Exact Solutions for Solitary Waves in a Bose-Einstein Condensate under the Action of a Four-Color Optical Lattice

We address dynamics of Bose-Einstein condensates (BECs) loaded into a one-dimensional four-color optical lattice (FOL) potential with commensurate wavelengths and tunable intensities. This configuration lends system-specific symmetry properties. The analysis identifies specific multi-parameter forms of the FOL potential which admits exact solitary-wave solutions. This newly found class of potentials includes more particular species, such as frustrated double-well superlattices, and bichromatic and three-color lattices, which are subject to respective symmetry constraints. Our exact solutions provide options for controllable positioning of density maxima of the localized patterns, and tunable Anderson-like localization in the frustrated potential. A numerical analysis is performed to establish dynamical stability and structural stability of the obtained solutions, which makes them relevant for experimental realization. The newly found solutions offer applications to the design of schemes for quantum simulations and processing quantum information.

Predictive modeling of COVID-19 case growth highlights evolving racial and ethnic risk factors in Tennessee and Georgia

IntroductionThe SARS-CoV-2 (COVID-19) pandemic has exposed the need to understand the risk drivers that contribute to uneven morbidity and mortality in US communities. Addressing the community-specific social determinants of health (SDOH) that correlate with spread of SARS-CoV-2 provides an opportunity for targeted public health intervention to promote greater resilience to viral respiratory infections.MethodsOur work combined publicly available COVID-19 statistics with county-level SDOH information. Machine learning models were trained to predict COVID-19 case growth and understand the social, physical and environmental risk factors associated with higher rates of SARS-CoV-2 infection in Tennessee and Georgia counties. Model accuracy was assessed comparing predicted case counts to actual positive case counts in each county.ResultsThe predictive models achieved a mean R2 of 0.998 in both states with accuracy above 90% for all time points examined. Using these models, we tracked the importance of SDOH data features over time to uncover the specific racial demographic characteristics strongly associated with COVID-19 incidence in Tennessee and Georgia counties. Our results point to dynamic racial trends in both states over time and varying, localized patterns of risk among counties within the same state. For example, we find that African American and Asian racial demographics present comparable, and contrasting, patterns of risk depending on locality.ConclusionThe dichotomy of demographic trends presented here emphasizes the importance of understanding the unique factors that influence COVID-19 incidence. Identifying these specific risk factors tied to COVID-19 case growth can help stakeholders target regional interventions to mitigate the burden of future outbreaks.

A METHOD FOR INTEGRATIVE ANALYSIS OF LOCAL AND GLOBAL BRAIN DYNAMICS

The most common pipelines for studying time-varying network connectivity in resting state functional magnetic resonance imaging (rs-fMRI) operate at the whole brain level, capturing a small discrete set of 'states' that best represent time-resolved joint measures of connectivity over all network pairs in the brain. This whole-brain hidden Markov model (HMM) approach 'uniformizes' the dynamics over what is typically more than 1000 pairs of networks, forcing each time-resolved high-dimensional observation into its best-matched high-dimensional state. While straightforward and convenient, this HMM simplification obscures functional and temporal nonstationarities that could reveal systematic, informative features of resting state brain dynamics at a more granular scale. We introduce a framework for studying functionally localized dynamics that intrinsically embeds them within a whole-brain HMM frame of reference. The approach is validated in a large rs-fMRI schizophrenia study where it identifies group differences in localized patterns of entropy and dynamics that help explain consistently observed differences between schizophrenia patients and controls in occupancy of whole-brain dFNC states more mechanistically.

Cells exploit a phase transition to mechanically remodel the fibrous extracellular matrix

Through mechanical forces, biological cells remodel the surrounding collagen network, generating striking deformation patterns. Tethers—tracts of high densification and fibre alignment—form between cells, thinner bands emanate from cell clusters. While tethers facilitate cell migration and communication, how they form is unclear. Combining modelling, simulation and experiment, we show that tether formation is a densification phase transition of the extracellular matrix, caused by buckling instability of network fibres under cell-induced compression, featuring unexpected similarities with martensitic microstructures. Multiscale averaging yields a two-phase, bistable continuum energy landscape for fibrous collagen, with a densified/aligned second phase. Simulations predict strain discontinuities between the undensified and densified phase, which localizes within tethers as experimentally observed. In our experiments, active particles induce similar localized patterns as cells. This shows how cells exploit an instability to mechanically remodel the extracellular matrix simply by contracting, thereby facilitating mechanosensing, invasion and metastasis.

Koala Retrovirus in Northern Australia Shows a Mixture of Stable Endogenization and Exogenous Lineage Diversification within Fragmented Koala Populations

The koala population in northern Australia has become increasingly fragmented due to natural and man-made barriers and interventions. This situation has created a unique opportunity to study both endogenous and exogenous koala retrovirus (KoRV). To determine the impact that population isolation has had on KoRV diversity in Queensland, 272 koalas from six fragmented koala populations were profiled for their KoRV provirus across two natural biogeographical barriers (the St Lawrence Gap and the Brisbane Valley Barrier), one man-made geographical barrier (the city of Brisbane) and two translocation events (the single movement of koalas to an island and the repeated movement of koalas into a koala sanctuary). Analysis revealed that all koalas tested were KoRV-A positive, with 90 - 96% of the detected KoRV provirus from each koala representing a single, likely endogenous, KoRV-A strain. The next most abundant proviral sequence was a defective variant of the dominant KoRV-A strain, accounting for 3 – 10% of detected provirus. The remaining KoRV provirus represented expected exogenous strains of KoRV and included geographically localized patterns of KoRV-B, -C, -D, -F, -G, and -I. These results indicate that lineage diversification of exogenous KoRV is actively ongoing. In addition, comparison of KoRV provirus within known dam-sire-joey family groups from the koala sanctuary revealed that joeys consistently had KoRV proviral patterns more similar to their dams than their sires in KoRV-B, -C and -D provirus composition. Collectively, this study highlights both the consistency of endogenous KoRV and the diversity of exogenous KoRV across the fragmented koala populations in northern Australia. IMPORTANCE KoRV infection has become a permanent part of koalas in northern Australia. With KoRV presence and abundance linked to more severe chlamydial disease and neoplasia in these koalas, understanding how KoRV exists throughout an increasingly fragmented koala population is a key first step in designing conservation and management strategies. This survey of KoRV provirus in Queensland koalas indicates that endogenous KoRV provirus is ubiquitous and consistent throughout the state while exogenous KoRV provirus is diverse and distinct in fragmented koala populations. Understanding the prevalence and impact of both endogenous and exogenous KoRV will be needed to ensure a future for all koala populations.