Range Of Relaxation Times Research Articles

Accurate and efficient determination of glass thermo-viscoelastic properties using creep compliance master curve construction approach

An accurate and efficient method for determining the thermo-viscoelastic properties of glass was proposed using a creep compliance master curve construction approach based on the time-temperature superposition principle. This method mainly involved obtaining creep compliance at multiple temperatures, constructing the master curve, and converting into relaxation modulus. By applying this method, the shear relaxation modulus and Williams-Landel-Ferry constants were successfully obtained for K9 glass. A smooth creep compliance master curve at 590 °C was constructed covering a vast timescale up to 2.6×105 seconds, despite a single curve's duration being only 619 seconds. Consequently, the derived relaxation modulus encompassed a broad range of relaxation times spanning six orders of magnitude. The high accuracy of the determined thermo-viscoelastic properties was firmly validated across all tested temperatures. Furthermore, the detrimental impact of friction on the method's accuracy can be effectively minimized by selecting a suitably large height-to-diameter ratio for the cylindrical glass specimen.

Impact of anti-coagulant choice on blood elongational behavior.

Blood is a highly complex fluid with rheological properties that have a significant impact on various flow phenomena. In particular, it exhibits a non-Newtonian elongational viscosity that is comparable to polymer solutions. In this study, we investigate the effect of three different anticoagulants, namely EDTA (ethylene diamine tetraacetic acid), heparin, and citrate, on the elongational properties of both human and swine blood. We observe a unique two stage thinning process and a strong dependency of the characteristic relaxation time on the chosen anticoagulant, with the longest relaxation time and thus the highest elongational viscosity being found for the case of citrate. Our findings for the latter are consistent with the physiological values obtained from a dripping droplet of human blood without any anticoagulant. Furthermore, our study resolves the discrepancy found in the literature regarding the reported range of characteristic relaxation times, confirming that the elongational viscosity must be taken into account for a full rheological characterization of blood. These results have important implications for understanding blood flow in various physiological, pathological and technological conditions.

Dynamics of non-equilibrium concentration fluctuations during free-diffusion in highly stratified solutions of glycerol and water.

We investigate the non-equilibrium fluctuations occurring during free diffusion between two solutions of glycerol and water with various concentration differences. The non-linearity of the system, determined by the strong stratification of the sample, requires introducing an interpretation model able to characterize the dependence of the correlation properties of the non-equilibrium fluctuations on the local thermophysical variables of the system. The proposed model allows us to characterize the dynamics of non-equilibrium fluctuations in the presence of a wide range of relaxation times determined by the strong stratification of the sample, at variance with the cumulant methods commonly used in dynamic light scattering experiments, which work well in the presence of a moderate dispersion of relaxation times.

Study of the impact of various porous media on pore space utilization and CO2 storage by injection of microbubbles into oil reservoirs

CO2 capture and storage technology have the potential to help reach net zero emissions. CO2-enhanced oil recovery (CO2 EOR) is a favourable method. Limited pilot testing has provided preliminary evidence that the unique physical properties of gas microbubbles (MBs) can be used to improve pore utilization efficiency. In this study, supercritical CO2 injection at 0.05 mL/min into sand samples with different grain sizes under reservoir conditions was investigated by nuclear magnetic resonance (NMR). The spatial distribution of the CO2 and oil and the dynamic pore occupancy mechanism were determined for the first time, and the results from normal bubbles (NBs) and MBs were compared. The results show a more significant left shift of the transverse relaxation time in the case of MB injection, which means that CO2 can easily occupy a wide range of large pore spaces. Dynamic changes in the oil volume in the four types of pores classified by the transverse relaxation time indicate that the oil in large pores is flushed earlier when MB is injected and that the CO2 saturation in minimal pores (T2 relaxation time range from 5 ms to 100 ms) and small pores (T2 relaxation time range from 100 ms to 500 ms) increases. The cumulative oil volume fraction decreases by 9.0% when injecting MBs. From the perspective of carbon storage, the gas storage potential is significantly enhanced within low-permeability sand when injected with MBs. The maximum volume of free CO2 was enhanced by 16.9% in this case. In addition, the storage efficiency is enhanced up to 5.1% for low-permeability sand and 1.6% for medium-permeability sand. However, bubble flow is not as advantageous in high-permeability sand. Considering dissolution trapping, the storage efficiency reaches 26.3%.

NMR-based petrophysical parameter calculation with sparse inversion in tight reservoirs

Porosity, permeability, and saturation are important parameters reflecting the petrophysical properties of cores. The petrophysical parameters can be calculated from the inverted nuclear magnetic resonance (NMR) spectra. However, the continuous relaxation time distribution in the traditional NMR spectra is inconsistent with the sparse NMR relaxation signatures of the pore fluid. In this paper, a sparse inversion method was proposed to process NMR data in tight reservoirs, and the petrophysical parameters were calculated from the sparse NMR spectra. In the sparse inversion process, the relaxation time range of the core was first determined, only one new relaxation time was added to the sparse inversion in each iteration, and then the insignificant signal was eliminated. The signal amplitudes of sparse NMR spectra are constrained by the amplitude of the first echo to avoid the influence of noise. Compared with the traditional NMR spectra, the relaxation time is sparse and unfixed in the sparse NMR spectra. The T2 data of tight sandstone and T1-T2 data of shale were processed, and petrophysical parameters were evaluated to verify the effectiveness of the proposed method. The results indicate that the sparse NMR spectra can be better used to accurately calculate the petrophysical parameters in tight reservoirs, including porosity, permeability, and saturation.

Silicone-based materials with tailored MR relaxation characteristics for use in reduced coil visibility and in tissue-mimicking phantom design.

The development of materials with tailored signal intensity in MR imaging is critically important both for the reduction of signal from non-tissue hardware, as well as for the construction of tissue-mimicking phantoms. Silicone-based phantoms are becoming more popular due to their structural stability, stretchability, longer shelf life, and ease of handling, as well as for their application in dynamic imaging of physiology in motion. Moreover, silicone can be also used for the design of stretchable receive radio-frequency (RF) coils. Fabrication of materials with tailored signal intensity for MRI requires knowledge of precise T1 and T2 relaxation times of the materials used. In order to increase the range of possible relaxation times, silicone materials can be doped with gadolinium (Gd). In this work, we aim to systematically evaluate relaxation properties of Gd-doped silicone material at a broad range of Gd concentrations and at three clinically relevant magnetic field strengths (1.5 T, 3 T, and 7 T). We apply the findings for rendering silicone substrates of stretchable receive RF coils less visible in MRI. Moreover, we demonstrate early stage proof-of-concept applicability in tissue-mimicking phantom development. Ten samples of pure and Gd-doped Ecoflex silicone polymer samples were prepared with various Gd volume ratios ranging from 1:5000 to 1:10, and studied using 1.5T and 3T clinical and 7T preclinical scanners. T1 and T2 relaxation times of each sample were derived by fitting the data to Bloch signal intensity equations. A receive coil made from Gd-doped Ecoflex silicone polymer was fabricated and evaluated in vitro at 3T. With the addition of a Gd-based contrast agent, it is possible to significantly change T2 relaxation times of Ecoflex silicone polymer (from 213ms to 20ms at 1.5T; from 135ms to 17ms at 3T; and from 111.4ms to 17.2ms at 7T). T1 relaxation time is less affected by the introduction of the contrast agent (changes from 608ms to 579ms; from 802.5ms to 713ms at 3T; from 1276ms to 979ms at 7T). First results also indicate that liver, pancreas, and white matter tissues can potentially be closely mimicked using this phantom preparation technique. Gd-doping reduces the appearance of the silicone-based coil substrate during the MR scan by up to 81%. Gd-based contrast agents can be effectively used to create Ecoflex silicone polymer-based phantoms with tailored T2 relaxation properties. The relative low cost, ease of preparation, stretchability, mechanical stability, and long shelf life of Ecoflex silicone polymer all make it a good candidate for "MR invisible" coil development and bears promise for tissue-mimicking phantom development applicability.

Viscoelastic Liquid Matrix with Faster Bulk Relaxation Time Reinforces the Cell Cycle Arrest Induction of the Breast Cancer Cells via Oxidative Stress

The reactivating of disseminated dormant breast cancer cells in a soft viscoelastic matrix is mostly correlated with metastasis. Metastasis occurs due to rapid stress relaxation owing to matrix remodeling. Here, we demonstrate the possibility of promoting the permanent cell cycle arrest of breast cancer cells on a viscoelastic liquid substrate. By controlling the molecular weight of the hydrophobic molten polymer, poly(ε-caprolactone-co-D,L-lactide) within 35-63 g/mol, this study highlights that MCF7 cells can sense a 1000 times narrower relaxation time range (80-290 ms) compared to other studies by using a crosslinked hydrogel system. We propose that the rapid bulk relaxation response of the substrate promotes more reactive oxygen species generation in the formed semi-3D multicellular aggregates of breast cancer cells. Our finding sheds light on the potential role of bulk stress relaxation in a viscous-dominant viscoelastic matrix in controlling the cell cycle arrest depth of breast cancer cells.

T1 relaxation time of ISMRM/NIST T1 phantom spheres at 7T.

T1 relaxation times of the 14 T1 phantom spheres that make up the standard International Society for Magnetic Resonance in Medicine (ISMRM)/National Institute of Standards and Technology (NIST) system phantom are reported at 7 T. T1 values of six of the 14 T1 spheres at 7 T (with T1 > 270 ms) have been reported previously, but, to the best of our knowledge, not all of the T1s of the 14 T1 spheres at 7 T have been reported before. Given the increasing number of 7-T MRI systems in clinical settings and the increasing need for T1 phantoms that cover a wide range of T1 relaxation times to evaluate rapid T1 mapping techniques at 7 T, it is of high interest to obtain accurate T1 values for all the ISMRM/NIST T1 spheres at 7 T. In this work, T1 relaxation time was measured on a 7-T MRI scanner using an inversion-recovery spin-echo pulse sequence and derived by curve fitting to a signal equation that exhibits insensitivity to inhomogeneity. Day-to-day reproducibility was within 0.4% and differences between two different RF coils within 1.5%. T1s of a subset of the 14 spheres were also measured by NMR at 7 T for comparison, and the T1 results were consistent between the MRI and NMR measurements. T1 measurements performed at 3 T on the same 14 spheres using the same sequence and fitting method yielded good agreement (mean percentage difference of -0.4%) with the reference T1 values available from the NIST, reflecting the accuracy of the reported technique despite being without the standard phantom housing. We found that the T1 values of all 14 NiCl2 spheres are consistently lower at 7T than at 3T. Although our results were well reproduced, this study represents initial work to quantify the 7-T T1 values of all 14 NIST T1 spheres outside of the standard housing and does not warrant reproducibility of the ISMRM/NIST system phantom as a whole. A future study to assess the T1 values of a version of the ISMRM/NIST system phantom that fits inside typical commercial coils at 7T will be very helpful. Nonetheless, the details on our acquisition and curve-fitting methods reported here allow the T1 measurements to be reproduced elsewhere. The T1 values of all 14 spheres reported here will be valuable for the development of quantitative MR fingerprinting and rapid T1 mapping for a large variety of research projects, not only in neuroimaging but also in body MRI, musculoskeletal MRI, and gadolinium contrast-enhanced MRI, each of which is concerned with much shortened T1.

Mechanical Behavior of Polymer Nanocomposites via Atomistic Simulations: Conformational Heterogeneity and the Role of Strain Rate.

Polymer nanohybrids with a high fraction of nanofillers have been found to exhibit improved mechanical properties compared to the neat polymer homogeneous systems. Since polymer-based materials are characterized by a broad range of relaxation times, it is expected that their response under external load would depend on the actual rate of the applied deformation. In this work, we investigate the heterogeneous mechanical behavior in glassy poly(ethylene oxide)/silica nanoparticles (PEO/SiO2) nanocomposites via detailed atomistic molecular dynamics simulations. Our goal is to unravel the effect of strain rate on the mechanism of polymer nanocomposite reinforcement, within the glassy state, by directly probing the mechanical properties at the molecular level. By applying tensile deformations with various strain rates we clearly demonstrate that the value of the applied strain rate strongly affects the mechanical properties of the PEO/SiO2 model systems, inducing a transition from a rubber-like behavior, at low strain rate, to a more brittle one, at high strain rates. Then, we further investigate the mechanical heterogeneity in glassy PEO/SiO2 systems by probing directly the stress and strain fields for various conformations of adsorbed (trains, tails, loops, and bridges), and free polymer chains. Our data emphasize the importance of both train and bridge conformations on the mechanical reinforcement of the polymer nanocomposites. Last, we also probe the mobility of various chain conformations, under different applied strain rates, and their contribution to the overall mechanical behavior of the nanocomposite, during the deformation process.

Multiscale Analysis of Segmental Relaxation in PC/PETg Multilayers: Evidence of Immiscible Nanodroplets

This work highlights the influence of layer thicknesses on glass transition and molecular mobility in polycarbonate (PC) and poly(ethylene terephthalate glycol) (PETg) multilayered films obtained by the layer-multiplying coextrusion process. By combining modulated temperature scanning calorimetry (MT-DSC) and dielectric relaxation spectroscopy (DRS) measurements, the average values of the cooperative rearranging region (CRR) size in a wide range of relaxation times and temperatures have been calculated. The size reduction from micro- to nanoscale is accompanied by a significant deviation of the structural and dynamical properties compared to the bulk. Furthermore, we have evidenced significant differences in PETg and PC behaviors: PETg plays the role of a “hard-confined” polymer, while PC behaves as a “free-confined” polymer, implying opposite variations of the glass transition temperature. The determination of the relaxation parameters for each individual polymer has been possible even for very low layer thicknesses (below 10 nm), for which the multilayer structure is not observed. This result shows that even when PETg and PC are brought into very intimate contact, they maintain their own structural behavior and segmental relaxation, suggesting the formation of immiscible nanodroplets when the multilayer structure disappears.

Prediction of Li-ion battery capacity degradation considering polarization recovery with a hybrid ensemble learning model

Polarization recovery is a phenomenon that significantly affects the capacity degradation behavior of lithium-ion battery (LIB). In this study, we demonstrated that capacity fluctuation during fading was highly correlated with polarization recovery through micro-Roman and rate performance tests. A series of aging experiments with a wide range of relaxation times (0.08 h to 200 h) were developed to analyze the effects of polarization recovery on discharge capacity. The experimental dataset includes 30,696 charge-discharge cycles under various conditions based on LiFePO4/graphite and LiNi0.8Co0.15Al0.05O2/graphite battery cells. Here, a hybrid ensemble learning model (HEL) was proposed to achieve accurate predictions while considering polarization recovery. Multiple highly correlated stress factors of polarization recovery were identified and then utilized as the input data of HEL. Our analysis shows that HEL is capable of precisely capturing capacity degradation with fluctuations due to polarization recovery, the implication of which is critical to the advancement of lifetime management in battery energy storage applications.

A New Monotonicity for Principal Eigenvalues with Applications to Time-Periodic Patch Models

A new monotonocity of principal eigenvalues in time-periodic patch environments is established. As an application, a patch model for two competing species in spatio-temporally varying environments is investigated. When two species are identical except for their relaxation time, the species with the shorter relaxation time will always drive the other one to extinction. When two species are identical except for their diffusion rates, our results suggest that the faster diffusing species could be favored for some intermediate range of relaxation time, while the slower diffusing species will be favored for both short and long relaxation time. In general, short relaxation time and slow diffusion rate tend to help species gain advantage in competition.

Why the Cox–Merz rule and Gleissle mirror relation work: A quantitative analysis using the Wagner integral framework with a fractional Maxwell kernel

In this work, we mathematically derive the conditions for which empirical rheometric relations such as the Cox–Merz rule and Gleissle mirror relationship are satisfied. We consider the Wagner integral constitutive framework, which is a special limiting case of the Kaye–Bernstein Kearsley Zapas (K-BKZ) constitutive equation to derive analytical expressions for the complex viscosity, the steady shear viscosity, and the transient stress coefficient in the start-up of steady shear. We use a fractional Maxwell liquid model as the linear relaxation modulus or memory kernel within a non-linear integral constitutive framework. This formulation is especially well-suited for describing complex fluids that exhibit a broad relaxation spectrum and can be readily reduced to the canonical Maxwell model for describing viscoelastic liquids that exhibit a single dominant relaxation time. To incorporate the nonlinearities that always become important in real complex fluids at large strain amplitudes, we consider both an exponential damping function as well as a more general damping function. By evaluating analytical expressions for small amplitude oscillatory shear, steady shear, and the start-up of steady shear using these different damping functions, we show that neither the Cox–Merz rule nor the Gleissle mirror relation can be satisfied for materials with a single relaxation mode or narrow relaxation spectrum. We then evaluate the same expressions using asymptotic analysis and direct numerical integration for more representative complex fluids having a wide range of relaxation times and nonlinear responses characterized by damping functions of exponential or Soskey–Winter form. We show that for materials with broad relaxation spectra and sufficiently strong strain-dependent damping the empirical Cox–Merz rule and the Gleissle mirror relations are satisfied either exactly, or to within a constant numerical factor of order unity. By contrast, these relationships are not satisfied in other classes of complex viscoelastic materials that exhibit only weak strain-dependent damping or strain softening.

Electrochemical Dual Transducer for Fluidic Self-Sensing Actuation.

An electrochemical dual transducer (ECDT) based on a chemical reaction is a new fluidic machine for self-sensing actuation. Recently, incorporating sensors has enhanced the multifunctionality of soft robots with fluidic machines such as pumps or compressors. However, conventional fluidic systems have limitations such as heavy weight, noise, bloat, and complexity. In our previous research, we adopted small-sized, lightweight, and quiet electrohydrodynamic pumps for soft robots. In this paper, we propose a new ECDT by exploring the possibility of an electrohydrodynamic (EHD) pump to sense the flow of the working fluid. The current in the ECDT is proportional to 1/3 of the inflowing velocity. We also clarify its mechanism, mathematical model, range of detectable flow rate, sensitivity factor, relaxation time, response speed, and pumping characteristics. The advantages of the ECDT are their small size, light weight, simple fabrication process, extensibility of the sensing range, and sensitivity. We also demonstrate a suction cup driven by the ECDT, which can detect, hold, and release objects. We expect a bidirectional ECDT will realize a small, multifunctional, and straightforward fluidic system.

Variation in the stellar mass function along stellar streams

ABSTRACT Stellar streams are the inevitable end product of star cluster evolution, with the properties of a given stream being related to its progenitor. We consider how the dynamical history of a progenitor cluster, as traced by the evolution of its stellar mass function, is reflected in the resultant stream. We generate model streams by evolving star clusters with a range of initial half-mass relaxation times and dissolution times via direct N-body simulations. Stellar streams that dissolve quickly show no variation in the stellar mass function along the stream. Variation is, however, observed along streams with progenitor clusters that dissolve after several relaxation times. The mass function at the edges of a stream is approximately primordial, as it is populated by the first stars to escape the cluster before segregation occurs. Moving inwards the mass function steepens as the intermediate parts of the stream consist of mostly low-mass stars that escaped the cluster after some segregation has occurred. The centre of the stream is then marked by a flatter mass function, as the region is dominated by high-mass stars that quickly segregated to the progenitor cluster’s centre and were the last stars to become unbound. We further find that the maximum slope of the mass function along the stream and the rate at which it decreases with distance from the dissolved progenitor serve as proxies for the dynamical state reached by the progenitor cluster before dissolution; this may be able to be applied to observed streams with near-future observations.

Myofibrillar protein composite gels: effect of esterified potato starch, lard and peanut oil on the gel properties.

Heat-induced composite gels were prepared with 20 g kg-1 myofibrillar protein (MP) sol, 20 g kg-1 modified starch and 100 g kg-1 lipid pre-emulsified by MP in 0.6mol L-1 NaCl, at pH6.2. The effects of esterified potato starch (EPS) and emulsified lipid (lard or peanut oil) on the rheology, texture properties and nuclear magnetic resonance characterization of MP gel were evaluated. The addition of starch and lipid significantly improved the gel strength and water holding capacity (WHC) of the MP gel. Analysis of the relaxation time compared with the WHC tests showed that the variation range of the transverse T22 relaxation time of a gel was positively proportional to changes in WHC of the composite gel, and the lower the T22 relaxation time, the better the WHC of composite gel. Moreover, MP gel with starch and emulsified lard added at the same time has the lowest T2 relaxation time, and also the best WHC of the gel. Environmental scanning electron microscopy showed that emulsified oil droplets embedded the gaps in the protein network, and the gelatinized starch contributed to restrict the oil droplet size, resulting in thicker MP gel. Emulsified lipid and modified starch have an important influence on the rheology and microstructure of MP gels, indicating the subtle interaction between starch, lipid and protein. The results suggest the potential feasibility of modified starch and vegetable oil to improve the textural properties in comminuted meat products. © 2021 Society of Chemical Industry.

Toward magnetic resonance fingerprinting for low-field MR-guided radiation therapy.

The acquisition of multiparametric quantitative magnetic resonance imaging (qMRI) is becoming increasingly important for functional characterization of cancer prior to- and throughout the course of radiation therapy. The feasibility of a qMRI method known as magnetic resonance fingerprinting (MRF) for rapid T1 and T2 mapping was assessed on a low-field MR-linac system. A three-dimensional MRF sequence was implemented on a 0.35T MR-guided radiotherapy system. MRF-derived measurements of T1 and T2 were compared to those obtained with gold standard single spin echo methods, and the impacts of the radiofrequency field homogeneity and scan times ranging between 6 and 48 min were analyzed by acquiring between 1 and 8 spokes per time point in a standard quantitative system phantom. The short-term repeatability of MRF was assessed over three measurements taken over a 10-h period. To evaluate transferability, MRF measurements were acquired on two additional MR-guided radiotherapy systems. Preliminary human volunteer studies were performed. The phantom benchmarking studies showed that MRF is capable of mapping T1 and T2 values within 8% and 10% of gold standard measures, respectively, at 0.35T. The coefficient of variation of T1 and T2 estimates over three repeated scans was<5% over a broad range of relaxation times. The T1 and T2 times derived using a single-spoke MRF acquisition across three scanners were near unity and mean percent errors in T1 and T2 estimates using the same phantom were<3%. The mean percent differences in T1 and T2 as a result of truncating the scan time to 6 min over the large range of relaxation times in the system phantom were 0.65% and 4.05%, respectively. The technical feasibility and accuracy of MRF on a low-field MR-guided radiation therapy device has been demonstrated. MRF can be used to measure accurate T1 and T2 maps in three dimensions from a brief 6-min scan, offering strong potential for efficient and reproducible qMRI for future clinical trials in functional plan adaptation and tumor/normal tissue response assessment.

Submicron Metal 3D Printing by Ultrafast Laser Heating and Induced Ligand Transformation of Nanocrystals.

Currently, light-based three-dimensional (3D) printing with submicron features is mainly developed based on photosensitive polymers or inorganic-polymer composite materials. To eliminate polymer/organic additives, a strategy for direct 3D assembly and printing of metallic nanocrystals without additives is presented. Ultrafast laser with intensity in the range of 1 × 1010 to 1 × 1012 W/cm2 is used to nonequilibrium heat nanocrystals and induce ligand transformation, which triggers the spontaneous fusion and localized assembly of nanocrystals. The process is due to the operation of hot electrons as confirmed by a strong dependence of the printing rate on laser pulse duration varied in the range of electron-phonon relaxation time. Using the developed laser-induced ligand transformation (LILT) process, direct printing of 3D metallic structures at micro and submicron scales is demonstrated. Facile integration with other microscale additive manufacturing for printing 3D devices containing multiscale features is also demonstrated.

Probabilistic magnetometry with a two-spin system in diamond

Solid-state magnetometers like the nitrogen-vacancy (NV) center in diamond have been of paramount importance for the development of quantum sensing with nanoscale spatial resolution. The underlying protocol is a Ramsey sequence, that imprints an external static magnetic field into the phase of the quantum sensor, which is subsequently read out. In this theoretical work we propose a sensing scheme that harnesses the hyperfine coupling between the NV center and a nearby nuclear spin to set a post-selection protocol. We show that concentrating valuable sensing information into a single successful measurement yields an improvement in sensitivity over Ramsey in the range of short transverse relaxation times. By considering realistic experimental conditions, we found that the detection of weak magnetic fields in the μT range can be achieved with a sensitivity of few tens of nTHz−1/2 at cryogenic temperature (4 K), and μTHz−1/2 at room temperature.

Frustration-induced emergent Hilbert space fragmentation

Although most quantum systems thermalize locally on short time scales independent of initial conditions, recent developments have shown this is not always the case. Lattice geometry and quantum mechanics can conspire to produce constrained quantum dynamics and associated glassy behavior, a phenomenon that falls outside the rubric of the eigenstate thermalization hypothesis. Constraints "fragment" the many-body Hilbert space due to which some states remain insulated from others and the system fails to attain thermal equilibrium. Such fragmentation is a hallmark of geometrically frustrated magnets with low-energy "icelike manifolds" exhibiting a broad range of relaxation times for different initial states. Focusing on the highly frustrated kagome lattice, we demonstrate these phenomena in the Balents-Fisher-Girvin Hamiltonian (easy-axis regime), and a three-coloring model (easy-plane regime), both with constrained Hilbert spaces. We study their level statistics and relaxation dynamics to develop a coherent picture of fragmentation in various limits of the XXZ model on the kagome lattice.