Martin Burghoff - Academia.edu (original) (raw)

Papers by Martin Burghoff

arXiv (Cornell University), Jun 26, 2019

The feasibility of using ultra-low-field magnetic resonance (ULF MR) for direct neuronal current ... more The feasibility of using ultra-low-field magnetic resonance (ULF MR) for direct neuronal current imaging (NCI) is investigated by phantom measurements. The aim of NCI is to improve the current localization accuracy for neuronal activity of established methods like electroencephalography (EEG) or magnetoencephalography (MEG) (~1 cm). A measurement setup was developed addressing the main challenge of reaching the necessary sensitivity in order to possibly resolve the faint influence of neuronal magnetic fields on 1 H nuclear spin precession. Phantom measurements close to physiology conditions are performed simulating a specific long-lasting neuronal activity evoked in the secondary somatosensory cortex showing that the signal-to-noise ratio (SNR) of the setup needs to be further increased by at least a factor of 2.

2018 Conference on Precision Electromagnetic Measurements (CPEM 2018), 2018

A novel technique to extract the quotient of gyromagnetic ratios in a comagnetometer system is pr... more A novel technique to extract the quotient of gyromagnetic ratios in a comagnetometer system is presented. This technique aims to probe the quotient in a regime which is free from the spin-relaxation related systematic effects. It is based on the measurement of spin precession frequencies in a gaseous mixture of 129Xe and3He at ultralow magnetic field. The resultant quotient value appears to be close to the literature value.

Otto J, Migas K, Järvinen H, Burghoff M. Interkulturelle Kompetenz von Lehrkräften. Mythos, Trend... more Otto J, Migas K, Järvinen H, Burghoff M. Interkulturelle Kompetenz von Lehrkräften. Mythos, Trend oder pädagogische Notwendigkeit? In: McElvany N, Bos W, Holtappels HG, Jungermann A, eds. Ankommen in der Schule. Chancen und Herausforderungen bei der Integration von Kindern und Jugendlichen mit Fluchterfahrung. Münster: Waxmann; 2017: 69-85

Klinische Neurophysiologie, 2004

Superconductor Science and Technology, 2016

Globally, the demand for improved health care delivery while managing escalating costs is a major... more Globally, the demand for improved health care delivery while managing escalating costs is a major challenge. Measuring the biomagnetic fields that emanate from the human brain already impacts the treatment of epilepsy, brain tumours and other brain disorders. This roadmap explores how superconducting technologies are poised to impact health care. Biomagnetism is the study of magnetic fields of biological origin. Biomagnetic fields are typically very weak, often in the femtotesla range, making their measurement challenging. The earliest in vivo human measurements were made with room-temperature coils. In 1963, Baule and McFee (1963 Am. Heart J. 55 95−6) reported the magnetic field produced by electric currents in the heart ('magnetocardiography'), and in 1968, Cohen (1968 Science 161 784−6) described the magnetic field generated by alpha-rhythm currents in the brain ('magnetoencephalography').

Advances in Biomagnetism, 1989

High resolution magnetocardiography (HR MCG) is a new and promising method of studying heart acti... more High resolution magnetocardiography (HR MCG) is a new and promising method of studying heart activity. One of the most interesting clinical applications of HR MCG is the localization of pathological cardiac sources which has often been demonstrated (Erne, 1985, Fenici et al., 1985, Katila et al., 1987). For the localization appropriate source and thorax models are needed.

Journal of Clinical Engineering, 1997

Magnetic fields over the lower back generated by electric action currents in stimulated leg nerve... more Magnetic fields over the lower back generated by electric action currents in stimulated leg nerves were recorded inside a magnetically shielded room with a multichannel dc-SQUID system. Spatio-temporal field maps show the propagation of these action currents along the nerves. The proposed analysis of the nerve magnetic fields is based on the multipole expansion and takes into account that activated nerve segments are linearly extended field sources. This source analysis allows the estimation of characteristic source parameters, such as depth below the body surface, spatial extent, and current strength.

Physics Letters B, 2015

We report a new limit on a possible short range spin-dependent interaction from the precise measu... more We report a new limit on a possible short range spin-dependent interaction from the precise measurement of the ratio of Larmor precession frequencies of stored ultracold neutrons and 199 Hg atoms confined in the same volume. The measurement was performed in a ∼1 µT vertical magnetic holding field with the apparatus searching for a permanent electric dipole moment of the neutron at the Paul Scherrer Institute. A possible coupling between freely precessing polarized neutron spins and unpolarized nucleons of the wall material can be investigated by searching for a tiny change of the precession frequencies of neutron and mercury spins. Such a frequency change can be interpreted as a consequence of a short range spin-dependent interaction that could possibly be mediated by axions or axion-like particles. The interaction strength is proportional to the CP violating product of scalar and pseudoscalar coupling constants g S g P. Our result confirms limits from complementary experiments with spin-polarized nuclei in a model-independent way. Limits from other neutron experiments are improved by up to two orders of magnitude in the interaction range of 10 −6 < λ < 10 −4 m.

Physics of Particles and Nuclei, 2013

Polarization of 3 He gas by means of optical pumping is well known since the early 1960s witȟ rst... more Polarization of 3 He gas by means of optical pumping is well known since the early 1960s witȟ rst applications in fundamental physics. Some thirty years later it was discovered that one can use hyperpolarized 3 He as contrast agent for magnetic resonance imaging of the lung. The wide interest in this new method made it necessary toˇnd ways of polarizing 3 He in large quantities with high polarization degrees. A high performance polarizing facility has been developed at the University of Mainz, designed for centralized production of hyperpolarized 3 He gas. We present the Mainz concept as well as some examples of numerous applications of spin polarized 3 He in fundamental research and medical applications.

The knowledge of the temporal relation between neuronal activity and the accompanying changes in ... more The knowledge of the temporal relation between neuronal activity and the accompanying changes in the vascular system of the brain may foster a better understanding of fMRI. We have devised a triple-modality measurement setup comprising broadband DC-magnetoencephalography (DC-MEG), time-resolved near-infrared spectroscopy (trNIRS) and peripheral physiological signal monitoring. The neuronal activity was measured using a broadband DC-MEG with a temporal resolution on the scale of tens of ms. In order to obtain trNIRS signals reflecting cortical vascular processes the variance was derived for the distributions of time-of-flight of photons. Confounding physiological signals such as heart beat, respiration, and electromyographical activity (EMG) were recorded simultaneously. The subjects had to repeat a sequence of 30 s of finger movement followed by 30s of rest motivating the EMG. Independent component analysis (ICA) was applied separately to the DC-MEG and the trNIRS data for preproces...

Klinische Neurophysiologie, 2012

Springer Proceedings in Physics, 2012

The detection of neuronal currents (NC) may foster the understanding of the flow of information i... more The detection of neuronal currents (NC) may foster the understanding of the flow of information in the brain. Existing methods of NC detection like electro- and magnetoencephalography (EEG/MEG) are limited by the ambiguity of the inverse problem, while imaging methods like fMRI monitor secondary effects (e.g., blood oxygenation changes). On the other hand, attempts to directly detect NC in high field NMR techniques by a local shift of the 1H resonance frequency have yielded controversial results. In magnetic fields around 1 microTesla, the relative contribution of the biomagnetic field generated by neuronal currents is orders of magnitude higher than in conventional high fields. This may make the situation much more favourable.

Physics Letters B, 2014

The neutron gyromagnetic ratio has been measured relative to that of the 199 Hg atom with an unce... more The neutron gyromagnetic ratio has been measured relative to that of the 199 Hg atom with an uncertainty of 0.8 ppm. We employed an apparatus where ultracold neutrons and mercury atoms are stored in the same volume and report the result γ n /γ Hg = 3.8424574(30).

Physics Procedia, 2011

The measurement of the neutron electric dipole moment (nEDM) constrains the contribution of CP-vi... more The measurement of the neutron electric dipole moment (nEDM) constrains the contribution of CP-violating terms within both the Standard Model and its extensions. The experiment uses ultracold neutrons (UCN) stored in vacuum at room temperature. This technique provided the last (and best) limit by the RAL/Sussex/ILL collaboration in 2006: d n < 2.9 × 10 −26 e cm (90% C.L.). We aim to improve the experimental sensitivity by a factor of 5 within 2-3 years, using an upgrade of the same apparatus. We will take advantage of the increased ultracold neutron density at the Paul Scherrer Institute (PSI) and of a new concept including both, external magnetometers and a cohabiting magnetometer. In parallel, a next generation apparatus with two UCN storage chambers and an elaborate magnetic field control is being designed aiming to achieve another order of magnitude increase in sensitivity, allowing us to put a limit as tight as d n < 5 × 10 −28 e cm (95% C.L.), if not establishing a finite value.

Biomedical Engineering / Biomedizinische Technik, 2012

Magnetoencephalography, 2014

Neuronal current imaging (NCI) aims at detecting the influence of neuronal magnetic fields on an ... more Neuronal current imaging (NCI) aims at detecting the influence of neuronal magnetic fields on an NMR signal which might be easier at ultralow fields (∼μT) than at high fields (∼T). In the so-called DC effect, long-lived neuronal activity shifts the Larmor frequency of the surrounding protons and changes the NMR line shape. An alternative strategy is to use fast neuronal activity as a tipping pulse. This so-called AC effect requires the proton Larmor frequency to match the frequency of the neuronal activity. Phantom studies validating both principal working mechanisms are described assessing the feasibility of NCI at ultralow fields. MRI on phantoms taken at Larmor frequencies of 100 and 731 Hz are also shown and discussed in an attempt to combine the AC effect and ULF MRI. These frequencies are examples of brain activity triggered by electrostimulation of the median nerve.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009

The existence of a mirror world holding a copy of our ordinary particle spectrum could lead to os... more The existence of a mirror world holding a copy of our ordinary particle spectrum could lead to oscillations between the neutron (n) and its mirror partner (n 0). Such oscillations could manifest themselves in storage experiments with ultracold neutrons whose storage lifetime would depend on the applied magnetic field. Here, extended details and measurements from the first dedicated experimental search for nn 0 oscillations published in [G.

Neuroscience Letters, 1997

Based on low-noise superconducting quantum interference devices (SQUIDs) magnetoencephalography a... more Based on low-noise superconducting quantum interference devices (SQUIDs) magnetoencephalography allows the noninvasive detection of low-amplitude high-frequency brain responses evoked about 20 ms after electric hand nerve stimulation. The main spectral energy of these brief oscillatory bursts (near 600 Hz) is in the range typical for rapidly repeated action potentials. Here, the magnetic fields of median and ulnar nerve evoked 600 Hz bursts are shown to exhibit a somatotopic arrangement at the primary somatosensory hand cortex closely resembling that of the concomitant postsynaptic primary cortical response ('N20m'). Two possible burst generators are discussed: (1) repetitive spike volleys conducted along the terminal segments of somatotopically arranged thalamocortical axons, and (2) early intracortical spike activity in nerve-specific subterritories of the 3b hand area.