Production of polyhydroxyalkanoate from sesame seed wastewater by sequencing batch reactor cultivation process of Haloferax mediterranei

Due to the high cost of bioplastic production, sesame wastewater, generated from the sesame seed hulling process, was investigated to be used as inexpensive and renewable carbon source for the production of biodegradable polyhydroxyalkanoate (PHA) by extreme Haloferax mediterranei. The sesame wastewater (SWW) was hydrolyzed using different concentrations of hydrochloric acid (0.4. 1.00 and 2.00 M) at different period of times (15, 60 and 90 min). The concentration of salt (NaCl) and nitrogen source (NH₄Cl and yeast) required for H. mediterranei cells growth and the accumulation of PHA biopolymer was optimized. A maximum 0.53 g/L concentration of PHA was achieved when the SWW extract media was supplemented with 100 g/L NaCl and 6.0 g/L yeast extract. The cultivation was scaled-up using sequencing batch reactor (SBR) fermentation under non-sterile conditions. The SBR results showed that SWW needs an auxiliary carbon source to obtain high PHA production. Consequently, the system fed with SWW and glucose produced higher PHA (20.9 g/L) than the system fed with SWW.     

Morphologies of diblock copolymer thin films before and after crystallization

Spin-coated thin films of about 100nm of low-molecular-weight hydrogenated poly(butadiene-b- ethyleneoxide) (PB_h-PEO) diblock copolymers have been crystallized at various constant temperatures. Crystallization has been observed in real time by light microscopy. Detailed structural information was obtained by atomic force microscopy, mainly enabled by the large viscoelastic contrast between amorphous and crystalline regions. The behavior in thin films is compared to the bulk properties of the polymer. Crystallization started from an annealed microphase separated melt where optical microscopy indicated a lamellar orientation parallel to the substrate. A small difference in the length of the crystallizable block produced significantly different crystallization behavior, both in the bulk and in thin films. For thin films of the shortest diblock copolymer (45% PEO content) and for an undercooling larger than about 10 degrees, crystallization created vertically oriented lamellae. These vertical lamellae could be preferentially aligned over several micrometers when crystallization occurred close to a three-phase contact line. Annealing at temperatures closer to the melting point or keeping the sample at room temperature for several months allowed the formation of a lamellar structure parallel to the substrate. A tentative interpretation based on kinetically caused chain folding and relaxation within the crystalline state, with implications on general aspects of polymer crystallization, is presented. Received 19 March 1999 and Received in final form 14 December 1999     

Solid-like friction of a polymer chain

We propose a simple friction model for isolated polymer chains on a solid substrate. The chains are pulled at constant velocity by one end, the other end can be trapped on the solid substrate on localised sites. We focus on the energy dissipation due to the traps. This simple model leads to nontrivial friction laws, depending on the velocity and the distance between traps. Some refinements of the model such as the effect of thermal fluctuations are also reported. Received 20 March 2000     

An implicit solution of bi-penalty approximation with orthogonality projection for the numerical simulation of Bingham fluid flow

1.IntroductionItisamajordiffct.encefi-omtheNewtonnuidflowthattheBinghammodelofNonNewtonfluidflowischaracterizedbytwoparameters:ayieldstressandaviscosity.WhenthestressoftheBinghalnmaterialbelowtheyieldstress,materialisrigidotherwisethequasiNewtolliannowresultstll:'71.Hence,therearesomeofthefloating"rigidcores"involvedintheBinghamfluidfloworsomeofthe'rigidcores"attachedtotheboundaries,inwhichthelocationsalldshapesofthese"rigidcores"maychangeforthetransientBinghamfluid,flow.ThisBingllammodelh…     

Secondary super-structures in random copolymers

Secondary domain superstructures in correlated random block copolymers are considered theoretically using the concept of the second order parameter related to fluctuations of the local mean block length. It is shown that the size of secondary domains, , is much larger than the primary domain size, L: , while , where is a small parameter defining the composition asymmetry. Different secondary morphologies are characterized. It is also shown that separation of the system in two macroscopic phases with different primary morphologies predicted earlier using the free energy expansion up to ( is the usual order parameter related to local composition) is an artifact of this widely accepted theoretical model. Received 15 July 1998 and Received in final form 18 January 1999     

中国现代金的分析技术的发明与革新

回顾了中国金的分析技术的发展历程,重点论述了活性碳柱分离技术和泡沫塑料分离富集金技术的发明和革新对现代金的分析技术体系建立和发展的重要作用;阐述了纳微金分析技术革新和金的活动态分析、地电化学(泡塑)样品分析技术的新进展。     

聚氨酯软质塑料的合成工艺

聚氨酯(polyurethane)是主链上含有重复氨基甲酸酯基团聚合物的总称,由聚二异氰酸酯或多异氰酸酯与多羟基化合物加聚而得。其合成工艺投资大,耗电多,浪费大。本文的合成路线则较合理地解决这些问题。     

微波消解ICP-AES法测定ABS中Pb、Cd、Hg

以ABS塑料为研究对象,采用微波消解法进行样品的前处理,使用电感耦合等离子体发射光谱法测定ABS塑料中Pb、Cd、Hg,结果表明,Pb、Cd、Hg加标回收率均在95~105%之间,测试精密度均小于3%,该方法在缩短样品前处理时间的同时得到较高的元素消解回收率和较为理想的精确度,适用于ABS塑料中重金属含量的快速测定。     

精确计算Bingham流体圆管层流压降及速度分布规律的新方法

Bingham(宾汉)模型情况下,多采用通用公式进行圆管层流压降的解析计算,即将Bingham模型本构方程代入粘性流体圆管层流流动通用公式进行计算,仅能得到压降的解析解.新方法结合Bingham流体本构方程与运动方程,建立有关力学平衡方程,并运用代数方程的根式解理论对圆管层流流动时的非线性方程进行求解,可直接求得Bingham流体圆管层流压降及速度流核区半径的解析解,进一步可求得圆管层流速度解析解;Bingham流体圆管层流速度的直接影响因素为流量、塑性粘度和屈服值,研究发现速度流核宽度与屈服值成正比,与流量及塑性粘度成反比,且流核的宽度越大,流核区的速度越小.