Abstract: Preform for an optical waveguide containing a core with a non-circular geometry and at least one cladding layer, in which the dopand concentration of the cladding layer is increased compared to the dopand concentration of a preform with circular core geometry and identical NA. A method for the production of a preform for an optical fiber is provided. An optical waveguide with a nominal dopand concentration of c(eff)×F?c(nom) in at least one cladding layer is also provided.

Abstract: Preform for an optical waveguide containing a core with a non-circular geometry and at least one cladding layer, in which the dopand concentration of the cladding layer is increased compared to the dopand concentration of a preform with circular core geometry and identical NA. A method for the production of a preform for an optical fiber is provided. An optical waveguide with a nominal dopand concentration of c(eff) x F?c(nom) in at least one cladding layer is also provided.

Abstract: A cardiac pacemaker has a pulse generator which emits stimulation pulses which are respectively separated by stimulation intervals and which collectively have an average duration. A modulation device alternatingly shortens and lengthens the stimulation intervals, without changing the average duration. An evaluation unit analyzes signals detected after each stimulation pulse and determines the electric restitution of the heart at the average stimulation interval duration on the basis of a measurement of the duration of the action potential. Changes in a measuring variable, associated with the duration of the action potential, caused by the modulation of the stimulation intervals is determined in a relationship to the average duration of the stimulation interval. This relationship is compared with at least one predetermined value, and the average duration of the stimulation interval is controlled on the basis of this comparison.

Abstract: The invention relates to a method for improving the quality of soldered connections between large-area SMD components and wiring carriers, in the case of which the parts to be joined are electrically and mechanically connected to one another by reflow soldering, a flux being used to activate the solder. The intention of the invention is to provide a method of improving the quality of soldered connections which is simple to realize and particularly effective and with which the number of voids can be drastically reduced. According to the invention, this is achieved by the parts to be joined being positioned one over the other and connected to each other by forming a force of adhesion and by the parts to be joined being arranged in such a way that they are tilted at a predetermined tilting angle with respect to the normal plane, at least during the melting of the solder paste. The tilting angle during the melting should lie between greater than 0° and less than 180° and preferably be about 90°.

Abstract: The invention relates to a method for improving the quality of soldered connections between large-area SMD components and wiring carriers, in the case of which the parts to be joined are electrically and mechanically connected to one another by reflow soldering, a flux being used to activate the solder. The intention of the invention is to provide a method of improving the quality of soldered connections which is simple to realize and particularly effective and with which the number of voids can be drastically reduced. According to the invention, this is achieved by the parts to be joined being positioned one over the other and connected to each other by forming a force of adhesion and by the parts to be joined being arranged in such a way that they are tilted at a predetermined tilting angle with respect to the normal plane, at least during the melting of the solder paste. The tilting angle during the melting should lie between greater than 0° and less than 180° and preferably be about 90°.

Abstract: In a method and apparatus for operating an implantable cardiac pacemaker, the stimulation rate is modulated, while a patient in whom the pacemaker is implanted is experiencing a number of different levels of physical stress, and a number of signal sequences corresponding to a non-mechanical physiological characteristic are obtained, one sequence being obtained for each physical stress level. These signal sequences form a reference field, which is stored in the pacemaker. A current signal sequence of the non-mechanical physiological characteristic is subsequently obtained, and this signal sequence is compared to all of the signal sequences in the stored reference field, and one of the reference field signal sequences having the highest correlation with the current signal sequence is selected. The stimulation rate is then set at a rate equal to the basic stimulation rate for the modulation which produced the highest correlating sequence in the reference field.

Abstract: A pressure and heart movement sensor for a heart stimulator, includes an electrode system for implantation with an electrode cable containing at least two electrical conductors leading to electrode poles. A measurement device is arranged to measure an electrical quantity between the electrical conductors, which quantity varying according to the pressure applied to the electrode cable. Alternately, the electrode cable contains at least one electrical conductor, and the measurement device is arranged to measure the impedance between the conductor and ambient medium and to deliver an output signal, which varies according to the impedance measured, when the electrode cable is subjected to pressure.

Abstract: An arrangement, in particular a heart pacemaker, has a measuring device for recording a heart activity measurement parameter. In order to record the measurement parameter in such a way that it is rid of disturbing signals, and can thus be used to evaluate the physiological functions of the heart pacemaker, the arrangement contains switching means which evaluate the signal curve of a measurement parameter during a heart cycle (n+1) as a function of the frequency (f) or duration (t.sub.S) of the previous heart cycle (n).

Abstract: An electrode arrangement for a cardiac defibrillator includes one or more physiological sensors disposed in an electrode carrier for planar application against the exterior of the heart. The sensor contained in the electrode carrier is connected to a housing, containing a defibrillation power source and signal processing circuitry, via a sensor line, and the electrical signals obtained from the sensor are used for controlling operation of the defibrillator.

Abstract: During optimization intervals prescribed by the heart pacemaker, the stimulation frequency is periodically changed and an acquisition of a measured value that is dependent on the cardiac minute output is respectively phase-synchronized with the change in stimulation frequency. An identification is thereby made whether the measured value that is dependent on the cardiac minute output changes given the change of the stimulation frequency. A number of curves are stored representing different relationships between a regulating variable, derived from the measured value, and the stimulation frequency. The stimulation frequency of the pacemaker is set based on one of these curves, as selected by an optimization controller to which the regulating variable is supplied.

Abstract: A rate-responsive pacing method and system senses the minimum blood oxygen saturation in the right atrium of a patient's heart and uses such minimum blood oxygen saturation as a control parameter for indicating the muscular activity of a patient. Because the oxygen content of the venous blood in the right atrium varies significantly as venous blood from all parts of the body is introduced therein, evidencing differing levels of oxygen demand throughout the patient's body, the minimum oxygen content of the venous blood provides an accurate and reliable measure of those portions of the patient's body experiencing the greatest oxygen demand, i.e., experiencing muscular activity. A rate-responsive pacing system includes means for sensing the minimum oxygen content in the right atrium over a prescribed time interval, and using such minimum oxygen content as a control parameter for adjusting the rate of the pacemaker.

Abstract: A catheter of the type suitable for implantation in a human heart has a catheter tip and a preset curvature spaced along the catheter a distance from the tip. The catheter includes an integrated measuring probe with a measurement window, the measuring probe and window being disposed between the tip and the preset curvature at respective distances from each so that, given the aforementioned location of the catheter tip, it is insured that the measurement window of the probe will not lie against a wall of the heart, which would degrade the operation of the measuring probe, and moreover insures that the measuring probe and measurement window will be disposed at an optimum location for undertaking the desired measurement.

Abstract: A sensor arrangement for controlling an implantable device, such as a heart pacemaker, has a number of individual sensors connected to an evaluation circuit through a catheter having at least two leads. The sensors are respectively activated in chronological succession by a shared control circuit, with both the sensors and the control circuit being arranged in the catheter. The corresponding measured signals are transmitted via the same leads, and also being offset chronologically. The arrangement permits a number of sensors to be connected to a catheter while maintaining only two lines in the catheter, so that the flexibility and reliability of the catheter, which are best with the fewest possible leads, remain unimpaired.

Abstract: An implantable arrangement for operating a body-assist device, the body-assist device including circuitry for generating electrical signals and also being implanted in a patient, includes circuitry for controlling the generation of the electric signals, a measuring probe in the patient for obtaining signals to be used by the control circuitry, a single current conductor electrically connecting the control circuitry and the measuring probe and forming a first current path therebetween, and spaced electrodes connected to the measuring probe and the control circuitry disposed in the patient with body tissue therebetween such that a second current path is formed in the body tissue.

Abstract: A follower control matches the stimulation frequency of a heart pacemaker to patient load condition by obtaining measurement values S.sub.02 corresponding to the central venous blood oxygen saturation in the heart according to the principle of reflection oximetry, by forming control values B.sub.S1 according to the quotient .DELTA.S.sub.02 /.DELTA.S.sub.02max where the numerator is the difference between the current measurement value and a stored reference value (e.g. S.sub.02max or S.sub.02min) and the denominator serves to standardize the control value based on the maximum change of the measurement value over a relatively long time interval, and by changing the stimulation frequency by an amount dependent on the magnitude of the control value. Preferably, the stimulation frequency f.sub.p is set directly as a function of the control value B.sub.S1 and most preferably according to the function ##EQU1## where f.sub.min is a prescribed minimum frequency, .DELTA.f.sub.max is the maximum frequency difference, c.

Abstract: A measuring instrument for obtaining an intracardial signal indicative of blood oxygen saturation, which may be used to control the stimulation frequency of a heart pacemaker, has a measuring probe which contains a light transmitter and a light receiver. The light receiver receives light from the light transmitter reflected by the blood. The light transmitter and the light receiver are connected in parallel to an evaluation circuit via two leads. A constant current source is connected in series with the light transmitter. The current generated by the light receiver, indicative of blood oxygen saturation, can be identified by forming the difference between current flowing in the measuring probe and the constant current. A reference measurement to compensate for factors in the total current resulting from the lead resistances and the measuring probe temperature is not necessary.

Abstract: An apparatus for impedance measurement of body tissue has a signal source which impresses an electrical signal in body tissue, circuitry for acquiring an impedance signal from the body tissue dependent on the impressed electrical signal, and an evaluation stage for evaluating the impedance signal by filtering higher frequency components and low frequency components from the impedance signal which correspond to the conductance of the tissue. A correction stage corrects the high frequency signal components with the low frequency signal components by eliminating the higher frequency signal components of influences due to changes in the tissue conductance. The corrected signal is supplied at an output of the correction stage.

Abstract: A measuring instrument for the intracardial acquistion of the blood oxygen saturation of a patient for use in controlling a heart pacemaker implanted in the patient has a measuring probe with a measuring current path which includes a light transmitter and a light receiver which receives light emitted by the light transmitter and reflected by the blood. The measuring probe is connected to an evaluation circuit via two lines. A useful signal measurement and a reference measurement, independent of the blood reflection, are made and the blood oxygen saturation is identified by comparing the two signals. A separate evaluation of the useful signal measurement and the reference signal measurement is enabled by making the useful signal measurement chronologically offset with respect to the reference measurement in one embodiment, or by using the amplitude of the current from the light receiver to make one measurement, and using the voltage amplitude to make the other measurement in another embodiment.

Abstract: An apparatus for measuring the impedance of body tissue has a signal source connected to the tissue to be measured which supplies an electrical signal to the tissue, a unit for acquiring an impedance signal from the body tissue dependent on the electrical signal, and an evaluation stage for the impedance signal. The evaluation stage filters out low frequency signal components corresponding to the conductance of the tissue, and has a signal output to which the signal components which were filtered out are supplied.

Abstract: The stimulation frequency of a heart pacemaker is controlled dependent on a signal representative of the blood oxygen content of the patient. The blood oxygen dependent signal is generated by a blood oxygen sensor. A temperature sensor generates a separate signal dependent on blood temperature. The blood oxygen and blood temperature signals are combined such that the blood oxygen signal is lowered, i.e., the value thereof is reduced, in ranges of higher physical load indicated by an increase in the temperature dependent signal. The combined signal is used to control the stimulation frequency of a heart pacemaker so that the stimulation frequency is increased, if blood oxygen saturation is decreasing and/or blood temperature is increasing.