979 resultados para Dorsal vessel
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This data set was obtained during the R. V. POLARSTERN cruise ANT-XXVIII/3. Current velocities were measured nearly continuously when outside territorial waters along the ship's track with a vessel-mounted TRD Instruments' 153.6-kHz Ocean Surveyor ADCP. The transducers were located 11 m below the water line and were protected against ice floes by an acoustically transparent plastic window. The current measurements were made using a pulse of 2s and vertical bin length of 4 m. The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Heading, roll and pitch data from the ship's gyro platforms and the navigation data were used to convert the ADCP velocities into earth coordinates. Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. The ADCP data were processed using the Ocean Surveyor Sputum Interpreter (OSSI) software developed by GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel. The averaging interval was set to 120 seconds. The reference layer was set to bins 5 to 16 avoiding near surface effects and biases near bin 1. Sampling interval setting: 2s; Number of bins: 80; Bin length: 4m; Pulse length: 4m; Blank beyond transmit length: 4m. Data processing setting: Top reference bin: 5; Bottom reference bin: 16; Average: 120s; Misalignment amplitude: 1.0276 +/- 0.1611, phase: 0.8100 +/- 0.7190. The precision for single ping and 4m cell size reported by TRDI is 0.30m/s. Resulting from the single ping precision and the number of pings (most of the time 36) during 120seconds the velocity accuracy is nearly 0.05m/s. (Velocity accuracy = single ping precision divided by square root of the number of pings).
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Ethanol-dependent individuals who reduce or discontinue its use may present Alcohol Withdrawal Syndrome, which is characterized by unpleasant signs and symptoms, such as anxiety, that may trigger relapses. Ethanol, a psychotropic drug, is able to promote behavioral and neurophysiological changes, acting on different neurotransmitter systems, including the serotonergic, which has also been directly associated with aversive states, including anxiety. This study aimed to investigate the participation of type 7 serotonin receptor (5-HT7) of the dorsal periaqueductal gray (DPAG) on basal experimental anxiety and that caused by ethanol withdrawal. For this, 75-100 days old Wistar rats were subjected to two experiments. On the first one, animals underwent stereotactic surgery for implantation of guide cannulas used for administration of the drug directly into the DPAG. After seven days, the animals received doses of 2.5; 5 and 10 nmols of type 7 receptor antagonist SB269970 (SB) or vehicle intra-DPAG and, ten minutes after, they were exposed to elevated plus maze (EPM). In the following day, the animals were submitted to the same treatment and tested in the open field (OF). In the second experiment, animals received increasing concentrations (2%, 4%, 6%) of ethanol as the only source of liquid diet or water (control group), both with free access to chow. Seventy two hours and ninety six hours after the ethanol withdrawal, animals received SB (2.5 and 5.0 nmols) intraDPAG ten minutes before the test in the LCE and OF, respectively. In experiment 1, the dose of antagonist 10 nmols was able of reversing the anxiety generated by EPM. In the experiment 2, ineffective SB doses on the LCE (2.5 and 5.0 nmol) were not able to reverse the anxiety caused by the ethanol withdrawal in the EPM, although the dose of 2.5 nmols of SB has reversed its hipolocomotor effect in this test. This result suggests that the 5-HT7 receptor is involved in the modulation of the basal experimental anxiety in rats, but not in the anxiety caused by ethanol withdrawal in the DPAG.
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Ethanol withdrawn individuals present a wealth of signs and symptoms, some of them related with anxiety. To better understand brain areas involved in anxiety caused by ethanol abstinence, preclinical studies have been employing models of ethanol consumption followed by withdrawal in rodents submitted to behavioral tests of anxiety, such as the elevated plus-maze. The aim of this study was to investigate if short- or long-term ethanol withdrawal could alter both anxiety-related behaviors in the elevated plus-maze (EPM) and open field tests and the number of serotonin immunorreactive cels in the dorsal raphe nucleus, a midbrain area associated with anxiety. Female Wistar rats (90 days old) were submitted to increasing concentrations of ethanol (2% for 3 days, 4% for 3 days and 6% for 15 days) as the only source of liquid diet and the control group received water ad libitum. Both groups received food ad libitum. In the behavioral experiments, on 21st day of consumption, ethanol was substituted by water (withdrawal) and 72 h or 21 days after withdrawal animals were submitted to the EPM, where it was evaluated the percentage of time and entries in the open arms and the entries in the enclosed arms during 5 minutes. Twenty and four hours after testing in the EPM, animals were submitted to the open field test for 15 minutes, where the distance traveled by the animals was observed along this period. During the first 5 minutes, the distance traveled, entries and time spent in the center of the test were analyzed. In the immunohistochemistry study, animals were submitted to 21 days of consumption of ethanol followed or not by 72 hours and 21 days of withdrawal previously perfusion, brain tissue preparation and quantification of serotonin dyed cells in the dorsal and caudal portions in the dorsal raphe nucleus. Behavioral data showed that both short- and long-term ethanol withdrawals reduced the open arms exploration in the EPM. In the open field test there were no locomotor activity changes during the total 15 minutes; however, longterm ethanol withdrawal reduced the exploration in the center of the open field during the first 5 minutes. In the immunohistochemistry step, there were no differences, when short- and long-term withdrawn groups were compared with control group; nevertheless, the chronic consumption of ethanol decreased the number of serotonergic immunorreactive cells in the dorsal part of dorsal raphe nucleus. Taken together, results here obtained suggest that both short- and long-term ethanol withdrawals promoted an anxiogenic-like effect that was not related with changes in the serotonin immunorreactivity in the dorsal and caudal parts of the dorsal raphe nucleus.
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To predict the maneuvering performance of a propelled SPAR vessel, a mathematical model was established as a path simulator. A system-based mathematical model was chosen as it offers advantages in cost and time over full Computational Fluid Dynamics (CFD) simulations. The model is intended to provide a means of optimizing the maneuvering performance of this new vessel type. In this study the hydrodynamic forces and control forces are investigated as individual components, combined in a vectorial setting, and transferred to a body-fixed basis. SPAR vessels are known to be very sensitive to large amplitude motions during maneuvers due to the relatively small hydrostatic restoring forces. Previous model tests of SPAR vessels have shown significant roll and pitch amplitudes, especially during course change maneuvers. Thus, a full 6 DOF equation of motion was employed in the current numerical model. The mathematical model employed in this study was a combination of the model introduced by the Maneuvering Modeling Group (MMG) and the Abkowitz (1964) model. The new model represents the forces applied to the ship hull, the propeller forces and the rudder forces independently, as proposed by the MMG, but uses a 6DOF equation of motion introduced by Abkowitz to describe the motion of a maneuvering ship. The mathematical model was used to simulate the trajectory and motions of the propelled SPAR vessel in 10˚/10˚, 20˚/20˚ and 30˚/30˚ standard zig-zag maneuvers, as well as turning circle tests at rudder angles of 20˚ and 30˚. The simulation results were used to determine the maneuverability parameters (e.g. advance, transfer and tactical diameter) of the vessel. The final model provides the means of predicting and assessing the performance of the vessel type and can be easily adapted to specific vessel configurations based on the generic SPAR-type vessel used in this study.
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Acknowledgements This study was part of the Tursiops Project of the Dolphin Research Centre of Caprera, La Maddalena. Financial and logistical support was provided by the Centro Turistico Studentesco (CTS) and by the National Park of the Archipelago de La Maddalena. We thank the Natural Reserve of Bocche di Bonifacio for the support provided during data collection. The authors thank the numerous volunteers of the Caprera Dolphin Research Centre and especially Marco Ferraro, Mirko Ugo, Angela Pira and Maurizio Piras whose assistance during field observation and skills as a boat driver were invaluable.
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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.
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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
Contributions of Dorsal/Ventral Hippocampus and Dorsolateral/Dorsomedial Striatum to Interval Timing
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Humans and animals have remarkable capabilities in keeping time and using time as a guide to orient their learning and decision making. Psychophysical models of timing and time perception have been proposed for decades and have received behavioral, anatomical and pharmacological data support. However, despite numerous studies that aimed at delineating the neural underpinnings of interval timing, a complete picture of the neurobiological network of timing in the seconds-to-minutes range remains elusive. Based on classical interval timing protocols and proposing a Timing, Immersive Memory and Emotional Regulation (TIMER) test battery, the author investigates the contributions of the dorsal and ventral hippocampus as well as the dorsolateral and the dorsomedial striatum to interval timing by comparing timing performances in mice after they received cytotoxic lesions in the corresponding brain regions. On the other hand, a timing-based theoretical framework for the emergence of conscious experience that is closely related to the function of the claustrum is proposed so as to serve both biological guidance and the research and evolution of “strong” artificial intelligence. Finally, a new “Double Saturation Model of Interval Timing” that integrates the direct- and indirect- pathways of striatum is proposed to explain the set of empirical findings.
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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.
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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
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The mixing regime of the upper 180 m of a mesoscale eddy in the vicinity of the Antarctic Polar Front at 47° S and 21° E was investigated during the R.V. Polarstern cruise ANT-XVIII/2 within the scope of the iron fertilization experiment EisenEx. On the basis of hydrographic CTD and ADCP profiles we deduced the vertical diffusivity Kz from two different parameterizations. Since these parameterizations bear the character of empirical functions, based on theoretical and idealized assumptions, they were inter alia compared with Cox-number and Thorpe-scale related diffusivities deduced from microstructure measurements, which supplied the first direct insights into turbulence of this ocean region. Values of Kz in the range of 10**-4 - 10**-3 m**2/s appear as a rather robust estimate of vertical diffusivity within the seasonal pycnocline. Values in the mixed layer above are more variable in time and reach 10**-1 m**2/s during periods of strong winds. The results confirm a close agreement between the microstructure-based eddy diffusivities and eddy diffusivities calculated after the parameterization of Pacanowski and Philander [1981, Journal of Physical Oceanography 11, 1443-1451, doi:10.1175/1520-0485(1981)011<1443:POVMIN>2.0.CO;2].