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ABSTRACT We studied near‐instantaneous temperature responses of light‐saturated photosynthesis (A_sat) and the operating efficiency of photosystem II (ΦPSII) in relation to acclimation of photosynthetic biochemistry to temperature at the timescale of 1–8 days. We grew two closely relatedBrassica oleraceaL. accessions under diurnal temperature ranges of 15°C–25°C and 5°C–15°C, representing the warm and cool native environments of the two accessions. Near‐instantaneous temperature responses ofA_satand ΦPSII were measured on acclimated plants exposed to a temperature ramp from 10°C to 45°C. Biochemical acclimation was quantified by switching plants between warm and cool regimes before measuring photosynthetic variables at Day 1 and Day 8 after the switch. Near‐instantaneous temperature optima ofA_satand ΦPSII functionally shifted towards the acclimated growth temperatures in both accessions, and both accessions achieved their highest instantaneous maximum values ofA_satand ΦPSII when grown under representative native regimes. Differences in maximum carboxylation capacity were evident by Day 1; no further change was detected by Day 8. Our results highlight functional coordination between adaptation, acclimation and near‐instantaneous temperature responses of photochemistry and biochemistry. Moreover, our results suggest photosynthetic biochemistry can acclimate to temperature changes within a day. 

Abstract We measured the rotationally resolved infrared spectra of helium solvated methyl fluoride at 3 μm and 10 μm, wherein lies C−H and C−F stretching bands, respectively. The linewidths (FWHM) were found to increase with increasing vibrational energy and range from 0.002 cm⁻¹in thev₃band (C−F stretch) at ~1047 cm⁻¹, to 0.65 cm⁻¹in thev₄band (asymmetric C−H stretch) at ~2997 cm⁻¹. In between these two bands we observed the lower and upper components of the Fermi triad bands (ν₁/2ν₂/2ν₅) at ~2859 and ~2961 cm⁻¹. We carried out Stark spectroscopy on the lower band on account of its narrower linewidths (0.04 vs. 0.14 cm⁻¹, respectively). The objective of performing Stark spectroscopy was to see if there is any evidence for a rotational linewidth dependence on the external field strength, due to a reduced difference in between methyl fluorides rotational energy gap and the roton‐gap of superfluid helium. We did not find any evidence for such an effect, which we largely attribute to the rotational energy gap not increasing significantly enough by the external field. We point to another molecule (formaldehyde) whose energy levels are predicted to show a more promising response to application of an external field. 

Abstract The discovery of a new kind of experience can teach an agent what that kind of experience is like. Such a discovery can be epistemically transformative, teaching an agent something they could not have learned without having that kind of experience. However, learning something new does not always require new experience. In some cases, an agent can merely expand their existing knowledge using, e.g., inference or imagination that draws on prior knowledge. We present a computational framework, grounded in the language of partially observable Markov Decision Processes (POMDPs), to formalize this distinction. We propose that epistemically transformative experiences leave a measurable “signature” distinguishing them from experiences that are not epistemically transformative. For epistemically transformative experiences, learning in a new environment may be comparable to “learning from scratch” (since prior knowledge has become obsolete). In contrast, for experiences that are not transformative, learning in a new environment can be facilitated by prior knowledge of that same kind (since new knowledge can be built upon the old). We demonstrate this in a synthetic experiment inspired by Edwin Abbott’s Flatland, where an agent learns to navigate a 2D world and is subsequently transferred either to a 3D world (epistemically transformative change) or to an expanded 2D world (epistemically non-transformative change). Beyond the contribution to understanding epistemic change, our work shows how tools in computational cognitive science can formalize and evaluate philosophical intuitions in new ways.