An electronic instability in bismuth far beyond the quantum limit

We present a transport study of semi-metallic bismuth in presence of a magnetic field applied along the trigonal axis extended to 55 T for electric conductivity and to 45 T for thermoelectric response. The results uncover a new field scale at about 40 T in addition to the previously detected ones. Large anomalies in all transport properties point to an intriguing electronic instability deep in the ultraquantum regime. Unexpectedly, both the sheer magnitude of conductivity and its metallic temperature dependence are enhanced by this instability.Comment: 5 pages, 4 figure

Microdroplet fabrication of silver–agarose nanocomposite beads for SERS optical accumulation

Microdroplets have been used as reactors for the fabrication of agarose beads with high uniformity in shape and size, and densely loaded with silver ions, which were subsequently reduced into nanoparticles using hydrazine. The resulting nanocomposite beads not only display a high plasmonic activity, but can also trap/concentrate analytes, which can be identified by means of surface-enhanced Raman scattering (SERS) spectroscopy. The size of the beads is such that it allows the detection of a single bead under a conventional optical microscope, which is very useful to reduce the amount of material required for SERS detectio

Josephson radiation in a superconductor-quantum dot-superconductor junction

We investigate the Josephson radiation emitted by a junction made of a quantum dot coupled to two conventional superconductors. Close to resonance, the particle-hole symmetric Andreev states that form in the junction are detached from the continuum above the superconducting gap in the leads, while a gap between them opens near the Fermi level. Under voltage bias, we formulate a stochastic model that accounts for non-adiabatic processes, which change the occupations of the Andreev states. This model allows calculating the current noise spectrum and determining the Fano factor. Analyzing the finite-frequency noise, we find that the model may exhibit either an integer or a fractional AC Josephson effect, depending on the bias voltage and the size of the gaps in the Andreev spectrum. Our results assess the limitations in using the fractional Josephson radiation as a probe of topology.Comment: 5+4 pages, 4 + 2 figure

Haemobilia in a previously stented hilar cholangiocarcinoma: successful haemostasis after the insertion of fcSEMS

Haemobilia describes blood loss from the biliary tract and classically presents as Quincke's triad: upper gastrointestinal bleeding (UGIB), jaundice and right upper quadrant abdominal pain. We discuss the case of a 70-year-old male with a previously stented Bismuth 1 hilar cholangiocarcinoma who presented with haematemesis. He had a similar presentation a month ago where a forward viewing gastroscope identified fresh and altered blood in the distal stomach but no clear source of bleeding. During this admission, a side-viewing duodenoscope identified bleeding from the periampullary region, which was managed by inserting a fully covered self-expanding metal stent (fcSEMS) within his pre-existing uncovered SEMS to tamponade the haemorrhage. This case highlights the importance of using a side-viewing duodenoscope for patients with UGIB on a background of a stented cholangiocarcinoma and inserting a fcSEMS within an uncovered SEMS is feasible and effective in managing these patients

Are COVID-19 models blind to the social determinants of health? A systematic review protocol

Introduction Infectious disease models are important tools to inform public health policy decisions. These models are primarily based on an average population approach and often ignore the role of social determinants in predicting the course of a pandemic and the impact of policy interventions. Ignoring social determinants in models may cause or exacerbate inequalities. This limitation has not been previously explored in the context of the current pandemic, where COVID-19 has been found to disproportionately affect marginalised racial, ethnic and socioeconomic groups. Therefore, our primary goal is to identify the extent to which COVID-19 models incorporate the social determinants of health in predicting outcomes of the pandemic. Methods and analysis We will search MEDLINE, EMBASE, Cochrane Library and Web of Science databases from December 2019 to August 2020. We will assess all infectious disease modelling studies for inclusion of social factors that meet the following criteria: (a) focused on human spread of SARS-CoV-2; (b) modelling studies; (c) interventional or non-interventional studies; and (d) focused on one of the following outcomes: COVID-19-related outcomes (eg, cases, deaths), non-COVID-19-related outcomes (ie, impacts of the pandemic or control policies on other health conditions or health services), or impact of the pandemic or control policies on economic outcomes. Data will only be extracted from models incorporating social factors. We will report the percentage of models that considered social factors, indicate which social factors were considered, and describe how social factors were incorporated into the conceptualisation and implementation of the infectious disease models. The extracted data will also be used to create a narrative synthesis of the results. Ethics and dissemination Ethics approval is not required as only secondary data will be collected. The results of this systematic review will be disseminated through peer-reviewed publication and conference proceedings. PROSPERO registration number CRD42020207706

Duality and ontology

A ‘duality’ is a formal mapping between the spaces of solutions of two empirically equivalent theories. In recent times, dualities have been found to be pervasive in string theory and quantum field theory. Naïvely interpreted, duality-related theories appear to make very different ontological claims about the world—differing in e.g. space-time structure, fundamental ontology, and mereological structure. In light of this, duality-related theories raise questions familiar from discussions of underdetermination in the philosophy of science: in the presence of dual theories, what is one to say about the ontology of the world? In this paper, we undertake a comprehensive and non-technical survey of the landscape of possible ontological interpretations of duality-related theories. We provide a significantly enriched and clarified taxonomy of options—several of which are novel to the literature

N-Heterocyclic carbene iron complexes catalyze the ring-opening polymerization of lactide.

Poly(lactic acid), PLA, which holds great promise as a biodegradable substitute of fossil resource-derived polyolefins, is industrially produced by the ring-opening polymerization of lactide using a potentially harmful tin catalyst. Based on mechanistic insights into the reaction of N-heterocyclic carbene (NHC) iron complexes with carbonyl substrates, we surmised and demonstrate here that such complexes are excellent catalysts for the bulk polymerization of lactide. We show that an iron complex with a triazolylidene NHC ligand is active at lactide/catalyst ratios of up to 10 000 : 1, produces polylactide with relatively high number-average molecular weights (up to 50 kg mol-1) and relatively narrow dispersity (Đ ∼ 1.6), and features an apparent polymerization rate constant k app of up to 8.5 × 10-3 s-1, which is more than an order of magnitude higher than that of the industrially used tin catalyst. Kinetic studies and end-group analyses support that the catalytically active species is well defined and that the polymerization proceeds via a coordination-insertion mechanism. The robustness of the catalyst allows technical grade lactide to be polymerized, thus offering ample potential for application on larger scale in an industrially relevant setting

Response of an artificially blown clarinet to different blowing pressure profiles

Using an artificial mouth with an accurate pressure control, the onset of the pressure oscillations inside the mouthpiece of a simplified clarinet is studied experimentally. Two time profiles are used for the blowing pressure: in a first set of experiments the pressure is increased at constant rates, then decreased at the same rate. In a second set of experiments the pressure rises at a constant rate and is then kept constant for an arbitrary period of time. In both cases the experiments are repeated for different increase rates. Numerical simulations using a simplified clarinet model blown with a constantly increasing mouth pressure are compared to the oscillating pressure obtained inside the mouthpiece. Both show that the beginning of the oscillations appears at a higher pressure values than the theoretical static threshold pressure, a manifestation of bifurcation delay. Experiments performed using an interrupted increase in mouth pressure show that the beginning of the oscillation occurs close to the stop in the increase of the pressure. Experimental results also highlight that the speed of the onset transient of the sound is roughly the same, independently of the duration of the increase phase of the blowing pressure.Comment: 14 page