963 resultados para Projective synchronization


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Universidade Estadual de Campinas. Faculdade de Educação Física

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Universidade Estadual de Campinas . Faculdade de Educação Física

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Avaliaram-se os efeitos de dietas com níveis crescentes de milho em grão moído (0, 22, 37 e 49% na MS) em substituição ao feno de coast-cross mantendo-se diferentes relações proteína:carboidratos não-fibrosos (PB:CNF = 1,01; 0,39; 0,33 e 0,27) sobre o metabolismo ruminal de búfalos. Utilizaram-se quatro búfalos fistulados no rúmen, mantidos em delineamento quadrado latino 4 × 4, para a coleta de amostras do líquido ruminal, colhidas em cada período experimental (de 28 dias) nos tempos 0, 2, 4 e 8 horas após a alimentação. Em geral, os bubalinos apresentaram boa capacidade tamponante no rúmen, com pH médio alto (6,70) e aumento da ingestão de milho em grão moído. O acréscimo nos níveis de milho na dieta promoveu aumento da produção de ácido butírico. Somente a dieta com 49% de milho promoveu melhor fermentação ruminal, com menor propoção de ácidos acético:propiônico. A relação PB:CNF de 1,01 indica deficiência de energia da dieta disponível para microrganismos no rúmen ao longo do dia, enquanto dietas com PB:CNF entre 0,39 e 0,27 promovem fermentações ruminais semelhantes, o que indica sincronismo na utilização de nitrogênio e energia pelos microrganismos no rúmen nessas condições.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The objective of the present study was to evaluate the effects of light and temperature on germination of Cereus pernambucensis seeds, a species of columnar cactus native to Brazil and naturally incident in the restinga. Cereus pernambucensis seeds were incubated under different temperatures, from 5 to 45 °C, with 5 °C intervals, and under alternating temperatures of 15-20 °C, 15-30 °C, 20-25 °C, 20-30 °C, 20-35 °C, 25-30 °C, 25-35 °C, and 30-35 °C, both under continuous white light and dark. The seeds were also incubated in a gradient of phytochrome photoequilibrium at 25 °C. The highest percentage germination in this species was between 25 and 30 °C. The minimum temperature was between 15 and 20 °C and the maximum between 35 and 40 °C. Alternating temperatures did not affect the percentage of seed germination, but it did alter the rate and synchronization indexes. Seeds incubated in the dark did not germinate under any of the conditions tested, indicating that this species when cultivated present light sensitive seeds controlled by phytochrome. The seeds can tolerate a lot of shade conditions, germinating under very low fluence response of phytochrome.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Corpus luteum is a temporary endocrine gland that regulates either the estrous cycle and pregnancy. It presents extreme dependency on the adequate blood supply. This work aims to evaluate goat corpus luteum (CL) vascular density (VD) over the estrous cycle. For that purpose, 20 females were submitted to estrus synchronization/ovulation treatment using a medroxyprogesterone intra-vaginal sponge as well as intramuscular (IM) application of cloprostenol and equine chorionic gonadotrophine (eCG). After sponge removal, estrus was identified at about 72hs. Once treatment was over, female goats were then subdivided into 4 groups (n=5 each) and slaughtered on days 2, 12, 16 and 22 after ovulation (p.o). Ovaries were collected, withdrawn and weighted. CL and ovaries had size and area recorded. Blood samples were collected and the plasma progesterone (P4) was measured through RIA commercial kits. The VD was 24.42±6.66, 36.26±5.61, 8.59±2.2 and 3.97±1.12 vessels/mm² for days 2, 12, 16 and 22 p.o, respectively. Progesterone plasma concentrations were 0.49±0.08, 2.63±0.66, 0.61±0.14 and 0.22±0.04ng/ml for days 2, 12, 16 e 22 p.o, respectively. Studied parameters were affected by the estrous cycle phase. Values greater than 12 p.o were observed. In the present work we observed that ovulation occurred predominantly in the right ovary (70% of the animals), which in turn presented bigger measures than the contra lateral one. There is a meaningful relationship between the weight and size of the ovary and these of CL (r=0.87, r=0.70, respectively, p<0.05). It is possible to conclude that morphology of goat's ovaries and plasma progesterone concentration changed according to estrous cycle stages. We propose these parameters can be used as indicators of CL functional activity.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

O presente estudo visou avaliar os efeitos da associação da medroxiprogesterona (análogo sintético da progesterona) ao protocolo Ovsynch sobre o crescimento folicular, a ovulação e a taxa de concepção de búfalas criadas na Amazônia Oriental (Tracuateua-PA). Vinte e sete fêmeas adultas (G1 n=14 e G2 n=13), cíclicas, sem bezerro ao pé e com ECC 3,5 foram submetidas a Ovsynch. Os animais do G2 receberam 60 mg de medroxiprogesterona entre D0 e D7 (D0=início do tratamento). A ultra-sonografia ovariana foi realizada nos D 0, 7, 9 e 10. O contingente de folículos pequenos diferiu no D7 (G1: 4,57±0,60 versus G2: 6,54±0,67; P=0,05). Tempo e tratamento influenciaram o diâmetro folicular no D7. O crescimento do folículo dominante entre D7 e D9 foi maior nos animais tratados (G1: 2,05±0,49 mm/dia versus 3,48±0,41 mm/dia; P<0,05). Mais animais do G1 ovularam precocemente (35,71% versus 30,77%), porém isso não afetou as taxas de concepção (G1: 50,00% e G2: 30,77%; P>0,05). Os achados sugerem que a medroxiprogesterona (1) aumenta recrutamento folicular e retarda o crescimento dos folículos com diâmetro maior que 5,0 mm entre D0 e D7; (2) sua retirada incrementa em 1,7 vezes o crescimento folicular do D7 ao D9; (3) pode contribuir para a ovulação de folículos maiores e, em tese, para maior formação de tecido luteínico; (4) não promove ovulação precoce após o Ovsynch; (5) não eleva as taxas de concepção após sincronização de fêmeas cíclicas e com bom escore corporal, devendo ser avaliada para uso em fêmeas acíclicas ou com ECC mais baixo.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An extension of the uniform invariance principle for ordinary differential equations with finite delay is developed. The uniform invariance principle allows the derivative of the auxiliary scalar function V to be positive in some bounded sets of the state space while the classical invariance principle assumes that. V <= 0. As a consequence, the uniform invariance principle can deal with a larger class of problems. The main difficulty to prove an invariance principle for functional differential equations is the fact that flows are defined on an infinite dimensional space and, in such spaces, bounded solutions may not be precompact. This difficulty is overcome by imposing the vector field taking bounded sets into bounded sets.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Background: Expectation is a very potent pain modulator in both humans and animals. There is evidence that pain transmission neurons are modulated by expectation preceding painful stimuli. Nonetheless, few studies have examined the influence of pain expectation on the pain-related neuronal activity and the functional connectivity within the central nociceptive network. Results: This study used a tone-laser conditioning paradigm to establish the pain expectation in rats, and simultaneously recorded the anterior cingulate cortex (ACC), the medial dorsal thalamus (MD), and the primary somatosensory cortex (SI) to investigate the effect of pain expectation on laser-induced neuronal responses. Cross-correlation and partial directed coherence analysis were used to determine the functional interactions within and between the recorded areas during nociceptive transmission. The results showed that under anticipation condition, the neuronal activity to the auditory cue was significantly increased in the ACC area, whereas those to actual noxious stimuli were enhanced in all the recorded areas. Furthermore, neuronal correlations within and between these areas were significantly increased under conditions of expectation compared to those under non-expectation conditions, indicating an enhanced synchronization of neural activity within the pain network. In addition, information flow from the medial (ACC and MD) to the lateral (SI cortex) pain pathway increased, suggesting that the emotion-related neural circuits may modulate the neuronal activity in the somatosensory pathway during nociceptive transmission. Conclusion: These results demonstrate that the nociceptive processing in both medial and lateral pain systems is modulated by the expectation of pain.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Oscillator networks have been developed in order to perform specific tasks related to image processing. Here we analytically investigate the existence of synchronism in a pair of phase oscillators that are short-range dynamically coupled. Then, we use these analytical results to design a network able of detecting border of black-and-white figures. Each unit composing this network is a pair of such phase oscillators and is assigned to a pixel in the image. The couplings among the units forming the network are also dynamical. Border detection emerges from the network activity.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Synchronization plays an important role in telecommunication systems, integrated circuits, and automation systems. Formerly, the masterslave synchronization strategy was used in the great majority of cases due to its reliability and simplicity. Recently, with the wireless networks development, and with the increase of the operation frequency of integrated circuits, the decentralized clock distribution strategies are gaining importance. Consequently, fully connected clock distribution systems with nodes composed of phase-locked loops (PLLs) appear as a convenient engineering solution. In this work, the stability of the synchronous state of these networks is studied in two relevant situations: when the node filters are first-order lag-lead low-pass or when the node filters are second-order low-pass. For first-order filters, the synchronous state of the network shows to be stable for any number of nodes. For second-order filter, there is a superior limit for the number of nodes, depending on the PLL parameters. Copyright (C) 2009 Atila Madureira Bueno et al.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The study checked possible theory-methodologic assumptions into Physical Education PCNs by the teachers of the last years of elementary school. The analyses in the publishing allow us to identify the different didactic procedures when compared with those which set up the traditional expectations. From these elements and using the projective method, it was developed an interview with focal group. The data obtained showed us docent perceptions which rearrange the educative practice, and interpretation allows us to realize which of the teachers views approaches the propositions in the official document, even if no reference has been done to it.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The relationship between the level of cell confluence near the plateau phase of growth and blastocyst yield following somatic cell cloning is not well understood. We examined the effect of distinct cell culture confluence levels on in vitro development of cloned bovine embryos. In vitro-matured bovine oocytes were manually bisected and selected by DNA staining. One or two enucleated hemi-cytoplasts were paired and fused with an adult skin somatic cell. Cultured skin cells from an adult Nellore cow harvested at three distinct culture confluence levels (70-80, 80-90, and > 95%) were used for construction of embryos and hemi-embryos. After activation, structures were cultured in vitro as one embryo (1 x 100%) or as aggregates of two hemi-embryos (2 x 50%) per microwell. Fusion, cleavage and blastocyst rates were compared using the chi(2) test. The fusion rate for hemi-embryos (51.4%) was lower than for embryos (67.6%), with no influence of degree of cell confluence. However, blastocyst rates improved linearly (7.0, 17.5, and 29.4%) with increases in cell confluence. We conclude that degree of cell culture confluence significantly influences subsequent embryo development; use of a cell population in high confluence (> 90%) for nuclear transfer significantly improved blastocyst yield after cloning.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Cell cycle synchronization by serum starvation (SS) induces apoptosis in somatic cells. This side effect of SS is hypothesized to negatively affect the outcome of somatic cell nuclear transfer (SCNT). We determined whether apoptotic fibroblasts affect SCNT yields. Serum-starved, adult, bovine fibroblasts were stained with annexin V-FITC/propidium iodide to allow apoptosis detection by flow cytometry. Positive and negative cells sorted by fluorescence activated cell sorting (FACS) and an unsorted control group were used as nuclear donors for SCNT. Reconstructed embryos were cultured in vitro and transferred to synchronized recipients. Apoptosis had no effect on fusion and cleavage rates; however, it resulted in reductions in blastocyst production and quality measured by apoptotic index. However, reconstructed embryos with apoptotic cells resulted in pregnancy rates similar to that of the control on day 30, and generated one live female calf. In conclusion, we showed that apoptotic cells present in serum-starved cultures negatively affect embryo production after SCNT without compromising full-term development. Further studies will evaluate the ability of the oocyte to reprogram cells in specific phases of apoptosis.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Several experimental studies have altered the phase relationship between photic and non-photic environmental, 24 h cycles (zeitgebers) in order to assess their role in the synchronization of circadian rhythms. To assist in the interpretation of the complex activity patterns that emerge from these ""conflicting zeitgeber'' protocols, we present computer simulations of coupled circadian oscillators forced by two independent zeitgebers. This circadian system configuration was first employed by Pittendrigh and Bruce (1959), to model their studies of the light and temperature entrainment of the eclosion oscillator in Drosophila. Whereas most of the recent experiments have restricted conflicting zeitgeber experiments to two experimental conditions, by comparing circadian oscillator phases under two distinct phase relationships between zeitgebers (usually 0 and 12 h), Pittendrigh and Bruce compared eclosion phase under 12 distinct phase relationships, spanning the 24 h interval. Our simulations using non-linear differential equations replicated complex non-linear phenomena, such as ""phase jumps'' and sudden switches in zeitgeber preferences, which had previously been difficult to interpret. Our simulations reveal that these phenomena generally arise when inter-oscillator coupling is high in relation to the zeitgeber strength. Manipulations in the structural symmetry of the model indicated that these results can be expected to apply to a wide range of system configurations. Finally, our studies recommend the use of the complete protocol employed by Pittendrigh and Bruce, because different system configurations can generate similar results when a ""conflicting zeitgeber experiment'' incorporates only two phase relationships between zeitgebers.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

It is well known that resonance can be induced by external noise or diversity. Here we show that resonance can be induced even by a phase disorder in coupled excitable neurons with subthreshold activity. In contrast to the case of identical phase, we find that phase disorder plays an active role in enhancing neuronal activity. We also uncover that the presence of phase disorder can induce a double resonance phenomenon: phase disorder and coupling strength both can enhance neuronal firing activity. A physical theory is formulated to help understand the mechanism behind this double resonance phenomenon.