SYMBIOSIS OF RUGOSE CORALS WITH THE CYSTOPORATE BRYOZOAN FISTULIPORA PRZHIDOLENSIS IN THE PRIDOLI (LATEST SILURIAN) OF SAAREMAA, ESTONIA

ABSTRACT In the Silurian, the most common hosts of endobiotic rugose corals were stromatoporoids followed by tabulate corals. Here we describe the relationship between rugose corals and a bryozoan. Solitary rugosans and the cystoporate bryozoan Fistulipora przhidolensis Kopajevich, 1990 formed a symbiotic association in the late Silurian (Pridoli) of Saaremaa, Estonia. The syn vivo nature of the association is indicated by complete intergrowth of both organisms and the perpendicular orientation of the rugosans to the bryozoan growth surface. There are one to seven endobiotic rugosans per bryozoan colony. This is the first detailed study of coral-bryozoan symbiosis from the Silurian; all previous reports describe Late Ordovician, Devonian, or Cenozoic material. The lack of malformations and decrease in the size of bryozoan zooids near the rugosans suggest there were no strong negative effects of the rugosans on the bryozoan. The rugosans likely benefited from their association with the bryozoan, which served as an anchor to stabilize them in hydrodynamically active waters, and the bryozoan may have benefited by protection against some types of predators. The associations described here were most likely mutualistic.

Структура и магнетизм сверхрешеток Co/Dy

The influence of structural properties on the formation of perpendicular magnetic anisotropy in Co/Dy superlattices is investigated. It is established that superlattices are a compositionally modulated alloy in which, on the one hand, a strict periodicity is maintained in the thickness and composition of the layers, and on the other hand, the interdiffusion of Co and Dy at the interlayer boundaries leads to a periodic change with the depth of the concentration of Co and Dy. It is shown that the perpendicular magnetic anisotropy in Co/Dy is due to the perpendicular orientation of the magnetization in the alloying CoDy layers, while the magnetization of the Co layers is oriented in the sample plane.

Synthesis and Characterization of Novel Ti3SiC2 Reinforced Ni-Matrix Multilayered Composite-Based Solid Lubricants

We report the synthesis and characterization of two different types of Ni-based laminated composites (Types I and II). In Type-I composites, layers of Ni and Ti3SiC2 (Ni–Ti3SiC2) were interleaved with Ni, whereas in Type-II composites, Ni–Ti3SiC2 layers were interleaved with Al and Ni. The laminate thickness and Ti3SiC2 content in the individual Ni–Ti3SiC2 layers were systematically varied in both the composites. Detailed SEM studies showed that Ti3SiC2 particulates are well distributed in the Ni-matrix with little or no interfacial reactions with interparticle porosity. However, there were interfacial reactions between Ni and Al in Type II composites. In general, Type I multilayered composites had higher ultimate compressive strength (UCS) in parallel orientation as compared to perpendicular orientation (layers are aligned parallel or perpendicular to the wear surface then it will be referred to as parallel or perpendicular orientation). Comparatively, in Type II composites, the UCS was greater in perpendicular orientation as compared to parallel due to the presence of Al layers as bonding layers. Both the composite designs showed triboactive behavior against alumina disks and sensitivity to laminate thickness and orientation. In Type-I composites, the decrease in µ and wear rate (WR) with laminate thickness was more pronounced in the perpendicular orientation as compared to the parallel orientation. Comparatively, Ni–Ti3SiC2/Al/Ni composites showed that the parallel orientation was more effective in enhancing the triboactive performance. SEM analysis of tribosurfaces showed signs of triboxidation and abrasion, which led to the formation of O-rich tribofilms.