BẢN TIN KHOA HỌC

Ba Ngoc Vu, Thien Ngoc Bui, Phong Thu Nguyen Huynh, Hao Cong Le, Phuong Truc Huynh, Hong Loan Thi Truong

Journal of Radioanalytical and Nuclear Chemistry

Abstract:

In this work, the radon exhalation, annual effective dose and excess lifetime cancer risks due to the exposure of radon released from raw building materials containing fly ash of different fractions were evaluated. The ²²⁶Ra and ²²²Rn concentrations were evaluated by the measurements on HPGe gamma spectrometer, RAD 7 radon detector combined with model calculation of radon exhalation for standard rooms. The results indicated that the emanation fraction for fly ash is lower than the corresponding value for soils and rocks. The surveyed building materials of containing fly ash can result in an indoor radon concentration up to 1.7 Bq m⁻³ which is below the recommended value of 100 Bq m⁻³ by WHO, the annual effective dose increases from 0.007 to 0.022 mSv year⁻¹, the excess lifetime cancer risks ranges from 0.027 × 10^–3 to 0.085 × 10^–3 with the ratio of 3.2 for the additional fly ash content in cement up to 75%. In the meanwhile, it has a down trend and influences inconsiderably on these parameters for sand. The obtained mean annual effective doses are lower than the dose limitation of 10 mSv year⁻¹ recommended for occupational workers.

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N. Tomida, T.N.T.Ngan, et al.

Physical Review Letters 124, 202501 (2020)

Abstract:

We measured missing mass spectrum of the 12C(γ,p) reaction for the first time in coincidence with potential decay products from η' bound nuclei. We tagged an (η + p) pair associated with the η'N → ηN process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observedinthebound-stateregion.An upper limit of the signal cross section in the opening angle cosθ^ηp_lab < -0.9 was obtained to be 2.2 nb/sr at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree η' production rate. Our results indicate a small branching fraction of the η'N → ηN process and/or a shallow η'-nucleus potential.

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Author: Thu T.C.Nguyen, Binh T.Nguyen, Nhon V.Mai

Purpose

Under geometrical uncertainties, different plan evaluation methods have been suggested but the dose distribution at a specified confidence level being highly desirable is lacking. In this work, we used the DVPH (Dose Volume Population Histogram) tool to evaluate the dose distribution of CTVs and OARs (Organs at Risk) and validate the PTV concept at a certain confidence level.

Methods

The plans were evaluated using PTV DVH and the DVPH approach. The DVPH approach is based on statistical analyzing of multiple CTV DVHs under geometrical errors with corresponding occurring probabilities. The random and systematic geometrical errors, assumed to follow a Gaussian distribution, are simulated by shifting the CT images.

Results

For target doses, the results showed that the minimum dose to PTV does not represent the minimum dose to the CTV. For two prostate cases, the minimum doses reduced from 98% and 95% of prescribed dose from PTV DVH to 89% and 92% of prescribed dose from CTV 90% CL-DVPH (90% Confidence Level-DVPH). This reduction was also seen in head and neck cases, from 95% to 68% and 74% of prescribed dose. For OAR doses, OAR DVHs underestimated the OAR dose receiving.

Conclusions

With the DVPH tool, the results showed that the minimum dose to the PTV is not a representative of the minimum dose to the CTV in IMPT at the 90% confidence level. The OAR DVH does not match any OAR CL-DVPHs.

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Rapid method for determining elemental composition in oxide powder sample using Rayleigh-COMPTON scattering technique

Le Hoang Minh, Pham Thi Anh Nhung, Huynh Dinh Chuong, Nguyen Thi Truc Linh, Phan Nguyen Hoang Long, Tran Thien Thanh

Radiation Physics and Chemistry, Available online 28 March 2024

Abstract:

This study presents an innovative approach utilizing gamma scattering techniques to precisely determine the composition percentage in a two-component oxide compound. The experiment involved a ²⁴¹Am gamma-ray source emitting 59.54 keV radiation and a Si(Li) detector to capture Rayleigh and Compton scattering signals from oxide powder samples. These samples were meticulously prepared by blending Pb₃O₄ and ZnO, with Pb₃O₄ proportions ranging from 0% to 100%. To ensure accuracy, eleven standard samples were employed to generate standard curves for Rayleigh intensity, Compton intensity, and the Rayleigh-Compton ratio. The key finding of this research was the calculation of composition percentages for the four samples under investigation, derived from experimental data and the standard curve. Validation against reference materials revealed a minimal relative deviation of approximately 1.0% when estimating the Pb₃O₄ ratio, showcasing the precision and potential applicability of this method in material science and analysis.

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Phương pháp xác định nhanh bề dày ống thép bằng kỹ thuật tán xạ gamma

Võ Hoàng Nguyên, Huỳnh Đình Chương, Nguyễn Duy Thông, Huỳnh Thanh Nhẫn, Nguyễn Hữu Bảo, Lê Thị Thu Thảo, Trần Thiện Thanh, Châu Văn Tạo

Tạp chí Phát triển Khoa học và Công nghệ – Natural Sciences, 5(4):1-7

Tóm tắt:

Trong các phép đo nhằm phát hiện khuyết tật bên trong vật liệu bằng kỹ thuật gamma tán xạ, cường độ tán xạ một lần thường được chú ý. Tuy nhiên, việc xử lý phổ để xác định cường độ tán xạ một lần cần có thời gian, gây bất lợi đối với những phép kiểm tra nhanh. Nghiên cứu này hướng đến việc sử dụng cường độ tán xạ tổng để xác định bề dày của vật liệu. Trong các phép đo thực nghiệm, cường độ tán xạ tổng có thể được xác định một cách trực tiếp mà không cần xử lý phổ, nhờ đó thời gian kiểm tra mẫu được rút ngắn. Để tính toán bề dày của vật liệu, tỉ số cường độ tán xạ tổng R=I_x/I_Ref được sử dụng. Một đường chuẩn của R theo bề dày vật liệu được xây dựng bằng số liệu mô phỏng sử dụng MCNP6. Hệ đo tán xạ gamma sử dụng đầu dò NaI(Tl), nguồn phóng xạ ¹³⁷Cs, bia tán xạ là các ống thép có đường kính ngoài 273 mm, góc tán xạ 120^o. Dựa vào đường chuẩn R, bề dày của các ống thép thực tế được xác định bằng thực nghiệm đo tán xạ gamma. Kết quả tính toán cho thấy bề dày của các ống thép được xác định với độ sai biệt dưới 4% so với thực tế. Ngoài ra, các tính toán cũng cho thấy bề dày bão hòa của thép đối với cường độ tán xạ tổng là lớn hơn đáng kể so với cường độ tán xạ một lần, nhờ đó có thể mở rộng giới hạn về bề dày của mẫu cần đo đạc.

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Phân tích hàm lượng selen (Se) trong móng chân bệnh nhân ung thư đại trực tràng

Huỳnh Trúc Phương, Trần Tuấn Anh, Nguyễn Văn Hạnh, Nguyễn Thị Trúc Linh, Trương Thị Hồng Loan, Hồ Mạnh Dũng, Nguyễn Văn Đông, Đinh Thanh Bình

Tạp chí Phát triển Khoa học và Công nghệ – Khoa học Tự nhiên, 5(1):969-974

Tóm tắt:

Selenium (Se) là nguyên tố vết có vai trò quan trọng trong các chức năng sinh học của cơ thể con người. Móng chân được xem như là vật liệu thích hợp cho việc tìm ra mối liên hệ giữa hàm lượng nguyên tố vết với bệnh tật ở con người. Mục tiêu của nghiên cứu này là phân tích và đánh giá hàm lượng Se trong móng chân của bệnh nhân ung thư đại trực tràng nhằm tìm ra nguy cơ ung thư ở con người. Hàm lượng Se trong móng chân của 60 bệnh nhân ung thư đại trực tràng (nam giới chiếm 63,3%) và 22 người bình thường (nam giới chiếm 54,5%) được phân tích bằng phương pháp chuẩn hóa k0 trong kỹ thuật phân tích kích hoạt neutron dụng cụ (k0-INAA). Kết quả của phép phân tích cho thấy hàm lượng Se đối với người bình thường là 1,13 μg/g và 1,32 μg/g tương ứng với nam giới và nữ giới; đối với bệnh nhân ung thư đại tràng là 0,70 μg/g và 0,84 μg/g tương ứng với nam giới và nữ giới; đối với bệnh nhân ung thư trực tràng là 0,86 μ g/g và 0,82 μ g/g tương ứng với nam giới và nữ giới. Bằng phép phân tích thống kê nghiên cứu này cho thấy rằng hàm lượng Se trong móng chân có sự khác biệt đáng kể giữa bệnh nhân và người bình thường (p <0,05), nhưng không có sự khác biệt đáng kể giữa nữ giới và nam giới. Kết luận của nghiên cứu này là móng chân của các bệnh nhân ung thư đại trực tràng có hàm hượng Se thấp hơn so với người bình thường.

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