Hidden symmetry operators for asymmetric generalized quantum Rabi models

The hidden Z2 symmetry of the asymmetric quantum Rabi model(AQRM)has recently been revealed via a systematic construction of the underlying symmetry operator.Based on the AQRM result,we propose an ansatz for the general form of the symmetry operators for AQRM-related models.Applying this ansatz we obtain the symmetry operator for three models:the anisotropic AQRM,the asymmetric Rabi–Stark model(ARSM),and the anisotropic ARSM.     

Triplet and reversed triplet mechanism CIDEP studied by quenching experiments

Quenching experiments are shown to provide a convenient tool to check for the presence of triplet mechanism (TM) spin polarisation in time-resolved EPR spectra following laser flash photolysis. The effect of the triplet quenchers, trans-1,3-pentadiene, fumaronitrile, azo-tert-butane and azo-n-butane upon the spectra following laser photolysis of acetone/propan-2-ol and benzophenone/propan-2-ol photosystems show that no TM polarisation is present in the former system but emissive TM is present in the latter. Use of 2,2′-azo-bis[isobutryronitrile] produces an anomalous emissive polarisation upon quenching, which is tentatively attributed to a reversed TM in the triplet sensitised azo-compound.     

Electrochemical Detection and Characterisation of Polymer Nanoparticles

We report the detection and characterisation of polymer nanoparticles using electrochemistry using poly(N‐vinylcarbazole) nanoparticles (PVK NPs) as a model system. These were synthesised using the reprecipitation method. The number of electrons (n=2) transferred per PVK monomer was characterised by drop‐casting method. Sticking and sensing experiments were then conducted, which involve PVK nanoparticle immobilisation on the electrode surface and subsequent oxidative sensing, to enable rapid detection of polymer nanoparticles in aqueous solution. It is shown for the first time, that using this “stick and sense” method, polymer nanoparticles in aqueous solution can be immobilised, preconcentrated and quantified.     

Superior non-woven sheet forming characteristics of low-density cationic polymer-cellulose nanofibre colloids

This work examines the addition of cationic polymers, cationic polyacrylamide (CPAM) and polyamide–amine–epichlorohydrin (PAE), to cellulose nanofibres to produce superior forming characteristics. The addition of 2 mg of high MW CPAM/g of nanofibres halved the drainage time to under 1 min at 0.1 wt% solids content due to increasing the floc size and the fibre forming a bulky and porous filter medium during drainage. The more open structure created in the wet state was partially preserved during the drying process, reducing the sheet density from 760 to 680 kg/m³, at the highest level of polymer addition. The addition of CPAM resulted in significant additional bridging between nanofibres, which then substantially increased the non-uniformity of the filter medium. PAE addition at 10 mg/g of micro fibrillated cellulose (MFC), also reduced drainage time, while increasing retention, but without changing the sheet uniformity. Wet strength increased continuously with PAE addition level, reaching 31.6 kN m/kg at the highest level of 20 mg of PAE/g of MFC.     

Ultra‐small Palladium Nanoparticle Decorated Carbon Nanotubes: Conductivity and Reactivity

Carbon nanotubes decorated with ultra‐small metal nanoparticles are of great value in catalysis. We report that individual multiwalled carbon nanotubes decorated with ultra‐small palladium nanoparticles can be detected by using the nano‐impacts method. The high conductivity and reactivity of each decorated carbon nanotube is directly evidenced; this is achieved through studying the proton‐reduction reaction for the underpotential deposition of hydrogen onto the nanoparticles decorated on the carbon nanotube walls. The reductive spikes from current amplification are analyzed to estimate the approximate length of the decorated carbon nanotubes, revealing that the decorated carbon nanotubes are electroactive along its entire length of several micrometers.     

Voltammetric Study of the Influence of Various Phosphate Anions on Silver Nanoparticle Oxidation

The antibacterial properties of silver are strongly controlled by the redox couple of silver/silver(I). This work reports the influence of phosphate anions on silver nanoparticle oxidation, which is important given the abundance of phosphate species in biological systems. The three different species of anions were found to have a varying degree of influence on silver oxidation with the order PO₄³⁻>HPO₄²⁻>H₂PO₄⁻. It was found that in the presence of phosphate anions, the silver oxidation potential shifts to a less positive value, which indicated the increasing ease of the oxidation reaction of silver. Given that the interplay between silver and its cation is crucial to its antibacterial properties and significant concentrations of the HPO₄²⁻ anion are present at biological pH (near neutral), it is essential that the influence of the dibasic anion (HPO₄²⁻) on silver oxidation dynamics be considered for biological systems.     

Measuring comodules — their applications

Measuring comodules are defined and shown to provide a useful generalization of the set of maps between modules with a broad range of applications. Three applications are described. Connections on bundles are described in terms of measuring comodules, enabling curvature to be defined under general algebraic circumstances. Loop algebras are realized via a short exact sequence of measuring comodules, with the central extension given by the curvature. Finally dual comodules provide a method of dualizing representations, which when applied to representations of loop algebras yield positive energy representations, and when applied to representations of totally disconnected groups leads to the smooth dual.     

Surface-sensitive method to determine calcium carbonate filler contents in cellulose matrices

This paper describes a method using attenuated total reflectance infra-red spectroscopy to determine the surface concentration of calcium carbonate in paper samples, by applying the linear relationship between the relative infra-red absorption integrals and the concentration. The method was able to detect micro-variations in the surface concentration and could also distinguish between different sheets as well as between the top and bottom side of one sheet. The samples were also split and the calcium carbonate concentration was determined within and compared to bulk calcium carbonate concentration determined from ash testing. The surface results were also compared with analysed scanning electron microscopy images generated from back-scattering electrons. The comparison shows that both sets of results are in excellent agreement. Depending on the sample, large errors (95% confidence) were observed. These, however, are caused by micro-variations of the surface concentration, rather than by inaccuracies of the technique, which is estimated to be less than 1%. Furthermore, measurements of various sample orientations suggest that anisotropic polarisation effects can be neglected. The method can be applied to paper and cellulose matrices having calcium carbonate filler contents of less than 50%. Due to spectral overlaps it is not suitable to determine kaolin filler contents.