Dual drive actuators

A new class of electromechanical actuators is described. These dual drive actuators were developed for the NASA-JPL Galileo Spacecraft. The dual drive actuators are fully redundant and therefore have high inherent reliability. They can be used for a variety of tasks, and they can be fabricated quickly and economically

Brushless DC motor control system responsive to control signals generated by a computer or the like

A control system for a brushless DC motor responsive to digital control signals is disclosed. The motor includes a multiphase wound stator and a permanent magnet rotor. The motor is arranged so that each phase winding, when energized from a DC source, will drive the rotor through a predetermined angular position or step. A commutation signal generator responsive to the shaft position provides a commutation signal for each winding. A programmable control signal generator such as a computer or microprocessor produces individual digital control signals for each phase winding. The control signals and commutation signals associated with each winding are applied to an AND gate for that phase winding. Each gate controls a switch connected in series with the associated phase winding and the DC source so that each phase winding is energized only when the commutation signal and the control signal associated with that phase winding are present. The motor shaft may be advanced one step at a time to a desired position by applying a predetermined number of control signals in the proper sequence to the AND gates and the torque generated by the motor be regulated by applying a separate control signal and each AND gate which is pulse width modulated to control the total time that each switch connects its associated winding to the DC source during each commutation period

The measurement of respiratory electron-transport activity in marine phytoplankton

A tetrazolium-reduction method for the measurement of the respiratory electron-transport activity in plankton is described . The method is sensitive to 0.03 µg cell nitrogen and can be used to estimate total plankton respiration

Respiration and respiratory electron transport activity in plankton from the Northwest African upwelling area

Microplankton and zooplankton respiration were calculated from ETS activity measurements in the upwelled waters off Cape Blanc, Mauritania. The mean respiration was 14.4 mgC h-1m-2 for microplankton and 6.4 mgC h-1m-2 for zooplankton. Mixing kept the microplankton from accumulating in the surface waters so that vertical profiles were nearly uniform with depth. High levels of ETS activity below the euphotic zone reflected this mixing...

The Galeleo spacecraft magnetometer boom

The Galileo spacecraft utilizes a deployable lattice boom to position three science instruments at remote distances from the spacecraft body. An improved structure and mechanism to precisely control deployment of the boom, and the unique deployment of an outer protective cover are described

Respiration and vertical carbon flux in the Gulf of Maine water column

The transport of carbon from ocean surface waters to the deep sea is a critical factor in calculations of planetary carbon cycling and climate change. This vertical carbon flux can be calculated by integrating the vertical profile of the seawater respiration rate but is rarely done because measuring seawater respiration is so difficult. However, seawater respiratory oxygen consumption is the product of the combined activity of all the respiratory electron transfer systems in a seawater community of bacterioplankton, phytoplankton, and zooplankton. This respiratory electron transfer system (ETS) is the membrane bound enzymatic system that controls oxygen consumption and ATP production in all eukaryots and in almost all bacteria and archaea. As such, it represents potential respiratory oxygen consumption. Exploiting this, we measured plankton-community ETS activity in water column profiles in the Gulf of Maine to give the potential-respiration of the water column. To interpret these potentials in terms of actual seawater respiration we made use of previous measurements of respiratory oxygen consumption and ETS activity in the Gulf of Maine to calculate a ratio of respiratory potential to actual respiration. Armed with this ratio we calculated seawater respiration depth profiles from the ETS activity measurements. These profiles were characterized by: (1) high oxygen consumption rates in the euphotic zone; (2) subsurface maxima near the subsurface chlorophyll maxima (SCM); (3) rapid declines associated with thermoclines; (4) low declining rates below 50 m; (5) and elevated values occasionally near the bottom. Sea surface values ranged from 229 to 489 pmol O2 min-1 L-1. Euphotic zone maximum values ranged from 457 to 682 pmol O2 min-1 L-1 while the minimum values below 70 m ranged from 10 to 27 pmol O2 min-1 L-1. A depth-normalized power function described the respiratory profiles between their maxima and minima. Integrating these respiratory oxygen consumption profiles from the respiratory maximum to the near bottom minimum, we calculated carbon flux profiles. The vertical carbon fluxes through the 30 m, 50 m, and 100 m levels were 3.09 ± 1.55, 1.76 ± 0.96, and 0.93 ± 0.68 μmol C min-1 m-2, respectively

Denitrification rates in the eastern tropical South Pacific

Measurements of microbial metabolism suggest that the denitrification rate in the oxygen deficient waters of the eastern tropical South Pacific was approximately 2.5 × 1013g N yr-1 during September 1976-May 1977. This rate may be considerably higher than the rate that existed before ~ 1972...

Brushless DC motor control system responsive to control signals generated by a computer or the like

A control system for a brushless DC motor responsive to digital control signals is disclosed. The motor includes a multiphase wound stator and a permanent magnet rotor. The rotor is arranged so that each phase winding, when energized from a DC source, will drive the rotor through a predetermined angular position or step. A commutation signal generator responsive to the shaft position provides a commutation signal for each winding. A programmable control signal generator such as a computer or microprocessor produces individual digital control signals for each phase winding. The control signals and commutation signals associated with each winding are applied to an AND gate for that phase winding. Each gate controls a switch connected in series with the associated phase winding and the DC source so that each phase winding is energized only when the commutation signal and the control signal associated with that phase winding are present. The motor shaft may be advanced one step at a time to a desired position by applying a predetermined number of control signals in the proper sequence to the AND gates and the torque generated by the motor may be regulated by applying a separate control signal to each AND gate which is pulse width modulated to control the total time that each switch connects its associated winding to the DC source during each commutation period

Electrochemical standardization of the dehydrogenase assay used in the estimation of respiration rates

A primary coulometric titration is proposed as a standardization technique for the succinate dehydrogenase assay used in the estimation of respiration rates in marine plankton. The coulometric method, which is shown to be simple, accurate, and reproducible, eliminates the difficulties of using a chemical reducing agent. An alternative method using polarography is also discussed

Nitrate reductase activity in the subsurface waters of the Peru Current

In March 1976 and 1977, nitrate reductase, nitrate, nitrite, and oxygen were measured between depths of 30 and 250m in the subsurface waters overlying the Peruvian continental shelf and shelf edge at 15S latitude. Oxygen concentrations of less than 1 ml/1 began between 20 and 30m in both years. The oxygen deficient waters extended to the bottom on the shelf and to 440m at the shelf edge...