Impact of heart failure on COVID-19 patients: An insight from nationwide inpatient sample.

BACKGROUND: Patients with COVID-19 have been reported to experience adverse cardiovascular outcomes, such as myocarditis, acute myocardial infarction, and heart failure. Among these complications, heart failure (HF) has emerged as the most common critical complication during exacerbations of COVID-19, potentially leading to increased mortality rates and poorer clinical outcomes. We aimed to investigate the in-hospital outcomes of COVID-19 patients with HF. METHODS: We analyzed the Nationwide Inpatient Sample (NIS) dataset to select COVID-19 patients aged over 18 years who were hospitalized between January 1, 2020, and December 31, 2020, using ICD-10. Based on the presence of acute HF, the patients were divided into two cohorts. The clinical outcomes and complications were assessed at index admissions using STATA v.17." RESULTS: 1,666,960 COVID-19 patients were hospitalized in 2020, of which 156,755 (9.4%) had associated HF. COVID-19 patients with HF had a mean age of (72.38 ± 13.50) years compared to (62.3 ± 17.67) years for patients without HF. The HF patients had a higher prevalence of hypertension, hyperlipidemia, type 2 diabetes, smoking, and preexisting cardiovascular disease. Additionally, after adjusting for baseline demographics and comorbidities, COVID-19 patients with HF had higher rates of in-hospital mortality (23.86% vs. 17.63%, p<0.001), acute MI (18.83% vs. 10.91%, p<0.001), acute stroke (0.78% vs. 0.58%, p=0.004), cardiogenic shock (2.56% vs. 0.69%, p<0.001), and sudden cardiac arrest (5.54% vs. 3.41%, p<0.001) compared to those without HF. CONCLUSION: COVID-19 patients admitted with acute HF had worse clinical outcomes, such as higher mortality, myocardial infarction, cardiogenic shock, cardiac arrest, and a higher length of stay and healthcare than patients without HF.

The Prevalence of Cardiovascular Complications and Causes of AngioJet Failure: A Post-Marketing Surveillance Study Based on the MAUDE (Manufacturer and User Facility Device Experience) Database.

Background and objective Aspiration thrombectomy devices, such as the AngioJet Solent Omni (Boston Scientific Corporation, Marlborough, MA) have been approved by the US FDA for the treatment of thrombi in peripheral arterial disease, venous disease, and AV fistulas. However, there is a dearth of real-world data on the most common modes of failure and complications associated with the AngioJet Solent Omni. In this study, we aimed to address this scarcity of data. Methods The MAUDE (Manufacturer and User Facility Device Experience) database was queried for reports of device failure and adverse events spanning the period from October 2012 to December 2021. Results A total of 499 events were reported during the study period. After the exclusion of duplicate reports, the final analysis included 450 reports. The most common mode of failure was catheter breakage/kinking during suction thrombectomy with 137 reports (30%). The most common vessel associated with events was the superficial femoral artery or vein, which was documented in 82 reports (18.2%). The most common adverse clinical outcome was the embedding of a piece of the device in the patient, which occurred in seven reports (1.6%). There were seven (1.6%) events of death reported during the period studied. Conclusions Based on our findings, theAngioJet Solent Omni device provides promising results; however, it is important to evaluate device safety. It is associated with complications including device embedment, catheter breakage/kinking, and death, and these adverse events are linked to patient characteristics and risk factors.

Predictors and Outcomes of Sudden Cardiac Arrest in Heart Failure With Preserved Ejection Fraction: A Nationwide Inpatient Sample Analysis.

Sudden cardiac arrest (SCA) is the leading cause of cardiovascular mortality in heart failure with preserved ejection fraction (HFpEF), contributing to around 25% of deaths observed in pivotal HFpEF trials. However, predictors and outcomes of in-hospital SCA in HFpEF have not been well characterized. We queried the Nationwide Inpatient Sample (2016 to 2017) to identify adult hospitalizations with a diagnosis of HFpEF. Patients with acute or chronic conditions associated with SCA (e.g., acute myocardial infarction, acute pulmonary embolism, sarcoidosis) were excluded. We ascertained whether SCA occurred during these hospitalizations, identified predictors of SCA using multivariate logistic regression, and determined outcomes of SCA in HFpEF. Of 2,909,134 hospitalizations, SCA occurred in 1.48% (43,105). The mean age of the SCA group was 72.3 ± 12.4 years, 55.8% were women, and 66.4% were White. Presence of third-degree atrioventricular block (odds ratio [OR] 5.95, 95% confidence interval [CI] 5.31 to 6.67), left bundle branch block (OR 1.96, 95% CI 1.72 to 2.25), and liver disease (OR 1.87, 95% CI 1.73 to 2.02) were the leading predictors of SCA in HFpEF. After excluding patients with do-not-resuscitate status, the SCA group versus those without SCA had higher mortality (25.9% vs 1.6%), major bleeding complications (4.1% vs 1.7%), increased use of percutaneous coronary intervention (2.5% vs 0.7%), and mechanical circulatory assist device (1.2% vs 0.1%). These observational inpatient data suggest identifiable risk factors for SCA in HFpEF including cardiac arrhythmias. Further research is warranted to identify the best tools to risk-stratify patients with HFpEF to implement targeted SCA prevention strategies.

A Sniff Away From Death: A Rare Case of Cocaine-Induced Triple Vessel Coronary Artery Disease in a 41-Year-Old Male Patient.

Cocaine-associated coronary artery disease and ST-segment elevation myocardial infarction (STEMI) have been well described in the literature. However, very few cases of cocaine-induced multivessel coronary artery disease have been reported. We report a very rare case of cocaine-associated triple vessel coronary artery disease in a 41-year-old male patient. The patient underwent urgent catheterization that revealed occlusion of his proximal left anterior descending artery (LAD), mid-circumflex artery, and right coronary artery with angioplasty and stent placement. His hospitalization course was complicated by cardiogenic shock, shock liver, acute renal failure, and sepsis.

Sodium-Glucose Cotransporter 2 Inhibitors: A Scoping Review of the Positive Implications on Cardiovascular and Renal Health and Dynamics for Clinical Practice.

Cardiorenal benefits of sodium-glucose cotransporter 2 inhibitors (SGLT2is) have been demonstrated in patients with type 2 diabetes in multiple trials. We aim to provide a comprehensive review of the role of SGLT2i in cardiovascular disease. Reducing blood glucose to provide more effective vascular function, lowering the circulating volume, reducing cardiac stress, and preventing pathological cardiac re-modeling and function are the mechanisms implicated in the beneficial cardiovascular effects of SGLT2 inhibitors. Treatment with SGLT2i was associated with a decrease in cardiovascular and all-cause mortality, acute heart failure exacerbation hospitalization, and composite adverse renal outcomes. Improved symptoms, better functional status, and quality of life were also seen in heart failure with reduced ejection fraction (HFrEF), heart failure and mildly reduced ejection fraction (HFmrEF), and heart failure with preserved ejection fraction (HFpEF) patients. Recent trials have shown a notable therapeutic benefit of SGLT2is in acute heart failure and also suggest that SGLT2is have the potential to strengthen recovery after acute myocardial infarction (AMI) in percutaneous coronary Intervention (PCI) patients. The mechanism behind the cardio-metabolic and renal-protective effects of SGLT2i is multifactorial. Adverse events may occur with their usage including increased risk of genital infections, diabetic ketoacidosis, and perhaps limited amputations; however, all of them are preventable. Overall, SGLT2i clearly has many beneficial effects, and the benefits of using SGLT2i by far outweigh the risks.

Imatinib-Induced Pleuro-Pericardial Effusion and Atrial Fibrillation: An Unusual Side Effect Following the Treatment of a Rare Gastrointestinal Tumor.

Gastrointestinal stromal tumors (GISTs) are one of the most prevalent non-epithelial tumors of the GI mesenchyme. While stromal tumors account for less than 1% of all malignancies, a knowledge of their etiology and signaling pathways can aid in identifying new molecular targets for the potential development of therapeutics. One of the drugs that have shown remarkable action against GIST is imatinib, a tyrosine kinase inhibitor (TKI). We present a case of a female patient with a long-term history of heart failure (HF) with preserved ejection fraction (EF) and minimal pericardial effusion who had recently started imatinib therapy and was hospitalized after new-onset atrial fibrillation (AF) and the development of significantly increased pericardial and pleural effusion. She had been diagnosed with GIST a year ago and started on imatinib. She presented to the ER with complaints of left-sided chest pain. ECG revealed a new AF. The patient was started on rate control and anticoagulation. After a few days, she returned to the ER with complaints of shortness of breath (SOB). The patient was found to have pericardial and pleural effusions on imaging. Fluids from both effusions were aspirated and sent to pathology to rule out malignancy. The patient developed recurrent bilateral pleural effusions after discharge, which were later drained on subsequent hospitalization. Although imatinib is generally well tolerated, it does cause both AF and pleural/pericardial effusions in rare cases. In such cases, it is essential to perform a thorough workup to rule out other possibilities such as metastasis, malignancy, or infection.

Comparison of Sex-Based In-Hospital Procedural Outcomes and Hospital Readmission Frequency After Patent Foramen Ovale Occluder Device Placement: A Propensity Matched National Cohort.

Patent foramen ovale (PFO) occluder device has been shown to reduce the chance of recurrent stroke. Per guidelines, stroke is higher in females but procedural efficacy and complications based on sex difference is understudied. The nationwide readmission database (NRD) was used to create sex cohorts using ICD-10 Procedural code for elective PFO occluder device placement performed during the years 2016-2019. The 2 groups were compared using propensity score matching (PSM) and multivariate regression models that matched for confounders to report multivariate odds ratio (mOR) for primary and secondary cardiovascular outcomes. Outcomes included in-hospital mortality, acute kidney injury (AKI), acute ischemic stroke, postprocedure bleeding, and cardiac tamponade. Statistical analysis was performed using STATA v. 17. A total of 5818 patients who underwent PFO occluder device placement were identified, of which 3144 (54.0%) were females, and 2673 (46.0%) were males. There was no difference in periprocedural in-hospital mortality, new onset acute ischemic stroke, postprocedural bleeding, or cardiac tamponade between both sexes undergoing occluder device placement. AKI incidence was higher in males compared to females after matching for CKD (mOR = 0.66; 95% CI [0.48-0.92]; P = 0.016) this can be procedural or can be secondary to volume status or nephrotoxins. Males also had a higher length of stay (LOS) at their index hospitalization (2 days vs 1 day) which led to slightly higher total hospitalization cost ($26,585 vs $24,265). Our data did not show a statistically significant difference in the readmission LOS trends between the 2 groups at 30, 90, and 180 days. This national retrospective cohort study of PFO occluder outcomes shows similar efficacy and complication rates between sexes, with the exception of AKI incidence which was higher in males. AKI occurrence was high in males that can be limited due to unavailability of data about hydration status and nephrotoxic medications.

A Systematic Review and Meta-Analysis of Prevalence and Outcomes of Cardiac Metastasis of Neuroendocrine Malignancies.

Neuroendocrine tumors (NETs) are a rare group of malignancies which are aggressive and widely metastatic. Cardiac metastases (CMs) are rarely reported because of NET. We aim to analyze the available literature to study the proportional prevalence of CM because of NET and its location and effect on the ejection fraction (EF) and survival rate. Our search strategy and meta-analysis are in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) AMSTAR-2 (Assessing the methodological quality of systematic Reviews-2) Guidelines. A literature search was conducted on MEDLINE (EMBASE and PubMed) for randomized clinical trials, pilot trials, and retrospective and prospective studies. Statistical analysis was performed using the CRAN-R software (https://CRAN.R-project.org/doc/FAQ/R-FAQ.html). The quality assessment of the included articles was performed using the Cochrane Risk of Bias and Newcastle-Ottawa Scale. A total of 16,685 patients were included in the study. The mean age of patients included in the study was 61.28 ± SD 9.89 years. Of these, 257 patients had a total of 283 CM. Metastasis was mainly located in the left ventricle with a pooled proportion of 0.48, 95% confidence interval (CI) 0.4 to 0.56, pericardium: 0.34, 95% CI 0.19 to 0.53, right ventricle 0.28, 95% CI 0.16 to 0.44, interventricular septum 0.25, 95% CI 0.16 to 0.37, left atrium 0.1, 95% CI 0.03 to 0.26 and right atrium 0.05, 95% CI 0.01 to 0.20. Decrease in EF at the time of CM diagnosis was the effect most consistently reported in patients with CM. Pooled mean survival was 35.89, 95% CI 8.27 to 155.68 months after the diagnosis of CM. CM due to NET was <2% and the left ventricle is the most common metastatic location, followed by the pericardium. Decreased EF was the most common clinical picture observed. Further studies are needed to analyze the clinical impact of NET CM.

Outcomes of Catheter-Based Pulmonary Artery Embolectomy in Patients With Sub-Massive to Massive Pulmonary Embolism.

Background Pulmonary embolism (PE) is the third leading cause of cardiovascular death after myocardial infarction and stroke. The ideal therapeutic approach for these patients remains undetermined. We report our single-center outcome data for using a catheter-based pulmonary artery thrombectomy using the FlowTriever (Inari Medical, Irvine, CA) device as management for patients with submassive PE. Methods We retrospectively collected data from a single center of patients who underwent thrombectomy using INARI FlowTriever device. The data on baseline characteristics, procedural and clinical outcomes was collected and analysed Results A total of 38 patients with PE treated endovascularly with the FlowTriever device were identified: 33 with submassive PE and five with massive PE. The mean age was 65.9 years (95% CI 61.9 - 69.8), and most patients were male (73.7%). All patients had right heart strain as the main indication for thrombectomy. Four patients (10.53%) required pressor support before the procedure. In 31 patients, pre- and post-thrombectomy average mean pulmonary artery pressure (mPAP) was improved significantly by 22% (p < 0.01). Two patients had significant adverse events at 48 hours (5.26%). One patient experienced procedure-related access site hematoma and life-threatening bleeding, while another developed intraprocedural-related massive hemoptysis and cardiopulmonary arrest. Overall post-procedural length of stay was 7.7 ± 5.6 days; 52.63% of patients (n = 20) required intensive care. Three patients (7.89%) required pressor support before the procedure, and 78.9% of patients (n = 30 of 38) survived hospital discharge. Thirty patients who survived were discharged with oral anticoagulation. There were no device-related complications. Conclusion Randomized trials of interventional devices for submassive PE are warranted to either support or alert the medical community of the safety and efficacy of their use for patients with submassive and massive PE. In time, pulmonary embolism response team (PERT) may generate outcome data that better inform treatment decisions.

Electric-Field Control of a Single-Atom Polar Bond.

We expose the polar covalent bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) to an external electric field. For one field orientation, the Au─C bond is strong enough to sustain the mechanical load of partially detached graphene, while for the opposite orientation, the bond breaks easily. Calculations based on density-functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling bond forces that reflect the polar character of the bond. Field-induced charge transfer between the atomic orbitals modifies the polarity of the different electronegative reaction partners and the Au─C bond strength.

Clinicobiochemical Parameters and Predictors of Liver Disease in Hospitalized Asian Indian Pregnant Women in a Tertiary Care Center in Northern India.

Introduction  During pregnancy, liver dysfunction is more frequent than expected and may require specialized care. For the early diagnosis, it is important to determine if changes in liver physiology may develop into liver disease. Liver disease during pregnancy may require intervention from a hepatologist for adequate monitoring of mother-fetus health outcomes. This study was aimed to evaluate the clinical profile and predictors of maternal mortality in patients with liver diseases among Asian-Indian-females. Methods We conducted a prospective, open-label, consecutive all-comers study of 2,663 pregnant Asian Indian women admitted in the hospital, which included 92 with liver dysfunction. The medical aspects of the pregnancy were then followed prospectively with laboratory and clinical data during the hospital stay and analyzed. The current study was approved by the Institutional Ethical Committee. Results We found that 92 out of 2,663 patients had liver dysfunction with a prevalence of 3.45%. Fifty-four (58.7%) patients had icterus followed by fever in 23 (25.0%), hypertension in 22 (23.9%), central nervous system manifestations in 21 (22.8%), abdominal pain in 19 (20.6%), vomiting in 19 (20.6%), and pruritus in six (6.5%). Predictors of maternal mortality were icterus (p = 0.04), hepatomegaly (p = 0.04), presenting serum-bilirubin greater than 10 milligram% (mg%) (p = 0.008). The most common etiology was acute viral hepatitis (45.6%), followed by a hypertensive disorder of pregnancy (29.3%), acute fatty liver of pregnancy (1.1%), cholestatic jaundice (9.8%), hyperemesis gravidarum (2.2%), septicemic hepatitis (3.3%), dengue immunoglobulin M (IgM), and plasmodium vivax malaria antigen positive in (2.2%) each. Four patients (4.3%) were leptospira IgM reactive and had co-infection with hepatitis E virus. There was one patient (1.1%) with underlying chronic liver disease. Idiopathic liver disease was present in 5.4% of patients. Conclusion Liver disease is relatively common in Indian pregnant women. It is associated with high maternal and perinatal mortality, even in a tertiary referral center. When managing pregnancy in a tertiary care center, for adequate follow-up of the disease and to prevent adverse consequences for mother and child, it is important to discard liver alterations early. For this purpose, liver disease during pregnancy needs early diagnosis for proper management. Furthermore, it is difficult to manage patients with preexisting liver disease, and it may require specialized intervention from a hepatologist and a gastroenterologist.

A Rare Case of Varicella-Zoster Virus Reactivation Following Recovery From COVID-19.

In patients with coronavirus disease 2019 (COVID-19), various cutaneous symptoms have been observed. Herpes zoster (HZ) is an infectious skin disease caused by the varicella-zoster virus (VZV) that, after a primary chickenpox infection, persists dormant in the dorsal root ganglia of cutaneous nerves. Unusual prolonged dermatological symptoms from recovered COVID-19 patients have rarely been recorded. In this report, we describe a case of HZ following recovery from COVID-19.

Manipulation of the two-site Kondo effect in linear CoCu n CoCu m clusters.

Artificially assembled linear atomic clusters, CoCu n CoCu m , are used to explore variations of the Kondo effect at the two Co sites. For all investigated Cu n chain lengths ([Formula: see text]) the addition of a single Cu atom to one edge Co atom of the chain ([Formula: see text]) strongly reduces the amplitude of the Abrikosov-Suhl-Kondo resonance of that Co atom. Concomitantly, the resonance line width is more than halved. On the contrary, the Kondo effect of the opposite edge Co atom remains unaffected. Hybridization together with the linear geometry of the cluster are likely to drive the effect.

Exciting vibrons in both frontier orbitals of a single hydrocarbon molecule on graphene.

Vibronic excitations in molecules are key to the fundamental understanding of the interaction between vibrational and electronic degrees of freedom. In order to probe the genuine vibronic properties of a molecule even after its adsorption on a surface appropriate buffer layers are of paramount importance. Here, vibrational progression in both molecular frontier orbitals is observed with submolecular resolution on a graphene-covered metal surface using scanning tunnelling spectroscopy. Accompanying calculations demonstrate that the vibrational modes that cause the orbital replica in the progression share the same symmetry as the electronic states they couple to. In addition, the vibrational progression is more pronounced for separated molecules than for molecules embedded in molecular assemblies. The entire vibronic spectra of these molecular species are moreover rigidly shifted with respect to each other. This work unravels intramolecular changes in the vibronic and electronic structure owing to the efficient reduction of the molecule-metal hybridization by graphene.

Surface engineered lipid nanoparticle-mediated site-specific drug delivery system for the treatment of inflammatory bowel disease.

The major challenge for the treatment of inflammatory bowel disease (IBD) is the incompetence to deliver the drug molecule selectively at the site of inflammation. Taking this into consideration, we proposed development of mannosylated nanostructured lipid carrier system (Mn-NLCs) for active targeting and site-specific delivery of budesonide to the inflamed tissues. The developed Mn-NLCs were characterized for particle size and size distribution, zeta potential, %entrapment efficiency, FTIR and TEM analysis. Furthermore, to ensure delivery of developed cargo to the colonic region, the Mn-NLCs were encapsulated using Eudragit® S100 coated pellets. The in vivo evaluation of developed system was performed by employing oxazolone colitis rat model. The average particle size of Mn-NLCs (301.7 ± 2.88 nm) was found to be more than that of unconjugated NLCs (284.0 ± 4.53 nm) with marginally reduced % entrapment efficiency (90.88 ± 3.86%). The in vitro cytotoxicity studies using J774A.1 cell line revealed that Mn-NLCs were non-toxic as compared to pure drug. The in vivo evaluation depicted that Mn-NLCs showed significant reduction in clinical activity scoring, macroscopic and microscopic indexing, colonic myeloperoxidase activity and inflammatory cytokines. In conclusion, the developed Mn-NLCs appear to be promising for the treatment of IBD by selectively targeting inflamed colonic region as compared to unconjugated nanoparticulate system.

Process, optimization, and characterization of budesonide-loaded nanostructured lipid carriers for the treatment of inflammatory bowel disease.

The major challenge involved in the treatment of inflammatory bowel disease is targeted delivery of the drug at the site of inflammation. As nanoparticles possess the ability to accumulate at the site of inflammation, present investigation aims at development of Budesonide-loaded nanostructured lipid carrier systems (BDS-NLCs) for the treatment of inflammatory bowel disease. BDS-NLCs were prepared by employing a high pressure homogenization technique. Various preliminary trials were performed for optimization of the NLCs in which different processes, as well as formulation parameters, were studied. The BDS-NLCs was optimized statistically by applying a 3-factor/3-level Box-Behnken design. Drug concentration, surfactant concentration, and emulsifier concentration were selected as independent variables, and % entrapment efficiency and particle size were selected as dependent variables. The best batch comprises of 10%, 7%, and 20% w/w concentration of drug, surfactant, and emulsifier, respectively, with % entrapment efficiency of 92.66 ± 3.42% and particle size of 284.0 ± 4.53 nm. Further, in order to achieve effective delivery of nanoparticulate system to colonic region, the developed BDS-NLCs were encapsulated in Eudragit® S100-coated pellets. The drug release studies of pellets depict intactness of BDS-NLCs during palletization process, with f2 value of 75.879. The in vitro evaluation of enteric-coated pellets revealed that a coating level of 15% weight gain is needed in order to impart lag time of 5 h (transit time to reach colon). The results of the study demonstrate that the developed BDS-NLCs could be used as a promising tool for the treatment of inflammatory bowel disease.

Ordered Superstructures of a Molecular Electron Donor on Au(111).

The molecular donor tetraphenyldibenzoperiflanthene (DBP) forms coverage-dependent superstructures on Au(111). At submonolayer coverage, the molecules align parallel to each other. They arrange in row-like structures, which exhibit a nearly rectangular primitive unit cell. By contrast, the molecular monolayer is characterized by a herringbone-type DBP arrangement spanned by an almost square unit cell containing two molecules. Both superstructures occur simultaneously in a narrow coverage range close to completion of the molecular monolayer. The adsorbate-substrate interaction is similar to other physisorbed molecular films on Au(111), but differs for the two adsorption phases as inferred from the different modification of the Au(111) surface reconstruction. Structural properties were consistently probed in real and reciprocal space by scanning tunneling microscopy and low-energy electron diffraction, respectively.

Impact of Atomic-Scale Contact Geometry on Andreev Reflection.

Charge transport has been examined in junctions comprising the normal-metal tip of a low-temperature scanning tunneling microscope, the surface of a conventional superconductor, and adsorbed C_{60} molecules. The Bardeen-Cooper-Schrieffer energy gap gradually evolves into a zero-bias peak with decreasing electrode separation. The peak is assigned to the spectroscopic signature of Andreev reflection. The conductance due to Andreev reflection is determined by the atomic termination of the tip apex and the molecular adsorption orientation. Transport calculations unveil the finite temperature and the strong molecule-electrode hybridization as the origin to the surprisingly good agreement between spectroscopic data and the Blonder-Tinkham-Klapwijk model that was conceived for macroscopic point contacts.

Asymmetry parameter of peaked Fano line shapes.

The spectroscopic line shape of electronic and vibrational excitations is ubiquitously described by a Fano profile. In the case of nearly symmetric and peaked Fano line shapes, the fit of the conventional Fano function to experimental data leads to difficulties in unambiguously extracting the asymmetry parameter, which may vary over orders of magnitude without degrading the quality of the fit. Moreover, the extracted asymmetry parameter depends on initially guessed values. Using the spectroscopic signature of the single-Co Kondo effect on Au(110) the ambiguity of the extracted asymmetry parameter is traced to the highly symmetric resonance profile combined with the inevitable scattering of experimental data. An improved parameterization of the conventional Fano function is suggested that enables the nonlinear optimization in a reduced parameter space. In addition, the presence of a global minimum in the sum of squared residuals and thus the independence of start parameters may conveniently be identified in a two-dimensional plot. An angular representation of the asymmetry parameter is suggested in order to reliably determine uncertainty margins via linear error propagation.

Lateral Electron Confinement with Open Boundaries: Quantum Well States above Nanocavities at Pb(111).

We have studied electron states present at the Pb(111) surface above Ar-filled nanocavities created by ion beam irradiation and annealing. Vertical confinement between the parallel crystal and nanocavity surfaces creates a series of quantum well state subbands. Differential conductance data measured by scanning tunneling spectroscopy contain a characteristic spectroscopic fine structure within the highest occupied subband, revealing additional quantization. Unexpectedly, reflection at the open boundary where the thin Pb film recovers its bulk thickness gives rise to the lateral confinement of electrons.