Nutritional status of a nereidid polychaete cultured in sand filters of mariculture wastewater

This study examined the nutritional composition of the intertidal marine polychaete Perinereis helleri (Nereididae)when artificially cultured in sand filters treating mariculture wastewater. Moisture levels in harvested P. helleri ranged from 758 to 855 g kg1, and ash, from 23 to 61 g kg1 wet matter (WM). Stocking density and graded size after harvest significantly affected their composition. Higher total lipid contents were found in large (>0.6 g) P. helleri(16–19 g kg1 WM) and those grown at the lowest density(1000 m2: 18 g kg 1 WM) than in small (≤0.6 g) ones (14 g kg1 WM) and those grown at the highest densities (4000–6000 m2: 13–16 g kg1 WM). Several fatty acids within a very broad profile (some 30 identified) reflected this pattern, yet their ARA/EPA/DHA ratios were relatively unaffected. Feeding the polychaete-assisted sand filters (PASF) with fish meal to increase worm biomass productivity significantly increased their DHA content. Other components (e.g. protein, phospholipids, cholesterol, carbohydrate, amino acids, nitrogen, minerals and bromophenols) and nutritional factors (e.g. maturity, feeding seaweed and endemic shrimp viral content) were also investigated. Results suggest that PASF-produced P. helleri have a well-balanced nutritional profile for penaeid shrimp and fish broodstock.

Developing enterprise curriculum: Building on rock, not sand

Entrepreneurial education is the process of providing individuals with the ability to recognise commercial opportunities and the insight, self-esteem, knowledge and skills to act on them. It includes instruction in opportunity recognition, commercialising a concept, marshalling resources in the face of risk, and initiating a business venture. It also includes instruction in traditional business disciplines such as management, marketing, information systems and finance. The purpose of this paper is to describe the design and introduction of a new program in Entrepreneurship at the University of Tasmania. Rather than adopt a traditional business school (passive learning) approach, within this program the method and responsibility of learning has largely been reversed through the process of student centred learning. This method of learning represents a challenging departure from the traditional mainstream teaching practices. In considering the benefits achievable from this teaching method, this paper also considers the difficulties in transferring increased responsibility to students to manage their futures.

1-D hydrogen-bonded organization of hexanuclear {3d-4f-5d} complexes: evidence for slow relaxation of the magnetization for [{LMe2Ni(H2O)Ln(H2O)4.5}2{W(CN)8}2] with Ln = Tb and Dy

Heterometallic {3d-4f-5d} aggregates with formula [{LMe2Ni(H2O)Ln(H2O)4.5}2{W(CN)8}2]·15H2O, (LMe2 stands for N,N-2,2-dimethylpropylenedi(3-methoxysalicylideneiminato) Schiff-base ligand) with Ln = Gd, Tb, Dy, have been obtained by reacting bimetallic [LMe2Ni(H2O)2Ln(NO3)3] and Cs3{W(CN)8} in H2O. The hexanuclear complexes are organized in 1-D arrays by means of hydrogen bonds established between the solvent molecules coordinated to Ln and the CN ligands of an octacyanometallate moiety. The X-ray structure was solved for the Tb derivative. Magnetic behavior indicates ferromagnetic {W–Ni} and {Ni–Ln} interactions (JNiW = 18.5 cm-1, JNiGd = 1.85 cm-1) as well as ferromagnetic intermolecular interactions mediated by the H-bonds. Dynamic magnetic susceptibility studies reveal slow magnetic relaxation processes for the Tb and Dy derivatives, suggesting SMM type behavior for these compounds.

Effects of 17α-ethinyl estradiol on the mating system of the sand goby (Pomatoschistus minutus)

In aquatic environments, endocrine disrupting chemicals (EDCs) that interfere with the endocrinology of males and females form a threat to the maintenance of populations. EDCs are a diverse group of natural and manmade chemicals that already at very low concentrations (at nanogram levels) can have severe effects on reproduction by individuals, e.g. complete sex reversal, feminisation of males, impaired reproduction even resulting in near extinction of populations. With regard to fish, despite the extensive literature on physiological effects of EDCs, very little is known about potential population-level effects. In this thesis, I examined how 17α-ethinyl estradiol (EE2), a synthetic estrogen used in oral contraceptive pills, affects the reproductive behaviour of a marine fish, the sand goby (Pomatoschistus minutus). The aims were fourfold. First, I investigated how exposure to EE2 affects courtship and parental care of sand goby males. Secondly, I looked at effects on the mating system and sexual selection. In the third study, I observed the effects of exposure in a social context where exposed males had to compete with non-exposed males for resources and mates. Finally, I studied the effects of exposure on male-male competition and male aggressive behaviour. This work revealed that EE2 exposure impairs the ability of males to acquire and defend a nest, as well as diminishes the attractiveness of males to females by decreasing their courtship and aggressive behaviour. These effects are harmful for a male whose reproductive success is determined by the ability to compete for limited resources and to attract mates. Furthermore, this thesis showed that selection on male size was relaxed after EE2 exposure and male size had a smaller effect on mating success. These effects can be of a profound nature as they interfere with sexual selection, and may in the long run lead to the loss of traits maintained through sexual selection. The thesis shows that an exposure to environmentally relevant levels of EE2 clearly reduces the chances of individuals to reproduce successfully. Furthermore, it strongly suggests that several types of biomarkers should be used to detect and assess the effects of EDC exposure because severe behavioural effects can sometimes be seen before effects are detectable at the molecular or morphometric level. Behavioural assays should be considered an important complementary tool for the standard ecotoxicological assays because observed behavioural changes have direct and negative effects on fitness, while the connection between changes in molecular expression and fitness may be less obvious.

Context-dependent mate choice in the sand goby, Pomatoschistus minutus

The results presented in this thesis show that all females of a given population do not necessarily choose similar mating partners. Specifically, partner preferences of a fish, the sand goby (Pomatoschistus minutus), varied among individual females and depended on the social context at the time of choice. I also show that females assess multiple mate choice cues simultaneously; partner preferences were based more strongly on an interaction effect between different choice cues than on any individual cue. Furthermore, I found that preferred matings involved fitness benefits in the form of increased offspring success, but these benefits were not significantly affected by mate compatibility. Hence, mate choice for partner compatibility does not appear to be an important determinant of the observed variation in female mate preferences in this species. The context-dependency of female mating preferences revealed is relevant to how genetic variation in sexually selected traits might be maintained: as the mating success of a certain male type varies according to the choice context, directional sexual selection on male traits is shown to be less intense than generally thought making for a slower loss of genetic variation in these traits. Mating preferences of sand gobies were assessed by giving females a binary choice between males that differed in body size and/or other focus traits. These association preferences were found to be sexually motivated, repeatable and to correspond to actual mating decisions.

A novel intermediate in the interaction of thiosemicarbazide with sheep liver serine hydroxymethyltransferase

An unusual intermediate bound to the enzyme was detected in the interaction of thiosemicarbazide with sheep liver serine hydroxymethyltransferase. This intermediate had absorbance maxima at 464 and 440 nm. Such spectra are characteristic of resonance stabilized intermediates detected in the interaction of substrates and quasi-substrates with pyridoxal phosphate enzymes. An intermediate of this kind has not been detected in the interaction of thiosemicarbazide with other pyridoxal phosphate enzymes. This intermediate was generated slowly (t 1/2 = 4 min) following the addition of thiosemicarbazide (200 microM) to sheep liver serine hydroxymethyltransferase (5 microM). It was bound to the enzyme as evidenced by circular dichroic bands at 464 and 440 nm and the inability to be removed upon Centricon filtration. The kinetics of interaction revealed that thiosemicarbazide was a slow binding reversible inhibitor in this phase with a k(on) of 11 M-1 s-1 and a k(off) of 5 x 10(-4) s-1. The intermediate was converted very slowly (k = 4 x 10(-5) s-1) to the final products, namely the apoenzyme and the thiosemicarbazone of pyridoxal phosphate. A minimal kinetic mechanism involving the initial conversion to the intermediate absorbing at longer wavelengths and the conversion of this intermediate to the final product, as well as, the formation of pyridoxal phosphate-thiosemicarbazone directly by an alternate pathway is proposed.

Role of Arg-401 of cytosolic serine hydroxymethyltransferase in subunit assembly and interaction with the substrate carboxy group.

In an attempt to identify the arginine residue involved in binding of the carboxylate group of serine to mammalian serine hydroxymethyltransferase, a highly conserved Arg-401 was mutated to Ala by site-directed mutagenesis. The mutant enzyme had a characteristic visible absorbance at 425 nm indicative of the presence of bound pyridoxal 5'-phosphate as an internal aldimine with a lysine residue. However, it had only 0.003% of the catalytic activity of the wild-type enzyme. It was also unable to perform reactions with glycine, beta-phenylserine or d-alanine, suggesting that the binding of these substrates to the mutant enzyme was affected. This was also evident from the interaction of amino-oxyacetic acid, which was very slow (8.4x10(-4) s-1 at 50 microM) for the R401A mutant enzyme compared with the wild-type enzyme (44.6 s-1 at 50 microM). In contrast, methoxyamine (which lacks the carboxy group) reacted with the mutant enzyme (1.72 s-1 at 250 microM) more rapidly than the wild-type enzyme (0.2 s-1 at 250 microM). Further, both wild-type and the mutant enzymes were capable of forming unique quinonoid intermediates absorbing at 440 and 464 nm on interaction with thiosemicarbazide, which also does not have a carboxy group. These results implicate Arg-401 in the binding of the substrate carboxy group. In addition, gel-filtration profiles of the apoenzyme and the reconstituted holoenzyme of R401A and the wild-type enzyme showed that the mutant enzyme remained in a tetrameric form even when the cofactor had been removed. However, the wild-type enzyme underwent partial dissociation to a dimer, suggesting that the oligomeric structure was rendered more stable by the mutation of Arg-401. The increased stability of the mutant enzyme was also reflected in the higher apparent melting temperature (Tm) (61 degrees C) than that of the wild-type enzyme (56 degrees C). The addition of serine or serinamide did not change the apparent Tm of R401A mutant enzyme. These results suggest that the mutant enzyme might be in a permanently 'open' form and the increased apparent Tm could be due to enhanced subunit interactions.

Slow pressure modes in thin accretion discs

Thin accretion discs around massive compact objects can support slow pressure modes of oscillations in the linear regime that have azimuthal wavenumber m = 1. We consider finite, flat discs composed of barotropic fluid for various surface density profiles and demonstrate through WKB analysis and numerical solution of the eigenvalue problem - that these modes are stable and have spatial scales comparable to the size of the disc. We show that the eigenvalue equation can be mapped to a Schrodinger like equation. The analysis of this equation shows that all eigenmodes have discrete spectra. We find that all the models we have considered support negative frequency eigenmodes; however, the positive eigenfrequency modes are only present in power-law discs, albeit for physically uninteresting values of the power-law index beta and barotropic index gamma.

Effect of reinforcement form on the bearing capacity of square footings on sand

This paper presents the results of laboratory model loading tests and numerical studies carried out on square footings supported on geosynthetic reinforced sand beds. The relative performance of different forms of geosynthetic reinforcement (i.e. geocell, planar layers and randomly distributed mesh elements) in foundation beds is compared; using same quantity of reinforcement in each test. A biaxial geogrid and a geonet are used for reinforcing the sand beds. Geonet is used in two forms of reinforcement, viz. Planar layers and geocell, while the biaxial geogrid was used in three forms of reinforcement, viz. planar layers, geocell and randomly distributed mesh elements. Laboratory load tests on unreinforced and reinforced footings are simulated in a numerical model and the results are analyzed to understand the distribution of displacements and stresses below the footing better. Both the experimental and numerical studies demonstrated that the geocell is the most advantageous form of soil reinforcement technique of those investigated, provided there is no rupture of the material during loading. Geogrid used in the form of randomly distributed mesh elements is found to be inferior to the other two forms. Some significant observations on the difference in reinforcement mechanism for different forms of reinforcement are presented in this paper.

Oxide Particle Surface Chemistry and Ion Transport in "Soggy Sand" Electrolytes

The crucial role of oxide surface chemical composition on ion transport in "soggy sand" electrolytes is discussed in a systematic manner. A prototype soggy sand electrolytic system comprising aerosil silica functionalized with various hydrophilic and hydrophobic moieties dispersed in lithium perchlorate-ethylene glycol solution was used for the study. Detailed rheology studies show that the attractive particle network in the case of the composite with unmodified aerosil silica (with surface silanol groups) is most favorable for percolation in ionic conductivity, as well as rendering the composite with beneficial elastic mechanical properties: Though weaker in strength compared to the composite with unmodified aerosil particles, attractive particle networks are also observed in composites of aerosil particles with surfaces partially substituted with hydrophobic groups. The percolation in ionic conductivity is, however, dependent on the size of the hydrophobic moiety. No spanning attractive particle network was formed for aerosil particles with surfaces modified with stronger hydrophilic groups (than silanol), and as a result, no percolation in ionic conductivity was observed. The composite with hydrophilic particles was a sol, contrary to gels obtained in the case of unmodified aerosil, and partially substituted with hydrophobic groups.

Inverted slot-mode slow-wave structures for traveling-wave tubes

The dispersion and impedance characteristics of an inverted slot-mode (ISM) slow-wave structure computed by three different techniques, i.e., an analytical model based on a periodic quasi-TEM approach, an equivalent-circuit model, and 3-D electromagnetic simulation are obtained and compared. The comparison was carried out for three different slot-mode structures at S-, C-, and X-bands. The approach was also validated with experimental measurements on a practical X-band ISM traveling-wave tube. The design of ferruleless ISM slow-wave structures, both in circular and rectangular formats, has also been proposed and the predicted dispersion characteristics for these two geometries are compared with 3-D simulation and cold-test measurements. The impedance characteristics for all three designs are also compared.

Epigallocatechin gallate is a slow-tight binding inhibitor of enoyl-ACP reductase from Plasmodium falciparum

Epigallocatechin gallate (EGCG) is known to have numerous pharmacological properties. In the present study, we have shown that EGCG inhibits enoyl–acyl carrier protein reductase of Plasmodium falciparum (PfENR) by following a two-step, slow, tight-binding inhibition mechanism. The association/isomerization rate constant (k5) of the reversible and loose PfENR–EGCG binary complex to a tight [PfENR–EGCG]* or EI* complex was calculated to be 4.0 × 10−2 s−1. The low dissociation rate constant (k6) of the [PfENR–EGCG]* complex confirms the tight-binding nature of EGCG. EGCG inhibited PfENR with the overall inhibition constant (Ki*) of 7.0 ± 0.8 nM. Further, we also studied the effect of triclosan on the inhibitory activity of EGCG. Triclosan lowered the k6 of the EI* complex by 100 times, lowering the overall Ki* of EGCG to 97.5 ± 12.5 pM. The results support EGCG as a promising candidate for the development of tea catechin based antimalarial drugs.