Performance of a tandem-rotor/tandem-stator conical-flow compressor designed for a pressure ratio of 3

A conical-flow compressor stage with a large radius change through the rotor was tested at three values of rotor tip clearance. The stage had a tandem rotor and a tandem stator. Peak efficiency at design speed was 0.774 at a pressure ratio of 2.613. The rotor was tested without the stator, and detailed survey data were obtained for each rotor blade row. Overall peak rotor efficiency was 0.871 at a pressure ratio of 2.952

Biophysical investigation of M-DNA

M-DNA is a complex formed between normal double-stranded DNA and the transition metal ions Zn2+, Ni2+, and Co2+ that is favoured by an alkaline pH. Previous studies have suggested that M-DNA formation involves replacement of the imino protons of G and T bases by the transition metal ions involved in forming the complex. Owing to the conductive properties of this unique DNA conformation, it has potential applications in nanotechnology and biosensing. This work was aimed at improving existing methods and developing new methods of characterizing M-DNA. The effects of base substitutions, particularly those of G and T, were evaluated in light of the proposed structure. Differences between M-DNA conformations induced by Zn2+ and Ni2+ were also investigated with a variety of techniques and compared to the effects of Cd2+ and Mg2+ on double-stranded DNA. M-DNA formation and stability were studied with an ethidium bromide (EtBr) based assay, M-DNA induced fluorescence quenching of DNA labelled with fluorescein and a compatible quenching molecule, isothermal titration calorimetry (ITC), and surface plasmon resonance (SPR). Production of monoclonal antibodies against the conformation was also attempted but was unsuccessful. The EtBr-based assay showed Ni(II) M-DNA to be much more stable than Zn(II) M-DNA as a function of pH and in the presence of ethylenediaminetetraacetic acid. Sequence-dependency and the effect of base substitutions were measured as a function of pH. With regards to sequence, d(G)n•d(C)n tracts were found to form the conformation most easily. Base substitutions with G and T analogues that lowered the pKa of these bases were found to stabilize M-DNA more strongly than other base substitutions. A combination of temperature-dependant EtBr and ITC assays showed M-DNA formation to be endothermic, and therefore entropy driven. The SPR studies demonstrated many qualitative differences between Zn(II) and Ni(II) M-DNA formation, allowed characterization of Zn2+, Ni2+, Cd2+, and Mg2+ complexes with single-stranded DNA, and provided unambiguous evidence that M-DNA formation results in very little denaturation of double-stranded DNA. Specifically, the SPR study showed Ni(II) M-DNA to be more stable than Zn(II) M-DNA in the absence of transition metal ions, but also showed that Ni(II) M-DNA required higher concentrations of Ni2+ than Zn2+ to fully form the respective M-DNA conformations. Finally, quenching studies demonstrated Zn(II) M-DNA formation over a pH range from 6.5 to 8.5 provided that a Zn2+:H+ ratio of roughly 105 was maintained. The Keq for this interaction was 1.3 x 10-8 with 1.4 H+ being liberated per base bair of M-DNA formed. These results support the proposed structural model of M-DNA, as lowering the pKa of the bases having titratable protons over the pH range studied facilitated M-DNA formation. The fact that Zn(II) M-DNA formation was observed by fluorescence quenching at any pH provided that a constant ratio of Zn2+:H+ was maintained was consistent with a simple mass-action interaction for M-DNA formation. The differences between Zn(II) and Ni(II) M-DNA formation show that although it requires a higher pH or transition metal ion concentration, Ni(II) M-DNA is more stable than Zn(II) M-DNA once formed. This difference could play an important role in applications of M-DNA which required modulation in the stability of the M-DNA conformation

Kaposi’s sarcoma at the University Teaching Hospital, Lusaka, Zambia in the antiretroviral therapy era

With great interest, we read the recent publication “Kaposi’s sarcoma in HIV-infected patients in South Africa: Multicohort study in the antiretroviral therapy era” by Bohlius et al. We congratulate the authors for their contribution to this field. In this study the authors observed a decrease in incidence of Kaposi’s sarcoma (KS) in patients treated with anti-retroviral therapy (ART) when compared to patients who are not on ART. These results are encouraging because of the ongoing HIV epidemic in sub-Saharan Africa where KS is still one of the most prevalent cancers. Also, it is a relevant topic to study in South Africa; a country that has a high prevalence of both HIV and Kaposi’s sarcoma-associated herpesvirus (KSHV) infections

Kaposi’s sarcoma at the University Teaching Hospital, Lusaka, Zambia in the antiretroviral therapy era

With great interest, we read the recent publication “Kaposi’s sarcoma in HIV-infected patients in South Africa: Multicohort study in the antiretroviral therapy era” by Bohlius et al. We congratulate the authors for their contribution to this field. In this study the authors observed a decrease in incidence of Kaposi’s sarcoma (KS) in patients treated with anti-retroviral therapy (ART) when compared to patients who are not on ART. These results are encouraging because of the ongoing HIV epidemic in sub-Saharan Africa where KS is still one of the most prevalent cancers. Also, it is a relevant topic to study in South Africa; a country that has a high prevalence of both HIV and Kaposi’s sarcoma-associated herpesvirus (KSHV) infections

Lack of CD8+ T-cell co-localization with Kaposi’s sarcoma- associated herpesvirus infected cells in Kaposi’s sarcoma tumors

Despite the close association between Kaposi’s sarcoma (KS) and immune dysfunction, it remains unclear whether tumor infiltrating immune cells (TIIC), by their absence, presence, or dysfunction, are mechanistically correlated with KS pathogenesis. Therefore, their potential capacity to serve as prognostic biomarkers of KS disease progression or control is unclear. Because epidemic-KS (EpKS) occurs with HIV-1 co-infection, it is particularly important to compare TIIC between EpKS and HIV-negative African endemic-KS (EnKS) to dissect the roles of HIV-1 and Kaposi Sarcoma-associated herpesvirus (KSHV) in KS pathogenesis. This cross-sectional study of 13 advanced KS (4 EnKS, 9 EpKS) patients and 3 healthy controls utilized single-color immunohistochemistry and dual-color immunofluorescence assays to characterize and quantify KSHV infected cells in relation to various TIIC in KS biopsies. Analysis of variance (ANOVA) and Mann-Whitney tests were used to assess differences between groups where P-values \u3c 0.05 were considered significant. The abundance of KSHV infected cells was heterogeneous in KS biopsies. Despite the presence of T-cell chemoattractant chemokine CxCL-9 in biopsies, CD8+ T-cells were sparsely distributed in regions with evident KSHV infected cells but were readily detectable in regions devoid of KSHV infected cells (P \u3c 0.0001). CD68+ (M1) macrophages were evenly and diffusely distributed in KS biopsies, whereas, the majority of CD163+ (M2) macrophages were localized in regions devoid of KSHV infected cells (P \u3c 0.0001). Overall, the poor immune cell infiltration or co-localization in KS biopsies independent of HIV-1 co-infection suggests a fundamental tumor immune evasion mechanism that warrants further investigation

Designing the Space Shuttle Propulsion System

The major elements of the Space Shuttle Main Propulsion System include two reusable solid rocket motors integrated into recoverable solid rocket boosters, an expendable external fuel and oxidizer tank, and three reusable Space Shuttle Main Engines. Both the solid rocket motors and space shuttle main engines ignite prior to liftoff, with the solid rocket boosters separating about two minutes into flight. The external tank separates after main engine shutdown and is safely expended in the ocean. The SSME's, integrated into the Space Shuttle Orbiter aft structure, are reused after post landing inspections. Both the solid rocket motors and the space shuttle main engine throttle during early ascent flight to limit aerodynamic loads on the structure. The configuration is called a stage and a half as all the propulsion elements are active during the boost phase, and the SSME's continue operation to achieve orbital velocity approximately eight and a half minutes after liftoff. Design and performance challenges were numerous, beginning with development work in the 1970 s. The solid rocket motors were large, and this technology had never been used for human space flight. The SSME s were both reusable and very high performance staged combustion cycle engines, also unique to the Space Shuttle. The multi body side mount configuration was unique and posed numerous integration and interface challenges across the elements. Operation of the system was complex and time consuming. This paper discusses a number of the system level technical challenges including development and operations

Space Shuttle Propulsion Materials, Manufacturing, and Operational Challenges

Presentations in this session include: (1) External Tank (ET) Materials, Manufacturing, and Operational Challenges; (2) Space Shuttle Main Engine (SSME) Materials, Manufacturing, and Operational Challenges,(3) Reusable Solid Rocket Motor (RSRM) Materials, Manufacturing, and Operational Challenges and (4) Solid Rocket Booster (SRB) Materials, Manufacturing, and Operational Challenges

Can sacrificial feeding areas protect aquatic plants from herbivore grazing? Using behavioural ecology to inform wildlife management

Effective wildlife management is needed for conservation, economic and human well-being objectives. However, traditional population control methods are frequently ineffective, unpopular with stakeholders, may affect non-target species, and can be both expensive and impractical to implement. New methods which address these issues and offer effective wildlife management are required. We used an individual-based model to predict the efficacy of a sacrificial feeding area in preventing grazing damage by mute swans (Cygnus olor) to adjacent river vegetation of high conservation and economic value. The accuracy of model predictions was assessed by a comparison with observed field data, whilst prediction robustness was evaluated using a sensitivity analysis. We used repeated simulations to evaluate how the efficacy of the sacrificial feeding area was regulated by (i) food quantity, (ii) food quality, and (iii) the functional response of the forager. Our model gave accurate predictions of aquatic plant biomass, carrying capacity, swan mortality, swan foraging effort, and river use. Our model predicted that increased sacrificial feeding area food quantity and quality would prevent the depletion of aquatic plant biomass by swans. When the functional response for vegetation in the sacrificial feeding area was increased, the food quantity and quality in the sacrificial feeding area required to protect adjacent aquatic plants were reduced. Our study demonstrates how the insights of behavioural ecology can be used to inform wildlife management. The principles that underpin our model predictions are likely to be valid across a range of different resource-consumer interactions, emphasising the generality of our approach to the evaluation of strategies for resolving wildlife management problems

Vestibular Effects on Cerebral Blood Flow

Background: Humans demonstrate a number of unique adaptations that allow for the maintenance of blood pressure and brain blood flow when upright. While several physiological systems, including cerebral autoregulation, are involved in this adaptation the unique role the vestibular system plays in helping to maintain brain blood flow is just beginning to be elucidated. In this study, we tested the hypothesis that stimulation of the vestibular system, specifically the otoliths organs, would result in changes in cerebral blood flow. Results: To test our hypothesis, we stimulated the vestibular organs of 25 healthy subjects by pitch tilt (stimulates both canals and otoliths) and by translation on a centrifuge (stimulates otoliths and not the canals) at five frequencies: 0.5, 0.25, 0.125 and 0.0625 Hz for 80 sec and 0.03125 Hz for 160 sec. Changes in cerebral flow velocity (by transcranial Doppler) and blood pressure (by Finapres) were similar during both stimuli and dependent on frequency of stimulation (P < 0.01). However, changes in cerebral blood flow were in opposition to changes in blood pressure and not fully dependent on changes in end tidal CO2. Conclusion: The experimental results support our hypothesis and provide evidence that activation of the vestibular apparatus, specifically the otolith organs, directly affects cerebral blood flow regulation, independent of blood pressure and end tidal CO2 changes