Kan snedskarvning vara ett ekonomiskt lämpligt komplement till fingerskarvning? Kvistfritt listmaterial av furu är mycket eftertraktat inom träindustrin där fingerskarvning numera är den mest förekommande metoden. Det är viktigt att listmaterial har en hanteringsstyrka god nog för att hålla ihop vid montering eftersom konstruktionsstyrkan inte är den begränsande faktorn. Denna studie innehåller en jämförelse i draghållfasthet för lister gjorda med fingerskarv, MDF och snedskarv där det lägsta vinkelförhållandet som uppfyller kraven på skarven är sökt från 1:1 till 1:5. Tidigare tester framhåller förhållandet 1:8 när det är till för konstruktionsändamål, denna studie hävdar att 1:3 är tillräckligt för lister. / Could scarf jointing be an economical suitable complement to finger jointing? Knot-free lath material of pine wood is highly requested in the timber industry where finger jointing nowadays is a commonly used method. It is important that the lath material has a handling strength good enough to hold the assembly since structural strength is not the limited factor. This study contains a comparison of tensile strength in laths made of finger joints, MDF (Medium Density Fibreboard) and scarf joints where the lowest ratio of angular relationship that meets the demands of the scarf is searched from 1:1 to 1:5. Previous testing only holds a ratio of 1:8 for construction purposes whereas this study claims a result of 1:3 for laths.

[pt] Visando adequar a sociedade do consumo a uma existência menos impactante ao meio ambiente, a busca por materiais oriundos de fontes renováveis e passíveis de biodegradação é crescente. No entanto, para que esta transição seja mais eficiente, se faz necessário mudar não só os materiais que são produzidos, mas também a logística da produção e os processos produtivos utilizados. Com base nisto, o objetivo deste trabalho é desenvolver e caracterizar uma chapa de fibras, desenvolvida a partir de resíduos da agro indústria do palmito de pupunha (Bactris Gasipaes), a ser produzida por meio da capacitação dos agricultores locais, com processos de baixa complexidade tecnológica, baixo custo de implementação e mínimo impacto ambiental associado à sua produção. Os ensaios foram realizados de acordo a norma ABNT 15316 - 2:2009, que determina parâmetros de amostragem e métodos de ensaio das chapas de fibras de média densidade (MDF). Como adesivo, aglomerante, foi utilizada a resina poliuretana, de base vegetal, em diferentes proporções fibra/matriz. Os resultados foram analisados seguindo a norma ABNT 15316 – 3: 2009, que estabelece os requisitos para chapas de densidades diferentes, produzidas para os mais diversos fins (estrutural, geral, forro, parede, dentre outros). Dessa forma, foi possível atestar a viabilidade de produção da chapa em pequena escala, garantindo a parcial substituição das chapas MDF disponíveis no mercado, o que comprova a real oportunidade de crescimento sustentável, através da geração de renda e desenvolvimento sócio ambiental. / [en] Aiming to adapt the consumer society to a life less harmful to the environment, the research for materials produced from renewable sources and subject to biodegradation is increasing. However, for this transition to be more efficient, it is necessary to change not only the materials that are being produced but also the production logistics and production processes used. On this basis, the objective of this work is to develop and characterize a fiberboard, developed from the agro-industry waste of Pupunha`s palm heart (Bactris gasipaes), to be produced through the training of local farmers, processes with low complexity technology, low cost of implementation and minimal environmental impact associated with its production. The tests were performed according to the ABNT 15316 - 2:2009, which determines the parameters of sampling and test methods for medium density fiberboard (MDF). The vegetal based polyurethane was used as adhesive/ binder. The samples were produced in different proportions fiber / matrix. The results were analyzed following the ABNT 15316-3: 2009, which establish the requirements for plates of different densities, produced for different purposes (structural, general, lining, wall, among others). Thus it was possible to demonstrate the feasibility of a small scale production of the alternative fiberboard, ensuring the partial replacement of the medium density fiberboards usually available on the market. This points out to the growth opportunity of the rural comunitys through income generation and socio-environmental development.

In this paper we suggest a lightning detection system capable of warning a local populous of incoming lightning weather using a combination of the AS3935 sensor and the one-board-computer Raspberry Pi, in an attempt to design a product that is cheap, mobile and easy to use. The product is composed of a sensor net that registers and reports lightnings on a webserver. The server is reachable as a normal website based on the LAMP method. The project reached a stadium which should satisfy a “proof of concept”, however, the product is far from complete, as it lacks the necessary algorithms needed for proper data computation. The current system only uses Raspberry pi, but it is theoretically possible to introduce other hardware to the system, but the current developed product does not support such functionality. / I den här rapporten föreslår vi ett blixtlokaliseringssystem kapabelt att varna lokal befolkningen om inkommande blixtväder med hjälp av en kombination av sensorn AS3935 och enchipsdatorn Raspberry Pi, i ett försök att skapa en produkt som är billig, mobil och användarvänlig. Systemet består av ett nät av sensorer som registrerar och rapporterar blixtaktivitet på en webbserver. Servern är nåbar som en vanlig hemsida som är byggd enligt LAMP metoden. Projektet har nått ett stadium som borde uppnå kraven för ett ”bevis av ett koncept”, men produkten är långt ifrån färdig, då den saknar de nödvändiga algoritmerna som krävs för ordentlig databehandling. Det nuvarande systemet använder sig enbart av Rasberry Pi:s, men i teorin vore det fullt möjligt att introducera ny hårdvara i nätet, men den nuvarande produkten stöder inte sådan funktionalitet.

Constata-se, atualmente, uma grande demanda de crescimento na produção de painéis MDF de madeira de eucalipto em relação à do pinus, comumente utilizada na indústria. Pelo exposto, o presente trabalho teve como objetivo caracterizar os componentes morfológicos da madeira de cavacos de Eucalyptus grandis, “in natura” e submetidas a três condições diferentes de desfibramento (tempo, pressão e energia), sendo denominadas de condição intermediária, de menor e de maior intensidade de refino (A, B e C, respectivamente). As características tecnológicas das chapas MDF obtidas para as três condições de desfibramento foram, da mesma forma, analisadas segundo a norma NBR 15316. No desenvolvimento do trabalho foram coletados para as três condições de desfibramento, em toda a cadeia produtiva do painel MDF: cavacos de madeira, material lenhoso desfibrado e painéis MDF final em escala industrial e laboratorial. Os cavacos de madeira foram caracterizados com respeito a sua estrutura microscópica; o material lenhoso desfibrado nas 3 condições foi avaliado através do seu fracionamento em peneiras seguindo-se a classificação morfológica e a caracterização microscópica dos componentes celulares de cada fração. Os resultados mostraram que os cavacos de madeira coletados no silo da unidade fabril apresentaram-se homogêneos nas 3 pré-condições avaliadas e não exerceram qualquer influência nos tratamentos. A condição de desfibramento mais branda induziu a formação de feixes de fibra e manutenção de vasos e parênquima com as fibras apresentando maior comprimento médio. A condição de desfibramento mais drástica induziu o rompimento da parede das fibras, com polpa apresentando fibras de menor comprimento e com baixa freqüência de vasos e de parênquima. As características de coloração foram observadas, sendo que a massa de fibras mais escura foi decorrente da alta pressão, maior tempo e mais energia de refinação aplicada. Os painéis MDF obtidos na condição mais branda apresentaram maior resistência ao arranque de parafuso, ao contrário dos painéis MDF confeccionados com polpa da condição de desfibramento mais drástica mostrando menores propriedades mecânicas de resistência à tração perpendicular e superficial e maiores valores de inchamento e de absorção. Os resultados do trabalho evidenciam a importância das variáveis de produção relacionadas com os tratamentos da madeira e do material fibroso nas propriedades tecnológicas dos painéis MDF de eucalipto. / Currently is evidenced a great demand of growth in eucalypts MDF panels production in relation with pinus, commonly used in the industry. The present study had the objective to characterize the morphologic components of Eucalyptus grandis wood chips “in natura” submitted in three different refining conditions (time, pressure and energy), named intermediate, smaller and biggest intensity of refining (A, B and C, respectively). The technological characteristics of MDF panels from three refining conditions were analyzed according standard NBR 15316. During this development were collected for three refining conditions, in all the productive chain of the MDF panels: wood chips, wooden dissociated material and panels MDF in industrial and laboratorial scale. The wood chips structure were microscopically characterized; the dissociated wood cells suspended in water of 3 refining conditions were evaluated through its separation in sieves and each fraction of woody material was morphologically classified and microscopically described. The results showed that the wood chips collected in industry storage compartment were homogeneous in the 3 refining preconditions and not influenced the MDF panel's treatments. The softness refining condition induced the shives formation and maintenance of vessels, parenchyma and the longest fibers. The more drastic refining condition induced the fiber cell walls broking, with wood pulp presenting shortest fibers and lower vessels and parenchyma frequency. The coloration characteristics were observed, and the fiber pulp was darker as result of the high pressure, greater time and more refinement energy applied. The MDF panels elaborated by softness refining condition presented greater resistance to screw pull in contrast of panels confectioned with hardness refining condition showing lesser mechanical properties of perpendicular and superficial tensile strength and bigger values of swelling and absorption. The results showed the importance of the variable related production with the wood and pulp wood treatments in technological properties of eucalypts MDF panels.

Constata-se, atualmente, uma grande demanda de crescimento na produção de painéis MDF de madeira de eucalipto em relação à do pinus, comumente utilizada na indústria. Pelo exposto, o presente trabalho teve como objetivo caracterizar os componentes morfológicos da madeira de cavacos de Eucalyptus grandis, “in natura” e submetidas a três condições diferentes de desfibramento (tempo, pressão e energia), sendo denominadas de condição intermediária, de menor e de maior intensidade de refino (A, B e C, respectivamente). As características tecnológicas das chapas MDF obtidas para as três condições de desfibramento foram, da mesma forma, analisadas segundo a norma NBR 15316. No desenvolvimento do trabalho foram coletados para as três condições de desfibramento, em toda a cadeia produtiva do painel MDF: cavacos de madeira, material lenhoso desfibrado e painéis MDF final em escala industrial e laboratorial. Os cavacos de madeira foram caracterizados com respeito a sua estrutura microscópica; o material lenhoso desfibrado nas 3 condições foi avaliado através do seu fracionamento em peneiras seguindo-se a classificação morfológica e a caracterização microscópica dos componentes celulares de cada fração. Os resultados mostraram que os cavacos de madeira coletados no silo da unidade fabril apresentaram-se homogêneos nas 3 pré-condições avaliadas e não exerceram qualquer influência nos tratamentos. A condição de desfibramento mais branda induziu a formação de feixes de fibra e manutenção de vasos e parênquima com as fibras apresentando maior comprimento médio. A condição de desfibramento mais drástica induziu o rompimento da parede das fibras, com polpa apresentando fibras de menor comprimento e com baixa freqüência de vasos e de parênquima. As características de coloração foram observadas, sendo que a massa de fibras mais escura foi decorrente da alta pressão, maior tempo e mais energia de refinação aplicada. Os painéis MDF obtidos na condição mais branda apresentaram maior resistência ao arranque de parafuso, ao contrário dos painéis MDF confeccionados com polpa da condição de desfibramento mais drástica mostrando menores propriedades mecânicas de resistência à tração perpendicular e superficial e maiores valores de inchamento e de absorção. Os resultados do trabalho evidenciam a importância das variáveis de produção relacionadas com os tratamentos da madeira e do material fibroso nas propriedades tecnológicas dos painéis MDF de eucalipto. / Currently is evidenced a great demand of growth in eucalypts MDF panels production in relation with pinus, commonly used in the industry. The present study had the objective to characterize the morphologic components of Eucalyptus grandis wood chips “in natura” submitted in three different refining conditions (time, pressure and energy), named intermediate, smaller and biggest intensity of refining (A, B and C, respectively). The technological characteristics of MDF panels from three refining conditions were analyzed according standard NBR 15316. During this development were collected for three refining conditions, in all the productive chain of the MDF panels: wood chips, wooden dissociated material and panels MDF in industrial and laboratorial scale. The wood chips structure were microscopically characterized; the dissociated wood cells suspended in water of 3 refining conditions were evaluated through its separation in sieves and each fraction of woody material was morphologically classified and microscopically described. The results showed that the wood chips collected in industry storage compartment were homogeneous in the 3 refining preconditions and not influenced the MDF panel's treatments. The softness refining condition induced the shives formation and maintenance of vessels, parenchyma and the longest fibers. The more drastic refining condition induced the fiber cell walls broking, with wood pulp presenting shortest fibers and lower vessels and parenchyma frequency. The coloration characteristics were observed, and the fiber pulp was darker as result of the high pressure, greater time and more refinement energy applied. The MDF panels elaborated by softness refining condition presented greater resistance to screw pull in contrast of panels confectioned with hardness refining condition showing lesser mechanical properties of perpendicular and superficial tensile strength and bigger values of swelling and absorption. The results showed the importance of the variable related production with the wood and pulp wood treatments in technological properties of eucalypts MDF panels.

Polymerem impregnované cementové materiály představují zajímavou a perspektivní alternativu klasických portlandských cementových past. Hlavním zástupcem těchto materiálů jsou macrodefect-free (MDF) kompozity, složené z anorganického pojiva a organického polymeru. I přes řadu vynikajících mechanických vlastností je plné zavedení MDF kompozitů na trh omezené především z důvodu jejich relativně nízké odolnosti vůči vlhkosti. Jednou z možností jak zvýšit odolnost výsledného MDF vůči vlhkosti je „in situ“ síťování polymeru. V této práci byla připravena počáteční série MDF kompozitů na bázi hlinitanového cementu a polyvinylalkoholu se třemi typy organo-titanátových síťovacích činidel (Tyzory). Efekt modifikace MDF kompozitů byl hodnocen na základě zkoušek pevnosti v tahu za ohybu po uložení materiálů v různých vlhkostních podmínkách.

The purpose of this thesis was to develop an economical, sustainable, and environmentally friendly straw Medium Density Fibreboard (MDF) process, capable of full-scale manufacturing and to produce MDF of requested quality. The investigated straw was based on wheat (Triticum aestivum L.) and rice (Oryzae sativa L.). In this thesis three different methods were taken for manufacture of straw MDF; (A) wheat-straw fibre was blowline blended with melamine-modified urea-formaldehyde (MUF), (B) rice-straw fibre was mixed with methylene diphenyl diisocyanate (MDI) in a resin drum-blender, and (C) wheat-straw fibre was activated in the blowline by the addition of Fenton’s reagent (H2O2/Fe2+) for production of non-resin MDF panels.  The MUF/wheat straw MDF panels were approved according to the requirements of the EN standard for MDF (EN 622-5, 2006). The MDI/rice-straw MDF panels were approved according to requirements of the standard for MDF of the American National Standard Institute (ANSI A208.2-2002). The non-resin wheat-straw panels showed mediocre MDF panel properties and were not approved according to the requirements in the MDF standard. The dry process for wood-based MDF was modified for production of straw MDF. The straw MDF process was divided into seven main process steps. 1.       Size-reduction (hammer-milling) and screening of straw 2.       Wetting and heating of straw 3.       Defibration 4.       Resination of straw fibre 5.       Mat forming 6.       Pre-pressing 7.       Hot-pressing       The primary results were that the straw MDF process was capable of providing satisfactory straw MDF panels based on different types of straw species and adhesives. Moreover, the straw MDF process was performed in pilot-plant scale and demonstrated as a suitable method for producing straw MDF from straw bales to finished straw MDF panels. In the environmental perspective the agricultural straw-waste is a suitable source for producing MDF to avoid open field burning and to capture carbon dioxide (CO2), the biological sink for extended time into MDF panels, instead of converting straw directly into bio energy or applying straw fibre a few times as recycled paper. Additionally, the straw MDF panels can be recycled or converted to energy after utilization. A relationship between water retention value (WRV) of resinated straw fibres, the thickness swelling of corresponding straw MDF panels, and the amount of applied adhesive was determined. WRV of the straw fibre increased and the TS of straw MDF declined as a function of the resin content. The empirical models developed were of acceptable significance and the R2 values were 0.69 (WRV) and 0.75 (TS), respectively. Reduced thickness swelling of MDF as the resin content is increased is well-known. The increase of WRV as a function of added polymers is not completely established within the science of fibre swelling. Fortunately, more fundamental research can be initiated and likely a simple method for prediction of thickness swelling of MDF by analysis of the dried and resinated MDF fibres is possible. / Syftet med denna avhandling var att lägga grunden för en ekonomisk, hållbar och miljövänlig MDF process för halmråvara, kapabel för fullskalig produktion av MDF och goda skivegenskaper. Framställningen av MDF skivor utgick från halm av vete (Triticum aestivum L.) och ris (Oryzae sativa L.). Tre olika metoder användes för att producera MDF av halm; (A) fibrer av vetehalm belimmades i blåsledning med ett melaminmodifierat urea-formaldehydlim (MUF), (B) fibrer av rishalm belimmades i en limblandare med metylen difenyl diisocyanate (MDI), (C) Limfria MDF skivor av vetehalm framställdes med aktivering av fibrer genom tillsats av Fenton´s reagens (H2O2/Fe2+) i blåsledning utan någon tillsats av syntetiskt lim. Sammanfattningsvis kan det understrykas att framställda MDF-skivor av MUF/vetehalm var godkända enligt standard för MDF (EN 622-5, 2006). Dessutom var framställda MDF skivor av MDI/rishalm också godkända enligt krav i standard för MDF ”American National Standard Institute” (ANSI A2008.2-2002). Limfria vetehalmskivor visade på måttliga skivegenskaper och klarade inte kraven i MDF standard.   Fiberframställningsprocessen för MDF modifierades till en produktion utgående från halm. MDF processen för halm delades upp i sju primära processoperationer.   (1)            Storleksreducering och sållning av halm (2)            Vätning och uppvärmning av halm (3)            Defibrering (4)            Belimning av halmfiber (5)            Mattformning (6)            Förpressning (7)            Pressning   De viktigaste resultaten från denna studie är att MDF av halm kunde produceras utgående från olika typer av halmsorter och lim. Dessutom utfördes MDF-processen i pilotskala och visade på en lämplig metod för framställning av MDF-skivor från halmbalar till färdiga halmfiberskivor. Det miljömässiga perspektivet på att använda jordbruksavfall till framställning av halmskivor är att undvika förbränning av halm ute på fältet, men det är även möjligt att binda koldioxid (CO2) i halmskivor under längre tid än att omsätta halmråvaran omedelbart som bioenergi eller använda halmfiber som returpapper några få gånger. Dessutom kan MDF återanvändas eller bli omsatt till energi efter användning.   Ett förhållande mellan ”water retention value” (WRV), av belimmade halmfiber, tjocklekssvällning för motsvarande MDF av halmskivor och mängden av tillsatt lim vid olika nivåer har undersökts. Med ökande limhalt tilltog WRV fibersvällning, vidare minskade tjocklekssvällning för motsvarande MDF skivor. De framtagna empiriska modellerna var godtagbara och beräknade R2 värden var 0.69 (WRV) och 0.75 (TS). Minskad tjocklekssvällning med ökad limhalt är dokumenterad sen tidigare. Ökad fibersvällning WRV vid tillsats av polymerer (limmer) är inte fullständigt etablerad inom vetenskapen för fibersvällning. Lyckligtvis kan grundläggande forskning initieras och sannolikt föreligger en enkel metod för att prediktera tjocklekssvällning av MDF genom analyser av torkade och belimmad MDF fiber.

The mechanisms and kinetics of combustion of waste wood as well as the phases during combustion processes are important to eliminate these wastes without any possible damage to environment. In the present study, combustion mechanisms, activation energy and pre-exponential constants, and phases of combustion were investigated for untreated natural pine and treated Medium Density Fiberboard (MDF), plywood and particleboard samples that involve some chemicals and additives. Waste wood samples were heated in air at 10, 20 and 30oC/min heating rates in a Thermo Gravimetric Analyzer (TGA) from room temperature to 900oC. Thermogravimetry (TG) and Derivative Thermogravimetry (DTG) curves for all samples were obtained. The gases formed during combustion reactions were directly fed to a Fourier Transform Infrared Spectroscopy (FTIR) instrument coupled to TGA. Emission characteristics of the samples were determined in-situ by using the FTIR spectrums. As a result of TG analysis, thermal decomposition of treated samples was observed at lower temperatures as compared to the untreated pine sample because of the catalyzing effects of the chemicals in the treated samples. Therefore, there were less flammable products, lower weight losses in the main oxidation region, decrease in the max. weight loss temperatures and formation of more char for treated samples as compared to untreated pine sample. In other words, chemicals used during production of these samples lead to decrease in the combustibility of the treated samples. Thermal kinetic constants for the samples were calculated by using Coats Redfern and Broido Methods. In order to find out the mechanisms responsible for the oxidation of the waste wood samples in different regions, six solid state mechanisms of Coats Redfern Method were tested. As a result of FTIR analysis of the emitted gases from TG analysis, several chemical groups were detected from pine and treated samples. Combustion of all samples revealed some gases containing aromatics, C-H groups, CO2 and CO. However, there were some toxic and carcinogenic gases like formaldehyde, isocyanate group, ammonia, phenyl group and benzoylbromide among the emissions of treated samples which need utmost attention when recovering energy from treated waste woods.

Cette thèse traite le sujet du micro-actionnement multistable employant des radiations optiques pour atteindre les différentes positions offertes par le micro-actionneur. Dans le cadre des travaux réalisés, un mécanisme bistable reposant sur un principe de doubles poutres préformées situées en position antagoniste est proposé, et, sur cette brique élémentaire, un micro-actionneur quadristable a été conçu. Afin de valider le principe de fonctionnement de micro-actionneur, des procédés de fabrication Laser (sur le matériau « médium - MDF») puis DRIE (sur un wafer SOI de silicium) ont été utilisés. Sur le prototype en silicium, permettant une réduction des courses du rang interne et du rang externe du micro-actionneur, celles-ci ont été fixées à 300 µm et 200 µm respectivement. L’actionnement à distance de ce micro-actionneur a été prouvé en utilisant le chauffage laser d’un élément actif en Nitinol structuré par un dépôt de SiO2, ceci générant un effet « deux sens » de l’élément actif permettant d’annuler la charge sur les poutres du micro-actionneur une fois celui-ci déclenché puis en position stable. L’utilisation d’un banc expérimental incluant une membrane MEMS de balayage laser a permis de démontrer la quadristabilité du micro-actionneur sur 90 000 cycles. Afin de réduire davantage la course de ce micro-actionneur, des concepts de dispositifs de réduction de course ont été développés pour démontrer, à partir de prototypes fabriqué en MDF par usinage laser, la capacité à atteindre une course de 1 µm. Enfin, à la suite de ces travaux de réduction de course, un concept de nano-actionneur multistable a été proposé. Ce nano-actionneur est composé de quatre modules bistables liés et disposés en parallèle pour offrir 16 positions discrètes sur une course rectiligne. Les simulations de cet actionneur montrent la possibilité d’atteindre les 15 positions espacées de 10 nm sur une course de 150 nm. / In this work, a bistable mechanism based on antagonistic pre-shaped double beams was proposed. Employing the proposed bistable mechanism, a quadristable micro-actuator was designed. ln order to validate the quadristability of the device, a meso-scaled prototype was fabricated from MDF by laser cutting. After the quadristability was experimentally confirmed, a quadristable micro-actuator was realized on SOl wafer using DRIE technique. Strokes for inner row and outer row were reduced to 300 µm and 200 µm respectively. For the actuation of the quadristable micro-actuator,laser heated SMA elements with deposited Si02 layer were used to realize the optical wireless actuation. With the help of a laser beam steering micro-mirror, both inner row and outer row were successfully actuated. ln order to further reduce the stroke, a bistable actuator with stroke reducing structure was designed and a prototype eut from MDF was tested. Bistability was validated and a stroke of 1µm was experimentally achieved. Based on this bistable module, a multistable nano-actuator, which contains four parallel coupled bistable modules,was designed and simulated. The simulated result have indicated that it was capable of outputs 16 discrete stable positions available from 0 nm to 150 nm with a step of 10 nm between two stable positions.

Το αξιόπιστο πειραματικό μοντέλο της ωοθηκεκτομής σε επίμυες εφαρμόστηκε για τη μελέτη των παθογενετικών μηχανισμών της οστεοπόρωσης. Σκοπός της παρούσας διδακτορικής διατριβής ήταν η διερεύνηση του ρόλου της λεπτίνης και των κυτοκινών RANKL και οστεοπροτεγερίνης (OPG) στην εξέλιξη της οστεοπόρωσης. Για την διεκπεραίωση της μελέτης χρησιμοποιήθηκαν 40 ενήλικοι θηλυκοί επίμυες ηλικίας 9 μηνών. Πριν την ωοθηκεκτομή στους επίμυες εφαρμόστηκε η τεχνική της ποσοτικής υπολογιστικής τομογραφίας (pQCT) παράλληλα με την πρωτοποριακή μη επεμβατική τεχνική του θερμοδυναμικού συντελεστή εσωτερικής απόσβεσης (MDF) ώστε να διαπιστωθεί η κατάσταση της οστικής πυκνότητας των πειραματόζωων. Σε χρονικά διαστήματα 20, 40 και 60 ημερών μετά την ωοθηκεκτομή πραγματοποιήθηκαν τυχαίες ομαδικές θυσίες με σκοπό τη συλλογή αίματος και την απομόνωση μηριαίων οστών και οστών κνήμης. Την 60η ημέρα πριν τη θυσία στην τελευταία ομάδα των ωοθηκεκτομήθέντων επίμυων επαναλήφθηκαν οι μετρήσεις pQCT και MDF για να διαπιστωθεί η εγκατάσταση σοβαρής οστεοπόρωσης με τη λήξη της πειραματικής πορείας. Οι οροί αίματος που συλλέχθηκαν από όλα τα χρονικά πειραματικά σημεία χρησιμοποιήθηκαν για τη διερεύνηση των επιπέδων έκφρασης των βιοχημικών δεικτών του οστικού μεταβολισμού NTx και οστεοκαλσίνης καθώς και της ελεύθερης λεπτίνης με την τεχνική της ενζυμικής ανοσοπροσρόφησης (ELISA). Στα οστά της κνήμης εφαρμόστηκε η τεχνική της ιστομορφομετρίας για τη μελέτη των μεταβολών της μικροαρχιτεκτονικής δομής των οστών κατά την εξέλιξη της οστεοπόρωσης. Επιπρόσθετα η τεχνική της ανοσοϊστοχημείας εφαρμόστηκε στα οστά της κνήμης για τη διερεύνηση των μεταβολών που προκαλεί η ωοθηκεκτομή στα επίπεδα έκφρασης του υποδοχέα της λεπτίνης και των κυτοκινών RANKL και οστεοπροτεγερίνης στους οστικούς κυτταρικούς πληθυσμούς. Στα μηριαία οστά εφαρμόστηκαν οι τεχνικές της ηλεκτροφόρησης σε πηκτή πολυακρυλαμιδίου (SDS-PAGE electrophoresis) και του ανοσοστυπώματος (Western Blot) για να συλλεχθούν επιπλέον πληροφορίες σχετικά με τις μεταβολές στα επίπεδα έκφρασης του υποδοχέα της λεπτίνης και των κυτοκινών RANKL και οστεοπροτεγερίνης κατά την εξέλιξη της οτεοπόρωσης. Τα συμπεράσματα που διεξάγονται από τα επιμέρους πειραματικά δεδομένα επιβεβαιώνουν την υπόθεση ότι η λεπτίνη κατέχει σημαντικό ρόλο στη ρύθμιση του οστικού μεταβολισμού και συμμετέχει ενεργά μέσω κάποιου άγνωστου μέχρι στιγμής μηχανισμού στη διαδικασία της οστικής ανακατασκευής στην οστεοπόρωση. Όσον αφορά τις ρυθμιστικές κυτοκίνες της οστεοκλαστογένεσης RANKL και OPG, διαπιστώθηκε ότι μεταβάλλονται σημαντικά κατά την εξέλιξη της οστεοπόρωσης στους ωοθηκεκτομηθέντες επίμυες, υποδηλώνοντας τη σημαντικότητα του ρόλου τους στον οστικό μεταβολισμό. / Ovariectomy in mature rats mimics the changes in bone metabolism observed in postmenopausal women and results in osteoporosis. The aim of this thesis was to investigate the role of leptin and the cytokine RANKL and Osteoprotegerin (OPG) in the progression of ovariectomy-induced osteoporosis. Nine–month-old female Wistar rats were bilaterally ovariectomized (n=40). Before the operation, pQCT and MDF technology were applied on rats in order to estimate the bone mineral density of the animals. On days 20, 40 and 60 after the operation the rats were randomly sacrificed and blood samples, dissected knees and femurs were collected. On day 60, pQCT and MDF techniques were applied in order to confirm the establishment of severe osteoporosis until the end of the experimental procedure. Leptin, and the biochemical markers of bone metabolism, osteocalcin and NTx, were measured in blood serum from all time points, by an ELISA method. Bone sections from the knees of the rats were examined by histomorphometric techniques in order to investigate the alterations in the micro-architectural structure of the skeleton caused by ovariectomy. Furthermore, immunohistochemistry was applied on knee sections and SDS-PAGE electrophoresis and western blot techniques were performed in femur homogenized tissueς, in order to investigate whether the expression levels of leptin receptor, RANKL and OPG were altered during the progression of osteoporosis. The results indicate that leptin is involved in the molecular mechanisms of bone remodeling in osteoporosis. The regulators of osteoclastogenesis, RANKL and OPG are also important players in the field of bone metabolism