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Sample records for desiccant dehumidification system

  1. Desiccant-based dehumidification system and method

    DOEpatents

    Fischer, John C.

    2004-06-22

    The present invention provides an apparatus for dehumidifying air supplied to an enclosed space by an air conditioning unit. The apparatus includes a partition separating the interior of the housing into a supply portion and a regeneration portion. The supply portion has an inlet for receiving supply air from the air conditioning unit and an outlet for supplying air to the enclosed space. A regeneration fan creates the regeneration air stream. The apparatus includes an active desiccant wheel positioned such that a portion of the wheel extends into the supply portion and a portion of the wheel extends into the regeneration portion, so that the wheel can rotate through the supply air stream and the regeneration air stream to dehumidify the supply air stream. A heater warms the regeneration air stream as necessary to regenerate the desiccant wheel. The invention also comprises a hybrid system that combines air conditioning and dehumidifying components into a single integrated unit.

  2. Desiccant dehumidification and cooling systems assessment and analysis

    SciTech Connect

    Collier, R.K. Jr.

    1997-09-01

    The objective of this report is to provide a preliminary analysis of the principles, sensitivities, and potential for national energy savings of desiccant cooling and dehumidification systems. The report is divided into four sections. Section I deals with the maximum theoretical performance of ideal desiccant cooling systems. Section II looks at the performance effects of non-ideal behavior of system components. Section III examines the effects of outdoor air properties on desiccant cooling system performance. Section IV analyzes the applicability of desiccant cooling systems to reduce primary energy requirements for providing space conditioning in buildings. A basic desiccation process performs no useful work (cooling). That is, a desiccant material drying air is close to an isenthalpic process. Latent energy is merely converted to sensible energy. Only when heat exchange is applied to the desiccated air is any cooling accomplished. This characteristic is generic to all desiccant cycles and critical to understanding their operation. The analyses of Section I show that desiccant cooling cycles can theoretically achieve extremely high thermal CoP`s (>2). The general conclusion from Section II is that ventilation air processing is the most viable application for the solid desiccant equipment analyzed. The results from the seasonal simulations performed in Section III indicate that, generally, the seasonal performance of the desiccant system does not change significantly from that predicted for outdoor conditions. Results from Section IV show that all of the candidate desiccant systems can save energy relative to standard vapor-compression systems. The largest energy savings are achieved by the enthalpy exchange devise.

  3. Dehumidification Performance of Hybrid Type Humidity Control System Coupling a Desiccant Rotor in a Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Horibe, Akihiko; Takaki, Sadao; Inaba, Hideo; Haruki, Naoto

    Desiccant air-conditioning system is a promising technology because the exhaust heat can be effectively used in the future. We have reported the proposed system that combines a desiccant rotor with a vapor compression refrigerator. The confirmation experiment of stability and the performance was conducted with the experimental prototype. The result showed that it had the performance that was necessary for dehumidification driving in the summer and the humidification driving in the winter. In this report, we examined the influence on humidity controlling performance of the processing air temperature and humidity. As a result, we got high dehumidification efficiency and clarified the dehumidification characteristic in dehumidification driving in the summer. Dehumidification efficiency about 4.0 kg/kWh and COP of the system about 2.0 in summer driving mode were obtained.

  4. Review of Desiccant Dehumidification Technology

    SciTech Connect

    Pesaran, A. A.

    1994-10-01

    This paper overviews applications of desiccant technology for dehumidifying commercial and institutional buildings. Because of various market, policy, and regulatory factors, this technology is especially attractive for dehumidification applications in the I990s.

  5. Solar-regenerated desiccant dehumidification

    NASA Astrophysics Data System (ADS)

    Haves, P.

    1982-02-01

    The dehumidification requirements of buildings are discussed, and the most suitable desiccant material is identified as silica gel. Several conceptual designs for solar regenerated desiccant dehumidifiers using a solid desiccant are described. The construction and operation of a laboratory experiment to determine the performance of a packed bed of silica gel at low flow rate is described. The experimental results are presented and compared to the predictions of a simple computer model which assumes local equilibrium between the desiccant and the airstream. The simulations used to predict desiccant bed performance and the integration of the desiccant bed simulation with a simulation of the thermal performance of a passively cooled residence are described. Results for an average July day are presented. Sizing relationships derived from the simulation are described, and an economic analysis and recommendations for further work are presented.

  6. Desiccant-Based Dehumidification for Army Facilities

    DTIC Science & Technology

    1992-11-01

    desiccants are absorbei.ts; they physically zid/or chemically change as they pick up water. Triethylene glycol is a common liquid desiccant . Typically, liquid...AD-A263 305 fc USACERL Technical Report FE-93/10November 1992 Desiccant Cooling/Dehumidification for Army Facilities US A Imy Corps of Engineers...Construction Engineering Research Laboratory Desiccant -Based Dehumidification for Army Facilities by Gerald L. Cler The U.S. Army maintains over 1 billion

  7. Successive dehumidification/regeneration cycles by LiCL desiccant for air-conditioning system

    NASA Astrophysics Data System (ADS)

    Bouzenada, S.; Kaabi, A. N.; Fraikin, L.; Léonard, A.

    2017-02-01

    Dehumidification by desiccant is a new application in air-conditioning system. This technology is providing important advantages in solving many problems and brings environmentally friendly products. Desiccants are natural substances that are capable of showing a strong attraction for water vapour and can be regenerated. They can undergo continuous cycles. An experimental study is carried out on successive phases of absorption/regeneration, during 7 days by using LiCl desiccant and on separate phases. The effect of climatic parameters on moisture removal rate and salt concentration on absorption and regeneration processes is discussed. The results show that higher air humidity gives a higher mass transfer potential then a higher moisture rate absorbed dm/dt. The decrease of salt concentration affects the dm/dt and vapour pressure. Also, these results show that at regeneration temperature, the amount of water desorbed is nearly equal to the amount of water absorbed (equilibrium condition) for a complete cycle. The amount of 7.87 mg of water vapor can be absorbed in the first hour of absorption cycle for 12.6144 mg at 50% of relative humidity, and 7.004mg for 36.31 mg of initial mass subjected at 70% RH. The LiCl desiccant is able to return to almost its original concentration 31.39% during regeneration phase. Also, LiCl desiccant is able to be regenerated at low temperature 40°C which can be easily obtained by using solar energy. Then, the LiCl is a good hygroscopic material for using in liquid desiccant air-conditioning system.

  8. Efficiency of a liquid desiccant dehumidification system regenerated by using solar collectors/regenerators with photovoltaic fans

    SciTech Connect

    Tsair-Wang Chung; Wei-Yih Wu; Wen-Jih Yan; Ching-Lin Huang

    1995-04-01

    A hybrid solar dehumidification air-conditioning system was used to study the absorption of water vapor from moist air by contacting the air with aqueous solutions that contained from 90 to 94% triethylene glycol (TEG). For the packings of 2-inch polypropylene Jaeger Tri-Packs, which have a surface-to-volume ratio of 157 m{sup 2}/m{sup 3} (48 ft{sup 2}/ft{sup 3}), the efficiency of dehumidification can reach 93.3%. The environmental air was introduced into the dehumidifier cocurrently flowing with the liquid desiccant, and the liquid desiccant was sprayed on the top of the packing material. The air-to-liquid mass flow ratio was controlled in a range of 0.46 to 1.36. As the moisture was absorbed from air by the TEG solution, the solution was diluted. The regeneration of the solution was carried out in 20-piece (38.8 m{sup 2}) basin-type solar collectors/regenerators whose regeneration coefficients of performance are above 0.2. Air generated by photovoltaic fans was blown into the solar collectors/regenerators and carried away the water vapor from the evaporation of the aqueous desiccant solution. On the basis of the experimental results, the system performance is acceptable for most applications.

  9. A review of desiccant dehumidification technology

    SciTech Connect

    Pesaran, A.A.

    1994-10-01

    This paper overviews applications of desiccant technology for dehumidifying commercial and institutional buildings. Because of various market, policy, and regulatory factors, this technology is especially attractive for dehumidification applications in the 1990s. After briefly reviewing the principle of operation, the authors present three case studies-for supermarkets, a hotel, and an office building. The authors also discuss recent advances and ongoing research and development activities.

  10. Energy and economic performance analysis of an open cycle solar desiccant dehumidification air-conditioning system for application in Hong Kong

    SciTech Connect

    Li, Yutong; Lu, Lin; Yang, Hongxing

    2010-12-15

    In this article, a transient simulation model and the EnergyPlus were used to study the energy performance and economical feasibility for integrating a solar liquid desiccant dehumidification system with a conventional vapor compression air-conditioning system for the weather condition of Hong Kong. The vapor compression system capacity in the solar assisted air-conditioning system can be reduced to 19 kW from original 28 kW of a conventional air-conditioning system as a case study due to the solar desiccant cooling. The economical performance of the solar desiccant dehumidification system is compared with that of the conventional air-conditioning system. The results show that the energy saving potentials due to incorporation of the solar desiccant dehumidification system in a traditional air-conditioning system is significant for the hot wet weather in Hong Kong due to higher COP resulted from higher supply chilled water temperature from chiller plants. The annual operation energy savings for the hybrid system is 6760 kWh and the payback period of the hybrid system is around 7 years. The study shows that the solar assisted air-conditioning is a viable technology for utilizations in subtropical areas. (author)

  11. An assessment of desiccant cooling and dehumidification technology

    SciTech Connect

    Mei, V.C.; Chen, F.C.; Lavan, Z.; Collier, R.K. Jr.; Meckler, G.

    1992-07-01

    Desiccant systems are heat-actuated cooling and dehumidification technology. With the recent advances in this technology, desiccant systems can now achieve a primary energy coefficient of performance (COP) between 1.3 and 1.5, with potential to go to 1.7 and higher. It is becoming one of the most promising alternatives to conventional cooling systems. Two important and well-known advantages of desiccant cooling systems are that they are CFC free and they can reduce the electricity peak load. Another important but lesser-known advantage of desiccant technology is its potential for energy conservation. The energy impact study in this report indicated that a possible 13% energy saving in residential cooling and 8% in commercial cooling is possible. Great energy saving potential also exists in the industrial sector if industrial waste heat can be used for desiccant regeneration. The latest study on desiccant-integrated building heating, ventilating, and air conditioning (HVAC) systems indicated that the initial cost for the conventional cooling equipment was greatly reduced by using desiccant technology because of downsized compressors, fans, and ductworks. This cost reduction was more than enough to offset the cost of desiccant equipment. Besides, the system operation cost was also reduced. All these indicate that desiccant systems are also cost effective. This study provides an updated state-of-the-art assessment forsiccant technology in the field of desiccant materials, systems, computer models, and theoretical analyses. From this information the technology options were derived and the future research and development needs were identified. Because desiccant technology has already been applied in the commercial building sector with very encouraging results, it is expected that future market breakthroughs will probably start in this sector. A market analysis for the commercial building application is therefore included.

  12. An assessment of desiccant cooling and dehumidification technology

    SciTech Connect

    Mei, V.C.; Chen, F.C. ); Lavan, Z. ); Collier, R.K. Jr. ); Meckler, G. )

    1992-07-01

    Desiccant systems are heat-actuated cooling and dehumidification technology. With the recent advances in this technology, desiccant systems can now achieve a primary energy coefficient of performance (COP) between 1.3 and 1.5, with potential to go to 1.7 and higher. It is becoming one of the most promising alternatives to conventional cooling systems. Two important and well-known advantages of desiccant cooling systems are that they are CFC free and they can reduce the electricity peak load. Another important but lesser-known advantage of desiccant technology is its potential for energy conservation. The energy impact study in this report indicated that a possible 13% energy saving in residential cooling and 8% in commercial cooling is possible. Great energy saving potential also exists in the industrial sector if industrial waste heat can be used for desiccant regeneration. The latest study on desiccant-integrated building heating, ventilating, and air conditioning (HVAC) systems indicated that the initial cost for the conventional cooling equipment was greatly reduced by using desiccant technology because of downsized compressors, fans, and ductworks. This cost reduction was more than enough to offset the cost of desiccant equipment. Besides, the system operation cost was also reduced. All these indicate that desiccant systems are also cost effective. This study provides an updated state-of-the-art assessment forsiccant technology in the field of desiccant materials, systems, computer models, and theoretical analyses. From this information the technology options were derived and the future research and development needs were identified. Because desiccant technology has already been applied in the commercial building sector with very encouraging results, it is expected that future market breakthroughs will probably start in this sector. A market analysis for the commercial building application is therefore included.

  13. Gas Engine-Driven Heat Pump with Desiccant Dehumidification

    SciTech Connect

    Shen, Bo; Abu-Heiba, Ahmad

    2017-01-01

    About 40% of total U.S. energy consumption was consumed in residential and commercial buildings. Improved air-conditioning technology has by far the greatest potential impact on the electric industry compared to any other technology that uses electricity. This paper describes the development of an innovative natural gas, propane, LNG or bio-gas IC engine-driven heat pump (GHP) with desiccant dehumidification (GHP/DD). This integrated system has higher overall efficiencies than conventional equipment for space cooling, addresses both new and existing commercial buildings, and more effectively controls humidity in humid areas. Waste heat is recovered from the GHP to provide energy for regenerating the desiccant wheel and to augment heating capacity and efficiency. By combining the two technologies, an overall source COP of greater that 1.5 (hot, humid case) can be achieved by utilizing waste heat from the engine to reduce the overall energy required to regenerate the desiccant. Moreover, system modeling results show that the sensible heat ratio (SHR- sensible heat ratio) can be lowered to less 60% in a dedicated outdoor air system application with hot, humid cases.

  14. Dehumidification and simultaneous removal of selected pollutants from indoor air by a desiccant wheel using a 1M type desiccant

    SciTech Connect

    Popescu, M.; Ghosh, T.K.

    1999-02-01

    Solid-desiccant dehumidifiers are increasingly becoming an integral part of desiccant based air-conditioning systems because of their effective handling of latent heat loads compared to conventional vapor compression units. In these units, either a silica gel or a molecular sieve is used for dehumidification of air. Both of them have the capability to co-adsorb various chemical pollutants during dehumidification of air. However, the shape of the isotherm for water vapor on these materials is not favorable for desiccant cooling applications. A mixture (1M desiccant) containing a silica gel, a molecular sieve, and a hydrophobic molecular sieve that was coated on an aluminum foil was studied for its capability for simultaneous removal of moisture and some selected pollutants from air. Experimental data were obtained in a fixed bed adsorber that simulated the operation of a rotary desiccant wheel. Air to be dehumidified and cleaned and the hot regeneration air were cycled in a specific time interval through this bed. The shape of the water isotherm on 1M desiccant was found to be in between that of silica gel and molecular sieve 13{times}, but its uptake capacity was significantly lower than that of either silica gel or molecular sieve. A flow rate of about 100 L/min that provided a face velocity of about 132 cm/s was used in the adsorption step. The flow rate during regeneration was about 50 L/min. The temperature of the inlet air was about 23 C and its relative humidity was varied between 20% and 80%. The concentrations of pollutants were as follows; carbon dioxide: 1050 and 2300 ppm; toluene: 32 ppm; 1,1,1-trichloroethane: 172 ppm, and formaldehyde: 0.35 ppm. A complete breakthrough of all the pollutants was observed during an adsorption cycle.

  15. Hollow Fiber Membrane Dehumidification Device for Air Conditioning System.

    PubMed

    Zhao, Baiwang; Peng, Na; Liang, Canzeng; Yong, Wai Fen; Chung, Tai-Shung

    2015-11-16

    In order to provide a comfortable living and working environment indoors in tropical countries, the outdoor air often needs to be cooled and dehumidified before it enters the rooms. Membrane separation is an emerging technology for air dehumidification and it is based on the solution diffusion mechanism. Water molecules are preferentially permeating through the membranes due to its smaller kinetic diameter and higher condensability than the other gases. Compared to other dehumidification technologies such as direct cooling or desiccation, there is no phase transition involved in membrane dehumidification, neither the contact between the fresh air stream and the desiccants. Hence, membrane dehumidification would not only require less energy consumption but also avoid cross-contamination problems. A pilot scale air dehumidification system is built in this study which comprises nine pieces of one-inch PAN/PDMS hollow fiber membrane modules. A 150 h long-term test shows that the membrane modules has good water vapor transport properties by using a low vacuum force of only 0.78 bar absolute pressure at the lumen side. The water vapor concentration of the feed humid air decreases dramatically from a range of 18-22 g/m³ to a range of 13.5-18.3 g/m³. Most importantly, the total energy saving is up to 26.2% compared with the conventional air conditioning process.

  16. Hollow Fiber Membrane Dehumidification Device for Air Conditioning System

    PubMed Central

    Zhao, Baiwang; Peng, Na; Liang, Canzeng; Yong, Wai Fen; Chung, Tai-Shung

    2015-01-01

    In order to provide a comfortable living and working environment indoors in tropical countries, the outdoor air often needs to be cooled and dehumidified before it enters the rooms. Membrane separation is an emerging technology for air dehumidification and it is based on the solution diffusion mechanism. Water molecules are preferentially permeating through the membranes due to its smaller kinetic diameter and higher condensability than the other gases. Compared to other dehumidification technologies such as direct cooling or desiccation, there is no phase transition involved in membrane dehumidification, neither the contact between the fresh air stream and the desiccants. Hence, membrane dehumidification would not only require less energy consumption but also avoid cross-contamination problems. A pilot scale air dehumidification system is built in this study which comprises nine pieces of one-inch PAN/PDMS hollow fiber membrane modules. A 150 h long-term test shows that the membrane modules has good water vapor transport properties by using a low vacuum force of only 0.78 bar absolute pressure at the lumen side. The water vapor concentration of the feed humid air decreases dramatically from a range of 18–22 g/m3 to a range of 13.5–18.3 g/m3. Most importantly, the total energy saving is up to 26.2% compared with the conventional air conditioning process. PMID:26580660

  17. Active Desiccant Dehumidification Module Integration with Rooftop Packaged HVAC

    SciTech Connect

    Fischer, J

    2002-04-17

    This report summarizes a research and development program that produced a stand-alone active desiccant module (ADM) that can be easily integrated with new or existing packaged cooling equipment. The program also produced a fully integrated hybrid system, combining the active desiccant section with a conventional direct expansion air-conditioning unit, that resulted in a compact, low-cost, energy-efficient end product. Based upon the results of this investigation, both systems were determined to be highly viable products for commercialization. Major challenges--including wheel development, compact packaging, regeneration burner development, control optimization, and low-cost design--were all successfully addressed by the final prototypes produced and tested as part of this program. Extensive laboratory testing was completed in the SEMCO laboratory for each of the two ADM system approaches. This testing confirmed the performance of the ADM systems to be attractive compared with that of alternate approaches currently used to precondition outdoor air, where a return air path is not readily available for passive desiccant recovery or where first cost is the primary design criterion. Photographs, schematics, and performance maps are provided for the ADM systems that were developed; and many of the control advantages are discussed. Based upon the positive results of this research and development program, field tests are under way for fully instrumented pilot installations of ADM systems in both a hotel/motel and a restaurant.

  18. Simple predictive model for performance of desiccant beds for solar dehumidification

    NASA Astrophysics Data System (ADS)

    Barlow, R.

    1981-08-01

    A computer model for the absorption/desorption process that predicts the performance of desiccant beds for solar regenerated dehumidification of passively cooled buildings is outlined. The model uses simple algebraic equations for steady state heat and mass exchangers. The validity and accuracy of the model is demonstrated. The physics of the adsorption process in two psychrometric process lines is discussed.

  19. Performance of Desiccant Particle Dispersion Type Air Conditioning System

    NASA Astrophysics Data System (ADS)

    Hatano, Hiroyuki; Suzuki, Koichi; Kojima, Hiromitsu

    An investigation of desiccant air conditioning system is performed to demonstrate its performance in a dispersed desiccant particle systems, based on its higher gas solid contacting efficiency and isothermal dehumidification. Particle dispersion is achieved using the risers of a circulating fluidized bed, CFB, or of a pneumatic conveyer. The risers used for dehumidification are 1390 mm in height and 22 mm in diameter. The former is used to evaluate the overall dehumidification performance and the latter is used to measure the axial humidity distribution under 0.88 m/s of a superficial air velocity. Based on the results of the overall performance by changing solid loading rates, Gs, from 0.4 kg/m2s up to 6 kg/m2s, desiccant particle dispersion shows higher performance in dehumidification, while axial humidity distribution shows very rapid adsorption rate in the entrance zone of the riser. Removal of adsorption heat accelerates dehumidification rate compared to the adiabatic process.

  20. Seminar 14 - Desiccant Enhanced Air Conditioning: Desiccant Enhanced Evaporative Air Conditioning (Presentation)

    SciTech Connect

    Kozubal, E.

    2013-02-01

    This presentation explains how liquid desiccant based coupled with an indirect evaporative cooler can efficiently produce cool, dry air, and how a liquid desiccant membrane air conditioner can efficiently provide cooling and dehumidification without the carryover problems of previous generations of liquid desiccant systems. It provides an overview to a liquid desiccant DX air conditioner that can efficiently provide cooling and dehumidification to high latent loads without the need for reheat, explains how liquid desiccant cooling and dehumidification systems can outperform vapor compression based air conditioning systems in hot and humid climates, explains how liquid desiccant cooling and dehumidification systems work, and describes a refrigerant free liquid desiccant based cooling system.

  1. Relation between Water Vapor Adsorption Isotherms and Dynamic Dehumidification Performances of Desiccant Rotor

    NASA Astrophysics Data System (ADS)

    Inoue, Koji; Matsuguma, Shingo; Jin, Wei-Li; Okano, Hiroshi; Teraoka, Yasutake; Hirose, Tsutomu

    Desiccant rotors with different water vapor adsorption properties were fabricated by the synthesis of silica gels inside the honeycomb matrices. Dynamic dehumidification performances of the rotors were measured under different conditions and they were discussed in relation to water vapor adsorption isotherms. At the reactivation air temperatures of 80 and 140 oC, the best dynamic performance was observed with the rotor on which the adsorbed amount of water vapor at lower relative humidity was highest. When the reactivation air temperature was 50 oC, on the other hand, the rotor of which the isotherm exhibited monotonic and nearly linear increase up to higher relative humidity was the most suitable. The normalized changes of absolute humidity and adsorbed amount were defined, and these phenomena were analyzed. When the dependences of both parameters against the relative humidity were similar, the rotor showed the best dehumidification performance.

  2. 4-rotor Desiccant Cooling Process Equipped with a Double Stage Dehumidification

    NASA Astrophysics Data System (ADS)

    Ando, Kosuke; Kodama, Akio; Okano, Hiroshi; Asada, Toshinobu

    2-rotor desiccant cooling process consisting of a honeycomb rotor dehumidifier and a sensible heat exchanger is a mainstream of the desiccant cooling process which are practically applied to supermarket, hospital and so on. However, this process cannot produce a sufficient dehumidifying performance in high humidity region. In this study, 4-rotor desiccant cooling process equipped with a double stage dehumidification was proposed and investigated experimentally. In this process, regeneration temperature around 60°C could produce a sufficient dehumidifying performance even at high ambient humidity. “Serial heat supply” mode was considered to improve the heat efficiency by the cascade use of regeneration heat inside the cooling cycle. The dehumidifying performance of the “serial heat supply” mode was only slightly lower than that of a “parallel heat supply” mode at which the same temperature hot air was supplied to the both heaters. However, dehumidifying performance of this “serial heat supply” mode was much higher than that of conventional 2-rotor desiccant cooling process. Furthermore, the desiccant rotors of 0.1m in thickness were mounted to 4-rotor desiccant cooling process in place of the 0.2m desiccant rotors. It was found that the drop of dehumidifying performance of the process equipped with 0.1m desiccant rotors was only by 10 percents comparing with the 0.2m rotor process. Moreover, it was found that optimization of rotation speed of the desiccant rotor was needed to improve the energy efficiency. Regarding the supply point of return air, it was also found that return air should be supplied to the regeneration inlet of the second stage for higher dehumidifying performance.

  3. Correlations for film regeneration and air dehumidification for a falling desiccant film with air in cross flow

    SciTech Connect

    Park, M.S.; Howell, J.R.; Vliet, G.C.

    1995-11-01

    The coupled heat and mass transfer between a falling triethylene glycol (TEG) desiccant film and air in cross flow have previously been presented and solved numerically for the cases of regeneration and dehumidification. Here, correlations for the effects of independent variables on the rate of regeneration in the regenerator and on the rate of dehumidification and sensible cooling in the absorber are developed by statistical analysis of the numerical results. The functional correlations developed should be useful in the design of regenerators and absorbers having falling liquid desiccant films and air in cross flow.

  4. Adiabatic air dehumidification in laminar flow desiccant matrices

    SciTech Connect

    Pesaran, A A

    1987-07-01

    Adiabatic step transient heat- and mass-transfer and pressure drop experimental data were obtained for a dehumidifier test matrix that contained microbead-silica-gel desiccant in a parallel-plate geometry. The data were analyzed and compared with the results of two other test dehumidifiers: a parallel-plate matrix using crushed silica gel, and a staggered, parallel-strip matrix using microbead silica gel. The analysis showed that the overall heat- and mass-transfer Nusselt numbers of the staggered, parallel-strip matrix were about 70% to 80% larger than those of the parallel-plate matrices. It also showed that the solid-side resistance to moisture diffusion in the smaller microbead silica gel was about 45% less than that of crushed silica gel because the particle size was 60% smaller. The ratio of heat- or mass-transfer coefficient to pressure drop of the microbead-silica-gel staggered, parallel-strip matrix was higher than the other two test dehumidifiers. Based on these findings, a dehumidifier using microbead silica-gel in a staggered, parallel-strip geometry can be made more compact than the other combinations. 15 refs., 9 figs., 5 tabs.

  5. Indirect evaporative cooler using membrane-contained, liquid desiccant for dehumidification

    SciTech Connect

    Kozubal, Eric Joseph

    2016-12-13

    An indirect evaporative cooler for cooling inlet supply air from a first temperature to a second, lower temperature using a stream of liquid coolant and a stream of exhaust or purge air. The cooler includes a first flow channel for inlet supply air and a second flow channel adjacent the first for exhaust air. The first and second flow channels are defined in part by sheets of a membrane permeable to water vapor such that mass is transferred as a vapor through the membrane from the inlet supply air to a contained liquid desiccant for dehumidification and also to the exhaust air as heat is transferred from the inlet supply air to the liquid coolant. A separation wall divides the liquid desiccant and the coolant but allows heat to be transferred from the supply air to the coolant which releases water vapor to the counter or cross flowing exhaust air.

  6. Indirect evaporative cooler using membrane-contained, liquid desiccant for dehumidification

    SciTech Connect

    Kozubal, Eric Joseph; Slayzak, Steven Joseph

    2014-07-08

    An indirect evaporative cooler for cooling inlet supply air from a first temperature to a second, lower temperature using a stream of liquid coolant and a stream of exhaust or purge air. The cooler includes a first flow channel for inlet supply air and a second flow channel adjacent the first for exhaust air. The first and second flow channels are defined in part by sheets of a membrane permeable to water vapor such that mass is transferred as a vapor through the membrane from the inlet supply air to a contained liquid desiccant for dehumidification and also to the exhaust air as heat is transferred from the inlet supply air to the liquid coolant. A separation wall divides the liquid desiccant and the coolant but allows heat to be transferred from the supply air to the coolant which releases water vapor to the counter or cross flowing exhaust air.

  7. (Dehumidification system for high humidity areas)

    SciTech Connect

    Stark, W.

    1990-10-26

    The indoor swimming pool at Glen Cove YMCA, Glen Cove, New York, installed a dehumidification and water heating system. This report is the specifications of the new system, which includes dehumidifier/air handler, condenser/water heater, and outdoor condenser. (JF)

  8. Double-stage Dehumidification achieved in 2-rotor Desiccant Cooling Process

    NASA Astrophysics Data System (ADS)

    Asada, Toshinobu; Kodama, Akio

    A multi-divided rotary adsorber was proposed to realize a double-stage dehumidification in 2-rotor desiccant cooling process. In this process, once dehumidified and cooled air was dehumidified again at the different adsorption zone of the same desiccant rotor. Four process flow configurations were experimentally tested for investigations of the appropriate outside air inlet position and rotating directions of the rotary adsorber and rotary heat exchanger. It was found that dehumidifying performance was strongly influenced by the supply position of outside air to the adsorbent rotor. Humid outside air should be supplied to the latter half of the adsorption zone and once dehumidified air should be sent to the first half of the adsorption zone. This is because the increase in the amount adsorbed at the first half of the adsorption step resulted in a poor adsorbabilty at the latter half of the adsorption step for the once dehumidified dry air. Therefore, the effective use of the adsorbent rotor could be done by considering the angular distribution of the amount of adsorbed. Consequently, 30% larger amount of dehumidification than that of conventional processes under a humid summer condition was confirmed. Regarding the product air temperature, the process configurations at which secondary dehumidified air was cooled at the first half of the sensible rotor produced roughly 5 °C lower temperature air than that of the other. This implied that the directions of rotation of the adsorbent rotor and the rotary heat exchanger, or dehumidification - cooling sequence, also had a great impact on the product air condition.

  9. Solar Assisted Adsorptive Desiccant Cooling System

    NASA Astrophysics Data System (ADS)

    Ohkura, Masashi; Kodama, Akio

    Solar assisted desiccant coo1ing process is an effective means to reduce a latent heat load of the ventilation air. This paper describes the influences of ambient humidity and sensible heat factor (SHF) of the indoor room on the performance and scale of the desiccant cooling system. Two process configurations termed “ambient air mode” and “mixed air mode” were assumed. At “ambient air mode”, only ambient air is dehumidified and cooled in the desiccant process. The dehumidified air stream is mixed with return air and further cooled in the cooling coil. At “mixed air mode”, ambient air is mixed with return air and this mixed air stream is dehumidified in the desiccant process and cooled at the cooling coil. At “ambient air mode”, ambient air humidity had a significant impact on required amount of dehumidification since humid ambient air entered the desiccant process directly. In this case, higher temperature level and quantity, which is impossible to be supplied from commonly commercialized flat panel solar collectors, was required. At “mixed air mode”, the influence of increase of ambient humidity was not significant since humidity of the air entering the desiccant process became low by mixing with return air. At this mode, it was expected that 70°C of the circulating water and 37m2 of surface area of solar collector could produce a sufficient dehumidifying performance even in high latent heat condition. The contributing ratio of the desiccant wheel was also estimated. The ratio increased in higher latent heat condition due to increase of required amount of dehumidification. The contributing ratio of the thermal wheel became lower due to increase of saturated air temperature in the evaporative cooler.

  10. Dehumidification System with Steam Permeability Films

    NASA Astrophysics Data System (ADS)

    Ishikwa, Masaaki; Sekimori, Souji; Ogiwara, Shigeaki; Ochiai, Tetsunari; Hirata, Tetsuo

    In a factory with a clean room facility in cold regions, dew-condensation on walls of the facility is one of the most serious problems in winter. In this study, a new dehumidification system in which a steam permeability film is located between humid air in a clean room and dry air from outside to exchange steam is proposed. This system can treat a lot of humid air with small energy only for driving fans to flow air. Some films are examined in two kinds of steam exchangers; double tube type and flat p1ate type. Steam permeability resistance and therma1 resistance of each film are first obtained in a double tube type exchanger. An analytica1 model for a flat plate type exchanger is then proposed, which shows good agreement with experimental data. Steam and heat transfer characteristics of a flat plate type exchanger are also evaluated experimentally. One film on a flat plate type exchanger shows dehumidification capacity of 0.033g/s(=120g/h )with its area of 2.232m2.

  11. Residential Dehumidification Systems Research for Hot-Humid Climates

    SciTech Connect

    2005-02-01

    Twenty homes were tested and monitored in the hot-humid climate of Houston, Texas, to evaluate the humidity control performance and operating cost of six integrated dehumidification and ventilation systems.

  12. Fabrication and Properties of Micro-Nanoencapsulated Phase Change Materials for Internally-Cooled Liquid Desiccant Dehumidification.

    PubMed

    Niu, Xiaofeng; Xu, Qing; Zhang, Yi; Zhang, Yue; Yan, Yufeng; Liu, Tao

    2017-04-29

    Micro-nanoencapsulated phase change materials (M-NEPCMs) are proposed to be useful in liquid desiccant dehumidification by restraining the temperature rise in the moisture-removal process and improving the dehumidification efficiency. In this paper, the n-octadecane M-NEPCMs with desirable thermal properties for internally-cooled dehumidification were fabricated by using compound emulsifiers through the in-situ polymerization method. Melamine-formaldehyde resin was used as the shell material. The effects of the mixing ratio, emulsification methods and amount of the compound emulsifiers on the morphology, size and thermal properties of the M-NEPCMs were investigated experimentally. The optimum weight mixing ratio of the compound emulsifiers is SDS (sodium dodecyl sulfate):Tween80 (polyoxyethylene sorbitan monooleate):Span80 (sorbitan monooleate) = 0.1:0.6:0.3, which achieves the best stability of the n-octadecane emulsion. When the compound emulsifiers are 10 wt. % of the core material, the melting enthalpy of M-NEPCMs reaches its maximum of 145.26 J/g of capsules, with an encapsulation efficiency of 62.88% and a mean diameter of 636 nm. The sub-cooling of the prepared M-NEPCMs is lower than 3 °C, with an acceptable thermal reliability after the thermal cycling test. A pre-emulsification prior to the addition of deionized water in the emulsification is beneficial to the morphology of the capsules, as the phase change enthalpy can be increased by 123.7%.

  13. Fabrication and Properties of Micro-Nanoencapsulated Phase Change Materials for Internally-Cooled Liquid Desiccant Dehumidification

    PubMed Central

    Niu, Xiaofeng; Xu, Qing; Zhang, Yi; Zhang, Yue; Yan, Yufeng; Liu, Tao

    2017-01-01

    Micro-nanoencapsulated phase change materials (M-NEPCMs) are proposed to be useful in liquid desiccant dehumidification by restraining the temperature rise in the moisture-removal process and improving the dehumidification efficiency. In this paper, the n-octadecane M-NEPCMs with desirable thermal properties for internally-cooled dehumidification were fabricated by using compound emulsifiers through the in-situ polymerization method. Melamine-formaldehyde resin was used as the shell material. The effects of the mixing ratio, emulsification methods and amount of the compound emulsifiers on the morphology, size and thermal properties of the M-NEPCMs were investigated experimentally. The optimum weight mixing ratio of the compound emulsifiers is SDS (sodium dodecyl sulfate):Tween80 (polyoxyethylene sorbitan monooleate):Span80 (sorbitan monooleate) = 0.1:0.6:0.3, which achieves the best stability of the n-octadecane emulsion. When the compound emulsifiers are 10 wt. % of the core material, the melting enthalpy of M-NEPCMs reaches its maximum of 145.26 J/g of capsules, with an encapsulation efficiency of 62.88% and a mean diameter of 636 nm. The sub-cooling of the prepared M-NEPCMs is lower than 3 °C, with an acceptable thermal reliability after the thermal cycling test. A pre-emulsification prior to the addition of deionized water in the emulsification is beneficial to the morphology of the capsules, as the phase change enthalpy can be increased by 123.7%. PMID:28468282

  14. High COP rotating wheel solid desiccant system

    SciTech Connect

    Macriss, R.A.; Zawacki, T.S.

    1982-06-01

    This paper presents a technical assessment of a third-generation desiccant cooling unit approaching ARI (American Refrigeration Institute) design-point Coefficient of Performance (COP) for cooling of 0.95, at a design-point Energy Efficiency Ratio(EER) of over 20, and a Seasonal Coefficient of Performance (SCOP) for heating of 0.75. Typically, solar-gas desiccant systems operate on open-cycle principles and can provide cooling, heating, ventilation, and/or humidification/dehumidification and use ambient air as the working fluid, thus avoiding the need for high-pressure, or highvacuum, sealed-refrigerant assemblies. Among several alternative solar-desiccant systems, the adiabatic, rotary-regenerative system is the most advanced open-cycle, solid-desiccant, heating-cooling system presently considered for solar applications. In addition to space heating and cooling, the system can inexpensively provide fresh makeup air due to its regenerative nature. Since 1974, two residential-size units have been under development, and laboratory, field, and manufacturing-cost evaluations have highlighted their potential advantages for space conditioning. Recently, a third ''advanced'' unit was designed, which incorporates identical technology to that of the earlier models and a higher effectiveness heat exchanger. Projected rated and seasonal cooling performance comparison between the ''advanced'' and earlier models are also presented for three climatic regions.

  15. Desiccant systems save money

    SciTech Connect

    Kister, P.

    1996-10-01

    Desiccant systems can save the Navy money through lower utility bills. Traditional vapor compression air conditioning systems are required to remove both sensible heat and latent heat (humidity) by cooling the outside air below the dewpoint in order to condense out water vapor. In some cases the air is then required to be reheated to a comfortable level. This requires large amounts of electricity at peak billing rates. Desiccant systems, on the other hand, use a desiccant to remove moisture from the outside air prior to cooling the air using traditional chillers. The desiccant is then reactivated using natural gas heat. This will shift up to 40 percent of the cooling load of the building to natural gas which in many areas of the country is cheaper than electricity, especially during the peak hours in the summer. It also eliminates inefficient reheating and in most cases the temperature of the building can be raised since dry air is more comfortable at higher temperatures than humid air. Many buildings also require special humidity control which is most effectively and efficiently met using a desiccant system. These buildings include hospitals, commissaries, avionics rooms, BOQ`s and BEQ`s, etc.

  16. Thermally Activated Desiccant Technology for Heat Recovery and Comfort

    SciTech Connect

    Jalalzadeh, A. A.

    2005-11-01

    Desiccant cooling is an important part of the diverse portfolio of Thermally Activated Technologies (TAT) designed for conversion of heat for the purpose of indoor air quality control. Thermally activated desiccant cooling incorporates a desiccant material that undergoes a cyclic process involving direct dehumidification of moist air and thermal regeneration. Desiccants fall into two categories: liquid and solid desiccants. Regardless of the type, solid or liquid, the governing principles of desiccant dehumidification systems are the same. In the dehumidification process, the vapor pressure of the moist air is higher than that of the desiccant, leading to transfer of moisture from the air to the desiccant material. By heating the desiccant, the vapor pressure differential is reversed in the regeneration process that drives the moisture from the desiccant. Figure 1 illustrates a rotary solid-desiccant dehumidifier. A burner or a thermally compatible source of waste heat can provide the required heat for regeneration.

  17. Development of Desiccant System using Wakkanai Siliceous Shale

    NASA Astrophysics Data System (ADS)

    Nakabayashi, Saya; Nagano, Katsunori; Nakamura, Makoto; Togawa, Junya; Kurokawa, Asami

    The aim of this study is to develop a desiccant system using Wakkanai siliceous shale. A honeycombed desiccant rotor containing this shale's powder and chlorides was made and evaluated. However a specific surface area and a pore volume were smaller than a silica-gel rotor or a zeolite rotor, the maximum amount of water adsorption was twice as other rotors. We have verified the function of this desiccant rotor concerning adsorption and desorption of moisture from the draft experiments. The rotor containing the shale could adsorb moisture stably in the cyclic test, and be regenerated by 40°C air under this experimental condition. This means that the exhaust heat from the heat pump can be used for regenerating rotor. Furthermore, the numerical simulation was carried out on the assumption that this rotor was used for a dehumidification for the residential air conditioning in Tokyo. This rotor could adsorb 37.1% moisture of the required dehumidification amount for the hottest day in 2008. When we employed a pre-cooling before dehumidification, the amount of adsorption increased to 66.2%.

  18. High COP rotating wheel solid desiccant system

    SciTech Connect

    Macriss, R.A.; Zawacki, T.S.

    1982-01-01

    Solar and solar-gas activated desiccant space-conditioning systems can be reasonably compact, simple and void of high technology components, with operation that is intrinsically safe, of potentially long-life, and with moderate servicing demands. They can, further, operate in any US climate and utilize, even under maximum design conditions, low-grade thermal input, typical of low-cost, flat-plate collectors. A technical assessment is presented of a third-generation desiccant cooling unit approaching ARI (American Refrigeration Institute) design-point Coefficient of Performance (COP) for cooling of 0.95, at a design-point Energy Efficiency Ratio (EER) of over 20, and a Seasonal Coefficient of Performance (SCOP) for heating of 0.75. Typically, solar-gas desiccant systems operate on open-cycle principles and can provide cooling, heating, ventilation, and/or humidification/dehumidification and use ambient air as the working fluid, thus avoiding the need for high-pressure, or highvacuum, sealed-refrigerant assemblies. Among several alternative solar-desiccant systems, the adiabatic, rotary-regenerative system is the most advanced open-cycle, solid-desiccant, heating-cooling system presently considered for solar applications. In addition to space heating and cooling, the system can inexpensively provide fresh make-up air due to its regenerative nature. Since 1974, two residential-size units have been under development, and laboratory, field, and manufacturing-cost evaluations have highlighted their potential advantages for space conditioning. Recently, a third advanced unit was designed, which incorporates identical technology to that of the earlier models and a higher effectiveness heat exchanger. Projected rated and seasonal cooling performance comparison between the advanced and earlier models are also presented for three climatic regions.

  19. Application of chemical dehumidification system to a roof fan house at Michoud Assembly Facility at New Orleans, Louisiana

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The feasibility of a chemical dehumidification system to reduce the energy consumption associated with dehumidification of the chilled air is assessed. A comparative energy consumption and cost analysis of the chemical dehumidification and existing systems and the savings offered by the proposed chemical dehumidification system over the existing air washer-reheat system are presented.

  20. Commercial high efficiency dehumidification systems using heat pipes

    SciTech Connect

    Not Available

    1993-09-01

    An improved heat pipe design using separately connected two-section one-way flow heat pipes with internal microgrooves instead of wicks is described. This design is now commercially available for use to increase the dehumidification capacity of air conditioning systems. The design also includes a method of introducing fresh air into buildings while recovering heat and controlling the humidity of the incoming air. Included are applications and case studies, load calculations and technical data, and installation, operation, and maintenance information.

  1. Dehumidification Performance of Humidity Control System with Double Ventilation Sorbent Rotor

    NASA Astrophysics Data System (ADS)

    Takaki, Sadao; Horibe, Akihiko; Haruki, Naoto; Nishina, Yuki; Inaba, Hideo

    The desiccant air-conditioning will be suitable for effective use of the exhaust heat. We have reported high dehumidification efficiency of the proposed system that is composed of a sorbent rotor and a refrigerating cycle. In this study, to improve the sorption efficiency of the rotor, the double ventilation rotor is proposed. After the processing air is dehumidified at the sorption area 1 of the rotor, the air is cooled and has higher relative humidity. And then, the air is blew into the sorption area 2 from the rotor opposite. The double ventilation characteristics on the influence of the division area of the rotor, the flow rate, the recovery temperature, and the temperature of the air cooler were investigated. As a result, the behavior of the double ventilation rotor is clarified and it is found that the quantity of dehumidification of the rotor is greater in the case of 1:1:2 (sorption(1): sorption(2): desorption ) division rate of the rotor than that of 1:1:1.

  2. Heat pipes for terrestrial applications in dehumidification systems

    NASA Technical Reports Server (NTRS)

    Khattar, Mukesh K.

    1988-01-01

    A novel application of heat pipes which greatly enhances dehumidification performance of air-conditioning systems is presented. When an air-to-air heat pipe heat exchanger is placed between the warm return air and cold supply air streams of an air conditioner, heat is efficiently transferred from the return air to the supply air. As the warm return air precools during this process, it moves closer to its dew-point temperature. Therefore, the cooling system works less to remove moisture. This paper discusses the concept, its benefits, the challenges of incorporating heat pipes in an air-conditioning system, and the preliminary results from a field demonstration of an industrial application.

  3. Desiccant degradation in desiccant cooling systems: An experimental study

    SciTech Connect

    Pesaran, A.A.

    1993-11-01

    The authors conducted experiments to quantify the effects of thermal cycling and exposure to contamination on solid desiccant materials that may be used in desiccant cooling systems. The source of contamination was cigarette smoke, which is considered one of the worst pollutants in building cooling applications. The authors exposed five different solid desiccants to ``ambient`` and ``contaminated`` humid air: silica gel, activated alumina, activated carbon, molecular sieves, and lithium chloride. They obtained the moisture capacity of samples as a function of exposure time. Compared to virgin desiccant samples, the capacity loss caused by thermal cycling with humid ambient air was 10 percent to 30 percent for all desiccants. The capacity loss because of combined effect of thermal cycling with ``smoke-filled`` humid air was between 30 percent to 70 percent. The higher losses occurred after four months of experiment time, which is equivalent to four to eight years of field operation. Using a system model and smoke degradation data on silica gel, the authors predicted that, for low-temperature regeneration, the loss in performance of a ventilation-cycle desiccant cooling system would be between 10 percent to 35 percent, in about eight years, with higher value under worst conditions.

  4. Potential Evaluation of Solar Heat Assisted Desiccant Hybrid Air Conditioning System

    NASA Astrophysics Data System (ADS)

    Tran, Thien Nha; Hamamoto, Yoshinori; Akisawa, Atsushi; Kashiwagi, Takao

    The solar thermal driven desiccant dehumidification-absorption cooling hybrid system has superior advantage in hot-humid climate regions. The reasonable air processing of desiccant hybrid air conditioning system and the utility of clean and free energy make the system environment friendly and energy efficient. The study investigates the performance of the desiccant dehumidification air conditioning systems with solar thermal assistant. The investigation is performed for three cases which are combinations of solar thermal and absorption cooling systems with different heat supply temperature levels. Two solar thermal systems are used in the study: the flat plate collector (FPC) and the vacuum tube with compound parabolic concentrator (CPC). The single-effect and high energy efficient double-, triple-effect LiBr-water absorption cooling cycles are considered for cooling systems. COP of desiccant hybrid air conditioning systems are determined. The evaluation of these systems is subsequently performed. The single effect absorption cooling cycle combined with the flat plate collector solar system is found to be the most energy efficient air conditioning system.

  5. Influence of Ventilation Ratio on Desiccant Air Conditioning System's Efficiency Performance

    NASA Astrophysics Data System (ADS)

    Tran, Thien Nha; Akisawa, Atsushi; Kashiwagi, Takao; Hamamoto, Yoshinori

    Ventilation air is a concern for engineers since ventilated air controls indoor air contamination; additional ventilation, however, increases the energy consumption of buildings. The study investigates the energy efficiency performance of the desiccant dehumidification air conditioning system in the context of ventilation for a hot-humid climate such as summer in Japan. The investigation focuses on the variable ratio of ventilation air as required by the application of air conditioning system. The COP of the desiccant air conditioning system is determined. The evaluation is subsequently performed by comparing the desiccant based system with the conventional absorption cooling system and the vapor compression cooling system. Based on 12 desiccant rotor simulations, it is found that the desiccant regeneration temperature required varies between 47°C to 85°C as ventilation ratio increases from 0. 0 to 100%, and up to 52. 5°C as the ventilation ratio achieves 14%. The heat required for regenerating desiccant accounts for 55% and higher of the system's total heat consumption; the system is expected to be energy efficient by using wasted heat from the absorption chiller for desiccant regeneration; and its energy efficiency expands as the ratio of ventilation air rises above 15% compared with the conventional absorption cooling system. The energy efficiency also benefits as the ratio rises beyond 70% against the conventional vapor compression cooling system.

  6. Evaporative Cooling and Dehumidification Garment for Portable Life Support Systems

    NASA Technical Reports Server (NTRS)

    Izenson, Michael; Chen, Weibo; Bue, Grant

    2013-01-01

    This paper describes the design and development of an innovative thermal and humidity control system for future space suits. The system comprises an evaporation cooling and dehumidification garment (ECDG) and a lithium chloride absorber radiator (LCAR). The ECDG absorbs heat and water vapor from inside the suit pressure garment, while the LCAR rejects heat to space without venting water vapor. The ECDG is built from thin, flexible patches with coversheets made of non-porous, water-permeable membranes that -enclose arrays of vapor flow passages. Water vapor from inside the spacesuit diffuses across the water permeable membranes, enters the vapor flow channels, and then flows to the LCAR, thus dehumidifying the internal volume of the space suit pressure garment. Additional water evaporation inside the ECDG provides cooling for sensible heat loads. -The heat released from condensation and absorption in the LCAR is rejected to the environment by thermal radiation. We have assembled lightweight and flexible ECDG pouches from prototypical materials and measured their performance in a series of separate effects tests under well-controlled, prototypical conditions. Sweating hot plate tests at typical space suit pressures show that ECDG pouches can absorb over 60 W/ft of latent heat and 20 W/ft of sensible heat from the pressure garment environment. These results are in good agreement with the predictions of our analysis models.

  7. Modeling of a solar-assisted hybrid absorption/desiccant system for applications in Puerto Rico and the Caribbean

    SciTech Connect

    Hernandez, H.R.; Gonzalez, J.E.; Khan, A.Y.

    1996-11-01

    This study is concerned with the feasibility of different arrangements of solar-assisted air conditioning systems for applications in Puerto Rico. The thermodynamic performance of an absorption system alone and coupled to a liquid or a solid desiccant dehumidification system was investigated under variable cooling load conditions. The dynamic modeling was based on heat and mass balances for the systems components. Simulations for climatic conditions in Puerto Rico show that average solar fractions of more than 85% can be achieved with both the absorption system and the hybrid systems for medium size cooling loads. Results indicate that higher coefficients of performance are obtained when the solar assisted absorption system is not coupled to a desiccant dehumidification system.

  8. Development of a Ventilation and Air-conditioning System using Fixed Bed Desiccant Units

    NASA Astrophysics Data System (ADS)

    Miyazaki, Takahiko; Akisawa, Atsushi; Ueda, Yuki; Shindoh, Shinji; Godo, Masazumi; Takatsuka, Takeshi

    The study investigated fixed bed desiccant units for ventilation and air-conditioning. The role of the system is the dehumidification of the outdoor fresh air to be supplied to an air-conditioned room. Hence, the latent heat load of the air-conditioner in the room can be mitigated. The system consisted of two pairs of a desiccant unit and a heat storage unit. The microwave irradiation to the desiccant unit was examined as a candidate of the regeneration method of the system, and the performance of the microwave regeneration was compared with that of the hot air regeneration in terms of the supply air humidity ratio, outdoor air based COP, and the process air temperatures. The results revealed the effects of the switching time and the irradiation timing on the performance of the microwave irradiation.

  9. Desiccant humidity control system

    NASA Technical Reports Server (NTRS)

    Amazeen, J. (Editor)

    1973-01-01

    A regenerable sorbent system was investigated for controlling the humidity and carbon dioxide concentration of the space shuttle cabin atmosphere. The sorbents considered for water and carbon dioxide removal were silica gel and molecular sieves. Bed optimization and preliminary system design are discussed along with system optimization studies and weight penalites.

  10. Desiccant Humidity Control System Using Waste Heat of Water Source Heat Pump

    NASA Astrophysics Data System (ADS)

    Wada, Kazuki; Mashimo, Kouichi; Takahashi, Mikio; Tanaka, Kitoshi; Toya, Saburo; Tateyama, Ryotaro; Miyamoto, Kazuhiro; Yamaguchi, Masahiro

    The authors hope to develop an air-conditioning system that processes the latent heat load and the sensible heat load separately. This would enable the efficiency of the chilling unit to be improved because the temperature of the chilled water used for cooling would be higher than normal. However, if lukewarm water is used, there is insufficient cooling and dehumidification. Therefore, a dehumidifier such as a desiccant air-conditioning system is needed. Using the waste heat generated when the desiccant air-conditioning system is in operation increases efficiency. The authors are developing a prototype desiccant humidity control system that makes use of the waste heat generated by a water source heat pump. This paper describes the results of an experiment that was conducted for this prototype based on the assumption that it would be installed in an office building. The dehumidification performance achieved was sufficient to process the indoor latent heat load. The prototype was able to adjust the indoor relative humidity from 40% to 60% under conditions in which the indoor latent heat load varied. Humidification without the use of water was possible even in the absence of an indoor latent heat load when the outdoor absolute humidity was 3.5 g/kg' or more.

  11. Field Demonstration of Active Desiccant-Based Outdoor Air Preconditioning Systems, Final Report: Phase 3

    SciTech Connect

    Fischer, J.

    2001-07-09

    This report summarizes an investigation of the performance of two active desiccant cooling systems that were installed as pilot systems in two locations--a college dormitory and a research laboratory--during the fall of 1999. The laboratory system was assembled in the field from commercially available Trane air-handling modules combined with a standard total energy recovery module and a customized active desiccant wheel, both produced by SEMCO. The dormitory system was a factory-built, integrated system produced by SEMCO that included both active desiccant and sensible-only recovery wheels, a direct-fired gas regeneration section, and a pre-piped Trane heat pump condensing section. Both systems were equipped with direct digital control systems, complete with full instrumentation and remote monitoring capabilities. This report includes detailed descriptions of these two systems, installation details, samples of actual performance, and estimations of the energy savings realized. These pilot sites represent a continuation of previous active desiccant product development research (Fischer, Hallstrom, and Sand 2000; Fischer 2000). Both systems performed as anticipated, were reliable, and required minimal maintenance. The dehumidification/total-energy-recovery hybrid approach was particularly effective in all respects. System performance showed remarkable improvement in latent load handling capability and operating efficiency compared with the original conventional cooling system and with the conventional system that remained in another, identical wing of the facility. The dehumidification capacity of the pilot systems was very high, the cost of operation was very low, and the system was cost-effective, offering a simple payback for these retrofit installations of approximately 5 to 6 years. Most important, the dormitory system resolved numerous indoor air quality problems in the dormitory by providing effective humidity control and increased, continuous ventilation air.

  12. Hybrid Type Humidity Control System Coupling a Desiccant Rotor in a Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Horibe, Akihiko; Takaki, Sadao; Inaba, Hideo; Haruki, Naoto

    This paper describes a new hybrid humidity control system that combines a desiccant rotor with a vapor compression refrigerator. This rotor uses a kind of advanced sorbent and desorption at low temperature below 50°C is possible. Therefore the rotor can be recovered by exhaust heat of a condenser. Applying the new hybrid system, we installed an experimental prototype and investigated its performance. As a result, dehumidification can be achieved even if the absolute humidity of the processing air is less than 0.002 kg/kg'. This suggests that water can be taken out from the exhausting air to humidify the returning air in winter. Furthermore, dehumidification efficiency is 4.1kg/kWh, system COP1.8 for the processing air 30°C, 62%RH. That corresponds with the summer weather condition. If it is winter, the dehumidification efficiency is 1.9kg/kWh, system COP0.97 for the processing air 22°C, 50%RH.

  13. A low-cost-solar liquid desiccant system for residential cooling

    NASA Astrophysics Data System (ADS)

    Ware, Joel D., III

    The use of liquid desiccants for dehumidification of heating, ventilation, and air conditioning (HVAC) process air is becoming a more promising concept as the drive for energy conservation continues to grow. Recently, liquid desiccant systems have been implemented on the commercial level in conjunction with evaporative coolers and have recorded energy savings upwards of 50%. The aim of this research is to test the potential liquid desiccant systems have on the residential level when paired with a conventional vapor compression cycle and to construct a system that would overcome some of its barriers to the residential market. A complete low-cost-solar liquid desiccant system was designed, constructed, and tested in the Off-Grid Zero Emissions Building (OGZEB) at the Florida State University. Key design characteristics include turbulent process air flow through the conditioner and airside heating in the regenerator. The system was tested in the two following ways: (1) for the energy savings while maintaining a constant temperature over a twenty four hour period and (2) for the energy savings over a single cooling cycle. The liquid desiccant system achieved a maximum energy savings of 38% over a complete day and 52% over a single cooling cycle. It was projected that the system has the potential to save 1064 kWh over the course of a year. When combined with a renewable source of heat for regeneration, liquid desiccant systems become very cost effective. The levelized cost of energy for the combination of the liquid desiccant system and solar thermal collectors was calculated to be 7.06 C/kWh with a payback period of 4.4 years. This research provides evidence of the technology's potential on the residential sector and suggests ways for it to become competitive in the market.

  14. Parametric study of the cyclic behaviour of a hygroscopic matrix in a desiccant airflow system

    NASA Astrophysics Data System (ADS)

    Ruivo, C. R.; Costa, J. J.; Figueiredo, A. R.

    2011-09-01

    The study of the transport phenomena in desiccant airflow systems has been addressed in numerous research works, some of them concerning combined processes of cooling, dehumidification and energy recovery. In this paper a detailed numerical model is used to simulate the behaviour of a parallel-plate channel, cyclically exposed to two airflows with different inlet conditions, the plate being composed by a substrate and a desiccant porous layer. The modelled channel is considered to be representative of a real channel of a hygroscopic matrix that is operating at steady state regime, like it occurs in desiccant or enthalpy rotors. The numerical results are treated in order to represent the global behaviour of the hygroscopic rotor under steady state conditions. Results of a parametric study are presented as maps of isovalues of the heat and mass transfer rates and of the outlet states of both airflows, considering channels of distinct wall thickness, of different thickness of the desiccant and the subtract layers, together with wide ranges of the rotation speed and of the wheel partition. The mapped results presented provide an overview of the operation characteristics of hygroscopic rotors, allowing a quick determination of the optimum range of values for relevant parameters, such as the rotation speed and the wheel partition. The model is thus an interesting tool for design and manufacture purposes of enthalpy and desiccant wheels.

  15. Experimental performance study of a proposed desiccant based air conditioning system.

    PubMed

    Bassuoni, M M

    2014-01-01

    An experimental investigation on the performance of a proposed hybrid desiccant based air conditioning system referred as HDBAC is introduced in this paper. HDBAC is mainly consisted of a liquid desiccant dehumidification unit integrated with a vapor compression system (VCS). The VCS unit has a cooling capacity of 5.27 kW and uses 134a as refrigerant. Calcium chloride (CaCl2) solution is used as the working desiccant material. HDBAC system is used to serve low sensible heat factor applications. The effect of different parameters such as, process air flow rate, desiccant solution flow rate, evaporator box and condenser box solution temperatures, strong solution concentration and regeneration temperature on the performance of the system is studied. The performance of the system is evaluated using some parameters such as: the coefficient of performance (COPa), specific moisture removal and energy saving percentage. A remarkable increase of about 54% in the coefficient of performance of the proposed system over VCS with reheat is achieved. A maximum overall energy saving of about 46% is observed which emphasizes the use of the proposed system as an energy efficient air conditioning system.

  16. Experimental performance study of a proposed desiccant based air conditioning system

    PubMed Central

    Bassuoni, M.M.

    2013-01-01

    An experimental investigation on the performance of a proposed hybrid desiccant based air conditioning system referred as HDBAC is introduced in this paper. HDBAC is mainly consisted of a liquid desiccant dehumidification unit integrated with a vapor compression system (VCS). The VCS unit has a cooling capacity of 5.27 kW and uses 134a as refrigerant. Calcium chloride (CaCl2) solution is used as the working desiccant material. HDBAC system is used to serve low sensible heat factor applications. The effect of different parameters such as, process air flow rate, desiccant solution flow rate, evaporator box and condenser box solution temperatures, strong solution concentration and regeneration temperature on the performance of the system is studied. The performance of the system is evaluated using some parameters such as: the coefficient of performance (COPa), specific moisture removal and energy saving percentage. A remarkable increase of about 54% in the coefficient of performance of the proposed system over VCS with reheat is achieved. A maximum overall energy saving of about 46% is observed which emphasizes the use of the proposed system as an energy efficient air conditioning system. PMID:25685475

  17. Performance assessment of radiant cooling system integrated with desiccant assisted DOAS with solar regeneration

    DOE PAGES

    Khan, Yasin; Singh, Gaurav; Mathur, Jyotirmay; ...

    2017-06-13

    The Radiant cooling system integrated with Dedicated Outdoor Air System (DOAS) is a viable substitution for conventional all air system in order to reduce primary energy consumption, as it decouples the cooling and ventilation task. In DOAS major portion of energy is consumed in cooling coil where it dehumidifies the process supply air. This study describes an alternate solution for dehumidification, with the substitution of the desiccant wheel with solar regeneration in place of a chilled water coil based dehumidifier. In this paper, simulations were carried out using EnergyPlus on a reference medium office building to investigate the contribution ofmore » solar energy towards the total energy consumption of desiccant assisted DOAS with radiant cooling system. To evaluate the system performance and energy saving potential, desiccant based DOAS is compared with cooling coil assisted DOAS integrated with Radiant cooling system. Simulations were carried out for different solar collector area to evaluate primary energy savings. Results indicate that from 7.4 % to 28.6 % energy saving (according to different collector area) can be achieved due to the solar regeneration in desiccant assisted DOAS, the impact of different solar collector area on potential of energy savings is also described.« less

  18. Open cycle liquid desiccant dehumidifier and hybrid solar/electric absorption refrigeration system. Annual report, January 1993--December 1993. Calendar year 1993

    SciTech Connect

    Nimmo, B.G.; Thornbloom, M.D.

    1995-04-01

    This annual report presents work performed during calendar year 1993 by the Florida Solar Energy Center under contract to the US Department of Energy. Two distinctively different solar powered indoor climate control systems were analyzed: the open cycle liquid desiccant dehumidifier, and an improved efficiency absorption system which may be fired by flat plate solar collectors. Both tasks represent new directions relative to prior FSEC research in Solar Cooling and Dehumidification.

  19. Development of a Dehumidification System for a Passive Sampler for Determining 1,3-Butadiene.

    PubMed

    Sakurai, Kenji; Miyake, Yuichi; Amagai, Takashi

    2016-09-01

    The passive sampler is a simple device for collecting gaseous compounds. It is affected by environmental conditions such as relative humidity, but a dehumidification system (DHS) has not been developed for it. We have developed a dehumidification device for the passive sampler for determining 1,3-butadiene. It consists of a passive sampler surrounded by a DHS consisting of a basket filled with granular magnesium perchlorate as the dehumidification agent. The passive sampler consists of a porous polytetrafluoroethylene tube packed with Carboxen 1000 adsorbent. We compared the amounts of water adsorbed on the Carboxen 1000 adsorbent in the presence and in the absence of the DHS; the results showed that the DHS prevented water from entering the sampler. Volatile organic compounds that entered the sampler were collected by the Carboxen 1000 adsorbent. In the case of 1,3-butadiene, much higher amounts were collected by the passive sampler with the DHS than without it. This may be due to interference of adsorption or acceleration of 1,3-butadiene degradation by the water-soluble oxidant on the surface of the Carboxen 1000 adsorbent.

  20. Solar Assisted Adsorptive Desiccant Cooling System

    NASA Astrophysics Data System (ADS)

    Ohkura, Masashi; Kodama, Akio

    Desiccant cooling processes can supply dry air by using lower temperature heat energy such as waste heat or solar heat. Especially, solar heat is useful heat source for the desiccant cooling since solar heat in summer tends to be surplus. This paper discusses the hourly cooling performance of the solar assisted desiccant cooling system, which consists of a desiccant wheel, a thermal wheel, two evaporative coolers, a cooling coil and flat plate solar water heater, assuming that the cooling system is applied to an office room of 250m3 in volume. The estimation indicated that the surface area needed to satisfy the dehumidifying performance in a sunny day was at least 30m2. Furthermore, surface area of 40m2 or larger provided a surplus dehumidifying performance causing a sensible cooling effect in evaporative cooler. Surface area of 30 m2 did not satisfy the dehumidifying performance required for high humidity condition, over 18.0g/kg(DA). The cooling demand of the cooling coil increased in such humidity condition due to the decrease in the sensible cooling effect of evaporative cooler. Auxiliary heater was required in a cloudy day since the temperature of water supplied from solar water heater of 40m2 did not reach sufficient level.

  1. Desiccant-Based Combined Systems: Integrated Active Desiccant Rooftop Hybrid System Development and Testing Final Report- Phase 4

    SciTech Connect

    Fischer, J

    2005-05-06

    This report summarizes the results of a research and development (R&D) program to design and optimize an active desiccant-vapor compression hybrid rooftop system. The primary objective was to combine the strengths of both technologies to produce a compact, high-performing, energy-efficient system that could accommodate any percentage of outdoor air and deliver essentially any required combination of temperature and humidity, or sensible heat ratio (SHR). In doing so, such a product would address the significant challenges imposed on the performance capabilities of conventional packaged rooftop equipment by standards 62 and 90.1 of the American Society of Heating, Refrigerating and Air-Conditioning Engineers. The body of work completed as part of this program built upon previous R&D efforts supported by the U.S. Department of Energy and summarized by the Phase 3b report ''Active Desiccant Dehumidification Module Integration with Rooftop Packaged HVAC Units'' (Fischer and Sand 2002), in addition to Fischer, Hallstrom, and Sand 2000; Fischer 2000; and Fischer and Sand 2004. All initial design objectives established for this development program were successfully achieved. The performance flexibility desired was accomplished by a down-sized active desiccant wheel that processes only a portion of the supply airflow, which is pre-conditioned by a novel vapor compression cycle. Variable-speed compressors are used to deliver the capacity control required by a system handling a high percentage of outdoor air. An integrated direct digital control system allows for control capabilities not generally offered by conventional packaged rooftop systems. A 3000-cfm prototype system was constructed and tested in the SEMCO engineering test laboratory in Columbia, MO, and was found to operate in an energy-efficient fashion relative to more conventional systems. Most important, the system offered the capability to independently control the supply air temperature and humidity content to

  2. Experimental study of the heat and mass transfer in a packed bed liquid desiccant air dehumidifier

    SciTech Connect

    Oeberg, V.; Goswami, D.Y.

    1998-11-01

    Desiccant cooling systems have the ability to provide efficient humidity and temperature control while reducing the electrical energy requirement for air conditioning as compared to a conventional system. Naturally, the desiccant air dehumidification process greatly influences the overall performance of the desiccant system. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer are of great interest. Due to the complexity of the dehumidification process, theoretical modeling relies heavily upon experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed absorption tower using high liquid flow rates. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of dehumidification, as well as the effectiveness of the dehumidification process are assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, a comparison between the findings in the present study and findings previously reported in the literature is made. The results obtained from this study make it possible to characterize the important variables which impact the system design.

  3. Low-Flow Liquid Desiccant Air Conditioning: General Guidance and Site Considerations

    SciTech Connect

    Kozubal, E.; Herrmann, L.; Deru, M.; Clark, J.

    2014-09-01

    Dehumidification or latent cooling in buildings is an area of growing interest that has been identified as needing more research and improved technologies for higher performance. Heating, ventilating, and air-conditioning (HVAC) systems typically expend excessive energy by using overcool-and-reheat strategies to dehumidify buildings. These systems first overcool ventilation air to remove moisture and then reheat the air to meet comfort requirements. Another common strategy incorporates solid desiccant rotors that remove moisture from the air more efficiently; however, these systems increase fan energy consumption because of the high airside pressure drop of solid desiccant rotors and can add heat of absorption to the ventilation air. Alternatively, liquid desiccant air-conditioning (LDAC) technology provides an innovative dehumidification solution that: (1) eliminates the need for overcooling and reheating from traditional cooling systems; and (2) avoids the increased fan energy and air heating from solid desiccant rotor systems.

  4. Composite desiccant structure

    DOEpatents

    Fraioli, Anthony V.; Schertz, William W.

    1987-01-01

    A composite formed of small desiccant particles retained in a dark matrix composed of a porous binder containing a transition metal oxide with pores to provide moisture transport with respect to the particles, and metallic fibers to remove the heat of condensation during dehumidification and provide heat for the removal of moisture during regeneration. The moisture absorbing properties of the composite may be regenerated by exposure of the dark matrix to solar radiation with dehumidification occurring at night.

  5. Composite desiccant structure

    DOEpatents

    Fraioli, A.V.; Schertz, W.W.

    1984-06-06

    This patent discloses a composite formed of small desiccant particles retained in a dark matrix composed of a porous binder containing a transition metal oxide with pores to provide moisture transport with respect to the particles, and metallic fibers to remove the heat of condensation during dehumidification and provide heat for the removal of moisture during regeneration. The moisture absorbing properties of the composite may be regenerated by exposure of the dark matrix to solar radiation with dehumidification occurring at night.

  6. Overview of Open-Cycle Desiccant Cooling Systems and Materials

    SciTech Connect

    Collier, R.; Arnold, F.; Barlow, R.

    1981-09-01

    This paper has presented a review of the thermodynamics of three desiccant cooling cycles: the ventilation cycle, the recirculation cycle, and the Dunkle cycle. For the ventilation cycle the qualitative effects of changes in the effectiveness of individual components were analyzed. There are two possible paths to improved dehumidifier performance: changing the design of dehumidifiers using currently available desiccants so as to increase effectiveness without increasing parasitic losses, or developing new desiccants specifically tailored for solar cooling applications. The later part of this paper has considered the second option. A list of desirable desiccant properties was defined, properties of currently used solid and liquid desiccants were compared to this list, and a hypothetical desiccant type that would give improved system performance was discussed.

  7. Experimental evaluation of commercial desiccant dehumidifier wheels

    SciTech Connect

    Slayzak, S.J.; Pesaran, A.A.; Hancock, C.E.

    1996-01-01

    The National Renewable Energy Laboratory is currently characterizing the state-of-the-art in desiccant dehumidifiers, the key component of desiccant cooling systems. The data are being obtained in our HVAC Equipment Test Facility in accordance with the proposed ASHRAE test standard. The experimental data will provide industry and end users with independent performance evaluation and the United States Department of Energy and NREL with the information necessary to assess advances in the energy savings potential of the technology. This paper proposes several figures of merit for evaluating performance. The results of these tests indicate that dehumidification capacity performance parameters can be correlated to process inlet air relative humidity.

  8. Low-Flow Liquid Desiccant Air-Conditioning: Demonstrated Performance and Cost Implications

    SciTech Connect

    Kozubal, E.; Herrmann, L.; Deru, M.; Clark, J.; Lowenstein, A.

    2014-09-01

    Cooling loads must be dramatically reduced when designing net-zero energy buildings or other highly efficient facilities. Advances in this area have focused primarily on reducing a building's sensible cooling loads by improving the envelope, integrating properly sized daylighting systems, adding exterior solar shading devices, and reducing internal heat gains. As sensible loads decrease, however, latent loads remain relatively constant, and thus become a greater fraction of the overall cooling requirement in highly efficient building designs, particularly in humid climates. This shift toward latent cooling is a challenge for heating, ventilation, and air-conditioning (HVAC) systems. Traditional systems typically dehumidify by first overcooling air below the dew-point temperature and then reheating it to an appropriate supply temperature, which requires an excessive amount of energy. Another dehumidification strategy incorporates solid desiccant rotors that remove water from air more efficiently; however, these systems are large and increase fan energy consumption due to the increased airside pressure drop of solid desiccant rotors. A third dehumidification strategy involves high flow liquid desiccant systems. These systems require a high maintenance separator to protect the air distribution system from corrosive desiccant droplet carryover and so are more commonly used in industrial applications and rarely in commercial buildings. Both solid desiccant systems and most high-flow liquid desiccant systems (if not internally cooled) add sensible energy which must later be removed to the air stream during dehumidification, through the release of sensible heat during the sorption process.

  9. Solar desalination system of combined solar still and humidification-dehumidification unit

    NASA Astrophysics Data System (ADS)

    Ghazy, Ahmed; Fath, Hassan E. S.

    2016-11-01

    Solar stills, as a simple technology, have many advantages such as simple design; unsophisticated fabrication; low capital and operation costs and easily maintained. However, their low daily production has put constraints on their usage. A radical improvement in the performance of solar stills can be achieved by the partial recovery of the energy losses from the glass cover of the still. This paper simulates a direct solar distillation system of combined solar still with an air heating humidification-dehumidification (HDH) sub-system. The main objective of the Still-HDH system is to improve the productivity and thermal efficiency of the conventional solar still by partially recovering the still energy losses to the ambient for additional water production. Various procedures have been employed to improve the thermal performance of the integrated system by recovering heat losses from one component in another component of the system. Simulations have been carried out for the performance of the Still-HDH system under different weather conditions. A comparison has been held between the Still-HDH system and a conventional solar still of the same size and under the same operating conditions.

  10. Performance Simulation of an Air-Heated Humidification Dehumidification Desalination System

    NASA Astrophysics Data System (ADS)

    He, W. F.; Han, D.

    2017-07-01

    This paper focus on an air-heated humidification dehumidification (HDH) desalination system driven by low grade waste heat. The working processes within the air-heated HDH desalination system are demonstrated, and the performance of the HDH desalination unit is gained and analyzed on the basis of the building mathematical models. In addition of the energy analysis, the entropy generation of the desalination system is also obtained to validate the energy efficiency. The simulation results show that the performance of the HDH desalination system is especially sensitive to the mass flow rate ratio between the working seawater and humid air. It was found that the actual maximum value of gained output ratio (GOR) is GOR=1.80 at the case of m sw /m da =0.68. Furthermore, the maximum value of GOR is consistent with the minimum entropy generation within the desalination, which validate the performance analysis in some extent. The obtained results provide some significant references for the design and optimization of the HDH desalination system.

  11. Study of Room Temperature and Humidity Control Method on Dehumidification System Reheated by Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Nakamura, Hiroo; Funakoshi, Sunao; Yokoyama, Hidenori; Morimoto, Motoo; Saito, Kiyoshi

    The new ways to control the humidity and the temperature of the room accurately during the dehumidification operation reheated by refrigeration cycle on room air conditioners using R 410A was investigated. The indoor heat exchanger is divided into a condensing part and an evaporating part by a dehumidification valve which is located between these two heat exchangers. The indoor air cooled and dehumidified by the evaporating part is heated by the condensing part. The dehumidification capacity increased according to increasing the compressor rotational speed. And the reheating capacity increased according to decreasing the outdoor fan rotational speed. So the humidity and the temperature of the room was controlled to the setting values exactly by regulating the compressor rotational speed and the outdoor fan rotational speed alternately.

  12. Experimental study on performance of celdek packed liquid desiccant dehumidifier

    NASA Astrophysics Data System (ADS)

    Kumar, Rakesh; Asati, A. K.

    2016-09-01

    Dehumidifier is the main component of liquid desiccant dehumidification system. Effect of the inlet parameters on various outlet parameters of the dehumidifier is studied in the present paper with structured pads as packing material and calcium chloride as liquid desiccant to process the air. The outlet parameters are change in specific humidity, mass transfer coefficient, moisture removal rate, air temperature, solution temperature, effectiveness and the corresponding inlet process parameters; mass flow rate of air, temperature of air, temperature and flow rate of desiccant solution. It is observed that mass transfer coefficient and moisture removal rate increase with increasing mass flow rate of the air and desiccant while these parameters decrease with increasing temperature of air and desiccant solution. Dehumidifier effectiveness gets increased with increasing solution flow rate. The present investigations are compared with the results of the researchers in the past.

  13. USAF Dehumidification Efforts for Corrosion Control

    DTIC Science & Technology

    2011-08-16

    Stored AGE Renewable energy powers dehumidification equipment (DH) DH maintains dry air in storage booths, protecting AGE equipment from...lighting also powered by renewable energy 11 CHP Shelters • Used to prevent corrosion on outer skin • Being developed for the F-22 at...DH can be Sheltered or Unsheltered • Air Dehydration Units - Uses a self rejuvenating desiccant wheel dehumidifier - Closed or open loop

  14. Desiccation-inducible genes are related to N(2)-fixing system under desiccation in a terrestrial cyanobacterium.

    PubMed

    Katoh, Hiroshi

    2012-08-01

    Terrestrial cyanobacteria have various desiccation-tolerant systems, which are controlled by desiccation tolerance-related genes. Anabaena (Nostoc) sp. strain PCC 7120 is a derivative of the terrestrial cyanobacterium Nostoc and is a useful strain for molecular biological analysis. To identify desiccation tolerance-related genes, we selected and disrupted various genes (all0801, all0875, alr3090, alr3800, all4052, all4477, and alr5182) and examined their gene expression patterns and predicted their functions. Analyses of gene disruptants showed that viability of the disruptants only decreased under N(2)-fixing conditions during desiccation, and the decrease in viability was negatively correlated with the gene expression pattern during desiccation. These data suggest that terrestrial cyanobacteria may acclimate to desiccation stress via N(2) fixation by using desiccation inducible genes, which are not only related to nitrogen fixation or nitrogen metabolism but also to other systems such as metabolism, transcription, and protein repair for protection against desiccation damage under nitrogen-fixing conditions. Further, a photosynthetic gene is required for desiccation tolerance. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

  15. Microporous coordination polymers as efficient sorbents for air dehumidification.

    PubMed

    Guo, Ping; Wong-Foy, Antek G; Matzger, Adam J

    2014-03-04

    Air drying is a widespread and critical industrial process. Removal of water from air is commonly accomplished by passage through a desiccant such as alumina; modest water capacity and energy intensive regeneration are limitations of currently used sorbents. Microporous coordination polymers (MCPs) are demonstrated here to be efficient desiccants for the dehumidification of air, and a comparison of their capacity, regenerability, and efficiency with commercial activated alumina is conducted. Complete regeneration using dry air with mild heating is achieved. The attainment of high capacity for the adsorption of water coupled to facile regeneration indicates that gas dehumidification may be an important application for MCPs.

  16. Active Desiccant-Based Preconditioning Market Analysis and Product Development

    SciTech Connect

    Fischer, J.

    2001-01-11

    The Phase 1 report (ORNL/Sub/94-SVO44/1), completed earlier in this program, involved a comprehensive field survey and market analysis comparing various specialized outdoor air handling units. This initial investigation included conventional cooling and reheat, conventional cooling with sensible recovery, total energy recovery systems (passive desiccant technology) and various active desiccant systems. The report concluded that several markets do promise a significant sales opportunity for a Climate Changer-based active desiccant system offering. (Climate Changer is a registered trademark of Trane Company.) This initial market analysis defined the wants and needs of the end customers (design engineers and building owners), which, along with subsequent information included in this report, have been used to guide the determination of the most promising active desiccant system configurations. This Phase 2 report begins with a summary of a more thorough investigation of those specific markets identified as most promising for active desiccant systems. Table 1 estimates the annual sales potential for a cost-effective product line of active desiccant systems, such as that built from Climate Changer modules. The Product Development Strategy section describes the active desiccant system configurations chosen to best fit the needs of the marketplace while minimizing system options. Key design objectives based on market research are listed in this report for these active desiccant systems. Corresponding performance goals for the dehumidification wheel required to meet the overall system design objectives are also defined. The Performance Modeling section describes the strategy used by SEMCO to design the dehumidification wheels integrated into the prototype systems currently being tested as part of the U.S. Department of Energy's Advanced Desiccant Technology Program. Actual performance data from wheel testing was used to revise the system performance and energy analysis

  17. Development of an Integrated Residential Heating, Ventilation, Cooling, and Dehumidification System for Residences

    SciTech Connect

    Hoeschele, M.A.; D.A. Springer

    2008-06-18

    The Need and the Opportunity Codes such as ASHRAE 90.2 and IECC, and programs such as Energy Star and Builders Challenge, are causing new homes to be built to higher performance standards. As a result sensible cooling loads in new homes are going down, but indoor air quality prerogatives are causing ventilation rates and moisture loads to increase in humid climates. Conventional air conditioners are unable to provide the low sensible heat ratios that are needed to efficiently cool and dehumidify homes since dehumidification potential is strongly correlated with cooling system operating hours. The project team saw an opportunity to develop a system that is at least as effective as a conventional air conditioner plus dehumidifier, removes moisture without increasing the sensible load, reduces equipment cost by integrating components, and simplifies installation. Project Overview Prime contractor Davis Energy Group led a team in developing an Integrated Heating, Ventilation, Cooling, and Dehumidification (I-HVCD) system under the DOE SBIR program. Phase I and II SBIR project activities ran from July 2003 through December 2007. Tasks included: (1) Mechanical Design and Prototyping; (2) Controls Development; (3) Laboratory and Field Testing; and (4) Commercialization Activities Technology Description. Key components of the prototype I-HVCD system include an evaporator coil assembly, return and outdoor air damper, and controls. These are used in conjunction with conventional components that include a variable speed air handler or furnace, and a two-stage condensing unit. I-HVCD controls enable the system to operate in three distinct cooling modes to respond to indoor temperature and relative humidity (RH) levels. When sensible cooling loads are high, the system operates similar to a conventional system but varies supply airflow in response to indoor RH. In the second mode airflow is further reduced, and the reheat coil adds heat to the supply air. In the third mode, the

  18. Analysis of a desiccant aided evaporative cooling system

    SciTech Connect

    Wang, S.H.

    1984-01-01

    The typically humid climate of the southeastern portion of the United States is not amenable to present evaporative cooling systems. This study seeks to develop a system that would include drying the humid air (by using a desiccant) for efficient use in the evaporative cooler. The analysis employs a high efficiency desiccant that could be regenerated by solar energy and uses designs engaging an indoor comfort range technique instead of a design-point to achieve realistic optimum systems. The simulated results compare well with three previously constructed prototypes and the study also provides a design, operation, and sensitivity analysis for a residential cooling example. Finally, based on energy consumption, a comparison between typical vapor compression air conditioners and this desiccant aided evaporative cooling system is made. Results indicate that the evaporative system consumes less total energy.

  19. The performance of various types of regenerators for liquid desiccants

    SciTech Connect

    Peng, C.S.P.; Howell, J.R.

    1984-05-01

    A solar-assisted cooling system is very attractive because the available solar energy and the required cooling load are generally in phase. Of all the solar-assisted cooling methods developed to date, the absorption cooling system and the desiccant dehumidification/evaporative cooling system are considered most suitable for solar or other low-grade thermal energy applications. An efficient liquid desiccant cooling/dehumidification system has been proposed and analyzed by the authors. This system promises low operating parasitic power requirements, and it accepts thermal energy at a temperature as low as 60/sup 0/C, which can be efficiently obtained in a flat-plate solar collector. A schematic diagram of this system is shown. Briefly, this system operates by bringing outside air plus recycled air in contact with a liquid desiccant solution (triethylene glycol, in this case) in the absorber unit. A portion of the dried air is then cycled through the evaporator in contact with the falling water film, thus cooling the water. Cooled water from the evaporator is recycled to cool the absorber unit and hold down the desiccant temperature, and and thereby produce cool and dry air.

  20. Effect on air quality and flow rate of fresh water production in humidification and dehumidification system

    NASA Astrophysics Data System (ADS)

    Rajasekar, K.; Pugazhenthi, R.; Selvaraju, A.; Manikandan, T.; Saravanan, R.

    2017-03-01

    Water is the vital need of any living organisms of the world when water fails, functions of nature cease the world. The water scarcity is one of the major problems to be faced by the developing world, which indicates a critical need to develop inexpensive small-scale desalination technologies. The cost of the desalination process takes more, so the world expecting the desalination plants with minimum operating cost, so the utilization of renewable energy source is a preferable one. This research article provides a glimpse of an overview of the humidification-dehumidification (HDH) based desalination method which uses the solar energy. The HDH based desalination method monitored and evaluated the performance parameters, i.e. mass flow rates of water and air.

  1. Study of the application of solar chemical dehumidification system to wind tunnel facilities of NASA Lewis Research Center at Cleveland, Ohio

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Energy utilization and cost payback analyses were prepared for proposed modifications. A 50,000 CFM standard compact packaged solid desiccant dehumidifier utilizing high temperature hot water (HTHW) for desiccant regeneration was added. The HTHW is generated by utilizing solar energy and is stored in a storage tank. A steam boiler is provided as a back-up for the solar system. A 50,000 CFM standard compact package solid desiccant dehumidifier utilizing high temperature hot water (HTHW) for desiccant regeneration was added. The HTHW is generated by utilizing a steam boiler and a heat exchanger and is stored in a storage tank.

  2. Desiccant outdoor air preconditioners maximize heat recovery ventilation potentials

    SciTech Connect

    Meckler, M.

    1995-12-31

    Microorganisms are well protected indoors by the moisture surrounding them if the relative humidity is above 70%. They can cause many acute diseases, infections, and allergies. Humidity also has an effect on air cleanliness and causes the building structure and its contents to deteriorate. Therefore, controlling humidity is a very important factor to human health and comfort and the structural longevity of a building. To date, a great deal of research has been done, and is continuing, in the use of both solid and liquid desiccants. This paper introduces a desiccant-assisted system that combines dehumidification and mechanical refrigeration by means of a desiccant preconditioning module that can serve two or more conventional air-conditioning units. It will be demonstrated that the proposed system, also having indirect evaporative cooling within the preconditioning module, can reduce energy consumption and provide significant cost savings, independent humidity and temperature control, and, therefore, improved indoor air quality and enhanced occupant comfort.

  3. Solar-powered saline sorbent-solution heat pump/storage system

    NASA Astrophysics Data System (ADS)

    Robison, H.; Houston, S.

    Coastal Energy Laboratory Chemical Heat Pump (CEL-CHEAP) is a redesigned open-cycle liquid desiccant air conditioner. Heat is discharged to shallow-well water by dehumidification-humidification for cooling and extracted by humidification-dehumidification for heating. Direct solar radiation concentrates the desiccant. For continuous operation, a small uninsulated tank stores concentrated solution. This chemical heat pump needs no mechanical compressor, condenser, vacuum system, or pressure system. The collector-regenerators are inexpensive. The refrigerant is water and the desiccant is calcium chloride. First cost and operating expenses are very low.

  4. Desiccant cooling using unglazed transpired solar collectors

    NASA Astrophysics Data System (ADS)

    Pesaran, A. A.; Wipke, K.

    1992-05-01

    The use of unglazed solar collectors for desiccant regeneration in a solid desiccant cooling cycle was investigated because these collectors are lower in cost than conventional glazed flat-plate collectors. Using computer models, the performance of a desiccant cooling ventilation cycle integrated with either unglazed transpired collectors or conventional glazed flat-plate collectors was obtained. We found that the thermal performance of the unglazed system was lower than the thermal performance of the glazed system because the unglazed system could not take advantage of the heat of adsorption released during the dehumidification process. For a 3-ton cooling system, although the area required for the unglazed collector was 69 percent more than that required for the glazed collector, the cost of the unglazed collector array was 44 percent less than the cost of the glazed collector array. The simple payback period of the unglazed system was half of the payback period of the glazed collector when compared to an equivalent gas-fired system. Although the use of unglazed transpired collectors makes economic sense, some practical considerations may limit their use in desiccant regeneration.

  5. Desiccant cooling using unglazed transpired solar collectors

    SciTech Connect

    Pesaran, A.A. ); Wipke, K. )

    1992-05-01

    The use of unglazed solar collectors for desiccant regeneration in a solid desiccant cooling cycle was investigated because these collectors are lower in cost than conventional glazed flat-plate collectors. Using computer models, the performance of a desiccant cooling ventilation cycle integrated with either unglazed transpired collectors or conventional glazed flat-plate collectors was obtained. We found that the thermal performance of the unglazed system was lower than the thermal performance of the glazed system because the unglazed system could not take advantage of the heat of adsorption released during the dehumidification process. For a 3-ton cooling system, although the area required for the unglazed collector was 69% more than that required for the glazed collector, the cost of the unglazed collector array was 44% less than the cost of the glazed collector array. The simple payback period of the unglazed system was half of the payback period of the glazed collector when compared to an equivalent gas-fired system. Although the use of unglazed transpired collectors makes economic sense, some practical considerations may limit their use in desiccant regeneration. 8 refs.

  6. Characterization of a starch based desiccant wheel dehumidifier

    NASA Astrophysics Data System (ADS)

    Beery, Kyle Edward

    Starch, cellulose, and hemicellulose have an affinity for water, and adsorb water vapor from air. Materials made from combinations of these biobased sugar polymers also have been found to possess adsorptive properties. An interesting possible application of these starch-based adsorbents is the desiccant wheel dehumidifier. The desiccant wheel dehumidifier is used in conjunction with a standard air conditioning system. In this process, ambient air is passed through a stationary section while a wheel packed with desiccant rotates through that section. The desiccant adsorbs humidity (latent load) from the air, and the air conditioning system then cools the air (sensible load). Several starch based adsorbents were developed and tested for adsorptive capacity in a new high throughput screening system. The best formulations from the high throughput screening system, also taking into account economic considerations and structural integrity, were considered for use in the desiccant wheel dehumidifier. A suitable adsorbent was chosen and formulated into a matrix structure for the desiccant wheel system. A prototype desiccant wheel system was constructed and the performance was investigated under varying regeneration temperatures and rotation speeds. The results from the experiments showed that the starch based desiccant wheel dehumidification system does transfer moisture from the inlet process stream to the outlet regeneration stream. The DESSIM model was modified for the starch based adsorbent and compared to the experimental results. Also, the results when the wheel parameters were varied were compared to the predicted results from the model. The results given by the starch based desiccant wheel system show the desired proof of concept.

  7. Design of a test facility for gas-fired desiccant-based air conditioning systems

    SciTech Connect

    Jalalzadeh-Azar, A.A.; Steele, W.G.; Hodge, B.K.

    1996-12-31

    The design of a facility for testing desiccant-based air conditioning systems is presented. The determination of the performance parameters of desiccant systems is discussed including moisture removal capacity, latent and total cooling capacities, and efficiency indexes. The appropriate procedures and key measurements for determining these parameters are identified using uncertainty analysis.

  8. Development of a desiccated cadaver delivery system to apply entomopathogenic nematodes for control of soil pests

    USDA-ARS?s Scientific Manuscript database

    Pentomopathogenic nematodes may be more capable of controlling soil pests when they are harbored by desiccated cadavers. A small-scale system was developed from a modified crop seed planter to effectively deliver desiccated nematode-infected cadavers into the soil. The system mainly consists of a me...

  9. A Field-Test of Solar Assisted Adsorptive Desiccant Cooling System

    NASA Astrophysics Data System (ADS)

    Ohkura, Masashi; Kodama, Akio; Hirose, Tsutomu

    A field-test of solar assisted desiccant evaporative cooling process has been carried out, which is a quite attractive cooling / dehumidification process considering various environmental problems caused by conventional electricity driven air conditioners. The process performance has been examined by means of temperature drop between outside air and supply air and COPs (COP value based on solar irradiation). This cooling performance was strongly influenced by solar irradiation and ambient air condition. Stable irradiation produced a higher regeneration temperature resulting higher dehumidifying performance. At one day with as table solar irradiation, the cooling process could produce cool supply air of 18.7°C against the ambient air of 30.1°C and averaged COP, was 0.41. On the other hand, unstable irradiation due to some clouds made the dehumidifying performance lower. However, decrease in the cooling performance was small compared to that obtained at the stable irradiation condition. This is due to buffering by thermal storage of the water circulating in solar collectors. Influence of ambient humidity on the cooling performance was rather serious. At higher humidity condition, the amount of dehumidified water became larger due to increase of effective adsorption capacity of the desiccant rotor. However, the temperature drop was decreased to 6.9°C. This behavior was mainly due to simultaneous increase of humidity and temperature in the dehumidified air. In this situation, an effective evaporation in the following water spray evaporative cooler did not occur.

  10. Impact of ambient pressure on performance of desiccant cooling systems

    SciTech Connect

    Pesaran, A.A.

    1991-12-01

    The impact of ambient pressure on the performance of the ventilation cycle desiccant cooling system and its components was studied using computer simulations. The impact of ambient pressure depended on whether the system was designed for fixed-mass flow rate or fixed-volume flow rate operation. As ambient pressure decreased from 1.0 to 0.8 atm, the system thermal coefficient of performance increased by 8% for both fixed-mass and fixed-volume flow rate, the cooling capacity of the system (in kW) was decreased by 14% for the fixed-volume flow rate system and increased by 7% for the fixed-mass flow rate system, the electric power requirements for the system with fixed-volume flow rate did not change, and the electric power requirement for the fixed-mass flow rate system increased by 44%. The overall coefficient of performance increased up to 5% for the fixed-volume flow rate systems, and decreased up to 4% for the fixed-mass flow rate system. 16 refs.

  11. Solar space heating and cooling by selective use of the components of a desiccant cooling system

    NASA Astrophysics Data System (ADS)

    Abbud, Ihsan Aladdin

    The economic advantages of by-passing various components of a desiccant cooling system under conditions not requiring their use are estimated by evaluating the annual costs of heating and cooling a commercial building in three representative U.S. cities. Life-cycle costs of systems employing solar heat for space heating and desiccant regeneration are compared with those using electric heat. The costs of purchasing and operating heating and desiccant cooling systems, with and without solar heat supply, are compared with those employing conventional heating and vapor compression cooling. The conditions under which commercial buildings can be cooled with desiccant systems at costs competitive with conventional systems are identified. A commercially available vapor compression air conditioner is used as a standard of comparison for energy consumption and room comfort. Heating and cooling requirements of the building are determined by use of the BLAST computer model in a simulation of long term system operation. Performance of the desiccant cooling system and life cycle savings obtained by its use are determined by simulation employing the TRNSYS computer model. TRNSYS compatible subroutines are developed to simulate operation of the desiccant equipment, the building, and the controllers that operate and monitor the system components. The results are presented in tabular and graphical form. This study shows that in the widely different climates represented in Los Angeles, New York, and Miami, by-passing various components in the desiccant cooling system when they are not needed is economically advantageous. Operation cost of the complete system decreased by 47.3% in Los Angeles, by 30.9% in New York City, and by 23.9% in Miami by not operating the desiccant wheel and other elements. The ventilation desiccant cooling system has major economic advantage over conventional systems under conditions of moderate humidity, as in Los Angeles and New York City. In Miami, however

  12. Documenting the Effectiveness of Cosorption of Airborne Contaminants by a Field-Installed Active Desiccant System: Final Report - Phase 2D

    SciTech Connect

    Fischer, J

    2003-01-23

    were operated in a recirculation mode. (3) Almost all major medical, university, and research facilities face the dilemma that the air exhausted from a building exits near the intake of another building. As a result, contaminants exhausted outdoors are pulled back into the same or an adjacent building. The removal of contaminants from outdoor air that an active desiccant system offers would be attractive to applications in such cases. The primary objective of this research project was to quantify the ability of the SEMCO composite desiccant dehumidification wheel to purify outdoor and recirculated air streams by removing gaseous contaminants commonly encountered in actual applications. This contaminant removal is provided simultaneously with dehumidification (removing the latent load) of these air streams at conditions encountered in HVAC applications. This research builds upon initial seed work completed by the Georgia Tech Research Institute (GTRI) during 1993 (Bayer and Downing 1993).

  13. Mathematical Modeling of Dual Layer Shell Type Recuperation System for Biogas Dehumidification

    NASA Astrophysics Data System (ADS)

    Gendelis, S.; Timuhins, A.; Laizans, A.; Bandeniece, L.

    2015-12-01

    The main aim of the current paper is to create a mathematical model for dual layer shell type recuperation system, which allows reducing the heat losses from the biomass digester and water amount in the biogas without any additional mechanical or chemical components. The idea of this system is to reduce the temperature of the outflowing gas by creating two-layered counter-flow heat exchanger around the walls of biogas digester, thus increasing a thermal resistance and the gas temperature, resulting in a condensation on a colder surface. Complex mathematical model, including surface condensation, is developed for this type of biogas dehumidifier and the parameter study is carried out for a wide range of parameters. The model is reduced to 1D case to make numerical calculations faster. It is shown that latent heat of condensation is very important for the total heat balance and the condensation rate is highly dependent on insulation between layers and outside temperature. Modelling results allow finding optimal geometrical parameters for the known gas flow and predicting the condensation rate for different system setups and seasons.

  14. Gas-fired desiccant system for retail super center

    SciTech Connect

    Spears, J.W.; Judge, J.

    1997-10-01

    Concerns about indoor air quality have led to increasing outside air requirements that have prompted HVAC system designers to rethink how to handle outside air. The resulting increase in latent load can cause a variety of problems such as uncomfortably high humidity, mold and mildew, sweating ducts and higher energy cost. These problems occur not only in very humid climates but also in moderate climates during the swing season when the sensible load is low and the outside humidity is high. This combined with increasing concern for occupant comfort has led engineers to look for HVAC designs that provide good temperature and humidity control while still providing adequate quantities of outside air ventilation. This article describes the results of a one-year monitored evaluation of a gas-fired desiccant makeup air system used in a Wal-Mart super center. The system provides continuous fresh-air ventilation and independent temperature and humidity control. It also demonstrates the potential for energy savings and reduced first cost of the HVAC system. This approach, investigated by the owners` design team and independently monitored and verified in this Gas Research Institute-funded field study, has proven to be a cost-effective solution to meeting the new ventilation standard.

  15. Study of parameters affecting the performance of solar desiccant cooling systems

    SciTech Connect

    Pesaran, A A; Hoo, E A

    1993-01-01

    The performance of a solar desiccant cooling system depends on the performance of its components, particularly the desiccant dehumidifier and solar collectors. The desiccant dehumidifier performance is affected by the properties of the desiccant, particularly the shape of the isotherm and the regeneration temperature. The performance of a solar collector, as one would expect, depends on its operating temperature, which is very close to the desiccant regeneration temperature. The purpose of this study was to identify the desiccant isotherm shape (characterized by separation factor) that would result in the optimum performance - based on thermal coefficient of performance and cooling capacity - of a desiccant cooling cycle operating in ventilation mode. Different regeneration temperatures ranging from 65{degree}C to 160{degree}C were investigated to identify the corresponding optimum isotherm shape at each. Thermal COP dictates the required area of the solar collectors, and the cooling capacity is an indication of the size and cost of the cooling equipment. Staged and no-staged regeneration methods were studied.

  16. Study of parameters affecting the performance of solar desiccant cooling systems

    SciTech Connect

    Pesaran, A.A.; Hoo, E.A.

    1993-01-01

    The performance of a solar desiccant cooling system depends on the performance of its components, particularly the desiccant dehumidifier and solar collectors. The desiccant dehumidifier performance is affected by the properties of the desiccant, particularly the shape of the isotherm and the regeneration temperature. The performance of a solar collector, as one would expect, depends on its operating temperature, which is very close to the desiccant regeneration temperature. The purpose of this study was to identify the desiccant isotherm shape (characterized by separation factor) that would result in the optimum performance - based on thermal coefficient of performance and cooling capacity - of a desiccant cooling cycle operating in ventilation mode. Different regeneration temperatures ranging from 65[degree]C to 160[degree]C were investigated to identify the corresponding optimum isotherm shape at each. Thermal COP dictates the required area of the solar collectors, and the cooling capacity is an indication of the size and cost of the cooling equipment. Staged and no-staged regeneration methods were studied.

  17. An effective desiccant system to regulate the humidity inside the chambers of the solid dosage forms.

    PubMed

    Lehto, Vesa-Pekka; Erling, Ida

    2007-11-01

    The most common way to protect moisture-sensitive pharmaceutical powders is to utilize protective packaging. However, the most convenient package materials are all permeable to water molecules to some extent and limited protection is normally achieved with this arrangement even though desiccants are employed. In the present study we introduce a novel system that can regulate the internal humidity of the containers used with solid dosage forms for a desired time at a requested level. Instead of the widely used solid adsorbents the system utilizes saturated salt solutions loaded in desiccant bags made of various polymer materials with appropriate permeation properties. By utilizing salt solutions the size of the desiccant bag can be further reduced. A wide variety of commonly used powder chambers and desiccant bags are tested, proving the effectiveness of the introduced system.

  18. Performance Assessment of a Desiccant Cooling System in a CHP Application with an IC Engine

    SciTech Connect

    Jalalzadeh-Azar, A. A.; Slayzak, S.; Judkoff, R.; Schaffhauser, T.; DeBlasio, R.

    2005-04-01

    Performance of a desiccant cooling system was evaluated in the context of combined heat and power (CHP). The baseline system incorporated a desiccant dehumidifier, a heat exchanger, an indirect evaporative cooler, and a direct evaporative cooler. The desiccant unit was regenerated through heat recovery from a gas-fired reciprocating internal combustion engine. The system offered sufficient sensible and latent cooling capacities for a wide range of climatic conditions, while allowing influx of outside air in excess of what is typically required for commercial buildings. Energy and water efficiencies of the desiccant cooling system were also evaluated and compared with those of a conventional system. The results of parametric assessments revealed the importance of using a heat exchanger for concurrent desiccant post cooling and regeneration air preheating. These functions resulted in enhancement of both the cooling performance and the thermal efficiency, which are essential for fuel utilization improvement. Two approaches for mixing of the return air and outside air were examined, and their impact on the system cooling performance and thermal efficiency was demonstrated. The scope of the parametric analyses also encompassed the impact of improving the indirect evaporative cooling effectiveness on the overall cooling system performance.

  19. Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers.

    PubMed

    Tu, Y D; Wang, R Z; Ge, T S; Zheng, X

    2017-01-12

    Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8-3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump's efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications.

  20. Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers

    NASA Astrophysics Data System (ADS)

    Tu, Y. D.; Wang, R. Z.; Ge, T. S.; Zheng, X.

    2017-01-01

    Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8–3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump’s efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications.

  1. Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers

    PubMed Central

    Tu, Y. D.; Wang, R. Z.; Ge, T. S.; Zheng, X.

    2017-01-01

    Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8–3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump’s efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications. PMID:28079171

  2. Dehumidification via membrane separation for space-based applications

    NASA Technical Reports Server (NTRS)

    Gienger, Jane Kucera; Ray, Roderick J.; Chullen, Cinda

    1988-01-01

    The paper describes the development of a membrane-based dehumidification process for space-based applications, such as spacecraft cabins and EVA space suits. Results presented are from: (1) screening tests conducted to determine the efficacy of various membranes to separate water vapor from air, and (2) parametric and long-term tests of membranes operated at conditions that simulate the range of environmental conditions (e.g., temperature and relative humidity) expected in the planned Space Station. Also included in this paper is a discussion of preliminary designs of membrane-based dehumidification processes for the Space Station and EVA space suits. These designs result in compact and energy-efficient systems that offer significant advantages over conventional dehumidification processes.

  3. Dehumidification via membrane separation for space-based applications

    NASA Technical Reports Server (NTRS)

    Gienger, Jane Kucera; Ray, Roderick J.; Chullen, Cinda

    1988-01-01

    The paper describes the development of a membrane-based dehumidification process for space-based applications, such as spacecraft cabins and EVA space suits. Results presented are from: (1) screening tests conducted to determine the efficacy of various membranes to separate water vapor from air, and (2) parametric and long-term tests of membranes operated at conditions that simulate the range of environmental conditions (e.g., temperature and relative humidity) expected in the planned Space Station. Also included in this paper is a discussion of preliminary designs of membrane-based dehumidification processes for the Space Station and EVA space suits. These designs result in compact and energy-efficient systems that offer significant advantages over conventional dehumidification processes.

  4. Performance assessment and transient optimization of multi-stage solid desiccant air conditioning systems with building PV/T integration

    NASA Astrophysics Data System (ADS)

    Gadalla, Mohamed; Saghafifar, Mohammad

    2016-09-01

    One of the popular solar air conditioning technologies is desiccant air conditioning. Nonetheless, single stage desiccant air conditioning systems' coefficient of performance (COP) are relatively low. Therefore, multi-stage solid desiccant air conditioning systems are recommended. In this paper, an integrated double-stage desiccant air conditioning systems and PV/T collector is suggested for hot and humid climates such as the UAE. The results for the PV/T implementation in the double-stage desiccant cooling system are assessed against the PV/T results for a single-stage desiccant air conditioning system. In order to provide a valid comparative evaluation between the single and double stage desiccant air conditioning systems, an identical PV/T module, in terms of dimensions, is incorporated into these systems. The overall required auxiliary air heating is abated by 46.0% from 386.8 MWh to 209.0 MWh by replacing the single stage desiccant air conditioning system with the proposed double stage configuration during June to October. Moreover, the overall averaged solar share during the investigated months for the single and double stage systems are 36.5% and 43.3%.

  5. Vapor pressures of the aqueous desiccants

    SciTech Connect

    Chung, T.W.; Luo, C.M.

    1999-09-01

    The vapor pressures of the aqueous desiccants lithium chloride, lithium bromide, calcium chloride, ethylene glycol, propylene glycol, and their mixtures were measured at their typical operating concentrations and at temperatures from 298 K to 313 K. The experimental data were fitted to an Antoine type of equation, ln[P(kPa)] = A {minus} B/[T(K) + C], where A, B, and C are constants and are concentration dependent. Vapor pressure data were further used to predict the effectiveness of dehumidification in liquid desiccant dehumidifiers.

  6. Desiccant Enhanced Evaporative Air-Conditioning (DEVap): Evaluation of a New Concept in Ultra Efficient Air Conditioning

    SciTech Connect

    Kozubal, E.; Woods, J.; Burch, J.; Boranian, A.; Merrigan, T.

    2011-01-01

    NREL has developed the novel concept of a desiccant enhanced evaporative air conditioner (DEVap) with the objective of combining the benefits of liquid desiccant and evaporative cooling technologies into an innovative 'cooling core.' Liquid desiccant technologies have extraordinary dehumidification potential, but require an efficient cooling sink. DEVap's thermodynamic potential overcomes many shortcomings of standard refrigeration-based direct expansion cooling. DEVap decouples cooling and dehumidification performance, which results in independent temperature and humidity control. The energy input is largely switched away from electricity to low-grade thermal energy that can be sourced from fuels such as natural gas, waste heat, solar, or biofuels.

  7. [Optimization analysis of ventilation and dehumidification in manned spacecraft].

    PubMed

    Ji, X; Liang, X G; Ren, J X; Zhang, X R; Xu, X H

    2001-08-01

    To achieve the optimized design of system operational parameters and system components in air ventilation and dehumidification of manned spacecraft. Mathematical-physical model of air ventilation and dehumidification system was established. Through the design of optimal operational parameters for system performance, heat and moisture in the cabin of manned spacecraft could be removed effectively, dewing could be prevented, and the comfort demand of the astronauts could be met. Equivalent mass of the system in different operational parameters and system components was analyzed by calculation. The dew point temperature and the comfortability depended on the temperature and humidity of the influx, ventilation rate, and evaporation of moisture in the cabin. There were two ways to control the operational parameters of air ventilation and dehumidification system. The method based on controlling temperature didn't use recuperative heat exchangers in the loop, and the system structure for the design was simple, but it didn't meet the requirement of dissipating moisture in some conditions. The other method was based on controlling the moisture, and it could steadily keep the dew point temperature in the cabin and control the occurrence of dew. But the system structure of this design was relatively complex. Mass and power consumption of the system could be reduced by selecting appropriate parameters and adopting the measures of optimization.

  8. Improvement of Dehumidification Performance on Room Air Conditioner Adopting Dehumidification Method Reheated by Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Nakamura, Hiroo; Funakoshi, Sunao; Yokoyama, Hidenori; Morimoto, Motoo; Saito, Kiyoshi

    The ways to increase dehumidification capacity during the dehumidification operation reheated by refrigeration cycle on room air conditioners using R 410A was investigated, keeping electric power consumption lower, noise level lower and outlet air temperature constant. The indoor heat exchanger is divided into a condensing part and an evaporating part by a dehumidification valve which is located between these two heat exchangers. The cooled and dehumidified indoor air is heated by the condensing part. The noise occurred from the two-phase refrigerant flow passing through this valve. So the compressor rotational speed was increased properly to increase dehumidification capacity. Moreover a new dehumidification valve was developed to reduce the refrigerant flow noise. This valve has two expansion processes and each expansion process has plural notch throttles. As the result, 1.5 times dehumidification capacity was gained, keeping lower electric power consumption, lower noise level and constant outlet air temperature.

  9. Application of Heat Pump Dehumidification : A Case Study : Drying Lumber at Diamond Wood Products.

    SciTech Connect

    Wilson, James B.

    1990-09-01

    A case study was conducted of a new dehumidification kiln used for drying four-quarter red alder. To determine the energy and drying costs, the study included the measurement of all process parameters such as electricity and natural gas use, water extraction, wet- and dry-bulb temperatures, venting, and total drying. For comparative purposes wood from the same source was dried in a conventional kiln and similar measurements were taken. Dehumidification equipment is essentially a heat recovery system based on a refrigeration unit that condenses the water vapor in the kiln onto a cold coil where the heat of condensation is transferred to the refrigerant. The heat in the refrigerant is then pumped back into the kiln to maintain drying. The potential exists to reduce dehumidification drying costs by following recommended changes to equipment and operation. There were a number of reasons why the dehumidification kiln did not function as expected, some of which can be corrected to improve both energy efficiency and drying cost. Although the dehumidification kiln studied did not provide the drying cost and energy savings expected, dehumidification drying of wood should not be excluded as an alternative drying method when considering new equipment for most lumber species. A properly designed and installed system can offer significant energy and cost savings over conventional kilns. 10 figs., 11 tabs.

  10. Understanding desiccation tolerance using the resurrection plant Boea hygrometrica as a model system.

    PubMed

    Mitra, Jayeeta; Xu, Guanghui; Wang, Bo; Li, Meijing; Deng, Xin

    2013-01-01

    Vegetative tissues of Boea hygrometrica, a member of the Gesneriaceae family, can tolerate severe water loss to desiccated state and fully recover upon rehydration. Unlike many other so called "resurrection plants," the detached leaves of B. hygrometrica also possess the same level of capacity for desiccation tolerance (DT) as that of whole plant. B. hygrometrica is distributed widely from the tropics to northern temperate regions in East Asia and grows vigorously in areas around limestone rocks, where dehydration occurs frequently, rapidly, and profoundly. The properties of detached B. hygrometrica leaves and relative ease of culture have made it a useful system to study the adaptive mechanisms of DT. Extensive studies have been conducted to identify the physiological, cellular, and molecular mechanisms underlying DT in the last decade, including specific responses to water stress, such as cell wall folding and pigment-protein complex stabilizing in desiccated leaves. In this review, the insight into the structural, physiological, and biochemical, and molecular alterations that accompany the acquisition of DT in B. hygrometrica is described. Finally a future perspective is proposed, with an emphasis on the emerging regulatory roles of retroelements and histone modifications in the acquisition of DT, and the need of establishment of genome sequence database and high throughput techniques to identify novel regulators for fully understanding of the matrix of DT.

  11. Understanding desiccation tolerance using the resurrection plant Boea hygrometrica as a model system

    PubMed Central

    Mitra, Jayeeta; Xu, Guanghui; Wang, Bo; Li, Meijing; Deng, Xin

    2013-01-01

    Vegetative tissues of Boea hygrometrica, a member of the Gesneriaceae family, can tolerate severe water loss to desiccated state and fully recover upon rehydration. Unlike many other so called “resurrection plants,” the detached leaves of B. hygrometrica also possess the same level of capacity for desiccation tolerance (DT) as that of whole plant. B. hygrometrica is distributed widely from the tropics to northern temperate regions in East Asia and grows vigorously in areas around limestone rocks, where dehydration occurs frequently, rapidly, and profoundly. The properties of detached B. hygrometrica leaves and relative ease of culture have made it a useful system to study the adaptive mechanisms of DT. Extensive studies have been conducted to identify the physiological, cellular, and molecular mechanisms underlying DT in the last decade, including specific responses to water stress, such as cell wall folding and pigment-protein complex stabilizing in desiccated leaves. In this review, the insight into the structural, physiological, and biochemical, and molecular alterations that accompany the acquisition of DT in B. hygrometrica is described. Finally a future perspective is proposed, with an emphasis on the emerging regulatory roles of retroelements and histone modifications in the acquisition of DT, and the need of establishment of genome sequence database and high throughput techniques to identify novel regulators for fully understanding of the matrix of DT. PMID:24273545

  12. Dehumidification for coating and lining projects

    SciTech Connect

    Wyatt, C.H.

    1995-12-31

    When owners make the decision to refurbish tanks or vessels, quality workmanship that insures the long life of the coating or lining, and quick turnaround become paramount issues. However, if the tank is empty merely because the painting/lining contractor can not complete the project due to adverse weather conditions, something can be done to remedy the problem. Namely, include the use of dehumidification in the project specifications. Such a specification will enable an owner to receive his tank on a timely basis--the contractor will be able to optimize his personnel--and the material supplier will have his material applied in a more ideal condition. All components of the painting project will benefit and should be accomplished with little or no increase in cost of the lining project. However, if the intangible cost factor of not receiving the tank back for operation as per the contract is included in the cost analysis the incorporation of dehumidification actually becomes a cost savings. This environmental control can be realized, and utilized, even when the substrate is typically considered to be an external surface. For example, should the contractor have to enclose the work area--a bridge, a high rise tower, or even a ground storage tank to comply with external environmental regulations (dust from blasting operations, lead based paint removal, or even normal paint overspray), this created enclosure can be considered a tank. A closed loop system can be employed here and will be discussed in more detail in the formal paper. Therefore, the author will use the term enclosure throughout the paper with the definition of enclosure being the actual interior of the tank or any volume of air that exists between a tank and a plastic (or canvas) shroud that is used to enclose a blast area.

  13. Thermodynamic performance of a hybrid air cycle refrigeration system using a desiccant rotor

    NASA Astrophysics Data System (ADS)

    Hwang, Kyudae; Song, Chan Ho; Kim, Sung Ki; Saito, Kiyoshi; Kawai, Sunao

    2013-03-01

    Due to the concern on global warming, the demand for a system using natural refrigerant is increasing and many researches have been devoted to develop systems with natural refrigerants. Among natural refrigerant systems, an air cycle system has emerged as one of alternatives of Freon gas system due to environmentally friendly feature in spite of the inherent low efficiency. To overcome the technical barrier, this study proposed combination of multiple systems as a hybrid cycle to achieve higher efficiency of an air cycle system. The hybrid air cycle adopts a humidity control units such as an adsorber and a desorber to obtain the cooling effect from latent heat as well as sensible heat. To investigate the efficacy of the hybrid air cycle, the cooling performance of a hybrid air cycle is investigated analytically and experimentally. From the simulation result, it is found that COP of the hybrid air cycle is two times higher than that of the conventional air cycle. The experiments are conducted on the performance of the desiccant system according to the rotation speed in the system and displayed the feasibility of the key element in the hybrid air cycle system. From the results, it is shown that the system efficiency can be enhanced by utilization of the exhausted heat through the ambient heat exchanger with advantage of controlling the humidity by the desiccant rotor.

  14. Investigation of Desiccants and CO2 Sorbents for Advanced Exploration Systems 2015-2016

    NASA Technical Reports Server (NTRS)

    Knox, James C.; Watson, David W.; Wingard, Charles D.; West, Phillip W.; Cmarik, Gregory E.; Miller, Lee A.

    2016-01-01

    Advanced Exploration Systems are integral to crewed missions beyond low earth orbit and beyond the moon. The long-term goal is to reach Mars and return to Earth, but current air revitalization systems are not capable of extended operation within the mass, power, and volume requirements of such a mission. Two primary points are the mechanical stability of sorbent pellets and recovery of sorbent productivity after moisture exposure in the event of a leak. In this paper, we discuss the present efforts towards screening and characterizing commercially-available sorbents for extended operation in desiccant and CO2 removal beds.

  15. A simplified method for defining air humidification and dehumidification requirements

    NASA Astrophysics Data System (ADS)

    Korjenic, Azra; Bednar, Thomas

    2012-10-01

    Nowadays, the use of ventilation systems is very common. In museums and exhibition rooms, they are used to guarantee the optimal temperature and humidity conditions for valuable and irreplaceable objects. Ventilation systems are increasingly used even in residential and office buildings. In Austria and other similar climates, winter outdoor air is very dry. Because of the constant air exchange using a ventilation system, the relative humidity of indoor air is often lower than the comfort limit, so that air humidification is necessary. In the same rooms, air must be dehumidified during the summer months. Humidification and dehumidification should be minimized as they are processes that consume a large amount of energy. The problem is that until now, it has been unclear how much humidification or dehumidification is necessary and could not be calculated easily. In this investigation, a simplified method for determining the humidification and dehumidification demands taking into account the effective moisture capacity of the room was developed. The developed model is used for the calculation of the energy balance and will be integrated into the program for energy certification in Austria.

  16. Desiccant humidity control system. [for space shuttle cabins

    NASA Technical Reports Server (NTRS)

    Lunde, P. J.; Kester, F. L.

    1975-01-01

    A water vapor and carbon dioxide sorbent material (designated HS-C) was developed for potential application to the space shuttle and tested at full scale. Capacities of two percent for carbon dioxide and four percent for water vapor were achieved using space shuttle cabin adsorption conditions and a space vacuum for desorption. Performance testing shows that water vapor can be controlled by varying the air process flow, while maintaining the ability to remove carbon dioxide. A 2000 hour life test was successfully completed, as were tests for sensitivity to cleaning solvent vapors, vibration resistance, and flammability. A system design for the space shuttle shows a 200 pound weight advantage over competitive systems and an even larger advantage for longer missions.

  17. Free Breathing Static Dehumidification Systems.

    DTIC Science & Technology

    1987-01-01

    1?336 FREE NNERTHIN STATIC DMIDIFICATIOU SYS*kNS(U) RJR In__ FORME PRCKRGING EVJRTIN ROENCY WIIT-RTTERMO WD ON S A M~Y Jfh 97 DST -7-R-1 LOL lSSFFI...0 . LiW- M -. ’*5 iq - a . L O 37 Figure 12. Field Layout at SM-ALC/ DST , McClellan AFB CA .tr 4j w, I , D 4.- 4, 4J 4) :3 4j CCD ko LL o. 0.U UU -4 4...USAeLE11 I Wash DC 20330 HQ Ar’SC/LG’ I O)C-ALC/ DST Tinker Ar’B OK 73145 U0-ALC/ OST 1 Hill AFB UT 84406 SA-ALC/ DST i I. Kelly AeBN TIX 78241 SM-ALC

  18. Study on the marine ejector refrigeration-rotary desiccant air-conditioning system

    NASA Astrophysics Data System (ADS)

    Zheng, C. Y.; Zheng, G. J.; Yu, W. S.; Chen, W.

    2017-08-01

    A newly developed ejector refrigeration-rotary desiccant air-conditioning (ERRD A/C) system is proposed to recover ship waste heat as far as possible. Its configuration is built firstly, then its advantages are analyzed, after that, with the help of psychrometric chart, some important parameters such as power consumption, steam consumption and COP of ERRD A/C system are calculated theoretically under design conditions of a real marine A/C, and comparative analysis with conventional A/C is deployed. The results show that the power consumption of ERRD A/C system is only 32.87% of conventional A/C, which meant that ERRD A/C system has potential to make full use of ship waste heat to realize energy saving and environmental protection when using green refrigerant such as water.

  19. Solar-powered saline sorbent-solution heat pump/storage system. [Coastal Energy Laboratory-Chemical Heat Pump (CEL-CHEAP)

    SciTech Connect

    Robison, H.; Houston, S.

    1981-01-01

    Coastal Energy Laboratory Chemical Heat Pump (CEL-CHEAP) is a redesigned open-cycle liquid desiccant air conditioner. Heat is discharged to shallow-well water by dehumidification-humidification for cooling and extracted by humidification-dehumidification for heating. Direct solar radiation concentrates the desiccant. For continuous operation, a small uninsulated tank stores concentrated solution. 6 refs.

  20. Investigation of Desiccants and CO2 Sorbents for Advanced Exploration Systems 2015-2016

    NASA Technical Reports Server (NTRS)

    Knox, James C.; Cmarik, Gregory E.; Watson, David

    2016-01-01

    Design of advanced carbon dioxide removal systems begins with the study of sorbents. Specifically, new CO2 sorbents and desiccants need to be studied to enable greater productivity from existing and future spaceflight systems. This presentation will discuss the studies used as input for selecting future CO2 sorbent materials. Also, the adjoining issues of understanding the effects of water co-adsorption and material selection for desiccant beds will be discussed. Current sorbents for CO2 removal are based on 5A zeolites, but a transition to sorbents derived from 13X will be necessary as CO2 levels in cabin air become leaner. Unfortunately, these 13X zeolites are more susceptible to long-term performance loss due to water co-adsorption than 5A due at achievable regeneration temperatures. A study on how impactful the presence of trace water will be to the cyclic operation of small-scale beds will be discussed. Also, methods to recover the performance of beds in a space environment after a major moisture adsorption event will be discussed. The information obtained from the water co-adsorption studies will play a major part in selecting a CO2 sorbent for advanced removal systems. Pellet structural properties play another major role in the selection process. One factor for long-term, hands-off operation of a system is pellet integrity. Maintaining integrity means preventing pellet fracture and the generation of fines due to various thermal and mechanical means which would eventually clog filters or damage downstream systems. Either of these problems require significant shutdowns and maintenance operations and must be avoided. Therefore, study of high-integrity pellets and design of new pellets will be discussed.

  1. Investigation of Desiccants and CO2 Sorbents for Exploration Systems 2016-2017

    NASA Technical Reports Server (NTRS)

    Knox, James C.; Watson, David W.; Giesy, Timothy J.; Cmarik, Gregory E.; Miller, Lee A.

    2017-01-01

    NASA has embarked on the mission to enable humans to explore deep space, including the goal of sending humans to Mars. This journey will require significant developments in a wide range of technical areas as resupply and early return are not possible. Additionally, mass, power, and volume must be minimized for all phases to maximize propulsion availability. Among the critical areas identified for development are life support systems, which will require increases in reliability as well as reduce resource usage. Two primary points for reliability are the mechanical stability of sorbent pellets and recovery of CO2 sorbent productivity after off-nominal events. In this paper, we discuss the present efforts towards screening and characterizing commercially-available sorbents for extended operation in desiccant and CO2 removal beds. With minimized dusting as the primary criteria, a commercial 13X zeolite was selected and tested for performance and risk.

  2. Procedures for Calculating Residential Dehumidification Loads

    SciTech Connect

    Winkler, Jon; Booten, Chuck

    2016-06-01

    Residential building codes and voluntary labeling programs are continually increasing the energy efficiency requirements of residential buildings. Improving a building's thermal enclosure and installing energy-efficient appliances and lighting can result in significant reductions in sensible cooling loads leading to smaller air conditioners and shorter cooling seasons. However due to fresh air ventilation requirements and internal gains, latent cooling loads are not reduced by the same proportion. Thus, it's becoming more challenging for conventional cooling equipment to control indoor humidity at part-load cooling conditions and using conventional cooling equipment in a non-conventional building poses the potential risk of high indoor humidity. The objective of this project was to investigate the impact the chosen design condition has on the calculated part-load cooling moisture load, and compare calculated moisture loads and the required dehumidification capacity to whole-building simulations. Procedures for sizing whole-house supplemental dehumidification equipment have yet to be formalized; however minor modifications to current Air-Conditioner Contractors of America (ACCA) Manual J load calculation procedures are appropriate for calculating residential part-load cooling moisture loads. Though ASHRAE 1% DP design conditions are commonly used to determine the dehumidification requirements for commercial buildings, an appropriate DP design condition for residential buildings has not been investigated. Two methods for sizing supplemental dehumidification equipment were developed and tested. The first method closely followed Manual J cooling load calculations; whereas the second method made more conservative assumptions impacting both sensible and latent loads.

  3. Experimental and numerical investigations on the performance of dehumidifying desiccant beds composed of silica-gel and thermal energy storage particles

    NASA Astrophysics Data System (ADS)

    Rady, M. A.

    2009-03-01

    Enhanced efficiency of the adsorption process in the dehumidifier is a key element for improved performance of desiccant cooling systems. Due to the exothermic nature of the adsorption process, the dehumidification and cooling capacity are limited by significant temperature changes in the adsorption column. In the present study, the effects of integration of sensible and latent heat storage particles in the desiccant bed for in situ management of released adsorption heat are investigated. For this purpose, column experiments are performed using an initially dry granular bed made of silica-gel particles or a homogeneous mixture of silica gel and inert sensible or latent heat storage particles. The packed bed is subject to a sudden uniform air flow at selected values of temperature and humidity. Also, a packed bed numerical model is developed that includes the coupled non-equilibrium heat and moisture transfer in the solid and gas phases. Investigations of the heat and mass transfer characteristics are reported using the composite structure and the results are compared with the base case of simple silica gel bed. Improved desiccant cooling system performance can be obtained by appropriate adjustment of desiccant cycle operation and proper choice of the volume ratio of thermal energy storage particles.

  4. Experimental investigation of a solar desiccant cooling installation

    SciTech Connect

    Bourdoukan, P.; Wurtz, E.; Joubert, P.

    2009-11-15

    Desiccant cooling is a technique based on evaporative cooling and air dehumidification using desiccant regenerated by thermal energy. It is particularly interesting when it is driven by waste or solar heat making this technique environmentally friendly. In this paper, an experimental investigation is carried on a desiccant air handling unit powered by vacuum-tube solar collectors. First, the components are studied under various operating conditions. Then overall performance of the installation is evaluated over a day for a moderately humid climate with regeneration solely by solar energy. In these conditions the overall efficiency of the solar installation is 0.55 while the thermodynamic coefficient of performance is 0.45 and the performance indicator based on the electrical consumption is 4.5. Finally, the impact of outside and regeneration conditions on the performance indicators is studied. (author)

  5. Liquid Desiccant in Air Conditioners: Nano-Engineered Porous Hollow Fiber Membrane-Based Air Conditioning System

    SciTech Connect

    2010-09-02

    BEETIT Project: UTRC is developing an air conditioning system that is optimized for use in warm and humid climates. UTRC’s air conditioning system integrates a liquid drying agent or desiccant and a traditional vapor compression system found in 90% of air conditioners. The drying agent reduces the humidity in the air before it is cooled, using less energy. The technology uses a membrane as a barrier between the air and the liquid salt stream allowing only water vapor to pass through and not the salt molecules. This solves an inherent problem with traditional liquid desiccant systems—carryover of the liquid drying agent into the conditioned air stream—which eliminates corrosion and health issues

  6. Dehumidification Performance of Organic Powder Sorbent in a Fluidized Bed during Batch Cycle Operation

    NASA Astrophysics Data System (ADS)

    Horibe, Akihiko; Inaba, Hideo; Haruki, Naoto; Fujita, Naotoshi

    The air conditioning system with organic sorbent is able to utilize the low temperature waste heat. This paper has dealt with dynamic sorption of powder organic sorbent in a fluidized bed during batch cycle operation. The experiments were carried out under the various conditions such as cycle time, inlet air flow velocity, temperature of the heat exchanger, amount of sorbent. As a result, the cycle time which maximizes the amount of dehumidification became clear. The most suitable cycle time was decided by the balance of the speed of sorption reaction and the effects of heating and cooling. The heating effect and the cooling effect were controlled by the temperature of the heat exchanger. With a rise of the desorption temperature, the most suitable cycle time became short and the amount of dehumidification increased but heat efficiency dropped. On the other hand, with a rise of the sorption temperature, the amount of dehumidification decreased but this system showed an enough dehumidification performance when the sorption temperature is 30°C.

  7. High Efficiency Liquid-Desiccant Regenerator for Air Conditioning and Industrial Drying

    SciTech Connect

    Andrew Lowenstein

    2005-12-19

    Over 2 quads of fossil fuels are used each year for moisture removal. This includes industrial and agricultural processes where feedstocks and final products must be dried, as well as comfort conditioning of indoor spaces where the control of humidity is essential to maintaining healthy, productive and comfortable working conditions. Desiccants, materials that have a high affinity for water vapor, can greatly reduce energy use for both drying and dehumidification. An opportunity exists to greatly improve the competitiveness of advanced liquid-desiccant systems by increasing the efficiency of their regenerators. It is common practice within the chemical process industry to use multiple stage boilers to improve the efficiency of thermal separation processes. The energy needed to regenerate a liquid desiccant, which is a thermal separation process, can also be reduced by using a multiple stage boiler. In this project, a two-stage regenerator was developed in which the first stage is a boiler and the second stage is a scavenging-air regenerator. The only energy input to this regenerator is the natural gas that fires the boiler. The steam produced in the boiler provides the thermal energy to run the second-stage scavenging-air regenerator. This two-stage regenerator is referred to as a 1?-effect regenerator. A model of the high-temperature stage of a 1?-effect regenerator for liquid desiccants was designed, built and successfully tested. At nominal operating conditions (i.e., 2.35 gpm of 36% lithium chloride solution, 307,000 Btu/h firing rate), the boiler removed 153 lb/h of water from the desiccant at a gas-based efficiency of 52.9 % (which corresponds to a COP of 0.95 when a scavenging-air regenerator is added). The steam leaving the boiler, when condensed, had a solids concentration of less than 10 ppm. This low level of solids in the condensate places an upper bound of about 6 lb per year for desiccant loss from the regenerator. This low loss will not create

  8. Research and development needs for desiccant cooling technology 1992--1997. (Supplement to the NREL report, Desiccant Cooling: State-of-the-Art Assessment)

    SciTech Connect

    Pesaran, A A

    1992-12-01

    This report is a supplement to Desiccant Cooling: State-of-the-Art Assessment (NREL/TP-254-4147, DE93000013). In this supplement document we have described a detailed program assuming sufficient funding to implement the R&D activities needed. Desiccant dehumidification is a mature technology for industrial applications, and in recent years the technology has been used for air conditioning a number of institutional and commercial buildings. Our proposal is based on argumentative discussions at various national meetings with leaders of the technology. The goal is the penetration of the broad air conditioning market. This work is funded by the Buildings technology Office of the US Department of Energy.

  9. Moving Advanced Desiccant Materials into Mainstream Non-CFC Cooling Products

    SciTech Connect

    Sand, J. R.; Grossman, T.; Rice, C. K.; Fairchild, P. D.; Gross, I. L.

    2004-12-30

    Desiccant dehumidification technology is emerging as a technically viable alternative for comfort conditioning in many commercial and institutional buildings. Attempts to improve the indoor air quality of buildings has resulted in increasingly stringent guidelines for occupant outdoor air ventilation rates. Additionally, revised building heating, ventilating, and air-conditioning (HVAC) design criteria based on regional peak dew point data highlight the important of the latent (moisture removal) building load relative to the sensible (temperature) building load.

  10. Research and development needs for desiccant cooling technology 1992--1997

    SciTech Connect

    Pesaran, A.A.

    1992-12-01

    This report is a supplement to Desiccant Cooling: State-of-the-Art Assessment (NREL/TP-254-4147, DE93000013). In this supplement document we have described a detailed program assuming sufficient funding to implement the R D activities needed. Desiccant dehumidification is a mature technology for industrial applications, and in recent years the technology has been used for air conditioning a number of institutional and commercial buildings. Our proposal is based on argumentative discussions at various national meetings with leaders of the technology. The goal is the penetration of the broad air conditioning market. This work is funded by the Buildings technology Office of the US Department of Energy.

  11. Measure Guideline: Supplemental Dehumidification in Warm-Humid Climates

    SciTech Connect

    Rudd, Armin

    2014-10-01

    This document covers a description of the need and applied solutions for supplemental dehumidification in warm-humid climates, especially for energy efficient homes where the sensible cooling load has been dramatically reduced. Cooling loads are typically high and cooling equipment runs a lot to cool the air in older homes in warm-humid climates. The cooling process also removes indoor moisture, reducing indoor relative humidity. However, at current residential code levels, and especially for above-code programs, sensible cooling loads have been so dramatically reduced that the cooling system does not run a lot to cool the air, resulting in much less moisture being removed. In these new homes, cooling equipment is off for much longer periods of time especially during spring/fall seasons, summer shoulder months, rainy periods, some summer nights, and winter days. In warm-humid climates, those long-off periods allow indoor humidity to become elevated due to internally generated moisture and ventilation air change. Elevated indoor relative humidity impacts comfort, indoor air quality, and building material durability. Industry is responding with supplemental dehumidification options, but that effort is really in its infancy regarding year-round humidity control in low-energy homes. Available supplemental humidity control options are discussed. Some options are less expensive but may not control indoor humidity as well as more expensive and comprehensive options. The best performing option is one that avoids overcooling and adding unnecessary heat to the space by using waste heat from the cooling system to reheat the cooled and dehumidified air to room-neutral temperature.

  12. Measure Guideline: Supplemental Dehumidification in Warm-Humid Climates

    SciTech Connect

    Rudd, A.

    2014-10-01

    This document covers a description of the need and applied solutions for supplemental dehumidification in warm-humid climates, especially for energy efficient homes where the sensible cooling load has been dramatically reduced. In older homes in warm-humid climates, cooling loads are typically high and cooling equipment runs a lot to cool the air. The cooling process also removes indoor moisture, reducing indoor relative humidity. However, at current residential code levels, and especially for above-code programs, sensible cooling loads have been so dramatically reduced that the cooling system does not run a lot to cool the air, resulting in much less moisture being removed. In these new homes, cooling equipment is off for much longer periods of time especially during spring/fall seasons, summer shoulder months, rainy periods, some summer nights, and some winter days. In warm-humid climates, those long off periods allow indoor humidity to become elevated due to internally generated moisture and ventilation air change. Elevated indoor relative humidity impacts comfort, indoor air quality, and building material durability. Industry is responding with supplemental dehumidification options, but that effort is really in its infancy regarding year-round humidity control in low-energy homes. Available supplemental humidity control options are discussed. Some options are less expensive but may not control indoor humidity as well as more expensive and comprehensive options. The best performing option is one that avoids overcooling and avoids adding unnecessary heat to the space by using waste heat from the cooling system to reheat the cooled and dehumidified air to room-neutral temperature.

  13. Tardigrades Use Intrinsically Disordered Proteins to Survive Desiccation.

    PubMed

    Boothby, Thomas C; Tapia, Hugo; Brozena, Alexandra H; Piszkiewicz, Samantha; Smith, Austin E; Giovannini, Ilaria; Rebecchi, Lorena; Pielak, Gary J; Koshland, Doug; Goldstein, Bob

    2017-03-16

    Tardigrades are microscopic animals that survive a remarkable array of stresses, including desiccation. How tardigrades survive desiccation has remained a mystery for more than 250 years. Trehalose, a disaccharide essential for several organisms to survive drying, is detected at low levels or not at all in some tardigrade species, indicating that tardigrades possess potentially novel mechanisms for surviving desiccation. Here we show that tardigrade-specific intrinsically disordered proteins (TDPs) are essential for desiccation tolerance. TDP genes are constitutively expressed at high levels or induced during desiccation in multiple tardigrade species. TDPs are required for tardigrade desiccation tolerance, and these genes are sufficient to increase desiccation tolerance when expressed in heterologous systems. TDPs form non-crystalline amorphous solids (vitrify) upon desiccation, and this vitrified state mirrors their protective capabilities. Our study identifies TDPs as functional mediators of tardigrade desiccation tolerance, expanding our knowledge of the roles and diversity of disordered proteins involved in stress tolerance.

  14. Dust Generation Resulting from Desiccation of Playa Systems: Studies on Mono and Owens Lakes, California

    NASA Astrophysics Data System (ADS)

    Gill, Thomas Edward

    1995-01-01

    Playas, evaporites, and aeolian sediments frequently are linked components within the Earth system. Anthropogenic water diversions from terminal lakes form playas that release fugitive dust. These actions, documented worldwide, simulate aeolian processes activated during palaeoclimatic pluvial/interpluvial transitions, and have significant environmental impacts. Pluvial lakes Russell and Owens in North America's Great Basin preceded historic Mono and Owens Lakes, now desiccated by water diversions into dust-generating, evaporite -encrusted playas. Geochemical and hydrologic cycles acting on the Owens (Dry) Lake playa form three distinct crust types each year. Although initial dust production results from deflation of surface efflorescences after the playa dries, most aerosols are created by saltation abrasion of salt/silt/clay crusts at crust/ sand sheet contacts. The warm-season, clastic "cemented" crust is slowest to degrade into dust. If the playa surface is stabilized by an unbroken, non-efflorescent crust, dust formation is discouraged. When Mono Lake's surFace elevation does not exceed 1951 meters (6400 feet), similar processes will also generate dust from its saline lower playa. Six factors--related to wind, topography, groundwater, and sediments--control dust formation at both playas. These factors were combined into a statistical model relating suspended dust concentrations to playa/lake morphometry. The model shows the extent and severity of Mono Lake dust storms expands significantly below the surface level 6376 feet (1943.5 meters). X-ray diffraction analysis of Mono Basin soils, playa sediments, and aerosols demonstrates geochemical cycling of materials through land, air and water during Mono Lake's 1982 low stand. Soils and clastic playa sediments contain silicate minerals and tephra. Saline groundwater deposited calcite, halite, thenardite, gaylussite, burkeite and glauberite onto the lower playa. Aerosols contained silicate minerals (especially

  15. [Development of the new desiccator system for measuring the removal effect of the formaldehyde as an indoor air pollutant by the adsorbent].

    PubMed

    Tsutsumi, Hiromu; Mihara, Yuichi; Ogawa, Norihiro; Hoshino, Toru; Kumagai, Takeshi; Yokota, Katsushi

    2005-06-01

    The new desiccator system with measures for the prevention of dew drops and the processing of the formaldehyde (FA) gas discharged from the final desiccator was produced, and the FA removal rate for various adsorbents was examined. For the prevention of dew drops in the desiccator, a hygroscopic bottle containing silica gel was used next to the FA gas generator, and humidity was adjusted by adjusting the interval between the FA gas outlet (a) and the desiccant (b). The removal of the harmful FA gas discharged from the final desiccator (n=5) is an important in the environmental preservation. To solve this problem, the FA gas was passed through an oxidation bottle containing KMnO(4)-H(2)SO(4) solution, and it was possible to confirm the complete decomposition of the FA by increase of the CO(2) and elimination of the FA. For the determination of the FA concentration in the desiccator, 100 ml air was beforehand collected using a gas collector into a 100 ml vial bottle containing 2 ml distilled water, and 50 ml of air from each desiccator was injected using a glass syringe. This was left under a slightly reduced pressure for 20 min, and the FA concentration was determined by the AHMT method. The FA removal rate after 1 h for each adsorbent (0.5 g) was 50% or more for chitin, KIMCO and silica gel. The removal efficacy for activated carbon was higher for fine particles than for coarse particles, and a dose-response relationship was established.

  16. Desiccant contamination research: Report on the desiccant contamination test facility

    SciTech Connect

    Pesaran, A.A.; Bingham, C.E.

    1991-07-01

    The activity in the cooling systems research involves research on high performance dehumidifiers and chillers that can operate efficiently with the variable thermal outputs and delivery temperatures associated with solar collectors. It also includes work on advanced passive cooling techniques. This report describes the work conducted to improve the durability of solid desiccant dehumidifiers by investigating the causes of degradation of desiccant materials from airborne contaminants and thermal cycling. The performance of a dehumidifier strongly depends on the physical properties and durability of the desiccant material. To make durable and reliable dehumidifiers, an understanding is needed of how and to what degree the performance of a dehumidifier is affected by desiccant degradation. This report, an account of work under Cooling Systems Research, documents the efforts to design and fabricate a test facility to investigate desiccant contamination based on industry and academia recommendations. It also discusses the experimental techniques needed for obtaining high-quality data and presents plans for next year. Researchers of the Mechanical and Industrial Technology Division performed this work at the Solar Energy Research Institute in FY 1988 for DOE's Office of Solar Heat Technologies. 7 refs., 19 figs., 1 tab.

  17. 90. View looking southwest at dehumidification plant in foreground and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    90. View looking southwest at dehumidification plant in foreground and power house in background. - Sloss-Sheffield Steel & Iron, First Avenue North Viaduct at Thirty-second Street, Birmingham, Jefferson County, AL

  18. Simulated soil crust conditions in a chamber system provide new insights on cyanobacterial acclimation to desiccation.

    PubMed

    Raanan, Hagai; Oren, Nadav; Treves, Haim; Berkowicz, Simon M; Hagemann, Martin; Pade, Nadin; Keren, Nir; Kaplan, Aaron

    2016-02-01

    Environmental research often faces two major hurdles: (i) fluctuating spatial and temporal conditions and consequently large variability in the organisms' abundance and performance, and (ii) complex, costly logistics involved in field experiments. Measurements of physiological parameters or molecular analyses often represent single shot experiments. To study desiccation acclimation of filamentous cyanobacteria, the founders and main primary producers in desert biological soil crusts (BSC), we constructed an environmental chamber that can reproducibly and accurately simulate ambient conditions and measure microorganism performance. We show that recovery from desiccation of BSC cyanobacteria and Leptolyngbya ohadii isolated thereof are strongly affected by dehydration rate following morning dew. This effect is most pronounced in cells exposed to high light and temperature in the dry phase. Simultaneous measurements of water content, gas exchange and fluorescence were performed during dehydration. Photosynthetic performance measured by fluorescence begins declining when light intensity reaches values above 100 μmol photons m(-2) s(-1), even in fully hydrated cells. In contrast, photosynthetic rates measured using O2 evolution and CO2 uptake increased during rising irradiance to the point where the water content declined below ∼ 50%. Thus, fluorescence cannot serve as a reliable measure of photosynthesis in desert cyanobacteria. The effects of drying on gas exchange are discussed.

  19. Field Test and Performance Verification: Integrated Active Desiccant Rooftop Hybrid System Installed in a School - Final Report: Phase 4A

    SciTech Connect

    Fischer, J

    2005-12-21

    This report summarizes the results of a field verification pilot site investigation that involved the installation of a hybrid integrated active desiccant/vapor-compression rooftop heating, ventilation, and air-conditioning (HVAC) unit at an elementary school in the Atlanta Georgia area. For years, the school had experienced serious humidity and indoor air quality (IAQ) problems that had resulted in occupant complaints and microbial (mold) remediation. The outdoor air louvers of the original HVAC units had been closed in an attempt to improve humidity control within the space. The existing vapor compression variable air volume system was replaced by the integrated active desiccant rooftop (IADR) system that was described in detail in an Oak Ridge National Laboratory (ORNL) report published in 2004 (Fischer and Sand 2004). The IADR system and all space conditions have been monitored remotely for more than a year. The hybrid system was able to maintain both the space temperature and humidity as desired while delivering the outdoor air ventilation rate required by American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 62. The performance level of the IADR unit and the overall system energy efficiency was measured and found to be very high. A comprehensive IAQ investigation was completed by the Georgia Tech Research Institute before and after the system retrofit. Before-and-after data resulting from this investigation confirmed a significant improvement in IAQ, humidity control, and occupant comfort. These observations were reported by building occupants and are echoed in a letter to ORNL from the school district energy manager. The IADR system was easily retrofitted in place of the original rooftop system using a custom curb adapter. All work was completed in-house by the school's maintenance staff over one weekend. A subsequent cost analysis completed for the school district by the design engineer of record concluded that the IADR system

  20. District Heating and Cooling Technology Development Program: Phase 2, Investigation of reduced-cost heat-actuated desiccant cooling systems for DHC applications

    SciTech Connect

    Patch, K.D.; DiBella, F.A.; Becker, F.E.

    1992-02-01

    A detailed assessment has been completed of the use of desiccant-based customer-sited heat-actuated cooling for District Heating and Cooling (DHC) systems, showing that introduction of a reduced-cost desiccant cooling system would result in widespread market penetration. This program consisted of three principal components: a market study of existing and future reduced-cost liquid desiccant cooling (LDC) systems; an examination of the installed costs of these existing and reduced-cost LDC systems; and four detailed case studies. Both the installed cost and equivalent chilled water cost of existing large LDC systems were found to be quite competitive with district chilled water, while the high capital cost of small LDC systems made them more expensive than district chilled water. Potential total system sales in this existing large-scale LDC market are quite low, since most of the market for DHC space conditioning is in smaller equipment sizes. Cost savings realized from producing a reduced-cost LDC system would result in small LDC systems (sized well below 6,000 cfm) becoming competitive with the current range of district chilled water costs.

  1. Analysis of the adsorption process and of desiccant cooling systems: a pseudo- steady-state model for coupled heat and mass transfer. [DESSIM, DESSIM2, DESSIM4

    SciTech Connect

    Barlow, R.S.

    1982-12-01

    A computer model to simulate the adiabatic adsorption/desorption process is documented. Developed to predict the performance of desiccant cooling systems, the model has been validated through comparison with experimental data for single-blow adsorption and desorption. A literature review on adsorption analysis, detailed discussions of the adsorption process, and an initial assessment of the potential for performance improvement through advanced component development are included.

  2. Operation and cost of a small dehumidification dry kiln

    Treesearch

    Richard D. Bergman

    2008-01-01

    Obtaining small quantities of custom kiln-dried lumber can be an expensive process for an individual woodworker. Building and operating a small kiln capable of drying custom cuts of lumber (such as slabs, bowl blanks) gives woodworkers another option. Our approach was to build and operate a small dehumidification dry kiln. The four charges of lumber ranged from 600 to...

  3. Dehumidification of Iberia by enhanced summer upwelling

    NASA Astrophysics Data System (ADS)

    Miranda, P. M.; Costa, V.; Nogueira, M.; Semedo, A.

    2015-12-01

    Dehumidification of Iberia by enhanced summer upwelling Miranda PMA, Costa V, Semedo AIDL, Faculdade de Ciências, University of LisbonA 24-year simulation of the recent Iberian climate, using the WRF model at 9km resolution forced by ERA-Interim reanalysis (1989-2012), is analysed for the decadal evolution of the upwelling forcing coastal wind and for column integrated Precipitable water vapour (PWV). Results indicate that, unlike what was found by Bakun et al. (2009) for the Peruvian region, a statistically significant trend in the upwelling favourable (northerly) wind has been accompanied by a corresponding decrease in PWV, not only inland but also over the coastal waters. Such increase is consistent with a reinforced northerly coastal jet in the maritime boundary layer contributing to atmospheric Ekman pumping of dry continental air into the coastal region. Diagnostics of the prevalence of the Iberian thermal low following Hoinka and Castro (2003) also show a positive trend in its frequency during an extended summer period (April to September). These results are consistent with recent studies indicating an upward trend in the frequency of upwelling in SW Iberia (Alves and Miranda 2013), and may be relevant for climate change applications as an increase in coastal upwelling (Miranda et al 2013) may lead to substantial regional impacts in the subtropics. Aknowledgements: Study supported by FCT Grant RECI/GEO-MET/0380/2012Alves JMR, Miranda PMA (2013) Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses, Tellus A 2013, http://dx.doi.org/10.3402/tellusa.v65i0.19245.Bakun et al (2010) Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems, Global Change Biology, doi: 10.1111/j.1365-2486.2009.02094.xHoinka KP, Castro M (2003) The Iberian Peninsula thermal low. QJRMS, 129, 1491- 1511, doi: 10.1256/qj.01.189.Miranda et al (2013) Climate change and upwelling: response of Iberian upwelling to atmospheric

  4. Evaluation of the Performance of Houses With and Without Supplemental Dehumidification in a Hot-Humid Climate

    SciTech Connect

    Kerrigan, P.

    2014-10-01

    This report describes a research study that was conducted by the Building Science Corporation (BSC) Building America Research Team. BSC seeks to research and report on the field monitoring of the performance of in-situ supplemental dehumidification systems in low energy, high performance homes in a hot-humid climate. The purpose of this research project was to observe and compare the humidity control performance. Specifically, the study sought to compare the interior conditions and mechanical systems operation between two distinct groups of houses; homes with a supplemental dehumidifier installed in addition to HVAC system, and homes without any supplemental dehumidification. The subjects of the study were 10 single-family, new construction homes in New Orleans, LA.

  5. Desiccant cooling: State-of-the-art assessment

    SciTech Connect

    Pesaran, A.A.; Penney, T.R.; Czanderna, A.W.

    1992-10-01

    The objectives of this document are to present an overview of the work accomplished to date on desiccant cooling to provide assessment of the state of the art of desiccant cooling technology in the field of desiccant material dehumidifier components, desiccant systems, and models. The report also discusses the factors that affect the widespread acceptance of desiccant cooling technology. This report is organized as follows. First, a basic description and historical overview of desiccant cooling technology is provided. Then, the recent research and development (R D) program history (focusing on DOE's funded efforts) is discussed. The status of the technology elements (materials, components, systems) is discussed in detail and a preliminary study on the energy impact of desiccant technology is presented. R D needs for advancing the technology in the market are identified. The National Renewable Energy Laboratory's unique desiccant test facilities and their typical outputs are described briefly. Finally, the results of a comprehensive literature search on desiccant cooling are presented in a bibliography. The bibliography contains approximately 900 citations on desiccant cooling.

  6. Desiccant cooling: State-of-the-art assessment

    SciTech Connect

    Pesaran, A.A.; Penney, T.R.; Czanderna, A.W.

    1992-10-01

    The objectives of this document are to present an overview of the work accomplished to date on desiccant cooling to provide assessment of the state of the art of desiccant cooling technology in the field of desiccant material dehumidifier components, desiccant systems, and models. The report also discusses the factors that affect the widespread acceptance of desiccant cooling technology. This report is organized as follows. First, a basic description and historical overview of desiccant cooling technology is provided. Then, the recent research and development (R&D) program history (focusing on DOE`s funded efforts) is discussed. The status of the technology elements (materials, components, systems) is discussed in detail and a preliminary study on the energy impact of desiccant technology is presented. R&D needs for advancing the technology in the market are identified. The National Renewable Energy Laboratory`s unique desiccant test facilities and their typical outputs are described briefly. Finally, the results of a comprehensive literature search on desiccant cooling are presented in a bibliography. The bibliography contains approximately 900 citations on desiccant cooling.

  7. Alterations in the sugar metabolism and in the vacuolar system of mesophyll cells contribute to the desiccation tolerance of Haberlea rhodopensis ecotypes.

    PubMed

    Georgieva, K; Rapparini, F; Bertazza, G; Mihailova, G; Sárvári, É; Solti, Á; Keresztes, Á

    2017-01-01

    Haberlea rhodopensis belongs to the small group of resurrection plants having the unique ability to survive desiccation to air dry state retaining most of its chlorophyll content and then resume normal function upon rehydration. It prefers the shady valleys and northward facing slopes of limestone ridges in mountain zones with high average humidity. Nevertheless, it can be found rarely on rocks directly exposed to the sunlight, without the coverage of the canopy. In the present study, we follow the alterations in the subcellular organization of mesophyll cells and sugar metabolism upon desiccation of shade and sun H. rhodopensis plants. Composition and content of soluble carbohydrates during desiccation and rehydration were different in plants grown below the trees or on the sunny rocks. Sucrose, however, was dominating in both ecotypes. The amount of starch grains in chloroplasts was inversely related to that of sugars. Concomitantly with these changes, the number of vacuoles was multiplied in the cells. This can be explained by the development of small (secondary) vacuoles peripherally in the cytoplasm, rather than by the fragmentation of the single vacuole, proposed earlier in the literature. Accordingly, the centripetal movement of chloroplasts and other organelles may be a result of the dynamic changes in the vacuolar system. Upon rehydration, the inner vacuoles enlarged and the organelles returned to their normal position.

  8. Energy and economic assessment of desiccant cooling systems coupled with single glazed air and hybrid PV/thermal solar collectors for applications in hot and humid climate

    SciTech Connect

    Beccali, Marco; Finocchiaro, Pietro; Nocke, Bettina

    2009-10-15

    This paper presents a detailed analysis of the energy and economic performance of desiccant cooling systems (DEC) equipped with both single glazed standard air and hybrid photovoltaic/thermal (PV/t) collectors for applications in hot and humid climates. The use of 'solar cogeneration' by means of PV/t hybrid collectors enables the simultaneous production of electricity and heat, which can be directly used by desiccant air handling units, thereby making it possible to achieve very energy savings. The present work shows the results of detailed simulations conducted for a set of desiccant cooling systems operating without any heat storage. System performance was investigated through hourly simulations for different systems and load combinations. Three configurations of DEC systems were considered: standard DEC, DEC with an integrated heat pump and DEC with an enthalpy wheel. Two kinds of building occupations were considered: office and lecture room. Moreover, three configurations of solar-assisted air handling units (AHU) equipped with desiccant wheels were considered and compared with standard AHUs, focusing on achievable primary energy savings. The relationship between the solar collector's area and the specific primary energy consumption for different system configurations and building occupation patterns is described. For both occupation patterns, sensitivity analysis on system performance was performed for different solar collector areas. Also, this work presents an economic assessment of the systems. The cost of conserved energy and the payback time were calculated, with and without public incentives for solar cooling systems. It is worth noting that the use of photovoltaics, and thus the exploitation of related available incentives in many European countries, could positively influence the spread of solar air cooling technologies (SAC). An outcome of this work is that SAC systems equipped with PV/t collectors are shown to have better performance in terms of

  9. Desiccation: An environmental and food industry stress that bacteria commonly face.

    PubMed

    Esbelin, Julia; Santos, Tiago; Hébraud, Michel

    2018-02-01

    Water is essential for all living organisms, for animals as well as for plants and micro-organisms. For these latter, the presence of water or a humid environment with a high air relative humidity (RH) is necessary for their survival and growth. Thus, variations in the availability of water or in the air relative humidity constitute widespread environmental stresses which challenge microorganisms, and especially bacteria. Indeed, in their direct environment, bacteria are often faced with conditions that remove cell-bound water through air-drying of the atmosphere. Bacterial cells are subject to daily or seasonal environmental variations, sometimes going through periods of severe desiccation. This is also the case in the food industry, where air dehumidification treatments are applied after the daily cleaning-disinfection procedures. In plants producing low-water activity products, it is also usual to significantly reduce or eliminate water usage. Periodic desiccation exposure affects bacteria viability and so they require strategies to persist. Negative effects of desiccation are wide ranging and include direct cellular damage but also changes in the biochemical and biophysical properties of cells for which planktonic cells are more exposed than cells in biofilm. Understanding the mechanisms of desiccation adaptation and tolerance has a biological and biotechnological interest. This review gives an overview of the factors influencing desiccation tolerance and the biological mechanisms involved in this stress response. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Investigation of Desiccants and CO2 Sorbents for Advanced Exploration Systems 2015-2016

    NASA Technical Reports Server (NTRS)

    Cmarik, Gregory E.; Knox, Jim

    2016-01-01

    Advanced Environmental Control and Life Support System (ECLSS) design is critical for human space flight beyond Earth. Current systems enable extended missions in low-Earth orbit, but for deep-space missions, not only will astronauts be outside the reach of resupply operations from Earth but they will also need to handle malfunctions and compensate for the degradation of materials. These two daunting challenges must be overcome for long-term independent space flight. In order to solve the first, separation and reuse of onboard atmosphere components is required. Current systems utilize space vacuum to fully regenerate adsorbent beds, but this is not sustainable thus necessitating a closed-loop system. The second challenge stems from material and performance degradation due to operational cycling and on-board contaminants. This report will review the recent work by the ECLSS team at Marshall Space Flight Center towards overcoming these challenges by characterizing materials via novel methods for use in future systems.

  11. Investigation of Desiccants and CO2 Sorbents for Advanced Exploration Systems 2016-2017

    NASA Technical Reports Server (NTRS)

    Knox, Jim; Cmarik, Gregory E.

    2017-01-01

    Advanced Environmental Control and Life Support System (ECLSS) design is critical for manned space flight beyond Earth. Current systems enable extended missions in low-Earth orbit, but for deep-space missions, not only will astronauts be outside the reach of resupply operations from Earth but they will also need to handle malfunctions and compensate for the degradation of materials. These two daunting challenges must be overcome for long-term independent space flight. In order to solve the first, separation and recycling of onboard atmosphere is required. Current systems utilize space vacuum to fully regenerate CO2 sorbent beds, but this is not sustainable. The second challenge stems from material and performance degradation due to operational cycling and on-board contaminants. This report will review the recent work by the ECLSS team at Marshall Space Flight Center towards overcoming these challenges by characterizing materials via novel methods and by assessing new air revitalization systems.

  12. Fan cycling strategies and heat pipe heat exchangers provide energy efficient dehumidification

    SciTech Connect

    Shirey, D.B. III

    1995-03-01

    This article describes two methods to reduce energy consumption and peak demand in buildings that require humidity control that were demonstrated at the Salvador Dali Museum in St. Petersburg, Florida. The first method centered on alternative indoor fan cycling strategies and the second method involved the use of heat pipe heat exchangers. Both approaches increased the dehumidification performance of the existing air-conditioning systems and provided substantial savings. Simple, low cost alternative fan cycling strategies were used. When possible, auto fan control replaced constant fan operation to avoid excess fan energy consumption, ventilation load and compressor operation. The alternative fan control strategies reduced indoor humidity fluctuations in all zones, and significantly reduced overall humidity levels in the museum lobby and storage area. An HPHX was installed within one of the two gallery RTUs to improve the unit`s dehumidification performance. The passive HPHX significantly reduced electric reheat and compressor operation while maintaining the precise temperature and humidity requirements within the gallery. The second gallery RTU now operates primarily as a back-up unit to the heat pipe-assisted air-conditioning unit.

  13. Development of an Air-Source Heat Pump Integrated with a Water Heating / Dehumidification Module

    SciTech Connect

    Rice, C Keith; Uselton, Robert B.; Shen, Bo; Baxter, Van D; Shrestha, Som S

    2014-01-01

    A residential-sized dual air-source integrated heat pump (AS-IHP) concept is under development in partnership between ORNL and a manufacturer. The concept design consists of a two-stage air-source heat pump (ASHP) coupled on the air distribution side with a separate novel water heating/dehumidification (WH/DH) module. The motivation for this unusual equipment combination is the forecast trend for home sensible loads to be reduced more than latent loads. Integration of water heating with a space dehumidification cycle addresses humidity control while performing double-duty. This approach can be applied to retrofit/upgrade applications as well as new construction. A WH/DH module capable of ~1.47 L/h water removal and ~2 kW water heating capacity was assembled by the manufacturer. A heat pump system model was used to guide the controls design; lab testing was conducted and used to calibrate the models. Performance maps were generated and used in a TRNSYS sub-hourly simulation to predict annual performance in a well-insulated house. Annual HVAC/WH energy savings of ~35% are predicted in cold and hot-humid U.S. climates compared to a minimum efficiency baseline.

  14. Using EnergyPlus to Perform Dehumidification Analysis on Building America Homes: Preprint

    SciTech Connect

    Fang, X.; Winkler, J.; Christensen, D.

    2011-03-01

    A parametric study was conducted using EnergyPlus version 6.0 to investigate humidity issues on a typical mid-1990s reference home, a 2006 International Energy Conservation Code home, and a high-performance home in a hot-humid climate. The impacts of various dehumidification equipment and controls are analyzed on the high performance home. The study examined the combined effects of infiltration and mechanical ventilation with balanced and unbalanced mechanical ventilation systems. Indoor relative humidity excursions were examined; specifically, the number of excursions, average excursion length, and maximum excursion length. Space relative humidity, thermal comfort, and whole-house source energy consumption were analyzed for indoor relative humidity set points of 50%, 55%, and 60%. The study showed and explained why similar trends of high humidity were observed in all three homes regardless of energy efficiency, and why humidity problems are not necessarily unique in high-performance homes. Thermal comfort analysis indicated that occupants are unlikely to notice indoor humidity problems. The study confirmed that supplemental dehumidification should be provided to maintain space relative humidity below 60% in a hot-humid climate.

  15. Zero Carryover Liquid-Desiccant Air Conditioner for Solar Applications: Preprint

    SciTech Connect

    Lowenstein, A.; Slayzak, S.; Kozubal, E.

    2006-07-01

    A novel liquid-desiccant air conditioner that dries and cools building supply air will transform the use of direct-contact liquid-desiccant systems in HVAC applications, improving comfort, air quality, and providing energy-efficient humidity control.

  16. A Humidity Control System with an Adsorption Material and Indoor Air Quality Improvement

    NASA Astrophysics Data System (ADS)

    Moriya, Yoshifumi; Ishii, Noriaki

    The present study introduces a humidity control apparatus which can hygienically and automatically maintain the appropriate humidity level of indoor air without either a water supply or drainage system. In humidification, the desiccant takes up water vapor from the outdoor air in the adsorption process, and release it indoors by desorption. Therefore, no water supply is required to humidify. An apparatus having no water supply is more hygienic, because it does not propagate bacteria and does not scatter the calcium and magnesium salts found in the water. In dehumidification, water vapor is removed from the indoor air by the desiccant and is released outdoors by desorption, eliminating the need for a drainage system. The absence of a drainage system also eliminates problems such as water leakage and installation. The performance of a system based on this new method was compared with that of conventional products, whereby the modes of dehumidification, humidification and humidification with ventilation were evaluated. In addition, the new system was tested to reveal the time-dependent charaeteristics of the concentration of indoor odor and the dust collection efficiency.

  17. The performance of a solar-regenerated open-cycle desiccant bed grain cooling system

    SciTech Connect

    Ismail, M.Z.; Angus, D.E. ); Thorpe, G.R. )

    1991-01-01

    The cooling of stored food grains suppresses the growth of populations of insect pests, inhibits spoilage by fungi and helps to preserve grain quality. In temperate and subtropical climates, grains may be effectively cooled by ventilating them with ambient air. In tropical climates, the enthalpy of the air must be reduced before it can be used for cooling grain. One method of achieving this is to isothermally reduce the humidity of the air. This paper describes experiments carried out on a simple-to-build solar-regenerated open-cycle grain cooling system. The device consists of a 5.85 m{sup 2} collector coupled with two beds of silica gel. Results from a series of experiments suggest that the device may be used to cool up to 200 tons of grain. The electrical power consumption of the device is of the order of 0.3 watt per ton of grain cooled, and the total electrical energy consumption is of the order of 0.7 kWh per ton of grain stored for a six-month period. The effectiveness of the device is a function of air flow rate and the enthalpy of ambient air, and results presented in this paper suggest that the solar cooling device is particularly effective in tropical climates.

  18. Evidence of El Niño driven desiccation cycles in a shallow estuarine lake: The evolution and fate of Africa's largest estuarine system, Lake St Lucia

    NASA Astrophysics Data System (ADS)

    Humphries, M. S.; Green, A. N.; Finch, J. M.

    2016-12-01

    Projections of an increase in drought frequency and intensity over the next century are expected to have severe implications for a number of globally important coastal ecosystems. In this paper, we present geochemical data from three sediment cores extracted from the main depositional basins of Lake St Lucia, Africa's largest estuarine system. Lake St Lucia is subject to extreme natural variations in salinity. The sedimentary record documents the evolution of the system from a relatively deep-water, open lagoon to a confined, shallow estuarine lake that today is highly sensitive to changes in freshwater supply. This is particularly evident in the northern portions of the system, where the presence of distinct halite-enriched horizons document episodes of prolonged drought. The lateral persistence of these halite layers, as revealed by seismic profiling, point to a system-wide onset of desiccation associated with a major shift in the regional hydroclimate. The most severe drought events identified, which may have lasted several years, occur at 1100 and 1750 cal year BP, and are associated with known peaks in El Niño frequency and intensity. Our analyses suggest that past cycles of desiccation and hyper-salinity have been controlled by climatic changes related to ENSO intensification. This study provides a valuable new record from a key ENSO-sensitive region of the Southern Hemisphere. Our findings have important relevance for understanding ENSO variability across the Indo-Pacific region and the influence exerted on systems sensitive to changes in moisture balance.

  19. Moving Advanced Desiccant Materials into Mainstream Non-CFC Cooling Products

    SciTech Connect

    Sand, J R; Grossman, G; Rice, C K; Fairchild, P D; Gross, I L

    1994-01-01

    Desiccant air-conditioning systems can be used as alternatives for conventional air-conditioning equipment in any commercial or residential building. Recent breakthroughs in desiccant materials technology and the creation of new markets by Indoor Air Quality issues make desiccant-based air-conditioning equipment practical for many space-conditioning applications.

  20. Using liquid desiccant as a regenerable filter for capturing and deactivating contaminants

    DOEpatents

    Slayzak, Steven J.; Anderson, Ren S.; Judkoff, Ronald D.; Blake, Daniel M.; Vinzant, Todd B.; Ryan, Joseph P.

    2007-12-11

    A method, and systems for implementing such method, for purifying and conditioning air of weaponized contaminants. The method includes wetting a filter packing media with a salt-based liquid desiccant, such as water with a high concentration of lithium chloride. Air is passed through the wetted filter packing media and the contaminants in are captured with the liquid desiccant while the liquid desiccant dehumidifies the air. The captured contaminants are then deactivated in the liquid desiccant, which may include heating the liquid desiccant. The liquid desiccant is regenerated by applying heat to the liquid desiccant and then removing moisture. The method includes repeating the wetting with the regenerated liquid desiccant which provides a regenerable filtering process that captures and deactivates contaminants on an ongoing basis while also conditioning the air. The method may include filtration effectiveness enhancement by electrostatic or inertial means.

  1. Desiccation tolerance of prokaryotes.

    PubMed Central

    Potts, M

    1994-01-01

    The removal of cell-bound water through air drying and the addition of water to air-dried cells are forces that have played a pivotal role in the evolution of the prokaryotes. In bacterial cells that have been subjected to air drying, the evaporation of free cytoplasmic water (Vf) can be instantaneous, and an equilibrium between cell-bound water (Vb) and the environmental water (vapor) potential (psi wv) may be achieved rapidly. In the air-dried state some bacteria survive only for seconds whereas others can tolerate desiccation for thousands, perhaps millions, of years. The desiccated (anhydrobiotic) cell is characterized by its singular lack of water--with contents as low as 0.02 g of H2O g (dry weight)-1. At these levels the monolayer coverage by water of macromolecules, including DNA and proteins, is disturbed. As a consequence the mechanisms that confer desiccation tolerance upon air-dried bacteria are markedly different from those, such as the mechanism of preferential exclusion of compatible solutes, that preserve the integrity of salt-, osmotically, and freeze-thaw-stressed cells. Desiccation tolerance reflects a complex array of interactions at the structural, physiological, and molecular levels. Many of the mechanisms remain cryptic, but it is clear that they involve interactions, such as those between proteins and co-solvents, that derive from the unique properties of the water molecule. A water replacement hypothesis accounts for how the nonreducing disaccharides trehalose and sucrose preserve the integrity of membranes and proteins. Nevertheless, we have virtually no insight into the state of the cytoplasm of an air-dried cell. There is no evidence for any obvious adaptations of proteins that can counter the effects of air drying or for the occurrence of any proteins that provide a direct and a tangible contribution to cell stability. Among the prokaryotes that can exist as anhydrobiotic cells, the cyanobacteria have a marked capacity to do so. One

  2. Desiccation tolerance of prokaryotes.

    PubMed

    Potts, M

    1994-12-01

    The removal of cell-bound water through air drying and the addition of water to air-dried cells are forces that have played a pivotal role in the evolution of the prokaryotes. In bacterial cells that have been subjected to air drying, the evaporation of free cytoplasmic water (Vf) can be instantaneous, and an equilibrium between cell-bound water (Vb) and the environmental water (vapor) potential (psi wv) may be achieved rapidly. In the air-dried state some bacteria survive only for seconds whereas others can tolerate desiccation for thousands, perhaps millions, of years. The desiccated (anhydrobiotic) cell is characterized by its singular lack of water--with contents as low as 0.02 g of H2O g (dry weight)-1. At these levels the monolayer coverage by water of macromolecules, including DNA and proteins, is disturbed. As a consequence the mechanisms that confer desiccation tolerance upon air-dried bacteria are markedly different from those, such as the mechanism of preferential exclusion of compatible solutes, that preserve the integrity of salt-, osmotically, and freeze-thaw-stressed cells. Desiccation tolerance reflects a complex array of interactions at the structural, physiological, and molecular levels. Many of the mechanisms remain cryptic, but it is clear that they involve interactions, such as those between proteins and co-solvents, that derive from the unique properties of the water molecule. A water replacement hypothesis accounts for how the nonreducing disaccharides trehalose and sucrose preserve the integrity of membranes and proteins. Nevertheless, we have virtually no insight into the state of the cytoplasm of an air-dried cell. There is no evidence for any obvious adaptations of proteins that can counter the effects of air drying or for the occurrence of any proteins that provide a direct and a tangible contribution to cell stability. Among the prokaryotes that can exist as anhydrobiotic cells, the cyanobacteria have a marked capacity to do so. One

  3. Introduction to desiccation biology: from old borders to new frontiers.

    PubMed

    Leprince, Olivier; Buitink, Julia

    2015-08-01

    A special issue reviews the recent progress made in our understanding of desiccation tolerance across various plant and animal kingdoms. It has been known for a long time that seeds can survive near absolute protoplasmic dehydration through air drying and complete germination upon rehydration because of their desiccation tolerance. This property is present both in prokaryotes and eukaryotes across all life kingdoms. These dry organisms suspend their metabolism when dry, are extremely tolerant to acute environmental stresses and are relatively stable during long periods of desiccation. Studies aiming at understanding the mechanisms of survival in the dry state have emerged during the past 40 years, moving from in vitro to genomic models and comparative genomics, and from a view that tolerance is an all-or-nothing phenomenon to a quantitative trait. With the prospect of global climate change, understanding the mechanisms of desiccation tolerance appears to be a promising avenue as a prelude to engineering crops for improved drought tolerance. Understanding desiccation is also useful for seed banks that rely on dehydration tolerance to preserve plant genetic resources in the form of these propagules. Articles in this special issue explore the recent progress in our understanding of desiccation tolerance, including the evolutionary mechanisms that have been adopted across various plant (algae, lichens, seeds, resurrection plants) and animal model systems (Caenorhabditis elegans, brine shrimp). We propose that the term desiccation biology defines the discipline dedicated to understand the desiccation tolerance in living organisms as well as the limits and time constraints thereof.

  4. Degradation of desiccants upon contamination: An experimental study

    SciTech Connect

    Pesaran, A A

    1990-11-01

    Experiments were conducted to quantify the effects of thermal cycling and exposure to contamination on solid desiccant materials that may be used in desiccant cooling systems. A test apparatus was used to thermally cycle several desiccant samples and expose them to ambient or contaminated humid air. The source of contamination was cigarette smoke. Six different solid desiccants were tested: two types of silica gel, activated alumina, activated carbon, molecular sieves, and lithium chloride. The exposed desiccant samples were removed after 0.5, 1, 2, 4, or 11 months of exposure and their moisture capacities were measured. Other tests were conducted to characterize pollutants deposited on the exposed samples or to evaluate impact of exposure on internal structure of the samples. Compared to fresh samples, the capacity loss due to thermal cycling with ambient air was generally 10% to 30%. The capacity loss due to only cigarette smoke was generally between 20% to 50%. 7 refs., 8 figs., 3 tabs.

  5. Low-Cost "Vacuum Desiccator"

    NASA Astrophysics Data System (ADS)

    Sweet, Frederick

    2004-10-01

    Described are individualized, low-cost, and safe desiccators that can be efficiently and rapidly made with an inexpensive kitchen aid sold for shrink-wrapping food. The device can be used for enclosing small vials or bottles and also jars that are too large to be placed in conventional glass or plastic desiccators. This shrink-wrapping device is proposed for producing "vacuum desiccators" in large undergraduate chemistry laboratories or in graduate and research laboratories.

  6. Polymers as advanced materials for desiccant applications, 1988

    SciTech Connect

    Czanderna, A.W.; Neidlinger, H.H.

    1990-09-01

    This report documents work to identify a next-generation, low-cost material with which solar energy or heat from another low-cost energy source can be used for regenerating the water vapor sorption activity of the desiccant. The objective of the work is to determine how the desired sorption performance of advanced desiccant materials can be predicted by understanding the role of the material modifications and material surfaces. The work concentrates on solid materials to be used for desiccant cooling systems and which process water vapor in an atmosphere to produce cooling. The work involved preparing modifications of polystyrene sulfonic acid sodium salt, synthesizing a hydrogel, and evaluating the sorption performances of these and similar commercially available polymeric materials; all materials were studied for their potential application in solid commercial desiccant cooling systems. Background information is also provided on desiccant cooling systems and the role of a desiccant material within such a system, and it includes the use of polymers as desiccant materials. 31 refs., 16 figs., 5 tabs.

  7. Evaluation of the Performance of Houses With and Without Supplemental Dehumidification in a Hot-Humid Climate

    SciTech Connect

    Kerrigan, P.; Norton, P.

    2014-10-01

    This report, Evaluation of the Performance of Houses with and without Supplemental Dehumidification in a Hot-Humid Climate, describes a research study that that was conducted by the Building Science Corporation (BSC) Building America Research Team. BSC seeks to research and report on the field monitoring of the performance of in-situ supplemental dehumidification systems in low energy, high performance, homes in a Hot-Humid climate. The purpose of this research project was to observe and compare the humidity control performance of new, single family, low energy, and high performance, homes. Specifically, the study sought to compare the interior conditions and mechanical systems operation between two distinct groups of houses, homes with a supplemental dehumidifier installed in addition to HVAC system, and homes without any supplemental dehumidification. The subjects of the study were ten single-family new construction homes in New Orleans, LA.Data logging equipment was installed at each home in 2012. Interior conditions and various end-use loads were monitored for one year. In terms of averages, the homes with dehumidifiers are limiting elevated levels of humidity in the living space. However, there was significant variation in humidity control between individual houses. An analysis of the equipment operation did not show a clear correlation between energy use and humidity levels. In general, no single explanatory variable appears to provide a consistent understanding of the humidity control in each house. Indoor humidity is likely due to all of the factors we have examined, and the specifics of how they are used by each occupant.

  8. Polymers as advanced materials for desiccant applications

    SciTech Connect

    Czanderna, A.W.

    1990-12-01

    This research is concerned with solid materials used as desiccants for desiccant cooling systems (DCSs) that process water vapor in an atmosphere to produce cooling. Background information includes an introduction to DCSs and the role of the desiccant as a system component. The water vapor sorption performance criteria used for screening the modified polymers prepared include the water sorption capacity from 5% to 80% relative humidity (R.H.), isotherm shape, and rate of adsorption and desorption. Measurements are presented for the sorption performance of modified polymeric advanced desiccant materials with the quartz crystal microbalance. Isotherms of polystyrene sulfonic acid (PSSA) taken over a 5-month period show that the material has a dramatic loss in capacity and that the isotherm shape is time dependent. The adsorption and desorption kinetics for PSSA and all the ionic salts of it studied are easily fast enough for commercial DCS applications with a wheel rotation speed of 6 min per revolution. Future activities for the project are addressed, and a 5-year summary of the project is included as Appendix A. 34 refs., 20 figs., 3 tabs.

  9. Graphene oxide papers with high water adsorption capacity for air dehumidification.

    PubMed

    Liu, Renlong; Gong, Tao; Zhang, Kan; Lee, Changgu

    2017-08-29

    Graphene oxide (GO) has shown a high potential to adsorb and store water molecules due to the oxygen-containing functional groups on its hydrophilic surface. In this study, we characterized the water absorbing properties of graphene oxide in the form of papers. We fabricated three kinds of graphene oxide papers, two with rich oxygen functional groups and one with partial chemical reduction, to vary the oxygen/carbon ratio and found that the paper with high oxygen content has higher moisture adsorption capability. For the GO paper with reduction, the overall moisture absorbance was reduced. However, the absorbance at high humidity was significantly improved due to direct formation of multilayer water vapor in the system, which derived from the weak interaction between the adsorbent and the adsorbate. To demonstrate one application of GO papers as a desiccant, we tested grape fruits with and without GO paper. The fruits with a GO paper exhibited longer-term preservation with delayed mold gathering because of desiccation effect from the paper. Our results suggest that GO will find numerous practical applications as a desiccant and is a promising material for moisture desiccation and food preservation.

  10. Tolerance to environmental desiccation in moss sperm.

    PubMed

    Shortlidge, Erin E; Rosenstiel, Todd N; Eppley, Sarah M

    2012-05-01

    • Sexual reproduction in mosses requires that sperm be released freely into the environment before finding and fertilizing a receptive female. After release from the male plant, moss sperm may experience a range of abiotic stresses; however, few data are available examining stress tolerance of moss sperm and whether there is genetic variation for stress tolerance in this important life stage. • Here, we investigated the effects of environmental desiccation and recovery on the sperm cells of three moss species (Bryum argenteum, Campylopus introflexus, and Ceratodon purpureus). • We found that a fraction of sperm cells were tolerant to environmental desiccation for extended periods (d) and that tolerance did not vary among species. We found that this tolerance occurs irrespective of ambient dehydration conditions, and that the addition of sucrose during dry-down improved cell recovery. Although we observed no interspecific variation, significant variation among individuals within species in sperm cell tolerance to environmental desiccation was observed, suggesting selection could potentially act on this basic reproductive trait. • The observation of desiccation-tolerant sperm in multiple moss species has important implications for understanding bryophyte reproduction, suggesting the presence of a significant, uncharacterized complexity in the ecology of moss mating systems.

  11. Exploring the mechanism of Physcomitrella patens desiccation tolerance through a proteomic strategy.

    PubMed

    Wang, Xiao Qin; Yang, Ping Fang; Liu, Zheng; Liu, Wei Zhong; Hu, Yong; Chen, Hui; Kuang, Ting Yun; Pei, Zhen Ming; Shen, Shi Hua; He, Yi Kun

    2009-04-01

    The moss Physcomitrella patens has been shown to tolerate abiotic stresses, including salinity, cold, and desiccation. To better understand this plant's mechanism of desiccation tolerance, we have applied cellular and proteomic analyses. Gametophores were desiccated over 1 month to 10% of their original fresh weight. We report that during the course of dehydration, several related processes are set in motion: plasmolysis, chloroplast remodeling, and microtubule depolymerization. Despite the severe desiccation, the membrane system maintains integrity. Through two-dimensional gel electrophoresis and image analysis, we identified 71 proteins as desiccation responsive. Following identification and functional categorization, we found that a majority of the desiccation-responsive proteins were involved in metabolism, cytoskeleton, defense, and signaling. Degradation of cytoskeletal proteins might result in cytoskeletal disassembly and consequent changes in the cell structure. Late embryogenesis abundant proteins and reactive oxygen species-scavenging enzymes are both prominently induced, and they might help to diminish the damage brought by desiccation.

  12. Physicochemical characteristics and sensory profile of honey samples from stingless bees (Apidae: Meliponinae) submitted to a dehumidification process.

    PubMed

    Carvalho, Carlos A L; Sodré, Geni S; Fonseca, Antonio A O; Alves, Rogério M O; Souza, Bruno A; Clarton, Lana

    2009-03-01

    This study was conducted to evaluate the effect of a dehumidification process on the physicochemical and sensory characteristics of stingless-bee honey. Melipona scutellaris and M. quadrifasciata honey samples were submitted to a dehumidification process and to physicochemical (reducing sugars, apparent sucrose, moisture, diastatic activity, hydroxymethylfurfural, ash, pH, acidity, and electric conductivity) and sensory evaluations (fluidity, color, aroma, crystallization,flavor,and acceptability). The results indicated that the dehumidification process does not interfere with honey quality and acceptability.

  13. District Heating and Cooling Technology Development Program: Phase 2, Investigation of reduced-cost heat-actuated desiccant cooling systems for DHC applications. Final report, August 20, 1990--January 1, 1992

    SciTech Connect

    Patch, K.D.; DiBella, F.A.; Becker, F.E.

    1992-02-01

    A detailed assessment has been completed of the use of desiccant-based customer-sited heat-actuated cooling for District Heating and Cooling (DHC) systems, showing that introduction of a reduced-cost desiccant cooling system would result in widespread market penetration. This program consisted of three principal components: a market study of existing and future reduced-cost liquid desiccant cooling (LDC) systems; an examination of the installed costs of these existing and reduced-cost LDC systems; and four detailed case studies. Both the installed cost and equivalent chilled water cost of existing large LDC systems were found to be quite competitive with district chilled water, while the high capital cost of small LDC systems made them more expensive than district chilled water. Potential total system sales in this existing large-scale LDC market are quite low, since most of the market for DHC space conditioning is in smaller equipment sizes. Cost savings realized from producing a reduced-cost LDC system would result in small LDC systems (sized well below 6,000 cfm) becoming competitive with the current range of district chilled water costs.

  14. [Postgenomic analysis of desiccation tolerance].

    PubMed

    Buitink, Julia; Leprince, Olivier

    2008-01-01

    Desiccation tolerance is the capacity to survive complete drying. It is an ancient trait that can be found in prokaryotes, fungi, primitive animals (often at the larval stages), whole plants, pollens and seeds. In the dry state, metabolism is suspended and the duration that anhydrobiotes can survive ranges from years to centuries. Whereas genes induced by drought stress have been successfully enumerated in tissues that are sensitive to cellular desiccation, we have little knowledge as to the adaptive role of these genes in establishing desiccation tolerance at the cellular level. This paper reviews postgenomic approaches in a variety of desiccation tolerant organisms in which the genetic responses have been investigated when they acquire the capacity of tolerating extremes of dehydration or when they are dry. Accumulation of non-reducing sugars, LEA proteins and a coordinated repression of metabolism appear to be the essential and universal attributes that can confer desiccation tolerance. The protective mechanisms of these attributes are described. Furthermore, it is most likely that other mechanisms have evolved since the function of about 30% of the genes involved in desiccation tolerance remains to be elucidated. The question of the overlap between desiccation tolerance and drought tolerance is briefly addressed.

  15. The Analysis of A Hybrid Cooling System - Phase 2,

    NASA Astrophysics Data System (ADS)

    Yang, Kuan-Hsiung

    During the first phase of study, the mathematical modelling and the performance of the hybrid cooling system using solid desiccants were analyzed numerically. During this phase of study, the experimental investigation was conducted which yielded successful results with 5 % deviation as compared with the operational data of available commerical dehumidifiers. Furthmore, a prototype hybrid cooling system was actually constructed in the Refrigeration & Air-Conditioning Lab of National Sun Yat-Sen University (NSYSU), which generated good correlations with 7% deviation only, as compared with the analytical results. In other words, the good correlations obtained among the math modeling, the commercial unit operational data, and the NSYSU prototype system warrant the potential applications of this system for many industrial dehumidification and drying processes.

  16. A Novel Absorption Cycle for Combined Water Heating, Dehumidification, and Evaporative Cooling

    SciTech Connect

    CHUGH, Devesh; Gluesenkamp, Kyle R; Abdelaziz, Omar; Moghaddam, Saeed

    2014-01-01

    In this study, development of a novel system for combined water heating, dehumidification, and space evaporative cooling is discussed. Ambient water vapor is used as a working fluid in an open system. First, water vapor is absorbed from an air stream into an absorbent solution. The latent heat of absorption is transferred into the process water that cools the absorber. The solution is then regenerated in the desorber, where it is heated by a heating fluid. The water vapor generated in the desorber is condensed and its heat of phase change is transferred to the process water in the condenser. The condensed water can then be used in an evaporative cooling process to cool the dehumidified air exiting the absorber, or it can be drained if primarily dehumidification is desired. Essentially, this open absorption cycle collects space heat and transfers it to process water. This technology is enabled by a membrane-based absorption/desorption process in which the absorbent is constrained by hydrophobic vapor-permeable membranes. Constraining the absorbent film has enabled fabrication of the absorber and desorber in a plate-and-frame configuration. An air stream can flow against the membrane at high speed without entraining the absorbent, which is a challenge in conventional dehumidifiers. Furthermore, the absorption and desorption rates of an absorbent constrained by a membrane are greatly enhanced. Isfahani and Moghaddam (Int. J. Heat Mass Transfer, 2013) demonstrated absorption rates of up to 0.008 kg/m2s in a membrane-based absorber and Isfahani et al. (Int. J. Multiphase Flow, 2013) have reported a desorption rate of 0.01 kg/m2s in a membrane-based desorber. The membrane-based architecture also enables economical small-scale systems, novel cycle configurations, and high efficiencies. The absorber, solution heat exchanger, and desorber are fabricated on a single metal sheet. In addition to the open arrangement and membrane-based architecture, another novel feature of the

  17. Proteomics of desiccation tolerance during development and germination of maize embryos.

    PubMed

    Huang, Hui; Møller, Ian Max; Song, Song-Quan

    2012-02-02

    Maize seeds were used to identify the key embryo proteins involved in desiccation tolerance during development and germination. Immature maize embryos (28N) during development and mature embryos imbibed for 72 h (72HN) are desiccation sensitive. Mature maize embryos (52N) during development are desiccation tolerant. Thiobarbituric acid reactive substance and hydrogen peroxide contents decreased and increased with acquisition and loss of desiccation tolerance, respectively. A total of 111 protein spots changed significantly (1.5 fold increase/decrease) in desiccation-tolerant and -sensitive embryos before (28N, 52N and 72HN) and after (28D, 52D and 72HD) dehydration. Nine pre-dominantly proteins, 17.4 kDa Class I heat shock protein 3, late embryogenesis abundant protein EMB564, outer membrane protein, globulin 2, TPA:putative cystatin, NBS-LRR resistance-like protein RGC456, stress responsive protein, major allergen Bet v 1.01C and proteasome subunit alpha type 1, accumulated during embryo maturation, decreased during germination and increased in desiccation-tolerant embryos during desiccation. Two proteins, Rhd6-like 2 and low-molecular-weight heat shock protein precursor, showed the inverse pattern. We infer that these eleven proteins are involved in seed desiccation tolerance. We conclude that desiccation-tolerant embryos make more economical use of their resources to accumulate protective molecules and antioxidant systems to deal with maturation drying and desiccation treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Desiccation tolerance in Staphylococcus aureus.

    PubMed

    Chaibenjawong, Plykaeow; Foster, Simon J

    2011-02-01

    Staphylococcus aureus is a multidrug-resistant pathogen that not only causes a diverse array of human diseases, but also is able to survive in potentially dry and stressful environments, such as the human nose, on skin and on inanimate surfaces such as clothing and surfaces. This study investigated parameters governing desiccation tolerance of S. aureus and identified several components involved in the process. Initially, the role of environmental parameters such as temperature, growth phase, cell density, desiccation time and protectants in desiccation tolerance were determined. This established a robust model of desiccation tolerance in which S. aureus has the ability to survive on dry plastic surfaces for more than 1,097 days. Using a combination of a random screen and defined mutants, clpX, sigB and yjbH were identified as being required for desiccation tolerance. ClpX is a part of the ATP-dependent ClpXP protease, important for protein turnover, and YjbH has a proposed linked function. SigB is an accessory sigma factor with a role in generalized stress resistance. Understanding the molecular mechanisms that govern desiccation tolerance may determine the break points to be exploited to prevent the spread of this dangerous pathogen in hospitals and communities.

  19. Distinguishing biogeochemical processes influencing phosphorus dynamics in oxidizing and desiccating mud deposits from a freshwater wetland system

    NASA Astrophysics Data System (ADS)

    Saaltink, Rémon; Dekker, Stefan C.; Wassen, Martin J.; Griffioen, Jasper

    2015-04-01

    Focus and aim: Currently, lake Markermeer (680 km2) provides poor environmental conditions for the development of flora and fauna due to a thick fluffy layer that prevails at the lake's bed. To improve the conditions in the lake, large wetlands will be built from this fluffy layer, possibly mixed with sand or with the underlying Southern Sea deposit. The aim of this study is to distinguish biogeochemical processes influencing phosphorus dynamics in porewater during oxidation and desiccation of mud deposits from this lake. We focus on three important aspects that potentially influence these processes: granulometry, sediment type and modification by plants. Material and methods: A greenhouse experiment was conducted with three types of sediment that potentially will function as building material for the islands: fluffy mud (FM), sandy mud (SM) and Southern Sea deposit (SSD). Reed (Phragmites australis) was planted in half of the pots to distinguish influence by plants. For six months, the porewater-, soil- and plant quality was monitored to determine important biogeochemical processes. Variables measured from the porewater include: Cl-, NO2-, NO3-, PO43- and SO42- (IC); Ca, Fe, K, Mn, Na, P, Si, Sr (ICP-OES); as well as Fe2+, pH, alkalinity and EC. A phosphorus fractionation was carried out on the sediment to determine the phosphorus pools and the major elements of the sediments were determined following an aqua regia destruction using ICP-OES. Plant tissue was analysed for N, P, K and C content as well as the above- and belowground biomass. Results and discussion: It was found that sulfate production was the most important process influencing phosphorus availability in these soils. Due to oxidation processes in the mud, sulfate (SO42-) concentrations rose drastically in porewater from 100 ppm at the beginning of the experiment to well over 2000 ppm at the end of the experiment. This effect was strongest in SSD soils, likely due to higher presence of pyrite that gets

  20. Analysis of radial fin assembly heat transfer with dehumidification

    SciTech Connect

    Rosario, L.; Rahman, M.M.

    1996-12-31

    The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing heat transfer rate with and without fins under the same operating conditions. Numerical calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. Results were compared to those published for rectangular fin under humid condition showed excellent agreement when the present model was used to compute that limiting condition. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature.

  1. Protein oxidation: key to bacterial desiccation resistance?

    PubMed

    Fredrickson, James K; Li, Shu-mei W; Gaidamakova, Elena K; Matrosova, Vera Y; Zhai, Min; Sulloway, Heather M; Scholten, Johannes C; Brown, Mindy G; Balkwill, David L; Daly, Michael J

    2008-04-01

    For extremely ionizing radiation-resistant bacteria, survival has been attributed to protection of proteins from oxidative damage during irradiation, with the result that repair systems survive and function with far greater efficiency during recovery than in sensitive bacteria. Here we examined the relationship between survival of dry-climate soil bacteria and the level of cellular protein oxidation induced by desiccation. Bacteria were isolated from surface soils of the shrub-steppe of the US Department of Energy's Hanford Site in Washington State. A total of 63 isolates were used for phylogenetic analysis. The majority of isolates were closely related to members of the genus Deinococcus, with Chelatococcus, Methylobacterium and Bosea also among the genera identified. Desiccation-resistant isolates accumulated high intracellular manganese and low iron concentrations compared to sensitive bacteria. In vivo, proteins of desiccation-resistant bacteria were protected from oxidative modifications that introduce carbonyl groups in sensitive bacteria during drying. We present the case that survival of bacteria that inhabit dry-climate soils are highly dependent on mechanisms, which limit protein oxidation during dehydration.

  2. Exceptional desiccation tolerance of Acinetobacter radioresistens.

    PubMed

    Jawad, A; Snelling, A M; Heritage, J; Hawkey, P M

    1998-07-01

    The taxonomy of the genus Acinetobacter, which includes several important nosocomial pathogens, has been confused due to a lack of discriminatory phenotypic characteristics for identification. Molecular methods such as amplified ribosomal DNA restriction analysis (ARDRA) now enable the accurate identification of species. Ten clinical isolates of Acinetobacter radioresistens had genospecies confirmed by ARDRA but the APJ 20NE system, commonly used in clinical microbiology laboratories, mis-identified them as Acinetobacter lwoffii. Desiccation resistance of Acinetobacter spp. is an important attribute for their survival in the clinical environment. We investigated the ability of A. radioresistens to survive desiccation using an established glass surface model and compared the results to A. lwoffii and Acinetobacter baumannii. The 10 strains of A. radioresistens were extremely resistant to desiccation and survived for an average of 157 days at 31% relative humidity (RH). In contrast, two strains of A. lwoffii and three strains of A. baumannii survived for an average of three and 20 days respectively, at 31% RH, which was used as an approximation to climatic conditions in UK hospitals. A. radioresistens is thus well adapted for survival in the hospital environment and carriage on human skin and yet it is reported less frequently than A. lwoffii amongst clinical isolates. Cases of A. radioresistens infection may be under-reported due to mis-identification as A. lwoffii and further studies that use molecular identification methods are required to elucidate the role of A. radioresistens in human disease.

  3. Dehumidification of Moist Air by Direct Contact Heat and Mass Transfer in Cold Water Solution

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Horibe, Akihiko; Haruki, Naoto; Ishioka, Tohru; Takeuchi, Yoshiyuki

    This paper has dealt with the direct contact heat and mass transfer characteristics of dehumidification of flowing moist air bubbles in a cold water solution (propylene glycoI). The saturated water-vapor humidity of propylene glycol water solution was measured under some conditions of temperature and mass concentration of the water solution. Experiments on dehumidification of air bubbles were performed by ascending air bubbles in the water absorbing solution for various parameters of air temperature, humidity and flow rate etc. The experimental data of air bubble diameter, dehumidification rate and apparent heat transfer coefficient were correlated by means of some experimental parameters such as air temperature, humidity, flow rate and height of water solution layer.

  4. Global Screening of Salmonella enterica Serovar Typhimurium Genes for Desiccation Survival

    PubMed Central

    Mandal, Rabindra K.; Kwon, Young M.

    2017-01-01

    Salmonella spp., one of the most common foodborne bacterial pathogens, has the ability to survive under desiccation conditions in foods and food processing facilities for years. This raises the concerns of Salmonella infection in humans associated with low water activity foods. Salmonella responds to desiccation stress via complex pathways involving immediate physiological actions as well as coordinated genetic responses. However, the exact mechanisms of Salmonella to resist desiccation stress remain to be fully elucidated. In this study, we screened a genome-saturating transposon (Tn5) library of Salmonella Typhimurium (S. Typhimurium) 14028s under the in vitro desiccation stress using transposon sequencing (Tn-seq). We identified 61 genes and 6 intergenic regions required to overcome desiccation stress. Salmonella desiccation resistance genes were mostly related to energy production and conversion; cell wall/membrane/envelope biogenesis; inorganic ion transport and metabolism; regulation of biological process; DNA metabolic process; ABC transporters; and two component system. More than 20% of the Salmonella desiccation resistance genes encode either putative or hypothetical proteins. Phenotypic evaluation of 12 single gene knockout mutants showed 3 mutants (atpH, atpG, and corA) had significantly (p < 0.02) reduced survival as compared to the wild type during desiccation survival. Thus, our study provided new insights into the molecular mechanisms utilized by Salmonella for survival against desiccation stress. The findings might be further exploited to develop effective control strategies against Salmonella contamination in low water activity foods and food processing facilities.

  5. Insect capa neuropeptides impact desiccation and cold tolerance

    PubMed Central

    Terhzaz, Selim; Teets, Nicholas M.; Cabrero, Pablo; Henderson, Louise; Ritchie, Michael G.; Nachman, Ronald J.; Dow, Julian A. T.; Denlinger, David L.; Davies, Shireen-A.

    2015-01-01

    The success of insects is linked to their impressive tolerance to environmental stress, but little is known about how such responses are mediated by the neuroendocrine system. Here we show that the capability (capa) neuropeptide gene is a desiccation- and cold stress-responsive gene in diverse dipteran species. Using targeted in vivo gene silencing, physiological manipulations, stress-tolerance assays, and rationally designed neuropeptide analogs, we demonstrate that the Drosophila melanogaster capa neuropeptide gene and its encoded peptides alter desiccation and cold tolerance. Knockdown of the capa gene increases desiccation tolerance but lengthens chill coma recovery time, and injection of capa peptide analogs can reverse both phenotypes. Immunohistochemical staining suggests that capa accumulates in the capa-expressing Va neurons during desiccation and nonlethal cold stress but is not released until recovery from each stress. Our results also suggest that regulation of cellular ion and water homeostasis mediated by capa peptide signaling in the insect Malpighian (renal) tubules is a key physiological mechanism during recovery from desiccation and cold stress. This work augments our understanding of how stress tolerance is mediated by neuroendocrine signaling and illustrates the use of rationally designed peptide analogs as agents for disrupting protective stress tolerance. PMID:25730885

  6. Insect capa neuropeptides impact desiccation and cold tolerance.

    PubMed

    Terhzaz, Selim; Teets, Nicholas M; Cabrero, Pablo; Henderson, Louise; Ritchie, Michael G; Nachman, Ronald J; Dow, Julian A T; Denlinger, David L; Davies, Shireen-A

    2015-03-03

    The success of insects is linked to their impressive tolerance to environmental stress, but little is known about how such responses are mediated by the neuroendocrine system. Here we show that the capability (capa) neuropeptide gene is a desiccation- and cold stress-responsive gene in diverse dipteran species. Using targeted in vivo gene silencing, physiological manipulations, stress-tolerance assays, and rationally designed neuropeptide analogs, we demonstrate that the Drosophila melanogaster capa neuropeptide gene and its encoded peptides alter desiccation and cold tolerance. Knockdown of the capa gene increases desiccation tolerance but lengthens chill coma recovery time, and injection of capa peptide analogs can reverse both phenotypes. Immunohistochemical staining suggests that capa accumulates in the capa-expressing Va neurons during desiccation and nonlethal cold stress but is not released until recovery from each stress. Our results also suggest that regulation of cellular ion and water homeostasis mediated by capa peptide signaling in the insect Malpighian (renal) tubules is a key physiological mechanism during recovery from desiccation and cold stress. This work augments our understanding of how stress tolerance is mediated by neuroendocrine signaling and illustrates the use of rationally designed peptide analogs as agents for disrupting protective stress tolerance.

  7. Using EnergyPlus to Perform Dehumidification Analysis on Building America Homes

    SciTech Connect

    Fang, Xia; Winkler, Jon; Christensen, Dane

    2011-03-01

    This study used EnergyPlus to investigate humidity issues on a typical mid-1990s reference home, a 2006 International Energy Conservation Code home, and a high-performance home in a hot-humid climate; the study confirmed that supplemental dehumidification should be provided to maintain space relative humidity below 60% in a hot-humid climate.

  8. Drying hard maple (Acer saccharum L.) lumber in a small dehumidification kiln

    Treesearch

    Neal. Bennett

    2013-01-01

    Portable sawmill owners quickly recognize the advantage to kiln drying lumber they produce. Having the ability to provide properly kiln-dried lumber opens new market opportunities and can increase profit margins. However, the construction and operation of a dry kiln must be economical and simple. A small dehumidification dry kiln constructed and tested in Princeton, WV...

  9. Advanced Dehumidification Analysis on Building America Homes Using EnergyPlus: Preprint

    SciTech Connect

    Fang, X.; Winkler, J.; Christensen, D.

    2010-08-01

    A parametric study was conducted using EnergyPlus version 4.0 to analyze the impact of various dehumidification equipment and control strategies on a typical mid-1990's reference home, a 2006 IECC home, and a high-performance home in a hot humid climate.

  10. Building America Case Study: Evaluation of the Performance of Houses With and Without Supplemental Dehumidification in a Hot-Humid Climate, New Orleans, Louisiana (Fact Sheet)

    SciTech Connect

    Not Available

    2014-11-01

    This report, Evaluation of the Performance of Houses with and without Supplemental Dehumidification in a Hot-Humid Climate, describes a research study that that was conducted by the Building Science Corporation (BSC) Building America Research Team. BSC seeks to research and report on the field monitoring of the performance of in-situ supplemental dehumidification systems in low energy, high performance, homes in a Hot-Humid climate. The purpose of this research project was to observe and compare the humidity control performance of new, single family, low energy, and high performance, homes. Specifically, the study sought to compare the interior conditions and mechanical systems operation between two distinct groups of houses, homes with a supplemental dehumidifier installed in addition to HVAC system, and homes without any supplemental dehumidification. The subjects of the study were ten single-family new construction homes in New Orleans, LA. Data logging equipment was installed at each home in 2012. Interior conditions and various end-use loads were monitored for one year. In terms of averages, the homes with dehumidifiers are limiting elevated levels of humidity in the living space. However, there was significant variation in humidity control between individual houses. An analysis of the equipment operation did not show a clear correlation between energy use and humidity levels. In general, no single explanatory variable appears to provide a consistent understanding of the humidity control in each house. Indoor humidity is likely due to all of the factors we have examined, and the specifics of how they are used by each occupant.

  11. Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

    PubMed

    Proctor, Michael C F; Ligrone, Roberto; Duckett, Jeffrey G

    2007-06-01

    pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

  12. Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

    PubMed

    Proctor, Michael C F; Ligrone, Roberto; Duckett, Jeffrey G

    2007-01-01

    data from the pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

  13. Attempting to control mite allergens with mechanical ventilation and dehumidification in British houses.

    PubMed

    Niven, R; Fletcher, A M; Pickering, A C; Custovic, A; Sivour, J B; Preece, A R; Oldham, L A; Francis, H C

    1999-05-01

    Allergen avoidance is of considerable interest in the treatment and even prevention of asthma. Attempts to control house dust mites have included environmental manipulation in homes in an attempt to reduce humidity below a level that favors mite survival. This appears to have some benefit in Scandinavia, but a previous attempt with mechanical ventilation heat pump recovery (MVHR) units in the UK failed to achieve the desired results. We report a study using an additional central dehumidification modification of the MVHR (MVHRcd) in an attempt to reduce allergen levels in houses of asthmatic subjects. Ten houses of asthmatic patients allergic to dust mites and 10 architectural control houses were studied. The active houses were fitted with an MVHRcd unit in November/December 1994 and activated in January 1995. The active and control houses were monitored continuously for internal temperature and humidity by using digital sensors in the asthmatic and control bedrooms. Dust samples were collected to determine allergen levels at baseline (January 1994) and 3, 6, 9, and 15 months after switching on the units. The winter seasonal average humidity fell from 50% relative humidity (RH) in control bedrooms to 37% RH in asthmatic bedrooms compared with 72% RH in the ambient air as measured on the intake of the MVHRcd systems. There was no corresponding change in seasonal mean temperature within the houses. Although the temperature and humidity weekly and seasonal means remained below the study target of 45% RH or 7 g/kg absolute humidity at 21 degrees C, there were transient rises in humidity detected by the sensors in the houses with MVHRcd systems. Allergen levels fell both in active and control houses during the study period, but there was no significant advantage gained from the installation of MVHRcd systems. The MVHRcd system failed to confer a benefit in terms of mite allergen reduction despite apparently adequate control of temperature and humidity.

  14. Antioxidant defences in hydrated and desiccated states of the tardigrade Paramacrobiotus richtersi.

    PubMed

    Rizzo, Angela M; Negroni, Manuela; Altiero, Tiziana; Montorfano, Gigliola; Corsetto, Paola; Berselli, Patrizia; Berra, Bruno; Guidetti, Roberto; Rebecchi, Lorena

    2010-06-01

    Reactive oxygen species (ROS) are formed in all aerobic organisms, potentially leading to oxidative damage of all biological molecules. A number of defence mechanisms have developed to protect the organism from attack by ROS. Desiccation tolerance is correlated with an increase in the antioxidant potential in several organisms, but the regulation of the antioxidant defence system is complex and its role in desiccation-tolerant organisms is not yet firmly established. To determine if anhydrobiotic tardigrades have an antioxidant defence system, capable of counteracting ROS, we compared the activity of several antioxidant enzymes, the fatty acid composition and Heat shock protein expression in two physiological states (desiccated vs. hydrated) of the tardigrade Paramacrobiotus richtersi. In hydrated tardigrades, superoxide dismutase and catalase show comparable activities, while in desiccated specimens the activity of superoxide dismutase increases. Both glutathione peroxidase and glutathione were induced by desiccation. The percentage of fatty acid composition of polyunsaturated fatty acids and the amount of thiobarbituric acid reactive substances are higher in desiccated animals than in hydrated ones. Lastly, desiccated tardigrades did not differ significantly from the hydrated ones in the relative levels of Hsp70 and Hsp90. These results indicate that the possession of antioxidant metabolism could represent a crucial strategy to avoid damages during desiccation in anhydrobiotic tardigrades.

  15. Measurement uncertainty of adsorption testing of desiccant materials

    SciTech Connect

    Bingham, C E; Pesaran, A A

    1988-12-01

    The technique of measurement uncertainty analysis as described in the current ANSI/ASME standard is applied to the testing of desiccant materials in SERI`s Sorption Test Facility. This paper estimates the elemental precision and systematic errors in these tests and propagates them separately to obtain the resulting uncertainty of the test parameters, including relative humidity ({plus_minus}.03) and sorption capacity ({plus_minus}.002 g/g). Errors generated by instrument calibration, data acquisition, and data reduction are considered. Measurement parameters that would improve the uncertainty of the results are identified. Using the uncertainty in the moisture capacity of a desiccant, the design engineer can estimate the uncertainty in performance of a dehumidifier for desiccant cooling systems with confidence. 6 refs., 2 figs., 8 tabs.

  16. Microbiological quality of desiccated coconut.

    PubMed Central

    Kinderlerer, J. L.; Clark, R. A.

    1986-01-01

    A microbial survey of Sri Lankan desiccated coconut has been made on material purchased in supermarkets in Sheffield or on material obtained directly from the processing company. The total viable count (TVC) was reduced by spoilage and pasteurization from 10(4)/g to 10(3)/g. Most samples contained low levels of coagulase-positive Staphylococcus aureus suggesting that this commodity had been handled during production. One focus of contamination with Aspergillus flavus was found for each 8.34 g of desiccated coconut (mean contamination). The number of bacteria and moulds in spoiled coconut was significantly lower than that in coconut obtained from the processor or purchased from retail outlets. It is suggested that the accumulation of free fatty acids, aliphatic methyl ketones and secondary alcohols produced during fungal spoilage has had a bactericidal and fungicidal effect. The use of microbial specifications for foods is questioned in situations where there is evidence of microbial spoilage having taken place. PMID:3081627

  17. Annual Performance of a Two-Speed, Dedicated Dehumidification Heat Pump in the NIST Net-Zero Energy Residential Test Facility.

    PubMed

    Payne, W Vance

    2016-01-01

    A 2715 ft(2) (252 m(2)), two story, residential home of the style typical of the Gaithersburg, Maryland area was constructed in 2012 to demonstrate technologies for net-zero energy (NZE) homes (or ZEH). The NIST Net-Zero Energy Residential Test Facility (NZERTF) functions as a laboratory to support the development and adoption of cost-effective NZE designs, technologies, construction methods, and building codes. The primary design goal was to meet the comfort and functional needs of the simulated occupants. The first annual test period began on July 1, 2013 and ended June 30, 2014. During the first year of operation, the home's annual energy consumption was 13039 kWh (4.8 kWh ft(-2), 51.7 kWh m(-2)), and the 10.2 kW solar photovoltaic system generated an excess of 484 kWh. During this period the heating and air conditioning of the home was performed by a novel air-source heat pump that utilized a reheat heat exchanger to allow hot compressor discharge gas to reheat the supply air during a dedicated dehumidification mode. During dedicated dehumidification, room temperature air was supplied to the living space until the relative humidity setpoint of 50% was satisfied. The heat pump consumed a total of 6225 kWh (2.3 kWh ft(-2,) 24.7 kWh m(-2)) of electrical energy for cooling, heating, and dehumidification. Annual cooling efficiency was 10.1 Btu W(-1)h(-1) (2.95 W W(-1)), relative to the rated SEER of the heat pump of 15.8 Btu W(-1)h(-1) (4.63 W W(-1)). Annual heating efficiency was 7.10 Btu W(-1)h(-1) (2.09 W W(-1)), compared with the unit's rated HSPF of 9.05 Btu W(-1)h(-1) (2.65 W W(-1)). These field measured efficiency numbers include dedicated dehumidification operation and standby energy use for the year. Annual sensible heat ratio was approximately 70%. Standby energy consumption was 5.2 % and 3.5 % of the total electrical energy used for cooling and heating, respectively.

  18. Annual Performance of a Two-Speed, Dedicated Dehumidification Heat Pump in the NIST Net-Zero Energy Residential Test Facility

    PubMed Central

    Payne, W. Vance

    2017-01-01

    A 2715 ft2 (252 m2), two story, residential home of the style typical of the Gaithersburg, Maryland area was constructed in 2012 to demonstrate technologies for net-zero energy (NZE) homes (or ZEH). The NIST Net-Zero Energy Residential Test Facility (NZERTF) functions as a laboratory to support the development and adoption of cost-effective NZE designs, technologies, construction methods, and building codes. The primary design goal was to meet the comfort and functional needs of the simulated occupants. The first annual test period began on July 1, 2013 and ended June 30, 2014. During the first year of operation, the home's annual energy consumption was 13039 kWh (4.8 kWh ft-2, 51.7 kWh m-2), and the 10.2 kW solar photovoltaic system generated an excess of 484 kWh. During this period the heating and air conditioning of the home was performed by a novel air-source heat pump that utilized a reheat heat exchanger to allow hot compressor discharge gas to reheat the supply air during a dedicated dehumidification mode. During dedicated dehumidification, room temperature air was supplied to the living space until the relative humidity setpoint of 50% was satisfied. The heat pump consumed a total of 6225 kWh (2.3 kWh ft-2, 24.7 kWh m-2) of electrical energy for cooling, heating, and dehumidification. Annual cooling efficiency was 10.1 Btu W-1h-1 (2.95 W W-1), relative to the rated SEER of the heat pump of 15.8 Btu W-1h-1 (4.63 W W-1). Annual heating efficiency was 7.10 Btu W-1h-1 (2.09 W W-1), compared with the unit's rated HSPF of 9.05 Btu W-1h-1 (2.65 W W-1). These field measured efficiency numbers include dedicated dehumidification operation and standby energy use for the year. Annual sensible heat ratio was approximately 70%. Standby energy consumption was 5.2 % and 3.5 % of the total electrical energy used for cooling and heating, respectively. PMID:28729740

  19. Desiccant-Based Preconditioning Market Analysis

    SciTech Connect

    Fischer, J.

    2001-01-11

    A number of important conclusions can be drawn as a result of this broad, first-phase market evaluation. The more important conclusions include the following: (1) A very significant market opportunity will exist for specialized outdoor air-handling units (SOAHUs) as more construction and renovation projects are designed to incorporate the recommendations made by the ASHRAE 62-1989 standard. Based on this investigation, the total potential market is currently $725,000,000 annually (see Table 6, Sect. 3). Based on the market evaluations completed, it is estimated that approximately $398,000,000 (55%) of this total market could be served by DBC systems if they were made cost-effective through mass production. Approximately $306,000,000 (42%) of the total can be served by a non-regenerated, desiccant-based total recovery approach, based on the information provided by this investigation. Approximately $92,000,000 (13%) can be served by a regenerated desiccant-based cooling approach (see Table 7, Sect. 3). (2) A projection of the market selling price of various desiccant-based SOAHU systems was prepared using prices provided by Trane for central-station, air-handling modules currently manufactured. The wheel-component pricing was added to these components by SEMCO. This resulted in projected pricing for these systems that is significantly less than that currently offered by custom suppliers (see Table 4, Sect. 2). Estimated payback periods for all SOAHU approaches were quite short when compared with conventional over-cooling and reheat systems. Actual paybacks may vary significantly depending on site-specific considerations. (3) In comparing cost vs benefit of each SOAHU approach, it is critical that the total system design be evaluated. For example, the cost premium of a DBC system is very significant when compared to a conventional air handling system, yet the reduced chiller, boiler, cooling tower, and other expense often equals or exceeds this premium, resulting in a

  20. Effects of dehumidification drying environment on drying speed of one component waterborne wood top coating

    NASA Astrophysics Data System (ADS)

    Lu, Zeguang; Tang, Tong; Zhou, Ge; Jia, Wanda; Wang, Meng; Xu, Jing; Bai, Shihong

    2016-03-01

    In this study, the effects of dehumidification drying environment including air temperature and relative humidity and velocity on drying speed of one component waterborne wood top coating are studied by Orthogonal experimental design and the results are analyzed creatively by Duncan analyses. It is found that during the dehumidification drying process, hard drying time is decreasing with the increasing air temperature and velocity and decreasing relative humidity. Air velocity is extremely significant to hard drying time, which is more significant than relative humidity, and relative humidity is more significant than air temperature. The difference of hard drying time is significant when the difference is 5 min and above, and it is extremely significant when the difference is 10 min and above, which are critical to judge the hard time in practice.

  1. Flow structure of natural dehumidification over a horizontal finned-tube

    NASA Astrophysics Data System (ADS)

    Hirbodi, Kamran; Yaghoubi, Mahmood

    2016-08-01

    In the present study, structure of water drops formation, growth, coalescence and departure over a horizontal finned-tube during natural dehumidification is investigated experimentally. Starting time of repelling the drops as well as heat transfer rate and the rate of dripping condensates in quasi-steady-state conditions are presented. Furthermore, cold airflow pattern around the horizontal finned-tube is visualized by using smoke generation scheme during natural dehumidification process. The finned-tube has a length of 300 mm, and inner and outer fin diameters, fin thickness and fin spacing are 25.4, 56, 0.4 and 2 mm, respectively. The tests are conducted in an insulated control room with dimensions of 5.8 m × 3 m × 4 m. Ambient air temperature, relative humidity and fin base temperature are selected from 25 to 35 °C, from 40 to 70 % and from 4 to 8 °C, respectively. Observations show that natural condensation from humid air over the test case is completely dropwise. Droplets only form on the edge of the fin and lateral fin surfaces remain almost dry. Dehumidification process over the tested finned-tube is divided into four stages; nucleation, formation, growth and departure of drops. It is also observed that the condensate inundation leaves the tube bottom in the form of droplets. Smoke visualization depicts that humid airflows downward around the cold finned-tube surface without noticeable turbulence and separation in the initial stages of dehumidification process. But the airflow has some disturbances in the intermediate stage and especially during drop departure on the edge of the fins.

  2. Antioxidant defense during desiccation of the resurrection plant Haberlea rhodopensis.

    PubMed

    Georgieva, Katya; Dagnon, Soleya; Gesheva, Emiliya; Bojilov, Dimitar; Mihailova, Gergana; Doncheva, Snezhana

    2017-05-01

    Maintaining a strong antioxidant system is essential for preventing drought-induced oxidative stress. Thus, in the present study we investigated the role of some non-enzymic and enzymic antioxidants in desiccation tolerance of Haberlea rhodopensis. The effects of high light upon desiccation on antioxidant capacity was estimated by comparing the response of shade and sun plants. The significant enhancement of the antioxidant capacity at 8% RWC corresponded to an enormous increase in flavonoid content. The important role of ascorbate-glutathione cycle in overcoming oxidative stress during drying of H. rhodopensis was established. The antioxidant capacity increased upon dehydration of both shade and sun plants but some differences in non-enzymatic and enzymatic antioxidants were observed. Investigations on the role of polyphenols in desiccation tolerance are scarce. In the present study the polyphenol profiles (fingerprints) of the resurrection plant Haberlea rhodopensis, including all components of the complex are obtained for the first time. It was clarified that the polyphenol complex of H. rhodopensis includes only two types of glycosides - phenylethanoid glucosides and hispidulin 8-C-glucosides. Upon desiccation the polyphenol content increase and the main role of phenylethanoid glucosides in the protection of H. rhodopensis was revealed. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  3. Aquatic insects dealing with dehydration: do desiccation resistance traits differ in species with contrasting habitat preferences?

    PubMed

    Pallarés, Susana; Velasco, Josefa; Millán, Andrés; Bilton, David T; Arribas, Paula

    2016-01-01

    Desiccation resistance shapes the distribution of terrestrial insects at multiple spatial scales. However, responses to drying stress have been poorly studied in aquatic groups, despite their potential role in constraining their distribution and diversification, particularly in arid and semi-arid regions. We examined desiccation resistance in adults of four congeneric water beetle species (Enochrus, family Hydrophilidae) with contrasting habitat specificity (lentic vs. lotic systems and different salinity optima from fresh- to hypersaline waters). We measured survival, recovery capacity and key traits related to desiccation resistance (fresh mass, % water content, % cuticle content and water loss rate) under controlled exposure to desiccation, and explored their variability within and between species. Meso- and hypersaline species were more resistant to desiccation than freshwater and hyposaline ones, showing significantly lower water loss rates and higher water content. No clear patterns in desiccation resistance traits were observed between lotic and lentic species. Intraspecifically, water loss rate was positively related to specimens' initial % water content, but not to fresh mass or % cuticle content, suggesting that the dynamic mechanism controlling water loss is mainly regulated by the amount of body water available. Our results support previous hypotheses suggesting that the evolution of desiccation resistance is associated with the colonization of saline habitats by aquatic beetles. The interespecific patterns observed in Enochrus also suggest that freshwater species may be more vulnerable than saline ones to drought intensification expected under climate change in semi-arid regions such as the Mediterranean Basin.

  4. Relaxation nuclear magnetic resonance imaging (R-NMRI) of desiccation in M9787 silicone pads.

    SciTech Connect

    Alam, Todd M; Cherry, Brian Ray; Alam, Mary Kathleen

    2004-06-01

    The production and aging of silicone materials remains an important issue in the weapons stockpile due to their utilization in a wide variety of components and systems within the stockpile. Changes in the physical characteristics of silicone materials due to long term desiccation has been identified as one of the major aging effects observed in silicone pad components. Here we report relaxation nuclear magnetic resonance imaging (R-NMRI) spectroscopy characterization of the silica-filled and unfilled polydimethylsiloxane (PDMS) and polydiphenylsiloxane (PDPS) copolymer (M9787) silicone pads within desiccating environments. These studies were directed at providing additional details about the heterogeneity of the desiccation process. Uniform NMR spin-spin relaxation time (T2) images were observed across the pad thickness indicating that the drying process is approximately uniform, and that the desiccation of the M9787 silicone pad is not a H2O diffusion limited process. In a P2O5 desiccation environment, significant reduction of T2 was observed for the silica-filled and unfilled M9787 silicone pad for desiccation up to 225 days. A very small reduction in T2 was observed for the unfilled copolymer between 225 and 487 days. The increase in relative stiffness with desiccation was found to be higher for the unfilled copolymer. These R-NMRI results are correlated to local changes in the modulus of the material

  5. Aquatic insects dealing with dehydration: do desiccation resistance traits differ in species with contrasting habitat preferences?

    PubMed Central

    Velasco, Josefa; Millán, Andrés; Bilton, David T.; Arribas, Paula

    2016-01-01

    Background Desiccation resistance shapes the distribution of terrestrial insects at multiple spatial scales. However, responses to drying stress have been poorly studied in aquatic groups, despite their potential role in constraining their distribution and diversification, particularly in arid and semi-arid regions. Methods We examined desiccation resistance in adults of four congeneric water beetle species (Enochrus, family Hydrophilidae) with contrasting habitat specificity (lentic vs. lotic systems and different salinity optima from fresh- to hypersaline waters). We measured survival, recovery capacity and key traits related to desiccation resistance (fresh mass, % water content, % cuticle content and water loss rate) under controlled exposure to desiccation, and explored their variability within and between species. Results Meso- and hypersaline species were more resistant to desiccation than freshwater and hyposaline ones, showing significantly lower water loss rates and higher water content. No clear patterns in desiccation resistance traits were observed between lotic and lentic species. Intraspecifically, water loss rate was positively related to specimens’ initial % water content, but not to fresh mass or % cuticle content, suggesting that the dynamic mechanism controlling water loss is mainly regulated by the amount of body water available. Discussion Our results support previous hypotheses suggesting that the evolution of desiccation resistance is associated with the colonization of saline habitats by aquatic beetles. The interespecific patterns observed in Enochrus also suggest that freshwater species may be more vulnerable than saline ones to drought intensification expected under climate change in semi-arid regions such as the Mediterranean Basin. PMID:27635346

  6. Effects of periodic desiccation on the synthesis of the UV-screening compound, scytonemin, in cyanobacteria.

    PubMed

    Fleming, Erich D; Castenholz, Richard W

    2007-06-01

    Scytonemin is an ultraviolet radiation (UVR)-screening compound synthesized by some sheathed cyanobacteria exposed to high solar and sky radiation. It is primarily produced in response to UVA radiation, but certain environmental stresses can enhance synthesis. This study focuses on the effects of periodic desiccation on scytonemin synthesis in three desiccation-tolerant cyanobacterial strains, Nostoc punctiforme PCC 73102, Chroococcidiopsis CCMEE 5056 and Chroococcidiopsis CCMEE 246. Nostoc punctiforme and Chroococcidiopsis CCMEE 5056 exposed to UVA radiation produced more concentrated scytonemin screens when experiencing periodic desiccation (i.e. 1 day desiccated for every 2 days hydrated) than when continuously hydrated. A more concentrated scytonemin screen would reduce the amount of UVR damage accrued when cells are desiccated and metabolically inactive. This might allow the cyanobacteria to allocate more energy to systems other than UVR damage repair during rehydration, which would facilitate recovery. The scytonemin screen is extremely stable, remaining largely intact in the sheaths of desiccated N. punctiforme even when continuously exposed to UVA radiation for about 2 months. In contrast to the above findings, scytonemin synthesis in Chroococcidiopsis CCMEE 246, a strain that produces scytonemin constitutively under low visible light (no UVA), was partially inhibited by periodic desiccation.

  7. Monitoring Vadose Zone Desiccation with Geophysical Methods

    SciTech Connect

    Truex, Michael J.; Johnson, Timothy C.; Strickland, Christopher E.; Peterson, John E.; Hubbard, Susan S.

    2013-05-01

    Soil desiccation was recently field tested as a potential vadose zone remediation technology. Desiccation removes water from the vadose zone and significantly decreases the aqueous-phase permeability of the desiccated zone, thereby decreasing movement of moisture and contaminants. The 2-D and 3-D distribution of moisture content reduction over time provides valuable information for desiccation operations and for determining when treatment goals have been reached. This type of information can be obtained through use of geophysical methods. Neutron moisture logging, cross-hole electrical resistivity tomography, and cross-hole ground penetrating radar approaches were evaluated with respect to their ability to provide effective spatial and temporal monitoring of desiccation during a treatability study conducted in the vadose zone of the DOE Hanford Site in WA.

  8. Breathing air purification; Desiccant vs. refrigerated

    SciTech Connect

    McKay, K.L.; Swanson, A.L. )

    1986-07-01

    Carbon monoxide (CO) is a common contaminant of ambient air - levels as high as 200 ppm are not uncommon in urban, industrial, or high automotive-traffic areas. Carbon monoxide may also be produced by the oxidation of lubricating oil in overheated compressors. Air from an oil-lubricated compressor, even when an aftercooler is used, often contains significant quantities of oil mist and vapor. Even where a breathing air (non-oil-lubricated) compressor is used , oil. levels in the air taken into the compressor can still exceed Grade D standards, especially in industrial environments. Other contaminants (gaseous hydrocarbons, particulate matter, and odors), while not addressed by the Grade D criteria, are also present in harmful or objectionable levels in industrial environments; therefore, they must be taken into account in the design of the air purification systems. This paper discusses two basic types of breathing air purifiers: desiccant and refrigerated purifiers.

  9. Ecological significance of seed desiccation sensitivity in Quercus ilex

    PubMed Central

    Joët, Thierry; Ourcival, Jean-Marc; Dussert, Stéphane

    2013-01-01

    Background and Aims Several widespread tree species of temperate forests, such as species of the genus Quercus, produce recalcitrant (desiccation-sensitive) seeds. However, the ecological significance of seed desiccation sensitivity in temperate regions is largely unknown. Do seeds of such species suffer from drying during the period when they remain on the soil, between shedding in autumn and the return of conditions required for germination in spring? Methods To test this hypothesis, the Mediterranean holm oak (Quercus ilex) forest was used as a model system. The relationships between the climate in winter, the characteristics of microhabitats, acorn morphological traits, and the water status and viability of seeds after winter were then investigated in 42 woodlands sampled over the entire French distribution of the species. Key Results The percentages of germination and normal seedling development were tightly linked to the water content of seeds after the winter period, revealing that in situ desiccation is a major cause of mortality. The homogeneity of seed response to drying suggests that neither intraspecific genetic variation nor environmental conditions had a significant impact on the level of desiccation sensitivity of seeds. In contrast, the water and viability status of seeds at the time of collection were dramatically influenced by cumulative rainfall and maximum temperatures during winter. A significant effect of shade and of the type of soil cover was also evidenced. Conclusions The findings establish that seed desiccation sensitivity is a key functional trait which may influence the success of recruitment in temperate recalcitrant seed species. Considering that most models of climate change predict changes in rainfall and temperature in the Mediterranean basin, the present work could help foresee changes in the distribution of Q. ilex and other oak species, and hence plant community alterations. PMID:23388882

  10. Desiccation response of mammalian cells: anhydrosignaling.

    PubMed

    Huang, Zebo; Tunnacliffe, Alan

    2007-01-01

    Dehydration through evaporation, or air drying, is expected to have both similarities and differences to osmostress. Both stresses involve water loss, but the degree of dehydration will ultimately be more severe during desiccation. Despite the severity of desiccation stress, there are examples of organisms that can survive almost complete water loss, including resurrection plants and plant seeds, certain invertebrates among the nematodes, brine shrimps, tardigrades and bdelloid rotifers, and many microorganisms, including bakers' yeast. During desiccation, these organisms enter a state of suspended animation, a process known as anhydrobiosis ("life without water"). For other organisms, desiccation is lethal, but there is considerable interest in using what is known about anhydrobiosis to confer desiccation tolerance on sensitive cell types, such as mammalian cells. Success with this approach, which we have termed anhydrobiotic engineering, will require a more complete knowledge of the mechanisms of desiccation tolerance and the sensing and response of nontolerant organisms to extreme dehydration. With this goal in mind, we have attempted to characterize the response of human tissue culture cells to desiccation and to compare this response with osmotic upshift. This chapter describes some of the methods used to begin to uncover the response to evaporative water loss in human cell cultures.

  11. Review of the aquifer seasonal thermal energy storage building HVAC system at the Melville, New York, Mid-Island Mail Facility

    SciTech Connect

    Marseille, T.J.; Wilke, D.A.

    1992-08-01

    The successful widespread commercialization of aquifer thermal energy storage (ATES) in the United States will depend on the effectiveness with which the experiences gained from early full-scale systems are used as guides in the design, installation and operation of future projects. One such early system from which both anecdotal and quantitative information is available is the Mid-Island Postal Facility in Melville, New York. At this facility, built in the mid-1980s, an ATES system has been integrated with the building`s central heating and cooling plant. ``Cold`` wells are charged with water that is cooled during the winter by heat pump and closed circuit cooler operation. Water from these cold wells is then used to meet the facility`s cooling load during the summer, before being pumped back into the ground at ``Warm`` wells. Dehumidification during summer operation is accomplished by a liquid desiccant system that uses propane boilers to provide a heat source for desiccant regeneration. This system will also add water to the air during periods of low humidity. This paper provides an overview of the project, and describes the analysis being performed to assess energy and economic merits of this innovative system.

  12. Review of the aquifer seasonal thermal energy storage building HVAC system at the Melville, New York, Mid-Island Mail Facility

    SciTech Connect

    Marseille, T.J.; Wilke, D.A.

    1992-08-01

    The successful widespread commercialization of aquifer thermal energy storage (ATES) in the United States will depend on the effectiveness with which the experiences gained from early full-scale systems are used as guides in the design, installation and operation of future projects. One such early system from which both anecdotal and quantitative information is available is the Mid-Island Postal Facility in Melville, New York. At this facility, built in the mid-1980s, an ATES system has been integrated with the building's central heating and cooling plant. Cold'' wells are charged with water that is cooled during the winter by heat pump and closed circuit cooler operation. Water from these cold wells is then used to meet the facility's cooling load during the summer, before being pumped back into the ground at Warm'' wells. Dehumidification during summer operation is accomplished by a liquid desiccant system that uses propane boilers to provide a heat source for desiccant regeneration. This system will also add water to the air during periods of low humidity. This paper provides an overview of the project, and describes the analysis being performed to assess energy and economic merits of this innovative system.

  13. Water isotopes in desiccating lichens

    PubMed Central

    Cuntz, Matthias; Máguas, Cristina; Lakatos, Michael

    2009-01-01

    The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition. PMID:19888598

  14. [Desiccation cracking of soil body: a review].

    PubMed

    Pei, Yin-Ge; Xu, Ze-Min; Zhang, Jia-Ming

    2012-04-01

    Desiccation cracking of soil body is a complex physical process, which can affect the strength, stability, and permeability of soil body, and involve in several disciplines such as soil science, agricultural science, engineering geology, and environmental science. This paper introduced the significances of the study on the desiccation cracking of soil body, reviewed the related theoretical and applied researches and the quantitative analysis of crack morphology, and discussed the deficiencies in the research fields, research contents, and research methods. The future research directions about the desiccation cracking of soil body were pointed out.

  15. Experimental and Numerical Investigations of Soil Desiccation for Vadose Zone Remediation: Report for Fiscal Year 2007

    SciTech Connect

    Ward, Andy L.; Oostrom, Mart; Bacon, Diana H.

    2008-02-04

    Apart from source excavation, the options available for the remediation of vadose zone metal and radionuclide contaminants beyond the practical excavation depth (0 to 15 m) are quite limited. Of the available technologies, very few are applicable to the deep vadose zone with the top-ranked candidate being soil desiccation. An expert panel review of the work on infiltration control and supplemental technologies identified a number of knowledge gaps that would need to be overcome before soil desiccation could be deployed. The report documents some of the research conducted in the last year to fill these knowledge gaps. This work included 1) performing intermediate-scale laboratory flow cell experiments to demonstrate the desiccation process, 2) implementing a scalable version of Subsurface Transport Over Multiple Phases–Water-Air-Energy (STOMP-WAE), and 3) performing numerical experiments to identify the factors controlling the performance of a desiccation system.

  16. Seed desiccation mechanisms co-opted for vegetative desiccation in the resurrection grass Oropetium thomaeum.

    PubMed

    VanBuren, Robert; Wai, Ching Man; Zhang, Qingwei; Song, Xiaomin; Edger, Patrick P; Bryant, Doug; Michael, Todd P; Mockler, Todd C; Bartels, Dorothea

    2017-10-01

    Resurrection plants desiccate during periods of prolonged drought stress, then resume normal cellular metabolism upon water availability. Desiccation tolerance has multiple origins in flowering plants, and it likely evolved through rewiring seed desiccation pathways. Oropetium thomaeum is an emerging model for extreme drought tolerance, and its genome, which is the smallest among surveyed grasses, was recently sequenced. Combining RNA-seq, targeted metabolite analysis and comparative genomics, we show evidence for co-option of seed-specific pathways during vegetative desiccation. Desiccation-related gene co-expression clusters are enriched in functions related to seed development including several seed-specific transcription factors. Across the metabolic network, pathways involved in programmed cell death inhibition, ABA signalling and others are activated during dehydration. Oleosins and oil bodies that typically function in seed storage are highly abundant in desiccated leaves and may function for membrane stability and storage. Orthologs to seed-specific LEA proteins from rice and maize have neofunctionalized in Oropetium with high expression during desiccation. Accumulation of sucrose, raffinose and stachyose in drying leaves mirrors sugar accumulation patterns in maturing seeds. Together, these results connect vegetative desiccation with existing seed desiccation and drought responsive pathways and provide some key candidate genes for engineering improved drought tolerance in crop plants. © 2017 John Wiley & Sons Ltd.

  17. Understanding the Dehumidification Performance of Air-Conditioning Equipment at Part-Load Conditions

    SciTech Connect

    Don B. Shirey III; Hugh I. Henderson Jr; Richard A. Raustad

    2006-01-01

    Air conditioner cooling coils typically provide both sensible cooling and moisture removal. Data from a limited number of field studies (Khattar et al. 1985; Henderson and Rengarajan 1996; Henderson 1998) have demonstrated that the moisture removal capacity of a cooling coil degrades at part-load conditions--especially when the supply fan operates continuously while the cooling coil cycles on and off. Degradation occurs because moisture that condenses on the coil surfaces during the cooling cycle evaporates back into air stream when the coil is off. This degradation affects the ability of cooling equipment to maintain proper indoor humidity levels and may negatively impact indoor air quality. This report summarizes the results of a comprehensive project to better understand and quantify the moisture removal (dehumidification) performance of cooling coils at part-load conditions. A review of the open literature was initially conducted to learn from previous research on this topic. Detailed performance measurements were then collected for eight cooling coils in a controlled laboratory setting to understand the impact of coil geometry and operating conditions on transient moisture condensation and evaporation by the coils. Measurements of cooling coil dehumidification performance and space humidity levels were also collected at seven field test sites. Finally, an existing engineering model to predict dehumidification performance degradation for single-stage cooling equipment at part-load conditions (Henderson and Rengarajan 1996) was enhanced to include a broader range of fan control strategies and an improved theoretical basis for modeling off-cycle moisture evaporation from cooling coils. The improved model was validated with the laboratory measurements, and this report provides guidance for users regarding proper model inputs. The model is suitable for use in computerized calculation procedures such as hourly or sub-hourly building energy simulation programs (e

  18. Desiccation Tolerance in the Moss Polytrichum formosum: Physiological and Fine-structural Changes during Desiccation and Recovery

    PubMed Central

    Proctor, Michael C. F.; Ligrone, Roberto; Duckett, Jeffrey G.

    2007-01-01

    similar to those seen in published data from the pteridophyte Selaginella lepidophylla. Conclusions Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses. PMID:17158142

  19. Solute Leakage Resulting from Leaf Desiccation

    PubMed Central

    Leopold, A. Carl; Musgrave, Mary E.; Williams, Kathleen M.

    1981-01-01

    The leakage of solutes from foliar tissue is utilized as a dynamic measure of apparent changes in membrane integrity in response to desiccation. It is found that rehydrating leaf discs of cowpea (Vigna sinensis [L.] Endl.) show increasing leakiness in proportion to the extent of prior desiccation, whereas Selaginella lepidophylla Spring., a resurrection plant, does not. The elevated leakage rate of cowpea after desiccation recovers with time, and the passage of time in the stressed condition results in reduced subsequent leakiness. These characteristics are interpreted as suggesting that the leakage of solute reflects the condition of cellular membranes, and that desiccation stress leads to lesions in the membranes. The kinetics of solute leakage is suggested as a simple means of following changes in membrane lesions and associated features of membrane repair and hardening. PMID:16662082

  20. Induction of Hsp70 by desiccation, ionising radiation and heat-shock in the eutardigrade Richtersius coronifer.

    PubMed

    Jönsson, K Ingemar; Schill, Ralph O

    2007-04-01

    The physiology and biochemistry behind the extreme tolerance to desiccation shown by the so-called anhydrobiotic animals represents an exciting challenge to biology. The current knowledge suggests that both carbohydrates and proteins are often involved in protecting the dry cell from damage, or in the repair of induced damage. Tardigrades belong to the most desiccation-tolerant multicellular organisms, but very little research has been reported on the biochemistry behind desiccation tolerance in this group. We quantified the induction of the heat-shock protein Hsp70, a very wide-spread stress protein, in response to desiccation, ionising radiation, and heating, in the anhydrobiotic tardigrade Richtersius coronifer using an immuno-westernblot method. Elevated levels of Hsp70 were recorded after treatment of both heat and ionising radiation, and also in rehydrated tardigrades after a period of desiccation. In contrast, tardigrades in the desiccated (dry) state had reduced Hsp70 levels compared to the non-treated control group. Our results suggest that Hsp70 may be involved in the physiological and biochemical system underlying desiccation (and radiation) tolerance in tardigrades, and that its role may be connected to repair processes after desiccation rather than to biochemical stabilization in the dry state.

  1. A simple analytical method to estimate all exit parameters of a cross-flow air dehumidifier using liquid desiccant

    PubMed Central

    Bassuoni, M.M.

    2013-01-01

    The dehumidifier is a key component in liquid desiccant air-conditioning systems. Analytical solutions have more advantages than numerical solutions in studying the dehumidifier performance parameters. This paper presents the performance results of exit parameters from an analytical model of an adiabatic cross-flow liquid desiccant air dehumidifier. Calcium chloride is used as desiccant material in this investigation. A program performing the analytical solution is developed using the engineering equation solver software. Good accuracy has been found between analytical solution and reliable experimental results with a maximum deviation of +6.63% and −5.65% in the moisture removal rate. The method developed here can be used in the quick prediction of the dehumidifier performance. The exit parameters from the dehumidifier are evaluated under the effects of variables such as air temperature and humidity, desiccant temperature and concentration, and air to desiccant flow rates. The results show that hot humid air and desiccant concentration have the greatest impact on the performance of the dehumidifier. The moisture removal rate is decreased with increasing both air inlet temperature and desiccant temperature while increases with increasing air to solution mass ratio, inlet desiccant concentration, and inlet air humidity ratio. PMID:25685485

  2. A simple analytical method to estimate all exit parameters of a cross-flow air dehumidifier using liquid desiccant.

    PubMed

    Bassuoni, M M

    2014-03-01

    The dehumidifier is a key component in liquid desiccant air-conditioning systems. Analytical solutions have more advantages than numerical solutions in studying the dehumidifier performance parameters. This paper presents the performance results of exit parameters from an analytical model of an adiabatic cross-flow liquid desiccant air dehumidifier. Calcium chloride is used as desiccant material in this investigation. A program performing the analytical solution is developed using the engineering equation solver software. Good accuracy has been found between analytical solution and reliable experimental results with a maximum deviation of +6.63% and -5.65% in the moisture removal rate. The method developed here can be used in the quick prediction of the dehumidifier performance. The exit parameters from the dehumidifier are evaluated under the effects of variables such as air temperature and humidity, desiccant temperature and concentration, and air to desiccant flow rates. The results show that hot humid air and desiccant concentration have the greatest impact on the performance of the dehumidifier. The moisture removal rate is decreased with increasing both air inlet temperature and desiccant temperature while increases with increasing air to solution mass ratio, inlet desiccant concentration, and inlet air humidity ratio.

  3. Clay with Desiccation Cracks is an Advection Dominated Environment

    NASA Astrophysics Data System (ADS)

    Baram, S.; Kurtzman, D.; Sher, Y.; Ronen, Z.; Dahan, O.

    2012-04-01

    Heavy clay sediments are regarded "safe" from the hydrological point of view due to their low hydraulic conductivities. However, the formation of desiccation cracks in dispersive clays may dramatically change their bulk hydraulic properties. The impact of desiccation cracks on water percolation, dissolved salts and contaminants transport and redox related reactions (microbial ammonium oxidation and denitrification) were investigated in 6 -12 m clay layer near a diary farm waste lagoon. The study implemented unique vadose-zone monitoring systems that enable in-situ measurements of the temporal variation of the sediment's water content along with frequent sampling of the sediment's pore water along the entire vadose zone (> 30 m). Results from four years of continuous measurements showed quick rises in sediment water content following rain events and temporal wastewater overflows. The percolation pattern indicated dominance of preferential flow through a desiccation-cracks network crossing the entire clay sediment layer. High water-propagation velocities (0.4 - 23.6 m h-1) were observed, indicating that the desiccation-crack network remains open and serves as a preferential flow pathway year-round, even at high sediment water content (~0.50 m3 m-3). The rapid percolation bypassed the most bio-geo-active parts of the soil, transporting even highly sorptive contaminants (testosterone and estrogen) in to the deep sections of the vadose zone, accelerating the underlying groundwater contamination. The ammonium and nitrate concentrations in the vadose zone and the high number of nitrifying and denitrifying bacteria (~108 gene copies gdry-sediemt-1, each) found in the sediment indicated that the entire vadose zone is aerated even at high water content conditions (~0.55 m3 m-3). The dissolved salts concentration in the pore-water and the δ2H-H2O and δ18O-H2O values of the pore-water substantially increased with depth (becoming less depleted) in the clay sediment

  4. Relative predation risk and risk of desiccation co-determine oviposition preferences in Cope's gray treefrog, Hyla chrysoscelis.

    PubMed

    Pintar, Matthew R; Resetarits, William J

    2017-06-01

    Habitat permanence and threat of predation are primary drivers of community assembly and composition in lentic freshwater systems. Pond-breeding amphibians select oviposition sites to maximize fitness and minimize risks of predation and desiccation of their offspring, typically facing a trade-off between the two as predation risk often increases as desiccation risk decreases. To experimentally determine if Hyla chrysoscelis partition oviposition along gradients of relative desiccation risk and predation risk, we tested oviposition site preference in a natural population of treefrogs colonizing experimental ponds that varied in water depth and contained predatory larvae of two Ambystoma salamander species. Hyla chrysoscelis selected habitats with both lower predation risk, avoiding A. talpoideum over A. maculatum, and lower desiccation risk, selecting ponds with three times greater depth. We demonstrate that adult oviposition site choices simultaneously minimize relative predation risk and desiccation risk and that closely related salamander species produce functionally different responses among colonizing animals.

  5. Molecular strategies of the Caenorhabditis elegans dauer larva to survive extreme desiccation.

    PubMed

    Erkut, Cihan; Vasilj, Andrej; Boland, Sebastian; Habermann, Bianca; Shevchenko, Andrej; Kurzchalia, Teymuras V

    2013-01-01

    Massive water loss is a serious challenge for terrestrial animals, which usually has fatal consequences. However, some organisms have developed means to survive this stress by entering an ametabolic state called anhydrobiosis. The molecular and cellular mechanisms underlying this phenomenon are poorly understood. We recently showed that Caenorhabditis elegans dauer larva, an arrested stage specialized for survival in adverse conditions, is resistant to severe desiccation. However, this requires a preconditioning step at a mild desiccative environment to prepare the organism for harsher desiccation conditions. A systems approach was used to identify factors that are activated during this preconditioning. Using microarray analysis, proteomics, and bioinformatics, genes, proteins, and biochemical pathways that are upregulated during this process were identified. These pathways were validated via reverse genetics by testing the desiccation tolerances of mutants. These data show that the desiccation response is activated by hygrosensation (sensing the desiccative environment) via head neurons. This leads to elimination of reactive oxygen species and xenobiotics, expression of heat shock and intrinsically disordered proteins, polyamine utilization, and induction of fatty acid desaturation pathway. Remarkably, this response is specific and involves a small number of functional pathways, which represent the generic toolkit for anhydrobiosis in plants and animals.

  6. Molecular Strategies of the Caenorhabditis elegans Dauer Larva to Survive Extreme Desiccation

    PubMed Central

    Erkut, Cihan; Vasilj, Andrej; Boland, Sebastian; Habermann, Bianca; Shevchenko, Andrej; Kurzchalia, Teymuras V.

    2013-01-01

    Massive water loss is a serious challenge for terrestrial animals, which usually has fatal consequences. However, some organisms have developed means to survive this stress by entering an ametabolic state called anhydrobiosis. The molecular and cellular mechanisms underlying this phenomenon are poorly understood. We recently showed that Caenorhabditis elegans dauer larva, an arrested stage specialized for survival in adverse conditions, is resistant to severe desiccation. However, this requires a preconditioning step at a mild desiccative environment to prepare the organism for harsher desiccation conditions. A systems approach was used to identify factors that are activated during this preconditioning. Using microarray analysis, proteomics, and bioinformatics, genes, proteins, and biochemical pathways that are upregulated during this process were identified. These pathways were validated via reverse genetics by testing the desiccation tolerances of mutants. These data show that the desiccation response is activated by hygrosensation (sensing the desiccative environment) via head neurons. This leads to elimination of reactive oxygen species and xenobiotics, expression of heat shock and intrinsically disordered proteins, polyamine utilization, and induction of fatty acid desaturation pathway. Remarkably, this response is specific and involves a small number of functional pathways, which represent the generic toolkit for anhydrobiosis in plants and animals. PMID:24324795

  7. Metabolic profiling of the resurrection plant Haberlea rhodopensis during desiccation and recovery.

    PubMed

    Moyankova, Daniela; Mladenov, Petko; Berkov, Strahil; Peshev, Darin; Georgieva, Desislava; Djilianov, Dimitar

    2014-12-01

    Desiccation tolerance is among the most important parameters for crop improvement under changing environments. Resurrection plants are useful models for both theoretical and practical studies. We performed metabolite profiling via gas chromatography coupled with mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) and analyzed the antioxidant capacity of the endemic resurrection plant Haberlea rhodopensis at desiccation and recovery. More than 100 compounds were evaluated. Stress response included changes in both primary and secondary metabolic pathways. The high amounts of the specific glycoside myconoside and some phenolic acids - e.g. syringic and dihydrocaffeic acid under normal conditions tend to show their importance for the priming of H. rhodopensis to withstand severe desiccation and oxidative stress. The accumulation of sucrose (resulting from starch breakdown), total phenols, β-aminoisobutyric acid, β-sitosterol and α-tocopherol increased up to several times at later stages of desiccation. Extracts of H. rhodopensis showed high antioxidant capacity at stress and normal conditions. Myconoside was with the highest antioxidant properties among tested phenolic compounds. Probably, the evolution of resurrection plants under various local environments has resulted in unique desiccation tolerance with specific metabolic background. In our case, it includes the accumulation of a relatively rare compound (myconoside) that contributes alone and together with other common metabolites. Further systems biology studies on the involvement of carbohydrates, phenolic acids and glycosides in the desiccation tolerance and antioxidant capacity of H. rhodopensis will definitely help in achieving the final goal - improving crop drought tolerance.

  8. Desiccation tolerance in Bryophytes: relevance to the evolution of desiccation tolerance in Land Plants

    USDA-ARS?s Scientific Manuscript database

    The majority of desiccation-tolerant plants are found in the less complex clades that constitute the algae, lichens and bryophytes. However, within the larger and more complex groups of vascular land plants there are some 120-130 species that exhibit some degree of vegetative desiccation tolerance. ...

  9. High-Efficiency Variable Dehumidification for Air Conditioners: ClimaStat

    SciTech Connect

    West, Michael K., Ph.D. P.E.

    2006-04-30

    Advantek has successfully developed the first low-cost technology offering significant improvement in both Seasonal Energy Efficiency (SEER) and comfort & humidity control. A production prototype was constructed based on a commercial roof top package unit. The prototype was operated under a wide range of psychrometric conditions. Test data was analyzed to identify refinements, which were implemented to further improve performance in an iterative procedure that resulted in a fully optimized technology. The latest results show an increase in dehumidification capacity of 56% with ClimaStat™ in full dehumidify mode vs. with ClimaStat™ off. Dehumidification improved by a factor of 1.7 to 1.9 – meaning that the unit can provide nearly twice the water removal per unit of sensible cooling load. Performance testing results have been consistent, verifiable and repeatable. . ClimaStat™ cost-effectively controls humidity on-demand and improves indoor air quality while reducing annual energy costs. Test data clearly shows that ClimaStat™ costs 20% to 60% less to operate. ClimaStat™ is ready for market.

  10. Desiccation tolerance in bryophytes: The dehydration and rehydration transcriptomes in the desiccation-tolerant bryophyte Bryum argenteum.

    PubMed

    Gao, Bei; Li, Xiaoshuang; Zhang, Daoyuan; Liang, Yuqing; Yang, Honglan; Chen, Moxian; Zhang, Yuanming; Zhang, Jianhua; Wood, Andrew J

    2017-08-08

    The desiccation tolerant bryophyte Bryum argenteum is an important component of desert biological soil crusts (BSCs) and is emerging as a model system for studying vegetative desiccation tolerance. Here we present and analyze the hydration-dehydration-rehydration transcriptomes in B. argenteum to establish a desiccation-tolerance transcriptomic atlas. B. argenteum gametophores representing five different hydration stages (hydrated (H0), dehydrated for 2 h (D2), 24 h (D24), then rehydrated for 2 h (R2) and 48 h (R48)), were sampled for transcriptome analyses. Illumina high throughput RNA-Seq technology was employed and generated more than 488.46 million reads. An in-house de novo transcriptome assembly optimization pipeline based on Trinity assembler was developed to obtain a reference Hydration-Dehydration-Rehydration (H-D-R) transcriptome comprising of 76,206 transcripts, with an N50 of 2,016 bp and average length of 1,222 bp. Comprehensive transcription factor (TF) annotation discovered 978 TFs in 62 families, among which 404 TFs within 40 families were differentially expressed upon dehydration-rehydration. Pfam term enrichment analysis revealed 172 protein families/domains were significantly associated with the H-D-R cycle and confirmed early rehydration (i.e. the R2 stage) as exhibiting the maximum stress-induced changes in gene expression.

  11. Transcriptomic analysis of Salmonella desiccation resistance.

    PubMed

    Li, Haiping; Bhaskara, Anuhya; Megalis, Christina; Tortorello, Mary Lou

    2012-12-01

    The survival of Salmonella in low moisture foods and processing environments remains a great challenge for the food industry and public health. To explore the mechanisms of Salmonella desiccation resistance, we studied the transcriptomic responses in Salmonella Tennessee (Tennessee), using Salmonella Typhimurium LT2 (LT2), a strain weakly resistant to desiccation, as a reference strain. In response to 2 h of air-drying at 11% equilibrated relative humidity, approximately one-fourth of the open reading frames (ORFs) in the Tennessee genome and one-fifth in LT2 were differentially expressed (>2-fold). Among all differentially expressed functional groups (>5-fold) in both strains, the expression fold change associated with fatty acid metabolism was the highest, and constituted 51% and 35% of the total expression fold change in Tennessee and LT2, respectively. Tennessee showed greater changes in expression of genes associated with stress response and envelope modification than LT2, while showing lesser changes in protein biosynthesis expression. Expression of flagella genes was significantly more inhibited in stationary phase cells of Tennessee than LT2 both before and after desiccation. The accumulation of the osmolyte trehalose was significantly induced by desiccation in Tennessee, but no increase was detectable in LT2, which is consistent with the expression patterns of the entire trehalose biosynthesis and degradation pathways in both strains. Results from this study present a global view of the dynamic desiccation responses in Salmonella, which will guide future research efforts to control Salmonella in low moisture environments.

  12. Heat and mass transfer in packed bed liquid desiccant regenerators -- An experimental investigation

    SciTech Connect

    Martin, V.; Goswami, D.Y.

    1999-08-01

    Liquid desiccant cooling can provide control of temperature and humidity, while at the same time lowering the electrical energy requirement for air conditioning. Since the largest energy requirement associated with desiccant cooling is low temperature heat for desiccant regeneration, the regeneration process greatly influences the overall system performance. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer on the regeneration process are of great interest. Due to the complexity of the regeneration process, which involves simultaneous heat and mass transfer, theoretical modeling must be verified by experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed regenerator using high liquid flow rates. To regenerate the desiccant, it is heated to temperatures readily obtainable from flat-plate solar collectors. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of water evaporation, as well as the effectiveness of the regeneration process is assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, the findings in the present study are compared to findings previously reported in the literature. Also, the results presented here characterize the important variables that impact the system design.

  13. Breakthrough Video: Desiccant Enhanced Evaporative Air Conditioning

    SciTech Connect

    2012-01-01

    Researchers at the National Renewable Energy Laboratory (NREL) invented a breakthrough technology that improves air conditioning in a novel way—with heat. NREL combined desiccant materials, which remove moisture from the air using heat, and advanced evaporative technologies to develop a cooling unit that uses 90% less electricity and up to 80% less total energy than traditional air conditioning (AC). This solution, called the desiccant enhanced evaporative air conditioner (DEVAP), also controls humidity more effectively to improve the comfort of people in buildings.

  14. Efficacy of Metarhizium anisopliae isolate MAX-2 from Shangri-la, China under desiccation stress

    PubMed Central

    2014-01-01

    valid laboratory bioassay system in evaluating M. anisopliae efficacy under desiccation stress. PMID:24383424

  15. Desiccation tolerance mechanism in resurrection fern-ally Selaginella tamariscina revealed by physiological and proteomic analysis.

    PubMed

    Wang, Xiaonan; Chen, Sixue; Zhang, Heng; Shi, Lei; Cao, Fenglin; Guo, Lihai; Xie, Yongming; Wang, Tai; Yan, Xiufeng; Dai, Shaojun

    2010-12-03

    Drought is one of the most severe limitations to plant growth and productivity. Resurrection plants have evolved a unique capability to tolerate desiccation in vegetative tissues. Fern-ally Selaginella tamariscina (Beauv.) is one of the most primitive vascular resurrection plants, which can survive a desiccated state and recover when water becomes available. To better understand the mechanism of desiccation tolerance, we have applied physiological and proteomic analysis. Samples of S. tamariscina were water-deprived for up to seven days followed by 12 h of rewatering. Our results showed that endogenous abscisic acid (ABA) increased to regulate dehydration-responsive genes/proteins and physiological processes. In the course of dehydration, the contents of osmolytes represented by soluble sugars and proline were increased to maintain cell structure integrity. The activities of four antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione reductase (GR)) also increased. In contrast, both the rate of photosynthesis and the chlorophyll content decreased, and plasma membrane integrity was lost. We identified 138 desiccation-responsive two-dimensional electrophoresis (2-DE) spots, representing 103 unique proteins. Hierarchical clustering analysis revealed that 83% of the proteins were down-regulated upon dehydration. They were mainly involved in photosynthesis, carbohydrate and energy metabolism, stress and defense, protein metabolism, signaling, membrane/transport, cell structure, and cell division. The dynamic expression changes of the desiccation-responsive proteins provide strong evidence that cell structure modification, photosynthesis reduction, antioxidant system activation, and protein post-transcriptional/translational modifications are essential to the poikilochlorophyllous fern-ally S. tamariscina in response to dehydration. In addition, our comparative analysis of dehydration-responsive proteins in vegetative tissues

  16. Modeling and Simulation of Membrane-Based Dehumidification and Energy Recovery Process

    SciTech Connect

    Gao, Zhiming; Abdelaziz, Omar; Qu, Ming

    2017-01-01

    This paper introduces a first-order physics-based model that accounts for the fundamental heat and mass transfer between a humid-air vapor stream on feed side to another flow stream on permeate side. The model comprises a few optional submodels for membrane mass transport; and it adopts a segment-by-segment method for discretizing heat and mass transfer governing equations for flow streams on feed and permeate sides. The model is able to simulate both dehumidifiers and energy recovery ventilators in parallel-flow, cross-flow, and counter-flow configurations. The predicted tresults are compared reasonably well with the measurements. The open-source codes are written in C++. The model and open-source codes are expected to become a fundament tool for the analysis of membrane-based dehumidification in the future.

  17. Graphene oxide membranes with high permeability and selectivity for dehumidification of air

    SciTech Connect

    Shin, Yongsoon; Liu, Wei; Schwenzer, Birgit; Manandhar, Sandeep; Chase-Woods, Dylan; Engelhard, Mark H.; Devanathan, Ram; Fifield, Leonard S.; Bennett, Wendy D.; Ginovska, Bojana; Gotthold, David W.

    2016-09-01

    Hierarchically stacked 2D graphene oxide (GO) membranes are a fascinating and promising new class of materials with the potential for radically improved water vapor/gas separation with excellent selectivity and high permeability. This paper details dehumidification results from flowing gas mixtures through free-standing GO membrane samples prepared by a casting method. The first demonstrated use of free-standing GO membranes for water vapor separation reveals outstanding water vapor permeability and H2O/N2 selectivity. Free-standing GO membranes exhibit extremely high water vapor permeability of 1.82 x 105 Barrer and a water vapor permeance of 1.01 x 10-5 mol/m2sPa, while the nitrogen permeability was below the system’s detection limit, yielding a selectivity >104 in 80% relative humidity (RH) air at 30.8 °C. The results show great potential for a range of energy conversion and environmental applications

  18. Dehumidification of moist air simultaneous removal of selected indoor pollutants by triethylene glycol solutions in a packed-bed absorber

    SciTech Connect

    Chung, T.W.; Ghosh, T.K.; Hines, A.L.

    1995-04-01

    A packed bed absorber-stripper system was used to remove selected indoor pollutants during the dehumidification of air by triethylene glycol solutions. Triethylene glycol concentrations of 90% and 95% by weight in water were used. Both random and structured packings were employed to provide the contact surface between the liquid and gas phases. A six-inch I.D. absorption column was operated between the liquid and gas phases. A six-inch I.D. absorption column was operated between 50% and 80% of flooding conditions. The heights of a transfer unit for mass transfer for randomly packed 5/8-inch polypropylene Flexi rings and 1/2-inch ceramic Intalox saddles varied from 0.12 m to 0.17 m when dehumidifying air only. However, the height of a transfer unit was in the range of 0.31 m to 0.40 m for the cross corrugated cellulose and PVC structured packings. Heat and mass transfer coefficients were also calculated from the experimental data and were correlated with various process variables. The values predicted by these correlations were within {+-}10% of the experimental data. Pollutants used in the study included formaldehyde, toluene, 1,1,1-trichloroethane and carbon dioxide, and their concentrations in the air were controlled to 0.02{+-}0.005 ppm, 3{+-}0.02 ppm, 24{+-}0.1 ppm, and 1000{+-}5 ppm, respectively. Although nearly 100% of the toluene and 1,1,1-trichloroethane were removed by the 95% triethylene glycol solution, only 56% of the carbon dioxide and 30% of the formaldehyde could be removed from the air stream under similar conditions. As expected, the removal of these pollutants by the triethylene glycol solution was not affected by varying the relative humidity of the air.

  19. Numerical investigation of transient heat and mass transfer in a parallel-flow liquid-desiccant absorber

    NASA Astrophysics Data System (ADS)

    Diaz, Gerardo

    2010-12-01

    Liquid desiccant systems have received significant attention as a way to reduce latent loads. Tests of liquid desiccant systems in humid climates have shown significant reductions in energy consumption. As moisture in the air is absorbed at the dehumidifier, the temperature of the liquid desiccant increases due to the addition of heat from the enthalpy of condensation of the water vapor. Thus, the coupled effects of heat and mass transfer are relevant for these applications. A two-dimensional mathematical model of the transient heat and mass transfer for an absorber where a thin film of liquid desiccant flows down its walls and dehumidifies the air in parallel-flow configuration is developed and the dynamics of the modeled system are analyzed.

  20. A randomized trial of dehumidification in the control of house dust mite.

    PubMed

    Hyndman, S J; Vickers, L M; Htut, T; Maunder, J W; Peock, A; Higenbottam, T W

    2000-08-01

    House dust mites (HDM) are sensitive to humidity. Few studies have adequately examined the potential of dehumidification in reducing HDM numbers. The study examined the effect of portable domestic dehumidifiers, and a behavioural programme to reduce humidity, on HDM counts and HDM allergen levels. A randomized controlled trial was undertaken. A total of 76 homes were allocated to three groups that received a portable domestic dehumidifier, a behavioural programme, or no intervention. Humidity, temperature, HDM counts (trap and vacuum samples), HDM allergen, and other details of the home environment were measured on four occasions over a period of 1 year. Interventions and measurements were concerned predominantly with one bedroom. There was a reduction in relative humidity in the dehumidifier group, but not the behavioural group. A decline in HDM trap counts was observed for all three groups. Change scores did not indicate that the dehumidifier group had a greater decline than the other groups. A secondary analysis examining presence or absence of HDM showed a shift from households having HDM at baseline to households not having HDM in the final round for some trap measures. Change score analysis indicated that this shift was greater in the dehumidifier group compared with other groups. The dehumidifier group did not show a greater decline in HDM allergen than that seen in the other two groups. Neither the dehumidifier nor the behavioural intervention had a major effect on HDM counts or allergen levels. However, the study did have a number of limitations relating to size, timing of intervention, and running of the dehumidifiers. The secondary data analysis may indicate some effect of dehumidification, but clearly this effect was small. There is a need for more information on the effects of reducing ambient humidity on the distribution of HDM within their habitats.

  1. Rapid Reactivation of Cyanobacterial Photosynthesis and Migration upon Rehydration of Desiccated Marine Microbial Mats

    PubMed Central

    Chennu, Arjun; Grinham, Alistair; Polerecky, Lubos; de Beer, Dirk; Al-Najjar, Mohammad A. A.

    2015-01-01

    Desiccated cyanobacterial mats are the dominant biological feature in the Earth’s arid zones. While the response of desiccated cyanobacteria to rehydration is well-documented for terrestrial systems, information about the response in marine systems is lacking. We used high temporal resolution hyperspectral imaging, liquid chromatography, pulse-amplitude fluorometry, oxygen microsensors, and confocal laser microscopy to study this response in a desiccated microbial mat from Exmouth Gulf, Australia. During the initial 15 min after rehydration chlorophyll a concentrations increased 2–5 fold and cyanobacterial photosynthesis was re-established. Although the mechanism behind this rapid increase of chlorophyll a remains unknown, we hypothesize that it involves resynthesis from a precursor stored in desiccated cyanobacteria. The subsequent phase (15 min–48 h) involved migration of the reactivated cyanobacteria toward the mat surface, which led, together with a gradual increase in chlorophyll a, to a further increase in photosynthesis. We conclude that the response involving an increase in chlorophyll a and recovery of photosynthetic activity within minutes after rehydration is common for cyanobacteria from desiccated mats of both terrestrial and marine origin. However, the response of upward migration and its triggering factor appear to be mat-specific and likely linked to other factors. PMID:26733996

  2. Do subtoxic levels of chlorate influence the desiccation tolerance of Egeria densa?

    PubMed

    Palma, Alvaro T; Schwarz, Alex; Henríquez, Luís A; Alvarez, Ximena; Fariña, José M; Lu, Qimiao

    2013-02-01

    Among the different factors hypothesized to be responsible for the virtual disappearance of Egeria densa, once a dominant aquatic macrophyte in a southern Chile wetland ecosystem, are the negative effects of certain chemical compounds (mainly chlorate) and harsh environmental conditions (desiccation caused by prolonged atmospheric exposure). The authors performed an integrated experiment in which E. densa plants were first exposed for four weeks inside a mesocosm system to levels of chlorate that existed in the wetland at the time of the plant's demise and then exposed to desiccation conditions that also resembled those that the system had experienced. Hence, the authors tested the hypothesis that E. densa plants exposed to sublethal levels of chlorate are more susceptible to the deleterious effect of desiccation compared with plants that had not been exposed to chlorate. This hypothesis was tested by means of quantifying physiologically related parameters in plants right after the four weeks under water and then after the desiccation period of 6 h. Their results rejected this hypothesis, because all plants, regardless of their history, are equally affected by desiccation. Copyright © 2012 SETAC.

  3. Comparative metabolic profiling between desiccation-sensitive and desiccation-tolerant species of Selaginella reveals insights into the resurrection trait

    USDA-ARS?s Scientific Manuscript database

    Spike-mosses (Selaginellaceae) represent an ancient lineage of vascular plants in which some species have evolved or revolved desiccation tolerance (DT). A sister group comparison was conducted between a desiccation-tolerant species, Selaginella lepidophylla, and a desiccation-sensitive species, S. ...

  4. Analysis of Dehumidification Effects on Cooling Capacity of an Evaporative Cooler

    NASA Astrophysics Data System (ADS)

    Saidi, Mohammad Hassan; Aghanajafi, Cyrus; Mohammadian, Masoud

    In this study, effect of desiccant wheel, heat exchanger and cooling coil will be evaluated on decreasing the wet bulb temperature of entering air to cooling tower and decreasing the outlet cold water temperature. For this purpose, change effect of desiccant wheel parameters will be investigated on wet bulb temperature of outlet air from heat exchanger. After that, optimum parameters and minimum wet bulb temperature will be selected. Then, outlet cold water temperature will be achieved for various cooling coil surface temperature with definition of by pass factor and also by using optimum desiccant wheel parameters and entrance air wet bulb temperature to tower related to cooling coil surface temperature. To calculate wet bulb temperature, a mathematical model will be used that shows physical properties of air. After that a nomograph will be used to predict effect of decrease of entrance air wet bulb temperature on reducing the outlet water temperature and it will be done for several cities in Iran. At the end, an equation will be used to calculate required water to air mass flow rate for each outlet cold water temperature. With considering of known circulating water mass flow rate, required air for tower would be calculated and suitable desiccant wheel can be selected.

  5. Trehalose Accumulation Triggers Autophagy during Plant Desiccation.

    PubMed

    Williams, Brett; Njaci, Isaac; Moghaddam, Lalehvash; Long, Hao; Dickman, Martin B; Zhang, Xiuren; Mundree, Sagadevan

    2015-12-01

    Global climate change, increasingly erratic weather and a burgeoning global population are significant threats to the sustainability of future crop production. There is an urgent need for the development of robust measures that enable crops to withstand the uncertainty of climate change whilst still producing maximum yields. Resurrection plants possess the unique ability to withstand desiccation for prolonged periods, can be restored upon watering and represent great potential for the development of stress tolerant crops. Here, we describe the remarkable stress characteristics of Tripogon loliiformis, an uncharacterised resurrection grass and close relative of the economically important cereals, rice, sorghum, and maize. We show that T. loliiformis survives extreme environmental stress by implementing autophagy to prevent Programmed Cell Death. Notably, we identified a novel role for trehalose in the regulation of autophagy in T.loliiformis. Transcriptome, Gas Chromatography Mass Spectrometry, immunoblotting and confocal microscopy analyses directly linked the accumulation of trehalose with the onset of autophagy in dehydrating and desiccated T. loliiformis shoots. These results were supported in vitro with the observation of autophagosomes in trehalose treated T. loliiformis leaves; autophagosomes were not detected in untreated samples. Presumably, once induced, autophagy promotes desiccation tolerance in T.loliiformis, by removal of cellular toxins to suppress programmed cell death and the recycling of nutrients to delay the onset of senescence. These findings illustrate how resurrection plants manipulate sugar metabolism to promote desiccation tolerance and may provide candidate genes that are potentially useful for the development of stress tolerant crops.

  6. Trehalose Accumulation Triggers Autophagy during Plant Desiccation

    PubMed Central

    Moghaddam, Lalehvash; Long, Hao; Dickman, Martin B; Zhang, Xiuren; Mundree, Sagadevan

    2015-01-01

    Global climate change, increasingly erratic weather and a burgeoning global population are significant threats to the sustainability of future crop production. There is an urgent need for the development of robust measures that enable crops to withstand the uncertainty of climate change whilst still producing maximum yields. Resurrection plants possess the unique ability to withstand desiccation for prolonged periods, can be restored upon watering and represent great potential for the development of stress tolerant crops. Here, we describe the remarkable stress characteristics of Tripogon loliiformis, an uncharacterised resurrection grass and close relative of the economically important cereals, rice, sorghum, and maize. We show that T. loliiformis survives extreme environmental stress by implementing autophagy to prevent Programmed Cell Death. Notably, we identified a novel role for trehalose in the regulation of autophagy in T.loliiformis. Transcriptome, Gas Chromatography Mass Spectrometry, immunoblotting and confocal microscopy analyses directly linked the accumulation of trehalose with the onset of autophagy in dehydrating and desiccated T. loliiformis shoots. These results were supported in vitro with the observation of autophagosomes in trehalose treated T. loliiformis leaves; autophagosomes were not detected in untreated samples. Presumably, once induced, autophagy promotes desiccation tolerance in T.loliiformis, by removal of cellular toxins to suppress programmed cell death and the recycling of nutrients to delay the onset of senescence. These findings illustrate how resurrection plants manipulate sugar metabolism to promote desiccation tolerance and may provide candidate genes that are potentially useful for the development of stress tolerant crops. PMID:26633550

  7. Desiccation Tolerance Studied in the Resurrection Plant Craterostigma plantagineum.

    PubMed

    Bartels, Dorothea

    2005-11-01

    This review will focus on the acquisition of desiccation tolerance in the resurrection plant Craterostigma plantagineum. Molecular aspects of desiccation tolerance in this plant will be compared with the response of non-tolerant plants to dehydration. Unique features of C. plantagineum are described like the CDT-1 (Craterostigma desiccation tolerance gene-1) gene and the carbohydrate metabolism. Abundant proteins which are associated with the desiccation tolerance phenomenon are the late embryogenesis abundant (=LEA) proteins. These proteins are very hydrophilic and occur in several other species which have acquired desiccation tolerance.

  8. Effects of temperature on desiccant catalysis of refrigerant and lubricant decomposition. Final report

    SciTech Connect

    Rohatgi, N.D.T.

    1998-06-01

    Accelerated aging at high temperatures (149 C) for short aging times (28 days) is effective in screening the compatibility of different materials in refrigeration systems. However, in actual applications temperatures are usually lower and operating times much longer. Therefore plots to allow for interpolation or extrapolation of experimental data to actual operating conditions are needed. In the current study, aging of refrigerant/lubricant/desiccant/metal systems was conducted at five different temperatures, and for each temperature at four different aging times. The data collected from this study provided plots relating refrigerant or lubricant decomposition to aging time, aging temperature, and type of desiccant, which can be used for interpolation or extrapolation.

  9. SOIL DESICCATION TECHNIQUES STRATEGIES FOR IMMOBILIZATION OF DEEP VADOSE CONTAMINANTS AT THE HANFORD CENTRAL PLATEAU

    SciTech Connect

    BENECKE MW; CHRONISTER GB; TRUEX MJ

    2012-01-30

    Deep vadose zone contamination poses some of the most difficult remediation challenges for the protection of groundwater at the Hanford Site where processes and technologies are being developed and tested for use in the on-going effort to remediate mobile contamination in the deep vadose zone, the area deep beneath the surface. Historically, contaminants were discharged to the soil along with significant amounts of water, which continues to drive contaminants deeper in the vadose zone toward groundwater. Soil desiccation is a potential in situ remedial technology well suited for the arid conditions and the thick vadose zone at the Hanford Site. Desiccation techniques could reduce the advance of contaminants by removing the pore water to slow the rate of contaminants movement toward groundwater. Desiccation technologies have the potential to halt or slow the advance of contaminants in unsaturated systems, as well as aid in reduction of contaminants from these same areas. Besides reducing the water flux, desiccation also establishes capillary breaks that would require extensive rewetting to resume pore water transport. More importantly, these techniques have widespread application, whether the need is to isolate radio nuclides or address chemical contaminant issues. Three different desiccation techniques are currently being studied at Hanford.

  10. The response of Asterochloris erici (Ahmadjian) Skaloud et Peksa to desiccation: a proteomic approach.

    PubMed

    Gasulla, Franscico; Jain, Renuka; Barreno, Eva; Guéra, Alfredo; Balbuena, Tiago S; Thelen, Jay J; Oliver, Melvin J

    2013-07-01

    The study of desiccation tolerance of lichens, and of their chlorobionts in particular, has frequently focused on the antioxidant system that protects the cell against photo-oxidative stress during dehydration/rehydration cycles. In this study, we used proteomic and transcript analyses to assess the changes associated with desiccation in the isolated phycobiont Asterochloris erici. Algae were dried either slowly (5-6 h) or rapidly (<60 min), and rehydrated after 24 h in the desiccated state. To identify proteins that accumulated during the drying or rehydration processes, we employed two-dimensional (2D) difference gel electrophoresis (DIGE) coupled with individual protein identification using trypsin digestion and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Proteomic analyses revealed that desiccation caused an increase in relative abundance of only 11-13 proteins, regardless of drying rate, involved in glycolysis, cellular protection, cytoskeleton, cell cycle, and targeting and degradation. Transcripts of five Hsp90 and two β-tubulin genes accumulated primarily at the end of the dehydration process. In addition, transmission electron microscopy (TEM) images indicate that ultrastructural cell injuries, perhaps resulting from physical or mechanical stress rather than metabolic damage, were more intense after rapid dehydration. This occurred with no major change in the proteome. These results suggest that desiccation tolerance of A. erici is achieved by constitutive mechanisms. © 2013 John Wiley & Sons Ltd.

  11. Drying R-407C and R-410A refrigerant blends with molecular sieve desiccants

    SciTech Connect

    Cohen, A.P.; Tucker, D.M.

    1998-10-01

    The hydrofluorocarbon (HFC) R-32 (CF{sub 2}H{sub 2}) is a component of refrigerant blends in the 407 and 410 series being tested and commercialized for use as replacements for R-502 and the hydrochlorofluorocarbon (HCFC) R-22. The molecular sieve desiccants used with chlorofluorocarbon (CFC) and HCFC mineral oil systems in the past have achieved high water capacity by excluding the refrigerant and adsorbing only the water. Unfortunately, R-32 is adsorbed on commercial type 3A molecular sieve desiccant products. The result of this adsorption is a loss of water capacity when drying R-32 compared to drying R-22 or R-502 and a reduced level of chemical compatibility of the desiccant with the refrigerant. Some compressor manufacturers are seeking a water concentration as low as 10 mg/kg (ppm[wt]) in the circulating refrigerant of polyolester-lubricated refrigerating equipment using these HFC blends. This paper compares unmodified commercial type 3A molecular sieve desiccants with a recently developed, modified 3A molecular sieve that excludes R-32. The modified 3A has better chemical compatibility with R-32 and high water capacity in liquid R-407C and R-410A. The drying rates of the two desiccants in R-407C and R-410A are similar. Data and test methods are reported on refrigerant adsorption, water capacity, drying rate, and chemical compatibility.

  12. Hydrogen sulfide exposure increases desiccation tolerance in Drosophila melanogaster.

    PubMed

    Zhong, Jian-Feng; Wang, Shu-Ping; Shi, Xiao-Qin; Mu, Li-li; Li, Guo-Qing

    2010-12-01

    Hydrogen sulfide (H(2)S) has been shown to effect physiological alterations in several animals, frequently leading to an improvement in survival in otherwise lethal conditions. In the present paper, a volatility bioassay system was developed to evaluate the survivorship of Drosophila melanogaster adults exposed to H(2)S gas that emanated from a K(2)S donor. Using this bioassay system, we found that H(2)S exposure significantly increased the survival of flies under arid and food-free conditions, but not under humid and food-free conditions. This suggests that H(2)S plays a role in desiccation tolerance but not in nutritional stress alleviation. To further confirm the suggestion, the mRNA levels of two desiccation tolerance-related genes Frost and Desat2, and a starvation-related gene Smp-30, from the control and treated flies were measured by quantitative real-time PCR. These genes were up-regulated within 2h when the flies transferred to the arid and food-free bioassay system. Addition of H(2)S further increased Frost and Desat2 mRNA levels, in contrast to Smp-30. Thus, our molecular results were consistent with our bioassay findings. Because of the molecular and genetic tools available for Drosophila, the fly will be a useful system for determining how H(2)S regulates various physiological alterations. Copyright © 2010 Elsevier Ltd. All rights reserved.

  13. Desiccant wheels as gas-phase absorption (GPA) air cleaners: evaluation by PTR-MS and sensory assessment.

    PubMed

    Fang, L; Zhang, G; Wisthaler, A

    2008-10-01

    Two experiments were conducted to investigate the use of the co-sorption effect of a desiccant wheel for improving indoor air quality. One experiment was conducted in a climate chamber to investigate the co-sorption effect of a desiccant wheel on the chemical removal of indoor air pollutants; another experiment was conducted in an office room to investigate the resulting effect on perceived air quality. A dehumidifier with a silica-gel desiccant wheel was installed in the ventilation system of the test chamber and office room to treat the recirculation airflow. Human subjects, flooring materials and four pure chemicals (formaldehyde, ethanol, toluene and 1,2-dichloroethane) were used as air pollution sources. Proton-Transfer-Reaction--Mass Spectrometry (PTR-MS) and sensory subjects were used to characterize the effectiveness of chemical and sensory pollution removal of the desiccant wheel. The experiments revealed that all the measured VOCs were removed effectively by the desiccant wheel with an average efficiency of 94% or higher; more than 80% of the sensory pollution load was removed and the percentage dissatisfied with the air quality decreased from 70% to 20%. These results indicate that incorporating a regenerative desiccant wheel in a ventilation system is an efficient way of removing indoor VOCs. This study may lead to the development of new air cleaners and validates a new concept for the design of ventilation systems that can improve indoor air quality and reduce energy consumption.

  14. Development of Separate Sensible and Latent Cooling System Using Electrochemical Compressor

    SciTech Connect

    Abdelaziz, Omar; Qu, Ming; Sun, Xiao-Guang; Bahar, Bamdad; Parmelee, William; Fackler, Scott; Sherrer, Richard; Zerby, Jacob; Chouhan, Ashish; Prasad, Ajay

    2017-01-01

    Separate sensible and latent cooling systems offer superior energy efficiency performance compared to conventional vapor compression air conditioning systems. In this paper we describe an innovative non-vapor compression system that uses electrochemical compressor (ECC) to pump hydrogen between 2-metal hydride reservoirs to provide the sensible cooling effect. The heat rejected during this process is used to regenerate the ionic liquid (IL) used for desiccant dehumidification. The overall system design is illustrated. The Xergy version 4C electrochemical compressor, while not designed as a high pressure system, develops in excess of 2 MPa (300 psia) and pressure ratios > 30. The projected base efficiency improvement of the electrochemical compressor is expected to be ~ 20% with higher efficiency when in low capacity mode due to being throttleable to lower capacity with improved efficiency. The IL was tailored to maximize the absorption/desorption rate of water vapor at moderate regeneration temperature. This IL, namely, [EMIm].OAc, is a hydrophilic IL with a working concentration range of 28.98% when operating between 25 75 C. The ECC metal hydride system is expected to show superior performance to typical vapor compression systems. As such, the combined efficiency gains from the use of ECC and separate and sensible cooling would offer significant potential savings to existing vapor compression cooling technology. A high efficiency Window Air Conditioner system is described based on this novel configuration. The system s schematic is provided. Models compared well with actual operating data obtained by running the prototype system. Finally, a model of an LiCl desiccant system in conjunction with the ECC-based metal hydride heat exchangers is provided.

  15. The study of Lake Urmia desiccation: morphometry impress

    NASA Astrophysics Data System (ADS)

    Moradi, Ayoub; Rasouli, Ali Akbar; Roostaei, Shahram

    2017-04-01

    Located in northwestern Iran, the hypersaline Lake Urmia has started a serious uninterrupted desiccation since 1995. The lake has lost about eight meters of water level and about 75% of water surface area during past 20 years. In particular, the lake water volume decrement has been accelerated in recent years. The importance of the Lake Urmia for human life in northwestern Iran, and its destructive effects on a vast region if totally dry up, demands comprehensive studies of the lake level fluctuations mechanism. According to literature review, the water volume of the lake behaves sometimes differently from the water storage of the whole basin. Our time series analysis using Land Data Assimilation Systems also confirms those differences within last decades. In other hand, many studies addressed the lake desiccation to climatic changes and/or anthropogenic influences such as excessive dam constructions in the watershed during last decades. As water leaves the lake only through evaporation, the fluctuation of evaporation has a distinctive role in the lake level variations. Dramatic decreament in the lake extent indicates of a special morphometry. The lake's morphometry has made it vulnerable to temperature and salinity changes. It strongly controls the lake's water heat capacity and water density. And, it therefore controls the rate of evaporation from water surface. We study the role of lake's morphometry on the lake desiccation. Although, the global climatic change is known as the primary reason for current droughts in the Middle East generally, our preliminary results show that the lake's morphometry is the main cause for the accelerating of water volume lost in Lake Urmia. In particular, after 2007, lake's water temperature and density show significant variations. Water heat capacity and evaporation rate are consistent with information of lake's hypsometry.

  16. LEA gene expression, RNA stability and pigment accumulation in three closely related Linderniaceae species differing in desiccation tolerance.

    PubMed

    Juszczak, Ilona; Bartels, Dorothea

    2017-02-01

    Desiccation-tolerant plants (Craterostigma plantagineum and Lindernia brevidens) evolved a highly efficient strategies to prevent dehydration-induced irreversible damage. The protection system involves synthesis of LEA proteins, decrease of photosynthetic activity and activation of antioxidant systems. The regulation of these processes requires joint action of multiple proteins. Here, we present comparative analyses of accumulation of transcripts encoding components of the protection machinery, such as selected LEA proteins, enzymes of the chlorophyll degradation pathway and anthocyanin biosynthesis enzymes in total and polysomal RNA pools. The analyses revealed that desiccation-tolerant plants recruit mRNAs to ribosomes with higher efficiency than the desiccation-sensitive species L. subracemosa. Desiccation-tolerant species accumulated high amounts of LEA transcripts during dehydration and precisely controlled the amounts of chlorophyll keeping it at a level sufficient to activate photosynthesis after rehydration. In contrast, mRNA of L. subracemosa was prone to dehydration-induced degradation, decomposition of the photosynthetic apparatus and degradation of free chlorophyll. Thus, the results of the studies point to differences in the control of gene expression and degradation of chlorophyll in desiccation-tolerant versus desiccation-sensitive species when the plants were subjected to dehydration. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  17. TOR and RAS pathways regulate desiccation tolerance in Saccharomyces cerevisiae

    PubMed Central

    Welch, Aaron Z.; Gibney, Patrick A.; Botstein, David; Koshland, Douglas E.

    2013-01-01

    Tolerance to desiccation in cultures of Saccharomyces cerevisiae is inducible; only one in a million cells from an exponential culture survive desiccation compared with one in five cells in stationary phase. Here we exploit the desiccation sensitivity of exponentially dividing cells to understand the stresses imposed by desiccation and their stress response pathways. We found that induction of desiccation tolerance is cell autonomous and that there is an inverse correlation between desiccation tolerance and growth rate in glucose-, ammonia-, or phosphate-limited continuous cultures. A transient heat shock induces a 5000–fold increase in desiccation tolerance, whereas hyper-ionic, -reductive, -oxidative, or -osmotic stress induced much less. Furthermore, we provide evidence that the Sch9p-regulated branch of the TOR and Ras-cAMP pathway inhibits desiccation tolerance by inhibiting the stress response transcription factors Gis1p, Msn2p, and Msn4p and by activating Sfp1p, a ribosome biogenesis transcription factor. Among 41 mutants defective in ribosome biogenesis, a subset defective in 60S showed a dramatic increase in desiccation tolerance independent of growth rate. We suggest that reduction of a specific intermediate in 60S biogenesis, resulting from conditions such as heat shock and nutrient deprivation, increases desiccation tolerance. PMID:23171550

  18. The structure of the desiccated Richtersius coronifer (Richters, 1903).

    PubMed

    Czerneková, Michaela; Jönsson, K Ingemar; Chajec, Lukasz; Student, Sebastian; Poprawa, Izabela

    2017-05-01

    Tun formation is an essential morphological adaptation for entering the anhydrobiotic state in tardigrades, but its internal structure has rarely been investigated. We present the structure and ultrastructure of organs and cells in desiccated Richtersius coronifer by transmission and scanning electron microscopy, confocal microscopy, and histochemical methods. A 3D reconstruction of the body organization of the tun stage is also presented. The tun formation during anhydrobiosis of tardigrades is a process of anterior-posterior body contraction, which relocates some organs such as the pharyngeal bulb. The cuticle is composed of epicuticle, intracuticle and procuticle; flocculent coat; and trilaminate layer. Moulting does not seem to restrict the tun formation, as evidenced from tardigrade tuns that were in the process of moulting. The storage cells of desiccated specimens filled up the free inner space and surrounded internal organs, such as the ovary and digestive system, which were contracted. All cells (epidermal cells, storage cells, ovary cells, cells of the digestive system) underwent shrinkage, and their cytoplasm was electron dense. Lipids and polysaccharides dominated among reserve material of storage cells, while the amount of protein was small. The basic morphology of specific cell types and organelles did not differ between active and anhydrobiotic R. coronifer.

  19. A desiccation-related Elip-like gene from the resurrection plant Craterostigma plantagineum is regulated by light and ABA.

    PubMed

    Bartels, D; Hanke, C; Schneider, K; Michel, D; Salamini, F

    1992-08-01

    The resurrection plant Craterostigma plantagineum tolerates an extreme loss of cellular water. Therefore this plant is being studied as model system to analyse desiccation tolerance at the molecular level. Upon dehydration, new transcripts are abundantly expressed in different tissues of the plant. One such desiccation-related nuclear gene (dsp-22 for desiccation stress protein) encodes a mature 21 kDa protein which accumulates in the chloroplasts. Sequence analysis indicates that dsp-22 is closely related to early light inducible genes (Elip) of higher plants and to a carotene biosynthesis related gene (cbr) isolated from the green alga Dunaliella bardawil. In contrast to other desiccation-related genes, light is an essential positive factor regulating the expression of dsp-22: ABA-mediated gene activation leads to the accumulation of the transcript only in the presence of light. During the desiccation process, light acts at the transcriptional and post-transcriptional levels. The implications of these different controls and the possible role of the dsp-22 protein in the desiccation/rehydration process are discussed.

  20. Dehydration-induced redistribution of amphiphilic molecules between cytoplasm and lipids is associated with desiccation tolerance in seeds.

    PubMed

    Buitink, J; Leprince, O; Hoekstra, F A

    2000-11-01

    This study establishes a relationship between desiccation tolerance and the transfer of amphiphilic molecules from the cytoplasm into lipids during drying, using electron paramagnetic resonance spectroscopy of amphiphilic spin probes introduced into imbibed radicles of pea (Pisum sativum) and cucumber (Cucumis sativa) seeds. Survival following drying and a membrane integrity assay indicated that desiccation tolerance was present during early imbibition and lost in germinated radicles. In germinated cucumber radicles, desiccation tolerance could be re-induced by an incubation in polyethylene glycol (PEG) before drying. In desiccation-intolerant radicles, partitioning of spin probes into lipids during dehydration occurred at higher water contents compared with tolerant and PEG-induced tolerant radicles. The difference in partitioning behavior between desiccation-tolerant and -intolerant tissues could not be explained by the loss of water. Consequently, using a two-phase model system composed of sunflower or cucumber oil and water, physical properties of the aqueous solvent that may affect the partitioning of amphiphilic spin probes were investigated. A significant relationship was found between the partitioning of spin probes and the viscosity of the aqueous solvent. Moreover, in desiccation-sensitive radicles, the rise in cellular microviscosity during drying commenced at higher water contents compared with tolerant or PEG-induced tolerant radicles, suggesting that the microviscosity of the cytoplasm may control the partitioning behavior in dehydrating seeds.

  1. Dehydration-Induced Redistribution of Amphiphilic Molecules between Cytoplasm and Lipids Is Associated with Desiccation Tolerance in Seeds1

    PubMed Central

    Buitink, Julia; Leprince, Olivier; Hoekstra, Folkert A.

    2000-01-01

    This study establishes a relationship between desiccation tolerance and the transfer of amphiphilic molecules from the cytoplasm into lipids during drying, using electron paramagnetic resonance spectroscopy of amphiphilic spin probes introduced into imbibed radicles of pea (Pisum sativum) and cucumber (Cucumis sativa) seeds. Survival following drying and a membrane integrity assay indicated that desiccation tolerance was present during early imbibition and lost in germinated radicles. In germinated cucumber radicles, desiccation tolerance could be re-induced by an incubation in polyethylene glycol (PEG) before drying. In desiccation-intolerant radicles, partitioning of spin probes into lipids during dehydration occurred at higher water contents compared with tolerant and PEG-induced tolerant radicles. The difference in partitioning behavior between desiccation-tolerant and -intolerant tissues could not be explained by the loss of water. Consequently, using a two-phase model system composed of sunflower or cucumber oil and water, physical properties of the aqueous solvent that may affect the partitioning of amphiphilic spin probes were investigated. A significant relationship was found between the partitioning of spin probes and the viscosity of the aqueous solvent. Moreover, in desiccation-sensitive radicles, the rise in cellular microviscosity during drying commenced at higher water contents compared with tolerant or PEG-induced tolerant radicles, suggesting that the microviscosity of the cytoplasm may control the partitioning behavior in dehydrating seeds. PMID:11080316

  2. Antioxidative response of ascorbate-glutathione pathway enzymes and metabolites to desiccation of recalcitrant Acer saccharinum seeds.

    PubMed

    Pukacka, Stanisława; Ratajczak, Ewelina

    2006-12-01

    Ascorbate-glutathione systems were studied during desiccation of recalcitrant seeds of the silver maple (Acer saccharinum L.). The desiccated seeds gradually lost their germination capacity and this was strongly correlated with an increase in electrolyte leakage from seeds. Simultaneously the increase of reactive oxygen species (ROS) (superoxide radical - O(2)(-*) and hydrogen peroxide - H(2)O(2)) production was observed. The results indicate that remarkable changes in the concentrations and redox status of ascorbate and glutathione occur in embryo axes and cotyledons. After shedding, concentrations of ascorbic acid (ASA) and the reduced form of glutathione (GSH) are higher in embryo axes than in cotyledons and their redox status is high in both embryo parts. Cotyledons in freshly shed seeds are devoid of GSH. At the first stages of desiccation, up to a level of 43% of moisture content, ASA content in embryo axes and GSH content in cotyledons increased. Below this level of moisture content, the antioxidant contents as well as their redox status rapidly decreased. The enzymes of the ascorbate-glutathione pathway: ascorbate peroxidase (APX) (EC 1.11.1.11), monodehydroascorbate reductase (MR) (EC 1.6.5.4), dehydroascorbate reductase (DHAR) (EC 1.8.5.1) and glutathione reductase (GR) (EC 1.6.4.2) increased their activity during desiccation, but mainly in embryonic axes. The changes are probably required for counteracting the production of ROS during desiccation. The relationship between ascorbate and glutathione metabolism and their relevance during desiccation of recalcitrant Acer saccharinum seeds is discussed.

  3. The response of Asterochloris erici (Ahmadjian) Skaloud et Peksa to desiccation: a proteomic approach

    USDA-ARS?s Scientific Manuscript database

    The study of desiccation tolerance of lichens, and of their photobionts in particular, has frequently focused on the antioxidant system that protects the cell against photo-oxidative stress during dehydration/rehydration cycles. Thus, in this work we carried out proteomic and transcript analyses of ...

  4. Development of Membrane-Based Desiccant Fiber for Vacuum Desiccant Cooling.

    PubMed

    Yang, Yifan; Rana, Dipak; Lan, Christopher Q; Matsuura, Takeshi

    2016-06-22

    A novel hydrophobic membrane-based desiccant fiber (MDF) was developed by loading lithium chloride into hydrophobic hollow fiber membranes. The MDF thus made was then tested for vapor absorption under controlled conditions. Furthermore, an MDF pad, which was made by weaving MDF into a piece of garment, was built into a laboratory vacuum desiccant cooling (VDC) setup, which included the MDF pad as the desiccant layer and a cooling towel saturated with water as the water reservoir, to test the cooling effects at atmospheric pressure and vacuum of 25 in. of Hg. Results indicate that MDF is suitable for applications such as in VDC. Mass and heat transfer of vapor absorption by MDF were also analyzed.

  5. Nanoparticles Embedded in Amphiphilic Membranes for Carbon Dioxide Separation and Dehumidification.

    PubMed

    Yong, Wai Fen; Ho, Yan Xun; Chung, Tai-Shung

    2017-08-17

    Polymers containing ethylene oxide (EO) groups have gained significant interest as the EO groups have favorable interactions with polar molecules such as H2 O, quadrupolar molecules such as CO2 , and metal ions. However, the main challenges of poly(ethylene oxide) (PEO) membranes are their weak mechanical properties and high crystallinity nature. The amphiphilic copolymer made from PEO terephthalate and poly(butylene terephthalate) (PEOT/PBT) comprises both hydrophilic and hydrophobic segments. The hydrophilic PEOT segment is thermosensitive, which facilities gas transports whereas the hydrophobic PBT segment is rigid, which provides mechanical robustness. This work demonstrates a new strategy to design amphiphilic mixed matrix membranes (MMMs) by incorporating zeolitic imidazolate framework, ZIF-71, into the PEOT/PBT copolymer. The resultant membrane shows an enhanced CO2 permeability with an ideal CO2 /N2 selectivity surpassing the original PEOT/PBT and Robeson's Upper bound line. The nanoparticles-embedded amphiphilic membranes exhibit characteristics of high transparency and mechanical robustness. Mechanically strong composite hollow fiber membranes consisting of PEOT/PBT/ZIF-71 as the selective layer were also prepared. The resultant hollow fibers possess an excellent CO2 permeance of 131 GPU (gas permeation units), CO2 /N2 selectivity of 52.6, H2 O permeance of 9300 GPU and H2 O/N2 selectivity of 3700, showing great potential for industrial CO2 capture and dehumidification. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Energy-efficient regenerative liquid desiccant drying process

    DOEpatents

    Ko, Suk M.; Grodzka, Philomena G.; McCormick, Paul O.

    1980-01-01

    This invention relates to the use of desiccants in conjunction with an open oop drying cycle and a closed loop drying cycle to reclaim the energy expended in vaporizing moisture in harvested crops. In the closed loop cycle, the drying air is brought into contact with a desiccant after it exits the crop drying bin. Water vapor in the moist air is absorbed by the desiccant, thus reducing the relative humidity of the air. The air is then heated by the used desiccant and returned to the crop bin. During the open loop drying cycle the used desiccant is heated (either fossil or solar energy heat sources may be used) and regenerated at high temperature, driving water vapor from the desiccant. This water vapor is condensed and used to preheat the dilute (wet) desiccant before heat is added from the external source (fossil or solar). The latent heat of vaporization of the moisture removed from the desiccant is reclaimed in this manner. The sensible heat of the regenerated desiccant is utilized in the open loop drying cycle. Also, closed cycle operation implies that no net energy is expended in heating drying air.

  7. Technology Solutions Case Study: Evaluation of the Performance of Houses With and Without Supplemental Dehumidification in a Hot-Humid Climate, New Orleans, Louisiana

    SciTech Connect

    2014-11-01

    The purpose of this project by Building Science Corporation was to evaluate the humidity control performance of new single family high performance homes, and compare the interior conditions and mechanical systems operation between two distinct groups of houses: homes with a supplemental dehumidifier installed in addition to HVAC system, and homes without any supplemental dehumidification. The subjects of the study were 10 single-family new construction homes in New Orleans, LA. Data logging equipment was installed at each home in 2012, and interior conditions and various end-use loads were monitored for one year. In terms of averages, the homes with dehumidifiers are limiting elevated levels of humidity in the living space; however, there was significant variation in humidity control between individual houses. An analysis of the equipment operation did not show a clear correlation between energy use and humidity levels. In general, no single explanatory variable appears to provide a consistent understanding of the humidity control in each house. Indoor humidity is likely due to all of the factors we have examined, and the specifics of how they are used by each occupant.

  8. Biofilm resilience to desiccation in groundwater aquifers: a laboratory and field study.

    PubMed

    Weaver, L; Webber, J B; Hickson, A C; Abraham, P M; Close, M E

    2015-05-01

    Groundwater is used as a precious resource for drinking water worldwide. Increasing anthropogenic activity is putting increasing pressure on groundwater resources. One impact of increased groundwater abstraction coupled with increasing dry weather events is the lowering of groundwater levels within aquifers. Biofilms within groundwater aquifers offer protection to the groundwater by removing contaminants entering the aquifer systems from land use activities. The study presented investigated the impact of desiccation events on the biofilms present in groundwater aquifers using field and laboratory experiments. In both field and laboratory experiments a reduction in enzyme activity (glucosidase, esterase and phosphatase) was seen during desiccation compared to wet controls. However, comparing all the data together no significant differences were seen between either wet or desiccated samples or between the start and end of the experiments. In both field and laboratory experiments enzyme activity recovered to start levels after return to wet conditions. The study shows that biofilms within groundwater systems are resilient and can withstand periods of desiccation (4 months). Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Performance investigation of a cogeneration plant with the efficient and compact heat recovery system

    NASA Astrophysics Data System (ADS)

    Myat, Aung; Thu, Kyaw; Kim, Young-Deuk; Choon, Ng Kim

    2012-06-01

    This paper presents the performance investigation of a cogeneration plant equipped with an efficient waste heat recovery system. The proposed cogeneration system produces four types of useful energy namely: (i) electricity, (ii) steam, (iii) cooling and (iv) dehumidification. The proposed plant comprises a Capstone C30 micro-turbine which generates 24 kW of electricity, a compact and efficient waste heat recovery system and a host of waste heat activated devices namely (i) a steam generator, (ii) an absorption chiller, (iii) an adsorption chiller and (iv) a multi-bed desiccant dehumidifier. The numerical analysis for the host of waste heat recovery system and thermally activated devices using FORTRAN power station linked to powerful IMSL library is performed to investigate the performance of the overall system. A set of experiments, both part load and full load, of micro-turbine is conducted to examine the electricity generation and the exhaust gas temperature. It is observed that energy utilization factor (EUF) could achieve as high as 70% while Fuel Energy Saving Ratio (FESR) is found to be 28%.

  10. Proteome analysis of leaves of the desiccation-tolerant grass, sporobolus stapfianus, in response to desiccation

    USDA-ARS?s Scientific Manuscript database

    Sporobolus stapfianus is a resurrection grass native to South Africa which can tolerate the complete drying of its vegetative tissue structure; i.e., desiccation, and recover fully within hours of rewetting. Gene expression studies have demonstrated that the grass employs a strategy of gene inductio...

  11. Comparative genome sequencing reveals genomic signature of extreme desiccation tolerance in the anhydrobiotic midge

    PubMed Central

    Gusev, Oleg; Suetsugu, Yoshitaka; Cornette, Richard; Kawashima, Takeshi; Logacheva, Maria D.; Kondrashov, Alexey S.; Penin, Aleksey A.; Hatanaka, Rie; Kikuta, Shingo; Shimura, Sachiko; Kanamori, Hiroyuki; Katayose, Yuichi; Matsumoto, Takashi; Shagimardanova, Elena; Alexeev, Dmitry; Govorun, Vadim; Wisecaver, Jennifer; Mikheyev, Alexander; Koyanagi, Ryo; Fujie, Manabu; Nishiyama, Tomoaki; Shigenobu, Shuji; Shibata, Tomoko F.; Golygina, Veronika; Hasebe, Mitsuyasu; Okuda, Takashi; Satoh, Nori; Kikawada, Takahiro

    2014-01-01

    Anhydrobiosis represents an extreme example of tolerance adaptation to water loss, where an organism can survive in an ametabolic state until water returns. Here we report the first comparative analysis examining the genomic background of extreme desiccation tolerance, which is exclusively found in larvae of the only anhydrobiotic insect, Polypedilum vanderplanki. We compare the genomes of P. vanderplanki and a congeneric desiccation-sensitive midge P. nubifer. We determine that the genome of the anhydrobiotic species specifically contains clusters of multi-copy genes with products that act as molecular shields. In addition, the genome possesses several groups of genes with high similarity to known protective proteins. However, these genes are located in distinct paralogous clusters in the genome apart from the classical orthologues of the corresponding genes shared by both chironomids and other insects. The transcripts of these clustered paralogues contribute to a large majority of the mRNA pool in the desiccating larvae and most likely define successful anhydrobiosis. Comparison of expression patterns of orthologues between two chironomid species provides evidence for the existence of desiccation-specific gene expression systems in P. vanderplanki. PMID:25216354

  12. Adsorption / Desorption Behavior of Water Vapor in an Adsorbent Desiccant Rotor

    NASA Astrophysics Data System (ADS)

    Tsujiguchi, Takuya; Kodama, Akio

    Adsorption / desorption behavior of water vapor onto desiccant rotor has been investigated to improve the desiccant cooling system by means of computer simulation. In this paper, we paid attention to the relationship between the equilibrium amount of water adsorbed onto the desiccant material and the relative humidity, that is adsorption isotherm as a principal characteristic feature of adsorbent. Considering actual adsorbents, five types of adsorption isotherms were assumed to clarify the influence of adsorption isotherm on the dehumidifying performance. After the investigation on the influences of some operating conditions on the dehumidifying performance at each selected adsorption isotherm, it was found that higher dehumidifying performance and reduction of length of desiccant rotor could be achieved by selecting appropriate adsorption isotherm. It was also predicted that S-shaped adsorption isotherm which is raised sharply at relative humidity around 15 % could produce the lowest air humidity at regeneration air temperature 80 °C. Moreover influence of the intraparticle diffusion coefficient which significantly influence on the adsorption / desorption rate was discussed choosing two adsorption isotherm from the above five isotherms. It seems that effective range of the intraparticle diffusion coefficient for the significant improvement of the dehumidifying performance was strongly influenced by the shape of adsorption isotherm.

  13. The precipitation response to the desiccation of Lake Chad

    SciTech Connect

    Lauwaet D.; VanWeverberg K.; vanLipzig, N. P. M., Weverberg, K. V., Ridderb, K. D., and Goyens, C.

    2012-04-01

    Located in the semi-arid African Sahel, Lake Chad has shrunk from a surface area of 25000 km2 in 1960 to about 1350 km2 due to a series of droughts and anthropogenic influences. The disappearance of such a large open-water body can be expected to have a noticeable effect on the meteorology in the surroundings of the lake. The impact could extend even further to the west as westward propagating convective systems pass Lake Chad in the rainfall season. This study examines the sensitivity of the regional hydrology and convective processes to the desiccation of the lake using a regional atmospheric model. Three Lake Chad scenarios are applied reflecting the situation in 1960, the current situation and a potential future scenario in which the lake and the surrounding wetlands have disappeared. The model simulations span the months July-September in 2006, which includes the rainfall season in the Lake Chad area. Total precipitation amounts and the components of the hydrological cycle are found to be hardly affected by the existence of the lake. A filled Lake Chad does, however, increase the precipitation at the east side of the lake. The model results indicate that the boundary layer moisture and temperature are significantly altered downwind of the lake. By investigating a mesoscale convective system (MCS) case, this is found to affect the development and progress of the system. At first, the MCS is intensified by the more unstable boundary layer air but the persistence of the system is altered as the cold pool propagation becomes less effective. The proposed mechanism is able to explain the differences in the rainfall patterns nearby Lake Chad between the scenarios. This highlights the local sensitivity to the desiccation of Lake Chad whereas the large-scale atmospheric processes are not affected.

  14. Molecular mechanisms of desiccation tolerance in resurrection plants.

    PubMed

    Gechev, Tsanko S; Dinakar, Challabathula; Benina, Maria; Toneva, Valentina; Bartels, Dorothea

    2012-10-01

    Resurrection plants are a small but diverse group of land plants characterized by their tolerance to extreme drought or desiccation. They have the unique ability to survive months to years without water, lose most of the free water in their vegetative tissues, fall into anabiosis, and, upon rewatering, quickly regain normal activity. Thus, they are fundamentally different from other drought-surviving plants such as succulents or ephemerals, which cope with drought by maintaining higher steady state water potential or via a short life cycle, respectively. This review describes the unique physiological and molecular adaptations of resurrection plants enabling them to withstand long periods of desiccation. The recent transcriptome analysis of Craterostigma plantagineum and Haberlea rhodopensis under drought, desiccation, and subsequent rehydration revealed common genetic pathways with other desiccation-tolerant species as well as unique genes that might contribute to the outstanding desiccation tolerance of the two resurrection species. While some of the molecular responses appear to be common for both drought stress and desiccation, resurrection plants also possess genes that are highly induced or repressed during desiccation with no apparent sequence homologies to genes of other species. Thus, resurrection plants are potential sources for gene discovery. Further proteome and metabolome analyses of the resurrection plants contributed to a better understanding of molecular mechanisms that are involved in surviving severe water loss. Understanding the cellular mechanisms of desiccation tolerance in this unique group of plants may enable future molecular improvement of drought tolerance in crop plants.

  15. Streptococcus pneumoniae Is Desiccation Tolerant and Infectious upon Rehydration

    PubMed Central

    Walsh, Rebecca L.; Camilli, Andrew

    2011-01-01

    ABSTRACT Streptococcus pneumoniae (pneumococcus) is a frequent colonizer of the nasopharynx and one of the leading causative agents of otitis media, pneumonia, and meningitis. The current literature asserts that S. pneumoniae is transmitted person to person via respiratory droplets; however, environmental surfaces (fomites) have been linked to the spread of other respiratory pathogens. Desiccation tolerance has been to shown to be essential for long-term survival on dry surfaces. This study investigated the survival and infectivity of S. pneumoniae following desiccation under ambient conditions. We recovered viable bacteria after all desiccation periods tested, ranging from 1 h to 4 weeks. Experiments conducted under nutrient limitation indicate that desiccation is a condition separate from starvation. Desiccation of an acapsular mutant and 15 different clinical isolates shows that S. pneumoniae desiccation tolerance is independent of the polysaccharide capsule and is a species-wide phenomenon, respectively. Experiments demonstrating that nondesiccated and desiccated S. pneumoniae strains colonize the nasopharynx at comparable levels, combined with their ability to survive long-term desiccation, suggest that fomites may serve as alternate sources of pneumococcal infection. PMID:21610120

  16. Tolerance of thermophilic and hyperthermophilic microorganisms to desiccation.

    PubMed

    Beblo, Kristina; Rabbow, Elke; Rachel, Reinhard; Huber, Harald; Rettberg, Petra

    2009-05-01

    We examined short- and long-term desiccation tolerance of 31 strains of thermophilic and hyperthermophilic Archaea and thermophilic phylogenetically deep-branching Bacteria. Seventeen organisms showed a significant high ability to withstand desiccation. The desiccation tolerance turned out to be species-specific and was influenced by several parameters such as storage temperature, pH, substrate or presence of oxygen. All organisms showed a higher survival rate at low storage temperatures (-20 degrees C or below) than at room temperature. Anaerobic and microaerophilic strains are influenced negatively in their survival by the presence of oxygen during desiccation and storage. The desiccation tolerance of Sulfolobales strains is co-influenced by the pH and the substrate of the pre-culture. The distribution of desiccation tolerance in the phylogenetic tree of life is not domain specific. Surprisingly, there are dramatic differences in desiccation tolerance among organisms from the same order and even from closely related strains of the same genus. Our results show that tolerance of vegetative cells to desiccation is a common phenomenon of thermophilic and hyperthermophilic microorganisms although they originated from quite different non-arid habitats like boiling acidic springs or black smoker chimneys.

  17. Factors Predicting the Ocular Surface Response to Desiccating Environmental Stress

    PubMed Central

    Alex, Anastasia; Edwards, Austin; Hays, J. Daniel; Kerkstra, Michelle; Shih, Amanda; de Paiva, Cintia S.; Pflugfelder, Stephen C.

    2013-01-01

    Purpose. To identify factors predicting the ocular surface response to experimental desiccating stress. Methods. The ocular surfaces of both eyes of 15 normal and 10 dry eye subjects wearing goggles were exposed to a controlled desiccating environment (15%–25% relative humidity and 2–5 L/min airflow) for 90 minutes. Eye irritation symptoms, blink rate, tear meniscus dimensions, noninvasive (RBUT) and invasive tear break-up time, and corneal fluorescein and conjunctival lissamine green-dye staining were recorded before and after desiccating stress. Pre- and postexposure measurements were compared, and Pearson correlations between clinical parameters before and after desiccating stress were calculated. Results. Corneal and conjunctival dye staining significantly increased in all subjects following 90-minute exposure to desiccating environment, and the magnitude of change was similar in normal and dry eye subjects; except superior cornea staining was greater in dry eye. Irritation severity in the desiccating environment was associated with baseline dye staining, baseline tear meniscus height, and blink rate after 45 minutes. Desiccation-induced change in corneal fluorescein staining was inversely correlated to baseline tear meniscus width, whereas change in total ocular surface dye staining was inversely correlated to baseline dye staining, RBUT, and tear meniscus height and width. Blink rate from 30 to 90 minutes in desiccating environment was higher in the dry eye than normal group. Blink rate significantly correlated to baseline corneal fluorescein staining and environmental-induced change in corneal fluorescein staining. Conclusions. Ocular surface dye staining increases in response to desiccating stress. Baseline ocular surface dye staining, tear meniscus height, and blink rate predict severity of ocular surface dye staining following exposure to a desiccating environment. PMID:23572103

  18. Transcriptomic analysis reveals numerous diverse protein kinases and transcription factors involved in desiccation tolerance in the resurrection plant Myrothamnus flabellifolia.

    PubMed

    Ma, Chao; Wang, Hong; Macnish, Andrew J; Estrada-Melo, Alejandro C; Lin, Jing; Chang, Youhong; Reid, Michael S; Jiang, Cai-Zhong

    2015-01-01

    The woody resurrection plant Myrothamnus flabellifolia has remarkable tolerance to desiccation. Pyro-sequencing technology permitted us to analyze the transcriptome of M. flabellifolia during both dehydration and rehydration. We identified a total of 8287 and 8542 differentially transcribed genes during dehydration and rehydration treatments respectively. Approximately 295 transcription factors (TFs) and 484 protein kinases (PKs) were up- or down-regulated in response to desiccation stress. Among these, the transcript levels of 53 TFs and 91 PKs increased rapidly and peaked early during dehydration. These regulators transduce signal cascades of molecular pathways, including the up-regulation of ABA-dependent and independent drought stress pathways and the activation of protective mechanisms for coping with oxidative damage. Antioxidant systems are up-regulated, and the photosynthetic system is modified to reduce ROS generation. Secondary metabolism may participate in the desiccation tolerance of M. flabellifolia as indicated by increases in transcript abundance of genes involved in isopentenyl diphosphate biosynthesis. Up-regulation of genes encoding late embryogenesis abundant proteins and sucrose phosphate synthase is also associated with increased tolerance to desiccation. During rehydration, the transcriptome is also enriched in transcripts of genes encoding TFs and PKs, as well as genes involved in photosynthesis, and protein synthesis. The data reported here contribute comprehensive insights into the molecular mechanisms of desiccation tolerance in M. flabellifolia.

  19. Transcriptomic analysis reveals numerous diverse protein kinases and transcription factors involved in desiccation tolerance in the resurrection plant Myrothamnus flabellifolia

    PubMed Central

    Ma, Chao; Wang, Hong; Macnish, Andrew J; Estrada-Melo, Alejandro C; Lin, Jing; Chang, Youhong; Reid, Michael S; Jiang, Cai-Zhong

    2015-01-01

    The woody resurrection plant Myrothamnus flabellifolia has remarkable tolerance to desiccation. Pyro-sequencing technology permitted us to analyze the transcriptome of M. flabellifolia during both dehydration and rehydration. We identified a total of 8287 and 8542 differentially transcribed genes during dehydration and rehydration treatments respectively. Approximately 295 transcription factors (TFs) and 484 protein kinases (PKs) were up- or down-regulated in response to desiccation stress. Among these, the transcript levels of 53 TFs and 91 PKs increased rapidly and peaked early during dehydration. These regulators transduce signal cascades of molecular pathways, including the up-regulation of ABA-dependent and independent drought stress pathways and the activation of protective mechanisms for coping with oxidative damage. Antioxidant systems are up-regulated, and the photosynthetic system is modified to reduce ROS generation. Secondary metabolism may participate in the desiccation tolerance of M. flabellifolia as indicated by increases in transcript abundance of genes involved in isopentenyl diphosphate biosynthesis. Up-regulation of genes encoding late embryogenesis abundant proteins and sucrose phosphate synthase is also associated with increased tolerance to desiccation. During rehydration, the transcriptome is also enriched in transcripts of genes encoding TFs and PKs, as well as genes involved in photosynthesis, and protein synthesis. The data reported here contribute comprehensive insights into the molecular mechanisms of desiccation tolerance in M. flabellifolia. PMID:26504577

  20. Gene transfer to the desiccation-tolerant cyanobacterium Chroococcidiopsis.

    PubMed

    Billi, D; Friedmann, E I; Helm, R F; Potts, M

    2001-04-01

    The coccoid cyanobacterium Chroococcidiopsis dominates microbial communities in the most extreme arid hot and cold deserts. These communities withstand constraints that result from multiple cycles of drying and wetting and/or prolonged desiccation, through mechanisms which remain poorly understood. Here we describe the first system for genetic manipulation of Chroococcidiopsis. Plasmids pDUCA7 and pRL489, based on the pDU1 replicon of Nostoc sp. strain PCC 7524, were transferred to different isolates of Chroococcidiopsis via conjugation and electroporation. This report provides the first evidence that pDU1 replicons can be maintained in cyanobacteria other than Nostoc and Anabaena. Following conjugation, both plasmids replicated in Chroococcidiopsis sp. strains 029, 057, and 123 but not in strains 171 and 584. Both plasmids were electroporated into strains 029 and 123 but not into strains 057, 171, and 584. Expression of P(psbA)-luxAB on pRL489 was visualized through in vivo luminescence. Efficiencies of conjugative transfer for pDUCA7 and pRL489 into Chroococcidiopsis sp. strain 029 were approximately 10(-2) and 10(-4) transconjugants per recipient cell, respectively. Conjugative transfer occurred with a lower efficiency into strains 057 and 123. Electrotransformation efficiencies of about 10(-4) electrotransformants per recipient cell were achieved with strains 029 and 123, using either pDUCA7 or pRL489. Extracellular deoxyribonucleases were associated with each of the five strains. Phylogenetic analysis, based upon the V6 to V8 variable regions of 16S rRNA, suggests that desert strains 057, 123, 171, and 029 are distinct from the type species strain Chroococcidiopsis thermalis PCC 7203. The high efficiency of conjugative transfer of Chroococcidiopsis sp. strain 029, from the Negev Desert, Israel, makes this a suitable experimental strain for genetic studies on desiccation tolerance.

  1. Desiccation of the resurrection plant Haberlea rhodopensis at high temperature.

    PubMed

    Mihailova, Gergana; Petkova, Snejana; Büchel, Claudia; Georgieva, Katya

    2011-05-01

    Haberlea rhodopensis plants, growing under low irradiance in their natural habitat, were desiccated to air-dry state at a similar light intensity (about 30 μmol m(-2) s(-1)) under optimal (23/20°C, day/night) or high (38/30°C) temperature. Dehydration of plants at high temperature increased the rate of water loss threefold and had a more detrimental effect than either drought or high temperature alone. Water deficit decreased the photochemical activity of PSII and PSI and the rate of photosynthetic oxygen evolution, and these effects were stronger when desiccation was carried out at 38°C. Some reduction in the amount of the main PSI and PSII proteins was observed especially in severely desiccated Haberlea leaves. The results clearly showed that desiccation of the homoiochlorophyllous poikilohydric plant Haberlea rhodopensis at high temperature had more damaging effects than desiccation at optimal temperature and in addition recovery was slower. Increased thermal energy dissipation together with higher proline and carotenoid content in the course of desiccation at 38°C compared to desiccation at 23°C probably helped in overcoming the stress.

  2. Proteome dynamics during post-desiccation recovery reveal convergence of desiccation and gamma radiation stress response pathways in Deinococcus radiodurans.

    PubMed

    Ujaoney, Aman Kumar; Padwal, Mahesh Kumar; Basu, Bhakti

    2017-09-01

    Deinococcus radiodurans is inherently resistant to both ionizing radiation and desiccation. Fifteen months of desiccation was found to be the LD50 dose for D. radiodurans. Desiccated cells of D. radiodurans entered 6h of growth arrest during post-desiccation recovery (PDR). Proteome dynamics during PDR were mapped by resolving cellular proteins by 2-dimensional gel electrophoresis coupled with mass spectrometry. At least 41 proteins, represented by 51 spots on proteome profiles, were differentially expressed throughout PDR. High upregulation in expression was observed for DNA repair proteins involved in single strand annealing (DdrA and DdrB), nucleotide excision repair (UvrA and UvrB), homologous recombination (RecA) and other vital proteins that contribute to DNA replication, recombination and repair (Ssb, GyrA and GyrB). Expression of CRP/FNR family transcriptional regulator (Crp) remained high throughout PDR. Other pathways such as cellular detoxification, protein homeostasis and metabolism displayed both, moderately induced and repressed proteins. Functional relevance of proteomic modulations to surviving desiccation stress is discussed in detail. Comparison of our data with the published literature revealed convergence of radiation and desiccation stress responses of D. radiodurans. This is the first report that substantiates the hypothesis that the radiation stress resistance of D. radiodurans is incidental to its desiccation stress resistance. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Frost Growth CFD Model of an Integrated Active Desiccant Rooftop Unit

    SciTech Connect

    Geoghegan, Patrick J; Petrov, Andrei Y; Vineyard, Edward Allan; Zaltash, Abdolreza; Linkous, Randall Lee

    2008-01-01

    A frost growth model is incorporated into a Computational Fluid Dynamics (CFD) simulation of a heat pump by means of a user-defined function in FLUENT, a commercial CFD code. The transient model is applied to the outdoor section of an Integrated Active Desiccant Rooftop (IADR) unit in heating mode. IADR is a hybrid vapor compression and active desiccant unit capable of handling 100% outdoor air (dedicated outdoor air system) or as a total conditioning system, handling both outdoor air and space cooling or heating loads. The predicted increase in flow resistance and loss in heat transfer capacity due to frost build-up are compared to experimental pressure drop readings and thermal imaging. The purpose of this work is to develop a CFD model that is capable of predicting frost growth, an invaluable tool in evaluating the effectiveness of defrost-on-demand cycles.

  4. Composite desiccant material "CaCl2/Vermiculite/Saw wood": a new material for fresh water production from atmospheric air

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Yadav, Avadhesh

    2016-04-01

    In this study a novel composite desiccant material "CaCl2/Vermiculite/Saw wood" have been synthesized and tested for the water generation from atmospheric air. The vermiculite- saw wood used as a host matrix and CaCl2 as a hygroscopic salt. A solar glass desiccant box type system with a collector area of 0.36 m2 has been used. Design parameters for water generation are height of glass from the desiccant material bed as 0.22 m, inclination in angle as 30º, the effective thickness of glass as 3 mm and number of glazing as single. It has been found that the concentration of calcium chloride is the most influencing factor for fresh water generation from atmospheric air. The maximum amount of water produced by using novel composite desiccant material is 195 ml/kg/day.

  5. Composite desiccant material "CaCl2/Vermiculite/Saw wood": a new material for fresh water production from atmospheric air

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Yadav, Avadhesh

    2017-09-01

    In this study a novel composite desiccant material "CaCl2/Vermiculite/Saw wood" have been synthesized and tested for the water generation from atmospheric air. The vermiculite- saw wood used as a host matrix and CaCl2 as a hygroscopic salt. A solar glass desiccant box type system with a collector area of 0.36 m2 has been used. Design parameters for water generation are height of glass from the desiccant material bed as 0.22 m, inclination in angle as 30º, the effective thickness of glass as 3 mm and number of glazing as single. It has been found that the concentration of calcium chloride is the most influencing factor for fresh water generation from atmospheric air. The maximum amount of water produced by using novel composite desiccant material is 195 ml/kg/day.

  6. Effect of desiccation of marine environment on beam structure

    NASA Astrophysics Data System (ADS)

    Chen, Da; Wang, Na; Hou, Li-jun; Liao, Ying-di

    2013-03-01

    This paper presents the study on the effect of desiccation for different part of offshore structure corresponding to the water level. A coupled elastoplastic damage model is proposed to describe the mechanical behavior of cement-based materials under external loading and desiccation, in which both the plastic and damage behaviors under multi-axial stress are considered in composition with the desiccation effect. The comparison between numerical simulation and experimental data indicates that the proposed model can well predict the mechanical characteristics of cement-based materials with different saturations. In addition, a series of small beams subjected to desiccation are further analyzed to reveal the response of structure in the drying process.

  7. Retention of Preservative Levels of Formaldehyde in Desiccated Biological Products

    PubMed Central

    Pemberton, John R.

    1975-01-01

    Concentrations ranging from 8 to 100% of the preservative level of formalin (37% formaldehyde solution) were retained by desiccated biologics, with most products retaining about 50% regardless of the amount originally present. PMID:972183

  8. Desiccant Enhanced Evaporative Air Conditioning: Parametric Analysis and Design; Preprint

    SciTech Connect

    Woods, J.; Kozubal, E.

    2012-10-01

    This paper presents a parametric analysis using a numerical model of a new concept in desiccant and evaporative air conditioning. The concept consists of two stages: a liquid desiccant dehumidifier and a dew-point evaporative cooler. Each stage consists of stacked air channel pairs separated by a plastic sheet. In the first stage, a liquid desiccant film removes moisture from the process (supply-side) air through a membrane. An evaporatively-cooled exhaust airstream on the other side of the plastic sheet cools the desiccant. The second-stage indirect evaporative cooler sensibly cools the dried process air. We analyze the tradeoff between device size and energy efficiency. This tradeoff depends strongly on process air channel thicknesses, the ratio of first-stage to second-stage area, and the second-stage exhaust air flow rate. A sensitivity analysis reiterates the importance of the process air boundary layers and suggests a need for increasing airside heat and mass transfer enhancements.

  9. The relationship between water binding and desiccation tolerance in tissues

    NASA Technical Reports Server (NTRS)

    Vertucci, C. W.; Leopold, A. C.

    1987-01-01

    In an effort to define the nature of desiccation tolerance, a comparison of the water sorption characteristics was made between tissues that were resistant and tissues that were sensitive to desiccation. Water sorption isotherms were constructed for germinated and ungerminated soybean axes and also for fronds of several species of Polypodium with varying tolerance to dehydration. The strength of water binding was determined by van't Hoff as well as D'Arcy/Watt analyses of the isotherms at 5, 15, and/or 25 degrees C. Tissues which were sensitive to desiccation had a poor capacity to bind water tightly. Tightly bound water can be removed from soybean and pea seeds by equilibration at 35 degrees C over very low relative humidities; this results in a reduction in the viability of the seed. We suggest that region 1 water (i.e. water bound with very negative enthalpy values) is an important component of desiccation tolerance.

  10. Desiccation of the Aral Sea and climate change in Central Asia: Interplay and mutual feedbacks

    NASA Astrophysics Data System (ADS)

    Zavialov, Peter; Huang, Huei-Ping

    2013-04-01

    In this presentation, we report results of a research project supported by US Civil Research and Development Foundation aimed at investigating the interplays between the Aral Sea desiccation, anthropogenic impacts, and climate change in Central Asia, and quantify principal feedbacks in the climatic system of the Aral Sea region by means of numerical model experiments as well as analyses of historical and newly obtained observational data. Aral Sea desiccation has been recognized as one of the worst anthropogenic ecological disasters ever. However, it is believed that a part of the desiccation may have been due to the natural climate variability manifested in larger scale warming trends across the Central Asia. The interaction between the lake and the climate change is a "two-way street": the shrinking of the Aral Sea leads to reduction in evaporation and precipitation, thus affecting regional moisture and temperature regimes, and atmospheric circulation. The altered meteorological condition may, in turn, induce further changes in the Aral Sea. In this study, we attempted to quantify the relative contribution from the alterations in the lake's hydrology and surface area to the regional climate change, and, reciprocally, from the large-scale and regional climate trends to the desiccation of the Aral Sea. We show, in particular, that the Aral Sea desiccation has led to significant changes in the regional precipitation, snow cover, and air temperature regimes. On the other hand, the large-scale variability of climate across Central Asia has modulated the hydrology of the lake and caused at least a part of the water level drop. We assessed the long-term trends of air temperature at different isobaric surfaces in the Aral Sea region basing on reanalysis and historical data. Temperature and rainfall daily measurements from 223 meteorological stations of the former USSR in period from 1936 to 1990 were used, as well as the NCAR/NCEP reanalysis data. The differences between

  11. Desiccation tolerance of Hymenophyllacea filmy ferns is mediated by constitutive and non-inducible cellular mechanisms.

    PubMed

    Garcés Cea, Marcelo; Claverol, Stephan; Alvear Castillo, Carla; Rabert Pinilla, Claudia; Bravo Ramírez, León

    2014-04-01

    desiccation takes place therefore precludes the induction of protective systems, suggesting a constitutive mechanism of cellular protection. Copyright © 2014 Académie des sciences. Published by Elsevier SAS. All rights reserved.

  12. Genetic Analysis of Desiccation Tolerance in Saccharomyces cerevisiae

    PubMed Central

    Calahan, Dean; Dunham, Maitreya; DeSevo, Chris; Koshland, Douglas E.

    2011-01-01

    Desiccation tolerance, the ability to survive nearly total dehydration, is a rare strategy for survival and reproduction observed in all taxa. However, the mechanism and regulation of this phenomenon are poorly understood. Correlations between desiccation tolerance and potential effectors have been reported in many species, but their physiological significance has not been established in vivo. Although the budding yeast Saccharomyces cerevisiae exhibits extreme desiccation tolerance, its usefulness has been hampered by an inability to reduce tolerance more than a few fold by physiological or genetic perturbations. Here we report that fewer than one in a million yeast cells from low-density logarithmic cultures survive desiccation, while 20–40% of cells from saturated cultures survive. Using this greatly expanded metric, we show that mutants defective in trehalose biosynthesis, hydrophilins, responses to hyperosmolarity, and hypersalinity, reactive oxygen species (ROS) scavenging and DNA damage repair nevertheless retain wild-type levels of desiccation tolerance, suggesting that this trait involves a unique constellation of stress factors. A genome-wide screen for mutants that render stationary cells as sensitive as log phase cells identifies only mutations that block respiration. Respiration as a prerequisite for acquiring desiccation tolerance is corroborated by respiration inhibition and by growth on nonfermentable carbon sources. Suppressors bypassing the respiration requirement for desiccation tolerance reveal at least two pathways, one of which, involving the Mediator transcription complex, is associated with the shift from fermentative to respiratory metabolism. Further study of these regulators and their targets should provide important clues to the sensors and effectors of desiccation tolerance. PMID:21840858

  13. Genetic analysis of desiccation tolerance in Sachharomyces cerevisiae.

    PubMed

    Calahan, Dean; Dunham, Maitreya; DeSevo, Chris; Koshland, Douglas E

    2011-10-01

    Desiccation tolerance, the ability to survive nearly total dehydration, is a rare strategy for survival and reproduction observed in all taxa. However, the mechanism and regulation of this phenomenon are poorly understood. Correlations between desiccation tolerance and potential effectors have been reported in many species, but their physiological significance has not been established in vivo. Although the budding yeast Saccharomyces cerevisiae exhibits extreme desiccation tolerance, its usefulness has been hampered by an inability to reduce tolerance more than a few fold by physiological or genetic perturbations. Here we report that fewer than one in a million yeast cells from low-density logarithmic cultures survive desiccation, while 20-40% of cells from saturated cultures survive. Using this greatly expanded metric, we show that mutants defective in trehalose biosynthesis, hydrophilins, responses to hyperosmolarity, and hypersalinity, reactive oxygen species (ROS) scavenging and DNA damage repair nevertheless retain wild-type levels of desiccation tolerance, suggesting that this trait involves a unique constellation of stress factors. A genome-wide screen for mutants that render stationary cells as sensitive as log phase cells identifies only mutations that block respiration. Respiration as a prerequisite for acquiring desiccation tolerance is corroborated by respiration inhibition and by growth on nonfermentable carbon sources. Suppressors bypassing the respiration requirement for desiccation tolerance reveal at least two pathways, one of which, involving the Mediator transcription complex, is associated with the shift from fermentative to respiratory metabolism. Further study of these regulators and their targets should provide important clues to the sensors and effectors of desiccation tolerance.

  14. Genome structure of bdelloid rotifers: shaped by asexuality or desiccation?

    PubMed

    Gladyshev, Eugene A; Arkhipova, Irina R

    2010-01-01

    Bdelloid rotifers are microscopic invertebrate animals best known for their ancient asexuality and the ability to survive desiccation at any life stage. Both factors are expected to have a profound influence on their genome structure. Recent molecular studies demonstrated that, although the gene-rich regions of bdelloid genomes are organized as colinear pairs of closely related sequences and depleted in repetitive DNA, subtelomeric regions harbor diverse transposable elements and horizontally acquired genes of foreign origin. Although asexuality is expected to result in depletion of deleterious transposons, only desiccation appears to have the power to produce all the uncovered genomic peculiarities. Repair of desiccation-induced DNA damage would require the presence of a homologous template, maintaining colinear pairs in gene-rich regions and selecting against insertion of repetitive DNA that might cause chromosomal rearrangements. Desiccation may also induce a transient state of competence in recovering animals, allowing them to acquire environmental DNA. Even if bdelloids engage in rare or obscure forms of sexual reproduction, all these features could still be present. The relative contribution of asexuality and desiccation to genome organization may be clarified by analyzing whole-genome sequences and comparing foreign gene and transposon content in species which lost the ability to survive desiccation.

  15. Development of switchable hygroscopic materials. Final technical report FY 1980-1981

    SciTech Connect

    1982-01-01

    The following are covered: current considerations in desiccant dehumidification materials, switchable desiccant theory, candidate materials, test methods, test results, product design considerations, and future research.

  16. Change in desiccation tolerance of maize embryos during development and germination at different water potential PEG-6000 in relation to oxidative process.

    PubMed

    Huang, Hui; Song, Songquan

    2013-07-01

    Desiccation tolerance is one of the most important traits determining seed survival during storage and under stress conditions. However, the mechanism of seed desiccation tolerance is still unclear in detail. In the present study, we used a combined model system, desiccation-tolerant and -sensitive maize embryos with identical genetic background, to investigate the changes in desiccation tolerance, malonyldialdehyde (MDA) level, hydrogen peroxide (H₂O₂) content and antioxidant enzyme activity during seed development and germination in 0, -0.6 and -1.2 MPa polyethylene glycol (PEG)-6000 solutions. Our results indicated that maize embryos gradually acquired and lost desiccation tolerance during development and germination, respectively. The acquirement and loss of desiccation tolerance of embryos during development and germination were related to the ability of antioxidant enzymes including superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6), glutathione reductase (GR, EC 1.6.4.2) and dehydroascorbate reductase (DHAR, EC 1.8.5.1) to scavenge reactive oxygen species (ROS) and to control MDA content. Compared with treatment in water, PEG-6000 treatment could markedly delay the loss of desiccation tolerance of germinating embryos by delaying water uptake and time course of germination, increasing GR activity and decreasing MDA content. Our data showed the combination of antioxidant enzyme activity and MDA content is a good parameter for assessing the desiccation tolerance of maize embryos. In addition, H₂O₂ accumulated in mature embryos and PEG-treated embryos after drying, which was at least partially related to a longer embryo/seedling length in rehydration and the physiological mechanisms of priming. Copyright © 2013. Published by Elsevier Masson SAS.

  17. Polypropylene Fiber Amendments to Alleviate Initiation and Evolution of Desiccation Cracks in Bentonite Liners

    NASA Astrophysics Data System (ADS)

    Tuller, M.; Gebrenegus, T. B.

    2009-12-01

    Sodium saturated bentonite is a major constituent of compacted and geosynthetic liners and covers for hydraulic isolation of hazardous waste, playing a crucial role in protecting groundwater and other environmental resources from harmful landfill leachates. Due to favorable hydraulic properties (i.e., low permeability), large surface area and associated adsorption capacity for particular contaminants, and relative abundance and low cost, bentonite is the material of choice in many modern waste containment systems. However, long-term interactions between bentonite and waste leachate and exposure of bentonite to desiccative conditions may significantly deteriorate liner or cover performance and ultimately lead to failure of containment systems. In the presented study, the potential usefulness of polypropylene fiber amendments for preventing initiation and evolution of desiccation cracks, while maintaining acceptably low permeability under saturated conditions was investigated. Well-controlled desiccation experiments were conducted using initially saturated bentonite-sand mixtures that contained varying amounts of polypropylene fibers. Initiation and evolution of surface cracks were observed by means of X-Ray Computed Tomography (CT). Advanced image analysis techniques were employed to characterize and quantify 2-D and 3-D features of the evolving crack networks. Potential negative effects of employed additives on saturated hydraulic conductivity were determined with fully-automated Flexible Wall Permeametry (FWP).

  18. An easily reversible structural change underlies mechanisms enabling desert crust cyanobacteria to survive desiccation.

    PubMed

    Bar-Eyal, Leeat; Eisenberg, Ido; Faust, Adam; Raanan, Hagai; Nevo, Reinat; Rappaport, Fabrice; Krieger-Liszkay, Anja; Sétif, Pierre; Thurotte, Adrien; Reich, Ziv; Kaplan, Aaron; Ohad, Itzhak; Paltiel, Yossi; Keren, Nir

    2015-10-01

    Biological desert sand crusts are the foundation of desert ecosystems, stabilizing the sands and allowing colonization by higher order organisms. The first colonizers of the desert sands are cyanobacteria. Facing the harsh conditions of the desert, these organisms must withstand frequent desiccation-hydration cycles, combined with high light intensities. Here, we characterize structural and functional modifications to the photosynthetic apparatus that enable a cyanobacterium, Leptolyngbya sp., to thrive under these conditions. Using multiple in vivo spectroscopic and imaging techniques, we identified two complementary mechanisms for dissipating absorbed energy in the desiccated state. The first mechanism involves the reorganization of the phycobilisome antenna system, increasing excitonic coupling between antenna components. This provides better energy dissipation in the antenna rather than directed exciton transfer to the reaction center. The second mechanism is driven by constriction of the thylakoid lumen which limits diffusion of plastocyanin to P700. The accumulation of P700(+) not only prevents light-induced charge separation but also efficiently quenches excitation energy. These protection mechanisms employ existing components of the photosynthetic apparatus, forming two distinct functional modes. Small changes in the structure of the thylakoid membranes are sufficient for quenching of all absorbed energy in the desiccated state, protecting the photosynthetic apparatus from photoinhibitory damage. These changes can be easily reversed upon rehydration, returning the system to its high photosynthetic quantum efficiency.

  19. Effects of Porous Medium Heterogeneity on Vadose Zone Desiccation: Intermediate-scale Laboratory Experiments and Simulations

    SciTech Connect

    Oostrom, Martinus; Freedman, Vicky L.; Wietsma, Thomas W.; Dane, Jacob H.; Truex, Michael J.

    2012-11-01

    Soil desiccation (drying), involving water evaporation induced by dry gas injection, is a potentially robust vadose zone remediation process to limit contaminant transport through the vadose zone. A series of four intermediate-scale flow cell experiments was conducted in homogeneous and simple layered heterogeneous porous medium systems to investigate the effects of heterogeneity on desiccation of unsaturated porous media. The permeability ratios of porous medium layers ranged from about five to almost two orders of magnitude. The insulated flow cell was equipped with twenty humidity and temperature sensors and a dual-energy gamma system was used to determine water saturations at various times. The multiphase code STOMP was used to simulate the desiccation process. Results show that injected dry gas flowed predominantly in the higher permeability layer and delayed water removal from the lower permeability material. For the configurations tested, water vapor diffusion from the lower to the higher permeability zone was considerable over the duration of the experiments, resulting in much larger relative humidity values of the outgoing air than based on permeability ratios alone. Acceptable numerical matches with the experimental data were obtained when an extension of the saturation-capillary pressure relation below the residual water saturation was used. The agreements between numerical and experimental results suggest that the correct physics are implemented in the simulator and that the thermal and hydraulic properties of the porous media, flow cell wall and insulation materials were properly represented.

  20. Rate of Dehydration and Cumulative Desiccation Stress Interacted to Modulate Desiccation Tolerance of Recalcitrant Cocoa and Ginkgo Embryonic Tissues1

    PubMed Central

    Liang, Yongheng; Sun, Wendell Q.

    2002-01-01

    Rate of dehydration greatly affects desiccation tolerance of recalcitrant seeds. This effect is presumably related to two different stress vectors: direct mechanical or physical stress because of the loss of water and physicochemical damage of tissues as a result of metabolic alterations during drying. The present study proposed a new theoretic approach to represent these two types of stresses and investigated how seed tissues responded differently to two stress vectors, using the models of isolated cocoa (Theobroma cacao) and ginkgo (Ginkgo biloba) embryonic tissues dehydrated under various drying conditions. This approach used the differential change in axis water potential (ΔΨ/Δt) to quantify rate of dehydration and the intensity of direct physical stress experienced by embryonic tissues during desiccation. Physicochemical effect of drying was expressed by cumulative desiccation stress [∫\\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\pagestyle{empty} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{o}^{t}}}\\end{equation*}\\end{document}f(ψ,t)], a function of both the rate and time of dehydration. Rapid dehydration increased the sensitivity of embryonic tissues to desiccation as indicated by high critical water contents, below which desiccation damage occurred. Cumulative desiccation stress increased sharply under slow drying conditions, which was also detrimental to embryonic tissues. This quantitative analysis of the stress-time-response relationship helps to understand the physiological basis for the existence of an optimal dehydration rate, with which maximum desiccation tolerance could be achieved. The established numerical analysis model will prove valuable for the design of experiments that aim to elucidate biochemical and physiological mechanisms of desiccation tolerance. PMID:11950981

  1. Solar-Powered, Liquid-Desiccant Air Conditioner for Low-Electricity Humidity Control: Report and Summary Report

    SciTech Connect

    Dean, J.; Kozubal, E.; Herrmann, L.; Miller, J.; Lowenstein, A.; Barker, G.; Slayzak, S.

    2012-11-01

    The primary objective of this project was to demonstrate the capabilities of a new high-performance, liquid-desiccant dedicated outdoor air system (DOAS) to enhance cooling efficiency and comfort in humid climates while substantially reducing electric peak demand at Tyndall Air Force Base (AFB), which is 12 miles east of Panama City, Florida.

  2. Developing sporophytes transition from an inducible to a constitutive ecological strategy of desiccation tolerance in the moss Aloina ambigua: effects of desiccation on fitness

    PubMed Central

    Stark, Lloyd R.; Brinda, John C.

    2015-01-01

    Background and Aims Two ecological strategies of desiccation tolerance exist in plants, constitutive and inducible. Because of difficulties in culturing sporophytes, very little is known about desiccation tolerance in this generation and how desiccation affects sexual fitness. Methods Cultured sporophytes and vegetative shoots from a single genotype of the moss Aloina ambigua raised in the laboratory were tested for their strategy of desiccation tolerance by desiccating the shoot–sporophyte complex and vegetative shoots at different intensities, and comparing outcomes with those of undried shoot–sporophyte complexes and vegetative shoots. By using a dehardened clonal line, the effects of field, age and genetic variance among plants were removed. Key Results The gametophyte and embryonic sporophyte were found to employ a predominantly inducible strategy of desiccation tolerance, while the post-embryonic sporophyte was found to employ a moderately constitutive strategy of desiccation tolerance. Further, desiccation reduced sporophyte fitness, as measured by sporophyte mass, seta length and capsule size. However, the effects of desiccation on sporophyte fitness were reduced if the stress occurred during embryonic development as opposed to postembryonic desiccation. Conclusions The effects of desiccation on dehardened sporophytes of a bryophyte are shown for the first time. The transition from one desiccation tolerance strategy to the other in a single structure or generation is shown for only the second time in plants and for the first time in bryophytes. Finding degrees of inducible strategies of desiccation tolerance in different life phases prompts the formulation of a continuum hypothesis of ecological desiccation tolerance in mosses, where desiccation tolerance is not an either/or phenomenon, but varies in degree along a gradient of ecological inducibility. PMID:25578378

  3. Developing sporophytes transition from an inducible to a constitutive ecological strategy of desiccation tolerance in the moss Aloina ambigua: effects of desiccation on fitness.

    PubMed

    Stark, Lloyd R; Brinda, John C

    2015-03-01

    Two ecological strategies of desiccation tolerance exist in plants, constitutive and inducible. Because of difficulties in culturing sporophytes, very little is known about desiccation tolerance in this generation and how desiccation affects sexual fitness. Cultured sporophytes and vegetative shoots from a single genotype of the moss Aloina ambigua raised in the laboratory were tested for their strategy of desiccation tolerance by desiccating the shoot-sporophyte complex and vegetative shoots at different intensities, and comparing outcomes with those of undried shoot-sporophyte complexes and vegetative shoots. By using a dehardened clonal line, the effects of field, age and genetic variance among plants were removed. The gametophyte and embryonic sporophyte were found to employ a predominantly inducible strategy of desiccation tolerance, while the post-embryonic sporophyte was found to employ a moderately constitutive strategy of desiccation tolerance. Further, desiccation reduced sporophyte fitness, as measured by sporophyte mass, seta length and capsule size. However, the effects of desiccation on sporophyte fitness were reduced if the stress occurred during embryonic development as opposed to postembryonic desiccation. The effects of desiccation on dehardened sporophytes of a bryophyte are shown for the first time. The transition from one desiccation tolerance strategy to the other in a single structure or generation is shown for only the second time in plants and for the first time in bryophytes. Finding degrees of inducible strategies of desiccation tolerance in different life phases prompts the formulation of a continuum hypothesis of ecological desiccation tolerance in mosses, where desiccation tolerance is not an either/or phenomenon, but varies in degree along a gradient of ecological inducibility. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email

  4. Heterogeneity in Desiccated Solutions: Implications for Biostabilization

    PubMed Central

    Ragoonanan, Vishard; Aksan, Alptekin

    2008-01-01

    Biopreservation processes such as freezing and drying inherently introduce heterogeneity. We focused on exploring the mechanisms responsible for heterogeneity in isothermal, diffusively dried biopreservation solutions that contain a model protein. The biopreservation solutions used contained trehalose (a sugar known for its stabilization effect) and salts (LiCl, NaCl, MgCl2, and CaCl2). Performing Fourier transform infrared spectroscopy analysis on the desiccated droplets, spatial distributions of the components within the dried droplet, as well as their specific interactions, were investigated. It was established that the formation of multiple thermodynamic states was induced by the spatial variations in the cosolute concentration gradients, directly affecting the final structure of the preserved protein. The spatial distribution gradients were formed by two competing flows that formed within the drying droplet: a dominant peripheral flow, induced by contact line pinning, and the Marangoni flow, induced by surface tension gradients. It was found that the changes in cosolute concentrations and drying conditions affected the spatial heterogeneity and stability of the product. It was also found that trehalose and salts had a synergistic stabilizing effect on the protein structure, which originated from destructuring of the vicinal water, which in turn mediated the interactions of trehalose with the protein. This interaction was observed by the change in the glycosidic CO, and the CH stretch vibrations of the trehalose molecule. PMID:18055531

  5. Molecular mechanisms of desiccation tolerance in the resurrection glacial relic Haberlea rhodopensis.

    PubMed

    Gechev, Tsanko S; Benina, Maria; Obata, Toshihiro; Tohge, Takayuki; Sujeeth, Neerakkal; Minkov, Ivan; Hille, Jacques; Temanni, Mohamed-Ramzi; Marriott, Andrew S; Bergström, Ed; Thomas-Oates, Jane; Antonio, Carla; Mueller-Roeber, Bernd; Schippers, Jos H M; Fernie, Alisdair R; Toneva, Valentina

    2013-02-01

    well as particular secondary metabolites accumulating during rehydration. This observation, together with the complex antioxidant system and the constitutive expression of stress protective genes suggests that both constitutive and inducible mechanisms contribute to the extreme desiccation tolerance of H. rhodopensis.

  6. Microbial biosynthesis of wax esters during desiccation: an adaptation for colonization of the earliest terrestrial environments?

    NASA Astrophysics Data System (ADS)

    Finkelstein, D. B.; Brassell, S. C.; Pratt, L. M.

    2008-12-01

    Biosynthesis of wax esters (WE) by prokaryotes in natural systems, notably bacteria from hot springs and marine phytoplankton, is poorly documented, primarily because saponification is a routine step in the analysis of microbial mat lipids. Use of this preparative procedure, critical for characterization of the diagnostic distributions of carboxylic acids in phospholipids, precludes recovery of intact WE. Examination of non-saponified lipids in emergent and desiccated mats with comparable microbial communities from the Warner Lake region, Oregon, reveals increases in the relative abundance (18.6 to 59.9μg/g Corg) and average chain length (C38 to C46) of WE in the latter, combined with assimilation of phytol and tocopherol moieties. Prokaryotes can accumulate WE as storage lipids in vitro, notably at elevated temperature or under nitrogen limiting conditions, but we propose that biosynthesis of long-chain WE that have a low solubility and are resistant to degradation/oxidation may represent an evolutionary strategy to survive desiccation in evaporative environments. Moreover, aeolian transport of desiccated mat-rip-ups between lake flats allows for migration of microbial communities within and between lake flats and basins during arid conditions. Subsequent rehydration within an alkaline environment would naturally saponify WE, and thereby regenerate alcohol and acid moieties that could serve as membrane lipids for the next viable microbial generation. The evolutionary cradle of WE was likely abiotic generation under hydrothermal conditions, which is consistent with the antiquity of the ester linkage necessitated by its integral role in the membranes of Eubacteria (though not Archaea) and in bacteriochlorophyll. The subsequent capability of microbes to biosynthesize WE may have facilitated their survival when nutrients were limiting, and production of long-chain WE (>C40) may represent a further critical evolutionary threshold that enabled their persistence through

  7. Regulatory network analysis reveals novel regulators of seed desiccation tolerance in Arabidopsis thaliana

    PubMed Central

    González-Morales, Sandra Isabel; Chávez-Montes, Ricardo A.; Hayano-Kanashiro, Corina; Alejo-Jacuinde, Gerardo; Rico-Cambron, Thelma Y.; de Folter, Stefan; Herrera-Estrella, Luis

    2016-01-01

    Desiccation tolerance (DT) is a remarkable process that allows seeds in the dry state to remain viable for long periods of time that in some instances exceed 1,000 y. It has been postulated that seed DT evolved by rewiring the regulatory and signaling networks that controlled vegetative DT, which itself emerged as a crucial adaptive trait of early land plants. Understanding the networks that regulate seed desiccation tolerance in model plant systems would provide the tools to understand an evolutionary process that played a crucial role in the diversification of flowering plants. In this work, we used an integrated approach that included genomics, bioinformatics, metabolomics, and molecular genetics to identify and validate molecular networks that control the acquisition of DT in Arabidopsis seeds. Two DT-specific transcriptional subnetworks were identified related to storage of reserve compounds and cellular protection mechanisms that act downstream of the embryo development master regulators LEAFY COTYLEDON 1 and 2, FUSCA 3, and ABSCICIC ACID INSENSITIVE 3. Among the transcription factors identified as major nodes in the DT regulatory subnetworks, PLATZ1, PLATZ2, and AGL67 were confirmed by knockout mutants and overexpression in a desiccation-intolerant mutant background to play an important role in seed DT. Additionally, we found that constitutive expression of PLATZ1 in WT plants confers partial DT in vegetative tissues. PMID:27551092

  8. The limits and frontiers of desiccation-tolerant life.

    PubMed

    Alpert, Peter

    2005-11-01

    Drying to equilibrium with the air is lethal to most species of animals and plants, making drought (i.e., low external water potential) a central problem for terrestrial life and a major cause of agronomic failure and human famine. Surprisingly, a wide taxonomic variety of animals, microbes, and plants do tolerate complete desiccation, defined as water content below 0.1 g H(2)O g(-1) dry mass. Species in five phyla of animals and four divisions of plants contain desiccation-tolerant adults, juveniles, seeds, or spores. There seem to be few inherent limits on desiccation tolerance, since tolerant organisms can survive extremely intense and prolonged desiccation. There seems to be little phylogenetic limitation of tolerance in plants but may be more in animals. Physical constraints may restrict tolerance of animals without rigid skeletons and to plants shorter than 3 m. Physiological constraints on tolerance in plants may include control by hormones with multiple effects that could link tolerance to slow growth. Tolerance tends to be lower in organisms from wetter habitats, and there may be selection against tolerance when water availability is high. Our current knowledge of limits to tolerance suggests that they pose few obstacles to engineering tolerance in prokaryotes and in isolated cells and tissues, and there has already been much success on this scientific frontier of desiccation tolerance. However, physical and physiological constraints and perhaps other limits may explain the lack of success in extending tolerance to whole, desiccation-sensitive, multicellular animals and plants. Deeper understanding of the limits to desiccation tolerance in living things may be needed to cross this next frontier.

  9. Desiccation tolerance of Sphagnum revisited: a puzzle resolved.

    PubMed

    Hájek, T; Vicherová, E

    2014-07-01

    As ecosystem engineers, Sphagnum mosses control their surroundings through water retention, acidification and peat accumulation. Because water retention avoids desiccation, sphagna are generally intolerant to drought; however, the literature on Sphagnum desiccation tolerance (DT) provides puzzling results, indicating the inducible nature of their DT. To test this, various Sphagnum species and other mesic bryophytes were hardened to drought by (i) slow drying; (ii) ABA application and (iii) chilling or frost. DT tolerance was assessed as recovery of chlorophyll fluorescence parameters after severe desiccation. We monitored the seasonal course of DT in bog bryophytes. Under laboratory conditions, following initial de-hardening, untreated Sphagnum shoots lacked DT; however, DT was induced by all hardening treatments except chilling, notably by slow drying, and in Sphagnum species of the section Cuspidata. In the field, sphagna in hollows and lawns developed DT several times during the growing season, responding to reduced precipitation and a lowered water table. Hummock and aquatic species developed DT only in late autumn, probably as a response to frost. Sphagnum protonemata failed to develop DT; hence, desiccation may limit Sphagnum establishment in drier habitats with suitable substrate chemistry. Desiccation avoiders among sphagna form compact hummocks or live submerged; thus, they do not develop DT in the field, lacking the initial desiccation experience, which is frequent in hollow and lawn habitats. We confirmed the morpho-physiological trade-off: in contrast to typical hollow sphagna, hummock species invest more resources in water retention (desiccation avoidance), while they have a lower ability to develop physiological DT. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.

  10. Effective Operation for an Adsorptive Desiccant Cooling Process using a Double-Stage Regeneration of Honeycomb Rotary Dehumidifier

    NASA Astrophysics Data System (ADS)

    Kodama, Akio; Ando, Kouke; Hirose, Tsutomu; Goto, Motonobu; Tuziguchi, Takuya; Okano, Hiroshi

    A double-stage regeneration concept has been applied to a rotary dehumidifier to achieve a high efficient desiccant cooling process. In this concept, regeneration zone of the dehumidifier was divided into two zones. One was pre-regeneration zone where the desiccant rotor was regenerated by warm air heated at the sensible heat exchanger, and the other was heating regeneration zone where the rotor was further regenerated by hot air heated up to the controlled temperature at a heating system. In this paper, the influence of the area ratio of these two zones on the dehumidifying/cooling performance and energy efficiency of this desiccant system were mainly discussed at several levels of the regeneration temperature, supply air velocity and inlet air humidity. Experimental results indicated that the area ratio of the heating regeneration zone should be optimized to produce a sufficient dehumidifying/cooling performance with high energy efficiency, considering humidity requested in supply air. It was also found that the amount of energy input was rather decreased than the decrease of the cooling performance as the area ratio of the heating regeneration zone decreased, and this tendency was more remarkable at higher regeneration temperature. Finally, the double-stage regeneration was confirmed to be an effective operating method for the desiccant cooling process equipped with a otary dehumidifier.

  11. Increasing intracellular trehalose is sufficient to confer desiccation tolerance to Saccharomyces cerevisiae.

    PubMed

    Tapia, Hugo; Young, Lindsey; Fox, Douglas; Bertozzi, Carolyn R; Koshland, Douglas

    2015-05-12

    Diverse organisms capable of surviving desiccation, termed anhydrobiotes, include species from bacteria, yeast, plants, and invertebrates. However, most organisms are sensitive to desiccation, likely due to an assortment of different stresses such as protein misfolding and aggregation, hyperosmotic stress, membrane fracturing, and changes in cell volume and shape leading to an overcrowded cytoplasm and metabolic arrest. The exact stress(es) that cause lethality in desiccation-sensitive organisms and how the lethal stresses are mitigated in desiccation-tolerant organisms remain poorly understood. The presence of trehalose in anhydrobiotes has been strongly correlated with desiccation tolerance. In the yeast Saccharomyces cerevisiae, trehalose is essential for survival after long-term desiccation. Here, we establish that the elevation of intracellular trehalose in dividing yeast by its import from the media converts yeast from extreme desiccation sensitivity to a high level of desiccation tolerance. This trehalose-induced tolerance is independent of utilization of trehalose as an energy source, de novo synthesis of other stress effectors, or the metabolic effects of trehalose biosynthetic intermediates, indicating that a chemical property of trehalose is directly responsible for desiccation tolerance. Finally, we demonstrate that elevated intracellular maltose can also make dividing yeast tolerant to short-term desiccation, indicating that other disaccharides have stress effector activity. However, trehalose is much more effective than maltose at conferring tolerance to long-term desiccation. The effectiveness and sufficiency of trehalose as an antagonizer of desiccation-induced damage in yeast emphasizes its potential to confer desiccation tolerance to otherwise sensitive organisms.

  12. Alternative splicing enhances transcriptome complexity in desiccating seeds.

    PubMed

    Srinivasan, Arunkumar; Jiménez-Gómez, José M; Fornara, Fabio; Soppe, Wim J J; Brambilla, Vittoria

    2016-12-01

    Before being dispersed in the environment, mature seeds need to be dehydrated. The survival of seeds after dispersal depends on their low hydration in combination with high desiccation tolerance. These characteristics are established during seed maturation. Some key seed maturation genes have been reported to be regulated by alternative splicing (AS). However, so far AS was described only for single genes and a comprehensive analysis of AS during seed maturation has been lacking. We investigated gene expression and AS during Arabidopsis thaliana seed development at a global level, before and after desiccation. Bioinformatics tools were developed to identify differentially spliced regions within genes. Our data suggest the importance and shows the peculiar features of AS during seed desiccation. We identified AS in 34% of genes that are expressed at both timepoints before and after desiccation. Most of these AS transcript variants had not been found before in other tissues. Among the AS genes some seed master regulators could be found. Interestingly, 6% of all expressed transcripts were not transcriptionally regulated during desiccation, but only modified by AS. We propose that AS should be more routinely taken into account in the analysis of transcriptomic data to prevent overlooking potentially important regulators. © 2016 Institute of Botany, Chinese Academy of Sciences.

  13. Wheat seedlings as a model to understand desiccation tolerance and sensitivity.

    PubMed

    Farrant, Jill M.; Bailly, Christophe; Leymarie, Juliette; Hamman, Brigitte; Côme, Daniel; Corbineau, Françoise

    2004-04-01

    The coleoptiles of wheat (Triticum aestivum L.) seedlings of cultivar Trémie are desiccation tolerant when 3 days old, although the roots are not. Cutting some of the coleoptiles open prior to dehydration rapidly increased the drying rate. This rendered the coleoptiles sensitive to desiccation, providing a useful model with which to study desiccation tolerance. Both sensitive and tolerant seedlings were dehydrated to 0.3 g H(2)O g(-1) dry mass (g.g) and thereafter rehydrated. Sensitive tissues accr- ued the lipid peroxidation products H(2)O(2)and MDA, and substantial subcellular damage was evident in dry tissues. H(2)O(2) and MDA accumulated slightly only in dry tolerant coleoptiles and no subcellular damage was evident. The activity of antioxidant enzymes glutathione reductase (EC1.6.2.4), superoxide dismutase (EC 1.14.1.1) and catalase (EC 1.11.1.6) increased on drying in both tolerant and sensitive tissues, but were sustained on rehydration in only the tolerant tissues. It is proposed that free radical damage sustained during rapid drying exceeded the ameliorating capacity of antioxidant systems, allowed accrual of lethal subcellular damage. Slow drying enabled sufficient detoxification by antioxidants to minimize damage and allow tolerance to drying. Three LEA- (p11 and Asp 52) and dehydrin- (XV8) like proteins were detected by western blots in tolerant coleoptiles dried to 3.0 g.g and below. Only one (Asp 52) was induced at low water content in rapidly dried sensitive coleoptiles. None were present in root tissues. XV8 RNA (northern analyses) was induced on drying only in tolerant coleoptiles and correlated with protein expression. These stress-putative protein protectants (and XV8 transcripts) appear to be down-regulated during germination but wheat seedlings temporarily retain the ability to reproduce them if drying is slow. Sucrose accumulation during dehydration was similar for both sensitive and tolerant tissues, suggesting that this sugar has little

  14. The Effects of Desiccation on Methanogens Under Aerobic and Anaerobic Conditions

    NASA Astrophysics Data System (ADS)

    Murphy, C.; Kral, T. A.

    2010-04-01

    Survival of methanogens following desiccation depends on whether they are maintained under aerobic or anaerobic conditions. Cells maintained in a desiccated state in the presence of oxygen did not survive as well as those maintained anaerobically.

  15. Bacterial survival responses to extreme desiccation and high humidity

    NASA Astrophysics Data System (ADS)

    Yang, Yinjie; Yokobori, Shinichi; Yamagishi, Akihiko

    The presence of water is thought to be essential for life and strongly considered in life searching operation on extraterrestrial planets. In this study we show different survival responses of bacterial species to water availability and temperatures (25, 4 and - 70 o C). At these temperatures, E.coli lost viability much faster under extreme desiccation than under high humidity. Deinococcus radiodurans exhibited much higher survival rate under desiccation than under high humidity at 25 o C, while its survivals under desiccation and high humidity increased to the same level at 4 and - 70 o C. Bacillus pumilus spores generally survived well under all tested conditions. Water is favorable for the survival of most microorganisms but not a "safeguard" for all microorganisms. Microbial survival at low temperatures may not be affected by water availability. Water absence should not preclude us from seeking life on other planets.

  16. Function of desiccate in gustatory sensilla of drosophila melanogaster

    PubMed Central

    Kawano, Takeshi; Ryuda, Masasuke; Matsumoto, Hitoshi; Ochiai, Masanori; Oda, Yasunori; Tanimura, Teiichi; Csikos, Gyorge; Moriya, Megumi; Hayakawa, Yoichi

    2015-01-01

    Desiccate (Desi), initially discovered as a gene expressing in the epidermis of Drosophila larvae for protection from desiccation stress, was recently found to be robustly expressed in the adult labellum; however, the function, as well as precise expression sites, was unknown. Here, we found that Desi is expressed in two different types of non-neuronal cells of the labellum, the epidermis and thecogen accessory cells. Labellar Desi expression was significantly elevated under arid conditions, accompanied by an increase in water ingestion by adults. Desi overexpression also promoted water ingestion. In contrast, a knockdown of Desi expression reduced feeding as well as water ingestion due to a drastic decrease in the gustatory sensillar sensitivity for all tested tastants. These results indicate that Desi helps protect insects from desiccation damage by not only preventing dehydration through the integument but also accelerating water ingestion via elevated taste sensitivities of the sensilla. PMID:26610608

  17. Great Salt Lake halophilic microorganisms as models for astrobiology: evidence for desiccation tolerance and ultraviolet irradiation resistance

    NASA Astrophysics Data System (ADS)

    Baxter, Bonnie K.; Eddington, Breanne; Riddle, Misty R.; Webster, Tabitha N.; Avery, Brian J.

    2007-09-01

    Great Salt Lake (GSL) is home to halophiles, salt-tolerant Bacteria and Archaea, which live at 2-5M NaCl. In addition to salt tolerance, GSL halophiles exhibit resistance to both ultraviolet (UV) irradiation and desiccation. First, to understand desiccation resistance, we sought to determine the diversity of GSL halophiles capable of surviving desiccation in either recently formed GSL halite crystals or GSL Artemia (brine shrimp) cysts. From these desiccated environments, surviving microorganisms were cultured and isolated, and genomic DNA was extracted from the individual species for identification by 16S rRNA gene homology. From the surface-sterilized cysts we also extracted DNA of the whole microbial population for non-cultivation techniques. We amplified the archaeal or bacterial 16S rRNA gene from all genomic DNA, cloned the cyst population amplicons, and sequenced. These sequences were compared to gene databases for determination of closest matched species. Interestingly, the isolates from the crystal dissolution are distinct from those previously isolated from GSL brine. The cyst population results reveal species not found in crystals or brine, and may indicate microorganisms that live as endosymbionts of this hypersaline arthropod. Second, we explored UV resistance in a GSL haloarchaea species, "H. salsolis." This strain resists UV irradiation an order of magnitude better than control species, all of which have intact repair systems. To test the hypothesis that halophiles have a photoprotection system, which prevents DNA damage from occurring, we designed an immunoassay to detect thymine dimers following UV irradiation. "H. salsolis" showed remarkable resistance to dimer formation. Evidence for both UV and desiccation resistance in these salt-tolerant GSL halophiles makes them well-suited as models for Astrobiological studies in pursuit of questions about life beyond earth.

  18. Traits underpinning desiccation resistance explain distribution patterns of terrestrial isopods.

    PubMed

    Dias, André T C; Krab, Eveline J; Mariën, Janine; Zimmer, Martin; Cornelissen, Johannes H C; Ellers, Jacintha; Wardle, David A; Berg, Matty P

    2013-07-01

    Predicted changes in soil water availability regimes with climate and land-use change will impact the community of functionally important soil organisms, such as macro-detritivores. Identifying and quantifying the functional traits that underlie interspecific differences in desiccation resistance will enhance our ability to predict both macro-detritivore community responses to changing water regimes and the consequences of the associated species shifts for organic matter turnover. Using path analysis, we tested (1) how interspecific differences in desiccation resistance among 22 northwestern European terrestrial isopod species could be explained by three underlying traits measured under standard laboratory conditions, namely, body ventral surface area, water loss rate and fatal water loss; (2) whether these relationships were robust to contrasting experimental conditions and to the phylogenetic relatedness effects being excluded; (3) whether desiccation resistance and hypothesized underlying traits could explain species distribution patterns in relation to site water availability. Water loss rate and (secondarily) fatal water loss together explained 90% of the interspecific variation in desiccation resistance. Our path model indicated that body surface area affects desiccation resistance only indirectly via changes in water loss rate. Our results also show that soil moisture determines isopod species distributions by filtering them according to traits underpinning desiccation resistance. These findings reveal that it is possible to use functional traits measured under standard conditions to predict soil biota responses to water availability in the field over broad spatial scales. Taken together, our results demonstrate an increasing need to generate mechanistic models to predict the effect of global changes on functionally important organisms.

  19. An improved method of isolating salmonellae from contaminated desiccated coconut

    PubMed Central

    Iveson, J. B.; Kovacs, N.; Laurie, Wm.

    1964-01-01

    A report is given on results obtained in the examination of desiccated coconut from Ceylon and the Philippines using two or three media in parallel, the aim being to investigate the efficacy of the enrichment medium introduced by Rappaport, Konforti, and Navon (1956). Although the claims of Rappaport et al. related only to examination of faeces the Rappaport enrichment medium has been found to give higher recovery rates of salmonella from desiccated coconut than the selenite and tetrathionate media. The differences are so striking as to justify an expansion of this work. PMID:14100009

  20. Value of Desiccated Swabs for Streptococcal Epidemiology in the Field

    PubMed Central

    Taplin, David; Lansdell, Lyle

    1973-01-01

    Streptococcal surveys in foreign countries or remote areas may be greatly enhanced by the use of calcium alginate swabs desiccated in sterile silica gel. Delays of up to 4 weeks before return to a base laboratory are feasible, and the need for fresh media or laboratory facilities in the field may be eliminated. Comparison of direct plating on crystal violet blood agar versus delayed silica gel preservation during surveys in Uganda, Haiti, Colombia, and Miami, Fla., showed no significant loss of positive cultures from skin lesions and suggests that desiccated swabs increase the recovery of bacitracin-sensitive Streptococcus pyogenes (presumptive group A) from throats. PMID:4346975

  1. Inheritance of seed desiccation sensitivity in a coffee interspecific cross: evidence for polygenic determinism.

    PubMed

    Dussert, Stéphane; Engelmann, Florent; Louarn, Jacques; Noirot, Michel

    2004-07-01

    The genetic determinism of seed desiccation sensitivity was studied using a cross between two coffee species exhibiting a large difference for this trait, Coffea pseudozanguebariae (tolerant) and C. liberica (sensitive). Throughout the whole study, seed desiccation tolerance was quantified both in terms of water content and water activity. Whatever the parameter used, the level of seed desiccation tolerance in F1 hybrids corresponded to that of the mid-parent, thus indicating an additive inheritance of seed desiccation tolerance at the F1 level. A broad variation was observed among hybrids backcrossed to C. liberica (BCs) for seed desiccation tolerance, independent of the parameter used to quantify it. This variation was continuous and BCs showed transgression in the direction of the most desiccation sensitive parent, indicating (i) that desiccation tolerance is a polygenic trait in coffee species, and (ii) that C. pseudozanguebariae does not present the most favourable alleles for all the genes involved in seed desiccation tolerance. No significant difference was observed between the two reciprocal backcrosses, F1xC. liberica and C. libericaxF1, for the level of desiccation tolerance of their seeds, showing the absence of a maternal effect on this trait. There was no significant effect of the number of seeds harvested from each BC on the level of desiccation tolerance of its seeds. Moreover, there was no significant correlation within BCs between seed size, seed viability, and water content before desiccation and desiccation tolerance.

  2. Inactivation of two homologues of proteins presumed to be involved in the desiccation tolerance of plants sensitizes Deinococcus radiodurans R1 to desiccation.

    PubMed

    Battista, J R; Park, M J; McLemore, A E

    2001-09-01

    Mutational inactivation of the genes designated DR1172 and DRB0118 in Deinococcus radiodurans R1 greatly sensitizes this species to desiccation, but not to ionizing radiation. These genes encode proteins that share features with the desiccation-induced LEA76 proteins of many plants and the PCC13-62 protein of Craterostigma plantagineum, suggesting that D. radiodurans may serve as a useful model for the study of desiccation tolerance in higher organisms. Copyright 2001 Elsevier Science (USA).

  3. Effect of Desiccating Stress on Mouse Meibomian Gland Function

    PubMed Central

    Suhalim, Jeffrey L.; Parfitt, Geraint J.; Xie, Yilu; De Pavia, Cintia S.; Pflugfelder, Stephen C.; Shah, Tejas N.; Potma, Eric O.; Brown, Donald J.; Jester, James V.

    2013-01-01

    Purpose Mice exposed to standardized desiccating environmental stress to induce dry eye-like symptoms have been used as a model to study the underlying mechanisms of evaporative dry eye. While studies have shown marked inflammatory and immune changes, the effect of such stress on meibomian gland function remains largely unknown. We sought to evaluate the effects of desiccating stress on meibocyte proliferation and meibum quality. Methods Ten mice were treated with scopolamine and subjected to a drafty low humidity environment (30–35%). Five and ten days after treatment, eyelids were harvested and cryosections stained with Ki67 antibody to identify cycling cells. Sections were also imaged using stimulated Raman scattering (SRS) microscopy to characterize the gland compositional changes by detecting the vibrational signatures of methylene (lipid) and amide-I (protein). Results Desiccating stress caused a 3-fold increase in basal acinar cell proliferation from 18.3 ± 11.1% in untreated mice to 64.4 ± 19.9% and 66.6 ± 13.4% after 5 and 10 days exposure, respectively (P < .001). In addition, SRS analysis showed a wider variation in the protein-to-lipid ratio throughout the gland, suggesting alterations in meibocyte differentiation and lipid synthesis. Conclusions These data are consistent with a model that a desiccating environment may have a direct effect on meibomian gland function, leading to a significant increase in basal acinar cell proliferation, abnormal meibocyte differentiation, and altered lipid production. PMID:24439047

  4. Transcriptional response of Saccharomyces cerevisiae to desiccation and rehydration.

    PubMed

    Singh, Jatinder; Kumar, Deept; Ramakrishnan, Naren; Singhal, Vibha; Jervis, Jody; Garst, James F; Slaughter, Stephen M; DeSantis, Andrea M; Potts, Malcolm; Helm, Richard F

    2005-12-01

    A transcriptional analysis of the response of Saccharomyces cerevisiae strain BY4743 to controlled air-drying (desiccation) and subsequent rehydration under minimal glucose conditions was performed. Expression of genes involved in fatty acid oxidation and the glyoxylate cycle was observed to increase during drying and remained in this state during the rehydration phase. When the BY4743 expression profile for the dried sample was compared to that of a commercially prepared dry active yeast, strikingly similar expression changes were observed. The fact that these two samples, dried by different means, possessed very similar transcriptional profiles supports the hypothesis that the response to desiccation is a coordinated event independent of the particular conditions involved in water removal. Similarities between "stationary-phase-essential genes" and those upregulated during desiccation were also noted, suggesting commonalities in different routes to reduced metabolic states. Trends in extracellular and intracellular glucose and trehalose levels suggested that the cells were in a "holding pattern" during the rehydration phase, a concept that was reinforced by cell cycle analyses. Application of a "redescription mining" algorithm suggested that sulfur metabolism is important for cell survival during desiccation and rehydration.

  5. Survival of methanogens during desiccation: implications for life on Mars.

    PubMed

    Kendrick, Michael G; Kral, Timothy A

    2006-08-01

    The relatively recent discoveries that liquid water likely existed on the surface of past Mars and that methane currently exists in the martian atmosphere have fueled the possibility of extant or extinct life on Mars. One possible explanation for the existence of the methane would be the presence of methanogens in the subsurface. Methanogens are microorganisms in the domain Archaea that can metabolize molecular hydrogen as an energy source and carbon dioxide as a carbon source and produce methane. One factor of importance is the arid nature of Mars, at least at the surface. If one is to assume that life exists below the surface, then based on the only example of life that we know, liquid water must be present. Realistically, however, that liquid water may be seasonal just as it is at some locations on our home planet. Here we report on research designed to determine how long certain species of methanogens can survive desiccation on a Mars soil simulant, JSC Mars-1. Methanogenic cells were grown on JSC Mars-1, transferred to a desiccator within a Coy anaerobic environmental chamber, and maintained there for varying time periods. Following removal from the desiccator and rehydration, gas chromatographic measurements of methane indicated survival for varying time periods. Methanosarcina barkeri survived desiccation for 10 days, while Methanobacterium formicicum and Methanothermobacter wolfeii were able to survive for 25 days.

  6. Survival of Methanogens During Desiccation: Implications for Life on Mars

    NASA Astrophysics Data System (ADS)

    Kendrick, Michael G.; Kral, Timothy A.

    2006-08-01

    The relatively recent discoveries that liquid water likely existed on the surface of past Mars and that methane currently exists in the martian atmosphere have fueled the possibility of extant or extinct life on Mars. One possible explanation for the existence of the methane would be the presence of methanogens in the subsurface. Methanogens are microorganisms in the domain Archaea that can metabolize molecular hydrogen as an energy source and carbon dioxide as a carbon source and produce methane. One factor of importance is the arid nature of Mars, at least at the surface. If one is to assume that life exists below the surface, then based on the only example of life that we know, liquid water must be present. Realistically, however, that liquid water may be seasonal just as it is at some locations on our home planet. Here we report on research designed to determine how long certain species of methanogens can survive desiccation on a Mars soil simulant, JSC Mars-1. Methanogenic cells were grown on JSC Mars-1, transferred to a desiccator within a Coy anaerobic environmental chamber, and maintained there for varying time periods. Following removal from the desiccator and rehydration, gas chromatographic measurements of methane indicated survival for varying time periods. Methanosarcina barkeri survived desiccation for 10 days, while Methanobacterium formicicum and Methanothermobacter wolfeii were able to survive for 25 days.

  7. The desert moss Pterygoneurum lamellatum (Pottiaceae) exhibits an inducible ecological strategy of desiccation tolerance: effects of rate of drying on shoot damage and regeneration.

    PubMed

    Stark, Lloyd R; Greenwood, Joshua L; Brinda, John C; Oliver, Melvin J

    2013-08-01

    Bryophytes include clades that incorporate constitutive desiccation tolerance, especially terrestrial species. Here we test the hypothesis that the opposing ecological strategy of desiccation tolerance, inducibility, is present in a desert moss, and address this hypothesis by varying rates of drying in a laboratory study. Desiccation tolerance is arguably the most important evolutionary innovation relevant to the colonization of land by plants; increased understanding of the ecological drivers of this trait will eventually illuminate the responsible mechanisms and ultimately open doors to the potential for the application of this trait in cultivated plants. Plants were cloned, grown in continuous culture (dehardened) for several months, and subjected to rates of drying (drying times) ranging from 30 min to 53 h, rehydrated and tested for recovery using chlorophyll fluorescence, leaf damage, and regeneration of protonema and shoots. Rate of drying significantly affected all recovery responses, with very rapid drying rates severely damaging the entire shoot except the shoot apex and resulting in slower growth rates, fewer regenerative shoots produced, and a compromised photosynthetic system as inferred from fluorescence parameters. For the first time, a desert moss is shown to exhibit an ecological strategy of desiccation tolerance that is inducible, challenging the assumption that arid-land bryophytes rely exclusively on constitutive protection. Results indicate that previous considerations defining a slow-dry event in bryophytes need reevaluation, and that the ecological strategy of inducible desiccation tolerance is probably more common than currently understood among terrestrial bryophytes.

  8. Desiccation enhances phosphorylation of PSII and affects the distribution of protein complexes in the thylakoid membrane.

    PubMed

    Gao, Shan; Gu, Wenhui; Xiong, Qian; Ge, Feng; Xie, Xiujun; Li, Jian; Chen, Weizhou; Pan, Guanghua; Wang, Guangce

    2015-03-01

    Desiccation has significant effects on photosynthetic processes in intertidal macro-algae. We studied an intertidal macro-alga, Ulva sp., which can tolerate desiccation, to investigate changes in photosynthetic performance and the components and structure of thylakoid membrane proteins in response to desiccation. Our results demonstrate that photosystem II (PSII) is more sensitive to desiccation than photosystem I (PSI) in Ulva sp. Comparative proteomics of the thylakoid membrane proteins at different levels of desiccation suggested that there were few changes in the content of proteins involved in photosynthesis during desiccation. Interestingly, we found that both the PSII subunit, PsbS (Photosystem II S subunit) (a four-helix protein in the LHC superfamily), and light-harvesting complex stress-related (LHCSR) proteins, which are required for non-photochemical quenching in land plants and algae, respectively, were present under both normal and desiccation conditions and both increased slightly during desiccation. In addition, the results of immunoblot analysis suggested that the phosphorylation of PSII and LHCII increases during desiccation. To investigate further, we separated out a supercomplex formed during desiccation by blue native-polyacrylamide gel electrophoresis and identified the components by mass spectrometry analysis. Our results show that phosphorylation of the complex increases slightly with decreased water content. All the results suggest that during the course of desiccation, few changes occur in the content of thylakoid membrane proteins, but a rearrangement of the protein complex occurs in the intertidal macro-alga Ulva sp. © 2014 Scandinavian Plant Physiology Society.

  9. Cryopreservation of Citrus aurantifolia seeds and embryonic axes using a desiccation protocol.

    PubMed

    Cho, Eun Gi; Noor, Normah M; Kim, Haeng Hoon; Rao, V Ramanatha; Engelmann, Florent

    2002-01-01

    The desiccation and freezing tolerance of seeds, with and without testas, and embryonic axes of Citrus aurantifolia were investigated. Seeds were desiccated with silica gel, under the laminar air flow cabinet or by placing them on a laboratory bench. Whatever the desiccation method employed, survival before and after cryopreservation was higher for seeds without testas. When freezing intact seeds, the highest survival percentage (41.3 %) was achieved after desiccation to 7.3 % moisture content (fresh weight basis) on the laboratory bench. Survival of seeds cryopreserved without testas could reach up to 85 % after desiccation under the laminar air flow cabinet or on the laboratory bench, corresponding to moisture contents of 7.1 and 4.5 %, respectively. After desiccation with silica gel, survival reached a maximum of 60.0 %, for a seed moisture content of 3.3 %. Survival of control embryonic axes was high (80-100 %) whatever the sucrose concentration in the preculture medium and the duration of the desiccation period. After cryopreservation, no survival was noted with embryonic axes, which had not been precultured nor desiccated. Survival of non-desiccated embryonic axes after cryopreservation increased progressively in line with increasing sucrose concentrations in the preculture medium, from 7.5 % with 0.1 M sucrose to 77.5 % with 0.7 M sucrose. Survival of desiccated and cryopreserved embryos was always high, whatever the preculture treatment and desiccation period, ranging from 55.8 % to 92.5 %.

  10. [Desiccation tolerance in seeds of Prosopisferox and Pterogyne nitens (Fabaceae)].

    PubMed

    Morandini, Marcelo Nahuel; Giamminola, Eugenia Mabel; de Viana, Marta Leonor

    2013-03-01

    The high number of endemisms and species diversity together with the accelerated biodiversity loss by deforestation, especially in North Western Argentina, points out the need to work on species conservation combining ex situ and in situ strategies. The aim of this work was to study the desiccation tolerance in seeds of P ferox and P nitens for long term ex situ conservation at the Germplasm Bank of Native Species (BGEN) of the National University of Salta (Argentina). The fruits were collected from ten individuals in P ferox at the National Park Los Cardones and from two sites (Orán and Rivadavia) for P nitens. Desiccation tolerance was assessed following previous established methodologies. The moisture content (MC) of the seeds was determined by keeping them in oven at 103 degreeC and weighting the samples at different intervals till constant weight. Germination essays were carried out with two treatments (control and scarification), with different seed MC (fresh, 10-12%, 3-5%) and in desiccated seeds (3-5% MC) stored six months at -20 degreeC. The MC in P ferox seeds was 14.2% and 10% in P nitens, for both populations studied. Percentage germination in P ferox was higher in the scarification treatments (<82%). The difference between treatments increased with the reduction in MC and the storage for six months at -20 degreeC. Fresh seeds of P nitens do not need scarification treatment, but it is required with the reduction in MC and storage. Mean germination percentage of desiccated seeds stored six months at -20 degreeC was similar in both populations and greater than 82%.We concluded that both species are probably orthodox because seeds tolerated desiccation to 3-5% and storage for six months at -20 degree C.

  11. Deep Vadose Zone Treatability Test for the Hanford Central Plateau: Interim Post-Desiccation Monitoring Results

    SciTech Connect

    Truex, Michael J.; Oostrom, Martinus; Strickland, Christopher E.; Johnson, Timothy C.; Johnson, Christian D.; Clayton, Ray E.; Chronister, Glen B.

    2013-09-01

    A field test of desiccation is being conducted as an element of the deep vadose zone treatability test program. Desiccation technology relies on removal of water from a portion of the subsurface such that the resultant low moisture conditions inhibit downward movement of water and dissolved contaminants. Previously, a field test report (Truex et al. 2012a) was prepared describing the active desiccation portion of the test and initial post-desiccation monitoring data. Additional monitoring data have been collected at the field test site during the post-desiccation period and is reported herein along with interpretation with respect to desiccation performance. This is an interim report including about 2 years of post-desiccation monitoring data.

  12. Deep Vadose Zone Treatability Test for the Hanford Central Plateau. Interim Post-Desiccation Monitoring Results, Fiscal Year 2015

    SciTech Connect

    Truex, Michael J.; Strickland, Christopher E.; Oostrom, Martinus; Johnson, Christian D.; Tartakovsky, Guzel D.; Johnson, Timothy C.; Clayton, Ray E.; Chronister, Glen B.

    2015-09-01

    A field test of desiccation is being conducted as an element of the Deep Vadose Zone Treatability Test Program. The active desiccation portion of the test has been completed. Monitoring data have been collected at the field test site during the post-desiccation period and are reported herein. This is an interim data summary report that includes about 4 years of post-desiccation monitoring data. The DOE field test plan proscribes a total of 5 years of post-desiccation monitoring.

  13. A pilot study to investigate the effects of combined dehumidification and HEPA filtration on dew point and airborne mold spore counts in day care centers.

    PubMed

    Bernstein, J A; Levin, L; Crandall, M S; Perez, A; Lanphear, B

    2005-12-01

    Meteorological factors such as relative humidity directly correlate with airborne fungal levels outdoors and indoors. While dehumidification alone is effective at reducing moisture necessary for mold growth, it is inadequate as a single intervention as it does not remove viable and non-viable fungal spores that are potentially allergenic. The purpose of this pilot study was to investigate whether dehumidification in combination with high-efficiency particulate arrestance (HEPA) filtration is effective at reducing airborne mold spore levels in day care centers. Two day care centers within a 2-mile radius of each other were selected. Day care center A was 2 years old with eight rooms while day care center B was 15 years old with six rooms. A high efficiency Santa Fe dehumidification unit equipped with a HEPA filter was installed in half the rooms (intervention) of each day care facility. Electronic HOBO data loggers continuously measured outdoor and indoor room dew point and temperature every 2 h throughout the study. Dew point and airborne fungal spore measurements from selected rooms with controlled air conditions were analyzed by comparing baseline measurements to those obtained at subsequent time periods over 1 year. Regression models accounted for correlations between measurements in the same room over time. Intervention resulted in a lowered average dew point from baseline by 8.8 degrees C compared with a decrease of 7.1 degrees C in non-intervention rooms across all time periods in both facilities (P<0.001). Fungal analyses demonstrated lower baseline (P=0.06) and follow-up means in intervention rooms (P<0.05), however the change from baseline to end of follow-up differed between intervention and non-intervention rooms in the two facilities. Log transformation was applied to approximate normality of fungal measurements. Dehumidification with HEPA filtration was effective at controlling indoor dew point in both facilities and at reducing airborne culturable

  14. A molecular physiological review of vegetative desiccation tolerance in the resurrection plant Xerophyta viscosa (Baker).

    PubMed

    Farrant, Jill M; Cooper, Keren; Hilgart, Amelia; Abdalla, Kamal O; Bentley, Joanne; Thomson, Jennifer A; Dace, Halford J W; Peton, Nashied; Mundree, Sagadevan G; Rafudeen, Mohamed S

    2015-08-01

    Provides a first comprehensive review of integrated physiological and molecular aspects of desiccation tolerance Xerophyta viscosa. A synopsis of biotechnological studies being undertaken to improve drought tolerance in maize is given. Xerophyta viscosa (Baker) is a monocotyledonous resurrection plant from the family Vellociacea that occurs in summer-rainfall areas of South Africa, Lesotho and Swaziland. It inhabits rocky terrain in exposed grasslands and frequently experiences periods of water deficit. Being a resurrection plant it tolerates the loss of 95% of total cellular water, regaining full metabolic competency within 3 days of rehydration. In this paper, we review some of the molecular and physiological adaptations that occur during various stages of dehydration of X. viscosa, these being functionally grouped into early and late responses, which might be relevant to the attainment of desiccation tolerance. During early drying (to 55% RWC) photosynthesis is shut down, there is increased presence and activity of housekeeping antioxidants and a redirection of metabolism to the increased formation of sucrose and raffinose family oligosaccharides. Other metabolic shifts suggest water replacement in vacuoles proposed to facilitate mechanical stabilization. Some regulatory processes observed include increased presence of a linker histone H1 variant, a Type 2C protein phosphatase, a calmodulin- and an ERD15-like protein. During the late stages of drying (to 10% RWC) there was increased expression of several proteins involved in signal transduction, and retroelements speculated to be instrumental in gene silencing. There was induction of antioxidants not typically found in desiccation-sensitive systems, classical stress-associated proteins (HSP and LEAs), proteins involved in structural stabilization and those associated with changes in various metabolite pools during drying. Metabolites accumulated in this stage are proposed, inter alia, to facilitate subcellular

  15. Characterization of Membrane Properties in Desiccation-Tolerant and -Intolerant Carrot Somatic Embryos.

    PubMed Central

    Tetteroo, FAA.; De Bruijn, A. Y.; Henselmans, RNM.; Wolkers, W. F.; Van Aelst, A. C.; Hoekstra, F. A.

    1996-01-01

    In previous studies, we have shown that carrot (Daucus carota L.) somatic embryos acquire complete desiccation tolerance when they are treated with abscisic acid during culture and subsequently dried slowly. With this manipulable system at hand, we have assessed damage associated with desiccation intolerance. Fast drying caused loss of viability, and all K+ and carbohydrates leached from the somatic embryos within 5 min of imbibition. The phospholipid content decreased by about 20%, and the free fatty acid content increased, which was not observed after slow drying. However, the extent of acyl chain unsaturation was unaltered, irrespective of the drying rate. These results indicate that, during rapid drying, irreversible changes occur in the membranes that are associated with extensive leakage and loss of germinability. The status of membranes after 2 h of imbibition was analyzed in a freeze-fracture study and by Fourier transform infrared spectroscopy. Rapidly dried somatic embryos had clusters of intramembraneous particles in their plasma membranes, and the transition temperature of isolated membranes was above room temperature. Membrane proteins were irreversibly aggregated in an extended [beta]-sheet conformation and had a reduced proportion of [alpha]-helical structures. In contrast, the slowly dried somatic embryos had irregularly distributed, but non-clustered, intramembraneous particles, the transition temperature was below room temperature, and the membrane proteins were not aggregated in a [beta]-sheet conformation. We suggest that desiccation sensitivity of rapidly dried carrot somatic embryos is indirectly caused by an irreversible phase separation in the membranes due to de-esterification of phospholipids and accumulation of free fatty acids. PMID:12226295

  16. Effect of different artificial tears against desiccation in cultured human epithelial cells

    PubMed Central

    Tost, Frank; Keiss, Ramona; Großjohann, Rico; Jürgens, Clemens; Giebel, Jürgen

    2012-01-01

    Summary Background A large number of artificial tears is widely used to treat dry eye symptoms. To test the efficacy of these drugs independent of individual parameters in vitro models are required. As described previously, we employed a reproducible in vitro cell culture system to evaluate the desiccation protection capability of some artificial tears. In the present paper data is presented of another set of pharmaceutical agents. Material/Methods Conjunctival epithelial cell line Chang 1-5c-4 (series 1) and the corneal cell line 2.040 pRSV-T (series 2) were cultured under standard conditions. Confluent cells were wetted for 20 min with artificial tears (Arufil® Uno, Arufil®, Lacrimal®, Lacophthal® sine, Siccaprotect®, Tears Again®, Vidisept® EDO, Vistil®, Wet Comod®) or PBS as a control. After exposure to a constant air flow for 0, 15, 30 and 45 minutes respectively, cells were incubated with the vital dye alamarBlue. Subsequently, absorption of the oxidised form of the dye was assessed using an ELISA-Reader. Results Cell best survival rates in series 1 after 15 min were found for Lacrimal® (0.89), Wet Comod® (0.84) compared to PBS (0.66) and in series 2 for Vidisept® EDO (0.57) and Lacrimal® (0.56) compared to PBS (0.01). After 45 min highest survival was seen in series 1 for Lacrimal® (0.46) and Lacophthal® sine (0.36) compared to PBS (0.33) and in series 2 for Lacrimal® (−0.06) and Arufil (−0.16) compared to PBS (−0.23). Conclusions Both cell lines tested showed different susceptibility towards desiccation and the artificial tears showed differences in preventing cells from desiccation. PMID:22534701

  17. The re-establishment of desiccation tolerance in germinated Arabidopsis thaliana seeds and its associated transcriptome.

    PubMed

    Maia, Julio; Dekkers, Bas J W; Provart, Nicholas J; Ligterink, Wilco; Hilhorst, Henk W M

    2011-01-01

    The combination of robust physiological models with "omics" studies holds promise for the discovery of genes and pathways linked to how organisms deal with drying. Here we used a transcriptomics approach in combination with an in vivo physiological model of re-establishment of desiccation tolerance (DT) in Arabidopsis thaliana seeds. We show that the incubation of desiccation sensitive (DS) germinated Arabidopsis seeds in a polyethylene glycol (PEG) solution re-induces the mechanisms necessary for expression of DT. Based on a SNP-tile array gene expression profile, our data indicates that the re-establishment of DT, in this system, is related to a programmed reversion from a metabolic active to a quiescent state similar to prior to germination. Our findings show that transcripts of germinated seeds after the PEG-treatment are dominated by those encoding LEA, seed storage and dormancy related proteins. On the other hand, a massive repression of genes belonging to many other classes such as photosynthesis, cell wall modification and energy metabolism occurs in parallel. Furthermore, comparison with a similar system for Medicago truncatula reveals a significant overlap between the two transcriptomes. Such overlap may highlight core mechanisms and key regulators of the trait DT. Taking into account the availability of the many genetic and molecular resources for Arabidopsis, the described system may prove useful for unraveling DT in higher plants.

  18. The Re-Establishment of Desiccation Tolerance in Germinated Arabidopsis thaliana Seeds and Its Associated Transcriptome

    PubMed Central

    Maia, Julio; Dekkers, Bas J. W.; Provart, Nicholas J.; Ligterink, Wilco; Hilhorst, Henk W. M.

    2011-01-01

    The combination of robust physiological models with “omics” studies holds promise for the discovery of genes and pathways linked to how organisms deal with drying. Here we used a transcriptomics approach in combination with an in vivo physiological model of re-establishment of desiccation tolerance (DT) in Arabidopsis thaliana seeds. We show that the incubation of desiccation sensitive (DS) germinated Arabidopsis seeds in a polyethylene glycol (PEG) solution re-induces the mechanisms necessary for expression of DT. Based on a SNP-tile array gene expression profile, our data indicates that the re-establishment of DT, in this system, is related to a programmed reversion from a metabolic active to a quiescent state similar to prior to germination. Our findings show that transcripts of germinated seeds after the PEG-treatment are dominated by those encoding LEA, seed storage and dormancy related proteins. On the other hand, a massive repression of genes belonging to many other classes such as photosynthesis, cell wall modification and energy metabolism occurs in parallel. Furthermore, comparison with a similar system for Medicago truncatula reveals a significant overlap between the two transcriptomes. Such overlap may highlight core mechanisms and key regulators of the trait DT. Taking into account the availability of the many genetic and molecular resources for Arabidopsis, the described system may prove useful for unraveling DT in higher plants. PMID:22195004

  19. Late Pleistocene desiccation of Lake Tana, source of the Blue Nile

    NASA Astrophysics Data System (ADS)

    Lamb, Henry F.; Bates, C. Richard; Coombes, Paul V.; Marshall, Michael H.; Umer, Mohammed; Davies, Sarah J.; Dejen, Eshete

    2007-02-01

    High-resolution seismic data from Lake Tana, the source of the Blue Nile in northern Ethiopia, reveal a deep sedimentary sequence divided by four strong reflectors. Data from nearshore cores show that the uppermost strong reflector represents a stiff silt unit, interpreted as a desiccation surface. Channel cuts in this surface, bordered by levee-like structures, are apparent in the seismic data from near the lake margin, suggesting fluvial downcutting and over-bank deposition during seasonal flood events. Periphytic diatoms and peat at the base of a core from the deepest part of the lake overlie compacted sediments, indicating that desiccation was followed by development of shallow-water environments and papyrus swamp in the central basin between 16,700 and 15,100 cal BP. As the lake level rose, open-water evaporation from the closed lake caused it to become slightly saline, as indicated by halophytic diatoms. An abrupt return to freshwater conditions occurred at 14,750 cal BP, when the lake overflowed into the Blue Nile. Further reflection surfaces with downcut structures are identifiable in seismic images of the overlying sediments, suggesting at least two lesser lake-level falls, tentatively dated to about 12,000 and 8000 cal BP. Since Lake Victoria, the source of the White Nile, was also dry until 15,000 cal BP, and did not reach overflow until 14,500 cal BP, the entire Nile system must have been reduced to intermittent seasonal flow until about 14,500 cal BP, when baseflow was re-established with almost simultaneous overflow of the headwater lakes of both the White and Blue Nile rivers. Desiccation of the Nile sources coincides with Heinrich event 1, when cessation of northward heat transport from the tropical Atlantic disrupted the Atlantic monsoon, causing drought in north tropical Africa. The strong reflectors at deeper levels in the seismic sequence of Lake Tana may represent earlier desiccation events, possibly contemporaneous with previous Late

  20. Expression profiling and cross-species RNA interference (RNAi) of desiccation-induced transcripts in the anhydrobiotic nematode Aphelenchus avenae

    PubMed Central

    2010-01-01

    of the anhydrobiotic gene set in A. avenae. It also demonstrates the potential of RNAi for the analysis of anhydrobiosis and provides the first genetic data to underline the importance of effective antioxidant systems in metazoan desiccation tolerance. PMID:20085654

  1. Biomass production, nutritional and mineral content of desiccation-sensitive and desiccation-tolerant species of sporobolus under multiple irrigation regimes

    USDA-ARS?s Scientific Manuscript database

    The development of low-water-input forages of high quality would be useful for expanding or improving the water use efficiency of livestock production in semi-arid and arid regions. In this study, three Sporobolus species, the desiccation tolerant (DT) species, S. stapfianus Gandoger, and two desicc...

  2. Increasing intracellular trehalose is sufficient to confer desiccation tolerance to Saccharomyces cerevisiae

    PubMed Central

    Tapia, Hugo; Young, Lindsey; Fox, Douglas; Bertozzi, Carolyn R.; Koshland, Douglas

    2015-01-01

    Diverse organisms capable of surviving desiccation, termed anhydrobiotes, include species from bacteria, yeast, plants, and invertebrates. However, most organisms are sensitive to desiccation, likely due to an assortment of different stresses such as protein misfolding and aggregation, hyperosmotic stress, membrane fracturing, and changes in cell volume and shape leading to an overcrowded cytoplasm and metabolic arrest. The exact stress(es) that cause lethality in desiccation-sensitive organisms and how the lethal stresses are mitigated in desiccation-tolerant organisms remain poorly understood. The presence of trehalose in anhydrobiotes has been strongly correlated with desiccation tolerance. In the yeast Saccharomyces cerevisiae, trehalose is essential for survival after long-term desiccation. Here, we establish that the elevation of intracellular trehalose in dividing yeast by its import from the media converts yeast from extreme desiccation sensitivity to a high level of desiccation tolerance. This trehalose-induced tolerance is independent of utilization of trehalose as an energy source, de novo synthesis of other stress effectors, or the metabolic effects of trehalose biosynthetic intermediates, indicating that a chemical property of trehalose is directly responsible for desiccation tolerance. Finally, we demonstrate that elevated intracellular maltose can also make dividing yeast tolerant to short-term desiccation, indicating that other disaccharides have stress effector activity. However, trehalose is much more effective than maltose at conferring tolerance to long-term desiccation. The effectiveness and sufficiency of trehalose as an antagonizer of desiccation-induced damage in yeast emphasizes its potential to confer desiccation tolerance to otherwise sensitive organisms. PMID:25918381

  3. Transcriptomes of the desiccation-tolerant resurrection plant Craterostigma plantagineum.

    PubMed

    Rodriguez, Maria C Suarez; Edsgärd, Daniel; Hussain, Syed S; Alquezar, David; Rasmussen, Morten; Gilbert, Thomas; Nielsen, Bjørn H; Bartels, Dorothea; Mundy, John

    2010-07-01

    Studies of the resurrection plant Craterostigma plantagineum have revealed some of the mechanisms which these desiccation-tolerant plants use to survive environments with extreme dehydration and restricted seasonal water. Most resurrection plants are polyploid with large genomes, which has hindered efforts to obtain whole genome sequences and perform mutational analysis. However, the application of deep sequencing technologies to transcriptomics now permits large-scale analyses of gene expression patterns despite the lack of a reference genome. Here we use pyro-sequencing to characterize the transcriptomes of C. plantagineum leaves at four stages of dehydration and rehydration. This reveals that genes involved in several pathways, such as those required for vitamin K and thiamin biosynthesis, are tightly regulated at the level of gene expression. Our analysis also provides a comprehensive picture of the array of cellular responses controlled by gene expression that allow resurrection plants to survive desiccation.

  4. STANDARDS CONTROLLING AIR EMISSIONS FOR THE SOIL DESICCATION PILOT TEST

    SciTech Connect

    BENECKE MW

    2010-09-08

    This air emissions document supports implementation of the Treatability Test Plan for Soil Desiccation as outlined in the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau (DOE/RL-2007-56). Treatability testing supports evaluation of remedial technologies for technetium-99 (Tc-99) contamination in the vadose zone at sites such as the BC Cribs and Trenches. Soil desiccation has been selected as the first technology for testing because it has been recommended as a promising technology in previous Hanford Site technology evaluations and because testing of soil desiccation will provide useful information to enhance evaluation of other technologies, in particular gas-phase remediation technologies. A soil desiccation pilot test (SDPT) will evaluate the desiccation process (e.g., how the targeted interval is dried) and the long-term performance for mitigation of contaminant transport. The SDPT will dry out a moist zone contaminated by Tc-99 and nitrate that has been detected at Well 299-E13-62 (Borehole C5923). This air emissions document applies to the activities to be completed to conduct the SDPT in the 200-BC-1 operable unit located in the 200 East Area of the Hanford Site. Well 299-E13-62 is planned to be used as an injection well. This well is located between and approximately equidistant from cribs 216-B-16, 216-B-17, 216-B-18. and 216-B-19. Nitrogen gas will be pumped at approximately 300 ft{sup 3}/min into the 299-EI3-62 injection well, located approximately 12 m (39 ft) away from extraction well 299-EI3-65. The soil gas extraction rate will be approximately 150 ft{sup 3}/min. The SDPT will be conducted continuously over a period of approximately six months. The purpose of the test is to evaluate soil desiccation as a potential remedy for protecting groundwater. A conceptual depiction is provided in Figure 1. The soil desiccation process will physically dry, or evaporate, some of the water from the moist zone of interest. As such, it is

  5. X-ray crystal structures of a severely desiccated protein.

    PubMed Central

    Bell, J. A.

    1999-01-01

    Unlike most protein crystals, form IX of bovine pancreatic ribonuclease A diffracts well when severely dehydrated. Crystal structures have been solved after 2.5 and 4 days of desiccation with CaSO4, at 1.9 and 2.0 A resolution, respectively. The two desiccated structures are very similar. An RMS displacement of 1.6 A is observed for main-chain atoms in each structure when compared to the hydrated crystal structure with some large rearrangements observed in loop regions. The structural changes are the result of intermolecular contacts formed by strong electrostatic interactions in the absence of a high dielectric medium. The electron density is very diffuse for some surface loops, consistent with a very disordered structure. This disorder is related to the conformational changes. These results help explain conformational changes during the lyophilization of protein and the associated phenomena of denaturation and molecular memory. PMID:10548049

  6. Development and Analysis of Desiccant Enhanced Evaporative Air Conditioner Prototype

    SciTech Connect

    Kozubal, E.; Woods, J.; Judkoff, R.

    2012-04-01

    This report documents the design of a desiccant enhanced evaporative air conditioner (DEVAP AC) prototype and the testing to prove its performance. Previous numerical modeling and building energy simulations indicate a DEVAP AC can save significant energy compared to a conventional vapor compression AC (Kozubal et al. 2011). The purposes of this research were to build DEVAP prototypes, test them to validate the numerical model, and identify potential commercialization barriers.

  7. Reversible Inactivation and Desiccation Tolerance of Silicified Viruses

    SciTech Connect

    Laidler, James J.; Shugart, Jessica A.; Cady, Sherry L.; Bahjat, Keith S.; Stedman, Kenneth M.

    2013-11-19

    Long-distance host-independent virus dispersal is poorly understood, especially for viruses found in isolated ecosystems. To demonstrate a possible dispersal mechanism, we show that bacteriophage T4, archaeal virus SSV-K and Vaccinia are reversibly inactivated by mineralization in silica under conditions similar to volcanic hot springs. By contrast, bacteriophage PRD1 is not silicified. Moreover silicification provides viruses with remarkable desiccation resistance, which could allow extensive aerial dispersal.

  8. Reversible inactivation and desiccation tolerance of silicified viruses.

    PubMed

    Laidler, James R; Shugart, Jessica A; Cady, Sherry L; Bahjat, Keith S; Stedman, Kenneth M

    2013-12-01

    Long-distance host-independent virus dispersal is poorly understood, especially for viruses found in isolated ecosystems. To demonstrate a possible dispersal mechanism, we show that bacteriophage T4, archaeal virus Sulfolobus spindle-shaped virus Kamchatka, and vaccinia virus are reversibly inactivated by mineralization in silica under conditions similar to volcanic hot springs. In contrast, bacteriophage PRD1 is not silicified. Moreover, silicification provides viruses with remarkable desiccation resistance, which could allow extensive aerial dispersal.

  9. Triiodothyronine and thyroxine content of desiccated thyroid tablets.

    PubMed

    Rees-Jones, R W; Larsen, P R

    1977-11-01

    Triiodothyronine (T3) and thyroxine (T4) were measured by radioimmunoassay in Pronase hydrolysates of four lots each of 1- and 2-grain tablets of desiccated thyroid (Thyroid, Armour) and thyroglobulin (Proloid, Warner-Chilcott). The methodology used was verified by studies of tablets containing known quantities of T4 and T3. One grain of desiccated thyroid contained 12 +/- 1 and 64 +/- 3 microgram (mean +/- SD) of T3 and T4 per tablet, respectively (T4/T3 molar ratio, 4.3). A 1-grain tablet of thyroglobulin contained 16 +/- 2 and 55 +/- 5 microgram of T3 and T4, respectively with a T4/T3 ratio of 2.9. Two-grain tablets generally contained twice the quantity of T3 and T4 in the 1-grain preparations. The variation in T3 and T4 content between the four lots of each tablet strength for each product was 10% or less. These estimates of T3 and T4 content are 1.5- to 2-fold greater than those previously published. This difference probably results from the more sophisticated methodology now available which does not require chromatographic separation of T3 and T4 or iodometry. Using calculations based on published estimates of T4 and T3 absorption and of the T3/T4 potency ratio, it would appear that the T3 content of desiccated thyroid and thyroglobulin provide approximately 39% and 51%, respectively, of the thyromimetic activity of these two medications.

  10. Crater floor polygons: Desiccation patterns of ancient lakes on Mars?

    NASA Astrophysics Data System (ADS)

    El Maarry, M. R.; Markiewicz, W. J.; Mellon, M. T.; Goetz, W.; Dohm, J. M.; Pack, A.

    2010-10-01

    Global mapping of intermediate-size (100-200 m) polygonal troughs occurring mainly in impact crater floors was carried out using high-resolution images from spacecraft currently orbiting Mars. Earlier works have classified these polygonal networks as periglacial features on account of their apparent occurrence at higher latitudes and morphological similarities to thermal contraction polygons (TCPs). Crater floor polygons (CFPs) have diameters ranging from 15 to 350 m. They morphologically resemble terrestrial TCPs and desiccation cracks. Their size distribution, however, is significantly different from that of TCPs that are ubiquitous in the high latitudes. An analytical model based on fracture mechanics reveals that under current climatic conditions, the maximum fracture spacing attainable by thermal stresses alone is 75 m at the most. More reasonable values fall within 18 and 22 m, which is the range for TCPs on Mars. As a result, we propose desiccation to be a dominant mechanism for the formation of CFPs without ruling out thermal contraction as a possible contributor in some cases. This implies that lakes or water-rich sediments occupied the craters in the past. Many such aqueous environments have no apparent external source of water, and thus, hydrothermal processes occurring shortly after the impact event may be viable explanations for the observed evidence. The association of features, which correspond to terrestrial lakes such as sedimentary deposits, mounds, and shorelines, corroborates lake formation and their eventual desiccation to form CFPs. The variation of CFP sizes with location can be indicative of different hydrologic environments.

  11. Heat and mass transfer in liquid desiccant air-conditioning process at low flow conditions

    NASA Astrophysics Data System (ADS)

    Peng, S. W.; Pan, Z. M.

    2009-09-01

    This paper investigates the transient heat and mass transfer in liquid desiccant air-conditioning process at low flow conditions. Using local volumetric average approach, one-dimensional non-equilibrium heat and mass transfer models are developed to describe the humid air and liquid desiccant interaction at counter flow configuration. Using triethylene glycol solution as desiccant, some experimental studies are completed. Experimental results are used to justify the numerical models. Numerical results are then obtained to demonstrate process characteristics. The models include a transient desiccant flow model for initial liquid desiccant building-up process, empirical wetted specific surface ratio for mass transfer, and heat and mass transfer coefficients. The objective of this research is to develop a process analytical tool for liquid desiccant air-conditioner design.

  12. Photosynthesis in desiccation tolerant plants: energy metabolism and antioxidative stress defense.

    PubMed

    Dinakar, Challabathula; Djilianov, Dimitar; Bartels, Dorothea

    2012-01-01

    Resurrection plants are regarded as excellent models to study the mechanisms associated with desiccation tolerance. During the past years tremendous progress has been made in understanding the phenomenon of desiccation tolerance in resurrection plants, but many questions are open concerning the mechanisms enabling these plants to survive desiccation. The photosynthetic apparatus is very sensitive to reactive oxygen species mediated injury during desiccation and must be maintained or quickly repaired upon rehydration. The photosynthetic apparatus is a primary source of generating reactive oxygen species. The unique ability of plants to withstand the oxidative stress imposed by reactive oxygen species during desiccation depends on the production of antioxidants. The present review considers the overall strategies and the mechanisms involved in the desiccation tolerance in the first part and will focus on the effects on photosynthesis, energy metabolism and antioxidative stress defenses in the second part. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  13. An Experimental Evolution Test of the Relationship between Melanism and Desiccation Survival in Insects

    PubMed Central

    Rajpurohit, Subhash; Peterson, Lisa Marie; Orr, Andrew J.; Marlon, Anthony J.; Gibbs, Allen G.

    2016-01-01

    We used experimental evolution to test the ‘melanism-desiccation’ hypothesis, which proposes that dark cuticle in several Drosophila species is an adaptation for increased desiccation tolerance. We selected for dark and light body pigmentation in replicated populations of D. melanogaster and assayed several traits related to water balance. We also scored pigmentation and desiccation tolerance in populations selected for desiccation survival. Populations in both selection regimes showed large differences in the traits directly under selection. However, after over 40 generations of pigmentation selection, dark-selected populations were not more desiccation-tolerant than light-selected and control populations, nor did we find significant changes in mass or carbohydrate amounts that could affect desiccation resistance. Body pigmentation of desiccation-selected populations did not differ from control populations after over 140 generations of selection, although selected populations lost water less rapidly. Our results do not support an important role for melanization in Drosophila water balance. PMID:27658246

  14. Mechanisms associated with cellular desiccation tolerance of Artemia encysted embryos from locations around the world.

    PubMed

    Hengherr, Steffen; Schill, Ralph O; Clegg, J S

    2011-10-01

    Using differential scanning calorimetry we demonstrated the presence of biological glasses and measured the glass transition temperatures (Tg) in dry encysted gastrula embryos (cysts) of the brine shrimp, Artemia, from eleven different locations, two of which provided cysts from parthenogenetic animals. Values for Tg were highest, by far, in Artemia franciscana cysts from the Mekong Delta, Vietnam (VN), these cysts having been produced from previous sequential inoculations into growth ponds of cysts from the San Francisco Bay, California, USA. Tg values for three groups of A. franciscana cysts were significantly higher than those of other cysts (except those of Artemia persimilis) studied here, as well as all other desiccation-tolerant animal systems studied to date. We also measured three stress proteins (hsc70, artemin and p26) in all these cysts as well as the total alcohol soluble carbohydrates (ASC), about 90% of which is the disaccharide trehalose, a known component of biological glasses. We interpret the results in terms of mechanisms involved with desiccation tolerance and, to some extent, with thermal conditions at the sites of cyst collection. Copyright © 2011 Elsevier Inc. All rights reserved.

  15. Need for desiccant in containers exposed to atmospheric conditions for long periods of time

    SciTech Connect

    Mead, K.E.

    1981-11-01

    Current component and system designs are required to perform satisfactorily up to 25 years. A maximum leak rate of 1 x 10/sup -6/ cc(STP) helium/sec-atm is a frequent requirement for component containers. Calculations show that undesiccated component containers continuously exposed to 50% relative humidity at 20/sup 0/C and having an internal free volume of less than 300 cc and the above leak rate will allow the internal dew point to rise enough for potential liquid condensation in less than four years. For the same vapor pressure differential, the moisture permeation rate through one linear inch of silicone o-ring is 750 times as fast as moisture enters a welded container whose leak rate is 1 x 10/sup -6/ cc(STP) helium/sec-atm. For ethylene propylene o-ring material this ratio is about 13. These values correspond to the ratios of the quantities of desiccant required to maintain an acceptable dew point temperature when the moisture capacity of the free volume is not included. Charts are provided for estimating the amount of desiccant required for helium leak tested containers and for containers sealed with elastomeric o-rings.

  16. Physiological and biochemical changes during the loss of desiccation tolerance in germinating Adenanthera pavonina L. seeds.

    PubMed

    Soares, Giuliana C M; Dias, Denise C F S; Faria, José M R; Borges, Eduardo E L

    2015-01-01

    We investigated the loss of desiccation tolerance (DT) in Adenanthera pavonina seeds during germination. Seeds were subjected to imbibition for 0, 24, 36, 48, 60 and 81 h, then dried to their initial moisture content (13%), rehydrated and evaluated for survival (resumption of growth and development of normal seedlings) and membrane system integrity (electrolyte leakage). Embryonic axes of seeds subjected only to imbibition during the same early time periods were used to investigate the electrophoretic patterns of heat-stable proteins and the relative nuclear DNA content. In A. pavonina seeds, DT remained unchanged until 36 h of imbibition (resulting in germination and 82% normal seedlings), after which it was progressively lost, and seeds with a protruded radicle length of 1 mm did not withstand dehydration. The loss of desiccation tolerance could not be related to either membrane damage caused by drying or the resumption of the cell cycle during germination. However, the decrease in heat-stable protein contents observed throughout germination may be related to the loss of DT in A. pavonina seeds.

  17. Comparative metabolic profiling between desiccation-sensitive and desiccation-tolerant species of Selaginella reveals insights into the resurrection trait.

    PubMed

    Yobi, Abou; Wone, Bernard W M; Xu, Wenxin; Alexander, Danny C; Guo, Lining; Ryals, John A; Oliver, Melvin J; Cushman, John C

    2012-12-01

    Spike mosses (Selaginellaceae) represent an ancient lineage of vascular plants in which some species have evolved desiccation tolerance (DT). A sister-group contrast to reveal the metabolic basis of DT was conducted between a desiccation-tolerant species, Selaginella lepidophylla, and a desiccation-sensitive species, Selaginella moellendorffii, at 100% relative water content (RWC) and 50% RWC using non-biased, global metabolomics profiling technology, based on GC/MS and UHLC/MS/MS(2) platforms. A total of 301 metabolites, including 170 named (56.5%) and 131 (43.5%) unnamed compounds, were characterized across both species. S.  lepidophylla retained significantly higher abundances of sucrose, mono- and polysaccharides, and sugar alcohols than did S. moellendorffii. Aromatic amino acids, the well-known osmoprotectant betaine and flavonoids were also more abundant in S. lepidophylla. Notably, levels of γ-glutamyl amino acid, linked with glutathione metabolism in the detoxification of reactive oxygen species, and with possible nitrogen remobilization following rehydration, were markedly higher in S. lepidophylla. Markers for lipoxygenase activity were also greater in S. lepidophylla, especially at 50% RWC. S. moellendorffii contained more than twice the number of unnamed compounds, with only a slightly greater abundance than in S. lepidophylla. In contrast, S. lepidophylla contained 14 unnamed compounds of fivefold or greater abundance than in S. moellendorffii, suggesting that these compounds might play critical roles in DT. Overall, S. lepidophylla appears poised to tolerate desiccation in a constitutive manner using a wide range of metabolites with some inducible components, whereas S. moellendorffii mounts only limited metabolic responses to dehydration stress. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

  18. Salinity effects on the dynamics and patterns of desiccation cracks

    NASA Astrophysics Data System (ADS)

    Shokri, N.; Zhou, P.

    2012-12-01

    Cracking arising from desiccation is a ubiquitous phenomenon encountered in various industrial and geo-environmental applications including drying of clayey soil, cement, ceramics, gels, and many more colloidal suspensions. Presence of cracks in muddy sediments modifies the characteristics of the medium such as pore structure, porosity, and permeability which in turn influence various flow and transport processes. Thus it remains a topic of great interest in many disciplines to describe the dynamics of desiccation cracking under various boundary conditions. To this end, we conducted a comprehensive study to investigate effects of NaCl concentrations on cracking dynamics and patterns during desiccation of Bentonite. Mixtures of Bentonite and NaCl solutions were prepared with NaCl concentration varying from 2 to 10 percent in 0.5 percent increment (totally 17 configurations). The slurry was placed in a Petri dish mounted on a digital balance to record the evaporation dynamics. The atmospheric conditions were kept constant using an environmental chamber. An automatic camera was used to record the dynamics of macro-cracks (mm scale) at the surface of desiccating clay each minute. The obtained results illustrate the significant effects of salt concentration on the initiation, propagation, morphology and general dynamics of macro-cracks. We found that higher salt concentrations results in larger macro cracks' lengths attributed to the effects of NaCl on compressing the electric double layer of particles at increasing electrolyte concentrations which reduce considerably the repulsive forces among the particles and causing instability of the slurry and flocculation of the colloidal particles. Rheological measurements by means of a stress controlled rheometer revealed that the yield stress of the slurry decreases as NaCl concentration increases which may indicate aggregation of larger units in the slurry as a result of flocculation causing larger cracks' lengths due to

  19. Desiccation resistance and contamination as mechanisms of gaia.

    PubMed

    Brown, S; Margulis, L; Ibarra, S; Siqueiros, D

    1985-01-01

    The gaia hypothesis, formulated by J.E. Lovelock, asserts the composition of the reactive gases, the oxidation-reduction state and the temperature of the lower atmosphere of the planet Earth are actively regulated by the biota. Lovelock and Watson, using highly simplified mathematical models, have shown that the modulation of atmospheric temperature can be achieved by exponentially growing populations of differently colored organisms ("dark and light daisies"). It is more likely that the modulation of atmospheric gas composition is based on the colligative properties of exponentially growing mixed populations of microorganisms rather than on "daisies". Exponential growth of one population of microorganisms leads to gaseous and other metabolic products released to the environment, which favor the exponential growth of different populations, each with their own unique emissions. Extremely high densities of mixed populations of microorganisms ensue. These populations form structured microbial communities composed of members in varying states of activity. Growth potential of metabolically diverse populations most likely provides the basis for the responsiveness of the biota to changing environments. We have attempted to measure an aspect of the growth potential and diversity of one microbial community, that from a flat laminated microbial mat dominated by the cyanobacterium, Microcoleus. Microbial mat samples collected at yearly intervals between 1977 and 1982 were allowed to dry. Subsamples were revived under laboratory conditions by rewetting, and the resulting complex microbial populations were analyzed. Greater than 10(4) viable organisms per ml were estimated to be present in the desiccated samples. Only a portion of the diverse community could be characterized. There were at least 115 different types of desiccation resistant microorganisms present in these samples, primarily bacteria. However, more than a dozen types of rather uncommon fungi and protoctists were

  20. Method and composition for molding low density desiccant syntactic foam articles

    DOEpatents

    Lula, James W.; Schicker, James R.

    1984-01-01

    A method and a composition are provided for molding low density desiccant syntactic foam articles. A low density molded desiccant article may be made as a syntactic foam by blending a thermosetting resin, microspheres and molecular sieve desiccant powder, molding and curing. Such articles have densities of 0.2-0.9 g/cc, moisture capacities of 1-12% by weight, and can serve as light weight structural supports.

  1. Desiccation as a Long-Term Survival Mechanism for the Archaeon Methanosarcina barkeri

    PubMed Central

    Anderson, Kimberly L.; Apolinario, Ethel E.

    2012-01-01

    Viable methanogens have been detected in dry, aerobic environments such as dry reservoir sediment, dry rice paddies and aerobic desert soils, which suggests that methanogens have mechanisms for long-term survival in a desiccated state. In this study, we quantified the survival rates of the methanogenic archaeon Methanosarcina barkeri after desiccation under conditions equivalent to the driest environments on Earth and subsequent exposure to different stress factors. There was no significant loss of viability after desiccation for 28 days for cells grown with either hydrogen or the methylotrophic substrates, but recovery was affected by growth phase, with cells desiccated during the stationary phase of growth having a higher rate of recovery after desiccation. Synthesis of methanosarcinal extracellular polysaccharide (EPS) significantly increased the viability of desiccated cells under both anaerobic and aerobic conditions compared with that of non-EPS-synthesizing cells. Desiccated M. barkeri exposed to air at room temperature did not lose significant viability after 28 days, and exposure of M. barkeri to air after desiccation appeared to improve the recovery of viable cells compared with that of desiccated cells that were never exposed to air. Desiccated M. barkeri was more resistant to higher temperatures, and although resistance to oxidative conditions such as ozone and ionizing radiation was not as robust as in other desiccation-resistant microorganisms, the protection mechanisms are likely adequate to maintain cell viability during periodic exposure events. The results of this study demonstrate that after desiccation M. barkeri has the innate capability to survive extended periods of exposure to air and lethal temperatures. PMID:22194299

  2. ProP is required for the survival of desiccated Salmonella enterica serovar typhimurium cells on a stainless steel surface.

    PubMed

    Finn, Sarah; Händler, Kristian; Condell, Orla; Colgan, Aoife; Cooney, Shane; McClure, Peter; Amézquita, Aléjandro; Hinton, Jay C D; Fanning, Séamus

    2013-07-01

    Consumers trust commercial food production to be safe, and it is important to strive to improve food safety at every level. Several outbreaks of food-borne disease have been caused by Salmonella strains associated with dried food. Currently we do not know the mechanisms used by Salmonella enterica serovar Typhimurium to survive in desiccated environments. The aim of this study was to discover the responses of S. Typhimurium ST4/74 at the transcriptional level to desiccation on a stainless steel surface and to subsequent rehydration. Bacterial cells were dried onto the same steel surfaces used during the production of dry foods, and RNA was recovered for transcriptomic analysis. Subsequently, dried cells were rehydrated and were again used for transcriptomic analysis. A total of 266 genes were differentially expressed under desiccation stress compared with a static broth culture. The osmoprotectant transporters proP, proU, and osmU (STM1491 to STM1494) were highly upregulated by drying. Deletion of any one of these transport systems resulted in a reduction in the long-term viability of S. Typhimurium on a stainless steel food contact surface. The proP gene was critical for survival; proP deletion mutants could not survive desiccation for long periods and were undetectable after 4 weeks. Following rehydration, 138 genes were differentially expressed, with upregulation observed for genes such as proP, proU, and the phosphate transport genes (pstACS). In time, this knowledge should prove valuable for understanding the underlying mechanisms involved in pathogen survival and should lead to improved methods for control to ensure the safety of intermediate- and low-moisture foods.

  3. Quantitative genetic analysis suggests causal association between cuticular hydrocarbon composition and desiccation survival in Drosophila melanogaster

    PubMed Central

    Foley, B R; Telonis-Scott, M

    2011-01-01

    Survival to low relative humidity is a complex adaptation, and many repeated instances of evolution to desiccation have been observed among Drosophila populations and species. One general mechanism for desiccation resistance is Cuticular Hydrocarbon (CHC) melting point. We performed the first Quantitative Trait Locus (QTL) map of population level genetic variation in desiccation resistance in D. melanogaster. Using a panel of Recombinant Inbred Lines (RILs) derived from a single natural population, we mapped QTL in both sexes throughout the genome. We found that in both sexes, CHCs correlated strongly with desiccation resistance. At most desiccation resistance loci there was a significant association between CHCs and desiccation resistance of the sort predicted from clinal patterns of CHC variation and biochemical properties of lipids. This association was much stronger in females than males, perhaps because of greater overall abundance of CHCs in females, or due to correlations between CHCs used for waterproofing and sexual signalling in males. CHC evolution may be a common mechanism for desiccation resistance in D. melanogaster. It will be interesting to compare patterns of CHC variation and desiccation resistance in species which adapt to desiccation, and rainforest restricted species which cannot. PMID:20389309

  4. A footprint of desiccation tolerance in the genome of Xerophyta viscosa.

    PubMed

    Costa, Maria-Cecília D; Artur, Mariana A S; Maia, Julio; Jonkheer, Eef; Derks, Martijn F L; Nijveen, Harm; Williams, Brett; Mundree, Sagadevan G; Jiménez-Gómez, José M; Hesselink, Thamara; Schijlen, Elio G W M; Ligterink, Wilco; Oliver, Melvin J; Farrant, Jill M; Hilhorst, Henk W M

    2017-03-27

    Desiccation tolerance is common in seeds and various other organisms, but only a few angiosperm species possess vegetative desiccation tolerance. These 'resurrection species' may serve as ideal models for the ultimate design of crops with enhanced drought tolerance. To understand the molecular and genetic mechanisms enabling vegetative desiccation tolerance, we produced a high-quality whole-genome sequence for the resurrection plant Xerophyta viscosa and assessed transcriptome changes during its dehydration. Data revealed induction of transcripts typically associated with desiccation tolerance in seeds and involvement of orthologues of ABI3 and ABI5, both key regulators of seed maturation. Dehydration resulted in both increased, but predominantly reduced, transcript abundance of genomic 'clusters of desiccation-associated genes' (CoDAGs), reflecting the cessation of growth that allows for the expression of desiccation tolerance. Vegetative desiccation tolerance in X. viscosa was found to be uncoupled from drought-induced senescence. We provide strong support for the hypothesis that vegetative desiccation tolerance arose by redirection of genetic information from desiccation-tolerant seeds.

  5. Trehalose transporter from African chironomid larvae improves desiccation tolerance of Chinese hamster ovary cells.

    PubMed

    Chakraborty, Nilay; Menze, Michael A; Elmoazzen, Heidi; Vu, Halong; Yarmush, Martin L; Hand, Steven C; Toner, Mehmet

    2012-04-01

    Dry preservation has been explored as an energy-efficient alternative to cryopreservation, but the high sensitivity of mammalian cells to desiccation stress has been one of the major hurdles in storing cells in the desiccated state. An important strategy to reduce desiccation sensitivity involves use of the disaccharide trehalose. Trehalose is known to improve desiccation tolerance in mammalian cells when present on both sides of the cell membrane. Because trehalose is membrane impermeant the development of desiccation strategies involving this promising sugar is hindered. We explored the potential of using a high-capacity trehalose transporter (TRET1) from the African chironomid Polypedilum vanderplanki[21] to introduce trehalose into the cytoplasm of mammalian cells and thereby increase desiccation tolerance. When Chinese hamster ovary cells (CHO) were stably transfected with TRET1 (CHO-TRET1 cells) and incubated with 0.4M trehalose for 4h at 37°C, a sevenfold increase in trehalose uptake was observed compared to the wild-type CHO cells. Following trehalose loading, desiccation tolerance was investigated by evaporative drying of cells at 14% relative humidity. After desiccation to 2.60g of water per gram dry weight, a 170% increase in viability and a 400% increase in growth (after 7days) was observed for CHO-TRET1 relative to control CHO cells. Our results demonstrate the beneficial effect of intracellular trehalose for imparting tolerance to partial desiccation. Copyright © 2011 Elsevier Inc. All rights reserved.

  6. Effect of nitrogen starvation on desiccation tolerance of Arctic Microcoleus strains (cyanobacteria).

    PubMed

    Tashyreva, Daria; Elster, Josef

    2015-01-01

    Although desiccation tolerance of Microcoleus species is a well-known phenomenon, there is very little information about their limits of desiccation tolerance in terms of cellular water content, the survival rate of their cells, and the environmental factors inducing their resistance to drying. We have discovered that three Microcoleus strains, isolated from terrestrial habitats of the High Arctic, survived extensive dehydration (to 0.23 g water g(-1) dry mass), but did not tolerate complete desiccation (to 0.03 g water g(-1) dry mass) regardless of pre-desiccation treatments. However, these treatments were critical for the survival of incomplete desiccation: cultures grown under optimal conditions failed to survive even incomplete desiccation; a low temperature enabled only 0-15% of cells to survive, while 39.8-65.9% of cells remained alive and intact after nitrogen starvation. Unlike Nostoc, which co-exists with Microcoleus in Arctic terrestrial habitats, Microcoleus strains are not truly anhydrobiotic and do not possess constitutive desiccation tolerance. Instead, it seems that the survival strategy of Microcoleus in periodically dry habitats involves avoidance of complete desiccation, but tolerance to milder desiccation stress, which is induced by suboptimal conditions (e.g., nitrogen starvation).

  7. Effect of nitrogen starvation on desiccation tolerance of Arctic Microcoleus strains (cyanobacteria)

    PubMed Central

    Tashyreva, Daria; Elster, Josef

    2015-01-01

    Although desiccation tolerance of Microcoleus species is a well-known phenomenon, there is very little information about their limits of desiccation tolerance in terms of cellular water content, the survival rate of their cells, and the environmental factors inducing their resistance to drying. We have discovered that three Microcoleus strains, isolated from terrestrial habitats of the High Arctic, survived extensive dehydration (to 0.23 g water g-1 dry mass), but did not tolerate complete desiccation (to 0.03 g water g-1 dry mass) regardless of pre-desiccation treatments. However, these treatments were critical for the survival of incomplete desiccation: cultures grown under optimal conditions failed to survive even incomplete desiccation; a low temperature enabled only 0–15% of cells to survive, while 39.8–65.9% of cells remained alive and intact after nitrogen starvation. Unlike Nostoc, which co-exists with Microcoleus in Arctic terrestrial habitats, Microcoleus strains are not truly anhydrobiotic and do not possess constitutive desiccation tolerance. Instead, it seems that the survival strategy of Microcoleus in periodically dry habitats involves avoidance of complete desiccation, but tolerance to milder desiccation stress, which is induced by suboptimal conditions (e.g., nitrogen starvation). PMID:25904909

  8. Desiccation-induced physiological and biochemical changes in resurrection plant, Selaginella bryopteris.

    PubMed

    Pandey, Vivek; Ranjan, Sanjay; Deeba, Farah; Pandey, Ashutosh K; Singh, Ruchi; Shirke, Pramod A; Pathre, Uday V

    2010-11-01

    Selaginella bryopteris is a lycophyte resurrection plant, which incurves during desiccation and recovers on availability of moisture. The aim of the study was to test and understand the various physiological and biochemical changes the fronds undergo during desiccation and rehydration, to get an insight as to how this plant adapts and survives through the dry phase. Upon desiccation, S. bryopteris fronds showed drastic inhibition in net photosynthesis (A) and maximal photochemical efficiency of PSII (F(v)/F(m)) however, chlorophyll content did not show much variation. Dark respiration (R(d)) continued even at 10% relative water content (RWC), and showed a burst after rehydration, which is proposed to be crucial to establish protection mechanisms. Desiccation caused an enhanced production of reactive oxygen species (ROS) and increased lipid peroxidation. Proline accumulation increased substantially by 11-fold. Sucrose and starch contents decreased upon desiccation as compared to control. The antioxidative enzymes viz. superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) along with soluble acid invertase increased during desiccation. S. bryopteris shows mechanical as well as physiological mechanisms for tolerance to extreme levels of desiccation stress. The rapid and almost complete recovery of F(v)/F(m) after rehydration clearly indicates the absence of marked photoinhibitory or thermal injury to PSII during desiccation. This along with the homoiochlorophyllous characteristics enables S. bryopteris to recover its A. The antioxidant metabolism further plays an important role in the desiccation tolerance of S. bryopteris.

  9. The physiological links of the increased photosystem II activity in moderately desiccated Porphyra haitanensis (Bangiales, Rhodophyta) to the cyclic electron flow during desiccation and re-hydration.

    PubMed

    Gao, Shan; Niu, Jianfeng; Chen, Weizhou; Wang, Guangce; Xie, Xiujun; Pan, Guanghua; Gu, Wenhui; Zhu, Daling

    2013-09-01

    Photosynthetic electron flow changed considerably during desiccation and re-hydration of the intertidal macroalgae Porphyra haitanensis. Activities of both photosystem (PSI) and photosystem (PSII) increased significantly at moderate desiccation levels. Whereas PSII activity was abolished at an absolute water content (AWC) <24 %, PSI remained active with progressive decreases in AWC to values as low as 16 %. This result suggested that cyclic electron flow around PSI was still active after inactivation of linear electron flow following severe desiccation. Moreover, the PSI activity was restored more rapidly than that of PSII upon re-hydration. Pretreatment of the blades with 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU) suppressed PSII activity following desiccation to an AWC of ~16 % AWC. Cyclic electron flow around PSI decreased markedly in blades pretreated with DCMU than in blades without pretreatment of DCMU during re-hydration in seawater containing DCMU. All results suggested that the activity of PSII under desiccation conditions plays an important role in the operation of cyclic electron flow during desiccation and its recovery during re-hydration. Therefore, we proposed the PSII activity during desiccation could eventually lead to the accumulation of NADPH, which could serve as electron donor for P700(+) and promote its recovery during re-hydration, thereby favoring the operation of cyclic electron flow.

  10. Effect of supply/regeneration section area ratio on the performance of desiccant wheels in hot and humid climates: an experimental investigation

    NASA Astrophysics Data System (ADS)

    Zendehboudi, Alireza; Esmaeili, Hossein

    2016-06-01

    Desiccant cooling system is a suitable alternative option for conventional cooling system in humid climates. It is an environmental protection technique for cooling buildings. This study has investigated the effect of supply/regeneration section area ratio on the performance of desiccant wheels in hot and humid climates, using Silica Gel (WSG) and Molecular Sieve (LT3) desiccants. To this end, some parameters such as outlet air humidity ratio, process removed moisture, process outlet temperature, reactivation outlet temperature and reactivation outlet moisture have been examined as a function of rotational speed and inlet air humidity ratio in 1:3, 1:2 and 1:1 split. In this study, desiccant materials are regenerated using a constant regeneration temperature of 80 °C, wheel rotation speed range of 4-12 RPH (revolutions per hour) and variable humidity. The results show that a rise in area ratio causes an increase in process removed moisture, process outlet temperature, reactivation outlet temperature and a drop in reactivation outlet moisture and outlet humidity ratio of process air.

  11. Dehydration-mediated activation of the xanthophyll cycle in darkness: is it related to desiccation tolerance?

    PubMed

    Fernández-Marín, B; Míguez, F; Becerril, J M; García-Plazaola, J I

    2011-09-01

    The development of desiccation tolerance by vegetative tissues was an important step in the plants' conquest of land. To counteract the oxidative stress generated under these conditions the xanthophyll cycle plays a key role. Recent reports have shown that desiccation itself induces de-epoxidation of xanthophyll cycle pigments, even in darkness. The aim of the present work was to study whether this trait is a common response of all desiccation-tolerant plants. The xanthophyll cycle activity and the maximal photochemical efficiency of PS II (F(v)/F(m)) as well as β-carotene and α-tocopherol contents were compared during slow and rapid desiccation and subsequent rehydration in six species pairs (with one desiccation-sensitive and one desiccation-tolerant species each) belonging to different taxa. Xanthophyll cycle pigments were de-epoxidised in darkness concomitantly with a decrease in F(v)/F(m) during slow dehydration in all the desiccation-tolerant species and in most of the desiccation-sensitive ones. De-epoxidation was reverted in darkness by re-watering in parallel with the recovery of the initial F(v)/F(m). The stability of the β-carotene pool confirmed that its hydroxylation did not contribute to zeaxanthin formation. The α-tocopherol content of most of the species did not change during dehydration. Because it is a common mechanism present in all the desiccation-tolerant taxa and in some desiccation-sensitive species, and considering its role in antioxidant processes and in excess energy dissipation, the induction of the de-epoxidation of xanthophyll cycle pigments upon dehydration in the dark could be understood as a desiccation tolerance-related response maintained from the ancestral clades in the initial steps of land occupation by plants.

  12. Desiccation tolerance of iron bacteria biofilms on Mars regolith simulants

    NASA Astrophysics Data System (ADS)

    Feyh, Nina; Szewzyk, Ulrich

    2010-05-01

    Iron oxidizing bacteria play an important role in the geological redox cycling of iron on earth. The redox change between Fe(II) and Fe(III) can be used for biological energy production [1]. Therefore iron oxidation in the iron rich martian soils may be or may have been microbially mediated. The microbial conversion of iron is considered to be an ancient form of metabolism [2], so it might have evolved on Mars as well. However, to exist in recent martian soils, bacteria must be able to endure dry and cold conditions. Neutrophilic iron oxidizers can be found in various iron rich aquatic environments, where they lead to the precipitation of insoluble ferric hydroxides. Some of these environments fall temporarily dry, what could have led to an adaptation to desiccation by bacteria, existing there. One strategy of iron bacteria to endure drought stress might be the formation of biofilms by excreting Extracellular Polymeric Substances (EPS). The deposition of iron hydroxides could enable them to endure dry conditions as well. For our experiments, neutrophilic iron oxidizing bacteria have been isolated from a creek in Bad Salzhausen/Hesse and temporarily drying out pools in Tierra del Fuego. Strains from aquatic environments in the national park "Unteres Odertal" and from water wells in Berlin/Brandenburg are included in the tests as well. In desiccation experiments, the capability of iron bacteria to tolerate dry conditions are investigated. The aim of our first experiment is the adaptation to dry conditions. Biofilms of 15 strains are grown on ceramic beads in liquid medium containing complexed Fe(II), established biofilms contain Fe(III) precipitates. The cultures are desiccated in a sterile airflow until the weight of the cultures remained constant. After a desiccation period of 9 h up to 7 d, the beads are transferred to fresh liquid medium. Adapted strains are used in further desiccation experiments, where biofilms are grown on two martian regolith simulants. These

  13. Salinity Effects on Cracking Morphology and Dynamics in Desiccating Clays

    NASA Astrophysics Data System (ADS)

    DeCarlo, K.; Shokri, N.

    2013-12-01

    Saline conditions induce not only chemical but physical changes in swelling clays, and have a significant influence on the crack dynamics in desiccating clays. In this study, we used X-ray computerized tomography (CT) to experimentally investigate the effects of sodium chloride on the morphology and dynamics of desiccation cracks in three-dimensional mixtures of sand-bentonite slurry under varying rheological conditions. Rectangular glass containers (40.5x40.5x56 mm^3) were packed with sand-bentonite slurries of different salt concentrations, with the top boundary exposed to air for evaporation. The growth and propagation of the cracking network that subsequently formed was visualized in 3D at multiple intervals. 3D characterization of cracking dynamics shows a high extent of localized superficial crack networks at low salinity, with a transition to less extensive but deeper, more centralized crack networks with increased salinity. The observed behavior was described in the context of rheological and colloidal properties of the clay, which suggest the transition from a voluminous and poorly-sorted stacked clay structure to a more compact and highly cohesive entangled clay structure as salt concentration increases in the evaporating samples. This is further corroborated by vertical profiles of sample water distribution, which shows localized uniform drying at the higher salt concentrations. Our results provide new insights regarding the formation, patterns, dynamics and characteristics of desiccation cracks formed during evaporation from 3D saline clay structures, which will be useful in various hydrological applications including water management, land surface evaporation, and subsurface contaminant transport.

  14. The respiratory pattern in Drosophila melanogaster selected for desiccation resistance is not associated with the observed evolution of decreased locomotory activity.

    PubMed

    Williams, Adrienne E; Rose, Michael R; Bradley, Timothy J

    2004-01-01

    We examined spontaneous locomotory behavior and respiratory pattern in replicate outbred populations of Drosophila melanogaster selected for desiccation resistance or starvation resistance, as well as their control and ancestral populations. Use of these populations allows us to compare evolved behavioral changes in response to different stress selections. We also reasoned that previously observed changes in respiratory patterns following selection for increased desiccation resistance might be associated with or even caused by changes in locomotory behavior. We measured spontaneous locomotory behavior using video recordings and a computer-based tracking system while simultaneously measuring patterns of CO(2) release from single fruit flies. Statistically significant differences in behavior were observed to be correlated with selection regime. Reduced levels of spontaneous locomotory activity were observed in moist air in both desiccation- and starvation-selected populations compared with their controls. Interestingly, in dry air, only the desiccation-selected flies continue to show reduced spontaneous locomotory activity. No correlation was found between the level of locomotory activity of individual flies and the respiratory patterns of those flies, indicating that the reduced activity levels that have evolved in these flies did not directly cause the documented changes in their respiratory pattern.

  15. [The effect of gamma-radiation and desiccation on the viability of the soil bacteria isolated from the alienated zone around the Chernobyl Nuclear Power Plant].

    PubMed

    Romanovskaia, V A; Rokitko, P V; Mikheev, A N; Gushcha, N I; Malashenko, Iu R; Chernaia, N A

    2002-01-01

    Methylobacterium extorquens, M. mesophilicum, and Bacillus subtilis strains were found to be resistant to gamma-radiation, irrespective of whether they were isolated from the alienated zone around the Chernobyl Nuclear Power Plant or outside this zone. The LD90 of Methylobacterium and B. subtilis strains with respect to gamma-radiation was 2.0-3.4 and 3.7-4.4 kGy, respectively, whereas their LD99.99 values were 4.5-6.9 and more than 10 kGy, respectively. The high threshold levels of gamma-radiation for Methylobacterium and B. subtilis imply the efficient functioning of DNA repair systems in these bacteria. Unlike Bacillus polymyxa cells, the cells of M. extorquens, M. mesophilicum, and B. subtilis were also resistant to desiccation. Pseudomonas sp., Nocardia sp., and nocardioform actinomycetes were sensitive to both gamma-radiation and desiccation. Similar results were obtained when the bacteria studied were exposed to hydrogen peroxide and ultraviolet radiation. The results obtained indicate that the bacteria that are resistant to gamma-radiation are also resistant to desiccation, UV radiation, and hydrogen peroxide. The possibility of using simple laboratory tests (such as the determination of bacterial resistance to UV light and desiccation) for the evaluation of bacterial resistance to gamma-radiation is discussed.

  16. Enzymes and Metabolites in Carbohydrate Metabolism of Desiccation Tolerant Plants.

    PubMed

    Zhang, Qingwei; Song, Xiaomin; Bartels, Dorothea

    2016-12-15

    Resurrection plants can tolerate extreme water loss. Substantial sugar accumulation is a phenomenon in resurrection plants during dehydration. Sugars have been identified as one important factor contributing to desiccation tolerance. Phylogenetic diversity of resurrection plants reflects the diversity of sugar metabolism in response to dehydration. Sugars, which accumulate during dehydration, have been shown to protect macromolecules and membranes and to scavenge reactive oxygen species. This review focuses on the performance of enzymes participating in sugar metabolism during dehydration stress. The relation between sugar metabolism and other biochemical activities is discussed and open questions as well as potential experimental approaches are proposed.

  17. Enzymes and Metabolites in Carbohydrate Metabolism of Desiccation Tolerant Plants

    PubMed Central

    Zhang, Qingwei; Song, Xiaomin; Bartels, Dorothea

    2016-01-01

    Resurrection plants can tolerate extreme water loss. Substantial sugar accumulation is a phenomenon in resurrection plants during dehydration. Sugars have been identified as one important factor contributing to desiccation tolerance. Phylogenetic diversity of resurrection plants reflects the diversity of sugar metabolism in response to dehydration. Sugars, which accumulate during dehydration, have been shown to protect macromolecules and membranes and to scavenge reactive oxygen species. This review focuses on the performance of enzymes participating in sugar metabolism during dehydration stress. The relation between sugar metabolism and other biochemical activities is discussed and open questions as well as potential experimental approaches are proposed. PMID:28248249

  18. Trehalose expression confers desiccation tolerance on human cells.

    PubMed

    Guo, N; Puhlev, I; Brown, D R; Mansbridge, J; Levine, F

    2000-02-01

    Many organisms that withstand desiccation express the disaccharide trehalose. We have now expressed the otsA and otsB genes of Escherichia coli, which encode trehalose biosynthetic enzymes, in human primary fibroblasts using a recombinant adenovirus vector. Infected cells produced increased amounts of trehalose with increasing multiplicity of infection (MOI). Human primary fibroblasts expressing trehalose could be maintained in the dry state for up to five days. Fourier transform infrared spectroscopy indicated that dry, but viable, human cells contained no detectable water. This study shows that mammalian cells can be engineered to retain viability in the absence of water.

  19. Key genes involved in desiccation tolerance and dormancy across life forms

    USDA-ARS?s Scientific Manuscript database

    The ability to survive desiccation is widespread in seeds, whereas it is rare in vegetative tissues of adult flowering plants. Some genetic traits conserved among desiccation-tolerant seeds and resurrection plants have been detected but more molecular aspects need to be revealed to formulate hypothe...

  20. Rapid desiccation hardening changes the cuticular hydrocarbon profile of Drosophila melanogaster.

    PubMed

    Stinziano, Joseph R; Sové, Richard J; Rundle, Howard D; Sinclair, Brent J

    2015-02-01

    The success of insects in terrestrial environments is due in large part to their ability to resist desiccation stress. Since the majority of water is lost across the cuticle, a relatively water-impermeable cuticle is a major component of insect desiccation resistance. Cuticular permeability is affected by the properties and mixing effects of component hydrocarbons, and changes in cuticular hydrocarbons can affect desiccation tolerance. A pre-exposure to a mild desiccation stress increases duration of desiccation survival in adult female Drosophila melanogaster, via a decrease in cuticular permeability. To test whether this acute response to desiccation stress is due to a change in cuticular hydrocarbons, we treated male and female D. melanogaster to a rapid desiccation hardening (RDH) treatment and used gas chromatography to examine the effects on cuticular hydrocarbon composition. RDH led to reduced proportions of unsaturated and methylated hydrocarbons compared to controls in females, but although RDH modified the cuticular hydrocarbon profile in males, there was no coordinated pattern. These data suggest that the phenomenon of RDH leading to reduced cuticular water loss occurs via an acute change in cuticular hydrocarbons that enhances desiccation tolerance in female, but not male, D. melanogaster.

  1. A footprint of desiccation tolerance in the genome of Xerophyta viscosa

    USDA-ARS?s Scientific Manuscript database

    To better understand the genetic mechanisms enabling vegetative desiccation tolerance (DT) we produced a high-quality whole-genome sequence for the resurrection plant Xerophyta viscosa and assessed transcriptome changes in response to desiccation and ABA. Phylogenetically close to cereals, it serves...

  2. The competence to acquire cellular desiccation tolerance is independent of seed morphological development.

    PubMed

    Golovina, E A; Hoekstra, F A; Van Aelst, A C

    2001-05-01

    Acquisition of desiccation tolerance and the related changes at the cellular level in wheat (Triticum aestivum cv. Priokskaya) kernels during normal development and premature drying on the ear were studied using a spin probe technique and low temperature scanning electron microscopy. During normal development, the ability of embryos to germinate after rapid drying and rehydration was acquired after completion of morphological development, which is a few days before mass maturity. The acquisition of desiccation tolerance, as assessed by germination, was associated with an upsurge in cytoplasmic viscosity, the onset of accumulation of protein and oil bodies, and the retention of membrane integrity upon dehydration/rehydration. These features were also used to assess cellular desiccation tolerance in the cases when germination could not occur. Slow premature drying was used to decouple the acquisition of cellular desiccation tolerance from morphogenesis. Upon premature drying of kernels on the ears of plants cut at 5 d after anthesis, desiccation-tolerant dwarf embryos were formed that were able to germinate. When plants were cut at earlier stages poorly developed embryos were formed that were unable to germinate, but cellular desiccation tolerance was nevertheless acquired. In such prematurely dried kernels, peripheral meristematic endosperm cells had already passed through similar physiological and ultrastructural changes associated with the acquisition of cellular desiccation tolerance. It is concluded that despite the apparent strong integration in seed development, desiccation tolerance can be acquired by the meristematic cells in the developing embryo and cambial layer of endosperm, independently of morphological development.

  3. Freezing and Desiccation Tolerance in Entomopathogenic Nematodes: Diversity and Correlation of Traits

    USDA-ARS?s Scientific Manuscript database

    The ability of entomopathogenic nematodes to tolerate environmental stress such as desiccating or freezing conditions, can contribute significantly to biocontrol efficacy. Our objective was to compare inter and intraspecific variation in freeze and desiccation tolerance among a broad array of entom...

  4. A sister group metabolomic contrast delineates the biochemical regulation underlying desiccation tolerance in Sporobolus stapfianus

    USDA-ARS?s Scientific Manuscript database

    Understanding how plant cells tolerate dehydration is a vital prerequisite for developing strategies for improving drought tolerance. The desiccation tolerant grass Sporobolus stapfianus and the desiccation sensitive S. pyramidalis were used to form a sister-group contrast to reveal adaptive metabo...

  5. Proteomic profiling and redox status alteration of recalcitrant tea (Camellia sinensis) seed in response to desiccation.

    PubMed

    Chen, Qi; Yang, Liming; Ahmad, Parvaiz; Wan, Xiaochun; Hu, Xiangyang

    2011-03-01

    Tea seed is believed to be recalcitrant based on its sensitivity to chilling or drying stress. Reactive oxygen species (ROS) and alterations in cytosolic redox status have been implicated in intolerance to desiccation by recalcitrant seed, but there is little information available regarding how ROS are regulated in seeds susceptible to drying stress. We investigated changes in protein expression and activity in tea embryo in response to desiccation using physiological and proteomic methods. Results showed that desiccation treatment dramatically induced the accumulation of H(2)O(2) in tea embryos, accompanied by increased activities of antioxidant enzymes like ascorbate peroxidase (APX) and superoxide dismutase (SOD). Proteomic analyses also demonstrated that 23 proteins associated with defense response, metabolism and redox status were up-regulated following desiccation. Increase in antioxidants, ascorbic acid (AsA) and catalase (CAT) (H(2)O(2) scavengers) partially assuaged desiccation damage to tea seed, resulting in improved germination rates. Higher accumulation of H(2)O(2) aggravated desiccation damage to seeds leading to lower germination activity. We propose that desiccation causes an over-accumulation of ROS that are not efficiently scavenged by increased levels of antioxidant enzymes. High levels of ROS alter the redox status and are detrimental to seed viability. Reducing ROS to appropriate concentrations is an efficient way to reduce desiccation damage and improve germination rates of recalcitrant seeds.

  6. Constitutive components and induced gene expression are involved in the desiccation tolerance of Selaginella tamariscina.

    PubMed

    Liu, Mao-Sen; Chien, Ching-Te; Lin, Tsan-Piao

    2008-04-01

    Selaginella tamariscina, one of the most primitive vascular plants, can remain alive in a desiccated state and resurrect when water becomes available. To evaluate the nature of desiccation tolerance in this plant, we compared the composition of soluble sugars and saturation ratios of phospholipids (PLs) between hydrated and desiccated tissues of S. tamariscina using gas chromatography. In this study, differences in gene expression and ABA contents were also analyzed during dehydration. The results revealed that trehalose (at >130 mg g(-1) DW) was the major soluble sugar, and low saturated fatty acid content in PLs (0.31) was maintained in both hydrated and desiccated tissues. In addition, the ABA content of S. tamariscina increased 3-fold, and genes involved in ABA signaling and cellular protection were up-regulated while photosystem-related genes were down-regulated during dehydration. The biochemical and molecular findings suggest that both constitutive and inducible protective molecules contribute to desiccation tolerance of S. tamariscina.

  7. Meta-analysis of geographical clines in desiccation tolerance of Indian drosophilids.

    PubMed

    Rajpurohit, Subhash; Nedved, Oldrich; Gibbs, Allen G

    2013-02-01

    Tropical fruit flies (Drosophilidae) differ from temperate drosophilids in several ecophysiological traits, such as desiccation tolerance. Moreover, many species show significant differences in desiccation tolerance across geographical populations. Fruit flies from the tropical and subtropical Indian subcontinent show a clinal pattern for desiccation tolerance which is similar for more than a dozen species studied so far, suggesting adaptation to climatic differences. We performed a meta-analysis to investigate which particular climatic patterns modulate desiccation tolerance in natural populations of drosophilids. Latitude of the sampling site explained most of the variability. Seasonal thermal amplitude (fluctuations in temperature expressed as coefficient of variation) was the strongest climatic factor shaping desiccation tolerance of flies, while factors measuring humidity directly were not important. Implications for survival of flies after future climate change are suggested. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. Extracellular superoxide production associated with secondary root growth following desiccation of Pisum sativum seedlings.

    PubMed

    Roach, Thomas; Kranner, Ilse

    2011-10-15

    The seedling stage is arguably the most vulnerable phase in the plant life cycle, where the young establishing plant is extremely sensitive to environmental stresses such as drought. Here, the production of superoxide (O(2)(-)), a molecule involved in stress signaling, was measured in response to desiccation of Pisum sativum L. seedlings. Following desiccation that was sufficient to kill the radicle meristem, viability could be retained by seedlings that grew secondary roots. Upon rehydration, secondary roots formed in a region that had displayed intense extracellular O(2)(-)production on desiccation. Treating partially desiccated seedlings with hydrogen peroxide (H(2)O(2)) prevented viability loss. In summary, reactive oxygen species (ROS) appear to participate in the signaling required for secondary root formation following desiccation stress of P. sativum seedlings.

  9. Extended periods of hydration do not elicit dehardening to desiccation tolerance in regeneration trials of the moss Syntrichia caninervis

    USDA-ARS?s Scientific Manuscript database

    Dehardening (deacclimation) to water stress is seldom studied in plants, and yet is an integral phase of desiccation tolerance. Most bryophytes are desiccation tolerant (DT), and yet even fully DT species lose a significant portion of their ability to withstand desiccation if dehardened. Shoots of t...

  10. Variation of desiccation tolerance and longevity in fern spores.

    PubMed

    Ballesteros, Daniel; Hill, Lisa M; Walters, Christina

    2017-04-01

    This work contributes to the understanding of plant cell responses to extreme water stress when it is applied at different intensity and duration. Fern spores are used to explore survival at relative humidity (RH)<85% because their unicellular nature eliminates complexities that may arise in multicellular organisms from slower drying and variable responses of different cell types. Fern spore cytoplasm solidifies between 30 and 60% RH and spores survive this transition, but subsequently lose viability. We characterized the kinetics of viability loss in terms of the fluid to solid transition using concepts of water activity (i.e., sorption) and glass transition (Tg), two concepts that dominate studies of food and pharmaceutical stability. For all fern species studied, longest survival times were observed in spores placed at about 10-25% RH and mortality rates increased sharply above and below this moisture level. A RH of 10-25% corresponds well to sorption behavior parameters and is below the glass transition, measured using differential scanning calorimetry. Though response to RH was similar among species, the kinetics of deterioration varied considerably among species and this implies differences in the structure or mobility of molecules within the solidified cytoplasm. Our work suggests that desiccation damage occurs in desiccation tolerant cells, and that it is expressed as a time-dependent response, otherwise known as aging. Copyright © 2017 Elsevier GmbH. All rights reserved.

  11. Halophilic Archaea: Life with Desiccation, Radiation and Oligotrophy over Geological Times.

    PubMed

    Stan-Lotter, Helga; Fendrihan, Sergiu

    2015-07-28

    Halophilic archaebacteria (Haloarchaea) can survive extreme desiccation, starvation and radiation, sometimes apparently for millions of years. Several of the strategies that are involved appear specific for Haloarchaea (for example, the formation of halomucin, survival in fluid inclusions of halite), and some are known from other prokaryotes (dwarfing of cells, reduction of ATP). Several newly-discovered haloarchaeal strategies that were inferred to possibly promote long-term survival-halomucin, polyploidy, usage of DNA as a phosphate storage polymer, production of spherical dormant stages-remain to be characterized in detail. More information on potential strategies is desirable, since evidence for the presence of halite on Mars and on several moons in the solar system increased interest in halophiles with respect to the search for extraterrestrial life. This review deals in particular with novel findings and hypotheses on haloarchaeal long-term survival.

  12. Halophilic Archaea: Life with Desiccation, Radiation and Oligotrophy over Geological Times

    PubMed Central

    Stan-Lotter, Helga; Fendrihan, Sergiu

    2015-01-01

    Halophilic archaebacteria (Haloarchaea) can survive extreme desiccation, starvation and radiation, sometimes apparently for millions of years. Several of the strategies that are involved appear specific for Haloarchaea (for example, the formation of halomucin, survival in fluid inclusions of halite), and some are known from other prokaryotes (dwarfing of cells, reduction of ATP). Several newly-discovered haloarchaeal strategies that were inferred to possibly promote long-term survival—halomucin, polyploidy, usage of DNA as a phosphate storage polymer, production of spherical dormant stages—remain to be characterized in detail. More information on potential strategies is desirable, since evidence for the presence of halite on Mars and on several moons in the solar system increased interest in halophiles with respect to the search for extraterrestrial life. This review deals in particular with novel findings and hypotheses on haloarchaeal long-term survival. PMID:26226005

  13. Listeria monocytogenes ability to survive desiccation: Influence of serotype, origin, virulence, and genotype.

    PubMed

    Zoz, Fiona; Grandvalet, Cosette; Lang, Emilie; Iaconelli, Cyril; Gervais, Patrick; Firmesse, Olivier; Guyot, Stéphane; Beney, Laurent

    2017-02-21

    Listeria monocytogenes, a bacterium that is responsible for listeriosis, is a very diverse species. Desiccation resistance has been rarely studied in L. monocytogenes, although it is a stress that is largely encountered by this microorganism in food-processing environments and that could be managed to prevent its presence. The objective of this study was to evaluate the resistance of 30 L. monocytogenes strains to moderate desiccation (75% relative humidity) and evaluate the correlation of such resistance with the strains' virulence, serotype and genotype. The results showed a great heterogeneity of strains regarding their ability to survive (loss of cultivability between 0.4 and 2.0 log). Strains were classified into three groups according to desiccation resistance (sensitive, intermediate, or resistant), and the strain repartition was analyzed relative to serotype, virulence level and environmental origin of the strains. No correlation was found between isolate origin and desiccation resistance. All serotype 1/2b strains were classified into the group of resistant strains. Virulent and hypovirulent strains were distributed among the three groups of desiccation resistance. Finally, a genomic comparison was performed based on 31 genes that were previously identified as being involved in desiccation resistance. The presence of those genes was localized among the genomes of some strains and compared regarding strain-resistance levels. High nucleotide conservation was identified between resistant and desiccation-sensitive strains. In conclusion, the findings regarding the strains of serotype 1/2b indicate potential serotype-specific resistance to desiccation, and thus, to relative humidity fluctuations potentially encountered in food-related environments. The genomic comparison of 31 genes associated to desiccation tolerance did not reveal differences among four strains which have different level of resistance to desiccation.

  14. Rapid changes in desiccation resistance in Drosophila melanogaster are facilitated by changes in cuticular permeability.

    PubMed

    Bazinet, Aimee L; Marshall, Katie E; MacMillan, Heath A; Williams, Caroline M; Sinclair, Brent J

    2010-12-01

    Insects can improve their desiccation resistance by one or more of (1) increasing their water content; (2) decreasing water loss rate; or (3) increasing the amount of water able to be lost before death. Female Drosophila melanogaster have previously been reported to increase their resistance to desiccation after a desiccation pre-treatment and recovery, but the mechanism of this increased desiccation resistance has not been explored. We show that female, but not male adult D. melanogaster increased their resistance to desiccation after 1h of recovery from a 3 to 4.5h pre-treatment that depletes them of 10% of their water content. The pre-treatment did not result in an increase in water content after recovery, and there is a slight increase in water content at death in pre-treated females (but no change in males), suggesting that the amount of water loss tolerated is not improved. Metabolic rate, measured on individual flies with flow-through respirometry, did not change with pre-treatment. However, a desiccation pre-treatment did result in a reduction in water loss rate, and further investigation indicated that a change in cuticular water loss rate accounted for this decrease. Thus, the observed increase in desiccation resistance appears to be based on a change in cuticular permeability. However, physiological changes in response to the desiccation pre-treatment were similar in male and female, which therefore does not account for the difference in rapid desiccation hardening between the sexes. We speculate that sex differences in fuel use during desiccation may account for the discrepancy.

  15. Desiccation tolerance in Anopheles coluzzii: the effects of spiracle size and cuticular hydrocarbons.

    PubMed

    Arcaz, Arthur C; Huestis, Diana L; Dao, Adama; Yaro, Alpha S; Diallo, Moussa; Andersen, John; Blomquist, Gary J; Lehmann, Tovi

    2016-06-01

    The African malaria mosquitoes Anopheles gambiae and Anopheles coluzzii range over forests and arid areas, where they withstand dry spells and months-long dry seasons, suggesting variation in their desiccation tolerance. We subjected a laboratory colony (G3) and wild Sahelian mosquitoes during the rainy and dry seasons to desiccation assays. The thoracic spiracles and amount and composition of cuticular hydrocarbons (CHCs) of individual mosquitoes were measured to determine the effects of these traits on desiccation tolerance. The relative humidity of the assay, body water available, rate of water loss and water content at death accounted for 88% of the variation in desiccation tolerance. Spiracle size did not affect the rate of water loss or desiccation tolerance of the colony mosquitoes, as was the case for the total CHCs. However, six CHCs accounted for 71% of the variation in desiccation tolerance and three accounted for 72% of the variation in the rate of water loss. Wild A. coluzzii exhibited elevated desiccation tolerance during the dry season. During that time, relative thorax and spiracle sizes were smaller than during the rainy season. A smaller spiracle size appeared to increase A. coluzzii's desiccation tolerance, but was not statistically significant. Seasonal changes in CHC composition were detected in Sahelian A. coluzzii Stepwise regression models suggested the effect of particular CHCs on desiccation tolerance. In conclusion, the combination of particular CHCs along with the total amount of CHCs is a primary mechanism conferring desiccation tolerance in A. coluzzii, while variation in spiracle size might be a secondary mechanism. © 2016. Published by The Company of Biologists Ltd.

  16. Correlation of Intracellular Trehalose Concentration with Desiccation Resistance of Soil Escherichia coli Populations

    PubMed Central

    Zhang, Qian

    2012-01-01

    Naturalized soil Escherichia coli populations need to resist common soil desiccation stress in order to inhabit soil environments. In this study, four representative soil E. coli strains and one lab strain, MG1655, were tested for desiccation resistance via die-off experiments in sterile quartz sand under a potassium acetate-induced desiccation condition. The desiccation stress caused significantly lower die-off rates of the four soil strains (0.17 to 0.40 day−1) than that of MG1655 (0.85 day−1). Cellular responses, including extracellular polymeric substance (EPS) production, exogenous glycine betaine (GB) uptake, and intracellular compatible organic solute synthesis, were quantified and compared under the desiccation and hydrated control conditions. GB uptake appeared not to be a specific desiccation response, while EPS production showed considerable variability among the E. coli strains. All E. coli strains produced more intracellular trehalose, proline, and glutamine under the desiccation condition than the hydrated control, and only the trehalose concentration exhibited a significant correlation with the desiccation-contributed die-off coefficients (Spearman's ρ = −1.0; P = 0.02). De novo trehalose synthesis was further determined for 15 E. coli strains from both soil and nonsoil sources to determine its prevalence as a specific desiccation response. Most E. coli strains (14/15) synthesized significantly more trehalose under the desiccation condition, and the soil E. coli strains produced more trehalose (106.5 ± 44.9 μmol/mg of protein [mean ± standard deviation]) than the nonsoil reference strains (32.5 ± 10.5 μmol/mg of protein). PMID:22885754

  17. Desiccation tolerance in Anopheles coluzzii: the effects of spiracle size and cuticular hydrocarbons

    PubMed Central

    Arcaz, Arthur C.; Huestis, Diana L.; Dao, Adama; Yaro, Alpha S.; Diallo, Moussa; Andersen, John; Blomquist, Gary J.; Lehmann, Tovi

    2016-01-01

    ABSTRACT The African malaria mosquitoes Anopheles gambiae and Anopheles coluzzii range over forests and arid areas, where they withstand dry spells and months-long dry seasons, suggesting variation in their desiccation tolerance. We subjected a laboratory colony (G3) and wild Sahelian mosquitoes during the rainy and dry seasons to desiccation assays. The thoracic spiracles and amount and composition of cuticular hydrocarbons (CHCs) of individual mosquitoes were measured to determine the effects of these traits on desiccation tolerance. The relative humidity of the assay, body water available, rate of water loss and water content at death accounted for 88% of the variation in desiccation tolerance. Spiracle size did not affect the rate of water loss or desiccation tolerance of the colony mosquitoes, as was the case for the total CHCs. However, six CHCs accounted for 71% of the variation in desiccation tolerance and three accounted for 72% of the variation in the rate of water loss. Wild A. coluzzii exhibited elevated desiccation tolerance during the dry season. During that time, relative thorax and spiracle sizes were smaller than during the rainy season. A smaller spiracle size appeared to increase A. coluzzii's desiccation tolerance, but was not statistically significant. Seasonal changes in CHC composition were detected in Sahelian A. coluzzii. Stepwise regression models suggested the effect of particular CHCs on desiccation tolerance. In conclusion, the combination of particular CHCs along with the total amount of CHCs is a primary mechanism conferring desiccation tolerance in A. coluzzii, while variation in spiracle size might be a secondary mechanism. PMID:27207644

  18. Dehumidification Grain Dryer

    SciTech Connect

    Lula, J.W.; Bohnert, G.W.

    1998-05-13

    A new technique developed during this project dries grain with mildly heated, dehumidified air in a closed-loop process. This proposed technique uses about one-tenth the energy and dries grain at a lower temperature, producing less damage to the kernels.Approximately 250 million automotive and truck tires are discarded each year in the U.S. The very properties that ensure a safe ride and long service life make the disposal of these scrap tires difficult. In spite of this, scrap tire recycling/reuse has rapidly grown from 10% in 1985 to over 90% today. The majority of scrap tires that are recycled/reused are burned for fuel in power plants and cement kilns. Since tires have somewhat higher heating value than coal, this would at first seem to be an acceptable option. But burning scrap tires recovers only 25% of the energy originally used to manufacture the rubber. An alternative is to use the scrap tires in the form of crumb rubber, by which 98% of the original energy is recovered. This project sought to explore potential formulations of crumb rubber with various thermoplastic binders, with one goal being developing a material for a low-cost, high-performance roofing composition. What was the state-of-the-art of the product/process prior to initiation of the project? Why was the project needed (e.g., performance, quality, cost, time to market)? Describe the strengths and interests of each party and how they are complementary with respect to the project. What KCP expertise was needed and how did it complement the partner's capabilities?

  19. Developmental changes in the germinability, desiccation tolerance, hardseededness, and longevity of individual seeds of Trifolium ambiguum

    PubMed Central

    Hay, F. R.; Smith, R. D.; Ellis, R. H.; Butler, L. H.

    2010-01-01

    Background and Aims Using two parental clones of outcrossing Trifolium ambiguum as a potential model system, we examined how during seed development the maternal parent, number of seeds per pod, seed position within the pod, and pod position within the inflorescence influenced individual seed fresh weight, dry weight, water content, germinability, desiccation tolerance, hardseededness, and subsequent longevity of individual seeds. Methods Near simultaneous, manual reciprocal crosses were carried out between clonal lines for two experiments. Infructescences were harvested at intervals during seed development. Each individual seed was weighed and then used to determine dry weight or one of the physiological behaviour traits. Key Results Whilst population mass maturity was reached at 33–36 days after pollination (DAP), seed-to-seed variation in maximum seed dry weight, when it was achieved, and when maturation drying commenced, was considerable. Individual seeds acquired germinability between 14 and 44 DAP, desiccation tolerance between 30 and 40 DAP, and the capability to become hardseeded between 30 and 47 DAP. The time for viability to fall to 50 % (p50) at 60 % relative humidity and 45 °C increased between 36 and 56 DAP, when the seed coats of most individuals had become dark orange, but declined thereafter. Individual seed f. wt at harvest did not correlate with air-dry storage survival period. Analysing survival data for cohorts of seeds reduced the standard deviation of the normal distribution of seed deaths in time, but no sub-population showed complete uniformity of survival period. Conclusions Variation in individual seed behaviours within a developing population is inherent and inevitable. In this outbreeder, there is significant variation in seed longevity which appears dependent on embryo genotype with little effect of maternal genotype or architectural factors. PMID:20228084

  20. Mechanisms associated with cellular desiccation tolerance in the animal extremophile artemia.

    PubMed

    Hengherr, Steffen; Schill, Ralph O; Clegg, James S

    2011-01-01

    Using differential scanning calorimetry, we demonstrated the presence of biological glasses and measured the transition temperatures in dry encysted embryos (cysts) of the brine shrimp, Artemia franciscana. Cysts from the following three geographic locations were studied: San Francisco Bay (SFB); the Great Salt Lake, Utah (GSL); and the Mekong Delta, Vietnam (VN; these cysts were produced from previous sequential inoculations of SFB cysts into growth ponds). Values for the glass transition temperature, T(g), were highest in VN cysts. This study indicates that the composition and properties of these biological glasses can be altered by natural selection and thermal adaptation. To our knowledge, T(g) values for all three kinds of cysts were significantly higher than those for any other desiccation-tolerant animal system. To gain insight into the significance of T(g), we examined the thermal stability of these dry cysts at 80 °C. GSL cysts were the least tolerant, by far, with VN cysts being extremely tolerant and SFB cysts not far behind. Those results correlated with the thermal transition values. Also measured were alcohol-soluble carbohydrates, ~90% of which is the disaccharide trehalose, a known component of biological glasses. Amounts in the GSL cysts were significantly less than those in the other two kinds of cysts. Several stress proteins were measured in the three groups of cysts, with all of them being in lesser amounts in GSL cysts compared with the SFB and VN cysts. We interpret the data in terms of mechanisms involved with desiccation tolerance and thermal conditions at the sites of cyst collection.

  1. Developmental changes in the germinability, desiccation tolerance, hardseededness, and longevity of individual seeds of Trifolium ambiguum.

    PubMed

    Hay, F R; Smith, R D; Ellis, R H; Butler, L H

    2010-06-01

    Using two parental clones of outcrossing Trifolium ambiguum as a potential model system, we examined how during seed development the maternal parent, number of seeds per pod, seed position within the pod, and pod position within the inflorescence influenced individual seed fresh weight, dry weight, water content, germinability, desiccation tolerance, hardseededness, and subsequent longevity of individual seeds. Near simultaneous, manual reciprocal crosses were carried out between clonal lines for two experiments. Infructescences were harvested at intervals during seed development. Each individual seed was weighed and then used to determine dry weight or one of the physiological behaviour traits. Whilst population mass maturity was reached at 33-36 days after pollination (DAP), seed-to-seed variation in maximum seed dry weight, when it was achieved, and when maturation drying commenced, was considerable. Individual seeds acquired germinability between 14 and 44 DAP, desiccation tolerance between 30 and 40 DAP, and the capability to become hardseeded between 30 and 47 DAP. The time for viability to fall to 50 % (p(50)) at 60 % relative humidity and 45 degrees C increased between 36 and 56 DAP, when the seed coats of most individuals had become dark orange, but declined thereafter. Individual seed f. wt at harvest did not correlate with air-dry storage survival period. Analysing survival data for cohorts of seeds reduced the standard deviation of the normal distribution of seed deaths in time, but no sub-population showed complete uniformity of survival period. Variation in individual seed behaviours within a developing population is inherent and inevitable. In this outbreeder, there is significant variation in seed longevity which appears dependent on embryo genotype with little effect of maternal genotype or architectural factors.

  2. Method and apparatus for extracting water from air using a desiccant

    DOEpatents

    Spletzer, Barry L.; Callow, Diane Schafer

    2003-01-01

    The present invention provides a method and apparatus for extracting liquid water from moist air using minimal energy input. The method can be considered as four phases: (1) adsorbing water from air into a desiccant, (2) isolating the water-laden desiccant from the air source, (3) desorbing water as vapor from the desiccant into a chamber, and (4) isolating the desiccant from the chamber, and compressing the vapor in the chamber to form liquid condensate. The liquid condensate can be removed for use. Careful design of the dead volumes and pressure balances can minimize the energy required. The dried air can be exchanged for fresh moist air and the process repeated. An apparatus comprises a first chamber in fluid communication with a desiccant, and having ports to intake moist air and exhaust dried air. The apparatus also comprises a second chamber in fluid communication with the desiccant. The second chamber allows variable internal pressure, and has a port for removal of liquid condensate. Each chamber can be configured to be isolated or in communication with the desiccant. The first chamber can be configured to be isolated or in communication with a course of moist air. Various arrangements of valves, pistons, and chambers are described.

  3. Changes in body melanisation and desiccation resistance in highland vs. lowland populations of D. melanogaster.

    PubMed

    Parkash, Ravi; Rajpurohit, Subhash; Ramniwas, Seema

    2008-06-01

    Wild caught samples of Drosophila melanogaster from five highland localities showed parallel changes in melanisation and desiccation resistance in darker versus lighter phenotypes, i.e. darker flies (>45% melanisation) showed significantly higher desiccation resistance than lighter flies (<30% melanisation). In order to find an association between body melanisation and desiccation resistance, highland and lowland populations from tropical and subtropical regions (11.15-31.06 degrees N) of the Indian subcontinent were raised and investigated at 21 degrees C for four physiological traits, i.e. per cent body melanisation, desiccation resistance, rate of water loss and rate of water absorption. On the basis of mother-offspring regression, body melanisation and desiccation resistance showed higher heritability (0.58-0.68) and thus these traits are suitable for laboratory analyses. Significantly higher melanisation as well as desiccation resistance were observed in highland populations as compared with lowland populations. The rates of water loss as well as absorption were negatively correlated with body melanisation, i.e. darker flies from highlands showed a reduced rate of water loss as well as a lower rate of water absorption while the reverse trend was observed in lighter flies from lowlands. On the basis of multiple regressions, significant effects due to combined altitude and latitude were observed for all the four physiological traits. Local climatic conditions (i.e. annual average temperature and relative humidity) helped in explaining parallel changes in body melanisation and desiccation resistance in D. melanogaster.

  4. Desiccation tolerance in resurrection plants: new insights from transcriptome, proteome and metabolome analysis.

    PubMed

    Dinakar, Challabathula; Bartels, Dorothea

    2013-01-01

    Most higher plants are unable to survive desiccation to an air-dried state. An exception is a small group of vascular angiosperm plants, termed resurrection plants. They have evolved unique mechanisms of desiccation tolerance and thus can tolerate severe water loss, and mostly adjust their water content with the relative humidity in the environment. Desiccation tolerance is a complex phenomenon and depends on the regulated expression of numerous genes during dehydration and subsequent rehydration. Most of the resurrection plants have a large genome and are difficult to transform which makes them unsuitable for genetic approaches. However, technical advances have made it possible to analyze changes in gene expression on a large-scale. These approaches together with comparative studies with non-desiccation tolerant plants provide novel insights into the molecular processes required for desiccation tolerance and will shed light on identification of orphan genes with unknown functions. Here, we review large-scale recent transcriptomic, proteomic, and metabolomic studies that have been performed in desiccation tolerant plants and discuss how these studies contribute to understanding the molecular basis of desiccation tolerance.

  5. Desiccation tolerance in resurrection plants: new insights from transcriptome, proteome and metabolome analysis

    PubMed Central

    Dinakar, Challabathula; Bartels, Dorothea

    2013-01-01

    Most higher plants are unable to survive desiccation to an air-dried state. An exception is a small group of vascular angiosperm plants, termed resurrection plants. They have evolved unique mechanisms of desiccation tolerance and thus can tolerate severe water loss, and mostly adjust their water content with the relative humidity in the environment. Desiccation tolerance is a complex phenomenon and depends on the regulated expression of numerous genes during dehydration and subsequent rehydration. Most of the resurrection plants have a large genome and are difficult to transform which makes them unsuitable for genetic approaches. However, technical advances have made it possible to analyze changes in gene expression on a large-scale. These approaches together with comparative studies with non-desiccation tolerant plants provide novel insights into the molecular processes required for desiccation tolerance and will shed light on identification of orphan genes with unknown functions. Here, we review large-scale recent transcriptomic, proteomic, and metabolomic studies that have been performed in desiccation tolerant plants and discuss how these studies contribute to understanding the molecular basis of desiccation tolerance. PMID:24348488

  6. Resistance and resilience of benthic biofilm communities from a temperate saltmarsh to desiccation and rewetting.

    PubMed

    McKew, Boyd A; Taylor, Joe D; McGenity, Terry J; Underwood, Graham J C

    2011-01-01

    Periods of desiccation and rewetting are regular, yet stressful events encountered by saltmarsh microbial communities. To examine the resistance and resilience of microbial biofilms to such stresses, sediments from saltmarsh creeks were allowed to desiccate for 23 days, followed by rewetting for 4 days, whereas control sediments were maintained under a natural tidal cycle. In the top 2 mm of the dry sediments, salinity increased steadily from 36 to 231 over 23 days, and returned to seawater salinity on rewetting. After 3 days, desiccated sediments had a lower chlorophyll a (Chl a) fluorescence signal as benthic diatoms ceased to migrate to the surface, with a recovery in cell migration and Chl a fluorescence on rewetting. Extracellular β-glucosidase and aminopeptidase activities decreased within the first week of drying, but increased sharply on rewetting. The bacterial community in the desiccating sediment changed significantly from the controls after 14 days of desiccation (salinity 144). Rewetting did not cause a return to the original community composition, but led to a further change. Pyrosequencing analysis of 16S rRNA genes amplified from the sediment revealed diverse microbial responses, for example desiccation enabled haloversatile Marinobacter species to increase their relative abundance, and thus take advantage of rewetting to grow rapidly and dominate the community. A temporal sequence of effects of desiccation and rewetting were thus observed, but the most notable feature was the overall resistance and resilience of the microbial community.

  7. Resistance and resilience of benthic biofilm communities from a temperate saltmarsh to desiccation and rewetting

    PubMed Central

    McKew, Boyd A; Taylor, Joe D; McGenity, Terry J; Underwood, Graham J C

    2011-01-01

    Periods of desiccation and rewetting are regular, yet stressful events encountered by saltmarsh microbial communities. To examine the resistance and resilience of microbial biofilms to such stresses, sediments from saltmarsh creeks were allowed to desiccate for 23 days, followed by rewetting for 4 days, whereas control sediments were maintained under a natural tidal cycle. In the top 2 mm of the dry sediments, salinity increased steadily from 36 to 231 over 23 days, and returned to seawater salinity on rewetting. After 3 days, desiccated sediments had a lower chlorophyll a (Chl a) fluorescence signal as benthic diatoms ceased to migrate to the surface, with a recovery in cell migration and Chl a fluorescence on rewetting. Extracellular β-glucosidase and aminopeptidase activities decreased within the first week of drying, but increased sharply on rewetting. The bacterial community in the desiccating sediment changed significantly from the controls after 14 days of desiccation (salinity 144). Rewetting did not cause a return to the original community composition, but led to a further change. Pyrosequencing analysis of 16S rRNA genes amplified from the sediment revealed diverse microbial responses, for example desiccation enabled haloversatile Marinobacter species to increase their relative abundance, and thus take advantage of rewetting to grow rapidly and dominate the community. A temporal sequence of effects of desiccation and rewetting were thus observed, but the most notable feature was the overall resistance and resilience of the microbial community. PMID:20596071

  8. The effectiveness of commercial desiccants and uncooked rice in removing moisture from hearing aids.

    PubMed

    Nelson, Lauri H; White, Karl R; Baker, Dirk V; Hayden, Angela; Bird, Scott

    2017-04-01

    In many low- and middle-income countries, the availability of hearing technology is limited, with few options for hearing aid repairs. Minimising moisture damage to hearing aid electronics improves function and longevity; however, desiccants that absorb moisture from hearing aid components are unavailable in many regions. This study compared the effectiveness of uncooked white rice and seven commercial silica gel desiccants in removing moisture from hearing aids. Relative humidity measurements in a test chamber were obtained from a water-saturated BTE hearing aid prior to and after placement in uncooked white rice and seven different silica gel desiccants. Two BTE hearing aids, seven silica gel desiccants and white rice comprised the study sample. All desiccants and the white rice were effective in removing moisture from hearing aids, with Hal Hen Super Dri Aid showing the largest mean reduction in relative humidity. Based on analysis of covariance results, white rice was statistically similar to several of the commercial desiccants. White rice shows promise as an effective alternative to commercial desiccants in reducing moisture in hearing aids when silica gel products are unavailable. As this study was conducted in a relatively dry region, additional research may be needed.

  9. Comparison of frozen versus desiccated reference human red blood cells for hemagglutination assays.

    PubMed

    Ho, David; Schierts, Jennifer; Zimmerman, Zea; Gadsden, Isaac; Bruttig, Stephen

    2009-10-01

    Red blood cells (RBCs) are commonly used fresh or stored in frozen format for identification of patients' antibodies and serologic specificity of such antibodies at reference laboratories. However, maintaining a large pool of fresh RBCs is impossible in a blood-banking environment and blood in frozen format poses a logistic disadvantage in terms of accessibility, maintenance cost, safety, and sample recovery. This study explores an alternative, desiccation storage method for RBCs to provide a reagent that supports greater utilization and flexibility for reference laboratories. RBCs from five donors were used in the study. RBCs were processed and kept in either frozen or desiccated format. Study variables for either the frozen or the desiccated cells included cell recovery as quantified by cell counts, gross microscopic examination, and hemagglutination assays. The mean percentage of cell recovery for thawed and washed frozen RBCs was 20% versus 50% for rehydrated and washed desiccated RBCs. Microscopic examination of thawed cells from the frozen preparation showed cells with irregular shapes, a sharp contrast when compared with rehydrated cells from the desiccated preparation, where cells are mostly intact, smooth surface, and biconcave in structure. Cells in both preparations performed well in manual agglutination tests. Desiccation preservation of RBCs provides a somewhat better RBC recovery and cell structure stability, while maintaining the necessary antigen-antibody reactions for cell surface markers, which will allow desiccated RBCs to be archived in blood collecting and processing reference laboratories.

  10. Comparative proteomic analysis of Cronobacter sakazakii by iTRAQ provides insights into response to desiccation.

    PubMed

    Hu, Shuangfang; Yu, Yigang; Wu, Xinwei; Xia, Xingzhou; Xiao, Xinglong; Wu, Hui

    2017-10-01

    Cronobacter sakazakii is a foodborne pathogen throughout the world and survives extremely desiccation stress. However, the molecular basis involved in desiccation resistance of C. sakazakii is still unknown. In this study, the potential desiccation resistance factors of C. sakazakii ATCC 29544 were determined using iTRAQ-based quantitative proteomic analysis. A total of 2775 proteins were identified by iTRAQ, of which 233 showed a different protein expression between control group and desiccation stress group. Among these 233 proteins identified as desiccation resistance proteins, there were 146 proteins downregulated and 87 proteins upregulated. According to the comprehensive proteome coverage analysis, C. sakazakii increased its resistance to desiccation by reducing the gene involved with unnecessary survival functions such as those used for virulence, adhesion, invasion and flagella assembly, while increasing gene expression of genes used in withstanding osmotic stress such as those genes involved in trehalose and betaine uptake. However, the mechanism involved in amino acid metabolism in an osmotic stress response, including the producing of γ-aminobutyric acid in C. sakazakii is still uncertain. This is the first report to determine the potential desiccation resistant factors of C. sakazakii at the proteomic levels. Copyright © 2017. Published by Elsevier Ltd.

  11. The desiccation tolerant secrets of Selaginella lepidophylla: what we have learned so far?

    PubMed

    Pampurova, Suzana; Van Dijck, Patrick

    2014-07-01

    Selaginella lepidophylla is a desiccation tolerant plant able to survive complete vegetative tissue dehydration and revive ('resurrect') in water conditions. Vegetative desiccation tolerance is an adaptive feature acquired by S. lepidophylla to withstand the long dry periods in its natural habitat, the Chihuahuan desert. Understanding the molecular basis of its drought stress tolerance may be of great benefit to help in developing novel strategies for improvement of drought stress tolerance in crops. Cell biological (e.g. gene discovery, comparative EST analysis, proteomics, metabolite profiling), ultrastructural and physiological studies have brought modest but already important insights in the desiccation tolerance mechanisms adapted by S. lepidophylla. Until recently, the desiccation tolerant mechanism of S. lepidophylla was related to its high trehalose levels. However, large-scale comparative metabolic analysis between S. lepidophylla and its desiccation susceptible relative Selaginella moellendorffii, unexpectedly revealed that S. moellendorffii contains higher trehalose levels than S. lepidophylla. Interestingly, polyols, such as sorbitol and xylitol are 100× more abundant in S. lepidophylla compared to S. moellendorffii. Whether this is linked to the higher stress tolerance remains to be established. Apart from these metabolites, we will also discuss the ultrastructural features that seem to play an important role in the desiccation tolerance of S. lepidophylla. Finally we discuss desiccation tolerance mechanism in other plant species.

  12. Crucial Role of Extracellular Polysaccharides in Desiccation and Freezing Tolerance in the Terrestrial Cyanobacterium Nostoc commune

    PubMed Central

    Tamaru, Yoshiyuki; Takani, Yayoi; Yoshida, Takayuki; Sakamoto, Toshio

    2005-01-01

    The cyanobacterium Nostoc commune is adapted to the terrestrial environment and has a cosmopolitan distribution. In this study, the role of extracellular polysaccharides (EPS) in the desiccation tolerance of photosynthesis in N. commune was examined. Although photosynthetic O2 evolution was not detected in desiccated colonies, the ability of the cells to evolve O2 rapidly recovered after rehydration. The air-dried colonies contained approximately 10% (wt/wt) water, and field-isolated, natural colonies with EPS were highly water absorbent and were rapidly hydrated by atmospheric moisture. The cells embedded in EPS in Nostoc colonies were highly desiccation tolerant, and O2 evolution was not damaged by air drying. Although N. commune was determined to be a mesophilic cyanobacterium, the cells with EPS were heat tolerant in a desiccated state. EPS could be removed from cells by homogenizing colonies with a blender and filtering with coarse filter paper. This treatment to remove EPS did not damage Nostoc cells or their ability to evolve O2, but O2 evolution was significantly damaged by desiccation treatment of the EPS-depleted cells. Similar to the EPS-depleted cells, the laboratory culture strain KU002 had only small amount of EPS and was highly sensitive to desiccation. In the EPS-depleted cells, O2 evolution was also sensitive to freeze-thaw treatment. These results strongly suggest that EPS of N. commune is crucial for the stress tolerance of photosynthesis during desiccation and during freezing and thawing. PMID:16269775

  13. Molecular mechanisms involved in the response to desiccation stress and persistence in Acinetobacter baumannii.

    PubMed

    Gayoso, Carmen M; Mateos, Jesús; Méndez, José A; Fernández-Puente, Patricia; Rumbo, Carlos; Tomás, María; Martínez de Ilarduya, Oskar; Bou, Germán

    2014-02-07

    Desiccation tolerance contributes to the maintenance of bacterial populations in hospital settings and may partly explain its propensity to cause outbreaks. Identification and relative quantitation of proteins involved in bacterial desiccation tolerance was made using label-free quantitation and iTRAQ labeling. Under desiccating conditions, the population of the Acinetobacter baumannii clinical strain AbH12O-A2 decreased in the first week, and thereafter, a stable population of 0.5% of the original population was maintained. Using label-free quantitation and iTRAQ labeling, 727 and 765 proteins, respectively, were detected; 584 of them by both methods. Proteins overexpressed under desiccation included membrane and periplasmic proteins. Proteins associated with antimicrobial resistance, efflux pumps, and quorum quenching were overexpressed in the samples subjected to desiccation stress. Electron microscopy revealed clear morphological differences between desiccated and control bacteria. We conclude that A. baumannii is able to survive long periods of desiccation through the presence of cells in a dormant state, via mechanisms affecting control of cell cycling, DNA coiling, transcriptional and translational regulation, protein stabilization, antimicrobial resistance, and toxin synthesis, and that a few surviving cells embedded in a biofilm matrix are able to resume growth and restore the original population in appropriate environmental conditions following a "bust-and-boom" strategy.

  14. Crucial role of extracellular polysaccharides in desiccation and freezing tolerance in the terrestrial cyanobacterium Nostoc commune.

    PubMed

    Tamaru, Yoshiyuki; Takani, Yayoi; Yoshida, Takayuki; Sakamoto, Toshio

    2005-11-01

    The cyanobacterium Nostoc commune is adapted to the terrestrial environment and has a cosmopolitan distribution. In this study, the role of extracellular polysaccharides (EPS) in the desiccation tolerance of photosynthesis in N. commune was examined. Although photosynthetic O2 evolution was not detected in desiccated colonies, the ability of the cells to evolve O2 rapidly recovered after rehydration. The air-dried colonies contained approximately 10% (wt/wt) water, and field-isolated, natural colonies with EPS were highly water absorbent and were rapidly hydrated by atmospheric moisture. The cells embedded in EPS in Nostoc colonies were highly desiccation tolerant, and O2 evolution was not damaged by air drying. Although N. commune was determined to be a mesophilic cyanobacterium, the cells with EPS were heat tolerant in a desiccated state. EPS could be removed from cells by homogenizing colonies with a blender and filtering with coarse filter paper. This treatment to remove EPS did not damage Nostoc cells or their ability to evolve O2, but O2 evolution was significantly damaged by desiccation treatment of the EPS-depleted cells. Similar to the EPS-depleted cells, the laboratory culture strain KU002 had only small amount of EPS and was highly sensitive to desiccation. In the EPS-depleted cells, O2 evolution was also sensitive to freeze-thaw treatment. These results strongly suggest that EPS of N. commune is crucial for the stress tolerance of photosynthesis during desiccation and during freezing and thawing.

  15. Identification of proteins involved in desiccation tolerance in the red seaweed Pyropia orbicularis (Rhodophyta, Bangiales).

    PubMed

    López-Cristoffanini, Camilo; Zapata, Javier; Gaillard, Fanny; Potin, Philippe; Correa, Juan A; Contreras-Porcia, Loretto

    2015-12-01

    Extreme reduction in cellular water content leads to desiccation, which, if persistent, affects the physiology of organisms, mainly through oxidative stress. Some organisms are highly tolerant to desiccation, including resurrection plants and certain intertidal seaweeds. One such species is Pyropia orbicularis, a rhodophycean that colonizes upper intertidal zones along the Chilean coast. Despite long, daily periods of air exposure due to tides, this alga is highly tolerant to desiccation. The present study examined the proteome of P. orbicularis by 2DE and LC-MS/MS analyses to determine the proteins associated with desiccation tolerance (DT). The results showed that, under natural conditions, there were significant changes in the protein profile during low tide as compared to naturally hydrated plants at high tide. These changes were mainly in newly appeared proteins spots such as chaperones, monodehydroascorbate reductase, and manganese superoxide dismutase, among others. Previously undescribed proteins under desiccation conditions included phycobiliproteins, glyoxalase I, and phosphomannomutase. These changes evidenced that several physiological responses involved in DT are activated during low tide, including decreased photosynthetic activity, increased antioxidant capacity, and the preservation of cell physiology by regulating water content, cell wall structure, and cell volume. Similar responses have been observed in resurrection plants and bryophytes exposed to desiccation. Therefore, the coordinated activation of different desiccation tolerance pathways in P. orbicularis could explain the successful biological performance of this seaweed in the upper intertidal rocky zones.

  16. Changes in some thylakoid membrane proteins and pigments upon desiccation of the resurrection plant Haberlea rhodopensis.

    PubMed

    Georgieva, Katya; Röding, Anja; Büchel, Claudia

    2009-09-15

    The changes in some proteins involved in the light reactions of photosynthesis of the resurrection plant Haberlea rhodopensis were examined in connection with desiccation. Fully hydrated (control) and completely desiccated plants (relative water content (RWC) 6.5%) were used for thylakoid preparations. The chlorophyll (Chl) a to Chl b ratios of thylakoids isolated from control and desiccated leaves were very similar, which was also confirmed by measuring their absorption spectra. HPLC analysis revealed that beta-carotene content was only slightly enhanced in desiccated leaves compared with the control, but the zeaxanthin level was strongly increased. Desiccation of H. rhodopensis to an air-dried state at very low light irradiance led to a little decrease in the level of D1, D2, PsbS and PsaA/B proteins in thylakoids, but a relative increase in LHC polypeptides. To further elucidate whether the composition of the protein complexes of the thylakoid membranes had changed, we performed a separation of solubilized thylakoids on sucrose density gradients. In contrast to spinach, Haberlea thylakoids appeared to be much more resistant to the same solubilization procedure, i.e. complexes were not separated completely and complexes of higher density were found. However, the fractions analyzed provided clear evidence for a move of part of the antenna complexes from PSII to PSI when plants became desiccated. This move was also confirmed by low temperature emission spectra of thylakoids. Overall, the photosynthetic proteins remained comparatively stable in dried Haberlea leaves when plants were desiccated under conditions similar to their natural habitat. Low light during desiccation was enough to induce a rise in the xanthophyll zeaxanthin and beta-carotene. Together with the extensive leaf shrinkage and some leaf folding, increased zeaxanthin content and the observed shift in antenna proteins from PSII to PSI during desiccation of Haberlea contributed to the integrity of the

  17. Generational Differences in Response to Desiccation Stress in the Desert Moss Tortula inermis

    PubMed Central

    Stark, Lloyd R.; Oliver, Melvin J.; Mishler, Brent D.; McLetchie, D. Nicholas

    2007-01-01

    Background and Aims Active growth in post-embryonic sporophytes of desert mosses is restricted to the cooler, wetter months. However, most desert mosses have perennial gametophytes. It is hypothesized that these life history patterns are due, in part, to a reduced desiccation tolerance for sporophytes relative to gametophytes. Methods Gametophytes with attached post-embryonic sporophytes of Tortula inermis (early seta elongation phenophase) were exposed to two levels of desiccation stress, one rapid-dry cycle and two rapid-dry cycles, then moistened and allowed to recover, resume development, and/or regenerate for 35 d in a growth chamber. Key Results Gametophytes tolerated the desiccation treatments well, with 93 % survival through regenerated shoot buds and/or protonemata. At the high stress treatment, a significantly higher frequency of burned leaves and browned shoots occurred. Sporophytes were far more sensitive to desiccation stress, with only 23 % surviving after the low desiccation stress treatment, and 3 % surviving after the high desiccation stress treatment. While the timing of protonemal production and sporophytic phenophases was relatively unaffected by desiccation stress, shoots exposed to one rapid-dry cycle produced shoots more rapidly than shoots exposed to two rapid-dry cycles. Conclusions It is concluded that sporophytes of Tortula inermis are more sensitive to rapid drying than are maternal gametophytes, and that sporophyte abortion in response to desiccation results from either reduced desiccation tolerance of sporophytes relative to gametophytes, or from a termination of the sporophyte on the part of the gametophyte in response to stress. PMID:17098752

  18. Water Content, Raffinose, and Dehydrins in the Induction of Desiccation Tolerance in Immature Wheat Embryos

    PubMed Central

    Black, Michael; Corbineau, Françoise; Gee, Harry; Côme, Daniel

    1999-01-01

    Desiccation tolerance is initiated in wheat (Triticum aestivum L.) embryos in planta at 22 to 24 d after anthesis, at the time that the embryo water content has decreased from about 73% fresh weight (2.7 g water/g dry weight) to about 65% fresh weight (1.8 g water/g dry weight). To determine if desiccation tolerance is fully induced by the loss of a relatively small amount of water, detached wheat grains were treated to reduce the embryo water content by just a small amount to approximately 69% (2.2 g water/g dry weight). After 24 h of such incipient water loss, subsequently excised embryos were able to withstand severe desiccation, whereas those embryos that had not previously lost water could not. Therefore, a relatively small decrease in water content for only 24 h acts as the signal for the development of desiccation tolerance. Embryos that were induced into tolerance by a 24-h water loss had no detectable raffinose. The oligosaccharide accumulated at later times even in embryos of detached grains that had not become desiccation tolerant, although tolerant embryos (i.e. those that previously had lost some water) contained larger amounts of the carbohydrate. It is concluded that desiccation tolerance and the occurrence of raffinose are not correlated. Immunodetected dehydrins accumulated in embryos in planta as desiccation tolerance developed. Detachment of grains induced the appearance of dehydrins at an earlier age, even in embryos that had not been made desiccation tolerant by incipient drying. It is concluded that a small reduction in water content induces desiccation tolerance by initiating changes in which dehydrins might participate but not by their interaction with raffinose. PMID:10364397

  19. Effect of desiccation level and storage temperature on green spore viability of Osmunda japonica.

    PubMed

    Li, Yang; Shi, Lei

    2014-06-01

    In order to effectively preserve green spores, which have relatively higher water content and lose viability more quickly than non-green spores, we studied the effect of desiccation level and storage temperature on Osmunda japonica spores. The water content of fresh spores was 11.20%. After 12h desiccation by silica gel, the water content decreased to 6% but spore viability did not change significantly. As the desiccation continued, the decrease in water content slowed, but spore viability dropped. For almost all storage periods, the effects of storage temperature, desiccation level, and temperature×desiccation level were significantly different. After seven days of storage, spores at any desiccation level stored at 4°C obtained high germination rates. After more than seven days storage, liquid nitrogen (LN) storage obtained the best results. Storage at -18°C led to the lowest germination rates. Spores stored at room temperature and -18°C all died within three months. For storage at 4°C and in LN, spores desiccated 12 and 36 h obtained better results. Spores without desiccation had the highest germination rates after being stored at room temperature, but suffered the greatest loss after storage at -18°C. These results suggest that LN storage is the best method of long-term storage of O. japonica spores. The critical water content of O. japonica spores is about 6% and reduction of the water content to this level improves outcome after LN storage greatly. The reason for various responses of O. japonica spores to desiccation and storage temperatures are discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Expression profile of desiccation tolerance factors in intertidal seaweed species during the tidal cycle.

    PubMed

    Fierro, Camila; López-Cristoffanini, Camilo; Meynard, Andrés; Lovazzano, Carlos; Castañeda, Francisco; Guajardo, Eduardo; Contreras-Porcia, Loretto

    2017-06-01

    The transcriptional modulation of desiccation tolerance factors in P. orbicularis explains its successful recuperation after water deficit. Differential responses to air exposure clarify seaweed distribution along intertidal rocky zones. Desiccation-tolerant seaweed species, such as Pyropia orbicularis, can tolerate near 96% water loss during air exposure. To understand the phenotypic plasticity of P. orbicularis to desiccation, several tolerance factors were assessed by RT-qPCR, Western-blot analysis, and enzymatic assays during the natural desiccation-rehydration cycle. Comparative enzymatic analyses were used to evidence differential responses between P. orbicularis and desiccation-sensitive species. The results showed that during desiccation, the relative mRNA levels of genes associated with basal metabolism [trehalose phosphate synthase (tps) and pyruvate dehydrogenase (pdh)] were overexpressed in P. orbicularis. Transcript levels related to antioxidant metabolism [peroxiredoxin (prx); thioredoxin (trx); catalase (cat); lipoxygenase (lox); ferredoxin (fnr); glutathione S-transferase (gst)], cellular detoxification [ABC transporter (abc) and ubiquitin (ubq)], and signal transduction [calmodulin (cam)] increased approximately 15- to 20-fold, with the majority returning to basal levels during the final hours of rehydration. In contrast, actin (act) and transcription factor 1 (tf1) transcripts were down-regulated. ABC transporter protein levels increased in P. orbicularis during desiccation, whereas PRX transcripts decreased. The antioxidant enzymes showed higher specific activity in P. orbicularis under desiccation, and sensitive species exhibited enzymatic inactivation and scarce ABC and PRX protein detection following prolonged desiccation. In conclusion, the reported findings contribute towards understanding the ecological distribution of intertidal seaweeds at the molecular and functional levels.

  1. Heat and mass transfer analysis of a desiccant dehumidifier matrix

    SciTech Connect

    Pesaran, A.A.

    1986-07-01

    This report documents the SERI Single-Blow Test Facility's design, fabrication, and testing for characterizing desiccant dehumidifiers for solar cooling applications. The first test article, a silica-gel parallel-plate dehumidifier with highly uniform passages, was designed and fabricated. Transient heat and mass transfer data and pressure drop data across the dehumidifier were obtained. Available heat and mass transfer models were extended to the parallel-place geometry, and the experimental data were compared with model predictions. Pressure drop measurements were also compared with model predictions of the fully developed laminar flow theory. The comparisons between the lumped-capacitance model and the experimental data were satisfactory. The pressure drop data compared satisfactorily with the theory (within 15%). A solid-side resistance model that is more detailed and does not assume symmetrical diffusion in particles was recommended for performance. This study has increased our understanding of the heat and mass transfer in silica gel parallel-plate dehumidifiers.

  2. Laboratory and Modeling Evaluations in Support of Field Testing for Desiccation at the Hanford Site

    SciTech Connect

    Truex, Michael J.; Oostrom, Martinus; Freedman, Vicky L.; Strickland, Christopher E.; Wietsma, Thomas W.; Tartakovsky, Guzel D.; Ward, Anderson L.

    2011-02-23

    The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau includes testing of the desiccation technology as a potential technology to be used in conjunction with surface infiltration control to limit the flux of technetium and other contaminants in the vadose zone to the groundwater. Laboratory and modeling efforts were conducted to investigate technical uncertainties related to the desiccation process and its impact on contaminant transport. This information is intended to support planning, operation, and interpretation of a field test for desiccation in the Hanford Central Plateau.

  3. Tolerance to oxidative stress induced by desiccation in Porphyra columbina (Bangiales, Rhodophyta)

    PubMed Central

    Contreras-Porcia, Loretto; Thomas, Daniela; Flores, Verónica; Correa, Juan A.

    2011-01-01

    Unravelling the mechanisms underlying desiccation tolerance is crucial in order to understand the position of algal species in the intertidal zone. The alga Porphyra columbina lives in the uppermost part of the rocky intertidal zones around the world and was selected as a model for this study. Naturally desiccated plants were collected during low tide and studied for morphological changes, oxidative burst induction, biomolecule oxidation, antioxidant responses, and photosynthetic status. Naturally hydrated plants collected during high tides were used for comparative purposes. In addition, changes induced by desiccation were assessed in vitro and the capacity to recover from desiccation was determined by rehydrating the fronds in seawater. The global results show that desiccation induces morphological and cellular alterations accompanied by a loss of ∼96% of the water content. Overproduction of reactive oxygen species (ROS) was induced by desiccation and two peaks of H2O2 were detected at 1 and 3 h of desiccation. However, during in vitro rehydration post-desiccation, the ROS quickly returned to the basal levels. At the biomolecular level, only a low production of oxidized proteins was recorded during desiccation, whereas the activity of diverse antioxidant enzymes increased. However, this activity diminished to near basal levels during rehydration. The photosynthetic efficiency (Fv/Fm) during desiccation declined by 94–96% of the values recorded in hydrated plants. This reduction was generated by the low levels of trapped energy flux per cross-section (TRo/CS), electron transport flux per CS (ETo/CS), and density of reaction centres (RC/SCo) as well as the chlorophyll content. The inverse pattern was observed for the levels of phycocyanin and phycoerythrin content. Fv/Fm and the photosynthetic indicators were restored to normal levels after only 5 min of rehydration. The results indicate that desiccation in P. columbina causes overproduction of ROS that is

  4. Tolerance to oxidative stress induced by desiccation in Porphyra columbina (Bangiales, Rhodophyta).

    PubMed

    Contreras-Porcia, Loretto; Thomas, Daniela; Flores, Verónica; Correa, Juan A

    2011-03-01

    Unravelling the mechanisms underlying desiccation tolerance is crucial in order to understand the position of algal species in the intertidal zone. The alga Porphyra columbina lives in the uppermost part of the rocky intertidal zones around the world and was selected as a model for this study. Naturally desiccated plants were collected during low tide and studied for morphological changes, oxidative burst induction, biomolecule oxidation, antioxidant responses, and photosynthetic status. Naturally hydrated plants collected during high tides were used for comparative purposes. In addition, changes induced by desiccation were assessed in vitro and the capacity to recover from desiccation was determined by rehydrating the fronds in seawater. The global results show that desiccation induces morphological and cellular alterations accompanied by a loss of ∼96% of the water content. Overproduction of reactive oxygen species (ROS) was induced by desiccation and two peaks of H(2)O(2) were detected at 1 and 3 h of desiccation. However, during in vitro rehydration post-desiccation, the ROS quickly returned to the basal levels. At the biomolecular level, only a low production of oxidized proteins was recorded during desiccation, whereas the activity of diverse antioxidant enzymes increased. However, this activity diminished to near basal levels during rehydration. The photosynthetic efficiency (F(v)/F(m)) during desiccation declined by 94-96% of the values recorded in hydrated plants. This reduction was generated by the low levels of trapped energy flux per cross-section (TRo/CS), electron transport flux per CS (ETo/CS), and density of reaction centres (RC/SCo) as well as the chlorophyll content. The inverse pattern was observed for the levels of phycocyanin and phycoerythrin content. F(v)/F(m) and the photosynthetic indicators were restored to normal levels after only 5 min of rehydration. The results indicate that desiccation in P. columbina causes overproduction of ROS

  5. The signature of seeds in resurrection plants: a molecular and physiological comparison of desiccation tolerance in seeds and vegetative tissues.

    PubMed

    Illing, Nicola; Denby, Katherine J; Collett, Helen; Shen, Arthur; Farrant, Jill M

    2005-11-01

    Desiccation-tolerance in vegetative tissues of angiosperms has a polyphyletic origin and could be due to 1) appropriation of the seed-specific program of gene expression that protects orthodox seeds against desiccation, and/or 2) a sustainable version of the abiotic stress response. We tested these hypotheses by comparing molecular and physiological data from the development of orthodox seeds, the response of desiccation-sensitive plants to abiotic stress, and the response of desiccation-tolerant plants to extreme water loss. Analysis of publicly-available gene expression data of 35 LEA proteins and 68 anti-oxidant enzymes in the desiccation-sensitive Arabidopsis thaliana identified 13 LEAs and 4 anti-oxidants exclusively expressed in seeds. Two (a LEA6 and 1-cys-peroxiredoxin) are not expressed in vegetative tissues in A. thaliana, but have orthologues that are specifically activated in desiccating leaves of Xerophyta humilis. A comparison of antioxidant enzyme activity in two desiccation-sensitive species of Eragrostis with the desiccation-tolerant E. nindensis showed equivalent responses upon initial dehydration, but activity was retained at low water content in E. nindensis only. We propose that these antioxidants are housekeeping enzymes and that they are protected from damage in the desiccation-tolerant species. Sucrose is considered an important protectant against desiccation in orthodox seeds, and we show that sucrose accumulates in drying leaves of E. nindensis, but not in the desiccation-sensitive Eragrostis species. The activation of "seed-specific" desiccation protection mechanisms (sucrose accumulation and expression of LEA6 and 1-cys-peroxiredoxin genes) in the vegetative tissues of desiccation-tolerant plants points towards acquisition of desiccation tolerance from seeds.

  6. New features of desiccation tolerance in the lichen photobiont Trebouxia gelatinosa are revealed by a transcriptomic approach.

    PubMed

    Carniel, Fabio Candotto; Gerdol, Marco; Montagner, Alice; Banchi, Elisa; De Moro, Gianluca; Manfrin, Chiara; Muggia, Lucia; Pallavicini, Alberto; Tretiach, Mauro

    2016-06-01

    Trebouxia is the most common lichen-forming genus of aero-terrestrial green algae and all its species are desiccation tolerant (DT). The molecular bases of this remarkable adaptation are, however, still largely unknown. We applied a transcriptomic approach to a common member of the genus, T. gelatinosa, to investigate the alteration of gene expression occurring after dehydration and subsequent rehydration in comparison to cells kept constantly hydrated. We sequenced, de novo assembled and annotated the transcriptome of axenically cultured T. gelatinosa by using Illumina sequencing technology. We tracked the expression profiles of over 13,000 protein-coding transcripts. During the dehydration/rehydration cycle c. 92 % of the total protein-coding transcripts displayed a stable expression, suggesting that the desiccation tolerance of T. gelatinosa mostly relies on constitutive mechanisms. Dehydration and rehydration affected mainly the gene expression for components of the photosynthetic apparatus, the ROS-scavenging system, Heat Shock Proteins, aquaporins, expansins, and desiccation related proteins (DRPs), which are highly diversified in T. gelatinosa, whereas Late Embryogenesis Abundant Proteins were not affected. Only some of these phenomena were previously observed in other DT green algae, bryophytes and resurrection plants, other traits being distinctive of T. gelatinosa, and perhaps related to its symbiotic lifestyle. Finally, the phylogenetic inference extended to DRPs of other chlorophytes, embryophytes and bacteria clearly pointed out that DRPs of chlorophytes are not orthologous to those of embryophytes: some of them were likely acquired through horizontal gene transfer from extremophile bacteria which live in symbiosis within the lichen thallus.

  7. High-frequency zone of river desiccation disasters in China and influencing factors.

    PubMed

    Jiongxin, X

    2001-07-01

    In recent years, the desiccation of the lower Yellow River has raised concerns in the government, public, and scientific community in China. Long-term and widespread desiccation of rivers is a disaster with many adverse environmental implications. It has been found in this study that there exists a high-frequency zone of river desiccation disasters at 34 degrees -42 degrees N in the North China Plain. The hazardous environment is characterized by semiarid climate, widely distributed thick loess in the basin and a "hanging river bed" in the plain as well as unfavorable man-water-land coupling relationships. In this setting, the sharply increased water diversion by man since the late 1950s led to the occurrence of river desiccation disasters in the lower reaches of the river in this area.

  8. cis-3-Chloroacrylic Acid: A New Cotton Defoliant and Crop Desiccant.

    PubMed

    Herrett, R A; Kurtz, A N

    1963-09-20

    cis-3-Chloroacrylic acid is a potent cotton defoliant and a crop desiccant. Relationships between structure and activity indicate a relatively high degree of specificity, since minor modifications in structure result in loss of activity.

  9. 9 CFR 113.29 - Determination of moisture content in desiccated biological products.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... than 2.5 kPa. (i) Transfer hot bottles and stoppers into the desiccator and allow to cool to room... hours for the weighing bottle to cool to room temperature or for its weight to reach equilibrium. (ii...

  10. 9 CFR 113.29 - Determination of moisture content in desiccated biological products.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... than 2.5 kPa. (i) Transfer hot bottles and stoppers into the desiccator and allow to cool to room... hours for the weighing bottle to cool to room temperature or for its weight to reach equilibrium. (ii...

  11. 9 CFR 113.29 - Determination of moisture content in desiccated biological products.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... than 2.5 kPa. (i) Transfer hot bottles and stoppers into the desiccator and allow to cool to room... hours for the weighing bottle to cool to room temperature or for its weight to reach equilibrium. (ii...

  12. 9 CFR 113.29 - Determination of moisture content in desiccated biological products.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... than 2.5 kPa. (i) Transfer hot bottles and stoppers into the desiccator and allow to cool to room... hours for the weighing bottle to cool to room temperature or for its weight to reach equilibrium. (ii...

  13. 9 CFR 113.29 - Determination of moisture content in desiccated biological products.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... than 2.5 kPa. (i) Transfer hot bottles and stoppers into the desiccator and allow to cool to room... hours for the weighing bottle to cool to room temperature or for its weight to reach equilibrium. (ii...

  14. Development of desiccant based air conditioning for hotels and motels. Final report, phase 1

    SciTech Connect

    Banks, N.J.

    1994-10-01

    This report contains final reports from two phases of field tests: Phase I at the Marriott Courtyard in West Palm Beach, completed in October 1991, and Phase II at the Walt Disney World Swan Hotel in Orlando, completed in August 1993. The goal was to measure the performance and reliability of the desiccant units. The successfull program proved the value of the gas-fired desiccant technology to the hospitality industry. The desiccant units reduced moisture by 15 to 20% relative humidity. Measurements of temperature, humidity, and wallboard moisture content showed a dramatic reduction in the humidity levels experienced prior to installation of the units and in the control areas without desiccants. Moisture damage was kept in check and remodelling due to it was eliminated.

  15. The glyoxylate shunt is essential for desiccation tolerance in C. elegans and budding yeast

    PubMed Central

    Erkut, Cihan; Gade, Vamshidhar R; Laxman, Sunil; Kurzchalia, Teymuras V

    2016-01-01

    Many organisms, including species from all kingdoms of life, can survive desiccation by entering a state with no detectable metabolism. To survive, C. elegans dauer larvae and stationary phase S. cerevisiae require elevated amounts of the disaccharide trehalose. We found that dauer larvae and stationary phase yeast switched into a gluconeogenic mode in which metabolism was reoriented toward production of sugars from non-carbohydrate sources. This mode depended on full activity of the glyoxylate shunt (GS), which enables synthesis of trehalose from acetate. The GS was especially critical during preparation of worms for harsh desiccation (preconditioning) and during the entry of yeast into stationary phase. Loss of the GS dramatically decreased desiccation tolerance in both organisms. Our results reveal a novel physiological role for the GS and elucidate a conserved metabolic rewiring that confers desiccation tolerance on organisms as diverse as worm and yeast. DOI: http://dx.doi.org/10.7554/eLife.13614.001 PMID:27090086

  16. Responses of the Lichen Photobiont Trebouxia erici to Desiccation and Rehydration (II) Proteomics

    USDA-ARS?s Scientific Manuscript database

    Lichen desiccation tolerance is associated with cellular protection mechanisms directed against the oxidative stress produced during dehydration and/or rehydration, however, these mechanisms are not well understood. In other poikilohydric organisms, changes in the synthesis of proteins have bee...

  17. Influence of osmotic stress on desiccation and irradiation tolerance of (hyper)-thermophilic microorganisms.

    PubMed

    Beblo-Vranesevic, Kristina; Galinski, Erwin A; Rachel, Reinhard; Huber, Harald; Rettberg, Petra

    2017-01-01

    This study examined the influence of prior salt adaptation on the survival rate of (hyper)-thermophilic bacteria and archaea after desiccation and UV or ionizing irradiation treatment. Survival rates after desiccation of Hydrogenothermus marinus and Archaeoglobus fulgidus increased considerably when the cells were cultivated at higher salt concentrations before drying. By doubling the concentration of NaCl, a 30 times higher survival rate of H. marinus after desiccation was observed. Under salt stress, the compatible solute diglycerol phosphate in A. fulgidus and glucosylglycerate in H. marinus accumulated in the cytoplasm. Several different compatible solutes were added as protectants to A. fulgidus and H. marinus before desiccation treatment. Some of these had similar effects as intracellularly produced compatible solutes. The survival rates of H. marinus and A. fulgidus after exposure to UV-C (254 nm) or ionizing X-ray/gamma radiation were irrespective of the salt-induced synthesis or the addition of compatible solutes.

  18. Sugar sweet springtails: on the transcriptional response of Folsomia candida (Collembola) to desiccation stress.

    PubMed

    Timmermans, M J T N; Roelofs, D; Nota, B; Ylstra, B; Holmstrup, M

    2009-11-01

    Several species of Collembola survive stressful desiccating conditions by absorbing water vapour from the environment. To obtain insight into the transcriptomic responses underlying this 'water vapour absorption' mechanism we subjected Folsomia candida (Collembola) to transcriptome profiling. We show that ecologically relevant desiccation stress leads to strong time-dependent transcriptomic changes. Exposure of F. candida to 98.2% relative humidity over an interval of 174 h resulted in a high number of gene transcripts being differentially expressed (up to 41%; P-value < 0.05). Additional Gene Ontology analyses suggest that carbohydrate transport, sugar catabolism and cuticle maintenance are biological processes involved in combating desiccation. However, many additional pathways seem to be affected; additional experiments are needed to elucidate which responses are primarily linked to desiccation resistance.

  19. Desiccation survival in an Antarctic nematode: molecular analysis using expressed sequenced tags

    PubMed Central

    Adhikari, Bishwo N; Wall, Diana H; Adams, Byron J

    2009-01-01

    Background Nematodes are the dominant soil animals in Antarctic Dry Valleys and are capable of surviving desiccation and freezing in an anhydrobiotic state. Genes induced by desiccation stress have been successfully enumerated in nematodes; however we have little knowledge of gene regulation by Antarctic nematodes which can survive multiple environmental stresses. To address this problem we investigated the genetic responses of a nematode species, Plectus murrayi, that is capable of tolerating Antarctic environmental extremes, in particular desiccation and freezing. In this study, we provide the first insight into the desiccation induced transcriptome of an Antarctic nematode through cDNA library construction and suppressive subtractive hybridization. Results We obtained 2,486 expressed sequence tags (ESTs) from 2,586 clones derived from the cDNA library of desiccated P. murrayi. The 2,486 ESTs formed 1,387 putative unique transcripts of which 523 (38%) had matches in the model-nematode Caenorhabditis elegans, 107 (7%) in nematodes other than C. elegans, 153 (11%) in non-nematode organisms and 605 (44%) had no significant match to any sequences in the current databases. The 1,387 unique transcripts were functionally classified by using Gene Ontology (GO) hierarchy and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The results indicate that the transcriptome contains a group of transcripts from diverse functional areas. The subtractive library of desiccated nematodes showed 80 transcripts differentially expressed during desiccation stress, of which 28% were metabolism related, 19% were involved in environmental information processing, 28% involved in genetic information processing and 21% were novel transcripts. Expression profiling of 14 selected genes by quantitative Real-time PCR showed 9 genes significantly up-regulated, 3 down-regulated and 2 continuously expressed in response to desiccation. Conclusion The establishment of a desiccation EST

  20. Global changes in DNA methylation in seeds and seedlings of Pyrus communis after seed desiccation and storage.

    PubMed

    Michalak, Marcin; Barciszewska, Mirosława Z; Barciszewski, Jan; Plitta, Beata P; Chmielarz, Paweł

    2013-01-01

    The effects of storage and deep desiccation on structural changes of DNA in orthodox seeds are poorly characterized. In this study we analyzed the 5-methylcytosine (m(5)C) global content of DNA isolated from seeds of common pear (Pyrus communis L.) that had been subjected to extreme desiccation, and the seedlings derived from these seeds. Germination and seedling emergence tests were applied to determine seed viability after their desiccation. In parallel, analysis of the global content of m(5)C in dried seeds and DNA of seedlings obtained from such seeds was performed with a 2D TLC method. Desiccation of fresh seeds to 5.3% moisture content (mc) resulted in a slight reduction of DNA methylation, whereas severe desiccation down to 2-3% mc increased DNA methylation. Strong desiccation of seeds resulted in the subsequent generation of seedlings of shorter height. A 1-year period of seed storage induced a significant increase in the level of DNA methylation in seeds. It is possible that alterations in the m(5)C content of DNA in strongly desiccated pear seeds reflect a reaction of desiccation-tolerant (orthodox) seeds to severe desiccation. Epigenetic changes were observed not only in severely desiccated seeds but also in 3-month old seedlings obtained from these seeds. With regard to seed storage practices, epigenetic assessment could be used by gene banks for early detection of structural changes in the DNA of stored seeds.

  1. Zero Energy Communities with Central Solar Plants using Liquid Desiccants and Local Storage: Preprint

    SciTech Connect

    Burch, J.; Woods, J.; Kozubal, E.; Boranian, A.

    2012-08-01

    The zero energy community considered here consists of tens to tens-of-thousands of residences coupled to a central solar plant that produces all the community's electrical and thermal needs. A distribution network carries fluids to meet the heating and cooling loads. Large central solar systems can significantly reduce cost of energy vs. single family systems, and they enable economical seasonal heat storage. However, the thermal distribution system is costly. Conventional district heating/cooling systems use a water/glycol solution to deliver sensible energy. Piping is sized to meet the peak instantaneous load. A new district system introduced here differs in two key ways: (i) it continuously distributes a hot liquid desiccant (LD) solution to LD-based heating and cooling equipment in each home; and (ii) it uses central and local storage of both LD and heat to reduce flow rates to meet average loads. Results for piping sizes in conventional and LD thermal communities show that the LD zero energy community reduces distribution piping diameters meeting heating loads by {approx}5X and meeting cooling loads by {approx}8X for cooling, depending on climate.

  2. Thermal Inactivation of Desiccation-Adapted Salmonella spp. in Aged Chicken Litter

    PubMed Central

    Chen, Zhao; Diao, Junshu; Dharmasena, Muthu; Ionita, Claudia; Rieck, James

    2013-01-01

    Thermal inactivation of desiccation-adapted Salmonella spp. in aged chicken litter was investigated in comparison with that in a nonadapted control to examine potential cross-tolerance of desiccation-adapted cells to heat treatment. A mixture of four Salmonella serovars was inoculated into the finished compost with 20, 30, 40, and 50% moisture contents for a 24-h desiccation adaptation. Afterwards, the compost with desiccation-adapted cells was inoculated into the aged chicken litter with the same moisture content for heat treatments at 70, 75, 80, 85, and 150°C. Recovery media were used to allow heat-injured cells to resuscitate. A 5-log reduction in the number of the desiccation-adapted cells in aged chicken litter with a 20% moisture content required >6, >6, ∼4 to 5, and ∼3 to 4 h of exposure at 70, 75, 80, and 85°C, respectively. As a comparison, a 5-log reduction in the number of nonadapted control cells in the same chicken litter was achieved within ∼1.5 to 2, ∼1 to 1.5, ∼0.5 to 1, and <0.5 h at 70, 75, 80, and 85°C, respectively. The exposure time required to obtain a 5-log reduction in the number of desiccation-adapted cells gradually became shorter as temperature and moisture content were increased. At 150°C, desiccation-adapted Salmonella cells survived for 50 min in chicken litter with a 20% moisture content, whereas control cells were detectable by enrichment for only 10 min. Our results demonstrated that the thermal resistance of Salmonella in aged chicken litter was increased significantly when the cells were adapted to desiccation. This study also validated the effectiveness of thermal processing being used for producing chicken litter free of Salmonella contamination. PMID:24014540

  3. Shoot desiccation and hydraulic failure in temperate woody angiosperms during an extreme summer drought.

    PubMed

    Nardini, Andrea; Battistuzzo, Marta; Savi, Tadeja

    2013-10-01

    Plant water status and hydraulics were measured in six woody angiosperms growing in a karstic woodland, during an extreme summer drought. Our aim was to take advantage of an unusual climatic event to identify key traits related to species-specific drought damage. The damage suffered by different species was assessed in terms of percentage of individuals showing extensive crown desiccation. Stem water potential (Ψstem ) and percent loss of hydraulic conductivity (PLC) were measured in healthy and desiccated individuals. Vulnerability to cavitation was assessed in terms of stem water potential inducing 50% PLC (Ψ50 ). Stem density (ρstem ) was also measured. Species-specific percentage of desiccated individuals was correlated to Ψ50 and ρstem . Crown desiccation was more widespread in species with less negative Ψ50 and lower ρstem . Desiccated individuals had lower Ψstem and higher PLC than healthy ones, suggesting that hydraulic failure was an important mechanism driving shoot dieback. Drought-vulnerable species showed lower safety margins (Ψstem  - Ψ50 ) than resistant ones. The Ψ50 , safety margins and ρstem values emerge as convenient traits to be used for tentative predictions of differential species-specific impact of extreme drought events on a local scale. The possibility that carbohydrate depletion was also involved in induction of desiccation symptoms is discussed.

  4. Anhydrobiosis quotient: a novel approach to evaluate stability in desiccated bacterial cells.

    PubMed

    Hernández, A; Zamora, J; González, N; Salazar, E; Sánchez, M D C

    2009-08-01

    The major objective of this study was the development of a methodology to quantify the anhydrobiotic ability of bacteria and its application to evaluate the stability of desiccated bacterial cells using the biocontrol agent Tsukamurella paurometabola C-924 as a model of anhydrobiote. Tsukamurella paurometabola C-924 was desiccated by spray-drying. Samples of desiccated cells were stored at several temperatures and viability and residual moisture were measured at different intervals of time. The term anhydrobiosis quotient (epsilon) was defined, and a scale of anhydrobiotic ability for classifying micro-organisms in terms of tolerance to desiccation was established (1 < or = epsilon < or = 15). The anhydrobiosis quotient was used to evaluate the stability of the anhydrobiotic cells. As a main result, changes in the anhydrobiosis quotient at several temperatures were fitted using a reparameterized Weibull model, which was found to be robust for the prediction of the stability at 4 degrees C. A novel methodology was developed to evaluate the desiccated state in bacteria. The anhydrobiosis quotient allows the quantitative estimation of the anhydrobiotic ability, and the mathematical model developed allows the prediction of the desiccated state of bacterial populations. The new methodology could be applied in studying the anhydrobiosis state of bacterial populations as a predictive tool for industrial and environmental microbiology.

  5. What distinguishes cyanobacteria able to revive after desiccation from those that cannot: the genome aspect.

    PubMed

    Murik, Omer; Oren, Nadav; Shotland, Yoram; Raanan, Hagai; Treves, Haim; Kedem, Isaac; Keren, Nir; Hagemann, Martin; Pade, Nadin; Kaplan, Aaron

    2017-02-01

    Filamentous cyanobacteria are the main founders and primary producers in biological desert soil crusts (BSCs) and are likely equipped to cope with one of the harshest environmental conditions on earth including daily hydration/dehydration cycles, high irradiance and extreme temperatures. Here, we resolved and report on the genome sequence of Leptolyngbya ohadii, an important constituent of the BSC. Comparative genomics identified a set of genes present in desiccation-tolerant but not in dehydration-sensitive cyanobacteria. RT qPCR analyses showed that the transcript abundance of many of them is upregulated during desiccation in L. ohadii. In addition, we identified genes where the orthologs detected in desiccation-tolerant cyanobacteria differs substantially from that found in desiccation-sensitive cells. We present two examples, treS and fbpA (encoding trehalose synthase and fructose 1,6-bisphosphate aldolase respectively) where, in addition to the orthologs present in the desiccation-sensitive strains, the resistant cyanobacteria also possess genes with different predicted structures. We show that in both cases the two orthologs are transcribed during controlled dehydration of L. ohadii and discuss the genetic basis for the acclimation of cyanobacteria to the desiccation conditions in desert BSC. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  6. Method and composition for molding low-density desiccant syntactic-foam articles

    DOEpatents

    Not Available

    1981-12-07

    These and other objects of the invention are achieved by a process for molding to size a desiccant syntactic foam article having a density of 0.2 to 0.9 g/cc and a moisture capacity of 1 to 12% by weight, comprising the steps of: charging a mold with a powdery mixture of an activated desiccant, microspheres and a thermosetting resin, the amount of the desiccant being sufficient to provide the required moisture capacity, and the amounts of the microspheres and resin being such that the microspheres/desiccant volume fraction exceeds the packing factor by an amount sufficient to substantially avoid shrinkage without causing excessively high molding pressures; covering the mold and heating the covered mold to a temperature and for an amount of time sufficient to melt the resin; and tightly closing the mold and heating the closed mold to a temperature and for an amount of time sufficient to cure the resin, and removing the resultant desiccant syntactic foam article from the mold. In a composition of matter aspect, the present invention provides desiccant syntactic foam articles, and a composition of matter for use in molding the same.

  7. Calorimetric Properties of Dehydrating Pollen (Analysis of a Desiccation-Tolerant and an Intolerant Species).

    PubMed Central

    Buitink, J.; Walters-Vertucci, C.; Hoekstra, F. A.; Leprince, O.

    1996-01-01

    The physical state of water in the desiccation-tolerant pollen of Typha latifolia L. and the desiccation-sensitive pollen of Zea mays L. was studied using differential scanning calorimetry in an attempt to further unravel the complex mechanisms of desiccation tolerance. Melting transitions of water were not observed at water content (wc) values less than 0.21 (T. latifolia) and 0.26 (Z. mays) g H2O/g dry weight. At moisture levels at which melting transitions were not observable, water properties could be characterized by changes in heat capacity. Three hydration regions could be distinguished with the defining wc values changing as a function of temperature. Shifts in baseline power resembling second-order transitions were observed in both species and were interpreted as glass-to-liquid transitions, the glass-transition temperatures being dependent on wc. Irrespective of the extent of desiccation tolerance, both pollens exhibited similar state diagrams. The viability of maize pollen at room temperature decreased gradually with the removal of the unfrozen water fraction. In maize, viability was completely lost before grains were sufficiently dried to enter into a glassy state. Apparently, the glassy state per se cannot provide desiccation tolerance. From the existing data, we conclude that, although no major differences in the physical behavior of water could be distinguished between desiccation-tolerant and -intolerant pollens, the physiological response to the loss of water varies between the two pollen types. PMID:12226289

  8. Campomanesia adamantium (Cambess.) O. Berg seed desiccation: influence on vigor and nucleic acids.

    PubMed

    Dresch, Daiane M; Masetto, Tathiana E; Scalon, Silvana P Q

    2015-01-01

    The aim of this study was to evaluate the sensitivity of Campomanesia adamantium seeds to desiccation by drying in activated silica gel (fast) and under laboratory conditions (slow). To assess the sensitivity of the seeds to desiccation, we used drying with silica gel and drying under laboratory conditions (25 °C), in order to obtain seeds with moisture content of 45, 35, 30, 25, 20, 15, 10 and 5%. The physiological potential of the seeds after desiccation was evaluated by measuring primary root protrusion, percentage of normal seedlings, germination seed index, seedling length, total seedling dry mass, electrical conductivity and DNA and RNA integrities. The C. adamantium seeds were sensitive to desiccation and to a reduction in moisture content to 21.1% or less by desiccation using silica gel, and to 17.2% or less by desiccation under laboratory conditions; impairment of the physiological potential of the seeds was observed at these low moisture content levels. The integrity of the seed genomic DNA was not affected after drying seeds in the two methods. However, drying in silica gel to 4.5% moisture content and drying under laboratory conditions to 5.4% moisture content resulted in the loss of seed RNA integrity.

  9. Distinct contractile and cytoskeletal protein patterns in the Antarctic midge are elicited by desiccation and rehydration.

    PubMed

    Li, Aiqing; Benoit, Joshua B; Lopez-Martinez, Giancarlo; Elnitsky, Michael A; Lee, Richard E; Denlinger, David L

    2009-05-01

    Desiccation presents a major challenge for the Antarctic midge, Belgica antarctica. In this study, we use proteomic profiling to evaluate protein changes in the larvae elicited by dehydration and rehydration. Larvae were desiccated at 75% relative humidity (RH) for 12 h to achieve a body water loss of 35%, approximately half of the water that can be lost before the larvae succumb to dehydration. To evaluate the rehydration response, larvae were first desiccated, then rehydrated for 6 h at 100% RH and then in water for 6 h. Controls were held continuously at 100% RH. Protein analysis was performed using 2-DE and nanoscale capillary LC/MS/MS. Twenty-four identified proteins changed in abundance in response to desiccation: 16 were more abundant and 8 were less abundant; 84% of these proteins were contractile or cytoskeletal proteins. Thirteen rehydration-regulated proteins were identified: 8 were more abundant and 5 were less abundant, and 69% of these proteins were also contractile or cytoskeletal proteins. Additional proteins responsive to desiccation and rehydration were involved in functions including stress responses, energy metabolism, protein synthesis, glucogenesis and membrane transport. We conclude that the major protein responses elicited by both desiccation and rehydration are linked to body contraction and cytoskeleton rearrangements.

  10. Impact of darker, intermediate and lighter phenotypes of body melanization on desiccation resistance in Drosophila melanogaster.

    PubMed

    Parkash, Ravi; Rajpurohit, Subhash; Ramniwas, Seema

    2009-01-01

    A possible link between melanization and desiccation resistance can be inferred if within population differences in melanization find significant correlations with desiccation resistance and its mechanistic basis i.e. rate of water loss/hr. Accordingly, darker, intermediate and lighter phenotypes of body melanization were analyzed in wild and laboratory reared Drosophila melanogaster L. (Diptera: Clyclorrapha) populations from highland and lowland sites located in close proximity at five different latitudinal locations (11.15 degrees N to 31.06 degrees N) within the Indian subcontinent. In large population samples, occurrence of significant within population variability made it possible to assort non-overlapping phenotypes of body coloration (i.e. lighter (< 25%), intermediate (30 to 40%) and darker (> 45%)) for all the populations which were further investigated for desiccation resistance and rate of water loss/hr. Significantly, higher desiccation resistance but much reduced rate of water loss/hr were observed in darker and intermediate phenotypes in all the populations. By contrast, lighter phenotypes exhibited lower desiccation tolerance but higher rate of water loss/hr. A regression analysis between traits provided similar slope values for wild and laboratory populations. For all three physiological traits, predicted trait values from multiple regression analysis as a simultaneous function of annual average temperature and relative humidity, matched the observed values. We infer that parallel changes in melanization and desiccation resistance may result from decreasing annual average temperature and relative humidity along increasing latitude as well as altitude on the Indian subcontinent.

  11. Radical formation and accumulation in vivo, in desiccation tolerant and intolerant mosses.

    PubMed

    Seel, W; Hendry, G; Atherton, N; Lee, J

    1991-01-01

    Water loss in a desiccation-sensitive moss resulted in destruction of chlorophyll, loss of carotenoids and increased lipid peroxidation, indicating the presence of damaging forms of activated oxygen. These effects were exaggerated when the plants were desiccated at high light intensities. During water-deprivation there was a build up of a free radical, detected in vivo, with a close correlation between molecular damage and radical accumulation. In contrast, in a desiccation-tolerant moss there was almost no indication of molecular (oxidative) damage. However a stable radical similar in type and concentration to that found in the desiccation-sensitive species accumulated, particularly under high irradiances. The stable radical appears to be one of the end-products of a process initiated by environmental stress, desiccation and high irradiance: its association with molecular damage depending on the degree to which the species is tolerant of desiccation. Identification of the radical in intact tissue from EPR and ENDOR studies, suggests that this is not a short-lived peroxy-radical but instead is relatively stable and carbon-centred.

  12. Desiccation tolerance of gastrointestinal nematode third-stage larvae: exploring the effects on survival and fitness.

    PubMed

    Chylinski, C; Lherminé, E; Coquille, M; Cabaret, J

    2014-08-01

    The free-living third-stage larvae (L3) of gastrointestinal nematodes are able to tolerate extreme weather conditions such as desiccation, but little is known about the consequent effects this has on their fitness. This study explored how the desiccation of Haemonchus contortus L3 larvae affected their absolute fitness by examining their success at consequent life cycle stages for a complete generation, and comparing them against a control. The stages examined include establishment, fecundity, larval development and pathogenicity. The results show that while desiccation greatly reduced the survival of the L3 prior to infection in sheep, their absolute fitness was not negatively impacted. Instead, it appears desiccation slightly augmented H. contortus fitness by triggering increases in fecundity. The study further explored what influence different gastrointestinal nematode (GIN) species (H. contortus, Trichostrongylus colubriformis, Teladorsagia circumcincta), isolates and age of L3 had on their capacity to revive following various periods of desiccation. The results showed desiccation tolerance varied as a function of each of these variables. The greatest L3 survival was found in Te. circumcincta followed by Tr. colubriformis and finally H. contortus. Significant variation was observed between individual species isolates and as a function of age. The results of this study carry important practical implications for the epidemiological understanding of gastrointestinal nematode species of economic importance.

  13. A comparative study between Solenopsis invicta and Solenopsis richteri on tolerance to heat and desiccation stresses.

    PubMed

    Chen, Jian; Rashid, Tahir; Feng, Guolei

    2014-01-01

    Solenopsis invicta and Solenopsis richteri are two very closely related invasive ant species; however, S. invicta is a much more successful invader. Physiological tolerance to abiotic stress has been hypothesized to be important to the success of an invasive species. In this study, we tested the hypothesis that S. invicta is more tolerant to heat and desiccation stress than S. richteri. The data strongly support our hypothesis. S. invicta was found to be significantly less vulnerable than S. richteri to both heat and desiccation stress. Despite S. richteri having significantly higher body water content, S. invicta was less sensitive to desiccation stress due to its significantly lower water loss rate (higher desiccation resistance). After the cuticular lipid was removed, S. invicta still had a significantly lower water loss rate than S. richteri, indicating that cuticular lipids were not the only factors accounting for difference in the desiccation resistance between these two species. Since multiple biological and/or ecological traits can contribute to the invasion success of a particular species, whether the observed difference in tolerance to heat and desiccation stresses is indeed associated with the variation in invasion success between these two species can only be confirmed by further extensive comparative study.

  14. Moss antheridia are desiccation tolerant: Rehydration dynamics influence sperm release in Bryum argenteum.

    PubMed

    Stark, Lloyd R; McLetchie, D Nicholas; Greenwood, Joshua L; Eppley, Sarah M

    2016-05-01

    Free-living sperm of mosses are known to be partially desiccation tolerant. We hypothesized that mature moss antheridia should also tolerate desiccation and that rehydration to partial turgor (prehydration) or rehydration to full turgor (rehydration) before immersion in water is required for full recovery from any damaging effects of prior desiccation. Bryum argenteum (silvery-thread moss) was grown in continuous culture for several months, produced mature perigonia (clusters of antheridia), and these were subjected to a slow rate of drying (∼36 h from full turgor to desiccation) and equilibration with 50% relative humidity. Perigonia were prehydrated (exposed to a saturated atmosphere) or rehydrated (planted upright in saturated media) for 0, 45, 90, 135, 180, and 1440 min, then immersed in sterile water. Time to first sperm mass release, number of antheridia releasing sperm masses, and the integrity of the first sperm mass released were assessed. Rehydration of dried antheridia for at least 3 h before immersion in water resulted in antheridia functioning similar to control undried antheridia. Compared with rehydration, prehydration was not effective in the recovery of antheridia from desiccation. For the first time, moss antheridia are shown to be fully desiccation tolerant at a functional level, capable of releasing fully functional sperm following a slow drying event provided the antheridia are allowed to rehydrate at least 3 h before immersion in water. © 2016 Botanical Society of America.

  15. Effect of different arrangements of sector on the performance of desiccant wheel

    NASA Astrophysics Data System (ADS)

    Yadav, Laxmikant; Yadav, Avadhesh

    2017-07-01

    In this paper, desiccant wheel is divided into three sections, namely process, regeneration and the third small section or sector (TSS). The Performance of the desiccant wheel changes when TSS is installed in different positions. So this study numerically investigated the position of TSS in the desiccant wheel by installing the TSS in four different arrangements. In the first arrangement there is only two sections i.e. process and regeneration, in the second arrangement the TSS has been installed in the process section while in the third arrangement, it has been installed in the regeneration portion of the desiccant wheel. In the fourth arrangement, the same TSS section has been installed in such a manner that half the portion of the TSS is in regeneration side and remaining half is in the process side. A comparative performance study among these arrangements of desiccant wheel reveals that for low exit humidity, TSS should be installed in the process side while for the air conditioning application (where humidity is expected to be moderate, DCOP should be high and the increase in temperature of process air should be less), TSS be installed on the regeneration side of the desiccant wheel.

  16. Extracellular superoxide production, viability and redox poise in response to desiccation in recalcitrant Castanea sativa seeds.

    PubMed

    Roach, Thomas; Beckett, Richard P; Minibayeva, Farida V; Colville, Louise; Whitaker, Claire; Chen, Hongying; Bailly, Christophe; Kranner, Ilse

    2010-01-01

    Reactive oxygen species (ROS) are implicated in seed death following dehydration in desiccation-intolerant 'recalcitrant' seeds. However, it is unknown if and how ROS are produced in the apoplast and if they play a role in stress signalling during desiccation. We studied intracellular damage and extracellular superoxide (O(2)(.-)) production upon desiccation in Castanea sativa seeds, mechanisms of O(2)(.-) production and the effect of exogenously supplied ROS. A transient increase in extracellular O(2)(.-) production by the embryonic axes preceded significant desiccation-induced viability loss. Thereafter, progressively more oxidizing intracellular conditions, as indicated by a significant shift in glutathione half-cell reduction potential, accompanied cell and axis death, coinciding with the disruption of nuclear membranes. Most hydrogen peroxide (H(2)O(2))-dependent O(2)(.-) production was found in a cell wall fraction that contained extracellular peroxidases (ECPOX) with molecular masses of approximately 50 kDa. Cinnamic acid was identified as a potential reductant required for ECPOX-mediated O(2)(.-) production. H(2)O(2), applied exogenously to mimic the transient ROS burst at the onset of desiccation, counteracted viability loss of sub-lethally desiccation-stressed seeds and of excised embryonic axes grown in tissue culture. Hence, extracellular ROS produced by embryonic axes appear to be important signalling components involved in wound response, regeneration and growth.

  17. Photosynthetic recovery following desiccation of desert green algae (Chlorophyta) and their aquatic relatives.

    PubMed

    Gray, Dennis W; Lewis, Louise A; Cardon, Zoe G

    2007-10-01

    Recent molecular data suggest that desert green algae have evolved from freshwater ancestors at least 14 times in three major classes (Chlorophyceae, Trebouxiophyceae and Charophyceae), offering a unique opportunity to study the adaptation of photosynthetic organisms to life on land in a comparative phylogenetic framework. We examined the photorecovery of phylogenetically matched desert and aquatic algae after desiccation in darkness and under illumination. Desert algae survived desiccation for at least 4 weeks when dried in darkness, and recovered high levels of photosynthetic quantum yield within 1 h of rehydration in darkness. However, when 4 weeks of desiccation was accompanied by illumination, three of six desert taxa lost their ability to recover quantum yield during rehydration in the dark. Aquatic algae, in contrast, recovered very little during dark rehydration following even just 24 h of desiccation. Re-illuminating rehydrated algae produced a nearly complete recovery of quantum yield in all desert and two of five aquatic taxa. These contrasts provide physiological evidence that desert green algae possess mechanisms for photosynthetic recovery after desiccation distinct from those in aquatic relatives, corroborating molecular evidence that they are not happenstance, short-term visitors from aquatic environments. Photosensitivity during desiccation among desert algae further suggests that they may reside in protected microsites within crusts, and species specificity of photosensitivity suggests that disturbances physically disrupting crusts could lead to shifts or losses of taxonomic diversity within these habitats.

  18. Field Demonstration of Active Desiccant Modules Designed to Integrate with Standard Unitary Rooftop Package Equipment - Final Report: Phase 3

    SciTech Connect

    Fischer, J

    2004-03-15

    This report summarizes the investigation of two active desiccant module (ADM) pilot site installations initiated in 2001. Both pilot installations were retrofits at existing facilities served by conventional heating, ventilating, and air-conditioning (HVAC) systems that had encountered frequent humidity control, indoor air quality (IAQ), and other operational problems. Each installation involved combining a SEMCO, Inc., ADM (as described in Fischer and Sand 2002) with a standard packaged rooftop unit built by the Trane Company. A direct digital control (DDC) system integral to the ADM performed the dual function of controlling the ADM/rooftop combination and facilitating data collection, trending, and remote performance monitoring. The first installation involved providing preconditioned outdoor air to replace air exhausted from the large kitchen hood and bathrooms of a Hooters restaurant located in Rome, Georgia. This facility had previously added an additional rooftop unit in an attempt to achieve occupant comfort without success. The second involved conditioning the outdoor air delivered to each room of a wing of the Mountain Creek Inn at the Callaway Gardens resort. This hotel, designed in the ''motor lodge'' format with each room opening to the outdoors, is located in southwest Georgia. Controlling the space humidity always presented a serious challenge. Uncomfortable conditions and musty odors had caused many guests to request to move to other areas within the resort. This is the first field demonstration performed by Oak Ridge National Laboratory where significant energy savings, operating cost savings, and dramatically improved indoor environmental conditions can all be claimed as the results of a retrofit desiccant equipment field installation. The ADM/rooftop combination installed at the restaurant resulted in a reduction of about 34% in the electricity used by the building's air-conditioning system. This represents a reduction of approximately 15% in

  19. Glycine betaine improves Listeria monocytogenes tolerance to desiccation on parsley leaves independent of the osmolyte transporters BetL, Gbu and OpuC.

    PubMed

    Dreux, N; Albagnac, C; Sleator, R D; Hill, C; Carlin, F; Morris, C E; Nguyen-the, C

    2008-04-01

    To investigate the effect of glycine betaine (GB) on the survival of Listeria monocytogenes on leaf surfaces under low relative humidity (RH). The addition of GB (> or = 25 mmol l(-1)) improved the survival of L. monocytogenes under low RH on parsley leaves, thus suggesting that GB can improve the tolerance of L. monocytogenes to desiccation. Ten times less GB was needed to improve L. monocytogenes survival under low RH on nonbiological surfaces compared with parsley leaves, suggesting that, on the leaf surface, L. monocytogenes may have to compete for the available GB with autochthonous bacteria and/or the plant itself. Wild type and mutants carrying deletions in the three GB uptake systems, BetL, Gbu and OpuC, behaved similarly with and without added GB on parsley leaves (P > 0.05). In addition, preaccumulation of GB, triggered by osmotic stress prior to inoculation, failed to improve survival under low RH compared with osmotic stress without GB accumulation. Exogenous GB had a protective effect on L. monocytogenes cells from desiccation during survival on parsley leaves. This effect was independent of intracellular GB accumulation by the known uptake systems. Presence of GB could improve the survival of L. monocytogenes to desiccation on leaf surfaces and nonbiological surfaces.

  20. Pluvial Drainage Patterns and Holocene Desiccation Influenced the Genetic Architecture of Relict Dace, Relictus solitarius (Teleostei: Cyprinidae)

    PubMed Central

    Houston, Derek D.; Evans, R. Paul; Shiozawa, Dennis K.

    2015-01-01

    Changing drainage patterns have played a significant role in the evolution of western North American aquatic taxa. Relict dace, Relictus solitarius, is a Great Basin endemic cyprinid with a native range that is restricted to four valleys in eastern Nevada. Relictus solitarius now occupies spring systems that are the remnants of Pleistocene-era pluvial lakes, although it may have occurred in the area for much longer. Here we use mitochondrial DNA sequence data to assess range-wide genetic diversity of R. solitarius, and to estimate divergence times to determine whether pluvial drainages played an important role in shaping intraspecific genetic diversity. Genetic diversification within R. solitarius began during the early to mid-Pleistocene, separating populations within two sets of valleys (Butte/Ruby and Goshute/Steptoe). Additional diversification in each of the two sets of valleys occurred more recently, in the mid- to late-Pleistocene. Holocene desiccation has further isolated populations, and each population sampled contains unique mtDNA haplotypes. Pluvial drainage patterns did contribute to the genetic structure observed within R. solitarius, but most of the intraspecific diversification does not appear to be associated with the Last Glacial Maximum. Holocene desiccation has also contributed to the observed genetic structure. The relict dace populations we sampled are all unique, and we recommend that future management efforts should strive to preserve as much of the genetic diversity as possible. PMID:26394395

  1. Pluvial Drainage Patterns and Holocene Desiccation Influenced the Genetic Architecture of Relict Dace, Relictus solitarius (Teleostei: Cyprinidae).

    PubMed

    Houston, Derek D; Evans, R Paul; Shiozawa, Dennis K

    2015-01-01

    Changing drainage patterns have played a significant role in the evolution of western North American aquatic taxa. Relict dace, Relictus solitarius, is a Great Basin endemic cyprinid with a native range that is restricted to four valleys in eastern Nevada. Relictus solitarius now occupies spring systems that are the remnants of Pleistocene-era pluvial lakes, although it may have occurred in the area for much longer. Here we use mitochondrial DNA sequence data to assess range-wide genetic diversity of R. solitarius, and to estimate divergence times to determine whether pluvial drainages played an important role in shaping intraspecific genetic diversity. Genetic diversification within R. solitarius began during the early to mid-Pleistocene, separating populations within two sets of valleys (Butte/Ruby and Goshute/Steptoe). Additional diversification in each of the two sets of valleys occurred more recently, in the mid- to late-Pleistocene. Holocene desiccation has further isolated populations, and each population sampled contains unique mtDNA haplotypes. Pluvial drainage patterns did contribute to the genetic structure observed within R. solitarius, but most of the intraspecific diversification does not appear to be associated with the Last Glacial Maximum. Holocene desiccation has also contributed to the observed genetic structure. The relict dace populations we sampled are all unique, and we recommend that future management efforts should strive to preserve as much of the genetic diversity as possible.

  2. Proteomics of seed development, desiccation tolerance, germination and vigor.

    PubMed

    Wang, Wei-Qing; Liu, Shu-Jun; Song, Song-Quan; Møller, Ian Max

    2015-01-01

    Proteomics, the large-scale study of the total complement of proteins in a given sample, has been applied to all aspects of seed biology mainly using model species such as Arabidopsis or important agricultural crops such as corn and rice. Proteins extracted from the sample have typically been separated and quantified by 2-dimensional polyacrylamide gel electrophoresis followed by liquid chromatography and mass spectrometry to identify the proteins in the gel spots. In this way, qualitative and quantitative changes in the proteome during seed development, desiccation tolerance, germination, dormancy release, vigor alteration and responses to environmental factors have all been studied. Many proteins or biological processes potentially important for each seed process have been highlighted by these studies, which greatly expands our knowledge of seed biology. Proteins that have been identified to be particularly important for at least two of the seed processes are involved in detoxification of reactive oxygen species, the cytoskeleton, glycolysis, protein biosynthesis, post-translational modifications, methionine metabolism, and late embryogenesis-abundant (LEA) proteins. It will be useful for molecular biologists and molecular plant breeders to identify and study genes encoding particularly interesting target proteins with the aim to improve the yield, stress tolerance or other critical properties of our crop species. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  3. [Prevention of peritoneal desiccation in acute adhesive intestinal obstruction].

    PubMed

    2014-01-01

    The research study was carried out on 30 white Wistar rats, which were divided into three groups. In the first group the effect of carboxyperitoneum on visceral peritoneum during a two hour period at a pressure of 9-10 mm Hg and after 20 minutes its further fractional replacement during 10 seconds was examined. In the second group, the study was carried out after modeling 12-hours acute adhesive intestinal obstruction. To the third group at the beginning was given a single injection of four component mixture (carboxyperitoneum gel carboxymetiltcellulose novocaine and antibiotic) into the abdominal cavity. In the first group under the condition of tension carboxyperitoneum after a day of use there were signs of desiccations of visceral peritoneum. The increase of lipid peroxidation products and decrease of antioxidant enzymes were also observed. In the second group of animals these processes were exacerbated by acute adhesive intestinal obstruction. In the third group intraabdominal use of four component disperse mixture reduced the negative organic and functional changes in visceral peritoneum and improved its protective properties.

  4. Cellular Biochemical Changes in Selaginella tamariscina (Beauv.) Spring and Sellaginella plana (Desv. ex Poir.) Heiron. as Induced by Desiccation

    PubMed Central

    Agduma, Angelo Rellama; Sese, Maribel Dionisio

    2016-01-01

    The biochemical changes in two Selaginella species namely, S. tamariscina (Beauv.) Spring and S. plana (Desv. ex Poir.) Heiron., as induced by desiccation and subsequent rehydration were explored. Plants were allowed to dehydrate naturally by withholding irrigation until shoot’s relative water content (RWC) reached <10%. After which, dehydrated plants were watered until fully rehydrated states were obtained which was about 90% RWC or more. Desiccation-tolerance characteristics were observed in S. tamariscina while desiccation-sensitivity features were seen in S. plana. Membrane integrity was maintained in S. tamariscina but not in S. plana as evidenced in the relative electrolyte leakage measurements during desiccation phase and the subsequent rehydration stage. Pigment analyses revealed conservation of some chlorophylls and carotenoids during desiccation and reaching control levels following rehydration in S. tamariscina. Very low pigment contents were found in S. plana during desiccation phase and the pigments were not recovered during rehydration attempt. Meanwhile, compatible solute determination showed rise in total sugar and proline contents of desiccated S. tamariscina only, indicating presence of biochemical protection machineries in this species and absence of such in S. plana during dehydrating conditions. These data indicate that one key element for desiccation-tolerance in lower vascular plants is the ability to protect tissues from severe damages caused by intense desiccation. PMID:27688850

  5. Phospholipase Dα1-mediated phosphatidic acid change is a key determinant of desiccation-induced viability loss in seeds.

    PubMed

    Chen, Hongying; Yu, Xiaomei; Zhang, Xudong; Yang, Lan; Huang, Xing; Zhang, Jie; Pritchard, Hugh W; Li, Weiqi

    2017-02-02

    High sensitivity of seeds to water loss is a widespread phenomenon in the world's plant species. The molecular basis of this trait is poorly understood but thought to be associated with critical changes in membrane function. We profiled membrane lipids of seeds in eight species with varying levels of desiccation tolerance and found a close association between reducing seed viability and increasing phosphatidic acid (PA). We applied hydration-dehydration cycles to Arabidopsis seeds, which are normally desiccation tolerant, to mimic the onset of desiccation sensitivity with progression towards germination and examined the role of phospholipase D (PLD) in desiccation stress-induced production of PA. We found that PLDα1 became more abundant and migrated from the cytosol to the membrane during desiccation, whereas PLDδ did not change, and that all desiccation-induced PA was derived from PLDα1 hydrolysis. When PLDα1 was suppressed, the germination level after each hydration-dehydration cycle improved significantly. We further demonstrated that PLDα1-mediated PA formation modulates desiccation sensitivity as applying its inhibitor improved seed desiccation tolerance and its suppression in protoplasts enhanced survival under dehydration. The insights provided by comparative lipidomics enable us to propose a new membrane-based model for seed desiccation stress and survival.

  6. Desiccation resistance in pre-diapause, diapause and post-diapause larvae of Choristoneura fumiferana (Lepidoptera: Tortricidae).

    PubMed

    Bauce E; Han, E

    2001-10-01

    Desiccation resistance was examined in pre-diapause, diapause and post-diapause larvae of the spruce budworm, Choristoneura fumiferana (Clemens), in terms of passive water evaporation under three desiccation conditions: freeze-drying, desiccant-drying at 2 degrees C and desiccant-drying at 18 degrees C. Diapausing second instar larvae and post-diapause non-feeding second instar larvae showed strongest desiccation resistance: a significant amount of water was retained after repeated drying under desiccating conditions, while pre-diapause first instar larvae and post-diapause feeding second instar larvae lost almost all their water content after one or two drying cycles. A hibernaculum covering had no effect on water evaporation. While dead larvae tended to lose significantly more water than their living counterparts, particularly among first instar larvae, such an impact was much weaker among diapausing second instar larvae. Desiccation resistance was lost when post-diapause second instar larvae were allowed access to water while the level of desiccation resistance was maintained or enhanced when the larvae did not have access to water. These results are discussed in the context of overwintering ecology of the species and possible mechanisms for the desiccation resistance are also discussed.

  7. PSI-driven cyclic electron flow allows intertidal macro-algae Ulva sp. (Chlorophyta) to survive in desiccated conditions.

    PubMed

    Gao, Shan; Shen, Songdong; Wang, Guangce; Niu, Jianfeng; Lin, Apeng; Pan, Guanghua

    2011-05-01

    Ulva sp. (Chlorophyta) is a representative species of the intertidal macro-algae responsible for the green tides that occurred along the shores of Qingdao in 2008 and had detrimental effects on the preparation for the 2008 Beijing Olympic Games sailing competition. In view of its significance, we have investigated the photosynthetic performance of the photosystems and the changes in photosynthetic electron transport that occur during desiccation and rehydration of Ulva sp. The PSII activity in Ulva sp. declined gradually during the course of desiccation, which was reflected by the decreased maximum quantum yield and effective quantum yield, whereas the PSI activity fluctuated significantly. In contrast, the electron transport rates of PSII approached zero at severe levels of desiccation, but the electron transport of PSI, which still operated, could be suppressed effectively by a specific inhibitor. Furthermore, the electron transport of PSI during rehydration of desiccated thalli was recovered faster than that of PSII. All these results implied that the linear electron flow was abolished in desiccated Ulva sp., whereas the cyclic PSI activity was significantly elevated, was still active at severe levels of desiccation and could be restored faster than PSII activity. Based on these results, we concluded the PSI-driven cyclic electron flow might provide desiccation tolerance and additional flexibility for the cell physiology of Ulva sp. under desiccation conditions, which might be one of the most important factors that make Ulva sp. well suited to experience daily cycles of desiccation at low tide and rehydration at high tide.

  8. Desiccation stress and tolerance in green algae: consequences for ultrastructure, physiological and molecular mechanisms

    PubMed Central

    Holzinger, Andreas; Karsten, Ulf

    2013-01-01

    Although most green algae typically occur in aquatic ecosystems, many species also live partly or permanently under aeroterrestrial conditions, where the cells are exposed to the atmosphere and hence regularly experience dehydration. The ability of algal cells to survive in an air-dried state is termed desiccation tolerance. The mechanisms involved in desiccation tolerance of green algae are still poorly understood, and hence the aim of this review is to summarize recent findings on the effects of desiccation and osmotic water loss. Starting from structural changes, physiological, and biochemical consequences of desiccation will be addressed in different green-algal lineages. The available data clearly indicate a range of strategies, which are rather different in streptophycean and non-streptophycean green algae. While members of the Trebouxiophyceae exhibit effective water loss-prevention mechanisms based on the biosynthesis and accumulation of particular organic osmolytes such as polyols, these compounds are so far not reported in representatives of the Streptophyta. In members of the Streptophyta such as Klebsormidium, the most striking observation is the appearance of cross-walls in desiccated samples, which are strongly undulating, suggesting a high degree of mechanical flexibility. This aids in maintaining structural integrity in the dried state and allows the cell to maintain turgor pressure for a prolonged period of time during the dehydration process. Physiological strategies in aeroterrestrial green algae generally include a rapid reduction of photosynthesis during desiccation, but also a rather quick recovery after rewetting, whereas aquatic species are sensitive to drying. The underlying mechanisms such as the affected molecular components of the photosynthetic machinery are poorly understood in green algae. Therefore, modern approaches based on transcriptomics, proteomics, and/or metabolomics are urgently needed to better understand the molecular

  9. Genes Associated with Desiccation and Osmotic Stress in Listeria monocytogenes as Revealed by Insertional Mutagenesis.

    PubMed

    Hingston, Patricia A; Piercey, Marta J; Truelstrup Hansen, Lisbeth

    2015-08-15

    Listeria monocytogenes is a foodborne pathogen whose survival in food processing environments may be associated with its tolerance to desiccation. To probe the molecular mechanisms used by this bacterium to adapt to desiccation stress, a transposon library of 11,700 L. monocytogenes mutants was screened, using a microplate assay, for strains displaying increased or decreased desiccation survival (43% relative humidity, 15°C) in tryptic soy broth (TSB). The desiccation phenotypes of selected mutants were subsequently assessed on food-grade stainless steel (SS) coupons in TSB plus 1% glucose (TSB-glu). Single transposon insertions in mutants exhibiting a change in desiccation survival of >0.5 log CFU/cm(2) relative to that of the wild type were determined by sequencing arbitrary PCR products. Strain morphology, motility, and osmotic stress survival (in TSB-glu plus 20% NaCl) were also analyzed. The initial screen selected 129 desiccation-sensitive (DS) and 61 desiccation-tolerant (DT) mutants, out of which secondary screening on SS confirmed 15 DT and 15 DS mutants. Among the DT mutants, seven immotile and flagellum-less strains contained transposons in genes involved in flagellum biosynthesis (fliP, flhB, flgD, flgL) and motor control (motB, fliM, fliY), while others harbored transposons in genes involved in membrane lipid biosynthesis, energy production, potassium uptake, and virulence. The genes that were interrupted in the 15 DS mutants included those involved in energy production, membrane transport, protein metabolism, lipid biosynthesis, oxidative damage control, and putative virulence. Five DT and 14 DS mutants also demonstrated similar significantly (P < 0.05) different survival relative to that of the wild type when exposed to osmotic stress, demonstrating that some genes likely have similar roles in allowing the organism to survive the two water stresses.

  10. Effect of desiccation on microleakage of five Class 5 restorative materials.

    PubMed

    Bouschlicher, M R; Vargas, M A; Denehy, G E

    1996-01-01

    Resin-modified glass ionomers, combinations of resin and glass-ionomer chemistry, have resulted in materials with longer working times and command set by visible light activation. These materials are easier to use and more resistant to early moisture contamination and fracture. A glass-ionomer or resin-modified glass-ionomer restoration may be inadvertently desiccated by isolation of the same quadrant for subsequent restorative procedures. The present study is an assessment of the effects of desiccation on microleakage of three resin-modified glass-ionomers: Vitremer, Photac-Fil, Fuji II LC; a glass-ionomer, Ketac-Fil; and a microfill resin, Silux Plus. Fifty extracted molars were prepared with class 5 preparations buccal and lingual and randomly assigned to 10 groups (n = 10). Restorations were placed according to the manufacturers' specifications and finished wet after the manufacturers' specified setting interval. All samples were thermocycled 300 cycles between 50 and 500 degrees C. Samples were stored in water at all times until the five groups to be desiccated were air dried and stored dry for 45 minutes. Desiccated groups were then rehydrated for 24 hours prior to AgNO3 staining. Teeth were sectioned mesiodistally and four buccolingual sections (0.6 mm thick) through each class 5 restoration were obtained with a Silverstone-Taylor hard tissue microtome. Each section was scored on a scale of 0-4 for microleakage, and the highest score for dye penetration was used as the score for that restoration. An increase in microleakage was observed in all desiccated groups. Three materials showed a statistically significant increase in microleakage (P < 0.05) following desiccation. Microleakage increases following a brief period of desiccation corresponding to typical treatment times indicate that clinicians need to protect previously placed restorations from undue drying during subsequent dental treatment.

  11. Desiccation stress and tolerance in green algae: consequences for ultrastructure, physiological and molecular mechanisms.

    PubMed

    Holzinger, Andreas; Karsten, Ulf

    2013-01-01

    Although most green algae typically occur in aquatic ecosystems, many species also live partly or permanently under aeroterrestrial conditions, where the cells are exposed to the atmosphere and hence regularly experience dehydration. The ability of algal cells to survive in an air-dried state is termed desiccation tolerance. The mechanisms involved in desiccation tolerance of green algae are still poorly understood, and hence the aim of this review is to summarize recent findings on the effects of desiccation and osmotic water loss. Starting from structural changes, physiological, and biochemical consequences of desiccation will be addressed in different green-algal lineages. The available data clearly indicate a range of strategies, which are rather different in streptophycean and non-streptophycean green algae. While members of the Trebouxiophyceae exhibit effective water loss-prevention mechanisms based on the biosynthesis and accumulation of particular organic osmolytes such as polyols, these compounds are so far not reported in representatives of the Streptophyta. In members of the Streptophyta such as Klebsormidium, the most striking observation is the appearance of cross-walls in desiccated samples, which are strongly undulating, suggesting a high degree of mechanical flexibility. This aids in maintaining structural integrity in the dried state and allows the cell to maintain turgor pressure for a prolonged period of time during the dehydration process. Physiological strategies in aeroterrestrial green algae generally include a rapid reduction of photosynthesis during desiccation, but also a rather quick recovery after rewetting, whereas aquatic species are sensitive to drying. The underlying mechanisms such as the affected molecular components of the photosynthetic machinery are poorly understood in green algae. Therefore, modern approaches based on transcriptomics, proteomics, and/or metabolomics are urgently needed to better understand the molecular

  12. Genes Associated with Desiccation and Osmotic Stress in Listeria monocytogenes as Revealed by Insertional Mutagenesis

    PubMed Central

    Hingston, Patricia A.; Piercey, Marta J.

    2015-01-01

    Listeria monocytogenes is a foodborne pathogen whose survival in food processing environments may be associated with its tolerance to desiccation. To probe the molecular mechanisms used by this bacterium to adapt to desiccation stress, a transposon library of 11,700 L. monocytogenes mutants was screened, using a microplate assay, for strains displaying increased or decreased desiccation survival (43% relative humidity, 15°C) in tryptic soy broth (TSB). The desiccation phenotypes of selected mutants were subsequently assessed on food-grade stainless steel (SS) coupons in TSB plus 1% glucose (TSB-glu). Single transposon insertions in mutants exhibiting a change in desiccation survival of >0.5 log CFU/cm2 relative to that of the wild type were determined by sequencing arbitrary PCR products. Strain morphology, motility, and osmotic stress survival (in TSB-glu plus 20% NaCl) were also analyzed. The initial screen selected 129 desiccation-sensitive (DS) and 61 desiccation-tolerant (DT) mutants, out of which secondary screening on SS confirmed 15 DT and 15 DS mutants. Among the DT mutants, seven immotile and flagellum-less strains contained transposons in genes involved in flagellum biosynthesis (fliP, flhB, flgD, flgL) and motor control (motB, fliM, fliY), while others harbored transposons in genes involved in membrane lipid biosynthesis, energy production, potassium uptake, and virulence. The genes that were interrupted in the 15 DS mutants included those involved in energy production, membrane transport, protein metabolism, lipid biosynthesis, oxidative damage control, and putative virulence. Five DT and 14 DS mutants also demonstrated similar significantly (P < 0.05) different survival relative to that of the wild type when exposed to osmotic stress, demonstrating that some genes likely have similar roles in allowing the organism to survive the two water stresses. PMID:26025900

  13. Response of human cells to desiccation: comparison with hyperosmotic stress response

    PubMed Central

    Huang, Zebo; Tunnacliffe, Alan

    2004-01-01

    Increasing interest in anhydrobiosis (‘life without water’) has prompted the use of mammalian cells as a model in which candidate adaptations suspected of conferring desiccation tolerance can be tested. Despite this, there is no information on whether mammalian cells are able to sense and respond to desiccation. We have therefore examined the effect of desiccation on stress signalling pathways and on genes which are proposed to be expressed in response to water loss through osmotic stress. Depending on the severity of the drying regime, human cells survived for at least 24 h. Both SAPK/JNK and p38 mitogen-activated protein kinases (MAPKs) were activated within 30 min by desiccation as well as by all osmotica tested, and therefore MAPK pathways probably play an important role in both responses. Gene induction profiles differed under the two stress conditions, however: quantitative polymerase chain reaction (PCR) experiments showed that AR, BGT-1 and SMIT, which encode proteins governing organic osmolyte accumulation, were induced by hypersalinity but not by desiccation. This was surprising, since these genes have been proposed to be regulated by ionic strength and cell volume, both of which should be significantly affected in drying cells. Further investigation demonstrated that AR, BGT-1 and SMIT expression was dependent on the nature of the osmolyte. This suggests that their regulation involves factors other than intracellular ionic strength and cell volume changes, consistent with the lack of induction by desiccation. Our results show for the first time that human cells react rapidly to desiccation by MAPK activation, and that the response partially overlaps with that to hyperosmotic stress. PMID:15146043

  14. Protein dynamics in thylakoids of the desiccation-tolerant plant Boea hygroscopica during dehydration and rehydration.

    PubMed

    Navari-Izzo, F; Quartacci, M F; Pinzino, C; Rascio, N; Vazzana, C; Sgherri, C L

    2000-11-01

    Plants of Boea hygroscopica F. Muell were dehydrated to 9% relative water content (RWC) by withholding water for 26 d, and afterward the plants were rehydrated. Leaves were taken from control plants after 7, 12, and 26 d from the beginning of dehydration, and after 6 and 48 h from rehydration. The RWC decreased by 80% during dehydration, but the leaves regained RWC with rehydration. Dehydrated plants showed lesser amounts of proteins, lipids, and chlorophyll, all of which increased following rewatering. The lipid-to-protein ratio, which decreased during dehydration, returned to control level after 48 h of rehydration. Thylakoid lipids were more unsaturated when RWC reached the value of 9%. EPR measurements of spin-labeled proteins showed the presence of three different groups of proteins with different mobility in thylakoid membranes. The rotational correlation time of groups 1 and 2 increased with dehydration and decreased upon rehydration, whereas group 3 showed little changes. Desiccation did not cause thylakoid swelling or breakage, but the membrane system assemblage showed changes in thylakoid stacking. After 48 h of rehydration the membrane system recovered completely the organization of the fully hydrated state, showing several well-defined and regularly distributed grana.

  15. Assessment of desiccants and their instructions for use in rapid diagnostic tests.

    PubMed

    Barbé, Barbara; Gillet, Philippe; Beelaert, Greet; Fransen, Katrien; Jacobs, Jan

    2012-09-13

    Malaria rapid diagnostic tests (RDTs) are protected from humidity-caused degradation by a desiccant added to the device packaging. The present study assessed malaria RDT products for the availability, type and design of desiccants and their information supplied in the instructions for use (IFU). Criteria were based on recommendations of the World Health Organization (WHO), the European Community (CE) and own observations. Silica gel sachets were defined as self-indicating (all beads coated with a humidity indicator that changes colour upon saturation), partial-indicating (part of beads coated) and non-indicating (none of the beads coated). Indicating silica gel sachets were individually assessed for humidity saturation and (in case of partial-indicating silica gels) for the presence of indicating beads. Fifty malaria RDT products from 25 manufacturers were assessed, 14 (28%) products were listed by the "Global Fund Quality Assurance Policy" and 31 (62%) were CE-marked. All but one product contained a desiccant, mostly (47/50, 94%) silica gel. Twenty (40%) RDT products (one with no desiccant and 19 with non-indicating desiccant) did not meet the WHO guidelines recommending indicating desiccant. All RDT products with self- or partial-indicating silica gel (n = 22 and 8 respectively) contained the toxic cobalt dichloride as humidity indicator. Colour change indicating humidity saturation was observed for 8/16 RDT products, at a median incidence of 0.8% (range 0.05%-4.6%) of sachets inspected. In all RDTs with partial-indicating silica gel, sachets with no colour indicating beads were found (median proportion 13.5% (0.6%-17.8%) per product) and additional light was needed to assess the humidity colour. Less than half (14/30, 47%) IFUs of RDT products with indicating desiccants mentioned to check the humidity saturation before using the test. Information on properties, safety hazards and disposal of the desiccant was not included in any of the IFUs. There were no

  16. The effect of desiccation on the emission of volatile bromocarbons from two common temperate macroalgae

    NASA Astrophysics Data System (ADS)

    Leedham Elvidge, E. C.; Phang, S.-M.; Sturges, W. T.; Malin, G.

    2014-07-01

    Exposure of intertidal macroalgae during low tide has been linked to the emission of a variety of atmospherically-important trace gases into the coastal atmosphere. In recent years, several studies have investigated the role of inorganic iodine and organoiodides as antioxidants and their emission during exposure to combat oxidative stress, yet the role of organic bromine species during desiccation is less well understood. In this study the emission of dibromomethane (CH2Br2) and bromoform (CHBr3) during exposure and desiccation of two common temperate macroalgae, Fucus vesiculosus and Ulva intestinalis, is reported. Determination of the impact exposure may have on algal physiological processes is difficult as intertidal species are adapted to desiccation and may undergo varying degrees of desiccation before their physiology is affected. For this reason we include comparisons between photosynthetic capacity (Fv / Fm) and halocarbon emissions during a desiccation time series. In addition, the role of rewetting with freshwater to simulate exposure to rain was also investigated. Our results show that an immediate flux of bromocarbons occurs upon exposure, followed by a decline in bromocarbon emissions. We suggest that this immediate bromocarbon pulse may be linked to volatilisation or emissions of existing bromocarbon stores from the algal surface rather than the production of bromocarbons as an antioxidant response.

  17. The effect of desiccation on the emission of volatile bromocarbons from two common temperate macroalgae

    NASA Astrophysics Data System (ADS)

    Leedham Elvidge, E. C.; Phang, S.-M.; Sturges, W. T.; Malin, G.

    2015-01-01

    Exposure of intertidal macroalgae during low tide has been linked to the emission of a variety of atmospherically-important trace gases into the coastal atmosphere. In recent years, several studies have investigated the role of inorganic iodine and organoiodides as antioxidants and their emission during exposure to combat oxidative stress, yet the role of organic bromine species during desiccation is less well understood. In this study the emission of dibromomethane (CH2Br2) and bromoform (CHBr3) during exposure and desiccation of two common temperate macroalgae, Fucus vesiculosus and Ulva intestinalis, is reported. Determination of the impact exposure may have on algal physiological processes is difficult as intertidal species are adapted to desiccation and may undergo varying degrees of desiccation before their physiology is affected. For this reason we include comparisons between photosynthetic capacity (Fv/Fm) and halocarbon emissions during a desiccation time series. In addition, the role of rewetting with freshwater to simulate exposure to rain was also investigated. Our results show that an immediate flux of bromocarbons occurs upon exposure, followed by a decline in bromocarbon emissions. We suggest that this immediate bromocarbon pulse may be linked to volatilisation or emissions of existing bromocarbon stores from the algal surface rather than the production of bromocarbons as an antioxidant response.

  18. Molecular approaches for improving desiccation tolerance: insights from the brine shrimp Artemia franciscana.

    PubMed

    Hand, Steven C; Menze, Michael A

    2015-08-01

    We have evaluated the endogenous expression and molecular properties of selected Group 3 LEA proteins from Artemia franciscana , and the capacity of selected Groups 1 and 3 proteins transfected into various desiccation-sensitive cell lines to improve tolerance to drying. Organisms inhabiting both aquatic and terrestrial ecosystems frequently are confronted with the problem of water loss for multiple reasons--exposure to hypersalinity, evaporative water loss, and restriction of intracellular water due to freezing of extracellular fluids. Seasonal desiccation can become severe and lead to the production of tolerant propagules and entry into the state of anhydrobiosis at various stages of the life cycle. Such is the case for gastrula-stage embryos of the brine shrimp, Artemia franciscana. Physiological and biochemical responses to desiccation are central for survival and are multifaceted. This review will evaluate the impact of multiple late embryogenesis abundant proteins originating from A. franciscana, together with the non-reducing sugar trehalose, on prevention of desiccation damage at multiple levels of biological organization. Survivorship of desiccation-sensitive cells during water stress can be improved by use of the above protective agents, coupled to metabolic preconditioning and rapid cell drying. However, obtaining long-term stability of cells in the dried state at room temperature has not been accomplished and will require continued efforts on both the physicochemical and biological fronts.

  19. Surviving metabolic arrest: photosynthesis during desiccation and rehydration in resurrection plants.

    PubMed

    Challabathula, Dinakar; Puthur, Jos T; Bartels, Dorothea

    2016-02-01

    Photosynthesis is the key process that is affected by dehydration in plants. Desiccation-tolerant resurrection plants can survive conditions of very low relative water content. During desiccation, photosynthesis is not operational, but is recovered within a short period after rehydration. While homoiochlorophyllous resurrection plants retain their photosynthetic apparatus during desiccation, poikilochlorophyllous resurrection species dismantle chloroplasts and degrade chlorophyll but resynthesize them again during rehydration. Dismantling the chloroplasts avoids the photooxidative stress in poikilochlorophyllous resurrection plants, whereas it is minimized in homoiochlorophyllous plants through the synthesis of antioxidant enzymes and protective proteins or metabolites. Although the cellular protection mechanisms in both of these species vary, these mechanisms protect cells from desiccation-induced damage and restore photosynthesis upon rehydration. Several of the proteins synthesized during dehydration are localized in chloroplasts and are believed to play major roles in the protection of photosynthetic structures and in recovery in resurrection species. This review focuses on the strategies of resurrection plants in terms of how they protect their photosynthetic apparatus from oxidative stress during desiccation without membrane damage and with full recovery during rehydration. We review the role of the dehydration-induced protection mechanisms in chloroplasts and how photosynthesis is restored during rehydration.

  20. Intraspecific variation in desiccation survival time of Aedes aegypti (L.) mosquito eggs of Australian origin.

    PubMed

    Faull, Katherine J; Williams, Craig R

    2015-12-01

    Aedes aegypti (L.) mosquitoes preferentially oviposit in natural and artificial receptacles where their eggs are able to withstand drying as water levels fluctuate. Desiccation-resistant eggs also increase the potential for establishment in non-native habitats while providing logistical impediments to control programs. Viability and mean survival times of eggs stored under three dryness conditions for up to 367 days were investigated among three field-derived colonies of Australian Ae. aegypti to understand variation in desiccation survival. Further investigations compared egg survival between an established colony and its wild counterpart. Our results confirmed that Ae. aegypti eggs can withstand desiccation for extended periods of time with approximately 2-15% egg viability recorded after one year and viability remaining above 88% under all conditions through 56 days. Intraspecific variations in egg survival times were recorded, suggesting local adaptation while each of the colonies demonstrated a consistent preference for higher humidity. Egg volume varied between the populations, suggesti