482 research outputs found
Black Writing Ink Analysis By Direct Infusion Electrospray Mass Spectroscopy
An optimized method of extraction, an instrumental analysis method and data analysis was proposed for black writing inks based on direct infusion electrospray-mass spectrometry (ESI-MS). The sampling and analysis method is both minimally destructive and able to assess differences in inks from a reference collection of thirty ballpoint, gel, and rollerball inks. The methanol extracts of ink on paper samples were analyzed with three direct infusion (ESI-MS) methods. Each method varied scan voltage negative and positive, ESI fragmentor applied voltage (+120V, +0V, and -120V), and mobile phase additive. Direct infusion ESI-MS analysis, followed by pair-wise comparisons of the observed ion data in binary form allowed inks to be distinguished from each other. The photobleaching of the dye Basic Violet 3 (BV3) in ink-onpaper samples was examined to determine the use of degradation products as a marker of the age of the writing sample. The extent of photobleaching of BV3 was determined using several illumination sources. Pair-wise comparison of observed ion data was able to distinguish 29 of 30 ink samples using the combined three instrumental methods. Out of 435 pair-wise comparisons 429 pairs could be discriminated from each other using the combined three methods. This is a 98.6% discrimination with the combined analysis schem
Simulating multiple merger pathways to the central kinematics of early-type galaxies
Two-dimensional integral field surveys such as ATLAS^3D are producing rich
observational data sets yielding insights into galaxy formation. These new
kinematic observations have highlighted the need to understand the evolutionary
mechanisms leading to a spectrum of fast-rotators and slow-rotators in
early-type galaxies. We address the formation of slow and fast rotators through
a series of controlled, comprehensive hydrodynamical simulations sampling
idealized galaxy merger scenarios constructed from model spiral galaxies.
Idealized and controlled simulations of this sort complement the more
'realistic' cosmological simulations by isolating and analyzing the effects of
specific parameters, as we do in this paper. We recreate minor and major binary
mergers, binary merger trees with multiple progenitors, and multiple sequential
mergers. Within each of these categories of formation history, we correlate
progenitor gas fraction, mass ratio, orbital pericenter, orbital ellipticity,
and spin with remnant kinematic properties. We create kinematic profiles of
these 95 simulations comparable to ATLAS^3D data. By constructing remnant
profiles of the projected specific angular momentum (lambda_R = /
, triaxiality, and measuring the incidences of kinematic
twists and kinematically decoupled cores, we distinguish between varying
formation scenarios. We find that binary mergers nearly always form fast
rotators. Slow rotators can be formed from zero initial angular momentum
configurations and gas-poor mergers, but are not as round as the ATLAS^3D
galaxies. Remnants of binary merger trees are triaxial slow rotators.
Sequential mergers form round slow rotators that most resemble the ATLAS^3D
rotators.Comment: MNRAS, in press, 12 pages, 15 figure
Stereoselective synthesis of highly substituted tetrahydrofurans by diverted carbene O–H insertion reaction
Copper or rhodium catalyzed reaction of diazocarbonyl compounds with β-hydroxyketones gives highly substituted tetrahydrofurans with excellent diastereoselectivity, under mild conditions, in a single step process that starts as a carbene O–H insertion reaction but is diverted by an intramolecular aldol reaction
Stereoselective synthesis of highly substituted tetrahydrofurans by diverted carbene O–H insertion reaction
Copper or rhodium catalyzed reaction of diazocarbonyl compounds with β-hydroxyketones gives highly substituted tetrahydrofurans with excellent diastereoselectivity, under mild conditions, in a single step process that starts as a carbene O–H insertion reaction but is diverted by an intramolecular aldol reaction
Diverse Structural Evolution at z > 1 in Cosmologically Simulated Galaxies
From mock Hubble Space Telescope images, we quantify non-parametric
statistics of galaxy morphology, thereby predicting the emergence of
relationships among stellar mass, star formation, and observed rest-frame
optical structure at 1 < z < 3. We measure automated diagnostics of galaxy
morphology in cosmological simulations of the formation of 22 central galaxies
with 9.3 < log10 M_*/M_sun < 10.7. These high-spatial-resolution zoom-in
calculations enable accurate modeling of the rest-frame UV and optical
morphology. Even with small numbers of galaxies, we find that structural
evolution is neither universal nor monotonic: galaxy interactions can trigger
either bulge or disc formation, and optically bulge-dominated galaxies at this
mass may not remain so forever. Simulated galaxies with M_* > 10^10 M_sun
contain relatively more disc-dominated light profiles than those with lower
mass, reflecting significant disc brightening in some haloes at 1 < z < 2. By
this epoch, simulated galaxies with specific star formation rates below 10^-9.7
yr^-1 are more likely than normal star-formers to have a broader mix of
structural types, especially at M_* > 10^10 M_sun. We analyze a cosmological
major merger at z ~ 1.5 and find that the newly proposed MID morphology
diagnostics trace later merger stages while G-M20 trace earlier ones. MID is
sensitive also to clumpy star-forming discs. The observability time of typical
MID-enhanced events in our simulation sample is less than 100 Myr. A larger
sample of cosmological assembly histories may be required to calibrate such
diagnostics in the face of their sensitivity to viewing angle, segmentation
algorithm, and various phenomena such as clumpy star formation and minor
mergers.Comment: 23 pages, 16 figures, MNRAS accepted versio
Total synthesis of the cyclic dodecapeptides wewakazole and wewakazole B
The cyclic dodecapeptides wewakazole and wewakazole B have been synthesized by a divergent strategy via a common tris-proline containing oxazole octapeptide and two separate bisoxazole containing tetrapeptide units, followed by peptide coupling and macrocyclization. The three oxazole amino acid fragments are readily accessible by rhodium(II)-catalysed amide N–H insertion of diazocarbonyl compounds, or by the cycloaddition of rhodium carbenoids with nitriles
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