Route following by one-eyed ants suggests a revised model of normal route following

The prevailing account of visually controlled routes is that an ant learns views as it follows a route, while guided by other path-setting mechanisms. Once a set of route views is memorised, the insect follows the route by turning and moving forwards when the view on the retina matches a stored view. We engineered a situation in which this account cannot suffice in order to discover whether there may be additional components to the performance of routes. One-eyed wood ants were trained to navigate a short route in the laboratory, guided by a single black, vertical bar placed in the blinded visual field. Ants thus had to turn away from the route to see the bar. They often turned to look at or beyond the bar and then turned to face in the direction of the goal. Tests in which the bar was shifted to be more peripheral or more frontal than in training produced a corresponding directional change in the ants' paths, demonstrating that they were guided by the bar. Examination of the endpoints of turns towards and away from the bar indicate that ants use the bar for guidance by learning how large a turn-back is needed to face the goal. We suggest that the ants' zigzag paths are in part controlled by turns of a learnt amplitude and that these turns are an integral part of visually guided route following.

Short Protecting Group-free Syntheses of CDE Synthon of Racemic Camptothecin

A practical and concise total synthesis of tricyclic ketone 7 (CDE ring), a valuable intermediate for the synthesis of racemic camptothecin and analogs, was described (8 chemical steps and 29% overall yield). The synthesis starts with two inexpensive, readily available materials and is operationally simple to perform. It is worth mentioning that the reported protecting group-free synthesis, with advantages of a short route, would be helpful for the future development of industry-scale syntheses of camptothecin-family alkaloids.

Route following by one-eyed ants suggests a revised model of normal route following

SummaryThe prevailing account of visually controlled routes is that an ant learns views as it follows a route, while guided by other path-setting mechanisms. Once a set of route views is memorised, the insect follows the route by turning and moving forwards when the view on the retina matches a stored view. We have engineered a situation in which this account cannot suffice in order to discover whether there may be additional components to the performance of routes. One-eyed wood ants were trained to navigate a short route in the laboratory guided by a single black, vertical bar placed in the blinded visual field. Ants thus had to turn away from the route to see the bar. They often turned to look at or beyond the bar and then turned to face in the direction of the goal. Tests in which the bar was shifted to be more peripheral or more frontal than in training produced a corresponding change in the ants’ paths, demonstrating that they were guided by the bar, presumably obtaining information during scanning turns towards the bar. Examination of the endpoints of turns away from the bar suggest that ants use the bar for guidance by learning how large a turn-back is needed to face the goal. We suggest that the ants’ zigzag paths are an integral part of visually guided route following. In addition, on some runs in which ants did not take a direct path to the goal, they still turned to face and sometimes approach the goal for a short stretch. This off-route goal facing indicates that they store a vector from start to goal and use path integration to track their position relative to the endpoint of the vector.

Reductive Condensation of a Nitro Group with Carboxylic Acids Promoted by Phosphorus(III) Compounds: A Short Route to 5H-Dibenzo[b,e][1,4]diazepin-11(10H)-ones

Tributyl- or triphenylphosphine promotes a one-pot, three-step method for the synthesis of differently substituted dibenzodiazepinones from N-aryl-2-nitroanilines. Pyridine analogues and the corresponding thiazepinones can also be formed using this method. The process involves deoxygenation of the nitro group, then formation of an iminophosphorane intermediate and its intramolecular condensation with a carboxyl group placed in the N-aryl group. The role of the carboxyl group in the formation of the iminophosphorane and the mode of cyclization are discussed.

Cortico-subthalamic projections send brief stop signals to halt visually-guided locomotion

SummaryGoal-directed locomotion necessitates control signals that propagate from higher-order areas to regulate spinal mechanisms. The cortico-subthalamic hyperdirect pathway offers a short route for cortical information to reach locomotor centers in the brainstem. We developed a task where head-fixed mice run to a visual landmark, then stop and wait to collect reward, and examined the role of secondary motor cortex (M2) projections to the subthalamic nucleus (STN) in controlling locomotion. Our modeled behavioral strategy indicates a switching point in behavior, suggesting a critical neuronal control signal at stop locations. Optogenetic activation of M2 axons in STN leads the animal to stop prematurely. By imaging M2 neurons projecting to STN, we find neurons that are active at the onset of stops, when executed at the landmark but not spontaneously elsewhere. Our results suggest that the M2-STN pathway can be recruited during visually-guided locomotion to rapidly and precisely control the mesencephalic locomotor region through the basal ganglia.

Short-route synthesis method of N-doped exfoliated graphite whit catalytic activity for the oxygen reduction reaction.

We report the synthesis of metal-free nitrogen-doped electrocatalysts obtained from graphite and urea as carbon and nitrogen precursor, respectively. High-energy milling and thermal annealing were carried out to obtain low cost electrocatalysts. Additionally, this method has shorter synthesis times, is environmentally friendly and use high-availability raw materials. A short-route synthesis consisted in the partial exfoliation of graphite by mechanical milling with urea. Afterwards, nitrogen was integrated into the exfoliated graphite lattice by thermal annealing at 500°C. XPS analyses shows up to 1.7 at. % was incorporated to the graphitic lattice. Scanning Electron Microscopy, X-ray diffraction and Raman Spectroscopy were used to analyse the morphology and structural features. The catalytic activity for the oxygen reduction reaction in basic media was evaluated by the rotating disk electrode technique.

A short route to access oxaspiro[n,3,3]propellanes

Two different oxapropellane derivatives have been prepared from a common α-propargyl-β-ketoester.