Sapienza University of Rome

About: Sapienza University of Rome is a education organization based out in Rome, Lazio, Italy. It is known for research contribution in the topics: Population & Medicine. The organization has 62002 authors who have published 155468 publications receiving 4397244 citations. The organization is also known as: La Sapienza & Università La Sapienza di Roma.

The dawn of human matrilineal diversity.

Abstract: The quest to explain demographic history during the early part of human evolution has been limited because of the scarce paleoanthropological record from the Middle Stone Age. To shed light on the structure of the mitochondrial DNA (mtDNA) phylogeny at the dawn of Homo sapiens, we constructed a matrilineal tree composed of 624 complete mtDNA genomes from sub-Saharan Hg L lineages. We paid particular attention to the Khoi and San (Khoisan) people of South Africa because they are considered to be a unique relic of hunter-gatherer lifestyle and to carry paternal and maternal lineages belonging to the deepest clades known among modern humans. Both the tree phylogeny and coalescence calculations suggest that Khoisan matrilineal ancestry diverged from the rest of the human mtDNA pool 90,000–150,000 years before present (ybp) and that at least five additional, currently extant maternal lineages existed during this period in parallel. Furthermore, we estimate that a minimum of 40 other evolutionarily successful lineages flourished in sub-Saharan Africa during the period of modern human dispersal out of Africa approximately 60,000–70,000 ybp. Only much later, at the beginning of the Late Stone Age, about 40,000 ybp, did introgression of additional lineages occur into the Khoisan mtDNA pool. This process was further accelerated during the recent Bantu expansions. Our results suggest that the early settlement of humans in Africa was already matrilineally structured and involved small, separately evolving isolated populations.

A Survey on MAC Strategies for Cognitive Radio Networks

Abstract: Dynamic spectrum policies combined with software defined radio are powerful means to improve the overall spectral efficiency allowing the development of new wireless services and technologies. Medium Access Control (MAC) protocols exploit sensing stimuli to build up a spectrum opportunity map (cognitive sensing). Available resources are scheduled (dynamic spectrum allocation), improving coexistence between users that belong to heterogeneous systems (dynamic spectrum sharing). Furthermore, MAC protocols may allow cognitive users to vacate selected channels when their quality becomes unacceptable (dynamic spectrum mobility). The contribution of this survey is threefold. First, we show the fundamental role of the MAC layer and identify its functionalities in a cognitive radio (CR) network. Second, a classification of cognitive MAC protocols is proposed. Third, advantages, drawbacks, and further design challenges of cognitive MAC protocols are discussed.

Deltorphins: a family of naturally occurring peptides with high affinity and selectivity for delta opioid binding sites.

Abstract: Deltorphins are endogenous linear heptapeptides, isolated from skin extracts of frogs belonging to the genus Phyllomedusa, that have a higher affinity and selectivity for delta opioid binding sites than any other natural compound known. Two deltorphins with the sequence Tyr-Ala-Phe-Asp(or Glu)-Val-Val-Gly-NH2 have been isolated from skin extracts of Phyllomedusa bicolor. The alanine in position 2 is in the D configuration. These peptides, [D-Ala2]deltorphins I and II, show an even higher affinity for delta receptors than the previously characterized deltorphin, which contains D-methionine as the second amino acid. These peptides show some similarity to another constituent of Phyllomedusa skin, dermorphin, which is highly selective for mu-opioid receptors. These peptides all have the N-terminal sequence Tyr-D-Xaa-Phe, where D-Xaa is either D-alanine or D-methionine. While this structure seems to be capable of activating both mu and delta opioid receptors, differences in the C-terminal regions of these peptides are probably responsible for the observed high receptor selectivity of dermorphin and deltorphin.