A dynamical model of a GRID market

We discuss potential market mechanisms for the GRID. A complete dynamical model of a GRID market is defined with three types of agents. Providers, middlemen and users exchange universal GRID computing units (GCUs) at varying prices. Providers and middlemen have strategies aimed at maximizing profit while users are 'satisficing' agents, and only change their behavior if the service they receive is sufficiently poor or overpriced. Preliminary results from a multi-agent numerical simulation of the market model shows that the distribution of price changes has a power law tail.Comment: 4 pages, 3 figure

Scaling behavior in steady-state contractile actomyosin network flow

Contractile actomyosin network flows are crucial for many cellular processes including cell division and motility, morphogenesis and transport. How local remodeling of actin architecture tunes stress production and dissipation and regulates large-scale network flow remains poorly understood. Here, we generate contractile actomyosin networks with rapid turnover in vitro, by encapsulating cytoplasmic Xenopus egg extracts into cell-sized 'water-in-oil' droplets. Within minutes, the networks reach a dynamic steady-state with continuous inward flow. The networks exhibit homogenous, density-independent contraction for a wide range of physiological conditions, indicating that the myosin-generated stress driving contraction is proportional to the effective network viscosity. We further find that the contraction rate approximately scales with the network turnover rate, but this relation breaks down in the presence of excessive crosslinking or branching. Our findings suggest that cells use diverse biochemical mechanisms to generate robust, yet tunable, actin flows by regulating two parameters: turnover rate and network geometry

Seeing into the Future: HeartMate 3 to the Systemic Right Ventricle in a Completely Blind Patient with Congenitally-corrected Transposition of the Great Arteries

A 24-year-old, blind male with congenitally-corrected transposition of the great arteries and systemic right ventricular failure presented with New York Heart Association class IV heart failure despite home inotropic therapy. He was not a transplant candidate due to psychosocial issues. He underwent a successful HeartMate 3 (Abbott Laboratories) placement with the implementation of techniques to guide home ventricular assist device care despite blindness

Centering and symmetry breaking in confined contracting actomyosin networks

Centering and decentering of cellular components is essential for internal organization of cells and their ability to perform basic cellular functions such as division and motility. How cells achieve proper localization of their components is still not well-understood, especially in large cells such as oocytes. Here, we study actin-based positioning mechanisms in artificial cells with persistently contracting actomyosin networks, generated by encapsulating cytoplasmic Xenopus egg extracts into cell-sized water-in-oil droplets. We observe size-dependent localization of the contraction center, with a symmetric configuration in larger cells and a polar one in smaller cells. In the symmetric state, the contraction center is actively centered, via a hydrodynamic mechanism based on Darcy friction between the contracting network and the surrounding cytoplasm. During symmetry breaking, transient attachments to the cell boundary drive the contraction center to a polar location near the droplet boundary. Our findings demonstrate a robust, yet tunable, mechanism for subcellular localization

Comparison of Body Composition to Strength, Balance, and Function in Parkinson’s Disease: A Pilot Study

PURPOSE: To determine the relationship between body composition and strength, balance, and function in people with Parkinson\u27s disease (PD). METHODS: All subjects signed written consent to participate in this IRB approved study. Twelve subjects with PD underwent dual x-ray absorptiometry (DXA) followed by strength, balance, and functional measures: 1 repetition maximum (RM) leg press, 30 second chair stand (30 CST), the Fullerton Advanced Balance test (FAB), and the MiniBestest (MB) in a randomized order. An independent t-test was used for outcomes between gender. Pearson’s correlation was used to determine a relationship between body composition and all outcome measures. Significance was set at 0.05. RESULTS: Six men (65.7 ± 5.9), and 6 women (72.7 ± 5.1) were analyzed. There was no significant difference in the MB, FAB, or 30 CST between gender (p = 0.69, p = 0.902, p = 0.361). In men, there was a strong negative correlation between body fat % (BF%) and the MB (-0.926, p = 0.008) and FAB scores (-0.743, p = 0.09). A moderate negative correlation between BF% and TUG (0.428, p = 0.397) and 30 CST (-0.495, p = 0.318). No correlation was found between total lean body mass (LBM) and the MB, TUG, or FAB, but a moderate correlation between LBM and 30 CST (0.253, p = 0.628) was found. In women, there was a moderate negative correlation between BF% and the TUG (-0.479, p = 0.337), and a low negative correlation between BF% and the MB (-0.218, p = 0.678), FAB (-0.246, p = 0.638), and 30 CST (-0.239, p = 0.649). A moderate negative correlation was found between LBM and the TUG (-0.475, p = 0.341), FAB (-0.539, p = 0.27), and 1RM (-0.457, p = 0.362). CONCLUSION: Body fat % in both genders showed negative effects on strength, balance and function, where LBM has mixed results by gender. These findings highlight the importance of body composition in assessing and managing strength, balance, and function in people with PD

Synergistic drug combinations from electronic health records and gene expression.

ObjectiveUsing electronic health records (EHRs) and biomolecular data, we sought to discover drug pairs with synergistic repurposing potential. EHRs provide real-world treatment and outcome patterns, while complementary biomolecular data, including disease-specific gene expression and drug-protein interactions, provide mechanistic understanding.MethodWe applied Group Lasso INTERaction NETwork (glinternet), an overlap group lasso penalty on a logistic regression model, with pairwise interactions to identify variables and interacting drug pairs associated with reduced 5-year mortality using EHRs of 9945 breast cancer patients. We identified differentially expressed genes from 14 case-control human breast cancer gene expression datasets and integrated them with drug-protein networks. Drugs in the network were scored according to their association with breast cancer individually or in pairs. Lastly, we determined whether synergistic drug pairs found in the EHRs were enriched among synergistic drug pairs from gene-expression data using a method similar to gene set enrichment analysis.ResultsFrom EHRs, we discovered 3 drug-class pairs associated with lower mortality: anti-inflammatories and hormone antagonists, anti-inflammatories and lipid modifiers, and lipid modifiers and obstructive airway drugs. The first 2 pairs were also enriched among pairs discovered using gene expression data and are supported by molecular interactions in drug-protein networks and preclinical and epidemiologic evidence.ConclusionsThis is a proof-of-concept study demonstrating that a combination of complementary data sources, such as EHRs and gene expression, can corroborate discoveries and provide mechanistic insight into drug synergism for repurposing

Self-organized stress patterns drive state transitions in actin cortices

Biological functions rely on ordered structures and intricately controlled collective dynamics. This order in living systems is typically established and sustained by continuous dissipation of energy. The emergence of collective patterns of motion is unique to nonequilibrium systems and is a manifestation of dynamic steady states. Mechanical resilience of animal cells is largely controlled by the actomyosin cortex. The cortex provides stability but is, at the same time, highly adaptable due to rapid turnover of its components. Dynamic functions involve regulated transitions between different steady states of the cortex. We find that model actomyosin cortices, constructed to maintain turnover, self-organize into distinct nonequilibrium steady states when we vary cross-link density. The feedback between actin network structure and organization of stress-generating myosin motors defines the symmetries of the dynamic steady states. A marginally cross-linked state displays divergence-free long-range flow patterns. Higher cross-link density causes structural symmetry breaking, resulting in a stationary converging flow pattern. We track the flow patterns in the model actomyosin cortices using fluorescent single-walled carbon nanotubes as novel probes. The self-organization of stress patterns we have observed in a model system can have direct implications for biological functions