University of Vienna

About: University of Vienna is a education organization based out in Vienna, Austria. It is known for research contribution in the topics: Population & Stars. The organization has 44686 authors who have published 95840 publications receiving 2907492 citations.

Squeezed light from a silicon micromechanical resonator

Abstract: Monitoring a mechanical object’s motion, even with the gentle touch of light, fundamentally alters its dynamics. The experimental manifestation of this basic principle of quantum mechanics, its link to the quantum nature of light and the extension of quantum measurement to the macroscopic realm have all received extensive attention over the past half-century. The use of squeezed light, with quantum fluctuations below that of the vacuum field, was proposed nearly three decades ago as a means of reducing the optical read-out noise in precision force measurements. Conversely, it has also been proposed that a continuous measurement of a mirror’s position with light may itself give rise to squeezed light. Such squeezed-light generation has recently been demonstrated in a system of ultracold gas-phase atoms whose centre-of-mass motion is analogous to the motion of a mirror. Here we describe the continuous position measurement of a solid-state, optomechanical system fabricated from a silicon microchip and comprising a micromechanical resonator coupled to a nanophotonic cavity. Laser light sent into the cavity is used to measure the fluctuations in the position of the mechanical resonator at a measurement rate comparable to its resonance frequency and greater than its thermal decoherence rate. Despite the mechanical resonator’s highly excited thermal state (10^4 phonons), we observe, through homodyne detection, squeezing of the reflected light’s fluctuation spectrum at a level 4.5 ± 0.2 percent below that of vacuum noise over a bandwidth of a few megahertz around the mechanical resonance frequency of 28megahertz. With further device improvements, on-chip squeezing at significant levels should be possible, making such integrated microscale devices well suited for precision metrology applications.

Parabolic Geometries I

Abstract: The first monograph on parabolic geometry in the literature following several ground-braking results achieved by the authors and their collaborators in the last two decades. The volume will be followed by the second one focused on mathematical applications

Podoplanin, novel 43-kd membrane protein of glomerular epithelial cells, is down-regulated in puromycin nephrosis.

Abstract: Puromycin aminonucleoside nephrosis (PAN), a rat model of human minimal change nephropathy, is characterized by extensive flattening of glomerular epithelial cell (podocyte) foot processes and by severe proteinuria For comparison of expression of glomerular membrane proteins of normal and PAN rats, a membrane protein fraction of isolated rat glomeruli was prepared and monoclonal antibodies were raised against it An IgG-secreting clone designated LF3 was selected that specifically immunolabeled podocytes of normal but not of PAN rats The antigen of LF3 IgG was identified as a 43-kd glycoprotein Molecular cloning of its cDNA was performed in a delta gt11 expression library prepared from mRNA of isolated rat glomeruli The predicted amino acid sequence indicated a 166-amino-acid integral membrane protein with a single membrane-spanning domain, two potential phosphorylation sites in its short cytoplasmic tail, and six potential O-glycosylation sites in the large ectodomain High amino acid sequence identities were found to membrane glycoproteins of rat lung and bone and mouse thymus epithelial cells as well as to a phorbol-ester-induced protein in a mouse osteoblast cell line and to a canine influenza C virus receptor In PAN, expression of this 43-kd protein was selectively reduced to < 30%, as determined by quantitative immunogold electron microscopy, immunoblotting, and Northern blotting These data provide evidence that transcription of the 43-kd transmembrane podocyte glycoprotein is specifically down-regulated in PAN To indicate that this protein could be associated with transformation of arborized foot processes to flat feet (Latin, pes planus) we have called it podoplanin

The ecological coherence of high bacterial taxonomic ranks

Abstract: The species is a fundamental unit of biological organization, but its relevance for Bacteria and Archaea is still hotly debated. Even more controversial is whether the deeper branches of the ribosomal RNA-derived phylogenetic tree, such as the phyla, have ecological importance. Here, we discuss the ecological coherence of high bacterial taxa in the light of genome analyses and present examples of niche differentiation between deeply diverging groups in terrestrial and aquatic systems. The ecological relevance of high bacterial taxa has implications for bacterial taxonomy, evolution and ecology.