The effect of a single supernova explosion on the cuspy density profile of a small-mass dark matter halo

Some observations of galaxies, and in particular dwarf galaxies, indicate a presence of cored density profiles in apparent contradiction with cusp profiles predicted by dark matter N-body simulations. We constructed an analytical model, using particle distribution functions (DFs), to show how a supernova (SN) explosion can transform a cusp density profile in a small-mass dark matter halo into a cored one. Considering the fact that an SN efficiently removes matter from the centre of the first haloes, we study the effect of mass removal through an SN perturbation in the DFs. We find that the transformation from a cusp into a cored profile occurs even for changes as small as 0.5 per cent of the total energy of the halo, which can be produced by the expulsion of matter caused by a single SN explosion.

Revision of the new wandering spider genus Ohvida and taxonomic remarks on Celaetycheus Simon, 1897 (Araneae: Ctenidae)

The new ctenid genus Ohvida is proposed to include eight species: Ohvida fulvorufa (Franganillo, 1931) comb. nov. (type species) (=Celaetycheus cabriolatus Franganillo, 1930 syn. nov.; = C. cabriolatus pardosiformis Franganillo, 1930 syn. nov.; = C. fulvorufus afoliatus Franganillo, 1931 syn. nov.), O. isolata (Bryant, 1940) comb. nov., O. vernalis (Bryant, 1940) comb. nov., O. brevitarsus (Bryant, 1940) comb. nov., O. coxanus (Bryant, 1940), comb. nov., and three new species, O. turquino sp. nov. (all species from Cuba), and O. andros sp. nov. and O. bimini sp. nov. (both species from The Bahamas). Species of Ohvida differ from all other ctenid spiders by the presence of a retrodorsal projection on the cymbium of the male pedipalp and by a basal position of the lateral spurs on the female epigyne. The genus Celaetycheus Simon, 1897 is reviewed to only include its type species, C. flavostriatus Simon, 1897 from Brazil. We propose the following synonyms and new combinations: Ctenus ottleyi (Petrunkevitch, 1930) (= Celaetycheus strenuus Bryant, 1942 syn. nov. and C. modestus Bryant, 1942 syn. nov.); Ctenus delesserti (Caporiacco, 1947) comb. nov., and Leptoctenus paradoxus (F.O. P.-Cambridge, 1900) comb. nov. Celaetycheus modestus Bryant, 1942 is considered incertae sedis.

Review and cladistic analysis of the Neotropical tarantula genus Ephebopus Simon 1892 (Araneae : Theraphosidae) with notes on the Aviculariinae

The tarantula genus Ephebopus Simon 1892 is reviewed and includes the type species, E. murinus (Walckenaer 1837), and E. uatuman Lucas, Silva & Bertani 1992, E. cyanognathus West & Marshall 2000, E. rufescens West & Marshall 2000 and Ephebopus foliatus, sp. nov., from Guyana. Ephebopus violaceus Mello-Leitao 1930 is transferred to Tapinauchenius Ausserer, where it is a senior synonym of Tapinauchenius purpureus Schmidt 1995 new synonymy. Ephebopus fossor Pocock 1903 is considered a nomen dubium. Ephebopus occurs in northeastern South America where it is known only from Brazil, Guyana, Suriname, and French Guiana. Spiders of the genus are generally fossorial; however, Ephebopus murinus has a developmental stage that is arboreal. A cladistic analysis of the Theraphosidae retrieves the Aviculariinae as monophyletic, including Avicularia Lamarck, Iridopelma Pocock 1901, Pachistopelma Pocock 1901, Tapinauchenius, Psalmopoeus Pocock, Ephebopus, Stromatopelma Karsch and Heteroscodra Pocock, having as a synapomorphy the well-developed scopulae on tarsi and metatarsi I-II that is very laterally extended.

Revalidation and revision of the genus Magulla Simon 1892 (Araneae, Mygalomorphae, Theraphosidae)

The genus Magulla Simon 1892 is revalidated and redescribed. The female of the type species M. obesa Simon 1892 is redescribed and the male is described for the first time. Magulla janeirus (Keyserling 1891) is considered a valid species. Magulla symmetrica Bucherl 1949 is transferred to Plesiopelma Pocock 1901, and considered a junior synonym of P. insulare (Mello-Leitao 1923). Additionally, two new species are described from Brazil: M. buecherli n. sp. from Ilhabela, Sao Paulo and M. brescoviti n. sp. from Sao Francisco de Paula, Rio Grande do Sul.

A revision of the spider genera Chaetopelma ausserer 1871 and Nesiergus simon 1903 (Araneae, theraphosidae, ischnocolinae)

Chaetopelma Ausserer 1871 and Nesiergus Simon 1903 are revised. Cratorrhagus Simon 1891 is considered a junior synonym of Chaetopelma. Cratorrhagus tetramerus (Simon 1873) and the female of Cratorrhagus concolor (Simon 1873) are conspecific with C. olivaceum (C. L. Koch 1841). Ischnocolus gracilis Ausserer 1871, Ischnocolus syriacus Ausserer 1871, Chaetopelma shabati Hassan 1950 and Ischnocolus jerusalemensis Smith 1990 are also treated here as junior synonyms of C. olivaceum. Chaetopelma adenense Simon 1890 is proposed as a junior synonym of Ischnocolus jickelii L. Koch 1875. Chaetopelma gardineri Hirst 1911 is transferred to Nesiergus. Hence, Chaetopelma comprises three valid species: C. olivaceum (C. L. Koch 1841); C. karlamani Vollmer 1997; C. concolor (Simon 1873) n. comb. from the Middle East and northeastern Africa. Nesiergus, which appears endemic to the Seychelles archipelago, now comprises three valid species: N. gardineri (Hirst 1911) n. comb.; N. halophilus Benoit 1978; N. insulanus Simon 1903.

Observation of the antimatter helium-4 nucleus

High-energy nuclear collisions create an energy density similar to that of the Universe microseconds after the Big Bang(1); in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high-energy accelerator of heavy nuclei provides an efficient means of producing and studying antimatter. The antimatter helium-4 nucleus ((4)(He) over bar), also known as the anti-alpha ((alpha) over bar), consists of two antiprotons and two antineutrons (baryon number B = -4). It has not been observed previously, although the alpha-particle was identified a century ago by Rutherford and is present in cosmic radiation at the ten per cent level(2). Antimatter nuclei with B -1 have been observed only as rare products of interactions at particle accelerators, where the rate of antinucleus production in high-energy collisions decreases by a factor of about 1,000 with each additional antinucleon(3-5). Here we report the observation of (4)<(He) over bar, the heaviest observed antinucleus to date. In total, 18 (4)(He) over bar counts were detected at the STAR experiment at the Relativistic Heavy Ion Collider (RHIC; ref. 6) in 10(9) recorded gold-on-gold (Au+Au) collisions at centre-of-mass energies of 200 GeV and 62 GeV per nucleon-nucleon pair. The yield is consistent with expectations from thermodynamic(7) and coalescent nucleosynthesis(8) models, providing an indication of the production rate of even heavier antimatter nuclei and a benchmark for possible future observations of (4)(He) over bar in cosmic radiation.