Production of triploid Kuruma shrimp, Marsupenaeus (Penaeus) japonicus (Bate) nauplii through inhibition of polar body I, or polar body I and II extrusion using 6-dimethylaminopurine

This study investigated the chromosome ploidy level of Marsupenaeus (Penaeus) japonicus (Bate) non-viable (unhatched) embryos and nauplii after exposure to 6-dimethylaminopurine (6-DMAP), timed to stop either polar body (PB) I, or PBI and II extrusion. Embryos from eight separate families or spawnings were exposed to 150 or 200 mu M 6-DMAP from 1- to 3-min post-spawning detection (psd) for a 4- to 5-min duration (timed to stop PBI extrusion). Separate aliquots of embryos from five of the same spawnings were also exposed to 200 mu M of 6-DMAP from 1- to 3-min psd for a 16-min duration (timed to stop both PBI and II extrusion). For one spawning, a third aliquot of embryos was exposed to 400 p M of 6-DMAP from 1- to 3-min psd for a 16-min duration (timed to stop both PBI and II extrusion). At 18-h psd, non-viable embryo and nauplii samples were taken separately for fluorescent activated cell sorting (FACS). FACS revealed that there were diploids and triploids among all treated non-viable embryos and nauplii. All control non-viable embryos and nauplii were diploid. Percentages of triploid induction for the 4- to 5-min and 16-min durations were not significantly different (P > 0.05). Additionally, no difference was found in the triploidy level of nonviable embryos compared to nauplii in these treatments. The percentage of triploid embryos and nauplii when exposed to 6-DMAP for a 4- to 5-min duration ranged from 29.57% to 99.23% (average 55.28 +/- 5.45%) and from 5.60% to 98.85% (average 46.70 +/- 7.20%), respectively. The percentage of triploid embryos and nauplii when exposed to 6-DMAP for a 16-min duration ranged from 11.71% to 98.96% (average 52.49 +/- 11.00%) and from 47.5% to 99.24% (average 79.38 +/- 5.24%), respectively. To our knowledge, this is the first documentation of successful PBI or PBI and II inhibition in shrimp. This study conclusively shows that treatment of M. japonicus embryos with 6-DMAP at 1- to 3-min pscl for either a 4- to 5-min duration (timed to stop PBl extrusion) or 16-min duration (timed to stop both PBI and II extrusion) results in viable triploid nauplii. (c) 2006 Elsevier B.V. All rights reserved.

Effect of extrusion parameters on flavour retention, functional and physical properties of mixtures of starch and D-limonene encapsulated in milk protein

The purpose of this research was to investigate the retention of flavour volatiles encapsulated in water-insoluble systems during high temperature–short time extrusion process. A protein precipitation method was used to produce water-insoluble capsules encapsulating limonene, and the capsules were added to the extruder feed material (cornstarch). A twin-screw extruder was used to evaluate the effect of capsule level of addition (0–5%), barrel temperature (125–145 °C) and screw speed (145–175 r.p.m.) on extruder parameters (torque, die pressure, specific mechanical energy, residence time distribution) and extrudate properties [flavour retention, texture, colour, density, expansion, water absorption index, water solubility index (WSI)]. Capsule level had a significant effect on extrusion conditions, flavour retention and extrudate physical properties. Flavour retention increased with the increase in capsule level from 0% to 2.5%, reached a maximum value at capsule level of 2.5% and decreased when the capsule level increased from 2.5% to 5%. The die pressure, torque, expansion ratio, hardness and WSI exhibited the opposite effect with the presence of capsules.

The mechanics of the conform continuous extrusion process

The work describes the programme of activities relating to a mechanical study of the Conform extrusion process. The main objective was to provide a basic understanding of the mechanics of the Conform process with particular emphasis placed on modelling using experimental and theoretical considerations. The experimental equipment used includes a state of the art computer-aided data-logging system and high temperature loadcells (up to 260oC) manufactured from tungsten carbide. Full details of the experimental equipment is presented in sections 3 and 4. A theoretical model is given in Section 5. The model presented is based on the upper bound theorem using a variation of the existing extrusion theories combined with temperature changes in the feed metal across the deformation zone. In addition, constitutive equations used in the model have been generated from existing experimental data. Theoretical and experimental data are presented in tabular form in Section 6. The discussion of results includes a comprehensive graphical presentation of the experimental and theoretical data. The main findings are: (i) the establishment of stress/strain relationships and an energy balance in order to study the factors affecting redundant work, and hence a model suitable for design purposes; (ii) optimisation of the process, by determination of the extrusion pressure for the range of reduction and changes in the extrusion chamber geometry at lower wheel speeds; and (iii) an understanding of the control of the peak temperature reach during extrusion.

The mechanisms of melt stabilisation of polyolefins

The effects of melt stabilisers on the oxidative degradation of polyolefins (polypropylene, low density polyethylene) have been studied under a variety of processing conditions . The changes in the both chemical and physical properties of unstabilised polymers occurring during processing were found to be strongly dependent on the amount of oxygen present in the mixer. 2 ,6 ,3' ,5' -tetra-tert-butyl-4'-phenoxy-4-methylene-2, 5-cyclohexadiene-1- one (galvinoxyl), iodine, nitroxyl radicals and cupric stearate were found to be very efficient melt stabilisers particularly when processed in a restricted amount of air. The mechanisms of their melt stabilising action have been investigated and a common cyclical regenerative mechanism involving both chain-breaking electron acceptor (CB-A) and chain-breaking electron donor (CB-D) antioxidant activity was found to be involved in each case. 2,6,3',5'-tetra-tert-butyl-4'-hydroxy phenyl-4-rrethylene-2,5-cyclohexadiene- 1-one (hydrogalvinoxy1), 4-hydroxy, 2,2,6, 6-tetra methyl-N-hydroxy piperidine and hydrogen iodide were formed together with olefinic unsaturation in the substrates during the melt processing of the polymers containing galvinoxyl, 4-hydroxy, 2,2,6, 6-tetra methyl piperidine oxyl and iodine respectively. No bonding of the melt stabilisers to the polymers was found to occur. Cupric stearate was found to undergo a similar redox reaction during its action as a melt stabiliser with the formation of unsaturation in the polymer. Evidence for the above processes is presented. The behaviours of melt stabilisers in the subsequent thermal and photooxidation of polyolefins have also been studied. Galvinoxyl which is very effective under both mild and severe processing canditions has been found to be an effective antioxidant during thermal oxidation (oven ageing) and it is also moderately good. as a photo-stabiliser. Iodine and cupric stearate acted efficiently during melt stabilisation of polymers, however they were both ineffective as thermo-oxidative antioxidants and UV stabilisers. Although the melt stabilisation effectiveness of stable nitroxyl radicals (e.g. 4-hydroxy, 2,2,6,6-tetra methyl piperidineoxyl and Bis- (2,2,6 ,6-tetra methyl-4- piperidinyl-N-oxyl) sebacate) is not as high as that of galvinoxyl during processing particularly in excess of air, they have been found to be much more efficient as UV stabilisers for polyolefins. The reasons for this are discussed.

Energy absorbed in impact extrusion

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Melt processable biomaterials for degradable surgical fixation devices

There are currently few biomaterials which combine controlled degradation rates with ease of melt processability. There are however, many applications ranging from surgical fixation devices to drug delivery systems which require such combination properties. The work in this thesis is an attempt to increase the availability of such materials. Polyhydroxybutyrate-polyhydroxyvalerate copolymers are a new class of potentially biodegradable materials, although little quantitative data relating to their in vitro and in vivo degradation behaviour exists. The hydrolytic degradation of these copolymers has been examined in vitro under conditions ranging from `physiological' to extremes of pH and elevated temperature. Progress of the degradation process was monitored by weight loss and water uptake measurement, x-ray diffractometry, optical and electron microscopy, together with changes in molecular weight by gel permeation chromatography. The extent to which the degradation mechanism could be modified by forming blends with polysaccharides and polycaprolactone was also investigated. Influence of the valerate content, molecular weight, crystallinity, together with the physical form of the sample, the pH and the temperature of the aqueous medium on the hydrolytic degradation was investigated. Its progress was characterised by an initial increase in the wet weight, with concurrent decrease in the dry weight as the amorphous regions of the polymer are eroded, thereby producing an increase in matrix porosity. With the polysaccharide blends, this initial rate is dramatically affected, and erosion of the polysaccharide from the matrix markedly increases the internal porosity which leads to the eventual collapse of the matrix, a process which occurs, but less rapidly, in the degradation of the unblended polyhydroxybutyrate-polyhydroxyvalerate copolymers. Surface energy measurement and goniophotometry proved potentially useful in monitoring the early stages of the degradation, where surface rather than bulk processes predominate and are characterised by little weight loss.

Time scale analysis for fluidized bed melt granulation I: granule-granule and granule-droplet collision rates

Fluidized bed spray granulators (FBMG) are widely used in the process industry for particle size growth; a desirable feature in many products, such as granulated food and medical tablets. In this paper, the first in a series of four discussing the rate of various microscopic events occurring in FBMG, theoretical analysis coupled with CFD simulations have been used to predict granule–granule and droplet–granule collision time scales. The granule–granule collision time scale was derived from principles of kinetic theory of granular flow (KTGF). For the droplet–granule collisions, two limiting models were derived; one is for the case of fast droplet velocity, where the granule velocity is considerable lower than that of the droplet (ballistic model) and another for the case where the droplet is traveling with a velocity similar to the velocity of the granules. The hydrodynamic parameters used in the solution of the above models were obtained from the CFD predictions for a typical spray fluidized bed system. The granule–granule collision rate within an identified spray zone was found to fall approximately within the range of 10-2–10-3 s, while the droplet–granule collision was found to be much faster, however, slowing rapidly (exponentially) when moving away from the spray nozzle tip. Such information, together with the time scale analysis of droplet solidification and spreading, discussed in part II and III of this study, are useful for probability analysis of the various event occurring during a granulation process, which then lead to be better qualitative and, in part IV, quantitative prediction of the aggregation rate.

A comparative study of the structure of sodium borophosphates made by sol-gel and melt-quench methods

The atomic scale structure of sodium borophosphates made by the sol-gel method is compared to those made by the melt-quench method. It is found that although the sol-gel generated materials have a higher tendency towards crystallization, they nevertheless show a qualitatively similar crystallization trend with composition to their melt-quench analogues; the progressive introduction of boron oxide into the phosphate network initially inhibits then promotes crystallization. At the composition associated with the most stable amorphous sodium borophosphate (20 mol% boron oxide), it is found that the atomic scale structure of the sol-gel synthesized network glass is almost identical to that of the corresponding melt-quenched one.

A study of the formation of amorphous calcium phosphate and hydroxyapatite on melt quenched Bioglass(A (R)) using surface sensitive shallow angle X-ray diffraction

Melt quenched silicate glasses containing calcium, phosphorous and alkali metals have the ability to promote bone regeneration and to fuse to living bone. These glasses, including 45S5 Bioglass(A (R)) [(CaO)(26.9)(Na2O)(24.4)(SiO2)(46.1)(P2O5)(2.6)], are routinely used as clinical implants. Consequently there have been numerous studies on the structure of these glasses using conventional diffraction techniques. These studies have provided important information on the atomic structure of Bioglass(A (R)) but are of course intrinsically limited in the sense that they probe the bulk material and cannot be as sensitive to thin layers of near-surface dissolution/growth. The present study therefore uses surface sensitive shallow angle X-ray diffraction to study the formation of amorphous calcium phosphate and hydroxyapatite on Bioglass(A (R)) samples, pre-reacted in simulated body fluid (SBF). Unreacted Bioglass(A (R)) is dominated by a broad amorphous feature around 2.2 A...(-1) which is characteristic of sodium calcium silicate glass. After reacting Bioglass(A (R)) in SBF a second broad amorphous feature evolves similar to 1.6 A...(-1) which is attributed to amorphous calcium phosphate. This feature is evident for samples after only 4 h reacting in SBF and by 8 h the amorphous feature becomes comparable in magnitude to the background signal of the bulk Bioglass(A (R)). Bragg peaks characteristic of hydroxyapatite form after 1-3 days of reacting in SBF.