4,060 research outputs found
Calculated line lists for H216O and H218O with extensive comparisons to theoretical and experimental sources including the HITRAN2016 database
New line lists are presented for the two most abundant water isotopologues; H216O and H218O. The H216O line list extends to 25710 cm with intensity stabilities provided via ratios of calculated intensities obtained from two different semi-empirical potential energy surfaces. The line list for H218O extends to 20000 cm. The minimum intensity considered for all is cm molecule at 296 K, assuming 100% abundance for each isotopologue. Fluctuation of calculated intensities caused by changes in the underlying potential energy are found to be significant, particularly for weak transitions. Direct comparisons are made against eighteen different sources of line intensities, both experimental and theoretical, many of which are used within the HITRAN2016 database. With some exceptions, there is excellent agreement between our line lists and the experimental intensities in HITRAN2016. In the infrared region, many H216O bands which exhibit intensity differences of 5–10% between to the most recent ’POKAZATEL’ line list (Polyansky et al., [Mon. Not. Roy. Astron. Soc. 480, 2597 (2018)] and observation, are now generally predicted to within 1%. For H218O, there are systematic differences in the strongest intensities calculated in this work versus those obtained from semi-empirical calculations. In the visible, computed cross sections show smaller residuals between our work and both HITRAN2016 and HITEMP2010 than POKAZATEL. While our line list accurately reproduces HITEMP2010 cross sections in the observed region, residuals produced from this comparison do however highlight the need to update line positions in the visible spectrum of HITEMP2010. These line lists will be used to update many transition intensities and line positions in the HITRAN2016 database
An off-board quantum point contact as a sensitive detector of cantilever motion
Recent advances in the fabrication of microelectromechanical systems (MEMS)
and their evolution into nanoelectromechanical systems (NEMS) have allowed
researchers to measure extremely small forces, masses, and displacements. In
particular, researchers have developed position transducers with resolution
approaching the uncertainty limit set by quantum mechanics. The achievement of
such resolution has implications not only for the detection of quantum behavior
in mechanical systems, but also for a variety of other precision experiments
including the bounding of deviations from Newtonian gravity at short distances
and the measurement of single spins. Here we demonstrate the use of a quantum
point contact (QPC) as a sensitive displacement detector capable of sensing the
low-temperature thermal motion of a nearby micromechanical cantilever.
Advantages of this approach include versatility due to its off-board design,
compatibility with nanoscale oscillators, and, with further development, the
potential to achieve quantum limited displacement detection.Comment: 5 pages, 5 figure
Searching for O in the SMC:Constraints on Oxygen Chemistry at Low Metallicities
We present a 39 h integration with the Odin satellite on the ground-state
118.75 GHz line of O2 towards the region of strongest molecular emission in the
Small Magellanic Cloud. Our 3sigma upper limit to the O2 integrated intensity
of <0.049 K km/s in a 9'(160 pc) diameter beam corresponds to an upper limit on
the O2/H2 abundance ratio of <1.3E-6. Although a factor of 20 above the best
limit on the O2 abundance obtained for a Galactic source, our result has
interesting implications for understanding oxygen chemistry at sub-solar metal
abundances. We compare our abundance limit to a variety of astrochemical models
and find that, at low metallicities, the low O2 abundance is most likely
produced by the effects of photo-dissociation on molecular cloud structure.
Freeze-out of molecules onto dust grains may also be consistent with the
observed abundance limit, although such models have not yet been run at
sub-solar initial metallicities.Comment: 4 pages, accepted to A&A Letter
Seasonal winter forecasts and the stratosphere
Published© 2016 Royal Meteorological Society. We investigate seasonal forecasts of the winter North Atlantic Oscillation (NAO) and their relationship with the stratosphere. Climatological frequencies of sudden stratospheric warming (SSW) and strong polar vortex (SPV) events are well represented and the predicted risk of events varies between 25 and 90% from winter to winter, indicating predictability beyond the deterministic range. The risk of SSW and SPV events relates to predicted NAO as expected, with NAO shifts of -6.5 and +4.8hPa in forecast members containing SSW and SPV events. Most striking of all is that forecast skill of the surface winter NAO vanishes from these hindcasts if members containing SSW events are excluded.This work was supported by the Joint DECC/Defra Met Office
Hadley Centre Climate Programme (GA01101), the UK Public
Weather Service research program and the European Union
Framework 7 SPECS project. The contribution of AYK is funded
by FMI’s tenure track program and the Academy of Finland
under grant 286298
Applying Recent Argumentation Methods to Some Ancient Examples of Plausible Reasoning
Plausible (eikotic) reasoning known from ancient Greek (late Academic) skeptical philosophy is shown to be a clear notion that can be analyzed by argu- mentation methods, and that is important for argumentation studies. It is shown how there is a continuous thread running from the Sophists to the skeptical philosopher Carneades, through remarks of Locke and Bentham on the subject, to recent research in artificial intelligence. Eleven characteristics of plausible reasoning are specified by analyzing key examples of it recognized as important in ancient Greek skeptical philosophy using an artificial intelligence model called the Carneades Argumentation System (CAS). By applying CAS to ancient examples it is shown how plausible reasoning is especially useful for gaining a better understanding of evidential reasoning in law, and argued that it can also be applied to everyday argumentation. Our analysis of the snake and rope example of Carneades is also used to point out some ways CAS needs to be extended if it is to more fully model the views of this ancient philosopher on argumentation
Open Problems on Central Simple Algebras
We provide a survey of past research and a list of open problems regarding
central simple algebras and the Brauer group over a field, intended both for
experts and for beginners.Comment: v2 has some small revisions to the text. Some items are re-numbered,
compared to v
Antioxidant Activity of the Phenolic Leaf Extracts from Monechma ciliatum in Stabilization of Corn Oil
The total phenolic content and the antioxidan potential of methanolic extract (ME), ethyl acetate extract (EAE), and hexane extract (HE) from Monechma ciliatum leaves (MCL) were evaluated. The Folin-Ciocalteu, b-carotene bleaching, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and the accelerated oxidation methods were used for evaluation. Both the extraction yield and the antioxidant activity (AOA) were strongly dependent on the solvent. Among the extracts, ME exhibited highest total phenolic compounds (TPC) and IC50 values for DPPH, followed by EAE and HE, respectively. Peroxide value (PV), anisidine value (AV) conjugated dienes (CD), and thiobarbituric acid reactive substances (TBARS) were taken as the parameters for evaluation of stabilization efficacy of MCL extracts and results revealed MCL to be a potent antioxidant for the stabilization of corn oil. As a general trend, increased AOA was observed for increased extract concentration. The predominant phenolic compounds identified by HPLC-DAD in MCL extracts were p-coumaric acid, vanillin and ferulic acid
Antioxidant Activity of the Phenolic Leaf Extracts from Monechma ciliatum in Stabilization of Corn Oil
The total phenolic content and the antioxidan potential of methanolic extract (ME), ethyl acetate extract (EAE), and hexane extract (HE) from Monechma ciliatum leaves (MCL) were evaluated. The Folin-Ciocalteu, b-carotene bleaching, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and the accelerated oxidation methods were used for evaluation. Both the extraction yield and the antioxidant activity (AOA) were strongly dependent on the solvent. Among the extracts, ME exhibited highest total phenolic compounds (TPC) and IC50 values for DPPH, followed by EAE and HE, respectively. Peroxide value (PV), anisidine value (AV) conjugated dienes (CD), and thiobarbituric acid reactive substances (TBARS) were taken as the parameters for evaluation of stabilization efficacy of MCL extracts and results revealed MCL to be a potent antioxidant for the stabilization of corn oil. As a general trend, increased AOA was observed for increased extract concentration. The predominant phenolic compounds identified by HPLC-DAD in MCL extracts were p-coumaric acid, vanillin and ferulic acid
Quantum phase transition in a single-molecule quantum dot
Quantum criticality is the intriguing possibility offered by the laws of
quantum mechanics when the wave function of a many-particle physical system is
forced to evolve continuously between two distinct, competing ground states.
This phenomenon, often related to a zero-temperature magnetic phase transition,
can be observed in several strongly correlated materials such as heavy fermion
compounds or possibly high-temperature superconductors, and is believed to
govern many of their fascinating, yet still unexplained properties. In contrast
to these bulk materials with very complex electronic structure, artificial
nanoscale devices could offer a new and simpler vista to the comprehension of
quantum phase transitions. This long-sought possibility is demonstrated by our
work in a fullerene molecular junction, where gate voltage induces a crossing
of singlet and triplet spin states at zero magnetic field. Electronic tunneling
from metallic contacts into the quantum dot provides here the
necessary many-body correlations to observe a true quantum critical behavior.Comment: 8 pages, 5 figure
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