Investigating the micromechanics of soil reinforced with recycled tyres using the Discrete Element Method

This PhD program aims to provide insights into the behaviour of tyre reinforced sand, and to further the understanding of the reinforcement mechanisms. The discrete element method (DEM) using the software PFC3D version 5.0, is used to investigate the micro- mechanics of tyre-reinforced sand based on pull-out tests. A series of numerical direct shear tests have been performed. A full investigation of the individual particle shape descriptors (e.g., elongation index, flatness index, convexity and roundness) is presented, highlighting their influence on the macroscopic behaviour (e.g., failure mode and volumetric response). MorphologI G3 at UCL helps to obtain the quantitative particle shape information on Fujian Standard Sand. The sand information is incorporated in the results of particle shape studies to propose a representative particle shape for Fujian Standard Sand to model direct shear tests, leading to the calibration of pure sand. Then, a new three-dimensional DEM model for tyre rubber is developed based on uniaxial tensile tests. The model can capture the key volume change characteristics of tyres with a Poisson’s ratio of 0.5 independent of the tyre dimensions. Tyre rubber is modelled using body-centred-cubic (BCC) packing with linear inter-particle bonds. Next, a systematic parametric study is presented, which includes the effects of different packings, particle overlapping, particle radii and sample aspect ratios on the mechanical response of the tyre model using Young’s modulus and Poisson’s ratio. The DEM parameters are set to match corresponding experimental Young’s modulus data, completing the calibration of tyre. Lastly, the tyre – sand interface coefficient friction is calibrated from numerical and laboratory interface direct shear tests. All DEM parameters are used in tyre reinforced sand pull-out tests simulations. Micro analyses (such as particle displacement, velocity, contact force) presented in simulations show that the DEM tyre-sand pullout test simulation can capture the progress failure of tyre rubber during the pull-out process, and the intrusive capabilities of the discrete element method are used to gain insight into the reinforcement mechanisms between tyre and sand

Measurement of Cardiac Mechanical Function in Isolated Ventricular Myocytes from Rats and Mice by Computerized Video-Based Imaging

Isolated adult cardiac ventricular myocytes have been a useful model for cardiovascular research for more than 20 years. With the recent advances in cellular physiology and transgenic techniques, direct measurement of isolated ventricular myocyte mechanics is becoming an increasingly important technique in cardiac physiology that provides fundamental information on excitation-contraction coupling of the heart, either in drug intervention or pathological states. The goal of this article is to describe the isolation of ventricular myocytes from both rats and mice, and the use of real-time beat-to-beat simultaneous recording of both myocyte contraction and intracellular Ca(2+) transient

The random lattice as a regularization scheme

A semi-analytic method to compute the first coefficients of the renormalization group functions on a random lattice is introduced. It is used to show that the two-dimensional $O(N)$ non-linear $\sigma$-model regularized on a random lattice has the correct continuum limit. A degree $\kappa$ of ``randomness'' in the lattice is introduced and an estimate of the ratio $\Lambda_{random}/\Lambda_{regular}$ for two rather opposite values of $\kappa$ in the $\sigma$-model is also given. This ratio turns out to depend on $\kappa$.Comment: PostScript file. 22 pages. Revised and enlarged versio

Influence of local strain heterogeneity on high piezoelectricity in 0.5Ba(Zr0.2Ti0.8)O3−0.5(Ba0.7Ca0.3)TiO3 ceramics

Dielectric and mechanical spectroscopies have been used to investigate ferroelectric transitions and twin wall dynamics in the lead-free ceramic 0.5Ba(Zr0.2Ti0.8)O3−0.5(Ba0.7Ca0.3)TiO3 (abbreviated as BZT-50BCT), which is known to have a high piezoelectric coefficient (d33>545pC/N). Results from dynamical mechanical analysis in the frequency range 0.2–20 Hz and resonant ultrasound spectroscopy in the frequency range ∼0.1–1.2MHz confirm the existence of three phase transitions with falling temperature, at ∼360K (cubic-tetragonal), ∼304K (tetragonal-orthorhombic), and ∼273K (orthorhombic-rhombohedral). In comparison with BaTiO3, however, the transitions are marked by rounded rather than sharp minima in the shear modulus. The pattern of acoustic loss is also quite different from that shown by BaTiO3 in having a broad interval of high loss at low temperatures, consistent with a spectrum of relaxation times for interactions of ferroelastic twin walls. Differences in the dielectric properties also suggest more relaxor like characteristics for BZT-50BCT. It is proposed that the overall pattern of behavior is significantly influenced by strain heterogeneity at a local length scale in the perovskite structure due to the substitution of cations with different ionic radii. The existence of this strain heterogeneity and its influence on the elastic behavior near the transition points could be contributory factors to the development of adaptive nanoscale microstructures and enhanced piezoelectric properties

dCas9-based epigenome editing suggests acquisition of histone methylation is not sufficient for target gene repression.

Distinct epigenomic profiles of histone marks have been associated with gene expression, but questions regarding the causal relationship remain. Here we investigated the activity of a broad collection of genomically targeted epigenetic regulators that could write epigenetic marks associated with a repressed chromatin state (G9A, SUV39H1, Krüppel-associated box (KRAB), DNMT3A as well as the first targetable versions of Ezh2 and Friend of GATA-1 (FOG1)). dCas9 fusions produced target gene repression over a range of 0- to 10-fold that varied by locus and cell type. dCpf1 fusions were unable to repress gene expression. The most persistent gene repression required the action of several effector domains; however, KRAB-dCas9 did not contribute to persistence in contrast to previous reports. A 'direct tethering' strategy attaching the Ezh2 methyltransferase enzyme to dCas9, as well as a 'recruitment' strategy attaching the N-terminal 45 residues of FOG1 to dCas9 to recruit the endogenous nucleosome remodeling and deacetylase complex, were both successful in targeted deposition of H3K27me3. Surprisingly, however, repression was not correlated with deposition of either H3K9me3 or H3K27me3. Our results suggest that so-called repressive histone modifications are not sufficient for gene repression. The easily programmable dCas9 toolkit allowed precise control of epigenetic information and dissection of the relationship between the epigenome and gene regulation

Brainstem metastases treated with Gamma Knife stereotactic radiosurgery: the Indiana University Health experience

Brainstem metastases offer a unique challenge in cancer treatment, yet stereotactic radiosurgery (SRS) has proven to be an effective modality in treating these tumors. This report discusses the clinical outcomes of patients with brainstem metastases treated at Indiana University with Gamma Knife (GK) radiosurgery from 2008 to 2016. 19 brainstem metastases from 14 patients who had follow-up brain imaging were identified. Median tumor volume was 0.04 cc (range: 0.01-2.0 cc). Median prescribed dose was 17.5 Gy to the 50% isodose line (range: 14-22 Gy). Median survival after GK SRS treatment to brainstem lesion was 17.2 months (range: 2.8-45.6 months). The experience at Indiana University confirms the safety and efficacy of range of GK SRS prescription doses (14-22 Gy) to brainstem metastases

Clinical efficacy of semiconductor laser-assisted minocycline in moderate-to-severe chronic periodontitis patients with type 2 diabetes mellitus

Purpose: To study the clinical efficacy of semiconductor laser-assisted minocycline in the treatment of moderate-to-severe chronic periodontitis (CP) in type 2 diabetes mellitus (T2DM) patients.Methods: A total of 109 cases of CP combined with T2DM and obesity admitted to The First Affiliated Hospital, Medical School of Xi'an Jiaotong University, Xi’an, China, from November 2016 to November 2017 were included in the study. Among them, 54 patients in the study group were treated with semiconductor laser-assisted minocycline, while 55 patients in the control group were treated with minocyclin injection. Periodontitis, blood glucose and blood lipid levels were compared between the two groups before and after treatment.Results: Post-treatment (12 weeks), bleeding on probing, gingival index, periodontal probing depth (PD), plaque index (PLI), clinical attachment loss (CAL), and sulcus bleeding index (SBI) in the two groups of patients were significantly improved (p < 0.05). The levels of PD, BOP, PLI, and CAL in the positive SBI group (4.06 ± 0.25, 20.37 %, 0.50 ± 0.28, 3.42 ± 0.27, and 1.43 ± 0.26, respectively) were significantly lower than the corresponding levels in the control group (p < 0.05. Fasting plasma glucose (FPG) and HbA1c for the two groups were significantly improved, when compared with values prior to treatment (p < 0.05), but there was no significant difference in FPG level between the two groups. Significantly lower HbA1c levels were found in the treatment group than in the control group (t = 4.2360, p = 0.0001). Post-treatment, triglyceride (TG), total cholesterol (TC) and body mass index (BMI) did not improve significantly in the two groups, nor were there significant differences in these parameters before and after treatment (p > 0.05).Conclusion: Semiconductor laser-assisted minocycline is effective in treating moderate and severe chronic periodontitis patients with type 2 diabetes, and can improve blood glucose. However, its effect on body weight needs further studies.Keywords: Semiconductor laser, Minocycline, Chronic periodontitis, Type 2 diabetes, Obesit

Possible Experimental Test of Continuous Medium Model for Fractal Media

We use the fractional integrals to describe fractal media. We consider the fractal media as special ("fractional") continuous media. We discuss the possible experimental testing of the continuous medium model for fractal media that is suggested in Phys. Lett. A. 336 (2005) 167-174. This test is connected with measure of period of the Maxwell pendulum with fractal medium cylinder.Comment: 9 page