Attenuation of Synaptic Potentials in Dendritic Spines

Dendritic spines receive the majority of excitatory inputs in many mammalian neurons, but their biophysical properties and exact role in dendritic integration are still unclear. Here, we study spine electrical properties in cultured hippocampal neurons using an improved genetically encoded voltage indicator (ArcLight) and two-photon glutamate uncaging. We find that back-propagating action potentials (bAPs) fully invade dendritic spines. However, uncaging excitatory post-synaptic potentials (uEPSPs) generated by glutamate photorelease, ranging from 4 to 27 mV in amplitude, are attenuated by up to 4-fold as they propagate to the parent dendrites. Finally, the simultaneous occurrence of bAPs and uEPSPs results in sublinear summation of membrane potential. Our results demonstrate that spines can behave as electric compartments, reducing the synaptic inputs injected into the cell, while receiving bAPs are unmodified. The attenuation of EPSPs by spines could have important repercussions for synaptic plasticity and dendritic integration

Molecular dynamics simulations of the Cx26 hemichannel: Evaluation of structural models with Brownian dynamics

The recently published crystal structure of the Cx26 gap junction channel provides a unique opportunity for elucidation of the structure of the conductive connexin pore and the molecular determinants of its ion permeation properties (conductance, current–voltage [I-V] relations, and charge selectivity). However, the crystal structure was incomplete, most notably lacking the coordinates of the N-terminal methionine residue, which resides within the pore, and also lacking two cytosolic domains. To allow computational studies for comparison with the known channel properties, we completed the structure. Grand canonical Monte Carlo Brownian dynamics (GCMC/BD) simulations of the completed and the published Cx26 hemichannel crystal structure indicate that the pore is too narrow to permit significant ion flux. The GCMC/BD simulations predict marked inward current rectification and almost perfect anion selectivity, both inconsistent with known channel properties. The completed structure was refined by all-atom molecular dynamics (MD) simulations (220 ns total) in an explicit solvent and POPC membrane system. These MD simulations produced an equilibrated structure with a larger minimal pore diameter, which decreased the height of the permeation barrier formed by the N terminus. GCMC/BD simulations of the MD-equilibrated structure yielded more appropriate single-channel conductance and less anion/cation selectivity. However, the simulations much more closely matched experimentally determined I-V relations when the charge effects of specific co- and posttranslational modifications of Cx26 previously identified by mass spectrometry were incorporated. We conclude that the average equilibrated structure obtained after MD simulations more closely represents the open Cx26 hemichannel structure than does the crystal structure, and that co- and posttranslational modifications of Cx26 hemichannels are likely to play an important physiological role by defining the conductance and ion selectivity of Cx26 channels. Furthermore, the simulations and data suggest that experimentally observed heterogeneity in Cx26 I-V relations can be accounted for by variation in co- and posttranslational modifications

Comparisons of TDOA Triangulation Solutions for Indoor Positioning

ABSTRACT In most of the location systems, the RF signal is used as a transmission medium. But, in the indoor environment, the multipath effect is very severe. So, the RF signal is not adequate for indoor environment. Rather it is used in the outdoor positioning such as in the GPS. To overcome the limitation of indoor positioning, the UWB positioning is recently developed and is being vigorously studied. Some standardizations on the UWB are in progress at IEEE 802.15 committee. In developing the UWB positioning system, we should consider the synchronization of sensor nodes, positioning algorithms, arrangement of sensor nodes, and so on. This paper presents a comparison of positioning algorithms that are widely used in the location systems. Two algorithms are compared; the one algorithm is derived by a linearization solution (LS algorithm), and the other algorithm is by analytic solution (CH algorithm). Simulation results show that the CH algorithm is superior to the linearized least square in the indoor environment. The CH algorithm shows consistent with the positioning performance regardless of the visibility and the geometry of basestations

Efficacy of a Health App for Obesity and Overweight Management: A Hidden Markov Model

We examined the efficacy of a mobile app for personal weight management by using a hidden Markov modeling approach, which captures the dynamics in the state of self-regulation of individuals to achieve their desired weight reduction objectives. The model illuminates the direct and indirect treatments that affect self-regulation state and success of overweight and obesity management. Results show that two self-regulation states (weak and strong) are optimal for describing the dynamics in the data. Relatively easy direct treatments, such as reducing calorie intake and relying on artificial electronic assistance, are more effective in the weak self-regulation state, whereas strenuous interventions, such as exercising, are more helpful in the strong state. The use of the mobile app is considerably more effective than the use of its PC channel in influencing users’ self-regulation states. Individuals who do not use either channel fail to transition from the weak to the strong state

Gaussian process regression-based Bayesian optimization of the insulation-coating process for Fe–Si alloy sheets

High-efficiency Fe–Si alloy sheets have recently gained increasing attention in the automobile industry, and these sheets must be coated with insulation to reduce energy loss. However, it is difficult to maintain the coating without peeling and to realize high electrical insulation in the high-temperature heat treatment process during coating. In this study, using an artificial intelligence algorithm— Gaussian process regression (GPR)-assisted Bayesian optimization (BO)—we successfully developed a zirconia-based coating material for Fe–Si alloy sheets, yielding high heat resistance and high-quality surface properties. The coating material developed through the optimized process exhibits a high-quality silvery-white surface, the absence of coating damage even after heat treatment at temperatures exceeding 1100 K, and a surface current value of 600 mA or less, which is a measure of insulation. Notably, compared to the existing trial-and-error method, the number of experiments required to simultaneously achieve the target characteristics was reduced to less than 0.1% using the GPR-assisted BO, demonstrating the feasibility of the approach. This result also validates the efficiency and effectiveness of the proposed method in achieving multidimensional nonlinear optimization in the actual mass production of steel

Large-scale synthesis of TiO2 nanorods via nonhydrolytic sol-gel ester elimination reaction and their application to photocatalytic inactivation of E. coli

A simple method of synthesizing a large quantity of TiO2 nanorods was developed. A nonhydrolytic sol-gel reaction between titanium(IV) isopropoxide and oleic acid at 270 degrees C generated 3.4 nm (diameter) x 38 nm (length) sized TiO2 nanocrystals. The transmission electron microscopic image showed that the particles have a uniform diameter distribution. X-ray diffraction and selected-area electron diffraction patterns combined with high-resolution transmission electron microscopic image showed that the TiO2 nanorods are highly crystalline anatase crystal structure grown along the [001] direction. The diameters of the TiO2 nanorods were controlled by adding 1-hexadecylamine to the reaction mixture as a cosurfactant. TiO2 nanorods with average sizes of 2.7 nm x 28 nm, 2.2 nm x 32 nm, and 2.0 nm x 39 nm were obtained using 1, 5, and 10 mmol of 1-hexadecylamine, respectively. The optical absorption spectrum of the TiO2 nanorods exhibited that the band gap of the nanorods was 3.33 eV at room temperature, which is 130 meV larger than that of bulk anatase (3.2 eV), demonstrating the quantum confinement effect. Oleic acid coordinated on the nanorod surface was removed by the reduction of the carboxyl group of oleic acid, and the Brunauer-Emmett-Teller surface area of the resulting naked TiO2 nanorods was 198 m(2)/g. The naked TiO2 nanorods exhibited higher photocatalytic activity than the P-25 photocatalyst for the photocatalytic inactivation of E. coli.

Role of Halide Ions for Controlling Morphology of Copper Nanocrystals in Aqueous Solution

This paper reports the influence of halide ions on the morphology-controlled synthesis of Cu nanocrystals in the aqueous phase. Cu nanocrystals with controlled shapes, including 2D plates, 1D wires, and 3D polyhedral particles were obtained by a reduction reaction between Cu-halide and ascorbic acid, and branched polyethyleneimine (BPEI) was used as a stabilizing agent in the process. Density functional theory (DFT) calculations showed that this morphological control was caused by the selective adsorption of halide ions depending on the facets of the Cu nanocrystals. The thickness and lateral size of the Cu nanoplates were tuned easily using a co-stabilizer, the addition of Br- ions, and varying the pH of the reaction solution. Furthermore, the resulting Cu nanocrystals possessed great stability, showing very little change after exposure to the ambient atmosphere for 40 days. Overall, this synthetic procedure could be a potential method for the mass synthesis of morphology-controlled Cu nanocrystals for industrial applications because of the superior reaction conditions, such as the air atmosphere, low reaction temperature, water-phase-based synthetic condition as well as the use of nontoxic and inexpensive reagents.11Nsciescopu