We present semiempirical model atmospheres for the darkest parts of large sunspot umbrae, regions we call umbral cores. Our approach is based on general-purpose computational procedures that are applicable to different types of stellar atmospheres. We show that recent umbral intensity measurements of the spectral energy distribution may be accounted for by an umbral core atmospheric model that varies with time during the solar cycle; the observed center-limb variation can be accounted for by the properties of the model. Three umbral core models are presented, corresponding to the early, middle, and late phases of the solar cycle. These three models also may be regarded as having the properties of dark, average, and bright umbral cores respectively. The effects of atomic, opacity, and abundance data uncertainties on the model calculations are briefly discussed. We also give for comparison a new reference model for the average quiet solar photosphere.

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Friction and wear between moving surfaces is unavoidable and is an important reason for failure of mechanical components. A wear‐resistant and low‐friction coating can prolong the lifetime of an engineered component. Here we demonstrate a new concept for the design of low‐friction nanocomposite carbide coatings with an intrinsic driving force to form amorphous carbon (C–C bonds). Ti–Al–C has been chosen as a model system, but the idea is general and should be applicable to a wide class of materials. The ability to intrinsically form amorphous carbon is achieved by a substitutional solid solution of the weak‐carbide‐forming metal (Al) into the thermodynamically stable monocarbide (TiC). This creates, in a controllable manner, a driving force for phase separation of carbide particles embedded in a matrix of amorphous carbon. In a tribological contact the amorphous carbon can be further graphitized and thereby lower the friction coefficient. Consequently, the model system has a self‐lubricating mechanism but at the same time a tunable share of the two phases, which gives excellent possibilities to design wear resistance and toughness. In this paper we show that the friction coefficient can be lowered by more than 50 % for Al‐containing TiC coatings without severe loss in mechanical characteristics.

The purpose of this paper is to present calculations of total costs of 13 alien invasive species (AIS) in Sweden. All species are subject to control by Swedish public authorities, and estimates for most AIS include either damage cost or actual control cost. The results indicate a total annual cost between approximately 1620 and 5080 million SEK, which correspond to SEK 175 and SEK 565 per capita in Sweden. The estimates are well within the range of similar calculations for other countries, but differ with respect to the composition of costs of different AIS. Whereas costs for the agricultural and forestry sectors dominate in most other studies, the costs of AIS in Sweden are more equally divided among different categories. The results also indicate that the highest costs are attributable to unintentionally introduced AIS and that the most reliable cost estimates are related to human and animal health.

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Investigating the reliability of the assumption of instantaneous chemical equilibrium (ICE) for calculating the CO number density in the solar atmosphere is of crucial importance for the resolution of the long-standing controversy over the existence of "cool clouds" in the chromosphere and for determining whether the cool gas owes its existence to CO radiative cooling or to a hydrodynamical process. Here we report the first results of such an investigation in which we have carried out time-dependent gas-phase chemistry calculations in radiation hydrodynamical simulations of solar chromospheric dynamics. We show that while the ICE approximation turns out to be suitable for modeling the observed infrared CO lines at the solar disk center, it may substantially overestimate the "heights of formation" of strong CO lines synthesized close to the edge of the solar disk, especially concerning vigorous dynamic cases resulting from relatively strong photospheric disturbances. This happens because during the cool phases of the hydrodynamical simulations, the CO number density in the outer atmospheric regions is smaller than what is stipulated by the ICE approximation, resulting in decreased CO opacity in the solar chromosphere. As a result, the cool CO-bearing gas that produces the observed molecular lines must be located at atmospheric heights not greater than ∼700 km. We conclude that taking into account the nonequilibrium chemistry improves the agreement with the available on-disk and off-limb observations but that the hydrodynamical simulation model has to be even cooler than anticipated by the ICE approximation, and this has to be the case at the "new" (i.e., deeper) formation regions of the rovibrational CO lines.

5-Fluorouracil (5-FU) is an anticancer drug and pyrimidine analogue. A problem in 5-FU therapy is acquired resistance to the drug. To find out more about the mechanisms of resistance, we screened a plasmid library in yeast for genes that confer 5-FU resistance when overexpressed. We cloned five genes: CPA1, CPA2, HMS1, HAM1 and YJL055W. CPA1 and CPA2 encode a carbamoyl phosphate synthase involved in arginine biosynthesis and HMS1 a helix-loop-helix transcription factor. Our results suggest that CPA1, CPA2, and HMS1 confer 5-FU resistance by stimulating pyrimidine biosynthesis. Thus, they are unable to confer 5-FU resistance in a ura2 mutant, and inhibit the uptake and incorporation into RNA of both uracil and 5-FU. In contrast, HAM1 and YJL055W confer 5-FU resistance in a ura2 mutant, and selectively inhibit incorporation into RNA of 5-FU but not uracil. HAM1 is the strongest resistance gene, but it partially depends on YJL055W for its function. This suggests that HAM1 and YJL055W function together in mediating resistance to 5-FU. Ham1p encodes an inosine triphosphate pyrophosphatase that has been implicated in resistance to purine analogues. Our results suggest that Ham1p could have a broader specificity that includes 5-FUTP and other pyrimidine analogoue triphosphates.