196 research outputs found
Contributions to the helminth fauna of South Africa
Whereas the South American and Australian helminth-fauna is comparatively well known, that of South Africa has been sadly neglected until recent years. The probable reason of this is that scientific explorers do not generally trouble to collect intestinal parasites either because of the extra trouble incurred, or else underestimating the importance of this factor for faunistic studies. It was with this fact in mind that Sir Arnold Theiler, K.C.M.G., Director of the Veterinary Research Laboratory, Onderstepoort, Pretoria, had collected all the intestinal parasites from the animals shot for museum purposes in the districts outlying Pretoria. This valuable collection, which was presented to Prof. 0. Fuhrmann a few years ago, consists chiefly of nematodes and of avian cestodes, the mammalian cestodes studied in this paper representing about one-quarter of the whole collection. As was to be expected, of the twenty-two species examined, nine are new to science, including two new genera and one new family. Of the nineteen hosts, fifteen have to our knowledge never been recorded before as harbouring cestode parasites.
We have been able to clear up certain points of systematic interest. This represents, however, an infinitesimal portion of the work left to be done with regard to mammalian cestodes. Certain genera are in much need of revision: the genus Taenia s. str. is an example. To our mind, only good results are to be obtained from the study of the original species, and any species insufficiently described of which no types or cotypes exist should be suppressed. This seems to be the only way of straightening out the synonymy of certain groups, in which much confusion has been caused of late by "occasional helminthologists," whose only aim seems to be to place their name behind a species. The results of our studies have showed us that authors do not generally take into consideration the individual variation of a species, variation which, as we will show, may be very great in certain cases. The role of the host should also be considered, and would prevent authors committing such absurdities as the recording of species of Anoplocephala, Davainea, and Hymenolepis from marine fishes!Includes bibliographical referencesThe articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.ab202
Inclusive particle production at HERA: Higher-order QCD corrections to the resolved quasi-real photon contribution
We calculate in next-to-leading order inclusive cross sections of
single-particle production via resolved photons in collisions at HERA.
Transverse-momentum and rapidity distributions are presented and the scale
dependence is studied. The results are compared with first experimental data
from the H1 Collaboration at HERA.Comment: 11 pages with 15 uuencoded PS figures. Preprint DESY 93-03
A matching of matrix elements and parton showers
We propose a simple scheme to start a parton-shower evolution description
from a given jet configuration in annihilation events. This allows a
convenient combination of the full angular information content of matrix
elements with the detailed sub-jet structure of parton showers, and should give
a realistic overall description of event properties. Explicit studies with this
hybrid approach are presented for the four-jet case, as a simple testing ground
of the ideas.Comment: 1+8 pages, LaTeX2e, 5 postscript figures include
PYTHIA 6.4 Physics and Manual
The PYTHIA program can be used to generate high-energy-physics `events', i.e.
sets of outgoing particles produced in the interactions between two incoming
particles. The objective is to provide as accurate as possible a representation
of event properties in a wide range of reactions, within and beyond the
Standard Model, with emphasis on those where strong interactions play a role,
directly or indirectly, and therefore multihadronic final states are produced.
The physics is then not understood well enough to give an exact description;
instead the program has to be based on a combination of analytical results and
various QCD-based models. This physics input is summarized here, for areas such
as hard subprocesses, initial- and final-state parton showers, underlying
events and beam remnants, fragmentation and decays, and much more. Furthermore,
extensive information is provided on all program elements: subroutines and
functions, switches and parameters, and particle and process data. This should
allow the user to tailor the generation task to the topics of interest.Comment: 576 pages, no figures, uses JHEP3.cls. The code and further
information may be found on the PYTHIA web page:
http://www.thep.lu.se/~torbjorn/Pythia.html Changes in version 2: Mistakenly
deleted section heading for "Physics Processes" reinserted, affecting section
numbering. Minor updates to take into account referee comments and new colour
reconnection option
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
Standard Model backgrounds to supersymmetry searches
This work presents a review of the Standard Model sources of backgrounds to
the search of supersymmetry signals. Depending on the specific model, typical
signals may include jets, leptons, and missing transverse energy due to the
escaping lightest supersymmetric particle. We focus on the simplest case of
multijets and missing energy, since this allows us to expose most of the issues
common to other more complex cases. The review is not exhaustive, and is aimed
at collecting a series of general comments and observations, to serve as
guideline for the process that will lead to a complete experimental
determination of size and features of such SM processes.Comment: To appear in the J. Wess memorial volume, "Supersymmetry on the Eve
of the LHC", to be published in European Physical Journal
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at sqrt(s) up to 209 GeV
A search for the lightest neutral CP-even and neutral CP-odd Higgs bosons of
the Minimal Supersymmetric Standard Model is performed using 216.6 pb-1 of data
collected with the L3 detector at LEP at centre-of-mass energies between 203
and 209 GeV. No indication of a signal is found. Including our results from
lower centre-of-mass energies, lower limits on the Higgs boson masses are set
as a function of tan(beta) for several scenarios. For tan(beta) greater than
0.7 they are mh > 84.5 GeV and mA > 86.3 GeV at 95% confidence level
Identification of regulatory variants associated with genetic susceptibility to meningococcal disease
Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes
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