2,799 research outputs found
Correlated fluctuations in the exciton dynamics and spectroscopy of DNA
The absorption of ultraviolet light creates excitations in DNA, which
subsequently start moving in the helix. Their fate is important for an
understanding of photo damage, and is determined by the interplay of electronic
couplings between bases and the structure of the DNA environment. We model the
effect of dynamical fluctuations in the environment and study correlation,
which is present when multiple base pairs interact with the same mode in the
environment. We find that the correlations strongly affect the exciton
dynamics, and show how they are observed in the decay of the anisotropy as a
function of a coherence and a population time in a non-linear optical
experiment
The international fight against terrorism and the protection of human rights: with recommendations to the German government and parliament
Die englische Kurzfassung der Studie "Internationale Terrorismusbekämpfung und Menschenrechte" thematisiert wesentliche Entwicklungen der Terrorismusbekämpfung im Rahmen der Vereinten Nationen, der EU und der G8-Staatengruppe in den Jahren 2003 und 2004. Die Studie schließt mit zehn Empfehlungen an die deutsche Außen- und Verteidigungspolitik
Involvement of BMP-2, TGF-ß2 and TGF-ß3 Signaling in Initial and Early Stages of Heterotopic Ossification in a rat Experimental Model
This study focused on the localization and expression of bone morphogenetic protein 2 (BMP-2) and different isoforms of transforming growth factor s (TGF-s1, TGF-s2 and TGF-s3) in the initial and early stages of heterotopic ossification (HO) employing an animal model mimicking the situation after total hip arthroplasty (THA). Bone growth was induced in rats using s-tricalcium phosphate implants immersed either in osteoinductive rhBMP-2 solution or in saline and implanted at the site where the HO is usually expected to develop after THA. Implants were removed at 3 or 21 days after the operation and handled according to stereology principles. mRNA expression and protein staining of growth factors in different types of tissues was determined by in situ hybridization and immunohistochemistry, respectively. After three days, TGF-s3 content in the undifferentiated mesenchymal-like cells in the rhBMP-2 treated implants was, as assessed by immunohistochemistry, 49.6% higher compared to the saline treated group (p=0.024). This was also supported by in situ hybridization of mRNA of TGF-s3, which showed stronger expression in rhBMP-2 treated group. Immunohistochemical investigation showed that after 21 days the connective tissue in the rhBMP-2 treated implants contained more TGF-s1, TGF-s2 and TGF-s3, compared to BMP-2 and osteoblasts contained significantly (27.2%) more TGF-s3 compared to TGF-s1 (p=0.045). In the formed HO the proportion of the TGF-s2 and TGF-s3 producing bone tissue was increased by 32.1% and 47.8% respectively, compared to the TGF-s1 producing bone tissue (p=0.007 and p=0.006) and although this difference was not so clear at mRNA level, this suggests that TGF-s2 and TGF-s3 signaling seem to play an important role during initial and early stages of HO formation.
A haplome alignment and reference sequence of the highly polymorphic Ciona savignyi genome
The high degree of polymorphism in the genome of the sea squirt Ciona savignyi complicated the assembly of sequence contigs, but a new alignment method results in a much improved sequence
Visible-to-telecom quantum frequency conversion of light from a single quantum emitter
Quantum frequency conversion (QFC), a nonlinear optical process in which the
frequency of a quantum light field is altered while conserving its
non-classical correlations, was first demonstrated 20 years ago. Meanwhile, it
is considered an essential tool for the implementation of quantum repeaters
since it allows for interfacing quantum memories with telecom-wavelength
photons as quantum information carriers. Here we demonstrate efficient (>30%)
QFC of visible single photons (711 nm) emitted by a quantum dot (QD) to a
telecom wavelength (1,313 nm). Analysis of the first and second-order coherence
before and after wavelength conversion clearly proves that important
properties, such as the coherence time and photon antibunching, are fully
conserved during the frequency translation process. Our findings underline the
great potential of single photon sources on demand in combination with QFC as a
promising technique for quantum repeater schemes.Comment: 11 pages, 4 figure
- …