Large Eddy Simulations of Rayleigh-Bénard Convection in a Cubic Cavity

This paper conducts a Large Eddy Simulation (LES) of Rayleigh Bénard convection in a cubic cavity based on the WMLES S-Omega subgrid-scale model. For a cubic cavity with a vertical temperature difference of 6.7°C and 20°C, the velocity pulsation profiles and the mean velocity profiles of the vertical section in the middle of the cubic cavity were simulated, respectively. And they are consistent with the experiment results. Furthermore, the mean velocity field of the vertical cross-section in the middle of the cavity was calculated. Structures of the mean velocity field in the two cases are similar. A counterclockwise large vortex is found to occupy the cavity, and there are two small clockwise vortices in the lower left and upper right corners, and the mean velocity fields at two different temperature differences are consistent with the experimental results. The two-dimensional instantaneous temperature field and mean temperature field with different cross-sections in the z-direction, as well as the three-dimensional instantaneous isothermal surface structure, indicate that the large-scale circulation motion within the cubic cavity is moving diagonally. In addition, the structure of the mean streamline also illustrates this viewpoint. For the reverse vortex formed at two corners in the mean streamline structure, we used the Q criterion to identify and obtain two vortex structures similar to boomerangs. The basic turbulent structure in RB thermal convection includes the rising and falling plumes generated by buoyancy effects.

134例老年急性髓系白血病的临床特点及预后分析

目的:分析老年急性髓系白血病(acute myeloid leukemia,AML)(非早幼粒细胞白血病)的临床特点,治疗方式以及疗效和预后特点。方法:收集2015年1月至2023年2月北京大学国际医院收治的134例老年AML患者资料,回顾性分析患者初诊时的白细胞计数、骨髓原始细胞计数、细胞遗传学及分子学特点、ELN危险分层,根据不同治疗方案将患者分为高强度化疗组和低剂量治疗组,观察在治疗过程中强化疗是否能给患者带来生存获益以及影响老年患者生存的因素。结果:高强度化疗患者36例,22例完全缓解(complete response,CR)(61.1%),低剂量治疗90例中46例获得CR(51.1%),其中19例阿扎胞苷(AZA)联合维奈克拉(VEN)治疗换着中14例获得CR(73.7%);高强度化疗与低剂量治疗的总生存期(overall survival,OS)分别为15个月和14.5个月(P=0.226)。欧洲白血病网(ELN)危险分层低、中、高危组患者OS分别为18、14、9个月(P=0.009),低危组高强度化疗和低剂量治疗的OS分别为22个月和15个月(P=0.745),中危组分别为9个月和15个月(P=0.783),高危组分别为9个月和8个月(P=0.739)。强化疗(36例)与阿扎胞苷+维奈克拉治疗(19例)相比OS分别为15个月和17个月(P=0.689)。TP53基因突变者6例,预后明显差于无突变者,中位生存期分别为2个月和14个月(P=0.004)。低、中、高危患者的1年生存率为79%、53%和44%,3年生存率分别为41%、20%和3%。多因素分析显示外周血高白细胞计数(P=0.034)、ELN危险分层(P=0.002)、合并症(P=0.017)与OS相关,而治疗强度、年龄、性别、骨髓原始细胞计数与OS无明显相关性。高强度化疗在老年AML中没有显示明显的生存获益,但这一结果在低危患者中有待于进一步观察。TP53突变者预后较差。多因素分析预测老年AML的生存期时,基线的分子学特征、白细胞计数、合并症比治疗强度更重要。

Analysis on nasal airway by using scale-adaptive simulation combined with standard κ-ω model and 3D printing modeling physical experiment

The physiological structure of the upper respiratory tract is complex and varies with each individual,and the circulating air has turbulent performance.In this paper,based on computed tomography(CT)medical images published online and the three-dimensional(3D)printing technology,a 3D model of the human upper respiratory tract was reconstructed and an experimental device of the upper respiratory tract was made.We implemented the respiratory experiment and measured the flow rate,and a scale-adaptive κ-ω model is applied for numerical simulation,the results are in good agreement.The flow field during respiratory was analyzed by coronal velocity cross section,vortex line and particle tracks.We found that the relatively strong shear effect happens at the areas of nasal valve and nasopharynx.In the middle and upper nasal tract,vortex line separation occurs and there is significant passage effect.The results indicate that SAS method is effective in studying upper respiratory airflow.

Remarkably different results between two studies from North America on genomic mutations and sensitivity to DNA demethylating agents for myelodysplastic syndromes

Sekeres et al. （1） conducted a multicenter randomized, controlled trial to compare whether azacitidine-based combinations with lenalidomide or vorinostat produce superior overall response rates to azacitidine in the treatment of myelodysplastic syndromes （MDS）. In that trial, 224 patients with higher-risk MDS and 53 with chronic myelomonocytic leukemia （CMML） were enrolled and randomly assigned to the ＂azacitidine＂ group, ＂azacitidine plus lenalidomide＂ group or ＂azacitidine plus vorinostat＂ group. The researchers found that patients with MDS treated with azacitidine-based combinations had similar response rate to azacitidine monotherapy. Using genomic mutation analysis, they found that the overall response rate to azacitidine-based treatment was higher for patients with mutations in DNMT3A and lower for those with mutations in SRSF2. Whereas in another study, Welch et al. enrolled 26 patients with MDS and 90 with acute myeloid leukemia （AML） who were treated with decitabine, and they found that patients with TP53 mutations had a higher response rate, but not those with DNMT3A mutations （2）. We propose that this big discrepancy in the conclusions between the two studies might have been caused by the presence of many co-interacting factors, e.g. study aims, DNA demethylating agents, treatment protocols, and patient sources.

An Experimental Set-Up for the in Vitro Simulation of a Physiological Pulsatile Flow in the Abdominal Aorta

In vitro experimental set-up is an important tool for investigating abdominal aortic aneurysm (AAA). Accurate reproduction of the physiological pulsatile flow waveform in the abdominal aorta at various anatomic locations is an important component of these experimental methods. The objective of this study is to establish an experimental set-up to generate a physiological pulsatile flow for in vitro simulations of the abdominal aorta. The physiological flow was established by a computer-controlled peristaltic pump and the flow field in a circular straight pipe is measured under pulsatile flow conditions by a 2-dimensional particle image velocimetry system (2D-PIV). Experimental results show that the in vitro experimental set-up provides a flow with a period of 2 s, a reasonable cross-sectional velocity distribution and an approximate inlet velocity profile that is close to the human abdominal aorta.

The current state of chemotherapy for the treatment of gastrointestinal stromal tumors with different genotypes:a narrative review

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm of the digestive system and are not sensitive to traditional chemotherapy. Therefore, historically, surgical resection was the only effective therapy. However, the emergence of tyrosine kinase inhibitors (TKIs) has revolutionized the treatment of GISTs, because they target c-Kit and PDGF receptor-α (PDGFRA), which are important in GIST development and progression. As research into c-Kit and PDGFRA continues, an increasing number of different TKIs are being used in the clinical setting. This review aims to discuss the current state of chemotherapy for the treatment of GISTs with different genotypes.

Risk factors for anastomotic leakage after gastrectomy for Siewert type Ⅱ/Ⅲ adenocarcinoma of the esophagogastric junction:a retrospective case-control study

Objective:To identify risk factors for anastomotic leakage after gastrectomy in patients with Siewert type II/III adenocarcinoma(AEG)of the esophagogastric junction.Methods:This was a retrospective case-control study of 903 patients with Siewert type II/III AEG treated from January 2012 to January 2015 at the Shanxi Cancer Hospital in China.All patients underwent gastrectomy,and their clinical characteristics were analyzed to identify associations with anastomotic leakage.Independent risk factors were identified by binary logistic regression.The 2-year disease-free survival was calculated and compared between patients with anastomotic leakage and control patients.The study was approved by the Institutional Review Board of Shanxi Medical University(approval No.2014-09-39)on September 19,2014.Results:Out of the 903 patients were included in the study,80(8.86%,80/903)experienced anastomotic leakage.The mortality rate attributed to anastomotic leakage was 8.75%(7/80).Logistic regression analysis revealed that preoperative hypoalbuminemia(odds ratio(OR)=3.249,95%confidence interval(CI):1.569-6.725,P=0.002),type of reconstruction(OR=1.795,95%CI:1.026-3.142,P=0.040),and combined organ resection(OR=1.807,95%CI:1.069-3.055,P=0.027)were independent risk factors for anastomotic leakage.Conclusion:Preoperative hypoalbuminemia,type of reconstruction,and combined organ resection were identified as risk factors for anastomotic leakage in patients undergoing gastrectomy for Siewert type Ⅱ/Ⅲ AEG.