Automated optimization of a reduced layer 5 pyramidal cell model based on experimental data.

The construction of compartmental models of neurons involves tuning a set of parameters to make the model neuron behave as realistically as possible. While the parameter space of single-compartment models or other simple models can be exhaustively searched, the introduction of dendritic geometry causes the number of parameters to balloon. As parameter tuning is a daunting and time-consuming task when performed manually, reliable methods for automatically optimizing compartmental models are desperately needed, as only optimized models can capture the behavior of real neurons. Here we present a three-step strategy to automatically build reduced models of layer 5 pyramidal neurons that closely reproduce experimental data. First, we reduce the pattern of dendritic branches of a detailed model to a set of equivalent primary dendrites. Second, the ion channel densities are estimated using a multi-objective optimization strategy to fit the voltage trace recorded under two conditions - with and without the apical dendrite occluded by pinching. Finally, we tune dendritic calcium channel parameters to model the initiation of dendritic calcium spikes and the coupling between soma and dendrite. More generally, this new method can be applied to construct families of models of different neuron types, with applications ranging from the study of information processing in single neurons to realistic simulations of large-scale network dynamics

Experience applicable to the Viking lander from a study of related space flight projects

Related space mission data for baseline evaluation of Viking Lander design and operatio

Transition Administration

The period from November 3, 2020 to January 20, 2021, was unlike any presidential transition in our history. President Donald Trump refused to accept his ballot-box defeat, instead battling to overturn the election’s outcome. This dramatic public campaign was waged in state and federal courts, state legislatures, the offices of state and local election officials, the Department of Justice, and finally the halls of Congress, where on January 6, 2021, a mob incited by the President stormed the Capitol with the explicit goal of preventing the final counting of electoral votes for Joe Biden. These efforts had more mundane and less visible aspects as well. Not least, the President’s rejection of the election’s outcome led to delay and obstruction of the Biden transition team. Under the circumstances, the transition was remarkably successful. But the avoided threat to the law and norms of presidential transitions—constitutional, statutory, and conventional—calls for a taking of stock. What mechanisms enabled even moderate success in such circumstances, and what changes can be made to help ensure smoother sailing in the future? Even in ordinary times, when unsuccessful presidential candidates concede defeat, congratulate victorious rivals, and facilitate the transfer of power, presidential transitions can be fraught and uncertain affairs. It is a truism that “the country has only one President at a time,” and reading the Constitution seems to confirm that understanding. But while the Constitution largely ignores the President-elect, statutes and conventions do not, establishing a regime in which the President-elect is not simply a private citizen waiting in the wings. To an ever-increasing extent, the President-elect, Vice President elect, and the sweeping transition apparatus are intertwined with and inseparable from the operations of the federal government. The complex status of transitions raises a number of questions regarding authority and obligation. This Article seeks to address those questions. As we show, the scaffolding of law and, at least as important, practice that surrounds transitions goes far to make the peaceful and effective transfer of power possible. A central challenge is avoiding the risk that profound political and ideological hostilities will derail the process; the current regime does so by ensuring federal support for the transition operation, by requiring cooperation on the part of the outgoing administration, and, perhaps most importantly, by placing primary responsibility in career agency employees rather than political appointees. In the modern era, this regime has been largely successful. But it fails to go far enough in relying on career officials, and in some key respects, does not center those officials as fully as it should. The Article concludes with a discussion of a number of possible statutory reforms, including to the defect that received the most attention in 2020: reliance on the Administrator of the General Services Administration to “ascertain” the apparent victor in order to trigger the provision of post-election resources

The Transition Is Already Happening (And It’s Going Fine So Far)

Even if Trump were resolved to thwart a smooth transition, much of the process lies entirely outside his control. Sometime in early to mid-November, if October polling holds and the infrastructure of our democracy basically functions, Joe Biden is likely to be declared the winner of the 2020 presidential election. At that point, he will have just more than two months to prepare to take over the leadership of a country still in the grips of a once-in-a-century pandemic, with more than 12 million Americans unemployed, tens of millions of children out of school, and COVID-19 deaths barreling toward 300,000. Transitions can be challenging even under the best circumstances. And President Donald Trump, to say the least, may not be psychologically or temperamentally predisposed to a thoughtful, well-planned transition. Even back when he was the incoming president, his on-ramp to the presidency was extraordinarily haphazard, disorganized, and incomplete. Add in his petulance and expected fury at the outcome, and there is surely reason to fear the havoc the president and his team could wreak on their way to the exits

Statistical mechanics of temporal association in neural networks with transmission delays

We study the representation of static patterns and temporal sequences in neural networks with signal delays and a stochastic parallel dynamics. For a wide class of delay distributions, the asymptotic network behavior can be described by a generalized Gibbs distribution, generated by a novel Lyapunov functional for the determination dynamics. We extend techniques of equilibrium statistical mechanics so as to deal with time-dependent phenomena, derive analytic results for both retrieval quality and storage capacity, and compare them with numerical simulations

Electron beam seals outer surfaces of porous bodies

Porous tungsten plugs provide even airflow for frictionless bearings used in air bearing supported gyros. The plugs have their outer cylindrical surface sealed by an electron beam process to ensure unidirectional airflow through their exit ends

Zebrafish Exploit Visual Cues and Geometric Relationships to Form a Spatial Memory

Animals use salient cues to navigate in their environment, but their specific cognitive strategies are largely unknown. We developed a conditioned place avoidance paradigm to discover whether and how zebrafish form spatial memories. In less than an hour, juvenile zebrafish, as young as 3 weeks, learned to avoid the arm of a Y-maze that was cued with a mild electric shock. Interestingly, individual fish solved this task in different ways: by staying in the safe center of the maze or by preference for one, or both, of the safe arms. In experiments in which the learned patterns were swapped, rotated, or replaced, the animals could transfer the association of safety to a different arm or to a different pattern using either visual cues or location as the conditioned stimulus. These findings show that juvenile zebrafish exhibit several complementary spatial learning modes, which generate a flexible repertoire of behavioral strategies