Experimental determination of a time–temperature-transformation diagram of the undercooled Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy using the containerless electrostatic levitation processing technique

High temperature high vacuum electrostatic levitation was used to determine the complete time–temperature–transformation (TTT) diagram of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass forming alloy in the undercooled liquid state. This is the first report of experimental data on the crystallization kinetics of a metallic system covering the entire temperature range of the undercooled melt down to the glass transition temperature. The measured TTT diagram exhibits the expected "C" shape. Existing models that assume polymorphic crystallization cannot satisfactorily explain the experimentally obtained TTT diagram. This originates from the complex crystallization mechanisms that occur in this bulk glass-forming system, involving large composition fluctuations prior to crystallization as well as phase separation in the undercooled liquid state below 800 K

Metallic glass formation in highly undercooled Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 during containerless electrostatic levitation processing

Various sample sizes of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 with masses up to 80 mg were undercooled below Tg (the glass transition temperature) while electrostatically levitated. The final solidification product of the sample was determined by x-ray diffraction to have an amorphous phase. Differential scanning calorimetry was used to confirm the absence of crystallinity in the processes sample. The amorphous phase could be formed only after heating the samples above the melting temperature for extended periods of time in order to break down and dissolve oxides or other contaminants which would otherwise initiate heterogeneous nucleation of crystals. Noncontact pyrometry was used to monitor the sample temperature throughout processing. The critical cooling rate required to avoid crystallization during solidification of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy fell between 0.9 and 1.2 K/s

Hemispherical total emissivity and specific heat capacity of deeply undercooled Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 melts

High-temperature high-vacuum electrostatic levitation (HTHVESL) and differential scanning calorimetry (DSC) were combined to determine the hemispherical total emissivity epsilon T, and the specific heat capacity cp, of the undercooled liquid and throughout the glass transition of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass forming alloy. The ratio of cp/epsilon T as a function of undercooling was determining from radiative cooling curves measured in the HTHVESL. Using specific heat capacity data obtained by DSC investigations close to the glass transition and above the melting point, epsilon T and cp were separated and the specific heat capacity of the whole undercooled liquid region was determined. Furthermore, the hemispherical total emissivity of the liquid was found to be about 0.22 at 980 K. On undercooling the liquid, the emissivity decreases to approximately 0.18 at about 670 K, where the undercooled liquid starts to freeze to a glass. No significant changes of the emissivity are observed as the alloy undergoes the glass transition

Multi-contrast imaging and digital refocusing on a mobile microscope with a domed LED array

We demonstrate the design and application of an add-on device for improving the diagnostic and research capabilities of CellScope--a low-cost, smartphone-based point-of-care microscope. We replace the single LED illumination of the original CellScope with a programmable domed LED array. By leveraging recent advances in computational illumination, this new device enables simultaneous multi-contrast imaging with brightfield, darkfield, and phase imaging modes. Further, we scan through illumination angles to capture lightfield datasets, which can be used to recover 3D intensity and phase images without any hardware changes. This digital refocusing procedure can be used for either 3D imaging or software-only focus correction, reducing the need for precise mechanical focusing during field experiments. All acquisition and processing is performed on the mobile phone and controlled through a smartphone application, making the computational microscope compact and portable. Using multiple samples and different objective magnifications, we demonstrate that the performance of our device is comparable to that of a commercial microscope. This unique device platform extends the field imaging capabilities of CellScope, opening up new clinical and research possibilities

An Intervention for the Transition From Pediatric or Adolescent to Adult-Oriented HIV Care: Protocol for the Development and Pilot Implementation of iTransition

Background: In the United States, adolescents and young adults are disproportionately affected by HIV and have poorer HIV-related health outcomes than adults. Health care transition (HCT) from pediatric or adolescent to adult-oriented HIV care is associated with disruptions to youths' care retention, medication adherence, and viral suppression. However, no evidence-based interventions exist to improve HCT outcomes for youth living with HIV. Objective: There are 2 phases of this project. Phase 1 involves the iterative development and usability testing of a Social Cognitive Theory-based mobile health (mHealth) HIV HCT intervention (iTransition). In phase 2, we will conduct a pilot implementation trial to assess iTransition's feasibility and acceptability and to establish preliminary efficacy among youth and provider participants. Methods: The iterative phase 1 development process will involve in-person and virtual meetings and a design team comprising youth living with HIV and health care providers. The design team will both inform the content and provide feedback on the look, feel, and process of the iTransition intervention. In phase 2, we will recruit 100 transition-eligible youth across two clinical sites in Atlanta, Georgia, and Philadelphia, Pennsylvania, to participate in the historical control group (n=50; data collection only) or the intervention group (n=50) in a pilot implementation trial. We will also recruit 28 provider participants across the pediatric or adolescent and adult clinics at the two sites. Data collection will include electronic medical chart abstraction for clinical outcomes as well as surveys and interviews related to demographic and behavioral characteristics; Social Cognitive Theory constructs; and intervention feasibility, acceptability, and use. Analyses will compare historical control and intervention groups in terms of HCT outcomes, including adult care linkage (primary), care retention, and viral suppression (secondary). Interview data will be analyzed using content analysis to understand the experience with use and acceptability. Results: Phase 1 (development) of iTransition research activities began in November 2019 and is ongoing. The data collection for the phase 2 pilot implementation trial is expected to be completed in January 2023. Final results are anticipated in summer 2023. Conclusions: The development and pilot implementation trial of the iTransition intervention will fill an important gap in understanding the role of mHealth interventions to support HCT outcomes for youth living with HIV