Spatial-temporal evolution of the current filamentation instability

The spatial-temporal evolution of the purely transverse current filamentation instability is analyzed by deriving a single partial differential equation for the instability and obtaining the analytical solutions for the spatially and temporally growing current filament mode. When the beam front always encounters fresh plasma, our analysis shows that the instability grows spatially from the beam front to the back up to a certain critical beam length; then the instability acquires a purely temporal growth. This critical beam length increases linearly with time and in the non-relativistic regime it is proportional to the beam velocity. In the relativistic regime the critical length is inversely proportional to the cube of the beam Lorentz factor $\gamma_{0b}$. Thus, in the ultra-relativistic regime the instability immediately acquires a purely temporal growth all over the beam. The analytical results are in good agreement with multidimensional particle-in-cell simulations performed with OSIRIS. Relevance of current study to recent and future experiments on fireball beams is also addressed

Enhanced grain surface effect on magnetic properties of nanometric La0.7Ca0.3MnO3 manganite : Evidence of surface spin freezing of manganite nanoparticles

We have investigated the effect of nanometric grain size on magnetic properties of single phase, nanocrystalline, granular La0.7Ca0.3MnO3 (LCMO) sample. We have considered core-shell structure of our LCMO nanoparticles, which can explain its magnetic properties. From the temperature dependence of field cooled (FC) and zero-field cooled (ZFC) dc magnetization (DCM), the magnetic properties could be distinguished into two regimes: a relatively high temperature regime T > 40 K where the broad maximum of ZFC curve (at T = Tmax) is associated with the blocking of core particle moments, whereas the sharp maximum (at T = TS) is related to the freezing of surface (shell) spins. The unusual shape of M (H) loop at T = 1.5 K, temperature dependent feature of coercive field and remanent magnetization give a strong support of surface spin freezing that are occurring at lower temperature regime (T < 40 K) in this LCMO nanoparticles. Additionally, waiting time (tw) dependence of ZFC relaxation measurements at T = 50 K show weak dependence of relaxation rate [S(t)] on tw and dM/dln(t) following a logarithmic variation on time. Both of these features strongly support the high temperature regime to be associated with the blocking of core moments. At T = 20 K, ZFC relaxation measurements indicates the existence of two different types of relaxation processes in the sample with S(t) attaining a maximum at the elapsed time very close to the wait time tw = 1000 sec, which is an unequivocal sign of glassy behavior. This age-dependent effect convincingly establish the surface spin freezing of our LCMO nanoparticles associated with a background of superparamagnetic (SPM) phase of core moments.Comment: 41 pages, 10 figure

DC field induced enhancement and inhibition of spontaneous emission in a cavity

We demonstrate how spontaneous emission in a cavity can be controlled by the application of a dc field. The method is specially suitable for Rydberg atoms. We present a simple argument for the control of emission.Comment: 3-pages, 2figure. accepted in Phys. Rev.

Loss of α-Synuclein Does Not Affect Mitochondrial Bioenergetics in Rodent Neurons.

Increased α-synuclein (αsyn) and mitochondrial dysfunction play central roles in the pathogenesis of Parkinson's disease (PD), and lowering αsyn is under intensive investigation as a therapeutic strategy for PD. Increased αsyn levels disrupt mitochondria and impair respiration, while reduced αsyn protects against mitochondrial toxins, suggesting that interactions between αsyn and mitochondria influences the pathologic and physiologic functions of αsyn. However, we do not know if αsyn affects normal mitochondrial function or if lowering αsyn levels impacts bioenergetic function, especially at the nerve terminal where αsyn is enriched. To determine if αsyn is required for normal mitochondrial function in neurons, we comprehensively evaluated how lowering αsyn affects mitochondrial function. We found that αsyn knockout (KO) does not affect the respiration of cultured hippocampal neurons or cortical and dopaminergic synaptosomes, and that neither loss of αsyn nor all three (α, β and γ) syn isoforms decreased mitochondria-derived ATP levels at the synapse. Similarly, neither αsyn KO nor knockdown altered the capacity of synaptic mitochondria to meet the energy requirements of synaptic vesicle cycling or influenced the localization of mitochondria to dopamine (DA) synapses in vivo. Finally, αsyn KO did not affect overall energy metabolism in mice assessed with a Comprehensive Lab Animal Monitoring System. These studies suggest either that αsyn has little or no significant physiological effect on mitochondrial bioenergetic function, or that any such functions are fully compensated for when lost. These results implicate that αsyn levels can be reduced in neurons without impairing (or improving) mitochondrial bioenergetics or distribution

Opportunities for integrated pest management to control the poultry red mite, Dermanyssus gallinae

Dermanyssus gallinae is the most economically important ectoparasite of laying hens in Europe. Control of D. gallinae is already hampered by issues of pesticide resistance and product withdrawal and, with the prohibition of conventional cages in 2012 and the resulting switch to more structurally complex housing which favours red mite, the importance of managing this pest will increase. Integrated Pest Management (IPM), as often employed in agricultural pest control, may be a way to address these issues where a combination of different novel control methods could be used with/without conventional management techniques to provide a synergistic and more efficacious effect. Work at in our laboratory has shown that essential oils including thyme and garlic may act as effective D. gallinae repellents and acaricides, whilst preliminary vaccine studies have demonstrated a significant increase in mite mortality in vitro using concealed antigens. Work elsewhere 27 has considered predators and fungi for D. gallinae control and other husbandry techniques such as manipulating temperature and lighting regimes in poultry units. This paper will review the available and emerging techniques for D. gallinae control and discuss which techniques might be suitable for inclusion in an integrated management programme (e.g. synthetic acaricides and diatomaceous earths)

Inelastic X-ray scattering study of the collective dynamics in liquid sodium

Inelastic X-ray scattering data have been collected for liquid sodium at T=390 K, i.e. slightly above the melting point. Owing to the very high instrumental resolution, pushed up to 1.5 meV, it has been possible to determine accurately the dynamic structure factor, $S(Q,\omega)$, in a wide wavevector range, $1.5 \div 15$ nm$^{-1}$, and to investigate on the dynamical processes underlying the collective dynamics. A detailed analysis of the lineshape of $S(Q,\omega)$, similarly to other liquid metals, reveals the co-existence of two different relaxation processes with slow and fast characteristic timescales respectively. The present data lead to the conclusion that: i) the picture of the relaxation mechanism based on a simple viscoelastic model fails; ii) although the comparison with other liquid metals reveals similar behavior, the data do not exhibit an exact scaling law as the principle of corresponding state would predict.Comment: RevTex, 7 pages, 6 eps figures. Accepted by Phys. Rev.

Nonlinear photoluminescence spectra from a quantum dot-cavity system: Direct evidence of pump-induced stimulated emission and anharmonic cavity-QED

We investigate the power-dependent photoluminescence spectra from a strongly coupled quantum dot-cavity system using a quantum master equation technique that accounts for incoherent pumping, pure dephasing, and fermion or boson statistics. Analytical spectra at the one-photon correlation level and the numerically exact multi-photon spectra for fermions are presented. We compare to recent experiments on a quantum dot-micropiller cavity system and show that an excellent fit to the data can be obtained by varying only the incoherent pump rates in direct correspondence with the experiments. Our theory and experiments together show a clear and systematic way of studying stimulated-emission induced broadening and anharmonic cavity-QED.Comment: We have reworked our previous arXiv paper and submitted this latest version for peer revie

The relation between symmetry in food packaging and approach and avoidance words

Research on aesthetic science has demonstrated that people generally prefer symmetrical over asymmetrical compositions. However, it remains unclear whether and how such compositions relate to the concepts of approach and avoidance motivation, especially in consumer contexts. In addition, it is not known how symmetry may influence such concepts in contexts where objects can differ in terms of their hedonic values (symmetry/product taste congruency). In the present research, we evaluated the relation between visual symmetry of the packaging of products with different hedonic value (sweet, non-sweet, non-food) and approach and avoidance words. In two experiments, we found evidence that people associate symmetrical designs with approach words more often than asymmetrical designs. Importantly, however, we did not find evidence that such an effect is influenced by the hedonic value of the products. Our results have value for scholars and practitioners interested in the effect of aesthetic features of brand elements (such as a product’s packaging) on consumer motivation