Nonturbulent Environments Research Articles

Development of business-to-business relationships in turbulent environments

This research examines business relationship structure, formation, development, and maintenance where the socio-political and economic environment for both exchange partners is highly turbulent. Based on multiple case-study data from 33 firms located in the Middle East, we find that turbulent environments create perceptions of uncertainty, dependence, vulnerability, urgency, and crises, leading to the formation of interimistic relationships different from those found within non-turbulent environments. These relationships are characterised by a constant search for new partners and the maintenance of a diverse portfolio of relationships. Relationships typically develop rapidly comprising three phases where a unique dynamic and structure is apparent. Dominant relationship characteristics include competence-based trust alongside control, high levels of instantaneous commitment, informal and rapid adaptation, frequent informal communication, and significant and ongoing efforts at strengthening social bonds with existing and potential partners.

Petrogenesis of the Eppawala carbonatites, Sri Lanka: A cathodoluminescence and electron microprobe study

Field and petrographic investigations, cathodoluminescence (CL) studies as well as microprobe analyses of major rock-forming minerals were conducted to establish the crystallization processes in the Eppawala carbonatites, Sri Lanka. The well preserved magmatic textures and crystal morphologies combined with the chemistry of apatite, calcite and dolomite indicate two major stages of crystal growth, which were accompanied by dynamic crystallization conditions. Initially, nucleation of apatite, ilmenite and possibly olivine was associated with rapid crystal growth during slow cooling of the carbonatite melt at depth. The heat loss through the roof and crystallization processes induced the development of turbulent convective currents, which in turn prevented further nucleation and growth of crystals and led to the dispersion of these earlier formed crystals within the magma chamber. Then, rapid upward movement of magma along structural weaknesses led to (i) the transport of mineral clusters, (ii) deformation of ilmenite, (iii) fracturing of apatite and (iv) the emplacement of the carbonatite melt as dykes. Here, the conditions were favourable for the simultaneous crystallization of magnetite, calcite and dolomite in a non-turbulent environment. Subsequent subsolidus alteration caused the hydrothermal overprint of the documented mineral assemblages, particularly along grain boundaries. The study demonstrates that detailed textural examinations of carbonatites combined with mineral chemical analyses and CL investigations can reveal the crystallization processes within carbonatite melts.

EXPLORING TEMPORAL PATTERNS IN FIRMS' SCALE AND SCOPE ACTIVITIES AND THEIR PERFORMANCE IMPLICATIONS.

The article looks at business firms to determine whether those competing in turbulent or non-turbulent environments show chaotic or random patterns in their scale and scope activities. Results imply that a level of determinism may lead to better performances for turbulent environment businesses. Determinism is a property of chaotic behavior, but not of random behavior. Research of industrial organization has found that firms that are skilled in adapting to competitive environments will generate above-average profits.

The social conditions of cumulation

Unlike philosophy, a sociological theory of cumulation cannot legislate the logical or metaphysical criteria which make cumulation in science universally possible. Instead, sociology must explain under which structural conditions cumulation events are more likely to occur than different varieties of change. Organizationally, cumulation events are rational myths, which tend to surface on ritual and ceremonial frontstages directed at concerned and skeptical outsiders. Historically, cumulation presupposes the retrospective closure and coherent periodization of episodes. Structurally, cumulation tends to occur when the intellectual and design spaces of a network or specialty are highly focussed on narrow and isolated dimensions of performance. Technically, much as in natural evolution, cumulative advances are more likely when experimental controls allow for restrictive tinkering on machines and machine-like devices. Cumulation is local, not global; it occurs in the short, not the long, run, and prefers non-turbulent environments.

Phytoplankton dynamics in the stratified water column of Lake Bonney, Antarctica

Phytoplankton populations in perennially ice-covered Lake Bonney, Antarctica grow in a unique non-turbulent environment. The absence of turbulence generated by winds or major streams, combined with strong vertical gradients in temperature and nutrients, create vertically stratified environmental conditions that support three discrete phytoplankton populations in the east lobe of this lake. Phytoplankton biomass and photosynthesis were measured in the east lobe of Lake Bonney during the winter-spring transicion (September) to mid-summer (January). During this period, irradiance beneath the ice increased from 0.03 to 1.9 mol quanta m−2 d−1. Chlorophylla concentrations ranged from 0.03 to 3.8 μl−1 within the trophogenic zone (just beneath the permanent ice cover to 20 m) and photosynthesis ranged from below detection to 3.2 μg Cl−1 d−1. Our results indicate: (1) phytoplankton photosynthesis began in late winter (before 9 September, our earliest sampling date); (2) maxima for phytoplankton biomass and production developed sequentially in time from the top to the bottom of the trophogenic zone, following the seasoral increase in irradiance; and (3) the highest photosynthetic efficiencies occurred in early spring, then decreased over the remainder of the phytoplankton growth season. The spring decrease in photosynthetic rates for shallower phytoplankton appeared to be related to nutrient availability, while photosynthesis in the deeper populations was solely lightdependent.

Sphere wakes at moderate Reynolds numbers in a turbulent environment

The structure of sphere wakes in a turbulent environment was measured over the following test range: sphere Reynolds numbers from 135 to 1560, ambient turbulence intensities of roughly 4%, ratios of streamwise spatial integral scales to sphere diameters of 11-59, and ratios of Kolmogorov length scales to sphere diameters of 0.080.80. At these conditions, some phenomena observed for sphere wakes at comparable Reynolds numbers in nonturbulent environments were suppressed, like the fast-decaying and self-preserving turbulent wake regions; instead, while the wakes were turbulent, their mean streamwise velocities scaled like self-preserving laminar wakes but with enhanced viscosities due to turbulence. Effective turbulent viscosities were relatively independent of position and ratios of integral length scales and Kolmogorov microscales to sphere diameters; however, they progressively increased with sphere Reynolds numbers. Low and high Reynolds number regimes were observed, separated by a transition regime involving sphere Reynolds numbers in the range from 300 to 600, which was associated with conditions where effects of vortex shedding were prominent in the temporal power spectra measured in the near-wake region.

Adsorption and Desorption Kinetics of Pyrene onto a Great Lakes Sediment

The rate of adsorption and desorption of hydrophobic pollutants with lake sediments, or other particulate matter, may influence the ultimate fate of these chemicals. This study examined the kinetics of pyrene adsorption onto, and desorption from, a Great Lake sediment. The data were evaluated by two separate mathematical models. The batch pore surface diffusion model (BPSDM) predicted initial kinetics much better than a radial diffusion model (RDM). This is because the BPSDM incorporates film diffusion which the RDM neglects. In nonturbulent environments, or systems of low particle concentration, film diffusion has been shown to be the rate limiting step for the initial adsorption rate. Hysteresis was experimentally observed for pyrene desorption; therefore, both models overpredicted the rate of pyrene desorption. These results indicate that 1) hydrophobic chemicals may be less available for biological degradation and 2) particle concentration may influence the initial rates of adsorption and desorption.

African American and White Managers:

Research points to differences in the experiences and response of African Americans and whites to organizational situations. This paper presents the results of a study which investigated differences in the management styles in eight local social service agency offices managed by African Americans and eight managed by whites. When the environment was turbulent, white managers responded by becoming more supportive of staff, while African American managers increased problem-solving communications. Staff in African American offices in turbulent environments had higher levels of job satisfation than either white offices of African Americans in nonturbulent environments.

Grazing in a turbulent environment: energy dissipation, encounter rates, and efficacy of feeding currents in Centropages hamatus.

The creation of feeding currents by calanoid copepods increases encounter rates of copepods with their food and provides and advantage in dilute nutritional environments. Small-scale turbulence has also been hypothesized to increase the encounter rate between planktonic predators and their food. Centropages hamatus was exposed to turbulent and nonturbulent environments at two prey concentrations to quantify the influence of turbulence on feeding current efficacy. Turbulent energy dissipation rates used in the experiment were in the range of 0.05-0.15 cm2. sec-3. In the nonturbulent environments, feeding currents increased the encounter rates of C. hamatus 3-5 times that of control encounter areas. In turbulent environments, encounter rates were not increased by feeding currents, yet C. hamatus continued to create feeding currents. Energetic calculations indicate a tradeoff in the value of turbulence to a copepod feeding on phytoplankton. While turbulence is probably beneficial at low food concentrations, it may be deleterious at high food concentrations.

Grazing in a turbulent environment: behavioral response of a calanoid copepod, Centropages hamatus.

Models of marine ecosystem productivity rely on estimates of small-scale interactions, particularly those between copepods and their algal food sources. Rothschild and Osborn [Rothschild, B. J. & Osborn, T. R. (1988) J. Plankton Res. 10, 465-474], hypothesized that small-scale turbulence in aquatic systems increases the perceived abundance of prey to predators. We tested this hypothesis by exposing the planktonic copepod Centropages hamatus to turbulent and nonturbulent environments at different prey concentrations. Our results fell into two main categories. First, the response to turbulence was characterized by an initial period having a high number of escape reactions. This period was followed by one of increased foraging. C. hamatus responded to the higher encounter rates due to turbulence as if it were experiencing altered prey concentrations. Second, the termination of turbulence resulted in an increased foraging response, which was not directly related to the encounter rate. Functional response curves do not adequately explain this foraging response because the time course of the foraging response depends on prior encounter experience and foraging motivation.

An apparatus for monitoring and controlling turbidity in biological experiments

Turbidity is an important ecological factor which affects feeding and growth in marine organisms. Because of the rapidity with which suspended solids settle out of the water column in nonturbulent environments, maintenance of controlled levels of tubidity in laboratory investigations has been problematic. Ideally, turbidity levels should be measured and adjusted frequently enough to ensure no significant changes over time. A computer controlled, recirculating aquarium system is described which constantly monitors the turbidity in several treatment levels and responds appropriately to maintain treatments at the desired level. This system allows long-term turbidity experiments to be performed while continuously recording all turbidity measurements collected for each treatment during the course of the experiment.

Feasibility Test of an Airborne Pulse-Doppler Meteorological Radar

Abstract A vertically scanning, airborne, pulse-Doppler radar is described. Data processing methods to yield pseudo-dual-Doppler horizontal winds are presented. Results of an intercomparison with a ground-based dual-Doppler network are presented and discussed. These results indicate that the accuracy of the Doppler estimates are not seriously degraded by the aircraft's motion in a nonturbulent environment. Reasonable wind velocities were obtained in a stratiform precipitation (pre-warm-frontal) regime despite relatively long time periods for data gathering (∼20 min). Potential error sources are discussed, with the principal conclusion being that the uncertainty in the airborne Doppler mean velocity estimates are slightly larger than would be expected for a ground-based Doppler. However, the time period over which data are gathered is much longer than for a ground-based dual-Doppler network. Potential modifications to the antenna and data system to improve data quality are also discussed.

Turbulent buoyant convection from a source in a confined region

This paper considers the effect of continuous convection from small sources of buoyancy on the properties of the environment when the region of interest is bounded. The main assumptions are that the entrainment into the turbulent buoyant region is at a rate proportional to the local mean upward velocity, and that the buoyant elements spread out at the top of the region and become part of the non-turbulent environment at that level. Asymptotic solutions, valid at large times, are obtained for the cases of plumes from point and line sources and also periodically released thermals. These all have the properties that the environment is stably stratified, with the density profile fixed in shape, changing at a uniform rate in time at all levels, and everywhere descending (with ascending buoyant elements).The analysis is carried out in detail for the point source in an environment of constant cross-section. Laboratory experiments have been conducted for this case, and these verify the major predictions of the theory. It is then shown how the method can be extended to include more realistic starting conditions for the convection, and a general shape of bounded environment. Finally, the model is applied quantitatively to a variety of problems in engineering, the atmosphere and the ocean, and the limitations on its use are discussed.