Strategies for the Surgical Management of Highly Aggressive Williams Syndrome Aortopathy: A Three Case Report.

Severe aortopathy in Williams syndrome can sometimes present with an initial ascending aortic pathology, followed in short order by more distal multilevel obstruction and recurrence requiring reintervention. In this series, an early, comprehensive surgical approach using a combination of various access and perfusion strategies yielded excellent long-term results.

Heteropolymetallic [FeFe]-Hydrogenase Mimics: Synthesis and Electrochemical Properties.

The synthesis and electrochemical properties of tetranuclear [Fe2S2]-hydrogenase mimic species containing Pt(II), Ni(II), and Ru(II) complexes have been studied. To this end, a new tetranuclear [Fe2S2] complex containing a 5,5'-diisocyanide-2,2'-bipyridine bridging ligand has been designed and coordinated to the metal complexes through the bipyridine moiety. Thus, the tetranuclear [Fe2S2] complex (6) coordinates to Pt(II), Ni(II) and Ru(II) yielding the corresponding metal complexes. The new metal center in the bipyridine linker modulates the electronic communication between the redox-active [Fe2S2] units. Thus, electrochemical studies and DFT calculations have shown that the presence of metal complexes in the structure strongly affect the electronic communication between the [Fe2S2] centers. In the case of diphosphine platinum compounds 10, the structure of the phosphine ligand plays a crucial role to facilitate or to hinder the electronic communication between [Fe2S2] moieties. Compound 10a, bearing a dppe ligand, shows weak electronic communication (ΔE = 170 mV), whereas the interaction is much weaker in the Pt-dppp derivative 10b (ΔE = 80 mV) and virtually negligible in the Pt-dppf complex 10c. The electronic communication is facilitated by incorporation of a Ru-bis(bipyridine) complex, as observed in the BF4 salt 12 (ΔE = 210 mV) although the reduction of the [FeFe] centers occurs at more negative potentials. Overall, the experimental-computational procedure used in this work allows us to study the electronic interaction between the redox-active centers, which, in turn, can be modulated by a transition metal.

Outcomes and Risk Factors of Interventions for Pediatric Post-operative Pulmonary Vein Stenosis.

Pulmonary vein stenosis (PVS) in children is a challenging condition with poor outcomes. Post-operative stenosis can occur after repair of anomalous pulmonary venous return (APVR) or stenosis within native veins. There is limited data on the outcomes of post-operative PVS. Our objective was to review our experience and assess surgical and transcatheter outcomes. Single-center retrospective study was performed including patients < 18 years who developed restenosis after baseline pulmonary vein surgery that required additional intervention(s) from 1/2005 to 1/2020. Non-invasive imaging, catheterization and surgical data were reviewed. We identified 46 patients with post-operative PVS with 11 (23.9%) patient deaths. Median age at index procedure was 7.2 months (range 1 month-10 years), and median follow-up was 10.8 months (range 1 day-13 years). Index procedure was surgical in 36 (78.3%) and transcatheter in 10 (21.7%). Twenty-three (50%) patients developed vein atresia. Mortality was not associated with number of affected veins, vein atresia, or procedure type. Single ventricle physiology, complex congenital heart disease (CCHD), and genetic disorders were associated with mortality. Survival rate was higher in APVR patients (p = 0.03). Patients with three or more interventions had a higher survival rate compared to patients with 1-2 interventions (p = 0.02). Male gender, necrotizing enterocolitis, and diffuse hypoplasia were associated with vein atresia. In post-operative PVS, mortality is associated with CCHD, single ventricle physiology, and genetic disorders. Vein atresia is associated with male gender, necrotizing enterocolitis, and diffuse hypoplasia. Multiple repeated interventions may offer a patient survival benefit; however, larger prospective studies are necessary to elucidate this relationship further.

Left Ventricular Strain Normalizes After Balloon Aortic Valvuloplasty in Infants with Congenital Aortic Stenosis.

Severe aortic stenosis (AS) causes left ventricular (LV) afterload and subendocardial ischemia. Despite this, most infants with AS have normal LV ejection fraction (EF). Strain analysis using two-dimensional speckle tracking echocardiography (2DSTE) may identify more sensitive markers of systolic dysfunction. We sought to show changes in LV strain after balloon aortic valvuloplasty (BAV) in infants with AS. Twenty-seven infants ≤ 1 year of age with AS who underwent BAV from 2007 to 2017 were included. Echocardiograms before/after BAV were retrospectively analyzed with 2DSTE. Median age was 29 days (interquartile range 3-52) and LV EF was 64 ± 10%. Global longitudinal strain (GLS) significantly improved post-BAV (- 17 ± 5 vs. - 20 ± 4%, p = 0.001) with no difference in global circumferential strain. Peak longitudinal strain was abnormal at the inferoseptal base and mid-ventricle (- 15 ± 6 and - 17 ± 5 = 7%, respectively) and significantly improved in the basal and mid-anterolateral segments (- 17 ± 5 vs. - 21 ± 5%, p < 0.01; - 17 ± 6% vs. - 20 ± 5%, p = 0.01, respectively). Five (20%) patients underwent reintervention, and had significantly higher peak-to-peak pre and post-BAV AS gradients (86 ± 14 vs. 61 ± 20 mmHg, p = 0.02; 33 ± 17 vs. 21 ± 10 mmHg, p = 0.04, respectively). In conclusion, longitudinal strain is abnormal in infants with AS and improves to previously published normal values after BAV.

MYPT1 is targeted by miR-145 inhibiting viability, migration and invasion in 2D and 3D HeLa cultures.

The miR-143/145 cluster is down-regulated in cervical tumor cells suggesting a role in tumorigenesis including cytoskeleton remodeling, a key event for tumor progression. The aim of the present work was to determine the role of miR-143/145 in the modulation of the myosin regulator phospho-myosin light chain (pMLC). HeLa monolayer and tridimensional cultures were transfected with miR-143 or miR-145 mimics inhibiting cell viability, proliferation, migration and invasion, mainly through miR-145. MiR-145 transfection increased pMLC levels by targeting the MYPT1 subunit of the regulatory myosin phosphatase. MYPT1 knockdown by siRNAs reproduced miR-145 effects suggesting miR-145 as a tumor suppressor through MYPT1 targeting, leading to a subsequent increase of pMLC levels with implications for cervical cell viability, migration and invasion.

Transcatheter stenting of superior vena cava obstruction after pediatric heart transplantation: A single-center experience assessing risk factors and outcomes.

Transcatheter stent implantation for SVC obstruction following OHT has been well described, particularly in pediatric patients. This study describes a large single-center pediatric heart transplant experience that investigates the risk factors for SVC stenosis requiring stent implantation and its associated outcomes. All pediatric OHTs between January 1, 2000, and December 12, 2016, were examined for risk factors. Twelve of 349 (3.4%) OHTs required SVC stent implantation. Patients who required stents were younger (2.5 years vs 10.0 years, P = 0.0097), weighed less (8.6 kg vs 26.0 kg, P = 0.0024), and were more likely to have had CHD (83% vs 32%, P = 0.001) or previous SCPA (58% vs 18%, P = 0.002). Bicaval anastomosis was not associated with subsequent SVC stent implantation. Symptoms included SVC syndrome and chylous effusions. All 12 patients had evidence of significant SVC obstruction by both echocardiographic Doppler interrogation and transcatheter angiography. There were no acute procedural complications; however, reinterventions were common (four of 12 patients) and occurred at a mean of 5.7 ± 3.6 months poststent implantation. In conclusion, transcatheter SVC stent implantation is safe and effective after OHT. There were significant associations between SVC stent implantation and younger age, smaller weight, CHD, and history of SCPA, but not with bicaval anastomosis or donor-recipient weight ratio.

Dynamics of N2 sticking on W(100): the decisive role of van der Waals interactions.

The reactive dynamics of N2 on W(100) has been investigated by means of quasi-classical trajectory calculations using an interpolated six-dimensional potential energy surface (PES) based on density functional theory energies obtained employing the vdW-DF2 functional. The dynamics are compared to those obtained using the PW91 functional and to experimental data. The results show that the new PES provides a significant improvement in the description of the reactivity in this system. We show that the long standing problem that constituted the large qualitative disagreement between the simulations performed with the PW91-PES and the experiments was due to the presence of energy barriers in the entrance channel that disappear when vdW forces are accounted for.

Cardiac Catheterization in Pediatric Patients Supported by Extracorporeal Membrane Oxygenation: A 15-Year Experience.

Cardiac catheterization is commonly performed in patients being supported by extracorporeal membrane oxygenation (ECMO). We aimed to evaluate the safety, benefit, and outcomes of catheterization in pediatric patients supported by ECMO. Retrospective review of cardiac catheterizations performed in patients ≤18 years of age while on ECMO at a large tertiary care center between January 2000 and May 2015. A total of 55 catheterizations were performed on 51 patients during 53 unique ECMO courses. Indications for ECMO include ventricular dysfunction (22), cardiac arrest (20), inability to wean from cardiopulmonary bypass (7), and persistent cyanosis (4). Catheterizations included purely diagnostic studies (11), atrial septostomies (34), stenting of vessels or surgical shunts (6), adjustment of a stent (1), coil embolization (1), and endomyocardial biopsy (1). Septostomy was elective in 58.8% of cases (20) and emergent in 41.2% (14). Forty-six catheterizations had either surgical or catheter intervention during the same or subsequent study (83.6%). High severity complications occurred in three patients (5.6%), including one death due to hemothorax after pulmonary artery stent placement. There were no complications during patient transport. In total, 38 out of 53 (71.7%) ECMO courses resulted in decannulation, 29 (54.7%) patients survived to discharge from the hospital, and 25 (47.2%) were alive at follow-up. Cardiac catheterization can be safely performed on patients supported by ECMO. Cardiac catheterization is a critical tool in the early recognition, diagnosis, and direct treatment of hemodynamic/anatomic abnormalities in patients supported by ECMO.

When Is It Better to Wait? Surgical Timing and Recurrence Risk for Children Undergoing Repair of Subaortic Stenosis.

Recurrence of subaortic stenosis (SAS) after surgery is common in children. The effects of patient characteristics and surgical timing on disease recurrence are largely unknown. We performed a retrospective study, assessing the relative effects of patient age and left ventricular outflow tract (LVOT) gradient on the need for reoperation for recurrent SAS. We included all children <20 years of age who underwent initial surgical resection of SAS at our center, January 2003-December 2013. Stratified logistic regression was performed, considering the effects of patient demographics, clinical characteristics, echocardiographic parameters, and operative technique, and clustering standard errors by surgeon. The multivariable model was used to simulate predicted probabilities of recurrent SAS for children at varying ages and baseline LVOT gradients. Sixty-three patients (38 males) underwent initial operation for SAS. Patients were followed for a median of 3.7 years (IQR 1.2-7.1). Twenty-one percent of patients (n = 13) underwent reoperation for SAS. Twelve were male. For every 10 mmHg increase in preoperative peak gradient in boys, the odds of reoperation for SAS doubled (OR 2.01, CI 1.5-2.72, p < 0.001), and for every additional 6 months of age, the odds of reoperation decreased by 14% (OR 0.86, CI 0.84-0.88, p < 0.001). Both younger age and higher preoperative outflow tract gradient are independently associated with risk of reoperation. Clinicians should consider the age and rate of LVOT gradient change-and not just the absolute gradient-in determining initial surgical timing.

Genomic Loads and Genotypes of Respiratory Syncytial Virus: Viral Factors during Lower Respiratory Tract Infection in Chilean Hospitalized Infants.

The clinical impact of viral factors (types and viral loads) during respiratory syncytial virus (RSV) infection is still controversial, especially regarding newly described genotypes. In this study, infants with RSV bronchiolitis were recruited to describe the association of these viral factors with severity of infection. RSV antigenic types, genotypes, and viral loads were determined from hospitalized patients at Hospital Roberto del Río, Santiago, Chile. Cases were characterized by demographic and clinical information, including days of lower respiratory symptoms and severity. A total of 86 patients were included: 49 moderate and 37 severe cases. During 2013, RSV-A was dominant (86%). RSV-B predominated in 2014 (92%). Phylogenetic analyses revealed circulation of GA2, Buenos Aires (BA), and Ontario (ON) genotypes. No association was observed between severity of infection and RSV group (p = 0.69) or genotype (p = 0.87). After a clinical categorization of duration of illness, higher RSV genomic loads were detected in infants evaluated earlier in their disease (p < 0.001) and also in infants evaluated later, but coursing a more severe infection (p = 0.04). Although types and genotypes did not associate with severity in our children, higher RSV genomic loads and delayed viral clearance in severe patients define a group that might benefit from new antiviral therapies.

Percutaneous coronary artery revascularization procedures in pediatric heart transplant recipients: A large single center experience.

OBJECTIVES: To describe our experience, at a large pediatric heart transplant center, with percutaneous coronary interventions (PCI) for cardiac allograft vasculopathy (CAV). BACKGROUND: CAV is a leading cause of late graft failure, mortality, and re-transplantation in pediatric heart transplant (HTx) recipients. Studies of PCI in adult patients have shown some short-term improvements, but no significant change in long-term outcomes. There are limited data on PCI for CAV in pediatric patients. We describe the largest single-center experience to date. METHODS: We performed a retrospective chart review of all pediatric HTx recipients who underwent PCI for a diagnosis of CAV from 2005 to 2014. RESULTS: Twenty-three procedures were performed in 13 patients, at a median age of 16.4 years (range 5.6-21.2) and median time from HTx to first PCI of 8.3 years (range 2.9-20.3). Three cases consisted of angioplasty alone, two cases had bare metal stents implanted, and the remaining 18 had drug-eluting stents implanted. There was acute procedural success in all but one case, and there was only one procedure-related complication (rebleeding from access site). During the follow-up interval (median 10.4 months, range 0.2-111.8), 7/13 patients had repeat PCI performed, two patients died (at 1.8 and 5.8 months post-PCI), and five were re-transplanted (range 0.2-18 months post-PCI). Freedom from death or retransplant by Kaplan-Meier analysis was 54% at 1 year. CONCLUSIONS: PCI can be performed safely and effectively in pediatric HTx recipients with CAV. Similar to the adult experience, there remains a high rate of disease progression and graft failure. © 2016 Wiley Periodicals, Inc.

Aortic Root Distortion and Aortic Insufficiency During Balloon Angioplasty of the Right Ventricular Outflow Tract Prior to Transcatheter Pulmonary Valve Replacement.

OBJECTIVE: To describe the significance of aortic root distortion (AD) and/or aortic valve insufficiency (AI) during balloon angioplasty of the right ventricular outflow tract (RVOT) performed to rule out coronary artery compression prior to transcatheter pulmonary valve (TPV) implantation. METHODS: AD/AI was assessed by retrospective review of all procedural aortographies performed to evaluate coronary anatomy prior to TPV implantation. AD/AI was also reviewed in all pre-post MPV implant echocardiograms to assess for progression. RESULTS: From 04/2007 to 3/2015, 118 pts underwent catheterization with intent for TPV implant. Mean age and weight were 24.5 ± 12 years and 64.3 ± 20 kg, respectively. Diagnoses were: TOF (53%), D-TGA/DORV (18%), s/p Ross (15%), and Truncus (9%). Types of RV-PA connections were: conduits (96), bioprosthetic valves (14), and other (7). Successful TPV implant occurred in 91 pts (77%). RVOT balloon angioplasty was performed in 43/118 pts (36%). Aortography was performed in 18/43 pts with AD/AI noted in 6/18 (33%); 2 with D-TGA (1 s/p Lecompte, 1 s/p Rastelli), 2 with TOF, 1 Truncus and 1 s/p Ross. Procedure was aborted in the 2 who developed severe AD/AI. TPV was implanted in 3/4 patients with mild AD/AI. Review of pre-post TPV implantation echocardiograms in 83/91 pts (91%) revealed no new/worsened AI in any patient. CONCLUSION: AD/AI is relatively common on aortography during simultaneous RVOT balloon angioplasty. Lack of AI progression by echocardiography post-TPV implant suggests these may be benign findings in most cases. However, AD/AI should be carefully evaluated in certain anatomic subtypes with close RVOT/aortic alignments.

Preparation of oxocene terpenes. The first enantiospecific synthesis of cytotoxic arenaran A.

The first syntheses of cytotoxic marine arenarans A and B starting from commercial (-)-sclareol are reported. The oxocene ring of the target compound is formed via ring-closing metathesis, a process that depends on certain structural requirements. The trans-fused structure of the natural product is confirmed by comparison with the cis-fused isomer, which was synthesized. This synthetic strategy is also applicable to the synthesis of other oxocene terpenes.

Implementation of Methodology for Quality Improvement in Pediatric Cardiac Catheterization: A Multi-center Initiative by the Congenital Cardiac Catheterization Project on Outcomes-Quality Improvement (C3PO-QI).

The Congenital Cardiac Catheterization Project on Outcomes (C3PO) launched in 2007 as a multi-center collaborative to establish standardized and comparable metrics for pediatric cardiac catheterization procedures. The limitations of larger registries at the time led to the development of the next phase in 2013, C3PO-Quality Improvement (C3PO-QI), focusing on instituting QI initiatives within the field. The objective of this manuscript is to provide a detailed overview of C3PO-QI and report data on case characteristics and outcome metrics being explored. C3PO-QI was designed to cultivate institutional collaboration during implementation of its initiatives. A database and website were developed to support data entry and on-demand reporting. The registry prospectively captures pediatric cardiac catheterization data among 15 hospitals. The present study includes case demographic data (n) and quality metric reporting by case type, age, and radiation dose variables. This dataset includes 13,135 cases entered into the database between 1/1/2014 and 12/31/2015. Interventional cases make up the highest percentage by case mix distribution (48 %), and patients <1 years make up the highest percentage by age distribution (26 %). The ratio of diagnostic and interventional procedures performed changes by age group. Application of QI metric shows all procedure types surpassing metric goals. Large volume data collection, such as in C3PO-QI, allows for meaningful interpretation of data. C3PO-QI is uniquely poised to deliver fast-paced changes in the field. Although the project initiatives are specific to pediatric cardiac catheterization, the implementation of the project and utilization of real-time reporting is generalizable to other specialties and multi-center collaboratives.

Iatrogenic aortopulmonary communications after transcatheter interventions on the right ventricular outflow tract or pulmonary artery: Pathophysiologic, diagnostic, and management considerations.

OBJECTIVES: To investigate the spectrum, etiology, and management of traumatic aortopulmonary (AP) communications after transcatheter interventions on the pulmonary circulation. BACKGROUND: An iatrogenic AP communication is an unusual complication after balloon pulmonary artery (PA) angioplasty or stenting, or transcatheter pulmonary valve replacement (TPVR). However, with the increasing application of transcatheter therapies for postoperative PA stenosis and right ventricular outflow tract (RVOT) dysfunction, including percutaneous pulmonary valve replacement, consideration of the etiology, diagnosis, and management of this problem is important for interventional cardiologists performing such procedures. METHODS AND RESULTS: We present three new cases, as well as gross anatomy and histopathology data, related to AP communications after PA interventions. We also review the literature relevant to this topic. Including these new cases, there have been 18 reported cases of iatrogenic AP communication after transcatheter interventions on the PAs or RVOT, primarily patients with transposition of the great arteries who underwent PA angioplasty after an arterial switch operation, or after TPVR in patients who had undergone a Ross procedure. The likely cause of such defects is PA trauma plus distortion of the neo-aortic anastomosis resulting from angioplasty or stenting of the RVOT or central PAs, with subsequent dissection through the extravascular connective tissue and into the closely adjacent vessel through the devitalized tissue at the anastomosis. CONCLUSIONS: Cardiologists performing PA or RVOT interventions should be aware of the possibility of a traumatic AP communication and consider this diagnosis when confronted with suggestive signs and symptoms.

Balloon valvuloplasty for congenital aortic stenosis: Multi-center safety and efficacy outcome assessment.

OBJECTIVE: To describe contemporary outcomes of balloon aortic valvuloplasty (BAVP) performed in 22 US centers. BACKGROUND: BAVP constitutes first-line therapy for congenital aortic stenosis (cAS) in many centers. METHODS: We used prospectively-collected data from two active, multi-institutional, pediatric cardiac catheterization registries. Acute procedural success was defined, for purposes of this review, as a residual peak systolic gradient≤35 mm Hg and no more than mild aortic regurgitation (AR) for patients with isolated cAS. For patients with mixed aortic valve disease, a residual peak systolic gradient≤35 mm Hg without worsening of AR was considered successful outcome. RESULTS: In 373 patients with a median age of 8 months (1 day to 40 years of age) peak systolic gradient had a median of 59 [50, 71] mm Hg pre-BAVP and 22 [15, 30] mm Hg post-BAVP (P<0.001). Procedural success was achieved in 160 patients (71%). The factors independently associated with procedural success were: first time intervention (OR=2.0 (1.0, 4.0) P=0.04), not-prostaglandin dependent, (OR=3.5 (1.5, 8.1); P=0.003), and isolated cAS (absence of AR) (OR=2.1 (1.1-3.9); P=0.03). Twenty percent of patients experienced adverse events, half of which were of high severity. There was no procedural mortality. Neonatal status was the only factor associated with increased risk of high severity adverse events (OR 3.7; 95% CI 1.5-9.0). CONCLUSION: In the current era, BAVP results in procedural success (gradient reduction with minimal increase in AR) in 71% of patients treated at US centers where BAVP is considered first-line therapy relative to surgery.

Incidence and management of life-threatening adverse events during cardiac catheterization for congenital heart disease.

Continued advancements in congenital cardiac catheterization and interventions have resulted in increased patient and procedural complexity. Anticipation of life-threatening events and required rescue measures is a critical component to preprocedural preparation. We sought to determine the incidence and nature of life-threatening adverse events in congenital and pediatric cardiac catheterization, risk factors, and resources necessary to anticipate and manage events. Data from 8905 cases performed at the 8 participating institutions of the Congenital Cardiac Catheterization Project on Outcomes were captured between 2007 and 2010 [median 1,095/site (range 133-3,802)]. The incidence of all life-threatening events was 2.1 % [95 % confidence interval (CI) 1.8-2.4 %], whereas mortality was 0.28 % (95 % CI 0.18-0.41 %). Fifty-seven life-threatening events required cardiopulmonary resuscitation, whereas 9 % required extracorporeal membrane oxygenation. Use of a risk adjustment model showed that age <1 year [odd ratio (OR) 1.9, 95 % CI 1.4-2.7, p < 0.001], hemodynamic vulnerability (OR 1.6, 95 % CI 1.1-2.3, p < 0.01), and procedure risk (category 3: OR 2.3, 95 % CI 1.3-4.1; category 4: OR 4.2, 95 % CI 2.4-7.4) were predictors of life-threatening events. Using this model, standardized life-threatening event ratios were calculated, thus showing that one institution had a life-threatening event rate greater than expected. Congenital cardiac catheterization and intervention can be performed safely with a low rate of life-threatening events and mortality; preprocedural evaluation of risk may optimize preparation of emergency rescue and bailout procedures. Risk predictors (age < 1, hemodynamic vulnerability, and procedure risk category) can enhance preprocedural patient risk stratification and planning.

Simultaneous stent implantation for pulmonary artery bifurcation stenosis in infants.

OBJECTIVES: Pulmonary artery (PA) bifurcation stenosis often requires simultaneous stent placement, which may be technically challenging. Limited data exist regarding this practice in infants. We aim to report the procedural outcomes and safety of bifurcation stent placement in infants. METHODS: We performed a single-center retrospective review of infants younger than 12 months who underwent simultaneous stent placement for PA bifurcation stenosis from January 1, 2001 through December 31, 2019. RESULTS: Seventeen infants underwent simultaneous PA bifurcation stent placement. The median age was 6.4 months (1.1-10.1 months), and weight was 5.8 kg (3-10.6 kg). Nine (52.9%) patients had had prior PA intervention. Most stents were placed in central PAs (28, 82.4%), followed by lobar branches (6, 17.6%). All patients received pre-mounted stents. The peak gradient across each branch decreased from 47.4 ± 16 to 18.7 ± 13 mm Hg (P less than .0001). The right ventricle to systemic systolic pressure ratio decreased from systemic (1.0 ± 0.3) to just over half systemic (0.58 ± 0.2) (P = .0001). The minimum vessel diameter increased from 3.6 ± 1.5 to 6.0 ± 1.9 mm (P less than .0001). There were 4 (23.5%) patients with high severity adverse events. There were no procedure-related deaths. The median follow-up period was 83.8 months (5.3 months-19.4 years). All patients had subsequent PA re-intervention at a median time of 8.1 months (2.9 months-8.8 years), and median time to re-operation was 19.1 months (2.9 months-7.5 years). CONCLUSIONS: Simultaneous PA stent placement is an effective strategy for relief of bifurcation stenosis in infants. Future transcatheter interventions are necessary to account for patient growth, but may delay the need for re-operation.

Single-Atom Substituents in Copper Surfaces May Adsorb Multiple CO Molecules.

Copper is a good CO2 electroreduction catalyst as products beyond CO form, but efficiency and selectivity is low. Experiments have shown that an admixture of other elements can help, and computational screening studies have pointed out various promising candidates based on the adsorption of a single CO molecule as a descriptor. Our calculations of CO adsorption on surfaces where a first row transition metal atom replaces a Cu atom show that multiple CO molecules, not just one, bind to the substitutional atom. For Fe, Co, and Ni atoms, a decrease in binding energy is found, but the reverse trend, namely, increasing bond strength, is found for V, Cr, and Mn and the first three CO molecules. Magnetic moment, charge, and position of the substitutional atom are also strongly affected by the CO adsorption in most cases. Magnetic moment is stepwise reduced to zero, and the outward displacement of the substitutional atom increased.

Evidence of Sharp Transitions between Octahedral and Capped Trigonal Prism States of the Solvation Shell of the Aqueous Fe3+ Ion.

The structure of the solvation shell of the aqueous Fe3+ ion has been a subject of controversy due to discrepancies between experiments and different levels of theory. We address this issue by performing simulations for a wide range of ion concentrations, using various potential energy functions, supplemented by density functional theory calculations of selected configurations. The solvation shell undergoes abrupt transitions between two states: a hexacoordinated octahedral (OH) state and a capped trigonal prism (CTP) state with 7-fold coordination. The lifetime of these states is dependent on concentration. In dilute FeCl3 solutions, the lifetimes of both are similar (≈1 ns). However, the lifetime of the OH state increases with ion concentration, while that of the CTP state decreases slightly. When a uniform negative background charge is used instead of explicit counterions, the lifetime of the OH state is greatly overestimated. These findings underscore the need for further experimental measurements and higher-level simulations.