Development of a machine learning interatomic potential for exploring pressure-dependent kinetics of phase transitions in germanium.

We introduce a data-driven potential aimed at the investigation of pressure-dependent phase transitions in bulk germanium, including the estimate of kinetic barriers. This is achieved by suitably building a database including several configurations along minimum energy paths, as computed using the solid-state nudged elastic band method. After training the model based on density functional theory (DFT)-computed energies, forces, and stresses, we provide validation and rigorously test the potential on unexplored paths. The resulting agreement with the DFT calculations is remarkable in a wide range of pressures. The potential is exploited in large-scale isothermal-isobaric simulations, displaying local nucleation in the R8 to ß-Sn pressure-induced phase transformation, taken here as an illustrative example.

Nanostructured 3C-SiC on Si by a network of (111) platelets: a fully textured film generated by intrinsic growth anisotropy.

In this paper, we address the unique nature of fully textured, high surface-to-volume 3C-SiC films, as produced by intrinsic growth anisotropy, in turn generated by the high velocity of the stacking fault growth front in two-dimensional (111) platelets. Structural interpretation of high resolution scanning electron microscopy and transmission electron microscopy data is carried out for samples grown in a hot-wall low-pressure chemical vapour deposition reactor with trichlorosilane and ethylene precursors, under suitable deposition conditions. By correlating the morphology and the X-ray diffraction analysis we also point out that twinning along (111) planes is very frequent in such materials, which changes the free-platelet configuration.

An electric field tunable energy band gap at silicene/(0001) ZnS interfaces.

The interaction of silicene, the silicon counterpart of graphene, with (0001) ZnS surfaces is investigated theoretically, using first-principles simulations. The charge transfer occurring at the silicene/(0001) ZnS interface leads to the opening of an indirect energy band gap of about 0.7 eV in silicene. Remarkably, the nature (indirect or direct) and magnitude of the energy band gap of silicene can be controlled by an external electric field: the energy gap is predicted to become direct for electric fields larger than about 0.5 V Å(-1), and the direct energy gap decreases approximately linearly with the applied electric field. The predicted electric field tunable energy band gap of the silicene/(0001) ZnS interface is very promising for its potential use in nanoelectronic devices.

[Hospital infection surveillance in 5 Roman intensive care units]. / Sorveglianza multicentrica delle infezioni ospedaliere in cinque terapie intensive romane.

The A.A. carried out a survey on hospital acquired infection (HAI) in the intensive care units (ICU) of five roman hospitals. The study monitored the following site-specific infection rates: pneumonia (PNE), blood stream infections (BSI), urinary tract infections (UTI), surgical site infections (SSI). According to CDC definitions all patients developing infection 48 hours or more after ward admission were included. Furthermore risk factors (i.e. age, sex, SAPS II), invasive procedures (i.e. endotracheal intubation, vascular and urinary catheterisation), microbiological isolates and their antibiotic susceptibility were screened. The overall 503 patients characteristics (i.e., age, length of stay, case-mix...) showed the wards as general ICU's. Although the SAPS II score was similar, mortality (18.2%-42.9%) and general infection rates (15.4%-40.4%) among the five ICU's were considerably variable (p < 0.05), as HAI episodes distribution by type: PNE (37-88%), BSI (6-42%), UTI (6-24%), SSI (3-7%) (p < 0.05). Also device-associated infection rates such as Ventilator-associated PNE (11.6-24.6@1000), Vascular catheter-associated BSI (3.4-19.2@1000). Urinary catheter-associated UTI (2.6-14.0@1000) and invasive procedures management were different. Among the infected patients the most commonly isolated microorganisms were P. aeruginosa and Staphylococcus spp., which presented a considerable antibiotic resistance. The study showed: 1) sampling (i.e. blood cultures, tracheal aspirate and urine samples) and laboratory methodology indispensable for a correct HAI diagnosis were not standardized in the five ICU's; 2) hospital infection control policy was not carried out in all ICU's. The study showed a lack of standardization which limits the comparability of the general roman ICU's.

[Arteriosclerotic aneurysms of the subclavian artery]. / Aneurismi arteriosclerotici dell'arteria succlavia.

OBJECTIVE: To evaluate diagnostic investigations, operative management and long-term outcome of atherosclerotic aneurysms of the subclavian artery. DESIGN: A retrospective clinical study through a follow-up period of 68 months (8 months to 11 years). SETTING: Department of Vascular Surgery, University Hospital. PATIENTS: Between 1983 and 1995, 5 patients with atherosclerotic aneurysms of the extrathoracic subclavian artery were reviewed. All patients presented a pulsatile supraclavicular mass. Ultrasonography and angiography confirmed the diagnosis and were useful in planning the operation. INTERVENTIONS: Four patients were submitted, through a supraclavicular incision, to resection of the aneurysm and replacement of a prosthetic graft (dacron in 2 cases, PTFE in the remaining 2 cases). In one patient, with a small saccular aneurysm, a tangential aneurysmectomy with a patch angioplasty (PTFE) was performed. RESULTS: All patients recovered after a mean hospital-stay of 9 days and had a valid radial pulsation. During the follow-up period, a dacron graft failure occurred 38 months later in one patient: she remains today asymptomatic. CONCLUSIONS: Resection is today recommended for all patients with diagnosed subclavian artery aneurysms. Because of unknown natural history of asymptomatic aneurysms, with an unpredictable risk of complications, more accurate evaluations are required for optimal clinical decision making (early surgery vs watchful waiting?).

[Hemorheologic and blood coagulation studies in 94 patients with chronic obstructive peripheral arterial disease]. / Studio emoreologico ed emocoagulativo in 94 pazienti affetti da arteriopatia ostruttiva cronica periferica.

During the last three years we have analyzed, in 94 patients with chronic arterial occlusive disease, in order to assess the hemorheological and hemocoagulative balance, the following parameters: prothrombin time, partial thromboplastin time, antithrombin III, antiplasmin, fibrinogen, factor VIII, erythrocyte sedimentation rate, platelet aggregation, erythrocyte filterability and hematocrit values. The main findings were: in 56 patients the hematocrit value was higher than 44%; Katz index was above normal values in 61.7% of the cases; ATIII showed a trend to lower values; platelet aggregation was increased; no significant variations in comparison to normal values were found in FVIII, antiplasmin levels, prothrombin time and partial thromboplastin time. Erythrocyte filterability values were decreased at a level as lower as more advanced was the clinical stage of the disease. These findings show, in agreement with those of other authors, the presence of hyperviscosity and hypercoagulative state in patients with chronic arterial occlusive disease.