Induced current method

Our derivation of the local-mode fields is sometimes called the adiabatic approximation, since it assumes all changes in profile occur over such large distances that there is a negligible change in the power of the local mode [2]. Thus, although a local mode is an excellent approximation for a slowly varying fiber, it is not an exact solution. The small correction to the local-mode fields is determined by the methods of coupled local modes in Chapter 28 or by the induced current method of Section 22-10. 

In Section 22-5 we determined the attenuation of the fundamental mode on a weakly guiding, step-profile fiber due to radiation from a sinusoidal perturbation of the interface, using free-space antenna methods and correction factors. Here we consider the situation when the radiation field is well approximated by a single leaky mode, which can be realized by having an on-axis sinusoidal nonuniformity of the form of Eq. (22-14). The azimuthal symmetry ensures that only HEi leaky modes are excited. Further, the direction of radiation should coincide with the direction of the leaky-mode radiation [23]. If we represent the nonuniformity and the incident fundamental-mode fields by the induced current method, as in Section 22-5, the direction condition is satisfied by setting C = in Eq. (24-43), whence... 

Under certain resonance conditions, a small perturbation of the fiber leads to the transfer of a large proportion of total power between only two modes of the complete set of modes of the unperturbed fiber, e.g. resonant coupling on a sinusoidally deformed fiber as discussed below. The coupled mode equations describe arbitrary power transfer exactly, whereas the induced-current method of Chapter 22 is inaccurate, since it assumes only a slight transfer of total mode power. If we ignore the weak power transfer to all other modes, the set of coupled mode equations reduces to just two equations for the resonant modes. 

However, before we begin, we emphasize that coupled local-mode theory is particularly useful in situations when there is a large transfer of power between local modes. Apart from such exceptional situations, power transfer is slight and-the induced-current methods of Sections 22-10 and 22-11 are sufficient. 

As noted eailier, the dynamic sensitivity of VCD carries it beyond the Bom-Oppenheimer approximation (17, 18). Even though non-Bom-Oppenheimer calculations have recently been initiated (116-119), the use of molecular orbital methods to describe these vibrationally induced currents is lagging behind the measurement and interpretation of VCD based on such currents. Nevertheless, the empirical basis that is now emerging for understanding VCD intensities based on chirally oriented oscillators and induced currents makes possible the immediate application of this methodology to stereochemical problems of widespread interest. 

A new method has been developed for stimulation of the brain trans-cranial magnetic stimulation [TMS]. Magnetic stimulation of the brain may offer a means to examine the importance of the convulsion for ECT effects. TMS is a novel noninvasive method for the stimulation of neurons (for review, see Barker 1991]. High electrical current flow in a spiral of wire induces a magnetic field. The magnetic field produces an electric field that initiates ion flow and consequent membrane depolarization directly in brain tissues. Therefore, magnetic stimulation of deep structures may be achieved with relatively little induced current in the skin or skull and without convulsions [Barker 1991]. 

Other indirect methods for measuring lifetimes often involve device structures such as p-n junctions. The electron-beam-induced current (EBIC) technique, for example, measures the increase injunction current as an impinging electron beam moves close to the junction, i.e., within a few minority-carrier diffusion lengths. If a diffusion constant can be estimated, say by knowledge of the minority-carrier mobility, then the minority-carrier lifetime can be calculated. However, SI GaAs does not form good junctions, so such methods are really not applicable. 

A powerful method for the characterization of the origin of losses on structured surfaces is provided by the EBIC (Electron Beam Induced Current) technique also known as charge collection microscopy (23. 24). 

Besides the traditional capacitance versus voltage (C/V) measurements, which are mainly used for the characterisation of MOS and EIS capacitances, the scanned light pulse technique (SLPT) was introduced by Engstrom and Aim [13], first for MOS structures. This technique utilises a fight source to illuminate a local area of the MOS structure. Thus, a local photo-effect-induced current can be measured, which only depends on the local properties and energy states of the illuminated region of the MOS structure. In 1988, Hafeman et al. combined this SLPT method with EIS structures to develop the LAPS [14,15]. This sensor is capable of measuring the surface potential of the electrolyte-transducer interface with a lateral resolution. Hence, the surface... 

This chapter describes the basic characteristics of viruses and the relatively limited number of drugs that can act selectively as antiviral agents. Methods of preventing viral infections (antiviral vaccines) are also briefly discussed. Finally, the current methods of treating a specific viral-induced disease—AIDS—are presented. Rehabilitation specialists often treat patients who are in the active stages of a viral infection, as well as those suffering from the sequelae of viral disorders, such as gastroenteritis, encephalitis, and influenza. Hence, the pharmacotherapeutic treatment and prophylaxis of viral infections should concern physical therapists and occupational therapists. 

GIMIC) method, as a quantitative measure of the strength of the induced current ... 

The current methods for the synthesis of mesoporous silica materials can be divided into three main types bottom-up, based on the polymerization of orthosilicic acid derivatives top-down, based on the reorganization of silica and evaporation-induced self-assembly,5 6 all of them promoted by surfactant templation. 

Further speculation however is unwarranted at this time as it is likely that choice of body site, the nature of induction of xerosis (natural versus surfactant/solvent induced), differing methods of RT-PCR and filaggrin extraction and quantification protocols may all contribute to the current lack of clarity in our understanding. 

Nineteenth-century records report successful electrochemical healing of broken bones (Stevens, 1812). The beginnings of a modem phase in this work are attributed to Brighton at the University of Pennsylvania (1966). The technique has been developed so that it is an accepted method in orthopedics. The beginning of a noninvasive technique using a Helmholtz coil to induce currents is attributed to Pilla (1974). Both dc and ac currents have been used. Typically, the methods employ pulses lasting 5 x 1(T3 s with a repetition rate of 15 per second. 

This method is based on the principles of electromagnetic induction. A coil carrying an alternating current in the vicinity of the test sample produces an induced or eddy current in the sample, and the changes in the magnetic field due to the induced currents are monitored. The induced currents in the test sample are affected by electrical conductivity, permeability, the dimensions and the homogeneity of the sample. 

Fowler, Steiner et al.244,245 have used a specific method of selecting the origin of the vector potential (the ipsocentric choice, where the induced current density at each point is calculated with that point as origin) to develop a... 

Section II deals with knowledge and manipulation of quantitative physiocochemical data of a number of aqueous—organic mixtures and with the procedures designed to minimize the variations induced by cosolvent addition and/or temperature variations, which would permit improvement of current methods of protein fractionation. 

The laser-induced fluorescence method is capable of greater efficiency in detecting molecules distributed over a small number of quantum states than electron bombardment detection (see Section IV). Using current laser technology, it should be possible to measure angular distributions of molecules in individual quantum states. At present the technique is limited to molecules with low-lying excited states, but as laser technology extends... 

As was pointed out, the remarkable simplicity of Doll s theory is related to the fact that interaction of induced currents is neglected. In order to take into account this effect and improve the quality of an interpretation of logging data, a new approach, also an approximate one. was suggested (Kaufman, 1962). This method allows us relatively quickly to evaluate the field, subjected to an influence of the skin effect in a formation, when there are both cylindrical and horizontal interfaces. Much later, this rather complicated problem was solved by V. Dimitriev, L. Tabarovsky, V. Zakharov using the method of integral equations. 

At the same time it is possible to derive a simple expression for the apparent conductivity which is valid for larger values of parameter L/h proceeding from the method which takes into account the skin effect in the external area (Chapter 3). Having assumed that within the bed induced currents are shifted in phase by 90° and interax tion between currents in the bed and the surrounding medium is absent we obtain ... 

Comparison with calculations based on a solution of the system of integral equations has permitted us to establish boundaries of application of this approximate method, i.e. the range of parameters when induced currents in the borehole and invasion zone arise due to only the primary electric field and the skin effect in the formation and in the surrounding medium manifests in the same manner as in the horizontally layered medium. With error which does not exceed 10% this range of parameters is defined as ... 

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