Theoretical investigation of the scope of sequential ligand tuning using a bifunctional scorpionate tris(1,2,4-triazolyl)borate-based architecture

The donor properties of a series of tripodal mixed N-donor/carbene ligands derived through sequential alkylation of hydrotris(1,2,4-triazolyl)borate have been investigated by density functional theory (DFT) methods. The structures of complexes of the form [Mo(L)(CO)3]- were optimized (L = [HB(1,2,4-triazolyl)n(1,2,4-triazol-5-ylidene)3-n]- (n = 0 – 3), hydrotris(pyrazolyl)borate, hydrotris(3,5-dimethylpyrazolyl)borate and hydrotris(imidazol-2-ylidene)borate) and nuCO frequencies for these complexes and partial charges of their Mo(CO)3 fragments were determined. Results show that ligand donation is highly tunable when compared to similar experimentally known ligands with a shift in the symmetric nuCO stretching mode of -39 cm -1 on going from the tris(1,2,4-triazolyl)borate complexes to that of the triscarbene hydrotris(1,2,4-triazol-5-ylidene) and an increase in partial charge (distributed multipole analysis) of the Mo(CO)3 fragment from -0.23 to -0.48

CO2_2 Infrared Phonon Modes in Interstellar Ice Mixtures

CO$_2$ ice is an important reservoir of carbon and oxygen in star and planet forming regions. Together with water and CO, CO$_2$ sets the physical and chemical characteristics of interstellar icy grain mantles, including desorption and diffusion energies for other ice constituents. A detailed understanding of CO$_2$ ice spectroscopy is a prerequisite to characterize CO$_2$ interactions with other volatiles both in interstellar ices and in laboratory experiments of interstellar ice analogs. We report laboratory spectra of the CO$_2$ longitudinal optical (LO) phonon mode in pure CO$_2$ ice and in CO$_2$ ice mixtures with H$_2$O, CO, O$_2$ components. We show that the LO phonon mode position is sensitive to the mixing ratio of various ice components of astronomical interest. In the era of JWST, this characteristic could be used to constrain interstellar ice compositions and morphologies. More immediately, LO phonon mode spectroscopy provides a sensitive probe of ice mixing in the laboratory and should thus enable diffusion measurements with higher precision than has been previously possible

Singing and COPD: exploring the experiences of people attending a group activity

Aim/objective To understand the lived experiences of participants with COPD attending a singing group. Rationale The research into singing groups for people living with COPD suggests that participants find the groups enjoyable and report it to be beneficial with regards to improving symptoms. However, the quantitative data from a companion paper (Clift, Skingley, Meadows and Dickinson, 2022) are not consistent with these findings and further research is needed to understand the underpinning explanations from the participant perspective. Approach Semi-structured interviews were conducted with five participants who have been diagnosed with COPD, recruited from a singing group designed to support them with breathlessness. Participants were asked about their experiences of living with COPD as well as of the singing programme. An Interpretative Phenomenological Analysis (IPA) approach was applied to the data gathered from these interviews. The Common Sense Model of illness representation was used to inform the analysis. Findings The study identified five explanatory themes: blame and the restrictive impact of COPD, changes in self-efficacy and a sense of control over COPD, positive social connections within the group, positive emotional and cognitive changes during and after the group, and the value of breathing techniques. Discussion and conclusion The participants reported stigma over their condition before the group and that COPD has a restrictive impact on their lives. Following attending the singing group, the participants experienced a change in their attitudes towards their condition, feeling a greater sense of confidence and control over their condition. The participants felt the factors involved in this change were the social connections both with their peers and the group leader, the positive emotional changes during and following the group and the impact of the breathing techniques they were taught. Future work should therefore aim to promote self-efficacy and self-management for participants

Polar orbit electrostatic charging of objects in shuttle wake

A survey of DMSP data has uncovered several cases where precipitating auroral electron fluxes are both sufficiently intense and energetic to charge spacecraft materials such as teflon to very large potentials in the absence of ambient ion currents. Analytical bounds are provided which show that these measured environments can cause surface potentials in excess of several hundred volts to develop on objects in the orbiter wake for particular vehicle orientations

CO diffusion and desorption kinetics in CO2_2 ices

Diffusion of species in icy dust grain mantles is a fundamental process that shapes the chemistry of interstellar regions; yet measurements of diffusion in interstellar ice analogs are scarce. Here we present measurements of CO diffusion into CO$_2$ ice at low temperatures (T=11--23~K) using CO$_2$ longitudinal optical (LO) phonon modes to monitor the level of mixing of initially layered ices. We model the diffusion kinetics using Fick's second law and find the temperature dependent diffusion coefficients are well fit by an Arrhenius equation giving a diffusion barrier of 300 $\pm$ 40 K. The low barrier along with the diffusion kinetics through isotopically labeled layers suggest that CO diffuses through CO$_2$ along pore surfaces rather than through bulk diffusion. In complementary experiments, we measure the desorption energy of CO from CO$_2$ ices deposited at 11-50 K by temperature-programmed desorption (TPD) and find that the desorption barrier ranges from 1240 $\pm$ 90 K to 1410 $\pm$ 70 K depending on the CO$_2$ deposition temperature and resultant ice porosity. The measured CO-CO$_2$ desorption barriers demonstrate that CO binds equally well to CO$_2$ and H$_2$O ices when both are compact. The CO-CO$_2$ diffusion-desorption barrier ratio ranges from 0.21-0.24 dependent on the binding environment during diffusion. The diffusion-desorption ratio is consistent with the above hypothesis that the observed diffusion is a surface process and adds to previous experimental evidence on diffusion in water ice that suggests surface diffusion is important to the mobility of molecules within interstellar ices

On classification of Poisson vertex algebras

We describe a conjectural classification of Poisson vertex algebras of CFT type and of Poisson vertex algebras in one differential variable (= scalar Hamiltonian operators)

Three-dimensional calculation of shuttle charging in polar orbit

The charged particles environment in polar orbit can be of sufficient intensity to cause spacecraft charging. In order to gain a quantitative understanding of such effects, the Air Force is developing POLAR, a computer code which simulates in three dimensions the electrical interaction of large space vehicles with the polar ionospheric plasma. It models the physical processes of wake generation, ambient ion collection, precipitating auroral electron fluxes, and surface interactions, including secondary electron generation and backscattering, which lead to vehicle charging. These processes may be followed dynamically on a subsecond timescale so that the rapid passage through intense auroral arcs can be simulated. POLAR models the ambient plasma as isotropic Maxwellian electrons and ions (0+, H+), and allows for simultaneous precipitation of power-law, energetic Maxwellian, and accelerated Gaussian distributions of electrons. Magnetic field effects will be modeled in POLAR but are currently ignored

Polynomial Construction of Complex Hadamard Matrices with Cyclic Core

Conditions are given which are necessary and sufficient to ensure invariance of an M-sequence under periodic rearrangement. In conjunction with a certain uniformity property of polynomial coefficients, these conditions yield a simple method by which complex Hadamard matrices with cyclic core can be constructed. In such cases, a real p-ary linear cyclic error correcting code may be associated with the complex Hadamard matrix

Error Correcting Codes Associated with Complex Hadamard Matrices

For primes p \u3e 2, the generalized Hadamard matrix H(p,pt) can be expressed as H = xA, where the notation means hij = xaij. It is shown that the row vectors of A represent a p-ary error correcting code. Depending upon the value of t, either linear or nonlinear codes emerge. Code words are equidistant and have minimum Hamming distance d = (p − 1)t. The code can be extended so as to possess N = p2t code words of length pt − 1