5,129 research outputs found
Cryogenic scanning force microscopy of quantum Hall samples: Adiabatic transport originating in anisotropic depletion at contact interfaces
Anisotropic magneto resistances and intrinsic adiabatic transport features
are generated on quantum Hall samples based on an (Al,Ga)As/GaAs
heterostructure with alloyed Au/Ge/Ni contacts. We succeed to probe the
microscopic origin of these transport features with a cryogenic scanning force
microscope (SFM) by measuring the local potential distribution within the
two-dimensional electron system (2DES). These local measurements reveal the
presence of an incompressible strip in front of contacts with insulating
properties depending on the orientation of the contact/2DES interface line
relatively to the crystal axes of the heterostructure. Such an observation
gives another microscopic meaning to the term 'non-ideal contact' used in
context with the Landauer-B\"uttiker formalism applied to the quantum Hall
effect.Comment: 5 pages, 4 figure
Management of Acute GI Bleeding in Patients Who Refuse Blood or Blood Products
Background and Significance: The Gastroenterology consult service evaluates patients who are admitted to the hospital with gastrointestinal (GI) tract bleeding. Prompt endoscopic evaluation is the mainstay for the diagnosis and treatment of clinically significant GI tract bleeding and occurs in concert with the initiation of supportive measures, including replacement of lost blood, correction of coagulopathy, treatment of hemorrhagic shock, and stimulation of erythropoiesis. There have been several case reports of patients who exsanguinated from acute GI tract bleeding due to refusal of blood or blood products on religious grounds. Management of such patients presents many treatment and ethical challenges. The Jehovah\u27s Witnesses population literally interprets the Bible passages Genesis 9:4, But flesh with the life thereof, which is the blood thereof, shall ye not eat. and Leviticus 17: 15, And every soul that eateth that which died of itself, or that which was torn with beasts, whether it be one of your own country, or a stranger, he shall both wash his clothes, and bathe himself in water, and be unclean until the even: then shall he be clean. to mean that they should not ingest blood and thus they do not accept blood or blood products. Nonetheless, there are alternatives, albeit limited, to transfusion of human blood products for patients with acute blood loss secondary to GI tract bleeding. For example, research studies have demonstrated favorable outcomes following the use of recombinant factor Vila to treat anemia and achieve hemostasis (Boffard et. Al, 2005). In addition, as noted by Berend and Levi (2009), there are several unique lessons to be learned from the management of Jehovah\u27s Witnesses with GI tract bleeding, including learning how to seek and utilize alternative treatment options, and understand medical views and beliefs of patients from different cultures and religions. To date, there are no published guidelines that address the management of patients who refuse transfusion of blood or blood products for faith-based reasons. Purpose: To develop an evidence-based treatment protocol for the management of patients who refuse transfusion of blood or blood products for faith-based reasons. Methods: Current evidence was appraised and comparisons were made among the various treatment options for patients who refuse transfusion of blood or blood products for faith-based reasons. Using critical appraisal and synthesis, research studies were scored and beneficial interventions from high-quality studies were incorporated into the evidence-based treatment protocol. Practice recommendations were then organized into a treatment algorithm. Analyses: The algorithm was critiqued by an expert review panel and subsequently revised based on its comments and recommendations. The revised algorithm will be presented to the panel for final approval. Implications: This treatment algorithm will provide clinicians with an evidence-based guide for the medical management of patients who refuse transfusion of blood or blood product
SN2002kg -- the brightening of LBV V37 in NGC 2403
SN2002kg is a type IIn supernova, detected in October 2002 in the nearby
spiral galaxy NGC 2403. We show that the position of SN2002kg agrees within the
errors with the position of the LBV V37. Ground based and HST ACS images
however show that V37 is still present after the SN2002kg event. We compiled a
lightcurve of V37 which underlines the variablity of the object, and shows that
SN2002kg was the brightening of V37 and not a supernova. The recent brightening
is not a giant eruption, but more likely part of an S Dor phase. V37 shows
strong Halpha +[NII] emission in recent images and in the SN2002kg spectrum,
which we interprete as the signature of the presence of an LBV nebula. A
historic spectrum lacks emission, which may hint that we are witnessing the
formation of an LBV nebula.Comment: 4 pages, 5 figures, accepted in A&A Letter, paper with images in full
resolution at http://www.astro.ruhr-uni-bochum.de/kweis/publications.htm
Correlated electron tunneling through two separate quantum dot systems with strong capacitive interdot coupling
A system consisting of two independently contacted quantum dots with strong
electrostatic interaction shows interdot Coulomb blockade when the dots are
weakly tunnel coupled to their leads. It is studied experimentally how the
blockade can be overcome by correlated tunneling when tunnel coupling to the
leads increases. The experimental results are compared with numerical
renormalization group calculations using predefined (measured) parameters. Our
results indicate Kondo correlations due to the electrostatic interaction in
this double quantum dot system.Comment: 5 pages, 3 figures, published in Phys. Rev. Lett. Oct. 30t
Outflow or galactic wind: The fate of ionized gas in the halos of dwarf galaxies
Context: H\alpha images of star bursting irregular galaxies reveal a large
amount of extended ionized gas structures, in some cases at kpc-distance away
from any place of current star forming activity. A kinematic analysis of
especially the faint structures in the halo of dwarf galaxies allows insights
into the properties and the origin of this gas component. This is important for
the chemical evolution of galaxies, the enrichment of the intergalactic medium,
and for the understanding of the formation of galaxies in the early universe.
Aims: We want to investigate whether the ionized gas detected in two
irregular dwarf galaxies (NGC 2366 and NGC 4861) stays gravitationally bound to
the host galaxy or can escape from it by becoming a freely flowing wind.
Methods: Very deep H\alpha images of NGC 2366 and NGC 4861 were obtained to
detect and catalog both small and large scale ionized gas structures down to
very low surface brightnesses. Subsequently, high-resolution long-slit echelle
spectroscopy of the H\alpha line was performed for a detailed kinematic
analysis of the most prominent filaments and shells. To calculate the escape
velocity of both galaxies and to compare it with the derived expansion
velocities of the detected filaments and shells, we used dark matter halo
models.
Results: We detected a huge amount of both small scale (up to a few hundred
pc) and large scale (about 1-2 kpc of diameter or length) ionized gas
structures on our H\alpha images. Many of the fainter ones are new detections.
The echelle spectra reveal outflows and expanding bubbles/shells with
velocities between 20 and 110 km/s. Several of these structures are in
accordance with filaments in the H\alpha images. A comparison with the escape
velocities of the galaxies derived from the NFW dark matter halo model shows
that all gas features stay gravitationally bound.Comment: 15 pages, 13 figures, accepted for publication in A&
A novel mechanism for binding of galactose-terminated glycans by the C-type carbohydrate recognition domain in blood dendritic cell antigen 2
Blood dendritic cell antigen 2 (BDCA-2; also designated CLEC4C or CD303) is uniquely expressed on plasmacytoid dendritic cells. Stimulation of BDCA-2 with antibodies leads to an anti-inflammatory response in these cells, but the natural ligands for the receptor are not known. The C-type carbohydrate recognition domain in the extracellular portion of BDCA-2 contains a signature motif typical of C-type animal lectins that bind mannose, glucose, or GlcNAc, yet it has been reported that BDCA-2 binds selectively to galactose-terminated, biantennary N-linked glycans. A combination of glycan array analysis and binding competition studies with monosaccharides and natural and synthetic oligosaccharides have been used to define the binding epitope for BDCA-2 as the trisaccharide Galβ1–3/4GlcNAcβ1–2Man. X-ray crystallography and mutagenesis studies show that mannose is ligated to the conserved Ca2+ in the primary binding site that is characteristic of C-type carbohydrate recognition domains, and the GlcNAc and galactose residues make additional interactions in a wide, shallow groove adjacent to the primary binding site. As predicted from these studies, BDCA-2 binds to IgG, which bears galactose-terminated glycans that are not commonly found attached to other serum glycoproteins. Thus, BDCA-2 has the potential to serve as a previously unrecognized immunoglobulin Fc receptor
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