Quantum super-resolution for imaging two pointlike entangled photon sources

We investigate the resolution for imaging two pointlike entangled sources by using the method of the moments and the spatial-mode demultiplexing (SPADE), where the pointlike entangled sources can be generated by injecting single-mode sources with arbitrary quantum statistics distribution into an optical parametric amplifier (OPA). We demonstrate that the separation estimation sensitivity is mainly determined by the photon distribution in each detected modes and it can be enhanced by either increasing the squeezed parameter of the OPA or eliminating the relative phase difference of the entangle sources. Furthermore, in the limiting case of infinitely small source separation, the usage of entangled sources can have better resolution than those using incoherent and coherent sources. The results here can find important applications for the quantum super-resolution imaging and quantum metrology

A MPPT Method based on Improved Fibonacci Search Photovoltaic Array

The P-U curve of photovoltaic arrays (PVAs) has multi-peak characteristics under uneven illumination environments, and the maximum power point tracking (MPPT) strategy for the single peak may fail. An improved Fibonacci search algorithm is proposed to carry out MPPT of photovoltaic arrays under uniform illumination or light mutation. A multiple-interval search algorithm based on a circuit analysis method is presented for different topology arrays and illumination distributions. The series array analysis adopts the current analysis method, the parallel array analysis adopts the voltage analysis method, and the series and parallel array analysis adopts the current and voltage analysis method; then, the output control volume is determined, and the search interval is divided. The search steps in the Fibonacci method and the real-time changes of parameters in the optimization process can be observed by MATLAB simulation. Experimental results show that the algorithm uses less computation time and small area search instead of global search

Biocompatible Silk/Polymer Energy Harvesters Using Stretched Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) Nanofibers

Energy harvested from human body movement can produce continuous, stable energy to portable electronics and implanted medical devices. The energy harvesters need to be light, small, inexpensive, and highly portable. Here we report a novel biocompatible device made of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers on flexible substrates. The nanofibers are prepared with electrospinning followed by a stretching process. This results in aligned nanofibers with diameter control. The assembled device demonstrates high mechanical-to-electrical conversion performance, with stretched PVDF-HFP nanofibers outperforming regular electrospun samples by more than 10 times. Fourier transform infrared spectroscopy (FTIR) reveals that the stretched nanofibers have a higher β phase content, which is the critical polymorph that enables piezoelectricity in polyvinylidene fluoride (PVDF). Polydimethylsiloxane (PDMS) is initially selected as the substrate material for its low cost, high flexibility, and rapid prototyping capability. Bombyx Mori silkworm silk fibroin (SF) and its composites are investigated as promising alternatives due to their high strength, toughness, and biocompatibility. A composite of silk with 20% glycerol demonstrates higher strength and larger ultimate strain than PDMS. With the integration of stretched electrospun PVDF-HFP nanofibers and flexible substrates, this pilot study shows a new pathway for the fabrication of biocompatible, skin-mountable energy devices

Simulation study on the optical processes at deep-sea neutrino telescope sites

The performance of a large-scale water Cherenkov neutrino telescope relies heavily on the transparency of the surrounding water, quantified by its level of light absorption and scattering. A pathfinder experiment was carried out to measure the optical properties of deep seawater in South China Sea with light-emitting diodes (LEDs) as light sources, photon multiplier tubes (PMTs) and cameras as photon sensors. Here, we present an optical simulation program employing the Geant4 toolkit to understand the absorption and scattering processes in the deep seawater, which helps to extract the underlying optical properties from the experimental data. The simulation results are compared with the experimental data and show good agreements. We also verify the analysis methods that utilize various observables of the PMTs and the cameras with this simulation program, which can be easily adapted by other neutrino telescope pathfinder experiments and future large-scale detectors.Comment: 27 pages, 11 figure

Structural analysis of metalloform-selective inhibition of methionine aminopeptidase

One of the challenges in the development of methionine aminopeptidase (MetAP) inhibitors as antibacterial and anticancer agents is to define the metal ion actually used by MetAP in vivo and to discover MetAP inhibitors that can inhibit the metalloform that is relevant in vivo. Two distinct classes of novel nonpeptidic MetAP inhibitors that are not only potent but also highly selective for either the MnII or CoII form have been identified. Three crystal structures of Escherichia coli MetAP complexed with the metalloform-selective inhibitors 5-(2,5-dichlorophenyl)furan-2-carboxylic acid (2), 5-[2-(trifluoromethyl)phenyl]furan-2-carboxylic acid (3) and N-cyclopentyl-N-(thiazol-2-yl)oxalamide (4) have been solved and analysis of these structures has revealed the structural basis for their metalloform-selective inhibition. The MnII-form selective inhibitors (2) and (3) both use their carboxylate group to coordinate with the two MnII ions at the dinuclear metal site and both adopt a non-coplanar conformation for the two aromatic rings. The unique coordination geometry of these inhibitors may determine their MnII-form selectivity. In contrast, the CoII-form selective inhibitor (4) recruits an unexpected third metal ion, forming a trimetallic enzyme–metal–inhibitor complex. Thus, an important factor in the selectivity of (4) for the CoII form may be a consequence of a greater preference for a softer N,O-donor ligand for the softer CoII