2,917 research outputs found
Feasibility of using Non-Contrast Spoiled Gradient Echo Magnetic Resonance Fingerprinting for the Quantification of Cerebral Blood Volume
Benzobisoxazole cruciforms: a tunable, cross-conjugated platform for the generation of deep blue OLED materials
Four new cross-conjugated small molecules based on a central benzo[1,2-d:4,5-dâČ]bisoxazole moiety possessing semi-independently tunable HOMO and LUMO levels were synthesized and the properties of these materials were evaluated experimentally and theoretically. The molecules were thermally stable with 5% weight loss occurring well above 350 °C. The cruciforms all exhibited blue emission in solution ranging from 433â450 nm. Hostâguest OLEDs fabricated from various concentrations of these materials using the small molecule host 4,4âČ-bis(9-carbazolyl)-biphenyl (CBP) exhibited deep blue-emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.15 †x †0.17, 0.05 †y †0.11), and maximum luminance efficiencies as high as âŒ2 cd Aâ1. These results demonstrate the potential of benzobisoxazole cruciforms as emitters for developing high-performance deep blue OLEDs.We would like to thank Dr Sarah Cady, Dr Kamel Harrata and Mr Steven Veysey of Iowa State University (ISU) Chemical Instrumentation Facility for compound analysis. We thank Eeshita Manna for technical assistance. We also thank the National Science Foundation (CHE-1413173) for financial support of this work. RK and JS were partially supported by Basic Energy Sciences, Division of Materials Science and Engineering, USDOE. Ames Laboratory is operated by Iowa State University for the US Department of Energy (USDOE) under Contract No. DE-AC 02-07CH11358. Computational resources were provided in part by the MERCURY consortium (http://mercuryconsortium.org/) under NSF grants CHE-0116435, CHE-0521063, CHE-0849677, and CHE-1229354. (CHE-1413173 - National Science Foundation; Basic Energy Sciences, Division of Materials Science and Engineering, USDOE; DE-AC 02-07CH11358 - Iowa State University for the US Department of Energy (USDOE); CHE-0116435 - MERCURY consortium under NSF; CHE-0521063 - MERCURY consortium under NSF; CHE-0849677 - MERCURY consortium under NSF; CHE-1229354 - MERCURY consortium under NSF)http://pubs.rsc.org/en/Content/ArticleLanding/2016/TC/C5TC03622D#!divAbstractPublished versio
Issues and Ramifications in Quantized Fractal Space Time: An Interface with Quantum Superstrings
Recently a stochastic underpinning for space time has been considered, what
may be called Quantized Fractal Space Time. This leads us to a number of very
interesting consequences which are testable, and also provides a rationale for
several otherwise inexplicable features in Particle Physics and Cosmology.
These matters are investigated in the present paper.Comment: 27 pages, TeX, This is from the forthcoming book The Chaotic Univers
Effects of Rotation on the Minimum Mass of Primordial Progenitors of Pair Instability Supernovae
The issue of which stars may reach the conditions of electron/positron pair
formation instability is of importance to understand the final evolution both
of the first stars and of contemporary stars. The criterion to enter the pair
instability regime in density and temperature is basically controlled by the
mass of the oxygen core. The main sequence masses that produce a given oxygen
core mass are, in turn, dependent on metallicity, mass loss, and convective and
rotationally-induced mixing. We examine the evolution of massive stars to
determine the minimum main sequence mass that can encounter pair-instability
effects, either a pulsational pair instability (PPISN) or a full-fledged
pair-instability supernova (PISN). We concentrate on zero-metallicity stars
with no mass loss subject to the Schwarzschild criterion for convective
instability, but also explore solar metallicity and mass loss and the Ledoux
criterion. As expected, for sufficiently strong rotationally-induced mixing,
the minimum main sequence mass is encountered for conditions that induce
effectively homogeneous evolution such that the original mass is converted
almost entirely to helium and then to oxygen. For this case, we find that the
minimum main sequence mass is ~40 Msun to encounter PPISN and ~65 Msun to
encounter a PISN. When mass-loss is taken into account those mass limits become
~50 Msun for PPISN and ~80 Msun for PISN progenitors. The implications of these
results for the first stars and for contemporary supernovae is discussed.Comment: 23 pages, 8 figure
Quantum phase properties of two-mode Jaynes-Cummings model for Schr\"odinger-cat states: interference and entanglement
In this paper we investigate the quantum phase properties for the coherent
superposition states (Schr\"odinger-cat states) for two-mode multiphoton
Jaynes-Cummings model in the framework of the Pegg-Barnett formalism. We also
demonstrate the behavior of the Wigner () function at the phase space
origin. We obtain many interesting results such as there is a clear
relationship between the revival-collapse phenomenon occurring in the atomic
inversion (as well as in the evolution of the function) and the behavior of
the phase distribution of both the single-mode and two-mode cases. Furthermore,
we find that the phase variances of the single-mode case can exhibit
revival-collapse phenomenon about the long-time behavior. We show that such
behavior occurs for interaction time several times smaller than that of the
single-mode Jaynes-Cummings model.Comment: 23, 8 figure
Star formation histories of dwarf galaxies in the FIRE simulations: dependence on mass and Local Group environment
We study star formation histories (SFHs) of dwarf galaxies
(stellar mass ) from FIRE-2 cosmological zoom-in
simulations. We compare dwarfs around individual Milky Way (MW)-mass galaxies,
dwarfs in Local Group (LG)-like environments, and true field (i.e. isolated)
dwarf galaxies. We reproduce observed trends wherein higher-mass dwarfs quench
later (if at all), regardless of environment. We also identify differences
between the environments, both in terms of "satellite vs. central" and "LG vs.
individual MWvs. isolated dwarf central." Around the individual MW-mass hosts,
we recover the result expected from environmental quenching: central galaxies
in the "near field" have more extended SFHs than their satellite counterparts,
with the former more closely resemble isolated ("true field") dwarfs (though
near-field centrals are still somewhat earlier forming). However, this
difference is muted in the LG-like environments, where both near-field centrals
and satellites have similar SFHs, which resemble satellites of single MW-mass
hosts. This distinction is strongest for but
exists at other masses. Our results suggest that the paired halo nature of the
LG may regulate star formation in dwarf galaxies even beyond the virial radii
of the MW and Andromeda. Caution is needed when comparing zoom-in simulations
targeting isolated dwarf galaxies against observed dwarf galaxies in the LG.Comment: Main text: 11 pages, 8 figures; appendices: 4 pages, 4 figures.
Submitted to MNRAS; comments welcom
A review of size and geometrical factors influencing resonant frequencies in metamaterials
Although metamaterials and so-called left-handed media have originated from theoretical considerations, it is only by their practical fabrication and the measurement of their properties that they have gained credibility and can fulfil the potential of their predicted properties. In this review we consider some of the more generally applicable fabrication methods and changes in geometry as they have progressed, exhibiting resonant frequencies ranging from radio waves to the visible optical region
Fast in-situ annealing stage coupled with EBSD: A suitable tool to observe quick recrystallization mechanisms
The Role of Electron Captures in Chandrasekhar Mass Models for Type Ia Supernovae
The Chandrasekhar mass model for Type Ia Supernovae (SNe Ia) has received
increasing support from recent comparisons of observations with light curve
predictions and modeling of synthetic spectra. It explains SN Ia events via
thermonuclear explosions of accreting white dwarfs in binary stellar systems,
being caused by central carbon ignition when the white dwarf approaches the
Chandrasekhar mass. As the electron gas in white dwarfs is degenerate,
characterized by high Fermi energies for the high density regions in the
center, electron capture on intermediate mass and Fe-group nuclei plays an
important role in explosive burning. Electron capture affects the central
electron fraction Y_e, which determines the composition of the ejecta from such
explosions. Up to the present, astrophysical tabulations based on shell model
matrix elements were only available for light nuclei in the sd-shell. Recently
new Shell Model Monte Carlo (SMMC) and large-scale shell model diagonalization
calculations have also been performed for pf-shell nuclei. These lead in
general to a reduction of electron capture rates in comparison with previous,
more phenomenological, approaches. Making use of these new shell model based
rates, we present the first results for the composition of Fe-group nuclei
produced in the central regions of SNe Ia and possible changes in the
constraints on model parameters like ignition densities and burning front
speeds.Comment: 26 pages, 8 figures, submitted to Ap
Meat tenderness: advances in biology, biochemistry, molecular mechanisms and new technologies
Meat tenderness is an important quality trait critical to consumer acceptance, and determines satisfaction, repeat purchase and willingness-to-pay premium prices. Recent advances in tenderness research from a variety of perspectives are presented. Our understanding of molecular factors influencing tenderization are discussed in relation to glycolysis, calcium release, protease activation, apoptosis and heat shock proteins, the use of proteomic analysis for monitoring changes, proteomic biomarkers and oxidative/nitrosative stress. Each of these structural, metabolic and molecular determinants of meat tenderness are then discussed in greater detail in relation to animal variation, postmortem influences, and changes during cooking, with a focus on recent advances. Innovations in postmortem technologies and enzymes for meat tenderization are discussed including their potential commercial application. Continued success of the meat industry relies on ongoing advances in our understanding, and in industry innovation. The recent advances in fundamental and applied research on meat tenderness in relation to the various sectors of the supply chain will enable such innovation
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