Gradient Strength Research Articles

Effect of concentration gradient on spiral wave dynamics in the Belousov-Zhabotinsky reaction system.

The oscillatory Belousov-Zhabotinsky (BZ) reaction is often used for the study of rotating spiral waves that are responsible for life-threatening cardiac arrhythmia. In this work, we explore the influence of a concentration gradient on the dynamics of spiral waves in the BZ-reaction system. Using ion-exchange resin beads, we introduce a gradient of hydrogen ions in a thin layer of BZ gel hosting a spiral wave. By monitoring the drift of the spiral tips from their initial position, we show that a gradient of hydrogen-ions can manoeuvre the position of the spiral. The magnitude of the drift is found to depend on the gradient strength and relative position of the spiral from the resin beads. Our experimental study is supported with numerical simulations carried out on a modified Oregonator model that we have developed from the Field, Körös, Noyes mechanism of the BZ.

Factors of the effectiveness of competitive activity of arm wrestlers aged 14-15 years at the stage of preliminary basic training

Background and Study Aim. Considering that there are no studies aimed at identifying the components of physical and functional fitness in arm wrestling at the stage of preliminary basic training, and it is not advisable to transfer training of adult athletes to training of young men, then determining the influence and comparison of various aspects of fitness on the effectiveness of competitive activity of arm wrestlers acquires both theoretical and practical importance. Hence the purpose of the study – to determine the significance of the influence of various aspects of fitness (functional, physical) to identify factors influencing the effectiveness of competitive activity of junior armwrestlers aged 14-15. Material and Methods. The study involved 29 young men aged 14–15 years involved in arm wrestling, they were divided into two groups: 9 athletes (14.67 ± 0.17 years) who were distinguished by high competitive performance and 20 athletes (14.45 ± 0.11 years) of the general group. Morphofunctional data, indicators of general physical, special strength and speed-strength preparedness were determined using test exercises. Statistical analysis of the obtained data was performed using licensed programs Microsoft Excel and STATISTICA 10. In the course of statistical analysis, the following parameters were determined and calculated: maximum (F) and relative (F1 = ƩF / m) strength, kg; total strength index in four strength exercises (ƩF = F1 + F2 + F3 + F4), kg; average strength, index of four exercises ( F = ƩF / 4), kg; time to reach maximum strength (Ʃt = t1 + t2 + t3 + t4), s; speed-strength index (J = ƩF / Ʃt), kg*ms-1; total strength gradient of four exercises (Ʃt0,5F), ms; speed-strength index in the first 500 ms (J500 = ƩF500 / Ʃt500), kg*ms-1; time to reach 1 kg force (t1 = Ʃt0.5F / (0.5×F), ms*kg-1; factor analysis. Results. According to anthropometric parameters, the leaders have significantly better results in weight and height (p < 0.01), and the body mass index was higher in the general group, but the difference was not significant (p > 0.05). Functional parameters differed significantly only in the Stange and Genchi tests (p < 0.01), as well as in the strength index of both arms (p < 0.05). Analysis of the general physical fitness of the leaders and the general group parameters revealed significant differences in 5 of the 6 exercises tested. The significantly high result of the arm wrestlers is supported by high parameters of special physical fitness, namely: strength parameters in two test exercises (hook and wrist bending), as well as the overall total strength parameter of the left and right arms (p<0.05). The speed-strength indicators of both hands also differed significantly in the average strength indicator, strength gradient, strength at 500 ms, speed-strength index at 500 ms, relative strength, and time to achieve a force of 1 kg (Student's t-test ranged from 2.06 to 5.84 at p < 0.05–0.001). Factor analysis confirmed the high influence of anthropometric data and speed-strength fitness indicators on the effectiveness of arm wrestlers’ competitive activities at the studied stage of preparation. Conclusions. In order to create the foundations for high results and sports improvement at the stage of preliminary basic training, it is necessary to provide for a predominantly significant development of strength and speed-strength capabilities, since the results obtained indicate that the growth of athletes' performance with the appropriate system of sports training is accompanied by a significant increase in maximum strength, an improvement in the indicators of starting, acceleration and fast strength in the first 500 ms of muscle tension, due to an improvement in the index and gradient of strength, the time to achieve a strength of 1 kg.

Waves and non-propagating modes in stratified MHD turbulence subject to a weak mean magnetic field

In this study we consider a freely decaying, stably stratified homogeneous magnetohydrodynamic turbulent plasma with a weak vertical background magnetic field ( $\boldsymbol {B}_0=B_0\hat {\boldsymbol {z}}),$ aligned with the density gradient of strength $N$ (i.e. Brunt–Väisälä frequency). Both linear theory and direct numerical simulations (DNS) are used to analyse the flow dynamics for a Boussinesq fluid with unitary magnetic and thermal Prandtl numbers. We implemented a normal mode decomposition emphasizing different types of motions depending on whether both the Froude $F_r$ and Alfvén–Mach $M$ numbers are small or only $F_r$ is small but $M$ is finite. In the former case, there is a non-propagating (NP) mode and fast modes: Alfvén waves with frequency $\omega _a$ and magnetogravity waves with frequency $\omega _{ag}$ . In the latter case, there are fast gravity waves with frequency $\omega _g$ and slow modes: NP mode and slow Alfvén waves. The numerical simulations carried out are started from initial isotropic conditions with zero initial magnetic and density fluctuations, so that the initial energy of the NP mode is strictly zero, for $0< B_0/(L_iN)\leqslant 0.12$ and a weak mean magnetic field ( $B_0=0.2$ or $B_0=0.4),$ where $L_i$ denotes the isotropic integral length scale. The DNS results indicate a weak turbulence regime for which $F_r$ is small and $M$ is finite. It is found that the vertical magnetic energy as well as the energy of the NP mode are drastically reduced as $N$ increases, while there is instead a forward cascade even for the magnetic field. The contribution coming from the energy of fast (gravity) waves does not exceed $50\,\%,$ while that coming from the energy of the NP mode does not exceed $10\,\%.$ Vertical motions are more affected by the effect of stratification than by the effect of the mean magnetic field, while it is the opposite for horizontal motions. We show that the spectrum of slow (Alfvén) waves and fast (gravity) waves tends to follow the power law $k_\perp ^{-3}$ for a wide range of time, $3< t<20$ . At high vertical (or horizontal) wavenumbers, the main contribution to total energy comes from the energy of slow Alfvén waves. At large and intermediate horizontal (or vertical) scales, the spectra of the energy of NP mode exhibit a flat shape.

Assessing the ducting phenomenon and its potential impact on Global Navigation Satellite System (GNSS) radio occultation refractivity retrievals over the northeast Pacific Ocean using radiosondes and global reanalysis

Abstract. In this study, high-resolution radiosondes from the Marine Atmospheric Radiation Measurement (ARM) Global Energy and Water Experiment (GEWEX) Cloud System Study (GCSS) Pacific Cross-section Intercomparison (GPCI) Investigation of Clouds (MAGIC) field campaign and ECMWF Reanalysis version 5 (ERA5) global reanalysis data are used to assess characteristics of the elevated ducting layer along a transect over the northeastern Pacific Ocean from Los Angeles, California, to Honolulu, Hawaii. The planetary boundary layer (PBL) height (PBLH) increases as the strength of the refractivity gradient decreases westward along the transect. The thickness of the prevailing ducting layer remains remarkably consistent (∼ 110 m) in the radiosonde data. On the other hand, the ERA5 reanalysis generally resolves the ducting features well, but it underestimates the ducting height and strength, especially over the trade cumulus region near Hawaii. A simple two-step end-to-end simulation is used to evaluate the impact of the elevated ducting layer on radio occultation (RO) refractivity retrievals. A systematic negative refractivity bias (N bias) below the ducting layer is observed throughout the transect, peaking (−5.42 %) slightly below the PBLH and gradually decreasing towards the surface (−0.5 %). The N bias shows a strong positive correlation with the ducting strength. The ERA5 data underestimate the N bias, with the magnitude of the underestimation increasing westward along the transect.

Velocity gradient partitioning in turbulent flows

The velocity gradient tensor can be decomposed into normal straining, pure shearing and rigid rotation tensors, each with distinct symmetry and normality properties. We partition the strength of turbulent velocity gradients based on the relative contributions of these constituents in several canonical flows. These flows include forced isotropic turbulence, turbulent channels and turbulent boundary layers. For forced isotropic turbulence, the partitioning is in excellent agreement with previous results. For wall-bounded turbulence, the partitioning collapses onto the isotropic partitioning far from the wall, where the mean shearing is relatively weak. By contrast, the near-wall partitioning is dominated by shearing. Between these two regimes, the partitioning collapses well at sufficiently high friction Reynolds numbers and its variations in the buffer layer and the log-law region can be reasonably modelled as a function of the mean shearing strength. Altogether, our results highlight the expressivity and broad applicability of the velocity gradient partitioning as advantages for turbulence modelling.

Ultra-high gradient performance 3-Tesla MRI for super-fast and high-quality prostate imaging: initial experience

ObjectivesTo implement and evaluate a super-fast and high-quality biparametric MRI (bpMRI) protocol for prostate imaging acquired at a new ultra-high gradient 3.0-T MRI system.MethodsParticipants with clinically suspected prostate cancer prospectively underwent a multiparametric MRI (mpMRI) on a new 3.0-T MRI scanner (maximum gradient strength: 200 mT/m, maximum slew rate: 200 T/m/s). The bpMRI protocol was extracted from the full mpMRI protocol, including axial T2-weighted and diffusion-weighted (DWI) sequences (b0/800, b1500). Overall image quality was rated by two readers on a five-point Likert scale from (1) non-diagnostic to (5) excellent. PI-RADS 2.1 scores were assessed by three readers separately for the bpMRI and mpMRI protocols. Cohen’s and Fleiss’ κ were calculated for PI-RADS agreement between protocols and interrater reliability between readers, respectively.ResultsSeventy-seven male participants (mean age, 66 ± 8 years) were included. Acquisition time of the bpMRI protocol was reduced by 62% (bpMRI: 5 min, 33 ± 21 s; mpMRI: 14 min, 50 ± 42 s). The bpMRI protocol showed excellent overall image quality for both the T2-weighted (median score both readers: 5 [IQR: 4–5]) and DWI (b1500) sequence (median score reader 1: 4 [IQR: 4–5]; reader 2: 4 [IQR: 4–4]). PI-RADS score agreement between protocols was excellent (Cohen’s κ range: 0.91–0.95 [95% CI: 0.89, 0.99]) with an overall good interrater reliability (Fleiss’ κ, 0.86 [95% CI: 0.80, 0.92]).ConclusionUltra-high gradient MRI allows the establishment of a high-quality and rapidly acquired bpMRI with high PI-RADS agreement to a full mpMRI protocol.Trials registrationClinicaltrials.gov, NCT06244680, Registered 06 February 2024, retrospectively registered, https://classic.clinicaltrials.gov/ct2/show/NCT06244680.Critical relevance statementA novel 3.0-Tesla MRI system with an ultra-high gradient performance enabled high-quality biparametric prostate MRI in 5.5 min while achieving excellent PI-RADS agreement with a standard multiparametric protocol.Key PointsMulti- and biparametric prostate MRIs were prospectively acquired utilizing a maximum gradient of 200 mT/m.Super-fast biparametric MRIs showed excellent image quality and had high PI-RADS agreement with multiparametric MRIs.Implementation of high gradient MRI in clinical routine allows accelerated and high-quality biparametric prostate examinations.Graphical

Revisiting Tide‐Induced Near‐Field Mixing in the Abyssal Ocean

AbstractVertical two‐dimensional numerical experiments incorporating Garrett‐Munk (GM) internal waves are conducted to investigate tide‐induced near‐field mixing over a finite‐amplitude sinusoidal seafloor, conventionally attributed to the breaking of high‐wavenumber internal tidal waves. Turbulent mixing is characterized by tidal excursion parameter (Te) and topographic steepness parameter (Sp) measuring tidal current strength and seafloor slope gradient, respectively. Under strong tidal currents (Te > 1), high‐wavenumber internal lee waves propagate upward from the seafloor. Even when Te and Sp are set to produce nearly the same upward energy flux, the vertical profile of mixing hotspots varies with Sp. For Sp 0.2, near‐inertial currents above the seafloor rapidly amplify by absorbing energy of internal lee waves from below, hindering their upward propagation and creating “short mixing hotspots.” For Sp < 0.2, these near‐inertial currents diminish, allowing internal lee waves to propagate upward and interact with the GM background internal waves, creating “tall mixing hotspots.”

Strength gradient in impact-induced metallic bonding

Solid-state bonding can form when metallic microparticles impact metallic substrates at supersonic velocities. While the conditions necessary for impact-induced metallic bonding are relatively well understood, the properties emerging at the bonded interfaces remain elusive. Here, we use in situ microparticle impact experiments followed by site-specific micromechanical measurements to study the interfacial strength across bonded interfaces. We reveal a gradient of bond strength starting with a weak bonding near the impact center, followed by a rapid twofold rise to a peak strength significantly higher than the yield strength of the bulk material, and eventually, a plateau covering a large portion of the interface towards the periphery. We show that the form of the native oxide at the bonded interface—whether layers, particles, or debris—dictates the level of bond strength. We formulate a predictive framework for impact-induced bond strength based on the evolution of the contact pressure and surface exposure.

The diversity of glycan chains in jellyfish mucin of three Cubozoan species: the contrast in molecular evolution rates of the peptide chain and Glycans.

The O-glycan composition of jellyfish (JF) mucin (qniumucin: Q-mucin) extracted from three Cubozoan species was studied after the optimization of the purification protocol. Application of a stepwise gradient of ionic strength to anion exchange chromatography (AEXC) was effective for isolating Q-mucin from coexisting impurities. In the three species, the amino acid sequence of the tandem repeat (TR) region in Q-mucin in all three Cubozoans seemed to remain the same as that in all Scyphozoans, although their glycan chains seemed to exhibit clear diversity. In particular, the amounts of acidic moieties on the glycan chains of Q-mucin from the Cubozoans markedly varied even in these genetically close species. In two of the three Cubozoan species, the fraction of disaccharides was large, showing a sharp contrast to that of the glycans of Q-mucin in Scyphozoans. This study also indicates that the simple sequence of TR commonly inherited in all Cubozoan and Scyphozoan JF species after the long term of evolution over 500Myears. According to this research, the glycans and the TR of mucin-type glycoproteins (MTGPs), forming a hierarchical structure, appear to complement each other in the evolutionary changes because the time required for their hereditary conversion is considerably different. The cooperation of these mechanisms is a strategy to achieve the contradictory functions of biosystems, namely species conservation and diversity acquisition.

Construction of a Wilms tumor risk model based on machine learning and identification of cuproptosis-related clusters

BackgroundCuproptosis, a recently identified type of programmed cell death triggered by copper, has mechanisms in Wilms tumor (WT) that are not yet fully understood. This research focuses on examining the link between WT and Cuproptosis-related genes (CRGs), with the goal of developing a predictive model for WT.MethodsFour gene expression datasets related to WT were sourced from the GEO database. Subsequently, expression profiles of CRGs were extracted for differential analysis and immune infiltration studies. Utilizing 105 WT samples, clusters related to Cuproptosis were identified. This involved analyzing associated immune cell infiltration and conducting functional enrichment analysis. Disease-characteristic genes were pinpointed using weighted gene co-expression network analysis. Finally, the WT risk prediction model was constructed by four machine learning methods: random forest, support vector machine (SVM), generalized linear and extreme gradient strength model. The best-performing machine learning model was chosen, and a nomogram was created. The effectiveness of this predictive model was validated using methods such as the calibration curve, decision curve analysis, and by appiying it to the TARGET-GTEx dataset.ResultsThirteen differentially expressed Cuproptosis-related genes were identified. The infiltration level of CD8 + T cells in WT children was lower than that in Normal tissue (NT) children, and the level of M0 infiltration of macrophages and T follicular helper cells was higher than that in NT children. In addition, two clusters of cuproptosis-related WT were identified. Enrichment analysis results indicated that genes in cluster 2 were primarily involved in cell division, nuclear division regulation, DNA biosynthesis process, ubiquitin-mediated proteolysis. The SVM model was judged to be the optimal model using 5 genes. Its accuracy was confirmed through a calibration curve and decision curve analysis, demonstrating satisfactory performance on the TARGET-GTEx validation dataset. Additional analysis revealed that these five genes exhibited high expression in both the TARGET-GTEx validation dataset and sequencing data.ConclusionThis research established a link between WT and Cuproptosis. It developed a predictive model for assessing the risk of WT and pinpointed five key genes associated with the disease.

Inertial Ferrofluidic Sensor for Vibration, Displacement and Impulse Measurement with a Linear Output Signal

The aim of the work is to develop the uniaxial ferrofluid sensor suitable for use either as an accelerometer for low-frequency vibrations or as a ballistic device or seismic sensor for shock loads. The goal is achieved by solving the following problems: development of a magnetic suspension system with a linear axial gradient of the magnetic field strength, calculation of the viscous friction force of the magnetic fluid filling the coaxial layer between the magnetic cylinder and the non-magnetic body wall, manufacturing of the sensor and its static and dynamic tests. The most significant result of the work is the experimental confirmation of the linearity of the electromechanical system of the sensor, corresponding to the model representations of a linear dissipative oscillating system with one degree of freedom. The significance of the obtained results lies in the appearance of cheap and simple linear inertial sensors. The principle of operation of the sensor is based on the registration of the motion of an inert mass deviating from the equilibrium position under the action of an external force to be measured. The inert mass, consisting of ring permanent magnets, levitates in a coaxial layer of magneto-fluid lubricant. The sensor, depending on its parameters, can measure either quasi-static force, or force impulse, or coordinate displacement, which is in demand in monitoring systems for critical structures and buildings, as well as in navigation systems for vehicles operating under conditions of small, slowly changing accelerations (microgravity).

Age-related alterations in human cortical microstructure across the lifespan: Insights from high-gradient diffusion MRI.

The human brain undergoes age-related microstructural alterations across the lifespan. Soma and Neurite Density Imaging (SANDI), a novel biophysical model of diffusion MRI, provides estimates of cell body (soma) radius and density, and neurite density in gray matter. The goal of this cross-sectional study was to assess the sensitivity of high-gradient diffusion MRI toward age-related alterations in cortical microstructure across the adult lifespan using SANDI. Seventy-two cognitively unimpaired healthy subjects (ages 19-85 years; 40 females) were scanned on the 3T Connectome MRI scanner with a maximum gradient strength of 300mT/m using a multi-shell diffusion MRI protocol incorporating 8 b-values and diffusion time of 19 ms. Intra-soma signal fraction obtained from SANDI model-fitting to the data was strongly correlated with age in all major cortical lobes (r = -0.69 to -0.60, FDR-p < 0.001). Intra-soma signal fraction (r = 0.48-0.63, FDR-p < 0.001) and soma radius (r = 0.28-0.40, FDR-p < 0.04) were significantly correlated with cortical volume in the prefrontal cortex, frontal, parietal, and temporal lobes. The strength of the relationship between SANDI metrics and age was greater than or comparable to the relationship between cortical volume and age across the cortical regions, particularly in the occipital lobe and anterior cingulate gyrus. In contrast to the SANDI metrics, all associations between diffusion tensor imaging (DTI) and diffusion kurtosis imaging metrics and age were low to moderate. These results suggest that high-gradient diffusion MRI may be more sensitive to underlying substrates of neurodegeneration in the aging brain than DTI and traditional macroscopic measures of neurodegeneration such as cortical volume and thickness.

Stellar Metallicities and Gradients in the Faint M31 Satellites Andromeda XVI and Andromeda XXVIII

We present ∼300 stellar metallicity measurements in two faint M31 dwarf galaxies, Andromeda XVI (M V = −7.5) and Andromeda XXVIII (M V = –8.8), derived using metallicity-sensitive calcium H and K narrowband Hubble Space Telescope imaging. These are the first individual stellar metallicities in And XVI (95 stars). Our And XXVIII sample (191 stars) is a factor of ∼15 increase over literature metallicities. For And XVI, we measure 〈[Fe/H]〉=−2.17−0.05+0.05 , σ[Fe/H]=0.33−0.07+0.07 , and ∇[Fe/H] = −0.23 ± 0.15 dex Re−1 . We find that And XVI is more metal-rich than Milky Way ultrafaint dwarf galaxies of similar luminosity, which may be a result of its unusually extended star formation history. For And XXVIII, we measure 〈[Fe/H]〉=−1.95−0.04+0.04 , σ[Fe/H]=0.34−0.05+0.05 , and ∇[Fe/H]= −0.46 ± 0.10 dex Re−1 , placing it on the dwarf galaxy mass–metallicity relation. Neither galaxy has a metallicity distribution function (MDF) with an abrupt metal-rich truncation, suggesting that star formation fell off gradually. The stellar metallicity gradient measurements are among the first for faint (L ≲ 106 L ⊙) galaxies outside the Milky Way halo. Both galaxies’ gradients are consistent with predictions from the FIRE simulations, where an age–gradient strength relationship is the observational consequence of stellar feedback that produces dark matter cores. We include a catalog for community spectroscopic follow-up, including 19 extremely metal-poor ([Fe/H] < –3.0) star candidates, which make up 7% of And XVI’s MDF and 6% of And XXVIII’s.

Assessing tumor microstructure with time-dependent diffusion imaging: Considerations and feasibility on clinical MRI and MRI-Linac.

Quantitative imaging biomarkers (QIBs) can characterize tumor heterogeneity and provide information for biological guidance in radiotherapy (RT). Time-dependent diffusion MRI (TDD-MRI) derived parameters are promising QIBs, as they describe tissue microstructure with more specificity than traditional diffusion-weighted MRI (DW-MRI). Specifically, TDD-MRI can provide information about both restricted diffusion and diffusional exchange, which are the two time-dependent effects affecting diffusion in tissue, and relevant in tumors. However, exhaustive modeling of both effects can require long acquisitions and complex model fitting. Furthermore, several introduced TDD-MRI measurements can require high gradient strengths and/or complex gradient waveforms that are possibly not available in RT settings. In this study, we investigated the feasibility of a simple analysis framework for the detection of restricted diffusion and diffusional exchange effects in the TDD-MRI signal. To promote the clinical applicability, we use standard gradient waveforms on a conventional 1.5 T MRI system with moderate gradient strength (Gmax=45 mT/m), and on a hybrid 1.5 T MRI-Linac system with low gradient strength (Gmax=15 mT/m). Restricted diffusion and diffusional exchange were simulated in geometries mimicking tumor microstructure to investigate the DW-MRI signal behavior and to determine optimal experimental parameters. TDD-MRI was implemented using pulsed field gradient spin echo with the optimized parameters on a conventional MRI system and a MRI-Linac. Experiments in green asparagus and 10 patients with brain lesions were performed to evaluate the time-dependent diffusion (TDD) contrast in the source DW-images. Simulations demonstrated how the TDD contrast was able to differentiate only dominating diffusional exchange in smaller cells from dominating restricted diffusion in larger cells. The maximal TDD contrast in simulations with typical cancer cell sizes and in asparagus measurements exceeded 5% on the conventional MRI but remained below 5% on the MRI-Linac. In particular, the simulated TDD contrast in typical cancer cell sizes (r=5-10µm) remained below or around 2% with the MRI-Linac gradient strength. In patients measured with the conventional MRI, we found sub-regions reflecting either dominating restricted diffusion or dominating diffusional exchange in and around brain lesions compared to the noisy appearing white matter. On the conventional MRI system, the TDD contrast maps showed consistent tumor sub-regions indicating different dominating TDD effects, potentially providing information on the spatial tumor heterogeneity. On the MRI-Linac, the available TDD contrast measured in asparagus showed the same trends as with the conventional MRI but remained close to typical measurement noise levels when simulated in common cancer cell sizes. On conventional MRI systems with moderate gradient strengths, the TDD contrast could potentially be used as a tool to identify which time-dependent effects to include when choosing a biophysical model for more specific tumor characterization.

Magnetic resonance microscopy for submillimeter samples in a horizontal MR scanner

The spatial resolution in magnetic resonance imaging is mainly limited by low SNR, which is commonly addressed by long measurement times or dedicated hardware. In single digit micron resolutions, diffusion becomes a further limiting factor since depending on the gradient strength, the diffusion length of particles may approach the target resolutions. Spatial resolution improvement has been addressed by microscopy inserts comprising dedicated gradient systems and RF-coils, usually designed for NMR spectrometers that are often equipped with a deuterium lock for field drift compensations. The presented microscopy insert has been designed to provide single-digit micron resolutions on horizontal preclinical imaging systems utilizing their full imaging and user interface capabilities. The incorporated gradient provides an efficiency of 0.135 T/(m∙A) which in combination with the system’s gradient amplifiers yields a maximum of 27 T/m. With the additional low noise amplifier added to the RF-path a three-fold SNR improvement could be achieved for small samples. Furthermore, a modified constant time imaging sequence was introduced to improve the capability of the setup for ultra‐high-resolution imaging demonstrated on zebrafish embryos at different development stages with (9 μm)³ resolution.

Stability analysis of tunnel heading in clay with nonstationary random fields of undrained shear strength

The stability problem of a tunnel heading in clay remains a significant challenge in geotechnical engineering. Specifically, when considering the spatial variability of the soil, the stability factor may be influenced by geographically random fields. This study investigates the effect of random fields on a probabilistic analysis of a tunnel heading in undrained clay. The study assumes that the undrained shear strength of the clay increases linearly with depth due to a strength gradient factor. The random adaptive finite element limit analysis is employed to calculate the stability numbers for tunnel headings. Nonstationary random fields with varying vertical correlation lengths are simulated using Monte Carlo simulation technique. The stability analysis takes into account geometry parameters (i.e., cover depth ratio) and nonstationary random field of undrained shear strength parameters. (i.e., strength gradient, coefficient of variation, and vertical correlation length). The results of tunnel face stability using random adaptive finite element limit analysis have also been utilised to assess the probability of design failure over a practical range of deterministic factors of safety. In the context of probabilistic failure analysis, the failure mechanism resulting from varying vertical correlation lengths could influence the probability of design failure. The findings of this study can be of significant interest to tunnel engineering practitioners during the design phase of tunnel heading projects.

On the use of dioxane as reference for determination of the hydrodynamic radius by NMR spectroscopy

Measuring the compaction of a protein or complex is key to our understanding of the interactions within and between biomolecules. Experimentally, protein compaction is often probed either by estimating the radius of gyration (Rg) obtained from small-angle x-ray scattering (SAXS) experiments or the hydrodynamic radius (Rh) obtained, for example, by pulsed field gradient NMR (PFG NMR) spectroscopy. PFG NMR experiments generally report on the translational diffusion coefficient, which in turn can be used to estimate Rh using an internal standard to account for sample viscosity and uncertainty about the gradient strength. 1,4-Dioxane is one such commonly used internal standard, and the reference value of Rh is therefore important. We have revisited the basis for the commonly used reference value for the Rh of dioxane (2.12 Å) that is used to convert measured diffusion coefficients into a hydrodynamic radius. We followed the same approach that was used to establish the current reference value by measuring SAXS and PFG NMR data for a set of seven different proteins and using these as standards. Our analysis shows that the current Rh reference value for dioxane Rh is underestimated, and we instead suggest a new value of 2.27 ± 0.04 Å. Using this updated reference value results in a ∼7% increase in Rh values for proteins whose hydrodynamic radii have been measured by PFG NMR. These results are particularly important when the absolute value of Rh is of interest such as when determining or validating ensemble descriptions of intrinsically disordered proteins.

Numerical investigation of punch-through mitigation in stiff-over-soft clays using skirted spudcan

Punch-through failure, a critical issue in offshore engineering, occurs when a foundation penetrates through strong-over-weak soil layers. This paper presents a study on the effectiveness of skirt addition to spudcans in addressing punch-through failure through numerical simulations using the axisymmetric Particle Finite Element Method (PFEM). The validity of the PFEM is verified by simulating a spudcan penetration centrifuge test. Subsequently, PFEM simulations are conducted to analyse the penetration behaviour of both generic and skirted spudcans in stiff-over-soft clays. Results from the simulations reveal the bearing responses of spudcans as they penetrate into clays, elucidate associated failure mechanisms, and underscore the significant of considering the spudcan-driving process in estimating punch-through failure mitigation. Findings indicate that, the skirt effectively mitigates punch-through failure by increasing plug height in the lower soft layer, thus reducing the rate of bearing capacity reduction. Furthermore, critical factors such as skirt length, upper layer thickness, lower layer strength gradient, and the strength ratio between lower and upper layers are assessed through comprehensive parametric studies to evaluate the efficacy of skirted spudcans in mitigating punch-through failure, with eventual goal to provide essential guidance for practical design considerations in offshore foundation systems.

Digital analysis of fabrication accuracy and fit in additively and subtractively manufactured implant-supported fixed complete dentures

ObjectivesTo digitally evaluate the trueness and fit of additively and subtractively manufactured fixed complete dentures in materials intended for definitive use. MethodsAn edentulous maxillary model with implants at the left first molar, left canine, right canine, and right first molar site was digitized and a fixed complete denture was designed. This design was used to fabricate fixed dentures in an additively manufactured resin for definitive use (AM), a high-impact polymer composite (SM-CR), and a strength gradient zirconia (SM-ZR) (n = 10). Each fixed denture was digitized and the surface (overall, occlusal, except occlusal, and abutments), linear, and interimplant distance deviations were analyzed. The fit was assessed with the triple-scan protocol. Data were analyzed with Welch analysis of variance and Games-Howell tests (α = 0.05). ResultsSM-ZR led to lower overall deviations than AM, which had the highest occlusal and the lowest abutments deviations (P ≤ 0.007). SM-ZR had the lowest occlusal and SM-CR had the highest except occlusal deviations (P ≤ 0.002). AM mostly had higher linear and SM-CR mostly had higher interimplant distance deviations (P ≤ 0.043). AM led to the highest marginal gap at the left canine site, while SM-CR had the highest and SM-ZR had the lowest gaps at the right canine site (P ≤ 0.022). ConclusionsSM-ZR dentures mostly had trueness and marginal fit similar to or better than the other groups. Tested fixed complete dentures were mostly smaller than the design file in terms of interimplant distances.

Resource allocation scheduling scheme for task migration and offloading in 6G Cybertwin internet of vehicles based on DRL

AbstractAs vehicular technology advances, intelligent vehicles generate numerous computation‐intensive tasks, challenging the computational resources of both the vehicles and the Internet of Vehicles (IoV). Traditional IoV struggles with fixed network structures and limited scalability, unable to meet the growing computational demands and next‐generation mobile communication technologies. In congested areas, near‐end Mobile Edge Computing (MEC) resources are often overtaxed, while far‐end MEC servers are underused, resulting in poor service quality. A novel network framework utilizing sixth‐generation mobile communication (6G) and digital twin technologies, combined with task migration, promises to alleviate these inefficiencies. To address these challenges, a task migration and re‐offloading model based on task attribute classification is introduced, employing a hybrid deep reinforcement learning (DRL) algorithm—Dueling Double Q Network DDPG (QDPG). This algorithm merges the strengths of the Deep Deterministic Policy Gradient (DDPG) and the Dueling Double Deep Q‐Network (D3QN), effectively handling continuous and discrete action domains to optimize task migration and re‐offloading in IoV. The inclusion of the Mini Batch K‐Means algorithm enhances learning efficiency and optimization in the DRL algorithm. Experimental results show that QDPG significantly boosts task efficiency and computational performance, providing a robust solution for resource allocation in IoV.