Search results for "SELE"

Cost of host radiation in an RNA virus.

2000

Abstract Although host radiation allows a parasite to expand its ecological niche, traits governing the infection of multiple host types can decrease fitness in the original or alternate host environments. Reasons for this reduction in fitness include slower replication due to added genetic material or modifications, fitness trade-offs across host environments, and weaker selection resulting from simultaneous adaptation to multiple habitats. We examined the consequences of host radiation using vesicular stomatitis virus (VSV) and mammalian host cells in tissue culture. Replicate populations of VSV were allowed to evolve for 100 generations on the original host (BHK cells), on either of two …

The population genetics and evolutionary epidemiology of RNA viruses.

2004

Key Points The authors discuss the main mechanisms of RNA virus evolution — mutation, recombination, natural selection, genetic drift and migration, and how these interact to shape the genetic structure of populations.The quasispecies model of RNA virus evolution is explained and the question of whether this model provides an accurate description of RNA virus evolution is discussed.Experiments that can be carried out to test the basic principles of evolutionary theory are briefly described. The authors review what such experiments have told us about virus evolution and, more widely, what these experiments have revealed in terms of general evolutionary principles.RNA viruses evolve quickly, …

Selezione di Portafoglio e Metaeuristiche

2013

Il problema della selezione del portafoglio (PSP) ha come obiettivo quello di determinare, disponendo di un dato insieme di titoli, il portafoglio che minimizza una misura di rischio per un dato livello di rendimento minimo richiesto. Sebbene nella sua formulazione originaria il PSP può essere risolto utilizzando algoritmi di programmazione lineare o quadratica, l'inclusione di ulteriori vincoli ed obiettivi rende il problema computazionalmente difficile. Nel presente lavoro viene proposto un approccio metaeuristico al PSP in cui vengono considerate diverse misure di distanza tra i portafogli della frontiera efficiente (Mean-Variance) ed il portafoglio ottimo che si ottiene in corrispondenz…

Selective propane oxidation over MoVSbO catalysts. On the preparation, characterization and catalytic behavior of M1 phase

2009

Nb-free (SbO)(2)M(20)O(56) catalysts (M = Mo, V) presenting pure M1 phase have been prepared by a post-synthesis treatment with hydrogen peroxide of a heat-treated MoVSbO mixed metal oxide catalyst previously prepared by hydrothermal method. The characterization of catalysts and their results for propane oxidation suggest that the optimization in the preparation of the M1 phase depends strongly on the washing procedure. The optimal removing of Sb species formed during post-synthesis treatment can explain the improvement in the catalytic activity; while the better selectivity to acrylic acid of the catalysts obtained by post-synthesis treatment can be explained by the elimination of M2 phase…

Postpartum Hemorrhage: Conservative Treatments

2023

Postpartum hemorrhage (PPH) is an obstetric emergency representing the first cause of obstetric mortality and a frequent cause of severe maternal morbidity. It can complicate vaginal or cesarean deliveries and accounts for 25% of all maternal deaths worldwide, as reported by the World Health Organization (WHO). Primary PPH is defined as blood loss from the genital tract of at least 500 ml after vaginal or 1000 ml following cesarean delivery within 24 h postpartum, whereas secondary PPH is defined as any significant bleeding from the birth canal occurring between 24 h and 12 weeks postnatally. Uterine atony is reported as the main cause of PPH and accounts for 75%–90% of primary PPH. When ut…

Mutagenesis scanning uncovers evolutionary constraints on tobacco etch Potyvirus membrane-associated 6K2 protein

2019

RNA virus high mutation rate is a double-edged sword. At the one side, most mutations jeopardize proteins functions; at the other side, mutations are needed to fuel adaptation. The relevant question then is the ratio between beneficial and deleterious mutations. To evaluate this ratio, we created a mutant library of the 6K2 gene of tobacco etch potyvirus that contains every possible single-nucleotide substitution. 6K2 protein anchors the virus replication complex to the network of endoplasmic reticulum membranes. The library was inoculated into the natural host Nicotiana tabacum, allowing competition among all these mutants and selection of those that are potentially viable. We identified 1…

KAMA: A Temperature-Driven Model of Mate Choice Using Dynamic Partner Representations

2008

KAMA is a model of mate-choice based on a gradual, stochastic process of building up representations of potential partners through encounters and dating, ultimately leading to marriage. Individuals must attempt to find a suitable mate in a limited amount of time with only partial knowledge of the individuals in the pool of potential candidates. Individuals have multiple-valued character profiles, which describe a number of their characteristics (physical beauty, potential earning power, etc.), as well as preference profiles, that specify their degree of preference for those characteristics in members of the opposite sex. A process of encounters and dating allows individuals to gradually bui…

Multi-objective DSE algorithms' evaluations on processor optimization

2013

Very complex micro-architectures, like complex superscalar/SMT or multicore systems, have lots of configurations. Exploring this huge design space and trying to optimize multiple objectives, like performance, power consumption and hardware complexity is a real challenge. In this paper, using the multi-objective design space exploration tool FADSE, we tried to optimize the hardware parameters of the complex superscalar Grid ALU Processor. We compared how different heuristic algorithms handle the DSE optimization. Three of these algorithms are taken from the jMetal library (NSGAII, SPEA2 and SMPSO) while the other two, CNSGAII and MOHC were implemented by us. We show that in this huge design …

Risk assessment of selection for restistant PrP alleles on milk production in Valle del Belice

2006

Mating strategies and resulting patterns in mate guarding crustaceans : an empirical and theoretical approach

2012

Because of strong costs associated with each mating event, females are usually not as available for reproduction as males at any given time. Males are therefore in competition with each other for access to receptive females, hence leading to strong sexual selection. One textbook case of such a mating system occurs in moulting crustaceans where females can only be fertilized during a short period following their moult. This has favoured the evolution male strategies to monopolize females before their period of receptivity. Such a precopulatory mate guarding is widespread among many taxa and represents one of the most striking example of males’ competitive traits favoured by sexual selection.…