לוח שנה משולב

Perceivers experience the world around them as organized, with sensory impressions clearly separated into entities. What makes a perceptual object, and what framework relates it to its composing features? A key insight is that under natural conditions, feature and object information is acquired actively, via sensor movements. Motor and sensory variables affect one another reciprocally, forming a closed-loop system. I therefore hypothesize that percepts signifying an object emerge when the motor-sensory loop’s dynamics converge towards a stable attractor. Using snout and whisker tracking data from freely-moving behaving rats, I outline such an attractor for object detection. I demonstrate that whisker-object contact elicits robust signals on a motor-sensory phase-plane, comprised of the derivatives of whisker base-angle and base-curvature. Over consecutive contact epochs, trajectories on the phase-plane converge to a specific area. The area is characterized by a basin of attraction during contact, more so than in free-air whisking. Differences in head-movement behavior are associated with proximity to the attractor, suggesting that the animal makes use of this proposed coding-scheme. Finally, to build upon these insights, I present a novel paradigm for the study of volitional perceptual exploration, in both rewarded and unrewarded contexts. It supports high-resolution study of motor-sensory development starting at birth, throughout task-learning and until mastery. Taken together, these results highlight a novel framework for the study of the perception of features and objects as motor-sensory attractors.

TBA...

In recent decades, various temperature proxies have been developed and further established in the scientific community, at both low and high accuracy, however, not every method can be applied without restriction to all minerals or rocks. Evaporitic rocks, for example, are abundant chemical sediments at the Earth's surface that are deposited from supersaturated brines in marine, terrestrial, and lacustrine environments. Halite is the most abundant rock-forming mineral in this group, which during crystal formation entraps tiny water droplets (fluid inclusions, FIs) that store the chemical composition of the parent brine at a specific pressure-temperature dependent density. Such FIs are therefore excellent records of the original physicochemical conditions of the source brine.
Brillouin spectroscopy (BS) is a novel laser-based technique that uses density fluctuations in FIs to directly measure entrapment temperatures and thus the initial brine temperature during crystal growth. In this seminar, the BS method will be introduced and two application cases will be presented using salt layers from the Dead Sea which were deposited during two interglacial periods. In addition to the basic principles, both the recommended sampling strategy and pitfalls along with associated limitations will be presented.
The conclusion will be that the salt layers commonly deposited in the Dead Sea basin consist of two types that formed preferentially in summer (coarse-grained crystals) and winter (fine-grained crystals), which is mainly controlled by the degree of salt saturation of the lake water. Furthermore, it will be shown how (1) lake bottom temperatures have fluctuated seasonally (summer/winter), and that (2) paleo temperature trends can be reconstructed for an entire halite layer that was deposited during holomictic periods in the Dead Sea basin. This method is particularly promising for evaporites that formed near the surface if the material has not been affected by external processes such as tectonic burial/uplift, erosion, or mineral replacement.