2,568 research outputs found
Reactivity of (3-Methylpentadienyl)iron(1+) Cation: Late-stage Introduction of a (3-Methyl-2Z,4-pentadien-1-yl) Side Chain
The 3-methyl-2Z,4-pentadien-1-yl sidechain is found in various sesquiterpenes and diterpenes. A route for the late stage introduction of this functionality was developed which relies on nucleophilic attack on the (3-methylpentadienyl)iron(1+) cation, followed by oxidative decomplexation. This methodology was applied to the synthesis of the proposed structure of heteroscyphic acid A methyl ester. Realization of this synthesis led to a correction of the proposed structure
Unlocking the power of local knowledge: a novel framework to cost community-based adaptation to climate change
A Continuous Non-demolition Measurement of the Cs Clock Transition Pseudo-spin
We demonstrate a weak continuous measurement of the pseudo-spin associated
with the clock transition in a sample of Cs atoms. Our scheme uses an optical
probe tuned near the D1 transition to measure the sample birefringence, which
depends on the z-component of the collective pseudospin. At certain probe
frequencies the differential light shift of the clock states vanishes and the
measurement is non-perturbing. In dense samples the measurement can be used to
squeeze the collective clock pseudo-spin, and has potential to improve the
performance of atomic clocks and interferometers.Comment: 4 pages, 4 figures, ReVTeX, modified text in response to referee's
comment
Large-Scale Music Genre Analysis and Classification Using Machine Learning with Apache Spark
The trend for listening to music online has greatly increased over the past decade due to the number of online musical tracks. The large music databases of music libraries that are provided by online music content distribution vendors make music streaming and downloading services more accessible to the end-user. It is essential to classify similar types of songs with an appropriate tag or index (genre) to present similar songs in a convenient way to the end-user. As the trend of online music listening continues to increase, developing multiple machine learning models to classify music genres has become a main area of research. In this research paper, a popular music dataset GTZAN which contains ten music genres is analysed to study various types of music features and audio signals. Multiple scalable machine learning algorithms supported by Apache Spark, including naïve Bayes, decision tree, logistic regression, and random forest, are investigated for the classification of music genres. The performance of these classifiers is compared, and the random forest performs as the best classifier for the classification of music genres. Apache Spark is used in this paper to reduce the computation time for machine learning predictions with no computational cost, as it focuses on parallel computation. The present work also demonstrates that the perfect combination of Apache Spark and machine learning algorithms reduces the scalability problem of the computation of machine learning predictions. Moreover, different hyperparameters of the random forest classifier are optimized to increase the performance efficiency of the classifier in the domain of music genre classification. The experimental outcome shows that the developed random forest classifier can establish a high level of performance accuracy, especially for the mislabelled, distorted GTZAN dataset. This classifier has outperformed other machine learning classifiers supported by Apache Spark in the present work. The random forest classifier manages to achieve 90% accuracy for music genre classification compared to other work in the same domain
Peeling from a patterned thin elastic film
Inspired by the observation that many naturally occurring adhesives arise as
textured thin films, we consider the displacement controlled peeling of a
flexible plate from an incision-patterned thin adhesive elastic layer. We find
that crack initiation from an incision on the film occurs at a load much higher
than that required to propagate it on a smooth adhesive surface; multiple
incisions thus cause the crack to propagate intermittently. Microscopically,
this mode of crack initiation and propagation in geometrically confined thin
adhesive films is related to the nucleation of cavitation bubbles behind the
incision which must grow and coalesce before a viable crack propagates. Our
theoretical analysis allows us to rationalize these experimental observations
qualitatively and quantitatively and suggests a simple design criterion for
increasing the interfacial fracture toughness of adhesive films.Comment: 8 pages, To appear in Proceedings of Royal Society London, Ser.
Crystal and molecular structure of bis(8-phenylmenthyl) 2-(2-methyl-5-oxo-3-cyclohexen-1-yl)propandioate, C\u3csub\u3e42\u3c/sub\u3eH\u3csub\u3e54\u3c/sub\u3eO\u3csub\u3e5\u3c/sub\u3e• CH\u3csub\u3e3\u3c/sub\u3eCN
The X-ray crystal structure of the title compound, as crystallized from acetonitrile-water was determined. The relative stereochemistry of the cyclohexenone ring with respect to the 8-phenylmenthyl esters was determined. The title compound crystallizes in the noncentrosymmetric space group P21, with a=8.9850(10) Å, b=15.575(3) Å, c=14.478(2) Å, β=94.61(2)°, and D calc=1.118 g cm−3 for Z=2
Robust Ferroelectric State in Multiferroic MnZnWO
We report the remarkably robust ferroelectric state in the multiferroic
compound MnZnWO. The substitution of the magnetic Mn
with nonmagnetic Zn reduces the magnetic exchange and provides control
of the various magnetic and multiferroic states of MnWO. Only 5 % of Zn
substitution results in a complete suppression of the frustrated collinear
(paraelectric) low temperature phase. The helical magnetic and ferroelectric
phase develops as the ground state. The multiferroic state is stable up to a
high level of substitution of more than 50 %. The magnetic, thermodynamic, and
dielectric properties as well as the ferroelectric polarization of single
crystals of MnZnWO are studied for different substitutions up
to x=0.5. The magnetic phases have been identified in single crystal neutron
scattering experiments. The ferroelectric polarization scales with the neutron
intensity of the incommensurate peak of the helical phase.Comment: 6 pages, 8 figure
Sprectral data for Generation of Molecular Complexity from Cyclooctatetraene Using Dienyliron and Olefin Metathesis
Spectral data used in the course of researching Generation of molecular complexity from cyclooctatetraene using dienyliron and olefin metathesis methodology .
Transformation of the simple hydrocarbon cyclooctatetraene into a variety of polycyclic skeletons was achieved by sequential coordination to iron, reaction with electrophiles followed by allylated nucleophiles, decomplexation and olefin metathesis
- …