Comparison of Iteration Schemes for the Solution of the Multidimensional Schrödinger-Poisson Equations

We present a fast and robust iterative method for obtaining self-consistent solutions to the coupled system of Schrödinger's and Poisson's equations in quantum structures. A simple expression describing the dependence of the quantum electron density on the electrostatic potential is used to implement a predictor – corrector type iteration scheme for the solution of the coupled system of differential equations. This approach simplifies the software implementation of the nonlinear problem, and provides excellent convergence speed and stability. We demonstrate the algorithm by presenting an example for the calculation ofthe two-dimensional bound electron states within the cross-section of a GaAs-AlGaAs based quantum wire. For this example, six times fewer iterations are needed when our predictor – corrector approach is applied, compared to a corresponding underrelaxation algorithm

Tunneling Between Multimode Stacked Quantum Wires

Tunneling between vertically stacked quantum wires has been investigated. The wires are assumed to have the dimension perpendicular to the tunneling barrier much smaller than the other transverse dimension, so that only the lowest mode in such direction is to be taken into account, while many modes in the other direction are filled. A model with hard-wall confinement has been used for the investigation of the transport problem, and the tunneling conductance has been computed, via a recursive Green's functions procedure

Hepatocellular carcinoma locoregional therapies for patients in the waiting list. Impact on transplantability and recurrence rate

The practice of treating candidates to liver transplantation (LT) for hepatocellular carcinoma (HCC) with locoregional therapies is common in most transplant centers. However, for T1 tumors and expected waiting times to LT <6 months, there is no evidence that these treatments are beneficial. For T2 tumors and for longer waiting times, neo-adjuvant treatments are usually performed with transarterial chemoembolization (TACE), ablation techniques, and liver resection in selected cases. The treatment choice should be based on the BCLC staging system. At present, there is no evidence of the superiority of ablation/resection vs. TACE, but some studies showed better results of the former in achieving a complete response. The response to neo-adjuvant treatments should be evaluated through mRECIST criteria, but few studies adopted these criteria and properly analyzed factors affecting response. The simultaneous evaluation of the impact of neo-adjuvant therapies on dropout rate, post-LT HCC recurrence and patient survival is rarely reported. Tumor stage and volume, alpha-fetoprotein levels, response to treatments and liver function affect pre-LT outcomes. These same factors, together with vascular invasion and poor tumor differentiation are major determinants of poor post-LT outcomes. Due to the low number of prospective studies with well defined entry criteria and the variability of results, the role of downstaging is still to be defined. Novel molecular markers seem promising for the estimation of prognosis and/or response to treatments. With a persistent scarcity of organ donors, neo-adjuvant treatments can help in identifying patients with different probabilities of cancer progression, and consequently in balancing the priority of HCC and non-HCC-candidates through revised additional scores for HCC

Hierarchy of Full Band Structure Models for Monte Carlo Simulation

This paper discusses the various hierarchy levels that are possible when the full band structure is considered. At the highest level, the scatterings are treated using complete k-k' transition rates, which entail extremely memory intensive computational applications. At the lowest level, the scattering anisotropy is neglected and the scattering rate is considered to be a constant average value on energy isosurfaces of the bandstructure. This model is more practical for device simulation. In between the two extremes, it is possible to design intermediate models which preserve some essential features of both. At all levels of the band structure hierarchy of models, there are similar issues of numerical noise, related to the sampling of real and momentum space that the Monte Carlo method necessarily performs with a relatively small number of particles. We discuss here computationally efficient approaches based on the assignment of variable weights to the simulated particles, in conjunction with careful gatherscatter procedures to split particles of large weight and combine particles of small weight

The effect of lipoprotein-associated phospholipase A2 deficiency on pulmonary allergic responses in Aspergillus fumigatus sensitized mice.

BackgroundLipoprotein-associated phospholipase A2 (Lp-PLA2)/platelet-activating factor acetylhydrolase (PAF-AH) has been implicated in the pathogenesis of cardiovascular disease. A therapeutic targeting of this enzyme was challenged by the concern that increased circulating platelet activating factor (PAF) may predispose to or increase the severity of the allergic airway response. The aim of this study was to investigate whether Lp-PLA2 gene deficiency increases the risk of PAF and IgE-mediated inflammatory responses in vitro and in vivo using mouse models.MethodsLp-PLA2-/- mice were generated and back crossed to the C57BL/6 background. PAF-AH activity was measured using a hydrolysis assay in serum and bronchoalveolar lavage (BAL) samples obtained from mice. Aspergillus fumigatus (Af)-specific serum was prepared for passive allergic sensitization of mice in vivo and mast cells in vitro. β- hexosaminidase release was studied in bone marrow derived mast cells sensitized with Af-specific serum or DNP-IgE and challenged with Af or DNP, respectively. Mice were treated with lipopolysaccharide (LPS) and PAF intratracheally and studied 24 hours later. Mice were sensitized either passively or actively against Af and were studied 48 hours after a single intranasal Af challenge. Airway responsiveness to methacholine, inflammatory cell influx in the lung tissue and BAL, immunoglobulin (ELISA) and cytokine (Luminex) profiles were compared between the wild type (WT) and Lp-PLA2-/- mice.ResultsPAF-AH activity was reduced but not completely abolished in Lp-PLA2-/- serum or by in vitro treatment of serum samples with a high saturating concentration of the selective Lp-PLA2 inhibitor, SB-435495. PAF inhalation significantly enhanced airway inflammation of LPS treated WT and Lp-PLA2-/- mice to a similar extent. Sensitized WT and Lp-PLA2-/- bone-marrow derived mast cells released β-hexosaminidase following stimulation by allergen or IgE crosslinking to equivalent levels. Wild type and Lp-PLA2-/- mice responded to passive or active allergic sensitization by significant IgE production, airway inflammation and hyperresponsiveness after Af challenge. BAL cell influx was not different between these strains while IL-4, IL-5, IL-6 and eotaxin release was attenuated in Lp-PLA2-/- mice. There were no differences in the amount of total IgE levels in the Af sensitized WT and Lp-PLA2-/- mice.ConclusionsWe conclude that Lp-PLA2 deficiency in C57BL/6 mice did not result in a heightened airway inflammation or hyperresponsiveness after PAF/LPS treatment or passive or active allergic sensitization and challenge

Two Dimensional Quantum Mechanical Modeling of Nanotransistors

Quantization in the inversion layer and phase coherent transport are anticipated to have significant impact on device performance in 'ballistic' nanoscale transistors. While the role of some quantum effects have been analyzed qualitatively using simple one dimensional ballistic models, two dimensional (2D) quantum mechanical simulation is important for quantitative results. In this paper, we present a framework for 2D quantum mechanical simulation of a nanotransistor / Metal Oxide Field Effect Transistor (MOSFET). This framework consists of the non equilibrium Green's function equations solved self-consistently with Poisson's equation. Solution of this set of equations is computationally intensive. An efficient algorithm to calculate the quantum mechanical 2D electron density has been developed. The method presented is comprehensive in that treatment includes the three open boundary conditions, where the narrow channel region opens into physically broad source, drain and gate regions. Results are presented for (i) drain current versus drain and gate voltages, (ii) comparison to results from Medici, and (iii) gate tunneling current, using 2D potential profiles. Methods to reduce the gate leakage current are also discussed based on simulation results.Comment: 12 figures. Journal of Applied Physics (to appear

Sarcopenia Predicts Major Complications after Resection for Primary Hepatocellular Carcinoma in Compensated Cirrhosis

The burden of post-operative complications of patients undergoing liver resection for hepatocellular carcinoma (HCC) is a cause of morbidity and mortality. Recently, sarcopenia has been reported to influence the outcome of patients with cirrhosis. We aimed to assess factors associated with sarcopenia and its prognostic role in liver surgery candidates. We included all patients with compensated advanced chronic liver disease (cACLD) undergoing liver resection for primary HCC consecutively referred to the University of Bologna from 2014 to 2019 with an available preoperative abdominal CT-scan performed within the previous three months. A total of 159 patients were included. The median age was 68 years, and 80.5% of the patients were male. Sarcopenia was present in 82 patients (51.6%). Age and body mass index (BMI) were associated with the presence of sarcopenia at multivariate analysis. Thirteen (8.2%) patients developed major complications and 14 (8.9%) presented PHLF grade B-C. The model for end-stage liver disease score was associated with the development of major complications, whereas cACLD presence, thrombocytopenia, portal hypertension (PH), Child-Pugh score and Albumin-Bilirubin score were found to be predictors of clinically significative PHLF. The rate of major complications was 11.8% in sarcopenic patients with cACLD compared with no complications (0%) in patients without sarcopenia and cACLD (p = 0.032). The rate of major complications was significantly higher in patients with (16.3%) vs. patients without (0%) sarcopenia (p = 0.012) in patients with PH. In conclusion, sarcopenia, which is associated with age and BMI, may improve the risk stratification of post-hepatectomy major complications in patients with cACLD and PH

Are the Expanded Baveno VI Criteria really safe to screen compensated cirrhotic patients for high-risk varices?

The Expanded Baveno VI criteria [1] have been recently proposed as a new screening strategy for high-risk varices (HRV), able to increase the rate of spared upper endoscopies (EGDs) and improve upon the original Baveno VI Criteria [2]. To date, few studies have investigated the performance and safety of these criteria [3,4]. The recent work by Bae et al. [4] is the first one to report a high rate (&gt;5%) of missed HRV by the expanded criteria, questioning their efficiency in safely ruling out HRV (sensitivity 81%, NPV 93%, LR- 0.30

Transient Analysis of Warm Electron Injection Programming of Double Gate SONOS Memories by means of Full Band Monte Carlo Simulation

In this paper we investigate "Warm Electron Injection" as a mechanism for NOR programming of double-gate SONOS memories through 2D full band Monte Carlo simulations. Warm electron injection is characterized by an applied VDS smaller than 3.15 V, so that electrons cannot easily accumulate a kinetic energy larger than the height of the Si/SiO2 barrier. We perform a time-dependent simulation of the program operation where the local gate current density is computed with a continuum-based method and is adiabatically separated from the 2D full Monte Carlo simulation used for obtaining the electron distribution in the phase space. In this way we are able to compute the time evolution of the charge stored in the nitride and of the threshold voltages corresponding to forward and reverse bias. We show that warm electron injection is a viable option for NOR programming in order to reduce power supply, preserve reliability and CMOS logic level compatibility. In addition, it provides a well localized charge, offering interesting perspectives for multi-level and dual bit operation, even in devices with negligible short channel effects

The Adriatic Basin Forecasting System: new model and system development

The Adriatic Basin Forecasting System implemented within the framework of the ADRICOSM Partnership (ADRIatic sea integrated COstal areaS and river basin Management system), nested to the operational general circulation model of the Mediterranean Sea, has recently been upgraded both in terms of system design and model parameterizations. The operational forecast is now daily, producing 9 days forecast, and a new near real time quality control has been introduced. From the modeling point of view the system has been upgraded in resolution (vertically from 21 to 31 sigma levels, and horizontally from approximately 1/22° to approximately 1/45°). Realistic fresh water fluxes have been introduced through the surface boundary condition taking into account evaporation, precipitation and river runoff, and the Smolarckiwicz advection scheme has been changed to the MUSCL scheme. The details of these developments will be presented, together with the model validation in delayed and real time mod