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Francesco Mauri

Publications and source records attributed to Francesco Mauri.

27 records · Page 2Linked to original sources
PubMed2003

First-principles calculation of vibrational Raman spectra in large systems: signature of small rings in crystalline SiO2.

We present an approach for the efficient calculation of vibrational Raman intensities in periodic systems within density functional theory. The Raman intensities are computed from the second order derivative of the electronic density matrix with respect to a uniform electric field. In contrast to previous approaches, the computational effort required by our method for the evaluation of the intensities is negligible compared to that required for the calculation of vibrational frequencies. As a first application, we study the signature of 3- and 4-membered rings in the Raman spectra of several polymorphs of SiO2, including a zeolite (H-ZSM-18) having 102 atoms per unit cell.

Journal Article↗
PubMed2003

Accurate first principles prediction of 17O NMR parameters in SiO2: assignment of the zeolite ferrierite spectrum.

17O NMR parameters, both the chemical shifts and the quadrupolar parameters, are calculated for SiO2 polymorphs using density functional theory with the generalized gradient-corrected PBE functional. The gauge including projector augmented wave (GIPAW) method (Pickard, C. J.; Mauri, F. Phys. Rev. B2001, 63, 245101) ensures the reproduction of all electron results while using computationally efficient pseudopotentials. The use of plane-waves permits fully converged calculations to be performed on structures containing 144 atoms in the unit cell, without the need to resort to the cluster approximation. The calculated NMR parameters of cristobalite, quartz, coesite, and faujasite are in excellent agreement with experimental data. This demonstrates that density functional theory is able to reproduce with high accuracy the 17O NMR parameters in SiO2 systems. This precision is used to assign the spectrum of the zeolite ferrierite. The data calculated for SiO2 are used to confirm that no simple correlation between the chemical shift and Cq NMR parameters and Si-O-Si angle exists, emphasizing the importance of predictive theories in this field.

Journal Article↗
PubMed2002

Multiple ionic-plasmon resonances in naturally occurring multiwall nanotubes: infrared spectra of chrysotile asbestos.

Chrysotile asbestos is formed by densely packed bundles of multiwall hollow nanotubes. Each wall in the nanotubes is a cylindrically wrapped layer of Mg(3)Si(2)O(5)(OH)(4). We show by experiment and theory that the infrared spectra of chrysotile present multiple ionic-plasmon resonances in the Si-O stretching bands. These collective charge excitations are universal features of the nanotubes that are obtained by cylindrically wrapping an anisotropic material. The multiple plasmons can be observed if the width of the resonances is sufficiently small as in chrysotile.

Asbestos, Serpentine↗
PubMed2002

Clinical value of 12-lead electrocardiography to predict the long-term prognosis of GISSI-1 patients.

OBJECTIVES: We evaluated the prognostic relevance of the extent of myocardial injury, as measured by a standard electrocardiographic (ECG) method, on the patients' long-term prognosis, its time dependence and its relation to fibrinolytic therapy efficacy. BACKGROUND: Many clinical and instrumental variables influence the short- and long-term prognoses of patients with acute myocardial infarction (MI). The extent of myocardial injury is relevant to predict both the short-term prognosis and the benefit of fibrinolytic treatment. METHODS: In 8,731 patients with MI enrolled in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto (GISSI-1) study, the number of ECG leads with ST-segment elevation was used to define the extent of myocardial injury and four different severity groups: A, B, C and D, with ST-segment elevation in two or three leads, four or five leads, six or seven leads and more than eight leads, respectively. RESULTS: At 10 years, the mortality rates were 36.6%, 41.0%, 47.9% and 51.2% in groups A, B, C and D, respectively. At 30 days, according to the extent of myocardial injury, the relative risk (RR) of death was significantly higher for groups B, C and D, compared with group A (RR 1.19 and 95% confidence interval [CI] 1.06 to 1.34 for group B; RR 1.54 and 95% CI 1.31 to 1.80 for group C; RR 2.01 and 95% CI 1.69 to 2.39 for group D). At one-year follow-up, the RR of death remained higher for groups C and D, whereas, subsequently, the extent of myocardial injury did not influence the RR of death. At 10 years, the differences in fibrinolytic treatment benefit between the four groups were similar to those at hospital discharge. CONCLUSIONS: At 10 years, the survival rate appears to be related to the extent of myocardial injury, as evaluated by ST-segment elevation on the admission ECG.

Aged↗
PubMed2002

First-principles theory of the EPR g tensor in solids: defects in quartz.

A theory for the reliable prediction of the EPR g tensor for paramagnetic defects in solids is presented. It is based on density functional theory and on the gauge including projector augmented wave approach to the calculation of all-electron magnetic response. The method is validated by comparison with existing quantum chemical and experimental data for a selection of diatomic radicals. We then perform the first prediction of EPR g tensors in the solid state and find the results to be in excellent agreement with experiment for the E(1)(prime) and substitutional phosphorus defect centers in quartz.

Journal Article↗
PubMed2002

Prognostic value of thymidine phosphorylase expression in breast carcinoma.

Thymidine phosphorylase (TP), also known as platelet-derived endothelial cell growth factor (PD-ECGF), is an enzyme that catalyzes the reversible dephosphorylation of thymidine, deoxyuridine and their analogs. TP has also angiogenic properties, although the precise mechanism by which it promotes angiogenesis is not known. We examined TP expression using immunohistochemistry (654-1 Mab) in 182 invasive breast carcinomas (67 N0 and 115 N1/2; median follow-up 78 months [range, 3-177]; 51 patients treated with adjuvant systemic cyclophosphamide, methotrexate and 5-fluorouracil [CMF] chemotherapy and 82 with tamoxifen). High TP expression was found in 142 cases (78%) and correlated with lower histologic grade and low p53 expression. No correlation was found between TP expression and vascular density. TP-positive tumors had a significant increase in both disease-free survival (DFS; p = 0.0025) and overall survival (OS; p = 0.0070) in the total cohort of patients and in the subgroups of node-positive patients and patients treated with CMF adjuvant therapy; no significant difference in either DFS or OS was observed in patients without CMF treatment. Our findings suggest that TP has little effect on tumor angiogenesis of breast carcinoma, whereas it could represent an interesting marker that could predict response to CMF chemotherapy.

Antineoplastic Agents, Hormonal↗
PubMed2002

Crooke's hyalinization in silent corticotroph adenoma: report of two cases.

Corticotroph adenomas rarely show Crooke's hyaline change in neoplastic cells, a feature similar to that of normal corticotroph cells exposed to excess cortisol. Crooke's cell adenomas are usually associated with Cushing's disease. Nonfunctioning examples are uncommon. We report two clinically silent corticotroph adenomas featuring extensive Crooke's hyalinization in neoplastic cells. The two patients were 49 and 59 yr of age and neither had Cushing's disease. Serum and urinary cortisol were normal. One patient had elevated serum adrenocorticotropic hormone. In our experience, the two patients accounted for 0.4% of pituitary adenomas operated on from January 1992 to December 2001 and 3.5% of all corticotroph adenomas. The two lesions had features of the subtype 1 silent corticotroph adenoma. Cytogenetic analysis performed on one lesion showed a normal karyotype (46;XY). Hyalinization in clinically silent Crooke's cell adenoma indicates that hyaline changes do not always relate to excess cortisol. It is known that neoplastic Crooke's cells show immunoreactivity for glucocorticoid receptors stronger than nontumorous Crooke's corticotrophs. This fact suggests that receptor overexpression or lack of receptor downregulation may result in hypersensitivity of neoplastic Crooke's cells to physiologic cortisol plasma levels.

Adenoma↗
PubMed2002

[Cost reduction in the assessment of thoracic pain with the chest pain unit in first aid].

BACKGROUND: The evaluation of chest pain is a constant challenge for cardiologists, due to its clinical, organizational, economical and legal implications. The costs of the diagnostic classification of non-specific thoracic pain during ordinary, albeit short, hospitalization are here compared with a quick screening of the same symptoms in a "Chest Pain Unit", which may form an appendix of the emergency room (ER). METHODS: The study involves patients admitted to the hospital used as reference during the year 2000 and discharged with a diagnosis of thoracic pain or precordial pain, as identified by ICD-9-CM codes 786.50, 786.51, 786.52, 786.59. According to DRG 143 tariffs, the hospitalization of such a patient costs Itl 4,346,000 epsilon 2244.52). If a Chest Pain Unit should monitor the same patients in the ER for at least 12 hours, during which time the examination at admission has to followed by two ECGs, 4 seriated evaluation of cardio-specific enzymes, an echocardiogram and a stress test, the individual cost concerning payment for ER services, would be of Itl 879,000 ([symbol: see text] 453.97). Even adding Itl 508,000 ([symbol: see text] 262.36) to pay the 12-hour monitoring provided for by the short protocol, the total amount would be Itl 1,387,000 epsilon 716.33). This evaluation has also been applied to the 47,775 patients hospitalized with the same diagnosis in all Italian hospitals during the year 1999. RESULTS: Three hundred and thirty-eight patients admitted to the hospital used as reference were discharged with the above reported diagnosis. Among them 215 (64%) were hospitalized in the cardiology ward. The total cost for hospitalization for the 338 patients evaluated was Itl 1,468,948,000 epsilon 758,648.33) as compared to Itl 297,102,000 epsilon 153,440.37) that the short-term therapy would have required. Countrywide the same cost was Itl 207,543,230,000 epsilon 107,187,132.99) as compared to Itl 41,976,645,000 epsilon 21,679,127.91) for the short-term therapy, using which would have led to save Itl 166,566,585,000 epsilon 86,024,461.98). CONCLUSIONS: The suggested strategy, corroborated by many previous experiences, is an effective and efficient alternative for thoracic pain evaluation, especially in a time when economical resources are being drastically reduced, thus requiring research and application of optimized diagnostic procedures.

Chest Pain↗