Magnetization of the oceanic crust: TRM or CRM?

A model was proposed in which chemical remanent magnetization (CRM) acquired within the first 20 Ma of crustal evolution may account for 80% of the bulk natural remanent magnetization (NRM) of older basalts. The CRM of the crust is acquired as the original thermoremanent magnetization (TRM) is lost through low temperature alteration. The CRM intensity and direction are controlled by the post-emplacement polarity history. This model explains several independent observations concerning the magnetization of the oceanic crust. The model accounts for amplitude and skewness discrepancies observed in both the intermediate wavelength satellite field and the short wavelength sea surface magnetic anomaly pattern. It also explains the decay of magnetization away from the spreading axis, and the enhanced magnetization of the Cretaceous Quiet Zones while predicting other systematic variations with age in the bulk magnetization of the oceanic crust. The model also explains discrepancies in the anomaly skewness parameter observed for anomalies of Cretaceous age. Further studies indicate varying rates of TRM decay in very young crust which depicts the advance of low temperature alteration through the magnetized layer

Effect Of Orius insidiosus (Hemiptera: Anthocoridae) And Spinosad (Conserve®) On Western Flower Thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), Populations In Transvaal Daisy Flowers

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a major insect pest of greenhouse-grown horticultural crops. Greenhouse producers typically apply insecticides to suppress WFT populations. However, continual reliance on insecticides can lead to the development of resistant in WFT populations. The insidious flower bug, Orius insidiosus (Say) (Hemiptera: Anthocoridae), is a commercially available predatory bug of WFT that offers an alternative to using insecticides for WFT suppression. Therefore, we investigated the efficacy of one or two O. insidiosus adults compared to spray applications of the standard insecticide, spinosad (Conserve®) in suppressing WFT adult populations in transvaal daisy (Gerbera jamesonii), cut-flowers under greenhouse conditions. Percent adult WFT mortality was significantly lower when one or two O. insidiosus adults were released into the flowers (mean range: 32 to 34%; n=747), compared to the untreated and water control (8 to 9%; n=431). The highest percent mortality of WFT adults was associated with the spinosad (Conserve®) treatment (100%; n= 203)

Composite CDMA - A statistical mechanics analysis

Code Division Multiple Access (CDMA) in which the spreading code assignment to users contains a random element has recently become a cornerstone of CDMA research. The random element in the construction is particular attractive as it provides robustness and flexibility in utilising multi-access channels, whilst not making significant sacrifices in terms of transmission power. Random codes are generated from some ensemble, here we consider the possibility of combining two standard paradigms, sparsely and densely spread codes, in a single composite code ensemble. The composite code analysis includes a replica symmetric calculation of performance in the large system limit, and investigation of finite systems through a composite belief propagation algorithm. A variety of codes are examined with a focus on the high multi-access interference regime. In both the large size limit and finite systems we demonstrate scenarios in which the composite code has typical performance exceeding sparse and dense codes at equivalent signal to noise ratio.Comment: 23 pages, 11 figures, Sigma Phi 2008 conference submission - submitted to J.Stat.Mec

Effects of Neutral Hydrogen on Cosmic Ray Precursors in Supernova Remnant Shock Waves

Many fast supernova remnant shocks show spectra dominated by Balmer lines. The H$\alpha$ profiles have a narrow component explained by direct excitations and a thermally Doppler broadened component due to atoms that undergo charge exchange in the post-shock region. However, the standard model does not take into account the cosmic-ray shock precursor, which compresses and accelerates plasma ahead of the shock. In strong precursors with sufficiently high densities, the processes of charge exchange, excitation and ionization will affect the widths of both narrow and broad line components. Moreover, the difference in velocity between the neutrals and the precursor plasma gives rise to frictional heating due to charge exchange and ionization in the precursor. In extreme cases, all neutrals can be ionized by the precursor. In this paper we compute the ion and electron heating for a wide range of shock parameters, along with the velocity distribution of the neutrals that reach the shock. Our calculations predict very large narrow component widths for some shocks with efficient acceleration, along with changes in the broad- to-narrow intensity ratio used as a diagnostic for the electron-ion temperature ratio. Balmer lines may therefore provide a unique diagnostic of precursor properties. We show that heating by neutrals in the precursor can account for the observed H$\alpha$ narrow component widths, and that the acceleration efficiency is modest in most Balmer line shocks observed thus far.Comment: 9 pages, 3 figure

Spiral Waves in Media with Complex Excitable Dynamics

The structure of spiral waves is investigated in super-excitable reaction-diffusion systems where the local dynamics exhibits multi-looped phase space trajectories. It is shown that such systems support stable spiral waves with broken symmetry and complex temporal dynamics. The main structural features of such waves, synchronization defect lines, are demonstrated to be similar to those of spiral waves in systems with complex-oscillatory dynamics.Comment: to appear in International Journal of Bifurcation and Chao

Nonadiabatic Dynamics in Open Quantum-Classical Systems: Forward-Backward Trajectory Solution

A new approximate solution to the quantum-classical Liouville equation is derived starting from the formal solution of this equation in forward-backward form. The time evolution of a mixed quantum-classical system described by this equation is obtained in a coherent state basis using the mapping representation, which expresses $N$ quantum degrees of freedom in a 2N-dimensional phase space. The solution yields a simple non-Hamiltonian dynamics in which a set of $N$ coherent state coordinates evolve in forward and backward trajectories while the bath coordinates evolve under the influence of the mean potential that depends on these forward and backward trajectories. It is shown that the solution satisfies the differential form of the quantum-classical Liouville equation exactly. Relations to other mixed quantum-classical and semi-classical schemes are discussed.Comment: 28 pages, 1 figur

Removal of monocular interactions equates rivalry behavior for monocular, binocular, and stimulus rivalries

When the two eyes are presented with conflicting stimuli, perception starts to fluctuate over time (i.e., binocular rivalry). A similar fluctuation occurs when two patterns are presented to a single eye (i.e., monocular rivalry), or when they are swapped rapidly and repeatedly between the eyes (i.e., stimulus rivalry). Although all these cases lead to rivalry, in quantitative terms these modes of rivalry are generally found to differ significantly. We studied these different modes of rivalry with identical intermittently shown stimuli while varying the temporal layout of stimulation. We show that the quantitative differences between the modes of rivalry are caused by the presence of monocular interactions between the rivaling patterns; the introduction of a blank period just before a stimulus swap changed the number of rivalry reports to the extent that monocular and stimulus rivalries were inducible over ranges of spatial frequency content and contrast values that were nearly identical to binocular rivalry. Moreover when monocular interactions did not occur the perceptual dynamics of monocular, binocular, and stimulus rivalries were statistically indistinguishable. This range of identical behavior exhibited a monocular (∼50 ms) and a binocular (∼350 ms) limit. We argue that a common binocular, or pattern-based, mechanism determines the temporal constraints for these modes of rivalry