Precarious Housing Associated with Unsuppressed Viral load, sub-optimal Access to HIV Treatment and Unmet Health care Needs, Among Women Living with HIV in Metro Vancouver, Canada.

We investigated associations between (1) housing status (four categories measuring housing stability) and outcomes along the HIV care continuum (not currently on antiretroviral therapy [ART]; sub-optimal ART adherence [< 95% in the last 3-4 weeks]; unsuppressed viral load [> 200 copies/ml], median CD4 < 200 in the last six months), and (2) housing status and unmet primary, dental and mental health care needs in the last six months among WLWH. Housing status was defined according to the Canadian Definition of Homelessness and had four categories: unsheltered (i.e., living in ≥ 1 unsheltered location [e.g., street, abandoned buildings]), unstable (i.e., living in ≥ 1 unstable location [e.g., shelter, couch surfing]), supportive housing (i.e., only living in supportive housing), and stable housing (i.e., only living in one's own housing; reference). At baseline, in the last six months, 47.3% of participants reported unstable housing, followed by 24.4% unsheltered housing, 16.4% stable housing, and 11.9% supportive housing. Overall, 19.1% of the full sample (N = 336, 2010-2019) reported not currently on ART; among participants on ART, 28.0% reported sub-optimal ART adherence. Overall, 32.1% had recent unsuppressed viral load. Among a subsample (n = 318, 2014-2019), 15.7% reported unmet primary care needs, 26.1% unmet dental care needs, and 16.4% unmet mental health care needs. In adjusted models, being unsheltered (vs. stable housing) was associated with not currently on ART, unsuppressed viral load, and unmet primary and dental care needs. Housing and health services need to be developed with and for WLWH to address structural inequities and fulfill basic rights to housing and health.

Thermal Transport through Polymer-Linked Gold Nanoparticles.

Polymer-nanoparticle networks have potential applications in molecular electronics and nanophononics. In this work, we use all-atom molecular dynamics to reveal the fundamental mechanisms of thermal transport in polymer-linked gold nanoparticle (AuNP) dimers at the molecular level. Attachment of the polymers to AuNPs of varying sizes allows the determination of effects from the flexibility of the chains when their ends are not held fixed. We report heat conductance (G) values for six polymers-viz. polyethylene, poly(p-phenylene), polyacene, polyacetylene, polythiophene, and poly(3,4-ethylenedioxythiophene)-that represent a broad range of stiffness. We address the multimode effects of polymer type, AuNP size, polymer chain length, polymer conformation, system temperature, and number of linking polymers on G. The combination of the mechanisms for phonon boundary scattering and intrinsic phonon scattering has a strong effect on G. We find that the values of G are larger for conjugated polymers because of the stiffness in their backbones. They are also larger in the low-temperature region for all polymers owing to the quenching of segmental rotations at low temperature. Our simulations also suggest that the total G is additive as the number of linking polymers in the AuNP dimer increases from 1 to 2 to 3.

The prevalence and social-structural correlates of housing status among women living with HIV in Vancouver, Canada.

BACKGROUND: Women living with HIV (WLWH) experience numerous social and structural barriers to stable housing, with substantial implications for access to health care services. This study is the first to apply the Canadian Definition of Homelessness (CDOH), an inclusive national guideline, to investigate the prevalence and correlates of housing status among WLWH in Metro Vancouver, Canada. METHODS: Our study utilized data from a longitudinal open cohort of cisgender and trans WLWH aged 14 years and older, in 2010-2019. Cross-sectional descriptive statistics of the prevalence of housing status and other social and structural variables were summarized for the baseline visits. Bivariate and multivariable logistic regression analyses were conducted using generalized linear mixed models (GLMM) for repeated measures to investigate the relationship between social and structural correlates and housing status among WLWH. RESULTS: The study included 336 participants with 1930 observations over 9 years. Housing status derived from CDOH included four categories: unsheltered, unstable, supportive housing, and stable housing (reference). Evidence suggested high levels of precarious housing, with 24% of participants reporting being unsheltered, 47% reporting unstable housing, 11.9% reporting supportive housing, and 16.4% reporting stable housing in the last six months at baseline. According to the multivariable models, living in the Downtown Eastside (DTES) neighbourhood of Metro Vancouver, hospitalization, physical/sexual violence, and stimulant use were associated with being unsheltered, compared to stable housing; DTES residence, hospitalization, and physical/sexual violence were associated with unstable housing; DTES residence and stimulant use were associated with living in supportive housing. CONCLUSION: Complex social-structural inequities are associated with housing instability among WLWH. In addition to meeting basic needs for living, to facilitate access to housing among WLWH, housing options that are gender-responsive and gender-inclusive and include trauma- and violence-informed principles, low-barrier requirements, and strong connections with supportive harm reduction services are critical.

Nanoscale 3D spatial addressing and valence control of quantum dots using wireframe DNA origami.

Control over the copy number and nanoscale positioning of quantum dots (QDs) is critical to their application to functional nanomaterials design. However, the multiple non-specific binding sites intrinsic to the surface of QDs have prevented their fabrication into multi-QD assemblies with programmed spatial positions. To overcome this challenge, we developed a general synthetic framework to selectively attach spatially addressable QDs on 3D wireframe DNA origami scaffolds using interfacial control of the QD surface. Using optical spectroscopy and molecular dynamics simulation, we investigated the fabrication of monovalent QDs of different sizes using chimeric single-stranded DNA to control QD surface chemistry. By understanding the relationship between chimeric single-stranded DNA length and QD size, we integrated single QDs into wireframe DNA origami objects and visualized the resulting QD-DNA assemblies using electron microscopy. Using these advances, we demonstrated the ability to program arbitrary 3D spatial relationships between QDs and dyes on DNA origami objects by fabricating energy-transfer circuits and colloidal molecules. Our design and fabrication approach enables the geometric control and spatial addressing of QDs together with the integration of other materials including dyes to fabricate hybrid materials for functional nanoscale photonic devices.

Molecular Structure of Single-Stranded DNA on the ZnS Surface of Quantum Dots.

DNA-based nanoparticle assemblies have emerged as leading candidates in the development of bioimaging materials, photonic devices, and computing materials. Here, we combine atomistic simulations and experiments to characterize the wrapping mechanism of chimeric single-stranded DNA (ssDNA) on CdSe-ZnS (core-shell) quantum dots (QDs) at different ratios of the phosphorothioate (PS) modification of the bases. We use an implicit solvent, all-atom ssDNA model to match the experimentally calculated ssDNA conformation at low salt concentrations. Through simulation, we find that 3-mercaptopropionic acid (MPA) induces electrostatic repulsion and O-(2-mercaptoethyl)-Ó-methyl-hexa (ethylene glycol) (mPEG) induces steric exclusion, and both reduce the binding affinity of ssDNA. In both simulation and experiment, we find that ssDNA is closer to the QD surface when the QD size is larger. The effect of the PS-base ratio on the conformation of ssDNA is also elaborated in this work. We found through MD simulations, and confirmed by transmission electron microscopy, that the maximum valence numbers are 1, 2, and 3 on QDs of 6, 9, and 14 nm in diameter, respectively. We conclude that the maximum ssDNA valence number is linearly related to the QD size, n ∝ R, and justify this finding through an electrostatic repulsion mechanism.

Contagion dynamics in self-organized systems of self-propelled agents.

We investigate the susceptible-infectious-recovered contagion dynamics in a system of self-propelled particles with polar alignment. Using agent-based simulations, we analyze the outbreak process for different combinations of the spatial parameters (alignment strength and Peclet number) and epidemic parameters (infection-lifetime transmissibility and duration of the individual infectious period). We show that the emerging spatial features strongly affect the contagion process. The ordered homogeneous states greatly disfavor infection spreading, due to their limited mixing, only achieving large outbreaks for high values of the individual infectious duration. The disordered homogeneous states also present low contagion capabilities, requiring relatively high values of both epidemic parameters to reach significant spreading. Instead, the inhomogeneous ordered states display high outbreak levels for a broad range of parameters. The formation of bands and clusters in these states favor infection propagation through a combination of processes that develop inside and outside of these structures. Our results highlight the importance of self-organized spatiotemporal features in a variety of contagion processes that can describe epidemics or other propagation dynamics, thus suggesting new approaches for understanding, predicting, and controlling their spreading in a variety of self-organized biological systems, ranging from bacterial swarms to animal groups and human crowds.

Phases and homogeneous ordered states in alignment-based self-propelled particle models.

We study a set of models of self-propelled particles that achieve collective motion through similar alignment-based dynamics, considering versions with and without repulsive interactions that do not affect the heading directions. We explore their phase space within a broad range of values of two nondimensional parameters (coupling strength and Peclet number), characterizing their polarization and degree of clustering. The resulting phase diagrams display equivalent, similarly distributed regions for all models with repulsion. The diagrams without repulsion exhibit differences, in particular for high coupling strengths. We compare the boundaries and representative states of all regions, identifying various regimes that had not been previously characterized. We analyze in detail three types of homogeneous polarized states, comparing them to existing theoretical and numerical results by computing their velocity and density correlations, giant number fluctuations, and local order-density coupling. We find that they all deviate in one way or another from the theoretical predictions, attributing these differences either to the remaining inhomogeneities or to finite-size effects. We discuss our results in terms of the generic or specific features of each model, their thermodynamic limit, and the high mixing and low mixing regimes. Our study provides a broad, overarching perspective on the multiple phases and states found in alignment-based self-propelled particle models.

Building blocks for autonomous computing materials: Dimers, trimers, and tetramers.

Autonomous computing materials for data storage and computing offer an opportunity for next generation of computing devices. Patchy nanoparticle networks, for example, have been suggested as potential candidates for emulating neuronal networks and performing brain-like computing. Here, we use molecular dynamics (MD) simulations to show that stable dimers, trimers, and tetramers can be built from citrate capped gold nanoparticles (cit-AuNPs) linked by poly(allylamine hydrochloride) (PAH) chains. We use different lengths of PAHs to build polymer-networked nanoparticle assemblies that can emulate a complex neuronal network linked by axons of varying lengths. We find that the tetramer structure can accommodate up to 11 different states when the AuNP pairs are connected by either of two polymer linkers, PAH200 and PAH300. We find that the heavy AuNPs contribute to the assembly's structure stability. To further illustrate the stability, the AuNP-AuNP distances in dimer, trimer, and tetramer structures are reduced by steering the cit-AuNPs closer to each other. At different distances, these steered structures are all locally stable in a 10 ns MD simulation time scale because of their connection to the AuNPs. We also find that the global potential energy minimum is at short AuNP-AuNP distances where AuNPs collapse because the -NH3 + and -COO- attraction reduces the potential energy. The stability and application of these fundamental structures remain to be further improved through the use of alternative polymer linkers and nanoparticles.

Engineered nanoparticle network models for autonomous computing.

Materials that exhibit synaptic properties are a key target for our effort to develop computing devices that mimic the brain intrinsically. If successful, they could lead to high performance, low energy consumption, and huge data storage. A 2D square array of engineered nanoparticles (ENPs) interconnected by an emergent polymer network is a possible candidate. Its behavior has been observed and characterized using coarse-grained molecular dynamics (CGMD) simulations and analytical lattice network models. Both models are consistent in predicting network links at varying temperatures, free volumes, and E-field (E⃗) strengths. Hysteretic behavior, synaptic short-term plasticity and long-term plasticity-necessary for brain-like data storage and computing-have been observed in CGMD simulations of the ENP networks in response to E-fields. Non-volatility properties of the ENP networks were also confirmed to be robust to perturbations in the dielectric constant, temperature, and affine geometry.