We present a lattice QCD calculation of the double-virtual neutral pion transition form factor, with the goal to cover the kinematic range relevant to hadronic light-by-light scattering in the muon ...g−2. Several improvements have been made compared to our previous work. First, we take into account the effects of the strange quark by using the Nf=2+1 coordinated lattice simulation gauge ensembles. Second, we have implemented the on-shell O(a) improvement of the vector current to reduce the discretization effects associated with Wilson quarks. Finally, in order to have access to a wider range of photon virtualities, we have computed the transition form factor in a moving frame as well as in the pion rest frame. After extrapolating the form factor to the continuum and to physical quark masses, we compare our results with phenomenology. We extract the normalization of the form factor with a precision of 3.5% and confirm within our uncertainty previous somewhat conflicting estimates for a low-energy constant that appears in chiral perturbation theory for the decay π0→γγ at the next-to-leading order. With additional input from experiment and theory, we reproduce recent estimates for the decay width Γ(π0→γγ). We also study the asymptotic large-Q2 behavior of the transition form factor in the double-virtual case. Finally, we provide as our main result a more precise model-independent lattice estimate of the pion-pole contribution to hadronic light-by-light scattering in the muon g−2: aμHLbL;π0=(59.7±3.6)×10−11. Using in addition the normalization of the form factor obtained by the PrimEx experiment, we get the lattice and data-driven estimate aμHLbL;π0=(62.3±2.3)×10−11.
We present the use of Multi-angle Dynamic Light Scattering (MADLS®) for the measurement of nanoparticle concentration. We describe the theory of the method and its application to nanoparticles made ...of gold, silica and polystyrene, with diameters ranging from 30 to 400 nm, and demonstrate some of the limitations with particles of sizes 500 nm and above. We evaluate the method accuracy, linearity and reproducibility, as well as the operational nanoparticle concentration and size range. We show that the concentration working range depends on the material’s optical properties, size and concentration. Here it is shown that the level of accuracy that can be expected for the concentration of particles is typically within 50% of the nominal value across a range of materials and sizes and, for some samples, within 20%. The repeatability of the measurements, in terms of relative standard deviation, is typically below 30%. A linearity of within 40% across a concentration range of 3·10
8
to 2·10
11
mL
−1
for concentration measurements was also demonstrated by using gold nanoparticles and gravimetric dilutions for method validation. Overall, we show that MADLS® is a rapid and straightforward method for the reproducible measurement of particle concentration, as well as size, requiring minimal sample preparation, without the need to calibrate using a pre-determined concentration series, and applicable to a broad range of materials. These features make it an ideal tool to support both development and quality control of particle materials for a broad range of applications.
The coacervates of the Poly (2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylonitrile) / β-Galactosidase complex are characterized using several techniques (Turbidimetry, dynamic and static ...light scattering (DLS / SLS), optical microscopy, image dynamic light scattering (IDLS), and ultra-small angles light scattering (USALS)). Turbidity and SLS were used to accurately determine the critical pHs of complex formation (pHc, pHϕ1, pHopt, and pHϕ2), DLS was used to probe the microscopic structure of coacervate droplets rich in proteins and polyelectrolytes in liquid-liquid phase separation, and IDLS and USALS have been introduced to better understand, during aging, the topology of the network formed of materials based on fractals in the dense phase. Observations of the architecture, the spatial inhomogeneity, and the size distributions of liquid complex coacervate droplets and fractal solid precipitates, were performed by optical microscopy. The pair-distance distribution function, P(r), presented in this review, is a new methodology of calculus for determining with precision the radius of gyration Rg of droplets coacervates. These techniques show that aging improves the stability of swollen condensates, the growth of the coacervate droplets is due to the attractive electrostatic interactions within the complex and does not undergo Ostwald ripening, except for the case of pHopt and having fractal dimensions Df generated by diffusion-limited cluster aggregation (DLCA).
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•The capability of electrostatic interactions to form complex in the transition phase.•Pair-distance distribution function, P(r), for determining the size of droplets coacervates.•Fractal dimensions Df caused by diffusion-limited cluster aggregation (DLCA).•Spatial inhomogeneities produced by aging.•outer and inner surfaces of the coacervates hollow as concentric shells.
Exosomes participate in cancer metastasis, but studying them presents unique challenges as a result of their small size and purification difficulties. Asymmetrical field flow fractionation with ...in-line ultraviolet absorbance, dynamic light scattering, and multi-angle light scattering was applied to the size separation and characterization of non-labeled B16-F10 exosomes from an aggressive mouse melanoma cell culture line. Fractions were collected and further analyzed using batch mode dynamic light scattering, transmission electron microscopy and compared with known size standards. Fractogram peak positions and computed radii show good agreement between samples and across fractions. Ultraviolet absorbance fractograms in combination with transmission electron micrographs were able to resolve subtle heterogeneity of vesicle retention times between separate batches of B16-F10 exosomes collected several weeks apart. Further, asymmetrical field flow fractionation also effectively separated B16-F10 exosomes into vesicle subpopulations by size. Overall, the flow field flow fractionation instrument combined with multiple detectors was able to rapidly characterize and separate exosomes to a degree not previously demonstrated. These approaches have the potential to facilitate a greater understanding of exosome function by subtype, as well as ultimately allow for “label-free” isolation of large scale clinical exosomes for the purpose of developing future exosome-based diagnostics and therapeutics.
Figure
Flow path of exosome sample through the asymmetrical field flow fractionation instrument, detectors, and transmission electron microscope.
The open-source code ADDA is described, which implements the discrete dipole approximation (DDA), a method to simulate light scattering by finite 3D objects of arbitrary shape and composition. ...Besides standard sequential execution, ADDA can run on a multiprocessor distributed-memory system, parallelizing a
single DDA calculation. Hence the size parameter of the scatterer is in principle limited only by total available memory and computational speed. ADDA is written in C99 and is highly portable. It provides full control over the scattering geometry (particle morphology and orientation, and incident beam) and allows one to calculate a wide variety of integral and angle-resolved scattering quantities (cross sections, the Mueller matrix, etc.). Moreover, ADDA incorporates a range of state-of-the-art DDA improvements, aimed at increasing the accuracy and computational speed of the method. We discuss both physical and computational aspects of the DDA simulations and provide a practical introduction into performing such simulations with the ADDA code. We also present several simulation results, in particular, for a sphere with size parameter 320 (100-wavelength diameter) and refractive index 1.05.
►Simulation of light scattering by 3D objects of arbitrary shape and composition. ►Open-source parallel code implementing the discrete dipole approximation. ► Single simulation executed on a multiprocessor distributed-memory system. ►Sphere with 100-wavelength diameter and refractive index 1.05. ►ADDA includes state-of-the art improvements of the DDA.
This research volume outlines the scientific foundations that are central to our current understanding of light scattering, absorption and polarization processes involving ice crystals. It also ...demonstrates how data from satellite remote sensing of cirrus clouds can be combined with radiation parameterizations in climate models to estimate the role of these clouds in temperature and precipitation responses to climate change. Providing a balanced treatment of the fundamentals and applications, this book synthesizes the authors' own work, as well as that of other leading researchers in this area. Numerous illustrations are included, including three-dimensional schematics, to provide a concise discussion of the subject and enable easy visualization of the key concepts. This book is intended for active researchers and advanced graduate students in atmospheric science, climatology, and remote sensing, as well as scholars in related fields such as ice microphysics, electromagnetic wave propagation, geometric optics, radiative transfer and cloud-climate interactions.
In this work, the antifungal activity of rhamnolipids produced by Pseudomonas aeruginosa #112 was evaluated against Aspergillus niger MUM 92.13 and Aspergillus carbonarius MUM 05.18. It was ...demonstrated that the di-rhamnolipid congeners were responsible for the antifungal activity exhibited by the crude rhamnolipid mixture, whereas mono-rhamnolipids showed a weak inhibitory activity. Furthermore, in the presence of NaCl (from 375 mM to 875 mM), the antifungal activity of the crude rhamnolipid mixture and the purified di-rhamnolipids was considerably increased. Dynamic Light Scattering studies showed that the size of the structures formed by the rhamnolipids increased as the NaCl concentration increased, being this effect more pronounced in the case of di-rhamnolipids. These results were confirmed by Confocal Scanning Laser Microscopy, which revealed the formation of giant vesicle-like structures (in the µm range) by self-assembling of the crude rhamnolipid mixture in the presence of 875 mM NaCl. In the case of the purified mono- and di-rhamnolipids, spherical structures (also in the µm range) were observed at the same conditions. The results herein obtained demonstrated a direct relationship between the rhamnolipids antifungal activity and their aggregation behaviour, opening the possibility to improve their biological activities for application in different fields.
Gold nanoflowers (GNFs) exhibit stronger light scattering ability than gold nanospheres (GNSs) with the same diameter, thereby contributing to enhancing the sensitivity of the scattering-based ...sensing method. However, the application of GNFs in biosensors based on dynamic light scattering (DLS) has not been yet reported. Herein, we describe for the first time an improved no-wash immunosensor based on dynamic light scattering for the detection of Escherichia coli O157:H7 (E. coli O157:H7) in milk using GNFs for sensitive signal transduction. To achieve this goal, a thiolated amphiphilic carboxyl ligand was introduced to modify the GNF surface and improve solution stability and antibody functionalization. Several key factors that affect the detection sensitivity of our developed GNF_DLS immunosensor were systematically investigated. Under the optimal conditions, our proposed GNF_DLS immunosensor provided an excellent linear detection for E. coli O157:H7 within the range from 6 × 100 to 6 × 104 colony-forming units (CFU)/mL, with a limit of detection of 2.7 CFU/mL. Combined with our previously reported two-step large-volume immunomagnetic separation (IMS) method, the designed GNF_DLS immunosensor can sensitively, selectively, and accurately detect the presence of E. coli O157:H7 in pasteurized milk. The potential of our GNF_DLS method for monitoring the presence of a single bacterial cell in 1 mL of sample solution was also demonstrated. Overall, the developed GNF_DLS immunosensor can be used for the rapid and high-sensitivity determination of pathogenic bacteria and can be extended for the ultrasensitive no-wash detection of other trace analytes.
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