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[en] Spiral lattices are derived by allowing growing discs to aggregate under a close-packing rule. Both Fibonacci and Lucas numbers of visible spirals arise naturally, dependent only on the choice of growth centre. Both the rate of convergence towards an ideal spiral, and chirality, are determined by the initial placement of the first few discs (initial conditions). Thus the appearance of spiral packings is no more or less mysterious than the appearance of hexagonal packed arrays of equal discs
[en] We study the net chirality created by the Dzyaloshinkii-Moriya interaction (DMI) at the boundary between hexagonal layers of magnetic and non-magnetic materials. It is shown that another mechanism besides elastic torsion is required to understand the change in chirality observed in Dy/Y multilayers during field-cooling. The paper shows that due to the overlap between magnetic and non-magnetic atoms, interfacial steps may produce a DMI normal to the interface in magnetic heterostructures.
[en] Connecting three zigzag graphene nanoribbons (ZGNRs) together through the sp3 hybrid bonds forms a star-like ZGNR (S-ZGNR). Its band structure shows that there are four edge states at k = 0.5, in which the three electrons distribute at three outside edge sites, and the last electron is shared equally (50%) by two sites near the central site. The lowest conductance step in the valley is 2, two times higher than that of monolayer ZGNR (M-ZGNR). Furthermore, in one quasi-three-dimensional hexagonal lattice built, both of the Dirac points and the zero-energy states appear in the band structure along the z-axis for the fixed zero k-point in the x–y plane. In addition, it is an insulator in the x–y plane due to band gap 4 eV, however, for any k-point in the x–y plane the zero-energy states always exist at k z = 0.5. (paper)
[en] We study the formation and interaction of discretons, solitary waves with an almost compact support (tails decaying at a super-exponential rate), on a hexagonal lattice and its spatial extension. Discretons are shown to be robust and their interaction though not entirely, is quite clean.
[en] Long-range diffusion of the substitutional impurity in the otherwise monoatomic hcp-like lattices (H1 type) via the monovacancy mechanism has been considered within the encounter approximation. A five-frequency model (valid for cubic lattices) extends here naturally into a sixteen-frequency model, leaving fourteen normalized frequencies, the latter describing an anisotropic part of the self-correlation function. Two simplified cases can be distinguished: A self-diffusion being described by a single normalized frequency and a true hcp lattice, where only three normalized frequencies remain independent of each other. A general formalism is discussed and a few examples are evaluated numerically. (orig.)
[en] In the present work, we consider the electronic properties of graphene with Kekule structure formed from two different C–C bonds in its hexagonal lattice. When the C–C bond alternation was introduced, a small band gap has been opened in the band structure of graphene and it increases linearly by a difference in the bond lengths δ. While the applied strain along the zigzag or armchair direction causes band gap to decrease rapidly to zero, the strain in the other directions can increase the band gap. Interestingly, when the graphene with Kekule structure is strained, its band gap is inversely proportional to the bond length difference δ. Opening a band gap in graphene due to bond alternation and strain can open up new applications in nanoelectronic devices. (paper)
[en] The transcriptionally active forms of p73 are capable of inducing apoptosis, and the isoforms termed TAp73 are important players when E2F and its oncogenic activators induce programmed cell death. However, the conditions under that TAp73 can kill a cell remain to be clarified. Recently, it has been found that p73 proteins are not merely floating in the nucleoplasm but rather can associate with specific compartments in the cell. Examples of intranuclear compartments associated with p73 proteins include the PML oncogenic domains and the nuclear matrix. In addition, p73 is found in the cytoplasm. It remains to be seen whether p73 might also associate with mitochondria, in analogy with p53. The relocalization of p73 is expected to be mediated by specific binding partners, mostly other proteins. Here, we discuss the possibility that the compartmentalization of p73, and the cooperation with the corresponding binding partners, might decide about its apoptosis-inducing activity
[en] It has been found that LiI films evaporated on SiO2 substrates at pressures lower than 10-3 Torr exhibit hexagonal type structure (for film thickness at least up to 50 μm) as confirmed by the X-ray analysis data. The electrical conductivity of these films was studied as a function of temperature and thickness. An irreversible structural transition from hexagonal to the ordinary cubic phase wast detected at about 85 C, accompanied by a hump on the conductivity curve. The activation energy of the hexagonal phase was equal to ∼0.5 eV. The character of the frequency dependence of the ac conductivity indicates that the main contribution comes from ionic transport in polycrystalline grains. 9 refs.; 4 tabs