流动注射-分光光度法测定自来水中游离氯的研究

设计了游离氯流动注射自动在线检测仪,并研究了仪器的最佳测试条件.该仪器采用改进的N,N-二乙基-1,4-苯二胺(DPD)比色原理,通过流动注射进样技术,结合光电转化、数字信号处理及自动化控制技术,克服了DPD分光光度法中手工操作的缺陷,实现了样品分析的自动化.结果证明,此系统的试剂用量少、测定范围宽(0.05～6.00...     

DPD Simulation on the Transformation and Stability of O/W and W/O Microemulsions

The dissipative particle dynamics simulation method is adopted to investigate the microemulsion systems prepared with surfactant (H1T1), oil (O) and water (W), which are expressed by coarse-grained models. Two topologies of O/W and W/O microemulsions are simulated with various oil and water ratios. Inverse W/O microemulsion transform to O/W microemulsion by decreasing the ratio of oil-water from 3:1 to 1:3. The stability of O/W and W/O microemulsion is controlled by shear rate, inorganic salt and the temperature, and the corresponding results are analyzed by the translucent three-dimensional structure, the mean interfacial tension and end-to-end distance of H1T1. The results show that W/O microemulsion is more stable than O/W microemulsion to resist higher inorganic salt concentration, shear rate and temperature. This investigation provides a powerful tool to predict the structure and the stability of various microemulsion systems, which is of great importance to developing new multifunctional microemulsions for multiple applications.     

A new type of microemulsion containing task-special ionic liquid [NH2ebim][BF4]

The formation of microemulsions in the presence of cyclohexane, Triton X-100, n-butanol, water, and task-special ionic liquid (TSIL) (1-2-aminoethyl-3-butylimidazolium tetrafluoroborate) was studied at 25°C. The phase behavior of this ternary system was investigated. Three subregions (namely, water-in-oil phase, bicontinuous phase, and oil-in-water phase) were identified in the single-phase region by dynamic light scattering (DLS) technique and electrical conductivity measurement. Microstructures of microemulsions with different water contents have been predicted by using dissipative particle dynamics (DPD) simulation. It was found that the DPD simulations successfully reproduce the experimental results in the article. The location of TSIL in the microemulsions was predicted by DPD simulation further. The result indicates that TSIL is more easy to locate in the surfactant and cosurfactant layer and has amphiphilicity, which provides us new insights into the potential applications of TSIL-based microemulsions in separation and new nano-scale material preparation because of the interaction of TSIL with some special components at the interface of oil and water.     

An environmentally friendly flow system for high-sensitivity spectrophotometric determination of free chlorine in natural waters

A green and highly sensitive analytical procedure was developed for the determination of free chlorine in natural waters, based on the reaction with N,N-diethyl-p-phenylenediamine (DPD). The flow system was designed with solenoid micro-pumps in order to improve mixing conditions by pulsed flows and to minimize reagent consumption as well as waste generation. A 100-cm optical path flow cell based on a liquid core waveguide was employed to increase sensitivity. A linear response was observed within the range 10.0 to 100.0 µg L^− 1, with the detection limit, coefficient of variation and sampling rate estimated as 6.8 µg L^− 1 (99.7% confidence level), 0.9% (n = 20) and 60 determinations per hour, respectively. The consumption of the most toxic reagent (DPD) was reduced 20,000-fold and 30-fold in comparison to the batch method and flow injection with continuous reagent addition, respectively. The results for natural and tap water samples agreed with those obtained by the reference batch spectrophotometric procedure at the 95% confidence level.     

A novel (18)O inverse labeling-based workflow for accurate bottom-up mass spectrometry quantification of proteins separated by gel electrophoresis

In the present work we report on a novel and fast protocol for accurate bottom-up protein quantification that overcomes the drawbacks of in-gel digestion and MALDI analysis, while maintaining their benefits. It relies on the following steps: (i) gel electrophoresis separation of proteins, (ii) fast in-gel protein digestion with trypsin, (iii) (18)O-labeling through the decoupled method, (iv) quantification through selected peptides previously chosen using the (18)O inverse labeling approach and that, finally, (v) it takes advantage of software specifically developed to select the peptides that will drive the quantification of the protein in an automated mode. We have accurately quantified the following six proteins: glycogen phosphorylase, BSA, ovalbumin, carbonic anhydrase, trypsin inhibitor, and α-lactalbumin. As a case study we have quantified the protein vitellogenin in plasma of Cyprinus carpio exposed to high levels of estrogens. The proposed new protocol was validated against the traditional ELISA method; both were found to provide comparable results (non-parametric Mann-Whitney U-test).     

Time-dependent and outflow boundary conditions for Dissipative Particle Dynamics

We propose a simple method to impose both no-slip boundary conditions at fluid-wall interfaces and at outflow boundaries in fully developed regions for Dissipative Particle Dynamics (DPD) fluid systems. The procedure to enforce the no-slip condition is based on a velocity-dependent shear force, which is a generalized force to represent the presence of the solid-wall particles and to maintain locally thermodynamic consistency. We show that this method can be implemented in both steady and time-dependent fluid systems and compare the DPD results with the continuum limit (Navier-Stokes) results. We also develop a force-adaptive method to impose the outflow boundary conditions for fully developed flow with unspecified outflow velocity profile or pressure value. We study flows over the backward-facing step and in idealized arterial bifurcations using a combination of the two new boundary methods with different flow rates. Finally, we explore the applicability of the outflow method in time-dependent flow systems. The outflow boundary method works well for systems with Womersley number of O(1), i.e., when the pressure and flowrate at the outflow are approximately in-phase.     

Laser infrared spectroscopy of vinyl fluoride in the 1280–1400 cm−1 region

The infrared spectra of CH₂=CHF have been investigated in the ν₅ and ν₆ band regions between 1280 and 1400?cm^?1, at a resolution of about 0.002?cm^?1, using a tunable diode laser spectrometer. These vibrations of symmetry species A′ give rise to a/b-hybrid bands with different contributions from both the components. Spectral analysis resulted in the identification of 1565 (J≤46, K _a ≤11) and 1651 (J≤48, K _a ≤15) transitions of the ν₅ and ν₆ fundamentals, respectively. Both bands are perturbed by the nearby states ν₈?+?ν₉ and ν₉?+?ν₁₁ through different Coriolis resonances and an anharmonic interaction. Using Watson's A-reduction Hamiltonian in the I^r representation and perturbation operators almost all the transitions have been fitted simultaneously to a model including six resonances within the tetrad ν₅/ν₆/ν₈?+?ν₉/ν₉?+?ν₁₁. A set of spectroscopic constants for the ν₅ and ν₆ bands, as well as parameters for the dark states ν₈?+?ν₉ and ν₉?+?ν₁₁ and coupling constants, have been determined. From spectral simulations the dipole moment ratio |Δμ _a /Δμ _b | was estimated to be 0.6?±?0.1 and 2.0±0.3 for the ν₅ and ν₆ bands, respectively.     

Structure–Property Relationship of Sulfosuccinic Acid Diester Sodium Salt Micelles: 3D-QSAR Model and DPD Simulation

The objective of this study was to develop structure–property relationship of a series of sulfosuccinic acid diester sodium salts required for industrial purposes. In this paper, three-dimensional quantum structure–activity relationship (3D-QSAR) method studies are performed to elucidate the relationship between critical micelle concentration (CMC) activity and molecular 3D structural features. Two regression models are developed by partial least squares (PLS) and genetic function approximation (GFA), respectively. The training set of PLS-QSAR model generates a correlation coefficient (R²) = 0.94539300 and sum of square of residues (S²) = 0.32764200. For the GFA-QSAR model, the training set yields R² = 1.00000000. It is shown that the GAF method effectively improves the test accuracy significantly. Dissipative particle dynamics (DPD) mesoscopic molecular simulation method is carried out on the aggregation behavior of polyoxyethylene (n) stearyl ether sodium sulfosuccinate (PSSE-n) surfactant micelles. In the DPD simulation, water molecular (solvent) and colloidal particles are replaced by a set of DPD particles. The results demonstrated that sensitive PSSE-n molecules can assemble into special structures in specific solution concentration, such as star-shaped micelle, spherical micelle, rodlike micelle, and lamellar phase. DPD simulation can be used as an efficient method for studying the structure–property relationship of sulfosuccinic acid diester sodium salts.     

Polymer translocation through nanopore under external electric field: dissipative particle dynamics study

The DNA sequencing technology has achieved a leapfrog development in recent years. As a new generation of the DNA sequencing technology, nanopore sequencing has shown a broad application prospect and attracted vast research interests since it was proposed. In the present study, the dynamics of the electric-driven translocation of a homopolymer through a nanopore is investigated by the dissipative particle dynamics(DPD), in which the homopolymer is modeled as a worm-like chain(WLC). The DPD simulations show that the polymer chain undergoes conformation changes during the translocation process. The different structures of the polymer in the translocation process, i.e., single-file, double folded, and partially folded, and the induced current blockades are analyzed. It is found that the current blockades have different magnitudes due to the polymer molecules traversing the pore with different folding conformations. The nanoscale vortices caused by the concentration polarization layers(CPLs) in the vicinity of the sheet are also studied. The results indicate that the translocation of the polymer has the effect of eliminating the vortices in the polyelectrolyte solution. These findings are expected to provide the theoretical guide for improving the nanopore sequencing technique.