10,682 research outputs found
Behavioral Differences Between Two Recently Sympatric Paper Wasps, the Native \u3ci\u3ePolistes Fuscatus\u3c/i\u3e and the Invasive \u3ci\u3ePolistes Dominulus\u3c/i\u3e
Polistes dominulus (Christ), an old world paper wasp, was introduced into the eastern United States in the 1970s and has been rapidly spreading westward. Recently, it has displaced the native Polistes fuscatus (F.) in at least some areas of Michigan. In order to understand why P. dominulus has been so successful, several behavioral attributes were compared between P. dominulus and P. fuscatus at a Michigan field site that contained colonies of both species nest- ing semi-naturally in plywood nestboxes.
Preworker colonies of P. dominulus had a significantly greater tendency to store nectar (and had significantly higher proportions of cells with nectar) than preworker colonies of P. fuscatus. This finding may explain the higher survivorship of P. dominulus foundresses reported in a previous study. P. dominulus also had a significantly greater tendency to build vertical nests and had significantly more pedicels per comb and per cell than P. fuscatus. These findings suggest that compared to P. fuscatus, P. dominulus may have more flexibility in the positioning of its combs and, because of a possibly stronger attachment of the comb to a substrate, may be less susceptible to bird predation. The higher winter survivorship reported for P. fuscatus over P. dominulus in a previous study does not appear to be due to differences in the proportions of gynes stranded on their nests late in the fall. Finally, behavioral evidence from videography was consistent with previous reports that P. dominulus is not replacing P. fuscatus through direct agonistic interactions
Mother Tongue Influence on English Pronunciation: A Case study in College Students
Mother tongue interference can affect students’ English speaking skill especially in pronouncing the
words intrinsically. Considering Tamil language is the dominant mother language used by students
at College level, the students as EFL learners often use their mother tongue in daily communication
and at campus, and College students pronounce English words in a different way. This study
investigated the forms of Tamil language interfering students in pronouncing English words, and
how they were interfered. This was a descriptive study in the field of English pronunciation
elaborated in a qualitative way. Recorded interviews and pronunciation testing were the main
techniques of collecting data. Interview guide, validated pronunciation test, and document analysis
were the instruments. In conclusion, the interference was positive since Tamil language’s phonemic
sounds have some similarities to those of English, so this condition does not potentially change the
meanings of English words
Evidence for strong evolution in galaxy environmental quenching efficiency between z = 1.6 and z = 0.9
Indexación: Web of Science; Scopus.We analyse the evolution of environmental quenching efficiency, the fraction of quenched cluster galaxies which would be star forming if they were in the field, as a function of redshift in 14 spectroscopically confirmed galaxy clusters with 0.87 < z < 1.63 from the Spitzer Adaptation of the Red-Sequence Cluster Survey. The clusters are the richest in the survey at each redshift. Passive fractions rise from 42-13 +10 per cent at z ~ 1.6 to 80-9 +12 per cent at z ~ 1.3 and 88-3 +4 per cent at z < 1.1, outpacing the change in passive fraction in the field. Environmental quenching efficiency rises dramatically from 16-19 +15 per cent at z ~ 1.6 to 62-15 +21 per cent at z~1.3 and 73-7 +8 per cent at z ≲ 1.1. This work is the first to show direct observational evidence for a rapid increase in the strength of environmental quenching in galaxy clusters at z ~ 1.5, where simulations show cluster-mass haloes undergo non-linear collapse and virialization.https://academic.oup.com/mnrasl/article/465/1/L104/241728
Primordia initiation of mushroom (Agaricus bisporus) strains on axenic casing materials
The mushroom (Agaricus bisporus) has a
requirement for a ‘‘casing layer’’ that has specific
physical, chemical and microbiological properties
which stimulate and promote the initiation of primordia.
Some of these primordia then may develop
further into sporophores, involving differentiation of
tissue. Wild and commercial strains of A. bisporus
were cultured in axenic and nonaxenic microcosms,
using a rye grain substrate covered by a range of organic
and inorganic casing materials. In axenic culture,
A. bisporus (commercial strain A15) was capable
of producing primordia and mature sporophores on
charcoal (wood and activated), anthracite coal, lignite
and zeolite, but not on bark, coir, peat, rockwool,
silica or vermiculite. Of six strains tested, only
the developmental variant mutant, B430, produced
rudimentary primordia on axenic peat-based casing
material. However, none of these rudimentary primordia
developed differentiated tissues or beyond 4
mm diameter, either on axenic casing material in the
microcosms or in larger-scale culture. In larger-scale,
nonaxenic culture, strain B430 produced severely
malformed but mature sporophores in similar numbers
to those of other strains. Typically, 3–6% of primordia
developed into mature sporophores, but significant
differences in this proportion, as well as in
the numbers of primordia produced, were recorded
between 12 A. bisporus strains
Stellar mass function of cluster galaxies at z ~ 1.5: evidence for reduced quenching efficiency at high redshift
Indexación: Web of ScienceWe present the stellar mass functions (SMFs) of passive and star-forming galaxies with a limiting mass of 10(10.1) M-circle dot in four spectroscopically confirmed Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) galaxy clusters at 1 : 37 < z < 1 : 63. The clusters have 113 spectroscopically confirmed members combined, with 8-45 confirmed members each. We construct Ks-bandselected photometric catalogs for each cluster with an average of 11 photometric bands ranging from u to 8 mu m. We compare our cluster galaxies to a field sample derived from a similar Ks-band-selected catalog in the UltraVISTA / COSMOS field. The SMFs resemble those of the field, but with signs of environmental quenching. We find that 30 +/- 20% of galaxies that would normally be forming stars in the field are quenched in the clusters. The environmental quenching e ffi ciency shows little dependence on projected cluster-centric distance out to similar to 4 Mpc, providing tentative evidence of pre-processing and/or galactic conformity in this redshift range. We also compile the available data on environmental quenching efficiencies from the literature, and find that the quenching e ffi ciency in clusters and in groups appears to decline with increasing redshift in a manner consistent with previous results and expectations based on halo mass growth.http://www.aanda.org/articles/aa/abs/2016/08/aa28663-16/aa28663-16.htm
Long-Term Impact of Leucaena-Based Grazing Systems on Soil Acidity
Soil acidification and land degradation issues are assuming increasing importance in Australia and challenging the concept of sustainablity of current land management systems. In this study the impact of a 22 year old Leucaena leucocephala / Urochloa mosambicensis (Leucaena) pasture production system on soil acidification and selected soil chemical properties was compared to an adjacent Urochloa mosambicensis (Sabi) area. Significant acidification and cation depletion was observed to 70 cm under the Leucaena when compared to the Sabi system. The net acidification rate for the Leucaena system was estimated to be 2.73 kmol H+ ha-1 yr-1 of which 0.17 kmol H+ ha-1 yr-1 was estimated to have originated from animal product removal. These preliminary results bring into question the long-term sustainability of these legume based production systems
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