bluuebunny/crossref_metadata_2025 huggingface dataset:
Black phosphorus-enhanced injectable hydrogel for infected soft tissue healing
Authors: Zhao Yaochao , Chen Zhijie , Shao Wenjun , Yang Shu , Cui Wenguo , Cai Zhengwei , Cheng Liang , Lin Ruixin
Published: January 2023

The misuse of antibiotics makes clinical treatment of soft tissue infection a huge challenge in prosthesis replacement. In this study, a black phosphorus (BP)-enhanced antibacterial injectable hydrogel (HAABP) was developed by the dynamic coordinative cross-linking among thiolated hyaluronic acid, silver ion (Ag+), and BP. HAABP has been proven to possess typical porous structures, excellent injectability, and rapid self-healing properties. In addition, the shear modulus was positive correlative to the concentration of BP. In vitro, HAABP maintained good cytocompatibility and showed a highly efficient synergistic inhibitory effect on Staphylococcus aureus through the irradiation of near infrared light and the release of Ag+. In vivo, HAABP not only inhibited the persistent infection but also accelerated the deposition of collagen fibers and angiogenesis by down-regulating the inflammatory factor TNF-α in the infectious wound defect, thereby repairing the natural barrier of tissue. This study developed a BP-enhanced injectable hydrogel that provided a simple and efficient synergistic antibacterial strategy to treat soft tissue infections around prostheses.
Tau and tubulin protein aggregation characterization by solid-state nanopore method and atomic force microscopy
Authors: Acharjee Mitu C. , Li Haopeng , Rollings Ryan , Ma Bo , Tung Steve , Li Jiali
Published: January 2023

In this study, a silicon nitride nanopore-based sensing system was used to measure tau and tubulin monomers and their aggregations in salt solution at a single molecule level. Nanopores (6–30 nm) were fabricated on silicon nitride membranes supported by silicon substrates using a combination of focused ion beam milling and ion beam sculpting. When a charged protein molecule in the salt solution passes through a nanopore driven by an applied voltage, the protein molecule increases pore resistivity, which induces an ionic current drop that can be measured. The current drop amplitude is directly proportional to the local excluded volume of the protein molecule in the nanopore. We measured the monomers and aggregations of tau and tubulin proteins at biased voltages from 60 to 210 mV in a solution of pH 7.0–10. Our results showed that (1) the nanopore method was able to differentiate tau and tubulin proteins in their monomer and aggregated forms by their excluded volumes; (2) the most probable aggregation form was dimer for α- and β-tubulin and pentamer for αβ tubulin plus tau under experimental conditions; (3) the protein excluded volumes measured by the nanopore method depended on the applied voltage, and this observation could be explained by the nonuniform charge distribution of proteins. The monomer and aggregated proteins were further analyzed using atomic force spectroscopy (AFM), and protein volumes estimated by AFM were consistent with nanopore results.
Frequency-domain probe beam deflection method for measurement of thermal conductivity of materials on micron length scale
Authors: Sun Jinchi , Lv Guangxin , Cahill David G.
Published: January 2023

Time-domain thermoreflectance and frequency-domain thermoreflectance (FDTR) have been widely used for non-contact measurement of anisotropic thermal conductivity of materials with high spatial resolution. However, the requirement of a high thermoreflectance coefficient restricts the choice of metal coating and laser wavelength. The accuracy of the measurement is often limited by the high sensitivity to the radii of the laser beams. We describe an alternative frequency-domain pump-probe technique based on probe beam deflection. The beam deflection is primarily caused by thermoelastic deformation of the sample surface, with a magnitude determined by the thermal expansion coefficient of the bulk material to measure. We derive an analytical solution to the coupled elasticity and heat diffusion equations for periodic heating of a multilayer sample with anisotropic elastic constants, thermal conductivity, and thermal expansion coefficients. In most cases, a simplified model can reliably describe the frequency dependence of the beam deflection signal without knowledge of the elastic constants and thermal expansion coefficients of the material. The magnitude of the probe beam deflection signal is larger than the maximum magnitude achievable by thermoreflectance detection of surface temperatures if the thermal expansion coefficient is greater than 5 × 10−6 K−1. The uncertainty propagated from laser beam radii is smaller than that in FDTR when using a large beam offset. We find a nearly perfect matching of the measured signal and model prediction, and measure thermal conductivities within 6% of accepted values for materials spanning the range of polymers to gold, 0.1–300 W/(m K).
Relativistic equation of state using a screened-hydrogenic model
Authors: Faussurier Gérald
Published: January 2023

We present a self-consistent model based on a non-relativistic screened-hydrogenic model with ℓ-splitting to calculate the relativistic equation of state of matter in local thermodynamic equilibrium. Arbitrary degeneracy is allowed for the relativistic free electrons. Ion properties and cold curve are determined using the quotidian equation of state multiphase equation of state. The whole model is fast, robust, and reasonably accurate over a wide range of temperatures and densities.
Rate and noise-induced tipping working in concert
Authors: Slyman Katherine , Jones Christopher K.
Published: January 2023

Rate-induced tipping occurs when a ramp parameter changes rapidly enough to cause the system to tip between co-existing, attracting states. We show that the addition of noise to the system can cause it to tip well below the critical rate at which rate-induced tipping would occur. Moreover, it does so with significantly increased probability over the noise acting alone. We achieve this by finding a global minimizer in a canonical problem of the Freidlin–Wentzell action functional of large deviation theory that represents the most probable path for tipping. This is realized as a heteroclinic connection for the Euler–Lagrange system associated with the Freidlin–Wentzell action and we find it exists for all rates less than or equal to the critical rate. Its role as the most probable path is corroborated by direct Monte Carlo simulations.
Self-adaptive retro-reflective Doppler cloak based on planar space-time modulated metasurfaces
Authors: Fang X. , Li M. , Ramaccia D. , Toscano A. , Bilotti F. , Ding D.
Published: January 2023

As engineered electromagnetic covers based on (space-) time modulated metamaterials and metasurfaces, Doppler cloaks are able to compensate the Doppler effect induced by the motion of a scatterer, making it appear as if it were at rest to a detecting radar system. Perfect Doppler compensation can be theoretically always achieved for any relative velocity and motion direction of the cloaked scatterer with respect to the detecting system. However, the motion can be still detected from the cross section variation of the Doppler cloaked scatterer, especially under oblique incidence illumination. The challenge is, therefore, to have a proper Doppler compensation and maintain the amount of scattered energy toward the detection system as much constant as possible with respect to the illumination angle. In this Letter, we propose the design of self-adaptive retro-reflective planar Doppler cloak composed of a pair of space-time modulated metasurfaces: the first metasurface focuses the incident field in a specific location on the second metasurface, which is designed for enabling retro-reflection and Doppler frequency shift compensation. Here, the self-adaptive Doppler cloak is applied to a metallic planar reflector, moving toward its normal direction, and illuminated by an oblique plane wave. We demonstrate that the proposed Doppler cloak can perform frequency conversion and simultaneously maintain the radar cross section of the reflector as much stable as possible within an angular range of about 60° centered at the normal direction. The self-adaptive Doppler cloak may enhance the undetectability of cloaked moving objects.
Exchange bias model including setting process: Investigation of antiferromagnetic alignment fraction due to thermal activation
Authors: Khamtawi R. , Daeng-am W. , Chureemart P. , Chantrell R. W. , Chureemart J.
Published: January 2023

An exchange bias (EB) model taking the setting process into account is developed to study the effect of the crucial parameters, such as the AFM anisotropy constant (KAF), the setting temperature (Tset), and the physical microstructure on the exchange bias field of an AFM/FM system. The magnetization dynamics of the EB system is treated using the kinetic Monte Carlo approach and by integrating the Landau–Lifshitz–Gilbert equation for AFM and FM layers, respectively. We first investigate the variation of the exchange bias field (HEB) as a function of KAF in the IrMn/CoFe system. It is found that HEB strongly depends on the energy barrier dispersion determined by dispersions of KAF and the grain volume. It is shown that the HEB is affected by the physical microstructure of the IrMn layer: film thickness and grain diameter. We also demonstrate that the maximum setting fraction (fset) related to HEB can be achieved by optimizing the value of KAF and Tset. The simulation results of the setting process are in good agreement with previous experimental works. This confirms the validity of the EB model, including the setting process that can be used as a powerful tool for the application of spintronics, especially for read sensor design to achieve high thermal stability with scaling down of components.
Downstream migration of telemetry-tagged adult common galaxias (
Authors: Koster W. M. , Dawson D. , Pomorin K. , Morrongiello J. R.
Published: January 2023

Many migratory species are under threat globally. Management actions to conserve these species require a quantitative understanding of their life-history requirements, such as cues for migration. Migrations to spawn are a critical component of the life-cycle of diadromous fishes but are often poorly understood. Downstream migration patterns of common galaxias (Galaxias maculatus) were investigated in the Bunyip–Tarago River system, southern Australia, using passive integrated transponder technology. Fish undertook rapid (typically 1–3 days) downstream migration (up to 50 km) from the upper reaches to the lowland reaches near the estuary. Migration occurred from March to May during the known spawning period, with peak movement between late April and mid-May. Migration was also related to increased river discharge, with fish being more likely to migrate on days when flow was high compared with the previous 2 days, and a waxing moon (i.e. increasing illumination). Our results fill an important knowledge gap in the life history of this widely distributed diadromous species. Importantly, the knowledge about the likely drivers of movement can inform management actions such as providing environmental flows in austral autumn and at appropriate moon phases to trigger the downstream migration of adult common galaxias from freshwater reaches to estuarine spawning areas.
Integrating pH into the metabolic theory of ecology to predict bacterial diversity in soil
Authors: Luan Lu , Jiang Yuji , Dini-Andreote Francisco , Crowther Thomas W. , Li Pengfa , Bahram Mohammad , Zheng Jie , Xu Qinsong , Zhang Xue-Xian , Sun Bo
Published: January 2023

Microorganisms play essential roles in soil ecosystem functioning and maintenance, but methods are currently lacking for quantitative assessments of the mechanisms underlying microbial diversity patterns observed across disparate systems and scales. Here we established a quantitative model to incorporate pH into metabolic theory to capture and explain some of the unexplained variation in the relationship between temperature and soil bacterial diversity. We then tested and validated our newly developed models across multiple scales of ecological organization. At the species level, we modeled the diversification rate of the model bacterium
Pseudomonas fluorescens
evolving under laboratory media gradients varying in temperature and pH. At the community level, we modeled patterns of bacterial communities in paddy soils across a continental scale, which included natural gradients of pH and temperature. Last, we further extended our model at a global scale by integrating a meta-analysis comprising 870 soils collected worldwide from a wide range of ecosystems. Our results were robust in consistently predicting the distributional patterns of bacterial diversity across soil temperature and pH gradients—with model variation explaining from 7 to 66% of the variation in bacterial diversity, depending on the scale and system complexity. Together, our study represents a nexus point for the integration of soil bacterial diversity and quantitative models with the potential to be used at distinct spatiotemporal scales. By mechanistically representing pH into metabolic theory, our study enhances our capacity to explain and predict the patterns of bacterial diversity and functioning under current or future climate change scenarios.
ATOH8 binds SMAD3 to induce cellular senescence and prevent Ras-driven malignant transformation
Authors: Liu Ximeng , Li Xu , Wang Shuang , Liu Qin , Feng Xianming , Wang Wenting , Huang Zhangduo , Huang Yongbo , Wu Jueheng , Cai Muyan , Cai Xiuyu , Xu Xiaonan , Cai Junchao , Li Mengfeng
Published: January 2023

The process of oncogene-induced senescence (OIS) and the conversion between OIS and malignant transformation during carcinogenesis is poorly understood. Here, we show that following overactivation of oncogene Ras in lung epithelial cells, high-level transforming growth factor β1 (TGF-β1)–activated SMAD3, but not SMAD2 or SMAD4, plays a determinant role in inducing cellular senescence independent of the p53/p16/p15 senescence pathways. Importantly, SMAD3 binds a potential tumor suppressor ATOH8 to form a transcriptional complex that directly represses a series of cell cycle–promoting genes and consequently causes senescence in lung epithelial cells. Interestingly, the prosenescent SMAD3 converts to being oncogenic and essentially facilitates oncogenic Ras-driven malignant transformation. Furthermore, depleting Atoh8 rapidly accelerates oncogenic Ras-driven lung tumorigenesis, and lung cancers driven by mutant Ras and Atoh8 loss, but not by mutant Ras only, are sensitive to treatment of a specific SMAD3 inhibitor. Moreover, hypermethylation of the
ATOH8
gene can be found in approximately 12% of clinical lung cancer cases. Together, our findings demonstrate not only epithelial cellular senescence directed by a potential tumor suppressor–controlled transcriptional program but also an important interplay between the prosenescent and transforming effects of TGF-β/SMAD3, potentially laying a foundation for developing early detection and anticancer strategies.
Mechanism for plasmon-generated solvated electrons
Authors: Al-Zubeidi Alexander , Ostovar Behnaz , Carlin Claire C. , Li Boxi Cam , Lee Stephen A. , Chiang Wei-Yi , Gross Niklas , Dutta Sukanya , Misiura Anastasiia , Searles Emily K. , Chakraborty Amrita , Roberts Sean T. , Dionne Jennifer A. , Rossky Peter J. , Landes Christy F. , Link Stephan
Published: January 2023

Solvated electrons are powerful reducing agents capable of driving some of the most energetically expensive reduction reactions. Their generation under mild and sustainable conditions remains challenging though. Using near-ultraviolet irradiation under low-intensity one-photon conditions coupled with electrochemical and optical detection, we show that the yield of solvated electrons in water is increased more than 10 times for nanoparticle-decorated electrodes compared to smooth silver electrodes. Based on the simulations of electric fields and hot carrier distributions, we determine that hot electrons generated by plasmons are injected into water to form solvated electrons. Both yield enhancement and hot carrier production spectrally follow the plasmonic near-field. The ability to enhance solvated electron yields in a controlled manner by tailoring nanoparticle plasmons opens up a promising strategy for exploiting solvated electrons in chemical reactions.
OGT controls mammalian cell viability by regulating the proteasome/mTOR/ mitochondrial axis
Authors: Li Xiang , Yue Xiaojing , Sepulveda Hugo , Burt Rajan A. , Scott David A. , A. Carr Steven , A. Myers Samuel , Rao Anjana
Published: January 2023

O
-GlcNAc transferase (OGT) modifies serine and threonine residues on nuclear and cytosolic proteins with
O
-linked N-acetylglucosamine (GlcNAc). OGT is essential for mammalian cell viability, but the underlying mechanisms are still enigmatic. We performed a genome-wide CRISPR–Cas9 screen in mouse embryonic stem cells (mESCs) to identify candidates whose depletion rescued the block in cell proliferation induced by OGT deficiency. We show that the block in cell proliferation in OGT-deficient cells stems from mitochondrial dysfunction secondary to mTOR (mechanistic target of rapamycin) hyperactivation. In normal cells, OGT maintains low mTOR activity and mitochondrial fitness through suppression of proteasome activity; in the absence of OGT, increased proteasome activity results in increased steady-state amino acid levels, which in turn promote mTOR lysosomal translocation and activation, and increased oxidative phosphorylation. mTOR activation in OGT-deficient mESCs was confirmed by an independent phospho-proteomic screen. Our study highlights a unique series of events whereby OGT regulates the proteasome/ mTOR/ mitochondrial axis in a manner that maintains homeostasis of intracellular amino acid levels, mitochondrial fitness, and cell viability. A similar mechanism operates in CD8
+
T cells, indicating its generality across mammalian cell types. Manipulating OGT activity may have therapeutic potential in diseases in which this signaling pathway is impaired.
Qualitative approaches in L2 research abroad
Authors: Shively Rachel L.
Published: January 2023

The goal of this chapter is to provide a critical look at qualitative approaches in the context of research about study abroad and language learning. The chapter begins with an overview of qualitative scholarship focused on study abroad, highlighting methodological approaches and theoretical orientations, as well as historical trends. In the following section, some of the many contributions of qualitative research about study abroad are outlined, with a focus on aspects related to identity and social interaction. Limitations and gaps in the literature are then discussed with regard to participants and data collection and analysis. The chapter concludes with recommendations for how researchers can continue to advance our understanding of study abroad through qualitative approaches. Suggestions for future directions include diversifying the voices represented in research and placing greater emphasis on reflexivity.
Mixed methods research on language learning in study abroad
Authors: Kinginger Celeste , Schrauf Robert W.
Published: January 2023

Although research involving the theorized, principled, systematic integration of quantitative and qualitative approaches – mixed methods – is relatively rare in the literature on study abroad, there have been seminal, interesting, and impactful multiple methods contributions to this literature. This chapter first explores extant research on language learning in study abroad that involves both quantitative and qualitative data. The chapter will then present the key feature of mixed methods research: the principled integration of quantitative and qualitative data and analysis. Worked examples of these moments of integration – termed ‘points of interface’ – are drawn from our own current research and a published study. The chapter closes with reflection on how mixed methods might strengthen and extend the empirical case for study abroad.
Translation and diaspora
Authors: Pokorn Nike K.
Published: January 2023

This article revisits Gideon Toury’s (1995, 2012) definition of translation as a fact of the target culture by highlighting the transfer of cultural images through literary translation in the periodicals of a US diaspora in the interwar period between the US Immigration Act of 1924 and the beginning of World War II in 1939. I argue that literary translations in diaspora periodicals fulfilled different roles and were used for strengthening not only intercultural but also intracultural links. The analysis of 4897 interwar issues of two periodical publications of the Slovene Americans shows that these periodicals continuously published literary translations: not only from different languages into Slovene, but also from Slovene into English. By means of the latter, Slovene immigrant diaspora attempted to construct their own representation of Slovene culture, and communicate this image to other immigrant communities, mainstream US culture, and the new generations who no longer spoke Slovene. The immigrant community thus became the promoter, creator, and receiver of these translations and simultaneously represented the source and target cultures, blurring clearly circumscribed borders of a distinct cultural unity.
Changes in thermal properties of 7075 aluminium alloy by aging heat treatment
Authors: Kim Youngchan , Choi Seweon , Kim Yumi , Kang Changseog , Hong Sungkil
Published: January 2023

This study investigated the effects of aging heat treatment on the change of thermal properties of 7075 Al alloy using differential scanning calorimetry and a laser flash apparatus. The thermal diffusivity showed different trends in the three temperature ranges: In the range from room temperature to 160°C, the thermal diffusivity increased with increasing temperature. Between 160 and 240°C, the thermal diffusivity increased with an increase in the temperature of the specimen. Precipitation was completed at 240°C or higher, and the thermal diffusivity decreased with an increase in the temperature of the specimen. The amount of precipitation of η′ and η phases did not affect the change in thermal diffusivity but only contributed to the improvement of micro-hardness.
The effect of Penning ionization reactions on the evolution of He with O2 admixtures plasma jets
Authors: Lazarou C , Anastassiou C , Topala I , Chiper A S , Mihaila I , Pohoata V , Georghiou G E
Published: January 2023

In this study, the effect of the O2 and N2 Penning ionization reactions on the evolution a capillary helium atmospheric pressure plasma jet (APPJ) with and without the presence of oxygen admixtures is investigated numerically using a two dimensional axi-symmetric model. In order to better understand potential applications of plasma surface interaction, the He and He + O2 (1000 ppm) APPJ is launched into a dielectric target. Moreover, the numerical model is compared with experimental measurements showing that the model captures the right physics and can elucidate the discharge dynamics. The comparison is realized for axial and radial measurements in order to have a complete picture of the plasma jet evolution. In this paper, the velocity and the shape of the plasma guided streamer were chosen as indicators of plasma jet evolution. In particular, the investigation is accomplished experimentally by tracking the spatio-temporal resolved emission of 706.5 nm (3s3S → 2p3P) line and numerically by calculating the reaction rate for the same transition. The O2 and N2 Penning reactions are then independently considered in the numerical model in order to isolate their contribution to the plasma evolution. It is shown that for the pure helium plasma, the N2 Penning reactions are more important to the plasma evolution. However, when oxygen admixtures are added to the plasma gas, the O2 Penning reactions become more important than the N2 ones.
The stability of the b-family of peakon equations
Authors: Charalampidis Efstathios G , Parker Ross , Kevrekidis Panayotis G , Lafortune Stéphane
Published: January 2023

In the present work we revisit the b-family model of peakon equations, containing as special cases the b = 2 (Camassa–Holm) and b = 3 (Degasperis–Procesi) integrable examples. We establish information about the point spectrum of the peakon solutions and notably find that for suitably smooth perturbations there exists point spectrum in the right half plane rendering the peakons unstable for b < 1. We explore numerically these ideas in the realm of fixed-point iterations, spectral stability analysis and time-stepping of the model for the different parameter regimes. In particular, we identify exact, stationary (spectrally stable) lefton solutions for

b
<
−
1

, and for

−
1
<
b
<
1

, we dynamically identify ramp-cliff solutions as dominant states in this regime. We complement our analysis by examining the breakup of smooth initial data into stable peakons for b > 1. While many of the above dynamical features had been explored in earlier studies, in the present work, we supplement them, wherever possible, with spectral stability computations.
Modeling of the

N2+

ion in cold helium plasma II: transport properties of

N2+

in helium
Authors: Paláček S , Beseda M , Kalus R , Benhenni M , Gadéa F X , Leininger T , Yousfi M
Published: January 2023

A detailed modeling of N

2
+

transport properties in helium gas has been performed by employing Monte Carlo calculations based on ab initio collision cross-sections reported by our group in a preceding paper (S Paláček et al 2022 Plasma Sources Sci. Technol. 31 105004). A broad range of the reduced electric field (

E

/

N

) is considered to provide data directly usable in macroscopic modeling of processes in cold helium plasmas. The N

2
+

mobility in helium gas at room temperature (T = 300 K), the characteristic energies of its longitudinal and transversal diffusion, and the rate constant of the N

2
+

dissociation induced by collisions with helium atoms have been calculated. The effect of the N

2
+

initial rotational-vibrational excitation is investigated as well as the effect of the rotational alignment of the N

2
+

molecule. A direct comparison with N

2
+

/He mobility experimental data is performed as well as indirect tests of theoretical estimates of the characteristic diffusion energies by comparing the latter with pseudo-experimental data obtained from mobility experiments via an inverse-method approach.
Optimizing the flatness of 4H-silicon carbide wafers by tuning the sequence of lapping
Authors: Zhang Xi , Liu Xiaoshuang , Wang Yazhe , Zhu Ruzhong , Zhang Xuqing , Zhang Yiqiang , Wang Rong , Yang Deren , Pi Xiaodong
Published: January 2023

In this letter, we optimize the flatness of 4H silicon carbide (4H-SiC) wafers by tuning the sequence of single-sided lapping, enlightened by the different mechanical properties of the Si face and C face of 4H-SiC. After wire sawing, the coarse lapping and fine lapping are carried out to rapidly remove the surface damage and optimize the flatness of 4H-SiC wafers. From the point of view of controlling the values of the bow and warp of 4H-SiC wafers, the coarse-lapping sequence of the C-face lapping followed by Si-face lapping is beneficial, while the preferred fine-lapping sequence is Si-face lapping followed by C-face lapping. Nanoindentation tests indicate that the C face has higher hardness and lower fracture toughness than the Si face. This gives rise to thicker surface damage at the C face after the wire sawing. After removing the same amount of wire-sawing induced surface damage, the thickness of residual surface damage of the C face is higher than that of the Si face after the coarse lapping. The fine lapping basically removes all the surface damage and creates the near-perfect C face and Si face. The higher amount of surface damage of the C face after the coarse lapping and the higher fracture toughness of the near-perfect Si face after the fine lapping can tolerate more plastic deformations, which gives rise to the superior flatness of the C-face-followed-by-Si-face coarse lapped and the Si-face-followed-by-C-face fine lapped 4H-SiC wafers, respectively.
Assessment of the creep behavior of siltstone for the Snowy 2.0 hydropower station using multistage uniaxial creep tests
Authors: Kheir S Abou , Bamford B , Brogiato A , Carli G De , Lambrughi A
Published: January 2023

Multistage uniaxial creep tests with durations up to four months were performed to investigate the time-dependent behavior of the siltstone rock formations into which the Snowy 2.0 hydropower station will be excavated. Short term experimental tests are used to determine the stress levels of the creep tests and to assess the effect of creep on the short-term parameters of the siltstone. The samples have been collected from boreholes at a depth of about 650-850 meters beneath the surface where the power station complex will be constructed. The samples are extracted from the Ravine Beds unit formation and the main lithology is composed of siltstones with interlaminated to interbedded sandstones. The relative percentage of siltstone/sandstone within the rock mass ranges from 80/20% to 50/50% and on average is 70/30%. The siltstone features a medium strength matrix, a very stiff matrix, and a very low porosity. During the creep tests, the results show consistently negligible secondary creep deformations after the full development of the primary stage, and this finding was found to be valid regardless of the initial water content of the specimens. Additionally, a tertiary creep is observed on some of the tests under failure stress levels, where the tertiary creep of the siltstone is described with sudden brittle creep deformations. Ultimately, empirical and rheological creep models are used to interpret and fit the creep deformations. The results of the models are compared to creep deformations measured in the laboratory.
Cross-scale rockmass characterization by high resolution seismic imaging around tunnels
Authors: Cosma Calin , Enescu Nicoleta
Published: January 2023

Reflection seismic surveys are relevant to the detailed characterisation of crystalline bedrock. Relatively small-scale features, even single fractures, can demonstrably be detected. Integrated analysis and modelling of geological, hydrogeological and geophysical data is instrumental in the interpretation of reflection seismic data. This requires the inference of the nature of the reflectors, e.g. lithological contacts or deformation zones and resolving the orientation ambiguity of the reflectors. Brittle deformation zones and large fractures may be heterogeneous in their detailed structure, making their characterization a challenging task. Several examples of structure characterization ahead and around tunnels are presented, with focus on the safety assessment for engineering and mining applications. Seismic imaging techniques adapted for tunnels and galleries are presented with examples from high resolution seismic surveys carried out at ONKALO (Finland) and Äspö HRL (Sweden). Studies performed over a span of several years demonstrate that large fractures identified initially through geological mapping, can also be found, positioned and characterized by seismics at the small scale of tunnels and/or boreholes. We show that reflection seismic surveys are relevant to the detailed characterization of crystalline bedrock. The detection of some distinctive features, even large-scale, can be uncertain if the survey layout is spatially constrained. Combinations of borehole and tunnel measurements using measuring arrays with diverse orientations helped reduce the location ambiguities and are recommended to be used in mining and tunneling rock characterization surveys wherever possible.
Method to obtain 3D point clouds of tunnels using smartphone LiDAR and comparison to photogrammetry
Authors: Torkan Masoud , Janiszewski Mateusz , Uotinen Lauri , Rinne Mikael
Published: January 2023

Remote sensing methods, for example, photogrammetry and laser scanning can be employed to scan rock masses by digitizing underground spaces or slopes. To reconstruct a 3D model by photogrammetry, plenty of photos should be captured. This process is time-consuming and can be dangerous when the rock mass is unstable. Therefore, rapid capturing methods are needed to reduce the acquisition time. This can be achieved with LiDAR scanners that capture a 3D point cloud with a high-speed pulsed laser beam. However, the cost of laser scanners is high, which limits their usability. Apple’s iPhone 12 Pro Max smartphone is equipped with a LiDAR sensor and is much cheaper than conventional laser scanners. Several mobile applications for 3D models using the smartphone Lidar have been developed, making the scanning process easy. Therefore, smartphones can be used for rapid scanning of unstable surfaces of tunnels and slopes. In this study, 3D point clouds (3DPC) of a tunnel wall of the Underground Research Laboratory of Aalto University (URLA) are obtained by a high-resolution digital camera and smartphone LiDAR. The models are analyzed and compared. The results show the quality of the smartphone LiDAR sensor is adequate for generating 3D models of underground spaces.
Influence of Temperature and Deviatoric Stress on Creep Behavior of Rock Salt
Authors: Moslehy A , Alshibli K A
Published: January 2023

Rock salt deposits are used as depositories for hazardous wastes and oil due to their excellent mechanical properties for depositories such as low permeability and self-healing. The creep behavior of rock salt plays a major role in the long-term stability of rock salt depositories. Temperature and deviatoric stress significantly impact the creep behavior of rock salt. This paper studies the influences of temperature and deviatoric stress on the creep behavior of natural single-crystal rock salt specimens using creep experiments. A special triaxial thermal cell was developed to conduct the experiments. Prismatic specimens were cut out of a large mass of a sample that was acquired from Windsor Salt Mine, Ontario, Canada. The prepared specimens were tested in one-dimensional creep experiments at 20, 100, and 150° C temperatures and under 1 MPa confining pressure. Constant deviatoric stresses (σd) of 4, 10, and 12 MPa were applied to the specimens. Increasing the applied deviatoric stress and temperature caused an increase in the accumulated strain during the experiments and resulted in higher steady-state strain rates. Although the transient strain rate is increased at elevated temperatures, it appears to be insensitive to the applied deviatoric stress.
Coupled Thermo-Mechanical Study of Crack Initiation Stress Threshold in Porous Sandstone
Authors: Moravej S , Mutaz E , Serati M , Williams D J
Published: January 2023

The increasing depth of tunnels and underground mining operations worldwide has resulted in the rise of deep mines at temperatures well above 50°C. Such unwanted thermal gradients not only adversely impact the physical and mechanical behaviours of the rock mass but could also affect the safety of underground mines leading to temporarily and permanently shutting down the operation. The combination of high temperature and high-stress conditions further culminates in explosion-like fractures like rockburst and spalling, which are the main problems in deep mining and tunnel constructions. Spalling is identified as an abrupt explosion-like rock failure that occurs spontaneously and can endanger tunnelling and mining operations, causing injuries and fatalities, and necessitating investigation of the effect of temperature on rock behaviour. It is known that the spalling strength is correlated with the internal crack initiation in low-porosity and brittle crystalline rocks. This paper investigates this phenomenon and examines the influence of coupled thermo-mechanical conditions on the crack initiation stress level of sandstone samples. True triaxial compression tests were carried out on 50 mm sandstone cubes from room temperature (25°C) to 100°C using a high temperature true triaxial testing facility. The results suggest that temperature can have a significant impact on crack initiation and the spalling strength of rock, particularly at low confinement.
Experimental Device for the Determination of Fracture Toughness at High Pressure
Authors: Muñoz-Ibáñez A , Herbón-Penabad M , Delgado-Martín J
Published: January 2023

Mode I fracture toughness (KIC
) is a relevant property in many applications involving rock mechanics. However, the conventional methods for its determination only consider ambient pressure conditions. Although the available experimentation on high pressure fracture toughness shows that KIC
tends to increase with confining pressure not all the published results provide with the same evidence. Among the available methodologies for KIC
testing, the pseudo-compact tension (pCT) test approach provides with a number of operational advantages over other alternatives and makes it a good candidate for its extension to high pressure research. Based on it, we have designed and constructed a simple high-pressure cell that may be easily installed in any conventional compression frame without modifications to test pCT specimens. The cell may accommodate either a gas or liquid as confining fluids and work with samples of up to 50 mm (~2”) diameter. In order to verify the expected performance, we have conducted different calibration tests, including leak rate and the assessment of axial friction. For the demonstration and validation of the experimental approach presented, we have selected virtually impervious poly-methacrylate (PMMA) and Corvio sandstone samples. Results obtained at room conditions and at high pressure are compared and discussed.
Laboratory block model tests simulating rock anchoring in rock mass
Authors: Grindheim B , Aasbø K S , Li C C , Høien A H
Published: January 2023

Rock anchors are used to stabilise large scale infrastructures. Failure of rock anchors could threaten the stability and lead to severe economic and social consequences. The design of rock anchors is based on four principal failure modes, which are breakage of the steel tendon, tendon-grout interface failure, grout-rock interface failure and rock mass failure around the anchor. The current dimensioning methods are uncertain due to limited knowledge of the grout-rock bond strength and the rock mass failure. The dimensioning method against rock mass failure is based upon the weight of the overlying rock mass in an inverted cone and the shear strength of the rock mass along the inverted cone, which results in conservative design of rock anchors. A small laboratory model was developed to evaluate the rock mass failure of a rock anchor at maximum pullout load. The model contained small concrete blocks set in a staggered pattern representing the rock mass. The loading of the model showed that the load was transferred to the sides by rotation and lifting of the blocks, which created a small load bearing arch in each layer during loading. This resulted in the model being able to carry much higher loads than what was calculated with the dimensioning methods. Back calculation of the results from the physical tests in UDEC showed the same arching effect in each layer during loading. The testing has improved the knowledge on the concept of how the load transfer from a rock anchor to the rock mass.
Interpreting ultrasonic pulse velocities and elastic properties of lac du bonnet granite under compression
Authors: McDonald M R , Gaines S N , Diederichs M S
Published: January 2023

The measurement of ultrasonic velocities in rock core is a straightforward, non-destructive, economic method to estimate rock material properties conducted by emitting high frequency acoustic waves through the rock core. The velocities of compressional and shear waves (P- and S-waves, respectively) are influenced by the unique microstructural characteristics of the rock. Once wave velocities and bulk density for each sample have been determined, the dynamic elastic material constants such as Young’s modulus, Poisson’s ratio, and shear modulus can be calculated. In theory, it is expected that the dynamic properties would be similar to the static properties calculated in uniaxial compression strength (UCS) tests. In UCS tests, elastic parameters are estimated using stress-strain relationships at approximately 50% of the peak strength. However, dynamic properties from the UPV method often do not match static properties. In this study, dynamic testing of the rock core is completed under two broad stress conditions: no compression and axial compression (UCS). This allows for a direct comparison between dynamic UPV testing data, and static data, and should produce a closer match between the dynamic and static testing data when dynamic UPV testing is conducted under stress conditions similar to the static testing stress state.
High-speed train induced vibration measurements in fresh tunnel shotcrete layer
Authors: Siren T , Dahlström M , Cronvall T
Published: January 2023

Existing coastal railway track has been undergoing for renovation and improvement work aiming to raise train speed and shorten the travel time between Turku and Helsinki. The track has 16 existing tunnels of which 14 has been renovated between 2019 and 2021. Majority of the tunnels have been reinforced by system and shotcrete and rock bolts. The water seepage control has been solved by using PE sheets with additional 100 mm fibre shotcrete layer as fire protection layer. After the track and tunnel improvements, the track was test driven with two different trains: a high speed SM train unit and a two storey intercity train unit. The speeds used were higher than the current allowed speeds aiming to study the potential to increase the travel speed. One of the most restrictive parameters for the increase is the pressure shock of high speed train entering the tunnel. Too high pressure shock will cause inconvenience for the passengers and can cause damage in tunnel lining structures. Also currently no clear guideline exists what speed limits need to be used for trains entering tunnels with curing shotcrete. To study these matters the test run train units were instrumented including with pressure sensors. The conclusions about the pressure shocks are investigated briefly in the paper.
Intact rock deformation bimodularity: an experimental study
Authors: Muñiz-Menéndez Mauro , Pérez-Rey Ignacio
Published: January 2023

Rock deformability under tensile stresses plays an important role in different scenarios like, e.g., in the mechanical behaviour of roofs in underground openings, hydraulic fracturing, dilatometer tests performed in massive rock masses or in tensile strength tests. Different authors have proved that the tensile deformation modulus of the intact rock can be significantly different than that obtained under compressive load, being this so-called ‘bimodularity’ often ignored. In this work, we present preliminary results from uniaxial compressive and tensile strength tests carried out in three rocks with a testing apparatus recently modified to be able to perform both types of tests. Experimental results show that the deformational behaviour of the rocks studied is dependent on the type of load applied. The present work aims at contributing to a better understanding of the deformational behaviour of rocks, in particular when subjected to uniaxial tensile loads as well as in dealing with future updates of existing test methodologies.
Comparison of different methods to characterise the abrasivity potential and mechanical properties of carbonates with respect to its relevance for practical purposes in excavation technologies
Authors: Aderhold M , Disselkamp C , Formanski R , Grimberg M , Grineisen A M , Kroenert L M , Ogan M S , Romahn H , Sandkühler R , Skonetzki C , Ullah F , Zinke B H , Duda M , Witte L C , Brajer C , Backers T
Published: January 2023

The characterisation of the abrasivity potential of carbonates plays an important role for drilling-based excavation technologies, for example in tunneling or geothermal exploration. Although carbonates are known to have a rather low abrasivity, they have been associated with severe excavation performance reductions. We compared different methods to characterise the abrasivity potential of carbonates with respect to its applicability for practical purposes in excavation technologies. In this study, seven carbonate rocks were investigated which differ with respect to their microstructural properties and degrees of dolomitisation. These carbonate rock samples were selected from different lithological units in Germany (Jurassic: Kelheimer limestone, Wachenzell dolomite, Solnhofen limestone, Pappenheim limestone, Treuchtlingen limestone; Devonian: Wülfrath limestone, Brilon limestone). Rock samples were characterised with respect to basic physical properties (density, ultrasound velocity), microstructure (thin section analysis, XRD), mechanical properties (uniaxial compressive strength UCS, splitting tensile strength STS) and commonly applied abrasivity indices (Cerchar abrasivity index test CAI, LCPC test) as well as derived indices (equivalent quartz content eQu). Our results confirm that the tested carbonate rocks show low abrasivity indices in terms of CAI, LCPC and eQu with an increase in abrasivity potential with increasing dolomite content. The microstructural properties play an important role for the abrasiveness of purely calcitic carbonates. Uniaxial compressive strength and splitting tensile strength were high and can additionally be, as has been shown before, particularly sensitive to sample preparation. We conclude that carefully determining the mechanical properties of carbonate rock samples in combination with common approaches to determine the abrasivity potential is key to properly predict tool wear, and required to derive information on performance in carbonate rocks. This study is the outcome of a research-oriented teaching program at Ruhr-University Bochum within the Geoscience curriculum for students with focus on Engineering Geology. Student authors are listed in alphabetical order (Aderhold to Zinke).