1,344 research outputs found
Combined effect of frustration and dimerization in ferrimagnetic chains and square lattice
Within the zero-temperature linear spin-wave theory we have investigated the
effect of frustration and dimerization of a Heisenberg system with alternating
spins and on one- and two-dimensional lattices. The combined
effect most visibly appears in the elementary excitation spectra. In contrast
to the ground state energy that decreases with dimerization and increases with
frustration, the excitation energies are shown to be suppressed in energy by
both dimerization and frustration. The threshold value of frustration that
signals a transition from a classical ferrimagnetic state to a spiral state,
decreases with dimerization, showing that dimerization further helps in the
phase transition. The correlation length and sublattice magnetization decrease
with both dimerization and frustration indicating the destruction of the
long-range classical ferrimagnetic. The linear spin wave theory shows that in
the case of a square lattice, dimerization initially opposes the
frustration-led transition to a spiral magnetic state, but then higher
magnitudes of lattice deformation facilitate the transition. It also shows that
the transition to spiral state is inhibited in a square lattice beyond a
certain value of dimerization.Comment: 8 pages, latex, 12 postscript figure
Prenatal inhibition of the tryptophan–kynurenine pathway alters synaptic plasticity and protein expression in the rat hippocampus
Glutamate receptors sensitive to N-methyl-d-aspartate (NMDA) are important in early brain development, influencing cell proliferation and migration, neuritogenesis, axon guidance and synapse formation. The kynurenine pathway of tryptophan metabolism includes an agonist (quinolinic acid) and an antagonist (kynurenic acid) at these receptors. Rats were treated in late gestation with 3,4-dimethoxy-N-[4-(3-nitrophenyl)thiazol-2-yl]-benzene-sulphonamide (Ro61-8048), an inhibitor of kynurenine-3-monoxygenase which diverts kynurenine metabolism to kynurenic acid. Within 5 h of drug administration, there was a significant decrease in GluN2A expression and increased GluN2B in the embryo brains, with changes in sonic hedgehog at 24 h. When injected dams were allowed to litter normally, the brains of offspring were removed at postnatal day 21 (P21). Recordings of hippocampal field excitatory synaptic potentials (fEPSPs) showed that prenatal exposure to Ro61-8048 increased neuronal excitability and paired-pulse facilitation. Long-term potentiation was also increased, with no change in long-term depression. At this time, levels of GluN2A, GluN2B and postsynaptic density protein PSD-95 were all increased. Among several neurodevelopmental proteins, the expression of sonic hedgehog was increased, but DISC1 and dependence receptors were unaffected, while raised levels of doublecortin and Proliferating Cell Nuclear Antigen (PCNA) suggested increased neurogenesis. The results reveal that inhibiting the kynurenine pathway in utero leads to molecular and functional synaptic changes in the embryos and offspring, indicating that the pathway is active during gestation and plays a significant role in the normal early development of the embryonic and neonatal nervous system
Human Resource Planning: Sector Specific Considerations
The aim of human resource planning (HRP) is to have the right people in the right place at the right time. While the public sector has moved from a civil service to a human resources paradigm, the literature indicates a lack of successful HRP implementation in this sector. This paper explores key issues around HRP in the public sector. Evidence suggests that effective HRP is critical to meeting internal and external organisational challenges, however, relevant processes and practices do not seem to be strategic or integrated in the public sector. If not addressed, the absence of HRP in the public sector can lead to poor organisational performance, increased costs, a lack of continuity and other negative impacts
Coping Strategies of Jordanian Adolescents With Cancer: An Interpretive Phenomenological Analysis Study
Interpretive phenomenological analysis methodology was used to explore coping strategies used by hospitalized Jordanian adolescents with cancer. In-depth face-to-face interviews were conducted with 10 Jordanian adolescents, aged 13 to18 years, who were receiving chemotherapy for cancer. During treatment, participants were confronted with physical, psychosocial, and emotional distresses resulting from the disease process, the treatment, and its associated side-effects. To cope with the impact of their illness, participants utilized 4 coping strategies: "Strengthening spiritual convictions," "Being optimistic and rebuilding hope," "Enhancing appearance," and "Finding self again." The findings of this study can assist health team members to promote positive psychological care to Arab Muslim adolescents with cancer in a supportive and therapeutic treatment environment
Single-crystal growth and dependences on the hole concentration and magnetic field of the magnetic ground state in the edge-sharing CuO chain system CaYCuO
We have succeeded in growing large-size single-crystals of
CaYCuO with and measured the
magnetic susceptibility, specific heat and magnetization curve, in order to
study the magnetic ground state in the edge-sharing CuO chain as a function
of hole concentration and magnetic field. In , it has been
found that an antiferromagnetically ordered phase with the magnetic easy axis
along the b-axis is stabilized and that a spin-flop transition occurs by the
application of magnetic fields parallel to the b-axis. The antiferromagnetic
transition temperature decreases with increasing and disappears around 1.4. Alternatively, a spin-glass phase appears around . At where the hole concentration is 1/3 per Cu, it appears that a
spin-gap state is formed owing to the formation of spin-singlet pairs. No sign
of the coexistence of an antiferromagnetically ordered state and a spin-gap one
suggested in CaCuO has been found in
CaYCuO.Comment: 13 pages, 12 figures, 1 tabl
Moving walls accelerate mixing
Mixing in viscous fluids is challenging, but chaotic advection in principle
allows efficient mixing. In the best possible scenario,the decay rate of the
concentration profile of a passive scalar should be exponential in time. In
practice, several authors have found that the no-slip boundary condition at the
walls of a vessel can slow down mixing considerably, turning an exponential
decay into a power law. This slowdown affects the whole mixing region, and not
just the vicinity of the wall. The reason is that when the chaotic mixing
region extends to the wall, a separatrix connects to it. The approach to the
wall along that separatrix is polynomial in time and dominates the long-time
decay. However, if the walls are moved or rotated, closed orbits appear,
separated from the central mixing region by a hyperbolic fixed point with a
homoclinic orbit. The long-time approach to the fixed point is exponential, so
an overall exponential decay is recovered, albeit with a thin unmixed region
near the wall.Comment: 17 pages, 13 figures. PDFLaTeX with RevTeX 4-1 styl
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