35 research outputs found
The synthesis of single enantiomers of α-mycolic acids of M.tuberculosis with alternative cyclopropane stereochemistries
We report the synthesis of three stereoisomers of a mycolic acid from Mycobacterium tuberculosis containing a di-cis-cyclopropane and of two stereoisomers of a mycolic acid containing a proximal trans-cyclopropane and a distal cis-cyclopropane.</jats:p
Supernovae in isolated galaxies, in pairs and in groups of galaxies
In order to investigate the influence of the environment on the supernova
(SN) production we have performed a statistical investigation of the SNe
discovered in isolated galaxies, in pairs and in groups of galaxies. 22 SNe in
18 isolated galaxies, 48 SNe in 40 galaxies members of 37 pairs and 211 SNe in
170 galaxies members of 116 groups have been selected and studied. We found
that the radial distributions of core-collapse SNe in galaxies located in
different environments are similar, and consistent with that reported by
Bartunov, Makarova & Tsvetkov (1992). SNe discovered in pairs do not privilege
a particular direction with respect to the companion galaxy. Also the azimuthal
distributions inside the hosts members of galaxy groups are consistent with
being isotropics. The fact that SNe are more frequent in the brighter
components of the pairs and groups is expected from the dependence of the SN
rates on the galaxy luminosity. There is an indication that the SN rate is
higher in galaxy pairs compared with that in groups. This can be related to the
enhanced star formation rate in strongly interacting systems. It is concluded
that, with the possible exception of strongly interacting system, the parent
galaxy environment has no direct influence on the SN productionComment: 10 pages, accepted for publication to MNRA
Mapping physiological G protein-coupled receptor signaling pathways reveals a role for receptor phosphorylation in airway contraction.
G protein-coupled receptors (GPCRs) are known to initiate a plethora of signaling pathways in vitro. However, it is unclear which of these pathways are engaged to mediate physiological responses. Here, we examine the distinct roles of Gq/11-dependent signaling and receptor phosphorylation-dependent signaling in bronchial airway contraction and lung function regulated through the M3-muscarinic acetylcholine receptor (M3-mAChR). By using a genetically engineered mouse expressing a G protein-biased M3-mAChR mutant, we reveal the first evidence, to our knowledge, of a role for M3-mAChR phosphorylation in bronchial smooth muscle contraction in health and in a disease state with relevance to human asthma. Furthermore, this mouse model can be used to distinguish the physiological responses that are regulated by M3-mAChR phosphorylation (which include control of lung function) from those responses that are downstream of G protein signaling. In this way, we present an approach by which to predict the physiological/therapeutic outcome of M3-mAChR-biased ligands with important implications for drug discovery.This study is funded by the Medical Research Council (MRC) through funding of program leaders provided by the MRC Toxicology Unit (to A.B.T.)
Theoretical Light Curves of Type II-P SNe and Applications to Cosmology
Based on an extensive grid of stellar models between 13 and 25 Mo and a wide
range of metallicities, we have studied the light curves of core collapse
supernovae, their application to cosmology and evolutionary effects with
redshift. The direct link between the hydro and radiation transport allows to
calculate monochromatic light curves.
With decreasing metallicity Z and increasing mass, progenitors tend to
explode as compact Blue Supergiants and produce sub-luminous supernovae that
are about 1.5 mag dimmer compared to "normal" SNe II with Red
Supergiant progenitors (RSGs). Progenitors with small masses tend to explode
as RSGs even at low Z. The consequences are obvious for probing the chemical
evolution, namely, a strong bias when using the statistics of core collapse
supernovae to probe the history of star formation.
Our study is limited in scope with respect to the explosion energies and the
production of radioactive Ni. Within the class of "extreme SNe II-P"
supernovae, the light curves are rather insensitive with respect to the
progenitor mass and explosion energy compared to analytic models which are
based on parameterized stellar structures. We expect a wider range of
brightness due to variations in Ni56 because radioactive energy is a main
source of luminosity.
However, the overall insensitivity of LCs may allow their use as
quasi-standard candles for distance determination.Comment: 14 pages, 16 figures, accepted for publication in MNRA
Recommended from our members
Track A Basic Science
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138319/1/jia218438.pd
NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics
Xenarthrans â anteaters, sloths, and armadillos â have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset
Synthetic trehalose di- and mono-esters of alpha-, methoxy- and keto-mycolic acids
Synthetic mycolic acids matching the overall structure of the major mycolic acids of Mycobacterium tuberculosis are coupled to trehalose to generate the corresponding synthetic trehalose monomycolate (TMM) and trehalose dimycolate (TDM; cord factor), either with two identical or two different mycolic acids