High sink strength prevents photosynthetic down-regulation in cassava grown at elevated CO2 concentration.

Cassava has the potential to alleviate food insecurity in many tropical regions, yet few breeding efforts to increase yield have been made. Improved photosynthetic efficiency in cassava has the potential to increase yields, but cassava roots must have sufficient sink strength to prevent carbohydrates from accumulating in leaf tissue and suppressing photosynthesis. Here, we grew eight farmer-preferred African cassava cultivars under free-air CO2 enrichment (FACE) to evaluate the sink strength of cassava roots when photosynthesis increases due to elevated CO2 concentrations ([CO2]). Relative to the ambient treatments, elevated [CO2] treatments increased fresh (+27%) and dry (+37%) root biomass, which was driven by an increase in photosynthesis (+31%) and the absence of photosynthetic down-regulation over the growing season. Moreover, intrinsic water use efficiency improved under elevated [CO2] conditions, while leaf protein content and leaf and root cyanide concentrations were not affected. Overall, these results suggest that higher cassava yields can be expected as atmospheric [CO2] increases over the coming decades. However, there were cultivar differences in the partitioning of resources to roots versus above-grown biomass; thus, the particular responses of each cultivar must be considered when selecting candidates for improvement.

Effect of galcanezumab on severity and symptoms of migraine in phase 3 trials in patients with episodic or chronic migraine.

BACKGROUND: Galcanezumab, a humanized monoclonal antibody that binds calcitonin gene-related peptide, has demonstrated a significant reduction in monthly migraine headache days compared with placebo. Here, we analyze data from 3 randomized clinical trials (2 episodic trials [EVOLVE-1, EVOLVE-2] and 1 chronic trial [REGAIN]), to examine if galcanezumab also alleviates the severity and symptoms of migraine. METHODS: The episodic migraine trials were 6-month, double-blind studies in patients with episodic migraine (4-14 monthly migraine headache days). The chronic migraine trial was a 3-month, double-blind study in patients with chronic migraine (≥ 15 headache days per month, where ≥ 8 met criteria for migraine). Patients (18-65 years) were randomized to placebo or galcanezumab 120 mg with a 240-mg loading dose or 240 mg. Patients recorded headache characteristics, duration, severity, and presence of associated symptoms with each headache. The outcomes analyzed were changes from baseline in number of monthly migraine headache days with nausea and/or vomiting, photophobia and phonophobia, aura, and prodromal symptoms other than aura. Additional outcomes analyzed included the number of moderate-to-severe monthly migraine headache days, number of severe migraine headache days, and mean severity of remaining migraine headache days. Change from baseline in the proportion of days with nausea and/or vomiting and the proportion of days with photophobia and phonophobia among the remaining monthly migraine headache days were also analyzed. RESULTS: Galcanezumab was superior to placebo in reducing the frequency of migraine headache days with associated symptoms of migraine such as nausea and/or vomiting, photophobia and phonophobia, and prodromal symptoms. Galcanezumab reduced the frequency of migraine headache days with aura in the episodic migraine studies. There was a significant reduction in the proportion of remaining migraine headache days with nausea and/or vomiting for the episodic and chronic migraine studies, and with photophobia and phonophobia for the episodic migraine studies. Galcanezumab was superior to placebo in reducing the number of monthly moderate-to-severe migraine headache days and the overall and monthly severe migraine headache days. CONCLUSIONS: Galcanezumab reduces the frequency of migraine headache days and can alleviate potentially disabling non-pain symptoms on days when migraine is present in patients with episodic or chronic migraine. TRIAL REGISTRATION: NCT, NCT02614183 (EVOLVE-1), registered 25 November 2015; NCT, NCT02614196 , (EVOLVE-2), registered 25 November 2015; NCT, NCT02614261 (REGAIN), registered 25 November 2015.

Phosphorus and species regulate N2 fixation by herbaceous legumes in longleaf pine savannas.

Longleaf pine savannas house a diverse community of herbaceous N2-fixing legume species that have the potential to replenish nitrogen (N) losses from fire. Whether legumes fill this role depends on the factors that regulate symbiotic fixation, including soil nutrients such as phosphorus (P) and molybdenum (Mo) and the growth and fixation strategies of different species. In greenhouse experiments, we determined how these factors influence fixation for seven species of legumes grown in pure field soil from two different regions of the southeastern US longleaf pine ecosystem. We first added P and Mo individually and in combination, and found that P alone constrained fixation. Phosphorus primarily influenced fixation by regulating legume growth. Second, we added N to plants and found that species either downregulated fixation (facultative strategy) or maintained fixation at a constant rate (obligate strategy). Species varied nearly fourfold in fixation rate, reflecting differences in growth rate, taxonomy and fixation strategy. However, fixation responded strongly to P addition across all species in our study, suggesting that the P cycle regulates N inputs by herbaceous legumes.

Transition metal photoredox catalysis of radical thiol-ene reactions.

We describe the anti-Markovnikov hydrothiolation of olefins using visible-light-absorbing transition metal photocatalysts. The key thiyl radical intermediates are generated upon quenching of photoexcited Ru*(bpz)3(2) with a variety of thiols. The adducts of a wide variety of olefins and thiols are formed in excellent yield (73-99%).

Nitrogen removal performance in roadside stormwater bioretention cells amended with drinking water treatment residuals.

Bioretention cells, a type of green stormwater infrastructure, have been shown to reduce runoff volumes and remove a variety of pollutants. The ability of bioretention cells to remove nitrogen and phosphorus, however, is variable, and bioretention soil media can act as a net exporter of nutrients. This is concerning as excess loading of nitrogen and phosphorus can lead to eutrophication of surface waters, which green stormwater infrastructure is intended to ameliorate. Drinking water treatment residuals (DWTR), metal (hydr)oxide-rich by-products of the drinking water treatment process, have been studied as an amendment to bioretention soil media due to their high phosphorus sorption capacity. However, very few studies have specifically addressed the effects that DWTRs may have on nitrogen removal performance within bioretention cells. Here, we investigated the effects of DWTR amendment on nitrogen removal in bioretention cells treating stormwater in a roadside setting. We tested the capacity of three different DWTRs to either retain or leach dissolved inorganic nitrogen in the laboratory and also conducted a full-scale field experiment where DWTR-amended bioretention cells and experimental controls were monitored for influent and effluent nitrogen concentrations over two field seasons. We found that DWTRs alone exhibit some capacity to leach nitrate and ammonium, but when integrated into sand- and compost-based bioretention soil media, DWTRs have little to no effect on the removal of nitrogen in bioretention cells. These results suggest that DWTRs can be used in bioretention media for enhanced phosphorus retention without the risk of contributing to nitrogen export in bioretention effluent.

Phosphorus removal, metals dynamics, and hydraulics in stormwater bioretention systems amended with drinking water treatment residuals.

Drinking water treatment residuals (DWTRs) are a promising media amendment for enhancing phosphorus (P) removal in bioretention systems, but substantial removal of dissolved P by DWTRs has not been demonstrated in field bioretention experiments. We investigated the capacity of a non-amended control media (Control) and a DWTR-amended treatment media (DWTR) to remove soluble reactive P (SRP), dissolved organic P (DOP), particulate P (PP), and total P (TP) from stormwater in a two-year roadside bioretention experiment. Significant reductions m SRP, PP and TP concentrations and loads were observed in both the Control and DWTR media. However, the P removal efficiency of the DWTR cells were greater than those of the Control cells for all P species, particularly during the second monitoring season as P sorption complexes likely began to saturate in the Control cells. The difference in P removal efficiency between the Control and DWTR cells was greatest during large storm events, which transported the majority of dissolved P loads in this study. We also investigated the potential for DWTRs to restrict water flow through bioretention media or leach heavy metals. The DWTRs used in this study did not affect the hydraulic performance of the bioretention cells and no significant evidence of heavy metal leaching was observed during the study period. Contrasting these results with past studies highlights the importance of media design in bioretention system performance and suggests that DWTRs can effectively capture and retain P without affecting system hydraulics if properly incorporated into bioretention media.

Balancing Hydraulic Control and Phosphorus Removal in Bioretention Media Amended with Drinking Water Treatment Residuals.

Green stormwater infrastructure like bioretention can reduce stormwater runoff volumes and trap sediments and pollutants. However, bioretention soil media can be both a sink and source of phosphorus (P). We investigated the potential tradeoff between hydraulic conductivity and P sorption capacity in drinking water treatment residuals (DWTRs), with implications for bioretention media design. Batch isotherm and flow-through column experiments were used to quantify the maximum P sorption capacity (Smax) and rate of P sorption for three DWTR sources. Smax values varied greatly among DWTR sources and methodologies, which has implications for regulatory standards. We also conducted a large column experiment to determine the hydraulic and P removal effects of amending bioretention media with solid and mixed layers of DWTRs. When applied to bioretention media, the impact of DWTRs on hydraulic conductivity and P removal depended on layering strategy. Although DWTR addition in solid and mixed layer designs improved P removal, the solid layer restricted water flow and exhibited incomplete P removal, while the mixed layer had no effect on flow and removed ~100% of P inputs. We recommend that DWTRs be mixed with sand in bioretention media to simultaneously achieve stormwater drainage and P reduction goals in green stormwater infrastructure.

Crossed Intermolecular [2+2] Cycloaddition of Styrenes by Visible Light Photocatalysis.

We report a method for the crossed [2+2] cycloaddition of styrenes using visible light photocatalysis. Few methods for the synthesis of unsymmetrically substituted cyclobutanes by photochemical [2+2] cycloaddition are known. We show that careful tuning of the electrochemical properties of a ruthenium photocatalyst enable the efficient crossed [2+2] cycloaddition of styrenes upon irradiation with visible light. We outline the logic that enables high crossed chemoselectivity, and we also demonstrate that this reaction is remarkably efficient; gram-scale reactions can be conducted with as little as 0.025 mol% of the photocatalyst.