Continuous Elastic Phase Transitions in Pure and Disordered Crystals

We review the theory of second--order (ferro--)elastic phase transitions, where the order parameter consists of a certain linear combination of strain tensor components, and the accompanying soft mode is an acoustic phonon. In three--dimensional crystals, the softening can occur in one-- or two--dimensional soft sectors. The ensuing anisotropy reduces the effect of fluctuations, rendering the critical behaviour of these systems classical for a one--dimensional soft sector, and classical with logarithmic corrections in case of a two--dimensional soft sector. The dynamical critical exponent is $z = 2$, and as a consequence the sound velocity vanishes as $c_s \propto | T - T_c |^{1/2}$, while the phonon damping coefficient is essentially temperature--independent. Disorder may lead to a variety of precursor effects and modified critical behaviour. Defects that locally soften the crystal may induce the phenomenon of local order parameter condensation. When the correlation length of the pure system exceeds the average defect separation $n_{\rm D}^{-1/3}$, a disorder--induced phase transition to a state with non--zero average order parameter can occur at a temperature $T_c(n_{\rm D})$ well above the transition temperature $T_c^0$ of the pure crystal. Near $T_c^0$, the order--parameter curve, susceptibility, and specific heat appear rounded. For $T < T_c(n_{\rm D})$ the spatial inhomogeneity induces a static central peak with finite $q$ width in the scattering cross section, accompanied by a dynamical component that is confined to the very vicinity of the disorder--induced phase transition.Comment: 26 pages, Latex (rs.sty now IS included), 11 figures can be obtained from U.C. T\"auber ([email protected]); will appear in Phil. Trans. Roy. Soc. Lond. A (October 1996

Optically-ambidextrous circularly-polarised reflection from the chiral cuticle of the scarab beetle Chrysina resplendens

This is the author accepted manuscript. The final version is available from Royal Society via the DOI in this record.The evolution of structural colour mechanisms in biological systems has given rise to many interesting optical effects in animals and plants. The instance of the scarab beetle Chrysina resplendens is particularly distinctive. Its exoskeleton has a bright, golden appearance and reflects both right-handed and left-handed circularly-polarized light concurrently. The chiral nanostructure responsible for these properties is a helicoid, in which birefringent dielectric planes are assembled with an incremental rotation. This study correlates details of the beetle’s circularly-polarized reflectance spectra directly with physical aspects of its structural morphology. Electron micrography is used to identify and measure the physical dimensions of the key constituent components. These include a chiral multilayer configuration comprising two chirped, lefthanded helicoids that are separated by a birefringent retarder. A scattering matrix technique is used to simulate the system’s optical behaviour in which the roles of each component of the morphological substructure are elucidated by calculation of the fields throughout its depth.This work was supported by AFOSR grant number FA9550-10-1- 0020

Updated world map of the Köppen-Geiger climate classification

International audienceAlthough now over 100 years old, the classification of climate originally formulated by Wladimir Köppen and modified by his collaborators and successors, is still in widespread use. It is widely used in teaching school and undergraduate courses on climate. It is also still in regular use by researchers across a range of disciplines as a basis for climatic regionalisation of variables and for assessing the output of global climate models. Here we have produced a new global map of climate using the Köppen-Geiger system based on a large global data set of long-term monthly precipitation and temperature station time series. Climatic variables used in the Köppen-Geiger system were calculated at each station and interpolated between stations using a two-dimensional (latitude and longitude) thin-plate spline with tension onto a 0.1°×0.1° grid for each continent. We discuss some problems in dealing with sites that are not uniquely classified into one climate type by the Köppen-Geiger system and assess the outcomes on a continent by continent basis. Globally the most common climate type by land area is BWh (14.2%, Hot desert) followed by Aw (11.5%, Tropical savannah). The updated world Köppen-Geiger climate map is freely available electronically in the Supplementary Material Section

Deglacial landform assemblage records fast ice-flow and retreat, Inner Hebrides, Scotland

High-resolution bathymetric data have been central to recent advances in the understanding of past dynamics of the former British–Irish Ice Sheet (BIIS). As approximately two-thirds of the former BIIS was probably marine-based during the Last Glacial Maximum (LGM) (c. 29–23 ka), geomorphic observations of the seabed are required increasingly to understand the extent, pattern and timing of past glaciation. Until recently, glacial reconstructions for the Inner Hebrides, offshore of western Scotland, have been based primarily on terrestrial observations. Previous workers have proposed generalized reconstructions in which the Inner Hebrides are located within a significant former ice-sheet flow pathway that drained the western Scottish sector of the BIIS, feeding the Barra Fan during the LGM and earlier glaciations (Fig. 1). Results from numerical ice-sheet modelling suggest that former ice-flow velocities within the region were on the order of hundreds to thousands of metres per year, but yield further insight by demonstrating how dynamic binge/purge cycles may have affected ice-sheet mass balance over time (Hubbard et al. 2009). Following the LGM, ice-sheet retreat through the area is estimated to have been in the order of 20 m per year (Clark et al. 2012). Here we present swath-bathymetric data from the Inner Hebrides that provide in situ constraints on ice-sheet flow and subsequent retreat dynamics from within this important sector of the BIIS

Circularly polarized reflection from the scarab beetle Chalcothea smaragdina: light scattering by a dual photonic structure

Helicoidal architectures comprising various polysaccharides, such as chitin and cellulose, have been reported in biological systems. In some cases, these architectures exhibit stunning optical properties analogous to ordered cholesteric liquid crystal phases. In this work, we characterize the circularly polarized reflectance and optical scattering from the cuticle of the beetle Chalcothea smaragdina (Coleoptera: Scarabaeidae: Cetoniinae) using optical experiments, simulations and structural analysis. The selective reflection of left-handed circularly polarized light is attributed to a Bouligand-type helicoidal morphology within the beetle's exocuticle. Using electron microscopy to inform electromagnetic simulations of this anisotropic stratified medium, the inextricable connection between the colour appearance of C. smaragdina and the periodicity of its helicoidal rotation is shown. A close agreement between the model and the measured reflectance spectra is obtained. In addition, the elytral surface of C. smaragdina possesses a blazed diffraction grating-like surface structure, which affects the diffuse appearance of the beetle's reflected colour, and therefore potentially enhances crypsis among the dense foliage of its rainforest habitat

Effectiveness of respectful care policies for women using routine intrapartum services: a systematic review

Several studies have identified how mistreatment during labour and childbirth can act as a barrier to the use of health facilities. Despite general agreement that respectful maternity care (RMC) is a fundamental human right, and an important component of quality intrapartum care that every pregnant woman should receive, the effectiveness of proposed policies remains uncertain. We performed a systematic review to assess the effectiveness of introducing RMC policies into health facilities providing intrapartum services. We included randomized and non-randomized controlled studies evaluating the effectiveness of introducing RMC policies into health facilities. We searched PubMed, CINAHL, LILACS, AJOL, WHO RHL, and Popline, along with ongoing trials registers (ISRCT register, ICTRP register), and the White Ribbon Respectful Maternity Care Repository. Included studies were assessed for risk of bias. Certainty of evidence was assessed using GRADE criteria. Five studies were included. All were undertaken in Africa (Kenya, Tanzania, Sudan, South Africa), and involved a range of components. Two were cluster RCTs, and three were before/after studies. In total, over 8000 women were included at baseline and over 7500 at the endpoints. Moderate certainty evidence suggested that RMC interventions increases women's experiences of respectful care (one cRCT, approx. 3000 participants; adjusted odds ratio (aOR) 3.44, 95% CI 2.45-4.84); two observational studies also reported positive changes. Reports of good quality care increased. Experiences of disrespectful or abusive care, and, specifically, physical abuse, were reduced. Low certainty evidence indicated fewer accounts of non-dignified care, lack of privacy, verbal abuse, neglect and abandonment with RMC interventions, but no difference in satisfaction rates. Other than low certainty evidence of reduced episiotomy rates, there were no data on the pre-specified clinical outcomes. Multi-component RMC policies appear to reduce women's overall experiences of disrespect and abuse, and some components of this experience. However, the sustainability of the demonstrated effect over time is unclear, and the elements of the programmes that have most effect have not been examined. While the tested RMC policies show promising results, there is a need for rigorous research to refine the optimum approach to deliver and achieve RMC in all settings

Circularly polarised colour of the scarab beetle Chalcothea smaragdina: light scattering by a dual photonic structure

This is the author accepted manuscript. The final version is available from the Royal Society via the DOI in this record.Helicoidal architectures comprising various polysaccharides such as chitin and cellulose have been reported in biological systems. In some cases, these architectures exhibit stunning optical properties analogous to ordered cholesteric liquid crystal phases. In this work, we characterise the circularly polarised reflectance and optical scattering from the cuticle of the beetle Chalcothea smaragdina (Coleoptera: Scarabaeidae: Cetoniinae) using optical experiments, simulations and structural analysis. The selective reflection of left-handed circularly polarised light is attributed to a Bouligand-type helicoidal morphology within the beetle’s exocuticle. Using electron microscopy to inform electromagnetic simulations of this anisotropic stratified medium, the inextricable connection between the colour appearance of C. smaragdina and the periodicity of its helicoidal rotation is shown. A close agreement between the model and the measured reflectance spectra is obtained. In addition, the elytral surface of C. smaragdina possesses a blazed diffraction grating-like surface structure, which affects the diffuse appearance of the beetle’s reflected colour, and therefore potentially enhances crypsis amongst the dense foliage of its rainforest habitat.This work was financially supported by the National Centre of Competence in Research BioInspired Materials and the Ambizione program of the Swiss National Science Foundation SNSF (PZ00P2 168223, to BDW)

Effects of once-weekly semaglutide on appetite, energy intake, control of eating, food preference and body weight in subjects with obesity.

AIM: To investigate the mechanism of action for body weight loss with semaglutide. MATERIALS AND METHODS: This randomised, double-blind, placebo-controlled, two-period crossover trial investigated the effects of 12 weeks treatment with once-weekly subcutaneous semaglutide, dose-escalated to 1.0 mg, in 30 subjects with obesity. Ad libitum energy intake, ratings of appetite, thirst, nausea and well-being, control of eating, food preference, resting metabolic rate, body weight and body composition were assessed. RESULTS: After a standardised breakfast, semaglutide, compared with placebo, led to a lower ad libitum energy intake during lunch (-1255 kJ; P < 0.0001), and during the subsequent evening meal (P = 0.0401) and snacks (P = 0.0034), resulting in a 24% reduction in total energy intake across all ad libitum meals throughout the day (-3036 kJ; P < 0.0001). Fasting overall appetite suppression scores were improved with semaglutide versus placebo, while nausea ratings were similar. Semaglutide was associated with less hunger and food cravings, better control of eating and a lower preference for high-fat foods. Resting metabolic rate, adjusted for lean body mass, did not differ between treatments. Semaglutide led to a reduction from baseline in mean body weight of 5.0 kg, predominantly from body fat mass. CONCLUSION: After 12 weeks' treatment, ad libitum energy intake was substantially lower with semaglutide versus placebo with a corresponding loss of body weight observed with semaglutide. In addition to reduced energy intake, likely mechanisms for semaglutide-induced weight loss included less appetite and food cravings, better control of eating and lower relative preference for fatty, energy-dense foods

Routine immunization experience and practices during the COVID-19 pandemic of caregivers attending a tertiary hospital in Cape Town

IntroductionImmunizations are successful, cost-effective interventions for the control of infectious diseases and preventing mortality. Lockdown restrictions during the COVID-19 pandemic had adverse effects on child-health including access to immunizations. Our study aimed to document immunization status, describe caregiver experiences around accessing immunizations during the COVID-19 pandemic and identify any significant factors associated with immunization status.MethodsCaregivers, with children between the ages of 10 to 33 months, attending Tygerberg Hospital Paediatric Department were invited to complete an anonymous survey from 15th September–15th December 2022. Data was captured using a REDCap questionnaire and analysed using Stata Version 17.Results171 caregivers completed the survey. Immunizations were up to date in 81%. Most (155, 88%) agreed it was important to immunize their child. A third of caregivers (55) felt it was unsafe to attend the clinic and 37% (62) agreed it was difficult to attend. Caregivers receiving a social grant (p = 0.023) or who felt safe attending clinic (p = 0.053) were more likely to be up to date with immunizations. Three-quarters (128, 78%) were aware of recommendations to continue immunization. These caregivers were more likely to think it was important to immunize on time (p = 0.003) and to receive family encouragement (p = 0.001). Caregivers were more likely to attend clinic if they felt it was important to vaccinate on time (p &lt; 0.001) or felt safe attending clinic (p = 0.036).ConclusionImmunization rates were higher than expected but below global targets. Although caregivers feel immunizations are important, unknowns still instilled fear of attending clinics. Social factors such as family support and social grants improve vaccine seeking behaviour