744 research outputs found
meso-4,5-Diphenylimidazolidin-2-one
The crystal structure determination of the title compound, C15H14N2O, confirms the cis relationship between the phenyl groups at the 4- and 5-positions on the imidazolidine ring. The dihedral angle between the two phenyl rings is 48.14 (6)°. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link molecules into centrosymmetric dimers. These dimers are, in turn, linked into a two-dimensional network via weak N—H⋯π(arene) interactions and π–π stacking interactions with centroid–centroid distances of 3.6937 (11) Å
Interpretation of UV Absorption Lines in SN1006
We present a theoretical interpretation of the broad silicon and iron UV
absorption features observed with the Hubble Space Telescope in the spectrum of
the Schweizer-Middleditch star behind the remnant of Supernova 1006. These
features are caused by supernova ejecta in SN1006. We propose that the
redshifted SiII2 1260 A feature consists of both unshocked and shocked SiII.
The sharp red edge of the line at 7070 km/s indicates the position of the
reverse shock, while its Gaussian blue edge reveals shocked Si with a mean
velocity of 5050 km/s and a dispersion of 1240 km/s, implying a reverse shock
velocity of 2860 km/s. The measured velocities satisfy the energy jump
condition for a strong shock, provided that all the shock energy goes into
ions, with little or no collisionless heating of electrons. The line profiles
of the SiIII and SiIV absorption features indicate that they arise mostly from
shocked Si. The total mass of shocked and unshocked Si inferred from the SiII,
SiIII and SiIV profiles is M_Si = 0.25 \pm 0.01 Msun on the assumption of
spherical symmetry. Unshocked Si extends upwards from 5600 km/s. Although there
appears to be some Fe mixed with the Si at lower velocities < 7070 km/s, the
absence of FeII absorption with the same profile as the shocked SiII suggests
little Fe mixed with Si at higher (before being shocked) velocities. The column
density of shocked SiII is close to that expected for SiII undergoing steady
state collisional ionization behind the reverse shock, provided that the
electron to SiII ratio is low, from which we infer that most of the shocked Si
is likely to be of a fairly high degree of purity, unmixed with other elements.
We propose that the ambient interstellar density on the far side of SN1006 is
anomalously low compared to the density around the rest of the remnant. ThisComment: 24 pages, with 8 figures included. Accepted for publication in the
Astrophysical Journa
Phospho‐RNA‐seq: a modified small RNA‐seq method that reveals circulating mRNA and lncRNA fragments as potential biomarkers in human plasma
Extracellular RNAs (exRNAs) in biofluids have attracted great interest as potential biomarkers. Although extracellular microRNAs in blood plasma are extensively characterized, extracellular messenger RNA (mRNA) and long non‐coding RNA (lncRNA) studies are limited. We report that plasma contains fragmented mRNAs and lncRNAs that are missed by standard small RNA‐seq protocols due to lack of 5′ phosphate or presence of 3′ phosphate. These fragments were revealed using a modified protocol (“phospho‐RNA‐seq”) incorporating RNA treatment with T4‐polynucleotide kinase, which we compared with standard small RNA‐seq for sequencing synthetic RNAs with varied 5′ and 3′ ends, as well as human plasma exRNA. Analyzing phospho‐RNA‐seq data using a custom, high‐stringency bioinformatic pipeline, we identified mRNA/lncRNA transcriptome fingerprints in plasma, including tissue‐specific gene sets. In a longitudinal study of hematopoietic stem cell transplant patients, bone marrow‐ and liver‐enriched exRNA genes were tracked with bone marrow recovery and liver injury, respectively, providing proof‐of‐concept validation as a biomarker approach. By enabling access to an unexplored realm of mRNA and lncRNA fragments, phospho‐RNA‐seq opens up new possibilities for plasma transcriptomic biomarker development.SynopsisA modified RNA‐seq method (Phospho‐RNA‐seq) revealed a new population of mRNA/lncRNA fragments in plasma, including ones that track with disease. This opens up new possibilities for disease detection via RNA profiling of plasma and other biofluids.Phospho‐RNA‐seq reveals a large population of mRNA and long non‐coding RNA fragments in human plasma, which are missed by standard small RNA‐seq protocols that depend on target RNAs having a 5′ P and 3′ OH.Accurate detection of plasma mRNA and lncRNA fragments requires a stringent bioinformatic analysis pipeline to avoid false positive alignments to mRNA and lncRNA genes.Phospho‐RNA‐seq identified ensembles of tissue‐specific transcripts in plasma of hematopoietic stem cell transplant patients, which show co‐expression patterns that vary dynamically and track with pathophysiological processes.By enabling access to an unexplored space of extracellular mRNA and lncRNA fragments, phospho‐RNA‐seq opens up new possibilities for monitoring health and disease via transcriptome fragment profiling of plasma and potentially other biofluids.A modified RNA‐seq method reveals a large population of mRNA/lncRNA fragments in plasma that are missed by standard small RNA‐seq protocols including ones that are associated with disease.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/1/embj2019101695_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/2/embj2019101695-sup-0002-EVFigs.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/3/embj2019101695.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/4/embj2019101695-sup-0001-Appendix.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/5/embj2019101695.reviewer_comments.pd
An ellipsoidal mirror for focusing neutral atomic and molecular beams
Manipulation of atomic and molecular beams is essential to atom optics applications including atom lasers, atom lithography, atom interferometry and neutral atom microscopy. The manipulation of charge-neutral beams of limited polarizability, spin or excitation states remains problematic, but may be overcome by the development of novel diffractive or reflective optical elements. In this paper, we present the first experimental demonstration of atom focusing using an ellipsoidal mirror. The ellipsoidal mirror enables stigmatic off-axis focusing for the first time and we demonstrate focusing of a beam of neutral, ground-state helium atoms down to an approximately circular spot, (26.8±0.5) μm×(31.4±0.8) μm in size. The spot area is two orders of magnitude smaller than previous reflective focusing of atomic beams and is a critical milestone towards the construction of a high-intensity scanning helium microscope
An ellipsoidal mirror for focusing neutral atomic and molecular beams
Manipulation of atomic and molecular beams is essential to atom optics applications including atom lasers, atom lithography, atom interferometry and neutral atom microscopy. The manipulation of charge-neutral beams of limited polarizability, spin or excitation states remains problematic, but may be overcome by the development of novel diffractive or reflective optical elements. In this paper, we present the first experimental demonstration of atom focusing using an ellipsoidal mirror. The ellipsoidal mirror enables stigmatic off-axis focusing for the first time and we demonstrate focusing of a beam of neutral, ground-state helium atoms down to an approximately circular spot, (26.8±0.5) μm×(31.4±0.8) μm in size. The spot area is two orders of magnitude smaller than previous reflective focusing of atomic beams and is a critical milestone towards the construction of a high-intensity scanning helium microscope
Measurement of the Luminosity in the ZEUS Experiment at HERA II
The luminosity in the ZEUS detector was measured using photons from electron
bremsstrahlung. In 2001 the HERA collider was upgraded for operation at higher
luminosity. At the same time the luminosity-measuring system of the ZEUS
experiment was modified to tackle the expected higher photon rate and
synchrotron radiation. The existing lead-scintillator calorimeter was equipped
with radiation hard scintillator tiles and shielded against synchrotron
radiation. In addition, a magnetic spectrometer was installed to measure the
luminosity independently using photons converted in the beam-pipe exit window.
The redundancy provided a reliable and robust luminosity determination with a
systematic uncertainty of 1.7%. The experimental setup, the techniques used for
luminosity determination and the estimate of the systematic uncertainty are
reported.Comment: 25 pages, 11 figure
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