Prevalence and direct costs of patients with neuromyelitis optica: data from Campania region in southern Italy

The study aimed to estimate the prevalence and direct costs of neuromyelitis optica (NMO) patients in Campania, Italy. Materials & methods: We retrospectively evaluated 53 NMO patients (mean age: 50.9 ± 16.5 years; 34% men) from the Campania Region administrative databases identified through disease exemption codes in 2018 and analyzed the incidence of NMO among the Campania region population and the disease-related cost. Results: The prevalence of NMO was 0.91 per 100,000 individuals. The average regional cost per NMO patient was 10,836.2 euros. The highest cost was related to drugs (60.6%), followed by hospitalizations (32.7%), diagnostics (4.8%) and laboratory tests (1.0%). Conclusion: NMO is an extremely rare disease with an annual disease-related cost of 0.005% of public health expenditur

Nanoscale characterization of electrical transport at metal/3C-SiC interfaces

In this work, the transport properties of metal/3C-SiC interfaces were monitored employing a nanoscale characterization approach in combination with conventional electrical measurements. In particular, using conductive atomic force microscopy allowed demonstrating that the stacking fault is the most pervasive, electrically active extended defect at 3C-SiC(111) surfaces, and it can be electrically passivated by an ultraviolet irradiation treatment. For the Au/3C-SiC Schottky interface, a contact area dependence of the Schottky barrier height (ΦB) was found even after this passivation, indicating that there are still some electrically active defects at the interface. Improved electrical properties were observed in the case of the Pt/3C-SiC system. In this case, annealing at 500°C resulted in a reduction of the leakage current and an increase of the Schottky barrier height (from 0.77 to 1.12 eV). A structural analysis of the reaction zone carried out by transmission electron microscopy [TEM] and X-ray diffraction showed that the improved electrical properties can be attributed to a consumption of the surface layer of SiC due to silicide (Pt2Si) formation. The degradation of Schottky characteristics at higher temperatures (up to 900°C) could be ascribed to the out-diffusion and aggregation of carbon into clusters, observed by TEM analysis

A novel GaN HEMT degradation mechanism observed during HTST test

The maximum drain current (Imax) reduction after high temperature short term (HTST) tests in RF-GaN HEMT was investigated. A \u201ccritical-voltage\u201d like degradation was observed with voltage levels correlated with the pinch-off voltage of the MIS structure formed by the device field-plate terminal (FP). The recoverable nature of the observed phenomena and the positive temperature dependence of both the Imax reduction and leakage currents within the passivation layer allowed us to propose a novel interpretation based on a charge-injection process from the FP into SiN/AlGaN electrons trap within the device gate-drain access region

Study of threshold voltage instability in E-mode GaN MOS-HEMTs

In this work, the threshold instability in E-mode GaN MOS-HEMTs was investigated. In particular, the shift of VTH as a function of the applied positive gate voltage during device characterization was monitored, resulting in positive VTH shifts up to 1 V. A complete VTH recovery required more than one day of unbiased storage, but a partial recovery of the observed VTH shift was observed after few seconds. These results could be related to different positions of trap states: fast states, localized at the dielectric/GaN interface and slow states, the traps inside the dielectric layer. Moreover, VTH shift of 0.2 and 0.8 V for fast and slow states, respectively, was obtained. To gain insight into the physical mechanism involved in the observed phenomena, numerical simulation were also carried out. A VTH shift was obtained adding the interface states. Moreover, three different distributions of traps were compared. In particular, the concentration of filled traps was monitored to understand the impact of the distribution on the electrical behaviour. An increment in filled trap concentration at the increasing of the applied VGS, which in turns correlates with experimentally evaluated device behaviour, was obtained if the distribution of traps states is also above the GaN conduction band energy

A novel test methodology for RON and VTH monitoring in GaN HEMTs during switch-mode operation

One of the critical issues limiting the performances and reliability of GaN power devices is the degradation of their on-resistance (Ron) when they are operated at high drain-source voltages. Being able to monitor RON variation during device operation thus becomes a necessary task in order to investigate the physical mechanisms leading to the observed drifts. Standard measurement equipment does not allow to perform easily this task, specifically when Ron variation should be monitored when the device operates in switch-mode. Moreover, to better understand the physical mechanisms involved it is very important to monitor other device parameters such as its threshold-voltage VTH which is typically not monitored during device switch-mode operation. Therefore, in this work is presented a novel testing methodology which allows the simultaneous monitoring of device Ron and Vth during switchmode operation with the ability to capture the variation of said parameters starting from the very first switching cycles

Recycling and recovery of fiber polymeric wastes PE-PP-PET based as aggregate replacement in lightweight mortar: evaluation as environmental friendly application

Waste polymeric material, classified as secondary raw material, mainly consisting of selected polyolefins, PE and PP, and PET has brought great pressure on the environment, due to the large quantities produced by the urban lifestyles and economic activity. This research evaluated the possibility to reuse the plastic waste as aggregates in hydraulic lime based composite mortars. The composite mortars were prepared by replacing the conventional aggregate, silica sand, with 10, 15, and 20 % of fiber polymeric waste in a mixture of lime and water. The chemico-physical interaction between the recycled plastic aggregates and the lime matrix was examined through FTIR, X-Ray diffraction and morphological analyses. The effect of fiber polymeric waste on the degree of hydration and mechanical performances of the produced composites was also evaluated. Experimental results show that the good chemical interaction between the fiber plastic aggregates and the mortar induced an improvement of ductility of mortar composites. However, the plastic waste limited the degree of hydration of the hydraulic lime, due to the organic characterof the plastic as opposed to the inorganic character of lime

Correlation between dynamic Rdson transients and Carbon related buffer traps in AlGaN/GaN HEMTs

One of the critical issues limiting the performances and reliability of GaN power devices is the degradation of their on-resistance (RON) when they are operated at high drain-source voltages. Being able to monitor RON variation during device operation thus becomes a necessary task in order to investigate the physical mechanisms leading to the observed drifts. Standard measurement equipment does not allow to perform easily this task, specifically when RON variation should be monitored when the device operates in switch-mode. Moreover, to better understand the physical mechanisms involved it is very important to monitor other device parameters such as its threshold-voltage VTH which is typically not monitored during device switch-mode operation. Therefore, in this work is presented a novel testing methodology which allows the simultaneous monitoring of device RON and VTH during switchmode operation with the ability to capture the variation of said parameters starting from the very first switching cycles

Correlation between dynamic Rdson transients and Carbon related buffer traps in AlGaN/GaN HEMTs

The on resistance increment observed when the device is operated at high drain-source voltages is one the topics that limits the performance of the AlGaN/GaN HEMT devices. In this paper, the physical mechanisms responsible of the RDSon degradation are investigated. The dynamic RDSon transient method is used in order to get insight to characterize the traps states. By calculating the Arrhenius plot associated with the RDSon transients an activation energy of 0.86eV was extracted, that can be correlated to the traps due to the incorporation of Carbon inside the buffer. This hypothesis was further supported by the analyses performed on a simpler structure (TLM). By applying a negative substrate bias the effect of only the buffer traps was studied. A fairly close value of the activation energy (0.9eV) to the one extracted when analyzing the RDSon transient was obtained