Characterizing Cardiac Function in ICU Survivors of Sepsis: A Pilot Study Protocol.

Background: Sepsis is one of the most common reasons for ICU admission and a leading cause of mortality worldwide. More than one-half of survivors experience significant physical, psychological, or cognitive impairments, often termed post-intensive care syndrome (PICS). Sepsis is recognized increasingly as being associated with a risk of adverse cardiovascular events that is comparable with other major cardiovascular risk factors. It is plausible that sepsis survivors may be at risk of unidentified cardiovascular disease, and this may play a role in functional impairments seen after ICU discharge. Research Question: What is the prevalence of myocardial dysfunction after an ICU admission with sepsis and to what extent might it be associated with physical impairments in PICS? Study Design and Methods: Characterisation of Cardiovascular Function in ICU Survivors of Sepsis (CONDUCT-ICU) is a prospective, multicenter, pilot study characterizing cardiovascular function and functional impairments in survivors of sepsis taking place in the west of Scotland. Survivors of sepsis will be recruited at ICU discharge and followed up 6 to 10 weeks after hospital discharge. Biomarkers of myocardial injury or dysfunction (high sensitivity troponin and N-terminal pro B-type natriuretic peptide) and systemic inflammation (C-reactive protein, IL-1ß, IL-6, IL-10, and tumor necrosis factor alpha) will be measured in 69 patients at recruitment and at follow-up. In addition, a cardiovascular magnetic resonance substudy will be performed at follow-up in 35 patients. We will explore associations between cardiovascular magenetic resonance indexes of cardiac function, biomarkers of cardiac dysfunction and inflammation, and patient-reported outcome measures. Interpretation: CONDUCT-ICU will provide data regarding the cause and prevalence of cardiac dysfunction in survivors of sepsis and will explore associations with functional impairment. It will provide feasibility data and operational learning for larger studies investigating mechanisms of functional impairment after ICU admission and the association between sepsis and adverse cardiovascular events. Trial Registry: ClinicalTrials.gov; No.: NCT05633290; URL: www.clinicaltrials.gov.

Cardiac dysfunction in survivors of sepsis: a scoping review.

BACKGROUND: Sepsis is associated with an increased risk of adverse cardiovascular events in a magnitude comparable to other major cardiovascular risk factors. Sepsis is one of the most common reasons for intensive care admission and survivors often have significant functional limitations following discharge. However, it is not clear to what extent chronic cardiovascular dysfunction might mediate these functional impairments, or how we might screen and manage these patients at risk of chronic cardiovascular disease. We conducted a scoping review to map existing evidence and identify research gaps relating to cardiovascular dysfunction following sepsis. METHODS: We conducted a systematic search of MEDLINE, Embase and CINAHL databases using a concept, context, population (CoCoPop) framework. Studies examining cardiovascular outcomes or symptoms following an episode of sepsis in adults were included. Data were mapped based on the population assessed, cardiovascular outcomes examined, inclusion of objective measures of cardiac dysfunction such as biomarkers or cardiovascular imaging, or whether cardiovascular symptoms or patient-reported functional outcomes measures were recorded. RESULTS: We identified 11 210 articles of which 70 were eligible for full text review and 28 were included in final analysis. Across our dataset, a wide range of incident cardiovascular outcomes were reported in the literature including incidence of congestive heart failure (13/28), arrhythmia (6/28), myocardial infarction (24/28) or cardiovascular death or all-cause mortality (20/28). Only 39% (11/28) of articles reported objective measures of cardiovascular function and only one article related cardiovascular function to functional impairment via patient-reported outcome measures. CONCLUSION: There are significant gaps in our understanding of cardiac dysfunction following sepsis . While the research highlights the strong association of sepsis with a variety of adverse cardiovascular outcomes, further prospective work is required to understand the mechanisms that mediate this phenomenon and how we can best identify and manage patients at risk.

Fast and accurate prediction of material properties with three-body tight-binding model for the periodic table.

Parametrized tight-binding models fit to first-principles calculations can provide an efficient and accurate quantum mechanical method for predicting properties of molecules and solids. However, well-tested parameter sets are generally only available for a limited number of atom combinations, making routine use of this method difficult. Furthermore, many previous models consider only simple two-body interactions, which limits accuracy. To tackle these challenges, we develop a density functional theory database of nearly 1 000 000 materials, which we use to fit a universal set of tight-binding parameters for 65 elements and their binary combinations. We include both two-body and three-body effective interaction terms in our model, plus self-consistent charge transfer, enabling our model to work for metallic, covalent, and ionic bonds with the same parameter set. To ensure predictive power, we adopt a learning framework where we repeatedly test the model on new low-energy crystal structures and then add them to the fitting data set, iterating until predictions improve. We distribute the materials database and tools developed in this paper publicly.

High-Throughput DFT-Based Discovery of Next Generation Two-Dimensional (2D) Superconductors.

High-throughput density functional theory (DFT) calculations allow for a systematic search for conventional superconductors. With the recent interest in two-dimensional (2D) superconductors, we used a high-throughput workflow to screen over 1000 2D materials in the JARVIS-DFT database and performed electron-phonon coupling calculations, using the McMillan-Allen-Dynes formula to calculate the superconducting transition temperature (Tc) for 165 of them. Of these 165 materials, we identify 34 dynamically stable structures with transition temperatures above 5 K, including materials such as W2N3, NbO2, ZrBrO, TiClO, NaSn2S4, Mg2B4C2, and the previously unreported Mg2B4N2 (Tc = 21.8 K). Finally, we performed experiments to determine the Tc of selected layered superconductors (2H-NbSe2, 2H-NbS2, ZrSiS, FeSe) and discuss the measured results within the context of our DFT results. We aim that the outcome of this workflow can guide future computational and experimental studies of new and emerging 2D superconductors by providing a roadmap of high-throughput DFT data.

Magnon-phonon hybridization in 2D antiferromagnet MnPSe3.

Magnetic excitations in van der Waals (vdW) materials, especially in the two-dimensional (2D) limit, are an exciting research topic from both the fundamental and applied perspectives. Using temperature-dependent, magneto-Raman spectroscopy, we identify the hybridization of two-magnon excitations with two phonons in manganese phosphorus triselenide (MnPSe3), a magnetic vdW material that hosts in-plane antiferromagnetism. Results from first-principles calculations of the phonon and magnon spectra further support our identification. The Raman spectra's rich temperature dependence through the magnetic transition displays an avoided crossing behavior in the phonons' frequency and a concurrent decrease in their lifetimes. We construct a model based on the interaction between a discrete level and a continuum that reproduces these observations. Our results imply a strong hybridization between each phonon and a two-magnon continuum. This work demonstrates that the magnon-phonon interactions can be observed directly in Raman scattering and provides deep insight into these interactions in 2D magnetic materials.

Database of Wannier tight-binding Hamiltonians using high-throughput density functional theory.

Wannier tight-binding Hamiltonians (WTBH) provide a computationally efficient way to predict electronic properties of materials. In this work, we develop a computational workflow for high-throughput Wannierization of density functional theory (DFT) based electronic band structure calculations. We apply this workflow to 1771 materials (1406 3D and 365 2D), and we create a database with the resulting WTBHs. We evaluate the accuracy of the WTBHs by comparing the Wannier band structures to directly calculated spin-orbit coupling DFT band structures. Our testing includes k-points outside the grid used in the Wannierization, providing an out-of-sample test of accuracy. We illustrate the use of WTBHs with a few example applications. We also develop a web-app that can be used to predict electronic properties on-the-fly using WTBH from our database. The tools to generate the Hamiltonian and the database of the WTB parameters are made publicly available through the websites https://github.com/usnistgov/jarvis and https://jarvis.nist.gov/jarviswtb .

Computational scanning tunneling microscope image database.

We introduce the systematic database of scanning tunneling microscope (STM) images obtained using density functional theory (DFT) for two-dimensional (2D) materials, calculated using the Tersoff-Hamann method. It currently contains data for 716 exfoliable 2D materials. Examples of the five possible Bravais lattice types for 2D materials and their Fourier-transforms are discussed. All the computational STM images generated in this work are made available on the JARVIS-STM website ( https://jarvis.nist.gov/jarvisstm ). We find excellent qualitative agreement between the computational and experimental STM images for selected materials. As a first example application of this database, we train a convolution neural network model to identify the Bravais lattice from the STM images. We believe the model can aid high-throughput experimental data analysis. These computational STM images can directly aid the identification of phases, analyzing defects and lattice-distortions in experimental STM images, as well as be incorporated in the autonomous experiment workflows.

Distinct magneto-Raman signatures of spin-flip phase transitions in CrI3.

The discovery of 2-dimensional (2D) materials, such as CrI3, that retain magnetic ordering at monolayer thickness has resulted in a surge of both pure and applied research in 2D magnetism. Here, we report a magneto-Raman spectroscopy study on multilayered CrI3, focusing on two additional features in the spectra that appear below the magnetic ordering temperature and were previously assigned to high frequency magnons. Instead, we conclude these modes are actually zone-folded phonons. We observe a striking evolution of the Raman spectra with increasing magnetic field applied perpendicular to the atomic layers in which clear, sudden changes in intensities of the modes are attributed to the interlayer ordering changing from antiferromagnetic to ferromagnetic at a critical magnetic field. Our work highlights the sensitivity of the Raman modes to weak interlayer spin ordering in CrI3.

Data-driven discovery of 3D and 2D thermoelectric materials.

In this work, we first perform a systematic search for high-efficiency three-dimensional (3D) and two-dimensional (2D) thermoelectric materials by combining semiclassical transport techniques with density functional theory (DFT) calculations and then train machine-learning models on the thermoelectric data. Out of 36 000 three-dimensional and 900 two-dimensional materials currently in the publicly available JARVIS-DFT database, we identify 2932 3D and 148 2D promising thermoelectric materials using a multi-steps screening procedure, where specific thresholds are chosen for key quantities like bandgaps, Seebeck coefficients and power factors. We compute the Seebeck coefficients for all the materials currently in the database and validate our calculations by comparing our results, for a subset of materials, to experimental and existing computational datasets. We also investigate the effect of chemical, structural, crystallographic and dimensionality trends on thermoelectric performance. We predict several classes of efficient 3D and 2D materials such as Ba(MgX)2 (X = P, As, Bi), X2YZ6 (X = K, Rb, Y=Pd, Pt, Z = Cl, Br), K2PtX2 (X = S, Se), NbCu3X4 (X = S, Se, Te), Sr2XYO6 (X = Ta, Zn, Y=Ga, Mo), TaCu3X4 (X = S, Se, Te), and XYN (X = Ti, Zr, Y=Cl, Br). Finally, as high-throughput DFT is computationally expensive, we train machine learning models using gradient boosting decision trees and classical force-field inspired descriptors for n-and p-type Seebeck coefficients and power factors, to quickly pre-screen materials for guiding the next set of DFT calculations. The dataset and tools are made publicly available at the websites: https://www.ctcms.nist.gov/~knc6/JVASP.html, https://www.ctcms.nist.gov/jarvisml/and https://jarvis.nist.gov/.

High-throughput Discovery of Topologically Non-trivial Materials using Spin-orbit Spillage.

We present a novel methodology to identify topologically non-trivial materials based on band inversion induced by spin-orbit coupling (SOC) effect. Specifically, we compare the density functional theory (DFT) based wavefunctions with and without spin-orbit coupling and compute the 'spin-orbit-spillage' as a measure of band-inversion. Due to its ease of calculation, without any need for symmetry analysis or dense k-point interpolation, the spillage is an excellent tool for identifying topologically non-trivial materials. Out of 30000 materials available in the JARVIS-DFT database, we applied this methodology to more than 4835 non-magnetic materials consisting of heavy atoms and low bandgaps. We found 1868 candidate materials with high-spillage (using 0.5 as a threshold). We validated our methodology by carrying out conventional Wannier-interpolation calculations for 289 candidate materials. We demonstrate that in addition to Z2 topological insulators, this screening method successfully identified many semimetals and topological crystalline insulators. Importantly, our approach is applicable to the investigation of disordered or distorted as well as magnetic materials, because it is not based on symmetry considerations. We discuss some individual example materials, as well as trends throughout our dataset, which is available at the websites: https://www.ctcms.nist.gov/~knc6/JVASP.html and https://jarvis.nist.gov/ .

High-throughput first principles search for new ferroelectrics.

We use a combination of symmetry analysis and high-throughput density functional theory calculations to search for new ferroelectric materials. We use two search strategies to identify candidate materials. In the first strategy, we start with non-polar materials and look for unrecognized energy-lowering polar distortions. In the second strategy, we consider polar materials and look for related higher symmetry structures. In both cases, if we find new structures with the correct symmetries that are also close in energy to experimentally known structures, then the material is likely to be switchable in an external electric field, making it a candidate ferroelectric. We find sixteen candidate materials, with variety of properties that are rare in typical ferroelectrics, including large polarization, hyperferroelectricity, antiferroelectricity, and multiferroism.

Flux States and Topological Phases from Spontaneous Time-Reversal Symmetry Breaking in CrSi(Ge)Te_{3}-Based Systems.

We study adatom-covered single layers of CrSiTe_{3} and CrGeTe_{3} using first-principles calculations based on hybrid functionals. We find that the insulating ground state of a monolayer of La (Lu) deposited on single-layer CrSiTe_{3} (CrGeTe_{3}) carries spontaneously generated current loops around the Cr sites. These "flux states" induce antiferromagnetically ordered orbital moments on the Cr sites and are also associated with nontrivial topological properties. The calculated Chern numbers for these systems are predicted to be ±1 even in the absence of spin-orbit coupling, with sizable gaps on the order of 100 meV. The flux states and the associated topological phases result from spontaneous time-reversal symmetry breaking due to the presence of nonlocal Coulomb interactions.

First principles search for n-type oxide, nitride, and sulfide thermoelectrics.

Oxides have many potentially desirable characteristics for thermoelectric applications, including low cost and stability at high temperatures, but thus far there are few known high zT n-type oxide thermoelectrics. In this work, we use high-throughput first principles calculations to screen transition metal oxides, nitrides, and sulfides for candidate materials with high power factors and low thermal conductivity. We find a variety of promising materials, and we investigate these materials in detail in order to understand the mechanisms that cause them to have high power factors. These materials all combine a high density of states near the Fermi level with dispersive bands, reducing the trade-off between the Seebeck coefficient and the electrical conductivity, but they do so for several different reasons. In addition, our calculations indicate that many of our candidate materials have low thermal conductivity.

Intertwined Rashba, Dirac, and Weyl Fermions in Hexagonal Hyperferroelectrics.

By means of density functional theory based calculations, we study the role of spin-orbit coupling in the new family of ABC hyperferroelectrics [Garrity, Rabe, and Vanderbilt Phys. Rev. Lett. 112, 127601 (2014)]. We unveil an extremely rich physics strongly linked to ferroelectric properties, ranging from the electric control of bulk Rashba effect to the existence of a three-dimensional topological insulator phase, with concomitant topological surface states even in the ultrathin film limit. Moreover, we predict that the topological transition, as induced by alloying, is followed by a Weyl semimetal phase of finite concentration extension, which is robust against disorder, putting forward hyperferroelectrics as promising candidates for spin-orbitronic applications.

Reproducibility in density functional theory calculations of solids.

The widespread popularity of density functional theory has given rise to an extensive range of dedicated codes for predicting molecular and crystalline properties. However, each code implements the formalism in a different way, raising questions about the reproducibility of such predictions. We report the results of a community-wide effort that compared 15 solid-state codes, using 40 different potentials or basis set types, to assess the quality of the Perdew-Burke-Ernzerhof equations of state for 71 elemental crystals. We conclude that predictions from recent codes and pseudopotentials agree very well, with pairwise differences that are comparable to those between different high-precision experiments. Older methods, however, have less precise agreement. Our benchmark provides a framework for users and developers to document the precision of new applications and methodological improvements.

Hyperferroelectrics: proper ferroelectrics with persistent polarization.

All known proper ferroelectrics are unable to polarize normal to a surface or interface if the resulting depolarization field is unscreened, but there is no fundamental principle that enforces this behavior. In this work, we introduce hyperferroelectrics, a new class of proper ferroelectrics which polarize even when the depolarization field is unscreened, this condition being equivalent to instability of a longitudinal optic mode in addition to the transverse-optic-mode instability characteristic of proper ferroelectrics. We use first-principles calculations to show that several recently discovered hexagonal ferroelectric semiconductors have this property, and we examine its consequences both in the bulk and in a superlattice geometry.

Orthorhombic ABC semiconductors as antiferroelectrics.

We use a first-principles rational-design approach to identify a previously unrecognized class of antiferroelectric materials in the Pnma MgSrSi structure type. The MgSrSi structure type can be described in terms of antipolar distortions of the nonpolar P6(3)/mmc ZrBeSi structure type, and we find many members of this structure type are close in energy to the related polar P6(3)mc LiGaGe structure type, which includes many members we predict to be ferroelectric. We highlight known ABC combinations in which this energy difference is comparable to the antiferroelectric-ferroelectric switching barrier of PbZrO(3). We calculate structural parameters and relative energies for all three structure types, both for reported and as-yet hypothetical representatives of this class. Our results provide guidance for the experimental realization and further investigation of high-performance materials suitable for practical applications.

Chern insulators from heavy atoms on magnetic substrates.

We propose searching for Chern insulators by depositing atomic layers of elements with large spin-orbit coupling (e.g., Bi) on the surface of a magnetic insulator. We argue that such systems will typically have isolated surface bands with nonzero Chern numbers. If these overlap in energy, a metallic surface with large anomalous Hall conductivity will result; if not, a Chern-insulator state will typically occur. Thus, our search strategy reduces to looking for examples having the Fermi level in a global gap extending across the entire Brillouin zone. We verify this search strategy and identify several candidate systems by using first-principles calculations to compute the Chern number and anomalous Hall conductivity of a large number of such systems on MnTe, MnSe, and EuS surfaces. Our search reveals several promising Chern insulators with gaps of up to 140 meV.

Hexagonal ABC semiconductors as ferroelectrics.

We use a first-principles rational-design approach to identify a previously unrecognized class of ferroelectric materials in the P6(3)mc LiGaGe structure type. We calculate structural parameters, polarization, and ferroelectric well depths both for reported and as-yet hypothetical representatives of this class. Our results provide guidance for the experimental realization and further investigation of high-performance materials suitable for practical applications.

Prestroke modified rankin stroke scale has moderate interobserver reliability and validity in an acute stroke setting.

BACKGROUND AND PURPOSE: The modified Rankin Scale (mRS) is the recommended functional outcome assessment in stroke trials. Utility of mRS may be limited by interobserver variability. prestroke function, described using mRS, is often used as trial entry criterion. We assessed the reliability and validity of prestroke mRS in acute stroke. METHODS: We present two complementary analyses of the properties of prestroke mRS: (1) Paired interviewers (trained in mRS) performed independently a blinded assessment of mRS and prestroke mRS. Interobserver variability was described using percentage agreement and weighted (kw) κ statistics with 95% confidence interval (95% CI). Validity was assessed by comparing prestroke mRS with other markers of function (comorbidity; medication count; need for carers). (2) We further assessed validity using a larger retrospective dataset. We compared prestroke mRS with Charlson comorbidity index (CCI) and the Rockwood frailty index. Rank correlation coefficient or Fisher exact test were used as appropriate. RESULTS: Paired interviewers assessed 74 stroke survivors. Median standard mRS was 4 (interquartile range [IQR], 2-4), median prestroke mRS was 1 (IQR, 0-3; range, 0-4). Reliability for standard mRS interview was 56% agreement, kw=0.55 (95% CI, 0.39-0.71). Reliability for prestroke mRS was 70%, kw=0.70 (95% CI, 0.53-0.87). The retrospective dataset described 231 subjects. In this data set, Spearman Rho for prestroke mRS and frailty index was J. 0.82 (95% CI, 0.78-0.86); CCI 0.50 (95% CI, 0.40-0.59); patient age 0.45 (95% CI, 0.34-0.54); medication count 0.28 (95% CI, 0.15-0.40). There was no association between need for carers and prestroke mRS (p=0.10). CONCLUSIONS: Interobserver reliability of prestroke mRS is limited but comparable with standard mRS. Poor correlation of prestroke mRS with certain markers of function suggests limited validity. Our data would suggest that relying on mRS alone may be a suboptimal measure of prestroke function and could potentially bias trial samples.