• Least squares estimation of spatial autoregressive models for large-scale social networks

  Huang, Danyang; Lan, Wei; Zhang, Hao Helen; Wang, Hansheng; Univ Arizona (INST MATHEMATICAL STATISTICS, 2019)

  Due to the rapid development of various social networks, the spatial autoregressive (SAR) model is becoming an important tool in social network analysis. However, major bottlenecks remain in analyzing largescale networks (e.g., Facebook has over 700 million active users), including computational scalability, estimation consistency, and proper network sampling. To address these challenges, we propose a novel least squares estimator (LSE) for analyzing large sparse networks based on the SAR model. Computationally, the LSE is linear in the network size, making it scalable to analysis of huge networks. In theory, the LSE is root n-consistent and asymptotically normal under certain regularity conditions. A new LSE-based network sampling technique is further developed, which can automatically adjust autocorrelation between sampled and unsampled units and hence guarantee valid statistical inferences. Moreover, we generalize the LSE approach for the classical SAR model to more complex networks associated with multiple sources of social interaction effect. Numerical results for simulated and real data are presented to illustrate performance of the LSE.
• Revisiting the maximum mass of differentially rotating neutron stars in general relativity with realistic equations of state

  Espino, Pedro L.; Paschalidis, Vasileios; Univ Arizona, Dept Astron; Univ Arizona, Dept Phys (AMER PHYSICAL SOC, 2019-04-30)

  We study the solution space of general relativistic, axisymmetric, equilibria of differentially rotating neutron stars with realistic, nuclear equations of state. We find that different types of stars, which were identified by earlier works for polytropic equations of state, arise for realistic equations of state, too. Scanning the solution space for the sample of realistic equations of state we treat, we find lower limits on the maximum rest masses supported by cold, differentially rotating stars for each type of stars. We often discover equilibrium configurations that can support more than 2 times the mass of a static star. We call these equilibria "overmassive," and in our survey we find overmassive stars that can support up to 2.5 times the maximum rest mass that can be supported by a cold, nonrotating star with the same equation of state. This is nearly 2 times larger than what previous studies employing realistic equations of state had found, and which did not uncover overmassive neutron stars. Moreover, we find that the increase in the maximum rest mass with respect to the nonspinning stellar counterpart is larger for moderately stiff equations of state. These results may have implications for the lifetime and the gravitational wave and electromagnetic counterparts of hypermassive neutron stars formed following binary neutron star mergers.
• Silicone optical elements for cost-effective freeform solar concentration

  Cui, Sifang; Lyons, Nicholas P; Diaz, Liliana Ruiz; Ketchum, Remington; Kim, Kyung-Jo; Yuan, Hao-Chih; Frasier, Mike; Pan, Wei; Norwood, Robert A; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2019-04-15)

  The use of silicone optical elements is demonstrated for a concentrated photovoltaic system. These components show over 96% transmission through most of the solar spectrum and excellent temperature stability. Unique moldability enables the use of complex freeform designs. A light, compact, and cost-effective concentrated photovoltaic system based on silicone optics is proposed. In this system, air-plasma treatment is utilized to overcome the mechanical properties of silicone and difficulties with coating to reduce Fresnel loss. Lens arrays and waveguides are fabricated by injection molding following freeform optical design by LightTools. First-order characterizations are also performed. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
• Serum Amyloid P Component Binds Fungal Surface Amyloid and Decreases Human Macrophage Phagocytosis and Secretion of Inflammatory Cytokines

  Behrens, Nicole E; Lipke, Peter N; Pilling, Darrell; Gomer, Richard H; Klotz, Stephen A; Univ Arizona, Dept Immunobiol; Univ Arizona, Dept Med (AMER SOC MICROBIOLOGY, 2019-03-12)

  In patients with invasive fungal diseases, there is often little cellular inflammatory response. We tested the idea that binding of the human constitutive plasma protein serum amyloid P component (SAP) (also called PTX2) to Candida albicans dampens the innate immune response to this fungus. Many pathogenic fungi have cell surface amyloid-like structures important for adhesion and biofilm formation. Human SAP bound to fungi that expressed functional cell surface amyloid, but SAP had minimal binding to fungi with reduced expression of cell surface amyloid. In the absence of SAP, phagocytosis of fungi by human macrophages was potentiated by expression of amyloid on the fungi. SAP binding to fungi inhibited their phagocytosis by macrophages. Macrophages pretreated with SAP displayed reduced fungal phagocytosis, reduced secretion of inflammatory cytokines (IFN-γ, IL-6, and TNF-α), and increased secretion of the anti-inflammatory cytokine IL-10. SAP bound to fungi or added to the medium upregulated the expression of the anti-inflammatory receptor CD206 on macrophages. These findings suggest that SAP bound to amyloid-like structures on fungal cells dampens the host cellular immune response in fungal diseases such as invasive candidiasis.IMPORTANCE Macrophages are a key part of our innate immune system and are responsible for recognizing invading microbes, ingesting them, and sending appropriate signals to other immune cells. We have found that human macrophages can recognize invading yeast pathogens that have a specific molecular pattern of proteins on their surfaces: these proteins have structures similar to the structures of amyloid aggregates in neurodegenerative diseases like Alzheimer's disease. However, this surface pattern also causes the fungi to bind a serum protein called serum amyloid P component (SAP). In turn, the SAP-coated yeasts are poorly recognized and seldom ingested by the macrophages, and the macrophages have a more tolerant and less inflammatory response in the presence of SAP. Therefore, we find that surface structures on the yeast can alter how the macrophages react to invading microbes.
• Parameters associated with efficacy of epidural steroid injections in the management of postherpetic neuralgia: the Mayo Clinic experience

  Ghanavatian, Shirin; Wie, Christopher S; Low, Rhonda S; Butterfield III, Richard J; Zhang, Nan; Dhaliwal, Gurman Singh; Montoya, Jordan M; Swanson, David L; Univ Arizona, Coll Med Phoenix (DOVE MEDICAL PRESS LTD, 2019-04-23)

  Purpose: Thirty percent of patients with postherpetic neuralgia (PHN) receiving conservative treatment report unsatisfactory pain relief. Epidural steroid injections (ESIs) are commonly used as a therapeutic intervention in these patients. In this study, we aimed to determine if there are variables that predict the efficacy of ESI in patients with PHN. Patients and methods: We retrospectively identified patients seen at Mayo Clinic who had PHN and received ESI. From their medical records, we abstracted the demographic variables, concurrent medication use, anatomic approach and medication for ESI, and degree of pain relief at 2 and 12 weeks' postintervention. Results: None of the studied variables were significantly associated with efficacy of ESI in patients with PHN. PHN that began < 11 months before treatment was predictive of a response to ESI at 12 weeks postintervention (positive predictive value, 55%). Patients who reported poor ESI efficacy 2 weeks after the intervention had a 94% chance of still having pain at 12 weeks. Conclusion: For this cohort of patients with PHN being treated with ESI, no demographic characteristics, concurrently used medications, or type of ESI were associated with ESI treatment efficacy at 2 or 12 weeks after the intervention.

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