Coevolución en el sector de agencias de viajes

Las teorías más recientes para el análisis de mercados imperfectos se enfocan en estudios dinámicos de las organizaciones a través del tiempo, lo que les permite determinar las evoluciones o cambios de las firmas y su ambiente. En este grupo de estudios se encuentra el de coevolución, según el cual las empresas evolucionan simultáneamente con su ambiente, pero los cambios que afrontan no son fruto de la casualidad sino que siguen una relación endógena entre estas dos entidades complejas. Utilizando la teoría de la coevolución, el presente trabajo pretende mostrar su existencia en el sector de agencias de viajes, para lo cual también se hará uso de los análisis de turbulencia y de fuerzas del mercado que permitirán encontrar los diferentes factores generadores de cambio tanto en el sector como en las empresas que lo conforman y la relación causal existente entre los mismos.

Ciencias de la complejidad: estado actual

Los aportes teóricos y aplicados de la complejidad en economía han tomado tantas direcciones y han sido tan frenéticos en las últimas décadas, que no existe un trabajo reciente, hasta donde conocemos, que los compile y los analice de forma integrada. El objetivo de este proyecto, por tanto, es desarrollar un estado situacional de las diferentes aplicaciones conceptuales, teóricas, metodológicas y tecnológicas de las ciencias de la complejidad en la economía. Asimismo, se pretende analizar las tendencias recientes en el estudio de la complejidad de los sistemas económicos y los horizontes que las ciencias de la complejidad ofrecen de cara al abordaje de los fenómenos económicos del mundo globalizado contemporáneo.

Explorando modelos in vivo para caracterizar a microcirculação periférica : um estudo piloto

Nos últimos anos, a circulação cutânea surgiu como uma janela interessante para analisar a função microcirculatória e os mecanismos de disfunção. Tecnologias não-invasivas, incluindo a Fluxometria por Laser Doppler (FLD), gasimetria transcutânea e a Perda Transepidérmica de Água (PTEA), ajudaram a considerar a circulação cutânea como um modelo de translação útil na doença vascular. Neste estudo procurou-se avaliar o perfil de resposta de um grupo de indivíduos jovens saudáveis ​​(n = 8), de ambos os sexos (24,5 ± 0,8 anos de idade) a três manobras de condicionamento da perfusão no membro inferior - A: elevação da perna enquanto sentado, B: elevação da perna enquanto em decúbito dorsal; C: oclusão supra-sistólica com um torniquete. As técnicas de medição incluiram FLD, pressões parciais transcutâneas (tc) pO2 e pCO2 por gasimetria e PTEA por evaporimetria. Foram aplicados testes de estatística descritiva e não paramétrica, sendo adotado um nível de confiança de 95%. As tcpO2 e tcpCO2 alteraram-se significativamente durante as manobras. Foi registado um perfil de evolução recíproca para FLD e PTEA em A e C, o que pode sugerir que, sob as condições experimentais as condições de perfusão local podem influenciar a função epidérmica "barreira". Os modelos propostos parecem ser adequados para caracterizar a microcirculação periférica in vivo, o que justifica estudos de desenvolvimento posteriores.

Vegetation development and human occupation in the Damascus region of southwestern Syria from the Late Pleistocene to Holocene

Rockshelter Baaz in the Damascus region of Syria provided a variety of botanical remains from the Late Pleistocene and Early Holocene period. These remains provide new information about the vegetation evolution in this region. The earliest occupational levels correspond with a moisture peak during the Late Pleistocene, between ca. 34-32 kyr b.p., when pine expanded. The next occupations took place during extreme arid conditions, ca. 23-21 kyr b.p., and probably during the Last Glacial Maximum when a steppe vegetation was established. The occupation level of the Younger Dryas, represented by Natufian remains, suggests that the area had been covered by almond-pistachio steppe, similar to later periods of the Early Holocene, and was probably located just outside the range of dense wild cereal stands. There is no drastic impact of the Younger Dryas visible on the vegetation in the botanical remains. The lack of fruits and seeds at Baaz indicates that the site was more likely to have been a temporary hunting post rather than a plant processing site for much of its history. It is ideally suited to this purpose because of its location over the Jaba'deen Pass and the associated springs. However, archaeological remains from the Natufian period, suggest that the site was more permanently occupied during this time.

The Brain as a Cultural Artefact

Where does biology end and culture begin? While the human body is now widely accepted as being both biological and cultural, the brain is still considered by archaeologists as being a biological entity that provides the capacity for culture and is subject to no further change after the evolution of Homo sapiens. This article reviews recent research that suggests that the brain has continued to evolve at an increasing rate in recent times under the influence Of culturally created environments and that both the anatomy and function of individual brains can be manipulated by cultural behaviour. It describes an experiment in which one of us successfully changed his own brain in response to his cultural activity.

Studying the Human Gut Microbiota in the Trans-Omics Era - Focus on Metagenomics and Metabonomics

The human gut microbiota comprises a diverse microbial consortium closely co-evolved with the human genome and diet. The importance of the gut microbiota in regulating human health and disease has however been largely overlooked due to the inaccessibility of the intestinal habitat, the complexity of the gut microbiota itself and the fact that many of its members resist cultivation and are in fact new to science. However, with the emergence of 16S rRNA molecular tools and "post-genomics" high resolution technologies for examining microorganisms as they occur in nature without the need for prior laboratory culture, this limited view of the gut microbiota is rapidly changing. This review will discuss the application of molecular microbiological tools to study the human gut microbiota in a culture independent manner. Genomics or metagenomics approaches have a tremendous capability to generate compositional data and to measure the metabolic potential encoded by the combined genomes of the gut microbiota. Another post-genomics approach, metabonomics, has the capacity to measure the metabolic kinetic or flux of metabolites through an ecosystem at a particular point in time or over a time course. Metabonomics thus derives data on the function of the gut microbiota in situ and how it responds to different environmental stimuli e. g. substrates like prebiotics, antibiotics and other drugs and in response to disease. Recently these two culture independent, high resolution approaches have been combined into a single "transgenomic" approach which allows correlation of changes in metabolite profiles within human biofluids with microbiota compositional metagenomic data. Such approaches are providing novel insight into the composition, function and evolution of our gut microbiota.

Gene conversion and evolution of Xq28 duplicons involved in recurring inversions causing severe hemophilia A

Inversions breaking the 1041 bp int1h-1 or the 9.5-kb int22h-1 sequence of the F8 gene cause hemophilia A in 1/30,000 males. These inversions are due to homologous recombination between the above sequences and their inverted copies on the same DNA molecule, respectively, int1h-2 and int22h-2 or int22h-3. We find that (1) int1h and int22h duplicated more than 25 million years ago; (2) the identity of the copies (>99%) of these sequences in humans and other primates is due to gene conversion; (3) gene conversion is most frequent in the internal regions of int22h; (4) breakpoints of int22h-related inversions also tend to involve the internal regions of int22h; (5) sequence variations in a sample of human X chromosomes defined eight haplotypes of int22h-1 and 27 of int22h-2 plus int22h-3; (6) the latter two sequences, which lie, respectively, 500 and 600 kb telomeric to int22h-1 are five-fold more identical when in cis than when in trans, thus suggesting that gene conversion may be predominantly intrachromosomal; (7) int1h, int22h, and flanking sequences evolved at a rate of about 0.1% substitutions per million years during the divergence between humans and other primates, except for int1h during the human-chimpanzee divergence, when its rate of evolution was significantly lower. This is reminiscent of the slower evolution of palindrome arms in the male specific regions of the Y chromosome and we propose, as an explanation, that intrachromosomal gene conversion and cosegregation of the duplicated regions favors retention of the ancestral sequence and thus reduces the evolution rate.

Microbial relatives of the seed storage proteins of higher plants: conservation of structure and diversification of function during evolution of the cupin superfamily.

This review summarizes the recent discovery of the cupin superfamily (from the Latin term "cupa," a small barrel) of functionally diverse proteins that initially were limited to several higher plant proteins such as seed storage proteins, germin (an oxalate oxidase), germin-like proteins, and auxin-binding protein. Knowledge of the three-dimensional structure of two vicilins, seed proteins with a characteristic beta-barrel core, led to the identification of a small number of conserved residues and thence to the discovery of several microbial proteins which share these key amino acids. In particular, there is a highly conserved pattern of two histidine-containing motifs with a varied intermotif spacing. This cupin signature is found as a central component of many microbial proteins including certain types of phosphomannose isomerase, polyketide synthase, epimerase, and dioxygenase. In addition, the signature has been identified within the N-terminal effector domain in a subgroup of bacterial AraC transcription factors. As well as these single-domain cupins, this survey has identified other classes of two-domain bicupins including bacterial gentisate 1, 2-dioxygenases and 1-hydroxy-2-naphthoate dioxygenases, fungal oxalate decarboxylases, and legume sucrose-binding proteins. Cupin evolution is discussed from the perspective of the structure-function relationships, using data from the genomes of several prokaryotes, especially Bacillus subtilis. Many of these functions involve aspects of sugar metabolism and cell wall synthesis and are concerned with responses to abiotic stress such as heat, desiccation, or starvation. Particular emphasis is also given to the oxalate-degrading enzymes from microbes, their biological significance, and their value in a range of medical and other applications.

Germin and germin-like proteins: evolution, structure, and function

Germin and germin-like proteins (GLPs) are encoded by a family of genes found in all plants. They are part of the cupin superfamily of biochemically diverse proteins, a superfamily that has a conserved tertiary structure, though with limited similarity in primary sequence. The subgroups of GLPs have different enzyme functions that include the two hydrogen peroxide-generating enzymes, oxalate oxidase (OxO) and superoxide dismutase. This review summarizes the sequence and structural details of GLPs and also discusses their evolutionary progression, particularly their amplification in gene number during the evolution of the land plants. In terms of function, the GLPs are known to be differentially expressed during specific periods of plant growth and development, a pattern of evolutionary subfunctionalization. They are also implicated in the response of plants to biotic (viruses, bacteria, mycorrhizae, fungi, insects, nematodes, and parasitic plants) and abiotic (salt, heat/cold, drought, nutrient, and metal) stress. Most detailed data come from studies of fungal pathogenesis in cereals. This involvement with the protection of plants from environmental stress of various types has led to numerous plant breeding studies that have found links between GLPs and QTLs for disease and stress resistance. In addition the OxO enzyme has considerable commercial significance, based principally on its use in the medical diagnosis of oxalate concentration in plasma and urine. Finally, this review provides information on the nutritional importance of these proteins in the human diet, as several members are known to be allergenic, a feature related to their thermal stability and evolutionary connection to the seed storage proteins, also members of the cupin superfamily.

Convergent evolution: floral guides, stingless bee nest entrances, and insectivorous pitchers

Several recent hypotheses, including sensory drive and sensory exploitation, suggest that receiver biases may drive selection of biological signals in the context of sexual selection. Here we suggest that a similar mechanism may have led to convergence of patterns in flowers, stingless bee nest entrances, and pitchers of insectivorous plants. A survey of these non-related visual stimuli shows that they share features such as stripes, dark centre, and peripheral dots. Next, we experimentally show that in stingless bees the close-up approach to a flower is guided by dark centre preference. Moreover, in the approach towards their nest entrance, they have a spontaneous preference for entrance patterns containing a dark centre and disrupted ornamentation. Together with existing empirical evidence on the honeybee's and other insects' orientation to flowers, this suggests that the signal receivers of the natural patterns we examined, mainly Hymenoptera, have spontaneous preferences for radiating stripes, dark centres, and peripheral dots. These receiver biases may have evolved in other behavioural contexts in the ancestors of Hymenoptera, but our findings suggest that they have triggered the convergent evolution of visual stimuli in floral guides, stingless bee nest entrances, and insectivorous pitchers.

A framework for revitalisation of rural education and training systems in sub-Saharan Africa: Strengthening the human resource base for food security and sustainable livelihoods

Recent studies of the current state of rural education and training (RET) systems in sub-Saharan Africa have assessed their ability to provide for the learning needs essential for more knowledgeable and productive small-scale rural households. These are most necessary if the endemic causes of rural poverty (poor nutrition, lack of sustainable livelihoods, etc.) are to be overcome. A brief historical background and analysis of the major current constraints to improvement in the sector are discussed. Paramount among those factors leading to its present 'malaise' is the lack of a whole-systems perspective and the absence of any coherent policy framework in most countries. There is evidence of some recent innovations, both in the public sector and through the work of non-governmental organisations (NGOs), civil society organisations (CSOs) and other private bodies. These provide hope of a new sense of direction that could lead towards meaningful 'revitalisation' of the sector. A suggested framework offers 10 key steps which, it is argued, could largely be achieved with modest internal resources and very little external support, provided that the necessary leadership and managerial capacities are in place. (C) 2006 Elsevier Ltd. All rights reserved.

Understanding the alphaviruses: Recent research on important emerging pathogens and progress towards their control

The alphaviruses were amongst the first arboviruses to be isolated, characterized and assigned a taxonomic status. They are globally very widespread, infecting a large variety of terrestrial animals, insects and even fish, and circulate both in the sylvatic and urban/peri-urban environment, causing considerable human morbidity and mortality. Nevertheless, despite their obvious importance as pathogens, there are currently no effective antiviral drugs with which to treat humans or animals infected by any of these viruses. The EU-supported project—VIZIER (Comparative Structural Genomics of Viral Enzymes Involved in Replication, FP6 Project: 2004-511960) was instigated with an ultimate view of contributing to the development of antiviral therapies for RNA viruses, including the alphaviruses [Coutard, B., Gorbalenya, A.E., Snijder, E.J., Leontovich, A.M., Poupon, A., De Lamballerie, X., Charrel, R., Gould, E.A., Gunther, S., Norder, H., Klempa, B., Bourhy, H., Rohayemj, J., L’hermite, E., Nordlund, P., Stuart, D.I., Owens, R.J., Grimes, J.M., Tuckerm, P.A., Bolognesi, M., Mattevi, A., Coll, M., Jones, T.A., Åqvist, J., Unger, T., Hilgenfeld, R., Bricogne, G., Neyts, J., La Colla, P., Puerstinger, G., Gonzalez, J.P., Leroy, E., Cambillau, C., Romette, J.L., Canard, B., 2008. The VIZIER project: preparedness against pathogenic RNA viruses. Antiviral Res. 78, 37–46]. This review highlights some of the major features of alphaviruses that have been investigated during recent years. After describing their classification, epidemiology and evolutionary history and the expanding geographic distribution of Chikungunya virus, we review progress in understanding the structure and function of alphavirus replicative enzymes achieved under the VIZIER programme and the development of new disease control strategies.

Human language as a culturally transmitted replicator

Human languages form a distinct and largely independent class of cultural replicators with behaviour and fidelity that can rival that of genes. Parallels between biological and linguistic evolution mean that statistical methods inspired by phylogenetics and comparative biology are being increasingly applied to study language. Phylogenetic trees constructed from linguistic elements chart the history of human cultures, and comparative studies reveal surprising and general features of how languages evolve, including patterns in the rates of evolution of language elements and social factors that influence temporal trends of language evolution. For many comparative questions of anthropology and human behavioural ecology, historical processes estimated from linguistic phylogenies may be more relevant than those estimated from genes.

Speciation and bursts of evolution

A longstanding debate in evolutionary biology concerns whether species diverge gradually through time or by rapid punctuational bursts at the time of speciation. The theory of punctuated equilibrium states that evolutionary change is characterised by short periods of rapid evolution followed by longer periods of stasis in which no change occurs. Despite years of work seeking evidence for punctuational change in the fossil record, the theory remains contentious. Further there is little consensus as to the size of the contribution of punctuational changes to overall evolutionary divergence. Here we review recent developments which show that punctuational evolution is common and widespread in gene sequence data.