Giant optical birefringence of semiconductor nanowire metamaterials

Semiconductor nanowires exhibit large polarization anisotropy for the absorption and emission of light, making them ideal building blocks for novel photonic metamaterials. Here, we demonstrate that a high density of aligned nanowires exhibits giant optical birefringence, a collective phenomenon observable uniquely for collections of wires. The nanowire material was grown on gallium phosphide (GaP) (111) in the form of vertically standing GaP nanowires. We obtain the largest optical birefringence to date, with a difference between the in-plane and out-of-plane refractive indices of 0.80 and a relative birefringence of 43%. These values exceed by a factor of 75 the natural birefringence of quartz and a by more than a factor of two the highest values reported so far in other artificial materials. By exploiting the specific crystallographic growth directions of the nanowires on the substrate, we further demonstrate full control over the orientation of the optical birefringence effect in the metamaterial.Comment: 10 pages, 4 figure

Changes in the Diagnosis of Stroke and Cardiovascular Conditions in Primary Care During First 2 COVID-19 Waves in the Netherlands

BACKGROUND AND OBJECTIVES: Although there is evidence of disruption in acute cerebrovascular and cardiovascular care during the coronavirus disease 2019 (COVID-19) pandemic, its downstream effect in primary care is less clear. We investigated how the pandemic affected utilization of cerebrovascular and cardiovascular care in general practices (GPs) and determined changes in GP-recorded diagnoses of selected cerebrovascular and cardiovascular outcomes. METHODS: From electronic health records of 166,929 primary care patients aged 30 or over within the Rotterdam region, the Netherlands, we extracted the number of consultations related to cerebrovascular and cardiovascular care, and first diagnoses of selected cerebrovascular and cardiovascular risk factors (hypertension, diabetes, lipid disorders), conditions, and events (angina, atrial fibrillation, TIA, myocardial infarction, stroke). We quantified changes in those outcomes during the first COVID-19 wave (March–May 2020) and thereafter (June–December 2020) by comparing them to the same period in 2016–2019. We also estimated the number of potentially missed diagnoses for each outcome. RESULTS: The number of GP consultations related to cerebrovascular and cardiovascular care declined by 38% (0.62, 95% confidence interval 0.56–0.68) during the first wave, as compared to expected counts based on prepandemic levels. Substantial declines in the number of new diagnoses were observed for cerebrovascular events: 37% for TIA (0.63, 0.41–0.96) and 29% for stroke (0.71, 0.59–0.84), while no significant changes were observed for cardiovascular events (myocardial infarction [0.91, 0.74–1.14], angina [0.77, 0.48–1.25]). The counts across individual diagnoses recovered following June 2020, but the number of GP consultations related to cerebrovascular and cardiovascular care remained lower than expected throughout the June to December period (0.93, 0.88–0.98). DISCUSSION: While new diagnoses of acute cardiovascular events remained stable during the COVID-19 pandemic, diagnoses of cerebrovascular events declined substantially compared to prepandemic levels, possibly due to incorrect perception of risk by patients. These findings emphasize the need to improve symptom recognition of cerebrovascular events among the general public and to encourage urgent presentation despite any physical distancing measures

Brief cognitive behavioral therapy compared to general practitioners care for depression in primary care: a randomized trial

<p>Abstract</p> <p>Background</p> <p>Depressive disorders are highly prevalent in primary care (PC) and are associated with considerable functional impairment and increased health care use. Research has shown that many patients prefer psychological treatments to pharmacotherapy, however, it remains unclear which treatment is most optimal for depressive patients in primary care.</p> <p>Methods/Design</p> <p>A randomized, multi-centre trial involving two intervention groups: one receiving brief cognitive behavioral therapy and the other receiving general practitioner care. General practitioners from 109 General Practices in Nijmegen and Amsterdam (The Netherlands) will be asked to include patients aged between 18-70 years presenting with depressive symptomatology, who do not receive an active treatment for their depressive complaints. Patients will be telephonically assessed with the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) to ascertain study eligibility. Eligible patients will be randomized to one of two treatment conditions: either 8 sessions of cognitive behavioral therapy by a first line psychologist or general practitioner's care according to The Dutch College of General Practitioners Practice Guideline (NHG- standaard). Baseline and follow-up assessments are scheduled at 0, 6, 12 and 52 weeks following the start of the intervention. Primary outcome will be measured with the Hamilton Depression Rating Scale-17 (HDRS-17) and the Patient Health Questionnaire-9 (PHQ-9). Outcomes will be analyzed on an intention to treat basis.</p> <p>Trial Registration</p> <p>ISRCTN65811640</p

Glass transition behavior of polymer films of nanoscopic dimensions

Glass transition behavior of nanoscopically thin polymer films is investigated by means of molecular dynamics simulations. We study thin polymer films composed of bead-spring model chains and supported on an idealized FCC lattice substrate surface. The impact on the glass transition temperature of the strength of polymer-surface interaction, and of chain grafting to the surface is investigated. Three different methods -volumetric, energetic, and dynamic -are used to determine the glass transition temperature of the films. Based on these, we are able to distinguish two different transition temperatures. When the temperature is lowered, a first transition occurs when the beads order locally. This transition is characterized by an anomaly in the heat capacity. Upon decreasing the temperature further, the point is reached at which internal relaxation times diverge, as calculated, using for instance mode coupling theory. In qualitative agreement with the experiments, the former temperature depends on the characteristics of the polymer-surface interaction. By contrast, the latter temperature, is independent of these