190 research outputs found
Joint Observatories Kavli Science Forum
The Joint Observatories Kavli Science Forum in Chile was organised in a
hybrid mode with the aim of encouraging collaborations, not only with the
Chilean institutions but also between the different observing facilities based
in Chile. The meeting featured scientific talks showing results obtained with
the astronomical facilities based in Chile, but significant time was also
dedicated to round-table discussions on Life Balance,
Diversity-Equity-Inclusion, and the Road Ahead (i.e., the future of those
Chile-based facilities).Comment: 2 pages, 2 figures, Conference Repor
The orbital period of the recurrent nova V2487 Oph revealed
We present the first reliable determination of the orbital period of the
recurrent nova V2487 Oph (Nova Oph 1998). We derived a value of d ( h) from the radial velocity curve of the intense He II
4686 emission line as detected in time-series X-shooter spectra. The
orbital period is significantly shorter than earlier claims, but it makes V2487
Oph one of the longest period cataclysmic variables known. The spectrum of
V2487 Oph is prolific in broad Balmer absorptions that resemble a white dwarf
spectrum. However, we show that they come from the accretion disc viewed at low
inclination. Although highly speculative, the analysis of the radial velocity
curves provides a binary mass ratio and a donor star mass M, assuming the reported white dwarf mass
M. A subgiant M-type star is tentatively suggested as the donor star.
We were lucky to inadvertently take some of the spectra when V2487 Oph was in a
flare state. During the flare, we detected high-velocity emission in the Balmer
and He II 4686 lines exceeding km s at close to orbital
phase 0.4. Receding emission up to km s at about phase 0.3 is
also observed. The similarities with the magnetic cataclysmic variables may
point to magnetic accretion on to the white dwarf during the repeating flares.Comment: Accepted for publication in MNRAS (October 9, 2023
New 9-Terpenyl(7-Terpenyl)Purines: synthesis and cytotoxicity
The purine ring system is one of the most widely distributed N-heterocycles in Nature [1] and many structurally
modified purine nucleosides and nucleotides have activities ranging from antineoplastic and antiviral to
antihypertensive, antiasthmatic, antituberculosis, etc [2]. Among the purine derivatives, we have put our
attention on natural N-alkylpurines such as the asmarines or agelasimines, a group of secondary metabolites
isolated from marine sponges with very interesting biological properties [3]. They have a diterpenoid moiety
attached to the N-7 nitrogen atom of an adenine and are usually isolated in very small quantities, which limited
their structure-activity relationship studies.
Our research group has been involved for years in the design, synthesis and biological evaluation of cytotoxic
compounds related to natural products, including the chemoinduction of bioactivity on inactive terpenoids [4].
These diterpenoid include compounds such as communic or cupressic acids that bear decaline moieties very
close to those present in the above-mentioned marine natural products.
These facts prompted us to design and prepare new terpenylpurine derivatives starting from natural
monoterpenoids and diterpenoids, commercially available or isolated from their natural sources and transformed
into appropriate alkylated agents.
Thus, we have prepared purines alkylated at N-7 and N-9 positions with isoprenoids, monoterpenoids and
diterpenoids, using two different synthetic approaches: from 6-chloropurine or from
4,5-diamine-6-chloropyrimidine. The structure of the synthesized purines are shown in the following figure. The purine analogues synthesized have been evaluated for their cytotoxicity against four tumour human cell lines
(breast, non-small lung, cervical and hepatocellular carcinoma) and non-tumour cells (porcine liver primary
cells). The most cytotoxic derivatives were those with a diterpenoid rest on the purine. The results obtained
allowed to draw conclusions on the structure-activity relationship of the compounds in order to evaluate the
influence of the terpenyl size on their cytotoxic properties
Disacåridos cianogénicos y benzoilados en hojas de Psydrax Locuples
Las plantas del género Psydrax y otras Rubiaceas relacionadas son usadas en la
medicina popular africana frente a malaria, fiebre, dolores de cabeza, reumatismos,
diarrea, conjuntivitis, micosis y otros cuadros infecciosos. Apenas existe bibliografĂa
fitoquĂmica sobre este gĂ©nero: Ășnicamente tres compuestos en la especie Psydrax
livida [1]. Recientemente hemos comunicado las propiedades antioxidantes y
citotĂłxicas de los extractos obtenidos de hojas de Psydrax locuples, planta arbĂłrea
utilizada particularmente en Mozambique para tratar la âdoença da luaâ en niños y
reciĂ©n nacidos, un sĂndrome relacionado con la epilepsia caracterizado por fiebre,
vĂłmitos, diarrea, dolor de cabeza y cĂłlicos abdominales [2].
A partir del extracto de acetato de etilo de sus hojas se han aislado, mediante
sucesivas cromatografĂas en columna y cromatografĂas en capa fina preparativas,
varios disacĂĄridos acetilados con estructura de (2R)-ÎČ-D-apiofuranosil-(1â6)-ÎČ-Dglucopiranosa.
Estos disacĂĄridos se pueden clasificar en dos familias en funciĂłn de si el
hidroxilo de la posiciĂłn 1 de la ÎČ-D-glucopiranosa se encuentra benzoilado o si se
encuentra unido a un residuo de mandelonitrilo formando glicósidos cianogénicos
relacionados con la oxyanthina presente en Psydrax livida [1].Estos disacĂĄridos son prĂĄcticamente desconocidos en el reino vegetal, tanto los
benzoilados como los cianogĂ©nicos, siendo la mayorĂa nuevos productos naturales
A revised view of the Canis Major stellar overdensity with DECam and Gaia: new evidence of a stellar warp of blue stars
We present DECam imaging combined with Gaia DR2 data to study the Canis Major
overdensity. The presence of the so-called Blue Plume stars in a low-pollution
area of the color-magnitude diagram allows us to derive the distance and proper
motions of this stellar feature along the line of sight of its hypothetical
core. The stellar overdensity extends on a large area of the sky at low
Galactic latitudes, below the plane, and between 230. According to the orbit derived for Canis Major, it presents an
on-plane rotation around the Milky Way. Moreover, additional overdensities of
Blue Plume stars are found around the plane and across the Galaxy, proving that
these objects are not only associated with that structure. The spatial
distribution of these stars, derived using Gaia astrometric data, confirms that
the detection of the Canis Major overdensity results more from the warped
structure of the Milky Way disk than from the accretion of a dwarf galaxy.Comment: 11 pages, 9 figures, accepted for publication in MNRA
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