Connecting polymer collapse and the onset of jamming.

Previous studies have shown that the interiors of proteins are densely packed, reaching packing fractions that are as large as those found for static packings of individual amino-acid-shaped particles. How can the interiors of proteins take on such high packing fractions given that amino acids are connected by peptide bonds and many amino acids are hydrophobic with attractive interactions? We investigate this question by comparing the structural and mechanical properties of collapsed attractive disk-shaped bead-spring polymers to those of three reference systems: static packings of repulsive disks, of attractive disks, and of repulsive disk-shaped bead-spring polymers. We show that the attractive systems quenched to temperatures below the glass transition T≪T_{g} and static packings of both repulsive disks and bead-spring polymers possess similar interior packing fractions. Previous studies have shown that static packings of repulsive disks are isostatic at jamming onset, i.e., the number of interparticle contacts N_{c} matches the number of degrees of freedom, which strongly influences their mechanical properties. We find that repulsive polymer packings are hypostatic at jamming onset (i.e., with fewer contacts than degrees of freedom) but are effectively isostatic when including stabilizing quartic modes, which give rise to quartic scaling of the potential energy with displacements along these modes. While attractive disk and polymer packings are often considered hyperstatic with excess contacts over the isostatic number, we identify a definition for interparticle contacts for which they can also be considered as effectively isostatic. As a result, we show that the mechanical properties (e.g., scaling of the potential energy with excess contact number and low-frequency contribution to the density of vibrational modes) of weakly attractive disk and polymer packings are similar to those of isostatic repulsive disk and polymer packings. Our results demonstrate that static packings generated via attractive collapse or compression of repulsive particles possess similar structural and mechanical properties.

A Symposium on the Clinic of the Future and Telehealth: Highlights and Future Directions.

Children's National Hospital held a virtual symposium on "The Clinic of the Future and Telehealth" in December 2020. The goal of the symposium was to explore future trends in these domains. We also discussed how the coronavirus disease 2019 (COVID-19) pandemic accelerated ongoing changes in healthcare. We explored what is on the horizon in these fields and how these changes might affect care delivery in the future. Specifically, we discussed the "Clinic of the Future" with clinical teams from genetics and metabolism, orthopedic surgery, and primary care while our telehealth discussion involved genetics and metabolism, psychiatry, and telerehabilitation. As one example, wearable technology could be adopted among primary care practices and drive a shift in outpatient care from center-based care to patient-based care. We also examined technological innovations in physical exam instruments, gait analysis, imaging integration, and cast technology that could modernize the orthopedic surgery clinic. Telemedicine has rapidly expanded among all fields of medicine, especially since the COVID-19 pandemic, and has spurred innovation to improve the effectiveness of virtual physician visits. The development of technology to improve the virtual physical exam, during a telemedicine visit, further increases the utility of online appointments and increases access to care in all specialties. The incorporation of photogrammetry technology, in genetics and metabolism dysmorphology exams, will offer standardized tracking of patients that could improve diagnosis and treatment. Psychiatry has found nearly equal efficacy in diagnosis and treatment with telehealth visits and the additional benefit of gaining insight in the setting of the patients' home. Robotics has become increasingly common in rehabilitation, which can now incorporate a gaming experience that can be remotely updated and increase engagement and adherence in pediatric patients. The continued exploration of new ideas promises to improve both in-person and virtual care options.