697 research outputs found
The growth and erosion of cinder cones in Guatemala and El Salvador: Models and statistics
Morphologic data for 147 cinder cones in southern Guatemala andwestern El Salvador are comparedwith data from
the San Francisco volcanic field, Arizona (USA), Cima volcanic field, California (USA), Michoácan–Guanajuato
volcanic field, Mexico, and the Lamongan volcanic field, East Java. The Guatemala cones have an average height of
110+/-50 m, an average basal diameter of 660+/-230 m and an average top diameter of 180+/-150 m. The
generalmorphology of these cones can be described by their average cone angle of slope (24+/-7), average heightto-
radius ratio (0.33+/-0.09) and their flatness (0.24+/-0.18). Although the mean values for the Guatemalan
cones are similar to those for other volcanic fields (e.g., San Francisco volcanic field, Arizona; Cima volcanic field,
California; Michoácan–Guanajuato volcanic field, Mexico; and Lamongan volcanic field, East Java), the range of
morphologies encompasses almost all of those observed worldwide for cinder cones.
Three new 40Ar/39Ar age dates are combined with 19 previously published dates for cones in Guatemala and El
Salvador. There is no indication that the morphologies of these cones have changed over the last 500–1000 ka.
Furthermore, a re-analysis of published data for other volcanic fields suggests that only in the Cima volcanic field (of
those studied) is there clear evidence of degradation with age.
Preliminary results of a numerical model of cinder cone growth are used to show that the range of morphologies
observed in the Guatemalan cinder cones could all be primary, that is, due to processes occurring at the time of
eruption
The growth and erosion of cinder cones in Guatemala and El Salvador: Models and statistics
Morphologic data for 147 cinder cones in southern Guatemala andwestern El Salvador are comparedwith data from
the San Francisco volcanic field, Arizona (USA), Cima volcanic field, California (USA), Michoácan–Guanajuato
volcanic field, Mexico, and the Lamongan volcanic field, East Java. The Guatemala cones have an average height of
110+/-50 m, an average basal diameter of 660+/-230 m and an average top diameter of 180+/-150 m. The
generalmorphology of these cones can be described by their average cone angle of slope (24+/-7), average heightto-
radius ratio (0.33+/-0.09) and their flatness (0.24+/-0.18). Although the mean values for the Guatemalan
cones are similar to those for other volcanic fields (e.g., San Francisco volcanic field, Arizona; Cima volcanic field,
California; Michoácan–Guanajuato volcanic field, Mexico; and Lamongan volcanic field, East Java), the range of
morphologies encompasses almost all of those observed worldwide for cinder cones.
Three new 40Ar/39Ar age dates are combined with 19 previously published dates for cones in Guatemala and El
Salvador. There is no indication that the morphologies of these cones have changed over the last 500–1000 ka.
Furthermore, a re-analysis of published data for other volcanic fields suggests that only in the Cima volcanic field (of
those studied) is there clear evidence of degradation with age.
Preliminary results of a numerical model of cinder cone growth are used to show that the range of morphologies
observed in the Guatemalan cinder cones could all be primary, that is, due to processes occurring at the time of
eruption
HIV subtype and drug resistance patterns among drug naïve persons in Jos, Nigeria
To determine HIV-1 subtypes and antiretroviral drug resistance mutations for 16 infected, pregnant women in Jos, Nigeria, part of pol (1040 bp) was amplified from patient PBMC DNA, sequenced andanalyzed. Eight of the samples were subtype G, three were CRF02_AG and 2 were unique recombinant forms (URF) between G and CRF02_AG. The remaining consisted of 3 different strains: one was subtypeC, and the other 2 were unrelated URF. Nearly full-length genome sequences were completed for 6 of the strains: 4 subtype G and 2 CRF02_AG. In the 14 drug-naïve subjects, no primary resistance-associated mutations were found, but secondary mutations were identified in 7 different codons of the gene coding for protease: PR K20I, M36I, L63A/P/V, V82I, L10M/I and I93L. In addition, the K238R mutation was identified in the reverse transcriptase gene of 3 viruses. The PR K20I and M36I mutations occurred in all of the strains, and the L10M and V82I mutations occurred only in subtype G. The mutation, I93L, was carried by subtype C viruses. Two of the women that had prior niverapine treatment, had primary resistance-associated mutations, RT M184V and K103N, archived in their proviral DNA several months after treatment cessation. The study reports a predominance of clade G and CRF02_AG, and provides many more examples of nearly full-length genome sequences for subtype G viruses from Nigeria. The ubiquitous presence of PI secondary resistance-associated mutations, as well as primary resistanceassociatedmutations in 2 previously treated women, underscores the need to ensure adherence compliance to treatment
ATLASGAL: 3-mm class I methanol masers in high-mass star formation regions
We analyzed the 3-mm wavelength spectral line survey of 408 ATLASGAL clumps
observed with the IRAM 30m-telescope, focusing on the class I methanol masers
with frequencies near 84, 95 and 104.3 GHz. We detect narrow, maser-like
features towards 54, 100 and 4 sources in the maser lines near 84, 95 and 104.3
GHz, respectively. Among them, fifty 84 GHz masers, twenty nine 95 GHz masers
and four rare 104.3 GHz masers are new discoveries. The new detections increase
the number of known 104.3 GHz masers from 5 to 9. The 95 GHz class I methanol
maser is generally stronger than the 84 GHz maser counterpart. We find 9
sources showing class I methanol masers but no SiO emission, indicating that
class I methanol masers might be the only signpost of protostellar outflow
activity in extremely embedded objects at the earliest evolutionary stage.
Class I methanol masers that are associated with sources that show SiO line
wings are more numerous and stronger than those without such wings. The total
integrated intensity of class I methanol masers is well correlated with the
integrated intensity and velocity coverage of the SiO (2--1) emission. The
properties of class I methanol masers are positively correlated with the
bolometric luminosity, clump mass, peak H column density of their
associated clumps but uncorrelated with the luminosity-to-mass ratio, dust
temperature, and mean H volume density. We suggest that the properties of
class I masers are related to shocks traced by SiO. Based on our observations,
we conclude that class I methanol masers at 84 and 95 GHz can trace a similar
evolutionary stage as HO maser, and appear prior to 6.7 and 12.2 GHz
methanol and OH masers. Despite their small number, the 104.3 GHz class I
masers appear to trace a short and more evolved stage compared to the other
class I masers. [abridged]Comment: 23 pages, 27 figures, 8 tables, accepted for publication in A&
Fission barriers and asymmetric ground states in the relativistic mean field theory
The symmetric and asymmetric fission path for 240Pu, 232Th, and 226Ra is
investigated within the relativistic mean field model. Standard
parametrizations which are well fitted to nuclear ground state properties are
found to deliver reasonable qualitative and quantitative features of fission,
comparable to similar nonrelativstic calculations. Furthermore, stable octupole
deformations in the ground states of Radium isotopes are investigated. They are
found in a series of isotopes, qualitatively in agreement with nonrelativistic
models. But the quantitative details differ amongst the models and between the
various relativsitic parametrizations.Comment: 30 pages RevTeX, 7 tables, 12 low resolution Gif figures (high
resolution PostScript versions are available at
http://www.th.physik.uni-frankfurt.de/~bender/nucl_struct_publications.html
or at ftp://th.physik.uni-frankfurt.de/pub/bender
Evaluation of a Bayesian inference network for ligand-based virtual screening
Background
Bayesian inference networks enable the computation of the probability that an event will occur. They have been used previously to rank textual documents in order of decreasing relevance to a user-defined query. Here, we modify the approach to enable a Bayesian inference network to be used for chemical similarity searching, where a database is ranked in order of decreasing probability of bioactivity.
Results
Bayesian inference networks were implemented using two different types of network and four different types of belief function. Experiments with the MDDR and WOMBAT databases show that a Bayesian inference network can be used to provide effective ligand-based screening, especially when the active molecules being sought have a high degree of structural homogeneity; in such cases, the network substantially out-performs a conventional, Tanimoto-based similarity searching system. However, the effectiveness of the network is much less when structurally heterogeneous sets of actives are being sought.
Conclusion
A Bayesian inference network provides an interesting alternative to existing tools for ligand-based virtual screening
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