SummaryPCR-based detection of single nucleotide polymorphisms is a powerful tool for the plant geneticist. Cleaved amplified polymorphic sequence analysis is the most widely used approach for the detection of single nucleotide polymorphisms. However, this technique is limited to mutations which create or disrupt a restriction enzyme recognition site. This paper presents a modification of this technique where mismatches in a PCR primer are used to create a polymorphism based on the target mutation. This technique is useful for following known mutations in segregating populations and genetic mapping of isolated DNAs used for positional based cloning of new genes. In addition, a computer program has been developed that facilitates the design of these PCR primers.

We introduce an open-loop control scheme for stochastic resonators; the scheme permits the enhancement or suppression of the spectral response to threshold-crossing events triggered by a timeperiodic signal in background noise. The control is demonstrated in experiments using a Schmitt trigger. A generic two-state theory captures the essential features observed in our experiments and in numerical simulations; this suggests the generality of the effect. [S0031-9007(99)09258-3] PACS numbers: 05.40.Ca, 02.50.Ey, 47.20.Ky, 85.25.Dq Stochastic resonance (SR) is a nonlinear noise-mediated cooperative phenomenon wherein the coherent response to a deterministic signal can be enhanced in the presence of an optimal amount of noise. Since its inception in 1981 [1], SR [2] has been demonstrated in diverse systems including sensory neurons, mammalian neuronal tissue, lasers, SQUIDs, tunnel diodes, and communications devices. Variations and extensions of the classical definition of SR to include aperiodic (e.g., dc or wideband) signals, with the detector response quantified by various information-theoretic [3] or spectral cross-correlation [4] measures, have also appeared in the literature.In this Letter, we introduce a control scheme which allows us, at will, to either enhance or suppress the spectral response in the basic SR effect. Our control strategy is applicable when input information is transmitted via the crossing of either a threshold or potential energy barrier. This raises the intriguing possibility that in situations where external signals might be potentially deleterious, e.g., electromagnetic field interactions with neuronal tissue [5], their effects could be substantially reduced or even eliminated via (externally applied) control signals.The experiments were carried out in a modified Schmitt trigger (ST) electronic circuit. The Schmitt trigger is one of the simplest threshold systems [6,7], possessing a static hysteretic nonlinearity. We denote the lower and upper threshold voltages in the Schmitt trigger by V L and V U , respectively, with 2b being the (static) threshold separation. A subthreshold 64 Hz time-sinusoidal signal S͑t͒ A S sinv S t ͑A S , b͒ and Gaussian noise [8] are applied to the input. For fixed, equal and opposite V L and V U , standard SR curves can be obtained by measuring the output signal power (SP) at the fundamental frequency v S as a function of input noise power [9]. To realize the control scheme we modulate the upper and lower thresholds sinusoidally, V U ͑t͒ b 1 A M sin͑v M t 1 f͒, V L ͑t͒ 2V U ͑t͒, which results in a "breathing" oscillation ( Figs. 1 and 2) of the barriers with frequency v M . We keep the signal and threshold modulating amplitudes fixed such that A M 1 A S , b (no deterministic switching) and investigate the system's response as a function of the phase offset f and the input noise power. Note that in this work we only consider integer frequency ratios n v M ͞v S ͑ 1, 2͒.Our experimental results are shown in the gray-scale plots of Fig. 3, where signal output pow...

It is well known that overdamped unforced dynamical systems do not oscillate. However, well-designed coupling schemes, together with the appropriate choice of initial conditions, can induce oscillations (corresponding to transitions between the stable steady states of each nonlinear element) when a control parameter exceeds a threshold value. In recent publications [A. Bulsara, Phys. Rev. E 70, 036103 (2004); V. In, ibid. 72, 045104 (2005)], we demonstrated this behavior in a specific prototype system, a soft-potential mean-field description of the dynamics in a hysteretic "single-domain" ferromagnetic sample. These oscillations are now finding utility in the detection of very weak "target" magnetic signals, via their effect on the oscillation characteristics--e.g., the frequency and asymmetry of the oscillation wave forms. We explore the underlying dynamics of a related system, coupled bistable "standard quartic" dynamic elements; the system shows similarities to, but also significant differences from, our earlier work. dc as well as time-periodic target signals are considered; the latter are shown to induce complex oscillatory behavior in different regimes of the parameter space. In turn, this behavior can be harnessed to quantify the target signal.

Unforced bistable dynamical systems having dynamics of the general form cannot oscillate (i.e. switch between their stable attractors). However, a number of such systems subject to carefully crafted coupling schemes have been shown to exhibit oscillatory behavior under carefully chosen operating conditions. This behavior, in turn, affords a new mechanism for the detection and quantification of target signals having magnitude far smaller than the energy barrier height in the potential energy function U(x) for a single (uncoupled) element. The coupling-induced oscillations are a feature that appears to be universal in systems described by bi- or multi-stable potential energy functions U(x), and are being exploited in a new class of dynamical sensors being developed by us. In this work we describe one of these devices, a coupled-core fluxgate magnetometer (CCFM), whose operation is underpinned by this dynamic behavior. We provide an overview of the underlying dynamics and, also, quantify the performance of our test device; in particular, we provide a quantitative performance comparison to a conventional (single-core) fluxgate magnetometer via a ‘resolution’ parameter that embodies the device sensitivity (the slope of its input–output transfer characteristic) as well as the noise floor.

Frequency-related oscillations in coupled oscillator systems, in which one or more oscillators oscillate at different frequencies than the other oscillators, have been studied using group theoretical methods by Armbruster and Chossat [Phys. Lett. A 254, 269 (1999)] and more recently by Golubitsky and Stewart [in Geometry, Mechanics, and Dynamics, edited by P. Newton, P. Holmes, and A. Weinstein (Springer, New York, 2002), p. 243]. We demonstrate, experimentally, via electronic circuits, the existence of frequency-related oscillations in a network of two arrays of N oscillators, per array, coupled to one another. Under certain conditions, one of the arrays can be induced to oscillate at N times the frequency of the other array. This type of behavior is different from the one observed in a driven system because it is dictated mainly by the symmetry of the coupled system.

We present a programmable continuous-time floating-gate Fourier processor that decomposes the incoming signal into frequency bands by analog bandpass filters, multiplies each channel by a nonvolitile weight, and then recombines the frequency channels. A digital signal processor would take a similar approach of computing a fast Fourier transform (FFT), multiplying the frequency components by a weight and then computing an inverse FFT. We decompose the frequency bands of the incoming signal using the transistor-only version of the autozeroing floating-gate amplifier (AFGA), also termed the capacitively coupled current conveyer (C 4 ). Each band decomposition is then fed through a floating-gate multiplier to perform the band weighting. Finally, the multiplier outputs are summed using Kirchoff current law to give a band-weighted output of the original signal. We examine many options to reduce second-order harmonic problems inherent in the single-sided C 4 . We present a method for programming arrays of floating-gate devices that are used in the weighting of the bands. All of these pieces fit together to form an elegant and systematic Fourier processor.

Chaos control has been applied to control atrial fibrillation in humans. Results are presented on the application and evaluation of chaos control for slowing and regularizing local electrical activation of the right atrium of humans during induced atrial fibrillation.

It is well known that overdamped and unforced dynamical systems do not oscillate. However, well-designed coupling schemes, together with the appropriate choice of initial conditions, can induce oscillations when a control parameter exceeds a threshold value. We demonstrate this effect in a specific system, a soft-potential mean-field description of the dynamics in a (hysteretic) single-domain ferromagnetic sample. Using a specific (unidirectional, with cyclic boundary conditions) coupling scheme, together with nonidentical initial conditions, one can cause the coupled system of N elements (N odd) to oscillate when the coupling coefficient is swept through a critical value. The ensuing oscillations could find utility in the detection of very weak "target" signals, via their effect on the oscillation characteristics.