Small Volume Change Research Articles

A Method to Improve the Accuracy for the Comparison of Consecutively Determined Upper Limb Cross-Sectional Area Profiles of Test Subjects: Impact on (Segmental) Limb Volume and Local Limb Circumference.

Background: Chronic edema management depends on measuring small volume changes over time. Therefore, a highly sensitive, accurate, and reliable technique is needed to objectively judge sequential measurements. Methods and Results: The prototype of the Peracutus Aqua Meth (PAM), a new volumetric measuring device, was used in an experimental study. Thirty-nine healthy test subjects were measured three times. The measuring principle of the PAM is based on obtaining a profile of cross-sectional areas along the length of an object or limb. Besides total arm volumes, the volume of any chosen segment can be determined. The utmost tip of the middle finger appeared to be an unreliable reference point. Instead, the concept of "hand median" was introduced to align and compare profiles of cross-sectional areas of sequential measurements. Using the hand median strongly improved the measuring accuracy, rendering standard deviation values of 0.4%-1.3% for (segmental) volume determination. Conclusions: Measurements with the PAM show that accurate local/segmental volume determination of a limb is possible. Standard deviations of less than 1.3% are easily obtained for cross-sectional area and volume determination.

A three-in-one strategy of high-entropy, single-crystal, and biphasic approaches to design O3-type layered cathodes for sodium-ion batteries

O3-type layered oxides are promising cathodes for sodium-ion batteries (SIBs). However, severe volume changes, irreversible phase transitions, and sluggish Na+ ion transport kinetics lead to structural collapse and severe capacity loss. Herein, a three-in-one strategy “high entropy, single crystal, and biphase” is proposed to design O3-type layered cathodes for SIBs, which achieves enhanced structural stability and Na+ transport kinetics by the combination effect of multimetal high-entropy, the single crystal, and Li substitution. The as-prepared high-entropy oxide (HEO) cathode, Na(Fe1/6Co1/6Ni1/6Mn1/6Ti1/6)Li1/6O2, exhibits a high reversible capacity of 140.3 mAh g−1, robust cycling stability, exceptional rate capability (86 mAh g−1 at rates of 15C), excellent air-stability, and water-resistance ability. In situ X-ray diffraction reveals that the HEO cathode has highly reversible phase transitions and small volume change (ΔV=3.28 %). Ex situ X-ray absorption spectroscopy reveals that reversible Ni2+/Ni4+, Fe3+/Fe3.6+, and Co3+/Co3.6+ redox couples provide charge compensation for the high-entropy cathode at 2.0∼4.2 V. Notably, the full-cell battery based on the high-entropy cathode and hard carbon anode delivers a specific capacity of 134.3 mAh g−1 and an energy density of 390.8 Wh kg−1. This work provides valuable insights into the design of novel high-performance high-entropy cathodes for SIBs, highlighting a promising avenue for advancing rechargeable battery technology.

Analysis of charging performance of thermal energy storage system with graded metal foam structure and active flip method

The latent heat thermal energy storage (LHTES) technology based on solid-liquid phase change material (PCM) is characterized by high energy storage density, small volume change, and constant operation temperature, which is widely employed in waste heat recovery, solar thermal utilization, and equipment thermal management. This paper introduces active flipping and graded porous to strengthen natural convection and heat conduction to alleviate the issue of low thermal conductivity and non-uniform phase change of PCM. Based on the fixed grid system, the enthalpy-porosity method combined with time-dependent gravity and non-Darcy porous effect is employed to solve the solid-liquid phase change problem under different porosity gradients, dimensionless flipping times (t*), and modified Ra (Ra*) numbers. Furthermore, the effects of the Ra* on the optimal t* and porosity gradient are also discussed. The results show that the flipping method can significantly enhance flow and heat transfer within the container, improve temperature field uniformity, and increase the proportion of latent heat storage. With the increase of porosity gradient and t*, the melting time initially decreases and then increases and the optimal thermal performance is achieved at a 6 % porosity gradient and t* = 0.4. Compared to the uniform porous structure without flipping, it can shorten melting time by 49.37 % and improve thermal energy storage rate (TESR) by 76.23 %. Additionally, the optimal porosity gradient is 6 % under different Ra*, but the optimal t* decreases with the increase of Ra*. This paper explores the charging performance of the thermal energy storage system with the graded metal foam structure and active flip method, which can contribute to the study of heat transfer enhancement in LHTES technology.

Favored Amorphous LixSi Process with Restrained Volume Change Enabling Long Cycling Quasi-Solid-State SiOx anode.

Silicon-based anodes are becoming promising materials due to their high specific capacity. However, the intrinsically large volume change brought about by the alloying reaction results in the crushing of the active particles and destruction of the electrode structure, which severely limits its practical application. Various structured and modified silica-based anodes exhibit improved cycling stability and the demonstrated ability to mitigate their volume changes through interfacial and binder strategies. However, the issue of large volume changes in silicon-based anodes remains. Herein, we report a gel polymer electrolyte (GPE) prepared through an in situ thermal polymerization process that is suitable for SiOx anode materials and achieving long-term cycling stability. GPE-based cells essentially mitigate the volume change of SiOx anodes by guiding the unique lithiation/delithiation mechanism that tends to favor the formation and delithiation of amorphous-LixSi (a-LixSi) with smaller volume change, thereby mitigating electrode damage and cracking, and achieving the significant improvement in cycling performance. The prepared GPE-SiOx cells retained 693.80 mAh g-1 reversible capacity after 450 cycles at 500 mA g-1. In addition, the prelithiation process was incorporated to mitigate capacity fluctuations and improve the Initial Coulombic Efficiency (ICE), and a reversible capacity of 641.90 mAh g-1 was retained after 480 cycles.

Simulation and Experimental Investigation of the Effect of Pore Shape on Heat Transfer Behavior of Phase Change Materials in Porous Metal Structures.

With the gradual increase in energy demand in global industrialization, the energy crisis has become an urgent problem. Due to high heat storage density, small volume change, and nearly constant transition temperature, phase change materials (PCMs) provide a promising method to store thermal energy. In this work, we designed and fabricated three kinds of porous metal structures with hexagonal, rectangular, and circular pores and explored the phase change process of PCMs within them. A two-dimensional numerical model was established to investigate the heat transfer process of PCMs within different shapes of porous metal structures and analyze the influence of heat source location on the thermal performance of the thermal storage units. Visualization experiments were also carried out to reveal the melting process of PCMs within different porous metal structures by a digital camera. The results show that paraffin in a porous metal structure with hexagonal pores has the fastest melting rate, while that in a porous metal structure with circular pores has the slowest melting rate. Under the bottom heating mode, the melting time of the paraffin in porous metal structures with hexagonal pores is shortened by 18.6% compared to that in porous metal structures with circular pores. Under the left heating mode, the corresponding melting time is shortened by 16.7%. These findings in this work will offer an effective method to design and optimize the structure of porous metal and improve the thermal properties of PCMs.

Wrinkling of fluid deformable surfaces.

Wrinkling instabilities of thin elastic sheets can be used to generate periodic structures over a wide range of length scales. Viscosity of the thin elastic sheet or its surrounding medium has been shown to be responsible for dynamic processes. We here consider wrinkling of fluid deformable surfaces. In contrast with thin elastic sheets, with in-plane and out-of-plane elasticity, these surfaces are characterized by in-plane viscous flow and out-of-plane elasticity and have been established as model systems for biomembranes and cellular sheets. We use this hydrodynamic theory and numerically explore the formation of wrinkles and their coarsening, either by a continuous reduction of the enclosed volume or bythe continuous increase of the surface area. Both lead to almost identical results for wrinkle formation and the coarsening process, for which a scaling law for the wavenumber is obtained for a broad range of surface viscosity and rate of change of volume or area. However, for large Reynolds numbers and small changes in volume or area, wrinkling can be suppressed and surface hydrodynamics allows for global shape changes following the minimal energy configurations of the Helfrich energy for corresponding reduced volumes.

Orthostatic Hemifacial Spasm in Idiopathic Intracranial Hypertension.

Among the symptoms seen in idiopathic intracranial hypertension (IIH), hemifacial spasm (HFS) is rare. Orthostatic-induced HFS preceding lumbar puncture (LP) is previously unreported. We treated two patients with unusual IIH presentations. This case series reviews the few reports of HFS in IIH and proposes a mechanism for spasm occurrence. Case 1: A woman in her mid-40s with previously controlled IIH developed daily headache, pulsatile tinnitus, right-sided trigeminal paresthesia, and right-sided HFS. The latter 2 symptoms occurred exclusively when moving from a sitting to a standing position. Imaging was unremarkable; opening pressure (OP) on LP was 46 cmH2O with normal cerebrospinal fluid (CSF) components. Case 2: A woman in her late 40s presented with severe daily headache, pulsatile tinnitus, and left-sided HFS following weight gain. Imaging was unremarkable; OP on LP was 32 cmH2O with normal CSF components. HFS episodes persisted following LP in both patients. Increasing and initiating acetazolamide, respectively, resolved all symptoms. Earlier suggested mechanisms of HFS are based on elevated intracranial pressure (ICP) shifting the facial nerve into proximity of a vascular structure. HFS appearing upon standing and continuing after LP, and thus a lower ICP, contradicts this. We propose a mechanism based on the degree of ICP change. This theory is grounded in the lack of intracranial compliance in IIH, wherein substantial pressure changes occur following small volume changes.

Bismuth-constructed high-speed channeled for Bi/Sb2SnO5@PCFs composite as high-rate and long-life anode for sodium-ion batteries

To cope with the charging-time and driving-range issues of the power batteries, a composite and phase modification tactics is manifested to increase the cycling stability and rate capability of the Sb2SnO5 (SSO) anode for sodium-ion batteries (SIBs). The as-fabricated Bi/SSO@PCFs composite with Bi nanocrystals homogeneously dispersed on and around the SSO surface is prepared by an electrospinning method. The excellently dispersed Bi nanocrystals realize an effective contact with SSO, which effectively lowers the electron conduction barriers and promotes the sodium ion release as well as the transport upon the desodiation/sodiation process, increasing the rate capacity and cycle stability of the SSO anode. Importantly, a high-speed ion channel is constructed through the special layered Bi, and SbBi phase. The prepared Bi/SSO@PCFs anodes deliver a high rate capacity up to 25 A g−1 and long cycle life of 5000 cycles with 83 % capacity retention rate, sustaining an average capacity loss of 0.0034 % for each cycle. Particularly, the intercalation of Na+ between layer-structure Bi and SbBi galleries provides a good basis for excellent cycle performance due to small volume change and unobstructed ion channels. This finding provides an effective strategy to establish ion transport highways, which essentially increase the rate-capacity and cycle-life of the SSO-based anodes for SIBs.

Suppressed phase separation in high-voltage LiNi0.5Mn1.5O4 cathode via Co-doping

Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material with high operating voltage and energy density. However, the poor rate performance caused by the two-phase reaction during charging and discharging limits its large-scale application. In this work, Co3+ doped LNMO cathode materials are prepared by co-precipitation method, and the effect of Co3+ doping replacing Mn4+, as well as the amount of Co3+ doping (LiNi0.5CoxMn1.5-xO4) are explored. Co3+ doping increases the content of Mn3+, thus improving the electronic conductivity of LNMO. Co3+ doping suppresses the phase transition of LNMO during discharging, which results in a smaller volume change and improves cycling stability. The presence of a solid solution intermediate allows for more uniform changes within the particles during the discharge process, thus increasing the diffusion rate of Li+ ion. LiNi0.5Co0.05Mn1.45O4 exhibits the best electrochemical performance compared to other samples, with a discharge specific capacity of 111.1 mAh g−1 after 500 cycles at 1 C and a capacity retention of 92.4%. At 10 C high rate, the specific discharge capacity is 106.8 mAh g−1. Our research reveals that Co3+ doping can improve the electrochemical performance of LNMO and provide a deeper insight into Co3+ doping of other cathode materials.

Boron-doped high-entropy oxide toward high-rate and long-cycle layered cathodes for wide-temperature sodium-ion batteries

O3-type layered metal oxides hold great promise for sodium-ion batteries cathodes owing to their energy density advantage. However, the severe irreversible phase transition and sluggish Na+ diffusion kinetics pose significant challenges to achieve high-performance layered cathodes. Herein, a boron-doped O3-type high entropy oxide Na(Fe0.2Co0.15Cu0.05Ni0.2Mn0.2Ti0.2)B0.02O2 (NFCCNMT-B0.02) is designed and the covalent B–O bonds with high entropy configuration ensure a robust layered structure. The obtained cathode NFCCNMT-B0.02 exhibits impressive cycling performance (capacity retention of 95% and 82% after 100 cycles and 300 cycles at 1 and 10 C, respectively) and outstanding rate capability (capacity of 83 mAh g−1 at 10 C). Furthermore, the NFCCNMT-B0.02 demonstrates a superior wide-temperature performance, maintaining the same capacity level (113.4 mAh g−1@−20 °C, 121 mAh g−1@25 °C, and 119 mAh g−1@60 °C) and superior cycle stability (90% capacity retention after 100 cycles at 1 C at −20 °C). The high-entropy configuration design with boron doping strategy contributes to the excellent sodium-ion storage performance. The high-entropy configuration design effectively suppresses irreversible phase transitions accompanied by small volume changes (ΔV = 0.65 Å3). B ions doping expands the Na layer distance and enlarges the P3 phase region, thereby enhancing Na+ diffusion kinetics. This work offers valuable insights into design of high-performance layered cathodes for sodium-ion batteries operating across a wide temperature.

Bismuth-doping boosting Na+ diffusion kinetics of layered oxide cathode with radially oriented {010} active lattice facet for sodium-ion batteries.

O3-type layered oxide cathodes (NaxTMO2) for sodium-ion batteries (SIBs) have attracted significant attention as one of the most promising potential candidates for practical energy storage applications. The poor Na+ diffusion kinetics is, however, one of the major obstacles to advancing large-scale practical application. Herein, we report bismuth-doped O3-NaNi0.5Mn0.5O2 (NMB) microspheres consisting of unique primary nanoplatelets with the radially oriented {010} active lattice facets. The NMB combines the advantages of the oriented and exposed electrochemical active planes for direct paths of Na+ diffusion, and the thick primary nanoplatelets for less surface parasitic reactions with the electrolyte. Consequently, the NMB cathode exhibits a long-term stability with an excellent capacity retention of 72.5% at 1C after 300 cycles and an enhanced rate capability at a 0.1C to 10C rate (1C = 240 mA g-1). Furthermore, the enhancement is elucidated by the small volume change, thin cathode-electrolyte-interphase (CEI) layer, and rapid Na+ diffusion kinetics. In particular, the radial orientation-based Bi-doping strategy is demonstrated to be effective at boosting electrochemical performance in other layered oxides (such as Bi-doped NaNi0.45Mn0.45Ti0.1O2 and NaNi1/3Fe1/3Mn1/3O2). The results provide a promising strategy of utilizing the advantages of the oriented active facets of primary platelets and secondary particles to develop high-rate layered oxide cathodes for SIBs.

Deep learning segmentation and registration-driven lung parenchymal volume and movement CT analysis in prone positioning.

To conduct a volumetric and movement analysis of lung parenchyma in prone positioning using deep neural networks (DNNs). We included patients with suspected interstitial lung abnormalities or disease who underwent full-inspiratory supine and prone chest CT at a single institution between June 2021 and March 2022. A thoracic radiologist visually assessed the fibrosis extent in the total lung (using units of 10%) on supine CT. After preprocessing the images into 192×192×192 resolution, a DNN automatically segmented the whole lung and pulmonary lobes in prone and supine CT images. Affine registration matched the patient's center and location, and the DNN deformably registered prone and supine CT images to calculate the x-, y-, z-axis, and 3D pixel movements. In total, 108 CT pairs had successful registration. Prone positioning significantly increased the left lower (90.2±69.5 mL, P = 0.000) and right lower lobar volumes (52.5±74.2 mL, P = 0.000). During deformable registration, the average maximum whole-lung pixel movements between the two positions were 1.5, 1.9, 1.6, and 2.8 cm in each axis and 3D plane. Compared to patients with <30% fibrosis, those with ≥30% fibrosis had smaller volume changes (P<0.001) and smaller pixel movements in all axes between the positions (P = 0.000-0.007). Forced vital capacity (FVC) correlated with the left lower lobar volume increase (Spearman correlation coefficient, 0.238) and the maximum whole-lung pixel movements in all axes (coefficients, 0.311 to 0.357). Prone positioning led to the preferential expansion of the lower lobes, correlated with FVC, and lung fibrosis limited lung expansion during prone positioning.

Preparation and thermal properties of zeolite/MgSO4 composite sorption material for heat storage

Thermochemical sorption heat storage based on salt hydrates offers the potential advantages such as high energy density, negligible heat loss, small volume change and flexible working modes. Magnesium sulphate (MgSO4) is a high energy density hydrated salt available for the thermochemical sorption heat storage. In this work, different types of zeolites (including 3A, 5A and 13X zeolites) have been selected as mass-transfer-enhancing and structural stabilizing materials, and a series of zeolite/MgSO4 composites have been fabricated. To investigate the thermal energy storage performance of zeolite/MgSO4 composites, the properties of the composites, such as micro-morphology, pore structure, chemical composition and sorption-desorption behavior, have been characterized and analyzed. Results indicated that the mass transfer performance of the composite materials is significantly better than that of the pure zeolites. As the mass fraction of MgSO4 in the composite sorbents increases, the specific surface area and porosity of the composite sorbent decreases, and the sorption performance has been enhanced. Compared with 3A zeolite-based and 5A zeolite-based composites, 13X zeolite/MgSO4 composite materials show the best heat storage performance. At the condition of 25 °C and 60% RH, the 13XM20 has the highest sorption capacity of 0.21 g/g, which is 24% higher than that of pure zeolite 13X. Accordingly, the maximum heat storage density is 438.4 kJ/kg, which exhibits the superior heat storage performance among of the hydrated salt sorbents. The potential of 13X zeolite/MgSO4 as sorption heat storage material in efficient utilization of solar heat and low-grade industrial waste heat has been revealed.

Theoretical prediction of B5C8 monolayer as a high-performance anode material for lithium-ion batteries

The demand for high-performance energy storage systems has stimulated intensive research on high-performance electrode materials for lithium-ion batteries (LIBs). Two-dimensional (2D) materials have emerged as promising candidates for anode materials due to their unique structural and physicochemical properties. Based on first-principles calculations, we propose a 2D material, B5C8 monolayer, as an excellent anode material for LIBs. B5C8 monolayer exhibits inherent metallicity and outstanding dynamic, mechanical, and thermal stability. Furthermore, B5C8 monolayer shows not only remarkably high storage capacity (2856 mA h g−1) but also low barrier energy (0.25 eV) and small volume change (2.1%). More importantly, B5C8 possesses strong wettability toward commonly used electrolytes in LIBs, namely, solvent molecules and metal salts, indicating prime compatibility. Based on the above distinguished findings, we hope B5C8 monolayer can act as a well-balanced performance anode material for LIBs.

Variable swelling behavior of and drug encapsulation in a maleimide-modified hyaluronic acid nanogel-based hydrogel

Hyaluronic acid (HA) has garnered much attention in the development of novel hydrogels. Hydrogels, as drug delivery systems, are very important in tissue engineering applications. In this study, we developed a novel HA nanogel containing a cholesterol and maleimide derivative (HAMICH) and its corresponding crosslinked hydrogel (HAMICH gel) to encapsulate drugs for their subsequent release. HAMICH gels self-assemble into nanoparticles via hydrophobic interactions. Dynamic light scattering analysis of HAMICH revealed that the particle size tended to decrease with increasing degree of cholesterol moiety substitution. The HAMICH gel was prepared through a Michael addition reaction between HAMICH and pentaerythritol tetra(mercaptoethyl)polyoxyethylene. The concentration of HAMICH needed for gelation depends on the degree of cholesterol moiety substitution; the higher the substitution degree is, the greater the concentration of HAMICH needed. The HAMICH gel exhibited less swelling and a smaller volume change than the gel with an unmodified cholesterol moiety in phosphate-buffered saline (pH 7.4). The HAMICH gel displayed enhanced peptide and protein trapping abilities without hydrogel swelling, suggesting its potential as a HA hydrogel for biomedical applications.

Moderate active Fe3+ doping enables improved cationic and anionic redox reactions for wide-voltage-range sodium storage

Layered metal oxides are promising cathode materials for sodium-ion batteries (SIBs) due to their high theoretical specific capacity and wide Na+ diffusion channels. However, the irreversible phase transitions and cationic/anionic redoxes cause fast capacity decay. Herein, P2-type Na0.67Mg0.1Mn0.8Fe0.1O2 (NMMF-1) cathode material with moderate active Fe3+ doping has been designed for sodium storage. Uneven Mn3+/Mn4+distribution is observed in NMMF-1 and the introduction of Fe3+ is beneficial for reducing the Mn3+ contents both at the surface and in the bulk to alleviate the Jahn–Teller effect. The moderate Fe3+/Fe4+ redox can realize the best tradeoff between capacity and cyclability. Therefore, the NMMF-1 demonstrates a high capacity (174.7 mAh g−1 at 20 mA g−1) and improved cyclability (78.5% over 100 cycles) in a wide-voltage range of 1.5–4.5 V (vs. Na+/Na). In-situ X-ray diffraction reveals a complete solid-solution reaction with a small volume change of 1.7% during charge/discharge processes and the charge compensation is disclosed in detail. This study will provide new insights into designing high-capacity and stable layered oxide cathode materials for SIBs.

Spontaneous redox reaction-mediated interfacial charge transfer in titanium dioxide/graphene oxide nanoanodes for rapid and durable lithium storage.

Titanium dioxide (TiO2) anodes show significant advantages in ion storage owing to their low cost, abundant sources, and small volume change during cycling. However, their intrinsic low electronic conductivity and sluggish ion diffusion coefficient restrict the application of TiO2 anodes, especially at high current densities. The construction of a covalently-bonded interface in TiO2-based composite anodes is an effective approach to solve these issues. Covalent bonds are usually formed in situ during materials synthesis processes, such as high-energy ball milling, solvothermal reactions, plasma-assisted thermal treatment, and addition of a linking agent for covalent coupling. In this study, we demonstrate that a spontaneous redox reaction between defective TiO2 powder and an oxidative graphene oxide (GO) substate can be used to form interfacial covalent bonds in composites. Different structural characterization techniques confirmed the formation of interfacial covalent bonds. Electrochemical measurements on an optimized sample showed that a specific capacity of 281.3 mA h g-1 after 200 cycles can be achieved at a current density of 1 C (1 C = 168 mA g-1). Even at a high rate of 50 C, the electrode maintained a reversible capacity of 97.0 mA h g-1. The good lithium storage performance of the electrode is a result of the uniquely designed composite electrodes with strong interfacial chemical bonds.

A Scalable and Effective Strategy for Boosting the Initial Coulombic Efficiency of Silicon Suboxide Anode

Silicon suboxide (SiO x ) is one of the most attractive candidates for anode materials for high-energy-density lithium-ion batteries due to its high specific capacity and its relatively lower volume expansion than that of Si. However, its low initial Coulombic efficiency (ICE) seriously affects its practical applications. In this work, we demonstrate a scalable and effective strategy to enable a high ICE of the SiO x electrode through a MnO-assisted disproportionation reaction. The obtained Mn 2 SiO 4 –Si–SiO x @C (MSS@C) material shows a reduced lithium irreversible consumption in the first cycle. The Mn 2 SiO 4 phase can store lithium through a conversion reaction with a smaller volume change (33%) than SiO x , which helps to maintain the structural stability of MSS@C during cycling. Meanwhile, the metallic Mn nanoparticles generated from Mn 2 SiO 4 during the lithiation process facilitate electron conduction, thus improving the electrode reaction kinetics. Owing to the synergetic effects, the MSS@C material exhibits a higher ICE (79.51%) compared to 60.91% of pure SiO x , and a superior cyclic performance (832 mAh g −1 at 0.5 A g −1 after 350 cycles with a capacity retention of 90.4%). This work offers a new approach to increase the ICE while improving the electrode reaction kinetics and cycling stability of SiO x -based materials.

High-Temporal-Resolution Rock Slope Monitoring Using Terrestrial Structure-from-Motion Photogrammetry in an Application with Spatial Resolution Limitations

Research on high-temporal-resolution rock slope monitoring has tended to focus on scenarios where spatial resolution is also high. Accordingly, there is a lack of understanding of the implications for rock slope monitoring results in cases with high temporal resolution but low spatial resolution, which is the focus of this study. This study uses automatically captured photos taken at a daily frequency by five fixed-base cameras in conjunction with multi-epoch Structure-from-Motion (SfM) photogrammetric processing techniques to evaluate changes in a rock slope in Majes, Arequipa, Peru. The results of the monitoring campaign demonstrate that there are potential issues with the common notion that higher frequency change detection is always superior. For lower spatial resolutions or when only large changes are of concern, using a high-frequency monitoring method may cause small volume changes that eventually aggrade into larger areas of change to be missed, whereas most of the total volume change would be captured with lower-frequency monitoring intervals. In this study, daily change detection and volume calculation resulted in a cumulative rockfall volume of 4300 m3 over about 14 months, while change detection and volume calculation between dates at the start and end of the 14-month period resulted in a total rockfall volume of 12,300 m3. High-frequency monitoring is still the most accurate approach for evaluating slope evolution from a rockfall frequency and size distribution perspective, and it allows for the detection of short accelerations and pre-failure deformations, but longer-term comparison intervals may be required in cases where spatial resolution is low relative to temporal resolution to more accurately reflect the total volume change of a given rock slope over a long period of time.

Strain Imaging of Electrode Materials in Li-Ion Batteries

Li-ion batteries operate through the migration of Li ions between the electrodes. Therefore, non-destructive observation of the migration with high spatial resolution is important.When charging and discharging, Li-ions are extracted or inserted into electrode materials, which generally causes changes in volume. An atomic force microscope (AFM) can detect and image these volume changes through current collectors with high spatial resolution, which enables us to investigate Li-ion migration without destruction. AFM detects surface displacements synchronizing the charging/discharging cycle, and provides strain images along with topography of the current collector.1) Here, we present our results of lithium titanate oxide (LTO: Li x Ti5O12). LTO is an anode material with high safety having a theoretical capacity of 160 mA h g−1 (from LiTi2O4 to Li2Ti2O4). But the phase change from spinel to rock-salt lead to very small volume changes. Therefore, it might be difficult to observe the Li migration by this method.However, Li4Ti5O12 with a spinel structure has high resistivity, whereas charged Li7Ti5O12 with a rock-salt structure is a conductor. The former is a transparent semiconductor and the latter is a dark metal. The state of charge of LTO can be observed by an optical microscope. The spatial resolution is not enough though the method is easy-to-use.2) High-resolution method has been proposed.3) Photoinduced strain imaging discriminates semi-conductors having bandgap from metallic materials with no bandgap. The method images bandgap variations based on the detection of electric strains caused by electron-hole pair generation. When electron-hole pairs are generated by photon injection, strains are induced, because the lattice constants are determined as the energy of the electron band structure becomes minimum, and the generation changes the energy configuration. The generation of electron-hole pairs is determined from the magnitude relationship between photon and bandgap energies. Bandgap energies can be measured quantitatively by scanning the injected photon energy. When the photon energies are larger than bandgap energies, strains are generated by electron-hole pairs generation. Therefore, mapping of the strains reveals changes in bandgap energies, that is, state-of-charge of LTO.The lithium metal anode has fruitful advantages that are the lowest electrode potential of Li+/Li and low density of Li, which are −3.04 V and 0.534 g/cm3, respectively. However, the lithium dendrite issue is a serious barrier standing in way of the development of high-energy-density batteries with a lithium metal anode.We have been successful in imaging electrochemical reactions in the interface between lithium metal and electrolyte using strain imaging. Precipitation and dissolution of lithium ions in the surface of lithium metal, and electrolyte flow induced by the gradient of lithium-ion concentration should cause the surface displacements of the current collector. We will be able to get a lot of knowledge and information from this observation.