More Like this

1. Mesophyll conductance response to short‐term changes in p CO2 is related to leaf anatomy and biochemistry in diverse C4 grasses

   https://doi.org/10.1111/nph.18427  

   Pathare, Varsha S. ; DiMario, Robert J. ; Koteyeva, Nuria ; Cousins, Asaph B. ( September 2022 , New Phytologist)

   Mesophyll CO₂conductance (g_m) in C₃species responds to short‐term (minutes) changes in environment potentially due to changes in leaf anatomical and biochemical properties and measurement artefacts. Compared with C₃species, there is less information ong_mresponses to short‐term changes in environmental conditions such as partial pressure of CO₂(pCO₂) across diverse C₄species and the potential determinants of these responses.

   Using 16 C₄grasses we investigated the response ofg_mto short‐term changes inpCO₂and its relationship with leaf anatomy and biochemistry.

   In general,g_mincreased aspCO₂decreased (statistically significant increase in 12 species), with percentage increases ing_mranging from +13% to +250%. Greater increase ing_mat lowpCO₂was observed in species exhibiting relatively thinner mesophyll cell walls along with greater mesophyll surface area exposed to intercellular air spaces, leaf N, photosynthetic capacity and activities of phosphoenolpyruvate carboxylase and Rubisco. Species with greater CO₂responses ofg_mwere also able to maintain their leaf water‐use efficiencies (TE_i) under low CO₂.

   Our study advances understanding of CO₂response ofg_min diverse C₄species, identifies the key leaf traits related to this response and has implications for improving C₄photosynthetic models and TE_ithrough modification ofg_m.

    

   more » « less
2. Reaction of ethylene over a typical Fischer‐Tropsch synthesis Co/ TiO2 catalyst

   https://doi.org/10.1002/eng2.12232  

   Zhang, Yusheng ; Tshwaku, Mgcini ; Yao, Yali ; Chang, Jianli ; Lu, Xiaojun ; Liu, Xinying ; Hildebrandt, Diane ( July 2020 , Engineering Reports)

   In order to identify the potential reaction paths of C₂H₄and their product distribution in Fischer‐Tropsch synthesis (FTS), a series of experiments were designed over a Co/TiO₂catalyst in the absence of CO. C₂H₄did quickly react with H₂to produce C_1‐6products under Fischer‐Tropsch (FT) reaction conditions. Although the dominant reaction is C₂H₄hydrogenation to ethane, changing the reaction conditions (temperature and partial pressure of reactants) can lead to the other reaction pathways being enhanced, resulting in varying product selectivity to both linear and branch olefins and paraffins. Possible reaction pathways had been summarized and discussed, which including C₂H₄reaction to ethylidene followed by dimerization; C₂H₄insertion into C₂surface species and dimerization and C₄decomposition and/or direct C₂hydrogenolysis. Furthermore, the products obtained from C₂H₄reactions were fit to a typical FTS product distribution, which indicate that both the chain growth initiators and monomers are not necessarily only derived from hydrogenation of CO but also from the secondary reactions of olefins.

    

   more » « less
3. Spectrophotometric analysis of the CO2 system in aqueous solutions: A freshwater example from the Snake River, Idaho, USA

   https://doi.org/10.1002/lom3.10525  

   Hudson‐Heck, Ellie ; Byrne, Robert H. ( November 2022 , Limnology and Oceanography: Methods)

   This work describes a new, generally applicable method to comprehensively characterize the inorganic carbon system of aqueous solutions. The method requires only simple spectrophotometric measurements and is appropriate for not only open‐ocean seawater (where convenient assumptions and approximations may be made) but also the more challenging case of freshwaters. The overall approach is to (1) measure pH in the field at the time of sample collection and (2) measure sample pH, carbonate alkalinity (A_C), and total alkalinity (A_T) later in the laboratory. All required equipment is inexpensive and portable. The paired laboratory measurements of pH andA_Ccan be used to obtain the concentration of total inorganic carbon (C_T). ThisC_Tcan in turn be paired with the field pH measurements to comprehensively characterize carbon‐system parameters in the sampled water body at in situ conditions. To our knowledge, this method is the first to spectrophotometrically measureA_Cand thus the first to completely characterizeC_Tand the carbon system of freshwaters using spectrophotometric measurements only. The concurrent measurements ofA_CandA_Tcan also be used to partition alkalinity into its carbonate and noncarbonate components. This work additionally describes how to quantitatively correct for artifacts that may arise (especially in freshwater samples) from using HgCl₂to halt respiration in sample bottles. The use of these methods is illustrated using samples collected from the Snake River (Idaho, USA) before and during the 2020 spring flow.

    

   more » « less
4. Separation of C2–C4 hydrocarbons from methane by zeolite MFI hollow fiber membranes fabricated from 2D nanosheets

   https://doi.org/10.1002/aic.17048  

   Min, Byunghyun ; Korde, Akshay ; Yang, Shaowei ; Kim, Youngjo ; Jones, Christopher W. ; Nair, Sankar ( September 2020 , AIChE Journal)

   Separation of higher hydrocarbons from methane is an important and energy‐intensive operation in natural gas processing. We present a detailed investigation of thin and oriented MFI zeolite membranes fabricated from 2D MFI nanosheets on inexpensive α‐alumina hollow fiber supports, particularly for separation ofn‐butane, propane, and ethane (“natural gas liquids”) from methane. These membranes display high permeances and selectivities for C₂–C₄hydrocarbons over methane, driven primarily by stronger adsorption of C₂–C₄hydrocarbons. We study the separation characteristics under unary, binary, ternary, and quaternary mixture conditions at 298 K and 100–900 kPa feed pressures. The membranes are highly effective in quaternary mixture separation at elevated feed pressures, for example allowingn‐butane/methane separation factors of 170–280 andn‐butane permeances of 710–2,700 GPU over the feed pressure range. We parametrize and apply multicomponent Maxwell–Stefan transport equations to predict the main trends in separation behavior over a range of operating conditions.

    

   more » « less
5. Acid‐ and base‐catalyzed epoxy‐phenol thermosets from catechol, resorcinol and hydroquinone: A structure–property study

   https://doi.org/10.1002/app.50995  

   Roy Choudhury, Shreya ; Houston, Katelyn R. ; Mason, Dawn ; Dingemans, Theo J. ( May 2021 , Journal of Applied Polymer Science)

   In order to better understand the design rules of epoxy–phenol thermosets we will report on the chemistry and (thermo)mechanical properties of cured epoxy–phenol thermoset films.Ortho‐,meta‐andpara‐isomers of dihydroxybenzene (DHB) were reacted with the diglycidyl ether of bisphenol A (DGEBA) in the presence of an acid catalyst or triphenylphosphine (PPh₃). The glass transition temperatures (T_g) of the cross‐linked films decreases in the order ofmeta‐ (T_g = 115°C) > ortho‐(T_g = 102°C) > para‐DHB (T_g = 96°C) as measured by differential scanning calorimetry. Uniaxial tensile testing of cross‐linked films showed excellent stress–strain behavior. The average ultimate strength values ranged from 65 to 82 MPa and the average values of the strain‐at‐break ranged from 4.8% to 6.9% at 25°C for all cross‐linked films. When a PPh₃was used, the network properties were profoundly different. The base catalyzed thermoset of DGEBA andmeta‐DHB shows aT_gof 85°C, which is 30°C lower than theT_gof the acid‐catalyzed analog. Tensile films appear to be more ductile, as they exhibit a strain‐at‐break of 20%. The results of this study confirm that simple dihydroxybenzene hardeners can be used to prepare cross‐linked films with excellent thermomechanical properties.

    

   more » « less