Invazivni ponto-kaspijski glavoči: riječni glavočić (Neogobius fluviatilis), glavočić okrugljak
(Neogobius melanostomus), keslerov glavočić (Ponticola kessleri) nedavno su uzrokovali
dramatične ...promjene struktura ribljih zajednica diljem europskih riječnih sustava. Iako je
njihova prisutnost u hrvatskom dijelu dunavskog slijeva primjećena i distribucija izučena,
njihova ishrana, utjecaj na autohtone populacije riba, kondicija, dob i rast, zastupljenost
haplotipova i porijeklo, do sada su bili nepoznati. Analiza sadržaja probavnog trakta
riječnog glavočića (Neogobius fluviatilis) ukazuje da mu je ishrana vrlo raznolika, ali
prevladavaju Trichoptera, Chironomidae, Bivalvia i Odonata. Ishrana mu se u znatnoj
mjeri preklapa s ishranom glavočića okrugljaka (Neogobius melanostomus), kojem u
ishrani prevladava Gastropoda. Mala riba i Gammarus sp. prevladavaju u ishrani
keslerova glavočića (Ponticola kessleri). Usporedba sadržaja probavnog trakta s plijenom
dostupnim u okolini ukazuje da riječni glavočić i glavočić okrugljak preferiraju Trichoptera,
Megaloptera i Coleoptera, a keslerov glavočić Trichoptera, Gammarus sp. i Pisces.
Analize ukazuju na potencijalno pozitivan utjecaj prisustva ponto-kaspijskih glavoča na
neke populacije riba: glavočića okrugljaka i keslerova glavočića na zlatnog vijuna
(Sabanejewia balcanica), riječnog glavočića na šarana (Cyprinus carpio), karasa
(Carassius carassius), manjića (Lota lota) i velikog vijuna (Cobitis elongata). Međutim,
postoje i naznake da keslerov glavočić negativno utječe na klena (Squalius cephalus), a
glavočić okrugljak na malog vretenca (Zingel streber). Pozitivan alometrijski rast utvrđen
je za sve tri analizirane vrste ponto-kaspijskih glavoča upućujući na vremenski duže
prisutne populacije. Kondicijski faktor najveći je za glavočića okrugljaka, a najmanji za
riječnog glavočića. Za riječnog glavočića je utvrđena dob I, II i III, a za glavočića
okrugljaka i keslerova glavočića I, II, III i IV, s tim da najveću brzinu rasta ima riječni
glavočić, a najmanju glavočić okrugljak. Za svaku od analiziranih vrsta ponto-kaspijskih
glavoča utvrđen je jedan crnomorski haplotip. Malen broj haplotipova upućuje na relativno
malobrojne populacije ponto-kaspijskih glavoča što potencijalno smanjuje visinu njihova
invazivnog potencijala u savskom slijevu.
Invazivni ponto-kaspijski glavoči: riječni glavočić (Neogobius fluviatilis), glavočić okrugljak
(Neogobius melanostomus), keslerov glavočić (Ponticola kessleri) nedavno su uzrokovali
dramatične promjene struktura ribljih zajednica diljem europskih riječnih sustava. Iako je
njihova prisutnost u hrvatskom dijelu dunavskog slijeva primjećena i distribucija izučena,
njihova ishrana, utjecaj na autohtone populacije riba, kondicija, dob i rast, zastupljenost
haplotipova i porijeklo, do sada su bili nepoznati. Analiza sadržaja probavnog trakta
riječnog glavočića (Neogobius fluviatilis) ukazuje da mu je ishrana vrlo raznolika, ali
prevladavaju Trichoptera, Chironomidae, Bivalvia i Odonata. Ishrana mu se u znatnoj
mjeri preklapa s ishranom glavočića okrugljaka (Neogobius melanostomus), kojem u
ishrani prevladava Gastropoda. Mala riba i Gammarus sp. prevladavaju u ishrani
keslerova glavočića (Ponticola kessleri). Usporedba sadržaja probavnog trakta s plijenom
dostupnim u okolini ukazuje da riječni glavočić i glavočić okrugljak preferiraju Trichoptera,
Megaloptera i Coleoptera, a keslerov glavočić Trichoptera, Gammarus sp. i Pisces.
Analize ukazuju na potencijalno pozitivan utjecaj prisustva ponto-kaspijskih glavoča na
neke populacije riba: glavočića okrugljaka i keslerova glavočića na zlatnog vijuna
(Sabanejewia balcanica), riječnog glavočića na šarana (Cyprinus carpio), karasa
(Carassius carassius), manjića (Lota lota) i velikog vijuna (Cobitis elongata). Međutim,
postoje i naznake da keslerov glavočić negativno utječe na klena (Squalius cephalus), a
glavočić okrugljak na malog vretenca (Zingel streber). Pozitivan alometrijski rast utvrđen
je za sve tri analizirane vrste ponto-kaspijskih glavoča upućujući na vremenski duže
prisutne populacije. Kondicijski faktor najveći je za glavočića okrugljaka, a najmanji za
riječnog glavočića. Za riječnog glavočića je utvrđena dob I, II i III, a za glavočića
okrugljaka i keslerova glavočića I, II, III i IV, s tim da najveću brzinu rasta ima riječni
glavočić, a najmanju glavočić okrugljak. Za svaku od analiziranih vrsta ponto-kaspijskih
glavoča utvrđen je jedan crnomorski haplotip. Malen broj haplotipova upućuje na relativno
malobrojne populacije ponto-kaspijskih glavoča što potencijalno smanjuje visinu njihova
invazivnog potencijala u savskom slijevu.
Invasive Ponto-Caspian gobies have recently caused dramatic changes in fish
assemblage structures throughout the Danube basin. While their presence in the Croatian
part of the basin has been noted and distribution studied, their dietary habits, impact on
native fish communities, condition, age and growth, presence of haplotypes and origin,
until now, have been unknown. In 2011, 17 locations in the Sava River Basin were
sampled for fish and 15 for benthic invertebrates. Fish population monitoring data,
available for nine seasons (2003-2006 and 2010-2014) and 12 locations, were used to
analyse the impacts of Ponto-Caspian gobies on benthic fish abundance. Gut content
analysis indicates that the monkey goby (Neogobius fluviatilis) diet is very diverse, but
dominated by Trichoptera, Chironomidae, Bivalvia and Odonata. The diet overlaps
considerably with the round goby (Neogobius melanostomus) diet, although Gastropoda
are dominant in the latter's diet. Small fish and Gammarus sp. dominate the bighead goby
(Ponticola kessleri) diet. Comparison of gut content with the prey available in the
environment indicates that monkey and round gobies exhibit preference for Trichoptera,
Megaloptera and Coleoptera, and bighead goby for Trichoptera, Gammarus sp. and
Pisces. Ponto-Caspian gobies in the Sava River are spreading upstream, towards the
reaches with lower fish diversity. Analyses indicate potentially positive impacts of PontoCaspian
gobies presence on some fish populations: round and bighead goby on Balkan
golden loach (Sabanejewia balcanica) and monkey goby on common carp (Cyprinus
carpio), crucian carp (Carassius carassius), burbot (Lota lota) and Balkan loach (Cobitis
elongata). However, there are also indications that bighead and round goby could
adversely impact the native chub (Squalius cephalus) and zingel (Zingel streber)
populations, respectively. Positive allometric growth has been determined for all three
analyzed Ponto-Caspian goby species, suggesting that they have been present for a
longer period of time. Condition factor, as a function of available energy resources, is the
largest for the round goby and the lowest for the monkey goby. Age I, II, III have been
determined for the monkey goby and age I, II, III, IV for the round and bighead goby, with
the highest growth rate determined for the monkey goby and the lowest for the round
goby. For each of the analyzed Ponto-Caspian goby species only one haplotype,
originated from native Black Sea populations, has been found. Determined monkey goby
haplotype has also been found in Ukraine and Slovakia and determined round goby
haplotype in Ukraine, Bulgaria, Slovakia, Serbia, Poland and Belgium. Determined
bighead goby haplotype has also been found only in Ukraine. A small number of
haplotypes indicates a relatively small number of Ponto-Caspian goby populations and
potentially reduces their invasive potential in the Sava River Basin. Although the PontoCaspian
goby caused significant disruptions in some areas of the Danube basin, density
of its population and impacts are relatively limited in the Sava River and its tributaries. As
Ponto-Caspian gobies are still in the expansionary period of invasion and the ecosystem
still adapting to new circumstances, continued monitoring of fish population dynamics in
the Sava basin is needed to determine the outcome and impacts of this invasion.
The evolution and explosion of metal-free stars with masses 10-100 M are followed, and their nucleosynthetic yields, light curves, and remnant masses determined. Such stars would have been the first ...to form after the big bang and may have left a distinctive imprint on the composition of the early universe. When the supernova yields are integrated over a Salpeter initial mass function (IMF), the resulting elemental abundance pattern is qualitatively solar, but with marked deficiencies of odd-Z elements with 7 <= Z <= 13. Neglecting the contribution of the neutrino wind from the neutron stars that they form, no appreciable abundances are made for elements heavier than germanium. The computed pattern compares favorably with what has been observed in metal-deficient stars with Z --3. The amount of ionizing radiation from this generation of stars is ~2.16 MeV per baryon (4.15 B per M ; where 1 B = 1 Bethe = 1051 erg) for a Salpeter IMF, and may have played a role in reionizing the universe. Neglecting rotation, most of the stars end their lives as blue supergiants and form supernovae with distinctive light curves resembling SN 1987A, but some produce primary nitrogen due to dredge-up and become red supergiants. These make brighter supernovae like typical Type IIp's. For the lower mass supernovae considered, the distribution of remnant masses clusters around typical modern neutron star masses, but above 20-30 M , with the value depending on explosion energy, black holes are copiously formed by fallback, with a maximum hole mass of ~40 M . A novel automated fitting algorithm is developed for determining optimal combinations of explosion energy, mixing, and IMF in the large model database to agree with specified data sets. The model is applied to the low-metallicity sample of Cayrel et al. and the two ultra-iron-poor stars HE0107-5240 and HE1327-2326. Best agreement with these very low metallicity stars is achieved with very little mixing, and none of the metal-deficient data sets considered show the need for a high-energy explosion component. In contrast, explosion energies somewhat less than 1.2 B seem to be preferred in most cases.
We report Keck/HIRES and Hubble Space Telescope/COS spectroscopic studies of extrasolar rocky planetesimals accreted onto two hydrogen atmosphere white dwarfs, G29-38 and GD 133. In G29-38, eight ...elements are detected, including C, O, Mg, Si, Ca, Ti, Cr, and Fe while in GD 133, O, Si, Ca, and marginally Mg are seen. These two extrasolar planetesimals show a pattern of refractory enhancement and volatile depletion. For G29-38, the observed composition can be best interpreted as a blend of a chondritic object with some refractory-rich material, a result from post-nebular processing. Water is very depleted in the parent body accreted onto G29-38, based on the derived oxygen abundance. The inferred total mass accretion rate in GD 133 is the lowest of all known dusty white dwarfs, possibly due to non-steady state accretion. We continue to find that a variety of extrasolar planetesimals all resemble to zeroth order the elemental composition of bulk Earth.
Abundances of C, N, and O are determined in four bright red giants that span the known abundance range for light (Na and Al) and s-process (Zr and La) elements in the globular cluster NGC 1851. The ...abundance sum C+N+O exhibits a range of 0.6 dex, a factor of 4, in contrast to other clusters in which no significant C+N+O spread is found. Such an abundance range offers support for the Cassisi et al. scenario in which the double subgiant branch populations are coeval but with different mixtures of C+N+O abundances. Further, the Na, Al, Zr, and La abundances are correlated with C+N+O, and therefore NGC 1851 is the first cluster to provide strong support for the scenario in which asymptotic giant branch stars are responsible for the globular cluster light element abundance variations.
We present a new algorithm for generating merger trees and halo catalogs which explicitly ensures consistency of halo properties (mass, position, and velocity) across time steps. Our algorithm has ...demonstrated the ability to improve both the completeness (through detecting and inserting otherwise missing halos) and purity (through detecting and removing spurious objects) of both merger trees and halo catalogs. In addition, our method is able to robustly measure the self-consistency of halo finders; it is the first to directly measure the uncertainties in halo positions, halo velocities, and the halo mass function for a given halo finder based on consistency between snapshots in cosmological simulations. We use this algorithm to generate merger trees for two large simulations (Bolshoi and Consuelo) and evaluate two halo finders (ROCKSTAR and BDM). We find that both the ROCKSTAR and BDM halo finders track halos extremely well; in both, the number of halos which do not have physically consistent progenitors is at the 1%-2% level across all halo masses. Our code is publicly available at http://code.google.com/p/consistent-trees. Our trees and catalogs are publicly available at http://hipacc.ucsc.edu/Bolshoi/.
We conduct a comprehensive analysis of the relationship between central galaxies and their host dark matter halos, as characterized by the stellar mass-halo mass (SM-HM) relation, with rigorous ...consideration of uncertainties. Our analysis focuses on results from the abundance matching technique, which assumes that every dark matter halo or subhalo above a specific mass threshold hosts one galaxy. We provide a robust estimate of the SM-HM relation for 0 < z < 1 and discuss the quantitative effects of uncertainties in observed galaxy stellar mass functions (including stellar mass estimates and counting uncertainties), halo mass functions (including cosmology and uncertainties from substructure), and the abundance matching technique used to link galaxies to halos (including scatter in this connection). Our analysis results in a robust estimate of the SM-HM relation and its evolution from z = 0 to z = 4. The shape and the evolution are well constrained for z < 1. The largest uncertainties at these redshifts are due to stellar mass estimates (0.25 dex uncertainty in normalization); however, failure to account for scatter in stellar masses at fixed halo mass can lead to errors of similar magnitude in the SM-HM relation for central galaxies in massive halos. We also investigate the SM-HM relation to z = 4, although the shape of the relation at higher redshifts remains fairly unconstrained when uncertainties are taken into account. We find that the integrated star formation at a given halo mass peaks at 10%-20% of available baryons for all redshifts from 0 to 4. This peak occurs at a halo mass of 7 x 10{sup 11} M{sub sun} at z = 0 and this mass increases by a factor of 5 to z = 4. At lower and higher masses, star formation is substantially less efficient, with stellar mass scaling as M{sub *} {approx} M {sup 2.3}{sub h} at low masses and M{sub *} {approx} M {sup 0.29}{sub h} at high masses. The typical stellar mass for halos with mass less than 10{sup 12} M{sub sun} has increased by 0.3-0.45 dex for halos since z {approx} 1. These results will provide a powerful tool to inform galaxy evolution models.
The recent discovery of terrestrial-type organic species such as methyl formate and dimethyl ether in the cold interstellar gas has proved that the formation of organic matter in the Galaxy begins at ...a much earlier stage of star formation than was previously thought. This discovery represents a challenge for astrochemical modelers. The abundances of these molecules cannot be explained by the previously developed "warm-up" scenario, in which organic molecules are formed via diffusive chemistry on surfaces of interstellar grains starting at 30 K, and then released to the gas at higher temperatures during later stages of star formation. In this article, we investigate an alternative scenario in which complex organic species are formed via a sequence of gas-phase reactions between precursor species formed on grain surfaces and then ejected into the gas via efficient reactive desorption, a process in which non-thermal desorption occurs as a result of conversion of the exothermicity of chemical reactions into the ejection of products from the surface. The proposed scenario leads to reasonable if somewhat mixed results at temperatures as low as 10 K and may be considered as a step toward the explanation of abundances of terrestrial-like organic species observed during the earliest stages of star formation.
We perform non-LTE calculations of lithium in late-type stars for a wide range of stellar parameters, including quantum mechanical cross-sections for collisions with neutral hydrogen and the negative ...hydrogen ion. Non-LTE abundance corrections for the lithium resonance line at 670.7 nm and the subordinate line at 610.3 nm, are calculated using 1D MARCS model atmospheres spanning a grid Teff = 4000, 8000 K, log g = 1.0, 5.0, and Fe/H = 0.0, -3.0, for lithium abundances in the range A(Li) = -0.3, 4.2. The competing effects of ultraviolet over-ionization and photon losses in the resonance line govern the behaviour of the non-LTE effects with stellar parameters and lithium abundance. The size and sign of the non-LTE abundance corrections vary significantly over the grid for the 670.7 nm line, but are typically positive and below 0.15 dex for the 610.3 nm, line. The new collisional data play a significant role in determining the abundance corrections.
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