Search results for "Light scattering"

<title>Pressure sensitivity of the side-glowing optical fibers</title>

2001

Remarkable impact of external mechanical pressure to the transmitted radiation intensity has been observed for glowing fibers with various silica core diameters and side- scattering efficiencies. A physical model on deformation- simulated light scattering has been developed and discussed. The results of experimental studies confirmed the basic model assumptions.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Beer-Lambert law for optical tissue diagnostics: current state of the art and the main limitations.

2021

Abstract. Significance: Beer–Lambert law (BLL) is a widely used tool for contact and remote determination of absorber concentration in various media, including living tissues. Originally proposed in the 18th century as a simple exponential expression, it has survived numerous modifications and updates. The basic assumptions of this law may not be fulfilled in real measurement conditions. This can lead to mistaken or misinterpreted results. In particular, the effects to be additionally taken into account in the tissue measurements include anisotropy, scattering, fluorescence, chemical equilibria, interference, dichroism, spectral bandwidth disagreements, stray radiation, and instrumental eff…

Hadronic light-by-light scattering contribution to the muon $g-2$ on the lattice

2018

International Workshop on “Flavour Changing and Conserving Processes, FCCP2017, Anacapri, Italy, 7 Sep 2017 - 9 Sep 2017; The European physical journal / Web of Conferences 179, 01017 (2018). doi:10.1051/epjconf/201817901017

Indications of Two Separate Relaxators in the Subphonon Region of Tetragonal BaTiO 3

1994

Significant discrepancies were generally reported in the dynamics of BaTiO3 between results deduced from various experimental techniques. Here dielectric and quasi-elastic light scattering measurements are investigated on high-quality BaTiO3 crystals. We show that two relaxators have to be introduced below the soft-phonon frequency. A complete dielectric dispersion in a very wide frequency range is thus achieved which consistently relies the high-frequency dielectric results and the Raman data. There is also a qualitative agreement between our two-relaxator model and the dynamics which were deduced some time ago from EPR experiments.

1978

Theoretical relations for the dependence of the z-average radius of gyration Rz as a function of the mass average molar mass Mw are derived for expanded coils, persistence coils with persistence of direction, persistence coils with persistence of direction and curvature, and for needles, all exhibiting a Schulz-distribution of their molar masses. These relations are applied to experimental data from light scattering of polystyrene in toluene and DNA-Na in aqueous NaCl-solution of 200 mol NaCl per m3 at room temperature. In the case of DNA it becomes evident that the double helix shows no important persistence of curvature and that the experimental data can be described adequately by a persi…

Molekülgrößenbestimmungen an makromolekularen Stoffen (Kritik und Vergleich der Methoden)

1952

A survey is given of the most important methods for determination of molecular weight (osmotic pressure, ultracentrifuge and diffusion, light scattering, viscosity). All the methods require an extrapolation to zero concentration in order to use equations valid for ideal solutions. Furthermore the polymolecularity of the examined substance must be considered, since each method yields a characteristic average of molecular weight differing from the others. The present limits of the methods are given and their results compared.

Interdiffusion in blends of polystyrene and polymethylstyrene studied by light scattering after temperature jumps across the phase boundary

1992

Abstract We describe a simple light scattering set-up for measuring interdiffusion coefficients D in polymer blends by generating spinodal decomposition and subsequent dissolution after temperature jumps across the phase boundary. In blends of polystyrene and polymethylstyrene (random copolymer of 60% m-methylstyrene and 40% p-methylstyrene) D values were obtained between 10−11 and 10−15 cm2s−1 at temperatures up to 50 K above the upper critical solution temperature. The results are discussed in relation to tracer diffusion in the same system.

Experimental and theoretical study of dense YBO3 and the influence of non-hydrostaticity.

2021

[EN] YBO3 is used in photonics applications as a host for red phosphors due to its desirable chemical stability, high quantum efficiency and luminescence intensity. Despite its fundamental thermodynamic nature, the isothermal bulk modulus of YBO3 has remained a contentious issue due to a lack of comprehensive experimental and theoretical data and its vibrational modes are far from being understood. Here, we present an experimental-theoretical structural and vibrational study of YBO3. From structural data obtained from synchrotron X-ray diffraction data and ab initio calculations, we have determined the YBO3 bulk modulus, isothermal compressibility tensor and pressure-volume (P-V) equation o…

Protein crystallization: universal thermodynamic vs. specific effects of PEG

2008

The interest of nucleation of protein crystals and aggregates (including oligomerization) spans from basic physics theory all the way to biophysics, nanophysics, clinical sciences, biotechnologies, food technologies and polymer–solvent interactions. Understanding nucleation within a theoretical framework capable of providing quantitative predictions and control of nucleation rates, or even the very occurrence of crystallization, is a long-sought goal of remarkable relevance to each of the above fields. A large amount of work has been aimed at such goal, but success has been so far rather limited. Work at our laboratory has more recently highlighted a direct link between nucleation rates and…

A coumarin based gold(i)-alkynyl complex: a new class of supramolecular hydrogelators.

2014

A phosphine-gold(I)-alkynyl-coumarin complex, [Au{7-(prop-2-ine-1-yloxy)-1-benzopyran-2-one}(DAPTA)] (1), was synthesized and the formation of long luminescent fibers in solution was characterized via fluorescence microscopy and dynamic light scattering. The fibers presented strong blue and green luminescence, suggesting that the gold(I) in the complex increased intersystem crossing due to the heavy atom effect, resulting in a significant increase in triplet emission. The X-ray structure of the fibers indicates that both aurophilic, π–π interactions and hydrogen bonding contribute to their formation in aqueous solvents.