Physical gelation of binary mixtures of hydrocarbons mediated by n-lauroyl-L-alanine and characterization of their thermal and mechanical properties

Fatty acid amides, such as n-lauroyl-L-alanine, gelate both aliphatic and aromatic hydrocarbon solvents efficiently. In addition this compound is found to gelate the binary solvent mixtures comprised of aromatic hydrocarbon, e.g., toluene and aliphatic hydrocarbons, e.g., n-heptane. Scanning electron microscopy and atomic force microscopy show that the fiber thickness of the gel assembly increases progressively in the binary mixture of n-heptane and toluene with increasing percentage of toluene. The self-assembly patterns of the gels in individual solvents, n-heptane and toluene, are however different. The toluene gel consists of predominantly one type of morphological species, while n-heptane gel has more than one species leading to the polymorphic nature of the gel. The n-heptane gel is thermally more stable than the toluene gel as evident from the measurement using differential scanning calorimetry. The thermal stability of the gels prepared in the binary mixture of n-heptane and toluene is dependent on the composition of solvent mixture. Rheology of the gels shows that they are shear-thinning material and show characteristic behavior of soft viscoelastic solid. For the gels prepared from binary solvent mixture of toluene and n-heptane, with incorporation of more toluene in the binary mixture, the gel becomes a more viscoelastic solid. The time sweep rheology experiment demonstrates that the gel made in n-heptane has faster gel formation kinetics than that prepared in toluene.     

Synthesis of a tetrasaccharide related to the triterpenoid saponin Bellisoside isolated from Bellis perennis (compositae)

A concise synthesis of a tetrasaccharide related to the triterpenoid saponins Bellisoside has been accomplished from commercially available monosaccharides through rational protecting group manipulations and stereoselective glycosylations. For the glycosylation reactions, H₂SO₄–silica has been successfully used as an alternative to conventional Lewis acids such as TfOH or TMSOTf. The target tetrasaccharide has been synthesized in the form of its p-methoxyphenyl glycoside which leaves scope for further glyco-conjugate formation through the selective deprotection of p-methoxyphenyl glycoside followed by trichloroacetimidate chemistry.     

The first examples of terminally thiol‐functionalized alkoxycyanobiphenyls

In this communication, we report the synthesis of the first examples of terminally thiol‐functionalized alkoxycyanobiphenyls. The thermal behaviour of these mesogens and their intermediates was investigated by polarizing optical microscopy, differential scanning calorimetry and X‐ray diffractometry.     

Composite lifting of group inequalities and an application to two-row mixing inequalities

Given a valid inequality for the mixed integer infinite group relaxation, a composite lifting approach that combines sequential lifting and the use of a fill-in function is proposed that can be used to strengthen this inequality. Properties of this composite lifting such as bounds on the solution of the lifting problem and some necessary conditions for the lifted inequality to be minimal for the mixed integer infinite group relaxation are presented. Finally, this composite lifting approach is used to generate a strengthened version of the two-row mixing inequality that provides a new class of extreme inequalities for the two-row mixed integer infinite group relaxation.     

Chalcogels: porous metal-chalcogenide networks from main-group metal ions. Effect of surface polarizability on selectivity in gas separation

We report the synthesis of metal-chalcogenide gels and aerogels from anionic chalcogenide clusters and linking metal ions. Metal ions such as Sb(3+) and Sn(2+), respectively chelated with tartrate and acetate ligands, react in solution with the chalcogenide clusters to form extended polymeric networks that exhibit gelation phenomena. Chalcogenide cluster anions with different charge densities, such as [Sn(2)S(6)](4-) and [SnS(4)](4-), were employed. In situ rheological measurements during gelation showed that a higher charge density on the chalcogenide cluster favors formation of a rigid gel network. Aerogels obtained from the gels after supercritical drying have BET surface areas from 114 to 368 m(2)/g. Electron microscopy images coupled with nitrogen adsorption measurements showed the pores are micro (below 2 nm), meso (2-50 nm), and macro (above 50 nm) regions. These chalcogels possess band gaps in the range of 1.00-2.00 eV and selectively adsorb polarizable gases. A 2-fold increase in selectivity toward CO(2)/C(2)H(6) over H(2) was observed for the Pt/Sb/Ge(4)Se(10)-containing aerogel compared to aerogel containing Pt(2)Ge(4)S(10). The experimental results suggest that high selectivity in gas adsorption is achievable with high-surface-area chalcogenide materials containing heavy polarizable elements.     

Proteomic evaluation and location of UVB-induced photo-oxidation in wool

Photo-oxidation of proteinaceous fibres correlates directly to lowered appearance retention and performance, with particular commercial significance for wool and human hair. We here outline the first detailed proteomic evaluation of differential photo-oxidation occurring in the cuticle and cortex of wool fibres.After exposure of whole wool to UVB irradiation, physical disruption techniques designed to minimise further oxidative modification were utilised to prepare enriched cuticle and cortex fractions. This was followed by comprehensive redox proteomic analyses of photo-oxidation via the location within the fibre components of modifications to aromatic residues. An oxidative classification system was developed and applied to provide further insight into differential photo-oxidation. These results were compared with coloration changes observed within the cuticular and cortical components of the fibre.In this study, although the cuticle was observed to have a higher level of baseline oxidation, the cortex exhibited significantly higher levels of photo-oxidation under UVB irradiation. These proteomic results were supported by the observation of significantly higher photoyellowing within the cortex than within the cuticle. It has been assumed that fibre photo-oxidation was predominantly confined to the wool cuticle, and that changes within the cuticle had the greatest effect on appearance retention. These results provide new insight into the contribution of the cortex to photo-induced discoloration of proteinaceous animal fibres.     

Role of Capping Ligands on the Nanoparticles in the Modulation of Properties of a Hybrid Matrix of Nanoparticles in a 2D Film and in a Supramolecular Organogel

We incorporate various gold nanoparticles (AuNPs) capped with different ligands in two‐dimensional films and three‐dimensional aggregates derived from N‐stearoyl‐L ‐alanine and N‐lauroyl‐L ‐alanine, respectively. The assemblies of N‐stearoyl‐L ‐alanine afforded stable films at the air–water interface. More compact assemblies were formed upon incorporation of AuNPs in the air–water interface of N‐stearoyl‐L ‐alanine. We then examined the effects of incorporation of various AuNPs functionalized with different capping ligands in three‐dimensional assemblies of N‐lauroyl‐L ‐alanine, a compound that formed a gel in hydrocarbons. The profound influence of nanoparticle incorporation into physical gels was evident from evaluation of various microscopic and bulk properties. The interaction of AuNPs with the gelator assembly was found to depend critically on the capping ligands protecting the Au surface of the gold nanoparticles. Transmission electron microscopy (TEM) showed a long‐range directional assembly of certain AuNPs along the gel fibers. Scanning electron microscopy (SEM) images of the freeze‐dried gels and nanocomposites indicate that the morphological transformation in the composite microstructures depends significantly on the capping agent of the nanoparticles. Differential scanning calorimetry (DSC) showed that gel formation from sol occurred at a lower temperature upon incorporation of AuNPs having capping ligands that were able to align and noncovalently interact with the gel fibers. Rheological studies indicate that the gel–nanoparticle composites exhibit significantly greater viscoelasticity compared to the native gel alone when the capping ligands are able to interact through interdigitation into the gelator assembly. Thus, it was possible to define a clear relationship between the materials and the molecular‐level properties by means of manipulation of the information inscribed on the NP surface.     

Green synthesis of silver nanoparticles using seed extract of Jatropha curcas

An eco-friendly process for rapid synthesis of silver nanoparticles has been reported using aqueous seed extract of Jatropha curcas. Formation of stable silver nanoparticles at different concentration of AgNO₃ gives mostly spherical particles with diameter ranging from 15 to 50 nm. The resulting silver particles are characterized using HRTEM, XRD and UV–vis spectroscopic techniques. XRD study shows that the particles are crystalline in nature with face centered cubic geometry.     

A new approach by two‐dimensional wavelets operational matrix method for solving variable‐order fractional partial integro‐differential equations

In this paper, a new computational scheme based on operational matrices (OMs) of two‐dimensional wavelets is proposed for the solution of variable‐order (VO) fractional partial integro‐differential equations (PIDEs). To accomplish this method, first OMs of integration and VO fractional derivative (FD) have been derived using two‐dimensional Legendre wavelets. By implementing two‐dimensional wavelets approximations and the OMs of integration and variable‐order fractional derivative (VO‐FD) along with collocation points, the VO fractional partial PIDEs are reduced into the system of algebraic equations. In addition to this, some useful theorems are discussed to establish the convergence analysis and error estimate of the proposed numerical technique. Furthermore, computational efficiency and applicability are examined through some illustrative examples.