Cavity-Controlled Collective Scattering at the Recoil Limit

We study collective scattering with Bose-Einstein condensates interacting with a high-finesse ring cavity. The condensate scatters the light of a transverse pump beam superradiantly into modes which, in contrast to previous experiments, are not determined by the geometrical shape of the condensate, but specified by a resonant cavity mode. Moreover, since the recoil-shifted frequency of the scattered light depends on the initial momentum of the scattered fraction of the condensate, we show that it is possible to employ the good resolution of the cavity as a filter selecting particular quantized momentum states.Comment: 4 pages, 4 figure

Entwicklung eines iterativen Rekonstruktionsalgorithmus mit Einbeziehung anatomischen Vorwissens für die 23Na-Magnetresonanztomographie

In dieser Arbeit wird ein iteratives Rekonstruktionsverfahren für die 23Na-MRT entwickelt. Neben einer totalen Variation zweiter Ordnung (TV2) wurden A-priori-Informationen aus der 1H-MRT in Form einer Trägerregion (BM) und als anatomisch gewichtete TV2 (AnaWeTV) eingebunden. Anhand simulierter Kopfdaten und In-vivo-Messungen wurde das Leistungsvermögen des Algorithmus bei verschiedenen Auflösungen, Unterabtastungen (UAF) und Rauschpegeln analysiert. In allen Bildern wurden Gibbs-Oszillationen und Unterabtastungsartefakte wirkungsvoll unterdrückt. Bei In-vivo-Messungen an acht Probanden und zwei Patienten (Hirntumor und Multiple Sklerose) konnte ein deutlich erhöhtes Signal-Rausch-Verhältnis (SNR) im Vergleich zur herkömmlichen Gridding-Methode erreicht werden (8 Probanden: +(46+-3)% bei TV2, +(25+-2)% bei BM&TV2 in weißer Substanz (WM); Multiple-Sklerose-Patient mit AnaWeTV: +133% in WM, +55% im lateralen Ventrikel). Der SNR-Gewinn hängt dabei von der Größe der anatomischen Struktur ab. Die AnaWeTV erhöht die Auflösung bekannter Strukturen und verringert Partialvolumeneffekte. In Simulationen (2mm isotrope Auflösung, UAF = 10) konnte der Intensitätsfehler in vier kleinen Läsionen von (20,3+-3,2)% (Gridding) auf (3,2+-2,3)% (AnaWeTV) reduziert werden. Nach Anwendung eines Hammingfilters betrug er (12,6+-3,3)%. Der Algorithmus ist robust gegenüber Fehlregistrierung der 1H-Bilder um (1,5-3)mm. Auch Strukturen, für die keine anatomischen A-priori-Informationen vorliegen, werden mit hohem Kontrast dargestellt. Die BM&TV2-Rekonstruktion ist vorzuziehen, wenn nicht bekannt ist, ob Strukturen im 23Na-Bild ein anatomisches Korrelat im 1H-Bild besitzen (z.B. bei Hirntumoren)

Cavity-Controlled Collective Scattering at the Recoil Limit

We study collective scattering with Bose-Einstein condensates interacting with a high-finesse ring cavity. The condensate scatters the light of a transverse pump beam superradiantly into modes which, in contrast to previous experiments, are not determined by the geometrical shape of the condensate, but specified by a resonant cavity mode. Moreover, since the recoil-shifted frequency of the scattered light depends on the initial momentum of the scattered fraction of the condensate, we show that it is possible to employ the good resolution of the cavity as a filter selecting particular quantized momentum states.Comment: 4 pages, 4 figure

The metal – ionic liquid interface as characterized by impedance spectroscopy and in-situ scanning tunneling microscopy

We summarize our results of electrochemical measurements carried out on inert or close-to-inert metals in ionic liquids, with the aim to explore the metal | ionic liquid interface structure. To this we used electrochemical methods: cyclic voltammetry, impedance spectroscopy, potential of zero total charge measurements and structure-sensitive techniques, such as in-situ scanning tunneling spectroscopy. The studied systems were mostly single crystals of noble metals in imidazolium-based ionic liquids. The two main findings are: (i) in the potential window where no Faradaic reactions occur, the interfacial capacitance exhibits a frequency dependence due to double-layer rearrangement processes and (ii) in certain cases ordered anion and cation structures exist at the interface

Sodium MRI of the human heart at 7.0 T: preliminary results

The objective of this work was to examine the feasibility of three-dimensional (3D) and whole heart coverage 23Na cardiac MRI at 7.0 T including single-cardiac-phase and cinematic (cine) regimes. A four-channel transceiver RF coil array tailored for 23Na MRI of the heart at 7.0 T (f = 78.5 MHz) is proposed. An integrated bow-tie antenna building block is used for 1H MR to support shimming, localization and planning in a clinical workflow. Signal absorption rate simulations and assessment of RF power deposition were performed to meet the RF safety requirements. 23Na cardiac MR was conducted in an in vivo feasibility study. 3D gradient echo (GRE) imaging in conjunction with Cartesian phase encoding (total acquisition time TAQ = 6 min 16 s) and whole heart coverage imaging employing a density-adapted 3D radial acquisition technique (TAQ = 18 min 20 s) were used. For 3D GRE-based 23Na MRI, acquisition of standard views of the heart using a nominal in-plane resolution of (5.0 x 5.0) mm2 and a slice thickness of 15 mm were feasible. For whole heart coverage 3D density-adapted radial 23Na acquisitions a nominal isotropic spatial resolution of 6 mm was accomplished. This improvement versus 3D conventional GRE acquisitions reduced partial volume effects along the slice direction and enabled retrospective image reconstruction of standard or arbitrary views of the heart. Sodium cine imaging capabilities were achieved with the proposed RF coil configuration in conjunction with 3D radial acquisitions and cardiac gating. Cardiac-gated reconstruction provided an enhancement in blood-myocardium contrast of 20% versus the same data reconstructed without cardiac gating. The proposed transceiver array enables 23Na MR of the human heart at 7.0 T within clinical acceptable scan times. This capability is in positive alignment with the needs of explorations that are designed to examine the potential of 23Na MRI for the assessment of cardiovascular and metabolic diseases

Allele-Level KIR Genotyping of More Than a Million Samples: Workflow, Algorithm, and Observations

The killer-cell immunoglobulin-like receptor (KIR) genes regulate natural killer cell activity, influencing predisposition to immune mediated disease, and affecting hematopoietic stem cell transplantation (HSCT) outcome. Owing to the complexity of the KIR locus, with extensive gene copy number variation (CNV) and allelic diversity, high-resolution characterization of KIR has so far been applied only to relatively small cohorts. Here, we present a comprehensive high-throughput KIR genotyping approach based on next generation sequencing. Through PCR amplification of specific exons, our approach delivers both copy numbers of the individual genes and allelic information for every KIR gene. Ten-fold replicate analysis of a set of 190 samples revealed a precision of 99.9%. Genotyping of an independent set of 360 samples resulted in an accuracy of more than 99% taking into account consistent copy number prediction. We applied the workflow to genotype 1.8 million stem cell donor registry samples. We report on the observed KIR allele diversity and relative abundance of alleles based on a subset of more than 300,000 samples. Furthermore, we identified more than 2,000 previously unreported KIR variants repeatedly in independent samples, underscoring the large diversity of the KIR region that awaits discovery. This cost-efficient high-resolution KIR genotyping approach is now applied to samples of volunteers registering as potential donors for HSCT. This will facilitate the utilization of KIR as additional selection criterion to improve unrelated donor stem cell transplantation outcome. In addition, the approach may serve studies requiring high-resolution KIR genotyping, like population genetics and disease association studies

Ionic liquids at electrified interfaces

Until recently, “room-temperature” (<100–150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)–(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of “first-generation” room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the “later generation” RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in “cocktails” of one’s choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost “universal” solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) “sister-systems”.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules

Properties and structure of the electrified gold/ionic liquid interface

The electrochemical interface of gold in ionic liquids has been characterized by cyclic voltammetry, electrochemical impedance spectroscopy and in situ STM, especially in two distinct potential ranges. In the vicinity of the potential of zero total charge charging of the double layer is rather slow; it appears as if the ions comprising the ionic liquid would slowly exchange each other at the surface. In the other, very negative region the ordering of the cations has been observed by STM