SUMMARYThe environmental concern about diffuse pollution from nitrogen (N) fertilizers has led to increased research on the diagnosis of crop N status. The SPAD chlorophyll (Chl) meter is the most commonly used tool for rice (Oryza sativa L.) N status diagnosis, but measurements are conducted at a specific point and readings are affected by different leaf positions. Many measurements per plant must be taken in order to increase the accuracy of N status diagnosis, which limits its application. The present paper attempts to determine rice N status at the canopy level using Multiplex®, a new hand-held optical fluorescence sensor. The fluorescence emission of rice leaves under light excitation was utilized by Multiplex® to non-destructively assess rice leaf Chl and phenolic compound content. A field experiment was conducted in 2011 using a completely randomized split-plot design, with main-plot treatments being six N fertilizer application rates and subplot treatments being different plant densities. Leaf Chl and phenolic compounds were evaluated using the ratio of far-red fluorescence (FRF) to red fluorescence (RF) emission under red light excitation (simple fluorescence ratio, SFR_R) (R2 = 0·35, P < 0·01) and the ratio of decadic logarithm of red to ultra-violet (UV) fluorescence emission (R2 = 0·30, P < 0·01), respectively. Both SPAD reading and fluorescence-based indices including flavonoids (FLAV), nitrogen balance index (NBI_R) and SFR_R could be used to predict rice leaf N contents. The canopy FLAV, SFR_R and NBI_R were all highly correlated to average SPAD readings (R2 > 0·70 in most cases, P < 0·01). Therefore, Multiplex® can be used as an alternative to SPAD to determine rice N status in paddy fields.
Microalgae have great, yet relatively untapped potential as a highly productive crop for the production of animal and aquaculture feed, biofuels, and nutraceutical products. Compared to conventional terrestrial crops they have a very fast growth rate and can be produced on non-arable land. During microalgae cultivation, carbon dioxide (CO2) is supplied as the carbon source for photosynthesising microalgae. There are a number of potential CO2 supplies including air, flue gas and purified CO2. In addition, several strategies have been applied to the delivery of CO2 to microalgae production systems, including directly bubbling CO2-rich gas, microbubbles, porous membrane spargers and non-porous membrane contactors. This article provides a comparative analysis of the different CO2 supply and delivery strategies and how they relate to each other.
A hybrid-functional material consisting of Ni as catalyst, CaO as CO sorbent, and CaSiO as polymorphic "active" spacer was synthesized by freeze-drying a mixed solution containing Ni, Ca and Si precursors, respectively, to be deployed during sawdust decomposition that generated gases mainly containing H, CO, CO and CH. The catalytic activity showed a positive correlation to the Ni loading, but at the expense of lower porosity and surface area with Ni loading beyond 20 wt %, indicating an optimal Ni loading of 20 wt % for Ni-CaO-CaSiO hybrid-functional materials, which enables ∼626 mL H (room temperature, 1 atm) produced from each gram of sawdust, with H purity in the product gas up to 68 vol %. This performance was superior over a conventional supported catalyst Ni-CaSiO that produced 443 mL H g-sawdust under the same operating condition with a purity of ∼61 vol %. Although the Ni-CaO bifunctional material in its fresh form generated a bit more H (∼689 mL H g-sawdust), its cyclic performance decayed dramatically, resulting in H yield reduced by 62% and purity dropped from 73 to 49 vol % after 15 cycles. The "active" CaSiO spacer offers porosity and mechanical strength to the Ni-CaO-CaSiO hybrid-functional material, corresponding to its minor loss in reactivity over cycles (H yield reduced by only 7% and H purity dropped from 68 to 64 vol % after 15 cycles).
Microalgae cultures have promise as a CO2 sink for atmospheric carbon and as a sustainable source of food and chemical feedstocks. However, large-scale microalgae cultivation is currently limited by the need to provide carbon dioxide from point sources, as the diffusion of atmospheric CO2 is too slow. Carbonic anhydrase (CA) is an effective enzyme to facilitate the dissolution of atmospheric CO2 that could be used to enhance the photosynthetic uptake of this greenhouse gas. Here we investigate a means of retaining CA at the surface of algae ponds to facilitate direct air capture by cross-linking CA with glutaraldehyde (GA) before encapsulation into buoyant calcium alginate beads. Coomassie Blue dyeing and Wilbur–Anderson assays confirmed the successful bonding of CA to the beads. Microscopic images showed the paraffin-embedded alginate framework. The CA–GA beads retain virtually all hydrase activity throughout 10 assay cycles. Compared with a natural growth rate of 22.7 ± 0.5 mg L–1 day–1, free CA and CA–GA beads increased the productivity of Nannochloropsis salina to 37 ± 3 mg L–1 day–1 and 40 ± 1 mg L–1 day–1, respectively. The CA–GA beads further provided a stable growth enhancement for three rounds of microalgae cultivation, confirming that these buoyant beads can be readily recovered and re-used, which is promising for industrial biomass production.
The pyrolysis behaviors of three types of biomass (cellulose, sawdust and straw) in three cases (no catalyst, Ni-CaO-Ca 2 SiO 4 and Ni-Ca 2 SiO 4) were investigated by non-isothermal thermogravimetric analysis. The non-isothermal pyrolysis was implemented with four different heating rates: 20, 30, 40 and 50 /min and the yield rates of the produced gases were measured by TG-MS. For kinetic analysis, the activation energy was obtained using four isoconversional analysis methods (Flynn-Wall-Ozawa (FWO) method, Kissinger-Akahira-Sunose (KAS) method, Starink method, and the Miura distributed activation energy model (DAEM)). Ni-CaO-Ca 2 SiO 4 and Ni-Ca 2 SiO 4 was found to intensify the decomposition of biomass to produce more H 2 and CO. The correlation R 2 , of all fitting lines in all cases, was above 0.9 which demonstrated that FWO, KAS, Starink methods and DAEM were suitable for calculating the activation energy of the biomass catalytic pyrolysis. Ni-CaO-Ca 2 SiO 4 showed the obvious catalytic effects in the decrease of activation energy of biomass pyrolysis to produce additional H 2 and CO from the breakage of light organic molecules.
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