Robotertechnik zur diffraktometrischen Charakterisierung von Restspannungs-, Textur-, Phasenentwicklung an technischen Komponenten

Am Materialforschungsdiffraktometer STRESS-SPEC der Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) wurde vor einiger Zeit ein BMBF gefördertes Robotersystem in Betrieb genommen. Damit wurde es erstmals möglich kompakte Proben von technischen Dimensionen bezüglich kristallographischer Textur, Restspannungen und Phasenzusammensetzungen automatisch zu charakterisieren. Der Roboter verfügt über drei Funktionen, die den Messablauf entscheidend vereinfachen und für Neutronenmessungen sehr wichtig teure Messzeit einsparen. Texturmessungen sind häufig Serienuntersuchungen zur Texturentwicklung als Funktion von Umformgrad, Umformtemperatur und Legierungszusammensetzung, so dass der Roboter als automatischer Probenwechsler erhebliche Zeitersparnis bringt. Zweitens fungiert der Roboter nicht nur als Probenwechsler, sondern ersetzt gleichzeitig auch die Eulerwiege zum Abfahren der einzelnen Polfiguren. Die dritte Funktion ist die Scanfunktion des Roboters, um zum Beispiel die Informationen über den Umfang von Rohren oder über Schweißnähten automatisch Messen zu können

Formation of m2G6 in Methanocaldococcus jannaschii tRNA catalyzed by the novel methyltransferase Trm14

The modified nucleosides N2-methylguanosine and N22-dimethylguanosine in transfer RNA occur at five positions in the D and anticodon arms, and at positions G6 and G7 in the acceptor stem. Trm1 and Trm11 enzymes are known to be responsible for several of the D/anticodon arm modifications, but methylases catalyzing post-transcriptional m2G synthesis in the acceptor stem are uncharacterized. Here, we report that the MJ0438 gene from Methanocaldococcus jannaschii encodes a novel S-adenosylmethionine-dependent methyltransferase, now identified as Trm14, which generates m2G at position 6 in tRNACys. The 381 amino acid Trm14 protein possesses a canonical RNA recognition THUMP domain at the amino terminus, followed by a γ-class Rossmann fold amino-methyltransferase catalytic domain featuring the signature NPPY active site motif. Trm14 is associated with cluster of orthologous groups (COG) 0116, and most closely resembles the m2G10 tRNA methylase Trm11. Phylogenetic analysis reveals a canonical archaeal/bacterial evolutionary separation with 20–30% sequence identities between the two branches, but it is likely that the detailed functions of COG 0116 enzymes differ between the archaeal and bacterial domains. In the archaeal branch, the protein is found exclusively in thermophiles. More distantly related Trm14 homologs were also identified in eukaryotes known to possess the m2G6 tRNA modification

Quantitative Neutron and X-ray texture analysis of Quartz mylonites - a comparative study

We investigated five mylonitic quartz veins from the Adamello pluton (southern Alps, Italy) which accumulated different amounts of shear deformation in the range between 4.5 to over 15. All quartz mylonites consist of a fine grained (35-40 m grainsize) dynamically recrystallized aggregate and show a strong crystallographic preferred orientation (CPO or texture), dominated by a strong Y-maximum of c-axis, whose intensity is expected to strengthen with increasing strain. The CPO has been measured by different texture diffraction methods at the Neutron Material Science Diffractometer STRESS-SPEC at the research reactor FRM II in Garching near Munich and with an x-ray diffractometer optimized for geological sample material located at the University of G\uf6ttingen. The high penetration capabilities of neutrons allowed the texture determination of the complete cubic quartz sample volume of about 4 cm3. In contrast, 90% of the x-ray CuK radiation detected from the sample in reflection geometry has penetration depths of up to 45 m in quartz (Wenk 1998). Applying a beam diameter of about 7 mm by means of a glass fibre polycapillary results in a measured sample volume of 1.73 mm3. Combining the measurements of three orthogonal sample directions, the measured sample volume sums up to 5.19 mm3. Due to the defocussing effect in X-ray diffraction, a correction function derived from randomly oriented powder samples has to be applied and only incomplete pole figures (tilt angle 75\ub0) could be obtained. To obtain complete pole figures, we (1) combined the measurements of three orthogonal sample sections and (2) applied the WIMValgorithm (e.g.Wenk et al 1998) as an orientation distribution function (ODF) to recalculate complete pole figures. For a quantitative comparison with the X-ray data, the WIMV-algorithm was also applied on the neutron diffraction data to also obtain a quantitative texture analysis. The experimental and recalculated pole figures of the three orthogonal sample directions measured by X-ray are very similar between the individual directions. This proves a high texture homogeneity and a reliable defocussing correction. Consequently the added experimental pole figures from the three sample directions show a very good agreement as well. The comparison between the X-ray and neutron pole figures shows in general a good accordance. Minor differences are related to grain statistics, small sample heterogeneities and minor effects from the defocusing correction. From the geological view these are negligible. Furthermore, this study shows that the STRESS-SPEC neutron diffractometer, although optimized for material science applications is well suitable for the measurement of geological samples, when critical grain-size/volume ratios are not exceeded. References: Wenk, H.-R. (1998): Pole figure measurements with diffraction techniques. In: Texture and Anisotropy (edited by Kocks, U. F., Tom\ue9, C. N., Wenk, H.-R.), Cambridge University Press 1998, pp. 126-177 Wenk, H. R., S. Matthies, J. Donovan, and D. Chateigner (1998): BEARTEX: A Windows-based program system for quantitative texture analysis, J. Appl. Crystallogr., 31(2), 262\u2013269, doi: 10.1107/ S002188989700811X

Femoral defects in revision hip arthroplasty: a therapy-oriented classification

Introduction!#!The complex field of femoral defects in revision hip arthroplasty displays a lack of standardized, intuitive pre- and intraoperative assessment. To address this issue, the femoral defect classification (FDC) is introduced to offer a reliable, reproducible and an intuitive classification system with a clear therapeutic guideline.!##!Materials and methods!#!The FDC is based on the integrity of the main femoral segments which determine function and structural support. It focuses on the femoral neck, the metaphysis consisting of the greater and lesser trochanter, and the femoral diaphysis. The four main categories determine the location of the defect while subcategories a, b and c are being used to classify the extent of damage in each location. In total, 218 preoperative radiographs were retrospectively graded according to FDC and compared to intraoperatively encountered bone defects. To account for inter-rater and intra-rater agreement, 5 different observers evaluated 80 randomized cases at different points in time.!##!Results!#!A Cohens kappa of 0.832 ± 0.028 could be evaluated, accounting for excellent agreement between preoperative radiographs and intraoperative findings. To account for inter-rater reliability, 80 patients have been evaluated by 5 different observers. Testing for inter-rater reliability, a Fleiss Kappa of 0.688 could be evaluated falling into the good agreement range. When testing for intra-rater reliability, Cohens Kappa of each of the 5 raters has been analyzed and the mean was evaluated at 0.856 accounting for excellent agreement.!##!Conclusion!#!The FDC is a reliable and reproducible classification system. It combines intuitive use and structured design and allows for consistent preoperative planning and intraoperative guidance. A therapeutic algorithm has been created according to current literature and expert opinion. Due to the combination of the FDC with the recently introduced Acetabular Defect Classification (ADC) a structured approach to the entire field of hip revision arthroplasty is now available

Acetabular defects in revision hip arthroplasty: a therapy-oriented classification

Introduction!#!The treatment of severe acetabular bone loss remains a difficult challenge. No classification system is available that combines intuitive use, structured design and offers a therapeutic recommendation according to the current literature and modern state of the art treatment options. The goal of this study is to introduce an intuitive, reproducible and reliable guideline for the evaluation and treatment of acetabular defects.!##!Methods!#!The proposed Acetabular Defect Classification (ADC) is based on the integrity of the acetabular rim and supporting structures. It consists of 4 main types of defects ascending in severity and subdivisions narrowing down-defect location. Type 1 presents an intact acetabular rim, type 2 includes a noncontained defect of the acetabular rim ≤ 10 mm, in type 3 the rim defect exceeds 10 mm and type 4 includes different kinds of pelvic discontinuity. A collective of 207 preoperative radiographs were graded according to ADC and correlated with intraoperative findings. Additionally, a randomized sample of 80 patients was graded according to ADC by 5 observers to account for inter- and intra-rater reliability.!##!Results!#!We evaluated the agreement of preoperative, radiographic grading and intraoperative findings presenting with a k value of 0.74. Interobserver agreement presented with a k value of 0.62 and intraobserver at a k value of 0.78.!##!Conclusion!#!The ADC offers an intuitive, reliable and reproducible classification system. It guides the surgeon pre- and intraoperatively through a complex field of practice

Establishment of a Periprosthetic Acetabular Bone Defect in an In Vivo Model

The biological reconstruction of periprosthetic acetabular defects is essential for the success of revision total hip arthroplasty. However, a standardized in vivo defect model with good analogy to the human situation is still lacking, which has significantly limited the research and development of this highly important clinical entity. A defined animal defect model might be a possible solution as it offers the possibility to evaluate different biomaterials for periacetabular bone reconstruction in a reproducible setting. In an ovine periacetabular defect model (n = 27), a defined bone defect (1.5 × 1.5 × 1.5 cm/3.375 cm3) in the cranial load-bearing area of the acetabulum was augmented with two different biomaterials as well as autologous cancellous bone in an ovine periprosthetic defect model and bridged with a Ganz reinforcement ring (n = 9 animals per group). Eight months after implantation, radiological and macroscopic examination was performed. The operation with the establishment of a defined periacetabular defect could be performed in all cases. There were no intraoperative complications in the three groups. During the course of the experiment, three sheep had to be excluded due to complications. A macroscopic evaluation after 8 months showed a firm neocapsula surrounding the hip joint with macroscopic consolidation of the bony defect and a stable inlying implant. There were no detectable differences between the three groups in the macroscopic or radiological evaluation. In summary, the presented ovine model might offer the possibility to create a defined bone defect and investigate bone defect reconstruction with different materials

Quantitative sensory phenotyping in chronic neuropathic pain patients treated with unilateral L4-dorsal root ganglion stimulation

Background!#!In a previous study, we reported that selective dorsal root ganglion stimulation (DRG!##!Methods!#!Twelve refractory CRPS patients (4 female; 8 male; mean age 69 ± 9 years) received standardized quantitative sensory testing (QST) protocol at baseline and after 3 months of unilateral L4-DRG!##!Results!#!At baseline, CRPS subjects showed significantly increased thresholds for warmth, tactile and vibration detection (WDT, MDT and VDT) and exaggerated pain summation (WUR). After 3 months of unilateral L4-DRG!##!Conclusions!#!Selective L4-DR