BẢN TIN KHOA HỌC

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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Optimization of uranium separation using silica gel impregnated tri‐n‐butyl phosphate for alpha spectrometry analysis of soil samples

Van Thang Nguyen, Xuan Son Vi, Nguyen Phong Thu Huynh, Cong Hao Le

Abstract:

Silica gel impregnated tri-n-butyl phosphate was used as a chromatography column for extraction of uranium radioisotopes from soil samples. Diluted HNO3 and H2SO4 were used as the mobile and striping phases, respectively. In these stages, concentrations of HNO3 and H2SO4 solutions for the uranium extraction yield were optimized. We found that 5 M HNO3 and 3 M H2SO4 were the best solutions for uranium separation. Effects of electrodeposition conditions on uranium deposition yield were considered. Results showed that current of 1.5 mA, deposition time of 75 min, pH 2 and electrode gap of 1.5 cm were optimal conditions for electrodeposition.

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Optimization of the Entropy-Based Wavelet Method for Removing Strong RF and AC Interferences in a Charge Detection Linear Ion Trap Mass Spectrometer

Minh Cong Dang, Avinash A. Patil, Thị Khánh Ly Lại, Szu-Wei Chou, Trang Kieu Thi Hoang, Mhar Ian Cua Estayan, and Wen-Ping Peng

Analytical Chemistry 2025 97 (9), 5066-5076

Abstract:

We developed an entropy-based wavelet method to effectively remove interference from strong radio frequency (RF) and auxiliary alternating current (AC) fields in a linear ion trap (LIT) mass spectrometer coupled to a charge sensing particle detector (CSPD). By optimizing the energy-to-Shannon entropy, we identified the optimal mother wavelet family and decomposition level and determined suitable threshold values based on the median of sub-band coefficients at each decomposition level. These thresholds were applied as rigid criteria across all decomposition levels to eliminate noise interferences and avoid the arbitrary choice of the threshold. This entropy wavelet-based method successfully denoised high-mass protein mass spectra, achieving significant improvements in signal-to-noise ratio (S/N) for immunoglobulin G (IgG) and alpha-2 macroglobulin (A2M) ions, with increases of 68.03% and 81.73%, respectively. Our method surpasses previously reported baseline correction techniques, such as orthogonal wavelet packet decomposition (OWPD) filtering, and enhances the
sensitivity of LIT mass spectrometry (LIT-MS) in analyzing high-mass protein ions.

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Le Thi Ngoc Trang, Huynh Dinh Chuong, Tran Thien Thanh

Journal of Radioanalytical and Nuclear Chemistry (2020)

Abstract:

In this study, the optimization of the p-type HPGe detector model has been performed to improve the accuracy of Monte Carlo simulation in calculating full energy peak efficiency. The optimized detector model was validated by comparison of simulated efficiencies with experimental efficiencies for measurement configurations of point-like sources at various distances from the detector surface and cylindrical sources on the detector surface. The obtained results showed an excellent agreement between the simulated and experimental efficiencies with relative deviations of less than 4% in the energy range from 53 to 1847 keV.

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Onset of collectivity for argon isotopes close to $N = 32$

B. D. Linh et al.

Phys. Rev. C 109, 034312

Abstract:

The shell closure at $N = 32$ has been investigated by a first spectroscopy of the $N = 31$ nucleus $49 Ar$ at the Radioactive Isotope Beam Factory. Using the $50 Ar (p, p n)$ reaction channel in inverse kinematics, $50 Ar$ projectiles at 217 MeV/nucleon impinged on a 150 mm long liquid hydrogen target, part of the MINOS device. Prompt deexcitation $γ$ rays were measured with the NaI(Tl) array ${DALI 2}^{+}$ . Reaction products were analyzed with the SAMURAI spectrometer, which allowed the measurement of the momentum distributions and angular momentum transfer. Data were compared to state-of-the-art theoretical predictions, including shell-model, energy-density functional, and ab initio calculations. An onset of collectivity is suggested besides the spherical configuration typical of a closed shell nucleus, such as for $52 Ca$ .

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