•This paper uses retired government officials who were hired as independent directors to define the firm's political connections.•We estimate the value of political connections by examining stock ...price reactions to sudden deaths of retired government officials who were acting as independent directors of private firms in China.•We use the exogenous shock – sudden death – to solve the endogeneity problem of political connections.•We explore the reasons why the sudden loss of political connections has negative effects on the private firm's market value.
This paper estimates the value of political connections by examining stock price reactions to sudden deaths of retired government officials who were acting as independent directors of private firms in China from 2003 to 2012. Employing an event study, we find that, if a private firm loses political connections because of the sudden death of an independent director who was previously a government official, its stock price drops 3.61% on average within ten trading days. After the loss of political connections, we find that it is possible but infeasible for a private firm to reestablish political connections with the government in a short period of time. Moreover, the sudden death of a retired government official leads to a reduction in the economic benefits (e.g., bank loans, tax preference, and government subsidies) obtained by a private firm, which provides a reasonable explanation for the negative stock price reaction after losing political connections.
To solve the problem of the global energy shortage and the pollution of the environment, in recent years, semiconductor photocatalytic technology that converts solar energy into chemical fuel has ...been widely studied. Regarding semiconductor-based photocatalysts, CdS has attracted extensive attention due to its relatively narrow bandgap for visible-light response and sufficiently negative potential of the conduction band edge for the reduction of protons. Studies have shown that CdS-based photocatalysts possess excellent photocatalytic performance in terms of solar-fuel generation and environmental purification. This critical review presents the recent advances and progress in the design and synthesis of various CdS and CdS-based photocatalysts. The basic physical and chemical properties of CdS and the related growth mechanism have been briefly summarized. Moreover, the applications of CdS-based photocatalysts have been discussed such as in photocatalytic hydrogen production, reduction of CO
2
to hydrocarbon fuels and degradation of pollutants. Finally, a brief perspective on the challenges and future directions for the development of CdS and CdS-based photocatalysts are also presented.
The review summarizes the recent progress in the synthesis, fundamental properties, morphology, photocatalytic applications and challenges of CdS-based photocatalysts.
The exploration of advanced and novel photocatalytic materials has been widely investigated in recent years. MXene, a new two-dimensional (2D) transition metal material, is gaining attention as a ...suitable alternative for promoting photocatalytic performance because of its flexible adjustability of elemental composition, regular layered structure, and excellent electrical conductivity. This Perspective summarizes the recent significant advancements in 2D MXene-based photocatalysts for solar fuel conversion. The rational design and specific effects of MXene-based photocatalysts for photocatalytic solar fuel generation are described. Moreover, the different roles of MXene in MXene-based photocatalysts, such as functional group provider, photocatalytic electronic acceptor, substrate, and cocatalyst, for improving photocatalytic performance are discussed. Further discussion about the challenges and optimizations for improvements of 2D MXene and MXene-based photocatalysts in the context of promising solar fuel generation is also presented.
The current semiconductor photocatalysts only exhibit unsatisfactory photocatalytic efficiency due to the easy recombination of photogenerated carriers. Regulating the separation and transfer of ...photogenerated carriers and reducing the recombination of photogenerated carriers are essential for improving the catalytic efficiency of photocatalysts. The recombination of photogenerated carriers is produced by the attraction of Coulombic force. Consequently, reducing the recombination of photogenerated carriers requires an additional driving force to counteract the attraction of Coulombic force. However, exploring the mechanism of photogenerated carrier regulation from the perspective of the driving force of photogenerated carrier separation and transfer has received only sporadic attention. This review first starts with the fundamental mechanism of photogenerated carrier recombination and the impairment of photogenerated carrier recombination to photocatalytic performance. Then it focuses on several main strategies for regulating the behavior of photogenerated carriers from the aspect of the driving force for the separation and transfer of photogenerated carriers, including heterojunction design, construction of an intramolecular donor-acceptor (D-A) system, exciton regulation, and electron spin regulation. Subsequently, advanced characterization techniques and the latest developments of theoretical calculations in the separation and migration of photogenerated carriers have been introduced. At the end, we summarize the current challenges of photogenerated carrier regulation and put forward the prospects for future development.
This review explores the mechanism of photogenerated carrier regulation from the aspect of the driving force of separation and transfer for photogenerated carrier dynamics.
It is greatly intriguing yet remains challenging to construct single‐atomic photocatalysts with stable surface free energy, favorable for well‐defined atomic coordination and photocatalytic carrier ...mobility during the photoredox process. Herein, an unsaturated edge confinement strategy is defined by coordinating single‐atomic‐site Ni on the bottom‐up synthesized porous few‐layer g‐C3N4 (namely, Ni5‐CN) via a self‐limiting method. This Ni5‐CN system with a few isolated Ni clusters distributed on the edge of g‐C3N4 is beneficial to immobilize the nonedged single‐atomic‐site Ni species, thus achieving a high single‐atomic active site density. Remarkably, the Ni5‐CN system exhibits comparably high photocatalytic activity for CO2 reduction, giving the CO generation rate of 8.6 µmol g−1 h−1 under visible‐light illumination, which is 7.8 times that of pure porous few‐layer g‐C3N4 (namely, CN, 1.1 µmol g−1 h−1). X‐ray absorption spectrometric analysis unveils that the cationic coordination environment of single‐atomic‐site Ni center, which is formed by Ni‐N doping‐intercalation the first coordination shell, motivates the superiority in synergistic N–Ni–N connection and interfacial carrier transfer. The photocatalytic mechanistic prediction confirms that the introduced unsaturated Ni‐N coordination favorably binds with CO2, and enhances the rate‐determining step of intermediates for CO generation.
The unsaturated edge confinement Ni‐anchored g‐C3N4 system is designed by coordinating single‐atomic‐site Ni species on the bottom‐up synthesized porous few‐layer g‐C3N4. The high single‐atomic active site density and the cationic coordination environment are formed by Ni‐N doping‐intercalation, and motivate the superiority in improving the interfacial carrier dynamics, thus boosting the photocatalytic CO2 reduction activity.
Polymeric graphitic carbon nitride (g‐C3N4) and various carbon materials have experienced a renaissance as viable alternates in photocatalysis due to their captivating metal‐free features, favorable ...photoelectric properties, and economic adaptabilities. Although numerous efforts have focused on the integration of both materials with optimized photocatalytic performance in recent years, the direct parameters for this emerging enhancement are not fully summarized yet. Fully understanding the synergistic effects between g‐C3N4 and carbon materials on photocatalytic action is vital to further development of metal‐free semiconductors in future studies. Here, recent advances of carbon/g‐C3N4 hybrids on various photocatalytic applications are reviewed. The dominant governing factors by inducing carbon into g‐C3N4 photocatalysts with involving photocatalytic mechanism are highlighted. Five typical carbon‐induced enhancement effects are mainly discussed here, i.e., local electric modification, band structure tailoring, multiple charge carrier activation, chemical group functionalization, and abundant surface‐modified engineering. Photocatalytic performance of carbon‐induced g‐C3N4 photocatalysts for addressing directly both the renewable energy storage and environmental remediation is also summarized. Finally, perspectives and ongoing challenges encountered in the development of metal‐free carbon‐induced g‐C3N4 photocatalysts are presented.
The review focuses on significant progress of carbon/g‐C3N4 hybrids for heterogeneous photocatalysis, including CO2 photoreduction, photocatalytic H2 generation, contaminant photodegradation, and N2 fixation. Especially, comprehensive analysis involving synergistic effects between g‐C3N4 and carbon materials on emerging photocatalytic action is summarized, such as local electric modification, band structure tailoring, multiple charge carrier activation, chemical group functionalization, and surface‐modified engineering.
Summary
Akkermansia muciniphila (A. muciniphila), an intestinal symbiont colonizing in the mucosal layer, is considered to be a promising candidate as probiotics. A. muciniphila is known to have an ...important value in improving the host metabolic functions and immune responses. Moreover, A. muciniphila may have a value in modifying cancer treatment. However, most of the current researches focus on the correlation between A. muciniphila and diseases, and little is known about the causal relationship between them. Few intervention studies on A. muciniphila are limited to animal experiments, and limited studies have explored its safety and efficacy in humans. Therefore, a critical analysis of the current knowledge in A. muciniphila will play an important foundation for it to be defined as a new beneficial microbe. This article will review the bacteriological characteristics and safety of A. muciniphila, as well as its causal relationship with metabolic disorders, immune diseases and cancer therapy.
Akkermansia muciniphila (A. muciniphila), an intestinal symbiont colonizing in the mucosal layer, is considered to be a promising candidate as a probiotics. Most of the current researches focus on the correlation between A. muciniphila and diseases, and little is known about the causal relationship between them. This article will review the bacteriological characteristics and safety of A. muciniphila, as well as its causal relationship with metabolic disorders, immune diseases, and cancer therapy.
In this brief, attitude control is investigated for a quadrotor under gust wind via a dual closed-loop control framework. In the dual closed-loop framework, active disturbance rejection control and ...proportional-derivative control are used in the inner and outer loops, respectively. The perturbations of gust wind are considered as dynamic disturbances, which are estimated by an extended state observer in the inner loop. Both convergence and stabilization are given for the extended state observer and the closed-loop system, respectively. Experimental results are given to show the effectiveness of the proposed method for quadrotors.
In recent years, virtual reality (VR) has been tested as a therapeutic tool in neurorehabilitation research. However, the impact effectiveness of VR technology on for Parkinson's Disease (PD) ...patients is still remains controversial unclear. In order to provide a more scientific basis for rehabilitation of PD patients' modality, we conducted a systematic review of VR rehabilitation training for PD patients and focused on the improvement of gait and balance.
An comprehensive search was conducted using the following databases: PubMed, Web of Science, Cochrane Library, CINHAL, Embase and CNKI (China National Knowledge Infrastructure).Articles published before 30 December 2018 and of a randomized controlled trial design to study the effects of VR for patients with PD were included. The study data were pooled and a meta-analysis was completed. This systematic review was conducted in accordance with the PRISMA guideline statement and was registered in the PROSPERO database (CRD42018110264).
A total of sixteen articles involving 555 participants with PD were included in our analysis. VR rehabilitation training performed better than conventional or traditional rehabilitation training in three aspects: step and stride length (SMD = 0.72, 95%CI = 0.40,1.04, Z = 4.38, P<0.01), balance function (SMD = 0.22, 95%CI = 0.01,0.42, Z = 2.09, P = 0.037), and mobility(MD = -1.95, 95%CI = -2.81,-1.08, Z = 4.41, P<0.01). There was no effect on the dynamic gait index (SMD = -0.15, 95%CI = -0.50,0.19, Z = 0.86, P = 0.387), and gait speed (SMD = 0.19, 95%CI = -0.03,0.40, Z = 1.71, P = 0.088).As for the secondary outcomes, compared with the control group, VR rehabilitation training demonstrated more significant effects on the improvement of quality of life (SMD = -0.47, 95%CI = -0.73,-0.22, Z = 3.64, P<0.01), level of confidence (SMD = -0.73, 95%CI = -1.43,-0.03, Z = 2.05, P = 0.040), and neuropsychiatric symptoms (SMD = -0.96, 95%CI = -1.27,-0.65, Z = 6.07, P<0.01), while it may have similar effects on global motor function (SMD = -0.50, 95%CI = -1.48,0.48, Z = 0.99, P = 0.32), activities of daily living (SMD = 0.25, 95%CI = -0.14,0.64, Z = 1.24, P = 0.216), and cognitive function (SMD = 0.21, 95%CI = -0.28,0.69, Z = 0.84, P = 0.399).During the included interventions, four patients developed mild dizziness and one patient developed severe dizziness and vomiting.
According to the results of this study, we found that VR rehabilitation training can not only achieve the same effect as conventional rehabilitation training. Moreover, it has better performance on gait and balance in patients with PD. Taken together, when the effect of traditional rehabilitation training on gait and balance of PD patients is not good enough, we believe that VR rehabilitation training can at least be used as an alternative therapy. More rigorous design of large-sample, multicenter randomized controlled trials are needed to provide a stronger evidence-based basis for verifying its potential advantages.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A novel β-coronavirus (2019-nCoV) caused severe and even fetal pneumonia explored in a seafood market of Wuhan city, Hubei province, China, and rapidly spread to other provinces of China and other ...countries. The 2019-nCoV was different from SARS-CoV, but shared the same host receptor the human angiotensin-converting enzyme 2 (ACE2). The natural host of 2019-nCoV may be the bat Rhinolophus affinis as 2019-nCoV showed 96.2% of whole-genome identity to BatCoV RaTG13. The person-to-person transmission routes of 2019-nCoV included direct transmission, such as cough, sneeze, droplet inhalation transmission, and contact transmission, such as the contact with oral, nasal, and eye mucous membranes. 2019-nCoV can also be transmitted through the saliva, and the fetal-oral routes may also be a potential person-to-person transmission route. The participants in dental practice expose to tremendous risk of 2019-nCoV infection due to the face-to-face communication and the exposure to saliva, blood, and other body fluids, and the handling of sharp instruments. Dental professionals play great roles in preventing the transmission of 2019-nCoV. Here we recommend the infection control measures during dental practice to block the person-to-person transmission routes in dental clinics and hospitals.
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