Improved Catalytic Activity of Spherical Nucleic Acid Enzymes by Hybridization Chain Reaction and Its Application for Sensitive Analysis of Aflatoxin B1.

Conventional spherical nucleic acid enzymes (SNAzymes), made with gold nanoparticle (AuNPs) cores and DNA shells, are widely applied in bioanalysis owing to their excellent physicochemical properties. Albeit important, the crowded catalytic units (such as G-quadruplex, G4) on the limited AuNPs surface inevitably influence their catalytic activities. Herin, a hybridization chain reaction (HCR) is employed as a means to expand the quantity and spaces of G4 enzymes for their catalytic ability enhancement. Through systematic investigations, we found that when an incomplete G4 sequence was linked at the sticky ends of the hairpins with split modes (3:1 and 2:2), this would significantly decrease the HCR hybridization capability due to increased steric hindrance. In contrast, the HCR hybridization capability was remarkably enhanced after the complete G4 sequence was directly modified at the non-sticky end of the hairpins, ascribed to the steric hindrance avoided. Accordingly, the improved SNAzymes using HCR were applied for the determination of AFB1 in food samples as a proof-of-concept, which exhibited outstanding performance (detection limit, 0.08 ng/mL). Importantly, our strategy provided a new insight for the catalytic activity improvement in SNAzymes using G4 as a signaling molecule.

Simulation of binary collision of liquid drops using smoothed particle hydrodynamics with adaptive spatial resolution.

The binary collision of water drops in the air is studied by two-dimensional numerical simulation utilizing smoothed particle hydrodynamics with adaptive spatial resolution. The numerical method is validated by comparing the simulation with experiment. Three basic modes of equal-size drop collision are observed in numerical simulations at Weber number 3≤We≤120 and impact parameter 0≤x≤0.8, namely, reflexive separation, stretching separation, and coalescence collision. Based on the numerical results of different collision modes, the specific phenomena, evolution patterns, and physical principles are discussed. In particular, the detailed processes of the necking phenomenon and the propagation of surface wave in separation collision are obtained, corroborating the "end-pinching" theory proposed in the literature. At higher Weber numbers, the recoalescence of satellite drops is observed. The collision of unequal-size drops is also investigated. The effects of three dimensionless parameters, namely, drop diameter ratio, Weber number, and impact parameter are discussed. The physical mechanisms of some special phenomena are expressed in detail.

Neoadjuvant Chemotherapy Compared with Surgery for Oesophageal Carcinoma: A Retrospective Study and Missing Evidence.

Background: Negative evidence for the use of neoadjuvant chemotherapy (NAC) to treat oesophageal squamous cell carcinoma (ESCC) has been reported in Western countries in the past century. However, in China, most ESCC patients underwent paclitaxel and platinum-based NAC without evidence from local RCTs. Empiricism or a lack of evidence does not necessarily mean that the evidence is negative. However, there was no way to compensate for the missing evidence. The only way to obtain evidence is by conducting a retrospective study using propensity score matching (PSM) to compare the effects of NAC and primary surgery on overall survival (OS) and disease-free survival (DFS) among ESCC patients in China, which is the country with the highest prevalence of ESCC patients. Methods: From January 1, 2015, to December 31, 2018, a total of 5443 patients with oesophageal cancer/oesophagogastric junction carcinoma who underwent oesophagectomy were retrospectively identified at Henan Cancer Hospital. After PSM, 826 patients were selected for the retrospective study and divided into the NAC and primary surgery groups. The median follow-up period was 54.08 months. Toxicity and tumour responses to NAC, intraoperative and postoperative outcomes, recurrence, DFS and OS were analysed. Results: The postoperative complication rates were not significantly different between the two groups. The 5-year DFS rates were 57.48% (95% CI, 52.05% to 62.53%) for the NAC group and 49.93% (95% CI, 44.56% to 55.05%) for the primary surgery group (P=0.0129). The 5-year OS rates were 62.95% (95% CI, 57.63% to 67.79%) for the NAC group and 56.29% (95% CI, 50.99% to 61.25%) for the primary surgery group (P=0.0397). Conclusion: Compared with primary surgery, NAC with paclitaxel and platinum-based chemotherapy and two-field extensive mediastinal lymphadenectomy might be associated with long-term survival benefits among ESCC patients.

Estimation of Daily Ground-Received Global Solar Radiation Using Air Pollutant Data.

Ground-received solar radiation is affected by several meteorological and air pollution factors. Previous studies have mainly focused on the effects of meteorological factors on solar radiation, but research on the influence of air pollutants is limited. Therefore, this study aimed to analyse the effects of air pollution characteristics on solar radiation. Meteorological data, air quality index (AQI) data, and data on the concentrations of six air pollutants (O3, CO, SO2, PM10, PM2.5, and NO2) in nine cities in China were considered for analysis. A city model (model-C) based on the data of each city and a unified model (model-U) based on national data were established, and the key pollutants under these conditions were identified. Correlation analysis was performed between each pollutant and the daily global solar radiation. The correlation between O3 and daily global solar radiation was the highest (r = 0.575), while that between SO2 and daily global solar radiation was the lowest. Further, AQI and solar radiation were negatively correlated, while some pollution components (e.g., O3) were positively correlated with the daily global solar radiation. Different key pollutants affected the solar radiation in each city. In Shenyang and Guangzhou, the driving effect of particles on the daily global solar radiation was stronger than that of pollutants. However, there were no key pollutants that affect solar radiation in Shanghai. Furthermore, the prediction performance of model-U was not as good as that of model-C. The model-U showed a good performance for Urumqi (R2 = 0.803), while the difference between the two models was not particularly significant in other areas. This study provides significant insights to improve the accuracy of regional solar radiation prediction and fill the gap regarding the absence of long-term solar radiation monitoring data in some areas.

Estimation of hourly average illuminance under clear sky conditions in Chongqing.

Satellite-based methods are proposed for the estimation of clear day average hourly illuminance from satellite data under local climate conditions. First, aerosol optical depth (AOD) data collected using a ground-based sun photometer were used to calibrate the satellite remote sensing AOD data. Next, we screened for the factors affecting the illuminance of clear sky and detected three important factors, namely the sine of the solar altitude angle, aerosol optical thickness, and atmospheric precise water content. Finally, based on the AOD data of satellite remote sensing, combined with the local illumination data and meteorological data, a clear sky average hourly illumination model in Chongqing was established via the regression method. There was good agreement between the calculated and the measured values of clear day average hourly illuminance, with a root mean square difference and mean bias difference of 22% and -0.05%, respectively. The model was used to map clear day annual, quarterly, and monthly average hourly illuminance. The maps show the clear day annual, seasonal, and monthly variations of average hourly illuminance in Chongqing.