Total hip joint prostheses made of CoCrMo heads versus ultra high molecular weight polyethylene (UHMWPE) cups have a limited lifetime, mainly due to the wear of the UHMWPE cups as a result of high friction between the articulating surfaces leading to osteolysis and implant loosening with revision surgery becoming inevitable in more active patients. Tribology plays an important role in developing the design, minimizing wear and reducing friction of hip joint prostheses in order to improve their long-term performance, with good lubricating properties. Metal-on-metal hip resurfacing prostheses have shown significantly lower wear rates compared with conventional metal-on-polyethylene implants and thus osteolysis is potentially reduced leading to increased lifetime of the prosthesis. Nevertheless, excessive wear of metal-on-metal joints leads to metal ion release, causing pseudo-tumours and osteolysis. An alternative approach to such bearings is the use of newly developed carbon fiber-reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups articulating against ceramic femoral heads due to their better wear resistance compared to UHMWPE. In this study, therefore, friction and lubrication properties of large diameter, as cast, Co-Cr-Mo metal-on-metal hip resurfacing implants with various diameters and clearances have been investigated and compared to those of the newly developed zirconia toughened alumina (ZTA) ceramic femoral heads articulating against carbon fiber reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups with different diameters and clearances. Friction hip simulator was used to measure frictional torque and then friction factors were calculated along with Sommerfeld numbers leading to Stribeck analysis and hence the lubricating mode was also investigated. This involved using lubricants based on pure bovine serum (BS) and diluted bovine serum (25 vol. %BS+75 vol. %distilled water) with and without carboxymethyl cellulose (CMC) (as gelling agent). Standard Rheometer was used to measure lubricant viscosity ranged from 0.0014 to 0.236 Pas at a shear rate of 3000 . Pure bovine serum, diluted bovine serum without CMC and with CMC (25BS+75DW+0.5gCMC and +1gCMC) showed pseudoplastic flow behaviour up to shear rate of ~139 s⁻¹ above which a Newtonian flow with significant increase in shear stress was observed. The viscosity flow curves for the 25BS+75DW+2gCMC, +3.5gCMC and +5gCMC showed only shear thinning up to a shear rate of 3000 . The shear rate application modified the flow behaviour of bovine serum from a pseudoplastic to a Newtonian flow depending on its purity and CMC content. This will cause a different frictional behaviour depending on joint diameter and clearance, as seen in this work. The experimental data were compared with theoretical iv predictions of the lubricating regimes by calculating theoretical film thickness and lambda ratio. The metal-on-metal Biomet ReCaps showed similar trends of Stribeck curves, i.e. friction factors decreased from ~0.12 to ~0.05 as Sommerfeld numbers increased in the range of viscosities ~0.001-0.04Pas indicating mixed lubrication regimes above which the friction factor increased to ~0.13 at a viscosity of 0.236Pas. The Stribeck analyses suggested mixed lubrication as the dominant mode with the lowest friction factor in the range ~0.09 - ~0.05 at the physiological viscosities of ~0.01 to ~0.04 Pas and that such joints can be used for more active patients as compared to the conventional total hip replacement joints with 28mm diameter. The Stribeck curves for all ZTA ceramic-on-CFR PEEK components illustrated a similar trend with BS fluids showing higher friction factors (in the range 0.22-0.13) than the diluted BS+CMC fluids (in the range 0.24-0.05). The friction tests revealed boundary-mixed lubrication regimes for the ZTA ceramic-on-CFR-PEEK joints. The results, so far, are promising and suggest clearly that the newly developed ZTA ceramic femoral heads articulating against CFR PEEK cups have similar friction and lubrication behaviour at optimum clearances to those of currently used metal-onmetal hip resurfacing implants at the range of viscosities 0.00612 to 0.155Pas. These results clearly suggest that the ZTA ceramic-on-CFR-PEEK joints showed low friction at the physiological viscosities of ~0.01Pas in the range ~0.1-0.05, suggesting that these novel joints may be used as an alternative material choice for the reduction of osteolysis. The result of this investigation has suggested that the optimum clearance for the 52mm diameter MOM Biomet ReCaps could be ~170μm. However, 48 and 54mm joints showed lower friction due to clearances to be >200μm. For the 52mm ZTA ceramic-on-CFR-PEEK joints the optimum clearance seems to be ≥ 630μm radial clearance. These results suggested that increased clearance bearings have the potential to generate low friction and hence no risk of micro- or even macro-motion for the ceramic-on-CFR-PEEK joints. This study found no correlation between theoretical predictions and experimental data for all metal-onmetal and ZTA ceramic-on-CFR PEEK bearings at the physiological viscosity (0.0127Pas). However, at lubricant viscosity of 0.00157Pas, the theoretical prediction of lubrication regime correlated well with the experimental data, both illustrating boundary lubrication. As expected, a decrease in viscosity resulted decrease in the film thickness.

Lors de ces travaux de thèse, nous nous sommes intéressés au développement de deux voies différentes de cycloaddition dipolaire-1,3 (CD-1,3) asymétrique pour accéder à des acides aminés disubstitués polyfonctionnels nouveaux de façon stéréochimiquement contrôlée.Dans la première partie, nous avons réalisé l’étude de la cycloaddition dipolaire-1,3 diastéréosélective entre différentes nitrones fonctionnelles et différents éthers vinyliques chiraux. La CD-1,3 de la cétonitrone aspartique et de l’éther vinylique du (R) ou (S) stéricol s'opère avec un double contrôle diastéréochimique élevé. Ce contrôle est possible en raison de la stabilité de la nitrone sous une forme (E) qui favorise l’approche exo, facialement contrôlée par le dipolarophile. La N-déprotection chimiosélective de l'adduit fournit une isoxazolidine sous une forme diastéréo- et énantiomériquement pure qui peut être transformée en dérivé d’acide aminé après N-acylation et coupure de la liaison N-O selon un processus dismutatif.Dans la deuxième partie, nous avons réalisé une étude approfondie de la cycloaddition dipolaire-1,3 organocatalysée entre différentes cétonitrones dérivées d’acides aminés vis-à-vis de dipolarophiles pauvres en électrons de type énal ou ynal. Avec le (E)-crotonalldéhyde, de hautes diastéréo- et énantiosélectivités sont obtenues en présence du catalyseur de MacMillan. Cette réaction organocatalysée a été étendue à une variété de d'α-carboxy cétonitrones différemment substituées, ainsi qu'à différents énals β-substitués par un groupement alkyle moyennant une modification de la nature du co-acide. En revanche, les ynals ne montrent aucune réactivité vis à vis des cétonitrones en conditions organocatalytiques. Notre étude a été complétée par l’accès des dérivés d’amino-acides polyhydroxylés par ouverture des adduits obtenus par la voie énantiosélective en utilisant les énals comme dipolarophiles. Cette étude préliminaire permet d’envisager d’accéder à des analogues de la myriocine. / During this thesis, we were interested to develop two different ways of 1,3 dipolar cycloaddition to reach enantiopure disubstituted polyfunctionnal amino acids.We have described in a first part the diastereoselective 1,3-dipolar cycloaddition between an aspartic nitrone and chiral vinyl ethers. The aspartic ketonitrone and vinyl ether of (R) or (S) stericol led to high diastreocontrols. This control is due to the stability of the nitrone under (E) geometry which favors the exo approach, facially controlled by the dipolarophile. The chemoselective N-deprotection of this adduct leads to a diastereo- and enantiomerically pure isoxazolidine which affords the target DAA after N-acylation and N-O ring opening by a dismutative pathway. In a second part, we describe the synthesis of isoxazolidines obtained by organocatalytic enantioselective 1,3-dipolar cycloaddition between an alanine-derived nitrone and an enal or an ynal as the dipolarophile. With enals β-substituted by alkyl groups, good diastereoselectivities and ees were obtained in the presence of the MacMillan catalyst. These organocatalyzed conditions can be applied to a range of carboxy ketonitrones, and to different enals, provided an appropriate choice of the co-acid. Ynals show no reactivity under these organocatalytic conditions, although they lead regioselectively to polyfunctional quaternary isoxazolines under thermal conditions.Our study was achieved by the access of polyhydroxylated amino acids derived from opening adducts obtained by the enantioselective route using enals as dipolarophiles. This study allows to envisage the enantioselective synthesis of analogs of myriocin.

La faible densité et les propriétés mécaniques remarquables des composites polymères en font des matériaux de choix pour remplacer les métaux. Cependant, leurs propriétés physicochimiques rendent leurs surfaces peu adhésives pour divers types de revêtements. Pour améliorer l’adhérence de revêtements métalliques sur des substrats de PEEK, et pour mieux comprendre les mécanismes de l’adhésion, les propriétés de surface du matériau ont été modifiées par des procédés physiques en voie sèche.D’une part, cette étude montre que les traitements par plasma oxydants (à basse pression, ou à pression atmosphérique) permettent d’améliorer la mouillabilité de la surface et l’adhérence de revêtements métalliques, par l’augmentation de la polarité de la surface, quantifiée par XPS. D’autre part, cette étude montre que l’ablation laser infrarouge à impulsion femtoseconde permet la gravure d’un motif dense, induisant de meilleures tenues mécaniques de l’assemblage. Enfin, cette étude montre que la modification de la chimie et de la topographie combinées améliore davantage ce potentiel d’adhérence.Le but de cette étude est d’ouvrir une voie vers un modèle décrivant les mécanismes de l’adhésion, influencés par la chimie de surface et la géométrie d’un motif, en s’appuyant sur un modèle mécanique permettant de décrire la dynamique des contraintes se propageant au travers de l’interface, en tenant compte des propriétés mécaniques des matériaux. / Thanks to their low densities and good mechanical properties, polymer composites are good candidates for metal alloys substitutes. However, their physicochemical properties limit their adhesion potential towards several types of coatings. In order to improve metallic thin films adhesion on PEEK substrates, and to better comprehend adhesion mechanisms, dry-phase methods have been used to alter the surface properties of the material.First, this study shows that oxidative plasma treatments (at low or at atmospheric pressure) improve the wettability and the practical adhesion of metallic coatings, by an increase of the polar component of the surface, as measured by XPS. Second, this study shows that dense patterns etched by an infrared femtosecond laser allow good practical adhesion of the metallic thin films on the substrate. Finally, this study shows that the modification of both surface chemistry and the surface topography at the same time further improves the practical adhesion of the metallic thin films.The goal of this study is to propose a route towards a model describing the combined influence of surface texture and chemistry, with the support of a mechanical model describing the dynamics of the stress dissipation through the interface while taking into account the mechanicals properties of the interfacial materials.

No description available.

Depuis quelques années, le domaine de l’extraction végétale est en pleine mutation, avec à la fois un intérêt croissant des consommateurs pour des ingrédients d’origine naturelle, combiné à des préoccupations environnementales. Il apparaît dès lors indispensable de remplacer les procédés actuels utilisant des solvants pétrochimiques nocifs par de nouveaux procédés d’extraction réduisant le besoin énergétique, la toxicité du solvant et la quantité de déchets tout en s’assurant du rendement et de la qualité de l’extrait obtenu. L’objectif de cette thèse a donc consisté à développer un nouveau procédé d’extraction mettant en œuvre des gaz liquéfiés comme solvants. Ce manuscrit présentera tout d’abord l’état de l’art sur les gaz liquéfiés existants et leur mise en œuvre pour l’extraction des produits naturels. A l’issue de cette présentation, 3 gaz liquéfiés ont été sélectionnés (n-butane, HFO-1234ze et le DME) comme solvants pour mener des essais au laboratoire, grâce à un prototype dont la conception est détaillée dans le chapitre II. Dans un second temps, les essais réalisés à l’aide de ces gaz liquéfiés pour l’extraction de composés lipophiles ont été décrits. L’approche expérimentale a été couplée à une approche prédictive par l’utilisation d’outils d’aide à la décision : les paramètres de solubilité de Hansen et le modèle COSMO-RS. La prédiction théorique ainsi que les essais expérimentaux ont confirmé l’intérêt des gaz liquéfiés pour la solubilisation et l’extraction de composés lipophiles d’intérêt biologique et à haute valeur ajoutée. Parallèlement l’étude des impacts du procédé sur l’environnement, la qualité, la réglementation et la sécurité ont montré que l’extraction par gaz liquéfié était un procédé facilement transposable à l’échelle industrielle. / In recent years, the industrial sector of vegetable extraction has been evolving due to the growing interest of consumers for natural food ingredients combined with growing environmental concerns. Therefore, it seems essential to replace existing processes using toxic petroleum bases solvents with greener extraction processes with lower energy consumption, less wastes but higher extract quality. The objective of this thesis has consisted in the research and development of a new extraction process using liquefied gases as liquid solvents. First, this manuscript will outline the state of the art on the liquefied gases and how they are used for extraction of natural products. After this survey, 3 liquefied gases (n-butane, HFO-1234ze and DME) have been selected for laboratory scale experiments performed using a dedicated extraction unit whose design is detailed in chapter II. Then, the tests performed with these 3 gases for extraction of lipophilic compounds from several plant materials has been described. The experimental approach has been combined with a predictive one using decision tools: Hansen Solubility Parameters and COSMO-RS model. This survey demonstrated that liquefied gases are interesting solvents for solubilization and extraction of lipophilic compounds of interest. In parallel, the impacts of the process on environment, safety regulation and quality showed that liquefied gas extraction could be easily transposed at industrial scale.

Synthesis and Studies of Dendritic Poly(Ether Imine) Boronates and Cholesteryl-Functionalized Mesogens SYNOPSIS Dendrimers are hyperbranched synthetic macromolecules having branches-upon-branches structures, high molecular weights, globular shapes and monodispersities. Dendrimers possess a large number of modifiable functional groups at their peripheries. Initial efforts were largely concerned with the synthesis, design and development of new dendrimers. Exploring the chemical, biological and material applicability of these macromolecules are relevant to current interests, as a result of the unique structural features of dendrimers. Incorporation of transition metals and organic moieties at the peripheries of the dendrimers was studied to determine their efficacies in catalysis. Evolution of dendritic effects was observed in few instances, that were non-linear in nature. On the other hand, dendritic peripheries were also utilized to study mesogenic properties in liquid crystals. Chapter 1 of the Thesis gives an overview of the types of dendrimers, its structural features and their application in catalysis and as liquid crystalline materials. Chapter 2 describes the synthesis of a new type of poly(ethyl ether imine) dendrimer, having nitrogen as a branching unit, ethylene moiety as the spacer and an oxygen as the connecting linker. Synthesis, characterization, and studies of the photophysical properties of these dendrimers are described in this chapter. The molecular structure of second generation dendrimer is shown in Figure 1. Synthesis of this dendrimer was initiated using 2,2'-oxy-bis(ethan-1¬amine) as the core. The reaction sequence of two alternate nucleophilic substitutions and two alternate reductions, involving ethyl bromoacetate and bromoacetonitrile as monomers was employed in the synthesis of the dendrimer. The formation of dendrimers having ether linkage and tertiary amines as branching unit was established by spectroscopies and mass spectrometry. A number of functional groups, such as, acid, alcohol, amine, ester and nitrile are present at the peripheries of each generation the dendrimers that open up the possibilities for further studies. Carboxylic acid terminated poly(ethyl ether imine) dendrimers are substituted iminodiacetic acids, belonging to the class of polyaminocarboxylic acid. Methyl iminodiacetic acid boronates with NB coordination have emerged as an excellent substitute for unstable boronic acids. Upon increasing the steric bulk on the nitrogen moiety, the hydrolytic stability of the boronates to a base-catalyzed hydrolysis is increased. Combining the structure of carboxylic acid terminated dendrimer and the stability of the dendritic boronates, such dendritic iminodiacetic acids were reacted with arylboronic acids to prepare bis-and tetrakis-boronates (Figure 2). Kinetic hydrolytic studies of boronates were conducted to assess the stabilities of the newly synthesized dendritic boronates. From the studies it was observed that the tetrakis-boronate was ~20 times more stable in comparison with dimeric and monomeric boronates (Figure 3). Subsequent to synthesis and hydrolytic stability studies, C-C bond-forming Suzuki-Miyaura cross-coupling reactions were conducted. A comparison of the reactivities among monomeric, dimeric and tetrameric arylboronates in C-C bond-forming reactions showed a higher reactivity of monomeric and dimeric boronates, than the tetrameric aryl boronate to construct ter-and tetra-aryl in one-pot iterative manner (Figure 4). Chapter 3 of this Thesis describes the synthesis and characterization of dendritic boronates and studies of their hydrolytic stability in Suzuki-Miyaura cross¬coupling reactions to construct ter-and tetraaryls. Figure 4. Synthesis of (a) ter-(6) and (b) tetra-aryls (7) by following one-pot iterative cross-coupling reactions. Step-wise iterative synthesis of dendrimer allows a uniform branching throughout the structure. The first and second generation poly(ether imine) dendrimer series, having hydroxyl groups at their peripheries were chosen for further modification. A versatile mesogenic group, namely, cholesterol was covalently attached at the peripheries of the dendrimers with succinic moiety as linker, so as to install 4 and 8 cholesteryl moieties at the peripheries of the dendrimers (Figure 5), that were characterized by H, C NMR spectroscopies and elemental analysis, so as to confirm their structural homogeneities. Figure 5. Molecular structures of the first and second generation dendritic mesogens. Subsequent to synthesis and characterization, liquid crystalline properties of all the dendritic mesogens was assessed through differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD) studies. In POM study, broken fan or leaf like texture revealed the lamellar arrangement, whereas homeotropic appearance of texture on surfactant (cetyltrimethylammonium bromide) coated substrate indicated the lamellar nature of G1-Et-(OCS)4, G1-Pr-(OCS)4 and G2-Pr-(OCS)8 (Figure 6). From DSC studies, the change in enthalpy was found to increase with increase in generation and change in enthalpy per mesogenic unit was found to be ~ -1 1-2 kJ mol, which indicated the mesophase arrangement to be lamellar. Decrease in the length of spacer dendritic backbone and increase in the generation increased the isotropization temperature of the dendritic liquid crystals. Variable temperature XRD studies were undertaken to characterize the mesophase property. Two sharp peaks in small angle region and a diffused halo in wide angle region in XRD pattern of the material suggested the smectic A (SmA) liquid crystalline arrangement of G1-Et-(OCS)4, G1-Pr-(OCS)4 and G2-Pr-(OCS)8 (Figure 7). Figure 6. POM textures of (a) G1-Et-(OCS)4 at 136 oC; (b) G2-Et-(OCS)8 at 129 oC; (c) G1-Pr-(OCS)4 at 92 oC; (d) G2-Pr-(OCS)8 at 118 oC and (e) transition temperatures for dendromesogens (DSC second heating cycle, heating-cooling rate = 10 oC min-1). Figure 7. Small angle XRD profiles of: (a) G1-Pr-(OCS)4 and (b) G2-Et-(OCS)8 at 60 o C (black), 150 oC (red) and 180 oC (green), (Insets: Lorentzean fit of wide angle peak). The second generation ethyl-linker dendrimer G2-Et-(OCS)8 exhibited a layered structure with a superimposed in-plane modulation (SmÃ), the length of which corresponded to a rectangular column width. Chapter 4 describes the synthesis, characterization and studies of mesophase property and fluorescence property of cholesterol functionalized homologous pairs of the PETIM dendritic liquid crystals. Peripheral functionalization of the dendrimers provides an easy access to dendritic liquid crystalline materials. The covalent functionalization was extended further with the dendrimers for both the series, so as to have 2, 4, 8 and 16 cholesteryl groups at the peripheries of 0, 1, 2 and 3 generation dendrimers, respectively, having succinic amide and phthalic ester functionalities for 1, 2 and 3 generation dendrimers with 4, 8 and 16 cholesteryl groups. Molecular structures of third generation dendrimers are shown in Figure 8. Figure 8. Molecular structures of third generation G3-Pr-(NHCS)16 and G3-Pr-(OCP)16. Subsequent to synthesis and characterization, mesophase property was studied through POM, DSC and XRD techniques. In POM study, a birefringent texture was observed in heating and cooling cycles. Leaflet, broken fan or bâtonnet like texture suggested the layered arrangement of the molecules (Figure 9). In DSC studiues, it was observed that the amide-linked dendrimers showed higher glass transition and isotropization temperatures than that of ester-linked dendrimers within the same generation irrespective of the back-bone of the dendrimer. Succinic moiety linked dendrimers showed lower glass transition temperature than that of phthalic moiety linked dendrimers and consequently, larger mesophase range. The change in enthalpy for isotropization was found to increase with increase in generation, whereas change in -1 enthalpy per mesogenic unit was 1-2 kJ mol, indicative of a layered arrangement in the mesophase. Figure 9. POM textures (20x) of (a) G3-Pr-(NHCS)16 at 90 oC; (b) G3-Pr-(OCS)16 at 90 ooo C; (c) PG1-(NHCS)4 at 134 C; (d) G3-Pr-(OCP)16 at 98 C and (e) transition temperatures for dendromesogens (second cycle, heating-cooling rate = 10 oC min-1). Appearance of two sharp peaks in small angle region and a wide halo in wide angle region in XRD pattern supported lamellar mesophase property of the material (Figure 10). On decreasing the temperature, increase in the layer thickness also suggested the smectic A arrangement of the molecules except third generation phthalate derivative G3-Pr-(OCP)16, which showed rectangular columnar mesophase. For all the dendromesogens, the layer thickness increased with the increase in generation. Upon protonation, the first generation dendrimer showed a change in mesophase from simple smectic A to modulated smectic A with decrease in layer thickness. The change in liquid crystal property of the dendromesogens from lamellar to columnar mesophase by changing the linker of the mesogen is unknown so far in the dendrimer liquid crystals. Chapter 5 gives details of synthesis, characterization and mesophase property study of ester-and amide-linked dendritic liquid crystals. Overall, the Thesis establishes a synthetic methodology for the synthesis of a new homologous series of poly(ether imine) dendrimers with ethyl spacer; synthesis of dendritic boronates and their studies in cross-coupling reactions through in-situ slow release of boronic acid; hydrolytic stability study showed higher stability of dendritic boronates which was used in one-pot iterative cross-coupling reactions to construct ter-and tetra-aryls. decrease in linker length in dendrimer backbone modified the thermal, as well as, mesophase behavior of the dendritic liquid crystals; change in the linker functionality from ester to amide changed the thermal behavior of dendritic liquid crystals; a switching of mesophase property from lamellar to columnar was observed by changing the rigidity of the linker from succinate to phthalate without changing the linker length. The results of the above chapters are in different stages of publications: 1 Dendritic iminodiacetic acids and their boronates in Suzuki-Miyaura cross¬coupling reactions. Sharma, A.; Kumar, P.; Pal, R.; Jayaraman, N. Revised Manuscript submitted. 2 In-plane modulated smectic à vs smectic A lamellar structures in homologous pairs of dendritic liquid crystals. Kumar, P.; Rao, D. S. S.; Prasad, S. K.; Jayaraman, N. Revised Manuscript submitted. 3 Effect of protonation on dendritic liquid crystals of poly(ether imine) dendrimers: structure property relationship studies. Kumar, P.; Rao, D. S. S.; Prasad, S. K.; Jayaraman, N. Manuscript submitted. 4 Smectic to rectangular columnar switch from succinic to phthalic linker alteration in poly(ether imine) dendritic liquid crystals. Kumar, P.; Rao, D. S. S.; Prasad, S. K.; Jayaraman, N. Manuscript in preparation.

No description available.

Experimental data were obtained for the computation of mole fraction solubilities of three dichloronitrobenzenes in organic solvents at 25oC, and solubility ratios were obtained from this data. Abraham model equations were developed for solutes in tributyl phosphate that describe experimental values to within 0.15 log units, and correlations were made to describe solute partitioning in systems that contain either "wet" or "dry" tributyl phosphate. Abraham model correlations have also been developed for solute transfer into anhydrous diisopropyl ether, and these correlations fit in well with those for other ethers. Abraham correlations for the solvation of enthalpy have been derived from experimental and literature data for mesitylene, p-xylene, chlorobenzene, and 1,2-dichlorobenzene at 298.15 K. In addition, the enthalpy contribution of hydrogen bonding between these solutes and acidic solvents were predicted by these correlations and were in agreement with an established method. Residual plots corresponding to Abraham models developed in all of these studies were analyzed for trends in error between experimental and calculated values.

This paper uses a back-propagating neural network (BPN) to predict the price movements of major crypto currencies, leveraging technical factors as well as measurements of collective sentiment derived from the micro-blogging network Twitter. Our dataset consists of daily, hourly and minutely price levels for Bitcoin, Ether and Litecoin along with 8 popular technical indicators, as well as all tweets with the currencies' cash tags during respective time periods. Insprired by previous research which suggest that artificial neural networks are superior forecasting models in this setting, we were able to create a system generating automated investment decisions on a daily, hourly and minutely time basis. The study concluded that price trends are indeed predictable, with a correct prediction rate above 50% for all models, and corrensponding profitable trading strategies for all currencies on an hourly basis when neglecting trading fees, buy-sell spreads and order delays. The overall highest predictability is obtained on the hourly trading interval for Bitcoin, yielding an accuracy of 55.74% and a cumulative return of 175.1% between October 16, 2021 and December 31, 2021. / I denna studie används ett bakåtpropagerande neoronnät (BPN) för att förutsäga prisrörelser i större kryptovalutor med hjälp av tekniska faktorer och kvantifiering av kollektivt sentimentet från mikrobloggnätverket Twitter. Vårt dataset består av dagliga, timvisa och minutvisa prisnivåer för Bitcoin, Ether och Litecoin tillsammans med 8 populära tekniska indikatorer, samt alla tweets med valutornas "cash tags" under respektive tidsperiod. Med inspiration från tidigare forskning som hävdar att artificiella nauronnät är överlägsna prognosmodeller i denna typ av analys kunde vi skapa ett system som genererar automatiska investeringsbeslut på daglig, timvis och minutvis basis. Vi hävdar med denna studie att pristrender är förutsägbara för dessa kryptovalutor, med en korrekt förutsägelsefrekvens på över 50% för alla modeller, och med lönsamma handelsstrategier för alla valutor på timbasis när man bortser från handelsavgifter, köp- och säljspreadar och orderfördröjningar. Den högsta förutsägbarheten erhålls på timhandelsintervallet för Bitcoin, vilket ger en nogrannhet på 55,74% och en ackumulerad avkastning på 175,1% mellan den 16 oktober 2021 och den 31 december 2021.

Total hip joint prostheses made of CoCrMo heads versus ultra high molecular weight polyethylene (UHMWPE) cups have a limited lifetime, mainly due to the wear of the UHMWPE cups as a result of high friction between the articulating surfaces leading to osteolysis and implant loosening with revision surgery becoming inevitable in more active patients. Tribology plays an important role in developing the design, minimizing wear and reducing friction of hip joint prostheses in order to improve their long-term performance, with good lubricating properties. Metal-on-metal hip resurfacing prostheses have shown significantly lower wear rates compared with conventional metal-on-polyethylene implants and thus osteolysis is potentially reduced leading to increased lifetime of the prosthesis. Nevertheless, excessive wear of metal-on-metal joints leads to metal ion release, causing pseudo-tumours and osteolysis. An alternative approach to such bearings is the use of newly developed carbon fiber-reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups articulating against ceramic femoral heads due to their better wear resistance compared to UHMWPE. In this study, therefore, friction and lubrication properties of large diameter, as cast, Co-Cr-Mo metal-on-metal hip resurfacing implants with various diameters and clearances have been investigated and compared to those of the newly developed zirconia toughened alumina (ZTA) ceramic femoral heads articulating against carbon fiber reinforced poly-ether-ether-ketone (CFR PEEK) acetabular cups with different diameters and clearances. Friction hip simulator was used to measure frictional torque and then friction factors were calculated along with Sommerfeld numbers leading to Stribeck analysis and hence the lubricating mode was also investigated. This involved using lubricants based on pure bovine serum (BS) and diluted bovine serum (25 vol. %BS+75 vol. %distilled water) with and without carboxymethyl cellulose (CMC) (as gelling agent). Standard Rheometer was used to measure lubricant viscosity ranged from 0.0014 to 0.236 Pas at a shear rate of 3000 . Pure bovine serum, diluted bovine serum without CMC and with CMC (25BS+75DW+0.5gCMC and +1gCMC) showed pseudoplastic flow behaviour up to shear rate of ¿139 above which a Newtonian flow with significant increase in shear stress was observed. The viscosity flow curves for the 25BS+75DW+2gCMC, +3.5gCMC and +5gCMC showed only shear thinning up to a shear rate of 3000 . The shear rate application modified the flow behaviour of bovine serum from a pseudoplastic to a Newtonian flow depending on its purity and CMC content. This will cause a different frictional behaviour depending on joint diameter and clearance, as seen in this work. The experimental data were compared with theoretical iv predictions of the lubricating regimes by calculating theoretical film thickness and lambda ratio. The metal-on-metal Biomet ReCaps showed similar trends of Stribeck curves, i.e. friction factors decreased from ~0.12 to ~0.05 as Sommerfeld numbers increased in the range of viscosities ~0.001-0.04Pas indicating mixed lubrication regimes above which the friction factor increased to ~0.13 at a viscosity of 0.236Pas. The Stribeck analyses suggested mixed lubrication as the dominant mode with the lowest friction factor in the range ~0.09 - ~0.05 at the physiological viscosities of ~0.01 to ~0.04 Pas and that such joints can be used for more active patients as compared to the conventional total hip replacement joints with 28mm diameter. The Stribeck curves for all ZTA ceramic-on-CFR PEEK components illustrated a similar trend with BS fluids showing higher friction factors (in the range 0.22-0.13) than the diluted BS+CMC fluids (in the range 0.24-0.05). The friction tests revealed boundary-mixed lubrication regimes for the ZTA ceramic-on-CFR-PEEK joints. The results, so far, are promising and suggest clearly that the newly developed ZTA ceramic femoral heads articulating against CFR PEEK cups have similar friction and lubrication behaviour at optimum clearances to those of currently used metal-onmetal hip resurfacing implants at the range of viscosities 0.00612 to 0.155Pas. These results clearly suggest that the ZTA ceramic-on-CFR-PEEK joints showed low friction at the physiological viscosities of ~0.01Pas in the range ~0.1-0.05, suggesting that these novel joints may be used as an alternative material choice for the reduction of osteolysis. The result of this investigation has suggested that the optimum clearance for the 52mm diameter MOM Biomet ReCaps could be ~170¿m. However, 48 and 54mm joints showed lower friction due to clearances to be >200¿m. For the 52mm ZTA ceramic-on-CFR-PEEK joints the optimum clearance seems to be ¿ 630¿m radial clearance. These results suggested that increased clearance bearings have the potential to generate low friction and hence no risk of micro- or even macro-motion for the ceramic-on-CFR-PEEK joints. This study found no correlation between theoretical predictions and experimental data for all metal-onmetal and ZTA ceramic-on-CFR PEEK bearings at the physiological viscosity (0.0127Pas). However, at lubricant viscosity of 0.00157Pas, the theoretical prediction of lubrication regime correlated well with the experimental data, both illustrating boundary lubrication. As expected, a decrease in viscosity resulted decrease in the film thickness.