Hypoxia/Temperature/pH Triple Stimuli–Responsive Block Copolymers: Synthesis,Self-Assembly,and Controlled Drug Release

The amphiphilic block copolymer poly(methacrylic acid-co-2-nitroimidazole acrylate)-b-poly(2-(N,N-dimethylamino)ethyl methacrylate) (P(MAA-co-NIMA)-b-PDMAEMA) with the hypoxia/temperature/pH triple responsiveness is synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT), hydrolysis, and 3-(3-dimethylaminopropyl)-1-ethylcarbodiimide (EDC) reactions, and successfully self-assembled into micelles. The hypoxia response in vitro is realized, and then the sensitivity of the self-assembled micelles to the hypoxia condition is studied by controlling the grafting amount of aminated 2-nitroimidazole. Because 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA) is a typical material sensitive to temperature and pH conditions, the self-assembled micelles are also responsive to temperature and different acidic/basic conditions. In addition, the cumulative release rate of doxorubicin (DOX) at 42 °C, pH = 6.0, and hypoxic conditions increases significantly, and verifies the synergistic promotion effect of the above stimulations. This intelligent polymer with triple response mechanism improves the controllability and efficiency of drug release, and is expected to be a drug carrier for cancer treatment.     

材料表面可控修饰新技术

聚合物"刷"是端接枝超薄聚合物层的形象描述,在材料表面形成聚合物"刷"是控制材料表面性质的一种有效手段.因其在材料表面结构分子设计中具有突出的优越性,近年引起了材料表面改性专家的广泛关注.介绍了表面引发可控/"活性"聚合制备可控聚合物"刷"技术,并展示了其在材料表面可控修饰中的应用.     

Soft and Hard Adhesion

The force needed to pull a cylindrical stud from a soft elastomeric film depends on their elastic and geometric properties. For a rigid stud and a thick elastomeric film, the pull-off stress (σ) depends on the elastic modulus (E) of the film and the radius (a) of the stud as σ ∼ (E/a)^1/2 (soft adhesion). However, when the film is very thin, the pull-off stress is significantly higher than the case with thick films, and its value depends on the elastic modulus and the thickness (h) of the film as σ ∼ (E/h)^1/2 (hard adhesion). Here, we study the pull-off behavior of a soft cylindrical stud, one flat end of which is coated with a high modulus thin baseplate. As the flexural rigidity of this baseplate is varied, we observe the transition between the two types of adhesion. We present a simple physical interpretation of the problem, which could be of value in understanding various biofouling and adhesive situations.     

Nafcillin release from poly(acrylic acid–co–methyl methacrylate) hydrogels

Summary Copolymeric poly(acrylic acid-co-methyl methacrylate) hydrogels for three different compositions: (90/10), (80/20) and (60/40), have been studied. Drug release has been examined as a function of the hydrogel composition by HPLC (High Pressure Liquid Cromatography). The release experiments were carried out at 37 °C. The fraction of available drug release was linear in t^1/2. The values of the diffusional coefficient (0.50<n<1.0) indicate that the nafcillin release mechanism from the hydrogels in study is non-Fickian. The diffusion coefficients for this drug release have been calculated. The molecular diffusion of nafcillin through hydrogels is controlled by the swelling.     

焦炭高温反应炉温度控制系统的改进

介绍了焦炭高温反应炉的温控工艺及程控曲线，给出了程控曲线的控制结构、主回路以及实现多套PI参数控制的方法。     

Calculated effect of pulsed pheromone release on range of attraction

In order to assess the possible function of pulsed release of windborne pheromones, calculations were performed to predict the concentration pattern downwind of the source. Two patterns of pulsed releases (sinusoidal and instantaneous) were compared to a constant release pattern. In all three cases, the average rate of release was the same. Assuming the receiving animal needs only a momentary exposure to concentrations above threshold to respond, it is clear that sinusoidal release has a greater distance of detection than constant release and that instantaneous release is even better. The relative magnitude of the increase in range of detection depends on the ratio of average release rate to threshold concentration. Pulsed releases have a greater advantage when the threshold is high and the range of attraction is inherently short. Under these conditions, sinusoidal release can double the range of attraction and instantaneous release can increase it 10-fold. In contrast, with a low threshold and consequent long range of attraction, the pulsed patterns are lost and the increase in range is insignificant. Several testable predictions are derived from the hypothesis that the primary function of pulsed release is to extend the range and time over which a given quantity of pheromone can act.     

Numerical Analysis of the Constrained Blister Test

The constrained blister test is investigated through finite element analysis to determine the applicabilities and the limitations of the new technique. Numerical results confirm that the strain energy release rate asymptotically approaches a constant value. These results also show that the test technique and the approximate solution for strain energy release rate are applicable for some practical cases.     

吸附型固载二氧化氯释放特性的测定与应用研究

通过实验研究 ,定义并测定了吸附型固载二氧化氯的释放特性参数 ,并以临界释放速率UC =0 .0 0 5μg/(h·cm3)作为释放终点 ,将其分为长效、快速和中速释放 3种类型。长效型释放速率峰值Umax <2 0 μg/(h·cm3) ,峰值时间τmax >360h ,有效释放时间τcs >60d ;快速释放型Umax >60 μg/(h·cm3) ,τmax <1 2h ,τcs <7d ;中速释放型则处于两者之间。讨论了固载二氧化氯释放特性的控制方法和不同类型产品的适用范围 ,为产品释放特性的定量研究和应用开发提供了依据。     

Heat-release mechanism in ammonium dinitramide flame

To verify the adequacy of various models of heat release in ammonium dinitramide flame to real processes, chemical processes in products of thermal decomposition at a pressure of 10 torr and in ammonium dinitramide [ADN; NH₄N(NO₂)₂] flame at a pressure of 0.4 to 60 atm are numerically simulated. The calculations are performed on the basis of a detailed kinetic mechanism and boundary conditions correlated with experimental data, thermodynamic properties, and chemical composition of ADN. The kinetic mechanism includes submechanisms that describe high-temperature chemical processes in NH₃/N₂O/NO/NO₂/HNO₂/HNO₃ and NH₃/HN(NO₂)₂ mixtures, and the global stages of aerosol decomposition. Based on calculated and experimental data, the role of dinitraminic acid HN(NO₂)₂, aerosols, and ADN vapor in heat release in the ADN flame zone adjacent to the burning surface is estimated. The calculations predict that the main source of heat release in the cold flame zone at p ≥ 3 atm is dinitraminic acid incoming through the channel of dissociative evaporation ADN_liq → NH₃ + HN(NO₂)₂ from the burning surface. In the high-temperature flame zone, heat release is caused by the reaction that occurs in the NH₃/N₂O/NO/NO₂/HNO₂/HNO₃ mixture. At moderate pressures, the high-temperature and low-temperature zones are separated by an induction zone. The stage governing production of the OH radical, which plays an important role in combustion, in the induction zone is the reaction HNO₃ + M → OH + NO₂ + M. Because of a high activation energy of the stage, small temperature perturbations in the induction zone at low pressures lead to a finite change in the stand-off distance between the high-temperature flame zone and the burning surface. Therefore, small temperature perturbations in the induction zone, which are caused by admixtures in the sample or by heat transfer between the reacting gas and the ambient medium, may be responsible for disagreement between various experimental data and between experimental and calculated data on the stand-off distance between the high-temperature flame zone and the burning surface. In numerical calculations, the position of the high-temperature zone is effectively controlled by varying rate constants of elementary stages within admissible limits. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 64–76, September–October, 2007.     

An integrated job release and scheduling approach on parallel machines: An application in electric wire-harness industry

This paper presents a new job release (JR) and scheduling methodology for one-stage parallel machines where sequence dependent setup times exist. A decision support system (DSS) based on job release is developed in order to enable the application of the methodology. First, mathematical programming models for both job release and job scheduling are devised. Then, due to the NP-hard nature of the problems, heuristics are proposed. As for the interaction between JR and scheduling, job scheduling is integrated with job release for the proposed heuristic solutions so that the capacity achievement provided by scheduling can be utilized for job release. In brief, product design characteristics oriented scheduling affects JR in the proposed approach. Moreover, value stream mapping (VSM) approach is used with the aim of stating the effect of the proposed methodology. Furthermore, the presented methodology was applied in a real life electric wire-harness production system. The application, based on 120-day production data, revealed that the proposed methodology provided 25% decrease in in-plant manufacturing lead time.