Analisi e simulazione di un sistema per la misura sperimentale del dipolo magnetico residuo di micro-satelliti

La dinamica dell'assetto di un satellite artificiale rappresenta uno degli aspetti più delicati della missione che esso stesso andrà a svolgere in orbita attorno ad un qualche corpo celeste, quale appunto il pianeta Terra. Il seguente lavoro di tesi si propone di analizzare la causa di una delle principali componenti di disturbo dell'assetto appena menzionato, preponderante per satelliti dalle piccole dimensioni, fornendo la spiegazione, validata attraverso una simulazione, della messa a punto di un metodo sperimentale per la valutazione della stessa. La componente in questione è la coppia di disturbo magnetica, ed è generata dall'interazione tra il campo magnetico terrestre ed il cosiddetto 'dipolo magnetico residuo' del satellite stesso, ossia quel campo magnetico che esso, in modalità operativa e non, risulta generare a causa del materiale ferromagnetico presente al suo interno, e delle correnti elettriche circolanti nei vari cavi conduttori. Ci si è dunque occupati dell'analisi e messa a punto di un metodo che possa consentire sperimentalmente di rilevare l'entità del dipolo residuo. Il lavoro di simulazione è stato svolto prendendo in considerazione le dimensioni e le possibili caratteristiche del dipolo residuo del micro-satellite ESEO (European Student Earth Orbiter), sviluppato da studenti di diverse università europee ed ora in fase di progetto dettagliato (fase C) presso i laboratori dell'azienda ALMASpace S.r.l. di Forlì. Il metodo in esame consiste nel rilevare il campo magnetico generato dal satellite, posto all'interno di un sistema tridimensionale di bobine di Helmholtz per avere una zona libera da campi magnetici esterni. Il rilevamento del dipolo avviene per mezzo di un magnetometro a tre assi, e dalla suddetta misura si può pervenire alla conoscenza delle componenti del dipolo stesso, quali posizione, orientamento ed intensità; siccome però la misura del magnetometro non è ideale, ma risulta affetta da errori, per una più corretta caratterizzazione del dipolo è necessario utilizzare un numero maggiore di magnetometri (oppure, il che è lo stesso, un unico magnetometro spostato mano a mano) in punti diversi attorno al satellite in modo da avere più misure di campo magnetico e poter così sfruttare una procedura numerica di ottimizzazione per risalire alle componenti del dipolo. Questa intera parte di calcolo è stata realizzata in MatLab®, simulando quindi le misure ottenute dai magnetometri, 'sporcandole' con i predetti errori, ed utilizzando le funzioni di minimizzazione lsqnonlin ed fmincon per verificare la funzionalità del sistema; si sono infatti analizzati i grafici rappresentanti i livelli di errore commessi dall'algoritmo di stima sulle varie componenti del dipolo, per le tipologie di errore dei magnetometri menzionate in precedenza. Si è così cercato di suggerire una configurazione ottimale di magnetometri in grado di fornire una stima caratterizzata da un buon compromesso tra numero di magnetometri da utilizzare non troppo elevato ed errore derivante accettabile.

Expression, purification and low-resolution structure of human vitamin C transporter SVCT1 (SLC23A1)

Expression and purification of human membrane proteins for structural studies represent a great challenge. This is because micro- to milligram amounts of pure isolated protein are required. To this aim, we successfully expressed the human vitamin C transporter-1 (hSVCT1; SLC23A1) in Xenopus laevis oocytes and isolated highly pure protein in microgram amounts. Recombinant hSVCT1 was functional when expressed in oocytes and glycosylated. Structural analysis of purified hSVCT1 by transmission electron microscopy and single particle analysis unveiled its shape, dimensions and low-resolution structure as well as the existence of a major monomeric and minor dimeric population. Chemical crosslinking of isolated oocyte membranes containing expressed hSVCT1 indicated similar oligomeric states of hSVCT1 in lipid bilayers. This work reports the first purification and structural analysis of a human SVCT protein and opens the way for future functional and structural studies using purified hSVCT1.

Analysis of ⁸⁵Kr: a comparison at the 10-14 level using micro-liter samples

The isotopic abundance of 85Kr in the atmosphere, currently at the level of 10−11, has increased by orders of magnitude since the dawn of nuclear age. With a half-life of 10.76 years, 85Kr is of great interest as tracers for environmental samples such as air, groundwater and ice. Atom Trap Trace Analysis (ATTA) is an emerging method for the analysis of rare krypton isotopes at isotopic abundance levels as low as 10−14 using krypton gas samples of a few micro-liters. Both the reliability and reproducibility of the method are examined in the present study by an inter-comparison among different instruments. The 85Kr/Kr ratios of 12 samples, in the range of 10−13 to 10−10, are measured independently in three laboratories: a low-level counting laboratory in Bern, Switzerland, and two ATTA laboratories, one in Hefei, China, and another in Argonne, USA. The results are in agreement at the precision level of 5%.

Factores territoriales y desempeños de las micro y pequeñas empresas industriales. Un abordaje desde las dinámicas de la proximidad

Para abordar el tema de las Micro y Pequeñas empresas (Mypes) industriales, y los factores y relaciones territoriales que influyen en su trayectoria económica, es necesario construir un marco teórico-metodológico que dé cuenta de la multiplicidad de los aspectos involucrados. El interés por este objeto de estudio está legitimado por el hecho de que las Mypes industriales constituyen actores de relevancia en los procesos de desarrollo local, que implican el despliegue de las fuerzas endógenas de una determinada región, las cuales poseen una fuerte connotación territorial que puede cualificarse con conceptos como: identidad y compromiso locales, interés regional, interacciones de proximidad y sinergias locales. Teniendo en cuenta los factores territoriales, el acercamiento a través del análisis de las interacciones basadas en las dinámicas de la proximidad se vislumbra como uno de los más fructíferos desde la disciplina geográfica.

Factores territoriales y desempeños de las micro y pequeñas empresas industriales. Un abordaje desde las dinámicas de la proximidad

Para abordar el tema de las Micro y Pequeñas empresas (Mypes) industriales, y los factores y relaciones territoriales que influyen en su trayectoria económica, es necesario construir un marco teórico-metodológico que dé cuenta de la multiplicidad de los aspectos involucrados. El interés por este objeto de estudio está legitimado por el hecho de que las Mypes industriales constituyen actores de relevancia en los procesos de desarrollo local, que implican el despliegue de las fuerzas endógenas de una determinada región, las cuales poseen una fuerte connotación territorial que puede cualificarse con conceptos como: identidad y compromiso locales, interés regional, interacciones de proximidad y sinergias locales. Teniendo en cuenta los factores territoriales, el acercamiento a través del análisis de las interacciones basadas en las dinámicas de la proximidad se vislumbra como uno de los más fructíferos desde la disciplina geográfica.

Apropiación de energías alternativas en micro-emprendimientos productivos

Este trabajo presenta reflexiones teóricas, metodológicas, epistemológicas y operativas, efectuadas por un equipo de investigación interdisciplinario en el marco del proyecto: "Familia, trabajo y estrategias de sobre vivencia en universos muy pobres, en base a la apropiación de energías alternativas. Estudios de casos. Catamarca Argentina". El objetivo general propone mejorar la calidad de vida del asentamiento, en componentes materiales y no materiales y diseñar estrategias conjuntas para la construcción de ciudadanía crecientemente emancipatoria. Los objetivos específicos se orientan a describir las relaciones intra e interfamiliares que constituyen soporte de redes de supervivencia, conocer sus prácticas de gestión y concretar microproyectos de desarrollo con fuentes de energía alternativa. Inicialmente fue posible monitorear cambios operados en el universo con motivo de la apropiación de energía solar en su cotidianeidad. Luego, conforme a la visión de las familias, fue viable aplicarla en micro emprendimientos productivos pensados desde sus saberes pre-existentes. Ello permitió mutar acciones de ventas al menudeo, por estrategias sustentables. Además se ejercitaron formas de organización familiar, distribución de autoridad y asunción de roles significativos. La estrategia metodológica se inscribe en una investigación acción, con perfil cuali-cuantitativo y demandó la construcción de herramientas metodológicas y categorías conceptuales

Factores territoriales y desempeños de las micro y pequeñas empresas industriales. Un abordaje desde las dinámicas de la proximidad

Para abordar el tema de las Micro y Pequeñas empresas (Mypes) industriales, y los factores y relaciones territoriales que influyen en su trayectoria económica, es necesario construir un marco teórico-metodológico que dé cuenta de la multiplicidad de los aspectos involucrados. El interés por este objeto de estudio está legitimado por el hecho de que las Mypes industriales constituyen actores de relevancia en los procesos de desarrollo local, que implican el despliegue de las fuerzas endógenas de una determinada región, las cuales poseen una fuerte connotación territorial que puede cualificarse con conceptos como: identidad y compromiso locales, interés regional, interacciones de proximidad y sinergias locales. Teniendo en cuenta los factores territoriales, el acercamiento a través del análisis de las interacciones basadas en las dinámicas de la proximidad se vislumbra como uno de los más fructíferos desde la disciplina geográfica.

Animation of micro-computed tomography of bioerosion trace Entobia megastoma made by East Australian bioeroding sponge Cliona celata

Endolithic bioerosion is difficult to analyse and to describe, and it usually requires damaging of the sample material. Sponge erosion (Entobia) may be one of the most difficult to evaluate as it is simultaneously macroscopically inhomogeneous and microstructurally intricate. We studied the bioerosion traces of the two Australian sponges Cliona celata Grant, 1826 (sensu Schönberg 2000) and Cliona orientalis Thiele, 1900 with a newly available radiographic technology: high resolution X-ray micro-computed tomography (MCT). MCT allows non-destructive visualisation of live and dead structures in three dimensions and was compared to traditional microscopic methods. MCT and microscopy showed that C. celata bioerosion was more intense in the centre and branched out in the periphery. In contrast, C. orientalis produced a dense, even trace meshwork and caused an overall more intense erosion pattern than C. celata. Extended pioneering filaments were not usually found at the margins of the studied sponge erosion, but branches ended abruptly or tapered to points. Results obtained with MCT were similar in quality to observations from transparent optical spar under the dissecting microscope. Microstructures could not be resolved as well as with e.g. scanning electron microscopy (SEM). Even though sponge scars and sponge chips were easily recognisable on maximum magnification MCT images, they lacked the detail that is available from SEM. Other drawbacks of MCT involve high costs and presently limited access. Even though MCT cannot presently replace traditional techniques such as corrosion casts viewed by SEM, we obtained valuable information. Especially for the possibility to measure endolithic pore volumes, we regard MCT as a very promising tool that will continue to be optimised. A combination of different methods will produce the best results in the study of Entobia.

Micro- and picoplankton in waters of the Saint Paul Island, Pribilof Islands, Bering Sea

On the basis of materials collected in June-August 1994 characteristic data on microplankton were gathered in three biotopes of the eastern shelf of the Bering Sea: open shelf (coastal zone), the harbor, and the salt lagoon of Saint Paul Island (Pribiof Islands). The following parameters of microplanktonic communities were analyzed: abundance, biomass, and production of autotrophic picoplankton (picoalgae and cyanobacteria); abundance, biomass, growth rate constant, and production of bacterioplankton; role of filiform bacteria in bacterioplankton; species composition of heterotrophic flagellates and ciliates, their abundance, and biomass. Growth rates and consumption rates of picoplankton and bacterioplankton by heterotrophic nano- and microplankton were estimated in the experiments using the dilution method. Temporal dynamics of all structural and functional parameters of microplankton were analyzed. The minor role of autotrophic picoplankton and significant role of bacterioplankton as well as heterotrophic nano- and microplankton in planktonic communities of studied biotopes during summer months was shown. During certain periods, bacterial biomass was as high as 50-65% of phytoplankton biomass, and production of bacteria was as high as 20-40% of primary production. In the middle of the season biomass of nano- and microheterotrophic organisms in different biotopes exceeded biomass of mesozooplankton 2-10 times. Average consumption of bacterial production by nano- and microplankton during the period of observations was 85-94%.

UV laser-induced high resolution cleaving of Si wafers for micro-nano devices and polymeric waveguide characterization

In this work we propose a method for cleaving silicon-based photonic chips by using a laser based micromachining system, consisting of a ND:YVO4laser emitting at 355 nm in nanosecond pulse regime and a micropositioning system. The laser makes grooved marks placed at the desired locations and directions where cleaves have to be initiated, and after several processing steps, a crack appears and propagate along the crystallographic planes of the silicon wafer. This allows cleavage of the chips automatically and with high positioning accuracy, and provides polished vertical facets with better quality than the obtained with other cleaving process, which eases the optical characterization of photonic devices. This method has been found to be particularly useful when cleaving small-sized chips, where manual cleaving is hard to perform; and also for polymeric waveguides, whose facets get damaged or even destroyed with polishing or manual cleaving processing. Influence of length of the grooved line and speed of processing is studied for a variety of silicon chips. An application for cleaving and characterizing sol–gel waveguides is presented. The total amount of light coupled is higher than when using any other procedure.

Hydration of C3S, C2S and their Blends. Micro- and Nanoscale Characterization

This study forms part of wider research conducted under a EU 7 th Framework Programme (COmputationally Driven design of Innovative CEment-based materials or CODICE). The ultimate aim is the multi-scale modelling of the variations in mechanical performance in degraded and non-degraded cementitious matrices. The model is being experimentally validated by hydrating the main tri-calcium silicate (T1-C3S) and bi-calcium silicate (β-C2S), phases present in Portland cement and their blends. The present paper discusses micro- and nanoscale studies of the cementitious skeletons forming during the hydration of C3S, C2S and 70 % / 30 % blends of both C3S/C2S and C2S/C3S with a water/cement ratio of 0.4. The hydrated pastes were characterized at different curing ages with 29 Si NMR, SEM/TEM/EDS, BET, and nanoindentation. The findings served as a basis for the micro- and nanoscale characterization of the hydration products formed, especially C-S-H gels. Differences were identified in composition, structure and mechanical behaviour (nanoindentation), depending on whether the gels formed in C3S or C2S pastes. The C3S gels had more compact morphologies, smaller BET-N2 specific surface area and lesser porosity than the gels from C2S-rich pastes. The results of nanoindentation tests appear to indicate that the various C-S-H phases formed in hydrated C3S and C2S have the same mechanical properties as those formed in Portland cement paste. Compared to the C3S sample, the hydrated C2S specimen was dominated by the loose-packed (LP) and the low-density (LD) C-S-H phases, and had a much lower content of the high density (HD) C-S-H phase

Targeted overexpression of protein kinase C β2 isoform in myocardium causes cardiomyopathy

Increased cardiovascular mortality occurs in diabetic patients with or without coronary artery disease and is attributed to the presence of diabetic cardiomyopathy. One potential mechanism is hyperglycemia that has been reported to activate protein kinase C (PKC), preferentially the β isoform, which has been associated with the development of micro- and macrovascular pathologies in diabetes mellitus. To establish that the activation of the PKCβ isoform can cause cardiac dysfunctions, we have established lines of transgenic mice with the specific overexpression of PKCβ2 isoform in the myocardium. These mice overexpressed the PKCβ2 isoform transgene by 2- to 10-fold as measured by mRNA, and proteins exhibited left ventricular hypertrophy, cardiac myocyte necrosis, multifocal fibrosis, and decreased left ventricular performance without vascular lesions. The severity of the phenotypes exhibited gene dose-dependence. Up-regulation of mRNAs for fetal type myosin heavy chain, atrial natriuretic factor, c-fos, transforming growth factor, and collagens was also observed. Moreover, treatment with a PKCβ-specific inhibitor resulted in functional and histological improvement. These findings have firmly established that the activation of the PKCβ2 isoform can cause specific cardiac cellular and functional changes leading to cardiomyopathy of diabetic or nondiabetic etiology.

Measurements of hydrogen, oxygen and carbon isotope variability in Sphagnum moss along a micro-topographical gradient in a southern Patagonian peatland

Funded by Natural Environment Research Council PRECIP and PATAGON