The stabilization of black-phase formamidinium lead iodide (α-FAPbI
) perovskite under various environmental conditions is considered necessary for solar cells. However, challenges remain regarding ...the temperature sensitivity of α-FAPbI
and the requirements for strict humidity control in its processing. Here we report the synthesis of stable α-FAPbI
, regardless of humidity and temperature, based on a vertically aligned lead iodide thin film grown from an ionic liquid, methylamine formate. The vertically grown structure has numerous nanometer-scale ion channels that facilitate the permeation of formamidinium iodide into the lead iodide thin films for fast and robust transformation to α-FAPbI
A solar cell with a power-conversion efficiency of 24.1% was achieved. The unencapsulated cells retain 80 and 90% of their initial efficiencies for 500 hours at 85°C and continuous light stress, respectively.
Two-dimensional Ruddlesden–Popper phase (2DRP) perovskites are known to exhibit improved photostability and environmental stability compared with their three-dimensional (3D) counterparts. However, ...fundamental questions remain over the interaction between the bulky alkylammoniums and the 2DRP perovskite framework. Here, we unambiguously demonstrate that a sulfur–sulfur interaction is present for a new bulky alkylammonium, 2-(methylthio)ethylamine hydrochloride (MTEACl). In addition to a weaker van der Waals interaction, the interaction between sulfur atoms in two MTEA molecules enables a (MTEA)2(MA)4Pb5I16 (n = 5) perovskite framework with enhanced charge transport and stabilization. The result is 2DRP perovskite solar cells with significantly improved efficiency and stability. Cells with a power conversion efficiency as high as 18.06% (17.8% certified) are achieved, along with moisture tolerance for up to 1,512 h (under 70% humidity conditions), thermal stability for 375 h (at 85 °C) and stability under continuous light stress (85% of the initial efficiency retained over 1,000 h of operation at the maximum power point).Two-dimensional perovskite solar cells have been engineered to be robust against moisture, high temperatures and light stress.
Abstract
Methionine restriction, a dietary regimen that protects against metabolic diseases and aging, represses cancer growth and improves cancer therapy. However, the response of different cancer ...cells to this nutritional manipulation is highly variable, and the molecular determinants of this heterogeneity remain poorly understood. Here we report that hepatocyte nuclear factor 4α (HNF4α) dictates the sensitivity of liver cancer to methionine restriction. We show that hepatic sulfur amino acid (SAA) metabolism is under transcriptional control of HNF4α. Knocking down HNF4α or SAA enzymes in HNF4α-positive epithelial liver cancer lines impairs SAA metabolism, increases resistance to methionine restriction or sorafenib, promotes epithelial-mesenchymal transition, and induces cell migration. Conversely, genetic or metabolic restoration of the transsulfuration pathway in SAA metabolism significantly alleviates the outcomes induced by HNF4α deficiency in liver cancer cells. Our study identifies HNF4α as a regulator of hepatic SAA metabolism that regulates the sensitivity of liver cancer to methionine restriction.
The continuous contributions made by long time contributors ( LTCs ) are a key factor enabling open source software (OSS) projects to be successful and survival. We study Github as it has a large ...number of OSS projects and millions of contributors, which enables the study of the transition from newcomers to LTCs . In this paper, we investigate whether we can effectively predict newcomers in OSS projects to be LTCs based on their activity data that is collected from Github . We collect Github data from GHTorrent, a mirror of Github data. We select the most popular 917 projects, which contain 75,046 contributors. We determine a developer as a LTC of a project if the time interval between his/her first and last commit in the project is larger than a certain time <inline-formula><tex-math notation="LaTeX">T</tex-math> <mml:math><mml:mi>T</mml:mi></mml:math><inline-graphic xlink:href="xia-ieq1-2918536.gif"/> </inline-formula>. In our experiment, we use three different settings on the time interval: 1, 2, and 3 years. There are 9,238, 3,968, and 1,577 contributors who become LTCs of a project in three settings of time interval, respectively. To build a prediction model, we extract many features from the activities of developers on Github , which group into five dimensions: developer profile, repository profile, developer monthly activity, repository monthly activity, and collaboration network. We apply several classifiers including naive Bayes, SVM, decision tree, kNN and random forest. We find that random forest classifier achieves the best performance with AUCs of more than 0.75 in all three settings of time interval for LTCs . We also investigate the most important features that differentiate newcomers who become LTCs from newcomers who stay in the projects for a short time. We find that the number of followers is the most important feature in all three settings of the time interval studied. We also find that the programming language and the average number of commits contributed by other developers when a newcomer joins a project also belong to the top 10 most important features in all three settings of time interval for LTCs . Finally, we provide several implications for action based on our analysis results to help OSS projects retain newcomers.
Methyltransferase-like 3 (METTL3) and N
-methyladenosine (m
A) are involved in many types of biological and pathological processes, including DNA repair. However, the function and mechanism of METTL3 ...in DNA repair and chemotherapeutic response remain largely unknown. In present study, we identified that METTL3 participates in the regulation of homologous recombination repair (HR), which further influences chemotherapeutic response in both MCF-7 and MDA-MB-231 breast cancer (BC) cells. Knockdown of METTL3 sensitized these BC cells to Adriamycin (ADR; also named as doxorubicin) treatment and increased accumulation of DNA damage. Mechanically, we demonstrated that inhibition of METTL3 impaired HR efficiency and increased ADR-induced DNA damage by regulating m6A modification of EGF/RAD51 axis. METTL3 promoted EGF expression through m6A modification, which further upregulated RAD51 expression, resulting in enhanced HR activity. We further demonstrated that the m6A 'reader,' YTHDC1, bound to the m6A modified EGF transcript and promoted EGF synthesis, which enhanced HR and cell survival during ADR treatment in BC. Our findings reveal a pivotal mechanism of METTL3-mediated HR and chemotherapeutic drug response, which may contribute to cancer therapy.
During software development and maintenance, developers spend a considerable amount of time on program comprehension activities. Previous studies show that program comprehension takes up as much as ...half of a developer's time. However, most of these studies are performed in a controlled setting, or with a small number of participants, and investigate the program comprehension activities only within the IDEs. However, developers' program comprehension activities go well beyond their IDE interactions. In this paper, we extend our ActivitySpace framework to collect and analyze Human-Computer Interaction (HCI) data across many applications (not just the IDEs). We follow Minelli et al.'s approach to assign developers' activities into four categories: navigation, editing, comprehension, and other. We then measure the comprehension time by calculating the time that developers spend on program comprehension, e.g., inspecting console and breakpoints in IDE, or reading and understanding tutorials in web browsers. Using this approach, we can perform a more realistic investigation of program comprehension activities, through a field study of program comprehension in practice across a total of seven real projects, on 78 professional developers, and amounting to 3,148 working hours. Our study leverages interaction data that is collected across many applications by the developers. Our study finds that on average developers spend ~58 percent of their time on program comprehension activities, and that they frequently use web browsers and document editors to perform program comprehension activities. We also investigate the impact of programming language, developers' experience, and project phase on the time that is spent on program comprehension, and we find senior developers spend significantly less percentages of time on program comprehension than junior developers. Our study also highlights the importance of several research directions needed to reduce program comprehension time, e.g., building automatic detection and improvement of low quality code and documentation, construction of software-engineering-specific search engines, designing better IDEs that help developers navigate code and browse information more efficiently, etc.
Due to the additional introduction of bulky organic ammonium and the competition between bulky organic ammonium and methyl ammonium in 2D Ruddlesden‐Popper (2DRP) perovskite, the crystallization ...process becomes complicated. Here, it is demonstrated that the rapid crystallization controlled by processing solvents plays an important role in achieving high‐quality 2DRP perovskite films. It is found that the processing solvents, e.g., dimethylacetamide (DMAC), N,N‐dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), with a different polarity and boiling point, have almost no effect on crystal structure and phase distribution but have a remarkable effect on crystallization kinetics, crystal growth orientation, and crystallinity of 2DRP perovskite. Compared to polar aprotic solvent DMF and DMSO with a high boiling point, DMAC with low polarity and a suitable boiling point has a weak coordination to lead and ammonium salts and is easy to escape during solution processing, which is able to accelerate the crystallization rate of 2DRP perovskite. Benefitting from the rapid crystallization enabled high‐quality 2DRP perovskite films, the best‐performing device with improved stability and a power conversion efficiency of 12.15% is obtained using DMAC solvent. These findings may give guidance for solvent engineering for highly efficient 2DRP perovskite solar cells in the future.
Rapid crystallization is demonstrated to be necessary in achieving high‐quality 2DRP perovskite films by comparing dimethylacetamide (DMAC), N,N‐dimethylformamide, and dimethyl sulfoxide solvents. The improved stability and efficiency are observed using DMAC due to the accelerating crystallization rate of 2DRP perovskite crystals.
Here, we report an alternative environmentally friendly room-temperature molten salt, methylammonium acetate (MAAc), as a novel solvent for facile fabrication of perovskite solar cells (PSCs) in ...ambient air. MAAc possesses excellent chemical properties along with high viscosity, negligible vapor pressure, and a nonhazardous nature. Complete solubility of both methylammonium and lead salts by hydrogen bonds in MAAc was observed. Dense and pinhole-free perovskite films with high reproducibility can be readily prepared by a simple one-step method without an anti-solvent even under a relative humidity of over 80%. Under optimized processing conditions, we achieved an average power conversion efficiency of 18.42% and a maximum efficiency of 20.05% in CH3NH3PbI3-based planar heterojunction structure. In addition, devices without encapsulation remained above 93% of their original efficiency for more than 1,000 h in ambient air. These findings may open up the possibility of developing a new approach for further improving PSC performance with higher reproducibility and reliability in ambient atmosphere.
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•Room-temperature molten salt for facile fabrication of perovskite films in air•No post-deposition treatment is needed (e.g., anti-solvent)•The resulting perovskite solar cells are highly efficient and stable•A universal solvent for all common salts used in perovskite devices
Organic-inorganic hybrid perovskites have recently attracted extensive attention for their potential uses in photovoltaics. However, solvent-handling issues and toxicology concerns represent a major challenge in solution-processed perovskite thin films. Here, we demonstrate that an environmentally- and industrially friendly room-temperature molten salt (RTMS), methylammonium acetate (MAAc), can produce high-quality perovskite films in ambient air, leading to the development of perovskite solar cells (PSCs) with 20% efficiency and stability for more than 1,000 h. MAAc is a universal solvent for all common perovskite-based salts and may open up the potential of using RTMS solvent for facile fabrication of PSCs. Moreover, this work represents a new direction in the development of efficient and stable PSCs and other optoelectronic devices.
A solvent is vital to the control of crystallization and crystal growth in state-of-the-art solution-processed hybrid organic-inorganic perovskites. We demonstrate an alternative environmentally friendly room-temperature molten salt, methylammonium acetate (MAAc), as a solvent characterized by high viscosity, negligible vapor pressure, and nonhazardous nature, which can be used to produce highly efficient perovskite solar cells (PSCs) in ambient air. The resulting PSCs exhibited excellent stability under light and dark conditions.
One potential advantage of perovskite solar cells (PSCs) is the ability to solution process the precursors and deposit films from solution
. At present, spin coating, blade coating, spray coating, ...inkjet printing and slot-die printing have been investigated to deposit hybrid perovskite thin films
. Here we expand the range of deposition methods to include screen-printing, enabled by a stable and viscosity-adjustable (40-44,000 cP) perovskite ink made from a methylammonium acetate ionic liquid solvent. We demonstrate control over perovskite thin-film thickness (from about 120 nm to about 1,200 nm), area (from 0.5 × 0.5 cm
to 5 × 5 cm
) and patterning on different substrates. Printing rates in excess of 20 cm s
and close to 100% ink use were achieved. Using this deposition method in ambient air and regardless of humidity, we obtained the best efficiencies of 20.52% (0.05 cm
) and 18.12% (1 cm
) compared with 20.13% and 12.52%, respectively, for the spin-coated thin films in normal devices with thermally evaporated metal electrodes. Most notably, fully screen-printing devices with a single machine in ambient air have been successfully explored. The corresponding photovoltaic cells exhibit high efficiencies of 14.98%, 13.53% and 11.80% on 0.05-cm
, 1.00-cm
and 16.37-cm
(small-module) areas, respectively, along with 96.75% of the initial efficiency retained over 300 h of operation at maximum power point.
Abstract
Standing posteroanterior radiographs have been the golden standard to quantify the severity of scoliosis deformity. However, it exposes ionizing radiation to scoliosis patients, and cannot ...be used for routine screening and monitoring. This study aimed to develop a protocol of measuring postural indexes by using the noninvasive and radiation-free two-dimensional (2D) photogrammetry method and identify its clinical value in scoliosis screening and monitoring. The five postural indexes were measured from the posterior view of 110 participants. One-way ANOVA with post hoc Tukey HSD/Games–Howell analysis was used to compare the differences between the participants in the scoliosis group and the non-scoliosis group. Pearson coefficients of correlation were analyzed to identify the relationships between Cobb angles and each of the five quantitative postural indexes. Based on 2D photogrammetry, the postural indexes of C7 deviation (
p
= 0.02), shoulder alignment (
p
< 0.001), scapula alignment (
p
< 0.001), waist angle discrepancy (
p
< 0.001), and PSIS alignment (
p
< 0.001) could significantly differentiate scoliosis and non-scoliosis patients during screening. The waist angle discrepancy (r = 0.4,
p
= 0.01; r = 0.8,
p
= 0.03; r = 0.7,
p
= 0.01) and shoulder alignment (r = 0.6,
p
= 0.03) had moderate to strong positive correlations with the Cobb angles, which supported their clinical values in monitoring scoliotic curvature changes of adolescent idiopathic scoliosis (AIS) patients.
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