26 research outputs found
Methanol: a diagnostic tool for high-mass star-forming regions
We here present an innovative technique to handle the problem of deriving
physical parameters from observed multi-line spectra of methanol, based on the
simultaneous fit of all the lines with a synthetic spectrum computed under the
Large Velocity Gradient approximation; the best physical parameters are found
using numerical methods.Comment: 4 pages, 2 figures. (Co)authored by members of the MPIfR
(Sub)millimeter Astronomy Group. To appear in the Proceedings of the 4th
Cologne-Bonn-Zermatt-Symposium "The Dense Interstellar Medium in Galaxies"
eds. S. Pfalzner, C. Kramer, C. Straubmeier, & A. Heithausen (Springer:
Berlin
Quantifying the Evolution and Impact of Antimalarial Drug Resistance: Drug Use, Spread of Resistance, and Drug Failure over a 12-Year Period in Papua New Guinea
Background. Antimalarial use is a key factor driving drug resistance and reduced treatment effectiveness in Plasmodium falciparum malaria, but there are few formal, quantitative analyses of this process. Methods. We analyzed drug usage, drug failure rates, and the frequencies of mutations and haplotypes known to be associated with drug resistance over a 12-year period (1991-2002) in a site in Papua New Guinea. This period included 2 successive treatment policies: amodiaquine (AQ) or chloroquine (CQ) from 1991 through 2000 and their subsequent replacement by sulfadoxine-pyrimethamine (SP) plus AQ or SP plus CQ. Results. Drug use approximated 1 treatment per person-year and was associated with increasing frequencies of pfcrt and pfmdr1 mutations and of treatment failure. The frequency of pfdhfr mutations also increased, especially after the change in treatment policy. Treatment failure rates multiplied by 3.5 between 1996 and 2000 but then decreased dramatically after treatment policy change. Conclusions. With high levels of resistance to CQ, AQ, and SP, the deployment of the combination of both drugs appears to increase clinical effectiveness but does not decelerate growth of resistance. Our estimates of mutation and haplotype frequencies provide estimates of selection coefficients acting in this environment, which are key parameters for understanding the dynamics of resistanc
Walk on the Low Side: LOFAR explores the low-frequency radio emission of GASP jellyfish galaxies
Jellyfish galaxies, characterized by long filaments of stripped interstellar
medium extending from their disks, are the prime laboratories to study the
outcomes of ram pressure stripping. At radio wavelengths, they often show
unilateral emission extending beyond the stellar disk, and an excess of radio
luminosity with respect to that expected from their current star formation
rate. We present new 144 MHz images provided by the LOFAR Two-metre Sky Survey
for a sample of six galaxies from the GASP survey. These galaxies are
characterized by a high global luminosity at 144 MHz ( W
Hz), in excess compared to their ongoing star formation rate. The
comparison of radio and H images smoothed with a Gaussian beam
corresponding to 10 kpc reveals a sub-linear spatial correlation between
the two emissions with an average slope . In their stellar disk we
measure , which is close to the radio-to-star formation linear
relation. We speculate that, as a consequence of the ram pressure, in these
jellyfish galaxies the cosmic rays transport is more efficient than in normal
galaxies. Radio tails typically have higher radio-to-H ratios than the
disks, thus we suggest that the radio emission is boosted by the electrons
stripped from the disks. In all galaxies, the star formation rate has decreased
by a factor within the last yr. The observed radio emission
is consistent with the past star formation, so we propose that this recent
decline may be the cause of their radio luminosity-to-star formation rate
excess.Comment: 22 pages, 7 figures. Accepted for publication on ApJ on 24/08/202
Systematics of Hypocrea citrina and related taxa
Morphological studies and phylogenetic analyses of DNA sequences from three
genomic regions – the internal transcribed spacer (ITS) regions of the
nuclear ribosomal gene repeat, a partial sequence of RNA polymerase II subunit
(rpb2), and a partial sequence of translation elongation factor
(tef1) – were used to investigate the systematics of
Hypocrea citrina and related species. A neotype specimen is
designated for H. citrina that conforms to Persoon's description of a
yellow effuse fungus occurring on leaf litter. Historical information and
results obtained in this study provide the foundation for selection of a
lectotype specimen from Fries's herbarium for H. lactea. The results
indicate that (1) Hypocrea citrina and H. pulvinata are
distinct species; (2) H. lactea sensu Fries is a synonym of the older
name H. citrina; (3) H. pulvinata, H. protopulvinata, and
H. americana are phylogenetically distinct species that form a
well-supported polyporicolous clade; (4) H. citrina is situated in a
clade closely related to H. pulvinata; and (5) H.
microcitrina and H. pseudostraminea reside in a highly supported
clade phylogenetically distinct from H. citrina. Hypocrea protopulvinata,
H. microcitrina, H. megalocitrina, H. pseudostraminea, and a new species,
H. aurantiistroma, are reported and described from North America.
Variation in rpb2 and tef1 gene sequences suggests
geographical subgroupings between European and North American isolates of
H. pulvinata. The phylogenies inferred from ITS, rpb2, and
tef1 gene sequences are concordant. Hypocrea citrina var.
americana is elevated to species status, Hypocrea
americana
Molecular phylogenetics of Pleosporales: Melanommataceae and Lophiostomataceae re-circumscribed (Pleosporomycetidae, Dothideomycetes, Ascomycota)
The classification of Pleosporales has posed major challenges due
to the lack of clear understanding of the importance of the morphological
characters used to distinguish between different groups in the order. This has
resulted in varied taxonomic treatments of many families in the group
including Melanommataceae and Lophiostomataceae. In this
study we employ two nuclear DNA gene markers, nuclear ribosomal large subunit
DNA and translation elongation factor 1-alpha in order to examine the
molecular phylogenetics of Pleosporales with strong emphasis on the
families Melanommataceae and Lophiostomataceae. Phylogenetic
analyses recovered Melanommataceae, Lophiostomataceae,
Hypsostromataceae, and a few others as strongly supported clades
within the Pleosporales. Melanommataceae as currently
circumscribed was found to be polyphyletic. The genera Byssosphaeria,
Melanomma, and Pseudotrichia were recovered within the family,
while others such as Ostropella and Xenolophium nested
outside in a weakly supported group along with Platystomum compressum
and Pseudotrichia guatopoensis that may correspond to the family
Platystomaceae. The genus Byssosphaeria was recovered as a
strongly supported group within the Melanommataceae while
Melanomma was weakly supported with unclear relationships among the
species. The genera Herpotrichia and Bertiella were also
found to belong in the Melanommataceae. Lophiostomataceae
occurs as a strongly supported group but its concept is here expanded to
include a new genus Misturatosphaeria that bears morphology
traditionally not known to occur in the family. The strongly supported clade
of Misturatosphaeria contains nine species that have gregarious,
papillate ascomata with lighter coloured apices and plugged ostioles and that
vary in ascospore morphology from 1- to 3-septate to muriform. Along with a
strongly supported Lophiostoma clade, also within the family are
Thyridaria macrostomoides based on new sequences from Kenyan
collections and Massariosphaeria triseptata, M. grandispora, Westerdykella
cylindrica and Preussia terricola based on GenBank sequences.
The family Hypsostromataceae was recovered as a strongly supported
monophyletic group nested within the Pleosporales
A systematic account of the genus Plagiostoma (Gnomoniaceae, Diaporthales) based on morphology, host-associations, and a four-gene phylogeny
Members of the genus Plagiostoma inhabit leaves, stems, twigs, and
branches of woody and herbaceous plants predominantly in the temperate
Northern Hemisphere. An account of all known species of Plagiostoma
including Cryptodiaporthe is presented based on analyses of
morphological, cultural, and DNA sequence data. Multigene phylogenetic
analyses of DNA sequences from four genes (β-tubulin, ITS,
rpb2, and tef1-α) revealed eight previously
undescribed phylogenetic species and an association between a clade composed
of 11 species of Plagiostoma and the host family Salicaceae.
In this paper these eight new species of Plagiostoma are described,
four species are redescribed, and four new combinations are proposed. A key to
the 25 accepted species of Plagiostoma based on host, shape, and size
of perithecia, perithecial arrangement in the host, and microscopic
characteristics of the asci and ascospores is provided. Disposition of
additional names in Cryptodiaporthe and Plagiostoma is also
discussed
Perspective from a Younger Generation -- The Astro-Spectroscopy of Gisbert Winnewisser
Gisbert Winnewisser's astronomical career was practically coextensive with
the whole development of molecular radio astronomy. Here I would like to pick
out a few of his many contributions, which I, personally, find particularly
interesting and put them in the context of newer results.Comment: 14 pages. (Co)authored by members of the MPIfR (Sub)millimeter
Astronomy Group. To appear in the Proceedings of the 4th
Cologne-Bonn-Zermatt-Symposium "The Dense Interstellar Medium in Galaxies"
eds. S. Pfalzner, C. Kramer, C. Straubmeier, & A. Heithausen (Springer:
Berlin
Mycosphaerella is polyphyletic
Mycosphaerella, one of the largest genera of ascomycetes,
encompasses several thousand species and has anamorphs residing in more than
30 form genera. Although previous phylogenetic studies based on the ITS rDNA
locus supported the monophyly of the genus, DNA sequence data derived from the
LSU gene distinguish several clades and families in what has hitherto been
considered to represent the Mycosphaerellaceae. Several important
leaf spotting and extremotolerant species need to be disposed to the genus
Teratosphaeria, for which a new family, the
Teratosphaeriaceae, is introduced. Other distinct clades represent
the Schizothyriaceae, Davidiellaceae, Capnodiaceae,
and the Mycosphaerellaceae. Within the two major clades, namely
Teratosphaeriaceae and Mycosphaerellaceae, most anamorph
genera are polyphyletic, and new anamorph concepts need to be derived to cope
with dual nomenclature within the Mycosphaerella complex
Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales
The Gnomoniaceae are characterised by ascomata that are generally
immersed, solitary, without a stroma, or aggregated with a rudimentary stroma,
in herbaceous plant material especially in leaves, twigs or stems, but also in
bark or wood. The ascomata are black, soft-textured, thin-walled, and
pseudoparenchymatous with one or more central or eccentric necks. The asci
usually have a distinct apical ring. The Gnomoniaceae includes
species having ascospores that are small, mostly less than 25 μm long,
although some are longer, and range in septation from non-septate to
one-septate, rarely multi-septate. Molecular studies of the
Gnomoniaceae suggest that the traditional classification of genera
based on characteristics of the ascomata such as position of the neck and
ascospores such as septation have resulted in genera that are not
monophyletic. In this paper the concepts of the leaf-inhabiting genera in the
Gnomoniaceae are reevaluated using multiple genes, specifically
nrLSU, translation elongation factor 1-alpha (tef1-α), and RNA
polymerase II second largest subunit (rpb2) for 64 isolates. ITS sequences
were generated for 322 isolates. Six genera of leaf-inhabiting
Gnomoniaceae are defined based on placement of their type species
within the multigene phylogeny. The new monotypic genus
Ambarignomonia is established for an unusual species, A.
petiolorum. A key to 59 species of leaf-inhabiting Gnomoniaceae is
presented and 22 species of Gnomoniaceae are described and
illustrated