Fetal ECG (FECG) monitoring using abdominal maternal signals is a non-invasive technique that allows early detection of changes in fetal wellbeing. Several other signal components have stronger energy than the FECG, the most important being maternal ECG (MECG) and, especially during labor, uterine EMG. This study proposes a new method to subtract MECG after detecting and removing abdominal signal segments with high-amplitude variations due to uterine contractions. The method removes MECG from abdominal signals using an approximation of the current MECG segment based on a linear combination of previous MECG segments aligned on the R-peak. The coefficients of the linear model are computed so that the squared error of the approximation over the whole current segment is minimized. Abdominal signal segments strongly affected by uterine contractions are detected by applying median filtering. The methods proposed are tested on real abdominal data recorded during labor, with FECG recorded using scalp electrodes synchronously recorded for comparison.

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The adaptive noise canceller (ANC) is a commonly used linear system method for noise reduction in cases where the disturbing noise can be separately recorded (reference signal) and is not correlated with the signal of interest. In case of a periodic disturbing signal, special solutions are described in literature. Problems, however, arise when the propagation of the noise from the source to the recording sensors passes nonlinear structures. An ANC modification proposed for this case by Strobach et al. and applied by several other researchers, thus, uses an artificial reference signal, based on event triggered averaging of segments of the recorded wanted (but disturbed) signal in order to obtain a template for the repetitive distortion sequence and to construct the artificial reference signal. The effect of the averaging and the error introduced by this approximation of the real disturbing signal was not addressed in literature until now, thus, this paper presents some basic theoretical considerations on this topic. Methods are demonstrated in simulations and real biosignal processing, and application aspects are discussed.

Several imaging techniques have identified different brain areas involved in the processing of noxious stimulation and thus in the constitution of pain. However, only little is known how these brain areas communicate with one another after activation by stimulus processing and which areas directionally affect or modulate the activity of succeeding areas. One measure for the analysis of such interactions is represented by the Granger Causality Index (GCI). In applying time-varying bivariate and partial variants of this concept (tvGCI), the aim of the present study was to investigate the interaction of neural activities between a set of scalp electrodes that best represent the brain electrical neural activity of major cortical areas involved in the processing of noxious laser-heat stimuli and their variation in time. Bivariate and partial tvGCIs were calculated within four different intervals of laser-evoked event-related potentials (LEPs) including a baseline period prior to stimulus application and three intervals immediately following stimulus application, i.e., between 170 and 200 ms (at the N2 component), between 260 and 320 ms (P2 component), and between 320 and 400 ms (P3 component of LEPs). Results show some similarities, but also some striking differences between bivariate and partial tvGCIs. These differences might be explained by the nature of bivariate and partial tvGCIs. However, both tvGCI approaches revealed a directed interaction between medial and lateral electrodes of the centroparietal region. This result was interpreted as a directed interaction between the anterior cingulate cortex and the secondary somatosensory cortex and the insula, structures that are significantly involved in the constitution of pain.

With a view to advancing electrochemical sensor technology, considerable interest is currently being shown in the design and synthesis of redox-active molecules that contain a redox center in close proximity to a host binding site."] These systems are capable of recognizing electrochemically the complexation of a guest through space interactions between the redox center and the receptor site. Perturbation of the electrochemical response of the redox center is observed in the presence of the target host, allowing its amperometric or potentiometric titration. In particular, electrochemical recognition and sensing of Group 1 and 2 metal cations by ferrocene crown ether and cryptand ionophores has been successfully achieved in homogeneous solution.["2JFor the development of novel prototypes of electrochemical sensors, it is a challenge to synthesize molecular electrodes based on these redox receptors, which must retain their complexation and recognition behavior after immobilization onto an electrode surface. For instance, incorporating a redox-active receptor into a polymer matrix such as a functionalized polypyrrole film can provide great convenience in fabricating sensors.[31 In this communication, we present the first example of electropolymerization of a pyrrole-substituted ferrocene crown ether and the remarkable behavior of the resulting polymer film modified electrode towards the amperometric recognition of barium and calcium cations.The new ligand L was synthesized according to Scheme 1. Its electrochemistry was investigated by cyclic voltammetry (CV) in lo-' mol L-' tetra-n-butylammonium perchlorate (TBAP) + CH3CN electrolyte. The CV curve is characterized by a quasi-reversible redox wave at 0.53 V, corresponding to the ferrocene/ferricinium couple. This Scheme 1. Synthesis of L.wave is followed at a higher potential by a large peak (Epa = 0.97 V), which is due to the irreversible oxidation of both the pyrrole group and the benzo-crown ether moiety of L. The oxidation of the latter occurs at EPa = 1.13 V in the parent pyrrole-free ferrocene crown ether.[41 It is now well established that the electrooxidative polymerization of functionalized pyrroles is an effective method for carrying out the coating of electrode surfaces by non-passivating polymer layers containing redox-active centers.['] The growth of polyL films on the Pt electrode surface was accomplished by repeated CV scans over the 0 V to 0.8 V potential range, or by controlled potential electrolysis at 0.8 V in millimolar solutions of L. The resulting modified electrodes transferred to clean CH3CN electrolyte display a stable electrochemical response for immobilized L at Efi2 = 0.56 V (Fig. 1, curve 1). Fig. 1. CV curve of a Pt/polyL modified electrode (5 mm diameter) in CH3CN + lo-' rno1L-l T B A P E vs. Ag/lO-* molL-' AgNO, + lo-' mol L-' TBAP + CHICN; scan rate 0.1 V 8; T L = 2 x lo-* molcm-*; [BaZ0] = 0 (I), 10. ' mo1L-I (2),2 x moILY (3).Adv. Mater. 1997,9, No. 9 0 VCH Verlagsgesellschaft mbH, 0-69469 Weinheim, 1997 0935-9648/97/0907-0711$17.5...