Graphene nanosheet/silicone composite with enhanced thermal conductivity and its application in heat dissipation of high-power light-emitting diodes

Hai Yan Zhang,Yingxi Lin,Danfeng Zhang,Wenguang Wang,Yuxiong Xing,Jin Lin,Haoqun Hong,Chunhui Li 한국물리학회 2016 Current Applied Physics Vol.16 No.12

Heat dissipation from light-emitting diodes (LEDs) has become a serious problem because of the LEDs' high luminosity and power. This problem could be solved by improving the dissipation efficiency of each LED system component. A microwave-reduced graphene nanosheet/silicone (GN/silicone) composite with a high thermal conductivity and stability was prepared by mechanical blending. The thermal conductivity of the composite reaches 2.7 W/(m K) with only 1.5 wt% loading, and is 12 times higher than the pure silicone matrix. When used as a thermal interface material between high-power LED chip module substrates and heat sinks, the thermal conductive GN/silicone composite could decrease the temperature difference between the substrate and shell. It could also improve the system heat transfer efficiency. The temperature gap between the heat slug and the heat sink was less than 2 C with a 1.5 wt% loading of GNs.

Analysis of the Growth and Metabolites of a Pyruvate Dehydrogenase ComplexDeficient Klebsiella pneumoniae Mutant in a Glycerol-Based Medium

Danfeng Xu,Zongxiao Jia,Lijuan Zhang,Shuilin Fu,Heng Gong 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.5

To determine the role of pyruvate dehydrogenase complex (PDHC) in Klebsiella pneumoniae, the growth and metabolism of PDHC-deficient mutant in glycerol-based medium were analyzed and compared with those of other strains. Under aerobic conditions, the PDHC activity was fourfold higher than that of pyruvate formate lyase (PFL), and blocking of PDHC caused severe growth defect and pyruvate accumulation, indicating that the carbon flux through pyruvate to acetyl coenzyme A mainly depended on PDHC. Under anaerobic conditions, although the PDHC activity was only 50% of that of PFL, blocking of PDHC resulted in more growth defect than blocking of PFL. Subsequently, combined with the requirement of CO2 and intracellular redox status, it was presumed that the critical role of PDHC was to provide NADH for the anaerobic growth of K. pneumoniae. This presumption was confirmed in the PDHC-deficient mutant by further blocking one of the formate dehydrogenases, FdnGHI. Besides, based on our data, it can also be suggested that an improvement in the carbon flux in the PFL-deficient mutant could be an effective strategy to construct highyielding 1,3-propanediol-producing K. pneumoniae strain.

Optimal Design of Central Drainage Ditch Buried Depth for Highway Tunnel in Seasonally Frozen Region

Yuanfu Zhou,Mingyong Li,Danfeng Zhang,Xiaoqing Suo,Xuefu Zhang,Ke Dong 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.4

In seasonally frozen regions, the drainage ditch of highway tunnels is usually set below the maximum frost depth. Hence, the deeply buried drainage ditch is often used, which increases the cost, difficulty, and time of tunnel construction. And it affects the stability of the surrounding rock and the tunnel structure safety. To solve these difficulties, this study investigated the optimal design of buried depth of central drainage ditch by numerical simulation. Based on a tunnel in Northwest China, a transient heat transfer model, which involves heat conduction and phase transition, was established. Then, the influences of different water amounts and thermal insulation technologies on the minimum buried depth of central drainage ditch were investigated. The results indicate that the thermal insulation layer, regardless of whether it is an internal thermal insulation layer, external thermal insulation layer, or foam concrete backfilled in invert arch, can prevent the drainage ditch from freezing and increase its elevation. The findings of this study can be helpful in optimizing the buried depth, selecting reasonable thermal insulation technology for central drainage ditch in seasonally frozen regions.

Comparative Analysis of Outcomes and Clinicopathological Characteristics of Synchronous and Metachronous Contralateral Breast Cancer: A Study of the SEER Database

Ruiyue Qiu,Wen Zhao,Jiao Yang,Yanwei Shen,Biyuan Wang,Pan Li,Andi Zhao,Qi Tian,Mi Zhang,Min Yi,Jin Yang,Danfeng Dong 한국유방암학회 2019 Journal of breast cancer Vol.22 No.2

Purpose: Numerous previous studies have reported inconsistent results about the differences between synchronous contralateral breast cancer (sCBC) and metachronous contralateral breast cancer (mCBC). This study aimed to compare the clinical characteristics and outcomes between sCBC and mCBC and determine predictive factors for the survival of sCBC and mCBC patients. Methods: Using the Surveillance, Epidemiology, and End Results Program database, we identified sCBC or mCBC patients from 2000 to 2010. The Kaplan-Meier method and Cox proportional hazards regression analysis were used to analyze overall survival and breast cancer-specific survival (BCSS) rates of sCBCs and mCBCs, respectively. Results: Overall, 14,057 sCBC (n = 8,139, 57.9%) and mCBC (n = 5,918, 42.1%) patients were included. The first tumors of sCBC were more likely to have higher stage and more lymph and distant metastases, whereas those of mCBC were more often infiltrating ductal carcinoma (IDC), had localized stage, were estrogen receptor (ER) and progesterone receptor (PR) negative, and had less axillary nodal involvement. The second tumors of mCBC tended to be IDC and have higher grade, adverse stage, ER and PR-negativity; and more axillary nodal involvement, compared to the second tumors of sCBC. mCBC patients had significantly favorable 5-year BCSS but worse long-term BCSS compared with sCBC patients. Moreover, subgroup analysis revealed no significant difference of BCSS between sCBC and mCBC among patients aged 18–60 years. Multivariate analysis indicated that age, grade, and stage of 2 tumors; surgery for second tumor; and ER status of the second tumor were independent prognostic factors for BCSS of contralateral breast cancer (CBC). Conclusion: The characteristics and outcomes of sCBCs and mCBCs were substantially different. sCBC and mCBC patients may have different prognosis, and the prognosis of CBC depends on the first and second tumors.

Chitosan-chelated zinc modulates cecal microbiota and attenuates inflammatory response in weaned rats challenged with Escherichia coli

Dan Feng,Minyang Zhang,Shiyi Tian,Jing Wang,Weiyun Zhu 한국미생물학회 2020 The journal of microbiology Vol.58 No.9

Escherichia coli (E. coli) infection is very common among young growing animals, and zinc supplementation is often used to alleviate inflammation induced by this disease. Therefore, the objective of this study was to evaluate whether chitosan- chelated zinc (CS-Zn) supplementation could attenuate gut injury induced by E. coli challenge and to explore how CSZn modulates cecal microbiota and alleviates intestinal inflammation in weaned rats challenged with E. coli. 36 weaned rats (55.65 ± 2.18 g of BW, n = 12) were divided into three treatment groups consisting of unchallenged rats fed a basal diet (Control) and two groups of rats challenged with E. coli and fed a basal diet or a diet containing 640 mg/kg CS-Zn (E. coli + CS-Zn, containing 50 mg/kg Zn) for a 14-day experiment. On days 10 to 12, each rat was given 4 ml of E. coli solution with a total bacteria count of 1010 CFU by oral gavage daily or normal saline of equal dosage. CS-Zn supplementation mitigated intestinal morphology impairment (e.g. higher crypt depth and lower macroscopic damage index) induced by E. coli challenge (P < 0.05), and alleviated the increase of Myeloperoxidase (MPO) activity after E. coli challenge (P < 0.05). 16S rRNA sequencing analyses revealed that E. coli challenge significantly increased the abundance of Verrucomicrobia and E. coli (P < 0.05). However, CS-Zn supplementation increased the abundance of Lactobacillus and decreased the relative abundance of Proteobacteria, Desulfovibrio and E. coli (P < 0.05). The concentrations of butyrate in the cecal digesta, which decreased due to the challenge, were higher in the E. coli + CS-Zn group (P < 0.05). In addition, CS-Zn supplementation significantly prevented the elevation of pro-inflammatory cytokines IL-6 concentration and upregulated the level of anti-inflammatory cytokines IL-10 in cecal mucosa induced by E. coli infection (P < 0.05). In conclusion, these results indicate that CS-Zn produces beneficial effects in alleviating gut mucosal injury of E. coli challenged rats by enhancing the intestinal morphology and modulating cecal bacterial composition, as well as attenuating inflammatory response.