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A double-grid ionization chamber(GIC) based on the 10B(n,α)7Li and 6Li(n,α)T nuclear reaction has been developed for neutron energy spectrum measurement in the energy region below 150 keV of CSNS/Back-n by time of flight method. According to the strong adjoint gamma-flash features, the structure design of thin window and thin bottom lining is adopted. In view of the characteristics of strong gamma-flash neutron beam, the structure design of thin bottom lining is adopted. Garfield++, SRIM and Simcenter Magnet Electric simulation programs are used to simulate the working parameters such as working gas, electrode spacing and electric field distribution of the GIC. CF4, which has fast electron drift speed and small diffusion coefficient and great organizing ability, is selected as the working gas for the CSNS/Back-n beam test with cathode-grid and grid-anode spacing of 20 mm and 5 mm, respectively. The collecting area within 74 mm can be considered as the uniform electric field area, and the relative deviation of the field strength is not more than 0.03%. The performance of the GIC was tested by α source. The GIC has good energy resolution for 239Pu/241Am/244Cm mixed α surface source with CF4. And the best energy resolution is 2.4%@5.48 MeV. Compared with the measured results of the parallel-plate chamber and the silicon microstrip detector, the advantages of energy resolution of the GIC developed in this work are verified.

Background: The placement of inferior vena cava (IVC) filters often emerges as an alternative preventative measure against pulmonary embolism in patients with upper gastrointestinal (GI) bleeding and isolated distal deep vein thrombosis (DVT). We aimed to investigate the association of IVC filter placement and the incidence of venous thromboembolism (VTE) recurrence in this patient population. Methods: We performed a retrospective cohort study including 450 patients with upper GI bleeding and isolated distal DVT. Propensity score matching using logistic regression was conducted to mitigate potential selection bias. Logistic regression models and additional sensitivity analyses were conducted to estimate the association between IVC filter implantation and VTE recurrence. Interaction and stratified analyses were also performed according to the background covariates. Results: Patients who underwent IVC filter placement were significantly younger than patients in the surveillance group (55.8 ± 9.0 vs 58.4 ± 11.2 years, p = 0.034). Patients in the IVC filter group demonstrated a higher distal thrombus burden. The VTE recurrence composite was significantly higher in patients who underwent IVC filter placement (44.1% [45/102] vs 25% [87/348], p < 0.001). Unmatched crude logistic regression analysis identified a significant association between IVC filter placement and VTE recurrence composite (OR = 2.37; 95% CI, 1.50–3.75). Sensitivity analyses yielded congruent outcomes. Conclusion: This study revealed an increased risk of VTE recurrence among patients receiving IVC filter placement, suggesting that IVC filter placement may not be suitable as a primary treatment for patients with upper GI bleeding and isolated distal DVT. [ABSTRACT FROM AUTHOR]