Binomial frequency response to non-binomial pulse sequences for efficient water suppression

Summary This article reports on the use of short-hard pulse and spin-lock pulse combinations giving a binomial-like frequency response for the measurement of NMR spectra in aqueous solutions of quite dilute samples. The pulse sequence proposed provides excellent water suppression and does not introduce any linear or higher order phase errors. Application to the measurement of 2D NOESY data of a 0.25 mM solution of a double-stranded DNA fragment is presented.     

Leaf and root growth dynamics in Eucalyptus globulus seedlings grown in drying soil

Summary Seedlings of Eucalyptus globulus growing in soil columns were subjected to a 24 day soil drying treatment. Water and solute potentials of both young expanding and fully expanded leaves declined under reduced soil water availability, while slightly higher turgor was sustained by the fully expanded leaves. Although leaf area of unwatered seedlings was smaller, the corresponding leaf dry weight was quite similar to that of well-watered seedlings. Soon after rewatering, leaf area of plants experiencing water shortage was comparable to that of well-watered plants. It seems that a difference in wall properties between juvenile and mature leaves allows for an effective pattern of water use by eucalypt plants growing in drying soil. Some stomatal opening is sustained and therefore, presumably, some carbon may be fixed, keeping the carbon balance of the whole plant positive, and allowing a continuous cell division despite the limited water supply. The highest root density of both well-watered and unwatered plants was found in the upper soil layers. However, root growth of unwatered seedlings was gradually increased in the deeper soil layers, where thicker root apices and higher soil water depletion rates per unit root length were recorded. As a consequence, root absorbing surface area was as large in unwatered plants as in well-watered plants.     

Changes in the chemical composition of mire-water samples during storage

Abstract. Solutes in mire-water samples vary greatly in their tendency to change on storage. In repeated analyses of samples from Malham Tarn, Yorkshire, U.K., concentrations of Na+ and Cl^- proved very stable on storage, and Mg²+ hardly less so, whether the samples had been filtered or not. K+ concentrations declined slowly in filtered samples kept at room temperature, falling after two years to about two-thirds of the original value. In unfiltered samples, K+ concentrations rose on average by about 25 % over a period of two months. At low concentrations Ca²⁺ changed little on storage, but above 40 - 50 mg/l equilibration of CO₂ with the air led to precipitation of carbonate and loss of dissolved Ca²+. Fe concentrations were rather stable in ombrogenous bog waters, but in fen waters showed rapid decreases on storage. SO₄^2- showed little change in most samples, but there were a few large increases in unfiltered samples probably due to oxidation of sulphide. Unfiltered fen water samples generally developed high concentrations of NO₃^- (rarely NH₄⁺) on storage; by contrast acid bog waters typically developed high NH₄⁺ concentrations, but did not nitrify. Bog waters showed a small rise in pH and some reduction in colour (dissolved humic substances). Fen waters changed erratically in pH, depending on the balance of production and loss of CO₂ in the sample. Some recommendations are given for storage and analysis of samples.     

Managing water-use trade-offs in a semi-arid river delta to sustain multiple ecosystem services: a modeling approach

Managing trade-offs among water uses in a river basin to sustain multiple ecosystem services is crucial for adaptation to changing river flow regimes. Here we analyze the trade-off between irrigation and fisheries in the Amudarya, a semi-arid river basin in Central Asia, using an optimal control and an agent-based modeling approach. With the optimal control approach (OCA), we identify the economic and ecological conditions for water sharing in a regime where a social manager controls water withdrawals and fish harvesting. With the agent-based model (ABM), we relax some of the assumptions of the OCA to investigate how localized, individual agents with varied water use histories adapt their water use activities to local resource conditions. Variation in the farmers’ initial labor allocations to the two activities results in regimes with only one activity or both. Global returns and income equality are highest in a mixed regime. The mixed regimes also are more robust to water variability because fishing activities can compensate for decreased agricultural performance in the midstream regions. Thus, allowing for multiple uses can improve the coupled social-ecological system’s performance and its resilience. We also observe a lock-in effect similar to the current situation in the Amudarya, where agriculture is the dominant water use and transition to a more balanced allocation has proven to be extremely difficult. As in the ABM, this can to some extent be attributed to the difficulties of achieving sufficient revenues from fishing when agricultural activities upstream are high. Regulations or incentives are needed to overcome those barriers, and to facilitate progress towards integrated water management.     

Reaction pattern and mechanism of light induced oxidative water splitting in photosynthesis

This mini review is an attempt to briefly summarize our current knowledge on light driven oxidative water splitting in photosynthesis. The reaction leading to molecular oxygen and four protons via photosynthesis comprises thermodynamic and kinetic constraints that require a balanced fine tuning of the reaction coordinates. The mode of coupling between electron (ET) and proton transfer (PT) reactions is shown to be of key mechanistic relevance for the redox turnover of Y_Z and the reactions within the WOC. The WOC is characterized by peculiar energetics of its oxidation steps in the WOC. In all oxygen evolving photosynthetic organisms the redox state S₁ is thermodynamically most stable and therefore this general feature is assumed to be of physiological relevance. Available information on the Gibbs energy differences between the individual redox states S_i+1 and S_i and on the activation energies of their oxidative transitions are used to construct a general reaction coordinate of oxidative water splitting in photosystem II (PS II). Finally, an attempt is presented to cast our current state of knowledge into a mechanism of oxidative water splitting with special emphasis on the formation of the essential O-O bond and the active role of the protein environment in tuning the local proton activity that depends on time and redox state S_i. The O-O linkage is assumed to take place within a multistate equilibrium at the redox level of S₃, comprising both redox isomerism and proton tautomerism. It is proposed that one state, S₃(P), attains an electronic configuration and nuclear geometry that corresponds with a hydrogen bonded peroxide which acts as the entatic state for the generation of complexed molecular oxygen through S₃(P) oxidation by Y_Z^ox.     

Non-electrolyte diffusion across the frog gastric mucosa under osmotic gradients

Serosal-to-mucosal and mucosal-to-serosal diffusion of ¹⁴C-labelled inulin, sucrose, erythritol and propionamide was compared with ³HHO diffusion in mucosae incubated with isosmotic solutions at both surfaces, as well as isosmotic solution at serosal surface and hyperosmotic solution at the mucosal surface. The use of a hyperosmotic solution at the mucosal surface significantly increases unidirectional diffusion fluxes of inulin and of sucrose. To a nonsignificant extent, it affects the fluxes of erythritol and propionamide and significantly reduces the ³HHO diffusion. A size increment of the diffusion path utilized by the larger molecules is proposed.     

A creative collaboration between the science of ecosystem restoration and art for sustainable stormwater management on an urban college campus

This article presents an interdisciplinary, on‐campus, student project, titled “The Rain Project” that I designed as an urban ecosystem restoration model as well as a collaborative pedagogical approach between ecological science and art at George Mason University (GMU), Virginia, U.S.A. A group of students from several disciplines (e.g. environmental science, art, civil engineering, biology, communication, and film/media) participated in designing and constructing a floating wetland for a campus stormwater pond as part of sustainable stormwater management. The Rain Project has numerous implications for college education, scholarship, and service while presenting a novel way of building a sense of community among undergraduate students for ecological awareness and literacy. The work of Jackie Brookner, a renowned eco‐artist who worked extensively on stormwater, and its relevance to the project is discussed. I strongly suggest the need for linking art and the science of ecosystem restoration to best obtain improvements in much‐needed communication for the success of community participatory restoration projects. I also believe that this kind of interdisciplinary, campus project can facilitate the changes we need to train higher education students to be able to both think differently and communicate effectively. The Rain Project introduced students to new learning strategies that connected “systems thinking” with art, ecological science, and restoration practices.