Spitzer spectroscopy of circumstellar disks in the 5 Myr old upper Scorpius OB association

We present mid-infrared spectra between 5.2 and 38 μm for 26 disk-bearing members of the ~5 Myr old Upper Scorpius OB association obtained with the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope. We find clear evidence for changes in the spectral characteristics of dust emission between the early-type (B+A) and late-type (K+M) infrared excess stars. The early-type members exhibit featureless continuum excesses that become apparent redward of ~8 μm. In contrast, 10 and 20 μm silicate features or polycyclic aromatic hydrocarbon emission are present in all but one of the late-type excess members of Upper Scorpius. The strength of silicate emission among late-type Upper Scorpius members is spectral-type dependent, with the most prominent features being associated with K5-M2-type stars. By fitting the spectral energy distributions (SED) of a representative sample of low-mass stars with accretion disk models, we find that the SEDs are consistent with models having inner disk radii ranging from ~0.2 to 1.2 AU. Complementary high-resolution (R ~ 33,000) optical (λλ4800-9200) spectra for the Upper Scorpius excess stars were examined for signatures of gaseous accretion. Of the 35 infrared excess stars identified in Upper Scorpius, only seven (all late-type) exhibit definitive signatures of accretion. Mass-accretion rates (M) for these stars were estimated to range from 10^–11 to 10^–8.9 M⊙ yr^–1. Compared to Class II sources in Taurus-Auriga, the disk population in Upper Scorpius exhibits reduced levels of near- and mid-infrared excess emission and an order of magnitude lower mass-accretion rates. These results suggest that the disk structure has changed significantly over the 2-4 Myr in age separating these two stellar populations. The ubiquity of depleted inner disks in the Upper Scorpius excess sample implies that such disks are a common evolutionary pathway that persists for some time

Evidence for Mass-dependent Circumstellar Disk Evolution in the 5 Myr Old Upper Scorpius OB Association

We present 4.5, 8, and 16 µm photometry from the Spitzer Space Telescope for 204 stars in the Upper Scorpius OB association. The data are used to investigate the frequency and properties of circumstellar disks around stars with masses between ~0.1 and 20 M_☉ at an age of ~5 Myr. We identify 35 stars that have emission at 8 or 16 µm in excess of the, stellar photosphere. The lower mass stars (~0.1–1.2M_☉) appear surrounded by primordial optically thick disks based on, the excess emission characteristics. Starsmoremassive than ~1.8M_☉ have lower fractional excess luminosities suggesting, that the inner ~10 AU of the disk has been largely depleted of primordial material. None of the G and F stars (~1.2–1.8 M_☉) in our sample have an infrared excess at wavelengths ≤16 µm. These results indicate that the mechanisms for, dispersing primordial optically thick disks operate less efficiently, on average, for low-mass stars, and that longer timescales are available for the buildup of planetary systems in the terrestrial zone for stars with masses ≾1 M_☉

Quasielastic Scattering of Thermal Neutrons by CH3OH and CH3SH

We report measurements of the line broadening of thermal neutrons quasielastically scattered from room temperature methyl alcohol and methyl mercaptan in the liquid phase. The linewidths for CH3SH are found to be approximately twice those of CH3OH. This is interpreted to be additional evidence of the relative freedom of molecular motions and lack of hydrogen bonding in CH3SH. The linewidth data are discussed in terms of the simple diffusion model, and for methanol, in terms of a globular diffusion model. For methanol a diffusion constant of 3.25 × 10−5 cm2sec−1 and a diffusing globule mass of ∼3.5 molecules are in agreement with the data. An upper limit of D  =  6.5 × 10−5cm2sec−1D=6.5×10−5cm2sec−1 is found for the diffusion constant of CH3SH.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70369/2/JCPSA6-51-12-5543-1.pd

Effect of sequence and metal ions on UVB-induced anti cyclobutane pyrimidine dimer formation in human telomeric DNA sequence

Irradiation of G-quadruplex forming human telomeric DNA with ultraviolet B (UVB) light results in the formation of anti cyclobutane pyrimidine dimers (CPDs) between loop 1 and loop 3 in the presence of potassium ions but not sodium ions. This was unexpected because the sequences involved favor the nonphotoreactive hybrid conformations in K+ solution, whereas a potentially photoreactive basket conformation is favored in Na+ solution. To account for these contradictory results, it was proposed that the loops are too far apart in the basket conformation in Na+ solution but close enough in a two G-tetrad basket-like form 3 conformation that can form in K+ solution. In the current study, Na+ was still found to inhibit anti CPD formation in sequences designed to stabilize the form 3 conformation. Furthermore, anti CPD formation in K+ solution was slower for the sequence previously shown to exist primarily in the proposed photoreactive form 3 conformation than the sequence shown to exist primarily in a nonphotoreactive hybrid conformation. These results suggest that the form 3 conformation is not the principal photoreactive conformation, and that G-quadruplexes in K+ solution are dynamic and able to access photoreactive conformations more easily than in Na+ solution

An ALMA Constraint on the GSC 6214-210 B Circum-Substellar Accretion Disk Mass

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of GSC 6214-210 A and B, a solar-mass member of the 5-10 Myr Upper Scorpius association with a 15 $\pm$ 2 Mjup companion orbiting at $\approx$330 AU (2.2"). Previous photometry and spectroscopy spanning 0.3-5 $\mu$m revealed optical and thermal excess as well as strong H$\alpha$ and Pa~$\beta$ emission originating from a circum-substellar accretion disk around GSC 6214-210 B, making it the lowest mass companion with unambiguous evidence of a subdisk. Despite ALMA's unprecedented sensitivity and angular resolution, neither component was detected in our 880 $\mu$m (341 GHz) continuum observations down to a 3-$\sigma$ limit of 0.22 mJy/beam. The corresponding constraints on the dust mass and total mass are <0.15 Mearth and <0.05 Mjup, respectively, or <0.003% and <0.3% of the mass of GSC 6214-210 B itself assuming a 100:1 gas-to-dust ratio and characteristic dust temperature of 10-20 K. If the host star possesses a putative circum-stellar disk then at most it is a meager 0.0015% of the primary mass, implying that giant planet formation has certainly ceased in this system. Considering these limits and its current accretion rate, GSC 6214-210 B appears to be at the end stages of assembly and is not expected to gain any appreciable mass over the next few Myr.Comment: Accepted to ApJ

Physicochemical Properties and Catalytic Behavior of the Molecular Sieve SSZ-70

SSZ-70 is synthesized using 1,3-bis(isobutyl)imidazolium, 1,3-bis(cyclohexyl)imidazolium, and 1,3-bis(cycloheptyl)imidazolium structure directing agents (SDAs), and the solids obtained are characterized by powder X-ray diffraction (XRD), ^(29)Si magic angle spinning nuclear magnetic resonance (MAS NMR), electron microscopy, nitrogen and hydrocarbon adsorption, and thermogravimetric analyses. The physicochemical properties of SSZ-70 show that it is a new molecular sieve that has similarities to MWW-type materials. The catalytic behavior of SSZ-70 is evaluated through the use of the constraint index (CI) test. Distinct differences in the reactivity between Al-SSZ-70 and SSZ-25 (MWW) are observed and are the consequences of the structural differences between these two molecular sieves

PARASITOIDS AND PARASITES OF \u3ci\u3eSPODOPTERA FRUGIPERDA\u3c/i\u3e (LEPIDOPTERA: NOCTUIDAE) IN THE AMERICAS AND CARIBBEAN BASIN: AN INVENTORY

An inventory of parasitoids and parasites of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), was conducted using references describing parasitized FAW eggs, larvae, pupae and adults collected from different crops or habitats throughout the Americas and the Caribbean Basin. The crops and countries where these parasites were reported occurring in the Americas is also inventoried. Maize was the crop where the FAW was more frequently collected followed by rice. Overall, Chelonus insularis (Cresson) had the broadest natural distribution in the Americas. For the North American region C. insulares , Chelonus sp., and Euplectrus platyhypenae (Howard) were the most relevant parasitoids. In Central America, C. insularis was the most prevalent parasitoid, and in the South American region the most prevalent parasites were Archytas incertus (Macq.), A. marmoratus (Tns.), C. insularis , and Meteorus laphygmae (Viereck). Diapetimorpha introita (Cresson) is the most important pupal parasitoid of FAW occurring mainly in North America. An acugutturid, Noctuidonema guyanense (Remillet & Silvain), is the most important ectoparasitic nematode attacking adults of FAW and other noctuid moths in South and Southeastern US, and Mexico in North America, Caribbean Basin, Central America, and Northern South America

Successful unrelated donor cord blood transplantation for Glanzmann’s thrombasthenia

GT, a rare disorder of platelet function, can lead to life-threatening bleeding, particularly following the development of antiplatelet antibodies. Curative therapy includes HCT but previous reports are limited predominantly to matched siblings and have excluded CBT. Delayed or non-engraftment of platelets because of antiplatelet antibodies might be particularly concerning after CBT for GT. Here, we report two successful unrelated cord blood transplants for GT. Recurrent life-threatening bleeding was the primary indication for HCT, with one patient developing antiplatelet antibodies pre-HCT. Bleeding risks associated with delivery of the conditioning regimen and the toxicity that follows should be carefully considered, including tunneled central venous line catheter placement, inclusion of B cell-specific therapy to potentially decrease antiplatelet antibody production, and targeted busulfan dosing. This is the first report of successful unrelated cord blood HCT for GT and indicates that modifications to supportive care can improve the safety of this potentially curative therapy for patients with severe, life-threatening disease manifestations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78580/1/j.1399-3046.2009.01251.x.pd