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Higher Fertilizer Inputs Increase Fitness Traits of Brown Planthopper in Rice.
Rice (Oryza sativa L.) is the primary staple food source for more than half of the world's population. In many developing countries, increased use of fertilizers is a response to increase demand for rice. In this study, we investigated the effects of three principal fertilizer components (nitrogen, phosphorus and potassium) on the development of potted rice plants and their effects on fitness traits of the brown planthopper (BPH) [Nilaparvata lugens (Stål) (Homoptera: Delphacidae)], which is a major pest of rice in Bangladesh and elsewhere. Compared to low fertilizer inputs, high fertilizer treatments induced plant growth but also favored BPH development. The BPH had higher survival, developed faster, and the intrinsic rate of natural increase (r m ) was higher on well-fertilized than under-fertilized plants. Among the fertilizer inputs, nitrogen had the strongest effect on the fitness traits of BPH. Furthermore, both the "Plant vigor hypothesis" and the "Plant stress hypothesis" were supported by the results, the former hypothesis more so than the latter. These hypotheses suggest that the most suitable/attractive hosts for insect herbivores are the most vigorous plants. Our findings emphasized that an exclusive focus on yield increases through only enhanced crop fertilization may have unforeseen, indirect, effects on crop susceptibility to pests, such as BPH
Evolutionary quantum cosmology in a gauge-fixed picture
We study the classical and quantum models of a flat
Friedmann-Robertson-Walker (FRW) space-time, coupled to a perfect fluid, in the
context of the consensus and a gauge-fixed Lagrangian frameworks. It is shown
that, either in the usual or in the gauge-fixed actions, the evolution of the
universe based on the classical cosmology represents a late time power law
expansion, coming from a big-bang singularity in which the scale factor goes to
zero for the standard matter, and tending towards a big-rip singularity in
which the scale factor diverges for the phantom fluid. We then employ the
familiar canonical quantization procedure in the given cosmological setting to
find the cosmological wave functions in the corresponding minisuperspace. Using
a gauge-fixed (reduced) Lagrangian, we show that, it may lead to a
Schr\"{o}dinger equation for the quantum-mechanical description of the model
under consideration, the eigenfunctions of which can be used to construct the
time dependent wave function of the universe. We use the resulting wave
function in order to investigate the possibility of the avoidance of classical
singularities due to quantum effects by means of the many-worlds and
ontological interpretation of quantum cosmology.Comment: 15 pages, 10 figures, typos corrected, Refs. adde
Does Positronium Form in the Universe ?
Positronium (the bound state of electron and positron) has been thought to be
formed after proton decay (yr) through collisional recombination and
then decays by pair annihilation, thereby changing the matter content of the
universe. We revisit the issue of the formation of positronium in the long-term
future of the universe in light of recent indication that the universe is
dominated by dark energy and dark matter. We find that if the equation of state
of dark energy is less than -1/3 (including the cosmological constant
), then the formation of positronium would not be possible, while it is
possible through bound-bound transitions for -1/3\siml w\siml-0.2, or through
collisional recombination for w\simg-0.2. The radiation from \epm pair
annihilation cannot dominate over \epm, while that from proton decay will
dominate over baryon and \epm for a while but not over dark matter.Comment: 13 pages, to appear in JCA
Streamflow disaggregation: a nonlinear deterministic approach
International audienceThis study introduces a nonlinear deterministic approach for streamflow disaggregation. According to this approach, the streamflow transformation process from one scale to another is treated as a nonlinear deterministic process, rather than a stochastic process as generally assumed. The approach follows two important steps: (1) reconstruction of the scalar (streamflow) series in a multi-dimensional phase-space for representing the transformation dynamics; and (2) use of a local approximation (nearest neighbor) method for disaggregation. The approach is employed for streamflow disaggregation in the Mississippi River basin, USA. Data of successively doubled resolutions between daily and 16 days (i.e. daily, 2-day, 4-day, 8-day, and 16-day) are studied, and disaggregations are attempted only between successive resolutions (i.e. 2-day to daily, 4-day to 2-day, 8-day to 4-day, and 16-day to 8-day). Comparisons between the disaggregated values and the actual values reveal excellent agreements for all the cases studied, indicating the suitability of the approach for streamflow disaggregation. A further insight into the results reveals that the best results are, in general, achieved for low embedding dimensions (2 or 3) and small number of neighbors (less than 50), suggesting possible presence of nonlinear determinism in the underlying transformation process. A decrease in accuracy with increasing disaggregation scale is also observed, a possible implication of the existence of a scaling regime in streamflow
Magnetic soft modes in the locally distorted triangular antiferromagnet alpha-CaCr2O4
In this paper we explore the phase diagram and excitations of a distorted
triangular lattice antiferromagnet. The unique two-dimensional distortion
considered here is very different from the 'isosceles'-type distortion that has
been extensively investigated. We show that it is able to stabilize a 120{\deg}
spin structure for a large range of exchange interaction values, while new
structures are found for extreme distortions. A physical realization of this
model is \alpha-CaCr2O4 which has 120{\deg} structure but lies very close to
the phase boundary. This is verified by inelastic neutron scattering which
reveals unusual roton-like minima at reciprocal space points different from
those corresponding to the magnetic order.Comment: 5 pages, 3 figures and lots of spin-wave
Asymmetric Thermal Lineshape Broadening in a Gapped 3-Dimensional Antiferromagnet - Evidence for Strong Correlations at Finite Temperature
It is widely believed that magnetic excitations become increasingly
incoherent as temperature is raised due to random collisions which limit their
lifetime. This picture is based on spin-wave calculations for gapless magnets
in 2 and 3 dimensions and is observed experimentally as a symmetric Lorentzian
broadening in energy. Here, we investigate a three-dimensional dimer
antiferromagnet and find unexpectedly that the broadening is asymmetric -
indicating that far from thermal decoherence, the excitations behave
collectively like a strongly correlated gas. This result suggests that a
temperature activated coherent state of quasi-particles is not confined to
special cases like the highly dimerized spin-1/2 chain but is found generally
in dimerized antiferromagnets of all dimensionalities and perhaps gapped
magnets in general
Ward Round - Crocodile bites in Malawi: microbiology and surgical management
We present a case series of 5 patients admitted over 5 months to Queen Elizabeth Central Hospital who had sustained injuries from a crocodile bite. Three patients required amputation of a limb. The severe soft tissue injury associated with a crocodile bite and the unusual normal oral flora of the crocodile create challenges in treatment. Progressive tissue destruction and haemolysis are complications of such infected wounds. An antibiotic regime is recommended that covers gram negative rods, anaerobes and may include doxycycline, as well as the need to have a low threshold for early amputation. Malawi Medical Journal Vol. 21 (1) 2009: pp. 29-3
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