On Locally Gabriel Geometric Graphs

Let \(P\) be a set of \(n\) points in the plane. A geometric graph \(G\) on \(P\) is said to be locally Gabriel if for every edge \((u,v)\) in \(G\), the Euclidean disk with the segment joining \(u\) and \(v\) as diameter does not contain any points of \(P\) that are neighbors of \(u\) or \(v\) in \(G\). A locally Gabriel graph(LGG) is a generalization of Gabriel graph and is motivated by applications in wireless networks. Unlike a Gabriel graph, there is no unique LGG on a given point set since no edge in a LGG is necessarily included or excluded. Thus the edge set of the graph can be customized to optimize certain network parameters depending on the application. The unit distance graph(UDG), introduced by Erdos, is also a LGG. In this paper, we show the following combinatorial bounds on edge complexity and independent sets of LGG: (i) For any \(n\), there exists LGG with \(\Omega (n^{5/4})\) edges. This improves upon the previous best bound of \(\Omega (n^{1+\frac{1}{\log \log n}})\). (ii) For various subclasses of convex point sets, we show tight linear bounds on the maximum edge complexity of LGG. (iii) For any LGG on any \(n\) point set, there exists an independent set of size \(\Omega (\sqrt{n}\log n)\).     

Total synthesis of arenamide A and its diastereomer

Arenamide A and its diastereomer have been synthesized in a convergent fashion. The key steps involved in this synthesis are Sharpless asymmetric epoxidation, C–C bond formation, and macrolactamization.     

Synthesis and Antibacterial Activity of Novel 3-N-Substituted 1,8-Naphthyridin-2(1H)-ones

Russian Journal of General Chemistry - Synthesis of novel N-protected and unprotected 3-N-substituted 1,8-naphthyridin-2(1H)-ones with potential inhibiting activity of penicillin-binding protein 6...     

Nuclearity Control in Molecular Copper Phosphates Derived from a Bulky Arylphosphate: Synthesis,Structural and Magnetic Studies

Starting from sterically encumbered 2,6-di-tert-butylphenyl phosphate (dtbppH₂) and co-ligand 3,5-dimethyl pyrazole (dmpz), it is possible to isolate either mono-, di- or tetranuclear copper phosphates by varying the copper source and making attendant changes in the reaction conditions. For example, reaction of copper nitrate with dtbppH₂ and dmpz at 60 °C leads to the isolation of the mononuclear copper phosphate [Cu(dtbppH)₂(dmpz)(MeOH)₂] ( 1 ) as the only product. However, the use of copper acetate in place of copper nitrate and conducting the reaction at the room temperature leads to the formation of both dinuclear [Cu(dtbpp)(dmpz)₂]₂ ( 2 ) and tetranuclear [Cu₂(dtbpp)(dmpz)₂(OAc)(MeO)]₂ ( 3 ) from the same reaction mixture. Compounds 2 and 3 could be isolated in pure form through fractional crystallization. Copper phosphates 1 – 3 have been characterized by both analytical and spectroscopic methods including EPR and magnetic measurements. The molecular structures of all three compounds were established through single crystal diffraction studies. Dc magnetic measurements indicate antiferromagnetic interactions between the metal centres in all the compounds.     

Thermokinetic responses of the metabolic activity of <Emphasis Type="Italic">Staphylococcus lentus</Emphasis> cultivated in a glucose limited mineral salt medium

Biocalorimetric experiments were performed to investigate the metabolic thermal responses of the halotolerant species Staphylococcus lentus in glucose limited mineral salt medium. Growth factors were optimized in both shaker flask and calorimetric experiments. A limiting value of 5 g/L glucose was found to be the optimum for S. lentus growth. The heat flux profiles, OUR, biomass growth, and substrate depletion profiles were compared to deduce the metabolic activity of S. lentus. Shifts in heat flux due to the shifts in substrate uptake and three distinct phases of growth are noticeable in heat profile curves. Respirogram (OUR) and heat profiles are seen to follow the biomass growth curve. Oxycalorific coefficient is validated with the theoretical studies and those noticed in published literature.     

Bioconversion of Sodium Dodecyl Sulphate to Rhamnolipid by Pseudomonas aeruginosa: A Novel and Cost-Effective Production Strategy

The utility of rhamnolipids in industry is currently limited due to the high constraints in its economic production. In this scenario, the novel utility of sodium dodecyl sulphate (SDS) as carbon source could serve as promising cost-effective strategy. Screening of effective SDS biodegraders led to the isolation of Pseudomonas aeruginosa S15 capable of concomitant SDS degradation and biosurfactant synthesis. SDS-based rhamnolipid production was proved on SDS minimal agar plates using cetyl trimethylammonium bromide–methylene blue method and optimised in SDS-based minimal salt (SBS) medium. SDS proved to be an ideal carbon source for rhamnolipid synthesis with a high substrate to product conversion rate yielding 6.9 g/l of rhamnolipids from 1 g/l SDS in 5 days. Fast atom bombardment mass spectroscopy analysis of the purified biosurfactant proved the presence of mono- and di-rhamnolipids, viz., Rha-C₁₀-C₁₀, Rha-C₁₀-C₁₂ and Rha-Rha-C₁₀-C₁₀ with surface active properties. The secreted rhamnolipids were not utilised by S15 as a carbon source, but it caused a dispersion of bacterial biofilms in SBS medium. To the best of our knowledge, this is the first report on bioconversion of synthetic detergent to biodetergent. This SDS-based novel methodology presents a more economised mode of rhamnolipid synthesis utilising SDS as sole carbon source.     

Preparation and Characterizations of New Hybrid PVA-InAlO Thin Films by Dip Coating Method

New hybrid PVA-InAlO thin films were successfully prepared by using the dip coating method. Functional group analysis confirms the presence of metal-oxide vibration in the prepared films. Structural analysis revealed that the prepared film was amorphous in nature whereas annealed films were polycrystalline in nature. Morphological images show that films are compact and have homogeneous grains of various sizes ranging between 200 and 400 nm. The compositional analysis confirms the presence of In, Al, and O. Dielectric constant values vary from 4.65 to 19.89 and dielectric loss values were ≤0.977. Activation energy was found to be very low. The results suggest that the new hybrid PVA-InAlO thin films could be used as high k layer in thin film transistor applications.     

Preparation, characterization, and electrochemical application of metal/metal ion loaded fullerene nanowhiskers

Ce-doped C₆₀ nanowhiskers were prepared by liquid–liquid interfacial precipitation method using C₆₀-saturated benzene and Ce-containing isopropyl alcohol solution. The optical microscopy and scanning electron microcopy images of the Ce-doped nanowhiskers revealed the formation of lengthy nanowhiskers with uniform diameter. The X-ray diffraction pattern of the as-prepared and heat-treated Ce-doped nanowhiskers elucidated the face-centered cubic crystalline nature and the formation of CeO₂ phase at 400 °C. Raman spectroscopic studies on the Ce-doped nanowhiskers revealed the polymerization of the C₆₀ molecules in the nanowhiskers. The diameter of the nanowhiskers was calculated from the transmission electron microscopy (TEM) image, and it varied in the range of 150–300 nm. The scanning TEM mapping analysis was shown to confirm the Ce doping and the location of the Ce ion doping in the nanowhiskers. The electrochemical characterization of the nanowhiskers does not show any sufficient response because of the poor electrical conductivity of the nanowhiskers.     

Rational design of interfacial properties of ferric (hydr)oxide nanoparticles by adsorption of fatty acids from aqueous solutions

Notwithstanding the great practical importance, still open are the questions how, why, and to what extent the size, morphology, and surface charge of metal (hydr)oxide nanoparticles (NPs) affect the adsorption form, adsorption strength, surface density, and packing order of organic (bio)molecules containing carboxylic groups. In this article, we conclusively answer these questions for a model system of ferric (hydr)oxide NPs and demonstrate applicability of the established relationships to manipulating their hydrophobicity and dispersibility. Employing in situ Fourier transform infrared (FTIR) spectroscopy and adsorption isotherm measurements, we study the interaction of 150, 38, and 9 nm hematite (α-Fe(2)O(3)) and ～4 nm 2-line ferrihydrite with sodium laurate (dodecanoate) in water. We discover that, independent of morphology, an increase in size of the ferric (hydr)oxide NPs significantly improves their adsorption capacity and affinity toward fatty acids. This effect favors the formation of bilayers, which in turn promotes dispersibility of the larger NPs in water. At the same time, the local order in self-assembled monolayer (SAM) strongly depends on the morphological compatibility of the NP facets with the geometry-driven well-packed arrangements of the hydrocarbon chains as well as on the ratio of the chemisorbed to the physically adsorbed carboxylate groups. Surprisingly, the geometrical constraints can be removed, and adsorption capacity can be increased by negatively polarizing the NPs due to promotion of the outer-sphere complexes of the fatty acid. We interpret these findings and discuss their implications for the nanotechnological applications of surface-functionalized metal (hydr)oxide NPs.