Rolling-sliding-contact fatigue damage of the gear tooth flanks

Bokovi zuba evolventnih zupčanika izloženi su tijekom zahvata cikličkom djelovanju kontaktnih pritisaka te kombinaciji kotrljanja i klizanja. Spomenuto opterećenje može izazvati specifičnu vrstu zamora materijala koja se naziva kotrljajno-klizno-kontaktni zamor. U radu su opisane faze procesa zamaranja materijala izloženog djelovanju cikličkih opterećenja. Klasificirana su zamorna oštećenja boka zuba zupčanika te su za svaku vrstu navedeni njezini uzroci i značajke. Navedene informacije mogu poslužiti kao pomoć pri sprečavanju ili naknadnoj identifikaciji i uklanjanju problema sa zamornim oštećenjima zupčanika u prijenosnicima snage.During the meshing of involute gears, their teeth flanks are subjected to cyclic contact pressure loading and simultaneous rolling and sliding. The mentioned loading can induce a specific type of material fatigue that is commonly denoted as rolling-sliding-contact fatigue. In this work, individual phases of fatigue occurring due to the cyclic loading are described. Furthermore, different types of fatigue damage of gear teeth flanks are classified and for each type, its causes and features are given. The information presented can be used for prevention or subsequent identification and remedial action in the case of fatigue damage of gears in power transmissions

Fluor-schorl, a new member of the tourmaline supergroup, and new data on schorl from the cotype localities

Fluor-schorl, NaFe^(2+) _3Al_6Si_6O_(18)(BO_3)_3(OH)_3F, is a new mineral species of the tourmaline supergroup from alluvial tin deposits near Steinberg, Zschorlau, Erzgebirge (Saxonian Ore Mountains), Saxony, Germany, and from pegmatites near Grasstein (area from Mittewald to Sachsenklemme), Trentino, South Tyrol, Italy. Fluor-schorl was formed as a pneumatolytic phase and in high-temperature hydrothermal veins in granitic pegmatites. Crystals are black (pale brownish to pale greyish-bluish, if distance (r^2 = 0.93). This correlation indicates that Fe^(2+)-rich tourmalines from the investigated localities clearly tend to have a F-rich or F-dominant composition. A further strong positive correlation (r^2 = 0.82) exists between the refined F content and the Y–W (F,OH) distance, and the latter may be used to quickly estimate the F content

Limitations of Fe^(2+) and Mn^(2+) site occupancy in tourmaline: Evidence from Fe^(2+)- and Mn^(2+)-rich tourmaline

Fe^(2+)- and Mn^(2+)-rich tourmalines were used to test whether Fe^(2+) and Mn^(2+) substitute on the Z site of tourmaline to a detectable degree. Fe-rich tourmaline from a pegmatite from Lower Austria was characterized by crystal-structure refinement, chemical analyses, and Mössbauer and optical spectroscopy. The sample has large amounts of Fe^(2+) (~2.3 apfu), and substantial amounts of Fe^(3+) (~1.0 apfu). On basis of the collected data, the structural refinement and the spectroscopic data, an initial formula was determined by assigning the entire amount of Fe^(3+) (no delocalized electrons) and Ti^(4+) to the Z site and the amount of Fe^(2+) and Fe^(3+) from delocalized electrons to the Y-Z ED doublet (delocalized electrons between Y-Z and Y-Y): X(Na_(0.9)Ca_(0.1)) ^Y(Fe^(2+)_(2.0)Al_(0.4)Mn^(2+)_(0.3)Fe^(3+)_(0.2)) ^Z(Al_(4.8)Fe^(3+)_(0.8)Fe^(2+)_(0.2)Ti^(4+)_(0.1)) ^T(Si_(5.9)Al_(0.1))O_(18) (BO_3)_3^V(OH)_3 ^W[O_(0.5)F_(0.3)(OH)_(0.2)] with α = 16.039(1) and c = 7.254(1) Å. This formula is consistent with lack of Fe^(2+) at the Z site, apart from that occupancy connected with delocalization of a hopping electron. The formula was further modified by considering two ED doublets to yield: ^X(Na_(0.9)Ca_(0.1)) ^Y(Fe^(2+)_(1.8)Al_(0.5)Mn^(2+)_(0.3)Fe^(3+)_(0.3)) ^Z(Al_(4.8)Fe^(3+)_(0.7)Fe^(2+)_(0.4)Ti^(4+)_(0.1)) ^T(Si_(5.9_Al_(0.1))O_(18) (BO_3)_3 ^V(OH)_3 ^W[O_(0.5)F_(0.3)(OH)_(0.2)]. This formula requires some Fe^(2+) (~0.3 apfu) at the Z site, apart from that connected with delocalization of a hopping electron. Optical spectra were recorded from this sample as well as from two other Fe^(2+)-rich tourmalines to determine if there is any evidence for Fe^(2+) at Y and Z sites. If Fe^(2+) were to occupy two different 6-coordinated sites in significant amounts and if these polyhedra have different geometries or metal-oxygen distances, bands from each site should be observed. However, even in high-quality spectra we see no evidence for such a doubling of the bands. We conclude that there is no ultimate proof for Fe^(2+) at the Z site, apart from that occupancy connected with delocalization of hopping electrons involving Fe cations at the Y and Z sites. A very Mn-rich tourmaline from a pegmatite on Elba Island, Italy, was characterized by crystal-structure determination, chemical analyses, and optical spectroscopy. The optimized structural formula is ^X(Na_(0.6)□_(0.4)) ^Y(Mn^(2+)_(1.3)Al_(1.2)Li_(0.5)) ^ZAl_6 ^TSi_6O_(18) (BO_3)_3 ^V(OH)_3 ^W[F_(0.5)O_(0.5)], with α = 15.951(2) and c = 7.138(1) Å. Within a 3σ error there is no evidence for Mn occupancy at the Z site by refinement of Al ↔ Mn, and, thus, no final proof for Mn^(2+) at the Z site, either. Oxidation of these tourmalines at 700–750 °C and 1 bar for 10–72 h converted Fe^(2+) to Fe^(3+) and Mn^(2+) to Mn^(3+) with concomitant exchange with Al of the Z site. The refined ^ZFe content in the Fe-rich tourmaline increased by ~40% relative to its initial occupancy. The refined YFe content was smaller and the distance was significantly reduced relative to the unoxidized sample. A similar effect was observed for the oxidized Mn^(2+)-rich tourmaline. Simultaneously, H and F were expelled from both samples as indicated by structural refinements, and H expulsion was indicated by infrared spectroscopy. The final species after oxidizing the Fe^(2+)-rich tourmaline is buergerite. Its color had changed from blackish to brown-red. After oxidizing the Mn^(2+)-rich tourmaline, the previously dark yellow sample was very dark brown-red, as expected for the oxidation of Mn^(2+) to Mn^(3+). The unit-cell parameter α decreased during oxidation whereas the c parameter showed a slight increase

Neuronal Aneuploidy in Health and Disease: A Cytomic Approach to Understand the Molecular Individuality of Neurons

Structural variation in the human genome is likely to be an important mechanism for neuronal diversity and brain disease. A combination of multiple different forms of aneuploid cells due to loss or gain of whole chromosomes giving rise to cellular diversity at the genomic level have been described in neurons of the normal and diseased adult human brain. Here, we describe recent advances in molecular neuropathology based on the combination of slide-based cytometry with molecular biological techniques that will contribute to the understanding of genetic neuronal heterogeneity in the CNS and its potential impact on Alzheimer's disease and age-related disorders

Mechanical Properties and Dimensional Effects of ZnO- and SnO2-Based Varistors

A comparison between traditional ZnO-(modified Matsuoka system, [ZnO]) and SnO2-based varistors (98.9%SnO211% CoO10.05%Nb2O510.05%Cr2O3, [SCNCr]) regarding their mechanical properties, finite element (FE) modeling, and macroscopic response with current pulse is presented in this work. The experimental values of the elastic (static and dynamic) modulus and bending strength are given. Both the static and the dynamic modulus were two times higher for SnO2 (B200 GPa) with respect to ZnO (B100 GPa). A similar behavior was found for the bending strength, confirming the superior mechanical properties of SCNCr associated with a homogeneous microstructure. The finite element analyses yielded the most appropriate thickness/diameter aspect ratio (H/D), while thermomechanical stress is minimized. The values of (H/D) were lower for the SCNCr in comparison with the ZnO-based varistors, allowing the production of smaller pieces that can resist the same thermomechanical stress. Finally, preliminary analyses of the macroscopic failures for samples treated with degradation pulses of 8/20-ls type allowed to confirm the absence of failures due to cracking and/or puncture in the SCNCr. The absence of these failures originates from the good thermomechanical propertiesPeer reviewe

Bioinformatics

Hofestädt R, Lengauer T, Löffler M, Schomburg D, eds. Bioinformatics. LNCS. Vol 1278 1. Edition. Berlin: Springer; 1997

An Evolutionary Approach for Identifying Driver Mutations in Colorectal Cancer

The traditional view of cancer as a genetic disease that can successfully be treated with drugs targeting mutant onco-proteins has motivated whole-genome sequencing efforts in many human cancer types. However, only a subset of mutations found within the genomic landscape of cancer is likely to provide a fitness advantage to the cell. Distinguishing such “driver” mutations from innocuous “passenger” events is critical for prioritizing the validation of candidate mutations in disease-relevant models. We design a novel statistical index, called the Hitchhiking Index, which reflects the probability that any observed candidate gene is a passenger alteration, given the frequency of alterations in a cross-sectional cancer sample set, and apply it to a mutational data set in colorectal cancer. Our methodology is based upon a population dynamics model of mutation accumulation and selection in colorectal tissue prior to cancer initiation as well as during tumorigenesis. This methodology can be used to aid in the prioritization of candidate mutations for functional validation and contributes to the process of drug discovery

Interaction Profiles and Stability of Rigid and Polymer-Tethered Lipid Bilayer Models at Highly Charged and Highly Adhesive Contacts

Preprint version of the article Bilotto, P., Lengauer, M., Andersson, J., Ramach, U., Mears, L. L. E., & Valtiner, M. (2019). Interaction Profiles and Stability of Rigid and Polymer-Tethered Lipid Bilayer Models at Highly Charged and Highly Adhesive Contacts. Langmuir, 35(48), 15552–15563. https://doi.org/10.1021/acs.langmuir.9b01942Understanding interaction force versus distance profiles of supported lipid bilayers (SLBs) is relevant to a number of areas, which rely on these model systems, including, e.g., characterization of ligand/receptor interactions or bacterial adhesion. Here, the stability of 4 different SLB architectures was compared using the surface forces apparatus (SFA) and atomic force microscopy (AFM). Specifically, the outer envelope of the bilayer systems remained constant as 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The inner layer was varied between DPPC and 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP) both on mica, and self-assembled monolayers (SAMs) of hexadecanethiol and the polymer-tethered diphytanylglycerol-tetraethylene glycol-lipoid acid (DPhyTL) on smooth gold surfaces. In that same order these gave an increasing strength of interaction between the inner layer and the supporting substrate and hence improved stability under highly adhesive conditions. Detachment profiles from highly charged and highly adhesive contacts were characterized, and approach characteristics were fitted to DLVO models. We find increasing stability under highly adhesive loads, approaching the hydrophobic limit of the adhesive energy between the inner and outer layers for the SAM-based systems. For all four SLBs we further compare AFM surface topographies, which strongly depend on preparation conditions, and the DLVO fitting of the SFA approach curves finds a strong charge regulation behavior during interaction, dependent on the particular model system. In addition, we find undulation characteristics during approach and separation. The increased stability of the complex architectures on a gold support makes these model systems an ideal starting point for studying more complex strongly adhesive/interacting systems, including, for example, ligand/receptor interactions, biosensing interactions, or cell/surface interactions.Europäischer Forschungsrat (ERC)