983 resultados para tertiary transition
Resumo:
The relation between agricultural development and rural poverty reduction in six Central Eurasian countries, namely Azerbaijan (South Caucasus) and Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan (Central Asia), is discussed by presenting and analyzing ten propositions. These propositions cover a broad range of issues that relate to rural poverty in this region, such as: the state of income and non-income poverty; the diverse processes of land reform and farm restructuring, and agricultural policy reform; and finally, the institutional and market framework that is needed for dynamic agricultural and rural development. The paper contends that rural poverty is not responding as robustly to rapid economic growth in these countries, and that agricultural growth, in particular in the newly emerging peasant farm sector, is necessary to promote rural poverty reduction.
Resumo:
En este trabajo analizaremos en primer lugar la presencia i la importancia de los alimentos que caracterizan la dieta mediterránea en los sistemas alimentarios españoles del siglo XIX. Veremos como evoluciona esta presencia y el su peso a la dieta dentro del proceso de transición nutricional moderna española, contemplando dos períodos: desde finales del XIX hasta la década de 1930, y la segunda mitad del XX, períodos caracterizados por un aumento de la ingesta de alimentos, cereales y patatas primer, y de productos de origen animal después, y por la progresiva convergencia con las dietes de les sociedades desarrolladas, que diluirían o minimizarían progresivamente las características diferenciales mediterráneos. Situaremos los cambios que se producen a España en el contexto europeo, i finalmente, analizaremos en que medida, en la etapa inicial, la dieta seguida se ajustaba a les necesidades de la población y a la dieta actualmente recomendada, y si se produjeron cambios significativos en el curso de la transición alimentaria.
Resumo:
Population genetic differentiation characterizes the repartition of alleles among populations. It is commonly thought that genetic differentiation measures, such as GST and D, should be near zero when allele frequencies are close to their expected value in panmictic populations, and close to one when they are close to their expected value in isolated populations. To analyse those properties, we first derive analytically a reference function f of known parameters that describes how important features of genetic differentiation (e.g. gene diversity, proportion of private alleles, frequency of the most common allele) are close to their expected panmictic and isolation value. We find that the behaviour of function f differs according to three distinct mutation regimes defined by the scaled mutation rate and the number of populations. Then, we compare GST and D to f, and demonstrate that their signal of differentiation strongly depends on the mutation regime. In particular, we show that D captures well the variations of genetic diversity when mutation is weak, otherwise it overestimates it when panmixia is not met. GST detects population differentiation when mutation is intermediate but has a low sensitivity to the variations of genetic diversity when mutation is weak. When mutation is strong the domain of sensitivity of both measures are altered. Finally, we also point out the importance of the number of populations on genetic differentiation measures, and provide recommendations for the use of GST and D.
Resumo:
A cryo-electron microscopy study of supercoiled DNA molecules freely suspended in cryo-vitrified buffer was combined with Monte Carlo simulations and gel electrophoretic analysis to investigate the role of intersegmental electrostatic repulsion in determining the shape of supercoiled DNA molecules. It is demonstrated here that a decrease of DNA-DNA repulsion by increasing concentrations of counterions causes a higher fraction of the linking number deficit to be partitioned into writhe. When counterions reach concentrations likely to be present under in vivo conditions, naturally supercoiled plasmids adopt a tightly interwound conformation. In these tightly supercoiled DNA molecules the opposing segments of interwound superhelix seem to directly contact each other. This form of supercoiling, where two DNA helices interact laterally, may represent an important functional state of DNA. In the particular case of supercoiled minicircles (178 bp) the delta Lk = -2 topoisomers undergo a sharp structural transition from almost planar circles in low salt buffers to strongly writhed "figure-eight" conformations in buffers containing neutralizing concentrations of counterions. Possible implications of this observed structural transition in DNA are discussed.
Resumo:
We propose a new theory of the demographic transition based on the evidence that body development during childhood is an important predictor of adult life expectancy. This theory is embodied in an OLG framework where fertility, longevity and education all result from individual decisions. The model displays different regimes, allowing the economy to move slowly from an initial Malthusian regime towards the Modern era. The dynamics reproduces the key features of the demographic transition, including the permanent increase in life expectancy, resulting from improvements in body development, the hump in both population growth and fertility, and a late increase in secondary educational attainments.
Resumo:
The specific interactions of the pairs laminin binding protein (LBP)-purified tick-borne encephalitis viral surface protein E and certain recombinant fragments of this protein, as well as West Nile viral surface protein E and certain recombinant fragments of that protein, are studied by combined methods of single-molecule dynamic force spectroscopy (SMDFS), enzyme immunoassay and optical surface waves-based biosensor measurements. The experiments were performed at neutral pH (7.4) and acid pH (5.3) conditions. The data obtained confirm the role of LBP as a cell receptor for two typical viral species of the Flavivirus genus. A comparison of these data with similar data obtained for another cell receptor of this family, namely human αVβ3 integrin, reveals that both these receptors are very important. Studying the specific interaction between the cell receptors in question and specially prepared monoclonal antibodies against them, we could show that both interaction sites involved in the process of virus-cell interaction remain intact at pH 5.3. At the same time, for these acid conditions characteristic for an endosome during flavivirus-cell membrane fusion, SMDFS data reveal the existence of a force-induced (effective already for forces as small as 30-70 pN) sharp globule-coil transition for LBP and LBP-fragments of protein E complexes. We argue that this conformational transformation, being an analog of abrupt first-order phase transition and having similarity with the famous Rayleigh hydrodynamic instability, might be indispensable for the flavivirus-cell membrane fusion process. Copyright © 2014 John Wiley & Sons, Ltd.
Resumo:
BACKGROUND/OBJECTIVES: There is little objective information regarding nutrition transition in African countries. We assessed trends in nutrition patterns in the Seychelles between 1989 and 2011. SUBJECTS/METHODS: Population-based samples were obtained in 1989, 1994 and 2011 and participants aged 25-44 are considered in this study (n=493, 599 and 471, respectively). Similar, although not identical, food frequency questionnaires (FFQs) were used in each survey and the variables were collapsed into homogenous categories for the purpose of this study. RESULTS: Between 1989 and 2011, consumption frequency of fish (5+/week) decreased from 93 to 74%, whereas the following increased: meat (5+/week) 25 to 51%, fruits (1+/week) 48 to 94%, salty snacks (1+/week) 22 to 64% and sweet snacks (1+/week) 38 to 67% (P<0.001 for all). Consumption frequency decreased for home-brewed alcoholic drinks (1+/week) 16 to 1%, but increased for wine (1+/week) 5 to 33% (both P<0.001). Between 2004 and 2011, consumption frequency decreased for rice (2/day) 62 to 57% and tea (1+/day) 72 to 68%, increased for poultry (1+/week) 86 to 96% (all P<0.01), and did not change for vegetables (70.3 to 69.8%, P=0.65). CONCLUSIONS: Seychelles is experiencing nutrition transition characterized by a decreased consumption frequency of traditional staple foods (fish, polished rice), beverages (tea) and of inexpensive home brews, and increased consumption frequency of meat, poultry and snacks. Food patterns also became more varied along with a broader availability of products in the 22-year interval. The health impact of these changes should be further studied.
Resumo:
Prostate cancer is the most common carcinoma in the male population. In its initial stage, the disease is androgen-dependent and responds therapeutically to androgen deprivation treatment but it usually progresses after a few years to an androgen-independent phase that is refractory to hormonal manipulations. The proteasome is a multi-unit protease system that regulates the abundance and function of a significant number of cell proteins, and its inhibition results in cancer cell growth inhibition and apoptosis and is already exploited in the clinic with the use of proteasome inhibitor bortezomib in multiple myeloma. In order to be recognized by the proteasome, a target protein needs to be linked to a chain of the small protein ubiquitin. In this paper, we review the role of ubiquitin-proteasome system (UPS) in androgen receptor-dependent transcription as well as in the castration resistant stage of the disease, and we discuss therapeutic opportunities that UPS inhibition offers in prostate cancer.
Resumo:
The equilibrium dynamics of native and introduced blowflies is modelled using a density-dependent model of population growth that takes into account important features of the life-history in these flies. A theoretical analysis indicates that the product of maximum fecundity and survival is the primary determinant of the dynamics. Cochliomyia macellaria, a blowfly native to the Americas and the introduced Chrysomya megacephala and Chrysomya putoria, differ in their dynamics in that the first species shows a damping oscillatory behavior leading to a one-point equilibrium, whereas in the last two species population numbers show a two-point limit cycle. Simulations showed that variation in fecundity has a marked effect on the dynamics and indicates the possibility of transitions from one-point equilibrium to bounded oscillations and aperiodic behavior. Variation in survival has much less influence on the dynamics.