486 research outputs found
Synthesis of pyrroles by nickel-catalysed arylative cyclisations of alkynamides
A nickel-based catalytic system for the anti-carbometallative cyclisations of alkynamides to arylboronic acids is described. The reactions proceed using catalytic nickel and (rac)-Ph-PHOX, to provide alkenylnickel species which can undergo reversible E/Z-isomerisation, followed by cyclisation onto an N-tosylamide to give 2,3,4-trisubstituted pyrroles.
Pyrroles are of widespread chemical significance, being present in numerous biologically active natural products. This methodology was used to generate a series of multisubstituted pyrroles and perform concise syntheses of BODIPY derivative and pyrrolyl propionic acid
Disentangling Boosted Higgs Boson Production Modes with Machine Learning
Higgs Bosons produced via gluon-gluon fusion (ggF) with large transverse
momentum () are sensitive probes of physics beyond the Standard Model.
However, high Higgs Boson production is contaminated by a diversity of
production modes other than ggF: vector boson fusion, production of a Higgs
boson in association with a vector boson, and production of a Higgs boson with
a top-quark pair. Combining jet substructure and event information with modern
machine learning, we demonstrate the ability to focus on particular production
modes. These tools hold great discovery potential for boosted Higgs bosons
produced via ggF and may also provide additional information about the Higgs
Boson sector of the Standard Model in extreme phase space regions for other
production modes as well.Comment: 17 pages, 9 figure
Exploring the Universality of Hadronic Jet Classification
The modeling of jet substructure significantly differs between Parton Shower
Monte Carlo (PSMC) programs. Despite this, we observe that machine learning
classifiers trained on different PSMCs learn nearly the same function. This
means that when these classifiers are applied to the same PSMC for testing,
they result in nearly the same performance. This classifier universality
indicates that a machine learning model trained on one simulation and tested on
another simulation (or data) will likely be optimal. Our observations are based
on detailed studies of shallow and deep neural networks applied to simulated
Lorentz boosted Higgs jet tagging at the LHC.Comment: 25 pages, 7 figures, 7 table
Disordered Fe vacancies and superconductivity in potassium-intercalated iron selenide (K2-xFe4+ySe5)
The parent compound of an unconventional superconductor must contain unusual
correlated electronic and magnetic properties of its own. In the high-Tc
potassium intercalated FeSe, there has been significant debate regarding what
the exact parent compound is. Our studies unambiguously show that the
Fe-vacancy ordered K2Fe4Se5 is the magnetic, Mott insulating parent compound of
the superconducting state. Non-superconducting K2Fe4Se5 becomes a
superconductor after high temperature annealing, and the overall picture
indicates that superconductivity in K2-xFe4+ySe5 originates from the Fe-vacancy
order to disorder transition. Thus, the long pending question whether magnetic
and superconducting state are competing or cooperating for cuprate
superconductors may also apply to the Fe-chalcogenide superconductors. It is
believed that the iron selenides and related compounds will provide essential
information to understand the origin of superconductivity in the iron-based
superconductors, and possibly to the superconducting cuprates
Synthesis of multisubstituted pyrroles by nickel-catalyzed arylative cyclizations of N-tosyl alkynamides
The synthesis of multisubstituted pyrroles by the nickel-catalyzed reaction of N-tosylalkynamides with arylboronic acids is reported. These reactions are triggered by alkyne arylnickelation, followed by cyclization of the resulting alkenylnickel species onto the amide. The reversible E/Z isomerization of the alkenylnickel species is critical for cyclization. This method was applied to the synthesis of pyrroles that are precursors to BODIPY derivatives and a biologically active compound
The squeeze film effect on micro-electromechanical resonators
The air squeeze film damping effect on the dynamic responses of clamped micro- electromechanical resonators is investigated in this study. A dynamic model for a clamped micro-electromechanical resonator with the damping consideration is derived using Lagrange’s equation. The corresponding resonator eigen solutions are formulated and solved by employing the assumed-mode method. The effect of different parameters; i.e. the resonator size, ambient temperature and pressure on the squeeze film damping characteristics were simulated and investigated. The results indicate that the squeeze film damping effect may significantly affect the dynamic responses of micro-scale electromechanical resonator
Toward Joint Language Modeling for Speech Units and Text
Speech and text are two major forms of human language. The research community
has been focusing on mapping speech to text or vice versa for many years.
However, in the field of language modeling, very little effort has been made to
model them jointly. In light of this, we explore joint language modeling for
speech units and text. Specifically, we compare different speech tokenizers to
transform continuous speech signals into discrete units and use different
methods to construct mixed speech-text data. We introduce automatic metrics to
evaluate how well the joint LM mixes speech and text. We also fine-tune the LM
on downstream spoken language understanding (SLU) tasks with different
modalities (speech or text) and test its performance to assess the model's
learning of shared representations. Our results show that by mixing speech
units and text with our proposed mixing techniques, the joint LM improves over
a speech-only baseline on SLU tasks and shows zero-shot cross-modal
transferability.Comment: EMNLP findings 202
POWER: PhylOgenetic WEb Repeater—an integrated and user-optimized framework for biomolecular phylogenetic analysis
POWER, the PhylOgenetic WEb Repeater, is a web-based service designed to perform user-friendly pipeline phylogenetic analysis. POWER uses an open-source LAMP structure and infers genetic distances and phylogenetic relationships using well-established algorithms (ClustalW and PHYLIP). POWER incorporates a novel tree builder based on the GD library to generate a high-quality tree topology according to the calculated result. POWER accepts either raw sequences in FASTA format or user-uploaded alignment output files. Through a user-friendly web interface, users can sketch a tree effortlessly in multiple steps. After a tree has been generated, users can freely set and modify parameters, select tree building algorithms, refine sequence alignments or edit the tree topology. All the information related to input sequences and the processing history is logged and downloadable for the user's reference. Furthermore, iterative tree construction can be performed by adding sequences to, or removing them from, a previously submitted job. POWER is accessible at
Does Long-Term Use of Silver Nanoparticles Have Persistent Inhibitory Effect on H. pylori Based on Mongolian Gerbil’s Model?
It is urgent to find alternative agents due to increasing failure rate of Helicobacter pylori (H. pylori) eradication. The study surveyed the long-term effect of silver nanoparticles (AgNP) on H. pylori based on Mongolian gerbil's model
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