An analog experiment of magma fragmentation: behavior of rapidly decompressed starch sirup

Paper reports a result of analog experiments regarding the simulation of magma fragmentation. We filled a starch sirup foam, as an analog material, in a 117–240 mm long and a 50 mm diameter high pressure chamber and exposed it to a rapid decompression. The foam was prepared by mixing starch sirups of dynamic viscosities ranging from 5 to 10¹² Pa· s at temperatures ranging from 293 to 343 K with nitrogen at 2.5 MPa gauge pressure. In ejecting high-pressure foams into a low-pressure chamber, diagnostics of foam’s fragmentation process were pressure measurment and high-speed video recording. Prior to decompression experiments, we examined visco-elastic properties of foam specimens by using a rheometer. The foam deformation under decompression was found to be axial–symmetrical, and strongly coupled with bubble growth and coalescence. These effects contributed even more efficiently to fragmentation processes than previous laboratory experiments using other analog materials. Fragment shapes varied widely depending on the temperature and water concentration of starch sirup foams, which proved that fragmentation process was governed by not only ductile deformation but also brittle failure, and determined by the degree of visco-elasticities of starch sirup foams.      

2-(p-toluidino)-6-naphthalene sulfonate as a fluorescent probe for flocculation studies of cationic potato amylopectin and nanosized silica particles 1. 2-p-(toluidino)-6-naphthalene sulfonate binding to cationic amylopectin

2-(p-toluidino)-6-naphthalene sulfonate (TNS) is a probe that fluoresces strongly when bound to certain proteins and polymers, but weakly in aqueous solution. Absorption and fluorescence spectroscopy were used to study the interaction of TNS with native amylopectin potato starch (NApS) and cationized amylopectin potato starch (CApS) in aqueous solution. The anionic TNS binds to CApS at a single type of binding site, with an affinity which has both electrostatic and nonelectrostatic contributions (including hydrogen bonding), whereas binding to NApS occurs at the same type of site but only by nonelectrostatic means. The affinity to CApS decreases strongly with increasing salt concentration, due to screening of the electrostatic attraction, whereas with NApS increasing salt concentration slightly enhances the binding affinity, most likely due to screening of a weak repulsive interaction between TNS and phosphate residues on NApS. The association constant for binding of TNS to CApS in 5 mM NaCl is 110 ± 20 M⁻¹. This comparatively weak binding makes TNS a useful probe in kinetic investigations of the flocculation of anionic silica particles by CApS. Received: 14 August 1998 Accepted in revised form: 4 December 1998     

TEMPO-derivatives as catalysts in the oxidation of primary alcohol groups in carbohydrates

Primary hydroxyl groups in aqueous starch, pullulan and methyl α- -glucopyranoside were oxidised to the corresponding carboxylic acid functionalities by TEMPO-(4-X)-derivatives using sodium hypochlorite as the primary oxidant. All the combinations of substrates and nitroxyl radicals resulted in stoichiometric conversions, and the selectivity for oxidation of primary hydroxyls was high. Some depolymerisation occurred throughout the oxidation, especially when 4-acetoxy and 4-mesyl-TEMPO were used. The pH window of the activity of the inexpensive 4-acetamido-TEMPO was found to be substantially lower from that of the other tested TEMPO-derivatives; thus allowing milder reaction conditions. At pH 8, the rate of oxidation was ca. two times higher when 4-acetamido-TEMPO was used compared to the other catalysts.     

Characterization of a Novel Mesophilic Bacterial Amylase Secreted by ZW2531-1, a Strain Newly Isolated from Soil

A novel mesophilic bacterial amylase, named oligosaccharide-producing multifunctional amylase(OPMA), was discovered and characterized. OPMA is an extracellular enzyme secreted by ZW2531-1, a strain newly isolated from Chinese soil. It could be purified to homogeneity from the culture supernatant of ZW2531-1 by 30%―60% saturated ammonium sulfate precipitation, followed by twice Sephadex gel filtration chromatography. OPMA is a 66 kDa protein based on SDS-PAGE and has an isoelectric point(pI) at pH=5.3 by Iso...     

Hydrolysis of starch or pullulan by glucoamylase or pullulanase immobilized on poly(N-isopropylacrylamide) gel

Starch or pullulan was hydrolyzed using glucoamylase or pullulanase immobilized on N-isopropylacrylamide gel. The gel used is temperature sensitive; its mesh size becomes smaller at higher temperatures (30 °C) and larger at lower temperatures (20 °C). The molecular weight distribution of starch is wide and it consists of high-molecular-weight amylopectin, amylose and glucose. From the change in the chromatograms for the substrate and products, it was found that the hydrolysis rate at 30 °C was faster than that at 20 °C for amylose, though it was the reverse for amylopectin. This finding suggests that the smaller molecular sized amylose can enter the gel phase at both temperature, while the larger molecular sized amylopectin can hardly do so; only the end group, which can partly enter the gel phase at 20 °C (larger mesh size), was hydrolyzed. Further, several molecular weight pullulans (monodisperse) were hydrolyzed and the experimental chromatograms for substrate and products confirm the hydrolysis mechanism estimated. Received: 14 July 1998 Accepted in revised form: 26 August 1998     

Solution Properties of Mixed Starch/Chitosan Revealed by Resonance Light Scattering

The association behavior of starch and chitosan and the dilute solution properties of the starch/chitosan complex were investigated by means of resonance light scattering(RLS) spectra. The interaction between starch and chiotsan was proved by RLS. Based on the results, the appropriate association condition was selected. However, the solution property of starch/chitosan was affected greatly by external factors such as pH value and metal ionic strength. The change of pH, which causes the irreversible transition of solution from transparent into murky, provides some important information of partitioning behavior of the complex in solution. The durative enhancement of RLS intensity for the complex exhibited two inflexions and a plateau in the presence of a certain amount of Fe³⁺. It indicates that Fe³⁺ not only increases the RLS intensity, but also induces the micell-aggregate transition of the complex in solution. Moreover, the thermodynamic parameters for micell formation process at different temperatures, based on the RLS values, were calculated.     

六水合硝酸镁增塑改性淀粉-聚乙烯醇复合膜的合成与性能

以六水合硝酸镁[Mg(NO₃)₂·6H₂O]为增塑剂, 采用流延法制备了增塑改性的淀粉-聚乙烯醇(PVA)复合膜, 并研究了改性后淀粉-PVA复合膜的性能. 研究结果表明, Mg(NO₃)₂·6H₂O与淀粉和PVA发生一定的相互作用, 破坏了淀粉和PVA中的结晶结构. 因此, Mg(NO₃)₂·6H₂O的加入可提高淀粉与PVA间的相容性, 改变了淀粉-PVA复合膜的力学性能, 使其拉伸强度下降, 断裂伸长率提高.     

Chromatographic determination of residual monomers in starch-g-polyacrylonitrile and starch-g-polyacrylate

Summary A reverse-phase HPLC method for simultaneous determination of acrylonitrile (AN), acrylamide (AM) and acrylic acid (AC) was developed. The residual monomer AC was quantified in several industrial polymers as well as grafted copolymers. Products of biodegradation of these copolymers were also identified.     

Temperature dependence of the viscosity of highly starch-filled poly(hydroxy ester ether) biodegradable composites

 The temperature dependence of the viscosity of starch-filled poly(hydroxy ester ether) (PHEE) biodegradable composites was analyzed using Arrhenius and WLF equations. Corn starch/PHEE materials were extruded using a twin screw extruder with starch volume fractions from 0.27 to 0.66. Dynamic strain sweep measurements were carried out at 10 rad/s at six different temperatures from 100 °C to 150 °C. Both Arrhenius and WLF equations model equally well the temperature effect on viscosity of PHEE and starch/PHEE composites with starch volume fractions up to 0.36. Arrhenius equation with stress correction describes the stress dependence of viscosity of starch/PHEE composites with higher starch volume fractions. The activation energy using both Arrhenius equation and Arrhenius equation with stress correction is 62.7 kJ/mol for pure PHEE and starch/PHEE composites. Received: 10 September 1999 Accepted: 27 March 2000