A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b

GJ 436b is a warm—approximately 800 kelvin—exoplanet that periodically eclipses its low-mass (half the mass of the Sun) host star, and is one of the few Neptune-mass planets that is amenable to detailed characterization. Previous observations have indicated that its atmosphere has a ratio of methane to carbon monoxide that is 10^5 times smaller than predicted by models for hydrogen-dominated atmospheres at these temperatures. A recent study proposed that this unusual chemistry could be explained if the planet’s atmosphere is significantly enhanced in elements heavier than hydrogen and helium. Here we report observations of GJ 436b’s atmosphere obtained during transit. The data indicate that the planet’s transmission spectrum is featureless, ruling out cloud-free, hydrogen-dominated atmosphere models with an extremely high significance of 48σ. The measured spectrum is consistent with either a layer of high cloud located at a pressure level of approximately one millibar or with a relatively hydrogen-poor (three per cent hydrogen and helium mass fraction) atmospheric composition

α-L-Aspartylglycine Monohydrate

C6H10N2O5, H2O, orthorhombic, P212121, a = 4·844 (5), b = 9·916 (3), c = 18·070(4) Å, V = 868·05 Å3, Z = 4, Dc = 1·59, Dm (flotation in chloroform/iodoform) = l·60 (1) Mg m-3; R1 = 0·040, R2 = 0·033 for 1088 observations. The dipeptide crystallizes as a zwitterion with the main-chain carboxyl ionized and the side-chain amino group protonated. The overall dipeptide conformation is highly extended and the molecule is extensively hydrogen bonded

α-L-Glutamylglycine

C7H12N 2O5, orthorhombic, P212121, a = 5·525(5), b = 12·565(4), c = 13·211(6) Å, Z = 4, Dc = l·48, Dm (flotation in chloroform/ methylene chloride) = 1·48(1) Mg m-3, R1 = 0·039, R2 = 0·040 for 1172 observations. The dipeptide crystallizes as a zwitterion with the main-chain carboxyl ionized and the amino terminus protonated. The conformation of the peptide group is trans; the glutamyl side chain is extended, but the carboxy terminus is held by hydrogen bonding in a non-extended conformation with a torsional angle ΦGly = -74.1°

Timing of primary tooth emergence among U.S. racial and ethnic groups

ObjectivesTo compare timing of tooth emergence among groups of American Indian (AI), Black and White children in the United States at 12 months of age.MethodsData were from two sources – a longitudinal study of a Northern Plains tribal community and a study with sites in Indiana, Iowa and North Carolina. For the Northern Plains study, all children (n = 223) were American Indian, while for the multisite study, children (n = 320) were from diverse racial groups. Analyses were limited to data from examinations conducted within 30 days of the child’s first birthday.ResultsAI children had significantly more teeth present (Mean: 7.8, Median: 8.0) than did Whites (4.4, 4.0, P < 0.001) or Blacks (4.5, 4.0, P < 0.001). No significant differences were detected between Black and White children (P = 0.58). There was no significant sex difference overall or within any of the racial groups.ConclusionsTooth emergence occurs at a younger age for AI children than it does for contemporary White or Black children in the United States.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135387/1/jphd12154.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135387/2/jphd12154_am.pd

Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b

Recent surveys have revealed that planets intermediate in size between Earth and Neptune (‘super-Earths’) are among the most common planets in the Galaxy. Atmospheric studies are the next step towards developing a comprehensive understanding of this new class of object. Much effort has been focused on using transmission spectroscopy to characterize the atmosphere of the super-Earth archetype GJ 1214b, but previous observations did not have sufficient precision to distinguish between two interpretations for the atmosphere. The planet’s atmosphere could be dominated by relatively heavy molecules, such as water (for example, a 100 per cent water vapour composition), or it could contain high-altitude clouds that obscure its lower layers. Here we report a measurement of the transmission spectrum of GJ 1214b at near-infrared wavelengths that definitively resolves this ambiguity. The data, obtained with the Hubble Space Telescope, are sufficiently precise to detect absorption features from a high mean-molecular-mass atmosphere. The observed spectrum, however, is featureless. We rule out cloud-free atmospheric models with compositions dominated by water, methane, carbon monoxide, nitrogen or carbon dioxide at greater than 5σ confidence. The planet’s atmosphere must contain clouds to be consistent with the data