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Results for “Environment, Controlled”

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At least 73 records · Page 4Linked to original sources

PubMed1997

Diffuse light and wheat radiation-use efficiency in a controlled environment.

Radiation-use efficiency (dry matter produced per unit absorbed radiation) of a spring wheat (Triticum aestivum L., cv. Veery-10) was 40% higher in controlled growth chamber experiments than under optimal field conditions. Simulations with CERES-Wheat, a field model modified to account for growth chamber conditions, suggest that the observed increase in radiation-use efficiency was due to the large fraction of diffuse light in the experimental chamber. Under optimal conditions in the field, the highest crop growth rates occur when the daily photosynthetic photon flux (PPF) is at its highest levels (50-60 mol m-2 d-1). However, these high growth rates do not appear to be associated with the highest radiation-use efficiency. High PPF levels in the field occur on clear days when the fraction of direct radiation is high and the diffuse fraction is low. In controlled environments with reflective walls, high PPF levels with a large fraction of diffuse radiation can be obtained. Diffuse radiation penetrates to the lower leaves of a canopy better than direct radiation, with the result that the upper leaves are less light saturated and the lower leaves receive more light, increasing radiation-use efficiency, and thus growth rates. The data and model simulations presented here suggest that when diffuse light is a high fraction of the total PPF crop productivity can exceed the highest values attainable in the field under optimal conditions.

Computer Simulation↗

PubMed1987

Stimulating productivity of hydroponic lettuce in controlled environments with triacontanol.

Triacontanol (1-triacontanol) applied as a foliar spray at 10(-7) M to 4-day-old, hydroponically grown leaf lettuce (Lactuca sativa L.) seedlings in a controlled environment increased leaf fresh and dry weight 13% to 20% and root fresh and dry weight 13% to 24% 6 days after application, relative to plants sprayed with water. When applied at 8 as well as 4 days after seeding, triacontanol increased plant fresh and dry weight, leaf area, and mean relative growth rate 12% to 37%. There was no benefit of repeating application of triacontanol in terms of leaf dry weight gain.

Biomass↗

PubMedDate not supplied

High-throughput study of poly(ethylene glycol)/ibuprofen formulations under controlled environment using FTIR imaging.

Simultaneous analysis of many samples under identical conditions improves the effectiveness of research and accelerates product design. A novel spectroscopic imaging approach using a multichannel detector has been developed for parallel analysis of pharmaceutical formulations under controlled environments. Samples of formulations of ibuprofen in poly(ethylene glycol) have been prepared with ibuprofen concentrations ranging from 0 to 100% using a microdroplet deposition approach. The concentration of ibuprofen in PEG at which dimerization of ibuprofen molecules can be avoided has been determined via simultaneous measurement of all samples using in situ FTIR spectroscopic imaging. FTIR spectra from all samples have been analyzed to assess the molecular state of the drug and the degree of polymer swelling as a function of drug concentration. The effect of elevated temperature on the stability of all formulations was also studied. This high-throughput approach identified the concentration range for stable formulations and provided evidence that hydrogen bonding between ibuprofen and the polymer is responsible for enhanced stability at higher temperatures. This high-throughput imaging approach, based on a miniature sampling system, significantly reduces the experimental time by allowing many (potentially a few thousand) experiments to be run in parallel and increases the accuracy by minimizing variations between experiments.

Drug Stability↗

PubMed1985

The Minitron system for growth of small plants under controlled environment conditions.

The design and operation of a system is described in which small plants can be grown under controlled environment conditions. Important features of this "Minitron" system include precise control of temperature and CO2 concentration in a flowing atmosphere. Plants can be grown either hydroponically or in solid root support medium. For either culture method, nutrient solution or water is added from an external reservoir, altering neither atmospheric composition nor temperature equilibrium within a closed Minitron chamber.

Air Conditioning↗

PubMedDate not supplied

Home-environment controls for the mobility-impaired.

One aspect of self-care and independence for many older individuals concerns their ability to control their home environment when their mobility is impaired. Although rehabilitation devices have often been custom designed, the availability of these devices has been limited because of high manufacturing costs and a lack of production and marketing channels. It should therefore be recognized that many devices already available to consumers offer a wide range of environmental control without the problems associated with custom design.

Aged↗

PubMed1980

Controlled environment treatment (CET).

The use of a new method of improving certain physical aspects of the environment imposed on the extremity is discussed. This follows the use of Controlled Environment Treatment in amputation surgery and other specific Centres in the United Kingdom and United States of America. The protocol did not attempt to establish any system of controls, the results being based on observation and clinical impression. In other words it is an extension of CET use in an attempt to obtain a wider experience of its application. One hundrec ases involving 128 treatments are listed over a wide variety of clinical presentations. Recordings were made of the presence or absence of oedema, infection, ischaemia and pain, amongst other relevant data. Certain conclusions proved possible and staff acceptance of the system was obtained. The evidence suggests that the continued use of CET is justified in certain carefully selected clinical conditions. Further, it appears necessary to set up controlled scientific assessments of the system particularly within vascular laboratories where many relevant investigative procedures are carried out on a routine basis.

Adolescent↗

PubMedDate not supplied

Airborne transmission of Salmonella enteritidis infection between groups of chicks in controlled-environment isolation cabinets.

Although direct contact with infected birds and indirect contact with contaminated environmental surfaces are known to be important factors in the dissemination of Salmonella enteritidis in poultry flocks, the potential role of airborne transmission is less clearly defined. This study considered the mechanism by which S. enteritidis might spread between groups of chicks housed in controlled-environment disease transmission cabinets, separated by an unoccupied space that prevented any direct or indirect contact. Airflow in these cabinets was directed across the unoccupied area from one ("upstream") group of chicks to the other ("downstream") group. In each of four replicate trials, two groups of 25 chicks were placed in the upstream ends of transmission cabinets and orally inoculated with S. enteritidis at 1 week of age. One day later, 25 1-day-old chicks were placed in the downstream end of each cabinet. When chicks were removed and sampled at 3 and 7 days postinoculation, S. enteritidis was found on the feathers of 77% of the downstream chicks. Moreover, 33% of the downstream chicks became infected with S. interitidis. The comparative frequencies of recovery of S. enteritidis from various downstream sampling sites suggested that infection was apparently transmitted principally by oral ingestion, perhaps from environmental surfaces contaminated by airborne movement of the pathogen. Reducing the airborne movement of S. enteritidis in poultry houses should thus help limit the spread of infection within flocks and thereby diminish the incidence of production of contaminated eggs.

Air Microbiology↗

PubMed1999

Understanding plant-soil relationships using controlled environment facilities.

Although soil is a component of terrestrial ecosystems, it is comprised of a complex web of interacting organisms, and therefore can be considered itself as an ecosystem. Soil microflora and fauna derive energy from plants and plant residues and serve important functions in maintaining soil physical and chemical properties, thereby affecting net primary productivity (NPP), and in the case of contained environments, the quality of the life support system. We have been using 3 controlled-environment facilities (CEF's) that incorporate different levels of soil biological complexity and environmental control, and differ in their resemblance to natural ecosystems, to study relationships among plant physiology, soil ecology, fluxes of minerals and nutrients, and overall ecosystem function. The simplest system utilizes growth chambers and specialized root chambers with organic-less media to study the physiology of plant-mycorrhizal associations. A second system incorporates natural soil in open-top chambers to study soil bacterial and fungal population response to stress. The most complex CEF incorporates reconstructed soil profiles in a "constructed" ecosystem, enabling close examination of the soil foodweb. Our results show that closed ecosystem research is important for understanding mechanisms of response to ecosystem stresses. In addition, responses observed at one level of biological complexity may not allow prediction of response at a different level of biological complexity. In closed life support systems, incorporating soil foodwebs will require less artificial manipulation to maintain system stability and sustainability.

Biological Transport↗

PubMed1989

Current and potential productivity of wheat for a Controlled Environment Life Support System.

The productivity of higher plants is determined by the incident photosynthetic photon flux (PPF) and the efficiency of the following four physiological processes: absorption of PPF by photosynthetic tissue, carbon fixation (photosynthesis), carbon use (respiration), and carbon partitioning (harvest index). These constituent processes are analyzed to determine theoretical and potentially achievable productivity. The effects of optimal environmental and cultural factors on each of these four factors is also analyzed. Results indicate that an increase in the percentage of absorbed photons is responsible for most of the improvement in wheat yields in an optimal controlled environment. Several trials confirm that there is an almost linear increase in wheat yields with increasing PPF. An integrated PPF of 150 mol m-2 d-1 (2.5 times summer sunlight) has produced 60 g m-2 d-1 of grain. Apparently, yield would continue to increase with even higher PPF's. Energy efficiency increased with PPF to about 600 micromoles m-2 s-1, then slowly decreased. We are now seeking to improve efficiency at intermediate PPF levels (1000 micromoles m-2 s-1) before further exploring potential productivity. At intermediate and equal integrated daily PPF levels, photoperiod had little effect on yield per day or energy efficiency. Decreasing temperature from 23 degrees to 17 degrees increased yield per day by 20% but increased the life cycle from 62 to 89 days. We hope to achieve both high productivity and energy efficiency.

Biomass↗

PubMed1996

Characterizing photosynthesis and transpiration of plant communities in controlled environments.

CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.

Carbon Dioxide↗

PubMed1987

Wheat production in controlled environments.

Our goal is to optimize conditions for maximum yield and quality of wheat to be used in a controlled-environment, life-support system (CELSS) in a Lunar or Martian base or perhaps in a space craft. With yields of 23 to 57 g m-2 d-1 of edible biomass, a minimum size for a CELSS would be between 12 and 30 m2 per person, utilizing about 600 W m-2 of electrical energy for artificial light. Temperature, irradiance, photoperiod, carbon-dioxide levels, humidity, and wind velocity are controlled in state-of-the-art growth chambers. Nutrient solutions (adjusted for wheat) are supplied to the roots via a recirculating system that controls pH by adding HNO3 and controlling the NO3/NH4 ratio in solution. A rock-wool plant support allows direct seeding and densities up to 10,000 plants per meter2. Densities up to 2000 plants m-2 appear to increase seed yield. Biomass production increases almost linearly with increasing irradiance from 400 to 1700 micromoles m-2 s-1 of photosynthetic photon flux (PPF), but the efficiency of light utilization decreases over this range. Photoperiod and temperature both have a profound influence on floral initiation, spikelet formation, stem elongation, and fertilization. High temperatures (25 to 27 degrees C) and long days shorten the life cycle and promote rapid growth, but cooler temperatures (20 degrees C) and shorter days greatly increase seed number per head and thus yield (g m-2). The life cycle is lengthened in these conditions but yield per day (g m-2 d-1) is still increased. We have evaluated about 600 cultivars from around the world and have developed several breeding lines for our controlled conditions. Some of our ultra-dwarf lines (30 to 50 cm tall) look especially promising with high yields and high harvest indices (percent edible biomass).

Biomass↗

PubMed2003

Simulated tennis matchplay in a controlled environment.

The aim of this study was to develop an exercise protocol to simulate tennis matchplay on a 'category 2' surface. Match analyses were used to form the basis for the design of the protocol. The protocol involved playing against a tennis ball serving machine. Part A of the protocol comprised 92 min 46 s of simulated tennis matchplay; Part B consisted of continuous hitting to the point of 'volitional fatigue' or when the required hitting frequency for two consecutive ball feeds could no longer be maintained. Ten elite tennis players (5 males, 5 females) volunteered to participate in the study, which was performed on an indoor tennis court (Matchplay, En-Tout-Cas). Their age, body mass and estimated maximal oxygen uptake were as follows: males, 21.7 +/- 1.0 years, 73.6 +/- 2.6 kg and 58.0 +/- 1.7 ml x kg(-1) x min(-1), respectively; females, 21.9 +/- 1.3 years, 62.3 +/- 2.0 kg and 42.2 +/- 0.7 ml x kg x min(-1), respectively (mean +/- sx). Heart rate, change in body mass and time to volitional fatigue were monitored. The heart rate responses of the participants to the simulated matchplay (range: 140-157 beats x min(-1), 73-81% peak heart rate) were consistent with the results of previous studies, for 'actual' matchplay. This protocol was successful in simulating similar physiological responses in Part A to 'actual' matchplay on a 'category 2' surface, in a controlled environment; it was also a sensitive evaluation tool of skilled performance in Part B. The current protocol may be used as a baseline protocol for studying the influence of, for example, training and dietary intervention on performance.

Adult↗

PubMed2000

The correlation dimension of rat hearts in an experimentally controlled environment.

The electric response of several isolated rat hearts in a controlled environment was studied experimentally. The correlation dimension D(2) was estimated and was found to be between 4 and 6.5 when the response was nearly periodic. The variation of D(2) with the concentration of calcium was studied and a general trend of its increase with increasing concentration was found. Two types of ventricular fibrillation (VF) were observed, one that corresponds to a stochastic signal where D(2) is unbounded and the other to a low dimensional dynamical system with 3.5</=D(2)</=4. It was found also that for the heart the correlation dimension is only an approximate concept. A new method for the estimation of D(2), that is suitable for the case when it is only approximate was introduced. A surrogate data method suitable for the analysis of nearly periodic series was implemented. (c) 2000 American Institute of Physics.

Journal Article↗

PubMedDate not supplied

Culturing primary brain astrocytes under a fully controlled environment in a novel bioreactor.

We report the first approach for growth and maintenance of primary astrocytes on a fully controlled environment. For this purpose, cells were immobilized in Cytodex microcarriers and grown in a stirred tank bioreactor. The distribution of astrocytes at the microcarrier surface was visualized using confocal microscopy and glial fibrillary acidic protein (GFAP) labeling, a specific glial probe. Crucial bioreaction parameters such as agitation rate, microcarrier type, and concentration, as well as cell inoculum concentration were assessed. Cytodex 3 proved the best microcarrier for astrocyte growth, with the highest cell densities obtained for 6 g/l of Cytodex 3 using an inoculum of approx. 0.15 x 10(6) cells/ml in vessels operated at 60 rpm, using a refeed operational mode consisting of complete medium replacement every 5 days. Using such optimized conditions, cells were maintained in steady-state for approximately 24 days, allowing online monitoring and control of environmental variables such as temperature, pH, and O(2). To test further the advantages of this fully controlled system, astrocytes were also subjected to hypoxic stress for 5 hr; the cell number was not affected by hypoxia but the glycolytic flux was enhanced during the stress imposed. The culture system described is a novel tool to study brain cell metabolism, allowing sampling over time and the monitoring of cellular behavior through stressful conditions and during recovery.

Animals↗

PubMed1976

Studies on normal human bone marrow cultures in controlled environment thin-film culture systems.

Two thin film culture systems, the controlled environment steady state system (SS) and the rocker tube configuration of that system (RT), were used to identify some of the conditions that appear to maintain morphologic and functional characteristics of cells of human bone marrow explants in vitro. The systems configuration assured continual gassing, control and easy monitoring of the cultures. Cytocentrifuge preparations of media of specimens cultured in RT disclosed, though in decreasing numbers, various hematopoietic cells for periods exceeding one month. Hematopoietic cells shed from specimens cultured in the SS system were retained in the culture tubes; cells of the myelocytic series predominated for the first two weeks while an increasing number of monocytes and macrophages appeared in the media of of older cultures. Histologic examination of cultured explants disclosed preservation of the marrow architecture and the persistence of hematopoietic cells. Specimens cultured in RT tubes tended to be less cellular than similar cultures placed in dialysis bags or as cultured in the SS system. Immunoglobulins (Ig) were released into the culture media at a constant rate throughout the period of culture. Specimens that were cultured at a controlled pH of 7.4 released 2 to more than 4 times as much Ig as similar specimens maintained at a pH level of 7.1. There were no definitive differences in Ig levels in the cultures maintained at comparable pH levels and overlaid with various CO2 concentrations, i.e. 2%, 5%, 10% similarly, no differences in Ig levels were found in specimens cultured in media containing fetal bovine sera as opposed to horse sera.

Bone Marrow↗

PubMed1976

Controlled environment treatment (CET) for patients with below-knee amputations.

This paper describes a new approach to early postsurgical wound management of the patient with a below-knee amputation. The method involves using the Controlled Environment Treatment (CET) machine, which wasdeveloped in England. A brief explanation of the components of the machine and its capabilities are listed. Ambient pressure, temperature, sterility, and humidity are easily controllable; advantages and disadvantages of this device over immediate post-operative plaster and conventional dressings as they relate both to wound environment and to physical therapy are mentioned. The early postsurgical therapy program used at Prosthetics Research Study is outlined.

Air Pressure↗

PubMedDate not supplied

Measuring team situation awareness in decentralized command and control environments.

Decentralized command and control settings like those found in the military are rife with complexity and change. These settings typically involve dozens, if not hundreds to thousands, of heterogeneous players coordinating in a distributed fashion in a dynamically networked battlefield laden with sensor data, intelligence reports, communications, and plans emanating from many different perspectives. Consider the concept of team situation awareness in this setting. What does it mean for a team to be aware of a situation or, more importantly, of a critical change in a situation? Is it sufficient or necessary for all individuals on the team to be independently aware? Or is there some more holistic awareness that emerges as team members interact? We re-examine the concept of team situation awareness in decentralized systems beyond an individual-oriented knowledge-based construct by considering it as a team interaction-based phenomenon. A theoretical framework for a process-based measure called 'coordinated awareness of situations by teams' is outlined.

Awareness↗

PubMed2003

[The working environment control of anhydride hardeners from an epoxy resin system].

Epoxy resins are widely used in adhesives, coatings, materials for molds and composites, and encapsulation. Acid anhydrides such as methyltetrahydrophthalic anhydride are being used as curing agents for epoxy resins. The anhydride hardeners are well-known industrial inhalant allergens, inducing predominantly type I allergies. In the electronic components industry, these substances have been consumed in large quantities. Therefore, safe use in the industry demands control of the levels of exposure causing allergic diseases in the workshop. We conducted a prospective survey of two electronics plants to clarify how to control the atmospheric level of the anhydrides in the work environment. Measurements of the levels of the anhydrides in air started according to the Working Environment Measurement Standards (Ministry of Labour Notification No. 46, 1976) in April 2000, along with improvements in the work environment. A value of 40 micrograms/m3 was adopted as the administrative control level to judge the propriety of the working environment control. A total of 2 unit work areas in both plants belonged to Control Class III. The exposure originated from manual loading, casting, uncured hot resins, and leaks in an impregnating-machine or curing ovens. In order to achieve the working environment control, complete enclosure of the source, installation of local exhaust ventilation, and improvement or maintenance of the local exhaust ventilation system were performed on the basis of the results of the working environment measurement, with the result that the work environment was improved (Control Class I). It became evident that these measures were effective just like other noxious substances.

Air Pollutants, Occupational↗