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Extensive research efforts have been focused on customizing the microstructure, macrostructure, and phase composition of calcium phosphate for enhanced biocompatibility and bioactivity in scaffolds for bone substitutes. Despite significant progress, achieving precise phase composition and microstructure remains a challenge, primarily due to the necessity of scaffold sintering. This study addresses the challenges in developing customized patient‐specific bone substitutes by proposing a sequential approach that reduces processing steps while providing control over the phase and morphology of the scaffolds’ structure. The methodology utilizes freeze‐casting and sintering for highly porous the scaffolds’ preparation, followed by hydrothermal treatment to modify the microstructure. The introduction of CaCO3 induces a phase transformation of tricalcium phosphate, increasing the hydroxyapatite content, while the overall macrostructure retains the characteristics of freeze‐casting. The surface morphology undergoes a transition from equiaxial grains to whiskers‐like structures and hexagonal rods, impacting compressive strength. Following hydrothermal treatment, the formation of whiskers‐like hydroxyapatite grains leads to a notable strength increase from 2.8 to 5.7 MPa. Remarkably, the scaffolds undergo nearly complete phase transformation, shifting from 100% tricalcium phosphate to 99% hydroxyapatite, all while conserving the macrostructure. [ABSTRACT FROM AUTHOR]

This paper investigates the post-hoc calibration of confidence for "exploratory" machine learning classification problems. The difficulty in these problems stems from the continuing desire to push the boundaries of which categories have enough examples to generalize from when curating datasets, and confusion regarding the validity of those categories. We argue that for such problems the "one-versus-all" approach (top-label calibration) must be used rather than the "calibrate-the-full-response-matrix" approach advocated elsewhere in the literature. We introduce and test four new algorithms designed to handle the idiosyncrasies of category-specific confidence estimation using only the test set and the final model. Chief among these methods is the use of kernel density ratios for confidence calibration including a novel algorithm for choosing the bandwidth. We test our claims and explore the limits of calibration on a bioinformatics application (PhANNs) as well as the classic MNIST benchmark. Finally, our analysis argues that post-hoc calibration should always be performed, may be performed using only the test dataset, and should be sanity-checked visually. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics have been widely used in high precision sensors such as vibration detection, but piezoelectric accelerometers in high-temperature applications are very rare. We prepared ($1- {x}$) BiFeO3- ${x}$ BaTiO3-0.0035MnO2-0.001Li2CO3(BF- ${x}$ BT) ceramics by a solid state approach, and investigated the effect of BT content(${x}$) on the phase structure, microstructure, dielectric properties, ferroelectric properties, piezoelectric properties, temperature stability, and especially the sensitivity of the piezoelectric accelerometer. The crystal structure of the sample is pure perovskite structure with the MPB (R and P phases) locating in a composition range of $0.28\le {x} \le0.32$ for BF-xBT ceramics, and the single R phase exist at $0.20\le {x} < 0.28$. When ${x} $ = 0.30, the ceramic presents both high Curie temperature and ${d}_{33}$. Notably, the sensitivity of BF-0.30BT piezoelectric accelerometer reaches the highest value of about 40 pC/g and shows an excellent stability until 400 °C, indicating that this material is a promising candidate for high-temperature piezoelectric accelerometer applications. [ABSTRACT FROM AUTHOR]

Dielectric energy-storage ceramics have the advantages of high power density and fast charge and discharge rates, and are considered to be excellent candidate materials for pulsed power-storage capacitors. At present, the application of dielectric energy-storage ceramics is hindered by their low energy density and the fact that most of them contain elemental lead. Therefore, lead-free dielectric energy-storage ceramics with high energy storage density have become a research hot spot. In this paper, we first present the requirements that dielectric energy-storage capacitors impose on the properties of ceramic materials. We then review our previous research work combined with research progress into bismuth (Bi)-based lead-free energy-storage ceramics including Bi0.5Na0.5TiO3 (BNT), BiFeO3, and Bi0.2Sr0.7TiO3, in which the composition design ideas and related energy-storage characteristics of BNT-based lead-free energy-storage ceramics are emphasized. At the same time, we highlight the problems faced by Bi-based lead-free energy-storage ceramics and some strategies for addressing them. Finally, we examine the future prospects of research into Bi-based lead-free energy-storage ceramics. [ABSTRACT FROM AUTHOR]

Energy storage materials and their applications have attracted attention among both academic and industrial communities. Over the past few decades, extensive efforts have been put on the development of lead-free high-performance dielectric capacitors. In this review, we comprehensively summarize the research progress of lead-free dielectric ceramics for energy storage, including ferroelectric ceramics, composite ceramics, and multilayer capacitors. The results indicate that dielectric capacitors with both high energy density and high efficiency are feasible using the materials providing high breakdown electric field and a slim hysteresis loop. This article also lists the factors affecting the fabrication cost of dielectric capacitors, such as sintering temperature, raw material costs, and types of internal electrodes, to promote the industrial application of ceramic energy storage capacitors. [ABSTRACT FROM AUTHOR]

For any given bacteriophage genome or phage-derived sequences in metagenomic data sets, we are unable to assign a function to 50–90% of genes, or more. Structural protein-encoding genes constitute a large fraction of the average phage genome and are among the most divergent and difficult-to-identify genes using homology-based methods. To understand the functions encoded by phages, their contributions to their environments, and to help gauge their utility as potential phage therapy agents, we have developed a new approach to classify phage ORFs into ten major classes of structural proteins or into an "other" category. The resulting tool is named PhANNs (Phage Artificial Neural Networks). We built a database of 538,213 manually curated phage protein sequences that we split into eleven subsets (10 for cross-validation, one for testing) using a novel clustering method that ensures there are no homologous proteins between sets yet maintains the maximum sequence diversity for training. An Artificial Neural Network ensemble trained on features extracted from those sets reached a test F1-score of 0.875 and test accuracy of 86.2%. PhANNs can rapidly classify proteins into one of the ten structural classes or, if not predicted to fall in one of the ten classes, as "other," providing a new approach for functional annotation of phage proteins. PhANNs is open source and can be run from our web server or installed locally. Author summary: Bacteriophages (phages, viruses that infect bacteria) are the most abundant biological entity on Earth. They outnumber bacteria by a factor of ten. As phages are very different from each other and from bacteria, and we have relatively few phage genes in our database compared to bacterial genes, we are unable to assign function to 50–90% of phage genes. In this work, we developed PhANNs, a machine learning tool that can classify a phage gene as one of ten structural roles, or "other". This approach does not require a similar gene to be known. [ABSTRACT FROM AUTHOR]

Recently developed Na1/2Bi1/2TiO3 (NBT)-based relaxor ferroelectric ceramics are promising lead-free candidates for dielectric energy storage applications because of their non-toxicity and outstanding energy storage properties. Their commercialization currently faces a challenge in that high recoverable energy-storage density (Wrec) and high energy-storage efficiency (η) cannot be achieved simultaneously. Different from the normal relaxor ferroelectrics whose energy storage density was improved by reducing the remanent polarization and increasing the electric breakdown strength, in this work, a lead-free antiferroelectric (AFE) was utilized to partially replace the NBT-based relaxor (RE) to change the shape of the polarization curve and increase the electric breakdown strength, while maintaining large maximum polarization. Based on this concept, a lead-free RE/AFE 0.94(Na0.82K0.18)1/2Bi1/2TiO3–0.06FeNbO4/0.96NaNbO3–0.04CaZrO3 (NKBT–FN/NN–CZ) composite ceramic is designed and investigated. Through heat treatment of powder and the traditional solid phase reaction method, NKBT–FN/NN–CZ relaxor/antiferroelectric composites with multi-phase structure of an antiferroelectric embedded in a relaxor ferroelectric were established, and narrow and oblique double hysteresis loops were achieved in these composites. A high Wrec of 2.85 J cm−3 and high η of 80% were simultaneously realized at the composition with a mass ratio of 70/30 at room temperature (RT). Furthermore, the newly developed composites exhibit better energy storage characteristics at 120 °C, with a high Wrec of 3.5 J cm−3 as well as a high η of 91%. This study demonstrates that the design of a relaxor/antiferroelectric composite provides a highly effective method to improve the energy storage performance of lead-free ceramics. [ABSTRACT FROM AUTHOR]

The improvement of breakdown strength for NBT-based ceramics is currently the main challenge in applications of lead-free dielectric energy-storage materials. In this study, large-polarization 0.65Na0.5Bi0.5TiO3–0.35SrTiO3 (NBST) and high-efficiency 0.45Na0.5Bi0.5TiO3–0.55Sr0.7Bi0.2TiO3 (NBSBT) ceramics were selected to construct layered ceramics. The effect of the number of interfaces on breakdown behavior and polarization was investigated by controlling the stacking of layered ceramics. The single-layer NBST/NBSBT alternately stacked layered ceramics achieved a maximum breakdown strength of 242 kV cm−1, resulting in high recoverable energy storage density (4.48 J cm−3) and efficiency (∼90%). Meanwhile, the energy storage performance of NBST/NBSBT layered ceramics also exhibits excellent frequency (10–200 Hz) and temperature (25–125 °C) stability. The results prove that the large number of interfaces is beneficial to obtain high breakdown strength and maximum polarization, which brings new enlightenment to further improve the energy storage density of NBT-based materials. [ABSTRACT FROM AUTHOR]

We present a case of prenatal hydrops secondary to congenital high airway obstruction syndrome (CHAOS) that was treated with fetoscopy-assisted needle decompression. A 22-year-old G3P2 woman presented after a 21-week ultrasound demonstrated CHAOS. The fetus developed hydrops at 25 weeks, characterized by abdominal ascites, pericardial effusion, and scalp edema. Fetal MRI showed complete obstruction of the glottis and subglottic airway, suggestive of laryngeal atresia. At 27 weeks, due to the progression of the hydrops, operative fetoscopy was proposed and performed. Fetal laryngoscopy confirmed fusion of the vocal cords and laryngeal atresia. The atretic segment was a solid cartilaginous block, preventing intubation. Using the fetoscope to stabilize the fetal head and neck, we performed ultrasound-guided percutaneous needle drainage of the cervical trachea through the anterior fetal neck. We removed 17 mL of viscous fluid from the lower trachea, resulting in immediate lung decompression. Two weeks later, ultrasound confirmed hydrops resolution. The patient was delivered and tracheostomy performed at 30 weeks via an ex utero intrapartum treatment (EXIT) procedure after progression of preterm labor. At 27 days of life, the infant was stable on minimal ventilator support. To our knowledge, this is the first successful report of an ultrasound-guided percutaneous tracheal decompression through the anterior neck of a fetus with CHAOS secondary to laryngeal atresia. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectrics are promising candidates for pulsed power dielectric capacitor applications because of their excellent energy-storage properties. Different from most relaxor ferroelectrics whose energy-storage density was improved by increasing the breakdown strength and reducing the remanent polarization, in this study, anti-ferroelectric (AFE) AgNbO3 (AN) was used to partially substitute the relaxor ferroelectric 0.76Bi0.5Na0.5TiO3–0.24SrTiO3 (BNT–ST) of morphotropic phase boundary (MPB) composition to reduce the remanent polarization while maintaining large maximum polarization. In this way, a large recoverable energy-storage density (2.03 J cm−3) was obtained in the BNT–ST–5AN ceramics under lower electric field of 120 kV cm−1, which is superior to other lead-free energy-storage materials under similar electric fields. Moreover, excellent temperature (25–175 °C) and frequency (1–100 Hz) stabilities are achieved. This performance demonstrates that the BNT–ST–5AN ceramics form a promising class of dielectric capacitive material for high-temperature pulsed power capacitors with large energy-storage density. [ABSTRACT FROM AUTHOR]

Abstract: The traditional method for shaping ceramics is by slip casting on gypsum molds; however, its application for near‐net shaping of ceramic components is limited due to contamination by calcium ions. The focus of this study is the modification of the mold to limit Ca2+ contamination and to maintain favorable sucking properties. Cement was added to a standard gypsum mold to suppress its erosion, and a decrease in the sucking rate was observed due to its reduced macroporosity. The highest values of green densities were obtained at gypsum/cement weight ratios of 90/10 and 70/30. The microstructure analysis showed that alumina blocks prepared from the molds containing higher quantities of cement (30 or 50 wt%) were resistant to abnormal grain growth caused by Ca2+ contamination from the gypsum. The gypsum/cement mixtures for making molds for slip casting significantly limit mold erosion due to a lower sucking rate and abnormal grain growth of the slip cast samples because of the decreased diffusivity of Ca2+ ions. Therefore, the present modification of the mold renders the slip casting method more suitable for the near‐net shaping of ceramics. [ABSTRACT FROM AUTHOR]

The aim of this work was to study rapid sintering of alumina and zirconia ceramics of relatively large size and to reveal a role of surface diffusion on their densification. Pressure-less rapid rate sintering in a specially designed furnace with the heating rates of 100 °C/min and 1500 °C/min was found as a possible way for preparing defect free and nearly dense (> 95%TD) alumina and zirconia ceramics which represents a crucial benefit for big scale sintering process in ceramic industry. Our results also showed that rapid transition over the intermediate temperature range in which surface diffusion dominates is not strictly required for achieving high density. [ABSTRACT FROM AUTHOR]

Pressure-less spark plasma sintering (SPS) is a new approach during which rapid densification of ceramic nanopowder green bodies is accompanied by rapid grain growth. Although the origin of this phenomenon has not yet been fully understood significant, difference in grain growth between pressure-less and pressure-assisted SPS was expected. In this work 3Y-TZP nanopowder with average particle size of 12 nm was consolidated using two-step approach: (1) at an intermediate temperature (600°C to 1000°C) SPS warm pressing followed by (2) high temperature (1400°C to 1600°C) pressure-less SPS. The standard one step pressure-assisted SPS experiments were quoted as references. Rapid grain growth was observed during both pressure-less and standard SPS. The samples prepared by both approaches at the same sintering temperature (1400°C- 1600°C) achieved identical grain size and grain size distribution, if large pores were eliminated in early stage by SPS warm pressing. The electric current, electromagnetic field, and mechanical pressure is proven to have a negligible direct influence on grain growth in 3Y-TZP ceramics at temperatures above 1000°C under standard SPS conditions. [ABSTRACT FROM AUTHOR]

Heating of a ceramic green body is a key step in sintering. We have created inside a spark plasma sintering apparatus pressure-less sintering conditions that allow homogeneous and extremely rapid heating. Dense and crack-free zirconia ceramic was sintered at heating rates of up to 500°Cmin-1 and dwell times of 2min. This extremely fast sintering process is accompanied by extremely rapid grain growth, indicating a non classical sintering mechanism. No grain size gradients were observed inside the sintered zirconia ceramics. [ABSTRACT FROM AUTHOR]

The spark plasma sintering (SPS) process is known for its rapid densification of metals and ceramics. The mechanism behind this rapid densification has been discussed during the last few decades and is yet uncertain. During our SPS experiments we noticed oscillations in the applied pressure, related to a change in electric current. In this study, we investigated the effect of pulsed electrical current on the applied mechanical pressure and related changes in temperature. We eliminated the effect of sample shrinkage in the SPS setup and used a transparent quartz die allowing direct observation of the sample. We found that the use of pulsed direct electric current in our apparatus induces pressure oscillations with the amplitude depending on the current density. While sintering Ti samples we observed temperature oscillations resulting from pressure oscillations, which we attribute to magnetic forces generated within the SPS apparatus. The described current--pressure--temperature relations might increase understanding of the SPS process. [ABSTRACT FROM AUTHOR]

Abstract: Spark plasma sintering (SPS) was used to investigate the densification and deformation behaviour of Ti–TiB2 composites. Fully densified samples were prepared with Ti addition larger than 5%. The prepared composites can be deformed under compression at 1700°C to achieve a strain of 50% without cracking. At lower temperatures, cracks were initiated due to low ductility of TiB2 and low content of Ti. During the sintering and deformation, TiB is formed via a reaction between Ti and TiB2. To elucidate the formation mechanism of TiB in the SPS process, reactive sintering of TiB using element precursors was also performed. Fully dense samples were prepared but it was not possible to prepare pure uniphase TiB. The reactive sintering resulted in the formation of TiB and TiB2 mixtures at low temperatures and a mixture of TiB2 and Ti3B4 at high temperature. [Copyright &y& Elsevier]

Using spark plasma sintering techniques, homogeneous microstructures of titanium diboride (TiB2) ceramics were obtained by sintering of boron and titanium powder mixtures. The results show that an additional electric current is essential for achieving a large number of evenly distributed ignition points that ensure that the self-propagating reaction simultaneously takes place within the entire volume. The effects of the electric current, the use of Mg additions, and the heating rates on the resulting TiB2 ceramic densities and microstructures are discussed. [ABSTRACT FROM AUTHOR]

Abstract: α-Sialons with varied chemical compositions and starting precursors were sintered in spark plasma sintering (SPS) furnace to verify the influence of electrical conduction, mechanical pressure and heat transfer efficiency. The internal temperature that the sample was exposed to and its evolution during the heating were experimentally estimated and discussed. XRD and SEM grain size analysis were carried out to evaluate the phase and microstructure evolution. Mechanical pressure was eliminated to create a free sintering condition under SPS. By free sintering and surrounding the sample with graphite wool the heat transfer was sufficiently retarded and a usual slow reaction was demonstrated. It is verified that the efficiency of heat transfer is more influential in the enhancement of α-sialon formation and grain growth by SPS than the efficiency of electric conduction. [Copyright &y& Elsevier]

Abstract: A Y-α-sialon was prepared using a specially designed temperature regime supporting formation of α-sialon and the amount of non-crystalline phase was remarkably reduced by a chemical treatment. Chemical composition of the sample was determined by EDX analysis. Crystal structure of Y-α-sialon was refined using high quality time-of-flight neutron powder diffraction data taken with the General Purpose Powder Diffractometer (GPPD) at the IPNS, Argonne National Laboratory. Unrestrained structure refinement was done in the P31c space group. The list of simultaneously refined parameters included profile parameters, atomic coordinates, individual isotropic temperature parameters and the occupancy parameter of Y. The contents of Y in the cell refined to 0.38(1) and calculated Si–N distances in tetrahedra varied from 1.716(3) to 1.773(3)Å, but their distributions in the respective tetrahedra differ as in the parent structure of α-Si3N4. Anisotropic temperature parameters refinement, as well as constrained refinements of the occupancy parameters of Si–Al and N–O pairs, were also attempted, but they all ended with unphysical values. Variation of the background was analyzed using RDF formalism. Three peaks centered around 1.7Å (with a shoulder at 2.2Å), 2.8Å and 3.5Å proved that the composition of amorphous phase was close to that of crystalline. Ab initio cluster calculations performed at the B3LYP/6-31G** level of theory excluded configuration with O atoms bonded to three Si atoms and proved that the most probable is the configuration where an O atom is shared by three Al atoms. [Copyright &y& Elsevier]