Instability Mechanism of Cavity-Bearing Formation under Tunnel Excavation Disturbance

Urban subway construction inevitably causes disturbances to the rock strata. It can even cause ground collapse accidents when construction encounters a bad geological body in the stratum. To verify the influence of cavities on surface settlement and the mechanism of formation instability, the instability mechanism of cavity-bearing strata under tunnel excavation disturbance was herein studied by tests using self-designed indoor models and numerical simulations. This study was based on the concrete project case of Qingdao Metro. Two groups of experiments (with and without cavities) were designed to simulate the four-step excavation by staged unloading of an airbag. The results show that the settlement value in the cavity state was about twice as much as that in the nonvoid state at the same stage. Besides the first step of excavation, in the numerical simulation, the settlement value of the same stage is about 1.3 times that of the model test. Simulating the deformation process of the surrounding rock in model tests shows that, in the excavation of the tunnel, the collapse surface of the tunnel arch roof will be connected with the sliding surface of the formation cavity. The cavity will gradually change from a regular circle to an ellipse or may even close, resulting in a sudden increase in land subsidence or even ground collapse. This indicates that disturbance during tunnel excavation would cause greater instability in a stratum when bad geological bodies, such as cavities, exist in the stratum

Eukaryotic DNA Mismatch Repair In Vitro

Mismatch repair corrects biosynthetic errors generated during DNA replication. Mismatch repair deficiency causes a mutator phenotype and directly underlies hereditary nonpolyposis colorectal cancer and some sporadic cancers. Because of remarkably high conservation of the mismatch repair machinery between the budding yeast (Saccharomyces cerevisiae) and humans, the study of mismatch repair in yeast has provided tremendous insights into the mechanisms of this repair pathway in humans. Here we describe a set of practical protocols for how to prepare the yeast and HeLa cell-free nuclear extracts and site-specific DNA mismatch substrates, and how to carry out the in vitro mismatch repair assay. We validated the yeast cell-free system by the mismatch repair deficient strain (Δmsh2) and the complementation assay with purified yeast MutSα

Transcriptional response of Musca domestica larvae to bacterial infection.

The house fly Musca domestica, a cosmopolitan dipteran insect, is a significant vector for human and animal bacterial pathogens, but little is known about its immune response to these pathogens. To address this issue, we inoculated the larvae with a mixture of Escherichia coli and Staphylococcus aureus and profiled the transcriptome 6, 24, and 48 h thereafter. Many genes known to controlling innate immunity in insects were induced following infection, including genes encoding pattern recognition proteins (PGRPs), various components of the Toll and IMD signaling pathways and of the proPO-activating and redox systems, and multiple antimicrobial peptides. Interestingly, we also uncovered a large set of novel immune response genes including two broad-spectrum antimicrobial peptides (muscin and domesticin), which might have evolved to adapt to house-fly's unique ecological environments. Finally, genes mediating oxidative phosphorylation were repressed at 48 h post-infection, suggesting disruption of energy homeostasis and mitochondrial function at the late stages of infection. Collectively, our data reveal dynamic changes in gene expression following bacterial infection in the house fly, paving the way for future in-depth analysis of M. domestica's immune system

Applications of graphene transistor optimized fabrication process in monolithic integrated driving gallium nitride micro-light-emitting diode

In the information display field, micro-light-emitting diodes (micro-LEDs) possess high potentials and they are expected to lead the direction of developing the next-generation new display technologies. Their display performances are superior to those produced by the currently prevailing liquid crystal and organic light-emitting diode based technologies. However, the micro-LED pixels and their driving circuits are often fabricated on different wafers, which implies that the so-called mass transfer seems to be inevitable, thus facing an obvious bottleneck. In this paper, the emerging graphene field effect transistors are used as the driving elements and integrated onto the GaN micro-LEDs, which is because the pixels and drivers are prepared directly on the same wafer, the technical problem of mass transfer is fundamentally bypassed. Furthermore, in traditional lithographic process, the ultraviolet photoresist directly contacts the graphene, which introduces severe carrier doping, thereby leading to deteriorated graphene transistor properties. This, not surprisingly, further translates into lower performances of the integrated devices. In the present work, proposed is a technique in which the polymethyl methacrylate (PMMA) thin films act as both the protection layers and the interlayers when optimizing the graphene field effect transistor processing. The PMMA layers are sandwiched between the graphene and the ultraviolet photoresist, which is a brand new device fabrication process. First, the new process is tested in discrete graphene field effect transistors. Compared with those devices that are processed without the PMMA protection thin films, the graphene devices fabricated with the new technology typically show their Dirac point at a gate voltage (Vg) deviation from Vg = 0, that is, 22 V lower than their counterparts. In addition, an increase in the carrier mobility of 32% is also observed. Finally, after applying the newly developed fabrication process to the pixel-and-driver integrated devices, it is found that their performances are improved significantly. With this new technique, the ultraviolet photoresist no longer directly contacts the sensitive graphene channel because of the PMMA protection. The doping effect and the performance dropping are dramatically reduced. The technique is facile and cheap, and it is also applicable to two-dimensional materials besides graphene, such as MoS2 and h-BN. It is hoped that it is of some value for device engineers working in this field

Summary of the <i>M. domestica</i> transcriptome.

<p>Summary of the <i>M. domestica</i> transcriptome.</p