934 research outputs found
Potassium Permanganate in Liquid Ammonia. An Effective Reagent in the Chichibabin Amination of Azines
A special section of the SNHreaction, notably Chichibabin aminations has been reviewed involving KNH2/NH3/KlVIn04system as an reagent for amino-dehydrogenatio
Jack-of-all-trades effects drive biodiversity-ecosystem multifunctionality relationships in European forests
Fons van der Plas [et al.].- Received 8 September 2015, Accepted 19 February 2016, Published 24 March 2016There is considerable evidence that biodiversity promotes multiple ecosystem functions (multifunctionality), thus ensuring the delivery of ecosystem services important for human well-being. However, the mechanisms underlying this relationship are poorly understood, especially in natural ecosystems. We develop a novel approach to partition biodiversity effects on multifunctionality into three mechanisms and apply this to European forest data. We show that throughout Europe, tree diversity is positively related with multifunctionality when moderate levels of functioning are required, but negatively when very high function levels are desired. For two well-known mechanisms, âcomplementarityâ and âselectionâ, we detect only minor effects on multifunctionality. Instead a third, so far overlooked mechanism, the âjack-of-all-tradesâ effect, caused by the averaging of individual species effects on function, drives observed patterns. Simulations demonstrate that jack-of-all-trades effects occur whenever species effects on different functions are not perfectly correlated, meaning they may contribute to diversityâmultifunctionality relationships in many of the worldâs ecosystems.Peer reviewe
Evaluation of scalarization methods and NSGA-II/SPEA2 genetic algorithms for multi-objective optimization of green supply chain design
This paper considers supply chain design in green logistics. We formulate the choice of an environmentally conscious chain design as a multi-objective optimization (MOO) problem and approximate the Pareto front using the weighted sum and epsilon constraint scalarization methods as well as with two popular genetic algorithms, NSGA-II and SPEA2. We extend an existing case study of green supply chain design in the South Eastern Europe region by optimizing simultaneously costs, CO2 and fine dust (also known as PM - Particulate Matters) emissions. The results show that in the considered case the scalarization methods outperform genetic algorithms in finding efficient solutions and that the CO2 and PM emissions can be lowered by accepting a marginal increase of costs over their global minimum
Dust masses of disks around 8 Brown Dwarfs and Very Low-Mass Stars in Upper Sco OB1 and Ophiuchus
We present the results of ALMA band 7 observations of dust and CO gas in the
disks around 7 objects with spectral types ranging between M5.5 and M7.5 in
Upper Scorpius OB1, and one M3 star in Ophiuchus. We detect unresolved
continuum emission in all but one source, and the CO J=3-2 line in two
sources. We constrain the dust and gas content of these systems using a grid of
models calculated with the radiative transfer code MCFOST, and find disk dust
masses between 0.1 and 1 M, suggesting that the stellar mass / disk
mass correlation can be extrapolated for brown dwarfs with masses as low as
0.05 M. The one disk in Upper Sco in which we detect CO emission, 2MASS
J15555600, is also the disk with warmest inner disk as traced by its H - [4.5]
photometric color. Using our radiative transfer grid, we extend the correlation
between stellar luminosity and mass-averaged disk dust temperature originally
derived for stellar mass objects to the brown dwarf regime to , applicable to spectral types
of M5 and later. This is slightly shallower than the relation for earlier
spectral type objects and yields warmer low-mass disks. The two prescriptions
cross at 0.27 L, corresponding to masses between 0.1 and 0.2 M
depending on age.Comment: 9 pages,6 figures, accepted to ApJ on 26/01/201
The narrow, inner CO ring around the magnetic Herbig Ae star, HD 101412
We describe and model emission lines in the first overtone band of CO in the
magnetic Herbig Ae star HD 101412. High-resolution CRIRES spectra reveal
unusually sharp features which suggest the emission is formed in a thin disk
centered at 1 AU with a width 0.32 AU or less. A wider disk will not fit the
observations. Previous observations have reached similar conclusions, but the
crispness of the new material brings the emitting region into sharp focus.Comment: Accepted as Astronomy and Astrophysics Letter; 4 pages, 5 figure
Warm gas at 50 AU in the disk around Herbig Be star HD 100546
The disk atmosphere is one of the fundamental elements of theoretical models
of a protoplanetary disk. However, the direct observation of the warm gas (>>
100 K) at large radius of a disk (>> 10 AU) is challenging, because the line
emission from warm gas in a disk is usually dominated by the emission from an
inner disk. Our goal is to detect the warm gas in the disk atmosphere well
beyond 10 AU from a central star in a nearby disk system of the Herbig Be star
HD 100546. We measured the excitation temperature of the vibrational transition
of CO at incremental radii of the disk from the central star up to 50 AU, using
an adaptive optics system combined with the high-resolution infrared
spectrograph CRIRES at the VLT. The observation successfully resolved the line
emission with 0".1 angular resolution, which is 10 AU at the distance of HD
100546. Population diagrams were constructed at each location of the disk, and
compared with the models calculated taking into account the optical depth
effect in LTE condition. The excitation temperature of CO is 400-500 K or
higher at 50 AU away from the star, where the blackbody temperature in
equilibrium with the stellar radiation drops as low as 90 K. This is
unambiguous evidence of a warm disk atmosphere far away from the central star.Comment: 7 pages, 5 figures, A&A in pres
Pragmatic rules for comparability of biological medicinal products
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