Dillon F. Hanlon

Addresses a need to gain scientific insights from one-dimensional (1D) scientific spectra in model-independent ways. A powerful approach for this is to take differences between pairs of spectra and look for meaningful changes that might indicate underlying chemical, structural, or other modifications. The challenge is that the difference curve may contain uninteresting differences such as experimental inconsistencies and benign physical changes such as the effects of thermal expansion. allows researchers to apply simple transformations, or “morphs,” to one of the datasets to remove the unwanted differences, revealing, when they are present, nontrivial differences. is an open-source Python package available on the Python Package Index and conda-forge. Here, we describe its functionality and apply it to solve a range of experimental challenges on diffraction and pair distribution function data from x-rays and neutrons, though we note that it may be applied to any 1D function in principle.

In this Letter, we present the experimental observation of squeezed phonon generation in semiconductor germanium (Ge) induced by x-ray excitation. Prior x-ray pump, x-ray probe studies reported coherent longitudinal acoustic phonon generation in insulating oxides like strontium titanate and potassium tantalate. In contrast, such signals were not observed in semiconductors likely due to limited signal-to-noise ratio. Now, with an improved experimental setup, we observe a phonon response in single-crystal germanium. Utilizing x-ray split-delay optics with enhanced stability, we extract the phonon dispersion relation, which shows strong agreement with the calculated transverse acoustic phonon mode. Our results reveal that responses to x-ray excitations in semiconductors are of a similar nature to optical excitations. This suggests that the initial response to x-ray core–hole excitations rapidly diffuses to a non-local excitation, similar to what is observed with optical laser valence excitation on a femtosecond timescale.

Brillouin spectroscopy was used to probe the viscoelastic properties of a natural gastropod mucus at GHz frequencies over the range −11 °C ≤ T ≤ 52 °C. Anomalies in the temperature dependence of mucus longitudinal acoustic mode peak parameters and associated viscoelastic properties at T = −2.5 °C, together with the appearance of a peak due to ice at this temperature, suggest that the mucus undergoes a phase transition from a viscous liquid state to one in which liquid mucus and solid ice phases coexist. Failure of this transition to proceed to completion even at −11 °C is attributed to glycoprotein–water interaction. The temperature dependence of the viscoelastic properties and the phase behaviour suggest that water molecules bind to glycoprotein at a temperature above the onset of freezing and that the reduced ability of this bound water to take on a configuration that facilitates freezing is responsible for the observed freezing point depression and gradual nature of the liquid–solid transition.

We performed molecular dynamics simulations to investigate the viscoelastic properties of aqueous protein solutions containing an antifreeze protein, a toxin protein, and bovine serum albumin. These simulations covered a temperature range from 280 K to 340 K. Our findings demonstrate that lower temperatures are associated with higher viscosity as well as a lower bulk modulus and speed of sound for all the systems studied. Furthermore, we observe an increase in the bulk modulus and speed of sound as the temperature increases up to a weak maximum while the viscosity decreases. Moreover, we analyzed the influence of protein concentration on the viscoelastic properties of the antifreeze protein solution. We observed a consistent increase in the bulk modulus, speed of sound, and viscosity as the protein concentration increased. Remarkably, our molecular dynamics simulations results closely resemble the trends observed in Brillouin scattering experiments on aqueous protein solutions. The similarity thus validates the use of simulations in studying the viscoelastic properties of protein water solutions. Ultimately, this work provides motivation for the integration of computer simulations with experimental data and holds potential for advancing our understanding of both simple and complex systems.

Brillouin light scattering spectroscopy was used along with detailed composition information obtained from electron probe microanalysis to study the influence of octahedral site chemistry on the elastic properties of biotite crystals. Elastic wave velocities for a range of directions in the AC and BC crystallographic planes were obtained for each crystal by application of the Brillouin equation with refractive indices and phonon frequencies obtained from the Becke line test and spectral peak positions, respectively. In general, velocities increase with decreasing Fe content, approach those of muscovite at low Fe concentrations. 12 of the 13 elastic constants for the full monoclinic symmetry were obtained for each crystal by fitting analytic expressions for the velocities as functions of propagation direction and elastic constants to corresponding experimental data, with the remaining constant estimated using hexagonal symmetry. Elastic constants C11, C22, and C66 are comparable to those of muscovite and show little change with Fe concentration due to strong bonding within layers. In contrast, nearly all remaining constants show a pronounced dependence on Fe content, likely due to the weak interlayer bonding. Similar behaviour is shown by elastic stability, which falls greatly as Fe concentration increases, and elastic anisotropy within the basal cleavage plane, which decreases with Fe content. This consistent dependency of all measured elastic constants on Fe content suggests that biotite elasticity is a function of octahedral site chemistry and gives a method to determine the elastic constants and elastic stability of most biotite compositions provided, Fe or Mg concentrations are known. Moreover, the good agreement between elastic constants of Fe-poor biotite and those of phlogopite obtained from DFT simulations indicate a method to predict elastic properties of biotites.