Deterministically driven random walks in a random environment on Z

We introduce the concept of a deterministic walk in a deterministic environment on a countable state space (DWDE). For the deterministic walk in a fixed environment we establish properties analogous to those found in Markov chain theory, but for systems that do not in general have the Markov property. In particular, we establish hypotheses ensuring that a DWDE on $\Z$ is either recurrent or transient. An immediate consequence of this result is that a symmetric DWDE on $\Z$ is recurrent. Moreover, in the transient case, we show that the probability that the DWDE diverges to $+ \infty$ is either 0 or 1. In certain cases we compute the direction of divergence in the transient case

An evaluation of strategies for production of Nile Tilapia (Oreochromis Niloticus L.) fry suitable for hormonal treatment

Intensive methods for the mass production of Oreochromis niloticus (Chitralada strain) seed using concrete tanks, hapas within earthen ponds and earthen ponds were investigated. On the basis of these trials, the productivity and economic performance of various production strategies for hormonally sex-reversed Oreochromis fry (MT fry) were then compared and modelled for adoption in Central and Northeast Thailand. Regular disturbance and harvesting of seed after a short period of spawning opportunity (5-10 days) was found to increase seed production in concrete spawning tanks. Exchange of female broodfish increased synchrony of breeding. A change in conditioning and spawning environment had no effect on seed yield from spawning tanks and hapas (area =12.57 m2and 40m2 respectively). Seed wet weight, seed clutch size and weight was greater in female fish spawned in tanks than hapas. Females conditioned in hapas however produced heavier seed clutches of larger absolute and relative size than tank conditioned fish. Records of tagged females indicated considerable differences in the frequency of spawning; in hapas the distribution was normal wheras in tanks it was skewed. The evidence suggests that hierarchy is important in the control of reproduction and exerts it's strongest effect in clear water, densely stocked tanks. Selective female broodfish exchange optimised seed yield per unit weight of broodfish and seed production was not improved by conditioning females for periods longer than 10 days. Male broodfish exchange did not significantly improve (P > 0.05) seed yields. Early nutrition of broodfish raised under different supplemental feeding regimes in fertilised earthen ponds had a significant effect on later spawning frequency in concrete tanks. However, this effect was confined to broodfish maintained at densities lower or higher than optimal for seed production. Broodfish stocked over a range of densities for extended periods (201 days) showed greater variability of seed production in hapa than tank production systems. This was mainly due to periods of poor water quality in hapas; when water quality was high seed production was significantly higher in hapas than tanks over a range of broodfish densities. The optimal density of broodfish for seed production was exceeded in tanks but not hapas. The relationship between seed production and broodfish density over time suggested that both stocking biomass and number have an effect on fry output. Density of broodfish showed an inverse relationship to clutch size in both tanks and hapas and synchrony of spawning in tanks. Production of swim-up fry in large earthen ponds (area=1740m2) was not significantly different (P>0.05) at 2 levels of harvest intensity. The use of small broodfish however produced double the yield of hormone treatable fry than a similar biomass of larger broodfish of the same cohort. A commercial scale incubation system was devised and evaluated in order to allow tank and hapa systems harvesting unhatched seed to be compared with the production of swim-up fry obtained from earthen ponds. Seed removed from mouthbrooding females was roughly staged and incubated in batches of similar development to give information on survival to swim-up fry. A simple incubation system was designed with a capacity for hatching >100,000 eggs/set. A mean survival of 75% of all harvested seed to swim-up fry was obtained over several trials. A trend to intensification (fry/mVday) from ponds to hapas to tanks was evident when yields of swim-up fry are compared. Productivity exceeded any in the published literature for comparable systems, largely because of the intensity of broodstock management and early and efficient harvest of seed. Broodfish productivities (fry/kg female/month) were also higher across the range of systems tested often by a factor of 1.5-3. The best strategies were selected over a range of total investment cost using dominance analysis. Economic analysis suggested that for a start-up operation in Central Thailand fry production in earthen ponds can give the best return on levels of investment of less than Baht 0.8 million. Substitution of techniques into current carp fry production operations in Northeast Thailand indicated that more intensive methods (production in tanks and hapas) are more attractive over a range of investment levels. The break-even price of MT fry after hormone treatment in nylon hapas was approximately half the cost of treatment in a recirculated water concrete tank system. The break-even price in Central Thailand was lower than the Northeast by a factor of around 1.5 but the break-even price for both areas was lower than the current price of untreated Oreochromis fry

The Profundity of Polychoralism: Exploring the work of Jonathan David Little [Interview and CD review]

Extended (7000-word) composer interview and CD review of "Woefully Arrayed: Sacred & Secular Choral & Polychoral Music of Jonathan David Little", by London-based international music critic, Colin Clarke. [INTERVIEW:] "The disc of sacred and secular choral and polychoral music by Jonathan David Little, Woefully Arrayed … is nothing short of remarkable. Stunningly recorded, the pure sonic joy is visceral. On a personal level, I haven’t experienced such revelation in choral terms since the Tallis Scholars’ first recording of the Allegri Miserere. As an interviewee, it turns out, Little is every inch as fascinating as his music. The following in-depth interview may be seen as an indispensable complement to the listening experience itself." [CD REVIEW:] "Jonathan David Little is a composer whose music is vital, urgent and yet somehow timeless at the same time. … Woefully Arrayed has a mesmeric element to it … [and] is a masterpiece of time-stretching. As lines float and interact throughout the soundspace, there is a distinct impression of atemporality, of altering the way the listener experiences time. … sound is superb, full and reverberant … magnificently handled … A superb disc, one that simply gets better on each and every listening. There is a radiance to Little’s writing that seems shot through with spiritual light and which speaks on a very deep level to the listener." PROJECT OVERVIEW: International Polychoral Music Composition, Recording and Dissemination Project (2015-17) “The lost potential of the acoustics of performing spaces begins to be rediscovered in these works.” A complex and ambitious, large-scale, two-year “polychoral” music creation and recording project was commissioned by the Australia Council – involving communicating how “re-discovered” ancient Renaissance and Baroque techniques of acoustically-innovative performer placement may be revived within new, original, contemporary contexts. One aim was to generate interest in largely long-forgotten, but still hugely useful and aurally impressive composition methods. Following a period of research and experimentation, several new, accessible choral works were created – most featuring intricate, a cappella, polychoral-inspired techniques. Therefore different sections of the choir, or different “sub-choirs” and/or vocal soloists, are sometimes placed in various arrangements around and above the audience (occasionally also involving movement). Due to the incorporation of such techniques, a striking extra dimension is added both to recordings and live performances – where the aural “spatial” interest creates a quasi-theatrical effect. OPEN-ACCESS ONLINE CD BOOKLET (including contextual essay, spatial configuration diagrams, lyrics, pictures and notes): http://www.navonarecords.com/catalog/nv6113/booklet---woefully-arrayed---jonathan-little.htm

Bars and Cold Dark Matter Halos

The central part of a dark matter halo reacts to the presence and evolution of a bar. Not only does the halo absorb angular momentum from the disk, it can also be compressed and have its shape modified. We study these issues in a series of cosmologically motivated, highly resolved N-body simulations of barred galaxies run under different initial conditions. In all models we find that the inner halo's central density increases. We model this density increase using the standard adiabatic approximation and the modified formula by Gnedin et al. and find that halo mass profiles are better reproduced by this latter. In models with a strong bar, the dark matter in the central region forms a bar-like structure (``dark matter bar''), which rotates together with the normal bar formed by the stellar component (``stellar bar''). The minor-to-major axial ratio of a halo bar changes with radius with a typical value 0.7 in the central disk region. DM bar amplitude is mostly a function of the stellar bar strength. Models in which the bar amplitude increases or stays roughly constant with time, initially large (40%-60%) misalignment between the halo and disk bars quickly decreases with time as the bar grows. The halo bar is nearly aligned with the stellar bar (~10 degrees lag for the halo) after ~2 Gyr. The torque, which the halo bar exerts on the stellar bar, can serve as a mechanism to regulate the angular momentum transfer from the disk to the halo.Comment: Modified version after referee's suggestions. 17 pages, 12 figures, accepted by Ap

The reaction of Escherichia coli cytochrome bo with H202: Evidence for the formation of an oxyferryl species by two distinct routes

AbstractWe have re-examined the reaction of fast oxidised cytochrome bo with H2O2 in a stopped-flow spectrophotometer. Monitoring the reaction at 582 nm allows us to observe the formation and decay of a spectroscopically distinct intermediate which accumulates transiently prior to the formation of an oxyferryl species previously characterised in this laboratory (Watmough, N.J., Cheesman, M.R., Greenwood, C. and Thomson, A.J. (1994) Biochem. J. 300, 469–475 [1]). The reaction shows three distinct phases of which the fast and intermediate phases are bimolecular and show a marked pH dependence. Initially these results appeared incompatible with the report that only one equivalent of H2O2 is required to generate the oxyferryl species (Moody, A.J. and Rich, P.R. (1994) Eur. J. Biochem. 226, 731–737 [2]). However, these data can be reconciled by a branched reaction mechanism whose contributions differ according to the peroxide concentration used

Warm Dark Matter versus Bumpy Power Spectra

In this paper we are exploring the differences between a Warm Dark Matter model and a CDM model where the power on a certain scale is reduced by introducing a narrow negative feature ("dip"). This dip is placed in a way so as to mimic the loss of power in the WDM model: both models have the same integrated power out to the scale where the power of the Dip model rises to the level of the unperturbed CDM spectrum again. Using N-body simulations we show that some of the large-scale clustering patterns of this new model follow more closely the usual CDM scenario while simultaneously suppressing small scale structures (within galactic halos) even more efficiently than WDM. The analysis in the paper shows that the new Dip model appears to be a viable alternative to WDM but it is based on different physics. Where WDM requires the introduction of a new particle species the Dip model is based on a non-standard inflationary period. If we are looking for an alternative to the currently challenged standard LCDM structure formation scenario, neither the LWDM nor the new Dip model can be ruled out based on the analysis presented in this paper. They both make very similar predictions and the degeneracy between them can only be broken with observations yet to come.Comment: 7 pages, 8 figures, replaced with MNRAS accepted version (minor revisions), high-resolution figures at http://astronomy.swin.edu.au/staff/aknebe

Growing Green: the emergent role of non-tilapia attributes in marketing tilapia

This paper is focussed upon the emergent emphasis of environmentally friendly (ENVF) attributes in fish with particular regard to tilapia in the UK. The focus is upon the technical production issues, marketing implications, public health and adoption responses from a 3 years multidisciplinary Research Councils UK project which examined the prospects for UK (agricultural) farmers to diversify into production of warmwater tilapia. The proposed production process and product characteristics abound with green credentials, consistent with emergent market demands. This combination might enable small scale producers to access growing UK niche markets for fresh fish and to compete through upmarket positions with expanding EU tilapia imports. Having ascertained the wider market characteristics, primary research was undertaken through consumer focus groups and in-depth interviews with organisational channel members. The results supported the initial premise of niche markets existing for tilapia produced from local, small-scale environmentally-friendly units. Three target groups in the UK were identified: ethnic consumers, green consumers and discrete segments (gastro-pubs and upscale fish restaurants) within foodservice. Having established favourable market prospects the propensity of farmers to diversify into this novel area of activity was explored. Investigation of farmer entrepreneurship, undertaken in 2006 and 2007, explored perceived challenges in the new aquaculture venture. In-depth face to face and telephone interviews with agricultural farmers identified a number of factors that both encouraged and dissuaded them from diversification into tilapia. Despite the ongoing interests of some, and other emergent adopters, the majority seem disinclined to commercialise their interest. The paper concludes that a more holistic support perspective will be required to promote a more favourable reaction and reviews the prognosis for the success of local fish production