Generalized Hamilton's Principle with Fractional Derivatives

We generalize Hamilton's principle with fractional derivatives in Lagrangian L(t,y(t),{}_0D_t^\al y(t),\alpha) so that the function $y$ and the order of fractional derivative $\alpha$ are varied in the minimization procedure. We derive stationarity conditions and discuss them through several examples

The metalanguage of a lexicographic definition in the descriptive dictionary (based on the dictionaries of the Serbian language)

In this paper we present the continuous hierarchical ordering of the first part of the definition of lexemes from the thematic group ‘buildings’ by analyzing the vertical organization of superordination of concepts in the lexicographical definition. We demonstrate that the vertical sequence mounts from a higher level of conceptual categorization, ‘localizer,’ in the form of complex and simple primitives (PLACE > SPACE [WHERE], SPACE > EXPANSE [SOMETHING THAT IS (BOUNDLESSLY) SPREADING IN EVERY DIRECTION]) and descends toward a lower hyperonimic level of ‘buildings’. The suggested model links meanings systematically, on a micro-level of meaning within the polysemic structure, and on a macrolevel of meanings of lexemes belonging to a thematic group/class, which is significant for the descriptive lexicography and for the modeling of semantic description in the electronic dictionary of the contemporary Serbian language. Such description could facilitate the cross-referencing of lexemes and advanced search, which is essential both for linguists and dictionary users.[Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 178009: Lingvistička istraživanja savremenog srpskog jezika i izrada Rečnika srpskohrvatskog književnog i narodnog jezika SANU

The Crystal Structure of RosB: Insights into the Reaction Mechanism of the First Member of a Family of Flavodoxin-like Enzymes

8-demethyl-8-aminoriboflavin-5′-phosphate (AFP) synthase (RosB) catalyzes the key reaction of roseoflavin biosynthesis by forming AFP from riboflavin-5′-phosphate (RP) and glutamate via the intermediates 8-demethyl-8-formylriboflavin-5′-phosphate (OHC-RP) and 8-demethyl-8-carboxylriboflavin-5′-phosphate (HO2C-RP). To understand this reaction in which a methyl substituent of an aromatic ring is replaced by an amine we structurally characterized RosB in complex with OHC-RP (2.0Å) and AFP (1.7Å). RosB is composed of four flavodoxin-like subunits which have been upgraded with specific extensions and a unique C-terminal arm. It appears that RosB has evolved from an electron- or hydride-transferring flavoprotein to a sophisticated multi-step enzyme which uses RP as a substrate (and not as a cofactor). Structure-based active site analysis was complemented by mutational and isotope-based mass-spectrometric data to propose an enzymatic mechanism on an atomic basis

Ultra-light nanocomposite aerogels of bacterial cellulose and reduced graphene oxide for specific absorption and separation of organic liquids

Novel materials based on sustainable materials with high absorption capacity are still rare for the separation of organic liquids or oil spills and water. In this report, ultra-light nanocomposite aerogels consisting of sustainable bacterial cellulose (BC) and graphene oxide (GO) were constructed after an eco-friendly freeze-drying process for the first time. Due to the hydrophilic properties of both materials and the highly porous structure, BC/GO aerogels could highly absorb not only organic liquids, such as cyclohexane and DMF, but also water. Specific absorption for organic liquids was achieved after the reduction of GO using H-2 gas, which led to nanocomposite aerogels of BC and reduced GO. They could specifically absorb 135-150 g organic liquids per g of their own weight, even with a high content of 80 BC in the nanocomposite aerogel