Analyzing the Impact of COVID-19 Lockdowns on Violent Crime.

Existing research suggests that COVID-19 lockdowns tend to contribute to a decrease in overall urban crime rates. Most studies have compared pre-lockdown and post-lockdown periods to lockdown periods in Western cities. Few have touched on the fine variations during lockdowns. Equally rare are intracity studies conducted in China. This study tested the relationship between violent crime and COVID-19 lockdown policies in ZG City in southern China. The distance from the isolation location to the nearest violent crime site, called "the nearest crime distance", is a key variable in this study. Kernel density mapping and the Wilcoxon signed-rank test are used to compare the pre-lockdown and post-lockdown periods to the lockdown period. Panel logistic regression is used to test the fine variations among different stages during the lockdown. The result found an overall decline in violent crime during the lockdown and a bounce-back post-lockdown. Violent crime moved away from the isolation location during the lockdown. This outward spread continued for the first two months after the lifting of the lockdown, suggesting a lasting effect of the lockdown policy. During the lockdown, weekly changes in COVID-19 risk ratings at the district level in ZG City also affected changes in the nearest crime distance. In particular, an increase in the risk rating increased that distance, and a drop in the risk rating decreased that distance. These findings add new results to the literature and could have policy implications for joint crime and pandemic prevention and control.

Comprehensive recovery of arsenic and antimony from arsenic-rich copper smelter dust.

In view of reducing contaminant and recovery arsenic and antimony, a novel technology was proposed to recover arsenic and antimony from arsenic-rich copper smelter dust comprehensively. The technique route includes three stages: arsenic and antimony trioxides were leached from the copper smelter dust with hydrochloric acid; trivalent arsenic ions (As3+) were then reduced to less toxic simple arsenic (As) by sodium hypophosphate (NaH2PO2) and recovered; and stepwise recovery of antimony by SbCl3 was achieved by the continuous distillation technique. The results indicates that the leaching efficiency of As and Sb was over 97.5% and 96.8% under conditions of initial 4.0 mol/L HCl, liquid-solid ratio (L/S) of 6:1, leaching temperature of 363 K and time of 2 h. Over 92.5% arsenic was recovered by NaH2PO2 reduction under the suitable conditions: 363 K, 1.5 h and 2.0 times addition of NaH2PO2. The recovery rate of Sb is more than 97.53% at 393 K. The distillation temperature of SbCl3 was optimized between 463 K and 473 K. The corresponding mechanisms of the leaching and recovering of arsenic and antimony were systematically investigated and confirmed by E-pH diagram, thermodynamic calculation, arsenic speciation, composition analysis and XRD characterization.

A high precision MUA-spaced single-cell sensor for cellular receptor assay based on bifunctional Au@Cu-PbCQD nanoprobes.

A single-cell sensor with a spatial architecture was firstly fabricated for realizing high precision single-cell analysis using an 11-mercaptoundecanoic acid (MUA)-spaced sensing interface to prop up single cells and provide a suitable space for effective nanoprobe labeling. Mercapto acids (MA) with different carbon chain lengths were optimized and MUA was selected to provide optimal interspace on the electrodeposited PANI/AuNP substrates, and its carboxyl could couple with folic acid to capture cancer cells. Bifunctional Au@Cu-PbCQD nanoprobes, in which the AuNP cores were linked with lead-coadsorbed carbon quantum dots (PbCQDs) by a copper(ii) ion bridge, were firstly synthesized and applied as highly sensitive electrochemiluminescence (ECL) probes and electrochemical probes. Hyaluronic acid (HA)-functionalized Au@Cu-PbCQD nanoprobes were labelled on MCF-7 cells via specific recognition to the CD44 receptor, which served as the research model. The ECL response of the sensor was applied to evaluate the validity of nanoprobe labeling. With MUA modified, the sensor was able to enhance the ECL intensity by 37.5 ± 3.9%, indicating the remarkable amelioration of the accuracy of single-cell analysis. To take advantage of the bifunctional nanoprobes, differential pulse voltammetry (DPV) was further applied to confirm the feasibility of the proposed single-cell sensor with a spatial architecture. Therefore, the novel strategy provides a single-cell analysis platform to acquire high-precision analytical results, and more accurately to elucidate cellular heterogeneity and biological function.

Real-time quartz crystal microbalance cytosensor based on a signal recovery strategy for in-situ and continuous monitoring of multiple cell membrane glycoproteins.

A real-time quartz crystal microbalance (QCM) cytosensor based on a signal recovery strategy was first developed for in-situ and continuous monitoring of multiple cell membrane glycoproteins. In this work, gold nanoparticles (AuNPs) were linked with ligands to fabricate ligand-functionalized mass nanoprobes with signal amplification for increasing monitoring sensitivity. The mass nanoprobes bound to cell surface could be eluted with glycine-hydrochloric acid buffer, which led to a quick recovery of resonance frequency. Using the strategy, folate receptors (FR), CD44 molecule and epidermal growth factor receptor (EGFR) on cell membrane as the models were monitored continuously. The quantification result of MDA-MB-231 cells showed a range of linearity of 3.0 × 104 to 1.0 × 106 cells and a detection limit of 5.0 × 103 cells. Furthermore, the multianalyte cytosensor exhibited three sensitive and recoverable frequency shifts during continuous monitoring for in-situ and continuous evaluation of the expression levels of FR, CD44 and EGFR on cell membrane, which exhibited that the average numbers of molecules of FR, CD44 and EGFR per MDA-MB-231 cell were 0.5 × 106, 0.2 × 106 and 1.4 × 105 with the relative standard deviation of 4.8%, 4.5% and 5.1%, respectively. Compared with monolithic multichannel QCM, the multianalyte cytosensor based on a single microbalance could not only exclude acoustic interference but also reduce instrumental cost. This work provided a simple and efficient QCM cytosensor for in-situ and continuous monitoring of multiple cell membrane glycoproteins that offered a new avenue for early diagnosis of cancer.

A single-cell analysis platform for electrochemiluminescent detection of platelets adhesion to endothelial cells based on Au@DL-ZnCQDs nanoprobes.

A novel single-cell analysis platform (SCA) was developed for the investigation of platelets adhesion to single human umbilical vein endothelial cell (HUVEC) via using the adhesion molecule (E-selectin) on the damaged HUVEC as the marker site, and integrating electrochemiluminescence (ECL) with the ultrasensitive Au@DL-ZnCQDs nanoprobes. The Au@DL-ZnCQDs nanocomposite, a kind of double layer zinc-coadsorbed carbon quantum dot (ZnCQDs) core-shell nanoprobe, was firstly constructed by using gold nanoparticles (AuNPs) as the core to load with ZnCQDs and then the citrate-modified silver nanoparticles (AgNPs) as the bridge to link AuNPs-ZnCQDs with ZnCQDs to form the core-shell with double layer ZnCQDs (DL-ZnCQDs) nanoprobe, revealed a 10-fold signal amplification. The H2O2-induced oxidative damage HUVECs were utilized as the cellular model on which anti-E-selectin functionalized nanoprobes specially recognized E-selectin, the SCA showed that the ECL signals decreased with platelets adhesion to single HUVEC. The proposed SCA could effectively and dynamically monitor the adhesion between single HUVEC and platelets in the absence and presence of collagen activation, moreover, be able to quantitatively detect the number of platelets adhesion to single HUVEC, and show a good analytical performance with linear range from 1 to 15 platelets. In contrast, the HUVEC was down-regulated the expression of adhesion molecules by treating with quercetin inhibitor, and the SCA also exhibited the feasibility for analysis of platelets adhesion to single HUVEC. Therefore, the single-cell analysis platform provided a novel and promising protocol for analysis of the single intercellular adhesion, and it will be beneficial to elucidate the pathogenesis of cardiovascular diseases.

Novel Single-Cell Analysis Platform Based on a Solid-State Zinc-Coadsorbed Carbon Quantum Dots Electrochemiluminescence Probe for the Evaluation of CD44 Expression on Breast Cancer Cells.

A novel single-cell analysis platform was fabricated using solid-state zinc-coadsorbed carbon quantum dot (ZnCQDs) nanocomposites as an electrochemiluminescence (ECL) probe for the detection of breast cancer cells and evaluation of the CD44 expression level. Solid-state ZnCQDs nanocomposite probes were constructed through the attachment of ZnCQDs to gold nanoparticles and then the loading of magnetic beads to amplify the ECL signal, exhibiting a remarkable 120-fold enhancement of the ECL intensity. Hyaluronic acid (HA)-functionalized solid-state probes were used to label a single breast cancer cell by the specific recognition of HA with CD44 on the cell surface, revealing more stable, sensitive, and effective tagging in comparison with the water-soluble CQDs. This strategy exhibited a good analytical performance for the analysis of MDA-MB-231 and MCF-7 single cells with linear range from 1 to 18 and from 1 to 12 cells, respectively. Furthermore, this single-cell analysis platform was used for evaluation of the CD44 expression level of these two cell lines, in which the MDA-MB-231 cells revealed a 2.8-5.2-fold higher CD44 expression level. A total of 20 single cells were analyzed individually, and the distributions of the ECL intensity revealed larger variations, indicating the high cellular heterogeneity of the CD44 expression level on the same cell line. The as-proposed single-cell analysis platform might provide a novel protocol to effectively study the individual cellular function and cellular heterogeneity.