On Schreier graphs of gyrogroup actions

The notion of a group action can be extended to the case of gyrogroups. In this article, we examine a digraph and graph associated with a gyrogroup action on a finite nonempty set, called a Schreier digraph and graph. We show that algebraic properties of gyrogroups and gyrogroup actions such as being gyrocommutative, being transitive, and being fixed-point-free are reflected in their Schreier digraphs and graphs. We also prove graph-theoretic versions of the three fundamental theorems involving actions: the Cauchy–Frobenius lemma (also known as the Burnside lemma), the orbit-stabilizer theorem, and the orbit decomposition theorem. Finally, we make a connection between gyrogroup actions and actions of symmetric groups by evaluation via Schreier digraphs and graphs.     

Vinylogous dieckmann condensation: an application of Baldwin's rules.

Vinylogous Dieckmann condensations equivalent to enolexo-exo-trig and enolendo-exo-trig cyclisations have been investigated. Five membered rings were smoothly obtained from the former whereas the latter cyclisations occurred with six but not with five membered ring systems.     

Flow injection dialysis for the determination of anions using ion chromatography

Flow injection dialysis (FID) coupling with ion chromatography (IC) is proposed for simultaneous determination of some anions (bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate). A standard or sample containing the anions is injected into a donor stream of a mixture (0.022 M Na(2)CO(3) and 0.028 M NaHCO(3)) flowing into a dialysis cell. The bolus of the dialysate containing the anions, in the acceptor stream of water, flows to the IC injection valve where a portion of the bolus is injected into the IC and analysed under normal IC conditions, with a conductivity detector. FID provides on-line separation and dilution of the analytes from matrix especially from some species such as proteins, surfactant, particulates which may cause damage to the IC columns. Prolongation of life-time of the IC columns is an additional advantage to others which will be discussed. On-line dialysis-IC was also investigated.     

15β-Hydroxylation of Lithocholic Acid by cunninghamella sp.

The microbiological transformation of lithocholic acid (3α-hydroxy-5β-cholanic acid) into 3α, 15β-dihydroxy-5β-cholanic acid by Cunninghamella sp. is Investigated. The structure has been determined on the basis of two-dimensional ¹H-NMR.     

The co-solubility of 2-ethylhexanoic acid and some liquid alcohols in supercritical carbon dioxide

The co-solubility in supercritical carbon dioxide of 1-butanol, 1-pentanol, 2-ethyl-1-hexanol, or 1-decanol in the presence of 2-ethylhexanoic acid in the pressure range of 100–180 bar and at 313 or 323 K was measured. The solubility of these alcohols in the presence of 2-ethylhexanoic acid is lower than in the systems alcohol + CO₂ and remains nearly constant in the pressure range of 120–180 bar, with the exception of 1-decanol. The lower selectivities in the ternary systems are explained by strong intermolecular hydrogen bonding between alcohol molecules and 2-ethylhexanoic acid molecules. The FT-IR spectra of mixtures of alcohols and 2-ethylhexanoic acid at a 1:1 mole ratio in the liquid CCl₄ confirmed this conclusion.     

Prevulcanisation of skim latex: morphology and its use in natural rubber based composite material

The prevulcanisation of skim latex, a by-product of field natural rubber (NR) latex concentrated by centrifugation, using sulphur and peroxide systems was investigated. Compared to the peroxide prevulcanisation, the lower swelling ratio of film casted from sulphur-prevulcanised skim (SPVS) latex was observed. The latter was then employed for preparation of NR/SPVS core–shell particles by using heterocoagulation technique whose driving force was an interpolymer complex between poly(ethylene oxide) (PEO) moieties of a non-ionic surfactant (Nonidet) adsorbed on small SPVS particles and the indigenous surfactant (protein–lipid) on a large NR particle. The value of zeta potential of heterocoagulated particle and the better oil resistance of films casted from the composite latex when compared to that of the NR film revealed the NR/SPVS core–shell structure.     

Parallel and multiplexed bead-based assays and encoding strategies

Advances in high throughput screening (HTS), together with the rapid progress in combinatorial chemistry, genomic and proteomic sciences have dramatically stimulated the development of a variety tools to enable the drug discovery process to become more efficient. Major future challenges in HTS include obtaining high density and good quality data based on assays that are rapid, reliable, inexpensive, sensitive, simple and miniaturised. This paper reviews the development and role of bead-based assays for HTS including DNA and single nucleotide polymorphism (SNP) assays, particularly from a multiplex perspective and evaluating the recent advances in bead-based arrays. The encoding strategies that are commonly used in bead-based assays are highlighted, while the importance of magnetic beads in genomic and proteomic purifications is discussed. In conclusion, bead-based assays offer a powerful promising approach for many aspects of drug discovery.     

Aspartame degradation study using electrospray ionization mass spectrometry

Electrospray mass spectrometry was used to simultaneously determine aspartame (APM) and five of its degradation products; aspartic acid, aspartylphenylalanine, 5-benzyl-3,6-dioxo-2-piperazieacetic acid (diketopiperazine), phenylalanine, and phenylalanine methyl ester. Under the ionization conditions used, there was no interfering fragmentation for any of the six compounds, i.e., no fragmentation of the compound being tested into other species also being monitored. A study of APM degradation in solution at various pH's and at various temperatures using this method was performed.     

Metal-support interaction in mesoporous silica supported cobalt Fischer-Tropsch catalysts

Summary The pore structure of silica supports (SiO₂ or MCM-41) has little influence on the metal-support interaction in silica supported cobalt catalysts. Cobalt dispersion, reduction behavior, and catalytic properties for the Fischer-Tropsch synthesis were primarily affected by the metal particle size.     

Preparation and characterization of inclusion complexes containing fixolide, a synthetic musk fragrance and cyclodextrins

AHTN (7-Acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene), commercially known as fixolide or tonalide, is a synthetic fragrance widely used in replace of natural musk odor which is more expensive. It is a popular fragrance material added in the manufacturing of personal care and household products, such as perfumes, soaps, shampoos, detergents, and fabric softeners. AHTN is semivolatile and is degraded under light exposure and high temperature. This work focuses on the complexation of AHTN with cyclodextrins in the effort to stabilize the fragrance material. AHTN was complexed with β-cyclodextrin, methyl (MβCD), and hydroxypropyl (HPβCD) derivatives in the mole ratio 1:1, 1:2, and 1:3 guest:host, and the complexes formed by physical mixing, co-precipitation, kneading, and freeze-drying were analyzed by DSC and FTIR. Percent AHTN included in the complex was also determined by hexane extraction and GC analysis. It was found that no inclusion complex was formed in the physical mixture. When co-precipitation method was performed, only βCD could form inclusion complex with AHTN, while the other two derivatives could not. Using 1:2 AHTN:βCD, no free AHTN was left in the complex as evidenced by DSC and FTIR spectrum. In kneading and freeze-drying methods, complexes could be formed with all CDs tested. However, co-precipitation method with 1:2 AHTN:βCD and kneading method with 1:2 AHTN:MβCD provided the highest complex yield with highest amount of AHTN included in the complex. AHTN in the complex form was more stable against high temperature and UV exposure than its free form.