Development of synthetic methods of silicon nanocrystals functionalized with photoactive molecules

The thesis is focused on the development of a method for the synthesis of silicon nanocrystals with different sizes, narrow size distribution, good optical properties and stability in air. The resulting silicon nanocrystals have been covalently functionalized with different chromophores with the aim to exploit the new electronic and chemical properties that emerge from the interaction between silicon nanocrystal surface and ligands. The purpose is to use these chromophores as light harvesting antennae, increasing the optical absorption of silicon nanocrystals. Functionalized silicon nanocrystals have been characterized with different analytical techniques leading to a good knowledge of optical properties of semiconductor quantum dots.

Quality control of virgin olive oils with regard to different storage and shipment conditions

Virgin olive oil(VOO) is a product characterized by high economic and nutritional values, because of its superior sensory characteristics and minor compounds (phenols and tocopherols) contents. Since the original quality of VOO may change during its storage, this study aimed to investigate the influence of different storage and shipment conditions on the quality of VOO, by studying different solutions such as filtration, dark storage and shipment inside insulated containers to protect it. Different analytical techniques were used to follow-up the quality changes during virgin olive oil storage and simulated shipments, in terms of basic quality parameters, sensory analysis and evaluation of minor components (phenolic compounds, diglycerides, volatile compounds). Four main research streams were presented in this PhD thesis: The results obtained from the first experimental section revealed that the application of filtration and/or clarification can decrease the unavoidable quality loss of the oil samples during storage, in comparison with unfiltered oil samples. The second section indicated that the virgin olive oil freshness, evaluated by diglycerides content, was mainly affected by the storage time and temperature. The third section revealed that fluctuation in temperature during storage may adversely affect the virgin olive oil quality, in terms of hydrolytic rancidity and oxidation quality. The fourth section showed that virgin olive oil shipped inside insulated containers showed lower hydrolytic and oxidation degradation than those without insulation cover. Overall, this PhD thesis highlighted that application of adequate treatment, such as filtration or clarification, in addition to a good protection against other external variables, such as temperature and light, will improve the stability of virgin olive oil during storage.

Co-frangitura oliva e nocciola: Studio del prodotto

In recent times, the choices of consumers have been more conscious and oriented to foods with health benefits. The present paper deals with the study of oil from crushing of olive and huzelnut with the aim of obtaining a “functional food”. Different samples of oil derived from the crushing of olive (O), olive with 5% of hazelnut (O5N) and olive with 10% of hazelnut (O10N), exposed to different temperatures (28 and 35°C) and times (15 and 30 minutes) of malaxation. The samples of oil were initially subjected to a qualitative assessment by the analysis of peroxide and free acidity. Following further analyses were carried out namely the determination of fatty acids and triglycerides by FAST GC-FID, the determination of tocopherols by HPLC-FLC, the analysis of sterols by GC/MS and the spectroscopic analysis with FT-MIR combined with statistical analysis with PCA and PLS. The results showed that increasing the time and temperature of malaxation there aren’t relevant significant differences (p<0,05) in the composition of fatty acids, triglycerides and tocopherols in the different oils, but there are higher extraction yields. The increase of content of hazelnut in phase of crushing causes the decrease of triglycerides C50 and C52, the increase of the class C54, total tocopherols and of total sterols as well. The samples analysed with FT-MIR spectroscopy have showed, on the contrary to conventional analytical techniques, a good discrimination between different oils despite of the similar chemical composition of olive and hazelnuts. After the PLS models were built from spectra FT-MIR in order to estimate the content of triglycerides C50, C52 and C54 and total tocopherols, with good R2 in full cross validation (R2>0,821).

Characterization of harmonic tremor at Santiaguito volcano and its implications for eruption mechanisms

We observed Santiaguito volcano in southwestern Guatemala from March 2008 - March 2010. Seismic and infrasound data collected between January and March of 2009 contain records of many diverse processes occurring at the dacitic dome complex, including the recurrence of short lived (30-200 seconds in duration) harmonic tremor concurrent with ash poor gas emissions from the volcano. We employ several different analytical techniques to examine different portions of the tremor and source mechanisms. We use the parameters derived by this analysis to compare the feasibility of several suggested models of eruption mechanisms, and determine that this type of harmonic tremor is most justifiably generated by the flow of gas through crack networks generated by shear fracture along the magma conduit margin.

Advanced mechanics of materials with microstructure

The study of advanced materials aimed at improving human life has been performed since time immemorial. Such studies have created everlasting and greatly revered monuments and have helped revolutionize transportation by ushering the age of lighter–than–air flying machines. Hence a study of the mechanical behavior of advanced materials can pave way for their use for mankind’s benefit. In this school of thought, the aim of this dissertation is to broadly perform two investigations. First, an efficient modeling approach is established to predict the elastic response of cellular materials with distributions of cell geometries. Cellular materials find important applications in structural engineering. The approach does not require complex and time-consuming computational techniques usually associated with modeling such materials. Unlike most current analytical techniques, the modeling approach directly accounts for the cellular material microstructure. The approach combines micropolar elasticity theory and elastic mixture theory to predict the elastic response of cellular materials. The modeling approach is applied to the two dimensional balsa wood material. Predicted properties are in good agreement with experimentally determined properties, which emphasizes the model’s potential to predict the elastic response of other cellular solids, such as open cell and closed cell foams. The second topic concerns intraneural ganglion cysts which are a set of medical conditions that result in denervation of the muscles innervated by the cystic nerve leading to pain and loss of function. Current treatment approaches only temporarily alleviate pain and denervation which, however, does not prevent cyst recurrence. Hence, a mechanistic understanding of the pathogenesis of intraneural ganglion cysts can help clinicians understand them better and therefore devise more effective treatment options. In this study, an analysis methodology using finite element analysis is established to investigate the pathogenesis of intraneural ganglion cysts. Using this methodology, the propagation of these cysts is analyzed in their most common site of occurrence in the human body i.e. the common peroneal nerve. Results obtained using finite element analysis show good correlation with clinical imaging patterns thereby validating the promise of the method to study cyst pathogenesis.

Statistical characterization and development of summary measures of non-normal distributions of nuclear morphometry data from prostate cancer cells for use as prognostic indicators

Nuclear morphometry (NM) uses image analysis to measure features of the cell nucleus which are classified as: bulk properties, shape or form, and DNA distribution. Studies have used these measurements as diagnostic and prognostic indicators of disease with inconclusive results. The distributional properties of these variables have not been systematically investigated although much of the medical data exhibit nonnormal distributions. Measurements are done on several hundred cells per patient so summary measurements reflecting the underlying distribution are needed.^ Distributional characteristics of 34 NM variables from prostate cancer cells were investigated using graphical and analytical techniques. Cells per sample ranged from 52 to 458. A small sample of patients with benign prostatic hyperplasia (BPH), representing non-cancer cells, was used for general comparison with the cancer cells.^ Data transformations such as log, square root and 1/x did not yield normality as measured by the Shapiro-Wilks test for normality. A modulus transformation, used for distributions having abnormal kurtosis values, also did not produce normality.^ Kernel density histograms of the 34 variables exhibited non-normality and 18 variables also exhibited bimodality. A bimodality coefficient was calculated and 3 variables: DNA concentration, shape and elongation, showed the strongest evidence of bimodality and were studied further.^ Two analytical approaches were used to obtain a summary measure for each variable for each patient: cluster analysis to determine significant clusters and a mixture model analysis using a two component model having a Gaussian distribution with equal variances. The mixture component parameters were used to bootstrap the log likelihood ratio to determine the significant number of components, 1 or 2. These summary measures were used as predictors of disease severity in several proportional odds logistic regression models. The disease severity scale had 5 levels and was constructed of 3 components: extracapsulary penetration (ECP), lymph node involvement (LN+) and seminal vesicle involvement (SV+) which represent surrogate measures of prognosis. The summary measures were not strong predictors of disease severity. There was some indication from the mixture model results that there were changes in mean levels and proportions of the components in the lower severity levels. ^

Spring temperature variability and eutrophication history inferred from sedimentary pigments in the varved sediments of Lake Żabińskie, north-eastern Poland, AD 1907–2008

Varved lake sediments are excellent natural archives providing quantitative insights into climatic and environmental changes at very high resolution and chronological accuracy. However, due to the multitude of responses within lake ecosystems it is often difficult to understand how climate variability interacts with other environmental pressures such as eutrophication, and to attribute observed changes to specific causes. This is particularly challenging during the past 100 years when multiple strong trends are superposed. Here we present a high-resolution multi-proxy record of sedimentary pigments and other biogeochemical data from the varved sediments of Lake Żabińskie (Masurian Lake District, north-eastern Poland, 54°N–22°E, 120 m a.s.l.) spanning AD 1907 to 2008. Lake Żabińskie exhibits biogeochemical varves with highly organic late summer and winter layers separated by white layers of endogenous calcite precipitated in early summer. The aim of our study is to investigate whether climate-driven changes and anthropogenic changes can be separated in a multi-proxy sediment data set, and to explore which sediment proxies are potentially suitable for long quantitative climate reconstructions. We also test if convoluted analytical techniques (e.g. HPLC) can be substituted by rapid scanning techniques (visible reflectance spectroscopy VIS-RS; 380–730 nm). We used principal component analysis and cluster analysis to show that the recent eutrophication of Lake Żabińskie can be discriminated from climate-driven changes for the period AD 1907–2008. The eutrophication signal (PC1 = 46.4%; TOC, TN, TS, Phe-b, high TC/CD ratios total carotenoids/chlorophyll-a derivatives) is mainly expressed as increasing aquatic primary production, increasing hypolimnetic anoxia and a change in the algal community from green algae to blue-green algae. The proxies diagnostic for eutrophication show a smooth positive trend between 1907 and ca 1980 followed by a very rapid increase from ca. 1980 ± 2 onwards. We demonstrate that PC2 (24.4%, Chl-a-related pigments) is not affected by the eutrophication signal, but instead is sensitive to spring (MAM) temperature (r = 0.63, pcorr < 0.05, RMSEP = 0.56 °C; 5-yr filtered). Limnological monitoring data (2011–2013) support this finding. We also demonstrate that scanning visible reflectance spectroscopy (VIS-RS) data can be calibrated to HPLC-measured chloropigment data and be used to infer concentrations of sedimentary Chl-a derivatives {pheophytin a + pyropheophytin a}. This offers the possibility for very high-resolution (multi)millennial-long paleoenvironmental reconstructions.

Dissolution-Precipitation in Porous Media: Experiments and Modelling

The evolution of porosity due to dissolution/precipitation processes of minerals and the associated change of transport parameters are of major interest for natural geological environments and engineered underground structures. We designed a reproducible and fast to conduct 2D experiment, which is flexible enough to investigate several process couplings implemented in the numerical code OpenGeosys-GEM (OGS-GEM). We investigated advective-diffusive transport of solutes, effect of liquid phase density on advective transport, and kinetically controlled dissolution/precipitation reactions causing porosity changes. In addition, the system allowed to investigate the influence of microscopic (pore scale) processes on macroscopic (continuum scale) transport. A Plexiglas tank of dimension 10 × 10 cm was filled with a 1 cm thick reactive layer consisting of a bimodal grain size distribution of celestite (SrSO4) crystals, sandwiched between two layers of sand. A barium chloride solution was injected into the tank causing an asymmetric flow field to develop. As the barium chloride reached the celestite region, dissolution of celestite was initiated and barite precipitated. Due to the higher molar volume of barite, its precipitation caused a porosity decrease and thus also a decrease in the permeability of the porous medium. The change of flow in space and time was observed via injection of conservative tracers and analysis of effluents. In addition, an extensive post-mortem analysis of the reacted medium was conducted. We could successfully model the flow (with and without fluid density effects) and the transport of conservative tracers with a (continuum scale) reactive transport model. The prediction of the reactive experiments initially failed. Only the inclusion of information from post-mortem analysis gave a satisfactory match for the case where the flow field changed due to dissolution/precipitation reactions. We concentrated on the refinement of post-mortem analysis and the investigation of the dissolution/precipitation mechanisms at the pore scale. Our analytical techniques combined scanning electron microscopy (SEM) and synchrotron X-ray micro-diffraction/micro-fluorescence performed at the XAS beamline (Swiss Light Source). The newly formed phases include an epitaxial growth of barite micro-crystals on large celestite crystals (epitaxial growth) and a nano-crystalline barite phase (resulting from the dissolution of small celestite crystals) with residues of celestite crystals in the pore interstices. Classical nucleation theory, using well-established and estimated parameters describing barite precipitation, was applied to explain the mineralogical changes occurring in our system. Our pore scale investigation showed limits of the continuum scale reactive transport model. Although kinetic effects were implemented by fixing two distinct rates for the dissolution of large and small celestite crystals, instantaneous precipitation of barite was assumed as soon as oversaturation occurred. Precipitation kinetics, passivation of large celestite crystals and metastability of supersaturated solutions, i.e. the conditions under which nucleation cannot occur despite high supersaturation, were neglected. These results will be used to develop a pore scale model that describes precipitation and dissolution of crystals at the pore scale for various transport and chemical conditions. Pore scale modelling can be used to parameterize constitutive equations to introduce pore-scale corrections into macroscopic (continuum) reactive transport models. Microscopic understanding of the system is fundamental for modelling from the pore to the continuum scale.

Reseña sobre las metodologías de campo, analíticas y estadísticas empleadas en la determinación y manejo de datos de los elementos de tierras raras en el sistema suelo-planta

El presente artículo es una revisión detallada de estudios científicos publicados que tratan el tema relacionado con la determinación de los elementos de las tierras raras (REEs) en el sistema suelo-planta. Los estudios han sido llevados a cabo principalmente en países europeos y asiáticos. Cabe señalar que la investigación en los países latinoamericanos es muy escasa; sin embargo, es creciente el interés de analizar la aportación de estos elementos al suelo y la planta, lo cual se debe a la aplicación de fertilizantes que contienen dosis elevadas de estos elementos en su composición. Diversas técnicas de muestreo, experimentación y análisis han sido empleadas para la determinación de los REEs. No obstante, se considera que el manejo de los datos ha sido incorrecto estadísticamente. El contenido del presente artículo aborda: (i) las generalidades de los REEs; (ii) el análisis de la bibliografía disponible con el fin de conocer las metodologías de muestreo y análisis más utilizadas en 37 artículos en total, señalando algunos puntos que se consideran todavía deficientes; (iii) dos ejemplos de la aplicación de técnicas estadísticas (intervalo de confianza de la media y pruebas de significancia de la relación F de Fisher y t de Student) utilizando datos reportados en dos artículos. Los resultados mostraron, con los datos del primer artículo analizado, que: a) no se aplicó una metodología estadística para evaluar la calidad de datos; b) al aplicar estadística se encontró que existen diferencias sistemáticas entre los datos determinados en el laboratorio y los certificados. En el segundo artículo analizado se demostró, mediante pruebas de significancia, que existen diferencias significativas en las medias de Ce y Eu (los dos elementos tomados como ejemplos) en las plantas de un sitio a otro.

Composition of aerosols collected in the Western Russian Arctic in August-September 1991

In August-September 1991 during the SPASIBA expedition (Scientific Program on the Arctic and Siberian Aquatorium) aboard R/V Yakov Smirnitzky in the Laptev Sea ten samples of aerosols were collected by nylon nets. A combined approach including various analytical techniques, such as single-particle analysis, instrumental neutron activation analysis, and atomic absorption spectrophotometry, was used to study composition of the samples. Mass concentration of coarse-grained (>0.001 mm) insoluble fraction of aerosols ranged from 80 to 460 ng/m**3. In all the samples remains of land vegetation were found to be the dominant component. Organic carbon content of the aerosols ranged from 23 to 49%. Inorganic part of the samples was represented mainly by alumosilicates and quartz. Anthropogenic ''fly ash'' particles were observed in all the samples. Temporal variations of element concentrations resulted from differences in air masses entering the studied area.

Chemical composition of altered volcanic rocks from ODP Sites 193-1188 and 193-1189

The conventional model of leaching volcanic rocks as a source of metals in a seafloor hydrothermal systems has been tested by examining the behavior of Pb and other trace elements during hydrothermal alteration. ODP Leg 193 drill sites 1188 (Snowcap) and 1189 (Roman Ruins) on Pual Ridge in the eastern Manus Basin offshore eastern Papua New Guinea provide a unique three-dimensional window into an active back-arc hydrothermal system. We investigate by means of a LA-ICP-MS microbeam technique the capacity of Pb to be leached from a host volcanic rock exposed to various types and intensities of alteration. Our results are in general agreement with previous studies that utilized bulk analytical techniques but provide a more detailed explanation of the processes. Fresh representative dacitic lavas from the Pual Ridge have an average whole rock Pb content of 5.2 ppm, an average interstitial glass Pb content of 5.6 ppm and an average plagioclase Pb content of 1.0 ppm. Altered matrix samples have highly variable Pb values ranging from 0 to 52.4 ppm. High Pb values in altered samples are associated with a low temperature chlorite and clay mineral assemblage, in some cases overprinted by a high temperature (up to 350°C) silica-rich "bleaching" alteration. Only the most highly altered matrix samples have REE patterns that differ from the fresh Pual Ridge dacite. This may represent either different lava histories or alteration characteristics that have affected normally immobile REEs. Altered samples with the highest Pb values have similar REE patterns to those of the local unaltered lavas. They are compositionally similar to typical Pual Ridge dacites indicating a genetic relationship between the main regional volcanic suite and the subseafloor hydrothermally altered, Pb-enriched material. Relative loss/gain for Pb between the analyzed altered samples and a calculated precursor show a maximum relative gain of 901%. Samples with relative Pb gain from both drill sites are associated with lower temperature alteration mineral assemblages characterized by pervasive chloritization. The related lower temperature (220-250°C) neutral to slightly acidic fluids have been ascribed by others to return circulation of hydrothermal fluids that did not interact with seawater. Because altered samples have a higher Pb content than the fresh precursor, leaching of fresh volcanic rocks cannot be the source of Pb in the hydrothermal systems.

Compilation of quality controlled nutrient profiles from the Mediterranean Sea

In the last decades, a striking amount of hydrographic data, covering the most part of Mediterranean basin, have been generated by the efforts made to characterize the oceanography and ecology of the basin. On the other side, the improvement in technologies, and the consequent perfecting of sampling and analytical techniques, provided data even more reliable than in the past. Nutrient data enter fully in this context, but suffer of the fact of having been produced by a large number of uncoordinated research programs and of being often deficient in quality control, with data bases lacking of intercalibration. In this study we present a computational procedure based on robust statistical parameters and on the physical dynamic properties of the Mediterranean sea and its morphological characteristics, to partially overcome the above limits in the existing data sets. Through a data pre filtering based on the outlier analysis, and thanks to the subsequent shape analysis, the procedure identifies the inconsistent data and for each basin area identifies a characteristic set of shapes (vertical profiles). Rejecting all the profiles that do not follow any of the spotted shapes, the procedure identifies all the reliable profiles and allows us to obtain a data set that can be considered more internally consistent than the existing ones.

Geochemistry measured on sediment core GeoB12309-5

Laminated sediment records from the oxygen minimum zone in the Arabian Sea offer unique ultrahigh-resolution archives for deciphering climate variability in the Arabian Sea region. Although numerous analytical techniques are available it has become increasingly popular during the past decade to analyze relative variations of sediment cores' chemical signature by non-destructive X-ray fluorescence (XRF) core scanning. We carefully selected an approximately 5 m long sediment core from the northern Arabian Sea (GeoB12309-5: 24°52.3' N; 62°59.9' E, 956 m water depth) for a detailed, comparative study of high-resolution techniques, namely non-destructive XRF core scanning (0.8 mm resolution) and ICP-MS/OES analysis on carefully selected, discrete samples (1 mm resolution). The aim of our study was to more precisely define suitable chemical elements that can be accurately analyzed and to determine which elemental ratios can be interpretated down to sub-millimeter-scale resolutions. Applying the Student's t-test our results show significantly correlating (1% significance level) elemental patterns for all S, Ca, Fe, Zr, Rb, and Sr, as well as the K/Ca, Fe/Ti and Ti/Al ratios that are all related to distinct lithological changes. After careful consideration of all errors for the ICP analysis we further provide respective factors of XRF Core Scanner software error's underestimation by applying Chi-square-tests, which is especially relevant for elements with high count rates. As demonstrated by these new, ultra-high resolution data core scanning has major advantages (high-speed, low costs, few sample preparation steps) and represents an increasingly required alternative over the time consuming, expensive, elaborative, and destructive wet chemical analyses (e.g., by ICP-MS/OES after acid digestions), and meanwhile also provides high-quality data in unprecedented resolution.

Ar and U-Th-Pb age determinations for minerals from ODP Holes of ODP Legs 173 and 210

We report U-Pb and 39Ar-40Ar measurements on plutonic rocks recovered from the Ocean Drilling Program (ODP) Legs 173 and 210. Drilling revealed continental crust (Sites 1067 and 1069) and exhumed mantle (Sites 1070 and 1068) along the Iberia margin and exhumed mantle (Site 1277) on the conjugate Newfoundland margin. Our data record a complex igneous and thermal history related to the transition from rifting to seafloor spreading. The results show that the rift-to-drift transition is marked by a stuttering start of MORB-type magmatic activity. Subsequent to initial alkaline magmatism, localized mid-oceanic ridge basalts (MORB) magmatism was again replaced by basin-wide alkaline events, caused by a low degree of decompression melting due to tectonic delocalization of deformation. Such "off-axis" magmatism might be a common process in (ultra-) slow oceanic spreading systems, where "magmatic" and "tectonic" spreading varies in both space and time.