1,480 research outputs found
NUV/Blue spectral observations of sprites in the 320-460 nm region: (2PG) Emissions
A near-ultraviolet (NUV) spectrograph (320-460 nm) was flown on the EXL98
aircraft sprite observation campaign during July 1998. In this wavelength range
video rate (60 fields/sec) spectrographic observations found the NUV/blue
emissions to be predominantly N2 (2PG). The negligible level of N2+ (1NG)
present in the spectrum is confirmed by observations of a co-aligned, narrowly
filtered 427.8 nm imager and is in agreement with previous ground-based
filtered photometer observations. The synthetic spectral fit to the
observations indicates a characteristic energy of ~1.8 eV, in agreement with
our other NUV observations.Comment: 7 pages, 2 figures, 1 table, JGR Space Physics "Effects of
Thunderstorms and Lightning in the Upper Atmosphere" Special Sectio
Solving Games with Functional Regret Estimation
We propose a novel online learning method for minimizing regret in large
extensive-form games. The approach learns a function approximator online to
estimate the regret for choosing a particular action. A no-regret algorithm
uses these estimates in place of the true regrets to define a sequence of
policies.
We prove the approach sound by providing a bound relating the quality of the
function approximation and regret of the algorithm. A corollary being that the
method is guaranteed to converge to a Nash equilibrium in self-play so long as
the regrets are ultimately realizable by the function approximator. Our
technique can be understood as a principled generalization of existing work on
abstraction in large games; in our work, both the abstraction as well as the
equilibrium are learned during self-play. We demonstrate empirically the method
achieves higher quality strategies than state-of-the-art abstraction techniques
given the same resources.Comment: AAAI Conference on Artificial Intelligence 201
Ultralight reactive metal foams produced as structural shapes in space: System design
This autonomous experiment for foaming metals in space involved: (1) payload support structure; (2) furnace and foaming apparatus; (3) electronic controls; (4) battery power; and (5) metallurgy. Emphasis was laid on a modular design which was easily modifiable and which offered maximum durability, safety, and failure tolerance
Effect of calf-starter protein solubility on calf performance
Three starters containing differently processed protein supplements were fed
to Holstein heifer calves, using an early weaning program. One starter contained
soybean meal. The other starters contained soybean grits processed through an
extrusion cooker to reduce the protein solubility to an intermediate (PDI> 50%) or
low (PDI < 15 %) level. Calf performance was similar on all three starters
Alien Registration- Morrill, Germaine J. (Limerick, York County)
https://digitalmaine.com/alien_docs/3237/thumbnail.jp
Overconsumption of Antibiotics
We applaud Thomas Van Boeckel and colleagues1 for their large analysis of antibiotic consumption in 71 countries. A 36% increase in use of antibiotics worldwide, 76% of which was in Brazil, Russia, India, China, and South Africa, is a concerning finding. In Europe and the USA, practitioners are increasingly aware of the importance of infection control and antimicrobial stewardship. However, 50% of antimicrobials, irrespective of setting, are used inappropriately.2,3 We agree that most increases in global antibiotic consumption are probably caused by inappropriate use and that coordinated efforts to improve antimicrobial use internationally are desperately needed
UV solar irradiance in observations and the NRLSSI and SATIRE-S models
Total solar irradiance and UV spectral solar irradiance have been monitored
since 1978 through a succession of space missions. This is accompanied by the
development of models aimed at replicating solar irradiance by relating the
variability to solar magnetic activity. The NRLSSI and SATIRE-S models provide
the most comprehensive reconstructions of total and spectral solar irradiance
over the period of satellite observation currently available. There is
persistent controversy between the various measurements and models in terms of
the wavelength dependence of the variation over the solar cycle, with
repercussions on our understanding of the influence of UV solar irradiance
variability on the stratosphere. We review the measurement and modelling of UV
solar irradiance variability over the period of satellite observation. The
SATIRE-S reconstruction is consistent with spectral solar irradiance
observations where they are reliable. It is also supported by an independent,
empirical reconstruction of UV spectral solar irradiance based on UARS/SUSIM
measurements from an earlier study. The weaker solar cycle variability produced
by NRLSSI between 300 and 400 nm is not evident in any available record. We
show that although the method employed to construct NRLSSI is principally
sound, reconstructed solar cycle variability is detrimentally affected by the
uncertainty in the SSI observations it draws upon in the derivation. Based on
our findings, we recommend, when choosing between the two models, the use of
SATIRE-S for climate studies
Catalyzed oxidation of aniline by hydrogen peroxide in the presence of cnts: A Possible case of a nanodimension reaction
The oxidation of aniline by hydrogen peroxide produces nitrosobenzene as the initial product, which undergoes further oxidation to nitrobenzene. The nitrosobenzene formation is catalyzed by functionalized multiwalled carbon nanotubes (CNT) followed by a coupling reaction between nitrosobenzene and aniline to produce azobenzene. This reaction proceeds rapidly resulting in the UV-VIS absorption spectrum showing a maxima at 327 nm and 425 nm. The nitrosobenzene yield in the presence of CNTs is controlled by the amount present in the medium. As the reaction is not catalyzed by unfunctionalized CNTs or graphitic particles, the uniqueness of the functionalized multiwalled CNTs in this catalysis suggests a nano dimensional reaction pathway
Regioselective Radical Arene Amination for the Concise Synthesis of <i>ortho</i>-Phenylenediamines.
The formation of arene C-N bonds directly from C-H bonds is of great importance and there has been rapid recent development of methods for achieving this through radical mechanisms, often involving reactive N-centered radicals. A major challenge associated with these advances is that of regiocontrol, with mixtures of regioisomeric products obtained in most protocols, limiting broader utility. We have designed a system that utilizes attractive noncovalent interactions between an anionic substrate and an incoming radical cation in order to guide the latter to the arene ortho position. The anionic substrate takes the form of a sulfamate-protected aniline and telescoped cleavage of the sulfamate group after amination leads directly to ortho-phenylenediamines, key building blocks for a range of medicinally relevant diazoles. Our method can deliver both free amines and monoalkyl amines allowing access to unsymmetrical, selectively monoalkylated benzimidazoles and benzotriazoles. As well as providing concise access to valuable ortho-phenylenediamines, this work demonstrates the potential for utilizing noncovalent interactions to control positional selectivity in radical reactions
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