Pano Kente: estrutura e estética africana

The fractal geometry of nature is seen in organizations and has set handcrafted artifacts, among them African Kente cloth traditionally produced by Ewe and Ashanti of West Africa. Incorporating parameters also classify products as carriers of fractal geometry, the Kente fabrics exhibit built from geometric shapes classified as seeds or unique architecture. This article aims to analyze examples of Kente cloths and establish the existence of geometric structures formed from a parent cell, exposing how this cell and how its architecture and formed patterns are maintained throughout the finished product.

The Ultraviolet Protection Factor of Naturally-pigmented Cotton

Textile Technology: The sun-blocking properties of a textile are enhanced when a dye, pigment, delustrant, or ultraviolet absorber finish is present that absorbs ultraviolet radiation and blocks its transmission through a fabric to the skin. For this reason, dyed fabrics provide better sun protection than bleached fabrics. Since naturally-colored cottons contain pigments that produce shades ranging from light green to tan and brown, it seemed reasonable to postulate that they would provide better sun protection than conventional bleached cotton, and that natural pigments might prove more durable to laundering and light exposure than dyes, but there is no published research on the ultraviolet transmission values for naturally-pigmented cottons. The purpose of this study was to determine the ultraviolet protection (UPF) values of naturally-pigmented cotton in three shades (green, tan, and brown), and the effect of light exposure and laundering on the sun-blocking properties of naturally-pigmented cotton. Naturally-pigmented cotton specimens were exposed to xenon light and accelerated laundering, ultraviolet transmission values measured, and UPF values calculated following light exposure and laundering. The naturally-pigmented cottons exhibited significantly higher UPF values than conventional cotton (bleached or unbleached). Although xenon light exposure and laundering caused some fading, the UPF values of naturally-pigmented cotton continue to be sufficiently high so that all three shades continue to provide good sun protection after the equivalent of 5 home launderings and 80 American Association of Textile Chemists and Colorists fading units (AFUs) of xenon light exposure.

Geochemical signatures of metasedimentary rocks of high-pressure granulite facies and their relation with partial melting: Carvalhos Klippe, Southern Brasilia Belt, Brazil

High-grade metasedimentary rocks can preserve geochemical signatures of their sedimentary protolith if significant melt extraction did not occur. Retrograde reaction textures provide the main evidence for trapped melt in the rock fabrics. Carvalhos Klippe rocks in Southern Brasilia Orogen, Brazil, present a typical high-pressure granulite assemblage with evidence of mica breakdown partial melting (Ky + Grt + Kfs +/- Bt +/- Rt). The metamorphic peak temperatures obtained by Zr-in-Rt and ternary feldspar geothermometers are between 850 degrees C and 900 degrees C. The GASP bane peak pressure obtained using grossular rich garnet core is 16 kbar. Retrograde reaction textures in which the garnet crystals are partially to totally replaced by Bt + Qtz +/- Fsp intergrowths are very common in the Carvalhos Klippe rocks. These reactions are interpreted as a result of interactions between residual phases and trapped melt during the retrograde path. In the present study the geochemical signatures of three groups of Carvalhos Klippe metasedimentary rocks are analysed. Despite the high metamorphic grade these three groups show well-defined geochemical features and their REE patterns are similar to average compositions of post-Archean sedimentary rocks (PAAS, NASC). The high-pressure granulite facies Grt-Bt-Pl gneisses with immature arenite (wacke, arkose or lithic-arenite) geochemical signatures present in the Carvalhos Klippe are compared to similar rocks in amphibolite facies from the same tectonic framework (Andrelandia Nappe System). The similar geochemical signatures between Grt-Bt-Pl gneisses metamorphosed in high-pressure granulite facies and Grt-Bt-Pl-Qtz schists from the Andrelandia and Liberdade Nappes, with minimal to absent melting conditions, are suggestive of low rates of melt extraction in these high-grade rocks. The rocks with pelitic compositions most likely had higher melt extraction and even under such circumstances nevertheless tend to show REE patterns similar to average compositions of post-Archean sedimentary rocks (PAAS, NASC). (C) 2012 Elsevier Ltd. All rights reserved.

Complex, 3D strain patterns in a synkinematic tonalite batholith from the Aracuai Neoproterozoic orogen (Eastern Brazil): Evidence from combined magnetic and isotopic chronology studies

This work combines structural and geochronological data to improve our understanding of the mechanical behaviour of continental crust involving large amount of magma or partially melted material in an abnormally hot collisional belt. We performed a magnetic and geochronological (U/Pb) study on a huge tonalitic batholith from the Neoproterozoic Aracual belt of East Brazil to determine the strain distribution through space and time. Anisotropy of magnetic susceptibility, combined with rock magnetism investigations, supports that the magnetic fabric is a good proxy of the structural fabric. Field measurements together with the magnetic fabrics highlight the presence in the batholith of four domains characterized by contrasted magmatic flow patterns. The western part is characterized by a gently dipping, orogen-parallel (similar to NS) magmatic foliation that bears down-dip lineations, in agreement with westward thrusting onto the Sao Francisco craton. Eastward, the magmatic foliation progressively turns sub-vertical with a lineation that flips from sub-horizontal to sub-vertical over short distances. This latter domain involves an elongated corridor in which the magmatic foliation is sub-horizontal and bears an orogen-parallel lineation. Finally the fourth, narrow domain displays sub-horizontal lineations on a sub-vertical magmatic foliation oblique (similar to N150 degrees E) to the trend of the belt. U/Pb dating of zircons from the various domains revealed homogeneity in age for all samples. This, together with the lack of solid-state deformation suggests that: 1) the whole batholith emplaced during a magmatic event at similar to 580 Ma, 2) the deformation occurred before complete solidification. and 3) the various fabrics are roughly contemporaneous. The complex structural pattern mapped in the studied tonalitic batholith suggests a 3D deformation of a slowly cooling, large magmatic body and its country rock. We suggest that the development of the observed 3D flow field was promoted by the low viscosity of the middle crust that turned gravitational force as an active tectonic force combining with the East-West convergence between the Sao Francisco and Congo cratons. (C) 2012 Elsevier Ltd. All rights reserved.

Magnetic fabric of Araguainha complex impact structure (Central Brazil): Implications for deformation mechanisms and central uplift formation

The weakening mechanisms involved in the collapse of complex impact craters are controversial. The Araguainha impact crater, in Brazil, exposes a complex structure of 40 km in diameter, and is an excellent object to address this issue. Its core is dominated by granite. In addition to microstructural observations, magnetic studies reveal its internal fabric acquired during the collapse phase. All granite samples exhibit impact-related planar deformation features (PDFs) and planar fractures (PFs), which were overprinted by cataclasis. Cataclastic deformation has evolved from incipient brittle fracturing to the development of discrete shear bands in the center of the structure. Fracture planes are systematically decorated by tiny grains (<10 mu m) of magnetite and hematite, and the orientation of magnetic lineation and magnetic foliation obtained by the anisotropies of magnetic susceptibility (AMS) and anhysteretic remanence (AAR) are perfectly coaxial in all studied sites. Therefore, we could track the orientation of deformation features which are decorated by iron oxides using the AMS and AAR. The magnetic fabrics show a regular pattern at the borders of the central peak, with orientations consistent with the fabric of sediments at the crater's inner collar and complex in the center of the structure. Both the cataclastic flow revealed from microstructural observations and the structural pattern of the magnetic anisotropy match the predictions from numerical models of complex impact structures. The widespread occurrence of cataclasis in the central peak, and its orientations revealed by magnetic studies indicate that acoustic fluidization likely operates at all scales, including the mineral scales. The cataclastic flow made possible by acoustic fluidization results in an apparent plastic deformation at the macroscopic scale in the core. (C) 2012 Elsevier B.V. All rights reserved.

Chain extension of poly (ethylene terephthalate) by reactive extrusion with secondary stabilizer

Poly(ethylene tereftalate) (PET) is a polymer highly susceptible to the hydrolytic reactions that occur during applications and mainly in thermomechanical processing. These reactions lead to the decrease of molecular weight of the polymer, limiting the recycling number of the material. The reactive extrusion of the PET in presence of chain extenders is an alternative to recover mechanical and rheological properties that were depreciated by the polymer degradation. In this study, PET wastes from nonwoven fabrics production were extruded in presence of the secondary stabilizer Irgafos 126 (IRG) on variable concentrations. The results showed that Irgafos 126 increased molecular weight, decreased crystallinity and changed processing behavior of the PET, similarly to the effects produced by the well-known chain extender pyromellitic dianhydride (PMDA), showing that the secondary stabilizer Irgafos 126 can also act as a chain extender for the PET.

Rock of ages

[EN] Granite is emplaced deep in the Earth's crust. It cools and crystallises and is subjected to thermal and magmatic events, and to recurrent stresses. It develops textures or fabrics as well as strain patterns which, as erosion brings the rock mass near the surface, find expression in various fracture sets and systems.

Shape fabric development during progressive deformation

Zusammenfassung:Das Ziel dieser Arbeit ist ein besseres Verständnis von der Art und Weise wie sich Formregelungsgefüge entwicklen. Auf dieser Basis wird der Nutzen von Formregelungsgefügen für die Geologie evaluiert. Untersuchungsmethoden sind Geländearbeit und -auswertung, numerische Simulationen und Analogexperimente. Untersuchungen an Formregelungsgefügen in Gesteinen zeigen, daß ein Formregelungsgefüge nur zu einem begrenzten Grad als Anzeiger für die Stärke der Verformung benutzt werden kann. Der angenommene Grund hierfür ist der Einfluß des Verhältnisses von ursprünglicher zu rekristallisierter Korngröße auf die Gefügeentwicklung und von der Art und Weise wie dynamische Rekristallisation ein Gefüge verändert. Um diese Beobachtung zu evaluieren, wurden verschiedene numerische Simulationen von dynamischer Rekristallisation durchgeführt. Ein neuer Deformationsapparat, mit dem generelle Fließregime modelliert werden können, wurde entwickelt. Die rheologischen Eigenschaften von Materialien, die für solche Experimente benutzt werden, wurden untersucht und diskutiert. Ergebnisse von Analogexperimenten zeigen, daß die Intensität eines Formregelungsgefüges positiv mit der Abnahme der 'kinematic vorticity number' und einem nicht-Newtonianischen, 'power law' Verhalten des Materixmaterials korreliert ist. Experimente, in denen die Formveränderung von viskosen Einschlüssen während der progressiven Verformung modelliert werden, zeigen, daß verschiedene Viskositätskontraste zwischen Matrix- und Einschlußmaterial in charakteristische Formgefüge resultieren.

New polymeric materials for vascular surgery

The dramatic impact that vascular diseases have on human life quality and expectancy nowadays is the reason why both medical and scientific communities put great effort in discovering new and effective ways to fight vascular pathologies. Among the many different treatments, endovascular surgery is a minimally-invasive technique that makes use of X-ray fluoroscopy to obtain real-time images of the patient during interventions. In this context radiopaque biomaterials, i.e. materials able to absorb X-ray radiation, play a fundamental role as they are employed both to enhance visibility of devices during interventions and to protect medical staff and patients from X-ray radiations. Organic-inorganic hybrids are materials that combine characteristics of organic polymers with those of inorganic metal oxides. These materials can be synthesized via the sol-gel process and can be easily applied as thin coatings on different kinds of substrates. Good radiopacity of organic-inorganic hybrids has been recently reported suggesting that these materials might find applications in medical fields where X-ray absorption and visibility is required. The present PhD thesis aimed at developing and characterizing new radiopaque organic-inorganic hybrid materials that can find application in the vascular surgery field as coatings for the improvement of medical devices traceability as well as for the production of X-ray shielding objects and garments. Novel organic-inorganic hybrids based on different polyesters (poly-lactic acid and poly-ε-caprolactone) and polycarbonate (poly-trimethylene carbonate) as the polymeric phase and on titanium oxide as the inorganic phase were synthesized. Study of the phase interactions in these materials allowed to demonstrate that Class II hybrids (where covalent bonds exists between the two phases) can be obtained starting from any kind of polyester or polycarbonate, without the need of polymer pre-functionalization, thanks to the occurrence of transesterification reactions operated by inorganic molecules on ester and carbonate moieties. Polyester based hybrids were successfully coated via dip coating on different kinds of textiles. Coated textiles showed improved radiopacity with respect to the plain fabric while remaining soft to the touch. The hybrid was able to coat single fibers of the yarn rather than coating the yarn as a whole. Openings between yarns were maintained and therefore fabric breathability was preserved. Such coatings are promising for the production of light-weight garments for X-ray protection of medical staff during interventional fluoroscopy, which will help preventing pathologies that stem from chronic X-ray exposure. A means to increase the protection capacity of hybrid-coated fabrics was also investigated and implemented in this thesis. By synthesizing the hybrid in the presence of a suspension of radiopaque tantalum nanoparticles, PDMS-titania hybrid materials with tunable radiopacity were developed and were successfully applied as coatings. A solution for enhancing medical device radiopacity was also successfully investigated. High metal radiopacity was associated with good mechanical and protective properties of organic-inorganic hybrids in the form of a double-layer coating. Tantalum was employed as the constituent of the first layer deposited on sample substrates by means of a sputtering technique. The second layer was composed of a hybrid whose constituents are well-known biocompatible organic and inorganic components, such as the two polymers PCL and PDMS, and titanium oxide, respectively. The metallic layer conferred to the substrate good X-ray visibility. A correlation between radiopacity and coating thickness derived during this study allows to tailor radiopacity simply by controlling the metal layer sputtering deposition time. The applied metal deposition technique also permits easy shaping of the radiopaque layer, allowing production of radiopaque markers for medical devices that can be unambiguously identified by surgeons during implantation and in subsequent radiological investigations. Synthesized PCL-titania and PDMS-titania hybrids strongly adhered to substrates and show good biocompatibility as highlighted by cytotoxicity tests. The PDMS-titania hybrid coating was also characterized by high flexibility that allows it to stand large substrate deformations without detaching nor cracking, thus being suitable for application on flexible medical devices.

Performance evaluation of low environmental impact asphalt concretes using the mechanistic empirical design method based on laboratory fatigue and permanent deformation models

The "sustainability" concept relates to the prolonging of human economic systems with as little detrimental impact on ecological systems as possible. Construction that exhibits good environmental stewardship and practices that conserve resources in a manner that allow growth and development to be sustained for the long-term without degrading the environment are indispensable in a developed society. Past, current and future advancements in asphalt as an environmentally sustainable paving material are especially important because the quantities of asphalt used annually in Europe as well as in the U.S. are large. The asphalt industry is still developing technological improvements that will reduce the environmental impact without affecting the final mechanical performance. Warm mix asphalt (WMA) is a type of asphalt mix requiring lower production temperatures compared to hot mix asphalt (HMA), while aiming to maintain the desired post construction properties of traditional HMA. Lowering the production temperature reduce the fuel usage and the production of emissions therefore and that improve conditions for workers and supports the sustainable development. Even the crumb-rubber modifier (CRM), with shredded automobile tires and used in the United States since the mid 1980s, has proven to be an environmentally friendly alternative to conventional asphalt pavement. Furthermore, the use of waste tires is not only relevant in an environmental aspect but also for the engineering properties of asphalt [Pennisi E., 1992]. This research project is aimed to demonstrate the dual value of these Asphalt Mixes in regards to the environmental and mechanical performance and to suggest a low environmental impact design procedure. In fact, the use of eco-friendly materials is the first phase towards an eco-compatible design but it cannot be the only step. The eco-compatible approach should be extended also to the design method and material characterization because only with these phases is it possible to exploit the maximum potential properties of the used materials. Appropriate asphalt concrete characterization is essential and vital for realistic performance prediction of asphalt concrete pavements. Volumetric (Mix design) and mechanical (Permanent deformation and Fatigue performance) properties are important factors to consider. Moreover, an advanced and efficient design method is necessary in order to correctly use the material. A design method such as a Mechanistic-Empirical approach, consisting of a structural model capable of predicting the state of stresses and strains within the pavement structure under the different traffic and environmental conditions, was the application of choice. In particular this study focus on the CalME and its Incremental-Recursive (I-R) procedure, based on damage models for fatigue and permanent shear strain related to the surface cracking and to the rutting respectively. It works in increments of time and, using the output from one increment, recursively, as input to the next increment, predicts the pavement conditions in terms of layer moduli, fatigue cracking, rutting and roughness. This software procedure was adopted in order to verify the mechanical properties of the study mixes and the reciprocal relationship between surface layer and pavement structure in terms of fatigue and permanent deformation with defined traffic and environmental conditions. The asphalt mixes studied were used in a pavement structure as surface layer of 60 mm thickness. The performance of the pavement was compared to the performance of the same pavement structure where different kinds of asphalt concrete were used as surface layer. In comparison to a conventional asphalt concrete, three eco-friendly materials, two warm mix asphalt and a rubberized asphalt concrete, were analyzed. The First Two Chapters summarize the necessary steps aimed to satisfy the sustainable pavement design procedure. In Chapter I the problem of asphalt pavement eco-compatible design was introduced. The low environmental impact materials such as the Warm Mix Asphalt and the Rubberized Asphalt Concrete were described in detail. In addition the value of a rational asphalt pavement design method was discussed. Chapter II underlines the importance of a deep laboratory characterization based on appropriate materials selection and performance evaluation. In Chapter III, CalME is introduced trough a specific explanation of the different equipped design approaches and specifically explaining the I-R procedure. In Chapter IV, the experimental program is presented with a explanation of test laboratory devices adopted. The Fatigue and Rutting performances of the study mixes are shown respectively in Chapter V and VI. Through these laboratory test data the CalME I-R models parameters for Master Curve, fatigue damage and permanent shear strain were evaluated. Lastly, in Chapter VII, the results of the asphalt pavement structures simulations with different surface layers were reported. For each pavement structure, the total surface cracking, the total rutting, the fatigue damage and the rutting depth in each bound layer were analyzed.

Finite-strain analysis in orthogneiss of the Gran Paradiso massif, Western Alps, Italy

A finite-strain study in the Gran Paradiso massif of the Italian Western Alps has been carried out to elucidate whether ductile strain shows a relationship to nappe contacts and to shed light on the nature of the subhorizontal foliation typical of the gneiss nappes in the Alps. The Rf/_ and Fry methods used on feldspar porphyroclasts from 143 augengneiss and 11 conglomerate samples of the Gran Paradiso unit (upper tectonic unit of the Gran Paradiso massif), as well as, 9 augengneiss (Erfaulet granite) and 3 quartzite conglomerate samples from the underlying Erfaulet unit (lower unit of the Gran Paradiso massif), and 1 sample from mica schist. Microstructures and thermobarometric data show that feldspar ductility at temperatures >~450°C occurred only during high-pressure metamorphism, when the rocks were underplated beneath the overriding Adriatic plate. Therefore, the finite-strain data can be related to high-pressure metamorphism in the Alpine subduction zone. The augen gneiss was heterogeneously deformed and axial ratios of the strain ellipse in XZ sections range from 2.1 to 69.8. The long axes of the finite-strain ellipsoids trend W/WNW and the short axes are subvertical associated with a subhorizontal foliation. The strain magnitudes do not increase towards the nappe contacts. Geochemical work shows that the accumulation of finite strain was not associated with any significant volume strain. Hence, the data indicate flattening strain type in the Gran Paradiso unit and constrictional strain type in the Erfaulet unit and prove deviations from simple shear. In addition, electron microprobe work was undertaken to determine if the analysed fabrics formed during high-P metamorphism. The chemistry of phengites in the studied samples suggests that deformation and final structural juxtaposition of the Gran Paradiso unit against the Erfaulet took place during high-pressure metamorphism. On the other hand, nappe stacking occurred early during subduction probably by brittle imbrication and that ductile strain was superimposed on and modified the nappe structure during high-pressure underplating in the Alpine subduction zone. The accumulation of ductile strain during underplating was not by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gran Paradiso massif. It is concluded that this foliation formed during thrusting of the nappes onto each other suggesting that nappe stacking was associated with vertical shortening. The primary evidence for this interpretation is an attenuated metamorphic section with high-pressure metamorphic rocks of the Gran Paradiso unit juxtaposed against the Erfaulet unit. Therefore, the exhumation during high-pressure metamorphism in the Alpine subduction zone involved a component of vertical shortening, which is responsible for the subhorizontal foliation within the nappes.

Sustainable inorganic Binders and Their Applications in Building Engineering: A Green Alternative to Ordinary Portland Cement

In the last decades, the building materials and construction industry has been contributing to a great extent to generate a high impact on our environment. As it has been considered one of the key areas in which to operate to significantly reduce our footprint on environment, there has been widespread belief that particular attention now has to be paid and specific measures have to be taken to limit the use of non-renewable resources.The aim of this thesis is therefore to study and evaluate sustainable alternatives to commonly used building materials, mainly based on ordinary Portland Cement, and find a supportable path to reduce CO2 emissions and promote the re-use of waste materials. More specifically, this research explores different solutions for replacing cementitious binders in distinct application fields, particularly where special and more restricting requirements are needed, such as restoration and conservation of architectural heritage. Emphasis was thus placed on aspects and implications more closely related to the concept of non-invasivity and environmental sustainability. A first part of the research was addressed to the study and development of sustainable inorganic matrices, based on lime putty, for the pre-impregnation and on-site binding of continuous carbon fiber fabrics for structural rehabilitation and heritage restoration. Moreover, with the aim to further limit the exploitation of non-renewable resources, the synthesis of chemically activated silico-aluminate materials, as metakaolin, ladle slag or fly ash, was thus successfully achieved. New sustainable binders were hence proposed as novel building materials, suitable to be used as primary component for construction and repair mortars, as bulk materials in high-temperature applications or as matrices for high-toughness fiber reinforced composites.

Nukleation pflanzlicher Mikrotubuli: Expression relevanter Gene

Die wichtigsten Bestandteile des Cytoskeletts in pflanzlichen Zellen sind die Actinfilamente und die Mikrotubuli. Die Mikrotubuli spielen in der Organisation und der Morphogenese von pflanzlichen Zellen eine wichtige Rolle. Sie sind zusammen mit den Cellulosefibrillen an der Formgebung der Pflanzenzelle beteiligt. Sie bilden das Präprophaseband, das die Zellteilungsebene bestimmt und die Mitosespindel, die für die Trennung der Chromosomen sorgt, sowie den Phragmoplasten, der die Zellwand zwischen den Tochterzellen bildet. Weiterhin geben die Mikrotubuli durch Interaktion mit den Cellulose-Synthase-Komplexen die Richtung der Zellexpansion vor (GRANGER und CYR, 2001; LLOYD und CHAN, 2002; BASKIN, 2002). Die Mikrotubuli sind auch an der Stabilisierung der Zellform und an Transportprozessen beteiligt. Als Bestandteil der Mikrotubuli-organisierenden Zentren (MTOCs) wurde das γ-Tubulin identifiziert, das sehr wahrscheinlich an der Nukleation der Mikrotubuli beteiligt ist, indem es die Assemblierung der αβ-Tubulindimere zu Mikrotubuli einleitet. In tierischen Zellen ist durch intensive Forschung inzwischen relativ viel über die Funktion von γ-Tubulin, vor allem im Verlauf der Zellteilung bekannt, wie z. B. die Lokalisation in Centrosomen mit ihren paarweise angeordneten Centriolen, die die MTOCs darstellen. In pflanzlichen Zellen sind bisher nur wenige Funktionen des Proteins hinreichend geklärt. Die höheren Pflanzen besitzen keine Centriolen und keine Centrosomen. Über die Zellteilung hinaus gibt es kaum Anhaltspunkte über das Vorhandensein oder eventuelle Aufgaben von γ-Tubulin in expandierenden und voll expandierten Zellkulturen und Pflanzengeweben. In dieser Arbeit wurde die Expression über PCR und die Messung des Proteingehalts von cytoskelett-relevanten Proteinen in den Entwicklungsstadien der Zellsuspensionskultur (BY-2) und von Blattstadien der Tabakpflanze (SR1) von Nicotiana tabacum gemessen. Primäres Ziel war es eine Aussage zu erhalten, in welchem Ausmaß γ-Tubulin in expandierenden und voll expandierten Zellen noch exprimiert wird und ob bzw. wie eine Regulation (transkriptionell oder posttranskriptionell) des γ-Tubulins in der Pflanze stattfindet. Für den Nachweis des γ-Tubulins auf der Proteinebene wurde ein pflanzenspezifischer γ-Tubulin Antikörper zu entwickelt. Bei diesem Antikörper handelte es sich um einen polyklonalen Antikörper, der spezifisch gegen eine Sequenz in pflanzlichem γ-Tubulin gerichtet ist. Dabei zeigte der in der Arbeit entwickelte Antikörper gegen die pflanzliche JOSHI-Domäne spezifische Signale. Der erfolgte Nachweis von γ-Tubulin auf der Proteinebene und der Transkripte zeigte bis in die ältesten untersuchten Stadien der Zellsuspensionskultur (BY-2) und in Geweben der Blattstadien der Tabakpflanze (SR1) deutliche Signale für γ-Tubulin. Es war somit nicht nur in meristematisch aktiven Zellen und Geweben von Nicotiana tabacum, sondern auch in nichtmitotischen Zellen und Geweben vorhanden. Hierbei war über die Phasen der Zellteilung und der Zellformgebung hinweg auf beiden Ebenen eine parallele Entwicklung mit relativ konstanten starken Signalen zu beobachten. Nach dem Einstellen der Teilungsaktivität fiel der Gehalt an mRNA deutlich ab. Dabei nahm die Konzentration des Proteins im Vergleich zur mRNA zeitlich verzögert ab. Diese Ergebnisse bei der Zellsuspensionskultur (BY-2) und Tabakpflanze (SR1) gehen mit der möglichen Nukleationstätigkeit des Proteins konform. Es waren geringere aber doch deutlichen Signale bei Absterbenden Zellen der Zellkultur, bzw. bei expandierenden und voll expandierten und seneszenten Blättern der Tabakpflanze (SR1) nachzuweisen. Dies lässt die Folgerung zu, dass die nachgewiesene mRNA von γ-Tubulin nicht posttranskriptionell reguliert wird, sondern dass das γ-Tubulin auch eine wichtige Rolle außerhalb der Zellteilung in den postmitotischen Stadien, z. B. als organisierender Faktor bei der Umgestaltung oder Stabilisierung des Mikrotubuli-Cytoskeletts, spielt. Der γ-Tubulin-Gehalt in den Geweben der SR1-Pflanze zeigte über die Zellkultur hinaus, dass die Expression von α-Tubulin nach Einstellen der Teilungsaktivität kontinuierlich abnimmt. Dieses Ergebnis legt die Vermutung nahe, dass γ-Tubulin in älteren Blattgeweben zusätzliche Aufgaben übernehmen könnte, die nicht auf eine gleichzeitige Expression von α-Tubulin angewiesen sind. So kann beispielsweise eine Beteiligung von γ-Tubulin an der Stabilisierung der Mikrotubuli, und damit einhergehend eine Abnahme der dynamischen Instabilität dieser Filamente, eine denkbare Funktion des Proteins in expandierendem und voll expandiertem Gewebe sein. Die Aufgaben von γ-Tubulin in sehr altem Gewebe mit deutlichen Anzeichen der Seneszenz können allerdings nach dem derzeitigen Stand der Forschung nicht eindeutig beantwortet werden und bedürfen weitergehenden Untersuchungen, da dadurch ein die Komplexität und die Dynamik des pflanzlichen Cytoskeletts geklärt werden kann.

Fiber-reinforced ceramics for thermostructural applications, produced by polymer impregnation pyrolysis

Several CFCC (Continuous Fiber Composite Ceramics) production processes were tested, concluding that PIP (Polymer Impregnation, or Infiltration, Pyrolysis) and CBC (Chemically Bonded Ceramics) based procedures have interesting potential applications in the construction and transportation fields, thanks to low costs to get potentially useful thermomechanical performances. Among the different processes considered during the Doctorate (from the synthesis of new preceramic polymers, to the PIP production of SiC / SiC composites) the more promising results came from the PIP process with poly-siloxanes on basalt fabrics preforms. Low processing time and costs, together with fairly good thermomechanical properties were demonstrated, even after only one or two PIP steps in nitrogen flow. In alternative, pyrolysis in vacuum was also tested, a procedure still not discussed in literature, but which could originate an interesting reduction of production costs, with only a moderate detrimental effect on the mechanical properties. The resulting CFCC is a basalt / SiCO composite that can be applied for continuous operation up to 600°C, also in oxidant environment, as TG and XRD demonstrated. The failure upon loading is generally pseudo-plastic, being interlaminar delamination the most probable rupture mechanism. . The strength depends on several different factors (microstructure, polymer curing and subsequent ceramic phase evolution, fiber pull-out, fiber strength, fiber percentage) and can only be optimized empirically. In order to be open minded in selecting the best technology, also CBC (Chemically Bonded Ceramics) matrixes were considered during this Doctorate, making some preliminary investigations on fire-resistant phosphate cements. Our results on a commercial product evidenced some interesting thermomechanical capabilities, even after thermal treatments. However the experiments showed also phase change and possible cracking and deformations even on slow drying (at 130°C) and easy rehydration upon exposure to environmental humidity.

Tipologia e diffusione delle produzioni ceramiche in Romagna tra XIII e XV secolo

In questo lavoro si è avuta la possibilità di studiare e confrontare i reperti ceramici provenienti da tre recenti scavi condotti nella zona della Romagna dall’Università di Bologna: il monastero di San Severo a Classe (RA), il castello di Rontana (Brisighella-RA) e la pieve di S. Reparata a Terra del Sole (FC). Si tratta di scavi ancora inediti differenti tra loro sia per connotazione distrettuale di appartenenza che per tipologia insediativa La cesura cronologica che si è preso in esame va dal XIII a XV secolo. Il XIII secolo corrisponde a un periodo in cui si assiste ad una riapertura dei trasporti a lunga distanza e si diffonde la tendenza al trasferimento dei saperi tecnici da Oriente verso Occidente, fenomeno che include l’introduzione di nuove tecnologie produttive in campo ceramico come l’ingobbio e la maiolica in diversi centri urbani. Si passa poi attraverso il XIV secolo, momento in cui alcune produzioni, come quella della maiolica, raggiungono la loro massima diffusione, con una diversificazione qualitativa dei prodotti, raggiungendo anche l’ambito rurale, e si assiste alla moltiplicazione dei centri di produzione. Si arriva così al XV secolo periodo in cui iniziano ad affermarsi dei veri e propri centri produttivi “industriali”, rappresentativi anche di una specializzazione regionale dei prodotti di qualità medio-alta. La possibilità di confrontare materiali di siti così differenti tra loro ha dato modo di sottolineare analogie e differenze anche tra città e campagna, in un territorio come quello romagnolo che ancora risente del peso della lunga tradizione antiquaria che ha caratterizzato gli studi fino al secolo scorso.