Lanthanoid based materials in advanced CMOS technology

Ph.DDOCTOR OF PHILOSOPH

Experimental and computational Fluid Dynamics study of separation gap effect on gas explosion mitigation for methane storage tanks

This paper presented both experimental and numerical assessments of separation gap effect on vented explosion pressure in and around the area of a tank group. A series of vented gas explosion layouts with different separation gaps between tanks were experimentally investigated. In order to qualitatively determine the relationship between the separation gap distance and explosion pressure, intensive computational Fluid Dynamics (CFD) simulations, verified with testing data, were conducted. Good agreement between CFD simulation results and experimental data was achieved. By using CFD simulation, more gas explosion cases were included to consider different gas cloud coverage scenarios. Separation gap effects on internal and external pressures at various locations were investigated

TRIM29 acts as a potential senescence suppressor with epigenetic activation in nasopharyngeal carcinoma.

Epigenetic alterations marked by DNA methylation are frequent events during the early development of nasopharyngeal carcinoma (NPC). We identified that TRIM29 is hypomethylated and overexpressed in NPC cell lines and tissues. TRIM29 silencing not only limited the growth of NPC cells in vitro and in vivo, but also induced cellular senescence, along with reactive oxygen species (ROS) accumulation. Mechanistically, we found that TRIM29 interacted with voltage-dependent anion-selective channel 1 (VDAC1) to activate mitophagy clearing up damaged mitochondria, which are the major source of ROS. In patients with NPC, high levels of TRIM29 expression are associated with an advanced clinical stage. Moreover, we detected hypomethylation of TRIM29 in patient nasopharyngeal swab DNA. Our findings indicate that TRIM29 depends on VDAC1 to induce mitophagy and prevents cellular senescence by decreasing ROS. Detection of aberrantly methylated TRIM29 in the nasopharyngeal swab DNA could be a promising strategy for the early detection of NPC

Methylation profiling of twenty promoter-CpG islands of genes which may contribute to hepatocellular carcinogenesis

BACKGROUND: Hepatocellular carcinoma (HCC) presents one of the major health threats in China today. A better understanding of the molecular genetics underlying malignant transformation of hepatocytes is critical to success in the battle against this disease. The methylation state of C5 of the cytosine in the CpG di-nucleotide that is enriched within or near the promoter region of over 50 % of the polymerase II genes has a drastic effect on transcription of these genes. Changes in the methylation profile of the promoters represent an alternative to genetic lesions as causative factors for the tumor-specific aberrant expression of the genes. METHODS: We have used the methylation specific PCR method in conjunction with DNA sequencing to assess the methylation state of the promoter CpG islands of twenty genes. Aberrant expression of these genes have been attributed to the abnormal methylation profile of the corresponding promoter CpG islands in human tumors. RESULTS: While the following sixteen genes remained the unmethylated in all tumor and normal tissues: CDH1, APAF1, hMLH1, BRCA1, hTERC, VHL, RARβ, TIMP3, DAPK1, SURVIVIN, p14(ARF), RB1, p15(INK4b), APC, RASSF1c and PTEN, varying degrees of tumor specific hypermethylation were associated with the p16(INK4a ), RASSF1a, CASP8 and CDH13 genes. For instance, the p16(INK4a )was highly methylated in HCC (17/29, 58.6%) and less significantly methylated in non-cancerous tissue (4/29. 13.79%). The RASSF1a was fully methylated in all tumor tissues (29/29, 100%), and less frequently methylated in corresponding non-cancerous tissue (24/29, 82.75%). CONCLUSIONS: Furthermore, co-existence of methylated with unmethylated DNA in some cases suggested that both genetic and epigenetic (CpG methylation) mechanisms may act in concert to inactivate the p16(INK4a )and RASSF1a in HCC. Finally, we found a significant association of cirrhosis with hypermethylation of the p16(INK4a )and hypomethylation of the CDH13 genes. For the first time, the survey was carried out on such an extent that it would not only provide new insights into the molecular mechanisms underscoring the aberrant expression of the genes in this study in HCC, but also offer essential information required for a good methylation-based diagnosis of HCC

The DNA Methylome of Human Peripheral Blood Mononuclear Cells

Analysis across the genome of patterns of DNA methylation reveals a rich landscape of allele-specific epigenetic modification and consequent effects on allele-specific gene expression

Response of buried box-shaped road tunnel against internal BLEVE and its damage mitigation

Box-shaped road tunnels have been widely used in urban areas and might face the threats of accidental Boiling Liquid Expansion Vapor Explosions (BLEVEs) due to ever-increasing liquified petroleum transportation. However, very limited study has investigated the response of popularly used buried box-shaped road tunnels (i.e., box-shaped tunnels buried in soil mass) subjected to internal BLEVEs. In this study, the dynamic response of a typical two-cell box-shaped road tunnel buried in soil subjected to internal BLEVEs induced by the burst of a 20 m3 liquified petroleum gas (LPG) tank is numerically investigated by using LS-DYNA. The results show that the tunnel experiences severe damage under BLEVEs with liquid-filling ratios equal to or more than 65% while it suffers only minor damage with the load carrying capacity not compromised under BLEVE with 50% filled-liquid. The effects of BLEVE occurring locations on the tunnel response are then investigated. It is found that the tunnel subjected to the BLEVE occurring on the lane near middle wall experiences more significant response in general than that away from the middle wall. In addition, to mitigate the tunnel damage under BLEVEs, strengthening soil mass around the tunnel using soil–cement mixture is considered and its performance is examined. An empirical formula is also proposed for the design of using soil–cement mixture to enhance the buried box-shaped tunnel against internal BLEVEs

A state-of-the-art review of road tunnel subjected to blast loads

Road tunnels are critical components in road transportation networks. In their service life they may subject to explosion loads from terrorist bombing attacks, engineering blasting for construction and accidental explosions from transported flammable goods. These extreme loading conditions might not only lead to catastrophic damages to tunnel structures, severe casualties and economic losses, but also have immeasurable social impacts. Therefore, it is imperative for engineers, researchers and policy regulators to understand the performance of road tunnels under explosion loads towards a reliable blast-resistant design of tunnel structures. This paper presents a state-of-the-art review of dynamic response, damage assessment and damage mitigation of tunnels under blast loads. The common road tunnels, various explosion scenarios, and the corresponding blast wave characteristics are reviewed first. Then the dynamic response and damage characteristics of tunnel structures under blast loads including the analysis methods of tunnel response, types of tunnel response and key factors influencing tunnel response are reviewed and discussed. The assessment criteria of tunnel damage and the damage mitigation measures for tunnels against blast loads are also reviewed. Finally, concluding remarks and several key research areas for future work are presented

Numerical prediction of ground vibrations induced by LPG boiling liquid expansion vapour explosion (BLEVE) inside a road tunnel

Accidental boiling liquid expansion vapour explosions (BLEVEs) caused by the bursting of liquified petroleum gas (LPG) tank inside a tunnel can induce vibrations of its surrounding geological media and threaten the stability of adjacent tunnels and structures. Therefore, it is essential to understand the characteristics of vibrations induced by LPG BLEVEs inside the tunnel for the safety design of its adjacent structures. Owing to the difficulty in effectively predicting the LPG BLEVE loads, the current practice usually employs equivalent methods, e.g., the TNT-equivalency method, in LPG BLEVE load predictions for structural response analysis, which may lead to inaccurate response predictions. This study compares ground vibrations induced by a BLEVE inside an arched road tunnel with those induced by its equivalent TNT explosion via high-fidelity numerical simulations. The results demonstrate that the frequency of BLEVE-induced vibrations is lower than that induced by the TNT explosion at the same scaled distance. The intensity of LPG BLEVE-induced vibrations at relatively small-scaled distances is lower than that of TNT explosion-induced vibrations at the same scaled distance, but becomes higher after a certain scaled distance because of the relatively low attenuation rate. In addition, parametric analysis is conducted to evaluate the effects of various factors on the characteristics of LPG BLEVE-induced ground vibrations. It is found that the surrounding rock type, the rock porosity, and the cover depth of the tunnel have more significant influences than the concrete grade of the tunnel lining. The recommendation for the tunnel design is also given based on the intensity and frequency characteristics of BLEVE-induced vibrations

Performance of road tunnel subjected to BLEVE occurring inside adjacent tunnel

Twin tunnel is a common and popular type of road tunnel. The safety of twin tunnel (i.e. with left and right branches) subjected to Boiling Liquid Expansion Vapour Explosions (BLEVEs) is important but less investigated in open literature. The present study numerically investigates the dynamic response of right branch of a twin-arched-tunnel subjected to a BLEVE with a 20 m3 Liquified Petroleum Gas tanker occurring inside the left branch by using LS-DYNA. The BLEVE loads and the model of tunnel lining and rock mass subjected to blast loading have been calibrated by the authors in earlier studies. Based on the calibrated numerical model, the response of right branch of the twin-tunnel due to stress waves caused by the BLEVE occurring inside the left branch is first compared with that of the equivalent TNT explosion. It is found that the lining damage of the right branch under BLEVE-induced stress waves can be underestimated by using the TNT equivalence method. In addition, the influences of tunnel cover depths, twin-tunnel separation distances, rock types around tunnels, and concrete strengths of tunnel lining on the dynamic response of the right branch of twin-tunnel against BLEVE-induced stress waves are investigated. Compared to enhancing the concrete strength, increasing the twin-tunnel separation distance is more effective to reduce the damage of the tunnel surrounded by the rock mass with weak mechanical properties under BLEVE-induced stress waves. In addition, empirical formulae for prediction of the PPV and tensile stress on adjacent tunnel surface induced by BLEVE are proposed, which can be used for the determination of the safe separation distance between the twin tunnels against accidental BLEVE loads

Microscopic simulation of symmetric boost fission with antisymmetrized molecular dynamics

We present our first results for a microscopic simulation of symmetric boost fission in terms of the antisymmetrized molecular dynamics (AMD) model. In AMD model, ground states of fissioning nuclei were prepared by a frictional cooling method and symmetrical boost momenta were given to nucleons inside to split the ground-state into fission fragments. After the simulation, we calculated the mass numbers and total kinetic energy (TKE) of the fission fragments. We also calculated orbital angular momenta of each fragment and identified them as spins, their mutual orientation and their orientation with respect to the linear momenta which defined the fission axis. Moreover, we found spin distribution of fission fragments was similar to the one given by the Fermi-gas model if spin cut-off parameter was adjusted. Finally, several ternary fission events were observed, emitting Tritium or 4He from the neck region, and average energy and angles of these ternary particles with respect to the fission axis were found to be in accord with experimental data