Preparation,rheological and drag reduction properties of hydrophobically associating polyacrylamide polymer

Hydrophobically associating polymer (HAMDP) was synthesized by using acrylamide, acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid and dodecyl 2-methylacrylate as main monomers. Dynamic rheometer and self-made simulation evaluation apparatus were used to test the rheological and drag reduction properties of HAMDP. With the mass concentration increased, the apparent viscosity of HAMDP increased. The critical aggregation concentration was 2.29g/L. With the changement of the strain, the elastic modulus was larger than viscous modulus. With the increment of HAMDP, the area of thixotropic loop increased. Compared with commercial polyacrylamide, the drag reduction rate of HAMDP could be up to 62.38%.     

Strain softening in stretched DNA

The microscopic mechanics of DNA stretching was characterized using extensive molecular dynamics simulations. By employing an anisotropic pressure-control method, realistic force-extension dependences of effectively infinite DNA molecules were obtained. A coexistence of B and S DNA domains was observed during the overstretching transition. The simulations revealed that strain softening may occur in the process of stretching torsionally constrained DNA. The latter observation was qualitatively reconciled with available experimental data using a random-field Ising model.     

尺度缩小合成孔径激光成像雷达的孔径合成实验

设计了一种尺度缩小的合成孔径激光成像雷达(SAIL),在实验室平台上模拟实施远场传输条件,相应地解决了波前测量和外差质量监视技术,实现了一个目标点的方位向孔径合成实验,实验结果与理论预测相近.     

Origin7．5软件在大学物理综合设计性实验教学中的应用探讨

本文采用origin7．5软件对大学物理综合设计性实验数据的处理进行了探讨。实验结果揭示出了热敏电阻温度特性、光敏电阻伏安特性和光照特性。     

Two Optimal Value Functions in Parametric Conic Linear Programming

Journal of Optimization Theory and Applications - We consider the conic linear program given by a closed convex cone in an Euclidean space and a matrix, where vector on the right-hand side of the...     

Periodic quenching modulated quantum phase transitions in transverse XY spin-chains

The European Physical Journal D - Bent crystals are a compact and versatile tool to manipulate ultra-relativistic particle beams in accelerators. Indeed, the unrivaled steering power achievable...     

Oriented Antibody Immobilization and Immunoassay Based on Boronic Acid-containing Polymer Brush

High sensitive immunoassay platforms have gained intense attention due to their vital roles in early-stage disease diagnosis and therapeutic information feedback.Although random covalent-binding of antibody has been widely adopted in immunoassays due to its simplicity and effectiveness,it readily loses its activity and fails to exhibit high antigen-binding capacity.In this work,copolymer of zwitterionic sulfobetaine methacrylate (SBMA) and glycidyl methacrylate (GMA) brushes were immobilized onto inert polypropylene (PP) via surface-initiated atom transfer radical polymerization (ATRP) based on biomimetic dopamine pretreatment.Subsequently,boronic acid (BA) groups were covalently bonded via active GMA units,followed by the introduction of oriented immobilization of antibody.Owing to the oriented immobilization of antibody facilitated by BA groups in polymer brush,the bioactivity of antibody is well preserved,which endows the surface with significantly enhanced antigen-binding capacity.Moreover,the existence of SBMA segments in polymer brushes renders the surface high resistance to nonspecific protein adsorption,significantly alleviating the signal interference of antigen recognition.This strategy could find potential applications in developing high sensitive immunoassay platforms based on the different substrates.     

An oligosorbent-based aptamer affinity column for selective extraction of aflatoxin B<Subscript>2</Subscript> prior to HPLC with fluorometric detection

The article describes an aptamer affinity column for selective solid-phase extraction of aflatoxin B₂ (AFB₂). Amino-modified aptamer against AFB₂ was immobilized on CNBr-activated Sepharose through a covalent bond. The effects of oligosorbents based on 3′- or 5′-amino-modified sequences with a C6 or a C7 spacer arm were evaluated by UV spectroscopy at 260 nm. The extraction recovery was evaluated by HPLC with fluorometric detection. The extraction of AFB₂ was optimized. Under the optimum conditions, the aptamer affinity column has a linear response to AFB₂ in the range of 0.5–80 ng, with a capacity of 84.6 ng. Control supports without immobilized aptamers and a nonspecific oligosorbent immobilized with a negative control oligonucleotide were studied in order to demonstrate selectivity. The method was tested with spiked peanut sample (0.5–50 μg·kg^?1 AFB₂) and gave average recoveries of 80.9% and a mean relative standard deviation of 1.9%. The limit of detection is 25 pg·mL^?1. This is much lower than the maximum residue limits suggested by the European Union. The columns can be re-used up to five times without any loss of performance. The oligosorbent was also applied to clean-up of AFB₂ from peanut sample extracts before HPLC analysis. Results were further confirmed by ultra-fast liquid chromatography with tandem mass spectrometry. Conceivably, the method may also be applied to other samples, such as food, agricultural products, and traditional Chinese medicines.

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Graphical abstract Schematic illustration of the fabrication procedures of aptamer affinity column, AAC (a), its principle of aptamer bound to aflatoxin B₂ (b) and the obtained AAC (c).

     

Synthesis of nanocrystals via microreaction with temperature gradient: towards separation of nucleation and growth

By utilizing the symmetrical temperature distribution in a tube furnace chamber, a capillary microreactor was designed with the microchannel passing two well-controlled, stable temperatures in steep temperature gradients. The two-temperature microreator, first developed and implemented by this research team, provides an opportunity to separate the nucleation and growth of semiconductor nanocrystals, leading to better control of nucleation and growth kinetics. For the synthesis of CdSe nanocrystals as a model system, we demonstrated the improved size uniformity achieved by the two-temperature approach, confirming the success of the use of high temperature to burst nucleation and low temperature to promote growth.