Primary production of phytoplankton in the three types of Amazonian waters. V. Some investigations on the phytoplankton and its primary productivity in the clear water of the lower Rio Tapajós (Pará, Brazil)

Four limnological investigations were conducted in different seasons of the years 1968 and 1969 at the lower reaches of the Rio Tapajóz. The physical and chemical parameters generally correspond with earlier findings of other authors. Midriver areas show no stratification of the water body. In certain reaches of the river, distinct increases of pH-values temporarily occur due to strong phytoplankton activity. A few species of cyanophyceae and diatomeae make up the vast majority of phytoplankton in terms of nu,bers. Chlorophyceae, desmidiaceae, and other algae are characterized by high species variety but only occur in low or moderate densities. Despite of the low nutrient concentrations encountered, phytoplankton production is high, which can be attributed to the excellent light conditions in the river. The net production of 2.4 g C/m²/d exceeds by far production rates from várzea-lakes, although production densities are lower. A mighty productive zone in combination with extremely fast turn over rates male this unexpected high production per unit area possible. The shortest C turn over time of all samples was 0.3 days. Phytoplankton net production amounts to a calculated 5 t C hectare and year. Derived from primary production data, a theoretical fish production of 100 kg/ha/year can be estimated, which would allow yearly catches of at least 10 to 20 kg per hectare for human consumption without provocing ecological disturbances

Numbers of bacteria and algae and their interrelations in some Amazonian waters

In the Rio Solimões (Amazon River), in the Rio Negro and várzea lake (Lago do Castanho) in a three-monthly turn in the course of a year, the total numbers of bacteria and algae and the numbers of saprobiont bacteria (number of bacteria colonies) were determined and the relation between these numbers was studied. In the Rio Negro the numbers of algae and bacteria, and thus as well the relation between them, remained relatively constant and showed no significant fluctuations. The absolute quantities of these organisms were always very small. The latter was also the case in the Rio Solimões, however here, during the investigation period, more distinct alterations of the population densities of bacteria and algae occurred which were closely related to the situations in the lake. At the time of sinking water level the content in bacteria and algae which practically can originate only in the lakes connected to the river, increased considerably in the Solimões water

Closed-loop control of stochastic nonlinear systems

Technique resolves problems in complex control systems, such as those used for space vehicle guidance and control. Main disadvantage of procedure is that it is only appropriate in situations where trajectory concept is valid

Plasmonic Metamaterials: Physical Background and Some Technological Applications

New technological frontiers appear every year, and few are as intriguing as the field of plasmonic metamaterials (PMMs). These uniquely designed materials use coherent electron oscillations to accomplish an astonishing array of tasks, and they present diverse opportunities in many scientific fields. This paper consists of an explanation of the scientific background of PMMs and some technological applications of these fascinating materials. The physics section addresses the foundational concepts necessary to understand the operation of PMMs, while the technology section addresses various applications, like precise biological and chemical sensors, cloaking devices for several frequency ranges, nanoscale photovoltaics, experimental optical computing components, and superlenses that can surpass the diffraction limit of conventional optics

GEOS axial booms

A booms and mechanisms subsystem was designed, developed, and qualified for the geostationary scientific satellite GEOS. Part of this subsystem consist of four axial booms consisting of one pair of 1 m booms and one pair of 2.5 m booms. Each of these booms is carrying one bird cage electric field sensor. Alignment accuracy requirements led to a telescopic type solution. Deployment is performed by pressurized nitrogen. At deployment in orbit two of these booms showed some anomalies and one of these two deployed only about 80%. Following this malfunction a detailed failure investigation was performed resulting in a design modification of some critical components as release mechanism, guide sleeves of the telescopic elements, and pressure system

The effect of solid phase reactions on the ballistic properties of propellants

The combustion of NH4ClO4 composite propellants has been studied between 15 and 3000 psi. The emphasis in the program has been on determining the mechanisms by which the fuel components influence the burning rate of the composites. In order to have flexibility in the choice and concentration of the fuel component all combustion experiments were performed with pressed power strands. The fuels studied included those which affected the combustion mechanism of the composite primarily through their effect on: (1) the oxidizer decomposition mechanism and (2) the composite surface temperature. The combustion of pure and doped NH4ClO4 was studied using both pressed powder strands and pressed end burning motor grains. The experimental approach has been essentially a chemical one with emphasis on perturbing those reactions which occur on or immediately adjacent to the surface (zone of influence) of the composite