Quantitative Analysis of Electrotonic Structure and Membrane Properties of NMDA-Activated Lamprey Spinal Neurons

Parameter optimization methods were used to quantitatively analyze frequency-domain-voltage-clamp data of NMDA-activated lamprey spinal neurons simultaneously over a wide range of membrane potentials. A neuronal cable model was used to explicitly take into account receptors located on the dendritic trees. The driving point membrane admittance was measured from the cell soma in response to a Fourier synthesized point voltage clamp stimulus. The data were fitted to an equivalent cable model consisting of a single lumped soma compartment coupled resistively to a series of equal dendritic compartments. The model contains voltage-dependent NMDA sensitive (INMDA), slow potassium (IK), and leakage (IL) currents. Both the passive cable properties and the voltage dependence of ion channel kinetics were estimated, including the electrotonic structure of the cell, the steady-state gating characteristics, and the time constants for particular voltage- and time-dependent ionic conductances. An alternate kinetic formulation was developed that consisted of steady-state values for the gating parameters and their time constants at half-activation values as well as slopes of these parameters at half-activation. This procedure allowed independent restrictions on the magnitude and slope of both the steady-state gating variable and its associated time constant. Quantitative estimates of the voltage-dependent membrane ion conductances and their kinetic parameters were used to solve the nonlinear equations describing dynamic responses. The model accurately predicts current clamp responses and is consistent with experimentally measured TTX-resistant NMDA-induced patterned activity. In summary, an analysis method is developed that provides a pragmatic approach to quantitatively describe a nonlinear neuronal system

Targeted expression of truncated glued disrupts giant fiber synapse formation in Drosophila

Glued1 (Gl1) mutants produce a truncated protein that acts as a poison subunit and disables the cytoplasmic retrograde motor dynein. Heterozygous mutants have axonal defects in the adult eye and the nervous system. Here we show that selective expression of the poison subunit in neurons of the giant fiber (GF) system disrupts synaptogenesis between the GF and one of its targets, the tergotrochanteral motorneuron (TTMn). Growth and pathfinding by the GF axon and the TTMn dendrite are normal, but the terminal of the GF axon fails to develop normally and becomes swollen with large vesicles. This is a presynaptic defect because expression of truncated Glued restricted to the GF results in the same defect. When tested electrophysiologically, the flies with abnormal axons show a weakened or absent GF-TTMn connection. In Glued1 heterozygotes, GF-TTMn synapse formation appears morphologically normal, but adult flies show abnormal responses to repetitive stimuli. This physiological effect is also observed when tetanus toxin is expressed in the GFs. Because the GF-TTMn is thought to be a mixed electrochemical synapse, the results show that Glued has a role in assembling both the chemical and electrical components. We speculate that disrupting transport of a retrograde signal disrupts synapse formation and maturation

A Note on the Flexural Properties of Bark Board

Bending properties of particleboards made from soft maple, red oak, white oak, black cherry, beech, and yellow-poplar bark were obtained and compared with the specimen's density and thickness. Regression analyses indicated that the bending properties depend not only on species but also on density and/or specimen thickness. This dependence was not consistent among species

Effects of Relative Humidity and Shelf-Life on Selected Properties of Polyvinyl Acetate Adhesive Films

The effects of various relative humidities and shelf-lives on the tensile and thermal properties of a commercial polyvinyl acetate copolymer emulsion (PVAC) adhesive are reported. Adhesive-free films, from both crosslinkable and uncrosslinkable resins at three different shelf-life periods, were formed in an environmental chamber (72% relative humidity). After curing, specimens were cut from the films and divided into experimental units; and each unit was conditioned at a different relative humidity (0, 40, 60, and 90%). Tensile and differential scanning calorimetry tests were conducted after the films reached equilibrium at the various relative humidities. Tensile testing results indicate that at relative humidities greater than 40% the tensile strength and modulus of elasticity of both uncrosslinked and crosslinked films decrease. Shelf-life periods of 1.5, 2.5, and 3.5 months had relatively little effect on the tensile strength and modulus of elasticity values of either crosslinked or uncrosslinked PVAC films as compared to the effects of relative humidity. Regression analysis established that the mechanical properties varied mainly as a function of relative humidity. Differential scanning calorimetry specimens were cut from the same sheets of free film as the tensile specimens. Crosslinked and uncrosslinked specimens from an initial shelf-life period of 1.5 months were tested to determine the effects of relative humidities on the calorimetric properties of the films. The results indicate that relative humidity, especially at levels greater than 40%, affects some of the calorific values obtained from the films

Actor-Critic Policy Learning in Cooperative Planning

In this paper, we introduce a method for learning and adapting cooperative control strategies in real-time stochastic domains. Our framework is an instance of the intelligent cooperative control architecture (iCCA)[superscript 1]. The agent starts by following the "safe" plan calculated by the planning module and incrementally adapting its policy to maximize the cumulative rewards. Actor-critic and consensus-based bundle algorithm (CBBA) were employed as the building blocks of the iCCA framework. We demonstrate the performance of our approach by simulating limited fuel unmanned aerial vehicles aiming for stochastic targets. In one experiment where the optimal solution can be calculated, the integrated framework boosted the optimality of the solution by an average of %10, when compared to running each of the modules individually, while keeping the computational load within the requirements for real-time implementation.Boeing Scientific Research LaboratoriesUnited States. Air Force Office of Scientific Research (Grant FA9550-08-1-0086

Comparison of Selected Fuel and Chemical Content Values for Seven Populus Hybrid Clones

Fuel and chemical content values were determined for seven Populus clones by component (wood, bark, and wood/bark specimens) and tissue age (1 to 8 years old). The fuel and chemical content values obtained included: gross heat of combustion, extractives, holocellulose, alpha-cellulose, lignin, and ash. In general, analysis of the data for the wood, bark, and wood/bark specimens indicated that: 1) wood was higher in holocellulose and alpha-cellulose content than bark; 2) bark was higher in gross heat of combustion, lignin, extractive, and ash content values than wood; and 3) combined wood/bark fuel and chemical content values were usually between the individual values for the wood and bark.Statistical analyses indicated that significant differences existed within and among clones. Within the wood, bark, and wood/bark specimens, tissue age influenced the chemical content values more than the parentage. Potential chemical yields derived from the seven Populus hybrid clones investigated will depend on component and age with limited parentage effects

In Crisis: Medical Students in the COVID‐19 Pandemic

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156130/2/aet210450.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156130/1/aet210450_am.pd