Principal and syntactic congruences in congruence-distributive and congruence-permutable varieties

We give a new proof that a finitely generated congruence-distributive variety has finitely determined syntactic congruences (or, equivalently, term finite principal congruences), and show that the same does not hold for finitely generated congruence-permutable varieties, even under the additional assumption that the variety is residually very finite

Tidal Heating of Extra-Solar Planets

Extra-solar planets close to their host stars have likely undergone significant tidal evolution since the time of their formation. Tides probably dominated their orbital evolution once the dust and gas had cleared away, and as the orbits evolved there was substantial tidal heating within the planets. The tidal heating history of each planet may have contributed significantly to the thermal budget that governed the planet's physical properties, including its radius, which in many cases may be measured by observing transit events. Typically, tidal heating increases as a planet moves inward toward its star and then decreases as its orbit circularizes. Here we compute the plausible heating histories for several planets with measured radii, using the same tidal parameters for the star and planet that had been shown to reconcile the eccentricity distribution of close-in planets with other extra-solar planets. Several planets are discussed, including for example HD 209458 b, which may have undergone substantial tidal heating during the past billion years, perhaps enough to explain its large measured radius. Our models also show that GJ 876 d may have experienced tremendous heating and is probably not a solid, rocky planet. Theoretical models should include the role of tidal heating, which is large, but time-varying.Comment: Accepted for publication to Ap

Preparedness Exercises 2.0: Alternative Approaches to Exercise Design That Could Make Them More Useful for Evaluating and Strengthening Preparedness

This article appeared in Homeland Security Affairs (May 2011), v.7Preparedness exercises play central roles in both the building and assessment of organizational readiness for future incidents. Though processes for designing and evaluating exercises are well established, there are opportunities to improve the value of exercises for strengthening preparedness and as tools for gathering assessment data. This article describe the application of systems analytical approach adapted from engineering that examines response operations as systems with potential failure modes that could hurt performance at future incidents. This methodology, which has been applied previously to preparedness measurement, is explored here as a tool for exercise design to focus it more tightly on key potential problem areas and to make it easier to use exercise data to explore preparedness for incidents that could differ considerably from the specific exercised scenario.Approved for public release; distribution is unlimited

An X-ray absorption spectroscopic study at the mercury LIII edge on phenylmercury(II) oxygen species

The X-ray absorption spectra of the reference and model compounds HgCl2, PhHgCl, PhHgOAc and [(PhHg)2OH][BF4].H2O have been analysed in both the XANES and EXAFS regions, and the technique was extended to determine the structures of (PhHg)2O, PhHgOH, and the basic salts PhHgOH.PhHgNO3 and PhHgOH.(PhHg)2SO4, which were previously structurally uncharacterised. Results indicate that (PhHg)2O is a molecular species with Hg-O-Hg 135°, while PhHgOH contains the [(PhHg)2OH]+ cation and is better formulated as [(PhHg)2OH]OH. The same cation is also featured in the two basic salts. Electrospray mass spectral studies of PhHgOH in aqueous solutions show that [PhHgOH2]+, [(PhHg)2OH]+ and [(PhHg)3O]+ co-exist in solution in a pH-dependent equilibrium

Spectral and Structural Characterization of 5,6-Chrysenequinone Diimine Complexes of Rhodium(III): Evidence for a pH-Dependent Ligand Conformational Switch

Rhodium(III) complexes containing 9,10-phenanthrenequinone diimine (phi) ligands have been broadly applied for the construction of DNA binding and recognition molecules, and more recently, derivatives containing the 5,6-chrysenequinone diimine (chrysi) ligand have been shown specifically to recognize base mismatches in DNA. Here the structural properties of [Rh(bpy)_2(chrysi)]Cl_3 and spectroscopic properties of derivatives are examined and compared to those of phi complexes of rhodium. Although similar in many respects, phi and chrysi complexes display distinctly different protonation behavior. The pK_a values of chrysi complexes are as much as 1 unit lower than analogous phi compounds, and visible spectra of the chrysi complexes differ markedly from the phi counterparts in acidic but not basic solution. This protonation behavior is traced to the presence of a steric clash between a proton on the aromatic ring of the chrysi ligand and the acidic immino proton of the metal complex. In avoidance of this steric clash, a significant disruption in the planarity of the chrysi ligand is evident crystallographically in the structure of [Rh(bpy)_2(chrysi)]Cl_3·3CH_3CN·2H_2O (triclinic crystal system, space group P1̄ (No. 2), Z = 2, a = 9.079(3) Å, b = 10.970(3) Å, c = 21.192(8) Å, α = 86.71(3)°, β = 89.21(3)°, γ = 78.58(3)°, V = 2065.4(12) Å^3). Phi complexes, lacking the additional aromatic ring, require no similar distortion from ligand planarity. NMR spectra support this pH-dependent structural distortion for the chrysi complex. Rhodium complexes of chrysenequinone diimine, therefore, not only represent new DNA binding molecules targeted to mismatches but also provide an illustration of a pH “gated” ligand conformational switch

Low-noise 0.8-0.96- and 0.96-1.12-THz superconductor-insulator-superconductor mixers for the Herschel Space Observatory

Heterodyne mixers incorporating Nb SIS junctions and NbTiN-SiO/sub 2/-Al microstrip tuning circuits offer the lowest reported receiver noise temperatures to date in the 0.8-0.96- and 0.96-1.12-THz frequency bands. In particular, improvements in the quality of the NbTiN ground plane of the SIS devices' on-chip microstrip tuning circuits have yielded significant improvements in the sensitivity of the 0.96-1.12-THz mixers relative to previously presented results. Additionally, an optimized RF design incorporating a reduced-height waveguide and suspended stripline RF choke filter offers significantly larger operating bandwidths than were obtained with mixers that incorporated full-height waveguides near 1 THz. Finally, the impact of junction current density and quality on the performance of the 0.8-0.96-THz mixers is discussed and compared with measured mixer sensitivities, as are the relative sensitivities of the 0.8-0.96- and 0.96-1.12-THz mixers

H-Diplo Roundtable Review

Cambridge:Harvard University Press. 2014. ISBN: 9780674729711 (hardcover, $45.00/£29.95/€35.00) Modern European history was under the anniversary spotlight in 2014-2015. The centenary of the beginning of the First World War brought forth a steady stream of commemorations and publications. Standing out was Christopher Clark’s The Sleepwalkers, a global bestseller, whose controversial reinterpretation of the crisis of July 1914 and of the responsibility for its violent outcome ignited a widespread academic and public debate.1 Overshadowed by the anniversary of the Great War’s outbreak was the bicentenary of another great war’s conclusion, two hundred years after the end of the Napoleonic wars. In this relatively subdued realm, most of the attention was devoted to the final instance of armed conflict, with official commemorations of, books about, large-scale reenactments of, and multimedia exhibitions displaying the Battle of Waterloo

Recognition of Base Mismatches in DNA by 5,6-Chrysenequinone Diimine Complexes of Rhodium(III): A Proposed Mechanism for Preferential Binding in Destabilized Regions of the Double Helix

5,6-Chrysenequinone diimine (chrysi) complexes of rhodium(III) have been shown to be versatile and specific recognition agents for mismatched base pairs in DNA. The design of these compounds was based on the hypothesis that the sterically expansive chrysi ligand, which should be too wide to readily intercalate into B-DNA, would bind preferentially in the destabilized regions of the DNA helix near base mismatches. In this work, this recognition hypothesis is comprehensively explored. Comparison of the recognition patterns of the complex [Rh(bpy)_2(chrysi)]^(3+) with a nonsterically demanding analogue, [Rh(bpy)_2(phi)]^(3+) (phi = 9,10-phenanthrenequinone diimine), demonstrates that the chrysi ligand does indeed disfavor binding to B-DNA and generate mismatch selectivity. Examination of mismatch recognition by [Rh(bpy)_2(chrysi)]^(3+) in both constant and variable sequence contexts using photocleavage assays indicates that the recognition of base mismatches is influenced by the amount that a mismatch thermodynamically destabilizes the DNA helix. Thermodynamic binding constants for the rhodium complex at a range of mismatch sites have been determined by quantitative photocleavage titration and yield values which vary from 1 × 10^6 to 20 × 10^6 M^(-1). These mismatch-specific binding affinities correlate with independent measurements of thermodynamic destabilization, supporting the hypothesis that helix destabilization is a factor determining the binding affinity of the metal complex for the mismatched site. Although not the only factor involved in the binding of [Rh(bpy)_2(chrysi)]^(3+) to mismatch sites, a model is proposed where helix destabilization acts as the “door” which permits access of the sterically demanding intercalator to the base stack

The morphological mix of dwarf galaxies in the nearby Universe

© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We use a complete, unbiased sample of 257 dwarf (10 8 M < M < 10 9.5 M) galaxies at z < 0.08, in the COSMOS field, to study the morphological mix of the dwarf population in low-density environments. Visual inspection of extremely deep optical images and their unsharp-masked counterparts reveals three principal dwarf morphological classes. 43 per cent and 45 per cent of dwarfs exhibit the traditional ‘early-type’ (elliptical/S0) and ‘late-type’ (spiral) morphologies, respectively. However, 10 per cent populate a ‘featureless’ class, that lacks both the central light concentration seen in early-types and any spiral structure – this class is missing in the massive-galaxy regime. 14 per cent, 27 per cent, and 19 per cent of early-type, late-type, and featureless dwarfs respectively show evidence for interactions, which drive around 20 per cent of the overall star formation activity in the dwarf population. Compared to their massive counterparts, dwarf early-types show a much lower incidence of interactions, are significantly less concentrated and share similar rest-frame colours as dwarf late-types. This suggests that the formation histories of dwarf and massive early-types are different, with dwarf early-types being shaped less by interactions and more by secular processes. The lack of large groups or clusters in COSMOS at z < 0.08, and the fact that our dwarf morphological classes show similar local density, suggests that featureless dwarfs in low-density environments are created via internal baryonic feedback, rather than by environmental processes. Finally, while interacting dwarfs can be identified using the asymmetry parameter, it is challenging to cleanly separate early and late-type dwarfs using traditional morphological parameters, such as ‘CAS’, M 20, and the Gini coefficient (unlike in the massive-galaxy regime).Peer reviewe