Phospholipid Fatty Acids as Physiological Indicators of Paracoccus denitrificans Encapsulated in Silica Sol-Gel Hydrogels

The phospholipid fatty acid (PLFA) content was determined in samples of Paracoccus denitrificans encapsulated in silica hydrogel films prepared from prepolymerized tetramethoxysilane (TMOS). Immediately after encapsulation the total PLFA concentration was linearly proportional to the optical density (600 nm) of the input microbial suspension (R2 = 0.99). After 7 days this relationship remained linear, but with significantly decreased slope, indicating a higher extinction of bacteria in suspensions of input concentration 108 cells/mL and higher. trans-Fatty acids, indicators of cytoplasmatic membrane disturbances, were below the detection limit. The cy/pre ratio (i.e., ratio of cyclopropylated fatty acids (cy17:0 + cy19:0) to their metabolic precursors (16:1ω7 + 18:1ω7)), an indicator of the transition of the culture to a stationary growth-phase, decreased depending on co-immobilization of nutrients in the order phosphate buffer > mineral medium > Luria Broth rich medium. The ratio, too, was logarithmically proportional to cell concentration. These results confirm the applicability of total PLFA as an indicator for the determination of living biomass and cy/pre ratio for determination of nutrient limitation of microorganisms encapsulated in sol-gel matrices. This may be of interest for monitoring of sol-gel encapsulated bacteria proposed as optical recognition elements in biosensor construction, as well as other biotechnological applications

A Collection of Topological Types of Nanoclusters and Its Application to Icosahedron-Based Intermetallics

In this study, we carried out a topological and geometrical analysis of more than 27 000 intermetallics. More than 2000 topologically different nanoclusters were determined and stored in an electronic database as the Topological Types of Nanoclusters (TTN) collection. Besides the topology of the nanoclusters, the TTN collection contains the information on their occurrence as well as on motifs of their assembly in intermetallics; it is included to the set of the ToposPro topological collections. With the TTN collection we analyzed the topology of local binding and overall topological motifs in the 1528 intermetallics assembled with icosahedron-based building units. Taking the TTN collection as a starting point, we present the concept of a knowledge database and an expert system that can be used to process a huge set of data to find general regularities in the crystal structures of intermetallics and to predict some of their features

New Quasicrystal Approximant in the Sc\u2013Pd System: From Topological Data Mining to the Bench

Intermetallics contribute signi\ufb01cantly to our current demand for high-performance functional materials. However, understanding their chemistry is still an open and debated topic, especially for complex compounds such as approximants and quasicrystals. In this work, targeted topological data mining succeeded in (i) selecting all known Mackay-type approximants, (ii) uncovering the most important geometrical and chemical factors involved in their formation, and (iii) guiding the experimental work to obtain a new binary Sc 12Pd 1/1 approximant for icosahedral quasicrystals containing the desired cluster. Single-crystal X-ray di\ufb00raction data analysis supplemented by electron density reconstruction using the maximum entropy method, showed \ufb01ne structural peculiarities, that is, smeared electron densities in correspondence to some crystallographic sites. These characteristics have been studied through a comprehensive density functional theory modeling based on the combination of point defects such as vacancies and substitutions. It was con\ufb01rmed that the structural disorder occurs in the shell enveloping the classical Mackay cluster, so that the real structure can be viewed as an assemblage of slightly di\ufb00erent, locally ordered, four shell nanoclusters. Results obtained here open up broader perspectives for machine learning with the aim of designing novel materials in the fruitful \ufb01eld of quasicrystals and their approximants. This might become an alternative and/or complementary way to the electronic pseudogap tuning, often used before explorative synthesis