Compacted Anthropogenic Materials as Backfill for Buried Pipes

Buried pipe design requires knowledge about the fill to design the backfill structure. The interaction between the backfill envelope and the pipe impacts the structural performance of the buried pipe. The backfill material and compaction level respond to the backfill’s overall strength and, therefore, for pipe-soil interaction. The strength of backfill material is described in terms of modulus of soil reaction E’ and constrained modulus E_ode. As the E’ is an empirical parameter, the E_ode can be measured in the laboratory by performing the oedometer tests. In this study, we have performed extensive oedometric tests on five types of anthropogenic materials (AM). Three of them are construction and demolition materials (C–D materials) namely, recycled concrete aggregate (RCA), crushed brick (CB), and recycled asphalt pavement (RAP). Two of them are industrial solid wastes (ISW) namely, fly ash and bottom slag mix (FA + BS) and blast furnace slag (BFS). The results of the tests revealed that AM behaves differently from natural aggregates (NA). In general, the E_ode value for AM is lower than for NA with the same gradation. Despite that, some of AM may be used as NA substitute directly (RCA or BFS), some with special treatment like CB and some with extra compaction efforts like RAP or FA + BS.     

Recycling of Coal Fly Ash for the Fabrication of Porous Mullite/Alumina Composites

Coal fly ash with the addition of Al₂O₃ was recycled to produce mullite/alumina composites and the camphene-based freeze casting technique was processed to develop a controlled porous structure with improved mechanical strength. Many rod-shaped mullite crystals, formed by the mullitization of coal fly ash in the presence of enough silicate, melt. After sintering at 1300–1500 °C with the initial solid loadings of 30–50 wt.%, interconnected macro-sized pore channels with nearly circular-shaped cross-sections developed along the macroscopic solidification direction of camphene solvent used in freeze casting and a few micron-sized pores formed in the walls of the pore channels. The macro-pore size of the mullite/alumina composites was in the range 20–25 μm, 18–20 μm and 15–17 μm with reverse dependence on the sintering temperature at 30, 40 and 50 wt.% solid loading, respectively. By increasing initial solid loading and the sintering temperature, the sintered porosity was reduced from 79.8% to 31.2%, resulting in an increase in the compressive strength from 8.2 to 80.4 MPa.     

Review of the Effects of Supplementary Cementitious Materials and Chemical Additives on the Physical,Mechanical and Durability Properties of Hydraulic Concrete

Supplementary cementitious materials (SCMs) and chemical additives (CA) are incorporated to modify the properties of concrete. In this paper, SCMs such as fly ash (FA), ground granulated blast furnace slag (GGBS), silica fume (SF), rice husk ash (RHA), sugarcane bagasse ash (SBA), and tire-derived fuel ash (TDFA) admixed concretes are reviewed. FA (25–30%), GGBS (50–55%), RHA (15–20%), and SBA (15%) are safely used to replace Portland cement. FA requires activation, while GGBS has undergone in situ activation, with other alkalis present in it. The reactive silica in RHA and SBA readily reacts with free Ca(OH)₂ in cement matrix, which produces the secondary C-S-H gel and gives strength to the concrete. SF addition involves both physical contribution and chemical action in concrete. TDFA contains 25–30% SiO₂ and 30–35% CaO, and is considered a suitable secondary pozzolanic material. In this review, special emphasis is given to the various chemical additives and their role in protecting rebar from corrosion. Specialized concrete for novel applications, namely self-curing, self-healing, superhydrophobic, electromagnetic (EM) wave shielding and self-temperature adjusting concretes, are also discussed.     

Structural Formation of Soil Concretes Based on Loam and Fly Ash,Modified with a Stabilizing Polymer Additive

Finding new ways of recycling production waste to improve the characteristics of various building materials is an urgent scientific task. This article substantiates the possibility of the disposal of fly ash in the composition of soil concrete, which is used in the construction of the structural layers of road pavements, foundations of buildings and structures, as well as sites for various purposes. The scientific novelty lies in the fact that the structure formation of soil concretes based on loam and fly ash and modified with a stabilizing additive is being studied for the first time. It was found that the investigated fly ash, according to its hydraulic properties, is classified as latent active and can be introduced into the compositions of road soil concrete modified with additives of various resources. The effectiveness of the complex method of stabilization, due to changes in soil properties as a result of the use of the binding and stabilizing additives of polymer nature “Kriogelit”, is shown. It was found that the optimal content of binder and fly ash in the samples was 8 and 10 wt.%, respectively. It was established that the use of the stabilizing additive “Kriogelit” makes it possible to obtain soil concrete with the highest strength (compressive strength 2.5 MPa, flexural strength 0.5 MPa) and frost resistance of at least F15. The microstructure, the degree of dehydration and carbonization, and the phase composition of the initial raw mixtures and soil concretes stabilized with the addition of “Kriogelit” were studied by methods of scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. It was shown that organo-mineral complexes, with the participation of polymer and montmorillonite, are formed in stabilized soil concrete. It was revealed that structure formation is accompanied by the physical adsorption of the polymer on active centers of silicate minerals, carbonization, and hydration–dehydration processes. It was found that the reason for the increase in the strength of stabilized soil concretes is the hydrophobization of the porous structure of minerals, as well as the formation of calcium oxide silicate and dicalcium hydrated silicate. By the method of performing biotests with the test objects Daphnia magna Straus and Chlorella vulgaris Beijer, it was proven that the developed road concretes modified with the stabilizing additive “Kriogelit” do not have an acute toxic effect on the test objects and are safe for the environment and human health.     

Recycling of Sustainable Co-Firing Fly Ashes as an Alkali Activator for GGBS in Blended Cements

This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB) or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS). The mixture ratio of GGBS and co-firing fly ashes is 1:1 by weight. The results indicate that only CF fly ash of CFB boilers can effectively stimulate the potential characteristics of GGBS and provide strength as an alkali activator. CF fly ash consists of CaO₃ (48.5%), SiO₂ (21.1%), Al₂O₃ (13.8%), SO₃ (10.06%), Fe₂O₃ (2.25%) and others (4.29%). SA fly ash consists of Al₂O₃ (19.7%), SiO₂ (36.3%), Fe2O3 (28.4%) and others (15.6%). SB fly ash consists of Al₂O₃ (15%), SiO₂ (25.4%), Zn (20.6%), SO₃ (10.9%), Fe₂O₃ (8.78%) and others (19.32%). The mixtures of SA fly ash and SB fly ash with GGBS, respectively, were damaged in the compressive strength test during seven days of curing. However, the built up strength of the CF fly ash and GGBS mixture can only be maintained for 7–14 days, and the compressive strength achieves 70% of that of a controlled group (cement in hardening cement paste). The strength of blended CF fly ash and GGBS started to decrease after 28 days, and the phenomenon of ettrigite was investigated due to the high levels of sulfur content. The CaO content in sustainable co-firing fly ashes must be higher than a certain percentage in reacting GGBS to ensure the strength of blended cements.     

Effect of Compaction Ratio on Mechanical Properties of Low-Strength Hydraulically Bound Mixtures for Road Engineering

Road layers should be properly compacted to obtain an adequate bearing capacity and durability. Both the unbound and hydraulically bound mixtures used in the layers require compaction. After compaction and hardening, soil mixed with a binder acquires mechanical features that unbound soil lacks, including tensile strength (R_it) and unconfined compressive strength (R_c). The effect of the compaction ratio (D_Pr) of the low-strength cement-stabilised soils on these features has rarely been investigated. This study investigates the influence of the compaction ratio on the mechanical properties of hardened, stabilised mixtures of medium-grained sand with 5%, 6.5%, and 8% Portland cement. Cement–soil stabilisation tests showed that compressive strength depends exponentially on the compaction ratio, whereas tensile strength and the stiffness modulus depend linearly on the compaction ratio. For tensile strength and the dynamic stiffness modulus, the effect is not statistically significant, and the usual practice of ignoring compaction dependence is justified. For compressive strength, however, the effect is significant, especially when D_Pr = 98–100%. When the values of R_c and R_it strengths at various D_Pr were normalised by those at 100%, it was found that mixtures with higher strengths are the least resistant to changes in the compaction ratio. Knowing the percentage by which the value of a given parameter changes with compaction can be extremely valuable in engineering practice.     

Treatments of unruptured brain arteriovenous malformations: A systematic review and meta-analysis

Background:The best therapeutic option for unruptured brain arteriovenous malformations (bAVMs) patients is disputed.Objective:To assess the occurrence of obliteration and complications of patients with unruptured bAVMs after various treatments.Methods:A systematic literature search was performed in PubMed, EMBASE, Web of Science, and so on to identify studies fulfilling predefined inclusion criteria. Baseline, treatment, and outcomes data were extracted for statistical analysis.Results:We identified 28 eligible studies totaling 5852 patients. The obliteration rates were 98% in microsurgery group (95% confidence interval (CI): 96%–99%, I² = 74.5%), 97% in surgery group (95%CI: 95%–99%, I² = 18.3%), 87% in endovascular treatment group (95%CI: 80%–93%, I² = 0.0%), and 68% in radiosurgery group (95%CI: 66%–69%, I² = 92.0%). The stroke or death rates were 1% in microsurgery group (95%CI: 0%–2%, I² = 0.0%), 0% in surgery group (95%CI: 0%–1%, I² = 0.0%), 4% in endovascular treatment group (95%CI: 0%–8%, I² = 85.8%), and 3% in radiosurgery group (95%CI: 3%–4%, I² = 82.9%). In addition, the proportions of hemorrhage were 2% in microsurgery group (95%CI: 1%–4%, I² = 0.0%), 23% in endovascular treatment group (95%CI: 7%–39%), and 12% in radiosurgery group (95%CI: 12%–13%, I² = 99.2%). As to neurological deficit, the occurrence was 9% in microsurgery group (95%CI: 6%–11%, I² = 94.1%), 20% in surgery group (95%CI: 13%–27%, I² = 0.0%), 14% in endovascular treatment group (95%CI: 10%–18%, I² = 64.0%), and 8% in radiosurgery group (95%CI: 7%–9%, I² = 66.6%).Conclusions:We found that microsurgery might provide lasting clinical benefits in some unruptured bAVMs patients for its high obliteration rates and low hemorrhage. These findings are helpful to provide a reference basis for neurosurgeons to choose the treatment of patients with unruptured bAVMs.     

Experimental Investigation on Mechanical and Thermal Properties of Concrete Using Waste Materials as an Aggregate Substitution

The continuous growth of the concrete industry requires an increased quantity of cement and natural aggregates year after year, and it is responsible for a major part of the global CO₂ emissions. These aspects led to rigorous research for suitable raw materials. Taking into account that these raw materials must have a sustainable character and also a low impact on environmental pollution, the replacement of the conventional components of concrete by residual waste can lead to these targets. This paper’s aim is to analyze the density, compressive strength and the thermal conductivity of nine concrete compositions with various rates of waste: four mixes with 10%, 20%, 40% and 60% chopped PET bottles aggregates and 10% fly ash as cement partial substitution; a mix with 60% waste polystyrene of 4–8 mm and 10% fly ash; a mix with 20% waste polystyrene of 4–8 mm, 10% waste polystyrene of 0–4 mm and 10% fly ash; a mix with 50% waste polystyrene of 4–8 mm, 20% waste polystyrene of 0–4 mm and 20% fly ash two mixes with 10% fly ash and 10% and 40% waste sawdust, respectively. Using 60% PET aggregates, 60% polystyrene granules of 4–8 mm, or 20% polystyrene of 0–4 mm together with 50% polystyrene of 4–8 mm led to the obtainment of lightweight concrete, with a density lower than 2000 kg/m³. These mixes also registered the best results from a thermal conductivity point of view, after the concrete mix with 40% saw dust. Regarding compressive strength, the mix with 10% PET obtained a result very close to the reference mix, while those with 20% PET, 40% PET, 30% polystyrene, and 10% saw dust, respectively, registered values between 22 MPa and 25 MPa, values appropriate for structural uses.     

Corn Cob Ash versus Sunflower Stalk Ash,Two Sustainable Raw Materials in an Analysis of Their Effects on the Concrete Properties

The increased CO₂ emissions determined by the cement industry led to continuous and intensive research on the discovery of sustainable raw materials with cementitious properties. One such raw material category is agricultural waste. This study involved research on the effects of corn cob ash and sunflower stalk ash, respectively, on compressive strength measured after 28 days and 3 months, the flexural and splitting tensile strengths, the resistance to repeated freeze–thaw cycles, and on the resistance to chemical attack of hydrochloric acid of the concrete. A 2.5% and 5% replacement of the cement volume with corn cob ash (CCA) of A and B quality was applied, and with sunflower stalk ash (SSA) at A and B quality, respectively. The obtained results revealed that CCA and SSA decreased the compressive and tensile strength, but led to higher resistance of the concrete on repeated freeze–thaw cycles and to hydrochloric acid. The mixes with 2.5% SSA at A quality obtained the best results regarding splitting the tensile strength and resistance to repeated freeze–thaw cycles, the mixes with 2.5% SSA at B quality led to the highest resistance to hydrochloric acid, and those with 2.5% CCA at A quality led to the best values of compressive strength and flexural tensile strength.     

Effect of Delamination and Grain Refinement on Fracture Energy of Ultrafine-Grained Steel Determined Using an Instrumented Charpy Impact Test

Improving the balance of strength and toughness in structural materials is an ongoing challenge. Delamination and grain refinement are some of the methods used to do this. In this paper, two different steels, 0.15% C–0.3% Si–1.5% Mn–Fe and 0.4% C–2% Si–1% Cr–1% Mo–Fe (mass %), were prepared. Two steel bars with an ultrafine elongated grain (UFEG) structure were fabricated via multipass warm caliber rolling. The UFEG steels were characterized by a strong <110>//rolling-direction fiber texture. The transverse grain size, d_t, was 1.0 µm for the low-carbon steel and 0.26 µm for the medium-carbon steel. For comparison, conventional heat-treated steels were also fabricated. An instrumented Charpy impact test was performed, and the impact load (P) and deflection (u) during the test were recorded. The P–u relations at the test temperature at which delamination fracture occurred exhibited a unique curve. Delamination effectively enhances the low-temperature toughness, and this was characterized by a plateau region of constant load in the P–u curve. Assuming no delamination, two routes in the P–u curves, the ductile route and the brittle route, were proposed. The results showed that the proposed methods can be predicted by an energy curve for ultrafine grained steels. Delamination is a more effective method of enhancing toughness for ultra-high-strength steels.     

Pull-Out Strength and Bond Behavior of Prestressing Strands in Prestressed Self-Consolidating Concrete

With the extensive use of self-consolidating concrete (SCC) worldwide, it is important to ensure that such concrete can secure uniform in-situ mechanical properties that are similar to those obtained with properly consolidated concrete of conventional fluidity. Ensuring proper stability of SCC is essential to enhance the uniformity of in-situ mechanical properties, including bond to embedded reinforcement, which is critical for structural engineers considering the specification of SCC for prestressed applications. In this investigation, Six wall elements measuring 1540 mm × 2150 mm × 200 mm were cast using five SCC mixtures and one reference high-performance concrete (HPC) of normal consistency to evaluate the uniformity of bond strength between prestressing strands and concrete as well as the distribution of compressive strength obtained from cores along wall elements. The evaluated SCC mixtures used for casting wall elements were proportioned to achieve a slump flow consistency of 680 ± 15 mm and minimum caisson filling capacity of 80%, and visual stability index of 0.5 to 1. Given the spreads in viscosity and static stability of the SCC mixtures, the five wall elements exhibited different levels of homogeneity in in-situ compressive strength and pull-out bond strength. Test results also indicate that despite the high fluidity of SCC, stable concrete can lead to more homogenous in-situ properties than HPC of normal consistency subjected to mechanical vibration.     

Storage of molecular hydrogen in an ammonia borane compound at high pressure

We studied ammonia borane (AB), NH₃BH₃, in the presence of excess hydrogen (H₂) pressure and discovered a solid phase, AB(H₂)_x, where x ≈1.3–2. The new AB–H₂ compound can store an estimated 8–12 wt % molecular H₂ in addition to the chemically bonded H₂ in AB. This phase formed slowly at 6.2 GPa, but the reaction rate could be enhanced by crushing the AB sample to increase its contact area with H₂. The compound has 2 Raman H₂ vibron peaks from the absorbed H₂ in this phase: one (ν₁) at frequency 70 cm⁻¹ below the free H₂ vibron, and the other (ν₂) at higher frequency overlapping with the free H₂ vibron at 6 GPa. The peaks shift linearly over the pressure interval of 6–16 GPa with average pressure coefficients of dν₁/dP = 4 cm⁻¹/GPa and dν₂/dP = 6 cm⁻¹/GPa. The formation of the compound is accompanied by changes in the N–H and B–H stretching Raman peaks resulting from the AB interactions with H₂ which indicate the structural complexity and low symmetry of this phase. Storage of significant amounts of additional molecular H₂ in AB increases the already high hydrogen content of AB, and may provide guidance for developing improved hydrogen storage materials.     

Influence of Cu Content on Structure,Thermal Stability and Magnetic Properties in Fe72−xNi8Nb4CuxSi2B14 Alloys

The effect of substitution of Fe by Cu on the crystal structure and magnetic properties of Fe_72−xNi₈Nb₄Cu_xSi₂B₁₄ alloys (x = 0.6, 1.1, 1.6 at.%) in the form of ribbons was investigated. The chemical composition of the materials was established on the basis of the calculated minima of thermodynamic parameters: Gibbs free energy of amorphous phase formation ΔG^amorph (minimum at 0.6 at.% of Cu) and Gibbs free energy of mixing ΔG^mix (minimum at 1.6 at.% of Cu). The characteristic crystallization temperatures T_x1onset and T_x1 of the alpha-iron phase together with the activation energy E_a for the as-spun samples were determined by differential scanning calorimetry (DSC) with a heating rate of 10–100 °C/min. In order to determine the optimal soft magnetic properties, the wound cores were subjected to a controlled isothermal annealing process in the temperature range of 340–640 °C for 20 min. Coercivity Hc, saturation induction Bs and core power losses at B = 1 T and frequency f = 50 Hz P_10/50 were determined for all samples. Moreover, for the samples with the lowest Hc and P_10/50, the magnetic losses were determined in a wider frequency range 50 Hz–400 kHz. The real and imaginary parts of the magnetic permeability µ′, µ″ along with the cut-off frequency were determined for the samples annealed at 360, 460, and 560 °C. The best soft magnetic properties (i.e., the lowest value of Hc and P_10/50) were observed for samples annealed at 460 °C, with Hc = 4.88–5.69 A/m, Bs = 1.18–1.24 T, P_10/50 = 0.072–0.084 W/kg, µ′ = 8350–10,630 and cutoff frequency at 8–9.3 × 10⁴ Hz. The structural study of as-spun and annealed ribbons was carried out using X-ray diffraction (XRD) and a transmission electron microscope (TEM).     

Research on Dewatering Characteristics of Waste Slurry from Pipe Jacking Construction

A large amount of waste slurry is produced during the construction of pipe jacking projects. To avoid the waste slurry occupying too much urban land, it needs to be rapidly reduced. Due to the complex composition of waste slurry, the existing dewatering methods face the problem of low efficiency, and the soil after dewatering is difficult to recycle as soil materials due to high water content and low strength. There is currently a lack of research on dewatering and resource utilization of waste slurry from pipe jacking projects. In response to this problem, this paper studies the flocculation-settling characteristics of waste slurry and the mechanical properties of solidified sediment. It was found that the anionic polyacrylamide (APAM) 7126 obtained the best separation effect if the waste slurry contains bentonite, which increases the zeta potential, resulting in poor separation. Thus, FeCl₃·6H₂O and APAM 7126 can be used as compound conditioners. The sediment after settling was further added with 20–30% sulphate aluminum cement (SAC), and the unconfined compressive strength of the solidified sediment for 3 days could exceed 30 kPa. After flocculation-settling and solidification treatment, the waste pipe jacking slurry can be quickly dewatered into a soil material with a certain strength, which provides a reference for engineering applications.     

Prevalence and Risk Factors of Hypertension in Myanmar: A Systematic Review and Meta-Analysis

Hypertension (HPT) is the most common condition seen in primary care that can lead to health consequences and death if not detected early and treated appropriately.This study aimed to synthesize the prevalence, awareness, and control of HPT, and investigate the risk factors for HPT in Myanmar.We performed a meta-analysis of observational studies. Relevant studies were searched in electronic databases. The methodological quality of the included studies was assessed in 3 domains: selection bias, measurement bias, and bias related to data analysis. The overall prevalence and proportions was calculated using random-effect model of DerSimonian–Laird method. To identify the risk factors for HPT in Myanmar, we entered the ratio measures of the (adjusted) effect as a log odds ratio (OR) and the standard error of the log OR using generic inverse-variance weighting method. For stability of results, we performed leave-one-study-out sensitivity analysis by omitting individual studies one at a time from the meta-analysis.Seven studies (n = 20,901) were included in this analysis. Overall prevalence of HPT in Myanmar was 22% (95% confidence interval (CI): 14%–31.7%, I²: 99.6%), stratified as 21.5% (95% CI: 14.1%–29.9%, I²: 98.7%) in men and 22.7% (95% CI: 10.8%–34.6%, I²: 99.5%) in women. Overall, prevalence of HPT increased with an advancing age of the participants. The proportions of awareness and controlled HPT were 55% (95% CI: 43%–67%, I²: 97.7%) and 11% (95% CI: 6%–15%, I²: 93.8%), respectively. A weak but significant association was observed between HPT and alcohol drinking (summary OR: 1.38, 95% CI: 1.14%–1.65, I²: 0%) and smoking (summary OR: 1.32, 95% CI: 1.0%–1.74, I²: 50%). In sensitivity analysis, when a study that made confirmation of HPT by the former World Health Organization criteria was dropped, the prevalence increased to 26% (95% CI: 20.8%–32.1%, I²: 98.1%).HPT was considerably prevalent in Myanmar, while the levels of awareness and controlled HPT were low. Health promotion strategy tailored to the education on modifiable risk factors and establishment of blood pressure screening in primary health care context would be of immense value. Upcoming well-powered studies, using the standardized research design and covering more regions of the country are recommended.     

Hybrid Lime–Pozzolan Geopolymer Systems: Microstructural,Mechanical and Durability Studies

This work studies the possibility of using geopolymer materials to enhance the mechanical and durability properties of hydrated lime–pozzolan mixtures, which gave rise to the so-called “hybrid systems”. Two different waste types were used as pozzolan in the lime–pozzolan system: rice husk ash (RHA) and spent fluid catalytic cracking (FCC). The geopolymer fabricated with FCC was activated with commercial reagents (NaOH and Na₂SiO₃), and also with alternative sources of silica to obtain a lower carbon footprint in these mixtures. The alternative silica sources were RHA and residual diatomaceous earth (RDE) from the beer industry. The geopolymer mixture substituted the lime–pozzolan mixture for 30% replacement in weight. The hybrid systems showed better mechanical strengths for the short and medium curing ages in relation to the lime–pozzolan mixtures. Thermogravimetric analyses were performed to characterise the types of products formed in these mixtures. In the durability studies, hybrid systems better performed in freeze–thaw cycles and obtained lower capillarity water absorption values.     

Microstructure and Mechanical Properties of TiN–TiB2–hBN Composites Fabricated by Reactive Hot Pressing Using TiN–B Mixture

In this study, TiN–TiB₂–hBN composite ceramics were prepared via reactive hot pressing using TiN and amorphous B powders as raw materials. Different sintering temperatures and composition ratios were studied. The results show that the 70 vol% TiN–17.6 vol% TiB₂–12.4 vol% hBN ceramic composites obtained ideal comprehensive properties at 1600 °C. The relative density, Vickers hardness, bending strength, and fracture toughness were 99%, 11 GPa, 521 MPa, and 4.22 MPa·m^1/2, respectively. Densification was promoted by the highly active reaction product TiB₂, and the structural defects formed in the grains. Meanwhile, the good interfacial bonding between TiN and TiB₂ grains and the uniform dispersion of ultrafine hBN in the matrix contributed to the excellent bending strength. Moreover, the toughening mechanism of crack deflection and grain pull-out improved the fracture toughness.     

Printable and Machinable Dental Restorative Composites for CAD/CAM Application—Comparison of Mechanical Properties,Fractographic, Texture and Fractal Dimension Analysis

Thanks to the continuous development of light-curing resin composites it is now possible to print permanent single-tooth restorations. The purpose of this study was to compare resin composites for milling -Gandio Blocks (GR), Brilliant Crios (CR) and Enamic (EN) with resin composite for 3D printing—Varseo Smile Crown plus (VSC). Three-point bending was used to measure flexural strength (σ_f) and flexural modulus (E_f). The microhardness was measured using a Vickers method, while fractographic, microstructural, texture and fractal dimension (FD) analyses were performed using SEM, optical microscope and picture analysis methods. The values of σ_f ranged from 118.96 (±2.81) MPa for EN to 186.02 (±10.49) MPa for GR, and the values of E_f ranged from 4.37 (±0.8) GPa for VSC to 28.55 (±0.34) GPa for EN. HV01 ranged from 25.8 (±0.7) for VSC to 273.42 (±27.11) for EN. The filler content ranged from 19–24 vol. % for VSC to 70–80 vol. % for GR and EN. The observed fractures are typical for brittle materials. The correlation between FD of materials microstructure and E_f was observed. σ_f of the printed resin depends on layers orientation and is significantly lower than σ_f of GR and CR. E_f of the printed material is significantly lower than E_f of blocks for milling.     

Features of the Structure and Electrophysical Properties of Solid Solutions of the System (1-x-y) NaNbO3-xKNbO3-yCd0.5NbO3

Ferroelectric ceramic materials based on the (1-x-y) NaNbO₃-xKNbO₃-yCd_0.5NbO₃ system (x = 0.05–0.65, y = 0.025–0.30, Δx = 0.05) were obtained by a two-stage solid-phase synthesis followed by sintering using conventional ceramic technology. It was found that the region of pure solid solutions extends to x = 0.70 at y = 0.05 and, with increasing y, it narrows down to x ≤ 0.10 at y = 0.25. Going out beyond the specified concentrations leads to the formation of a heterogeneous region. It is shown that the grain landscape of all studied ceramics is formed during recrystallization sintering in the presence of a liquid phase, the source of which is unreacted components (Na₂CO₃ with T_melt. = 1126 K, K₂CO₃ with T_melt. = 1164 K, KOH with T_melt. = 677 K) and low-melting eutectics in niobate mixtures (NaNbO₃, T_melt. = 1260 K, KNbO₃, T_melt. = 1118 K). A study of the electrophysical properties at room temperature showed the nonmonotonic behavior of all dependences with extrema near symmetry transitions, which corresponds to the logic of changes in the electrophysical parameters in systems with morphotropic phase boundaries. An analysis of the evolution of dielectric spectra made it possible to distinguish three groups of solid solutions: classical ferroelectrics (y = 0.05–0.10), ferroelectrics with a diffuse phase transition (y = 0.30), and ferroelectrics relaxors (y = 0.15–0.25). A conclusion about the expediency of using the obtained data in the development of materials and devices based on such materials has been made.     

Fertility-preserving treatment in patients with early-stage endometrial cancer: A protocol for systematic review and meta-analysis

Background:Endometrial cancer (EC) is the second most common malignancy of the female reproductive system worldwide, and the standard treatment for early-stage EC potentially leads to permanent infertility. The objective of this study was to investigate the efficacies of different methods on fertility preservation in patients with early-stage EC.Methods:We searched the major online databases (PubMed, Embase, The Cochrane Library, and Web of Science) to collect the research literature on fertility preservation therapy in patients with early-stage well-differentiated EC aged ≤ 40 years from January 1999 to October 2019. The inclusion was performed using the R software (version R3.5.3) meta-analysis of a single rate. The efficacy of the following three fertility preservation treatments was evaluated from four aspects, the complete remission rate (CRR), recurrence rate (ReR), pregnancy rate (PregR), and live birth rate (LBR): a) taking oral progestin only therapy, b) hysteroscopic resection combined with progestin/levonorgestrel-releasing intrauterine system (LNG-IUS)/GnRH-a, c) LNG-IUS or combined with progestin/GnRH-a.Results:A total of 23 articles were included in this study, including 446 patients with early-stage EC. In the group that took oral progestin only (n = 279), CRR, ReR, PregR, and LBR were 82% (95% confidence interval [CI], 74%–92%, P = .01), 38% (95% CI, 31%-45%, P = .35), 70% (95% CI, 62%–79%, P = .68), and 63% (95% CI, 55%–73%, P = .55), respectively. Hysteroscopic resection combined with progestin/LNG-IUS/GnRH-a therapy group (n = 96) achieved a CRR, ReR, PregR, and LBR of 95% (95% CI, 90%–100%, P = .42), 16% (95% CI, 6%–39%, P = .03), 84% (95% CI, 73%–96%, P = .39), and 72% (95% CI, 59%–87%, P = .28), respectively. LNG-IUS or combined with progestin/GnRH-a therapy group (n = 91) achieved a CRR, ReR, PregR, and LBR of 69% (95% CI, 54%–89%, P < .01), 30% (95% CI, 19%–49%, P = .36), 48% (95% CI, 18%–100%, P < .01), and 36% (95% CI, 10%–100%, P < .01), respectively.Conclusion:It is safe and effective for young patients with early-stage EC to receive oral progestin, hysteroscopic resection combined with progestin/LNG-IUS/GnRH-a, LNG-IUS, or progestin/GnRH-a.INPLASY Registration number:DOI 10.37766/inplasy2020.12.0137