Large electrocaloric effect over a wide temperature span in lead-free bismuth sodium titanate-based relaxor ferroelectrics

For efficient solid-state refrigeration technologies based on electrocaloric effect (ECE), it is a great challenge of simultaneously obtaining a large adiabatic temperature change (ΔT) within a wide temperature span (Tspan) in lead-free ferroelectric ceramics. Here, we studied the electrocaloric effect (ECE) in (1-x)(Na0.5Bi0.5)TiO3-xCaTiO3 ((1-x)NBT-xCT) and explored the combining effect of morphotropic phase boundary (MPB) and relaxor feature. The addition of CT not only constructs a MPB region with the coexistence of rhombohedral and orthorhombic phases, but also enhances the relaxor feature. The ECE peak appears around the freezing temperature (Tf), and shifts toward to lower temperature with the increasing CT amount. The directly measured ECE result shows that the ceramic of x = 0.10, which is in the MPB region, has an optimal ECE property of ΔTmax = 1.28 K @ 60 °C under 60 kV/cm with a wide Tspan of 65 °C. The enhanced ECE originates from the electric-field-induced transition between more types of polar nanoregions and long-range ferroelectric macrodomains. For the composition with more relaxor feature in the MPB region, such as x = 0.12, the ECE is relatively weak under low electric fields but it exhibits a sharp increment under a sufficiently high electric field. This work provides a guideline to develop the solid–state cooling devices for electronic components

Effect of memory behavior on electric-field-induced phase transition and electrocaloric response in antiferroelectric ceramics

Field-induced phase transition in antiferroelectric (AFE) materials always facilitates giant positive/negative electrocaloric (EC) responses for a promising cooling application, while it is not only associated with external field conditions but also applied field history, i.e., memory behavior. Herein, we demonstrate that memory behavior increases the likelihood of observing an EC response when the operating field is parallel to the pre-poling field, as compared to the antiparallel condition. Additionally, when the temperature is slightly above the AFE-ferroelectric (FE) phase transition temperature, the field-off process induces a two-step microstructure change, characterized by a rapid domain rotation followed by a slow phase transition, which finally produces an abnormal EC heat flow signal. Through a Landau theory analysis, this kinetic behavior is contributed to the competition between the ferroelectric (FE) order pinned by memory behavior and the thermal agitation favored AFE state. This work deepens the understanding of the phase transition in the ferroelectric system

Anti-Hyperlipidemic Effects and Potential Mechanisms of Action of the Caffeoylquinic Acid-Rich <i>Pandanus tectorius</i> Fruit Extract in Hamsters Fed a High Fat-Diet

<div><p>Hyperlipidemia is considered to be one of the greatest risk factors contributing to the prevalence and severity of cardiovascular diseases. In this work, we investigated the anti-hyperlipidemic effect and potential mechanism of action of the <i>Pandanus tectorius</i> fruit extract in hamsters fed a high fat-diet (HFD). The <i>n</i>-butanol fraction of the <i>P. tectorius</i> fruit ethanol extract (PTF-b) was rich in caffeoylquinic acids (CQAs). Administration of PTF-b for 4 weeks effectively decreased retroperitoneal fat and the serum levels of total cholesterol (TC), triglycerides (TG) and low density lipoprotein–cholesterol (LDL-c) and hepatic TC and TG. The lipid signals (fatty acids, and cholesterol) in the liver as determined by nuclear magnetic resonance (NMR) were correspondingly reduced. Realtime quantitative PCR showed that the mRNA levels of PPARα and PPARα-regulated genes such as <i>ACO</i>, <i>CPT1</i>, <i>LPL</i> and <i>HSL</i> were largely enhanced by PTF-b. The transcription of <i>LDLR</i>, <i>CYP7A1</i>, and <i>PPARγ</i> was also upregulated. Treatment with PTF-b significantly stimulated the activation of AMP-activated protein kinase (AMPK) as well as the activity of serum and hepatic lipoprotein lipase (LPL). Together, these results suggest that administration of the PTF-b enriched in CQAs moderates hyperlipidemia and improves the liver lipid profile. These effects may be caused, at least in part, by increasing the expression of PPARα and its downstream genes and by upregulation of LPL and AMPK activities.</p></div

The primary caffeoylquinic acids present in the <i>P. tectorius</i> fruit extract PTF-b.

<p>(<b>A</b>) The total ion current profile corresponding to the UPLC-ESI-MS analysis of the PTF-b. (<b>B</b>) The skeleton of caffeoylquinic acid derivatives (IUPAC numbering). Peak numbers correspond to each of the caffeoylquinic acids (CQAs) identified in the PTF-b and are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0061922#pone.0061922.s003" target="_blank">Table S1</a>.</p

The CQA-rich PTF-b reduced serum total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-c) (C) without affecting food (A) and water (B) intake in hamsters.

<p>(D) Representative images of serum samples obtained from treated and untreated animals. The normal group was fed with a normal diet while the other groups were fed with a high fat-diet (HFD). The HFD+berberine and HFD+PTF-L, -M and -H groups were simultaneously supplemented with berberine (200 mg/kg) or the PTF-b at 50, 100 or 200 mg/kg, respectively. **<i>p</i><0.01 HFD group vs. normal group. ^†<i>p</i><0.05, ^‡<i>p</i><0.01 test group vs. HFD group.</p

Effects of the PTF-b on the weight of body, liver and retroperitoneal fat in hamster (n = 10).

*<p><i>p</i><0.05 HFD group Vs. Normal group, ^#<i>p</i><0.05, ^##<i>p</i><0.01 Test group Vs. HFD group.</p

The CQA-rich PTF-b upregulated the transcriptional expression of LPL and PPAR-α and -γ in the liver.

<p>Real-time PCR was conducted with gene specific oligonucleotide primers as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0061922#pone.0061922.s004" target="_blank">Table S2</a>. The amplification of β-actin served as the internal control. All groups were fed with a HFD. The HFD group (white) was treated with equal volume of distilled water, the HFD+berberine group (gray) was treated with 200 mg/kg of berberine and the HFD+PTF-b group (black) was treated with 100 mg/kg PTF-b. *p<0.05, **p<0.01 vs. HFD group.</p

Three caffeoylquinic acids isolated from the PTF-b exhibited significant lipid-lowering effects in HepG2 cells.

<p>Cells were starved in 0.02% BSA/DMEM for 12 h and then incubated with 1 µM of the individual CQAs (3, 4-di-O-caffeoyl quinic acid (CQA-1), 3, 5-di-O-caffeoyl quinic acid (CQA-2) and 3, 4, 5-tri-O-caffeoyl quinic acid (CAQ-3)) or 1 mM AICAR in 0.02% BSA+100 µM oleic acid (OA)/DMEM or in 0.02% BSA+100 µM OA/DMEM alone for 6 h. Subsequently, the cells were subjected to oil-red O staining (<b>A</b>) or TC (<b>B</b>) and TG (<b>C</b>) determination. *<i>p</i><0.05 OA group vs. normal group. ^†<i>p</i><0.05 test group vs. OA group.</p