[en] Transmission electron microscopy (TEM) and density functional theory (DFT) calculations were employed to investigate the interfacial characteristics and fracture behavior of Al–3Cu–2Li containing plate-like Al_2CuLi (known as the T_1 phase) precipitates at grain boundaries. TEM studies showed that T_1 plates form at grain boundaries, with a coherent interface on one side parallel to the {1 1 1} planes of the matrix and a non-coherent interface with no preferred orientation relative to the grain on the other side. The low energy of the coherent interface leads to a serration of the grain boundaries due to the growth of the grain boundary T_1 phase. Under tensile loading, the intergranular T_1 phase leads to the formation of nanopores at the non-coherent side, and fracture mostly through the non-coherent grain boundary T_1/matrix interface for under-, peak- and overaged conditions. DFT simulations showed that, under tensile loading, fracture is most likely to take place at the T_1/Al interface, and the non-coherent side of the grain boundary is weakest as the decohesion energy is 25% lower than that of the coherent interface

[en] Transmission electron microscopy was employed to investigate the configuration of dislocations emitted by a sharp crack in Al 1100 and Ni base superalloy in part to understand the role of different stacking fault energies. A dislocation free zone and a plastic zone were observed ahead of the cracks in both cases with different dislocation configurations. The experimentally measured values of these zones are in reasonably good agreement with models of crack-dislocation configuration based on a continuum distribution of dislocations ahead of the crack. However, these models fail to predict the total number of emitted dislocations in both cases, underlying the need for better analytical models

[en] Microstructural evolution has been investigated as a function of substrate temperature in Ge-4 at.%Cr films grown by molecular beam epitaxy (MBE), by employing transmission electron microscopy (TEM); the TEM results have been correlated to the magnetic properties. Magnetometry measurements show that samples grown at substrate temperatures of 200 deg. C and above are paramagnetic. Significantly different microstructures have been shown to evolve, depending on the substrate temperature (T_s) during MBE growth. For T_s=200 deg. C, the film consists of elongated rods, or 'noodles' of the equilibrium Cr₁₁Ge₁₉ phase. For T_s=400 deg. C, a nanodispersion of metastable Cr₁₁Ge₈ equiaxed precipitates form within the Ge-matrix. It is thus proposed that for T_s=400 deg. C a supersaturated Ge-Cr solid-solution is initially formed from the vapor phase, followed by solid-state precipitation. At T_s=200 deg. C, precipitation analogous to a cellular/discontinuous transformation results in the formation of cooperatively grown rod-like or noodle shaped microstructures

[en] A significant lattice rotation in the plastic zone of a fatigue crack at room temperature in highly oriented Al 1100 and Al 7075 alloys has been observed by employing X-ray diffraction (XRD) and transmission electron microscopy (TEM). The intensity of 111 peak gradually increases as compared to the intensity of 200 peak as we approach the crack, suggesting lattice rotation. The texture was seen to change gradually from nearly cubic, away from the crack, to a more random orientation close to the crack. We ascribe the lattice rotation to the increase in dislocation density in the plastic zone. The estimated average angle of rotation is approximately 11°, which is sufficient to disturb the cube texture close to the crack. In addition, the observed plastic zone, as estimated by the lattice rotation, is order of magnitude higher as compared to the theoretically predicted plastic zone. This is of great importance, as it leads to a new insight of the underlying physics of the deformation process in the plastic zone under cyclic loading.

[en] Four halogenated estrogen analogs - o-fluorohexestrol, and 1-fluoro-, 1-bromo-, and 1-iodohexestrol - have been prepared and tritium-labeled in high specific activity, to investigate their potential as estrogen-receptor-based agents for imaging breast tumors. These compounds bind with high affinity in vitro to the cytoplasmic uterine estrogen receptor from rat and lamb and sediment as 8S receptor complexes on sucrose gradients. After 1 hr in immature rats, these compounds show high uptake into the uterus, but low uptakes (10 to 25% of the uterine levels) into most nontarget tissues. The uterine uptake is estrogen specific since it is depressed by excess nonradioactive estradiol. Uptake selectivity is greatest for the fluorohexestrols and decreases for the bromo and iodo compounds. In mature rats bearing DMBA-induced mammary tumors, selective uptake by the uterus and tumors is seen with 1-fluoro[³H₄]hexestrol and o-fluoro[³H₃]hexestrol. The studies indicate that these four halogenated hexestrols are promising candidates as estrogen-receptor-based agents for the imaging of human breast tumors

[en] Erythro-1-dehydrohexestrol, an analog of the non-steroidal estrogen meso-hexestrol containing a double bond in the side chain, has been synthesized as a general precursor for the preparation of tritium-labeled hexestrol derivatives. It can be functionalized further as needed, and upon catalytic hydrogenation with tritium gas , it furnishes the desired erythro or meso diastereomer of the hexestrol derivatives. Its use is exemplified in the synthesis of ³H-o-azidohexestrol with high specific activity. (author)

[en] Influence of pH and that of added lattice and certain non-lattice ions has been studied towards instantaneous sorption of tracer ⁵¹CrO₄^2- ionic species on iodates of lead, barium and strontium. Carrying is postulated to take place by surface adsorption. In the presence of lattice ions, the mode of deposition is in accordance with the adsorptions rules. However, the presence of certain nonlattice cations with similar charge and ionic dimensions produces different types of behavior. Thus, it has been found that addition of Ba²⁺ or Sr²⁺ ions causes the carrying to fall on Pb(IO₃)₂ surface, Pb²⁺ ions on Ba(IB₃)₂carrier show the helpful role whereas Sr²⁺ ions suppress the carrying. Both Pb²⁺ and Ba²⁺ ions augment the deposition on the surface of Sr(IO₃)₃. An attempt has been made to explain these findings as a consequence of postulated masking of active adsorption centres on Pb(IO₃)₂ and Ba(IO₃)₂ surfaces under the given experimental conditions. (author)

[en] Short communication. 2 refs., 1 fig

[en] The level scheme of ⁶⁵Ga has been studied up to an excitation energy of 7035.3 keV and spin-parity values of (27/2⁺). Gamma-ray singles, γγ-coincidences, angular distributions and Doppler shift attenuation have been measured in the reaction ⁶³Cu(α, 2nγ) at 30 MeV. The spin and parity (J^π) assignments for several states belonging to the previously known bands are confirmed. The mean life and the parity of the 2814.7 keV state, hitherto unknown, are reported. The J^π for the 3733.2 keV state is proposed to be 15/2⁺ on the basis of angular distribution data and its decay characteristic to the lower-lying states. Experimental evidence is presented in favour of the 3733.2 keV state of being a band head for a rotation-like ΔΙ=2 positive-parity band with the excited members at 4547.5, 5643.5 and 7035.3 keV. The deduced B(E2) results indicate the presence of appreciable collectivity in the other positive-parity band built on the 9/2⁺, 2037.3 keV state. These bands in ⁶⁵Ga are discussed and compared with similar bands in the neighbouring odd-A nucleus ⁶⁷Ga

[en] The solid phase epitaxial growth of 3C–SiC, 2–5 nm thick, on (0 0 1) Si by annealing 1–2 nm carbon overlayers has been investigated by transmission electron microscopy and X-ray photoelectron spectroscopy. High-temperature annealing in the range of 850–950 °C results in solid phase cube-on-cube epitaxial growth of SiC films. This is accompanied by the formation of nanopores below the SiC epilayer in the Si substrate. Such nanopores, formed with truncated octahedron morphology consisting of {1 1 1} and (0 0 1) facets, are annihilated by diffusion of Ge deposited onto the SiC surface. It was also observed that the Ge islands on top of SiC exhibit a cube-on-cube orientation relation with SiC and the Ge overlayer reduces the density of faults in SiC considerably