RESUMO
Thermally conductive materials (TCMs) are highly desirable for thermal management applications to tackle the "overheating" concerns in the electronics industry. Despite recent progress, the development of high performance TCMs integrated with an in-plane thermal conductivity (TC) higher than 50.0 W (m K)-1 and a through-plane TC greater than 10.0 W (m K)-1 is still challenging. Herein, self-standing liquid metal@boron nitride (LM@BN) bulks with ultrahigh in-plane TC and through-plane TC were reported for the first time. In the LM@BN bulks, LM could serve as a bonding and thermal linker among the oriented BN platelets, thus remarkably accelerating heat transfer across the whole system. Benefiting from the formation of a unique structure, the LM@BN bulk achieved an ultrahigh in-plane TC of 82.2 W (m K)-1 and a through-plane TC of 20.6 W (m K)-1, which were among the highest values ever reported for TCMs. Furthermore, the LM@BN bulks exhibited superior compressive and leakage-free performances, with a high compressive strength (5.2 MPa) and without any LM leakage even after being crushed. It was also demonstrated that the excellent TCs of the LM@BN bulks made them effectively cool high-power light emitting diode modules. This work opens up one promising pathway for the development of high-performance TCMs for thermal management in the electronics industry.
RESUMO
OBJECTIVE: To observe the effect of combined intervention of electroacupuncture (EA) and astragaloside IV(ASIV) on cardiac hypertrophy and transforming growth factor β 1 (TGF-β 1)/Smad signaling in isoproterenol (ISO) induced cardiac hypertrophy rats, so as to investigate its underlying mechanisms in improving myocardial fibrosis. METHODS: A total of 50 SD rats were randomly divided into 5 groups: normal control, model (ISO), Propranolol (PRO)，ASIV and EA＋ASIV groups (n＝10 in each group). The myocardial fibrosis model was established by intraperitoneal injection (i.p.) of ISO (10 mg·kg－1·d－1), once daily for 30 days. Rats of the control group were given normal saline (i.p.), those of the PRO group given with PRO (40 mg·kg－1·d－1, gavage), and those of the ASIV and EA＋ASIV groups were treated by gavage of ASIV (40 mg·kg－1·d－1), once daily for 30 days. EA (20 Hz, 6 V) was applied to bilateral "Neiguan" (PC 6) for 10 min, once every day for 30 d. The heart mass index (HMI, whole heart weight/body weight) and left ventricular (LV) mass index (LVMI, weight of the LV/body weight) were calculated to assess the state of cardiac hypertrophy. The enzyme linked immunosorbent assay (ELISA) was used to determine the levels of procollagen I carboxy-terminal propeptide (PICP，a marker of extracellular matrix remodeling) and carboxyterminal telopeptide of type I collagen (ICTP, a metabolite of type I collagen) in serum, and Western blot was used to test protein contents of TGF- β 1, Smad 2 / 3, Smad 4, Smad 7 in the left ventricle tissue of the heart. RESULTS: After modeling, the HMI and LVMI, serum PICP and ICTP contents and the expression levels of myocardial TGF-β 1, Smad 2/3 and Smad 4 proteins were significantly increased in the model (ISO) group (P 0.05). CONCLUSIONS: EA stimulation of PC 6 combined with ASIV can relieve cardiac hypertrophy and myocardial fibrosis in rats, which may be associated with its effects in regulating myocardial TGF-β 1/Smad signaling pathway.
