Superconducting Nb-film LC resonator

Sputtered Nb thin-film LC resonators for low frequencies at 0.5 MHz have been fabricated and tested in the temperature range 0.05--1 K in magnetic fields up to 30 mT. Their Q value increases towards decreasing temperature as sqrt(T) and reaches 10^3 at 0.05 K. As a function of magnetic field Q is unstable and displays variations up to 50%, which are reproducible from one field sweep to the next. These instabilities are attributed to dielectric losses in the plasma deposited SiO_2 insulation layer, since the thin-film coil alone reaches a Q > 10^5 at 0.05 K.Comment: 6 pages, 7 figures, submitted to Review of Scientific Instrument

Bipolar programmable current supply for superconducting nuclear magnetic resonance magnets

In high resolution continuous-wave nuclear magnetic resonance(NMR) work well-reproducible, linear sweeps of current are needed. We have developed a microcontroller based programmable current supply, tested with superconducting magnets with inductance of 10 mH and 10 H. We achieved a resolution and noise of 4 ppm. The supply has an internal sweep with programmable ramping rate and a possibility for remote operation from a computer with either GPIB or RS232 interface. It is based on an 18-bit D/A converter. The maximum output current is ±10 A, the sweep rate can be set between 1 μA/s–140 mA/s, and the maximum output voltage is ±2.5 V. In work at ultralow temperatures, especially in superconducting quantum interference device NMR, all rf interference to the experiment should be avoided. One of the sources of this kind of unwanted input is the digital switching noise of fast logic devices. We discuss this problem in the context of our design.Peer reviewe

Central nervous system microstimulation: Towards selective micro-neuromodulation

Electrical stimulation technologies capable of modulating neural activity are well established for neuroscientific research and neurotherapeutics. Recent micro-neuromodulation experimental results continue to explain neural processing complexity and suggest the potential for assistive technologies capable of restoring or repairing of basic function. Nonetheless, performance is dependent upon the specificity of the stimulation. Increasingly specific stimulation is hypothesized to be achieved by progressively smaller interfaces. Miniaturization is a current focus of neural implants due to improvements in mitigation of the body's foreign body response. It is likely that these exciting technologies will offer the promise to provide large-scale micro-neuromodulation in the future. Here, we highlight recent successes of assistive technologies through bidirectional neuroprostheses currently being used to repair or restore basic brain functionality. Furthermore, we introduce recent neuromodulation technologies that might improve the effectiveness of these neuroprosthetic interfaces by increasing their chronic stability and microstimulation specificity. We suggest a vision where the natural progression of innovative technologies and scientific knowledge enables the ability to selectively micro-neuromodulate every neuron in the brain

Polarised target for Drell-Yan experiment in COMPASS at CERN, part I

In the polarised Drell-Yan experiment at the COMPASS facility in CERN pion beam with momentum of 190 GeV/c and intensity about $10^8$ pions/s interacted with transversely polarised NH$_3$ target. Muon pairs produced in Drel-Yan process were detected. The measurement was done in 2015 as the 1st ever polarised Drell-Yan fixed target experiment. The hydrogen nuclei in the solid-state NH$_3$ were polarised by dynamic nuclear polarisation in 2.5 T field of large-acceptance superconducting magnet. Large helium dilution cryostat was used to cool the target down below 100 mK. Polarisation of hydrogen nuclei reached during the data taking was about 80 %. Two oppositely polarised target cells, each 55 cm long and 4 cm in diameter were used. Overview of COMPASS facility and the polarised target with emphasis on the dilution cryostat and magnet is given. Results of the polarisation measurement in the Drell-Yan run and overviews of the target material, cell and dynamic nuclear polarisation system are given in the part II.Comment: 4 pages, 2 figures, Proceedings of the 22nd International Spin Symposium, Urbana-Champaign, Illinois, USA, 25-30 September 201

Polarization build up in COMPASS 6LiD target

The CERN COMPASS experiment uses a large double 424 cm3 cell polarized 6LiD target for the muon program. High nuclear spin polarization |P| > 50 % is obtained, typically in five days. The high cooling power of the COMPASS dilution refrigerator helps to build up the polarization fast at temperatures around 300 mK. At lower microwave power with lower spin and lattice temperatures, the polarization build up is slower. We discuss these features of the dynamic nuclear polarization of our 6LiD target

Multimodal, longitudinal assessment of intracortical microstimulation

The fundamental obstacle to neuroprostheses based on penetrating microstimulation is the tissue’s response to the device insertion and to the application of the electrical stimulation. Our long-term goal is to develop multichannel microstimulation of central nervous tissue for clinical therapy. The overall objective of this research is to identify the optimal parameters for a chronically implanted microstimulation device. In particular, the work presented here focuses on the effects of repeated stimulation and the reactive tissue response on the efficacy of stimulation-driven behavior. To this end, psychophysical experiments were performed using multichannel cortical implants in the auditory cortex of rats. Further, we investigated the effect of the device–tissue interfacial quality on the psychophysical threshold. Here, we report the effects of cortical depth, days postimplant on the psychophysical threshold of auditory cortical microstimulation, along with correlated impedance spectral changes and post vivo histology. We expect that these data will further enable neuroprosthetic development

Molecular organization of the tear fluid lipid layer

The tear fluid protects the corneal epithelium from drying out as well as from invasion by pathogens. It also provides cell nutrients. Similarly to lung surfactant, it is composed of an aqueous phase covered by a lipid layer. Here we describe the molecular organization of the anterior lipid layer of the tear film. Artificial tear fluid lipid layers (ATFLLs) composed of egg yolk phosphatidylcholine (60 mol %), free fatty acids (20 mol %), cholesteryl oleate (10 mol %), and triglycerides (10 mol %) were deposited on the air-water interface and their physico-chemical behavior was compared to egg-yolk phosphatidylcholine monolayers by using Langmuir-film balance techniques, x-ray diffraction, and imaging techniques as well as in silico molecular level simulations. At low surface pressures, ATFLLs were organized at the air-water interface as heterogeneous monomolecular films. Upon compression the ATFLLs collapsed toward the air phase and formed hemispherelike lipid aggregates. This transition was reversible upon relaxation. These results were confirmed by molecular-level simulations of ATFLL, which further provided molecular-scale insight into the molecular distributions inside and dynamics of the tear film. Similar type of behavior is observed in lung surfactant but the folding takes place toward the aqueous phase. The results provide novel information of the function of lipids in the tear fluid

The biological activity of serum bacterial lipopolysaccharides associates with disease activity and likelihood of achieving remission in patients with rheumatoid arthritis

Peer reviewe

Coexistence of Single and Double-Quantum Vortex Lines

We discuss the configurations in which singly and doubly quantized vortex lines may coexist in a rotating superfluid. General principles of energy minimization lead to the conclusion that in equilibrium the two vortex species segregate within a cylindrical vortex cluster in two coaxial domains where the singly quantized lines are in the outer annular region. This is confirmed with simulation calculations on discrete vortex lines. Experimentally the coexistence can be studied in rotating superfluid $^3$He-A. With cw NMR techniques we find the radial distribution of the two vortex species to depend on how the cluster is prepared: (i) By cooling through $T_c$ in rotation, coexistence in the minimum energy configuration is confirmed. (ii) A glassy agglomerate is formed if one starts with an equilibrium cluster of single-quantum vortex lines and adds to it sequentially double-quantum lines, by increasing the rotation velocity in the superfluid state. This proves that the energy barriers, which separate different cluster configurations, are too high for metastabilities to anneal.Comment: 12 pages, 11 figures; Changed content, 15 pages, 14 figure

The biological activity of serum bacterial lipopolysaccharides associates with disease activity and likelihood of achieving remission in patients with rheumatoid arthritis

Peer reviewe