Ecological and physiological aspects of aestivation-diapause in the larvae of two Pyralid stalk borers of maize in Kenya

Stalk borers are highly destructive to a large number of important graminaceous crops all over the world. Some examples of economically important stalk borers and a general description of their life-cycle are mentioned in chapter 1. In the same chapter difficulties in controlling the insects are described. The crucial role of aestivation- diapause in the life history of tropical stalk borers is elucidated and the importance of further research on this subject is demonstrated.Aestivation-diapause in two Pyralid stalk borers, Chilopartellus (Swinhoe) and Chilo orichalcociliella (Strand) was investigated under field and laboratory conditions.The relation between diapause and climate during three consecutive years is described in chapter 2. Yearly and seasonal fluctuations in the larval and pupal populations of the two stalk borers in maize appeared to be considerable. As long as the water conditions for plant growth were suitable, insects had a continuous development. Under these conditions larvae had pigmented spots and could not survive dry conditions. Soon after cessation of the rains (or irrigation) rates of pupation decreased. At that time larvae lost their cuticular pigmentation and became resistant to drought. Comparison of the incidence of aestivation in the field with the prevailing climatic conditions showed that only lack of rain could be associated with the arrested larval development. No effects of temperature, relative humidity or photoperiod could be found. These results indicate that the host plant may be involved in the induction of diapause.Chapter 3 is concerned with characteristics of pre-diapause and diapause larvae. Evidence was obtained that under natural conditions larvae do not feed during diapause as long as they are not disturbed. The physiological condition of field-collected stem borer larvae changed considerably upon entering diapause: a decreased rate of oxygen consumption, rate of heart beat and water content, an increased fat content, and arrested development of the testes were found. These changes normally occurred before larvae were turning unspotted and/or were becoming resistant to drought.The condition of the host plant in relation to diapause induction is described in chapter 4. Diapause could be induced inside maize plants of different developmental stages. It was shown that the first (physiological) signs of the diapause syndrome appear in larvae feeding in stems containing 70-80% water and very little (Marked differences were found in the consumption and utilization of stems of maize plants in different developmental stages. Its possible relevance to diapause is discussed.In chapter 5 experiments are described on the induction of aestivation-diapause by varying the food condition. Most early 5th instar larvae of C. partellus entered diapause after being introduced into aged maize stems containing 75% water, 8% sugar and 1.3% protein (fresh wt.). Pupation rate, cuticular pigmentation, QO 2 and water content of these larvae werecomparable to values obtained from field-collected aestivating larvae. Larvae which had developed beyond the early 5th instar were less sensitive to the diapause inducing factors of the aged maize stem : most of them pupated.Test of 30 different diets with varying protein, sugar and water contents, indicated that diets containing 0.9-1.1% protein and 70% water were best in inducing diapause. Early 5th instar larvae on diets with the above mentioned protein content grew slowly (but reached normal weights), moulted into the unspotted form and had a retarded rate of pupation. Larvae on diets with lower protein contents hardly developed at all, whereas on diets with higher protein contents larvae pupated normally. Larvae reared on diets in which the water content had been reduced from the normal level of 86% to 70%, resulted in areduction of the larval water content and respiratory rate, close to values normal for field-collected diapause larvae. Evidence was obtained that larvae reared on diapause inducing diets attained a certain degree of drought resistance. Early 5th instar or younger larvae were the most sensitive stages to diapause induction by diet.Many larvae on aged maize stems and artificial diets turned unspotted even though pupating soon thereafter. The relevance of the cuticular pigmentation as a criterion for aestivation-diapause is discussed. The endocrine involvement in the aestivation- diapause is described in chapter 6. From juvenile hormone titre determinations and ligation experiments evidence was obtained that the diapause is regulated by an intermediate level of JH. Application of JH to non-diapause larvae prevented pupation of these larvae but did not evoke other aspects of the diapause syndrome

An Offshore Port concept to reduce the Construction costs in offshore wind farm projects: By an analyses on the Market developments, Workability and Financial performances

In the 25 years of existence, the offshore wind market has developed on many aspects. Among others, the dimension of the turbines increased by a factor 15 and the distance to shore increased by a factor of 50. The developments of the offshore wind farms increase the requirements for the installation vessels and as a consequence the present day rates can be up to $300.000. The global potential of the offshore wind market by the year 2030 is forecasted to be 60 GW for Europe and 22GW for the US Atlantic coast. The developments in the market, lead to demands during the construction of offshore wind turbines. The construction phase became more demanding over the years, while the logistical strategy of sailing back and forth to the offshore wind farm with a jack-up vessel, is similar as applied in 1991. The six demands can be fulfilled by performing four required activities at the offshore port. The potential of seven support structures that fulfil the boundary conditions for the offshore port are determined. Important boundary conditions are a maximum vertical load of 12.600 ton, suitability in a water depth range between 30 and 50 meter and a minimum surface area of 17.500 m2. Besides boundary conditions that have to be fulfilled, there are also maximum allowed conditions that determine the workability of a port concept. For a floating port concept the motion response is the leading workability condition. Based on the mobility, motion response and a cost indication, three port concepts are selected. These port concepts are a single barge, a single jack-up barge and a combination of a small jack-up barge and a single barge. The current logistical strategy for construction of an offshore wind farm is compared to various logistical concepts that include an offshore port. The logistical concept with a feeder vessel that sails from the onshore to the offshore port and an installation vessel that sails between the offshore port and the wind farm has the highest potential saving. Taking into account the assumptions made throughout this research, for each executed project by the offshore port the savings are expected to be €23.000.000. These savings consist of a sooner generation of energy and by savings on the construction of an offshore wind farm. The discounted cash flows for the three port concepts shows a potential for the offshore port concept. The net present value of the three offshore port concepts deviates between 52 and 216 million euro. The financial results are most sensitive to the ratio between wind farm capacity and the turbine capacity, also the market share that is interest in applying the offshore port and the day rate of the vessels. When the offshore wind market follows the tendency of developments of the last years, there is a market potential for an offshore port concept to reduce the construction costs. The main recommendations are to analyse the interest of potential port owners, perform a motion response into more detail and validate the financial assumptions.<br/

Development of Vessel Connectors for Coronary Bypass Surgery

Mechanical Maritime and Materials Engineerin

Improving the last mile in a public transport trip with automated vehicles using an agent based simulation model: A Delft case study

The last mile in a public transport trip appears to be one of the main deterrents in public transport to be competitive with other modes of transport. The reason for this bad performance of the last mile can be related to the slow and inflexible character of the last mile. Where PRT systems aspire to deliver an on demand, direct service to a passenger, they are bound to fixed separated infrastructure and would therefore face high investment costs for the application of PRT systems on the last mile. As automated vehicles can make use of any kind of road that is available the investment costs are considerably lower. The system presented in this thesis is a last mile transportation service operated by automated vehicles on existing infrastructure. Multiple operational strategies have been simulated using an agent based simulation model in AnyLogic. This simulation model has been applied on the case study Delft Zuid - Technological Innovation campus. For this case study a travel demand survey has been conducted, from which the results serve as one of the main inputs of the simulation model. The outcomes of the simulations indicate that relocating empty vehicles, intermediate charging have a positive effect on the performance of the system on the last mile without compromising any other system performance parameter. Pre-booking of vehicles (via a smartphone app) showed to be very beneficial with regard to the average waiting time for a passenger. However, as vehicles are locked for a longer period the system capacity decreases. The speed of the vehicles appeared one of the main determinants for the energy use of the vehicles and therefore the available system capacity. Speed variations have shown large reductions in the average travel time for a passenger.Transport & PlanningCivil Engineering and Geoscience