2,867 research outputs found
N-(4-Butanoyl-3-hydroxyphenyl)butanamide
The title compound, C14H19NO3, was prepared via the intramolecular rearrangement of 3-(butanoylamino)phenyl butanoate in the presence of anhydrous aluminium chloride. The near coplanarity of the aromatic ring, the amide group and the carbonyl group of the butanoyl fragment [N—C—C—C = −179.65 (17) and O—C—C—C = −178.34 (17)°] results from the intramolecular O—H⋯O and C—H⋯O hydrogen bonds. In the crystal, the molecules form a one-dimensional polymeric structure via N—H⋯O interactions between their amide groups
Two-pole structures demystified: chiral dynamics at work
In the past two decades, one of the most puzzling phenomena discovered in
hadron physics is that a nominal hadronic state can actually correspond to two
poles on the complex energy plane. This phenomenon was first noticed for the
, and then for and to a less extent for
. In this Letter, we show explicitly how the two-pole structures
emerge from the underlying chiral dynamics describing the coupled-channel
interactions between heavy matter particles and Nambu-Goldstone bosons. In
particular, the fact that two poles appear between the two dominant coupled
channels can be attributed to the particular form of the leading order chiral
potentials of the Weinberg-Tomozawa form. Their lineshapes overlap with each
other because the degeneracy of the two coupled channels is only broken by
explicit chiral symmetry breaking of higher order. We predict that for
light-quark~(pion) masses heavier than their physical values, the two-pole
structures disappear, which can be easily verified by future lattice QCD
simulations. Furthermore, we anticipate similar two-pole structures in other
systems, such as the isopin coupled channel,
which await for experimental discoveries.Comment: 5 pages, 4 figure
Understanding the organic micropollutants transport mechanisms in the fertilizer-drawn forward osmosis process
© 2019 Elsevier Ltd We systematically investigated the transport mechanisms of organic micropollutants (OMPs) in a fertilizer-drawn forward osmosis (FDFO) membrane process. Four representative OMPs, i.e., atenolol, atrazine, primidone, and caffeine, were chosen for their different molecular weights and structural characteristics. All the FDFO experiments were conducted with the membrane active layer on the feed solution (FS) side using three different fertilizer draw solutions (DS): potassium chloride (KCl), monoammonium phosphate (MAP), and diammonium phosphate (DAP) due to their different properties (i.e., osmotic pressure, diffusivity, viscosity and solution pH). Using KCl as the DS resulted in both the highest water flux and the highest reverse solute flux (RSF), while MAP and DAP resulted in similar water fluxes with varying RSF. The pH of the FS increased with DAP as the DS due to the reverse diffusion of NH4+ ions from the DS toward the FS, while for MAP and DAP DS, the pH of the FS was not impacted. The OMPs transport behavior (OMPs flux) was evaluated and compared with a simulated OMPs flux obtained via the pore-hindrance transport model to identify the effects of the OMPs structural properties. When MAP was used as DS, the OMPs flux was dominantly influenced by the physicochemical properties (i.e., hydrophobicity and surface charge). Those OMPs with positive charge and more hydrophobic, exhibited higher forward OMP fluxes. With DAP as the DS, the more hydrated FO membrane (caused by increased pH) as well as the enhanced RSF hindered OMPs transport through the FO membrane. With KCl as DS, the structural properties of the OMPs were dominant factors in the OMPs flux, however the higher RSF of the KCl draw solute may likely hamper the OMPs transport through the membrane especially those with higher MW (e.g., atenolol). The pore-hindrance model can be instrumental in understanding the effects of the hydrodynamic properties and the surface properties on the OMPs transport behaviors
Production of and in decays as and molecules
The molecular nature of and have been
extensively studied from the perspective of their masses, decay properties, and
production rates. In this work, we study the weak decays of and by
invoking triangle diagrams where the meson first decays weakly into
and (), and then the
and are dynamically generated by the
final-state interactions of and via
exchanges of and mesons. The obtained absolute branching
fractions of Br are in reasonable
agreement with the experimental data, while the branching fractions of Br are smaller than the experimental central
values by almost a factor of two to three. We tentatively attribute such a
discrepancy to either reaction mechanisms missing in the present work or the
likely existence of a relatively larger component in the
wave function.Comment: 17 pages, 4 figure
Integrated Filtering Microstrip Duplex Antenna Array with High Isolation
This paper presents a 2 × 1 integrated filtering microstrip duplex antenna array with high isolation and same polarization. The antenna consists of two radiating patches fed by two T-shaped probes and a power distributing duplex network (PDDN). The PDDN is composed of two bandstop filters and a 180-degree phase shift power divider. And the PDDN is designed to achieve the functions of power division, frequency selectivity, and port isolation. A Transmission Line (TL) model is adopted to design the PDDN, and the detailed synthesis procedure is presented. For demonstration, the proposed antenna is designed and fabricated. The implemented antenna achieves an average gain of 10 dBi, a cross-polarization ratio of 20 dB, and an isolation of 35 dB within the operation band
Silicon nitride metalenses for unpolarized high-NA visible imaging
As one of nanoscale planar structures, metasurface has shown excellent
superiorities on manipulating light intensity, phase and/or polarization with
specially designed nanoposts pattern. It allows to miniature a bulky optical
lens into the chip-size metalens with wavelength-order thickness, playing an
unprecedented role in visible imaging systems (e.g. ultrawide-angle lens and
telephoto). However, a CMOS-compatible metalens has yet to be achieved in the
visible region due to the limitation on material properties such as
transmission and compatibility. Here, we experimentally demonstrate a divergent
metalens based on silicon nitride platform with large numerical aperture
(NA~0.98) and high transmission (~0.8) for unpolarized visible light,
fabricated by a 695-nm-thick hexagonal silicon nitride array with a minimum
space of 42 nm between adjacent nanoposts. Nearly diffraction-limit virtual
focus spots are achieved within the visible region. Such metalens enables to
shrink objects into a micro-scale size field of view as small as a single-mode
fiber core. Furthermore, a macroscopic metalens with 1-cm-diameter is also
realized including over half billion nanoposts, showing a potential application
of wide viewing-angle functionality. Thanks to the high-transmission and
CMOS-compatibility of silicon nitride, our findings may open a new door for the
miniaturization of optical lenses in the fields of optical fibers,
microendoscopes, smart phones, aerial cameras, beam shaping, and other
integrated on-chip devices.Comment: 16 pages, 7 figure
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