Performance analysis of an optically pumped magnetometer in Earth’s magnetic field

We experimentally investigate the influence of the orientation of optically pumped magnetometers in Earth’s magnetic field. We focus our analysis to an operational mode that promises femtotesla field resolutions at such field strengths. For this so-called light-shift dispersed Mz (LSD-Mz) regime, we focus on the key parameters defining its performance. That are the reconstructed Larmor frequency, the transfer function between output signal and magnetic field amplitude as well as the shot noise limited field resolution. We demonstrate that due to the use of two well balanced laser beams for optical pumping with different helicities the heading error as well as the field sensitivity of a detector both are only weakly influenced by the heading in a large orientation angle range

An optically pumped magnetometer working in the light-shift dispersed Mz mode

We present an optically pumped magnetometer working in a new operational mode— the light-shift dispersed Mz (LSD-Mz) mode. It is realized combining various features; (1) high power off-resonant optical pumping; (2) Mz configuration, where pumping light and magnetic field of interest are oriented parallel to each other; (3) use of small alkali metal vapor cells of identical properties in integrated array structures, where two such cells are pumped by circularly polarized light of opposite helicity; and (4) subtraction of the Mz signals of these two cells. The LSD-Mz magnetometer’s performance depends on the inherent and very complex interplay of input parameters. In order to find the configuration of optimal magnetometer resolution, a sensitivity analysis of the input parameters by means of Latin Hypercube Sampling was carried out. The resulting datasets of the multi-dimensional parameter space exploration were assessed by a subsequent physically reasonable interpretation. Finally, the best shot-noise limited magnetic field resolution was determined within that parameter space. As the result, using two 50 mm3 integrated vapor cells a magnetic field resolution below 10 fT/√Hz at Earth’s magnetic field strength is possible

Suppression of spin-exchange relaxation in tilted magnetic fields within the geophysical range

We present a detailed experimental and theoretical study on the relaxation of spin coherence due to the spin-exchange mechanism arising in the electronic ground states of alkali-metal vapor atoms. As opposed to the well-explored formation of a stretched state in a longitudinal geometry (magnetic field parallel to the laser propagation direction) we employ adapted hyperfine-selective optical pumping in order to suppress spin-exchange relaxation. By comparing measurements of the intrinsic relaxation rate of the spin coherence in the ground state of cesium atoms with detailed density-matrix simulations we show that the relaxation due to spin-exchange collisions can be reduced substantially even in a tilted magnetic field of geomagnetic strength, the major application case of scalar magnetic surveying. This explains the observed striking improvement in sensitivity and further deepens the understanding of the light- narrowed Mx magnetometer, which was presented recently. Additionally, new avenues for investigating the dynamics in alkali-metal atoms governed by the spin-exchange interaction and interacting with arbitrary external fields open up

OPM magnetorelaxometry in the presence of a DC bias field

Spatial quantitative information about magnetic nanoparticle (MNP) distributions is a prerequisite for biomedical applications like magnetic hyperthermia and magnetic drug targeting. This information can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation of previously aligned MNP’s magnetic moments is measured by sensitive magnetometers and an inverse problem is solved. To remove or minimize the magnetic shielding in which MRX imaging is carried out today, the knowledge of the influence of background magnetic fields on the MNP’s relaxation is a prerequisite. We show MRX measurements using an intensity-modulated optically pumped magnetometer (OPM) in background magnetic fields of up to 100μT. We show that the relaxation parameters alter or may be intentionally altered significantly by applying static fields parallel or antiparallel to the MNP’s alignment direction. Further, not only the relaxation process of the MNP’s magnetic moments could be measured with OPM, but also their alignment due to the MRX excitation field. © 2020, The Author(s)

A fatal case of spinal tuberculosis mistaken for metastatic lung cancer: recalling ancient Pott's disease

<p>Abstract</p> <p>Background</p> <p>Tuberculous spondylitis (Pott's disease) is an ancient human disease. Because it is rare in high-income, tuberculosis (TB) low incidence countries, misdiagnoses occur as sufficient clinical experience is lacking.</p> <p>Case presentation</p> <p>We describe a fatal case of a patient with spinal TB, who was mistakenly irradiated for suspected metastatic lung cancer of the spine in the presence of a solitary pulmonary nodule of the left upper lobe. Subsequently, the patient progressed to central nervous system TB, and finally, disseminated TB before the accurate diagnosis was established. Isolation and antimycobacterial chemotherapy were initiated after an in-hospital course of approximately three months including numerous health care related contacts and procedures.</p> <p>Conclusion</p> <p>The rapid diagnosis of spinal TB demands a high index of suspicion and expertise regarding the appropriate diagnostic procedures. Due to the devastating consequences of a missed diagnosis, Mycobacterium tuberculosis should be considered early in every case of spondylitis, intraspinal or paravertebral abscess. The presence of certain alarm signals like a prolonged history of progressive back pain, constitutional symptoms or pulmonary nodules on a chest radiograph, particularly in the upper lobes, may guide the clinical suspicion.</p

Localisation of buried ferromagnetic objects based on minimum-norm-estimations: a simulation study

Purpose – The purpose of this paper is to examine the localisation of ferromagnetic objects buried in the underground. More specifically, it deals with the reconstruction of the XY-positions, the depths (Z-positions), the number, and the extension of the objects based on geomagnetic measurements. This paper introduces a minimum-norm reconstruction approach and evaluates its performance in a simulation study. Design/methodology/approach – Aminimum-L2-norm estimation based on the truncated singular value decomposition method with lead field weighting is proposed in order to localise geomagnetic sources. The sensor setup and positions are taken from real measurements. The source space is formed by an automatically generated grid. At each grid point, a magneto-static dipole is assumed. Findings – Sources with different depths and XY-positions could be successfully reconstructed. The proposed approach is not overly sensitive to errors/noise in measurement values and sensor positions. Originality/value – The approach described in this paper can be used for applications like geoprospection, archaeology, mine clearing, and the clean-up of former waste deposits

Del DSM-IV-TR al DSM-5: análisis de algunos cambios

La publicación de la quinta edición del DSM ha avivado un debate iniciado tiempo atrás, desde el anuncio de los cambios en los criterios de diagnóstico propuestos por la APA. En este artículo se analizan algunas de estas modificaciones. Se plantean aspectos interesantes y acertados, como la inclusión de la dimensionalidad tanto en las clases diagnósticas como en algunos trastornos, la incorporación de un espectro obsesivo-compulsivo o la desaparición de los subtipos de esquizofrenia. También se analizan otros aspectos más controvertidos como la consideración del síndrome de psicosis atenuada, la descripción de un trastorno depresivo persistente, la reordenación en trastornos de síntomas somáticos los clásicos trastornos somatoformes, o el mantenimiento de los tres grandes grupos de trastornos de la personalidad,siempre insatisfactorios, junto con un planteamiento anunciado, pero marginal, de la perspec-tiva dimensional de las alteraciones de la personalidad. La nueva clasificación del DSM-5 abrenumerosos interrogantes acerca de la validez que se pretende mejorar en el diagnóstico, enesta ocasión, asumiendo un planteamiento más cercano a la neurología y la genética que a lapsicopatología clínica.The publication of the fifth edition of the DSM has intensified a debate begun some time agowith the announcement of the changes in diagnostic criteria proposed by the APA. This article analyzes some of these modifications. Some interesting points where it is right, such as the inclusion of dimensionality in both diagnostic classes and in some disorders, the inclusion of an obsessive-compulsive spectrum, and the disappearance of subtypes of schizophrenia. It also analyzes other more controversial points, such as the consideration of the attenuated psychosis syndrome, the description of a persistent depressive disorder, reorganization of the classic somatoform disorders as somatic symptom disorders, or maintenance of three large clusters of personality disorders, always unsatisfactory, along with an announced, but marginal, suggestion of the dimensional perspective of personality impairments. The new DSM-5 classification opens many questions about the diagnostic validity which it attempts to improve, this time taking an approach nearer to neurology and genetics than to clinical psychology

An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode

We present an optically pumped magnetometer working in a new operational mode—the light-shift dispersed Mz (LSD-Mz) mode. It is realized combining various features; (1) high power off-resonant optical pumping; (2) Mz configuration, where pumping light and magnetic field of interest are oriented parallel to each other; (3) use of small alkali metal vapor cells of identical properties in integrated array structures, where two such cells are pumped by circularly polarized light of opposite helicity; and (4) subtraction of the Mz signals of these two cells. The LSD-Mz magnetometer’s performance depends on the inherent and very complex interplay of input parameters. In order to find the configuration of optimal magnetometer resolution, a sensitivity analysis of the input parameters by means of Latin Hypercube Sampling was carried out. The resulting datasets of the multi-dimensional parameter space exploration were assessed by a subsequent physically reasonable interpretation. Finally, the best shot-noise limited magnetic field resolution was determined within that parameter space. As the result, using two 50 mm3 integrated vapor cells a magnetic field resolution below 10 fT/√Hz at Earth’s magnetic field strength is possible