1,191,818 research outputs found
On the Origin of Light Dark Matter Species
TeV-mass dark matter charged under a new GeV-scale gauge force can explain
electronic cosmic-ray anomalies. We propose that the CoGeNT and DAMA direct
detection experiments are observing scattering of light stable states --
"GeV-Matter" -- that are charged under this force and constitute a small
fraction of the dark matter halo. Dark higgsinos in a supersymmetric dark
sector are natural candidates for GeV-Matter that scatter off protons with a
universal cross-section of 5 x 10^{-38} cm^2 and can naturally be split by
10-30 keV so that their dominant interaction with protons is down-scattering.
As an example, down-scattering of an O(5) GeV dark higgsino can simultaneously
explain the spectra observed by both CoGeNT and DAMA. The event rates in these
experiments correspond to a GeV-Matter abundance of 0.2-1% of the halo mass
density. This abundance can arise directly from thermal freeze-out at weak
coupling, or from the late decay of an unstable TeV-scale WIMP. Our proposal
can be tested by searches for exotics in the BaBar and Belle datasets.Comment: 31 text pages, 4 figures, revision includes corrected Germanium
quenching factor and clarified text in Sec.
The origin and distribution of neotropical species of Campylopus
Of the 65 species of Campylopus known from tropical America, 33 are andine in distribution, 16 are found only in SE Brazil, 8 have wide ranges through Central and South America, 3 species are disjunct in SE-North America and Brazil, 3 are confined to the Caribbean and one species belongs to the circum-pacific and one to the tethyan element. For different parts of the Neotropics, the composition of phytogeographical elements is calculated. For the first time, bryophyte distributions are compared to the Pleistocene forest refuges proposed by zoologist and phanerogamists. The distribution of several rainforest species of Campylopus coincides with the major part of the montane refugia. Using an interpretation of the present-day ranges, a hypothetical survey is given of the origin and evolution of this genus in tropical South and Central America. The ranges of part of the species can be explained only by long distance dispersal, while the ranges of other species seem to be relictual
Growth of bifidobacteria in mammalian milk
Microbial colonization of the mammalian intestine begins at birth, when from a sterile state a newborn infant is exposed to an external environment rich in various bacterial species. An important group of intestinal bacteria comprises bifidobacteria. Bifidobacteria represent major intestinal microbiota during the breast-feeding period. Animal milk contains all crucial nutrients for babies’ intestinal microflora. The aim of our work was to test the influence of different mammalian milk on the growth of bifidobacteria. The growth of seven strains of bifidobacteria in human milk, the colostrum of swine, cow’s milk, sheep’s milk, and rabbit’s milk was tested. Good growth accompanied by the production of lactic acid was observed not only in human milk, but also in the other kinds of milk in all three strains of Bifidobacterium bifidum of different origin. Human milk selectively supported the production of lactic acid of human bifidobacterial isolates, especially the Bifidobacterium bifidum species. The promotion of bifidobacteria by milk is species-specific. Human milk contains a key factor for the growth of specific species or strains of human-origin bifidobacteria compared to other kinds of milk. In contrast, some components (maybe lysozyme) of human milk inhibited the growth of Bifidobacterium animalis. Animal-origin strains of bifidobacteria were not able to significantly grow even in milk of animal origin, with the exception of B. animalis subsp. lactis 1,2, which slightly grew in sheep’s milk
A common origin of all the species of high-energy cosmic rays?
Cosmic ray nuclei, cosmic ray electrons with energy above a few GeV, and the
diffuse gamma-ray background radiation (GBR) above a few MeV, presumed to be
extragalactic, could all have their origin or residence in our galaxy and its
halo. The mechanism accelerating hadrons and electrons is the same, the
electron spectrum is modulated by inverse Compton scattering on starlight and
on the microwave background radiation; the -rays are the resulting
recoiling photons. The spectral indices of the cosmic-ray electrons and of the
GBR, calculated on this simple basis, agree with observations. The angular
dependence and the approximate magnitude of the GBR are also explained.Comment: Includes a discussion of the contribution of inverse Compton
scattering of CR electrons by starlight in the halo to the gamma background
radiation. One corrected typo. Additional references, and figures to compare
predictions for the angular dependence of the gamma background radiation with
data. Conclusions are unchange
First European interception of the brown fir longhorn beetle, Callidiellum villosulum (Fairmaire, 1900) (Coleoptera, Cerambycidae)
A specimen of the brown fir longhorn beetle, Callidiellum villosulum villosulum found in Malta represents the first record of this invasive species for Europe. Historical details on world invasion of this species are provided as well as a short description, origin and biology. A brief pest risk analysis of this species is also presented.peer-reviewe
Campylopus, a modern and successful genus!?
Campylopus with nearly 200 revised species is one of the largest genera of mosses in the world and has extremely broad geographical, altitudinal and ecological ranges. Factors to be considered for the rich speciation are 1) the enormous anatomical plasticity of the structure of the costa, 2) the ability for vegetative propagation utilizing different methods, and 3) the special twist mechanism of the cygneous setae. Phytogeographical interpretations of present ranges of species of Campylopus lead to the conclusion that this genus is of Gondwanalandic origin. Most of the species seem to be cool temperate in origin. They have adapted to dry habitats in the Mesozoic and invaded the tropical mountains during the Tertiary, accompanied by rich speciation. This is supported by the physiology of these species. According to preliminary gas exchange measurements, tropical montane species do not differ from temperate species, and are not able to stand climatic conditions of the tropical lowland rainforests; a relatively young habitat for bryophytes. A cladistic analysis of the infrageneric categories of Campylopus using phytogeographical evaluations of apomorphic character states shows that the section Homalocarpus seems to be the most primitive and the subgenera Campylopidulum and Thysanomitrion the most derived
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