牛乳中体细胞数与乳成分和部分理化性质的相关性研究

对呼和浩特郊区一牧场30头荷斯坦乳牛进行6个月单个采样,共得452个有效样本,检测乳样包括:体细胞数、脂肪、蛋白质、乳糖、总固形物、细菌总数、比重、黏度、电导率、氯糖数、滴定酸度和pH值。结果表明,蛋白质质量分数与牛乳中的体细胞数(Somatic CellCount,SCC)SCC呈显著正相关(P<0.05);乳糖含量与SCC呈显著负相关(P<0.001);脂肪、总固形物质量分数、电导率、氯糖数与SCC呈极显著正相关(P<0.001)。细菌总数、比重、黏度、滴定酸度、pH值与SCC的相关性不显著。从5～10月,乳中体细胞数有逐渐降低趋势,9月骤然升高,其中5月和9月样品平均体细胞数较高,分别为78×104 mL-1和96×104 mL-1。10月份样品平均体细胞数最低为28×104 mL-1。     

模拟海水环境中X60管线钢的应力腐蚀裂纹扩展

在模拟海水环境中对X60管线钢的应力腐蚀开裂速率进行了测试,结果表明,在31.3g/L的NaCl水溶液中X60管线钢的应力腐蚀临界应力强度因子KISCC为76.470 8MPam(1/2),裂纹扩展速率da/dt为6.4×10-7 mm/s。     

基于KBRF算法的镍基690合金应力腐蚀裂纹扩展速率预测模型

镍基690合金广泛用于压水堆核电站核岛主设备关键部件及焊缝,高温高压水环境应力腐蚀开裂(SCC)是其潜在的失效机理。由于SCC行为影响因素多达二十余种,因此存在参数化模型预测精度不高的问题。本文通过融合随机森林机器学习算法(Random Forest, RF)与基于领域知识的MRP-386参数化模型,建立了镍基690合金SCC裂纹扩展速率KBRF(Knowledge-Based Random Forest)预测模型,结果表明,领域知识的引入增强了KBRF模型的鲁棒性,准确性较MRP-386参数化模型和RF等机器学习模型显著提高,预测结果与实验值较为接近,将应用于我国压水堆核电站镍基690合金部件及焊缝在反应堆冷却剂中的应力腐蚀裂纹扩展工程预测。     

磨削参数对硫化氢应力腐蚀试样表面质量的影响分析与优化

首先从理论上分析了影响硫化氢应力腐蚀试样表面质量的各种磨削参数,然后针对这些磨削参数设计出正交试验,进行研究和分析各参数的影响。试验结果表明,磨削过程中,磨削深度对试样表面残余应力影响最大,砂轮颗粒度对试样的表面粗糙度影响最大。试验结果证明,在砂轮线速度vs=30m/s的情况下,使用砂轮颗粒度为180#的砂轮,在工件转速vw=460r/min、轴向进给速度f=0.25mm/s、磨削深度ap=0.010mm的磨削条件下进行切削时表面质量最为优化。     

PZT-5铁电陶瓷恒载荷压痕裂纹在空气和水中的扩展过程

用Vickers硬度计作为加载装置,研究了极化锆钛酸铅(PZT-5)铁电陶瓷压痕裂纹恒载荷下在室温空气和水中的扩展规律.结果表明,恒载荷下,压痕裂纹在空气和水中不断扩展, 120 h后趋于稳定,从而就可获得裂纹扩展速率和裂纹止裂的门槛应力强度因子KISCC,它们均显示各向异性.研究表明,裂纹扩展速率和KISCC的各向异性与铁电陶瓷断裂韧性的各向异性有关,即裂纹扩展速率随KIC的增加而降低,而KISCC随KIC的增加而升高.平行极化方向裂纹的断裂韧性比垂直极化方向高,即KCICSCCc SCCa,dc/dt>dn/dt;与在空气中相比,在水中应力腐蚀更敏感,即裂纹扩展速率更高、门槛值更低.     

甲酸钠尾气吸收塔失效分析

采用扫描电镜观察、力学性能检测、化学成分分析和残余应力测定等方法系统分析了甲酸钠尾气吸收塔发生泄漏的原因。结果表明：泄漏部位的腐蚀产物含有钠、氯等元素,同时泄漏部位存在残余应力偏高问题,在不断遭受腐蚀和工作应力的共同作用下产生应力腐蚀开裂,最终导致设备的失效。     

Capabilities of TRANSURANUS code in simulating power ramp tests from the IFPE database

Investigations of fuel behavior are carried out in close connection with experimental research, operation feedback and computational analyses. OECD NEA sets up the “International Fuel Performance Experiments (IFPE) database”, a public domain database on nuclear fuel performance experiments with the purpose of model development and code validation. The objective of the activity (performed in the framework of the IAEA CRP FUMEX-III project) is to investigate the pellet-clad interaction mechanism and the capability of TRANSURANUS code in simulating the phenomena, processes occurring in the fuel rod during the power ramps, with focus on the parameters influencing the cladding failures. The experimental database adopted is the Studsvik PWR Super-Ramp subprogram, part of the IFPE database, which consists of 28 pressurized water reactor fuel rods power ramped at burnup from 28 to 45 MWd/kgU. Relevant results by TRANSURANUS are presented in connection with the experimental evidences. Focus is given on the PCI/SCC failure, demonstrating that the failure threshold, available in TRANSURANUS, results conservative both in case of KWU and W rods.     

Characterization and Differentiation of the Tumor Microenvironment (TME) of Orthotopic and Subcutaneously Grown Head and Neck Squamous Cell Carcinoma (HNSCC) in Immunocompetent Mice

For the development and evaluation of new head and neck squamous cell carcinoma (HNSCC) therapeutics, suitable, well-characterized animal models are needed. Thus, by analyzing orthotopic versus subcutaneous models of HNSCC in immunocompetent mice, we evaluated the existence of adenosine-related immunosuppressive B- and T lymphocyte populations within the tumor microenvironment (TME). Applying the SCC VII model for the induction of HNSCC in immunocompetent C3H/HeN mice, the cellular TME was characterized after tumor initiation over time by flow cytometry. The TME in orthotopic grown tumors revealed a larger population of tumor-infiltrating lymphocytes (TIL) with more B cells and CD4⁺ T cells than the subcutaneously grown tumors. Immune cell populations in the blood and bone marrow showed a rather distinct reaction toward tumor induction and tumor location compared to the spleen, lymph nodes, or thymus. In addition, large numbers of immunosuppressive B- and T cells were identified within the TME but also in secondary lymphoid organs, independently of the tumor initiation site. The altered immunogenic TME may influence the response to any treatment attempt. Moreover, when analyzing the TME and other lymphoid organs of tumor-bearing mice, we observed conditions reflecting largely those of patients suffering from HNSCC suggesting the C3H/HeN mouse model as a suitable tool for studies aiming to target immunosuppression to improve anti-cancer therapies.     

High ROS Production by Celecoxib and Enhanced Sensitivity for Death Ligand-Induced Apoptosis in Cutaneous SCC Cell Lines

Incidence of cutaneous squamous cell carcinoma (cSCC) and actinic keratosis has increased worldwide, and non-steroidal anti-inflammatory drugs as celecoxib are considered for treatment. We show here strong anti-proliferative effects of celecoxib in four cSCC cell lines, while apoptosis and cell viability largely remained unaffected. Impeded apoptosis was overcome in combinations with agonistic CD95 antibody or TNF-related apoptosis-inducing ligand (TRAIL), resulting in up to 60% apoptosis and almost complete loss of cell viability. Proapoptotic caspase cascades were activated, and apoptosis was suppressed by caspase inhibition. TRAIL receptor (DR5) and proapoptotic Bcl-2 proteins (Puma and Bad) were upregulated, while anti-apoptotic factors (survivin, XIAP, cFLIP, Mcl-1, and Bcl-w) were downregulated. Strongly elevated levels of reactive oxygen species (ROS) turned out as particularly characteristic for celecoxib, appearing already after 2 h. ROS production alone was not sufficient for apoptosis induction but may play a critical role in sensitizing cancer cells for apoptosis and therapy. Thus, the full therapeutic potential of celecoxib may be better used in combinations with death ligands. Furthermore, the immune response against cSCC/AK may be improved by celecoxib, and combinations with checkpoint inhibitors, recently approved for the treatment of cSCC, may be considered.     

Stress corrosion cracking of copper in swollen bentonite simulating nuclear waste disposal environment

Stress corrosion cracking (SCC) of pure copper in bentonite clay was examined using a slow strain rate test (SSRT). Bentonite was swollen with pure water or aqueous solutions containing NH₃ of 5 and 10 mM. Thick corrosion films and particulate deposits were formed on the copper surface after the SSRT. Typical tarnish rupture-type SCC occurred on pure copper in swollen bentonite with and without NH₃. The crack propagation rate was enhanced by NH₃. It is confirmed that a thick oxide layer was formed on copper during plastic deformation, resulting in tarnish crack-type SCC. Many particulate deposits observed on the surface were formed due to the rapid dissolution of Cu²⁺ ions to form porous CuO at local deformed sites, regardless of the SCC occurrence.