Confined subgroups in periodic simple finitary linear groups

A subgroupX of the locally finite groupG is said to beconfined, if there exists a finite subgroupF≤G such thatX ^g∩F≠1 for allg∈G. Since there seems to be a certain correspondence between proper confined subgroups inG and non-trivial ideals in the complex group algebra ℂG, we determine the confined subgroups of periodic simple finitary linear groups in this paper. Dedicated to the memory of our friend and collaborator Richard E. Phillips     

Intumescent flame retardants for polymers. IV. The polycarbonate–aromatic sulfonates system

The mechanism of action of aromatic sulfonates as flame retardant (FR) agents on poly(bisphenol-A carbonate) (PC) has been investigated. These compounds are capable of inducing a self-extinguence in PC even when present in very low amounts (0.2–1%). Thermogravimetric and flash pyrolysis–GC–MS data show the thermal degradation rate of PC enhanced, and the distribution of the volatile pyrolysis products was modified by these additives. Oxygen Index (OI) and Nitrous Oxide Index (NOI) measurements indicate a FR condensed-phase mechanism of these additives. Traces of polymer surface temperature against time, measured under forced flame conditions, show that the expanded carbon layer formed in the combustion of polycarbonate–aromatic sulfonate blends produces a heat insulating effect toward the undecomposed bulk. The overall evidence leads us to conclude that aromatic sulfonates cause the flame extinguishment in polycarbonate by an intumescent phenomenon.     

Synthesis and NMR characterization of beta-alanine-bridged hemispherodextrin, a very efficient chiral selector in EKC

A capped derivative of beta-CD (THALAH) was synthesized and characterized by NMR spectroscopy at different pH values. A trehalose moiety, bonded through beta-alanine bridges to the CD cavity, is included in the capping unit, giving peculiar properties to this molecule. The hemispherodextrin thus obtained was tested as a chiral selector in EKC. At neutral pH, the monocationic species of THALAH behaves as a very efficient selector separating successfully all the 11 tested enantiomeric pairs of dansyl-derivatives of amino acids, some of them even at concentrations as low as 0.15 mM. The differences observed in the migration order among the different systems give suggestions about the mechanism of molecular recognition between the selector and the analytes.     

Terahertz probe of individual subwavelength objects in a water environment

Terahertz (THz) spectroscopy and imaging have been heralded for some time as potentially revolutionary techniques for biomedical applications. Label‐free detection of molecules and recognition of molecular events are often mentioned as the most exciting possibilities. A crucial practical goal, however, is the ability to perform such measurements on tiny amounts of biological fluids or even on individual organic structures. Living cells, for instance, have diameters at most of some tens of micrometers, i.e. at least λ/10 even for few‐THz radiation. Furthermore, all analyses relevant for a biological perspective must be performed in a water environment, which presents a strong absorption across the whole THz spectral range, severely limiting the penetration of the electromagnetic field. Here, it is shown how both issues can be overcome with a lab‐on‐a‐chip approach based on a microfluidic platform coupled to a plasmonic antenna. Using a quantum cascade laser as THz illumination source, liquid volumes down to the picoliter range are probed, and direct operation on individual 10‐µm diameter microparticles flowing in water is shown. The present demonstration opens the way to the development of THz biosensing of individual living cells and small probe volumes.     

A new inclusion complex of amlodipine besylate and soluble β-cyclodextrin polymer: preparation, characterization and dissolution profile

Amlodipine besylate (AML) has become the most popular blood pressure medication for hypertensive pets. It belongs to the class I (high solubility and high permeability) according to BCS and is marketed in Europe only as white tablets equivalent to 2.5, 5.0 and 10.0 mg of amlodipine for oral administration. Unfortunately, oral AML dosage for cats and dogs is in the range 0.1–0.2 and 0.625–0.125 mg/kg/die respectively. Moreover, AML shows a slight solubility in water according to Ph. Eur. 7°. According to these considerations, the aim of this work was the complexation between soluble β-cyclodextrin polymer (CD) and AML using the solubilization/freeze-dried method to obtain powders easily dosable and soluble in water for the treatment of hypertension in pets. The complex in solution was evaluated by phase solubility studies that indicated the optimal 2:1 drug/CD ratio to form a stable complex. UV–Vis absorption and circular dichroism showed the formation of a complex with a weak bond such as confirmed by differential scanning calorimetry, infrared spectroscopy and fluorescence microscopy. In vitro dissolution/release tests were performed in water to investigate the influence of formulative parameters on drug dissolution/release properties. The inclusion of AML in CD increased its wettability, dissolution rate and solubility in water. This method could be a suitable approach for the administration of an extemporaneous solution of the antihypertensive drug to guarantee a correct dose to pets increasing the compliance.     

Analysis of poly(bisphenol A carbonate) by size exclusion chromatography/matrix-assisted laser desorption/ionization. 2. self-association due to phenol end groups

We report here a case of apparent failure of the size exclusion chromatography/matrix-assisted laser desorption/ionization (SEC/MALDI) method to provide polymer fractions with narrow molar mass distribution, showing that intermolecular chain association is responsible for this phenomenon. Poly(bisphenol A carbonate) (PC) chains terminated with hydroxyl groups undergo self-association by hydrogen bonding, providing macromolecular aggregates with higher hydrodynamic volume. These aggregates are eluted through SEC columns at the same volume as higher molar mass chains, which remain non-associated. Thus, self-association affects negatively the SEC fractionation experiments, and even the sharpest SEC fractions contain a heterogeneous mixture of PC chains of different size. When the off-line SEC/MALDI procedure is applied, the SEC fraction is diluted in the matrix which, being a dissociating medium (carboxylic acid) for hydrogen-bonded aggregates, suppresses the chains' self-association. Therefore, the MALDI spectra of these PC fractions indicate a polydisperse character, with irregular bimodal distributions of peaks. As a consequence, in the presence of chain association, the SEC/MALDI method for the calculation of molar masses of polymers cannot be directly applied. In the present case we have found that, under opportune experimental conditions, self-association in polycarbonates can be avoided, so that nearly monodisperse SEC fractions can be obtained and the SEC/MALDI method can be applied. Our results also show that MALDI is a very sensitive technique for the detection of association of polymers in dilute solutions. Copyright 1999 John Wiley & Sons, Ltd.     

Thermal Oxidation Products of Nylon 6 Determined by MALDI‐TOF Mass Spectrometry

Matrix‐assisted laser desorption ionisation (MALDI) mass spectrometry was used, in an attempt to find firm evidence for the structure of the species produced in the thermal oxidative degradation of Nylon 6 (Ny6), at 250°C in air. The MALDI spectra of the products showed the presence of polymer chains containing aldehydes, amides, methyl and N‐formamide terminal groups. The aldehydes undergo further oxidation to produce carboxylic end groups. The formation of azomethines, from the further reaction of aldehydes with amino‐terminated Ny6 chains, is also supported by the appearance of specific peaks in the MALDI spectra.     

Immobilized Rose Bengal as Photocatalyst for Metal-Free Thiocyanation of Azaheterocycles under Continuous Flow Conditions

The immobilization of Rose Bengal onto Merrifield resin and its application in the light-driven metal-free thiocyanation of azaheterocycles in continuo were investigated. The supported photocatalyst was used in batch reactions under heterogeneous conditions, with different azaheterocycles, and proved to efficiently promote the reaction. Its recovery and recycle were also demonstrated for up to four times. The resin-supported Rose Bengal was then employed under continuous flow conditions, affording thiocyanate functionalized azaheterocycles with higher space-time-yields than the in-batch transformations, and in a shorter reaction time. The easily modification of the SCN groups was also demonstrated by synthetizing trifluoromethyl thioethers and sulfenyl tetrazoles derivates in high yields.