On impedance in shock-refraction problems

Publications on shock-refraction problems typically predict wave patterns resulting from the interaction from the acoustic-impedance ratio. In this note, an analysis based on the shock-impedance ratio is used to derive conditions under which the acoustic-impedance ratio predicts the incorrect type of reflected wave. The range of density ratios for which incorrect types of reflected waves are predicted is found to be quite narro

Insulin Promotes Glycogen Storage and Cell Proliferation in Primary Human Astrocytes

In the human brain, there are at least as many astrocytes as neurons. Astrocytes are known to modulate neuronal function in several ways. Thus, they may also contribute to cerebral insulin actions. Therefore, we examined whether primary human astrocytes are insulin-responsive and whether their metabolic functions are affected by the hormone.Commercially available Normal Human Astrocytes were grown in the recommended medium. Major players in the insulin signaling pathway were detected by real-time RT-PCR and Western blotting. Phosphorylation events were detected by phospho-specific antibodies. Glucose uptake and glycogen synthesis were assessed using radio-labeled glucose. Glycogen content was assessed by histochemistry. Lactate levels were measured enzymatically. Cell proliferation was assessed by WST-1 assay.We detected expression of key proteins for insulin signaling, such as insulin receptor β-subunit, insulin receptor substrat-1, Akt/protein kinase B and glycogen synthase kinase 3, in human astrocytes. Akt was phosphorylated and PI-3 kinase activity increased following insulin stimulation in a dose-dependent manner. Neither increased glucose uptake nor lactate secretion after insulin stimulation could be evidenced in this cell type. However, we found increased insulin-dependent glucose incorporation into glycogen. Furthermore, cell numbers increased dose-dependently upon insulin treatment.This study demonstrated that human astrocytes are insulin-responsive at the molecular level. We identified glycogen synthesis and cell proliferation as biological responses of insulin signaling in these brain cells. Hence, this cell type may contribute to the effects of insulin in the human brain

Insulin-like growth factors and related proteins in plasma and cerebrospinal fluids of HIV-positive individuals

BACKGROUND: Clinically significant dysregulation of the insulin-like growth factor (IGF) family proteins occurs in HIV-infected individuals, but the details including whether the deficiencies in IGFs contribute to CNS dysfunction are unknown. METHODS: We measured the levels of IGF1, IGF2, IGFBP1, IGFBP2, and IGF2 receptor (IGF2R) in matching plasma and cerebrospinal fluid (CSF) samples of 107 HIV+ individuals from CNS HIV Antiretroviral Therapy Effects Research (CHARTER) and analyzed their associations with demographic and disease characteristics, as well as levels of several soluble inflammatory mediators (TNFα, IL-6, IL-10, IL-17, IP-10, MCP-1, and progranulin). We also determined whether IGF1 or IGF2 deficiency is associated with HIV-associated neurocognitive disorder (HAND) and whether the levels of soluble IGF2R (an IGF scavenging receptor, which we also have found to be a cofactor for HIV infection in vitro) correlate with HIV viral load (VL). RESULTS: There was a positive correlation between the levels of IGF-binding proteins (IGFBPs) and those of inflammatory mediators: between plasma IGFBP1 and IL-17 (β coefficient 0.28, P = 0.009), plasma IGFBP2 and IL-6 (β coefficient 0.209, P = 0.021), CSF IGFBP1 and TNFα (β coefficient 0.394, P < 0.001), and CSF IGFBP2 and TNF-α (β coefficient 0.14, P < 0.001). As IGFBPs limit IGF availability, these results suggest that inflammation is a significant factor that modulates IGF protein expression/availability in the setting of HIV infection. However, there was no significant association between HAND and the reduced levels of plasma IGF1, IGF2, or CSF IGF1, suggesting a limited power of our study. Interestingly, plasma IGF1 was significantly reduced in subjects on non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy (ART) compared to protease inhibitor-based therapy (174.1 ± 59.8 vs. 202.8 ± 47.3 ng/ml, P = 0.008), suggesting a scenario in which ART regimen-related toxicity can contribute to HAND. Plasma IGF2R levels were positively correlated with plasma VL (β coefficient 0.37, P = 0.021) and inversely correlated with current CD4+ T cell counts (β coefficient −0.04, P = 0.021), supporting our previous findings in vitro. CONCLUSIONS: Together, these results strongly implicate (1) an inverse relationship between inflammation and IGF growth factor availability and the contribution of IGF deficiencies to HAND and (2) the role of IGF2R in HIV infection and as a surrogate biomarker for HIV VL. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12974-015-0288-6) contains supplementary material, which is available to authorized users

An assessment of thermocline-control methods for packed-bed thermal-energy storage in CSP plants, Part 2:Assessment strategy and results

Three thermocline-control (TCC) methods are assessed through numerical simulations for a thermal-energy storage (TES) filled with a packed bed of rocks. Two previously suggested methods are based on extracting or injecting heat-transfer fluid (HTF) through ports, while the third is a novel method based on mixing HTF streams. The assessment was carried out using simulations with a model that resolves the packed bed in one dimension. Simulations of stand-alone TES with maximum allowed outflow temperature differences of 10% at quasi-steady conditions showed that the mixing method with three ports led to the largest utilization factors – the fraction of the maximum storage capacity that is actually utilized – of 90.8% and 85.1% for molten salt (MS) and compressed air (CA) as HTF, respectively. These represent relative improvements of 38.8% and 73.4% compared to the baseline configurations without TCC. The increased utilization factors come at the expense of small decreases in the cycle exergy efficiency. For the mixing method with three ports, the exergy efficiencies were 97.3% and 95.6% for MS and CA, respectively. Simulations of a TES with MS as HTF integrated into a CSP plant operating on a Rankine steam cycle showed that TCC increases the annually averaged plant efficiency and the annual net electricity generated solely from thermal energy supplied by the TES. These results suggest that the small decreases in the exergy efficiency of the TES are outweighed by the large increases in the utilization factor.</p

Design of a 100 MWhth Packed-bed Thermal Energy Storage

AbstractA thermal energy storage (TES) system was designed based on a packed bed of rocks as storing material and air as heat transfer fluid. A pilot-scale 6.5 MWhth TES unit was built and tested. A dynamic numerical heat transfer and fluid flow model was developed and experimentally validated with measurements obtained from the pilot-scale TES unit. The simulation model is applied to design an industrial-scale 100 MWhth TES unit for a solar power plant currently under construction in Morocco