7,470 research outputs found

    Shadowable Points for flows

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    A shadowable point for a flow is a point where the shadowing lemma holds for pseudo-orbits passing through it. We prove that this concept satisfies the following properties: the set of shadowable points is invariant and a GÎŽG_{\delta} set. A flow has the pseudo-orbit tracing property if and only if every point is shadowable. The chain recurrent and nonwandering sets coincide when every chain recurrent point is shadowable. The chain recurrent points which are shadowable are exactly those that can be are approximated by periodic points when the flow is expansive. We study the relations between shadowable points of a homeomorphism and the shadowable points of its suspension flow. We characterize the set of forward shadowable points for transitive flows and chain transitive flows. We prove that the geometric Lorenz attractor does not have shadowable points. We show that in the presence of shadowable points chain transitive flows are transitive and that transitivity is a necessary condition for chain recurrent flows with shadowable points whenever the phase space is connected. Finally, as an application these results we give concise proofs of some well known theorems establishing that flows with POTP admitting some kind of recurrence are minimal. These results extends those presented in [10].Comment: 18 page

    The Dynamics of Women’s Labour Supply in Developing Countries

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    This paper investigates cyclicality in women’s labour supply motivated by the hypothesis that it contributes to smoothing household consumption in environments characterised by income volatility. We use comparable individual data on about 1.1 million women in 63 developing and transition countries merged with country-level panel data on GDP during 1986-2006. The scope of these data is unprecedented in the small but growing literature on labour markets in developing countries. We find that the within-country relationship of women’s employment and income is, on average, negative in Asia and Latin America but positive in Africa. We suggest that amongst reasons why African women behave differently are that the conventional family structure with income pooling is less the norm, there are fewer opportunities for paid employment, and aggregate income shocks are more closely tied to rainfall variation. The findings are robust to controls for country-specific trends and potentially correlated shocks. In Asia and Latin America, characteristics that strengthen counter-cyclical responses include low education, being married, being married to men with low education, low wealth, no landownings, rural residence and fertility. These findings suggest that insurance motives underpin the dynamics of women’s work participation. Examination of cyclicality in the distribution of employment across types suggests that recessions in every region are associated with a rise in self-employment amongst women. In Asia and Latin America, there is a parallel rise in paid employment and a sharp drop in non-employment. In Africa, there is a decline in paid employment which overwhelms the rise in self-employment and this is how total employment comes to decline. The results have potentially important implications for understanding labour markets, fertility timing and child outcomes.insurance, women’s labour supply, added worker effect, business cycles, dynamics, Africa, Asia, Latin America.

    Raising your sights: the impact of friendship networks on educational aspirations

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    We use a unique longitudinal dataset on an adolescent friendship network to evaluate variations on educational aspirations of young people from disadvantaged and middle income backgrounds. We evaluate whether such people who have friends from wealthier backgrounds have higher aspirations than otherwise similar young people without such links. The results suggest that there are such effects. Individuals from low income families with friends from high income families are 15.2% more likely to expect to stay in full time education after they finish compulsory school. We find similar effects for the educational aspirations and expectations of middle income children. These effects are quantitatively and statistically significant, and robust to the inclusion of a wide range of control variables. We also show that friend’s mother’s aspirations matter too. Having friends whose mothers hope they will go to university increases the wish to carry on full time education by 30% points. This is conditional on the young person’s own mother’s aspirations for her/him.Networks, Friendships, Aspirations, Adolescents, Income, Education.

    Active inference and oculomotor pursuit: the dynamic causal modelling of eye movements.

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    This paper introduces a new paradigm that allows one to quantify the Bayesian beliefs evidenced by subjects during oculomotor pursuit. Subjects' eye tracking responses to a partially occluded sinusoidal target were recorded non-invasively and averaged. These response averages were then analysed using dynamic causal modelling (DCM). In DCM, observed responses are modelled using biologically plausible generative or forward models - usually biophysical models of neuronal activity

    Fluorescence in situ hybridisation detection of Lactobacillus plantarum group on olives to be used in natural fermentations

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    At present there are very few studies on the bacterial diversity of olives and on the importance of the microbial species for the fermentation of olives aimed to table olives production. Most of the authors report on the occurrence of Lactobacillus plantarum as principal member of these communities or at least as the species responsible for the fermentation. In this study, fluorescence in situ hybridisation (FISH) with 16S rRNA probes was used to evaluate the occurrence of L. plantarum in olives. A 18-bp oligonucleotide probe was used in FISH experiments to evaluate the specificity of detection among Lactobacillus species. The probe was tested against 30 Lactobacillus species and appeared to be specific for L. plantarum, L. paraplantarum and L. pentosus. The probe was then used to investigate the occurrence of these species in 25 samples of olives (cultivar “Leccino”) collected in Campania region (Southern Italy). The olives were washed in a saline solution and the suspensions were then analysed by FISH and observed by fluorescence microscopy. No hybridisation signal was detected in at least 30 fields of observation when the L. plantarum-specific probe was used, probably due to the low sensitivity of the FISH method. Olive samples were plated on Rogosa agar and about 40% of the samples did not give growth after 5 days. When colony growth was observed, bulk cells from Rogosa agar plates were collected and analysed by DNA extraction followed by 16S rDNA Polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE). The different microbial species were identified by direct sequencing of DGGE bands. Leuconostoc pseudomesenteroides was the most frequently found species, occurring in more than 50% of the samples that had shown growth on Rogosa agar. The closest relatives of the species of the genera: Leuconostoc, Pediococcus, Pseudomonas and Raoultella were also identified suggesting that guided fermentation by using selected LAB starters is advisable for a safe and desired table olives production

    The Dynamics of Women's Labour Supply in Developing Countries

    Get PDF
    This paper investigates cyclicality in women's labour supply motivated by the hypothesis that it contributes to smoothing household consumption in environments characterized by income volatility. We use comparable individual data on about 1.1 million women in 63 developing and transition countries merged with country-level panel data on GDP during 1986-2006. The scope of these data is unprecedented in the small but growing literature on labour markets in developing countries. We find that the within-country relationship of women's employment and income is, on average, negative in Asia and Latin America but positive in Africa. We suggest that amongst reasons why African women behave differently are that the conventional family structure with income pooling is less the norm, there are fewer opportunities for paid employment, and aggregate income shocks are more closely tied to rainfall variation. The findings are robust to controls for country-specific trends and potentially correlated shocks. In Asia and Latin America, characteristics that strengthen counter-cyclical responses include low education, being married, being married to men with low education, low wealth, no landownings, rural residence and fertility. These findings suggest that insurance motives underpin the dynamics of women's work participation. Examination of cyclicality in the distribution of employment across types suggests that recessions in every region are associated with a rise in self-employment amongst women. In Asia and Latin America, there is a parallel rise in paid employment and a sharp drop in non-employment. In Africa, there is a decline in paid employment which overwhelms the rise in self-employment and this is how total employment comes to decline. The results have potentially important implications for understanding labour markets, fertility timing and child outcomes.insurance, women's labour supply, added worker effect, business cycles, dynamics, Africa, Asia, Latin America
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