Crack Propagation Characteristics of Coal Samples Utilizing High-Voltage Electrical Pulses.

The technique of high-voltage electrical pulses (HVEP) is a new method to enhance the permeability of coal seams and improve the efficiency of coalbed methane (CBM) exploitation. This paper is aimed at investigating the crack propagation characteristics of samples of different strengths, proposing the improved procedure of HVEP in field application, and proving that the electrohydraulic effect has a wide use in field application of CBM extraction. In this paper, an experimental system utilizing HVEP in water condition is established, coal samples with different strengths are crushed, and the extended processes of cracks are analyzed. According to the research results, the electrohydraulic effect has a good breakage on the coal; the number of main cracks is 2-3 and the length of the main cracks is about 30 cm in the vertical direction of the hard samples; and the formation of cracks is relevant to the discharge voltage, discharge times, and mechanical parameters of the samples. The results of scanning electron microscopy (SEM) demonstrate that the cracks and pore connectivity of the coal samples are improved obviously, and the permeability results show that the permeability of crushed coal samples is 20% greater than that of the raw coal sample. Meanwhile, the generation process of cracks can be divided into four periods: namely, fatigue damage accumulation, slow development, rapid development, and failure; the rapid development stage is the optimal phase in field application. Moreover, the shock wave produced by HVEP via electrohydraulic effect can crush the samples mainly; furthermore, the energy produced by bubble rupture also has a great influence on the formation of cracks. This study can provide a foundation for the HVEP to improve CBM exploitation.

A methylated oligonucleotide inhibits IGF2 expression and enhances survival in a model of hepatocellular carcinoma.

IGF-II is a mitogenic peptide that has been implicated in hepatocellular oncogenesis. Since the silencing of gene expression is frequently associated with cytosine methylation at cytosine-guanine (CpG) dinucleotides, we designed a methylated oligonucleotide (MON1) complementary to a region encompassing IGF2 promoter P4 in an attempt to induce DNA methylation at that locus and diminish IGF2 mRNA levels. MON1 specifically inhibited IGF2 mRNA accumulation in vitro, whereas an oligonucleotide (ON1) with the same sequence but with nonmethylated cytosines had no effect on IGF2 mRNA abundance. MON1 treatment led to the specific induction of de novo DNA methylation in the region of IGF2 promoter hP4. Cells from a human hepatocellular carcinoma (HCC) cell line, Hep 3B, were implanted into the livers of nude mice, resulting in the growth of large tumors. Animals treated with MON1 had markedly prolonged survival as compared with those animals treated with saline or a truncated methylated oligonucleotide that did not alter IGF2 mRNA levels in vitro. This study demonstrates that a methylated sense oligonucleotide can be used to induce epigenetic changes in the IGF2 gene and that inhibition of IGF2 mRNA accumulation may lead to enhanced survival in a model of HCC.

A novel orthotopic tumor model to study growth factors and oncogenes in hepatocarcinogenesis.

An orthotopic xenograft tumor model of hepatocellular carcinoma was created by injection of Hep 3B cells directly into the liver parenchyma of nude mice. Tumors were localized primarily in the injected lobe of the liver, beginning from the third week after tumor cell implantation. Thereafter, tumors grew rapidly, and animals usually died from hepatocellular carcinoma within 2 months. Insulin-like growth factor II, an embryonic growth factor and mitogen, is overexpressed in these tumors at both mRNA and protein levels. Oncogenes, such as c-myc, c-fos, and c-jun, are also up-regulated in this model. alpha-Fetal protein can be detected shortly after implantation and correlates with tumor growth, and measurement of serum alpha-fetal protein serves as an early biomarker to monitor the effect of antitumor therapy. Using this model, we have shown that inhibition of insulin-like growth factor II expression by a short methylated oligonucleotide prolongs survival. This in situ tumor model thus provides a fast, reliable, and reproducible means to study the therapeutic effect of inhibitors of growth factors and oncogenes in liver cancer.