Aperture shape optimization in intensity-modulated radiation therapy planning

The gradient element of the aperture gradient map is utilized directly to generate the aperture shape without modulation.This process can be likened to choosing the direction of negative gradient descent for the generic aperture shape optimiza-tion.The negative gradient descent direction is more suitable under local conditions and has a slow convergence rate.To overcome these limitations,this study introduced conjugate gradients into aperture shape optimization based on gradient modulation.First,the aperture gradient map of the current beam was obtained for the proposed aperture shape optimiza-tion method,and the gradients of the aperture gradient map were modulated using conjugate gradients to form a modulated gradient map.The aperture shape was generated based on the modulated gradient map.The proposed optimization method does not change the optimal solution of the original optimization problem,but changes the iterative search direction when generating the aperture shape.The performance of the proposed method was verified using cases of head and neck cancer,and prostate cancer.The optimization results indicate that the proposed optimization method better protects the organs at risk and rapidly reduces the objective function value by ensuring a similar dose distribution to the planning target volume.Compared to the contrasting methods,the normal tissue complication probability obtained by the proposed optimization method decreased by up to 4.61%,and the optimization time of the proposed method decreased by 5.26%on average for ten cancer cases.The effectiveness and acceleration of the proposed method were verified through comparative experiments.According to the comparative experiments,the results indicate that the proposed optimization method is more suitable for clinical applications.It is feasible for the aperture shape optimization involving the proposed method.

Correlation of RUNX3 expression with microvessel density in colorectal adenocarcinoma tissues and clinical significance

Objective: To study the expression of RUNX3 in colorectal adenocarcinoma tissues and its correlation with microvessel density(MVD),and investigate the clinical pathological prognostic significance of RUNX3 and MVD in patients with colorectal cancer,Methods: The expression value of RUNX3 and MVD in 70 specimens' colorectal adenocarcinoma tissues were detected by immunohistochemistry staining technique,The correlation between their expression and the clinicopathologic features was also investigated,Results: The expression value of RUNX3 and the positive rates of RUNX3 in colorectal adenocarcinoma tissues were 3.25±1.14 and 25.71%(18/70),The expression value of MVD in colorectal adenocarcinoma tissues was 13.14±3.23,Expression of RUNX3 and MVD value were correlated with CEA,serosal invasion,liver metastasis,lymph node metastasis,and TNM stage(P<0.01),The expression value of RUNX3 had negative correlations with that of MVD,Conclusions: The high expression of RUNX3 could inhibit tumor microvascular generation in order to have negative control response on invasion and distant metastasis.

SMILE术中眼球移位对角膜切削精准度和屈光状态的影响

目的:评估飞秒激光小切口角膜基质透镜取出术(SMILE)激光扫描时眼球轻微移位对角膜切削精准度及术后屈光状态的影响。方法:纳入2019-01/2021-03于本院行SMILE手术的患者32例62眼,依据术中眼球有无轻微移位分为移位组和固视组,并选取单眼眼球轻微移位的患者进行双眼配对,比较移位组和固视组组间和单眼眼球轻微移位患者双眼间术后1mo实际与术前预估角膜切削厚度偏差绝对值(ACE)、散光偏差(AE)、屈光偏差绝对值(ARE)及视力偏差绝对值(AVE)的差异,并将手术图像量化,分析眼球移位幅度与AE的相关性,观察眼球轻微移位所处区域、层面及移位方向对ACE的影响。结果:移位组和固视组各观察指标均无差异(P>0.05)。术中单眼眼球轻微移位的患者双眼AE具有差异(0.57±0.31D vs 0.33±0.27D,P<0.05),且眼球移位幅度与术后1mo AE具有正相关性(r=0.564,P<0.05)。眼球轻微移位所处不同区域(中心区/周边区)、层面(透镜上层/透镜下层)及方向(鼻侧/颞侧)的患者术后1mo ACE比较均无差异(均P>0.05)。结论:SMILE手术中激光扫描时眼球轻微移位对角膜切削精准度无明显影响,主要引起偏中心切削,导致角膜散光改变,但对等效球镜度及视力影响甚微。

Correlation of caveolin-1 expression with microlymphatic vessel density in colorectal adenocarcinoma tissues and its correlation with prognosis

Objective: To study the expression of caveolin-1 in colorectal adenocarcinoma tissues and its correlation with microlymphatic vessel density(LMVD), and to investigate the clinical pathological prognostic significance of caveolin-1 and LMVD in patients with colorectal cancer. Methods: The expression of caveolin-1 and LMVD in 45 specimens of normal colorectal tissues, and 90 specimens of colorectal adenocarcinoma tissues were detected by immunohistochemistry technique. The correlation between their expression and the clinicopathologic features was analyzed. Muhivariable Cox regression was used to analyze the association between the laboratory indices and overall survival time. Results: The positive rates of caveolin-1 in colorectal adenocarcinoma tissues were significantly higher than those in normal colorectal tissues(P<0.01). LMVD in colorectal adenocarcinoma tissues were significantly higher than those in normal colorectal tissues(P<0.01). Mean LMVD in group with caveolin-1 positive was significantly higher than in that with caveolin-1 negative. The median survival time was 26.7 months. Cox regression analysis showed that the caveolin-1 expression, invation depth, lymph nodemetastasis, TNM stage, liver metastasis and LMVD were independent risk factors of overall survival time of patients with colorectal carcinoma. Conclusions: Caveolin-1 may contribute to the lymphangiogenesis in the tumor. During the occurrence and development of colorectal adenocarcinoma, there is a close relationship between the expression of caveolin-1 and lymphatic microvessel of tumor. Caveolin-1 expression and microlymphatic vessel density are significant prognostic value of colorectal carcinoma.

B4C/NRL flexible films for thermal neutron shielding

Boron carbide/natural rubber latex(B_4 C/NRL)flexible films were prepared via dip-molding with B_4 C content in the range of 5–55 wt% for thermal neutron(0.0253 e V) shielding. B_4 C was well dispersed in NRL according to microscopic observation. Both the inside and outside surfaces of the film were smooth. For B_4 C/NRL flexible films, the minimum elongation at break was greater than 600%, the minimum tensile strength was greater than 12 MPa, and the hardness was in the range of 35–55 HA,which were suitable for preparing flexible wearable products. The attenuation efficiencies of the B_4 C/NRL flexible films for thermal neutrons were also calculated. The B_4 C/NRL flexible films exhibit good attenuation effect for thermal neutrons.

Preparation and characterization of Bi2O3/XNBR flexible films for attenuating gamma rays

A bismuth oxide(Bi_2O_3)-dispersed carboxylated nitrile butadiene rubber(XNBR) flexible film was prepared as a flexible lead-free material for gamma ray(c-ray)attenuation.However,obtaining a uniform and stable dispersion of Bi_2O_3 in carboxylated nitrile butadiene rubber latex(XNBRL) is a challenge due to sedimentation induced by the remarkable density differences.Here,this challenge was approached by reducing the Bi_2O-3 particle radius,increasing the viscosity of the latex,and adding a dispersant.The experimental results confirmed that Bi2 O3 was well dispersed in the XNBRL in the concentration range of 30–70 wt%.The mechanical properties demonstrated that the Bi_2O_3/XNBR flexible films had a good resistance to oil,acid,alkali,and hot air.The linear attenuation coefficients of the Bi_2O_3/XNBR flexible films obtained from the experiments were in good agreement with the calculated values.The attenuation efficiencies of the Bi_2O_3/XNBR flexible films with different thicknesses and Bi_2O_3 contents were investigated for a few different γ-ray energies.These results showed that the Bi_2O_3/XNBRflexible films have wide application prospects for low-energy γ-ray attenuation.

Influence of Inclusion on Corrosion Behavior of E36 Grade Low-alloy Steel in Cargo Oil Tank Bottom Plate Environment

Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank(COT)bottom plate service environment(10% NaCl solution,pH=0.85).The corrosion behavior of inclusion was studied by in-situ scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).It was found that pitting corrosion was inclined to occur around the place where inclusions exist.After initial corrosion,an area of 10-20μm in diameter was formed as a circinate cathode around the edge of inclusion.MnS inclusion dissolved in the simulated COT corrosion solution before low-alloy steel matrix,and pitting was formed at the place where MnS dissolved.TiO2 inclusion dissolved in the simulated COT corrosion solution after low-alloy steel matrix,and pitting was formed at the place where steel matrix dissolved.The corrosion tended to occur at the area where the curvature radius of inclusion is smaller.The size of round TiO2 inclusions had little influence on corrosion behavior in this certain environment.

Influences of Alloying Elements on Oxidation Behavior of Steels and Microstructure of Oxide Scales

In order to figure out the oxidation behavior of steels during heating,five micro-alloyed steels were subjected to continuous and isothermal oxidation using the thermo gravimetric analyzer and the Gleeble-3500thermo-mechanical simulator.The microstructure of oxide scales,especially the thickness fractions of Fe2O3,Fe3O4 and FeO layers,was analyzed using the scanning electron microscope(SEM),electron probe microanalyzer(EPMA)and electron backscattered diffraction(EBSD)techniques.The micro-alloyed steels containing alloying elements(Si,Cr,Ni and Cu)show a higher oxidation resistance compared with the low carbon steel.It is found that alloying elements accumulated at scale/substrate interface during high temperature oxidation.Alloying elements function in two ways in the oxidation of steels:one is enhancing the scale/substrate interface and consequently suppressing the blister of scales;and the other is impeding the outward diffusion of iron cations from substrate to scales,resulting in the decrease of oxidation rate.As the diffusion of iron cations is impeded,the thickness fractions of Fe2O3 and Fe3O4of micro-alloyed steels are more than those of low carbon steels.

Tracking and Guiding Multiple Laser Beams for Beam and Target Alignment

An accurate and robust approach for tracking and guiding multiple laser beams is developed, which can be applied to the task of beam and target alignment. Multiple laser spots are firstly detected and recognized from the image sequences of the target and laser spots. Then, the contour tracking algorithm based on the chain code is investigated, in which the shape matching scheme based on the invariant moments is employed to distinguish different spots. When occlusion occurs in the multiple spots tracking procedure,the contour tracking combined with Kalman filter prediction is proposed to obtain the positions of multiple spots in real-time. In order to guide 3 spots to align the target, an incremental proportional integral(PI) controller is employed to make the image features of spots converge to the desired ones. Comparative experiments show that, the proposed tracking method can successfully cope with the fast motion, partial or complete occlusion. The experiment results on spots guiding also exhibit the accurate and robust performance of the strategy. The proposed visual system solves the problem of spots mixing, reduces the alignment time, improves the shooting accuracy and has been successfully applied to the experimental platform.

Tensile deformation behavior of nickel-free high-manganese austenitic cryogenic-temperature steel

Nickel-free high-manganese austenitic Fe–24.4Mn–4.04Al–0.057C steel was produced by smelting,and the homogenized forged billet was hot-rolled.The plastic deformation mechanism was investigated through tensile testing of the hot-rolled sample.Different characterization techniques such as scanning electron microscopy,transmission electron microscopy,electron backscattered diffraction,and X-ray diffraction were used to analyze the microstructural evolution of steel under different strain levels.The steel had a single austenite phase,which was stable during deformation.After hot rolling,annealing twins were observed in the microstructure of the steel.The steel showed an excellent combination of mechanical properties,like a tensile strength of 527 MPa,impact energy of 203 J at−196℃,and an elongation of 67%till fracture.At the initial deformation stage,the dislocations were generated within the austenite grains,entangled and accumulated at the grain boundaries and annealing twin boundaries.Annealing twins participated in plastic deformation and hindered the dislocation movement.As the deformation progressed,the dislocation slip was hindered and produced stress concentration,and the stacking faults evolved into mechanical twins,which released the stress concentration and delayed the necking.