Dipole-field-assisted charge extraction in metal-perovskite-metal back-contact solar cells

Hybrid organic-inorganic halide perovskites are low-cost solution-processable solar cell materials with photovoltaic properties that rival those of crystalline silicon. The perovskite films are typically sandwiched between thin layers of hole and electron transport materials, which efficiently extract photogenerated charges. This affords high-energy conversion efficiencies but results in significant performance and fabrication challenges. Herein we present a simple charge transport layer-free perovskite solar cell (PSC), comprising only a perovskite layer with two interdigitated gold back-contacts. Charge extraction is achieved via self-assembled molecular monolayers (SAMs) and their associated dipole fields at the metal/perovskite interface. Photovoltages of approximately 600 mV generated by SAM-modified PSCs are equivalent to the built-in potential generated by individual dipole layers. Efficient charge extraction results in photocurrents of up to 12.1 mA/cm2 under simulated sunlight, despite a large electrode spacing.Comment: 18 pages, 5 figure

Free-Form Composition Networks for Egocentric Action Recognition

Egocentric action recognition is gaining significant attention in the field of human action recognition. In this paper, we address data scarcity issue in egocentric action recognition from a compositional generalization perspective. To tackle this problem, we propose a free-form composition network (FFCN) that can simultaneously learn disentangled verb, preposition, and noun representations, and then use them to compose new samples in the feature space for rare classes of action videos. First, we use a graph to capture the spatial-temporal relations among different hand/object instances in each action video. We thus decompose each action into a set of verb and preposition spatial-temporal representations using the edge features in the graph. The temporal decomposition extracts verb and preposition representations from different video frames, while the spatial decomposition adaptively learns verb and preposition representations from action-related instances in each frame. With these spatial-temporal representations of verbs and prepositions, we can compose new samples for those rare classes in a free-form manner, which is not restricted to a rigid form of a verb and a noun. The proposed FFCN can directly generate new training data samples for rare classes, hence significantly improve action recognition performance. We evaluated our method on three popular egocentric action recognition datasets, Something-Something V2, H2O, and EPIC-KITCHENS-100, and the experimental results demonstrate the effectiveness of the proposed method for handling data scarcity problems, including long-tailed and few-shot egocentric action recognition

Self-retracting motion of graphite micro-flakes: superlubricity in micrometer scale

Through experimental study, we reveal superlubricity as the mechanism of self-retracting motion of micrometer sized graphite flakes on graphite platforms by correlating respectively the lock-up or self-retraction states with the commensurate or incommensurate contacts. We show that the scale-dependent loss of self-retractability is caused by generation of contact interfacial defects. A HOPG structure is also proposed to understand our experimental observations, particularly in term of the polycrystal structure. The realisation of the superlubricity in micrometer scale in our experiments will have impact in the design and fabrication of micro/nanoelectromechanical systems based on graphitic materials

Epidemiological and clinical characteristics of hospitalized unintentional injuries among children in central China from 2017–2023

ObjectivesTo examine the epidemiological and clinical characteristics of hospitalized unintentional injuries among children in Central China and theoretically propose preventive and control measures.MethodsWe conducted a retrospective study of children aged 0–18 years with unintentional injuries who were admitted to a tertiary hospital in Central China from January 2017 to December 2023. We examined various aspects of the unintentional injuries, including age, gender, urban-rural distribution, external causes, trends, location of injury, cost, and length of stay.ResultsA total of 20,166 children with hospitalized unintentional injuries were enrolled. The median age with IQR was 2.8 (1.6, 5.1) years, with majority of the patients (57.0%) were aged 1–3 years, while the fewest were aged 11–18 years. The male-to-female ratio was 1.8:1, and the urban-to-rural ratio was 1.1:1. The most common external causes were foreign bodies (41.7%), exposure to inanimate mechanical forces (25.1%), and falls (22.1%). The most frequently injured body parts were head (72.5%). The total number of unintentional injuries exhibited an increasing trend from 2017–2022, and a decreasing trend from 2022–2023. The urban-rural distribution reversed after 2020. The overall hospitalization cost was 20,810,870.4 USD, with an median cost of 758.7 (556.4, 1,186.2) USD per person.ConclusionUnintentional injuries imposed a heavy burden on society and families. However, the number of cases and the urban-rural distribution showed significant trend changes from 2017–2023. The external causes varied by age group, gender, and region, while prevention and control measures should be developed accordingly

Necrotizing pneumonia and purulent meningitis caused by bloodstream infection of CA-MRSA in a child: A rare case report

Case presentationWe report the case of a girl aged 2 years and 10 months who had fever for 2 days, vomiting, poor mental status for 1 day, and one episode of convulsions.Symptoms and signsThe patient experienced a rapid onset of symptoms with fever, vomiting, and convulsions. Upon physical examination on admission, she presented with the following: temperature 38.6°C; pulse 185 beats/min; respiration 49 beats/min; blood pressure 89/51 mmHg; drowsiness; piebald skin all over her body; rice-grain-sized pustular rashes scattered on the front chest and both lower limbs, protruding from the surface of the skin; bilateral pupils that were equal in size and a circle with a diameter of about 3.0 mm, and slow light reflex; cyanotic lips; shortness of breath; positive for the three-concave sign; a small amount of phlegm that could be heard in both lungs; capillary refill time of 5 s; cold extremities; and a positive Babinski sign.Diagnostic methodA chest computed tomography scan showed multiple nodular and flake-like high-density shadows of varying sizes in each lobe in bilateral lungs, and a cavity with blurred edges could be seen in some nodules. A cranial magnetic resonance imaging examination demonstrated that the hyperintensity of diffusion-weighted imaging could be observed on the left cerebellar hemisphere and left parietal blade. Blood cultures, sputum, cerebrospinal fluid, and bronchoalveolar lavage fluid (BALF) by fiberoptic bronchoscopy all indicated the growth of methicillin-resistant Staphylococcus aureus (MRSA).Treatment methodsAfter admission, the child was given meropenem combined with vancomycin, cefoperazone sulbactam combined with rifamycin, linezolid (oral) for anti-infection successively, and other adjuvant therapies.Clinical outcomesThe patient recovered clinically and was discharged from our hospital.Recommended readersNeurology; Respiratory Medicine; Infectious Diseases Department

Optimization and application of sand bailing technology for coalbed methane horizontal wells

Objective and Methods Coalbed methane (CBM) horizontal wells face challenges such as sand accumulation in completion strings, pipe wall scaling, and pump sticking, leading to declined CBM production or shutdown of these wells. This severely restricts continuous, stable CBM production. Removing pulverized coals and sands from wellbores through mechanical sand bailing is recognized as an effective technique to restore and improve the CBM production of horizontal wells. To address challenges such as poor string sealing performance, low efficiency, and sand consolidation in mechanical sand bailing, this study created optimized tools including claw-shaped scraper tips, sand-breaking drill bits, eccentric flaps, and mechanical rotating tools. By introducing hydraulic additional axial force into the mechanical model of the sand bailing string based on the working principle of pumps for mechanical sand bailing in horizontal wells, this study established a string-hydraulic coupling mechanical model. Accordingly, this study proposed a method for optimizing sand bailing operation parameters. Through engineering application, this study analyzed the impacts of the single-stroke reciprocating cycle of the sand bailing pump on the fluid flow velocity in sand storage pipes and pulverized coal migration, as well as the impact of the opening degree of the flap’s suction port on hydraulic additional axial force. Additionally, this study compared and analyzed the axial forces calculated using the string- hydraulic coupling model and a conventional mechanical model. Results and ConclusionsThe results indicate that claw-shaped scraper tips improve sand-breaking efficiency at the horizontal well bottom through structural optimization. The mechanical rotating tool, combined with sand-breaking drill bits and clip springs, effectively addresses the challenge of consolidated sand removal. Furthermore, the eccentric flap and ball-type check valve enhance the area of solid-liquid phases flowing through the flap and the string sealing performance. Under a single-stroke reciprocating cycle of 60 s, the ø110-mm sand bailing pump can transport coal debris with particles diameters ≤ 2.5 mm and a small quantity of coal debris with particle sizes ranging from 3 mm to 12 mm, thus effectively transporting pulverized coals accumulating within wellbores into sand storage pipes. Compared to the conventional tripping, the axial forces of the sand bailing string increased by 906.94 N and decreased by 37.41 N, respectively under upward/downward conditions of the sand bailing pump, suggesting improved calculation accuracy of forces applied to the string. Field applications to 10 horizontal wells in the Qinshui Basin demonstrated that optimized tools and technologies increased single-well and per-operation sand bailing volumes by 1.5 times and 0.9 times, respectively, with the gas and water production rising by 1 483.7 m³/d and 2.18 m³/d, respectively. The optimized tools and technologies provide technical support for stable high-yield CBM horizontal wells. They apply to horizontal and highly deviated wells with screen or perforated casing completions in coal seams at medium-to-shallow depths, holding great practical significance for efficient CBM exploitation

Phage vB_PaeS-PAJD-1 Rescues Murine Mastitis Infected With Multidrug-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is a Gram-negative pathogen that causes a variety of infections in humans and animals. Due to the inappropriate use of antibiotics, multi-drug resistant (MDR) P. aeruginosa strains have emerged and are prevailing. In recent years, cow mastitis caused by MDR P. aeruginosa has attracted attention. In this study, a microbial community analysis revealed that P. aeruginosa could be a cause of pathogen-induced cow mastitis. Five MDR P. aeruginosa strains were isolated from milk diagnosed as mastitis positive. To seek an alternative antibacterial agent against MDR, P. aeruginosa, a lytic phage, designated vB_PaeS_PAJD-1 (PAJD-1), was isolated from dairy farm sewage. PAJD-1 was morphologically classified as Siphoviridae and was estimated to be about 57.9 kb. Phage PAJD-1 showed broad host ranges and a strong lytic ability. A one-step growth curve analysis showed a relatively short latency period (20 min) and a relatively high burst size (223 PFU per infected cell). Phage PAJD-1 remained stable over wide temperature and pH ranges. Intramammary-administered PAJD-1 reduced bacterial concentrations and repaired mammary glands in mice with mastitis induced by MDR P. aeruginosa. Furthermore, the cell wall hydrolase (termed endolysin) from phage PAJD-1 exhibited a strong bacteriolytic and a wide antibacterial spectrum against MDR P. aeruginosa. These findings present phage PAJD-1 as a candidate for phagotherapy against MDR P. aeruginosa infection

Kinetics of the neutralising antibody response in patients with hand, foot, and mouth disease caused by EV-A71: A longitudinal cohort study in Zhengzhou during 2017-2019

BACKGROUND: Hand, foot, and mouth disease (HFMD) caused by enterovirus A71 (EV-A71) poses a serious threat to children's health. Kinetics of the neutralising antibody (NAb) response in EV-A71 infected HFMD patients remains unclear. The ideal sampling time of paired serum samples for serological diagnosis of EV-A71 infection is not well defined. METHODS: HFMD inpatients admitted to Henan Children's Hospital between February 15, 2017 and February 15, 2018 were enrolled. Serial serum samples collected during hospitalisation and up to 1.5 years after discharge were tested for NAb against EV-A71. Random intercept modelling with B-spline was conducted to characterize the kinetics of the EV-A71 NAb response over time after illness onset. FINDINGS: A total of 524 serum samples from 264 EV-A71 RNA positive HFMD inpatients were collected. NAb titres of EV-A71 infected patients were estimated to increase from 40 (95% CI: 9-180) at the day of onset to the peak of 2417 (95% CI: 1859-3143) at day 13, then remained above 1240 until 26 months. For serological diagnosis of EV-A71 infection, if at least a 4-fold rise in titre was used as the criteria, the acute phase serum should be collected at 0-4 days, the corresponding convalescent serum should be collected 14.9 days (95% CI: 9.1-23.8) after illness onset. INTERPRETATION: EV-A71 infection induced a strong and persistent humoral immune response in HFMD patients. The findings provide a scientific support for determining the collection time of paired serum samples for serological diagnosis of EV-A71 infected HFMD patients. FUNDING: National Science Fund for Distinguished Young Scholar