A Multi-Modal Sensor for a Bed-Integrated Unobtrusive Vital Signs Sensing Array.

In this paper, we present a novel unobtrusive multi-modal sensor for monitoring of physiological parameters featuring capacitive electrocardiogram (cECG), reflective photoplethysmogram (rPPG), and magnetic induction monitoring (MI) in a single sensor. The sensor system comprises sensor nodes designed and optimized for integration into a grid-like array of multiple sensors in a bed and a central controller box for data collection and processing. Hence, it is highly versatile in application and suitable for unobtrusive monitoring of vital signs, both in a professional setting and a home-care environment.

Analytical solution for time-dependent potentials in a fiber stimulated by an external electrode.

This study provides an analytical solution for time-dependent potentials in a 3D cylindrical fiber stimulated by an extracellular point electrode. The membrane is passive and represented by surface resistance and surface capacitance. Separation of variables solution expresses intracellular and extracellular potentials as sums involving modified Bessel functions; the coefficients ([Formula: see text] and [Formula: see text]) depend on time.

Asymptotic model of electrical stimulation of nerve fibers.

We present a novel theory and computational algorithm for modeling electrical stimulation of nerve fibers in three dimensions. Our approach uses singular perturbation to separate the full 3D boundary value problem into a set of 2D "transverse" problems coupled with a 1D "longitudinal" problem. The resulting asymptotic model contains not one but two activating functions (AF): the longitudinal AF that drives the slow development of the mean transmembrane potential and the transverse AF that drives the rapid polarization of the fiber in the transverse direction.

Variability of action potential duration in pharmacologically induced long QT syndrome type 1.

Long QT Syndrome (LQTS) is a congenital disorder associated with life-threatening arrhythmias. LQT1, a type of LQTS affecting the slow delayed rectifier potassium current, shows a higher incidence of arrhythmia associated with sympathetic stimulation than other types of LQTS. LQT1 patients show increased variability of repolarization with epinephrine infusion, as measured from the 12-lead ECG.

Spatial heterogeneity of restitution properties and the onset of alternans.

Traditionally, it was believed that cardiac rhythm stability was governed by the slope of the restitution curve (RC), which relates the duration of an action potential to the preceding diastolic interval. However, a single RC does not exist; rate-dependence leads to multiple distinct RCs. We measure spatial differences in the steady-state action potential duration (APD), as well as in three different RCs: the S1-S2 (SRC), constant-basic-cycle-length (BRC), and dynamic (DRC), and correlate these differences with the tissue's propensity to develop alternans.

Activating function of needle electrodes in anisotropic tissue.

We present an analytical solution for the electrical potential and activating function (AF) established by cylindrical needle electrodes in anisotropic tissue. We compare this activating function to (1) AF computed assuming line-source electrodes and (2) AF computed using a finite element program. The results show that when the fiber is two needle diameters away from the electrodes, the maximum of the AF for needle electrodes is 1.

Resonance fluorescence spectroscopy in laser-induced cavitation bubbles.

Laser-induced breakdown spectroscopy (LIBS) in liquids using a double-pulse Q-switched Nd:YAG laser system has provided reliable results that give trace detection limits in water. Resonant laser excitation has been added to enhance detection sensitivity. A primary laser pulse (at 532 nm), transmitted via an optical fiber, induces a cavitation bubble and shockwave at a target immersed in a 10 mg l(-1)-100 mg l(-1) indium (In) water suspension.

Double-pulse technique for optical emission spectroscopy of ablation plasmas of samples in liquids.

Sharp atomic and ionic line spectra of excimer-laser-induced ablation plasmas of samples in liquids were observed. A new double-pulse technique employing quartz fibers facilitates spectral analysis of samples in liquids in which spectral lines normally are strongly broadened and quenched. The first pulse generates a cavitation bubble on the sample surface, which provides a gaseous environment for optical emission spectroscopy on the ablation plasma induced by a second pulse fired into the bubble.

Laser-light induced chromosome aberrations in Chinese hamster cells.

Wild-type Chinese hamster cells CHO K1 and their radiosensitive mutant xrs5 were irradiated at 308 nm, using light pulses of a XeCl excimer laser with total energy fluences of 0.1 kJ/m2 to 4.08 kJ/m2.

Macroscopic and microscopic findings after excimer laser treatment of different tissue.

In reported tests, the interaction of excimer laser radiation with bone, meniscus, and tendon tissue was observed. Depending on various laser parameters, different tissue reactions were observed in all procedures. Ablation was performed in a liquid medium to ensure extended carbonizations even at low application energy and repetition rate.

[Ablation of hard biological tissue with the excimer laser].

Cutting and drilling of bone- and meniscus tissue were performed using a XeCl-excimer laser combined with a tapered fiber. Ablation speed on meniscus tissue is already sufficient, the thermal damage of the adjacent tissue is minimal. Increasing of energy transmission through special fibers promises higher ablation rates also on hard biological tissue and that promoted the interest in lasers again for accident surgeons.

New tool combination: XeCl-excimer laser and tapered fiber enhances potential for atraumatic hard tissue operations.

XeCl excimer lasers have already been used to ablate bone, however, until now the results have been unsatisfactory until now. First, ablation of bone in air produced macroscopic noticeable carbonizations similar to those produced by thermal infrared lasers. Second, ablation rates were very low even on meniscus tissue.

Ultrafast imaging of tissue ablation by a XeCl excimer laser in saline.

To determine the temporal evolution of laser induced tissue ablation, arterial wall specimens with either hard calcified or fatty plaques and normal tissue were irradiated in a 0.9% saline solution using a XeCl excimer laser (wavelength 308 nm, energy fluence 7 J/cm2, pulse width 30 ns) through a 600 microns fused silica fiber pointing perpendicular either at a 0.5 mm distance or in direct contact to the vascular surface.

Studies in fiber guided excimer laser surgery for cutting and drilling bone and meniscus.

Our experiments on transmitting high-power excimer laser pulses through optical fibers and our investigations on excimer laser ablation of hard tissue show the feasibility of using the excimer laser as an additional instrument in general and accident surgery involving minimal invasive surgery. By combining XeCl-excimer lasers and tapered fused silica fibers we obtained output fluences up to 32 J/cm2 and ablation rates of 3 microns/pulse of hard tissue. This enables us to cut bone and cartilage in a period of time which is suitable for clinical operations.

[Ablation of the trabecular meshwork].

In an experimental investigation we examined the possibility to create an open pathway between the anterior chamber and Schlemm's canal by excimer laser ablation of the trabecualr meshwork (AT) in enucleated eyes. A quartzfiber was directed through the anterior chamber to the opposite chamber angle. With an energy of 0.