Biomedical subjects

Francesco Mauri

Publications and source records attributed to Francesco Mauri.

At least 19 recordsLinked to original sources

PubMed2006

Long-term outcomes in difficult-to-treat patients with recurrent pericarditis.

Patients with many recurrences of acute pericarditis are commonly alarmed by the fear of constriction. We studied their long-term outcome and the possible presence of systemic diseases. Sixty-one Italian patients (36 men) were followed for an average of 8.3 years according to a predefined protocol, including testing for autoimmune diseases and familial Mediterranean fever. Symptomatic pericarditis lasted from 1 to 43 years (mean 5.4 years). Fifty-two patients had been referred to us after failure of previous therapies, including steroids. We observed 378 attacks with a mean of 1.6 per patient per year and 156 hospital admissions. Thirteen patients had a post-cardiac injury syndrome. In 43 (70.5%), the pericarditis remained idiopathic, whereas we made a new diagnosis of rheumatoid arthritis in 1 and of Sjogren's syndrome in 4 patients, but in these patients pericarditis represented the dominant clinical manifestation. Cardiac tamponade occurred during the initial attacks in 4 patients (6.5%) but never recurred. Pleural effusions were present during the first attack in 22 patients (36.0%) and liver involvement in 5 (8%). No patients developed constrictive pericarditis. Echocardiographic examination produced no evidence of chronic myocardial disease. Response to therapy was good. Thirty-one patients (50.8%) are in sustained remission, without any therapy; their total observation period has averaged 10.3 years. In idiopathic patients, antinuclear antibodies were present in 56.2% and anti-Ro/SSA in 8.3%. Mutations linked to familial Mediterranean fever were absent. In conclusion, in this large series of difficult patients with recurrent acute pericarditis and a very long follow-up, the long-term prognosis is good.

Acute Disease↗

PubMed2006

An unusual cause of pulmonary edema: acute rupture of noncoronary sinus of valsalva aneurysm into the left atrium.

We present the case of a patient admitted to hospital with pulmonary edema and atrial fibrillation. The transthoracic echocardiogram showed noncoronary sinus of Valsalva aneurysm ruptured into the left atrium, with a turbulent flow directed toward the left atrium floor and the pulmonary vein, which explained the clinical presentation. Echocardiography played a crucial role in identification of the cause and correct therapeutic approach.

Acute Disease↗

PubMed2006

[Prognostic value of serial measurements of left ventricular function and exercise performance in chronic heart failure].

INTRODUCTION AND OBJECTIVES: The prognostic value of a single measurement of ejection fraction and peak oxygen uptake in chronic heart failure has been extensively investigated. The aim of our study was to evaluate the prognostic significance of serial changes in ejection fraction and exercise performance in moderate to severe chronic heart failure. METHODS: 182 patients (156 men, 53 [47-58] years) underwent echocardiography and cardiopulmonary exercise testing at baseline and after 10 [8-12] months. Most patients had idiopathic dilated cardiomyopathy (69%) and all patients presented left ventricular ejection fraction <45%. Median follow-up was 21 [14-34] months; cardiac death and heart transplantation were the end-points. Hazard ratio (HR, per unit) is presented with its 95% confidence interval (CI). RESULTS: During follow-up 18 patients (9.9%) died and 14 (7.7%) underwent heart transplantation. Baseline ejection fraction (HR, 0.94, 95% CI, 0.89-0.98 P=.006) and mitral regurgitation (HR, 4.22, 95% CI, 1.63-10.92, P=.003), and delta (second examination-baseline) ejection fraction (HR, 0.93, 95% CI, 0.88-0.98, P=.01) were the only significant variables at univariate analysis. Both ejection fraction and delta ejection fraction remained independently associated with events at multivariate analysis. The prognostic power significantly increased between a model including ejection fraction alone and another one including ejection fraction plus delta ejection fraction. CONCLUSIONS: In clinically stable patients with chronic heart failure, ejection fraction and its changes were independently associated with outcome; on the contrary, serial cardiopulmonary exercise testing did not provide significant prognostic value. Baseline plus changes in ejection fraction showed better prognostic performance than baseline ejection fraction alone.

Chronic Disease↗

PubMed2005

Electron transport and hot phonons in carbon nanotubes.

We demonstrate the key role of phonon occupation in limiting the high-field ballistic transport in metallic carbon nanotubes. In particular, we provide a simple analytic formula for the electron transport scattering length, which we validate by accurate first principles calculations on (6, 6) and (11, 11) nanotubes. The comparison of our results with the scattering lengths fitted from experimental I-V curves indicates the presence of a nonequilibrium optical phonon heating induced by electron transport. We predict an effective temperature for optical phonons of thousands Kelvin.

Journal Article↗

PubMed2005

Theoretical explanation of superconductivity in C6Ca.

Using density functional theory, we demonstrate that superconductivity in C6Ca is phonon mediated with lambda = 0.83 and phonon frequency (omega)log = 24.7 meV. The calculated isotope exponents are alpha(Ca) = 0.24 and alpha(C) = 0.26. Superconductivity is due mostly to C vibrations perpendicular and Ca vibrations parallel to the graphite layers. Since the electron-phonon couplings of these modes are activated by the presence of an intercalant Fermi surface, the occurrence of superconductivity in graphite intercalated compounds requires a noncomplete ionization of the intercalant.

Journal Article↗

PubMed2005

Combined first-principles computational and experimental multinuclear solid-state NMR investigation of amino acids.

13C, 14N, 15N, 17O, and 35Cl NMR parameters, including chemical shift tensors and quadrupolar tensors for 14N, 17O, and 35Cl, are calculated for the crystalline forms of various amino acids under periodic boundary conditions and complemented by experiment where necessary. The 13C shift tensors and 14N electric field gradient (EFG) tensors are in excellent agreement with experiment. Similarly, static 17O NMR spectra could be precisely simulated using the calculation of the full chemical shift (CS) tensors and their relative orientation with the EFG tensors. This study allows correlations to be found between hydrogen bonding in the crystal structures and the 17O NMR shielding parameters and the 35Cl quadrupolar parameters, respectively. Calculations using the two experimental structures for L-alanine have shown that, while the calculated isotropic chemical shift values of 13C and 15N are relatively insensitive to small differences in the experimental structure, the 17O shift is markedly affected.

Amino Acids↗

PubMed2005

An investigation of weak CH...O hydrogen bonds in maltose anomers by a combination of calculation and experimental solid-state NMR spectroscopy.

Two-dimensional (1)H-(13)C MAS-J-HMQC solid-state NMR spectra of the two anomeric forms of maltose at natural abundance are presented. The experimental (1)H chemical shifts of the CH and CH(2) protons are assigned using first-principles chemical shift calculations that employ a plane-wave pseudopotential approach. Further calculations show that the calculated change in the (1)H chemical shift when comparing the full crystal and an isolated molecule is a quantitative measure of intermolecular C-H...O weak hydrogen bonding. Notably, a clear correlation between a large chemical shift change (up to 2 ppm) and both a short H...O distance (<2.7 A) and a CHO bond angle greater than 130 degrees is observed, thus showing that directionality is important in C-H...O hydrogen bonding.

Carbohydrate Conformation↗

PubMed2005

Extent of ST-segment depression and cardiac events in non-ST-segment elevation acute coronary syndromes.

AIMS: We sought to determine whether the extent of myocardial ischaemia on the admission electrocardiogram (ECG) has independent predictive value for short-term risk stratification of patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS). Although the presence of ischaemic ECG changes on admission has been shown to predict outcome, the relationship between the extent of ECG changes and the risk of cardiac events is still ill defined. METHODS AND RESULTS: We analysed the admission ECGs of 5192 ACS patients enrolled in the GUSTO-IIb trial, without an ECG indication for thrombolysis. ECG tracings showing one or more of the following were eligible: ST-segment depression >0.5 mm, T-wave inversion >1 mm, and ST-segment elevation >0.5 mm but <1 mm. ECG variables associated with unfavourable 30 day outcomes in a univariable analysis were further assessed in a multivariable logistic regression model including independent clinical predictors. In the multivariable clinical, enzymatic, and ECG model, the sum of ST-segment depression (in millimetres) in all leads was a powerful independent predictor of 30 day death (P<0.0001), with a continuous increase in risk with the extent of ST-segment depression. The sum of ST-segment depression (P<0.0001) and the presence of minimal inferior ST-segment elevation (P<0.0001) or anterior ST-segment elevation (P=0.0182) were also independent predictors of the composite of death and myocardial infarction or reinfarction. The extent of ST-segment depression showed a highly significant correlation with the prevalence of three-vessel (P<0.0001) or left main coronary disease (P<0.0001), and also with the peak levels of creatine kinase (P<0.0001) during the index episode of ACS. CONCLUSION: In patients with NSTE ACS, the sum of ST-segment depression in all ECG leads is a powerful predictor of all-cause mortality at 30 days, independent of clinical variables and correlates with the extent and severity of coronary artery disease. The presence of even minimal (<1 mm) ST-segment elevation in anterior or inferior leads is independently associated with adverse outcomes.

Acute Disease↗

PubMed2005

First-principles calculation of 17O and 25Mg NMR shieldings in MgO at finite temperature: rovibrational effect in solids.

The temperature dependence of (17)O and (25)Mg NMR chemical shifts in solid MgO have been calculated using a first-principles approach. Density functional theory, pseudopotentials, a plane-wave basis set, and periodic boundary conditions were used both to describe the motion of the nuclei and to compute the NMR chemical shifts. The chemical shifts were obtained using the gauge-including projector augmented wave method. In a crystalline solid, the temperature dependence is due to both (i) the variation of the averaged equilibrium structure and (ii) the fluctuation of the atoms around this structure. In MgO, the equilibrium structure at each temperature is uniquely defined by the cubic lattice parameters, which we take from experiment. We evaluate the effect of the fluctuations within a quasiharmonic approximation. In particular, the dynamical matrix, defining the harmonic Hamiltonian, has been computed for each equilibrium volume. This harmonic Hamiltonian was used to generate nuclear configurations that obey quantum statistical mechanics. The chemical shifts were averaged over these nuclear configurations. The results reproduce the previously published experimental NMR data measured on MgO between room temperature and 1000 degrees C. It is shown that the chemical shift behavior with temperature cannot be explained by thermal expansion alone. Vibrational corrections due to the fluctuations of atoms around their equilibrium position are crucial to reproduce the experimental results.

Journal Article↗

PubMed2005

Electronic-enthalpy functional for finite systems under pressure.

We introduce the notion of electronic enthalpy for first-principles structural and dynamical calculations of finite systems under pressure. An external pressure field is allowed to act directly on the electronic structure of the system studied via the ground-state minimization of the functional E+PV(q), where V(q) is the quantum volume enclosed by a charge isosurface. The Hellmann-Feynman theorem applies, and assures that the ionic equations of motion follow an isoenthalpic dynamics. No pressurizing medium is explicitly required, while coatings of environmental ions or ligands can be introduced if chemically relevant. We apply this novel approach to the study of group-IV nanoparticles during a shock wave, highlighting the significant differences in the plastic or elastic response of the diamond cage under load, and their potential use as novel nanostructured impact-absorbing materials.

Journal Article↗

PubMed2005

First-principles calculation of the 17O NMR parameters of a calcium aluminosilicate glass.

We have computed the (17)O NMR parameters of an amorphous calcium aluminosilicate (CAS) from first-principles. The atomic coordinates of a CAS glass of composition (CaO)(0.21)(Al(2)O (3))(0.12)(SiO (2))(0.67) were obtained by quenching a liquid to room temperature by the means of ab initio molecular-dynamics simulations of the Car-Parrinello type. The structure of the glass is found to be overall in good agreement with diffraction experiments. Some excess nonbridging O (NBO) atoms are found and are compensated by tricluster O atoms, i.e., by 3-fold coordinated O atoms to 4-fold coordinated Al or Si atoms. The glass coordinates were used to compute the (17)O NMR parameters using GGA-DFT and a correction of the Ca 3d orbital energy. The chemical shifts and the electric field gradients were obtained with the gauge including projector augmented-wave (GIPAW) and the projector augmented-wave (PAW) methods, respectively. The simulated 2D-3QMAS NMR spectrum of the CAS glass is in very good agreement with the available experimental data, notably because it takes into account the disorder present in the glass. This agreement further validates our CAS glass model. We show that the oxygen triclusters are not visible in a 2D-3QMAS NMR (17)O spectrum since their NMR parameters overlap with those of the Al-O-Si, Si-O-Si, or Al-O-Al sites. Finally, correlations between the structural characteristics and the values of the NMR parameters are extracted from the calculation with the aim of helping the interpretation of NMR spectra of glasses of similar compositions.

Journal Article↗

PubMed2005

[Atrial fibrillation and cardioversion: role of transesophageal echocardiography].

The most common cardiac arrhythmia is atrial fibrillation (AF). Echocardiography has been an important tool in the evaluation of patients with AF. Transesophageal echocardiography (TEE) offers excellent visualization of the atria and accurate identification or exclusion of atrial thrombi. Patients undergoing cardioversion are treated conventionally with therapeutic anticoagulation for 3 weeks before and 4 weeks after cardioversion to decrease the risk of thromboembolism. A TEE-guided strategy has been proposed as an alternative that may lower stroke and bleeding events. Patients without atrial thrombus by TEE are cardioverted on achievement of therapeutic anticoagulation, whereas cardioversion is delayed in patients with any thrombus. The two management strategies comparably lower the patient's embolic risk when the guidelines are properly followed. The TEE-guided approach offers the advantage of simplified anticoagulation management and may lower the incidence of bleeding complications.

Anticoagulants↗

PubMed2004

Kohn anomalies and electron-phonon interactions in graphite.

We demonstrate that graphite phonon dispersions have two Kohn anomalies at the Gamma-E(2g) and K-A'1 modes. The anomalies are revealed by two sharp kinks. By an exact analytic derivation, we show that the slope of these kinks is proportional to the square of the electron-phonon coupling (EPC). Thus, we can directly measure the EPC from the experimental dispersions. The Gamma-E(2g) and K-A'1 EPCs are particularly large, while they are negligible for all the other modes at Gamma and K.

Journal Article↗

PubMed2004

First-principles calculation of the 17O NMR parameters in Ca oxide and Ca aluminosilicates: the partially covalent nature of the Ca-O bond, a challenge for density functional theory.

We apply density functional theory (DFT) to the calculation of the (17)O NMR parameters in Ca and Mg oxides and aluminosilicates. We study the accuracy of the Perdew, Burke, and Ernzerhof (PBE) generalized-gradient approximation to DFT in the description of these systems and the origin of the experimentally observed large dependence of the (17)O chemical shift on the alkaline earth ion. We find that (i) the partially covalent nature of the Ca-O bond has a huge impact on the O chemical shifts. The Ca-O covalence alone explains why in Ca oxides and aluminosilicates the (17)O chemical shifts are much more deshielded than those of the corresponding Mg compounds. (ii) The Ca-O covalence is overestimated by the PBE functional. Thus PBE-DFT is not able to reproduce the measured (17)O NMR parameters in Ca oxide and Ca aluminosilicates. (iii) It is possible to correct for the PBE-DFT deficiency in a simple and transferable way and to predict very accurate (17)O NMR parameters. Such accuracy allows us to assign the (17)O NMR spectra of two important model systems: the grossite aluminate (CaAl(4)O(7)) and the wollastonite (CaSiO(3)) silicate.

Journal Article↗

PubMed2004

Combined ab initio computational and experimental multinuclear solid-state magnetic resonance study of phenylphosphonic acid.

1H, 13C, 17O and 31P NMR parameters, including chemical shift tensors and quadrupolar parameters for 17O, were calculated for phenylphosphonic acid, C6H5PO(OH)2, under periodic boundary conditions. The results are in very good agreement with experimental data and permit the unambiguous assignment of all the sites present in the structure. In particular, the 17O NMR parameters of the P=O and P-OH environments were precisely determined, which should help in the characterization of the bonding mode of phosphonate molecules in hybrid solids. Moreover, the effect of intermolecular interactions on the NMR parameters were investigated by comparing the results of the calculations in the crystal and in an isolated molecule of phenylphosphonic acid.

Algorithms↗

PubMed2004

In-hospital and one-year outcomes of patients with high-risk acute myocardial infarction treated with thrombolysis or primary coronary angioplasty.

BACKGROUND: The aim of this study was to observe the outcomes of high-risk patients with acute myocardial infarction treated with primary angioplasty and intravenous thrombolysis in a community setting. METHODS: A prospective study of the in-hospital and 12-month outcomes was conducted in 17 cardiology centers where primary angioplasty was available, and in 30 where it was not. Three thousand seventy-four patients in the first 12 hours of an evolving infarction were recruited; among these, 2227 patients who met one or more pre-defined criteria of increased risk were included in the study. RESULTS: Thrombolysis and primary angioplasty were respectively performed in 1090 and in 721 patients; 416 patients (18.7%) received no reperfusion treatment. The incidence of the primary combined in-hospital endpoint (death, non-fatal reinfarction and stroke) was similar in patients treated with thrombolysis (9.2%) and with primary angioplasty (10.7%) (odds ratio--OR 1.19, 95% confidence interval--CI 0.86-1.63, p = NS), and was higher (22.6%) in patients receiving no reperfusion treatment as compared to thrombolysis (OR 3.30, 95% CI 2.36-4.63, p < 0.0001). The occurrence of the 12-month endpoint (death, reinfarction, congestive heart failure and recurrent angina) was lower after primary angioplasty than after thrombolysis (26.8 vs 35.0%, OR 0.68, 95% CI 0.55-0.84, p = 0.0003), due to a lower incidence of angina. At multivariate analysis, older age, anterior infarction, Killip class > 1, high heart rate, and low systolic blood pressure on admission were all significantly associated with a higher incidence of both endpoints. The adjusted analysis confirmed that, despite similar in-hospital results after both reperfusion treatments, primary angioplasty was independently associated with better 1-year outcomes (relative risk 0.66, 95% CI 0.56-0.79, p < 0.0001). CONCLUSIONS: In this observation in the community setting, a strategy of primary angioplasty in patients with high-risk myocardial infarction was not better than thrombolysis in terms of mortality or recurrent infarction, but was associated with less angina at 1 year.

Aged↗

PubMed2003

Nonlocal pseudopotentials and magnetic fields.

We show how to describe the coupling of electrons to nonuniform magnetic fields in the framework of the widely used norm-conserving pseudopotential approximation for electronic structure calculations. Our derivation applies to magnetic fields that are smooth on the scale of the core region. The method is validated by application to the calculation of the magnetic susceptibility of molecules within density functional theory (DFT) in the local density approximation. Our results are compared with high-quality all-electron DFT results obtained using Gaussian basis sets and another recently proposed pseudopotential formalism.

Journal Article↗

PubMed2003

Phonon dispersion and lifetimes in MgB2.

We measure phonon dispersion and linewidth in a single crystal of MgB2 along the Gamma-A, Gamma-M, and A-L directions using inelastic x-ray scattering. We use density functional theory to compute the effect of both electron-phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E(2g) phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-phonon coupling.

Journal Article↗