Ab initio theory and modeling of water Chen, Mohan; Ko, Hsin-Yu; Remsing, Richard C. ...
Proceedings of the National Academy of Sciences - PNAS,
10/2017, Letnik:
114, Številka:
41
Journal Article
Recenzirano
Odprti dostop
Water is of the utmost importance for life and technology. However, a genuinely predictive ab initio model of water has eluded scientists. We demonstrate that a fully ab initio approach, relying on ...the strongly constrained and appropriately normed (SCAN) density functional, provides such a description of water. SCAN accurately describes the balance among covalent bonds, hydrogen bonds, and van der Waals interactions that dictates the structure and dynamics of liquid water. Notably, SCAN captures the density difference between water and ice Ih at ambient conditions, as well as many important structural, electronic, and dynamic properties of liquid water. These successful predictions of the versatile SCAN functional open the gates to study complex processes in aqueous phase chemistry and the interactions of water with other materials in an efficient, accurate, and predictive, ab initio manner.
In this report, 528 cases of monkeypox across 16 countries are described. Rash, mucosal lesions, fever, lethargy, and lymphadenopathy were common clinical findings. Few patients were hospitalized.
One atom or molecule binds to another through various types of bond, the strengths of which range from several meV to several eV. Although some computational methods can provide accurate descriptions ...of all bond types, those methods are not efficient enough for many studies (for example, large systems, ab initio molecular dynamics and high-throughput searches for functional materials). Here, we show that the recently developed non-empirical strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation (meta-GGA) within the density functional theory framework predicts accurate geometries and energies of diversely bonded molecules and materials (including covalent, metallic, ionic, hydrogen and van der Waals bonds). This represents a significant improvement at comparable efficiency over its predecessors, the GGAs that currently dominate materials computation. Often, SCAN matches or improves on the accuracy of a computationally expensive hybrid functional, at almost-GGA cost. SCAN is therefore expected to have a broad impact on chemistry and materials science.
Limited data are available describing donor adverse events (AEs) associated with filgrastim mobilized peripheral blood stem cell (PBSC) collections in unrelated volunteers. We report results in 2408 ...unrelated PBSC donors prospectively evaluated by the National Marrow Donor Program (NMDP) between 1999 and 2004. Female donors had higher rates of AEs, requiring central line placement more often (17% vs 4%, P < .001), experiencing more apheresis-related AEs (20% vs 7%, P < .001), more bone pain (odds ratio OR = 1.49), and higher rates of grades II-IV and III-IV CALGB AEs (OR = 2.22 and 2.32). Obese donors experienced more bone pain (obese vs normal, OR = 1.73) and heavy donors had higher rates of CALGB toxicities (> 95 kg vs < 70 kg, OR = 1.49). Six percent of donors experienced grade III-IV CALGB toxicities and 0.6% experienced toxicities that were considered serious and unexpected. Complete recovery is universal, however, and no late AEs attributable to donation have been identified. In conclusion, PBSC collection in unrelated donors is generally safe, but nearly all donors will experience bone pain, 1 in 4 will have significant headache, nausea, or citrate toxicity, and a small percentage will experience serious short-term adverse events. In addition, women and larger donors are at higher risk for donation-related AEs.
Within the framework of Kohn–Sham density functional theory (DFT), the ability to provide good predictions of water properties by employing a strongly constrained and appropriately normed (SCAN) ...functional has been extensively demonstrated in recent years. Here, we further advance the modeling of water by building a more accurate model on the fourth rung of Jacob’s ladder with the hybrid functional, SCAN0. In particular, we carry out both classical and Feynman path-integral molecular dynamics calculations of water with the SCAN0 functional and the isobaric–isothermal ensemble. To generate the equilibrated structure of water, a deep neural network potential is trained from the atomic potential energy surface based on ab initio data obtained from SCAN0 DFT calculations. For the electronic properties of water, a separate deep neural network potential is trained by using the Deep Wannier method based on the maximally localized Wannier functions of the equilibrated trajectory at the SCAN0 level. The structural, dynamic, and electric properties of water were analyzed. The hydrogen-bond structures, density, infrared spectra, diffusion coefficients, and dielectric constants of water, in the electronic ground state, are computed by using a large simulation box and long simulation time. For the properties involving electronic excitations, we apply the GW approximation within many-body perturbation theory to calculate the quasiparticle density of states and bandgap of water. Compared to the SCAN functional, mixing exact exchange mitigates the self-interaction error in the meta-generalized-gradient approximation and further softens liquid water toward the experimental direction. For most of the water properties, the SCAN0 functional shows a systematic improvement over the SCAN functional. However, some important discrepancies remain. The H-bond network predicted by the SCAN0 functional is still slightly overstructured compared to the experimental results.
We studied the effect of allele-level matching at human leukocyte antigen (HLA)-A, -B, -C, and -DRB1 in 1568 single umbilical cord blood (UCB) transplantations for hematologic malignancy. The primary ...end point was nonrelapse mortality (NRM). Only 7% of units were allele matched at HLA-A, -B, -C, and -DRB1; 15% were mismatched at 1, 26% at 2, 30% at 3, 16% at 4, and 5% at 5 alleles. In a subset, allele-level HLA match was assigned using imputation; concordance between HLA-match assignment and outcome correlation was confirmed between the actual and imputed HLA-match groups. Compared with HLA-matched units, neutrophil recovery was lower with mismatches at 3, 4, or 5, but not 1 or 2 alleles. NRM was higher with units mismatched at 1, 2, 3, 4, or 5 alleles compared with HLA-matched units. The observed effects are independent of cell dose and patient age. These data support allele-level HLA matching in the selection of single UCB units.
Key Points
Killer-cell immunoglobulin-like receptor (KIR) genes form a diverse, immunogenetic system. Group A and B KIR haplotypes have distinctive centromeric (Cen) and telomeric (Tel) gene-content motifs. ...Aiming to develop a donor selection strategy to improve transplant outcome, we compared the contribution of these motifs to the clinical benefit conferred by B haplotype donors. We KIR genotyped donors from 1409 unrelated transplants for acute myelogenous leukemia (AML; n = 1086) and acute lymphoblastic leukemia (ALL; n = 323). Donor KIR genotype influenced transplantation outcome for AML but not ALL. Compared with A haplotype motifs, centromeric and telomeric B motifs both contributed to relapse protection and improved survival, but Cen-B homozygosity had the strongest independent effect. With Cen-B/B homozygous donors the cumulative incidence of relapse was 15.4% compared with 36.5% for Cen-A/A donors (relative risk of relapse 0.34; 95% confidence interval 0.2-0.57; P < .001). Overall, significantly reduced relapse was achieved with donors having 2 or more B gene-content motifs (relative risk 0.64; 95% confidence interval 0.48-0.86; P = .003) for both HLA-matched and mismatched transplants. KIR genotyping of several best HLA-matched potential unrelated donors should substantially increase the frequency of transplants by using grafts with favorable KIR gene content. Adopting this practice could result in superior disease-free survival for patients with AML.
We report outcomes of 932 recipients of unrelated donor peripheral blood stem cell hematopoietic cell transplantation (URD-PBSC HCT) for acute myeloid leukemia, acute lymphoblastic leukemia, chronic ...myelogenous leukemia, and myelodysplastic syndrome enrolled on a prospective National Marrow Donor Program trial from 1999 through 2003. Preparative regimens included myeloablative (MA; N = 611), reduced-intensity (RI; N = 160), and nonmyeloablative (NMA; N = 161). For MA recipients, CD34+ counts greater than 3.8 × 106/kg improved neutrophil and platelet engraftment, whereas improved overall survival (OS) and reduced transplant-related mortality (TRM) were seen for all preparative regimens when CD34+ cell doses exceeded 4.5 × 106/kg. Higher infused doses of CD34+ cell dose did not result in increased rates of either acute or chronic graft-versus-host disease (GVHD). Three-year OS and disease-free survival (DFS) of recipients of MA, RI, and NMA approaches were similar (33%, 35%, and 32% OS; 33%, 30%, and 29% DFS, respectively). In summary, recipients of URD-PBSC HCT receiving preparative regimens differing in intensity experienced similar survival. Higher CD34+ cell doses resulted in more rapid engraftment, less TRM, and better 3-year OS (39% versus 25%, MA, P = .004; 38% versus 21% RI/NMA, P = .004) but did not increase the risk of GVHD. This trial was registered at www.clinicaltrials.gov as #NCT00785525.
We show that intercalation of cations (Na+, Ca2+, Ni2+, and Co2+) into the interlayer region of 1T-MoS2 is an effective strategy to lower the overpotential for the hydrogen evolution reaction (HER). ...In acidic media the onset potential for 1T-MoS2 with intercalated ions is lowered by ∼60 mV relative to that for pristine 1T-MoS2 (onset of ∼180 mV). Density functional theory (DFT) calculations show a lowering in the Gibbs free energy for H-adsorption (ΔG H) on these intercalated structures relative to intercalant-free 1T-MoS2. The DFT calculations suggest that Na+ intercalation results in a ΔG H close to zero. Consistent with calculation, experiments show that the intercalation of Na+ ions into the interlayer region of 1T-MoS2 results in the lowest overpotential for the HER.
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