A
bstract
Leptoquarks have recently received much attention especially because they may provide an explanation to the
R
D
*
and
R
K
*
anomalies in rare
B
meson decays. In a previous paper we proposed ...a systematic search strategy for all possible leptoquark flavors by focusing on leptoquark pair production. In this paper, we extend this strategy to large (order unity) leptoquark couplings which offer new search opportunities: single leptoquark production and
t
-channel leptoquark exchange with dilepton final states. We discuss the unique features of the different search channels and show that they cover complementary regions of parameter space. We collect and update all currently available bounds for the different flavor final states from LHC searches and from atomic parity violation measurements. As an application of our analysis, we find that current limits do not exclude a leptoquark explanation of the
B
physics anomalies but that the high luminosity run of the LHC will reach the most interesting parameter space.
Electrochemical water splitting powered by renewable energy sources has been considered as an attractive hydrogen generation technology with high‐purity product and zero carbon emission. However, the ...efficient realization of large‐scale water splitting is severely hampered by the sluggish hydrogen/oxygen evolution reaction (HER/OER). As an important class of functional materials, complex hollow electrocatalysts provide promising solutions to accelerate the HER/OER kinetics owing to their advantageous features, such as abundant exposed active sites, increased contact area between catalysts and electrolyte, and shortened mass/charge transport length. Herein, the recent advances in the development of complex hollow electrocatalysts and their outstanding performances in water splitting are summarized. Beginning with the introduction of reaction mechanisms and design principles, achievements in engineering complex hollow HER/OER electrocatalysts are highlighted with the focus on structural modulation, composition control, and electrocatalytic evaluation. Finally, some present challenges and future perspectives for advanced complex hollow electrocatalysts toward water splitting are further discussed.
Complex hollow nanostructures have attracted considerable interest in energy applications. In addition, the available component regulation could endow them with a further improved intrinsic activity. Herein, the recent progress in the design of micro‐/nanostructured hollow structures for water splitting is discussed according to the regulatory strategies of geometrical structure control and composition control. Some emergent opportunities and perspectives on the future research trends of hollow structures are also proposed.
Abstract
This study seeks to estimate the carbon implications of recent changes in China’s economic development patterns and role in global trade in the post-financial-crisis era. We utilised the ...latest socioeconomic datasets to compile China’s 2012 multiregional input-output (MRIO) table. Environmentally extended input-output analysis and structural decomposition analysis (SDA) were applied to investigate the driving forces behind changes in CO
2
emissions embodied in China’s domestic and foreign trade from 2007 to 2012. Here we show that emission flow patterns have changed greatly in both domestic and foreign trade since the financial crisis. Some economically less developed regions, such as Southwest China, have shifted from being a net emission exporter to being a net emission importer. In terms of foreign trade, emissions embodied in China’s exports declined from 2007 to 2012 mainly due to changes in production structure and efficiency gains, while developing countries became the major destination of China’s export emissions.
Based on the data of PM2.5 concentrations and Air Quality Index of 73 Chinese cities in 2013, this study empirically investigates the socioeconomic influential factors of urban PM2.5 concentrations ...in China. Specifically, it examines whether and how the socioeconomic development indicators such as GDP per capita, industry and transport would affect the air quality. Due to the existence of spatial autocorrelation of air pollution, conventional regression techniques that ignore the spatial autocorrelation would yield biased and inconsistent estimation results. Therefore, in this study two spatial econometric models, namely Spatial Lag Model (SLM) and Spatial Error Model (SEM), are utilized to control for spatial effects. According to the estimation results, the relationship between PM2.5 concentrations and per capita GDP is inverted U-shaped, suggesting the existence of the inverted-U shaped Environmental Kuznets Curve (EKC) for air quality in China. In addition, the vehicle population and the secondary industry have significant and positive influences on urban PM2.5 concentrations. As a result, a series of comprehensive measures in both social and economic aspects as well as the regional coordination of environmental policies are needed to hold China's air pollution in check.
•The influential factors of urban PM2.5 concentrations in China are investigated.•Two spatial econometric models are used to control for the spatial correlation of air pollution.•The EKC relationship between PM2.5 concentrations and economic development is verified.•Vehicle population and the secondary industry influence urban PM2.5 concentrations positively.
Poly(vinylidene fluoride) (PVDF) membranes have been extensively applied to scientific research and industrial process due to its outstanding properties such as high thermal stability, good chemical ...resistance and membrane forming properties. This article provides an overview of recent progress on the application and modification of PVDF membranes. The applications include water treatment, membrane distillation, gas separation, pollutants removal, bioethanol recovery, separator for lithium ion battery, support for preparing composite membranes, etc. Subsequently, on the basis of two major problems of PVDF membranes in applications, i.e., membrane fouling and membrane wetting, the hydrophilic modification and hydrophobic modification methods are comprehensively reviewed. Finally, the key issues associated with the modification of PVDF membranes for actual applications are discussed. This paper may provide an insight for the development of PVDF membranes in future.
•A broad overview of applications of PVDF membranes is presented.•Hydrophilic modification to reduce membrane fouling in water treatment.•Hydrophobic modification to improve wetting resistance in membrane contactor.•Improving membrane preparation process and modifying existing membranes.
Over the past few years, CuH‐catalyzed hydroamination has been discovered and developed as a robust and conceptually novel approach for the synthesis of enantioenriched secondary and tertiary amines. ...The success in this area of research was made possible through the large body of precedent in copper(I) hydride catalysis and the well‐explored use of hydroxylamine esters as electrophilic amine sources in related copper‐catalyzed processes. This Minireview details the background, advances, and mechanistic investigations in CuH‐catalyzed hydroamination.
Mild and abundant: CuH‐catalyzed hydroamination has recently been developed as a viable method for synthesizing a broad range of chiral aliphatic amines in excellent efficiencies and enantioselectivites. This Minireview highlights advancements made in this area of catalysis along with the precedent that has led to these discoveries.
For improving forecasting accuracy and trading performance, this paper proposes a new multi‐objective least squares support vector machine with mixture kernels to forecast asset prices. First, a ...mixture kernel function is introduced into taking full use of global and local kernel functions, which is adaptively determined following a data‐driven procedure. Second, a multi‐objective fitness function is proposed by incorporating level forecasting and trading performance, and particle swarm optimization is used to synchronously search the optimal model selections of least squares support vector machine with mixture kernels. Taking CO2 assets as examples, the results obtained show that compared with the popular models, the proposed model can achieve higher forecasting accuracy and higher trading performance. The advantages of the mixture kernel function and the multi‐objective fitness function can improve the forecasting ability of the asset price. The findings also show that the models with a high‐level forecasting accuracy cannot always have a high trading performance of asset price forecasting. In contrast, high directional forecasting usually means a high trading performance.
Copper oxide‐based materials effectively electrocatalyze carbon dioxide reduction (CO2RR). To comprehend their role and achieve high CO2RR activity, Cu+ in copper oxides must be stabilized. As an ...electrocatalyst, Cu2O nanoparticles were decorated with hexagonal boron nitride (h‐BN) nanosheets to stabilize Cu+. The C2H4/CO ratio increased 1.62‐fold in the CO2RR with Cu2O−BN compared to that with Cu2O. Experimental and theoretical studies confirmed strong electronic interactions between the two components in Cu2O−BN, which strengthens the Cu−O bonds. Electrophilic h‐BN receives partial electron density from Cu2O, protecting the Cu−O bonds from electron attack during the CO2RR and stabilizing the Cu+ species during long‐term electrolysis. The well‐retained Cu+ species enhanced the C2 product selectivity and improved the stability of Cu2O−BN. This work offers new insight into the metal‐valence‐state‐dependent selectivity of catalysts, enabling the design of advanced catalysts.
Strong electronic interactions between hexagonal boron nitride (h‐BN) and Cu2O protect the Cu−O bonds against electron attack through the transfer of accumulated electrons from Cu2O to h‐BN. This effect stabilizes the active Cu+ species during CO2 electroreduction.
Exploring leptophilic dark matter with NA64-μ Chen, Chien-Yi; Kozaczuk, Jonathan; Zhong, Yi-Ming
The journal of high energy physics,
10/2018, Letnik:
2018, Številka:
10
Journal Article
Recenzirano
Odprti dostop
A
bstract
We investigate the prospects for detecting light leptophilic dark sectors with a missing-momentum experiment at NA64 running in muon mode. In particular, we consider models in which dark ...matter connects to the visible sector through a lepton- or muon-specific scalar mediator. These scalars can also account for the ∼ 3.5
σ
discrepancy between the measured and predicted values of (
g
−2)
μ
. We emphasize the complementarity between NA64-
μ
and other terrestrial and astrophysical probes.
A
bstract
Leptoquarks occur in many new physics scenarios and could be the next big discovery at the LHC. The purpose of this paper is to point out that a model-independent search strategy covering ...all possible leptoquarks is possible and has not yet been fully exploited. To be systematic we organize the possible leptoquark final states according to a leptoquark matrix with entries corresponding to nine experimentally distinguishable leptoquark decays: any of {light-jet,
b
-jet, top} with any of {neutrino,
e
/
μ
,
τ
}. The 9 possibilities can be explored in a largely model-independent fashion with pair-production of leptoquarks at the LHC. We review the status of experimental searches for the 9 components of the leptoquark matrix, pointing out which 3 have not been adequately covered. We plead that experimenters publish bounds on leptoquark cross sections as functions of mass for as wide a range of leptoquark masses as possible. Such bounds are essential for reliable recasts to general leptoquark models. To demonstrate the utility of the leptoquark matrix approach we collect and summarize searches with the same final states as leptoquark pair production and use them to derive bounds on a complete set of Minimal Leptoquark models which span all possible flavor and gauge representations for scalar and vector leptoquarks.
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