Environmentally assisted fatigue of superelastic NiTi

Superelastic NiTi implants transforming cyclically in body fluids suffer from fatigue failures which are extremely difficult to predict. This clearly points out towards environmental effects promoting surface dominated fatigue degradation. The specialty of phase transforming NiTi shape memory alloy is that either the parent austenite or the product martensite phase exist at the excessively deforming metal/liquid interface covered by the thin TiO2 surface. In order to explore the environmental effects at such mechanically active metal/liquid interface, we have developed dedicated electrochemical apparatus and methods combining electrochemical cell, mechanical tester and thermal chamber. We are able to follow and/or control the mechanically triggered periodical breakdown/passivation process on the metal/liquid interface occurring during cyclic tensile tests on NiTi wires and springs in fluids. In this way we are able to analyze the effect of surface finishing treatments on fatigue performance and/or control it electrochemically. In this talk, we will introduce two in-situ electrochemical methods especially open circuit potential and potentiostatic polarization applied during fatigue testing. We will focus on the problem of non-stationary thermodynamic equilibrium established at the mechanochemically loaded wire surface. Kinetics of the surface reactions encountered during this type of environmental fatigue testing will be revealed. SIMS depth profile analysis and chemical imaging of the surfaces of fatigued wires was employed to prove the assumed electrochemical activity upon cycling, particularly to the hydrogen absorption and growth of passive oxide layer within cracks. Microcracks forming on the surface of fatigued wires were observed by 3D SEM/FIB sectioning method. Based on the results, mechanisms of environmental fatigue degradation of NiTi implants deforming cyclically in body fluids will be proposed

Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)

Petrological study and pseudosection modelling have been carried out in high-grade orthogneisses of the southern domain of the Orlica- Snieznik Dome (NE Bohemian Massif). The studied samples are from an outcrop dominated by two deformation fabrics, a sub-horizontal S1 foliation defined by bands of recrystallized K-feldspar, quartz and plagioclase folded by centimetre- to several metre-scale close to isoclinal folds associated with development of a new subvertical N-S trending foliation S2. Based on field features and textural observations, a gradual transition from banded mylonitic orthogneiss (Type I) to stromatitic (Type II), schlieren (type III) and nebulitic (type IV) textures typical of migmatities can be distinguished. The banded orthogneiss is composed of almost monomineral recrystallized K-feldspar layers (2 to 10 mm thick) alternating with layers of plagioclase and quartz (1 to 4mm thick), parallel to the S1 limb and the axial planar S2 foliation. The stromatitic migmatite shows 1 to 4 mm thick layers with macroscopically diffuse boundaries between plagioclase, quartz and K-feldspar rich domains. Boundaries between quartz and feldspar layers are poorly defined and interlobed with adjacent minerals. The schlieren migmatite is almost isotropic preserving small K-feldspar-rich domains within a matrix characterized by random distribution of phases, whereas in the nebulitic migmatite the microstructure is completely isotropic characterized by random distribution of phases. The transition from the Type I to IV is characterized by increasing nucleation of interstitial phases along like-like grain boundaries, by a decrease of grain size of all phases and by progressive disintegration of recrystallized K-feldspar grains by embayments of fine-grained myrmekite. The mineral assemblage of all types consists of biotite, white micas, garnet, quartz, K-feldspar and plagioclase, and accessory apatite, ilmenite, zircon and monazite. In the mineral equilibria modelling, the core of garnet (alm0.58, py0.02-0.03, grs0.34, sps0.05) and phengite (Si = 3.38-3.20 p.f.u) is consistent with a P-T peak at 10-13 kbar and 720-750 C in the dominant grt-bt-ph-rt-qtz-pl-kfs mineral assemblage. The garnet rim (alm0.68, py0.02-0.03, grs0.11, sps0.21), white mica rim (Si = 3.10 p.f.u) together with unzoned biotite (XFe = 0.76-0.78) match the modelled isopleths in the middle-P part of the grt-bt-ph-ilm-qtz-pl-kfs field to reach the solidus at 78 kbar and 630650 C. In addition, the absence of prograde garnet zoning in the Type I to III suggests that the garnet was completely re-equilibrated during the retrograde history, whereas in the Type IV the HP garnet chemistry was preserved. This is discussed in frame of melt presence in different migmatite types along their P-T path. Based on mineral equilibria modelling it is argued for fluid/melt-fluxed melting at HP conditions and on exhumation. The migmatite textural types are a result of grain-scale melt migration process and not of a localized melt transport in dykes as known from metasediments

PTt history from kyanite-sillimanite migmatites and garnet-staurolite schists from the Bayankhongor area, Mongolia indicates suprasubduction switching from extension to compression during Rodinia assembly

The tectonometamorphic evolution of the peri-Siberian tract of the Central Asian Orogenic Belt is mainly characterized by Baikalian Late Proterozoic - Early Cambrian cycle related to amalgamation of Proterozoic oceanic and continent fragments to Siberain landmass. Here we present in-situ monazite geochronology linked to P−T modelling of micashischsts and migmatite gneisses at the northern part of the Precambrian Baydrag block (central Mongolia) previously considered as a part of Baikalian metamorphic belt. Garnet-sillimanite-kyanite gneiss records first burial to the sillimanite stability at ~725 °C and 6.5 kbar, followed by burial to the kyanite stability at ~650 °C and ~8 kbar. The garnet-staurolite schist records burial to the staurolite-stability at ~620 °C and 6 kbar, followed by a nearly isothermal burial to ~580 °C and 9 kbar. The monazite data yield a continuum of 207Pb-corrected 238U/206Pb dates of c. 926−768 Ma in the Grt−Sil−Ky gneiss, and c. 937−754 Ma in the Grt-St schist. Based on monazite textural positon and internal zoning, the time of prograde burial and peak under a thermal gradient of 28-32 °C/km is estimated at c. 870−890 Ma. It is not clear whether such high grade conditions prevailed until a phase of further burial under a geothermal gradient of 18-22 °C/km and dated at 800−820 Ma. Additionally, monazite with dates of c. 568−515 Ma occurs as whole grains or as rims with sharp boundaries on Grenvillean monazite in Grt-St schist testifying for minor Baikalian overprint. Metamorphic zircon rims with Th/U ratio ~0.01-0.06 in Grt−Sil−Ky gneiss with 877 ± 7 Ma age, together with lower intercepts of zircon discordia lines in both Grt-Sil-Ky gneiss and Grt-St schist further support the Tonian age of high grade metamorphism. The P−T and geochronology data show anticlockwise P−T evolution from c. 930 to 750 Ma which is interpreted as a result of thickening of suprasubduction extensional and hot edifice - probably of back arc or arc type. This kind of prograde metamorphism was so far described only on the northern part of the Tarim block and interpreted as a result of initiation of peri-Rodinian subduction of Mirovoi Ocean. Here, we further discuss geodynamic consequences of a unique discovery of Tonian metamorphism in term of tectonic switch related to initiation of peri-Rodinian oceanic subduction during supercontinent assembly followed by strong mechanical coupling potentially related to onset of Rodinia splitting

Anticlockwise metamorphic paths at ca. 890−790 Ma from the NE Baidrag block, Mongolia, indicate back-arc compression at the Rodinia periphery

The processes leading to the assembly of the Rodinia supercontinent through Grenvillian collisional orogeny are relatively well known. In contrast, accretionary orogenic processes occurring at the supercontinent periphery following Rodinia assembly are poorly understood. To fill this gap, we have identified metamorphic rocks in the Mongolia collage of the Central Asian Orogenic Belt, where numerous data testify for Meso- to Neo-proterozoic magmatic reworking. The tectono-metamorphic evolution of the peri-Siberian tract of the Central Asian Orogenic Belt is mainly characterized by the late Proterozoic-early Cambrian (Baikalian) cycle. However, we document here a Tonian age metamorphism at the northern part of the Precambrian Baidrag block, previously considered as a typical example of the Baikalian metamorphic belt. This study incorporates zircon and in-situ monazite geochronology linked to P-T modelling of Grt-Sil-Ky migmatite gneiss and Grt-St micaschist. Grt-Sil-Ky gneiss records initial burial to the sillimanite stability field at ~720 °C and 6.0 kbar followed by further burial to the kyanite stability field at ~750 °C and ~9 kbar and decompression to ~650 °C and ~8 kbar. The Grt-St schist records initial burial to the staurolite stability field at ~620 °C and 6 kbar, followed by further burial to ~590 °C and 8.5 kbar. The monazite data yield a continuum of 207Pb-corrected 238U/206Pb dates of ca. 926−768 Ma in the Grt-Sil-Ky gneiss, and ca. 937−754 Ma in the Grt-St schist. Based on monazite textural positon, internal zoning, and REE patterns, the time of prograde burial to 6.0 kbar under a thermal gradient of 27-32 °C/km is estimated at ca. 890−853 Ma. It is not clear whether such high-grade conditions prevailed until a phase of further burial under a geothermal gradient of 18-22 °C/km dated at ca. 835−815 Ma. The late monazite recrystallization at ca. 790 Ma is related to decompression. Additionally, monazite with dates of ca. 568−515 Ma occur as whole grains or as rims with sharp boundaries on Tonian monazite in Grt-St schist suggesting a minor Baikalian overprint. Metamorphic zircon rims with Th/U ratios of ~0.01-0.06 in Grt-Sil-Ky gneiss with 877±7 Ma age, together with lower intercepts of detrital zircon discordia lines in both Grt-Sil-Ky gneiss and Grt-St schist further support the Tonian age of high-grade metamorphism. The anticlockwise P-T evolution is interpreted as a result of thickening of a supra-subduction extensional and hot edifice - probably of back-arc or arc type. This kind of prograde metamorphism has so far only been described on the northern part of the Tarim block and was interpreted to be a result of initiation of peri- Rodinian subduction of the Mirovoi Ocean. The geodynamic consequences of a unique discovery of Tonian metamorphism are discussed in terms of tectonic switch related to initiation of peri-Rodinian oceanic subduction during supercontinent assembly, followed by strong mechanical coupling potentially related to onset of Rodinia dispersal

Effect of pomiferin administration on kidney ischaemia-reperfusion injury in rats

The aim of the study was to analyse protective effects of different doses of pomiferin in therapy of reperfusion injury. Rats were randomly divided into five groups (n=10). One group was intact. Three medicated groups and one placebo group were subjected to ischaemia and reperfusion of the left kidney. Pomiferin was administrated by single gastric gavage in 2 ml of 0.5% Avicel solution in doses of 5, 10 and 20 mg/kg. The placebo group was given only Avicel solution. On day 15, all the animals were exsanguinated and the reperfused kidneys were recovered. Selected biochemical markers were assessed in blood: antioxidative enzymes, total antioxidative capacity, malondialdehyde, creatinine, urea and uric acid. Creatinine, urea and total proteins were analysed in urine and 24-hour diuresis was recorded. The kidney tissue samples were used for histopathological examination

Nutritional supplementation for type 2 diabetes: a systematic review

The role of nutritional supplementation is of increasing interest with regard to ocular disease. Randomised controlled trials have demonstrated the effectiveness of supplementation for age-related macular degeneration, and formulations are now being developed for use by people with diabetes and diabetic retinopathy. The aim of this review was to synthesise the evidence for use of nutritional supplementation in type 2 diabetes. MEDLINE and EMBASE databases were searched using a systematic approach. Only double-masked randomised controlled trials were selected. A total of 50 trials were identified as suitable for inclusion. The potential role of alpha-lipoic acid, chromium, folic acid, isoflavones, magnesium, Pycnogenol®, selenium, vitamin C, vitamin E, and zinc in the treatment of type 2 diabetes is discussed. The review of trials identifies positive effects of these nutrients on various outcome measures relating to insulin resistance and cardiovascular factors. Chromium was the most studied supplement, accounting for 16 of the 50 trials. A majority of the trials found a positive effect of chromium on fasting plasma glucose. Isoflavones were found to have a positive effect on insulin resistance and cardiovascular outcome measures, but only when combined with soy proteins. Vitamin E is reported to reduce oxidative stress at levels of 200 mg day-1 or more

Psychology and the theory of choice

The aim of my thesis is to give the reader the most comprehensive look at the parallel development of psychology and economics, to point out the possibilities, such information may be obtained in psychological experiments used for the enrichment of theoretical economics. The rst chapter deals with a historical development of economic concepts and the role that the human psychology plays there. The second chapter is devoted to behavioral economics and its approach to the relations in society. The third section summarizes the results of a range of experiments that brought behavioral economics (and other disciplines) since the 1970's to the present. The fourth chapter summarizes the possibilities how can be the experiments interpreted and suggest directions, which could (behavioral) economics take in it's further development

Teplotní a mechanické aspekty mechanizmů pohřbení a exhumace v moldanubickém orogenním kořeni na Jižní Moravě a v Dolním Rakousku

This thesis repÍesents results of petrological and stuctural investigations at the eastem margin of the Bohemian Massif. The main objective is the understanding of mechanical and thermal aspects of the formation and exhumation mechanisms of the Moldanubian orogenic root domain. The studies has been carried at the south-eastem margin of the Moldanubian zone in Lower Aushi4 at the contact with the Brunia basement and are presented in the frame of recently developed new concept of lower crust exhumation by vertical extrusion. The first part (Chapter 1-3) shows results of detailed structural mapping combined with petrological study and thermodynamical modeling of the metamorphic processes. Chapters I and 2 are concerned with the area around the Drosendorf window (Moldanubian domain, South Moravia and Lower Austria). The Chapter I deals with detailed petrological investigation of individual structwes in the E-W profile going from high-grade rocks of the Gftihl unit across the Drossendorf window to the Brunia basement. The petrological investigation shows existence of an internal domain (the Drosendorf window) composed of predominantly metasedimenatry rocks of mid-crustal origin that preserve a prograde metamorphism up to 8 kbar. This unit is surrounded by lower crustal rocks with peak metamorphic...Tato teze představuje výsledky petrologického a strukturního ;'i.il; '"."ýchodním ot<raji čes[eno masivu. Hlavním cílem je oá.r'"p*i mechanických u t.ř-ál''í"h aspektu mechanizmů tvorby a ilil'il; *áiJ*'uilrcho orogenního k9řen1 Studie probíhaly-na iiho.l.lchodním okaii moldanuĚiku n Dolním Rakousku na kontaktu ,';Jí";* rontlnĚnt.' brunie a výsledky jsou prezentovány v rámci v současnostt vyvrjeného nového konceptu exhumace spodní kůrypomocí vertikální extÍuze. První část práce (kapitoly 1-3) ukazuje výsledky detailního strukturniho .upon*í v tomuinaci s petrologickým studiem a i."""áv."'rckym modelováním metamorfních procesů. Kapitoly l a 2 se soustředí na ,6zemí v okolí drosendorfského okna [mo1oa,'uuit..'m, JiŽní Morava a Dolní Rakousko). Kapitola 1 se zabývá detailním.petrologicloým průzkumem jednotlivýďstrui::.::J];*Ť"ff''""*&lil"#"'Í::T"[,*Ťl:: wsoce metamorlovan ái"š""o".i'řě "ňo-u to"ei v horninách brunie..Petrologická studie 'l-'.l" .-i'.enci vnitřní domény (drosendorfské okno) složené pi*#"c' *eta"eoi-"*u*i.r.' iromin středně-korového původu které zachovávají prográdní metamorfózu do tlaků 8 kbar' Tato ;;J';[; je obkiopiná-spodně-korovými hominami s ma'rimálními ii"k"ňi;"d'ínr.u*i ůkbar, které tvoří její.strukturnípodloŽí na "y.ň"ác a nasouvají se na středně.korovou jednotku na zápaďé. Ye...Institute of Petrology and Structural GeologyÚstav petrologie a strukturní geologieFaculty of SciencePřírodovědecká fakult

Thermal and mechanical aspects of burial and exhumation mechanisms within the Moldanubian orogenic root in South Moravia and Lower Austria

This thesis repÍesents results of petrological and stuctural investigations at the eastem margin of the Bohemian Massif. The main objective is the understanding of mechanical and thermal aspects of the formation and exhumation mechanisms of the Moldanubian orogenic root domain. The studies has been carried at the south-eastem margin of the Moldanubian zone in Lower Aushi4 at the contact with the Brunia basement and are presented in the frame of recently developed new concept of lower crust exhumation by vertical extrusion. The first part (Chapter 1-3) shows results of detailed structural mapping combined with petrological study and thermodynamical modeling of the metamorphic processes. Chapters I and 2 are concerned with the area around the Drosendorf window (Moldanubian domain, South Moravia and Lower Austria). The Chapter I deals with detailed petrological investigation of individual structwes in the E-W profile going from high-grade rocks of the Gftihl unit across the Drossendorf window to the Brunia basement. The petrological investigation shows existence of an internal domain (the Drosendorf window) composed of predominantly metasedimenatry rocks of mid-crustal origin that preserve a prograde metamorphism up to 8 kbar. This unit is surrounded by lower crustal rocks with peak metamorphic..

Aspects thermo-mécaniques des mécanismes d'enfouissement et d'exhumation dans la racine orogénique Moldanubienne (Moravie du Sud et Basse Autriche)

The study of the SE margin of the Bohemian massif revealed preservation of a continuous profile of lower to middle crustal orogenic section overthrust by a second lower-crustal complex. The general view of the area is that the mid-crustal unit preserving steep fabrics forms a boudin in surrounding partially molten lower-crustal rocks with flat foliation. The interpretation is compatible with the whole eastern margin of the Bohemian massif. During initial shortening, the system produces a vertical fabric formed by synforms of rigid middle crust and antiforms of weak partially molten lower crust that are later thrust over the basement flat ramp and moving further in orogenic channel. The study of present lower crustal granulites traditionally interpreted as a result of UHT/HP metamorphism reveals that they record more complex history than previously reported. The HT and HP minerals represent two parts of a discontinuous history, hence they cannot be combined for thermobarometry.L'étude de la marge SE du Massif de Bohême met en évidence un profil depuis la croûte inférieure jusqu'à la croûte moyenne qui est chevauché par un deuxième complexe de croûte inférieure. Les roches de croûte moyenne à structures tectoniques verticales sont observées au sein de boudins incluent dans des roches de la croûte inférieure présentant des structures tectoniques horizontales. Pendant la compression initiale, le système se déforme et développe synformes de la croűte moyenne rigide et antiformes de la croûte inférieure partiellement fondue. Cette dernière est ensuite chauvauchante sur le socle et se déplace au sein d'un channel flow . Les granulites de la croûte inférieure interprétées comme le résultat d'un métamorphisme UHT/HP sont en fait le résultat d'une histoire plus complexe. Les minéraux de HT et HP sont représentatifs de deux parties d'une histoire discontinue, ils ne peuvent donc pas être utilisés pour la thermobarométrie comme des minéraux à l'équilibre.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF