Absorption Flux Research Articles

Experimental studies on carbon dioxide absorption using potassium carbonate solutions with amino acid salts

Absorption and desorption of CO2 using K2CO3 solutions promoted by three amino acid salts (AASs), potassium glycinate (PG), potassium lysinate (PL) and potassium L-argininate (PA), were evaluated using 40% CO2 at 40 °C and with pure N2 at 80 °C, respectively. The addition of all 3 AASs clearly enhanced both absorption and desorption of CO2 compared to single K2CO3 solution. PA + K2CO3 solution showed the highest CO2 cyclic capacity of 0.678 mol CO2/mol absorbent, while the highest CO2 absorption and desorption rates of 39.8 and 17.6 mol CO2 L−1 s−1 were achieved by PG + K2CO3 solution. Finally, simulated biogas containing 40% of CO2 and 60% of CH4 was used as test gas in a hollow fiber membrane contactor. PG and PA promoters presented higher CO2 absorption flux and removal efficiency than PL promoters in K2CO3 solution within low Gas/Liquid ratio region. Stable CO2 removal performances for all three promoters were observed at elevated temperature and pressure for 60 min operation.

Coordinated UV and X-Ray Spectroscopic Observations of the O-type Giant ξ Per: The Connection between X-Rays and Large-scale Wind Structure* †

Abstract We present new, contemporaneous Hubble Space Telescope STIS and XMM-Newton observations of the O7 III(n)((f)) star ξ Per. We supplement the new data with archival IUE spectra, to analyze the variability of the wind lines and X-ray flux of ξ Per. The variable wind of this star is known to have a 2.086-day periodicity. We use a simple, heuristic spot model that fits the low-velocity (near-surface) IUE wind line variability very well, to demonstrate that the low-velocity absorption in the new STIS spectra of N iv λ1718 and Si iv λ1402 vary with the same 2.086-day period. It is remarkable that the period and amplitude of the STIS data agree with those of the IUE spectra obtained 22 yr earlier. We also show that the time variability of the new XMM-Newton fluxes is also consistent with the 2.086-day period. Thus, our new, multiwavelength coordinated observations demonstrate that the mechanism that causes the UV wind line variability is also responsible for a significant fraction of the X-rays in single O stars. The sequence of events for the multiwavelength light-curve minima is Si iv λ1402, N iv λ1718, and X-ray flux, each separated by a phase of about 0.06 relative to the 2.086-day period. Analysis of the X-ray fluxes shows that they become softer as they weaken. This is contrary to expectations if the variability is caused by periodic excess absorption. Furthermore, the high-resolution X-ray spectra suggest that the individual emission lines at maximum are more strongly blueshifted. If we interpret the low-velocity wind line light curves in terms of our model, it implies that there are two bright regions, i.e., regions with less absorption, separated by 180°, on the surface of the star. We note that the presence and persistence of two spots separated by 180° suggest that a weak dipole magnetic field is responsible for the variability of the UV wind line absorption and X-ray flux in ξ Per.

Development of three-dimensional piezoelectric polyvinylidene fluoride-graphene oxide scaffold by non-solvent induced phase separation method for nerve tissue engineering

In this work, non-solvent induced phase separation method was applied to develop polyvinylidene fluoride (PVDF)/graphene oxide (GO) scaffold for nerve tissue engineering. Furthermore, the effects of GO concentration (0, 0.5, 1, 3 and 5 wt%) on the electrical, mechanical, physical and biological properties of scaffolds were also evaluated. Results demonstrated that, incorporation of GO nanosheets in the PVDF matrix decreased water contact angle, while enhanced the hydrophilicity, water absorption and water flux of the scaffolds. Moreover, mechanical properties of the nanocomposite scaffolds improved in the presence of GO nanosheets. Significantly, increasing GO content up to 3 wt% enhanced tensile modulus and strength of PVDF scaffold from 8.1 ± 1.4 and 0.8 ± 0.2 MPa to 17.0 ± 3.7 and 1.4 ± 0.4 MPa, respectively. Incorporation of GO nanosheets into the PVDF scaffold simultaneously enhanced β phase fraction, piezoelectricity and electrical conductivity of all nanocomposite scaffolds. Furthermore, PVDF-GO scaffolds significantly promoted cell proliferation, compared to PVDF scaffold, depending on the GO content. Finally, PVDF-GO scaffold could easily be converted in to a nerve guidance conduit with 4 internal longitudinally aligned channels making it appropriate for the nerve regeneration applications.

The nutritional status and fluorescence characteristics of maize cultivars with different chlorophyll content and yields

Chlorophyll (Chl) is generally positively related to corn grain yields; however, light-leaf-colored maize may also achieve high yields. Thus, Chl is seemingly not a key parameter for maize producers. Modern maize cultivars (55) were divided into four types, based on grain yields and ear leaf SPAD readings. The results revealed that there was no correlation between the SPAD readings and corn grain yields across different maize cultivars. High-yield maize possessed higher nitrogen, phosphorus, and potassium accumulation and utilization compared to that of low-yield maize; the N-transport efficiency of low yield and high SPAD was the lowest among various types of maize. Under normal conditions, parameters determining the high yield of maize in a sequence was leaf dry mass, Chl fluorescence indices, and light absorption flux per leaf cross section. A higher absorption flux, accompanied by high energy dissipation ratios, reduced the difference of trapped transport flux between high-SPAD and low-SPAD maize at high yield levels. At the low yield level, a higher absorption flux per reaction center compensated for the loss of PSII reaction center numbers in low-SPAD maize.

Experimental studies on mass transfer performance for CO2 absorption into aqueous N,N-dimethylethanolamine (DMEA) based solutions in a PTFE hollow fiber membrane contactor

CO2 absorption performance for various blended N,N-dimethylethanolamine (DMEA) solutions in the presence of absorption promoters including Monoethanolamine (MEA), Piperazine (PZ), 2-(Ethylamino)ethanol (EAE), 2-(Methylamino)ethanol (MAE) and 2-Amino-2-methyl-1-propanol (AMP) was investigated in terms of CO2 absorption flux by using a polytetrafluoroethylene (PTFE) hollow fiber membrane contactor. The experimental results show that the CO2 absorption flux increases with a reasonable increase in liquid velocity, liquid temperature and total amine concentration. Also, the CO2 absorption flux can increase by increasing gas velocity, CO2 partial pressure but decrease with the increased lean CO2 loading. In addition, it can be found that all of the investigated activated amines can improve the CO2 absorption flux of aqueous DMEA solution. For fresh amine solution, the order of CO2 absorption flux for the investigated amine blends can be ranked as: DMEA < DMEA + AMP < DMEA + MEA < DMEA + EAE < DMEA + MAE < DMEA + PZ. By contrast, for the amine solution with CO2 loading of over 0.3 mol/mol, the order has also changed accordingly and can be ranked as: DMEA < DMEA + AMP < DMEA + EAE < DMEA + MAE < DMEA + MEA < DMEA + PZ. The DMEA + PZ mixture presents a significant improvement up to 52.44% in CO2 absorption flux compared to that of single DMEA solution, and can be considered as a promising alternative for CO2 capture.

Impact of Fusarium verticillioides on chlorophyll fluorescence parameters of two maize lines

Fusarium verticillioides is one of the most common phytopathogenic fungi affecting maize production, worldwide. The early identification of F. verticillioides infection in maize could be helpful to prevent the spreading of the fungus. Therefore, this study represents the use of chlorophyll fluorescence parameters to identify F. verticillioides infection in maize. Chlorophyll a fluorescence of control and F. verticillioides infected plants showed a typical polyphasic OJIP transient curve in both MO17 and B73 lines. Infected plants from both maize lines showed a different pattern of OJIP transient curve when compared to the control plants, respectively. This indicated that F. verticillioides had an effect on the photosynthesis of infected maize plants. This study demonstrated the importance of parameters such as: the activity of the water-splitting complex on the donor side of PSII (Fv/F0), minimum fluorescence (F0), maximum fluorescence (Fm), and absorption flux per one active reaction center (ABS/RC) to identify F. verticillioides infection in maize.

Efficient Computation of Multidimensional Lambertian Optical Absorption

Approximate analytic expressions are given for the absorption of light emanating from a nonuniformly illuminated Lambertian surface into an absorptive layer having a spatially uniform coefficient of absorption, α. This situation is particularly relevant for silicon solar cells, which have deliberately textured surfaces and grid fingers that create nonuniform illumination. The approach uses Fourier superposition to represent spatial variation in the plane of the surface, represented by a series of wavenumbers in each axis. It is observed that the absorption rate and flux density at any given distance, z, into the layer is given by an effective wavenumber, keff, that is the root-sum-square of the wavenumbers in the two axes. This allows for simple analytic expressions that, for each Fourier component, depend only on the dimensionless terms keffz and αz. This Fourier-superposition approach is computationally efficient compared with ray tracing, and is particularly effective when the nonuniform illumination is periodic and symmetric in each axis, in which case the Fourier superposition becomes a cosine series of spatial harmonics. An example illustrates the good fidelity that can be obtained using as few as ten harmonics in each axis.

CREEPING FLOW ANALYSIS OF SLIGHTLY NON-NEWTONIAN FLUID IN A UNIFORMLY POROUS SLIT

This paper provides the analysis of the steady, creeping flow of a special class of slightly viscoelastic, incompressible fluid through a slit having porous walls with uniform porosity. The governing two dimensional flow equations along with non-homogeneous boundary conditions are non-dimensionalized. Recursive approach is used to solve the resulting equations. Expressions for stream function, velocity components, volumetric flow rate, pressure distribution, shear and normal stresses in general and on the walls of the slit, fractional absorption and leakage flux are derived. Points of maximum velocity components are also identified. A graphical study is carried out to show the effect of porosity and non-Newtonian parameter on above mentioned resulting expressions. It is observed that axial velocity of the fluid decreases with the increase in porosity and non-Newtonian parameter. The outcome of this theoretical study has significant importance both in industry and biosciences.

Swelling reduction of polyvinylidenefluoride hollow fiber membrane incorporated with silicoaluminophosphate-34 zeotype filler for membrane gas absorption

CO2 gas absorption is important in fuel purification and carbon capture. By incorporating a porous membrane with a large surface area in membrane gas absorption (MGA) system, the CO2 transfer between feed gas and liquid absorbent can be greatly improved. However, the absorption flux usually drops in the long-term operation due to membrane wetting by the common liquid absorbent, amine. Membrane wetting can lead to membrane swelling which induce the growth of mass transfer resistance. In this work, silicoaluminophosphate-34 (SAPO-34) zeolite was incorporated into polyvinylidene fluoride (PVDF) hollow fiber membrane to reduce flux decline caused by membrane swelling. The membrane porosity and pore size increased with increasing SAPO-34 loading. Nevertheless, significant changes in water contact angle or liquid entry pressure were not shown. PVDF hollow fiber membrane incorporated with 3 wt% of SAPO-34 showed slightly higher CO2 absorption flux to PVDF hollow fiber membrane in MGA with distilled water as the absorbent. However, the CO2 absorption flux of this PVDF/SAPO-34 membrane was greatly improved of about 140 % higher than the CO2 absorption flux of the neat membrane when diethanolamine was used as the absorption. The CO2 absorption flux of PVDF hollow fiber membrane dropped about 60 % after 96 hours. Although these membranes showed a similar water contact angle after being wetted by water or amine, they swelled differently. PVDF hollow fiber membrane swelled nearly 71.0 % after being wetted by amine, but only swelled about 2 % after being wetted by water. The incorporation of SAPO-34 into PVDF hollow fiber membrane reduced swelling by amine, down to 47.7 %. The swelling reduction could be a major cause of absorption improvement shown by PVDF/SAPO-34 hollow fiber membrane in MGA using diethanolamine.

Absorption kinetics of mercury (II) chloride into mono-ethylene glycol (MEG) solution

Different mercury species have been found in the oil and gas reservoirs. Dynamic absorption of mercury (II) chloride (HgCl2) into solutions of mono-ethylene glycol (MEG) is reported in this work. It was observed that absorption of HgCl2 into MEG solutions was comparable to the absorption in pure water and the effect on MEG was not seen for MEG concentrations of 2–30 v/v%. The absorption flux was mainly affected by the absorption temperature and the concentration of HgCl2 in the gas phase. Utilisation of several mercury analysis techniques such as flow injection mercury spectroscopy (FIMS), inductively couple plasma-mass spectroscopy (ICP-MS), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy show that no interactions between HgCl2 and MEG were detected for the test parameters studied. The findings from this work helps to improve the knowledge on the behaviour of HgCl2 within natural gas processing facilities, especially during transportation in pipelines and the MEG regeneration process.

Elevated CO2 Improves Photosynthesis Under High Temperature by Attenuating the Functional Limitations to Energy Fluxes, Electron Transport and Redox Homeostasis in Tomato Leaves.

Elevated atmospheric CO2 improves leaf photosynthesis and plant tolerance to heat stress, however, the underlying mechanisms remain unclear. In this study, we exposed tomato plants to elevated CO2 (800 μmol mol-1) and/or high temperature (42°C for 24 h), and examined a range of photosynthetic and chlorophyll fluorescence parameters as well as cellular redox state to better understand the response of photosystem II (PSII) and PSI to elevated CO2 and heat stress. The results showed that, while the heat stress drastically decreased the net photosynthetic rate (Pn), maximum carboxylation rate (Vcmax), maximum ribulose-1,5-bis-phosphate (RuBP) regeneration rate (Jmax) and maximal photochemical efficiency of PSII (Fv/Fm), the elevated CO2 improved those parameters under heat stress and at a 24 h recovery. Furthermore, the heat stress decreased the absorption flux, trapped energy flux, electron transport, energy dissipation per PSII cross section, while the elevated CO2 had the opposing effects that eventually decreased photoinhibition, damage to photosystems and reactive oxygen species accumulation. Similarly, the elevated CO2 helped the plants to maintain a reduced redox state as evidenced by the increased ratios of ASA:DHA and GSH:GSSG under heat stress and at recovery. Furthermore, the concentration of NADP+ and ratio of NADP+ to NADPH were induced by elevated CO2 at recovery. This study unraveled the crucial mechanisms of elevated CO2-mediated changes in energy fluxes, electron transport and redox homeostasis under heat stress, and shed new light on the responses of tomato plants to combined heat and elevated CO2.

Biocatalytic PVDF composite hollow fiber membranes for CO2 removal in gas-liquid membrane contactor

A highly efficient biocatalytic carbonic anhydrase (CA)-polydopamine (PDA)/polyethylenimine (PEI)-polyvinylidene fluoride (PVDF) (referred to as CA-m-PVDF) composite membrane was fabricated for CO2 conversion and capture in the gas-liquid membrane contactor (GLMC) process. The co-deposition of PDA/PEI with amino functional groups was employed to amine-functionalize a PVDF substrate as support for subsequent in-situ CA immobilization by cross-linking with glutaraldehyde. This enhances the enzyme stability and prolongs its lifespan, thus facilitates CO2 hydration efficiency in the GLMC process. In this work, different immobilization CA protocols were compared based on the CA activity and activity recovery. For biocatalytic CA-m-PVDF membranes, the best activity of 498 U m−2 (membrane) and a corresponding activity recovery of 31.5% were achieved (m(5 h)-PVDF as support, 0.67 (v/v)% GLU as cross-linking agent, 600 μg mL−1 CA solution, pH 8.0, temperature at 25 °C, and 24 h reaction time). By using water as absorbent with a liquid velocity of 0.25 m s−1 in a bench-scale GLMC setup, a high-efficiency CO2 absorption flux of 2.5 × 10−3 mol m−2 s−1 was obtained, which was ~165% higher than that of the non-biocatalytic m-PVDF membrane. The long-term stability test showed a good enzyme activity for CO2 hydration capacity for the CA-m-PVDF membranes during 40 days of test duration. Overall, the results achieved in this work may provide promising insights into enzyme immobilization on polymeric supports for the development of high-efficiency biocatalytic membranes for CO2 capture in GLMC applications.

RhizobacteriumBacillus subtilisreduces toxic effects of high electrical conductivity in soilless culture of lettuce

Quality of irrigation water is a critical factor for greenhouse production. A high concentration of soluble salts is the main reason for high electrical conductivity (EC) of irrigation water. The low water quality available for agriculture is the main problem in many places of the world. Plant growth-promoting bacteria are free-living soil bacteria that can help plant growth without having pathogenic effects. In the current study, three concentrations of NaCl (0, 40 and 80 mM, which resulted in EC of 1, 4 and 8 mS, respectively) were added to the irrigation water. Half of the salt-treated plants were fed with the rhizobacterium Bacillus subtilis (OD=0.6) to test whether it can reduce the problems of medium and high EC of irrigation water on lettuce plants, cultivated in Perlite medium. Growth parameters, including fresh and dry weights, leaf area, leaf number and plant height of control plants, were considerably improved by application of B. subtilis in the root medium of lettuce plants. Furthermore, the growth of plants exposed to medium and high EC was improved by the presence of B. subtilis in their rhizosphere. Polyphasic chlorophyll fluorescence transient parameters such as absorption flux, trapping flux and quantum yield for energy dissipation were decreased in plants with B. subtilis in their rhizosphere, while electron transport flux per reaction center was increased in B. subtilis-treated plants. In conclusion, B. subtilis can be used in the root medium of greenhouse plants to prevent the toxic effects of high EC of irrigation water.

Hydrophobic polyacrylonitrile membrane preparation and its use in membrane contactor for CO2 absorption

Based on the NH4Cl-catalyzed cycloaddition reaction between nitriles and azides, tetrazole polyacrylonitrile (TZ-PAN) copolymers were synthesized. The copolymers were further modified through alkylation reaction with bromodecane and bromohexadecane, respectively, to obtain alkylated TZ-PAN (D-TZ-PAN and H-TZ-PAN). The successful alkylation via the tetrazole group was confirmed by 1H NMR spectroscopy, and the degree of functionalization (DF) was well controlled by the doses of reactants (NH4Cl and NaN3). Porous membranes of D-TZ-PAN and H-TZ-PAN were prepared via nonsolvent induced phase separation. Due to the hydrophobic nature of the long alkyl chain, the hydrophobicity of the alkylated PAN membranes was improved. The water contact angle was 113 ± 2° for D-TZ-PAN with DF of 20% (D-TZ-PAN-20), much higher than that for the pristine PAN membrane (88 ± 1°). Both D-TZ-PAN and H-TZ-PAN membranes were used in a membrane contactor for CO2 absorption. The improvement in membrane hydrophobicity enhanced the wetting resistance as well as the CO2 absorption flux. The absorption flux at a water flow rate of 240 mL min‒1 was 1.897 mmol m‒2 s‒1 for D-TZ-PAN-20 membrane, 2.5 times higher than that for the pristine PAN membrane. This study proposed a novel method to fabricate hydrophobic PAN membrane and expanded its use for CO2 absorption.

Physical absorption of CO2 and H2S from synthetic biogas at elevated pressures using hollow fiber membrane contactors: The effects of Henry’s constants and gas diffusivities

The present study applies the mathematical model to investigate the physical absorption of CO2, H2S and CH4 from synthetic biogas at high pressure using hollow fiber membrane contactors. Henry’s constants are considered pressure and temperature dependent, while the polarity of H2S is included in the calculation of gas diffusivities. The model was validated with the experimental data using two hollow fiber membranes, i.e., polyvinylidenefluoride (PVDF) and polytetrafluoroethylene (PTFE), to analyze membrane wetting. The effects of pressure and temperature on the CO2 and H2S absorption and CH4 loss were investigated. From the model validation, the experimental results using PVDF and PTFE at 1 bar are in good agreement with non-wetting mode. At elevated pressures, non-wetting mode results correspond with the experimental results using PTFE, while the partially wetting mode well predicts the results of PVDF. The modeling results also indicate that increasing pressure and reducing temperature improves the absorption fluxes of CO2 and H2S, while the CH4 losses in this work are lower than 5.5%.

Experimental Investigation and Numerical analysis of SO2 Removal Using Polypropylene Membrane Contactor

In this study, polypropylene membrane contactor is designed for SO2 absorption of simulated flue gas. Water and the aqueous solution of Na2SO3 are used as an absorbent. Absorption performance of the longitudinal module is compared to novel transversal membrane contactor module. The result shows that the transversal configuration of hollow fiber module significantly enhances absorption performance over conventional longitudinal configuration. Absorption flux of SO2 in aqueous Na2SO2 is 1.8 times higher than water at optimum Na2SO3 concentration and gas flow rate. According to performance stability test, polypropylene hollow fiber membrane is successfully operated for 15 hours maintaining average absorption flux of 20 x 10−5 mol.m−2.s−1. Numerical simulation shows good agreement with physical absorption data.

Amine wetting evaluation on hydrophobic silane modified polyvinylidene fluoride/silicoaluminophosphate zeolite membrane for membrane gas absorption

Membrane wetting in membrane gas absorption is undesirable as it reduces the gas transfer in wet pores. This work aims to understand the improvement of membrane hydrophobicity using fluoroalkyl silane and its effects on membrane properties, separation performance and membrane wetting by amine. Polyvinylidene fluoride/silicoaluminophosphate zeolite membranes were prepared using non-solvent induced phase separation technique and then immersed into a mixture of (3,3,3-trifluoropropyl) trimethoxysilane and ethanol solution (volume ratio of 1: 100) for 20 min. The post-modification resulted in a slight improvement of water contact angle and liquid entry pressure. Hence, the highest CO2 absorption flux of 4.48 ± 0.36 × 10−4 mol.m−2. s−1 was achieved using silanated membrane, about 25 % of improvement in comparison to the neat membrane. The absorption flux of humid gas was slightly reduced (-16 %) due to pore wetting. Fluoroalkyl silane could be used to prevent water wetting, resulting improvement of CO2 absorption. The membranes were immersed in diethanolamine solution (2 M) for 50 h before characterization using goniometer, Fourier transform infrared spectroscopy and scanning electron microscope. The incorporation of zeolite reduced membrane wetting because membrane swelling could be prevented. The unfavorable interaction between fluoroalkyl and amine groups induced severe membrane wetting by amine.

Mass transfer performance and correlation for CO2 absorption into aqueous 1-Dimethylamino-2-propanol (1DMA2P) solution in a PTFE hollow fiber membrane contactor

1-Dimethylamino-2-propanol (1DMA2P), a tertiary amine, has been regarded as the promising absorbent with relative higher reaction rate and high capacity for CO2 capture. The CO2 absorption into aqueous 1-Dimethylamino-2-propanol (1DMA2P) solution in the polytetrafluoroethene (PTFE) hollow fiber membrane contactor (HFMC) was firstly studied experimentally in the present work. The CO2 absorption performance in terms of the CO2 absorption flux was comprehensively investigated by considering a series of operating parameters, including liquid velocity, gas velocity, liquid phase temperature, CO2 partial pressure, initial lean CO2 loading in the liquid phase, amine concentration and flow orientations. The experimental results indicated increasing liquid velocity can significantly enhance CO2 absorption performance over a reasonable range of liquid velocities while similar trends were observed by increasing gas velocity, liquid temperature, CO2 partial pressure and amine concentration properly. By contrast, there was a severe loss of CO2 absorption flux with increase in lean CO2 loading. Counter-current flow achieved the improvement of CO2 absorption performance compared to co-current flow. Besides, to predict the CO2 absorption performance at various operating parameters, satisfactory correlations of KG and JCO₂ were proposed for the 1DMA2P-CO2 system.

COMT1 Silencing Aggravates Heat Stress-Induced Reduction in Photosynthesis by Decreasing Chlorophyll Content, Photosystem II Activity, and Electron Transport Efficiency in Tomato.

Despite a range of initiatives to reduce global carbon emission, the mean global temperature is increasing due to climate change. Since rising temperatures pose a serious threat of food insecurity, it is important to further explore important biological molecules that can confer thermotolerance to plants. Recently, melatonin has emerged as a universal abiotic stress regulator that can enhance plant tolerance to high temperature. Nonetheless, such regulatory roles of melatonin were unraveled mainly by assessing the effect of exogenous melatonin on plant tolerance to abiotic stress. Here, we generated melatonin deficient tomato plants by silencing of a melatonin biosynthetic gene, CAFFEIC ACID O-METHYLTRANSFERASE 1 (COMT1), to unveil the role of endogenous melatonin in photosynthesis under heat stress. We examined photosynthetic pigment content, leaf gas exchange, and a range of chlorophyll fluorescence parameters. The results showed that silencing of COMT1 aggravated heat stress by inhibiting both the light reactions and the carbon fixation reactions of photosynthesis. The photosynthetic pigment content, light absorption flux, trapped energy flux, energy dissipation, density of active reaction center per photosystem II (PSII) cross-section, the photosynthetic electron transport rate, the maximum photochemical efficiency of PSII photochemistry, and the rate of CO2 assimilation all decreased in COMT1-silenced plants compared with that of non-silenced plants particularly under heat stress. However, exogenous melatonin alleviated heat-induced photosynthetic inhibition in both genotypes, indicating that melatonin is essential for maintaining photosynthetic capacity under stressful conditions. These findings provide genetic evidence on the vital role of melatonin in photosynthesis and thus may have useful implication in horticultural crop management in the face of climate change.

Modelling of CO2 absorption via hollow fiber membrane contactors: Comparison of pore gas diffusivity models

This paper discusses the modelling of CO2 absorption in water as an absorbent via a hollow fiber membrane contactor to predict the performance of the absorption process under various operational conditions. The governing equations are two dimensional. Since, the gas diffusion along the pores is responsible for the mass transfer across the membrane thickness, i.e. both the skin layer and the membrane bulk, how to estimate the effective gas diffusivity has a vital degree of importance. When small pores combined with low pressures are dealt with, a challenging issue appears, i.e. the effective gas diffusivity is a contributive phenomenon, in which, several mechanisms are cooperated. Selecting an inappropriate model, inevitably leads to unrealistic values for the tuning parameters. Conventionally, the Bosanquet equation has been widely used for modelling the gas diffusivity through the membrane pores. In the current paper, it is intended to prove that the Bosanquet model is a limiting form of Wakao et al. model, when we are far enough from the continuum region. The modelling results are compared with six sets of different membranes from the open literature including high and low pressures. The results show that, ignoring the viscous flow contribution in Dg,eff (the Bosanquet gas diffusivity model) causes underestimation of the absorption flux. Based on the observations, there is a meaningful consistency between the model and the experimental data once the contribution of the viscous flow in Deff (the Wakao et al. gas diffusivity model) is considered.