Barrier formation at metal/organic interfaces: dipole formation and the Charge Neutrality Level

The barrier formation for metal/organic semiconductor interfaces is analyzed within the Induced Density of Interface States (IDIS) model. Using weak chemisorption theory, we calculate the induced density of states in the organic energy gap and show that it is high enough to control the barrier formation. We calculate the Charge Neutrality Levels of several organic molecules (PTCDA, PTCBI and CBP) and the interface Fermi level for their contact with a Au(111) surface. We find an excellent agreement with the experimental evidence and conclude that the barrier formation is due to the charge transfer between the metal and the states induced in the organic energy gap.Comment: 7 pages, Proceedings of ICFSI-9, Madrid, Spain (September 2003), special issue of Applied Surface Science (in press

The Hydration Structure at Yttria-Stabilized Cubic Zirconia (110)-Water Interface with Sub-Angstrom Resolution

The interfacial hydration structure of yttria-stabilized cubic zirconia (110) surface in contact with water was determined with ~0.5 Å resolution by high-resolution X-ray reflectivity measurement. The terminal layer shows a reduced electron density compared to the following substrate lattice layers, which indicates there are additional defects generated by metal depletion as well as intrinsic oxygen vacancies, both of which are apparently filled by water species. Above this top surface layer, two additional adsorbed layers are observed forming a characteristic interfacial hydration structure. The first adsorbed layer shows abnormally high density as pure water and likely includes metal species, whereas the second layer consists of pure water. The observed interfacial hydration structure seems responsible for local equilibration of the defective surface in water and eventually regulating the long-term degradation processes. The multitude of water interactions with the zirconia surface results in the complex but highly ordered interfacial structure constituting the reaction front.ope

Late growth stages and post-growth diffusion in organic epitaxy: PTCDA on Ag(111)

The late growth stages and the post-growth diffusion of crystalline organic thin films have been investigated for 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111), a model system in organic epitaxy. In situ x-ray measurements at the anti-Bragg point during the growth show intensity oscillations followed by a time-independent intensity which is independent of the growth temperature. At T > 350 K, the intensity increases after growth up to a temperature-dependent saturation value due to a post-growth diffusion process. The time-independent intensity and the subsequent intensity recovery have been reproduced by models based on the morphology change as a function of the growth temperature. The morphology found after the post-growth diffusion processes has been studied by specular rod measurements.Comment: 9 pages, 8 figures, accepted for publication in Surface Scienc

Sterically hindered esters: mechanisms of saponification

This paper discusses the mechanisms of base catalyzed hydrolysis of the secondary-butyl ester of 2, 2-dimethyl-propanoic acid (secondary-butyl pivaloate). Kinetic studies were carried out at 53° and near neutral hydroxide ion concentrations, but due to the slow velocity of reaction, no conclusions concerning the order of the kinetics of hydrolysis could be drawn. Also discussed is a scheme for an experiment involving the utilization of 018 enriched water in the saponification reaction of secondary-butyl pivolate under similar conditions of pH and temperature. The purpose of this experiment is to determine the site of oxygen cleavage during the hydrolysis. The analysis is carried out by a Hewlett—Parkard System 5992 Gas Chromatograph/ Mass Spectrometer. As of the data of submission of this thesis, the results of this experiment are known; the data this experiment provides, along with a discussion concerning their significance, will be added to the body of this thesis at a later date

Reconstruction and subsurface lattice distortions in the (2 × 1)O-Ni(110) structure: A LEED analysis

LEED analysis of the reconstructed (2 × 1)O-Ni(110) system clearly favors the “missing row” structure over the “saw-tooth” and “buckled row” models. By using a novel computational procedure 8 structural parameters could be refined simultaneously, leading to excellent R-factors (RZJ = 0.09, RP = 0.18). The adsorbed O atoms are located 0.2 Å above the long bridge sites in [001] direction, presumably with a slight displacement ( 0.1 Å) in [1 0] direction to an asymmetric adsorption site. The nearest-neighbor Ni---O bond lengths (1.77 Å) are rather short. The separation between the topmost two Ni layers is expanded to 1.30 Å (bulk value 1.25 Å), while that between the second and third layer is slightly contracted to 1.23 Å. The third layer is, in addition, slightly buckled (±0.05 Å). The results are discussed on the basis of our present general knowledge about the structure of adsorbate covered metallic surfaces

Comparing nebivolol and spironolactone in the treatment of heart failure with a preserved ejection fraction

Objective: To assess the efficacy of improving diastolic dysfunction with the use of nebivolol, a selective beta-1 adrenergic receptor antagonist, as compared to spironolactone, a mineralocorticoid receptor antagonist, in the treatment of diastolic heart failure. To assess whether or not these medications have a favorable outcome in terms of improving exercise capacity in patients with Heart Failure with Preserved Ejection Fraction (HFpEF). Design: Systematic Literature Review. Methods: Searches in PubMed and the JMU online library database using mesh terms that included “diastolic heart failure”, “nebivolol”, and “spironolactone”. In order to narrow down relevant articles, filter terms included “humans”, “published in the last 5 years”, “full text” and “English.” This literature review includes three separate studies pertaining to different treatment modalities for diastolic heart failure. We focused on the use of nebivolol as compared to spironolactone as mainstay therapies in the treatment regimen for heart failure with a preserved ejection fraction. The Aldo-DHF randomized control trial was included for its research in assessing the efficacy of improving diastolic function and maximizing exercise capacity in patients with HFpEF. The study with a focus on treatment with spironolactone in elderly women with HFpEF was included because it focused on baseline and endpoint data concerning improvement in exercise capacity as well as left ventricular (LV) structure and function on echocardiogram and biomarkers such as brain natriuretic peptide (BNP). The ELANDD study was included because it discussed mechanisms of nitric oxide release and subsequent peripheral vasodilation, which was hypothesized to improve aortic and ventricular compliance and thus improve diastolic filling. Results – spironolactone was found to improve left ventricular diastolic function, but had no effect on maximal exercise capacity and did not improve patient symptoms or quality of life. Spironolactone was also shown to have beneficial effects on the remodeling of the ventricle. The selective beta-1 adrenergic receptor antagonist, nebivolol, was found to have no improvement in maximal exercise capacity and was found to have a neutral effect on both peak oxygen uptake during exercise and pro brain natriuretic peptide plasma levels (pro-BNP). Nebivolol did decrease resting and peak blood pressure and heart rate as compared to the placebo

Continuous versus Routine Electroencephalography in the Intensive Care Unit: A Review of Current Evidence.

Electroencephalography (EEG) has long been used to detect seizures in patients with disorders of consciousness. In recent years, there has been a drastically increased adoption of continuous EEG (cEEG) in the intensive care units (ICUs). Given the resources necessary to record and interpret cEEG, this is still not available in every center and widespread recommendations to use continuous instead of routine EEG (typically lasting 20 min) are still a matter of some debate. Considering recent literature and personal experience, this review offers a rationale and practical advice to address this question. Despite the development of increasingly performant imaging techniques and several validated biomarkers, EEG remains central to clinicians in the intensive care unit and has been experiencing expanding popularity for at least 2 decades. Not only does EEG allow seizure or status epilepticus detection, which in the ICU often present without clinical movements, but it is also paramount for the prognostic evaluation of comatose patients, especially after cardiac arrest, and for detecting delayed ischemia after subarachnoid hemorrhage. At the end of the last Century, improvements of technical and digital aspects regarding recording and storage of EEG tracings have progressively led to the era of cEEG and automated quantitative analysis. As compared to repeated rEEG, cEEG in comatose patients does not seem to improve clinical prognosis to a relevant extent, despite allowing a more performant of detection ictal events and consequent therapeutic modifications. The choice between cEEG and rEEG must therefore always be patient-tailored

Effect of defects on reaction of NiO surface with Pb-contained solution

In order to understand the role of defects in chemical reactions, we used two types of samples, which are molecular beam epitaxy (MBE) grown NiO(001) film on Mg(001) substrate as the defect free NiO prototype and NiO grown on Ni(110) single crystal as the one with defects. In-situ observations for oxide-liquid interfacial structure and surface morphology were performed for both samples in water and Pb-contained solution using high-resolution X-ray reflectivity and atomic force microscopy. For the MBE grown NiO, no significant changes were detected in the high-resolution X-ray reflectivity data with monotonic increase in roughness. Meanwhile, in the case of native grown NiO on Ni(110), significant changes in both the morphology and atomistic structure at the interface were observed when immersed in water and Pb-contained solution. Our results provide simple and direct experimental evidence of the role of the defects in chemical reaction of oxide surfaces with both water and Pb-contained solution.ope