Recently, incorporating guanidium (GA) cations into organolead halide perovskites is shown to effectively improve the stability and performance of the solar cells. However, the underlying mechanisms ...that govern the GA incorporation have remained unclear. Here, FAPbI3 is used as a basic framework to investigate experimentally and theoretically the role of cesium (Cs) and bromine (Br) substitutions in GA+ incorporation. It is found that simultaneous introduction of the small‐size Cs+ and Br– in the FAPbI3 lattice is critical to create sufficient space for the large GA+ and that the presence of the Cs+ prevents the formation of a GA‐contained low‐dimensional phase, which both assist GA+ incorporation. Upon entering the perovskite lattice, the GA+ can stabilize the lattice structure via forming strong hydrogen bonds with their neighboring halide ions. Such structure modification suppresses halide vacancy formation, thus leading to improved material properties. Compared to the GA‐free perovskite reference samples, the optimal system GA0.05Cs0.15FA0.8Pb(I0.85Br0.15)3 exhibits substantially improved thermal and photothermal stability, as well as increased photocarrier lifetime. Solar cells fabricated with the optimal material system show an excellent photovoltaic performance, with the champion device reaching a power conversion efficiency of 21.3% and an open circuit voltage of 1.229 V.
Through experimental and theoretical investigation, the synergetic effects of Cs and Br in assisting incorporation of guanidium (GA) in FAPbI3 are revealed. It is found that GA incorporation enhances the bonding with surrounding halides and elevates the formation energy of halide vacancies, resulting in improved stability and photovoltaic performance.
Wide bandgap (WB) organic–inorganic hybrid perovskites (OIHPs) with a bandgap ranging between 1.7 and 2.0 eV have shown great potential to improve the efficiency of single‐junction silicon or ...thin‐film solar cells by forming a tandem structure with one of these cells or with a narrow bandgap perovskite cell. However, WB‐OIHPs suffer from a large open‐circuit voltage (Voc) deficit in photovoltaic devices, which is associated with the phase segregation of the materials under light illumination. In this work the photoinstability is demonstrated and Voc loss can be addressed by combining grain crystallization and grain boundary passivation, achieved simultaneously through tuning of perovskite precursor composition. Using FA0.17Cs0.83PbI3–xBrx (x = 0.8, 1.2 1.5, and 1.8), with a varied bandgap from 1.72 to 1.93 eV, as the model system it is illustrated how precursor additive Pb(SCN)2 should be matched with a proper ratio of FAX (I and Br) to realize large grains with defect‐healed grain boundaries. The optimized WB‐OIHPs show good photostability at both room‐temperature and elevated temperature. Moreover, the corresponding solar cells exhibit excellent photovoltaic performances with the champion Voc/stabilized power output efficiency reaching 1.244 V/18.60%, 1.284 V/16.51%, 1.296 V/15.01%, and 1.312 V/14.35% for WB‐OIHPs with x = 0.8, 1.2, 1.5, and 1.8, respectively.
The photoinduced phase segregation in wide bandgap hybrid perovskites are greatly suppressed by combining grain crystallization and grain boundary passivation. As a result, the open‐circuit voltage (Voc) loss of the corresponding devices is highly reduced, demonstrating a monotonic increase of Voc with increasing of bandgap from 1.72 to 1.93 eV.
An efficient zinc(II)‐catalyzed alkyne oxidation/CH functionalization sequence was developed, thus leading to highly site‐selective synthesis of a variety of isoquinolones and β‐carbolines. ...Importantly, in contrast to the well‐established gold‐catalyzed intermolecular alkyne oxidation, over‐oxidation can be completely suppressed in this system and the reaction most likely proceeds by a Friedel–Crafts‐type pathway. Mechanistic studies and theoretical calculations are described.
Swap gold for zinc: The title reaction was achieved by a zinc(II)‐catalyzed alkyne oxidation/CH functionalization sequence. In contrast to the well‐established gold‐catalyzed intermolecular alkyne oxidation, the over‐oxidation can be suppressed in this system and the reaction most likely proceeds by a Friedel–Crafts‐type pathway. Tf=trifluoromethanesulfonyl, PG=protecting group.
Scaling up to a large number of qubits with high-precision control is essential in the demonstrations of quantum computational advantage to exponentially outpace the classical hardware and ...algorithmic improvements. Here, we develop a two-dimensional programmable superconducting quantum processor, Zuchongzhi, which is composed of 66 functional qubits in a tunable coupling architecture. To characterize the performance of the whole system, we perform random quantum circuits sampling for benchmarking, up to a system size of 56 qubits and 20 cycles. The computational cost of the classical simulation of this task is estimated to be 2–3 orders of magnitude higher than the previous work on 53-qubit Sycamore processor Nature 574, 505 (2019). We estimate that the sampling task finished by Zuchongzhi in about 1.2 h will take the most powerful supercomputer at least 8 yr. Our work establishes an unambiguous quantum computational advantage that is infeasible for classical computation in a reasonable amount of time. The high-precision and programmable quantum computing platform opens a new door to explore novel many-body phenomena and implement complex quantum algorithms.
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Background
Partial bile duct ligation (PBDL) model is a reliable cholestatic fibrosis experimental model that showed complex histopathological changes. Magnetic resonance imaging (MRI) features of ...PBDL have not been well characterized.
Purpose
To investigate the potential of MRI parameters in assessing fibrosis in PBDL and explore the relationships between MRI and pathological features.
Animal Model
Established PBDL models.
Population
Fifty‐four mice were randomly divided into four timepoints PBDL groups and one sham group.
Field Strength/Sequence
3.0 T; MRI sequences included T1‐weighted fast spin‐echo (FSE), T2‐weighted single shot FSE, variable flip angle T1 mapping, multi‐echo SE T2 mapping, multi‐echo gradient‐echo T2* mapping, and multi‐b‐value diffusion‐weighted imaging.
Assessment
MRI examination was performed at the corresponding timepoints after surgery. Native T1, ΔT1 (T1native‐T1post), T2, T2*, apparent diffusion coefficient (ADC) values, histogram parameters (skewness and kurtosis), intravoxel incoherent motion parameters (f, D, and D*) within the entire ligated (PBDL), non‐ligated liver (PBDL), and whole liver (sham) were obtained. Fibrosis and inflammation were assessed in Masson and H&E staining slices using the Metavir and activity scoring system.
Statistical Tests
One‐way ANOVA, Spearman's rank correlation, and receiver operating characteristic curves were performed. P < 0.05 was considered statistically significant.
Results
Fibrosis and inflammation were finally staged as F3 and A3 in ligated livers but were not observed in non‐ligated or sham livers. Ligated livers displayed significantly elevated native T1, ΔT1, T2, and reduced ADC and T2* than other livers. Spearman's correlation showed better correlation with inflammation (r = 0.809) than fibrosis (r = 0.635) in T2 and both ΔT1 and ADC showed stronger correlation with fibrosis (r = 0.704 and r = −0.718) than inflammation (r = 0.564 and r = −0.550). Area under the curve (AUC) for ΔT1 performed the highest (0.896). When combined with all relative parameters, AUC increased to 0.956.
Data Conclusion
Multiparametric MRI can evaluate and differentiate pathological changes in PBDL. ΔT1 and ADC better correlated with fibrosis while T2 stronger with inflammation.
Level of Evidence
1
Technical Efficacy
Stage 2
To ascertain if preoperative short-term radiotherapy followed by chemotherapy is not inferior to a standard schedule of long-term chemoradiotherapy in patients with locally advanced rectal cancer.
...Patients with distal or middle-third, clinical primary tumor stage 3-4 and/or regional lymph node-positive rectal cancer were randomly assigned (1:1) to short-term radiotherapy (25 Gy in five fractions over 1 week) followed by four cycles of chemotherapy (total neoadjuvant therapy TNT) or chemoradiotherapy (50 Gy in 25 fractions over 5 weeks, concurrently with capecitabine chemoradiotherapy; CRT). Total mesorectal excision was undertaken 6-8 weeks after preoperative treatment, with two additional cycles of CAPOX (intravenous oxaliplatin 130 mg/m
, once a day on day 1 and capecitabine 1,000 mg/m
, twice a day from days 1 to 14) in the TNT group and six cycles of CAPOX in the CRT group. The primary end point was 3-year disease-free survival (DFS).
Between August 2015 and August 2018, a total of 599 patients were randomly assigned to receive TNT (n = 302) or CRT (n = 297). At a median follow-up of 35.0 months, 3-year DFS was 64.5% and 62.3% in TNT and CRT groups, respectively (hazard ratio, 0.883; one-sided 95% CI, not applicable to 1.11;
< .001 for noninferiority). There was no significant difference in metastasis-free survival or locoregional recurrence, but the TNT group had better 3-year overall survival than the CRT group (86.5%
75.1%;
= .033). Treatment effects on DFS and overall survival were similar regardless of prognostic factors. The prevalence of acute grade III-V toxicities during preoperative treatment was 26.5% in the TNT group versus 12.6% in the CRT group (
< .001).
Short-term radiotherapy with preoperative chemotherapy followed by surgery was efficacious with acceptable toxicity and could be used as an alternative to CRT for locally advanced rectal cancer.
Monolayer MoS
2
has shown excellent photoresponse properties, but its promising applications in high-sensitivity photodetection suffer from the atomic-thickness-limited adsorption and band ...gap-limited spectral selectivity. Here we have carried out investigations on MoS
2
monolayer-based photodetectors with and without decoration of ZnO quantum dots (ZnO-QDs) for comparison. Compared with monolayer MoS
2
photodetectors, the monolayer ZnO-QDs/MoS
2
hybrid device exhibits faster response speed (1.5 s and 1.1 s, respectively), extended broadband photoresponse range (deep UV-visible), and enhanced photoresponse in visible spectrum, such as higher responsivity over 0.084 A/W and larger detectivity of 1.05 × 10
11
Jones, which results from considerable injection of carries from ZnO-QDs to MoS
2
due to the formation of I-type heterostructure existing in the contact interface of them.
Introducing extensively excess ammonium halides when forming perovskites has recently been demonstrated as an effective approach to improve the performance of perovskite light‐emitting diodes ...(PeLEDs). Here, Cs0.17FA0.83PbI2.5Br0.5 is used as a model system to elucidate the impact of introducing excess formamidinium iodide (FAI) on the crystallization process of the perovskite film and operation of the corresponding PeLED. The excess FAI ratio is varied from 0 to 120 mol% and the crystallization process of the perovskite through in situ absorbance, in situ photoluminescence, and ex situ X‐ray diffraction measurements is systematically monitored. The results suggest that excess FAI triggers formation of a compact wide‐bandgap intermediate phase in the as‐deposited film, which then transforms to isolated and highly crystalline perovskite grains upon annealing. Using excitation correlation photoluminescence spectroscopy it is found that excess FAI results in a lower density of deep trap states and therefore a reduction of nonradiative losses in the material. This leads to a greatly enhanced maximum external quantum efficiency (EQE) from 0.25% (stoichiometric) to 12.7% (90 mol% excess). Furthermore, the FAI‐excess perovskite film is optimized with Pb(SCN)2 and 5‐ammonium valeric acid iodide additives and achieve a record radiance of 965 W Sr−1 m−2 for near‐infrared PeLEDs and a high EQE of 17.4%.
Excess formamidinium iodide (FAI) in the Cs0.17FA0.83PbI2.5Br0.5 material system facilitates the formation of a compact wide‐bandgap intermediate phase in the as‐deposited thin film, which transforms to isolated and highly crystalline three‐dimensional perovskite crystals upon annealing. Excitation correlation photoluminescence measurement indicates that the perovskite films produced with excess FAI has a lower density of deep trap, thus improving device performance significantly.
Quantum coherence is the central element of particle states, and it characterizes the overall performance of various quantum materials. Bloch oscillation is a fundamental coherent behavior of ...particles under a static potential, which can be easily destroyed by Zener tunneling in multiband 2D lattice materials. The control of Zener tunneling therefore plays the key role in quantum engineering for complicated physical systems. Here, the inhibition and reconstruction of Zener tunneling in photonic honeycomb lattices are experimentally demonstrated. Deformed honeycomb lattices are integrated and an effective static potential is realized on the 2D lattice materials. Zener tunneling disappears in stretch‐type lattices and wave packets stay in the dispersionless upper energy band. On the contrary, Zener tunneling is greatly enhanced in compression‐type lattices and wave packets exhibit directional oscillations without branches, which manifest the preserved coherence of the wave packets. The results demonstrate the protection of photonic coherence by structurally controlling the Zener tunneling, representing a step toward flexible quantum engineering for large‐scale artificial quantum materials.
A precise site‐dependent photonic material has the ability of modifying momentum‐space properties and maintaining the coherence of bulk states in transport. Artificial honeycomb lattices with an effective force are constructed to realize highly controllable Zener tunneling and the coherence protection of particles transmitting on artificial quantum materials.
Disclosure of infectious disease status to social network peers can facilitate reaching and early detection among high-risk populations. In this era of social media, globally, HIV/AIDS represents a ...high burden of infectious disease. Thus, delivery of an HIV result e-report via social media presents a new approach that has the potential to improve contact with and enrollment of the high-risk population in research studies and routine practice.
This study explores the effectiveness and associated factors of a recruitment strategy (ie, WeChat-based HIV e-report delivery in social networks) on the enrollment of men who have sex with men (MSM) for an HIV testing intervention study.
This was an enrollment result analysis of an ongoing cluster randomized controlled trial (RCT) aiming to promote HIV testing among MSM. Recruitment of potential participants was based on the unit of an egocentric social network, which includes 1 core member (an offline tested ego as the recruiter) and several network members (online alters as network associates). Alters' enrollment and alters' transformation to ego-recruiters (alter-ego) were measured as outcomes. Recruitment outcomes were compared between the exchangeable and regular e-report groups of the RCT. Associated factors of both outcomes were also investigated, including sociodemographic characteristics, health behaviors, social network characteristics, e-report types, and online delivery information. Binary outcomes were modeled using logistic models, with Firth correction for rare events. Qualitative interviews were conducted to understand facilitators and barriers in detail for alter-ego as the subsequent wave's recruiter.
The e-report of 1157 egos who tested offline were delivered to 5165 alters in 3 recruitment waves; eventually, 1162 eligible alters enrolled in this RCT (response rate: 22.5%). In the exchangeable e-report group, 544 egos recruited 467 alters, of which 35 alters transformed to alter-egos (7.5%), whereas in the regular e-report group, 613 egos recruited 695 alters, of which 40 alters transformed to alter-egos (5.8%). Alters' enrollment at first wave was associated with a higher number of e-reports being forwarded by the egos. Alters' transformation to alter-egos for the subsequent wave was associated with the exchangeable e-report, higher income, being a Guangzhou resident, unprotected anal intercourse, preferring self-testing, and viewing senders' e-reports frequently. Qualitative interviews revealed that the lack of awareness of e-reports' function and inadequate access to e-reports at offline testing facilities were major barriers to alters' transformation to offline ego-recruiters.
The delivery of e-report was feasible in MSM social network, and the success and sustainability of online recruitment depended on high levels of familiarity among MSM with the digital tool. The HIV e-report exchange mechanism might promote MSM to test HIV offline to get their own e-report for exchange in the community. The e-report provides an innovative recruitment method with great potential to trace direct contacts for infectious diseases studies.
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