442 research outputs found
Constraining the circumbinary envelope of Z Canis Majoris via imaging polarimetry
No full textContext. Z CMa is a complex binary system composed of a Herbig Be and an FU Ori star. The Herbig star is surrounded by a dust cocoon of variable geometry, and the whole system is surrounded by an infalling envelope. Previous spectropolarimetric observations have reported a preferred orientation of the polarization angle, perpendicular to the direction of a very extended, parsec-sized jet associated with the Herbig star. Aims. The variability in the amount of polarized light has been associated to changes in the geometry of the dust cocoon that surrounds the Herbig star. We aim to constrain the properties of Z CMa by means of imaging polarimetry at optical wavelengths. Methods. Using ExPo, a dual-beam imaging polarimeter that operates at optical wavelengths, we have obtained imaging (linear) polarimetric data of Z CMa. Our observations were secured during the return to quiescence after the 2008 outburst. Results. We detect three polarized features over Z CMa. Two of these features are related to the two jets reported in this system: the large jet associated to the Herbig star, and the micro-jet associated to the FU Ori star. Our results suggest that the micro-jet extends to a distance ten times longer than reported in previous studies. The third feature suggests the presence of a hole in the dust cocoon that surrounds the Herbig star of this system. According to our simulations, this hole can produce a pencil beam of light that we see scattered off the low-density envelope surrounding the system
Towards rational axillary treatment in relation to neoadjuvant therapy in breast cancer
No full textAbstract not availableM.E. Straver, E.J.Th. Rutgers, N.S. Russell, H.S.A. Oldenburg, S. Rodenhuis, J. Wesseling, A. Vincent, M.T.F.D. Vrancken Peeter
FDG PET/CT during neoadjuvant chemotherapy may predict response in ER-positive/HER2-negative and triple negative, but not in HER2-positive breast cancer
No full textAbstract not availableBas B. Koolen, Kenneth E. Pengel, Jelle Wesseling, Wouter V. Vogel, Marie-Jeanne T.F.D. Vrancken Peeters, Andrew D. Vincent, Kenneth G.A. Gilhuijs, Sjoerd Rodenhuis, Emiel J.Th. Rutgers, Renato A. Valdés Olmo
Imaging the circumstellar environment of the young T Tauri star SU Aurigae
No full textThe circumstellar environments of classical T Tauri stars are challenging to directly image because of their high star-to-disk contrast ratio. One method to overcome this is by using imaging polarimetry where scattered and consequently polarised starlight from the star’s circumstellar disk can be separated from the unpolarised light of the central star. We present images of the circumstellar environment of SU Aur, a classical T Tauri star at the transition of T Tauri to Herbig stars. The images directly show that the disk extends out to 500 AU with an inclination angle of ~50°. Using interpretive models, we derived very small grains in the surface layers of its disk, with a very steep size- and surface-density distribution. Additionally, we resolved a large and extended nebulosity in our images that is most likely a remnant of the prenatal molecular cloud. The position angle of the disk, determined directly from our images, rules out a polar outflow or jet as the cause of this large-scale nebulosity
The color dependent morphology of the post-AGB star HD 161796
No full textContext. Many protoplanetary nebulae show strong asymmetries in their surrounding shells, pointing to asymmetries during the mass loss phase. Questions concerning the origin and the onset of deviations from spherical symmetry are important for our understanding of the evolution of these objects. Here we focus on the circumstellar shell of the post-AGB star HD 161796. Aims. We aim to detect signatures of an aspherical outflow, and to derive its properties. Methods. We used the imaging polarimeter the Extreme Polarimeter (ExPo), a visitor instrument at the William Herschel Telescope, to accurately image the dust shell surrounding HD 161796 in various wavelength filters. Imaging polarimetry allows us to separate the faint, polarized, light that comes from circumstellar material from the bright, unpolarized, light from the central star. Results. The shell around HD 161796 is highly aspherical. A clear signature of an equatorial density enhancement can be seen. This structure is optically thick at short wavelengths and changes its appearance to optically thin at longer wavelengths. In the classification of the two different appearances of planetary nebulae from HST images it changes from being classified as DUst-Prominent Longitudinally-EXtended (DUPLEX) at short wavelengths to star-obvious low-level-elongated (SOLE) at longer wavelengths. This strengthens the interpretation that these two appearances are manifestations of the same physical structure. Furthermore, we find that the central star is hotter than often assumed and the relatively high observed reddening is a consequence of circumstellar rather than interstellar extinction
The Undular Hydraulic Jump: On a numerical method for the computation of flows with curved streamlines
No full textFrom the theory composed of the method of characteristics and the set of all possible continuous ancillary conditions a closed theory is formed by introducing step functions together with overall mass and momentum conservation equations. However, this representation cannot be called realistic when the jump has the form of the undular hydraulic jump. The objective of the present study may novw be stated as follows: 1. to provide a closed and realistic theory which is able to describe the short wave radiation behind the hydraulic jump; 2. to investigate the reality of the usual "closure" of the quasi-linear wave theory, by proceeding to the next approxilnation that is provided by 1. As these aims are to be attained using a digital machine, they imply the construction of a closed and realistic numerical theory that will provide "contradictory" results under those conditions that provide instability in the hydraulic jump, manifest as some breaking-down of the short wave motion into turbulent motion.Hydraulic EngineeringCivil Engineering and Geoscience
Probing nanomotion and comparing antibiotic efficacy of a single E. coli bacterium on silicon and graphene
No full textWith the incline of multidrug resistant bacteria due to the widespread use of antibiotics, there has been an ongoing search for a faster and more effective method to test the effect of antibiotics on bacteria. With current techniques for investigation of bacterial resistance requiring a minimum of 24 hours to complete, a new technique is essential to reduce the widespread misuse of antibiotics worldwide. In the last decade, new methods of this so-called Antibiotic Susceptibility Testing have been on the rise, with an emphasis on the use of nanomechanical oscillators as highly sensitive sensors. In this thesis, a novel method based on cavities in silicon substrates is introduced to detect the motion of a single motile bacterium and is compared to a highly sensitive sensor based on graphene membranes. A sensor with bacteria attached will exhibit random oscillations and these oscillations can be monitored with a laser. The rigid silicon substrates are intuitively not showing any oscillations. Nonetheless, the motility of a bacterium can still be observed by the changes in the laser path. By using an interferometric setup and monitoring the fluctuation in the voltage signal, coming from bacterial biophysical processes, the Signal-to-Noise-Ratio is determined. The amplitude increase in the fluctuation of the signal is evidently correlated with the motility of the bacteria and is demonstrated to show an increasing trend when presented with a deterministically known topographical location of the bacteria. Subsequently, the ability to detect motile cells enables the capabilities of Antibiotic Susceptibility Testing on these substrates, by monitoring the change in motion of the bacteria prior and post exposure to an effective antibiotic. The motion change, due to antibiotic exposure, is observed to show a significant difference even for a single bacterium, which opens up opportunities for an elementary non-invasive monitoring tool based on silicon.Mechanical Engineering | Dynamics of Micro and Nano System
Sturen op transformatie: Een handreiking voor publieke en private partijen, teneinde transformatie van leegstaande kantoren te bevorderen
No full textTientallen gebouwen, honderden etages en miljoenen vierkante meters kantoorruimte staan leeg. De huidige Nederlandse kantorenmarkt heeft te maken met problemen. Er is sprake van een grote leegstand door een mismatch tussen vraag en aanbod. Daarnaast is er een grote behoefte aan nieuwe woonruimte voor bepaalde specifieke doelgroepen als studenten, jongeren en ouderen. Transformatie van leegstaande kantoren tot woningen kan een oplossing zijn voor bovenstaande problemen. Hiermee zou men twee vliegen in één klap kunnen slaan. Echter wordt transformatie nog beperkt toegepast. Er zijn verschillende mogelijkheden om transformatie van leegstaande kantoren te bevorderen, zowel vanuit de markt als vanuit de overheid. Dit rapport toont de resultaten van een onderzoek naar geschikte sturingsmiddelen om transformatie te stimuleren. Het betreft een verzameling van sturingsmiddelen, welke ingezet kunnen worden door zowel de markt- als de overheidspartijen. Het rapport beschrijft de reeds bestaande en nieuwe inzichten, waarin de mogelijkheden en een twaalftal potentiële sturingsmiddelen worden aangegeven.Design and Construction ManagementReal Estate & HousingArchitectur
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