Surface‐enhanced Raman scattering (SERS) spectroscopy on semiconductors has attracted increasing attention due to its high spectral reproducibility and unique selectively to target molecules. ...Recently, endeavors have been made in fabricating novel SERS‐active semiconductor substrates and exploring new enhancement mechanisms to improve the sensitivity of semiconductor substrates. This Minireview explains the enhancement mechanism of the semiconductor SERS effect in a brief tutorial and summarize recent developments of novel semiconductor substrates, in particular with regard to the remarkable SERS activity of amorphous semiconductor nanomaterials. Potential applications of semiconductor SERS are also a key issue of concern. We discuss a variety of promising applications of semiconductor SERS in the fields of in situ analytical chemistry, spectroelectrochemical analysis, biological sensing, and trace detection.
Amorphous and active: This Minireview explains the enhancement mechanism of the semiconductor SERS effect (SERS=surface‐enhanced Raman scattering) and summarizes recent developments in novel semiconductor substrates with a focus on the remarkable SERS activity of amorphous semiconductor nanomaterials. The variety of promising applications of semiconductor SERS is also discussed.
Basketball is a sport that is widely participated in all over the world. Accurately identifying the behavior in basketball training is beneficial to the improvement of athletes’ skills and the ...evaluation of training effects. The traditional basketball behavior detection methods are usually limited by complex sports scenes and various actions, which leads to the inaccuracy and low efficiency of the recognition results. The aim of this study is to use image optical processing technology to propose a fast behavior detection method to realize the accurate recognition and analysis of basketball training images. Based on the image optical processing technology, the behavior detection is carried out by shooting the image of the basketball training scene, and then using the image processing algorithm to extract the key information and features. Then the deep learning algorithm is used to classify and identify the behaviors in order to realize the accurate detection of different basketball training behaviors. Finally, through experimental verification and performance evaluation, the fast behavior detection method based on image optical processing has achieved remarkable results in recognizing the behavior in basketball training images. Compared with traditional methods, the proposed method has better performance in terms of accuracy and response time.
Conspectus The utilization of carboxylic acid esters as electrophiles in metal-catalyzed cross-coupling reactions is increasingly popular, as environmentally friendly and readily available ester ...derivatives can be powerful alternatives to the commonly used organohalides. However, key challenges associated with the use of these chemicals remain to be addressed, including the stability of ester substrates and the high energy barrier associated with their oxidative addition to low-valent metal species. Due to recent developments in nickel catalysis that make it easier to perform oxidative additions, chemists have become interested in applying less reactive electrophiles as coupling counterparts in nickel-catalyzed transformations. Hence, our group and others have independently investigated various ester group substitutions and functionalizations enabled by nickel catalysis. Such methods are of great interest as they enable the exchange of ester groups, which can be used as directing groups in metal-catalyzed C–H functionalizations prior to their replacement. Here, we summarize our recent efforts toward the development of nickel-catalyzed decarbonylative cross-coupling reactions of carboxylic esters. Achievements accomplished by other groups in this area are also included. To this day, a number of new transformations have been successfully developed, including decarbonylative arylations, alkylations, cyanations, silylations, borylations, aminations, thioetherifications, stannylations, and hydrogenolysis reactions. These transformations proceed via a nickel-catalyzed decarbonylative pathway and have shown a high degree of reactivity and chemoselectivity, as well as several other unique advantages in terms of substrate availability, due to the use of esters as coupling partners. Although the mechanisms of these reactions have not yet been fully understood, chemists have already provided some important insights. For example, Yamamoto explored the stoichiometric nickel-mediated decarbonylation process of esters and proposed a reaction mechanism involving a C(acyl)–O bond cleavage and a CO extrusion. Key nickel intermediates were isolated and characterized by Shi and co-workers, supporting the assumption of a nickel/N-heterocyclic carbene-promoted C(acyl)–O bond activation and functionalization. Our combined experimental and computational study of a ligand-controlled chemoselective nickel-catalyzed cross-coupling of aromatic esters with alkylboron reagents provided further insight into the reaction mechanism. We demonstrated that nickel complexes with bidentate ligands favor the C(aryl)–C bond cleavage in the oxidative addition step, resulting in decarbonylative alkylations, while nickel complexes with monodentate phosphorus ligands promote the activation of the C(acyl)–O bond, leading to the production of ketone products. Although more detailed mechanistic investigations need to be undertaken, the successful development of decarbonylative cross-coupling reactions can serve as a solid foundation for future studies. We believe that this type of decarbonylative cross-coupling reactions will be of significant value, in particularly in combination with the retrosynthetic analysis and synthesis of natural products and biologically active molecules. Thus, the presented ester substitution methods will pave the way for successful applications in the construction of complex frameworks by late-stage modification and functionalization of carboxylic acid derivatives.
Abstract
Background
The duration of humoral and T and B cell response after the infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains unclear.
Methods
We performed a ...cross-sectional study to assess the virus-specific antibody and memory T and B cell responses in coronavirus disease 2019 (COVID-19) patients up to 343 days after infection. Neutralizing antibodies and antibodies against the receptor-binding domain, spike, and nucleoprotein of SARS-CoV-2 were measured. Virus-specific memory T and B cell responses were analyzed.
Results
We enrolled 59 patients with COVID-19, including 38 moderate, 16 mild, and 5 asymptomatic patients; 31 (52.5%) were men and 28 (47.5%) were women. The median age was 41 years (interquartile range, 30–55). The median day from symptom onset to enrollment was 317 days (range 257 to 343 days). We found that approximately 90% of patients still have detectable immunoglobulin (Ig)G antibodies against spike and nucleocapsid proteins and neutralizing antibodies against pseudovirus, whereas ~60% of patients had detectable IgG antibodies against receptor-binding domain and surrogate virus-neutralizing antibodies. The SARS-CoV-2-specific IgG+ memory B cell and interferon-γ-secreting T cell responses were detectable in more than 70% of patients.
Conclusions
Severe acute respiratory syndrome coronavirus 2-specific immune memory response persists in most patients approximately 1 year after infection, which provides a promising sign for prevention from reinfection and vaccination strategy.
SARS-CoV-2-specific antibody and memory T and B cell responses were detectable in most patients approximately 1 year after infection, indicating that durable immunity against secondary COVID-19 disease is possible in most individuals.
Green tea drinking has been proven to lower lipid and exert cardiovascular protection, while the potential mechanism has not been fully determined. This study was to investigate whether the ...beneficial impact of epigallocatechingallate (EGCG), a type of catechin in green tea on lipids is associated with proprotein convertase subtilisin/kexin type 9 (PCSK9) pathways.
We studied the effects and underlying molecular mechanism of EGCG or green tea on regulating cholesterol from human, animal and in vitro.
In the age- and gender-matched case control observation, we found that individuals with frequent tea consumption (n = 224) had the lower plasma PCSK9 and low density lipoprotein cholesterol (LDL-C) levels compared with ones without tea consumption (n = 224, p < 0.05). In the high fat diet (HFD) fed rats, EGCG administration significantly lowered circulating PCSK9 concentration and liver PCSK9 expression, along with up-regulated LDL receptor (LDLR) expression but decreased level of LDL-C. In hepatic cell study, similar results were obtained regarding the impact of EGCG on LDLR and PCSK9 expression. The assay transposase-accessible chromatic with high-throughput sequencing (ATAC-seq) and subsequent results suggested that two transcription factors, hepatocyte nuclear factor-1α (HNF-1α) and forkhead box class O (FoxO) 3a involved in inhibitory action of EGCG on PCSK9 expression.
The present study demonstrates that EGCG suppresses PCSK9 production by promoting nuclear FoxO3a, and reducing nuclear HNF1α, resulting in up-regulated LDLR expression and LDL uptake in hepatocytes. Thereby inhibiting liver and circulating PCSK9 levels, and ultimately lowering LDL-C levels.
As core units of organ tissues, cells of various types play their harmonious rhythms to maintain the homeostasis of the human body. It is essential to identify the characteristics of cells in human ...organs and their regulatory networks for understanding the biological mechanisms related to health and disease. However, a systematic and comprehensive single-cell transcriptional profile across multiple organs of a normal human adult is missing.
We perform single-cell transcriptomes of 84,363 cells derived from 15 tissue organs of one adult donor and generate an adult human cell atlas. The adult human cell atlas depicts 252 subtypes of cells, including major cell types such as T, B, myeloid, epithelial, and stromal cells, as well as novel COCH
fibroblasts and FibSmo cells, each of which is distinguished by multiple marker genes and transcriptional profiles. These collectively contribute to the heterogeneity of major human organs. Moreover, T cell and B cell receptor repertoire comparisons and trajectory analyses reveal direct clonal sharing of T and B cells with various developmental states among different tissues. Furthermore, novel cell markers, transcription factors, and ligand-receptor pairs are identified with potential functional regulations in maintaining the homeostasis of human cells among tissues.
The adult human cell atlas reveals the inter- and intra-organ heterogeneity of cell characteristics and provides a useful resource in uncovering key events during the development of human diseases in the context of the heterogeneity of cells and organs.
Transition metal‐catalyzed decarbonylative coupling reactions have emerged as a powerful alternative to conventional cross‐coupling protocols due to the advantages associated with the use of ...carbonyl‐containing functionalities as coupling electrophiles instead of commonly used organohalides or sulfates. A wide variety of novel transformations based on this concept have been successfully achieved, including decarbonylative carbon–carbon and carbon–heteroatom bond forming reactions. In this Review, we summarize the recent progress in this field and present a comprehensive overview of metal‐catalyzed decarbonylative coupling reactions with carbonyl derivatives.
In view of the advantages of using carbonyl‐containing compounds as coupling electrophiles instead of the commonly used organohalides or sulfates, transition‐metal‐catalyzed decarbonylative coupling reactions have emerged as powerful alternatives to the conventional cross‐coupling protocols. A wide variety of novel transformations based on this concept have been achieved, including decarbonylative carbon–carbon and carbon–heteroatom bond forming‐reactions. In this Review, we summarize the recent progress in this field and present a comprehensive overview of transition‐metal‐catalyzed decarbonylative coupling reactions with carbonyl derivatives.
The Role of Polarization in Photocatalysis Chen, Fang; Huang, Hongwei; Guo, Lin ...
Angewandte Chemie International Edition,
July 22, 2019, Letnik:
58, Številka:
30
Journal Article
Recenzirano
Semiconductor photocatalysis as a desirable technology shows great potential in environmental remediation and renewable energy generation, but its efficiency is severely restricted by the rapid ...recombination of charge carriers in the bulk phase and on the surface of photocatalysts. Polarization has emerged as one of the most effective strategies for addressing the above‐mentioned issues, thus effectively promoting photocatalysis. This review summarizes the recent advances on improvements of photocatalytic activity by polarization‐promoted bulk and surface charge separation. Highlighted is the recent progress in charge separation advanced by different types of polarization, such as macroscopic polarization, piezoelectric polarization, ferroelectric polarization, and surface polarization, and the related mechanisms. Finally, the strategies and challenges for polarization enhancement to further enhance charge separation and photocatalysis are discussed.
Polar opposites: Macroscopic polarization, piezoelectric polarization, ferroelectric polarization, and surface polarization have emerged as promising strategies for accelerating the separation of photogenerated charge carriers either in the bulk phase or on the surface of semiconductor photocatalysts. Recent progress as well as future challenges are discussed.
Background: Whether a minimal width of keratinized mucosa (KM) is required to maintain peri‐implant tissue health has been a topic of interest. This systematic review and meta‐analysis aims to ...investigate the effect of KM on various peri‐implant health‐related parameters.
Methods: An electronic search of five databases (from 1965 to October 2012) and a hand search of peer‐reviewed journals for relevant articles were performed. Human cross‐sectional or longitudinal studies with data on the relationship between the amount of KM around dental implants and various peri‐implant parameters, with a follow‐up period of at least 6 months, were included.
Results: Eleven studies, seven cross‐sectional and four longitudinal, were included. Weighted mean difference (WMD) and confidence interval (CI) were calculated with meta‐analyses for each clinical parameter. The results showed statistically significant differences in plaque index (PI) and modified PI (WMD = −0.27, 95% CI = −0.43 to −0.11), modified gingival index (mGI) (WMD = −0.48, 95% CI = −0.70 to −0.27), mucosal recession (MR) (WMD = −0.60 mm, 95% CI = −0.85 to −0.36 mm), and attachment loss (AL) (WMD = −0.35 mm, 95% CI = −0.65 mm to −0.06 mm), all favoring implants with wide KM. However, comparisons of other parameters (bleeding on probing, modified bleeding index, GI, probing depth, and radiographic bone loss) did not reach statistically significant differences. The result of heterogeneity test showed only one parameter (AL, P value for the χ2 test = 0.30 and I2 test = 18%) had a low degree of heterogeneity among analyzed studies; meta‐analyses of other parameters presented moderate‐to‐high degree of heterogeneity. Limitations of the present review include limited number of selected studies (n = 11), existence of heterogeneity and publication bias, and only English‐written articles searched.
Conclusion: Based on current available evidence, a lack of adequate KM around endosseous dental implants is associated with more plaque accumulation, tissue inflammation, MR, and AL.
Aims
This review aimed at investigating the effect of membrane exposure on guided bone regeneration (GBR) outcomes at peri‐implant sites and edentulous ridges.
Material and Methods
Electronic and ...manual literature searches were conducted by two independent reviewers using four databases, including MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials, for articles up to February 2017. Articles were included if they were human clinical trials or case series reporting outcomes of GBR procedures with and without membrane exposure. A random‐effects meta‐analysis was conducted, and the weighted mean difference (WMD) between the two groups and 95% confidence interval (CI) were reported.
Results
Overall, eight articles were included in the quantitative analysis. The WMD of the horizontal bone gain at edentulous ridges was −76.24% (95% CI = −137.52% to −14.97%, p = .01) between sites with membrane exposure and without exposure. In addition, the WMD of the dehiscence reduction at peri‐implant sites was −27.27% (95% CI of −45.87% to −8.68%, p = .004). Both analyses showed significantly favorable outcomes at the sites without membrane exposure.
Conclusion
Based on the findings of this study, membrane exposure after GBR procedures has a significant detrimental influence on the outcome of bone augmentation. For the edentulous ridges, the sites without membrane exposure achieved 74% more horizontal bone gain than the sites with exposure. For peri‐implant dehiscence defects, the sites without membrane exposure had 27% more defect reduction than the sites with exposure.
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