10.13% Efficiency All-Polymer Solar Cells Enabled by Improving the Optical Absorption of Polymer Acceptors

The limited light absorption capacity for most polymer acceptors hinders the improvement of the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs). Herein, by simultaneously increasing the conjugation of the acceptor unit and enhancing the electron-donating ability of the donor unit, a novel narrow-bandgap polymer acceptor PF3-DTCO based on an A–D–A-structured acceptor unit ITIC16 and a carbon–oxygen (C–O)-bridged donor unit DTCO is developed. The extended conjugation of the acceptor units from IDIC16 to ITIC16 results in a red-shifted absorption spectrum and improved absorption coefficient without significant reduction of the lowest unoccupied molecular orbital energy level. Moreover, in addition to further broadening the absorption spectrum by the enhanced intramolecular charge transfer effect, the introduction of C–O bridges into the donor unit improves the absorption coefficient and electron mobility, as well as optimizes the morphology and molecular order of active layers. As a result, the PF3-DTCO achieves a higher PCE of 10.13% with a higher short-circuit current density (Jsc) of 15.75 mA cm−2 in all-PSCs compared with its original polymer acceptor PF2-DTC (PCE = 8.95% and Jsc = 13.82 mA cm−2). Herein, a promising method is provided to construct high-performance polymer acceptors with excellent optical absorption for efficient all-PSCs

Functionalizing tetraphenylpyrazine with perylene diimides (PDIs) as high-performance nonfullerene acceptors

Perylene diimide (PDI)-based small molecular acceptors with a three-dimensional structure are thought to be essential for efficient photocurrent generation and high power conversion efficiencies (PCEs). Herein, a couple of new perylene diimide acceptors (PPDI-O and PPDI-Se) have been designed and successfully synthesized using pyrazine as the core-flanking pyran and selenophene-fused PDIs, respectively. Compared to PPDI-O, PPDI-Se exhibits a blue-shifted absorption in the 400–600 nm range, a comparable LUMO level, and a more distorted molecular geometry. The PPDI-Se-based organic solar cell device with PDBT-T1 as the donor achieved the highest PCE of 7.47% and a high open-circuit voltage (Voc) of up to 1.05 V. The high photovoltaic performance of PPDI-Se-based devices can be attributed to its high LUMO energy level, complementary absorption spectra with donor materials, favorable morphology and balanced carrier transport. The results demonstrate the potential of this type of fullerene-free acceptor for high efficiency organic solar cells

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Heat acclimation training combined with hypoxia training enhances heat-tolerance ability

Objective To explore an effective method to improve the heat resistance of the body by combining classic heat acclimation and hypoxia training. Methods In 2018, a total of 60 healthy male volunteers who were strictly screened from a troop were recruited in this study. They were equally divided into control group, heat acclimation group, and hypoxia training combined heat acclimation group. Then they were trained for 12 d under a damp heat condition (temperature >33 ℃ and humidity >70%). Their ear temperature, heart rate, sweating amount, cardiopulmonary function, comprehensive feeling scores, physiological strain index (PSI), maximal oxygen uptake (VO2max), and physical work capacity at heart rate of 170 beats per minute (PWC170) were tested and evaluated before and after heat acclimation. Results Compared with the control group, the heat acclimation group and the combination group had significantly lower basic ear temperature and the ear temperature after heat test (P < 0.05), decreased basic and post-test heart rate (P < 0.05), and reduced PSI and respiratory rate (P < 0.05), but increased sweating amount, VO2max, PWC170, maximum cardiac output, oxygen consumption/maximal heart rate, maximum CO2 emission, and maximum lung ventilation (P < 0.05). What's more, the heart rate and ear temperature after heat test were obviously lower in the combination group than the heat acclimation group (P < 0.05), so were PSI and respiratory rate (P < 0.05). But the former group had notably higher sweating amount, VO2max, PWC170, maximum cardiac output, oxygen consumption/maximal heart rate, maximum CO2 emission, and maximum lung ventilation than the latter group (P < 0.05). Conclusion Based on the classic heat acclimation, combination of hypoxia training can promote heat acclimation more effectively

Existence and Uniqueness of Positive Periodic Solutions for a Delayed Predator-Prey Model with Dispersion and Impulses

An impulsive Lotka-Volterra type predator-prey model with prey dispersal in two-patch environments and time delays is investigated, where we assume the model of patches with a barrier only as far as the prey population is concerned, whereas the predator population has no barriers between patches. By applying the continuation theorem of coincidence degree theory and by means of a suitable Lyapunov functional, a set of easily verifiable sufficient conditions are obtained to guarantee the existence, uniqueness, and global stability of positive periodic solutions of the system. Some known results subject to the underlying systems without impulses are improved and generalized. As an application, we also give two examples to illustrate the feasibility of our main results

Air Duct Optimization Design Based on Local Turbulence Loss Analysis and IMOCS Algorithm

Considering the complex flow state of the duct flow field in the exhaust system, the structural parameters can significantly impact the internal flow field and noise. This paper takes the noise generated by the duct system under operating conditions as the research object, studies the mechanism of duct noise generation through theoretical analysis, numerical simulation and experimental test, and proposes an optimization design method, that is, to improve the duct structure by adding duct guide vanes. In order to maximize the optimization effect of the guide vane, a multiobjective optimization design of its profile is required, including the parametric expression of the guide vane profile, establishing the design variables and optimization objectives, and establishing the Kriging approximation model. The IMOCS algorithm is used to accurately and efficiently calculate the Pareto front solution to obtain the optimal profile of the duct guide vane and finally improve the noise-reduction performance of the duct system. This paper applies this design method to an integrated stove head duct to verify its accuracy, and prototype tests are conducted according to the optimization results. The test results show that the optimized integrated cooker has improved the outlet flow rate of the whole machine by 1.2 m3/min and reduced the noise by 2.3 dB