Onset of spin entanglement in doped carbon nanotubes studied by EPR.

Nanoscale semiconductors with isolated spin impurities have been touted as promising materials for their potential use at the intersection of quantum, spin, and information technologies. Electron paramagnetic resonance (EPR) studies of spins in semiconducting carbon nanotubes have overwhelmingly focused on spins more strongly localized by sp3-type lattice defects. However, the creation of such impurities is irreversible and requires specific reactions to generate them. Shallow charge impurities, on the other hand, are more readily and widely produced by simple redox chemistry, but have not yet been investigated for their spin properties. Here, we use EPR to study p-doped (6,5) semiconducting single-wall carbon nanotubes (s-SWNTs) and elucidate the role of impurity-impurity interactions in conjunction with exchange and correlation effects for the spin behavior of this material. A quantitative comparison of the EPR signals with phenomenological modeling combined with configuration interaction electronic structure calculations of impurity pairs shows that orbital overlap, combined with exchange and correlation effects, causes the EPR signal to disappear due to spin entanglement for doping levels corresponding to impurity spacings of 14 nm (at 30 K). This transition is predicted to shift to higher doping levels with increasing temperature and to lower levels with increasing screening, providing an opportunity for improved spin control in doped s-SWNTs.

Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units.

Herein, two new quadrupolar acceptor-π-donor-π-acceptor (A-π-D-π-A) chromophores have been prepared featuring a strongly electron-donating diborene core and strongly electron-accepting dimesitylboryl (BMes2 ) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BF Mes2 ) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry, and UV/Vis-NIR absorption and emission spectroscopy indicated that the compounds have extended conjugated π-systems spanning their B4 C8 cores. The combination of exceptionally potent π-donor (diborene) and π-acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm and very high extinction coefficients of ca. 120 000 m-1  cm-1 . Both molecules also display weak near-IR fluorescence with small Stokes shifts.

Stimulus-Triggered Formation of an Anion-Cation Exciplex in Copper(I) Complexes as a Mechanism for Mechanochromic Phosphorescence.

The investigation of the mechanisms of mechanochromic luminescence is of fundamental importance for the development of materials for photonic sensors, data storage, and luminescence switches. The structural origin of this phenomenon in phosphorescent molecular systems is rarely known and thus the formulation of structure-property relationships remains challenging. Changes in the M-M interactions have been proposed as the main mechanism with d10 coinage metal compounds. Herein, we describe a new mechanism-a mechanically induced reversible formation of a cation-anion exciplex based on Cu-F interactions-that leads to highly efficient mechanochromic phosphorescence and unusual large emission shifts from UV-blue to yellow for CuI complexes. The low-energy luminescence is thermo- and vaporesponsive, thus allowing the generation of white light as well as for recovering the original UV-blue emission.

Association of Diagnostic Stewardship for Blood Cultures in Critically Ill Children With Culture Rates, Antibiotic Use, and Patient Outcomes: Results of the Bright STAR Collaborative.

Importance: Blood culture overuse in the pediatric intensive care unit (PICU) can lead to unnecessary antibiotic use and contribute to antibiotic resistance. Optimizing blood culture practices through diagnostic stewardship may reduce unnecessary blood cultures and antibiotics. Objective: To evaluate the association of a 14-site multidisciplinary PICU blood culture collaborative with culture rates, antibiotic use, and patient outcomes. Design, Setting, and Participants: This prospective quality improvement (QI) collaborative involved 14 PICUs across the United States from 2017 to 2020 for the Bright STAR (Testing Stewardship for Antibiotic Reduction) collaborative. Data were collected from each participating PICU and from the Children's Hospital Association Pediatric Health Information System for prespecified primary and secondary outcomes. Exposures: A local QI program focusing on blood culture practices in the PICU (facilitated by a larger QI collaborative). Main Outcomes and Measures: The primary outcome was blood culture rates (per 1000 patient-days/mo). Secondary outcomes included broad-spectrum antibiotic use (total days of therapy and new initiations of broad-spectrum antibiotics ≥3 days after PICU admission) and PICU rates of central line-associated bloodstream infection (CLABSI), Clostridioides difficile infection, mortality, readmission, length of stay, sepsis, and severe sepsis/septic shock. Results: Across the 14 PICUs, the blood culture rate was 149.4 per 1000 patient-days/mo preimplementation and 100.5 per 1000 patient-days/mo postimplementation, for a 33% relative reduction (95% CI, 26%-39%). Comparing the periods before and after implementation, the rate of broad-spectrum antibiotic use decreased from 506 days to 440 days per 1000 patient-days/mo, respectively, a 13% relative reduction (95% CI, 7%-19%). The broad-spectrum antibiotic initiation rate decreased from 58.1 to 53.6 initiations/1000 patient-days/mo, an 8% relative reduction (95% CI, 4%-11%). Rates of CLABSI decreased from 1.8 to 1.1 per 1000 central venous line days/mo, a 36% relative reduction (95% CI, 20%-49%). Mortality, length of stay, readmission, sepsis, and severe sepsis/septic shock were similar before and after implementation. Conclusions and Relevance: Multidisciplinary diagnostic stewardship interventions can reduce blood culture and antibiotic use in the PICU. Future work will determine optimal strategies for wider-scale dissemination of diagnostic stewardship in this setting while monitoring patient safety and balancing measures.

Natural course following pediatric tracheostomy.

OBJECTIVE: To describe the hospital course of pediatric posttracheostomy patients, their underlying diagnosis, and their demographic characteristics. DESIGN: Retrospective, descriptive record review. SETTINGS: Academic tertiary Pediatric Critical Care Unit. METHODS AND RESULTS: One hundred and forty-one patients 1 month to 20 years old identified and included in the study. The length of in-hospital stay ranged from 14 to 280 days. The most common indications for tracheostomy were ventilation of chronic lung disease (CLD), subglottic stenosis, or combination at 44.7% of the cases followed by neurological cases 26.2%. Patients requiring prolonged stay were more likely to have pulmonary hypertension (odds ratio [OR] = 5.43), gastrointestinal reflux (OR = 2.09), prior episodes of failure to thrive (OR = 4.17), feeding failure requiring feeding tube (OR = 3.32), and tracheitis (OR = 4.17). The chances for home ventilation requirement increased with long preoperative in-hospital ventilation time and high ventilator respiratory rate on the day of tracheostomy as 0.98 days for each preoperative day and 0.94 days for each set ventilator breath (set respiratory rate per minute). The survival rate was 98.9% for the first 30 days and 78% afterward. CONCLUSION: Chronic lung disease, subglottic stenosis, and combinations are the most common causes for tracheostomy at present followed for tracheostomy due to neurological problems. Children requiring tracheostomy have lengthy hospital stay. Establishing an accurate diagnosis helps predict the length of hospitalization and the need for home ventilation; however, in less clear cases, the length of stay can be predicted from the presence of pulmonary hypertension, reflux, and failure to thrive. The mortality rate is low at the postoperative period and increases depending upon the underline reason for tracheostomy referral.

Highly conducting Wurster-type twisted covalent organic frameworks.

Covalent organic frameworks (COFs) define a versatile structural paradigm combining attractive properties such as crystallinity, porosity, and chemical and structural modularity which are valuable for various applications. For the incorporation of COFs into optoelectronic devices, efficient charge carrier transport and intrinsic conductivity are often essential. Here, we report the synthesis of two imine-linked two-dimensional COFs, WTA and WBDT, featuring a redox-active Wurster-type motif based on the twisted tetragonal N,N,N',N'-tetraphenyl-1,4-phenylenediamine node. By condensing this unit with either terephthalaldehyde (TA) or benzodithiophene dialdehyde (BDT), COFs featuring a dual-pore kagome-type structure were obtained as highly crystalline materials with large specific surface areas and mesoporosity. In addition, the experimentally determined high conduction band energies of both COFs render them suitable candidates for oxidative doping. The incorporation of a benzodithiophene linear building block into the COF allows for high intrinsic macroscopic conductivity. Both anisotropic and average isotropic electrical conductivities were determined with van der Pauw measurements using oriented films and pressed pellets, respectively. Furthermore, the impact of different dopants such as F4TCNQ, antimony pentachloride and iodine on the conductivities of the resulting doped COFs was studied. By using the strong organic acceptor F4TCNQ, a massive increase of the radical cation density (up to 0.5 radicals per unit cell) and long-term stable electrical conductivity as high as 3.67 S m-1 were achieved for the anisotropic transport in an oriented film, one of the highest for any doped COF to date. Interestingly, no significant differences between isotropic and anisotropic charge transport were found in films and pressed pellets. This work expands the list of possible building nodes for electrically conducting COFs from planar systems to twisted geometries. The achievement of high and stable electrical conductivity paves the way for possible applications of new COFs in organic (opto)electronics.

Decreasing Exposure to Radiation, Surgical Risk, and Costs for Pediatric Complicated Pneumonia: A Guideline Evaluation.

OBJECTIVES: This report describes the creation and successful implementation of a complicated pneumonia care algorithm at our institution. Outcomes are measured for specific goals of the algorithm: to decrease radiation exposure, surgical risk, and patient charges without adversely affecting clinical outcomes. METHODS: We describe steps involved in algorithm creation and implementation at our institution. To depict outcomes of the algorithm, we completed a retrospective cohort study of hospitalized pediatric patients with a diagnosis of complicated pneumonia at a single institution between January 2010 and April 2016 who met criteria for the algorithm. Charts were manually reviewed and data were analyzed via Wilcoxon rank sum, χ2, and Fisher's exact tests. RESULTS: Throughout the algorithm creation process, our institution began to see a change in practice. We saw a statistically significant decrease in the number of patients who underwent a chest computed tomography scan and an increase in patients who underwent a chest ultrasound (P < .001). We also saw an increase in the use of chest tube placement with fibrinolytics and a decrease in the use of video-assisted thoracoscopic surgery as the initial chest procedure (P ≤ .001) after algorithm implementation. These interventions reduced related charges without significantly affecting length of stay, readmission rate, or other variables studied. CONCLUSIONS: The collaborative creation and introduction of an algorithm for the management of complicated pneumonia at our institution, combined with an effort among physicians to incorporate evidence-based clinical care into practice, led to reduced radiation exposure, surgical risk, and cost to patient.