Phase Formation and Thermal Stability of Reactively Sputtered YTaO4-ZrO2 Coatings.

Y(1-x)/2Ta(1-x)/2ZrxO2 coatings with 0 to 44 mol% ZrO2 were synthesized by sputtering. Phase-pure M'-YTaO4 coatings were obtained at a substrate temperature of 900 °C. Alloying with ZrO2 resulted in the growth of M' along with t-Zr(Y,Ta)O2 for ≤15 mol%, while for ≥28 mol%, ZrO2 X-ray diffraction (XRD) phase-pure metastable t was formed, which may be caused by small grain sizes and/or kinetic limitations. The former phase region transformed into M' and M and the latter to an M' + t and M + t phase region upon annealing to 1300 and 1650 °C, respectively. In addition to M and t, T-YTa(Zr)O4 phase fractions were observed at room temperature for ZrO2 contents ≥28 mol% after annealing to 1650 °C. T phase fractions increased during in situ heating XRD at 80 °C. At 1650 °C, a reaction with the α-Al2O3 substrate resulted in the formation of AlTaO4 and an Al-Ta-Y-O compound.

Characterising the Microstructure of an Additively Built Al-Cu-Li Alloy.

Al-Cu-Li alloys are famous for their high strength, ductility and weight-saving properties, and have for many years been the aerospace alloy of choice. Depending on the alloy composition, this multi-phase system may give rise to several phases, including the major strengthening T1 (Al2CuLi) phase. Microstructure investigations have extensively been reported for conventionally processed alloys with little focus on their Additive Manufacturing (AM) characterised microstructures. In this work, the Laser Powder Bed Fusion (LPBF) built microstructures of an AA2099 Al-Cu-Li alloy are characterised in the as-built (no preheating) and preheat-treated (320 °C, 500 °C) conditions using various analytical techniques, including Synchrotron High-Energy X-ray Diffraction (S-HEXRD). The observed dislocations in the AM as-built condition with no detected T1 precipitates confirm the conventional view of the difficulty of T1 to nucleate on dislocations without appropriate heat treatments. Two main phases, T1 (Al2CuLi) and TB (Al7.5Cu4Li), were detected using S-HEXRD at both preheat-treated temperatures. Higher volume fraction of T1 measured in the 500 °C (75.2 HV0.1) sample resulted in a higher microhardness compared to the 320 °C (58.7 HV0.1) sample. Higher TB volume fraction measured in the 320 °C sample had a minimal strength effect.

Effect of data self-collection as an activating teaching method in a statistical software course in medical biometry - a pilot study.

Background: Biostatistics is an integral part of the studies of human medicine. Students learn the basics of analyzing and interpreting study results. It is important to demonstrate the subject's relevance by means of appropriate measures to maximize learning success. We investigated whether an active involvement of students in the process of data collection may improve test performance and motivation among medical students. Methods: We conducted a pilot study comparing active involvement of students (n1=45) in the process of data collection and standard education (n2=26). All students of this pilot study participated in an observational study assessing their preferences regarding sweets or salty munchies, and students of the experimental group subsequently used this data set during the exercises throughout the semester. Primary and secondary endpoints were examination success and motivation respectively. Results: Superiority of the activating teaching method could not be demonstrated (intervention: 109.0 points (SD 8.8), control: 113.8 points (SD 6.5)). The course ratings were superior in the intervention group (median grade 1 vs. median grade 2 in the control group), although this was not a significant improvement (p=0.487). Conclusions: Biostatistics education should incorporate approaches contributing to a better understanding of learning contents. Possible reasons why this pilot study failed to prove superiority of the intervention were a lack of sample size as well as the good grades in the control group. The presented teaching concept has to be evaluated by means of a larger sample enabling more valid conclusions. Furthermore, the considered research question in the experimental group may be changed to a more relevant one for medical practice.

Electron Probe Microanalysis of Ni Silicides Using Ni-L X-Ray Lines.

We report electron probe microanalysis measurements on nickel silicides, Ni5Si2, Ni2Si, Ni3Si2, and NiSi, which were done in order to investigate anomalies that affect the analysis of such materials by using the Ni L3-M4,5 line (Lα). Possible sources of systematic discrepancies between experimental data and theoretical predictions of Ni L3-M4,5 k-ratios are examined, and special attention is paid to dependence of the Ni L3-M4,5 k-ratios on mass-attenuation coefficients and partial fluorescence yields. Self-absorption X-ray spectra and empirical mass-attenuation coefficients were obtained for the considered materials from X-ray emission spectra and relative X-ray intensity measurements, respectively. It is shown that calculated k-ratios with empirical mass attenuation coefficients and modified partial fluorescence yields give better agreement with experimental data, except at very low accelerating voltages. Alternatively, satisfactory agreement is also achieved by using the Ni L3-M1 line (Lℓ) instead of the Ni L3-M4,5 line.

Natural course of scoliosis in proximal spinal muscular atrophy type II and IIIa: descriptive clinical study with retrospective data collection of 126 patients.

BACKGROUND: Progressive scoliosis, pelvic obliquity and increasing reduction of pulmonary function are among the most significant problems for patients with SMA type II and SMA type III once they have lost the ability to walk. The aim of this study was to examine and document the development and natural course of scoliosis in patients with spinal muscular atrophy type II and IIIa. METHODS: For the purposes of a descriptive clinical study, we observed 126 patients, 99 with SMA II and 27 with SMA IIIa and the data of scoliosis, pelvic obliquity and relative age-dependent inspiratory vital capacity were evaluated. RESULTS: Scoliosis and pelvic obliquity were regularly observed already in children under 4 years old in the group with SMA II. The severity and progression of both conditions were much more pronounced in the SMA II group than in the IIIa group. There was already a distinct reduction in relative vital capacity in the group of 4- to 6-year-olds with SMA II. CONCLUSIONS: The differences between the two SMA types II and IIIa described in this study should be taken into consideration when developing new treatments and in management of scoliosis in the childhood years of these patients.

Characterization of dual-phase steel microstructure by combined submicrometer EBSD and EPMA carbon measurements.

Electron backscatter diffraction (EBSD) and electron probe microanalysis (EPMA) measurements are combined to characterize an industrial produced dual-phase steel containing some bainite fraction. High-resolution carbon mappings acquired on a field emission electron microprobe are utilized to validate and improve the identification of the constituents (ferrite, martensite, and bainite) performed by EBSD using the image quality and kernel average misorientation. The combination eliminates the ambiguity between the identification of bainite and transformation-induced dislocation zones, encountered if only the kernel average misorientation is considered. The detection of carbon in high misorientation regions confirms the presence of bainite. These results are corroborated by secondary electron images after nital etching. Limitations of this combined method due to differences between the spatial resolution of EBSD and EPMA are assessed. Moreover, a quantification procedure adapted to carbon analysis is presented and used to measure the carbon concentration in martensite and bainite on a submicrometer scale. From measurements on reference materials, this method gives an accuracy of 0.02 wt% C and a precision better than 0.05 wt% C despite unavoidable effects of hydrocarbon contamination.

Influence of Si and N additions on structure and phase stability of Ge(2)Sb(2)Te(5) thin films.

The influence of Si and N in Ge(2)Sb(2)Te(5) (space group [Formula: see text]) on structure and phase stability thereof was studied experimentally by thin film growth and characterization as well as theoretically by ab initio calculations. It was found that Si and N most probably accumulate in the amorphous matrix embedding Ge(2)Sb(2)Te(5) grains. The incorporation of Si and N in these samples causes an increase of the crystallization temperature and the formation of finer grains. N is more efficient in increasing the crystallization temperature and in reducing the grain size than Si which can be understood based on the bonding analysis. The incorporation of both Si and N in Ge(2)Sb(2)Te(5) is energetically unfavourable, leading to finer grains and larger crystallization temperatures. While in the case of Si additions no significant changes in bonding are observed, N additions appear to enable the formation of strong Te-N bonds in the amorphous matrix, which are shown to be almost twice as strong as the strongest bonds in unalloyed Ge(2)Sb(2)Te(5).

Chemical strengthening of a dental lithium disilicate glass-ceramic material.

Chemical strengthening of dental ceramics by ion exchange has hitherto only been confirmed for feldspathic porcelains. The objective of this study was to examine whether the strength of lithium disilicate glass-ceramics can be increased by ion exchange as well. A lithium disilicate glass-ceramic material was treated in different molten salts. The concentration gradients of the relevant ions in the surface layer were investigated by means of electron probe microanalysis and secondary ion mass spectroscopy. Characteristic strength and Weibull modulus data were determined. An increase in strength of 25% was achieved by treatment in potassium nitrate. The chemical analyses revealed that the increase in strength resulted from an exchange of potassium for lithium ions. We conclude that ion-exchange treatments can increase the strength of lithium disilicate glass-ceramics. The improved material could be used for highly stressed applications, such as posterior crowns or inlay-retained bridges, with higher mechanical reliability.