Disruption of passive avoidance learning in the rat by electrical stimulation of the hippocampus.

Five experiments, with 184 male albino rats, examined the effect of electrical stimulation to discrete regions of the dorsal hippocampus on passive avoidance. Ss stepped from a brightly lit, white compartment to a dark compartment. Following footshock in the dark compartment, step-through latencies were recorded 1 min, 24 hrs, and 48 hrs after footshock. When given 20 step-through trials prior to footshock, dentate-stimulated Ss exhibited lack of passive avoidance with particularly short latencies at 1 min, and CA1-stimulated Ss showed reduced latencies compared with latencies of cortical and nonoperated controls. In Exp II, Ss given stimulation in the same regions performed the avoidance task without prior step-through experience. All groups showed less passive avoidance than the control group in Exp I, and there were no significant differences between groups. With a single step-through trial before the footshock trial, longer avoidance latencies were recorded, but again groups did not differ significantly. Dentate-implanted Ss, given 20 prior exposure trials but with stimulation at different stages of the task sequence, demonstrated a passive avoidance deficit at 1 min after footshock. Results are discussed in terms of the generation of expectancy that the black compartment was a safe place and the effects of brain stimulation on the expectancy, with particular reference to O. S. Vinogradova's (1975) theory of hippocampal function. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural and dielectric properties,and nonlinear electrical response of the CaCu3-xZnxTi4O12 ceramics: Experimental and computational studies

CaCu_3-xZn_xTi₄O₁₂ ceramics (x = 0, 0.05, 0.10) were successfully prepared by a conventional solid-state reaction method. Their structural and dielectric properties, and nonlinear electrical response were systematically inspected. The X-ray diffraction results indicated that single-phase CaCu₃Ti₄O₁₂ (JCPDS no. 75–2188) was obtained in all sintered ceramics. Changes in the lattice parameter are well-matched with the computational result, indicating an occupation of Zn²⁺ doping ions at Cu²⁺ sites. The overall tendency shows that the average grain size decreases when x increases. Due to a decrease in overall grain size, the dielectric permittivity of CaCu_3-xZn_xTi₄O₁₂ decreases expressively. Despite a decrease in the dielectric permittivity, it remains at a high level in the doped ceramics (~3,406–11,441). Besides retention in high dielectric permittivity, the dielectric loss tangent of x = 0.05 and 0.10 (~0.074–0.076) is lower than that of x = 0 (~0.227). A reduction in the dielectric loss tangent in the CaCu_3-xZn_xTi₄O₁₂ ceramics is closely associated with the enhanced grain boundary response. Increases in grain boundary resistance, breakdown electric field, and conduction activation energy of grain boundary as a result of Zn²⁺ substitution are shown to play a crucial role in improved grain boundary response. Furthermore, the XPS analysis shows the existence of Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺, indicating charge compensation due to the loss of oxygen lattice. Based on all results of this work, enhanced dielectric properties of the Zn-doped CCTO can be explained using the internal barrier layer capacitor model.     

Clozapine for the control of hemiballismus

Pharmacological agents used for the control of ballistic movements include chloral hydrate, barbiturates, paraldehyde, bromides, phenothiazines, progabide, haloperidol, pimozide, reserpine, tetrabenazine, sodium valproate, and dimethylaminoethanol. These agents are believed to act by different mechanisms, including modification of dopaminergic, GABAergic, or cholinergic mechanisms. We report a case where, after failure of haloperidol, phenobarbital, and pimozide, the hemiballistic movements were controlled with clozapine.     

Threshold computation for fault detection in linear discrete‐time Markov jump systems

This paper proposes a threshold computation scheme for an observer‐based fault detection (FD) in linear discrete‐time Markovian jump systems. An observer‐based FD scheme typically consists of two stages known as residual generation and residual evaluation. Even information of faults is contained inside a residual signal, a decision of faults occurrence is consequently made by a residual evaluation stage, which consists of residual evaluation function and threshold setting. For this reason, a successful FD strongly depends on a threshold setting for a given residual evaluation function. In this paper, Kalman filter (KF) is used as a residual generator. Based on an accessibility of Markov chain to KF, two types of residual generations are considered, namely mode‐dependent and mode‐independent residual generation. After that threshold is computed in a residual evaluation stage such that a maximum fault detection rate is achieved, for a given false alarm rate. Without any knowledge of a probability density function of residual signal before and after fault occurrence, a threshold is computed by using an estimation of residual evaluation function variance in a fault‐free case. Finally, a detection performance is demonstrated by a numerical example. Copyright © 2013 John Wiley & Sons, Ltd.     

Epileptic EEG detection using neural networks and post-classification

Electroencephalogram (EEG) has established itself as an important means of identifying and analyzing epileptic seizure activity in humans. In most cases, identification of the epileptic EEG signal is done manually by skilled professionals, who are small in number. In this paper, we try to automate the detection process. We use wavelet transform for feature extraction and obtain statistical parameters from the decomposed wavelet coefficients. A feed-forward backpropagating artificial neural network (ANN) is used for the classification. We use genetic algorithm for choosing the training set and also implement a post-classification stage using harmonic weights to increase the accuracy. Average specificity of 99.19%, sensitivity of 91.29% and selectivity of 91.14% are obtained.     

Efficient Room‐Temperature Oxidation of Hydrocarbons Mediated by Tricopper Cluster Complexes with Different Ligands

Six tricopper cluster complexes of the type [Cu^ICu^ICu^I( L )]¹⁺ supported by a series of multidentate ligands ( L ) have been developed as oxidation catalysts. These complexes are capable of mediating the facile oxygen‐atom transfer to hydrocarbon substrates like cyclohexane, benzene, and styrene (C₆H₁₂, C₆H₆ and C₈H₈) upon activation by hydrogen peroxide at room temperature. The processes are catalytic with high turnover frequencies (TOF), efficiently oxidizing the substrates to their corresponding alcohols, aldehydes, and ketones in moderate to high yields. The catalysts are robust with turnover numbers (TON) limited only by the availability of hydrogen peroxide used to drive the catalytic turnover. The TON is independent of the substrate concentration and the TOF depends linearly on the hydrogen peroxide concentration when the oxidation of the substrate mediated by the activated tricopper complex is rapid. At low substrate concentrations, the catalytic system exhibits abortive cycling resulting from competing reduction of the activated catalyst by hydrogen peroxide. This behaviour of the system is consistent with activation of the tricopper complex by hydrogen peroxide to generate a strong oxidizing intermediate capable of a facile direct “oxygen‐atom” transfer to the substrate upon formation of a transient complex between the activated catalyst and the substrate. Some substrate specificity has also been noted by varying the ligand design. These properties of the tricopper catalyst are characteristic of many enzyme systems, such as cytochrome P450, which participate in biological oxidations.     

Ge4+ doped CaCu2.95Zn0.05Ti4O12 ceramics: Two-step reduction of loss tangent

CaCu₃Ti₄O₁₂ ceramics have been extensively studied for their potential applications as capacitors in recent years; however, these materials exhibit very large dielectric losses. A novel approach to reducing the dielectric loss tangent in two steps, while increasing the dielectric permittivity, is presented herein. Doping CaCu₃Ti₄O₁₂ with a Zn dopant reduces the loss tangent of the ceramic material from 0.227 to 0.074, which is due to the increase in grain boundary (GB) resistance by an order of magnitude (from 6.3× 10³ to 3.93 × 10⁴ Ω cm). Zn-doping slightly changes the microstructure and dielectric permittivity of the CaCu₃Ti₄O₁₂ ceramic, which reveals that the primary role of the Zn dopant is to tune the intrinsic properties of the GBs. Surprisingly, the addition of the Ge⁴⁺ dopant into the Zn²⁺-doped CaCu₃Ti₄O₁₂ ceramic sample led to a further decrease in the loss tangent from 0.074 to 0.014, due to enhanced GB resistance (3.1 × 10⁵ Ω cm). The grain size increased remarkably from 2–3 μm to 85–90 μm, corresponding to a significant increase in the dielectric permittivity (~1–4 × 10⁴). The large increase in GB resistance is due to the intrinsic potential barrier height at the GBs and the segregation of the Cu-rich phase in the GB region. First-principles calculations revealed that Zn and Ge are preferentially located at the Cu sites in the CaCu₃Ti₄O₁₂ structure. The substitution of the Ge dopant does not hinder the role of the Zn dopant in terms of improving the electrical properties at the GBs. These phenomena are effectively explained by the internal barrier layer capacitor model. This study provides a way of improving the dielectric properties of ceramics for their practical use as capacitors.     

First-principles calculations and experimental study of enhanced nonlinear and dielectric properties of Sn4+-doped CaCu2.95Mg0.05Ti4O12 ceramics

High dielectric permittivity (ε′ ≈ 2000―6900) was accomplished in Sn⁴⁺-doped CaCu_2.95Mg_0.05Ti₄O₁₂ ceramics while retaining a low loss tangent (tanδ ≈ 0.027―0.075). Further, significant improvements in the nonlinear electrical properties, such as high values of the breakdown electric field (E_b ≈ 1.2―1.3 × 10⁴ V cm^?1) and nonlinear coefficient (α ≈ 31), were achieved. In addition, the nonlinear electrical parameters significantly improved, which is consistent with the increase in the electrical resistivities of the grains and grain boundaries due to the decrease in the Cu⁺/Cu²⁺ ratio. According to our first-principles calculations, the Sn atom at the Ti site prefers to be close to the Mg atom at the Cu site, while the oxygen vacancy prefers to be located at large distances from the Sn and Mg co-dopants. This confirms that the dielectric behavior and the nonlinear electrical properties originate from the interface between the grain and grain boundary.     

Safety of long-term levodopa therapy in malignant melanoma

Levodopa therapy is contraindicated in malignant melanoma because of its apparent carcinogenic effects reported by physicians in the early 1970s. We discuss the case of a 74-year-old man with Parkinson's disease who was treated with levodopa and whose malignant melanoma was later diagnosed. Before development of malignant melanoma, the patient received an estimated 5.7 kg levodopa over 6 years. Therapy with levodopa was continued for > 10 years, with a total dose of approximately 4.3 kg levodopa (together with carbidopa.) Recurrence of the melanoma was not observed. Based on our experience with this patient and an extensive literature review, we conclude that the natural history of malignant melanoma is not adversely influenced by concurrent levodopa therapy. Levodopa therapy should not be withheld for fear of accelerating malignant melanoma in parkinsonian patients.