Adaptive Synaptogenesis Constructs Neural Codes That Benefit Discrimination

Intelligent organisms face a variety of tasks requiring the acquisition of expertise within a specific domain, including the ability to discriminate between a large number of similar patterns. From an energy-efficiency perspective, effective discrimination requires a prudent allocation of neural resources with more frequent patterns and their variants being represented with greater precision. In this work, we demonstrate a biologically plausible means of constructing a single-layer neural network that adaptively (i.e., without supervision) meets this criterion. Specifically, the adaptive algorithm includes synaptogenesis, synaptic shedding, and bi-directional synaptic weight modification to produce a network with outputs (i.e. neural codes) that represent input patterns proportional to the frequency of related patterns. In addition to pattern frequency, the correlational structure of the input environment also affects allocation of neural resources. The combined synaptic modification mechanisms provide an explanation of neuron allocation in the case of self-taught experts

Historical Floods in New England

One or more of the great recent New England floods of 1927, 1936, 1938, and 1955 exceeded the greatest known historical floods on most of the major rivers. Locally, on tributary streams, the great floods of recent years probably exceeded historical floods, but the certainty diminishes for the floods that occurred prior to the observance of living witnesses. This report presents, by year, a condensation of the data on unusual historical floods (floods that occurred before establishment of gaging stations) and the sources of this evidence. This information will be helpful in the determination of the frequency of the highest flood or floods of record. Such determinations are necessary for studies of flood frequencies and magnitudes, which in turn are necessary for studies of relative costs and benefits of flood-control measures and of bridges, and for the evaluation of flood-plain insurance and zoning measures

Rowing Against the Tide: Getting Landowners to Manage Habitat for Their Favorite Wildlife Species, Bobwhites

A primary cause of the decline of northern bobwhite (Colinus virginianus) is that landowners often lack adequate motivation for the arduous task of creating and managing habitat. We gained insight into some of these motivations through survey questionnaires and focus groups in Missouri, and report findings from 3 studies containing 3,057 survey responses during 2004–2007. One of the surveys targeted Conservation Reserve Program (CRP) lands (‘CRP survey’), another lands with potential for bobwhite restoration (‘bobwhite survey’), and the third focused on grassland bird restoration. Landowners in each survey identified bobwhites as the most popular (.80% of respondents chose ‘somewhat’ or ‘very’ ‘important’ to have bobwhites ‘on my land’) natural resource among a list that included deer, turkeys, prairie-chickens, native plants, grassland birds, rabbits, hawks/owls, etc. Bobwhites were highly valued by landowners, but other answers in these surveys revealed many obstacles to habitat management including economics, time, knowledge, skill, and equipment. For example, only 39% of respondents in the bobwhite survey were interested in joining a habitat restoration cooperative, and ,50% of respondents in all surveys were willing to adopt quail-friendly habitat management (prescribed fire, disking, herbicides, moderate grazing, native vegetation, presence of weeds, etc.). Bobwhite restoration programs, because of the gap between landowners’ fondness for quail, but being less willing to take action, must include a comprehensive approach, ranging from local community involvement by agency biologists and non-government organizations to resource-use policy in Washington, D.C

Self-Generated Magnetic Fields in Galactic Cooling Flows

Interstellar magnetic fields in elliptical galaxies are assumed to have their origin in stellar fields that accompany normal mass loss from an evolving population of old stars. The seed fields are amplified by interstellar turbulence driven by stellar mass loss and supernova events. These disordered fields are further amplified by time-dependent compression in the inward moving galactic cooling flow and are expected to dominate near the galactic core. Under favorable circumstances, fields similar in strength to those observed $B \sim 1-10~(r/10~kpc)^{-1.2}\mu$G can be generated solely from these natural galactic processes. In general the interstellar field throughout elliptical galaxies is determined by the outermost regions in the interstellar gas where the turbulent dynamo process can occur. Because of the long hydrodynamic flow times in galactic cooling flows, currently observed magnetic fields may result from periods of intense turbulent field amplification that occurred in the outer galaxy in the distant past. Particularly strong fields in ellipticals may result from ancient galactic mergers or shear turbulence introduced at the boundary between the interstellar gas and ambient cluster gas.Comment: 21 pages in AASTEX LaTeX with 2 figures; accepted by Astrophysical Journa

1RXS J232953.9+062814: A Dwarf Nova with a 64-minute Orbital Period and a Conspicuous Secondary Star

We present spectroscopy and time-series photometry of the newly discovered dwarf nova 1RXS J232953.9+062814. Photometry in superoutburst reveals a superhump with a period of 66.06(6) minutes. The low state spectrum shows Balmer and HeI emission on a blue continuum, and in addition shows a rich absorption spectrum of type K4 +- 2. The absorption velocity is modulated sinusoidally at P_orb = 64.176(5) min, with semi-amplitude K = 348(4) km/s. The low-state light curve is double-humped at this period, and phased as expected for ellipsoidal variations. The absorption strength does not vary appreciably around the orbit. The orbital period is shorter than any other cataclysmic variable save for a handful of helium-star systems and V485 Centauri (59 minutes). The secondary is much hotter than main sequence stars of similar mass, but is well-matched by helium-enriched models, indicating that the secondary evolved from a more massive progenitor. A preliminary calculation in which a 1.2 solar-mass star begins mass transfer near the end of H burning matches this system's characteristics remarkably well.Comment: accepted to Astrophysical Journal Letters; 14 pages, 3 eps figures + 1 jpg greyscale figur

Housing and Business Investment in Nebraska\u27s Non-metropolitan Communities and Declining Urban Neighborhoods

This study focuses on one subject area of the Urban Affairs Committee\u27s charge: housing and business investment in Nebraska\u27s declining urban neighborhoods and non-metropolitan communities. From its beginning the study has had two primary objectives: First, to ascertain the demand for housing and business investment funds in the declining urban neighborhoods of Nebraska\u27s two major metropolitan cities, Omaha and Lincoln, and in the State\u27s non-metropolitan communities; and the perceptions of homeowners, renters, landlords and businessmen in these communities and neighborhoods regarding the availability to them of such funds. Second, to identify factors which discourage or hamper housing and business investment in the declining urban neighborhoods of Omaha and Lincoln and in the State\u27s non-metropolitan communities, and to recommend legislation and other measures to eliminate such factors and to provide incentives for increased investment in these neighborhoods and communities

Integrating ecology into macroevolutionary research

On 9 March, over 150 biologists gathered in London for the Centre for Ecology and Evolution spring symposium, ‘Integrating Ecology into Macroevolutionary Research’. The event brought together researchers from London-based institutions alongside others from across the UK, Europe and North America for a day of talks. The meeting highlighted methodological advances and recent analyses of exemplar datasets focusing on the exploration of the role of ecological processes in shaping macroevolutionary patterns

Comparison of (alpha, n) thick-target neutron yields and spectra from ORINGEN-S and SOURCES

Both ORIGEN-S and SOURCES generate thick-target neutron yields and energy spectra from ({alpha},n) reactions in homogeneous materials. SOURCES calculates yield and spectra for any material containing {alpha}-emitting and ({alpha},n) target elements by simulating reaction physics, using {alpha}-emission energy spectra, elemental stopping cross sections, ({alpha},n) cross sections for target nuclei, and branching fractions to produce-nuclide energy levels. This methodology results in accurate yield and spectra. ORIGEN-S has two options for calculating yields and spectra. The UO{sub 2} option (default) estimates yields and spectra assuming the input {alpha}-emitters to be infinitely dilute in UO{sub 2}. The borosilicate-glass option estimates yields from the total input material composition and generates spectra purportedly representative of spectra generated by {sup 238}Pu, {sup 241}Am, {sup 242}Cm, and {sup 244}Cm infinitely dilute in borosilicate glass, even if none of these four {alpha}-emitters are present in the input material composition. Because yields from the borosilicate-glass option in ORIGEN-S are based on entire input material composition and are reasonably accurate, the same is often assumed to be true for spectra. The input/output functionality of the borosilicate-glass option, along with ambiguity in ORIGEN-S documentation, gives the incorrect impression that spectra representative of input compositions are generated. This impression is reinforced by wide usage of the SCALE code system and its ORIGEN-S module and their sponsorship by the US Nuclear Regulatory Commission

The K2 Mission: Characterization and Early results

The K2 mission will make use of the Kepler spacecraft and its assets to expand upon Kepler's groundbreaking discoveries in the fields of exoplanets and astrophysics through new and exciting observations. K2 will use an innovative way of operating the spacecraft to observe target fields along the ecliptic for the next 2-3 years. Early science commissioning observations have shown an estimated photometric precision near 400 ppm in a single 30 minute observation, and a 6-hour photometric precision of 80 ppm (both at V=12). The K2 mission offers long-term, simultaneous optical observation of thousands of objects at a precision far better than is achievable from ground-based telescopes. Ecliptic fields will be observed for approximately 75-days enabling a unique exoplanet survey which fills the gaps in duration and sensitivity between the Kepler and TESS missions, and offers pre-launch exoplanet target identification for JWST transit spectroscopy. Astrophysics observations with K2 will include studies of young open clusters, bright stars, galaxies, supernovae, and asteroseismology.Comment: 25 pages, 11 figures, Accepted to PAS