Electrical Coupling

A partir de la meitat del segle xviii, s'escampa per Itàlia una gran curiositat pels fenòmens elèctrics, posats en evidència per les primeres màquines productores d'electricitat electrostàtica. És un interès compartit pels ambients acadèmics i pels salons freqüentats per l'elit de la noblesa. L'Institut de les Ciències de Bolonya ès una de les primeres acadèmies científiques que dóna legitimitat a

The pyloric rhythm of the lobster (Panulirus interruptus, Palinurus vulgaris) stomatogastric ganglion is generated by a set of 3 electrically coupled endogenously bursting neurons. The phasic coordinating effects of monosynaptic excitatory (EPSP) and inhibitory (IPSP) inputs to these neurons were examined in isolated nervous systems. Periodic stimulation of both inputs at frequencies near the endogenous frequency of the pacemakers can produce large cycle by cycle variations in the burst period of the system (Fig. 4). Similar variation in PD burst period is also observed in intact freely behaving animals (Fig. 2). The effect of both inputs depends on the phase at which they occur in the endogenous pacemaker cycle. Both EPSP's and IPSP's can advance or delay subsequent bursts. The two inputs exhibit qualitatively different characteristic phase response curves (Figs. 5, 6). Both EPSP's and IPSP's can entrain the endogenous rhythm (Figs. 7, 8). The coordinating effects of EPSP's are stronger when their repetition frequency is slightly higher than the endogenous pacemaker frequency, while those produced by IPSP's are stronger when the repetition frequency of the input is slightly slower than the repetition frequency of the oscillator. The phase relationships of the discharge of the pacemakers in the stimulus cycle are qualitatively different when the cyclic stimulus is slower or faster than the endogenous rhythm for both types of inputs (Fig. 9). The entrainment of the oscillator by EPSP inputs which repeat at a frequency which is greater than the endogenous frequency can be attributed to the input triggering the burst of spikes at a fixed latency (Fig. 10).

We propose a mechanism to explain suggested links between seismic activity and ionospheric changes detected overhead. Specifically, we explain changes in the natural extremely low-frequency (ELF) radio noise recently observed in the topside ionosphere aboard the DEMETER satellite at night, before major earthquakes. Our mechanism utilises increased electrical conductivity of surface layer air before a major earthquake, which reduces the surface-ionosphere electrical resistance. This increases the vertical fair weather current, and (to maintain continuity of electron flow) lowers the ionosphere. Magnitudes of crucial parameters are estimated and found to be consistent with observations. Natural variability in ionospheric and atmospheric electrical properties is evaluated, and may be overcome using a hybrid detection approach. Suggested experiments to investigate the mechanism involve measuring the cut-off frequency of ELF "tweeks", the amplitude and phase of very low frequency radio waves in the Earth-ionosphere waveguide, or medium frequency radar, incoherent scatter or rocket studies of the lower ionospheric electron density.

At present BiFeO3 (BFO) is the most attractive and sole example, which possesses low magnetization value, high leakage current and low polarization in ceramic form. Single-phase room temperature multiferroics are rare in nature. This paper deals with the improved magnetic and observed linear magneto-electric coupling in Co and Sm co-doped BiFeO3 ceramics synthesized by sol–gel process at low temperature ∼600 °C. As synthesized Bi0.9Sm0.10Fe0.95Co0.05O3 (BSFCO) showed high impurities phases (20%) over wide range of calcination temperatures. Impurity phases reduced drastically from 20% to 5% after leaching with nitric acid. However the electrical and the magnetic properties were almost the same for both phases. Well-defined magnetic hysteresis with high magnetic moment was found at room temperature. Ferroelectric polarization studies demonstrated similar values and shape as reported in literature for the pure bulk BFO. Linear magneto-electric (ME) coupling and weak ME coefficient (α) ∼ 0.6 e−10 s m−1 were observed in the co-doped BFO. The origin of the strong ferromagnetic property in our samples may be due to the presence of rare earth and transition metal ions at the lattice sites of BFO or due to impurity phase, since we have not seen any change in magnetization with reduction of impurity phase the later effect is more unlikely.► Present composition (Bi0.9Sm0.10Fe0.95Co0.05O3 (BSFCO) have shown very high magnetization compared to parent BFO. ► The magnetic hysteresis loops are well saturated with high saturation magnetization 2.89 emu/gm (unpoled and unleached) and 2.18 emu/gm (poled and unleached) respectively. ► Converse ME coupling were found 0.8e−10 s m−1 (H||E) and 0.6–0.8 × 10−10 s m−1 (H⊥E) which are better than the single phase multiferroic obeying linear ME coupling.

Lead–zirconate–titanate (PbZr0.53Ti0.47O3) nano powders and ceramics were prepared using a sol–gel method. Phase characterization of the lead–zirconate–titanate (PZT) material was identified by X-ray diffraction analysis (XRD). Micro-structure of the samples was examined by the scanning electron microscopy (SEM). Ferroelectric hysteresis loop, high-frequency dielectric response and piezoelectric constant d33 were measured. The remnant polarization (Pr) of the PZT ceramics pellet is about 20 μC cm−2 and the coercive field (EC) is about 30 kV cm−1. The dielectric constant is about 900 and the dielectric loss is lower than 0.02 in the radio-frequency (RF) region. The piezoelectric constant d33 is about 170 pC N−1. The experimental results show that the PZT material can be suitable for the applications of miniature RF front-end devices and force-electric coupling devices.

This mini-review considers certain factors related to the developmental decrease in rapid eye movement (REM) sleep, which occurs in favor of additional waking time, and its relationship to developmental factors that may influence its potential role in brain development. Specifically, we discuss some of the theories proposed for the occurrence of REM sleep and agree with the classic notion that REM sleep is, at the least, a mechanism that may play a role in the maturation of thalamocortical pathways. The developmental decrease in REM sleep occurs gradually from birth until close to puberty in the human, and in other mammals it is brief and coincides with eye and ear opening and the beginning of massive exogenous activation. Therefore, the purported role for REM sleep may change to involve a number of other functions with age. We describe recent findings showing that morphologic and physiologic properties as well as cholinergic, gamma amino-butyric acid, kainic acid, n-methyl-d-aspart...

Power applications of high-temperature superconducting (HTS) coated conductors will require stabilization against thermal runaway. We have developed conductive buffer layers to electrically couple the HTS layer to the underlying metal substrate. The structure comprises the layer sequence of SrRuO3 (SRO) on LaNiO3 (LNO) on biaxially textured Ni substrates. We report baseline investigations of compatibility of SRO/LNO multilayer structure with processing of Yba2Cu3O7−δ (YBCO) and demonstrate biaxially textured YBCO films on conductively buffered Ni tapes. These YBCO coatings exhibit self-field Jc values as high as 1.3 × 106 A/cm2 at 77 K, and the entire structure (HTS + conductive buffers + metal substrate) shows good electrical connectivity. These results demonstrate that SRO/LNO buffer layers may provide a basis for stabilized coated conductors.

Smooth muscle cells (SMC) of the human urinary bladder are believed to be electrically coupled. However, it has not been successfully demonstrated the nature of the underlying cell-cell communication. Here, we used Western blot technique to demonstrate the gap junction protein connexin 43 (Cx 43) in human bladder musculature and in smooth muscle cell cultures. We found expression of Cx 43 in all samples of the detrusor (Mdv, n=6) and in five of six samples of the internal sphincter (Mv). Cx 43 expression was less in cell cultures, 60% showing Cx 43 expression. Iontophoretic application of the gap junction permeable fluorescent dye lucifer yellow revealed a mean of 2.6±2.2 (mean±SD, n=8) coupled cells in cultured smooth muscle cells. Our findings support the notion that Cx 43 is constitutively expressed in human bladder SMC in vivo. Thus, the function of the bladder is likely to be influenced by the organisation of smooth muscle cells into functional syncytia.

This paper presents a quadrature voltage controlled oscillator (QVCO) based on the electric coupling of two identical LC voltage controlled oscillator in 0.35μm CMOS technology. The proposed design of QVCO accomplishes extensive tuning by using binary weighted switched varactor in addition to a linearly varying varactor. The simulated results show the multi-band frequency of proposed QVCO using in multi-standard wireless applications. This structure presents a 50% of tuning range carrier frequency at a range of 2.3 to 3.8 GHz. The phase noise is −130dBc/Hz at 1MHz offset frequency from carrier frequency of 3.5GHz. The power consumption of QVCO is 13.6mW.

Liquid-metal magnetohydrodynamic flow in a system of electrically coupled U-bends in a strong uniform magnetic field is studied. The ducts composing the bends are electrically conducting and have rectangular cross-sections. It has been anticipated that very strong global electric currents are induced in the system, which modify the flow pattern and produce a very high pressure drop compared to the flow in a single U-bend. A detailed asymptotic analysis of flow for high values of the Harmann number (in fusion blanket applications of the order of 103−104) shows that circulation of global currents results in several types of peculiar flow patterns. In ducts parallel to the magnetic field a combination of helical and recirculatory flow types may be present and vary from one bend to another. The magnitude of the recirculatory motion may become very high depending on the flow-rate distribution between the bends in the system. The recirculatory flow may account for about 50% of the flow in...

During neurogenesis in the embryonic cerebral cortex, the clas- sical neurotransmitters GABA and L-glutamate stimulate ionic conductance changes in ventricular zone (VZ) neuroblasts. Ly- sophosphatidic acid (LPA) is a bioactive phospholipid produc- ing myriad effects on cells including alterations in membrane conductances (for review, see Moolenaar et al., 1995). Devel- opmental expression patterns of its first cloned receptor gene, lpA1

Gap junctions are transcellular pathways that enable a dynamic metabolic coupling and a selective exchange of biological signaling mediators. Throughout the course of the brain development these intercellular channels are assembled into regionally and temporally defined patterns. The present review summarizes the possibilities of heterocellular gap junctional pairing in the brain parenchyma, involving glial cells, neurons and neural precursors as well as it highlights on the meaningfulness of these coupled arrays to the concept of brain functional compartments.