Exponential Line Research Articles

Evaluation of the VX2 rabbit auricle carcinoma as a model for head and neck cancer in humans

Introduction: This study investigates whether the VX2 carcinoma cell line, transplanted into the rabbit auricle, can be used as a head and neck cancer model. The biologic behaviour of this model is evaluated, comparing tumour transplantation with either tissue pieces or cell suspensions. Material: Thirty-six adult NZW rabbits received s.c. injections of VX2-suspensions (Group S) and 11 rabbits received solid VX2-pieces (Group P) into both auricles. Methods: In Group S, 16 rabbits were sacrificed at various days before (S1) and 15 after (S2) the 28th day following transplantation. In the other five rabbits transplantation failed. Animals from Group P were sacrificed every 2 weeks after the 28th day. At autopsy the size of the primary tumours and of lymph node, lung and other metastases were assessed. If transplantation failed, the maximal tumour size and the time at which regression took place were recorded. Exponential trend lines were used to create growth curves of metastases. Differences between groups were evaluated with the χ2test, correlations between parameters with Kendall's tau. Results: The tumour take-rate in Groups S and P was 78% and 59% respectively. The maximal size and time at which regression occurred was significantly different, amounting to 83±7 mm2at 10.4±1.6 days (Group S) and 243±30 mm2at 20.9±2.0 days (Group P), respectively. Development of lymph node metastases was not different. In Groups P and S2, over 90% of the necks contained lymph node metastases. There was a higher incidence of lung metastases in Group S2 when compared to Group P (47% vs. 14%) but it was not statistically significant. A significant correlation (p<0.05) between weight loss and the size of lung metastases was found. Conclusion: Transplantation of the VX2-tumour with cell suspensions produces a useful head and neck cancer model for loco-regional disease in which anti-tumour regimens against both the primary and lymph node metastases can be tested. Transplantation with tumour pieces is not advised as the take-rate is low and spontaneous remissions occur at a late stage.

Analysis of the stretched exponential photoluminescence decay from nanometer-sized silicon crystals in SiO2

Time resolved photoluminescence (PL) decays have been measured for Si nanocrystals embedded in silicon dioxide. The nanocrystals were formed by implanting 40 keV Si ions into a 1000 Å thick film of thermally grown SiO2, followed by thermal annealing at 1000–1200 °C. The observed luminescence, peaking at 700–850 nm, is compared to similar measurements performed on porous Si emitting in the same wavelength range. The results show that the PL from the nanocrystals exhibits a stretched exponential decay with characteristic decay time τ in the range 10–150 μs and dispersion factor β in the range 0.7–0.8. Both parameters are, however, higher for the nanocrystals compared to those of porous Si indicating superior passivation of the nanocrystals in the SiO2 matrix. Evidence is also presented for a single exponential behavior at the decay end suggesting a remaining fraction of excitons in isolated nanocrystals. We attribute the highly nonlinear dose dependence of the PL yield to a nucleation process for the nanocrystals and a more curved decay line shape for higher ion doses to a higher crystal density, promoting excitonic migration to nearby nanocrystals. These observations provide strong evidence that the origin of the stretched exponential line shape of the PL decay results from migration and trapping of excitons in a system of randomly distributed and interconnected nanocrystals with a dispersion in size.

Short-pulse transient and characteristics of lossy binomial transmission lines with arbitrary linear and nonlinear termination

Lossy binomial transmission lines with arbitrary linear and nonlinear loads are modeled for use as short-pulse transformers in electrical and optical high-speed interconnects. An efficient method is proposed in this paper to characterize these lines as an equivalent circuit that consist of a cascaded connection of lumped networks and lossy uniform transmission lines in the frequency domain, while nonlinear problems are formulated and solved with time-domain scattering equations via a convolution technique. Results indicate that binomial lines present an advantage over exponential lines or uniform lines for the nonlinear loading effect, and they can be effectively used as a short-pulse transformer in such systems and devices as laser diodes, junction transistors, and metal-oxide-semiconductor field-effect transistors to enhance power coupling efficiency and reshape digital signal waveforms.

Localization and fluctuations in quantum kicked rotors.

We address the issue of fluctuations, about an exponential line shape, in a pair of one-dimensional kicked quantum systems exhibiting dynamical localization. An exact renormalization scheme establishes the fractal character of the fluctuations and provides a method to compute the localization length in terms of the fluctuations. In the case of a linear rotor, the fluctuations are independent of the kicking parameter k and exhibit self-similarity for certain values of the quasienergy. For given k, the asymptotic localization length is a good characteristic of the localized line shapes for all quasienergies. This is in stark contrast to the quadratic rotor, where the fluctuations depend upon the strength of the kicking and exhibit local "resonances." These resonances result in strong deviations of the localization length from the asymptotic value. The consequences are particularly pronounced when considering the time evolution of a packet made up of several quasienergy states.

Measuring breathlessness during histamine challenge: a simple standardized procedure in asthmatic patients.

One of the problems in research on symptom perception during histamine challenge has been the difficulty in finding both a valid and practical parameter of the "perceptiveness" for bronchoconstriction in a subject. The purpose of this study was to validate whether the slope in the linear regression model between stimulus and sensation during histamine challenge is an appropriate index for the "perceptiveness" for bronchoconstriction by comparing it with the classical Stevens' law. One hundred and thirty-four asthmatic patients were included in the study and underwent a bronchial challenge with histamine. The relationship between the change in visual analogue scale (VAS) values and the change in forced expiratory volume in one second (FEV1) as percentage of baseline value was analysed by determining both the exponent n in deltaVAS=k x (%deltaFEV1)n and the slope alpha in deltaVAS=k + alpha(%deltaFEV1). The best-fitting line of both the exponential and the linear regression model were determined by the least-squares method in which the percentage explained variation (R2) was compared. The median value of R2 of the exponential regression line and the linear regression line was 0.76 and 0.83, respectively, and significantly different. The Spearman rank correlation coefficient between exponent n in the exponential model deltaVAS=k x (%deltaFEV1)n and the slope alpha in the linear regression model deltaVAS=k + alpha(%deltaFEV1) was 0.87 (95% confidence interval 0.83-0.91). On the basis of the results, it was concluded that the linear regression coefficient can be used as a valid expression to describe the "perceptiveness" of an asthmatic subject instead of Stevens' power function during histamine challenge.

LLAMPÜDKEÑ: A high-current, low-impedance pulser employing an auxiliary exponential transmission line

The design and constructional aspects of a novel pulse power generator for use in dense plasma research presently under construction are presented. The generator consists of two Marx capacitor banks, each of 0.25 μF, 480 kV, and 28.8 kJ. Each Marx generator drives a water transmission line, in which the live electrode is the central conductor. The transmission lines consist of a constant impedance section followed by a multielectrode gas linegap followed by an exponential taper to the load section. The novel feature is the use of an auxiliary exponential line coupled at the load. This line controls both the voltage and the effective impedance at the load section. In addition, by leaving this line circuit open, energy not coupled to the plasma in the initial high-impedance phase may be reflected back and deposited into the discharge, increasing the peak current by 50%. Circuit simulations using a real-time-varying load impedance show that the current pulse rises in an approximately linear way to a maximum of 1.2 MA at 250 ns. The current falls to zero in the following 250 ns. The current waveform may be flattened simply by disconnecting the auxiliary line, giving a rectangular pulse of 350 ns with a maximum value of 950 kA. The overall impedance of the entire system may be adjusted by varying the separation between the conductors. The equivalent source impedance at the load is 0.8 Ω. This low value is by virtue of the auxiliary line, which limits the voltage at the load section and reduces the insulator constraints. We present simulations of the generator under real load conditions. The model also is checked against analytical solutions of exponential line behavior and against other published models of pulse power generators.

Identification of peripheral vascular disease in elderly subjects using optical spectroscopy.

The purpose of this study was to determine the usefulness of near-infrared spectroscopy (NIRS) measurements to identify peripheral vascular disease (PVD). Usefulness was determined by the frequency of a successful test, as well as comparison with standard clinical assessments. Study subjects (N = 117, mean age = 67.8 +/- 8.1 yrs) responded to a free screening for PVD. NIRS was used to measure the relative O2 saturation of hemoglobin in the soleus muscle. The time to 1/2 recovery of O2 saturation (O2T1/2) was measured after 1 minute of repeated plantar flexions using a Cybex Eagle seated calf machine. O2T1/2 was used as many subjects had recovery curves that did not have an exponential line shape. The test was done on both legs and the worst leg was used for analysis. For comparative purposes, a clinical history and physical examination were performed by a physician or nurse practitioner, which included questions on intermittent claudication, examination of peripheral pulses, and questions to identify cardiovascular risk factors. NIRS signals were obtained on 105 of 117 subjects (89% success rate). Subjects with body mass index (BMI) values above 32 appeared to have NIRS O2T1/2 values that were less reliable than subjects with BMI values < or = 32 (77% success rate). The O2T1/2 was longer in subjects with claudication and reduced pulses than in subjects without these conditions. Sensitivity comparing O2T1/2 to claudication and reduced pulse varied from 51-76% and specificity from 65-80%, depending on the cutoff value for O2T1/2 that was used (normal value plus 1 or 2 SD). A longer O2T1/2 was significantly associated with incidence of diabetes, smoking, hypercholesterol, and coronary bypass surgery. In summary, successful NIRS O2T1/2 measurements were made in 77% of the subjects, with failure primarily occurring in obese subjects. NIRS O2T1/2 measurements showed reasonable although not strong agreements with clinical assessment of PVD, and with some risk factors for cardiovascular disease.

Explicit expressions of the reflection and transmission for two coupled identical exponential lines

The reflection and transmission problem of two coupled identical exponential lines is considered in this paper. The exact and explicit expressions for the co- and cross-line reflection and transmission coefficients are derived. The explicit expressions are validated by an independent numerical solution.

Modelling of single-phase nonuniform transmission lines in electromagnetic transient simulations

An exponential single-phase line model is introduced to represent nonuniform transmission lines. When the line parameters are assumed to vary exponentially, a set of two-port equations can be formed in the frequency domain, which contain frequency-dependent functions. These functions are then synthesized with rational functions of the minimum-phase-shift type. Utilizing a fast recursive convolution technique, the time-domain equations of the proposed model reduce to a form similar to those in Bergeron's method. Plus, the model is compatible with general electromagnetic transients programs such as the EMTP. Time-domain simulations with the proposed model show good agreement with published experimental results, and with those produced by a cascade multi-section model where the line is divided into many short sections of uniform transmission lines.

High speed driving of a gain-switched laser diode with an exponential transmission line

With the increase of information capacity of an airborne system, high speed driving of laser diodes have been of interest. In order to match the low resistive LD, proposed in this paper is an exponential transmission line, which is used as preshaping to compensate the pattern effect in gain switching of laser diodes. It also will be used to overcome the effect of parasitic elements in high speed driving to improve the rise and trail edges of the output waveform. An accurate circuit model of the exponential line for the PSPICE program has been developed and simulations are conveniently carried out by employing PSPICE.

水溶性染料のオゾン酸化による脱色と色度測定法による評価

Decoloration processes caused by the ozonation of sixteen water-soluble dyes were evaluated by several color measurement methods, and then, the characteristics and relationship between them were investigated. An attempt was made to propose a feasible color control method.Initial decoloration processes measured by absorbance method were represented as a pseudo-first order reaction. On the other hand, they were not represented by color difference method. The behavior of initial decoloration processes measured by dilution method was relatively similar to that measured by absorbance method. The values measured by both absorbance and dilution methods were correlated by an exponential regression line. Based on this correlation, a feasible color control method corresponding to an aesthetic sense was proposed.

Closed-form solution for lossy exponential transmission line problem in frequency and time domains

An exact and explicit solution for the reflection and transmission problem of a lossy exponential transmission line of finite length is derived in both the frequency and the time domain via a wave-splitting approach. The problem is formulated first in the frequency domain. Wave-splitting is defined and the solution for internal voltages and currents is derived. Closed-form solutions for the reflection and transmission coefficients are obtained. The explicit solution for a transmission line consisting of several exponential pieces (each with different taper) in series is then easily written down. To obtain the transient response of the lossy exponential line, a time domain Green function approach based on wave-splitting is used. Linear partial differential equations for the Green functions together with the initial and boundary conditions are derived and solved explicitly. The exact and explicit solutions for the transient reflection and transmission up to arbitrary large times are given.

Transient analysis of lossless single-phase nonuniform transmission lines

A new method has been developed to study the transient behavior of nonuniform transmission lines whose parameters can have any arbitrary space variation. Using the exponential line as a building block, s-domain expressions are obtained for the voltage and current at any point along the nonuniform line. An efficient numerical Laplace-transform inversion technique is then used to compute the time-domain solution. Computer simulations and comparisons with other solution methods are included. >

Transient responses of an exponential transmission line and its applications to high-speed backdriving in in-circuit test

Step responses of an exponential line terminated with resistive loads are evaluated by means of time-domain scattering parameters. The results are used to illustrate the interaction between a nonuniform line and a nonlinear load. We find that an exponential line could be used to compensate the nonlinear load effects in high-speed backdriving. >

In-beam Mössbauer spectroscopy on isomer shift and diffusion of interstitial Fe

In-beam Mossbauer spectroscopy (IBMS) is used to study single isolated57Fe impurities after implantation in metals and semiconductors with very restricted or even vanishing solubility for Fe. From the Mossbauer parameters it can be inferred that the Fe implants take up substitutional as well as interstitial sites. The strongly increased electron density at the interstitial position in metals is qualitatively explained by the pressure resulting from the small interstitial volume. In Si, Sc and Pb exponential line broadening due to interstitial diffusion has been observed. Additional information on the dynamic behavior and local magnetic structure in some of the systems presented comes from perturbed angular distribution experiments (PAD) performed on an isomeric state of54Fe.

Transients on lossless exponential transmission lines using Allen's method

Exact analytical expressions for the time-domain step response matrix of the lossless exponential transmission line are developed, thereby extending the range of problems for which Allen's method can be applied for the transient analysis of networks consisting of interconnections of linear distributed elements, lumped linear and/or nonlinear elements, and arbitrary sources. An indication as to the correctness of the expressions is obtained by comparing them to published results, which also helps to give a better physical insight into the step response matrix. The response to a step input and the transient response to a sudden sinusoidal excitation are presented. >

INVARIANT STRUCTURES IN GAUGE THEORIES AND CONFINEMENT

The problem of finding all gauge invariants is considered in connection with the problem of confinement. Polylocal gauge tensors are introduced and studied. It is shown (both in physical and pure geometrical approaches) that the path-ordered exponential is the only fundamental bilocal gauge tensor, which means that any irreducible polylocal gauge tensor is built of P-exponentials and local tensors (matter fields). The simplest invariant structures in electrodynamics, chromodynamics and a theory with the gauge group SU(2) are considered separately. As a consequence of gauge invariance any “elementary” charge is accompanied by an external static field located on the integration contour of a P- exponential, i.e. by a string. The Coulomb field is analyzed from this point of view; it is demonstrated that it can also be considered as made of exponential line integrals. In QCD strings can branch—it means that the interquark static field cannot be associated with a simple P-exponential. On the contrary, in pure gluodynamics strings do not branch. Different forms of confinements are briefly reviewed.

STRING-LIKE EXCITATIONS IN QED

The evolution of string-like excitations of fields (exponential line integrals) in free QED and in QED with static sources is investigated. It is shown that these excitations are not stable. They break down into electromagnetic radiation and the Coulomb field. The results are compared with calculations in the lattice QED.

The identification problem and image reconstruction of the exponential X‐ray transform

AbstractThe emission‐type CT which utilizes the radiation from the radioisotope (RI) injected into the body can reconstruct the biochemical information inside the body as an image. At present, the multicross‐sectional method is employed in reconstructing the three‐dimensional distribution of RI, as in the case of X‐ray CT.In this method, a spatial nonuniform resolution is produced in the reconstructed RI image. It should be noted, on the other hand, that RI injected into the body emits radiations in all directions in the space. By utilizing all those radiations, a three‐dimensional image can be reconstructed without a nonuniformity in the resolution.This paper shows that the three‐dimensional distribution of RI can directly be reconstructed from the radiations emitted spatially from inside the body. It is shown first that the problem to determine the three‐dimensional distribution of RI from the radiations is the inverse problem with the exponential line integral as the measured value. The relation between the Fourier transform of the projections by the exponential line integral and the Fourier transform of the original three‐dimensional image is analyzed. Then it is shown that the radiation attenuation coefficient of RI can be determined only from the projection data.Furthermore, based on the relation between the Fourier and Hankel transformations, a method is derived for the direct three‐dimensional image reconstruction from the radiation projection using the series expansion.

Time-domain scattering parameters of an exponential transmission line

The scattering parameters of an exponential line are studied in detail in both the frequency and time domains. By taking the causality condition into consideration, the time-domain scattering parameters are cast in a rapid-convergence power series. Each term of the power series represents a signal component generated by the exponential line when the signal travels a round trip. The time-domain scattering parameters of an exponential line lay the foundation for studies of interaction between nonuniform lines and linear/nonlinear loads, and pulse waveform alteration in the time domain. >