The half-life of <Superscript>198</Superscript>Au : High-precision measurement shows no temperature dependence

We have measured the half-life of the β -decay of ¹⁹⁸Au in a metallic environment, both at low temperature (19K), and also at room temperature. We find the half-lives at both temperatures to be the same within 0.04%, a finding that contradicts a recent report of a 3.6±1.0 % difference in the ¹⁹⁸Au half-life when measured at essentially the same two temperatures. Our results for the half-life, 2.6949±0.0009 d at room temperature and 2.6953±0.0008 d at 19K, also agree well with previous precision room temperature measurements.     

Bremsstrahlung emission accompanying the α -decay of 214Po

We analyze the bremsstrahlung emission obtained by the α -γ coincidence measurements to investigate on the α -decay dynamics of the ²¹⁴ Po nucleus. We performed the experiment using a radioactive ²²⁶ Ra source leading, by α -decays, to the ²¹⁴ Po nucleus, and the apparatus with the Si detector for α -particles, the NaI(Tl) detector able to collect photons with energies up to about 1 MeV. We compare the experimental data with the quantum-mechanical calculations and find a good agreement between theory and experiment for photon energies up to 765 keV. In the experimental data of the bremsstrahlung spectrum one can see the presence of slight oscillations.     

Decomposition of La- and Dy-rich amorphous alloys

An Al₂₅La₅₀Ni₂₅ and newly discovered Al₃₈Dy₅₀Ni₁₂, Al₃₈Dy₅₀Co₁₂ and Al₄₁Dy₄₇Ni₆Co₆ glasses prepared by melt-spinning were studied by means of electrical resistance (ER) and calorimetric measurements at constant and at linearly increasing temperatures as well as by X-ray diffraction (XRD) and microhardness studies after different heat treatments. Changes in short-range order during relaxation lead to prepeaks in XRD spectra, ER and hardness increases. The glass transitions are accompanied by endothermal heat effects and ER drops. In Al₂₅La₅₀Ni₂₅, crystallisation sets in above 240 °C via the formation of metastable LaNi and AlLa₃ phases which may transform into La(Ni, Al). The Al₃₈Dy₅₀Ni₁₂ glass crystallises only above 400 °C; fine precipitates of Dy₃Ni and probably DyAl appear before a Dy(Ni, Al) phase forms. The Co-containing materials possess still increased stability but are very brittle.     

Pressure-induced crystallization in a bulk amorphous Zr-based alloy

Crystallization of multi-component on amorphous Zr-based alloy (Zr₄₁Ti₁₄Cu_12.5Ni₉Be_22.5C₁) is investigated at different pressures and temperatures. We have previously found that the primary crystallization temperature decreases with increasing pressure below 6 GPa, and the crystallization follows a different process under high pressure when compared to that at ambient pressure. In this work, pressure-induced crystallization is observed by in situ X-ray diffraction (XRD) using synchrotron radiation in a diamond anvil cell at ∼25 GPa and room temperature. This phase transition between amorphous and crystalline is reversible and the crystallized sample returns to the amorphous state during decompression. The mechanism for pressure-induced crystallization is discussed. We suggest that the crystallized phases under high pressure are interstitial solid solution phases formed from the amorphous matrix without long-range atomic rearrangements.     

The effect of Sn addition on the glass-forming ability of Cu-Ti-Zr-Ni-Si metallic glass alloys

The effect of Sn substitution for Ni on the glass-forming ability was studied in Cu₄₇Ti₃₃Zr₁₁Ni_8−xSn_xSi₁ (x=0,2,4,6,8) alloys by using thermal analysis and X-ray diffractometry. With increasing x from 0 to 8, the glass transition temperature, T_g, of melt-spun Cu₄₇Ti₃₃Zr₁₁Ni_8−xSn_xSi₁ alloys increased gradually from 720 to 737 K. On the other hand, the crystallization temperature, T_x, increased from 757 K at x=0 to 765 K at x=2, being nearly same with further increase of x. Partial substitution of Ni by Sn in Cu₄₇Ti₃₃Zr₁₁Ni₈Si₁ promotes the glass formation. Both amorphous Cu₄₇Ti₃₃Zr₁₁Ni_8−xSn_xSi₁ alloys prepared by melt spinning and injection casting showed similar crystallization process during continuous heating in DSC. Temperature range of undercooled liquid region exhibits good correlation with the critical diameter for the formation of an amorphous phase in injection casting.     

Crystallization behaviour of Al-based metallic glasses below and above the glass-transition temperature

The present paper aims to report an effect of a supercooled liquid region on crystallization behaviour of the Al₈₅Y_8−xNd_xNi₅Co₂ metallic glasses produced by rapid solidification of the melt. The paper describes the crystallization process at different regimes of heat treatment. It is found that crystallization behaviour of the above-mentioned Al-based metallic glasses above the glass-transition temperature and below it follows different transformation mechanisms. Formation of the primary nanoscale α-Al particles was observed during continuous heating or after isothermal annealing above the glass-transition temperature. During isothermal annealing below the glass-transition temperature an unknown metastable phase is formed conjointly with α-Al. The metastable phase formed in the Nd-free alloy varies from that in the Nd-bearing alloys. Al₈₅Nd₈Ni₅Co₂ amorphous alloy exhibiting no glass transition crystallizes equally during isothermal calorimetry at different temperatures and during continuous heating.     

Limits of structures and the example of tree semi-lattices

The notion of left convergent sequences of graphs introduced by Lovász et al. (in relation with homomorphism densities for fixed patterns and Szemerédi’s regularity lemma) got increasingly studied over the past $10$ years. Recently, Ne?et?il and Ossona de Mendez introduced a general framework for convergence of sequences of structures. In particular, the authors introduced the notion of $QF$-convergence, which is a natural generalization of left-convergence. In this paper, we initiate study of $QF$-convergence for structures with functional symbols by focusing on the particular case of tree semi-lattices. We fully characterize the limit objects and give an application to the study of left convergence of $m$-partite cographs, a generalization of cographs.     

Preparation of chitosan–silica/PCL composite membrane as wound dressing with enhanced cell attachment

In the present study, the asymmetrical polycaprolactone membranes were synthesized using phase inversion method and modified by addition of Pluronic (F‐127) and sodium hydroxide treatment to improve the cell attachment. The chemical structure, physical properties and mechanical behavior of the membranes as well as cell attachment and proliferation on them were characterized and compared to determine the appropriate membrane used in wound dressing fabrication. Then, a composite membrane as wound dressing capable of drug controlled‐release was prepared composed of two merged layers: an asymmetrical poly(ε‐caprolactone) layer coated with a drug‐loaded chitosan – silica matrix. Drug release behavior and biocompatibility of the final system were evaluated. The results showed that the polycaprolactone modified membrane provides appropriate properties to expand fibroblast cell adhesion and proliferation. This in‐vitro study also showed that the controlled‐release composite wound dressing was developed with approximately 70% cumulative release rate, which provided a porous substrate to support skin cells. Copyright © 2017 John Wiley & Sons, Ltd.     

Alpha decay of the new isotopes 188,189Po

New neutron-deficient isotopes ^188,189Po have been produced in the complete fusion reaction of ⁵²Cr ions with a ¹⁴²Nd target at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of α-γ and α-conversion electron coincidence measurements and of α-α position and time correlations. In ¹⁸⁹Po a ground state to ground state α decay with E_α1= 7540(20) keV, T_1/2= 5(1) ms and two fine structure α-decays at E_α2= 7264(15) keV and E_α3= 7316(15) keV have been observed. In ¹⁸⁸Po (T_1/2= 400⁺²⁰⁰ ₋₁₅₀μs) a ground state to ground state α decay at E_α= 7915(25) keV and a fine structure α decay at E_α= 7350(40) keV have been found. Improved data on the α-decay of ¹⁸⁹Bi were obtained. Received: 15 October 1999