Confluent operator algebras and the closability property

Certain operator algebras A on a Hilbert space have the property that every densely defined linear transformation commuting with A is closable. Such algebras are said to have the closability property. They are important in the study of the transitive algebra problem. More precisely, if A is a two-transitive algebra with the closability property, then A is dense in the algebra of all bounded operators, in the weak operator topology. In this paper we focus on algebras generated by a completely nonunitary contraction, and produce several new classes of algebras with the closability property. We show that this property follows from a certain strict cyclicity property, and we give very detailed information on the class of completely nonunitary contractions satisfying this property, as well as a stronger property which we call confluence.Comment: Preliminary versio

Effect of humidity on transonic flow

An experimental investigation of the effects of humidity-induced condensation on shock/boundary-layer interaction has been conducted in a transonic wind-tunnel test. The test geometry considered was a wall-mounted bump model inserted in the test section of the wind tunnel. The formation of a λ-shape condensation shock wave was shown from schlieren visualization and resulted in a forward movement of the shock wave, reduced shock wave strength, and reduced separation. Empirical correlations of the shock wave strength and humidity/dew point temperature were established. For humidity levels below 0.15 or a dew point temperature of 268 K, the effect of humidity was negligible. The unsteady pressure measurements showed that if a condensation shock wave formed and interacted with a main shock wave, the flow becomes unsteady with periodic flow oscillations occurring at 720 Hz

Using The Resource-Based View To Explore The Jamaican Health Tourism Sector As A Service: A Preliminary Examination

Tourism plays a key role in the economy of the Caribbean Island of Jamaica, generating substantial revenues and contributing to employment.  Jamaica endeavors to grow its economy and achieve developed nation status within the next two decades and is looking to tourism to help the country reach this goal.  Specifically, Jamaica seeks to diversify its tourism offering by making a significant foray into what has been projected to be a highly lucrative health tourism market.  While the potential for Jamaica to capitalize on the opportunities presented by this sector is substantial, much remains undiscovered about Jamaica’s current position as well as what might be required to advance the nation in this area.  The purpose of this paper is to provide a preliminary examination of Jamaica’s health tourism sector within a resource-based view framework, highlighting the manner in which customers might serve as valuable resources and to examine a key element of the service delivery process. 

Radioecology of benthic fishes off Oregon, U.S.A.

Gamma-emitting radionuclides were found in benthic fishes from depths of 50-280O m off the Oregon coast from 1964-1971. 65Zn, 60Co, 54Mn, 144Ce, 137Cs and 40K were present. Zinc-65, originating mainly from the nuclear reactors on the Columbia River, was the predominant artifically-induced radionuclide. Levels of 6Zn per g and specific activities of 65Zn decreased markedly in several species of fishes between 1965 and 1971 because of the shutdown of reactors. This decrease was greater for small than large Lyopsetta exilis during 19 70-1971. Specific activities decreased with increasing depth, both for individual species inhabiting broad depth ranges and for different species inhabiting different depths. Specific activities of 65Zn were inversely related to body size for L. exilis and Sebastolobus. Other variations of 65Zn were related to trophic position. Fishes that preyed on low trophic level pelagic animals had higher specific activities than fishes that preyed on benthic invertebrates. Such pelagic feeders may play an important role in accelerating the transport of some radionuclides or elements to the sea floor.Keywords: Marine radioecology, benthic fishe

Ecological and radioecological studies in the Columbia River Estuary and adjacent Pacific Ocean

This report represents the progress in "Ecological and Radioecological Studies in the Columbia River Estuary and Adjacent Pacific Ocean" for the period 1 April 1975 through 31 March 1976. This research has been supported with funds from the Division of Biomedical and Environmental Research, U.S. Energy Research and Development Administration through Contract AT(45-1)-2227, Task Agreement 12. Our current research activities are dealt with in a descriptive fashion in the section on Research in Progress. The Research Completed section of the report includes manuscripts which have been submitted for publication during the reporting period, as well as reprints of papers published during this same period

Dilation theory and systems of simultaneous equations in the predual of an operator algebra. II

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46272/1/209_2005_Article_BF01163170.pd

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

This paper will investigate the validation of the NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as a baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet experiment conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a free-stream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the fanface diameter. The numerical simulations with and without tunnel walls are performed, quantifying tunnel wall effects on the BLI inlet flow. A comparison is made between the numerical simulations and the BLI inlet experiment for the baseline and VG vane cases at various inlet mass flow rates. A comparison is also made to a BLI inlet jet configuration for varying actuator mass flow rates at a fixed inlet mass flow rate. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCP avg, very well within the designed operating range of the BLI inlet. A comparison of the average total pressure recovery showed that the simulations were able to predict the trends but had a negative 0.01 offset when compared to the experimental levels. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion levels for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe rake indicated that the circumferential distortion levels are very sensitive to the symmetry of the flow and that a misalignment of the vanes in the experiment could have resulted in this difference. The numerical simulations of the BLI inlet with jets showed good agreement with the circumferential inlet distortion levels for a range of jet actuator mass flow ratios at a fixed inlet mass flow rate. The CFD simulations for the jet case also predicted an average total pressure recovery offset that was 0.01 lower than the experiment as was seen in the baseline. Comparisons of the flow features for the jet cases revealed that the CFD predicted a much larger vortex at the engine fan-face when compare to the experiment

Submersible observations of deep-reef fishes of Heceta Bank, Oregon

Rockfishes, Sebastes spp.. were the most numerous and speciose fishes seen during 16 submersible dives from 64 to 305 m depth in the vicinity of Heceta Bank off the coast of Oregon. Dense schools of juvenile rockfishes and large yellowtail rockfish, S. flavidus, were observed only over rocky, high relief areas near the top of the bank, and highest densities of small benthic rockfishes (up to 5-10/m2) on the flanks of the bank. These observations suggest that shallow, rocky portions of Heceta Bank are a nursery area for juvenile rockfishes. Two species groups of nonschooling fishes were identified based on transects over the diverse seafloor habitats around the bank: one comprised primarily of rockfishes in shallow water on rock and cobble, and the other comprised of flatfishes, agonids, sablefish, and some rockfishes in deep water over mud and cobble. Species composition of fishes observed from submersible dives differed from species composition of fishes taken from trawl catches in the same general areas.This publication is associated with the document Fish Assemblages of Rocky Banks of the Pacific Northwest: Final Report by M.A. Hixon, B.N. Tissot, and W.G. Pearcy, and its accompanying data reports

Three-dimensional plant architecture and sunlit-shaded patterns: a stochastic model of light dynamics in canopies

Background and Aims Diurnal changes in solar position and intensity combined with the structural complexity of plant architecture result in highly variable and dynamic light patterns within the plant canopy. This affects productivity through the complex ways that photosynthesis responds to changes in light intensity. Current methods to characterise light dynamics, such as ray-tracing, are able to produce data with excellent spatio-temporal resolution but are computationally intensive and the resultant data are complex and high dimensional. This necessitates development of more economical models for summarising the data and for simulating realistic light patterns over the course of a day. Methods High-resolution reconstructions of field-grown plants are assembled in various configurations to form canopies, and a forward ray-tracing algorithm is applied to the canopies to compute light dynamics at high (1 minute) temporal resolution. From the ray-tracer output, the sunlit or shaded state for each patch on the plants is determined, and these data are used to develop a novel stochastic model for the sunlit-shaded patterns. The model is designed to be straightforward to fit to data using maximum likelihood estimation, and fast to simulate from. Key Results For a wide range of contrasting 3D canopies, the stochastic model is able to summarise, and replicate in simulations, key features of the light dynamics. When light patterns simulated from the stochastic model are used as input to a model of photoinhibition, the predicted reduction in carbon gain is similar to that from calculations based on the (extremely costly) ray-tracer data. Conclusions The model provides a way to summarise highly complex data in a small number of parameters, and a cost-effective way to simulate realistic light patterns. Simulations from the model will be particularly useful for feeding into larger-scale photosynthesis models for calculating how light dynamics affects the photosynthetic productivity of canopies