Assessing Impact

We take this opportunity to communicate Heron's approach to assessing impact, with a particular audience in mind: our customers -- grantees, investees and applicants.We thought that it might be useful to outline how and why we support practitioners and their networks in results-based, management-oriented systems for assessing impact. Following this letter, we highlight four organizations that demonstrate impact at the local, regional and national levels

Origins of the Human Genome Project

Dr. Cook-Deegan recounts some of the scientific and political history leading to controversy about the proper mix of private and public roles in pursuing genome research and bringing its fruits to bear, e.g., in preventing and curing disease

SL2 homomorphic hash functions: Worst case to average case reduction and short collision search

We study homomorphic hash functions into SL(2,q), the 2x2 matrices with determinant 1 over the field with $q$ elements. Modulo a well supported number theoretic hypothesis, which holds in particular for concrete homomorphisms proposed thus far, we provide a worst case to average case reduction for these hash functions: upto a logarithmic factor, a random homomorphism is as secure as _any_ concrete homomorphism. For a family of homomorphisms containing several concrete proposals in the literature, we prove that collisions of length O(log(q)) can be found in running time O(sqrt(q)). For general homomorphisms we offer an algorithm that, heuristically and according to experiments, in running time O(sqrt(q)) finds collisions of length O(log(q)) for q even, and length O(log^2(q)/loglog(q))$ for arbitrary q. While exponetial time, our algorithms are faster in practice than all earlier generic algorithms, and produce much shorter collisions.Comment: Final version. To appear in Design Codes Cryptograph

Magnetic fields in the sun

The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according to whether the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 gauss. A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo

M dwarfs: Theoretical work

Theoretical work on the atmospheres of M dwarfs has progressed along lines parallel to those followed in the study of other classes of stars. Such models have become increasingly sophisticated as improvements in opacities, in the equation of state, and in the treatment of convection were incorporated during the last 15 to 20 years. As a result, spectrophotometric data on M dwarfs can now be fitted rather well by current models. The various attempts at modeling M dwarf photospheres in purely thermal terms are summarized. Some extensions of these models to include the effects of microturbulence and magnetic inhomogeneities are presented

Mass loss from warm giants: Magnetic effects

Among warm giant stars, rapid mass loss sets in along a well defined velocity dividing line (VDL). Hot corona also disappear close to the VDL and thermal pressure cannot drive the observed rapid mass loss in these stars. The VDL may be associated with magnetic fields changing from closed to open. Such a change is consistent with the lack of X-rays from late-type giants. A magnetic transition locus based on Pneuman's work on helmet streamer stability agrees well with the empirical VDL. The change from closed to open fields not only makes rapid mass loss possible, but also contributes to energizing the mass loss in the form of discrete bubbles

Magnetic effects and oversized M dwarfs in the young open cluster NGC 2516

By combining rotation periods with spectroscopic determinations of projected rotation velocity, Jackson, Jeffries & Maxted (2009) have found that the mean radii for low-mass M-dwarfs in the young, open cluster NGC 2516 are larger than model predictions at a given absolute I magnitude or I - K color and also larger than measured radii of magnetically inactive M-dwarfs. The relative radius difference is correlated with magnitude, increasing from a few per cent at MI = 7 to greater than 50 per cent for the lowest luminosity stars in their sample at MI about 9.5. Jackson et al (2009) have suggested that a two-temperature star spot model is capable of explaining the observations, but their model requires spot coverage fractions of at least 50 per cent in rapidly rotating M-dwarfs. Here we examine these results in terms of stellar models that include the inhibiting effects of magnetic fields on convective energy transport, with and without the effects of star spots. We find that a pure spot model is inconsistent with the color - magnitude diagram. The observations of radii versus color and radii versus absolute magnitude in NGC 2516 are consistent with models which include only magnetic inhibition or a combination of magnetic inhibition and spots. At a given mass we find a large dispersion in the strength of the vertical component of the magnetic field in the stellar photosphere but the general trend is that the vertical field increases with decreasing mass from a few hundred Gauss at 0.65 Msun to 600 - 900 Gauss, depending on spot coverage, in the lowest mass stars in the sample at 0.25 Msun.Comment: To appear in the Astrophysical Journal. arXiv admin note: text overlap with arXiv:1006.1308 by other author

Harmonising extended measures of parental childcare in the time-diary surveys of four countries – Proximity versus responsibility

Measures of childcare drawn from time-diary data are commonly based on the specific childcare activities a parent engages in throughout the day. This emphasis on activities has been criticised as it ignores the large quantity of time parents spend supervising their children. In order to provide more accurate estimates of childcare that incorporate supervisory childcare, researchers have turned to extended measures of care based on being i) in proximity to children or ii) responsible for children. There has been debate about the extent to which these approaches each measure the same aspect of childcare. In addition, it is thought they may be sensitive to the way surveys have been designed, which can affect the extent to which they can be compared crossnationally. We argue that measures of proximity and responsibility are conceptually interchangeable, and demonstrate that they can be harmonised and compared cross-nationally. Finally, we suggest ways in which these extended measures of childcare can be made increasingly comparable cross-nationally.Time-diary data, measurement of parental childcare, cross-national harmonisation of measures of childcare, time geography