Sulfur K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the distribution of sulfur types in two whole blood cell samples, in selected subcellular blood fractions, and in cell-free plasma from the tunicate Ascidia ceratodes. Whole blood cells are rich in sulfate, aliphatic sulfonate, and low-valent sulfur. The sulfur K-edge XAS spectrum of washed blood cell membranes revealed traces of sulfate and low-valent sulfur, but no sulfate ester or sulfonate. Sulfonate is thus exclusively cytosolic. Cell-free blood plasma contains primarily sulfate sulfur. Gaussian fitting and sulfate quantitation for two whole blood cell samples, each representing dozens of individuals from separate collections taken per annum, yielded average sulfur type concentrations for the two populations:  (first year, second year):  [sulfate], 110 mM, 150 mM; [sulfonate], 99 mM, 70 mM, and; [low-valent sulfur], 41 mM, 220 mM. On titration of sulfate with acid or V(III) in aqueous solution, the strong 2482.4 eV 1s → (v...

Sulfur Allocation and Vanadium−Sulfate Interactions in Whole Blood Cells from the Tunicate Ascidia ceratodes, Investigated Using X-ray Absorption Spectroscopy

2 – Acoustic Vibrational Modes in Quartz Crystals: Their Frequency, Amplitude, and Shape Determination

Neutron backscattering on vibrating silicon crystals has been measured in transmission geometry on the backscattering spectrometer IN10 at the Institute Laue-Langevin (ILL). The crystals were excited into longitudinal mechanical resonance vibrations by LiNbO3 transducers glued to the crystal surface. The transmitted intensity of the 111 Bragg reflection was measured as a function of the deformation amplitude at vibration frequencies from 2.5 MHz to 30 MHz. By vibrating the initially perfect silicon crystal, an increase in ΔE/E of the diffracted profile was achieved, accompanied by an increase of the backreflected intensity. The width of the reflection and the resolution is a linear function of the ultrasonic strain over a wide range of excitation strengths. ΔE/E can be easily tuned in a reproducible way by varying the voltage on the piezoelectric transducer. For the highest excited ultrasonic strain an increase of the backscattered intensity of about a factor of 50 is observed. Sound wave amplitudes can be determined from the measured width in ΔE/E of the transmission curves. The obtained results are relevant for the design and operation of intensity-to-resolution tunable monochromators for high resolution instruments.

Neutron backscattering on vibrating silicon crystals- experimental results on the neutron backscattering spectrometer IN10

The broadening of double-crystal rocking curves of two nearly perfect quartz single-crystal bars in (1,−1) setting has been investigated in three cases, i.e., when the first or the second or both crystals were excited in longitudinal vibrations. The quartz single-crystal bars had equal dimensions and therefore they were vibrating with the equal fundamental resonance frequency of longitudinal vibrations. In the course of these experiments the increase of the integrated intensity of diffracted neutrons has been observed in connection with vibrations of one or of both the single crystals. The observed experimental data are interpreted on the basis of the kinematical theory using the structure of the “crystalline layers” of the vibrating single crystal.



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Neutron diffraction by two vibrating quartz single crystals. I. Rocking curve effects

Two synchronously vibrating single crystals as a new type of high efficiency neutron chopper

The time modulation of neutrons diffracted by a quartz single crystal is investigated. The experimental results agree with the aberration and with the Doppler effect caused during neutron diffraction by vibrations of a single crystal.

Neutron diffraction effects due to the lattice displacement of a vibrating quartz single crystal

Diffraction of neutrons by a longitudinally vibrating quartz single-crystal bar was investigated for thicknesses of 3 and 13 mm. The 1st, 3rd and 5th harmonic frequencies were excited in the bar. The observed increase of the integrated intensity of diffracted neutrons as a function of the vibration amplitude of longitudinal vibrations of the quartz bar is compared with that calculated from an approximate theory considering the possibility of secondary reflexions of neutrons during their flight across the sample.

Secondary reflexions of neutrons diffracted by a single-crystal bar vibrating at high frequency

A generalized formula for the integrated intensity of neutrons diffracted by a vibrating perfect crystal is derived on the basis of the lamella structure with the symbols of Zachariasen's general theory. The formula is introduced together with new experimental data for diffraction from a longitudinally vibrating quartz single crystal.

B. Chalupa

Papers

Neutron diffraction effects due to the lattice displacement of a vibrating quartz single crystal

Secondary reflexions of neutrons diffracted by a single-crystal bar vibrating at high frequency

A vibrating perfect crystal assumed to be a real one