Development of gas sensor based on fractal substrate structures

Gas sensor plays a key role in many applications with sensitivity being a critical performance characteristic. Increasing the surface area of gas sensing material is one approach that can increase sensitivity. Fractal geometries, which have the large specific surface area and special fractal dimension, have previously been successfully used in the design of macrostructure and microstructure of gas sensors to improve their performance. In this article, the influence of geometrical structure of the substrate on the gas sensor performance has been investigated. Two fractal structures (Koch snowflake and Menger sponge) and one traditional structure (Cylinder) were fabricated by 3-D printing and coated in Ag-doped multiwalled carbon nanotube (Ag:MWCNT)-based sensing materials. The fabricated sensors were tested with nitrogen dioxide at different temperatures and humidity. Experimental results show that the sensitivity of gas sensors with fractal structures is increased more than twice that of those with traditional geometrical structures

Pulsed electromagnetic fields improve bone microstructure and strength in ovariectomized rats through a Wnt/Lrp5/β-catenin signaling-associated mechanism.

Growing evidence has demonstrated that pulsed electromagnetic field (PEMF), as an alternative noninvasive method, could promote remarkable in vivo and in vitro osteogenesis. However, the exact mechanism of PEMF on osteopenia/osteoporosis is still poorly understood, which further limits the extensive clinical application of PEMF. In the present study, the efficiency of PEMF on osteoporotic bone microarchitecture and bone quality together with its associated signaling pathway mechanisms was systematically investigated in ovariectomized (OVX) rats. Thirty rats were equally assigned to the Control, OVX and OVX+PEMF groups. The OVX+PEMF group was subjected to daily 8-hour PEMF exposure with 15 Hz, 2.4 mT (peak value). After 10 weeks, the OVX+PEMF group exhibited significantly improved bone mass and bone architecture, evidenced by increased BMD, Tb.N, Tb.Th and BV/TV, and suppressed Tb.Sp and SMI levels in the MicroCT analysis. Three-point bending test suggests that PEMF attenuated the biomechanical strength deterioration of the OVX rat femora, evidenced by increased maximum load and elastic modulus. RT-PCR analysis demonstrated that PEMF exposure significantly promoted the overall gene expressions of Wnt1, LRP5 and β-catenin in the canonical Wnt signaling, but did not exhibit obvious impact on either RANKL or RANK gene expressions. Together, our present findings highlight that PEMF attenuated OVX-induced deterioration of bone microarchitecture and strength in rats by promoting the activation of Wnt/LRP5/β-catenin signaling rather than by inhibiting RANKL-RANK signaling. This study enriches our basic knowledge to the osteogenetic activity of PEMF, and may lead to more efficient and scientific clinical application of PEMF in inhibiting osteopenia/osteoporosis

Therapeutic effects of 15 Hz pulsed electromagnetic field on diabetic peripheral neuropathy in streptozotocin-treated rats.

Although numerous clinical studies have reported that pulsed electromagnetic fields (PEMF) have a neuroprotective role in patients with diabetic peripheral neuropathy (DPN), the application of PEMF for clinic is still controversial. The present study was designed to investigate whether PEMF has therapeutic potential in relieving peripheral neuropathic symptoms in streptozotocin (STZ)-induced diabetic rats. Adult male Sprague-Dawley rats were randomly divided into three weight-matched groups (eight in each group): the non-diabetic control group (Control), diabetes mellitus with 15 Hz PEMF exposure group (DM+PEMF) which were subjected to daily 8-h PEMF exposure for 7 weeks and diabetes mellitus with sham PEMF exposure group (DM). Signs and symptoms of DPN in STZ-treated rats were investigated by using behavioral assays. Meanwhile, ultrastructural examination and immunohistochemical study for vascular endothelial growth factor (VEGF) of sciatic nerve were also performed. During a 7-week experimental observation, we found that PEMF stimulation did not alter hyperglycemia and weight loss in STZ-treated rats with DPN. However, PEMF stimulation attenuated the development of the abnormalities observed in STZ-treated rats with DPN, which were demonstrated by increased hind paw withdrawal threshold to mechanical and thermal stimuli, slighter demyelination and axon enlargement and less VEGF immunostaining of sciatic nerve compared to those of the DM group. The current study demonstrates that treatment with PEMF might prevent the development of abnormalities observed in animal models for DPN. It is suggested that PEMF might have direct corrective effects on injured nerves and would be a potentially promising non-invasive therapeutic tool for the treatment of DPN

Effects of 10-week PEMF exposure on tibial Wnt1, LRP5, β-catenin, RANKL, RANK total mRNA expressions in OVX rats by RT-PCR analysis.

<p>(<b>A</b>) representative RT-PCR images for Wnt1, LRP5, β-catenin, RANKL, RANK and β-actin expressions, (<b>B</b>) Wnt1/β-actin ratio (<i>n</i> = 10), (<b>C</b>) LRP5/β-actin ratio (<i>n</i> = 10), (<b>D</b>) β-catenin/β-actin ratio (<i>n</i> = 10), (<b>E</b>) RANKL/β-actin ratio (<i>n</i> = 10) and (<b>F</b>) RANKL/β-actin ratio (<i>n</i> = 10) in rat tibiae of Control, OVX and OVX+PEMF groups. Control, sham-operated control group; OVX, ovariectomy group; OVX+PEMF, ovariectomy with PEMF exposure group; Values are all expressed as mean ± S.D. ^**Significant difference from the OVX group with <i>P</i><0.01.</p

Trends of blood glucose levels in Control, DM and DM+PEMF groups in weeks 0, 1, 3, 5 and 7 after PEMF stimulation.

<p>Data are presented as means ± SEM for 8 rats in each group. **P<0.01, statistically significant compared to the Control group (Bonferroni-adjusted pairwise comparison regarding the main group effect after two-way repeated measures ANOVA).</p

3-D MicroCT images of trabecular bone microarchitecture in the distal femora in Control, OVX and OVX+PEMF rats.

<p>A volume of interest (VOI) with 1.6 mm height was selected for the analysis of trabecular bone microarchitecture, which is represented with yellow color in <b>Fig. 4A</b>. The VOI started at a distance of 0.4 mm (25 slices) from the lowest end of the growth plate and extended to the proximal end of the femur with a distance of 1.6 mm (100 slices). Representative 3-D MicroCT images of femoral trabecular bone microarchitecture determined by the VOI were shown in <b>Fig. 4B∼D</b>. (<b>Fig. 4B</b>): Control group; (<b>Fig. 4C</b>): OVX+PEMF group; (<b>Fig. 4D</b>): OVX group. The femur in the OVX group exhibited significant decrease in the trabecular number, trabecular connectivity and trabecular area as compared with that in the Control group. PEMF exposure partially inhibited OVX-induced trabecular bone loss and significantly improved trabecular bone mass and bone microarchitecture.</p

Effects of 10-week PEMF exposure on femoral trabecular MicroCT indices in OVX rats, including (A) bone mineral density (BMD), (B) trabecular number (Tb.N), (C) trabecular thickness (Tb.Th), (D) trabecular separation (Tb.Sp), (E) bone volume per tissue volume (BV/TV) and (F) structure model index (SMI).

<p>Control, sham-operated control group; OVX, ovariectomy group; OVX+PEMF, ovariectomy with PEMF exposure group; Values are all expressed as mean ± S.D. (<i>n</i> = 10). ^bSignificant difference from the Control group with <i>P</i><0.01; ^adSignificant difference from the Control group with <i>P</i><0.05 and OVX group with <i>P</i><0.01.</p