1,171 research outputs found
Strong Electron-Phonon Coupling in Superconducting MgB: A Specific Heat Study
We report on measurements of the specific heat of the recently discovered
superconductor MgB in the temperature range between 3 and 220 K. Based on a
modified Debye-Einstein model, we have achieved a rather accurate account of
the lattice contribution to the specific heat, which allows us to separate the
electronic contribution from the total measured specific heat. From our result
for the electronic specific heat, we estimate the electron-phonon coupling
constant to be of the order of 2, significantly enhanced compared to
common weak-coupling values . Our data also indicate that the
electronic specific heat in the superconducting state of MgB can be
accounted for by a conventional, s-wave type BCS-model.Comment: 4 pages, 4 figure
Development of a chicken 5 K microarray targeted towards immune function
<p>Abstract</p> <p>Background</p> <p>The development of microarray resources for the chicken is an important step in being able to profile gene expression changes occurring in birds in response to different challenges and stimuli. The creation of an immune-related array is highly valuable in determining the host immune response in relation to infection with a wide variety of bacterial and viral diseases.</p> <p>Results</p> <p>Here we report the development of chicken immune-related cDNA libraries and the subsequent construction of a microarray containing 5190 elements (in duplicate). Clones on the array originate from tissues known to contain high levels of cells related to the immune system, namely Bursa, Peyers patch, thymus and spleen. Represented on the array are genes that are known to cluster with existing chicken ESTs as well as genes that are unique to our libraries. Some of these genes have no known homologies and represent novel genes in the chicken collection. A series of reference genes (ie. genes of known immune function) are also present on the array. Functional annotation data is also provided for as many of the genes on the array as is possible.</p> <p>Conclusion</p> <p>Six new chicken immune cDNA libraries have been created and nearly 10,000 sequences submitted to GenBank [GenBank: <ext-link ext-link-type="gen" ext-link-id="AM063043">AM063043</ext-link>-<ext-link ext-link-type="gen" ext-link-id="AM071350">AM071350</ext-link>; <ext-link ext-link-type="gen" ext-link-id="AM071520">AM071520</ext-link>-<ext-link ext-link-type="gen" ext-link-id="AM072286">AM072286</ext-link>; <ext-link ext-link-type="gen" ext-link-id="AM075249">AM075249</ext-link>-<ext-link ext-link-type="gen" ext-link-id="AM075607">AM075607</ext-link>]. A 5 K immune-related array has been developed from these libraries. Individual clones and arrays are available from the ARK-Genomics resource centre.</p
On the Energy Transfer Performance of Mechanical Nanoresonators Coupled with Electromagnetic Fields
We study the energy transfer performance in electrically and magnetically
coupled mechanical nanoresonators. Using the resonant scattering theory, we
show that magnetically coupled resonators can achieve the same energy transfer
performance as for their electrically coupled counterparts, or even outperform
them within the scale of interest. Magnetic and electric coupling are compared
in the Nanotube Radio, a realistic example of a nano-scale mechanical
resonator. The energy transfer performance is also discussed for a newly
proposed bio-nanoresonator composed of a magnetosomes coated with a net of
protein fibers.Comment: 9 Pages, 3 Figure
Magnetic resonance force microscopy with a one-dimensional resolution of 0.9 nanometers
Magnetic resonance force microscopy (MRFM) is a scanning probe technique
capable of detecting MRI signals from nanoscale sample volumes, providing a
paradigm-changing potential for structural biology and medical research. Thus
far, however, experiments have not reached suffcient spatial resolution for
retrieving meaningful structural information from samples. In this work, we
report MRFM imaging scans demonstrating a resolution of 0.9 nm and a
localization precision of 0.6 nm in one dimension. Our progress is enabled by
an improved spin excitation protocol furnishing us with sharp spatial control
on the MRFM imaging slice, combined with overall advances in instrument
stability. From a modeling of the slice function, we expect that our
arrangement supports spatial resolutions down to 0.3 nm given suffcient
signal-to-noise ratio. Our experiment demonstrates the feasibility of
sub-nanometer MRI and realizes an important milestone towards the
three-dimensional imaging of macromolecular structures.Comment: 17 pages, 4 figure
Acacia saligna as a supplementary feed for grazing desert sheep and goats
Acacia saligna, a leguminous tree, has a high crude protein content, remains green all year and can be grown in deserts using only runoff water. However, dry matter intake (DMI) by sheep and goats of A. saligna is low, presumably due to its high tannin content. It has been suggested that DMI could be increased by such methods as wilting of the forage and by neutralizing the negative effects of tannins by tannin-complexing agents. The purpose of this study was to determine DMI of supplementary A. saligna (phyllodes and small stems) by grazing sheep (∼ 50 kg) and goats (∼ 37 kg) when the animals were (1) offered wilted or fresh material (Expt 1); and (2) administered with polyethylene glycol (PEG), a tannin-binding agent (Expt 2). In this second experiment, there were three 14-day periods in which one group each of sheep and goats was on a regime of: No PEG–PEG–No PEG, whereas another group was on a regime of: No PEG–No PEG–PEG. In Expt 1, the DMI of A. saligna was statistically higher in goats than in sheep, but there was no difference in intake between fresh and wilted material. Average DMI of A. saligna, both fresh and wilted, was 124·1 g/day or 8·41 g/kg0·75 per day for goats and 94·1 g/day or 5·05 g/kg0·75 per day for sheep. Goats and sheep consuming fresh A. saligna gained more body mass than their respective controls; the difference was significantly greater in goats but not in sheep. In Expt 2, DMI of fresh A. saligna in the first period (before PEG) was 104·1 g/day or 7·16 g/kg0·75 per day for goats and 84·8 g/day or 4·51 g/kg0·75 per day for sheep. Administration of PEG during the second period resulted in an increase in DMI of 62% in goats and 83% in sheep. These animals maintained a high A. saligna intake in the third period when PEG was withdrawn. Goats and sheep that did not receive PEG in the second period had similar A. saligna intake as in the first period, but increased intake by 62% and 47%, respectively, with PEG in the third period. Overall, the two goat groups and two sheep groups consuming A. saligna lost less body mass than their respective controls; the difference was significantly less in sheep but not in goats. It was concluded that wilting A. saligna did not increase DMI. Administration of PEG increased A. saligna intake and the intake remained high after PEG was withdrawn. Offering A. saligna as a supplement had a positive effect on body mass change
Controlling the quantum dynamics of a mesoscopic spin bath in diamond
Understanding and mitigating decoherence is a key challenge for quantum
science and technology. The main source of decoherence for solid-state spin
systems is the uncontrolled spin bath environment. Here, we demonstrate quantum
control of a mesoscopic spin bath in diamond at room temperature that is
composed of electron spins of substitutional nitrogen impurities. The resulting
spin bath dynamics are probed using a single nitrogen-vacancy (NV) centre
electron spin as a magnetic field sensor. We exploit the spin bath control to
dynamically suppress dephasing of the NV spin by the spin bath. Furthermore, by
combining spin bath control with dynamical decoupling, we directly measure the
coherence and temporal correlations of different groups of bath spins. These
results uncover a new arena for fundamental studies on decoherence and enable
novel avenues for spin-based magnetometry and quantum information processing
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