Diese Arbeit setzte sich zum Ziel, plasmonische Nanostrukturen mit Magnesiumfluorid zu beschichten. Magnesiumfluoridbeschichtungen sind zwar porös, weisen aber eine hohe mechanische Stabilität und außergewöhnliche optische Eigenschaften auf (niedrigen Brechungsindexes, großen optischen Fensters). Die Kombination dieser Eigenschaften mit den positiven Eigenschaften von plasmonischen Nanostrukturen kann zu fortschrittlichen plasmonischen Substraten für analytische Anwendungen führen. Diese Arbeit bietet zwei Ansätze für die Beschichtung der plasmonischen Nanostrukturen an die Core-Shell-Nanopartikelherstellung, die einen plasmonischen Core enthält und die Beschichtung von auf Glas immobilisierten plasmonischen Nanostrukturen. Über Metal@metal Fluoride Core-Shell-Nanopartikel wurde in der Literatur noch nichts berichtet. Daher Au@MgF2wurde ein Ansatz verfolgt, der auf dem Wissen über Metall-@Metalloxide und Metallfluoride@Metallfluoride basiert und die Synthese von Core-Shell-Nanopartikeln ermöglicht. Die erhaltenen Strukturen wurden mit elektronenmikroskopischen Methoden charakterisiert. Der zweite Ansatz bestand in der Immobilisierung von Goldnanopartikeln auf Glas und deren Beschichtung mit Magnesiumfluorid. Diese Fertigungsart verleiht eine hohe mechanische Stabilität und wissenswerte optische Eigenschaften an plasmonischen Substraten, die sich durch eine hohe nanoskopische Homogenität der Goldnanopartikelverteilung auszeichnen und optischer Signale, die echte analytische Anwendungen ermöglichen, ermittelt. Die Beschichtung von auf Glas mit Magnesiumfluorid immobilisierten Goldnanopartikeln führt zu einem sehr vielversprechenden Substrat , das in Zukunft für Sensorik und andere Anwendungen verwendet werden kann. / Plasmonic substrates can be a powerful tool for analytical applications. In order to broaden the spectrum of their applications and to push the detection limits of analytical spectroscopy, new plasmonic substrates are developed. The motivation of this work was to coat plasmonic nanostructures with magnesium fluoride. Coatings of magnesium fluoride are porous but exhibit high mechanical stability and extraordinary optical properties including a low refractive index and a wide optical window. Combining these properties with the beneficial properties of plasmonic nanostructures can lead to advanced plasmonic substrates for analytical applications. Two approaches for coating of the plasmonic nanostructures are proposed in this work: a core-shell nanoparticles fabrication and coating of plasmonic nanostructures immobilized on glass. The fabrication of Au@MgF2 core-shell nanoparticles turned out to be an extremely challenging approach. Such systems have not been reported in the literature yet. Therefore, an approach based on knowledge of metal@metal oxides and metal fluorides@metal fluorides core-shell nanoparticles synthesis was undertaken. The obtained structures were characterized using electron microscopy methods. Due to the numerous difficulties in the synthesis and characterization this way of coating plasmonic nanostructures with magnesium fluoride was not further processed. The approach based on immobilization of gold nanoparticles on glass and coating them with magnesium fluoride using a dip-coating method provides plasmonic substrates that are characterized by a high nanoscopic homogeneity of the gold nanoparticles distribution, a high mechanical stability, interesting optical properties and enhancement factors of optical signals that allow for real analytical applications. The coating of gold nanoparticles immobilized on the glass with magnesium fluoride results in very promising substrate that can be used for sensing and other applications in the future.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The large band gap (approximately 11.5-12.1 eV) and high transmission of calcium fluoride (CaF2) crystal in the ultraviolet (UV) and vacuum ultraviolet (VUV) region makes it an important material for optics for laser applications in UV. However, CaF2 degrades during long exposure to UV irradiation due to defect generation. The formation of selftrapped excitons (STE) is considered the first step in defect generation. In this project the possibility of observing STE states in CaF2 using a narrow bandwidth tunable VUV laser source is investigated. This is the first spectroscopy study of an alkaline earth fluoride using VUV tunable laser radiation instead of a fixed wavelength laser. The use of a VUV tunable laser source has potential for determining the energies of the STE states, which are unknown. Our main objective is addressed by developing techniques to measure absorption spectra of pure and doped CaF2 samples, using a VUV scanning monochromator and a tunable VUV laser, and by doing a literature study. The results obtained with the scanning monochromator show absorption features in 126-180 nm range of all our samples. These vary for different samples and correlate with information from the supplier on the samples’ fluorescence spectra. Total absorption of the VUV light by CaF2 in the 115-126 nm range is observed. With the narrow bandwidth tunable laser light, absorption spectra were obtained in the range of 143-146.7 nm of all our CaF2 samples. No significance peaks which can be related to the STE states in CaF2 were observed in the VUV laser absorption spectra, but the results are valuable to improve the technique. The conclusion is that either a different spectral range or fluorescence detection can be investigated in future. / AFRIKAANSE OPSOMMING: Die groot bandgaping (ongeveer 11.5-12.1 eV) en hoë transmissie van kalsiumfluoried (CaF2) kristal in die ultraviolet (UV) en die vakuum ultraviolet (VUV) gebied maak dit ’n belangrike materiaal vir optika vir laser toepassings in die UV. CaF2 degradeer egter gedurende langdurige blootstelling aan UV lig as gevolg van die generering van defekte. Die vorming van ’n elektron-holte paar wat deur die kristalstuktuur gestabiliseer word teen rekombinasie (self-trapped excitons, afgekort STE) word beskou as die eerste stap in defek generering. In hierdie projek word die moontlikheid ondersoek om STE toestande in CaF2 waar te neem deur die gebruik van ’n afstembare VUV laserbron met emissie in ’n smal spektrale band. Dit is die eerste spektroskopiese studie van ’n aardalkali-fluoried deur die gebruik van afstembare VUV laserlig in plaas van ’n vaste golflengte laser. Die gebruik van ’n afstembare VUV laserbron het potensiaal vir die bepaling van die energieë van die STE teostande, wat onbekend is. Ons hoofdoel word aangespreek deur die ontwikkeling van tegnieke vir die meet van absorpsie spektra van suiwer en gedoteerde CaF2 monsters met behulp van ’n VUV skanderende monochromator en ’n afstembare VUV laser, en deur ’n literatuurstudie. Die resultate wat behaal is met die skanderende monochromator toon die absorpsieprofiele van al ons monsters in die 126-180 nm spektrale gebied. Die absopsieprofiele varieer vir die verskillende monsters en korreleer met die inligting van die verskaffer oor die fluoressensie spektra van die monsters. Totale absorpsie van die VUV lig deur CaF2 in die 115-126 nm gebied is waargeneem. Met die smalband afstembare laserlig is absorpsie spektra in die 143-146.7 nm gebied vir al ons CaF2 monsters verkry. Geen beduidende pieke wat verband hou met die STE toestande in CaF2 is waargeneem in die VUV laser absorpsie spektra nie, maar die resultate is waardevol vir die verbetering van die tegniek. Die gevolgtrekking is dat of ’n ander spektraalgebied of fluoressensiedeteksie in die toekoms ondersoek kan word.

4 pp. / This short fact sheet is taken from "Arizona Well Owner's Guide to Water Supply" currently in print. We plan to complete part 2 of this fact sheet by the end of July, 2009. Please note that the text has already been incorporated into the eXtension Community of Practice web page - - I am the author for the COP/Drinking Water group text on chemistry of naturally occurring water contaminants. / Arizona well water is often contaminated with elevated concentrations of naturally occurring constituents that are a human health concern. This short fact sheet is the first in a two-part series about what naturally occurring contaminants may be found in your water supply well and includes a brief discussion on environmental pollutants that originate from land use activities. If you own a well in Arizona, you have the sole responsibility for checking to see if your drinking water is contaminated. Arizona state law does not require private well owners to test or treat their water for purity. The second part of this series outlines what to sample for and how to understand your analytical results.

No description available.

This thesis undertakes a complete reinvestigation of the archaeology of a large Early Bronze Age cemetery at İkiztepe in northern Turkey, by utilizing oxygen and strontium isotope analysis of human remains in combination with spatial and biodistance analysis and various dating techniques to identify potential immigrants to the site and to examine larger issues of residential mobility and social organization. The occupation of the Northern Anatolian site of İkiztepe is traditionally assigned to the Late Chalcolithic and Early Bronze Ages. However, the site’s chronological framework has been challenged in recent years. These chronological issues have been addressed by applying fluoride and AMS radiocarbon dating to the skeletal remains from the İkiztepe cemetery, to develop an absolute and relative chronology for the burials. These results have shown that the cemetery dates at least a millennium earlier than previously supposed. Oxygen and strontium isotope analyses allowed the identification of individuals whose bone chemistry suggests that they were possible long distance immigrants to the site of İkiztepe, as well as suggesting the existence of a group of mobile individuals who may represent a transhumant segment of the İkiztepe population. Spatial and biodistance analyses suggest that principles of cemetery organization in this period were highly complex. Immigrant individuals and nomadic or semi-nomadic segments of the population do not appear to have been distinguished in any observable way from their sedentary local counterparts, displaying similar burial types, grave goods and spatial locations. Furthermore, burial within the İkiztepe cemetery does not appear to have been kin structured. These results suggest that assumptions about funerary practices as important indicators of cultural identity and lineage affiliation may represent an over-simplification of complex patterns of interaction and integration among and within populations and cultural groups.

Background: Studies of assessing dietary fluoride intake in children have employed different dietary methods mainly “2-day duplicate” and “3-day food diary” methods. However, none of these methods have been validated or standardised. Main aims: The main aims of the current study were to develop a better understanding of strengths and weaknesses of dietary assessment methods “2-day duplicate plate” and “3-day food diary” by comparing dietary fluoride intake estimated by each method and evaluate the validity of the two methods for estimating dietary fluoride intake in young children. Methods: Sixty one healthy 4-6 year old children living in fluoridated area of the north-east of England since birth were recruited via 10 primary schools. Dietary information was collected using “2-day duplicate plate” and “3-day food diary” methods. Two 24-h urine samples and two samples of post brushing expectorate (a mixture of saliva, toothpaste and water used to rinse after brushing) from each child. Completeness of 24-h urine samples was checked using urinary excretion of creatinine and urinary flow rate. Validity of the two dietary assessment methods was checked by measuring urinary excretion of nitrogen and potassium as independent validity checks. Total daily fluoride intake from diet and toothpaste ingestion and urinary fluoride excretion was determined for each child. Results: All participated children completed all aspects of the study. According to the validity criteria, dietary data of 58 (95%) children, when collected by the 3-day food diary, were considered valid. However, when the dietary data were collected by the 2-day duplicate plate method, the data for 46 (75%) children were viewed as valid. Mean total dietary fluoride intake was 0.533 mg/d by the 3-day food diary method and 0.583 mg/d by the 2-day duplicate plate method. No statistically significant difference in total dietary fluoride intake was observed between the two methods. The mean difference in estimated dietary fluoride intake by the two dietary assessment methods was -0.050 mg/d with 95% limits of agreement of -0.501 to + 0.401 mg/d. Conclusion: Either the 3-day food diary or the 2-day duplicate plate method can be used when investigating mean total daily dietary fluoride intake of a population. However the methods cannot be used interchangeably at the individual level.