Ill-posedness of degenerate dispersive equations

In this article we provide numerical and analytical evidence that some degenerate dispersive partial differential equations are ill-posed. Specifically we study the K(2,2) equation $u_t = (u^2)_{xxx} + (u^2)_{x}$ and the "degenerate Airy" equation $u_t = 2 u u_{xxx}$. For K(2,2) our results are computational in nature: we conduct a series of numerical simulations which demonstrate that data which is very small in $H^2$ can be of unit size at a fixed time which is independent of the data's size. For the degenerate Airy equation, our results are fully rigorous: we prove the existence of a compactly supported self-similar solution which, when combined with certain scaling invariances, implies ill-posedness (also in $H^2$)

Melting of hexagonal skyrmion states in chiral magnets

Skyrmions are spiral structures observed in thin films of certain magnetic materials (Uchida et al 2006 Science 311 359–61). Of the phases allowed by the crystalline symmetries of these materials (Yi et al 2009 Phys. Rev. B 80 054416), only the hexagonally packed phases (SCh) have been observed. Here the melting of the SCh phase is investigated using Monte Carlo simulations. In addition to the usual measure of skyrmion density, chiral charge, a morphological measure is considered. In doing so it is shown that the low-temperature reduction in chiral charge is associated with a change in skyrmion profiles rather than skyrmion destruction. At higher temperatures, the loss of six-fold symmetry is associated with the appearance of elongated skyrmions that disrupt the hexagonal packing

Serfati solutions to the 2D Euler equations on exterior domains

We prove existence and uniqueness of a weak solution to the incompressible 2D Euler equations in the exterior of a bounded smooth obstacle when the initial data is a bounded divergence-free velocity field having bounded scalar curl. This work completes and extends the ideas outlined by P. Serfati for the same problem in the whole-plane case. With non-decaying vorticity, the Biot-Savart integral does not converge, and thus velocity cannot be reconstructed from vorticity in a straightforward way. The key to circumventing this difficulty is the use of the Serfati identity, which is based on the Biot-Savart integral, but holds in more general settings.Comment: 50 page

Grabežljiva stjenica Rhynocoris fuscipes (FABRICIUS) učinkovito potinula zaraženost mahuna Cajanus cajan od štetnika Helicoverpa armigera (HÜBNER), Nezara viridula (L.) i Riptortus clavatus Thunberg u kavezima u polju

Rhynocoris fuscipes effectively suppressed the infestation of Helicoverpa armigera, Nezara viridula and Riptortus clavatus in pigeonpea field cages. Reduced pod and flower damages were observed in R. fuscipes released field cages. R. fuscipes release significantly enhanced the yield of healthy pods (grains). Field observations suggested this predator\u27s pest suppression and grain damage reduction efficacy.Predator Rhynocoris fuscipes učinkovito je potisnuo zarazu vrstama Helicoverpa armigera, Nezara viridula i Riptortus clavatus u poljskim kavezima. Zapaženo je smanjenje šteta na mahunama i cvjetovima biljke kajan (Cajanus cajan) u kavezima u koje su ispušteni R. fuscipes. Prisutnost predatora signifikantno je povećala prirod zdravih mahuna i zrna. Poljski pokusi ukazuju na učinak predatora na smanjenje zaraze štetnicima i sniženje šteta

On Unitarity Based Relations Between Various Lepton Family Violating Processes

Simple "unitarity inspired" relations between two- and three-body lepton flavor violating decays are noted and discussed. In the absence of cancellations, the existing strong bounds on $\mu \to 3e$ and $\mu\to e\gamma\gamma$ severly constrain two-body lepton flavor violating decays.Comment: 5 pages, 3 figure

Coordination of Geological and Engineering Research in Support of the Gulf Coast Co-Production Program

Complex and heterogeneous Hackberry reservoirs at Port Arthur field were deposited in a submarine canyon/fan setting. Conventional fieldwide hydrocarbon recovery efficiencies are low, but the potential for secondary gas recovery is high. Free gas remains trapped in uncontacted and untapped compartments at reservoir abandonment. The total fieldwide resource amounts to 13.9 Bcf. The probable and possible resource for a single infill well is 6.5 Bcf in four separate stringers. Three optimum brine-disposal sands and the best brine-disposal site were selected in Northeast Hitchcock field based on sand-body complexity, thickness, depth, and brine-disposal capacity. The equilibrium distribution of inorganic species in different combinations in the produced waters at surface and formation temperatures and pH was estimated from chemical analyses. SOLMNEQ computations suggest carbonate scaling may occur in surface equipment of Miocene disposal sandstones unless inhibitors are used. At Northeast Hitchcock field, well-winnowed sandstones of shallow-marine origin compose the major reservoir sands and act as preferential conduits for fluid migration. Dislodged, abundant authigenic kaolinite in these sands can plug pores during production, suggesting a maximum rate of production will need to be determined to avoid reservoir damage.Bureau of Economic Geolog

Assessment of Gas Resources for Secondary Gas Recovery Technology

Unrecovered gas resources available through existing technology can be a significant source of reserve additions in maturely explored petroleum provinces. In this study, nonassociated and associated Texas reservoirs were analyzed for gas reserve growth potential. In the nonassociated fluvial Frio Brooks reservoir, infill drilling from 640 to 320 acres per well can potentially increase reserves by 15.7 percent of estimated ultimate recovery. Gas reserve additions may result from improved contact with isolated or partially isolated sandstones that are not effectively drained by conventional development practices. An additional 14.4 billion cubic feet (Bcf) of gas resources can be potentially recovered by strategic infill drilling down to 10-acre spacing in the Grayburg reservoirs of Dune field, one of many mature West Texas fields located on the Central Basin Platform. Infill wells strategically drilled in the Dune field grainstone facies are projected to be most cost-efficient and productive. Recoverable associated gas in selected plays is estimated to be from 3.4 trillion cubic feet (Tcf) to 5.8 Tcf. The greatest recovery potential for associated gas reserve growth in Texas is in carbonate reservoirs with complex facies architecture in the Permian Basin. Geologically based infill wells in areas of greatest reservoir heterogeneity can recover much of this unproduced gas resource.Bureau of Economic Geolog

Response of selected plant and insect species to simulated solid rocket exhaust mixtures and to exhaust components from solid rocket fuels

The effects of solid rocket fuel (SRF) exhaust on selected plant and and insect species in the Merritt Island, Florida area was investigated in order to determine if the exhaust clouds generated by shuttle launches would adversely affect the native, plants of the Merritt Island Wildlife Refuge, the citrus production, or the beekeeping industry of the island. Conditions were simulated in greenhouse exposure chambers and field chambers constructed to model the ideal continuous stirred tank reactor. A plant exposure system was developed for dispensing and monitoring the two major chemicals in SRF exhaust, HCl and Al203, and for dispensing and monitoring SRF exhaust (controlled fuel burns). Plants native to Merritt Island, Florida were grown and used as test species. Dose-response relationships were determined for short term exposure of selected plant species to HCl, Al203, and mixtures of the two to SRF exhaust