Origin and function of stomata in the moss Physcomitrella patens.

Stomata are microscopic valves on plant surfaces that originated over 400 million years (Myr) ago and facilitated the greening of Earth's continents by permitting efficient shoot-atmosphere gas exchange and plant hydration(1). However, the core genetic machinery regulating stomatal development in non-vascular land plants is poorly understood(2-4) and their function has remained a matter of debate for a century(5). Here, we show that genes encoding the two basic helix-loop-helix proteins PpSMF1 (SPEECH, MUTE and FAMA-like) and PpSCREAM1 (SCRM1) in the moss Physcomitrella patens are orthologous to transcriptional regulators of stomatal development in the flowering plant Arabidopsis thaliana and essential for stomata formation in moss. Targeted P. patens knockout mutants lacking either PpSMF1 or PpSCRM1 develop gametophytes indistinguishable from wild-type plants but mutant sporophytes lack stomata. Protein-protein interaction assays reveal heterodimerization between PpSMF1 and PpSCRM1, which, together with moss-angiosperm gene complementations(6), suggests deep functional conservation of the heterodimeric SMF1 and SCRM1 unit is required to activate transcription for moss stomatal development, as in A. thaliana(7). Moreover, stomata-less sporophytes of ΔPpSMF1 and ΔPpSCRM1 mutants exhibited delayed dehiscence, implying stomata might have promoted dehiscence in the first complex land-plant sporophytes

Strength calculation of sharp notched components

In this report the strength calculation of sharp notched components under static and cyclic loading is investigated and compared to the FKM code "Analytical strength assessment for machine components". The calculation of the strength of sharp notched components according to the guideline does not lead to satisfying solutions. Therefore different concepts of strength calculation with consideration of scale and notch effects are examined e.g. the gradient concept of Siebel/Stieler. This concept is implemented in the FKM code for the calculation of the notch sensitivity factor. In order to evaluate the numerical results. experimental tests with various sharp notched specimens under static and cyclic loading were carried out. Based on these experimental results the FKM code is extended to sharp notched components

Interlaminar fracture analysis of consolidated GF-PA6-tapes

Es ist wird der Zusammenhang zwischen Fertigungsprozess, Mikrostruktur und interlaminarem Grenzflächenversagen eines faserverstärkten Kunststoffes untersucht und modelliert. Hierfür werden Versuchsmaterialien hergestellt, werkstoffmechanisch geprüft und deren Mikrostruktur analysiert. Hieraus wird eine Modellierungsstrategie abgeleitet, welche das in den Versuchen gezeigte Werkstoffverhalten abbilden kann

Experimental investigation and numerical simulation of fatigue crack formation in polycrystalline materials

The present contribution is concerned with an experimental investigation of fatigue crack initiation in polycrystalline metals using a micro scale specimen testing technique. Based on the results of the experimental investigation and a fractographic investigation, a probabilistic microscale simulation procedure for prediction of the fatigue crack formation process is proposed

Effects of process parameters on the interlaminar fracture toughness of GF-PA6-tapes

Interlaminar fracture toughness of consolidated, continuous glass fiber reinforced polyamide-6 tapes, as well as its sensitivity to process parameters are investigated in this study. Therefore, consolidated plaques are manufactured, varying consolidation temperature and pressure, and their delamination behavior in mode I and mode II is analyzed by means of DCB and ENF tests

A technique for 3D in vivo quantification of proton density and magnetization transfer coefficients of knee joint cartilage.

AbstractObjective To develop an MR-based method for the in vivo evaluation of the structural composition of articular cartilage.Design Five sagittal magnetic resonance imaging (MRI) protocols were acquired throughout the knee joint of 15 healthy volunteers and the boundaries of the cartilage segmented from a previously validated sequence with high contrast between cartilage and surrounding tissue. The other sequences were matched to these data, using a 3D least-squares fit algorithm to exclude motion artefacts. In this way secondary images were computed that included information about the proton density (interstitial water content) and the magnetization transfer coefficient (macromolecules, collagen). The average signal intensities of the 3D cartilage plates were extracted from these data sets and related to a phantom.Results The signal intensity data showed a high interindividual variability for the proton density (patella 31%, lateral tibia 36%, medial tibia 29%); the patella displaying higher values than the tibia (P< 0.001). There were high correlations between the three plates. The magnetization transfer coefficient also showed high variability (patella 25%, lateral tibia 32%, medial tibia 30%) with the lowest values in the medial tibia (P< 0.01) and lower correlations between the plates. The slice-to-slice variation (medial to lateral) ranged from 9% to 24%.Conclusion An MR-based method has been developed for evaluating the proton density and magnetization transfer of articular cartilage in vivo and observing systematic differences between knee joint cartilage plates. The technique has the potential to supply information about the water content and collagen of articular cartilage, in particular at the early state of osteoarthritic degeneration