Experiments on downstream movement of recently emerged trout and salmon parr in Grassholme channels, 1983-1985

A number of authors have described the manner in which young salmonids, soon after emergence from the gravel, set up and defend territories. This leads to mortality or downstream displacement of the individuals which are unable to acquire territories and is widely accepted as the main method of population regulation amongst young salmonids. In some field experiments the fish were constrained in screened reaches and the option of downstream dispersal for the surplus fry was thus excluded. In order to explore some aspects of downstream dispersal more closely under conditions which gave more control than is obtained in a natural stream, four experimental channels were set up at Grassholme reservoir in Teesdale. The report describes the results of investigations on the timing and rate of downstream movement of young brown trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.) out of experimental channels, with special reference to the effect of water velocity on the rate of ���emigration���.

Thermodynamic and kinetic behavior of an argon plasma jet. Decomposition of nitric oxide between 1300 - 1750 degrees K in an argon plasma

<p>In the first part of the study, an RF coupled, atmospheric pressure, laminar plasma jet of argon was investigated for thermodynamic equilibrium and some rate processes. </p> <p>Improved values of transition probabilities for 17 lines of argon I were developed from known values for 7 lines. The effect of inhomogeneity of the source was pointed out.</p> <p>The temperatures, T, and the electron densities, n_e , were determined spectroscopically from the population densities of the higher excited states assuming the Saha-Boltzmann relationship to be valid for these states. The axial velocities, v_z, were measured by tracing the paths of particles of boron nitride using a three-dimentional mapping technique. The above quantities varied in the following ranges: 10¹² �� n_e �� 10¹⁵ particles/cm³, 3500 �� T �� 11000 ��K, and 200 �� v_z �� 1200 cm/sec.</p> <p>The absence of excitation equilibrium for the lower excitation population including the ground state under certain conditions of T and n_e was established and the departure from equilibrium was examined quantitatively. The ground state was shown to be highly underpopulated for the decaying plasma.</p> <p>Rates of recombination between electrons and ions were obtained by solving the steady-state equation of continuity for electrons. The observed rates were consistent with a dissociative-molecular ion mechanism with a steady-state assumption for the molecular ions. </p> <p>In the second part of the study, decomposition of NO was studied in the plasma at lower temperatures. The mole fractions of NO denoted by x_NO were determined gas-chromatographically and varied between 0.0012 �� x_NO �� 0.0055. The temperatures were measured pyrometrically and varied between 1300 �� T �� 1750��K. The observed rates of decomposition were orders of magnitude greater than those obtained by the previous workers under purely thermal reaction conditions. The overall activation energy was about 9 kcal/g mol which was considerably lower than the value under thermal conditions. The effect of excess nitrogen was to reduce the rate of decomposition of NO and to increase the order of the reaction with respect to NO from 1.33 to 1.85. The observed rates were consistent with a chain mechanism in which atomic nitrogen and oxygen act as chain carriers. The increased rates of decomposition and the reduced activation energy in the presence of the plasma could be explained on the basis of the observed large amount of atomic nitrogen which was probably formed as the result of reactions between excited atoms and ions of argon and the molecular nitrogen.</p>

An investigation of the reaction negative K��p ��� K������� at P_(lab) = 2 Gev/c

<p>The reaction K^-p���K^-��⁺n has been studied for incident kaon momenta of 2.0 GeV/c. A sample of 19,881 events was obtained by a measurement of film taken as part of the K-63 experiment in the Berkeley 72 inch bubble chamber. </p> <p>Based upon our analysis, we have reached four conclusions. (1) The magnitude of the extrapolated K�� cross section differs by a factor of 2 from the P-wave unitarity prediction and the K⁺n results; this is probably due to absorptive effects. (2) Fits to the moments yield precise values for the K�� S-wave which agree with other recent statistically accurate experiments. (3) An anomalous peak is present in our backward K^-p���(��+n) K^- u-distribution. (4) We find a non-linear enhancement due to interference similiar to the one found by Bland et al. (Bland 1966).</p>

The ionic basis of frequency selectivity in hair cells of the bullfrog's sacculus

<p>Hair cells from the bull frog's sacculus, a vestibular organ responding to substrate-borne vibration, possess electrically resonant membrane properties which maximize the sensitivity of each cell to a particular frequency of mechanical input. The electrical resonance of these cells and its underlying ionic basis were studied by applying gigohm-seal recording techniques to solitary hair cells enzymatically dissociated from the sacculus. The contribution of electrical resonance to frequency selectivity was assessed from microelectrode recordings from hair cells in an excised preparation of the sacculus.</p> <p>Electrical resonance in the hair cell is demonstrated by damped membrane-potential oscillations in response to extrinsic current pulses applied through the recording pipette. This response is analyzed as that of a damped harmonic oscillator. Oscillation frequency rises with membrane depolarization, from 80-160 Hz at resting potential to asymptotic values of 200-250 Hz. The sharpness of electrical tuning, denoted by the electrical quality factor, Q_e, is a bell-shaped function of membrane voltage, reaching a maximum value around eight at a membrane potential slightly positive to the resting potential.</p> <p>In whole cells, three time-variant ionic currents are activated at voltages more positive than -60 to -50 mV; these are identified as a voltage-dependent, non-inactivating Ca current (I_ca), a voltage-dependent, transient K current (I_a), and a Ca-dependent K current (I_c). The C channel is identified in excised, inside-out membrane patches on the basis of its large conductance (130-200 pS), its selective permeability to Kover Na or Cl, and its activation by internal Ca ions and membrane depolarization. Analysis of open- and closed-lifetime distributions suggests that the C channel can assume at least two open and three closed kinetic states.</p> <p>Exposing hair cells to external solutions that inhibit the Ca or C conductances degrades the electrical resonance properties measured under current-clamp conditions, while blocking the A conductance has no significant effect, providing evidence that only the Ca and C conductances participate in the resonance mechanism. To test the sufficiency of these two conductances to account for electrical resonance, a mathematical model is developed that describes I_ca, I_c, and intracellular Ca concentration during voltage-clamp steps. I_ca activation is approximated by a third-order Hodgkin-Huxley kinetic scheme. Ca entering the cell is assumed to be confined to a small submembrane compartment which contains an excess of Ca buffer; Ca leaves this space with first-order kinetics. The Ca- and voltage-dependent activation of C channels is described by a five-state kinetic scheme suggested by the results of single-channel observations. Parameter values in the model are adjusted to fit the waveforms of I_ca and I_c evoked by a series of voltage-clamp steps in a single cell. Having been thus constrained, the model correctly predicts the character of voltage oscillations produced by current-clamp steps, including the dependencies of oscillation frequency and Q_e on membrane voltage. The model shows quantitatively how the Ca and C conductances interact, via changes in intracellular Ca concentration, to produce electrical resonance in a vertebrate hair cell.</p>

CP and the three pion decay of the K��

<p>The time distribution of the decays of an initially pure K�� beam into ��+��-���� has been analyzed to determine the complex parameter W (also known as ��^+-�� and (x + iy)). The K�� beam was produced in a brass target by the interactions of a 2.85 GeV/c ��- beam which was generated on an internal target in the Lawrence Radiation Laboratory (LRL) Bevatron. The counters and hodoscopes in the apparatus selected for events with a neutral (K��) produced in the brass target, two charged secondaries passing through a magnet spectrometer and a ��-ray shower in a shower hodoscope. </p> <p>From the 275K apparatus triggers, 148 K ��� ��+��-���� events were isolated. The presence of a ��-ray shower in the optical shower chambers and a two-prong vee in the optical spark chambers were devices used to isolate the events. The backgrounds were further reduced by reconstructing the momenta of the two charged secondaries and applying kinematic constraints.</p> <p>The best fit to the final sample of 148 events distributed between .3 and 7.0 K_S lifetimes gives: </p> <p>ReW = -.05 ��.17</p> <p>ImW = +.39 +.35/-.37</p> <p>This result is consistent with both CPT invariance (ReW = 0) and CP invariance (W = 0). Backgrounds are estimated to be less than 10% and systematic effects have also been estimated to be negligible.</p> <p>An analysis of the present data on CP violation in this decay mode and other K�� decay modes has estimated the phase of �� to be 45.3 �� 2.3 degrees. This result is consistent with the super weak theories of CP violation which predicts the phase of �� to be 43��. This estimate is in turn used to predict the phase of ������ to be 48.0 �� 7.9 degrees. This is a substantial improvement on presently available measurements. The largest error in this analysis comes from the present limits on W from the world average of recent experiments. The K ��� ��u�� mode produces the next largest error. Therefore further experimentation in these modes would be useful.</p>

Reprodu����o de peixes de riachos: uma abordagem comparativa entre as estrat��gias r e K

No presente trabalho, objetivou-se caracterizar a estrat��gia reprodutiva, enfatizando o investimento energ��tico, de duas esp��cies de peixe do rio Ubatiba, Maric��, Rio de Janeiro: Parotocinclus maculicauda (K-estrategista) e Astyanax hastatus (r-estrategista). Foram realizadas coletas bimestrais de Junho de 2010 a Abril de 2011 totalizando 236 exemplares amostrados de A. hastatus e 234 de P. maculicauda. Para cada exemplar foram registrados os dados de comprimento padr��o (Cp, cm), peso total (Pt, g), peso gonadal (Pg, g), sexo e est��dio de matura����o. Atrav��s da estrutura de tamanho, observamos que as f��meas atingem maior comprimento, em rela����o aos machos, para as duas esp��cies. A rela����o peso/ comprimento evidenciou para ambas as esp��cies, crescimento alom��trico negativo (inferior a 3), demonstrando crescimento mais longel��neo. Para a propor����o sexual, o teste &#967;2 foi aplicado e indicou que, para as duas esp��cies, h�� significativamente mais f��meas. A distribui����o sexual no ano mostrou que as f��meas se mant��m em maioria durante todo o ano para P. maculicauda. Para A. hastatus este padr��o tamb��m se mant��m, por��m com exce����o do bimestre Novembro/Dezembro, quando o n��mero de machos torna-se um pouco maior. O tamanho de primeira matura����o mostrou-se o mesmo para ambas as esp��cies (2,5 a 3,0 cm). A varia����o temporal da freq����ncia de indiv��duos reprodutivos e n��o reprodutivos juntamente com a distribui����o temporal dos valores individuais de IGS mostrou que P. maculicauda se reproduz com maior intensidade nas esta����es chuvosas (Setembro a Abril), reduzindo sua atividade reprodutiva de maneira significativa nas esta����es secas (Maio a Agosto). J�� A. hastatus demonstrou regular atividade reprodutiva durante todo o ano com pequeno pico no bimestre Novembro/ Dezembro. Desova do tipo total foi registrada para Astyanax, enquanto que para Parotocinclus registrou-se desova parcelada em tr��s lotes. Em ambas as esp��cies foi observada rela����o inversa entre volume e a quantidade de ov��citos produzidos, com A. hastatus produzindo muitos ov��citos (fecundidade: 463 + 213 ov��citos/grama de peixe) de reduzido volume (di��metro = 800 &#956;m e volume = 0,26 mm3) e P. maculicauda produzindo n��mero bem inferior (fecundidade: 47 + 13 ov��citos/grama de peixe), por��m com volume superior (di��metro = 1.600 &#956;m e volume = 2,14 mm3). Com isso o valor energ��tico relativo tamb��m se mostrou superior, com A. hastaus produzindo ov��citos vitelog��nicos com 0,4+ 0,08 cal/unidade e P. maculicauda produzindo os mesmos ov��citos com 1,8+ 1,1 cal/unidade. Para a produ����o energ��tica total investida na produ����o de gametas, foi considerado o tipo de desova de cada esp��cie, com Astyanax investindo 50,5 + 24 calorias/grama/grama de peixe e Parotocinclus investindo 88,4 + 72,46 cal/grama/grama de peixe, por��m sem diferen��as significativas (Mann-Whitney; U =235,0, p=0,08), indicando, portanto que independente da estrat��gia adotada (r ou K), o gasto energ��tico na produ����o de ov��citos �� a mesma.

Avalia����o da concentra����o de Cl, K e Ca na urina, hemolinfa e t��bulos de Malpighi de Rhodnius prolixus usando a t��cnica de fluoresc��ncia de raios X por reflex��o total por radia����o s��ncrotron (SR-TXRF)

Neste trabalho utilizou-se a t��cnica fluoresc��ncia de raios X usando radia����o s��ncrotron (SR-TXRF) para estudar, quantitativamente, o transporte de cloro, pot��ssio e c��lcio na hemolinfa, urina e t��bulos de Malpighi (TM) em ninfas de quinto est��gio do Rhodnius prolixus (R. prolixus), considerando a excre����o destes elementos em diferentes dias ap��s o repasto sangu��neo. R. prolixus �� um dos principais vetores do Trypanosoma cruzi, agente causador da doen��a de Chagas. R. prolixus fornece um sistema modelo particularmente ��til porque seus TMs tanto secretam quanto reabsorvem ��ons a taxas elevadas. Os TMs filtram a hemolinfa e secretam um l��quido que �� muitas vezes comparado com a urina prim��ria em vertebrados. Os resultados obtidos mostram que a concentra����o de pot��ssio na urina �� substancialmente maior do que na hemolinfa. A concentra����o de cloro na hemolinfa �� menor do que na urina, mas a diferen��a n��o �� t��o marcada como no caso do pot��ssio. No caso do Rhodnius �� razo��vel interpretar a elevada concentra����o de pot��ssio na urina como adaptativo para o problema de excre����o imediato do inseto. A concentra����o de c��lcio nos TMs �� substancialmente maior em compara����o com os valores encontrados na hemolinfa e urina. Este resultado mostra que o c��lcio �� retido no corpo do R. prolixus e pouco eliminado. Os resultados obtidos est��o coerentes com a literatura. Avaliou-se tamb��m o efeito no transporte de Cl, K e Ca ap��s um repasto de sangue de coelho contaminado com HgCl2 de modo a avaliar o efeito da presen��a deste metal t��xico no balan��o i��nico nos fluidos de excre����o urina e hemolinfa e tamb��m pelo principal ��rg��o de transporte, os t��bulos de Malpighi. As excre����es de Cl e K pela urina s��o afetadas pela ingest��o. Este resultado �� esperado levando-se em considera����o a ingest��o de excesso de Cl atrav��s do HgCl2. O transporte de Cl, K e Ca na hemolinfa do Rhodnius prolixus n��o �� afetada pela ingest��o de HgCl2. Nos t��bulos de Malpighi, as altas concentra����es de Ca obtidas foram compar��veis ��quelas encontradas nos insetos controle. Pode-se concluir que SR-TXRF �� um m��todo muito promissor para an��lises diretas, r��pidas e confi��veis para a quantifica����o simult��nea de elementos envolvidos na regula����o do transporte e em todo o sistema excretor de insetos. Al��m disso, o estudo do transporte e a excre����o de elementos no inseto Rhodnius prolixus abrem oportunidade para a maior compreens��o de efeitos da polui����o em esp��cies de invertebrados.

Morphologie et hydrodynamique �� l'embouchure du fleuve Bandama

This study deals with the present morphology of the Bandama river mouth in Grand-Lahou (C��te d'Ivoire). At the interface water-sediment channels and shallows appear, covered respectively by fine and medium sands. Topographic surveys conducted from 1989 to 1993 show significant migration of the river mouth from east to west. The average migration rate is about 1.1 meter per mouth. Although for the past two years , a rate of about 3.5 meters per month was observed.