Optical Magnetometer Array for Fetal Magnetocardiography

We describe an array of spin-exchange relaxation free optical magnetometers designed for detection of fetal magnetocardiography (fMCG) signals. The individual magnetometers are configured with a small volume with intense optical pumping, surrounded by a large pump-free region. Spin-polarized atoms that diffuse out of the optical pumping region precess in the ambient magnetic field and are detected by a probe laser. Four such magnetometers, at the corners of a 7 cm square, are configured for gradiometry by feeding back the output of one magnetometer to a field coil to null uniform magnetic field noise at frequencies up to 200 Hz. Using this array, we present the first measurements of fMCG signals using an atomic magnetometer

Management system for building materials as a basis for closed loop material flow analysis considering material efficiency and climate change mitigation

Resource management is becoming increasingly important in the construction sector. In order to support the recycling of materials, it is necessary to determine the quantities in the building stock and those caused by construction activities. At present, a large number of different actors use different categories for construction materials and the raw materials they consist of as well as for waste categories, depending on their field of activity. This results in imprecisions that make it difficult to consistently track and influence mass flows and hinder targeted resource management. This is the starting point of this paper as it discusses possibilities to establish a consistent allocation of materials to context-typical groups following the approach of continuous material flow analysis. On the input-side, aspects of mineral planning and on the output-side aspects of waste and secondary raw material management are being considered and references to grey emissions are established along the entire process chain. In this way, cross-departmental planning relating to recycling management and climate protection will be supported. With regard to the object of consideration and the level of action, a distinction is made between two different spatial scale levels: on the one hand, the individual building level, where the material inventory approach is used to provide detailed information on the building\u27s material composition, and on the other hand the regional level, for which more aggregated information on building material groups is provided in the form of material cadastres. Current results of a research project in Germany are presented

Taxonomic corpus-based concept summary generation for document annotation.

Semantic annotation is an enabling technology which links documents to concepts that unambiguously describe their content. Annotation improves access to document contents for both humans and software agents. However, the annotation process is a challenging task as annotators often have to select from thousands of potentially relevant concepts from controlled vocabularies. The best approaches to assist in this task rely on reusing the annotations of an annotated corpus. In the absence of a pre-annotated corpus, alternative approaches suffer due to insufficient descriptive texts for concepts in most vocabularies. In this paper, we propose an unsupervised method for recommending document annotations based on generating node descriptors from an external corpus. We exploit knowledge of the taxonomic structure of a thesaurus to ensure that effective descriptors (concept summaries) are generated for concepts. Our evaluation on recommending annotations show that the content that we generate effectively represents the concepts. Also, our approach outperforms those which rely on information from a thesaurus alone and is comparable with supervised approaches

Small-sized dichroic atomic vapor laser lock

Two, lightweight diode laser frequency stabilization systems designed for experiments in the field are described. A significant reduction in size and weight in both models supports the further miniaturization of measurement devices in the field. Similar to a previous design, magnetic-field lines are contained within a magnetic shield enclosing permanent magnets and a Rb cell, so that these DAVLL systems may be used for magnetically sensitive instruments. The Mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long), and does not require cell heaters. An even smaller Micro-DAVLL system (9mm long) uses a micro-fabricated cell (3 mm square), and requires heaters. These new systems show no degradation in performance with regard to previous designs, while considerably reducing dimensions.Comment: 13 pages, 11 figures, published versio

Bichromatic electromagnetically induced transparency in cold rubidium atoms

In a three-level atomic system coupled by two equal-amplitude laser fields with a frequency separation 2$\delta$, a weak probe field exhibits a multiple-peaked absorption spectrum with a constant peak separation $\delta$. The corresponding probe dispersion exhibits steep normal dispersion near the minimum absorption between the multiple absorption peaks, which leads to simultaneous slow group velocities for probe photons at multiple frequencies separated by $\delta$. We report an experimental study in such a bichromatically coupled three-level $\Lambda$ system in cold $^{87}$Rb atoms. The multiple-peaked probe absorption spectra under various experimental conditions have been observed and compared with the theoretical calculations.Comment: RevTex, 4 pages, 6 figures, Email address: [email protected]

An Improved Neutron Electric Dipole Moment Experiment

A new measurement of the neutron EDM, using Ramsey's method of separated oscillatory fields, is in preparation at the new high intensity source of ultra-cold neutrons (UCN) at the Paul Scherrer Institute, Villigen, Switzerland (PSI). The existence of a non-zero nEDM would violate both parity and time reversal symmetry and, given the CPT theorem, might lead to a discovery of new CP violating mechanisms. Already the current upper limit for the nEDM (|d_n|<2.9E-26 e.cm) constrains some extensions of the Standard Model. The new experiment aims at a two orders of magnitude reduction of the experimental uncertainty, to be achieved mainly by (1) the higher UCN flux provided by the new PSI source, (2) better magnetic field control with improved magnetometry and (3) a double chamber configuration with opposite electric field directions. The first stage of the experiment will use an upgrade of the RAL/Sussex/ILL group's apparatus (which has produced the current best result) moved from Institut Laue-Langevin to PSI. The final accuracy will be achieved in a further step with a new spectrometer, presently in the design phase.Comment: Flavor Physics & CP Violation Conference, Taipei, 200

High contrast D1_{1} line electromagnetically induced transparency in nanometric-thin rubidium vapor cell

Electromagnetically induced transparency (EIT) on atomic D$_{1}$ line of rubidium is studied using a nanometric-thin cell with atomic vapor column length in the range of L= 400 - 800 nm. It is shown that the reduction of the cell thickness by 4 orders as compared with an ordinary cm-size cell still allows to form an EIT resonance for $L= \lambda$ ($\lambda =794$ nm) with the contrast of up to 40%. Remarkable distinctions of EIT formation in nanometric-thin and ordinary cells are demonstrated. Despite the Dicke effect of strong spectral narrowing and increase of the absorption for $L=$ $\lambda /2$, EIT resonance is observed both in the absorption and the fluorescence spectra for relatively low intensity of the coupling laser. Well resolved splitting of the EIT resonance in moderate magnetic field for $L=$ $\lambda$ can be used for magnetometry with nanometric spatial resolution. The presented theoretical model well describes the observed results.Comment: Submitted to Applied Physics B: Lasers and Optics, 9 pages, 10 figure

Study animal models with altered lipid storage to identify mechanisms of lipid droplet regulation

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