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High Performance Computing to Quantify the Evolution of Microscopic Concentration Gradients During Flash Processing

During the Flash process, the cross section of a plain-carbon or a low-alloy steel is austenitized through rapid heating and transformed on rapid cooling to a predominantly martensite + bainite structure with small amounts of retained austenite. Unlike conventional heat treating, homogeneity is intentionally avoided during Flash processing of steels. The Flash process assembly consists of a pair of rolls that transfer the steel sheets through the heating and cooling stage of the thermal cycle. The initial microstructure of the steel consists of ferrite (body-centered cubic iron) + carbide ((Fe,X)mCn) mixture. The heating rate through the peak temperature is a function of temperature and reaches a peak of about 300-400K/s and the cooling rate has a maximum value of 3000-4000K/s. The on-heating phase transformations include carbide dissolution, austenite (face-centered cubic iron) nucleation and growth, and diffusion of carbon and other substitutional elements in the steel. The on-cooling phase transformations include formation of martensite (body-centered tetragonal phase containing supersaturated solute) and bainite (ferrite plates with or without fine carbides). In this project, the focus is on Fe-C-Cr steels that are currently Flash processed for armor applications. The modeling effort proposed here will help optimize the Flash thermal cycle for these low alloy steels to achieve the target performance, which is an ongoing effort at SFP Works. A significant feature of Flash processed Fe-C-Cr steels is the presence of scatter in the through-thickness in the sheet. The variability in hardness results from a variability in the bainite + martensite microstructure that is sensitive to the local chemical concentration of C and Cr. Such a chemical inhomogeneity is intentionally obtained in the Flash process. Although such a microstructural gradient is presumably responsible for the exceptional properties of the Flash processed steel, it is very important to quantify the gradients as a function of Flash variabilities in processing parameters and the input microstructure. Understanding the mechanistic pathway that leads to microstructural gradients could be ground-breaking and instrumental for achieving better process control and optimized microstructural state to meet application-specific strength-ductility requirements. Since the final microstructure depends on setting up precise solute concentration gradients through a rapid heating process, and transforming these regions into various phases, it is important to understand how small changes in steel chemistry, input microstructure (carbide size and distribution), and process variables (Flash thermal cycle) will impact the solute concentration gradients.

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Treatment barriers in PANS/PANDAS: Observations from eleven health care provider families.

Pediatric acute-onset neuropsychiatric syndrome (PANS) and pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS) are severe but highly treatable postinfectious inflammatory brain conditions. Despite published diagnostic and treatment guidelines for this condition, there are long delays in obtaining appropriate care. The reasons for these delays are poorly understood. We sought to identify health care system barriers to timely treatment by examining cases of PANDAS/PANS occurring in children of health care professionals. We recruited families via e-mail request through the PANDAS Physicians Network. Participating parents completed a structured questionnaire and provided a written case description. Eleven families completed data collection, representing a broad spectrum of disease (child disease onset age 4-15, 7 males/4 females, mild to severe). Parents included 11 physicians, 2 mental health professionals, 2 nurses, and a PharmD. Nine cases (82%) had "very delayed" diagnosis and treatment (>4 weeks after onset). The most commonly encountered causes for treatment delay were clinician lack of awareness (82%), clinician skepticism (82%), overdependence on diagnostic testing (91%), and out-of-pocket expenses >$100 US (82%). Other common challenges included difficulties finding a provider to spearhead care (64%), psychological misdiagnosis (55%), and children's suppression of behaviors during assessments (55%). We found numerous barriers to treatment of PANDAS/PANS among children of health care providers. Our findings suggest that even among the medically sophisticated, PANDAS/PANS diagnosis and treatment remains challenging. Improvement in PANDAS/PANS education of clinicians who may encounter children with this disorder is 1 key step toward addressing our identified barriers. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

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