Protoplanetary Disk Properties in the Orion Nebula Cluster: Initial Results from Deep, High-Resolution ALMA Observations

We present ALMA 850 $\mu$m continuum observations of the Orion Nebula Cluster that provide the highest angular resolution ($\sim 0\rlap{.}''1 \approx 40$ AU) and deepest sensitivity ($\sim 0.1$ mJy) of the region to date. We mosaicked a field containing $\sim 225$ optical or near-IR-identified young stars, $\sim 60$ of which are also optically-identified "proplyds". We detect continuum emission at 850 $\mu$m towards $\sim 80$% of the proplyd sample, and $\sim 50$% of the larger sample of previously-identified cluster members. Detected objects have fluxes of $\sim 0.5$-80 mJy. We remove sub-mm flux due to free-free emission in some objects, leaving a sample of sources detected in dust emission. Under standard assumptions of isothermal, optically thin disks, sub-mm fluxes correspond to dust masses of $\sim 0.5$ to 80 Earth masses. We measure the distribution of disk sizes, and find that disks in this region are particularly compact. Such compact disks are likely to be significantly optically thick. The distributions of sub-mm flux and inferred disk size indicate smaller, lower-flux disks than in lower-density star-forming regions of similar age. Measured disk flux is correlated weakly with stellar mass, contrary to studies in other star forming regions that found steeper correlations. We find a correlation between disk flux and distance from the massive star $\theta^1$ Ori C, suggesting that disk properties in this region are influenced strongly by the rich cluster environment.Comment: Accepted for publication in Ap

Modeling Debris Disk Evolution

Understanding the formation, evolution, and architectures of planetary systems requires detailed knowledge of their components. Debris disks provide a means with which we can study them. The next decade will deliver a wealth of new information on the nearest systems. Parallel advances in modeling will be necessary to interpret these new datasets

Crystal structure and collagen-binding site of immune inhibitory receptor LAIR-1: unexpected implications for collagen binding by platelet receptor GPVI

Leukocyte-associated immunoglobulinlike receptor-1 (LAIR-1), one of the most widely spread immune receptors, attenuates immune cell activation when bound to specific sites in collagen. The collagenbinding domain of LAIR-1 is homologous to that of glycoprotein VI (GPVI), a collagen receptor crucial for platelet activation. Because LAIR-1 and GPVI also display overlapping collagen-binding specificities, a common structural basis for collagen recognition would appear likely. Therefore, it is crucial to gain insight into the molecular interaction of both receptors with their ligand to prevent unwanted cross-reactions during therapeutic intervention. We determined the crystal structure of LAIR-1 and mapped its collagen-binding site by nuclear magnetic resonance (NMR) titrations and mutagenesis. Our data identify R59, E61, and W109 as key residues for collagen interaction. These residues are strictly conserved in LAIR-1 and GPVI alike; however, they are located outside the previously proposed GPVI collagenbinding site. Our data provide evidence for an unanticipated mechanism of collagen recognition common to LAIR-1 and GPVI. This fundamental insight will contribute to the exploration of specific means of intervention in collagen-induced signaling in immunity and hemostasis. (Blood. 2010;115:1364-1373)

The Inner 25 au Debris Distribution in the ϵ Eri System

Debris disk morphology is wavelength dependent due to the wide range of particle sizes and size-dependent dynamics influenced by various forces. Resolved images of nearby debris disks reveal complex disk structures that are difficult to distinguish from their spectral energy distributions. Therefore, multi-wavelength resolved images of nearby debris systems provide an essential foundation to understand the intricate interplay between collisional, gravitational, and radiative forces that govern debris disk structures. We present the Stratospheric Observatory for Infrared Astronomy (SOFIA) 35 mu m resolved disk image of is an element of Eri, the closest debris disk around a star similar to the early Sun. Combining with the Spitzer resolved image at 24 mu m and 15-38 mu m excess spectrum, we examine two proposed origins of the inner debris in is an element of Eri: (1) in situ planetesimal belt(s) and (2) dragged-in grains from the cold outer belt. We find that the presence of in situ dust-producing planetesmial belt(s) is the most likely source of the excess emission in the inner 25 au region. Although a small amount of dragged-in grains from the cold belt could contribute to the excess emission in the inner region, the resolution of the SOFIA data is high enough to rule out the possibility that the entire inner warm excess results from dragged-in grains, but not enough to distinguish one broad inner disk from two narrow belts.NASA [NAS2-97001, SOF02-0061, SOF03-0092, NNX15AI86G]; Deutsches SOFIA Institut (DSI) under DLR [50 OK 0901]; DFG [Kr 2164/13-1, Kr 2164/15-1, Lo 1715/2-1]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

De novo gene mutations in normal human memory B cells

In the past years, the genomes of thousands of tumors have been elucidated. To date however, our knowledge on somatic gene alterations in normal cells is very limited. In this study, we demonstrate that tetanus-specific human memory B lymphocytes carry a substantial number of somatic mutations in the coding regions of the genome. Interestingly, we observed a statistically significant correlation between the number of exome mutations and those present in the immunoglobulin heavy variable regions. Our findings indicate that the majority of these genomic mutations arise in an antigen-dependent fashion, most likely during clonal expansion in germinal centers. The knowledge that normal B cells accumulate genomic alterations outside the immunoglobulin loci during development is relevant for our understanding of the process of lymphomagenesis