Remarkable Antibacterial Activity of Reduced Graphene Oxide Functionalized by Copper Ions

Despite long-term efforts for exploring antibacterial agents or drugs, potentiating antibacterial activity and meanwhile minimizing toxicity to the environment remains a challenge. Here, it is experimentally shown that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity that is significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two-orders-of-magnitude greater than the activity of its surrounding copper ions. It is demonstrated that rGO is functionalized through the cation–π interaction to massively adsorb copper ions to form a rGO–copper composite and result in an extremely low concentration level of surrounding copper ions (less than ≈0.5 µm ). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu²⁺ into Cu⁺, which greatly enhances the antibacterial activity. Notably, this rGO functionality through cation–π interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells.     

低功率激光对细胞质膜通透性及细胞功能的影响

目的:探索低功率激光对细胞质膜通透性及细胞功能的影响。方法:以波长为632.8nm,功率密度为5.4mW/cm~2的氦氖激光照射人外周血淋巴细胞15、30、60分钟,并采用钙荧光指示剂Fura—2/Am定量测试法检测淋巴细胞内游离钙浓度和质膜Ca~(2+)—Mg~(2+)—ATP酶活性变化。结果:照射后淋巴细胞内游离钙浓度明显低于正常(P<0.05);同时细胞膜Ca~(2+)—Mg~(2+)—ATP酶活性增加(P<0.05);而且照射后细胞内游离钙浓度降低与质膜上Ca~(2+)—Mg~(2+)—ATP酶的激活呈负相关。结论:低功率激光照射激活细胞膜Ca~(2+)—Mg~(2+)—ATP酶活性,使细胞膜对钙通透性发生变化,且影响到细胞内Ca~(2+)贮存,造成细胞膜通透性和细胞功能的改变。     

UML活动图到时间Petri网的映射方法

UML被广泛应用于嵌入式实时系统等领域的建模,而嵌入式实时系统对时间响应的要求非常严格,UML缺乏对系统时间约束的描述和形式化语义。因此,提出了一种结合MARTE与UML带有时间约束的UML活动图模型,并定义相应的映射规则,将该活动图模型映射到时间Petri 网模型,最后通过实例验证了该映射方法的正确性和实用性。     

Copper@ZIF-8 Core-Shell Nanowires for Reusable Antimicrobial Face Masks

SARS-CoV-2 and other respiratory viruses spread via aerosols generated by infected people. Face masks can limit transmission. However, widespread use of disposable masks consumes tremendous resources and generates waste. Here, a novel material for treating blown polypropylene filtration media used in medical-grade masks to impart antimicrobial activity is reported. To produce thin copper@ZIF-8 core-shell nanowires (Cu@ZIF-8 NWs), Cu NWs are stabilized using a pluronic F-127 block copolymer, followed by growth of ZIF-8 to obtain uniform core-shell structures. The Cu@ZIF-8 NWs are applied to filtration media by dip coating. Aerosol filtration efficiency decreases upon exposure to ethanol (solvent for dip-coating), but increases with addition of Cu@ZIF-8 NWs. Cu@ZIF-8 NWs shows enhanced antibacterial activity, compared to Cu NWs or ZIF-8 alone, against Streptococcus mutans and Escherichia coli. Antiviral activity against SARS-CoV-2 is assayed using virus-infected Vero E6 cells, demonstrating 55% inhibition of virus replication after 48 h by 1 µg of Cu@ZIF-8 NWs per well. Cu@ZIF-8 NWs’ cytotoxicity is tested against four cell lines, and their effect on inflammatory response in A549 cells is examined, demonstrating good biocompatibility. This low-cost, scalable synthesis and straightforward deposition of Cu@ZIF-8 NWs onto filter media has great potential to reduce disease transmission, resource consumption, and environmental impact of waste.     

High-Efficiency Reactive Oxygen Species Generation by Multiphase and TiO6 Distortion-Mediated Superior Piezocatalysis in Perovskite Ferroelectrics

Piezocatalysis, governed by piezo-potential within piezoelectrics, has gained prominence for reactive oxygen species (ROS) generation, which is significant to environmental and biological applications. However, designing piezocatalysts with excellent piezocatalytic performance in a wide temperature and efficient charge carrier separation ability is still challenging. Herein, eco-friendly BaTiO₃ (BT)-based perovskite ferroelectrics with tailored multiphase coexistence in a wide temperature range are constructed to boost higher piezoelectricity and large piezo-potential, which is attributed to decreased polarization anisotropy by flat Gibbs energy profile. Elevated piezo-potential in designed BT-based piezocatalyst guarantees high-efficient generation rate of •OH (200 µmol g⁻¹ h⁻¹) and •O₂⁻ (40 µmol g⁻¹ h⁻¹) by ultrasound stimulation, which is 3.5 times more than that of pure BT. Besides, piezocatalytic capacity to degrade dye wastewater shows a rate constant of 0.0182 min⁻¹ and gives an antibacterial rate of 95% within 30 min for eliminating E. coli. Theoretical simulations validate that the local distortion of TiO₆ octahedra also contributes to piezocatalytic performance by inducing electron–hole pairs separation in real space, and better response to slight structural deformation. This work is important to design high-performance piezocatalysts with high-efficiency ROS generation for sewage treatment and sonodynamic therapy.     

A multi coding technique to reduce transition activity in VLSI circuits

Advances in VLSI technology have enabled the implementation of complex digital circuits in a single chip, reducing system size and power consumption. In deep submicron low power CMOS VLSI design, the main cause of energy dissipation is charging and discharging of internal node capacitances due to transition activity. Transition activity is one of the major factors that also affect the dynamic power dissipation. This paper proposes power reduction analyzed through algorithm and logic circuit levels. In algorithm level the key aspect of reducing power dissipation is by minimizing transition activity and is achieved by introducing a data coding technique. So a novel multi coding technique is introduced to improve the efficiency of transition activity up to 52.3% on the bus lines, which will automatically reduce the dynamic power dissipation. In addition, 1 bit full adders are introduced in the Hamming distance estimator block, which reduces the device count. This coding method is implemented using Verilog HDL. The overall performance is analyzed by using Modelsim and Xilinx Tools. In total 38.2% power saving capability is achieved compared to other existing methods.     

含激活介质的一维光子晶体缺陷模特性研究

首先研究了(AB)6A(BA)6型一维光子晶体带隙特征,然后将激活介质C替代中间位置的A,构成(AB)6C(BA)6型光子晶体,并用数值模拟法研究了缺陷层C的厚度和折射率对光子晶体带隙的影响.结果显示这种含有激活介质的光子晶体具有一些新的特征,在原来的禁带位置出现了透射率大于1的透射窄带,并且透射窄带的数目和透射率可以通过改变缺陷层的相关参数调节.这些现象都可以用布拉格散射和法布里一珀罗共振原理得到解释.     

基于签到活跃度和时空概率模型的自适应兴趣点推荐方法

针对现有兴趣点(POI)推荐算法对不同签到特征的用户缺乏自适应性问题,该文提出一种基于用户签到活跃度(UCA)特征和时空(TS)概率模型的自适应兴趣点推荐方法UCA-TS。利用概率统计分析方法提取用户签到的活跃度特征,给出一种用户不活跃和活跃的隶属度计算方法。在此基础上,分别采用结合时间因素的1维幂律函数和2维高斯核密度估计来计算不活跃和活跃特征的概率值,同时融入兴趣点流行度来进行推荐。该方法能自适应用户的签到特征,并能更准确体现用户签到的时间和空间偏好。实验结果表明,该方法能够有效提高推荐精度和召回率。

     

Gold Nanoparticles and g‐C3N4‐Intercalated Graphene Oxide Membrane for Recyclable Surface Enhanced Raman Scattering

Toxic organic pollutants in the aquatic environment cause severe threats to both humans and the global environment. Thus, the development of robust strategies for detection and removal of these organic pollutants is essential. For this purpose, a multifunctional and recyclable membrane by intercalating gold nanoparticles and graphitic carbon nitride into graphene oxide (GNPs/g‐C₃N₄/GO) is fabricated. The membranes exhibit not only superior surface enhanced Raman scattering (SERS) activity attributed to high preconcentration ability to analytes through π–π and electrostatic interactions, but also excellent catalytic activity due to the enhanced electron–hole separation efficiency. These outstanding properties allow the membrane to be used for highly sensitive detection of rhodamine 6G with a limit of detection of 5.0 × 10^?14m and self‐cleaning by photocatalytic degradation of the adsorbed analytes into inorganic small molecules, thus achieving recyclable SERS application. Furthermore, the excellent SERS activity of the membrane is demonstrated by detection of 4‐chlorophenol at less than nanomolar level and no significant SERS or catalytic activity loss was observed when reusability is tested. These results suggest that the GNPs/g‐C₃N₄/GO membrane provides a new strategy for eliminating traditional, single‐use SERS substrates, and expands practical SERS application to simultaneous detection and removal of environmental pollutants.     

基于UML的无线网络镜像模型

镜像能够复现真实的网络环境,帮助开发人员定位系统中的错误以及发现潜在的问题。作为软件工程的标准建模语言,UML可以用于对实际问题进行建模和分析。使用UML对无线网络设备进行建模,并利用UML活动图给出了实际网络微缩镜像算法。基于此方法可以快速地构造高仿真的网络镜像,既压缩了网络规模又能保持网络的重要特征。