Thermal/structural analysis of a transpiration cooled nozzle

The 8-foot High Temperature Tunnel (HTT) at LaRC is a combustion driven, high enthalpy blow down wind tunnel. In Mar. 1991, during check out of the transpiration cooled nozzle, pieces of platelets were found in the tunnel test section. It was determined that incorrect tolerancing between the platelets and the housing was the primary cause of the platelet failure. An analysis was performed to determine the tolerance layout between the platelets and the housing to meet the structural and performance criteria under a range of thermal, pressure, and bolt preload conditions. Three recommendations resulted as a product of this analysis

Damage Tolerance Analysis of a Pressurized Liquid Oxygen Tank

A damage tolerance assessment was conducted of an 8,000 gallon pressurized Liquid Oxygen (LOX) tank. The LOX tank is constructed of a stainless steel pressure vessel enclosed by a thermal-insulating vacuum jacket. The vessel is pressurized to 2,250 psi with gaseous nitrogen resulting in both thermal and pressure stresses on the tank wall. Finite element analyses were performed on the tank to characterize the stresses from operation. Engineering material data was found from both the construction of the tank and the technical literature. An initial damage state was assumed based on records of a nondestructive inspection performed on the tank. The damage tolerance analyses were conducted using the NASGRO computer code. This paper contains the assumptions, and justifications, made for the input parameters to the damage tolerance analyses and the results of the damage tolerance analyses with a discussion on the operational safety of the LOX tank

Analysis of bilinear oscillators under harmonic loading using nonlinear output frequency response functions

In this paper, the new concept of Nonlinear Output Frequency Response Functions (NOFRFs) is extended to the harmonic input case, an input-independent relationship is found between the NOFRFs and the Generalized Frequency Response Functions (GFRFs). This relationship can greatly simplify the application of the NOFRFs. Then, beginning with the demonstration that a bilinear oscillator can be approximated using a polynomial type nonlinear oscillator, the NOFRFs are used to analyze the energy transfer phenomenon of bilinear oscillators in the frequency domain. The analysis provides insight into how new frequency generation can occur using bilinear oscillators and how the sub-resonances occur for the bilinear oscillators, and reveals that it is the resonant frequencies of the NOFRFs that dominate the occurrence of this well-known nonlinear behaviour. The results are of significance for the design and fault diagnosis of mechanical systems and structures which can be described by a bilinear oscillator model

Convalescent Plasma Therapy in Four Critically Ill Pediatric Patients With Coronavirus Disease 2019: A Case Series

Background: Coronavirus disease 2019 is a pandemic with no specific therapeutic agents or vaccination. Small published case series on critically ill adults suggest improvements in clinical status with minimal adverse events when patients receive coronavirus disease 2019 convalescent plasma, but data on critically ill pediatric patients are lacking. We report a series of four critically ill pediatric patients with acute respiratory failure who received coronavirus disease 2019 convalescent plasma as a treatment strategy for severe disease. Case Summary:  Patients ranged in age from 5 to 16 years old. All patients received coronavirus disease 2019 convalescent plasma within the first 26 hours of hospitalization. Additional disease modifying agents were also used. All patients made a full recovery and were discharged home off of oxygen support. No adverse events occurred from the coronavirus disease 2019 convalescent plasma transfusions. Conclusion: Coronavirus disease 2019 convalescent plasma is a feasible therapy for critically ill pediatric patients infected with severe acute respiratory syndrome coronavirus 2. Well-designed clinical trials are necessary to determine overall safety and efficacy of coronavirus disease 2019 convalescent plasma and additional treatment modalities in pediatric patients

Using intervention mapping to develop an implementation strategy to improve timely uptake of streamlined birth-dose vaccines in the Democratic Republic of the Congo

Despite the policy recommendation and effectiveness of administering the hepatitis B birth-dose vaccine (HepB-BD) to newborns to prevent mother-to-child hepatitis B transmission, timely uptake remains an issue. Countries adopting the HepB-BD to their national immunization schedule report programmatic challenges to administering the vaccine within the recommended 24-hour window after delivery. Further, while the World Health Organization recommends streamlining three birth-dose vaccines (HepB-BD, BCG, and OPV0), scarce Sub-Saharan(SSA)-based literature reports on a streamlined and timely approach to birth-dose vaccines. As more SSA countries adopt the new birth-dose vaccine to their immunization schedules, a systematically developed implementation strategy—Vaccination of Newborns–Innovative Strategies to Hasten Birth-Dose vaccines’ delivery (VANISH-BD)—will facilitate the adoption and implementation of timely birth-dose vaccine uptake. In this paper, we describe the development of the implementation strategy using intervention mapping, an evidence-based and theory-driven approach. We report on the development of our intervention, beginning with the needs assessment based in Kinshasa Province, Democratic Republic of the Congo (DRC), informing step 1 of intervention mapping. The intervention is contextually relevant, locally produced, sustainable, and designed to improve timely birth-dose vaccine uptake in the DRC. We intend to inform future implementers about improving timely and streamlined birth-dose vaccine uptake and for VANISH-BD to be adapted for similar contexts

Bio-Inspired Materials For Parsing Matrix Physicochemical Control Of Cell Migration: A Review

Cell motility is ubiquitous in both normal and pathophysiological processes. It is a complex biophysical response elicited via the integration of diverse extracellular physicochemical cues. The extracellular matrix directs cell motilityvia gradients in morphogens (a.k.a. chemotaxis), adhesive proteins (haptotaxis), and stiffness (durotaxis). Three-dimensional geometrical and proteolytic cues also constitute key regulators of motility. Therefore, cells process a variety of physicochemical signals simultaneously, while making informed decisions about migration viaintracellular processing. Over the last few decades, bioengineers have created and refined natural and synthetic in vitro platforms in an attempt to isolate these extracellular cues and tease out how cells are able to translate this complex array of dynamic biochemical and biophysical features into functional motility. Here, we review how biomaterials have played a key role in the development of these types of model systems, and how recent advances in engineered materials have significantly contributed to our current understanding of the mechanisms of cell migration

Low knowledge about hepatitis B prevention among pregnant women in Kinshasa, Democratic Republic of Congo

Infants infected perinatally with hepatitis B (HBV) are at the highest risk of developing chronic hepatitis and associated sequelae. Prevention of mother-to-child transmission (PMTCT) of HBV requires improved screening and awareness of the disease. This study evaluated existing HBV knowledge among pregnant mothers (n = 280) enrolled in two HBV studies in urban maternity centers in Kinshasa, Democratic Republic of the Congo. All mothers responded to three knowledge questions upon study enrollment. Baseline levels of knowledge related to HBV transmission, treatment, prevention, and symptoms were low across all participants: 68.8% did not know how HBV was transmitted, 70.7% did not know how to prevent or treat HBV MTCT, and 79.6% did not know signs and symptoms of HBV. Over half of participants responded “I don’t know” to all questions. HBV-positive women who participated in both studies (n = 46) were asked the same questions during both studies and showed improved knowledge after screening and treatment, despite no formal educational component in either study (p < 0.001). These findings highlight the need for intensified education initiatives in highly endemic areas to improve PMTCT efforts

Digital hoarding behaviours: measurement and evaluation

The social and psychological characteristics of individuals who hoard physical items are quite well understood, however very little is known about the psychological characteristics of those who hoard digital items and the kinds of material they hoard. In this study, we designed a new questionnaire (Digital Behaviours Questionnaire: DBQ) comprising 2 sections: the Digital Hoarding Questionnaire (DHQ) assessing two key components of physical hoarding (accumulation and difficulty discarding); and the second measuring the extent of digital hoarding in the workplace (Digital Behaviours in the Workplace Questionnaire: DBWQ). In an initial study comprising 424 adults we established the psychometric properties of the questionnaires. In a second study, we presented revised versions of the questionnaires to a new sample of 203 adults, and confirmed their validity and reliability. Both samples revealed that digital hoarding was common (with emails being the most commonly hoarded items) and that hoarding behaviours at work could be predicted by the 10 item DHQ. Digital hoarding was significantly higher in employees who identified as having ‘data protection responsibilities’, suggesting that the problem may be influenced by working practices. In sum, we have validated a new psychometric measure to assess digital hoarding, documented some of its psychological characteristics, and shown that it can predict digital hoarding in the workplace

North Carolina public school teachers’ contact patterns and mask use within and outside of school during the pre-vaccine phase of the COVID-19 pandemic

Background : Teachers are central to school-associated transmission networks, but little is known about their behavioral patterns during the COVID-19 pandemic. Methods : We conducted a cross-sectional survey of 700 North Carolina public school teachers in four districts open to in-person learning in November-December 2020 (pre-COVID-19 vaccines). We assessed indoor and outdoor time spent, numbers of people encountered at 94%) reported wearing masks inside school, stores, and salons; intermediate percentages (∼50%-85%) inside places of worship, bars/restaurants, and recreational settings; and few (<25%) in their or others’ homes. Approximately half reported daily close contact with students. Conclusions : As schools reopened in the COVID-19 pandemic, potential transmission opportunities arose through close contacts within and outside of school, along with suboptimal mask use by teachers and/or those around them. Our granular estimates underscore the importance of multi-layered mitigation strategies and can inform interventions and mathematical models addressing school-associated transmission

Programming errors in traversal programs over structured data

Traversal strategies \'a la Stratego (also \'a la Strafunski and 'Scrap Your Boilerplate') provide an exceptionally versatile and uniform means of querying and transforming deeply nested and heterogeneously structured data including terms in functional programming and rewriting, objects in OO programming, and XML documents in XML programming. However, the resulting traversal programs are prone to programming errors. We are specifically concerned with errors that go beyond conservative type errors; examples we examine include divergent traversals, prematurely terminated traversals, and traversals with dead code. Based on an inventory of possible programming errors we explore options of static typing and static analysis so that some categories of errors can be avoided. This exploration generates suggestions for improvements to strategy libraries as well as their underlying programming languages. Haskell is used for illustrations and specifications with sufficient explanations to make the presentation comprehensible to the non-specialist. The overall ideas are language-agnostic and they are summarized accordingly