120 research outputs found

    A new model with Serpent for the first criticality benchmarks of the TRIGA Mark II reactor

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    We present a new model, developed with the Serpent Monte Carlo code, for neutronics simulation of the TRIGA Mark II reactor of Pavia (Italy). The complete 3D geometry of the reactor core is implemented with high accuracy and detail, exploiting all the available information about geometry and materials. The Serpent model of the reactor is validated in the fresh fuel configuration, through a benchmark analysis of the first criticality experiments and control rods calibrations. The accuracy of simulations in reproducing the reactivity difference between the low power (10 W) and full power (250 kW) reactor condition is also tested. Finally, a direct comparison between Serpent and MCNP simulations of the same reactor configurations is presented

    Development of a Reduced Order Model for Fuel Burnup Analysis

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    Fuel burnup analysis requires a high computational cost for full core calculations, due to the amount of the information processed for the total reaction rates in many burnup regions. Indeed, they reach the order of millions or more by a subdivision into radial and axial regions in a pin-by-pin description. In addition, if multi-physics approaches are adopted to consider the effects of temperature and density fields on fuel consumption, the computational load grows further. In this way, the need to find a compromise between computational cost and solution accuracy is a crucial issue in burnup analysis. To overcome this problem, the present work aims to develop a methodological approach to implement a Reduced Order Model (ROM), based on Proper Orthogonal Decomposition (POD), in fuel burnup analysis. We verify the approach on 4 years of burnup of the TMI-1 unit cell benchmark, by reconstructing fuel materials and burnup matrices over time with different levels of approximation. The results show that the modeling approach is able to reproduce reactivity and nuclide densities over time, where the accuracy increases with the number of basis functions employed

    Editorial: Harnessing the sustainable valorization and exploitation of salt tolerant plants

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    Recruiting wild halophytes with economic potential was suggested several decades ago to reduce the problems associated with soil and water salinization and reduction of freshwater resources for agriculture.Tunisian Ministry of HigherEducation and Scienti!c Research and the Foundation for Scienceand Technology (FCT, Portugal); MCIN/AEI/10.13039/501100011033; Research and Innovation in the Mediterranean Area (PRIMA)info:eu-repo/semantics/publishedVersio

    Antithymocyte Globulin in Reduced-Intensity Conditioning Regimen Allows a High Disease-Free Survival Exempt of Long-Term Chronic Graft-versus-Host Disease

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    AbstractNonmyeloablative (NMA) regimens allow the use of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients considered unfit for standard myeloablative conditioning (MAC) regimens using high-dose alkylating agents with or without total body irradiation (TBI). Reduced-intensity conditioning (RIC) regimens, based on fludarabine (Flu), busulfan (Bu), and rabbit antithymocyte globulin (r-ATG), represent an intermediate alternative between NMA and MAC regimens. This platform was subsequently optimized by the introduction of i.v. Bu and the use of 5 mg/kg r-ATG, based on the hypothesis that these modifications would improve the safety of RIC allo-HSCT. Here we report a study conducted at our institution on 206 patients, median age 59 years, who underwent allo-HSCT after conditioning with Flu, 2 days of i.v. Bu, and 5 mg/kg r-ATG (FBx-ATG) between 2005 and 2012. The prevalence of grade III-IV acute graft-versus-host disease (GVHD) was 9%, and that of extensive chronic GVHD was 22%. Four-year nonrelapse mortality (NRM), relapse, and overall survival (OS) rates were 22%, 36%, and 54%, respectively. NRM tended to be influenced by comorbidities (hematopoietic cell transplantation–specific comorbidity index [HCT-CI] <3 versus HCT-CI ≄3: 18% versus 27%; P = .075), but not by age (<60 years, 20% versus ≄60 years, 25%; P = .142). Disease risk significantly influenced relapse (2 years: low, 8%, intermediate, 28%, high, 34%; very high, 63%; P = .017). Both disease risk (hazard ratio [95% confidence interval]: intermediate, 2.1 [0.8 to 5.2], P = .127; high, 3.4 [1.3 to 9.1], P = .013; very high, 4.0 [1.1 to 14], P = .029) and HCT-CI (hazard ratio [95% confidence interval]: HCT-CI ≄3, 1.7 (1.1 to 2.8), P = .018) influenced OS, but age and donor type did not. The FBx-ATG RIC regimen reported here is associated with low mortality and high long-term disease-free survival without persistent GVHD in both young and old patients. It represents a valuable platform for developing further post-transplantation strategies aimed at reducing the incidence of relapse, particularly in the setting of high-risk disease

    Peripheral Blood Stem Cells versus Bone Marrow for T Cell-Replete Haploidentical Transplantation with Post-Transplant Cyclophosphamide in Hodgkin Lymphoma.

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    Abstract Haploidentical stem cell transplantation (haplo-SCT) with post-transplant cyclophosphamide (PT-Cy) represents a potential curative strategy for patients with Hodgkin lymphoma (HL) when a matched related or unrelated donor is not available. The role of graft source, either bone marrow (BM) or peripheral blood stem cells (PBSCs), in this setting has not been fully elucidated. We performed a retrospective study on 91 patients with HL to compare the outcome after BM (n = 53) or PBSC (n = 38) transplant. Eighty-nine patients engrafted with no difference between BM and PBSCs in terms of median time for neutrophil (20 versus 20 days, P = .405) and platelet (26 versus 26.5 days, P = .994) engraftment. With a median follow-up of 40.2 months, 100-day cumulative incidences of grades II to IV acute graft-versus host disease (GVHD) and grades II to IV acute GVHD were 24% and 4%, respectively. Graft source was not associated with a different risk of acute GVHD both by univariate and multivariate analyses. Consistently, 1-year cumulative incidence of chronic GVHD was 7% with no differences between the 2 graft types (P = .761). Two-year rates of overall survival (OS), progression-free survival (PFS), nonrelapse mortality, and GVHD/relapse-free survival (GRFS) were 67%, 58%, 20%, and 52%, respectively. By univariate analysis, pretransplant disease status was the main variable affecting all outcomes. By multivariate analysis, PBSCs resulted in a protective factor for OS (hazard ratio [HR], .29; P = .006), PFS (HR, .38; P = .001), and GRFS (HR, .44; P = .020). The other independent variables affecting the final outcome were pretransplant disease status and hematopoietic cell transplant–specific comorbidity index. In conclusion, when planning a haplo-SCT with PT-Cy for patients with poor-risk HL, graft type is an important variable to take into account when selecting the best available donor

    A complicated case of pulmonary embolism in a patient with renal failure

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    We describe a case of pulmonary embolism with instable hemodynamics in a patient with renal failure; the case is complicated by heparin-induced thrombocytopenia (HIT). Renal failure has a high prevalence in hospitalized patients and is a restriction on administration of low molecular weight heparins (LMWH) and fondaparinux. HIT is a potentially life-threatening complication, therefore a precocious diagnosis is essential. Therapy consists in the immediate stop of heparin’s administration and in the administration of non-heparin antithrombotic drugs

    All-cause mortality in treated HIV-infected adults with CD4 ≄500/mm3 compared with the general population: evidence from a large European observational cohort collaboration

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    Background Using data from a large European collaborative study, we aimed to identify the circumstances in which treated HIV-infected individuals will experience similar mortality rates to those of the general population. Methods Adults were eligible if they initiated combination anti-retroviral treatment (cART) between 1998 and 2008 and had one prior CD4 measurement within 6 months. Standardized mortality ratios (SMRs) and excess mortality rates compared with the general population were estimated using Poisson regression. Periods of follow-up were classified according to the current CD4 count. Results Of the 80 642 individuals, 70% were men, 16% were injecting drug users (IDUs), the median age was 37 years, median CD4 count 225/mm3 at cART initiation and median follow-up was 3.5 years. The overall mortality rate was 1.2/100 person-years (PY) (men: 1.3, women: 0.9), 4.2 times as high as that in the general population (SMR for men: 3.8, for women: 7.4). Among 35 316 individuals with a CD4 count ≄500/mm3, the mortality rate was 0.37/100 PY (SMR 1.5); mortality rates were similar to those of the general population in non-IDU men [SMR 0.9, 95% confidence interval (95% CI) 0.7-1.3] and, after 3 years, in women (SMR 1.1, 95% CI 0.7-1.7). Mortality rates in IDUs remained elevated, though a trend to decrease with longer durations with high CD4 count was seen. A prior AIDS diagnosis was associated with higher mortality. Conclusions Mortality patterns in most non-IDU HIV-infected individuals with high CD4 counts on cART are similar to those in the general population. The persistent role of a prior AIDS diagnosis underlines the importance of early diagnosis of HIV infectio

    Addition of Rituximab in Reduced Intensity Conditioning Regimens for B-Cell Malignancies Does Not Influence Transplant Outcomes: EBMT Registry Analyses Following Allogeneic Stem Cell Transplantation for B-Cell Malignancies

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    Rituximab (R) is increasingly incorporated in reduced intensity conditioning (RIC) regimens for allogeneic hematopoietic cell transplantation (alloHCT) in patients with B-cell malignancies, not only to improve disease control, but also to prevent graft-versus-host disease (GVHD). There are no randomized prospective data to validate this practice, although single center data and the CIBMTR analysis have shown promising results. We aimed at validation of these findings in a large registry study. We conducted a retrospective analysis using the EBMT registry of 3,803 adult patients with B-cell malignancies undergoing alloHCT (2001–2013) with either rituximab (R-RIC-9%) or nonrituximab (RIC-91%) reduced intensity regimens respectively. Median age and median follow up were 55 years (range 19.1–77.3) and 43.2 months (range 0.3–179.8), respectively. There was no difference in transplant outcomes (R-RIC vs RIC), including 1-year overall survival (69.9% vs 70.7%), 1-year disease-free survival (64.4% vs 62.2%), 1-year non-relapse mortality (21% vs 22%), and day-100 incidence of acute GVHD 2-4° (12% vs 12%). In summary, we found that addition of rituximab in RIC regimens for B-cell malignancies had no significant impact on major transplant outcome variables. Of note, data on chronic GVHD was not available, limiting the conclusions that can be drawn from the present study
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