Dynamics in the ordered and disordered phases of barocaloric adamantane.

High-entropy order-disorder phase transitions can be used for efficient and eco-friendly barocaloric solid-state cooling. Here the barocaloric effect is reported in an archetypal plastic crystal, adamantane. Adamantane has a colossal isothermally reversible entropy change of 106 J K-1 kg-1. Extremely low hysteresis means that this can be accessed at pressure differences less than 200 bar. Configurational entropy can only account for about 40% of the total entropy change; the remainder is due to vibrational effects. Using neutron spectroscopy and supercell lattice dynamics calculations, it is found that this vibrational entropy change is mainly caused by softening in the high-entropy phase of acoustic modes that correspond to molecular rotations. We attribute this difference in the dynamics to the contrast between an 'interlocked' state in the low-entropy phase and sphere-like behaviour in the high-entropy phase. Although adamantane is a simple van der Waals solid with near-spherical molecules, this approach can be leveraged for the design of more complex barocaloric molecular crystals. Moreover, this study shows that supercell lattice dynamics calculations can accurately map the effect of orientational disorder on the phonon spectrum, paving the way for studying the vibrational entropy, thermal conductivity, and other thermodynamic effects in more complex materials.

The Impact of Surface Charges of Carboxylated Cellulose Nanofibrils on the Water Motions in Hydrated Films.

Cellulose nanofibrils (CNFs) with carboxylated surface ligands are a class of materials with tunable surface functionality, good mechanical properties, and bio-/environmental friendliness. They have been used in many applications as scaffold, reinforcing, or functional materials, where the interaction between adsorbed moisture and the CNF could lead to different properties and structures and become critical to the performance of the materials. In this work, we exploited multiple experimental methods to study the water movement in hydrated films made of carboxylated CNFs prepared by TEMPO oxidation with two different surface charges of 600 and 1550 µmol·g-1. A combination of quartz crystal microbalance with dissipation (QCM-D) and small-angle X-ray scattering (SAXS) shows that both the surface charge of a single fibril and the films' network structure contribute to the moisture uptake. The films with 1550 µmol·g-1 surface charges take up twice the amount of moisture per unit mass, leading to the formation of nanostructures with an average radius of gyration of 2.1 nm. Via the nondestructive quasi-elastic neutron scattering (QENS), a faster motion is explained as a localized movement of water molecules inside confined spheres, and a slow diffusive motion is found with the diffusion coefficient close to bulk water at room temperature via a random jump diffusion model and regardless of the surface charge in films made from CNFs.

Proton Dynamics in Palladium-Silver: An Inelastic Neutron Scattering Investigation.

Proton dynamics in Pd77Ag23 membranes is investigated by means of various neutron spectroscopic techniques, namely Quasi Elastic Neutron Scattering, Incoherent Inelastic Neutron Scattering, Neutron Transmission, and Deep Inelastic Neutron Scattering. Measurements carried out at the ISIS spallation neutron source using OSIRIS, MARI and VESUVIO spectrometers were performed at pressures of 1, 2, and 4 bar, and temperatures in the 330-673 K range. The energy interval spanned by the different instruments provides information on the proton dynamics in a time scale ranging from about 102 to 10-4 ps. The main finding is that the macroscopic diffusion process is determined by microscopic jump diffusion. In addition, the vibrational density of states of the H atoms in the metal lattice has been determined for a number of H concentrations and temperatures. These measurements follow a series of neutron diffraction experiments performed on the same sample and thus provide a complementary information for a thorough description of structural and dynamical properties of H-loaded Pd-Ag membranes.

Picosecond to nanosecond dynamics provide a source of conformational entropy for protein folding.

Myoglobin can be trapped in fully folded structures, partially folded molten globules, and unfolded states under stable equilibrium conditions. Here, we report an experimental study on the conformational dynamics of different folded conformational states of apo- and holomyoglobin in solution. Global protein diffusion and internal molecular motions were probed by neutron time-of-flight and neutron backscattering spectroscopy on the picosecond and nanosecond time scales. Global protein diffusion was found to depend on the α-helical content of the protein suggesting that charges on the macromolecule increase the short-time diffusion of protein. With regard to the molten globules, a gel-like phase due to protein entanglement and interactions with neighbouring macromolecules was visible due to a reduction of the global diffusion coefficients on the nanosecond time scale. Diffusion coefficients, residence and relaxation times of internal protein dynamics and root mean square displacements of localised internal motions were determined for the investigated structural states. The difference in conformational entropy ΔSconf of the protein between the unfolded and the partially or fully folded conformations was extracted from the measured root mean square displacements. Using thermodynamic parameters from the literature and the experimentally determined ΔSconf values we could identify the entropic contribution of the hydration shell ΔShydr of the different folded states. Our results point out the relevance of conformational entropy of the protein and the hydration shell for stability and folding of myoglobin.

CO2-mineralization and carbonation reactor rig: Design and validation for in situ neutron scattering experiments-Engineering and lessons learned.

CO2 mineralization via aqueous Mg/Ca/Na-carbonate (MgCO3/CaCO3/Na2CO3) formation represents a huge opportunity for the utilization of captured CO2. However, large-scale mineralization is hindered by slow kinetics due to the highly hydrated character of the cations in aqueous solutions (Mg2+ in particular). Reaction conditions can be optimized to accelerate carbonation kinetics, for example, by the inclusion of additives that promote competitive dehydration of Mg2+ and subsequent agglomeration, nucleation, and crystallization. For tracking mineralization and these reaction steps, neutron scattering presents unprecedented advantages over traditional techniques for time-resolved in situ measurements. However, a setup providing continuous solution circulation to ensure reactant system homogeneity for industrially relevant CO2-mineralization is currently not available for use on neutron beamlines. We, therefore, undertook the design, construction, testing and implementation of such a self-contained reactor rig for use on selected neutron beamlines at the ISIS Neutron and Muon Source (Harwell, UK). The design ensured robust attachment via suspension from the covering Tomkinson flange to stabilize the reactor assembly and all fittings (~25 kg), as well as facilitating precise alignment of the entire reactor and sample (test) cell with respect to beam dimension and direction. The assembly successfully accomplished the principal tasks of providing a continuous flow of the reaction mixture (~500 mL) for homogeneity, quantitative control of CO2 flux into the mixture, and temperature and pressure regulation throughout the reaction and measurements. The design is discussed, with emphasis placed on the reactor, including its geometry, components, and all technical specifications. Descriptions of the off-beamline bench tests, safety, and functionality, as well as the installation on beamlines and trial experimental procedure, are provided, together with representative raw neutron scattering results.

A Ferrotoroidic Candidate with Well-Separated Spin Chains.

The search of novel quasi-1D materials is one of the important aspects in the field of material science. Toroidal moment, the order parameter of ferrotoroidic order, can be generated by a head-to-tail configuration of magnetic moment. It has been theoretically proposed that 1D dimerized and antiferromagnetic (AFM)-like spin chain hosts ferrotoroidicity and has the toroidal moment composed of only two antiparallel spins. Here, the authors report a ferrotoroidic candidate of Ba6 Cr2 S10 with such a theoretical model of spin chain. The structure consists of unique dimerized face-sharing CrS6 octahedral chains along the c axis. An AFM-like ordering at ≈10 K breaks both space- and time-reversal symmetries and the magnetic point group of mm'2'allows three ferroic orders in Ba6 Cr2 S10 : (anti)ferromagnetic, ferroelectric, and ferrotoroidic orders. Their investigation reveals that Ba6 Cr2 S10 is a rare ferrotoroid ic candidate with quasi 1D spin chain, which can be considered as a starting point for the further exploration of the physics and applications of ferrotoroidicity.

The intimate relationship between structural relaxation and the energy landscape of monatomic liquid metals.

The characteristic property of a liquid, discriminating it from a solid, is its fluidity, which can be expressed by a velocity field. The reaction of the velocity field on forces is enshrined in the transport parameter viscosity. In contrast, a solid reacts to forces elastically through a displacement field, the particles are trapped in their potential minimum. The flow in a liquid needs enough thermal energy to overcome the changing potential barriers, which is supported through a continuous rearrangement of surrounding particles. Cooling a liquid will decrease the fluidity of a particle and the mobility of the neighbouring particles, resulting in an increase of the viscosity until the system comes to an arrest. This process with a concomitant slowing down of collective particle rearrangements might already start deep inside the liquid state. The idea of the potential energy landscape provides an attractive picture for these dramatic changes. However, despite the appealing idea there is a scarcity of quantitative assessments, in particular, when it comes to experimental studies. Here we present results on a monatomic liquid metal through a combination of ab initio molecular dynamics, neutron spectroscopy and inelastic x-ray scattering. We investigated the collective dynamics of liquid aluminium to reveal the changes in dynamics when the high temperature liquid is cooled towards solidification. The results demonstrate the main signatures of the energy landscape picture, a reduction in the internal atomic structural energy, a transition to a stretched relaxation process and a deviation from the high-temperature Arrhenius behavior of the relaxation time. All changes occur in the same temperature range at about [Formula: see text], which can be regarded as the temperature when the liquid aluminium enters the landscape influenced phase and enters a more viscous liquid state towards solidification. The similarity in dynamics with other monatomic liquid metals suggests a universal dynamic crossover above the melting point.

Diffusional Dynamics of Hydride Ions in the Layered Oxyhydride SrVO2H.

Perovskite-type oxyhydrides are hydride-ion-conducting materials of promise for several types of technological applications; however, the conductivity is often too low for practical use and, on a fundamental level, the mechanism of hydride-ion diffusion remains unclear. Here, we, with the use of neutron scattering techniques, investigate the diffusional dynamics of hydride ions in the layered perovskite-type oxyhydride SrVO2H. By monitoring the intensity of the elastically scattered neutrons upon heating the sample from 100 to 430 K, we establish an onset temperature for diffusional hydride-ion dynamics at about 250 K. Above this temperature, the hydride ions are shown to exhibit two-dimensional diffusion restricted to the hydride-ion sublattice of SrVO2H and that occurs as a series of jumps of a hydride ion to a neighboring hydride-ion vacancy, with an enhanced rate for backward jumps due to correlation effects. Analysis of the temperature dependence of the neutron scattering data shows that the localized jumps of hydride ions are featured by a mean residence time of the order of 10 ps with an activation energy of 0.1 eV. The long-range diffusion of hydride ions occurs on the timescale of 1 ns and with an activation energy of 0.2 eV. The hydride-ion diffusion coefficient is found to be of the order of 1 × 10-6 cm2 s-1 in the temperature range of 300-430 K, which is similar to other oxyhydrides but higher than for proton-conducting perovskite analogues. Tuning of the hydride-ion vacancy concentration in SrVO2H thus represents a promising gateway to improve the ionic conductivity of this already highly hydride-ion-conducting material.

Rotational dynamics of the imidazolium ion in cyanide-bridged dielectric framework materials.

Reorientation of organic cations in the cubic interstices of cyanoelpasolite molecular perovskites results in a variety of structural phase transitions, but far less is known about these cations' dynamics. We report quasielastic neutron scattering from the materials (C3H5N2)2K[MIII(CN)6], M = Fe,Co, which is directly sensitive to the rotation of the imidazolium ion. The motion is well described by a circular three-site hopping model, with the ion rotating within its plane in the intermediate-temperature phase, but tilting permanently in the high-temperature phase. Thus the two rhombohedral phases, which are crystallographically rather similar, have markedly different dynamics. The activation energy of rotation is about 10 kJ mol-1 and the barrier between orientations is 6 kJ mol-1. Our results explain two anomalous features in these materials' dielectric constants.

Quantum Versus Classical Spin Fragmentation in Dipolar Kagome Ice Ho3Mg2Sb3O14.

A promising route to realize entangled magnetic states combines geometrical frustration with quantum-tunneling effects. Spin-ice materials are canonical examples of frustration, and Ising spins in a transverse magnetic field are the simplest many-body model of quantum tunneling. Here, we show that the tripod-kagome lattice material Ho3Mg2Sb3O14 unites an icelike magnetic degeneracy with quantum-tunneling terms generated by an intrinsic splitting of the Ho3+ ground-state doublet, which is further coupled to a nuclear spin bath. Using neutron scattering and thermodynamic experiments, we observe a symmetry-breaking transition at T*≈0.32K to a remarkable state with three peculiarities: a concurrent recovery of magnetic entropy associated with the strongly coupled electronic and nuclear degrees of freedom; a fragmentation of the spin into periodic and icelike components; and persistent inelastic magnetic excitations down to T≈0.12K. These observations deviate from expectations of classical spin fragmentation on a kagome lattice, but can be understood within a model of dipolar kagome ice under a homogeneous transverse magnetic field, which we survey with exact diagonalization on small clusters and mean-field calculations. In Ho3Mg2Sb3O14, hyperfine interactions dramatically alter the single-ion and collective properties, and suppress possible quantum correlations, rendering the fragmentation with predominantly single-ion quantum fluctuations. Our results highlight the crucial role played by hyperfine interactions in frustrated quantum magnets and motivate further investigations of the role of quantum fluctuations on partially ordered magnetic states.

Aquaporin-like water transport in nanoporous crystalline layered carbon nitride.

Designing next-generation fuel cell and filtration devices requires the development of nanoporous materials that allow rapid and reversible uptake and directed transport of water molecules. Here, we combine neutron spectroscopy and first-principles calculations to demonstrate rapid transport of molecular H2O through nanometer-sized voids ordered within the layers of crystalline carbon nitride with a polytriazine imide structure. The transport mechanism involves a sequence of molecular orientation reversals directed by hydrogen-bonding interactions as the neutral molecules traverse the interlayer gap and pass through the intralayer voids that show similarities with the transport of water through transmembrane aquaporin channels in biological systems. The results suggest that nanoporous layered carbon nitrides can be useful for developing high-performance membranes.

Data Processing in Cellular Microphysiometry.

GOAL: This contribution points out the need for well-defined and documented data processing protocols in microphysiometry, an evolving field of label-free cell assays. The sensitivity of the obtained cell metabolic rates toward different routines of raw data processing is evaluated. METHODS: A standard microphysiometric experiment structured in discrete measurement intervals was performed on a platform with a pH- and O 2-sensor readout. It is evaluated using three different data evaluation protocols, based on A) fast Fourier transformation of such dynamics, B) linear regression (LIN) of pH(t) and O2(t) dynamics, and C) numerical simulation (SIM) with a subsequent fitting of dynamics for parameter estimation. RESULTS: We propose a sequence of well documented steps for an organized processing of raw sensor data. Figures of merit for the quality of raw data and the performance of data processing are provided. To estimate metabolic rates, a reaction-diffusion modeling approach is recommended if the necessary model input parameters such as the distribution of the active biomass, sensor response time, and material properties are available. CONCLUSION: The information about cellular metabolic activity contained by measured sensor data dynamics is superimposed by manifold sources of error. Careful consideration of data processing is necessary to eliminate these errors as much as possible and to avoid an incorrect interpretation of data.

Estimation of dynamic metabolic activity in micro-tissue cultures from sensor recordings with an FEM model.

We estimated the dynamic cell metabolic activity and the distribution of the pH value and oxygen concentration in tissue samples cultured in vitro by using real-time sensor records and a numerical simulation of the underlying reaction-diffusion processes. As an experimental tissue model, we used chicken spleen slices. A finite element method model representing the biochemical processes and including the relevant sensor data was set up. By fitting the calculated results to the measured data, we derived the spatiotemporal values of the pH value, the oxygen concentration and the absolute metabolic activity (extracellular acidification and oxygen uptake rate) of the samples. Notably, the location of the samples in relation to the sensors has a great influence on the detectable metabolic rates. The long-term vitality of the tissue samples strongly depends on their size. We further discuss the benefits and limitations of the model.

Molecular motions in lipid bilayers studied by the neutron backscattering technique.

We report a high energy-resolution neutron backscattering study to investigate slow motions on nanosecond time scales in highly oriented solid supported phospholipid bilayers of the model system DMPC-d54 (deuterated 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine), hydrated with heavy water. This technique allows to discriminate the onset of mobility at different length scales for the different molecular components, as, e.g., the lipid acyl-chains and the hydration water in between the membrane stacks, respectively, and provides a benchmark test regarding the feasibility of neutron backscattering investigations on these sample systems. We discuss freezing of the lipid acyl-chains, as observed by this technique, and observe a second freezing transition which we attribute to the hydration water.

Reaction-diffusion modelling for microphysiometry on cellular specimens.

Using modeling and simulation, we quantify the influence of spatiotemporal dynamics on the accuracy of data obtained from sensors placed in microscaled reaction volumes. The model refers to cellular reaction (i.e. proton extrusion and oxygen consumption) in complex, buffering solutions. Whole cells or viable tissues cultured in such devices are monitored in real time with integrated sensors for pH and dissolved oxygen. A 3D finite element model of diffusion and metabolic reaction was set up. With respect to pH, the effect of buffering species on proton diffusion is analysed in detail. To account for the delayed time response of real sensors, the sensor impulse response time was implemented by linear convolution. A validation of the model has been achieved by an electrochemical approach. The model reveals significant deviations of measured pH and O2, and values of these parameters actually occurring at different sites of the cell culture volume. It is applicable to any setting of (bio-) sensors involving reaction and diffusion of dissolved gases and particularly H(+) ions in buffered solutions.

Sensor-based cell and tissue screening for personalized cancer chemotherapy.

Personalized tumor chemotherapy depends on reliable assay methods, either based on molecular "predictive biomarkers" or on a direct, functional ex vivo assessment of cellular chemosensitivity. As a member of the latter category, a novel high-content platform is described monitoring human mamma carcinoma explants in real time and label-free before, during and after an ex vivo modeled chemotherapy. Tissue explants are sliced with a vibratome and laid into the microreaction chambers of a 24-well sensor test plate. Within these ~23 µl volume chambers, sensors for pH and dissolved oxygen record rates of cellular oxygen uptake and extracellular acidification. Robot-controlled fluid system and incubation are parts of the tissue culture maintenance system while an integrated microscope is used for process surveillance. Sliced surgical explants from breast cancerous tissue generate well-detectable ex vivo metabolic activity. Metabolic rates, in particular oxygen consumption rates have a tendency to decrease over time. Nonetheless, the impact of added drugs (doxorubicin, chloroacetaldehyde) is discriminable. Sensor-based platforms should be evaluated in explorative clinical studies for their suitability to support targeted systemic cancer therapy. Throughput is sufficient for testing various drugs in a range of concentrations while the information content obtained from multiparametric real-time analysis is superior to conventional endpoint assays.

Macromolecular dynamics in red blood cells investigated using neutron spectroscopy.

We present neutron scattering measurements on the dynamics of haemoglobin (Hb) in human red blood cells (RBCs) in vivo. Global and internal Hb dynamics were measured in the ps to ns time and Å length scales using quasi-elastic neutron backscattering spectroscopy. We observed the cross over from global Hb short-time to long-time self-diffusion. Both short- and long-time diffusion coefficients agree quantitatively with predicted values from the hydrodynamic theory of non-charged hard-sphere suspensions when a bound water fraction of around 0.23 gram H(2)O per gram Hb is taken into account. The higher amount of water in the cells facilitates internal protein fluctuations in the ps time scale when compared with fully hydrated Hb powder. Slower internal dynamics of Hb in RBCs in the ns time range were found to be rather similar to results obtained with fully hydrated protein powders, solutions and Escherichia coli cells.