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"Song, Lin"
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Two-Sided Price Discrimination by Media Platforms
A theory of two-sided markets where media platforms can price discriminate among both advertisers and consumers.
An increasingly common practice among media platforms is to provide premium content versions with fewer or even no ads. This practice leads to an intriguing question: how should ad-financed media price discriminate through versioning? I develop a two-sided media model and illustrate that price discrimination on one side can strengthen the incentive to discriminate on the other. Under this self-reinforcing mechanism, the ad allocations across different consumer types depend crucially on how much nuisance of an ad “costs” consumers relative to the value it brings to them. Interestingly, higher-type consumers, who value content and advertising quality highly, may see more ads than lower-type consumers if the nuisance cost is relatively low. Furthermore, the standard downward quality distortion generally fails to materialize in a two-sided market and may even be reversed: higher-type consumers may be exposed to too few ads that result in a lower total quality than the socially efficient level, whereas lower-type consumers may receive a socially excessive quality. The circumstances under which the self-reinforcing mechanism may be weakened and the implications for media platform design are explored.
Journal Article
Metal-catalyzed electrochemical diazidation of alkenes
Vicinal diamines are a common structural motif in bioactive natural products, therapeutic agents, and molecular catalysts, motivating the continuing development of efficient, selective, and sustainable technologies for their preparation. We report an operationally simple and environmentally friendly protocol that converts alkenes and sodium azide—both readily available feedstocks—to 1,2-diazides. Powered by electricity and catalyzed by Earth-abundant manganese, this transformation proceeds under mild conditions and exhibits exceptional substrate generality and functional group compatibility. Using standard protocols, the resultant 1,2-diazides can be smoothly reduced to vicinal diamines in a single step, with high chemoselectivity. Mechanistic studies are consistent with metal-mediated azidyl radical transfer as the predominant pathway, enabling dual carbon-nitrogen bond formation.
Journal Article
Visible quantum dot light-emitting diodes with simultaneous high brightness and efficiency
Quantum dot light-emitting diodes are promising light sources for applications in displays. However, to date, there have been no reports of devices that simultaneously offer both high brightness and high external quantum efficiency. Here, we report red, green and blue quantum dot light-emitting diodes based on CdSe/ZnSe core/shell structures that have these attributes. We demonstrate devices with maximum external quantum efficiencies of 21.6%, 22.9% and 8.05% for red, green and blue colours with corresponding brightness of 13,300 cd m–2, 52,500 cd m–2 and 10,100 cd m–2. The devices also offer peak luminance of 356,000 cd m–2, 614,000 cd m–2 and 62,600 cd m–2, respectively. We postulate that this high performance is due to the use of Se throughout the core/shell regions and the existence of alloyed bridging layers at the core/shell interfaces. This study suggests that in the future visible quantum dot light-emitting diodes will also be suitable for lighting applications.Red, green and blue CdSe/ZnSe quantum dot light-emitting diodes combine efficient operation with high brightness.
Journal Article
Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states
A spin-flip from a triplet to a singlet excited state, that is, reverse intersystem crossing (RISC), is an attractive route for improving light emission in organic light-emitting diodes, as shown by devices using thermally activated delayed fluorescence (TADF). However, device stability and efficiency roll-off remain challenging issues that originate from a slow RISC rate (kRISC). Here, we report a TADF molecule with multiple donor units that form charge-resonance-type hybrid triplet states leading to a small singlet–triplet energy splitting, large spin–orbit couplings, and a dense manifold of triplet states energetically close to the singlets. The kRISC in our TADF molecule is as fast as 1.5 × 107 s−1, a value some two orders of magnitude higher than typical TADF emitters. Organic light-emitting diodes based on this molecule exhibit good stability (estimated T90 about 600 h for 1,000 cd m−2), high maximum external quantum efficiency (>29.3%) and low efficiency roll-off (<2.3% at 1,000 cd m−2).An organic molecule, 5Cz-TRZ, with multiple donor units supports fast reverse intersystem crossing, allowing fabrication of high-performance organic light-emitting diodes.
Journal Article
Long-lived efficient delayed fluorescence organic light-emitting diodes using n-type hosts
Organic light-emitting diodes have become a mainstream display technology because of their desirable features. Third-generation electroluminescent devices that emit light through a mechanism called thermally activated delayed fluorescence are currently garnering much attention. However, unsatisfactory device stability is still an unresolved issue in this field. Here we demonstrate that electron-transporting n-type hosts, which typically include an acceptor moiety in their chemical structure, have the intrinsic ability to balance the charge fluxes and broaden the recombination zone in delayed fluorescence organic electroluminescent devices, while at the same time preventing the formation of high-energy excitons. The n-type hosts lengthen the lifetimes of green and blue delayed fluorescence devices by > 30 and 1000 times, respectively. Our results indicate that n-type hosts are suitable to realize stable delayed fluorescence organic electroluminescent devices.
OLEDs based on thermally activated delayed fluorescence have shown high fluorescence efficiency but poor lifetime. Herein, Cui et al. demonstrate that the use of n-type host molecules can increase the device lifetime by 30 times and 1000 times for green and blue OLEDs, respectively.
Journal Article
Pathogenesis of sarcopenia and the relationship with fat mass: descriptive review
Age‐associated obesity and muscle atrophy (sarcopenia) are intimately connected and are reciprocally regulated by adipose tissue and skeletal muscle dysfunction. During ageing, adipose inflammation leads to the redistribution of fat to the intra‐abdominal area (visceral fat) and fatty infiltrations in skeletal muscles, resulting in decreased overall strength and functionality. Lipids and their derivatives accumulate both within and between muscle cells, inducing mitochondrial dysfunction, disturbing β‐oxidation of fatty acids, and enhancing reactive oxygen species (ROS) production, leading to lipotoxicity and insulin resistance, as well as enhanced secretion of some pro‐inflammatory cytokines. In turn, these muscle‐secreted cytokines may exacerbate adipose tissue atrophy, support chronic low‐grade inflammation, and establish a vicious cycle of local hyperlipidaemia, insulin resistance, and inflammation that spreads systemically, thus promoting the development of sarcopenic obesity (SO). We call this the metabaging cycle. Patients with SO show an increased risk of systemic insulin resistance, systemic inflammation, associated chronic diseases, and the subsequent progression to full‐blown sarcopenia and even cachexia. Meanwhile in many cardiometabolic diseases, the ostensibly protective effect of obesity in extremely elderly subjects, also known as the ‘obesity paradox’, could possibly be explained by our theory that many elderly subjects with normal body mass index might actually harbour SO to various degrees, before it progresses to full‐blown severe sarcopenia. Our review outlines current knowledge concerning the possible chain of causation between sarcopenia and obesity, proposes a solution to the obesity paradox, and the role of fat mass in ageing.
Journal Article
Comparison of co-expression measures: mutual information, correlation, and model based indices
Background
Co-expression measures are often used to define networks among genes. Mutual information (MI) is often used as a generalized correlation measure. It is not clear how much MI adds beyond standard (robust) correlation measures or regression model based association measures. Further, it is important to assess what transformations of these and other co-expression measures lead to biologically meaningful modules (clusters of genes).
Results
We provide a comprehensive comparison between mutual information and several correlation measures in 8 empirical data sets and in simulations. We also study different approaches for transforming an adjacency matrix, e.g. using the topological overlap measure. Overall, we confirm close relationships between MI and correlation in all data sets which reflects the fact that most gene pairs satisfy linear or monotonic relationships. We discuss rare situations when the two measures disagree. We also compare correlation and MI based approaches when it comes to defining co-expression network modules. We show that a robust measure of correlation (the biweight midcorrelation transformed via the topological overlap transformation) leads to modules that are superior to MI based modules and maximal information coefficient (MIC) based modules in terms of gene ontology enrichment. We present a function that relates correlation to mutual information which can be used to approximate the mutual information from the corresponding correlation coefficient. We propose the use of polynomial or spline regression models as an alternative to MI for capturing non-linear relationships between quantitative variables.
Conclusion
The biweight midcorrelation outperforms MI in terms of elucidating gene pairwise relationships. Coupled with the topological overlap matrix transformation, it often leads to more significantly enriched co-expression modules. Spline and polynomial networks form attractive alternatives to MI in case of non-linear relationships. Our results indicate that MI networks can safely be replaced by correlation networks when it comes to measuring co-expression relationships in stationary data.
Journal Article
Bone vascular niche E-selectin induces mesenchymal–epithelial transition and Wnt activation in cancer cells to promote bone metastasis
How disseminated tumour cells engage specific stromal components in distant organs for survival and outgrowth is a critical but poorly understood step of the metastatic cascade. Previous studies have demonstrated the importance of the epithelial–mesenchymal transition in promoting the cancer stem cell properties needed for metastasis initiation, whereas the reverse process of mesenchymal–epithelial transition is required for metastatic outgrowth. Here we report that this paradoxical requirement for the simultaneous induction of both mesenchymal–epithelial transition and cancer stem cell traits in disseminated tumour cells is provided by bone vascular niche E-selectin, whose direct binding to cancer cells promotes bone metastasis by inducing mesenchymal–epithelial transition and activating Wnt signalling. E-selectin binding activity mediated by the α1-3 fucosyltransferases Fut3/Fut6 and Glg1 are instrumental to the formation of bone metastasis. These findings provide unique insights into the functional role of E-selectin as a component of the vascular niche critical for metastatic colonization in bone.
Esposito et al. report a role for bone vascular niche E-selectin in promoting mesenchymal–epithelial transition and Wnt signalling in breast cancer cells, thereby enhancing bone metastasis.
Journal Article
Pyogenic liver abscess in non‐liver cancer patients and liver cancer patients treated with TACE: Etiological characteristics, treatment, and outcome analysis
Clinical, laboratory, and microbiological features, clinical outcomes, and pyogenic liver abscess (PLA) prognosis evaluation in non‐liver cancer (Non‐LC) and liver cancer patients treated with transarterial chemoembolization (TACE, LC‐TACE). Clinical data of 48 consecutive PLA patients from January 2016 to December 2020 were retrospectively analyzed. Mortality between two PLA patient groups were compared, and mortality risk factors were evaluated. A total of 48 PLA patients (31 males and 17 females) from January 2016 to December 2020 met the study's inclusion criteria. There were 32 and 16 patients in the Non‐LC and LC‐TACE groups, respectively. Positive pus culture rate in the Non‐LC group was 87.5% and positive pus culture rate in LC‐TACE group was 81.3%. In the Non‐LC group, 28 patients improved after treatment, 1 patient did not improve, and 3 patients died during hospitalization, with a 9.4% mortality rate. In the LC‐TACE group, nine patients improved after treatment, three patients did not improve, and four patients died during hospitalization, with a 25% mortality rate. The Non‐LC group cure time was 37.4 ± 23.1 days, while the LC‐TACE group was 91.5 ± 49.7 days. PLA of the Non‐LC group and the LC‐TACE group were different in terms of pathogenic bacteria and cure time, and so on. A more comprehensive treatment should be considered for PLA after TACE.
Journal Article