346 research outputs found
Formation of runoff at the hillslope scale during intense precipitation
On 60 m<sup>2</sup> hillslope plots, at 18 mainly grassland locations in Switzerland rain was applied at rates of 50–100 mm/h for between 3 and 6 h. The generated flows were measured, including overland flow, near surface and subsurface flow 0.5–1.3 m below the surface. At some locations less than 2% of the rain flowed down the slope either on or below the surface, whereas at some others more than 90% of the rain ran off. At the majority of sites most runoff was overland flow, though at a few sites subsurface flow, usually via macropores was dominant. Data collected during each of 48 high intensity sprinkling experiments were used to distinguish, which processes were dominant in each experiment. Which dominant and subsidiary processes occurred depended on interactions between infiltration rate, change in soil water storage and drainage of the soil water. These attributes were often not directly linked to parameters usually considered important like vegetation, slope, soil clay content and antecedent soil moisture. Considering the structure of the soil in combination with these attributes, process determination was in many cases fairly straightforward, indicating the possibility of reliably predicting runoff processes at a site. However, at some sites, effects occurred that were not easily recognizable and led to surprising results
The CORALIE survey for southern extra-solar planets XV. Discovery of two eccentric planets orbiting HD4113 and HD156846
We report the detection of two very eccentric planets orbiting HD4113 and
HD156846 with the CORALIE Echelle spectrograph mounted on the 1.2-m Euler Swiss
telescope at La Silla. The first planet, HD4113b, has minimum mass of
, a period of days and an
eccentricity of . It orbits a metal rich G5V star at
AU which displays an additional radial velocity drift of 28 m s/yr
observed during 8 years. The combination of the radial-velocity data and the
non-detection of any main sequence stellar companion in our high contrast
images taken at the VLT with NACO/SDI, characterizes the companion as a
probable brown dwarf or as a faint white dwarf. The second planet, \object{HD
156846 b}, has minimum mass of M, a period
of days, an eccentricity of and is located
at AU from its parent star. HD156846 is a metal rich G0 dwarf and is
also the primary of a wide binary system ( AU, years). Its
stellar companion, \object{IDS 17147-1914 B}, is a M4 dwarf. The very high
eccentricities of both planets can be explained by Kozai oscillations induced
by the presence of a third object.Comment: 4 pages, 5 figures, A&A Letter accepte
A combined field and numerical approach to investigate flow processes in natural macroporous soils under extreme precipitation
International audienceA procedure involving simultaneous experimental and numerical research is described for the purposes of understanding the mechanisms involved when extreme precipitation is transformed to flood stream discharge. It is shown that experiments and model applications by themselves are not sufficient for process identification, but that their combined application provides considerable insight into the subsurface flow processes. The proposed approach is unconventional in that a numerical model, based on stringent continuity and momentum criteria, is used as a tool for process identification only. Unlike other studies, it is not intended to demonstrate the applicability of the utilised model for general hydrological applications, or to provide evidence of the suitability of particular model simplifications. Rather, different and sometimes conflicting model realisations are used to examine the plausibility of flow processes which may occur on natural hill slopes. Hereby, small scale effects such as those relating to the mechanisms of water entry into the macropores, and the movement of water to the surrounding matrix are identified from the results of well instrumented field experiments
Solving the riddle of the bright mismatches: hybridization in oligonucleotide arrays
HDONA technology is predicated on two ideas. First, the differential between
high-affinity (perfect match, PM) and lower-affinity (mismatch, MM) probes is
used to minimize cross-hybridization. Second, several short probes along the
transcript are combined, introducing redundancy. Both ideas have shown problems
in practice: MMs are often brighter than PMs, and it is hard to combine the
pairs because their brightness often spans decades. Previous analysis suggested
these problems were sequence-related; publication of the probe sequences has
permitted us an in-depth study of this issue. Our results suggest that
fluorescently labeling the nucleotides interferes with mRNA binding, causing a
catch-22 since, to be detected, the target mRNA must both glow and stick to its
probe: without labels it cannot be seen even if bound, while with too many it
won't bind. We show that this conflict causes much of the complexity of HDONA
raw data, suggesting that an accurate physical understanding of hybridization
by incorporating sequence information is necessary to perfect microarray
analysis.Comment: 4 figure
Optimierung einer Batch-Destillationskolonne unter Unsicherheiten basierend auf Messungen
C. Welz, B. Srinivasan, D. Bonvin Laboratoire dâAutomatique Ecole Polytechnique FĂ©dĂ©rale de Lausanne CH-1015 Lausanne, Schweiz O. Naef DĂ©partement de Chimie Ecole dâIngĂ©nieurs de Fribourg CH-1705 Fribourg, Schweiz Optimierung einer Batch-Destillationskolonne unter Unsicherheiten basierend auf Messungen Das Ziel der dynamischen Optimierung von binĂ€ren Batch-Destillationskolonnen ist die Maximierung der Destillatmenge am Ende einer Charge bei gleichzeitiger ErfĂŒllung der Endpunktbedingung fĂŒr die Reinheit des Destillats. Das optimale Steuerungsprofil fĂŒr das interne RĂŒcklaufverhĂ€ltnis (0 †r †1) wird durch 2 Intervalle angenĂ€hert: 1) Anlaufphase mit vollem RĂŒcklauf (r = 1), 2) Destillationsphase zur Produktion des Destillats (0 †r †1). I m Fall von Prozessunsicherheiten muss eine konservative und suboptimale ProzessfĂŒhrungsstrategie gewĂ€hlt werden, um die Endpunktbedingung zu erfĂŒllen. Anstelle einer konservativen Strategie schlĂ€gt dieser Beitrag die Implementierung der notwendigen OptimalitĂ€tsbedingungen vor, die aus Rand- und SensibilitĂ€tsBedingungen bestehen. Entscheidend fĂŒr das gegebene Optimierungsproblem ist es, d i e Randbedingungen zu erfĂŒllen, insbesondere die Endpunktbedingung. Die Endpunktbedingung fĂŒr die Reinheit des Destillats wird unter Verwendung von Messungen aktiv gehalten. Dies kann wĂ€hrend einer Charge durch die Verfolgung eines Referenzprofils fĂŒr die Reinheit des Destillats realisiert werden. Anstatt ein Modell zu aktualisieren, welches die Endpunktbedingung wĂ€hrend der Destillation voraussagt, wird das System durch V e r f o l g u n g des Referenzprofils zu der Endpunktbedingung gefĂŒhrt. Dieses R e f e r e n z p r o f i l wird mit Hilfe eines Tendenzmodells des Systems bestimmt. U n s i c h e r h e i t e n in der Verdampfungsrate werden durch eine Vorregelung in AbhĂ€ngigkeit von der Destillatmenge kompensiert, welche den Fortschritt der Destillation charakterisiert. Die Methode ist in der Lage, die KonservativitĂ€t zu reduzieren und die ProduktivitĂ€t u n m i t t e l b a r zu steigern. Abbildung 1 zeigt die Verfolgung eines linearen Referenzprofils fĂŒr die Reinheit des Destillats in einer Kolonne im LabormaĂstab. GegenĂŒber einer suboptimalen Fahrweise mit konstanter Destillatzusammensetzung kann der Ertrag dabei um 11% gesteigert werden. Abbildung 1: Verfolgung einer Referenz fĂŒr die Destillatzusammensetzung mit dem Ziel, die Endpunktbedingung zu erfĂŒllen
The CORALIE survey for southern extrasolar planets. XVI. Discovery of a planetary system around HD 147018 and of two long period and massive planets orbiting HD 171238 and HD 204313
We report the detection of a double planetary system around HD 140718 as well
as the discovery of two long period and massive planets orbiting HD 171238 and
HD 204313. Those discoveries were made with the CORALIE Echelle spectrograph
mounted on the 1.2-m Euler Swiss telescope located at La Silla Observatory,
Chile. The planetary system orbiting the nearby G9 dwarf HD 147018 is composed
of an eccentric inner planet (e=0.47) with twice the mass of Jupiter (2.1 MJup
) and with an orbital period of 44.24 days. The outer planet is even more
massive (6.6 MJup) with a slightly eccentric orbit (e=0.13) and a period of
1008 days. The planet orbiting HD 171238 has a minimum mass of 2.6 MJup, a
period of 1523 days and an eccentricity of 0.40. It orbits a G8 dwarfs at 2.5
AU. The last planet, HD 204313 b, is a 4.0 MJup -planet with a period of 5.3
years and has a low eccentricity (e = 0.13). It orbits a G5 dwarfs at 3.1 AU.
The three parent stars are metal rich, which further strengthened the case that
massive planets tend to form around metal rich stars.Comment: 6 pages, 6 figures, accepted for publication in A&
Exploring the transcriptional landscape of plant circadian rhythms using genome tiling arrays
BACKGROUND Organisms are able to anticipate changes in the daily environment with an internal oscillator know as the circadian clock. Transcription is an important mechanism in maintaining these oscillations. Here we explore, using whole genome tiling arrays, the extent of rhythmic expression patterns genome-wide, with an unbiased analysis of coding and noncoding regions of the Arabidopsis genome. RESULTS As in previous studies, we detected a circadian rhythm for approximately 25% of the protein coding genes in the genome. With an unbiased interrogation of the genome, extensive rhythmic introns were detected predominantly in phase with adjacent rhythmic exons, creating a transcript that, if translated, would be expected to produce a truncated protein. In some cases, such as the MYB transcription factor AT2G20400, an intron was found to exhibit a circadian rhythm while the remainder of the transcript was otherwise arrhythmic. In addition to several known noncoding transcripts, including microRNA, trans-acting short interfering RNA, and small nucleolar RNA, greater than one thousand intergenic regions were detected as circadian clock regulated, many of which have no predicted function, either coding or noncoding. Nearly 7% of the protein coding genes produced rhythmic antisense transcripts, often for genes whose sense strand was not similarly rhythmic. CONCLUSIONS This study revealed widespread circadian clock regulation of the Arabidopsis genome extending well beyond the protein coding transcripts measured to date. This suggests a greater level of structural and temporal dynamics than previously known
Montanlandschaft Oberhalbstein â prĂ€historische Kupferproduktion in GraubĂŒnden
Seit Jahrzehnten als prĂ€historisches Bergbaugebiet bekannt, war das Oberhalbstein in den vergangenen Jahren erstmals Gegenstand systematischer montanarchĂ€ologischer Forschungen. Dabei wurden nicht nur Dutzende neue Fundstellen entdeckt, sondern erstmals auch zentrale VerhĂŒttungsbefunde wie Ăfen und Röstbette ausgegraben. Zudem konnten gleich mehrere Kupferbergwerke aus der Bronze- und Eisenzeit untersucht werden â eine schweizweite Premiere! Dank ausfĂŒhrlicher GelĂ€ndearbeiten, Materialauswertungen und Laboranalysen kann nun der gesamte «Oberhalbstein-Prozess» vom Erz bis zum Metall rekonstruiert werden
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