Experimental and numerical study on crack propagation and coalescence in rock-like materials under compression

The discontinuous crack surface in a rock affects the stability of the whole rock system. The experiments in this paper were carried out by prefabricating rock-like specimens with different types of flaws, then the specimens were tested under uniaxial compression. Moreover, based on the theory of particle flow, PFC2D software was used for numerical simulation, and the comparative analysis of the experimental and simulative results was carried out to obtain the crack initiation sequence, propagation phenomenon, and failure mode of rock specimens with different flaw types. The results indicated that the wing crack started at the tip of flaw and the form of crack assumed split failure, followed by shear failure caused by the secondary crack. The tensile failure degree decreases and the influence of shear failure increases with the increase of flaw angle. The wing crack and secondary initiation stress value is 35%–55% and 85%–95% of the peak stress value. Crack coalescence appeared in adjacent flaws of rock-like specimens with multiple parallel single flaws, single-cross flaws and double-cross flaws, and the coalescence phenomenon always occurs when the stress peak value is reached. With the number of flaws increasing, the splitting failure of rock-like specimens became more and more serious, the splitting failure of double cross-flaw specimen is the most serious. As for the specimen with single-cross flaw, the wing crack would be produced at the tip of the flaw with larger obliquity. The results of this paper may offer certain reference value for the study on the mechanism of rock crack.

GEOLOGIA DA ÁREA NORDESTE DA FOLHA POÇO DA CRUZ, BACIA DE JATOBÁ, NORDESTE DO BRASIL

The Jatobá Basin is located in the south-central portion of Pernambuco state and northern Bahia and Alagoas, it has an area of approximately 5000 km² in a NE-SW preferred direction and sedimentary record has approximately 3 km. It is a rift basin developed under extensional tectonic events related to the rupture of the Gondwana supercontinent and it marks the northern limit of the aborted Recôncavo-Tucano-Jatobá rift system. The stratigraphic succession in the Campos district, Ibimirim (PE), comprises the Syneclise sequence and Rift Initiation sequence as well as part of the Rift Climax sequence of the basin. Using columnar sections and identifying sedimentary facies, six stratigraphic units were recognized, in addition to the quaternary coverage. The two lower fluvial-marine units are related to the siluro-devonian sedimentary records of the Syneclise sequence,while fluvial-eolic and lacustrine sediments of the upper units mark the Rift Initiation and Rift Climax sequences. The Aliança Formation, discussed in a particular way in this paper, represents the first sedimentary records of the beginning of the Neojurassic rift (Dom João stage). Since it was deposited in a lacustrine system, this formation has highly fossiliferous decimetric carbonate levels arranged in thick pelitic packages, suggesting deposition during times of energy variations within a shallow lake. The detailing of the stratigraphy of these deposits, associated with petrographic and paleontological studies, brings a new understanding of the depositional system that occurred in this environment and the first processes that started the opening of the rift during the Upper Jurassic.

Researches on Crack Propagation of the Two Filled Noncoalescent Coplanar Flaws under the High Strain Rate Loading by means of AUTODYN-Based Simulation

To study the influence of fillings on rock failure. By turning to the Drucker-Prager strength model and cumulative damage criteria, investigations are made, with the nonlinear AUTODYN software, into crack propagation behaviors in crack-filled and unfilled specimens under uniaxial dynamic loading. Under investigations are crack initiation position, sequence and angle, and coalescence mode. According to the mode of propagation and coalescence, cracks are divided into three types, i.e., the tensile wing, the antiwing, and the horsetail. The simulation results show that under uniaxial dynamic loading, differences are found in initiation position, angle, and coalescence mode for specimens with cracks filled or otherwise. However, filling does not affect crack initiation sequence. Under the same loading, the damage to filled specimen is less severe than that to the unfilled specimen.

RNA-seq reads of Influenza A genome appended with DNA-expression vector sequences facilitating protein transcription (18s) in Covid19 patients from Wuhan and Hong Kong - very worrying as this is unlikely to be contamination

Some viruses like Hepatitis C virus (HCV) have hijacked the human protein translation machinery [1], having by an ‘internal ribosome entry site (IRES) that can autonomously bind a 40S ribosomal subunit and accurately position it at the initiation codon. This binding involves both ribosomal protein and 18S ribosomal RNA (rRNA) interactions’ [2]. Expression vectors are designed to facilitate gene expression, by adding a promoter, a proper translation initiation sequence (a ribosomal binding site) and start/termination codon, followed by a transcription termination sequence.Metagenome from the bronchoalveolar lavage fluid of 5 Covid19 [3–5] patients from Wuhan (Accid:PRJNA605983) shows co-infection (sequences in SI.flu.zip) with influenza A virus (3 out of 5 patients). More worryingly,these reads show the presence of 18s sequences that are found in expression vectors to facilitate protein translation (Fig. 1), showing highest homology to a synthetic construct (H1N1 HA gene, Accid:KY199426.1)used in a ‘digital-to-biological converter for on-demand production of biologics’ [6]. Along with SARS-Cov2 infection, a few patients are also infected with Nipah [7]. Its inconceivable that a BSL-4 facility will have so many contamination. Furthermore, the sequencing was RNA-seq - while the expression vectors are DNA - and thus need to be transcribed to be seen in RNA-seq data.

One-Pot Production of RNA in High Yield and Purity Through Cleaving Tandem Transcripts

There is an increasing demand for efficient and robust production of short RNA molecules in both pharmaceutics and research. A standard method is in vitro transcription by T7 RNA polymerase. This method is sequence-dependent on efficiency and is limited to products longer than ~12 nucleotides. Additionally, the native initiation sequence is required to achieve high yields, putting a strain on sequence variability. Deviations from this sequence can lead to side products, requiring laborious purification, further decreasing yield. We here present transcribing tandem repeats of the target RNA sequence followed by site-specific cleavage to obtain RNA in high purity and yield. This approach makes use of a plasmid DNA template and RNase H-directed cleavage of the transcript. The method is simpler and faster than previous protocols, as it can be performed as one pot synthesis and provides at the same time higher yields of RNA.

Measuring the Reduction of the Confinement along the Evolution of a Burn Cut

We provide an analysis of a tunnel opening cut in a tunnel face. In particular, we focus on the effect of a “burn cut,” which is a typical parallel hole cut. As the evolution of the opening consists of an increase in the volume of the cut prism and the consequent reduction of confinement of the holes along the initiation sequence, we analyze such an evolution using photographic documentation, as well as evaluating the reduction of confinement by measuring the energy transferred from the explosive charge to the rock mass. The energy was estimated by monitoring and analyzing the vibrations induced by the blasting at three different points. We adopted low-cost shock sensors for monitoring the effect of the detonation times at short distance from the blast (about 10 m). The results show an evident reduction of the shock transfer to the rock mass (i.e., a reduction of confinement) with the increase of the cavity opening. Nevertheless, when only the response of the piezometric sensors was considered, a disparity in behavior among the sensors was noted. On the other hand, when the sensor response was integrated over time, the behavior of all sensors normalized, showing the need to focus both on the oscillation and the duration to properly address the shock effect.

Rescue of recombinant Newcastle disease virus: a promising vector with two decades of intensive vaccine research

Two decades have passed since the first reverse genetics system for the rescue of recombinant Newcastle disease virus was developed. Since then, the recombinant Newcastle disease virus vector has shown promising results as a safe and potent vector for development of many vaccines for both avian and human use. Herein, we review several technical topics that would be useful to further understanding of this technology. First, the effect of using helper plasmids encoding proteins belonging to strains other than the full-length cDNA and the possible incorporation of these expressed proteins into progeny virus will be discussed. Then, we will discuss the effect of removal of additional G residues from the T7 initiation sequence and finally, we will review different ways to improve rescue efficiency.

Floral development and anatomy of Macarthuria australis (Macarthuriaceae): key to understanding the unusual initiation sequence of Caryophyllales

We investigated the floral anatomy and development of Macarthuria australis Hügel ex Endl., an unusual genus endemic to Australia, in the context of floral evolution of core Caryophyllales. Flower initiation is spiral, with sepals developing quincuncially. The first two petals continue the sequence of sepal initiation, but the remaining petals arise from common stamen–petal primordia. The androecium develops sequentially as three inner antesepalous and five outer antepetalous stamens. The globular ovary is trimerous with a short symplicate zone and two arillate ovules per locule. The rapid emergence of the androecium leads to a partial absorption of the petal primordia within the androecial tissue. The two first-formed petals have more room for development and precede the androecium, supporting the fact that petals are not staminodial in origin. This heterochronic shift correlates with an inversed developmental sequence of the antesepalous stamens. The constraint caused by the spatial occupation of sepals and carpels leads to the loss of two stamens, and the re-arrangement of stamens and petals along the flanks of the carpels. The floral development of Macarthuria anticipates a syndrome of stamen and petal development in other core Caryophyllales and culminating in the Caryophyllaceae.