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The adsorption behavior of AgNPs-DNA nanocomposites on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phosphoserine (DMPS) lipid monolayers has been investigated by analyzing adsorption dynamic process, surface pressure-area isotherms (π-A), excess mean area ( $${\Delta \mathrm{A}}_{\mathrm{e}\mathrm{x}\mathrm{c}}$$ ), excess Gibbs free energy ( $$\Delta {\mathrm{G}}_{\mathrm{e}\mathrm{x}}$$ ) and the atomic force microscopy (AFM). The nanocomposites were prepared by sliver nanoparticles (AgNPs) and deoxyribonucleic acid (DNA) via electrostatic attraction. The result of ∆π/π and π-A isotherms indicated that the binding of AgNPs-DNA tends to adsorb on DMPC while the concentration of DNA exceeds 0.4 μg/mL. Excess mean area and thermodynamic analysis of excess Gibbs energy demonstrated that AgNPs-DNA enlarged the interval between DMPC and DMPS molecules, whose phenomena might be the electrostatic repulsion of each AgNPs-DNA molecule. AFM observation showed that the adsorption behavior of AgNPs-DNA on DMPS monolayers had a saturation point, while DMPC was not. Taken together, this work might provide a novel idea and useful basis for the development of metal nanoparticles-based biological materials.

In this work, the adsorptive behavior of Lycium barabrum polysaccharides (LBP) on 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and POPC/DPPC/Cholesterol (Chol) monolayer films were investigated using the Langmuir films technique and atomic force microscopy (AFM). For the POPC/DPPC system, the π-A isotherms shifted to larger areas and the surface pressure variations (Δπ) in the adsorption curves (10 mN/m and 35 mN/m) increased with the increase in the LBP concentration. For the POPC/DPPC/Chol system, π-A isotherms moved to larger areas with the addition of LBP, and the Δπ values were also lower than those of the POPC/DPPC system. These were ascribed to hydrogen bond network formation between LBP and the lipids. The excess per molecular area (ΔAexc) and the excess Gibbs free energy of mixing ( $$\Delta {\text{G}}_{mix}^{Exc}$$ ) revealed that the repulsion force was the interaction between POPC and DPPC molecules. Meanwhile, the repulsion force increased with the addition of LBP. The addition of cholesterol decreased the force. The interactions among molecules were also evaluated by the values of K (the speed of adsorption of LBP), Ap (the number of each lipid molecule combining with the polysaccharide molecules in the mixed monolayer), Γ (the surface excess concentration) and A (the area per molecule). As shown in AFM images, the morphology of the monolayer films also indicated that LBP was easily adsorbed onto the POPC/DPPC monolayer film via hydrogen bond and the weak Van der Waals interaction. In summary, cholesterol could affect spontaneous insertion of LBP into the POPC/DPPC monolayer films from phosphate buffer solution.

This paper considers the estimation of ruin probability in an insurance risk model with stochastic premium income. We first show that the ruin probability can be approximated by the complex Fourier series (CFS) expansion method. Then, we construct a nonparametric estimator of the ruin probability and analyze its convergence. Numerical examples are also provided to show the efficiency of our method when the sample size is finite.

In this work, we synthesized graphene oxide-silver nanoparticles (GO-AgNPs) hybrids by one-pot method. Since there are relatively few reports on whether GO-AgNPs bind and change the structure and function of trypsin, A variety of methods were employed to systematically characterize the molecular interaction between GO-AgNPs and trypsin. Results exhibited that GO-AgNPs bound with trypsin to form a ground state complex. GO-AgNPs had higher adsorption capacity for trypsin compared with single GO. Langmuir-Blodgett assembly method was used to confirm that AgNPs did not interfere with the adsorption of trypsin by GO. The secondary structure and the microenvironment of amino acid residues of trypsin were altered after interacting with GO-AgNPs. In addition, GO-AgNPs can enhance the activity of trypsin and promote the hydrolysis of bovine serum protein (BSA) by trypsin. These findings provide important support for the application of GO-based nanocomposites in the efficient immobilization of enzymes.

Since graphene oxide‑silver nanoparticles (GO-AgNPs) have special affinities to DNA, it become increasingly important in fields of biological analysis in which GO-AgNPs nanocomposites universally functioned as a quencher. In this paper, GO-AgNPs nanocomposites with different GO to AgNPs ratios were synthesized as a fluorescence quencher to interact with DNA labeled by methylene blue (MB). The results showed that the fluorescence intensity of DNA-MB system decreased with the increasing of GO-AgNPs nanocomposites concentration. The quenching phenomenon of DNA-MB by AgNPs and GO was not a simple additive effect but a synergistic effect. The quenching efficiency of synthesized GO-AgNPs nanocomposites with different ratios (1:1, 1:3, 1:5, 1:10) increased with the decrease of GO/Ag ratio. Thermodynamic analysis was employed to investigate the interaction of GO-AgNPs and DNA-MB, it can be concluded that the intermolecular force between GO-AgNPs and DNA-MB was hydrogen bonding. Our works will provide important theoretical and experimental bases for fluorescence sensing of DNA.

Herein, the fluorescence resonance energy transfer (FRET) system composed of Zinc sulfide quantum dots (ZnS QDs) and fluorescent silica nanoparticles (FS) and the influence of bovine hemoglobin (BHb) on the system were studied using spectroscopy. UV–vis, SEM and XRD were used to characterize ZnS QDs. FT-IR spectroscopy, Zeta potential, DLS and fluorescence spectroscopy confirmed the synthesis of FS. The mechanism and efficiency of FRET in aqueous solution and BHb solution has been analyzed by fluorescence spectroscopy and Forster's non-radiative energy transfer theory, which implied that in the absence of BHb, there is dynamic quenching between ZnS QDs and FS. In the presence of BHb, it is static quenching. And BHb interfered with the stability of the ZnS QDs-FS FRET system and reduced FRET efficiency. Moreover, steady-state, synchronous fluorescence spectra and Raman spectroscopy showed that ZnS QDs caused an increase of hydrophilicity of the chromophore microenvironment, and FS may induce heme degradation to form fluorescent heme product, resulting in increased fluorescence intensity. This investigation will be significant in exploring the toxicity profile of ZnS QDs-FS FRET system for their in vivo.

Multiple-row container-grown trees require specially designed sprayers to achieve efficient spray delivery. A five-port air-assisted sprayer with both automatic and manual control modes was developed to discharge adequate spray deposition inside multiple-row trees. The sprayer resulted from integration of a high-speed laser-scanning sensor with a sophisticated nozzle flow control system, an embedded computer with a touch screen, a Doppler speed sensor, a specially-designed algorithm and an air-assisted sprayer base. It was able to detect target tree presence and measure target tree size, shape and leaf density. The sprayer then controlled the spray output of each nozzle to match tree structures. The sprayer was tested for its sprayer deposition quality inside canopies in a four-row sterling silver linden (Tilia tomentosa 'Sterling Silver' Moench) field and another six-row northern red oak (Quercus rubra L.) field. Tests were conducted with the sprayer in variable-rate application (VRA) and constant-rate application (CRA) modes. The average spray deposit on foliage of trees was 1.37±0.47 μL cm−2 from VRA and 1.29±0.42 μL cm−2 from CRA in linden, and was 2.15±0.57 μL cm−2 from VRA and 2.72±0.94 μL cm−2 from CRA in red oak, respectively. In comparison, spray coverage on foliage of trees was 19.8±3.0% from VRA and 20.9±4.3% from CRA in the linden trial, and was 27.9±3.7% from VRA and 30.5±5.4% from CRA, respectively, in the red oak trial. The newly developed air-assisted sprayer in both VRA and CRA modes would be able to discharge adequate spray deposition inside multiple-row tree plants while conserving pesticide. Index words: environmental protection, pest control, pesticide, precision sprayer, spray coverage. Species used in this study: sterling silver linden (Tilia tomentosa 'Sterling Silver' Moench), northern red oak (Quercus rubra L.).

A simple and fast spectrofluorimetric method coupled with carbon quantum dots (CQDs) modified ZnO/CdS nanoparticles was developed for the detection of Ferric iron (Fe(III)). The fluorescence of CQDs/ZnO/CdS NPs was effectively quenched by Fe(III) due to the strong interaction between the CQDs/ZnO/CdS NPs and Fe(III). In addition, the detection limit of Fe(III) was about 1.72×10-7M. The effect of foreign ions on the fluorescence intensity of CQDs/ZnO/CdS NPs showed that the interference response in detecting of Fe(III) ions was low. Moreover, the quenching of Fe(III) and CQDs/ZnO/CdS NPs was discussed to be a static quenching procedure, which was proved by quenching constant KSV and fluorescence lifetime τ. The study of thermodynamics showed that the values of entropy change (ΔS) and enthalpy change (ΔH) were both positive, and the value of free energy (ΔG) was negative, which implied that the weak interaction of the molecular between CQDs/ZnO/CdS NPs and Fe(III) was hydrophobic force, and the quenching process was endothermic and spontaneous.

In this paper, a analog front-end (AFE) with front-amplifier and ADC is designed for Carbon nanotube (CNT) signal detection. The AFE circuit is based on a programmable gain amplifier (PGA) and a 8bit/20MHz pipelined ADC, and the good function and output signal-to-noise ratio (SNR) are obtained. The AFE is implemented in 0.18μm CMOS mixed-signal process. The test results show that with power supply voltage of 3.3V, in 1MHz signal bandwidth, the output Signal-to-Noise and Distortion Ratio (SNDR) is 45.3dB, the Effective Number of Bits (ENOB) is 7.23bits, which meet the detection resolution for CNTs.

Herein, we synthesized bovine serum albumin-functionalized gold nanoclusters (BSA-Au NCs) and BSA-Cu nanoclusters (Cu NCs) by a facile and environmentally-friendly method, and simply mixed them to develop a ratiometric fluorescent sensor for mercury (Hg2+) and copper (Cu2+) ions detection, respectively. The as-prepared BSA-Au NCs were known to emit pink color fluorescence (peaking at 616 nm) and BSA-Cu NCs were blue-emitting (peaking at 398 nm) upon the exposure of ultraviolet light (365 nm). Among them, BSA-Au NCS was used as the response signal and BSA-Cu NCs was the reference signal. Interestingly, when the easily prepared ratiometric probe were employed to detect 15 kinds of common metal ions, only Hg2+ and Cu2+ ions could significantly quench the pink fluorescence of BSA-Au NCs. We found that the fluorescence intensity ratio (I616 /I398) of the nanohybrid system was efficiently reduced by the addition of Hg2+ and Cu2+ ions compared to a series of metal ions. The response of the nanohybrid probe to Cu2+ showed an excellence linear relationships in the concentration range of 0.1∼1 μM and 1∼5 μM respectively, and its detection limit was 23.4 nM. Moreover, the fluorescence quenching caused by Hg2+ ions exhibited excellent and wide linear relationships from 0.06 to 1 μM and 1–4 μM respectively, with detection limits as low as 19.4 nM. With the increase of Cu2+/Hg2+ concentration, this nanohybrid probe also showed obvious fluorescence color changes that could be directly observed by the naked eye.