Carbon-coated CoFe-CoFe2O4 composite particles with high and dual-band electromagnetic wave absorbing properties.

SiO2 and TiO2, as conventional dielectric shells of ferromagnetic/dielectric composite particles, can protect ferromagnetic particles from aggregation and oxidation, but contribute little to electromagnetic loss. In this work, we designed nano-assembled CoFe-CoFe2O4@C composite particles, in which ferrites with high permeability were dielectric elements and carbon was introduced as protective layers, aiming for high-efficiency microwave absorption. These assembled particles with different CoFe contents were prepared through solvothermal methods and subsequent hydrogen-thermal reduction. CoFe nanoparticles were dispersed on a CoFe2O4 matrix via an in situ reduction transformation from CoFe2O4 to CoFe. The microstructure evolution of composite particles and corresponding electromagnetic properties tailoring were investigated. The content and size of CoFe as well as the porosity of composite particles increase gradually as the annealing temperature increases. A maximum reflection loss (RL max) of -71.73 dB is observed at 4.78 GHz in 3.4 mm thick coating using particles annealed at 500 °C as fillers. The coating presents double-band absorbing characteristics, as broad effective absorption bandwidth with RL > 5 (ERL 5) and high RL max are observed in both S-C and X-Ku bands. The tunability as well as the assembled characteristic of the electromagnetic property that endued from the composite structure contributes to the excellent electromagnetic wave absorbing performances.

Co7Fe3 and Co7Fe3@SiO2 Nanospheres with Tunable Diameters for High-Performance Electromagnetic Wave Absorption.

Ferromagnetic metal/alloy nanoparticles have attracted extensive interest for electromagnetic wave-absorbing applications. However, ferromagnetic nanoparticles are prone to oxidization and producing eddy currents, leading to the deterioration of electromagnetic properties. In this work, a simple and scalable liquid-phase reduction method was employed to synthesize uniform Co7Fe3 nanospheres with diameters ranging from 350 to 650 nm for high-performance microwave absorption application. Co7Fe3@SiO2 core-shell nanospheres with SiO2 shell thicknesses of 30 nm were then fabricated via a modified Stöber method. When tested as microwave absorbers, bare Co7Fe3 nanospheres with a diameter of 350 nm have a maximum reflection loss (RL) of 78.4 dB and an effective absorption with RL > 10 dB from 10 to 16.7 GHz at a small thickness of 1.59 mm. Co7Fe3@SiO2 nanospheres showed a significantly enhanced microwave absorption capability for an effective absorption bandwidth and a shift toward a lower frequency, which is ascribed to the protection of the SiO2 shell from direct contact among Co7Fe3 nanospheres, as well as improved crystallinity and decreased defects upon annealing. This work illustrates a simple and effective method to fabricate Co7Fe3 and Co7Fe3@SiO2 nanospheres as promising microwave absorbers, and the design concept can also be extended to other ferromagnetic alloy particles.

[Effect of electroacupuncture intervention on ERK 1/2 signaling and TNF-α and IL-1ß protein levels in the substantia Nigra in rats with Parkinson's Disease].

OBJECTIVE: To observe the effect of electroacupuncture(EA) on phosphalized extracellular regulated protein kinases(p-ERK) 1/2 signaling pathway and tumor necrosis factor (TNF)-α and IL-1ß protein levels in the substantia nigra (SN) in rats with Parkinson's disease (PD), so as to explore its mechanism underlying improvement of PD. METHODS: 32 male SD rats were randomly and averagely divided into normal control group, sham-operation group, model group and EA group. PD model was established by intra-dermal-injection of rotenone(1 mg/kg, dissolved in DMSO and saline, concentration: 0. 25 mg/mL) at the nape, once daily for 14 days. EA (2 Hz, 2 mA) was applied to "Fengfu"(GV 16)and "Taichong"(LR 3) for 20 min, once daily for 14 days. For sham-operation group, subcutaneous injection of the same dose of DMSO and saline was given in the same way. The expression levels of tyrosine hydroxylase (TH), p-ERK 1/2, inflammatory cytokines TNF-α and IL-1P proteins of the SN tissue were detected using Western blot. The rat's horizontal and vertical movement ability was assessed using open-field tests. RESULTS: The horizontal and vertical movement scores were significantly lower in the model group than in the normal control group, and markedly higher in the EA group than in the model group (P<0. 05). Compared with the normal control group, the expression level of TH protein in the SN was significantly reduced in the model group( P<0. 05 ),while the expression levels of p-ERK 1/2, TNF-α and IL-1ß proteins were significantly increased in the model group(P<0. 05). After EA intervention, the expression level of TH protein was significantly increased(P<0.05),and those of p-ERK 1/2, TNF-α and IL-1ß proteins were significantly down-regulated(P<0. 05) in the EA group compared to the model group. CONCLUSION: EA therapy may improve PD rats' movement ability, which may be associated with its effects in down-regulating the expression levels of p-ERK 1/2, TNF-α and IL-1ß proteins and up-regulating the expression of TH protein in the SN.

[Impacts of electroacupuncture on ubiquitin-proteasome system in rats with Parkinson's disease].

OBJECTIVE: To explore action mechanism of electroacupuncture (EA) on treatment and prevention of Parkinson's disease (PD). METHODS: Fifty clean-grade SD rats were randomly divided into a normal group, a control group, a model group, a pretreatment group and a treatment group, ten rats in each one. The PD model was established by subcutaneous injection of rotenone in neck-back skin (2 mg/kg, dissolved in sun-flower oil, 2 mg/mL in density). The equal-volume sun-flower oil that didn't include rotenone was applied in the control group at the same area as the model group. EA was applied in the treatment group at "Fengfu" (GV 16) and "Taichong" (LR 3) with interrupted wave, 2 Hz in frequency, 1 mA in density, for 20 min. The treatment was given once day for conti-nuous 28 days. Rats in the pretreatment group received the same EA as the treatment group for 7 days, and then put into model establishment. After the model establishment, the rats received no treatment and were sacrificed after 28 days. No EA was given in the normal group, model group and control group. The ethology changes were observed and scored. The expression of Parkin, ubiquitin C terminal hydrolase-L1 (UCH-L1) and ubiquitin activating enzyme-1 (UBE1) in substantia nigra was tested by Western-blot method. The positive cell numbers of alpha-synuclein, ubiquitin (UB) and tyrosine hydroxylase (TH) in substantia nigra was tested by immunohistochemical method. RESULTS: There were abnormal ethology manifestation such as yellow and coarse hair, arched back, weaken behavior of resisting arrest and slow movement, which was more relieved in the treatment group and pretreatment group. Compared with normal group and control group, the expression of Parkin, UCH-L1, UBE1, UB, TH in the model group was obviously decreased while alpha-synuclein was obviously increased (all P<0.01). After EA or pretreatment, the expression of Parkin, UCH-L1, UBE1, UB, TH in the treatment group and pretreatment group was higher than that in the model group while expression of alpha-synuclein in the treatment group and pretreatment group was lower than that in the model group (all P<0.01). CONCLUSION: EA or pretreatment could not only have protective effect for rats with PD, but also increase function of ubiquitin-proteasome system, indicating action mechanism of EA on treatment and prevention of PD may be related with ubiquitin-proteasome system.