An Improbable Solution to the Underluminosity of 2M1207B: A Hot Protoplanet Collision Afterglow

We introduce an alternative hypothesis to explain the very low luminosity of the cool (L-type) companion to the ~25 M_Jup ~8 Myr-old brown dwarf 2M1207A. Recently, Mohanty et al. (2007) found that effective temperature estimates for 2M1207B (1600 +- 100 K) are grossly inconsistent with its lying on the same isochrone as the primary, being a factor of ~10 underluminous at all bands between I (0.8 um) and L' (3.6 um). Mohanty et al. explain this discrepency by suggesting that 2M1207B is an 8 M_Jup object surrounded by an edge-on disk comprised of large dust grains producing 2.5^m of achromatic extinction. We offer an alternative explanation: the apparent flux reflects the actual source luminosity. Given the temperature, we infer a small radius (~49,000 km), and for a range of plausible densities, we estimate a mass < M_Jup. We suggest that 2M1207B is a hot protoplanet collision afterglow and show that the radiative timescale for such an object is >~1% the age of the system. If our hypothesis is correct, the surface gravity of 2M1207B should be an order of magnitude lower than predicted by Mohanty et al. (2007).Comment: ApJ Letters, in press (11 pages

New Risks Ahead:The Eastward Enlargement of the Eurozone

Eastward enlargement is one of the hot topics in European economics. The accession of central and eastern European Countries (CEEC) into the European Union (EU) is accompanied by an extension of the eurozone to this region. This paper surveys likely outcomes and challenges of this specific feature of EU enlargement. Moreover, the ar-ticle represents the start of an international research project dealing with these ques-tions. Research is structured along different markets. Hence, the impact of an adoption of the euro is analysed for capital and labour markets as well as with respect to exchange rate and monetary policies. Our main position is that the euro has in general beneficiary ef-fects for the CEEC and the current EU in all examined markets. However, these bene-fits evolve mainly in the long run, whereas the short-term costs of adaptation to the new situation may be high. Although we believe that the present value of long-term benefits exceeds these costs, it is by no means clear that policy-makers will share this view. Due to the usual political-economy transformation, the assessment of costs and benefits may be different for politicians than compared to any overall perspective. If of-ficial policies become unforeseeable, so will private behaviour. International investors may reverse their capital flows, draining precious liquidity, and leading to currency and financial crises whenever they perceive the authorities’ commitment to EMU less credi-ble. This article highlights some thinkable mechanisms how any such crisis could evolve. It, thus, sets the agenda for further research, mainly, with the focus on appropriate policy strategies to keep adaptation costs as low as possible, minimise other external risks, without hampering the long-term benefits.EMU, EU enlargement, monetary integration

Studies on sweet corn: Stewart's wilt forecasting, the effect of maize dwarf mosaic on foliar diseases, and herbicide sensitivity

Diseases and sensitivity to P450-metabolized herbicides can limit the production of high quality sweet corn. Separate studies were done to determine the probability of exceeding 1% and 5% incidence of Stewart’s wilt on sweet corn with different reactions to Pantoea stewartii, the effect of maize dwarf mosaic (MDM) on eight foliar diseases, and the effect of hybrid CYP genotype on sweet corn yield following postemergence applications of mesotrione or nicosulfuron. Stewart’s disease can be forecasted using the Stevens, Stevens-Boewe, or Iowa State forecasts. These forecasts assume a high degree of host susceptibility. Host resistance affects the incidence and severity of disease, and therefore can affect the accuracy forecasts of Stewart’s disease. Levels of host resistance affected the incidence of systemic seedling wilt within ranges of winter temperatures used by each of the forecasts. Frequency distributions of Stewart’s wilt incidence on moderate and resistant hybrids did not differ among the three temperature ranges above -2.8ºC (27ºF). Conversely, distributions of Stewart’s wilt incidence on susceptible hybrids differed among each of the four ranges of winter temperature from the Stevens-Boewe forecast (i.e., >0.6ºC, -1.1º to 0.6ºC, -2.8º to -1.1ºC, and <-2.8ºC). The probability of exceeding the 1% and 5% incidence thresholds that warrant the use of seed treatment insecticides also differed among hybrids with susceptible, moderate, or resistant reactions to Stewart’s wilt. The probability of exceeding 1% incidence of systemic Stewart’s wilt was greater than 0.5 on moderately susceptible to susceptible sweet corn hybrids when mean winter temperature was above -2.8ºC (27ºF). When mean winter temperature was below -2.8ºC (27ºF), using a seed treatment insecticide on moderate and resistant hybrids for Stewart’s wilt control was not economical because the probability of exceeding 1% incidence of systemic Stewart’s wilt was about 0.04. The probability of exceeding 5% incidence was less than 0.1 except when the mean winter temperature was above -2.8ºC (27ºF) and a moderately susceptible to susceptible hybrid was grown. A separate study also was done to evaluate the effect of MDM on eight foliar diseases of sweet corn. MDM-infection substantially increased the severity of five diseases including: southern corn leaf blight (SCLB), northern corn leaf spot (NCLS), gray leaf spot (GLS), Diplodia leaf streak (DLS), and eyespot. Among MDM-susceptible hybrids, mean severity ratings of SCLB, NCLS, GLS, DLS, and eyespot on MDM-infected plants typically were double those of virus-free plants. Three diseases not substantially increased by MDM-infection included: common rust, northern corn leaf blight, and Stewart’s wilt. MDM-infection appears to affect the severity of diseases caused by necrotrophic foliar fungi that colonize mesophyll tissue. MDM-infection did not appear to substantially affect diseases caused by pathogens which form haustoria or invade the vascular system. The extent to which SCLB severity is increased by MDM in terms of changes in level of host resistance also was determined. For MDM-susceptible hybrids, reactions to SCLB ranged from resistant to moderately-susceptible in virus-free treatments, but each of these hybrids was classified as moderately susceptible to susceptible when infected with MDM. Reactions to SCLB did not differ appreciably among viral treatments for MDM-resistant hybrids, ranging from moderately-resistant to moderately-susceptible. An additional study was done to determine if hybrid genotype at a major cytochrome P450 (CYP) locus on chromosome 5S affected yield following postemergence applications of mesotrione (HPPD-inhibiting herbicide) or nicosulfuron (ALS-inhibiting herbicide) at two growth stages. Yield of hybrids with two mutant cyp alleles (i.e., cypcyp) was reduced by applications of mesotrione. These hybrids were not evaluated for nicosulfuron because ALS-inhibiting herbicides kill these hybrids. Yield of hybrids heterozygous for mutant and functional CYP alleles (i.e., CYPcyp) were reduced by nicosulfuron but unaffected by mesotrione. Yield of hybrids with two functional CYP alleles (i.e., CYPCYP) were unaffected by mesotrione or nicosulfuron. Results of this experiment demonstrate that the genetic condition of hybrids at the CYP locus on chromosome 5S affects the yield of sweet corn following application of mesotrione or nicosulfuron at the V3 to V5 or the V5 to V7 growth stages

Modulation of the host Th1 immune response in pigeon protozoal encephalitis caused by Sarcocystis calchasi

Pigeon protozoal encephalitis (PPE) is an emerging central-nervous disease of domestic pigeons (Columba livia f. domestica) reported in Germany and the United States. It is caused by the apicomplexan parasite Sarcocystis calchasi which is transmitted by Accipter hawks. In contrast to other members of the Apicomplexa such as Toxoplasma and Plasmodium, the knowledge about the pathophysiology and host manipulation of Sarcocystis is scarce and almost nothing is known about PPE. Here we show by mRNA expression profiling a significant down-modulation of the interleukin (IL)-12/IL-18/interferon (IFN)-γ axis in the brains of experimentally infected pigeons during the schizogonic phase of disease. Concomitantly, no cellular immune response was observed in histopathology while immunohistochemistry and nested PCR detected S. calchasi. In contrast, in the late central-nervous phase, IFN-γ and tumor necrosis factor (TNF) α-related cytokines were significantly up-modulated, which correlated with a prominent MHC-II protein expression in areas of mononuclear cell infiltration and necrosis. The mononuclear cell fraction was mainly composed of T-lymphocytes, fewer macrophages and B-lymphocytes. Surprisingly, the severity and composition of the immune cell response appears unrelated to the infectious dose, although the severity and onset of the central nervous signs clearly was dose-dependent. We identified no or only very few tissue cysts by immunohistochemistry in pigeons with severe encephalitis of which one pigeon repeatedly remained negative by PCR despite severe lesions. Taken together, these observations may suggest an immune evasion strategy of S. calchasi during the early phase and a delayed-type hypersensitivity reaction as cause of the extensive cerebral lesions during the late neurological phase of disease

Self-limited self-assembly of chiral filaments

The assembly of filamentous bundles with controlled diameters is common in biological systems and desirable for the development of nanomaterials. We discuss dynamical simulations and free energy calculations on patchy spheres with chiral pair interactions that spontaneously assemble into filamentous bundles. The chirality frustrates long-range crystal order by introducing twist between interacting subunits. For some ranges of system parameters this constraint leads to bundles with a finite diameter as the equilibrium state, and in other cases frustration is relieved by the formation of defects. While some self-limited structures can be modeled as twisted filaments arranged with local hexagonal symmetry, other structures are surprising in their complexity.Comment: 5 pages, 5 figure