235 research outputs found
Ices in Star-Forming Regions: First Results from VLT-ISAAC
The first results from a VLT-ISAAC program on L- and M-band infrared
spectroscopy of deeply-embedded young stellar objects are presented. The advent
of 8-m class telescopes allows high S/N spectra of low-luminosity sources to be
obtained. In our first observing run, low- and medium-resolution spectra have
been measured toward a dozen objects, mostly in the Vela and Chamaeleon
molecular clouds. The spectra show strong absorption of H2O and CO ice, as well
as weak features at `3.47' and 4.62 mu. No significant solid CH3OH feature at
3.54 mu is found, indicating that the CH3OH/H2O ice abundance is lower than
toward some massive protostars. Various evolutionary diagnostics are
investigated for a set of sources in Vela.Comment: 8 pages, 4 figures, to appear in The Origins of Stars and Planets:
the VLT View, eds. J. Alves, M. McCaughrean (Springer Verlag
Potent and Broad-Spectrum Antimicrobial Activity of Analogs from the Scorpion Peptide Stigmurin
Scorpion venom constitutes a rich source of biologically active compounds with high potential for therapeutic and biotechnological applications that can be used as prototypes for the design of new drugs. The aim of this study was to characterize the structural conformation, evaluate the antimicrobial activity, and gain insight into the possible action mechanism underlying it, for two new analog peptides of the scorpion peptide Stigmurin, named StigA25 and StigA31. The amino acid substitutions in the native sequence for lysine residues resulted in peptides with higher positive net charge and hydrophobicity, with an increase in the theoretical helical content. StigA25 and StigA31 showed the capacity to modify their structural conformation according to the environment, and were stable to pH and temperature variation-results similar to the native peptide. Both analog peptides demonstrated broad-spectrum antimicrobial activity in vitro, showing an effect superior to that of the native peptide, being non-hemolytic at the biologically active concentrations. Therefore, this study demonstrates the therapeutic potential of the analog peptides from Stigmurin and the promising approach of rational drug design based on scorpion venom peptide to obtain new anti-infective agents.publishersversionpublishe
Scotogenic dark matter and Dirac neutrinos from unbroken gauged symmetry
We propose a simple extension of the standard model where neutrinos get
naturally small "scotogenic" Dirac masses from an unbroken gauged
symmetry, ensuring dark matter stability. The associated gauge boson gets mass
through the Stueckelberg mechanism. Two scenarios are identified, and the
resulting phenomenology briefly sketched.Comment: 9 pages, 3 tables, 1 figur
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Gastric lesions associated with the presence of Anisakis spp. Dujardin, 1845 (Nematoda: Anisakidae) in Cetaceans stranded on the coast of Ceara, Brazil
Efeito do gradiente de martensita induzida por deformação sobre o fenômeno de delayed cracking em aços inoxidáveis austeníticos
Echinoderms from Todos os Santos Bay and Aratu Bay (Bahia, Brazil)
Neste trabalho são registrados os equinodermos (exceto Holothuroidea) obtidos durante a execução do projeto "Marine Environmental Evaluation of the Todos os Santos Bay-MAREMBA" em julho/agosto de 1996 e durante o projeto "Geoecologia das comunidades bentônicas infralitorais da Baía de Todos os Santos (BTS), BA, Brasil: diversidade biótica e sedimentológica", (1997). Um total de 33 espécies pertencentes a 15 famílias foram registradas e re-descritas. A distribuição de Ophiactis brasiliensis Manso, 1988 e Amphiodia trychna H.L. Clark, 1918 é estendida para a região nordeste do Brasil. A classe Ophiuroidea foi dominante nas amostragens em termos de abundância e freqüência de ocorrência, em particular as espécies Amphiodia atra Stimpson, 1852, Amphipholis subtilis (Ljungman, 1867), Ophiactislymani Ljungman, 1871 e Ophiostigma isocanthum (Say, 1825). O asteróide Oreaster reticulatus (Linnaeus, 1758) é considerado vulnerável à exploração humana e foi escasso durante as coletas. Outras espécies encontradas na BTS, tais como os asteroides Luidia clathrata (Say, 1825) e L. senegalensis (Lamarck, 1816) e o equinóide Eucidaristribuloides (Lamarck, 1816) figuram na lista nacional de espécies de invertebrados aquáticos ameaçados de extinção._______________________________________________________________________________ ABSTRACT: We present the results of the studies on biodiversity of Echinodermata (except Holothuroidea) from the Projects "Marine Environmental Evaluation of the Todos os Santos Bay - MAREMBA" (July/August 1996) and "Geoecology of the Benthic Infralitoral Communities of Todos os Santos Bay (BTS), Bahia, Brazil" (1997). A total of 33 species from 15 families were registered and re-described. The distribution of Ophiactis brasiliensis Manso, 1988 and Amphiodia trychna H.L. Clark, 1918 is extended to northwestern Brazil. The class Ophiuroidea was dominant in samples in terms of abundance and frequency of occurrence, in particular Amphiodia atra Stimpson, 1852, Amphipholis subtilis (Ljungman, 1867), Ophiactislymani Ljungman, 1871and Ophiostigma isocanthum (Say, 1825). The asteroid Oreaster reticulatus (Linnaeus, 1758) is considered vulnerable to human exploration and was scarce during the surveys. Other species found at BTS, such the asteroids Luidia clathrata (Say, 1825) and L. senegalensis (Lamarck, 1816) and the echinoid Eucidaristribuloides (Lamarck, 1816)are included in the national list of threatened invertebrate species
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