Article

Analyzing model and miniature objects from the Roman northwest. PHILIP KIERNAN, MINIATURE VOTIVE OFFERINGS IN THE NORTH-WEST PROVINCES OF THE ROMAN EMPIRE (MenTor, Studien zu Metallarbeiten und Toreutik der Antike, Bd. 4; Verlag Franz Philipp Rutzen, Mainz-Ruhpolding 2009). Pp. vi + 300, many figs. including illustrated appendix. ISBN 978-3-941336-45-2; ISSN 1868-3614.

January 2010
Journal of Roman Archaeology 23:664-668

DOI:10.1017/S1047759400002907

Authors:

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Article

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January 1970

In the recent semiconductor device industry, electronic devices are highly integrated and miniaturized, and the device in which the size of elements are smaller than the electron mean free path is expected be put in practical use. However, it is known that the electronic properties in minute systems whose dimensions are approximately equal to the Fermi wavelength can be different from those in ... [Show full abstract] the bulk and the conductance is quantized in the unit of G 0 =2e 2 /h, where e is the electron charge and h is the Planck constant. We study on the conduction properties of the nanostructure having atomic scale dimension in order to explore the possibility of such new devices. So far, a lot of experimental researches for the electron-conduction properties through nanostructures have found that quantized conductance appears in single-row wires consisting of Na, Cu, Ag and Au, which are experimentally made using a scanning tunneling microscope and a mechanically controllable break junction. On the theoretical side, it is indicated that the conductance of the single-row wire made of Au and Na suspended between electrodes is quantized. Furthermore, an even-odd behavior, which is the oscillation of the conductance with the varying of the wire length, is found. These results are consistent with the experiment that the conductance trace of the Au wire oscillates during elongation, which is reported by Sim et al. [1]. In this study, we perform the first-principles calculations to examine electron conduction of the closed packed structure and single-row wires consisting of sodium atoms sandwiched between semi-infinite crystalline electrodes (Fig. 1), employing the overbridging boundary-matching method [2]. We find that the conductance of the closed packed structure and that of the single-row wires are ~3 G 0 and ~1 G 0 , respectively, and the result that the conductance of 2 G 0 is never manifested for the single-row wire is in agreement with the results of the experiment (Fig. 2). In addition, the even-odd behavior of the conductance occurs for the single-row wire [3]. We also study the conductance of the cylindrical wire suspended semi-infinite electrodes using the continuum structure made of jellium in order to explore the origin of the even-odd behavior. As shown in Fig. 3, the conductance is periodically varied according to the length of the wire. Consequently, we find that there is a bunch of the electron density of the length almost equal to the z component of the Fermi wavelength, λ z , in a sodium crystal. In the case that the distance between electrodes is integral multiple of λ z , the conductance is ~1 G 0 , and low conductance appears in the other cases. From above results, we conclude that the even-odd behavior of the conductance is associated with the relationship between the Fermi wavelength in the bulk and the distance from between electrodes.

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October 2012 · CHINESE JOURNAL OF ANALYTICAL CHEMISTRY

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July 2018

Surface plasmonics for communication has recently acquired research interest because of the promise of high data-transfer rate along with miniaturization. Electronic interconnects in solid-state circuitry are slow and cause significant transmission delays. Conventional optical interconnects are faster but their sizes ( > 500 nm) makes it difficult to integrate them with dense arrays of the much ... [Show full abstract] smaller electronic devices (10{50 nm). As the electromagnetic (EM) fields of surface-plasmon-polariton (SPP) waves are highly localized to dielectric/metal interfaces, SPP-wave-based optical interconnects hold promise. SPP-wave propagation along continuous planar dielectric/metal interfaces is heavily investigated for sensing and imaging, but information transmission by an SPP wave across discontinuities remains unexplored. With this motivation, we studied the scattering of a pulse-modulated SPP wave guided by an air/silver interface due to an abrupt discontinuity caused by the replacement of silver by air, as shown in Fig. 1(a). A custom finite-difference-time-domain algorithm was used to compute the temporal evolution of the EM fields everywhere in the computational domain, the SPP wave assumed to be launched from the leftmost end (x = -a) of that two-dimensional (xz) domain.

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February 1969

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Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a d...

January 1970

A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, coil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal ... [Show full abstract] proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signaling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level. 5 figs.

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There are many design challenges involved in the circuit design of implantable neural recording systems. A generic biopotential-recording system is illustrated in Fig. 2.1. First, weak neural signals must be amplified, conditioned, and then digitized. The information then needs to be wirelessly transmitted out of the body to avoid possible infection from transcutaneous connectors. The power ... [Show full abstract] consumption increases with the number of recording channels and the complexity of system. However, the power dissipation of miniature implantable devices is limited to prevent excessive tissue heating.

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R. Werman

Frog muscle endplates were explored with an extracellular microelectrode. An intracellular microelectrode nearby simultaneously monitored invasion of the endplate by a spike directly evoked by a third microelectrode placed away from the endplate in the same fiber. External positivities were seen only at sites generating miniature endplate potentials. The external positivity reached a maximum ... [Show full abstract] prior to the internally recorded potential and was followed by a small late negativity. Small movements away from active synaptic sites resulted in positive-negative-positive potential sequences characteristic of activity and propagation. Since the external potential is a function of membrane current, the absence of negativity associated with the rising phase of the spike indicates the absence of inward current at synaptic sites. Thus, the synaptic membrane appears not to be excited by a depolarization of the magnitude of an action potential. In an Appendix it is shown that the late negativity and earlier maximum of the external potential can be accounted for by capacitative current through passive membrane.

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Yuly M. Pulyer

According to the sinusoidal coil design theory discussed previously, a slotwise electro-magnetic system can reproduce with high accuracy one and poly-periodical sinusoidal air gap B-field distributions and consequently sinusoidal amplitude modulation as a function of angular position. In the sinusoidal electromagnetic systems discussed previously however there were stationary and rotary coils ... [Show full abstract] which necessitate these systems having brushes or special one- or two-phase ring transformers providing magnetic coupling as shown in Fig. 4.9 to transmit an output signal from the rotation coils. In motion control devices there are a variety of miniature electro-magnetic systems which provide a conceptually brushless one- or poly-periodical magnetic coupling. In such a brushless electro-magnetic system there would only be stationary coils (excitation and signaling) and not rotation coils which need brushes. The slotwise sinusoidal electromagnetic system discussed in this and previous chapters is called a silent rotor and stator electro-machine system (silent armature) in classical electrical machine technology. Such systems provide a regular air gap along the air gap circumference (except at teeth irregularity), i.e. specific permeance Go given by equation 3.19 is constant

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