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COVID-19 was declared a pandemic by the WHO in 2020. In light of the global shortage of PPE and concerns regarding the safety of healthcare providers, clinicians have resorted to the use of novel protective barriers, such as aerosol boxes and plastic sheets, during aerosol generating procedures, especially tracheal intubation. We compared the effect of these barriers on the tracheal intubation of simulated patients with severe COVID-19 in a crossover study. The study was approved by the Ethics Committee of King Faisal Specialist Hospital, and the procedures were compliant with the COVID-19 airway management guidelines of the Saudi Anesthesia Society. The time to intubation was our primary outcome. Secondary outcomes included number of optimization maneuvers, number of intubation attempts, time to glottic view and ventilation of the lungs, and damage to PPE. Thirteen consultant anesthetists performed 39 tracheal intubations on a manikin using each of three approaches (aerosol box, plastic sheet, and no-barrier). Data were collected via direct and video observation. The plastic sheet approach demonstrated the highest time to intubation (mean ± StE [95% CI]: 33.3s ± 3.5 [25.8– 40.9]) compared to the aerosol box (22.0s ± 2.5 [16.5 – 27.5], P < 0.01) and no-barrier approaches (16.1s ± 1.1 [13.7 – 18.4], P < 0.0001). Similarly, the plastic sheet approach had the highest time to glottic view, and ventilation intervals compared to the other two approaches, while the no-barrier approach had the shortest time intervals. There were no failed intubations or damage to the PPE sustained during the use of any of the three approaches. The aerosol box does not impose a significant delay in tracheal intubation using video laryngoscopy, unlike the plastic sheet barrier. Further research on the aerosolization risk is warranted before these protective barriers can be considered as mainstay approaches during aerosol generating procedures.

Abstract Background Radiation-induced gastrointestinal syndrome (RIGS) results from the acute loss of intestinal stem cells (ISC), impaired epithelial regeneration, and subsequent loss of the mucosal barrier, resulting in electrolyte imbalance, diarrhea, weight loss, sepsis, and mortality. The high radiosensitivity of the intestinal epithelium limits effective radiotherapy against abdominal malignancies and limits the survival of victims of nuclear accidents or terrorism. Currently, there is no approved therapy to mitigate radiation toxicity in the intestine. Here we demonstrate that BCN057, an anti-neoplastic small molecular agent, induces ISC proliferation and promotes intestinal epithelial repair against radiation injury. Methods BCN057 (90 mg/kg body weight, subcutaneously) was injected into C57Bl6 male mice (JAX) at 24 h following abdominal irradiation (AIR) and was continued for 8 days post-irradiation. BCN057-mediated rescue of Lgr5-positive ISC was validated in Lgr5-EGFP-Cre-ERT2 mice exposed to AIR. The regenerative response of Lgr5-positive ISC was examined by lineage tracing assay using Lgr5-EGFP-ires-CreERT2-TdT mice with tamoxifen administration to activate Cre recombinase and thereby marking the ISC and their respective progeny. Ex vivo three-dimensional organoid cultures were developed from surgical specimens of human colon or from mice jejunum and were used to examine the radio-mitigating role of BCN057 on ISC ex vivo. Organoid growth was determined by quantifying the budding crypt/total crypt ratio. Statistical analysis was performed using Log-rank (Mantel-Cox) test and paired two-tail t test. Results Treatment with BCN057 24 h after a lethal dose of AIR rescues ISC, promotes regeneration of the intestinal epithelium, and thereby mitigates RIGS. Irradiated mice without BCN057 treatment suffered from RIGS, resulting in 100% mortality within 15 days post-radiation. Intestinal organoids developed from mice jejunum or human colon demonstrated a regenerative response with BCN057 treatment and mitigated radiation toxicity. However, BCN057 did not deliver radio-protection to mouse or human colon tumor tissue. Conclusion BCN057 is a potential mitigator against RIGS and may be useful for improving the therapeutic ratio of abdominal radiotherapy. This is the first report demonstrating that a small molecular agent mitigates radiation-induced intestinal injury by inducing ISC self-renewal and proliferation.

A gradient-based optimization (GBO) method is presented for acoustic lens design and sound localization. GBO uses a semi-analytical optimization combined with the principle of acoustic reciprocity. The idea differs from earlier inverse designs that use topology optimization tools and generic algorithms. We first derive a formula for the gradients of the pressure at the focal point with respect to positions of a set of cylindrical scatterers. The analytic form of the gradients enhances modeling capability when combined with optimization algorithms and parallel computing. The GBO algorithm maximizes the sound amplification at the focal point and enhances the sound localization by evaluating pressure derivatives with respect to the cylinder positions and then perturbatively optimizing the position of each cylinder in the lens while incorporating multiple scattering between the cylindrical scatterers. The results of the GBO of the uni- and multi-directional broadband acoustic lens designs are presented including several performance measures for the frequency dependence and the incidence angle. A multi-directional broadband acoustic lens is designed to localize the sound and to focus acoustic incident waves received from multiple directions onto a predetermined localization region or focal point. The method is illustrated for configurations of sound hard and sound soft cylinders as well as clusters of elastic thin shells in water.

A reflection-mode carbon dioxide (CO2) fibre optic sensor (FOS) is developed based on the colorimetric change of pH indicator dye thymol blue. The CO2 sensing film comprises thymol blue and tetramethylammonium hydroxide in the form of an ion pair doped in an organically modified silica film. A dip coating process was conducted to coat the sensing film on the tip of optical fibre with a film thickness approximately 2.7 ± 0.1 μm. The observed reflection signal at a wavelength of 608 nm exhibits a reversible change for the concentration of CO2 range from 0 to 6% with a response time of 19 s and recovery time of 170 s for 6% of CO2. An optimal concentration of thymol blue in the preparation of coating solution that provides a highest sensitivity was found to be 2.9 mg/ml. Storing the FOS in a pure nitrogen atmosphere provided a stable film with a shelf-life of over 15 days as compared to a gradual degradation in film performance and complete loss of sensitivity after 10 days with storage in ambient air. The FOS response is affected by relative humidity (RH) and a humidity filter was demonstrated to reduce humidity levels in breath from 90% to 40–50% to reduce this effect. The developed FOS was used to measure the end-tidal breath CO2 for testing its applicability in healthcare. The CO2 measurement from breath sample using our FOS shows a good agreement (percentage error~3%) with a commercial CO2 datalogger (K-33 BLG, CO2 Meter, USA). Due to the limitation of response time, at present the FOS is limited to measuring variation of the CO2 from slow breath to breath. Keywords: Optical fibre CO2 sensor, Colorimetric change, pH indicator, Thymol blue, Sol-gel, End-tidal CO2

Including healthcare professionals in the design of medical devices/testing systems can have a significant impact on their success or failure.

The new strain of coronavirus (severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2)) emerged in 2019 and hence is often referred to as coronavirus disease 2019 (COVID-19). This disease causes hypoxic respiratory failure and acute respiratory distress syndrome (ARDS), and is considered as the cause of a global pandemic. Very limited reports in addition to ex vivo model systems are available to understand the mechanism of action of this virus, which can be used for testing of any drug efficacy against virus infectivity. COVID-19 induces tissue stem cell loss, resulting inhibition of epithelial repair followed by inflammatory fibrotic consequences. Development of clinically relevant models is important to examine the impact of the COVID-19 virus in tissue stem cells among different organs. In this review, we discuss ex vivo experimental models available to study the effect of COVID-19 on tissue stem cells.

The higher the energy of a particle is above equilibrium, the faster it relaxes because of the growing phase space of available electronic states it can interact with. In the relaxation process, phase coherence is lost, thus limiting high-energy quantum control and manipulation. In one-dimensional systems, high relaxation rates are expected to destabilize electronic quasiparticles. Here, we show that the decoherence induced by relaxation of hot electrons in one-dimensional semiconducting nanowires evolves nonmonotonically with energy such that above a certain threshold hot electrons regain stability with increasing energy. We directly observe this phenomenon by visualizing, for the first time, the interference patterns of the quasi-one-dimensional electrons using scanning tunneling microscopy. We visualize the phase coherence length of the one-dimensional electrons, as well as their phase coherence time, captured by crystallographic Fabry-Pèrot resonators. A remarkable agreement with a theoretical model reveals that the nonmonotonic behavior is driven by the unique manner in which one-dimensional hot electrons interact with the cold electrons occupying the Fermi sea. This newly discovered relaxation profile suggests a high-energy regime for operating quantum applications that necessitate extended coherence or long thermalization times, and may stabilize electronic quasiparticles in one dimension.