Cassiopeia A: dust factory revealed via submillimetre polarimetry

If Type-II supernovae - the evolutionary end points of short-lived, massive stars - produce a significant quantity of dust (>0.1 M_sun) then they can explain the rest-frame far-infrared emission seen in galaxies and quasars in the first Gyr of the Universe. Submillimetre observations of the Galactic supernova remnant, Cas A, provided the first observational evidence for the formation of significant quantities of dust in Type-II supernovae. In this paper we present new data which show that the submm emission from Cas A is polarised at a level significantly higher than that of its synchrotron emission. The orientation is consistent with that of the magnetic field in Cas A, implying that the polarised submm emission is associated with the remnant. No known mechanism would vary the synchrotron polarisation in this way and so we attribute the excess polarised submm flux to cold dust within the remnant, providing fresh evidence that cosmic dust can form rapidly. This is supported by the presence of both polarised and unpolarised dust emission in the north of the remnant, where there is no contamination from foreground molecular clouds. The inferred dust polarisation fraction is unprecedented (f_pol ~ 30%) which, coupled with the brief timescale available for grain alignment (<300 yr), suggests that supernova dust differs from that seen in other Galactic sources (where f_pol=2-7%), or that a highly efficient grain alignment process must operate in the environment of a supernova remnant.Comment: In press at MNRAS, 10 pages, print in colou

Full stress tensor measurement using colour centres in diamond

Stress and strain are important factors in determining the mechanical, electronic, and optical properties of materials, relating to each other by the material's elasticity or stiffness. Both are represented by second rank field tensors with, in general, six independent components. Measurements of these quantities are usually achieved by measuring a property that depends on the translational symmetry and periodicity of the crystal lattice, such as optical phonon energies using Raman spectroscopy, the electronic band gap using cathodoluminescence, photoelasticity via the optical birefringence, or Electron Back Scattering Diffraction (EBSD). A reciprocal relationship therefore exists between the maximum sensitivity of the measurements and the spatial resolution. Furthermore, of these techniques, only EBSD and off-axis Raman spectroscopy allow measurement of all six components of the stress tensor, but neither is able to provide full 3D maps. Here we demonstrate a method for measuring the full stress tensor in diamond, using the spectral and optical polarization properties of the photoluminescence from individual nitrogen vacancy (NV) colour centres. We demonstrate a sensitivity of order 10 MPa, limited by local fluctuations in the stress in the sample, and corresponding to a strain of about 10^-5, comparable with the best sensitivity provided by other techniques. By using the colour centres as built-in local sensors, the technique overcomes the reciprocal relationship between spatial resolution and sensitivity and offers the potential for measuring strains as small as 10^-9 at spatial resolution of order 10 nm. Furthermore it provides a straightforward route to volumetric stress mapping. Aside from its value in understanding strain distributions in diamond, this new approach to stress and strain measurement could be adapted for use in micro or nanoscale sensors.Comment: 12 pages, 5 figures - supplementary informations included in appendi

Image states in metal clusters

The existence of image states in small clusters is shown, using a quantum-mechanical many-body approach. We present image state energies and wave functions for spherical jellium clusters up to 186 atoms, calculated in the GW approximation, where G is the Green's function and W is the dynamically screened Coulomb interaction, which by construction contains the dynamic long-range correlation effects that give rise to image effects. In addition, we find that image states are also subject to quantum confinement. To extrapolate our investigations to clusters in the mesoscopic size range, we propose a semiclassical model potential, which we test against our full GW results

The effect of adverse employment circumstances on physical pain: Evidence from Australian panel data

Physical pain is a common health problem with great public health implications. Yet evidence on whether adverse employment circumstances shape physical pain is limited. Using longitudinal data from 20 waves (2001−2020) from the Household, Income and Labour Dynamics of Australia Survey (HILDA; N = 23,748), a lagged design, Ordinary Least Squares (OLS) regressions as well as multilevel mixed effect linear regressions, we investigated the association between past accumulated unemployment and recent employment circumstances with physical pain. We found that adults who spent more years unemployed and looking for work subsequently reported greater physical (b = 0.034, 95% CI = 0.023, 0.044) and pain interference (b = 0.031, 95% CI = 0.022, 0.038) than those who spent fewer years unemployed. We also found that those experiencing overemployment (working full-time while wanting to work fewer hours) and underemployment (working part-time while wanting to work more hours) reported greater subsequent physical pain (overemployment: b = 0.024, 95% CI = 0.009, 0.039; underemployment: b = 0.036, 95% CI = 0.014, 0.057) and pain interference (overemployment: b = 0.017, 95% CI = 0.005, 0.028; underemployment: b = 0.026, 95% CI = 0.009, 0.043) than those content with their working hours. These results held after controlling for socio-demographic characteristics, occupation, and other health-related factors. These findings are consistent with recent work that suggested that psychological distress can influence physical pain. Understanding how adverse employment circumstances impact physical pain is crucial to the design of health promotion policies

Global pain levels before and during the COVID-19 pandemic

Physical pain has trended upward globally over the last decade. Here, we explore whether the COVID-19 pandemic modified this alarming trend. We used data from 146 countries worldwide (510,247 respondents) to examine whether pain levels changed during the COVID-19 pandemic. Adjusted regressions across countries revealed that 33.3% of people were in pain in 2019, 32.8% in 2020, 32.5% in 2021, and 34.1% in 2022. The change in pain from 2019 to each of the pandemic years was not statistically significant. This suggests that, on average, there was no significant change in pain during the pandemic. However, from 2019 to 2020 there was a significant decline in pain among individuals over 55 years of age, those who were widowed, and those without children in the household. On a global scale, the COVID-19 pandemic was not associated with a significant change in pain levels. The concerning pre-pandemic elevation in global pain continued during this challenging period

Multiple Gluon Effects in q+qˉ→t+tˉ+Xq+\bar q\to t+\bar t + X at FNAL Energies: Semi-Analytical Results

We apply our Yennie-Frautschi-Suura exponentiated cross section formulas for the parton processes q + {^(} \bar q {^)}{^\prime} \ra q{^\prime}{^\prime} + {^(} \bar q {^)}{^\prime}{^\prime}{^\prime} + n(G) to the process q + \bar q \ra t + \bar t + n(G) at FNAL energies, where G is a QCD gluon. We use semi-analytical methods to compute the ratio $r_{exp}=\sigma_{exp}/\sigma_B$, where $\sigma_{exp}$ is our soft gluon YFS exponentiated cross section and $\sigma_B$ is the Born cross section. For $m_t= 0.176(0.199)$TeV, we get $r_{exp}=1.65(1.48)$, respectively, for $q=u$ for example. These results are not inconsistent with the recent observations by CDF and D0.Comment: 6 pages, latex replaces postscript at archiver's reques

The negatively charged nitrogen-vacancy centre in diamond: the electronic solution

The negatively charged nitrogen-vacancy centre is a unique defect in diamond that possesses properties highly suited to many applications, including quantum information processing, quantum metrology, and biolabelling. Although the unique properties of the centre have been extensively documented and utilised, a detailed understanding of the physics of the centre has not yet been achieved. Indeed there persists a number of points of contention regarding the electronic structure of the centre, such as the ordering of the dark intermediate singlet states. Without a sound model of the centre's electronic structure, the understanding of the system's unique dynamical properties can not effectively progress. In this work, the molecular model of the defect centre is fully developed to provide a self consistent model of the complete electronic structure of the centre. The application of the model to describe the effects of electric, magnetic and strain interactions, as well as the variation of the centre's fine structure with temperature, provides an invaluable tool to those studying the centre and a means to design future empirical and ab initio studies of this important defect.Comment: 24 pages, 6 figures, 10 table