Uniqueness of the inversive plane of order 7

A search has shown that any inversive plane of order 7 must be isomorphic with the Miquelian plane. The method used was explicitly set out in a companion paper, which was concerned with a plane of order 5.     

Recent results on the spin structure of the nucleon

The process of polarised deep inelastic scattering and the information it has given on the spin structure of the nucleon are introduced. The experimental programmes in this field are described and the latest inclusive and semi-inclusive data and analyses are reviewed. Proposed future measurements are summarised.     

(–)‐2‐(1,2,3,4,4a,5,6,7,8,8aα‐Decahydro‐4aβ,8α‐dimethyl‐7‐oxo‐2β‐naphthyl)propionic acid: catemeric hydrogen bonding in a bicyclic sesquiterpenoid ζ‐keto acid

In the title compound, C₁₅H₂₄O₃, derived from a naturally occurring sesquiterpenoid, the asymmetric unit consists of two mol­ecules differing by 167.4 (8)° in the rotational conformation of the carboxyl group. Each molecule aggregates separately with its own type as carboxyl‐to‐ketone hydrogen‐bonding catemers [O⋯O = 2.715 (6) and 2.772 (6) Å, and O—H⋯O = 169 and 168°]. This generates two crystallographically independent single‐strand hydrogen‐bonding helices passing through the cell in the b direction, with opposite end‐to‐end orientations. One intermolecular C—H⋯O=C close contact exists for the carboxyl group of one of the mol­ecules. The structure is isostructural with that of a closely related unsaturated keto acid reported previously.     

The characterisation of a novel, covalently modified, amphiphilic alginate derivative, which retains gelling and non-toxic properties

The characterisation of a novel amphiphilic material, Alg-C4, produced from butanol linked by esterification to alginate is presented. The novel derivative retains the gelling and non-toxic properties of native alginate. FTIR spectra of Alg-C4 contained the characteristic hydroxyl and carboxyl bands, but also featured additional peaks at 1736 and 1134 cm(-1), indicating the presence of ester bonds. NMR studies showed the presence of butyl groups. The endothermic peak and exothermic peak present in the DSC thermogram of native alginate were also apparent in the Alg-C4 thermogram, but had shifted to lower temperatures (from 106 to 87 degrees C and from 254 to 247 degrees C, respectively). In addition, the exothermic peak was significantly reduced for Alg-C4 (5 mW compared to 20 mW in native alginate). Scanning electron microscopy was used to examine surface topography. The native alginate beads appeared smooth while Alg-C4 beads had a different, rougher appearance. Using circular dichroism it was found that the ratio of mannuronic to guluronic residues in the Alg-C4 was markedly increased compared to the native alginate (1.33 to 2.47), suggesting the preferential esterification of butanol to the guluronic residues. Exposure of ovarian granulosa cells in vitro to the Alg-C4 material demonstrated that granulosa cell viability (MTT test) was unchanged when compared to native alginate, which is regarded as non-toxic. The novel material is very stable, giving identical FTIR, DSC and gelling performance after 12 months storage at temperatures ranging from 10 to 20 degrees C. The data support the successful preparation of a stable modified alginate with characteristic hydrophilic properties and, in addition, a novel hydrophobic character.     

Colloidal synthesis of wurtzite Cu2ZnSnS4 nanorods and their perpendicular assembly

The quaternary copper chalcogenide Cu(2)ZnSnS(4) is an important emerging material for the development of low-cost and sustainable solar cells. Here we report a facile solution synthesis of stoichiometric Cu(2)ZnSnS(4) in size-controlled nanorod form (11 nm × 35 nm). The monodisperse nanorods have a band gap of 1.43 eV and can be assembled into perpendicularly aligned arrays by controlled evaporation from solution.     

Identifying and localizing intracellular nanoparticles using Raman spectroscopy

Raman microscopy is employed to spectroscopically image biological cells previously exposed to fluorescently labelled polystyrene nanoparticles and, in combination with K-means clustering and principal component analysis (PCA), is demonstrated to be capable of localising the nanoparticles and identifying the subcellular environment based on the molecular spectroscopic signatures. The neutral nanoparticles of 50 nm or 100 nm, as characterised by dynamic light scattering, are shown to be non-toxic to a human lung adenocarcinoma cell-line (A549), according to a range of cytotoxicity assays including Neutral Red, Alamar Blue, Coomassie Blue and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Confocal fluorescence microscopy identifies intracellular fluorescence due to the nanoparticle exposure, but the fluorescence distribution is spatially diffuse, potentially due to detachment of the dye from the nanoparticles, and the technique fails to unambiguously identify the distribution of the nanoparticles within the cells. Raman spectroscopic mapping of the cells in combination with K-means cluster analysis is used to clearly identify and localise the polystyrene nanoparticles in exposed cells, based on their characteristic spectroscopic signatures. PCA identifies the local environment as rich in lipidic signatures which are associated with localisation of the nanoparticles in the endoplasmic reticulum. The importance of optimised cell growth conditions and fixation processes is highlighted. The preliminary study demonstrates the potential of the technique to unambiguously identify and locate nonfluorescent nanoparticles in cells and to probe not only the local environment but also changes in the cell metabolism which may be associated with cytotoxic responses.