Multineuronal spike classification based on multisite electrode recording, whole-waveform analysis, and hierarchical clustering

We proposed here a method of multineuronal spike classification based on multisite electrode recording, whole-waveform analysis, and hierarchical clustering for studying correlated activities of adjacent neurons in nervous systems. Multineuronal spikes were recorded with a multisite electrode placed in the hippocampal pyramidal cell layer of anesthetized rats. If the impedance of each electrode site is relatively low and the distance between electrode sites is sufficiently small, a spike generated by a neuron is simultaneously recorded at multielectrode sites with different amplitudes. The covariance between the spike waveform at each electrode site and a template was calculated as a damping factor due to the volume conduction of the spike from the neuron to the electrode site. Calculated damping factors were vectorized and analyzed by hierarchical clustering using a multidimensional statistical test. Since a cluster of damping vectors was shown to correspond to an antidromically identified neuron, spikes of different neurons are classified by referring to the distributions of damping vectors. Errors in damping vector calculation due to partially overlapping spikes were minimized by successively subtracting preceding spikes from raw data. Clustering errors due to complex spike bursts (i.e., spikes with variable amplitudes) were avoided by detecting such bursts and then using only the first spike of a burst for clustering. These special procedures produced better cluster separation than conventional methods, and enabled multiple neuronal spikes to be classified automatically. Waveforms of classified spikes were well superimposed. We concluded that this method is particularly useful for separating the activities of adjacent neurons that fire partially overlapping spikes and/or complex spike bursts.     

Thermal Properties of Al-50%Si Alloys

AS FOR Al-Si alloy,this alloy with the characteristicsuch as excellent in a low coefficient of thermalexpansion(CTE),high-heat-conductivity,and wearresistance is used for the piston material of the engine,the heat radiation material,and electronic application1'2.The CTE of the Al-Si alloy decreases further withincreasing Si content because the CTE of Si is low3.The strength and wear resistance of Al-Si alloydecrease with increasing Si content because eutectic Siis coarse grain size an…     

A GPU parallel computing method for LPUSS

We discuss the effective implementation of parallel processing for linear prediction-based uniform state sampling (LPUSS). In previous work, we proposed LPUSS as an optimization algorithm for mechanical motions that assures high optimality of the solutions and computational efficiency. In parallel computation, LPUSS requires balanced memory allocation and managed processing timing. In this paper, we propose an effective parallel computing method that assures high optimality and calculation efficiency in parallel processing using GPU processor. We conducted two experiments to validate the proposed method. In the first experiment, we compared single-thread processing for LPUSS and the proposed parallel processing. As a result of this experiment, calculation speed of LPUSS was about 4–20 times faster than that with single-thread CPU. In the second experiment, we applied the proposed method to the optimization of sixtuple inverted pendulum. As a result, the proposed method optimized the motion within 40 minutes. According to our survey, there is no other optimization method that is applicable to higher than quadruple inverted pendulum models with standard constraints.     

Superconductivity and Ferromagnetism of the Ru-1232 Compounds in the (Ru1−x Nb x )Sr2(GdCe1.8Sr0.2)Cu2O z System

The Ru-1232 compounds have been synthesized in the (Ru_1?xNb _x )Sr₂(GdCe_1.8Sr_0.2)Cu₂O _z system, and effects of Nb substitution for Ru on superconductivity and ferromagnetism of the Ru-1232 compounds have been investigated. First, X-ray powder diffraction study shows that nearly the single 1232 phase samples can be obtained in the x composition range from 0.0 to 0.3. Then, from the electrical resistivity study, it is found that each of the samples shows resistivity dropping phenomenon at two temperatures of T _c ^l and T _c ^h, which originates from superconductivity of the Ru-1232 phase and the Ru-1222 one, respectively. Both of the starting temperatures are lowering with increasing Nb content x. Lastly, from the magnetic susceptibility study, it is found that superconducting transition temperature T _c is 20 K for the Ru-1232 sample with x = 0.0 and the ferromagnetic transition temperature T _m is about 90 K. This study also shows that both of the values of T _c and T _m become low with increasing x from 0.0 to 0.3.     

Overstability of lamellar eutectic growth below the minimum-undercooling spacing

We investigate the stability of lamellar eutectic growth by thin-sample directional solidification experiments and two-dimensional phase-field simulations. We find that lamellar patterns can be morphologically stable for spacings smaller than the minimum undercooling spacing λ _m . Key to this finding is the direct experimental measurement of the relationship between the front undercooling and spacing, which identifies λ _m independently of the Jackson and Hunt (JH) theory and of uncertainties of alloy parameters. This finding conflicts with the common belief that patterns with λ<λ _m should be unstable, which is based on the Jackson-Hunt-Cahn assumption that lamellae grow normal to the envelope of the front. Our simulation results reveal that lamellae also move parallel to this envelope to reduce spacing gradients, thereby weakly violating this assumption but strongly overstabilizing patterns for a range of spacing below λ _m that increases with G/V (temperature gradient to growth rate ratio). This range is much larger than predicted by previous stability analyses and can be significant for standard experimental conditions. An analytical expression is obtained phenomenologically, which predicts well the variation of the smallest stable spacing with G/V. We also present results that shed light on the history-dependent selection and long-time evolution of the experimentally observed range of spacings.     

Temporal modulation normalization for robust speech feature extraction and recognition

Speech signals are produced by the articulatory movements with a certain modulation structure constrained by the regular phonetic sequences. This modulation structure encodes most of the speech intelligibility information that can be used to discriminate the speech from noise. In this study, we proposed a noise reduction algorithm based on this speech modulation property. Two steps are involved in the proposed algorithm: one is the temporal modulation contrast normalization, another is the modulation events preserved smoothing. The purpose for these processing is to normalize the modulation contrast of the clean and noisy speech to be in the same level, and to smooth out the modulation artifacts caused by noise interferences. Since our proposed method can be used independently for noise reduction, it can be combined with the traditional noise reduction methods to further reduce the noise effect. We tested our proposed method as a front-end for robust speech recognition on the AURORA-2J data corpus. Two advanced noise reduction methods, ETSI advanced front-end (AFE) method, and particle filtering (PF) with minimum mean square error (MMSE) estimation method, are used for comparison and combinations. Experimental results showed that, as an independent front-end processor, our proposed method outperforms the advanced methods, and as combined front-ends, further improved the performance consistently than using each method independently.     

End-group analysis of polymacromonomer formed in the radical polymerization of styrene-type PMMA macromonomers by using 2H NMR spectroscopy

Summary Isotactic (iso-) and syndiotactic (syn-) poly(methyl methacrylate) (PMMA) macromonomers having styrene group as a polymerizable function were polymerized with perdeuterated 2,2-azobisisobutyronitrile in toluene at 60°C. The resultant polymacromonomers were analyzed by ²H NMR spectroscopy to determine the number of initiator fragment in a polymacromonomer chain (N) and initiator efficiency (f). The N values were less than unity (0.500.72), indicating the chain transfer reaction to occur in the radical polymerization of macromonomer. The f values were 0.180.28 and much smaller than that for styrene polymerization (0.50.7). Iso-macromonomer gave larger N and f values than syn- one, suggesting that the tacticity of macromonomer affects the reaction pathway probably owing to the difference in chain mobility between iso- and syn-PMMA chains.     

DIA‐PDP with high luminous efficacy and increased vertical resolution

Abstract— A PDP utilizing a new cell configuration to improve the vertical resolution and luminous efficacy is proposed. In this configuration, a delta subpixel arrangement is adopted because it reduces the vertical pixel pitch by half and increases the vertical resolution. In this configuration, R, G, B subpixels form triangles which are diamond shaped, the rational for calling this technology “DIAPDP.” High luminous efficacy is achieved by reducing the reflectivity of the panel. The lower reflectivity enables increased transmittivity of the light‐reduction filter which is part of the PDP panel, thus ensuing sufficient contrast under bright conditions. The higher transmittivity increases the luminous efficacy with the filter. Results obtained for a 46‐in. panel demonstrate a 33% increase in the luminous efficacy when using the filter. The DIA cell configuration is further modified to be a “clustered DIA” in order to improve the color mixing. Through subjective evaluation, the color mixing was compared with that of panels based on a trio subpixel arrangement and DIA, and the effect on color mixing was confirmed. The luminous efficacy of clustered DIA is also shown to be equal to that of DIA.     

Flame retardancy and rearrangement reaction of polyphenylene-ether/polystyrene alloy

The flame retardancy and the rearrangement reaction of polyphenylene-ether [poly-(oxy-2,6-dimethyl-1,4-phenylene), PPE] and polyphenylene-ether/polystyrene (PS) alloys have been studied. The flame retardancy of PPE blended with phosphates was proportional to PPE content as well as to the phosphates. The surface temperatures of PPE during a combustion was higher than that of PS, whereas PPE is more flammable than PS. The element analysis of the polymer surface showed that carbon was richer compared with the content of the newly synthesized PPE. Four monomeric and eight dimeric scission products were recovered by thermogravimetric-mass (TGA-MASS) analysis at high temperature in inert atmosphere. These structures of the scission products suggested that the rearrangement reaction occurred in combustion at high temperature. Namely, the formation of carbonaceous materials on the surface followed the rearrangement reaction and dehydration which was accelerated by the addition of aromatic phosphates. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1175–1183, 1997     

Mobility control and modulus change by the interaction between low molecular weight component and aromatic polymer chain

An increase of flexural modulus was observed by blending liquid organic phosphorous compounds, having specific structure, with polyphenylene–ether (PPE) or polycarbonate (PC). Blending 35 wt % of bisphenol-A type compound with two phosphate atoms in a molecule was especially significant. Flexural modulus increases of 12 and 32% were observed for PPE and PC, respectively. In the case of PPE, the increase tended to depend on the molecular weight of organic phosphorous compounds. The analysis of polymer chain motion of PPE by dynamic viscoelastic spectrum showed a change in shape at the β-dispersion temperature zone. From the trend of activation energy of the dispersion peak top and temperature dependence of both stock and loss modulus, it was concluded that the organic phosphorous compounds formed a complex bonding with the polymer chain with subsequent restricted β-type chain motion. As a result, the increase of modulus was observed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2269–2277, 1997