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Introduction: The JAXA Hayabusa2 spacecraft collected surface regolith from C-type asteroid (162173) Ryugu during two separate touchdown events (stored in sample chambers A and C, respectively). Preliminary examinations of these samples by JAXA Curation [1] and Hayabusa2 Initial Analysis Teams [2,3] indicate a strong connection to Ivuna-type (CI) carbonaceous chondrites, in agreement with orbital-based near-infrared spectroscopy of the asteroid surface [4]. Scanning-transmission X-ray microscopy (STXM) and X-ray absorption near-edge structure spectroscopy (XANES) of Ryugu insoluble organic matter (IOM) residues also indicates a strong similarity with other aqueously-altered carbonaceous chondrites, specifically CI, CM, and the C-ungrouped Tagish Lake [3,5]. However, these studies also reported the presence of carbonaceous sub-grains with functional group distributions previously unseen in these chondrite groups. Here we further investigate the differences in organic macromolecular material between Ryugu and CI chondrites using correlated XANES, transmission electron microscopy (TEM), and nanoscale secondary ion mass spectroscopy (NanoSIMS). Samples and Methods: Ryugu regolith grains were prepared from aggregate samples A0108 (from Chamber A) and C0109 (from Chamber C). Samples were either prepared by sulfur embedding and ultramicrotomy or by a focused ion beam (FIB) liftout procedure, and a corresponding suite of samples were prepared from fragments from the CI chondrite Orgueil. STXM/XANES data were acquired at beamline 5.3.2.2 and 5.3.2.1 at the Advanced Light Source, or beamline BL-19 at the Photon Factory. Subsequently, TEM characterization was performed with an aberration-corrected Nion UltraSTEM 200-X at the U.S. Naval Research Laboratory using a 60 keV beam. Nitrogen and carbon isotopes of FIB section A0108-3 were also measured with a Cameca NanoSIMS 50L at the Carnegie Institution for Science. Results and discussion: The functional chemistry distribution of carbonaceous grains in Ryugu samples can be categorized into three main groups based on their XANES spectral shapes. The first two, IOM-like and Highly Aromatic, match the functional group diversity typically observed in nanoglobules from carbonaceous chondrites [6]. Likewise, carbonaceous grains in the Orgeuil samples also produced XANES spectra that matched either of these spectral "fingerprints". In contrast, Ryugu samples contained carbonaceous grains with a third spectral shape, characterized by a large, narrow peak at 285 eV (due to C=C bonds), little to no peak at 286.7 eV (ketone C=O), and broad intensity at 288-289 eV (a combination of aliphatic C-C and carboxyl COOH). This Aromatic spectral shape could be consistent with a macromolecular structure composed of small, highly-modified, polyaromatic moieties connected by long aliphatic side chains, which could have been generated on the Ryugu parent body during aqueous alteration. By correlating NanoSIMS, TEM and XANES data from FIB section A0108-3, we hope to glean information regarding the origin(s) of these three XANES spectral shapes. 15N/14N isotope ratios of most of the IOM-like and Aromatic carbonaceous grains in this FIB section were all anomalous relative to the bulk value of the section (i.e., diffuse organic matter interspersed within the fine-grained matrix). The two Highly Aromatic grains in the section contained slightly negative d15N/14N values (-89±58 and -120±66), indicating these grains formed from distinct reservoirs of organic precursors, than the IOM-like and Aromatic grains. These data also suggest that the presence of the Aromatic functional chemistry profile is unlikely to come from addition of a separate population of organic precursor material, but rather was generated on the parent body in combination with IOM-like products. [ABSTRACT FROM AUTHOR]

Introduction: Insoluble organic matter in carbonaceous chondrites has been studied extensively in order to constrain the history of the evolution of organic carbon in the solar system and the role of asteroids in delivery of prebiotic chemistry to the early Earth [1]. These studies have shown both that the organic matter can be considerably altered by hydrothermal processing on the asteroid, and that D and 15N isotopic composition indicators of outer nebula or molecular cloud origin can survive moderate levels of such parent body alteration. As revealing as the study of meteoritic organics has been, all such studies suffer from sampling biases associated with the factors necessary for meteorites to have reached Earth from the parent asteroid and survived atmospheric entry and the exposure to the terrestrial atmosphere. The direct laboratory study of organic matter in returned asteroid regolith, presently from Ctype asteroid Ryugu, and in future from asteroid Bennu, provides an unprecedented opportunity to examine asteroid organic matter with established provenance and minimal artifacts from terrestrial alteration. As part of the Hayabusa2 initial analysis of Ryugu samples, we have used to analytical transmission electron microscopy to study the microstructure, elemental composition, and functional chemistry of Ryugu insoluble organic matter, and the relationship to fine-grained minerals. Methods: The samples for these studies included whole particles, extracted focused ion beam (FIB) crosssections, microtomed slices of particles, and microtomed slice of insoluble organics isolates (IOM) from both the Chamber A and Chamber C collections. This range of samples and preparation methods allowed for investigation of a wide range of different aspects of the samples, such as the greatest preservation of mineral-organic textural relationships and possible soluble components in FIB sections, and observation of the few-nm to sub-nm features in the microtomed samples. Transmission electron microscopy studies were performed with two microscopes: a JEOL 2200FS operated at 200 kV for bright field imaging, and a Nion UltraSTEM-X operated at 60 kV and 200 kV for annular dark field imaging, energy dispersive x-ray spectroscopy (EDS) of the elemental composition and electron energy loss spectroscopy (EELS) of the C K-edge fine structure and plasmon regions. The EDS and EELS data were collected with Bruker Xflash 100 and Gatan Enfinium spectrometers attached to the UltraSTEM, respectively. Results: The results of the electron microscopy studies of the organic matter confirm a strong link between the Ryugu regolith samples and carbonaceous chondrites in general and are most similar to observations of organic matter in CI chondrites such as Orgueil that have undergone low temperature aqueous alteration. Diffuse organic carbon is abundant, intermixed with μm to sub-μm minerals, including Mg-rich phyllosilicates, magnetite, carbonates and sulfides. Solid and hollow nanoglobules are present as isolated particles, most commonly < 400 nm diameter, and in clusters, with a few individual nanoglobules extending to as large as 2 μm. Nanodiamonds are also present in clusters surrounded by amorphous carbon. Two FIB sections revealed secondary minerals with interior vesicles. One of these sections, sample A0108-3, transected vesicles in a calcite grain that contain diffuse organics and nanoscale silicates and sulfides. The other (AP002-g01T5) preserved closed vesicles in a pyrrhotite grain that contain C-rich fluids. The EELS observations of the C bonding indicate that the diffuse carbon interspersed in Mg-rich phyllosilicates has a strong absorption feature at 290.4 eV associated with CO3 groups, and varying amounts of other functional groups, including aromatic, ketone, aliphatic and carboxyl. The functional group chemistry of the nanoglobules includes particles that are dominated by aromatic groups (285 eV), and others with significant amounts of ketone (286.5) and carboxyl (288.5) groups. Finally, some aromatic carbon is present as coatings on nanoscale secondary minerals, including Fe and Cu-bearing sulfides. Taken together, the results demonstrate complex records of preaccretionary and parent body processing in the Hayabusa2 samples from Ryugu. [ABSTRACT FROM AUTHOR]

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010. [ABSTRACT FROM PUBLISHER]

All chondrites accreted ~3.5 wt.% C in their matrices, the bulk of which was in a macromolecular solvent and acid insoluble organic material (IOM). Similar material to IOM is found in interplanetary dust particles (IDPs) and comets. The IOM accounts for almost all of the C and N in chondrites, and a significant fraction of the H. Chondrites and, to a lesser extent, comets were probably the major sources of volatiles for the Earth and the other terrestrial planets. Hence, IOM was both the major source of Earth's volatiles and a potential source of complex prebiotic molecules. Large enrichments in D and 15 N, relative to the bulk solar isotopic compositions, suggest that IOM or its precursors formed in very cold, radiation-rich environments. Whether these environments were in the interstellar medium (ISM) or the outer Solar System is unresolved. Nevertheless, the elemental and isotopic compositions and functional group chemistry of IOM provide important clues to the origin(s) of organic matter in protoplanetary disks. IOM is modified relatively easily by thermal and aqueous processes, so that it can also be used to constrain the conditions in the solar nebula prior to chondrite accretion and the conditions in the chondrite parent bodies after accretion. Here we review what is known about the abundances, compositions and physical nature of IOM in the most primitive chondrites. We also discuss how the IOM has been modified by thermal metamorphism and aqueous alteration in the chondrite parent bodies, and how these changes may be used both as petrologic indicators of the intensity of parent body processing and as tools for classification. Finally, we critically assess the various proposed mechanisms for the formation of IOM in the ISM or Solar System.

Objective: Esophagitis, a complication of GERD, and gastric erosions are common findings in dyspeptic patients. Unfortunately, these findings cannot be predicted based on symptoms alone and require endoscopy for an accurate diagnosis. Noninvasive diagnosis of other gastrointestinal pathology by radiopharmaceuticals (GA 67, Tc 99m pertechnetate) has previously been studied. We hypothesized that endoscopically documented esophagitis and/or gastric erosions could also be detected by using dipyridamole thallium-201 imaging and, if they were of sufficient accuracy, could serve as a useful, noninvasive screening test for esophagitis and/or gastric erosions., Methods: A pilot study was undertaken in 12 patients undergoing endoscopy for symptoms of GERD or dyspepsia. Esophagitis was defined as the presence of either erosions or ulceration and gastric erosions were defined as discrete mucosal breaks measuring > or = 1 mm. Dipyridamole thallium-201 imaging was performed the following day on all 12 patients. A standard dose of dipyridamole (0.56 mg/kg) was infused over 4 min, followed by a 3-mCi dose of thallium-201. Initial stress tomographic images and reinjection (1 mCi) resting tomographic images 3-4 h later were obtained using a gamma camera. Tomographic images were read blinded to the endoscopy results. Thallium-201 uptake was graded on a 0-3+ scale using the liver uptake as the internal comparative standard (2+ = uptake equal to the liver). Abnormal thallium uptake was defined as > or = 2+ in the area of the esophagus or stomach., Results: Seven women and five men (mean age 41 yr, range 25-60 yr) were studied. Eight patients were taking histamine-2 receptor antagonists and none were on proton pump inhibitors, or promotility agents. All five patients with endoscopic esophagitis had a positive thallium-201 tomographic image. Seven patients had no evidence of esophagitis, and three had positive thallium-201 tomograms. Dipyridamole thallium-201 imaging sensitivity, specificity, and positive and negative predictive values for esophagitis were 100%, 57%, 63%, and 100%, respectively. All three patients with gastric erosions had positive thallium-201 tomograms. Six of nine patients without gastric erosions had positive tomograms. The sensitivity, specificity, and positive and negative predictive values of DT 201 gastric erosions were 100%, 33%, 33%, and 100%, respectively., Conclusions: Dipyridamole thallium-201 tomographic imaging has good sensitivity (100%) in detecting esophagogastric mucosal erosions, but its poor specificity (33-57%) results in an unacceptable accuracy as a screening test. Additionally, the cost of radiopharmaceuticals requires that sensitivity and specificity be at least equal to that of endoscopy for this test to be clinically valuable as a screening test. However, a noninvasive test for these diseases is inherently appealing, and further research in this area seems to be warranted.

Background: Mediastinal malignancies may involve the esophagus, leading to esophageal stenosis and dysphagia. Rigid and self-expanding esophageal stents have been used for effective palliation, but their use in extrinsic, compressive lesions is controversial., Methods: A retrospective review of self-expanding Gianturco-Rösch Z-stents that were successfully placed in 13 patients with malignant esophageal obstruction due to extrinsic lesions., Results: All patients had an improvement in dysphagia of at least two dysphagia grades. The mean dysphagia grade fell from 3.15 to 0.62. Mean survival was 2.2 months. Early (within 48 hours) procedure-related complications occurred in 4 of 13 patients and consisted of minor, transient chest pain that resolved within 6 hours (3 patients) and endoscopic stent dislodgment into the stomach (1 patient). Late complications (> 48 hours) occurred in 2 patients and consisted of a partial proximal stent migration and the development of a benign stricture proximal to the stent. There was no procedural or stent related mortality., Conclusions: Esophageal obstruction and malignant dysphagia from extrinsic, compressive mediastinal malignancies can be effectively and safely palliated with self-expanding Gianturco- Rösch Z-stents.