Ionospheric range-rate effects in satellite-to-satellite tracking

Investigation of ionospheric range and range-rate corrections in satellite-to-satellite tracking were investigated. Major problems were cited and the magnitude of errors that have to be considered for communications between satellites and related experiments was defined. The results point to the need of using a sophisticated modeling approach incorporating daily solar data, and where possible actual ionospheric measurements as update information, as a simple median model cannot possibly account for the complex interaction of the many variables. The findings provide a basis from which the residual errors can be estimated after ionospheric modeling is incorporated in the reduction. Simulations were performed for satellites at various heights: Apollo, Geos, and Nimbus tracked by ATS-6; and in two different geometric configurations: coplanar and perpendicular orbits

A Multistage Stochastic Programming Approach to the Dynamic and Stochastic VRPTW - Extended version

We consider a dynamic vehicle routing problem with time windows and stochastic customers (DS-VRPTW), such that customers may request for services as vehicles have already started their tours. To solve this problem, the goal is to provide a decision rule for choosing, at each time step, the next action to perform in light of known requests and probabilistic knowledge on requests likelihood. We introduce a new decision rule, called Global Stochastic Assessment (GSA) rule for the DS-VRPTW, and we compare it with existing decision rules, such as MSA. In particular, we show that GSA fully integrates nonanticipativity constraints so that it leads to better decisions in our stochastic context. We describe a new heuristic approach for efficiently approximating our GSA rule. We introduce a new waiting strategy. Experiments on dynamic and stochastic benchmarks, which include instances of different degrees of dynamism, show that not only our approach is competitive with state-of-the-art methods, but also enables to compute meaningful offline solutions to fully dynamic problems where absolutely no a priori customer request is provided.Comment: Extended version of the same-name study submitted for publication in conference CPAIOR201

Higher biomass accumulation by increasing phosphoribosylpyrophosphate synthetase activity in Arabidopsis thaliana and Nicotiana tabacum

Plants are able to produce all the organic compounds required for development and growth. As developmental processes and metabolic pathways use a common resource pool, the tight regulation of the distribution of metabolites between growth, production of defence compounds and storage products can be assumed. A transgenic approach was used to investigate the importance of supplying the key intermediate phosphoribosylpyrophosphate (PRPP) for plant growth and biomass accumulation in the model plant Arabidopsis thaliana and in Nicotiana tabacum. For this purpose, the Ashbya gossypii genes coding for either PRPP synthetase (PRS) or a mutated variant of the same gene were over-expressed under the control of a constitutive promoter. It was shown that increased PRS activity in A. thaliana or N. tabacum leads to a substantial increase in biomass accumulation under different standardized growth conditions. Growth enhancement was accompanied by significant changes in the amount of sugars and other metabolites. This study provides evidence that the supply of PRPP co-limits growth rates, and has obvious implications for biotechnological strategies aiming to increase plant biomass as an alternative renewable energy source

A 4-D dataset for validation of crystal growth in a complex three-phase material, ice cream

Four dimensional (4D, or 3D plus time) X-ray tomographic imaging of phase changes in materials is quickly becoming an accepted tool for quantifying the development of microstructures to both inform and validate models. However, most of the systems studied have been relatively simple binary compositions with only two phases. In this study we present a quantitative dataset of the phase evolution in a complex three-phase material, ice cream. The microstructure of ice cream is an important parameter in terms of sensorial perception, and therefore quantification and modelling of the evolution of the microstructure with time and temperature is key to understanding its fabrication and storage. The microstructure consists of three phases, air cells, ice crystals, and unfrozen matrix. We perform in situ synchrotron X-ray imaging of ice cream samples using in-line phase contrast tomography, housed within a purpose built cold-stage (-40 to +20oC) with finely controlled variation in specimen temperature. The size and distribution of ice crystals and air cells during programmed temperature cycling are determined using 3D quantification. The microstructural evolution of three-phase materials has many other important applications ranging from biological to structural and functional material, hence this dataset can act as a validation case for numerical investigations on faceted and non-faceted crystal growth in a range of materials

Active flow control systems architectures for civil transport aircraft

Copyright @ 2010 American Institute of Aeronautics and AstronauticsThis paper considers the effect of choice of actuator technology and associated power systems architecture on the mass cost and power consumption of implementing active flow control systems on civil transport aircraft. The research method is based on the use of a mass model that includes a mass due to systems hardware and a mass due to the system energy usage. An Airbus A320 aircraft wing is used as a case-study application. The mass model parameters are based on first-principle physical analysis of electric and pneumatic power systems combined with empirical data on system hardware from existing equipment suppliers. Flow control methods include direct fluidic, electromechanical-fluidic, and electrofluidic actuator technologies. The mass cost of electrical power distribution is shown to be considerably less than that for pneumatic systems; however, this advantage is reduced by the requirement for relatively heavy electrical power management and conversion systems. A tradeoff exists between system power efficiency and the system hardware mass required to achieve this efficiency. For short-duration operation the flow control solution is driven toward lighter but less power-efficient systems, whereas for long-duration operation there is benefit in considering heavier but more efficient systems. It is estimated that a practical electromechanical-fluidic system for flow separation control may have a mass up to 40% of the slat mass for a leading-edge application and 5% of flap mass for a trailing-edge application.This work is funded by the Sixth European Union Framework Programme as part of the AVERT project (Contract No. AST5-CT-2006-030914

Phase II study of a short course of weekly high-dose cisplatin combined with long-term oral etoposide in metastatic colorectal cancer.

In a phase I study of weekly administered cisplatin combined with oral etoposide, we observed a partial response in 4 out of 11 patients with metastatic colorectal cancer. Subsequently, we performed a phase II study to investigate the activity of this combination as first-line treatment in this disease. Fourteen patients with metastatic colorectal cancer were enrolled in this study. Treatment consisted of cisplatin, administered in 3% sodium chloride, at a dose of 70 mg m-2 on days 1, 8 and 15 and days 29, 36 and 43 combined with oral etoposide 50 mg absolute dose daily on days 1-15 of both courses. Patients with stable disease or better continued treatment with etoposide 50 mg m-2 orally on days 1-21 every 28 days. A partial response was observed in two patients with liver metastases (14%; 95% confidence limits 2-42%) for 30 and 32 weeks. Five patients had stable disease. Toxicity consisted mainly of anaemia, leucocytopenia, nausea and vomiting. Tinnitus was reported by six patients. The activity of the combination cisplatin-oral etoposide in the schedule is only minimal in metastatic colorectal cancer