Do Clark’s nutcrackers demonstrate what-where-when memory on a cache-recovery task?

What-where-when (WWW) memory during cache recovery was investigated in six Clark’s nutcrackers. During caching, both red- and blue-colored pine seeds were cached by the birds in holes filled with sand. Either a short (3 day) retention interval (RI) or a long (9 day) RI was followed by a recovery session during which caches were replaced with either a single seed or wooden bead depending upon the color of the cache and length of the retention interval. Knowledge of what was in the cache (seed or bead), where it was located, and when the cache had been made (3 or 9 days ago) were the three WWW memory components under investigation. Birds recovered items (bead or seed) at above chance levels, demonstrating accurate spatial memory. They also recovered seeds more than beads after the long RI, but not after the short RI, when they recovered seeds and beads equally often. The differential recovery after the long RI demonstrates that nutcrackers may have the capacity for WWW memory during this task, but it is not clear why it was influenced by RI duration

Frontal cortex differentiates between free and imposed target selection in multiple-target search

Cognitive control can involve proactive (preparatory) and reactive (corrective) mechanisms. Using a gaze-contingent eye tracking paradigm combined with fMRI, we investigated the involvement of these different modes of control and their underlying neural networks, when switching between different targets in multiple-target search. Participants simultaneously searched for two possible targets presented among distractors, and selected one of them. In one condition, only one of the targets was available in each display, so that the choice was imposed, and reactive control would be required. In the other condition, both targets were present, giving observers free choice over target selection, and allowing for proactive control. Switch costs emerged only when targets were imposed and not when target selection was free. We found differential levels of activity in the frontoparietal control network depending on whether target switches were free or imposed. Furthermore, we observed core regions of the default mode network to be active during target repetitions, indicating reduced control on these trials. Free and imposed switches jointly activated parietal and posterior frontal cortices, while free switches additionally activated anterior frontal cortices. These findings highlight unique contributions of proactive and reactive control during visual search

Correlation of ignimbrites using characteristic remanent magnetization and anisotropy of magnetic susceptibility, Central Andes, Bolivia

Large ignimbrite flare-ups provide records of profound crustal modification during batholith formation at depth. The locations of source calderas and volumes and ages of the eruptions must be determined to develop models for the tectonomagmatic processes that occur during these events. Although high-precision isotopic ages of the ignimbrites are critical, less expensive and more rapid techniques, such as paleomagnetism, can extend the temporal information from dated outcrops. Paleomagnetic and rock magnetic data, including characteristic remanent magnetization (ChRM) and anisotropy of magnetic susceptibility (AMS), from the Altiplano-Puna Volcanic Complex of the Central Andes reliably identify calderas and eight associated Mio-Pliocene ignimbrites. ChRM results indicate a larger between-site error for most ignimbrites, in comparison to within-site scatter. Part of this dispersion may be due to tumescence/detumescence associated with the caldera-forming eruptions, but most of the effect is probably due to the recording of paleosecular variation during cooling and vapor-phase crystallization of the thick ignimbrites. AMS data identify the source calderas for four ignimbrites and provide limits on possible post-emplacement rotations of the deposits. AMS data indicate significant topographic control on inferred flow directions, implying that the flows were dense and/or of low mobility

Climate Impacts on Agriculture: Implications for Crop Production

Changes in temperature, CO2, and precipitation under the scenarios of climate change for the next 30 yr present a challenge to crop production. This review focuses on the impact of temperature, CO2, and ozone on agronomic crops and the implications for crop production. Understanding these implications for agricultural crops is critical for developing cropping systems resilient to stresses induced by climate change. There is variation among crops in their response to CO2, temperature, and precipitation changes and, with the regional differences in predicted climate, a situation is created in which the responses will be further complicated. For example, the temperature effects on soybean [Glycine max (L.) Merr.] could potentially cause yield reductions of 2.4% in the South but an increase of 1.7% in the Midwest. The frequency of years when temperatures exceed thresholds for damage during critical growth stages is likely to increase for some crops and regions. The increase in CO2 contributes significantly to enhanced plant growth and improved water use efficiency (WUE); however, there may be a downscaling of these positive impacts due to higher temperatures plants will experience during their growth cycle. A challenge is to understand the interactions of the changing climatic parameters because of the interactions among temperature, CO2, and precipitation on plant growth and development and also on the biotic stresses of weeds, insects, and diseases. Agronomists will have to consider the variations in temperature and precipitation as part of the production system if they are to ensure the food security required by an ever increasing population

The Clementine Bistatic Radar Experiment

During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, beta, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around beta = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar observations of periodically solar-illuminated lunar surfaces, including the north pole, yielded no such enhancement. A probable explanation for these differences is the presence of low-loss volume scatterers, such as water ice, in the permanently shadowed region at the south pole

A Note on Lie-Lorentz Derivatives

The definition of ``Lie derivative'' of spinors with respect to Killing vectors is extended to all kinds of Lorentz tensors. This Lie-Lorentz derivative appears naturally in the commutator of two supersymmetry transformations generated by Killing spinors and vanishes for Vielbeins. It can be identified as the generator of the action of isometries on supergravity fields and its use for the calculation of supersymmetry algebras is revised and extended.Comment: Latex2e, 9 pages, AMS font