Control of structured populations by harvest

It has long been recognized that demographic structure within a population can significantly affect the likely outcomes of harvest. Many studies have focussed on equilibrium dynamics and maximization of the value of the harvest taken. However, in some cases the management objective is to maintain the population at a abundance that is significantly below the carrying capacity. Achieving such an objective by harvest can be complicated by the presence of significant structure (age or stage) in the target population. in such cases, optimal harvest strategies must account for differences among age- or stage-classes of individuals in their relative contribution to the demography of the population. In addition, structured populations are also characterized by transient non-linear dynamics following perturbation, such that even under an equilibrium harvest, the population may exhibit significant momentum, increasing or decreasing before cessation of growth. Using simple linear time-invariant models, we show that if harvest levels are set dynamically (e.g., annually) then transient effects can be as or more important than equilibrium outcomes. We show that appropriate harvest rates can be complicated by uncertainty about the demographic structure of the population, or limited control over the structure of the harvest taken. (c) 2006 Elsevier B.V. All rights reserved.

Optimum harvest maturity for guayule seed

Guayule (Parthenium argentatum Gray) is a rubber-producing shrub native to the semi-arid region of north central Mexico and southwestern Texas. Timely harvest is critical to achieve maximum seed viability, vigour, and yield. The objective of this study was to investigate possible indicators of optimum seed maturity in guayule. The optimum harvest maturity time for guayule was studied by comparing quality parameters at different times after flowering. Heat units expressed as growing degree-days after flowering were calculated and related to seed development stages and quality. Seed quality at different stages of development was assessed by germination, capitulum dry mass, 1000 seed mass, and percentage of filled seeds. The maximum seed quality was recorded at 329 growing degree-days (GDD). This was 28 days from time of flowering. At this date, the moisture content of the capitulum was 48% on a wet basis and the colour was comparable to cinnamon (Code 165C) on the Royal Horticultural Society (R.H.S.) standard colour chart. Of all the parameters GDD, 1000 seed mass, and percentage of filled seeds provided a more rapid and reliable measure of optimum seed maturity. Colour identification can be used as an additional indicator. (C) 2005 Elsevier B.V. All rights reserved.

Acibenzolar-S-methyl and methyl jasmonate treatments of glasshouse-grown freesias suppress post-harvest petal specking caused by Botrytis cinerea

Compounds that activate host plant defence responses potentially offer socio-environmentally sound alternative methods for disease control. In a series of glasshouse trials over 2 years, pre-harvest sprays with acibenzolar-S-methyl (ASM) and methyl jasmonate (MeJA) were tested for suppression of post-harvest infection of cut Freesia hybrida L. flowers by Botrytis cinerea. For the ASM treatments, variability in reducing the incidence of B. cinerea disease was observed between years freesia varieties, incubation temperatures and ASM concentrations. In the first year, the greatest reductions in lesion numbers on ASM-treated var. 'Cote d'Azur' were recorded using 2.86 mM ASM. For three different post-harvest temperature regimes, the relative reductions in lesion numbers, compared to untreated controls, were 45% at 5 degrees C, 40% at 12 degrees C and 30% at 20 degrees C, respectively. In the second year, lesion numbers were most reduced using 1.43 mM ASM to treat freesia var. 'Dukaat' flowers. Here, the relative reductions were to 44% at 5 degrees C, 26% at 12 degrees C and 51% at 20 degrees C. MeJA treatments were, in general, more consistently effective than ASM treatments in reducing lesion numbers and lesion diameters on cut freesia flowers. MeJA-treated (0.2 mM) freesia flowers (var. 'Dukaat') incubated at 20 degrees C showed relative reductions of 62%, and 45% for lesion number and lesion diameter, respectively. The differing efficacy between ASM and MeJA treatments could be attributed to their differential abilities to induce the salicylic acid (SA)-mediated vs. the jasmonic acid (JA)-mediated host defence pathways, respectively.

Exploring Visitors' Perceptions of Art Gallery Festivals

The contemporary directions of art galleries worldwide are changing as social patterns and demands, and visitor expectations of their experiences at art galleries change. New programs and strategies are being developed in galleries to make these institutions more appealing to people who would not normally visit them. One such strategy is the staging of special events, which in galleries take a variety of forms. As special events are increasingly being employed by galleries to inspire new audiences, it is important that these institutions develop an awareness of how their visitors understand and respond to such events. Festivals are one type of special event that visitors identify as having a distinct role and nature. This paper explores visitors’ perceptions of festivals in art galleries and identifies several characteristics that distinguish festivals from other special events. These characteristics include the focus of the event, the audience attending, the degree of interactivity offered, the timing, and the place at which the event is staged. Understanding visitors’ perceptions and expectations of festivals will enable galleries to develop and further enhance their programs and special events to meet visitors’ needs.

The production, harvest and adsorptive recovery of an infectious herpes simplex virus vaccine

At present there is not a reliable vaccine against herpes virus. Viral protein vaccines as yet have proved unsuccessful to meet the challenge of raising an appropriate immune response. Cantab Pharmaceuticals has produced a virus vaccine that can undergo one round of replication in the recipient in order to produce a more specific immune reaction. This virus is called Disabled Infectious Single Cycle Herpes Simplex Virus (DISC HSV) which has been derived by deleting the essential gH gene from a type 2 herpes virus. This vaccine has been proven to be effective in animal studies. Existing methods for the purification of viruses rely on laboratory techniques and for vaccine production would be on a far too small a scale. There is therefore a need for new virus purification methods to be developed in order to meet these large scale needs. An integrated process for the manufacture of a purified recombinant DISC HSV is described. The process involves culture of complementing Vero (CR2) cells, virus infection and manufacture, virus harvesting and subsequent downstream processing. The identification of suitable growth parameters for the complementing cell line and optimal limes for both infection and harvest are addressed. Various traditional harvest methods were investigated and found not to be suitable for a scaled up process. A method of harvesting, that exploits the elution of cell associated viruses by the competitive binding of exogenous heparin to virus envelope gC proteins, is described and is shown to yield significantly less contaminated process streams than sonication or osmotic approaches that involve cell rupture (with> 10-fold less complementing cell protein). High concentrations of salt (>0.8M NaCl) exhibit the same effect, although the high osmotic strength ruptures cells and increase the contamination of the process stream. This same heparin-gC protein affinity interaction is also shown to provide an efficient adsorptive purification procedure for herpes viruses which avoids the need to pre-treat the harvest material, apart from clarification, prior to chromatography. Subsequent column eluates provide product fractions with a 100-fold increase in virus titre and low levels of complementing cell protein and DNA (0.05 pg protein/pfu and 1.2 x 104 pg DNA/pfu respectively).

The influence of harvest and storage on the properties of and fast pyrolysis products from Miscanthus x giganteus

The research investigates the fuel property variations associated with the time of harvest and the duration of storage of Miscanthus x giganteus over a one year period. The crop has been harvested at three different times: early (September 2009), conventional (April 2010) and late (June 2010). Once harvested the crop was baled and stored. Biomass properties of samples taken from different storage zones were compared. The thermochemical properties have been investigated using a range of analytical equipment including thermogravimetric analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). In addition, bio-oil has been produced from the early, conventional and late harvest using a laboratory scale (300gh) fast pyrolysis unit. The potential organic liquid yield (ondry basis, also excluding the reaction water generated) based on the laboratory fast pyrolysis processing undertaken in this study, was found to vary between 2.82 and 3.18 dry tha for the early and the late harvest respectively. The bio-oil organic yield was reduced by approximately 11% (0.36tha) between the early and the late harvest. Char yield was also reduced by approximately 18% (0.61tha). The highest gas yield (18.03%-1.60tha) was observed for the conventional harvest. Gas chromatography-mass spectrometry (GC-MS) analysis of the bio-oil shows that levoglucosan, methylbenzaldehyde and 1,2-benzenediol all increase as a consequence of delayed harvest. It was also observed that by delaying the harvest time the O:C atomic ratio is reduced and a more carbonaceous feedstock is produced. © 2013 Elsevier Ltd.

Multi-agent Systems in the Harvest Prognosis

The paper presents a case study of geo-monitoring a region consisting in the capturing and encoding of human expertise into a knowledge-based system. As soon as the maps have been processed, the data patterns are detected using knowledge-based agents for the harvest prognosis.