Identification and characterization of catalytic active sites are the prerequisites for an atomic-level understanding of the catalytic mechanism and rational design of high-performance heterogeneous catalysts. Indirect evidence in recent reports suggests that platinum (Pt) single atoms are exceptionally active catalytic sites. We demonstrate that infrared spectroscopy can be a fast and convenient characterization method with which to directly distinguish and quantify Pt single atoms from nanoparticles. In addition, we directly observe that only Pt nanoparticles show activity for carbon monoxide (CO) oxidation and water-gas shift at low temperatures, whereas Pt single atoms behave as spectators. The lack of catalytic activity of Pt single atoms can be partly attributed to the strong binding of CO molecules.

The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey is a new survey of Galactic 13 CO J ¼ 1 ! 0 emission. The survey used the SEQUOIA multipixel array on the Five College Radio Astronomy Observatory 14 m telescope to cover a longitude range of l ¼ 18 55N7 and a latitude range of jbj < 1 , a total of 75.4 deg 2 . Using both position-switching and On-The-Fly mapping modes, we achieved an angular sampling of 22 00 , better than half of the telescope's 46 00 angular resolution. The survey's velocity coverage is À5 to 135 km s À1 for Galactic longitudes l 40 and À5 to 85 km s À1 for Galactic longitudes l > 40 . At the velocity resolution of 0.21 km s À1 , the typical rms sensitivity is (T Ã A ) $ 0:13 K. The survey comprises a total of 1,993,522 spectra. We show integrated intensity images (zeroth moment maps), channel maps, position-velocity diagrams, and an average spectrum of the completed survey data set. We also discuss the telescope and instrumental parameters, the observing modes, the data reduction processes, and the emission and noise characteristics of the data set. The Galactic Ring Survey data are available to the community online or in DVD form by request.

Kinematic distances to 750 molecular clouds identified in the 13 CO J = 1 → 0 Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (BU-FCRAO GRS) are derived assuming the Clemens rotation curve of the Galaxy. The kinematic distance ambiguity is resolved by examining the presence of HI self-absorption toward the 13 CO emission peak of each cloud using the Very Large Array Galactic Plane Survey (VGPS). We also identify 21 cm continuum sources embedded in the GRS clouds in order to use absorption features in the HI 21 cm continuum to distinguish between near and far kinematic distances. The Galactic distribution of GRS clouds is consistent with a four-arm model of the Milky Way. The locations of the Scutum-Crux and Perseus arms traced by GRS clouds match star count data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) star-count data. We conclude that molecular clouds must form in spiral arms and be short-lived (lifetimes < 10 7 yr) in order to explain the absence of massive, 13 CO bright molecular clouds in the inter-arm space.

The Boston University-Five College Radio Astronomy Observatory (BU-FCRAO) Galactic Ring Survey (GRS) of 13 CO J = 1 → 0 emission covers Galactic longitudes 18• < < 55.• 7 and Galactic latitudes |b| 1 • . Using the SEQUOIA array on the FCRAO 14 m telescope, the GRS fully sampled the 13 CO Galactic emission (46 angular resolution on a 22 grid) and achieved a spectral resolution of 0.21 km s −1 . Because the GRS uses 13 CO, an optically thin tracer, rather than 12 CO, an optically thick tracer, the GRS allows a much better determination of column density and also a cleaner separation of velocity components along a line of sight. With this homogeneous, fully sampled survey of 13 CO emission, we have identified 829 molecular clouds and 6124 clumps throughout the inner Galaxy using the CLUMPFIND algorithm. Here we present details of the catalog and a preliminary analysis of the properties of the molecular clouds and their clumps. Moreover, we compare clouds inside and outside of the 5 kpc ring and find that clouds within the ring typically have warmer temperatures, higher column densities, larger areas, and more clumps compared with clouds located outside the ring. This is expected if these clouds are actively forming stars. This catalog provides a useful tool for the study of molecular clouds and their embedded young stellar objects.

Supported metal oxide based olefin metathesis catalysts are widely used in the chemical industry. In comparison to their organometallic catalyst cousins, the oxide catalysts have much lower activity due to the very small fraction of active sites. We report that a simple pretreatment of MoO3/SiO2 and WO3/SiO2 under an olefin-containing atmosphere at elevated temperatures leads to a 100–1000-fold increase in the low-temperature propylene metathesis activity. The performance of these catalysts is comparable with those of the well-defined organometallic catalysts. Unprecedentedly, the catalyst can be easily regenerated by inert gas purging at elevated temperatures. Furthermore, using UV resonance Raman spectroscopy and electron microscopy, we provide strong evidence that the active sites for MoO3/SiO2 are derived from monomeric Mo­(O)2 dioxo species.