We investigate the impact of the Petermann-excess-noise factor K>/=1 on the possibility of intensity noise squeezing of laser light below the standard quantum limit. Using an N-mode model, we show that squeezing is limited to a floor level of 2(K-1) times the shot noise limit. Thus, even a modest Petermann factor significantly impedes squeezing, which becomes impossible when K>/=1.5. This appears as a serious limitation for obtaining sub-shot-noise light from practical semiconductor lasers. We present experimental evidence for our theory. 相似文献
Successful application of gene silencing approaches critically depends on systems that are able to safely and efficiently deliver genetic material such as small interfering RNA (siRNA). Due to their beneficial well‐defined dendritic nanostructure, self‐assembling dendrimers are emerging as promising nanovectors for siRNA delivery. However, these kinds of vectors are plagued with stability issues, especially when considered for in vivo applications. Therefore, in the present study, disulfide‐based temporarily fixed micelles are developed that can degrade upon reductive conditions, and thus lead to efficient cargo release. In detail, lipoic acid‐derived crosslinked micelles are synthesized based on small polymerizable dendritic amphiphiles. Particularly, one candidate out of this series is able to efficiently release siRNA due to its redox‐responsive biodegradable profile when exposed to simulated intracellular environments. As a result, the reduction‐triggered disassembly leads to potent gene silencing. In contrast, noncrosslinkable, structurally related constructs fails under the tested assay conditions, thereby confirming the applied rational design approach and demonstrating its large potential for future in vivo applications.
L ‐, P ‐, and E ‐Selectin are cell adhesion molecules that play a crucial role in leukocyte recruitment from the blood stream to the afflicted tissue in an acute and chronic inflammatory setting. Since selectins mediate the initial contact of leukocytes to the vascular endothelium, they have evolved as a valuable therapeutic target in diseases related to inflammation by inhibition of the physiological selectin–ligand interactions. In a previous study, it was demonstrated that dPGS, a fully synthetic heparin analogue, works as an efficient inhibitor towards L ‐ and P ‐selectin in vitro as well as in vivo. Herein, the focus is directed towards the effect of size and charge density of the polyanion. The efficiency of L ‐selectin inhibition via an SPR‐based in vitro assay and a cell‐based flow chamber assay is investigated with dPGS ranging from approximately 4 to 2000 kDa. SPR measurements show that the inhibitory potential of highly sulfated dPGS increases with size and charge density. Thereby, IC50 values from the micromolar to the low picomolar range are determined. The same tendency could be observed in a cell‐based flow chamber assay with three representative dPGS samples. This structure–affinity relationship of dPGS suggests that the strong inhibitory potential of dPGS is not only based on the strong electrostatic interaction with areas of cationic surface potential on L ‐selectin but is also due to a steric shielding of the carbohydrate binding site by large, flexible dPGS particles.
Dendrimers are characterized by a combination of high end‐group functionality and a compact, precisely defined molecular structure. These characteristics can be used in biomedical applications, for example, for the amplification or multiplication of effects on a molecular level, or to create extremely high local concentrations of drugs, molecular labels, or probe moieties. A brief summary of the current state of the art in the field is given, and focuses on the application of dendrimers both in diagnostics as well as in therapy. In diagnostics, dendrimers that bear GdIII complexes are used as contrast agents in magnetic resonance imaging. DNA dendrimers have potential for routine use in high‐throughput functional genomic analysis, as well as for DNA biosensors. Dendrimers are also being investigated for therapeutics, for example, as carriers for controlled drug delivery, in gene transfection, as well as in boron neutron‐capture therapy. Furthermore, the antimicrobial activity of dendrimers has been studied. 相似文献
It is proposed that the transmutation from possibilities to facts should be introduced as an essential element in fundamental theory. This has no bearing on TCP-invariance. If indeterminism is accepted it leads to a picture of an evolving history formed by individual events and causal ties. In the low density regime it can be compared with the treatment of multiple collisions in quantum field theory.Dedicated to Res Jost and Arthur Wightman, friends for many years and appreciators of unorthodox thought 相似文献
A systematic algorithm for finding solutions of Fokker Planck systems with time-dependent drift and fluctuation coefficients is developed. The solutions lag behind the adiabatic quasistationary distribution. This delay effect vanishes for slowly varying control parameters. In a first example the evolution of the phase transition from a monostable to a bistable system is treated. There is a fluctuation enhancement and the delay of the probability distribution leads to a transient central peak. In a second example a linear model with time-dependently shifted drift is considered. The introduced approximation scheme reproduces the exact solution already in first order. 相似文献
