Textured Potassium Sodium Niobate Lead-Free Ceramics with High d33 and Qm for Meeting High-Power Applications.

Potassium sodium niobate (KNN) lead-free piezoceramics have garnered significant attention for their environmentally friendly attributes, desired piezoelectric activity (d33), and high Curie temperature (Tc). However, the limited applicability of most KNN systems in high-power apparatus, including ultrasonic motors, transformers, and resonators, persists due to the inherent low mechanical quality factor (Qm). Herein, we proposed an innovative strategy for achieving high Qm accompanied by desirable d33 via synergistic chemical doping and texturing in KNN piezoceramics. Comprehensive electrical measurements along with quantitative structural characterization at multilength scales reveal that the excellent electromechanical properties (kp = 0.58, d33 ∼ 134 pC·N-1, Qm = 582, and Tc ∼ 415 °C) originate from the high <001> texturing degree, nanodomain, as well as acceptor hardening. Our findings provide an insight and guidance for achieving high-power performance in lead-free KNN-based piezoceramics, which were expected to be used in advanced transducer technology.

Outstanding Energy-Storage Density Together with Efficiency of above 90% via Local Structure Design.

Dielectric ceramic capacitors with high recoverable energy density (Wrec) and efficiency (η) are of great significance in advanced electronic devices. However, it remains a challenge to achieve high Wrec and η parameters simultaneously. Herein, based on density functional theory calculations and local structure analysis, the feasibility of developing the aforementioned capacitors is demonstrated by considering Bi0.25Na0.25Ba0.5TiO3 (BNT-50BT) as a matrix material with large local polarization and structural distortion. Remarkable Wrec and η of 16.21 J/cm3 and 90.5% have been achieved in Bi0.25Na0.25Ba0.5Ti0.92Hf0.08O3 via simple chemical modification, which is the highest Wrec value among reported bulk ceramics with η greater than 90%. The examination results of local structures at lattice and atomic scales indicate that the disorderly polarization distribution and small nanoregion (∼3 nm) lead to low hysteresis and high efficiency. In turn, the drastic increase in local polarization activated via the ultrahigh electric field (80 kV/mm) leads to large polarization and superior energy storage density. Therefore, this study emphasizes that chemical design should be established on a clear understanding of the performance-related local structure to enable a targeted regulation of high-performance systems.

AgNbO3-Based Multilayer Capacitors: Heterovalent-Ion-Substitution Engineering Achieves High Energy Storage Performances.

The demand for miniaturization and integration in next-generation advanced high-/pulsed-power devices has resulted in a strong desire for dielectric capacitors with high energy storage capabilities. However, practical applications of dielectric capacitors have been hindered by the challenge of poor energy-storage density (Urec) and efficiency (η) caused by large remanent polarization (Pr) and low breakdown strength (BDS). Herein, we take a method of heterovalent ion substitution engineering in combination with the multilayer capacitor (MLCC) technology and thus achieve a large maximum polarization (Pmax), zero Pr, and high BDS in the AgNbO3 (AN) system simultaneously and obtain excellent Urec and η. The substitution of Sm3+ for Ag+ in SmxAN+Mn MLCCs at x ≥ 0.01 decreases the M1-M2 phase transition temperature, and the antiferroelectric (AFE) M2 phase appears at room temperature, which is beneficial to achieving a low Pr value. Due to the low Pr value and high BDS ∼ 1300 kV·cm-1, an excellent Urec ∼9.8 J·cm-3 and PD,max ∼ 34.8 MW·cm-3 were achieved in SmxAN+Mn MLCCs at x = 0.03. The work suggests a paradigm that can enhance the energy storage capabilities of AFE MLCCs to meet the demanding requirements of advanced energy storage applications.

Heterovalent-doping-enabled atom-displacement fluctuation leads to ultrahigh energy-storage density in AgNbO3-based multilayer capacitors.

Dielectric capacitors with high energy storage performance are highly desired for next-generation advanced high/pulsed power capacitors that demand miniaturization and integration. However, the poor energy-storage density that results from the low breakdown strength, has been the major challenge for practical applications of dielectric capacitors. Herein, we propose a heterovalent-doping-enabled atom-displacement fluctuation strategy for the design of low-atom-displacements regions in the antiferroelectric matrix to achieve the increase in breakdown strength and enhancement of the energy-storage density for AgNbO3-based multilayer capacitors. An ultrahigh breakdown strength ~1450 kV·cm-1 is realized in the Sm0.05Ag0.85Nb0.7Ta0.3O3 multilayer capacitors, especially with an ultrahigh Urec ~14 J·cm-3, excellent η ~ 85% and PD,max ~ 102.84 MW·cm-3, manifesting a breakthrough in the comprehensive energy storage performance for lead-free antiferroelectric capacitors. This work offers a good paradigm for improving the energy storage properties of antiferroelectric multilayer capacitors to meet the demanding requirements of advanced energy storage applications.

Efficacy of plasma exchange in children with severe hemophagocytic syndrome: a prospective randomized controlled trial. / è¡€æµ†ç½®æ¢åœ¨å„¿ç«¥é‡ç—‡å™¬è¡€ç»†èƒžç»¼åˆå¾ä¸­åº”ç”¨çš„ç–—æ•ˆåˆ†æžï¼šå‰çž»æ€§éšæœºå¯¹ç §ç ”ç©¶.

OBJECTIVES: To investigate the efficacy and application value of plasma exchange as an adjuvant therapy in children with hemophagocytic syndrome (HPS). METHODS: A prospective randomized controlled trial was designed. Forty children with severe HPS were enrolled, who were treated in the pediatric intensive care unit (PICU) of Hunan Children's Hospital from October 2018 to October 2020. The children were randomly divided into a plasma exchange group and a conventional treatment group using a random number table, with 20 children in each group. The children in the conventional treatment group received etiological treatment and conventional symptomatic supportive treatment, and those in the plasma exchange group received plasma exchange in addition to the treatment in the conventional treatment group. The two groups were compared in terms of general information, clinical symptoms and signs before and after treatment, main laboratory markers, treatment outcome, and prognosis. RESULTS: Before treatment, there were no significant differences between the two groups in gender, age, course of the disease before admission, etiological composition, pediatric critical illness score, involvement of organ or system functions, and laboratory markers (P>0.05). After 7 days of treatment, both groups had remission and improvement in clinical symptoms and signs. After treatment, the plasma exchange group had significantly lower levels of C-reactive protein, procalcitonin, and serum protein levels than the conventional treatment group (P<0.05). The plasma exchange group also had significantly lower levels of alanine aminotransferase and total bilirubin than the conventional treatment group (P<0.05). The length of stay in the PICU in the plasma exchange group was significantly shorter than that in the conventional treatment group (P<0.05). The plasma exchange group had a significantly higher treatment response rate than the conventional treatment group (P<0.05). There were no significant differences between the two groups in the total length of hospital stay and 3-month mortality rate (P>0.05). CONCLUSIONS: Plasma exchange as an adjuvant therapy is effective for children with severe HPS. It can improve clinical symptoms and signs and some laboratory markers and shorten the length of stay in the PICU, and therefore, it may become an optional adjuvant therapy for children with severe HPS.

Ultrahigh Piezoelectric Performance through Synergistic Compositional and Microstructural Engineering.

Piezoelectric materials enable the conversion of mechanical energy into electrical energy and vice-versa. Ultrahigh piezoelectricity has been only observed in single crystals. Realization of piezoelectric ceramics with longitudinal piezoelectric constant (d33 ) close to 2000 pC N-1 , which combines single crystal-like high properties and ceramic-like cost effectiveness, large-scale manufacturing, and machinability will be a milestone in advancement of piezoelectric ceramic materials. Here, guided by phenomenological models and phase-field simulations that provide conditions for flattening the energy landscape of polarization, a synergistic design strategy is demonstrated that exploits compositionally driven local structural heterogeneity and microstructural grain orientation/texturing to provide record piezoelectricity in ceramics. This strategy is demonstrated on [001]PC -textured and Eu3+ -doped Pb(Mg1/3 Nb2/3 )O3 -PbTiO3 (PMN-PT) ceramics that exhibit the highest piezoelectric coefficient (small-signal d33 of up to 1950 pC N-1 and large-signal d33 * of ≈2100 pm V-1 ) among all the reported piezoelectric ceramics. Extensive characterization conducted using high-resolution microscopy and diffraction techniques in conjunction with the computational models reveals the underlying mechanisms governing the piezoelectric performance. Further, the impact of losses on the electromechanical coupling is identified, which plays major role in suppressing the percentage of piezoelectricity enhancement, and the fundamental understanding of loss in this study sheds light on further enhancement of piezoelectricity. These results on cost-effective and record performance piezoelectric ceramics will launch a new generation of piezoelectric applications.

Electrocaloric Performance of Multilayer Ceramic Chips: Effect of Geometric Structure Induced Internal Stress.

Driven by an ever-growing demand for environmentally benign cooling systems, the past decade has witnessed the booming development in the field of electrocaloric (EC) cooling technology, which is considered as a promising solid-state cooling approach. Multilayer ceramic chip capacitors (MLCCs) represent the optimum structure for EC cooling elements because of large breakdown strengths, low driving voltages, and high macroscopic volumes of active EC materials. However, fundamental relationships between the geometric parameters of MLCCs and the EC coefficient are less understood. In this study, 0.92Pb(Mg1/3Nb2/3)O3-0.08PbTiO3 (PMN-PT) MLCCs with controlled configurations, such as active/inactive layer thickness, number of layers, and active volume ratio, were fabricated, and their EC performance was evaluated. The electric properties of the MLCCs are confirmed to be closely related to the geometric structure, which influences not only the heat flow but also the internal stress, resulting in the variability of EC performance and reliability/breakdown strength. The internal stress arises due to the residual thermal stress originating from the densification-related shrinkage, thermal expansion mismatch during the sintering, and clamping stress arising from the inactive area due to the large strain from the active area under a high electric field. The geometric structure-based stress distribution and the magnitude of stress on the active layers in MLCCs were determined by finite element modeling (FEM) and correlated with the experimental EC coefficients. The results reveal that a low inactive volume percentage is beneficial toward increasing the breakdown field and enhancement of EC performance because of reduced clamping stress on active EC material.

Genetic Diversity and Prediction Analysis of Small Isolated Giant Panda Populations After Release of Individuals.

Release of individuals is an effective conservation approach to protect endangered species. To save this small isolated giant panda population in Liziping Nature Reserve, a few giant pandas have been released to this population. Here we assess genetic diversity and future changes in the population using noninvasive genetic sampling after releasing giant pandas. In this study, a total of 28 giant pandas (including 4 released individuals) were identified in the Liziping, China. Compared with other giant panda populations, this population has medium-level genetic diversity; however, a Bayesian-coalescent method clearly detected, quantified, and dated a recent decrease in population size. The predictions for genetic diversity and survival of the population in the next 100 years indicate that this population has a high risk of extinction. We show that released giant pandas can preserve genetic diversity and improve the probability of survival in this small isolated giant panda population. To promote the recovery of this population, we suggest that panda release should be continued and this population will need to release 10 males and 20 females in the future.

Temperature independence of piezoelectric properties for high-performance BiFeO3-BaTiO3 lead-free piezoelectric ceramics up to 300 °C.

The temperature-dependence behaviors of ferroelectric, piezoelectric, k p and electrical-field-induced strain were carefully evaluated for high-performance BiFeO3-0.3BaTiO3 (BF-0.3BT) ceramics. There results indicate, combined with Rayleigh analysis and temperature-dependence XRD and PFM, that the increase of strain and large signal with increasing the temperature from room temperature to 180 °C is related to the joint effect of intrinsic contribution (lattice expansion) and extrinsic contribution (domain switching). With further increasing the temperature to 300 °C, the large signal d 33 and electrical-field-induced strain mildly decrease because of the increase of conductivity for BF-0.3BT ceramics. However, different from strain and large signal the small signal d 33(E0) and k p exhibit excellent temperature stability behavior as the temperature increases from room temperature to 300 °C.

[Comparison of acute toxicity of two preparations of norcantharidin in mice].

OBJECTIVE: To compare the acute toxicity of common injection and sustained-release preparation of norcantharidin for mice so as to identify the attenuation of the sustained-release preparation of norcantharidin. METHODS: The poloxamer 407 was used as a sustained-release vehicle for topical administration of norcantharidin, and the acute toxicity of mice treated with common injection and sustained-release preparation of norcantharidin was observed. The median lethal dose (LD(50)) was calculated by Bliss software. RESULTS: The symptoms of mice were similar between the two groups, but the appearance of symptoms in norcantharidin/poloxamer 407 group was 4 hours later than that in norcantharidin group. The LD(50) of norcantharidin administered through vein injection was 12.6 mg/kg. The LD(50) of norcantharidin/poloxamer 407 administered through intraperitoneal injection, intrahepatic injection and intramuscular injection were 19.9, 19.1 and 20.9 mg/kg, respectively, and the LD(50) of the common preparation were 13.0, 13.1 and 15.1 mg/kg, respectively. CONCLUSION: The norcantharidin/poloxamer 407 is less toxic than the equivalent dose of norcantharidin, mainly because norcantharidin/poloxamer 407 may release norcantharidin sustainedly, thus reducing norcantharidin concentration in blood.