Preparation of PVDF UF Membranes under an External Electric Field with PVP as Additive

In this study, PVDF UF membranes were prepared with PVP as additive via a favorable method of applying high voltage external electric field (2kV) through the immersion precipitation phase inversion process. The influence of external electric field on the structure, surface functional groups, membrane potential, and surface hydrophilicity of the membranes were researched. In addition, anti-fouling property and separation performance of the membranes were also investigated. The results indicated that the protein adsorption amount on the electric treated membranes was distinctly reduced. Especially for the electric treated PVDF membrane with PVP K70 as additive, the value of water contact angle reached 75.4° and the protein adsorption amount decreased 76 %, reaching 20.39 µg·cm-2. The separation performance of the electric treated membrane was also superior to that of the un-treated membrane. All the experimental results indicated that this electric treated approach open a promising way for the modification of PVDF membrane because it combined membrane preparation and modification in only one physical step without additional chemical reagents

Image Restoration Based on the Hybrid Total-Variation-Type Model

We propose a hybrid total-variation-type model for the image restoration problem based on combining advantages of the ROF model with the LLT model. Since two L1-norm terms in the proposed model make it difficultly solved by using some classically numerical methods directly, we first employ the alternating direction method of multipliers (ADMM) to solve a general form of the proposed model. Then, based on the ADMM and the Moreau-Yosida decomposition theory, a more efficient method called the proximal point method (PPM) is proposed and the convergence of the proposed method is proved. Some numerical results demonstrate the viability and efficiency of the proposed model and methods

Serum MicroRNA Expression Profile Distinguishes Enterovirus 71 and Coxsackievirus 16 Infections in Patients with Hand-Foot-and-Mouth Disease

Altered circulating microRNA (miRNA) profiles have been noted in patients with microbial infections. We compared host serum miRNA levels in patients with hand-foot-and-mouth disease (HFMD) caused by enterovirus 71 (EV71) and coxsackievirus 16 (CVA16) as well as in other microbial infections and in healthy individuals. Among 664 different miRNAs analyzed using a miRNA array, 102 were up-regulated and 26 were down-regulated in sera of patients with enteroviral infections. Expression levels of ten candidate miRNAs were further evaluated by quantitative real-time PCR assays. A receiver operating characteristic (ROC) curve analysis revealed that six miRNAs (miR-148a, miR-143, miR-324-3p, miR-628-3p, miR-140-5p, and miR-362-3p) were able to discriminate patients with enterovirus infections from healthy controls with area under curve (AUC) values ranged from 0.828 to 0.934. The combined six miRNA using multiple logistic regression analysis provided not only a sensitivity of 97.1% and a specificity of 92.7% but also a unique profile that differentiated enterovirial infections from other microbial infections. Expression levels of five miRNAs (miR-148a, miR-143, miR-324-3p, miR-545, and miR-140-5p) were significantly increased in patients with CVA16 versus those with EV71 (p<0.05). Combination of miR-545, miR-324-3p, and miR-143 possessed a moderate ability to discrimination between CVA16 and EV71 with an AUC value of 0.761. These data indicate that sera from patients with different subtypes of enteroviral infection express unique miRNA profiles. Serum miRNA expression profiles may provide supplemental biomarkers for diagnosing and subtyping enteroviral HFMD infections

Preparation of Nanosilver Composite Plant Medium with Antimicrobial Capability through a Nontoxic Method

A nanosilver composite plant medium with a good antimicrobial capability was successfully prepared via a two-step method in this work. First, nanosilver particles were prepared in a silver nitrate (AgNO3) solution by using D-glucose as a reduction reagent at room temperature. The effect of AgNO3 concentration levels on the size of the nanosilver particles was investigated. The sedimentation activation energy of the nanosilver particles was also measured. Second, the solvent containing the nanosilver particles was added to a Murashige-Skoog medium (a plant growth medium used in the laboratory for the cultivation of plant cell cultures, which was invented by Toshio Murashige and Folke K. Skoog) to form a composite plant medium. The antimicrobial capability of the composite medium was investigated by cultivating in it some fresh strawberry slices. The results showed that the concentra‐ tion level of AgNO3 significantly influenced the average size of the prepared nanosilver particles. When the Ag‐ NO3 concentration was increased from 1.0×10−3 mol/L to 4.0×10−3 mol/L, the average diameter of the nanosilver particles increased from 52 nm to 72 nm, and the sedimen‐ tation activation energy of the particles increased from -20.0 kJ/mol to -63.3 kJ/mol. Images from the transmission electron microscope showed that the size distribution of the particles was within narrow parameters. The results of sedimentation activation energy strongly supported the size results obtained from the TEM measurement. It meant that the preparation method could offer good control over the size and size distribution of the nanosilver particles. The cultivation experiments proved that the composite medi‐ um has a good antimicrobial capability. Since D-glucose is a nontoxic material, this method of preparing the compo‐ site MS medium with an antimicrobial capability was a ‘green’ method

EFFECT OF ACID–BASE PROPERTY OF INORGANIC NANOPARTICLES ON ANTIFOULING PERFORMANCE OF PVDF COMPOSITE ULTRAFILTRATION MEMBRANES

Pure poly(vinylidene fluoride) (PVDF) membrane and PVDF composite membranes modified by three kinds of inorganic nanoparticles (SiO2, Al2O3, and TiO2) were made using a phase inversion method and characterized by pure water flux, retention efficiency of Bovine serum albumin (BSA), flux reduction coefficient, and scanning electron microscope (SEM). The results of flux reduction coefficient illustrated that PVDF membrane modified by nanoparticles had better antifouling property in the order of TiO2, Al2O3, SiO2. The Lewis acid–base properties of the nanoparticle materials were measured by inverse gas chromatography (IGC). The Lewis acid number, Ka, and Lewis base number, Kb, had the following order Ka TiO2 Kb Al2O3 > Kb SiO2. The experimental results indicated that PVDF membrane modified by nanoparticles with relatively strong base exhibited excellent antifouling performance.PVDF, ultrafiltration, nanoparticle, inverse gas chromatography

Influence of External Coagulant Water Types on the Performances of PES Ultrafiltration Membranes

In order to research the influence of cluster structure on the performances of membranes prepared through immersion precipitation phase inversion technique when water was used as external coagulant, in this paper, two types of water were prepared from distilled water and were used as external coagulant at room temperature. One type (water I) was prepared from boiled distilled water and another type (water II) was prepared from ice. Six polyethersulfone membranes were prepared by using polyvinylpyrrolidone as additive. Pure water flux, permeation flux of BSA solution and rejection to bovine serum albumin of the membranes were investigated. It was found that according to the statistically experimental results, the membranes prepared in water II always had larger pure water flux, permeation flux of BSA solution, rejection and swelling ratio than the membranes prepared in water I. Consequently, the types of water external coagulant had some influences on the separation performances of the prepared membranes but had no effects on the surface chemical groups. However, the present morphology characterization technology, such as SEM couldn't detect the tiny difference in the pore structures

Dynamic Pricing of Ride-Hailing Platforms considering Service Quality and Supply Capacity under Demand Fluctuation

Increasing attention is being paid to the pricing decisions of ride-hailing platforms. These platforms usually face market demand fluctuation and reflect supply and demand imbalances. Unlike existing studies, we focus on the optimal dynamic pricing of the platforms under imbalance between supply and demand caused by market fluctuation. Dynamic models are constructed based on the state change of supply and demand by using optimal control theory, with the aim of maximizing the platform’s total profit. We obtain the optimal trajectories of price, supply, and demand under three ride demand situations. The effects of some key parameters on pricing decisions, such as coefficient of demand fluctuation, service quality, and fixed commission rate, are examined. We find the optimal dynamic price can improve the match of supply-demand in ride-hailing market and enhance the revenue of platform

PREPARATION AND SURFACE ACID-BASE PROPERTIES OF POROUS CELLULOSE

Porous cellulose beads were prepared by solubilizing cellulose in sodium hydroxide/urea/sulfourea aqueous solution and then solidifying liquid beads in hydrochloric acid. Scanning electron microscopy (SEM) was used to characterize the morphologies of surface, cross section, and wall structures of the porous cellulose beads, which are folded and porous. The surface acid-base properties of porous cellulose beads were characterized in detail by inverse gas chromatography (IGC). The Lewis basic number Kb was found to be 0.854, which is indicative of a Lewis basic polymeric material. With the discussion of the results of SEM and IGC, a conclusion can be drawn that the porous cellulose beads showed a good ability of adsorbing the smoking tar of cigarettes