Measurement Of Properties Research Articles

Spatially resolved Thomson scattering measurements of electron properties across the acceleration region of a high-power magnetically shielded Hall effect thruster

Spatially resolved Thomson scattering measurements of electron properties across the acceleration region of a high-power magnetically shielded Hall effect thruster

Spirocyclic pyrrolidinyl nitroxides with exo-methylene substituents.

Nitroxides are stable organic radicals with exceptionally long lifetimes, which render them uniquely suitable as observable probes or polarising agents for spectroscopic investigation of biomolecular structure and dynamics. Radical-based probes for biological applications are ideally characterized by both robustness towards reductive degradation and beneficial electron spin relaxation parameters. These properties are largely influenced by the molecular structure of the nitroxide scaffold, and also by the conformations it prefers to adopt. In this study we present the synthesis of the first nitroxides based on a spirocyclic pyrrolidine scaffold with an exocyclic methylene substituent. The conformations adopted by these nitroxides were evaluated by X-ray crystallography, both with single nitroxide crystals and by inclusion of nitroxides in a microporous crystalline sponge. The kinetic and thermodynamic stability of the new nitroxides towards reduction was investigated by electron paramagnetic resonance (EPR) spectroscopy and cyclic voltammetry (CV). In combination with EPR measurements of electron spin relaxation properties, these results suggest that this new family of nitroxides can provide access to multifunctionalized probes and polarising agents suitable for use in biological environments at elevated temperatures.

An optical atomic clock using 4DJ states of rubidium

Abstract We analyze an optical atomic clock using two-photon 5 S 1 / 2 → 4 D J transitions in rubidium. Four one- and two-color excitation schemes to probe the 4 D 3 / 2 and 4 D 5 / 2 fine-structure states are considered in detail. We compare key characteristics of Rb 4 D J and 5 D 5 / 2 two-photon clocks. The 4 D J clock features a high signal-to-noise ratio due to two-photon decay at favorable wavelengths, low dc electric and magnetic susceptibilities, and minimal black-body shifts. Ac Stark shifts from the clock interrogation lasers are compensated by two-color Rabi-frequency matching. We identify a ‘magic’ wavelength near 1060 nm, which allows for in-trap, Doppler-free clock-transition interrogation with lattice-trapped cold atoms. From our analysis of clock statistics and systematics, we project a quantum-noise-limited relative clock stability at the 10 − 13 / τ ( s ) -level, with integration time τ in seconds, and a relative accuracy of ∼ 10 − 13 . We describe a potential architecture for implementing the proposed clock using a single telecom clock laser at 1550 nm, which is conducive to optical communication and long-distance clock comparisons. Our work could be of interest in efforts to realize small and portable Rb clocks and in high-precision measurements of atomic properties of Rb 4 D J -states.

Explaining the spread in measurement of PDMS elastic properties: influence of test method and curing protocol.

Accuracy in the measurement of mechanical properties is essential for precision engineering and for the interrogation of composition-property relationships. Conventional methods of mechanical testing, such as uniaxial tension, compression, and nanoindentation, provide highly repeatable and reliable results for stiff materials, for which they were originally developed. However, when applied to the characterization of soft and biological materials, the same cannot be said, and the spread of reported properties of similar materials is vast. Polydimethylsiloxane (PDMS), commonly obtained from Dow as SYLGARD 184, is a ubiquitous such material, which has been integral to the rapid development of biocompatible microfluidic devices and flexible electronics in recent decades. However, reported shear moduli of this material range over 2 orders of magnitude for similar chemical compositions. Taking advantage of the increased mechanical scrutiny afforded to SYLGARD 184 in recent years, we combine both published and new experimental data obtained using 9 mechanical test methods. A statistical analysis then elucidates the significant bias induced by the test method itself, and distinguishes this bias from the influence of curing protocols on the mechanical properties. The goal of this work is thus two-fold: (i) it provides a quantitative understanding of the different factors that influence reported properties of this particular material, and (ii) it serves as a cautionary tale. As researchers in the field of mechanics strive to quantify the properties of increasingly complex soft and biological materials, converging on a standardized measurement of PDMS is a necessary first step.

Relationship between coking properties measured by automatic Sapozhnikov plastometer with other measurements

ABSTRACT A Sapozhnikov plastometer is equipment that is commonly used, particularly in Asia, for measuring the contraction of the coal bed as well as the plastic layer thickness during the coking process. The relationship between the Sapozhnikov contraction X and the maximum plastic layer thickness Y values and other thermal rheology testing techniques is not fully understood. It leads to difficulties in the interpretation of data using different thermal rheology properties measurement techniques. In this work, a series of coal samples were analyzed in parallel using the automatic Sapozhnikov plastometer, the Gieseler plastometer, and the Ruhr dilatometer. The measurement results were compared to assist in the interpretation of data generated using different coal thermal rheology property measurement techniques. The Sapozhnikov X results are found not comparable due to the difference in sample particle size and testing conditions for component coals with the wide range of maximum mean reflectance (Ro), but a significant linear correlation on the contraction/expansion behavior between Sapozhnikov and Ruhr dilatation test is observed for experimental coal blends Ro between 1.00 and 1.20. Sapozhnikov Y results are linearly related to the melting range from both the Gieseler plastometer and the Ruhr dilatometer for all the experimental single coals and coal blends.

Exploring the dielectric loss of Martian regolith in the frequency domain using Zhurong radar data

Martian regolith is one of the primary science objectives of Mars exploration missions. The Rover Penetrating Radar carried by Zhurong rover allows for high-resolution subsurface imaging and in-situ measurements of Martian regolith dielectric properties, which are crucial to advance our understanding of Martian geology and hydrological evolution. While earlier studies have derived dielectric constants for the shallow subsurface, further characterization of subsurface materials requires the determination of attenuation properties. In this study, we applied the centroid-frequency shift method to explore the attenuation property of the Martian regolith in the frequency domain. Lateral attenuation variation was analyzed in detail by integrating subsurface radargram and navigation terrain images. The results show that, within a depth of ∼4 m, the attenuation of radar signal for Zhurong subsurface material is equal to a loss tangent of 0.0079, with a standard deviation of 0.001. Based on the loss tangent value, dielectric permittivity and ground characterization, we preclude the possibility that the regolith is predominantly igneous materials. The lateral variation of the attenuation property could likely be attributed to changes in the proportion of duricrusts, which are heterogeneously distributed along the rover traverse. Our findings offer valuable information for understanding the Martian regolith and its evolution, serving as a important reference for future Mars sample return missions.

Growth of Ba2CoWO6 single crystals and their magnetic, thermodynamic and electronic properties

This study explores the bulk crystal growth, structural characterization, and physical property measurements of the cubic double perovskite Ba2CoWO6(BCWO). In BCWO, Co2+ions form a face-centred cubic lattice with non-distorted cobalt octahedra. The compound exhibits long-range antiferromagnetic order belowTN= 14 K. Magnetization data indicated a slight anisotropy along with a spin-flop transition at 10 kOe, a saturation field of 310 kOe and an ordered moment of 2.17µB atT= 1.6 K. Heat capacity measurements indicate an effectivej= 1/2 ground state configuration, resulting from the combined effects of the crystal electric field and spin-orbit interaction. Surface photovoltage analysis reveals two optical gaps in the UV-Visible region, suggesting potential applications in photocatalysis and photovoltaics. The magnetic and optical properties highlight the significant role of orbital contributions within BCWO, indicating various other potential applications.

K3Y3(BO3)4: A Potential UV Nonlinear-Optical Crystal Designed by a Chemical Substitution Strategy.

Nonlinear-optical (NLO) crystals capable of controlling and manipulating light to generate coherent radiation at challenging wavelengths are of significant interest. However, designing a new UV NLO crystal remains difficult due to the rigid requirements for structure and properties. Herein, we have successfully designed and synthesized a novel noncentrosymmetric (NCS) rare-earth borate UV NLO crystal, K3Y3(BO3)4, through the heterovalence substitution of YAl3(BO3)4. K3Y3(BO3)4 (KYBO) crystallizes in the NCS and polar space group of P63mc, with the structure formed by the interconnectioned BO3 triangles and YO8 polyhedra through corner-sharing and edge-sharing. The property measurements indicate that KYBO is second-harmonic-generation-active with a moderate response, ∼2 × KDP. Meanwhile, KYBO can exhibit a short UV cutoff edge (λcutoff < 190 nm), indicating its potential as a new UV or deep-UV NLO crystal.

Measurement of Interlaminar Shear Properties of Pultruded CFRP Composites Based on Modified DNS Specimens

A double-notch shear (DNS) test was modified for a measurement of interlaminar shear properties of pultruded carbon-fibre-reinforced polymer (CFRP) composites under moderate through-thickness compressive stresses, which were applied by torqued bolts. A range of failure criteria were presented to compare with experimental results. An attempt was made to predict the shear stress-strain relationship in the combined stresses with through-thickness compressive and shear stresses. Results indicate that the modified 2DNS specimen makes the shear surface of the specimen more uniform and reduces the peel stress at the notch tip. The 2DNS fixture made it easier to study the influence of composite interlaminar shear strength and shear stress-strain relationship under moderate through-thickness compression. The initial shear stiffness was not affected by moderate through-thickness compressive stresses. Moderate through-thickness compressive stresses on pultruded CFRP materials can increase interlaminar shear strength and ductility. Of all the failure criteria, the Mohr-Coulomb criterion was preferred to predict the enhancement of the shear strength under moderate through-thickness compression. Based on the Mohr-Coulomb criterion and the inverse solution of Ramberg-Osgood model, a unified equation was proposed and can effectively characterise the interlaminar shear stress-strain relationship under moderate through-thickness compression.

Label-free live characterization of mesenchymal stem cell spheroids by biophysical properties measurement

Three-dimensional (3D) cell culture has become a consolidated method in the stem cell field, where mesenchymal stromal stem cells (MSCs) can be used to generate in vitro spheroid aggregates called MSC-Spheroids (MSph). MSph is a floating cluster of stem cells similar to those in literature are known as bone marrow-derived “mesenspheres”. Even though MSC properties are shared by MSph, depending on the cell type and their tissue source, the morphology and degree of compaction of the MSph can be variable, creating limitations in such a cell model. Thus, during culture, a variation in stem cell functionality and viability, in addition to the suitability for comparing MSph in some experimental protocols, can be affected by spheroid biophysical intrinsic properties like mass density. To investigate this limitation and provide a new method for researchers, MSph of seven different tissue sources were compared by combining mass density, weight, and size evaluations with viability assays for ATP measurement. MSph cultured in traditional static conditions showed decreased in viability over the days of culture, while mass density exhibited different trends among cell types. Additionally, treatment of MSph with a non-toxic concentration of a natural compound cell regulator, such as plumbagin, altered the mass density of a selected cell type, thereby confirming the efficacy of the biophysical approach in monitoring MSph variability post-treatment. The results encourage using MSph in the early days of culture after their formation to ensure viability and likely retention of the stem cell phenotype.

Influence of columnar versus vertical distribution of aerosol properties on the modulation of shortwave radiative effects

Quantifying the interaction of atmospheric aerosols with incoming solar radiation remains a challenge owing to the limitations associated with measuring aerosol optical properties. This study investigates how the distribution of aerosol properties, whether columnar or vertical, affects the aerosol radiative forcing (ARF) and heating rates (HRs) across different atmospheric layers under cloud-free conditions in the shortwave region. We also assess the atmospheric parameters, namely, pressure, temperature, water vapour density, and ozone density, from in-situ measurements, reanalysis data, and a standard tropical atmosphere to understand their impact on ARF and HR estimates across seasons. Our findings show that aerosol absorption is highest during monsoon, while it is lowest in the winter. Significant atmospheric warming due to aerosols resulted from the substantial cooling at the surface. Columnar properties of aerosols measured at limited or multiple wavelengths yield similar ARF and HR estimates, provided spectral dependency is considered using the Angstrom exponent across seasons. However, the vertical profiles of aerosol extinction, together with a constant single scattering albedo (SSA) along the atmospheric column versus an actual SSA profile, led to notable differences in ARF and HRs, specifically in pre-monsoon and monsoon periods. Free tropospheric aerosol absorption is underestimated when using columnar properties compared to vertical distribution, while boundary layer absorption is overestimated (> 10 Wm-2). The heterogeneity in aerosol types across atmospheric layers significantly influenced aerosol absorption, highlighting the importance of accurate vertical distribution information. HR profiles obtained with vertical distribution reflect the structure of aerosol extinction, whereas those estimated with columnar properties result in smoother profiles that fail to capture altitude gradients. Aerosol-induced HRs are higher within the boundary layer and free troposphere in the monsoon season for all scenarios of defined aerosol properties. These findings underscore the need for actual vertical profile measurements of aerosol properties to quantify aerosol radiation interaction.

GdWN3 is a nitride perovskite

Nitride perovskites ABN3 are an emerging and highly underexplored class of materials that are of interest due to their intriguing calculated ferroelectric, optoelectronic, and other functional properties. Incorporating novel A-site cations is one strategy to tune and expand such properties; for example, Gd3+ is compelling due to its large magnetic moment, potentially leading to multiferroic behavior. However, the theoretically predicted ground state of GdWN3 was a non-perovskite monoclinic structure. Here, we experimentally show that GdWN3−y crystallizes in a perovskite structure. High-throughput combinatorial sputtering with activated nitrogen is employed to synthesize thin films of Gd2−xWxN3−yOy with oxygen content y &amp;lt; 0.05. Ex situ annealing crystallizes a polycrystalline perovskite phase in a narrow composition window near x = 1. LeBail fits of synchrotron grazing incidence wide angle x-ray scattering data are consistent with a perovskite ground-state structure. Refined density functional theory calculations that included antiferromagnetic configurations confirm that the ground-state structure of GdWN3 is a distorted Pnma perovskite with antiferromagnetic ordering, in contrast to prior predictions. Initial property measurements find that GdWN3−y is paramagnetic down to T = 2 K with antiferromagnetic correlations and that the absorption onset depends on cation stoichiometry. This work provides an important path toward both the rapid expansion of the emerging family of nitride perovskites and understanding their potential multiferroic properties.

Sound speed prediction of seafloor sediments in the South Yellow Sea based on BP-AdaBoost model

Based on the sound speed and physical property measurements of seafloor sediments obtained in the central part of the South Yellow Sea, a multi-parameter prediction model for the sound speed of seafloor sediments based on seven parameters, including density, porosity, water content, liquid limit, plasticity index, compression coefficient, and median grain size, was developed by using the BP-AdaBoost fusion algorithm. The results show that the model, configured with 7 input layer neurons, 10 hidden layer neurons, 1 output node, a learning rate of 0.1, and 300 training iterations, achieved a correlation coefficient of 0.962. The mean absolute error (MAE) of the predicted sound speed was 10.19 m/s, and the mean relative error (MAPE) was 0.66%. These results are better than those of single-parameter and dual-parameter prediction equations and other machine learning models. The BP-AdaBoost model prediction method of sound speed of seafloor sediments established in this paper is better than the single-parameter and dual-parameter prediction equations and other prediction models, and it can provide a new way for the prediction of sound speed of seafloor sediments in the study area.

Non-linear stress-softening of the bacterial cell wall confers cell shape homeostasis.

The bacillus - or rod - is a pervasive cellular morphology among bacteria. Rod-shaped cells elongate without widening by reinforcing their cell wall anisotropically to prevent turgor pressure from inflating cell width. Here, we demonstrate that a constrictive force is also essential for avoiding pressure-driven widening in Gram-positive bacteria. Specifically, super-resolution measurements of the nonlinear mechanical properties of the cell wall revealed that across a range of turgor pressure cell elongation directly causes width constriction, similar to a "finger trap" toy. As predicted by theory, this property depends on cell-wall anisotropy and is precisely correlated with the cell's ability to maintain a rod shape. Furthermore, the acute non-linearities in the dependence between cell length and width deformation result in a negative-feedback mechanism that confers cell-width homeostasis. That is, the Gram-positive cell wall is a "smart material" whose exotic mechanical properties are exquisitely adapted to execute cellular morphogenesis.

An experimental system for detection and localization of hemorrhage using ultra-wideband microwaves with deep learning

Stroke is a leading cause of mortality and disability. Emergent diagnosis and intervention are critical, and predicated upon initial brain imaging; however, existing clinical imaging modalities are generally costly, immobile, and demand highly specialized operation and interpretation. Low-energy microwaves have been explored as a low-cost, small form factor, fast, and safe probe for tissue dielectric properties measurements, with both imaging and diagnostic potential. Nevertheless, challenges inherent to microwave reconstruction have impeded progress, hence conduction of microwave imaging remains an elusive scientific aim. Herein, we introduce a dedicated experimental framework comprising a robotic navigation system to translate blood-mimicking phantoms within a human head model. An 8-element ultra-wideband array of modified antipodal Vivaldi antennas was developed and driven by a two-port vector network analyzer spanning 0.6–9.0 GHz at an operating power of 1 mW. Complex scattering parameters were measured, and dielectric signatures of hemorrhage were learned using a dedicated deep neural network for prediction of hemorrhage classes and localization. An overall sensitivity and specificity for detection >0.99 was observed, with Rayleigh mean localization error of 1.65 mm. The study establishes the feasibility of a robust experimental model and deep learning solution for ultra-wideband microwave stroke detection.

Microstructural Instability and Its Effects on Thermoelectric Properties of SnSe and Na-Doped SnSe.

Effects of thermal cycling on the microstructure and thermoelectric properties are studied for the undoped and Na-doped SnSe samples using X-ray computed tomography and property measurements. It is observed that thermal cycling causes significant cracks to develop, which decrease both the electrical and lattice thermal conductivities but do not affect the thermopower. The zT values are drastically reduced after the repeated heat treatment. It is important to account for density changes during cycling to obtain accurate values of the thermal conductivity. Even before thermal cycling, the spark-plasma sintered (SPS) samples have a significant number of microcracks. The orientation of cracks within the SPS pellets and their effect on the microstructure are influenced by the presence of a Na-rich impurity. The SnSe and Sn0.995Na0.005Se samples without the impurity develop cracks and exhibit grain growth parallel to the pellet surface, which is also the plane of the 2D SnSe layers. The Sn0.97Na0.03Se sample containing the impurity develops cracks that are orthogonal to the pellet surface. Such an orientation of cracks in Sn0.97Na0.03Se inhibits grain growth. All samples appear mechanically unstable after thermal cycling.

Study on the Stability of Fe/Al2O3 Interface in Metal-Based Cermets Using Thermodynamic Modeling

Iron-based cermet has the advantages of high-temperature resistance, low price, good performance, and so on. At present, most of the studies on cermets are focused on the measurement of macroscopic properties and optical microscopic characterization, while there are few microscopic studies on the interface structure. In this paper, based on density functional theory (DFT), the stability of the Fe/Al2O3 interface is studied, and the stability difference and interface formation mechanism of different end combinations are investigated. By calculating the surface energy, adhesion work, interface energy, density of states, charge density, differential charge density, and so on, it was concluded that the stability of the O-terminal interface was greater than that of the Al interface. It has a certain guiding role in the preparation of Fe/Al2O3 cermet materials.

Spatiotemporal patterns of greenhouse gas fluxes in the subtropical wetland ecosystem of Indian Himalayan foothill.

The study characterized the temporal and spatial variability in greenhouse gas (GHG) fluxes (CO2, CH4, and N2O) between December 2020 and November 2021 and their regulating drivers in the subtropical wetland of the Indian Himalayan foothill. Five distinct habitats (M1-sloppy surface at swamp forest, M2-plain surface at swamp forest, M3-swamp surface with small grasses, M4-marshy land with dense macrophytes, and M5-marshy land with sparse macrophytes) were studied. We conducted in situ measurements of GHG fluxes, microclimate (AT, ST, and SMC(v/v)), and soil properties (pH, EC, N, P, K, and SOC) in triplicates in all the habitat types. Across the habitats, CO2, CH4, and N2O fluxes ranged from 125 to 536mgm-2h-1, 0.32 to 28.4mgm-2h-1, and 0.16 to 3.14mgm-2h-1, respectively. The habitats (M3 and M5) exhibited higher GHG fluxes than the others. The CH4 flux followed the summer > autumn > spring > winter hierarchy. However, CO2 and N2O fluxes followed the summer > spring > autumn > winter. CO2 fluxes were primarily governed by ST and SOC. However, CH4 and N2O fluxes were mainly regulated by ST and SMC(v/v) across the habitats. In the case of N2O fluxes, soil P and EC also played a crucial role across the habitats. AT was a universal driver controlling all GHG fluxes across the habitats. The results emphasize that long-term GHG flux monitoring in sub-tropical Himalayan Wetlands has become imperative to accurately predict the near-future GHG fluxes and their changing nature with the ongoing climate change.

Measurements of Thermoelectric Properties of Identical Bi-Sb Sample in Magnetic Fields and Influence of Sample Geometry

Measurements of Thermoelectric Properties of Identical Bi-Sb Sample in Magnetic Fields and Influence of Sample Geometry

The Effects of Foam Rolling at Different Speeds on Mechanical Properties of Quadriceps Femoris.

Foam rolling have gained popularity among elite athletes, but the effect of the speed parameter of foam rolling has not yet been determined. Our objective was to investigate the impact of different application speeds of foam roller on the mechanical properties of the quadriceps femoris muscle. Eighteen male professional basketball athletes (age 23 ± 4 years, body mass index 24.43 ± 1.59 kg/m2) participated in this study. We used a crossover design to randomize the order of the treatment speeds (30 beats per minute-FAST, 15 beats per minute-SLOW, and a self-determined speed-SELF) with a one-week washout period between each session. We measured dominant quadriceps femoris muscle tone, elasticity, and stiffness using the Myoton device before and after the interventions. We found that the average rate for SELF was 33±10 beats per minute, making SELF the fastest. All application speeds showed similar results in pre-intervention measurements of the mechanical properties of the tissues (P > 0.05). However, post hoc analysis revealed that a decrease was evident in SLOW compared to SELF in muscle tone in post-intervention measurements (P = 0.037). Also, we noted that comparison of pre- and post-intervention on FAST and SLOW showed a significant reduction in muscle tone (P = 0.002, P = 0.008). Slower foam rolling prior to training or competition may lead to a delay in the reaction time due to the reduction in tonus, that can increase the injury risks. Alternatively, the significant reduction in tonus may be useful in regulating the increased tonus after training and competition.