424 research outputs found
Transition into a low temperature superconducting phase of unconventional pinning in Sr_2RuO_4
We have found a sharp transition in the vortex creep rates at a temperature
T^\ast=0.05 T_c in a single crystal of Sr_2RuO_4 (T_{c}=1.03 K) by means of
magnetic relaxation measurements. For T<T^\ast, the initial creep rates drop to
undetectable low levels. One explanation for this transition into a phase with
such extremely low vortex creep is that the low-temperature phase of Sr_2RuO_4
breaks time reversal symmetry. In that case, degenerate domain walls separating
discreetly degenerate states of a superconductor can act as very strong pinning
centers.Comment: 3 pages, 2 figure
Public interest litigation: making the case in Australia
Litigation is widely and appropriately recognised as an important component of the public interest advocacy \u27toolkit\u27. Yet, little attention has been paid in Australian research and scholarship to an important question: under what circumstances is public interest litigation (PIL) an effective way to bring about progressive social change? Informed by a review of the international literature on PIL, the authors of this article argue for the importance of drawing on Australia\u27s rich history with PIL to develop a solid empirical evidence base which can inform future decision about the strategic employment of PIL in campaigns to address the concerns and needs of disadvantaged and marginalised sections of Australian society
Wireless Data Acquisition For Apiology Applications
Colony Collapse Disorder (CCD), a disease affecting honey bee colonies, is a problem threatening the food security and economy of the entire world. Discovering the cause of CCD is particularly difficult because of the variety of colony locations and environmental variables. In addition, CCD instances do not tend to follow an easily recognizable pattern with respect to apiary conditions, which is exacerbated by the subjective nature of manual apiary data recording methods. Traditional monitoring methods are typically too expensive for wide-scale deployment and often require manual collection of the data, reducing the quantity of data available for analysis. A general wireless data acquisition system was designed to improve the quantity and quality of data and to explore general issues related to wireless data acquisition systems. The system was constructed using off-the-shelf -components to reduce cost. The acquisition system and data management tools were programmed using freely available tools and software. Beehive data are transmitted to the Internet wirelessly through the use of a cellular GSM modem. Results show that it is feasible to build an economical, general purpose wireless data acquisition system that can gather quality data for an Apiology application with similar capabilities to higher-cost contemporary systems
The influence of chiral surface states on the London penetration depth in SrRuO
The London penetration depth for the unconventional superconductor
SrRuO is analyzed assuming an order parameter which breaks time
reversal symmetry and parity simultaneously. Such a superconducting state
possesses chiral quasiparticle states with subgap energies at the surface. We
show that these subgap states can give a significant contribution to the
low-temperature behavior of the London penetration depth yielding a
power-law even though bulk quasiparticle spectrum is gapped. The presence of
several electron bands gives rise to interband transition among the subgap
surface states and influences the properties of the surface impedance.
Furthermore, the surface states lead also to a non-linear Meissner effect.Comment: 4 pages, 1 figure, the definition of the Nambu field operator
introduced, and some typos correcte
Diversity and environmental adaptation of phagocytic cell metabolism
Phagocytes are cells of the immune system that play important roles in phagocytosis, respiratory burst and degranulation-key components of innate immunity and response to infection. This diverse group of cells includes monocytes, macrophages, dendritic cells, neutrophils, eosinophils, and basophils-heterogeneous cell populations possessing cell and tissue-specific functions of which cellular metabolism comprises a critical underpinning. Core functions of phagocytic cells are diverse and sensitive to alterations in environmental- and tissue-specific nutrients and growth factors. As phagocytic cells adapt to these extracellular cues, cellular processes are altered and may contribute to pathogenesis. The considerable degree of functional heterogeneity among monocyte, neutrophil, and other phagocytic cell populations necessitates diverse metabolism. As we review our current understanding of metabolism in phagocytic cells, gaps are focused on to highlight the need for additional studies that hopefully enable improved cell-based strategies for counteracting cancer and other diseases
Phenomenology of the superconducting state in Sr2RuO4
The symmetry of the superconducting phase of Sr2RuO4 is identified as the
odd-parity pairing state d(k)=\hat{z}(k_x \pm i k_y) based on recent
experiments. The experimental evidence for the so-called orbital dependent
superconductivity leads to a single-band description of superconductivity based
on spin fluctuation mechanism. It is shown that the state \hat{z}(k_x \pm i
k_y) can be stabilized by the spin fluctuation feedback mechanism analogous to
the A-phase in 3He and by spin-orbit coupling effects.Comment: 7 pages, 1 figure, to be published in Proc. of the conference
"Anomalous Complex Superconductors" (Crete, 1998
Observation of Vortex Coalescence, Vortex Chains and Crossing Vortices in the Anisotropic Spin-Triplet Superconductor
Scanning SQUID force microscopy is used to study magnetic flux
structures in single crystals of the layered spin triplet superconductor
SrRuO. Images of the magnetic flux configuration above the
-face of the cleaved crystal are acquired, mostly after
field-cooling the sample. For low applied magnetic fields, individual vortices
are observed, each carrying a single quantum of flux. Above 1 gauss,
coalescence of vortices is discovered. The coalescing vortices may indicate the
presence of domains of a chiral order parameter. When the applied field is
tilted from the -axis, we observe a gradual transition from vortex
domains to vortex chains. The in-plane component of the applied magnetic field
transforms the vortex domains to vortex chains by aligning them along the field
direction.This behavior and the inter-chain distance varies in qualitative
agreement with the Ginzburg Landau theory of anisotropic 3D superconductors.
The effective mass anisotropy of SrRuO, =20, is the
highest observed in three dimensional superconductors. When the applied field
is closely in plane, the vortex form flux channels confined between the
crystal-layers. Residual Abrikosov vortices are pinned preferentially on these
channels. Thus the in-plane vortices are decorated by crossing Abrikosov
vortices: two vortex orientations are apparent simultaneously, one along the
layers and the other perpendicular to the layers.Comment: to appear in Physica C M2S conference Dresde
Peritoneal tissue-resident macrophages are metabolically poised to engage microbes using tissue-niche fuels
The importance of metabolism in macrophage function has been reported, but the in vivo relevance of the in vitro observations is still unclear. Here we show that macrophage metabolites are defined in a specific tissue context, and these metabolites are crucially linked to tissue-resident macrophage functions. We find the peritoneum to be rich in glutamate, a glutaminolysis-fuel that is exploited by peritoneal-resident macrophages to maintain respiratory burst during phagocytosis via enhancing mitochondrial complex-II metabolism. This niche-supported, inducible mitochondrial function is dependent on protein kinase C activity, and is required to fine-tune the cytokine responses that control inflammation. In addition, we find that peritoneal-resident macrophage mitochondria are recruited to phagosomes and produce mitochondrially derived reactive oxygen species, which are necessary for microbial killing. We propose that tissue-resident macrophages are metabolically poised in situ to protect and exploit their tissue-niche by utilising locally available fuels to implement specific metabolic programmes upon microbial sensing
Upper Critical Field of the 3 Kelvin Phase in Sr2RuO4
The inhomogeneous 3 Kelvin phase is most likely a superconducting state
nucleating at the interface between micrometer-sized Ru-metal inclusions and
Sr2RuO4 above the bulk onset of superconductivity. This filamentary
superconducting state yields a characteristic temperature dependence of the
upper critical field which is sublinear, i.e., H_{c2} (T) \propto (T^* -
T)^{\gamma} with 0.5 \leq \gamma < 1 (T^*: nucleation temperature). The
Ginzburg-Landau theory is used to analyze the behavior of the nucleated
spin-triplet phase in a field and the characteristic features of H_{c2}
observed in the experiment are explained based on a two-component order
parameter in the presence of a filament of enhanced superconductivity with a
finite width.Comment: 4 pages, 3 figure
Electromagnetic Response of a Superconductor: Effect of Order Parameter Collective Modes
Effects of order parameter collective modes on electromagnetic response are
studied for a clean spin-triplet superconductor with orbital
symmetry, which has been proposed as a candidate pairing symmetry for
SrRuO. It is shown that the superconductor has
characteristic massive collective modes analogous to the clapping mode in the
A-phase of superfluid He. We discuss the contribution from the collective
modes to ultrasound attenuation and electromagnetic absorption. We show that in
the electromagnetic absorption spectrum the clapping mode gives rise to a
resonance peak well below the pair breaking frequency, while the ultrasound
attenuation is hardly influenced by the collective excitations.Comment: 4 pages RevTex, 1 eps figur
- …