We study the
n
-dimensional problem of finding the smallest ball enclosing the intersection of
p
given balls, the so-called Chebyshev center problem (
CC
B
). It is a minimax optimization problem and ...the inner maximization is a uniform quadratic optimization problem (
UQ
). When
p
≤
n
, (
UQ
) is known to enjoy a strong duality and consequently (
CC
B
) is solved via a standard convex quadratic programming (
SQP
). In this paper, we first prove that (
CC
B
) is NP-hard and the special case when
n
=
2
is polynomially solvable. With the help of a newly introduced linear programming relaxation (LP), the (
SQP
) relaxation is reobtained more directly and the first approximation bound for the solution obtained by (
SQP
) is established for the hard case
p
>
n
. Finally, also based on (LP), we show that (
CC
B
) is polynomially solvable when either
n
or
p
-
n
(
>
0
)
is fixed.
We report facile synthesis of low‐band‐gap mesoporous C4N particles and their use as responsive bifunctional oxygen catalysts for visible‐light‐sensitive (VLS) rechargeable Zn‐air battery (RZAB) and ...polymer‐air battery (RPAB). Compared to widely studied g‐C3N4, C4N shows a smaller band gap of 1.99 eV, with a larger photocurrent response, and it can function as visible‐light‐harvesting antenna and bifunctional oxygen reduction/evolution (ORR/OER) catalysts, enabling effective photocoupling to tune oxygen catalysis. The C4N‐enabled VLS‐RZAB displays a low charge voltage of 1.35 V under visible light, which is below the theoretical RZAB voltage of 1.65 V, corresponding to a high energy efficiency of 97.78 %. Pairing a C4N cathode with a polymer anode also endows an VLS‐RPAB with light‐boosted charge performance. It is revealed that the ORR and OER active sites in C4N are separate carbon sites near pyrazine‐nitrogen atoms and photogenerated energetic holes can activate OER for improved reaction kinetics.
A narrow‐band‐gap C4N material was explored as a visible‐light‐sensitive (VLS) organic bifunctional oxygen catalyst for application in photocoupled secondary batteries. The C4N‐enabled VLS rechargeable zinc‐air batteries (RZAB) and all‐polymer polymer‐air batteries (RPAB) exhibited markedly reduced charge voltage together with an increased energy efficiency under visible light.
This study analyzes the publication requirements of PhD programs in China. It is based on a representative sample of PhD programs from 164 Chinese universities from all fields of science. Our results ...show that Chinese PhD student significant pressures to publish in order to obtain their degree, with papers indexed in the Science Citation Index often a mandatory requirement for students to obtain their degree. Moreover, it is found that first authorship is also mandatory: only as first authors count towards the degree, which may affect PhD students’ collaborative behavior. These findings highlight the role of publications indexed in the Science Citation Index for China’s PhD programs and contributes to our understanding of the landscape of research evaluation in China’s higher education system.
The concept of blended learning, a combination of online and face-to-face learning, has become popular in educational settings. Using qualitative methods, this study investigates the role of blended ...learning and in-service teachers’ perceptions. Blended learning was used for 19 in-service teachers during their summer degree program at a Chinese university. After the course, teachers were asked to write their reflections on blended learning, its role in diverse classrooms, and using it in their teaching career. The results showed that the teachers appreciated the use of blended learning for diversity, but they were against adopting it in their teaching due to limited pedagogical skills and the exam-oriented education system in China. Moreover, some teachers believed that traditional teaching is more effective for providing students with the necessary knowledge, while blended learning was viewed as difficult to manage. The study provides a better understanding of teachers’ perception of blended learning which contributes to global educational development.
The development of highly luminescent two-dimensional covalent organic frameworks (COFs) for sensing applications remains challenging. To suppress commonly observed photoluminescence quenching of ...COFs, we propose a strategy involving interrupting the intralayer conjugation and interlayer interactions using cyclohexane as the linker unit. By variation of the building block structures, imine-bonded COFs with various topologies and porosities are obtained. Experimental and theoretical analyses of these COFs disclose high crystallinity and large interlayer distances, demonstrating enhanced emission with record-high photoluminescence quantum yields of up to 57% in the solid state. The resulting cyclohexane-linked COF also exhibits excellent sensing performance for the trace recognition of Fe3+ ions, explosive and toxic picric acid, and phenyl glyoxylic acid as metabolites. These findings inspire a facile and general strategy to develop highly emissive imine-bonded COFs for detecting various molecules.
Photoresponsive soft actuators with photomechanical energy conversion and flexibility have attracted significant interest in recent years owing to their unique merits of flexibility, contactless ...operation, and remote control, as well as their multiple technological applications ranging from bionic robotics and biomedical devices to nanomotors. Seeking efficient photoresponsive materials with high energy conversion efficiency and robust mechanical properties and identifying effective photoactuation mechanisms are of paramount significance for the development of advanced photoactuators. Due to their unique optical properties, high mechanical strength, superior electrical and thermal conductivity, good flexibility, and stability, carbon‐based materials are regarded as attractive candidates for high‐performance photoresponsive actuators. Furthermore, easy functionalization or hybridization with other functional species substantially extends the functions of these materials and widens the application scope for photoactuators. Herein, this review summarizes the recent progress of photoactuators based on various carbon‐based soft materials, including 0D, 1D, 2D, and 3D nanocarbons as well as their functional soft composites with other responsive materials. Multiple driving schemes of photoresponsive actuators including photothermal, photomechanical, photoelectronic, and photochemical effects, photoactuating architecture design, and potential technological applications of photoactuators are elucidated. Furthermore, certain future opportunities and challenges in the ever‐flourishing optical‐to‐mechanical energy conversion area are emphasized and discussed.
Photoresponsive actuators built from carbon‐based soft materials have emerged as a class of important remote photoactuators, allowing multiple different actuation modes and facile multifunctional integration for a wide range of technological applications. State‐of‐the‐art energy‐conversion schemes, carbon‐based photoactuating materials and architectures, as well as their potential device applications are comprehensively reviewed.
Covalent organic frameworks (COFs) are potential photocatalysts for artificial photosynthesis but they are much less explored for photocatalytic hydrogen evolution (PHE). COFs, while intriguing due ...to crystallinity, tunability, and porosity, tend to have low apparent quantum efficiency (AQE) and little is explored on atomistic structure–performance correlation. Here, adopting triphenylbenzene knots and phenyl linkers as a proof of concept, three structurally related COFs with different linkages are constructed to achieve a tunable COF platform and probe the effect of the linkage chemistry on PHE. Cyano‐substituted alkene‐linked COF (COF–alkene) yields a stable 2330 µmol h−1 g−1 PHE rate, much superior to imine‐ and imide‐linked counterparts (<40 µmol h−1 g−1) under visible light irradiation. Impressively, COF–alkene achieves an AQE of 6.7% at 420 nm. Combined femtosecond transient absorption spectroscopy and theoretical calculation disclose the critical role of cyano‐substituted alkene linkages toward high efficiency of charge separation and transfer in the presence of sacrificial electron donors—the decisive key to the superior PHE performance. Such alkene linkages can also be extended to design a series of high‐performance polymeric photocatalysts, highlighting a general design idea for efficient PHE.
Cyano‐substituted alkene linkages enable high‐efficiency of charge separation and transfer in covalent organic frameworks in the presence of sacrificial electron donors, which not only results in much superior photocatalytic hydrogen evolution performance to imide‐ and imine‐linked counterparts together with the apparent quantum efficiency of 6.7% at 420 nm, but also renders a general design idea for advanced polymeric photocatalysts.
Glioblastoma (GBM) remains one of the most malignant primary tumors in adults, with a 5-year survival rate less than 10% because of lacking effective treatment. Here, we aimed to explore whether ...B7-H3 could serve as a novel therapeutic target for GBM in chimeric antigen receptor (CAR) T cell therapy. In this study, a CAR targeting B7-H3 was constructed and transduced into T cells by lentivirus. Antitumor effects of B7-H3-specific CAR-T cells were assessed with primary and GBM cell lines both in vitro and in vivo. Our results indicated that B7-H3 was positively stained in most of the clinical glioma samples, and its expression levels were correlated to the malignancy grade and poor survival in both low-grade glioma (LGG) and GBM patients. Specific antitumor functions of CAR-T cells were confirmed by cytotoxic and ELISA assay both in primary glioblastoma cells and GBM cell lines. In the orthotropic GBM models, the median survival of the CAR-T-cell-treated group was significantly longer than that of the control group. In conclusion, B7-H3 is frequently overexpressed in GBM patients and may serve as a therapeutic target in CAR-T therapy.
•We fabricated reverse ordered Cu2O–ZnO heterojunctions by magnetron sputtering.•An obvious asymmetry was observed in the VBOs of Cu2O/ZnO–ZnO/Cu2O by XPS.•We analyzed the asymmetry by d–p electronic ...repulsion in the valence band of Cu2O.•Growth order can affect crystal structure of the top layer of the heterojunction.
X-ray photoelectron spectroscopy was used to investigate the valence-band offsets (VBOs) of the Cu2O–ZnO heterojunctions fabricated by magnetron sputtering. A significant forward–backward asymmetry was observed in the band alignments of Cu2O/ZnO–ZnO/Cu2O heterojunctions. The valence band offsets of 2.91eV and 2.52eV were achieved in Cu2O/ZnO and ZnO/Cu2O heterojunctions respectively. The asymmetry was attributed to the lattice distortion of the Cu2O at the interface of Cu2O/ZnO heterojunction. The compressed Cu2O lattices lead to the upward shift of the top of the valence-band of Cu2O, and thus the measured VBO of Cu2O/ZnO is larger than that of ZnO/Cu2O. Considering the band alignments, the ZnO/Cu2O structure is expected to have more advantage in photovoltaic application than Cu2O/ZnO structure.
Recently, B7-H3 was frequently reported to be overexpressed in various cancer types and has been suggested to be a promising target for cancer immunotherapy. In the present study, we analyzed the ...mRNA expression of B7-H3 in The Cancer Genome Atlas (TCGA) database and validated its expression across multiple cancer types. We then generated a novel B7-H3-targeted chimeric antigen receptor (CAR) and tested its antitumor activity both in vitro and in vivo. The B7-H3 expression heterogeneity and variation were frequent. Moderate or even high expression levels of B7-H3 were also observed in some tumor-adjacent tissues, but the staining intensity was weaker than that in tumor tissues. B7-H3 expression was absent or very low in normal tissues and organs. Flow cytometry indicated that the mean expression level of B7-H3 in eight bone marrow specimens from patients with acute myeloid leukemia (AML) was 57.2% (range 38.8–80.4). Furthermore, we showed that the B7-H3-targeted CAR-T cells exhibited significant antitumor activity against AML and melanoma in vitro and in xenograft mouse models. In conclusion, although B7-H3 represents a promising pan-cancer target, and B7-H3-redirected CAR-T cells can effectively control tumor growth, the expression heterogeneity and variation have to be carefully considered in translating B7-H3-targeted CAR-T cell therapy into clinical practice.
Zhang et al. demonstrated that B7-H3 is highly expressed in multiple cancer types, and then they generated a B7-H3-targeted CAR and validated its antitumor effects both on hematologic and solid tumors. Their data also suggested that the expression heterogeneity and variation must be considered in translating B7-H3-targeted therapy into clinical practice.
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