337 research outputs found
Gas dynamics in the inner few AU around the Herbig B[e] star MWC297: Indications of a disk wind from kinematic modeling and velocity-resolved interferometric imaging
We present near-infrared AMBER (R = 12, 000) and CRIRES (R = 100, 000)
observations of the Herbig B[e] star MWC297 in the hydrogen Br-gamma-line.
Using the VLTI unit telescopes, we obtained a uv-coverage suitable for aperture
synthesis imaging. We interpret our velocity-resolved images as well as the
derived two-dimensional photocenter displacement vectors, and fit kinematic
models to our visibility and phase data in order to constrain the gas velocity
field on sub-AU scales. The measured continuum visibilities constrain the
orientation of the near-infrared-emitting dust disk, where we determine that
the disk major axis is oriented along a position angle of 99.6 +/- 4.8 degrees.
The near-infrared continuum emission is 3.6 times more compact than the
expected dust-sublimation radius, possibly indicating the presence of highly
refractory dust grains or optically thick gas emission in the inner disk. Our
velocity-resolved channel maps and moment maps reveal the motion of the
Br-gamma-emitting gas in six velocity channels, marking the first time that
kinematic effects in the sub-AU inner regions of a protoplanetary disk could be
directly imaged. We find a rotation-dominated velocity field, where the blue-
and red-shifted emissions are displaced along a position angle of 24 +/- 3
degrees and the approaching part of the disk is offset west of the star. The
visibility drop in the line as well as the strong non-zero phase signals can be
modeled reasonably well assuming a Keplerian velocity field, although this
model is not able to explain the 3 sigma difference that we measure between the
position angle of the line photocenters and the position angle of the dust
disk. We find that the fit can be improved by adding an outflowing component to
the velocity field, as inspired by a magneto-centrifugal disk-wind scenario.Comment: 15 pages, 13 Figure
Charakterisierung von Sc(x)Al(1-x)N-Schichten für die Anwendung in der Magnetfeldsensorik
In dieser Bachelorarbeit erfolgt eine grundlegende Charakterisierung gesputterter Sc(x)Al(1-x)N-Schichten, welche als vielversprechendes piezoelektrisches Material für die Anwendung in der Magnetfeldsensorik im Bereich mikroelektromechanischer Systeme gelten. Durch die Einbindung eines bestimmten Anteils x an Scandium in die hexagonale Struktur des AlN erfolgt eine Änderung des Bindungscharakters im Materialsystem. Aus der so ansteigenden Fähigkeit der Polarisation in der Gitterstruktur resultiert ein starker piezoelektrischer Effekt, der zusammen mit einem magnetostriktiven Material als Magnetfeldsensor fungieren soll. Eine Reihe ausgewählter Sc(x)Al(1-x)N-Proben wird mittels Röntgenphotoelektronenspektroskopie auf ihre genaue Zusammensetzung, besonders auf den Scandiumgehalt x, untersucht. Anschließend wird in Abhängigkeit von x die Gitterkonstante c der hexagonalen Struktur mit Hilfe der Röntgendiffraktometrie ermittelt.
Zudem erfolgt eine optische Charakterisierung des Materials in Form der Raman- und Infrarotspektroskopie, um einen genauen Überblick der Änderung der Schwingungsbanden in Sc(x)Al(1-x)N in Abhängigkeit von x zu gewinnen.
Zusätzlich können anhand der gewonnen Daten Aussagen über die kristalline Qualität der Struktur getroffen werden. Zuletzt werden die gefundenen Ergebnisse der verschiedenen Messmethoden miteinander korreliert und verglichen.
Das weiterführende Ziel im Anschluss an diese Arbeit ist die genaue Quantifizierung der piezoelektrischen Reaktion von Sc(x)Al(1-x)N in mikroelektromechanischen Sensoren. Als Grundlage hierfür und für ein genaueres Verständnis des Materialsystems Sc(x)Al(1-x)N wurde diese Bachelorarbeit angefertigt.This bachelor thesis deals with the characterization of sputtered Sc(x)Al(1-x)N-layers, which promise a high piezoelectric response for implementation in microelectromechanical systems for measuring low magnetic fields. Within the integration of Scandium in the hexagonal structure of AlN, a change in binding character arises, resulting in the ability to create a high internal polarization and as a result, causing a wide piezoelectric reaction.
The X-Ray Photoemission spectroscopy, implemented in this thesis, allows determining the percentage x of Scandium in different samples of Sc(x)Al(1-x)N. Afterwards, the lattice parameter c of hexagonal Sc(x)Al(1-x)N is determined in dependence of x by X-Ray Diffraction.
Raman and Infrared spectroscopy allow making a point about the optical phonon modes in Sc(x)Al(1-x)N-alloys, influenced by Scandium-content x. On top, all measurements provide information about the crystal quality of the analyzed samples.
The next objective during this research-project is the quantification of the piezoelectric response of Sc(x)Al(1-x)N in microelectromechanical systems, for which this bachelor thesis presents one part of the fundamental research
A Critical Appraisal of "Surgery versus Physical Therapy for a Meniscal Tear and Osteoarthritis"
"Surgery versus Physical Therapy for a Meniscal Tear and Osteoarthritis" effectively employs a randomized, controlled trial and uses credible outcome measures and statistical analyses. Current literatures from primary sources are often used in the study's defense as well. Several limitations impact this study, however. 35% of physical therapy alone group patients crossed over to surgery within one year, severely impacting the aim and goal. Physical therapy protocols were also unstandardized regarding exercises and number of treatments. Efficacy of physical therapy treatment is thus hard to conclude. Overall, many takeaways can be gained from this study's results although its limitations limit these takeaways to generalizations
Analysis of the visually detectable wear progress on ball screws
The actual progression of pitting on ball screw drive spindles is not well known since previous studies have only relied on the investigation of indirect wear effects (e. g. temperature, motor current, structure-borne noise). Using images from a camera system for ball screw drives, this paper elaborates on the visual analysis of pitting itself. Due to its direct, condition-based assessment of the wear state, an image-based approach offers several advantages, such as: Good interpretability, low influence of environmental conditions, and high spatial resolution. The study presented in this paper is based on a dataset containing the entire wear progression from original condition to component failure of ten ball screw drive spindles. The dataset is being analyzed regarding the following parameters: Axial length, tangential length, and surface area of each pit, the total number of pits, and the time of initial visual appearance of each pit. The results provide evidence that wear development can be quantified based on visual wear characteristics. In addition, using the dedicated camera system, the actual course of the growth curve of individual pits can be captured during machine operation. Using the findings of the analysis, the authors propose a formula for standards-based wear quantification based on geometric wear characteristics
Leucine and Isoleucine derivatives as bioavailable alternatives for canonical amino acids in cell culture media to enable next generation bioprocesses
Please click Additional Files below to see the full abstract
Analysis of the Visually Detectable Wear Progress on Ball Screws
The actual progression of pitting on ball screw drive spindles is not well
known since previous studies have only relied on the investigation of indirect
wear effects (e. g. temperature, motor current, structure-borne noise). Using
images from a camera system for ball screw drives, this paper elaborates on the
visual analysis of pitting itself. Due to its direct, condition-based
assessment of the wear state, an image-based approach offers several
advantages, such as: Good interpretability, low influence of environmental
conditions, and high spatial resolution. The study presented in this paper is
based on a dataset containing the entire wear progression from original
condition to component failure of ten ball screw drive spindles. The dataset is
being analyzed regarding the following parameters: Axial length, tangential
length, and surface area of each pit, the total number of pits, and the time of
initial visual appearance of each pit. The results provide evidence that wear
development can be quantified based on visual wear characteristics. In
addition, using the dedicated camera system, the actual course of the growth
curve of individual pits can be captured during machine operation. Using the
findings of the analysis, the authors propose a formula for standards-based
wear quantification based on geometric wear characteristics
Pseudodoping of Metallic Two-Dimensional Materials by The Supporting Substrates
We demonstrate how hybridization between a two-dimensional material and its
substrate can lead to an apparent heavy doping, using the example of monolayer
TaS grown on Au(111). Combining calculations, scanning
tunneling spectroscopy experiments and a generic model, we show that strong
changes in Fermi areas can arise with much smaller actual charge transfer. This
mechanism, which we refer to as pseudodoping, is a generic effect for metallic
two-dimensional materials which are either adsorbed to metallic substrates or
embedded in vertical heterostructures. It explains the apparent heavy doping of
TaS on Au(111) observed in photoemission spectroscopy and spectroscopic
signatures in scanning tunneling spectroscopy. Pseudodoping is associated with
non-linear energy-dependent shifts of electronic spectra, which our scanning
tunneling spectroscopy experiments reveal for clean and defective TaS
monolayer on Au(111). The influence of pseudodoping on the formation of charge
ordered, magnetic, or superconducting states is analyzed.Comment: arXiv admin note: substantial text overlap with arXiv:1609.0022
Woodland and its use in central Bosnia during the late Neolithic. Results from anthracological investigations in the Visoko-basin
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