118 research outputs found
Alpha-Herpesvirus Infection Induces the Formation of Nuclear Actin Filaments
Herpesviruses are large double-stranded DNA viruses that replicate in the nuclei of infected cells. Spatial control of viral replication and assembly in the host nucleus is achieved by the establishment of nuclear compartments that serve to concentrate viral and host factors. How these compartments are established and maintained remains poorly understood. Pseudorabies virus (PRV) is an alpha-herpesvirus often used to study herpesvirus invasion and spread in the nervous system. Here, we report that PRV and herpes simplex virus type 1 infection of neurons results in formation of actin filaments in the nucleus. Filamentous actin is not found in the nucleus of uninfected cells. Nuclear actin filaments appear physically associated with the viral capsids, as shown by serial block-face scanning electron micropscopy and confocal microscopy. Using a green fluorescent protein-tagged viral capsid protein (VP26), we show that nuclear actin filaments form prior to capsid assembly and are required for the efficient formation of viral capsid assembly sites. We find that actin polymerization dynamics (e.g., treadmilling) are not necessary for the formation of these sites. Green fluorescent protein-VP26 foci co-localize with the actin motor myosin V, suggesting that viral capsids travel along nuclear actin filaments using myosin-based directed transport. Viral transcription, but not viral DNA replication, is required for actin filament formation. The finding that infection, by either PRV or herpes simplex virus type 1, results in formation of nuclear actin filaments in neurons, and that PRV infection of an epithelial cell line results in a similar phenotype is evidence that F-actin plays a conserved role in herpesvirus assembly. Our results suggest a mechanism by which assembly domains are organized within infected cells and provide insight into how the viral infectious cycle and host actin cytoskeleton are integrated to promote the infection process
Semi-orthogonal subspaces for value mediate a tradeoff between binding and generalization
When choosing between options, we must associate their values with the action
needed to select them. We hypothesize that the brain solves this binding
problem through neural population subspaces. To test this hypothesis, we
examined neuronal responses in five reward-sensitive regions in macaques
performing a risky choice task with sequential offers. Surprisingly, in all
areas, the neural population encoded the values of offers presented on the left
and right in distinct subspaces. We show that the encoding we observe is
sufficient to bind the values of the offers to their respective positions in
space while preserving abstract value information, which may be important for
rapid learning and generalization to novel contexts. Moreover, after both
offers have been presented, all areas encode the value of the first and second
offers in orthogonal subspaces. In this case as well, the orthogonalization
provides binding. Our binding-by-subspace hypothesis makes two novel
predictions borne out by the data. First, behavioral errors should correlate
with putative spatial (but not temporal) misbinding in the neural
representation. Second, the specific representational geometry that we observe
across animals also indicates that behavioral errors should increase when
offers have low or high values, compared to when they have medium values, even
when controlling for value difference. Together, these results support the idea
that the brain makes use of semi-orthogonal subspaces to bind features
together.Comment: arXiv admin note: substantial text overlap with arXiv:2205.0676
Doing What You\u27re Told: Following Task Instructions in Changing, but Hospitable Environments
The AnimNL project (Anim ation from N atural L anguage) has as its goal the automatic creation of animated task simulations from natural-language instructions. The question addressed in this paper is how agents can perform tasks in environments about which they have only partial relevant knowledge. The solution we describe involves enabling such agents to * develop expectations through instruction understanding and plan inference, and use those expectations in deciding how to act; * exploit generalized abilities in order to deal with novel geometric situations. The AnimNL project builds on an animation system, Jackā¢, that has been developed at the Computer Graphics Research Lab at the University of Pennsylvania, and draws upon a range of recent work in Natural Language semantics, planning and plan inference, philosophical studies of intention, reasoning about knowledge and action, and subsumption architectures for autonomous agents
Planning and Parallel Transition Networks: Animation\u27s New Frontiers
Animating realistic human agents involves more than just creating movements that look real . A principal characteristic of humans is their ability to plan and make decisions based on intentions and the local environmental context. Animated agents must therefore react to and deliberate about their environment and other agents. Our agent animation uses various low-level behaviors, sense-control-action loops, high-level planning, and parallel task networks. Several systems we developed will illustrate how these components contribute to the realism and efficacy of human agent animation
Control and optimization of semi-passively actuated multibody systems
The controlled multibody systems are under the consideration. At the lecture special emphasis is put on the study of underactuated and overactuated systems having different type of actuators (external powered drives, unpowered spring-damper like drives, etc.). Several questions are addressed about the role of inherent dynamics, and how much multibody system should be governed by external powered drives and how much by the systems inherent dynamics. The lecture consists of the following parts: introduction to the subject in question; mathematical statement of the optimal control problems that are suitable for modelling of controlled motion and optimization of semi-passively controlled multibody systems with different degrees of actuation; description of the methodology and the numerical algorithms for solution of control and optimization problems for semi-passively actuated multibody systems. The solutions of several optimal control problems for different kind of semi-passively actuated multibody systems are presented. Namely, the energy-optimal control of planar semi-passively controlled three-link manipulator robot, the energy-optimal control of closed-loop chain semi-passively actuated SCARA-like robot; optimization of the hydraulic and pneumatic drives of the multibody system modelled the human locomotor apparatus with above-knee prostheses, and others. Future perspectives in area of control and optimization problems of the semi-passively actuated multibody systems are discussed
Research Perspectives for Logic and Deduction
The article is meant to be kind of the author's manifesto for the role of logic and deduction within Intellectics. Based on a brief analysis of this role the paper presents a number of proposals for future scientic research along the various di-mensions in the space of logical explorations. These dimensions include the range of possible applications including modelling intelligent behavior, the grounding of logic in some semantic context, the choice of an appropriate logic from the great variety of alternatives, then the choice of an appropriate formal system for repre-senting the chosen logic, and nally the issue of developing the most ecient search strategies. Among the proposals is a conjecture concerning the treatment of cuts in proof search. Often a key advance is a matter of applying a small change to a single formula. Ray Kurzweil [Kur05, p.5]
Removing the invisibility cloak: Using space design to influence patron behavior and increase service desk usage
In small branch libraries, patrons seeking assistance from library staff outside of the
dedicated single-service desk often results in large staffing inefficiencies. This paper
presents a case study in which the authors applied behavioral psychology models to a
branch libraryās space arrangement to identify possible factors influencing patron service
point choices. A subsequent full space rearrangement was instituted which utilized human
behavior research, service desk design principles, and low-cost methods to create a space
that reduced barriers and influenced patrons back to the main service desk. The paper
reports on the 11-month study that followed and the impact the rearrangement had on
patron behavior. Results indicate that simple rearrangement of existing furniture and
equipment into new configurations have direct influence on service desk usage and can
encourage new patron behaviors. Space and human behavior are inherently connected and
library managers should establish goals for how they envision their spaces to be used and
arrange them in ways that encourage wanted behaviors.Ye
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