Biomedical subjects

A Bolz

Publications and source records attributed to A Bolz.

At least 19 recordsLinked to original sources

PubMed2001

[Artificial intelligence in sleep analysis (ARTISANA)--modelling visual processes in sleep classification].

We describe a novel approach to the problem of automated sleep stage recognition. The ARTISANA algorithm mimics the behaviour of a human expert visually scoring sleep stages (Rechtschaffen and Kales classification). It comprises a number of interacting components that imitate the stepwise approach of the human expert, and artificial intelligence components. On the basis of parameters extracted at 1-s intervals from the signal curves, artificial neural networks recognize the incidence of typical patterns, e.g. delta activity or K complexes. This is followed by a rule interpretation stage that identifies the sleep stage with the aid of a neuro-fuzzy system while taking account of the context. Validation studies based on the records of 8 patients with obstructive sleep apnoea have confirmed the potential of this approach. Further features of the system include the transparency of the decision-taking process, and the flexibility of the option for expanding the system to cover new patterns and criteria.

Adult↗

PubMed2001

[Conditions and success factors of telemedicine innovation].

Telemedicine and health telematics can play a significant role in improving the efficiency of health care systems. Currently, however, the potential of telemedical applications is far from being fully utilized. In the present study, an attempt has been made to identify factors that may aid the further dissemination and general acceptance of telemedical innovations. The results obtained suggest that apart from the factors under the sole control of legislation, and insurance providers, those that can be directly influenced by developers, manufacturers and providers of telemedical applications play an important role. Of particular importance for the successful and lasting use of such applications is the creation of promising business models, aspects of which are considered in the last part of the article.

Diffusion of Innovation↗

PubMed1998

Nuclear Magnetic Resonance Detection of Two Distinctly Different Chains in the Orthorhombic Crystalline Phase of Polyethylenes.

Several commercial and noncommercial, high- and low-density and ultraoriented polyethylene samples, as well as polyethylene samples with inorganic fillers, have been investigated by inversion-recovery cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (NMR). In all these samples two types of all-trans chains in orthorhombic crystalline domains are detected, which give two overlapping carbon-13 lines with different line widths and different relaxation times. From the NMR relaxation parameters we conclude that one type of the crystalline chains, which composes 60-90% of the crystalline fraction in all samples, can execute at room temperature 180 degrees flips with a frequency in the kilohertz domain. The other crystalline chains are more rigid and probably are found in more perfect structures in which such chain flips do not occur or occur on a much slower time scale. Adding kaoline filler particles to polyethylene enhances the contribution of the more mobile crystalline chains. The presence of the two distinctly different types of crystalline environments is found in all polyethylene samples investigated so far (more than 25 samples).

Journal Article↗

PubMed1998

A fractally coated, 1.3 mm2 high impedance pacing electrode.

Minimizing the geometric surface area of pacing electrodes increases impedance and reduces the current drain during stimulation, provided that voltage (pulse-width) thresholds remain unchanged. This may be feasible by coating the electrode surface to increase the capacity of the electrode tissue interface and to diminish polarization. Ten unipolar, tined leads with a surface area of 1.3 mm2 and a "fractal" coating of iridium (Biotronik SD-V137) were implanted in the ventricle, and electrogram amplitude (unfiltered), slew-rate, pacing threshold (0.5 ms), and impedance (2.5 V; 0.5 ms) were measured by the 5311 PSA (Medtronic). On days 0. 2. 5. 10, 28, 90, 180, 360 postimplant, sensing threshold (up to 7.0 mV, measuring range 1-14 mV on day 360 only) and the strength duration curve (0.5-4.0 V; 0.03-1.5 ms; steps: 0.5 V; 0.01 ms, respectively) were determined, the minimum charge delivered per pulse (charge threshold), and the impedance were taken from pacemaker telemetry (Intermedics 294-03). Data were compared with those of an earlier series of 20 unipolar, tined TIR-leads (Biotronik) with a surface area of 10 mm2 and a @actal" coating of titanium nitride. With the model SD-V137 versus TIR, intraoperative electrogram amplitudes were 15.1 +/- 6.1 versus 14.4 +/- 3.9 mV (NS), slew rates 3.45 +/- 1.57 versus 1.94 +/- 1.06 V/s (P < 0.05), pacing thresholds 0.16 +/- 0.05 versus 0.52 +/- 0.15 V (P < 0.01) and impedance measurements 1,136 +/- 175 versus 441 +/- 73 omega (P < 0.0001), respectively. During follow-up, sensing thresholds were the same with both leads. Differences in pulse width thresholds lost its significance on day 28 but resumed on day 360 (SD-V137; 0.08 +/- 0.04 ms; TIR: 0.16 +/- 0.06 ms at 2.5 V; P < 0.01). With an electrode surface of 1.3 mm2, charge per pulse and impedance consistently differed from control, being 0.15 +/- versus 0.66 +/- 0.20 microC (P < 0.001) and 1,344 +/- 376 versus 538 +/- 79 omega respectively, one year after implantation (P < 0.0001). In summary, "fractally" coated small surface electrodes do not compromise sensing; by more than doubling impedance against controls they offer pacing thresholds (mainly in terms of charge) that are significantly lower than with the reference electrode.

Aged↗

PubMed1998