Quantum-limited directional amplifiers with optomechanics

Directional amplifiers are an important resource in quantum information processing, as they protect sensitive quantum systems from excess noise. Here, we propose an implementation of phase-preserving and phase-sensitive directional amplifiers for microwave signals in an electromechanical setup comprising two microwave cavities and two mechanical resonators. We show that both can reach their respective quantum limits on added noise. In the reverse direction, they emit thermal noise stemming from the mechanical resonators and we discuss how this noise can be suppressed, a crucial aspect for technological applications. The isolation bandwidth in both is of the order of the mechanical linewidth divided by the amplitude gain. We derive the bandwidth and gain-bandwidth product for both and find that the phase-sensitive amplifier has an unlimited gain-bandwidth product. Our study represents an important step toward flexible, on-chip integrated nonreciprocal amplifiers of microwave signals

Origin Of The Far Off-Axis GRB171205A

We show that observed properties of the low luminosity GRB171205A and its afterglow, like those of most other low-luminosity (LL) gamma ray bursts (GRBs) associate with a supernova (SN), indicate that it is an ordinary SN-GRB, which was produced by inverse Compton scattering of glory light by a highly relativistic narrowly collimated jet ejected in a supernova explosion and viewed from a far off-axis angle. As such, VLA/VLBI follow-up radio observations of a superluminal displacement of its bright radio afterglow from its parent supernova, will be able to test clearly whether it is an ordinary SN-GRB viewed from far off-axis or it belongs to a distinct class of GRBs, which are different from ordinary GRBs, and cannot be explained by standard fireball models of GRBs as ordinary GRBsComment: 5 pages, 6 figures, updated data in Fig. 3, Corrected GRB angular distance used in Fig.

Biochemical basis of 5-aminolaevulinic acid-induced protoporphyrin IX accumulation: a study in patients with (pre)malignant lesions of the oesophagus.

Administration of 5-aminolaevulinic acid (ALA) leads to porphyrin accumulation in malignant and premalignant tissues, and ALA is used as a prodrug in photodynamic therapy (PDT). To understand the mechanism of porphyrin accumulation after the administration of ALA and to investigate whether ALA-induced protoporphyrin IX might be a suitable photosensitizer in Barrett's oesophagus and adenocarcinoma, we determined the activities of porphobilinogen deaminase (PBG-D) and ferrochelatase (FC) in various malignant and premalignant as well as in normal tissues of the human oesophagus. A PDT power index for ALA-induced porphyrin accumulation, the ratio of PBG-D to FC normalized for the normal squamous epithelium of the oesophagus, was calculated to evaluate intertissue variation in the ability to accumulate porphyrins. In malignant and premalignant tissue a twofold increased PBG-D activity and a marginally increased FC activity was seen compared with normal squamous epithelium. A significantly increased PDT power index in Barrett's epithelium and adenocarcinoma was found. Our results suggest that, after the administration of ALA, porphyrins will accumulate in a greater amount in Barrett's epithelium and adenocarcinoma of the oesophagus because of an imbalance between PBG-D and FC activities. The PDT power index here defined might be a useful indicative parameter for predicting the susceptibility of these tissues to ALA-PDT

Porphyrin biosynthesis in human Barrett's oesophagus and adenocarcinoma after ingestion of 5-aminolaevulinic acid

5-Aminolaevulinic acid (ALA)-induced porphyrin biosynthesis, which is used for ALA-based photodynamic therapy (ALA-PDT), was studied in tissues of 10 patients with Barrett’s oesophagus (BE) and adenocarcinoma of the oesophagus (AC) undergoing oesophagectomy at a mean time interval of 6.7 h after the ingestion of ALA (60 mg kg–1). In BE, AC, squamous epithelium (SQ) and gastric cardia, the activities of the haem biosynthetic enzymes porphobilinogen deaminase (PBG-D) and ferrochelatase (FC) and the PDT power index – the ratio between PBG-D and FC in BE and AC in comparison with SQ – were determined before ALA ingestion. Following ALA administration, ALA, porphobilinogen, uroporphyrin I and PPIX were determined in tissues and plasma. The PDT power index did not predict the level of intracellular accumulation of PPIX found at 6.7 h. In BE, there was no selectivity of PPIX accumulation compared to SQ, whereas in half of patients with AC selectivity was found. Higher haem biosynthetic enzyme activities (i.e. PBG-D) and lower PPIX precursor concentrations were found in BE and AC compared to SQ. It is therefore possible that PPIX levels will peak at earlier time intervals in BE and AC compared to SQ. © 2000 Cancer Research Campaig