Plant germination and growth can be influenced by sound, but the ecological significance of these responses is unclear. We asked whether acoustic energy generated by the feeding of insect herbivores ...was detected by plants. We report that the vibrations caused by insect feeding can elicit chemical defenses. Arabidopsis thaliana (L.) rosettes pre-treated with the vibrations caused by caterpillar feeding had higher levels of glucosinolate and anthocyanin defenses when subsequently fed upon by Pieris rapae (L.) caterpillars than did untreated plants. The plants also discriminated between the vibrations caused by chewing and those caused by wind or insect song. Plants thus respond to herbivore-generated vibrations in a selective and ecologically meaningful way. A vibration signaling pathway would complement the known signaling pathways that rely on volatile, electrical, or phloem-borne signals. We suggest that vibration may represent a new long distance signaling mechanism in plant–insect interactions that contributes to systemic induction of chemical defenses.
Electrocatalysts are critically important for a secure energy future, as they facilitate the conversion between electrical and chemical energy. Molecular catalysts offer precise control of structure ...that enables understanding of structure–reactivity relationships, which can be difficult to achieve with heterogeneous catalysts. Molecular electrocatalysts can be immobilized on surfaces by covalent bonds or through non‐covalent interactions. Advantages of surface immobilization include the need for less catalyst, avoidance of bimolecular decomposition pathways, and easier determination of catalyst lifetime. This Minireview highlights surface immobilization of molecular electrocatalysts for reduction of O2, oxidation of H2O, production of H2, and reduction of CO2.
The conversion between electrical and chemical energy by electrocatalysts means that they are critically important for a secure energy future. This Minireview highlights surface immobilization of molecular electrocatalysts for reduction of O2, oxidation of H2O, production of H2, and reduction of CO2 (see scheme).
Because of the continually rising levels of CO2 in the atmosphere, research for the conversion of CO2 into fuels using carbon-neutral energy is an important and current topic in catalysis. Recent ...research on molecular catalysts has led to improved rates for conversion of CO2 to formate, but the catalysts are based on precious metals such as iridium, ruthenium and rhodium and require high temperatures and high pressures. Using established thermodynamic properties of hydricity (ΔG H– ) and acidity (pK a), we designed a cobalt-based catalyst system for the production of formate from CO2 and H2. The complex Co(dmpe)2H (dmpe is 1,2-bis(dimethylphosphino)ethane) catalyzes the hydrogenation of CO2, with a turnover frequency of 3400 h–1 at room temperature and 1 atm of 1:1 CO2:H2 (74 000 h–1 at 20 atm) in tetrahydrofuran. These results highlight the value of fundamental thermodynamic properties in the rational design of catalysts.
There is widespread interest in the hydrogenation of CO2 to energy-rich products such as formate. However, first-row transition metal catalysts for the hydrogenation of CO2 to formate remain rare. ...Copper complexes are widely used in the reduction of organic substrates, but their use in the catalytic hydrogenation of CO2 has been limited. Here, we demonstrate that the copper(I) complex LCu(MeCN)PF6 is an active catalyst for CO2 hydrogenation in the presence of a suitable base. Screening of bases and studies of catalytic reactions by in operando spectroscopy revealed important and unusual roles for the base in promoting H2 activation and turnover.
Background
Ambiguities exist regarding the diagnosis of tree‐nut allergy, necessitating either their elimination or the performance of oral food challenges (OFCs).
Objective
To examine the ...coincidences of allergies among tree‐nuts and improve diagnostic testing to minimize the need for OFC.
Methods
Eighty‐three patients prospectively evaluated for walnut, pecan, cashew, pistachio, hazelnut, and almond allergy. A history of previous reactions was obtained, and standardized skin prick tests (SPTs) using finely ground tree‐nut solution and basophil activation tests (BAT) were performed. Patients underwent OFC for each tree‐nut they eliminated and to which a reaction in the previous 2 years was not documented.
Results
While most patients were sensitized to 5‐6 tree‐nuts, over 50% were allergic to only 1‐2 tree‐nuts. The highest rate of allergy in sensitized patients was observed for walnut (74.6%) and cashew (65.6%). The rate of co‐allergy for most tree‐nuts was <30%. Two‐thirds of walnut‐ and cashew‐allergic patients were also allergic to pecan and pistachio, respectively, while all pecan‐ and pistachio‐allergic patients were allergic to walnut and cashew, respectively. Receiver‐operating characteristic analysis for SPT and BAT was tree‐nut dependent and yielded area under the curve (AUC) values ranging from 0.75 to 0.94. Knowledge of coincident allergies in these pairs along with the combination of SPT and BAT correctly distinguished allergic from tolerant patients for walnut (87%), pecan (66%), cashew (71%), and pistachio (79%).
Conclusion
The data presented here should assist in differentiating between allergic and tolerant patients, decrease the need for OFC, and allow for appropriate elimination recommendations.
A variety of next-generation energy processes utilize the electrochemical interconversions of dioxygen and water as the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). ...Reported here are the first estimates of the standard reduction potential of the O2 + 4e – + 4H+ ⇋ 2H2O couple in organic solvents. The values are +1.21 V in acetonitrile (MeCN) and +0.60 V in N,N-dimethylformamide (DMF), each versus the ferrocenium/ferrocene couple (Fc+/0) in the respective solvent (as are all of the potentials reported here). The potentials have been determined using a thermochemical cycle that combines the free energy for transferring water from aqueous solution to organic solvent, −0.43 kcal mol–1 for MeCN and −1.47 kcal mol–1 for DMF, and the potential of the H+/H2 couple, – 0.028 V in MeCN and −0.662 V in DMF. The H+/H2 couple in DMF has been directly measured electrochemically using the previously reported procedure for the MeCN value. The thermochemical approach used for the O2/H2O couple has been extended to the CO2/CO and CO2/CH4 couples to give values of −0.12 and +0.15 V in MeCN and −0.73 and −0.48 V in DMF, respectively. Extensions to other reduction potentials are discussed. Additionally, the free energy for transfer of protons from water to organic solvent is estimated as +14 kcal mol–1 for acetonitrile and +0.6 kcal mol–1 for DMF.
One of the criteria used by many transplant centers in assessing psychosocial eligibility for solid organ transplantation is social support. Yet, social support is a highly controversial requirement ...that has generated ongoing debate between ethicists and clinicians who favor its consideration (i.e., utility maximizers) and those who object to its use on equity grounds (i.e., equity maximizers). The assumption underlying both of these approaches is that social support is not a commodity that can be purchased in the marketplace. This essay argues for the reconceptualization of social support as a product that can-and should-be purchased for transplant candidates to render them eligible for transplant.
Large-scale CO2 hydrogenation could offer a renewable stream of industrially important C1 chemicals while reducing CO2 emissions. Critical to this opportunity is the requirement for inexpensive ...catalysts based on earth-abundant metals instead of precious metals. We report a nickel–gallium complex featuring a Ni(0)→Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h–1), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, including a rare anionic d10 Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni–H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.
PDF
