bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bases for commutative semigroups and groups
Authors: HINDMAN NEIL , STRAUSS DONA 
Published: July 2008

AbstractAbasefor a commutative semigroup (S, +) is an indexed set 〈xt〉t∈AinSsuch that each elementx∈Sis uniquely representable as Σt∈FxtwhereFis a finite subset ofAand, ifShas an identity 0, then 0 = Σn∈Øxt. We investigate those commutative semigroups or groups which have a base. We obtain the surprising result thathas a base. More generally, we show that an abelian group has a base if and only if it has no elements of odd finite order.
Complex asymptotics of Poincaré functions and properties of Julia sets
Authors: DERFEL GREGORY , GRABNER PETER J. , VOGL FRITZ 
Published: July 2008

AbstractThe asymptotic behaviour of the solutions of Poincaré's functional equation f(λz) = p(f(z)) (λ > 1) for p a real polynomial of degree ≥ 2 is studied in angular regions W of the complex plain. It is known [9, 10] that f(z) ~ exp(zρF(logλz)), if f(z) → ∞ for z ∞ and z ∈ W, where F denotes a periodic function of period 1 and ρ = logλ deg(p). In this paper we refine this result and derive a full asymptotic expansion. The constancy of the periodic function F is characterised in terms of geometric properties of the Julia set of p. For real Julia sets we give inequalities for multipliers of Pommerenke-Levin-Yoccoz type. The distribution of zeros of f is related to the harmonic measure on the Julia set of p.
Challenges for maintaining sustainable agricultural systems in the United States
Authors: Hanson J.D. , Hendrickson John , Archer Dave 
Published: July 2008

AbstractDuring the 20th century, US agriculture underwent vast transformations. The number of farmers has decreased, more farmers are relying on off-farm income, agriculture's proportion of the US GDP has declined, and a minority of non-metro counties in the US are farming dependent. Agriculture's evolution will continue and we have identified key trends and future challenges to effectively manage our changing agricultural system. Eight current trends in US agriculture were identified. These included: (1) increased land degradation; (2) competing land uses; (3) focus on single ecosystem service; (4) increase in farm size; (5) movement toward commercialization; (6) genetic engineering; (7) global markets; and (8) changing social structure. Future trends likely to affect agriculture include: (1) diminishing and increasingly volatile farm incomes; (2) reduced government involvement in food regulation; (3) continued transition from farming to agribusiness; (4) land-use will become a major issue; (5) increasing animal protein consumption in the US; (6) increased public input on livestock production practices; (7) increasing urbanization of historically rural US counties; (8) increased public concern over food safety; (9) increased medicinal production from agriculture; (10) new tastes, markets and opportunities will emerge. We further postulated that future challenges facing US agriculture might include: (1) competitive pressures; (2) sustainable development; (3) resource conservation; and (4) research and development. Integrated agricultural systems may be flexible enough to address these challenges. However, robust principles will be needed to design adaptable integrated agricultural systems. We present a nonexclusive list of preliminary principles under the four general categories of (1) economics and economic policies; (2) environmental; (3) social and political; and (4) technological.
Interactions in integrated US agricultural systems: The past, present and future
Authors: Hendrickson J. , Sassenrath G.F. , Archer D. , Hanson J. , Halloran J. 
Published: July 2008

AbstractDuring the 20th century, American agriculture underwent dramatic changes. At the beginning, farms were more diverse, dependent on animal traction, on-farm inputs and income and, after initial land grants, nearly independent of government policy. However, external issues, such as government policies, mechanization, fossil fuel costs, increased consolidation and vertical integration of markets and increased societal awareness of the environment and concern with farming practices, have substantially altered the structure of agriculture. These external issues are significant drivers of agriculture and we grouped them into social/political, economic, environmental and technological drivers. Previous papers have examined specific effects of these drivers. Our objective is to examine how these drivers interact and influence today's agricultural systems. We developed four categories: (1) Commodity Crop Production, (2) Supply Chain Livestock Production, (3) Organic Production and (4) Extensive Livestock Production, to describe major current agricultural systems. These categories were developed as major and contrasting systems but do not represent all of American agriculture. Although it is not possible to predict the future, interactions among the various drivers will affect these systems differently. By examining multiple scenarios, we conclude the highly specialized systems (Nos. 1 and 2) are highly vulnerable to future changes, and that developing adaptive capacity is critical for dealing with new uncertainty. Sustainable agricultural systems will need balance among various domains to be able to adapt and survive. We suggest that the concept of dynamic-integrated agricultural systems may be the best way to meet this goal because of its ability to consider multiple goals and flexible producer decision-making.
Adding value in the organic sector: Characteristics of organic producer–handlers
Authors: Oberholtzer Lydia , Dimitri Carolyn , Greene Catherine 
Published: July 2008

AbstractSales of organic food have soared over the past decade. Although nearly all organic commodities pass through the hands of at least one intermediary on the way from the farmer to the consumer, there is a dearth of literature examining organic food marketing, especially for the middle section of the supply chain. This paper uses new survey data on organic intermediaries (organic handlers) to characterize firms that are certified to both handle and produce organic foods, or organic producer–handlers. Because of their direct link to the production level, the producer–handler has the potential to provide insight into value-added activities in the organic sector. A logistic regression is estimated in order to identify characteristics that make it more likely that a firm would be both a certified organic handler and a certified organic producer, while survey results are also used to describe some of the main challenges these producer–handlers face in handling their products. Organic producer–handlers ranked problems with ingredient procurement and supply and international trade issues as the highest barriers to growth. The model indicated that with few exceptions, many of the operational and procurement characteristics of organic producer–handlers are comparable to the entire organic handling population. However, those facilities dedicated solely to organic handling and those certified longer are more likely to be organic producer–handlers. Use of direct markets by organic handlers has the most robust relationship in the model, although marketing to natural products independent retailers and wholesalers are also important.
Galactic bulges: overview
Authors: Freeman K. C. 
Published: July 2008

AbstractThis overview of galactic bulges begins with a discussion of the various kinds of bulges (classical, boxy/peanut-shaped, pseudo) and their likely formation mechanisms. Other specific topics include the Galactic bar/bulge and its chemical evolution, the bulge of M31, the relation between bulges and metal-poor halos (often lumped together as spheroids), the morphology-density relation and the formation of S0 galaxies, the color-structure bimodality, and scaling laws for bulges. Finally I will briefly discuss the current difficulty of forming bulgeless disk galaxies in ΛCDM.
Fast and slow rotators: the build-up of the red sequence
Authors: Emsellem Eric , Cappellari Michele , Krajnović Davor , van de Ven Glenn , Bacon R. , Bureau M. , Davies Roger L. , de Zeeuw P. T. , Falcón-Barroso Jesús , Kuntschner Harald , McDermid Richard M. , Peletier Reynier F. , Sarzi Marc , van den Bosch Remco C. E. 
Published: July 2008

AbstractUsing the unique dataset obtained within the course of theSAURONproject, a radically new view of the structure, dynamics and stellar populations of early-type galaxies has emerged. We show that galaxies come in two broad flavours (slow and fast rotators), depending on whether or not they exhibit clear large-scale rotation, as indicated via a robust measure of the specific angular momentum of baryons. This property is also linked with other physical characteristics of early-type galaxies, such as: the presence of dynamically decoupled cores, orbital structure and anisotropy, stellar populations and dark matter content. I here report on the observed link between this baryonic angular momentum and a mass sequence, and how this uniquely relates to the building of the red sequence via dissipative/dissipationless mergers and secular evolution.
Constraining the internal dynamics of stellar systems using the NMAGIC particle code
Authors: De Lorenzi Flavio , Gerhard Ortwin , Debattista Victor P. , Sambhus Niranjan , Coccato L. , Arnaboldi M. , Capaccioli M. , Douglas N. G. , Freeman K. C. , Kuijken K. , Merrifield M. R. , Napolitano N. R. , Noordermeer E. , Romanowsky A. J. 
Published: July 2008

AbstractNMAGIC is a parallel implementation of our made-to-measure (χ2M2M) algorithm for constructing N-particle models of stellar systems from observational data, which extends earlier ideas by Syer & Tremaine (1996). The χ2M2M algorithm properly accounts for observational errors, is flexible, and can be applied to various systems and geometries. We show its ability to reproduce the internal dynamics of an oblate isotropic rotator model and report on the modeling of the dark matter (DM) halo of NGC 3379 combining SAURON and PN.S kinematic data. The χ2M2M algorithm is practical, reliable and can be applied to various dynamical systems without symmetry restrictions. We conclude that χ2M2M holds great promise for unraveling the internal dynamics of bulges.
The role of stellar feedback in the formation of galactic disks and bulges in a ΛCDM Universe
Authors: Ceverino Daniel , Klypin Anatoly 
Published: July 2008

AbstractAlthough supernova explosions and stellar winds happens at scales bellow 100 pc, they affect the interstellar medium (ISM) and galaxy formation. We use cosmological N-body+Hydrodynamics simulations of galaxy formation, as well as simulations of the ISM to study the effect of stellar feedback on galactic scales. Stellar feedback maintains gas with temperatures above a million degrees. This gas fills bubbles, super-bubbles and chimneys. Our model of feedback, in which 10%–30% of the feedback energy is coming from runaway stars, reproduces this hot gas only if the resolution is better than 50 pc. This is 10 times better than the typical resolution in cosmological simulations of galaxy formation. Only with this resolution, the effect of stellar feedback in galaxy formation is resolved without any assumption about sub-resolution physics. Stellar feedback can regulate the formation of bulges and can shape the inner parts of the rotation curve.
A new 3D potential-density basis set
Authors: Rahmati Alireza , Jalali Mir Abbas 
Published: July 2008

AbstractA set of bi-orthogonal potential-density basis functions is introduced to model the density and its associated gravitational field of three dimensional stellar systems. Radial components of our basis functions are weighted integral forms of spherical Bessel functions. We discuss on the properties of our basis functions and demonstrate their shapes for the latitudinal Fourier numberl= 2.
Elucidation of kinematical and dynamical structure of the Galactic bulge
Authors: Yano T. , Gouda N. , Ueda H. , Koyama H. , Kan-ya Y. , Taruya A. 
Published: July 2008

AbstractFuture space mission of astrometric satellite, GAIA and JASMINE (Japan Astrometry Satellite Mission for Infrared Exploration), will produce astrometric parameter, such as positions, parallaxes, and proper motions of stars in the Galactic bulge. Then kinematical information will be obtained in the future. Accordingly it is expected that our understanding of the dynamical structure will be greatly improved. Therefore it is important to make a method to construct a kinematical and dynamical structure of the Galactic bulge immediately.
Formation and evolution of galactic spheroids by mergers
Authors: Naab Thorsten , Burkert Andreas , Johansson Peter H. , Jesseit Roland 
Published: July 2008

AbstractGalactic spheroids can form as a result of galaxy interactions and mergers of disks. Detailed analyses of the photometric properties, the intrinsic orbital structure, the line-of-sight velocity distributions and the kinemetry of simulated merger remnants, which depend critically on the geometry and the gas content of the interacting progenitors, indicate that low and intermediate mass rotating ellipticals can form from mergers of disks. The masses and metallicities of all massive ellipticals and the kinematics of some massive non-rotating ellipticals cannot be explained by binary mergers. Thus these galaxies might have formed in a different way.
How galaxies gain and lose their angular momentum
Authors: D'Onghia Elena 
Published: July 2008

AbstractSpiral, fast-rotating galaxies like the Milky Way are the most common type in the Universe. One of the most pressing challenges faced by current models of galaxy formation is the origin of their angular momentum and disk. According to the standard tidal-torque theory the galactic spin is originated by tidal interactions between dark halos around galaxies and neighboring structures in the expanding Universe. We use a large cosmological N-body simulation to study the origin of possible correlations between the merging history and spin of cold dark matter halos. In particular, we examine claims that remnants of major mergers tend to have higher-than-average spins, and find that the effect is driven largely by unrelaxed systems: equilibrium dark matter halos show no significant correlation between spin and merging history. Out-of-equilibrium halos have, on average, higher spin than relaxed systems, suggesting that the virialization process leads to a net decrease in the value of the spin parameter. We present also high-resolution N-body/SPH cosmological simulations including cold gas and dark matter to investigate the processes by which gas loses its angular momentum during the protogalactic collapse phase, leading to simulated disk galaxies that are too compact with respect to the observations. We show that the gas and the dark matter have similar specific angular momenta until a merger event occurs at redshift 2. All the gas involved in the merger loses a substantial fraction of its specific angular momentum due to tidal torques and falls quickly into the center. Dynamical friction by small infalling substructures plays a minor role, in contrast to previous claims.
The hierarchical build-up of bulges in CDM
Authors: Khochfar Sadegh 
Published: July 2008

AbstractWe investigate the hierarchical build-up of stars in bulges within the standard Λ-cold dark matter scenario. By separating the population into stars born during starbursts that accompany the formation of spheroids in major mergers (starburst component), and stars that are previously formed in discs of progenitor galaxies (quiescent component) and added to the spheroid by dynamical interaction. Our results are summarised as follows: bulges that form early have larger starburst fraction and hence should be smaller than their counter parts that form later. The quiescent fraction in bulges is an increasing function of bulge mass, becoming constant at Mq/Mbul ~ 0.8, mainly due to the infall of satellite galaxies that contribute disc stars to the bulge. Minor mergers are an order of magnitude more frequent than major mergers and must play a significant role in the evolution of bulges. Above the critical mass Mc ~ 3 × 1010 M⊙ most of the stars in the universe are in spheroids, which at high redshift are exclusively elliptical galaxies and at low redshifts partly bulges. Due to the enhanced evolution of galaxies ending up in high density environments, the starburst fraction and the surface mass densities of bulges below Mc should be enhanced with respect to field galaxies. Dissipation during the formation of massive bulges in present day early-type spirals is less important than for the formation of present day elliptical galaxies of the same mass thereby explaining the possible difference in phase-space densities between spiral galaxies and elliptical galaxies.
Forming bulges during galaxy minor mergers
Authors: Cox T. J. , Younger J. , Hernquist L. , Hopkins P. F. 
Published: July 2008

AbstractThe hierarchical formation of structure suggests that dark halos, and the galaxies they host, are shaped by their merging history. While the idea that mergers between galaxies of equal mass, i.e., major merger, produce elliptical galaxies has received considerable attention, he galaxies that result from minor merger, i.e., mergers between galaxies with a large mass ratio, is much less understood. We have performed a large number of numerical simulations of minor mergers, including cooling, star formation, and black hole growth in order to study this process in more detail. This talk will present some preliminary results of this study, and in particular, the morphology and kinematics of minor merger remnants.
Bulges vs elliptical galaxies: some clues from their formation in a cosmological context
Authors: Domínguez-Tenreiro R. , Martínez-Serrano F. J. , Serna A. , Mollá M. , Oñorbe J. 
Published: July 2008

AbstractWe report on an extension, through cosmological simulations, of the two-phase formation scenario for elliptical galaxies to classical spiral bulges. In particular, we analyze the possibility that the old stellar population of bulges forms in a fast phase, while the younger stellar component forms or is assembled in a slow phase, in part from disk material suffering instabilities and in part through satellite capture or mergers.
Lopsidedness and sloshing in centres of advanced mergers of galaxies
Authors: Jog Chanda J. , Maybhate Aparna 
Published: July 2008

AbstractWe measure the non-axisymmetry in the luminosity distribution in the central few kpc of a sample of advanced mergers of galaxies, by analyzing their 2MASS images. All mergers show a high central asymmetry: the centres of isophotes show a striking sloshing pattern with a spatial variation of upto 30% within the central 1 kpc; and the Fourier amplitude for lopsidedness (m = 1) shows high values upto 0.2 within the central 5 kpc. The central asymmetry is estimated to be long-lived, lasting for ~ a few Gyr or ~ 100 local dynamical timescales. This will significantly affect the dynamical evolution of this region, by helping fuel the central active galactic nucleus, and also by causing the secular growth of the bulge driven by lopsidedness.
Star formation history and isophotal shapes of fossil central galaxies
Authors: Khosroshahi Habib G. , Nolan Louisa A. 
Published: July 2008

AbstractWe study the structure and stellar populations of the luminous elliptical galaxies dominating fossil groups and compare them with the brightest galaxies in ordinary groups. Despite being over-luminous, the fossil central galaxies do not show boxy stellar isophotes which are usually associated with luminous elliptical galaxies. Boxy isophotes, according to the numerical simulations, are produced in gas poor mergers. The isophotal shapes of the fossil central galaxies, therefore, suggest a gas rich merger for fossil central galaxies. Using a two-component spectral fitting, we show that the dominant stellar population of the fossil and non-fossil galaxies is old and the second population is either old or intermediate age. However, the second stellar component (recently-formed stars) in fossil central galaxies is significantly more metal poor than that in the brightest galaxies of non-fossil groups.
Variations in the 24 μm morphologies of nearby galaxies
Authors: Bendo G. J. 
Published: July 2008

AbstractTo study the distribution of star formation and dust emission within nearby galaxies, we measured five morphological parameters in the 24 μm wave band for 73 galaxies observed as part of the Spitzer Infrared Nearby Galaxies Survey. The morphological parameters demonstrate strong variations along the Hubble sequence, including statistically significant differences between S0/a-Sab and Sc-Sd galaxies. Early-type spiral galaxies are generally found to be compact, centralized, symmetric sources in the 24 μm band, whereas late-type spiral galaxies are generally found to be extended, asymmetric 24 μm sources. These results suggest that processes that increase the real or apparent sizes of galaxies' bulges also lead to more centralized 24 μm emission.
Bulge properties and dark matter content of early-type barred galaxies
Authors: Corsini E. M. 
Published: July 2008

AbstractThe dynamics of a barred galaxy depends on the pattern speed of its bar. The only direct method for measuring the pattern speed of a bar is the Tremaine-Weinberg technique. This method is best suited to the analysis of the distribution and dynamics of the stellar component. Therefore it has been mostly used for early-type barred galaxies. Most of them host a classical bulge. On the other hand, a variety of indirect methods, which are based on the analysis of the distribution and dynamics of the gaseous component, has been used to measure the bar pattern speed in late-type barred galaxies. Nearly all the measured bars are as rapidly rotating as they can be. By comparing this result with high-resolution numerical simulations of bars in dark matter halos, it is possible to conclude that these bars reside in maximal disks.
Bar strengths in early-type disk galaxies
Authors: Buta R. , Laurikainen E. , Salo H. , Knapen J. H. , Block D. L. 
Published: July 2008

AbstractUsing the gravitational torque indicator Qb, we derive the distribution of bar strengths for a sample of early-type disk galaxies. The sample is part of the Near-Infrared S0 Survey (NIRS0S), designed to examine the properties of bars, bulges, and disks in galaxies classified as types S0− to Sa. Although the survey is only partly finished, we find that the distribution of bar strengths in S0 galaxies differs from that in spirals by lacking an extended tail to high values of Qb. No S0 in our current sample has Qb > 0.25, while spirals extend to Qb ≈ 0.7. Bars having Qb > 0.25 first appear among S0/a to Sa galaxies.
Kinematics and stellar populations of the double-barred early-type galaxy NGC357
Authors: de Lorenzo-Cáceres Adriana , Vazdekis Alexandre , Aguerri J. Alfonso L. 
Published: July 2008

AbstractWe have carried out a kinematical and stellar population analysis of the double-barred galaxy NGC357 to provide a more complete characterization of these systems and their role in the formation of galaxy bulges. We clearly identify the presence of the inner bar in the radial velocity and velocity dispersion profiles. The age, metallicity and [Mg/Fe] abundance ratio estimates are very similar to those of ellipticals of equivalent central σ. The [Mg/Fe] value for the bulge of this galaxy suggests formation timescales shorter than 1Gyr.