Study of Marine Sand-Dwelling Dinoflagellate With Four New Records From the Central South Coast of Viet Nam

In this study, marine sand samples were collected from the shallow intertidal zone of Nha Trang bay, Viet Nam. Taxonomic observations were conducted for the sanddwelling dinoflagellates using light, epifluorescent and scanning electron microscopy. Morphology characterizations of the four species namely, Amphidiniopsis hexagona, Thecadinium pseudokofoidii, Amphidinium herdmanii and Fukuyoa ruetzleri have been reported as new records for Vietnamese coastal waters. The genus Amphidiniopsis and Thecadinium are a new addition to the dinoflagellates flora of Viet Nam. Taxomomic descriptions and photographs of these species have been provided. Bangladesh J. Plant Taxon. 28(2): 367-378, 2021 (December)

Taxonomical features of stigmas of tribe Lithospermeae DC. (Boraginaceae) species in Asiatic Russia

With the help of scanning electron microscopy, morphology of stigmas and shapes of papillae were studied for 11 species (from Asiatic Russia) of genera Lithospermum L., Buglossoides Moench, Cerinthe L., Echium L., and Onosma L., belonging to tribe Lithospermeae, and two species of the genus Botriospermum Bunge of unknown taxonomical affiliation in the family Boraginaceae. It was revealed that the shapes of the stigma and papillae can be useful for clarifying relationships among the species and genera, thus complementing the data for compiling a fuller and more correct taxonomy of the family Boraginaceae.

Carbon Nanotube Layer for Reduction of Fiber Print-Through in Carbon Fiber Composites

Fiber print-through effect is a limitation to the use of carbon fiber-reinforced composites in space applications, namely, mirror telescopes. Replica method is used for the production of lightweight telescope mirrors. However, this method requires a polished mandrel, increasing considerably the final cost. In this work, we report a cheaper and simpler alternative production method, which consists in the addition of a carbon nanotube filled epoxy resin layer on the surface of carbon reinforced composites, in order to reduce fiber print-through of the materials. The influence of different carbon nanotube functionalizations, concentrations, and dispersion levels are also assessed. The surface properties are evaluated by interferometry (roughness and waviness) and scanning electron microscopy (morphology). The results show that the waviness, roughness, and consequently fiber print-though are considerably reduced with the addition of a thin layer of nonfunctionalized carbon nanotubes.

A Study of Scratch Speed Effects on Ductile–Brittle Transition in Silicon

A unique rotational double-taper scratching setup is used to study ductile brittle transitions in single crystal (100) p-type silicon using a conical diamond tool at room temperature and scratching speeds ranging between 0.1 m/s and 0.3 m/s. In such a setup, transition from brittle to ductile occurs twice in a single-tapered scratch, during tool entry and tool exit. A well-defined way to determine critical depth of cut via linear crack density per unit crack length is proposed. The scratches were studied using scanning electron microscopy (morphology) and white light interferometry (depth measurements). A comprehensive study of critical depth of cut, compiled from the literature together with data from this study, with scratching speeds from very low to high shows that critical depth of cut decreases from very low scratch speeds to medium scratch speeds and then increases again at very high scratch speeds. An inference from this study is that diamond turning should be conducted at higher cutting speeds than being undertaken today to make use of larger critical depths of cut.