New Q matrices and their functional equations for the eight vertex model at elliptic roots of unity

The Q matrix invented by Baxter in 1972 to solve the eight vertex model at roots of unity exists for all values of N, the number of sites in the chain, but only for a subset of roots of unity. We show in this paper that a new Q matrix, which has recently been introduced and is non zero only for N even, exists for all roots of unity. In addition we consider the relations between all of the known Q matrices of the eight vertex model and conjecture functional equations for them.Comment: 20 pages, 2 Postscript figure

Halide Control of N,N-Coordination versus N,C-Cyclometalation and Stereospecific Phenyl Ring Deuteration of Osmium(II) p-Cymene Phenylazobenzothiazole Complexes

YesWe report the synthesis of halido Os(II) p-cymene complexes bearing bidentate chelating phenylazobenzothiazole (AZBTZ) ligands. Unlike the analogous phenylazopyridine (AZPY) complexes, AZBTZ-NMe2 is capable of both N,N-coordination to Os(II) and cyclometalation to form N,C-coordinated species. N,C-Coordination occurs via an azo nitrogen and an ortho carbon on the aniline ring, as identified by 1H NMR and X-ray crystallography of [Os(p-cym)(N,N-AZBTZ-NMe2)Cl]PF6 (1a), [Os(p-cym)(N,N-AZBTZ-NMe2)Br]PF6 (2a), [Os(p-cym)(N,C-AZBTZ-NMe2)Br] (2b), and [Os(p-cym)(N,C-AZBTZ-NMe2)I] (3b). The N,C-coordinated species is more stable and is not readily converted to the N,N-coordinated complex. Analysis of the crystal structures suggests that their formation is influenced by steric interactions between the p-cym and AZBTZ-NMe2 ligands: in particular, larger monodentate halide ligands favor N,C-coordination. The complexes [Os(p-cym)(N,N-Me2-AZBTZ-NH2)Cl]PF6 (4) and [Os(p-cym)(N,N-Me2-AZBTZ-NH2)I]PF6 (5) were synthesized with methyl groups blocking the ortho positions on the aniline ring, forcing an N,N-coordination geometry. 1H NMR NOE experiments confirmed hindered rotation of the arene ligand and steric crowding around the metal center. Complex 2b exhibited unexpected behavior under acidic conditions, involving regiospecific deuteration of the aniline ring at the meta position, as observed by 1H NMR and high-resolution ESI-MS. Deuterium exchange occurs only under acidic conditions, suggesting an associative mechanism. The calculated partial charges on 2b show that the meta carbon is significantly more negatively charged, which may account for the regiospecificity of deuterium exchange.ERC, EPSRC, The Royal Societ

Exploiting topology-directed nanoparticle disassembly for triggered drug delivery

YesThe physical properties of cyclic and linear polymers are markedly different; however, there are few examples which exploit these differences in clinical applications. In this study, we demonstrate that self-assemblies comprised of cyclic-linear graft copolymers are significantly more stable than the equivalent linear-linear graft copolymer assemblies. This difference in stability can be exploited to allow for triggered disassembly by cleavage of just a single bond within the cyclic polymer backbone, via disulfide reduction, in the presence of intracellular levels of l-glutathione. This topological effect was exploited to demonstrate the first example of topology-controlled particle disassembly for the controlled release of an anti-cancer drug in vitro. This approach represents a markedly different strategy for controlled release from polymer nanoparticles and highlights for the first time that a change in polymer topology can be used as a trigger in the design of delivery vehicles. We propose such constructs, which demonstrate disassembly behavior upon a change in polymer topology, could find application in the targeted delivery of therapeutic agents.ERC are acknowledged for support to M.C.A., A.P.D. (grant number: 681559) and R.O.R. (grant number: 615142)

Fabrication of crystals from single metal atoms

YesMetal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15 Å in diameter, within 1 h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium–osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms.We thank the Leverhulme Trust (Early Career Fellowship No. ECF-2013-414 to NPEB), the University of Warwick (Grant No. RDF 2013-14 to NPEB), the Swiss National Science Foundation (Grant No. PA00P2_145308 to NPEB and PBNEP2_142949 to APB), the ERC (Grant No. 247450 to PJS), EPSRC (EP/G004897/1 to RKOR, and EP/F034210/1 to PJS) and Science City (AWM/ERDF) for support. We thank the Wellcome Trust (Grant No. 055663/Z/98/Z) for funding the Electron Microscopy Facility, School of Life Sciences, University of Warwick. We also thank COST Action CM1105 for stimulating discussions, Thomas Wilks for supplying the micelle image for Figure 1, and the Australian Synchrotron and the University of Monash for allocation of time on the SAXS/ WAXS beamline and funding. The 2000FX Gatan Orius digital TEM camera used in this research was funded by Science City: Creating and Characterizing Next Generation Advanced Materials, with support from Advantage West Midlands and part funded by the European Regional Development Fund

Unified concepts for understanding and modelling turnover of dissolved organic matter from freshwaters to the ocean: the UniDOM model

The transport of dissolved organic matter (DOM) across the land-ocean-aquatic continuum (LOAC), from freshwater to the ocean, is an important yet poorly understood component of the global carbon budget. Exploring and quantifying this flux is a significant challenge given the complexities of DOM cycling across these contrasting environments. We developed a new model, UniDOM, that unifies concepts, state variables and parameterisations of DOM turnover across the LOAC. Terrigenous DOM is divided into two pools, T1 (strongly-UV-absorbing) and T2 (non- or weakly-UV-absorbing), that exhibit contrasting responses to microbial consumption, photooxidation and flocculation. Data are presented to show that these pools are amenable to routine measurement based on specific UV absorbance (SUVA). In addition, an autochtonous DOM pool is defined to account for aquatic DOM production. A novel aspect of UniDOM is that rates of photooxidation and microbial turnover are parameterised as an inverse function of DOM age. Model results, which indicate that ~5% of the DOM originating in streams may penetrate into the open ocean, are sensitive to this parameterisation, as well as rates assigned to turnover of freshly produced DOM. The predicted contribution of flocculation to DOM turnover is remarkably low, although a mechanistic representation of this process in UniDOM was considered unachievable because of the complexities involved. Our work highlights the need for ongoing research into the mechanistic understanding and rates of photooxidation, microbial consumption and flocculation of DOM across the different environments of the LOAC, along with the development of models based on unified concepts and parameterisations

Workplace productivity and office type: an evaluation of office occupier differences based on age and gender

Purpose Open plan office environments are considered to offer workplace productivity benefits because of the opportunities that they create for interaction and knowledge exchange, but more recent research has highlighted noise, distraction and loss of privacy as significant productivity penalties with this office layout. This study aims to investigate if the purported productivity benefits of open plan outweigh the potential productivity penalties. Design/methodology/approach Previous research suggests that office environments are experienced differently according to the gender and age of the occupier across both open-plan and enclosed configurations. Empirical research undertaken with office occupiers in the Middle East (N=220) led to evaluations to establish the impact different offices had on perceived productivity. Factor analysis was used to establish five underlying components of office productivity. The five factors are subsequently used as the basis for comparison between office occupiers based on age, gender and office type. Findings This research shows that benefits and penalties to workplace productivity are experienced equally across open-plan and enclosed office environments. The greatest impact on perceived workplace productivity however was availability of a variety of physical layouts, control over interaction and the 'downtime' offered by social interaction points. Male occupiers and those from younger generations were also found to consider the office environment to have more of a negative impact on their perceived workplace productivity compared to female and older occupiers. Originality/value The originality of this paper is that it develops the concept of profiling office occupiers with the aim of better matching office provision. This paper aims to establish different occupier profiles based on age, gender and office type. Data analysis techniques such as factor analysis and t-test analysis identify the need for different spaces so that occupiers can choose the most appropriate space to best undertake a particular work task. In addition, it emphasises the value that occupiers place on ‘downtime’ leading to the need for appropriate social space

The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles

In the G0 experiment, performed at Jefferson Lab, the parity-violating elastic scattering of electrons from protons and quasi-elastic scattering from deuterons is measured in order to determine the neutral weak currents of the nucleon. Asymmetries as small as 1 part per million in the scattering of a polarized electron beam are determined using a dedicated apparatus. It consists of specialized beam-monitoring and control systems, a cryogenic hydrogen (or deuterium) target, and a superconducting, toroidal magnetic spectrometer equipped with plastic scintillation and aerogel Cerenkov detectors, as well as fast readout electronics for the measurement of individual events. The overall design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method

Optic nerve head and retinal abnormalities associated with congenital fibrosis of the extraocular muscles

Congenital fibrosis of the extraocular muscles (CFEOM) is a congenital cranial dysinnervation disorder caused by developmental abnormalities affecting cranial nerves/nuclei innervating the extraocular muscles. Autosomal dominant CFEOM arises from heterozygous missense mutations of KIF21A or TUBB3. Although spatiotemporal expression studies have shown KIF21A and TUBB3 expression in developing retinal ganglion cells, it is unclear whether dysinnervation extends beyond the oculomotor system. We aimed to investigate whether dysinnervation extends to the visual system by performing high-resolution optical coherence tomography (OCT) scans characterizing retinal ganglion cells within the optic nerve head and retina. Sixteen patients with CFEOM were screened for mutations in KIF21A, TUBB3, and TUBB2B. Six patients had apparent optic nerve hypoplasia. OCT showed neuro-retinal rim loss. Disc diameter, rim width, rim area, and peripapillary nerve fiber layer thickness were significantly reduced in CFEOM patients compared to controls (p < 0.005). Situs inversus of retinal vessels was seen in five patients. Our study provides evidence of structural optic nerve and retinal changes in CFEOM. We show for the first time that there are widespread retinal changes beyond the retinal ganglion cells in patients with CFEOM. This study shows that the phenotype in CFEOM extends beyond the motor nerves