Detection of donor-specific hyporesponsiveness following late failure of human renal allografts

Detection of donor-specific hyporesponsiveness following late failure of human renal allografts. Limiting dilution assays to measure the frequency of interleukin-2-secreting peripheral blood T cells were carried out in patients, whose renal allografts had failed due to acute rejection (9 patients) and in patients whose grafts failed more than two years after transplantation without any recent evidence of acute rejection. Using a modified form of the assay we demonstrate that nearly half of 18 patients whose renal transplants had failed after more than two years have low or undetectable HTLp frequencies against donor, but not third-party DR antigens. No such difference was observed in any of the nine patients studied whose transplants were lost from early acute rejection. These results provide the first indication that, as in rodent models of transplantation, T cell unresponsiveness towards donor MHC antigens can occur following prolonged residence of an allograft in humans. Furthermore, the results suggest that chronic rejection may be driven by mechanisms other than direct allorecognition. The assay may be a valuable tool to study the evolution of donor-specific direct T cell alloresponsiveness in patients with well-functioning grafts

Foreground Predictions for the Cosmic Microwave Background Power Spectrum from Measurements of Faint Inverted Radio Sources at 5 GHz

We present measurements of a population of matched radio sources at 1.4 and 5 GHz down to a flux limit of 1.5 mJy in 7 sq. degs. of the NOAO Deep Field South. We find a significant fraction of sources with inverted spectral indices that all have 1.4 GHz fluxes less than 10 mJy, and are therefore too faint to have been detected and included in previous radio source count models that are matched at multiple frequencies. Combined with the matched source population at 1.4 and 5 GHz in 1 sq. deg. in the ATESP survey, we update models for the 5 GHz differential number counts and distributions of spectral indices in 5 GHz flux bins that can be used to estimate the unresolved point source contribution to the cosmic microwave background temperature anisotropies. We find a shallower logarithmic slope in the 5 GHz differential counts than in previously published models for fluxes < 100 mJy as well as larger fractions of inverted spectral indices at these fluxes. Because the Planck flux limit for resolved sources is larger than 100 mJy in all channels, our modified number counts yield at most a 10% change in the predicted Poisson contribution to the Planck temperature power spectrum. For a flux cut of 5 mJy with the South Pole Telescope and a flux cut of 20 mJy with the Atacama Cosmology Telescope we predict a ~30% and ~10% increase, respectively, in the radio source Poisson power in the lowest frequency channels of each experiment relative to that predicted by previous models.Comment: 14 pages, 9 figures, includes ApJ proof correction

The Antiferromagnetic Band Structure of La2CuO4 Revisited

Using the Becke-3-LYP functional, we have performed band structure calculations on the high temperature superconductor parent compound, La2CuO4. Under the restricted spin formalism (rho(alpha) equal to rho(beta)), the R-B3LYP band structure agrees well with the standard LDA band structure. It is metallic with a single Cu x2-y2/O p(sigma) band crossing the Fermi level. Under the unrestricted spin formalism (rho(alpha) not equal to rho(beta)), the UB3LYP band structure has a spin polarized antiferromagnetic solution with a band gap of 2.0 eV, agreeing well with experiment. This state is 1.0 eV (per formula unit) lower than that calculated from the R-B3LYP. The apparent high energy of the spin restricted state is attributed to an overestimate of on-site Coulomb repulsion which is corrected in the unrestricted spin calculations. The stabilization of the total energy with spin polarization arises primarily from the stabilization of the x2-y2 band, such that the character of the eigenstates at the top of the valence band in the antiferromagnetic state becomes a strong mixture of Cu x2-y2/O p(sigma) and Cu z2/O' p(z). Since the Hohenberg-Kohn theorem requires the spin restricted and spin unrestricted calculations give exactly the same ground state energy and total density for the exact functionals, this large disparity in energy reflects the inadequacy of current functionals for describing the cuprates. This calls into question the use of band structures based on current restricted spin density functionals (including LDA) as a basis for single band theories of superconductivity in these materials.Comment: 13 pages, 8 figures, to appear in Phys. Rev. B, for more information see http://www.firstprinciples.co

MRI: Acquisition of a SQUID Magnetometer for Analysis of Advanced Materials

Technical Summary: Superconducting quantum interference device (SQUID) magnetometry is a non-destructive technique that reveals detailed information about the electron spin interactions in many types of materials. This project will involve a state-of-the-art SQUID magnetometer and Magnetic Property Measurement System (MPMS), which is a critical tool for characterizing several types of materials currently being investigated by researchers within the Laboratory for Surface Science & Technology (LASST) and other University of Maine (UMaine) laboratories. Specific measurement capabilities include DC and AC magnetic susceptibility, magnetoresistivity, van der Paaw conductivity, and Hall mobility. State-of-the-art MPMS capabilities will be especially valuable to several research programs at UMaine pertaining to (i) surface magnetism in nanoparticles, (ii) magnetic anisotropies in sedimentary rocks, (iii) electrical transport in physical and chemical sensing devices, (iv) optical properties of nanostructures in high magnetic fields, and (v) magnetic nanoparticle based biosensors. The MPMS will serve as a focal point for training undergraduates, graduate students, postdocs, and visiting scientists in magnetic materials, nanotechnology, biophysics, and materials science. This instrument is a critical tool for expanding the capacity of UMaine research into magnetic aspects of nanotechnology, biophysics, sensor technology, and materials science. As no SQUID magnetometer currently exists in the State of Maine, the instrumentation will provide access for research projects from interested parties throughout the state, including non-Ph.D. granting institutions and small Maine businesses. The instrument is relatively easy to operate and provides direct information on electron spin interactions, and thus it will be a powerful tool to teach physics and nanotechnology concepts to several different constituents participating in UMaine outreach activities, including K-12 students and teachers, the general public, under-represented groups, and industry partners.Layman Summary: Superconducting quantum interference device (SQUID) magnetometry is a non-destructive technique that reveals detailed information about the electron spin interactions in many types of materials. Knowledge of electron interactions in materials is extremely important in building the next generation of computers, electronics, and contrast agents in biological magnetic screening techniques (i.e. MRI). To gain the necessary information, a system with control over both the magnetic field strength and temperature is critical. To this end, a SQUID/Magnetic Property Measurement System (MPMS) is ideal for these measurements. This project will purchase a state-of-the-art MPMS system and will be especially valuable to several research programs at UMaine pertaining to surface magnetism in nanoparticles, magnetic anisotropies in sedimentary rocks, electrical transport in physical and chemical sensing devices, and magnetic nanoparticle based biosensors. The proposed MPMS will serve as a focal point for training undergraduates, graduate students, postdocs, and visiting scientists in magnetic materials, nanotechnology, biophysics, and materials science. As no SQUID magnetometer currently exists in the State of Maine, the instrumentation will provide access for research projects from interested parties throughout the state, including non-Ph.D. granting institutions and small Maine businesses. The instrument is relatively easy to operate and provides direct information on electron spin interactions, and thus it will be a powerful tool to teach physics and nanotechnology concepts to several different constituents participating in UMaine outreach activities, including K-12 students and teachers, the general public, under-represented groups, and industry partners

The Membership and Distance of the Open Cluster Collinder 419

The young open cluster Collinder 419 surrounds the massive O star, HD 193322, that is itself a remarkable multiple star system containing at least four components. Here we present a discussion of the cluster distance based upon new spectral classifications of the brighter members, UBV photometry, and an analysis of astrometric and photometric data from the UCAC3 and 2MASS catalogs. We determine an average cluster reddening of E(B-V)=0.37 +- 0.05 mag and a cluster distance of 741 +- 36 pc. The cluster probably contains some very young stars that may include a reddened M3 III star, IRAS~20161+4035

Complete topology of cells, grains, and bubbles in three-dimensional microstructures

We introduce a general, efficient method to completely describe the topology of individual grains, bubbles, and cells in three-dimensional polycrystals, foams, and other multicellular microstructures. This approach is applied to a pair of three-dimensional microstructures that are often regarded as close analogues in the literature: one resulting from normal grain growth (mean curvature flow) and another resulting from a random Poisson-Voronoi tessellation of space. Grain growth strongly favors particular grain topologies, compared with the Poisson-Voronoi model. Moreover, the frequencies of highly symmetric grains are orders of magnitude higher in the the grain growth microstructure than they are in the Poisson-Voronoi one. Grain topology statistics provide a strong, robust differentiator of different cellular microstructures and provide hints to the processes that drive different classes of microstructure evolution.Comment: 5 pages, 6 figures, 5 supplementary page

Distribution of Topological Types in Grain-Growth Microstructures

An open question in studying normal grain growth concerns the asymptotic state to which microstructures converge. In particular, the distribution of grain topologies is unknown. We introduce a thermodynamic-like theory to explain these distributions in two- and three-dimensional systems. In particular, a bending-like energy $E_i$ is associated to each grain topology $t_i$, and the probability of observing that particular topology is proportional to $\frac{1}{s(t_i)}e^{-\beta E_i}$, where $s(t_i)$ is the order of an associated symmetry group and $\beta$ is a thermodynamic-like constant. We explain the physical origins of this approach, and provide numerical evidence in support.Comment: 6 pages, 5 figure

Correcting the z~8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias

We present a Bayesian framework to account for the magnification bias from both strong and weak gravitational lensing in estimates of high-redshift galaxy luminosity functions. We illustrate our method by estimating the $z\sim8$ UV luminosity function using a sample of 97 Y-band dropouts (Lyman break galaxies) found in the Brightest of Reionizing Galaxies (BoRG) survey and from the literature. We find the luminosity function is well described by a Schechter function with characteristic magnitude of $M^\star = -19.85^{+0.30}_{-0.35}$, faint-end slope of $\alpha = -1.72^{+0.30}_{-0.29}$, and number density of $\log_{10} \Psi^\star [\textrm{Mpc}^{-3}] = -3.00^{+0.23}_{-0.31}$. These parameters are consistent within the uncertainties with those inferred from the same sample without accounting for the magnification bias, demonstrating that the effect is small for current surveys at $z\sim8$, and cannot account for the apparent overdensity of bright galaxies compared to a Schechter function found recently by Bowler et al. (2014a,b) and Finkelstein et al. (2014). We estimate that the probability of finding a strongly lensed $z\sim8$ source in our sample is in the range $\sim 3-15 \%$ depending on limiting magnitude. We identify one strongly-lensed candidate and three cases of intermediate lensing in BoRG (estimated magnification $\mu>1.4$) in addition to the previously known candidate group-scale strong lens. Using a range of theoretical luminosity functions we conclude that magnification bias will dominate wide field surveys -- such as those planned for the Euclid and WFIRST missions -- especially at $z>10$. Magnification bias will need to be accounted for in order to derive accurate estimates of high-redshift luminosity functions in these surveys and to distinguish between galaxy formation models.Comment: Accepted for publication in ApJ. 20 pages, 13 figure