国内外缓释／控释肥料标准概况

为提高化肥利用率,国内外都致力于缓释/控释肥料的研究、产业化,为规范产业化行为,急需制定符合中国国情的缓释/控释肥料标准,为此,将国内外缓释/控释肥料标准的情况作一介绍。     

Recycling of pharmaceutical waste gelatin for controlled‐release applications. I. A 2,4‐dicholorphenoxy acetic acid based system

Gelatin is a natural macromolecular protein. It contains a wide variety of amino acids in its polymer structure, and it is colorless to yellowish, water‐soluble, and tasteless. It is used as a dispersing agent, sizing medium, and coating for photographic films and in pharmaceutical formulations. In this study, biodegradable mulching, based on waste gelatin from pharmaceutical gelatin scraps (derived from pharmaceutical soft gelatin capsule production), was formulated via the casting of water solutions or suspensions into flexible and consistent films. Gelatin was blended with synthetic materials such as poly(vinyl alcohol) and other natural wastes such as sugar cane bagasse and sawdust. To all formulations, 2,4‐dichlorophenoxy acetic acid (2,4‐D) was added as a herbicide. The morphology and mechanical properties of the samples were investigated with scanning electron microscopy and tensile testing, respectively. The results showed that the produced films had controlled‐release properties. The effects of various additives and crosslinking on the films and the release of the herbicide 2,4‐D from the films were also investigated. The introduction of synthetic and natural additives reduced the release rate of 2,4‐D. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2313–2319, 2004     

Release rates of tetradecen-1-ol acetates from polymeric formulations in relation to temperature and air velocity

An apparatus was developed for investigating the release rates of pheromone formulations at temperatures and air velocities that correspond with those in the field. Polyurethane foam proved an excellent adsorbent for the recovery of tetradecen-1-ol acetates, allowing high air flows at low differential pressure and without breakthrough of these compounds. The experimental setup and procedures are described. The release rates of all formulations investigated were almost proportional to the square root of air velocity, and their logarithms were proportional to the reciprocal of temperature (K). When temperature is increased from 15°C to 25°C, the release rates increase by about 2-2.5 ×. Both relationships were combined into one equation that allows a reliable estimate to be made of the actual release rates of a formulation, under varying conditions, on the basis of its specific parameters and the relevant meteorological data.     

螺旋侧板厚度对浮式风力机Spar平台涡激载荷的影响

Spar平台因其特殊的深吃水立柱式结构,在来流影响下极易发生涡激运动。为探究不同厚度螺旋侧板对浮式风力机Spar平台涡激载荷的影响,基于CFD方法,针对不同厚度螺旋侧板,对平台进行了数值模拟并详细分析平台的升阻力系数、压力场及涡量场等流场参数。结果表明:螺旋侧板可有效抑制涡激载荷,且随厚度增加,升力系数幅值先增加后减小,阻力系数逐步减小;在研究范围内,螺旋侧板厚度为0.10 D时,升力系数幅值最小,阻力系数与原型平台在同一范围内,对涡激载荷的抑制效果最好。     

A vapor collection and thermal desorption method to measure semiochemical release rates from controlled release formulations

Chemicals (bp 270–490 °C/1 atm) evaporated from a controlled-release formulation dispenser were carried by an airflow to a collector packed with a polymeric adsorbent. After a set time, the chemicals were recovered by thermally desorbing them onto a gas-liquid chromatograpic column. They were then separated and quantified. The apparatus is described, and the requirements for its successful use are discussed. The soundness of the thermal desorption technique was confirmed by comparison with another technique: solvent elution from the collector. The advantages of the former technique are discussed.Mention of a commercial or proprietary product in this paper does not constitute an endorsement of that product by the USDA.     

缓释、控释肥料生产、使用前景展望

从我国氮、磷、钾肥高消费、低利用率的现状,阐述了为什么缓控释肥被列为国家中长期科学技术发展计划的优先主题之一。介绍了哪些肥料是缓释、控释肥及当前世界生产、消费量。据估计,2005年世界缓释、控释肥料产量及消费量不超过100万t/a,若包括用于大田作物,具有一定缓释性能的包膜、包裹、包囊肥料,即广义的缓释、控释肥料世界生产、消费量已达120万t/a。展望了缓控释肥生产使用前景,在世界范围内,缓控释肥生产与消费的制约条件是产品价格;就国内而言,农民对肥料要求速效、速溶、速散是推广缓释、控释肥的主要思想障碍。降低生产成本,转变农民对缓释肥的认识,才能推动我国缓控释肥高速发展。     

From Molecular Clusters to Metal Nanoparticles

Different methods to prepare supported metal nanoparticles of uniform size are discussed. (i) Supported ruthenium particles were generated from Ru and Ru-Fe bimetallic molecular metal carbonyl cluster precursors (MCC). (ii) Gold nanoparticle formation in the supercage of Y zeolite was studied on Au/NaY, Au/HY and Au-Fe/HY system. (iii) Palladium nanoparticles were grown in liquid phase then deposited on an SiO₂ support or they were grown on the support surface in a solid-liquid interfacial layer. The particle size control was more efficient in the latter two cases than in the preparation starting from MCC.     

海藻酸微胶囊的制备及在药物控释中的研究进展

海藻酸具有相对温和的凝胶条件与良好的生物相容性 ,已广泛应用于药物缓释与生物医学工程。综述了海藻酸微胶囊的制作方法、增加海藻酸微囊的稳定性与控制物质扩散的主要方法及海藻酸凝胶在药物控释研究中的进展     

数字可控正弦信号发生器的设计

该文采用DDS架构设计了可控正弦信号的产生方法。首先分析了数字可控正弦信号的基本原理;其次,采用Verilog HDL语言进行编程,在FPGA平台上进行了仿真及板级调试;最后,在示波器上得到了正确波形。该成果可用作一般信号处理过程的信号发生器,具有科学、准确、易实现,灵活及便携等优点。     

Polymeric sodium alginate interpenetrating network beads for the controlled release of chlorpyrifos

Novel polymeric sodium alginate (Na‐Alg) interpenetrating network (IPN) beads have been prepared by crosslinking Na‐Alg blend with gelatin (GE) or egg albumin (EA) using glutaraldehyde (GA) as the crosslinking agent. These beads were used for the controlled release of chlorpyrifos. The swelling experiments were performed in water at different temperatures, and these data were used to calculate the molecular mass (M_C) between crosslinks as well as diffusion coefficients. Diffusion coefficients calculated from desorption data were lower by about two orders of magnitude than those calculated from sorption results. Higher values of M_C were obtained for the gelatin‐based IPNs than the neat Na‐Alg and egg albumin‐based matrices. Size of the beads did not vary significantly either by the network or by increasing the exposure time to the crosslinking agent. The scanning electron microscopy (SEM) was used to understand the surface characteristics of the beads. Differential scanning calorimetry (DSC) indicated a molecular level dispersion of chlorpyrifos in the polymer matrix. The percentage entrapment efficiency showed a dependence on the type of network polymer as well as time of exposure to the crosslinking agent. The encapsulation efficiency decreased with an increase in time of exposure to the crosslinking agent. In vitro release experiments have been performed to follow the release kinetics of chlorpyrifos from the matrices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 911–918, 2002