47 research outputs found
A 3D study on the amplification of regional haze and particle growth by local emissions
The role of new particle formation (NPF) events and their contribution to haze formation through subsequent growth in polluted megacities is still controversial. To improve the understanding of the sources, meteorological conditions, and chemistry behind air pollution, we performed simultaneous measurements of aerosol composition and particle number size distributions at ground level and at 260 m in central Beijing, China, during a total of 4 months in 2015-2017. Our measurements show a pronounced decoupling of gas-to-particle conversion between the two heights, leading to different haze processes in terms of particle size distributions and chemical compositions. The development of haze was initiated by the growth of freshly formed particles at both heights, whereas the more severe haze at ground level was connected directly to local primary particles and gaseous precursors leading to higher particle growth rates. The particle growth creates a feedback loop, in which a further development of haze increases the atmospheric stability, which in turn strengthens the persisting apparent decoupling between the two heights and increases the severity of haze at ground level. Moreover, we complemented our field observations with model analyses, which suggest that the growth of NPF-originated particles accounted up to similar to 60% of the accumulation mode particles in the Beijing-Tianjin-Hebei area during haze conditions. The results suggest that a reduction in anthropogenic gaseous precursors, suppressing particle growth, is a critical step for alleviating haze although the number concentration of freshly formed particles (3-40 nm) via NPF does not reduce after emission controls.Peer reviewe
Deciphering colorectal cancer genetics through multi-omic analysis of 100,204 cases and 154,587 controls of European and east Asian ancestries
In the version of this article initially published, the author affiliations incorrectly listed âCandiolo Cancer Institute FPO-IRCCS, Candiolo (TO), Italyâ as âCandiolo Cancer Institute, Candiolo, Italy.â The change has been made to the HTML and PDF versions of the article
Fine-mapping analysis including over 254,000 East Asian and European descendants identifies 136 putative colorectal cancer susceptibility genes
Genome-wide association studies (GWAS) have identified more than 200 common genetic variants independently associated with colorectal cancer (CRC) risk, but the causal variants and target genes are mostly unknown. We sought to fine-map all known CRC risk loci using GWAS data from 100,204 cases and 154,587 controls of East Asian and European ancestry. Our stepwise conditional analyses revealed 238 independent association signals of CRC risk, each with a set of credible causal variants (CCVs), of which 28 signals had a single CCV. Our cis-eQTL/mQTL and colocalization analyses using colorectal tissue-specific transcriptome and methylome data separately from 1299 and 321 individuals, along with functional genomic investigation, uncovered 136 putative CRC susceptibility genes, including 56 genes not previously reported. Analyses of single-cell RNA-seq data from colorectal tissues revealed 17 putative CRC susceptibility genes with distinct expression patterns in specific cell types. Analyses of whole exome sequencing data provided additional support for several target genes identified in this study as CRC susceptibility genes. Enrichment analyses of the 136 genes uncover pathways not previously linked to CRC risk. Our study substantially expanded association signals for CRC and provided additional insight into the biological mechanisms underlying CRC development
Hydrogenation of CO2 or CO2 Derivatives to Methanol under Molecular Catalysis: A Review
The atmospheric CO2 concentration has been continuously increasing due to fossil fuel combustion. The transformations of CO2 and CO2 derivatives into high value-added chemicals such as alcohols are ideal routes to mitigate greenhouse gas emissions. Among alcohol products, methanol is very promising as it fulfills the carbon neutral cycle and can be used for direct methanol fuel cells. Herein, we summarize the recent progress in the hydrogenation of CO2 or CO2 derivatives to methanol, and focus on those systems with homogeneous catalysts and molecular hydrogen as the reductant. Discussions on the catalytic systems, efficiencies, and future outlooks will be given
Hydrogenation of CO<sub>2</sub> or CO<sub>2</sub> Derivatives to Methanol under Molecular Catalysis: A Review
The atmospheric CO2 concentration has been continuously increasing due to fossil fuel combustion. The transformations of CO2 and CO2 derivatives into high value-added chemicals such as alcohols are ideal routes to mitigate greenhouse gas emissions. Among alcohol products, methanol is very promising as it fulfills the carbon neutral cycle and can be used for direct methanol fuel cells. Herein, we summarize the recent progress in the hydrogenation of CO2 or CO2 derivatives to methanol, and focus on those systems with homogeneous catalysts and molecular hydrogen as the reductant. Discussions on the catalytic systems, efficiencies, and future outlooks will be given
A Unified Tagging Approach to Text Normalization
This paper addresses the issue of text normalization, an important yet often overlooked problem in natural language processing. By text normalization, we mean converting âinformally inputted â text into the canonical form, by eliminating ânoisesâ in the text and detecting paragraph and sentence boundaries in the text. Previously, text normalization issues were often undertaken in an ad-hoc fashion or studied separately. This paper first gives a formalization of the entire problem. It then proposes a unified tagging approach to perform the task using Conditional Random Fields (CRF). The paper shows that with the introduction of a small set of tags, most of the text normalization tasks can be performed within the approach. The accuracy of the proposed method is high, because the subtasks of normalization are interdependent and should be performed together. Experimental results on email data cleaning show that the proposed method significantly outperforms the approach of using cascaded models and that of employing independent models.
Copper-Catalyzed CâH Azidation of Anilines under Mild Conditions
A novel and efficient copper-catalyzed azidation reaction
of anilines
via CâH activation has been developed. This method, in which
the primary amine acts as a directing group by coordinating to the
metal center, provides ortho azidation products regioselectively under
mild conditions. This effective route for the synthesis of aryl azides
is of great significance in view of the versatile reactivity of the
azide products
Metal-Free Nitrogenation of 2âAcetylbiphenyls: Expeditious Synthesis of Phenanthridines
An
intermolecular nitrogenation reaction toward the synthesis of
phenanthridines has been developed. This metal-free protocol provides
a novel nitrogen-incorporation transformation using azides as the
nitrogen source. Phenanthridines, which are of great interest in pharmaceutical
and medicinal chemistry, are synthesized efficiently in one step.
Moreover, the byproducts derived from the Schmidt reaction are inhibited,
which further demonstrated the high chemoselectivity of this transformation
Rh-Catalyzed NâO Bond Cleavage of Anthranil: A CâH Amination Reagent for Simultaneous Incorporation of Amine and a Functional Group
A novel
RhÂ(III)-catalyzed CâH bond amination with the simultaneous
release of a formyl group at distal positions is realized employing
anthranil as a new type of CâH amination reagent. This chemistry
provides an efficient protocol for the synthesis of 2-acyl diarylamines,
which are important structural motifs in many bioactive compounds.
This new type of CâH amination reagent possesses the advantages
of high atom economy, avoids the use of external oxidants, and enables
further transformation of the amination products