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The effect of porosity on the effective thermal conductivities calculation for continuous SiC fiber reinforced SiC matrix composites (SiC f /SiC) was studied in this work by finite element modeling. A three-dimensional representative volume element (RVE) containing detailed geometric features (fibers, matrix, fiber coatings and pores) was generated to rebuild the microstructure of SiC f /SiC and used to numerically calculate the effective transversal and longitudinal thermal conductivities of SiC f /SiC. Markworth model and parallel model were chosen as theoretical models to calculate the transversal and longitudinal thermal conductivities respectively. The numerical results obtained by RVE models were validated by comparison with the theoretical and experimental results. The results highlight the existing theoretical models cannot well predict the transversal thermal conductivity of SiC f /SiC with the existence of pores. In the analysis of the effect of porosity, real pore structure in SiC f /SiC was investigated to revel the relationship between porosity and the effective thermal conductivities. In the case of longitudinal thermal conductivity, the parallel model plus the linear term of porosity can still be used to predict the longitudinal thermal conductivity. As for the transversal thermal conductivity, a more proper Markworth model for SiC f /SiC transversal thermal conductivity calculation calibrated by incorporating porosity is proposed to efficiently calculate the transversal thermal conductivity at the end of this paper. [ABSTRACT FROM AUTHOR]

This work focuses on the anisotropic deformation and fracture mechanisms of a typical physical vapor deposited TiN/ZrN multilayer, employing novel nanoindentation and micropillar compression techniques. The results highlight a stronger nanoindentation response of the multilayer when loaded perpendicular (90°) to the layer orientation, and the deformation was mainly controlled by the plasticity of ZrN layers. In comparison, at parallel (0°) orientation, the kink banding and the induced cracking may weaken the constraint beneath the indenter, thus leading to degraded hardness. By considering the anisotropic deformation mechanisms, nanoindentation finite element modeling was further performed to give reliable predictions on the strength at the inclined orientation. The modeling results suggest a dominant deformation mechanism that occurred mainly in the ZrN layers, with minor contribution from the stiff TiN layers. As a result, a minimized hardness was predicted at 45° loading direction with respect to layer orientation. Finally, the micropillar compressions show a brittle nature of both 90° and 0° oriented micropillars, and a higher fracture strain was obtained at 90°, due to the observed crack termination mechanism at this orientation. [ABSTRACT FROM AUTHOR]

Probiotic products containing living microorganisms are gaining popularity, increasing the importance of their taxonomic status. A Bacillus -like isolate, 70 b, cultured from a probiotic feed additive, was ambiguity in taxonomic assignment and could be a novel member of Bacillus cereus group. The results of colony and cellular morphology, physiological and biochemical analysis mainly including growth performance, carbon source utilization, and rMLST and MLST were not conclusive. Fatty acids profile and molecular genetic analysis especially ANI, DDH, and core genome SNPs-based phylogenetic tree confirmed 70 b as one novel species of B. cereus group and proposed as Bacillus pfraonensis sp. nov. Comparative genomic analysis revealed the genetic differences between 70 b and other species of B. cereus group. Pseudomycoicidin was identified in 70 b. 70 b was active against multidrug-resistant pathogenic strains MRSA. The findings support 70 b is a novel species with low cytotoxicity and antimicrobial activity, and provides a better understanding of its unique characteristics and probiotic potential, and exploration of bioactive potential. [ABSTRACT FROM AUTHOR]

Abstract: A facile, low-cost and effective electrochemiluminescence (ECL) sensor based on Ru(bpy)3 2+ immobilized by graphene film without any auxiliary medium had been developed for the first time. The graphene film was directly formed on a glassy carbon electrode surface via an in situ wet-chemical reduction of graphene oxide (GO). It had fast electron-transfer rate and excellent stability for immobilizing Ru(bpy)3 2+ via π–π interaction. The cyclic voltammetry result indicated that the ECL sensor had high electrochemical activity. Moreover, ECL behaviors of this sensor were investigated in details using tripropylamine as the model. And the experimental results indicated that the sensor had excellent ECL efficiency and long-term stability. Furthermore, the sensor was successfully applied to detect oxalate in urine samples with high selectivity, sensitivity and reliability, which suggested the ECL sensor could be applicable for real sample analysis. [Copyright &y& Elsevier]

• Evaluation of the potential biological risk of commercial probiotic products. • All 48 Bacillus spp. isolates from products were resistant to lincomycin. • The genotyping showed ces existed in B. cereus 34b with the specific sequence type. Spore-forming probiotic Bacillus spp. have received extensively increasing scientific and commercial interest, but raised the concerns in the potential risks and pathogenesis. In this study, 50 commercial probiotic products were collected from all over the country and Bacillus spp. isolated from products were evaluated for the safety on the aspects of hemolytic activity, contamination profiles, toxin genes, cytotoxicity, antimicrobial resistance, and genotyping. 34 probiotic products (68%) exhibited hemolysis, including 19 human probiotics, 9 animal probiotics, and 6 plant probiotics. 28 products (56%) contained other bacteria not labeled in the ingredients. 48 strains in Bacillus spp. including 17 B. subtilis group isolates, 28 B. cereus , and 3 other Bacillus spp. were isolated from human, food animal, and plant probiotic products. Detection rates of enterotoxin genes, nheABC and hblCDA , and cytotoxin cytK2 in 48 Bacillus spp. isolates were 58%, 31%, and 46%, respectively. Also, one isolate B. cereus 34b from an animal probiotic product was positive for ces, encoding cereulide. 28 of 48 Bacillus spp. isolates were cytotoxic. 19 of 28 B. cereus isolates maintained to exhibit hemolysis after heat treatment. All 48 Bacillus spp. isolates exhibited resistance to lincomycin, and 5 were resistant to tetracycline. The genotyping of commercial probiotic Bacillus spp. reported in this study showed that ces existed in B. cereus 34b with the specific sequence type (ST1066). These findings support the hypothesis that probiotic products were frequently contaminated and that some commercial probiotics consisted of Bacillus spp. may possess toxicity and antimicrobial resistance genes. Thus, the further efforts are needed in regarding the surveillance of virulence factors, toxins, and antibiotic resistance determinants in probiotic Bacillus spp. [ABSTRACT FROM AUTHOR]

Abstract: Biosensor based on DNA hybridization holds great potential to get higher sensitivity as the optimal DNA hybridization efficiency can be achieved by controlling the distribution and orientation of probe strands on the transducer surface. In this work, an innovative strategy is reported to tap the sensitivity potential of current electrochemiluminescence (ECL) biosensing system by dispersedly anchoring the DNA beacons on the gold nanoparticles (GNPs) array which was electrodeposited on the glassy carbon electrode surface, rather than simply sprawling the coil-like strands onto planar gold surface. The strategy was developed by designing a “signal-on” ECL biosensing switch fabricated on the GNPs nanopatterned electrode surface for enhanced ultra-sensitivity detection of Hg2+. A 57-mer hairpin-DNA labeled with ferrocene as ECL quencher and a 13-mer DNA labeled with Ru(bpy)3 2+ as reporter were hybridized to construct the signal generator in off-state. A 31-mer thymine (T)-rich capture-DNA was introduced to form T–T mismatches with the loop sequence of the hairpin-DNA in the presence of Hg2+ and induce the stem-loop open, meanwhile the ECL “signal-on” was triggered. The peak sensitivity with the lowest detection limit of 0.1nM was achieved with the optimal GNPs number density while exorbitant GNPs deposition resulted in sensitivity deterioration for the biosensor. We expect the present strategy could lead the renovation of the existing probe-immobilized ECL genosensor design to get an even higher sensitivity in ultralow level of target detection such as the identification of genetic diseases and disorders in basic research and clinical application. [Copyright &y& Elsevier]

Characterization of jointed rock masses and evaluation of their mechanical properties are challenging tasks in rock engineering. This paper presents an experimental investigation of the response characteristics of drilling energy to the discontinuity of rock mass using a drilling method. The linear relationship between the drilling energy and discontinuity frequency is revealed, which only depends on the rock type, and is independent of calculation units. A new empirical method for determining the rock quality designation (RQD) versus the variation of drilling energy is proposed based on the discontinuity frequency. Comparison between the prediction and in situ investigation results demonstrates that the RQD can be estimated from this empirical method. The E m / E r (modulus ratio) and σ cm / σ c (strength ratio) versus RQD relations are modified for the determination of rock mass strength and deformation modulus in order to consider the continuous variation of E m / E r and σ cm / σ c with the model parameter η , which is related to the drilling energy and modulus of elasticity of intact rock and the variation of drilling energy for rock mass. The results show that the modified E m / E r (σ cm / σ c) versus RQD relations can give proper values compared with the field test results as well as compared with the various proposed relations from RMR, Q and GSI. The modified relations can provide a practical, fast and easy-to-use method for the estimated rock mass strength and deformation modulus, but they are only a first approximation. [ABSTRACT FROM AUTHOR]

Abstract Damage evolution salt rock under fatigue loading at different stress amplitudes, loading frequencies, and loading rates was investigated in the laboratory. Under conditions of fatigue loading, damage of salt rock can be divided into three stages: initial damage, constant-velocity damage, and accelerated damage. The results of the fatigue tests indicate that higher stress amplitudes, higher loading frequency, and higher loading rate lead to decreased fatigue lifetime. Based on the experiments, a model for the prediction of fatigue life versus stresses, frequency, and loading rate was proposed. Comparison between the model and the experimental results shows that fatigue lifetime can be estimated and predicted from this model. Based on the three-stage damage trend, the cumulative fatigue damage is numerically predicted by considering a double term power damage model. The proposed model captures the characteristics of damage evolution in salt rock under fatigue loading, with the parameters of the model obtained from experimental data. [ABSTRACT FROM AUTHOR]

The application of plasmonic-enhanced Raman imaging of cancer cells and drug delivery is gaining momentum. Here, we propose a new theranostic strategy based on an efficient plasmonic-tunable Raman/Fourier transform infrared (FTIR) spectroscopy imaging, to simultaneously evaluate the anticancer drug scattering cellular imaging and the Raman scattering molecular vibration signals in living cells. This technique allows to monitoring the drug release throughout the cell cycle and in vivo biodistribution and biocompatibility with low dose drug therapy (200 μg/mL) and low toxicity effect. This system can directly track in real-time the delivery and release of an anticancer drug (mitoxantrone, MTX) from gold nanostars in single living cells and in mice (healthy and lung cancer mice models), revealing a strong accumulation in the heart of healthy mice 5 min after administration and infiltration in the tumor site of lung cancer mice 5 h after systemic injection. This in vivo SERS detection method holds a great promise for application in image-guided cancer chemotherapy or as a nonspecific anti-inflammatory therapy for patients with cardiovascular diseases or chronic heart failure. [ABSTRACT FROM AUTHOR]

The dynamic shear modulus and damping ratio of rock are the main indicators that reflect the dynamic characteristics of rock masses under seismic and dynamic action. The multistage cyclic triaxial compression test is performed on granite and red sandstone under different confining pressures with two stress paths. To reasonably describe the dynamic characteristics of rock, a modified Hardin hyperbolic model is proposed to describe the backbone curve. The relationship between the dynamic shear modulus, damping ratio and cyclic shear strain is analysed under different confining pressure conditions with variable and same amplitude. Furthermore, an empirical formula is established for estimating the dynamic shear modulus and damping ratio. The obtained results show that with increasing shear strain, the damping ratio of red sandstone and granite decreases and then increases under the condition of variable amplitude. When the shear strain is constant, the damping ratio of red sandstone and granite is less affected by the confining pressure. Under the same amplitude conditions, as the shear strain increases, the dynamic shear modulus under different confining pressures shows an increasing trend. The two established empirical formulas can be used to predict the dynamic shear modulus and damping ratio under multistage cyclic loading. This has important reference significance for studying the dynamic characteristics of rock. • The multistage cyclic triaxial compression test is carried out on rock under different confining pressures with two stress paths. • A modified Hardin hyperbolic model is proposed to describe the backbone curve. • The relationship between dynamic shear modulus, damping ratio and cyclic shear strain is analysed. • An empirical formula for estimating dynamic shear modulus and damping ratio was established. [ABSTRACT FROM AUTHOR]

Prediction of the rockburst proneness of rock in the field is an important problem in rockburst research. In this paper, the analytical relationship between the strength ratio (the ratio of the unconfined compressive strength to the ultimate cutting strength) of rock and the friction angle is presented. A new perspective is presented for rockburst proneness considering the strength ratio and friction characteristics of rock materials. The relationships between the residual elastic energy index (the difference between the peak elastic energy density and failure energy density of the postpeak stage) and the strength ratio and friction coefficient are established to determine the rockburst proneness of rock materials. The linear relationship between the strength ratio and residual elastic energy index is obtained. A novel method is proposed to easily predict the rockburst proneness of rock materials in the field. The rockburst proneness values predicted from the proposed method for six types of rock are consistent with those obtained in the laboratory. This result shows the correlation between the rockburst proneness and friction characteristics of rock materials. The variation in the contact friction angle is similar to the variation in the residual elastic energy index along the borehole. This method is successfully applied to predict the rockburst proneness of the surrounding rock of four tunnel sections. [Display omitted] • The analytical relationship between the ultimate cutting strength and friction angle of rock is presented. • The relationships between the rockburst proneness and friction coefficient of rock materials are established. • A novel method is proposed to easily predict the rockburst proneness of rock materials using drilling data. [ABSTRACT FROM AUTHOR]

Brittleness is one of the most important mechanical properties of rock, especially in designing an efficient fracturing method for deep production of raw petroleum and shale gas. In this study, triaxial compression tests for sedimentary, igneous and metamorphic rocks are carried out to investigate the relationship between brittleness and yield under different confining pressures. To research the yield property in the deformation and failure process of rock, the referenced brittleness index BIM is adopted to analyze the brittle evolution of rock based on the energy dissipation characteristics. The experimental results show that the BIM following increasing axial strain presents N-shaped variation in the deformation process. The two inflection points are exactly marked as the compaction point and yield point in the rock deformation process. Accordingly, the scientific linear correlation between BIM and yield and peak strength is investigated to obtain the response of brittleness to the corresponding stress values increasing under different confining pressures. Based on this correlation, a new method for determining the yield strength by considering the energy dissipation is proposed. In comparison with the fitting correlation, the estimated BIM max values from other rock strengths are close to the correlation between yield and brittleness (error range within 10%). Accordingly, the proposed method may provide a reliable estimation of rock yield strength. • The relationship between brittleness and energy characteristic of sedimentary, igneous and metamorphic rock is investigated. • The brittle evolution of rock based on the energy dissipation characteristic is analyzed. • The BIM of rock provide a new method to determine the yield strength. [ABSTRACT FROM AUTHOR]

Field drilling can be a continuous, fast, and reliable technology to predict the cohesion, internal friction angle, and unconfined compressive strength (UCS) of rock in petroleum engineering. Herein, a theoretical model is established in an impregnated diamond bit considering some effective parameters including friction parameter, crushed zone, and bit geometry parameter. A novel method is proposed to determine field strength parameters including the cohesion, internal friction angle, and UCS of four types of rock using drilling logging data. Many drilling experiments in the field are conducted using a drilling process monitoring apparatus to obtain drilling logging data (thrust force, torque, penetration rate, and rotation speed). Experimental results on weak, medium-strong, and strong rock show that drilling with an impregnated diamond core bit includes two fully dependent and simultaneous processes: rock cutting and frictional contact, the dominant role of which is dependent on the cutting point. The cohesion, internal friction angle, and UCS estimated from the proposed method for the four types of rocks are close to those from standard laboratory tests. This practical method can provide practical, fast, and reliable estimation for field strength parameters of rock and should be highly beneficial to field applications in rock engineering. • A theoretical model is established in an impregnated diamond bit considering friction, crushed zone, and bit geometry. • A method was proposed to determine strength parameters including the cohesion, internal friction angle and UCS of rock. • This practical method can provide practical, fast, and reliable estimation for field strength parameters of rock. [ABSTRACT FROM AUTHOR]

Accurate, fast, and reliable estimation of field rock strength is significant for the assessment of rock mass strength. This paper presents a novel method to continuously estimate the field strength parameters of rock by incorporating a deep convolutional neural network (DCNN) technique into the drilling process. A DCNN model is established based on the stochastic pooling method and softmax loss. The proposed CNN model framework includes : (1) collecting drilling performance parameters of intact rock, (2) establishing a strength parameter database via standard laboratory tests , (3) training the proposed CNN model using images created from the dataset of drilling performance parameters and rock strength parameters (unconfined compressive strength (UCS), cohesion, and internal friction angle), and (4) performing a new estimation to evaluate the reliability of the trained CNN model. The experimental results show that the predicted rock strength parameters are within the accepted error range of 10% compared to the results from the conventional standard test. The proposed CNN shows superior performance for UCS estimation of various rock types and achieves higher accuracy than the Mohr–Coulomb criterion. In particular, the proposed method can overcome major limitations of analytical models based on the force limit and energy equilibrium method. This method enables continuous and reliable field measurements of rock strength parameters at a speed several orders of magnitude faster than the standard test. This continuous and practical technique has been applied in an engineering problem in the Hanjiang-to-Weihe River Project of China and shows potential for field applications in rock engineering. [ABSTRACT FROM AUTHOR]