1,518 research outputs found

    Predictions of the electrical conductivity and charging of the cloud particles in Jupiter's atmosphere

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    The electrical conductivity and electrical charge on cloud particles ( composed of ammonia, ammonium hydrosulfide, and water) in the atmosphere of Jupiter are computed for pressures between 5.5 and 0.1 bars. The source of ionization is galactic cosmic rays (GCR). The distribution of charge among the various reservoirs is a function of altitude and the total area of the aerosol particles. For pressures below 4 bars, the electrons are scavenged efficiently by the cloud particles, decreasing the electron- ion recombination rate and resulting in increased positive ion abundance over that in the absence of the particles. For the upper regions of each cloud layer, the area of the aerosols and the large diffusion rate of the electrons cause most aerosol particles to be negatively charged. Near the bases of the cloud layers, the larger total area of the aerosols causes most of the charge, positive and negative, to reside on particles. Where clouds are present, the reduction of the electron conductivity ranges from a factor of 30 at 0.1 bar to 10 4 at 4 bars. At pressures near 1 bar and 4 bars, the positive ion conductivity increases by a factor of 10 over that expected for the clear atmosphere. A parametric study of negative ions shows that they are likely to be insignificant. For altitudes below the 0.3- bar level the predicted positive and negative conductivities are well below the detection limit of the relaxation and mutual impedance instruments such as those employed on the Huygens entry probe

    Infrared spectroscopy of diatomic molecules - a fractional calculus approach

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    The eigenvalue spectrum of the fractional quantum harmonic oscillator is calculated numerically solving the fractional Schr\"odinger equation based on the Riemann and Caputo definition of a fractional derivative. The fractional approach allows a smooth transition between vibrational and rotational type spectra, which is shown to be an appropriate tool to analyze IR spectra of diatomic molecules.Comment: revised + extended version, 9 pages, 6 figure

    Late Miocene to early Pliocene biofacies of Wanganui and Taranaki Basins, New Zealand: Applications to paleoenvironmental and sequence stratigraphic analysis

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    The Matemateaonga Formation is late Miocene to early Pliocene (upper Tongaporutuan to lower Opoitian New Zealand Stages) in age. The formation comprises chiefly shellbeds, siliciclastic sandstone, and siltstone units and to a lesser extent non-marine and shallow marine conglomerate and rare paralic facies. The Matemateaonga Formation accumulated chiefly in shelf paleoenvironments during basement onlap and progradation of a late Miocene to early Pliocene continental margin wedge in the Wanganui and Taranaki Basins. The formation is strongly cyclothemic, being characterised by recurrent vertically stacked facies successions, bounded by sequence boundaries. These facies accumulated in a range of shoreface to mid-outer shelf paleoenvironments during conditions of successively oscillating sea level. This sequential repetition of facies and the biofacies they enclose are the result of sixth-order glacio-eustatic cyclicity. Macrofaunal associations have been identified from statistical analysis of macrofossil occurrences collected from multiple sequences. Each association is restricted to particular lithofacies and stratal positions and shows a consistent order and/or position within the sequences. This pattern of temporal paleoecologic change appears to be the result of lateral, facies-related shifting of broad biofacies belts, or habitat-tracking, in response to fluctuations of relative sea level, sediment flux, and other associated paleoenvironmental variables. The associations also show strong similarity in terms of their generic composition to biofacies identified in younger sedimentary strata and the modern marine benthic environment in New Zealand

    Ab initio Hartree-Fock Born effective charges of LiH, LiF, LiCl, NaF, and NaCl

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    We use the Berry-phase-based theory of macroscopic polarization of dielectric crystals formulated in terms of Wannier functions, and state-of-the-art Gaussian basis functions, to obtain benchmark ab initio Hartree-Fock values of the Born effective charges of ionic compounds LiH, LiF, LiCl, NaF, and NaCl. We find excellent agreement with the experimental values for all the compounds except LiCl and NaCl, for which the disagreement with the experiments is close to 10% and 16%, respectively. This may imply the importance of many-body effects in those systems.Comment: 11 pages, Revtex, 2 figures (included), to appear in Phys. Rev. B April 15, 200

    Methodological considerations in the analysis of fecal glucocorticoid metabolites in tufted capuchins (Cebus apella)

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    Analysis of fecal glucocorticoid (GC) metabolites has recently become the standard method to monitor adrenocortical activity in primates noninvasively. However, given variation in the production, metabolism, and excretion of GCs across species and even between sexes, there are no standard methods that are universally applicable. In particular, it is important to validate assays intended to measure GC production, test extraction and storage procedures, and consider the time course of GC metabolite excretion relative to the production and circulation of the native hormones. This study examines these four methodological aspects of fecal GC metabolite analysis in tufted capuchins (Cebus apella). Specifically, we conducted an adrenocorticotrophic hormone (ACTH) challenge on one male and one female capuchin to test the validity of four GC enzyme immunoassays (EIAs) and document the time course characterizing GC me- tabolite excretion in this species. In addition, we compare a common field-friendly technique for extracting fecal GC metabolites to an established laboratory extraction methodology and test for effects of storing “field extracts” for up to 1 yr. Results suggest that a corticosterone EIA is most sensitive to changes in GC production, provides reliable measures when extracted according to the field method, and measures GC metabolites which remain highly stable after even 12 mo of storage. Further, the time course of GC metabolite excretion is shorter than that described yet for any primate taxa. These results provide guidelines for studies of GCs in tufted capuchins, and underscore the importance of validating methods for fecal hormone analysis for each species of interest

    Phenotypic spectrum associated with de novo and inherited deletions and duplications at 16p11.2 in individuals ascertained for diagnosis of autism spectrum disorder

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    Background Recurrent microdeletions and microduplications of w555 kb at 16p11.2 confer susceptibility to autism spectrum disorder (ASD) in up to 1% of ASD patients. No physical or behavioural features have been identified that distinguish these individuals as having a distinct ASD subtype, but clinical data are limited. Methods We report five autistic probands identified by microarray analysis with copy number variation (CNV) of 16p11.2 (three deletions, two duplications). Each patient was assessed for ASD and dysmorphic features. We also describe a deletion positive 26-month-old female who has developmental delay (DD) and autistic features. Results Proband 1 (female with ASD, de novo deletion) is not dysmorphic. Proband 2 (male with autism, de novo deletion) and proband 3 and his brother (males with autism, inherited deletions) are dysmorphic, but the two probands do not resemble one another. The mother of proband 3 has mild mental retardation (MR), minor dysmorphism and meets the criteria for ASD. Proband 4 (dysmorphic autistic male, de novo duplication) had a congenital diaphragmatic hernia. Proband 5 (nondysmorphic ASD female with a duplication) has two apparently healthy duplication positive relatives. Probands 1 and 2 have deletion negative siblings with ASD and Asperger syndrome, respectively. Proband 6 (a female with DD and an inherited duplication) is dysmorphic, but has oligohydramnios sequence. Conclusions The phenotypic spectrum associated with CNV at 16p11.2 includes ASD, MR/DD and/or possibly other primary psychiatric disorders. Compared with the microduplications, the reciprocal microdeletions are more likely to be penetrant and to be associated with nonspecific major or minor dysmorphism. There are deletion positive ASD probands with a less severe phenotype than deletion negative ASD siblings underscoring the significant phenotypic heterogeneity.published_or_final_versio

    The Distribution and Origin of Smooth Plains on Mercury

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    Orbital images from the MESSENGER spacecraft show that ~27% of Mercury's surface is covered by smooth plains, the majority (greater than 65%) of which are interpreted to be volcanic in origin. Most smooth plains share the spectral characteristics of Mercury's northern smooth plains, suggesting they also share their magnesian alkali-basalt-like composition. A smaller fraction of smooth plains interpreted to be volcanic in nature have a lower reflectance and shallower spectral slope, suggesting more ultramafic compositions, an inference that implies high temperatures and high degrees of partial melting in magma source regions persisted through most of the duration of smooth plains formation. The knobby and hummocky plains surrounding the Caloris basin, known as Odin-type plains, occupy an additional 2% of Mercury’s surface. The morphology of these plains and their color and stratigraphic relationships suggest that they formed as Caloris ejecta, although such an origin is in conflict with a straightforward interpretation of crater size-frequency distributions. If some fraction is volcanic, this added area would substantially increase the abundance of relatively young effusive deposits inferred to have more mafic compositions. Smooth plains are widespread on Mercury, but they are more heavily concentrated in the north and in the hemisphere surrounding Caloris. No simple relationship between plains distribution and crustal thickness or radioactive element distribution is observed. A likely volcanic origin for some older terrain on Mercury suggests that the uneven distribution of smooth plains may indicate differences in the emplacement age of large-scale volcanic deposits rather than differences in crustal formational process

    Phytoestrogens

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    Collectively, plants contain several different families of natural products among which are compounds with weak estrogenic or antiestrogenic activity toward mammals. These compounds, termed phytoestrogens, include certain isoflavonoids, flavonoids, stilbenes, and lignans. The best-studied dietary phytoestrogens are the soy isoflavones and the flaxseed lignans. Their perceived health beneficial properties extend beyond hormone-dependent breast and prostate cancers and osteoporosis to include cognitive function, cardiovascular disease, immunity and inflammation, and reproduction and fertility. In the future, metabolic engineering of plants could generate novel and exquisitely controlled dietary sources with which to better assess the potential health beneficial effects of phytoestrogens

    Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis

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    On 2017 August 17, gravitational waves were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, optical and infrared light curves of SSS17a extending from 10.9 hours to 18 days post-merger. We constrain the radioactively-powered transient resulting from the ejection of neutron-rich material. The fast rise of the light curves, subsequent decay, and rapid color evolution are consistent with multiple ejecta components of differing lanthanide abundance. The late-time light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy elements, demonstrating that neutron star mergers play a role in r-process nucleosynthesis in the Universe.Comment: Accepted to Scienc
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