Numerical Study of Double-Layered Microchannel Heat Sinks with Different Cross-Sectional Shapes.

This work numerically studies the thermal and hydraulic performance of double-layered microchannel heat sinks (DL-MCHS) for their application in the cooling of high heat flux microelectronic devices. The superiority of double-layered microchannel heat sinks was assessed by a comparison with a single-layered microchannel heat sink (SL-MCHS) with the same triangular microchannels. Five DL-MCHSs with different cross-sectional shapes-triangular, rectangular, trapezoidal, circular and reentrant Ω-shaped-were explored and compared. The results showed that DL-MCHS decreased wall temperatures and thermal resistance considerably, induced much more uniform wall temperature distribution, and reduced the pressure drop and pumping power in comparison with SL-MCHS. The DL-MCHS with trapezoidal microchannels performed the worst with regard to thermal resistance, pressure drop, and pumping power. The DL-MCHS with rectangular microchannels produced the best overall thermal performance and seemed to be the optimum when thermal performance was the prime concern. Nevertheless, the DL-MCHS with reentrant Ω-shaped microchannels should be selected when pumping power consumption was the most important consideration.

Aspiration catheter tip flutter is a reliable indicator of successful clot aspiration in ADAPT.

BACKGROUND: A direct aspiration first pass technique (ADAPT) has emerged as a fast, safe, and efficacious method for treating acute large vessel occlusion. However, successful clot aspiration is not guaranteed in every ADAPT procedure. We have observed that when the catheter effectively ingested the clot, the catheter tip displayed a distinct fluttering motion, referred to herein as tip flutter. Thus this study aimed to assess whether this catheter tip flutter can be used as a sign of successful clot aspiration. METHODS: This retrospective study included 231 consecutive patients admitted to our institution due to acute ischemic stroke and treated with ADAPT between October 2018 and November 2023. We obtained baseline and procedural data from all patients. Additionally, we assessed the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of the tip flutter in predicting clot aspiration. RESULTS: The incidence of embolus translocation was significantly higher in the tip flutter positive group than in the tip flutter negative group (P<0.001). Also, hyperdense artery presentation was more prevalent in the positive group (P<0.001), whereas the clot burden score was higher in the negative group (P=0.002). Clot aspiration in the first pass occurred in 83 (96.5%) and 37 (25.5%) patients in the positive and negative groups, respectively (P<0.001). Multivariable logistic regression analysis showed the tip flutter sign (OR 1.09, 95% CI 0.16 to 1.29; P<0.001) was an independent predictor of successful clot aspiration. Sensitivity, specificity, PPV, NPV, and accuracy of the tip flutter for predicting clot aspiration were 69.2%, 97.3%, 96.5 %, 74.5%, and 82.7%, respectively. CONCLUSIONS: In this study, we found that tip flutter was a reliable indicator of successful clot aspiration during ADAPT.

Age and duration of hypertension are associated with carotid artery tortuosity.

Objective: Tortuosity of the carotid artery is a common angiographic finding that may impact blood flow and neuronal function. However, information on its prevalence and risk factors remains limited. In this study, we determined to explore the factors affecting carotid artery tortuosity. Methods: The head and neck computed tomography angiography (CTA) imaging and cerebral angiography data performed at the Second Affiliated Hospital of Wenzhou Medical University between January 2019 and September 2021 were collected, and a total of 356 cases were enrolled in the study after screening. Carotid artery tortuosity refers to the angle between the two adjacent segments of the carotid artery, from the opening of the aortic arch on either side to the external orifice of the carotid canal, being less than 150°. A retrospective analysis was performed to compare the general information, laboratory indicators, personal history, and medical history between the two groups. The χ2 test, t-test, and Mann-Whitney U-test were performed to compare the parameters between the two groups. If there were significant differences between the groups, multivariate logistic regression was performed to analyze the factors affecting carotid artery tortuosity. Results: A total of 222 of the 356 cases were determined to have carotid artery tortuosity, accounting for 63.6%. There were statistically significant differences in age, body mass index (BMI), duration of diabetes and hypertension, levels of low-density lipoprotein cholesterol (LDL-C), diastolic blood pressure, history of ischemic and hemorrhagic stroke, and the usage of antihypertensive drugs between the two groups. Multivariate logistic regression analysis of the above factors showed that age (OR = 5.063, 95% CI 2.963-10.26, p < 0.001) and duration of hypertension (OR = 2.356, 95% CI 1.353-8.625, p = 0.021) were associated with a higher incidence of carotid artery tortuosity. Compared to patients who did not consume antihypertensive drugs, the incidence of carotid artery tortuosity was significantly less (OR = 0.094, 95% CI 0.002-0.713, p = 0.019) in those consuming antihypertensive drugs. Conclusion: Carotid artery tortuosity is a relatively common carotid artery disease. The incidence of carotid artery tortuosity may increase with age and the duration of hypertension. The consumption of antihypertensive drugs may reduce the incidence of carotid artery tortuosity.

MMI-166, a selective matrix metalloproteinase inhibitor, promotes apoptosis in human pancreatic cancer.

MMI-166 is a third-generation selective matrix metalloproteinase (MMP) inhibitor that prevents tumor invasion and metastasis by downregulating the activity of MMP-2 and MMP-9. However, MMI-166's effect in pancreatic cancer cells has not been widely studied. Initially, we treated SW1990, human pancreatic cancer cells, with 0, 50 or 100 µg/ml of MMI-166 for 24 h. Apoptosis in the cells was then observed by inverted fluorescence microscope and flow cytometry; the apoptosis rate was dependent on MMI-166 concentration. We then injected nude mice with SW1990 cells. Volume of the resulting xenograft tumors in nude mice treated with MMI-166 was far less than that of the control group, whereas their apoptotic index was much greater. Expression of MMP-2, MMP-9, c-myc and survivin were markedly lower in tumors from the treated mice than in the control group. In cell experiments, MMP-2 and MMP-9 activities were downregulated by MMI-166 compared with controls, as were both mRNA and protein levels of MMP-2, MMP-9 and c-myc, although survivin expression did not differ. These results show that MMI-166 can induce apoptosis of pancreatic cancer cells in vitro and in vivo. The mechanism may be related to downregulation of c-myc by MMI-166.