Bridging Oxygen Research Articles

Effect of CaO/SiO2 and Al2O3/SiO2 Mass Ratios on Structure and Viscosity of Mold Flux for Continuous Casting High‐Mn High‐Al Steel

During continuous casting process of high‐Mn high‐Al steel, soluble Al in the steel typically reacts with SiO2 in the mold flux, resulting in a decrease in SiO2 content and an increase in Al2O3 contents in the flux. The structure of slags with varying CaO/SiO2 and Al2O3/SiO2 mass ratio is investigated using Raman spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. In the deconvolution results of Raman and NMR spectra, it is shown that the relative fractions of and significantly increase, while and gradually decrease with an increase in the CaO/SiO2 mass ratio from 0.52 to 1.02, resulting in depolymerization of the bridge oxygen structure. The silicon–oxygen tetrahedron transforms into aluminum–oxygen tetrahedron when the Al2O3/SiO2 mass ratio increased from 0.05 to 1.01. The viscosity of the slags with varying composition from 1573 to 1373 K is investigated. In the results, it is shown that with an increase in the CaO/SiO2 mass ratio, the viscosity decreases, and the complex SiO network structure is depolymerized. The viscosity decreases first as the Al2O3/SiO2 mass ratio increases from 0.05 to 0.24 and then increases as the mass ratio from 0.24 to 1.01, with the network formers transfer from SiO to SiAlO structures.

Reconstructing the Coordination Environment of Fe/Co Dual-atom Sites towards Efficient Oxygen Electrocatalysis for Zn-Air Batteries.

Dual-atom catalysts with nitrogen-coordinated metal sites embedded in carbon can drive the oxygen reduction and evolution reactions (ORR/OER) in rechargeable zinc-air batteries (ZABs), and the further improvement is limited by the linear scaling relationship of intermediate binding energies in the absorbate evolution mechanism (AEM). Triggering the lattice oxygen mechanism (LOM) is promising to overcome this challenge, but has yet been verified since the lacking of bridge oxygen (O) in the rigid coordination environment of the metal centers. Here, we demonstrate that suitably tailored dual-atom catalysts of FeCo-N-C can undergo out-plane and in-plane reconstruction to form the both axial O and bridge O at the metal centers, and thus activate the LOM pathway. The tailored FeCo-N-C with shortened Fe-N bonds also favor the ORR process, therefore is a promising dual-atom oxygen catalyst. The assembled rechargeable ZABs demonstrate a peak power density of 332 mW cm-2, and exhibit no notable decline after ~ 720 h of continuous cycling.

Abstract 4134712: Pheochromocytoma-Induced Cardiomyopathy Requiring Mechanical Support with Ejection Fracture Recovery Following Surgical Resection

Introduction: Pheochromocytomas are catecholamine-secreting tumors that arise from chromaffin cells of the adrenal medulla. The annual incidence is approximately 0.8 per 100,000 persons, though this is an underestimate given a high percentage diagnosed at autopsy. Classically, patients present with episodic headache, sweating, and tachycardia, however, pheochromocytomas can be associated with cardiomyopathy secondary to the catecholamine excess. We present an unusual case of pheochromocytoma-induced cardiogenic shock highlighting an excellent use of mechanical circulatory support with Impella and Extracorporeal Membrane Oxygenation (ECMO) bridging to surgical intervention resulting in left ventricular ejection fraction (LVEF) recovery. Case Description: A 49-year-old female with past medical history of asthma initially presented to an outside hospital for palpitations, chest pain, and hypertension. Transthoracic echo (TTE) showed preserved left ventricle ejection fraction (LVEF) while cardiac MRI showed a LVEF of 43% with dilated left ventricle and diffuse global hypokinesis consistent with a dilated cardiomyopathy. She underwent a coronary angiogram demonstrating nonobstructive CAD. She was then discharged with readmission a month later at our hospital for chest tightness, palpitations, vomiting, weakness, and dizziness. Repeat TTE showed a drop in LVEF to 10-15%. She progressed to cardiogenic shock requiring BiPAP and inotrope initiation, with progressive shock and hypotension ultimately requiring Impella 5.5 and venoartrial ECMO. Abdominal imaging was notable for 4.7 x 4.2 cm right adrenal nodule and further workup with serum and urine metanephrines confirmed pheochromocytoma. While supported, the patient underwent right adrenalectomy with subsequent wean of mechanical circulatory support and biventricular recovery on TTE. Discussion: Pheochromocytoma-induced heart failure is a rare but potentially life-threatening complication from excess catecholamine effects on the myocardium. Pheochromocytomas should be considered in the evaluation of idiopathic heart failure even in the absence of symptoms related to catecholamine excess. Early detection, pharmacological management, and surgical resection may prevent progression of myocardial remodeling. Mechanical circulatory support can be a valuable adjunct in managing refractory heart failure in these patients by providing temporary hemodynamic stabilization while awaiting definitive tumor resection.

Graphene Oxide-Enhanced Nucleation and Growth of Calcium-Silicate-Hydrate Gel at Nanoscale: A Molecular Dynamics Study.

Graphene oxide (GO) enhances the performance of cement-based materials by optimizing the microstructure of calcium-silicate-hydrate (C-S-H). However, the influence of GO on the nucleation and growth of C-S-H gel at nanoscale is unexplored. This study investigates this mechanism by molecular dynamics simulation at nano scale. Results show that GO can reduce the activation energy during the polymerization reaction of silicon oxide tetrahedra during the reaction process, and can increase the content of polymer Q3 and Q4. The influence of GO with epoxy (-O-), hydroxyl (-OH) and carboxyl (-COOH) groups on the radial distribution function (RDF), mean square displacement (MSD), and atomic spatial distribution of monomers are studied. Results show that GO-OH exhibits excellent performance, with the highest number of bridging oxygen atoms (about 0.6), the lowest Q0 monomer content (just 26.8%), the highest RDF (27.18), and the highest MSD (calcium and silicon content around 20,000 Å2). This paper elucidates the nucleation and growth mechanism of C-S-H influenced by GO to develop high performance cement.

Tunable green-blue luminescence of Dy2O3 doped borosilicate glasses for optoelectronic devices

The optical-structural correlated properties of the 40B2O3−40SiO2−10V2O5−(10−x)Fe2O3−xDy2O3 system, where 2, 4, and 6 mol%, were studied. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) confirmed the glassy and amorphous nature of the samples. Adding Dy2O3 promoted the formation of bridging oxygens (upto 4 mol%) by converting BO3 into BO4 units, however, above 4 mol% Dy2O3 act as a modifier. The optical band gap increased from 3.70 to 4.01 eV, while the refractive index decreased from 2.23 to 2.16. The CIE coordinates indicated that the emission spectra fall within the green-blue region. The as-prepared sample exhibited the highest correlated colour temperature value above 5000 K, suggesting its suitability for cool light-emitting diodes sensitive to human vision. These glasses have potential applications in light-emitting diodes and optoelectronic devices.

Photocatalyzed oxidation of water on oxygen pretreated rutile TiO2(110)

The oxygen evolution reaction (OER) is the bottleneck in the overall photocatalytic splitting of water. The active sites (terminal titanium or bridging oxygen) and active species (molecular or dissociative water) of the initial step of the photocatalyzed OER on the prototypical photocatalyst TiO2, remain debatable. Herein, the photocatalytic chemistry of monolayer water on oxygen-pretreated TiO2(110) (o-TiO2(110)) and reduced TiO2(110) (r-TiO2(110)) surfaces initiated by 400 nm light illumination was investigated by time-dependent two-photon photoemission spectroscopy (TD-2PPE). The photoinduced reduction of the H2O/o-TiO2(110) interface rather than the H2O/r-TiO2(110) interface was detected by TD-2PPE. The difference in 2PPE originated from the presence of the terminal hydroxyl anions (OHt¯) on H2O/o-TiO2(110), as identified by X-ray photoelectron spectroscopy and temperature-programmed desorption. Therefore, the evolution of the electronic structure of H2O/o-TiO2(110) was attributed to the photocatalyzed oxidation of the terminal hydroxyl anions, which most likely formed gaseous •OH radicals, reducing the interface. This work suggested that the oxidation of hydroxyl anions on top of the terminal titanium ions on TiO2, which were excluded previously in solution, need to be considered in the mechanistic studies of the photocatalyzed OER.

Influence of the substitution of CaO by SrO on the structure, degradation and in vitro apatite formation of sol–gel derived SiO2–CaO–SrO–P2O5system bioactive glasses

The present study investigates the influence of the substitution of CaO by SrO on the structure, degradation and in vitro apatite formation of sol–gel-derived bioactive glasses with composition of 58SiO2–(38-x)CaO–xSrO–4P2O5, where x varies between 0 and 10 mol.%. The IV-type nitrogen adsorption/desorption isotherms and pore size values (ranging from 5.41 to 12.56 nm) confirmed the mesoporous structure of the synthesized glasses. The detailed structural analysis was carried out by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). As network modifiers, the addition of Ca and Sr oxides disrupted the bonds of bridging oxygens (BOs) and resulted in the formation of non-bridging oxygens (NBOs), where the substitution of Ca with Sr led to an increase in Q1 units and a decrease in Q3 units. The effects of the addition of Sr on sample degradation and apatite formation were assessed using an assay in tris-(hydroxymethyl)-aminomethane and hydrochloric acid (Tris–HCl) and simulated body fluid (SBF). The results demonstrated that the substitution of CaO by SrO in the CaO–SiO2–P2O5 bioglass system altered the glass structure, resulting in reduced sample degradation and delayed apatite formation. This suggests that the incorporation of Sr into bioactive glasses may serve as a promising strategy to regulate the structure, dissolution behavior and apatite formation of silicate-based glasses, particularly concerning their long-term applications within the human body.

The exploration of effect for nano-Al2O3 on solid waste based superfine tailings cemented paste backfill: Pyrolysis property, hydration mechanism and environmental risk

Resource utilization of superfine tailings has become a key research direction in filling mining. This study analyzes the mechanical properties, pyrolysis mechanism and hydration mechanism of nano-Al2O3(NA)-doped solid waste based superfine tailings cemented paste backfill (SWSCPB) by multiple microscopic characterization methods and pyrolysis kinetic theory. The results show that the main temperature interval for the pyrolysis of SWSCPB to happen is 280–900 °C, which is divided into two stages of dehydroxylation and decarbonization. The apparent activation energy(E) and pre-index factor(A) of pyrolysis are higher than those of NA0 and NA2 at 1 % NA dosage, indicating that NA increases the energy barrier of pyrolysis, the percentage of activated molecules, and the collision probability of hydration products in SWSCPB, but decreases due to agglomeration at exceeds 1 % NA dosage. NA can enhance macroscopic strength of SWSCPB, with the highest strength at 1 % NA dosage. Compared with NA0 and NA2, more hydration products such as AFt and C-(A)-S-H are present in NA1, and the distribution of Q2 and Q4 in C-(A)-S-H is more pronounced, with a higher degree of polymerization, a stronger tendency for the conversion of non-bridging to bridging oxygen bonds, and fewer pores in the microstructure of SWSCPB. The NA dosage can provide more nuclei for the formation of AFt, C-(A)-S-H in SWSCPB, and can also promote the replacement of Si by Al for the conversion of C-S-H to C-(A)-S-H with higher polymerization. In addition, the leaching risk and mechanism of heavy metal ions from SWSCPB are preliminarily explored in combination with leaching experiments. The results provide new insights and guidance for the application of SWSCPB in filling mining under cleaner production targets.

Hydroxyl-modified g-C3N4/Al2O3 heterojunction connected with oxygen bridge for boosting photocatalytic H2O2 production

Hydroxyl-modified g-C3N4/Al2O3 heterojunction connected with oxygen bridge for boosting photocatalytic H2O2 production

Fe2O3/In2O3 composite materials for dual-selective detection of H2S and NO2: Study on sensing mechanisms and sensing transition

Developing concise and efficient dual-selective gas sensors has been a significant challenge in sensing technology. In this study, a Fe2O3/In2O3 (FIO) composite material was successfully synthesized via a water bath method for highly efficient dual-selective detection of H2S and NO2. The enhanced dual-selectivity of the composite material is attributed to the high-quality heterojunction formed at the Fe2O3 and In2O3 interface, which provides more active sites and optimizes the electronic structure, thereby greatly improving electron transport efficiency. Consequently, this unique structure significantly enhances the gas sensing response and stability of the composite material. The optimal FIO-3 composite shows significant responses: 14.7 at 80 °C with 100 ppm H2S and 64.3 at 100 °C with 700 ppb NO2, achieving 7- and 31-fold improvements over pure Fe2O3. Analysis indicates that the dual-selective response of the FIO composite material is attributed to synergistic enhancement mechanisms, primarily controlled by high-temperature activation effects. Further density functional theory (DFT) studies reveal changes in charge density at the composite material interface, particularly facilitated by the formation of oxygen bridges promoting electron transfer from In2O3 to Fe2O3. This study offers new insights into the sensing transition of dual-selective gas sensors.

Dinuclear Copper(II) Complex with Intramolecular O–H⋅⋅⋅O Hydrogen Bonding: Magneto‐Structural Correlation for Acylhydrazone‐Based Phenoxido Bridged Copper(II) Complexes

The μ‐phenoxido‐bridged dinuclear copper(II) complex, [Cu2(L1)2(dmso)(MeOH)] (1), has been synthesized using N′‐(4‐(diethylamino)‐2‐hydroxybenzylidene)‐1‐naphthohydrazide (H2L1) as ligand. The structural analysis of 1 reveals that the coordination geometry at the copper ions is best described as a square pyramidal with a Cu···Cu distance in the dinuclear complex of 303 pm which is supported by hydrogen bonding between the two apical oxygen donor ligands (O···O 277 pm). Magnetic studies indicate that 1 exhibits a strong antiferromagnetic interaction between the two copper(II) ions with a coupling constant of J = −450 cm−1. The magnetic exchange is transmitted through the central [Cu2(OR)2]2+ core, a fragment for which different magneto‐structural correlations have been reported depending on the substituent at the bridging oxygen atom. However, the properties of complex 1 cannot be explained by any of the established correlations. Nevertheless, complex 1, together with the series of compounds based on an acylhydrazone ligand framework reported so far, shows a magneto‐structural correlation as a function of the Cu−O−Cu bridging angle that significantly differs from all previously reported.

Enhanced optical and structural traits of irradiated lead borate glasses via Ce3+ and Dy3+ ions with studying Radiation shielding performance

Lead borate glass is the best radiation shielding glass when lead is in high concentration. However, it has low transparency after radiation exposure. Radiation decreases transparency due to chemical and physical changes in the glass matrix, such as creating or healing defects in the glass network. The addition of rare earth elements like cerium and dysprosium oxides to lead borate glasses can improve their transparency and durability as radiation shielding barriers. The newly manufactured glasses’ optical absorption, structural, and radiation shielding properties were measured. The optical characteristics of the generated samples were examined to determine the effect of the cerium/dysprosium ratio on the structural alterations, specifically in the presence of bridging oxygen (BO) and non-bridging oxygen (NBO). Incorporating Ce3+ results in peaks at 195 nm for borate units, 225 nm for Ce3+, and a broadened peak at 393 nm due to overlapping peaks for Ce3+ and Ce4+ in the UV region. By adding Dy, multiple peaks are observed at 825, 902, 1095, 1275, and 1684 nm, corresponding to the transition from 6H15/2 ground state to 6F5/2, 6F7/2, 6F9/2, 6F11/2, and 6H11/2. The samples were also tested before and after exposure to gamma irradiation from a 60Co source at a dose of 75 kGy to assess their stability against radiation. The energy gap value during irradiation shows decreased non-bridging oxygen. The energy gap difference before and after irradiation for the M4 sample shows higher NBO to BO conversion, reducing radiation damage and improving structural stability. Furthermore, X-ray photoelectron spectroscopy was utilized to get insight into the coordination chemistry of the created glass samples. The half-value layer (HVL), radiation protection efficiency (RPE), neutron removal cross-section (FRNCS), mean free path (MFP), mass attenuation coefficients (MAC), and effective atomic numbers (Zef) of the glassy structure were calculated theoretically to assess its radiation shielding qualities. The linear attenuation coefficient order for the prepared samples was M1 > M2 > M3 > M4. The FRNCS values were 0.090, 0.083, 0.081, and 0.079 cm−1 for samples M1, M2, M3, and M4, respectively.

Effect of sodium gluconate addition on setting, hardening, and microstructure behaviour of hybrid alkaline mortar

In this investigation, the influence of adding 2 %, 4 %, 7 %, and 10 % sodium gluconate (SG) on the setting time of hybrid alkaline paste, and hardened and microstructure properties of hybrid alkaline mortar mixes were examined, and the results were compared with a control mix that made without addition of sodium gluconate. The hybrid alkaline paste and mortar mixes were prepared using a fixed proportion of OPC/fly ash (25 %/75 %), NaOH solution molarity of 9 M, and sodium silicate to hydroxide ratio of 1.5. The results of this investigation found that the quick setting and abrupt loss of flowability of the control mix were improved by adding sodium gluconate, however, more promising results were observed at 7 % and 10 % sodium gluconate. The delay in polymerization due to lower availability of calcium ions, and adsorption of carboxyl and hydroxyl groups associated with sodium gluconate on the unreacted particles of binding materials and earlier formed products assisted in prolonging the time required for hardening. Further, the compressive strength declined at a higher dosage of sodium gluconate, however, the mortar mixes made with 2 % and 4 % sodium gluconate exhibited higher compressive strength than the control mix. The peak intensity of albite, nepheline, and C–S–H gel decreased at higher dosages of sodium gluconate, which was supported by a weaker microstructure characterized by more pores, micro-cracks, and partially reacted fly ash particles. Furthermore, the lower bridging oxygen content and greater Si–O–Na/ Si–O–T ratio at higher dosage of sodium gluconate confirms the delayed polymerization process.

Fluidity and structure of aluminate slags for smelting high-alumina iron ores: Effect of CaO/SiO2 mass ratio

Slag regulation is crucial for achieving smelting of high-alumina iron ore in blast furnaces. This study investigated the fluidity and structure of CaO-SiO2–10 wt.%MgO-30 wt.%Al2O3 slag by varying the CaO/SiO2 ratio (1.0–2.0). The results revealed that viscosity decreased with increasing CaO/SiO2 ratio, while the free running temperature, defined as the temperature at which the slag can flow freely, initially increased and then decreased, peaking at the range of 1.2–1.6. Interestingly, the free running temperature of slag at basicity 2.0 (1392 °C) was lower than that at basicity 1.0 (1398 °C). Spectroscopic analysis demonstrated that increasing basicity facilitated greater charge compensation of Al3+ ions, resulting in an increased amount of [AlO4] tetrahedra. Moreover, increasing free oxygen promoted the depolymerization of [SiO4] and [AlO4] tetrahedra, reducing bridging oxygen and increasing non-bridging oxygen. Consequently, the slag's overall polymerization degree decreased. Furthermore, MD simulations identified two distinct fracture mechanisms of bridging oxygen within the Si-O-Si structure.

Electron Paramagnetic Resonance Analysis of Hydroquinone Polymerization Catalyzed by Small Laccase

AbstractLaccases are multi‐copper oxidases (MCOs) that oxidize a broad range of substrates while reducing molecular oxygen to water. Although much effort has been made to elucidate the catalytic mechanism of laccases, information about reactive catalytic intermediates during catalysis is not yet fully understood. Herein, hydroquinone (HQ) polymerization catalyzed by prokaryotic small laccase (SLAC) was investigated by electron paramagnetic resonance (EPR) spectroscopy to provide more information on the catalytic mechanism. Briefly, free radical intermediates during the catalysis were investigated by real‐time in situ EPR measurement to monitor the formation and transformation of free radicals. A paramagnetic species was identified which was attributed to a copolymer formed by hydroquinone, benzoquinone, and semiquinone radical. In addition, the low‐temperature EPR spectrum of the trinuclear copper center during catalysis not only revealed tentative rotational motion of the histidine imidazole rings coordinating the TNC upon electron uptake but also provided evidence of the formation of oxygen bridge at TNC during the reaction, represented by the observation of a new type 2 copper component featured larger g// values and smaller A// values. Together, EPR spectroscopic insights into the catalytic intermediates during enzymatic hydroquinone polymerization have extended the knowledge of the biophysical characteristics and catalytic mechanism of SLAC.

Structure and dynamic viscosity of CaO–SiO2 and CaO–SiO2–B2O3 model slag systems

Correlation dependencies between the dynamic viscosity of slag and its structural parameters were studied to determine an optimal basicity of silicon smelting slag under the addition of boron oxide to eliminate slagging of the bottom of ore-smelting furnaces. Experimental studies were conducted on CaO–SiO2 and CaO– SiO2–B2O3 model slags obtained at 1600°С. Raman spectroscopic analysis was carried out using a Horiba JobinYvon HR800UV analyzer (France). Theoretical calculations of slag viscosity were performed using Urbain and Mills models. During the experiments, the key structural parameters of slag systems varied within the following limits: the experimental Raman spectrum deconvolution function from 1.41 to 2.45 and optical basicity from 0.58 to 0.68. The obtained experimental and theoretical data were related by mathematical dependencies. It was found that the dynamic viscosity of slag can be promptly determined by Raman spectroscopy on the basis of mathematical models. The dependence obtained shows that slag viscosity decreases upon an increase in the number of bridging oxygen atoms in the silicate anion structure. Notably, this decrease in slag viscosity is observed up to the value of the experimental Raman spectrum deconvolution function of ~1.55-1.60 or slag optical basicity of 0.60–0.62. When B2O3 is added, the viscosity undergoes a further decrease. In practice, for CaO–SiO2 slag systems, the use of boroncontaining flux as a liquefying agent is reasonable at CaO/SiO2 = 0.61–0.63 while maintaining the content of B2O3 in the slag at a level of 1%. The two models (classical and modified) proposed by Urbain were established to be more suitable for theoretical calculation of viscosity in CaO–SiO2 and CaO–SiO2–B2O3 systems. Mills’ model is not suitable for these purposes, since the correlation coefficients in the corresponding mathematical model are not sufficiently large. Further research in this direction is required in order to establish appropriate dependencies of slag viscosity on its structural parameters at different temperatures.

Proton-Coupled Electron Transfer in Photoelectrochemical Alcohol Oxidation Enhanced by Nickel-Based Cocatalysts.

Using biomass oxidation reactions instead of water oxidation reactions is optimal for accomplishing biomass conversion and effective hydrogen generation. Here, we report that α-Fe2O3 photoanodes with a NiOOH cocatalyst exhibit excellent performance for photoelectrochemical oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). The conversion efficiency for HMF reaches 98.5 %, while the selectivity for FDCA is 94.2 %. We revealed that HMF is oxidized through a spontaneous proton-coupled electron transfer (PCET) process with the high-valent phase of the Ni-based catalyst. The dangling oxygen and bridging oxygen of the high-valent phase species serve as proton-accepting sites. Furthermore, we pointed out that the deprotonated bond dissociation free energy difference between the catalysts and alcohols is the thermodynamic trigger for the PCET process. This study provides a reasonable explanation for the alcohol oxidation reaction, which is beneficial for designing biomass conversion systems.

High pressure-derived nonsymmetrical [Cu2O]2+ core for room-temperature methane hydroxylation.

Nonsymmetrical oxygen-bridged binuclear copper centers have been proposed and modeled as intermediates and transition states in several C─H oxidation pathways, leading to the postulation that structural dissymmetry enhances the reactivity of the bridging oxygen. However, experimentally characterizing the structure and reactivity of these transient species is remarkably challenging. Here, we report the high-pressure synthesis of a metastable nonsymmetrical dicopper-μ-oxo compound with exceptional reactivity toward the mono-oxygenation of aliphatic C─H bonds. The nonequivalent coordination environment of copper stabilizes localized mixed valency and greatly enhances the hydrogen atom abstraction activity of the bridging oxygen, enabling room-temperature hydroxylation of methane under pressure. These findings highlight the role of dissymmetry in the reactivity of binuclear copper centers and demonstrate precise control of molecular structures by mechanical means.

Survival After Extracorporeal Membrane Oxygenation Bridge to Lung Retransplantation

BackgroundExtracorporeal membrane oxygenation (ECMO) is increasingly used as a bridge to lung transplantation. Despite success in select populations, candidates requiring ECMO bridge to retransplantation have historically had poor 1-year survival. This study aimed to examine the characteristics of the recipient, donor, and transplant procedure type to guide selection of candidates for ECMO bridge to retransplantation. MethodsThis was a retrospective cohort study of all US adult lung retransplant recipients between May 5, 2005, and December 31, 2022. We evaluated 1-year survival of ECMO-bridged retransplant patients, stratified by time from initial transplant, procedure type (single or bilateral retransplant), and ECMO era (2005-2017 vs 2018-2022). ResultsIn this national cohort, 111 of 1296 (8.6%) retransplant recipients underwent ECMO bridge. One-year survival was worse for ECMO bridge retransplant recipients (52.2% vs 74.0%; P < .001) and has worsened in the contemporary era (2018-2022) of ECMO bridge to retransplantation compared with prior years (P = .03). Time from initial transplantation and use of bilateral retransplant after an initial bilateral transplant were most strongly associated with improved 1-year survival of ECMO-bridged retransplant recipients. Of bilateral recipients bridged to bilateral transplant more than 1 year after primary transplantation, survival was 65.9% in ECMO-bridged patients as opposed to 77.2% in nonbridged patients. ConclusionsCareful selection of candidates and surgical procedure type remains essential in determining candidacy for ECMO bridge to retransplantation.

Densification mechanism and structural transformation in glass: molecular dynamic simulation

The structure of GeO2 glass is investigated via molecular dynamic simulation. The influence of pressure to the structure of GeO2 glass is due to the change of short-range order, network structure, domain structure and free volume regions. The obtained results show that the structure of GeO2 was formed by a continuous random network of basic structural units linking to each other via with corner-sharing, edge-sharing, face-sharing bond. At low pressure, the basic structural units are mainly linked via one bridge oxygen (the corner sharing bonds). As pressure increases, the fraction of edge sharing bonds (two bridge oxygen) increases meanwhile the fraction of corner sharing bonds significantly decrease. There is a slight increase with the fraction of face- sharing bonds (three bridge oxygen). The Ge-O bond distance is almost not dependent on pressure, meanwhile the Ge-Ge and O-O bond distances are significantly dependent on pressure. Under compression, the average coordination number of Ge tends to increase from fourfold (at ambient pressure) to six-fold (at high pressure). Moreover, structure of GeO2 glass has two-domain near 15 and 25 GPa. And at ambient pressure or high pressures, the struture of GeO2 glass has single domain. The dependence of the distribution of free volumes on pressure in GeO2 glass has been examined. The distribution of void radius has the Gaussian form and the position of the peak tend to shift to the left under compression.