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An exciton–polariton condensate is a hybrid light–matter state in the quantum fluid phase. The photonic component endows it with characters of spin, as represented by circular polarization. Spin-polarization can form stochastically for quasi-equilibrium exciton–polariton condensates at parallel momentum vector k|| ∼ 0 from bifurcation or deterministically for propagating condensates at k|| > 0 from the optical spin-Hall effect (OSHE). Here, we report deterministic spin-polarization in exciton–polariton condensates at k|| ∼ 0 in microcavities containing methylammonium lead bromide perovskite (CH3NH3PbBr3) single crystals under non-resonant and linearly polarized excitation. We observe two energetically split condensates with opposite circular polarizations and attribute this observation to the presence of strong birefringence, which introduces a large OSHE at k|| ∼ 0 and pins the condensates in a particular spin state. Such spin-polarized exciton–polariton condensates may serve not only as circularly polarized laser sources but also as effective alternatives to ultracold atom Bose–Einstein condensates in quantum simulators of many-body spin–orbit coupling processes. [ABSTRACT FROM AUTHOR]

This paper compares the use of photoionization and flame ionization detectors (PID and FID, respectively) for the analysis of ethylene in plant physiological studies. It is shown that PID has the capability to analyse ethylene levels in the order of 1 mm3 m-3. This represents an increase in sensitivity over FID of several-fold. Evidence is presented that this enhanced sensitivity allows for measurement of the rate of ethylene production from plants in continuous-flow systems by taking air samples directly from the air stream, thus eliminating the need for selective collection and concentration of ethylene. [ABSTRACT FROM AUTHOR]

Depending on the applied concentration, nitrate can either stimulate or inhibit germination of dormant seeds of Sinapis arvensis L. (wild mustard). Seed NO[SUB3,SUP-] levels that corresponded to the maximal germination frequencies recorded, ranged from 0.3 to 4.4nmol seed[SUP-1] for applied NO[SUB3,SUP-] concentrations between 2.5 and 20 mol m[SUP-3]. Germination was significantly lower in seeds containing more than 5 nmol NO[SUB3,SUP-]. Although the presence of NO[SUB3,SUP-] within the seed was required to promote germination, seed NO[SUB3,SUP-] levels were 5 to 15 times less than levels calculated from the volume of solution taken up by the seeds. Seed NO[SUB3,SUP-] levels also responded in a passive fashion to the external NO[SUB3,SUP-] concentration when the seeds were incubated on filter paper or in soil. In a representative soil containing 26 mg NO[SUB3,SUP-]-N per kg dry weight and 8 to 16% water by weight, the amount of NO[SUB3,SUP-] taken up by the seeds reached inhibitory levels. Our results suggest that levels of inorganic nitrogen (NO[SUB3,SUP-], NH[SUB3,SUP-]) in managed soils may play an important role in regulating germination of dormant S. arvensis seeds. [ABSTRACT FROM AUTHOR]

Chenopodium album L. plants, grown under controlled environmental conditions on different levels of soil nitrate, produced seeds with proportionately differnt NO3- contents. Regardless of the endogenous NO3- content, few seeds germinated in water or upon treatment with KNO3. Ethylene promoted germination, and the extent of germination was positively correlated with the endogenous seed NO3- content. Combined application of ethylene and KNO3 in the dark had a synergistic effect on NO3--deficient seed. The synergism between ethylene and KNO3 was attributable to the NO3- moiety of the nitrate salt. Ethylene and light showed moderate synergism in seeds with low or high endogenous nitrate. Addition of nitrate, however, masked the interaction between ethylene and light. Gibberellic acid4+7 (GA4+7) or red light, each alone or combined with KNO3, had little effect on germination. When applied together in the dark, ethylene and GA4+7 synergistically enhanced the germination of NO3- deficient seed. The combined effects of the two hormones on this seed were further enhanced by the addition of KNO3. There was no synergism between ethylene and GA4+7 in NO3--rich seed. These interactions among GA4+7], ethylene and KNO3 were not affected by light. The results confirm and further elaborate our earlier finding that the sensitivity of C. album seeds to ethylene may depend on nitrate availability. [ABSTRACT FROM AUTHOR]