Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
4,205
result(s) for
"Chen, Xiaohong"
Sort by:
ESTIMATION OF NONPARAMETRIC CONDITIONAL MOMENT MODELS WITH POSSIBLY NONSMOOTH GENERALIZED RESIDUALS
This paper studies nonparametric estimation of conditional moment restrictions in which the generalized residual functions can be nonsmooth in the unknown functions of endogenous variables. This is a nonparametric nonlinear instrumental variables (IV) problem. We propose a class of penalized sieve minimum distance (PSMD) estimators, which are minimizers of a penalized empirical minimum distance criterion over a collection of sieve spaces that are dense in the infinite-dimensional function parameter space. Some of the PSMD procedures use slowly growing finite-dimensional sieves with flexible penalties or without any penalty; others use large dimensional sieves with lower semicompact and/or convex penalties. We establish their consistency and the convergence rates in Banach space norms (such as a sup-norm or a root mean squared norm), allowing for possibly noncompact infinite-dimensional parameter spaces. For both mildly and severely ill-posed nonlinear inverse problems, our convergence rates in Hubert space norms (such as a root mean squared norm) achieve the known minimax optimal rate for the nonparametric mean IV regression. We illustrate the theory with a nonparametric additive quantile IV regression. We present a simulation study and an empirical application of estimating nonparametric quantile IV Engel curves.
Journal Article
Near-infrared optogenetic engineering of photothermal nanoCRISPR for programmable genome editing
We herein report an optogenetically activatable CRISPR-Cas9 nanosystem for programmable genome editing in the second near-infrared (NIR-II) optical window. The nanosystem, termed nanoCRISPR, is composed of a cationic polymer-coated Au nanorod (APC) and Cas9 plasmid driven by a heat-inducible promoter. The APC not only serves as a carrier for intracellular plasmid delivery but also can harvest external NIR-II photonic energy and convert it into local heat to induce the gene expression of the Cas9 endonuclease. Due to high transfection activity, the APC shows strong ability to induce a significant level of disruption in different genomic loci upon optogenetic activation. Moreover, the precise control of genome-editing activity can be simply programmed by finely tuning exposure time and irradiation time in vitro and in vivo and also enables editing at multiple time points, thus proving the sensitivity and inducibility of such an editing modality. The NIR-II optical feature of nanoCRISPR enables therapeutic genome editing at deep tissue, by which treatment of deep tumor and rescue of fulminant hepatic failure are demonstrated as proof-of-concept therapeutic examples. Importantly, this modality of optogenetic genome editing can significantly minimize the off-target effect of CRISPR-Cas9 in most potential off-target sites. The optogenetically activatable CRISPR-Cas9 nanosystem we have developed offers a useful tool to expand the current applications of CRISPR-Cas9, and also defines a programmable genome-editing strategy toward high precision and spatial specificity.
Journal Article
Stepwise taming of triplet excitons via multiple confinements in intrinsic polymers for long-lived room-temperature phosphorescence
Polymeric materials exhibiting room temperature phosphorescence (RTP) show a promising application potential. However, the conventional ways of preparing such materials are mainly focused on doping, which may suffer from phase separation, poor compatibility, and lack of effective methods to promote intersystem crossing and suppress the nonradiative deactivation rates. Herein, we present an intrinsically polymeric RTP system producing long-lived phosphorescence, high quantum yields and multiple colors by stepwise structural confinement to tame triplet excitons. In this strategy, the performance of the materials is improved in two aspects simultaneously: the phosphorescence lifetime of one polymer (9VA-B) increased more than 4 orders of magnitude, and the maximum phosphorescence quantum yield reached 16.04% in halogen-free polymers. Moreover, crack detection is realized by penetrating steam through the materials exposed to humid surroundings as a special quenching effect, and the information storage is carried out by employing the Morse code and the variations in lifetimes. This study provides a different strategy for constructing intrinsically polymeric RTP materials toward targeted applications.
Materials with room temperature phosphorescence have potential in a range of applications, but preparing the systems can still be challenging. Here, the authors report an intrinsically polymeric room temperature phosphorescent material, applied in crack detection.
Journal Article
Dual donor-acceptor covalent organic frameworks for hydrogen peroxide photosynthesis
Constructing photocatalytically active and stable covalent organic frameworks containing both oxidative and reductive reaction centers remain a challenge. In this study, benzotrithiophene-based covalent organic frameworks with spatially separated redox centers are rationally designed for the photocatalytic production of hydrogen peroxide from water and oxygen without sacrificial agents. The triazine-containing framework demonstrates high selectivity for H
2
O
2
photogeneration, with a yield rate of 2111 μM h
−1
(21.11 μmol h
−1
and 1407 μmol g
−1
h
−1
) and a solar-to-chemical conversion efficiency of 0.296%. Codirectional charge transfer and large energetic differences between linkages and linkers are verified in the double donor-acceptor structures of periodic frameworks. The active sites are mainly concentrated on the electron-acceptor fragments near the imine bond, which regulate the electron distribution of adjacent carbon atoms to optimally reduce the Gibbs free energy of O
2
* and OOH* intermediates during the formation of H
2
O
2
.
In this study, benzotrithiophene-based covalent organic frameworks with spatially separated oxidative and reductive reaction centers are rationally designed for photocatalytic production of H
2
O
2
from water and oxygen without sacrificial agents.
Journal Article
Can information and communication technology reduce CO2 emission? A quantile regression analysis
By employing China’s provincial panel data covering period 2001–2016, the present study empirically investigates the impact of ICT on CO
2
emission intensity. Specifically, this paper utilizes Internet penetration and mobile phone penetration as proxies to measure ICT respectively and employs quantile regression method to estimate the benchmark model at five quantiles (0.1, 0.25, 0.5, 0.75, and 0.9). It is demonstrated that Internet penetration at the national level has a significant negative effect on the CO
2
emission intensity for all quantiles. In addition, Internet penetration has a significant negative effect on CO
2
emission intensity at all quantiles except for 0.1 quantile for China’s eastern provinces and has a significant negative effect on CO
2
emission intensity at all quantiles for China’s central provinces, whereas Internet penetration has no significant negative impact on CO
2
emission intensity at all quantiles for China’s western provinces. By comparison, the reduction effect of Internet penetration on CO
2
emission intensity in China’s eastern and central provinces is more obvious and in contrast with the reduction effect of Internet penetration on CO
2
emission intensity in China’s eastern provinces, it is greater in China’s central provinces. Finally, the impact of mobile phone penetration on CO
2
emission intensity is generally consistent with the impact of Internet penetration. This study provides further evidence that developing countries can simultaneously achieve economic development and reduce carbon emissions through ICT.
Journal Article
Algebro-Geometric Solutions of a (2+1)-Dimensional Integrable Equation Associated with the Ablowitz-Kaup-Newell-Segur Soliton Hierarchy
The (2+1)-dimensional Lax integrable equation is decomposed into solvable ordinary differential equations with the help of known (1+1)-dimensional soliton equations associated with the Ablowitz-Kaup-Newell-Segur soliton hierarchy. Then, based on the finite-order expansion of the Lax matrix, a hyperelliptic Riemann surface and Abel-Jacobi coordinates are introduced to straighten out the associated flows, from which the algebro-geometric solutions of the (2+1)-dimensional integrable equation are proposed by means of the Riemann θ functions.
Journal Article
Understanding Health Empowerment From the Perspective of Information Processing: Questionnaire Study
Massive, easily accessible online health information empowers users to cope with health problems better. Most patients search for relevant online health information before seeing a doctor to alleviate information asymmetry. However, the mechanism of how online health information affects health empowerment is still unclear.
To study how online health information processing affects health empowerment.
We conducted a cross-sectional questionnaire study that included 343 samples from participants who had searched online health information before the consultation. Respondents' perceptions of online information cues, benefits, health literacy, and health empowerment were assessed.
Perceived argument quality and perceived source credibility have significant and positive effects on perceived information benefits, but only perceived argument quality has a significant effect on perceived decision-making benefits. Two types of perceived benefits, in turn, affect health empowerment. The effects of perceived argument quality on perceived informational benefits and perceived decision-making benefits on health empowerment are significantly stronger for the high health literacy group than the low health literacy group (t
=7.156, P<.001; t
=23.240, P<.001). While, the effects of perceived source credibility on perceived informational benefits and perceived informational benefits on health empowerment are significantly weaker for the high health literacy group than the low health literacy group (t
=-10.497, P<.001; t
=-6.344, P<.001). The effect of perceived argument quality on perceived informational benefits shows no significant difference between high and low health literacy groups.
In the context of online health information, perceived information benefits and perceived decision-making benefits are the antecedents of health empowerment, which in turn will be affected by perceived argument quality and perceived source credibility. Health literacy plays a moderating role in the relationship of some variables. To maximize health empowerment, online health information providers should strengthen information quality and provide differentiated information services based on users' health literacy.
Journal Article
Long lifetimes white afterglow in slightly crosslinked polymer systems
Intrinsic polymer room-temperature phosphorescence (IPRTP) materials have attracted considerable attention for application in flexible electronics, information encryption, lighting displays, and other fields due to their excellent processabilities and luminescence properties. However, achieving multicolor long-lived luminescence, particularly white afterglow, in undoped polymers is challenging. Herein, we propose a strategy of covalently coupling different conjugated chromophores with poly(acrylic acid (AA)-AA-N-succinimide ester) (PAA-NHS) by a simple and rapid one-pot reaction to obtain pure polymers with long-lived RTPs of various colors. Among these polymers, the highest phosphorescence quantum yield of PAPHE reaches 14.7%. Furthermore, the afterglow colors of polymers can be modulated from blue to red by introducing three chromophores into them. Importantly, the acquired polymer TPAP-514 exhibits a white afterglow at room temperature with the chromaticity coordinates (0.33, 0.33) when the ratio of chromophores reaches a suitable value owing to the three-primary-color mechanism. Systematic studies prove that the emission comes from the superposition of different triplet excited states of the three components. Moreover, the potential applications of the obtained polymers in light-emitting diodes and dynamic anti-counterfeiting are explored. The proposed strategy provides a new idea for constructing intrinsic polymers with diverse white-light emission RTPs.
It is challenging to achieve multicolor long-lived room temperature phosphorescence in intrinsic polymers, especially for white afterglow. Here, the authors report a strategy to obtain pure white afterglow micro-crosslinked polymers by covalently coupling different conjugated chromophores with precursors through a simple and rapid one-pot reaction.
Journal Article
Knockdown of miR-21-5P targets and regulates PDCD4-induced apoptosis in ovarian granulosa cells and ameliorates in sulin resistance in polycystic ovary syndrom
This study examined the role of miRNA-21-5p in a rat model of polycystic ovary syndrome with insulin resistance (PCOS-IR) and its potential involvement in ovarian granulosa cell apoptosis. Female Sprague-Dawley rats were divided into four groups, with the PCOS-IR model established using dehydroepiandrosterone combined with a high-sugar, high-fat diet. Lentiviral transduction was utilized to silence miRNA-21-5p. Serum hormone levels were assessed via ELISA, while the protein expression of PDCD4, Bcl-2, and Caspase-3 in ovarian tissues was analyzed through Western blotting. Granulosa cell apoptosis was evaluated using CCK-8 assay, flow cytometry, and TUNEL staining. The targeting relationship between miRNA-21-5p and PDCD4 was confirmed via dual-luciferase reporter assay and further supported by AlphaFold3 and RNA immunoprecipitation (RIP) prediction. Compared to the PCOS-IR and si-NC groups, the si-miRNA-21-5p group displayed improved ovarian morphology, partially restored hormone levels, moderately enhanced insulin sensitivity, and reduced granulosa cell apoptosis, alongside altered PDCD4 expression. These findings suggest that miRNA-21-5p may play a role in the pathogenesis of PCOS-IR by regulating PDCD4 and influencing granulosa cell apoptosis. Inhibition of miRNA-21-5p shows potential in alleviating certain pathological features within this experimental model; however, further validation in human studies is needed to assess its clinical relevance and therapeutic applicability.
Journal Article