127 research outputs found
Note on the Preparation of Ethyl Cyclohexylidene-Cyanoacetate
Ethyl cyclohexylidene-cyanoacetate has been prepared by the condensation of ethyl cyanoacetate and cyclohexanone under pressure and in the presence of various catalysts i. e. sodium ethoxide, piperidirne pyridine , piperazine , acid amides, soluble salts of amines or quarternary ammonium bases with an organic acid, acetamide, and ammonium acetate and acetic acid
2-Dimethylaminopropyl Esters of Some Substituted Acetic Acids
2-dimethylaminopropyl esters of folowing acids were prepared: benzoic, phenylacetic, diphenylacetic, B, B -diphenylrpropionic, a- phenylbutyric, acetylmandelic and benzilic
2-Dimethylaminopropyl Esters of Some Substituted Acetic Acids
2-dimethylaminopropyl esters of folowing acids were prepared: benzoic, phenylacetic, diphenylacetic, B, B -diphenylrpropionic, a- phenylbutyric, acetylmandelic and benzilic
Phenomenological description of the nonlocal magnetization relaxation in magnonics, spintronics, and domain-wall dynamics
A phenomenological equation called Landau-Lifshitz-Baryakhtar (LLBar)
equation, which could be viewed as the combination of Landau-Lifshitz (LL)
equation and an extra "exchange damping" term, was derived by Baryakhtar using
Onsager's relations. We interpret the origin of this "exchange damping" as
nonlocal damping by linking it to the spin current pumping. The LLBar equation
is investigated numerically and analytically for the spin wave decay and domain
wall motion. Our results show that the lifetime and propagation length of
short-wavelength magnons in the presence of nonlocal damping could be much
smaller than those given by LL equation. Furthermore, we find that both the
domain wall mobility and the Walker breakdown field are strongly influenced by
the nonlocal damping.Comment: 10 pages, 6 figure
Termination Reaction in the Anionic Polymerization of Methacrylonitrile
The anionic polymerization of methacrylonitrile initiated by
triethylphosphine in dimethylformamide was studied. Experimental
evidence for two mechanisms of termination reaction was obtained.
By addition of water or alcohol in polymerizing system the rate of
polymerization and molecular weight of polymethacrylon1itrile
decrease, which proves the termination reaction to be bimolecular
and proceed by interaction of the active carbanion with water or
alcohol. The rate constant for termination of free anions with water
was determined, k~,0 = 2.2 x 102 dm3 moP s-1• The termination
reaction could not be excluded by purification and prolonged drying
of all components of the system, which indicates that the second
mechanism of termination is operative as well. Conductivity measurements gave evidence for a monomolecular spontaneous reaction leading to deactivation of the anion
Photometric selection and redshifts for quasars in the Kilo-Degree Survey Data Release 4
We present a catalog of quasars and corresponding redshifts in the
Kilo-Degree Survey (KiDS) Data Release 4. We trained machine learning (ML)
models, using optical ugri and near-infrared ZYJHK_s bands, on objects known
from Sloan Digital Sky Survey (SDSS) spectroscopy. We define inference subsets
from the 45 million objects of the KiDS photometric data limited to 9-band
detections. We show that projections of the high-dimensional feature space can
be successfully used to investigate the estimations. The model creation employs
two test subsets: randomly selected and the faintest objects, which allows to
fit the bias versus variance trade-off. We tested three ML models: random
forest (RF), XGBoost (XGB), and artificial neural network (ANN). We find that
XGB is the most robust model for classification, while ANN performs the best
for combined classification and redshift. The inference results are tested
using number counts, Gaia parallaxes, and other quasar catalogs. Based on these
tests, we derived the minimum classification probability which provides the
best purity versus completeness trade-off: p(QSO_cand) > 0.9 for r < 22 and
p(QSO_cand) > 0.98 for 22 < r < 23.5. We find 158,000 quasar candidates in the
safe inference subset (r < 22) and an additional 185,000 candidates in the
reliable extrapolation regime (22 < r < 23.5). Test-data purity equals 97% and
completeness is 94%; the latter drops by 3% in the extrapolation to data
fainter by one magnitude than the training set. The photometric redshifts were
modeled with Gaussian uncertainties. The redshift error (mean and scatter)
equals 0.01 +/- 0.1 in the safe subset and -0.0004 +/- 0.2 in the
extrapolation, in a redshift range of 0.14 < z < 3.63. Our success of the
extrapolation challenges the way that models are optimized and applied at the
faint data end. The catalog is ready for cosmology and active galactic nucleus
(AGN) studies.Comment: We publicly release the catalog at
kids.strw.leidenuniv.nl/DR4/quasarcatalog.php , and the code at
github.com/snakoneczny/kids-quasar
KiDS+GAMA:The weak lensing calibrated stellar-to-halo mass relation of central and satellite galaxies
We simultaneously present constraints on the stellar-to-halo mass relation
for central and satellite galaxies through a weak lensing analysis of
spectroscopically classified galaxies. Using overlapping data from the fourth
data release of the Kilo-Degree Survey (KiDS), and the Galaxy And Mass Assembly
survey (GAMA), we find that satellite galaxies are hosted by halo masses that
are dex (68\% confidence, detection) smaller than
those of central galaxies of the same stellar mass (for a stellar mass of
). This is consistent with galaxy formation
models, whereby infalling satellite galaxies are preferentially stripped of
their dark matter. We find consistent results with similar uncertainties when
comparing constraints from a standard azimuthally averaged galaxy-galaxy
lensing analysis and a two-dimensional likelihood analysis of the full shear
field. As the latter approach is somewhat biased due to the lens incompleteness
and as it does not provide any improvement to the precision when applied to
actual data, we conclude that stacked tangential shear measurements are
best-suited for studies of the galaxy-halo connection.Comment: 12 pages, 10 figures, accepted for publication in A&
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