Background COVID-19 is diagnosed via detection of SARS-CoV-2 RNA using real time reverse-transcriptase polymerase chain reaction (rtRT-PCR). Performance of many SARS-CoV-2 rtRT-PCR assays is not entirely known due to the lack of a gold standard. We sought to evaluate the false negative rate (FNR) and sensitivity of our laboratory-developed SARS-CoV-2 rtRT-PCR targeting the envelope (E) and RNA-dependent RNA-polymerase (RdRp) genes. Methods SARS-CoV-2 rtRT-PCR results at the Public Health Laboratory (Alberta, Canada) from January 21 to April 18, 2020 were reviewed to identify patients with an initial negative rtRT-PCR followed by a positive result on repeat testing within 14 days (defined as discordant results). Negative samples from these discordant specimens were re-tested using three alternate rtRT-PCR assays (targeting the E gene and N1/N2 regions of the nucleocapsid genes) to assess for false negative (FN) results. Results During the time period specified, 95,919 patients (100,001 samples) were tested for SARS-CoV-2. Of these, 49 patients were found to have discordant results including 49 positive and 52 negative swabs. Repeat testing of 52 negative swabs found five FNs (from five separate patients). Assuming 100% specificity of the diagnostic assay, the FNR and sensitivity in this group of patients with discordant testing was 9.3% (95% CI 1.5–17.0%) and 90.7% (95% CI 82.6–98.9%) respectively. Conclusions Studies to understand the FNR of routinely used assays are important to confirm adequate clinical performance. In this study, most FN results were due to low amounts of SARS-CoV-2 virus concentrations in patients with multiple specimens collected during different stages of infection. Post-test clinical evaluation of each patient is advised to ensure that rtRT-PCR results are not the only factor in excluding COVID-19.

Disease-based registries can form the basis of comparative research to improve and inform policy for optimizing outcomes, for example, in out-of-hospital cardiac arrest (OHCA). Such registries are often lacking in resource-limited countries and settings. Anecdotally, survival rates for OHCA in Asia are low compared to those in North America or Europe, and a regional registry is needed. The Pan-Asian Resuscitation Outcomes Study (PAROS) network of hospitals was established in 2009 as an international, multicenter, prospective registry of OHCA across the Asia-Pacific region, to date representing a population base of 89 million in nine countries. The network's goal is to provide benchmarking against established registries and to generate best practice protocols for Asian emergency medical services (EMS) systems, to impact community awareness of prehospital emergency care, and ultimately to improve OHCA survival. Data are collected from emergency dispatch, ambulance providers, emergency departments, and in-hospital collaborators using standard protocols. To date (March 2011), there are a total of 9,302 patients in the database. The authors expect to achieve a sample size of 13,500 cases over the next 2 years of data collection. The PAROS network is an example of a low-cost, self-funded model of an Asia-Pacific collaborative research network with potential for international comparisons to inform OHCA policies and practices. The model can be applied across similar resource-limited settings.

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Planted forest plays a significant role in carbon sequestration and climate change mitigation; however, little information has been available on the distribution patterns of carbon pools with stand ages in Pinus massoniana Plantations. We investigated the biomass stock and carbon sequestration across a chronosequence (3-, 5-, 7-, 9-, 12-, 15-, 19-, 29-, 35-and 42-year) of stands with the main objectives: (1) to determine the biomass and carbon stock of the forest ecosystem; and (2) to identify factors influencing their distribution across the age series. Simple random sampling was used for collecting field data in the ten (10) stand ages. Three 20 × 20 m standard plots were laid out in February 2015 across the chronosequence. The diameter at breast height (DBH) and tree height (H) of each tree within each plot were measured using calipers and height indicator. Sub-plots of 2 × 2 m were established in each main plot for collecting soil samples at a 0-30-and 30-60-cm depth. Plantation biomass increased with increasing stand ages, ranging from 0.84 tonnes per hectare (t· ha −1 ) in the three-year stand to 252.35 t· ha −1 in the 42-year stand.The aboveground biomass (AGB) contributed 86.51%; the maximum value is 300-times the minimum value. Carbon concentrations and storage in mineral soil decreased with

During the COVID-19 outbreak, educational institutions were closed, and students worldwide were confined to their homes. In an educational environment, students depend on collaborative learning (CL) to improve their learning performance. This study aimed to increase the understanding of social media adoption among students during the COVID-19 pandemic for the purpose of CL. Social media provides a learning platform that enables students to easily communicate with their peers and subject specialists, and is conducive to students' CL. This study addresses the key concept of CL during the COVID-19 pandemic by assessing social media use among students in higher education. The relationship between social media use and students' performance is crucial to understanding the role of social media during a pandemic. This study is based on constructivism theory and the technology acceptance model. Structural equation modeling was used to analyze the conceptual model using SmartPLS. The research findings indicate that social media plays an important role during the pandemic because it provides opportunities for students to enhance CL under the aforementioned situations. This study makes noteworthy theoretical and practical contributions.

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Purple soil is widely distributed in the hilly areas of the Sichuan basin, southwest China, and is highly susceptible to water erosion. The triggering of this process is related to slope, rainfall intensity and surface cover. Therefore, this study assesses the effects of different simulated rainfall intensities with different slopes on hydrological and erosional processes in un-mulched and mulched purple soils. Results show that the sediment and water losses increased with an increase of rainfall intensity and slope steepness. Generally, the slope contribution (Sc) on water and sediment losses decreased with increasing rainfall intensity and slope steepness under both un-mulched and mulched soil. In un-mulched conditions, water losses were independent of slope steepness (Sc < 50%) during the highest rainfall intensity. However, in mulched soil, the higher contributions of slope (Sc) and rainfall (Rc) were found for water and sediment losses, respectively, i.e., >50%, except during the increase in slope steepness from 15 • to 25 • under the highest rainfall intensity (120 mm·h −1 ). The effectiveness of mulch was more pronounced in reducing sediment losses (81%-100%) compared with water losses (14%-100%). The conservation effectiveness of mulch both decreased and increased with slope steepness for water and sediment losses, respectively, under higher rainfall intensities. Water infiltration and recharge coefficient (RC) decreased with an increase of slope steepness, while with an increase in rainfall intensity, the water infiltration and RC were increased and decreased, respectively, in both un-mulched and mulched soil. On the other hand, mulched soil maintained a significantly (α = 0.05) higher infiltration capacity and RC compared to that of the un-mulched soil.

Star-shaped three-dimensional (3D) twisted configured acceptors are a type of nonfullerene acceptors (NFAs) which are getting considerable attention of chemists and physicists on account of their promising photovoltaic properties and manifestly promoted the rapid progress of organic solar cells (OSCs). This report describes the peripheral substitution of the recently reported highly efficient 3D star-shaped acceptor compound, STIC, containing a 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) end-capped group and a subphthalocyanine (SubPc) core unit. The 3D star-shaped SubPc-based NFA compound STIC is peripherally substituted with well-known end-capped groups, and six new molecules ( S1–S6 ) are quantum chemically designed and explored using density functional theory (DFT) and time-dependent DFT (TDDFT). Density of states (DOS) analysis, frontier molecular orbital (FMO) analysis, reorganization energies of electrons and holes, open-circuit voltage, transition density matrix (TDM) surface, photophysical characteristics, and charge-transfer analysis of selected molecules ( S1–S6 ) are evaluated with the synthesized reference STIC. The designed molecules are found in the ambience of 2.52–2.27 eV with a reduction in energy gap of up to 0.19 eV compared to R values. The designed molecules S3–S6 showed a red shift in the absorption spectrum in the visible region and broader shift in the range of 605.21–669.38 nm (gas) and 624.34–698.77 (chloroform) than the R phase values of 596.73 nm (gas) and 616.92 nm (chloroform). The open-circuit voltages are found with the values larger than R values in S3–S6 (1.71–1.90 V) and comparable to R in the S1 and S2 molecules. Among all investigated molecules, S5 due to the combination of extended conjugation and electron-withdrawing capability of end-capped acceptor moiety A5 is proven as the best candidate owing to promising photovoltaic properties including the lowest band gap (2.27 eV), smallest λ e = 0.00232 eV and λ h = 0.00483 eV, highest λ max values of 669.38 nm (in gas) and 698.77 nm (in chloroform), and highest V oc = 1.90 V with respect to HOMO PTB7-Th –LUMO acceptor . Our results suggest that the selected molecules are fine acceptor materials and can be used as electron and/or hole transport materials with excellent photovoltaic properties for OSCs.