Dynamical Blueprints for Galaxies

We present an axisymmetric, equilibrium model for late-type galaxies which consists of an exponential disk, a Sersic bulge, and a cuspy dark halo. The model is specified by a phase space distribution function which, in turn, depends on the integrals of motion. Bayesian statistics and the Markov Chain Monte Carlo method are used to tailor the model to satisfy observational data and theoretical constraints. By way of example, we construct a chain of 10^5 models for the Milky Way designed to fit a wide range of photometric and kinematic observations. From this chain, we calculate the probability distribution function of important Galactic parameters such as the Sersic index of the bulge, the disk scale length, and the disk, bulge, and halo masses. We also calculate the probability distribution function of the local dark matter velocity dispersion and density, two quantities of paramount significance for terrestrial dark matter detection experiments. Though the Milky Way models in our chain all satisfy the prescribed observational constraints, they vary considerably in key structural parameters and therefore respond differently to non-axisymmetric perturbations. We simulate the evolution of twenty-five models which have different Toomre Q and Goldreich-Tremaine X parameters. Virtually all of these models form a bar, though some, more quickly than others. The bar pattern speeds are ~ 40 - 50 km/s/kpc at the time when they form and then decrease, presumably due to coupling of the bar with the halo. Since the Galactic bar has a pattern speed ~50 km/s/kpc we conclude that it must have formed recently.Comment: 54 pages, 20 figure

A Unified Theory of Matter Genesis: Asymmetric Freeze-In

We propose a unified theory of dark matter (DM) genesis and baryogenesis. It explains the observed link between the DM density and the baryon density, and is fully testable by a combination of collider experiments and precision tests. Our theory utilises the "thermal freeze-in" mechanism of DM production, generating particle anti-particle asymmetries in decays from visible to hidden sectors. Calculable, linked, asymmetries in baryon number and DM number are produced by the feeble interaction mediating between the two sectors, while the out-of-equilibrium condition necessary for baryogenesis is provided by the different temperatures of the visible and hidden sectors. An illustrative model is presented where the visible sector is the MSSM, with the relevant CP violation arising from phases in the gaugino and Higgsino masses, and both asymmetries are generated at temperatures of order 100 GeV. Experimental signals of this mechanism can be spectacular, including: long-lived metastable states late decaying at the LHC; apparent baryon-number or lepton-number violating signatures associated with these highly displaced vertices; EDM signals correlated with the observed decay lifetimes and within reach of planned experiments; and a prediction for the mass of the dark matter particle that is sensitive to the spectrum of the visible sector and the nature of the electroweak phase transition.Comment: LaTeX, 22 pages, 6 figure

A Trapping Experiment to Estimate the Bluegill Population in a Farm Pond

Estimates of fish populations from recapture of marked fish have, on several occasions, yielded estimates far below the population later shown to be present (Krumholz 1944, Carlander and Lewis 1948, Fredin 1950, Carlander 1952). Fredin (1950) suggested that the recapture of the fish by some method different from that used in the original capture might give less biased results. In the present investigation the bluegill population was estimated by the marking and recovery technique using seines and baited wire traps

Decentralization and Access to Agricultural Extension Services in Kenya

The form and content of decentralization has dominated development discourse and public sector reform agenda in Kenya in the last two decades. The case of agricultural extension service presents decentralization in a difficult context partly due to lack of information on its possible diverse impacts especially on resource poor farmers. This paper explores the effect of decentralization of agricultural extension on access, accountability and empowerment, and efficiency of delivering services to farmers. Secondary data, participatory research methods and primary data from a random sample of 250 farmers were used. Data was analyzed using descriptive statistics, multivariate analysis and logistic regression. The results show that there is improved access to extension services with increasing level of decentralization. Farmers from areas with higher decentralized extension also showed enhanced level of awareness of different channels for delivery of extension services. This improved knowledge, being an important component of empowerment of the farming community, resulted from the increase of service providers, who displayed synergy in their multiple methods of operation. Public delivery channels were the most affordable and were also ranked first for quality. Income, literacy levels, distance from towns and access to telephone significantly influenced access to extension services. Gender of the household-head was a key determinant for seeking out extension services in areas with high concentration of agricultural activities. For a pluralistic system to work there is need for better co-ordination between the various groups. Although there is evidence of partnership and synergy between service providers, there appeared to be little effective co-ordination of the groups involved. The government and other stakeholders should work towards developing a strong institutional framework that will guide and enhance this mutually beneficial partnership.extension services, decentralization, partnerships, policy reform, Kenya, Teaching/Communication/Extension/Profession,

ECONOMIC INSIGHTS INTO THE SITING PROBLEM: AN APPLICATION OF THE EXPECTED UTILITY MODEL

Despite the generally recognized need for facilities such as power plants, landfills, prisons, and medical laboratories, finding host sites has become extremely difficult. This study uses the expected utility (EU) model to explain individiuals' preferences in the hypothetical case of siting a municipal solid waste composting facility. The three principal factors which EU theory prescribes would affect the decision process- benefits of the proposed facility, losses from the facility, and the (perceived) probability of various scenarios occurring- embodied by the variables in a multinomial logit model explain a substantial amount of the variation in siting decisions.Public Economics,

Synergies in Wireless Telephony: Evidence from the Broadband PCS Auctions

We examine bid data from the first two broadband PCS spectrum auctions for evidence of value synergies. First, we estimate a benchmark regression for the determinants of final auction prices. Then, we include variables reflecting the extent to which bidders ultimately won or already owned the adjacent wireless properties. Consistent with geographic synergies in an ascending-bid auction, prices were higher when the highest-losing bidder had adjacent licenses. The footprints of winning bidders suggest that they were often successful in realizing these synergies.Auctions; Multi-Object Auctions; Spectrum Auctions

Cationic Alkylaluminum-Complexed Zirconocene Hydrides: NMR-Spectroscopic Identification, Crystallographic Structure Determination, and Interconversion with Other Zirconocene Cations

The ansa-zirconocene complex rac-Me_2Si(1-indenyl)_2ZrCl_2 ((SBI)ZrCl_2) reacts with diisobutylaluminum hydride and trityl tetrakis(perfluorophenyl)borate in hydrocarbon solutions to give the cation [(SBI)Zr(μ-H)_3(Al^iBu_2)_2]^+, the identity of which is derived from NMR data and supported by a crystallographic structure determination. Analogous reactions proceed with many other zirconocene dichloride complexes. [(SBI)Zr(μ-H)_3(Al^iBu2)_2]^+ reacts reversibly with ClAl^iBu_2 to give the dichloro-bridged cation [(SBI)Zr(μ-Cl)_2Al^iBu_2]^+. Reaction with AlMe_3 first leads to mixed-alkyl species [(SBI)Zr(μ-H)_3(AlMe_x^iBu_(2−x))_2^]+ by exchange of alkyl groups between aluminum centers. At higher AlMe_3/Zr ratios, [(SBI)Zr(μ-Me)_2AlMe_2]^+, a constituent of methylalumoxane-activated catalyst systems, is formed in an equilibrium, in which the hydride cation [(SBI)Zr(μ-H)_3(AlR_2)_2]^+ strongly predominates at comparable HAl^iBu_2 and AlMe_3 concentrations, thus implicating the presence of this hydride cation in olefin polymerization catalyst systems

Eccentricity of the Apical System and Peristome of Sand Dollars (Echinodermata: Echinoidea: Clypeasteroida: Scutellina)

Eccentricity, location of structures away from a central position, is associated with directional movement. Although sand dollars have directional movement, only eccentricity of the anus is apparent. Eccentricity of the apical system and peristome is less apparent. We have found the apical system and the peristome are statistically significantly slightly anterior in Mellita tenuis, Mellita quinquiesperforata, Mellita isometra, and Encope aberrans. The apical system of Leodia sexiesperforata is central and that of Echinarachnius parma is anterior, whereas the peristome of both is statistically significantly slightly posterior. The usual selective pressure for pronounced anterior location of the mouth in animals with directional movement may be countered by the mode of feeding in sand dollars that utilizes the oral surface. The basis for the eccentricity of the apical system is not known