2 resultados para Afro-descendants
em Universidade Complutense de Madrid
Resumo:
We present Keck I MOSFIRE spectroscopy in the Y and H bands of GDN-8231, a massive, compact, star-forming galaxy at a redshift of z ~ 1.7. Its spectrum reveals both Hα and [Nii] emission lines and strong Balmer absorption lines. The Hα and Spitzer MIPS 24 μm fluxes are both weak, thus indicating a low star-formation rate of SFR≲5-10 M_⨀ yr−1. This, added to a relatively young age of ~700 Myr measured from the absorption lines, provides the first direct evidence for a distant galaxy being caught in the act of rapidly shutting down its star formation. Such quenching allows GDN-8231 to become a compact, quiescent galaxy, similar to three other galaxies in our sample, by z ~ 1.5. Moreover, the color profile of GDN-8231 shows a bluer center, consistent with the predictions of recent simulations for an early phase of inside-out quenching. Its line-of-sight velocity dispersion for the gas, σ_LOG^gas = 127 ± 32 km s^−1, is nearly 40% smaller than that of its stars, σ_LOG^* = 215 ± 35 km s^−1. High-resolution hydro-simulations of galaxies explain such apparently colder gas kinematics of up to a factor of ~1.5 with rotating disks being viewed at different inclinations and/or centrally concentrated star-forming regions. A clear prediction is that their compact, quiescent descendants preserve some remnant rotation from their star-forming progenitors.
Resumo:
The HLA system is the most polymorphic genetic system described in humans. It consists of several closely linked loci encoding cell surface glycoproteins whose best known function is activating immune system response through antigenic presentation. New loci and new alleles have been described since the discovery of this genetic system and the presently available DNA typing and sequencing of these new alleles have increased the variety of HLA allelism. Due to the fact that HLA gene frequencies have a large degree of variability and a remarkable geographical correlation, HLA genes are an important and useful tool to infer genetic background and ethnical composition of modern human populations and also for tracing migration of ancient ones. In addition, certain combinations of contiguous alleles due to the strong linkage disequilibrium between HLA neighbouring loci show a characteristic frequency or are distinctive in many present day populations. Thus, HLA genetic system is a unique tool for studying the origin of relatively isolated groups, like Turkmen, Azeri and Kurd people, the populations under study, living in North Iran, in the surrounding area of Caspian Sea. Finally, HLA polymorphism is crucial for the compatibility between donor and receptor in organ transplantation and several HLA alleles have been linked to diseases and to response to drug treatments, which accomplishes relationships of certain variants with different pathologies treatment including AIDS. This is important in personalized treatments design. Turkmen could be descendants of Oghuz tribes from Seljuq branch coming from Transoxiana region (Central Asia) contemporarily to the foundation of the Seljuk Empire in 10th century AD. Conversely, this people could belong to another group within the Oghuz, arriving to Iran five centuries later. Migrations of this people were initially developed peacefully, being vassals of the Safavid Empire, and later by violent raids. They speak a language belonging to the Turkish-Oghuz group. In Iran, Turkmen live in Golestan province, mainly in Türkmensähra (“Turkmen plain”) area and amount 1.5 million people (2% of Iranian population). Most of this people are Sunni Muslims...