The antiferromagnetic spin-1/2 Heisenberg model on a kagome lattice is one of the most paradigmatic models in the context of spin liquids, yet the precise nature of its ground state is not ...understood. We use large-scale density matrix renormalization group simulations (DMRG) on infinitely long cylinders and find indications for the formation of a gapless Dirac spin liquid. First, we use adiabatic flux insertion to demonstrate that the spin gap is much smaller than estimated from previous DMRG simulation. Second, we find that the momentum-dependent excitation spectrum, as extracted from the DMRG transfer matrix, exhibits Dirac cones that match those of a π -flux free-fermion model the parton mean-field ansatz of a U(1) Dirac spin liquid.
Quantum magnets provide the simplest example of strongly interacting quantum matter, yet they continue to resist a comprehensive understanding above one spatial dimension. We explore a promising ...framework in two dimensions, the Dirac spin liquid (DSL) - quantum electrodynamics (QED
) with 4 Dirac fermions coupled to photons. Importantly, its excitations include magnetic monopoles that drive confinement. We address previously open key questions - the symmetry actions on monopoles on square, honeycomb, triangular and kagome lattices. The stability of the DSL is enhanced on triangular and kagome lattices compared to bipartite (square and honeycomb) lattices. We obtain the universal signatures of the DSL on triangular and kagome lattices, including those of monopole excitations, as a guide to numerics and experiments on existing materials. Even when unstable, the DSL helps unify and organize the plethora of ordered phases in correlated two-dimensional materials.
Introduction In very low birth weight (VLBW) infants, hypothermia immediately following birth is common even in countries rich in medical resources. The purpose of this study is to design a standard ...prevention bundle that decreases the rate of hypothermia among infants after birth and to investigate efficacy of the bundle and short-term outcomes for VLBW infants. Methods This quality improvement project was conducted from February 2017 to July 2018 on all VLBW preterm infants admitted at a single referral level III neonatal intensive care unit. The infants were classified into the pre-intervention (February to September 2017) and post-intervention (October 2017 to July 2018) groups according to the time periods when they were recruited. During the pre-intervention period, we analyzed the primary causes of hypothermia, developed solutions corresponding to each cause, integrated all solutions into a prevention bundle, and applied the bundle during the post-intervention period. Afterwards, the incidence of neonatal hypothermia and short-term outcomes, such as intraventricular hemorrhage (IVH), acidosis, and shock requiring inotropic agents, in each group were compared. Results A total of 95 VLBW infants were enrolled in the study, including 37 pre-intervention, and 58 post-intervention cases. The incidence of hypothermia in preterm infants decreased significantly upon the implementation of our prevention bundle, both in the delivery room (from 45.9% to 8.6%) and on admission (59.5% to 15.5%). In addition, the short-term outcomes of VLBW infants improved significantly, especially with the decreased incidence of IVH (from 21.6% to 5.2%, P = 0.015). Conclusions Our standardized prevention bundle for preventing hypothermia in VLBW infants is effective and decreased the IVH rate in VLBW infants. We strongly believe that this prevention bundle is a simple, low-cost, replicable, and effective tool that hospitals can adopt to improve VLBW infant outcomes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We study the spin liquid candidate of the spin-1/2 J_{1}-J_{2} Heisenberg antiferromagnet on the triangular lattice by means of density matrix renormalization group (DMRG) simulations. By applying an ...external Aharonov-Bohm flux insertion in an infinitely long cylinder, we find unambiguous evidence for gapless U(1) Dirac spin liquid behavior. The flux insertion overcomes the finite size restriction for energy gaps and clearly shows gapless behavior at the expected wave vectors. Using the DMRG transfer matrix, the low-lying excitation spectrum can be extracted, which shows characteristic Dirac cone structures of both spinon-bilinear and monopole excitations. Finally, we confirm that the entanglement entropy follows the predicted universal response under the flux insertion.
We propose a new type of quantum liquids, dubbed Stiefel liquids, based on (2+1)-dimensional nonlinear sigma models on target spaceSO(N)/SO(4), supplemented with Wess-Zumino-Witten terms. We argue ...that the Stiefel liquids form a class of critical quantum liquids with extraordinary properties, such as large emergent symmetries, a cascade structure, and nontrivial quantum anomalies. We show that the well-known deconfined quantum critical point andU(1)Dirac spin liquid are unified as two special examples of Stiefel liquids,N=5andN=6, respectively. Furthermore, we conjecture that Stiefel liquids withN>6are non-Lagrangian, in the sense that under renormalization group they flow to infrared (conformally invariant) fixed points that cannot be described by any renormalizable continuum Lagrangian. Such non-Lagrangian states are beyond the paradigm of parton gauge mean-field theory familiar in the study of exotic quantum liquids in condensed matter physics. The intrinsic absence of (conventional or partonlike) mean-field construction also means that, within the traditional approaches, will be difficult to decide whether a non-Lagrangian state can actually emerge from a specific UV system (such as a lattice spin system). For this purpose we hypothesize that a quantum state is emergible from a lattice system if its quantum anomalies match with the constraints from the (generalized) Lieb-Schultz-Mattis theorems. Based on this hypothesis, we find that some of the non-Lagrangian Stiefel liquids can indeed be realized in frustrated quantum spin systems, for example, on triangular or kagome lattice, through the intertwinement between noncoplanar magnetic orders and valence-bond-solid orders.
Comprising an emitting layer (EML) constituting a wide‐energy‐gap host, a thermally activated delayed fluorescence (TADF) sensitizer and a conventional fluorescent dopant, ...TADF‐sensitizing‐fluorescence organic light‐emitting diodes (TSF‐OLEDs) highly depend on component interplay to maximize their performance, which, however, is still under‐researched. Taking the host type (TADF or non‐TADF) and the recombination position (on the host or on the TADF sensitizer) into consideration, the interplay of host and TADF sensitizer is comprehensively studied and manipulated. A wide‐energy‐gap host with TADF and recombination of charges on it are both required to maximize device performances by triggering multiple sensitizing processes to eliminate exciton losses. Based on those findings, a maximum external quantum efficiency (EQE)/power efficiency (PE) of 23.2%/76.9 lm W−1 is realized with a newly developed TADF host, significantly outperforming the reference devices. Further device optimization leads to unprecedently high EQE/PE of 24.2%/89.5 lm W−1 and a half‐lifetime of over 400 h at an initial luminance of 2000 cd m−2, with the peak PE being the highest value among the reported TSF‐OLEDs. This work reveals the importance of manipulating the component interplay in EMLs, opening a new avenue toward highly efficient TSF‐OLEDs.
The interplay between the wide‐energy‐gap host and the thermally activated delayed fluorescence (TADF) sensitizer in fluorescent organic light‐emitting diodes is comprehensively studied. This reveals that an efficient TADF host and recombination on it are both required for multiple sensitizing processes, which leads to a maximum external quantum efficiency/power efficiency of 24.2%/89.5 lm W−1.
Curcumin and curcuminoids have been discussed frequently due to their promising functional groups (such as scaffolds of α,β-unsaturated β-diketone, α,β-unsaturated ketone and ...β'-hydroxy-α,β-unsaturated ketone connected with aromatic rings on both sides) that play an important role in various bioactivities, including antioxidant, anti-inflammatory, anti-proliferation and anticancer activity. A series of novel curcuminoid derivatives (a total of 55 new compounds) and three reference compounds were synthesized with good yields using three-step organic synthesis. The anti-proliferative activities of curcumin derivatives were examined for six human cancer cell lines: HeLaS3, KBvin, MCF-7, HepG2, NCI-H460 and NCI-H460/MX20. Compared to the IC
values of all the synthesized derivatives, most α,β-unsaturated ketones displayed potent anti-proliferative effects against all six human cancer cell lines, whereas β'-hydroxy-α,β-unsaturated ketones and α,β-unsaturated β-diketones presented moderate anti-proliferative effects. Two potent curcuminoid derivatives were found among all the novel derivatives and reference compounds: (
)-5-hydroxy-7-phenyl-1-(3,4,5-trimethoxyphenyl)hept-1-en-3-one (compound
) and (1
,4
)-1,7-bis(3,4,5-trimethoxyphenyl)hepta-1,4-dien-3-one (compound
). These were selected for further analysis after the evaluation of their anti-proliferative effects against all human cancer cell lines. The results of apoptosis assays revealed that the number of dead cells was increased in early apoptosis and late apoptosis, while cell proliferation was also decreased after applying various concentrations of (
)-5-hydroxy-7-phenyl-1-(3,4,5-trimethoxyphenyl)hept-1-en-3-one (compound
) and (1
,4
)-1,7-bis(3,4,5-trimethoxyphenyl)hepta-1,4-dien-3-one (compound
) to MCF-7 and HpeG2 cancer cells. Analysis of the gene expression arrays showed that three genes (GADD45B, SESN2 and BBC3) were correlated with the p53 pathway. From the quantitative PCR analysis, it was seen that (1
,4
)-1,7-bis(3,4,5-trimethoxyphenyl)hepta-1,4-dien-3-one (compound
) effectively induced the up-regulated expression of GADD45B, leading to the suppression of MCF-7 cancer cell formation and cell death. Molecular docking analysis was used to predict and sketch the interactions of the GADD45B-α,β-unsaturated ketone complex for help in drug design.
Multiple resonance (MR) emitters are promising for highly efficient organic light‐emitting diodes (OLEDs) with narrowband emission; however, they still face intractable challenges with ...concentration‐caused emission quenching, exciton annihilation, and spectral broadening. In this study, sterically wrapped MR dopants with a fluorescent MR core sandwiched by bulk substituents were developed to address the intractable challenges by reducing intermolecular interactions. Consequently, high photo‐luminance quantum yields of ≥90 % and small full width at half maximums (FWHMs) of ≤25 nm over a wide range of dopant concentrations (1–20 wt %) were recorded. In addition, we demonstrated that the sandwiched MR emitter can effectively suppress Dexter interaction when doped in a thermally activated delayed fluorescence sensitizer, eliminating exciton loss through dopant triplet. Within the above dopant concentration range, the optimal emitter realizes remarkably high maximum external quantum efficiencies of 36.3–37.2 %, identical small FWHMs of 24 nm, and alleviated efficiency roll‐offs in OLEDs.
Sterically wrapped multiple resonance (MR) dopants with the MR‐core sandwiched by bulk substituents have been developed to suppress molecular interactions, realizing organic light‐emitting diodes with remarkably high maximum external quantum efficiencies of 36.3–37.2 %, identical small FWHMs of 24 nm and alleviated efficiency roll‐offs over a wide range of dopant concentrations (1–20 wt %).
Lowland coastal plain rivers are important for navigation and ecosystems, having unique concerns regarding water and sediment management. The Apalachicola River in Florida, the lower end of the ACF ...(Apalachicola–Chattahoochee–Flint) system, had historical modifications beginning in the 1800s. Most impacts are attributable to the Apalachicola Navigation Project in the latter half of the 20th century, which included dredging, disposal, rock and snag removal, artificial cutoffs, and wing‐dike building.
As one of few studies using paired hydrographic surveys over a long reach and time (170 km, 50 years), we defined four zones of bed elevation change between 1960 and 2010 based on the cumulative thalweg elevation plots. The river has four bed change zones: (1) uppermost, marked degradation from river mile (RM) 106 to 85 because of dam construction; (2) middle, minimal degradation from RM 85 to 34; (3) artificial cutoff zone, highest degradation, from RM 34 to 27; and (4) lowermost zone, aggradation from RM 27 to Apalachicola Bay because of upstream bed and bank sediment disturbances. Artificial cutoffs and lithology influence lateral migration, with rates being highest in cutoff zones and least in areas with some bedrock upstream and finer sediments downstream. Length changes from 1941 to 2019 are stable, except for the middle reach, which lengthened nearly 10%, and the lower non‐tidal reach, where length shortened with cutoffs then regained in subsequent decades. Minimizing disturbance has led to 18% of the sand bar area revegetating since a decade of dredging ended. This framework helps in understanding historic and ongoing human activities, notably upstream water consumption, connectivity changes, sediment inputs, and climate change, that will affect the water and sediment management of the river, its floodplain, and bay, thus varying approaches for restoration.
This study synthesizes historical disturbance and channel change data along the Apalachicola River, Florida, USA. Thalweg elevation change between 1960 and 2010 (A) demonstrates four zones of riverbed changes including degradation associated with dam construction and artificial cutoffs in upper and middle reaches, and aggradation in the lowermost zone because of excess sediment production from upstream (B). Findings improve the understanding of impacts from anthropogenic activities that affect water levels and sediments in this lowland river system.
Aims and objectives
To assess the concurrent validity between logbooks and a single‐item rehabilitation adherence measurement for patients with stroke. Agreement between caregivers and patients and ...between caregivers and physical therapists regarding a single‐item measurement was investigated, and its predictive validity was explored.
Background
Adherence to therapy is a primary determinant of treatment success. There are no standard instruments for measuring rehabilitation adherence available for stroke patients.
Design
Prospective longitudinal study.
Methods
Seventy‐five patients with stroke were recruited, measured four times and followed for 6 months. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist was used to ensure comprehensive reporting. Adherence was documented in logbooks, and single‐item measurements were compared. Predictive validity was explored by assessing associations between adherence levels, self‐care ability and health‐related quality of life. The Spearman's correlation coefficients, weighted kappa, and generalised estimating equations statistics were used to explore the concurrent validity, measurement agreement, and predictive validity, respectively.
Results
Logbook records had a fair correlation (rs = .23, p = .04) with the single‐item rehabilitation adherence measurements. There was moderate agreement (kappa = 0.42, p < .001) between caregiver and patient assessments and fair agreement (kappa = 0.29, p = .017) between caregiver and physical therapist assessments of patients' rehabilitation adherence levels. Perfect rehabilitation adherence, based on the logbook and single‐item measurements, predicted better scores for self‐care ability and quality of life than imperfect rehabilitation adherence during 6 months after inclusion.
Conclusions
There was fair concurrent validity between logbooks and single‐item rehabilitation adherence measurements and moderate and fair adherence measure agreement between caregivers and patients and caregivers and physical therapists, respectively. Logbooks and single‐item rehabilitation adherence measurements had adequate predictive validity.
Relevance to clinical practice
Single‐item rehabilitation adherence measurement is a workable and straightforward method to assess stroke patients' rehabilitation adherence in busy clinical care settings. Caregivers can represent stroke patients regarding their reported rehabilitation adherence.
Patient or public contribution
Patients were diagnosed with stroke in the study hospital. Rehabilitation physicians transferred patients to a research nurse who then screened them for the inclusion criteria and invited them and their family caregivers to participate in this study if they met the requirements. We also recruited seven physical therapists responsible for the physical therapy of the study participants. After participants signed informed consent, the research nurse encouraged participants to respond to research questions face to face, including rehabilitation adherence data, daily physical function, and quality of life. Each participant was measured four times at baseline and at 1, 3, and 6 months after inclusion in this study. Physical therapists had to score their patients' rehabilitation adherence levels before discharge.
Trial registration details
Not applicable.
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