Microstructure and mechanical properties of hot extruded Mg–Al–Mn–Ca alloy produced by rapid solidification powder metallurgy

The microstructure and mechanical properties of hot extruded Mg–Al–Mn–Ca alloy was investigated. Both rapid solidified powders and cast billets were extruded at 573, 623 and 673 K to optimize the processing conditions for obtaining better mechanical response. Powder was consolidated to prepare the extrusion billets using both cold compaction and Spark Plasma Sintering at 473 K. The tensile properties of the extruded alloy were then evaluated and correlated to the observed microstructure. The results show that the use of rapid solidified powder could lead to effective grain refinement, which in turn resulted in the improved mechanical response, especially compared to the extruded conventional cast material.     

Surface investigations using monolayer-resolvable high-resolution Rutherford backscattering spectroscopy

Energy spectra of scattered 0.5 MeV He ions from a clean (001) surface of SnTe are measured with a 90° sector magnetic spectrometer (ΔE/E 0.1%). The ions scattered from successive atomic layers can be resolved in the energy spectra. Inelastic energy losses and charge state distributions of 0.5 MeV He ions scattered from the topmost atomic layer of the SnTe(001) are measured. A position-dependent stopping power at the surface is proposed from the observed energy losses. The observed charge state distribution shows the importance of the charge-exchange processes with valence electrons in the tail of the electron distribution at the surface.     

Effect of Surface Flaw Size on Fracture Strength of Alumina Ceramics

Semielliptical surface flaws of different sizes were introduced into Al₂O₃ by Knoop microhardness indentation. The specimens were fractured by four-point bending and the profiles of the indentation flaws were determined by observing the fracture surfaces with a scanning electron microscope. The relation between the indentation flaw size and the fracture strength could be well explained by applying the fracture-mechanics analysis for semielliptical surface flaw in bending. The calculated values of the as-indented critical stress intensity factor, K_IC, were lower than previously reported presumably because of the influence of the residual stresses produced by the indenter.     

An Investigation of Microstructure and Phase Transformation Behavior of Cu40Zn-1.0 wt.% Ti Brass Via Powder Metallurgy

The effects of Ti addition on phase transformation, precipitation behavior, and microhardness response of Cu40Zn brass were investigated at elevated heat treatment (HT) temperatures using the powder metallurgy method. The volume fraction of the α phase increased with the elevated temperatures, which showed an equal value as that of the β phase at 400 °C, and reached a maximum value of 55.9% at 500 °C. The solid solubility of Ti in Cu40Zn brass matrix decreased as the HT temperature increased. Supersaturated Ti showed high chemical potential for precipitates' reaction in Cu40Zn brass. Lower HT temperature retained higher Ti solid solubility and fine precipitates. The precipitates presented in form of Cu₂TiZn intermetallic compound, distributing uniformly in brass matrix which suppressed the phase and grain growth. After HT at elevated temperature, the precipitates coalesced, grew coarser, and segregated at the primary particle boundaries. The microhardness of the BS40-1.0Ti compact was primarily not only dependent on the solid solubility of Ti, but also dependent on the phase volume fraction of the α and β phases.     

Towards a Treatment for Neuroinflammation in Epilepsy: Interleukin-1 Receptor Antagonist,Anakinra, as a Potential Treatment in Intractable Epilepsy

Febrile Infection-Related Epilepsy Syndrome (FIRES) is a unique catastrophic epilepsy syndrome, and the development of drug-resistant epilepsy (DRE) is inevitable. Recently, anakinra, an interleukin-1 receptor antagonist (IL-1RA), has been increasingly used to treat DRE due to its potent anticonvulsant activity. We here summarized its effects in 38 patients (32 patients with FIRES and six with DRE). Of the 22 patients with FIRES, 16 (73%) had at least short-term seizure control 1 week after starting anakinra, while the remaining six suspected anakinra-refractory cases were male and had poor prognoses. Due to the small sample size, an explanation for anakinra refractoriness was not evident. In all DRE patients, seizures disappeared or improved, and cognitive function improved in five of the six patients following treatment. Patients showed no serious side effects, although drug reactions with eosinophilia and systemic symptoms, cytopenia, and infections were observed. Thus, anakinra has led to a marked improvement in some cases, and functional deficiency of IL-1RA was indicated, supporting a direct mechanism for its therapeutic effect. This review first discusses the effectiveness of anakinra for intractable epileptic syndromes. Anakinra could become a new tool for intractable epilepsy treatment. However, it does not currently have a solid evidence base.     

Effect of oxygen partial pressure on the high-temperature oxidation of CVD SiC

The oxidation behavior of chemically vapor-deposited silicon carbide (CVD SiC) was studied at 1670-2010 K in O₂-Ar and CO₂-Ar. The oxidation kinetics in O₂-Ar was parabolic or linear parabolic, and was parabolic in CO₂-Ar. The activation energy for the parabolic rate constants (k_p) was 210-220 kJ/mol in O₂-Ar, and was 290-300 kJ/mol in CO₂-Ar. The oxygen partial pressure (P_O2) dependence of k_p was expressed as k_p∝ (P_O2)ⁿ, where n=0.08-0.13 and 0.37-0.53 in O₂-Ar and CO₂-Ar, respectively. Bubbles were formed at more than 1985 K and P_O2>5 kPa. The bubble formation temperature decreased with decreasing P_O2 at P_O2<5 kPa.     

4-Hydroxyderricin from Angelica keiskei roots induces caspase-dependent apoptotic cell death in HL60 human leukemia cells

The ethyl acetate (EtOAc)-soluble fraction of a methanol extract of Angelica keiskei roots exhibited cytotoxic activity against 4 human tumor cell lines, HL60 (leukemia), CRL1579 (melanoma), A549 (lung), and AZ521 (stomach). Nine chalcones (1-9), 5 coumarins (10-14), and 4 flavanones (15-18), isolated from the EtOAc-soluble fraction, were examined for their cytotoxic activities in the 4 human tumor cell lines. Among the compounds tested, 4-hydroxyderricin (2), a major chalcone constituent, exhibited potent cytotoxic activities in all 4 tumor cell lines with IC(50) values of 5.5 μM (HL60), 4.8 μM (CRL1579), 10.2 μM (A549), and 4.2 μM (AZ521). 4-Hydroxyderricin induced early apoptosis in HL60 cells, observed as membrane phospholipid exposure in flow cytometry. Western blot analysis showed that 4-hydroxyderricin markedly reduced the levels of procaspases-3, -8, and -9, while increasing the levels of cleaved caspases-3, -8, and -9. In addition, 4-hydroxyderricin exhibited potent inhibitory activity on human DNA topoisomerase (Topo) II (IC(50) 21.9 μM). These results suggested that 4-hydroxyderricin induces apoptotic cell death in HL60 via both the death receptor-mediated pathway and the mitochondrial pathway by, at least in part, Topo II inhibition. 4-Hydroxyderricin may therefore hold promise as an effective antitumor agent.     

Synthesis of single-walled carbon nanotubes by an arc-discharge method using selenium as a promoter

Single-walled carbon nanotubes (SWCNTs) with high purity and very narrow diameter distribution have been synthesized using the dc arc-discharge method with Y–Ni alloy as catalyst and selenium (Se) as promoter. The SWCNTs show a very narrow diameter distribution mainly at about 1.5 nm, and can further be readily purified up to >99% purity with traditional purification including HNO₃ reflux and air oxidation. The key factor of the wetting effect of Se in the SWCNTs growth improvement process is proposed and discussed. Moreover, a new less-destructive purification method including electrolysis, air-oxidation and centrifugation has been introduced, and SWCNTs with semiconducting content up to 94% have been produced through density gradient ultracentrifugation method.