固化条件对热塑增韧环氧树脂的固化动力学和相分离的影响

Thermoplastic toughened epoxy resins are widely used as matrices in modern prepreg systems.Different curing conditions play a great role in affecting the cure kinetics and phase behaviour of thermoplastic modified epoxies which further result in different mechanical properties of polymer matrix composites.Since the morphology of the cured thermoplastic/epoxy blends is directly related to the mechanical properties,it is essential to control processing conditions for obtaining desirable morphology.A polyethersulphone (PES) modified multifunctional epoxies,triglycidylaminophenol (TGAP) and tetraglycidyldiaminodiphenylmethane (TGDDM),was used for investigation.The cure kinetics and cured morphology of polymer blends heated at different heating rates and cured at different temperature were studied.It is shown that higher cure temperature and higher heating rate display similar effects in the epoxy conversion and the domain size of phase separated structure.

Dietary combination of soy with a probiotic or prebiotic food significantly reduces total and LDL cholesterol in mildly hypercholesterolaemic subjects

Objective: We hypothesized that a dietary combination of soy with either a probiotic (yoghurt) or a prebiotic (resistant starch) would result in enhanced lipid-lowering effects compared with a control soy diet, possibly via improvements in isoflavone bioavailability.

Subjects: Mildly hypercholesterolaemic subjects (men and post-menopausal women) older than 45 years were recruited via the local media. Thirty-six subjects commenced the study; five withdrew.

Results: Soy+probiotic significantly decreased total cholesterol (4.72.0%; P=0.038) and soy+prebiotic significantly decreased total and low-density lipoprotein cholesterol (5.51.6%; P=0.003 and 7.32.2%; P=0.005, respectively). The bioavailabilities of daidzein, genistein or equol were not affected by probiotic or prebiotic consumption or associated with lipid changes.

Conclusion: Dietary combination of soy with either a probiotic or a prebiotic resulted in significant lipid lowering, not related to isoflavone bioavailability.

First isolation and structural determination of cyclic β-(1→2)-glucans from an alga, Chlorella pyrenoidosa

The aqueous extract of the edible green microalgae Chlorella pyrenoidosa is of interest because of its immunostimulatory activity. Some components in the extract have been identified previously, namely a unique type of arabinogalactan and a galactofuran. Further fractionation of this extract was accomplished by treating the aqueous solution of the fraction precipitated by addition of 1.5vol of 95% ethanol with cetyltrimethylammonium bromide. The residue obtained by concentration of the supernatant was fractionated further by anion-exchange chromatography and size-exclusion chromatography on Sephadex G-100. Two fractions from the latter column were retained, of which one was a starch-like alpha-(1-->4)-linked d-glucan with some alpha-(1-->6) branches, and the other contained a starch plus a mixture of beta-(1-->2)-d-glucans. ESI mass spectrometry was used to show that the mixture contained both cyclic and linear beta-(1-->2)-d-glucans in a cyclic:linear ratio of 64:36, based on intensities of mass spectral peaks. For the cyclic beta-(1-->2)-d-glucans, ring sizes ranged from 18 to 35 monosaccharides with the ring containing 21 glucose units (54% of the cyclic glucans) being greater than three times more abundant than the next most abundant component, the ring containing 22 glucose units (15%). No rings containing 20 glucose units were present. This is the first observation of cyclic beta-(1-->2)-d-glucans in algae, as far as we are aware. For the linear beta-(1-->2)-d-glucans, the component containing 20 glucoses was most abundant (35% of the linear glucans), while the component containing 21 glucose units was the next most abundant (17%). These relatively low-molecular-weight glucans had low immunostimulatory activity.

Partial purification and characterization of exoinulinase from kluyveromyces marxianus YS-1 for preparation of high-fructose syrup

An extracellular exoinulinase( ^{2, 1}- ß- D fructan fructanohydrolase, EC 3.2.1.7), which catalyzes the hydrolysis of inulin into fructose and glucose, was purified 23.5-fold by ethanol precipitation, followed by Sephadex G-100 gel permeation from a cell-free extract of Kluyveromyces marxianus YS-1. The partially purified enzyme exhibited considerable activity between pH 5 to 6, with an optimum pH of 5.5, while it remained stable(100%) for 3 h at the optimum temperature of 50º c. Mn²⁺ and Ca²⁺ produced a 2A-fold and 1.2-fold enhancement in enzyme activity, whereas Hg²⁺ and Ag²⁺  completely inhibited the inulinase. A preparation of the partially purified enzyme effectively hydrolyzed inulin, sucrose, and raffinose, yet no activity was found with starch, lactose, and maltose. The enzyme preparation was then successfully used to hydrolyze pure inulin and raw inulin from Asparagus racemosus for the preparation of a high-fructose syrup. In a batch system, the exoinulinase hydrolyzed 84.8% of the pure inulin and 86.7% of the raw Asparagus racemosus inulin, where fructose represented 43.6mg/ml and 41.3mg/ml, respectively.

Revisiting delta-6 desaturate regulation by C18 unsaturated fatty acids, depending on the nutritional status

Dietary polyunsaturated fatty acids (PUFA) play a key role in regulating delta-6 desaturase (D6D), the key enzyme for long-chain PUFA biosynthesis. Nevertheless, the extent of their effects on this enzyme remains controversial and difficult to assess. It has been generally admitted that C18 unsaturated fatty acids (UFAs) regulate negatively delta-6 desaturase (D6D). This inhibition has been evidenced in regard to a high glucose/fat free (HG/FF) diet used in reference. However, several nutritional investigations did not evidence any inhibition of desaturases when feeding fatty acids.

Because the choice of the basal diet appeared to be of primary importance in such experiments, our goal was to reconsider the specific role of dietary UFAs on D6D regulation, depending on nutritional conditions. For that, sixteen adult Wistar rats were fed purified linoleic acid, α-linolenic acid or oleic acid, included in one of two diets at 4% by weight: an HG/FF or a high starch base (HS) where the pure UFAs replaced a mixed vegetable oil. Our results showed first that D6D specific activity was significantly greater when measured in presence of an HG/FF than with an HS/4% vegetable oil diet. Secondly, we found that linoleic and alpha-linolenic acids added to HG/FF reduced the specific activity of D6D. In contrast, when pure UFAs were added to an HS base, D6D specific activities remained unchanged or increased. Concordant results were obtained on D6D mRNA expression.

Altogether, this study evidenced the importance of the nutritional status in D6D regulation by C18 UFAs: when used as control, HG/FF diet stimulates D6D compared with a standard control diet containing starch and 4% fats, leading to an overestimation of the D6D regulation by UFAs. Then, UFAs should be considered as repressors for unsaturated fatty acid biosynthesis only in very specific nutritional conditions.

Studies on dietary fibre : analysis, epidemiological and physiological aspects

This thesis involves an investigation in three areas; first, a study of an enzymatic-gravimetric method for the analysis of dietary fibre; second, a survey of dietary fibre intake in an area of a developing country, and finally, some observations on the functional aspects of gel-forming dietary fibre in the rat. A simple and rapid enzymatic-gravimetric assay for both soluble and insoluble dietary fibre has been critically investigated. Reference samples were also analysed by a more comprehensive, enzymatic gas chromatographic method to allow testing of the relative accuracy of the enzymatic-gravimetric method. The enzymatic-gravimetric method was found to be highly reproducible but gave a slightly higher value for total dietary fibre than the more comprehensive method. This discrepancy is probably due to the presence of small quantities of resistant starch and protein residue which are recovered in the enzymatic-gravimetric method. In the enzymatic-gas chromatographic method, protein residue is not measured, and resistant starch is estimated, but not counted as dietary fibre. The enzymatic-gravimetric method was applied to the analysis of foods commonly consumed in the Padang region of West Sumatra in Indonesia, in order to estimate dietary fibre intake in the region. Daily intakes of usual foods were estimated by use of a 24-hour recall procedure aided by food photographs to assist in the estimation of portion size. Samples of approximately 60 of the most commonly consumed foods were collected and analysed for dietary fibre. These appear to be the first data which report values for dietary fibre in Indonesion foods and they represent a significant improvement upon the existing data on crude fibre content. Knowledge of the amounts of foods usually consumed and their dietary fibre content allowed an estimation of usual intakes of dietary fibre. Fibre intake was found to be lower than in the developing countries of Africa and was comparable to intakes measured in the U.K. This is the first study to show that in this part of South East Asia, a developing country area using polished rice as a staple food, dietary fibre intakes are as low as in Western countries. Low intakes of fibre are believed to be related to the prevalence of a range of diseases and, in this study, preliminary data on the rates of non-infective, chronic diseases were collected from the two main hospitals in West Sumatra. Chronic, non-infectious diseases such as inguinal hernia, appendicitis, haemorrhoids, diabetes mellitus, hypertension and malignant neoplasms of the rectum are relatively frequent in West Sumatra. While no firm conclusions can be drawn from these data, they do show the possibility of a relationship between low intakes of dietary fibre and the prevalence of these diseases, and suggest that further investigation is necessary. Some observations were made of the effect of gel-forming dietary fibre on stomach emptying and intestinal transit rate in the rat. Xanthan gum was added to iso-osmotic solutions to produce increased viscosity and phenol sulphonphthalein (phenol red) was used as a non-absorbable marker. Gavage feeding of solutions with a range of viscosities was used to study the effect of viscosity on the rate of stomach emptying and intestinal transit. Increased viscosity was observed to slow gastro-intestinal transit and this provides one mechanism by which dietary fibre of the gel-forming type ray improve glucose tolerance.

The effect of vitamin : a deficiency on glucose uptake in the rat

This thesis describes an investigation of the effects of vitamin A deficiency on gut function, The central hypothesis to be tested was that acute vitamin A deficiency affects glucose uptake from the small intestine- The hypothesis was tested using a system involving perfusion of isolated segments of the small intestine in the anaesthetized rat. The system was used to study effects on glucose uptake under steady-state conditions. In the initial part of the study, experiments were diverted towards setting up the system for measuring steady-state uptake, and determining the relative contributions of active uptake and diffusion. Phenol red was found to be a reliable non-absorbable marker for determining net water movement. Phlorizin, generally at 1 mmol/L, was used as a competitive (reversible) inhibitor of active uptake. It is difficult however to confirm complete inhibition of active uptake by phlorizin because of the limited solubility of the inhibitor. The kinetics of glucose uptake f ram intra-luminal maltose were found to be, in general, not significantly different from those applying to the uptake of glucose from an equivalent glucose solution. Maltase activity in the perfused gut segment was found to be sufficient to hydrolyse most of the maltose (80 per cent or more) in the solution being perfused, a much greater proportion than was absorbed. Glucose absorptive capacity, measured on an intestinal dry weight basis, was greatest in the duodenum and progressively less in the jejunum and ileum. The rate of water uptake f ran the gut was increased by the presence of glucose in the lumen, and was linked to glucose uptake as shown by the inhibition of water uptake by phlorizin. Uptake of glucose by solvent drag was demonstrated by showing an increased rate of glucose uptake when the rate of water uptake was increased by perfusing a solution of reduced osmotic pressure. In the experiment a low intra-luminal glucose concentration was used to preclude net uptake by diffusion and active uptake was blocked with phlorizin. This process was further investigated using streptozotocin-diabetic rats in which the diabetes establishes a hyperosomotic blood with hyperglycaemia. Uptake by solvent drag was more obvious in diabetic animals. A back-diffusion (exsorption) of glucose from the tissues to the lumen was also shown; the rate being proportional to plasma glucose concentration. Vitamin A deficiency was established in weanling rats after 6-7 weeks feeding on a diet based on wheat starch, coconut oil, and casein washed with hot ethanol, together with vitamins and minerals. The vitamin A deficiency led to classic eye signs and was reversed by the addition to the diet of retinoic acid (5 g/g diet). Vitamin A deficiency decreased intestinal mucus production (dry weight) but had no detectable effect on the histology of the villous epithelium as shown under the light microscope. Using perfusion experiments it was shown that vitamin A deficiency had no significant effect on the rate of active uptake of glucose, but that deficiency increased the rate of passive uptake.

Associations between growth and diet in adolescence

There is much interest in the nature and quality of the diet consumed by adolescents. To determine whether there are significant associations between diet and gain in height and weight in this age group, the present study analysed data on food intake and weight and height obtained on three occasions over a 30-month period from a total of 326 adolescents aged between 12 and 15 years. Information on sociodemographic and other lifestyle factors, including an indicator of physical activity, was also obtained. Energy intake was found to be a significant positive predictor of both height and weight gain. In addition intake of fat, calcium and riboflavin were found to be significant positive predicators of height gain and intake of carbohydrate and starch significant positive predictors of weight gain. After controlling for energy intake only riboflavin approached significance as a positive predictor of height gain. A food group analysis identified intake of dairy foods as a significant predictor of height gain. Although statistically significant the dietary predictors explained only a small proportion of the variability in height and weight (≤3.5%). Given the difficulties in obtaining complete dietary records from this age group and the generally adequate nature of the diet in the study group, the small proportion of height and weight gain explained by diet is not unexpected. Nevertheless the nutrient predictors identified are consistent with nutrient requirements for growth during adolescence and highlight the importance, for this age group, of an adequate intake of nutrients specifically provided by dairy foods. Few significant associations were found between growth rates and the sociodemographic and the lifestyle factors measured in this study. The ethnic diversity of the study sample may have contributed to this outcome.

Control over the hydrophobic behavior of polystyrene surface by annealing temperature based on capillary template wetting method

The wetting behavior of water droplets was studied on tunable nanostructured polystyrene (PS) surfaces fabricated by temperature-induced capillary template wetting. The surface morphology of PS varied with the annealing temperature. Contact angle (CA) measurements showed that the wettability of polystyrene surfaces could be tuned from hydrophobic (CA = 104°) to superhydrophobic (CA = 161°) by rendering different morphologies, which could be explained by two distinct wetting modes, i.e., the Wenzel and Cassie–Baxter wetting state. Meanwhile, the critical annealing temperature inducing wetting transition between the Wenzel state and Cassie–Baxter state was obtained. This approach could be easily extended to produce superhydrophobic surfaces on other thermoplastic polymers.

Structure-property relationships of nylon 6, MXD6, their blends and nanocomposites

This research project aimed to develop an understanding of the structure-property relationships of nanocomposite materials (injection moulded and fibres) based on nylon 6, MXD6 and their blends, with a layered silicate in combination with polyhedral oligomeric silsesquioxane nanoparticles and SEBS rubber particles.

Tailoring enzymes for biofuel production with reference to Australian biomass

Manufacture of biofuels from existing biomass may provide a sustainable alternative to the extensive utilization of fossil fuels. Biomass offers environmental advantage over fossil fuels as it is a renewable energy source with low sulphur and nitrogen content and is carbon neutral over its production and utilization. Ranges of biomass are reported worldwide to be suitable raw material for bioethanol production. These can be generally classified into three groups; sucrose based (sugar cane), starch based (corn, wheat and barley) and lignocellulosic (which is mostly comprised of lignin, cellulose and hemicelluloses in grasses, wood and straw) materials. However, the limited supply of two biomass groups (sucrose and starch) will not satisfy society’s growing energy demands; thus biofuel technology based on lignocelluloses is under intense investigation. The main bottleneck in lignocellulosic biomass conversion for biofuel production is the enzymatic depolymerisation of cell wall polysaccharides into fermentable sugars. Protein engineering has recently been used to improve the performance of lignocelluloses degrading enzymes, as well as proteins involved in biofuel synthesis pathways. We have produced a recombinant enzyme that has the ability to produce monomeric sugars from a complex substrate. This presentation will summarize current efforts to develop an enzymatic treatment which would facilitate the economical processing of biomass available in Australia for bioenergy generation.

Sucrose as an added sweetener in diabetes mellitus

For many years the Diabetes Associations of several countries have recommended the dietary elimination of added sucrose. However, contrary to popular belief, there is no evidence that modest use of added sucrose is detrimental to diabetic control. In this study of 17 non-insulin dependent diabetics, the medium-term metabolic effects of the daily supplementation of a subject's usual diet with either 28 g of sucrose or with saccharin and starch of equivalent sweetener and energy value, were compared over six-week periods. Neither dietary period had any significant effect on fasting concentrations of blood glucose, plasma insulin, GIP or serum triglyceride. The metabolic responses to two different test meals, consisting of a standard breakfast supplemented with either sucrose or saccharin plus starch, did not differ significantly either between test meals or between dietary periods. Similarly neither dietary period had any significant effect on urinary excretion of glucose. Na+ or K+. There was no significant difference in mean blood pressure between dietary periods.

The results of this medium-term study indicate that there are no metabolic contraindications to including a moderate amount of sucrose (up to 28 g e 7 teaspoons) in the diets of patients with non-insulin dependent diabetes mellitus.

Characterisation of an out-of-autoclave resin film infusion process for textile composites

A new method to manufacture damage tolerant textile composites, which combines Resin Film Infusion with a fast and cost·efficient curing technology QuickstepTM, was investigated. The effect of process parameters on resin flow through carbon fibre preforms was analysed and model-based parameter optimisation resulted in considerable improvement of resin flow properties.

Effect of operating parameters and cleaning on the performance of ceramic membranes treating partially clarified sugar cane juice

The performance of ceramic membranes with pore sizes of 0.05 and 0.10 mm in purifying limed and partially clarified sugar cane juice was investigated under different operating conditions. From various operating conditions and strategies, switching off the permeate for 5 seconds for every 5 minutes (S5sT5 m) by an automated control valve provided higher flux. From the three pH experiments conducted on the 0.05 mm membrane, the best performance was observed at a pH of 7.5. Amongst the four fouling models tested, the cake filtration model fitted the performance of both membranes with higher accuracy at a transmembrane pressure of 0.5 bar. Filtering the cane juice through the membrane reduced the turbidity by 99.7%, color by 15%, and the starch concentration by 80% as well as increased the purity by 1.4%. The effective cleaning chemical composition from experimental results showed that 1% NaOH and 3000 ppm NaOCl solution performed the best but only for the experiments that were treating limed and partially clarified juice at pH 7.5.

Detection of brassinosteroids in pollen of Lolium perenne L. by immunocytochemistry

Bioactive brassinosteroids have been localized in developing and mature pollen of anhydrously fixed rye-grass (Lolium perenne) by immunocytochemistry using polyclonal antibodies to castasterone generated in rabbits. Tricellular pollen fixed by freeze-substitution was also labelled in the starch granules. Study of the developmental sequence of the pollen through the microsporocyte, microspore, bicellular and tricellular stages showed that the brassinosteroids were increasingly sequestered in starch granules as the amyloplasts matured, supporting the view that these are storage organelles for these potent plant growth promoters. In bicellular pollen, heavy labelling was seen in the zone within 0.5 μm of the starch granule, where stromal tissue remains. Thus, the stroma may be the site of synthesis of these compounds. During aqueous fixation, the brassinosteroids leached from the starch granules of tricellular pollen, indicating that they would be quickly available after imbibition to influence the physiology of germinating pollen. The results from high-performance liquid chromatography of dansylaminophenylboronates from partially purified extracts of freshly dehisced tricellular pollen of rye-grass showed 25-methylcastasterone may be a minor component, together with two unknown peaks. No specific binding of brassinolide to any soluble proteins extracted from tricellular rye-grass pollen was observed using the antibodies in gel electrophoresis or enzyme-linked immunosorbent assays.