On the near-zone inverse Doppler effect

Attention is invited to the recently discovered inverse Doppler effect which occurs in the near-zone field of an antenna emitting a continuous wave. On approaching the antenna, the received signal is blue-shifted in the far zone and then red-shifted in the near zone; and on receding from the antenna, the received signal is blue-shifted in the near zone and then red-shifted in the far zone. Calculations are presented for the ease where the antenna is a simple dipole. It is shown that this effect gives not only the vector velocity of the moving receiver but also its range, i.e., its distance from the antenna.     

Volatile anesthetics inhibit dihydropyridine binding to malignant hyperthermia-susceptible and normal pig skeletal muscle membranes

BACKGROUND: Surface membrane dihydropyridine receptor Ca2+ channels may play a role in the response of malignant hyperthermia-susceptible skeletal muscle to volatile anesthetics. METHODS: We determined the effect of halothane, enflurane, and isoflurane on the binding of the Ca2+ channel blocker PN200-110 to skeletal muscle membranes isolated from malignant hyperthermia-susceptible and normal pigs. RESULTS: In the presence of 0.4 mM halothane, the maximal [3H]PN200-110 binding to both normal and malignant hyperthermia membranes was reduced by 37-43% (P < 0.05). There was no difference in the equilibrium constant for the halothane-dependent inhibition of [3H]PN200-110 binding to these two types of membranes. There also was no significant difference among halothane, enflurane, or isoflurane in their ability to inhibit [3H]PN200-110 binding to either normal or malignant hyperthermia membranes. CONCLUSIONS: Volatile anesthetics inhibit the binding of PN200-110 to skeletal muscle membranes by decreasing the number of functionally active dihydropyridine receptor proteins. This inhibition is similar for membranes isolated from both normal and malignant hyperthermia-susceptible muscle, thus providing no evidence for a halothane-induced functional defect in this protein in malignant hyperthermia-susceptible muscle. However, the results of this study also indicate that the mechanism by which volatile anesthetics decrease surface membrane Ca2+ currents in skeletal muscle is by reducing the number of functional dihydropyridine receptor Ca2+ channels.     

Analysis of an experimental technique for determining Van der Polparameters of a transistor oscillator

The Van der Pol (VDP) model of a transistor oscillator describes the behaviour of the oscillator with three parameters. When operating in steady state, only two parameters can be determined by spectrum analysis, these being the oscillation frequency and amplitude of oscillation. In this paper, a technique for measuring the other VDP parameter is examined. In this approach, a periodically modulated voltage is added to the bias of the oscillator to perturb the operational state. A theoretical derivation shows that the power spectrum of the perturbed oscillator contains additional information for determination of the other VDP parameter. A simple analytical perturbation formula predicts the oscillator's response to the ramped bias. Our experimental results agree with the analytical perturbation solution and therefore, this allows one to read off the other VDP parameter from the experimental data. The VDP model allows one to predict the behaviour of coupled transistor oscillators more accurately and simply than does the traditional large-signal model of the transistor. This VDP model will simplify oscillator array design since the number of parameters needed to describe each oscillator is reduced from that which would be required using a large-signal circuit model     

Remote Laboratories for Optical Circuits

This paper presents a remote laboratory implementation for an optical circuits course. The process from design and implementation towards assessment and continuous improvement phase is outlined. The design of the experiments involved the research on remote access technology and the investigation of best practices for an experimental setup. The first pilot implementations were used to determine the possible shortfalls during an ldquoIntroduction to an Optical Communicationsrdquo course in fall 2004 at the University of Colorado, Boulder, and an ldquoOptical Circuitsrdquo course in fall 2005 at the University of Houston, Houston, TX. After improvements, two experiments were pilot tested during spring 2006 at the University of Houston. Assessment of learning outcomes and teaching methods were performed. The remote access methods, in addition to the delivery of the class and lectures, are presented in the paper. Delivery of a class with remote laboratories and videotaped lectures are also outlined under future directions of this project.     

Testing the smoking behavior of fire-retarded materials

The authors investigated the smoke generating behavior of a fire-retardant-treated urethane polymer using a newly designed test chamber and test method, which they believe provides more meaningful information than the currently used smoke tests.     

Voltage calibration of the direct electrooptic sampling technique

A detailed study of various voltage calibration factors or the direct electrooptic sampling technique is presented. In reflection mode optical probing, the circuit substrate forms an etalon for the optical probe beam. Analytical expressions for the calibration factors due to etalon effects and decaying surface potentials are derived. on the length of the sampling pulse relative to the substrate transit time, the etalon will affect either the voltage calibration factor or the system bandwidth: For pulses that are long compared to the transient time, interference at the surface results in a probe wavelength dependent storage time effect. The resulting electrooptic signal shows a resonant behavior as a function of wavelength or substrate thickness. For pulses that are short compared to the substrate transit time, multiple reflections reduce the effective system bandwidth to a bandwidth less than that given by the single transit time or the sampling pulse width. Experimental verification of the theoretical results is presented. Various deembedding procedures for implementing the voltage calibration are discussed     

Backscatter readout from serial microbending sensors

Backscattering measurements performed on test fibers perturbed by several serially placed microbending sensors reveal the surprising result that the loss induced in a given sensor is nearly independent of the losses induced in the other sensors. A simple theoretical model is constructed to predict the conditions under which this desirable phenomenon can occur.     

Structure‐Dependent Binding of Arylimidamides to the DNA Minor Groove

Heterocyclic diamidines are strong DNA minor‐groove binders and have excellent antiparasitic activity. To extend the biological activity of these compounds, a series of arylimidamides (AIAs) analogues, which have better uptake properties in Leishmania and Trypanosoma cruizi than diamidines, was prepared. The binding of the AIAs to DNA was investigated by T_m, fluorescence displacement titration, circular dichroism, DNase I footprinting, biosensor surface plasmon resonance, X‐ray crystallography and molecular modeling. These compounds form 1:1 complexes with AT sequences in the DNA minor groove, and the binding strength varies with substituent size, charge and polarity. These substituent‐dependent structure and properties provide a SAR that can be used to estimate K values for binding to DNA in this series. The structural results and molecular modeling studies provide an explanation for the differences in binding affinities for AIAs.     

Study of UV-bleached channel-waveguide performance in nonlinear optical polymer films

We report studies on UV-photobleached optical channel waveguides in nonlinear optical polymer films. The nonlinear optical polymer used is poly(methyl methacrylate)/DR1 side-chain polymer. The effective indices of the channel waveguides are measured with the prism-coupling technique, along with the effective indices of bleached and unbleached polymer films. The effective-index method was used to predict the effective indices of the channel waveguides from measurements of the slab waveguides, without detailed knowledge of the index distributions in the polymer films. Some local stress-related effects on the boundaries of the channel waveguides caused by the UV-bleaching process are identified by comparison between direct channel measurement and prediction. It is found that the technique used in this study can be employed to predict the performance of channel waveguides processed such that they have no excessive internal stress distributions.