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OBJECTIVES: The aim of the study was to analyze the perinatal outcome of twin gestations and estimate the influence of chorionicity on the outcome in a large cohort of twin pregnancies in Poland. MATERIAL AND METHODS: A retrospective analysis of 465 twin deliveries in 6 Polish centers in 2012 was conducted. Baseline characteristics, the course of pregnancy and labor, as well as the neonatal outcome were analyzed in the study group and according to chorionicity. RESULTS: A total of 356 twin pregnancies were dichorionic (DC group) (76.6%), and 109 were monochorionic (MC group) (23.4%). There were no differences in the occurrence of pregnancy complications according to chorionicity, except for IUGR of at least one fetus (MC 43.1% vs. DC 34.6%; p = 0.003). 66.5% of the women delivered preterm, significantly more in the MC group (78% vs. 62.9%; p = 0.004). Cesarean delivery was performed in 432 patients (92.9%). Mean neonatal birthweight was statistically lower in the MC group (2074 g vs. 2370 g; p < 0.001). Perinatal mortality of at least one twin was 4.3% (2.8% in the DC group vs. 9.2% in the MC group; p = 0.004). Neonatal complications, including NICU admission, respiratory disorders, and infections requiring antibiotic therapy, were significantly more often observed among the MC twins. CONCLUSIONS: The overall perinatal outcome in the presented subpopulation of Polish twins and its dependence on cho-rionicity is similar to the reports in the literature. Nevertheless, the rates of preterm and cesarean deliveries remain higher. It seems that proper counselling of pregnant women and education of obstetricians may result in reduction of these rates.
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Córion , Gravidez de Gêmeos/fisiologia , Gêmeos Dizigóticos , Gêmeos Monozigóticos , Adulto , Peso ao Nascer , Cesárea/estatística & dados numéricos , Córion/patologia , Córion/fisiopatologia , Feminino , Humanos , Recém-Nascido , Parto/fisiologia , Mortalidade Perinatal , Polônia/epidemiologia , Gravidez , Resultado da Gravidez/epidemiologiaRESUMO
The perovskite-structured materials Pb0.75Ba0.251-xCax(Zr0.7Ti0.3)O3 for x = 1 and 2 at.% were synthesized using the conventional mixed-oxide method and carbonates. Microstructural analysis, performed using a scanning electron microscope, revealed rounded grains with relatively inhomogeneous sizes and distinct grain boundaries. X-ray diffraction confirmed that the materials exhibit a rhombohedral structure with an R3c space group at room temperature. Piezoelectric resonance measurements were conducted to determine the piezoelectric and elastic properties of the samples. The results indicated that a small amount of calcium doping significantly enhanced the piezoelectric coefficient d31. The calcium-doped ceramics exhibited higher electrical permittivity across the entire temperature range compared to the pure material, as well as a significant value of remanent polarization. These findings indicate that the performance parameters of the base material have been significantly improved, making these ceramics promising candidates for various applications.
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Th-containing superconducting high entropy system with the nominal composition (NbTa)[Formula: see text](MoWTh)[Formula: see text] was synthesized. Its structural and physical properties were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, specific heat, resistivity and magnetic measurements. Two main phases of alloy were observed: major bcc structure and minor fcc. The experimental results were supported by numerical simulation by the DFT Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA).
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A series of Bi1-xLaxFeO3 samples with 0.00 ≤ x ≤ 0.30 was synthesized by the sol-gel method. The effects of lanthanum concentration on the phase formation, microstructure and cycloidal spin ordering were studied using X-ray diffraction, scanning electron microscopy and Mössbauer spectroscopy. The crystal structure of the La-doped bismuth ferrite transformed from rhombohedral R3c (x ≤ 0.05) to a mixture of R3c and cubic Pm3m (0.07 ≤ x ≤ 0.15) and finally to a mixture of R3c, Pm3m and orthorhombic Pbam (0.20 ≤ x ≤ 0.30). The Pbam phase, with characteristic porous microstructure shown by microscopy images, was observed in Bi1-xLaxFeO3 compounds for the first time. Based on the Mössbauer spectroscopy, it was found that the cycloidal spin ordering started to disappear at x = 0.07. With increasing La concentration the share of the cycloid decreased from 100% at 0.00 ≤ x ≤ 0.05 to 0% at x = 0.30. At the beginning, for x ≤ 0.02, the anharmonicity parameter, m, of the cycloidal spin ordering was about 0.5, which is typical of a pure BiFeO3 compound. In the range 0.05 ≤ x ≤ 0.25, the m parameter was of the order of 0.1, which indicated the practically harmonic character of the cycloid. The structural transition at x = 0.07 was accompanied by a substantial increase in magnetization.
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HYPOTHESIS: Fe(CO)5 was deposited on SBA-15 from gaseous phase and the adsorbed iron precursor was oxidized and hydrolyzed. We hypothesize that a novel method produces composites of unique and useful properties. The absence of sulfur and halides in the composites is of special importance with respect of their potential application as catalysts and catalyst supports. EXPERIMENTS: We obtained composites containing 1.3-157.5% of iron oxide with respect to silica (counted as 100%). The new materials were characterized by specific surface area, XRD (X-ray diffraction), Mossbauer spectroscopy, electron microscopy coupled with EDS (energy dispersive X-Ray spectroscopy), and microelectrophoresis. FINDINGS: In the composites low in iron (<57% of iron oxide) the Mossbauer spectra showed only doublets, which were interpreted as tiny nanoparticles of Fe(III) oxide in the pores of SBA-15. In the composites high in iron (>65%) the Mossbauer spectra showed doublets and sextets. The later were interpreted as larger nanocrystals of hematite, and the presence of such nanocrystals was confirmed by XRD. EDS confirmed that in the composites low in iron, iron oxide was evenly distributed in the entire volume of pores of SBA-15.
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Compostos Férricos , Dióxido de Silício , Catálise , Compostos de FerroRESUMO
Li-ion batteries are widely used as energy storage devices due to their excellent electrochemical performance. The cubic Li7La3Zr2O12 (c-LLZO) compound is regarded as a promising candidate as a solid-state electrolyte for lithium-ion batteries due to its high bulk Li-ion conductivity, excellent thermal performance, and chemical stability. The standard manufacturing procedure involves the high-temperature and lengthy annealing of powders. However, the formation of the tetragonal modification of LLZO and other undesired side phases results in the deterioration of electrochemical properties. The mechanical milling of precursor powders can enhance the powders' reactivity and can result in an easier formation of c-LLZO. The aim of this work was to study the influence of selected milling and annealing parameters on c-LLZO compound formation. The starting powders of La(OH)3, Li2CO3, and ZrO2 were subjected to milling in various ball mills, under different milling conditions. The powders were then annealed at various temperatures for different lengths of times. These studies showed that the phase transformation processes of the powders were not very sensitive to the milling parameters. On the other hand, the final phase composition and microstructure strongly depended on heat treatment conditions. Low temperature annealing (750 °C) for 3 h produced 90% of c-LLZO in the powder structure.
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Solid-state sintering method was used to prepare ceramic materials based on bismuth ferrite, i.e., (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions and the Aurivillius Bi5Ti3FeO15 compound. The structure of the materials was examined using X-ray diffraction, and the Rietveld method was applied to phase analysis and structure refinement. Magnetoelectric coupling was registered in all the materials using dynamic lock-in technique. The highest value of magnetoelectric coupling coefficient α ME was obtained for the Bi5Ti3FeO15 compound (α ME ~ 10 mVcm(-1) Oe(-1)). In the case of (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions, the maximum α ME is of the order of 1 and 2.7 mVcm(-1) Oe(-1), respectively. The magnitude of magnetoelectric coupling is accompanied with structural transformation in the studied solid solutions. The relatively high magnetoelectric effect in the Aurivillius Bi5Ti3FeO15 compound is surprising, especially since the material is paramagnetic at room temperature. When the materials were subjected to a preliminary electrical poling, the magnitude of the magnetoelectric coupling increased 2-3 times.
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INTRODUCTION: Ultrasonography is used routinely during pregnancy to screen and detect fetal abnormalities. However, there are some conditions like anhydramnios (a prevalent state in renal agenesis) or maternal obesity that may limit the diagnostic accuracy of ultrasonography. Magnetic resonance imaging has proven to be useful when ultrasound alone is insufficient to make a correct diagnosis. CASE PRESENTATION: We present the case of a 22-year-old Caucasian woman who was admitted to our unit at the 26th week of gestation for a detailed anatomy scan. Anhydramnios and failure to visualize the kidneys, bladder and renal vessels were confirmed with the use of sonography in our department. Since the lack of amniotic fluid limited the acoustic window for fetal ultrasonography, a magnetic resonance imaging scan was requested to confirm suspected renal agenesis. A fetal magnetic resonance imaging scan was performed and confirmed the suspected diagnosis. A baby boy was born by breech vaginal delivery after spontaneous onset of labor at the 34th week of gestation. The boy weighed 1690g, with Apgar scores of 6 and 4 at two and five minutes respectively, and died one hour after delivery. The diagnosis of bilateral renal agenesis was confirmed on autopsy. CONCLUSIONS: The aim of this study was to evaluate the potential contribution of magnetic resonance imaging in diagnostic procedure after inconclusive ultrasound examination during the assessment of fetal urinary tract abnormalities in the third trimester.