Effect of MnO2 on the dielectric and piezoelectric properties of alkaline niobate based lead free piezoelectric ceramics

Lead free ferroelectric ceramics of the KNN–LiTaO₃–LiSbO₃ system were prepared using the mixed oxide route. This work reports the effect of doping (K_0.44Na_0.52Li_0.04)(Nb_0.86Ta_0.1Sb_0.04)O₃ produced through the conventional solid state sintering method with different amounts of MnO₂. With 1 mol% of the dopant, ～96.5% of the theoretical density of the ceramics was achieved while grain growth inhibition was attained through pinning of the grain boundary movement. A polymorphic phase transition (PPT) was induced in the ceramic from the orthorhombic crystal structure to the tetragonal structure with increasing dopant amount. At lower temperatures, the doped samples had higher epsilon values but there was a decrease in both T_c (from 333 °C to 249 °C) and epsilon value at T_c (from ≈9500 to <6000). At temperatures below 300 °C however, the loss tangent in the doped samples (≈2.5 mol%) was much lower and steady when compared to the undoped one. The ferroelectric properties were slightly lowered with the addition of MnO₂. The remnant polarisation (P_r) was lowered from ～18 μC/cm² to ～9 μC/cm², the coercive field (E_c) from ～8.5 kV/cm to ～6.2 kV/cm and the piezoelectric charge coefficient (d₃₃) decreased as well.     

Dexamethasone adjunctive therapy for bacterial meningitis in children: a retrospective study in Brazil

Contribution of a case report of megacalycosis in a nine and a half-year old male child, in whom the disorder was diagnosed by our team when he was only four. The intense colic pains experienced by the child together with the isotopic renogram non responsive to seguril typical of obstruction, raised the diagnosis of superimposed stenosis of the pyeloureteral attachment. As a result, an Anderson-Hynes pyeloplasty was performed. Post-operative status after four years is absolutely normal from both a clinical and scintiscan point of view.     

TGF-alpha sustains clonal expansion by promoter-dependent, chemically initiated rat hepatocytes

A series of promoting and non-promoting barbiturates and hydantoins were examined for their ability to sustain the growth of a phenobarbital (PB)-dependent hepatocyte line in cell culture. The effective liver tumor promoters, pentobarbital, allobarbital and 5-ethyl-5-phenylhydantoin, replaced PB and supported 6/27C1 hepatocyte colony formation in vitro at 52-87% of the level induced by PB. The weak promoters secobarbital and amobarbital supported colony formation at only 11-19% of the PB control. A significant correlation was observed for in vivo and in vitro promotion activities of barbiturates and hydantoins, indicating that clonal expansion by 6/27C1 hepatocytes was promoter-dependent. Cell density also appeared to influence hepatocyte growth in vitro. Hepatocyte colonies acquired the ability to grow in the absence of PB, such that after 10 days incubation with PB, approximately 50% of colonies continued to grow in the absence of promoter. This phenomenon of clone-size-dependent hepatocyte growth suggested the operation of an autocrine growth factor pathway. Addition of the hepatocyte mitogen and autocrine growth factor, transforming growth factor-alpha (TGF-alpha), to culture medium lacking PB induced a dose-dependent increase in 6/27C1 hepatocyte colony formation. At the optimal concentration of 3 ng/ml, TGF-alpha sustained hepatocyte clonal expansion at 84% of the level induced by 2 mM PB. Individual 6/27C1 colonies that grew from single cells in the presence of TGF-alpha were tested for promoter-dependent colony formation. Either PB or TGF-alpha supported colony formation by these cells at similar levels and when combined at optimal concentrations, the response appeared to be saturated. When these factors were tested in combination at suboptimal concentrations, the two compounds were additive for supporting colony formation by the parental 6/27C1 line. The ability of TGF-alpha to replace PB and sustain hepatocyte clonal expansion was confirmed with the tumorigenic 6/15 hepatocyte line. These results suggest that TGF-alpha and PB may promote hepatocarcinogenesis by stimulating a common signal transduction pathway.     

反向凝固结晶器中流动与传热的计算机仿真研究

建立了描述反向凝固结晶器中流动与传热的数学模型，并在此模型基础上进行了计算机模拟和仿真。结果表明了反向凝固工艺母带增长的三阶段规律，即快速增长、平衡相持和快速回熔。通过比较母带厚度的实验值和模拟值，验证了模型的正确性。     

车轴坯皮下夹杂的改善与控制

阐述了车轴坯皮下夹杂的分布，组成，形态及形成原因，据此采取了切实可行的改进措施，改善了车轴坯的皮下夹杂，稳定了车轴坯质量，使车轴坯磁探废品率控制在2％以下。