Demonstration and imaging of cryogenic magneto-thermoelectric cooling in a van der Waals semimetal.

Attaining viable thermoelectric cooling at cryogenic temperatures is of considerable fundamental and technological interest for electronics and quantum materials applications. In-device temperature control can provide more efficient and precise thermal environment management compared with conventional global cooling. The application of a current and perpendicular magnetic field gives rise to cooling by generating electron-hole pairs on one side of the sample and to heating due to their recombination on the opposite side, which is known as the Ettingshausen effect. Here we develop nanoscale cryogenic imaging of the magneto-thermoelectric effect and demonstrate absolute cooling and an Ettingshausen effect in exfoliated WTe2 Weyl semimetal flakes at liquid He temperatures. In contrast to bulk materials, the cooling is non-monotonic with respect to the magnetic field and device size. Our model of magneto-thermoelectricity in mesoscopic semimetal devices shows that the cooling efficiency and the induced temperature profiles are governed by the interplay between sample geometry, electron-hole recombination length, magnetic field, and flake and substrate heat conductivities. The observations open the way for the direct integration of microscopic thermoelectric cooling and for temperature landscape engineering in van der Waals devices.

HLA B27 in Ankylosing Spondylitis: Differences in Frequency and Relative Risk in American Blacks and Caucasians.

Twenty-eight HLA alleles of the A and B loci were determined in 23 American Blacks and 50 Caucasians with primary ankylosing spondylitis (AS). The prevalence of HLA B27 was significantly increased in American Black patients (48 per cent) vs Black controls (two per cent), but was much less than the 94 per cent found in Caucasian patients (controls eight per cent). The lower prevalence of B27 in American Black patients vs Caucasian patients was significant (p < 0.001), and indicated that susceptibility to AS is not as closely associated with B27 in Blacks as in Caucasians. No other HLA antigen was significantly associated with AS in either racial group. Among B27 positive individuals, the relative risk of developing AS was significantly lower in American Blacks than in Caucasians. These data indicate that for diagnostic purposes, the absence of B27 is less important in ruling out AS in Blacks than in Caucasians.

Contexts of violence victimization and service-seeking among Latino/a/x immigrant adults in Maryland and the District of Columbia: A qualitative study.

In the United States (US), Latino/a/x immigrants are particularly vulnerable to discrimination and violence, which are associated with a host of negative physical and mental health consequences. Despite this, Latino/a/x immigrants may have limited access to resources and services to prevent and address its consequences. In-depth interviews (n = 17) and one focus group discussion (n = 5) were conducted among a maximum variation sample of adult Latino/a/x immigrants living in Maryland and the District of Columbia, following semi-structured interview guides to explore experiences of discrimination and violence, their impact on health, and barriers and facilitators to help-seeking. Experiences of discrimination and violence victimization were diverse in type and severity. Many women and one gender non-binary participant described experiences of intimate partner violence as well workplace violence. Men frequently described violence that occurred in public and in the workplace. Nearly all participants reported workplace discrimination. Lack of legal documentation, experiences of impunity in country of origin, and lack of knowledge of the US legal system presented barriers, while peers, social groups, and bystanders facilitated violence reporting and help-seeking. Results highlight clear opportunities to prevent and respond to violence through improved availability and accessibility of information, as well as expansion or adaptation of existing services across sectors.

Exploring bifurcations in Bose-Einstein condensates via phase field crystal models.

To facilitate the analysis of pattern formation and the related phase transitions in Bose-Einstein condensates, we present an explicit approximate mapping from the nonlocal Gross-Pitaevskii equation with cubic nonlinearity to a phase field crystal (PFC) model. This approximation is valid close to the superfluid-supersolid phase transition boundary. The simplified PFC model permits the exploration of bifurcations and phase transitions via numerical path continuation employing standard software. While revealing the detailed structure of the bifurcations present in the system, we demonstrate the existence of localized states in the PFC approximation. Finally, we discuss how higher-order nonlinearities change the structure of the bifurcation diagram representing the transitions found in the system.

Direct observation of vortices in an electron fluid.

Vortices are the hallmarks of hydrodynamic flow. Strongly interacting electrons in ultrapure conductors can display signatures of hydrodynamic behaviour, including negative non-local resistance1-4, higher-than-ballistic conduction5-7, Poiseuille flow in narrow channels8-10 and violation of the Wiedemann-Franz law11. Here we provide a visualization of whirlpools in an electron fluid. By using a nanoscale scanning superconducting quantum interference device on a tip12, we image the current distribution in a circular chamber connected through a small aperture to a current-carrying strip in the high-purity type II Weyl semimetal WTe2. In this geometry, the Gurzhi momentum diffusion length and the size of the aperture determine the vortex stability phase diagram. We find that vortices are present for only small apertures, whereas the flow is laminar (non-vortical) for larger apertures. Near the vortical-to-laminar transition, we observe the single vortex in the chamber splitting into two vortices; this behaviour is expected only in the hydrodynamic regime and is not anticipated for ballistic transport. These findings suggest a new mechanism of hydrodynamic flow in thin pure crystals such that the spatial diffusion of electron momenta is enabled by small-angle scattering at the surfaces instead of the routinely invoked electron-electron scattering, which becomes extremely weak at low temperatures. This surface-induced para-hydrodynamics, which mimics many aspects of conventional hydrodynamics including vortices, opens new possibilities for exploring and using electron fluidics in high-mobility electron systems.

Long-range nontopological edge currents in charge-neutral graphene.

Van der Waals heterostructures display numerous unique electronic properties. Nonlocal measurements, wherein a voltage is measured at contacts placed far away from the expected classical flow of charge carriers, have been widely used in the search for novel transport mechanisms, including dissipationless spin and valley transport1-9, topological charge-neutral currents10-12, hydrodynamic flows13 and helical edge modes14-16. Monolayer1-5,10,15-19, bilayer9,11,14,20 and few-layer21 graphene, transition-metal dichalcogenides6,7 and moiré superlattices8,10,12 have been found to display pronounced nonlocal effects. However, the origin of these effects is hotly debated3,11,17,22-24. Graphene, in particular, exhibits giant nonlocality at charge neutrality1,15-19, a striking behaviour that has attracted competing explanations. Using a superconducting quantum interference device on a tip (SQUID-on-tip) for nanoscale thermal and scanning gate imaging25, here we demonstrate that the commonly occurring charge accumulation at graphene edges23,26-31 leads to giant nonlocality, producing narrow conductive channels that support long-range currents. Unexpectedly, although the edge conductance has little effect on the current flow in zero magnetic field, it leads to field-induced decoupling between edge and bulk transport at moderate fields. The resulting giant nonlocality at charge neutrality and away from it produces exotic flow patterns that are sensitive to edge disorder, in which charges can flow against the global electric field. The observed one-dimensional edge transport is generic and nontopological and is expected to support nonlocal transport in many electronic systems, offering insight into the numerous controversies and linking them to long-range guided electronic states at system edges.

Seroprevalence of SARS-CoV-2 antibodies, associated epidemiological factors and antibody kinetics among healthcare workers in Connecticut.

BACKGROUND: Healthcare workers (HCWs) are at the front line of the ongoing coronavirus 2019 (COVID-19) pandemic. Comprehensive evaluation of the seroprevalence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) among HCWs in a large healthcare system could help to identify the impact of epidemiological factors and the presence of symptoms on the immune response to the infection over time. AIM: To determine the seroprevalence of SARS-CoV-2-specific antibodies among HCWs, identify associated epidemiological factors and study antibody kinetics. METHODS: A longitudinal evaluation of the seroprevalence and epidemiology of SARS-CoV-2-specific antibodies was undertaken in approximately 30,000 HCWs in the largest healthcare system in Connecticut, USA. FINDINGS: At baseline, the prevalence of SARS-CoV-2 antibody among 6863 HCWs was 6.3% [95% confidence interval (CI) 5.7-6.9%], and was highest among patient care support (16.7%), medical assistants (9.1%) and nurses (8.2%), and lower for physicians (3.8%) and advanced practice providers (4.5%). Seroprevalence was significantly higher among African Americans [odds ratio (OR) 3.26 compared with Caucasians, 95% CI 1.77-5.99], in participants with at least one symptom of COVID-19 (OR 3.00, 95% CI 1.92-4.68), and in those reporting prior quarantine (OR 3.83, 95% CI 2.57-5.70). No symptoms were reported in 24% of seropositive participants. Among the 47% of participants who returned for a follow-up serological test, the seroreversion rate was 39.5% and the seroconversion rate was 2.2%. The incidence of re-infection in the seropositive group was zero. CONCLUSION: Although there is a decline in the immunoglobulin G antibody signal over time, 60.5% of seropositive HCWs had maintained their seroconversion status after a median of 5.5 months.

Pre-Transplant Marital Status and Hematopoietic Cell Transplantation Outcomes

Background: Evidence about the impact of marital status before hematopoietic cell transplantation (hct) on outcomes after hct is conflicting. Methods: We identified patients 40 years of age and older within the Center for International Blood and Marrow Transplant Research registry who underwent hct between January 2008 and December 2015. Marital status before hct was declared as one of: married or living with a partner, single (never married), separated or divorced, and widowed. We performed a multivariable analysis to determine the association of marital status with outcomes after hct. Results: We identified 10,226 allogeneic and 5714 autologous hct cases with, respectively, a median follow-up of 37 months (range: 1-102 months) and 40 months (range: 1-106 months). No association between marital status and overall survival was observed in either the allogeneic (p = 0.58) or autologous (p = 0.17) setting. However, marital status was associated with grades 2-4 acute graft-versus-host disease (gvhd), p < 0.001, and chronic gvhd, p = 0.04. The risk of grades 2-4 acute gvhd was increased in separated compared with married patients [hazard ratio (hr): 1.13; 95% confidence interval (ci): 1.03 to 1.24], and single patients had a reduced risk of grades 2-4 acute gvhd (hr: 0.87; 95% ci: 0.77 to 0.98). The risk of chronic gvhd was lower in widowed compared with married patients (hr: 0.82; 95% ci: 0.67 to 0.99). Conclusions: Overall survival after hct is not influenced by marital status, but associations were evident between marital status and grades 2-4 acute and chronic gvhd. To better appreciate the effects of marital status and social support, future research should consider using validated scales to measure social support and patient and caregiver reports of caregiver commitment, and to assess health-related quality of life together with health care utilization.

Publisher Correction: Imaging work and dissipation in the quantum Hall state in graphene.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Imaging work and dissipation in the quantum Hall state in graphene.

Topology is a powerful recent concept asserting that quantum states could be globally protected against local perturbations1,2. Dissipationless topologically protected states are therefore of major fundamental interest as well as of practical importance in metrology and quantum information technology. Although topological protection can be robust theoretically, in realistic devices it is often susceptible to various dissipative mechanisms, which are difficult to study directly because of their microscopic origins. Here we use scanning nanothermometry3 to visualize and investigate the microscopic mechanisms that undermine dissipationless transport in the quantum Hall state in graphene. Simultaneous nanoscale thermal and scanning gate microscopy shows that the dissipation is governed by crosstalk between counterpropagating pairs of downstream and upstream channels that appear at graphene boundaries as a result of edge reconstruction. Instead of local Joule heating, however, the dissipation mechanism comprises two distinct and spatially separated processes. The work-generating process that we image directly, which involves elastic tunnelling of charge carriers between the quantum channels, determines the transport properties but does not generate local heat. By contrast, the heat and entropy generation process-which we visualize independently-occurs nonlocally upon resonant inelastic scattering from single atomic defects at graphene edges, and does not affect transport. Our findings provide an insight into the mechanisms that conceal the true topological protection, and suggest routes towards engineering more robust quantum states for device applications.

Metabolic syndrome and cardiovascular disease following hematopoietic cell transplantation: screening and preventive practice recommendations from CIBMTR and EBMT.

Metabolic syndrome (MetS) is a constellation of cardiovascular risk factors that increases the risk of cardiovascular disease, diabetes mellitus and all cause mortality. Long-term survivors of hematopoietic cell transplantation (HCT) have a substantial risk of developing MetS and cardiovascular disease, with the estimated prevalence of MetS being 31-49% among HCT recipients. Although MetS has not yet been proven to impact cardiovascular risk after HCT, an understanding of the incidence and risk factors for MetS in HCT recipients can provide the foundation to evaluate screening guidelines and develop interventions that may mitigate cardiovascular-related mortality. A working group was established through the Center for International Blood and Marrow Transplant Research and the European Group for Blood and Marrow Transplantation with the goal of reviewing literature and recommend practices appropriate to HCT recipients. Here we deliver consensus recommendations to help clinicians provide screening and preventive care for MetS and cardiovascular disease among HCT recipients. All HCT survivors should be advised of the risks of MetS and encouraged to undergo recommended screening based on their predisposition and ongoing risk factors.

Communicating with children and families about obesity and weight-related topics: a scoping review of best practices.

BACKGROUND: Healthcare professionals have called for direction on how best to communicate about weight-related topics with children and families. Established scoping review methodology was used to answer the question: 'How can healthcare professionals best communicate with children and their families about obesity and weight-related topics?' METHODS: We searched four scientific databases, two grey literature repositories and 14 key journals (2005-2016). Inclusion criteria were (i) children up to and including 18 years of age and/or their parents; (ii) communication about healthy weight, overweight, obesity or healthy/active living; and (iii) healthcare setting. RESULTS: Thirty-two articles were included. Evidence-based best practices were largely absent from the literature, although the following guiding principles were identified: (i) include all stakeholders in discussions; (ii) raise the topic of weight and health early and regularly; (iii) use strengths-based language emphasizing health over weight; (iv) use collaborative goal-setting to engage children and parents and (v) augment discussions with appropriate tools and resources. Guidance on how to implement these principles and how to negotiate relevant contextual factors (e.g. age, culture and disability) is still needed. CONCLUSION: Despite agreement on a number of guiding principles, evidence-based weight-related communication best practices are lacking. Rigorous, empirical evaluations of communication approaches are urgently required, especially those that include children's perspectives.

Simulating and Optimising Quantum Thermometry Using Single Photons.

A classical thermometer typically works by exchanging energy with the system being measured until it comes to equilibrium, at which point the readout is related to the final energy state of the thermometer. A recent paper noted that with a quantum thermometer consisting of a single spin/qubit, temperature discrimination is better achieved at finite times rather than once equilibration is essentially complete. Furthermore, preparing a qubit thermometer in a state with quantum coherence instead of an incoherent one improves its sensitivity to temperature differences. Implementing a recent proposal for efficiently emulating an arbitrary quantum channel, we use the quantum polarisation state of individual photons as models of "single-qubit thermometers" which evolve for a certain time in contact with a thermal bath. We investigate the optimal thermometer states for temperature discrimination, and the optimal interaction times, confirming that there is a broad regime where quantum coherence provides a significant improvement. We also discuss the more practical question of thermometers composed of a finite number of spins/qubits (greater than one), and characterize the performance of an adaptive protocol for making optimal use of all the qubits.

Ultrafast Stark-induced polaritonic switches.

A laser pulse, several meV red detuned from the excitonic line of a quantum well, has been shown to induce an almost instantaneous and rigid shift of the lower and upper polariton branches. Here we demonstrate that through this shift ultrafast all-optical control of the polariton population in a semiconductor microcavity should be achievable. In the proposed setup, a Stark field is used to bring the lower polariton branch in or out of resonance with a quasiresonant continuous-wave laser, thereby favoring or inhibiting the injection of polaritons into the cavity. Moreover, we show that this technique allows for the implementation of optical switches with extremely high repetition rates.

Mitrecin A, an endolysin-like bacteriolytic enzyme from a newly isolated soil streptomycete.

UNLABELLED: An open reading frame with homology to known endolysin genes was identified in the genome of Streptomyces sp. strain 212, which is a newly isolated soil bacterium. The heterologously expressed gene product of this endolysin-like gene, called Mitrecin A, demonstrated bacteriolytic activity against several Gram-negative bacteria. The genome of the bacterial strain was sequenced to draft quality using pyrosequencing followed by genome assembly and gene annotation. Within the sequence, a chromosomally located endolysin-like open reading frame was predicted. The gene product, designated Mitrecin A, was heterologously expressed and isolated from contaminating proteins as a fusion protein to a 6-histidine tag. Mitrecin A consists of 127 amino acids arranged in modular domains of activity. It has an estimated molecular weight of 14.3 kDa and retains sequence homology to the M15C peptidase subfamily of zinc metallocarboxypeptidases. The heat-labile purified recombinant protein has an overall positive charge, has optimal catalytic activities at 26°C in solution of pH 9 with 1% saline and has bacteriolytic activity against Gram-negative bacteria of the medically important genera Aeromonas, Escherichia, Salmonella, Shigella, Vibrio and Yersinia. SIGNIFICANCE AND IMPACT OF THE STUDY: The gene of a new protein antimicrobial, Mitrecin A, was discovered in the genome of a soil bacterium. The purified recombinant enzyme, resulting from heterologous over expression of the gene, was found to be tolerant of increased pH conditions and to have bacteriolytic activity against Gram-negative bacteria of the medically important genera Aeromonas, Escherichia, Salmonella, Shigella, Vibrio and Yersinia. Characterization of enzymes such as Mitrecin A from previously uncharacterized bacteria provides potential options for new biocontrol agents in medically and economically important applications like therapeutics, disinfectants, food preservatives, agricultural livestock antimicrobials, and inhibitors of biofilm production.

Adaptive quantum state tomography improves accuracy quadratically.

We introduce a simple protocol for adaptive quantum state tomography, which reduces the worst-case infidelity [1-F(ρ,ρ)] between the estimate and the true state from O(1/sqrt[N]) to O(1/N). It uses a single adaptation step and just one extra measurement setting. In a linear optical qubit experiment, we demonstrate a full order of magnitude reduction in infidelity (from 0.1% to 0.01%) for a modest number of samples (N ≈ 3 × 10(4)).

White blood cell SPECT during active period of cluster headache and in remission.

BACKGROUND AND PURPOSE: Cluster headache (CH) is an episodic headache disorder characterized by recurrent, unilateral attacks of excruciating pain in the temporal/orbital region. The pathophysiology of CH is largely unknown although involvement of immunological mechanisms has been suggested. The aim of our study was to investigate whether patients with CH show signs of intracranial inflammation, when using white blood cell single-photon emission computer tomography (WBC-SPECT). METHODS: We have examined 14 patients with CH, both in active period and in remission, and five control subjects at one occasion, with WBC-SPECT. To be able to precisely define regions of interest (ROI:s) in the brain, all patients with CH and control subjects underwent magnetic resonance imaging (MRI) of the brain. RESULTS: We found no significant difference in (99m)Tc-labeled WBC uptake between patients with CH in active period and controls. Furthermore, patients with CH in active period were not significantly different in uptake compared with patients with CH in remission. CONCLUSIONS: These results did not provide conclusive support for a hypothesis of a pathophysiological role of inflammation intracranially. Our conclusions are restricted to the advantages and limitations of the chosen method.

Interleukin-2 gene expression in different phases of episodic cluster headache--a pilot study.

BACKGROUND: The pathophysiology of cluster headache (CH) is still largely unknown. Immunological mechanisms have been suggested to be of importance. AIM: This study aimed to investigate cytokine interleukin-2 (IL-2) as a possible marker of immune system involvement in the pathophysiology of CH. METHODS: Eight episodic patients with CH and 16 healthy headache-free control subjects matched for age and gender were studied. Venous blood samples were drawn from the patients with CH on three occasions; during active period between headache attacks, during an attack and in remission. Venous blood samples were drawn once from each control subject. We analysed IL-2 gene expression, using quantitative real-time polymerase chain reaction. RESULTS: Patients with CH had significantly increased relative IL-2 gene expression levels between headache attacks during active CH period (median 9.9 IL-2 cDNA/glyceraldehyde-3-phosphate dehydrogenase cDNA; IQR 6.2-10.3) compared to during attacks (median 2.8; IQR 0.7-3.2, P = 0.012), remission (median 1.6; IQR 0.9-1.8, P = 0.017) and controls (median 0.9; IQR 0.6-1.9, P = 0.0001). CONCLUSION: The increment of IL-2 found during the active CH period may support a role for this cytokine and subsequently for the immune system in the pathophysiology of CH. An expansion of this study to a broader group of cytokines and a larger patient cohort is warranted.