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Journal articles on the topic 'Gaseous diffusion plants'
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1
Philippe, Sébastien, and Alexander Glaser. "Nuclear Archaeology for Gaseous Diffusion Enrichment Plants." Science & Global Security 22, no. 1 (January 2014): 27–49. http://dx.doi.org/10.1080/08929882.2014.871881.
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Guseva Canu, Irina, Ségolène Faust, Eric Knieczak, Michel Carles, Eric Samson, and Dominique Laurier. "Estimating historic exposures at the European Gaseous Diffusion plants." International Journal of Hygiene and Environmental Health 216, no. 4 (July 2013): 499–507. http://dx.doi.org/10.1016/j.ijheh.2012.07.002.
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Schiwinsky, Klaus, Wolfgang Grosse, and Dietrich Woermann. "Convective Gas Flow in Plant Aeration and Graham's Law of Diffusion." Zeitschrift für Naturforschung C 51, no. 9-10 (October 1, 1996): 681–90. http://dx.doi.org/10.1515/znc-1996-9-1013.
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Experiments with porous ceramic membranes and leaves of Nymphaea alba L. are described which demonstrate that the counter diffusion of gaseous components of different molar mass governed by Graham’s law of diffusion (not to be confused with Graham’s law of effusion) has to be taken into account to understand the exchange processes of gases between leaves of aquatic and amphibic plants and the outer atmosphere. The experiments are carried out under conditions under which the ratio of the maximum pore size r of the ceramic material to the mean free path length λ. of the molecules in air has a value of the order of λ/r ≈ 1
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Socolof, Maria Leet, Richard E. Saylor, and Lance N. McCold. "Replacement of chlorofluorocarbons at the DOE gaseous diffusion plants: An assessment of global impacts." Environmental Impact Assessment Review 17, no. 1 (January 1997): 39–51. http://dx.doi.org/10.1016/s0195-9255(96)00075-3.
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BINGHAM, E., K. RINGEN, J. DEMENT, W. CAMERON, W. MCGOWAN, L. WELCH, and P. QUINN. "Frequency and Quality of Radiation Monitoring of Construction Workers at Two Gaseous Diffusion Plants." Annals of the New York Academy of Sciences 1076, no. 1 (September 1, 2006): 394–404. http://dx.doi.org/10.1196/annals.1371.061.
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Nishida, Konosuke, Toshihumi Kobashi, Masahiro Osako, Kenichi Shishida, Takashi Higuchi, and Takaya Higuchi. "Studies on the elimination of gaseous pollutants by plants. Sorption model and diffusion coefficients." International Journal of Environmental Studies 42, no. 1 (September 1992): 17–26. http://dx.doi.org/10.1080/00207239208710776.
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Zhang, Hui, and Frank N. von Hippel. "Using commercial imaging satellites to detect the operation of plutonium‐production reactors and gaseous‐diffusion plants." Science & Global Security 8, no. 3 (January 2000): 261–313. http://dx.doi.org/10.1080/08929880008426479.
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Théroux-Rancourt, Guillaume, Adam B. Roddy, J. Mason Earles, Matthew E. Gilbert, Maciej A. Zwieniecki, C. Kevin Boyce, Danny Tholen, Andrew J. McElrone, Kevin A. Simonin, and Craig R. Brodersen. "Maximum CO 2 diffusion inside leaves is limited by the scaling of cell size and genome size." Proceedings of the Royal Society B: Biological Sciences 288, no. 1945 (February 24, 2021): 20203145. http://dx.doi.org/10.1098/rspb.2020.3145.
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Maintaining high rates of photosynthesis in leaves requires efficient movement of CO 2 from the atmosphere to the mesophyll cells inside the leaf where CO 2 is converted into sugar. CO 2 diffusion inside the leaf depends directly on the structure of the mesophyll cells and their surrounding airspace, which have been difficult to characterize because of their inherently three-dimensional organization. Yet faster CO 2 diffusion inside the leaf was probably critical in elevating rates of photosynthesis that occurred among angiosperm lineages. Here we characterize the three-dimensional surface area of the leaf mesophyll across vascular plants. We show that genome size determines the sizes and packing densities of cells in all leaf tissues and that smaller cells enable more mesophyll surface area to be packed into the leaf volume, facilitating higher CO 2 diffusion. Measurements and modelling revealed that the spongy mesophyll layer better facilitates gaseous phase diffusion while the palisade mesophyll layer better facilitates liquid-phase diffusion. Our results demonstrate that genome downsizing among the angiosperms was critical to restructuring the entire pathway of CO 2 diffusion into and through the leaf, maintaining high rates of CO 2 supply to the leaf mesophyll despite declining atmospheric CO 2 levels during the Cretaceous.
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Jeon, Ji-Won, Young-Ji Han, Seung-Hwan Cha, Pyung-Rae Kim, Young-Hee Kim, Hyuk Kim, Gwang-Seol Seok, and Seam Noh. "Application of the Passive Sampler Developed for Atmospheric Mercury and Its Limitation." Atmosphere 10, no. 11 (November 5, 2019): 678. http://dx.doi.org/10.3390/atmos10110678.
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In this study, a passive sampler for gaseous elemental mercury (GEM) was developed and applied to field monitoring. Three Radiello® diffusive bodies with gold-coated beads as Hg adsorbent were installed in an acrylic external shield. Hg uptake mass linearly increased as the deployment time increased until 8 weeks with an average gaseous Hg concentration of 2 ng m−3. The average of the experimental sampling rate (SR) was 0.083 m3 day−1 and showed a good correlation with theoretical SRs, indicating that a major adsorption mechanism was molecular diffusion. Nonetheless, the experimental SR was approximately 33% lower than the modeled SR, which could be associated with inefficient uptake of GEM in the sampler or uncertainty in constraining model parameters. It was shown that the experimental SR was statistically affected by temperature and wind speed but the calibration equation for the SR by meteorological variables should be obtained with a wider range of variables in further investigation. When the uptake rates were compared to the active Hg measurements, the correlation was not significant because the passive sampler was not sufficiently adept at detecting a small difference in the GEM concentration of from 1.8 to 2.0 ng m−3. However, the results for spatial Hg concentrations measured near cement plants in Korea suggest a possible application in field monitoring. Future research is needed to fully employ the developed passive sampler in quantitative assessment of Hg concentrations.
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Clough, T. J., R. R. Sherlock, K. C. Cameron, R. J. Stevens, R. J. Laughlin, and C. Müller. "Resolution of the 15N balance enigma?" Soil Research 39, no. 6 (2001): 1419. http://dx.doi.org/10.1071/sr00092.
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The enigma of soil nitrogen balance sheets has been discussed for over 40 years. Many reasons have been considered for the incomplete recovery of 15N applied to soils, including sampling uncertainty, gaseous N losses from plants, and entrapment of soil gases. The entrapment of soil gases has been well documented for rice paddy and marshy soils but little or no work appears to have been done to determine entrapment in drained pasture soils. In this study 15N-labelled nitrate was applied to a soil core in a gas-tight glovebox. Water was applied, inducing drainage, which was immediately collected. Dinitrogen and N2O were determined in the flux through the soil surface, and in the gases released into the glovebox as a result of irrigation or physical destruction of the core. Other components of the N balance were also measured, including soil inorganic-N and organic-N. Quantitative recovery of the applied 15N was achieved when the experiment was terminated 484 h after the 15N-labelled material was applied. Nearly 23% of the 15N was recovered in the glovebox atmosphere as N2 and N2O due to diffusion from the base of the soil core, convective flow after irrigation, and destructive soil sampling. This 15N would normally be unaccounted for using the sampling methodology typically employed in 15N recovery experiments.
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Mondal, M. K. "Mathematical Modeling of Wet Magnesia Flue Gas Desulphurization Process." Modelling and Simulation in Engineering 2008 (2008): 1–6. http://dx.doi.org/10.1155/2008/871479.
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Desulphurization of flue gases from various chemical industries in a techno-econo-enviro manner is a demanding technology. The concentrations of sulphur dioxide in and around these plants overshoot the danger point. In recent years, the process analysis of chemical absorption in a slurry has become important in rational design and development of wet scrubbing processes for the removal ofSO2from flue gases. The elementary steps encountered in wet scrubbing by slurries are diffusion and reaction of gaseous species and solid dissolution in liquid film. In the present work, the process of the absorption of sulphur dioxide into wet magnesia slurry was theoretically analyzed according to the two-reaction plane model incorporating the solid dissolution promoted by the reactions with absorbed sulphur dioxide in the liquid film. A model based on Fick's second law has been developed to calculate enhancement factor for absorption of Sulphur dioxide intoMg(OH)2slurry. The concentration of accumulated species in the bulk of the liquid phase (sulphite ions for this case) which substantially control the absorption rates was included in the model for the prediction of theoretical enhancement factor. The values of theoretical enhancement factors obtained from model were compared with experimental enhancement factors available in literature. The model values of enhancement factors agreed well with the values of experimental enhancement factor available in literature.
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Zhu, J., T. Wang, J. Bieser, and V. Matthias. "Source attribution and process analysis for atmospheric mercury in East China simulated by CMAQ-Hg." Atmospheric Chemistry and Physics Discussions 15, no. 7 (April 9, 2015): 10389–424. http://dx.doi.org/10.5194/acpd-15-10389-2015.
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Abstract. The contribution from different emission sources and atmospheric processes to gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), particulate bound mercury (PBM) and mercury deposition in East China were quantified using the Community Multi-scale Air Quality (CMAQ-Hg) modeling system run with nested grid resolution of 27 km. Natural source (NAT) and six categories of anthropogenic mercury sources (ANTH) including cement production (CEM), domestic life (DOM), industrial boilers (IND), metal production (MET), coal-fired power plants (PP) and traffic (TRA) were considered for source apportionment. NAT was responsible for 36.6% of annual averaged GEM concentration which was regard as the most important source for GEM in spite of obvious seasonal variation. Among ANTH, the influence of MET and PP on GEM were most evident especially in winter. ANTH dominated the variations of GOM and PBM concentration with a contribution of 86.7 and 79.1% respectively. Among ANTH, IND was the largest contributor for GOM (57.5%) and PBM (34.4%) so that most mercury deposition came from IND. The effect of mercury emitted from out of China was indicated by > 30% contribution to GEM concentration and wet deposition. The contribution from nine processes consisting of emissions (EMIS), gas-phase chemical production/loss (CHEM), horizontal advection (HADV), vertical advection (ZADV), horizontal advection (HDIF), vertical diffusion (VDIF), dry deposition (DDEP), cloud processes (CLDS) and aerosol processes (AERO) were calculated for processes analysis with their comparison in urban and non-urban regions of Yangtze River Delta (YRD). EMIS and VDIF affected surface GEM and PBM concentration most and tended to compensate each other all the time in both urban and non-urban areas. However, DDEP was the most important removal process for GOM with 7.3 and 2.9 ng m−3 reduced in the surface of urban and non-urban areas respectively in a whole day. Diurnal profile variation of processes revealed the transportation of GOM from urban area to non-urban area and the importance of CHEM/AERO in higher altitudes which caused diffusion of GOM downwards to non-urban area partly. Most of the anthropogenic mercury transported and diffused away from urban area by HADV and VDIF and made gain of mercury in non-urban areas by HADV. Natural emissions only influenced CHEM and AERO more significantly than anthropogenic. Local emission in the YRD contributed 8.5% more to GEM and ~ 30% more to GOM and PBM in urban areas compared to non-urban areas.
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Zhu, J., T. Wang, J. Bieser, and V. Matthias. "Source attribution and process analysis for atmospheric mercury in eastern China simulated by CMAQ-Hg." Atmospheric Chemistry and Physics 15, no. 15 (August 10, 2015): 8767–79. http://dx.doi.org/10.5194/acp-15-8767-2015.
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Abstract. The contribution from different emission sources and atmospheric processes to gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), particulate bound mercury (PBM) and mercury deposition in eastern China were quantified using the Community Multi-scale Air Quality (CMAQ-Hg) modeling system run with a nested domain. Natural sources (NAT) and six categories of anthropogenic mercury sources (ANTH) including cement production (CEM), domestic life (DOM), industrial boilers (IND), metal production (MET), coal-fired power plants (PP) and traffic (TRA) were considered for source apportionment. NAT were responsible for 36.6 % of annual averaged GEM concentration, which was regarded as the most important source for GEM in spite of obvious seasonal variation. Among ANTH, the influence of MET and PP on GEM were most evident especially in winter. ANTH dominated the variations of GOM and PBM concentrations with contributions of 86.7 and 79.1 %, respectively. Among ANTH, IND were the largest contributor for GOM (57.5 %) and PBM (34.4 %) so that most mercury deposition came from IND. The effect of mercury emitted from out of China was indicated by a > 30 % contribution to GEM concentration and wet deposition. The contributions from nine processes – consisting of emissions (EMIS), gas-phase chemical production/loss (CHEM), horizontal advection (HADV), vertical advection (ZADV), horizontal advection (HDIF), vertical diffusion (VDIF), dry deposition (DDEP), cloud processes (CLDS) and aerosol processes (AERO) – were calculated for process analysis with their comparison in urban and non-urban regions of the Yangtze River delta (YRD). EMIS and VDIF affected surface GEM and PBM concentrations most and tended to compensate each other all the time in both urban and non-urban areas. However, DDEP was the most important removal process for GOM with 7.3 and 2.9 ng m−3 reduced in the surface of urban and non-urban areas, respectively, in 1 day. The diurnal profile variation of processes revealed the transportation of GOM from urban area to non-urban areas and the importance of CHEM/AERO in higher altitudes which partly caused diffusion of GOM downwards to non-urban areas. Most of the anthropogenic mercury was transported and diffused away from urban areas by HADV and VDIF and increased mercury concentrations in non-urban areas by HADV. Natural emissions only influenced CHEM and AERO more significantly than anthropogenic. Local emissions in the YRD contributed 8.5 % more to GEM and ~ 30 % more to GOM and PBM in urban areas compared to non-urban areas.
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Duranceau, Muriel, Jaleh Ghashghaie, and Enrico Brugnoli. "Carbon isotope discrimination during photosynthesis and dark respiration in intact leaves of Nicotiana sylvestris: comparisons between wild type and mitochondrial mutant plants." Functional Plant Biology 28, no. 1 (2001): 65. http://dx.doi.org/10.1071/pp00068.
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Leaf gas-exchange, carbon isotope discrimination (D) during photosynthesis, carbon isotope composition (d13 C) of leaf dry matter, leaf carbohydrates and ‰ d13 C of dark respiratory CO 2 were measured both in wild type (WT) and in a respiratory mutant of Nicotiana sylvestris Spegazz. plants. The mutation caused a dysfunction of complex I of the respiratory chain which has been described in detail by Gutierres et al. 1997, PNAS, 94, 3436. The aim of this work was to verify if this mutation has an influence on carbon isotope discrimination during photosynthesis and dark respiration. Another objective was to study the possible effect of respiratory fractionation on the isotopic composition of dry matter and on the discrimination measured on-line, in comparison with the expected D based on the model developed by Farquhar et al. 1982, AJPP, 9, 121. On-line D measured on leaves during photosynthesis was lower in the mutants (16.5‰ 0.9) than in the WT (20.1‰ 0.6), mainly due to lower conductance to CO 2 diffusion (both across stomatal pores and in the gaseous and liquid phases across the mesophyll) in the mutants. No statistically significant difference in the fractionation during dark respiration was observed between WT and mutant plants. However, respiratory CO 2 was enriched in 13 C compared to sucrose and glucose by about 2–3 and 2.5–4‰, respectively. The enrichment in 13 C (about 2‰) observed in leaf metabolites and leaf organic matter in the mutants compared to the WT can be explained by differences in .during photosynthesis. However, the fractionation in the whole-leaf organic matter of both WT and mutant plants was higher (more depleted in 13C) than expected based on the .values obtained with on-line measurements during photosynthesis. The observed discrimination during dark respiration, releasing 13 C-enriched CO 2 , may partly explain the higher fractionation in the remaining leaf organic matter compared to the overall discrimination during photosynthesis, as measured on-line.
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Bakhchevnikov, O. N., and A. V. Braginets. "ПРИМЕНЕНИЕ ОЗОНА ДЛЯ ОБЕЗЗАРАЖИВАНИЯ КОРМОВОГО СЫРЬЯ (ОБЗОР)." TAURIDA HERALD OF THE AGRARIAN SCIENCES 2(26) (August 3, 2020): 41–61. http://dx.doi.org/10.33952/2542-0720-2021-2-26-41-61.
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The issues of disinfection of raw materials for feed production by the method of ozonation were considered in the review. Ozonation could be a universal method of plant raw materials disinfection in agricultural enterprises and formula-feed plants. A research objective is to generalize and analyze scientific publications devoted to the feed raw materials disinfection by ozone, as well as to clarify information on rational parameters of such type of disinfection and its effect on the quality of feed. Moreover, we assessed the possibility of further use of ozonation in the production process. For the research of the subject, we searched and selected scientific articles published from 2005 to 2020 and conducted a systematic review. Ozonation was found to be an effective method for feed decontamination that destroys pathogenic bacteria and fungi. This method is also used to detoxify feed and control pest insects. Ozonation is not yet widely used in agricultural production and formula-feed industry to ensure the biological safety of feed raw materials. Additional research aimed at improving the efficiency of ozonation by standardization of parameters for its implementation to ensure the broadest possible application of the method under study should be carried out. The development of technical solutions that increase the diffusion of gaseous ozone will significantly increase the safety and preservation of raw materials. Rational values of ozone concentration, processing time, etc., for each type of raw materials, as well as for mycotoxins, pesticides, microorganisms and insects, including different stages of their growth and development, should be defined. Special attention should be also focused on the study of the complex efficiency of ozonation concerning several pathogenic factors.
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Richter, Jörg, Kurt-Christian Kersebaum, and Ingo Willenbockel. "Gaseous Diffusion Reflecting Soil Structure." Zeitschrift für Pflanzenernährung und Bodenkunde 154, no. 1 (1991): 13–19. http://dx.doi.org/10.1002/jpln.19911540105.
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Dartois, E., B. Schmitt, D. Deboffle, and M. Bouzit. "Low temperature CH4 and CO2 clathrate hydrate near to mid-IR spectra." Proceedings of the International Astronomical Union 5, S263 (August 2009): 33–36. http://dx.doi.org/10.1017/s1743921310001456.
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AbstractThe physical behaviour of methane and carbon dioxide clathrate hydrates, specific crystallographic ice crystals are of major importance for the earth and may control the stability of gases in many astrophysical bodies such as the planets, comets and possibly interstellar grains. Such models claim they provide an alternative trapping mechanism modifying the absolute and relative composition of icy bodies and can be at the source of late time injection of gaseous species in planetary atmospheres. However, there is a clear need to detect them directly. We provide in this study the laboratory recorded signatures of clathrate hydrates in the near to mid-infrared for astrophysical remote detection. These laboratory experiments will in a near future allow to follow the kinetic formation by diffusion in dedicated experiments, another important step to implement, to understand and model their possible presence in space.
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Dakora, FD, and CA Atkins. "Diffusion of Oxygen in Relation to Structure and Function in Legume Root Nodules." Functional Plant Biology 16, no. 1 (1989): 131. http://dx.doi.org/10.1071/pp9890131.
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Although substantial rates of oxidative phosphorylation by bacteroids of Rhizobium are required to support sustained N2 fixation in legume nodules, the enzyme nitrogenase is extremely sensitive to oxygen. This apparent paradox indicates that nodules must exercise effective control over internal oxygen concentration. Structural features including lenticel development, the thickness and arrangement of cells and air spaces in the inner and outer cortex, the presence or completeness of the common endodermis as well as the distribution of infected cells, uninfected cells and air spaces in the nodule medulla are important to gaseous ventilation of the organ. Among these, the organisation of cells and water / gas- containing extracellular voids in the inner cortex bounding the infected medulla zone are critical components to overall diffusive resistance. These elements also appear to provide the means for the oper- ation of a reversible variable diffusion barrier to control gas movement. Inhibition of nodule functioning by a widely diverse range of factors, e. g. restricted H2O or photosynthate supply, exposure to acetylene or combined N, appears to be mediated through increased diffusion resistance.
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Masset, Frédéric S. "Planetary migration in gaseous protoplanetary disks." Proceedings of the International Astronomical Union 3, S249 (October 2007): 331–46. http://dx.doi.org/10.1017/s1743921308016797.
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AbstractTides come from the fact that different parts of a system do not fall in exactly the same way in a non-uniform gravity field. In the case of a protoplanetary disk perturbed by an orbiting, prograde protoplanet, the protoplanet tides raise a wake in the disk which causes the orbital elements of the planet to change over time. The most spectacular result of this process is a change in the protoplanet's semi-major axis, which can decrease by orders of magnitude on timescales shorter than the disk lifetime. This drift in the semi-major axis is called planetary migration. In a first part, we describe how the planet and disk exchange angular momentum and energy at the Lindblad and corotation resonances. Next we review the various types of planetary migration that have so far been contemplated: type I migration, which corresponds to low-mass planets (less than a few Earth masses) triggering a linear disk response; type II migration, which corresponds to massive planets (typically at least one Jupiter mass) that open up a gap in the disk; “runaway” or type III migration, which corresponds to sub-giant planets that orbit in massive disks; and stochastic or diffusive migration, which is the migration mode of low- or intermediate-mass planets embedded in turbulent disks. Lastly, we present some recent results in the field of planetary migration.
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Tanaka, Yuki A., Takeru K. Suzuki, and Shu-ichiro Inutsuka. "ATMOSPHERIC ESCAPE BY MAGNETICALLY DRIVEN WIND FROM GASEOUS PLANETS. II. EFFECTS OF MAGNETIC DIFFUSION." Astrophysical Journal 809, no. 2 (August 13, 2015): 125. http://dx.doi.org/10.1088/0004-637x/809/2/125.
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Hwa Yoo, Mung, Youn Jung Kwon, Ki-Cheol Son, and Stanley J. Kays. "Efficacy of Indoor Plants for the Removal of Single and Mixed Volatile Organic Pollutants and Physiological Effects of the Volatiles on the Plants." Journal of the American Society for Horticultural Science 131, no. 4 (July 2006): 452–58. http://dx.doi.org/10.21273/jashs.131.4.452.
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Foliage plants of Hedera helix L. (english ivy), Spathiphyllum wallisii Regal (peace lily), Syngonium podophyllum Schott. (nephthytis), and Cissus rhombifolia Vahl. (grape ivy) were evaluated for their ability to remove two indoor volatile organic air pollutants, benzene and toluene. Removal was monitored when the aerial portion of plants was exposed singly to 1 μL·L-1 or to 0.5 μL·L-1 of each gas in a closed environment over 6-hour periods during the day and the night. Selected physiological processes were assessed before and immediately after treatment to determine the effect of the gases on the plants. The effectiveness of plants in the removal of air pollutant(s) varied with species, time of day, and whether the gases were present singly or as a mixture. When exposed to a single gas, S. wallisii, S. podophyllum, and H. helix displayed higher removal efficiencies (ng·m-3·h-1·cm-2 leaf area) of either gas than C. rhombifolia during the day. The efficiency of removal changed when both gases were present; H. helix was substantially more effective in the removal of either benzene or toluene than the other species, with the removal of toluene more than double that of benzene. When exposed singly, the removal of both compounds was generally higher during the day than during the night for all species; however, when present simultaneously, H. helix removal efficiency during the night was similar to the day indicating that stomatal diffusion for english ivy was not a major factor. The results indicated an interaction between gases in uptake by the plant, the presence of different avenues for uptake, and the response of a single gas was not necessarily indicative of the response when other gases are present. Changes in the rates of photosynthesis, stomatal conductance, and transpiration before and after exposure indicated that the volatiles adversely affected the plants and the effects were not consistent across species and gases. Deleterious effects of volatile pollutants on indoor plants may be critical in their efficacy in improving indoor air quality and warrant further study.
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Atkins, Craig A., Stephen Hunt, and David B. Layzell. "Gaseous diffusive properties of soybean nodules cultured with non-ambient pO2." Physiologia Plantarum 87, no. 1 (January 1993): 89–95. http://dx.doi.org/10.1111/j.1399-3054.1993.tb08795.x.
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Barbosa, Vera L., and Richard M. Stuetz. "Performance of activated sludge diffusion for biological treatment of hydrogen sulphide gas emissions." Water Science and Technology 68, no. 9 (October 19, 2013): 1932–39. http://dx.doi.org/10.2166/wst.2013.444.
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Odours from wastewater treatment plants are comprised of a mixture of various gases with hydrogen sulphide (H2S) often being the dominant constituent. Activated sludge diffusion (ASD) as a biotreatment system for odour abatement has been conducted for over 30 years but has limited broad application due to disagreement in the literature regarding the effect that ASD may have on wastewater treatment performance. The effects of continuous H2S diffusion at 25 ppmv, with weekly peaks of approximately 100 ppmv, on H2S removal efficiency and wastewater treatment performance was evaluated over a 2-month period using an activated sludge pilot plant. H2S removal averaged 100% during diffusion at 25 ppmv, and 98.9% during the 100 ppmv peak periods. A significant increase in mixed liquor volatile suspended solids concentration (P < 0.01) was observed during H2S diffusion, which may be due to an increase in H2S-degrading microorganisms. There was no adverse effect of H2S on nitrification throughout the ASD trials. Ammonia (NH3) removal was slightly better in the test receiving H2S diffusion (87.6%) than in the control (85.4%). H2S diffusion appeared to improve robustness of the AS biomass to operational upsets.
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Pierens, Arnaud, Colin P. McNally, and Richard P. Nelson. "Hydrodynamical turbulence in eccentric circumbinary discs and its impact on the in situ formation of circumbinary planets." Monthly Notices of the Royal Astronomical Society 496, no. 3 (June 3, 2020): 2849–67. http://dx.doi.org/10.1093/mnras/staa1550.
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ABSTRACT Eccentric gaseous discs are unstable to a parametric instability involving the resonant interaction between inertial-gravity waves and the eccentric mode in the disc. We present three-dimensional global hydrodynamical simulations of inviscid circumbinary discs that form an inner cavity and become eccentric through interaction with the central binary. The parametric instability grows and generates turbulence that transports angular momentum with stress parameter α ∼ 5 × 10−3 at distances ≲ 7 abin, where abin is the binary semimajor axis. Vertical turbulent diffusion occurs at a rate corresponding to αdiff ∼ 1–2 × 10−3. We examine the impact of turbulent diffusion on the vertical settling of pebbles, and on the rate of pebble accretion by embedded planets. In steady state, dust particles with Stokes numbers St ≲ 0.1 form a layer of finite thickness Hd ≳ 0.1H, where H is the gas scale height. Pebble accretion efficiency is then reduced by a factor racc/Hd, where racc is the accretion radius, compared to the rate in a laminar disc. For accreting core masses with mp ≲ 0.1 M⊕, pebble accretion for particles with St ≳ 0.5 is also reduced because of velocity kicks induced by the turbulence. These effects combine to make the time needed by a Ceres mass object to grow to the pebble isolation mass, when significant gas accretion can occur, longer than typical disc lifetimes. Hence, the origins of circumbinary planets orbiting close to their central binary systems, as discovered by the Kepler mission, are difficult to explain using an in situ model that invokes a combination of the streaming instability and pebble accretion.
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Dartois, E., and F. Langlet. "Carbon dioxide clathrate hydrate formation at low temperature." Astronomy & Astrophysics 652 (August 2021): A74. http://dx.doi.org/10.1051/0004-6361/202140858.
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Context. The formation and presence of clathrate hydrates could influence the composition and stability of planetary ices and comets; they are at the heart of the development of numerous complex planetary models, all of which include the necessary condition imposed by their stability curves, some of which include the cage occupancy or host–guest content and the hydration number, but fewer take into account the kinetics aspects. Aims. We measure the temperature-dependent-diffusion-controlled formation of the carbon dioxide clathrate hydrate in the 155–210 K range in order to establish the clathrate formation kinetics at low temperature. Methods. We exposed thin water ice films of a few microns in thickness deposited in a dedicated infrared transmitting closed cell to gaseous carbon dioxide maintained at a pressure of a few times the pressure at which carbon dioxide clathrate hydrate is thermodynamically stable. The time dependence of the clathrate formation was monitored with the recording of specific infrared vibrational modes of CO2 with a Fourier Transform InfraRed spectrometer. Results. These experiments clearly show a two-step clathrate formation, particularly at low temperature, within a relatively simple geometric configuration. We satisfactorily applied a model combining surface clathration followed by a bulk diffusion–relaxation growth process to the experiments and derived the temperature-dependent-diffusion coefficient for the bulk spreading of clathrate. The derived apparent activation energy corresponding to this temperature-dependent-diffusion coefficient in the considered temperature range is Ea = 24.7 ± 9.7 kJ mol−1. The kinetics parameters favour a possible carbon dioxide clathrate hydrate nucleation mainly in planets or satellites.
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Barbosa, V. L., D. Dufol, J. L. Callan, R. Sneath, and R. M. Stuetz. "Hydrogen sulphide removal by activated sludge diffusion." Water Science and Technology 50, no. 4 (August 1, 2004): 199–205. http://dx.doi.org/10.2166/wst.2004.0262.
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Odours from wastewater treatment plants comprise a mixture of various gases, of which hydrogen sulphide (H2S) is the main constituent. Microorganisms commonly found in wastewater can degrade sulphurous compounds. Therefore, the use of activated sludge (AS) for odour control offers an alternative to traditional waste gas treatment processes, such as biofilters, bioscrubbers and biotrickling filters, both in practical terms (use of existing facilities) and economically (minimal capital cost). The performance of AS diffusion as a bioscrubber for removing H2S at concentrations at 25, 75 and 150 ppmv was evaluated. Pilot-scale trials were undertaken using parallel 60-L aeration tanks and 20-L clarifier reactors at the Bedford Sewage Treatment Works, Carington, UK. Olfactometry measurements were also carried out to determine whether there was any increase in odour concentration owing to H2S diffusion. Hydrogen sulphide removal rates of 100% were obtained, with no noticeable increase in odour concentration throughout the trials as measured by olfactometry. Odour concentration was highest at the beginning of the trials and lowest during the high H2S dosing period, with similar values being obtained for test and control. It was concluded that AS diffusion is an effective bioscrubber for the removal of H2S odour.
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Ehret, David L., and Peter A. Jolliffe. "Leaf injury to bean plants grown in carbon dioxide enriched atmospheres." Canadian Journal of Botany 63, no. 11 (November 1, 1985): 2015–20. http://dx.doi.org/10.1139/b85-281.
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Bush bean (Phaseolus vulgaris L.) plants grown in atmospheres enriched with CO2 (1400 μL L−1) showed marked reductions in photosynthetic capacity and accelerated chlorosis of primary leaves. Leaf injury was observed only in CO2-enriched plants, but the degree of injury was regulated by secondary factors, light and temperature. Conditions of relatively high light intensity (340–370 μmol m−2 s−1 photosynthetic photon flux density) or cool temperature (20 °C) promoted leaf injury of CO2-enriched plants. Leaf starch accumulation was highest under conditions that caused injury. The enhanced chlorosis and corresponding decline in photosynthetic activity, however, were not related to changes in stomatal diffusive resistance or leaf water status. Contaminant gases, such as ethylene, were not detectable in the CO2-enrichment chambers.
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Pontin, C. M., A. J. Barker, R. Hollerbach, Q. André, and S. Mathis. "Wave propagation in semiconvective regions of giant planets." Monthly Notices of the Royal Astronomical Society 493, no. 4 (March 13, 2020): 5788–806. http://dx.doi.org/10.1093/mnras/staa664.
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ABSTRACT Recent observations of Jupiter and Saturn suggest that heavy elements may be diluted in the gaseous envelope, providing a compositional gradient that could stabilize ordinary convection and produce a stably stratified layer near the core of these planets. This region could consist of semiconvective layers with a staircase-like density profile, which have multiple convective zones separated by thin stably stratified interfaces, as a result of double-diffusive convection. These layers could have important effects on wave propagation and tidal dissipation that have not been fully explored. We analyse the effects of these layers on the propagation and transmission of internal waves within giant planets, extending prior work in a local Cartesian model. We adopt a simplified global Boussinesq planetary model in which we explore the internal waves in a non-rotating spherical body. We begin by studying the free modes of a region containing semiconvective layers. We then analyse the transmission of internal waves through such a region. The free modes depend strongly on the staircase properties, and consist of modes with both internal and interfacial gravity wave-like behaviour. We determine the frequency shifts of these waves as a function of the number of steps to explore their potential to probe planetary internal structures. We also find that wave transmission is strongly affected by the presence of a staircase. Very large wavelength waves are transmitted efficiently, but small-scale waves are only transmitted if they are resonant with one of the free modes. The effective size of the core is therefore larger for non-resonant modes.
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Singha, Shuvra, and Mikael S. Hedenqvist. "A Review on Barrier Properties of Poly(Lactic Acid)/Clay Nanocomposites." Polymers 12, no. 5 (May 11, 2020): 1095. http://dx.doi.org/10.3390/polym12051095.
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Poly(lactic acid) (PLA) is considered to be among the best biopolymer substitutes for the existing petroleum-based polymers in the field of food packaging owing to its renewability, biodegradability, non-toxicity and mechanical properties. However, PLA displays only moderate barrier properties to gases, vapors and organic compounds, which can limit its application as a packaging material. Hence, it becomes essential to understand the mass transport properties of PLA and address the transport challenges. Significant improvements in the barrier properties can be achieved by incorporating two-dimensional clay nanofillers, the planes of which create tortuosity to the diffusing molecules, thereby increasing the effective length of the diffusion path. This article reviews the literature on barrier properties of PLA/clay nanocomposites. The important PLA/clay nanocomposite preparation techniques, such as solution intercalation, melt processing and in situ polymerization, are outlined followed by an extensive account of barrier performance of nanocomposites drawn from the literature. Fundamentals of mass transport phenomena and the factors affecting mass transport are also presented. Furthermore, mathematical models that have been proposed/used to predict the permeability in polymer/clay nanocomposites are reviewed and the extent to which the models are validated in PLA/clay composites is discussed.
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Dakora, Felix D., and Craig A. Atkins. "Effect of pO2 during Growth on the Gaseous Diffusional Properties of Nodules of Cowpea (Vigna unguiculata L. Walp.)." Plant Physiology 93, no. 3 (July 1, 1990): 956–61. http://dx.doi.org/10.1104/pp.93.3.956.
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Schumann, Helge, Gunther Richter, and Andreas Leineweber. "Crystallography of γ′-Fe4N formation in single-crystalline α-Fe whiskers." Journal of Applied Crystallography 53, no. 4 (June 12, 2020): 865–79. http://dx.doi.org/10.1107/s1600576720005981.
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Gaseous nitriding of steel and iron can significantly improve their properties, for example corrosion resistance, fatigue endurance and tribological properties. In order to obtain a better understanding of the early stages of formation of the initial cubic primitive γ′-Fe4N, the mechanism and crystallography of the α–γ′ phase transformation was investigated under simplified conditions. Single-crystal α-Fe whiskers were nitrided at 823 K and a nitriding potential of 0.7 atm−1/2 for 20 min. The resulting microstructure and phases, as well as the crystallographic orientation of crystallites belonging to a particular phase, were characterized by scanning electron microscopy coupled with electron backscatter diffraction. The habit planes were investigated by single- and two-surface trace analysis. The α-Fe whiskers partly transform into γ′-Fe4N, where γ′ grows mainly in a plate-like morphology. An orientation relationship close to the rational Pitsch orientation relationship and {0.078 0.432 0.898}α and {0.391 0.367 0.844}γ′ as habit planes were predicted by the phenomenological theory of martensite crystallography (PTMC), adopting a {101}α〈101〉α shear system for lattice invariant strain, which corresponds to a {1 1 1}γ′〈1 12〉γ′ shear system in γ′. The encountered orientation relationship and the habit planes exhibit excellent agreement with predictions from the PTMC, although the transformation definitely requires diffusion. The γ′ plates mainly exhibit one single internally untwinned variant. The formation of additional variants due to strain accommodation, as well as the formation of a complex microstructure, was suppressed to a considerable extent by the fewer mechanical constraints imposed on the transforming regions within the iron whiskers as compared to the situation at the surface of bulk samples.
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ARMSTRONG, J., W. ARMSTRONG, and P. M. BECKETT. "Phragmites australis: a critical appraisal of the ventilating pressure concept and an analysis of resistance to pressurized gas flow and gaseous diffusion in horizontal rhizomes." New Phytologist 110, no. 3 (November 1988): 383–89. http://dx.doi.org/10.1111/j.1469-8137.1988.tb00276.x.
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Chametla, Raúl O., and Frédéric S. Masset. "Numerical study of coorbital thermal torques on cold or hot satellites." Monthly Notices of the Royal Astronomical Society 501, no. 1 (November 26, 2020): 24–35. http://dx.doi.org/10.1093/mnras/staa3681.
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ABSTRACT We evaluate the thermal torques exerted on low-mass planets embedded in gaseous protoplanetary discs with thermal diffusion, by means of high-resolution three-dimensional hydrodynamics simulations. We confirm that thermal torques essentially depend on the offset between the planet and its corotation, and find a good agreement with analytic estimates when this offset is small compared to the size of the thermal disturbance. For larger offsets that may be attained in discs with a large pressure gradient or a small thermal diffusivity, thermal torques tend towards an asymptotic value broadly compatible with results from a dynamical friction calculation in an unsheared medium. We perform a convergence study and find that the thermal disturbance must be resolved over typically 10 zones for a decent agreement with analytic predictions. We find that the luminosity at which the net thermal torque changes sign matches that predicted by linear theory within a few percents. Our study confirms that thermal torques usually supersede Lindblad and corotation torques by almost an order of magnitude for low-mass planets. As we increase the planetary mass, we find that the ratio of thermal torques to Lindblad and corotation torques is progressively reduced, and that the thermal disturbance is increasingly distorted by the horseshoe flow. Overall, we find that thermal torques are dominant for masses up to an order of magnitude larger than implemented in recent models of planetary population synthesis. We finally briefly discuss the case of stellar or intermediate-mass objects embedded in discs around active galactic nuclei.
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Setter, TL, I. Waters, I. Wallace, P. Bhekasut, and H. Greenway. "Submergence of Rice. I. Growth and Photosynthetic Response to CO2 Enrichment of Floodwater." Functional Plant Biology 16, no. 3 (1989): 251. http://dx.doi.org/10.1071/pp9890251.
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Growth and photosynthetic response of lowland rice following complete submergence is related to the concentration of CO2 dissolved in floodwater. Submergence of plants in stagnant solution at low CO2 concentration or solution gassed with air at 0.03 kPa CO2 (equilibrium of 0.01 mol m-3 dissolved CO2) decreased carbohydrates, and little or no growth occurred. Plants submerged in solutions gassed with 3-20 kPa CO2 in air (equilibrium of 0.9-6 mol m-3 CO2) showed at most small decreases in carbohydrates, and growth was up to 100% of the non-submerged plants. At pH 7.5, there was little net photosynthetic O2 evolution by detached submerged leaves even at high HCO3- concentrations, which suggests that these rice leaves could utilise only CO2 and not HCO3-. At pH 6.5, O2 evolution in solutions in equilibrium with 7.4 kPa CO2 was 3-4 fold higher than in solutions in equilibrium with 0.6 kPa CO2. Photorespiration was indicated by a decrease in the rate of net O2 evolution with increasing external O2. In stagnant solutions this reduction of O2 evolution was pronounced; at a CO2 concentration of 0.25 mol m-3 net O2 evolution ceased when the O2 concentration in the water had reached only 0.125 mol m-3. The requirement of photosynthesis for a combination of high CO2 concentrations and low external O2 was presumably due to slow diffusion of these gases in the unstirred layer of solution around the leaves.
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Boasson, Rosalinda, and Michael Shaw. "The effects of CO2 and membranes on sporulation in axenic cultures of flax rust." Canadian Journal of Botany 63, no. 8 (August 1, 1985): 1418–22. http://dx.doi.org/10.1139/b85-196.
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Uredospore production by axenically grown flax rust (Melampsora lini (Ehrenb.) Lev.) was measured as carotenoids (extinction units at 458 nm) per milligram protein. Sporulation was not affected by raising (flushing with 1–5% (v/v) CO2 in air) or lowering (KOH well in culture flasks) the level of CO2 in the air space above the cultures. Significant (two- to four-fold) increases in sporulation occurred beneath impermeable membranes of Parafilm or Saran wrap placed on the surface of young (3 weeks from seeding) mycelial mats for 2 weeks. The stimulatory effect was confined strictly to those areas of the mycelial mats in contact with the membranes. Both Parafilm and Saran wrap were easily and cleanly peeled away from the mycelial mats. Permeable Unipore and HVHP membranes, to which the fungus adhered strongly, did not stimulate sporulation. The fungus did not adhere to Unipore or HVHP membranes treated with silicone or paraffin oil; membranes thus treated stimulated sporulation. The stimulatory effect of membranes on sporulation appears to depend on the nature of the contact between the membrane surface and the mycelium and to be unrelated to the effect of the membranes on the diffusion of gases or other volatile substances.
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Stępniewska, Zofia, and Weronika Goraj. "Transformation of methane in peatland environments." Forest Research Papers 75, no. 1 (March 1, 2014): 101–10. http://dx.doi.org/10.2478/frp-2014-0010.
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Abstract Wetlands and particularly peatlands are the main natural source of methane. Data indicate that 10-45% of methane emission comes from these sources. Methane emission from wetlands is the result of the balance between methanogenesis and methanotrophic processes and is actively affected by the wetland plant community composition. There are many factors affecting the balance of CH4: for instance, vegetation has a strong effect on CH4 emissions from wetland ecosystems by influencing methane production, consumption and transport in the soil. The effects of plants on methane fluxes may be mediated by: molecular diffusion, internal transport through plant aerenchyma tissues and ebullition. Methane is formed in the process of methanogenesis under anaerobic conditions. It may then be emitted into the atmosphere directly from the soil or by internal transport through the plant. Alternatively, it may undergo methane oxidation by methanotrophic bacteria, both free-living in the root zone and associated with the host plant in symbiosis. Sphagnum moss is of particular importance for this processes as it contains methanotrophic bacteria in its endophytic system. Methanotrophic bacteria live inside the dead hyaline cells or on the surface of Sphagnum leaves and are able to oxidise methane produced in the soil during methanogenesis, making peatlands a natural biofilter for methane, one of the main greenhouse gases
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Johnstone, C. P., M. Güdel, H. Lammer, and K. G. Kislyakova. "Upper atmospheres of terrestrial planets: Carbon dioxide cooling and the Earth’s thermospheric evolution." Astronomy & Astrophysics 617 (September 2018): A107. http://dx.doi.org/10.1051/0004-6361/201832776.
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Context.The thermal and chemical structures of the upper atmospheres of planets crucially influence losses to space and must be understood to constrain the effects of losses on atmospheric evolution.Aims.We develop a 1D first-principles hydrodynamic atmosphere model that calculates atmospheric thermal and chemical structures for arbitrary planetary parameters, chemical compositions, and stellar inputs. We apply the model to study the reaction of the Earth’s upper atmosphere to large changes in the CO2abundance and to changes in the input solar XUV field due to the Sun’s activity evolution from 3 Gyr in the past to 2.5 Gyr in the future.Methods.For the thermal atmosphere structure, we considered heating from the absorption of stellar X-ray, UV, and IR radiation, heating from exothermic chemical reactions, electron heating from collisions with non-thermal photoelectrons, Joule heating, cooling from IR emission by several species, thermal conduction, and energy exchanges between the neutral, ion, and electron gases. For the chemical structure, we considered ~500 chemical reactions, including 56 photoreactions, eddy and molecular diffusion, and advection. In addition, we calculated the atmospheric structure by solving the hydrodynamic equations. To solve the equations in our model, we developed the Kompot code and have provided detailed descriptions of the numerical methods used in the appendices.Results.We verify our model by calculating the structures of the upper atmospheres of the modern Earth and Venus. By varying the CO2abundances at the lower boundary (65 km) of our Earth model, we show that the atmospheric thermal structure is significantly altered. Increasing the CO2abundances leads to massive reduction in thermospheric temperature, contraction of the atmosphere, and reductions in the ion densities indicating that CO2can significantly influence atmospheric erosion. Our models for the evolution of the Earth’s upper atmosphere indicate that the thermospheric structure has not changed significantly in the last 2 Gyr and is unlikely to change signficantly in the next few Gyr. The largest changes that we see take place between 3 and 2 Gyr ago, with even larger changes expected at even earlier times.
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Huang, C. X., L. E. C. Ling, M. E. McCully, and M. J. Canny. "Cryo analytical microscopy: Multiple applications for plant structure and physiology." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 76–77. http://dx.doi.org/10.1017/s0424820100162843.
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Carleton University’s cyo-analytical SEM facility deals with a very wide range of specimens from all the sciences. One of its major specializations is the study of plant structure and function, as illustrated by reference to particular research programs, for example: Stabilization of structures that cannot be preserved by conventional fixation and embedding methods. Many plant tissues are constructed of extremely fragile cell walls containing large vacuoles with high turgor pressures within, interspersed with large volumes of air or fluid. Plants which grow under water are a conspicuous example, requiring large internal open channels for the transport of gases to and from the roots. Other fragile tissues and those having cell walls that are impermeable to solvents and resins have been preserved in roots of desert monocotyledons, and in tree roots. Fluids in spaces between cells. We have pioneered the discovery that many intercellular spaces in plant tissues, always believed to contain air, are in fact filled with fluid. These spaces in sugarcane stems (Figs. 1 & 2) have been shown to contain both strong sugar solution, and an endophyte that lives on this sugar and fixes atmospheric nitrogen. The large air spaces (aerenchyma) in some roots, always considered an aeration system, have been shown to contain water some of the time, and to enhance diffusion of solutes in roots. We have also discovered that roots, always considered to be organs for collecting water from soil, also excrete water to the soil at night. Distribution of nutrient ions in plant tissues. Quantitative analysis of nutrient ions (especially potassium) in individual cells of roots, stems and leaves are opening up new perspectives on the acquisition, use and transport of ions in plants. Bubbles of air and water.
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Du, Fengshuang, and Bahareh Nojabaei. "A Review of Gas Injection in Shale Reservoirs: Enhanced Oil/Gas Recovery Approaches and Greenhouse Gas Control." Energies 12, no. 12 (June 19, 2019): 2355. http://dx.doi.org/10.3390/en12122355.
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Shale oil and gas resources contribute significantly to the energy production in the U.S. Greenhouse gas emissions come from combustion of fossil fuels from potential sources of power plants, oil refineries, and flaring or venting of produced gas (primarily methane) in oilfields. Economic utilization of greenhouse gases in shale reservoirs not only increases oil or gas recovery, but also contributes to CO2 sequestration. In this paper, the feasibility and efficiency of gas injection approaches, including huff-n-puff injection and gas flooding in shale oil/gas/condensate reservoirs are discussed based on the results of in-situ pilots, and experimental and simulation studies. In each section, one type of shale reservoir is discussed, with the following aspects covered: (1) Experimental and simulation results for different gas injection approaches; (2) mechanisms of different gas injection approaches; and (3) field pilots for gas injection enhanced oil recovery (EOR) and enhanced gas recovery (EGR). Based on the experimental and simulation studies, as well as some successful field trials, gas injection is deemed as a potential approach for EOR and EGR in shale reservoirs. The enhanced recovery factor varies for different experiments with different rock/fluid properties or models incorporating different effects and shale complexities. Based on the simulation studies and successful field pilots, CO2 could be successfully captured in shale gas reservoirs through gas injection and huff-n-puff regimes. The status of flaring gas emissions in oilfields and the outlook of economic utilization of greenhouse gases for enhanced oil or gas recovery and CO2 storage were given in the last section. The storage capacity varies in different simulation studies and is associated with well design, gas injection scheme and operation parameters, gas adsorption, molecular diffusion, and the modelling approaches.
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Nickel, Hubertus, Willem J. Quadakkers, and Lorenz Singheiser. "Determination of Corrosion Layers and Protective Coatings on Steels and Alloys Used in Simulated Service Environment of Modern Power Plants." Journal of Pressure Vessel Technology 128, no. 1 (October 6, 2005): 130–39. http://dx.doi.org/10.1115/1.2137769.
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The development of modern power generation systems with higher thermal efficiency requires the use of constructional materials of higher strength and improved resistance to the aggressive service atmospheres. In this paper, the following examples are discussed. (i) The oxidation behavior of 9% Cr steels in simulated combustion gases: The effects of O2 and H2O content on the oxidation behavior of 9% Cr steels in the temperature range 600-800°C showed that in dry oxygen a protective scale was formed with an oxidation rate controlled by diffusion. In contrast, that in the presence of water vapor, after an incubation period, the scale became nonprotective as a result of a change in the oxidation mechanism. (ii) The development of NiCrAlY alloys for corrosion-resistant coatings and thermal barrier coatings of gas turbine components: The increase of component surface temperature in modern gas turbines leads to an enhanced oxidation attack of the blade coating. Considerable efforts have been made in the improvement of the temperature properties of MCrAlY coatings by the additions of minor elements, such as yttrium, silicon, and titanium. The experimental results show the positive, but different influence of the oxidation behavior of the MCrAlY coatings by the addition of these minor elements. (iii) The development of lightweight intermetallics of TiAl-basis: TiAl-based intermetallics are promising materials for future turbine components because of the combination of high-temperature strength and low density. These alloys, however, possess poor oxidation resistance at temperatures above 700°C. The experimental results showed that the oxidation behavior of TiAl-based intermetallics can be strongly improved by minor additions of 1-2at.% silver. (iv) The oxide-dispersion-strengthened (ODS) alloys provide excellent creep resistance up to much higher temperatures than can be achieved with conventional wrought or cast alloys in combination with suitable high-temperature oxidation/corrosion resistance. The growth mechanisms of protective chromia and alumina scales were examined by a two-stage oxidation method with O18 tracer. The distribution of the oxygen isotopes in the oxide scale was determined by secondary ion-mass spectroscopy and SNMS. The results show the positive influence of a Y2O3 dispersion on the oxidation resistance of the ODS alloys and its effect on growth mechanisms.
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Diadiun, K. V. "SYSTEM FOR CONTROLLING MASS BALANCE OF GASES AND REAGENTS DURING FORMATION OF ION-PLASMA COATINGS." Scientific Notes of Junior Academy of Sciences of Ukraine, no. 1(17) (2020): 67–75. http://dx.doi.org/10.51707/2618-0529-2020-17-08.
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Providing an increase in the working capacity of a metal-cutting tool, it is possible to significantly increase the productivity of mechanized labor, thereby reducing the cost of purchasing a new tool and saving on other accompanying technological components. During the operation of the cutting tool, the main load is transferred to its working part, this, as a rule, leads to partial wear or complete destruction of the planes and cutting edges. There are a number of technologies for processing working surfaces, which provides them with additional strengthening, the most effective of which is the method of applying special coatings to the surface of the cutting tool. Taking into account the specifics of the processes of formation of coatings, they can be divided into three main groups [1]. The first group includes methods in which the formation of coatings is carried out mainly due to diffusion reactions between saturating elements and structures of the instrumental material. The second group includes methods of forming coatings by a complex mechanism. The third group includes methods of forming coatings due to chemical and plasma-chemical reactions of particle flux simultaneously in volumes of space immediately adjacent to the saturable surfaces of the instrumental base. One such technology is the CIB (condensation and ion bombardment) method, which is a physical deposition of coatings. The most characteristic feature of coatings produced by this method is the absence of a transition zone between the coating and the tool material. This makes it possible to obtain a complex of properties on the working surfaces of the tool without deteriorating its original properties. The article is devoted to the issues of increasing the efficiency of ion-plasma technologies through the development and implementation of an automated system for analyzing and controlling the mass balance of reagent gases under conditions of several gases supply. Thus, the improvement of the technology of coating the working surfaces of the cutting tool, namely, the effective control of the process of applying ion-plasma coatings with the introduction of an automated system for analyzing and controlling the mass balance of reagent gases under conditions of supplying several gases is an urgent task.
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Gevorkyan, L., T. Shoji, D. R. Getsinger, O. I. Smith, and A. R. Karagozian. "Transverse jet mixing characteristics." Journal of Fluid Mechanics 790 (February 2, 2016): 237–74. http://dx.doi.org/10.1017/jfm.2016.5.
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This experimental study explores and quantifies mixing characteristics associated with a gaseous round jet injected perpendicularly into cross-flow for a range of flow and injection conditions. The study utilizes acetone planar laser-induced fluorescence imaging to determine mixing metrics in both centreplane and cross-sectional planes of the jet, for a range of jet-to-cross-flow momentum flux ratios ($2\leqslant J\leqslant 41$), density ratios ($0.35\leqslant S\leqslant 1.0$) and injector configurations (flush nozzle, flush pipe and elevated nozzle), all at a fixed jet Reynolds number of 1900. For the majority of conditions explored, there is a direct correspondence between the nature of the jet’s upstream shear layer instabilities and structure, as documented in detail in Getsingeret al.(J. Fluid Mech., vol. 760, 2014, pp. 342–367), and the jet’s mixing characteristics, consistent with diffusion-dominated processes, but with a few notable exceptions. When quantified as a function of distance along the jet trajectory, mixing metrics for jets in cross-flow with an absolutely unstable upstream shear layer and relatively symmetric counter-rotating vortex pair cross-sectional structure tend to show better local molecular mixing than for jets with convectively unstable upstream shear layers and generally asymmetric cross-sectional structures. Yet the spatial evolution of mixing with downstream distance can be greater for a few specific convectively unstable conditions, apparently associated with the initiation and nature of shear layer rollup as a trigger for improved mixing. A notable exception to these trends concerns conditions where the equidensity jet in cross-flow has an upstream shear layer that is already absolutely unstable, and the jet density is then reduced in comparison with that of the cross-flow. Here, density ratios below unity tend to mix less well than for equidensity conditions, demonstrated to result from differences in the nature of higher-density cross-flow entrainment into lower-density shear layer vortices.
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Torsky, Andrei, Alexander Volnenko, Leonid Plyatsuk, Larysa Hurets, Daulet Zhumadullayev, and Аbay Abzhabparov. "Study of dust collection effectiveness in cyclonic-vortex action apparatus." Technology audit and production reserves 1, no. 3(57) (February 27, 2021): 21–25. http://dx.doi.org/10.15587/2706-5448.2021.225328.
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The object of research is the efficiency of dust collection of fine dust in an apparatus with an intense turbulent mode of phase interaction. One of the most problematic areas of the existing dust and gas cleaning equipment is the low efficiency of collecting fine dust. Effective cleaning of exhaust gases from dust involves the use of multi-stage cleaning systems, including wet and dry dust cleaning devices, which entails high capital and operating costs. These disadvantages are eliminated in the developed design of the cyclone-vortex dust collector with two contact zones. The device implements both dry and wet dust collection mechanisms, which allows for high efficiency of dust removal at high productivity. The conducted studies of the total and fractional efficiency of dust collection when changing the operating parameters of the developed device showed that the efficiency of collecting fine dust is 98–99 %. The increase in the efficiency of dust collection in the dry stage of the device is due to an increase in centrifugal force. In the wet stage of contact, the efficiency reaches its maximum values due to the vortex crushing of the liquid in the nozzle zone of the apparatus. Studies of the fractional efficiency of the apparatus show that with an increase in the diameter of the captured particles, the efficiency of the dust collection process for dry and wet stages, as well as the overall efficiency, increases. With an increase in the density of irrigation, the overall efficiency of dust collection in the apparatus increases. It has been established that an increase in the efficiency of capturing highly dispersed particles occurs due to turbulent diffusion, the value of which is determined by the frequency of turbulent pulsations and the degree of entrainment of particles during the pulsating motion of packed bodies. To describe the results obtained, a centrifugal-inertial model for a dry contact stage and a turbulent-diffusion model of solid particle deposition for a wet contact stage are proposed, which make it possible to calculate the dust collection efficiency of the contact stages, as well as the overall efficiency of the cyclone-vortex apparatus. The results obtained show the prospects of using devices of this design at heat power plants and other industries.
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Anderson, Jeri L., A. Iulian Apostoaei, James H. Yiin, and Chih-Yu Tseng. "Exposure to Recycled Uranium Contaminants in Gaseous Diffusion Plants." Radiation Protection Dosimetry, January 16, 2017. http://dx.doi.org/10.1093/rpd/ncw379.
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"Some aspects of the biology of nitrogen-fixing organisms." Philosophical Transactions of the Royal Society of London. B, Biological Sciences 317, no. 1184 (September 24, 1987): 111–29. http://dx.doi.org/10.1098/rstb.1987.0051.
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Eukaryotic organisms do not fix nitrogen. Animals generally have no need to do so because of their complex food-acquisition and waste-disposal systems. Plants, by using carbon polymers for structural purposes, minimize their need for nitrogen. When very nitrogen-limited, to enter into symbiosis with nitrogen-fixing microorganisms may be the most controllable method for eukaryotes to obtain fixed nitrogen. Filamentous, heterocystous nitrogen-fixing cyanobacteria may be better adapted to a free-living than to a symbiotic existence, because of their complexity. In symbioses, their photosynthetic machinery becomes redundant and the need to differentiate heterocysts as well as derepress nif genes may be a disadvantage. This could in part account for the greater success of symbioses involving the structurally simpler genera Frankia , Rhizobium and Bradyrhizobium . Nitrogen fixation by legume nodules can be controlled by varying the oxygen supply. This control may be effected by a variable diffusion resistance, enabling oxygen required for ATP synthesis to be matched to available photosynthate. Such a resistance, which is probably located in the nodule cortex, may also be used to reduce nitrogen fixation in the presence of combined nitrogen and could also facilitate rapid responses to other forms of stress. Alternative resistances to gaseous diffusion may operate when water supplies are restricted. Rhizobium and Bradyrhizobium follow different patterns of differentiation into nitrogen-fixing bacteroids. These patterns are coupled with retention or loss of viability and with significant or no natural enrichment of the bacteroids with 15 N respectively. The basic patterns of each type are subject to host-modification. Recent studies on structures of primitive legume nodules show some parallels both with actinorhizas and with nodules on Parasponia induced by Bradyrhizobium . In particular, distribution of rhizobia in nodule tissues is intercellular and infection threads are formed only when bacteria ‘enter’ host cells; there is no intracellular ‘bacteroid’ stage. These threads are retained in the active nitrogen-fixing cells. Many legumes and some actinorhizas are not infected via root hairs. Therefore two of the stages often considered typical of the development of effective legume nodules, i.e. ‘release’ of bacteria into vesicles bounded by peribacteroid membrane and infection through root hairs, can be omitted; these omissions may be of use in attempts to transfer nodulating ability to new genera.
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Yeghikyan, Ararat. "The irreplaceable role of ubiquitous cosmic rays in the space chemistry: from the origin of complex species in interstellar molecular clouds to the ozone depletion in the atmospheres of Earth-like planets." Communications of the Byurakan Astrophysical Observatory, 2020, 37–54. http://dx.doi.org/10.52526/25792776-2020.67.1-37.
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A review is given of low-energy cosmic rays (1 MeV-10 GeV), which play an important role in the physics and chemistry of interstellar medium of our Galaxy. According to the generally accepted theory of star formation, cosmic rays penetrate into molecular clouds and ionize the dense gaseous medium of star formation centers besides due to a process of ambipolar diffusion they establish a star formation time scale of about 100-1000 thousand years. The source of cosmic rays in the Galaxy are supernovae remnants where diffusion acceleration at the shock front accelerates particles up to energies of 1015 eV. Being the main source of ionization in the inner regions of molecular clouds, cosmic rays play a fundamental role in the global chemistry of clouds, triggering the entire chain of ion-molecular reactions that make it possible to obtain basic molecules. The review also noted the importance of cosmic rays in atmospheric chemistry: playing a significant role in the formation of nitric oxide, especially with an increase in the flux, they cause a decrease in the concentration of ozone in the atmosphere with all climatic consequences.
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"Abatement of odour emissions by UV/Ozone oxidation process." Issue 3 20, no. 3 (October 25, 2018): 669–73. http://dx.doi.org/10.30955/gnj.002798.
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<p>The growing expectations of the population and the increasingly stringent regulations about air pollution have resulted in the need to minimize and conveniently treat the waste gas from different emission sources. The emissions from a large variety of plants, including waste and wastewater treatment plants, result mainly from the degradation of organic matter. These emissions are composed of a complex of substances emitted at low concentrations from diffusive sources. These characteristics make complex their treatment in economically efficient conditions. The design and management of environmental protection and industrial plants, therefore, require the implementation of focused processes for the control of the target compounds. The present study shows the applicability of an UV-Ozone lab-scale system for odours and VOCs removal. An artificial gaseous stream contaminated by toluene, at different incoming concentrations, was treated evaluating the abatement efficiencies in terms of odours and total VOCs as a function of power and contact time. The residue ozone concentrations was determined in order to optimize the set-up conditions. The results were discussed with the aim of evaluating the feasibility of the investigated solution for the advanced treatment of the waste gas from environmental facilities. Removal efficiencies up tp 91% were reached for the investigated conditions. Lower inlet concentrations resulted in high residue ozone outgoing the processes and, thus, it resulted over dimensioned for inlet load lower than 1,22 mg per minute.</p>
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"Comparative physiology of plant and arthropod land adaptation." Philosophical Transactions of the Royal Society of London. B, Biological Sciences 309, no. 1138 (April 2, 1985): 273–88. http://dx.doi.org/10.1098/rstb.1985.0087.
Full textAbstract:
Plants related to aquatic Charophycean green algae were probably terrestrial by the early to mid Silurian; these plants were the ancestors of the vascular plants that have dominated the Earth’s flora since the Devonian. The arthropods have been the major herbivores and carnivores in many terrestrial communities since the Devonian: they arose from a number of aquatic arthropod stocks which invaded the land from the Silurian onwards. The vascular plants and arthropods conduct their basic metabolism in the same way as their aquatic counterparts, but in the aerial environment which differs greatly from the aquatic in the exchange of materials, momentum and heat between organisms and their environment. Terrestrial organisms differ from their aquatic relatives in ( inter alia ) the water vapour loss attendant on the exchange of gases in photosynthesis and respiration; the potential for large and rapid changes in body temperature; and differences in the structural requirements for maintenance of posture and, in animals, locomotion. The (putatively) adaptive responses to these problems of terrestrial life show a number of im portant parallels between the vascular plants and arthropods, including internalization of gas-exchange surfaces, regulation of gas diffusion between the gas-exchange surfaces and the outside air, a wax layer over the general body surface which restricts non-respiratory and non-photosynthetic water loss, and the importance of rigid skeletal members (present in the ancestral aquatic arthropods, but not in algae). At the biochemical level many of the prerequisites for the special structures and functions found in terrestrial organisms can be traced in their algal and aquatic arthropod relatives. The seductive argument that increasing O 2 levels in the atmosphere in the Siluro-Devonian were of great significance in permitting larger phototrophs (absence of restriction of plants to shaded habitats to avoid ultraviolet, and increased bulk of non-photosynthetic parts permitted by greater O 2 availability) and larger and more active phagotrophs (as a result of greater O 2 availability) is, alas, very difficult to test quantitatively.
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Xu, Liangfei, Chuan Fang, Junming Hu, Siliang Cheng, Jianqiu Li, Minggao Ouyang, and Werner Lehnert. "Self-Humidification of a Polymer Electrolyte Membrane Fuel Cell System With Cathodic Exhaust Gas Recirculation." Journal of Electrochemical Energy Conversion and Storage 15, no. 2 (February 6, 2018). http://dx.doi.org/10.1115/1.4038628.
Full textAbstract:
Water management is critical for the operation of a polymer electrolyte membrane fuel cell (PEMFC). For the purposes of high power and long working-lifetime of PEMFCs, external humidifiers are always utilized as a necessary part of balance of plants to keep the imported air and fuel wet. However, they have several disadvantages, and it is beneficial to remove them so as to reduce system volume and to enhance the cold-starting capability. In this paper, a self-humidified PEMFC of an active area 250 cm2 and cell number 320 is proposed and investigated. The imported dry air on the cathode side is mixed with moisty exhaust gas by using a recirculation valve, and the dry hydrogen on the anode side is humidified by back-diffusion water through the membrane. A nonlinear model is set up based on mass transport and energy conservation equations to capture dynamics of gases in the supply and exhaust manifolds, the gas diffusion layers (GDLs), and the membrane. An analysis is conducted to investigate the influences of parameters on dynamic and stable performances. Simulation results show that system performances can be greatly affected by parameters such as air stoichiometry, current density, exhaust gas recirculation (EGR) ratio, and membrane thickness. By accurately controlling the EGR ratio and carefully selecting design and operation parameters, it is probably for a PEMFC without an external humidifier to have similar system efficiency compared to a traditional system.
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Revati Rajanya, Devanakonda, and Gurpreet Singh. "RECENT TRENDS IN OSMOTIC DEHYDRATION OF FRUITS: A REVIEW." PLANT ARCHIVES 21, no. 1 (April 19, 2021). http://dx.doi.org/10.51470/plantarchives.2021.v21.no1.013.
Full textAbstract:
The marvel of expulsion of water from lower solvent concentration to higher concentration by a semi-perimeable membrane is osmotic dehydration, resulting in equilibrium state on both sides of the membrane. As it decreases the water activity of fruits. It is found to be most widely used application for preserving food materials. Due to colour, scent, nutritional constituents and flavour compound retention value, osmotic dehydration is favoured over other methods. Drying, shower drying, freezedrying, solidifying, vacuum packing, canning, syrup conservation (osmotic dehydration), sugar crystallization, nourishment illumination and the addition of preservatives or inert gases such as carbon dioxide are typical methods of applying these processes. The solutes used in osmotic parchedness are ordinarily sugar syrup with fruit slices or 3d shapes, and salt (sodium chloride) or vegetable brine. This can be the method of multicomponent diffusion. Water moves from fruits or vegetables to the solution in this process and certain fruit and vegetable components such as minerals, vitamins, fruit acids, etc also pass into the solution along with water to the fruits and vegetables, sugar and salt migrate. Examples that are considered are Gooseberry Murabbas (Aonla), apples, sweets, candies of Different fruits and vegetables, including pethas, parwal, Osmosis-made sweets in sugar syrup are the most popular items of commercial value available in the market made from fruits. It is processed in a brine solution before drying in pickles made from raw mango. In brine, various vegetables are handled to lower their moisture content