Impact of membrane pore structure on protein detection sensitivity of affi nity-based immunoassay

Understanding a membrane’s morphology is important for controlling its fi nal performance during protein immobilization. Porous, symmetric membranes were prepared from a polyvinylidene fl uoride/N-methyl-2-pyrrolidinone solution by phase inversion process, to obtain membrane with various microsized pores. The concentration and surface area of aprotein dotted on the membrane surface were measured by staining with Ponceau S dye. The dotted protein was further scanned and analysed to perform quantitative measurements for relative comparison. The intensity of the red protein spot and its surface area varied depending on the membrane pore size, demonstrating the dependence of protein immobilization on this factor. The membrane with the smallest pore size (M3) showed the highest protein spot intensity and surface area when examined at different protein concentrations. An increase in the applied protein volume showed a linearity proportional trend to the total surface area, and an uneven round dot shape was observed at a large applied volume of protein solution

Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3b

We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC-2020 March 27 17:00 UTC). We conduct two independent searches: A generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate. © 2022. The Author(s). Published by the American Astronomical Society

Integration process for photonic integrated circuits using plasma damage induced layer intermixing

A new quantum-well intermixing process in GaAs/AlGaAs structures, based on ion bombardment damage, has been developed. Bandgap tuned lasers and extended cavity lasers have been fabricated. Results show that the quality of the material is still high after intermixing. Losses as low as 18 dB cm/sup -1/ have been measured in the passive waveguides of the extended-cavity lasers

Effect of p and n doping on neutral impurity and dielectric cap induced quantum well intermixing in GaAs/AlGaAs structures

We report the diffusion and quantum well intermixing (QWI) effects of the neutral impurities fluorine and boron in p- and n-type AlGaAs in the GaAs/AlGaAs system. Boron was found to show significant diffusion in p-doped AlGaAs material but only exhibited a very small amount of diffusion in n-doped material after furnace annealing. Boron was found to retard intermixing in p-AlGaAs. This may be due to the existence of interstitial B, which may reduce the native group III interstitial concentration. The mechanism of boron impurity-induced disordering (IID) in n-AlGaAs was proposed to be attributed to both the diffusion of point defects generated during ion implantation and the Fermi level effect from the deep acceptor . Extremely fast fluorine diffusion rates, which may be correlated to an interstitial diffusion mechanism, have been observed. Results from fluorine IID suggest the possibility of the ionization of fluorine which gives rise to a higher electron concentration during annealing, leading to higher degrees of intermixing in n-AlGaAs. The intermixing rate of impurity free vacancy disordering (IFVD) using an cap was found to be higher in n-type and intrinsic AlGaAs than in p-type AlGaAs, which suggests that the diffusion of the group III vacancy is inhibited in p-type material which has a higher group III interstitial concentration. These results imply that n-i-p structures should be more effective than conventional p-i-n structures for the IFVD process

Fabrication of multiple wavelength lasers in GaAs-AlGaAs structures using a one-step spatially controlled quantum-well intermixing technique

We have applied a new technique, based on impurity-free vacancy diffusion, to control the degree of intermixing across a wafer. Bandgap tuned lasers were fabricated using this technique. Five distinguishable lasing wavelengths were observed from five selected intermixed regions on a single chip. These lasers showed no significant change in transparency current, internal quantum efficiency or internal propagation loss, which indicates that the material quality was not degraded after intermixing

Transmission electron microscopy study of fluorine and boron implanted and annealed GaAs/AlGaAs

The residual damage in fluorine and boron ion implanted GaAs/AlGaAs has been studied using transmission electron microscopy both before and after rapid thermal processing. The results showed no extended defects in as‐implanted materials. A dense network of interstitial dislocation loops has been observed in boron implanted samples after annealing. Most of these dislocation defects were located in GaAs layers rather than in AlGaAs layers. Only a small number of dislocation loops were found in the fluorine implanted and annealed material. Compared to boron, fluorine is a better candidate for neutral impurity induced disordering applications

Study of reactive ion etching‐induced damage in GaAs/AlGaAs structures using a quantum well intermixing probe

We report the damage distribution induced by C2F6 and SiCl4 reactive ion etching (RIE) using quantum wells and quantum well intermixing (QWI) as probes. Photoluminescence emission at 77 K was measured both before and after rapid thermal annealing at 900 °C for 30 s. Our results show that the QWI probing technique can effectively be utilized as a sensitive probe of RIE damage. A damage depth of 650 Å before annealing and blue shifts of up to 65 meV after annealing were obtained in C2F6 RIE regions. A damage depth of 100 Å and blue shifts of up to 30 meV were observed in SiCl4 RIE regions

Study of C2F6 overetch induced damage and the effects of overetch on subsequent SiCl4 etch of GaAs/AlGaAs

A quantum well intermixing probe system has been used to study the damage in GaAs/AlGaAs due to exposure to C2F6 plasmas as a function of rf power. At an etching power of ≤80 W, the photoluminescence energy shift after rapid thermal processing is rf power dependent. The etch rate selectivities between SiO2 and GaAs, and between GaAs and AlGaAs were found to increase with decreasing power, while the etching of AlGaAs was inhibited at an rf power of 10 W and below. In situ reflectometry measurements during subsequent SiCl4 etching suggest that fluorocarbon contaminants are deposited on the GaAs surface during the C2F6 etch, that these contaminants protect the surface from oxidation in the air, and therefore the GaAs induction time in SiCl4 is reduced. However, during a SiCl4 etch of a GaAs/AlGaAs layered structure, these contaminants are redeposited on the AlGaAs surface resulting in an increased AlGaAs induction time, a nonconstant etch rate and surface roughening