Manufacturing conditioned wear of all-ceramic knee prostheses

To date, bioceramics have not been applied successfully in total knee joint endoprostheses. Sintered bioceramics can be machined only by grinding and polishing processes. Due to high quality requirements, there are significant challenges with regard to these machining technologies. An automated precise economical process chain for the manufacturing of a new all-ceramic knee implant design was developed. It was assumed the geometrical accuracy and the shape of implant contact geometry specified during the manufacturing process has a substantial influence on the wear behavior of the prosthesis. The importance of the surface quality of the ceramic implant surface remains unclear and warrants future examination

Instrument intercomparison in the high-energy mixed field at the CERN-EU reference field (CERF) facility

This paper discusses an intercomparison campaign performed in the mixed radiation field at the CERN-EU (CERF) reference field facility. Various instruments were employed: conventional and extended-range rem counters including a novel instrument called LUPIN, a bubble detector using an active counting system (ABC 1260) and two tissue-equivalent proportional counters (TEPCs). The results show that the extended range instruments agree well within their uncertainties and within 1σ with the H*(10) FLUKA value. The conventional rem counters are in good agreement within their uncertainties and underestimate H*(10) as measured by the extended range instruments and as predicted by FLUKA. The TEPCs slightly overestimate the FLUKA value but they are anyhow consistent with it when taking the comparatively large total uncertainties into account, and indicate that the non-neutron part of the stray field accounts for ∼30 % of the total H*(10

Mikroklima-Untersuchungen in Pflanzengesellschaften verschiedener Höhenstufen in Hochgebirgen der Nordwest- und Südmongolei

Im Rahmen der Mongolisch-Deutschen Biologischen Expeditionen wurden erste Mikroklimauntersuchungen im Jahre 1973 in ausgewählten Pflanzengesellschaften der Wüste und Halbwüste im $üdgobi-Aimak durchgeführt (HELMECKE u. SCHAMSRAN 1979). Auch von sowjetisfber (BERESNEVA 1974, 1981) und von polnischer Seite (vgl. KLIMEK 1980) liegen mikroklimatologische Untersuchungen für verschiedene Gebiete der MVR vor. Von den Gebirgen der MVR wurde besonders der Südteil des Changai berücksichtigt. Hier wurden Mikroklimamessungen in verschiedenen Höhenstufen durchgeführtl (BRZEZNIAK u. NIEDZWIEDZ 1980). Die von Biologen der Universitäten Halle-Wittenberg und Ulan-Bator von 1977 bis 1979 durchgeführten Untersuchungen in Hochebirgen der MVR (Charchiraa, Uvs Aimak; Ich-Bogd, Bajanchongor Aimak) schlosseh neben den floristisch-vegetationskundlichen und ökofaunistischen Arbeiten ebenfalls Mikroklimauntersuchungen in charakteristischen Pflanzengesellschaften verschiedeqer Höhenstufen der bei den Gebirge ein. über diese Untersuchungen soll zusammenfassend und vergleichend berichtet werden. Wir stellen nach Behandlung der untersuchten Pflanzengesellschaften, die durch Einzelaufnahme-Tabellen belegt werden, den Verlauf wesentlicher Klimawerte während ausgewählter, für den Witterungsverlauf wichtiger Wetterlagen in den einzelnen Gesellschaften dar und vergleichen die Verjhältnisse in den bei den Untersuchungsgebieten (UG) und ihren versch,iedenen Höhenstufen. Die durchgeführten Mikroklimauntersuchungen hatten nicht das Ziel, Energie- oder Wasserbilanzen aufzustellen. Vielmehr ging es uns um mikroklimatische Charakteristika der untersuchten Vegetationseinheiten zur Hauptvegetationszeit. Wir betrachten das Mikroklima als eine abiotische Komponente der Vegetationsdifferenzierung und als Grundlage für das Verständnis faunistischer Untersuchungen. Zusammenfassung In zwei Hochsgebirgsstöcken der Mongolei Volksrepublik, dem Charchiraa im Nordwesten und dem Ich-Bogd im Süden des Landes, führten wir in den Jahren 1977-1979 Vegetationsuntersuchungen in verschiedenen Höhenstufen durch. Dabei wurden jeweils 3 Meßstationen mit je 2 bis 3 Meßpunkten errichtet, an denen in charakteristischen Pflanzengesellschaften der jeweiligen Höhenstufe Mikroklimamessungen über einen Zeitraum von 3 Wochen erfolgten. Für diese Mikrokilmauntersuchungen wählten wir folgende Vegetationseinheiten aus: Kurzgrassteppe (Station I), anthropogene Wiesensteppe und Lärchenwald (Station II) sowie alpine Kobresia-Matte und Dryas-Bestand (Station III) im Charchiraa und Anabasis-Halbwüste und Weiderasen (Station I), Bergsteppe (Station II) sowie alpine Kobresia-Matten (Station III) im Ich-Bogd. In der vorliegenden Arbeit stellen wir die Tagesgänge verschiedener Meßgrößen (Bodentemperatur, Lufttemperatur, Luftfeuchtigkeit, Evaporation und Windgeschwindigkeit) von Strahlungs- und Regentagen und die Bodentemperaturen über den gesamten Meßzeitraum anhand zahlreicher Abbildungen dar. Dabei vergleichen wir die Mikroklimaverhältnisse der Höhenstufen untereinander und zwichen den beiden Gebirgen und stellen die Temperaturkurven der höhenstufenbedingten Vegetationsabfolge gegenüber. Summary In two high mountain regions of Mongolia, the Charchiraa in the northwest and Ich-Bogd in the south of the country, we investigated the vegetation of different altitudinal belts from 1977 until 1979. In both areas we established 3 measuring stations with 2-3 measuring points and made microclimatic measurements in plant communities typical for the altitudinal belts coming into question. The measurements took place 3 weeks each year. For the microclimatic investigations we chose the following plant communities: short grass steppe (station I), anthropogenous meadow steppe and larch forest (station II), alpine Kobresia-meadow and Dryas oxyodonta-vegetation (station III) in the Charchiraa; Anabasis brevifolia-semidesert and wet pasture ground (station I), mountain steppe (station II), alpine Kobresia-meadow (station III) in the Ich-Bogd. In the paper we present with many figures the course of different parameters (soil temperature, air temperature, air moisture, evaporation, wind velocity) during sunny and rainy days and the soil temperature during the whole measuring period. The microclimate differences between the altitudinal belts of one mountain system and between both high mountains are compared. The sequence of vegetation, related to the altitudinal belts, is compared with the sequence of temperature

Biodegradation of a magnesium alloy implant in the intercondylar femoral notch showed an appropriate response to the synovial membrane in a rabbit model in vivo

Degradable magnesium alloys are promising biomaterials for orthopedic applications. The aim of this study was to evaluate the potential effects on both the synovial membrane (synovialis) and the synovial fluid (synovia) of the degradation products of a MgYREZr-pin implanted in the intercondylar femoral notch in a rabbit model. Thirty-six animals were randomized into two groups (MgYREZr or Ti6Al4V alloy) of 18 animals each. Each group was then divided into three subgroups with implantation periods of 1, 4, and 12 weeks, with six animals in each subgroup. The initial inflammatory reaction caused by the surgical trauma declined after 12 weeks of implantation, and elucidated a progressive recovery of the synovial membrane. Compared with control Ti6Al4V pins, there were no significant differences between the groups. However, after 12 weeks, recovery of the synovial membrane was more advanced in the titanium group, in which 92% showed no signs of synovitis, than in the magnesium group. A cytotoxicity test with L929 cells and human osteoblasts (HOB) was also conducted, according to EN ISO 10993-5/12, and no toxic leachable products were observed after 24 h of incubation. In conclusion, the MgYREZr alloy seems to be a suitable material for intra-articular degradable implants. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav

Influence of stress on the degradation behavior of Mg LAE442 implant systems

In this paper the performance of a magnesium based implant system is analyzed. A special emphasis is placed on the impact of stress on the corrosion behavior of the magnesium alloy. An implant system containing a plate and 4 corresponding screws is machined from Mg LAE442. Its corrosion behavior is tested in-vivo in New Zealand White Rabbits for 6 and 12 weeks of implantation. The plate is monocortically fixated on the medial tibia. At the interface between screw and plate increased corrosion is observed. This phenomenon is stronger on the caudal side of the screw. Parallel to the in-vivo test the influence of stress load on the corrosion rate is analyzed for LAE442 in in-vitro tests. Compressive load is applied on cylindrical specimens in axial direction and the corrosion rate is measured in 0.9 wt% NaCl solution by eudiometry and mass loss. Additionally rectangular samples are bent to apply tensile stress on the surface. A drop of 5 wt% NaCl is deposited on the surface and the corrosion is evaluated by microscopic images. It is shown that stress essentially influences the corrosion rate. While tensile stress decreases the corrosion, compressive stress leads to higher corrosion rates

The Impact of Pyroglutamate: Sulfolobus acidocaldarius Has a Growth Advantage over Saccharolobus solfataricus in Glutamate-Containing Media

Microorganisms are well adapted to their habitat but are partially sensitive to toxic metabolites or abiotic compounds secreted by other organisms or chemically formed under the respective environmental conditions. Thermoacidophiles are challenged by pyroglutamate, a lactam that is spontaneously formed by cyclization of glutamate under aerobic thermoacidophilic conditions. It is known that growth of the thermoacidophilic crenarchaeon Saccharolobus solfataricus (formerly Sulfolobus solfataricus) is completely inhibited by pyroglutamate. In the present study, we investigated the effect of pyroglutamate on the growth of S. solfataricus and the closely related crenarchaeon Sulfolobus acidocaldarius. In contrast to S. solfataricus, S. acidocaldarius was successfully cultivated with pyroglutamate as a sole carbon source. Bioinformatical analyses showed that both members of the Sulfolobaceae have at least one candidate for a 5-oxoprolinase, which catalyses the ATP-dependent conversion of pyroglutamate to glutamate. In S. solfataricus, we observed the intracellular accumulation of pyroglutamate and crude cell extract assays showed a less effective degradation of pyroglutamate. Apparently, S. acidocaldarius seems to be less versatile regarding carbohydrates and prefers peptidolytic growth compared to S. solfataricus. Concludingly, S. acidocaldarius exhibits a more efficient utilization of pyroglutamate and is not inhibited by this compound, making it a better candidate for applications with glutamate-containing media at high temperatures

Amphiphilic Copolymers for Versatile, Facile, and In Situ Tunable Surface Biofunctionalization

Precision surface engineering is key to advanced biomaterials. A new platform of PEGylated styrene-maleic acid copolymers for adsorptive surface biofunctionalization is reported. Balanced amphiphilicity renders the copolymers water-soluble but strongly affine for surfaces. Fine-tuning of their molecular architecture provides control over adsorptive anchorage onto specific materials-which is why they are referred to as "anchor polymers" (APs)-and over structural characteristics of the adsorbed layers. Conjugatable with an array of bioactives-including cytokine-complexing glycosaminoglycans, cell-adhesion-mediating peptides and antimicrobials-APs can be applied to customize materials for demanding biotechnologies in uniquely versatile, simple, and robust ways. Moreover, homo- and heterodisplacement of adsorbed APs provide unprecedented means of in situ alteration and renewal of the functionalized surfaces. The related options are exemplified with proof-of-concept experiments of controlled bacterial adhesion, human umbilical vein endothelial cell, and induced pluripotent cell growth on AP-functionalized surfaces