Fundamental limitations on Earth-like planet detection with Extremely Large Telescopes

We analyse the fundamental limitations for the detection of extraterrestrial planets with Extremely Large Telescopes. For this task, a coronagraphic device combined to a very high order wavefront correction system is required but not sufficient to achieve the $10^{-10}$ contrast level needed for detecting an Earth-like planet. The stellar residuals left uncorrected by the wavefront correction system need to be calibrated and subtracted. In this paper, we consider a general model including the dynamic phase aberrations downstream the wavefront correction system, the static phase aberrations of the instrument and some differential aberrations provided by the calibration unit. A rather optimistic case of a filled circular pupil and of a perfect coronagraph is elsewhere assumed. As a result of the analytical study, the limitation mostly comes from the static aberrations. Using numerical simulations we confirm this result and evaluate the requirements in terms of phase aberrations to detect Earth-like planets on Extremely Large Telescopes.Comment: 8 pages, 8 figures, accepted in A&

Opening a new window to other worlds with spectropolarimetry

A high level of diversity has already been observed among the planets of our own Solar System. As such, one expects extrasolar planets to present a wide range of distinctive features, therefore the characterisation of Earth- and super Earth-like planets is becoming of key importance in scientific research. The SEARCH (Spectropolarimetric Exoplanet AtmospheRe CHaracerisation) mission proposal of this paper represents one possible approach to realising these objectives. The mission goals of SEARCH include the detailed characterisation of a wide variety of exoplanets, ranging from terrestrial planets to gas giants. More specifically, SEARCH will determine atmospheric properties such as cloud coverage, surface pressure and atmospheric composition, and may also be capable of identifying basic surface features. To resolve a planet with a semi major axis of down to 1.4AU and 30pc distant SEARCH will have a mirror system consisting of two segments, with elliptical rim, cut out of a parabolic mirror. This will yield an effective diameter of 9 meters along one axis. A phase mask coronagraph along with an integral spectrograph will be used to overcome the contrast ratio of star to planet light. Such a mission would provide invaluable data on the diversity present in extrasolar planetary systems and much more could be learned from the similarities and differences compared to our own Solar System. This would allow our theories of planetary formation, atmospheric accretion and evolution to be tested, and our understanding of regions such as the outer limit of the Habitable Zone to be further improved.Comment: 23 pages, accepted for publication in Experimental Astronom

Probablistic Power Flow Simulations Allowing Temporary Current Overloading

This paper presents a probabilistic power flow model subject to connection temperature constraints. Renewable power generation is included and modelled stochastically in order to reflect its intermittent nature. In contrast to conventional models that enforce connection current constraints, short-term current overloading is allowed. Temperature constraints are weaker than current constraints, and hence the proposed model quantifies the overload risk more realistically. Using such a constraint is justified the more by the intermittent nature of the renewable power source. Allowing temporary current overloading necessitates the incorporation of a time domain in our model. This substantially influences the choice of model for the renewable power source, as we explain. Wind power is modelled by use of an ARMA model, and appropriate accelerations of the power flow solution technique are chosen. Several IEEE test case examples illustrate the more realistic risk analysis. An example shows that a current constraint model may overestimate these risks, which may lead to unnecessary over-investments by grid operators in grid connections

An HPLC method for the determination of salicylic acid, phenacetin and paracetamol in serum, with indications; two case-reports of intoxication

Acetylsalicylic acid, paracetamol and phenacetin are the most frequently used non-narcotic analgesics in The Netherlands. Two new case reports, an intoxication by salicylate ointment and a paracetamol overdose, are described. Indications and methods for the determination of these compounds are discussed. We describe a newHplc method for the simultaneous determination of salicylic acid, paracetamol and phenacetin in serum. Some other analgesics, like aminophenazone, phenazone and dipyrone can be determined by this method at the same time, 100Μl of serum is mixed with 600Μl methanol, centrifuged and an aliquot is injected into theRP-5C18Hplc column. A methanol—buffer pH=3.0 (40 + 50) mixture is used as mobile phase. Salicylamide can be used as internal standard. Coefficients of variation of 3.4% for salicylic acid, 1.9% for paracetamol and 3.4% for phenacetin are found and recoveries from calf's serum are 98–101% (n=10 per drug at 50 mg/l serum). In neonatology the sample volume can be decreased from 100Μl to 10Μl. This method has proved to be reliable and suitable in clinical pharmacy and toxicology

Assessing the impact of uncertainty on benchmarking the eco-efficiency of dairy farming using fuzzy data envelopment analysis

The dairy sector is challenged to increase its eco-efficiency, which means, minimizing environmental impacts, while maintaining economic viability. To quantify eco-ef fi ciency, multiple environmental and economic indicators are needed. Data envelopment analysis (DEA) has been used to evaluate the eco-efficiency of agricultural systems accounting for multiple indicators simultaneously. In practice, how-ever, data used to calculate the economic and environmental performance of dairy farms can contain high levels of uncertainty. Standard DEA is deterministic and does not consider data uncertainty. FuzzyDEA is a useful approach to account for uncertainties when benchmarking the eco-efficiency of dairy farming. In this study we therefore demonstrate how fuzzy DEA can be used to evaluate the eco-efficiency of dairy farming. We used a case study of 55 dairy farms from different regions across Western Europe. We used N surplus, P surplus, land use, energy use as the environmental indicators and gross margin as the economic indicator. We found that accounting for uncertainty around the value of environmental and economic indicators can affect substantially the eco-efficiency of evaluated farms. In addition, fuzzy DEA identified different set of peers compared to the peers of the standard DEA. All the aforementioned findings showed the importance of taking uncertainty into consideration in the benchmarking process, and how fuzzy DEA can be used to do so