3D PRINTING IN LOW RESOURCE HEALTHCARE SETTINGS: ANALYSIS OF POTENTIAL IMPLEMENTATIONS

3D printing has gained significant momentum in the past ten years, and its unique advantages make it especially ideal for use in low resource healthcare settings, where many designs have already been successfully implemented. Yet, little has been studied on how 3D printing can be sustainably and functionally implemented in low resource healthcare systems as a manufacturing practice. In this report, three business models are proposed for this implementation: In-House Operator, Independent Operator, and Print Farm. These models were then tested over four months in Kisumu county, Kenya, at two workshops and seven public hospitals. I worked with local medical professionals, engineers, and government officials to create and test 3D printed medical products. Human centered design criteria were used to assess the models. All three business models proved to have individual distinct benefits and challenges for application. However, specific contextual considerations are necessary to decide which implementation is the most sustainable. Through these findings, others may begin implementing more robust 3D printing systems in low resource healthcare contexts throughout the globe

Shear wave structure of a transect of the Los Angeles basin from multimode surface waves and H/V spectral ratio analysis

We use broad-band stations of the ‘Los Angeles Syncline Seismic Interferometry Experiment’ (LASSIE) to perform a joint inversion of the Horizontal to Vertical spectral ratios (H/V) and multimode dispersion curves (phase and group velocity) for both Rayleigh and Love waves at each station of a dense line of sensors. The H/V of the autocorrelated signal at a seismic station is proportional to the ratio of the imaginary parts of the Green’s function. The presence of low-frequency peaks (∼0.2 Hz) in H/V allows us to constrain the structure of the basin with high confidence to a depth of 6 km. The velocity models we obtain are broadly consistent with the SCEC CVM-H community model and agree well with known geological features. Because our approach differs substantially from previous modelling of crustal velocities in southern California, this research validates both the utility of the diffuse field H/V measurements for deep structural characterization and the predictive value of the CVM-H community velocity model in the Los Angeles region. We also analyse a lower frequency peak (∼0.03 Hz) in H/V and suggest it could be the signature of the Moho. Finally, we show that the independent comparison of the H and V components with their corresponding theoretical counterparts gives information about the degree of diffusivity of the ambient seismic field

Autoregressive fragment-based diffusion for pocket-aware ligand design

In this work, we introduce AutoFragDiff, a fragment-based autoregressive diffusion model for generating 3D molecular structures conditioned on target protein structures. We employ geometric vector perceptrons to predict atom types and spatial coordinates of new molecular fragments conditioned on molecular scaffolds and protein pockets. Our approach improves the local geometry of the resulting 3D molecules while maintaining high predicted binding affinity to protein targets. The model can also perform scaffold extension from user-provided starting molecular scaffold.Comment: Accepted, NeurIPS 2023 Generative AI and Biology Workshop. OpenReview: https://openreview.net/forum?id=E3HN48zja

Foreshock sequence of the 1992 Landers, California, earthquake and its implications for earthquake nucleation

The June 28, 1992, Landers, California, earthquake(Mw=7.3) was preceded for about 7 hours by a foreshock sequence consisting of at least 28 events. In this study we examine the geometry and temporal development of the foreshocks using high-precision locations based on cross correlation of waveforms recorded at nearby stations. By aligning waveforms, rather than trying to obtain travel time picks for each event independently, we are able to improve the timing accuracy greatly and to make very accurate travel time picks even for emergent arrivals. We perform a joint relocation using the improved travel times and reduce the relative location errors to less than 100m horizontally and less than 200m vertically. With the improved locations the geometry of the foreshock sequence becomes clear. The Landers foreshocks occurred at a fight step of about 500m in the mainshock fault plane. The nucleation zone as defined by the foreshock sequence is southeast trending to the south and nearly north trending to the north of the right step. This geometry is confirmed by the focal mechanisms of the foreshock sequence, which are rightlateral and follow the trend as determined by the foreshock locations on the two straight segments of the fault, and are rotated clockwise for foreshocks that occur within the step. The extent of the foreshock sequence is approximately 1 km both vertically and horizontally. Modeling of the Coulomb stress changes due to all previous foreshocks indicates that the foreshocks probably did not trigger each other. This result is particularly clear for the Mw=4.4 immediate foreshock. Since stress transfer in the sequence appears not to have played a significant role in its development, we infer an underlying aseismic nucleation process, probably aseismic creep. Other studies have shown that earthquake nucleation may be controlled by fault zone irregularities. This appears to be true in the case of the Landers earthquake, although the size of the irregularity is so small that it is not detectable by standard location techniques