Shifting of the magnetic resonance peak to lower energy in the superconducting state of underdoped YBa_2Cu_3O_{6.8}

Inelastic neutron scattering has been used to determine the dynamic spin fluctuations in an underdoped high temperature superconductor YBCO_{6.8} single crystal. The magnetic resonance, that occurs around 40 meV in overdoped samples, is shifted to a lower energy, E_r= 34 meV. A constant ratio, $E_r/ k_B T_C= 4.9 \pm 0.2$, almost independent of the doping level, is found. According to numerous theoretical approaches, this finding supports the idea that the resonance energy is proportional (approximately twice) to the superconducting gap.Comment: 8 pages, 3 figures, accepted in Europhysics Lette

Observation of Macroscopic Structural Fluctuations in bcc Solid 4He

We report neutron diffraction studies of low density bcc and hcp solid 4He. In the bcc phase, we observed a continuous dynamical behaviour involving macroscopic structural changes of the solid. The dynamical behaviour takes place in a cell full of solid, and therefore represents a solidsolid transformation. The structural changes are consistent with a gradual rotation of macroscopic grains separated by low angle grain boundaries. We suggest that these changes are triggered by random momentary vibrations of the experimental system. An analysis of Laue diffraction patterns indicates that in some cases these structural changes, once initiated by a momentary impulse, seem to proceed at a constant rate over times approaching an hour. The energy associated with these macroscopic changes appears to be on the order of kT. Under similar conditions (temperature and pressure), these effects were absent in the hcp phase.Comment: 14 pages, 6 figure, accepted for PR

Experimental study of ultracold neutron production in pressurized superfluid helium

We have investigated experimentally the pressure dependence of the production of ultracold neutrons (UCN) in superfluid helium in the range from saturated vapor pressure to 20bar. A neutron velocity selector allowed the separation of underlying single-phonon and multiphonon pro- cesses by varying the incident cold neutron (CN) wavelength in the range from 3.5 to 10{\AA}. The predicted pressure dependence of UCN production derived from inelastic neutron scattering data was confirmed for the single-phonon excitation. For multiphonon based UCN production we found no significant dependence on pressure whereas calculations from inelastic neutron scattering data predict an increase of 43(6)% at 20bar relative to saturated vapor pressure. From our data we conclude that applying pressure to superfluid helium does not increase the overall UCN production rate at a typical CN guide.Comment: 18 pages, 8 figures Version accepted for publication in PR

Spin dynamics in high-TCT_C superconductors

Key features of antiferromagnetic dynamical correlations in high-$T_C$ superconductors cuprates are discussed. In underdoped regime, the sharp resonance peak, occuring exclusively in the SC state, is accompanied by a broader contribution located around $\sim$ 30 meV which remains above $T_C$. Their interplay may induce incommensurate structure in the superconducting state.Comment: HTS99 Proceedings Miami (January 7-11 1999

On the wellposedness of some McKean models with moderated or singular diffusion coefficient

We investigate the well-posedness problem related to two models of nonlinear McKean Stochastic Differential Equations with some local interaction in the diffusion term. First, we revisit the case of the McKean-Vlasov dynamics with moderate interaction, previously studied by Meleard and Jourdain in [16], under slightly weaker assumptions, by showing the existence and uniqueness of a weak solution using a Sobolev regularity framework instead of a Holder one. Second, we study the construction of a Lagrangian Stochastic model endowed with a conditional McKean diffusion term in the velocity dynamics and a nondegenerate diffusion term in the position dynamics

AGMIAL: implementing an annotation strategy for prokaryote genomes as a distributed system

We have implemented a genome annotation system for prokaryotes called AGMIAL. Our approach embodies a number of key principles. First, expert manual annotators are seen as a critical component of the overall system; user interfaces were cyclically refined to satisfy their needs. Second, the overall process should be orchestrated in terms of a global annotation strategy; this facilitates coordination between a team of annotators and automatic data analysis. Third, the annotation strategy should allow progressive and incremental annotation from a time when only a few draft contigs are available, to when a final finished assembly is produced. The overall architecture employed is modular and extensible, being based on the W3 standard Web services framework. Specialized modules interact with two independent core modules that are used to annotate, respectively, genomic and protein sequences. AGMIAL is currently being used by several INRA laboratories to analyze genomes of bacteria relevant to the food-processing industry, and is distributed under an open source license

Spatial models of cell distribution in human lumbar dorsal root ganglia

Dorsal root ganglia (DRG), which contain the somata of primary sensory neurons, have increasingly been considered as novel targets for clinical neural interfaces, both for neuroprosthetic and pain applications. Effective use of either neural recording or stimulation technologies requires an appropriate spatial position relative to the target neural element, whether axon or cell body. However, the internal three- dimensional spatial organization of human DRG neural fibers and somata has not been quantitatively described. In this study, we analyzed 202 cross- sectional images across the length of 31 human L4 and L5 DRG from 10 donors. We used a custom semi- automated graphical user interface to identify the locations of neural elements in the images and normalize the output to a consistent spatial reference for direct comparison by spinal level. By applying a recursive partitioning algorithm, we found that the highest density of cell bodies at both spinal levels could be found in the inner 85% of DRG length, the outer- most 25- 30% radially, and the dorsal- most 69- 76%. While axonal density was fairly homogeneous across the DRG length, there was a distinct low density region in the outer 7- 11% radially. These findings are consistent with previous qualitative reports of neural distribution in DRG. The quantitative measurements we provide will enable improved targeting of future neural interface technologies and DRG- focused pharmaceutical therapies, and provide a rigorous anatomical description of the bridge between the central and peripheral nervous systems.Dorsal root ganglia (DRG) are novel targets for neural interface technologies that treat neurological disorders, such as chronic pain and spinal cord injury. The three- dimensional cellular anatomy of DRG are not well- mapped, particularly in humans, limiting the effectiveness of neurotechnology. We developed a semi- automated algorithm to quantify the three- dimensional distribution of neural elements in histologically- processed tissue. We applied this algorithm to sequential NF200- stained histology slices obtained from human lumbar DRG and demonstrated that cell bodies typically congregate around the dorsal edge of the ganglia. These results are crucial to the development of safe and effective clinical neural interface technologies.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155471/1/cne24848_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155471/2/cne24848.pd

New excitations in bcc 4^{4}He - an inelastic neutron scattering study

We report neutron scattering measurements on bcc solid $^{4}$% He. We studied the phonon branches and the recently discovered ''optic-like'' branch along the main crystalline directions. In addition, we discovered another, dispersionless "optic-like'' branch at an energy around 1 meV ($\sim$~11K). The properties of the two "optic-like" branches seem different. Since one expects only 3 acoustic phonon branches in a monoatomic cubic crystal, these new branches must represent different type of excitations. One possible interpretation involves localized excitations unique to a quantum solid.Comment: 4 pages, 3 figures, accepted by PRB, Rapid Communication

In-vivo visualisation of the anatomical structures related to the acupuncture points Dai mai and Shen mai by MRI: A single-case pilot study

BACKGROUND: The concept of acupuncture point localisation in Traditional Chinese Medicine (TCM) is based on millenary practical experience. Modern imaging methods such as PET, MRI and SPECT have been used primary for the investigation of the mechanisms of action of acupuncture. In this pilot single-case study we have evaluated the technical possibilities for in-vivo imaging of the anatomical relations of acupuncture points using state of the art MRI. METHODS: Preliminary experiments relating to the quality of acupuncture needles under the setting of MRI were done both with stainless steel and gold needles. In a second step, in-vivo imaging was carried out. A licensed acupuncture practitioner (RM) chose two points belonging to the so-called extraordinary vessels. In 2 sequential, separate procedures, he inserted himself gold acupuncture needles using a neutral technique (known as Ping Bu Ping Xie) into the Dai mai and Shen mai points, i.e. gall bladder 26 and bladder 62. Imaging was done on a Siemens Magnetom Avanto MR scanner using a head array and body coil. Mainly T1-weighted imaging sequences, as routinely used for patient exams, were used to obtain multi-slice images. RESULTS: In the preliminary experiments only acupuncture needles made of gold showed enough stability in order to be used for further imaging procedures. Using an onion and a banana as an object, further studies showed that the gold needles produced a void defect that corresponds to the tip of the inserted needle, while at the same time an artefactually increased diameter was observed. The in-vivo experiments showed that the Dai mai point was in relation to the abdominal internal oblique muscle. The Shen mai point artefact showed up close to the longus and brevis peroneal tendons at the fibular malleolus. Side effects related to heating or burning were not observed. Improved anatomical recognition was obtained using 3D-volume rendering techniques. CONCLUSION: Through an adequate choice of acupuncture material (gold needles) as well as of ideal MRI imaging sequences it has been possible to visualize the anatomical characteristics at the acupuncture points Dai mai and Shen mai in-vivo. At the selected sites the needles showed a relation to tendino-fascial and muscular structures. These anatomical structures fit well into the recently described WOMED concept of lateral tension in which these acupuncture points play a regulatory role