19,306 research outputs found
The largest oxigen bearing organic molecule repository
We present the first detection of complex aldehydes and isomers in three
typical molecular clouds located within 200pc of the center of our Galaxy.
We find very large abundances of these complex organic molecules (COMs) in
the central molecular zone (CMZ), which we attribute to the ejection of COMs
from grain mantles by shocks. The relative abundances of the different COMs
with respect to that of CH3OH are strikingly similar for the three sources,
located in very different environments in the CMZ. The similar relative
abundances point toward a unique grain mantle composition in the CMZ. Studying
the Galactic center clouds and objects in the Galactic disk having large
abundances of COMs, we find that more saturated molecules are more abundant
than the non-saturated ones. We also find differences between the relative
abundance between COMs in the CMZ and the Galactic disk, suggesting different
chemical histories of the grain mantles between the two regions in the Galaxy
for the complex aldehydes. Different possibilities for the grain chemistry on
the icy mantles in the GC clouds are briefly discussed. Cosmic rays can play an
important role in the grain chemistry. With these new detections, the molecular
clouds in the Galactic center appear to be one of the best laboratories for
studying the formation of COMs in the Galaxy.Comment: 20 pages, 4 figures, accepted in Ap
Dot Immunobinding Assay for the Rapid Serodetection of Scedosporium/Lomentospora in Cystic Fibrosis Patients
Scedosporium; Cystic fibrosis; Serological detectionScedosporium; Fibrosi quística; Detecció serològicaScedosporium; Fibrosis quística; Detección serológicaThe detection of Scedosporium/Lomentospora is still based on non-standardized low-sensitivity culture procedures. This fact is particularly worrying in patients with cystic fibrosis (CF), where these fungi are the second most common filamentous fungi isolated, because a poor and delayed diagnosis can worsen the prognosis of the disease. To contribute to the discovery of new diagnostic strategies, a rapid serological dot immunobinding assay (DIA) that allows the detection of serum IgG against Scedosporium/Lomentospora in less than 15 min was developed. A crude protein extract from the conidia and hyphae of Scedosporium boydii was employed as a fungal antigen. The DIA was evaluated using 303 CF serum samples (162 patients) grouped according to the detection of Scedosporium/Lomentospora in the respiratory sample by culture, obtaining a sensitivity and specificity of 90.48% and 79.30%, respectively; positive and negative predictive values of 54.81% and 96.77%, and an efficiency of 81.72%. The clinical factors associated with the results were also studied using a univariate and a multivariate analysis, which showed that Scedosporium/Lomentospora positive sputum, elevated anti-Aspergillus serum IgG and chronic Pseudomonas aeruginosa infection were significantly associated with a positive result in DIA, while Staphylococcus aureus positive sputum showed a negative association. In conclusion, the test developed can offer a complementary, rapid, simple and sensitive method to contribute to the diagnosis of Scedosporium/Lomentospora in patients with CF.This research was funded by the Basque Government, grant numbers IT1362-19 and IT1657-22. L.M-S and M.A have received a predoctoral grant from the Basque Government and L.A-F from the University of the Basque Country (UPV/EHU)
Chemistry in isolation: High CCH/HCO+ line ratio in the AMIGA galaxy CIG 638
Multi-molecule observations towards an increasing variety of galaxies have
been showing that the relative molecular abundances are affected by the type of
activity. However, these studies are biased towards bright active galaxies,
which are typically in interaction. We study the molecular composition of one
of the most isolated galaxies in the local Universe where the physical and
chemical properties of their molecular clouds have been determined by intrinsic
mechanisms. We present 3 mm broad band observations of the galaxy CIG 638,
extracted from the AMIGA sample of isolated galaxies. The emission of the J=1-0
transitions of CCH, HCN, HCO+, and HNC are detected. Integrated intensity
ratios between these line are compared with similar observations from the
literature towards active galaxies including starburst galaxies (SB), active
galactic nuclei (AGN), luminous infrared galaxies (LIRG), and GMCs in M33. A
significantly high ratio of CCH with respect to HCN, HCO+, and HNC is found
towards CIG 638 when compared with all other galaxies where these species have
been detected. This points to either an overabundance of CCH or to a relative
lack of dense molecular gas as supported by the low HCN/CO ratio, or both. The
data suggest that the CIG 638 is naturally a less perturbed galaxy where a
lower fraction of dense molecular gas, as well as a more even distribution
could explain the measured ratios. In this scenario the dense gas tracers would
be naturally dimmer, while the UV enhanced CCH, would be overproduced in a less
shielded medium.Comment: Letter accepted for publication in A&
Novel domain architectures and functional determinants in atypical annexins revealed by phylogenomic analysis.
The fundamental cellular role and molecular interactions of annexins in vesicle trafficking and membrane remodeling remain to be further clarified in order to better understand and exploit their contributions to health and disease. We focused on distinctive features of atypical annexins from all domains of life using phylogenomic, molecular systematic and experimental approaches, to extend the current paradigm and better account for annexin diversity of structure, function and mechanistic role in membrane homeostasis. The analysis of gene duplications, organization of domain architectures and profile hidden Markov models of subfamily orthologs defined conserved structural features relevant to molecular interactions and functional divergence of seven family clades ANXA-G. Single domain annexins of bacteria, including cyanobacteria, were frequently coupled to enzymatic units conceivably related to membrane metabolism and remodeling. Multiple ANX domains (up to 20) and various distinct functional domains were observed in unique annexins. Canonical type 2 calcium binding ligands were well-preserved in roughly half of all ANX domains, but alternative structural motifs comprised of 'KGD', cysteine or tryptophan residues were prominently conserved in the same strategic interhelical loops. Selective evolutionary constraint, site-specific location and co-occurrence in all kingdoms identify alternative modes of fundamental binding interactions for annexins
Microcanonical finite-size scaling in specific heat diverging 2nd order phase transitions
A Microcanonical Finite Site Ansatz in terms of quantities measurable in a
Finite Lattice allows to extend phenomenological renormalization (the so called
quotients method) to the microcanonical ensemble. The Ansatz is tested
numerically in two models where the canonical specific-heat diverges at
criticality, thus implying Fisher-renormalization of the critical exponents:
the 3D ferromagnetic Ising model and the 2D four-states Potts model (where
large logarithmic corrections are known to occur in the canonical ensemble). A
recently proposed microcanonical cluster method allows to simulate systems as
large as L=1024 (Potts) or L=128 (Ising). The quotients method provides
extremely accurate determinations of the anomalous dimension and of the
(Fisher-renormalized) thermal exponent. While in the Ising model the
numerical agreement with our theoretical expectations is impressive, in the
Potts case we need to carefully incorporate logarithmic corrections to the
microcanonical Ansatz in order to rationalize our data.Comment: 13 pages, 8 figure
Mid-Cycle Changes in Eta Carinae
In late 2006, ground-based photometry of Car plus the Homunculus
showed an unexpected decrease in its integrated apparent brightness, an
apparent reversal of its long-term brightening. Subsequent HST/WFPC2 photometry
of the central star in the near-UV showed that this was not a simple reversal.
This multi-wavelength photometry did not support increased extinction by dust
as the explanation for the decrease in brightness. A spectrum obtained with
GMOS on the Gemini-South telescope, revealed subtle changes mid-way in
Car's 5.5 yr spectroscopic cycle 0when compared with HST/STIS spectra at the
same phase in the cycle. At mid-cycle the secondary star is 20--30 AU from the
primary. We suggest that the spectroscopic changes are consistent with
fluctuations in the density and velocity of the primary star's wind, unrelated
to the 5.5 yr cycle but possibly related to its latitude-dependent morphology.
We also discuss subtle effects that must be taken into account when comparing
ground-based and HST/STIS spectra.Comment: 34 pages, 9 Figure
Dynamical complexity of discrete time regulatory networks
Genetic regulatory networks are usually modeled by systems of coupled
differential equations and by finite state models, better known as logical
networks, are also used. In this paper we consider a class of models of
regulatory networks which present both discrete and continuous aspects. Our
models consist of a network of units, whose states are quantified by a
continuous real variable. The state of each unit in the network evolves
according to a contractive transformation chosen from a finite collection of
possible transformations, according to a rule which depends on the state of the
neighboring units. As a first approximation to the complete description of the
dynamics of this networks we focus on a global characteristic, the dynamical
complexity, related to the proliferation of distinguishable temporal behaviors.
In this work we give explicit conditions under which explicit relations between
the topological structure of the regulatory network, and the growth rate of the
dynamical complexity can be established. We illustrate our results by means of
some biologically motivated examples.Comment: 28 pages, 4 figure
Spin Dynamical Properties of the Layered Perovskite La1.2Sr1.8Mn2O7
Inelastic neutron-scattering measurements were performed on a single crystal
of the layered colossal magnetoresistance (CMR) material La1.2Sr1.8Mn2O7 (Tc ~
120K). We found that the spin wave dispersion is almost perfectly
two-dimensional with the in-plane spin stiffness constant D ~ 151meVA. The
value is similar to that of similarly doped La1-xSrxMnO3 though its Tc is three
times higher, indicating a large renormalization due to low dimensionality.
There exist two branches due to a coupling between layers within a
double-layer. The out-of-plane coupling is about 30% of the in-plane coupling
though the Mn-O bond lengths are similar.Comment: 3 pages, 3 figures J. Phys. Chem. Solids in pres
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