Simplified models for the thermodynamic properties along a combustor and their effect on thermoacoustic instability prediction

Accurately predicting the thermoacoustic modes of a combustor depends upon knowledge of the thermodynamic properties within the combustor; flame temperature, heat release rate, speed of sound and ratio of specific heats all have a strong effect. Calculating the global equilibrium properties resulting from fuel combustion is not straightforward due to the presence of complex multi-species and multi-step reaction mechanisms. A method which decouples the calculations of species dissociations is proposed in this work: this improves the precision of calculation when using few species and reduces the computational cost and complexity to a degree that embedding within low order thermoacoustic network codes is feasible. When used to calculate the combustion product mole fractions, temperature, heat release rate, speed of sound and ratio of specific heats for hydrocarbon-air flames, the method is found to be accurate and highly efficient across different operating conditions and fuel types. The method is then combined with improved low-order wave-based network modelling, the latter employing wave-based acoustic models which account for the variation of thermodynamic properties along the combustion chamber. For a laboratory-scale combustor with a large downstream temperature variation, it is shown that accurate prediction of thermoacoustic modal frequencies and growth rates does depend on accounting for the variation in thermodynamic properties

Isolation, phenotype, and allostimulatory activity of mouse liver dendritic cells

Donor liver-derived dendritic cells (DC) have recently been identified within various lymphoid and nonlymphoid tissues of organ allograft recipients, including nonimmunosuppressed mice transplanted with and permanently accepting major histocompatibility complex (MHC)-disparate hepatic allografts. These findings have raised questions about the basis of the tolerogenicity of the liver—and, in particular, about the properties of liver-derived DC. To study further the structure, immunophenotype and allostimu-latory activity of leukocytes resident in normal mouse (B10.BR; H-2k, I-Ek) liver, a procedure was developed to maximize the yield of viable, nonparenchymal cells (NPC) obtained following collagenase digestion of perfused liver fragments and density centrifugation (Per-coll). These cells comprised populations expressing lymphoid and myeloid cell surface antigens. As compared with spleen cells, they proved good allostimula-tors of naive (BIO; H-2b, I-E") splenic T cells when tested in primary mixed leukocyte reactions (MLR). After overnight (18-hr) incubation of the NPC, enrichment for transiently adherent, low-density (LD) cells on metrizamide gradients permitted the recovery of low numbers of cells (approx. 2-5 × 105 per liver), many of which displayed distinct DC morphology. Flow cytometric analysis revealed that these cells were CD3-, CD4-, CD8-, and B220-, but strongly expressed CD45 (leukocyte-common antigen), and mild-to-moderate levels of CD lib, heat-stable antigen, and CD44. The cells also expressed moderate intensity of NLDC 145 but not 33D1, DC restricted markers which have been shown to be differentially expressed on mouse DC isolated from various organs. This DC-enriched population was more strongly MHC class II(I-Ek)+ than NPC, as determined by immunocytochemistry and flow cytometry and exhibited much more potent allo-stimulatory activity for naive T cells. These findings demonstrate that freshly isolated murine liver NPC, and perhaps their counterparts in situ, exhibit allo-stimulatory activity that is enhanced in the nonadherent, low-density (DC-enriched) fraction after overnight culture. They further suggest that the © 1994 by Williams and Wilkins

In vitro propagation and homing of liver-derived dendritic cell progenitors to lymphoid tissues of allogeneic recipients: Implications for the establishment and maintenance of donor cell chimerism following liver transplantation

Dendritic cell (DC) progenitors were propagated in liquid culture from nonparenchymal cells resident in normal mouse (B10.BR; H-2k, I-E+) liver in response to granulocyte-macrophage colony stimulating factor (GM-CSF). The liver-derived DC progenitors were MHC class II-/dim and did not express counter receptors for CTLA-4, a structural homologue of the Т cell activation molecule CD28. Following subcutaneous or intravenous injection, these liver-derived cells migrated to Т cell-dependent areas of lymph nodes and spleen of unmodified, allogeneic (BIO; H-2b; I-E_) recipients, where they were identified 1-5 days, and 1 and 2 months after injection by their strong surface expression of donor MHC class II (I-Ek) and their dendritic morphology. Maximal numbers of liver-derived DC in the spleen were recorded 5 days after injection. Both clusters of strongly donor MHC class II+ cells— and (more rarely) dividing cells—could also be identified, suggesting cell replication in situ. Using the same techniques employed to generate DC progenitors from normal liver, GM-CSF-stimulated cells were propagated for 10 days from the bone marrow and spleen of nonimmunosuppressed mice sacrificed 14 days after orthotopic liver transplantation (B10;H-2b → C3H;H-2k). Immunocytochemical staining for recipient and donor MHC class II phenotype revealed the growth both of host cells with DC characteristics, and of cells expressing donor alloantigens (I-Ab). These results are consistent with the growth, in response to GM-CSF, of donor-derived DC from progenitors seeded from the liver allograft to recipient lymphoid tissue. The functional activity of the progenitors of chimeric DC and the possible role of these cells in the establishment and maintenance of donor-specific tolerance following liver transplantation remain to be determined. © 1995 by Williams and Wilkins

Particulate matter emissions from a heavy duty vehicle fuelled by petroleum diesel and used cooking oil blends

Fuel characteristic and exhaust particulate emissions tests were carried out for a EURO5 compliant Heavy Duty Vehicle operating on both pure petroleum diesel (PD) and used cooking oil (C2G Ultra Biofuel) PD blends under real world driving conditions. Fuel tests showed that fuel temperature, substitution ratio and engine speed play a key role in determining the spray characteristics of the Ultra Biofuel blends. However, under real world operating conditions, the Bioltec fuel blending system was found to overcome these effects by using lower C2G Ultra Biofuel:PD substitution ratios during cold start and low speed conditions. Overall the fuel tests suggested it to be convenient to operate the engine on blends with Ultra Biofuel content up to 80% to avoid higher fuel consumption and higher pollution load on the exhaust after treatment system, particularly at low temperatures and rpm. In the real world tests, average substitution ratios of 85% were achieved, with close to 100% Ultra Biofuel achieved for high speed steady state conditions, with no negative impact on particulate emissions. The vast majority (60-80%) of the particulate mass within the exhaust was found within size fractions below 2.5 μm for both fuels and was thus within the respirablem range. The PD produced around twice the concentration of particulates within these finer fractions compared to the equivalent trips using the blended fuel. Thermo-gravimetric Analysis demonstrated that the PD produced higher concentrations of black carbon (soot) and the Ultra Biofuel blends more organic carbon within the particulates. The tests demonstrate that when using an effective fuel substitution strategy, Ultra Biofuel has the potential to reduce both lifecycle CO2 and respirable particulate emissions leading to potential climate and air quality benefits

Impurity-free intermixing of InGaAs/GaAs-strained multiple quantum well infrared photodetectors

Interdiffusion effect has been investigated in highly strained InGaAs/GaAs multiple quantum well (MQW) IR photodetector. Impurity-free interdiffusion techniques was utilized via rapid thermal annealing (RTA) using electron- beam evaporated SiO2 cap layers at temperature 850 degrees C to study the optical and electrical properties of the interdiffused photodetector. Photoluminescence (PL) spectrum is blue shifted and PL linewidth remains almost the same, indicating no strain relaxation and deterioration of the heterostructure quality. Both transverse magnetic and transverse electric IR intersubband transitions are retained and observed after intermixing. The absorption peak wavelength is red shifted continuously from the as grown 10.20 to the interdiffused 10.5 and 11.17 micrometers , respectively, without appreciable degradation in absorption strength for 5 and 10 s annealing. Annealed responsivity spectra of both 0 degrees and 90 degrees polarization are of compatible amplitude and red shifted but with narrower spectra linewidth. Dark current of the annealed devices is found to be an order of magnitude large than the as-grown one at 77K.published_or_final_versio

Strategies for Foreign Construction-Related Consultancy Firms to Improve Performance in China

© 2015 American Society of Civil Engineers. With China being a member of the World Trade Organization (WTO), more foreign construction-related consultancy firms (foreign firms) are expected to operate in China. The aim of this research is to identify critical strategies and important practices that would improve a foreign firm's project performance. The results show foreign firms need to adopt a combination of both Western (differentiation, cost leadership) and Eastern strategies (risk responsiveness, swiftness) in order to achieve a higher level of performance in China. Foreign firms may assess their likely performance using the developed and validated models. Some instruments/practices to improve performance in China are also offered

Greatly attenuated experimental autoimmune encephalomyelitis in aquaporin-4 knockout mice

<p>Abstract</p> <p>Background</p> <p>The involvement of astrocyte water channel aquaporin-4 (AQP4) in autoimmune diseases of the central nervous system has been suggested following the identification of AQP4 autoantibodies in neuromyelitis optica, an inflammatory demyelinating disease.</p> <p>Results</p> <p>We investigated the involvement of AQP4 in disease severity in an established mouse model of experimental autoimmune encephalomyelitis (EAE) produced by immunization with myelin oligodendrocyte glycoprotein (MOG_35–55) peptide. EAE was remarkably attenuated in AQP4 null mice compared to identically treated wildtype mice. Whereas most wildtype mice developed progressive tail and hindlimb paralysis, clinical signs were virtually absent in AQP4 null mice. Brain and spinal cords from AQP1 null mice showed greatly reduced mononuclear cell infiltration compared to wildtype mice, with relatively little myelin loss and axonal degeneration.</p> <p>Conclusion</p> <p>The reduced severity of autoimmune encephalomyelitis in AQP4 deficiency suggests AQP4 as a novel determinant in autoimmune inflammatory diseases of the central nervous system and hence a potential drug target.</p

Estimation of the Heat Flow Variation in the Chad Basin Nigeria

Wireline logs from 14 oil wells from the Nigerian sector of the Chad Basin were analyzed and interpreted to estimate the heat flow trend in the basin. Geothermal gradients were computed from corrected bottomhole temperatures while the bulk effective thermal conductivity for the different stratigraphic units encountered in the wells were computed from the sonic logs data. The heat flow values were then calculated. A corrected average geothermal gradient of 3.4 oC/100 m and a regional range of 3.0 to 4.4 oC/100 m were obtained. A porosity range of2 to 79 % and average of 35 % were computed for Chad Basin Nigeria. Also the thermal conductivities vary from 1.70 and 3.11 Wm-1 oC-1, with an average value of 2.35 Wm-1 oC-1 computed for the various wells in the basin. A large variation in heat flow was recorded within the basin. Mean heat flow values computed for the basin vary from 63.6 to105.6 mWm-2, with a simple average of 80.6 mWm-2. Although there is no distinct trend on heat flow within the basin, the computed heat flow values are relatively lower at the southwestern and northeastern axis of the basin. And the values obtained in this study compared favorably with those of other world sedimentary basins (including NigerDelta) that are of similar history with the Chad Basin, suggesting that the Nigerian Chad Basin is a possible petroliferous basin