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Biomedical subjects

S Eggert

Publications and source records attributed to S Eggert.

At least 19 recordsLinked to original sources
PubMed2006

[Effects of electromagnetic fields emitted by cellular phone on auditory and vestibular labyrinth].

BACKGROUND: It is the subject of this study to investigate the biological effect of the HF radiation produced by the Global System for Mobile Communications-( GSM)-mobile phone on the inner ear with its sensors of the vestibular and auditive systems. METHODS/PATIENTS: Thermographic investigations made on various model materials and on the human temporal bone should show whether mobile phone does induce any increases of temperature which would lead to a relevant stimulus for the auditive and vestibular system or not. We carried out video-nystagmographic recordings of 13 subjects, brainstem electric response audiometry of 24 ears, and recordings of distorsion products of otoacoustic emissions of 20 ears. All tests were made with and without a mobile phone in use. The data was then analyzed for variation patterns in the functional parameters of the hearing and balance system that are subject to the (non)existence of electromagnetic radiation from the mobile phone. RESULTS: The thermographic investigations suggest that the mobile phone does not induce any increases of temperature which would lead to a relevant stimulus for the auditive and vestibular system. Video-nystagmographic recordings under field effect do not furnish any indication of vestibular reactions generated by field effects. Compared with the recording without field, the brainstem electric response audiometry under field effect did not reveal any changes of the parameters investigated, i. e. absolute latency of the peaks I, III, V and the interpeak latency between the peaks I and V. The distorsion products of otoacoustic emissions do not indicate, comparing the three measuring situations, i. e. before field effect, pulsed field and continuous field, any possible impacts of the HF field on the spectrum or levels of emissions for none of the probands. CONCLUSION: The investigations made show that the electromagnetic fields generated in using the mobile phone do not have an effect on the inner ear and auditive system to the colliculus inferior in the brainstem and on the vestibular receptors in the inner ear and the vestibular system.

Adult↗
PubMed2004

Real space imaging of one-dimensional standing waves: direct evidence for a Luttinger liquid.

Electronic standing waves with two different wavelengths were directly mapped near one end of a single-wall carbon nanotube as a function of the tip position and the sample bias voltage with high-resolution position-resolved scanning tunneling spectroscopy. The observed two standing waves caused by separate spin and charge bosonic excitations are found to constitute direct evidence for a Luttinger liquid. The increased group velocity of the charge excitation, the power-law decay of their amplitudes away from the scattering boundary, and the suppression of the density of states near the Fermi level were also directly observed or calculated from the two different standing waves.

Journal Article↗
PubMed2003

Local magnetic susceptibility of the positive muon in the quasi-one-dimensional S=1/2 antiferromagnet dichlorobis (pyridine) copper (II).

We report muon spin rotation measurements of the local magnetic susceptibility around a positive muon in the paramagnetic state of the quasi-one-dimensional spin 1/2 antiferromagnet dichlorobis (pyridine) copper (II). Signals from three distinct sites are resolved and have a temperature dependent frequency shift which is significantly different than the magnetic susceptibility. This difference is attributed to a muon induced perturbation of the spin 1/2 chain. The obtained frequency shifts are compared with transfer matrix density-matrix renormalization-group numerical simulations.

Journal Article↗
PubMed2002

Active medical implants and occupational safety--measurement and numerical calculation of interference voltage.

Low frequency electric and magnetic fields may interfere with implanted cardiac pacemakers causing a life-threatening malfunction of the device. In order to assess the safety of workers in the vicinity of industrial electrical devices the interference voltage at the input port of a pacemaker is an important measure. In order to investigate the coupling of fields emanating from electrical devices a numerical method for the calculation of interference voltages is presented and applied to the investigation of homogeneous electric and magnetic fields in the frequency range from 50 Hz to 1 MHz. Implantation of the pacemaker in the right pectoral, left pectoral and abdominal area using a realistic model of the human body as well as different grounding conditions are considered. The numerical method is successfully validated by measurements and shows good agreement with results in the literature.

Computer Simulation↗
PubMed2001

Phase diagram of an impurity in the spin-1/2 chain: two-channel Kondo effect versus Curie law.

We consider a magnetic S = 1/2 impurity in the antiferromagnetic spin chain as a function of two coupling parameters: the symmetric coupling of the impurity to two sites in the chain J1 and the coupling between the two sites J2. By using field theory arguments and numerical calculations we can identify all possible fixed points and classify the renormalization flow between them, which leads to a nontrivial phase diagram. Depending on the detailed choice of the two (frustrating) coupling strengths, the stable phases correspond either to a decoupled spin with Curie law behavior or to a non-Fermi-liquid fixed point with a logarithmically diverging impurity susceptibility as in the two-channel Kondo effect. Our results resolve a controversy about the renormalization flow.

Journal Article↗
PubMed2000

Scanning tunneling microscopy of a luttinger liquid

Explicit predictions for scanning tunneling microscopy (STM) on interacting one-dimensional electron systems are made using the Luttinger liquid formalism. The STM current changes with the distance from an impurity or boundary in a characteristic way, which reveals the spin-charge separation and the interaction strength in the system. The current exhibits Friedel-like oscillations, but also carries additional modulated behavior as a function of voltage and distance, which shows the spin-charge separation in real space. Moreover, very close to the boundary the current is strongly reduced, which is an indication of the interaction strength in the system.

Journal Article↗
PubMed2000

Microwaves emitted by cellular telephones affect human slow brain potentials.

The influence of electromagnetic fields (EMF) emitted by cellular telephones on preparatory slow brain potentials (SP) was studied in two experiments, about 6 months apart. In the first experiment, a significant decrease of SP was found during exposure to EMF in a complex visual monitoring task (VMT). This effect was replicated in the second experiment. In addition to the VMT, EMF effects on SP were analysed in two further, less demanding tasks: in a simple finger movement task to elicit a Bereitschaftspotential (BP) and in a two-stimulus task to elicit a contingent negative variation (CNV). In comparison to the VMT, no significant main EMF effects were found in BP and CNV tasks. The results accounted for a selective EMF effect on particular aspects of human information processing, but did not indicate any influence on human performance, well-being and health.

Adult↗
PubMed1998

Effects of microwaves emitted by cellular phones on human slow brain potentials.

The influence of electromagnetic fields (EMF) emitted by cellular phones on preparatory slow brain potentials (SP) was studied in two different experimental tasks: In the first, healthy male human subjects had to perform simple self-paced finger movements to elicit a Bereitschaftspotential; in the second, they performed a complex and cognitive demanding visual monitoring task (VMT). Both tasks were performed with and without EMF exposure in counterbalanced order. Whereas subjects' performance did not differ between the EMF exposure conditions, SP parameters were influenced by EMF in the VMT: EMF exposure effected a significant decrease of SPs at central and temporo-parieto-occipital brain regions, but not at the frontal one. In the simple finger movement task, EMF did not affect the Bereitschaftspotential.

Brain↗
PubMed1994

Prevalence of latent and manifest suprascapular neuropathy in high-performance volleyball players.

The aim of the present study was to evaluate the prevalence of latent and manifest suprascapular neuropathy in high-level male volleyball players. Thirty subjects were examined clinically and electrophysiologically. Suprascapular neuropathy, most probably at the level of the suprascapular notch, was demonstrated in 12 subjects, being latent in eight. Taking into account our clinical findings in a further 36 international-level players, a remarkably high overall prevalence of suprascapular nerve lesion of 33% (22 of 66 subjects) was found. All cases involved the side of the body with the player's smashing arm. These findings suggest that careful monitoring of suprascapular nerve function may be useful in high-performance volleyball players, as early diagnosis is essential to prevent more severe damage.

Athletic Injuries↗
PubMed1993

[Compression neuropathy of the suprascapular nerve in high performance volleyball players].

Individual observations during the course of the medical care of the German men's national volleyball team in international tournaments gave cause to investigate more thoroughly the increasing occurrence of an atrophy of the infraspinatus m. in volleyball players at international level. An examination of three men's national teams specially slanted to throw light on this problem revealed that 28% (10 out of 36 players) had an atrophy of the infraspinatus m. On the basis of these findings, a prospective study was carried out, with the object of clarifying to what extent a developing or manifest compression neuropathy of the suprascapularis n. was present in a defined population of high-level volleyball players (1st National League, men). 32 players were examined as to the extent to which a functional impairment of the suprascapularis n. occurred in the pursuit of the competitive sport of volleyball. The study revealed a functional impairment of the suprascapular n. in 45% of the both clinically and neurophysiologically examined sportsmen. It follows in consequence that a control examination is advisable in the case of a latent disorder, so as to detect any continuation or possible deterioration. In the event of a developing or manifest atrophy of the infraspinatus m. the operative relief of the suprascapular n. in the region of the scapular incisure may be considered in addition to conservative therapy.

Adult↗
PubMed1992

Influence of clinical findings, positional manoeuvres, and systolic ankle arterial pressure on transcutaneous oxygen tension in peripheral arterial occlusive disease.

The mutual effects of systolic ankle arterial pressures, positional manoeuvres, and calf artery occlusions on transcutaneous oxygen partial pressures (tcpO2) were studied in 388 legs of 258 patients with peripheral arterial occlusive disease (PAOD). The tcpO2-vs-perfusion pressure relationship could be satisfactorily fitted by a non-linear regression model deduced from the tcpO2 theory. Flow-insensitive ranges of tcpO2-vs-flow hyperbolas were reduced by both leg lowering and moving the electrode towards proximal measuring sites. Lower tcpO2 values were found in case of occluded compared to patent calf arteries at ankle arterial pressure indices below 0.4. The tcpO2 positional variability increased with worsening hemodynamic compensation and was most pronounced in critical limb ischaemia (ischaemic rest pain, non-healing ulcerations). According to a retrospective analysis, a critical ischaemia could be assumed if supine and sitting tcpO2-values exceed neither 10 nor 45 mmHg, respectively.

Adult↗