3,785 research outputs found
Multiplex giant magnetoresistive biosensor microarrays identify interferon-associated autoantibodies in systemic lupus erythematosus.
High titer, class-switched autoantibodies are a hallmark of systemic lupus erythematosus (SLE). Dysregulation of the interferon (IFN) pathway is observed in individuals with active SLE, although the association of specific autoantibodies with chemokine score, a combined measurement of three IFN-regulated chemokines, is not known. To identify autoantibodies associated with chemokine score, we developed giant magnetoresistive (GMR) biosensor microarrays, which allow the parallel measurement of multiple serum antibodies to autoantigens and peptides. We used the microarrays to analyze serum samples from SLE patients and found individuals with high chemokine scores had significantly greater reactivity to 13 autoantigens than individuals with low chemokine scores. Our findings demonstrate that multiple autoantibodies, including antibodies to U1-70K and modified histone H2B tails, are associated with IFN dysregulation in SLE. Further, they show the microarrays are capable of identifying autoantibodies associated with relevant clinical manifestations of SLE, with potential for use as biomarkers in clinical practice
Magnon-polaron and Spin-polaron Signatures in the Specific Heat and Electrical Resistivity of in Zero Magnetic Field, and the Effect of Bond Environment
, an perovskite manganite oxide,
exhibits a non trivial behavior in the vicinity of the sharp peak found in the
resistivity as a function of temperature in zero magnetic field. The
various features seen on are discussed in terms of competing phase
transitions. They are related to the bond environment depending on
the content of the crystallographic site. A Ginzburg-Landau type theory is
presented for incorporating concurrent phase transitions. The specific heat
of such a compound is also examined from 50 till 200 K. A log-log analysis
indicates different regimes. In the low temperature conducting ferromagnetic
phase, a collective magnon signature () is found as for what
are called magnon-polaron excitations. A law is found at
high temperature and discussed in terms of the fractal dimension of the
conducting network of the weakly conducting (so-called insulating) phase and
Orbach estimate of the excitation spectral behaviors. The need of considering
both independent spin scattering and collective spin scattering is thus
emphasized. The report indicates a remarkable agreement for the Fisher-Langer
formula, i.e. at second order phase transitions. Within
the Attfield model, we find an inverse square root relationship between the
critical temperature(s) and the total local strain.Comment: 19 pages, 5 figures; to be published in Phys Rev
Giant Magnetoresistive Biosensors for Time-Domain Magnetorelaxometry: A Theoretical Investigation and Progress Toward an Immunoassay.
Magnetorelaxometry (MRX) is a promising new biosensing technique for point-of-care diagnostics. Historically, magnetic sensors have been primarily used to monitor the stray field of magnetic nanoparticles bound to analytes of interest for immunoassays and flow cytometers. In MRX, the magnetic nanoparticles (MNPs) are first magnetized and then the temporal response is monitored after removing the magnetic field. This new sensing modality is insensitive to the magnetic field homogeneity making it more amenable to low-power portable applications. In this work, we systematically investigated time-domain MRX by measuring the signal dependence on the applied field, magnetization time, and magnetic core size. The extracted characteristic times varied for different magnetic MNPs, exhibiting unique magnetic signatures. We also measured the signal contribution based on the MNP location and correlated the coverage with measured signal amplitude. Lastly, we demonstrated, for the first time, a GMR-based time-domain MRX bioassay. This approach validates the feasibility of immunoassays using GMR-based MRX and provides an alternative platform for point-of-care diagnostics
Coexistence of glassy antiferromagnetism and giant magnetoresistance (GMR) in Fe/Cr multilayer structures
Using temperature-dependent magnetoresistance and magnetization measurements
on Fe/Cr multilayers that exhibit pronounced giant magnetoresistance (GMR), we
have found evidence for the presence of a glassy antiferromagnetic (GAF) phase.
This phase reflects the influence of interlayer exchange coupling (IEC) at low
temperature (T < 140K) and is characterized by a field-independent glassy
transition temperature, Tg, together with irreversible behavior having
logarithmic time dependence below a "de Almeida and Thouless" (AT) critical
field line. At room temperature, where the GMR effect is still robust, IEC
plays only a minor role, and it is the random potential variations acting on
the magnetic domains that are responsible for the antiparallel interlayer
domain alignment.Comment: 5 pages, 4 figure
Tidal Tails Test the Equivalence Principle in the Dark Sector
Satellite galaxies currently undergoing tidal disruption offer a unique
opportunity to constrain an effective violation of the equivalence principle in
the dark sector. Theories in which cold dark matter (CDM) couples to a light
scalar field naturally lead to a long-range force between dark matter
particles. An inverse-square-law force of this kind would manifest itself as a
violation of the equivalence principle in the dynamics of CDM compared to
baryons in the form of gas or stars. In a previous paper, we showed that an
attractive force would displace stars outwards from the bottom of the
satellite's gravitational potential well, leading to a higher fraction of stars
being disrupted from the tidal bulge further from the Galactic center. Since
stars disrupted from the far (near) side of the satellite go on to form the
trailing (leading) tidal stream, an attractive dark-matter force will produce a
relative enhancement of the trailing stream compared to the leading stream.
This distinctive signature of a dark-matter force might be detected through
detailed observations of the tidal tails of a disrupting satellite, such as
those recently performed by the Two-Micron All-Sky Survey (2MASS) and Sloan
Digital Sky Survey (SDSS) on the Sagittarius (Sgr) dwarf galaxy. Here we show
that this signature is robust to changes in our models for both the satellite
and Milky Way, suggesting that we might hope to search for a dark-matter force
in the tidal features of other recently discovered satellite galaxies in
addition to the Sgr dwarf.Comment: 29 pages, 13 figures, final version published in PR
The distance to the Orion Nebula
We have used the Very Long Baseline Array to measure the trigonometric
parallax of several member stars of the Orion Nebula Cluster showing
non-thermal radio emission. We have determined the distance to the cluster to
be 414 +/- 7 pc. Our distance determination allows for an improved calibration
of luminosities and ages of young stars. We have also measured the proper
motions of four cluster stars which, when accurate radial velocities are
measured, will put strong constraints on the origin of the cluster.Comment: 13 pages, 3 figures, to appear in Astronomy & Astrophyisc
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