A Study of Dark Matter and QCD-Charged Mediators in the Quasi-Degenerate Regime

We study a scenario in which the only light new particles are a Majorana fermion dark matter candidate and one or more QCD-charged scalars, which couple to light quarks. This scenario has several interesting phenomenological features if the new particles are nearly degenerate in mass. In particular, LHC searches for the light scalars have reduced sensitivity, since the visible and invisible products tend to be softer. Moreover, dark matter-scalar co-annihilation can allow even relatively heavy dark matter candidates to be consistent thermal relics. Finally, the dark matter nucleon scattering cross section is enhanced in the quasi-degenerate limit, allowing direct detection experiments to use both spin-independent and spin-dependent scattering to probe regions of parameter space beyond those probed by the LHC. Although this scenario has broad application, we phrase this study in terms of the MSSM, in the limit where the only light sparticles are a bino-like dark matter candidate and light-flavored squarks.Comment: 24 pages, 5 figures; as published in PRD with significant revision

A two-dimensional nematic phase of magnetic nanorods

We report a hybrid mesophase consisting of magnetic nanorods confined between the non-ionic surfactant bilayers of a lamellar phase. The magnetic field-induced ordering of the nanorods was measured experimentally and modeled by a two-dimensional Onsager theory including the third virial coefficient. The nanorods are strongly confined in layers, with no orientational coupling from one layer to the next. At high volume concentration they exhibit spontaneous in-plane orientational ordering and form a stack of independent two-dimensional nematic systems. This isotropic-nematic transition is first-order

Morphology of gold nanoparticles determined by full-curve fitting of the light absorption spectrum. Comparison with X-ray scattering and electron microscopy data

UV-Vis absorption spectroscopy is frequently used to characterize the size and shape of gold nanoparticles. We present a full-spectrum model that yields reliable results for the commonly encountered case of mixtures of spheres and rods in varying proportions. We determine the volume fractions of the two populations, the aspect ratio distribution of the nanorods (average value and variance) and the interface damping parameter. We validate the model by checking the fit results against small-angle X-ray scattering and transmission electron microscopy data and show that correctly accounting for the polydispersity in aspect ratio is essential for a quantitative description of the longitudinal plasmon peak

Infrared dichroism of gold nanorods controlled using a magnetically addressable mesophase

Gold nanorods have unique optical properties, which make them promising candidates for building nano-structured materials using a "bottom-up" strategy. We formulate stable bulk materials with anisotropic optical properties by inserting gold and iron oxide nanorods within a lamellar mesophase. Quantitative measurements of the order parameter by modelling the absorbance spectra show that the medium is macroscopically aligned in a direction defined by an external magnetic field. Under field, the system exhibits significant absorption dichroism in the infrared range, at the position of the longitudinal plasmon peak of the gold nanorods (about 1200 nm), indicating strong confinement of these particles within the water layers of the lamellar phase. This approach can yield soft and addressable optical elements

Being ‘with woman’ in contemporary midwifery practice: one Trust's response to the Francis report

Whilst the Report of the Mid Staffordshire NHS Foundation Trust (Francis, 2013a) largely focussed on the failings in the nursing and medical professions, it was also a reminder to maternity services to review its systems and the quality of its care in line with the Code (NMC, 2015). This article will outline an initiative set up by two labour ward matrons at Kettering General Hospital Foundation Trust entitled ‘Back to Basics’. Sue and Kathy reviewed clinical practises in their maternity unit and put in place an initiative to raise standards of care and ensure best practice was recognised, maintained and disseminated