Tandem cavity collapse in a high-speed droplet impinging on a constrained wall

A focusing shock wave can be generated during the high-speed impact of a droplet on a $180^\circ$ constrained wall, which can be used to realise energy convergence on a small scale. In this study, to realise high energy convergence and peak pressure amplification, a configuration of droplets embedded with cavities is proposed for high-speed impingement on a $180^\circ$ constrained wall. A multicomponent two-phase compressible flow model considering the phase transition is used to simulate the high-speed droplet impingement process. The properties of the embedded cavities can influence the collapse pressure peak. The collapse of an embedded single air cavity or vapour cavity, as well as the cavities in a tandem array, is simulated in this study. The physical evolution mechanisms of the impinging droplet and the embedded cavities are investigated qualitatively and quantitatively by characterising the focusing shock wave generated inside the droplet and its interaction with different cavity configurations. The interaction dynamics between the cavities is analysed and a theoretical prediction model for the intensity of each cavity collapse in the tandem array is established. With the help of this theoretical model, the influencing factors for the collapse intensities of the tandem cavities are identified. The results reveal that the properties of the initial shock wave and the interval between the cavities are two predominant factors for the amplification of the collapse intensity. This study enhances the understanding of the physical process of shock-induced tandem-cavity collapse.

A temporally resolved, multiplex molecular recorder based on sequential genome editing

DNA is naturally well-suited to serve as a digital medium for in vivo molecular recording. However, DNA-based memory devices described to date are constrained in terms of the number of distinct signals that can be concurrently recorded and/or by a failure to capture the precise order of recorded events. Here we describe DNA Ticker Tape, a general system for in vivo molecular recording that largely overcomes these limitations. Blank DNA Ticker Tape consists of a tandem array of partial CRISPR-Cas9 target sites, with all but the first site truncated at their 5' ends, and therefore inactive. Signals of interest are coupled to the expression of specific prime editing guide RNAs. Editing events are insertional, and record the identity of the guide RNA mediating the insertion while also shifting the position of the "write head" by one unit along the tandem array, i.e. sequential genome editing. In this proof-of-concept of DNA Ticker Tape, we demonstrate the recording and decoding of complex event histories or short text messages; evaluate the performance of dozens of orthogonal tapes; and construct "long tape" potentially capable of recording the order of as many as 20 serial events. Finally, we demonstrate how DNA Ticker Tape simplifies the decoding of cell lineage histories.

Major SCP/TAPS protein expansion in Lucilia cuprina is associated with novel tandem array organisation and domain architecture

Background Larvae of the Australian sheep blowfly, Lucilia cuprina, parasitise sheep by feeding on skin excretions, dermal tissue and blood, causing severe damage known as flystrike or myiasis. Recent advances in -omic technologies and bioinformatic data analyses have led to a greater understanding of blowfly biology and should allow the identification of protein families involved in host-parasite interactions and disease. Current literature suggests that proteins of the SCP (Sperm-Coating Protein)/TAPS (Tpx-1/Ag5/PR-1/Sc7) (SCP/TAPS) superfamily play key roles in immune modulation, cross-talk between parasite and host as well as developmental and reproductive processes in parasites. Methods Here, we employed a bioinformatics workflow to curate the SCP/TAPS protein gene family in L. cuprina. Protein sequence, the presence and number of conserved CAP-domains and phylogeny were used to group identified SCP/TAPS proteins; these were compared to those found in Drosophila melanogaster to make functional predictions. In addition, transcription levels of SCP/TAPS protein-encoding genes were explored in different developmental stages. Results A total of 27 genes were identified as belonging to the SCP/TAPS gene family: encoding 26 single-domain proteins each with a single CAP domain and a solitary double-domain protein containing two conserved cysteine-rich secretory protein/antigen 5/pathogenesis related-1 (CAP) domains. Surprisingly, 16 SCP/TAPS predicted proteins formed an extended tandem array spanning a 53 kb region of one genomic region, which was confirmed by MinION long-read sequencing. RNA-seq data indicated that these 16 genes are highly transcribed in all developmental stages (excluding the embryo). Conclusions Future work should assess the potential of selected SCP/TAPS proteins as novel targets for the control of L. cuprina and related parasitic flies of major socioeconomic importance.

Piperacillin/tazobactam resistance in a clinical isolate of Escherichia coli due to IS26-mediated amplification of blaTEM-1B

A phenotype of Escherichia coli and Klebsiella pneumoniae, resistant to piperacillin/tazobactam (TZP) but susceptible to carbapenems and 3rd generation cephalosporins, has emerged. The resistance mechanism associated with this phenotype has been identified as hyperproduction of the β-lactamase TEM. However, the mechanism of hyperproduction due to gene amplification is not well understood. Here, we report a mechanism of gene amplification due to a translocatable unit (TU) excising from an IS26-flanked pseudo-compound transposon, PTn6762, which harbours blaTEM-1B. The TU re-inserts into the chromosome adjacent to IS26 and forms a tandem array of TUs, which increases the copy number of blaTEM-1B, leading to TEM-1B hyperproduction and TZP resistance. Despite a significant increase in blaTEM-1B copy number, the TZP-resistant isolate does not incur a fitness cost compared to the TZP-susceptible ancestor. This mechanism of amplification of blaTEM-1B is an important consideration when using genomic data to predict susceptibility to TZP.