We collected information on demographic characteristics, exposure history, and illness timelines of laboratory-confirmed cases of NCIP that had been reported by January 22, 2020. We described characteristics of the cases and estimated the key epidemiologic time-delay distributions. In the early period of exponential growth, we estimated the epidemic doubling time and the basic reproductive number. RESULTSAmong the first 425 patients with confirmed NCIP, the median age was 59 years and 56% were male. The majority of cases (55%) with onset before January 1, 2020, were linked to the Huanan Seafood Wholesale Market, as compared with 8.6% of the subsequent cases. The mean incubation period was 5.2 days (95% confidence interval [CI], 4.1 to 7.0), with the 95th percentile of the distribution at 12.5 days. In its early stages, the epidemic doubled in size every 7.4 days. With a mean serial interval of 7.5 days (95% CI, 5.3 to 19), the basic reproductive number was estimated to be 2.2 (95% CI, 1.4 to 3.9). CONCLUSIONSOn the basis of this information, there is evidence that human-to-human transmission has occurred among close contacts since the middle of December 2019. Considerable efforts to reduce transmission will be required to control outbreaks if similar dynamics apply elsewhere. Measures to prevent or reduce transmission should be implemented in populations at risk. (Funded by the Ministry of Science and Technology of China and others.) a bs tr ac t Early Transmission Dynamics
of coronavirus disease (COVID-19) had been reported globally since December 2019 (1), severely burdening the healthcare system (2). The extremely fast transmission capability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has aroused concern about its various transmission routes.The main transmission routes for SARS-CoV-2 are respiratory droplets and close contact (3). Knowing the extent of environmental contamination of SARS-CoV-2 in COVID-19 wards is critical for improving safety practices for medical staff and answering questions about SARS-CoV-2 transmission among the public. However, whether SARS-CoV-2 can be transmitted by aerosols remains controversial, and the exposure risk for close contacts has not been systematically evaluated. Researchers have detected SARS-CoV-2 on surfaces of objects in a symptomatic patient's room and toilet area (4). However, that study was performed in a small sample from regions with few confirmed cases, which might not reflect real conditions in outbreak regions where hospitals are operating at full capacity. In this study, we tested surface and air samples from an intensive care unit (ICU) and a general COVID-19 ward (GW) at Huoshenshan Hospital in Wuhan, China (Figure 1). The StudyFrom February 19 through March 2, 2020, we collected swab samples from potentially contaminated objects in the ICU and GW as described previously (5). The ICU housed 15 patients with severe disease and the GW housed 24 patients with milder disease. We also sampled indoor air and the air outlets to detect aerosol exposure. Air samples were collected by using a SASS 2300 Wetted Wall Cyclone Sampler (Research International, Inc., https://www.resrchintl.com) at 300 L/min for of 30 min. We used sterile premoistened swabs to sample the floors, computer mice, trash cans, sickbed handrails, patient masks, personal protective equipment, and air outlets. We tested air and surface samples for the open reading frame (ORF) 1ab and nucleoprotein (N) genes of SARS-CoV-2 by quantitative real-time PCR. (Appendix, https://wwwnc.cdc.gov/EID/ article/26/7/20-0885-App1.pdf).Almost all positive results were concentrated in the contaminated areas (ICU 54/57, 94.7%; GW 9/9, 100%); the rate of positivity was much higher for the ICU (54/124, 43.5%) than for the GW (9/114, 7.9%) (Tables 1, 2). The rate of positivity was
2 Molecular design of non-fullerene acceptors (NFAs) is of vital importance for highefficiency organic solar cells. The branched alkyl chain modification is often regarded as a counter-intuitive approach as which may introduce undesirable steric hindrance that reduces charge transport in NFAs. Here we show the design and synthesis of a highly efficient NFA family by substituting the beta position of thiophene unit on Y6-based A-DAD-A backbone with branched alkyl chains. It was found that such modification of different alkyl chain length could completely change the molecular packing behavior of NFAs, leading to improved structure order and charge transport in thin films. Unprecedented efficiency of 18.32% (certified value of 17.9%) with a fill factor of 81.5% is achieved for single-junction organic solar cells. This work reveals the importance of branched alkyl chain topology in tuning the molecular packing and blend morphology that leads to improved organic photovoltaic performance.
In organic photovoltaics, morphological control of donor and acceptor domains on the nanoscale is key for efficient exciton diffusion and dissociation, carrier transport, and suppression of recombination losses. To realise this, here, we demonstrated a double-fibril network based on ternary donor:acceptor morphology with multi-length scales constructed by combining ancillary conjugated polymer crystallizers and non-fullerene acceptor filament assembly. Using this approach, we achieved an average power conversion efficiency of 19.3% (certified 19.2%). The success lies in the good match between the photoelectric parameters and the morphological characteristic lengths, which utilizes the excitons and free charges efficiently. This strategy leads to enhanced exciton diffusion length (hence exciton dissociation yield) and reduced recombination rate, hence minimizing photon-to-electron losses in the ternary devices as compared to their binary counterparts. The double-fibril network morphology strategy minimizes losses and maximizes the power output, offering the possibility towards 20% power conversion efficiencies in single-junction organic photovoltaics. MainOrganic semiconductors offer the advantage of high optical absorption and tunable energy levels, enabling thin-film solar cells with high light-to-electron conversion efficiencies over a wide range of wavelengths  . Desipte recent progresses, the performance of organic solar cells (OSCs) is still limited by non-ideal exciton and charge transport, which depend not only on the electronic structure of organic semiconductors but also on the nanostructure that is formed by material crystallization and phase separation in a bulk heterojunction (BHJ) setting  . A suitable sized phase-separated morphology that balances crystalline region and mixing domain on the nanoscale is therefore needed to further push the power conversion efficiency (PCE) of OSCs, however it is a
Plant RHO GTPases (RAC/ROPs) mediate multiple extracellular signals ranging from hormone to stress and regulate diverse cellular processes important for polarized cell growth, differentiation, development, reproduction, and responses to the environment. They shuttle between the GDP-bound inactive state and the GTP-bound activated state and their activation is predominantly mediated by a family of guanine nucleotide exchange factors (GEFs) referred to as ROPGEFs. Using the Arabidopsis ROPGEF1 as bait, we identified members of a receptor-like kinase (RLK) family as potential upstream regulators for RAC/ROP signaling. NADPH oxidase-derived reactive oxygen species (ROS) are emerging as important regulators for growth and development and play a crucial role in mediating RAC/ROP-regulated root hair development, a polarized cell growth process. We therefore screened T-DNA insertion mutants in these RLKs for root hair defects and found that mutations in one of them, At3g51550 encoding the FERONIA (FER) receptor-like kinase, induced severe root hair defects. We show that the fer phenotypes correlated with reduced levels of active RAC/ ROPs and NADPH oxidase-dependent, auxin-regulated ROS accumulation in roots and root hairs and that up-regulating RAC/ROP signaling in fer countered the mutant phenotypes. Taken together, these observations strongly support FER as an upstream regulator for the RAC/ROP-signaled pathway that controls ROS-mediated root hair development. Moreover, FER was pulled down by ROP2 GTPase in a guanine nucleotide-regulated manner implying a dynamic signaling complex involving FER, a ROPGEF, and a RAC/ROP.
Understanding the spatial organization of gene expression with single nucleotide resolution requires localizing the sequences of expressed RNA transcripts within a cell in situ. Here we describe fluorescent in situ RNA sequencing (FISSEQ), in which stably cross-linked cDNA amplicons are sequenced within a biological sample. Using 30-base reads from 8,742 genes in situ, we examined RNA expression and localization in human primary fibroblasts using a simulated wound healing assay. FISSEQ is compatible with tissue sections and whole mount embryos, and reduces the limitations of optical resolution and noisy signals on single molecule detection. Our platform enables massively parallel detection of genetic elements, including gene transcripts and molecular barcodes, and can be used to investigate cellular phenotype, gene regulation, and environment in situ.
Tolerance of plants to abiotic stressors such as drought and salinity is triggered by complex multicomponent signaling pathways to restore cellular homeostasis and promote survival. Major plant transcription factor families such as bZIP, NAC, AP2/ERF, and MYB orchestrate regulatory networks underlying abiotic stress tolerance. Sucrose non-fermenting 1-related protein kinase 2 and mitogen-activated protein kinase pathways contribute to initiation of stress adaptive downstream responses and promote plant growth and development. As a convergent point of multiple abiotic cues, cellular effects of environmental stresses are not only imbalances of ionic and osmotic homeostasis but also impaired photosynthesis, cellular energy depletion, and redox imbalances. Recent evidence of regulatory systems that link sensing and signaling of environmental conditions and the intracellular redox status have shed light on interfaces of stress and energy signaling. ROS (reactive oxygen species) cause severe cellular damage by peroxidation and de-esterification of membrane-lipids, however, current models also define a pivotal signaling function of ROS in triggering tolerance against stress. Recent research advances suggest and support a regulatory role of ROS in the cross talks of stress triggered hormonal signaling such as the abscisic acid pathway and endogenously induced redox and metabolite signals. Here, we discuss and review the versatile molecular convergence in the abiotic stress responsive signaling networks in the context of ROS and lipid-derived signals and the specific role of stomatal signaling.
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