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The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p–Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at sqrt[sNN] = 130 GeV using the STAR Time Projection Chamber at the Relativistic Heavy Ion Collider. The elliptic flow signal, v2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented.
Two-pion correlation functions in Au+Au collisions at sqrt[sNN] = 130 GeV have been measured by the STAR (solenoidal tracker at RHIC) detector. The source size extracted by fitting the correlations grows with event multiplicity and decreases with transverse momentum. Anomalously large sizes or emission durations, which have been suggested as signals of quark-gluon plasma formation and rehadronization, are not observed. The Hanbury Brown-Twiss parameters display a weak energy dependence over a broad range in sqrt[sNN].
We report first results on elliptic flow of identified particles at midrapidity in Au+Au collisions at sqrt[sNN] = 130 GeV using the STAR TPC at RHIC. The elliptic flow as a function of transverse momentum and centrality differs significantly for particles of different masses. This dependence can be accounted for in hydrodynamic models, indicating that the system created shows a behavior consistent with collective hydrodynamical flow. The fit to the data with a simple model gives information on the temperature and flow velocities at freeze-out.
The minimum-bias multiplicity distribution and the transverse momentum and pseudorapidity distributions for central collisions have been measured for negative hadrons ( h-) in Au+Au interactions at sqrt[sNN] = 130 GeV. The multiplicity density at midrapidity for the 5% most central interactions is dNh-/d eta | eta = 0 = 280±1(stat)±20(syst), an increase per participant of 38% relative to pp-bar collisions at the same energy. The mean transverse momentum is 0.508±0.012 GeV/c and is larger than in central Pb+Pb collisions at lower energies. The scaling of the h- yield per participant is a strong function of pperp. The pseudorapidity distribution is almost constant within | eta |<1.
We report results on the ratio of midrapidity antiproton-to-proton yields in Au+Au collisions at sqrt[sNN] = 130 GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of | y|<0.5 and 0.4<pt<1.0 GeV/c, the ratio is essentially independent of either transverse momentum or rapidity, with an average of 0.65±0.01(stat)±0.07(syst) for minimum bias collisions. Within errors, no strong centrality dependence is observed. The results indicate that at this RHIC energy, although the p-p-bar pair production becomes important at midrapidity, a significant excess of baryons over antibaryons is still present.
Single-molecule super-resolution microscopy allows imaging of fluorescently-tagged proteins in live cells with a precision well below that of the diffraction limit. Here, we demonstrate 3D sectioning with single-molecule super-resolution microscopy by making use of the fitting information that is usually discarded to reject fluorophores that emit from above or below a virtual-'light-sheet', a thin volume centred on the focal plane of the microscope. We describe an easy-to-use routine (implemented as an open-source ImageJ plug-in) to quickly analyse a calibration sample to define and use such a virtual light-sheet. In addition, the plug-in is easily usable on almost any existing 2D super-resolution instrumentation. This optical sectioning of super-resolution images is achieved by applying well-characterised width and amplitude thresholds to diffraction-limited spots that can be used to tune the thickness of the virtual light-sheet. This allows qualitative and quantitative imaging improvements: by rejecting out-of-focus fluorophores, the super-resolution image gains contrast and local features may be revealed; by retaining only fluorophores close to the focal plane, virtual-'light-sheet' single-molecule localisation microscopy improves the probability that all emitting fluorophores will be detected, fitted and quantitatively evaluated.
Since its founding in 1993 the International Long-term Ecological Research Network (ILTER) has gone through pronounced development phases. The current network comprises 44 active member LTER networks representing 700 LTER Sites and ~ 80 LTSER Platforms across all continents, active in the fields of ecosystem, critical zone and socio-ecological research. The critical challenges and most important achievements of the initial phase have now become state-of-the-art in networking for excellent science. At the same time increasing integration, accelerating technology, networking of resources and a strong pull for more socially relevant scientific information have been modifying the mission and goals of ILTER. This article provides a critical review of ILTER's mission, goals, development and impacts. Major characteristics, tools, services, partnerships and selected examples of relative strengths relevant for advancing ILTER are presented. We elaborate on the tradeoffs between the needs of the scientific community and stakeholder expectations. The embedding of ILTER in an increasingly collaborative landscape of global environmental observation and ecological research networks and infrastructures is also reflected by developments of pioneering regional and national LTER networks such as SAEON in South Africa, CERN/CEOBEX in China, TERN in Australia or eLTER RI in Europe. The primary role of ILTER is currently seen as a mechanism to investigate ecosystem structure, function, and services in response to a wide range of environmental forcings using long-term, place-based research. We suggest four main fields of activities and advancements for the next decade through development/delivery of a: (1) Global multi-disciplinary community of researchers and research institutes; (2) Strategic global framework and strong partnerships in ecosystem observation and research; (3) Global Research Infrastructure (GRI); and (4) a scientific knowledge factory for societally relevant information on sustainable use of natural resources.
The genus Afrodonta s. lat. is shown to comprise several lineages with distinctive shell characters primarily associated with the microsculpture of the protoconch and teleoconch, and the manner in which the apertural barriers are deposited. These lineages comprise Afrodonta s. str. and five new genera: Amatholedonta gen. nov., Biomphalodonta gen. nov., Costulodonta gen. nov., Iterodonta gen. nov. and Phialodonta gen. nov. Twelve new species are described, doubling the diversity of aperturally dentate charopid snails known from southern Africa. All new species are narrow-range endemics. A new subspecies of one of the more widely distributed species of Afrodonta s. str. is also described. Keys to genera and species are provided. New species and subspecies: Afrodonta geminodonta sp. nov., Af. inhluzaniensis leptolamellaris subsp. nov., Af. mystica sp. nov., Af. pentodon sp. nov., Amatholedonta fordycei gen. et sp. nov., Biomphalodonta forticostata gen. et sp. nov., Costulodonta bidens gen. et sp. nov., C. pluridens gen. et sp. nov., Iterodonta ammonita gen. et sp. nov., Phialodonta agulhasae gen. et sp. nov., P. atromontana gen. et sp. nov., P. aviana gen. et sp. nov. and P. rivalalea gen. et sp. nov. New synonyms: Afrodonta bilamellaris londonensis Solem, 1970 = Afrodonta bilamellaris Melvill & Ponsonby, 1908. New combinations: Afrodonta acinaces Connolly, 1933, Afrodonta burnupi Connolly, 1933 and Afrodonta trilamellaris Melvill & Ponsonby, 1908 are transferred to Costulodonta gen. nov.; Afrodonta bimunita Connolly, 1939 is transferred to Amatholedonta gen. nov.; Afrodonta introtuberculata Connolly, 1933 and Afrodonta perfida Burnup, 1912 are transferred to Phialodonta gen. nov.
A new genus and eight new species of urocyclid snails are described from eastern South Africa. The supra-specific taxa Kerkophorus Godwin-Austen, 1912 and Microkerkus Godwin-Austen, 1912 are considered distinct from Sheldonia Ancey, 1887 and are treated as separate genera. The diagnostic morphological features of all three genera are detailed and a fourth genus, for which there is no existing name, is described as new: Selatodryas gen. nov. A provisional key to genus-level taxa within Sheldonia s.l. is provided. Eight species are described as new: Kerkophorus piperatus sp. nov., K. vittarubra sp. nov., K. scrobicolus sp. nov., K. terrestris sp. nov., Microkerkus sibaya sp. nov., Selatodryas roseosoma gen. et sp. nov., S. luteosoma gen. et sp. nov. and Sheldonia fingolandensis sp. nov.
One new genus and five new species of land snails are described from high altitude, insular, Afrotemperate forest habitats in northern South Africa. The distribution of these species is discussed in relation to other narrowly endemic land snails occurring in this and neighbouring regions. The new genus is Ptilototheca gen. nov.; the five new species are: Gulella davisae sp. nov., G. hadroglossa sp. nov., Ptilototheca soutpansbergensis gen. et sp. nov., Sheldonia monsmaripi sp. nov. and S. wolkbergensis sp. nov.
Eight new species of Gulella Pfeiffer, 1856 are described from south-eastern South Africa, occurring over a linear distance of 550 km within the Maputaland-Pondoland-Albany biodiversity hotspot. Seven species are narrow-range endemics, while Gulella kenbrowni sp. nov. occurs somewhat patchily over most of this distance. The very similar G. fordycei sp. nov. is recorded from only one small nature reserve in medium-altitude mistbelt forest. Six species, G. crookesi sp. nov., G. maraisi sp. nov., G. mkombeni sp. nov., G. abbotti sp. nov., G. donaikeni sp. nov. and G. calcicola sp. nov. each occur at one or a few isolated localities along a narrow strip of 140 km at or near the coast. The latter two are found only in the Marble Delta region, where mining has badly degraded and continues to threaten their habitat, and appear to meet the criteria for Red-Listing as Critically Endangered. Six species occur in nature reserves, highlighting the importance of small pockets of protected habitat for the conservation of terrestrial snails.
The vetigastropod material collected on Walters Shoal during Cruise MD208 of the Tropical Deep-Sea Benthos programme is documented. In total, 50 species were obtained, 30 of which are new and apparently endemic to the seamount. Of the other 20 species, eight are regionally endemic to the south-western Indian Ocean, 11 are more widely distributed in the Indo-West Pacific and one is possibly of deep-water Atlantic origin. The primary affinities of the fauna are with warm temperate South Africa and the tropical western Indian Ocean, but one species is potentially a seamount endemic of southern affinity. A new pseudococculinid genus living on decomposing bird feathers is described, a biogenic substrate association previously unknown in the Mollusca. The following new genera are described: Imbricoscelis gen. nov. and Pterodacna gen. nov. The following new species are described: Akritogyra crenulata sp. nov., Bathymophila williamsae sp. nov., Benthobrookula araneum sp. nov., Be. galeneae sp. nov., Be. laticostata sp. nov., Be. scalaroides sp. nov., Be. semisculpta sp. nov., Bruceina areneformis sp. nov., Calliostoma pantopunctatum sp. nov., Cantrainea herosae sp. nov., Carinastele achrosta sp. nov., Cornisepta marshalli sp. nov., Emarginula lentiginosa sp. nov., E. nodulicostata sp. nov., E. retrogyra sp. nov., E. salebrosa sp. nov., Fluxinella dufresneae sp. nov., Gibbula roseosticta sp. nov., Hadroconus scobina sp. nov., Kaiparathina monticola sp. nov., Lissotesta wareni sp. nov., Microcollonia miniata sp. nov., Mikro crassus sp. nov., Parviturbo cicatricosus sp. nov., Phragmomphalina candida sp. nov., Pterodacna boucheti gen. et sp. nov., Solariella asaphea sp. nov., Spinicalliotropis lepidota sp. nov., Stomatella multilirata sp. nov. and Trenchia mcleani sp. nov. The following new combinations are proposed: Brookula coronis Barnard, 1963 is transferred to Imbricoscelis gen. nov., Cantharidus nolfi Poppe, Tagaro & H. Dekker, 2006 is transferred to Kaiparathina Laws, 1941 and Solariella incisura Melvill, 1909 is transferred to Phragmomphalina Herbert & Williams, 2020. The following new synonyms are proposed: Carinastele wareni Vilvens, 2014 is a synonym of Bruceina cognata (Marshall, 1988); Fluxinella stellaris Bozzetti, 2008 is a synonym of Agagus stellamaris Herbert, 1991.
Seven new species of very small Gulella Pfeiffer, 1856 are described from two regions in the interior of south-eastern South Africa within the Maputaland-Pondoland-Albany biodiversity hotspot. In addition, the status of Gulella darglensis benthodon van Bruggen, 1980 is revised and raised to species level. All species are very small-shelled and are narrow-range endemics. Six species, G. judithmastersae sp. nov., G. kevincolei sp. nov., G. hlathikhulu sp. nov., G. nkandla sp. nov., G. mystica sp. nov. and G. libertas sp. nov. are each known from only one locality. The first two as well as G. benthodon and G. mcmasteri sp. nov. are found only in the Amathole Mountains, where poaching, illegal harvesting of plant products and uncontrolled access of cattle take place, including in protected areas. The other four species each occur at one locality in north-central KwaZulu-Natal. The localities of three of the last-mentioned species are in protected areas although they are isolated and surrounded by a heavily transformed cultural landscape rendering enforcement of conservation legislation a challenge. Six species occur in nature reserves, highlighting the importance of small pockets of protected habitat for the conservation of terrestrial snails.
Ecological speciation assumes reproductive isolation to be the product of ecologically based divergent selection. Beside natural selection, sexual selection via phenotype-assortative mating is thought to promote reproductive isolation. Using the neotropical fish Poecilia mexicana from a system that has been described to undergo incipient ecological speciation in adjacent, but ecologically divergent habitats characterized by the presence or absence of toxic H2S and darkness in cave habitats, we demonstrate a gradual change in male body colouration along the gradient of light/darkness, including a reduction of ornaments that are under both inter- and intrasexual selection in surface populations. In dichotomous choice tests using video-animated stimuli, we found surface females to prefer males from their own population over the cave phenotype. However, female cave fish, observed on site via infrared techniques, preferred to associate with surface males rather than size-matched cave males, likely reflecting the female preference for better-nourished (in this case: surface) males. Hence, divergent selection on body colouration indeed translates into phenotype-assortative mating in the surface ecotype, by selecting against potential migrant males. Female cave fish, by contrast, do not have a preference for the resident male phenotype, identifying natural selection against migrants imposed by the cave environment as the major driver of the observed reproductive isolation.
In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axiorecombination, the "BCA processes." Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling gae and axion-photon interaction strength ga using the CAST phase-I data (vacuum phase). For ma <~ 10 meV/c2 we find ga gae < 8.1 × 10−23 GeV−1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivity into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission.