54 research outputs found
On the Complexity of Bayesian Generalization
We consider concept generalization at a large scale in the diverse and
natural visual spectrum. Established computational modes (i.e., rule-based or
similarity-based) are primarily studied isolated and focus on confined and
abstract problem spaces. In this work, we study these two modes when the
problem space scales up, and the of concepts becomes diverse.
Specifically, at the , we seek to answer how the
complexity varies when a visual concept is mapped to the representation space.
Prior psychology literature has shown that two types of complexities (i.e.,
subjective complexity and visual complexity) (Griffiths and Tenenbaum, 2003)
build an inverted-U relation (Donderi, 2006; Sun and Firestone, 2021).
Leveraging Representativeness of Attribute (RoA), we computationally confirm
the following observation: Models use attributes with high RoA to describe
visual concepts, and the description length falls in an inverted-U relation
with the increment in visual complexity. At the , we aim
to answer how the complexity of representation affects the shift between the
rule- and similarity-based generalization. We hypothesize that
category-conditioned visual modeling estimates the co-occurrence frequency
between visual and categorical attributes, thus potentially serving as the
prior for the natural visual world. Experimental results show that
representations with relatively high subjective complexity outperform those
with relatively low subjective complexity in the rule-based generalization,
while the trend is the opposite in the similarity-based generalization
Physics perspectives of heavy-ion collisions at very high energy
Heavy-ion collisions at very high colliding energies are expected to produce
a quark-gluon plasma (QGP) at the highest temperature obtainable in a
laboratory setting. Experimental studies of these reactions can provide an
unprecedented range of information on properties of the QGP at high
temperatures. We report theoretical investigations of the physics perspectives
of heavy-ion collisions at a future high-energy collider. These include initial
parton production, collective expansion of the dense medium, jet quenching,
heavy-quark transport, dissociation and regeneration of quarkonia, photon and
dilepton production. We illustrate the potential of future experimental studies
of the initial particle production and formation of QGP at the highest
temperature to provide constraints on properties of strongly interaction
matter.Comment: 35 pages in Latex, 29 figure
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
Dissection of full-length transcriptome and metabolome of Dichocarpum (Ranunculaceae): implications in evolution of specialized metabolism of Ranunculales medicinal plants
Several main families of Ranunculales are rich in alkaloids and other medicinal compounds; many species of these families are used in traditional and folk medicine. Dichocarpum is a representative medicinal genus of Ranunculaceae, but the genetic basis of its metabolic phenotype has not been investigated, which hinders its sustainable conservation and utilization. We use the third-generation high-throughput sequencing and metabolomic techniques to decipher the full-length transcriptomes and metabolomes of five Dichocarpum species endemic in China, and 71,598 non-redundant full-length transcripts were obtained, many of which are involved in defense, stress response and immunity, especially those participating in the biosynthesis of specialized metabolites such as benzylisoquinoline alkaloids (BIAs). Twenty-seven orthologs extracted from trancriptome datasets were concatenated to reconstruct the phylogenetic tree, which was verified by the clustering analysis based on the metabolomic profile and agreed with the Pearson correlation between gene expression patterns of Dichocarpum species. The phylogenomic analysis of phytometabolite biosynthesis genes, e.g., (S)-norcoclaurine synthase, methyltransferases, cytochrome p450 monooxygenases, berberine bridge enzyme and (S)-tetrahydroprotoberberine oxidase, revealed the evolutionary trajectories leading to the chemodiversity, especially that of protoberberine type, aporphine type and bis-BIA abundant in Dichocarpum and related genera. The biosynthesis pathways of these BIAs are proposed based on full-length transcriptomes and metabolomes of Dichocarpum. Within Ranunculales, the gene duplications are common, and a unique whole genome duplication is possible in Dichocarpum. The extensive correlations between metabolite content and gene expression support the co-evolution of various genes essential for the production of different specialized metabolites. Our study provides insights into the transcriptomic and metabolomic landscapes of Dichocarpum, which will assist further studies on genomics and application of Ranunculales plants
Anticancer Chemodiversity of Ranunculaceae Medicinal Plants: Molecular Mechanisms and Functions
Carboxylation of terminal alkynes at ambient CO2 pressure in ethylene carbonate
The CuI-catalyzed carboxylation of terminal alkynes with CO2 and alkyl halides using ethylene carbonate as the solvent under mild conditions was studied. DFT calculations reveal that the energy barrier for CO2 insertion into the sp-hybridized Cu-C bond could be reduced by employing ethylene carbonate as the solvent. Notably, the procedure was conducted under ambient CO2 pressure without any external ligands. A broad range of substrates with electron-withdrawing groups or electron-donating groups gave the corresponding products in reasonable yields
Copper(I)@Carbon-Catalyzed Carboxylation of Terminal Alkynes with CO<sub>2</sub> at Atmospheric Pressure
Activated
carbon supported CuBr was found to be an efficient catalyst
for the carboxylation of terminal alkynes under atmospheric pressure
of CO<sub>2</sub> using ethylene carbonate as solvent at 80 °C
for only 2 h, as verified with <sup>13</sup>CO<sub>2</sub>. Various
terminal alkynes could react smoothly with CO<sub>2</sub> and organic
halides under the reaction conditions to afford the corresponding
carboxylic esters. In addition, the catalyst can be easily recovered
and reused at least five times without significant loss of activity
A FACILE SYNTHESIS OF DERIVATIVES OF 4-ARYL-1,3,2-DIOXAPHOSPHORINANE-2-SULFIDE VIA LAWESSON'S REAGENT
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