Liquid-like Component Research Articles

Magnetic steering continuum robot for transluminal procedures with programmable shape and functionalities

Millimeter-scale soft continuum robots offer safety and adaptability in transluminal procedures due to their passive compliance, but this feature necessitates interactions with surrounding lumina, leading to potential medical risks and restricted mobility. Here, we introduce a millimeter-scale continuum robot, enabling apical extension while maintaining structural stability. Utilizing phase transition components, the robot executes cycles of tip-based elongation, steered accurately through programmable magnetic fields. Each motion cycle features a solid-like backbone for stability, and a liquid-like component for advancement, thereby enabling autonomous shaping without reliance on environmental interactions. Together with clinical imaging technologies, we demonstrate the capability of navigating through tortuous and fragile lumina to transport microsurgical tools. Once it reaches larger anatomical spaces such as stomach, it can morph into functional 3D structures that serve as surgical tools or sensing units, overcoming the constraints of initially narrow pathways. By leveraging this design paradigm, we anticipate enhanced safety, multi-functionality, and cooperative capabilities among millimeter-scale continuum robots, opening new avenues for transluminal robotic surgery.

Universal Two-Component Dynamics in Supercritical Fluids.

Despite the technological importance of supercritical fluids, controversy remains about the details of their microscopic dynamics. In this work, we study four supercritical fluid systems—water, Si, Te, and Lennard-Jones fluid—via classical molecular dynamics simulations. A universal two-component behavior is observed in the intermolecular dynamics of these systems, and the changing ratio between the two components leads to a crossover from liquidlike to gaslike dynamics, most rapidly around the Widom line. We find evidence to connect the liquidlike component dominating at lower temperatures with intermolecular bonding and the component prominent at higher temperatures with free-particle, gaslike dynamics. The ratio between the components can be used to describe important properties of the fluid, such as its self-diffusion coefficient, in the transition region. Our results provide an insight into the fundamental mechanism controlling the dynamics of supercritical fluids and highlight the role of spatiotemporally inhomogeneous dynamics even in thermodynamic states where no large-scale fluctuations exist in the fluid.

Effect of Size and Temperature on Water Dynamics inside Carbon Nano-Tubes Studied by Molecular Dynamics Simulation.

Water transport inside carbon nano-tubes (CNTs) has attracted considerable attention due to its nano-fluidic properties, its importance in nonporous systems, and the wide range of applications in membrane desalination and biological medicine. Recent studies show an enhancement of water diffusion inside nano-channels depending on the size of the nano-confinement. However, the underlying mechanism of this enhancement is not well understood yet. In this study, we performed Molecular Dynamics (MD) simulations to study water flow inside CNT systems. The length of CNTs considered in this study is 20 nm, but their diameters vary from 1 to 10 nm. The simulations are conducted at temperatures ranging from 260 K to 320 K. We observe that water molecules are arranged into coaxial water tubular sheets. The number of these tubular sheets depends on the CNT size. Further analysis reveals that the diffusion of water molecules along the CNT axis deviates from the Arrhenius temperature dependence. The non-Arrhenius relationship results from a fragile liquid-like water component persisting at low temperatures with fragility higher than that of the bulk water.

Unconventional 17O and 63Cu NMR shift components in cuprate superconductors

Nuclear magnetic resonance (NMR) is a fundamental bulk probe that provides key information about the electronic properties of materials. Very recently, the analysis of all available planar copper shift as well as relaxation data proved that while the shifts cannot be understood in terms of a single temperature-dependent spin component, relaxation can be explained with one dominating Fermi liquid-like component, without enhanced electronic spin fluctuations. For the shifts, a doping-dependent isotropic term as well as doping-independent anisotropic term became obvious. Here, we focus on planar [Formula: see text]O NMR shifts and quadrupole splittings. Surprisingly, we find that they demand, independently, a similar two-component scenario and confirm most of the previous conclusions concerning the properties of the spin components, in particular that a negative spin polarization survives in the superconducting state. This should have consequences for the pairing scenario.

1-7-2 石炭の熱時抽出における液状分子の生成消失挙動(1-7 改質・構造,Session 1 石炭・重質油等,研究発表)

1-7-2 石炭の熱時抽出における液状分子の生成消失挙動(1-7 改質・構造,Session 1 石炭・重質油等,研究発表)

T 1–T 2 Correlation and Biopolymer Diffusion Within Human Osteoarthritic Cartilage Measured with Nuclear Magnetic Resonance

Cartilage is a load-bearing tissue that provides smooth articulation during motion of human joints like the knee and hip. Cartilage deterioration in the form of osteoarthritis (OA) causes painful joint motion in more than 100 million patients worldwide, and thus there is great interest in improving our understanding of cartilage to further clinical treatment. Previous studies have examined many aspects of cartilage mechanics, including the flow of interstitial water and repulsion of neighboring glycosaminoglycan chains. However, the contributions of specific molecules to overall tissue properties remain unclear. In this study, we use nuclear magnetic resonance (NMR) diffusometry and relaxometry to examine the molecular dynamics of water and cartilage polymers in OA human articular cartilage. To our knowledge, this is the first identification of two macromolecular populations corresponding to collagen and proteoglycan in human cartilage through their diffusive properties. Further, we performed NMR T1–T2 correlation studies on human cartilage and observed two populations of water distinguished by differing NMR relaxation corresponding to a solid-like component and a liquid-like component. These results provide fundamental insight on the water behavior and polymeric interactions that drive the functional mechanics of cartilage. This study provides a basis to both expand our understanding of basic cartilage mechanics and provide molecular dynamics data for design of novel biomaterials to improve joint health.

Fast cation dynamics in the crystalline state of an imidazolium-based room temperature ionic liquid due to the presence of a tiny amount of H2O

We report the results of a 1H NMR spectroscopic study of cation dynamics in the RTIL, 1-butyl-3-methylimidazolium bromide, in its crystalline state with two different but considerably low water contents, 30 ppm and 200 ppm. The results indicate the presence of a minor liquid-like (or solution) component in the crystalline state in samples with the higher water contents. The relative fraction of this “liquid-like” phase in the crystal is estimated to be ca. 1% around room temperature and increases with increasing temperature up to the melting (liquidus) point, the behavior of which is well explained in terms of a two component phase diagram. It is also indicated based on the lever rule that H2O molecules exist at substantially high concentration in the liquid-like phase compared to in the supercooled liquid state, which can significantly change both microscopic and macroscopic properties of the RTIL. 1H NMR spectral line width and spin–lattice relaxation time measurements indicate that the cations in the liquid-like phase are characterized by a rotational dynamics that is distinct from that of the supercooled liquid state with significantly higher mobility. Such high cation mobility results from the interaction between the cations and H2O molecules in the liquid-like phase that reduces the Coulombic interaction between the cations and anions and decreases local viscosity.

Evolution of a short-T2 liquid-like 1H signal during the hydration of White Portland Cement

The kinetics of cement hydration has been studied by 1H-NMR, through the analysis of the Free Induction Decay (FID) combined with quasi-continuous T1 relaxation time distributions analysis, operating a sort of 2D T1–T2 correlation analysis on a somewhat more physical than mathematical basis. The analysis allowed us to distinguish two solid components, SS (Solid-Short) with T1 of a few milliseconds and SL (Solid-Long) with T1 of the order of a second, ascribable to 1H of anisotropically bound groups in the C–S–H gel, and to 1H nuclei of the Portlandite crystals and possibly to crystal water in Ettringite crystals, respectively. A liquid-like component LS (Liquid-Short) with very short T2 (∼80μs) and T1 a few milliseconds, both quite stable during hydration, was isolated and interpreted as water confined in the inter-layer spaces of the gel. Amounts of LS and SS increase together steadily during hydration, and these, divided by LL (Liquid-Long, the signal from the water in the pores), are proportional to 1/T1 for LL, confirming a surface relaxation effect for LL.

Dynamic processes and chemical composition of Lepidium sativum seeds determined by means of field-cycling NMR relaxometry and NMR spectroscopy

Proton nuclear magnetic resonance (NMR) techniques, such as field-cycling relaxometry, wide-line NMR spectroscopy, and magic angle spinning NMR spectroscopy, were applied to study the seeds of cress, Lepidium sativum. Field-cycling NMR relaxometry was used for the first time to investigate the properties of the whole molecular system of dry cress seeds. This method not only allowed the dynamics to be studied, but was also successful in the differentiation among the solid (i.e., carbohydrates, proteins, or fats forming a solid form of lipids) and liquid-like (oil compounds) components of the seeds. The (1)H NMR relaxation dispersion of oils was interpreted as a superposition of intramolecular and intermolecular contributions. The intramolecular part was described in terms of a Lorentzian spectral density function, whereas a log-Gaussian distribution of correlation times was applied for the intermolecular dipole-dipole contribution. The models applied led to very good agreement with the experimental data and demonstrate that the contribution of the intermolecular relaxation to the overall relaxation should not be disregarded, especially at low frequencies. A power-law frequency dependence of the proton relaxation dispersion was used for the interpretation of the solid components. From the analysis of the (1)H wide-line NMR spectra of the liquid-like component of hydrated cress seeds, we can conclude that the contribution of oil protons should always be taken into account when evaluating the spin-lattice relaxation times values or measuring the moisture and oil content. The application of (1)H magic angle spinning NMR significantly improves resolution in the liquid-like spectrum of seeds and allows the determination of the chemical composition of cress seeds.

Changes in protein structure and dynamics as a function of hydration from 1H second moments

We report the proton second moment obtained directly from the Free Induction Decay (FID) of the NMR signal of variously hydrated bovine serum albumin (BSA) and hen egg white lysozyme (HEWL) and from the width of the NMR Z-spectrum of the cross-linked protein gels of different concentrations. The second moment of the proteins decreases in a continuous stepwise way as a function of increasing water content, which suggests that the structural and dynamical changes occur in small incremental steps. Although the second moment is dominated by the short range distances of nearest neighbors, the changes in the second moment show that the protein structure becomes more open with increasing hydration level. A difference between the apparent liquid content of the sample as found from decomposition of the FID and the analytically determined water content demonstrates that water absorbed in the early stages of hydration is motionally immobilized and magnetically indistinguishable from rigid protein protons while at high hydration levels some protein side-chain protons move rapidly contributing to liquid-like component of the NMR signal.

Origin of the decrease in the torsional-oscillator period of solidHe4

A decrease in the rotational period observed in torsional oscillator measurements was recently taken as a possible indication of a putative supersolid state of helium. We reexamine this interpretation and note that the decrease in the rotation period is also consistent with a solidification of a small liquidlike component into a low-temperature glass. Such a solidification may occur by a low-temperature quench of topological defects (e.g., grain boundaries or dislocations) which we examined in an earlier work. The low-temperature glass can account for not only a monotonic decrease in the rotation period as the temperature is lowered but also explains the peak in the dissipation occurring near the transition point. Unlike the nonclassical rotational inertia scenario, which depends on the supersolid fraction, the dependence of the rotational period on external parameters, e.g., the oscillator velocity, provides an alternate interpretation of the oscillator experiments.

High-density liquidlike component facilitates plastic flow in a model amorphous silicon system.

Molecular dynamics simulations show that plastic deformation of amorphous Si modeled by the Stillinger-Weber potential is very sensitive to the density of the initial unstressed state. Low-density systems exhibit a pronounced yield phenomenon, strain softening, and a dramatic drop in pressure during deformation at a constant volume. This behavior is explained by the presence in every system of a certain concentration of solidlike and liquidlike components, the latter being denser and more amenable to plastic flow.

Analysis of 1H-NMR relaxation time distributions in L1 to L6 rat lumbar vertebrae

A better knowledge of the NMR relaxation behavior of bone tissue can improve the definition of imaging protocols to detect bone diseases like osteoporosis. The six rat lumbar vertebrae, from L1 to L6, were analyzed by means of both transverse (T(2)) and longitudinal (T(1)) relaxation of (1)H nuclei at 20 MHz and 30 degrees C. Distributions of relaxation times, computed using the multiexponential inversion software uniform penalty inversion, extend over decades for both T(2) and T(1) relaxation. In all samples, the free induction decay (FID) from an inversion-recovery (IR) T(1) measurement shows an approximately Gaussian (solid-like) component, exp[-1/2(t/T(GC))2], with T(GC) approximately 12 micros (GC for Gaussian component) and a liquid-like component (LLC) with initially simple-exponential decay. Averaging and smoothing procedures are adopted to obtain the ratio alpha between GC and LLC signals and to get separate T(1) distributions for GC and LLC. Distributions of T(1) for LLC show peaks centered at 300-500 ms and shoulders going down to 10 ms, whereas distributions of T(1) for GC are single broad peaks centered at roughly 100 ms. The T(2) distributions by Carr-Purcell-Meiboom-Gill at 600 micros echo spacing are very broad and extend from 1 ms to hundreds of ms. This long echo spacing does not allow one to see a peak in the region of hundreds of micros, which is better seen by single spin-echo T(2) measurements. Results of the relaxation analysis were then compared with densitometric data. From the study, a clear picture of the intratrabecular and intertrabecular (1)H signals emerges. In particular, the GC is presumed to be due to (1)H in collagen, LLC due to all the fluids in the bone including water and fat, and the very short T(2) peak due to the intratrabecular water. Overall, indications of some trends in composition and in pore-space distributions going from L1 to L6 appeared. Published results on rat vertebrae obtained by fitting the curves by discrete two-component models for both T(2) and T(1) are consistent with our results and can be better interpreted in light of the shown distributions of relaxation times.

Free volume and transport properties of homogeneous poly(ethylene- co-octene)s

Liquid and vapour n-hexane sorption/desorption were studied on homogeneous poly(ethylene- co-octene)s produced by metallocene-catalyzed polymerisation covering a crystallinity range from 3.5 to 72.4%. Crystal core contents determined by Raman spectroscopy were lower than those determined by density assessments, particularly at low degrees of crystallinity. The solubility showed deviation from Henry's law. The solubilities of n-hexane in the homogeneous copolymers depended in a non-linear manner on the content of penetrable polymer component and were lower than those earlier reported for heterogeneous copolymers at the same contents of penetrable component. The concentration dependence of the thermodynamic diffusivity predicted by the Cohen–Turnbull–Fujita free volume theory was confirmed by the data obtained by the differential method and the differences between the results obtained from the integral and differential methods were within the margins of experimental error. The fractional free volume of the penetrable polymer fraction increased with increasing fraction of penetrable polymer and with relative proportion of liquid-like component in the penetrable polymer fraction. The homogeneous copolymers showed a decreasing trend in the geometrical impedance factor with increasing degree of crystallinity.

Salt loaded heat pipes: steady-state operation and related heat and mass transport

Fluids in the deep-seated zones (3.5–4.5 km) of active geothermal zones are known to have increased salinity and acidity that can enhance interaction with surrounding porous rocks. A possible mechanism for brine generation is the separation of the rising magmatic fluid into a gas-like and a liquid-like component. This work illustrates the main features of this mechanism by investigating the conditions for heat pipe convection of natural brines in hydrothermal systems. The well-established heat pipe regime for convection of two-phase pure water (vapor–liquid) in a porous column is extended to the case of boiling brines. In particular, the NaCl–H 2O system is used to model the 1-D reactive flow with dissolution-precipitation in geothermal reservoirs. The quasi steady-state equations of the conservation of matter, Darcy’s law for the gas and liquid phases, and the heat balance equation have been examined while neglecting the temporal variation of porosity. A semi-analytical procedure is used to solve these equations for a two-phase fluid in equilibrium with a solid salt. The solution is in the form of the dependence of liquid volume fraction as a function of temperature for different heat fluxes. The solution is separated into two isolated regions by the temperature T=596°C, at the maximum fluid pressure for three-phase (H–L–V) equilibrium. In the case of unsaturated two-phase flow at the reference permeability of porous rocks (3·10 −16 m 2), the maximum heat flux that can be transferred through the porous column via convection is analytically estimated to be 4.3 W/m 2. This is close to the corresponding value for the three-phase case that is numerically calculated to be 6 W/m 2. Due to dissolution (partial leaching of oxide components by acid condensates) and precipitation of salt at the boiling front, heat transfer in a heat pipe in soluble media occurs in a direction opposite to the associated mass transfer. This can cause deep hydrothermal karsting that is manifested as surface subsidence at rates of about several cm/yr as observed in some active geothermal fields.

High-density liquid-like component facilitates plastic flow in a model amorphous silicon system

ABSTRACTMolecular dynamics simulations show that plastic deformation behavior of model Stillinger-Weber amorphous Si is very sensitive to the density of the initial unstressed state. Low-density systems exhibit a pronounced yield phenomenon, strain softening, and a dramatic drop in pressure during deformation at constant volume. This behavior is explained by the interplay in every system of the prevailing solid-like and liquid-like components, with the latter being denser and more amenable to plastic flow.

A study on solid-state drawn fibers of polyethylene by confocal Raman microspectrometry: evaluation of the orientation profiles of amorphous and crystalline phases across the fiber section

Polarized Raman macrospectrometry and confocal Raman microspectrometry have been used to evaluate the uniaxial draw of polyethylene (PE) at a draw ratio of ∼6. The draw was conducted by solid-state extrusion. The PE samples tested were synthesized to different molecular weights by slurry and gas phase processes at different temperatures. Raman spectra offer an important evaluation of draw, with bands identifiable for each: the amorphous, crystalline and interphase regions of the morphology. Such an interphase is preferentially located at the crystallite fold surface boundary and it has been associated with the presence of chain loops and entangled chain segments in this region. Orientations of the different phases are estimated by measuring the depolarization factors of the corresponding bands. Further, by confocal Raman microspectrometry, profiles of orientation across the fiber have been identified, by focusing the laser beam at different depths in the drawn PE. It was found that the crystalline component orients along the draw direction, while, across the fiber section, the interphase and the liquid-like amorphous component display preferred orientation normal to the draw direction. Correlations among orientation profiles, synthesis conditions and reactor powder ductility are discussed. Orientation profiles have been compared to the deformation profiles obtained by the displacement of pre-imprinted ink marks on the drawn fibers. A possible interpretation of the orientation profiles is attempted in terms of the relevant modes of deformation and alignment of chain segments in the different phases. The Raman results, in combination with wide angle X-ray analysis reveal steps in the drawn process that have implications for understanding the draw of PE and possibly for the general process of ‘necking’ on draw of semicrystalline thermoplastics.

Free volume and transport properties of heterogeneous poly(ethylene- co-octene)s

n-Hexane desorption measurements were performed on heterogeneous poly(ethylene- co-octene)s with hexyl branch contents between 0.8 and 3.9 mol% and crystallinities between 30 and 60%. Crystal core contents obtained by Raman spectroscopy were lower than the density-based crystallinity, particularly for the samples with the highest degree of branching. A modified Cohen–Turnbull–Fujita free volume model adequately described the diffusivity data. The free volume of the penetrable phases was strongly dependent on their total volume fraction, suggesting the presence of an interfacial penetrable component with low fractional free volume. The dependence of the fractional free volume of the penetrable phases on the phase composition suggests that mass transport takes place from the liquid-like component to the interfacial component and that the penetrant molecules are trapped at the interfacial sites. The decrease in geometrical impedance factor with increasing crystallinity may be explained by the presence of extraordinarily wide dominant crystal lamellae in the heterogeneous low crystallinity samples. The saturation concentration of n-hexane in a wide range of polyethylenes (including the heterogeneous poly(ethylene- co-octene)s, linear polyethylenes and poly(ethylene- co-butene)s reported earlier; crystallinity range: 30–94%) showed a complex non-linear dependence on crystallinity that was qualitative in accordance with rubber elasticity theory considering also molecular cilia.

Methane mobility in carbon nanotubes

Quasi-elastic neutron scattering has been used to characterize the diffusivity of CH 4 molecules condensed in single-wall carbon nanotubes. It is shown that the two sites of adsorption, previously observed by adsorption volumetry and calorimetry measurements, correspond to a solid-like phase for the more strongly bound site at T<120 K and to a liquid-like component for the more weakly bound site at 70< T<120 K. The diffusion coefficients of the mobile molecules range between 3×10 −7 to 15×10 −7 cm 2 s −1. The fraction of this viscous liquid diminishes as the temperature is decreased; the adsorbate is fully solidified at 50 K and below.

Dynamics NMR investigations of a glassy crystal confined in porous materials

The temperature dependence of the proton relaxation rates has been studied in molecular glassy crystals cyano-adamantane (C 10 H 15 CN) confined in the porous space of a silica glass of 60A and 150A nominal pore sizes. In the temperature range corresponding to the bulk plastic phase, the NMR proton lineshape of the confined materials revealed a two phase system consisting of a liquid-like component and a crystalline solid bulk-like component. As for the bulk, the a process, related to the dipolar axis motion, controlled both T 1z and T 1p in the largest pores. From the NMR results we concluded that the dynamics of this α-relaxation process is slightly enhanced by the confinement giving rise to a negative shift of the glass transition temperature. On the contrary, the confinement has no influence on the relaxation rates in the glassy state.