147 resultados para Low frequency


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The genus Corydoras, the highest among the Siluriformes, Callichthyidae is owned by the family, consisting of 177 valid species and widely distributed in cis-Andean portion of South America How striking feature has two longitudinal series of dermal plates covering almost the entire body. Cytogenetic studies in Callichthyidae show many chromosomal rearrangements, including events of polyploidy in their evolutionary history, particularly the genus Corydoras, in which the variation is the diploid number of 2n = 40 to 2n = 134 chromosomes. The absence of information on the frequency of chromosomes in the group Bs motivated this work with the species Corydoras aeneus. A population from the Tietê River basin in Ribeirão Claro (subbasin Corumbataí - Rio Claro, SP) was sampled a total of 20 subjects (10 males and 10 females) and 30 metaphases per individual were analyzed cytogenetically. Were carried out by impregnation techniques silver (Ag-NOR). The observed modal diploid number was 2n = 60 (26m +26 sm +8 st), with the variable occurrence of 1 or 2 Bs chromosomes in males and a B chromosome in females, both acrocentric. Regarding the variation in the frequency of chromosome Bs, the occurrence of two B chromosomes is directly linked to males, because there were no female sampled with the occurrence of two chromosomes Bs The low frequency of Bs in females suggests that this event can be sporadic this sex, different from males in which this appears to be set supernumerary chromosome showing a higher frequency of 2 Bs than the actual modal number of 2n = 60. Further studies will be performed to understand the dynamics of the B chromosome in the population

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Since the beginning of the railway industry until today, rail wheels are important components to the good working of a railway. For being a critical security item, design and maintenance are done with extremely care to avoid failures. Despite de fact of railway components be projected to support a big number of cyclic solicitation during its life, some accidents still occur. These accidents, despite the low frequency, always have great consequences, drawing in great financial, material, and people losses. Nowadays, railway component failure is relatively low, because it’s been projected to work below the materials Fatigue Resistance Limit, however, with the growing demand of faster trains and higher load for each axle, the occurrence probability is even bigger. This work includes a comparative study of two fabrication processes (casting and forging) applied in the production of rail wheels where it was measured the mechanical properties of traction and fatigue. The study also verified through microstructural analysis, hardness, traction and fatigue tests, statistical analysis of fatigue test results and fractographic analysis that forging process lead to better correlations between fatigue life and mechanical properties, providing more security in railroads, less wagon retention caused by corrective maintenance and smaller operational cost with its use

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Pós-graduação em Engenharia Mecânica - FEIS

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Pós-graduação em Engenharia Mecânica - FEIS

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Adolescence has been proposed as an ontogenic period of vulnerability to stress. Nevertheless, the impact of stressful events during adolescence in cardiovascular activity is poorly understood. Therefore, the purpose of this study was to investigate the immediate and long-lasting effects of exposure to stressful events during adolescence in cardiovascular function of rats. To this end, we compared the impact of 10-days exposure to two chronic stress protocols: the repeated restraint stress (RRS, homotypic) and chronic variable stress (CVS, heterotypic). Independent groups of animals were tested 24 h (immediate) or three weeks (long-lasting) following completion of stress period. Exposure to CVS, but not RRS, during adolescence increased basal HR values without affecting arterial pressure, which was followed by augmented power of oscillatory component at low frequency (sympathetic-related) of the pulse interval (PI). RRS enhanced variance of the PI with an increase in the power of both low and high (parasympathetic-related) frequency components. RRS also increased the baroreflex gain. Neither RRS nor CVS affected systolic arterial pressure variability. The RRS-evoked changes in PI variability were long-lasting and persisted into adulthood while all alterations evoked by the CVS were reversed in adulthood. These findings indicate a stress type-specific influence in immediate and long-term effects of stress during adolescence in cardiovascular function. While immediate changes in cardiovascular function were mainly observed following CVS, long-lasting autonomic consequences in adulthood were observed only in animals exposed to RRS during adolescence.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Genética e Melhoramento Animal - FCAV

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The Advanced LIGO gravitational wave detectors are second-generation instruments designed and built for the two LIGO observatories in Hanford, WA and Livingston, LA, USA. The two instruments are identical in design, and are specialized versions of a Michelson interferometer with 4 km long arms. As in Initial LIGO, Fabry-Perot cavities are used in the arms to increase the interaction time with a gravitational wave, and power recycling is used to increase the effective laser power. Signal recycling has been added in Advanced LIGO to improve the frequency response. In the most sensitive frequency region around 100 Hz, the design strain sensitivity is a factor of 10 better than Initial LIGO. In addition, the low frequency end of the sensitivity band is moved from 40 Hz down to 10 Hz. All interferometer components have been replaced with improved technologies to achieve this sensitivity gain. Much better seismic isolation and test mass suspensions are responsible for the gains at lower frequencies. Higher laser power, larger test masses and improved mirror coatings lead to the improved sensitivity at mid and high frequencies. Data collecting runs with these new instruments are planned to begin in mid-2015.

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The acute effects after exposure to different styles of music on cardiac autonomic modulation assessed through heart rate variability (HRV) analysis have not yet been well elucidated. We aimed to investigate the recovery response of cardiac autonomic modulation in women after exposure to musical auditory stimulation of different styles. The study was conducted on 30 healthy women aged between 18 years and 30 years. We did not include subjects having previous experience with musical instruments and those who had an affinity for music styles. The volunteers remained at rest for 10 min and were exposed to classical baroque (64-84 dB) and heavy metal (75-84 dB) music for 10 min, and their HRV was evaluated for 30 min after music cessation. We analyzed the following HRV indices: Standard deviation of normal-to-normal (SDNN) intervals, root mean square of successive differences (RMSSD), percentage of normal-to-normal 50 (pNN50), low frequency (LF), high frequency (HF), and LF/HF ratio. SDNN, LF in absolute units (ms (2) ) and normalized (nu), and LF/HF ratio increased while HF index (nu) decreased after exposure to classical baroque music. Regarding the heavy metal music style, it was observed that there were increases in SDNN, RMSSD, pNN50, and LF (ms (2) ) after the musical stimulation. In conclusion, the recovery response of cardiac autonomic modulation after exposure to auditory stimulation with music featured an increased global activity of both systems for the two musical styles, with a cardiac sympathetic modulation for classical baroque music and a cardiac vagal tone for the heavy metal style.