Spin-Dependent ππ

We present a detailed analysis of the electronic properties of graphene/Eu/Ni(111). By using angle- and spin-resolved photoemission spectroscopy and ab initio calculations, we show that the intercalation of Eu in the graphene/Ni(111) interface gives rise to a gapped freestanding dispersion of the ππ^{*} Dirac cones at the K[over ¯] point with an additional lifting of the spin degeneracy due to the mixing of graphene and Eu states. The interaction with the magnetic substrate results in a large spin-dependent gap in the Dirac cones with a topological nature characterized by a large Berry curvature and a spin-polarized Van Hove singularity, whose closeness to the Fermi level gives rise to a polaronic band.

Synthesis of mesoscale ordered two-dimensional π-conjugated polymers with semiconducting properties.

Two-dimensional materials with high charge carrier mobility and tunable band gaps have attracted intense research effort for their potential use in nanoelectronics. Two-dimensional π-conjugated polymers constitute a promising subclass because the band structure can be manipulated by varying the molecular building blocks while preserving key features such as Dirac cones and high charge mobility. The major barriers to the application of two-dimensional π-conjugated polymers have been the small domain size and high defect density attained in the syntheses explored so far. Here, we demonstrate the fabrication of mesoscale ordered two-dimensional π-conjugated polymer kagome lattices with semiconducting properties, Dirac cone structures and flat bands on Au(111). This material has been obtained by combining a rigid azatriangulene precursor and a hot dosing approach, which favours molecular diffusion and eliminates voids in the network. These results open opportunities for the synthesis of two-dimensional π-conjugated polymer Dirac cone materials and their integration into devices.

Temperature-induced molecular reorganization on Au(111) driven by oligomeric defects.

The formation of ordered molecular structures on surfaces is determined by the balance between molecule-molecule and molecule-substrate interactions. Whether the aggregation process is guided by non-covalent forces or on-surface reactions, a deeper understanding of these interactions is pivotal to formulating a priori predictions of the final structural features and the development of bottom-up fabrication protocols. Theoretical models of molecular systems corroborate the information gathered through experimental observations and help explain the thermodynamic factors that underpin on-surface phase transitions. Here, we report a scanning tunneling microscopy investigation of a tribromo-substituted heterotriangulene on the Au(111) surface, which initially forms an extended close-packed ordered structure stabilized by BrBr halogen bonds when deposited at room temperature. X-ray photoelectron spectroscopy reveals that annealing the self-assembled layer induces a fraction of the molecular precursors to partially dehalogenate that in turn leads to the formation of a less stable BrO non-covalent network which coexists with the short oligomers. Density functional theory (DFT) and Monte Carlo (MC) simulations illustrate how dimer moieties act as defects whose steric hindrance prevents the retention of the more stable configuration. A small number of dimers is sufficient to drive the molecular reorganization into a lower cohesive energy phase. Our study shows the importance of a combined DFT - MC approach to understand the evolution of molecular systems on substrates.

Binding geometry of hydrogen-bonded chain motif in self-assembled gratings and layers on Ag(111).

Upon adsorption on the (111) facet of Ag, 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid (PVBA) self-assembles into a highly ordered, chiral twin chain structure at submonolayer coverages with domains that can extend for micrometers in one dimension. Using polarization-dependent measurements of C and N K-shell excitations in near-edge X-ray absorption fine structure (NEXAFS) spectra, we determine the binding geometry of single PVBA molecules within this unique ensemble for both low and high coverage regimes. At submonolayer coverage, the molecule is twisted to facilitate the formation of hydrogen bonds. The gas-phase planarity is gradually recovered as the coverage is increased, with complete planarity coinciding with loss of order in the overlayer. Thermal treatment of the PVBA film results in deprotonation of the carboxyl tail of the molecule, but despite the suppression of the stabilizing hydrogen-bonds, the overlayer remains ordered.

Resonant circular dichroism of chiral metal-organic complex.

A sizable enhancement of the circular dichroism in photoelectron spectroscopy has been measured and computed for the metal complex Δ-cobalt(III) tris-acetylacetonate highest occupied molecular orbital state in the region of the Co 3p→3d Fano resonance. In the resonance the dichroism reaches the maximum value of 5% and even changes its sign as compared to the direct photoionization channel. We ascribe this enhancement to electron correlation processes, namely, with the coupling between discrete excitations and the continuum, which is correctly described in the time dependent density functional theory (TDDFT) framework. These findings open new physical aspects of photoelectron circular dichroism that now can be interpreted not only via the simple direct ionization, but also through more complex electron correlation processes.

The valence electronic structure and conformational flexibility of epichlorohydrin.

The electronic structure of epichlorohydrin is investigated in the whole valence region by a combined experimental and theoretical study. The issue of controversial assignments of the molecular electronic structure is here addressed. Photoelectron spectra (PES) and Threshold Photoelectron spectra (TPES) of room temperature molecules in the gas phase are recorded. Geometries and energies of the stable conformers due to internal rotation of the C-C-C-Cl dihedral angle, gauche-II (g-II), gauche-I (g-I), and cis, are calculated, and the effect of the conformational flexibility on the photoionization energetics is studied by DFT and 2h-1p Configuration Interaction (CI) methods. Strong breakdown of the Koopmans Theorem (KT) is obtained for the four outermost ionizations, which are further investigated by higher level ab initio calculations. The full assignment of the spectrum is put on a firm basis by the combination of experimental and theoretical results. The orbital composition from correlated calculations is found closer to the DFT orbitals, which are then used to analyze the electronic structure of the molecule. The Highest Occupied Molecular Orbital (HOMO) and HOMO--2 are n(O)/n(Cl) mixed orbitals. The nature of each valence MO is generally preserved in all the conformers, although the magnitude of the n(O)/n(Cl) mixing in HOMO and HOMO--2 varies to some extent with the C-C-C-Cl dihedral angle. The low energy part of the HOMO PE band is predicted to be substantially affected by the conformational flexibility, as experimentally observed in the spectra. The rest of the spectrum is described in terms of the dominant conformer g-II, and a good agreement between experiment and theory is found. The inner-valence PE spectrum is characterized by satellite structures, due to electron correlation effects, which are interpreted by means of 2h-1p CI calculations.

Chirality transfer from a single chiral molecule to 2D superstructures in alaninol on the Cu(100) surface.

The formation of 2D chiral monolayers obtained by self-assembly of chiral molecules on surfaces has been widely reported in the literature. Control of chirality transfer from a single molecule to surface superstructures is a challenging and important aspect for tailoring the properties of 2D nanostructures. However, despite the wealth of investigations performed in recent years, how chiral transfer takes place on a large scale still remains an open question. In this paper we report a coupling of scanning tunneling microscopy and low energy electron diffraction measurements with an original theoretical approach, combining molecular dynamics and essential dynamics with density functional theory, to investigate self-assembled chiral structures formed when alaninol adsorbs on Cu(100). The peculiarity of this system is related to the formation of tetrameric molecular structures which constitute the building blocks of the self-assembled chiral monolayer. Such characteristics make alaninol/Cu(100) a good candidate to reveal chiral expression changes. We find that the deposition of alaninol enantiomers results in the formation of isolated tetramers that are aligned along the directions of the substrate at low coverage or when geometrical confinement prevents long-range order. Conversely, a rotation of 14° with respect to the Cu(100) unit vectors is observed when small clusters of tetramers are formed. An insight to the process leading to a 2D globally chiral surface has been obtained by monitoring molecular assemblies as they grow from the early stages of adsorption, suggesting that the distinctive orientation of the self-assembled monolayer originates from a balance of cooperating forces which start acting only when tetramers pack together to form small clusters.

2-amino-1-propanol versus 1-amino-2-propanol: valence band and C 1s core-level photoelectron spectra.

Valence band and C 1s core-level photoelectron spectra of S-(+)-2-amino-1-propanol (alaninol) and S-(+)-1-amino-2-propanol (isopropanolamine) have been studied by means of synchrotron radiation photoelectron spectroscopy in gas phase. The alaninol, the reduced derivative of the alanine, is a good test system of amino acid-like structures. The isopropanolamine, presenting the inversion of the two functional groups of the alaninol at the chiral carbon, offers the opportunity to study the effect of -OH and -NH(2) structural position on the photoelectron spectra. The influence of the conformational contribution on the electronic structure and the photoelectron spectra has been interpreted using density functional and ab initio theoretical calculations. Agreement has been achieved by taking into account the presence, in gas phase, of two conformers with different population ratios in both chiral systems. The C 1s core-level spectra of alaninol and isopropanolamine are reported and the peak positions of the three carbon atoms of the molecules are assigned.

Vibrational state dependence of beta and D asymmetry parameters: the case of the highest occupied molecular orbital photoelectron spectrum of methyl-oxirane.

The beta angular asymmetry and D dichroic asymmetry parameters of the methyl-oxirane highest occupied molecular orbital (HOMO) band have been experimentally investigated with vibrational resolution using synchrotron radiation. A theoretical calculation of the Franck-Condon factors between vibrational ground state and different ionic vibrational states, in the Born-Oppenheimer harmonic approximation, has been performed in order to gain information on the vibrational states mainly involved in the HOMO photoelectron band. The general good agreement between theoretical and experimental results allows a reliable assignment of the major features. The experimental determination of beta and D shows their dependence on the different final vibrational states. This paper reports, for the first time, experimental evidence of the dependence of the dichroic D parameter on the vibrational excitation of the ion.

Valence photoionization dynamics in circular dichroism of chiral free molecules: the methyl-oxirane.

The dynamical behavior of circular dichroism for valence photoionization processes in pure enantiomers of randomly oriented methyl-oxirane molecules has been studied by circularly polarized synchrotron radiation. Experimental results of the dichroism coefficient obtained for valence photoionization processes as a function of photon energy have been compared with theoretical values predicted by state-of-the-art ab initio density-functional theory. The circular dichroism measured at low electron kinetic energies was as large as 11%. Trends in the experimental dynamical behavior of the dichroism coefficients D(i)(omega) have been observed. Agreement between experimental and theoretical results permits unambiguous identification of the enantiomer and of the individual orbitals.

Pericardial drainage for pericardial tamponade: surgical management criteria.

Aim of this study is the review of our experience in 82 patients treated by pericardial drainage for cardiac tamponade, to assess the efficacy and safety of different techniques and the related indications. The causes of pericardial effusion were: malignancy in 8 patients (9.7%), post-cardiac surgery in 12 (14.6%), while the others patients were admitted at our Institution with no identified preoperative diagnosis. Thirty-eight patients (46%) underwent subxiphoid pericardial drainage and 44 (54%) were operated on by catheter pericardiocentesis. There were no perioperative deaths. Two patients, who initially underwent pericardiocentesis, needed urgent sternotomy: the first patient developed a severe hypotension and bradicardia related to a vagal reaction and the other one because of accidental right ventricle puncture. Our experience indicates that subxiphoid pericardiocentesis provides expeditious, effective and durable treatment, with low morbidity, in case of pericardial effusions related to all causes. We believe that echocardiography is a powerful tool in the diagnosis and management of pericardial effusion. We conclude that pericardiocentesis seems to be the procedure of choice for patients with pericardial tamponade requiring an emergency treatment.

Isolated and preclinical impairment of left ventricular filling in insulin-dependent and non-insulin-dependent diabetic patients.

BACKGROUND: Diabetes mellitus can induce a pattern of myocardial pathology known as specific diabetic cardiomyopathy, even if this is not clearly specified. HYPOTHESIS: The aim of our study was to evaluate the presence of preclinical myocardial damage in insulin- and non-insulin-dependent diabetic patients and controls by assessment with Doppler echocardiography. METHODS: Twenty insulin-dependent diabetic (IDDM) patients, 10 non-insulin-dependent diabetic (NIDDM) patients, and 12 healthy individuals (C) as controls, matched for age, gender, and without overt cardiovascular disease, were assessed in this study. RESULTS: Systolic function parameters presented normal values in the three groups, with the exception of a slight reduction in ventricular volume indices in the NIDDM group. Diastolic function was clearly impaired in both groups of patients versus that in healthy controls. In particular, ventricular filling was impaired in the NIDDM compared with the IDDM patients, especially the peak early filling rate E (p < 0.001). Moreover, in the IDDM group, the duration of diabetes (p < 0.01) and glycosilated hemoglobin value (HbA1C, p < 0.02) were higher than in the NIDDM group. Multiple regression analysis showed a significant inverse correlation between HbA1C and peak late filling rate A (R2 = 0.28) in both groups of patients and a direct correlation between velocity time integral E and age, duration of diabetes, and HbA1C (R2 = 0.46). The two groups presented a small, homogeneous number of cases with initial microangiopathy and borderline autonomic neuropathy, associated with microalbuminuria. Doppler echocardiography showed an early impairment of left ventricular filling, as well as an early preclinical alteration of myocardial function in diabetic patients, especially in the NIDDM group. CONCLUSION: These early signs of cardiomyopathy could constitute a predisposing condition toward the high cardiac morbidity and mortality rate in diabetic patients.

[Doppler echocardiographic study of left ventricular function in patients with systemic lupus erythematosus]. / Studio ecocardiografico Doppler della funzione ventricolare sinistra in pazienti con lupus eritematoso sistemico.

This study was aimed at investigating abnormalities in left ventricular size and function in patients with systemic lupus erythematosus without overt cardiovascular manifestations, in order to detect a very early impairment in myocardial function. Seventeen females and 1 male with systemic lupus erythematosus of 4 to 20 year duration and without clinical evidence of heart disease were studied. Twelve healthy volunteers, matched for age, sex and quatelet index, were utilized as controls. Each patient had a two-dimensional M-mode echocardiographic and Doppler examination. In patients with systemic lupus erythematosus there was an increase in left ventricular ejection fraction (p < 0.001), a slight reduction of end-diastolic volume index and a significant decrease of end-systolic volume index (p < 0.001). In the same patients we also found prolongation of the isovolumic relaxation time (p < 0.02), a clear impairment of diastolic filling parameters. Peak E velocity was lower (p < 0.01), peak A velocity was higher (p < 0.01), with a clear lowering, of the corresponding E/A ratio (p < 0.001) in patients with systemic lupus erythematosus.

Myocardial indium-111 antimyosin uptake after uncomplicated coronary artery bypass surgery.

The prevalence of myocardial damage after coronary artery bypass grafting is related to the criteria of its evaluation. Indium-111 monoclonal antimyosin antibody scintigraphy has been shown to be highly sensitive and specific for even small areas of myocardial necrosis or injury like those of myocarditis or transplant rejection. Our purpose was to evaluate, by using this method, myocardial damage after uncomplicated coronary artery bypass grafting. Uptake of this radio tracer was evaluated after coronary artery bypass grafting in 14 informed and consenting consecutive patients without previous myocardial infarction, with no post-surgical complications and a favorable postoperative course, following coronary artery bypass grafting for stable angina pectoris. Monoclonal antimyosin antibody indium-111 74 MBq (Myoscint Centocor) was injected on the third postoperative day; planar images in the anterior, left anterior oblique 45 degrees and 70 degrees projections were obtained 24 and 48 h later and analyzed for myocardial uptake. Indium-111 antimyosin uptake was present in 10 out of 14 patients (71.4%); it was diffuse in 6 and localized in 4. The ratio of the maximal counts in the myocardium to the counts in the adjacent lung background was measured and found elevated: 1.94 +/- 0.23, higher than the normal values reported in the literature. Indium-111 antimyosin uptake was clear in a group of patients after uncomplicated coronary artery bypass grafting. No correlation was observed between indium-111 antimyosin uptake or heart to lung ratio and creatine kinase, creatine kinase isoenzyme MB, glutamic oxalacetic transferase levels, duration of cardiopulmonary bypass or aortic cross-clamp time, while elevated serum beta myosin heavy chain fragments (IRMA Pasteur) were observed (1378 +/- 238 microU/l). This study suggests that some degree of myocardial damage, though silent, is common after coronary artery bypass grafting.

Perioperative myocardial cell damage assessed by immunoradiometric assay of beta-myosin heavy chain serum levels in patients undergoing coronary bypass surgery.

In order to investigate myocardial cell damage in patients undergoing coronary bypass surgery, serum levels of cardiac myosin fragments, using monoclonal antibodies to myosin beta heavy chains, were measured in serial blood samples of 85 patients, 79 male and 6 female, 43-66 years old, after a total of 86 internal mammary artery and 137 saphenous vein graft implants. Eight patients had perioperative acute myocardial infarction (MI), detected by abnormal Q waves and a rise of CK-MB levels. After surgery, beta-myosin levels increased from post-operative day 3 and reached peak values on day 5 in patients without and in day 7 in patients with perioperative MI, in these 8 patients, myosin peak levels were greater as compared to 77 patients without perioperative MI (3452 +/- 1596 vs. 761 +/- 494; P < 0.01). There was a correlation between myosin peak levels and creatine kinase (CK) (r = 0.71; P < 0.05) and CK-MB peak levels (r = 0.74; P < 0.05) only in the patients with perioperative MI, but not in the patients without MI. There was no correlation between myosin peak levels and the times of aortic cross clamping or cardiopulmonary bypass. Peak myosin levels over 75% confidence limits of the mean were found in 23 patients; post-operative low output syndrome occurred in 10 of these 23 patients and in 7 out of 62 patients with peak myosin levels within 75% of the mean (P < 0.005). The increase in beta-myosin heavy chain serum levels observed in almost all patients undergoing coronary surgery suggests lesser perioperative damage of the contractile apparatus, which could be detected by the usual enzyme and ECG criteria. The higher prevalence of low output syndrome in patients with higher increases in myosin levels suggests more pronounced damage to the contractile apparatus in these patients. The higher myosin levels clearly indicate the presence of perioperative MI.

[Critical myocardial ischemia in systemic lupus erythematosus. Case report]. / Ischemia miocardica critica in corso di lupus eritematoso sistemico. Descrizione di un caso clinico.

We present the clinical case of a 26-year-old woman, suffering systemic lupus erythematosus for 15 years, who suddenly had coronary heart disease with angina pectoris on mild effort. Thallium 201 exercise test demonstrated clearcut anteroseptal and apical perfusion defects, whereas repeated echocardiography showed a hypokinetic anteroseptal segment; ECG also reported new Q wave in lead V4. After stronger corticosteroid and immunosuppressive treatment, angina pectoris attenuated and perfusion defects disappeared within few months. We hypothesize a coronary artery vasculitis in the course of systemic lupus erythematosus, probably associated with early coronary artery atherosclerosis.

[Radioisotope angiography in the differential diagnosis between aneurysm and pseudoaneurysm of left ventricle. Report of a case]. / L'angiografia radioisotopica nello studio discriminante tra aneurisma e pseudoaneurisma ventricolare sinistro. Descrizione di un caso.

We describe the case of a patient with large posteroinferior left ventricular aneurysm following myocardial infarction. Contrast ventriculography, Doppler echocardiography, as well as radionuclide angiography indicated a small orifice that was in communication with the ventricular cavity. These data suggested the presence of left ventricular pseudoaneurysm. Thus a short-term surgical intervention was performed, but the diagnosis was not confirmed by surgical observation; indeed the presence of a true aneurysm was demonstrated. Our study confirms the diagnostic difficulties by invasive and non invasive techniques in the precise identification of postinfarct pseudoaneurysm. This observation suggests the remarkable interest of our radionuclide ventriculographic results, not usually observed. Thus, we point out the possibilities of several nuclear cardiology imaging in the study of diagnostic problems concerning the analysis of these conditions of myocardial pathology.