Development of a spherically focused capacitive-film air-coupled ultrasonic transducer and a leak location array sensor for long-endurance spacecraft

This research work is focused on the development of a spherically focused (no-mirror) capacitive-film air-coupled ultrasonic transducer and a leak location array sensor for long-endurance spacecraft. For the development of a spherically focused capacitive-film air-coupled ultrasonic transducer, two transducers have been designed, fabricated, and their performance characterized, using a spherically deformed backplate and film. One has a 10-mm diameter and 25.4-mm geometric focal length, and another has a 50-mm diameter and 50.8-mm geometric focal length. Both spherically focused transducers have frequency spectra centered at 805 kHz with -6-dB points at 400 kHz and 1200 kHz. By performing rigorous feasibility tests; a flexible copper/polyimide circuit board material is employed as a backplate in place of the conventional silicon substrate. Utilizing its deformability and ease of microfabrication, we have demonstrated that spherically focused air-coupled ultrasonic transducers can be made to function without the need of an external focusing device, such as a zone plate or an acoustic mirror. We have also invented a simple and easily applied method to conform the metalized polymer film onto a spherically curved backplate, while suppressing wrinkling on the film. Good agreement has been shown between measurement and theory, suggesting that our transducers behave as ideal spherically focused piston transducers;For the development of a leak location array sensor for long-endurance spacecraft, we have developed and experimentally demonstrated a sensitive and reliable means to locate an air leak in a plate-like structure. The goals of this work are accomplished by developing a sophisticated leak location algorithm and a two-dimensional PZT array sensor. The proposed leak location algorithm is highly effective in finding the direction of the leaks, using a minimal number of sensors, and needing less computation time while still achieving high accuracy. In addition, it accounts for the multi-mode dispersive characteristics in a plate-like structure, and utilizes structure-borne noise generated by turbulence at an air leak. This leak location algorithm is implemented by a prototype of a 64-element array sensor

A Suspended Nanogap Formed by Field-Induced Atomically Sharp Tips

A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (\u3e109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers. VC 2012 American Institute of Physics

Factors Affecting the Extrusion Rate of Ventilation Tubes

ObjectivesThe objective of this study was to determine the various factors that affect the extrusion rate of ventilation tubes (VTs), including the nature of the middle ear effusion.MethodsA retrospective chart review of 82 pediatric patients (177 ears) who received VT insertion surgery under general anesthesia was carried out to evaluate the relationship between various factors and the VT extrusion rate. The factors we analyzed included age, gender, the adenoid size, the amount and content of the middle ear effusion after myringotomy, bleeding events, associated adenoidectomy and the findings of the tympanic membrane status, the tympanometry and the audiometry of the air bone gap.ResultsThe mean extrusion time was 254 days (range, 11 to 809 days). The patients with no history of previous VT insertion had a longer extrusion time (mean, 279 days) than did the patients who had undergone previous VT insertion (mean, 203 days). The patients with serous effusion had the shortest extrusion time (mean, 190 days) as compared to those patients with glue (273 days) and pus (295 days) effusions. Other factors had no statistical significant relationship with the extrusion time.ConclusionThe mean VT extrusion time was 254 days. The VT extrusion time was significantly related to the characteristics of the middle ear effusion and a history of previous VT insertion. Thus, the nature of middle ear effusion can provide a clinical clue to predict the VT extrusion time

Production of a SARS-CoV-2 Spike Protein Vaccine Using the Baculovirus Expression Vector System

Various COVID-19 vaccines are currently in development, as the COVID-19 pandemic has created an unmet need for protection against the SARS-CoV-2 virus. While there are many different types of vaccines, we focused on developing one that would be safe, affordable, and quickly available for emergency use. A vaccine synthesized using recombinant proteins utilizes a reliable and well-studied technological platform, avoids the safety risks inherent to viral vectors, and provides a cost-effective, scalable method of production of antigen used to induce an immune response. Other vaccines on the market notably include Pfizer’s and Moderna’s mRNA based vaccines. Although these are widely used, there is still a large demand for an inexpensive yet safe and effective vaccine. Herein, we propose the production of 500 million doses of a recombinant spike protein-based COVID-19 vaccine in a quick time frame and cost-effective manner, using the baculovirus expression vector system (BEVS). Our upstream process involves a three-stage cellular scale-up from shake flasks to WAVE bioreactors to perfusion to production bioreactors, as well as an additional two-stage viral amplification from flasks to WAVE bioreactors. Our downstream process involves a six-stage protein recovery with depth filtration, his-tag chromatography, viral inactivation, ion-exchange chromatography, viral filtration, and diafiltration. We will be partnering with a contract manufacturing organization (CMO) for this project, as we do not have the time to quickly build a plant to get these vaccines out for emergency use. This arrangement makes this process highly profitable. Selling each dose for $16 yields net earnings near$2 billion and an extremely high IRR due to the lack of permanent and fixed costs other than our rental fee. The IRR for the CMO is estimated to be at least 16% with the NPV of the plant at $855,000 and an ROI of 18%

Minimal Width for Universal Property of Deep RNN

A recurrent neural network (RNN) is a widely used deep-learning network for dealing with sequential data. Imitating a dynamical system, an infinite-width RNN can approximate any open dynamical system in a compact domain. In general, deep networks with bounded widths are more effective than wide networks in practice; however, the universal approximation theorem for deep narrow structures has yet to be extensively studied. In this study, we prove the universality of deep narrow RNNs and show that the upper bound of the minimum width for universality can be independent of the length of the data. Specifically, we show that a deep RNN with ReLU activation can approximate any continuous function or $L^p$ function with the widths $d_x+d_y+2$ and $\max\{d_x+1,d_y\}$, respectively, where the target function maps a finite sequence of vectors in $\mathbb{R}^{d_x}$ to a finite sequence of vectors in $\mathbb{R}^{d_y}$. We also compute the additional width required if the activation function is $\tanh$ or more. In addition, we prove the universality of other recurrent networks, such as bidirectional RNNs. Bridging a multi-layer perceptron and an RNN, our theory and proof technique can be an initial step toward further research on deep RNNs

Peccei-Quinn Inflation at the Pole and Axion Kinetic Misalignment

We propose a minimal extension of the Standard Model with the Peccei-Quinn (PQ) scalar field and explain the relic density of the QCD axion through the kinetic misalignment with a relatively small axion decay constant. To this purpose, we consider a slow-roll inflation from the radial component of the PQ field with the PQ conserving potential near the pole of its kinetic term and investigate the post-inflationary dynamics of the PQ field for reheating. The angular mode of the PQ field, identified with the QCD axion, receives a nonzero velocity during inflation due to the PQ violating potential, evolving with an approximately conserved Noether PQ charge. We determine the reheating temperature from the perturbative decays and scattering processes of the inflaton and obtain dark radiation from the axions produced from the inflaton scattering at a testable level in the future Cosmic Microwave Background experiments. We show the correlation between the reheating temperature, the initial velocity of the axion and the axion decay constant, realizing the axion kinetic misalignment for the correct relic density.Comment: 25 pagesm 3 figure